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Concentrated electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) have been proposed as an effective Li-compatible electrolyte for anode-free lithium metal batteries (AFLMBs). However, these electrolytes suffer from severe aluminum corrosion at an elevated potential. To address this issue, we propose a binary ionic liquid (IL) electrolyte additive comprising the 1-methyl-1-butyl pyrrolidinium cation (Pyr 14 + ), difluoro(oxalate)borate anion (DFOB – ), and difluorophosphate (PO 2 F 2 – ) anion to mitigate the Li inventory loss and Al corrosion in 4 M LiFSI/DME electrolyte simultaneously. On the anode side, the IL additive facilitates the formation of a robust Li 3 N- and LiF-rich solid electrolyte interphase, promoting highly reversible Li plating/stripping and uniform Li deposition. Additionally, the ILs alter the Li + solvation structure, leading to enhanced t Li + and rapid Li + desolvation kinetics. Concurrently, on the cathode side, the ILs aid in the generation of dense LiF- and AlF-rich passivation films against Al corrosion. By using the IL-added electrolyte, the Cu||LiMn 0.7 Fe 0.3 PO 4 cell operates stably at 4.5 V, and the Cu||NCM613 cell with a high loading of 4.0 mA h cm –2 sustains 142 cycles until 80% capacity retention. This research contributes to a deeper understanding of the IL additive mechanism at the electrode–electrolyte interfaces and offers a straightforward approach to designing practical high-voltage AFLMB electrolytes.
Zhou et al. (Fri,) studied this question.