Electrolyte Superwetting and Electrode Friendly of Porous Membrane for Better Cycling Stability of Lithium Metal Batteries.

Porous polymer membranes as separator plays important roles in separating cathode and anode, storing electrolytes, and transporting ions in energy storage devices. Here, an effective strategy is reported to prepare an electrolyte superwetting membrane, which shows good Li⁺ transport rate and uniformity, as well as electrode-friendly properties to afford the reduction and oxidation of electrodes. It thereby improves the cycle stability and safety of Li metal batteries. With the arrayed capillaries technique, a thin layer of polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) composite is uniformly coated on the surface and pores of polypropylene (PP) membrane with a total thickness of 30 µm. After treating it with n-butyllithium and LiNO₃ in turn, a chemically inert membrane with efficient and uniform ion transport is prepared, and the cycle stability of Li||Li symmetric cells is up to 1500 h, 4 times higher than that of PP membrane. Moreover, the Li||LiFePO₄ with as-prepared membranes achieve a higher capacity retention rate of 92% after 190 cycles at a current density of 3.6 mA cm^-2 and a capacity of 3.6 mAh cm^-2, and the Li||NCM721 batteries achieve a capacity retention rate of 71% after 600 cycles at a current density of 1.8 mA cm^-2.