High-Performance Bi-Doped NiFe₂O₄ Nanoparticles for Advanced Supercapacitors and Room-Temperature Magnetic Memory Applications

This study investigates the synthesis, characterization, and application of NiFe2-xBixO4 nanoparticles (NPs) with varying bismuth (Bi) doping concentrations (x = 0–20%) to enhance magnetic memory and electrochemical performance. X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed the successful incorporation of Bi3+ ions, while FE-SEM and EDX analyses revealed porous morphologies and accurate elemental compositions. Magnetic measurements indicated a significant room-temperature magnetic memory effect, suggesting a spin-glassy behavior. Electrochemical studies via cyclic voltammetry and galvanostatic charge–discharge techniques highlighted the superior performance of the 20% Bi doped NiFe2O4, achieving a specific capacitance of 339.16 F/g at a 5 mV/s scan rate and an energy density of 4.37 Wh/kg at 1 A/g current density. This composition also exhibited excellent cyclic stability, retaining 90.76% of its capacity after 5000 cycles. Furthermore, practical applicability was evaluated using a two-electrode system, where the 20% Bi doped NiFe2O4 electrode demonstrated a specific capacitance of 68.94 F/g at 0.1 A/g, along with a maximum energy density of 1.172 Wh/kg and power density of 35 W/kg, indicating robust performance under realistic device conditions. The two-electrode results reinforce the suitability of Bi-doped NiFe2O4 NPs for real-world energy storage applications. These findings underscore the potential of Bi-doped NiFe2O4 NPs as high-performance candidates for advanced supercapacitors and magnetic memory devices, bridging energy storage and electrochemical technologies.