In situ reactive coating of metallic and selenophilic Ag2Se on Se/C cathode materials for high performance Li–Se batteries

A facile methodology to fabricate a metallic and selenophilic Ag2Se coating on a Se/nitrogen-doped mesoporous carbon composite, has been successfully developed based on the in situ redox reaction between Se and AgNO3 under ambient conditions. The in situ reactive growth of Ag2Se on Se ensures the complete encapsulation of Se by the Ag2Se coating, which endows the Ag2Se coating with the dual effects of physical entrapment and chemical binding to effectively confine polyselenide intermediates within the cathodes. With the further assistance of mesopore confinement of the nitrogen-doped carbons, the Ag2Se-coated Se/nitrogen-doped mesoporous carbon composites present much improved electrochemical performances with a high initial discharge capacity of 652 mA h g(-1), a high coulombic efficiency of 95.4% and a high reversible capacity of 382 mA h g(-1) after 100 cycles. These encouraging results suggest that the in situ reactive construction of metallic and chalcogenophilic coating layers on the chalcogen (e.g. S, Se and Te)-based electrode materials should be a promising and easy to scale-up method for practical applications of lithium batteries in light of the very simple in situ reaction processes involved.