In this paper a detailed in-situ XRD investigation of structural properties as well as lithium diffusion coefficient determination of LiMn2O4, LiMn1.5Ni0.5O4 and LiMn1.5Ni0.45Cu0.05O4 cathode materials are presented. Kinetics of Li+ intercalation/deintercalation mechanism are corroborated with structural changes of the cathode materials during electrochemical reactions. In was found that substitution of Mn by Ni and Cu in LiMn2O4 ions leads to single-phased electrochemical operational mechanism in LixMn1.5Ni0.45Cu0.05O4 in the whole examined lithium concentration range.