Electrochemical intercalation of lithium in the titanium hydrogeno phosphate Ti(HPO4)2·H2O

The electrochemical reactivity of the layered titanium hydrogeno phosphate Ti(HPO4)2�H2O versus lithium has been studied. Lithium intercalation occurs at ?2.5 V with low polarization, leading to a new lithiated Ti(III) phase, LiTi(HPO4)2�H2O. Ti(HPO4)2�H2O exhibits a reversible capacity of 80 mAh g-1 in the voltage window 1.8-3.5 V at C/10 rate. The stable reversible capacity reveals that the presence of H2O lattice is not affecting the electrochemical reaction. The reversibility of the reaction is demonstrated by extracting lithium from LiTi(HPO4)2�H2O and the host structure is intact. The electrochemical behaviour of dehydrated phases Ti(HPO4)2 and TiP2O7 has also been investigated. � 2007 Elsevier B.V. All rights reserved.