A novel vanadium oxide deposit for the cathode of asymmetric lithium-ion supercapacitors

Hydrous vanadium oxide (denoted as VOx center dot yH(2)O) deposited at 0.4 V shows promising capacitive behavior in aqueous media containing concentrated Li ions. VOx center dot yH(2)O annealed in air at 300 degrees 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 VOx center dot 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. (C) 2010 Elsevier B.V. All rights reserved.