Patent ID: 7640150

Claim:
A propriety judging method of judging the propriety of a positive electrode active material for use as a positive electrode active material of a lithium secondary battery, the active material comprising particles each having a configuration comprising a central portion and a surface portion covering the surface of the central portion, the method comprising the steps of: constructing a particular atomic aggregate model that hypothetically represents a positive electrode active material particle in which the central portion is constituted of LiM 1-a D a O 2 (M represents Co or Ni, D represents a transition metal element or Al replacing a part of Co or Ni as M, and M is not the same as D) having an α-NaFeO 2 structure, a region between the outer surface of the central portion and the outermost surface of the particle is occupied by the surface portion, the surface portion is constituted of LiM 1-b E b O 2 (M represents Co or Ni, E represents a metal element replacing a part of Co or Ni as M, and M is not the same as E) having an α-NaFeO 2 structure, and the species of replacing element D and the value a of the central portion differ from the species of replacing element E and the value b of the surface portion, respectively; evaluating the bonding force between M and O atoms in the surface portion by use of the density functional method as a technique for solving the Schroedinger's wave equation governing the motion of electrons, thereby predicting the possibility of addition of elements D and E; and judging the propriety of the positive electrode active material on the basis of the prediction.