power storage device

Abstract

The power storage device of the present application includes at least one battery cell (43) including a cell case (44), a discharge valve (48) provided at a bottom of the battery cell, i.e., a first bottom (45), which opens when an internal pressure of the cell case reaches a predetermined value, a battery case that houses the battery cell, a concave-convex portion (49) formed in at least one of the first bottom and a second bottom that is a bottom of the battery case, which is located differently from the discharge valve in a vertical direction, and a thermally conductive material (60) that is bonded to the first bottom and the second bottom in a manner that avoids the discharge valve and contacts the concave-convex portion.

Description

Technical Field

[0001] This disclosure relates to an energy storage device. Background Technology

[0002] Japanese Patent Application Publication No. 2024-114439 discloses an energy storage device comprising: a battery module having multiple battery cells stacked in a predetermined direction, and a battery casing for housing the battery module.

[0003] Sometimes a discharge valve is provided at the bottom of the cell casing, which forms the shape of the battery cell. This discharge valve opens when the internal pressure of the cell casing reaches a predetermined value. Furthermore, sometimes the bottom of the battery casing and the bottom of each battery cell are fixed together by a thermally conductive material that acts as an adhesive with good thermal conductivity. Therefore, if the invention disclosed in Japanese Patent Application Publication No. 2024-114439 is constructed in this way, the battery cells can be cooled efficiently by transferring heat from each battery cell to the battery casing via the thermally conductive material.

[0004] When the internal pressure of the cell casing increases, the cell casing expands. At this time, the bottom of the cell casing sometimes deforms towards the internal space of the cell casing. In this case, the thermally conductive material sometimes fails to follow the deformation of at least one of the bottom of the cell casing and the bottom of the battery casing. In this situation, the thermally conductive material sometimes peels off from at least one of the bottom of the cell casing and the bottom of the battery casing. If this occurs, the thermally conductive material becomes inefficient in cooling the individual battery cells.

[0005] In addition, when the thermally conductive material is in contact with the bottom of the battery cell housing, the discharge valve may fail to open when the internal pressure of the battery cell housing reaches the specified value. Summary of the Invention

[0006] The present disclosure takes into account the above circumstances and aims to provide an energy storage device that has a structure that allows the discharge valve of the battery cell to open smoothly when the internal pressure of the battery cell housing reaches a specified value, and can suppress the decrease in the cooling function of the heat-conducting material provided between the first bottom of the battery cell and the second bottom of the battery housing even when the bottom of the battery cell housing deforms towards the internal space of the battery cell housing.

[0007] The first type of energy storage device includes: at least one battery cell with a cell housing; a discharge valve disposed at the bottom of the battery cell, i.e., a first bottom, which opens when the internal pressure of the cell housing reaches a predetermined value; a battery housing for housing the battery cell; a protrusion formed on at least one of the first bottom and the bottom of the battery housing, i.e., a second bottom, which is positioned differently from the discharge valve when viewed in the vertical direction; and a deformable thermally conductive material bonded to the first bottom and the second bottom in a manner that avoids the discharge valve and contacts the protrusion.

[0008] In the first embodiment of the energy storage device, at least one of the first bottom of the battery cell casing and the second bottom of the battery casing has a protrusion / recess for contact with a thermally conductive material. Therefore, the adhesive strength between the component with the protrusion / recess and the thermally conductive material is improved. Thus, when the battery cell casing expands due to internal pressure, even if the bottom of the battery cell casing deforms towards the internal space of the battery cell casing, the thermally conductive material is less likely to peel off from the component with the protrusion / recess. Therefore, even when the bottom of the battery cell casing deforms towards the internal space of the battery cell casing, the battery cell can be efficiently cooled using the thermally conductive material disposed between the first bottom of the battery cell and the second bottom of the battery casing.

[0009] In the first type of energy storage device, the position of the protrusions and recesses when viewed vertically differs from that of the discharge valve. Therefore, when the internal pressure of the battery cell casing reaches a specified value, the discharge valve of the battery cell opens smoothly.

[0010] The second type of energy storage device is constructed based on the first type, with the aforementioned concave and convex portions being multiple reinforcing ribs.

[0011] In the second type of energy storage device, the bonding strength between at least one of the first bottom of the cell housing and the second bottom of the battery housing and the thermally conductive material, as well as the mechanical strength of at least one of the first bottom of the cell housing and the second bottom of the battery housing, are improved by reinforcing ribs.

[0012] The third type of energy storage device is configured based on the second type, with the aforementioned reinforcing rib provided at the first bottom.

[0013] In the third type of energy storage device, the bonding strength between the first bottom of the cell casing and the thermally conductive material, as well as the mechanical strength of the cell casing, are improved by reinforcing ribs.

[0014] The fourth type of energy storage device is configured based on the third type, wherein the shape of the first bottom of the battery cell casing when viewed from above and below is a rectangle with a pair of long sides and a pair of short sides, and the reinforcing ribs extend in a direction parallel to the long sides.

[0015] In the fourth type of energy storage device, the bonding strength between the first bottom of the cell casing and the thermally conductive material is improved by reinforcing ribs.

[0016] The fifth form of the energy storage device is configured based on the third form, wherein the shape of the first bottom of the battery cell casing when viewed from above and below is a rectangle with a pair of long sides and a pair of short sides, and the reinforcing ribs extend in a direction parallel to the short sides.

[0017] In the fifth type of energy storage device, when the cell casing expands due to internal pressure, reinforcing ribs suppress the deformation of the bottom of the cell casing towards the internal space. Therefore, compared to the case where the bottom of the cell casing deforms significantly towards the internal space, the thermally conductive material is less likely to peel off from the first bottom of the cell casing.

