Fabrication of an ingenious metallic asymmetric supercapacitor by the integration of anodic iron oxide and cathodic nickel phosphide

[Display omitted] •The low-temperature synthesis of single-phase Fe3O4 and Ni2P nanoparticles.•Enhanced surface-active site contributes to improved storage capacity.•The fabricated device demonstrated improved energy and power density.•The device retained upgraded cyclic stability of around 20,000 cycles.•The metallic device’s posture as a prospective strategy for the energy systems. Energy storage systems play a vital role in rationalizing the imminent energy crisis and ecological discomfort. The modern tactic of resolving the lack of energy density dispute with flexible hybrid supercapacitors that could generate high power and energy density under different conditions in energy systems. Here, we introduce a simple solvothermal approach at low temperatures to prepare iron oxide and nickel phosphide nanoparticles. The formation of single-phase pure Fe3O4 and Ni2P with high crystallinity was identified through XRD analysis. The morphology of both the Fe3O4 and Ni2P was confirmed as uniformly distributed nanoparticles with an improved active surface area. The electrochemical activity of the prepared Fe3O4 and Ni2P electrodes revealed improved storage capacity (106 & 354 C g−1) and high retention capability (90%) at higher current densities with resilient cyclic stability (8000 cycles). Finally, a flexible asymmetric supercapacitor was fabricated and demonstrated superiorly high cyclic stability (20,000 cycles) with an improved energy density (31 Wh kg−1) and power density (6400 W kg−1). Therefore, the designed metallic Fe3O4 || Ni2P asymmetric system is anticipated to be a promising strategy toward the advancement of future energy systems.