High‐Rate, Large Capacity, and Long Life Dendrite‐Free Zn Metal Anode Enabled by Trifunctional Electrolyte Additive with a Wide Temperature Range

Aqueous Zn-ion batteries (AZIBs) have been recognized as promising energy storage devices due to their high theoretical energy density and cost-effectiveness. However, side reactions and Zn dendrite generation during cycling limit their practical application. Herein, ammonium acetate (CH₃ COONH₄ ) is selected as a trifunctional electrolyte additive to enhance the electrochemical performance of AZIBs. Research findings show that NH₄ ⁺ (oxygen ligand) and CH₃ COO⁻ (hydrogenligand) with preferential adsorption on the Zn electrode surface can not only hinder Zn anode directly contact with active H₂ O, but also regulate the pH value of the electrolyte, thus suppressing the parasitic reactions. Additionally, the formed SEI is mainly consisted of Zn₅ (CO₃ )₂ (OH)₆ with a high Zn²⁺ transference number, which could achieve a dendrite-free Zn anode by homogenizing Zn deposition. Consequently, the Zn||Zn symmetric batteries with CH₃ COONH₄ -based electrolyte can operate steadily at an ultrahigh current density of 40 mA cm⁻² with a cumulative capacity of 6880 mAh cm⁻² , especially stable cycling at -10 °C. The assembled Zn||MnO₂ full cell and Zn||activated carbon capacitor also deliver prominent electrochemical reversibility. This work provides unique understanding of designing multi-functional electrolyte additive and promotes a long lifespan at ultrahigh current density for AZIBs.