[0018] The sixth form of the energy storage device is configured such that, based on the second form, the aforementioned reinforcing rib is provided at the second bottom of the aforementioned battery casing.

[0019] According to the sixth form of the energy storage device, the bonding strength between the second bottom of the battery casing and the thermally conductive material, as well as the mechanical strength of the battery casing, are improved by reinforcing ribs.

[0020] The seventh form of the energy storage device is configured based on the sixth form, wherein the shape of the first bottom of the battery cell casing when viewed from above and below is a rectangle with a pair of long sides and a pair of short sides, and the reinforcing ribs extend in a direction parallel to the long sides.

[0021] In the seventh form of the energy storage device, when the bottom of the cell casing deforms towards the internal space of the cell casing and the heat-conducting material deforms accordingly, the reinforcing ribs do not easily prevent the second bottom from deforming along with the heat-conducting material. Therefore, compared to the case where the deformation of the second bottom of the battery casing is easily prevented, the heat-conducting material is less likely to peel off from the second bottom of the battery casing.

[0022] The energy storage device in the eighth form is configured based on any one of the first to seventh forms, wherein the aforementioned uneven parts are rough surfaces.

[0023] According to the eighth form of the energy storage device, the adhesion strength between at least one of the first bottom of the cell housing and the second bottom of the battery housing and the thermally conductive material is improved by the rough surface.

[0024] As explained above, the energy storage device disclosed herein has the following advantages: it has a structure that allows the discharge valve of the battery cell to open smoothly when the internal pressure of the battery cell housing reaches a specified value; and even when the bottom of the battery cell housing deforms toward the internal space of the battery cell housing, it can suppress the decrease in the cooling function of the heat-conducting material provided between the first bottom of the battery cell and the second bottom of the battery housing for the battery cell. Attached Figure Description

[0025] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein...

[0026] Figure 1 It is a cross-sectional view of a vehicle equipped with the battery pack according to the first embodiment, cut off at the center in the vehicle width direction.

[0027] Figure 2 It is a schematic exploded perspective view of the battery pack.

[0028] Figure 3 This is a schematic exploded perspective view of the lower casing of the battery housing and the battery module.

[0029] Figure 4 It is a schematic front view of the battery cell and thermal conductive materials.

[0030] Figure 5 It is along Figure 4 A schematic cross-sectional view with arrows 5-5.

[0031] Figure 6 It is a schematic bottom view of a battery cell.

[0032] Figure 7 It is along the expansion of the battery cell. Figure 4 A schematic cross-sectional view with arrows 5-5.

[0033] Figure 8 It is along the expansion of the battery cell. Figure 4 A schematic cross-sectional view with arrows 8-8.

[0034] Figure 9 The battery cells of the battery pack involved in the second embodiment are related to Figure 6 The same schematic bottom view.

[0035] Figure 10 It is the phenomenon when the battery cell expands. Figure 7 The same schematic cross-sectional view.

[0036] Figure 11 It is the phenomenon when the battery cell expands. Figure 8 The same schematic cross-sectional view.

[0037] Figure 12 The lower housing and battery module involved in the third embodiment are related to... Figure 3 The same exploded 3D diagram.

[0038] Figure 13 It is a schematic bottom view of a battery cell.

[0039] Figure 14 It is the phenomenon when the battery cell expands. Figure 7 The same schematic cross-sectional view.

[0040] Figure 15 It is the phenomenon when the battery cell expands. Figure 8 The same schematic cross-sectional view.

[0041] Figure 16The battery cells of the battery pack involved in the fourth embodiment are related to Figure 6 The same schematic bottom view.

[0042] Figure 17 The lower housing and battery module involved in the fifth embodiment are related to... Figure 3 The same exploded 3D diagram. Detailed Implementation

[0043] The following is for reference Figures 1 to 8 The battery pack (energy storage device) according to the first embodiment will be described. In addition, the arrows UP, FR and LH in each figure represent the upper side in the vertical direction of the vehicle, the front side in the longitudinal direction of the vehicle, and the left side in the horizontal direction of the vehicle, respectively.

[0044] like Figure 1 and Figure 2 As shown, the battery pack 20 of this embodiment is mounted on a vehicle (electric vehicle) 10. The vehicle 10 of this embodiment is an electric vehicle (BEV).

[0045] The vehicle 10 includes: a pair of front wheels 11F on the left and right; a pair of rear wheels 11R on the left and right; a pair of side beams 12 on the left and right, which are part of the vehicle frame components and extend along the front-rear direction of the vehicle; and a pair of crossbeams 14 on the front and rear, which extend along the width direction (left-right direction) of the vehicle and are fixed at both ends to the side beams 12 on the left and right, which are part of the vehicle frame components.

[0046] The battery pack 20 of this embodiment has a battery housing 22 and two battery modules 40. The power of the battery pack 20 (battery cells 43) is supplied, for example, to an electric motor (not shown) that provides driving force to the front wheel 11F and the rear wheel 11R.

[0047] like Figure 1 and Figure 2 As shown, the battery housing 22 has a lower housing 24 and an upper housing 35.

[0048] The lower housing 24 is a hollow body with an opening 25 formed on its upper surface. The lower housing 24 has a base plate (second bottom) 26, a peripheral wall 27, and an outer peripheral flange 28. The peripheral wall 27 has an annular planar shape, and its lower end is connected to the outer peripheral edge of the base plate 26. The outer peripheral flange 28 has an annular planar shape, and its inner peripheral edge is connected to the upper end of the peripheral wall 27. The lower housing 24 is, for example, made of metal.

