An Electrochemical Double Layer Capacitor Using an Activated Carbon Electrode with Gel Electrolyte Binder

An electric double layer capacitor (EDLC) was prepared with an activated carbon powder electrode with poly(vinylidene fluoridehexafluoropropylene) (PVdF‐HFP) based gel electrolyte. Ethylene carbonate (EC) and propylene carbonate (PC) were used as plasticizer and tetraethylammonium tetrafluoroborate was used as thesupporting electrolyte. An optimized gel electrolyte of mass ratio exhibited high ionic conductivity of , high electrode capacitance, and good mechanical strength. An electrode consisting of activated carbon (AC) with the gel electrolyte as the binder (AC/PVdF‐HFP based gel, 7/3 mass ratio) showed a higher specific capacitance and a lower ion diffusion resistance within the electrode than a carbon electrode, prepared with PVdF‐HFP binder without plasticizer. This suggests that an electrode mixed with the gel electrolyte has a lower ion diffusion resistance inside the electrode. The highest specific capacitance of was achieved with an electrode containing AC with a specific surface area of . A coin‐type EDLC cell with optimized components showed excellent cycleability exceeding cycles with ca. 100% coulombic efficiency achieved when charging and discharging was repeated between 1.0 and 2.5 V at . © 1999 The Electrochemical Society. All rights reserved.