SECONDARY BATTERY AND MANUFACTURING METHOD THEREOF

PROBLEM TO BE SOLVED: To provide a secondary battery configured to suppress local deposition of a metal foreign substance in a negative electrode within a shorter time and surely, and to provide a manufacturing method of the secondary battery capable of performing detoxification treatment of the metal foreign substance within a shorter time and surely.SOLUTION: The secondary battery comprises a positive electrode, a negative electrode and a separator interposed between the positive electrode and the negative electrode. Regarding the separator, air permeability resistivity Rp in a surface direction vertical to a thickness direction is 100 sec or less, and air permeability resistivity Rt in the thickness direction is higher than the air permeability resistivity Rp in the surface direction. The manufacturing method of the secondary battery includes: a fine charging step in which a constructed cell is charged into a charged state where a positive electrode potential is equal to or higher than an oxidization potential of a metal foreign substance which is expected to be mixed, and a negative electrode potential is equal to or higher than a reduction potential of a metal foreign substance which is expected to be mixed, for one hour or longer up to 0.01% to 0.5% of cell capacity, and such a charged state is maintained; and a step of performing initial conditioning charging.