Highly Adhesive Li-BN Nanosheet Composite Anode with Excellent Interfacial Compatibility for Solid-State Li Metal Batteries

Solid-state lithium metal batteries (SSLMBs) are promising energy storage devices by employing lithium metal anodes and solid-state electrolytes (SSEs) to offer high energy density and high safety. However, their efficiency is limited by Li metal/SSE interface barriers, including insufficient contact area and chemical/electrochemical incompatibility. Herein, a strategy to effectively improve the adhesiveness of Li metal to garnet-type SSE is proposed by adding only a few two-dimensional boron nitride nanosheets (BNNS) (5 wt %) into Li metal by triggering the transition from point contact to complete adhesion between Li metal and ceramic SSE. The interface between the Li-BNNS composite anode and the garnet exhibits a low interfacial resistance of 9 Ω cm², which is significantly lower than that of bare Li/garnet interface (560 Ω cm²). Furthermore, the enhanced contact and the additional BNNS in the interface act synergistically to offer a high critical current density of 1.5 mA/cm² and a stable electrochemical plating/striping over 380 h. Moreover, the full cell paired with the Li-BNNS composite anode and the LiFePO₄ cathode shows stable cycling performance at room temperature. Our results introduce an appealing composite strategy with two-dimensional materials to overcome the interface challenges, which provide more opportunities for the development of SSLMBs.