Designing Zwitterionic Bottlebrush Polymers to Enable Long‐Cycling Quasi‐Solid‐State Lithium Metal Batteries

Abstract Ionogel polymer electrolyte (IPE), incorporating ionic liquid (IL) within a polymer matrix, presents a promising avenue for safe quasi‐solid‐state lithium metal batteries. However, sluggish Li + kinetics, resulting from the formation of [Li(anion) n ] −(n−1) clusters and the occupation of Li + transport sites by organic cations, limit their practical applications. In this study, we have developed zwitterionic bottlebrush polymers‐based IPE with promoted Li + conduction by employing poly(sulfobetaine methacrylate)‐grafted poly(vinylidene fluoride‐ co ‐chlorotrifluoroethylene) (PVC‐ g ‐PSBMA) bottlebrushes as matrices of IL. The grafted zwitterionic side chains greatly facilitate the dissociation of [Li(anion) n ] −(n−1) clusters to produce more movable Li + . Moreover, the positively charged −NR 4 + groups in zwitterionic side chains effectively restrain anions migration, while the negatively charged −SO 3 − groups immobilize IL cations, preventing them from occupying Li + hopping sites and reducing the energy barrier for Li + migration. These synergistic effects contribute to a notable ionic conductivity (7.5×10 −4 S cm −1 ) and Li + transference number (0.62) of PVC‐ g ‐PSBMA IPE at 25 °C. As a result, PVC‐ g ‐PSBMA IPE enables ultralong‐term (over 6500 h) reversible and stable Li plating/stripping in Li||Li symmetric cells. Remarkably, the assembled Li||LiFePO 4 full batteries demonstrate unprecedented cycling stability of more than 2000 cycles with a superior capacity retention of 93.7 %.