Enhancement of surface stability of lithium manganese oxide spinel by silyl-group functionalized fluoride-responsive ionic liquid additives

[Display omitted] •Surface instability of LMO spinel is improved by IL additives with silyl-functional group.•Silyl-group functionalized fluoride-responsive ILs are synthesized and characterized.•IL with silyl functional group can effectively eliminate nucleophilic fluorides.•Chemical reactivity of IL with F− is confirmed by NMR analysis.•LMO spinel with IL additives exhibits excellent electrochemical performances. Spinel-structured lithium manganese oxides are considered as promising cathode material, however, their widespread commercial application remains hampered by their poor surface instability. To overcome these problems, we designed and synthesized task-specific ionic liquid additives that can effectively scavenge trace amounts of fluoride in the cell. Addition of ionic liquid additives in the electrolyte significantly improves cycling retention. 1H- and 19F-nuclear magnetic resonance spectroscopy measurements and inductively coupled plasma mass spectrometry elemental analysis collaboratively provides clear evidence that the ionic liquid additives selectively suppress parasitic reactions of the electrolyte with the surface of lithium manganese oxides cathode.