Lanthanum-zinc mixed metal oxide as electrode material for supercapacitor applications

We report the synthesis of mixed metal oxide of lanthanum and zinc through sol-gel combustion method. Two different compositions of the mixed oxides were produced at 4 and 7 pH. The morphology, purity and crystal structure of the developed compositions were analyzed through scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Raman spectroscopy. Further, electrodes were developed on Ni-foam substrate for both the compositions by mixing the mixed metal oxide powder with binder and additive. These electrodes were electrochemically characterized through cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS) for supercapacitor (SCs) applications. The electrode produced at 4 pH shows high charge storage ability as compared to 7 pH electrode and attained specific capacitance of 209.82 F/g at 2 mV/s and 188.54 F/g at 1 A/g, due to the presence of pure metal oxides and porous microstructure. In-depth study of the CV data established that the charge storage mechanism is purely diffusion base which provides the utilization of the inner surface atoms to store electrical charge. The pH 4 composition also exhibited high cyclic stability of 82 % after 5000 GCD cycles which make it a potential electrode material to be used in efficient and long life SCs devices.