Structure and Electrochemical Performance of Li[Ni_1−x−y Co _x Mn _y ]O₂ [0.025 ≤ x ≤ 0.4, 0.015 ≤ y ≤ 0.25] as Cathodes Compound for Lithium Ion Batteries

Li[Ni_1−x−y Co _x Mn _y ]O₂ (0.025 ≤ x ≤ 0.4, 0.015 ≤ y ≤ 0.25) electrode powders were prepared by a solid-state reaction. The phase purity and R-3m layered structure of the synthesized Li[Ni_1−x−y Co _x Mn _y ]O₂ materials were confirmed by X-ray diffraction analysis. The particle size of the powder/compounds was decreased with increasing Co and Mn contents to a minimum average particle size of 0.2∼0.3 μm for the LiNi_0.35Co_0.4Mn_0.25O₂ powder. A specific capacity of 187 mAh/g was obtained for the LiNi_0.35Co_0.4Mn_0.25O₂ electrode with good capacity retention when cycled in the potential region of 3.0–4.6 V with a current density of 20 mA/g at room temperature. Although the structural parameters of the LiNi_0.35Co_0.4Mn_0.25O₂ cathode material were similar to those of the LiNi_1/3Co_1/3Mn_1/3O₂ powder, its specific capacity was higher due to the higher Co contents.