Stable all-solid-state lithium metal batteries with Li₃N-LiF-enriched interface induced by lithium nitrate addition

All-solid-state lithium metal batteries (ASSLMBs) show great potential for high energy density as well as enhanced safety. However, the practical application is still hampered by uncontrollable dendrite growth and limited cycling stability. Herein, a stable Li₃N-LiF-enriched interface is in-situ induced between poly (ethylene oxide) (PEO)-based solid electrolyte and Li anode by introducing lithium nitrate (LiNO₃). Combining surface characterizations and molecular dynamics simulations, firstly, it reveals that the addition of LiNO₃ facilitates the decomposition of lithium bis(trifluoromethylsulfonyl) imide (LiTFSI) to preferentially form LiF. The Li₃N-LiF-enriched interface greatly improves interface contact between solid electrolyte and Li anode, leading to homogenous Li deposition. With LiNO₃ addition, the critical current density of PEO-based electrolyte can be enhanced to high value of > 0.9 mA cm^–2. Meanwhile, all-solid-state LMBs coupled with LiFePO₄ cathode show superior cycling stability and Coulombic efficiency (CE), especially, the initial CE is up to 94.12 % at 0.5 C. Even paired with high-potential NCM cathode, promoted electrochemical performances can be achieved, with 91.4 % capacity retention after 200 cycles at 0.3 C. What's more, this work illustrates the importance of interface modification in ASSLMBs from the perspective of the relationship between impedances and overpotentials.