BATTERY CELL CONNECTION STRUCTURE

In a battery cell connection structure for connecting two rectangular battery cells in series in a state where the two battery cells are stacked in the thickness direction thereof, a positive electrode tab of one of the battery cells and a negative electrode tab of the other of the battery cells are connected to each other in a state where the positive electrode tab and the negative electrode tab are stacked in the thickness direction while the positive electrode tab and the negative electrode tab are inclined with respect to a direction in which the two battery cells are stacked.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-001540 filed on Jan. 7, 2022, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a battery cell connection structure.

Description of the Related Art

JP 2008-186725 A discloses a battery cell connection structure. In this battery cell connection structure, an electrode of a battery cell and an electrode of another battery cell are fastened to each other by a screw.

SUMMARY OF THE INVENTION

The technique disclosed in JP 2008-186725 A has a problem in that a gap is generated between the battery cells, when the thickness of the battery cell is relatively thin with respect to the screw.

An object of the present invention is to solve the above-mentioned problem.

According to an aspect of the present invention, provided is a battery cell connection structure configured to connect two battery cells each having a rectangular shape in series in a state where the two battery cells are stacked in a thickness direction thereof, wherein a positive electrode tab and a negative electrode tab are provided on a first side of a plurality of sides of each of the battery cells, the two battery cells are stacked in a state where the first sides thereof are oriented in a same direction, the positive electrode tab of one of the battery cells and the negative electrode tab of another of the battery cells are connected to each other in a state of being stacked in the thickness direction, and the positive electrode tab of the one of the battery cells and the negative electrode tab of the other of the battery cells are connected to each other in a state of being stacked in the thickness direction while the positive electrode tab and the negative electrode tab are bent to be inclined with respect to a direction in which the two battery cells are stacked and with respect to a direction in which the first side of each of the battery cells is connected to a second side of each of the battery cells, the second side being opposite from the first side.

According to the present invention, the distance between the battery cells can be shortened.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

[Configuration of Battery Module]

FIG.1is a perspective view of a battery module10. In the following description of the structure of each member constituting the battery module10, the description will be made using the directions and orientations of the X axis, the Y axis, and the Z axis indicated by the arrows inFIG.1. Arrows indicating the X-axis, the Y-axis, and the Z-axis are also illustrated in the drawings other thanFIG.1, which will be described later. The directions and orientations of the X-axis, the Y-axis, and the Z-axis indicated by the arrows in the drawings other thanFIG.1correspond to the directions and orientations of the X-axis, the Y-axis, and the Z-axis indicated by the arrows inFIG.1.

The battery module10includes four battery cell stacks12. The four battery cell stacks12are arranged in the Y-axis direction in a state where the longitudinal direction of each battery cell stack12is oriented in the X-axis direction. Each battery cell stack12includes a plurality of battery cells14. In each battery cell stack12, the plurality of battery cells14are stacked side by side in the X-axis direction. That is, the stacking direction of the battery cells14is the same as the X-axis direction. The battery cells14are stacked in the thickness direction thereof. In each battery cell stack12, each battery cell14is connected in series with another battery cell14.

The battery module10includes a heat exchanger16. The heat exchanger16cools each battery cell14.

The battery module10includes four battery frames18. Each battery frame18holds each battery cell stack12. Each battery frame18applies pressure to the battery cell stack12from both sides in the X-axis direction. Thus, expansion of each battery cell14is suppressed.

[Configuration of Battery Cell]

FIG.2is a perspective view of the battery cell14.FIG.2shows a state in which two battery cells14are stacked.

The battery cell14is a laminated battery. The battery cell14is formed in a rectangular plate shape. The battery cell14is provided with a positive electrode tab20aand a negative electrode tab20b. The positive electrode tab20aand the negative electrode tab20bare provided on a first side14aof a plurality of sides of the battery cell14. The positive electrode tab20ais formed in a rectangular plate shape. The negative electrode tab20bis formed in a rectangular plate shape.

[Configuration of Heat Exchanger]

FIG.3is a perspective view of the battery cell stack12and the heat exchanger16. InFIG.3, a part of the battery cell stack12and a part of the heat exchanger16are illustrated.FIG.4is a perspective view of a first heat exchange plate22and a second heat exchange plate24.FIG.5is a cross-sectional perspective view of the battery cell stack12and the heat exchanger16. InFIG.5, a part of the battery cell stack12and a part of the heat exchanger16are illustrated.FIG.6is a cross-sectional view of the battery cell stack12and the heat exchanger16. InFIG.6, a part of the battery cell stack12and a part of the heat exchanger16are illustrated.

