Synthesis and electrochemical properties for LiNiO2 substituted by other elements

Li1+xNi1-xO2-yFy as the cathode materials for rechargeable lithium batteries were synthesized by co-substitution of nickel sites and oxygen sites for LiNiO2. The materials were found to possess good properties on charge/discharge cycling without significant deterioration of the initial capacity. In order to investigate the reason the cycle properties were improved. we performed experiments focusing on the crystallographic point of view using X-ray diffractometry accompanied by electrochemical property. These materials were found to restrain none of crystallographic change during charge/discharge regardless of the amount of substitution. According to the charge/discharge curve, the materials indicate relatively low internal impedance. Thus, the main reason for the improvements of the cycle properties may be caused by mechanism which has no direct relation to the above crystallographic change. (C) 1997 Published by Elsevier Science S.A.