Conformational Engineering of Solvent Molecules for High-Voltage and Fast-Charging Lithium Metal Batteries

Abstract

High-voltage and fast-charging lithium metal batteries (LMBs) are crucial for overcoming electric vehicle range and charging limitations. However, conventional carbonate electrolytes face intrinsic limitations in simultaneously achieving compatibility with high-voltage cathodes and lithium metal anodes. These limitations arise from sluggish Li⁺ transport kinetics and parasitic side reactions, both largely driven by excessive Li⁺ solvation energy inherent to carbonates. To address these challenges, we propose a conformational engineering strategy of fluorinated solvent molecules by developing a 2,2,3,3,4,4-hexafluoropentanedioic·anhydride (HFPA)-derived electrolyte (HFPE). The chair conformation of HFPA synergizes with its high F/C ratio to establish a low-polarity solvation environment, effectively reducing desolvation energy barriers. In addition, the HFPA-induced ligand preference for anion aggregation contributes to the formation of anion-rich dissolved sheaths while stabilizing the electrode–electrolyte interphases. The engineered HFPE demonstrates accelerated interfacial ion transport kinetics with an enhanced Li⁺ transference number of 0.64. When paired with LiNi_0.8Co_0.1Mn_0.1O₂ cathodes under stringent operating conditions (4.5 V cut-off voltage, 10 C-rate), HFPE-enabled cells exhibit exceptional cycling stability. Notably, industrial-scale 5.6 Ah lithium metal pouch cells employing HFPE maintain stable operation at 4.5 V, underscoring the practical viability of this conformation modulation approach. This work establishes a paradigm-shifting strategy for next-generation electrolyte design in practical high-energy-density LMBs.