Metallic Li is the ultimate choice for the anode of lithium batteries. However, the adverse effect retards the commercialization of Li-metal batteries (LMBs). Herein, by using Cu(NO3)2 to regulate the solvation behavior of the ester-based electrolyte without fluoroethylene carbonate (FEC), the properties of Li|NCM811 are improved evidently. The solvation degree and oxidation stability of the electrolyte are increased. The solvated NO3- and marginalized PF6- promote the formation of an inorganic-rich solid electrolyte interphase (SEI) film on the anode, effectively protecting the lithium metal. The voltage decay and the dissolution of transition metals in the Li|NCM811 cell are significantly suppressed. The cell exhibits a capacity retention as high as 95.73% after 600 cycles at room temperature and outstanding cycle performance for wide temperatures (0 and 50 °C). The cell also shows impressive cycle performance even under rigorous conditions. Our research elucidates the role of Cu(NO3)2 from the perspective of the solvation behavior and provides a new strategy for the application of nitrates in ester-based electrolytes for LMBs.
Keywords: Cu(NO3)2 additive; Li-metal battery; SEI; high stability; solvation behavior.