Patent ID: 12191527

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of a battery module according to the present disclosure will be described with reference to the drawings.

FIG.1is a perspective view of a battery module100according to an embodiment of the present disclosure.FIG.2is a plan view of the battery module100illustrated inFIG.1.FIG.3is an exploded perspective view of the battery module100illustrated inFIG.1.FIG.4is a perspective view of a battery cell1of the battery module100illustrated inFIG.3.FIG.5is an enlarged view of a region around a mechanical joint portion M between the battery groups10of the battery module100illustrated inFIG.1.

Hereinafter, the configuration of the battery module100will be sometimes described using an XYZ orthogonal coordinate system including the X-axis, Y-axis, and Z-axis that are parallel with the thickness direction, width direction, and height direction, respectively, of the battery cells1. The thickness direction, width direction, and height direction of the battery cells1may also be simply denoted by the “thickness direction (i.e., X-axis direction),” “width direction (i.e., Y-axis direction),” and “height direction (i.e., Z-axis direction),” respectively. In the following description, directions, such as upper and lower (or top and bottom), left and right, and longitudinal and lateral, are used only for convenience sake to describe the configuration of the battery module100, and do not limit the orientation of the battery module100during use.

The battery module100of the present embodiment constitutes an on-vehicle energy storage device that is mounted on a vehicle, such as an electric vehicle (EV), a hybrid vehicle (HV), or a plug-in hybrid vehicle (PHV), for example. The battery module100of the present embodiment has the following configuration, for example, though the details will be described later.

The battery module100includes a plurality of battery groups10. Each battery group10includes a plurality of battery cells1, and a first bus bar20P and a second bus bar20N that are adapted to connect the plurality of battery cells1in parallel. Each battery cell1includes a positive electrode terminal2P mainly containing aluminum and a negative electrode terminal2N mainly containing copper. The first bus bar20P mainly contains aluminum and is connected to the positive electrode terminals2P of the plurality of battery cells1of each battery group10via welding joint portions W1. The second bus bar20N mainly contains copper and is connected to the negative electrode terminals2N of the plurality of battery cells1of each battery group10via welding joint portions W2. The plurality of battery groups10are connected in series as a result of the first bus bar20P of one of the mutually adjacent battery groups10being connected to the second bus bar20N of the other battery group10via a mechanical joint portion M.

Hereinafter, the configuration of each portion of the battery module100of the present embodiment will be described in detail. The battery module100of the present embodiment includes the aforementioned plurality of battery groups10, a housing30, and a circuit board (not illustrated), for example. Each battery group10includes the plurality of battery cells1, the first bus bar20P, and the second bus bar20N as described above. It should be noted that among the plurality of battery groups10, the battery groups10arranged at opposite ends in the stacked direction (i.e., X-axis direction) of the battery cells1have a first end bus bar20PE and a second end bus bar20NE, respectively, instead of the first bus bar20P and the second bus bar20N.

The battery cells1are rectangular secondary battery cells in a flat rectangular shape, for example. More specifically, the battery cells1are rectangular lithium ion secondary battery cells. Each battery cell1has the positive electrode terminal2P and the negative electrode terminal2N arranged at opposite ends in the width direction (i.e., Y-axis direction) orthogonal to the thickness direction (i.e., X-axis direction) on an end face of the battery cell1along the thickness direction. More specifically, the battery cell1includes the positive electrode terminal2P, the negative electrode terminal2N, and a battery cell container3. Though not illustrated, the battery cell1also includes an electrode group, current collectors, an insulating member, an electrolytic solution, and the like housed in the battery cell container3.

