采用分段加热法合成了不同管径、不同硫含量的单质硫-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10~20 nm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1272.8 mAh·g-1,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720.1 mAh·g-1,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。
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 24 h followed by heating at 300℃ for 2 h 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 10-20 nm 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-1-sulfur and the capacity remaining after 80 cycles is 720. 1mAh·g-1-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.
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