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 (Pyr₁₄⁺), difluoro(oxalate)borate anion (DFOB^–), and difluorophosphate (PO₂F₂^–) 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 Li₃N- 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_0.7Fe_0.3PO₄ 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.

中文翻译：

---

离子液体添加剂减轻高压无阳极锂金属电池的锂损失和铝腐蚀


基于双（氟磺酰）酰亚胺锂 （LiFSI） 的浓电解质已被提议作为无阳极锂金属电池 （AFLMB） 的有效锂相容电解质。然而，这些电解质在高电位下会遭受严重的铝腐蚀。为了解决这个问题，我们提出了一种二元离子液体 （IL） 电解质添加剂，包括 1-甲基-1-丁基吡咯烷基阳离子 （Pyr₁₄⁺）、二氟（草酸盐）硼酸盐阴离子 （DFOB^–） 和二氟磷酸盐 （PO₂F₂^–） 阴离子，以同时减轻 4 M LiFSI/DME 电解质中的 Li 库存损失和 Al 腐蚀。在负极侧，IL 添加剂有助于形成坚固的富含 Li₃N 和 LiF 的固体电解质界面，促进高度可逆的 Li 电镀/剥离和均匀的 Li 沉积。此外，IL 会改变 Li⁺ 溶剂化结构，导致增强的 t_Li⁺ 和快速的 Li⁺ 脱溶剂化动力学。同时，在阴极侧，IL 有助于产生致密的富含 LiF 和 AlF 的钝化膜，以防止 Al 腐蚀。通过使用添加 IL 的电解质，Cu||LiMn_0.7Fe_0.3PO₄ 电池在 4.5 V 下稳定运行，Cu||NCM613 电池具有 4.0 mA h cm^–2 的高负载，可维持 142 次循环，直到 80% 的容量保持。这项研究有助于更深入地了解电极-电解质界面处的 IL 加成机制，并为设计实用的高压 AFLMB 电解质提供了一种直接的方法。