Hybrid-ion - A lithium-ion cell based on a sodium insertion material

This communication describes the performance characteristics of a graphite/Li+ electrolyte/Na3V2(PO4)(2)F-3 hybrid-ion cell. The properties of this system compare favorably with commercial lithium ion cells. During the initial charging of this cell, sodium ions are extracted from the fluorophosphate while concurrent lithium ion intercalation occurs at the graphite counter electrode. During subsequent cell cycling the cathode reaction is likely based on a mixed Li/Na insertion mechanism. Importantly we find that highly lithiated graphite is electrochemically stable in the presence of Na+ in the electrolyte phase, presumably due to the presence of the carbon passivation layer. (c) 2006 The Electrochemical Society.