Method for the preparation of cathode active material and method for the preparation of a non-aqueous electrolyte cell

A LiFePO carbon composite material is to be synthesized in a single phase satisfactorily to achieve superior cell characteristics. In preparing a cathode active material, starting materials for synthesis of a compound represented by the general formula LiFePO, where 0 < x ≤ 1, are mixed, milled and a carbon material is added to the resulting mass at an optional time point in the course of mixing, milling and sintering. LiPO, Fe(PO) or its hydrates Fe(PO) ·nHO, where n denotes the number of hydrates, are used as the starting materials for synthesis of LiFePO. The the temperature of a product from said sintering is set to 305°C or less when said product from said sintering is exposed to atmosphere. The oxygen concentration in a sintering atmosphere is set to 1012 ppm in volume or less at the time point of sintering.