Zn3(PO4)2 Protective Layer on Zn Anode for Improved Electrochemical Properties in Aqueous Zn-ion Batteries

Abstract

<p>Aqueous zinc-ion batteries are considered as promising alternatives to lithium-ion batteries for energy storage owing to their safety and cost efficiency. However, their lifespan is limited by the irreversibility of Zn anodes because of Zn dendrite growth and side reactions such as the hydrogen evolution reaction and corrosion during cycling. Herein, we present a strategy to restrict direct contact between the Zn anode and aqueous electrolyte by fabricating a protective layer on the surface of Zn foil via phosphidation method. The Zn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> protective layer effectively suppresses Zn dendrite growth and side reactions in aqueous electrolytes. The electrochemical properties of the Zn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>@Zn anode, such as the overpotential, linear polarization resistance, and hydrogen generation reaction, indicate that the protective layer can suppress interfacial corrosion and improve the electrochemical stability compared to that of bare Zn by preventing direct contact between the electrolyte and the active sites of Zn. Remarkably, MnO<sub>2</sub> || Zn<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>@Zn exhibited enhanced reversibility owing to the formation a stable porous layer, which effectively inhibited vertical dendrite growth by inducing the uniform plating of Zn<sup>2+</sup> ions underneath the formed layer.</p>