Battery pack

Abstract

To provide a battery pack that is easy to manufacture and that suppresses the movement of electrode bodies within the case during use. [Solution] The battery cell 10 of the battery pack 1 has an electrode body 20, a case 30, and a pressing part 100. The pressing part 100 is provided in the gap between the electrode body 20 and the case body 50 and presses the electrode body 20. The pressing part 100 also has a fixing point 110 fixed to the inner surface 54 of the pressing wall portion 51 of the case body 50, a pressing surface 120 that is pressed against the electrode body 20, and a deformable part 130 located between the fixing point 110 and the pressing surface 120. The deformable part 130 is made of a bimetal that deforms in a direction that moves the pressing surface 120 away from the pressing wall portion 51 as the temperature increases. In the normal temperature range, the pressing part 100 takes a pressing state in which the pressing surface 120 presses the electrode body 20, and in the low temperature range which is lower than the lower limit temperature of the normal temperature range, the pressing state is released.

Description

Technical Field

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[0001] The disclosed technology relates to a battery pack including a plurality of battery cells.

Background Art

[0002] In recent years, various structures of battery packs and battery cells constituting battery packs have been proposed. For example, Patent Document 1 discloses a battery pack having a battery cell configured to be housed inside a housing by moving an electrode body in its longitudinal direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the battery pack described in Patent Document 1 above, there is no configuration for holding the electrode body housed inside the battery cell. Further, in order to insert the electrode body into the case of the battery cell, a certain amount of clearance is required between the inner surface of the case and the electrode body. And when the electrode body inside the battery cell is not properly held, when the battery pack vibrates or the like, the electrode body may move inside the case by the amount of the clearance required at the time of insertion into the case. When the electrode body moves inside the case in response to the vibration of the battery pack, there is a concern that, for example, the electrode body may be damaged.

[0005] The disclosed technology aims to provide a battery pack that is easy to manufacture and can suppress the movement of the electrode body inside the case during use

Means for Solving the Problems

[0006] One aspect of the disclosed technology is a battery pack comprising a plurality of battery cells, each battery cell having a flattened, wound electrode body including positive and negative electrode plates, a case housing the electrode body, and a pressing portion provided in the gap between the electrode body and the case for pressing the electrode body, wherein the pressing portion has a fixing point fixed to the inner surface of the case wall, a pressing surface that is pressed against the electrode body, and a deformable portion made of a bimetal located between the fixing point and the pressing surface, which deforms in a direction that moves the pressing surface away from the case wall as the temperature increases, and the battery pack maintains a pressed state in which the electrode body is pressed by the pressing surface within a normal temperature range predetermined as the temperature range in which the battery cell is used by charging, discharging, or releasing, in a low temperature range lower than the lower limit temperature of the normal temperature range.

[0007] In the above-described embodiment, the battery pack can suppress the movement of the electrode body inside the case because the pressing part is in a pressed state within the normal temperature range. On the other hand, in the low-temperature range, the pressing state of the electrode body by the pressing part is released, allowing the electrode body to move smoothly relative to the case. Therefore, the above-described embodiment of the battery pack is easy to manufacture and can suppress the movement of the electrode body inside the case during use. [Effects of the Invention]

[0008] According to the disclosed technology, a battery pack is provided that is easy to manufacture and can suppress the movement of electrode bodies inside the case during use. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of the battery pack configuration. [Figure 2] This is a schematic diagram of the battery cell configuration. [Figure 3] This is a perspective view of the electrode body. [Figure 4] This is a cross-sectional view of the pressing area within the normal temperature range. [Figure 5] This diagram illustrates the placement of the electrode body into the case. [Figure 6] This is a cross-sectional view of the pressing area in the low-temperature range. [Figure 7] This diagram illustrates the bending moment acting on the pressing wall when there is a gap between the fixed points of the first pressing section and the second pressing section. [Figure 8] This diagram illustrates the bending moment acting on the pressing wall when there is no gap between the fixed points of the first pressing section and the second pressing section. [Figure 9] This is a diagram showing the deformed part of the first embodiment. [Figure 10] This figure shows the deformed part of the second embodiment. [Figure 11] This figure shows the deformed part of the third embodiment. [Figure 12] This figure shows the state of a pressing section having a deformable section that combines the second and third embodiments, in a low-temperature range. [Figure 13] This figure shows the state of a pressing section having a deformable section that combines the second and third embodiments, within the normal temperature range. [Figure 14] This diagram shows a configuration in which adjacent battery cells in a battery pack share the wall of the case. [Modes for carrying out the invention]

