Positive active material for nonaqueous electrolyte secondary battery, method of manufacturing the positive active material, electrode for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery and method of manufacturing the secondary battery

Abstract

An object of the present invention is to provide a positive active material for a nonaqueous electrolyte secondary battery which has a large discharge capacity and is superior in charge-discharge cycle performance, initial efficiency and high rate discharge performance, and a nonaqueous electrolyte secondary battery using the positive active material. The present invention pertains to a positive active material for a nonaqueous electrolyte secondary battery containing a lithium transition metal composite oxide which has a crystal structure of an α-NaFeOtype, is represented by a compositional formula LiMeO(Me is a transition metal element including Co, Ni and Mn, α>0), and has a molar ratio Li/Me of Li to the transition metal element Me of 1.2 to 1.6, wherein a molar ratio Co/Me of Co in the transition metal element Me is 0.02 to 0.23, a molar ratio Mn/Me of Mn in the transition metal element Me is 0.62 to 0.72, and the lithium transition metal composite oxide is observed as a single phase attributed to a space group R3-m on an X-ray diffraction chart when it is electrochemically oxidized up to a potential of 5.0 V (vs. Li/Li).