Abstract
Hydrous vanadium oxide (denoted as VO x •yH 2 O) deposited at 0.4 V shows promising capacitive behavior in aqueous media containing concentrated Li ions. VO x •yH 2 O annealed in air at 300 °C for 1 h shows highly reversible Li-ion intercalation/de- intercalation behavior with specific capacitance reaching ca. 737 and 606 F g - 1 at 25 and 500 mV s - 1 in 12 M LiCl between -0.2 and 0.8 V. In 14 M LiCl, retention of specific capacitance is about 95% when the scan rate is increased from 25 to 500 mV s - 1 . This work is the first report showing the ultrahigh rate of Li-ion intercalation/de-intercalation in VO x •yH 2 O. A so-called Li-ion supercapacitor of the asymmetric type consisting of a VO x . yH 2 O cathode and a WO 3 . zH 2 O anode is proposed here. © 2010 Elsevier B.V. All rights reserved.