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

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 −NR4+ groups in zwitterionic side chains effectively restrain anions migration, while the negatively charged −SO3− 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||LiFePO4 full batteries demonstrate unprecedented cycling stability of more than 2000 cycles with a superior capacity retention of 93.7 %. Zwitterionic bottlebrush‐based ionogel polymer electrolytes are rationally designed to enhance Li+ transport with multifunctional capabilities, including dissociating [Li(anion)n]−(n−1) clusters, anchoring anions via cationic groups, and accelerating Li+ migration through anionic groups. The assembled Li metal batteries demonstrate ultralong‐term reversible Li plating/stripping over 6500 h and unprecedented cycling stability over 2000 cycles with a superior capacity retention of 93.7 %.