Structure and electrochemical properties of Li(Ni0.5Mn0.5)1-xTixO2 prepared by one-step solid state reaction

The layered compound Li(Ni0.5Mn0.5)1-xTixO2 powders were prepared with Ni(OH)2, MnCO3, Li2CO3 and TiO2 by one-step solid state reaction. The effect of doping Ti on the structure and electrochemical properties was studied. The XRD results indicate that the powders with 0≤x≤0.05 have good layered structure and trace of impurity appears in the samples with x≥0.1. The SEM photographs show that the particle size distributes homogeneously and the sample with x=0.15 has larger particle size than other samples. The charge-discharge tests show that Li(Ni0.5Mn0.5)0.95Ti0.05O2 synthesized at 800 °C for 36 h exhibits good electrochemical properties. It firstly delivers 173 mA·h/g and maintains 90% of the initial discharge capacity after 30 cycles. The cyclic voltammetry and differential capacity vs voltage curves show that the major oxidation and reduction peaks are around 3.95 V and 3.75 V, respectively, assigned to Ni2+/Ni4+ oxidation-reduction process. A weak peak around 4.5 V is found during the oxidation process in the first cycle, which can be regarded as the main reason of the large drop of discharge capacity in the initial cycle.