Single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ as high performance cathode materials for Li-ion batteries

Single-crystal nickel-high materials (ST-LNCMO) LiNi_0.6Co_0.2Mn_0.2O₂ have been synthesized using a versatile hydrothermal method. The as-prepared samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), and selected area electron diffraction (SAED). The results show that the sample annealed at an optimized temperature of 850 °C reveals uniform fine well-crystallized single-particles with diameters of ∼ 800 nm. Electrochemical data demonstrate that the cell using this nickel-high material as the cathode exhibits excellent performance. The sample displays a high capacity of 183.7 mA h·g^-1 at 36 mA·g^-1 (0.2 C) and excellent cycling stability at different rates. It yields an initial discharge capacity of 153.6 mA h·g^-1 at a rate of 10C-rate and a voltage of 2.8 V - 4.3 V. The sample also has an outstanding rate capacity at a high cut-off voltage (4.6 V). This superior performance is attributed to the merits of the single-crystal structure, which may be beneficial to the transportation of the Li⁺ ion along the grain.