Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.ensm.2023.103163

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsaem.3c01513

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpcc.3c02992

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsami.3c06624

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Language：Japanese   Publishing type：Research paper (other academic)  

http://iartkasen.com/2023/07/5763/

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.23-00037

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpcc.3c01961

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)   Publisher：キャパシタフォーラム  

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

DOI： 10.5796/electrochemistry.22-00090

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.electacta.2022.141000

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Authorship：Corresponding author  

DOI： 10.1016/j.ceramint.2022.07.093

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Authorship：Corresponding author  

DOI： 10.1016/j.elecom.2022.107333

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Authorship：Corresponding author  

DOI： 10.1016/j.ensm.2022.04.030

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

Ionic liquids (ILs) possess low volatility and low flammability and are promising electrolytes for thermally stable Li-ion batteries (LIBs). Among ILs, bis(fluorosulfonyl)imide (FSI⁻) anion-based ILs have low viscosity and high ionic conductivity and FSI-based electrolytes are useful for achieving a high power density LIB. In this study, we investigated the effects of LiFSI concentration in IL electrolytes on the performance of LIBs. We prepared electrolytes composed of 1-ethyl-3-methyl imidazolium bis(fluorosulfonyl)imide (EMImFSI) and LiFSI. The ionic conductivity of the electrolyte decreased with increasing LiFSI concentration due to an increase in viscosity; however, the Li⁺ transference number increased with increasing LiFSI concentration. The IL electrolyte was tested in a LiNi_0.5Mn_0.3Co_0.2O₂/graphite pouch cell. The discharge rate capability of the cell was improved by increasing the LiFSI concentration. The higher LiFSI concentration was effective in suppressing the depletion of Li⁺ in the vicinity of the cathode during the high current discharge. Furthermore, we demonstrated that cells with IL electrolytes can be stably operated over 500 charge-discharge cycles at 25 °C and 60 °C.

DOI： 10.5796/electrochemistry.21-00075

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsaem.0c02063

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

High-performance advanced and futuristic products require batteries with higher energy densities than those of conventional batteries. Anion-redox active materials have high specific capacities, but they exhibit low life-cycle performance. In this study, the charge-discharge mechanism and the primary factors contributing to the capacity degradation of Co-substituted Li5AlO4 (CSLA) during charge-discharge cycling were investigated. X-ray absorption spectroscopy (XAS) was performed to determine the change in the electronic state of CSLA during the charge-discharge process. The changes in the XAS peak intensities were attributed to the formation and consumption of peroxide and superoxide, as observed in the O K-edge X-ray absorption near-edge structure (XANES) spectra of CSLA obtained over the first ten charge-discharge cycles. The results indicated that the redox reaction involving the formation and consumption of peroxide and superoxide allows for the charge compensation of CSLA. Furthermore, the intensity of the O K-edge XANES peak attributed to the formation and consumption of peroxide decreased with the increasing number of charge-discharge cycles of CSLA, which correlated with the capacity degradation of CSLA. This study provides new insights into the charge-discharge and capacity degradation mechanisms of anion-redox cathode materials.

DOI： 10.1016/j.matchemphys.2020.123619

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Sulfur is a promising material for next-generation cathodes, owing to its high energy and low cost. However, sulfur cathodes have the disadvantage of serious cyclability issues due to the dissolution of polysulfides that form as intermediate products during discharge/charge cycling. Filling sulfur into the micropores of porous carbon is an effective method to suppress its dissolution. Although microporous carbon-supported sulfur cathodes show an electrochemical behavior different from that of the conventional sulfur ones, the corresponding reaction mechanism is not clearly understood. In this study, we focused on clarifying the reaction mechanism of microporous carbon-supported sulfur cathodes by operando soft X-ray absorption spectroscopy. In the microporous carbon support, sulfur was present as smaller fragments compared to conventional sulfur. During the first discharge process, the sulfur species in the microporous carbon were initially reduced to S62− and S22− and then to Li2S. The S62− and S22− species were observed first, with S22− being the main polysulfide species during the discharge process, while Li2S was produced in the final discharge process. The narrow pores of microporous carbon prevent the dissolution of polysulfides and influence the reaction mechanism of sulfur cathodes.

DOI： 10.1039/d0ra08299f

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

Modern and future products such as electric vehicles and hybrid electric vehicles require batteries with higher energy densities than that of conventional batteries. Anion redox-type active materials are proposed as a new high-capacity positive electrode material for Li-ion batteries with high energy density. We developed Li5AlO4 as an anion redox-type active material with a higher stability than that of Co-substituted Li2O. Li5AlO4 was substituted with Co by mechanical alloying with LiCoO2 to enhance its conductivity and its reactivity as an oxide anion. Co-substituted Li5AlO4 showed a slightly higher electron conductivity and a remarkably higher oxide anion reactivity than the as-prepared Li5AlO4. From electrochemical analysis, it was shown that Co-substituted Li5AlO4 had a reversible capacity of approximately 140 mAh g(-1), while the as-prepared Li5AlO4 had no reversible capacity. According to the atomic valence of Co and Al and the partial structure for Co-substituted Li5AlO4 during the first charge-discharge cycle, we found that the charge capacity of Co-substituted Li5AlO4 is derived from the oxidation of oxide anions, the formation of peroxide and superoxide, and the fact that the partial structure of Co-substituted Li5AlO4 remains unchanged. These results indicate that the charge-discharge reaction of Co-substituted Li5AlO4 proceeds reversibly. Co-substituted Li5AlO4 demonstrates a relatively high specific capacity and good reversibility during the charge-discharge process.

DOI： 10.1016/j.ssi.2020.115374

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

DOI： 10.1016/j.carbon.2020.03.016

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

DOI： 10.1149/1945-7111/aba1a7

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Electric vehicles and hybrid electric vehicles require batteries with higher energy densities than conventional batteries. Anion redox-type active materials have been proposed as new high-capacity positive electrode materials for Li-ion batteries with high-energy densities. Co-substituted Li5AlO4 is a novel and promising high-capacity positive electrode material for Li-ion batteries. In this study, we investigated the influence of different synthesis conditions on the enhancement of the specific capacity. The material prepared via mechanical alloying of beta-Li5AlO4 with LiCoO2 at 300 rpm for 24 h exhibited a higher specific capacity than that prepared from alpha-Li5AlO4 and LiCoO2. Co-substituted beta-Li5AlO4 demonstrated a specific capacity of approximately 250 mA h g(-1). The specific capacity of Co-substituted a and beta-Li5AlO4 increased with increasing Co content in the samples. According to Xray absorption near edge structure measurements, the irreversible oxygen redox reaction and a reversible reaction involving the formation and consumption of peroxide were responsible for the charge compensation of Co-substituted beta-Li5AlO4 and alpha-Li5AlO4, respectively.

DOI： 10.1021/acsomega.0c02111

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/batt.202000061

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.5796/electrochemistry.20-63009

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.elecom.2020.106705

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.19-00027

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1155/2019/2501039

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijbiomac.2018.12.006

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

Ionic liquid (IL) electrolytes have been applied to lithium ion capacitors (LICs) composed of porous three-dimensional (3D) current collector. LIC cells containing IL electrolytes showed reversible charge-discharge potential profiles and their capacity degradation was hardly observed during 3000 cycles. In particular, a cell with 1-ethyl-3-methyl imidazolium bis(fluorosulfonyl)imide (EMImFSI) containing lithium FSI (LiFSI) as Li salt kept over 90% of its initial capacity even after 3000 cycles. The EMImFSI-based IL electrolyte system (LiFSI/EMImFSI) also provided better rate performance than that of a conventional LiPF6-based organic electrolyte system. Considering high-temperature (60 °C) characteristics in the IL system and LiPF6-based system, charge-discharge operation in LiFSI/EMImFSI was stable compared to that in the LiPF6-based solvent system. Moreover, the LIC cell with LiFSI/EMImFSI was stably cycled even at 0 °C and its discharge capacity was superior to that of the LiPF6-based solvent electrolyte at 0 °C.

DOI： 10.1016/j.electacta.2018.04.148

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

Based on electron microscope techniques developed for ionic liquids (ILs), which have both high stability under vacuum and an antistatic nature, specially-designed Li battery cells with all components contained in actual Li batteries were fabricated for in situ electron microscope observation. Various interesting anode behaviors in the Li battery were observed. For example, Si thin flake active material can store Li(I) electrochemically, causing the morphology to change into a ribbon-like or isotropic expanded structure. Surprisingly any damage to the Si material was not recognized by nanoscale imaging because of the thin layer structure that can release internal stress spontaneously during lithiation. In addition, the Li metal deposition process was directly observed and a similar approach can be applied to in situ X-ray photoelectron spectroscopic analysis.

DOI： 10.1016/j.electacta.2018.05.081

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Authorship：Corresponding author   Language：Japanese  

DOI： 10.5650/oleoscience.18.185

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Electrochemical Society of Japan  

We investigated effects of high lithium bis(fluorosulfonyl)imide (LiFSI) salt concentration or heat treatment before initial charge on charge-discharge performance of a graphite electrode in a 1-ethyl-3-methylimidazolium (EMImFSI)-based ionic liquid (IL) electrolyte. LiF was observed at the surface of graphite electrodes taken out from 2.00 mol kg-1 LiFSI/EMImFSI system and from 0.32 mol kg-1 LiFSI/EMImFSI system with pre-heat treatment before the initial charge. The surface LiF effectively suppresses the reductive decomposition of EMIm+. As a result, the irreversible capacity of initial cycle was significantly suppressed and the coulombic efficiency of subsequent cycles was greatly improved.

DOI： 10.5796/electrochemistry.17-00089

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Netherlands  

A novel gel electrolyte has been prepared using bacterial cellulose (BC) coated with chitosan (CTS) and alginate (Alg) layers, which contain 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4). The gel electrolyte was optimized for use in solvent-free solid-stage electric double-layer capacitors (EDLCs). The inoculated BC was oxidized and coated with alternating layers of CTS and Alg via ionic crosslinking to produce the gel electrolytes. The CTS content of the obtained gel electrolytes linearly increased with an increase in the number of CTS and Alg layers on the BC fibers. The results imply that the CTS and Alg layers successfully bound onto each BC fiber, which was consistent with Fourier transform infrared spectroscopy measurements. Based on a structural analysis, the fabricated gel electrolytes had a nanofibrous structure with a fiber diameter range of approximately 78.6–99.0 nm, a high thermal stability, and a significantly improved tensile strength compared to gel electrolytes of only CTS or Alg. In addition, EDLCs have been fabricated using the new gel electrolyte with activated carbon as the active material. The electrochemical performance of the EDLCs was determined via charge–discharge testing and alternating current impedance measurements. The EDLCs cell with a gel electrolyte of BC coated with 15 layers of CTS and Alg containing EMImBF4 showed a high discharge capacitance, implying that the high affinity of this gel electrolyte for the activated carbon electrode leads to reduced electrode/electrolyte interfacial resistance, which shows the potential of this approach compared with liquid-phase EMImBF4 to obtain high-performance, safety-oriented EDLCs.

