Incorporation of 2-Hydroxyethyl Cellulose Having Hydrogen Bonding, Amphiphilicity, and Zincophilicity in Zinc Sulfate Electrolytes for Enhancing Zinc Anodes

Aqueous zinc-ion batteries (ZIBs) are one of the most promising rechargeable batteries; however, the stability of the zinc anode is significantly reduced by corrosion, hydrogen evolution, and the formation and growth of zinc dendrites on the zinc anode surface. To resolve these problems, this work proposes to employ an eco-friendly and low-cost cellulose derivative, 2-hydroxyethyl cellulose (HEC), which contains a number of hydroxyl groups with excellent hydrogen bonding, amphiphilicity, and zincophilicity, as an electrolyte additive in a ZnSO₄ solution to elevate the performance of the zinc anode in aqueous zinc-ion batteries. These results suggest that the hydrogen bond strength of the entire electrolyte system and zinc-ion deposition kinetics could be regulated by the addition of trace HEC in the electrolyte. Besides, the added HEC could cover the surface of the zinc anode in the ZnSO₄ electrolyte to produce an adsorption film. Therefore, the additive HEC might effectively inhibit corrosion and hydrogen evolution, as well as the generation and growth of zinc dendrites. Consequently, the stability of zinc anodes and zinc-ion batteries might be boosted by the introduction of dilute HEC into the ZnSO₄ electrolyte. For example, the symmetric Zn||Zn battery, with the HEC/ZnSO₄ electrolyte, reached 1300 h of stable cycling at 5 mA cm^-2 and 1 mAh cm^-2, while the symmetric Zn||Zn battery with the blank ZnSO₄ electrolyte solution achieved only 136 h of stable cycling. At 5 mA cm^-2 and 5 mAh cm^-2, the Coulombic efficiency of the asymmetric Zn||Cu battery could be maintained at 95.8% after 500 cycles after the addition of HEC to the ZnSO₄ electrolyte. Overall, this study provides insight and guidance for employing natural products having unique hydrogen bonding, amphiphilicity, and zincophilicity for boosting zinc metal batteries.