Structure and application of various Saran-based carbons to aqueous electric double-layer capacitors

A new application to electric double-layer capacitor fields of Saran(R) resin using samples obtained directly from the production line was tried and investigated. These samples are prepared through a simple process by only heat-treatment with no additional activation process. Homogeneous polyvinylidenechloride (PVDC) based carbon heat-treated at 700degreesC showed a maximum specific capacitance of 92.5 F/g at 1 mA/cm(2) of current density (which is obtained by a unit cell system by two electrodes, equivalent to 370 F/g in a conventional three-electrode system). Other blended samples show a better capacitance at high current density over 300 mA/cm(2) than that of homogeneous PVDC, although the blends show poor characteristics at relatively low discharge current density. To clarify the relation between the pore size distribution and the capacitance, image analysis of transmission electron microscopy photographs was performed. The pore size distribution of each Saran resin is shifted according to the kind of blended polymer. The pore size distribution of Saran-based carbon is controllable by mixing with a copolymer. The simulation result of the electrolyte ion was used to clarify the capacitance behavior. (C) 2002 The Electrochemical Society.