Self‐Lithiation Homogenized Electron‐Ion Distribution Interlayer for All‐Solid‐State Li Metal Batteries

Abstract All‐solid‐state Li metal batteries (ASSLMBs) with sulfide solid‐state electrolytes (SSEs) are anticipated to be the next‐generation energy storage technology, potentially providing high energy density meanwhile enhancing safety. However, the complicated solid–solid interface between SSEs and Li metal leads to contact issues and Li dendrite. In this contribution, a multifunctional hierarchical silicon and carbon (H–Si/C) structure design is proposed as an interlayer between SSEs and the Li metal. A homogeneous electron‐ion transport network is established through the Li–Si alloy formed by Si self‐lithiation and the nano‐carbon layer on the surface, achieving compact interfacial contact and Li dendrite‐free interlayer. The ASSLMBs assembled with H–Si/C interlayer exhibit 70.28% capacity retention after 800 cycles at 0.5C. In addition, the H─Si/C interlayers can efficiently match with the high‐loading cathode, maintaining a capacity retention of 80.9% after 200 cycles under an areal capacity of 3.4 mAh cm −2 , and working well even at the ultra‐high loading of 6.9 mAh cm −2 . This finding provides novel insights to understand the design principles of the anode interface and is crucial for achieving high safety and long lifespan for ASSLMBs.