DOI： 10.1007/s11164-018-3348-6

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

Micropore-rich activated carbon with high surface area and pore volume was prepared by alkali activation of azulmic carbon (AZC) precursor as nitrogen-doped carbon; AZC was a carbonized product from azulmic acid. We successfully loaded a large amount of sulfur (S) into micropores of the activated AZC. Our two kinds of activated AZC (BET surface area: 1,747 and 2,319 m(2)g(-1)) can include S up to 55 and 62 wt%, respectively. The former activated AZC including S can be charged and discharged with lithium (Li) ion transfer stably and reversibly in glyme-based and carbonate-based electrolytes. The latter activated AZC can be charged and discharged in a glyme-based electrolyte. These different characteristics are due to a difference in fine pore structure between them. Our microporous activated AZC with high S loading is promising material as positive S electrode for rechargeable Li-S batteries. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.85.650

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

We prepared activated carbon (AC) and sulfur (S) composite cathodes. The present AC has developed micropores and a large pore volume. The composite could successfully include a large amount of S and exhibited stable cycle performance in a glyme-based electrolyte. An oxidation treatment of the AC with a concentrated nitric acid solution at 120 degrees C was found to improve S utilization in charge-discharge cycling. A cathode with the oxidized AC including S showed stable cycle performance with a high capacity in not only the glyme-based electrolyte but also a carbonate based electrolyte. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.85.671

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Understanding the electrochemical behavior and controlling the morphological variations of electrodes are critical for the design of high-capacity batteries. In this article, we describe a newly established operando scanning electron microscopy (SEM) to visualize the battery reactions in a modified coin cell, which allowed the simultaneous collection of electrochemical data and time-resolved images. The investigated silicon (Si)-polyimide-binder electrode exhibited a high capacity (similar to 1500 mAh g(-1)) and a desirable cyclability. Operando SEM revealed that the morphology of the Si anode drastically changed and cracks formed on the electrode because of the lithiation-induced volume exprision of the Si particles during the first charge process. Interestingly, the thickness variation in the Si composite layer was moderated in subsequent cycles. This strongly suggested that cracking caused by the breakage of the stiff binder alleviated the internal stress experienced by Si. On the basis of this finding by the operando SEM technique, patterned Si electrodes with controlled spacing were successfully fabricated, and their improved performance was confirmed.

DOI： 10.1021/acsami.7b12340

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We prepared a lithium bis(fluorosulfonyl) imide (LiFSI)-based low ethylene carbonate (EC) content electrolyte as a new electrolyte. LiFSI enough dissociates in mixed solvents containing only a small amount of EC and the LiFSI-based low EC content electrolyte shows a high ionic conductivity comparable to that of a conventional LiPF6-based high EC content electrolyte. In addition, the LiFSI-based low EC content electrolyte has an unusual solvation state of Li ion and we consider that the desolvation process from Li ion in our new electrolyte system is different from that in the conventional high EC content systems. A graphite half-cell assembled with our new electrolyte shows a quite low Li ion transfer resistance and outstanding charge and discharge rate performance compared to the conventional high EC content systems. A graphite/LiNi1/3Mn1/3Co1/3O2 cell assembled with our new electrolyte also shows superior charge and discharge rate performance and excellent long cycle stability. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2017.05.090

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.5796/electrochemistry.85.490

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

A comprehensive understanding of the charge/discharge behaviour of high-capacity anode active materials, e.g., Si and Li, is essential for the design and development of next-generation high-performance Li-based batteries. Here, we demonstrate the in situ scanning electron microscopy (in situ SEM) of Si anodes in a configuration analogous to actual lithium-ion batteries (LIBs) with an ionic liquid (IL) that is expected to be a functional LIB electrolyte in the future. We discovered that variations in the morphology of Si active materials during charge/discharge processes is strongly dependent on their size and shape. Even the diffusion of atomic Li into Si materials can be visualized using a back-scattering electron imaging technique. The electrode reactions were successfully recorded as video clips. This in situ SEM technique can simultaneously provide useful data on, for example, morphological variations and elemental distributions, as well as electrochemical data.

DOI： 10.1038/srep36153

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

The effect of Li+ addition at the interface of a 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide ([C(2)mim][FSA]) room-temperature ionic liquid (RTIL) and a Pt electrode is investigated by infrared-visible sum-frequency generation (IV-SFG) vibrational spectroscopy. Addition of Li+ to the Pt vertical bar[C(2)mim1[FSA] system results in the extension of the electrochemical window (EW) by >1.0 Vat its negative edge. The potential dependence of the SF signal reveals that the [FSA](-) anion of neat [C2mim][FSAI is desorbed at 1.5 V while it remains in place even at 2.0 V when Li+ is added. The SFG spectra indicate that the [FSA](-) anion at the Pt vertical bar[C(2)mim][FSA] interface interacts with Li+ at the interface with the negatively-charged Pt electrode. This [FSA](-) anion layer anchored through Li+ suppresses [C(2)mirr](+) cation adsorption on the negatively-charged Pt electrode, resulting in a wider electrochemical window. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elecom.2016.09.003

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We propose novel hybrid capacitors (HCs) with electrolyte-involved redox reactions of bromide or iodide species by pretreatment of an activated carbon positive electrode. The treatment is simple; impregnation of pores at an activated carbon fiber cloth (ACFC) as a positive electrode with bromine- or iodine-containing water before cell assembly. The treated positive electrode is applied to a HC cell with a non-treated negative electrode of ACFC and its electrochemical performance is investigated by galvanostatic cycling and leakage current tests. Few studies on such "electrolytic" charge storage systems have provided acceptable capacitor performance because of inevitable self-discharge caused by diffusion of charged species form an electrode to the other one through an electrolyte. Nevertheless, our electrolyte-redox-based HCs show excellent performance without undesirable diffusion of charged species. Moreover, the present HC utilizing a bromide redox system fulfills a practical cell voltage of 1.8 V in spite of an aqueous electrolyte system. This high voltage provides excellent energy density, which is 5 times higher than that in a conventional aqueous electric double-layer capacitor (EDLC), and 1.2 times higher even than that in a 2.7 V-class non-aqueous EDLC, while keeping high charge discharge rate capability. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2016.04.021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

The electrochemical and structural properties of the electrical double layers for two-component electrolytes were studied by Monte Carlo simulations using simple models. When the electrolyte contains two species of cations that have different diameters, the capacitance on the cathode dramatically increases as a large negative potential is applied. This behavior is qualitatively similar to the one reported in an experimental work that has used Li-containing ionic liquid as the electrolyte [M. Yamagata et al., Electrochim. Acta 110, 181-190 (2013)], in which it has also been reported that addition of Li ions to the electrolyte enhances the potential window to the negative side. The analysis of the ionic structure showed that the electrical double layer on the cathode is dominantly formed by the larger cations under small negative potentials, while they are replaced by the smaller cations under large negative potentials. This transition of the ionic structure with electrode potential is also consistent with the enhancement of the potential window that was found in the experimental work, which suggests that the organic cations are expelled from the electrical double layer under large negative potentials and the chance of decomposition is reduced. (C) 2016 AIP Publishing LLC.

DOI： 10.1063/1.4944927

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

Sulfur is an advantageous material as a promising next-generation positive electrode material for high-energy lithium batteries due to a high theoretical capacity of 1672 mA h g(-1) although its discharge potential is somewhat modest: ca. 2 V vs Li/Li+. However, a sulfur positive electrode has some crucial problems for practical use, which are mainly attributed to the dissolution of its intermediate products in charge-discharge processes. In order to resolve the dissolution problem of lithium polysulfide, we attempted to synthesize a sulfur-microporous activated carbon (AC) composite positive electrode. Moreover, we have systematically researched the battery performance of sulfur-microporous AC positive electrode with variations of electrolytes as well as negative electrodes, and found its promising positive electrode performance for a next generation rechargeable battery. (C) 2015 The Authors. Production and hosting by Elsevier B.V. on behalf of Chinese Materials Research Society.

DOI： 10.1016/j.pnsc.2015.11.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

A prototype lithium-ion battery with a bis(fluorosulfonyl)imide (FSI)-based ionic liquid electrolyte was developed. The prototype was mounted on a demonstration module of the "Hodoyoshi-3" microsatellite, which was successfully launched on June 20, 2014. Qualification tests for space application, including radiation tolerance and vacuum tests, revealed negligible degradation of the ionic liquid-based lithium-ion battery (IL-LIB) cell. According to the flight data, the IL-LIB cell can exist stably in an ultra-high vacuum environment despite its thin and flexible pouch casing without any rigid anti-vacuum reinforcements. Furthermore, the power unit showed the same charge-discharge performance as that predicted by the charge-discharge behavior of an identical cell on the ground, suggesting that the IL-LIB cell maintains performance in high vacuum a microgravity environment. These results prove that LIB cells with FSI-based ionic liquids can be used as a power source for space applications. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.83.918

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Language：Japanese   Publishing type：Research paper (scientific journal)  

J-GLOBAL

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Electrochemical Society Inc.  

Alginic acid (Alg-H) was applied as a novel aqueous binder for LiNi&lt
inf&gt
1/3&lt
/inf&gt
Co&lt
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1/3&lt
/inf&gt
Mn&lt
inf&gt
1/3&lt
/inf&gt
O&lt
inf&gt
2&lt
/inf&gt
(NMC) positive electrode for lithium-ion batteries (LIBs). We successfully obtained the pH-controlled aqueous slurry without any corrosion of NMC, which can also prevent a corrosion of an aluminum current collector. Using Alg-H can realize higher adhesive strength of the electrode even low content of 2 wt.% than using carboxymethyl cellulose and polyvinylidene difluoride. Galvanostatic charge-discharge cycle performances of both half cell and full cell composed of the NMC electrode with Alg-H are stable even at high voltage operation of 3.0-4.5 V, indicating that no side reaction including corrosion of the aluminum current collector and the decomposition of Alg-H binder occurs in this system. Moreover, this cell maintained over 90% of the initial discharge capacitance even after 100 cycles. These results suggest that the Alg-H binder has high potential to be used as an aqueous binder for positive electrodes of LIBs.

DOI： 10.1149/06418.0013ecst

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An alginate-based gel electrolyte with an ionic liquid (Alg/IL) is investigated for electric double-layer capacitors (EDLCs) by using physicochemical and electrochemical measurements. The Alg/EMImBF(4) (EMImBF(4) = 1-ethyl-3-methylimidazolium tetrafluoroborate) gel electrolyte is thermally stable up to 280 degrees C, where EMImBF4 decomposes. Furthermore, the EDLC with the gel electrolyte can be operated even at high temperature. The cell containing Alg/EMImBF(4) is also electrochemically stable even under high voltage (similar to 3.5 V) operation. Thus, the alginate is a suitable host polymer for the gel electrolyte for EDLCs. According to the result of charge discharge characteristics, the voltage drop in the charge discharge curve for the cell with Alg/EMImBF4 gel electrolyte is considerably smaller than that with liquid-phase EMImBF(4) electrolyte. To clarify the effect of Alg in contact with the activated carbon electrode, we also prepared an Alg-containing ACFC electrode (Alg ACFC), and evaluated its EDLC characteristics in liquid EMImBF(4). The results prove that the presence of Alg close to the active materials significantly reduces the internal resistance of the EDLC cell, which may be attributed to the high affinity of Alg to activated carbon. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2015.01.144

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We evaluate the effects of lithium salt on the charge-discharge performance of a graphite negative electrode in 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) ionic liquid-based electrolytes. Although the graphite negative electrode exhibits good cyclability and rate capability in both 0.43 mol dm(-3) LiFSI/EMImFSI and LiTFSI/EMImFSI (TFSI- = bis(trifluoromethylsulfonyl)imide) at room temperature, only the LiFSI/EMImFSI system enables the graphite electrode to be operated with sufficient discharge capacity at the low temperature of 0 degrees C, even though there is no noticeable difference in ionic conductivity, compared with LiTFSI/EMImFSI. Furthermore, a clear difference in the low-temperature behaviors of the two cells composed of EMImFSI with a high-concentration of lithium salts is observed. Additionally, charge-discharge operation of the graphite electrode at C-rate of over 5.0 can be achieved using of the high-concentration LiFSI/EMImFSI electrolyte. Considering the low-temperature characteristics in both high-concentration electrolytes, the stable and rapid charge-discharge operation in the high-concentration LiFSI/EMImFSI is presumably attributed to a suitable electrode/electrolyte interface with low resistivity. These results suggest that optimization of the electrolyte composition can realize safe and high-performance lithium-ion batteries that utilize ionic liquid-based electrolytes. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2015.01.070

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

We investigated the effect of electrolyte additives on an untreated, conventional micro-sized (non-nano) Si electrode prepared with a polyimide (PI) binder (PI-Si electrode). Both additives, vinylene carbonate (VC) and fluoroethylene carbonate (FEC), improved the cycle stability of a PI-Si electrode half-cell. The solid-electrolyte interphase (SEI) formed by FEC includes a large amount of LiF and shows quite low resistance. This SEI effectively suppresses electrolyte decomposition, and an electrolyte containing VC mainly forms a SEI with organic components, and shows a smaller suppression effect on the electrolyte's excessive decomposition. From the AC impedance measurement and SEM observation results, we found that the formation of a massive SEI prevents contacts among Si particles and increases the charge-transfer resistance of the PI-Si electrode. The applied FEC suppresses the revolution of this resistance, meaning that FEC functions as an electrolyte additive suitable for PI-Si electrodes. A PI, Si, and soft-carbon composite (PI-Si-SC) electrode half-cell shows excellent cycle stability and rate performance by an adjusted amount of FEC (10 wt%). A full-cell, which includes a LiNi1/3Mn1/3Co1/3O2 positive electrode, the PI-Si-SC negative electrode, and the electrolyte containing 10 wt% FEC, also exhibits quite good cycle stability. (C) The Author(s) 2014. Published by ECS. All rights reserved.

