High-voltage hydrous electrolytes for electrochemical energy storage

Abstract

Aqueous electrolytes with high electrochemical potential windows (>3 V) were obtained by “trapping” free water molecules in electrolytes. The effects achieved therein are like the hydrating effects of water-in-salt electrolytes (WISEs). In this method, polyethylene glycol (PEG) was added to the electrolytes to hydrate the water molecules, and sodium dodecyl sulfate (SDS) was utilized as a salt to afford ionic conductivity. The thermodynamic stability of the electrolytes improved considerably when the free water molecules bonded tightly to the ethylene oxide (EO) units of the PEG polymer chains. Many conventional salts can also be employed so that inexpensive high-voltage hydrous electrolytes can be obtained. These hydrous electrolytes can be employed in 2.3 V symmetrical supercapacitors (SC) with a specific energy of 18 Whkg−1.