Synthesis and characterization of layered LiNi_1/2Mn _1/2O₂ as cathode material for lithium ion batteries

Layered LiNi_1/2Mn_1/2O₂ was synthesized using a simplified co-precipitation method and characterized by XRD, SEM, charge discharge cycling, cyclic voltammetry (CV) and Electrochemistry impedance spectroscopy (EIS). Firstly, the mixture solution of the nickel hydroxide and manganese hydroxide was prepared by coprecipitation. Secondly, the precursor was prepared from the co-precipitated solution using a preoxidation method. Finally, the LiNi_1/2Mn_1/2O₂ was synthesized from the as-prepared precursor. The SEM and XRD results indicate that the material is composed of spherical particles with size of 100-200 nm and has well-defined layered structure. The charge discharge cycling tests reveal that the material synthesized at 900 °C for 9 h in air atmosphere exhibits stable capacities of about 140 mAh·g^-1 in the cutoff voltage of 2.8-4.6 V for charge and discharge at the end of 40^th cycle. The CV curves show that the material has irreversible phase change at the initial state of lithium deintercalation and reintercalation processes. EIS tests show that the LiNi_1/2Mn_1/2O₂ has good ability of Li-ion diffusion.