DOI： 10.1149/2.0581503jes

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

By exploiting characteristics such as negligible vapour pressure and ion-conductive nature of an ionic liquid (IL), we established an in situ scanning electron microscope (SEM) method to observe the electrode reaction in the IL-based Li-ion secondary battery (LIB). When 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide ([C(2)mim][FSA]) with lithium bis(trifluoromethanesulfonyl) amide (Li[TFSA]) was used as the electrolyte, the Si negative electrode exhibited a clear morphology change during the charge process, without any solid electrolyte interphase (SEI) layer formation, while in the discharge process, the appearance was slightly changed, suggesting that a morphology change is irreversible in the charge-discharge process. On the other hand, the use of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide ([C(2)mim][TFSA]) with Li[TFSA] did not induce a change in the Si negative electrode. It is interesting to note this distinct contrast, which could be attributed to SEI layer formation from the electrochemical breakdown of [C(2)mim](+) at the Si negative electrode vertical bar separator interface in the [C(2)mim][TFSA]based LIB. This in situ SEM observation technique could reveal the effect of the IL species electron-microscopically on the Si negative electrode reaction.

DOI： 10.1093/jmicro/dfv003

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We successfully improved the cycle stability of a silicon (Si) negative electrode that consisted of untreated, conventional micro-sized Si particles by applying polyimide (PI) with a low breaking elongation percentage and a high tensile strength as a binder. The strong adhesion of the PI binder suppresses the collapse of the Si negative electrode undergoing the expansion/contraction of Si particles during lithiation/delithiation so that the PI-Si electrode maintains a discharge capacity of 800 mAh g(-1) during 195 cycles at a current density of 800 mA g(-1). The electrodes prepared in this study contain a PI binder of 15 wt.% to maintain the electrode structure. Such a comparatively large amount of PI binder may prevent Li-ion access into Si particles. Nevertheless, the present Si negative electrode with sufficient electronic conductivity maintains a discharge capacity of 800 mAh g(-1) during 167 cycles even at a high rate (1600 mA g(-1)). Perhaps the PI binder does not hinder Li-ion access to Si particles. The cell containing a highly porous polyolefin film coated with ceramic as a separator for a facile supply of Li ion from a bulk electrolyte shows excellent cycle stability and maintains a discharge capacity of 800 mAh g(-1) during 300 cycles. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2014.09.096

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Now room-temperature ionic liquid (RTIL) is becoming a general term in the fields of science and technology owing to its useful physicochemical properties. A great number of applications with RTIL are proposed to date. Here we report an original electrochemical energy storage device with a Lewis acidic 60.0-40.0 mol% AlBr3-1-ethyl-3-methylimidazolioum bromide ([C(2)mim]Br) RTIL. The unique electrochemical reactions related to [AlBr4]-anion on the positive electrode have a crucial role in the energy storage device. The charge-discharge ratio for the beaker cell prepared in this investigation was almost 100% at 2.0 similar to 5.0 mA (150 similar to 370 mA g(-1) for activated carbon fiber cloth) if the cutoff voltage for the charging process was less than 1.70 V. The clear self-discharge behavior was not observed and the cell capacity after 100 cycles was identical to the maximum value. (C) The Author(s) 2014. Published by ECS.

DOI： 10.1149/2.029406jes

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Language：Japanese   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.82.622

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

The high-frequency induction heating method is an attractive way to synthesize LiFePO4/C within a few minutes. We optimize the heating conditions by a carbon crucible for the homogeneous heating of a precursor pellet from both sides. Compared with our previous samples, the lattice parameters of the LiFePO4/C synthesized in this work (an optimized sample) are improved and are much closer to the values reported by Padhi et al. Although the primary particle size of the optimized sample is slightly larger than that of the previous samples, it is sufficiently small to fully utilize the electrochemical performances of LiFePO4. We reduced the internal charge-transfer resistance of the optimized sample by improving the crystal structure because the Nyquist plots of the electrodes indicate decreased resistance, even though the optimized sample's electronic conductivity is almost the same as that of the previous sample. The electrode based on the optimized sample shows a specific discharge capacity of 168.0 mAh g-1, which achieves 99% theoretical specific capacity of the LiFePO4 phase. Moreover, its charge-discharge rate performance is superior to that of the previous sample. © 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2013.06.051

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We propose a novel low-cost synthesis method of a LiFePO4/C composite with excellent battery performances that combine high-frequency induction heating with carbothermal reduction. Our method uses a very inexpensive Fe2O3 as a Fe source. The LiFePO4/C is synthesized in far less time (within a few minutes) at 900 C than in a conventional method. Although the initially synthesized LiFePO4/C (LFP-120) contains such over-reduction impurities as Fe2P or Fe3P, optimized LiFePO4/C (LFP-90) containing no impurities is obtained by adjusting the heating time. Moreover, the primary particle size of the LFP-90 is sufficiently small to achieve fast Li-ion diffusion. The cathode containing LFP-90 has good charge discharge rate performance and shows discharge capacities of 1533 and 100.1 mAh g(-1) at 1/10 and 10Crates. The cathode with LFP-90 has excellent cycle stability and shows no degradation after high-rate charge discharge tests. Our method reasonably reduces the manufacturing cost of LiFePO4/C. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2013.06.040

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

Alginate salts (Alg-salt) were used as binders for graphite electrodes in both ionic liquid (IL)- and organic-electrolyte-based lithium-ion batteries (LIBs). Two different types of Alg-salt were used in this study: Alg-Na and Alg-Mg. According to the cyclic voltammograms and charge discharge measurements, a graphite negative electrode with the Alg-Na binder in both IL and conventional organic electrolytes exhibited reversible and high C-rate capability compared with an electrode with an SBR binder. This implies that the high affinity of Alg for graphite electrode active materials decreases the electrode/electrolyte interfacial resistance. We also fabricated full cells composed of the prepared graphite electrode with Alg-salt and LiNi1/3Co1/3Mn1/3O2 (NMC/C+Alg-X, X = Na+ or Mg2+). During high-voltage (3.0-4.5 V) operation, NMC/C+Alg-Mg showed the most stable cycle performance with high coulombic efficiency. These results suggest that the Alg-salt binder, especially the Alg-Mg binder, can be used in the fabrication of high-performance LIBs with either an IL- or organic-based electrolyte.

DOI： 10.1149/05329.0093ecst

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

The charge-discharge behavior of electric double-layer capacitors (EDLCs) composed of several ionic liquids and their lithium solutions were evaluated. The model EDLC cell with a Li+-containing ionic liquid electrolyte, LiTFSI/EMImFSI (LiTFSI = lithium bis(trifluoromethylsulfonyl)imide, EMImFSI = 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide), exhibited a higher discharge capacitance than the cell containing EMImFSI, whereas the discharge capacitance of the cell with LiTFSI/EMImTFSI was lower than that of the cell containing EMImTFSI. In addition, the cells composed of EMImBF(4)-based electrolytes displayed similar charge-discharge characteristics irrespective of the presence of the corresponding lithium salts. The distinctive results for the EDLCs with lithium-containing ionic liquid electrolytes are also discussed based on the application of the electrochemical impedance technique to model carbon electrodes in ionic liquids. According to the obtained differential capacitance of the model glassy carbon electrode in each ionic liquid electrolyte, the electric double-layer (compact layer) structure at the electrode/electrolyte interface depends on the component anion species of the ionic liquid and the co-existence of the anion and Lit. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.81.857

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

Chitosan-based gel electrolytes with ionic liquids (Chi/IL) were prepared and investigated for use in electric double-layer capacitors (EDLCs). The voltage drop for the test cell with Chi/EMImBF(4) (EMImBF(4) = 1-ethyl-3-methylimidazolium tetrafluoroborate) or Chi/DEMEBF4 (DEMEBF4 = N,N-diethyl-N-methyl-N-2-methoxyethylammonium tetrafluoroborate) and activated carbon fiber cloth electrodes (ACFCs) was smaller than that with the corresponding ionic liquid electrolyte. To clarify the effect of the presence of Chi in contact with the carbon electrode, we also prepared the Chi-containing ACFC electrode (Chi+ACFC) and evaluated its charge-discharge characteristics in EMImBF(4). The results proved that the presence of Chi on the active materials reduces the internal resistances of the cell and plays an important role in the improvement of the EDLC performance. In addition, the high-voltage operation of the test cells with Chi-based gel electrolytes was investigated. These results suggest that the Chi is suitable for use in practical high-performance and safe EDLCs. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.81.867

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

We evaluated charge-discharge behavior of four graphite electrodes-raw synthetic graphite (SG), shaped natural graphite (NG), soft carbon-coated natural graphite (SCNG), and hard carbon-coated natural graphite (HCNG)-in a 1-ethyl-3-methylimidazolium bis(fluorosulfonyl) imide (EMImFSI) ionic liquid containing lithium bis(trifluoromethylsulfonyl) imide (LiTFSI). According to charge-discharge curves at the first cycle in LiTFSI/EMImFSI, a capacity loss by an irreversible reaction was observed for cells with SG and SCNG, whereas the capacity loss for cells with NG and HCNG was relatively small. Coulombic efficiency with the cell cycling also proved that charge-discharge behavior of the graphite electrodes in LiTFSI/EMImFSI is strongly affected by surface structure of the graphite active materials and that basal-plane-oriented graphite, such as NG and HCNG, can reduce the loss of primary charge capacity.

DOI： 10.1149/05026.0317ecst

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Language：Japanese   Publisher：The Surface Science Society of Japan  

DOI： 10.1380/jsssj.34.389

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)  

Nonaqueous gel electrolytes based on chitosan and 1-ethyl-3- methylimidazolim tetrafluoroborate (Chi/EMImBF4) are prepared for electric double-layer capacitors (EDLCs). The transparent colorless gel sheet has the high levels of mechanical strength and ionic liquid retention required in EDLC cells. Charge-discharge measurements revealed that a model EDLC cell with a chitosan gel exhibits high discharge capacitance although a gel-state electrolyte was used, indicating that the high affinity of chitosan for the activated carbon electrode decreases the electrode-electrolyte interfacial resistance. A test cell with Chi/EMImBF4 maintained a Coulombic efficiency of more than 99.9% during 5000 cycles. © 2012 Elsevier Ltd.

DOI： 10.1016/j.electacta.2012.05.073

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

A nonaqueous solid-state electrolyte based on an alginate (Alg) with a conventional supporting electrolyte was prepared for use in electric double layer capacitors (EDLCs). According to the charge/discharge measurements, despite the use of a solid-state electrolyte, the model EDLC cells containing the Alg-based electrolyte possessed a higher discharge capacitance than the corresponding solution-based electrolyte, which implies that the high affinity of Alg for activated carbon electrodes decreases the electrode/electrolyte interfacial resistance. Because of its good affinity for carbon materials, we also applied Alg as a binder to an activated carbon-based composite electrode. The test cells with the composite electrodes containing Alg demonstrated a remarkably powerful EDLC performance using both a conventional organicsolution- based electrolyte and a highly viscous ionic liquid electrolyte. © The Electrochemical Society.

DOI： 10.1149/05043.0027ecst

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

An activated carbon composite electrode for nonaqueous electric double-layer capacitors was prepared with alginate. A model cell with this electrode showed an ultrahigh rate capability, presumably because of the high affinity of alginate for activated carbon, which decreased the internal resistance of the composite electrode.