The battery cell container3is hermetically sealed by welding a rectangular plate-like cell lid3bto the entire periphery of an opening of a closed-bottomed rectangular tube-shaped cell can3a. The battery cell container3has a flat rectangular shape, that is, a thin rectangular parallelepiped or hexahedron having a dimension in the thickness direction (i.e., X-axis direction) smaller than dimensions in the width direction (i.e., Y-axis direction) and the height direction (i.e., Z-axis direction). Among the faces of the battery cell container3of the battery cell1, a pair of wide side faces facing the thickness direction (i.e., X-axis direction) of the battery cell1each have the largest area, and a pair of narrow side faces facing the width direction (i.e., Y-axis direction) of the battery cell1each have the smallest area.

The positive electrode terminal2P and the negative electrode terminal2N, which are external terminals of the battery cell1, are arranged on one of a pair of narrow side faces that face the height direction (i.e., Z-axis direction) of the battery cell container3and are along the thickness direction (i.e., X-axis direction). The positive electrode terminal2P and the negative electrode terminal2N are arranged at opposite ends in the longitudinal direction of the rectangular cell lid3b, that is, in the width direction (i.e., Y-axis direction) of the battery cell1. Each of the positive electrode terminal2P and the negative electrode terminal2N has a stereoscopic shape of a generally rectangular parallelepiped protruding in the height direction (i.e., Z-axis direction) from the upper face of the cell lid3b. Resin insulating members are provided to electrically insulate the positive electrode terminal2P and the negative electrode terminal2N from the battery cell container3, and the current collectors and the electrode group from the battery cell container3.

The positive electrode terminal2P is formed using aluminum or a material mainly containing aluminum, such as aluminum alloy, for example. The negative electrode terminal2N is formed using copper or a material mainly containing copper, such as copper alloy, for example. The positive electrode terminal2P and the negative electrode terminal2N are connected to the current collectors of the positive electrode and the negative electrode, respectively, housed in the battery cell container3and are connected to the positive electrode and the negative electrode, respectively, of the electrode group via the respective current collectors.

The plurality of battery cells1of each battery group10are stacked and arranged in the same orientation along the thickness direction (i.e., X-axis direction) such that the plurality of positive electrode terminals2P and the plurality of negative electrode terminals2N are each aligned along the thickness direction (i.e., X-axis direction). Meanwhile, the plurality of battery groups10of the battery module100are stacked and arranged while being alternately inverted along the thickness direction (i.e., X-axis direction) such that the plurality of positive electrode terminals2P and the plurality of negative electrode terminals2N are alternately arranged along the thickness direction (i.e., X-axis direction).

In the present embodiment, each battery group10includes three battery cells1. Three respective positive electrode terminals2P of the three battery cells1of each battery group10are aligned in the thickness direction (i.e., X-axis direction) at ends of the battery cells1in one side of the width direction (i.e., Y-axis direction). Meanwhile, three respective negative electrode terminals2N of the three battery cells1of each battery group10are aligned in the thickness direction (i.e., X-axis direction) at ends of the battery cells1in one side of the width direction (i.e., Y-axis direction) on the side opposite to the positive electrode terminals2P. It should be noted that the number of the battery cells1of each battery group10is not particularly limited, and may be two or more than three.

Among the plurality of battery groups10stacked and arranged in the thickness direction (i.e., X-axis direction) of the battery cells1, two adjacent battery groups10have opposite arrangements of the positive electrode terminals2P and the negative electrode terminals2N of the battery cells1in the width direction (i.e., Y-axis direction). In the present embodiment, the battery module100includes four battery groups10. The four battery groups10are stacked and arranged while being alternately inverted in the thickness direction (i.e., X-axis direction) such that three positive electrode terminals2P and three negative electrode terminals2N are alternately arranged in the thickness direction (i.e., X-axis direction). It should be noted that the number of the battery groups10of the battery module100is not particularly limited, and may be two, three, or more than four.

FIG.6is a perspective view of the first bus bar20P adapted to be connected to the second bus bar20N via the mechanical joint portion M illustrated inFIG.5.FIG.7is a perspective view of the second bus bar20N adapted to be connected to the first bus bar20P via the mechanical joint portion M illustrated inFIG.5.FIG.8Ais a side view of the mechanical joint portion M illustrated inFIG.5as seen from the width direction (i.e., Y-axis direction) of the battery cells1.