[0010] The embodiments of the disclosed technology will be described in detail below with reference to the attached drawings.

[0011] Figure 1 shows a cross-sectional view of the battery pack 1. Figure 1 shows the X direction extending horizontally and the Z direction extending vertically. In this embodiment of the battery pack 1, the vertical direction will be described as the Z direction. Note that the depth direction in Figure 1 is the Y direction. The battery pack 1 has a first housing 2 and a second housing 3. The first housing 2 is tray-shaped and has an opening 4 at the upper end, which is one end in the Z direction. The second housing 3 is lid-shaped and closes the opening 4 of the first housing 2. Multiple battery cells 10 are housed in the space formed by the enclosure of the first housing 2 and the second housing 3. In this embodiment, the battery cells 10 are lithium-ion secondary batteries.

[0012] In the example of the battery pack 1 in FIG. 1, a plurality of battery cells 10 are arranged side by side in the Y direction. Further, the battery cells 10 each have a positive electrode terminal 11 and a negative electrode terminal 12 at both ends in the X direction. The positive electrode terminals 11 and the negative electrode terminals 12 of the battery cells 10 in the battery pack 1 are electrically connected as appropriate by a bus bar or the like.

[0013] FIG. 2 is a cross-sectional view of the battery cell 10. The battery cell 10 has an electrode body 20 and a case 30. The electrode body 20 is formed by laminating a positive electrode plate 21, a negative electrode plate 22, and a separator 23 by winding. The direction of the winding axis of the electrode body 20 is the X direction. The positive electrode plate 21 is a positive electrode plate, and the negative electrode plate 22 is a negative electrode plate. A separator 23 is sandwiched between the positive electrode plate 21 and the negative electrode plate 22 in the electrode body 20.

[0014] The electrode body 20 has a positive electrode portion 25, a negative electrode portion 26, and a laminated portion 27. The positive electrode portion 25 and the negative electrode portion 26 are respectively located at both ends of the laminated portion 27 in the X direction. The positive electrode portion 25 is a portion formed by laminating the positive electrode plate 21. The negative electrode portion 26 is a portion formed by laminating the negative electrode plate 22. The laminated portion 27 is a portion where the positive electrode plate 21 and the negative electrode plate 22 are laminated while the separator 23 is sandwiched therebetween. A positive electrode current collecting member 13 is connected to the positive electrode portion 25 of the electrode body 20. A negative electrode current collecting member 14 is connected to the negative electrode portion 26 of the electrode body 20.

[0015] As shown in FIG. 3, the electrode body 20 of this embodiment is a flat wound type. The thickness direction of the flat electrode body 20 is the Y direction. The electrode body 20 has a flat surface portion 40 and two curved surface portions 41, 42. The flat surface portion 40 is a portion where the two outer peripheral surfaces 45, 46 facing each other in the Y direction, which is the thickness direction, are both flat.

[0016] The outer circumferential surfaces 47 and 48 of the curved surfaces 41 and 42 are curved. In this embodiment, where the Z direction is vertical, the curved surface 41 is the upper curved surface 41 located above the flat surface 40, and the curved surface 42 is the lower curved surface 42 located below the flat surface 40. The outer circumferential surface 47 of the upper curved surface 41 connects one end each of the outer circumferential surfaces 45 and 46 of the flat surface 40. The outer circumferential surface 48 of the lower curved surface 42 connects the ends of the outer circumferential surfaces 45 and 46 of the flat surface 40 that are opposite to the outer circumferential surface 47 of the upper curved surface 41. The upper curved surface 41 and the lower curved surface 42 are located at both ends of the flat surface 40, respectively.

