Achieving dendrite-free zinc metal anode via a low-cost and pH buffer electrolyte additives

Aqueous zinc-ion batteries have garnered significant attention due to their excellent safety performance, low cost, and high theoretical capacity density. However, the widespread application of zinc batteries is limited by zinc dendrites and capacity degradation. This study uses low-cost ammonium bicarbonate (NH4HCO3) as an electrolyte additive to alleviate the formation of zinc dendrites and suppress side reactions. Density functional theory (DFT) calculation results show that NH4+ and HCO3- are preferentially adsorbed on the zinc anode, avoiding direct contact between water and zinc inhibits hydrogen evolution reaction. The pH monitoring experiment results show that NH4+ and HCO3- achieve pH buffering and preferentially contact with water, suppressing side reactions, thus obtaining dendrite-free zinc metal anode. As a result, the Zn||Zn symmetric battery containing NH4HCO3 electrolyte demonstrated stable operation for 3000 h at a current density of 2 mA cm-2, and the coulombic efficiency of the Zn||Cu battery remained stable over 1000 cycles at a current density of 2 mA cm-2 and 1 mAh cm-2. In addition, the cycle performance of the assembled Zn||V2O5 full battery had been improved. This work proposes a low-cost and effective strategy to alter galvanizing/stripping behavior and suppress hydrogen evolution reactions in aqueous solutions of zinc ion batteries.