Multifunctional heterostructured CoS2@Co3O4 nanosheets synergistically enhance polysulfide adsorption and conversion in lithium-sulfur batteries

Abstract

The practical application of lithium-sulfur (Li-S) batteries faces numerous challenges, primarily due to the shuttle effect of soluble lithium polysulfides (LiPSs) and the sluggish electrochemical reaction kinetics during their conversion to Li₂S, resulting in poor cycling performance. To address these issues, this study employed a vapor deposition technique to in situ construct a CoS₂@Co₃O₄ heterostructure with superior interfacial properties on a Co₃O₄ substrate, followed by crosslinking and optimization with reduced graphene oxide (rGO). Density functional theory (DFT) calculations reveal for the first time that the incorporation of S effectively modulates the d-band center of Co, which not only enhances the chemical adsorption capability of the heterointerface toward lithium polysulfides but also optimizes the catalytic pathway for sulfur species conversion. Comprehensive experimental results and theoretical calculations confirm that the CoS₂@Co₃O₄ heterostructure exhibits multiple advantages, including strong adsorption capability, high catalytic activity, rapid Li⁺ transport efficiency, and excellent electrical conductivity. The CoS₂@Co₃O₄ heterostructure not only significantly suppresses the LiPSs shuttle effect but also greatly accelerates the electrochemical reaction kinetics of LiPSs and Li₂S. Compared to materials composed solely of CoS₂ or Co₃O₄, the CoS₂@Co₃O₄ heterostructure demonstrates synergistically enhanced electrochemical performance in Li-S batteries. At a current density of 2C, a representative Li-S battery achieves nearly 100 % Coulombic efficiency, with a reversible specific capacity of 827 mAh g⁻¹ retained after 1000 cycles, corresponding to a capacity decay rate of only 0.007 % per cycle. Even under high sulfur loading conditions (5.1 mg cm⁻²), the battery maintains stable cycling performance. This work provides novel insights and directions for designing multifunctional heterostructures with synergistic effects for applications in lithium-ion batteries and catalytic fields.