[0017] As shown in Figure 2, the case 30 comprises a first lid 31, a second lid 32, and a case body 50. The case body 50 is a hollow member having a first opening 35 and a second opening 36 that open at both ends in the Y direction. As a result, the case body 50 forms an internal space 33 that connects from the first opening 35 to the second opening 36. The electrode body 20 is housed in the internal space 33 of the case body 50. The electrolyte 15 is also housed in the internal space 33 of the case body 50.

[0018] The first cover 31 and the second cover 32 cover the first opening 35 and the second opening 36 of the case body 50, respectively. The positive terminal 11 is provided on the first cover 31. The positive terminal 11 is electrically connected to the positive current collector 13 provided on the positive electrode portion 25 of the electrode body 20. The negative terminal 12 is provided on the second cover 32. The negative terminal 12 is electrically connected to the negative current collector 14 provided on the negative electrode portion 26 of the electrode body 20. Therefore, the battery cell 10 can be charged or discharged via the positive terminal 11 and the negative terminal 12.

[0019] Furthermore, as shown in Figure 2, the battery cell 10 has a pressing portion 100 in its internal space 33. The pressing portion 100 is provided in the gap between the electrode body 20 and the case 30. Figure 4 is a cross-sectional view of the battery cell 10 at position AA shown in Figure 2. Figure 4 shows a cross-section of the pressing portion 100. Figure 4 also shows the state of the battery cell 10 in the normal temperature range. The normal temperature range is a temperature range predetermined for use in the battery pack 1 by charging or discharging the battery cell 10. In this normal temperature range, the pressing portion 100 of the battery cell 10 is in a pressed state, pressing against the electrode body 20. In this embodiment, the battery cell 10 is provided with a first pressing portion 100A and a second pressing portion 100B as the pressing portion 100.

[0020] The case body 50 has wall portions 51 and 52 located at both ends in the Z direction, and wall portions 53A and 53B located at both ends in the Y direction. In this embodiment, wall portion 51 constitutes the upper side of the case body 50, and wall portion 52 constitutes the lower side of the case body 50. Wall portions 53A and 53B are side walls that extend vertically to connect wall portion 51 to wall portion 52. A gap is provided between the electrode body 20 and the wall portions 53A and 53B that are opposite to the electrode body 20 in the thickness direction.

[0021] The first pressing portion 100A has a fixing point 110, a pressing surface 120, and a deformable portion 130. The fixing point 110 is a part of the wall of the case 30 that is fixed to the inner surface 54 of the wall portion 51. The wall portion 51 to which the first pressing portion 100A is fixed may hereafter be referred to as the pressing wall portion 51. As a method for fixing the first pressing portion 100A to the pressing wall portion 51 and forming the fixing point 110, for example, welding, bonding, brazing, etc. can be used.

[0022] The pressing surface 120 is the surface that is pressed against the electrode body 20. In Figure 4, which shows the pressing state, the pressing surface 120 is pressed against the upper curved surface portion 41 of the electrode body 20. As a result, the first pressing portion 100A is in a pressed state, with the pressing surface 120 pressing against the electrode body 20. Furthermore, in the pressed state, the pressing surface 120 of the first pressing portion 100A is pressing against the first upper curved surface portion 41A, which is to the left of the center line B in the thickness direction of the electrode body 20 in Figure 4.

[0023] The deformable portion 130 is located between the fixed portion 110 and the pressing surface 120. The deformable portion 130 is a bimetal that deforms in a direction that moves the pressing surface 120 away from the pressing wall portion 51 of the case 30 as the temperature increases. The bimetallic deformable portion 130 is constructed by laminating a first metal material P1 and a second metal material P2, which have different coefficients of thermal expansion. In the deformable portion 130 shown in Figure 4, the first metal material P1 that constitutes the pressing wall portion 51 side is made of a material with a higher coefficient of thermal expansion than the second metal material P2 that constitutes the electrode body 20 side.

