Unraveling the regulation of a polyhydroxy electrolyte additive for a reversible, dendrite-free zinc anode

Abstract

Rechargeable aqueous Zn-ion batteries (AZIBs) are a promising candidate for electrochemical energy storage applications. However, the practical lifespan of AZIBs is severely compromised due to dendritic growth, hydrogen evolution, and corrosion of the Zn anode. Herein, we employ cost-effective, polyhydroxy sucrose (Suc) as a multifunctional electrolyte additive for AZIBs, which highly suppresses dendrites and parasitic side reactions of the Zn anode, thereby promoting even Zn plating/stripping for prolonged cycle lifespan. Combining experimental characterization and theoretical calculations, we find that the rich hydroxyl groups in Suc effectively regulate the solvation structure of hydrated Zn²⁺ and the Zn metal/electrolyte interface, inhibit the cracking of active water molecules and homogenize the interfacial electric fields. These superiorities effectively suppress parasitic reactions and Zn corrosion and promote uniform Zn nucleation during cycling, as evidenced by in situ optical microscopy. As a result, Zn//Zn symmetrical cells using a ZnSO₄ electrolyte containing Suc deliver ultrahigh cycling stability (over 2000 h at 1 mA cm⁻² with 1 mA h cm⁻²), far superior to that using pure ZnSO₄ electrolyte. When coupled with a V₂O₅ cathode, the as-assembled Zn//V₂O₅ can afford a high capacity retention of 81.3% after 2000 cycles.