Secondary battery and method for manufacturing same

A secondary battery comprising:

• an electrode assembly;
• a battery case accommodating the electrode assembly therein;
• a first electrolyte accommodated in the battery case, the first electrolyte primarily impregnating the electrode assembly, the first electrolyte being configured to be charged and discharged at a charging voltage 3 V or less;
• and
• a reinforcement electrolyte member which comprises a packaging material and a second electrolyte,
• wherein the packaging material is accommodated inside the battery case and has an oxidation part which is configured to be oxidized and decomposed at a predetermined voltage, the predetermined voltage being at least 3 V and greater than the charging voltage, and
• the second electrolyte is stored within the packaging material and is configured to be released to the outside of the packaging material upon decomposition of the oxidation part, thereby secondarily impregnating the electrode assembly, and
• wherein the second electrolyte has a different chemical composition than the first electrolyte, the second electrolyte configured to elute copper into the electrode assembly by reacting at a voltage below the predetermined voltage, thereby increasing the ionic conductivity of the electrode assembly.