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

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_0.8Co_0.1Mn_0.1O₂ (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.