Fluoride-Rich Solid Electrolyte Membrane in Solid-State Li–S Batteries: Improvement of Lithium Cycle Stability and Shuttle Effects

Although employing solid polymer electrolytes (SPEs) in solid-state Li–S batteries (SSLSBs) is a promising approach to obtain both high energy density and safety, the actual cycle property is still rather unsatisfactory. In this work, by combining experiments and calculations, we revealed that a coupling effect between lithium polysulfides (LiPSs) and polyethylene oxide (PEO)-based SPEs was the cause of interfacial instability of the poor cyclelife of lithium anode in SSLSBs. In light of this, a fluorine-rich polymer perfluoropolyether alcohol (PFA) was introduced as an interfacial layer between the SPE and lithium anode. PFA decouples from LiPSs because of the shielding effect of F in PFA on the electron cloud of O and the spatial effect. As a result, the PFA interlayer plays a role in preventing corrosion of the lithium metal from LiPSs and the electrochemical decomposition of PEO-based SPEs. The PEO-based SSLSBs with PFA showed a discharge capacity of 627.4 mA h gS–1 after 100 cycles at 0.05 mA cm–2 and 60 °C. This work emphasized the significance of SPE decoupling from LiPSs in SSLSBs and provided a feasible guidance for the design of high-performance SSLSBs.