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

Hydrous vanadium oxide (denoted as VOx·yH2O) deposited at 0.4 V shows promising capacitive behavior in aqueous media containing concentrated Li ions. VOx·yH2O 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 VOx·yH2O. A so-called Li-ion supercapacitor of the asymmetric type consisting of a VOx.yH2O cathode and a WO3.zH2O anode is proposed here.