LiNi1-yCoyO2 positive electrode materials: Relationships between the structure, physical properties and electrochemical behaviour

The LiNi1-yCoyO2 oxides crystallize in the rhombohedral system with alpha-NaFeO2 type structure. A structural study of these materials shows the presence of a few nickel ions in the Li plane for y less than or equal to 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 parallel to 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.