A LiODFP-Derived Multifunctional Interphase Enables Chemo-Mechanical Stability and Fast Interfacial Kinetics in Sulfide-Based All-Solid-State Batteries.

The lithium argyrodite-type electrolyte exhibits excellent ion transport properties for all-solid-state batteries (ASSBs). However, their practical implementation is limited by poor cycle stability, arising from the coupled chemo-mechanical degradation. To address these issues, we developed an effective interfacial engineering strategy by constructing the lithium difluoro(bisoxalato)phosphate (LiODFP)-derived conformal LiF/fluorophosphate-rich layer on the Li5.5PS4.5Cl1.5 (LPSC1.5) surface. The multifunctional interface layer acts as an electron-blocking barrier to suppress parasitic interfacial oxidation, and as a bridging agent to fill interparticle voids in composite cathodes, thereby reinforcing chemo-mechanical integrity during cycling. Consequently, the LiIn|LPSC@1%LP|NCM83-based cells retain 90% of their initial capacity after 2000 cycles at 1 C and 86% after 800 cycles at 2 C, enabling the ultra-stable operation at high-rate capabilities. It provides further insights into the chemical-mechanical coupling failure evolution at the electrolyte/cathode interface, and extends the electrolyte-centered interfacial functionalization engineering strategy for high-energy solid-state energy storage.