Polymer-based ionic liquids in lithium batteries

Abstract

Ionic liquids (ILs) offer advantages like low volatility, high stability, and conductivity, making them valuable in Li-ion and lithium-sulfur (Li–S) batteries compared to volatile organic solvents-based electrolytes and other green solvents such as deep eutectic solvents. ILs are propitious in Li–S batteries for reducing polysulfide solubility and preventing dendrite growth, but are hygroscopic, costly, and liquid in nature. Ionic liquids with polymerizable functionalities, such as vinyl groups, may undergo polymerization, thus resulting in a polymerized ionic liquid (PIL), which can be cast as film to serve as a separator loaded with lithium salts. The temperature dependence on ionic conductivity of PILs considering relaxation and segmental motion of the polymer chains are discussed with the help of mathematical expressions. Such PILs have significantly low moisture absorption, low or no flammability, and are castable as films, making them promising candidates for next-generation lithium battery electrolytes.