LiNi1–yCoyO2positive electrode materials: relationships between the structure, physical properties and electrochemical behaviour

The LiNi1–yCoyO2 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 LiNi1–yCoyO2 lamellar oxides are used as positive electrode materials in Li batteries. The Li‖LixNi1–yCoyO2 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.