NOVEL METHOD FOR MANUFACTURING SECONDARY BATTERY

The present invention provides a method of preparing a secondary battery which includes pre-lithiating an electrode assembly which includes an electrode structure including a plurality of electrodes and a plurality of separators and a metal substrate, wherein the electrode and the separator are alternatingly stacked, the metal substrate is disposed on an outermost surface of the electrode structure in a direction in which the electrode and the separator are stacked, the electrode includes a negative electrode including a negative electrode active material layer and a positive electrode including a positive electrode active material layer, and the positive electrode and the negative electrode are spaced apart from each other with the separator disposed therebetween, wherein the pre-lithiating includes a first step of supplying lithium ions from the positive electrode to the negative electrode up to a state of charge (SOC) of A% by electrically connecting the positive electrode and the negative electrode and applying a first current, a second step of supplying lithium ions from the metal substrate to the positive electrode up to B% of capacity of the positive electrode by electrically connecting the metal substrate and the positive electrode and applying a second current, after the first step, and a third step of resting the electrode assembly, after the second step, and A and B satisfy A>B.