原位MnO2包覆CMK-3/S复合材料在锂硫电池中的应用

Application of in-situ MnO2 coated CMK-3/S composites in lithium-sulfur batteries

利用高锰酸钾与硫的氧化还原反应,在CMK-3/S复合材料表面原位生成均匀的MnO2,以此作为锂硫电池的正极材料。选取不同质量的高锰酸钾与硫含量为80%的CMK-3/S复合材料,再通过乙醇洗去部分硫得到硫含量为70%的MnO2@CMK-3/S复合材料。与载硫量为70%的CMK-3/S复合材料相比,包覆了MnO2的复合材料表面开始变得粗糙。电化学分析表明,在0.5C倍率下循环300次后,包覆了MnO2的复合材料放电比容量410.6 mAh·g^-1,每圈容量衰减率为0.16%,库伦效率高达98%以上。电化学阻抗谱表明,包覆了MnO2的CMK-/S复合材料具有更高的电荷转移效率;可视化实验表明,MnO2包覆对多硫化物的溶解有明显的阻断作用。

Uniform manganese dioxide(MnO2) layer was in-situ generated on the surface of CMK-3/S composite material by redox reaction of potassium permanganate(KMnO4) and sulfur(S),and the MnO2@CMK-3/S composite was used as a cathode material for lithium-sulfur batteries. MnO2@CMK-3/S composite with 70% S content was obtained by reacting different mass of KMnO4 with CMK-3/S(S content:80 wt%),extra S was removed with ethanol. Compared with CMK-3/S composites without MnO2 coating,the surface of MnO2@CMK-3/S composites became rougher. Electrochemical analysis shows that after 300 cycles at 0.5 C rate,the discharge specific capacity of the MnO2@CMK-3/S composite is 410.6 mAh·g-1,with 0.16% per cycle of the capacity decay rate and over 98% of the coulomb efficiency. Electrochemical impedance spectroscopy and visualization experiment has demonstrated that MnO2 coated CMK-3/S composites obtain higher charge transfer efficiency and can block the solution of lithium polysulfides.