中文摘要：

采用分段加热法合成了不同管径、不同硫含量的单质硫一多壁碳纳米管（S-MWCNT）复合材料，利用电化学方法、SEM、TEM、比表面吸附等分析方法，筛选出以10～20mm直径的MWCNT为核，质量分数85％硫为壳的最优化条件下的复合材料。SEM测试显示单质硫均匀填充到MWCNT的中空管和层间的孔中形成了结构稳定的复合物。在最优化的条件下，复合材料首次放电比容量达1272．8mAh·g-2，活性物质利用率为76．0％，循环至第80周时放电容量还保持在720．1mAh·g-2，容量保持率高达64．4％。与未添加MWCNT的单质硫电极相比，硫复合电极活性物质的利用率和循环性能都得到了较大的改善。

英文摘要：

Multi-wall carbon nanotubes （MWCNTs） with different diameters were ball-milled with different amounts of elemental sulfur for 2 h under an argon atmosphere, and then heated at 155℃ for 24h followed by heating at 300℃ for 2h to prepare MWC- NT/S composites. The composites were characterized by N2 adsorption, scanning and transmission electron microscopy, and elec- trochemical tests. It was found that the composite showing the best performance was the one in which the MWCNT diameter was in the range 10-20nm and the sulfur content was 85 mass%. SEM confirms that the composite has a MWCNT-core and sulfur-shell structure. Sulfur not only covered the surface of the MWCNTs, but also filled the voids between the tubes. For the optimized com- posite the initial discharge capacity is 1272.8mAh.g-l-sulfur and the capacity remaining after 80 cycles is 720.1 mAh.g-l-sulfur. Its active material utilization and capacity retention rates are 76.0 and 64.4%, respectively. The active material utilization and cycling performance of the composite are greatly improved compared with a sulfur electrode without the MWCNTs, owing to a high electri- cal conductivity of the MWCNTs and the stable structure of the composite.