In order to enhance cycling stability, Rb+ has been incorporated into Li-rich manganese based layered oxide cathode materials for lithium-ion batteries (LIBs) by a co-precipitation method and a subsequent solid-state reaction. The influence of the content of Rb+ in the cathodes on the performance was investigated and the optimal content was identified to be x =0.03. The inter-slab distance exhibited a slight increase after the Rb+ incorporation, which reduced the energy barrier for the intercalation/deintercalation process of Li+ in the cathode. Electrochemical characterization showed that the as-synthesized cathode materials have an improved cycleability and rate performance compared with the pristine Li-rich manganese layered oxide based cathodes for LIBs. In addition, it was confirmed that the Rb+ doping clearly suppresses the process of the simultaneous lithium extraction along with oxygen activation at the high voltage region which could alleviate the irreversible loss of oxygen in the form of Li2O. The improved diffusion coefficient of Li ions in the Rb+ incorporated cathodes was confirmed by electrochemical impedance spectroscopy measurements.