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

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 (D₁₀, D₅₀, D₉₀) of Li₆PS₅Cl 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 D₉₀ will also result in reduced battery performance (3.5 ≤ D_90C/D_90SE). This study provides quantitative guiding principles for SSE particle engineering.