Electrodeposition of mesoporous V 2 O 5 with enhanced lithium-ion intercalation property Jin-Kyu Lee a , Gil-Pyo Kim a , In Kyu Song b , Sung-Hyeon Baeck a, * a Department of Chemical Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon 402-751, South Korea b School of Chemical and Biological Engineering, Seoul National University, Shinlim-dong, Kwanak-ku, Seoul 151-744, South Korea article info Article history: Received 20 May 2009 Accepted 27 May 2009 Available online 2 June 2009 Keywords: V 2 O 5 Mesoporous Electrodeposition Lithium-ion battery abstract Mesoporous vanadium oxide (V 2 O 5 ) thin films were deposited electrochemically onto indium tin oxide- coated glass substrates from an aqueous solution of vanadyl sulfate using CTAB (hexadecyltrimethylam- monium bromide) as a templating agent. For comparison, a control sample was electrodeposited without CTAB templating. Transmission electron microscopy and small angle X-ray diffraction indicated the pres- ence of mesoporosity with a well-ordered lamellar phase in the electrodeposited films. The crystallinity of the V 2 O 5 thin films was confirmed by X-ray diffraction. Cyclicvoltammetry and chronoamperometry were used to measure electrochemical properties of synthesized films. The mesoporous films prepared with CTAB templating had a much higher capacity and lithium-ion diffusion rate than the non-porous electrode prepared without CTAB templating. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction Transition metal oxide materials have attracted considerable interest as catalysts, electronic materials and battery electrodes [1–5]. In particular, vanadium pentoxide (V 2 O 5 ) is of particular interest for its potential applications in energy storage devices, such as lithium-ion batteries and supercapacitors, on account of its high intercalation properties, large specific capacity and good stability [6–8]. The synthesis of high surface area vanadium oxide is also of great interest due to the versatility in catalysis and energy storage device [9–12]. Specially, mesoporous vanadium oxide pro- vides a very short diffusion path for lithium ions allowing rapid charge and discharge. Moreover, the high surface area of the mes- oporous structure results in a higher capacity of lithium ions. Phys- ical and chemical methods have been proposed for the synthesis of mesoporous vanadium oxide, including chemical vapor deposition, sol–gel methods, sputtering and electrodeposition. Electrochemical methods for the fabrication of mesoporous thin films have many advantages over other methods in terms of eco- nomics and flexibility. Electrodeposition is carried out at low tem- peratures and pressures. A mesoporous structure can be fabricated using a small amount of templating agent because it utilizes only the assemblies on the surface of the electrode, which is formed by the electrochemical potential. A porous structure can be con- trolled by varying the electrodeposition conditions, such as deposi- tion voltage, deposition time and surfactant concentration. The electrode is synthesized directly without a binding or pasting pro- cess. The surfactant can be removed easily by washing with an appropriate solvent. In this study, an electrochemical method was used to fabricate meso-structured V 2 O 5 thin films with long-range order, and the performance of the synthesized mesoporous vanadium oxide as a cathode in a lithium battery cell was investigated. 2. Experimental 2.1. Electrodeposition of vanadium oxide films The electrolyte was prepared by dissolving 1.63 g VOSO 4 nH 2 O in 50 ml DI water, and 2.5 g CTAB (hexadecyltrimethylammonium bromide) was added to the solution to synthesize the mesoporous structure. The pH was then adjusted to 1.8 by adding 1 M H 2 SO 4 . Prior to electrodeposition, ITO (indium tin oxide)-coated glass was washed by ultrasonification for 15 min in a 1:1 mixed solution of iso-propanol and acetone. Electrodeposition was performed potentiostatically at 2.0 V for 10 min at 65 °C using ITO-coated glass as the substrate. Pt and Ag/AgCl electrodes were used as the counter and reference electrodes, respectively. For comparison, a control sample of V 2 O 5 was electrodeposited without CTAB. The resulting films were rinsed in a mixture of ethanol and DI water to remove the CTAB, and characterized after drying in air. The crys- tallinity was examined after calcining the as-synthesized sample at 350 °C for 1 h. 1388-2481/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2009.05.053 * Corresponding author. Tel.: +82 32 860 7474; fax: +82 32 872 0959. E-mail address: shbaeck@inha.ac.kr (S.-H. Baeck). Electrochemistry Communications 11 (2009) 1571–1574 Contents lists available at ScienceDirect Electrochemistry Communications journal homepage: www.elsevier.com/locate/elecom