In recent years, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices or an auxiliary power device. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as auxiliary power devices or vehicles, use a battery module having a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices.
Preferably, the battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell (unit battery) of the middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, the manufacturing cost of the pouch-shaped battery is low, and it is easy to modify the shape of the pouch-shaped battery.
In general, a high-output, large-capacity battery pack including a plurality of battery modules is configured to have a structure in which a plurality of battery cells or battery modules is stacked while being adjacent to each other, and the battery cell stack or the battery module stack is fixed to a base plate. In this structure, long bolts and additional fixing brackets connected to frames of the battery modules and the base plate in a surface contact fashion are used as means for fixing the battery modules to the base plate.
In the fastening structure using the long bolts and the fixing brackets, however, the battery cells may move in a direction in which the battery cells are stacked or a direction perpendicular to the ground when excessive impact is applied to the battery pack with the result that safety of the battery pack is lowered. In addition, the internal space of the battery pack is decreased, and the weight of the battery pack is increased, due to the use of the additional fixing brackets. Furthermore, a process of fastening the fixing brackets increases total process time.
Consequently, there is a high necessity for a battery module having a novel assembly structure that is capable of solving the above problems.