[0024] The deformable portion 130 deforms to curve as the temperature increases, thereby bringing the pressing surface 120 closer to the electrode body 20. In the first pressing portion 100A shown in Figure 4, the pressing surface 120 is a surface formed by the second metal material P2 that constitutes the electrode body 20 side of the deformable portion 130. The pressing surface 120 can also be formed by a pressing pad provided on the deformable portion 130.

[0025] As shown in Figures 2 and 4, the deformable portion 130 is a flat plate with its longitudinal direction in the X direction. The fixing points 110 of the first pressing portion 100A are provided on one end of the deformable portion 130 in the short direction. The fixing points 110 can be provided continuously along the longitudinal direction of the deformable portion 130. Alternatively, for example, the fixing points 110 may be provided intermittently along the longitudinal direction of the deformable portion 130. Specifically, for example, the fixing points 110 can be located at three locations: near both ends and near the center in the longitudinal direction of the deformable portion 130.

[0026] The second pressing portion 100B, like the first pressing portion 100A, has a fixed portion 110 fixed to the pressing wall portion 51, a pressing surface 120 that is pressed against the electrode body 20, and a deformable portion 130 located between the fixed portion 110 and the pressing surface 120. In this embodiment, the second pressing portion 100B is provided at the position of the center line B in the thickness direction of the electrode body 20, so as to be symmetrical with respect to the plane extending in the depth direction of Figure 4 with respect to the first pressing portion 100A. When pressed, the pressing surface 120 of the second pressing portion 100B presses the second upper curved surface portion 41B, which is to the right of the center line B in the thickness direction of the electrode body 20 in Figure 4, among the upper curved surface portion 41.

[0027] Here, an example of a manufacturing method for the battery cell 10 will be described. Figure 5 shows the electrode body 20 and the case body 50. In Figure 5, the electrode body 20 is before it is housed in the internal space 33 of the case body 50. The electrode body 20 is manufactured by winding a positive electrode plate 21, a negative electrode plate 22, and a separator 23 to form a flattened shape. A positive electrode current collector 13 and a negative electrode current collector 14 are connected to the electrode body 20. In Figure 5, the first lid 31 and the second lid 32 are not attached to the case body 50, and the first opening 35 and the second opening 36 are open.

[0028] Figure 5 shows the case in which the electrode body 20 is housed in the internal space 33 of the case body 50 by passing it through the first opening 35. Alternatively, the electrode body 20 may be housed in the case body 50 by passing it through the second opening 36. In this embodiment of the battery cell 10, the electrode body 20 is housed in the case body 50 with the temperature of at least the deformed portion 130 of the pressing portion 100 lowered.

[0029] Specifically, the temperature of the pressing portion 100 when housing the electrode body 20 is set to a temperature within the low-temperature range, which is lower than the lower limit temperature of the normal temperature range. Figure 6 shows a cross-sectional view of the pressing portion 100 in the low-temperature range. As mentioned above, the deformation portion 130 deforms in a direction that moves the pressing surface 120 away from the pressing wall portion 51 as the temperature increases. Conversely, when the temperature is low, the deformation portion 130 takes on a shape that brings the pressing surface 120 and the pressing wall portion 51 closer together, as shown in Figure 6. Specifically, in the low-temperature range, the deformation portion 130 takes on a shape that conforms more closely to the inner surface 54 of the pressing wall portion 51 than in the normal temperature range. As a result, the pressing portion 100 is in a non-pressing state in the low-temperature range, which is lower than the normal temperature range in which the battery cell 10 is expected to be used under normal conditions.

