Tailoring LiPF 6 -Based Electrolyte Solvation Structures via Solvent Regulation Strategies for Low-Temperature Lithium Metal Batteries

Abstract

Lithium metal batteries (LMB) offer exceptional energy density, yet practical application is limited by unstable solid electrolyte interphases (SEI) formation and sluggish Li⁺ transport, particularly under low-temperature conditions. Here, a carbonate electrolyte employing a cosolvent and dual-salt strategy is proposed to simultaneously tailor Li⁺ solvation and interfacial chemistry of LiPF 6 -based electrolytes. The introduction of ethyl methyl carbonate weakens the strong Li + -ethylene carbonate coordination, while difluoro(oxalato)borate anions preferentially undergo interfacial reduction to construct a robust, inorganic-rich SEI. This tailored solvation environment affords a low Li + diffusion energy barrier and effectively suppresses lithium dendrite formation. As a result, the electrolyte delivers exceptional low-temperature performance, achieving an ionic conductivity of 0.518 mS cm⁻ 1 at -40 o C and a reduced desolvation energy of 66.84 kJ mol⁻ 1 . High-loading LFP||Li full cells exhibit a specific capacity of 163.06 mAh g⁻ 1 at 0.2 C and retain 80% capacity after 200 cycles at 25 o C.Even at -30 o C, the cells maintain 58% capacity retention after 100 cycles. This work highlights the interplay between solvation chemistry, SEI composition, and interfacial ion transport, offering a viable design paradigm for high-performance carbonate electrolytes in low-temperature LMBs.