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

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 (Li_5.49P_0.99W_0.01S_4.47O_0.03Cl_1.5). 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 LiNi_0.92Co_0.05Mn_0.03O₂ 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 Li_5.5PS_4.5Cl_1.5 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.