Multiscale Ion‐Sieving Separator with Selective Zn²⁺ Channels and Excellent Zn²⁺ Desolvation Kinetics for Dendrite‐Free and Kinetics‐Enhanced Zinc Metal Batteries

Abstract Zn metal batteries have garnered considerable scientific and technological interests. However, the widespread commercial application of these batteries is impeded by the uncontrollable dendrite growth and consequent severe side effects. Herein, a functionalized separator is prepared by spraying polyaniline‐modified graphene oxide (denoted as NPGO)/polyvinylidene difluoride solution directly on one side of a common separator of glass fibers (GFs). The reversible transition between protonated and deprotonated states of quinolone imide on NPGO nanosheets can facilitate the rapid desolvation and transfer of Zn²⁺. Therefore, the spatial electric field as well as the Zn²⁺ flux is effectively homogenized due to the ion‐sieving effect of NPGO nanosheets that are oriented toward Zn anode. This engineering design of the NPGO@GFs separator harvests excellent rate and cycling performance (over 3000 cycles at 20 mA cm⁻²) for Zn metal symmetric batteries. Meanwhile, it provides an impressive commercial prospect (500 cycles with a capacity retention of 91.6% under 2000 mA g⁻¹) for MnO₂||Zn full batteries. Such a strategy can be generalized as a common way to protect metal anodes (Na, Zn, and K) in rechargeable batteries, which is highly cost‐effective and scalable.