NOVELTY - A secondary battery comprises: electrolytic solution; a positive electrode (21); and a negative electrode (22), where at least one of the positive electrode, the negative electrode, and the electrolytic solution contains alkyl carbonate of formula R-O-C(=O)-O-X, where R is linear, branched or halogenated 8-20C alkyl, and X is alkali metal element (preferably lithium (Li).    USE - As a secondary battery such as lithium ion secondary battery, used in battery pack, electric vehicle, electric power storage system, power tool and electronic appliance (claimed) such as video camera, digital still camera, mobile phone, laptop computer, cordless phone, headphone stereo cassette tape recorder, a portable radio, a portable television set, and personal digital assistant.    ADVANTAGE - The battery exhibits excellent battery characteristics.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a battery pack comprising: secondary battery; a control part for controlling the secondary battery; and a switch part for switching the secondary battery depending upon an instruction of the control part;    (2) an electric vehicle comprising: a secondary battery; a conversion part for converting an electric power fed from the secondary battery into a driving force; a drive part for driving depending upon the driving force; and a control part for controlling the secondary battery;    (3) an electric power storage system comprising: a secondary battery; at least one electric appliance; and a control part for controlling an electric power feed into the electric appliance or appliances from the secondary battery;    (4) a power tool comprising: a secondary battery; and a movable part into which an electric power is fed from the secondary battery; and    (5) an electronic appliance comprising: the secondary battery as an electric power feed source.    DESCRIPTION OF DRAWING(S) - The figure shows a sectional view of a secondary battery (cylindrical type).    Pair of insulating plates (12, 13)    Battery lid (14)    Electrode body (20)    Positive electrode (21)    Negative electrode (22)    Separator (23)    Center pin (24)