2005 Fiscal Year Final Research Report Summary
Mechanisms of Application of Anomaly Capacitive Effects of Electric Double Layer Capacitors
| Project/Area Number |
16350104
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional materials/Devices
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| Research Institution | Kansai University |
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Principal Investigator |
ISHIKAWA Masashi Kansai University, Fac. of Engr., Professor, 工学部, 教授 (30212856)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Electric Double Layer Capacitor / Gel Electrolyte / EV / High Rate Cycling / Rechargeable Battery / EDLC / Auxiliary Power Source / Buckup Power Source |
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| Research Abstract |
Anomaly capacitive effects of electric double layer capacitors have been investigated in an attempt to find a novel strategy expanding capacitance. The performance of electric double layer capacitors with an ionic liquid, 1-ethy-3-methylimidazolium tetrafluoroborate (EMIBF_4) electrolyte containing LiBF_4, was investigated and compared with that of electric double layer capacitors containing EMIBF_4 without LiBF_4 as well as containing a conventional organic electrolyte, triethylmethylammonium tetrafluoroborate/propylene carbonate (TEMABF_4/PC). Electric double layer capacitors with EMIBF_4+LiBF_4 showed an excellent electrochemical stability ; the electrolyte was not decomposed even at a cell voltage of ca. 3.6V. Calculated energy density in electric double layer capacitors with EMIBF_4+LiBF_4 was highest among electric double layer capacitors with the cited electrolytes. The addition of LiBF_4 to EMIBF_4 also improved double layer capacitance especially at a positive electrode. This suggests that the total capacitance should be controlled not only by a simple Helmholtz-type double layer model but also by a long-range or higher-order structure, namely an anomaly capacitive effect. The magnitude of this effect varied with a variation of applied potential, and depended on additives such as high-permittivity solvents and low-viscosity solvents. Such interpretation has been applied also to other systems, e.g., gel electrolyte and aqueous electrolyte systems.
Furthermore, we have developed a novel electrode system with activated carbon and deoxyribonucleic acids (DNA) composite for an aqueous electric double layer capacitor. The addition of DNA to the activated carbon electrode was found to provide not only enhanced long-range diffusion characteristics but also an additional, anomaly capacitive effect increasing double layer capacitance in meso-pore region.
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