Stable Cycling of High‐Voltage Ni‐Rich Lithium Metal Batteries through Solvation Structure Regulation by Functional Electrolyte Co‐Additives

Ether-based electrolytes with exceptional lithium metal compatibility and low-temperature performance are expected to be the alternative to conventional ester-based electrolytes for next-generation lithium metal batteries. However, the poor oxidation stability of ether solvent (<4.0 V vs Li⁺/Li) with high-voltage cathode materials prevents their further application. Herein, a localized high concentration electrolyte approach is demonstrated based on the simultaneous introduction of fluoroethylene carbonate and lithium nitrate (LiNO₃) as synergistic additives in 1,2-dimethoxyethane with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether as a diluent. The solvated structure of Li⁺ is regulated and the electrode-electrolyte interfaces are elaborately designed, which effectively inhibits the growth of lithium dendrites and protects cathode structure from being damaged. Finally, the Li||LiNi_0.8Mn_0.1Co_0.1O₂ (Li||NCM811) cell using modified electrolyte exhibits outstanding cycling stability at 5C, 4.4 V, delivering 71.3% capacity retention after 1000 cycles. The assembled 2 Ah Li||NCM811 pouch cell delivers a high energy density of 350 Wh kg^-1 and a high-capacity retention of 93.7% after 70 cycles at 1C, 4.4 V.