Ionically conductive polymer gel electrolytes prepared from vinyl acetate and methyl methacrylate for electric double layer capacitor

Abstract

In order to obtain highly conductive polymer electrolytes for an electric double layer capacitor, three kinds of polymer gel electrolytes were prepared. Vinyl acetate (VAc) and methyl methacrylate (MMA) were copolymerized with divinyl adipate (DA) and ethylene glycol dimethacrylate (EGDMA), respectively, in propylene carbonate (PC) containing tetraethylammonium tetrafluoroborate (TEATFB) to form network polymer gel electrolytes. MMA was also copolymerized with butylene glycol DMA for comparison. The polymer gel electrolytes obtained were characterized by means of thermogravimetry, complex impedance analysis, and cyclic voltammetry for use in the electric double layer capacitor. The ionic conductivities of the polymer gel electrolytes were dependent on the TEATFB concentration, temperature, and crosslinking degree. The polymer gel electrolytes in the VAc-DA system exhibited higher room temperature conductivities (10 Ϫ2 S/cm) than those in the MMA-EGDMA system. Further, the polymer gel electrolytes in the VAc-DA system showed good electrochemical stability windows ranging from Ϫ4.0 to 4.0 V versus Ag. Thermal analysis revealed that the polymer gel electrolytes in both systems were stable up to 150°C.