Battery Module

Abstract

To extend the life of a battery cell by setting binding force of the battery cell in the stacking direction to an appropriate size.SOLUTION: A battery pack 1 includes a battery cell 10 that has a pair of first surface portions 11 facing each other in a first direction, and is arranged such that a positive electrode plate 14a and a negative electrode plate 14b are arranged in the first direction, and laminated in the first direction, an outer shell 80 that houses the stacked battery cells 10, an elastic member 60 provided between the battery cells 10 adjacent to each other in the first direction, and a plurality of frames 20 for fixing each battery cell 10 to the outer shell 80. The elastic member 60 is arranged so as to cover the central portion of the first surface portion 11, and the frame 20 is arranged so as to cover the outer peripheral portion of the first surface portion 11.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The technology disclosed herein belongs to the technical field related to battery modules. [Background technology]

[0002] In recent years, vehicles that move using motor torque generated by a motor, such as electric vehicles and hybrid vehicles, are becoming more and more popular. Such vehicles are provided with a battery module that stores power to be supplied to the motor. Most battery modules provided in vehicles are formed by stacking multiple rectangular parallelepiped battery cells.

[0003] For example, the battery module described in Patent Document 1 comprises a cell stack in which multiple battery cells are stacked in a first direction with an insulator between them, a pair of end plates arranged on both sides of the cell stack in the first direction, and a pair of side frames arranged on both sides of the cell stack in a second direction perpendicular to the first direction, each side frame having a front flange portion extending toward each other along the front end plate and a rear flange portion extending toward each other along the rear end plate, the front flange portion being fastened to the front end plate and the rear flange portion being fastened to the rear end plate, and changes in the angles of the front flange portion and the rear flange portion allow expansion in the first direction due to deterioration of the battery cells.

[0004] Furthermore, the battery module described in Patent Document 2 comprises battery cells, a case that houses the battery cells, and a foam coating layer sandwiched between the outer surface of the battery cells and the inner surface of the case, and between the stacked battery cells, a partition plate extending from the case is disposed at a position corresponding to the outer periphery of the face of the battery cells in the stacking direction, and a gap is left in the portion corresponding to the center of the face of the battery cells. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-75281 A [Patent Document 2] JP 2013-191440 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, through extensive research, the inventors of the present application have found that there is a correlation between the restraining force in the stacking direction of the battery cells and the deterioration of the battery cells.

[0007] Specifically, in a configuration in which the expansion of a battery cell is absorbed by the bending of a flange provided on a side frame, as in the battery module described in Patent Document 1, the spring force of the flange becomes strong, particularly when the battery cell expands, and the restraining force in the stacking direction becomes strong. When the restraining force in the stacking direction becomes strong, the electrolyte repeatedly seeps into and seeps out of the electrodes, which increases the occurrence of uneven electrolyte concentration. This causes localized internal resistance to increase, deteriorating the battery cell.

[0008] Conversely, in a state where there are gaps between battery cells, as in the battery module described in Patent Document 2, the central part of the battery cell has almost zero binding force in the stacking direction. If the binding force in the stacking direction is too weak, the distance between the electrodes will be uneven. This will cause localized internal resistance to increase. In addition, in the case of a battery module for vehicle use, the electrodes will be easily displaced due to vehicle vibration, which will cause damage to the connection between the electrode body and the terminal due to the load applied to it, shortening the life of the battery cell.

[0009] The technology disclosed herein extends the life of a battery cell in a battery module formed by stacking a plurality of battery cells by setting the restraining force of the battery cells in the stacking direction to an appropriate value. [Means for solving the problem]

[0010] The inventors of the present application arranged soft members at parts of the battery cell that are prone to expansion, thereby restraining the parts with a low load.

[0011] Specifically, the technology disclosed herein is configured to include a battery cell having a pair of first surface portions facing a first direction, a pair of second surface portions facing a second direction perpendicular to the first direction, and a pair of third surface portions facing a third direction perpendicular to both the first direction and the second direction, and accommodating an electrode body in which positive and negative plates are arranged in the first direction within a space formed by the first surface portions, the second surface portions, and the third surface portions, and further comprising an outer shell portion accommodating the stacked battery cells, an elastic member provided between the battery cells adjacent to each other in the first direction, and a fixing portion for fixing each battery cell to the outer shell portion, wherein the elastic member is arranged to cover a central portion of the first surface portions, and the fixing portion is arranged to cover an outer circumferential portion of the first surface portions.

[0012] That is, the central portion of the first surface of the battery cell is easily expanded, and this expansion increases the binding force of the battery cell in the stacking direction. In contrast, in the above configuration, since an elastic member is disposed between the adjacent battery cells in the first direction, the elastic member is deformed to shrink in accordance with the expansion of the central portion of the first surface. As a result, compared to, for example, a case in which the central portion of the first surface of the battery cell is covered with a non-elastic member, an increase in the load on the battery cell due to expansion is suppressed. As a result, the battery cell is maintained in a state of being bound by a low load. In addition, by disposing the fixing portion on the outer periphery of the battery cell that is difficult to expand, an increase in the displacement amount of the battery cell due to vibration can be suppressed, and the fixing portion can also be suppressed from increasing the binding force of the battery cell in the stacking direction. As a result, while fixing the battery cell, unevenness in the distance between the electrodes and unevenness in the concentration of the electrolyte are suppressed, and an increase in the internal resistance of the battery cell can be suppressed, thereby extending the life of the battery cell.

