Investigation of Energy Storage Performance and Cycling Stability of Electrochemically Synthesized PANI–ZnFe2O4 Electrodes

Conducting polymer-metal oxide hybrids are promising electrode materials for supercapacitors, yet achieving a balance between high capacitance and long-term stability remains challenging. In this work, polyaniline (PANI) - zinc ferrite (ZnFe₂O₄) composites were synthesized by in situ electrochemical polymerization of aniline with controlled deposition duration for ZnFe2O4-nanoparticle incorporation. Structural and spectroscopic characterization confirmed uniform dispersion of ZnFe2O4 within the polymer matrix and the formation of fibrous nanostructures. Electrochemical analysis revealed a progressive enhancement of redox activity and charge storage with increasing ZnFe2O4 content. The optimized composite exhibited a specific capacitance of up to 1402 F g⁻¹ at 1 A g⁻¹, together with an energy density of 141.9 Wh kg⁻¹ and a power density of 404.9 W kg⁻¹. When assembled into a symmetric supercapacitor, the PANI-zinc ferrite composite retained 97.6% of its initial capacitance after 10,000 charge–discharge cycles. Electrochemical impedance spectroscopy further indicated that structural degradation under accelerated aging is primarily associated with particle and polymer chain cracking/breaking, leading to increased mass transport resistance, thereby reducing the energy storage capability.