Mechanics, Materials Science & Engineering, July 2017 – ISSN 2412-5954
Microstructure and Supercapacitor Properties of V2O5 Thin Film Prepared by Thermal Evaporation Method 1 M. Dhananjaya1, N. Guru Prakash1, G. Lakshmi Sandhya1, A. Lakshmi Narayana1, O.M. Hussain1 1 – Thin Film Laboratory, Dept. of Physics, Sri Venkateswara University, Tirupati, India a – hussainsvu@gmail.com DOI 10.2412/mmse.88.66.781 provided by Seo4U.link
Keywords: Vanadium pentoxide thin films, thermal evaporation, structure and electrochemical properties.
ABSTRACT. Transition metal oxide based supercapacitors perform excellent charge storage capability and long life time stability. Among transition metal oxides, vanadium pentoxide is one of the best suited materials for supercapacitve applications, because it has wide range of oxidation states, layered structure, high energy density (theoretical capacity of 440 mAhg−1), and low cost. The nano structured vanadium pentoxide thin films are deposited onto Ni substrates at various substrate temperature by thermal evaporation technique. The prepared V2O5 films at TS = 300 ˚C exhibited characteristic peaks with predominant (0 0 1) orientation signifying orthorhombic V2O5 phase with space group of Pmmn (59), and the calculated crystallite size is 25 nm. Raman studies confirmed the formation of V2O5 phase. The average grain size of the deposited film is about 148 nm. The films deposited at TS = 300 ˚C exhibited a high rate pseudo capacitance of 730 mFcm-2 at 1mAcm-2 of current density. The electrochemical impedance analysis revealed the films have a lower charge transfer resistance, resulting better capacitance.
Introduction. In recent decades, electrochemical capacitors have been considered as one of the prime candidate for the next generation energy storage devices due to their higher power densities (5 kW kg-1) with longer cycling life (105 cycles) than the batteries and higher energy density (100-200 W h kg-1) than conventional dielectric capacitors [1] . These outstanding properties made them as excellent candidates for hybrid electric vehicles, computers, electric mobile devices, camera-flash equipment, navigational devices and other applications. According to the charge storage mechanism, the electrochemical capacitors are classified into two types, viz electric double-layer capacitors (EDLCs) and pseudo capacitors. In EDLCs no electron transfer takes place between the electrodeelectrolyte interface during charge storage process (non-faradic), while in pseudo capacitors, charge storage process involve a reversible faradaic redox reaction at the electrode-electrolyte interface. Till to date, most extensively used electrode materials for super capacitors are carbon materials such as activated carbon fiber cloth, CNTs, carbon aerogels, conducting polymers, and transition metal oxides or hydroxides. One major disadvantage of carbon based EDLC is lower specific energy storage. Most of the available commercial products have a specific energy below 10 Wh/kg, whereas the lowest numeral for batteries is 35-40 Wh/kg. Transition metal oxides present an attractive alternative electrode materials because of high specific capacitance at low resistance, probably making it easier to construct high energy, high power super capacitors. Recently, oxide materials such as CuO, MnO2, NiO2, TiO2, V2O5, SnO2 etc which have been studied as electrode material for super capacitor. Among transition metal oxides, vanadium pentoxide (V2O5) has been studied as the active material for electrochemical pseudo capacitor applications because of its broad range of oxidation states, layered structure, high energy density, low cost and capability of fast response during charge-discharge process . Especially, V2O5 is interesting in the form of thin film for the possibility of integration into micro-electronic circuitry and its applications in electrochromic devices. The V2O5 thin films can be prepared by various types of techniques including RF/DC magnetron sputtering [2], pulsed laser 1
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