NOVELTY - Secondary battery comprises a cathode (21), an anode (22), and a non aqueous electrolytic solution (23) in a package member having a flat surface, where the non aqueous electrolytic solution includes substituted methylene cyclic carbonate compounds (I).    USE - The secondary battery is useful as: lithium secondary battery in a battery pack, an electric vehicle, an electric power storage system and an electric power tool; and as a power supply in an electronic unit (all claimed). The secondary battery is useful in portable electronic units such as video cameras, digital still cameras, cellular phones, notebook personal computers, cordless telephones, headphone stereos, portable radios, portable televisions, and personal digital assistants, portable home appliances such as electric shavers, memory units such as backup power supplies and memory cards, electric power tools such as electric drills and electric saws, battery packs used as power supplies of notebook personal computers, medical electronic units such as pacemakers and hearing aids, electric vehicles such as electric cars (including hybrid vehicles), and energy storage system such as household battery systems storing power in case of emergency.    ADVANTAGE - The lightweight secondary battery has good battery capacity, good cycle characteristics, and good storage characteristics.    DETAILED DESCRIPTION - Secondary battery comprises a cathode (21), an anode (22), and a non aqueous electrolytic solution (23) in a package member having a flat surface, where the non aqueous electrolytic solution includes substituted methylene cyclic carbonate compounds of formula (I).    R1, R2 = H, halo (preferably F, Cl, Br, or I), monovalent hydrocarbyl, monovalent halogenated hydrocarbyl, oxygen-containing monovalent hydrocarbyl or oxygen-containing monovalent halogenated hydrocarbyl, where R1 and R2 are optionally bonded to each other.    INDEPENDENT CLAIMS are included for:    (1) a battery pack comprising a secondary battery, a control section controlling a usage state of the secondary battery, and a switch section switching the usage state of the secondary battery to an instruction from the control section;    (2) an electric vehicle comprising a secondary battery, a conversion section converting power supplied from the secondary battery into driving force, a drive section driven by the driving force, and a control section controlling a usage state of the secondary battery;    (3) an energy storage system comprising a secondary battery, one or two or more electrical units receiving power from the secondary battery, and a control section controlling power supply from the secondary battery to the electrical unit; and    (4) an electric power tool comprising a secondary battery, and a movable section receiving power from the secondary battery.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a secondary battery.    Battery can (11)    Battery device (20)    Cathode (21)    Anode (22)    Separator. (23)