Method for manufacturing lithium secondary battery comprising lithium-rich manganese based oxide

A method for manufacturing a lithium secondary battery, the method comprising:

• preparing a battery cell including a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode contains a lithium-rich manganese-based oxide in which a content of manganese in all metals excluding lithium is 50 mol % or greater, and a ratio of a number of moles of lithium to a number of moles of all metals excluding lithium (Li/Me) is greater than 1;
• and
• activating by charging and discharging the battery cell while applying pressure to the battery cell within a pressure range of 0.1 kgf/cm2 to 10 kgf/cm2,
• wherein during the activating, the charging includes charging in a constant current mode until a charge cut-off voltage, and then further charging in a constant voltage mode, and
• wherein the charge cut-off voltage is greater than 4.35 V,
• wherein in the activating, the applying pressure includes:
• applying a first pressurization pressure P1 at a single constant charge rate from the beginning of the charging until SOC (state of charge) reaches to a point within a range from 10% to 20%, and
• then applying a second pressurization pressure P2, wherein the first pressurization pressure P1 and the second pressurization pressure P2 satisfy the following Equation (1):
• 5P1≤P2≤15P1. Equation (1).