Solvation Structure Design for Aqueous Zn Metal Batteries

Abstract

Aqueous Zn batteries are promising energy storage devices for large-scale energy-storage due to low cost and high energy density. However, their lifespan is limited by the water decomposition and Zn dendrite growth. Here, we suppress water reduction and Zn dendrite growth in dilute aqueous electrolyte by adding dimethyl sulfoxide (DMSO) into ZnCl₂-H₂O, in which DMSO replaces the H₂O in Zn²⁺ solvation sheath due to a higher Gutmann donor number (29.8) of DMSO than that (18) of H₂O. The preferential solvation of DMSO with Zn²⁺ and strong H₂O-DMSO interaction inhibit the decomposition of solvated H₂O. In addition, the decomposition of solvated DMSO forms Zn₁₂(SO₄)₃Cl₃(OH)₁₅·5H₂O, ZnSO₃, and ZnS enriched-solid electrolyte interphase (SEI) preventing Zn dendrite and further suppressing water decomposition. The ZnCl₂-H₂O-DMSO electrolyte enables Zn anodes in Zn||Ti half-cell to achieve a high average Coulombic efficiency of 99.5% for 400 cycles (400 h), and the Zn||MnO₂ full cell with a low capacity ratio of Zn:MnO₂ at 2:1 to deliver a high energy density of 212 Wh/kg (based on both cathode and anode) and maitain 95.3% of the capacity over 500 cycles at 8 C.

Keywords

Affiliated Institutions

• University of Maryland, College Park US
• Brookhaven National Laboratory US

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