Reactive and Adaptive Interphase Engineering for Regulating Interfacial Li ⁺ Transport in Li ₂ OHCl Antiperovskite Solid‐State Batteries

ABSTRACT Lithium‐rich antiperovskite solid electrolytes, exemplified by Li ₂ OHCl, are promising for all‐solid‐state lithium metal batteries. However, their practical implementation is severely constrained by interfacial instability with lithium metal, where nonuniform Li ⁺ flux and mechanical degradation induce dendrite growth. Herein, we introduce a MoS ₂ ‐enabled adaptive interlayer on Li ₂ OHCl that stabilizes the Li/SSE interface by regulating interfacial Li ⁺ transport. MoS ₂ establishes a dual‐regulated Li ⁺ transport mechanism, in which the intrinsically Li ⁺ migration barrier in the MoS ₂ bulk acts as a current‐limiting regulator, while the substantially lower diffusion barrier along the MoS ₂ surface enables rapid lateral Li ⁺ redistribution. This synergistic “current‐limiting and fast‐transfer” effect effectively homogenizes interfacial Li ⁺ flux and suppresses localized ion accumulation that initiates lithium dendrites. Meanwhile, electrochemical reactions between MoS ₂ and lithium metal form a composite interphase composed of lithiophilic Li ₂ S and conductive Mo, which collectively lower the lithium nucleation overpotential, accelerate interfacial charge transfer, and stabilize the deposition front. Consequently, lithium‐metal symmetric cells exhibit stable cycling for over 1000 h with prolonged short‐circuit time, and all‐solid‐state lithium‐metal full cells demonstrate markedly improved cycling stability. This work establishes interfacial ion‐transport regulation as a design principle for stabilizing lithium‐metal anodes and provides a strategy for interface engineering in antiperovskite solid‐state batteries.