$LiCoO_2$and $LiCo_{1-x}$$Ni_x$$O_2$ solid solutions were fabricated by the solid state reaction process. The structural cation mixing phenomena were investigated using XRD, SEM, particle size analysis and $^7$Li NMR,The synthesized LiCoO$_2$ and $LiCo_{1-x}Ni_XO_2$ microcrystallines showed the hexagonal layered structures. Mean particle sizes were increased with the increase of the amount of nickel in the solid solutions. The cation mixing effects were increased as increasing the fraction of nickel(x), x = 0.3, 0.5, 0.7. the peak frequency of $^7$Li NMR was shifted to the higher frequency and the line width increased as increasing the amount of nickel in the solid solutions.