[0013] In the battery module, the elastic member may be large enough to cover the entire electrode body when viewed from the first direction.

[0014] According to this configuration, since the size is large enough to cover the entire electrode, the part where the electrode is provided can be appropriately restrained. As a result, the load is applied evenly to the entire electrode, so that an increase in the internal resistance of the battery cell is more effectively suppressed, and the life of the battery cell can be extended.

[0015] In the battery module, the fixing portion may be composed of a resin frame formed to cover an outer peripheral portion of the battery cell, and the battery cell may be fixed to the outer shell portion by fixing the frame to the outer shell portion with the battery cell fitted within the frame.

[0016] According to this configuration, since the fixing portion is composed of a frame that covers the outer periphery of the battery cell, the entire battery cell can be supported by the frame. Also, since the outer periphery of the battery cell is not easily expanded, even if a rigid body is placed thereon, the internal resistance is not easily increased. Therefore, the battery cell can have a longer life.

[0017] In one embodiment of the battery module, the outer shell portion has a pair of end plates arranged to sandwich the entirety of the stacked battery cells from both sides in the first direction, and a pair of side plates extending in the first direction and arranged to sandwich the entirety of the stacked battery cells from both sides in the second direction, and the fixing portions are respectively positioned between each of the side plates and the battery cells and are respectively fixed to the pair of side plates.

[0018] According to this configuration, since the fixing portion is fixed to the side plate, it is difficult for the fixing portion to move in the first direction, and therefore no binding force in the first direction is generated on the battery cell. Since there is no binding force on the battery cell by the fixing portion, the binding force applied to the battery cell is applied by the elastic member. This makes it easier to make the binding force on the battery cell in the first direction appropriate, and makes it easier to extend the life of the battery cell.

[0019] In one embodiment, each of the side plates may have a flange portion provided on both side ends in the first direction, extending in the first direction, and then bending and extending toward the battery cell in the second direction, and each of the end plates may be configured to be connected to the flange portion with a bolt.

[0020] With this configuration, the connection between the end plate and the side plate is separated from the battery cell, so the connection between the end plate and the side plate has almost no effect on the binding force of the battery cell in the first direction. This makes it easier to make the binding force of the battery cell in the first direction appropriate, and makes it easier to extend the life of the battery cell.

[0021] In one embodiment, the battery stack may further include a housing to which a battery stack having the multiple battery cells housed in the outer shell is attached, each of the side plates having a bracket extending toward the opposite side of the battery cells in the second direction and fixed to the housing, and the housing may have a support portion that is connected to the bracket and supports the battery stack.

[0022] According to this configuration, the side plate is less likely to deform in the first direction. This makes it less likely that the side plate will generate a binding force in the first direction on the battery cell. As a result, the binding force in the first direction on the battery cell is kept at an appropriate level, and the battery cell can have a longer life.

[0023] In the embodiment in which the battery stack is attached to a housing, a plurality of the battery stacks may be arranged in the second direction and each attached to the housing, and the brackets may be multiple and attached to the support portion in a state in which they are placed on the support portion from a third direction, and each bracket provided on a side plate on one side in the second direction and each bracket provided on a side plate on the other side in the second direction may be arranged in a staggered pattern with respect to each other.

[0024] According to this configuration, the brackets of adjacent battery stacks can be arranged alternately on the support portion. This shortens the interval between the mounting portions and the support portion. The shorter interval between the mounting portions increases the resonant frequency of the battery module, making it easier to suppress vibration of the battery module. In addition, the adjacent battery stacks can be arranged as close as possible to each other, making the entire battery module compact.

[0025] In the battery module, a pressing force with which the elastic member presses the adjacent battery cell is preferably set to 1 kN to 10 kN.

[0026] The inventors of the present application have found that, although it depends on the internal electrode specifications and the size of the battery cell, if the restraining force in the first direction of the battery cell is set to about 1 kN to 10 kN, the internal resistance hardly changes even if the battery cell expands due to aging. Therefore, by adopting the above-mentioned configuration, it is possible to extend the life of the battery cell.

[0027] In the battery module, a length in the first direction of a battery stack in which the plurality of battery cells are housed in the outer shell portion may be equal to a length between a pair of side frames.

[0028] That is, since the battery cells only need to be restrained with a low restraining force in the first direction, the restraining force can be made uniform and the number of stacked battery cells can be increased as much as possible. Furthermore, if the length of the battery stack in the first direction is approximately equal to the length between the side frames, the battery capacity can be significantly increased. Therefore, the battery can be made large-capacity while having a long life. Effect of the Invention

[0029] As described above, according to the technique disclosed herein, the restraining force in the stacking direction of the battery cells can be set to an appropriate magnitude, thereby extending the life of the battery cells. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of a vehicle in which a battery pack according to an exemplary embodiment is disposed. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 2 is an exploded perspective view showing the configuration of one battery cell. [Diagram 5] FIG. 2 is a front view of the battery cells as viewed from the stacking direction. [Figure 6] 1 is a cross-sectional view of a right end portion of a battery stack in a stacking direction, the right end portion being cut along a plane parallel to the stacking direction and the up-down direction. [Figure 7] FIG. 2 is a plan view of the battery stack as viewed from above. [Figure 8] 10 is a graph showing the relationship between the restraining force in the stacking direction of the battery stack and the internal resistance. [Figure 9] FIG. 2 is a perspective view showing the relationship between the battery stack and a housing. [Figure 10] 11 is an enlarged plan view seen from above showing a portion of the battery stack that is attached to the housing. FIG. [Figure 11] 4 is a cross-sectional view showing a portion where the battery stack is attached to the housing. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Exemplary embodiments will now be described in detail with reference to the drawings.

