Hydrogen bond-based molecular self-clustering of a hyper-dendritic molecule for boosting ultra-long reversible zinc anodes

Abstract

In this study, an ecofriendly hyper-dendritic molecule (hyperbranched bis-MPA polyester-16-HY, simplified as HP-16) that could automatically process molecular self-clustering in aqueous solutions was employed as an additive in a zinc sulfate electrolyte solution to efficiently boost the zinc anode. It is found that an aqueous self-cluster solution of HP-16 could be yielded at a simple standing due to the strong inter-/intra-molecular hydrogen bond. It is demonstrated that the inclusion of HP-16 clusters in ZnSO₄ electrolytes could tune the electrolyte solution's zinc-ion deposition kinetics and plating/stripping process on the zinc anode surface during constant charge–discharge cycles of aqueous zinc-ion batteries (ZIBs). As a consequence, zinc corrosion, hydrogen evolution reaction and zinc dendrite formation on the zinc anode surface during the cycling of zinc-ion batteries could be effectively prevented, as evidenced by various in situ/ex situ determination. Hence, it was demonstrated that under the experimental conditions of 1 mA cm⁻² and 1 mAh cm⁻², symmetric Zn‖Zn batteries including HP-16 clusters in ZnSO₄ electrolytes (simplified as HP-16/ZnSO₄) could reach a cycle life of 5199 h (>7 months) at 25 °C and a cycle life of 426 h at 60 °C. The full Zn‖MnO₂ batteries were exhibited to maintain a capacity retention rate of >50% after 1000 cycles under a current of 2 A g⁻¹ by the inclusion of HP-16 in ZnSO₄ electrolytes, which was much superior to the one with a blank ZnSO₄ electrolyte. Hence, the suppression of zinc corrosion and hydrogen evolution and the formation and growth of zinc dendritic crystals by the introduction of HP-16 in zinc sulfate electrolyte solution were presented, which plays a central role in boosting the zinc anode and intensifying aqueous zinc ion batteries.