Poly(vinylidene chloride)based carbon as an electrode material for high power electric double layer capacitors

A series of poly vinylidene chloride (PVDC) based activated carbons was prepared by carbonization at 600-1100℃. Their formation , crystallinity, surface area and pore structure were characterized by thermogravimetry, X-ray diffraction and nitrogen adsorption. The electrochemical performance was investigated by cycle voltammetry, AC impedance and galvanostatic charge/discharge in a 30 wt. % KOH electrolyte. Results showed that the structure of PVDC-based carbons was amorphous and their high surface area (874-969 m²/g) and abundant micropores were formed during the solid phase carbonization. PVDC-based carbon had a high gravimetric capacitance and specific capacitance per surface area, owing to its optimum pore size distribution suitable for the formation of electric double layers. The PVDC-based carbon heat-treated at 900℃ had a maximum capacitance and an excellent power performance. The specific capacitance can reach as high as 256.9F/g at low discharge current density (50mA/g) and the capacitance retention ratio is 76.5% at high current density (5 000mA/g). The electrical conductivity of PVDC-based carbon increased and the diffusion resistance of electrolyte ions in pores decreased with increasing carbonization temperature, and the rate performance of the electric double layer capacitor is improved as a result