BSCFs oxides have been prepared by sol-gel process followed by high temperature treatment. The resulting powders show the same perovskite structural arrangement as well as identical morphology characteristics. BSCFs electrodes were tested in 5M LiNO₃ aqueous electrolyte, and have demonstrated promising pseudocapacitive behavior while performances depend on the Co/Fe ratio. A maximum capacitance of 87 F.g^-1 was obtained for the electrode based on the BSCF material with x = 0.80. Charge storage mechanism was investigated by in situ X-Ray Absorption Spectroscopy carried out on the ROCK beamline at SOLEIL Synchrotron (France) at both Fe and Co K-edges. Both Co and Fe were found being electrochemically involved in the charge storage mechanism. XAS in situ measurements allow to propose an advanced description of the charge storage mechanism. It shows the involvement of electrolytic cations but also of oxygenated moieties.

BSCFs oxides were also investigated in asymmetric devices using FeWO₄ or activated carbon as negative electrode. These two devices were operated between 0 and 1.6 V and have demonstrated a remarkable cycling ability with a high capacitance retention over 45,000 cycles. The advantages and limits of high density oxides with pseudocapacitive behavior operated in devices will also be highlighted in this study.