Performanc eof electric double layer capacitors with polymer gel electrolytes

摘要

Polymer gel electolytes consisting of poly (vinylidene fluoride) (PVdF), tetraethylammonium tetrafluoroborate (TEABF_4), and propylene carbonate (PC) as a plasticizer have been investigated for electric double layer capacitors. The PVdF gel electrolytes showed high ionic conductivity (ca. 6 mS cm~-1 298 K). To assmeble model capacitors with the PVdF gel electrolytes and activated carbon fiber cloth electrodes, a pair of the fixed electrodes was soakedin a precursor solution containing PC,PVdF, and TEABF_4, followed by evaporation fo the PC solvent in a vacuum over. The resulting gel electrolytes were in good contact with the electrodes. The model capacitors with the PVdF gel electrolytes showed a large value of capacitance and high coulombic efficiency in operation voltage ranges of 1-2 and 1-3 V. It is worth noting that the capacitors with the PVdF electrolytes showed long voltage retention in a self-discharge test. These good characteristics of our gel capacitors were comparable to those of typical double layer capacitors with a liquid organic electrolyte containing PC and TEABF_4; rather, the voltage retentivity of the PVdF gel capacitors was much superior to that of the capacitors with the organic electrolyte.