Synthesis and characterization of LiNi0.6CoxMn0.4-xO2 (x = 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3) with high-electrochemical performance for lithium-ion batteries

A series of Ni0.6CoxMn0.4-x(OH)2 hydroxide precursors with x = 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 are prepared by co-precipitation method from sulfate solutions using NaOH and NH4OH as precipitation and complexing agents. Then, well-ordered layered LiNi0.6CoxMn0.4-xO2 are synthesized by sintering the mixture of as-prepared precursors and LiOH · H2O at 820 °C for 12 h in flowing oxygen. Their structural and electrochemical properties are investigated using X-ray diffraction(XRD), scanning electron microscope(SEM), X-ray photoelectron spectroscopy(XPS), charge-discharge test, Cyclic voltammetry(C-V) and electrochemical impedance spectroscopy (EIS). The increase of the Co content in LiNi0.6CoxMn0.4−xO2 leads to the decrease of the tap-density of the powders, the increase of discharge capacity and the deterioration of cycling performance. It also leads to the enhancement of the ratio Ni3+/Ni2+ in LiNi0.6CoxMn0.4−xO2, confirmed by the XPS analysis. The results show that the sample with x = 0.2 has the highest tap-density, delivers an initial discharge capacity of 172.3 mAh g−1 at 1C rate between 2.8 and 4.3 V, more than 94.1% of that is retained after 100 cycles, and also with excellent rate capability and high-temperature performance.