DOI： 10.1039/c2ra22188h

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Language：Japanese   Publisher：THE CARBON SOCIETY OF JAPAN  

We propose a novel electrochemical capacitor (EC) that used electrolyte-based redox reactions of halogen species, which are induced by a novel pretreatment of an activated carbon positive electrode. This treatment, consisting of an impregnation of pores at a positive electrode of activated carbon fiber cloth (ACFC) with a halogenated solution such as bromine water before cell assembly, is simple and convenient. An aqueous sodium bromide solution is applied to an EC cell containing the treated positive electrode and a non-treated negative electrode of ACFC. Few studies have so far obtained ECs using an "electrolyte" charge storage system with practical performance due to diffusive loss of charged species from an electrode into an electrolyte or its shuttle migration between electrodes. Nonetheless, we have attained excellent capacitor performance with such a concept by suppressing an undesirable diffusion of electrolyte reactive species. This concept, electrolyte-based charge storage, is applicable to not only the above aqueous EC but also non-aqueous EC and lithium-ion capacitor application with dramatically improved performance.

DOI： 10.7209/tanso.2013.15

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Other Link： https://jlc.jst.go.jp/DN/JALC/10015100886?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We evaluated the charge-discharge behavior of a graphite electrode in a 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) ionic liquid. According to the charge-discharge tests, the graphite negative electrode exhibited a high rate of performance in LiTFSI/EMImFSI (TFSI- = bis(trifluoromethylsulfonyl)imide) in the voltage range of 0.005-1.5 V (vs. Li/Li+), and the performance was comparable to that in a conventional organic solution-based electrolyte, LiPF6/EC+DMC. Moreover, the addition of LiBOB (=lithium bis(oxalato)borate) improved the rate capability and low-temperature operation of the graphite negative electrode, most likely owing to the low-resistivity solid electrolyte interface (SEI) derived from LiBOB. These results suggest that EMImFSI is a suitable electrolyte for lithium-ion batteries utilizing graphite negative electrodes and that optimization of the electrolyte composition with an additive can improve battery performance. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2012.11.013

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

We propose a novel electrochemical capacitor (EC) utilizing an "electrolytic" charge-storage system of bromide species. The present EC cell is fabricated with 1.0 mol dm(-3) 1rethyl-3-methylimidazolium bromide dissolved in 1-ethyl-3-methylimidazolium tetrafluoroborate as an electrolyte and activated carbon fiber cloths (ACFCs) as electrodes. Although such a charge-storage concept would usually be useless due to inevitable, undesirable reactions, e.g. shuttle reaction or migration of active redox species between electrodes, we attain much-enhanced capacitance with an excellent reversibility by suppressing an undesirable diffusion process. In fact, the coulombic efficiency of the present cell is over 99.7% at 100 mA g(-1) The oxidation species such as Br-2 or Br-3(-) as charge accumulators do not diffuse from a positive electrode into the electrolyte. Moreover, the present EC cell has an excellent cycleability of at least 10,000 cycles. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.electacta.2012.01.031

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

We evaluated the charge-discharge behavior of a LiNi1/3Mn1/3Co1/3O2 (NMC) electrode in a 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMImFSI) ionic liquid. At 163 mAh g(-1) after 50 cycles, the discharge capacity of the NMC cathode in LiTFSI/EMImFSI (TFSI- = bis(trifluoromethylsulfonyl)imide) at 1.0 C in the voltage range 3.0-4.5V (vs. Li/Li+) is comparable to that in the conventional electrolyte, LiPF6/EC+DMC. Moreover, the rate capability of the cell with LiTFSI/EMImFSI exceeded that with LiPF6/EC+DMC, especially at high rates, probably owing to the low resistance at the electrode/electrolyte interface. These results suggest that EMImFSI is a suitable electrolyte for lithium-ion batteries utilizing an NMC cathode. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.80.808

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

The present LiFePO4/C cathode material is synthesized via carbothermal reduction by a high-frequency induction heating method in extremely short heating time (within a few minutes). The electric conductivity of LiFePO4/C is improved to 1.9 x 10(-2) S cm(-1) by a short-time annealing process following a sintering process at 900 degrees C. An increase in the particle size and formation of Fe2P as impurity are suppressed by annealing at a relatively low temperature: 700 degrees C. The cathode containing annealed LiFePO4/C shows discharge capacities of 156.0, 136.3, and 100.1 mAh g(-1) at 1/10, 1, and 10C-rates (1C = 170 mA g(-1)), respectively, and its polarization between charge and discharge is smaller than that of non-annealed LiFePO4/C. Furthermore, the annealed LiFePO4/C cathode shows better charge and discharge rate performance than the non-annealed LiFePO4/C cathode. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.80.825

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

We propose a novel electrochemical capacitor (EC) utilizing an "electrolytic" charge-storage system of bromide species. The present EC cell is fabricated with 1.0 mol dm(-3) 1-ethyl-3-methylimidazolium bromide dissolved in 1-ethyl-3-methylimidazolium tetrafluoroborate as an electrolyte and activated carbon fiber cloths as electrodes. Although such a charge-storage concept would usually be useless due to inevitable, undesirable reactions, e. g. shuttle reaction or migration of active redox species between electrodes, we attain much-enhanced capacitance with an excellent reversibility by suppressing an undesirable diffusion process. In fact, the coulombic efficiency of the present cell is over 99.7% at 100 mA g(-1). The oxidation species such as Br-2 or Br-3(-) as charge accumulators do not diffuse from a positive electrode into the electrolyte. Moreover, the present EC cell has an excellent cycleability of at least 10,000 cycles.

DOI： 10.1149/1.3693060

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

Non-aqueous gel electrolytes based on polysaccharides (alginate or chitosan) with hydrophobic 1-ethyl-3-methylimidazolim tetrafluoroborate (EMImBF(4)) were prepared for electric double layer capacitors (EDLCs). The transparent colorless gel sheets have high mechanical strength and high retentivity of EMImBF4 enough to construct EDLC cells. According to charge/discharge measurements, the model EDLC cells with alginate-and chitosan-based gels show high discharge capacitance in spite of using a gel-state electrolyte, implying that high affinity of alginate for an activated carbon electrode leads to a decrease in the electrode/electrolyte interfacial resistance. A test cell with Alg/EMImBF(4) maintains its coulombic efficiency over 99.8 % during 5,000 cycles.

DOI： 10.1149/1.3693061

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

J-GLOBAL

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Language：Japanese  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Non-aqueous gel electrolytes based on an alginate (Alg) and 1-ethyl-3-methylimidazolim tetrafluoroborate (EMImBF(4)) are prepared for electric double layer capacitors (EDLCs). The transparent colorless gel sheet has the high levels of mechanical strength and retentivity of ionic liquid needed to construct EDLC cells. According to charge/discharge measurements, a model EDLC cell with an Alg/EMImBF(4) gel shows high discharge capacitance in spite of using a gel-state electrolyte, implying that high affinity of alginate for an activated carbon electrode leads to a decrease in the electrode/electrolyte interfacial resistance. A test cell with Alg/EMImBF(4) maintains its coulombic efficiency over 99.8% during 5,000 cycles. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.020111esl] All rights reserved.

DOI： 10.1149/2.020111esl

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

We evaluated the electrochemical behavior of a LiNi1/3Mn1/3Co1/3O2 (NMC) electrode in a neat ionic liquid, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl) imide (EMImFSI), electrolyte. According to charge/discharge measurements, the discharge capacity of the NMC cathode in EMImFSI at 1 C in a voltage range of 3.0-4.5 (vs. Li/Li+) shows 165 mAh g(-1), which is higher than that in a conventional electrolyte, EC+DMC. The rate capability of a cell with EMImFSI exceeds that with EC+DMC, especially at high rates, probably due to a low resistance at the electrode/electrolyte interface. These results suggest that EMImFSI is a suitable electrolyte for Li-ion batteries utilizing a NMC cathode. Also, we applied fluorine-containing solvents (FCSs) to an electrolyte for Li-ion batteries with a cobalt oxide (LiCoO2) cathode to enhance the upper voltage limit and investigated its electrochemical properties in a proposed FCS-based electrolyte. A test cell containing a FCS-based electrolyte exhibits high and stable discharge capacity for 30 cycles even with a high upper cutoff voltage of 4.5 V when compared with a cell containing a conventional electrolyte.

DOI： 10.1149/1.3563087

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An ionic liquid electrolyte containing bis(fluorosulfonyl)imide (FSI) anion without any solvent is applied to a silicon-nickel-carbon (Si-Ni-carbon) composite anode for rechargeable lithium (Li)-ion batteries. The FSI-based ionic liquid electrolyte successfully provides a stable, reversible capacity for the Si-Ni-carbon anode, which is comparable to the performance observed in a typical commercialized solvent-based electrolyte, while a common ionic liquid electrolyte containing bis(trifluoromethanesulfonyl)imide (TFSI) anion without FSI presents no reversible capacity to the anode at all. Ac impedance analysis reveals that the FSI-based electrolyte provides very low interfacial and charge-transfer resistances at the Si-based composite anode, even when compared to the corresponding resistances observed in a typical solvent-based electrolyte. Galvanostatic cycling of the Si-based composite anode in the FSI-based electrolyte with a charge limitation of 800 mAh g(-1) is stable and provides a discharge capacity of 790 mAh g(-1) at the 50th cycle, corresponding to a cycle efficiency of 98.8%. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2010.01.011

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An acidic cellulose-chitin hybrid gel electrolyte consisting of cellulose, chitin, 1-butyl-3-methylimidazolium, 1-allyl-3-methylimidazolium bromide, and an aqueous H(2)SO(4) solution is investigated for electric double layer capacitors (EDLCs) with activated carbon fiber cloth electrodes. The acidic cellulose-chitin hybrid gel electrolyte shows a high ionic conductivity comparable to that for an aqueous 2 mol dm(-3) H(2)SO(4) solution at 0-80 degrees C. This system's temperature dependence in EDLC performance is investigated by galvanostatic charge-discharge measurement. An EDLC cell with the acidic hybrid gel electrolyte has higher capacitance than that with the aqueous H(2)SO(4) solution in the range of operation temperatures (-10 to 60 degrees C). Moreover, the capacitance retention of the EDLC cell with the acidic hybrid gel electrolyte is better than that of a cell with the H(2)SO(4) solution at 60 degrees C over 10,000 cycles. This suggests that the proposed acidic gel electrolyte has excellent stability in the presence of a strong acid, even at a high temperature of 60 degrees C. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2010.02.037

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

We applied fluorine-containing solvents (FCSs) to an electrolyte for lithium (Li)-ion batteries with a cobalt oxide (LiCoO2) cathode to enhance the upper voltage limit and investigated its electrochemical properties in a proposed FCS-based electrolyte. FCSs were expected to have high oxidation resistance by introducing electron withdrawing fluorine atoms. A test cell containing a FCS-based electrolyte exhibited high and stable discharge capacity in 30 cycles even with a high upper cutoff voltage of 4.5 V when compared with a cell containing a conventional electrolyte. This improvement in the cycle performance was confirmed by an electrochemical impedance measurement. We found that the FCS-based electrolyte provides a favorable solid electrolyte interface (SEI) at the LiCoO2 cathode, leading to reversible charge-discharge behavior of the cathode.

DOI： 10.5796/electrochemistry.78.345

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOC INC  

Non-aqueous gel electrolytes based on an alginate (Alg) and 1-ethyl-3-methylimidazolim tetrafluoroborate (EMImBF(4)) were prepared for electric double layer capacitors (EDLCs). The transparent colorless gel sheet has high mechanical intensity and high retentivity of ionic liquids enough to construct EDLC cells. According to charge/discharge measurements, the model EDLC cell with an Alg/EMImBF(4) gel shows high discharge capacitance in spite of using a gel-state electrolyte, implying that high affinity of alginate for an activated carbon electrode leads to a decrease in the electrode/electrolyte interfacial resistance. A test cell with Alg(3%)/EMImBF(4) maintains its coulombic efficiency over 99.8 % during 4,000 cycles.

