In Situ Reconstruction and Anion Blocking Interphase Strategy for High‐Performance Silicon‐Based Anodes in Liquid and Solid‐State Batteries

Abstract The silicon (Si) is one of the most promising anodes for next‐generation lithium‐ion batteries, but addressing the interfacial side reactions caused by volume expansion remains a key challenge. In this study, a composite of nano‐Si with covered and interstitial LaF₃ (Si@LaF₃) is synthesized via a low‐cost and scaleable ball milling process. Upon lithiation, the LaF₃ layer on the nano‐Si surface in situ reconstructs into an interface containing LiF and La. The LiF interface promotes the uniform formation of LiF‐rich solid electrolyte interphase (SEI), and La grains can block the penetration of electrolyte anions into an electrode, inducing the stable and thin SEI on the Si@LaF₃ anode. Additionally, the interstitial LaF₃ particles facilitate the migration of Li⁺ into Si and reduce local expansion stress in the Si anode by alleviated electrochemical sintering. Compared to micron‐ and nano‐Si anodes, the Si@LaF₃ anode demonstrates higher specific capacity and superior cycling stability. The Si@LaF₃||‐LiFePO₄ full battery retains a specific capacity of 125.1 mAh g⁻¹ after 200 cycles at 0.35 C, while the Si@LaF₃/graphite anode in all‐solid‐state battery maintains a capacity of 491 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹. This study provides new insights on the commercialization of Si‐based anodes and solid‐state batteries.