59Co and 6,7Li MAS NMR in Polytypes O2 and O3 of LiCoO2

Abstract

59Co and 6,7Li MAS NMR has been applied to polytypes O2 and O3 of LiCoO2 at three different magnetic field strengths (4.7, 7.1, and 11.7 T). The 59Co and 6,7Li quadrupole and anisotropic shift tensors have been determined by iterative fitting of the NMR line shapes at the three magnetic field strengths. The magnitude of the quadrupole coupling constant at the cobalt site is about 3 times as large for the O2 variety as that for the O3 one. In 6,7Li NMR, the 6,7Li−6,7Li and 6,7Li−59Co nuclear dipolar interactions had to be taken into account for a correct determination of the multiple interactions acting on the lithium nuclei. This was conveniently done by using a memory function approach. Calculations of the shift and quadrupole coupling parameters have been performed by using a point dipole and point monopole model, respectively. The shift tensor calculation shows that the magnetic susceptibility in both the O2 and O3 phases is due to Van Vleck paramagnetism for Co3+. In the approximation of an ionic crys...