NOVELTY - The battery (0) has a battery case (1) that is provided with an exhaust valve (4) to discharge the gas emitted in electric power generation unit (3) to the battery exterior. The valve is made of raw material whose rigidity is higher than circumference (41) of valve, and is opened and closed by transformation of elastic portion. The valve is opened, when internal pressure of battery reaches first predetermined value. The valve is closed, when internal pressure of battery becomes second predetermined value. The first predetermined value is larger than second predetermined value.    USE - Lithium ion secondary battery of lamination-type, coin shape, square shape, and cylindrical shape of secondary battery module (claimed), for use as electric equipment and power supply for electric power storage in hybrid electric vehicle or electric vehicle. Can also be used in nickel-hydrogen battery, nickel cadmium cell, fuel cell, and electrolysis type capacitor.    ADVANTAGE - The gas emitted in the electric power generation unit does not accumulate in the circumference of electric power generation unit, and cell layer, so that inhibition of cell reaction is suppressed, and the capacity and output of battery are maintained stable. Since the discharge path of gas is closed, permeation of air from battery exterior or the cell layer of moisture content is prevented efficiently. Atmospheric back flow is prevented by making the cross-sectional area of inside of battery larger than the cross-sectional area of battery outside. The conductivity of electron which is generated with the electrode is improved and the battery performance is improved.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a secondary battery module.    DESCRIPTION OF DRAWING(S) - The drawing shows a front view of the lamination-type secondary battery.    Lithium ion secondary battery (0)    Battery case (1)    Electric power generation unit (3)    Exhaust valve (4)    Circumference of exhaust valve (41)