LiNi1–yCoyO2 positive electrode materials: relationships between the structure, physical properties and electrochemical behaviour

Abstract

The LiNi_1–yCo_yO₂ oxides crystallize in the rhombohedral system with α-NaFeO₂ type structure. A structural study of these materials shows the presence of a few nickel ions in the Li plane for y⩽ 0.2. This phenomenon has been confirmed by a study of the magnetic and electrical properties. The LiNi_1–yCo_yO₂ lamellar oxides are used as positive electrode materials in Li batteries. The Li‖Li_xNi_1–yCo_yO₂ cells exhibit electrochemical behaviour strongly related to the existence of structural defects. A high specific energy (close to 500 W h kg^–1 of active material) is obtained for y= 0.3. These performances are attractive from an applications point of view.