[0049] The upper shell 35 is a hollow body with an opening 36 formed on its lower surface. The upper shell 35 has a top plate portion 37, a peripheral wall portion 38, and an outer peripheral flange 39. The peripheral wall portion 38 has an annular planar shape, and its upper end is connected to the outer peripheral edge of the top plate portion 37. The outer peripheral flange 39 has an annular planar shape, and its inner peripheral edge is connected to the lower end of the peripheral wall portion 38.

[0050] like Figure 2 As shown, two battery modules 40 are disposed inside the lower housing 24. The battery modules 40 are arranged in the left-right direction.

[0051] like Figure 3 As shown, the battery module 40 includes a battery stack 41, a pair of end plates 53, and four constraint components 55.

[0052] like Figure 3 As shown, in a top-down view, the battery stack 41 extending in the front-to-back direction includes multiple battery cells 43 and multiple insulating components 51 located between adjacent battery cells 43. Furthermore, in Figure 3 For simplicity, only three battery cells 43 are depicted in the diagram, but in reality, the battery stack 41 has more than three battery cells 43. Figure 4 As shown, the cell casing 44, which forms the shape of the battery cell 43 of a lithium-ion battery, includes a metal casing body 44A and an outer film 44F covering the surface of the casing body 44A. The casing body 44A is cubic in shape. The outer film 44F is in close contact with the discharge valve 48 and reinforcing rib 49 (described later), and is also in close contact with the surface of the casing body 44A. The outer film 44F is made of polypropylene. The bottom of the casing body 44A is formed by a bottom plate (first bottom) 45, and the upper surface of the casing body 44A is formed by an upper plate 46U. The planar shape of the bottom plate 45 and the upper plate 46U is a rectangle that is longer in the left-right direction than in the front-back direction. That is, as shown... Figure 6 As shown, the base plate 45 is composed of a pair of short sides 45S and a pair of long sides 45L. The short sides 45S are parallel to the front-rear direction, and the long sides 45L are parallel to the left-right direction. The front plate 46F and rear plate 46R of the main body 44A have the same front shape. The front shape of the front plate 46F and rear plate 46R is a rectangle that is longer in the left-right direction than in the top-bottom direction. Positive and negative electrodes (both omitted from the diagram) are provided on the left and right side plates 46S of the main body 44A.

[0053] like Figure 6As shown, a discharge valve 48 is provided in the center of the bottom plate portion 45 in the left-right direction of the main body 44A. The discharge valve 48 is a thin-walled portion with a + (positive) shape. That is, the mechanical strength of the discharge valve 48 is lower than that of other parts of the bottom plate portion 45. For example, if an internal short circuit occurs in the battery cell 43, causing the internal pressure of the cell housing 44 to reach a specified value, the discharge valve 48 will rupture. That is, the discharge valve 48 will open.

[0054] And as Figure 6 As shown, multiple reinforcing ribs (convex and concave portions) 49 protrude downwards from the left and right sides of the bottom plate portion 45 of the main body 44A. In a top view, each reinforcing rib 49 is parallel to the long side 45L of the bottom plate portion 45. Figure 6 It is clearly visible that the left and right reinforcing ribs 49 are set on the bottom plate 45 in a manner that avoids the discharge valve 48.

[0055] like Figure 3 As shown, the battery module 40 has a pair of end plates 53 at the front and rear. The front end plate 53 is located immediately in front of the frontmost battery cell 43, and the rear end plate 53 is located immediately behind the rearmost battery cell 43.

[0056] like Figure 3 As shown, four constraint members 55 extend in the front-to-back direction, with a cross-sectional shape approximately L-shaped. Each constraint member 55 covers the four corners of each battery cell 43 (cell housing 44) and end plate 53, and is fixed to the front and rear end plates 53 respectively. Therefore, the front-to-back length of each constraint member 55 is shorter than in its free state. That is, the front and rear end plates 53 are pulled closer together by the constraint members 55, thereby clamping the battery stack 41 from the front and back. In this way, the battery stack 41 and end plates 53 are integrated by the left and right constraint members 55. Thus, a battery module 40 comprising a battery stack 41, a pair of end plates 53, and four constraint members 55 is completed.

[0057] Furthermore, the battery module 40 has multiple busbars (not shown) and a cooler (not shown) connected to the positive and negative terminals of each battery cell 43.

[0058] like Figure 2 and Figure 3As shown, battery modules 40 are housed inside the lower housing 24, and each battery module 40 is fixed to the base plate 26. Specifically, two separate regions 26A and 26B extending in the front-rear direction on the upper surface of the base plate 26 are coated with a liquid thermally conductive material 60 as an adhesive. The thermally conductive material 60 is, for example, an epoxy resin adhesive, a silicone rubber adhesive, a polyethylene adhesive, or a fluoropolymer adhesive. The left-right dimensions of each region 26A and 26B are approximately the same as the left-right dimensions of each reinforcing rib 49 provided on the cell housing 44, and the front-rear dimensions of each region 26A and 26B are approximately the same as the front-rear dimensions of the battery module 40. Furthermore, the entire area of ​​each region 26A and 26B is coated with the thermally conductive material 60. That is, the thermally conductive material 60 has a first thermally conductive portion 61 coated on the left side of region 26A and a second thermally conductive portion 62 coated on the right side of region 26B. The thermally conductive material 60 has high thermal conductivity. That is, the thermal conductivity of the thermally conductive material 60 is higher than that of the insulating component 51.

