Low-Salt Cosolvent Driven Interfacial Behavior in Carboxylate-Based Electrolytes for Low-Temperature Lithium-Ion Batteries

Carboxylate esters are highly promising candidates for enhancing the low-temperature performance of lithium-ion battery electrolytes due to their ultralow melting points and wide electrochemical windows. However, they exhibit poor stability toward lithium metal, triggering significant side reactions with gas evolution and anode corrosion. Herein, we present a low-salt cosolvent strategy for regulating the interfacial chemistry of carboxylate-based electrolytes to improve compatibility with the lithium metal anode. On the one hand, fluorobenzene (FB) as a weak solvent was introduced into the methyl acetate (MA)-based electrolyte, tailoring the Li + solvation structure. On the other hand, functional additives (LiNO 3, MDFSA) were introduced to establish a stable electrode–electrolyte interface. The optimized MA-based electrolyte (LTMA) forms an inorganic-rich solid electrolyte interphase (SEI) on the lithium metal surface, which effectively suppresses gas evolution and dendrite growth. Li||NCM811 cells with the 0.5 M LTMA electrolyte exhibited an initial discharge capacity of 171.82 mAh g –1 and maintained a capacity retention of 99.98% after 200 cycles at −20 °C and 0.2C. The cells also retained 65.12% of their 25 °C capacity even under the extreme conditions of −50 °C and 0.1C. The assembled graphite||NCM811 pouch cells exhibited a capacity retention of 99.33% after 150 cycles at −10 °C and 0.1C. Our results indicate that advanced electrolyte engineering provides a viable pathway to the practical application of low-salt LTMA electrolytes.