Precise Lithiation Activation Breaks through Rate Performance Limits of Microsilicon All-Solid-State Batteries

Microsilicon (micro-Si) anode offers a cost-effective and stable alternative to lithium metal in sulfide all-solid-state batteries (ASSBs), but the poor rate performance hinders its application in electric vehicles. Here, we investigate the kinetic limitations governing the rate performance of micro-Si ASSBs. Electrochemical analysis identifies large lithiation overpotential and restricted delithiation capability as the key rate-limiting factors. The quantitative electrochemical characterizations and modeling attribute the kinetic limitations to an intrinsic "lithiation activation" characteristic, and demonstrate that the initially low electronic conductivity leads to the large lithiation overpotential, while the initially poor lithium diffusion coefficient restricts the delithiation capability. Based on these insights, we propose a precise prelithiation strategy to activate the micro-Si anode, achieving a significant improvement in delithiation capability with a capacity retention of 80.1% at 1C in the full cell. This study provides critical mechanistic insights and a quantitative prelithiation strategy for designing high-rate-performance micro-Si anodes in sulfide ASSBs.