Promoting operating voltage to 2.3 V by a superconcentrated aqueous electrolyte in carbon-based supercapacitor

Aqueous supercapacitors (SCs) have attracted more and more attention for their safety, fast charge/ discharge capability and ultra-long life. However, the application of aqueous SCs is limited by the low working voltage due to the narrow electrochemical stability window (ESW) of water. Herein, we report a new water in salt (WIS) electrolyte by dissolving potassium bis (fluorosulfonyl) amide (KFSI) in water with an ultra-high mass molar concentration of 37 mol/kg. The highly concentrated electrolyte can achieve a wide ESW of 2.8 V. The WIS electrolyte enables a safe carbon-based symmetrical supercapacitor to operate stably at 2.3 V with an ultra-long cycle life and excellent rate performance. The energy density reaches 20.5 Wh/kg at 2300 W/kg, and the capacity retention is 83.5% after 50,000 cycles at a current density of 5 A/g. This new electrolyte will be a promising candidate for future high-voltage aqueous supercapacitors. (c) 2021 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

The newly developed water in salt electrolyte shows great potential in supercapacitors, with a wide electrochemical stability window that allows carbon-based supercapacitors to operate safely and stably at higher voltages, with ultra-long cycle life and excellent energy density.