[0032] FIG. 1 shows a schematic configuration of an electric vehicle equipped with a battery module according to this embodiment. This vehicle is an electric car driven only by electric energy. The vehicle has an electric motor 2 as a drive source that is driven and rotated by electric power stored in a battery pack 1 having a battery module. An inverter 3 is provided between the battery pack 1 and the electric motor 2, which converts DC power stored in the battery pack 1 into AC power and supplies it to the electric motor 2. The inverter 3 is controlled by a controller 4 provided in the vehicle.

[0033] The electric motor 2 is interlocked with a pair of left and right drive shafts 7 via a gear train 5 and a differential gear 6. Front wheels 8 are coupled to the outer ends of each drive shaft 7 in the vehicle width direction. In other words, this vehicle is a so-called FF vehicle, in which the two left and right front wheels 8 are drive wheels and the two left and right rear wheels 9 are driven wheels.

[0034] When the vehicle is traveling with the accelerator (not shown) of the vehicle depressed, the electric motor 2 is driven by power supplied from the battery pack 1 to rotate the front wheels 8. In other words, when the vehicle is powered, the electric motor 2 is driven by power supplied from the battery pack 1 via the inverter 3, and the driving force of the electric motor 2 is transmitted to the front wheels 8 via the gear train 5, the differential device 6, and the drive shaft 7.

[0035] The vehicle is provided with a brake device B that applies braking force by friction to each of the front wheels 8 and the rear wheels 9. The brake device B may be of either a hydraulic or electric type.

[0036] Battery Stack As shown in FIG. 2 and FIG. 3, the battery pack 1 has a battery stack 100 in which a plurality of battery cells 10 are stacked. The number of stacked battery cells 10 is, for example, 36 to 40. In this embodiment, the battery pack 1 is arranged in the vehicle so that the stacking direction of the battery cells 10 is the left-right direction (i.e., the vehicle width direction). The length of the stacking direction of the battery stack 100 is equal to the length between a pair of left and right side frames. In the following description, the stacking direction is simply referred to as the left-right direction, and the direction perpendicular to the left-right direction and the up-down direction may be referred to as the front-back direction. In this case, the left-right direction corresponds to the first direction, the front-back direction corresponds to the second direction, and the up-down direction corresponds to the third direction. The stacking direction of the battery cells 10 is not limited to the left-right direction. The stacking direction of the battery cells 10 may be the front-back direction.

[0037] The battery stack 100 has an outer shell 80 (see FIG. 3 in particular) that houses the stacked battery cells 10. The outer shell 80 has a pair of end plates 30 arranged to sandwich the entire stacked battery cells 10 from both sides in the left-right direction, and a pair of side plates 40 extending in the left-right direction and arranged to sandwich the entire stacked battery cells 10 from both sides in the front-rear direction. The battery stack 100 has a plurality of frames 20 for fixing each battery cell 10 to the outer shell 80. In the following description, the left end plate 30 is referred to as the left end plate 30L, the right end plate 30 is referred to as the right end plate 30R, the front side plate 40 is referred to as the front side plate 40Fr, and the rear side plate is referred to as the rear side plate 40Rr. When the left and right end plates 30L, 30R are not differentiated from one another, they are simply referred to as end plates 30, and when the front and rear side plates 40Fr, 40Rr are not differentiated from one another, they are simply referred to as side plates 40.

[0038] <Battery Cell> Each battery cell 10 is a lithium ion battery. As shown in FIG. 4, each battery cell 10 has a rectangular parallelepiped shape that is flat in the left-right direction. Each battery cell 10 has a pair of first surfaces 11 facing each other in the left-right direction, a pair of second surfaces 12 facing each other in the front-rear direction, and a pair of third surfaces 13 facing each other in the up-down direction. The area of ​​the first surfaces 11 is significantly larger than the areas of the second surfaces 12 and the third surfaces 13. The first surfaces 11, the second surfaces 12, and the third surfaces 13 are each formed of, for example, aluminum or an aluminum alloy.

[0039] As shown in Fig. 6, each battery cell 10 contains an electrolyte and an electrode body 14 immersed in the electrolyte in a space formed by a first surface portion 11, a second surface portion 12, and a third surface portion 13. The electrode body 14 is formed into a flattened circular shape by spirally winding a positive electrode plate 14a and a negative electrode plate 14b and compressing them in the radial direction. As a result, the positive electrode plates 14a and the negative electrode plates 14b are arranged alternately in the left-right direction.