The first bus bar20P and the second bus bar20N of each battery group10are plate-like conductive metal members adapted to connect the plurality of battery cells1of each battery group10in parallel. The first bus bar20P is formed using aluminum or a material mainly containing aluminum, such as aluminum alloy, for example. The second bus bar20N is formed using copper or a material mainly containing copper, such as copper alloy, for example. That is, the first bus bar20P and the second bus bar20N are formed using metals similar to those of the positive electrode terminal2P and the negative electrode terminal2N, respectively, of each battery cell1and thus have excellent weldability to the positive electrode terminal2P and the negative electrode terminal2N, respectively.

The first bus bar20P is connected to the positive electrode terminals2P of the plurality of battery cells1of each battery group10via the welding joint portions W1. The second bus bar20N is connected to the negative electrode terminals2N of the plurality of battery cells1of each battery group10via the welding joint portions W2. That is, the first bus bar20P and the second bus bar20N are electrically connected to the positive electrode terminals2P and the negative electrode terminals2N, respectively, via the welding joint portions W1and W2each adapted to weld similar metals together and having excellent weldability. The first bus bar20P of one of the mutually adjacent battery groups10and the second bus bar20N of the other battery group10are connected via the mechanical joint portion M.

Each of the first bus bar20P and the second bus bar20N has a plate-like shape having a longitudinal direction along the thickness direction (i.e., X-axis direction) of the battery cells1and having a short direction along the width direction (i.e., Y-axis direction) of the battery cells1. The first bus bar20P and the second bus bar20N are connected to end faces of the plurality of positive electrode terminals2P and end faces of the plurality of negative electrode terminals2N, respectively, via the welding joint portions W1and W2in the height direction (i.e., Z-axis direction) orthogonal to the thickness direction (i.e., X-axis direction) and the width direction (Y-axis direction) of the battery cells1. The first bus bar20P and the second bus bar20N have the mechanical joint portion M at their ends adjacent to each other in the longitudinal direction (i.e., X-axis direction).

The first bus bar20P has a body21extending from the positive electrode terminal2P of the battery cell1arranged at one end of the plurality of battery cells1of each battery group10in the stacked direction (i.e., X-axis direction) of the battery cells1to the positive electrode terminal2P of the battery cell1arranged at the other end. Similarly, the second bus bar20N has a body21extending from the negative electrode terminal2N of the battery cell1arranged at one end of the plurality of battery cells1of each battery group10in the stacked direction (i.e., X-axis direction) of the battery cells1to the negative electrode terminal2N of the battery cell1arranged at the other end.

The body21has a rectangular plate-like shape having a longitudinal direction along the thickness direction (i.e., X-axis direction) of the battery cells1and having a short direction along the width direction (i.e., Y-axis direction) of the battery cells1in a plan view seen from the height direction (i.e., Z-axis direction) of the battery cells1. The body21has a plurality of flat portions22and a plurality of curved portions23. Each flat portion22is a flat, rectangular plate-like portion that faces the positive electrode terminal2P or the negative electrode terminal2N of the battery cell1and is adapted to be joined to the positive electrode terminal2P or the negative electrode terminal2N of the battery cell1via the welding joint portions W1or the welding joint portions W2, and has a through-hole22ain the center.

Each curved portion23is a curved portion provided between the adjacent flat portions22. The curved portion23is bent in the direction away from the battery cells1at an angle of about 90 degrees, for example, in the thickness direction of the flat portions22, that is, in the height direction (i.e., Z-axis direction) of the battery cells1from the flat portions22on the opposite sides. In addition, the curved portion23has a portion bent in a semicylindrical shape between the portions bent at an angle of about 90 degrees with respect to the flat portions22on the opposite sides. Accordingly, the curved portion23has a U curved shape in a side view seen from the short direction of the body21, that is, the width direction (i.e., Y-axis direction) of the battery cells1.

