Improved cycling and rate performance of Sm-doped LiNi0.5Mn1.5O4 cathode materials for 5V lithium ion batteries

Spinel powders of Sm-doped LiNi0.5Sm x Mn1.5-x O4 with different Sm contents (x =0, 0.01, 0.03, and 0.05) have been synthesized by a gelatin-assisted solid-state method. The structural and electrochemical properties of the electrode materials are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), cyclic voltammetry (CV), charge/discharge testing and electrochemical impedance spectroscopy (EIS). The partial substitution of Sm3+ for Mn3+ in LiNi0.5Mn1.5O4 leads to a decrease in the lattice parameter and unit cell volumes, resulting in an improvement of structural stability, enhance the electronic conductivity and diminish the polarization and the charge transfer resistance. As a result, the cyclic ability at 25 degree C performances and rate performances of LiNi0.5Mn1.5O4 electrode materials are significantly improved with the increasing Sm addition, compared to the pristine LiNi0.5Mn1.5O4, though high doping gives rise to a small reduction of the initial discharge capacity.