Lithium insertion in the high-pressure polymorph of FePO4 -: Computational predictions and experimental findings

The high pressure (HP) polymorphs of quartz-FePO4 and olivine-LiFePO4 crystallize in structures related to the CrVO4 structural-type. First principles calculations predict that HP-FePO4 is electrochemically active at 3.6 V vs Li + /Li. Accordingly, electrochemical experiments followed by in situ synchrotron X-ray diffraction prove that 0.22 Li ions can be inserted in HP-FePO4 at 3 V. The inserted lithium ions have been located, by Fourier difference analysis, at the initially empty tetrahedral sites of the structure, equivalent to those occupied by lithium in HP-LiFePO4. The lithium insertion reaction is reversible although it presents a very slow kinetics. (c) 2005 The Electrochemical Society.