Anion-oriented solvation regulation of a dual-salt electrolyte for lithium metal batteries

Designing suitable electrolytes and interphases is crucial for lithium metal batteries (LMBs), which are susceptible to excessive side reactions and lithium dendrite at the anode. Regulating the solvation ability of solvents and anions to tune the solvation structure and constructing an appropriate solid electrolyte interphase (SEI) are effective strategies for these problems. Herein, two different dissociated lithium salts (LiTFSI and LiBF 4 ) are screened to study the anion-oriented solvation regulation for SEI formation at the anode. It is found that BF 4 - is less likely to be displaced from the inner layer by solvents compared to TFSI - . Moreover, the resulting SEI with either an overly high or low content of inorganic components is not advantageous for long-term cycling performance. On the contrary, the dual salt electrolyte not only preferentially decomposes to form protective and balanced SEI with low impedance, but also maintains favorable bulk ion transport down to − 40 ℃. As a result, 4.3 V Li||LiCoO 2 full cells using the dual salt electrolyte deliver 88.7 % capacity retention after 200 cycles at 1C. This work highlights the significance of anion-oriented regulation in optimizing the performance of LMBs.