S@FeS₂ Core–Shell Cathode Nanomaterial for Preventing Polysulfides Shuttling and Forming Solid Electrolyte Interphase in High‐Rate Li–S Batteries

Lithium-sulfur (Li-S) battery is a potential next-generation energy storage technology over lithium-ion batteries for high capacity, cost-effective, and environmentally friendly solutions. However, several issues including polysulfides shuttle, low conductivity and limited rate-capability have hampered its practical application. Herein, a new class of cathode active material with perfect core-shell structure is reported, in which sulfur is fully encapsulated by conductivity-enhancing FeS₂ (named as S@FeS₂), for high-rate application. Surface-stabilized S@FeS₂ cathode exhibits a stable cycling performance under 2 - 20 times higher rates (1-2 C, charged in 30-60 min) than standard rates (e.g., 0.1-0.5 C, charged in 2-10 h), without polysulfides shuttle event. Surface analysis results reveal the unprecedented formation of a stable solid electrolyte interphase (SEI) layer on S@FeS₂ cathode, which is distinguished from other sulfur-based cathodes that are not able to form the SEI layer. The data suggest that the prevention of polysulfides shuttling is owing to the surface protection effect of FeS₂ shell and the SEI layer formation overlying core-shell S@FeS₂. This unique and potential material concept proposed in the present study will give insight into designing a prospective fast charging Li-S battery.