NOVELTY - Secondary battery comprises: a cathode (21) including a cathode active material layer (21B) on a cathode current collector (21A); an anode; and an electrolytic solution, where the cathode active material layer includes spherical active materials (211) each being a secondary particle and planular active materials (212) each being a secondary particle, the spherical active materials each being included in a region closer to the cathode current collector, and the planular active materials each being included in a region farther from the cathode current collector.    USE - The secondary battery is useful in battery pack, electric vehicle, electric power storage system and electric power tool, and as an electric power supply source in electronic apparatus (all claimed), where the secondary battery include mobile electronic apparatuses such as video camcorders, digital still cameras, mobile phones, notebook personal computers, cordless phones, headphone stereos, portable radios, portable televisions, or personal digital assistants, mobile lifestyle electric appliances such as electric shavers, memory devices such as backup electric power sources and memory cards, electric power tools such as electric drills and electric saws, medical electronic apparatuses such as pacemakers and hearing aids, electric vehicles such as electric automobiles (including hybrid automobiles), and electric power storage systems such as home battery systems for storing electric power.    ADVANTAGE - The secondary battery provides higher energy density than lead batteries or nickel cadmium batteries.    DETAILED DESCRIPTION - Secondary battery comprises: a cathode (21) including a cathode active material layer (21B) on a cathode current collector (21A); an anode; and an electrolytic solution, where the cathode active material layer includes spherical active materials (211) each being a secondary particle and planular active materials (212) each being a secondary particle, the spherical active materials each being included in a region closer to the cathode current collector, and the planular active materials each being included in a region farther from the cathode current collector, and primary particles of the spherical active materials having an average particle diameter that is larger than an average particle diameter of primary particles of the planular active materials. INDEPENDENT CLAIMS are included for:    (1) an electrode comprising an active material layer on a current collector;    (2) a battery pack comprising the secondary battery, a control section controlling a used state of the secondary battery, and a switch section switching the used state of the secondary battery according to an instruction of the control section;    (3) an electric vehicle comprising the secondary battery, a conversion section converting electric power supplied from the secondary battery into drive power, a drive section operating according to the drive power, and the control section;    (4) an electric power storage system comprising the secondary battery, one or more electric devices supplied with electric power from the secondary battery, and the control section controlling the supplying of the electric power from the secondary battery to the one or more electric devices; and    (5) an electric power tool comprising the secondary battery, and a movable section being supplied with electric power from the secondary battery.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a cathode.    Cathode (21)    Cathode current collector (21A)    Cathode active material layer (21B)    Spherical active material (211)    Planular active material. (212)