[0059] like Figure 2 As shown by the virtual lines, the bottom of the left battery module 40 is placed in region 26A, and the bottom of the right battery module 40 is placed in region 26B. Therefore, as Figure 6 As shown, the first heat-conducting part 61 contacts the reinforcing rib 49 on the left side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43 and the left side portion of the bottom plate portion 45. The second heat-conducting part 62 contacts the reinforcing rib 49 on the right side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43 and the right side portion of the bottom plate portion 45. In other words, the discharge valve 48 of each bottom plate portion 45 does not contact the first heat-conducting part 61 and the second heat-conducting part 62. If each heat-conducting material 60 is cured, each battery module 40 is fixed to each region 26A, 26B by the first heat-conducting part 61 and the second heat-conducting part 62. The Young's modulus of the cured heat-conducting material 60 is lower than that of the lower housing 24 and the cell housing 44, and the cured heat-conducting material 60 can be deformed.

[0060] And as Figure 2 As shown, the end plate 53 of each battery module 40 is fixed to the base plate 26 via a metal bracket 57 with an L-shaped cross-section. Specifically, each end plate 53 is fixed to the corresponding bracket 57 at a position parallel to the vertical direction via a fixing mechanism, and the lower end of each bracket 57, parallel to the horizontal direction, is fixed to the base plate 26 via a fixing mechanism. This fixing mechanism, for example, has a bolt passing through the bracket 57 and an internally threaded hole formed in the end plate 53 and the base plate 26, allowing the bolt to be threadedly engaged.

[0061] Furthermore, the outer peripheral flange 28 of the lower housing 24, which houses two battery modules 40, is entirely supported on the upper surface by a sealing member (not shown), and the outer peripheral flange 39 of the upper housing 35 is fixed to each other. Thus, the battery pack 20 is completed.

[0062] And as Figure 1 As shown, the battery casing 22 of the completed battery pack 20 is supported by the side beams 12 and the crossbeams 14. That is, with the top plate portion 37 and the peripheral wall portion 38 of the upper casing 35 located in the space enclosed by the side beams 12 and the crossbeams 14, the outer peripheral flange 39 is fixed to the lower surface of each side beam 12 and each crossbeam 14.

[0063] (Functions and Effects)

[0064] Next, the function and effects of the first embodiment will be explained.

[0065] For example, when each battery cell 43 of each battery module 40 supplies power to the electric motor, each battery cell 43 sometimes becomes hot. A portion of the heat from each battery cell 43 is transferred from the left and right sides (outer film 44F) of the bottom plate portion 45 of the cell housing 44 to the bottom plate portion 26 of the lower housing 24 via the first heat-conducting part 61 and the second heat-conducting part 62. In this way, the first heat-conducting part 61 and the second heat-conducting part 62 dissipate the heat from each battery cell 43 to the bottom plate portion 26, thereby preventing each battery cell 43 from becoming excessively hot. That is, each battery cell 43 is cooled by the thermally conductive material 60.

[0066] However, if an internal short circuit occurs in any battery cell 43 of any battery module 40, the internal pressure of the cell casing 44 will rise, such as... Figure 7 and Figure 8 As shown by the virtual lines, the front plate portion 46F and the rear plate portion 46R sometimes expand outwards. In this case, the expansion of the front plate portion 46F and the rear plate portion 46R sometimes causes the bottom plate portion 45 and the upper plate portion 46U to deform in a way that they are recessed into the internal space of the cell housing 44. That is, the bottom plate portion 45 sometimes deforms by displacing upwards at the portion between the two long sides 45L of the bottom plate portion 45. A reinforcing rib 49 is provided on the left side of the bottom plate portion 45 where the first heat-conducting part 61 is fixed, and a reinforcing rib 49 is provided on the right side of the bottom plate portion 45 where the second heat-conducting part 62 is fixed. Therefore, compared with the case where the lower surface of the bottom plate portion 45 is entirely flat, the adhesion strength between the first heat-conducting part 61 and the left side of the bottom plate portion 45, and the adhesion strength between the second heat-conducting part 62 and the right side of the bottom plate portion 45 are greater. Therefore, in this case, as Figure 7As shown, the first heat-conducting part 61, which contacts the reinforcing rib 49 on the left side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43 and the left side of the bottom plate portion 45, bends upward in a convex manner as the bottom plate portion 45 deforms. Furthermore, although not shown in the figure, the second heat-conducting part 62, which contacts the reinforcing rib 49 on the right side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43 and the right side of the bottom plate portion 45, bends upward in a convex manner as the bottom plate portion 45 deforms. Therefore, the bottom plate portion 26 of the lower housing 24, which is bonded to the first heat-conducting part 61 and the second heat-conducting part 62, also bends in a convex manner. Thus, even if the bottom plate portion 45 of the cell housing 44 of each battery cell 43 deforms towards the internal space of the cell housing 44, the heat-conducting material 60 is not easily peeled off from the left and right sides of the bottom plate portion 45 and the bottom plate portion 26 of the lower housing 24. Therefore, even if the bottom plate portion 45 of the cell housing 44 deforms toward the internal space of the cell housing 44, the cooling effect of the heat-conducting material 60 provided between the bottom plate portion 45 of the battery cell 43 and the bottom plate portion 26 of the lower housing 24 can be suppressed, thus preventing a decrease in the function of each battery cell 43.

[0067] Furthermore, the base plate 45 is provided with reinforcing ribs 49, thus the cell casing 44 has higher mechanical strength compared to a case where the lower surface of the base plate 45 is entirely flat. Therefore, the cell casing 44 is not easily damaged.

