Investigation of Ba 0.5 Sr 0.5 Co x Fe 1-x O 3-δ as a pseudocapacitive electrode material with high volumetric capacitance

Abstract : Ba0.5Sr0.5CoxFe1-xO3-d phases, with 0.75 < x < 0.90, so-called BSCFs, were investigated as pseudocapacitive electrode materials. These polycationic oxide phases were prepared by a modified glycine-nitrate process and show the same perovskite structural arrangement and similar morphological characteristics in the whole series. The electrochemical performance was evaluated in aqueous electrolytes at room temperature. BSCF powders showed promising pseudocapacitive behavior as electrode materials with high volumetric capacitances which depend on the Co/Fe ratio. A volumetric capacitance of 500 F cm-3 , i.e. five times higher than that of a standard activated carbon electrode, was measured in 5.0 M LiNO3 for the electrode based on Ba0.5Sr0.5Co0.8Fe0.2O3-d material composition (x = 0.80). The electrode also exhibited moderate self-discharge and 90% of capacitance retention over 2000 cycles. The charge storage mechanism seems to be dependent upon the nature of the ions in the electrolyte and on the Co/Fe ratio.