Study on the electrochemical performance of Cu-added LiNi_0.6Co_0.2Mn_0.2O₂

The precursor was prepared by co-precipitation and Li (Ni_0.6Co_0.2Mn_0.2)_1-xCu_xO₂ (x=0, 0.01, 0.015 and 0.02) was synthesized by high temperature solid-state reaction. In this study, the structure, morphology and electrochemical properties of Li (Ni_0.6Co_0.2Mn_0.2)_1-xCu_xO₂ were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), battery test system (BTS) and electrochemical workstation. The results showed that, with a small amount of Cu, α-NaFeO₂type structure was formed in all the samples with no impurities; the peak splitting of the sample (108)/(110) was obvious with a good layered structure; then, with the increase of Cu, c and c/a, interlayer distance and the deintercalation channels of Li+ all increased, so the conductivity improved. The ratios of I₍₀₀₃₎/I₍₁₀₄₎ were 1.467 and 1.438, respectively, with 1 % Cu and 1.5 % Cu, higher than the ratio of 1.431 without any addition of Cu and at the same time reducing cation mixing. The specific discharge capacities for the first time were 170.6, 164.1, 163.6 and 162.4 mAh/g, respectively. When x was 0, 1 %, 2 % after 100 cycles, the retention rates were 87.1 %, 98.7 %, and 87.7 %, respectively; when x was 1.5 %, the specific capacity increasing from 161.8 to 173.9 mAh/g, Li(Ni0.6Co0.2Mn0.2)_1-xCu_xO₂ obtained its best electrochemical performance.