On the diffusion of Li+ defects in LiCoO2 and LiNiO2

NMR spectra of Li-7 nucleus have been measured in LiCoO2 and LiNiO2. Line w idths of the spectra decreased with increasing temperature above 400 K. The decrease obviously indicates the motional narrowing originating from diffu sing Li+ defects. A simple ion hopping model revealed that the diffusion co nstant of LiCoO2 with an activation energy of 0.3 eV is larger than that of LiNiO2 with the activation energy of 0.6 eV. This suggests that lithium io ns are easier to diffuse in LiCoO2 than in LiNiO2 at high temperatures. (C) 2000 Elsevier Science B.V. All rights reserved.