Stable Cycling of Solid-State Lithium–Sulfur Batteries by In Situ Construction of Li ₃ PO ₄ /LiF-Enhanced Interface

Lithium-sulfur (Li-S) batteries are considered to be one of the most promising energy storage batteries due to their high energy density. Sulfurized polyacrylonitrile (SPAN) receives increasing interest as a competitive cathode material for sulfur can be trapped in pyrolyzed polymer backbones via the formation of chemical bonds. However, Li-S batteries with SPAN suffer from dendrite growth and electrically isolated Li loss during cycling, which presents a significant safety hazard and short lifespan. The construction of a robust solid electrolyte interface (SEI) can effectively inhibit the formation of Li dendrites. In this study, we construct a Li₃PO₄/LiF-rich SEI by introducing lithium fluorophosphate (LiDFP) additive and in situ polymerization of electrolyte simultaneously. The gel polymer electrolyte is in situ generated with encapsulation of the organic liquid component in a poly(vinylidene carbonate) skeleton, resulting in an oxidative stability up to 4.8 V (vs Li/Li⁺). The in situ/ex situ microscopic observation reveals a dense Li deposition behavior. A steady cycling exceeding 1500 h with a low voltage hysteresis is achieved for symmetric Li||Li batteries at a current density of 0.1 mA cm⁻². Furthermore, a decent capacity retention and approaching 100% Coulombic efficiency are present for the Li-S battery with a SPAN cathode over long-termcycling. This study offers a valuable reference for the construction of advanced solid-state Li-S batteries.