Abstract:

Lithium sulfur batteries are considered to be the most promising secondary battery because of its high theoretical specific capacity (1675 mA·h·g^-1). However, the sulfur cathode faces the challenges, such as poor conductivity, low utilization of sulfur and poor structure stability of cathode. Biomass-based porous carbon, with cheap and accessible agricultural waste corn bracts as raw material, was prepared by chemical activation with KOH, and then composited with sublimate sulfur through modelling-fused method to form sulfur/carbon composite. The microscopic structure and morphology of the composites were characterized by XRD, SEM, TEM, and BET. The results show that the biomass-based porous carbon material possesses lamellar structure, which is similar to graphene, and abundant mesoporous structure on the surface of carbon. Furthermore, sulfur particles homogeneously distribute in the carbon conductive network. In addition, the electrochemical properties were studied by galvanostatic charge-discharge tests and electrochemical impedance spectroscopy. The results show that the battery possesses high discharge capacity and good cycle-life performance. The main reasons are as follow:the porous carbon structure like graphene, enhancing conductivity of sulfur cathode; the huge specific surface area which make electrochemical reaction sites increased, improving the utilization of sulfur.

Key words: activation, preparation, biomass-based porous carbon, electrochemical performance, lithium-sulfur batteries

摘要：

锂硫电池因具有超高的理论比容量（1675 mA·h·g^-1）而被认为是最具有应用前景的二次电池。但硫基正极面临着硫导电性差、利用率低、正极结构稳定性差等问题。采用KOH化学活化法将廉价易得的农业废弃物玉米苞叶制备为多孔碳材料后，与升华硫复合获得硫/碳复合材料。利用XRD、SEM、TEM和BET对该硫/碳复合材料的微观结构、形貌等进行表征发现，玉米苞叶制备的多孔碳材料具有类石墨烯片层结构，且表面具有大量的介孔结构，硫元素均匀分布在多孔碳材料中。采用恒流充放电和交流阻抗法对该复合材料正极电化学性能进行测试发现其具有较高的放电比容量和良好的循环性能，这是由于类石墨烯片层结构的多孔碳材料提高了硫正极的导电性，且其极大的比表面积大幅增加了电化学反应位点，提高了硫的利用率。

关键词: 活化, 制备, 生物质多孔碳, 电化学性能, 锂硫电池