[0068] Furthermore, when viewing the battery cell 43 from above and below, the positions of the reinforcing rib 49 and the discharge valve 48 are different, and the heat-conducting material 60 does not contact the part of the base plate 45 where the discharge valve 48 is located (see reference). Figure 4 and Figure 6 Therefore, when the internal pressure of the cell casing 44 of the battery cell 43 reaches a predetermined value, the discharge valve 48 opens smoothly, and the contents (fragments) inside the cell casing 44 are smoothly discharged to the outside of the battery cell 43 through the discharge valve 48 and the rupture portion of the outer membrane 44F corresponding to the discharge valve 48. Furthermore, these contents include, for example, internal electrodes (current collector terminals), electrolyte, and gas.

[0069] Thus, the battery pack 20 of this embodiment has a structure that allows the discharge valve 48 to open smoothly when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value. Even if the bottom plate portion 45 of the cell housing 44 deforms toward the internal space of the cell housing 44, the cooling function of the heat-conducting material 60 on the battery cell 43 can be suppressed.

[0070] Next, refer to Figures 9-11 The second embodiment of this disclosure will be described. Furthermore, components identical to those in the first embodiment will be labeled with the same reference numerals, and detailed descriptions thereof will be omitted.

[0071] The difference between the battery pack 65 in the second embodiment and the first embodiment lies in the shape of the reinforcing ribs (concave and convex portions) 67 formed on the bottom plate portion 45 of the cell housing 44 of each battery cell 43.

[0072] like Figure 9 As shown, multiple reinforcing ribs 67 protrude downwards from the left and right sides of the bottom plate portion 45 of the cell casing 44. In a top view, each reinforcing rib 67 is parallel to the short side 45S of the bottom plate portion 45. Figure 9 It is clearly visible that the left and right reinforcing ribs 67 are set on the bottom plate 45 in a manner that avoids the discharge valve 48.

[0073] like Figure 9 As shown by the virtual line, in the second embodiment, the first heat-conducting part 61 also contacts the reinforcing rib 67 on the left side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43 and the left side portion of the bottom plate portion 45, and the second heat-conducting part 62 also contacts the reinforcing rib 67 on the right side of the bottom plate portion 45 of each battery cell 43 and the right side portion of the bottom plate portion 45. In other words, the discharge valve 48 of each bottom plate portion 45 does not contact the first heat-conducting part 61 and the second heat-conducting part 62. If each heat-conducting material 60 is cured, each battery module 40 is fixed to each region 26A, 26B by the first heat-conducting part 61 and the second heat-conducting part 62. And each battery module 40 is secured by multiple brackets 57 (in Figures 9-11 (Illustrations omitted) are fixed in areas 26A and 26B.

[0074] (Functions and Effects)

[0075] Next, the function and effects of the second embodiment will be explained.

[0076] In the second embodiment, if an internal short circuit occurs in any battery cell 43 of any battery module 40, the internal pressure of the cell casing 44 also increases, such as... Figure 10 and Figure 11 As shown by the virtual lines, the front plate portion 46F and the rear plate portion 46R sometimes expand outwards. In this case, the expansion of the front plate portion 46F and the rear plate portion 46R sometimes causes the upper plate portion 46U to deform in a way that it is recessed into the internal space of the cell housing 44. Furthermore, this expansion causes the bottom plate portion 45 to also tend to recess into the internal space of the cell housing 44. However, the reinforcing ribs 67 provided on the left and right sides of the bottom plate portion 45 inhibit the deformation of the left and right sides of the bottom plate portion 45 in a way that it is recessed into the internal space of the cell housing 44. In other words, since the reinforcing ribs 67 parallel to the short side 45S are provided on the left and right sides of the bottom plate portion 45, the bending stiffness of the left and right sides of the bottom plate portion 45 relative to the upward deformation is higher than that of the first embodiment. Therefore, as Figure 10As shown, the left and right sides of the base plate 45 remain almost undeformed. Therefore, the heat-conducting materials 60 (first heat-conducting part 61, second heat-conducting part 62) fixed to the left and right sides of the base plate 45, and the portion of the base plate 26 of the lower housing 24 located directly below the left and right sides of the base plate 45, also remain almost undeformed. Therefore, compared to the case where the left and right sides of the base plate 45 of the battery cell 43 deform significantly upwards, the heat-conducting material 60 is less likely to peel off from the left and right sides of the base plate 45 and the base plate 26 of the lower housing 24. Therefore, even if the front plate 46F and rear plate 46R of the battery cell 43 expand outwards, the cooling function of each battery cell 43 provided with the heat-conducting material 60 between the base plate 45 of the battery cell 43 and the base plate 26 of the lower housing 24 can be suppressed.

[0077] Furthermore, the central portion of the base plate 45 without reinforcing ribs 67 in the left-right direction, such as Figure 11 The upward deformation is shown. In the second embodiment, when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value, the discharge valve 48 is also opened smoothly, and the contents (fragments) inside the cell housing 44 are smoothly discharged to the outside of the battery cell 43 through the discharge valve 48.

[0078] Therefore, the battery pack 65 of the second embodiment is also constructed such that the discharge valve 48 opens smoothly when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value, and even if the bottom plate portion 45 of the cell housing 44 deforms toward the internal space side of the cell housing 44, the heat-conducting material 60 can be used to suppress the high temperature of the battery cell 43.

[0079] Next, refer to Figures 12-15 The third embodiment of this disclosure will be described. Furthermore, components identical to those in the first embodiment will be labeled with the same reference numerals, and detailed descriptions thereof will be omitted.

[0080] The difference between the battery pack 70 in the third embodiment and the first embodiment is that the bottom plate portion 45 of each battery cell 43 is not provided with reinforcing ribs 49, but instead, reinforcing ribs 71 are provided on the bottom plate portion 26 of the lower housing 24.

