Effect of lithium and sodium salt on the performance of Nb₂O₅/rGO nanocomposite based supercapacitor

The present work reports the synthesis of Nb₂O₅/rGO composite using hydrothermal method and thermal annealing process. The prepared composite was found to have suitable characteristics necessary to be used as electrode material in supercapacitors. These characteristics were ascertained employing the techniques of scanning electron microscopy (SEM), x-ray diffraction (XRD), Raman spectroscopy and N₂ adsorption-desorption isotherm. Further, the electrochemical performance of the prepared composite was compared in two different organic electrolytes, of lithium and sodium salt using the techniques of electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and charge-discharge measurements. The organic electrolyte solutions were prepared by dispersing 1 M LiClO₄/NaClO₄ in a mixture of ethylene carbonate/propylene carbonate (1:1 by volume). The observed results indicate that the composite of Nb₂O₅/rGO offers higher value of specific capacitance in sodium salt electrolyte and higher cyclic stability in lithium salt electrolyte. This is probably due to ion properties of electrolyte. Specific capacitance is observed according to efficient ion/charge diffusion/exchange and relaxation time (Li⁺ < Na⁺), while the cyclic stability is observed according to cation size (Na⁺ > Li⁺). Thus, the present study reveals the significant effect of electrolyte ions on electrochemical performance of Nb₂O₅/rGO composite.