Temperature-Dependent Electrochemical Performance of Ta-Substituted SrCoO₃ Perovskite for Supercapacitors

Developing new electrode materials with good temperature-dependent electrochemical performance has become a great issue for the deployment of hybrid supercapacitors with wide temperature tolerance. In this work, a series of Ta-substituted SrCo_1-x Ta_x O_3-δ (x=0.05, 0.10, 0.15, 0.20) perovskites have been studied as positive electrodes for hybrid supercapacitors in terms of their structures, elemental valence states and electrochemical performances. Incorporating Ta into SrCoO_3-δ perovskite not only stabilizes the crystallite structure but also notably improves electrochemical activities. The SrCo_0.95 Ta_0.05 O_3-δ @CC delivers the highest specific capacity (Q_sp ) of 227.91 C g^-1 at 1 A g^-1 , which is attributed to the highest oxygen vacancy content and the fastest oxygen diffusion kinetics. The hybrid supercapacitor SrCo_0.95 Ta_0.05 O_3-δ @CC//AC@CC exhibits a high energy density of 22.82 Wh kg^-1 @775.09 W kg^-1 and a stable long-term cycle life (5000 cycles) with 90.7 % capacity retention. As temperature increases from 25 to 85 °C, the capacitance properties are improved at elevated temperatures for both electrode and device due to the increased electrolyte conductivity. The outstanding electrochemical results present that SrCo_1-x Ta_x O_3-δ perovskite holds good prospects for hybrid supercapacitors with wide temperature tolerance.