The heat exchanger16includes a plurality of the first heat exchange plates22and a plurality of the second heat exchange plates24. The plurality of first heat exchange plates22and the plurality of second heat exchange plates24are stacked side by side in the X-axis direction. The plurality of first heat exchange plates22and the plurality of second heat exchange plates24are stacked in the thickness direction of the first heat exchange plates22and the thickness direction of the second heat exchange plates24. The plurality of first heat exchange plates22and the plurality of second heat exchange plates24are configured such that the first heat exchange plate22and the second heat exchange plate24are alternately stacked.

The structure of the second heat exchange plate24is the same as that of the first heat exchange plate22. In the heat exchanger16, the direction in which the first heat exchange plate22is disposed is different from the direction in which the second heat exchange plate24is disposed.

The first heat exchange plate22includes a first water jacket26. The longitudinal direction of the first water jacket26extends in the Y-axis direction. The first water jacket26includes a first forward flow path28and a first return flow path30. In the Z-axis direction, the first forward flow path28is provided on the Z-axis positive side of the center of the first water jacket26. In the Z-axis direction, the first return flow path30is provided on the Z-axis negative side of the center of the first water jacket26. Cooling water flows inside the first forward flow path28. The cooling water flows through the first forward flow path28from the negative side in the Y-axis direction toward the positive side in the Y-axis direction. The cooling water flows inside the first return flow path30. The cooling water flows through the first return flow path30from the positive side in the Y-axis direction toward the negative side in the Y-axis direction. That is, the Y-axis direction is the same as the flow direction in which the cooling water flows inside the first water jacket26.

The first heat exchange plate22includes a first water supply/discharge header32. The first water supply/discharge header32is attached to an end portion of the first water jacket26on the negative side in the Y axis direction. The first water supply/discharge header32includes a first water supply inlet34for supplying cooling water to the first forward flow path28. The first water supply inlet34includes a first water supply connection portion36. The first water supply connection portion36is inserted into the first water supply inlet34of another first heat exchange plate22located on the positive side in the X-axis direction. The first water supply connection portion36includes a seal groove36a. A seal member38is attached to the seal groove36a. The first water supply/discharge header32includes a first water discharge outlet40for discharging the cooling water from the first return flow path30. In the Y-axis direction, the first water discharge outlet40is disposed on the same side of the first water jacket26as the first water supply inlet34. The first water discharge outlet40includes a first water discharge connection portion42. The first water discharge connection portion42is inserted into the first water discharge outlet40of another first heat exchange plate22located on the positive side in the X-axis direction. The first water discharge connection portion42includes a seal groove42a. A seal member44is attached to the seal groove42a.

The first heat exchange plate22includes a first turn header46. The first turn header46is attached to an end portion of the first water jacket26on the positive side in the Y-axis direction. Thus, the first turn header46is disposed on the opposite side of the first water jacket26from the first water supply inlet34and the first water discharge outlet40. The first turn header46causes the cooling water flowing from the first forward flow path28to flow to the first return flow path30. The first turn header46is formed in a curved surface shape protruding toward the outer side of the first heat exchange plate22in the Y-axis direction. As a result, the first turn header46can smoothly change the direction of flow of the cooling water flowing from the first forward flow path28and cause the cooling water to flow to the first return flow path30.

The second heat exchange plate24includes a second water jacket48. The longitudinal direction of the second water jacket48extends in the Y-axis direction. The second water jacket48includes a second forward flow path50and a second return flow path52. In the Z-axis direction, the second forward flow path50is provided on the Z-axis positive side of the center of the second water jacket48. In the Z-axis direction, the second return flow path52is provided on the Z-axis negative side of the center of the second water jacket48. Cooling water flows inside the second forward flow path50. The cooling water flows through the second forward flow path50from the positive side in the Y-axis direction toward the negative side in the Y-axis direction. The cooling water flows inside the second return flow path52. The cooling water flows through the second return flow path52from the negative side in the Y-axis direction toward the positive side in the Y-axis direction. That is, the Y-axis direction is the same as the flow direction in which the cooling water flows inside the second water jacket48.

The second heat exchange plate24includes a second water supply/discharge header54. The second water supply/discharge header54is attached to an end portion of the second water jacket48on the positive side in the Y axis direction. The second water supply/discharge header54includes a second water supply inlet56for supplying cooling water to the second forward flow path50. In the Y-axis direction, the second water supply inlet56is provided on the opposite side of the first water jacket26and the second water jacket48from the first water supply inlet34. The second water supply inlet56includes a second water supply connection portion58. The second water supply connection portion58is inserted into the second water supply inlet56of another second heat exchange plate24located on the positive side in the X-axis direction. The second water supply connection portion58includes a seal groove58a. A seal member60is attached to the seal groove58a. The second water supply/discharge header54includes a second water discharge outlet62for discharging the cooling water from the second return flow path52. In the Y-axis direction, the second water discharge outlet62is disposed on the same side of the second water jacket48as the second water supply inlet56. In the Y-axis direction, the second water discharge outlet62is provided on the opposite side of the first water jacket26and the second water jacket48from the first water discharge outlet40. The second water discharge outlet62includes a second water discharge connection portion64. The second water discharge connection portion64is inserted into the second water discharge outlet62of another second heat exchange plate24located on the positive side in the X-axis direction. The second water discharge connection portion64includes a seal groove64a. A seal member (not shown) is attached to the seal groove64a.

