On the LixNi0.8Co0.2O2 system

LixNi0.8Co0.2O2 phases (0.4 less than or equal to x less than or equal to 1.0) have been obtained by electrochemical deintercalation from 2D LiNi0.8Co0.2O2. X-ray diffraction shows that, contrary to what is observed for LixNiO2, there is no phase transition during lithium deintercalation, in good agreement with the electrochemical behavior. The physical properties (magnetic susceptibility, electronic conductivity, and thermoelectronic measurements) show that nickel ions are predominantly oxidized to the tetravalent state, The good reversibility of the lithium intercalation process, due to the strictly 2D character of the LixNi0.8Co0.2O2 materials, the high cell voltage (but not too high due to the position of the Ni4+/Ni3+ couple vs the Co4+/Co3+ couple), and the presence of a relatively small cobalt content, makes this material a very promising one for some lithium battery applications. (C) 1998 Academic Press.