Porous Spheres of Nickel–Cobalt Bimetallic Organic Framework/Polyvinylpyrrolidone Nanocomposites as an Asymmetric Supercapacitor

The improvement of the morphology and structure of electrode materials is considered to be an effective way to improve their electrochemical performances. This study aims to search for resource-rich and inexpensive electrode materials that can improve specific capacity, energy density, and cycling stability. The NiCo-MOF nanocomposites are prepared by the solvothermal method with polyvinylpyrrolidone (PVP) as a regulator for the first time. The effect of PVP contents on the morphology, structure, and properties of NiCo-MOF is investigated. The prepared NiCo-MOF/Px nanocomposites are spherical in structure, formed by the accumulation of fine vertical nanosheets when the content of PVP was 40%, which has high specific capacity of 904 F g–1 at 1 A g–1 and smaller Rs (0.53 Ω) and Rct (0.89 Ω). The asymmetric supercapacitors, assembled with NiCo-MOF/P40% nanocomposites as the positive electrode and activated carbon as the negative electrode, have a high energy density and a power density, and it can retain an initial capacitance of approximately 87.36% after 10,000 charge/discharge cycles at 5 A g–1. The addition of PVP is demonstrated to effectively change the structure and morphology of the material to provide more redox active sites and convenient electrolyte ion diffusion channels, thus improving the electrochemical performance of the material.