Application of chitosan-based gel electrolytes with ionic liquids for high-performance and safe electric double layer capacitors

Abstract

Chitosan-based gel electrolytes with ionic liquids (Chi/IL) were prepared and investigated for use in electric doublelayer capacitors (EDLCs). The voltage drop for the test cell with Chi/EMImBF4 (EMImBF4 = 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 EMImBF4. 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. © The Electrochemical Society of Japan, All rights reserved.