[0030] In the non-pressed state, the pressing portion 100 is in a state where the pressing force on the electrode body 20 has been released. More specifically, in the non-pressed state of the pressing portion 100, there is enough space to form a gap between the electrode body 20 and the pressing surface 120. This is the same for both the first pressing portion 100A and the second pressing portion 100B. Therefore, in the low-temperature range, the electrode body 20 can be smoothly inserted into the internal space 33 of the case body 50 without contacting the pressing portion 100. Thus, the battery pack 1 is easy to manufacture.

[0031] The battery cell 10 can be manufactured by housing the electrode body 20 inside the case body 50, and then closing the first opening 35 and the second opening 36 with the first cover 31 and the second cover 32, respectively. The battery pack 1 can be manufactured by housing multiple battery cells 10 in the first housing 2 and then assembling the second housing 3 to the first housing 2.

[0032] Subsequently, even after the battery cell 10 has been mounted in the battery pack 1, the pressing state of the pressing part 100 is released when the temperature of the deformed part 130 drops to a low temperature range. However, within the normal temperature range in which the battery pack 1 is expected to be used normally, the pressing state of the pressing part 100 is maintained. Therefore, in the battery pack 1, the electrode body 20 is properly held by the pressing part 100 during normal use. This suppresses movement of the electrode body 20 within the case 30.

[0033] Furthermore, the position of the positive electrode current collector 13 and the negative electrode current collector 14 is stabilized by the holding of the electrode body 20 by the pressing portion 100. This stabilization of the positions of the positive electrode current collector 13 and the negative electrode current collector 14 allows for easy connection of, for example, the positive electrode current collector 13 to the positive terminal 11 and the negative electrode current collector 14 to the negative terminal 12 within the normal temperature range. In addition, it is possible to prevent the connection between the positive electrode current collector 13 and the positive terminal 11, and the connection between the negative electrode current collector 14 and the negative terminal 12 from being released due to movement of the electrode body 20. However, when the pressing portion 100 is not in a pressing state, if the electrode body 20, which is not held in the internal space 33, tilts, there is a possibility that the electrode body 20 may come into contact with the pressing surface 120.

[0034] Furthermore, as shown in Figure 4, the case body 50 is provided with a first restricting portion 56A and a second restricting portion 56B. In this embodiment, the first restricting portion 56A and the second restricting portion 56B are projections provided on the inner surface 55A side of the left wall portion 53A and the inner surface 55B side of the right wall portion 53B, respectively. As shown in Figure 4, the first restricting portion 56A is in contact with the first pressing portion 100A, which is in a pressed state. The first restricting portion 56A restricts the pressing surface 120 of the first pressing portion 100A from moving any further away from the pressing wall portion 51 of the case body 50. The second restricting portion 56B is in contact with the second pressing portion 100B, which is in a pressed state. The second restricting portion 56B restricts the pressing surface 120 of the second pressing portion 100B from moving any further away from the pressing wall portion 51.

[0035] Therefore, the first restricting section 56A and the second restricting section 56B prevent the electrode body 20 from receiving a pressing force exceeding a certain level due to the first pressing section 100A and the second pressing section 100B in a pressed state. As a result, in the battery cell 10, the movement of the electrode body 20 in the internal space 33 is suppressed while preventing damage to the electrode body 20.

[0036] Furthermore, in this embodiment, the pressing wall 51 to which the fixing point 110 of the pressing part 100 is fixed is a wall located on the upper side of the case 30 in the battery pack 1. Therefore, the electrode body 20 can be pressed downward by the pressing part 100. This suppresses a reduction in the area of ​​the electrode body 20 that is immersed in the electrolyte 15, and maintains a state in which the battery cell 10 can be charged and discharged smoothly. In addition, it is possible to suppress the pressing part 100 from coming into contact with the electrolyte 15. Therefore, even if the electrolyte 15 is a corrosive liquid, corrosion of the pressing part 100 can be suppressed. The pressing part 100 may be subjected to surface treatment such as plating to improve corrosion resistance.

