Construction of a Fluoride-Free and High-Voltage Lithium Metal Battery with a Li3N/Li2O Heterostructure Solid Electrolyte Interface

Abstract

Currently, the design of lithium metal batteries primarily focuses on improving cycling stability by increasing the lithium fluoride (LiF) content in the interfacial layer. However, the extensive use of fluorides poses severe environmental concerns. In this study, a novel strategy is proposed to construct a Li₃N/Li₂O heterostructure via the in situ decomposition of lithium perchlorate (LiClO₄) and lithium nitrate (LiNO₃), replacing the role of LiF in the SEI. This unique heterostructure combines excellent lithium-ion transport capability with robust electronic insulation properties, effectively preventing electron tunneling phenomena. When paired with the NCM811 cathode, the Li||NCM811 full cell exhibits exceptional electrochemical performance, including outstanding charge–discharge capabilities under extreme temperatures. At 60 °C and 1C conditions, the battery retains 82.11% of its capacity after 500 cycles; at 25 °C and 1C, it maintains a capacity retention rate of 80.61% after 800 cycles. Furthermore, under practical application conditions (100 µm lithium anode, N/P ratio of 3.09, and a 1.5 Ah pouch cell), the fluorine-free lithium metal battery (LMB) retains 77.93% capacity after 100 cycles, demonstrating the superiority and practical value of this strategy.