Growth and Electrochemical Properties of V 2 O 5 Nanotube Arrays
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Growth and Electrochemical Properties of V2O5 Nanotube Arrays
Ying Wang1, Katsunori Takahashi1,2, Huamei Shang1, Kyoungho Lee1,3 and Guozhong Cao1 1 Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA 2 Steel Research Laboratory, JFE Steel Corporation, Japan 3 Division of Materials and Chemical Engineering, Soonchunhyang University, Korea
ABSTRACT Nanotube arrays of amorphous vanadium pentoxide (V2O5) were synthesized through the template-based electrodeposition and its electrochemical properties were investigated for Li-ion intercalation applications. The nanotubes have a length of 10 µm, outer-diameter of 200 nm and inner-diameter of 100 nm. Electrochemical analyses demonstrate that the V2O5 nanotube array delivers a high initial capacity of 300 mAh/g, about twice that of the electrochemically-prepared V2O5 film. Although the V2O5 nanotube array shows a more drastic degradation than the film under electrochemical redox cycles, the nanotube array reaches a stabilized capacity of 160 mAh/g which remains about 1.3 times the stabilized capacity of the film. INTRODUCTION Vanadium pentoxide (V2O5) has attracted considerable attention as Li-ion intercalation material due to its layered structure [1,2]. Lithium ions can be intercalated and deintercalated between the adjacent layers of V2O5. As a result, electrical energy is stored in the V2O5 electrode during intercalation, and energy is released during deintercalation. Hence V2O5 finds wide applications in energy storage devices such as lithium batteries [3] and electrochemical supercapacitors[4]. However, the intercalation capacity and charge/discharge rate of V2O5 are limited by the moderate electrical conductivity (10-2-10-3 S/cm [5]) of V2O5 and the low diffusion coefficient of Li ions (1012 -10-13 cm2/s [6]) in V2O5 matrix. To overcome these disadvantages, increasing the surface area and shortening the diffusion distance of the intercalation electrode play an important role. Nanostructured materials possess large surface area and short diffusion paths, and thus offer promises to achieve significantly enhanced intercalation capacity. Ordered arrays of nanorods, nanotubes or core-shell nanocables are one of the Martin et al. most promising nanostructures for Li+-intercalation applications. investigated the electrochemical properties of V2O5 nanorod arrays made by depositing vanadium pentoxide sol within pores of polycarbonate (PC) membranes, and reported that nanorod arrays achieved 4 times the capacity of a thin-film electrode at high discharge rate [7]. We recently demonstrated single crystal V2O5 nanorod arrays grown by electrochemical deposition, surface condensation induced by a change of local pH as a result of H2O electrolysis, and sol-gel electrophoretic deposition, combined with template growth methods [8,9]. Single-crystal V2O5 nanorod-array electrode delivers 5 times higher capacity than sol-gel derived films at a current density of 0.7 A/g [9]. We have also prepared Ni-V2O5·nH2O nanocable arrays and demonstrated th
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