In the present embodiment, the first bus bar20P and the second bus bar20N also have bypass portions24P and24N, respectively, which extend inward along the width direction (i.e., Y-axis direction) of the battery cells1, at their ends adjacent to each other in the longitudinal direction (i.e., X-axis direction). The first bus bar20P and the second bus bar20N are connected via the mechanical joint portion M at their respective bypass portions24P and24N.

The bypass portion24P of the first bus bar20P extends inward from an end on the inner side of the flat portion22in the width direction (i.e., Y-axis direction) of the battery cell1at an end of the body21adjacent to the second bus bar20N. The bypass portion24P of the first bus bar20P extends toward the second bus bar20N beyond the end of the body21adjacent to the second bus bar20N, in the stacked direction (i.e., X-axis direction) of the battery cells1. The bypass portion24N of the second bus bar20N extends inward from an end on the inner side of the flat portion22in the width direction (i.e., Y-axis direction) of the battery cell1at an end of the body21adjacent to the first bus bar20P.

As described above, the bypass portion24P of the first bus bar20P extends in the longitudinal direction (i.e., X-axis direction) beyond the end of the body21adjacent to the second bus bar20N, and the bypass portion24N of the second bus bar20N extends inward along the width direction (i.e., Y-axis direction) of the battery cells1, for example. Accordingly, the bypass portion24P of the first bus bar20P and the bypass portion24N of the second bus bar20N are in contact with each other while overlapping at the mechanical joint portion M in the height direction (i.e., Z-axis direction) of the battery cells1. It is acceptable as long as at least one of the bypass portion24P of the first bus bar20P or the bypass portion24N of the second bus bar20N extends in the longitudinal direction beyond an end of its body21that is adjacent to an end of the body21on the other side, and the bypass portion24P of the first bus bar20P and the bypass portion24N of the second bus bar20N overlap at the mechanical joint portion M in the height direction (i.e., Z-axis direction) of the battery cells1.

The mechanical joint portion M includes, for example, a bolt m1and a nut m3that are adapted to fasten and connect the first bus bar20P and the second bus bar20N together. The mechanical joint portion M may also include a washer m2arranged between the bolt m1and the nut m3and the bypass portions24P and24N. Each of the bypass portion24P of the first bus bar20P and the bypass portion24N of the second bus bar20N has a through-hole24afor passing the bolt m1of the mechanical joint portion M at the position of overlap in the height direction (i.e., Z-axis direction) of the battery cells1. The nut m3is arranged on a face of the bypass portion24N of the second bus bar20N facing the battery cell1, for example.

The mechanical joint portion M is adapted to connect the first bus bar20P and the second bus bar20N by, for example, screwing the bolt m1, which has been inserted through the through-holes24aof the bypass portions24P and24N, into the nut m3, and fastening the bypass portions24P and24N together with the bolt m1and the nut m3. Accordingly, the first bus bar20P of one of the battery groups10that are adjacent to each other in the stacked direction and the second bus bar20N of the other battery group10are electrically connected via the mechanical joint portion M. Further, the first bus bar20P of one of the mutually adjacent battery groups10is connected to the second bus bar20N of the other battery group10via the mechanical joint portion M sequentially from one end to the other end of the battery groups10in the stacked direction, so that all of the battery groups10are connected in series.

The first bus bar20P and the second bus bar20N respectively have bent portions25between their bypass portions24P and24N and the flat portions22. Each bent portion25is bent at an angle of about 90 degrees, for example, from an end on the inner side of the flat portion22in the width direction (i.e., Y-axis direction) of the battery cells1, in the thickness direction of the flat portion22, that is, in the height direction (i.e., Z-axis direction) of the battery cells1and a direction opposite to the battery cells1. In addition, each bent portion25is also bent at an angle of about 90 degrees, for example, toward the battery cells1from an end on the outer side of the bypass portion24P or24N in the width direction (i.e., Y-axis direction) of the battery cells1, in the thickness direction of the bypass portion24P or24N, that is, in the height direction (i.e., Z-axis direction) of the battery cells1.

