Dual‐Function Electrolyte Additive for Highly Reversible Zn Anode

Abstract 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 ZnSO 4 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(H 2 O) 6 2+ by removing H 2 O molecules from the solvation sheath of Zn 2+ . 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 VO 2 //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.