Zwitterionic Organic Multifunctional Additive Stabilizes Electrodes for Reversible Aqueous Zn-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) exhibit significant potential for grid energy storage due to their low cost and safety. However, the commercial applications of AZIBs face challenges, particularly in the anode, such as zinc dendrites, hydrogen evolution reaction (HER), and zinc corrosion. In this study, a protonated triglycine (ggg) as a multifunctional electrolyte additive for AZIBs is employed. This ggg molecule can dissociate as zwitterion (both anion and cation) in mildly acidic ZnSO4 electrolytes. The NH3+ cation in ggg molecule can adsorb on the surface of the zinc anode, regulating the deposition of Zn2+ and slowing down the side reactions, and the spontaneously dissociated ggg anions will combine with Zn2+ to regulate the solvated Zn2+ chemistry in the electrolyte, establishing the electrostatic interaction via the strong adsorption ability to Zn2+. Theoretical calculations indicate that ggg molecule demonstrates a strong affinity toward Zn2+, enabling the reconstruction of Zn(H2O)62+ and facilitating subsequent de-solvation processes. As a result, Zn||Zn symmetric cells in ZnSO4/0.2 mM ggg electrolyte exhibited an extended cycling lifetime of approximate to 4500 h. Furthermore, the Zn||MnO2 full battery demonstrated enhanced capacity and cycling performance with the addition of ggg molecule. This study provides valuable insights into constructing a highly reversible electrolyte for AZIBs. Zwitterionic organic multifunctional additive named triglycine (ggg) is used as a multifunctional electrolyte. Theoretical calculations indicate that the ggg molecule demonstrates a strong affinity toward Zn2+, enabling the reconstruction of Zn(H2O)62+ and facilitating subsequent de-solvation processes. As a result, The Zn||Zn symmetric cells in ZnSO4/0.2 mm ggg electrolyte exhibited an extended cycling lifetime of approximate to 4500 h. Furthermore, the Zn||MnO2 full battery demonstrated enhanced capacity and cycling performance with the addition of ggg molecule. image