Synthesis and electrochemical performance of Li1+xNi0.5Mn0.3Co0.2O2+δ (0 ≤ x ≤ 0.15) cathode materials for lithium-ion batteries

In this work, layered lithium-excess materials Li1+xNi0.5Mn0.3Co0.2O2+δ (x = 0, 0.05, 0.10 and 0.15), of spherical morphology with primary nanoparticles assembled in secondary microspheres, were synthesized by a coprecipitation method. The effects of lithium content on the structure and electrochemical performance of these materials were evaluated by employing X-ray diffraction (XRD), inductive coupled plasma (ICP), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge tests. It is found that Li1.10Ni0.5Mn0.3Co0.2O2+δ, i.e., Li[(Ni0.5Mn0.3Co0.2)0.95Li0.05]O2 showed the best electrochemical performance due to the highly ordered layered structure, reduced cation mixing and the lowest charge transfer resistance. Li1.10Ni0.5Mn0.3Co0.2O2+δ delivered a discharge capacity of 145 mA h g−1 at 125 mA g−1 in the cut-off voltage of 2.5–4.3 V, and had a capacity retention of 100% after 50 cycles at room temperature.