It should be noted that the first end bus bar20PE and the second end bus bar20NE of the battery groups10arranged at opposite ends in the stacked direction (i.e., X-axis direction) have configurations similar to the first bus bar20P and the second bus bar20N except that they have no bypass portion24P or24N. In addition, the first end bus bar20PE and the second end bus bar20NE may have extension portions partially forming module terminals101P and101N of the positive electrode and the negative electrode, respectively, of the battery module100.

As illustrated inFIG.1, the housing30is in the shape of a generally rectangular parallelepiped having a longitudinal direction along the thickness direction (i.e., X-axis direction) of the battery cells1, and holds the plurality of battery cells1of the battery groups10. More specifically, the housing30includes a plurality of cell holders31, a pair of end plates32, a pair of side frames33, insulation covers34, and a module cover (not illustrated), for example.

The cell holders31are formed of a resin material, such as polybutylene terephthalate (PBT), for example. The cell holders31are provided between the mutually adjacent battery cells1of the plurality of battery cells1stacked in the thickness direction (i.e., X-axis direction), for example, and hold the individual battery cells1from their opposite sides in the thickness direction (i.e., X-axis direction). In the stacked direction (i.e., X-axis direction) of the plurality of battery cells1of the battery groups10, a pair of cell holders31arranged on the opposite sides of the battery groups10are provided with the module terminals101P and101N, respectively, that are the external terminals of the battery module100, for example.

The pair of end plates32are plate-like metal members, for example. The pair of end plates32are arranged at opposite ends of the battery groups10with interposed therebetween the pair of cell holders31, which are arranged on the opposite sides of the battery groups10, in the stacked direction (i.e., X-axis direction) of the plurality of battery cells1of the battery groups10. One face of each of the pair of end plates32faces the plurality of battery cells1held by the cell holders31so as to sandwich them.

The pair of side frames33are arranged on the opposite sides of the plurality of battery cells1of the battery groups10in the width direction (i.e., Y-axis direction) with the cell holders31interposed therebetween. The pair of side frames33are metal members in a generally rectangular frame shape, for example, and are arranged facing the opposite sides of the battery cells1in the width direction (i.e., Y-axis direction). Each of the pair of side frames33is in a generally rectangular frame shape, for example, and has a long-side direction, that is, a longitudinal direction along the stacked direction (i.e., X-axis direction) of the plurality of battery cells1of the battery groups10, and has a short-side direction, that is, a short direction along the height direction (i.e., Z-axis direction) of the plurality of battery cells1of the battery groups10. The opposite ends of the pair of side frames33in the longitudinal direction are fastened to the pair of end plates32with fastening members, such as rivets or bolts, for example, and the inner side of the pair of side frames33engages with projections provided on the plurality of cell holders31.

Each insulation cover34is a plate-like resin member, such as PBT, having an electrical insulating property, for example, and is arranged facing the upper end face, which is the narrow side face, of each battery cell container3provided with the positive electrode terminal2P and the negative electrode terminal2N of the battery cell1. The insulation cover34has an opening for exposing the upper end faces of the positive electrode terminals2P and the negative electrode terminals2N of the plurality of battery cells1, and also has partition walls for insulating the positive electrode terminals2P or the negative electrode terminals2N of the mutually adjacent battery cells1as well as insulating the first bus bar20P and the second bus bar20N that are adjacent to each other. The partitions walls of the insulation cover34are provided to surround the positive electrode terminals2P and the negative electrode terminals2N of the battery cells1as well as the first bus bars20P and the second bus bars20N, for example. In addition, the insulation cover34has disposed thereon various electric wires connected to the battery cells1and the circuit board.

