Stoichiometric changes in lithium conducting materials based on Li1+xAlxTi2−x(PO4)3: impedance, X-ray and NMR studies

The lithium fast-ion conductor, Li1+xAlxTi2−x(PO4)3 (LATP) has been modified via changes in stoichiometry during the processing steps. The resultant changes have been followed using 27Al MAS NMR, X-ray powder diffraction and impedance spectroscopy. The most important changes were those of the form Li1.3+4yAl0.3Ti1.7−y(PO4)3. It was possible to remove the AlPO4 phase (both tridymite and berlinite polymorphs), as monitored by X-ray diffractograms and 27Al NMR spectra. Consequently, these changes appear to result in increased grain boundary conductivity of the LATP material.