Enhanced electrochemical performances of layered LiNi0.5Mn0.5O2 as cathode materials by Ru doping for lithium-ion batteries

The pristine and Ru-doped LiNi0.5Mn0.5O2 cathode materials are synthesized by a wet chemical method, followed by a high-temperature calcination process. The influence of Ru substitution on the microstructure and electrochemical performances of the prepared materials are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and galvanostatic charge/discharge test. The XRD results show that, compared to the Ru-undoped sample, the LiNi0.5Mn0.45Ru0.05O2 owns a better hexagonal α-NaFeO2 structure and a smaller amount of cation mixing. The galvanostatic charge/discharge measurements demonstrate that the electrochemical properties of the LiNi0.5Mn0.5O2 sample are enhanced by Ru doping. At 5 and 10 C, the discharge capacity of LiNi0.5Mn0.45Ru0.05O2 is 118.61 and 105.43 mAh g−1, respectively, which is higher than those of LiNi0.5Mn0.5O2 (101.24 and 78.94 mAh g−1) due to the reduced charge-transfer resistance and the improved lithium-ion diffusion coefficient. On the basis of these results, Ru doping is considered an effective way to enhance the electrochemical performances of LiNi0.5Mn0.5O2 cathode materials.