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

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 | LiFePO4 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.