| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material excellent in cycle characteristics and high in safety. <P>SOLUTION: A positive electrode active material for a lithium ion secondary battery includes: a compound A belonging to a Pnma space group and represented as chemical formula: Li<SB POS="POST">x</SB>Mn<SB POS="POST">α</SB>Fe<SB POS="POST">β</SB>M<SB POS="POST">γ</SB>PO<SB POS="POST">4</SB>(in the formula, the relationships of 0<x≤1.2, 0<α<1.2, 0<β<1.2 and 0≤γ<1.2 are satisfied, and M represents Mg, Al, Ti or the like); and a compound B belonging to a Pnma space group and different from the compound A. When a lithium ion secondary battery manufactured using a positive electrode including the positive electrode active material is fully charged and an X-ray diffraction pattern of the positive electrode active material is measured, an intensity ratio I/I<SB POS="POST">0</SB>between a peak intensity I<SB POS="POST">0</SB>in a (200) face of a compound A comprising the compound A from which Li is desorbed, belonging to a Pnma space group and represented as chemical formula: Li<SB POS="POST">y</SB>Mn<SB POS="POST">α</SB>Fe<SB POS="POST">β</SB>M<SB POS="POST">γ</SB>PO<SB POS="POST">4</SB>(in the formula, the relationships of 0≤y<0.06 and x>y are satisfied) and a peak intensity I in a (200) face of the compound B is more than 0.0001 and less than 1, and an average particle size of primary particles constituting the positive electrode active material is less than 500 nm. <P>COPYRIGHT: (C)2013,JPO&INPIT |
