Electrochemically Composites Of Vanadium Oxide/Molybdenum Oxide And Its Properties For Supercapacitors

Supercapacitors,also called electrochemical capacitors,have attracted much attention due to their excellent energy storage performance at high power.However,their energy density requires improvement in order to meet the growing demand for energy storage systems.Transition metal oxides,such as vanadium oxides,store energy through fast and reversible electrochemical reactions,thus offering an effective strategy to improve the energy density of supercapacitors.Unfortunately,the capacitance and rate capability of vanadium oxides cannot fulfill the requirements for practical applications yet.Constructing heterogeneous nanostructure would promote electron and ion transfers in electrode materials,so as to enhance their electrochemical performance.In this essay,I use cyclic voltammograms(CV)to electro-deposit mixed valence vanadium oxide(VOx)nanorods on the partially exfoliated functionalized graphene(FEG).An ultra-thin MoO3 film is then galvanostatically grown on VOx nanorods to construct the heterogeneous nanostructures.The morphologies of the materials are characterized by scanning electron microscopy(SEM)and transmission electron microscopy(TEM),while the synergistic effects generated by the heterogeneous components are investigated by X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR)and electrochemical impedance spectroscopy(EIS).The results demonstrate that the ultra-thin MoO3 coating improves the conductivity of the electrode material and promotes the energy storage capability.It also prevents active material dissolution in the aqueous electrolyte(LiCl),so that the cycling stability is enhanced.The effect of MoO3 deposition periods on the electrode performance is further studied in detail,and the 9 s deposition shows the optimum behavior.The VOx@MoO39s electrode provides the highest areal capacitance of 1980 mF cm-2 at 2 mA cm-2.Even at a high current density of 100 mA cm-2,it still maintains a promising capacitance of 1166 mF cm-2.An asymmetric supercapacitor MnO2/CEG//VOx@MoO3-9 s/FEG was assembled using VOx@MoO3 as the anode and MnO2 deposited on cathodically exfoliated graphite foil(MnO2/CEG)as the cathode in 5 M LiCl electrolyte.A high energy density of 3.015 mWh cm3 is achieved at the power density of 0.0325 W cm-3,and 1.625 mWh cm-3 is obtained at the high power density of 0.65 W cm-3.