Organic-solvent-free primary solvation shell for low-temperature aqueous zinc batteries

Abstract

Conventional hybrid aqueous electrolytes with solvated organic co-solvents encounter sluggish desolvation kinetics, especially under low-temperature conditions, due to the strong binding of organic solvents with Zn²⁺. Here, we develop a class of hybrid aqueous electrolytes with an organic-solvent-free primary solvation shell, favoring facile desolvation. As demonstrated by 1 M zinc acetate with dimethyl sulfoxide (DMSO) dipolar aprotic solvent, CH₃COO⁻ and H₂O surround Zn²⁺, forming Zn²⁺(CH₃COO⁻)₂(H₂O)₄ clusters. The enhanced hydrogen bonds between solvated CH₃COO⁻ and H₂O hinder DMSO from replacing solvated H₂O. This weak solvation structure facilitates fast charge transfer kinetics and rapid Zn²⁺ flow through gradient solid electrolyte interphase. At −20°C, stable plating/stripping (5,600 h) and high Zn utilization (51%) are achieved. Furthermore, polyaniline||Zn batteries manifest low polarization (0.05 V), long cycling (8,800 cycles), and high rate. Importantly, this design strategy is generally extended to other hybrid electrolyte systems. This work represents advancements in electrolyte design for aqueous batteries.