Functional polyethylene separator with impurity entrapment and faster Li+ ions transfer for superior lithium-ion batteries

An organic/inorganic hybrid coating consisting of molecular sieve (MS)/sulfonated melamine formaldehyde condensate (SMF) is fabricated on the polyethylene (PE) separator by a simple dip-coating process. The MS/SMF coating with high polarity enhances the electrolyte uptake of PE separator, and therefore favors higher ionic conductivity and Li+ transference number of separators. By regulating the ratio of MS/SMF, much higher Li+ transference number up to 0.5 can be obtained compared with the original PE separator (0.25). The PE separator possesses highest effective Li+ ionic conductivity when the ratio of MS/SMF is 3:1, which promotes more uniform Li+ deposition on the lithium metal surface for excellent lithium plating/stripping cycling stability up to 1000 h without any signs of short-circuit. Moreover, the functional PE separator possesses excellent H2O and HF capturing ability due to strong adsorption of MS and SMF for H2O and the scavenging of SMF for HF. The MS-SMF@PE separator-employed LiCoO2/Li unit cell shows superior C-rates capability and cycling performance, and no obvious lithium dendrite growth is found on the surface of lithium metal anode after cycling.