Phase-Separation-Induced Porous Lithiophilic Polymer Coating for High-Efficiency Lithium Metal Batteries

Solid-electrolyte interphase (SEI) plays a pivotal role in stabilizing lithium (Li) metal anode for rechargeable batteries. However, electrolyte-derived SEI often suffers from poor stability, leading to Li dendrite growth, consumption of electrolyte, and short cycle life. Here, we report a porous lithiophilic polymer coating induced by phase separation of polyvinylidenefluoride-polyacrylonitrile (PVDF-PAN) blends for stabilizing Li metal anode. Different from single polymer coating, PVDF-PAN blends protective layer with porous structures caused by phase separation can provide effective Li⁺ transport channels and regulate uniform Li⁺ flux. The lithiophilic functional groups of C≡N and C-F can promote uniform Li deposition and accelerate Li⁺ diffusion at the same time during plating/stripping process. As a result, Li||NCM811 full cells using PVDF-PAN coated Li present an apparently improved cycling stability and higher Coulombic efficiency with lean electrolyte (7.5 μL mA h^-1), limited Li supply (N/P ratio = 2.4), and high areal capacity (4.0 mA h cm^-2).