Integrating battery-like materials into supercapacitors

Abstract

A binder-free composite hybrid electrode material was deposited through electrodeposition by combining carbon-based materials (graphene oxide) and battery like materials (NiO, ZnO and Al₂O₃) in a single electrode. The structural, morphological and electrochemical properties of CaAl₂O₄–ZnO/rGO composite thin film were studied to characterize the hybrid composites. The average crystallite size D of the hybrid composites is 23 nm with an average inter planar spacing of 1.90 Å and lattice constants (a = b = c = 1.456 Å) that reveal a rhombohedral structure. The introduction of Ni increases the cracks and nullifies the rod-like morphology of the undoped thin film while the presence of Ag reveals the nonexistence of cracks at lower concentrations of Ag dopant but densely packed homogenous noodle-like grains with cracks can be seen at a 0.03 M sample. EDX analysis confirmed the presence of deposited elements with the exception of Ag, and this could possibly be due to the low intensity of the Ag dopant or the low deposition voltage. Cyclic voltammetry curves show typical electrochemical behavior with clear oxidation and reduction peaks for most samples. The Ni_x = 0.06 doped CaAl₂O₄–ZnO/rGO composite thin films have the maximum specific capacitance of 673 F/g at a scan rate of 100 mV/s, while the Ag_x = 0.03 doped thin film has the minimum specific capacitance of 205 F/g at the same scan rate. indicating that NCZr3 has a good electrochemical behavior at 0.1 mA/g with an energy density and a power density of 59.83 W · h/Kg and 26.926 W · h/Kg, respectively. These results reveal the suitability of the Ni doped material as an electrode material for supercapacitor applications and confirm the model of roughening. Further studies should be explored by lowering scan rates (5–50 mV/s), adding binder materials, and properly varying Ag concentration and deposition time in order to explore more desirable properties for advanced applications.