To prevent the deterioration of discharge characteristics even if a battery is let to stand under extremely high temperature atmosphere by installing a jig with which a positive electrode and a negative electrode are slightly short-circuited.
A positive electrode plate 1 and a negative electrode plate 2 are spirally wound through a belt-shaped porous polyethylene separator 3 to form an electrode body, polypropylene insulating plates 4, 5 are placed on both ends of the electrode body, they are inserted into a battery case 6, a nonaqueous electrolyte prepared by dissolving the specified amount of an electrolyte in an equal volume mixture of ethylene carbonate and dimethoxyethane is poured in the battery case 6, and the battery case 6 is sealed with a sealing plate 8 to which a gasket 7 having conductivity is fit. The gasket 7 is produced by adding carbon base filler to polypropylene so as to have a volume resistivity of 1×108 Ωcm or less. The positive electrode 1 and the negative electrode 2 are kept in a slightly short-circuited state, and thereby, time during which battery voltage is exposed at decomposition voltage or higher of the electrolyte is shortened, and discharge characteristics are kept even under extremely high temperature atmosphere.
KAITA OSAMU
KANBARA TERUHISA
