Ultra‐Thin Lithium–Phosphorus–Sulfur (LPS) Interfacial Electrolyte Layer for All‐Solid‐State Lithium Metal Battery with High‐Rate and High‐Areal‐Capacity Performance

To solve the challenging interfacial issues of all‐solid‐state lithium batteries (ASSLBs), a novel strategy to construct a nano‐scale lithium‐phosphorus‐sulfur (LPS) electrolyte film by atomic layer deposition (ALD) technique and to coat it on Li6PS5Cl (LPSCl) electrolyte is proposed and demonstrated for the first time. The modified LPS@LPSCl electrolytes exhibit excellent compatibility with both high‐voltage cathodes and pure lithium metal anode with enhanced ionic conductivity, much reduced electronic conductivity, and modified mechanical strength, which can fill the gaps in the base electrolytes after electrolyte pellet pressing and reduce interfacial defects in the composite electrolytes. The sulfide‐based ASSLBs, assembled with LPS@LPSCl, Al‐GL@NCM811 materials, and a lithium indium anode, achieves a high areal capacity of 10.6 mAh cm−2 at high‐temperature and high mass loading (60 °C, 51.9 mg cm−2). Additionally, LPS@LPSCl has high stability toward lithium metal, suppressing interfacial side reactions and improving physical contact, enabling charge and discharge testing at a high current density of 1.5 mA cm−2. This study demonstrates that the nano‐scaled film formation of sulfide solid‐state electrolytes can significantly reduce the polarization voltage of traditional double‐layer electrolytes toward lithium metal, and provide a new approach for interfacial modification in sulfide solid‐state batteries.