[0040] The upper third surface portion 13 of each battery cell 10 has a pair of electrode terminals 15. The electrode terminals 15 have a positive terminal 15a connected to the positive electrode plate 14a and a negative terminal 15b connected to the negative electrode plate 14b. The electrode terminals 15 protrude upward from the upper third surface portion 13. Although not shown in the figure, the electrode terminals 15 of adjacent battery cells 10 are connected in series by a bus bar. One end of the bus bar is joined to the positive electrode terminal 15a of the battery cell 10, and the other end of the bus bar is joined to the negative electrode terminal 15b of the adjacent battery cell 10.

[0041] Frame As shown in FIG. 3 and FIG. 4, the frame 20 accommodates each battery cell 10 individually. Each frame 20 is made of a resin material such as polypropylene, polycarbonate, polybutylene terephthalate, etc. The frame 20 has a pair of front and rear frame bodies 21 for fixing the battery cells 10. Each pair of frame bodies 21 is U-shaped and is arranged with the U-shaped openings facing each other. As shown in FIG. 2 and FIG. 5, the frame body 21 covers the entire second surface portion 12 of the battery cell 10 and the front and rear ends of the third surface portion 13 when the two adjacent frames 20 are joined together. The distance between the middle portions in the vertical direction of the pair of frame bodies 21 is approximately the same as the length (length in the front and rear direction) of the long sides of the first surface portion 11 of the battery cell 10. In addition, the distance between the upper end portion and the lower end portion of each frame body 21 is approximately the same as the length (length in the vertical direction) of the short sides of the first surface portion 11 of the battery cell 10.

[0042] As shown in Figs. 4 and 5, a first partition wall 22 for dividing adjacent battery cells 10 in the left-right direction is provided in the inner portion of each frame body 21. Each first partition wall 22 is located at the center in the width direction of the frame body 21 and extends in the up-down direction. The lower ends and upper ends of each first partition wall 22 are connected by a second partition wall 23 that extends in the front-rear direction and divides adjacent battery cells 10 in the left-right direction. That is, a pair of frame bodies 21 are connected by the second partition wall 23. The first and second partition walls 22, 23 are arranged so as to cover the outer periphery of the first surface portion 11 (see Fig. 4 in particular). The first and second partition walls 22, 23 have the same thickness, which is about 2 to 3 mm.

[0043] Each frame body 21 has a connecting portion 25 at its upper end and lower end for connecting with an adjacent frame 20. The connecting portion 25 has a male-female structure. In the example shown in FIG. 4, a male portion is formed on the left side, and a female portion (not shown) is formed on the left side. By inserting the male portion into the female portion of the adjacent frame 20, the adjacent frames 20 are connected to each other, as shown in FIG. 3.

[0044] As shown in Fig. 6, when adjacent frames 20 are joined, the distance between adjacent second partition walls 23 in the left-right direction is approximately the same as the left-right width of the battery cell 10. Therefore, the battery cell 10 sandwiched between two frames 20 is less likely to move in the left-right direction. In other words, each battery cell is fixed to the outer shell by the second partition walls 23. The second partition walls 23 are arranged so as to be adjacent to an elastic member 60 described below in the up-down direction.

[0045] A claw portion 26 is provided on the outer surface of each frame body 21. The claw portion 26 is a portion for fixing the frame 20 to the side plate 40. The claw portion 26 enters an engagement hole 45 provided in the side plate 40 and is hooked on a main surface portion 41 of the side plate 40. As a result, each frame 20 is located between each side plate 40 and the battery cell 10 as shown in FIG. 5, and is fixed to each pair of side plates 40. Note that the method of fixing the frame 20 to the side plate 40 is not limited to the method using the claw portion 26 as described above. The frame 20 may be fixed to the side plate 40 by a bolt or an adhesive.

[0046] As shown in Fig. 6, end frames 27 are used for the battery cells 10 located at both ends in the left-right direction. The end frame 27 has the same basic configuration as the normal frame 20, but differs from the normal frame 20 in that the frame main body 21 is interrupted at the first and second partition walls 22, 23. Fig. 6 shows the right end frame 27. The left end frame 27 has a symmetrical configuration to the right end frame 27.

[0047] <Outer shell> As shown in Fig. 2 and Fig. 3, the end plate 30 is formed by bending a metal plate such as aluminum or an aluminum alloy into an L-shape. Specifically, the end plate 30 has a main surface portion 31 extending in the up-down direction and a bottom surface portion 32 extending in the left-right direction from a lower end of the main surface portion 31. The bottom surface portion 32 of the left end plate 30L extends leftward from the lower end of the main surface portion 31, and the bottom surface portion 32 of the right end plate 30R extends rightward from the lower end of the main surface portion 31. As shown in Fig. 3, the main surface portion 31 of each end plate 30 has two bolt holes 33 at both ends in the front-rear direction. The bolt holes 33 are formed spaced apart in the up-down direction.

[0048] Each side plate 40 has a rectangular main surface portion 41 extending in the front-rear direction. Each side plate 40 has a first flange portion 42 extending from both vertical end portions of the main surface portion 41 toward the battery cell 10. Specifically, the first flange portion 42 of the front side plate 40Fr extends from both vertical end portions of the main surface portion 41 toward the rear side, and the first flange portion 42 of the rear side plate 40Rr extends from both vertical end portions of the main surface portion 41 toward the front side. As shown in FIG. 5, the main surface portion 41 and the first flange portion 42 cover the frame main body 21 of the frame 20 from the outside.

