Battery pack and method for producing same
A battery pack includes battery modules and a base member on which the battery modules are mounted. The battery modules include a plurality of unit cells are stacked in a thickness direction, have a flat shape and positive and negative terminals for transferring input and output of electric power. The terminals are disposed on an opposite side of the base member side in the battery module. The unit cells include a cell body that includes a power generation element and an electrode tab. The battery module includes a pair of first cover members in the stacking direction and a pair of second cover members in a direction that intersects with the stacking direction and that intersects with a direction in which the electrode tab extends. The second cover members are joined to the first cover members while the stacked unit cells are pressurized in the stacking direction.
1. A battery pack comprising:
a plurality of battery modules including a plurality of unit cells are stacked in a stacking direction, each of the unit cells having a flat shape and positive and negative terminals for transferring input and output of electric power; and
a base member on which the battery modules are mounted,
the terminals of the battery modules being disposed at an end portion on a side opposite of the base member in the battery module, and the battery modules being arranged on a mounting surface of the base member,
each of the unit cells including a cell body that includes a power generation element and an electrode tab protruding out from the cell body,
each of the battery modules including a pair of first cover members for covering the unit cells from both sides in the stacking direction and a pair of second cover members for covering the unit cells from both sides in a direction that intersects with the stacking direction and that also intersects with a direction in which the electrode tab extends,
the second cover members being welded to the first cover members in a pressurized state in which the stacked unit cells are pressurized in the stacking direction by the first cover members such that a height of the plurality of stacked unit cells is lower in the pressurized state than a height of the plurality of stacked unit cells in a non-pressurized state,
at least one of the battery modules being mounted to the base member by bolts inserted through corners of each of the at least one of the battery modules,
an end portion of each of the bolts being attached to a bracket of the base member,
each of the at least one of the battery modules including bus bars connecting the electrode tabs, the terminals being joined to the bus bars and superimposed on the bus bars and the electrode tabs from an exterior of the battery module,
the terminals, electrode tabs, and bus bars being disposed between bolts on sides of the surface of the battery module, and,
the terminals of one of the battery modules and the terminals of an adjacent one of the battery modules, which face each other, being at different heights from the base member.
2. The battery pack according to claim 1 , wherein
each the battery modules is not stacked but is disposed on one level on the base member.
3. The battery pack according to claim 1 , wherein
each of the battery modules includes a stacked portion in which the unit cells are stacked and an insertion portion that receives the bolts,
a length of the bolts in the stacking direction is shorter than a length of the stacked portions,
for each of the battery modules, the stacked portion has a recessed portion disposed between the stacked portion and the insertion portion, and the brackets are connected to the battery modules by fitting into the recessed portion.
4. The battery pack according to claim 3 , wherein
each of the bolts has a head portion, and a length of the head portion does not exceed the length of the stacked portion.
5. The battery pack according to claim 1 , wherein
one of the battery modules is mounted on the base member in a state in which the stacking direction is perpendicular to the base member, and
another of the battery modules is mounted on the base member in which the stacking direction of the unit cells is parallel to the base member.
6. The battery pack according to claim 1 , wherein
one electrode tab of the electrode tabs of the unit cells and one bus bar of the bus bars are ultrasonically joined or welded, and
adjacent electrode tabs of the electrode tabs of the unit cells and adjacent bus bars of the bus bars are ultrasonically joined or welded.
7. The battery pack according to claim 1 , wherein
each of the unit cells comprises an external casing for covering the power generation element, and
each of the battery modules further comprises a heat transfer member disposed in any position in the stacking direction, the heat transfer member further includes a member having a higher thermal conductivity rate than the external casing.
8. The battery pack according to claim 1 , wherein
each of the battery modules uses the first cover members, regardless of a number of stacked layers of the unit cells.
9. The battery pack according to claim 1 , wherein
one of the battery modules further comprises an elastic member disposed in any position in the stacking direction, and the elastic member generates elastic force along the stacking direction.