Enhanced electrochemical performance of dendritic Fe₂O₃nanowires on hollow carbon nanofibers with manganese and phosphorus co-doping for solid-state symmetric supercapacitors

Maximizing the energy and power density of supercapacitors requires a sophisticated hierarchical three-dimensional structured active material allowing high accessibility to electrons and ions. The mass, charge, and mass balance between the anode and cathode are other hurdles in fabricating asymmetric supercapacitors due to the large specific capacitance difference. Herein, we report a symmetric supercapacitor based on hierarchical interconnected iron oxide on three-dimensional porous and hollow electrospun carbon nanofibers following in situ doping of Mn and P doping. X-ray absorption (XAS) studies revealed that the synergistic effect of Mn and P strengthens the electronic structure of Fe₂O₃. The introduction of Mn increases the electron density around the central metals, whereas P doping effectively strengthens chemical bonding to promote long-term chemical stability. As a result, Mn/P-Fe₂O₃-PCF exhibited an excellent areal specific capacitance of 2506 mF cm⁻², superior rate performance, and outstanding stability. Moreover, the assembled Mn/P-Fe₂O₃-PCF solid-state symmetric supercapacitor device delivered a high areal energy density of 85.41 μW h cm⁻²at a power density of 499.96 mWcm⁻². The delicate design of the binder-free nanostructures in this work suggests a new approach to inhibit growth and structure modulation for high-performance energy storage devices.