Poly(ionic liquid)-Based Quasi-Solid-State Copolymer Electrolytes for Dynamic-Reversible Adsorption of Lithium Polysulfides in Lithium–Sulfur Batteries

The shuttle of the long-chain lithium polysulfides (LiPSs) is the main obstacle to the practical application of lithium–sulfur batteries. Herein, a poly(butyl acrylate/1-ethyl-3-vinylimidazole bis[(trifluoromethyl)sulfonyl]imide)-based quasi-solid-state copolymer electrolyte poly(ethylene glycol) diacrylate (PEGDA-P(BA-co-[EVIm]TFSI) QPE-IL) was prepared for lithium–sulfur batteries. The butyl acrylate component with abundant ester groups ensures the strong chemical capture for LiPSs. What is more, the introduction of ionic liquid ([EVIm]TFSI) can greatly improve the ionic conductivity and lithium-ion migration rate. More importantly, the dynamic-reversible adsorption of LiPSs was realized by chemical adsorption of ester-rich groups and electrostatic repulsion of free-moving negatively charged ions. As a result, the lithium–sulfur battery assembled by a reduced graphene oxide/carbon nanotube film@sulfur (rGOCTF@S) self-supporting cathode and QPE-IL displayed a high initial discharge capacity of 1179 mA h g–1, good cycling stability (72% capacity retention after 200 cycles at 0.5 C), and superior rate performance.