Engineering the performance of negative electrode for supercapacitor by polyaniline coated Fe3O4 nanoparticles enables high stability up to 25,000 cycles

Abstract Supercapacitors (SCs) have proven remarkable interest in portable digital devices because of their long life span and high power densities. However, low energy densities of SCs hindered their applications due to the lack of high-performance negative electrode materials. In this work, we demonstrated the successful surface engineering of iron oxide nanoparticles (Fe3O4-NPs) by polyaniline (PANI) coating through a facile low-temperature hydrothermal method. The polyaniline coated iron oxide nanoparticles (Fe3O4/PANI-NPs) were characterized by a series of techniques including XRD, FT-IR, RAMAN, XPS, TGA, BET, SEM, and TEM. Fe3O4-NPs and Fe3O4/PANI-NPs are investigated as negative electrode materials for SCs in basic potassium hydroxide (KOH) electrolyte. The Fe3O4/PANI-NPs sample possesses specific capacitance of 1669.18 F g−1 while Fe3O4-NPs exhibits 1351.13 F g−1 at 1 A g−1 at identical conditions. The Fe3O4/PANI-NPs sample exhibits remarkable electrochemical cycling performance (96.5%) over pristine Fe3O4-NPs (92%) at high current density of 15 A g−1 by exceeding the 25,000 times charge/discharge cycles. The PANI coating not only offers a strong shell to avoid degradation of the material but also contributes to enhancing the capacitance with outstanding stability. Furthermore, we analyzed the charge storage contributions by implementing the power's law and interestingly Fe3O4/PANI-NPs sample exhibits high capacitive type storage (85% capacitive at 10 mVs−1). Based on our experiments, Fe3O4/PANI-NPs shows exceptional high electrochemical results in basic electrolyte with excellent stability and surpass most of recently reported work based on the iron oxides and their composites. Therefore, the proposed strategy can be applied to fabricate the high-performance negative electrode materials for supercapacitors.