If the IL ions preferentially migrate in an electric field instead of the Li⁺ ions, it can lead to a lowered transport number of the Li⁺ ions, ultimately limiting the battery's rate performance.


These zwitterionic liquids are similar to ILs but cannot migrate in an electric field. They help ensure that the Li⁺ ions can transport smoothly in the electrolyte.
The reaction involves the nucleophile 1-methylimidazole reacting with 1,3-propanesultone. The sultone undergoes ring opening at the α-carbon to produce the zwitterion with >98% yield. Zwitterionic ILs can act as Bronsted acids. This property makes them useful as catalysts and solvents. Example.