Synergistic Solvation Regulation by Dual-Salt Additives Enables Stable Li-ion Batteries at Low Temperatures

The poor low-temperature performance of lithium-ion batteries stems from sluggish ion transport and severe interfacial side reactions. To address this, we develop a dual-salt electrolyte (O1T9-N) of LiTFSI and LiODFB (9:1 molar ratio) in EC/EMC with 2 wt% LiNO 3 additive. Combined molecular dynamics and experiments reveal that LiNO 3 reconstructs the Li⁺ solvation sheath via competitive coordination. This significantly weakens Li⁺–solvent interaction (reducing the Li⁺–O(EC) coordination number from 8.06 to 2.39), promotes anion participation, and consequently lowers the Li⁺ desolvation energy barrier (activation energy of 32.3 kJ·mol⁻ 1 ). These effects yield superior ion transport, with an ionic conductivity of 4.56 mS·cm⁻ 1 and a Li⁺ transference number of 0.88 at –20 °C. Furthermore, LiNO 3 and LiODFB cooperate to form a thin (~3.83 nm), inorganic-rich cathode electrolyte interphase, suppressing side reactions and cathode degradation. Consequently, LiCoO 2 ||Li cells with O1T9-N electrolyte exhibit outstanding cycling stability (96.33% capacity retention after 100 cycles at –20 °C) and rate capability, significantly outperforming conventional electrolytes. This work elucidates the role of solvation structure regulation and provides an effective electrolyte design strategy for low-temperature lithium-ion batteries.