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

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.