(Invited) Investigation of Ba0,5Sr0,5CoxFe1-XO3-Δ As Pseudocapacitive Electrode for Aqueous Electrochemical Capacitor

Abstract

Supercapacitors are attractive electrochemical energy storage devices for high power applications. However, volumetric energy density is the main limitation for their integration in such applications as terrestrial transport systems. The use of high density pseudocapacitive oxides as electrode material could lead to a volumetric energy density improvement. With this aim, materials from Ba0,5Sr0,5CoxFe1-xO3-δ family, so called BSCFs, have been studied. Several compositions have been prepared and evaluated as positive electrode materials in aqueous neutral electrolyte. Volumetric capacitances have shown to be greater than those of activated carbons, already used in commercialized supercapacitors. Their electrochemical properties are strongly related to the cobalt to iron ratio, to the charging rate, to the electrolyte composition, and other key parameters. The study of the charge storage mechanism occuring in these materials has been investigated thanks to in situ X-Ray absorption spectroscopy and operando X-Ray diffraction performed at SOLEIL (France) and SPring-8 (Japan) synchrotron facilities respectively. Devices coupling BSCF based positive electrode with activated carbon or FeWO4 based negative electrode have demonstrated the added value of such materials to improve the volumetric energy density of supercapacitors.