Branched Molecule Carrying Multiple Amide Groups for Accelerating Zinc Anode, Testified by In Situ Monitoring and Improved Batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) have been recognized as a promising next generation of second-level energy storage systems, with fine characteristics of pronounced low cost and safety. However, zinc dendrite growth, zinc corrosion, and side reactions on the Zn anode surface in aqueous electrolyte cause severe challenges for the practical application of aqueous ZIBs. Inspired by protein facial film, this study proposed to employ low concentrations (10^-5 mol/L magnitude, 5.16 × 10^-4 wt %) of an amphilic, zincophilic, and ecofriendly branched molecule based on an ethylenediamine core, showing strong intra/inter modular hydrogen bonding, as an additive in zinc sulfate electrolyte to stabilize the zinc anode and improve aqueous zinc-ion cells. A variety of in situ and ex-situ surface and electrochemical means were used to uncover increased aqueous ZIBs by the studied additive in the electrolyte. It is demonstrated that this additive was firmly adsorbed on the zinc anode surface to inhibit the growth of zinc dendrite, corrosion, and side reactions in aqueous ZIBs by tuning zinc ion deposition kinetics and the desolvation of zinc ions in water-based electrolyte solution; thus, aqueous zinc-ion cells were greatly improved. For instance, symmetric Zn||Zn batteries including 5 × 10^-5 mol/L of the surveyed additive in the electrolyte showed long cycle stability of over 2700 h under 1mA·cm^-2, 1 mAh·cm^-2 at 298 K, 750 h at 45 °C, and 480 h at 55 °C. The full Zn||MnO₂ batteries carrying the studied additive displayed higher capacity and slower decay than those containing blank ZnSO₄ electrolyte after 2000 cycles, even at a high current density of 1 A·g^-1. This work provides valuable insights into the realization of rechargeable aqueous zinc-ion cells using a dendritic molecular additive including multiple amide groups in the electrolyte.