The circuit board (not illustrated) is disposed between each insulation cover34and the module cover (not illustrated), that is, on the side of the insulation cover34opposite to the battery cells1in the height direction of the housing30, and is connected to the first bus bars20P and the second bus bars20N via electric wires, for example. The module cover (not illustrated) is a plate-like resin member, such as PBT, having an electrical insulating property, for example. The module cover is disposed to cover each insulation cover34and the circuit board at the upper end of the housing30on the side opposite to the battery cells1in the height direction (i.e., Z-axis direction) of the housing30.

Hereinafter, the function of the battery module100of the present embodiment will be described.

As described above, the battery module100includes the plurality of battery groups10. Each battery group10includes the plurality of battery cells1, and the first bus bar20P and the second bus bar20N adapted to connect the plurality of battery cells1in parallel. Each battery cell1includes the positive electrode terminal2P mainly containing aluminum and the negative electrode terminal2N mainly containing copper. The first bus bar20P mainly contains aluminum and is connected to the positive electrode terminals2P of the plurality of battery cells1of each battery group10via the welding joint portions W1. The second bus bar20N mainly contains copper and is connected to the negative electrode terminals2N of the plurality of battery cells1of each battery group10via the welding joint portions W2. The plurality of battery groups10are connected in series as a result of the first bus bar20P of one of the mutually adjacent battery groups10being connected to the second bus bar20N of the other battery group10via the mechanical joint portion M.

According to such a configuration, power can be supplied from an external device, such as a power generator, to the plurality of battery cells1of the battery module100via the module terminals101P and101N, the first end bus bar20PE and the second end bus bar20NE, and the first bus bar20P and the second bus bar20N, for example, so that the plurality of battery cells1of each battery group10can be charged. It is also possible to supply power stored in the plurality of battery cells1of each battery group10to an external device, such as a motor, via the first bus bar20P and the second bus bar20N, the first end bus bar20PE and the second end bus bar20NE, and the module terminals101P and101N.

According to such a configuration, the plurality of battery cells1of a single battery group10can be connected in parallel by a single first bus bar20P or first end bus bar20PE mainly containing aluminum and by a single second bus bar20N or second end bus bar20NE mainly containing copper, via the plurality of welding joint portions W1and W2each adapted to weld similar metals together. In addition, as the first bus bar20P and the second bus bar20N mainly containing dissimilar metals are connected via the mechanical joint portion M, the plurality of battery groups10can be connected in series without using a clad material and thus avoiding dissimilar metal welding.

That is, the present embodiment can provide the battery module100including the plurality of battery groups10each having the plurality of battery cells1connected in parallel, the plurality of battery groups10being connected in series by the first bus bar20P and the second bus bar20N, for which a clad material is not used and thus dissimilar metal welding can be avoided. In addition, according to the battery module100of the present embodiment, releasing the joining at the mechanical joint portion M allows for replacement in units of the battery groups10and also allows for connection of a voltage sensing wire and the like to the mechanical joint portion M.

In the battery module100, each battery cell1has a flat rectangular shape, and has the positive electrode terminal2P and the negative electrode terminal2N arranged at opposite ends in the width direction (i.e., Y-axis direction) orthogonal to the thickness direction (i.e., X-axis direction) on an end face of the battery cell1along the thickness direction. The plurality of battery cells1of each battery group10are stacked and arranged in the same orientation along the thickness direction (i.e., X-axis direction) such that the plurality of positive electrode terminals2P and the plurality of negative electrode terminals2N are each aligned along the thickness direction (i.e., X-axis direction). Meanwhile, the plurality of battery groups10are stacked and arranged while being alternately inverted along the thickness direction (i.e., X-axis direction) such that the plurality of positive electrode terminals2P and the plurality of negative electrode terminals2N are alternately arranged in the thickness direction (i.e., X-axis direction).

