Preparation of ferromagnetic perovskite La_0.65Sr_0.35MnO₃ electrodes for supercapacitor applications

Ferromagnetic perovskite La₀.₆₅Sr₀₃₅MnO₃ (LSM) is prepared as an active material for electrodes with high active mass loading of 40 mg cm⁻² for applications in supercapacitors. The experimental approach of this investigation is based on the use of high energy ball milling and application of gallocyanine as an advanced catecholate-type chelating dispersant. We report a high capacitance of 3.75 F cm⁻² from cyclic voltammetry data at 2 mV s⁻¹ and 4.59 F cm⁻² from chronopotentiometry data at 3 mA cm⁻² for LSM. The electrodes show nearly ideal pseudocapacitive behavior and a low resistance. The capacitance of ferromagnetic perovskite LSM electrodes in a positive potential range is higher or on a par with capacitances of spinel ferrimagnetic electrodes for operation in a negative potential range in the same electrolyte. Cycling at fast charge–discharge rates shows capacitance increase, which is attributed to morphology changes and oxidation of Mn ions. The LSM electrodes were used for application in magnetic asymmetric devices, containing ferromagnetic LSM cathodes and ferrimagnetic CoFe₂O₄ based anodes with high active mass for operation in a neutral Na₂SO₄ electrolyte.