Method for manufacturing secondary battery and method for preparing positive electrode active material for secondary battery

A method for producing a secondary cell, the method comprising:

• step (A) of putting a solution having an electrochemically reversibly oxidizable/reducible organic compound and a supporting electrolyte dissolved therein into contact with a positive electrode active material, thereby oxidizing or reducing the positive electrode active material;
• and
• step (B) of accommodating the positive electrode active material processed by the step (A) and a negative electrode active material in a case in the state of facing each other with a separator being placed therebetween, and filling the case with an electrolyte solution,
• wherein the step (A) further comprises immersing an electrode containing the organic compound and a counter electrode in the solution having the supporting electrolyte dissolved therein, and applying a voltage between the electrode and the counter electrode, thereby oxidizing or reducing the organic compound and thus dissolving the organic compound in the solution.