EnhancedCycling Performance of High-Voltage Solid-StateLithium Batteries via In Situ Cathode–Electrolyte InterfaceConstruction

The [solvent-Li⁺] complex in poly(vinylidene fluoride) (PVDF)-based polymer electrolytes enables fast ion conduction but also makes it difficult to be compatible with high-voltage cathodes. Here, we demonstrate that the residual amount of solvent significantly affects the ion transport properties and interfacial stability of the electrolyte. In LiNi_<i>x</i>Co_<i>y</i>Mn_<i>z</i>O₂/Li batteries, a nonuniform and unstable double-layer CEI is formed due to the decomposition of desolvated NMP molecules and lithium salts, resulting in aggravated polarization and rapid capacity decay. Thus, lithium difluorophosphate (LDFP) is introduced as a sacrificial additive into the composite cathode to construct in situ a robust protective CEI layer. Computational and experimental results indicate that its strong adsorption on the NCM surface helps to form a uniform inorganic-rich interface and passivate the catalytic sites of NCM, thereby achieving stable long-term cycling of solid-state batteries.