Spinel ZnMn₂O₄/Ni-based metal-organic framework hybrid composite for high-performance asymmetric supercapacitors

Creation of advanced electrode materials with superior electrochemical performance is essential for advancing next-generation supercapacitors. Integrating spinel oxide with metal-organic frameworks significantly enhances the supercapacitor's electrochemical performance, energy, and power density. In this study, we synthesised a ZnMn₂O₄/Ni-MOF composite via the solvothermal technique and examined its structural and morphological characteristics using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), spectroscopy, high-resolution scanning electron microscopy (HR-SEM), and X-ray photoelectron spectroscopy (XPS). Further, the electrochemical analysis at a three-electrode system demonstrates exceptional performance characteristics, showing a specific capacitance (C_s) of 623 F g^-1 at 1 A g^-1 and impressive cyclic endurance, with 82% capacity retention and coulombic efficiency of 98% after 5000 cycles. Ex situ XRD and SEM analysis are employed to study the structural and morphological changes after cycling the electrodes. The aqueous asymmetric supercapacitor (AASC) configuration shows a C_s of 155 F g^-1 at 1 A g^-1, with a remarkable energy density of 55 Wh kg^-1 and power density of 800 W kg^-1. An asymmetric supercapacitor (ASC) device is also developed, and it exhibits a C_s of 15 F g^-1 at 1 A g^-1. Additionally, its efficacy is evaluated by connecting two ASCs in series to power the LEDs. These results demonstrate the excellent performance of the ZnMn₂O₄/Ni-MOF composite, which can be used in real-life applications to provide advanced energy storage solutions.