To enhance the electronic transmission capacity of the cathodes in lithium-sulfur batteries and reduce electrochemical polarization, MoN single crystal nanofibers loaded with MoO2 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, MoO2 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/MoO2 composites on lithium polysulfides was also investigated through the electrochemical performance of Li2S6 symmetric cells and Li2S potentiostatic nucleation experiment. After vacuum filtered the optimized MoN/MoO2 composites to the surface of the polypropylene separator, the assembled lithium sulfur battery equipped with MoN/MoO2 functionalized separator exhibited an initial capacity of 1 263 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 1 000 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/MoO2 functionalized separator could effectively improve the electrochemical performance of lithium sulfur batteries.

lithium sulfur battery; heterostructure; electrospin; modified separator; shuttle effect