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 (Na4EDTA) to a ZnSO4 electrolyte. This is shown to concomitantly suppress dendritic Zn deposition and H2 evolution. Findings confirm that EDTA anions are adsorbed on the Zn surface and dominate active sites for H2 generation and inhibit water electrolysis. Additionally, adsorbed EDTA promotes desolvation of Zn(H2O)62+ 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.

Strategies of regulating Zn2+solvation structures for dendrite-free and side reaction-suppressed zinc-ion batteries

“…The strategies of zinc-philic additives and the corresponding electrochemical performance are summarized in Table 3. 58,87,101,207–209,211,213,216–225 These zinc-philic additives can adsorb onto the zinc anode surface via physical/chemical adsorption to form a protective layer on the anode surface, which can effectively prevent the contact between H 2 O and zinc and guide the uniform zinc deposition. Besides, the adsorbed additive molecules promote the desolvation of Zn(H 2 O) 6 2+ by removing H 2 O molecules from the solvation sheath of Zn 2+ , which can suppress the HER, corrosion, and formation of by-products and zinc dendrites.…”

Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives

“…Thus, there is an additional demand for energy to overcome the strong interaction between Zn 2+ ions and H 2 O solvation sheath. Even worse, the free H 2 O molecules transferred from the electrolyte or generated after the desolvation process may participate in side reactions, causing hydrogen evolution and corrosion [ 51 ]. Anions in the electrolyte are also related to anode performance.…”

Issues and Opportunities Facing Aqueous Mn2+/MnO2‐based Batteries

“…Electrolyte additives are the mostly employed strategies on electrolyte in Mn 2 + /MnO 2 -based batteries, [19,20] of which the added ions could have catalysis effects on the Mn 2 + /MnO 2 reaction or directly enter into the crystal lattice of deposited MnO 2 and enhance the electronic conductivity. Besides the other functional additives such as redox mediators, electrolyte additives may also contribute to the protective coatings on the anode to address the issues of acidic corrosion, [36] H 2 evolution, [37] dendrites, [38] and so on. Besides, the hydrogel electrolytes were also applied in Mn 2 + / MnO 2 -based batteries, as it could achieve decoupled electrolyte without selective ion-exchange membrane in spite of large overpotential.…”