Breaking Solvation Compactness: Methyl Acetate Cosolvent Engineering Enables High-voltage Lithium Metal Batteries at Low Temperatures

Abstract

State-of-the-art lithium metal batteries (LMBs) offer exceptional energy density for next-generation energy storage. Yet, their practical application is hindered by unstable cathode-electrolyte interphases (CEIs) under high-voltage conditions and sluggish ionic transport kinetics at low temperatures. Here, we develop a small linear molecule, methyl acetate (MA), as a cosolvent in a fluorinated-based electrolyte (FBE) to address these challenges. MA presents a high binding energy with Li ions and weak repulsive interactions with fluorinated solvent molecules and PF6- anions. Consequently, small MA molecules can participate in the inner solvation sheath and disrupt the compact solvation structure constructed by fluorinated solvent molecules, thereby contributing to the generation of robust and stable CEIs and bulk electrolytes with superior Li+ transport kinetics. Based on the well-formulated MA-FBEs, the assembled LiNi0.8Co0.1Mn0.1O2||Li full cells with a low N/P ratio of 2 can stably operate under high voltage (181.2 mAh g-1 at 4.8 V), deliver high rate capability (142.8 mAh g-1 at 10 C), and maintain excellent low-temperature performance (159.1 mAh g-1 at 0.05 C and 99.1 mAh g-1 at 0.1 C at -70 °C), demonstrating the industrial viability of this developed electrolyte.