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 HO and HF capturing ability due to strong adsorption of MS and SMF for HO and the scavenging of SMF for HF. The MS-SMF@PE separator-employed LiCoO/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.