Highly Reversible Li Insertion at 4 V in ɛ-VOPOsub 4/α-LiVOPOsub 4 Cathodes

Electrochemical (and chemical) lithium intercalation into a new vanadium phosphate, , is a two‐phase process involving reduction of to at an attractive potential . X‐ray diffraction shows that this material and that obtained from reduction are structurally similar to high‐temperature . Increased stability and capacity are achieved with chemically lithiated when contact with the conductive additive is enhanced by mechanical grinding. Following the first charge cycle, reversible electrochemical lithium extraction/insertion at a cycling rate of affords a specific capacity of over that is stable for at least 100 cycles. This material demonstrates the best overall properties, thus far, of any polyanionic vanadium phosphate structure. ©2000 The Electrochemical Society