The second heat exchange plate24includes a second turn header68. The second turn header68is attached to an end portion of the second water jacket48on the negative side in the Y-axis direction. Thus, the second turn header68is disposed on the opposite side of the second water jacket48from the second water supply inlet56and the second water discharge outlet62. The second turn header68causes the cooling water flowing from the second forward flow path50to flow to the second return flow path52. The second turn header68is formed in a curved surface shape protruding toward the outer side of the second heat exchange plate24in the Y-axis direction. As a result, the second turn header68can smoothly change the direction of flow of the cooling water flowing from the second forward flow path50and cause the cooling water to flow to the second return flow path52.

FIG.7is a cross-sectional perspective view of the battery cell stack12and the heat exchanger16. InFIG.7, a part of the battery cell stack12and a part of the heat exchanger16are illustrated.

Two battery cells14are disposed between the first heat exchange plate22and the second heat exchange plate24in the X-axis direction. The two battery cells14are stacked in the thickness direction. Each of the outer surfaces of the two stacked battery cells14is in direct contact with the first water jacket26of the first heat exchange plate22or the second water jacket48of the second heat exchange plate24. Each battery cell14is disposed between the first heat exchange plate22and the second heat exchange plate24in a state where the positive electrode tab20aand the negative electrode tab20bface the positive side in the Z-axis direction.

FIG.8is a perspective view of the battery cell stack12.FIG.9is a perspective view of the battery cell stack12.FIG.10is a cross-sectional view of the battery cell stack12.

The positive electrode tab20aof each battery cell14is connected to the negative electrode tab20bof another adjacent battery cell14disposed on the positive side in the X-axis direction. The positive electrode tab20aand the negative electrode tab20bare stacked in the thickness direction. Each of the positive electrode tab20aand the negative electrode tab20bis bent to be inclined with respect to the X-axis direction. The X-axis direction is the same direction as the direction in which the battery cells14are stacked together. Each of the positive electrode tab20aand the negative electrode tab20bis bent to be inclined with respect to the Z-axis direction. The Z-axis direction is the same as the direction in which the first side14aof each battery cell14and a second side14b(FIG.2) on the opposite side from the first side14aare connected together.

In a state where the positive electrode tab20aand the negative electrode tab20bare sandwiched between a tab holder70and a retaining plate72, the tab holder70and the retaining plate72are fastened to each other by screws74.

[Configuration of Battery Frame]

FIG.11is a perspective view of the battery frame18.FIG.12is a side view of the battery frame18.

The battery frame18includes a pair of flat spring plates76, a pair of pressing plates78, and four connecting shafts80.

The pair of pressing plates78are provided between the pair of flat spring plates76. The battery cell stack12is provided between the pair of pressing plates78(FIG.1). Each connecting shaft80extends in the X-axis direction. Each connecting shaft80connects the pair of flat spring plates76.

Each flat spring plate76includes a central portion76aand four arm portions76b. Each arm portion76bextends from the central portion76a. Each arm portion76bextends toward the outer side of the battery frame18in the X-axis direction so as to be oblique relative to the Z-axis direction.

Each flat spring plate76includes first regions and a second region. Each of the first region is a region of a tip portion of each arm portion76b. The second region is a region other than the first regions. The second region includes the central portion76a. In the X-axis direction, the second region is located on the further inward of the battery frame18than the first regions.

Each pressing plate78is attached to the central portion76aof each flat spring plate76. Each pressing plate78may be attached to the second region of the arm portions76bof each flat spring plate76. Each pressing plate78is attached to each flat spring plate76by a screw82. Each pressing plate78may be attached to each flat spring plate76by welding.

In the Z-axis direction, the first regions of the arm portions76bof each flat spring plate76overlap each pressing plate78. In the Y-axis direction, the first regions of the arm portions76bof each flat spring plate76overlap each pressing plate78. The Z-axis direction and the Y-axis direction are the same as the direction orthogonal to the stacking direction of the battery cell stack12.

The connecting shafts80are respectively attached to the first regions of the arm portions76bof the flat spring plates76. Adjustment bolts84are screwed into each connecting shaft80on the outer side of each flat spring plate76. By tightening the adjustment bolts84in a state where the battery cell stack12is disposed between the pair of pressing plates78, the pressure applied from the pair of pressing plates78to the battery cell stack12increases. By adjusting the amount of tightening of the adjustment bolts84, the force applied to the battery cell stack12is set to 200 kPa to 400 kPa.

