Retuning Solvating Ability of Ether Solvent by Anion Chemistry toward 4.5 V Class Li Metal Battery

Abstract Ether‐based electrolytes have good compatibility for lithium metal, which is widely used in lithium metal batteries (LMBs). However, the electrolyte is not suitable for high voltage (>4.0 V) due to its poor anti‐oxidation behavior. Herein, an anion chemistry strategy is designed for a typical 1,2‐dimethoxyethane (DME)‐based electrolyte with 1 m lithium bis(fluorosulfonyl)imide (LiFSI), by using nitrate anion (NO 3 − ) with a high donor number (DN) value to regulate the coordination of DME and FSI – . It is evidenced that the interaction between them is weakened due to the competitive advantage of NO 3 − , therefore a weakly solvating electrolyte is achieved. It promotes the formation of an inorganic‐rich passivation layer on the cathode and facilitates the de‐solvation process, thus it is suitable for high voltage even at 4.5 V. The anion‐regulated weakly solvating electrolyte (ARWSE) designed here is different from the high‐concentration electrolyte (HCE), localized HCE, and WSE which are of high cost and complexity. The ARWSE is demonstrated to be an adjustable electrolyte system, effectively improving the interfacial chemistry of LMBs.