Anion engineering in a single ether solvent electrolyte enables a 4.7 V high-voltage lithium metal battery

Recent electrolyte solvent design based on ether-based has shown promise in enhancing cycling performance of Li-metal batteries. However, they inherently low oxidation potential (<4.0 V) limits their application to high-voltage batteries. Here, we report an approach employing stepwise anion utilization from three Li salts in 1,2-dimethoxyethane (DME) solvent to enhance high-voltage stability. Through synergistic modulation with strongly coordinating lithium nitrate (LiNO₃) and lithium difluorophosphate (LiPO₂F₂), the electrolyte forms a weakly solvating structure characterized by a low coordination number (CN) at a conventional Li salt concentration. Anion participation in the solvation sheath initiates a stepwise decomposition process (LiNO₃→LiPO₂F₂→lithium bis(fluorosulfonyl)imide (LiFSI)) within the 4.0.4.5 V range, leading to the formation of an inorganic dual-layer CEI. This CEI suppresses DME decomposition at the interface and improves the high-voltage resistance of the electrolyte. This electrolyte exhibited superior performance compared to state-of-the-art electrolytes, enabling Li∥LiNi_0.8-Co_0.1Mn_0.1O₂ cells to cycle stably for over 500 cycles with 80.35% capacity retention at 1 C at 2.8–4.3 V. Moreover, it enabled, for the first time, the operation of Li-rich cathode in Li∥Li_1.14(Ni_0.136Co_0.136Mn_0.542)O₂ cells cycling at 2.8–4.7 V using a single DME solvent electrolyte. This anion cooperative strategy effectively enhances the oxidation stability window of ether-based electrolytes while demonstrating practical application potential.