Li‐rich layered Mn‐based oxide (LMO) cathode materials, with the formation of Li2MnO3, have attracted much attention due to their potential in various applications with high energy density. However, these cathode materials for Lithium‐ion batteries still suffer from drawbacks such as poor rate capability and voltage decay, which makes further investigation vital and rational. Here, the doping strategy is employed to investigate the effect of TM = Ti, Cu, and Zn on Li2Mn0.5TM0.5O3 cathode materials for improving electrochemical performances of Li2MnO3. Electrochemical properties such as voltage, electrical conductivity, safety, structural stability, and kinetics and mechanism of Li‐ion diffusion are evaluated and compared. All doped cathodes decrease the voltage reduction and improve the electrical conductivity coefficient in comparison with LMO. Doping Cu notably increases the electrical conductivity of LMO by 77%. Ti doping exhibits the potential to increase the maximum voltage of LMO and structural stability. Doping Zn and Cu elements can delay the oxygen loss significantly, which leads to a higher life cycle and safety. In addition, doping Zn is expected to have a higher Li‐ion diffusion coefficient due to its low energy barrier and partial charge of oxygen atoms in its cathode structure. This first‐principle study of doping effects of TM = Ti, Cu, and Zn with α = 0.5 in Li2Mn0.5TMαO3 may be a useful leading study for further investigation into the synthesis of lithium‐rich materials with enhanced electrochemical performance.