[0037] Furthermore, since the pressing wall portion 51 is located on the upper side of the case 30 and the pressing portion 100 is positioned on the upper part of the electrode body 20, it is possible to prevent the thickness of the battery cell 10 from increasing due to the provision of the pressing portion 100. Unlike this embodiment, for example, if the pressing portion were provided in the gap between the electrode body and the case body, specifically in the thickness direction of the electrode body, the thickness of the battery cell would increase by the amount of the pressing portion. In a battery pack, this increase in thickness would be accumulated for each battery cell. In contrast, the battery pack 1 of this embodiment only becomes larger upwards by the amount of the pressing portion 100, regardless of the number of battery cells. Therefore, the battery pack 1 of this embodiment has high space efficiency.

[0038] Furthermore, Figure 4 shows the pressing direction CA of the upper curved surface 41 by the pressing surface 120 of the first pressing part 100A, and the pressing direction CB of the upper curved surface 41 by the pressing surface 120 of the second pressing part 100B, respectively, indicated by arrows. The pressing direction CA of the first pressing part 100A and the pressing direction CB of the second pressing part 100B are intersecting directions. As a result, the electrode body 20 is properly held in the internal space 33 of the case 30 by the pressing from the first pressing part 100A and the second pressing part 100B. This makes it possible to more effectively suppress the movement of the electrode body 20 in the internal space 33 of the case 30 in the battery cell 10.

[0039] Furthermore, it is preferable that the pressing surface 120 of the pressing portion 100 has a curved shape that conforms to the contact area of ​​the outer peripheral surface 47 of the upper curved portion 41 that is pressed against the electrode body 20. This is because it can suppress damage to the contact area of ​​the pressing surface 120 on the electrode body 20.

[0040] Furthermore, as shown in Figure 4, the pressing wall portion 51 is provided with a fracture-predicted portion 60. The fracture-predicted portion 60 is a weaker area than other parts of the pressing wall portion 51. In this embodiment, the fracture-predicted portion 60 is provided on the outside of the pressing wall portion 51 and is a notch that is narrower towards the inner surface 54 side of the pressing wall portion 51. When the pressing wall portion 51 undergoes deformation exceeding a certain amount, such as bulging outwards, the fracture-predicted portion 60 will fracture so as to penetrate through to the inner surface 54 of the pressing wall portion 51. The position of the fracture-predicted portion 60 in the X direction can be, for example, near the center of the pressing wall portion 51.

[0041] As described above, fixing points 110 for the first pressing portion 100A and the second pressing portion 100B are fixed to the inner surface 54 side of the pressing wall portion 51 where the fracture portion 60 is provided. Furthermore, the first pressing portion 100A and the second pressing portion 100B have deformable portions 130 that deform in a direction that moves the pressing surface 120 away from the pressing wall portion 51 of the case body 50 as the temperature increases. In addition, the case 30 has first restricting portions 56A and second restricting portions 56B that restrict deformation of the first pressing portion 100A and the second pressing portion 100B beyond a certain level.

[0042] Therefore, the pressing wall portion 51 receives pressure from the inside as a reaction force from the first pressing portion 100A and the second pressing portion 100B pressing the first restricting portion 56A and the second restricting portion 56B, respectively. The pressing load received by the pressing wall portion 51 from the inside by the first pressing portion 100A and the second pressing portion 100B increases as the temperature of the battery cell 10 rises. In other words, as the temperature of the battery cell 10 rises, the pressing wall portion 51 deforms more and more, bulging outwards. Then, in the temperature range above the fracture temperature, the portion 60 intended to fracture breaks in accordance with the deformation of the pressing wall portion 51, which is pressed from the inside by the first pressing portion 100A and the second pressing portion 100B.

[0043] In this embodiment, the fracture temperature at which the fracture-prone portion 60 fractures is set to a high-temperature range that is higher than the upper limit temperature of the normal temperature range. Therefore, the fracture-prone portion 60 does not fracture during normal use of the battery pack 1, but fractures when the temperature is in a high-temperature range that could cause malfunctions in the battery pack 1. This prevents the battery pack 1 from becoming excessively hot.

