Low-Temperature LiCoO2||Graphite Batteries Enabled by Multi-Salt and Acetone-Ester Solvent Regulation

The performance of lithium-ion batteries at low temperatures is severely constrained by sluggish desolvation kinetics and unstable electrode interfaces. Here, we develop a fluorinated-solvent-free, low-temperature electrolyte, FBN-442, composed of 1.0 m salts (LiFSI/LiODFB = 7:3) and 0.15 m LiNO3 additive dissolved in a mixed solvent of acetone (DMK), methyl acetate (MA), and vinylene carbonate (VC). Guided by theoretical calculations and comprehensive experimental analyses, we construct a tailored solvation structure, in which DMK promotes salt dissociation, MA provides moderate Li+ affinity and a low melting point, and VC contributes effective film formation. This optimized solvation environment balances bulk ion transport with interfacial charge-transfer kinetics and drives the formation of dense, inorganic-rich interphase layers. As a result, graphite and LiCoO2 electrodes exhibit markedly improved low-temperature and high-rate performance. The effectiveness of the electrolyte is further validated in pouch cells, which retain 78% of their room-temperature capacity even at -40 °C (0.85 Ah vs 1.1 Ah at 30 °C). These results highlight the critical role of solvation-structure regulation in enabling high-energy lithium-ion batteries to operate reliably across wide temperature ranges.