Precise Control of Li+ Directed Transport via Electronegative Polymer Brushes on Polyolefin Separators for Dendrite‐Free Lithium Deposition

Abstract Nonuniform ion flux triggers uneven lithium (Li) deposition and continuous dendrite growth, severely restricting the lifetime of Li‐metal batteries (LMBs). Herein, an electronegative poly(pentafluorophenyl acrylate) (PPFPA) polymer brush‐grafted Celgard separator signed as PPFPA‐g‐Celgard is designed to precisely construct one‐dimensionally directed Li + flux at the nanoscale so as to realize faster ion transport and ultra‐stable Li deposition. The grafting of PPFPA polymer chains is enabled by the simple bio‐inspired engineering of surface‐initiated atom transfer radical polymerization chemistry. Both theoretical and experimental analyses demonstrate an obvious increase by almost two times in Li + affinity and ion transfer kinetics for PPFPA‐g‐Celgard over the Celgard separator. Reversible and stable Li plating/stripping can be realized by rapidly switching from 0.5 to 6 mA cm ‐2 . Besides, the Li | PPFPA‐g‐Celgard | LiFePO 4 full cell exhibits universal and long‐term cyclability with a capacity retention of 83% over 700 cycles in ether electrolyte and 92.9% for over 300 cycles in carbonate electrolyte as well. This study represents a new direction for the general design of advanced separators with typical surface topochemistry and self‐limited ion transport channels in the application of high‐performance LMBs.