Electrochemical performance of LiNi0.5Mn0.5O2 with different synthesis methods

LiNi0.5Mn0.5O2 as a cathode material for Li-ion battery was prepared by the metal acetate decomposition method, sol–gel method, and carbonate co-precipitation method, respectively. The influences of synthesis methods on the physical and electrochemical behaviors of LiNi0.5Mn0.5O2 were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. XRD patterns show that both the sol–gel and carbonate co-precipitation methods can form single phase of layered structure, while a trace of NiO impurity is observed via the metal acetate decomposition method. SEM results show the as-prepared carbonate particle has a spherical morphology with an average diameter of 10 μm, consisted of primary nano-sized particles with particle diameter of 200 nm. The sample prepared by the carbonate co-precipitation method exhibits the highest discharge specific capacity and the best cycling stability, which results from the steady homogeneity of precursor constant by the fixation of CO32− group. It can deliver an initial discharge specific capacity of 186.3 mAh·g−1, and retain 170 mAh·g−1 after 100 cycles at a current rate of 20 mA·g−1 in the voltage range of 2.5–4.7 V at 25 °C. Moreover, even at the high temperature of 55 °C, it still delivers a reversible specific capacity of 222.6 mAh·g−1 with little capacity loss after 30 cycles.