Abstract: A method of manufacturing a secondary battery, which includes: electrochemically charging a pre-lithiation cell including a positive electrode. The positive electrode comprises a positive electrode active material comprising a lithium manganese-based oxide and a lithium metal counter electrode. The electrochemical charging over-lithiates the positive electrode to form an over-lithiated positive electrode. Then, separating the over-lithiated positive electrode from the pre-lithiation cell and fabricating a secondary battery including the over-lithiated positive electrode and a negative electrode including a negative electrode active material; subjecting the secondary battery to a first charging to form a first-charged secondary battery; resting the first-charged secondary battery; and subjecting the rested secondary battery to a second charging. The maximum voltage of the secondary battery in the first charging is lower than the maximum voltage of the secondary battery in the second charging.