NOVELTY - A battery comprises sealing components (16a, 16b) melt-bonded to cover an opening portion (13A) of a plastic battery case (13) and sandwich current collectors from both sides. The opening portion of the battery case is sealed. The sealing components are melt-bonded to the peripheral edge of the opening portion of the battery case and to the current collectors more firmly than the sealing components are melt-bonded to each other. The outer cover is sealed at location(s) corresponding to the opening portion of the battery case.    USE - A battery, preferably a lithium-ion battery, for a battery module (claimed).    ADVANTAGE - Necessary rigidity is ensured and sufficient hermeticity is achieved without impairing the lightness in weight of the plastic battery case. When the internal pressure of the battery rises to a certain level, the sealing portion at which the sealing components are melt-bonded to each other is split open and the gas is released outside. In other words, the sealed portion of the sealing components with each other function as a safety valve and serves as a gas release passage that can guide the gas in the battery to the outside. By making use of the sealed portion at the opening portion of the battery case, a gas release mechanism in the event of internal pressure increase is formed without additionally providing a safety valve. The parts count of the battery is reduced. The battery becomes lighter in weight and lower in cost.    DETAILED DESCRIPTION - A battery comprises a battery case (13) made of plastic; a power-generating component in an accommodating space of the battery case and comprising a positive electrode, a negative electrode and an electrolyte; current collectors respectively connected to the electrodes and spaced apart and extending outward from an opening portion (13A) of the battery case; an outer cover air-tightly and liquid-tightly enclosing the entire battery case and having layer(s) including a metal layer; and sealing components (16a, 16b) melt-bonded to cover the opening portion of the battery case and sandwich the current collectors from both sides. The opening portion of the battery case is sealed. The sealing components are melt-bonded to the peripheral edge of the opening portion of the battery case and to the current collectors more firmly than the sealing components are melt-bonded to each other. The outer cover is sealed at location(s) corresponding to the opening portion of the battery case.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a disassembled state of a battery case, a stacked electrode assembly and sealing components that constitute a battery.    Stacked electrode assembly (10)    Positive electrode current collector tabs (11)    Negative electrode current collector tabs (12)    Battery case (13)    Opening portion (13A)    Positive and negative electrode current collector leads (14, 15)    Sealing components (16a, 16b)