Li‐ion Exchange‐Driven Interfacial Buffer Layer for All‐Solid‐State Lithium Metal Batteries

The goal of achieving batteries with high energy density and high safety profile has been a driving force in developing all‐solid‐state lithium metal batteries (ASSLMBs). However, the complex issues arising from the interfacial interaction between lithium anode/cathode and solid‐state electrolytes (SSE) have hindered the progress of ASSLMBs. This study presents a strategy for constructing an organic/inorganic buffer layer via employing Li‐ion exchanging chemistry of H 1.6 Mn 1.6 O 4 (HMO) with a flexible matrix of polyethylene oxide (PEO). The buffer layer shows a remarkable ion conductivity of 3.21 × 10 −4 S cm −1 at 25 °C originating from the exceptional Li + ‐H + ion exchange capability of HMO. This PEO/HMO buffer layer not only establishes an intimate physical contact between the Li anode/cathode and the SSE but also functions as a dynamic Li + transfer station to facilitate Li + movement through the interfaces improving interfacial stability. By pairing with cathodes of LiFePO 4 (LFP) and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), the ASSLMBs feature high‐rate capability and stable cycling performance with low polarization. This marks the utilization of HMO as a superior interfacial material to replace conventional lithium salts, with improved ion transport, decreased polarization, and enhanced overall performances. This constitutes a significant advancement toward the next‐generation energy storage solutions for ASSLMBs.