Dual-Function Electrolyte Additive for Highly Reversible Zn Anode

Practical application of aqueous Zn-ion batteries (AZIBs) is significantly limited by poor reversibility of the Zn anode. This is because of 1) dendrite growth, and 2) water-induced parasitic reactions including hydrogen evolution, during cycling. Here for the first time an elegantly simple method is reported that introduces ethylene diamine tetraacetic acid tetrasodium salt (Na(4)EDTA) to a ZnSO4 electrolyte. This is shown to concomitantly suppress dendritic Zn deposition and H-2 evolution. Findings confirm that EDTA anions are adsorbed on the Zn surface and dominate active sites for H-2 generation and inhibit water electrolysis. Additionally, adsorbed EDTA promotes desolvation of Zn(H2O)(6)(2+) by removing H2O molecules from the solvation sheath of Zn2+. Side reactions and dendrite growth are therefore suppressed by using the additive. A high Zn reversibility with Coulombic efficiency (CE) of 99.5% and long lifespan of 2500 cycles at 5 mAh cm(-2), 2 mAh cm(-2) is demonstrated. Additionally, the highly reversible Zn electrode significantly boosts overall performance of VO2//Zn full-cells. These findings are expected to be of immediate benefit to a range of researchers in using dual-function additives to suppress Zn dendrite and parasitic reactions for electrochemistry and energy storage applications.

Automated summary

The study introduces a simple method using ethylene diamine tetraacetic acid tetrasodium salt (Na(4)EDTA) to suppress the poor reversibility of the Zn anode in aqueous Zn-ion batteries, effectively inhibiting dendrite growth and hydrogen evolution. Additionally, the added EDTA promotes desolvation of Zn, prolonging the electrode lifespan.