Stable Operation of Lithium Metal Batteries with Aggressive Cathode Chemistries at 4.9 V

High-voltage lithium metal batteries (LMBs) pose severe challenges for the matching of electrolytes with aggressive electrodes, especially at low temperatures. Here, we report a rational modification of the Li⁺ solvation structure to extend the voltage and temperature operating ranges of conventional electrolytes. Ion-ion and ion-dipole interactions as well as the electrochemical window of solvents were tailored to improve oxidation stability and de-solvation kinetics of the electrolyte. Meanwhile, robust and elastic B and F-rich interphases are formed on both electrodes. Such optimization enables Li||LiNi_0.5 Mn_1.5 O₄ cells (90.2 % retention after 400 cycles) and Li||LiNi_0.6 Co_0.2 Mn_0.2 O₂ (NCM622) cells (74.0 % retention after 200 cycles) to cycle stably at an ultra-high voltage of 4.9 V. Moreover, NCM622 cells deliver a considerable capacity of 143.5 mAh g^-1 at -20 °C, showing great potential for practical uses. The proposed strategy sheds light on further optimization for high-voltage LMBs.