Unlocking long-term stability: Electrolyte additives for suppressing zinc dendrite growth in aqueous zinc metal batteries

Abstract

Aqueous zinc-ion batteries (AZIBs) have attracted great attention for energy storage because of the safety of zinc metal in ambient air. However, the growth of zinc dendrites during repeated electrochemical cycles have hindered their practical use. To address this issue, we introduced ZnBr₂ as an additive in an aqueous 1 M ZnSO₄ electrolyte, effectively suppressing the dendritic growth on the surface of the zinc-metal anode. Significant improvement in Zn||Zn symmetric cell tests using 10 wt% ZnBr₂-added electrolyte was observed, with a lifespan of 12,500 cycles achieved even at a high current density of 50 mA cm⁻² with an areal capacity of 1 mAh cm⁻². Raman spectroscopy reveals formation of HBr in the electrolyte after 12 h deposition of zinc. The presence of HBr in the electrolyte effectively suppresses the dendritic growth of zinc, as visualized by an operando beaker-cell test and synchrotron tomography. We further demonstrated the compatibility and excellent rate performance of the additive-based electrolyte in Zn || NaV₃O₈ full cells. Our findings provide a simple and cost-effective method to suppress dendritic growth of zinc in zinc-metal batteries.