Secondary battery positive-electrode active material and method for producing same

In order to obtain a high-performance lithium-ion secondary battery or sodium-ion secondary battery, the present invention provides a secondary battery positive-electrode active material capable of effectively suppressing water absorption, and a method for producing the same. More specifically, the present invention provides a secondary battery positive-electrode active material in which a metal fluoride in the amount of 0.1-5 mass% and one or two types selected from carbons obtained by carbonizing a water-insoluble conductive carbon material and a water-soluble carbon material are supported on an oxide containing at least iron or manganese and represented by formula (A) LiFe a Mn b M c PO 4 , formula (B) Li 2 Fe d Mn e N f SiO 4 , or formula (C) NaFe g Mn h Q i PO 4 .