Effect of molybdenum substitution on electrochemical performance of Li[Li0.2Mn0.54Co0.13Ni0.13]O2 cathode material

Molybdenum doping is introduced to improve the electrochemical performance of lithium-rich manganese-based cathode material. X-ray diffraction (XRD) results illustrate that the crystallographic parameters a, c and lattice volume V become larger with the increase of Mo content. The scanning electron microscope (SEM) shows that the molybdenum substitution increases the crystallinity of the primary particles. When evaluated as cathode material, the as-prepared Li[Li0.2Mn0.54-x/3Ni0.13-x/3Co0.13-x/3Mox]O2 (x = 0.007) delivers a discharge capacity of 155.5 mA h g−1 at 5 C (1 C = 250 mA g−1) and exhibits the capacity retention of 81.8% at 1 C after 200 cycles. The results of cyclic voltammetry (CV) and electronic impedance spectroscopy (EIS) tests reflect that the molybdenum substitution is able to significantly reduce the electrode polarization and lower the charge-transfer resistance. Within appropriate amount of Mo doping, the lithium ion diffusion coefficient of the material can reach to 8.92 × 10-15 cm2 s−1, which is ~ 30 times higher than that of pristine materials (2.65 × 10-16 cm2 s−1).