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

Abstract

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_1.6Mn_1.6O₄ (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 LiNi_0.8Co_0.1Mn_0.1O₂ (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.