Lithium Nitrate-Based Electrolyte for High-Performance and High-Safety Li-Ion Batteries

Lithium hexafluorophosphate (LiPF₆) is widely employed as the primary lithium salt in commercial lithium-ion battery (LIB) electrolytes owing to its high solubility in organic solvents, excellent electrochemical stability, and favorable ionic conductivity. However, its pronounced hygroscopicity and limited thermal stability significantly compromise the cycling performance and overall safety of LIBs. In this study, lithium nitrate (LiNO₃) is employed as the primary salt due to its superior thermal and moisture stability, low cost, and environmentally benign characteristics, all of which collectively contribute to enhanced electrochemical stability, cost-effectiveness, and environmental sustainability of the electrolyte. Triethyl phosphate (TEP) is selected as the solvent for LiNO₃ based on its high donor number (DN) and intrinsic flame-retardant nature. Furthermore, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) is introduced as an inert cosolvent to regulate the Li⁺ solvation structure. The resulting electrolyte system (1 M LiNO₃ in TEP/TTE, 1:1 v/v, referred to as TT) demonstrates excellent compatibility with both graphite anodes and LFP cathodes, thereby supporting stable cycling performance. The Li||Graphite cell delivers a high initial Coulombic efficiency of 93.6% and maintains a stable capacity over 200 cycles. In parallel, the Li||LFP cell retains 100% of its initial capacity after 400 cycles, underscoring its outstanding cycling stability. This study provides meaningful insights into the design of LiNO₃-based electrolytes for advanced LIB applications, emphasizing their potential to improve electrochemical performance, safety, and environmental sustainability.