| 摘要 |
PURPOSE: To restrict rise of the internal pressure at the time of over-charge by forming a hydrophobic part in the surface of a separator opposite to a negative electrode at the predetermined area ratio. CONSTITUTION: An electrode group 5, which is formed by spirally winding laminated body of a paste type positive electrode 2, a separator 3 and a paste type negative electrode 4, is housed in a container 1 with the alkali electrolyte so as to form a battery. The separator 3 is made of polyolefine group non-woven fabric at 0.1-15μm of fiber diameter, and the hydrophilic surface is formed by graft copolymer of vinyl monomer such as acrylic acid. At this stage, emboss processing is performed to a part of the surface of the separator 3 opposite to the negative electrode 4, for example, at 2-25% of area ratio so as to form the hydrophobic surface. Since three-phase interface is generated in the surface of the negative electrode, consumption of the oxygen gas to be generated at the time of overcharge is increased, and the internal pressure of the battery is lowered. Since the surface of the positive electrode is formed with a layer, in which a large quantity of the electrolyte exists, arrival of the hydrogen gas, which is generated from the negative electrode at the time of maintenance at a high temperature, to the positive electrode through the separator is prevented, and self-discharge is thereby restricted. |
