Highly Safe All-Solid-State Lithium Metal Battery Enabled by Interface Thermal Runaway Regulation Between Lithium Metal and Solid-State Electrolyte

All-solid-state (ASS) Li-metal batteries are regarded as promising energy-storage devices due to their high energy density and improved safety. Recently, the interface thermal runaway issues between reactive Li-metal and solid-state electrolytes (SSEs) have attracted increasing attention, but it has been less studied. Here, using in situ high-resolution thermal imaging, a significant stress-release period before the interface catches fire and burns between Li metal and Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) SSE is found that can provide opportunities for early thermal runaway warning for the batteries. Further, a highly safe ASS Li-metal battery without external pressure package is reported by constructing a stable heterogeneous interface layer (HIL) consisting of ALD-coated aluminum oxide and PECVD-deposited amorphous silicon (a-Si), which significantly reduces the interface exothermic reaction and suppresses the interface thermal runaway both theoretically and experimentally. The ASS Li-metal symmetric battery shows a long cycling stability both at RT and high temperature over 150 °C being at least 8-times higher than that of the one without HIL. The assembled Li-CO 2 battery is capable of 100 stable cycles with <3.2 V low charge potential at 500 mAg −1 at 150 °C. This work paves a way for the development of the next-generation safe and high-energy lithium batteries.