Non-concentrated electrolyte with weak anion coordination enables low Li-ion desolvation energy for low-temperature lithium batteries

An electrolyte composed of dilute LiBF4 in trifluoropropylene carbonate and tetrahydrofuran co-solvent is found to exhibit loose Li+-anion binding in solvation shell, which stabilizes electrolyte/cathode interface and enhances Li+-desolvation at low temperature for building rechargeable lithium batteries. [Display omitted] •Lowering the anion amounts in the Li+-solvation shell is found to facilitate Li+ desolvation.•A dilute electrolyte constituting 0.5 M LiBF4 in THF/TFPC shows a low freezing point (−133 °C).•The regulated electrolyte exhibits a favorable anodic stability and compatibility with nickel-rich cathode materials.•A considerable specific capacity of 108.5 mAh g−1 was achieved at − 90 °C. Tailoring the lithium-ion solvation structure of ether-based electrolyte to accelerate charge transfer is of significance in low-temperature lithium batteries but remains largely unexplored. Herein, we propose a strategy based on carbonates mediating the anion coordination to realize cold-resistant electrolyte with superior kinetics and improved anodic stability. The combination of computational and experimental methods reveals that decreasing anions in the Li+-solvation structure reduces the desolvation energy of Li+ and enhances low-temperature performance. A formulated electrolyte composed of 0.5 M lithium tetrafluoroborate in hybrid solvent of tetrahydrofuran and trifluoropropylene carbonate features a high ionic conductivity of 0.45 mS cm−1 at − 90 °C and an ultra-low freezing point of − 133 °C. Furthermore, in such electrolyte, the LiNi0.8Co0.1Mn0.1O2 cathode can be reversibly cycled at low temperature of − 40 °C and delivers a considerable specific capacity of 108.5 mAh/g at − 90 °C.