Method of activating a lithium secondary battery including a positive electrode additive

A method of activating a lithium secondary battery, comprising:

• charging the lithium secondary battery to a state of charge (SOC) of 90% or more in an activation step, wherein the lithium secondary battery having an electrode assembly comprising a positive electrode and an electrolyte, wherein the positive electrode comprises a mixture layer having a positive electrode active material and a positive electrode additive;
• and
• degassing the lithium secondary battery during the activation step to remove gas inside the secondary battery,
• wherein the activation step further comprises:
• a first activation step wherein the lithium secondary battery is charged to a first level of SOC of 20% or less;
• a second activation step wherein the lithium secondary battery is charged to a second level of SOC of greater than 20% and 40% or less;
• a third activation step wherein the lithium secondary battery is charged to a third level of SOC of greater than 40% and 70% or less;
• and
• a fourth activation step wherein the lithium secondary battery is charged to a fourth level of SOC of 90% or more,
• wherein the degassing is performed between the first and second activation steps at the first level of SOC, the second and third activation steps at the second level of SOC, and the third and fourth activation steps at the third level of SOC.