The spin-lattice relaxation time, T-1, for Li-7 has been measured in LiCoO2 and LiSNiO2 (x = 1, 0.5) from 77 K to 680 K. The data in the high temperature region are interpreted by the relaxation mechanism of the diffusive motion of Li+ ion defects. The activation energy for the diffusion of the Li+ in LiCoO2 and LiNiO2 is estimated to be almost same value, 0.08 eV. From the analysis based on the fluctuating field model (BPP model) with the diffusion of Li+ defects, the dominant mechanism of the spin-lattice relaxation in LiCoO2 would be the quadrupole interaction at the high temperature region. On the other hand, the relaxation in LiNiO2 would be governed by the magnetic dipole interaction between Li nucleus and paramagnetic Ni ions in Li layer.