DOI： 10.1149/1.3414018

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A novel capacitor electrode auxiliary, deoxyribonucleic acid (DNA). is applied to an electric double layer capacitor (EDLC) containing an aqueous 3.5 M NaBr electrolyte The present electrode is composed of activated carbon (95 wt %) and DNA (2 5 wt %) with polytetrafluoroethylene (PTFE) as a binder (2 5 wt.%). An EDLC cell with the DNA-loading electrodes exhibits improved rate capability and discharge capacitance. Art EDLC cell with DNA-free electrodes cannot discharge above a cut rent density of 3000 mA g(-1) (of the electrode), while a cell with the DNA-loading electrodes can work at least up to 6000 mA g(-1) Moreover, an open-circuit potential (OCP) of the DNA-loading electrode sifts negatively with ca 0 2 V from an OCP of the corresponding electrode without DNA It is noteworthy that a small amount of DNA loading(2 5 wt %) to the activated carbon electrode not only improves the rate capability but also adjusts the working potential of the electrode to a more stable region. (C) 2009 Elsevier B.V. All rights reserved

DOI： 10.1016/j.jpowsour.2009.09.049

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.elecom.2010.01.012

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

An acidic cellulose-chitin hybrid gel electrolyte is prepared from cellulose, chitin, binary ionic liquids, and an aqueous H(2)SO(4) solution for an electric double-layer capacitor (EDLC). The obtained acidic hybrid gel shows a high ionic conductivity of 57.8 S m(-1) at a room temperature of 25 degrees C, which is comparable to 61.9 S m(-1) of an aqueous 2 mol dm(-3) H(2)SO(4) electrolyte. The acidic cellulose-chitin hybrid gel electrolyte is applied to an EDLC cell with activated carbon fiber cloths as polarizable electrodes, and its electrochemical performance is investigated by galvanostatic cycling, cyclic voltammetry, and a self-discharge test. The EDLC cell with the acidic cellulose-chitin hybrid gel electrolyte exhibits a higher capacitance and a better cycle life than cells with the reference aqueous H(2)SO(4) electrolyte. The self-discharge measurement suggests that leakage current and potential decay are suppressed by the application of the acidic cellulose-chitin hybrid gel electrolyte. These results indicate that the acidic cellulose-chitin hybrid gel electrolyte has a practical applicability to an advanced EDLC with excellent stability and working performance.

DOI： 10.1149/1.3270498

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Performances of electric double layer capacitors (EDLCs) based on an activated carbon electrode with acetonitrile (ACN), propylene carbonate (PC), or a ternary electrolyte, i.e., PC: ethylene carbonate (EC): diethyl carbonate (DEC), at 1 mol dm(-3) of magnesium perchlorate [Mg(ClO(4))(2)] salt have been investigated. The electrochemical responses were studied by impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge experiments at 25 degrees C in a three-electrode configuration. For a comparative evaluation, lithium perchlorate (LiClO(4)) salt-based systems were also evaluated. All the observed results showed typical EDLC characteristics within the potential range between 0 and 1V vs. an Ag/Ag(+) reference electrode. The Mg-based systems exhibited similar or rather better performances than the corresponding Li-based electrolytes; in particular, the rate capability of Mg-based ACN and PC electrolytes was much better than the corresponding Li-based electrolytes, indicating the high accessibility and utility of activated carbon pores by solvated Mg ions. (C) 2009 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jpowsour.2009.07.043

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An acidic cellulose-chitin hybrid gel electrolyte consisting of cellulose, chitin, 1-butyl-3-methylimidazo lium, 1-ally1-3-methylimidazo hum bromide, and an aqueous H2SO4 solution is investigated for electric double layer capacitors (EDLCs). This gel electrolyte shows a high ionic conductivity comparable to that observed in an aqueous 2 mol dm(-3) H2SO4 solution in 0-80 degrees C. An EDLC cell with the acidic hybrid gel electrolyte has higher capacitance than that with an aqueous H2SO4 solution in the operation temperature (-10-60 degrees C). Moreover, the capacitance retention of the EDLC cell with the acidic hybrid gel electrolyte is better than a cell with a H2SO4 solution at 60 degrees C over 10,000 cycles. This suggests that the present acidic gel electrolyte has excellent stability in the presence of a strong acid even at a high temperature of 60 degrees C.

DOI： 10.1149/1.3334797

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The electrochemical behavior of a graphitized electrode was investigated in a room-temperature ionic liquid based on bis(fluorosulfonyl)imide (FSI-) with the addition of propylene carbonate (PC) or vinylene carbonate (VC). The reversible, significant lithium-ion (Li+) insertion/extraction was observed in the additive-free FSI-based ionic liquid, while the additive systems showed weak, reversible responses (VC) and degraded responses (PC). AC impedance measurements suggested that the presence of FSI- extremely reduces the electrode/electrolyte interface impedance, which allows Li+ to intercalate into a graphitized electrode reversibly. By contrast, the addition of VC inhibits the reversible Li+ intercalation in spite of FSI- existence.

DOI： 10.5796/electrochemistry.77.696

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Introduction of bis(fluorosulfonyl)imide (FSI) as an anion to an ambient-temperature ionic liquid electrolyte based on 1-ethyl-3- methylimidazolium and lithium (Li) as cations can provide a reversible Li intercalation into a graphitized electrode, while the intercalation is completely irreversible without FSI. Laser desorption/ionization mass spectroscopy and ac impedance spectroscopy suggest that FSI-coordinated Li + is facilely mobile even without any solvents and is reversibly accessible to a graphite interior. ©The Electrochemical Society.

DOI： 10.1149/1.3123129

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Ionic liquid electrolytes containing a certain amount of bis(fluorosulfonyl)imide (FSI) anion can provide reversible capacity for a graphitized negative electrode without any additives such as a solvent. Cyclic voltammetry for a graphitized negative electrode in ionic liquid electrolytes containing FSI with other anions suggests that the reversibility of Li intercalation correlates with the relative quantity (or concentration) of FSI in the electrolytes, and that the correlative tendency depends on the other kind of anion. On the basis of the present results, we discuss the effect of FSI in the ionic systems on a graphitized electrode interface. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2008.07.053

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A novel acidic cellulose-chitin hybrid gel electrolyte including binary ionic liquids (ILs) with an aqueous H2SO4 solution was prepared for an electric double layer capacitor (EDLC). Its electrochemical characteristics were investigated by galvanostatic charge-discharge measurements. The cell with the hybrid gel containing binary ILs and H 2SO4 has higher capacitance than that containing only the aqueous H2SO4 solution. This hybrid gel electrolyte exhibits excellent high-rate discharge capability in a wide range of current densities as well as an aqueous H2SO4 solution. The discharge capacitance of the test cell can retain over 80% of its initial value in 100,000 cycles even at a high current density of 5,000 mA g-1. ©The Electrochemical Society.

DOI： 10.1149/1.3109629

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Electrochemical characteristics of an aqueous manganese nitrate [Mg(NO3)(2)] electrolyte system have been investigated for electric double layer capacitor (EDLC) applications. Its electrochemical activity has been examined in a concentration range from 0.1 to 1.0 mol dm(-3) by using a symmetric capacitor based on activated carbon (AC) electrodes. The capacitor performances were evaluated by impedance spectroscopy, cyclic voltammetry, and galvanostatic charge-discharge experiments at temperature 25 degrees C. The observed results show essentially capacitive behaviors within a tested potential region from 0 to 0.8 V vs. an Ag/AgCl reference electrode. The cell capacitance varies with the electrolyte concentration and the measured potential window. The maximum observed capacitance was 124 F g(-1) (energy density: 8.5 Wh kg(-1)). We have confirmed good reversibility of Mg2+ adsorption/desorption and the stability of the aqueous electrolyte within the applied potential limit. The results show an ideal capacitor nature with a significant energy density value.

DOI： 10.5796/electrochemistry.77.51

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A novel acidic cellulose-chitin hybrid gel electrolyte including binary ionic liquids (ILs) with an aqueous H(2)SO(4) solution was prepared for an electric double layer capacitor (EDLC). Its electrochemical characteristics were investigated by galvanostatic charge-discharge measurements. The test cell with a hybrid gel electrolyte shows a specific capacitance of 162 F g(-1) at room temperature, which is higher than that for a cell with an H(2)SO(4) electrolyte, 155 F g(-1). This hybrid gel electrolyte exhibits excellent high-rate discharge capability in a wide range of current densities as well as an aqueous H(2)SO(4) solution. The discharge capacitance of the test cell can retain over 80% of its initial value in 100,000 cycles even at a high current density of 5000 mA g(-1). (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.elecom.2008.10.039

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We demonstrate the effect of bundle structure, composed of multiwalled carbon nanotube (MWCNT) material in disordered MWCNT electrodes, on electric double-layer capacitor (EDLC) performance (i.e., their rate capability and specific capacitances). This is done by applying two types of MWCNTs with low (50-100) and high (2500-10,000) aspect ratios of their length to diameter. The use of these physically opposite values elucidates how the electronic pathways, pore distribution, and sidewall/edge balance of MWCNTs contribute to these electrodes' kinetic and capacitive performance for EDLC. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.3049907] All rights reserved.

DOI： 10.1149/1.3049907

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We demonstrate the effect of bundle structure, composed of multiwalled carbon nanotube (MWCNT) material in disordered MWCNT electrodes, on electric double-layer capacitor (EDLC) performance (i.e., their rate capability and specific capacitances). This is done by applying two types of MWCNTs with low (50-100) and high (2500-10,000) aspect ratios of their length to diameter. The use of these physically opposite values elucidates how the electronic pathways, pore distribution, and sidewall/edge balance of MWCNTs contribute to these electrodes' kinetic and capacitive performance for EDLC. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.3049907] All rights reserved.

DOI： 10.1149/1.3049907

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Alkaline polymer gel electrolytes mainly with modified Polyvinyl alcohol (PVA) have been prepared for an electric double layer capacitor (EDLC). Their electrochemical characteristics were evaluated by impedance spectroscopy and constant-current charge/discharge measurement. The prepared gel electrolyte film with KOH exhibits excellent flexibility and an ionic conductivity of about 7 x 10(-2) S cm(-1) at 298 K. The gel electrolyte EDLC shows comparable discharge capacitance to that for EDLC containing a conventional aqueous electrolyte. These results suggest that the gel electrolyte based on the modified PVA is promising material for use in EDLC.

DOI： 10.5796/electrochemistry.76.886

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An ionic liquid, 1-ethyl-3-methyl imidazolium bis(fluorosulfonyl)imide (EMI-FSI), has been applied to an electrolyte for electric double layer capacitors (EDLCs). The electrolyte exhibited high ionic conductivity comparable to that of a conventional organic electrolyte. EDLC prepared with EMI-FSI showed excellent rate capability although the electrolyte is a neat ionic liquid; this performance was observed irrespective of the presence of a binder in an activated carbon-based electrode. The self-discharge was suppressed by using EMI-FSI. A cycling durability test showed that the cell with EMI-FSI kept over 90% of the initial capacitance even after 10,000 cycles. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2008.08.086

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We successfully prepared a vertically aligned double-walled carbon nanotube (DWCNT) sheet by a transfer procedure from a silicon substrate as a DWCNT seedbed that was covered with catalyst grains to an aluminum sheet as a current collector for application to a high-performance electrode for an electric double layer capacitor (EDLC). The charge-discharge characteristics and EDLC performances of the aligned DWCNT electrode were evaluated and compared with those of a vertically aligned multi-walled CNT (MWCNT) electrode. The gravimetric capacitance of the DWCNT electrode was ca. four times larger than that of the MWCNT electrode. The rate capability of the DWCNT electrode was found to be excellent. This is mainly ascribed to our transfer technique. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2008.09.020

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Origins of cathodic stability of an ionic liquid electrolyte, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) containing lithium tetrafluoroborate (LiBF4), are investigated mainly by applying electrochemical impedance spectroscopy for a glassy-carbon electrode interface. Its Helmholtz layer capacitance in the EMIBF4 electrolyte containing Li+ becomes much higher than that in neat EMIBF 4 with increasing cathodic polarization. On the basis of such analyses as well as our hypotheses, a reasonable mechanism for the stabilizing effect induced by the Li salt addition is discussed. © The Electrochemical Society.