[0081] like Figure 12 As shown, multiple reinforcing ribs (concave and convex portions) 71 extending in the left-right direction are provided protruding upwards in each region 26A and each region 26B of the bottom plate portion 26 of the lower housing 24. That is, each reinforcing rib 71 is parallel to the long side 45L of the bottom plate portion 45. Furthermore, although in Figure 12 The diagram is omitted, but each region 26A is coated with a first heat-conducting part 61, and each region 26B is coated with a second heat-conducting part 62.

[0082] like Figure 13As shown, no reinforcing ribs 49 are formed on the bottom plate portion 45 of the cell casing 44 of the battery cell 43.

[0083] like Figure 13 As shown by the virtual line, in the third embodiment, the first heat-conducting part 61 also contacts the left side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43, and the second heat-conducting part 62 also contacts the right side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43. In other words, the discharge valve 48 of each bottom plate portion 45 does not contact the first heat-conducting part 61 and the second heat-conducting part 62. If each heat-conducting material 60 is cured, each battery module 40 is fixed to each region 26A, 26B by the first heat-conducting part 61 and the second heat-conducting part 62. Furthermore, each battery module 40 is secured by multiple brackets 57 (in Figures 12-15 (Illustrations omitted) are fixed in areas 26A and 26B.

[0084] (Functions and Effects)

[0085] Next, the function and effects of the third embodiment will be explained.

[0086] In the third embodiment, if an internal short circuit occurs in any one of the battery cells 43 of any battery module 40, the internal pressure of the cell housing 44 also increases, and the bottom plate portion 45 and the upper plate portion 46U may sometimes deform in a way that causes them to recess into the internal space of the cell housing 44. Therefore, in this case, if Figure 14 As shown, the first heat-conducting part 61, which contacts the left side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43, bends upward in a convex manner as the bottom plate portion 45 deforms. Furthermore, although not shown in the figure, the second heat-conducting part 62, which contacts the right side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43, also bends upward in a convex manner as the bottom plate portion 45 deforms. A reinforcing rib 71 is provided in region 26A of the bottom plate portion 26 of the lower housing 24 where the first heat-conducting part 61 is fixed, and a reinforcing rib 71 is provided in region 26B of the bottom plate portion 26 of the lower housing 24 where the second heat-conducting part 62 is fixed. Therefore, compared to the case where the bottom plate portion 26 is entirely flat, the adhesion strength between the first heat-conducting part 61 and region 26A, and the adhesion strength between the second heat-conducting part 62 and region 26B, are greater. Furthermore, each reinforcing rib 71 is parallel to the long side 45L of the bottom plate portion 45 of the cell casing 44 of the battery cell 43 in a top view. Therefore, when regions 26A and 26B (bottom plate portion 26) are to deform following the deformation of the bottom plate portion 45, each reinforcing rib 71 does not easily prevent regions 26A and 26B from deforming along with the bottom plate portion 45. Therefore, as Figure 14As shown, region 26A of the base plate portion 26 bonded to the first heat-conducting part 61 is also bent in an upward convex manner. Furthermore, although not shown in the figure, region 26B of the base plate portion 26 bonded to the second heat-conducting part 62 is also bent in an upward convex manner. Therefore, compared to the case where regions 26A and 26B are not bent in an upward convex manner, the heat-conducting material 60 is less likely to peel off from regions 26A and 26B. Thus, even if the base plate portion 45 of the cell housing 44 of each battery cell 43 deforms towards the internal space of the cell housing 44, the heat-conducting material 60 is less likely to peel off from regions 26A and 26B, as well as the left and right sides of the base plate portion 45. Therefore, even if the base plate portion 45 of the cell housing 44 deforms towards the internal space of the cell housing 44, the cooling function of the heat-conducting material 60 provided between the base plate portion 45 of the battery cell 43 and the base plate portion 26 of the lower housing 24 can be suppressed.

[0087] Furthermore, the base plate 26 is provided with reinforcing ribs 71, thus the base plate 26 has higher mechanical strength compared to a case where the entire base plate 26 is flat. Therefore, the base plate 26 (lower shell 24) is not easily damaged.

[0088] Furthermore, in the third embodiment, when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value, the discharge valve 48 is also opened smoothly, and the contents (fragments) inside the cell housing 44 are smoothly discharged to the outside of the battery cell 43 through the discharge valve 48.

[0089] Therefore, the battery pack 70 of the third embodiment is also constructed such that the discharge valve 48 is opened smoothly when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value, and even if the bottom plate portion 45 of the cell housing 44 deforms toward the internal space side of the cell housing 44, the cooling function of the heat-conducting material 60 on the battery cell 43 can be suppressed.

[0090] Next, refer to Figure 16 The fourth embodiment of this disclosure will be described. Furthermore, components identical to those in the first embodiment will be labeled with the same reference numerals, and detailed descriptions thereof will be omitted.

[0091] The battery pack 75 of the fourth embodiment differs from that of the first and second embodiments in that the reinforcing ribs 49 and 67 are not provided on the bottom plate portion 45 of each battery cell 43. Instead, a rough surface (uneven portion) 76 is provided on a portion of the outer film 44F that covers the left and right sides of the bottom plate portion 45. Hereinafter, the portion of the outer film 44F that covers the left and right sides of the bottom plate portion 45 will be referred to as the side portion 44F1.

[0092] like Figure 16As shown, multiple protrusions 77 are formed on the left and right sides 44F1 of the outer membrane 44F. These protrusions 77 form a rough surface 76. The left and right rough surfaces 76 are provided on the base plate 45 in a manner that avoids the discharge valve 48.

