POSITIVE ELECTRODE ACTIVE MATERIAL POWDER, METHOD FOR PRODUCING SAME, AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

摘要

The present invention relates to positive electrode active substance particles comprising a compound having at least a crystal system belonging to a space group of R-3m and a crystal system belonging to a space group of C2/m, and boron, wherein the compound is a composite oxide comprising at least Li, Mn, and Co and/or Ni; a relative intensity ratio [(a)/(b)] of a maximum diffraction peak intensity (a) observed at 2¸ = 20.8±1° in a powder X-ray diffraction pattern of the positive electrode active substance as measured using a Cu-K± ray to a maximum diffraction peak intensity (b) observed at 28 = 18.6±1° in the powder X-ray diffraction pattern, is 0.02 to 0.5; a content of Mn in the positive electrode active substance particles is controlled such that a molar ratio of Mn/(Ni + Co + Mn) therein is not less than 0.55; and the positive electrode active substance particles comprise the boron in an amount of 0.001 to 3% by weight. The positive electrode active substance particles of the present invention are produced by calcining a mixture comprising precursor particles comprising Mn, and Ni and/or Co, a lithium compound and a boron compound at a temperature of 500 to 1500°C. The positive electrode active substance particles of the present invention can provide a secondary battery which can be improved in charge/discharge capacity and cycle characteristics.