Co0.5TiOPO4: Crystal structure, magnetic and electrochemical properties

The new titanium oxyphosphate Co0.5TiPO5 has been prepared by solid state reaction. Its structure has been determined by single crystal X-ray diffraction and was further investigated by FT-IR spectroscopy and magnetic measurements. The compound crystallizes in the monoclinic system, S.G: P21/c [a = 7.358(1) Å, b = 7.378(2) Å, c = 7.383(3) Å, β = 119.66(3)°, Z = 4, R1 = 0.0142, wR2 = 0.0429]. The structure can be described as a network of very distorted TiO6 octahedra, in which the Ti4+ ions are displaced from the centres of the octahedra, and slightly distorted PO4 tetrahedra. Half of the octahedral cavities are occupied by Co atoms. The other half of octahedral sites is vacant and favourable for the electrochemical insertion of lithium. The insertion of lithium was studied by galvanostatic charging and discharging between different voltage limits.