[0093] like Figure 16 As shown by the virtual line, in the fourth embodiment, the first heat-conducting part 61 also contacts the rough surface 76 on the left side of the cell housing 44 of each battery cell 43, and the second heat-conducting part 62 also contacts the rough surface 76 on the right side of the cell housing 44 of each battery cell 43. In other words, the discharge valve 48 of each base plate 45 does not contact the first heat-conducting part 61 and the second heat-conducting part 62. If each heat-conducting material 60 is cured, each battery module 40 is fixed to each region 26A, 26B by the first heat-conducting part 61 and the second heat-conducting part 62. Furthermore, each battery module 40 is secured by multiple brackets 57 (in Figure 16 (Illustrations omitted) are fixed in areas 26A and 26B.

[0094] (Functions and Effects)

[0095] Next, the function and effects of the fourth embodiment will be explained.

[0096] In the fourth embodiment, if an internal short circuit occurs in any battery cell 43 of any battery module 40, the internal pressure of the cell housing 44 also increases, and the bottom plate portion 45 and the top plate portion 46U may deform in a way that causes them to recess into the internal space of the cell housing 44. However, rough surfaces 76 are formed on the left and right sides 44F1 of the outer film 44F covering the bottom plate portion 45 for bonding the first heat-conducting part 61 and the second heat-conducting part 62, respectively. Therefore, compared with the case where the lower surface of the bottom plate portion 45 (outer film 44F) is entirely flat (smooth), the bonding strength between the first heat-conducting part 61 and the left side portion 44F1 (rough surface 76) and the second heat-conducting part 62 and the right side portion 44F1 (rough surface 76) are greater. Therefore, in this case, the first heat-conducting part 61, which contacts the left side portion 44F1 (rough surface 76) of the cell housing 44 of each battery cell 43, bends upward in a convex manner along with the deformation of the base plate portion 45. Similarly, the second heat-conducting part 62, which contacts the right side portion 44F1 (rough surface 76) of the cell housing 44 of each battery cell 43, bends upward in a convex manner along with the deformation of the base plate portion 45. Consequently, regions 26A and 26B of the lower housing 24, which are bonded to the first and second heat-conducting parts 61 and 62, also bend upward in a convex manner. Thus, regions 26A and 26B deform in accordance with the deformation of each side portion 44F1. Therefore, even if the base plate portion 45 of the cell housing 44 of each battery cell 43 deforms towards the internal space of the cell housing 44, the heat-conducting material 60 is not easily peeled off from the left and right sides (outer film 44F) of the base plate portion 45 and the base plate portion 26 of the lower housing 24. Therefore, even if the bottom plate portion 45 of the cell housing 44 deforms toward the internal space side of the cell housing 44, the battery pack 75 of the fourth embodiment can suppress the cooling of the heat-conducting material 60 provided between the bottom plate portion 45 (outer film 44F) of the battery cell 43 and the bottom plate portion 26 of the lower housing 24, thus suppressing the decline in the cooling function of each battery cell 43.

[0097] Furthermore, in the fourth embodiment, when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value, the discharge valve 48 is also opened smoothly, and the contents (fragments) inside the cell housing 44 are smoothly discharged to the outside of the battery cell 43 through the discharge valve 48.

[0098] Therefore, the battery pack 75 of the fourth embodiment is also designed to allow the discharge valve 48 to open smoothly when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value, and even if the bottom plate portion 45 of the cell housing 44 deforms toward the internal space side of the cell housing 44, the cooling function of the heat-conducting material 60 on the battery cell 43 can be suppressed.

[0099] Next, refer to Figure 17The fifth embodiment of this disclosure will be described. Furthermore, components identical to those in the first embodiment will be labeled with the same reference numerals, and detailed descriptions thereof will be omitted.

[0100] The battery pack 80 of the fifth embodiment differs from the embodiments described above in that the bottom plate portion 45 of each battery cell 43 is not provided with reinforcing ribs 49, 67 and rough surface 76, but instead a rough surface (concave and convex portion) 81 is provided on the bottom plate portion 26 of the lower housing 24.

[0101] like Figure 17 As shown, a rough surface 81 is formed on the entirety of each region 26A and each region 26B of the bottom plate portion 26 of the lower housing 24. That is, a plurality of protrusions and depressions 82 are formed in each region 26A and each region 26B. The rough surface 81 is constituted by the plurality of protrusions and depressions 82.

[0102] Furthermore, although the illustration is omitted, each region 26A is entirely coated with a first heat-conducting part 61, and each region 26B is entirely coated with a second heat-conducting part 62. The first heat-conducting part 61 contacts the left side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43, and the second heat-conducting part 62 contacts the right side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43. In other words, the discharge valve 48 of each bottom plate portion 45 does not contact the first heat-conducting part 61 or the second heat-conducting part 62. Once the heat-conducting material 60 has cured, each battery module 40 is fixed to each region 26A, 26B (rough surface 81) by the first heat-conducting part 61 and the second heat-conducting part 62. Furthermore, each battery module 40 is secured by multiple brackets 57 (in... Figure 17 (Illustrations omitted) are fixed in areas 26A and 26B.

[0103] (Functions and Effects)

[0104] Next, the function and effects of the fifth embodiment will be explained.

