Zinc-ion conductive buffer polymer layer eliminating parasitic reactions of Zn anode in aqueous zinc-ion batteries

The spontaneous parasitic reactions (hydrogen evolution, dendrite growth, etc.) of Zn metal hinder the commercial application of aqueous zinc ion batteries. Herein, a highly adhesive zinc-ion conductive buffer polymer layer is constructed using polyvinyl formal (PVF) to prevent these parasitic reactions to enhance the reversibility of Zn deposition. This dense artificial buffer layer can not only effectively isolate the direct contact between the anode and the electrolyte, but also accommodate volume expansion during Zn plating/stripping and guide the process of Zn nucleation. Specifically, this PVF layer increases the nucleation overpotential and promotes Zn2+ three-dimensional diffusion process to homogenize the Zn2+ flux underneath the layer. Hence, the PVF@Zn exhibits no dendrites and high cycling stability with a lifespan of 5200 h, which is a 35-fold enhancement compared with Zn, and can even run at an ultrahigh current density of 40.0 mA cm−2. Moreover, the PVF@Zn∥Na2V6O16 full cell maintains a specific capacity of 172.4 mA h g−1 (2400 cycles at 1.0 A g−1). This proposed strategy provides a practical insight into designing an excellent-performance Zn anode by eliminating the parasitic reactions and modulating the nucleation of Zn deposition.