Transition metal-containing composite hydroxide and production method thereof, and production method of positive electrode active material for nonaqueous electrolyte secondary battery

A method for producing a transition metal-containing composite hydroxide as a precursor of a positive electrode active material for a secondary battery, by mixing a raw material aqueous solution including at least a transition metal element and an aqueous solution including a complexing agent to form a reaction aqueous solution, and performing a crystallization reaction, the method comprising:

• a nucleation step in which nucleation is performed in an oxidizing atmosphere in which the pH value at a standard liquid temperature of 25° C. of the reaction aqueous solution is adjusted to be within a range of 12.0 to 14.0, and the oxygen concentration exceeds 5% by volume;
• and
• a particle growth step in which the pH value at a standard liquid temperature 25° C. of the reaction aqueous solution including the nuclei obtained in the nucleation step is adjusted to lower than the pH value of the nucleation step and to be within a range of 10.5 to 12.0 to cause to growth of the nuclei;
• and
• the particle growth step comprising:
• a first stage of maintaining the oxidizing atmosphere from the start of the particle growth step;
• a second stage after the first stage of switching from the oxidizing atmosphere to a non-oxidizing atmosphere in which the oxygen concentration is 5% by volume or less, and maintaining the non-oxidizing atmosphere;
• a third stage after the second stage of switching from the non-oxidizing atmosphere to the oxidizing atmosphere, and maintaining the oxidizing atmosphere;
• and
• a fourth stage after the third stage of switching from the oxidizing atmosphere to the non-oxidizing atmosphere, and maintaining the non-oxidizing atmosphere.