Stable and long-life Zn anode enabled by an ion-conductive copolymer coating for rechargeable aqueous batteries

The Zn metal anode endows aqueous zinc-ion batteries (ZIBs) with merits in terms of low cost, high safety, and bivalent ions as charge carriers. Yet the current ZIB technology is immature due to some issues arising from the Zn anode, including the dendrite growth, formation of compound byproducts, and hydrogen gas evolution. Here, a nanoporous and ion-conductive polyvinylidene fluoride-hexafluoro propylene copolymer containing zinc trifluoromethanesulfonate (Zn²⁺-PVDF-HFP coating) is applied onto the Zn foil to improve its anode performance. The Zn anode covered with Zn²⁺-containing PVDF-HFP coating (Zn@Zn²⁺-PVDF-HEP) shows good anti-corrosion performance and much longer cycle life, compared to the bare Zn anode. Also, the byproduct growth and hydrogen gas evolution can be efficiently suppressed due to the Zn²⁺-conductive copolymer coating. For symmetric cells using Zn@Zn²⁺-PVDF-HFP, a long lifespan of 2200 cycles is achieved when tested at 1 mA cm⁻² and 1 mAh cm⁻². Even cycled at 10 mA cm⁻² and 5 mAh cm⁻², this cell can sustain for over 1800 h. The efficacies of Zn²⁺-PVDF-HFP coating in prolonging cycle life and enhancing areal capacity of the Zn anode are further verified in MnO₂- or V₂O₅-based full cells, for which the mechanisms are discussed in detail.