Abstract:

Lithium-sulfur batteries have become a promising energy storage device due to the advantages of high theoretical energy density and high theoretical specific capacity. However, the practical application has been impeded by the insulation of the active material sulfur and the lithium polysulfide, the considerable volume expansion effect during cycling, and the “shuttle effect” caused by the dissolution of polysulfide. Herein, the hollow sulfur spheres (HS) were synthesized by low temperature liquid phase method, while the nanoflower MoS₂/reduced graphene oxide (MoS₂/rGO) was prepared by the hydrothermal method. Then, MoS₂/rGO was coated on the surface of HS to obtain HS-MoS₂/rGO composite cathode material. The crystal structure and morphology of the composites were characterized by XRD, SEM, TEM and XPS, while the electrochemical performance of the HS-MoS₂/rGO and HS-rGO cathodes was tested by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge measurements. The results indicate that MoS₂/rGO shows strong polysulfide adsorption capability and high catalytic activity to limit the shuttle of polysulfides. Meanwhile, the unique hollow structure of the sulfur spheres can alleviate volume expansion to maintain the structural stability. Consequently, the HS-MoS₂/rGO cathode achieves excellent rate performance and cycling stability of lithium-sulfur batteries.

Key words: nanomaterials, adsorption, catalysis, hollow sulfur spheres, molybdenum disulfide, cathode, lithium-sulfur batteries

摘要：

锂硫电池凭借高理论能量密度和高理论比容量的优势成为极具发展前景的储能设备。然而，单质硫和硫化锂的绝缘性、放电过程中产生的体积膨胀及多硫化物溶解导致的“穿梭效应”等问题，限制其商业化发展。为解决上述问题，采用低温液相法合成中空硫球（HS），通过水热法制备纳米花状MoS₂/还原氧化石墨烯（MoS₂/rGO），随后将MoS₂/rGO包覆在HS表面获得HS-MoS₂/rGO复合正极材料。利用XRD、SEM、TEM、XPS等对该材料的晶体结构、形貌等性质进行表征，采用循环伏安法、交流阻抗法以及恒流充放电对复合正极进行电化学测试。研究表明，MoS₂/rGO对多硫化物具有强吸附能力和高催化活性，能够有效限制多硫化物的穿梭；同时硫球的中空结构能够缓解体积膨胀，保持正极结构稳定。HS-MoS₂/rGO正极展现出优异的倍率性能和循环稳定性。

关键词: 纳米材料, 吸附, 催化, 中空硫球, 二硫化钼, 正极, 锂硫电池