Designing Zwitterionic Bottlebrush Polymers to Enable Long‐Cycling Quasi‐Solid‐State Lithium Metal Batteries
Shimei Li, Hu Hong, Dedi Li, Xinru Yang, Shixun Wang, Dechao Zhang, Qi Xiong, Zhaodong Huang, Chunyi Zhi
Abstract
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 %.