聚偏二氯乙烯基炭用作高功率EDLC电极材料

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

在600℃～1100℃对聚偏二氯乙烯(PVDC)树脂仅进行炭化处理,制备了一系列PVDC基活性炭。由TG、XRD和N2吸附等温线(77K)分别测定了PVDC基炭经历的热解过程与其晶型、比表面积和孔结构;采用循环伏安、交流阻抗和恒电流充放电考察了它们在质量分数30%的KOH水溶液中的电容特性。结果表明:PVDC基炭属于无定形碳,其大的比表面积(874.5m2/g～969.2m2/g)和丰富的微孔在固相炭化过程中形成;PVDC基炭具有适于双电层形成的优异孔径分布、高的质量比电容和面积比电容;900℃炭化的PVDC基炭具有最高的比电容值和良好的功率特性,50mA/g电流密度时的放电比电容达256.9F/g,5000mA/g电流密度时的放电比电容保持率达76.5%;提高炭化温度可提高PVDC基炭的电导率,降低电解质离子在孔内的扩散阻抗,改善双电层电容器的功率性能。

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 resistance of electrolyte ions in pores decreased with increasing carbonization temperature, and the rate performance of the electric double laver capacitor is improved as a result.