Abstract: The lithium ion secondary battery includes: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolytic solution, in which the positive electrode has a metal foil and a positive electrode active material layer provided on the metal foil, a plurality of voids are formed on the positive electrode active material layer, and a transition metal oxide having an average particle size of 10 nm or more and 500 nm or less is provided on an inner wall portion of the voids, on which the voids and the electrolytic solution are in contact with each other.