[0049] Each side plate 40 has a second flange portion 43 that extends from both ends of the main surface portion 41 in the left-right direction to the left and right, respectively, and then bends and extends toward the battery cell 10. Specifically, the second flange portion 43 of the front side plate 40Fr extends from both ends of the main surface portion 41 in the left-right direction to the left and right, respectively, and then extends toward the rear side. On the other hand, the second flange portion 43 of the rear side plate 40Rr extends from both ends of the main surface portion 41 in the left-right direction to the left and right, respectively, and then extends toward the front side. Each second flange portion 43 has two bolt holes 43a. The two bolt holes 43a are formed to be spaced apart in the vertical direction so as to correspond to the bolt holes 33 of the end plates 30. When joining the end plate 30 and the side plate 40, first, the end plate 30 is placed against the second flange portion 43 so that the bolt holes 33 of the end plate 30 communicate with the bolt holes 43a of the second flange portion 43. Then, the bolts 101 are fastened to the bolt holes 33, 43a.

[0050] As shown in Figs. 5 and 7, each side plate 40 has a plurality of brackets 44 (six in Fig. 7) extending toward the opposite side from the battery cell 10 in the front-rear direction. Each bracket 44 is formed by bending an aluminum plate into an L-shape. One surface of each bracket 44 is welded to the main surface 41 of the side plate 40, and a hole is formed in the other surface of each bracket 44. The brackets 44 provided on the front side plate 40Fr and the brackets 44 provided on the rear side plate 40Rr are arranged in a staggered manner. Specifically, the brackets 44 of the rear side plate 40Rr are arranged in a staggered manner so that they are located at the portions corresponding to the centers of two adjacent brackets 44 of the front side plate 40Fr. As will be described in detail later, the brackets 44 are used to attach the battery stack 100 to a housing 70 described later.

[0051] As shown in Fig. 6, a spacer 50 is provided between the right end plate 30 and the right end frame 27. The spacer 50 has an area approximately equal to that of the first surface portion 11 of the battery cell 10. As shown in Fig. 7, stepped portions 51 into which the second flange portion 43 of the side plate 40 is fitted are formed on both end portions of the spacer 50 in the front-rear direction. The left spacer 50 has a similar configuration.

[0052] Elastic Member Here, the inventors of the present application conducted intensive research and found that there is a correlation between the restraining force of the battery cell 10 in the stacking direction of the battery cell 10 (here, the left-right direction), i.e., the pressing force pressing the battery cell 10 in the stacking direction, and the deterioration of the battery cell 10.

[0053] 8 is a graph showing the relationship between the restraining force in the stacking direction of the battery cell 10 and the internal resistance of the battery cell 10. The horizontal axis shows the restraining force in the stacking direction of the battery cell 10, and the vertical axis shows the internal resistance generated in the battery cell 10. The solid line represents an unused battery cell 10, and the dashed line represents a used battery cell 10.

[0054] As shown in FIG. 8, even if the battery cell 10 is unused or has been used to some extent, the relationship between the restraining force in the stacking direction of the battery cell 10 and the internal resistance of the battery cell 10 is a so-called bathtub curve. Specifically, it is found that the internal resistance rises in an area where the restraining force in the stacking direction of the battery cell 10 is excessively strong and an area where the restraining force is excessively weak. When the restraining force in the stacking direction is excessively strong, the electrolyte solution is repeatedly seeped into and seeped out of the electrode body 14 in the battery cell 10, which causes the concentration unevenness of the electrolyte solution to increase. This causes the internal resistance to rise locally. On the other hand, when the restraining force in the stacking direction is too weak, the distance between the positive electrode plate 14a and the negative electrode plate 14b becomes uneven. This causes the internal resistance to rise locally. In addition, in the case of the battery pack 1 provided in a vehicle as in this embodiment, the electrode body 14 is easily displaced by the vibration of the vehicle, and as a result, a load is applied to the connection portion between the electrode body 14 and the electrode terminal 15, which may be damaged.

[0055] In particular, if the restraining force is excessively strong, the internal resistance of the battery cell 10 increases significantly after it has been used to a certain extent. When a lithium-ion battery such as the battery cell 10 is continuously charged, lithium ions accumulate in the negative electrode plate 14b. The electrode body 14 becomes larger by the amount of these lithium ions, and the battery cell 10 expands in the stacking direction. This further strengthens the restraining force in the stacking direction, and the internal resistance rises sharply as shown in FIG. 8.

[0056] On the other hand, as shown by hatching in Fig. 8, if the restraining force in the stacking direction of the battery cell 10 is set to an appropriate value, the internal resistance can be maintained at a low level even if the battery cell 10 has deteriorated to a certain extent. As a result of research conducted by the present inventors, it has been found that the internal resistance of the battery cell 10 can be maintained at a low level if the restraining force in the stacking direction of the battery cell 10 is set to about 1 kN to 10 kN.