DOI： 10.1149/1.2985636

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Introduction of bis(fluorosulfonyl)imide (FSI) as an anion to an ambient-temperature ionic liquid electrolyte based on 1-ethyl-3-methylimidazolium (EMI) as well as lithium (Li) cations can provide a reversible Li intercalation into a graphitized electrode. while such intercalation is completely irreversible without FSI. The surface-layer components on the graphitized electrodes, cycled in the ionic liquid electrolytes with and without FSI, were found to be chemically similar based on X-ray photoelectron spectroscopy. Ac impedance spectroscopy revealed that the resistance of the electrode charged with FSI was Much lower even than that charged in a solvent electrolyte system containing ethylene carbonate (EC) and dimethyl carbonate (DMC). On the basis of these physicochemical analyses, the origins of cycleability in the presence of FSI are discussed. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2008.05.036

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

A variety of vertically aligned multiwalled carbon nanotube (MWCNT) electrodes, which maintain their original morphology prepared by a chemical vapor deposition technique, has been successfully fabricated by a transfer methodology from a seedbed substrate to a current collector. No ohmic potential drop on a galvanostatic discharge was observed for an electric double-layer capacitor (EDLC) containing electrodes with not only a MWCNT length of 10 mu m but also a length of 200 mu m. Cyclic voltammograms for electrodes with MWCNT lengths of both 10 and 200 mu m showed no distorted current response, even at an extremely high scan rate of 50 V s(-1). These results demonstrate that the present EDLC with the MWCNT electrodes can provide an outstanding rate capability irrespective of the MWCNT length when prepared by our transfer methodology. To find suitable MWCNT electrodes for high-performance EDLCs, we investigated several relationships among the specific capacitances of aligned MWCNT electrodes and their major properties, i.e., their gravimetric and volumetric capacitances, length, diameter, and number density. (c) 2008 The Electrochemical Society. [DOI: 10.1149/1.2988743] All rights reserved.

DOI： 10.1149/1.2988743

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

A variety of vertically aligned multiwalled carbon nanotube (MWCNT) electrodes, which maintain their original morphology prepared by a chemical vapor deposition technique, has been successfully fabricated by a transfer methodology from a seedbed substrate to a current collector. No ohmic potential drop on a galvanostatic discharge was observed for an electric double-layer capacitor (EDLC) containing electrodes with not only a MWCNT length of 10 mu m but also a length of 200 mu m. Cyclic voltammograms for electrodes with MWCNT lengths of both 10 and 200 mu m showed no distorted current response, even at an extremely high scan rate of 50 V s(-1). These results demonstrate that the present EDLC with the MWCNT electrodes can provide an outstanding rate capability irrespective of the MWCNT length when prepared by our transfer methodology. To find suitable MWCNT electrodes for high-performance EDLCs, we investigated several relationships among the specific capacitances of aligned MWCNT electrodes and their major properties, i.e., their gravimetric and volumetric capacitances, length, diameter, and number density. (c) 2008 The Electrochemical Society. [DOI: 10.1149/1.2988743] All rights reserved.

DOI： 10.1149/1.2988743

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11470/oubutsu.76.10_1150

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A novel electrode composed of activated carbon and DNA together with fluorinated binder has been prepared for an electric double layer capacitor (EDLC) with aqueous electrolytes. The DNA-loaded electrodes improve the rate capability and discharge capacitance of EDLC containing aqueous, neutral salt electrolytes. In contrast, the DNA-composite electrodes have a poor effect on the capacitance enhancement in acidic or basic electrolytes. The enhancement of discharge capacitance is significant especially at high-rate cycling in neutral salt electrolytes, because the presence of DNA reduces the internal resistance of an electrode and hence improves its rate capability.

DOI： 10.5796/electrochemistry.75.592

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Origins of cathodic stability of an ionic liquid electrolyte, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) containing lithium tetrafluoroborate (LiBF4), are investigated mainly by applying electrochemical impedance spectroscopy for a glassy-carbon electrode interface. Its Helmholtz layer capacitance in the EMIBF4 electrolyte containingr Li+ becomes much higher than that in neat EMIBF4 with increasing cathodic polarization. On the basis of such analyses as well as our hypotheses, a reasonable mechanism for the stabilizing effect induced by the Li salt addition is discussed.

DOI： 10.5796/electrochemistry.75.589

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A vertically aligned multi-walled carbon nanotube (MWCNT) electrode and a disordered MWCNT electrode are prepared to compare their structural differences and such capacitive performances as frequency response. The frequency response of a capacitor assembled with aligned MWCNT electrodes and a conventional PC-based electrolyte is much superior to a corresponding capacitor with disordered MWCNT electrodes. Such a merit of aligned MWCNT electrodes is observed even for an ionic liquid electrolyte system with high viscosity, diethylmethyl (2-methoxyethyl) ammonium tetrafluoroborate (DEMEBF4). The obtained results demonstrate that the aligned MWCNT electrode has ideal ion-accessible structure with excellent electron pathways that provide a high-rate capability regardless of electrolytes.

DOI： 10.5796/electrochemistry.75.586

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To increase the capacitance of an electric double layer capacitor (EDLC) containing 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) as an ionic liquid electrolyte, barium titanium oxide (BaTiO3) as a ferroelectric material is incorporated into activated carbon electrodes. An EDLC composed of BaTiO3 powder/activated carbon composite electrodes and the ionic liquid electrolyte EMIBF4 exhibits a large capacitance when compared to the corresponding EDLC without BaTiO3. Moreover, the rate performance of the EDLC containing BaTiO3 is improved when the electrodes are prepared by an improved method, i.e., vacuum penetration of BaTiO3-dispersed EMIBF4 into the activated carbon electrodes. No positive addition effect of BaTiO3 is observed for the corresponding EDLC with a typical organic electrolyte composed of a tetraalkylammonium salt and propylene carbonate as a solvent. These results suggest that BaTiO3 incorporated into the electrodes would improve the dissociation of the ionic liquid EMIBF4, and hence increase the carrier concentration available for the formation of an electric double layer. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2007.01.068

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.75.379

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

We prepare a vertically aligned multiwalled carbon nanotube (MWCNT) sheet by a transfer procedure from a silicon substrate, covered with catalyst grains as a CNT seedbed, to an aluminum sheet as a current collector for the application of the sheet to an electrode for an electric double-layer capacitor. It is noteworthy that the MWCNT sheet electrode provides a discharge capacity of 10-15 F g(-1) (of the aligned MWCNTs) even at an extremely high current density, 200 A g(-1), whereas no discharge capacitance is obtained at all with a typical high-performance activated carbon electrode at such a high current density. (c) 2007 The Electrochemical Society.

DOI： 10.1149/1.2437665

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The electrochemical treatment of activated carbon electrodes has been investigated as a novel method enhancing the capacitance of electric double layer capacitor (EDLC) electrodes. The treatment at 0.7 V floating in a week at 70 degrees C can be applied to EDLC with aqueous electrolytes. In 30 wt% H2SO4 / H2O electrolyte, the treatment causes a capacitance increase in a low voltage region: 0-0.4 V. On the other hand, in 3.5 M NaBr / H2O electrolyte, it results in a remarkable capacitance increase of 2.4 times in a high voltage region: 0.4-1.0 V. These results suggest that the treatment mechanisms in the above electrolyte systems should be different. We report herein the origins and mechanisms of these capacitance increases.

DOI： 10.5796/electrochemistry.75.273

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Ambient temperature ionic liquids composed of bis(fluorosulfonyl)imide (FSI) as an anion and 1-ethyl-3-methylimidazolium (EMI) orN-methyl-N-propylpyrrolidinium (P-13) as a cation have the following desirable physicochemical properties, particularly for a battery electrolyte: a high ionic conductivity, low viscosity, and a low melting point. While an irreversible cationic intercalation into graphene interlayers at ca. 0.5 V versus Li/Li+ has been a significant and common problem with usual ionic liquids, we found that ionic liquids containing FSI with the Li cation can prevent such an irreversible reaction and provide reversible Li intercalation into graphene interlayers. Our experimental results found the reversible capacity of a graphite negative electrode, in a half-cell with EMI-FSI containing the Li cation as an electrolyte, to be a stable value of approximately 360 mAh g(--1) during 30 cycles at a charge/discharge rate of 0.2 C, The present paper may be the first report that a "pure" ionic liquid can provide a stable, reversible capacity for a graphitized negative electrode at an ambient temperature without any additives or solvents when an appropriate counter anion, e.g., FSI, is selected. (C) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2006.02.077

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Surface Science Society of Japan  

In order to discuss quantitatively the effect of functional groups of activated carbon fibers (ACFs) on the electric double-layer characteristics, ACFs with various amounts of functional groups were prepared from the same ACFs by redox methods. The amounts of functional groups of ACF were determined and compared using two different methods of back titration and X-ray photoelectron spectroscopy (XPS). In the case of the aqueous electrolyte, the electric capacity depended more on oxygen functional groups than on BET surface area. At the greatest 30% increase in electric capacity was obtained by using ACFs with different amounts of oxygen functional groups between the positive and negative electrodes. It was considered that a larger number of functional groups promote not only the wettability of electrodes but also the negative charge of electrodes leading to an increase in capacity. On the other hand, in the case of the organic electrolyte, the pore structure seemed to be a more dominant factor than functional groups. Also, the characteristics of the electrodes after 30,000-cycle charge-discharge were determined to confirm the reliability in an extended cycle operation.

DOI： 10.1380/jsssj.27.461

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DOI： 10.1246/bcsj.68.2207

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Effects of ceramic fillers (alpha-Al2O3, gamma-Al2O3 and BaTiO3) have been investigated on the ionic conductance of polymeric complexes consisting of poly(ethylene oxide)-modified poly(methacrylate) (PEO-PMA) and lithium bis(trifluoromethylsulfonyl)imide, Li(CF(3)SODA and ceramic powder. The addition of ceramic powder increased the ionic conductivity over an ambient temperature range. Conductivity of 4.9 x 10(-5)S cm(-1) at 333K (60 degrees C) was obtained for the composite containing 15wt.% alpha-Al2O3 prepared by photo-polymerization. The optimum content of Al2O3 was different among the methods of polymerization. The highest conductivity was obtained for the composite containing 5 wt.% of alpha-, or gamma-Al2O3 prepared by thermal polymerization. The addition of the ceramic filler scarcely influenced the thermal properties of the polymer matrix. XRD and NMR experiments showed that the ionic mobility could be enhanced in the composites by addition of alpha-Al2O3. The addition of small amounts of ferroelectric BaTiO3 also increased the ionic conductivity of the polymeric complex, but its extent was smaller than the case of the Al2O3 addition. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ssi.2006.01.022

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Authorship：Lead author   Language：Japanese   Publisher：The Society of Polymer Science, Japan  

DOI： 10.1295/kobunshi.54.874

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A Li sheet electrode was galvanostatically cycled only once as a pretreatment process in a binary electrolyte, propylene carbonate (PC) with dimethyl carbonate (DMC), containing Li bis(perfluoroethylsulfonyl)imide [Li(C2F5SO2)(2)N] in the presence of an additive, aluminum iodide (AII(3)). The Li electrode pretreated in this manner showed a high cycleability in the subsequent cycles even after it was transferred to an electrolyte without any additives; its cycleability was higher than that of a Li electrode without the pretreatment. This means that the primary Li cycle in the presence of the additive can provide an enhanced Li cycleability no longer with the need for additives during the subsequent cycles. The enhancement effect was significant under various charge-discharge conditions, i.e., depth of discharge (DoD) and current density, when an appropriate amount of AII(3) was applied to the pretreatment process. Aluminum derived from the pretreatment was found to remain at the Li electrode still in charge-discharge cycles. Such residual Al in Li, inevitably composing Li alloy, contributes to stabilize the properties of Li electrode interface, e.g., an interfacial resistance, thereby enhancing the charge-discharge cycling efficiency of Li. Thus, the pretreatment of Li metal anode with a single cycle in Li(C2F5SO2)(2)N/PC-DMC electrolyte containing an appropriate amount of AII(3) can provide a durable Li interface with better Li cycleability even in an electrolyte without AII(3) under various charge-discharge conditions. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2005.03.007

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The performance of electric double layer capacitor, (EDLC) with an ionic liquid, 1-ethy-3-methylimidazolium tetrafluoroborate (EMIBF4) electrolyte containing LiBF4, has been investigated and compared with that of EDLC containing EMIBF4 without LiBF4 as well as containing a conventional organic electrolyte, triethylmethylammonium tetrafluoroborate/propylene carbonate (TEMABF(4)/PC). EDLC with EMIBF4 + LiBF4 showed an excellent electrochemical stability; the electrolyte was not decomposed even at a cell voltage of ca. 3.6 V. Calculated energy density in EDLC with EMIBF4 + LiBF4 was highest among EDLCs with the cited electrolytes. The addition of LiBF4 to EMIBF4 also improved double layer capacitance especially at a positive electrode.

