Advance Aqueous Asymmetric Supercapacitor Based on Large 2D NiCo2O4 Nanostructures and the rGO@Fe3O4 Composite.

Abstract

NiCo2O4 nanostructure is a widely studied pseudocapacitor material because of its high specific capacitance value. Most of the time, the thickness of the nanostructure inhibits the electrode material from whole-body participation and causes sluggish charge transportation. These phenomena directly interfere with the electrochemical performance of the electrode, such as specific capacitance value, stability, energy density, and so forth. Here, two different thin two-dimensional morphologies (nanosheet and nanoplate) of the NiCo2O4 nanocomposite with a large lateral size are reported using ammonia as a hydrolyzing agent. The large size and flat surface of the as-synthesized materials offer enormous active sites during the electrochemical reaction, and the thin wall makes the ion penetration and transportation very effective and facile. Therefore, the NiCo2O4 nanosheet and nanoplate structures exhibited high specific capacitance values of 1540 and 1333 F/g, respectively, with excellent rate and good cycling stability. Here also, two different advance aqueous asymmetric supercapacitors have been reported utilizing two NiCo2O4 nanostructure materials as positive electrodes and the rGO@Fe3O4 composite as a negative electrode, which exhibited excellent rate and high specific energy without sacrificing the specific power. We also studied the electrochemical activity of the rGO@Fe3O4 composite at different compositions.