[0057] Therefore, in this embodiment, an elastic member 60 is provided between each of the battery cells 10 adjacent to each other in the left-right direction (stacking direction). The elastic member 60 is made of, for example, a foam filler, a gel material, a rubber material, a resin material, or the like. As shown in FIG. 5, the elastic member 60 is disposed so as to cover the central portion of the first surface portion 11 when viewed from the left-right direction. The elastic member 60 has a size that covers the entire electrode body 14 when viewed from the left-right direction. Specifically, when sandwiched between the battery cells 10, the elastic member 60 has a rectangular shape when viewed from the left-right direction, and the length of the long side is equal to or greater than the length of the electrode body 14 in the winding axis direction (front-back direction) and the length of the short side is equal to or greater than the length of the electrode body 14 in the up-down direction.

[0058] As shown in FIG. 5 and FIG. 6, the elastic member 60 is located at the positions of the first and second partition walls 22, 23 in the left-right direction. The elastic member 60 is disposed in an area surrounded by the first and second partition walls 22, 23. The elastic member 60 has a thickness larger than that of the first and second partition walls 22, 23 in an unloaded state. The elastic member 60 becomes the same thickness as the first and second partition walls 22, 23 by being sandwiched and pressed by the battery cells 10 from both sides in the left-right direction. The elastic member 60 presses the battery cells 10 located on both the left and right sides by a repulsive force when pressed by the battery cells 10 from both sides in the left-right direction. At this time, the pressing force with which the elastic member 60 presses the adjacent battery cells 10 is set to 1 kN to 10 kN. This allows the restraining force in the stacking direction of the battery cells 10 to be 1 kN to 10 kN.

[0059] The elastic members 60 arranged at the left and right ends of the battery stack 100 are sandwiched in the left-right direction between the spacer 50 and the battery cell 10. At this time, the elastic members 60 need to apply the same repulsive force to the battery cells 10 at the ends as when the elastic members 60 are sandwiched between the battery cells 10. This can be achieved, for example, by making the spacer 50 into a hollow box shape similar to the battery cells 10 and making the left-right surface portions out of the same material and to the same thickness as the first surface portion 11 of the battery cell 10.

[0060] The restraining force of the elastic member 60 against the battery cells 10 can be adjusted by changing the material of the elastic member 60 and the thickness of the elastic member 60 relative to the thicknesses of the first and second partition walls 22, 23. That is, if the thickness of the elastic member 60 is increased under no load, the repulsive force of the elastic member 60 increases when the elastic member 60 is sandwiched between the battery cells 10 and has the same thickness as the first and second partition walls 22, 23. This makes it possible to adjust the restraining force of the elastic member 60 against the battery cells 10. The thickness of the elastic member 60 may be adjusted to a thickness that allows the restraining force of the battery cells 10 in the stacking direction to be 1 kN to 10 kN according to Hooke's law, depending on the spring constant of the material of the elastic member 60.

[0061] As described above, when the battery pack 1 is continuously charged, the battery cells 10 expand in the stacking direction. When the battery cells 10 expand in the stacking direction, the binding force of the elastic member 60 on the battery cells 10 changes. For this reason, it is preferable to select the material and thickness of the elastic member 60 so that the binding force of the elastic member 60 on the battery cells 10 is 1 kN to 10 kN even if the battery cells 10 expand in the stacking direction.

[0062] In this way, by setting the restraining force on the battery cell 10 to an appropriate value, it is possible to reduce the internal resistance of the battery cell 10 as much as possible, thereby enabling the life of the battery cell 10 to be extended.

[0063] <Battery pack> In the battery pack 1, the battery stack 100 configured as described above is attached to a resin housing 70. As shown in Fig. 9, the housing 70 is box-shaped, and a plurality of (five in Fig. 9) cross members 72 extending to connect left and right side wall portions 71 are arranged parallel to each other in the front-rear direction. As shown in Fig. 10, in the battery pack 1, the plurality of battery stacks 100 are attached to the housing 70 in a state where they are arranged in the front-rear direction. Although not shown, the housing 70 has a lid member that covers the battery stack 100 from above when the battery stack 100 is attached to the housing 70.

[0064] 11 , each bracket 44 of the side plate 40 is placed on the cross member 72 from above. Then, bolts 73 are passed through holes in each bracket 44 and fastened to the cross member 72, thereby supporting the battery stack 100 on the cross member 72. In other words, each cross member 72 corresponds to a support portion that is coupled to the bracket 44 of the side plate 40 and supports the battery stack 100.

[0065] Here, as shown in Fig. 10, the brackets 44 provided on the front and rear side plates 40Fr, 40Rr are arranged in a staggered pattern, so that the brackets 44 of one battery stack 100 can be positioned between the brackets of the adjacent battery stack 100. This allows the width of the cross member 72 to be made as small as possible, and the housing 70 to be made compact. As a result, the entire battery pack 1 can be made compact. In addition, the interval between the mounting parts of the battery stack 100 relative to the cross member 72 is shortened. By shortening the interval between the mounting parts, the resonant frequency of the battery stack 100 increases, making it easier to suppress vibration of the battery stack 100.

[0066] 11, when the battery stack 100 is supported by the cross member 72, the battery stack 100 is spaced apart from the bottom wall portion 74 of the housing 70. This makes it possible to minimize the number of contact points between the housing 70 and the battery stack 100. As a result, it is possible to minimize the transmission of vehicle vibrations to the battery cells 10.

