The structure of tavorite LiFePO4(OH) from diffraction and GGA + U studies and its preliminary electrochemical characterization.
Pure tavorite LiFePO4(OH) was synthesized through a hydrothermal route. A fine structural analysis was done by X-ray and neutron diffraction techniques. The structure consists of a three-dimensional network with iron(III) octahedra (FeO6) sharing corners, forming chains that run along the b direction. These chains are interconnected by PO4 tetrahedra, such as the resulting framework encloses tunnels of two different sizes running along the a and c axis. The lithium and hydrogen atoms were precisely localized in these tunnels. Theoretical (GGA + U) calculations performed for LiFePO4X materials (X = OH, F) confirmed our results and revealed that a unique lithium position is expected in LiFePO4(OH), as experimentally observed. For the first time, lithium intercalation was shown to occur in LiFePO4(OH) through the reduction of Fe3+ to Fe2+ at an average voltage of ~2.3 V (vs. Li(+)/Li) with a good cyclability.
Marx
Nicolas
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ICMCB-CNRS, Université de Bordeaux, IPB-ENSCBP - 87 av. Schweitzer, 33608 Pessac cedex, France. crog@icmcb-bordeaux.cnrs.fr.
Croquennec
Laurence
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Cartier
Dany
D
Wattiaux
Alain
A
Le Cras
Frédéric
F
Suard
Emmanuelle
E
Delmas
Claude
C