Abstract: Provided is a technique of achieving a longer-life lithium ion secondary battery. The lithium ion secondary battery includes a cathode including a cathode active material containing Mn, an anode including an anode active material containing graphite and non-aqueous electrolytic solution including electrolyte, and LiBF4 and LiPF6 are allowed to coexist in the non-aqueous electrolytic solution. Especially preferably LiPF6 is contained more than LiBF4 in the electrolytic solution. Preferably the electrolytic solution further includes iodide salt. As a result, an oxide of phosphor and boron is deposited on the cathode, thus preventing elution of Mn included in the cathode. The amount of these electrolytes is preferably in the decreasing order of phosphor, boron and then iodine.