Structural analysis of lanthanum-containing battery materials using 139La solid-state NMR

Abstract

139La solid-state NMR spectra, acquired at 21.1 and 11.7 T, have been used to evaluate the structural properties of the lithium ion battery materials, La32Li16Fe6.4O67 and Li3xLa2/3–xTiO3. In particular, atomic-level disorder in the second coordination sphere environment of lanthanum in these materials has been indicated by the observation of a distribution in the asymmetry parameters and the quadrupolar coupling constants derived from experimental NMR spectra, and supported by theoretical calculations. For comparison, 139La NMR has been obtained for the two model compounds La2O3 and LaNbO4, in which there is no atomic-level disorder. Quadrupolar coupling constants in the range of 17 to 59 MHz have been measured, and these values are supported by previous work as well as theoretical predictions performed in CASTEP. It has been shown that 139La NMR is a useful tool for the structural analysis of lithium ion battery materials, and when combined with 7Li MAS NMR and powder X-ray diffraction, can be used to determine the structure of complex solid-state electrolyte and electrode materials.