Tailoring Sulfide Particle Size for All‐Solid‐State Lithium Metal Batteries

ABSTRACT The precise control of sulfide solid electrolyte (SSE) particle size distribution is crucial for constructing efficient ion‐conducting networks in composite cathodes of all‐solid‐state lithium metal batteries (ASSLBs). This work systematically investigates the effects of key particle size parameters (D 10 , D 50 , D 90 ) of Li 6 PS 5 Cl SSE on battery performance through controlled mechanical grinding. In this study, the optimal SSE particle size composition enables exceptional electrochemical performance of ASSLB: a high reversible capacity of 202.2 mAh/g at 0.25C, superior rate capability (76% capacity retention of 5C/0.25C), and outstanding cyclability (81.5% and 80% capacity retention after 4000 cycles at 3C and 5C, respectively). Microstructural analysis indicates that the optimized SSE particle configuration, when 7.3 ≤ D 50Cathode /D 50SSE and 2.0 ≤ D 90Cathode /D 90SSE ≤ 3.5, forms a hierarchical ion‐conducting network. In this configuration, the fine particles of SSE in the composite cathode can effectively fill the cathode gaps, while the medium‐sized particles can provide rapid ion transport channels, resulting in excellent rate performance and reversible capacity. Larger electrolyte particles will lead to insufficient interfacial contact and “island‐like” ion transport paths. Additionally, excessively lowering D 90 will also result in reduced battery performance (3.5 ≤ D 90C /D 90SE ). This study provides quantitative guiding principles for SSE particle engineering.