7Li and 31P Magic Angle Spinning Nuclear Magnetic Resonance of LiFePO4-type materials

Abstract

LiFePO 4 and LiMnPO 4 have been characterized using 7 Li and 3 1 P magic angle spinning (MAS) nuclear magnetic resonance spectroscopy. LiFePO 4 was synthesized by a hydrothermal route and LiMnPO 4 was synthesized at high temperature in an inert atmosphere. Both compositions give rise to single isotropic 7 Li resonances. The MAS isotropic peak linewidth for LiFePO 4 is considerably larger than that for LiMnPO 4 , suggesting the presence of local disorder in the Li coordination sphere for LiFePO 4 . 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.