Role of Lithium Excess and Doping in Li1+xTi2-xMnx(PO4)3 (0.00 ≤ x ≤ 0.10)

The role of lithium excess and Mn doping on lithium titanium phosphate properties is studied by structural (X-ray and neutron diffraction) and spectroscopic (electron paramagnetic resonance and impedance) techniques. The dopant cation is present with 2+, 3+, and 4+ oxidation states in both the lithium and titanium sublattices: Mn2+ is preferentially located on Li sites and Mn4+ on Ti ones, and Mn3+ can occupy both the sites. The refinement of neutron diffraction patterns allowed us to identify the 18e crystallographic site as the preferred location of the excess Li ions. Cationic distribution and valence state are mainly related to sol-gel or solid-state synthesis routes. Consequently, the complex behavior of the bulk conductivity can be explained by the presence of Mn on the Li site and the amount of Li excess, while the effect of the sintering degree is comparable in all the samples as revealed by scanning electron microscopy.