Influence of Li and Mo co-doping for electrochemical performance of ternary cathode materials at room and low temperature for Li-ion power battery

The Li1+y[Ni(1−x)/3Mn(1−x)/3Co(1−x)/3Mox]O2(M = Ni(1−x)/3Mn(1−x)/3Co(1−x)/3Mox) ternary cathode material has been synthesized by solid state reactions with the industrial product Ni1/3Co1/3Mn1/3(OH)2 as a precursor. X-ray diffraction, laser particle size analyzer and surface analyzer are employed to investigate the lattice structure, particle size and specific surface area of the powder. Comprehensively considering the improvement of cycle life and the capacity decreased, Li/M = 1.16 is chosen as right lithium rich ingredients used to co-dope with Mo element. For the Mo/M = 0.02, Li/M = 1.16 sample, the discharge capability is best, which is 126.06 mAh g−1 at 750 mA g−1(5C) of discharge current density and at room temperature higher than 118.32 mAh g−1, that of the Li/M = 1.16 sample without Mo. At the same current density, the best discharge capacity at low temperature of −30 °C for the sample Mo/M = 0.02, Li/M = 1.16 is 65.41 mAh g−1 higher than 58.18 mAh g−1 of Li/M = 1.16 sample without Mo. Through the Li and Mo co-doping, unit cell volume V shows increasing trend and may be one of the most basic dominant factor about the improvement of low temperature electrochemical performance. Because of larger specific surface area and less median radius D50, the samples with Li and Mo co-doping has a big reaction activity, which is another important reason. Impedance changes could better explain the improvement trend of high rate discharge capability of cathode samples with Mo and Li co-doping at high current density.