Abstract

A series of poly vinylidene chloride (PVDC) based activated carbons was prepared by carbonization at 600-1 100 ℃. 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 % (mass fraction) 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 256.9 F/g at low discharge current density (50 mA/g) and the capacitance retention ratio is 76.5% at high current density (5 000 mA/g). The electrical conductivity of PVDC-based carbon increased and the diffusion resis ̄tance 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.

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