Positive electrode active material for secondary cell and nonaqueous electrolyte secondary cell using the same, and method for analysis of positive electrode active material for secondary cell

摘要

A positive electrode active material for use in a non-aqueous electrolyte secondary cell comprises a powdery metal oxide (LiCoO₂, LiNiO₂, LiMn₂O₄ or the like). When the positive electrode active material is classified with a classification precision index kappa of 0.7 or greater so as to obtain a coarse powder having a classification ratio in a range of 0.1% to 5%, a ratio (B/A) of the content (B) of an impurity metal element in the coarse powder obtained by the classification to the content (A) of the impurity metal element in the powder before the classification is 1.5 or less. The contents of the impurity metal elements are compared with respect to Ca, Mn, Fe, Cr, Cu, Zn and the like (exclusive of the metal element constituting the powdery metal oxide). The positive electrode active material for a secondary cell serves to improve cell performance capabilities and production yields.