A dual electrolyte additive strategy for achieving stable Zn anodes for zinc-ion batteries†

Aqueous zinc-ion batteries (AZIBs) have drawn substantial interest due to their high security, cost-effectiveness, and eco-friendly attributes. However, the prevalent challenges associated with the hydrogen evolution reaction (HER) and zinc dendrites are impeding their commercialization. Electrolyte engineering has emerged as a potent strategy for improving the stability of Zn anodes. In this study, we introduced glycine and graphene oxide (GO) into the ZnSO₄ electrolyte, functioning as dual additives, to improve the performance of Zn anodes. It is found that glycine can modulate the Zn²⁺ solvation structure, reducing the interaction between Zn²⁺ and SO₄²⁻. Thus, both the HER and sulfate byproducts can be inhibited. Moreover, GO can adsorb onto the electrode, forming an rGO layer, serving both as a protective layer and a nucleation layer. More significantly, it facilitates charge transfer and promotes uniform zinc deposition, thereby enabling a homogeneous electric field distribution. Consequently, the integration of glycine and GO into the ZnSO₄ electrolyte boosts the stability of Zn anodes. Zn||Zn cells can work steadily for over 700 h at 5 mA cm⁻² and 1 mA h cm⁻². An impressive CE of ca. 98.6% over 1300 cycles is achieved in Zn||Cu cells in the electrolyte with dual additives. Besides, Zn||VO₂ full cells utilizing the electrolyte with additives also exhibit the improved cycling stability. Therefore, this study introduces a feasible approach to simultaneously mitigate the HER and Zn dendrites.