A novel bifunctional zinc gluconate electrolyte for a stable Zn anode

• A new electrolyte of zinc gluconate is discovered for Zn-ion batteries (ZIBs). • A dendrite-free Zn anode is simply realized without electrolyte additives. • The zinc gluconate is safe, drinkable, practical and bifunctional for ZIBs. • The cation of zinc gluconate conducts stable Zn plating/stripping reactions. • The anion of zinc gluconate builds a functional interface layer on Zn anode. Aqueous zinc ions batteries, being developed rapidly as a promising type of energy storage devices, are troubled by dendrite growth on Zn anode surface. Herein, a novel bifunctional electrolyte—zinc gluconate, is employed as a new zinc salt for Zn-ion battery. This electrolyte possesses two important functions: acting as a nontoxic and even drinkable Zn salt to conduct stable and efficient electrochemical reactions of zinc plating/stripping, and supplying gluconate anions to construct artificial stable anionic interface for dendrite-free Zn deposition. Theoretical simulations and in-situ digital holography technology reveal the preferentially and horizontally adsorbed gluconate anions on metallic Zn to shield protuberances and fill concaves. As a result, an efficient and dendrite-free Zn anode interface can be simply achieved using 0.3 M zinc gluconate electrolyte without other electrolyte additives. This bifunctional zinc gluconate integrates cationic Zn 2+ source and anionic gluconate interface, which provides a simple yet practical solution to stable and dendrite-free Zn anode.