Space charge regulation for ultra-stable all-solid-state lithium batteries by engineering of argyrodite electrolyte

Abstract Space charge layer (SCL) formation at cathode–electrolyte interfaces severely limits the performance of sulfide-based all-solid-state Li batteries (ASSLBs). While conventional strategies focus on cathode modifications, we propose a novel electrolyte-centric approach by incorporating WO3 into argyrodite electrolyte (Li5.49P0.99W0.01S4.47O0.03Cl1.5). This design achieves a record-high ionic conductivity of 13.5 mS cm−1 (at 25°C) among O-substituted argyrodites. When paired with a LiNi0.92Co0.05Mn0.03O2 cathode, the full cell delivers 217 mAh g−1 at 0.1C, and retains 92% capacity after 1000 cycles (1C) and 80% capacity after 5000 cycles (5C), far outperforming the cells with frequently-used Li5.5PS4.5Cl1.5 argyrodite electrolytes (200 mAh g−1 at 0.1C; failure at 408 cycles at 1C). Mechanistic studies reveal that WO3 substitution modulates the electrolyte’s chemical potential to align with the cathode, reducing interfacial energy barriers and inhibiting Li+ depletion, and then significantly suppresses SCL effects. This work pioneers an electrolyte engineering strategy to mitigate SCL issues, enabling high-energy-density, ultra-stable ASSLBs.