1. Field of the Invention
The present invention relates to a laminate cell having a structure, in which pluralities of positive and negative electrode plates are alternately stacked while interposing separators therebetween to configure a power generating element, and the positive and negative electrode plates of the power generating element are connected to positive and negative tabs through pluralities of positive and negative leads, respectively. The present invention also relates to an assembled battery, a battery module and an electric vehicle, all of which use this laminate cell.
2. Description of the Related Art
In recent years, an electric vehicle which uses electricity as a power source and a hybrid car which runs by a combination of an engine and a motor have attracted attention due to the global problem of environmental air pollution caused by automobile exhaust gas. Thus, the development of a high-power battery to be mounted in these types of vehicles, which achieves high energy/power densities, occupies an important position in the industry.
Regarding this type of high-power battery, for example, there is a lithium ion battery. Specifically, among this type of battery, there is a laminate cell formed by stacking flat positive and negative electrode plates upon one another while interposing separators therebetween.
As for this laminate cell, one disclosed in Japanese Patent Application Laid-Open No. 2000-200585 has been proposed, which uses, as a cell package, a laminate film formed by stacking a metal film and a polymer film. In this specification, the laminate film is referred to as a metal composite film. This laminate cell is constructed in a such manner that a power generating element composed of positive and negative electrode plates and separators, all of which have an approximately rectangular flat shape, are hermetically sealed together with an electrolyte by the cell package made of the metal composite film, and a positive tab connected to the positive electrode plates of the power generating element and a negative tab connected to the negative electrode plates thereof are drawn outward from the end edges of the cell package.
The laminate cell thus constructed has an advantage in that it is easier to reduce the weight and thickness thereof in comparison with one which uses a metal can as the cell package.
Incidentally, in the laminate cell thus constructed, it is common that the respective positive electrode plates of the power generating element are connected to the positive tab through positive leads, and the respective negative electrode plates thereof are connected to the negative tab through negative leads. Specifically, in this type of laminate cell, one end of the positive tab is drawn to the outside of the cell package, and onto the other end thereof, the plurality of positive leads from the respective positive electrode plates of the stacked electrode are joined. Moreover, one end of the negative tab is drawn to the outside of the cell package, and onto the other end thereof, the plurality of negative leads from the respective negative electrode plates of the stacked electrode are joined.