Abstract: A precursor of a positive electrode material with which it is possible to obtain a lithium-ion secondary cell having an excellent discharge capacity and cycle characteristics, and a method for manufacturing the precursor. The precursor is a precursor of a positive electrode material used for a lithium-ion secondary cell, wherein the precursor is at least one substance selected from the group made of nickel-manganese composite hydroxides and nickel-manganese composite oxides, the precursor contains nickel and manganese, the ratio of the nickel content relative to the nickel content and the manganese content is 0.45-0.60 inclusive in molar ratio, and the average valence of manganese is below 4.0.

Abstract: A positive electrode active material for a lithium-ion secondary cell having exceptional lithium ion conductivity, the positive electrode active material being such that the absorption of moisture from the atmosphere can be suppressed. This positive electrode active material for a lithium-ion secondary cell has powder particles that include a specific composite oxide, and an organic silicon compound affixed to the surface of the powder particles, the organic functional groups of the organic silicon compound including at least one selected from the group made of C2-10 alkyl groups and C6-14 aryl groups.