According to such a configuration, the plurality of battery cells1can be connected in parallel by a single first bus bar20P and a single second bus bar20N. Thus, the productivity of the battery module100can be can increased. In addition, sequentially connecting the first bus bar20P of one of the mutually adjacent battery groups10to the second bus bar20N of the other battery group10via the mechanical joint portion M allows the plurality of battery groups10to be connected in series. That is, as the first bus bar20P and the second bus bar20N, which are longer than the conventional bus bars and contain dissimilar materials, are connected via the mechanical joint portion M, there is no need to form the first bus bar20P and the second bus bar20N as a single thin and elongated clad material. This can avoid the problems in production and cost associated with the use of a special clad material that is longer than the conventional bus bars.

In the battery module100, each of the first bus bar20P and the second bus bar20N has a plate-like shape having a longitudinal direction along the thickness direction (i.e., X-axis direction) of the battery cells1and having a short direction along the width direction (i.e., Y-axis direction) of the battery cells1. The first bus bar20P and the second bus bar20N are connected to end faces of the plurality of positive electrode terminals2P and end faces of the plurality of negative electrode terminals2N via the welding joint portions W1and W2, respectively, in the height direction (i.e., Z-axis direction) orthogonal to the thickness direction (i.e., X-axis direction) and the width direction (i.e., Y-axis direction) of the battery cells1, and have the mechanical joint portion M at their ends adjacent to each other in the longitudinal direction.

According to such a configuration, a single first bus bar20P is arranged above the plurality of positive electrode terminals2P of the plurality of battery cells1, and a single second bus bar20N is arranged above the plurality of negative electrode terminals2N of the plurality of battery cells1, and then, the welding joint portions W1and W2can be easily formed at a time by laser welding, for example. In addition, contact areas can be secured between the first bus bar20P and the positive electrode terminals2P of the battery cells1and between the second bus bar20N and the negative electrode terminals2N of the battery cells1. Further, in comparison with when individual bus bars, which are connected to external terminals of individual battery cells of a battery group, are connected one by one, it is only necessary to connect the mutually adjacent battery groups10via the mechanical joint portion M. Thus, the number of parts and the number of joint portions can be reduced. Thus, the productivity of the battery module100can be increased.

Further, since each of the first bus bar20P and the second bus bar20N has the curved portions23, the elasticity of each of the first bus bar20P and the second bus bar20N in the height direction (i.e., Z-axis direction) of the battery cells1can be increased. Accordingly, pressing the first bus bar20P and the second bus bar20N against the positive electrode terminals2P and the negative electrode terminals2N, respectively, of the plurality of battery cells1allows the first bus bar20P and the second bus bar20N to elastically deform in the height direction (i.e., Z-axis direction) of the battery cells1. This allows the first bus bar20P and the second bus bar20N to more reliably contact the positive electrode terminals2P and the negative electrode terminals2N, respectively, of the plurality of battery cells1, and thus increases the connection reliability of the plurality of battery cells1.

In the battery module100of the present embodiment, the first bus bar20P and the second bus bar20N have the bypass portions24P and24N, respectively, which extend inward along the width direction (i.e., Y-axis direction) of the battery cells1, at their ends adjacent to each other in the longitudinal direction (i.e., X-axis direction). In addition, the first bus bar20P and the second bus bar20N are connected via the mechanical joint portion M at their bypass portions24P and24N.

Such a configuration can secure a space for disposing the mechanical joint portion M without preventing a reduction in the size of the battery module100. Therefore, not only can fastening members, such as the bolt m1and the nut m3, be disposed, but also a space for disposing a jig or a probe that is necessary to form the welding joint portions W1and W2can be secured, for example. In addition, a sufficient contact area between the first bus bar20P and the second bus bar20N can be secured. Further, as the first bus bar20P and the second bus bar20N have the bypass portions24P and24N, respectively, stress applied to each portion of the battery module100can be relaxed.

