Ether‐Oxygen Groups Modified Carboxylic Ester Enabling High‐Voltage Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) operating at high cut‐off voltages can achieve an energy density exceeding 500 Wh kg −1 ; however, they often suffer from severe capacity degradation due to electrolyte decomposition. Herein, propylene glycol monomethyl ether acetate (PMA) is introduced as a novel solvent for LMB electrolytes. The unique ether‐oxygen functionality in PMA exhibits high steric hindrance, leading to weak lithium‐ion coordination, which promotes the formation of contact ion pairs (CIPs) in the electrolyte solvation structure, especially in the presence of dual salts. A Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) battery employing the formulated PMA‐based electrolyte demonstrates stable cycling at a high cut‐off voltage of 4.5 V for over 100 cycles, retaining 90.1% of its initial capacity even at 60 °C. Furthermore, a molecular interfacial model is proposed to elucidate the impact of the designed electrolyte on electrode interfacial behavior and battery performance, providing valuable insights for the development of high‐performance LMB electrolytes.