CoS₂@SC modified separator for high-performance lithium-sulfur batteries: suppression of polysulfide shuttling

Due to their high energy density and cost-effective electrode materials, lithium sulfur batteries (LSBs) have been considered as one promising candidate of energy devices. However, the practical application is impeded by the shuttle effect of lithium polysulfides and slow redox kinetics of electrode. Here, we report a successful synthesis of CoS₂@SC composite material via in-situ growth and sulfuration pyrolysis method and prepared CoS₂@SC modified separator. The carbon matrix derived from sucrose carbonization with a porous structure promotes the uniform distribution of active adsorption sites. According to Lewis acid–base interaction, CoS₂@SC separator exhibits strong chemisorption of lithium polysulfides, reducing the loss of active material during cycling. Furthermore, the enhanced wettability of the CoS₂@SC separator with the electrolyte accelerates the ion transfer, improving the reaction kinetics. Compared with the blank separator, the cell with CoS₂@SC separator has an initial specific capacity of 1135.5 mAh g⁻¹ and notably, the capacity decay rate of the modified battery is only 0.052% per cycle after 800 long cycles at 0.5 C. This unique attribute ensures enhanced stability and durability of the battery system. Consequently, LSBs with the CoS₂@SC separator exhibit an improved electrochemical performance.鉴于锂硫电池（LSBs）具备高能量密度且电极材料成本低廉，其被视作极具应用前景的储能器件之一。然而，多硫化锂（lithium polysulfides）的穿梭效应（shuttle effect）与电极氧化还原动力学（redox kinetics）缓慢的问题，掣肘了其实际应用。本研究通过原位生长硫化热解法（in-situ growth and sulfuration pyrolysis method）成功合成了CoS₂@SC复合材料，并制备了CoS₂@SC改性隔膜。由蔗糖碳化（sucrose carbonization）得到的多孔碳基质，可促进活性吸附位点均匀分布。基于路易斯酸碱相互作用（Lewis acid–base interaction），CoS₂@SC隔膜对多硫化锂展现出极强的化学吸附（chemisorption）能力，能够降低循环过程中活性物质的损耗。此外，CoS₂@SC隔膜与电解液（electrolyte）的润湿性（wettability）得到提升，可加速离子传输，优化反应动力学。与空白隔膜相比，搭载该改性隔膜的电池初始比容量（specific capacity）可达1135.5 mAh g⁻¹；尤为关键的是，在0.5 C倍率下经过800次长循环（cycle）后，该改性电池的容量衰减率（capacity decay rate）仅为每循环0.052%。这一独特优势保障了电池系统的稳定性与耐久性得以提升。因此，搭载CoS₂@SC隔膜的锂硫电池电化学性能得到显著改善。