The roles of constituting oxides in rare-earth cobaltite-based perovskites on their pseudocapacitive behavior

[Display omitted] •Role of oxides in La/Co/(Sr) US/pyrolytically synthesized oxide powders is examined.•The particles become more spherical with increased temperature.•The aggregation of the particles is less pronounced with increased temperature.•Csp is higher for the samples containing Sr as perovskite structure promoter.•Capacitive stability and rate capability are lower for the samples of higher Csp. The role and influence of strontium and its oxide on structure and capacitive response of materials containing mixed lanthanum cobalt oxides, LC, and lanthanum strontium cobalt oxides, LSC, as a capacitive materials were investigated in this study. The mixed oxides were synthesized by the single-step ultrasonic spray pyrolysis (USP) technique. The microstructures and electrochemical properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, cyclic voltammetry, potentiostatic electrochemical impedance spectroscopy and galvanostatic charge/discharge cycling. It was found that strontium oxide induces the formation of the perovskite structure of promoted pseudocapacitive behavior over an enhancement of redox transitions of cobalt. The measurements showed that the capacitive stability and rate capability were lower for the samples of higher specific capacitance. Among the prepared materials, the LSC prepared at a USP temperature 600 °C showed the best capacitive characteristics in 0.10 M KOH due to having the most defined spherical perovskite structure leading to well-defined reversible charge–discharge performances.