Unveiling the Critical Role of Ion Coordination Configuration of Ether Electrolytes for High Voltage Lithium Metal Batteries

Ethers with distinctive reduction stability are emerging as the promising solution to the issues of lithium (Li) metal anode. However, their inferior oxidation stability (<4.0 V vs. Li/Li+) cannot meet the ever-growing needs of high-voltage cathodes. Studies of ether electrolytes have been focusing on the archetype glyme structure with ethylene oxide moieties. Herein, we systematically vary the methylene units in the ether backbone and unveil the crucial effect of ion-ether coordination configuration on the electrolyte oxidation stability. The 1,3-dimethoxypropane (DMP, C3) molecule forms a unique six-membered chelating complex with Li+, whose stronger solvating ability suppresses undesired oxidation side reactions. In addition, the favored hydrogen transfer reaction between DMP and salt anion induces a dramatic enrichment of LiF (a total atomic ratio of 76.7%) on the cathode surface. As a result, the DMP-based electrolyte demonstrates stable cycling of nickel-rich cathodes under a high voltage of 4.7 V (87% capacity retention after 150 cycles). This study offers fundamental insights into rational electrolyte design with wide electrochemical stability window for developing high-energy-density batteries.