Abstract:

A graphene/nano-sulfur (RGO/nano-S) cathode composites was prepared by chemical precipitation of nano-sulfur onto graphene sheets, which were synthesized by pyrolyzing reduction of graphene oxide from Hummers method. The microscopic structure and morphology of the composites were characterized by FT-IR, XRD, SEM, TEM and Raman, while the electrochemical properties were studied by galvanostatic charge-discharge measurements, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that wrinkled surface on the thermally reduced graphene created a space to accommodate sulfur and polysulfur ions, which helped to hinder dissolving of active cathode materials and suppress migration of polysulfide ions. A homogeneous distribution of nano-sulfur in the graphene conductive network significantly enhanced the effective contact with electrolyte and increased electrochemical reaction area, so that improved discharge capacity and cycle-life performance of the lithium-sulfur batteries.

Key words: lithium-sulfur batteries, graphene, nano-sulfur, composites, electrochemical performance

摘要：

利用热解还原将Hummers法制得的氧化石墨烯还原为石墨烯，并采用化学沉淀法将纳米硫成功负载到石墨烯片层上，获得石墨烯/纳米硫（RGO/nano-S）正极复合材料。利用FT-IR、XRD、SEM、TEM和Raman对所制备复合材料的微观结构、形貌等进行表征，采用恒流充放电、循环伏安法和交流阻抗法对复合材料的电化学性能进行研究。研究结果表明，热还原所得石墨烯褶皱的表面形成容纳硫及多硫离子的空间，有助于缓解活性物质溶解和抑制多硫离子迁移；同时，均匀分布的纳米硫能更好地与电解液接触，在石墨烯的导电网络上增大了电化学反应面积，进而改善了该材料作为锂硫电池的实际放比电容量和倍率循环性能。

关键词: 锂硫电池, 石墨烯, 纳米硫, 复合材料, 电化学性能