Advantageous Effects

In the battery cell stack12of the present embodiment, the battery cells14adjacent to each other in the X-axis direction are connected in series. The positive electrode tab20aand the negative electrode tab20bare stacked in the thickness direction of the positive electrode tab20aand the negative electrode tab20b. In this state, the positive electrode tab20aand the negative electrode tab20bare fastened to each other by the screws74.

FIG.13is a schematic view showing a comparative example of the connection structure of the battery cells14. In the comparative example shown inFIG.13, the positive electrode tab20ais bent at a right angle toward the negative electrode tab20bof the adjacent battery cell14. The negative electrode tab20bis bent at a right angle toward the positive electrode tab20aof the adjacent battery cell14. In a state in which the positive electrode tab20aand the negative electrode tab20bare stacked in the Z-axis direction, the positive electrode tab20aand the negative electrode tab20bare fastened to each other by the screws74.

The thickness of the battery cell14, which is a laminated battery, is relatively thin with respect to the width of the head of the screw74. Therefore, in the example of the connection structure of the battery cells14shown inFIG.13, a gap is generated between the battery cells14.

FIG.14is a schematic view showing a comparative example of the connection structure of the battery cells14. In the comparative example shown inFIG.14, the positive electrode tab20aand the negative electrode tab20bare fastened to each other by the screws74in a state in which the positive electrode tab20aand the negative electrode tab20bare stacked in the X-axis direction. Thus, the battery cells14can be brought into contact with each other.

In the battery cell stack12, the battery cells14are stacked in the X-axis direction. In the example shown inFIG.14, when the positive electrode tab20aand the negative electrode tab20bare fastened to each other by the screws74, a tool for screwing the screws74interferes with another set of the positive electrode tab20aand the negative electrode tab20b.

FIG.15is a schematic view showing the connection structure of the battery cells14of the present embodiment. In the connection structure of the present embodiment, each of the positive electrode tab20aand the negative electrode tab20bis bent to be inclined with respect to the X-axis direction. Further, each of the positive electrode tab20aand the negative electrode tab20bis bent to be inclined with respect to the Z-axis direction. In this state, the positive electrode tab20aand the negative electrode tab20bare fastened to each other by the screws74. Therefore, when the positive electrode tab20aand the negative electrode tab20bare fastened to each other by the screws74, the tool does not interfere with another set of the positive electrode tab20aand the negative electrode tab20b.

In the connection structure of the battery cells14of the present embodiment, the tab holder70and the retaining plate72are fastened to each other by the screws74in a state where the positive electrode tab20aand the negative electrode tab20bare sandwiched between the tab holder70and the retaining plate72. As a result, the positive electrode tab20aand the negative electrode tab20bcan be reliably brought into contact with each other.

The present invention is not limited to the embodiment described above, and various configurations could be adopted therein without departing from the essence and gist of the present invention.

Invention Obtained from Embodiment

The invention that can be grasped from the above embodiment will be described below.

In the battery cell connection structure configured to connect the two battery cells (14) each having a rectangular shape in series in a state where the two battery cells are stacked in the thickness direction thereof, the positive electrode tab (20a) and the negative electrode tab (20b) are provided on the first side (14a) of the plurality of sides of each of the battery cells, the two battery cells are stacked in a state where the first sides thereof are oriented in the same direction, the positive electrode tab of one of the battery cells and the negative electrode tab of the other of the battery cells are connected to each other in a state of being stacked in the thickness direction, and the positive electrode tab of one of the battery cells and the negative electrode tab of the other of the battery cells are connected to each other in a state of being stacked in the thickness direction while the positive electrode tab and the negative electrode tab are bent to be inclined with respect to a direction in which the two battery cells are stacked and with respect to a direction in which the first side of each of the battery cells is connected to the second side (14b) of each of the battery cells, the second side being opposite from the first side. As a result, in a state where the positive electrode tab of the battery cell and the negative electrode tab of another battery cell are connected to each other, the distance between the battery cells can be shortened.

In the above-described battery cell connection structure, each of the battery cells may be a laminated battery. Thus, in a state where the positive electrode tab of the battery cell and the negative electrode tab of another battery cell are connected to each other, the distance between the battery cells can be shortened.

In the above-described battery cell connection structure, in a state where the positive electrode tab of one of the battery cells and the negative electrode tab of the other of the battery cells are sandwiched between the holder (70) and the plate (72), the plate and the holder are fastened to each other by the screw (74). As a result, the positive electrode tab and the negative electrode tab can be reliably brought into contact with each other.