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Crystal structure and lithium insertion properties of orthorhombic Li2TiFe(PO4)3 and Li2TiCr(PO4)3

2004; Elsevier BV; Volume: 6; Issue: 10 Linguagem: Inglês

10.1016/j.solidstatesciences.2004.07.028

1873-3085

Sébastien Patoux, Gwenaëlle Rousse, Jean‐Bernard Leriche, Christian Masquelier,

Advanced Battery Materials and Technologies

The crystal structures of orthorhombic Li2TiFe(PO4)3 and Li2TiCr(PO4)3 were determined from Rietveld refinement of neutron powder diffraction data. Both compounds are isostructural in the Pbna space group with a=8.543(1)Å, b=8.623(1)Å, c=11.978(1)Å and a=8.505(1)Å, b=8.589(1)Å, c=11.929(1)Å, respectively. Lithium ions are located in a single four-fold coordinated site Li(1). Electrochemical insertion of lithium proceeds through the reduction of Fe3+ into Fe2+ (∼2.8V vs. Li+/Li) and Ti4+ into Ti3+ (∼2.5V vs. Li+/Li) towards the new compositions Li3TiCr(PO4)3 and Li4TiFe(PO4)3. In situ X-ray diffraction and potentiostatic intermittent titration technique indicate a solid solution mechanism for the reversible lithium insertion/extraction. Chemical reaction of Li2TiFe(PO4)3 with n-BuLi leads to orthorhombic Li4TiFe(PO4)3.