PVDF/lithiated sulfonated poly (ether ether ketone) blend coated PE separators for high-performance lithium metal batteries

Ionic conductivity and lithium ion transference number ( t L i + ) of electrolytes are essential parameters governing the performances of high energy density lithium metal batteries. Although the importance of t L i + versus ionic conductivity has been theorized by simulation, the systematically experimental study of their respective effects on lithium dendrite suppression and battery performances is rarely carried out. Here, a series of polyvinylidene fluoride and lithated sulfonated poly (ether ether ketone) blend (PVDF/SPEEK-Li) coated polyethylene (PE) separators with exactly the same composition but different pore morphologies are fabricated by vapor and non-solvent induced phase separation. The effects of sulfonate group–ion interaction and pore morphologies on ionic conductivity and t L i + of the electrolytes are studied. The performances of lithium metal batteries can be obviously improved by subtle increase of the t L i + , especially at high charge rates and even with a decrease in conductivity. Even at a high current density of 3 C, the PVDF/SPEEK-Li coated PE separator assembled lithium metal battery using a LiFePO 4 cathode with a mass loading of 10.5 mg cm −2 can run stably for 200 cycles with a capacity retention of 79 %, which is superior to the PE separator assembled battery with a life of only 55 cycles. PVDF/sulfonated poly(ether ether ketone) coated separators with finely regulated morphologies were fabricated by vapor and non-solvent induced phase separation. The effect of Li + transference number versus ionic conductivity on battery performance was elaborated experimentally. The coating layer enabled effective ion selectivity and suppression of lithium dendrite growth. The assembled Li metal battery with high cathode mass loading showed a capacity retention of 79 % after 200 cycles even if the current density is up to 3 C. • Scalable and controllable VIPS method for the PVDF/SPEEK-Li coated separators. • Selective Li + transport enabled by sulfonate groups on the separators. • Correlations of ionic conductivity and Li + transference number with battery performance. • Stable cycling of Li.||LiFePO 4 batteries with high cathode mass loading and current density.