Solid-state NMR studies of Al-doped and Al2O3-coated LiCoO2

As a cathode material for commercial lithium rechargeable battery, Al-doped and Al2O3-coated LiCoO2 were structurally characterized and compared by using solid-state Li-7 and Al-27 magic angle spinning (MAS) NMR. The structural states of lithium and aluminum in those samples were successfully identified by calculation of NMR spectra. Li-7 MAS NMR spectra of samples had shown similar features having more than three lithium sites, which were determined as quadrupole coupling constant with the same asymmetric parameter (eta = 0.1; CQ = 1.10 MHz for octahedral site, and CQ = 2.97 MHz and CQ = 3.83 MHz for shoulders. Al-27 MAS NMR spectra of samples, however, showed significant difference in two observed aluminum sites. In the simulation of NMR spectrum for Al2O3-coated LiCoO2, the values of CQ and eta were obtained; 4.45 MHz and 17 = 0.86 for tetrahedral site and 4.31 MHz and 71 = 0.81 for octahedra. (C) 2004 Elsevier Ltd. All rights reserved.