7Li and 31P magic angle spinning nuclear magnetic resonance of LiFePO4-type materials

Abstract

LiFePO4 and LiMnPO4 have been characterized using 7Li and 31P magic angle spinning (MAS) nuclear magnetic resonance spectroscopy. LiFePO4 was synthesized by a hydrothermal route and LiMnPO4 was synthesized at high temperature in an inert atmosphere. Both compositions give rise to single isotropic 7Li resonances. The MAS isotropic peak linewidth for LiFePO4 is considerably larger than that for LiMnPO4, suggesting the presence of local disorder in the Li coordination sphere for LiFePO4. In both samples, the isotropic peak is accompanied by a large, asymmetric spinning sideband manifold, arising from bulk magnetic susceptibility broadening and the paramagnetic interaction between the lithium nucleus and transition metal unpaired electrons.