Solvation Structure Design for Aqueous Zn Metal Batteries

摘要

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 ZnCl_2-H_2O, in which DMSO replaces the H_2O in Zn~(2+) solvation sheath due to a higher Gutmann donor number (29.8) of DMSO than that (18) of H_2O. The preferential solvation of DMSO with Zn~(2+) and strong H_2O-DMSO interaction inhibit the decomposition of solvated H_2O. In addition, the decomposition of solvated DMSO forms Zn_(12)(SO_4)_3Cl_3(OH)_(15)· 5H_2O, ZnSO_3, and ZnS enriched-solid electrolyte interphase (SEI) preventing Zn dendrite and further suppressing water decomposition. The ZnCl_2-H_2O-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‖MnO_2 full cell with a low capacity ratio of Zn:MnO_2 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.