Cations Coordination-Regulated Reversibility Enhancement for Aqueous Zn-Ion Battery

Abstract

Aqueous Zn-ion batteries are emerging as a promising candidate for large-scale energy storage, while the short lifetime and poor reversibility of Zn anodes limit their further development. When attempting to enhance reversibility, most reported methods involve toxic and pollutive substances and decreased water content, which inevitably sacrificed safety level, rate performance, and environmentally benign characteristics. Herein, a series of low-cost and “green” molecules are introduced into the aqueous (ZnCl<inf>2</inf>, ZnSO<inf>4</inf>) electrolytes, featured with cations coordination capability, which can significantly inhibit the hydration step of Zn²⁺ and delay the formation of the key by-products (Zn<inf>5</inf>(OH)<inf>8</inf>Cl<inf>2</inf>·H<inf>2</inf>O, 3Zn(OH)<inf>3</inf>·ZnSO<inf>4</inf>·5H<inf>2</inf>O) in aqueous electrolytes via regulating the coordination status of Zn²⁺. In the optimized electrolyte system, a highly reversible Zn metal anode presents excellent electrochemical performance, featured with a long lifespan over 1185 h at 1 mA cm⁻² and smooth deposition morphology. Furthermore, Zn–MnO<inf>2</inf> batteries based on the electrolyte deliver high capacity retention of 82.9% after 200 cycles. These breakthroughs suggest that this method offers a versatile toolbox toward developing future advanced multivalent metal batteries for large-scale energy storage.