[0105] In the fifth embodiment, if an internal short circuit occurs in any one of the battery cells 43 of any battery module 40, the internal pressure of the cell housing 44 also increases, and the bottom plate portion 45 and the top plate portion 46U may deform in a way that causes them to recess into the internal space of the cell housing 44. Therefore, the first heat-conducting portion 61, which contacts the left side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43, bends upward in a convex manner as the bottom plate portion 45 deforms, and the second heat-conducting portion 62, which contacts the right side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43, bends upward in a convex manner as the bottom plate portion 45 deforms. Therefore, in this case, the first heat-conducting part 61, which contacts the left side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43, bends upward in a convex manner as the bottom plate portion 45 deforms. Similarly, the second heat-conducting part 62, which contacts the right side of the bottom plate portion 45 of the cell housing 44 of each battery cell 43, bends upward in a convex manner as the bottom plate portion 45 deforms. Furthermore, each region 26A and each region 26B is composed of a rough surface 81. Therefore, the adhesive strength between region 26A (rough surface 81) and the first heat-conducting part 61, and the adhesive strength between region 26B (rough surface 81) and the second heat-conducting part 62, is greater than when the upper surface of the bottom plate portion 26 is entirely flat (smooth). Therefore, regions 26A and 26B of the lower housing 24, which are bonded to the first heat-conducting part 61 and the second heat-conducting part 62, bend upward in a convex manner. Therefore, compared to regions 26A and 26B where they do not bend upwards, the thermally conductive material 60 is less likely to peel off from regions 26A and 26B. Thus, even if the bottom plate portion 45 of the cell housing 44 of each battery cell 43 deforms towards the internal space of the cell housing 44, the thermally conductive material 60 is less likely to peel off from the left and right sides of the bottom plate portion 45 and regions 26A and 26B of the bottom plate portion 26. Therefore, even if the bottom plate portion 45 of the cell housing 44 deforms towards the internal space of the cell housing 44, the battery pack 80 of the fifth embodiment can suppress the decrease in the cooling function of the thermally conductive material 60 provided between the bottom plate portion 45 of the battery cell 43 and the bottom plate portion 26 of the lower housing 24 for each battery cell 43.

[0106] Furthermore, in the fifth embodiment, when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value, the discharge valve 48 is also opened smoothly, and the contents (fragments) inside the cell housing 44 are smoothly discharged to the outside of the battery cell 43 through the discharge valve 48.

[0107] Therefore, the battery pack 80 of the fifth embodiment is also constructed such that the discharge valve 48 is opened smoothly when the internal pressure of the cell housing 44 of the battery cell 43 reaches a predetermined value, and even if the bottom plate portion 45 of the cell housing 44 deforms toward the internal space side of the cell housing 44, the cooling function of the heat-conducting material 60 on the battery cell 43 can be suppressed.

[0108] The battery packs involved in the various embodiments have been described above, but they can be appropriately modified without departing from the spirit of this disclosure.

[0109] For example, a reinforcing rib 71 or a rough surface 81 may be formed on the base plate portion 26 in the first embodiment and the second embodiment.

[0110] Reinforcing ribs 49, 67 or rough surfaces 76 may also be formed on the bottom plate portion 45 of the battery cell 43 in the third embodiment.

[0111] The battery pack can also have more than three battery modules.

[0112] The number of battery cells contained in a battery module can be any number.

[0113] Alternatively, the thermally conductive material 60 can be applied to the portion of the bottom plate 45 of the cell housing 44 that avoids the drain valve 48, instead of the bottom plate 26. In this case, the battery stack 41 is fixed to the upper surface of the bottom plate 26. In this case, in the first embodiment, it is preferable to apply the thermally conductive material 60 to the reinforcing rib 49, and in the fourth embodiment, it is preferable to apply it to the rough surface 76. Alternatively, the thermally conductive material 60 can be applied to both the portion of the bottom plate 45 of the cell housing 44 that avoids the drain valve 48 and the upper surface of the bottom plate 26.

[0114] The stacking direction of the battery cells in the battery pack (the extension direction of the battery module) can also be different from the front-to-back direction. In addition, the arrangement direction of the battery modules can also be different from the left-to-right direction.

[0115] The vehicle can also be an electric vehicle that differs from an electric vehicle and has an electric motor that utilizes the power of a battery pack. For example, the vehicle can also be a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV).

Claims

1. An energy storage device, wherein, have: At least one battery cell, having a cell casing; A discharge valve is located at the bottom of the battery cell, i.e., the first bottom, and opens when the internal pressure of the cell casing reaches a specified value. Battery casing, for housing the battery cells; The protrusions and recesses are formed on at least one of the first bottom and the bottom of the battery casing, i.e., the second bottom, and their positions when viewed in the vertical direction are different from those of the discharge valve. as well as A deformable thermally conductive material is bonded to the first and second bottoms in a manner that avoids the discharge valve and contacts the protrusions and recesses.

2. The energy storage device according to claim 1, wherein, The concave and convex portions are multiple reinforcing ribs.

3. The energy storage device according to claim 2, wherein, The reinforcing rib is provided at the first bottom.

4. The energy storage device according to claim 3, wherein, When viewed from above, the first bottom of the cell casing has a rectangular shape with a pair of long sides and a pair of short sides. The reinforcing rib extends in a direction parallel to the long side.

5. The energy storage device according to claim 3, wherein, When viewed from above, the first bottom of the cell casing has a rectangular shape with a pair of long sides and a pair of short sides. The reinforcing rib extends in a direction parallel to the short side.

6. The energy storage device according to claim 2, wherein, The reinforcing rib is provided at the second bottom of the battery casing.

7. The energy storage device according to claim 6, wherein, When viewed from above, the first bottom of the cell casing has a rectangular shape with a pair of long sides and a pair of short sides. The reinforcing rib extends in a direction parallel to the long side.

8. The energy storage device according to claim 1 or 2, wherein, The uneven portion is a rough surface.

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