title: High Performance Hybrid Energy Storage with Potassium Ferricyanide Redox Electrolyte.
abstract: We demonstrate stable hybrid electrochemical energy storage performance of a redox-active electrolyte, namely potassium ferricyanide in aqueous media in a supercapacitor-like setup. Challenging issues associated with such a system are a large leakage current and high self-discharge, both stemming from ion redox shuttling through the separator. The latter is effectively eliminated when using an ion exchange membrane instead of a porous separator. Other critical factors toward the optimization of a redox-active electrolyte system, especially electrolyte concentration and volume of electrolyte, have been studied by electrochemical methods. Finally, excellent long-term stability is demonstrated up to 10 000 charge/discharge cycles at 1.2 and 1.8 V, with a broad maximum stability window of up to 1.8 V cell voltage as determined via cyclic voltammetry. An energy capacity of 28.3 Wh/kg or 11.4 Wh/L has been obtained from such cells, taking the nonlinearity of the charge-discharge profile into account. The power performance of our cell has been determined to be 7.1 kW/kg (ca. 2.9 kW/L or 1.2 kW/m(2)). These ratings are higher compared to the same cell operated in aqueous sodium sulfate. This hybrid electrochemical energy storage system is believed to find a strong foothold in future advanced energy storage applications.
authors.affiliation: INM - Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany.|Department of Materials Science and Engineering, Saarland University , Campus D2 2, 66123 Saarbrücken, Germany.
authors.forename: Juhan
authors.initials: J
authors.lastname: Lee
authors.affiliation: INM - Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany.
authors.forename: Soumyadip
authors.initials: S
authors.lastname: Choudhury
authors.affiliation: INM - Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Weingarth
authors.affiliation: INM - Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany.|School of Energy, Materials and Chemical Engineering, Korea University of Technology and Education , Chungjeol-ro 1600, 31253 Cheonan, Republic of Korea.
authors.forename: Daekyu
authors.initials: D
authors.lastname: Kim
authors.affiliation: INM - Leibniz Institute for New Materials , Campus D2 2, 66123 Saarbrücken, Germany.|Department of Materials Science and Engineering, Saarland University , Campus D2 2, 66123 Saarbrücken, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Presser
keywords: energy storage; ion exchange membrane; redox electrolyte; redox shuttling; supercapacitor