DOI： 10.5796/electrochemistry.73.600

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A new polymeric gel electrolyte system conducting magnesium ion has been proposed. The gel electrolytes consisted of poly(ethylene oxide)-modified polymethacrylate (PEO-PMA) dissolving ionic liquid mixed with magnesium salt, Mg[(CF3SO2)(2)N](2). The polymeric gel films were self-standing, transparent and flexible with enough mechanical strength. The ionic conductance and the electrochemical properties of the gel films were investigated. Thermal analysis results showed that the polymeric gel is homogeneous and amorphous over a wide temperature range. The highest conductivity, 1.1 x 10(-4) S cm(-1) at room temperature (20degreesC), was obtained for the polymeric gel containing 50 wt.% of the ionic liquid in which the content of the magnesium salt was 20 mol%. The dc polarization of a Pt/Mg cell using the polymeric gel electrolyte proved that the magnesium ion (Mg2+) is mobile in the present polymeric system. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2004.07.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Non-aqueous polymeric gel complexes composed of poly(ethylene oxide)-modified polymethacrylate (PEO-PMA) dissolving anhydrous H3PO4 have been examined as solid electrolytes of electrochemical capacitors. High ionic conductivity of 10(-3) S cm(-1) (at 70degreesC) was obtained for non-aqueous gel systems based on PEO-PMA with proper amounts of organic plasticizers. The ionic conductivity depended on the composition of the gel, especially on the content of the dopant H3PO4. A test cell of the electric double layer capacitor (EDLC) was assembled using the present gel electrolyte with activated carbon fiber (ACF) cloth electrodes. It gave as high capacity as that obtained for the capacitor using an aqueous liquid electrolyte. High rate capability was obtained for the cell operating at 90degreesC. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.electacta.2004.02.053

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Polymeric gel electrolyte films consisting of poly(ethylene oxide)-based polyurethane containing lithium salt (LiClO4 or LiPF6) dissolved in propylene carbonate (PC) have been prepared. The ionic conductance and electrochemical properties of the gel films were examined. The obtained gel film was self-standing, transparent and flexible with high mechanical strength. Thermal analysis of the gel film showed that it is homogeneous and amorphous over a wide temperature range. The highest conductivity, 1.51 mS cm(-1) at 60degreesC, was obtained for the polymeric gel containing 50 wt.% of 1.5 mol dm(-3) LiClO4/PC. The applicability of the present gel system to a rechargeable lithium battery was briefly examined by cyclic voltammetry and constant-current polarization using metallic lithium electrodes. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.electacta.2004.01.128

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.71.1046

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.71.1067

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.71.1049

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0167-2738(02)00691-4

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOCIETY INC  

A novel polymeric gel electrolyte system for electrochemical devices has been developed and its proton conducting behavior was investigated at an ambient temperature range. The get system consists of a poly(ethylene oxide)-modified polymethaerylate (PEO-PMA) matrix with linear polyether (PEGDE) doped with inorganic and organic acids from aqueous solutions. About 2 x 10(-2) cm(-1) of the conductivity was obtained for the H3PO4 doped gel film at room temperature. The contents of acid and water in the gel, which depend on the doping conditions, gave critical influences on the conductance behavior of the resulting get. Applicability of the gel system was briefly examined by cyclic voltammetry using a cell with a gel electrolyte film.

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Gel electrolytes of poly-(fluorovinylidene-hexafluoropropylene) and (PVdF-HFP) with propylene carbonate (PC) as a plasticizer and the asymmetric ammonium salt triethylmethylammonium tetrafluoroborate (TEMABF(4)), have been applied to electric double layer capacitors (EDLCs), Ac impedance measurements show that the gel-type capacitors with TEMABF(4) have not only lower electrolyte-bulk resistances but also lower electrolyte/electrode-interface resistances in comparison with capacitors with a typical electrolytic salt tetraethylammoniurn tetrafluoroborate (TEABF(4)). The capacitors with TEMABF(4) have a higher capacitance than that with TEABF(4) especially under a high-rate cycling condition; the former capacitance is comparable to that observed in non-gel (usual liquid) systems with PC and TEMABF(4) even under a high-rate cycling condition.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0013-4686(03)00221-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0378-7753(03)00253-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/cm021076s

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0167-2738(02)00295-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0167-2738(02)00308-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0013-4686(02)00280-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0013-4686(02)00164-0

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

DOI： 10.4139/sfj.53.219

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

DOI： 10.1149/1.1403195

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

DOI： 10.4139/sfj.52.581

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0378-7753(01)00752-2

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0378-7753(01)00621-8

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.69.437

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.69.462

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0013-4686(00)00754-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0013-4686(00)00705-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0167-2738(00)00613-5

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOCIETY INC  

The electrochemical behavior of an LiCr0.1Mn1.9O4 positive electrode (cathode) has been studied in organic electrolyte solutions with different compositions. The results of cyclic voltammetry (CV) and constant current polarization (CCP) indicated that the redox response and the discharge capacity of the LiCr0.1Mn1.9O4 cathode depended much on the electrolyte composition. Higher initial capacity and rate capability were observed in the electrolyte compositions showing higher ionic conductivity. Good cathode performance was obtained in an LiBF4 solution with a mixed ternary solvent system of ethylene carbonate, dimethyl carbonate and 1,2-dimethoxyethane (EC+DMC+DME).

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0013-4686(00)00315-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0013-4686(99)00341-2

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.67.1200

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media LLC  

ABSTRACT

Polymer gel electrolytes consisting of poly(vinylidene fluoride) (PVdF), tetraethylammoniumtetrafluoroborate (TEABF₄), and propylene carbonate (PC) as a plasticizer have been investigatedfor electric double layer capacitors. The PVdF gel electrolytes showed high ionic conductivity (ca.6 mS cm^-1at 298 K). To assemble model capacitors with the PVdF gel electrolytes and activatedcarbon fiber cloth electrodes, a pair of the fixed electrodes was soaked in a precursor solutioncontaining PC, PVdF, and TEABF₄, followed by evaporation of the PC solvent in a vacuumoven. The resulting gel electrolytes were in good contact with the electrodes. The modelcapacitors with the PVdF gel electrolytes showed a large value of capacitance and high coulombicefficiency in operation voltage ranges of 1–2 and 1–3 V. It is worth noting that the capacitors withthe PVdF electrolytes showed long voltage retention in a self-discharge test. These goodcharacteristics of our gel capacitors were comparable to those of typical double layer capacitorswith a liquid organic electrolyte containing PC and TEABF₄; rather, the voltage retentivity of thePVdF gel capacitors was much superior to that of the capacitors with the organic electrolyte.

DOI： 10.1557/proc-575-423

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0022-0728(99)00170-9

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0378-7753(98)00213-4

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

DOI： 10.4139/sfj.50.839

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0378-7753(99)00225-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0013-4686(98)00284-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/kogyobutsurikagaku.66.1304

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

DOI： 10.1039/a806278a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0167-2738(98)00399-3

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media LLC  

ABSTRACT

Activated carbon fiber cloth (ACFC) electrodes whose surface was modified by “pulsed cold plasma”, i.e., low-temperature plasma generated by a pulsed electric power in argon-oxygen mixed gas at a reduced pressure, were applied to electric double layer (EDL) capacitors with an organic electrolyte composed of propylene carbonate and tetraethylammonium tetrafluoroborate (TEABF₄). The treatment of the ACFC electrodes with the pulsed cold plasma increased total capacitance in the EDL capacitors. The observed increase in the total capacitance was ascribed mainly to an ascertained increase in capacitance of a negative ACFC electrode involving TEA₊cation adsorption/desorption with the cold plasma treatment. No obvious increase in capacitance of a positive ACFC electrode involving BF₄- anion adsorption/desorption was observed with the plasma treatment. The chemical and electrochemical characteristics of a treated ACFC interface were found to be favorable for TEA₊cation adsorption/desorption.

DOI： 10.1557/proc-496-655

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0378-7753(96)02558-x

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0378-7753(97)02524-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

The suitability of organic electrolyte systems for highly graphitized carbon anodes has been discussed by considering the stability of co-solvents included in ethylene carbonate-based electrolytes and the stability of lithium salts. The side-reaction and the film formation on the graphitized anodes were found to affect the discharge capacity of the graphitized anodes. With respect to the lithium salts, lithium bistrifluoromethylsulfonyl imide offered high and stable capacity. Furthermore, the electrochemical behavior of a surface film on a lithium metal anode was investigated at various operating temperatures. It was found that the operating temperature during charge/discharge cycling influences the morphology of the film on a lithium metal anode, resulting in the variation in charge/discharge coulombic efficiency of a lithium metal anode. The results are discussed in view of the stability of electrolyte solutions and the film formation between the negative electrode and the organic electrolyte solution. © 1997 Elsevier Science S.A.

DOI： 10.1016/S0378-7753(97)02515-9

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOCIETY INC  

The effect of inorganic additives to electrolytes, aluminum iodide (AlI3) and tin (II) iodide (SnI2), on charge-discharge coulombic efficiency of a lithium (Li) metal anode has been investigated in binary solvent systems, i.e., propylene carbonate (PC) mixed with dimethyl carbonate (DMC) containing lithium perchlorate (LiClO4), PC+DMC/LiClO4, and ethylene carbonate (EC) mixed with DMC containing LiClO4, EC+DMC/LiClO4. AlI3 improved the coulombic efficiency of the Li metal anode in both the binary solvent systems while no obvious improvement of the efficiency was observed for the electrolyte systems with SnI2. The relationship between the coulombic efficiency and ac impedance behavior of a Li anode interface in the presence of the additives is discussed.

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Under low-temperature conditions (at 0 degrees C and -20 degrees C) the charge-discharge cycling efficiency of lithium (Lj) metal on a nickel substrate in propylene carbonate/dimethyl carbonate (1:I by vol.) with Li hexafluorophosphate was higher than that observed in the corresponding electrolyte system at 25 degrees C. When the charge-discharge cycling of Li in the low-temperature electrolyte was followed by the cycling at 25 degrees C, the charge-discharge at 25 degrees C maintained the high cycleability observed at the low temperatures. This suggests that the precycling under the low-temperature conditions improved the efficiency in the following cycles at room temperature (25 degrees C). Ac impedance analysis revealed that the precycling in the few-temperature electrolyte provided the low-resistance Li-interface which remained on the Li metal even after a rise in temperature to 25 degrees C.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

DOI： 10.5796/kogyobutsurikagaku.65.490

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Language：Japanese  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

DOI： 10.1149/1.1837563

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Other Link： https://iopscience.iop.org/article/10.1149/1.1837563/pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0925-8388(96)02642-4

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELECTROCHEMICAL SOCIETY INC  

Polymer gel electrolytes consisting of poly(vinylidene fluoride) (PVDF), tetraethylammonium tetrafluoroborate, and propylene carbonate as a plasticizer have been investigated for electric double-layer capacitors. The PVDF gel electrolytes showed high ionic conductivity (ca. 6 x 10(-3) S cm(-1) at 20 degrees C) and had good stability over a wide potential range (ca. 5 V). The model capacitors with the PVDF gel electrolytes and activated carbon fiber cloth,electrodes showed large values of capacitance and high coulombic efficiency in the operation voltage ranges of 1-2 and 1.5-2.5 V. Especially, it is worth noting that the capacitors with the PVDF electrolyte showed low leakage current, and long voltage retention in self discharge tests.

