Film-covered battery and assembled battery

Abstract

The invention provides a closed type battery comprising a battery element covered with a covering film and a heat fusion seal portion formed by heat fusion on a periphery of the covering film, wherein the cleaving strength upon an internal pressure rise of a seal portion positioned between a positive electrode terminal and a negative electrode terminal is larger than that of any other seal portion, and a safety valve adapted to release pressure upon a battery's internal pressure rise is located at a portion other than said inter-terminal seal portion. The invention also provides an assembled battery wherein a plurality of closed type batteries are stacked one upon another while a safety valve adapted to release pressure upon an increase in the internal pressure of the battery is located at a position in no contact with the covering film surface of an adjoining battery.

What is claimed is: 
     
         1 . A closed type battery comprising a battery element covered with a covering film and a heat fusion seal portion formed by heat fusion on a periphery of the covering film, characterized in that a cleaving strength upon an internal pressure rise of a seal portion positioned between a positive electrode terminal and a negative electrode terminal is larger than that of any other seal portion, and a safety valve adapted to release pressure upon a battery's internal pressure rise is located at a portion other than said inter-terminal seal portion. 
     
     
         2 . The closed type battery according to  claim 1 , wherein a heat fusion seal portion extending from an outer periphery of the battery around said inter-terminal seal portion to within the battery is wider than that positioned at any other seal portion. 
     
     
         3 . The closed type battery according to  claim 1 , wherein said inter-terminal seal portion is provided on its outer surface with a retaining member adapted to press the seal portion when the battery is incorporated in battery drive equipment. 
     
     
         4 . The closed type battery according to  claim 1 , characterized by being a lithium ion battery wherein a composite lithium manganese oxide having a composition formula Li 1+x Mn 2−x−y MyO 4−z  where 0.03≦x≦0.16, 0≦y≦0.1, −0.1≦z≦0.1, and M is at least one selected from Mg, Al, Ti, Co and Ni is used for a positive electrode active substance.