Low Temperature Syntheses of Transition Metal Bronzes with an Open Structure for High Rate Energy Storage

Abstract

ABSTRACTDevelopment of devices storing and delivering high-energy power such as supercapacitors is necessary to assist intermittent sources of energy. Most of the commercial systems are carbon-based, but due to their high surface charge, oxides offer a valuable alternative for high-rate energy storage. Among them, layered transition metal oxides with mixed valence properties present both good electronic and ionic conductivities suitable for application to electrochemical applications intermediate between capacitors and batteries. This work focuses on lamellar oxide bronzes based on cobalt MxCoO2 and vanadium MxV2O5 (M = H, Li, Na or K). A low temperature synthesis leads to high specific area particles (above 100 m2/g). Hydrated and anhydrous NaxCoO2 are promising cathode materials for aqueous supercapacitors, with a high capacity of more than 100 mAh/g obtained under 20 mV/s for the hydrated NaxCoO2. The MxV2O5 bronzes appear to be good candidates for organic supercapacitors, especially the LixV2O5 bronze, which shows a high stable capacity above 100 mAh/g (at 20 mV/s ie a charging time of 125 s).