Chelating dicarboxylic acid as a multi-functional electrolyte additive for advanced Zn anode in aqueous Zn-ion batteries

Aqueous zinc-ion batteries are promising due to their high safety, low cost, high specific capacity, and long cycle life. However, several critical issues, such as dendrite growth, hydrogen evolution, passivation, corrosion and low coulombic efficiency, hinder their commercialization. In this study, we propose a solution to these issues by introducing succinic acid (SA) to the traditional ZnSO4 electrolyte. The carboxyl group in SA has excellent coordination capability with Zn2+ ions, which replaces some of the active water molecules in the Zn2+ inner solvation shell. This process disrupts the hydrogen bond network, regulates the solvation structure of Zn2+ ions, and suppresses the possibility of hydrogen evolution. Additionally, the carboxyl group has a strong bonding force with Zn metal, which preferentially adsorbs and reacts with Zn2+ to generate a Zn-SA composite protective film on the surface of the Zn anode. This feature reduces by-products and enhances uniform zinc ion deposition, resulting in a symmetric cell configuration assembled with SA additive that can cycle stably for over 4000 h at 1 mA cm-2 and 1 mA h cm-2, with an average Coulombic Efficiency of 99.7% during Zn plating/stripping processes. Even at high current densities of up to 10 mA cm-2, the cell can achieve a stable cycle of 500 h. As a proof-of-concept, we assembled a Zn-V2O5 full cell with SA addition, which demonstrated distinguished rate performance and specific capacity retention over 1000 cycles.