Magnetic CuFe2O4 Spinel–Polypyrrole Pseudocapacitive Composites for Energy Storage

This investigation focused on the fabrication of ceramic ferrimagnetic CuFe₂O₄-conductive polypyrrole (PPy) composites for energy storage. CuFe₂O₄ with a crystal size of 20-30 nm and saturation magnetization of 31.4 emu g^-1 was prepared by hydrothermal synthesis, and PPy was prepared by chemical polymerization. High-active-mass composite electrodes were fabricated for energy storage in supercapacitors for operation in a sodium sulfate electrolyte. The addition of PPy to CuFe₂O₄ resulted in a decrease in charge transfer resistance and an increase in capacitance in the range from 1.20 F cm^-2 (31 F g^-1) to 4.52 F cm^-2 (117.4 F g^-1) at a 1 mV s^-1 sweep rate and from 1.17 F cm^-2 (29.9 F g^-1) to 4.60 F cm^-2 (120.1 F g^-1) at a 3 mA cm^-2 current density. The composites showed higher capacitance than other magnetic ceramic composites of the same mass containing PPy in the same potential range and exhibited improved cyclic stability. The magnetic behavior of the composites was influenced by the magnetic properties of ferrimagnetic CuFe₂O₄ and paramagnetic PPy. The composites showed a valuable combination of capacitive and magnetic properties and enriched materials science of magnetic supercapacitors for novel applications based on magnetoelectric and magnetocapacitive properties.