ALKALINE SECONDARY BATTERY

A nickel hydrogen secondary battery 2 includes an electrode group 22 including a positive electrode 24 and a negative electrode 26 that face each other via a separator 28, an outer package can 10 that has an opening at an upper end thereof, and accommodates the electrode group 22 therein together with an electrolyte, a sealing body 11 including a cover plate 14 fitted in the opening of the outer package can 10, and a positive electrode cap 20 which is electrically connected to an outer surface 14b of the cover plate 14, a positive electrode lead 30, one end portion 38 of which is electrically connected to an inner surface 14a of the cover plate 14 and the other end portion of which is electrically connected to the positive electrode 24, and an oxygen block layer 60 that covers at least a range where the one end portion 38 of the positive electrode lead 30 and the inner surface 14a of the cover plate 14 overlap each other, and suppresses permeation of oxygen therethrough, and a thickness of a thinnest portion of the oxygen block layer 60 is 3 µm or more.