[0067] <summary> Therefore, in this embodiment, the battery pack 1 has a pair of first surface portions 11 facing each other in the left-right direction (stacking direction), a pair of second surface portions 12 facing each other in the front-rear direction, and a pair of third surface portions 13 facing each other in the up-down direction, and is provided with a battery cell 10 that houses an electrode body 14 in which a positive electrode plate 14a and a negative electrode plate 14b are arranged side by side in the left-right direction within a space formed by the first surface portions 11, the second surface portions 12, and the third surface portions 13. The battery pack 1 has a plurality of battery cells 10 stacked in the left-right direction, and further includes an outer shell portion 80 that houses the stacked battery cells 10, elastic members 60 that are respectively provided between adjacent battery cells 10 in the left-right direction (stacking direction), and a plurality of frames 20 for fixing each battery cell 10 to the outer shell portion 80, and the elastic member 60 is arranged so as to cover a central portion of the first surface portion 11. In this configuration, the central portion of the first surface portion 11 of the battery cell 10 is prone to expansion, and this expansion increases the restraining force of the battery cell 10 in the stacking direction. In contrast, in this embodiment, the elastic member 60 is deformed to shrink in accordance with the expansion of the central portion of the first surface portion 11. As a result, compared to a case in which the central portion of the first surface portion 11 of the battery cell 10 is covered with a non-elastic member, an increase in the load on the battery cell 10 due to expansion is suppressed. As a result, the battery cell 10 is maintained in a state of being restrained by a low load. In addition, since each battery cell 10 is supported by the outer shell portion 80 by the frame 20, the displacement of the battery cell 10 due to vibration is also suppressed. In particular, by arranging the first and second partition walls 22, 23 of the frame 20 on the outer peripheral portion of the first surface portion 11 of the battery cell 10, which is difficult to expand, the displacement of each battery cell 10 in the left-right direction (stacking direction) is effectively suppressed. As a result, unevenness in the distance between the electrode plates 14a, 14b and unevenness in the concentration of the electrolyte are suppressed while fixing the battery cell 10. Therefore, an increase in the internal resistance of the battery cell 10 is suppressed, and the life of the battery cell 10 can be extended.

[0068] In addition, since the first and second partition walls 22, 23 are arranged on the outer periphery of the first surface portion 11 where expansion of each battery cell 10 is small, damage to the first and second partition walls 22, 23 due to expansion of each battery cell 10 is also prevented.

[0069] Moreover, since the second partition wall 23 is disposed adjacent to the elastic member 60 in the up-down direction, the battery module can be made compact in structure. Moreover, in this embodiment, the elastic member 60 absorbs the expansion of the battery cells 10 in the battery pack 1, so the length of the battery pack 1 in the left-right direction does not change. Therefore, it is not necessary to install a displacement absorption mechanism that is generally disposed in the fixed portion of the battery pack 1, and the battery pack 1 can be made compact.

[0070] Particularly in this embodiment, the elastic member 60 has a size sufficient to cover the entire electrode body 14 when viewed from the left-right direction. This makes it possible to appropriately restrain the portion of the battery cell 10 where the electrode body 14 is provided. As a result, an increase in the internal resistance of the battery cell 10 is more effectively suppressed, and the life of the battery cell 10 can be extended.

[0071] In this embodiment, the frame 20 is formed to cover the outer peripheral portion of the battery cell 10, and the frame 20 is fixed to the outer shell portion 80 with the battery cell 10 fitted in the frame 20, thereby fixing the battery cell 10 to the outer shell portion 80. This allows the frame 20 to support the entire battery cell 10. As a result, it is possible to prevent the battery cell 10 from moving and being damaged due to vibration of the vehicle, etc. In addition, since the outer peripheral portion of the battery cell 10 is unlikely to expand, even if a rigid body is placed thereon, the internal resistance is unlikely to increase. Therefore, the life of the battery cell 10 can be extended.

[0072] In this embodiment, the outer shell 80 has a pair of end plates 30 arranged to sandwich the entire stacked battery cells 10 from both sides in the left-right direction, and a pair of side plates 40 extending in the left-right direction and arranged to sandwich the entire stacked battery cells 10 from both sides in the front-rear direction, and the frame 20 is located between each side plate 40 and the battery cells 10 and is fixed to each of the pair of side plates 40. As a result, the frame 20 is fixed to the side plates 40, so it is difficult to move in the left-right direction and does not generate a binding force in the left-right direction on the battery cells 10. Since there is no binding force on the battery cells 10 by the frame 20, the binding force applied to the battery cells 10 is applied by the elastic member 60. As a result, it is easier to make the binding force in the left-right direction of the battery cells 10 an appropriate magnitude, and it is easier to extend the life of the battery cells 10.

[0073] In this embodiment, each side plate 40 has a second flange portion 43 that is provided on both side ends in the left-right direction, extends in the left-right direction, and then bends and extends toward the battery cell 10 in the front-rear direction, and each end plate 30 is connected to the second flange portion 43 with a bolt. As a result, the connection portion between the end plate 30 and the side plate 40 is located away from the battery cell 10, so the connection between the end plate 30 and the side plate 40 has almost no effect on the restraining force in the left-right direction of the battery cell 10. This makes it easier to make the restraining force in the left-right direction of the battery cell 10 appropriate, and makes it easier to extend the life of the battery cell 10.

