Anti-corrosive Hybrid Electrolytes for Rechargeable Aqueous Zinc Batteries

Abstract

Aqueous zinc(Zn)-metal cells with cost-effective components and high safety have long been a promising large-scale energy storage system, but Zn anodes are intrinsically unstable with common aqueous electrolytes, causing substantial underutilization of the theoretical capacity. In this work, we report a strictly neutral aqueous Zn electrolyte at a low cost by leveraging the dynamic hydrolysis equilibrium of a dual-salt Zn(Ac)2/NaAc(Ac: CH3COO−) formulation. With the pH regulation, the corrosion and hydrogen evolution encountered in Zn anodes can be suppressed significantly. This hybrid aqueous electrolyte not only enables dendrite-free Zn plating/stripping at a nearly 95% Coulombic efficiency[an increase of 24% compared to that of the single-salt 1 mol/L Zn(Ac)2 electrolyte], but also supports the reversible operation of Zn cells paired with either Na3V2(PO4)3 or iodine cathodes—the former delivers a high output voltage of 1.55 V with an energy level of 99.5 W·h/kg(based on the mass of the cathode), and the latter possesses a high specific capacity of 110.9 mA·h/g while yielding long-term cyclability(thousands of cycles). These findings open up a new avenue of modifying practical electrolytes having targeted properties to stabilize multivalent metal anodes.