MoN/MoO_(2)复合改性隔膜的制备及其锂硫电池性能

Preparation of MoN/MoO_(2) modified separator and its lithium-sulfur battery performance

为增强锂硫电池正极的电子传输能力并减小其电化学极化,采用静电纺丝、高温煅烧结合电沉积法制备了MoN单晶纳米纤维负载MoO_(2)纳米片的异质复合材料。研究了MoN纳米纤维的相组成、形貌和结构特征,发现MoN单晶纳米纤维的形成是高温氮化和碳化反应共同作用的结果,并分析了可能的反应机制。进一步采用电沉积法在MoN单晶纳米纤维表面制备MoO_(2)纳米片,通过调控电沉积时间,获得了不同MoO_(2)负载量的MoN/MoO_(2)复合材料,研究了MoN/MoO_(2)异质复合材料对多硫化锂的催化转化能力。最后将催化性能优化的MoN/MoO_(2)复合材料抽滤至聚丙烯隔膜表面作为改性隔膜组装锂硫电池。结果表明:组装的电池在0.2 C的放电倍率下可获得高达1263 mA·h/g的初始容量,而当放电倍率为1 C时的初始放电容量为990 mA·h/g,经1000次循环后仍可保持536 mA·h/g,对应于每圈容量衰减率仅为0.046%,说明MoN/MoO_(2)修饰的功能化隔膜可有效提升锂硫电池的电化学性能。

To enhance the electronic transmission capacity of the cathodes in lithium-sulfur batteries and reduce electrochemical polarization,MoN single crystal nanofibers loaded with MoO_(2) nanosheets were prepared through electrospinning,high temperature nitridation and electrodeposition methods successively.The phase composition,morphology and structure characteristics of MoN single crystal nanofibers were first investigated comprehensively.It is noticed that the formation of MoN single crystal nanofibers was due to the combination of nitridation and carbothermal reduction reaction.A possible reaction mechanism was also proposed based on the experimental results.Furthermore,MoO_(2) nanosheets have been prepared on the surface of MoN single crystal nanofibers by electrodeposition method,with the loading amount adjusted by controlling the electrodeposition time.The catalytic conversion ability of MoN/MoO_(2) composites on lithium polysulfides was also investigated through the electrochemical performance of Li_(2)S_(6) symmetric cells and Li 2S potentiostatic nucleation experiment.After vacuum filtered the optimized MoN/MoO_(2) composites to the surface of the polypropylene separator,the assembled lithium sulfur battery equipped with MoN/MoO_(2) functionalized separator exhibited an initial capacity of 1263 mA·h/g under the discharge rate of 0.2 C.Moreover,the initial discharge capacity of the above battery was 990 mA·h/g when the discharge rate reached 1 C.After 1000 cycles,it could still maintain the capacity of 536 mA·h/g,corresponding to the capacity decay of only 0.046% per cycle.This indicates that the MoN/MoO_(2) functionalized separator could effectively improve the electrochemical performance of lithium sulfur batteries.