[0074] (Other embodiments) The technology disclosed herein is not limited to the above-described embodiment, and may be substituted without departing from the spirit and scope of the claims.

[0075] For example, in the above-described embodiment, the size of the elastic member 60, when viewed from the stacking direction (left-right direction), is large enough to cover the entire electrode body 14. However, the size of the elastic member 60 is not limited to this, and may be slightly smaller than the electrode body 14 when viewed from the stacking direction.

[0076] In the above embodiment, the length of the battery stack 100 in the stacking direction is equal to the length between the pair of side frames. However, the length of the battery stack 100 in the stacking direction may be shorter than the length between the pair of side frames.

[0077] The above-described embodiments are merely illustrative and should not be construed as limiting the scope of the present disclosure. The scope of the present disclosure is defined by the claims, and all modifications and variations within the scope of the claims are within the scope of the present disclosure. [Industrial Applicability]

[0078] The technology disclosed herein is useful for a battery module having a pair of first surfaces facing each other in a first direction, a pair of second surfaces facing each other in a second direction perpendicular to the first direction, and a pair of third surfaces facing each other in a third direction perpendicular to both the first and second directions, and including a battery cell that houses an electrode body in which positive and negative plates are arranged side by side in the first direction within a space formed by the first surfaces, the second surfaces, and the third surfaces, and in which the battery cells are stacked in the first direction. [Explanation of symbols]

[0079] 1 Battery pack 10 Battery Cells 11 First surface 12 Second surface 13 Third Face 14 Electrode body 14a Positive electrode plate 14b Negative plate 20 Frame (fixed part) 30 End Plate 40 Side Plate 43 Second flange 44 Bracket 70 Case 72 Cross member (support part) 80 Outer shell 100 Battery stack 101 Volts

Claims

1. a battery cell having a pair of first surfaces opposed to each other in a first direction, a pair of second surfaces opposed to each other in a second direction perpendicular to the first direction, and a pair of third surfaces opposed to each other in a third direction perpendicular to both the first direction and the second direction, and housing an electrode assembly in which a positive electrode plate and a negative electrode plate are arranged side by side in the first direction within a space formed by the first surfaces, the second surfaces, and the third surfaces; A battery module in which the battery cells are stacked in the first direction, an outer shell portion that houses the stacked battery cells; An elastic member provided between the battery cells adjacent to each other in the first direction; a fixing portion for fixing each of the battery cells to the outer shell portion, the elastic member is disposed so as to cover a central portion of the first surface portion, The fixing portion is configured with a resin frame formed so as to cover an outer periphery of the battery cell, Each of the frames is a frame main body covering the entire second surface portion and a part of the third surface portion; a partition wall that is located at a center of the frame body in the first direction and that separates adjacent battery cells in the first direction; having The partition wall is disposed so as to cover an outer periphery of the first surface portion, The elastic member is disposed in an area surrounded by the partition wall. Teri module.

2. The battery module according to claim 1 , The battery module, wherein the elastic member has a size sufficient to cover the entire electrode body when viewed from the first direction.

3. The battery module according to claim 1 or 2, a battery cell mounted in the frame, the battery cell being fixed to the outer shell by fixing the frame to the outer shell with the battery cell fitted in the frame; Module.

4. The battery module according to any one of claims 1 to 3, The outer shell portion is A pair of end plates arranged to sandwich the entire stacked battery cells from both sides in the first direction; a pair of side plates extending in the first direction and arranged to sandwich the entirety of the stacked battery cells from both sides in the second direction; having the fixing portions are respectively positioned between the side plates and the battery cells, and are respectively fixed to the pair of side plates.

5. The battery module according to claim 4, Each of the side plates has a flange portion provided at each of both ends in the first direction, extending in the first direction, and then bending and extending toward the battery cell in the second direction, The battery module, wherein each of the end plates is connected to the flange portion by a bolt.

6. The battery module according to claim 4 or 5, a housing to which a battery stack having the plurality of battery cells housed in the outer shell portion is attached; each of the side plates includes a bracket extending toward an opposite side to the battery cell in the second direction and fixed to the housing; The battery module is characterized in that the housing has a support portion that is coupled to the bracket and supports the battery stack.

7. The battery module according to claim 6, A configuration in which a plurality of the battery stacks are attached to the housing in a state in which they are lined up in the second direction, The bracket is provided in a plurality of positions and is attached to the support portion in a state in which the bracket is placed on the support portion from a third direction, A battery module characterized in that each bracket provided on a side plate on one side in the second direction and each bracket provided on a side plate on the other side in the second direction are arranged in a staggered pattern.

8. The battery module according to any one of claims 1 to 7, The battery module is characterized in that the pressing force with which the elastic member presses the adjacent battery cell is set to 1 kN to 10 kN.

9. The battery module according to any one of claims 1 to 8, It is mounted on a vehicle, a length in the first direction of a battery stack in which the plurality of battery cells are housed in the outer shell portion is equal to a length between a pair of side frames.

10. The battery module according to claim 6 or 7, a battery module comprising: a battery stack supported by the support portion; and a portion of the battery stack other than the bracket separated from the housing.

Images