Lithium-rich ternary cathode material Li1.2Ni0.13Co0.13Mn0.54O2 and K+-doped Li1.2Ni0.13Co0.13Mn0.54O2 materials have been successfully prepared via co-precipitation method, followed by a high-temperature solid state process. The chemical component, crystal structure and morphology, surface valence states are conducted by ICP, XRD refinement, FESEM and XPS analysis. Electrochemical properties and Li+ diffusion behavior have been extensively studied. The Rietveld refinement results reveal that the c/a ratio increases induced by K+ doping. Electrochemical studies indicate that the reasonable amount of K+-doped material exhibits the better cycling stability and rate performance. The study indicates that K+ doping hinders the lithium ions migration, thus excesses of K+ doping leads to the cycling stability and rate performance degradation. (C) 2018 The Electrochemical Society.