Patent ID: 8409754

Claim:
A method for analysis of a positive electrode active material for a non-aqueous electrolyte secondary cell, comprising: preparing a powdery metal oxide as the positive electrode active material; classifying the powdery metal oxide by using a difference in particle diameter and density of its component particles to obtain a classified coarse powder having a classification ratio in a range of 0.1 to 5% and a remaining powder without the classified coarse powder, wherein the classification ratio is a mass ratio of an amount of the classified coarse powder to a total amount of the powdery metal oxide; measuring a content A of an impurity metal element in the powdery metal oxide before classifying and a content B of an impurity metal element in the classified coarse powder obtained by classifying; comparing the content B of the impurity metal element with the content A of the impurity metal element in order to evaluate an amount of particulate metal impurity contained in the powdery metal oxide before classifying; and selecting a whole of the powdery metal oxide containing the classified coarse powder and the remaining powder, of which a ratio (B/A) of the content B of the impurity metal element to the content A of the impurity metal element is 0.9or more and 1.4 or less, as the positive electrode active material, wherein the powdery metal oxide is classified to have a classification precision index κ of 0.7 or more, wherein the classification precision index κ is expressed with a ratio (D p25 /D p75 ), where D p25 is a particle diameter (μm) when a partial classification efficiency in a partial classification efficiency curve is 25% and D p75 is a particle diameter (μm) when the partial classification efficiency in the partial classification efficiency curve is 75%.