Potassium formate-based electrolytes for high performance aqueous electrochemical capacitors

Abstract

In this work we report the use of a water-in-salt (WiSE) electrolyte based on potassium formate (HCOOK). We showed that a solution of 14 M HCOOK in H2O displays promising transport properties and can be successfully utilized for the realization of electrochemical double layer capacitors (EDLCs) operating at 1.7 V, displaying high energy and power densities and extraordinary cycling stability (90% of capacitance retention after 1700 h of float at 1.7 V). Taking these results into account, and the fact that 14 M HCOOK in H2O is cheap, environmentally friendly and not toxic, this electrolyte can be certainly considered very promising for the realization of a novel generation of cheap and high performance aqueous EDLCs.