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 obs erved for LixNiO2, there is no phase transition during lithium deinter calation, in good agreement with the electrochemical behavior. The phy sical properties (magnetic susceptibility, electronic conductivity, an d thermoelectronic measurements) show that nickel ions are predominant ly oxidized to the tetravalent state, The good reversibility of the li thium intercalation process, due to the strictly 2D character of the L ixNi0.8Co0.2O2 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.