More specifically, for example, forces are applied to the first bus bar20P and the second bus bar20N due to steps resulting from the dimensional tolerance of each portion of the battery module100or due to impact or vibration applied to the battery module100. In addition, as the number of battery cells1over which the first bus bar20P and the second bus bar20N extend is greater and as the first bus bar20P and the second bus bar20N are longer, forces applied to the first bus bar20P and the second bus bar20N become greater.

However, as the first bus bar20P and the second bus bar20N have the bypass portions24P and24N, respectively, stress applied to each portion of the battery module100can be relaxed. Herein, relaxation of stress by the bypass portions24P and24N includes dispersion of the stress concentration portion for each portion of the battery module100and relaxation of stress applied to each portion due to the first bus bar20P and the second bus bar20N being deformed within the elastic range.

In the battery module100of the present embodiment, at least one of the bypass portion24P of the first bus bar20P or the bypass portion24N of the second bus bar20N extends in the longitudinal direction beyond an end of the first bus bar20P or the second bus bar20N in the longitudinal direction. In addition, the bypass portion24P of the first bus bar20P and the bypass portion24N of the second bus bar20N overlap with each other at the mechanical joint portion M in the height direction (i.e., Z-axis direction) of the battery cells1.

Such a configuration can secure a sufficient contact area between the bypass portion24P of the first bus bar20P and the bypass portion24N of the second bus bar20N, and thus can increase the reliability of connection between the first bus bar20P and the second bus bar20N via the mechanical joint portion M. In addition, it is possible to suppress an increase in the dimension of the battery module100in the height direction (i.e., Z-axis direction) of the battery cells1, and thus can achieve a reduction in the size of the battery module100.

In the battery module100of the present embodiment, the mechanical joint portion M includes the bolt m1and the nut m3that are adapted to fasten and connect the first bus bar20P and the second bus bar20N together. Accordingly, it is possible to allow the bolt m1to penetrate through the first bus bar20P and the second bus bar20N and be screwed into the nut m3, and then fasten the bolt m1and the nut m3together, thereby forming the mechanical joint portion M between the first bus bar20P and the second bus bar20N. It should be noted that the configuration of the mechanical joint portion M is not limited to the one including the bolt m1and the nut m3.

FIGS.8B and8Care side views each illustrating a variation of the mechanical joint portion M illustrated inFIG.8A. As illustrated inFIG.8B, the mechanical joint portion M of the battery module100may include a clip m4adapted to hold and connect the first bus bar20P and the second bus bar20N together. Alternatively, as illustrated inFIG.8C, the mechanical joint portion M may include a rivet m5adapted to connect the first bus bar20P and the second bus bar20N together by penetrating through the first bus bar20P and the second bus bar20N and thus undergoing plastic deformation. Such variations can also achieve advantageous effects similar to those of the mechanical joint portion M illustrated inFIG.8A.

As described above, according to the present embodiment, the plurality of battery cells1of a single battery group10can be connected in parallel by a single first bus bar20P mainly containing aluminum and a single second bus bar20N mainly containing copper, via the plurality of welding joint portions W1and W2each adapted to weld similar metals together. In addition, the first bus bar20P and the second bus bar20N mainly containing dissimilar metals are connected via the mechanical joint portion M. Thus, it is possible to connect the plurality of battery groups10in series without using a clad material and thus avoiding dissimilar metal welding. That is, the present embodiment can provide the battery module100including the plurality of battery groups10each having the plurality of battery cells1connected in parallel, the plurality of battery groups10being connected in series by the first bus bar20P and the second bus bar20N, for which a clad material is not used and thus dissimilar metal welding can be avoided.

Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, specific configurations are not limited thereto, and any designs changes that are within the spirit and scope of the present invention are included in the present disclosure.

REFERENCE SIGNS LIST

1Battery cell2P Positive electrode terminal2N Negative electrode terminal10Battery group20P First bus bar20N Second bus bar24P Bypass portion24N Bypass portion100Battery moduleM Mechanical joint portionm1Boltm3Nutm4Clipm5RivetW1Welding joint portionW2Welding joint portion