Solvent Polarity-Induced Regulation of Cation Solvation Sheaths for High-Voltage Zinc-Based Batteries with a 1.94 V Discharge Platform

Abstract

To address the challenge of low discharge platforms (<1.5 V) in aqueous zinc-based batteries, highly concentrated salts have been explored due to their wide electrochemical window (~3 V). However, these electrolytes mainly prevent hydrogen evolution and dendrite growth at the anode without significantly enhancing voltage performance. Herein we introduce an approach by adjusting solvent polarity to regulate cation solvation sheaths in hybrid electrolytes, reducing Zn/Zn2+ oxidation potential and water activity. Through strong cation-water coordination and hydrogen bonding between dimethylsulfoxide and water, the designed electrolyte, at a low concentration, achieves a broader electrochemical window (4 V) than conventional concentrated electrolytes. Using this electrolyte, a Zn/Zn battery showed an impressive cycle life of 4340 cycles, while a Zn/lithium manganate battery delivered a high discharge platform of over 1.9 V with exceptional cycling stability. A Zn-based micro-battery with a polyvinyl alcohol-based hybrid electrolyte also achieved a record-high discharge platform of 1.94 V. This work presents a promising strategy for developing low-concentration electrolytes for high-performance sustainable energy storage.