Stabilizing Solid Electrolyte-Anode Interface in Li-Metal Batteries by Boron Nitride-Based Nanocomposite Coating

Summary Solid-state Li-metal batteries are promising to improve both safety and energy density compared to conventional Li-ion batteries. However, various high-performance and low-cost solid electrolytes are incompatible with Li, which is indispensable for enhancing energy density. Here, we utilize a chemically inert and mechanically robust boron nitride (BN) film as the interfacial protection to preclude the reduction of Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) solid electrolyte by Li, which is validated by in situ transmission electron microscopy. When combined with ∼1–2 μm PEO polymer electrolyte at the Li/BN interface, Li/Li symmetric cells show a cycle life of over 500 h at 0.3 mA·cm −2 . In contrast, the same configuration with bare LATP dies after 81 h. The LiFePO 4 /LATP/BN/PEO/Li solid-state batteries show high capacity retention of 96.6% after 500 cycles. This study offers a general strategy to protect solid electrolytes that are unstable against Li and opens possibilities for adopting them in solid-state Li-metal batteries.