四硫化钒/钼复合石墨烯基锂硫电池正极材料电化学性能研究

Study on Electrochemical Performance of Tetrasulfide Vanadium/Molybdenum Composite Graphene-Based Cathode Materials for Lithium-Sulfur Batteries

摘要: 为了提高锂硫电池电化学性能，针对其面临的多硫化锂穿梭问题，本文以还原氧化石墨烯(rGO)为生长基质，结合四硫化钒(VS₄)与多价态钼(Mo)带来的吸附性能及硫空位修复优势，采用水热法制备了复合材料VS₄/Mo@rGO作为锂硫正极材料中的载体组分，它不仅有更多的活性点位缓解穿梭效应，还能减少VS₄本征硫空位的体积膨胀，为克制电解液中多硫化锂的溶解及极片失效粉化提供了较大帮助。通过熔融扩散法载硫后，该正极在负载量8 mg cm⁻²、0.3 C时首次放电915 mAh g⁻¹，在10 mg cm⁻²负载电极的倍率测试中，其放电比容量中值仍有513 mAh g⁻¹，整体倍率性能远高于rGO/S和CB@rGO/S。

Abstract: In order to improve the electrochemical performance of lithium-sulfur batteries, in view of the problem of lithium polysulfide shuttle, this paper uses reduced graphene oxide (rGO) as the growth substrate, combined with the adsorption properties and sulfur vacancy repair advantages brought by vanadium tetrasulfide (VS₄) and polyvalent molybdenum (Mo). The composite VS₄/ Mo@rGO was prepared by hydrothermal method as the carrier component in the lithium sulfur cathode material. It not only has more active sites to alleviate shuttle effect, but also can reduce the volume expansion of the intrinsic sulfur vacancy in VS₄, which provides a great help for controlling the dissolution of lithium polysulfide in the electrolyte and the failure powder of the electrode plate. After sulfur loading by melting diffusion method, the positive electrode discharged 915 mAh g⁻¹ for the first time when the load was 8 mg cm⁻², 0.3 C. The median discharge specific capacity of the electrode was still 513 mAh g⁻¹ when the load was 10 mg cm⁻², and the overall rate performance was much higher than that of rGO/S and CB@rGO/S.