Structural and Electrochemical Study of Li0.5Mn0.5Ti1.5Cr0.5(PO4)3

Materials from the Li(1-x)MnxTi(2-x)Crx(PO4)3 (x=0, 0.5, 1) solid solution were obtained by solid state reaction. The structure of the selected Li0.5Mn0.5Ti1.5Cr0.5(PO4)3 composition was determined from X-ray diffraction data using Rietveld analysis. It is similar to that of MnTiCr(PO4)3 (space group R c) with the Ti and Cr atoms in the Nasicon framework, while the Mn atoms are statistically distributed in the M1 sites. A comparative study of lithium intercalation in LiTi2(PO4)3, Mn0.5Ti2(PO4)3, and Li0.5Mn0.5Ti1.5Cr0.5(PO4)3 clearly illustrates that only the M2 sites are involved in the intercalation for Li0.5Mn0.5 Ti1.5Cr0.5 (PO4)3, showing thus that in the pristine material the M1 sites are fully occupied by 0.5 Li atom and 0.5 Mn atom.