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

The photoinduced electrochemical oxidation of benzyl alcohol to benzaldehyde in acidic acetonitrile proceeded with practically 100% product selectivity and ca. 100% current efficiency under visible-light irradiation in the presence of riboflavin-2,',3',4',5'-tetraacetate (RF) as a mediator. A double mediatory system involving duroquinone as well as RF resulted in remarkable acceleration of the benzaldehyde formation with maintenance of both the high product selectivity and high current efficiency.

DOI： 10.1246/cl.1996.953

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/s0378-7753(96)02413-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

Complexes of poly(ethylene oxide)-grafted poly(methylmethacrylate) (PEO-PMMA) and lithium (Li) salts have been prepared as polymeric solid electrolytes for rechargeable Li batteries. As high conductivities as 10-3 S cm -1 at room temperature were obtained for the PEO-PMMA-based electrolytes containing Li salts with a liquid plasticizer. Effects of the crown ethers in the electrolytes were examined on the ionic conductance behavior. The addition of 12-crown-4 (12Cr4) or 15-crown-5 (15Cr5) improved the ionic conductivity to a small extent. However, the ionic mobility of Li in the electrolyte was improved by the addition of 15Cr5. The transport number of Li+ in the electrolytes containing 15Cr5 was much higher than those in the electrolytes without crown ethers. The specific solvation of Li+-15Cr5 contributes not only to the improvement in the ionic mobility of Li+ but also to the suppression in the reaction rate of the Li electrode in the polymeric electrolytes.

DOI： 10.1016/0167-2738(96)00160-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：VCH PUBLISHERS INC  

Cerium(III) species have been immobilized in Nafion films coated on a glassy carbon electrode by a dipping method. The redox activity was characterized In aqueous acidic solutions by cyclic voltammetry. The redox process was diffusion-limited, suggesting that the cerium(III) species distributed in the multilayer of Nafion and that the diffusion of the charge-compensating anion in the film was rate-controlling. The cerium(III)-immobilized Nafion films showed a mediation activity for the electrochemical oxidation of substituted benzylalcohols to yield corresponding arylaldehydes and carboxylic acids. The activity and the selectivity of the process depended an the oxidation potential of the substrate compound. Macroelectrolysis of p-nitrobenzylalcohol using cerium(III)-immobilized electrodes gave corresponding p-nitrobenzaldehyde with a high rate and selectivity.

DOI： 10.1002/elan.1140080823

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Charge/discharge behavior of electric double-layer capacitors composed of activated carbon fiber cloth (ACFC) electrodes and an organic electrolyte was investigated. The modification of the ACFC electrodes was performed using cold plasma generated in argon-oxygen atmosphere. The effect of the cold plasma treatment of the ACFC electrodes on the capacitor performance was discussed on the basis of the physical and chemical properties of the ACFC surface such as pore radius distribution and surface atom concentration.

DOI： 10.1016/S0378-7753(96)80016-4

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Authorship：Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

DOI： 10.4139/sfj.47.498

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Language：Japanese  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

The electrochemical behavior of the interface between lithium (Li) alloy electrodes containing a small amount of metal [aluminum (Al) or tin (Sn)] and a propylene carbonate (PC)-based electrolyte has been investigated. The contents of Al and Sn were below 3.0wt.%. Ac impedance analysis revealed that Li-Al electrodes showed relatively low and stable resistance at the electrode/electrolyte interface during the electrode immersion in the electrolyte as well as during charge-discharge cycling. On the other hand, a Li-Sn electrode gave higher interfacial resistance than a "pure" Li electrode. Cyclic voltammetry measurement and galvanostatic charge-discharge cycling test revealed the Li-Al electrode exhibited small polarization from the ideal redox potential of Li/Li+ during charging and discharging while the Li-Sn electrode showed relatively large polarization. The polarization behavior of the various electrodes correlated with the interfacial resistance characterized by the ac impedance measurement.

DOI： 10.1016/0013-4686(95)00445-9

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Electrochemical lithium intercalation into graphite has been studied in ethylene carbonate (EC) based electrolytes using x-ray diffraction (XRD) and electrochemical quartz crystal microbalance techniques. The graphite electrode after cathodic polarization in EC mixed with dimethyl carbonate (DMC) showed a different XRD pattern from that polarized in EC mixed with propylene carbonate (PC). Changes in the resonance frequency of the graphite-coated quartz crystal proved that the cathodic intercalation of lithium into graphite is accompanied by the electrochemical decomposition of the electrolyte. The mass change per quantity of electricity in the potential range of 0.0 to 0.2 V vs. Li/Li+ was higher in EC+DMC than in EC+PC.

DOI： 10.1149/1.1836445

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Surface Finishing Society of Japan  

DOI： 10.4139/sfj.46.1193

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Polymer gel electrolytes consisting of poly(acrylonitrile) (PAN), propylene carbonate(PC) as a plasticizer and tetraalkylammonium salts such as tetrabutylammonium perchlorate, tetraethylammonium perchlorate and tetraethylammonium tetrafluoroborate have been investigated for electric double-layer capacitors with activated carbon fiber cloth electrodes. The PAN, PC and tetraalkylammonium composites showed high ionic conductivity (above 10(-3) Scm(-1) at 298 K). The ionic conductivity increased with an increase in the salt concentration and a decrease in the size of each ion. The composites were electrochemically stable over a wide potential range (ca. 5.O V). The application of the PAN and tetraethylammonium tetrafluoroborate composites to the electric double-layer capacitors with activated carbon fiber cloths as polarizable electrodes resulted in large values of capacitance and high coulombic efficiency. The low leakage current at constant voltage floating (2 V) and the long voltage retention in the self-discharge test were obtained in the capacitor with tetraethylammonium tetrafluoroborate.

DOI： 10.1016/0013-4686(95)00166-c

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Springer Science and Business Media LLC  

ABSTRACT

A variety of organic solvent-based electrolytes have been studied for ambient temperature, rechargeable lithium (ion) batteries. The ionic behavior of the electrolyte system was investigated through conductivity measurements. The electrochemical characteristics of carbon-based materials (carbon fiber and graphite) as the negative electrode were examined in different compositions of the organic electrolytes. The electrolyte composition as well as the structure of the electrode material greatly influenced the charge/discharge profiles of the electrode.

DOI： 10.1557/proc-393-195

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Polyaniline-poly[p-styrenesulfonic acid-co-methoxy-oligo(ethylene glycol)acrylate] composite (PANI-PSSA-co-MOEGA) electrode was prepared for an all-solid-state rechargeable lithium battery and a Li/PANI-PSSA-co-MOEGA model cell was fabricated by combining a cross-linked poly(ethylene oxide)-grafted poly(methylmethacrylate)RiClO(4) polymer electrolyte. PSSA-co-MOEGA dopant has anchored anion sites (benzenesulfonic acid site) for doping polyaniline and oligo-ethylene oxide side chains for improving the adhesion between the electrode and the polymer electrolyte. Li/PANI-PSSA-co-MOEGA cell exhibited good cyclability and high capacity over 40 cycles. A model cell was also assembled by using a polyaniline electrode doped with perchlorate anion, PANI-ClO4, and the capacity of Li/PANI-ClO4 cell decreases over 10 cycles. The differences are caused by two factors. First, the PANI-PSSA-co-MOEGA composite film became a partially cation-doped type polymer (by doping polymer anion). Second, the interface between the PANI-PSSA-co-MOEGA electrode and the polymer electrolyte is improved by incorporating the oligo-ethylene oxide side chains in both materials. The diffusion rate of the dopant ions in PANI-PSSA-co-MOEGA was faster than in the PANI-ClO4 film.

DOI： 10.1149/1.2048737

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：Japanese  

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Language：Japanese  

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)  

Polyaniline-p-styrenesulfonic acid (PANI-p-SSA) composites were synthesized by electrochemical oxidation of polyaniline in the p-styrenesulfonic acid aqueous solutions. p-Styrenesulfonic acid was incorporated in the polyaniline matrix as a dopant anion. PANI-p-SSA composite film (polymer-monomer composite) was converted to polyaniline-poly(p-styrenesulfonic acid) (PANI-PSSA, polymer-polymer) composite film by the post-polymerization process. A PANI-p-SSA film was soaked in benzoyl peroxide-CCl4 solution and the film was heated at 60 °C for 12 h under Ar atmosphere for post-polymerization. The film shrank about 17% after post-polymerization. The PANI-PSSA composite showed the ability of cation doping in organic electrolyte solution. © 1995.

DOI： 10.1016/0379-6779(94)03273-9

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Boron-carbon-nitrogen composite (BCxN) matrices (BC3N, BC7N, and BC10N) for rechargeable lithium batteries are synthesized by a thermal decomposition method. BC10NLi0.5 is prepared by the thermal decomposition of a mixture of the starting materials for BC10N and lithium hydroxide (LiOH). The charge/discharge behaviour of these layered-structure compounds is investigated in an organic electrolyte that contains lithium salts. The capacity increases with an increase in the carbon content. The LiOH treatment causes an increase in the discharge capacity of boron-carbon-nitrogen material.

DOI： 10.1016/0378-7753(94)02173-Z

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

The structure of a polyaniline-poly(styrene-4-sulfonate) (PAn-PSS) composite film was optimized as the positive electrode for rechargeable lithium batteries to improve the charge/discharge characteristics in organic electrolyte solutions. The composite films prepared in aqueous poly(styrene-4-sulfonic acid) (PSSH) solutions containing small amounts of HClO4 showed higher charge/discharge capacities than those prepared in PSSH without HClO4. However, the utilization of Li+-ion transport in the redox process decreased with an increase in the HClO4 concentration. A stacked PAn-ClO4/PAn-PSS film, which consists of an inner PAn layer doped with smaller size anion (ClO4-) and an outer PAn-PSS composite layer, was prepared by the electrolysis of aniline in aqueous HClO4 followed by the polymerization in a PSSH solution. The resulting films gave improved charge/discharge characteristics in organic electrolyte solutions and lead to higher energy density of the full cell with lithium negative electrode.

DOI： 10.1016/0378-7753(94)02069-F

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

New inorganic additives, tin(II) iodide and aluminum iodide (A1I(3)), improved charge/discharge cycling efficiency of a lithium (Li) electrode in propylene carbonate electrolyte containing lithium perchlorate as the electrolytic salt. The combination of different types of additive, i.e., the addition of A1I(3) together with 2-methylfuran to the electrolyte, resulted in an excellent cycling efficiency of the Li electrode. The electrochemical behavior of an Li electrolyte-organic electrolyte interface was investigated by in situ techniques such as a.c. impedance measurements and scanning vibrating electrode technique. The relation between the Li rechargeability and the interfacial behavior of the Li electrode in the organic electrolyte in the absence and the presence of the additives was discussed.

DOI： 10.1016/0378-7753(94)02088-K

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Layered polyaniline/polyanion composite films (PAn-X/PAn-PA) we re synthesized by electrochemical oxidation of aniline in aqueous acid solutions (HCl, HClO4) followed by polymerization in poly(styrene-4-sulfonic acid) (PSSH) solutions. The films consist of inner polyaniline (PAn layers doped with smaller size anions (X) and outer PSS-doped PAn layers. The resulting films showed high redox activities with cation-transfer properties in organic electrolyte solutions. The improved charge/discharge characteristics of the composite firms gave an expectation of higher energy density for the full cell with lithium negative electrode.

DOI： 10.1149/1.2043981

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

DOI： 10.5796/electrochemistry.62.1227

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC JAPAN  

The indirect electrooxidation of substituted methylbenzenes to arylaldehydes by Ce(IV) mediators has been studied. The yield and selectivity of the aldehyde varied with the combination between the substrate compound and the mediator. The reaction mode was characterized by the relationship between the oxidation potential of the substrate (E(s,ox)) and the apparent redox potential of the mediator (E(m,red)). The second-order rate constant for the oxidation of the methylbenzenes with the oxidized mediators depended on the potential difference, DELTAE = E(s,ox)-E(m,red). Marcus's electron-transfer theory was apparently applied for endothermic systems. High yields of aldehydes were obtained when the systems had moderate values of DELTAE.

DOI： 10.5796/electrochemistry.62.1206

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