Electron Localization at In‐on‐Li Antisites Enables High‐Current‐Density Compatibility of Chloride Solid Electrolytes with Lithium Metal

Lithium‐metal all‐solid‐state batteries offer a pathway toward high‐specific‐energy storage but remain limited by instability at the solid‐state electrolyte (SSE)/Li interface. Fluorinated chloride solid electrolytes exhibit improved kinetic stability toward Li metal at low current densities (≤0.2 mA cm −2 ), but become increasingly susceptible to electron injection at high current densities (≥1 mA cm −2 ), leading to sustained reductive decomposition and interfacial degradation. Here, we develop LiCl‑deficient Li 3‑x InCl 5.2‑x F 0.8 solid electrolytes to regulate interfacial electron transport. LiCl deficiency generates Li vacancies preferentially at 4 g sites and lowers the barrier for In migration into these vacancies, thereby forming In‐on‐Li antisites. These antisite‐centered defect environments serve as electron‐localization centers that trap injected electrons, suppress long‐range electronic transport, and inhibit the reduction of In 3+ to metallic In. This electron‐localization mechanism promotes a self‐passivating interphase and markedly improves high‐current‐density compatibility with Li metal. The optimized Li 2.76 InCl 4.96 F 0.8 composition exhibits an ionic conductivity of 1.24 mS cm −1 , stable Li plating/stripping at 1.0–1.5 mA cm −2 , and durable full‐cell cycling with LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cathodes at 1 mA cm −2 . These findings establish LiCl‐deficiency‐induced electron localization as an atomic‐scale electronic regulation strategy for enabling high‐current‐density compatibility between chloride solid electrolytes and Li‐metal anodes, thereby advancing the development of high‐specific‐energy all‐solid‐state lithium‐metal batteries.