Ion-Sieving Separator Functionalized by Natural Mineral Coating toward Ultrastable Zn Metal Anodes

Aqueous zinc-ion batteries (AZIBs) exhibit promising prospects in becoming large-scale energy storage systems due to environmental friendliness, high security, and low cost. However, the growth of Zn dendrites and side reactions remain heady obstacles for the practical application of AZIBs. To solve these challenges, a functionalized Janus separator is successfully constructed by coating halloysite nanotubes (HNTs) on glass fiber (GF). Impressively, the different electronegativity on the inner and outer surfaces of HNTs endows the HNT-GF separator with ion-sieving property, leading to a significantly high transference number of Zn²⁺ (t_Zn = 0.71). Meanwhile, the HNT-GF separator works as an interfacial ion comb to regular Zn²⁺ flux and realizes multisite progressive nucleation, bringing decreased nucleation overpotential and uniform Zn²⁺ deposition. Consequently, the HNT-GF separator enables the Zn anode to display an ultralong plating/stripping life of 3000 h and high rate tolerance with a stable long cycle life even under a density of 50 mA cm^-2. Moreover, the $$ full cell represents an ultrastable cycling stability with a high capacity retention of 93.4% even after 1000 cycles at a current density of 2 A g^-1. This work provides a convenient method for the separator modification of AZIBs.