Hierarchical catalysis tailoring Li2S2 solid-state dissociation for high-energy lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) exhibit exceptional theoretical capacity through solid-liquid-solid sulfur conversion in ether-based electrolytes, positioning them as next-generation energy storage candidates. However, their practical implementation faces two fundamental challenges: (1) sluggish redox kinetics arising from the high dissociation energy barrier (>1.5 eV) of insulating Li2S2/Li2S during solid-state conversion, and (2) severe capacity degradation caused by polysulfide shuttling under high sulfur loading. To address these issues, a CoS2-modified TiS2-Ti3C2Tx heterojunction catalyst (CoS2@TST) through interfacial engineering was designed. Density functional theory (DFT) calculations reveal that the CoS2 active sites significantly reduce the Li2S2 dissociation barrier to 0.40 eV, while the conductive Ti3C2Tx matrix ensures rapid electron transfer. In-situ Raman spectroscopy demonstrates the heterojunction's dual functionality: TiS2 chemically anchors lithium polysulfides (LiPSs) and surface functional groups catalyze their conversion, effectively suppressing shuttle effects. The optimized LSBs with CoS2@TST interlayers achieve an ultralow capacity decay rate of 0.031% per cycle over 500 cycles at 2 C. Notably, under practical conditions of 9.44 mg cm−2 sulfur loading, the battery delivers an areal capacity of 6.21 mA h cm−2, representing a critical advancement in balancing energy density and commercial viability.