Highly Reversible Zn Plating/Stripping Enabled by Polyvinyl Alcohol Coating Layers for Stable Aqueous Rechargeable Zinc Batteries

Abstract

Given their intrinsic safety, low cost, and high energy density, aqueous zinc (Zn) batteries hold substantial promise in large-scale energy storage applications. However, Zn dendrite formation and serious side reactions in metallic Zn anodes significantly compromise the reversibility of electrochemical Zn plating/stripping, restricting their lifespan and practical applications. Herein, we demonstrate that the polyvinyl alcohol (PVA) coated Zn anode can alleviate those issues. The PVA molecules at the Zn anode/electrolyte interface enable homogeneous Zn plating/stripping behavior by regulating the nucleation and ion diffusion barriers and effectively suppress the corrosion and hydrogen evolution reaction in mildly acidic electrolytes. As a result, a highly reversible and dendrite-free Zn anode can be obtained. The content of PVA plays a critical role in governing the cycling lifetime and stability. With the optimized content of PVA, stable Zn plating/stripping with a cycling capacity of 1 mAh cm-2 over 1500 hours has been achieved at 1 mA cm-2. In contrast, the bare Zn anode showed an unstable plating/stripping behavior with obvious polarization and limited cycling lifetime. Even at a high current density of 5 mA cm-2, the PVA-coated Zn anode remained stable for 1000 cycles. The present work provides a promising strategy to stabilize Zn anodes towards long-lifespan, cost-effective, and scalable aqueous rechargeable zinc-based batteries.