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 H1.6Mn1.6O4 (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 LiFePO4 (LFP) and LiNi0.8Co0.1Mn0.1O2 (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. [ABSTRACT FROM AUTHOR]