[0044] The parameters for evaluating the fracture of the planned fracture section 60 can be determined based on the stress intensity factor, etc. The stress intensity factor can be determined based on the shape and stress distribution near the location where the planned fracture section 60 is to be made, and the stress near the location where the planned fracture section 60 is to be made is determined based on the parameters of the pressing wall section 51, such as the thickness of the pressing wall section 51, and the bending moment applied to the location where the planned fracture section 60 is to be made. The bending moment at the location of the planned fracture section 60 is determined according to the magnitude and location of the load received by the pressing wall section 51. The depth and length of the planned fracture section 60, which is a notch, can be determined based on the location and magnitude of the load received by the pressing wall section 51 and the fracture toughness. The location of the load received by the pressing wall section 51 affects the stress intensity factor and is a parameter determined in the design solution space along with the depth of the notch and the number of bimetal layers explained in Figure 11. The magnitude of the load received by the pressing wall section 51 can be calculated based on the temperature characteristics of the deformed section 130 made of bimetal. In other words, the fracture temperature of the planned fracture section 60 can be determined with high precision during the design phase.

[0045] Furthermore, in this embodiment, as shown in Figure 4, there is a gap between the fixing points 110 of the first pressing portion 100A and the second pressing portion 100B. The portion to be fractured 60 is provided in the region D of the pressing wall portion 51 between the fixing point 110 of the first pressing portion 100A and the fixing point 110 of the second pressing portion 100B.

[0046] As mentioned above, the first pressing portion 100A acts as a reaction force to press the first restricting portion 56A toward the inside of the case 30, pressing the fixing point 110 of the first pressing portion 100A on the pressing wall portion 51 toward the outside of the case 30. In other words, the pressing load of the first pressing portion 100A acts downward on the side of the first restricting portion 56A and upward on the fixing point 110 of the first pressing portion 100A in Figure 7. Similarly, the second pressing portion 100B acts as a reaction force to press the second restricting portion 56B toward the inside of the case 30, pressing the fixing point 110 of the second pressing portion 100B on the pressing wall portion 51 toward the outside of the case 30. In other words, the pressing load of the second pressing portion 100B acts downward on the side of the second regulating portion 56B and upward on the fixing portion 110 of the second pressing portion 100B, as shown in Figure 7.

[0047] Figure 7 shows, graphically, the bending moment M in the Y direction of the pressing wall portion 51 applied by the pressing force of the first pressing portion 100A and the second pressing portion 100B. In the example in Figure 7, the value of the bending moment M applied to the pressing wall portion 51 is small at the end on the side of the first restricting portion 56A, and increases as it approaches the fixing point 110 of the first pressing portion 100A from the end on the side of the first restricting portion 56A. Also in the example in Figure 7, the value of the bending moment M applied to the pressing wall portion 51 is small at the end on the side of the second restricting portion 56B, and increases as it approaches the fixing point 110 of the second pressing portion 100B from the end on the side of the second restricting portion 56B. Furthermore, in the example in Figure 7, the value of the bending moment M applied to the pressing wall portion 51 is approximately constant at value M1 in the region D between the fixing point 110 of the first pressing portion 100A and the fixing point 110 of the second pressing portion 100B.

[0048] Figure 8 shows an example of a pressing section different from that shown in Figure 7. The configuration shown in Figure 8 is an example in which the fixing points 910 of both the first pressing section 900A and the second pressing section 900B are attached to a single location on the back side of the portion 60 intended to break in the pressing wall 51. The first pressing section 900A and the second pressing section 900B have a deformable portion 930 made of bimetal between the fixing point 910 and the pressing surface 920.

[0049] In the configuration shown in Figure 8, the pressing loads, which are reaction forces from the first pressing portion 900A and the second pressing portion 900B pressing the first restricting portion 56A and the second restricting portion 56B respectively, are concentrated on the back surface of the fracture-prone portion 60 in the pressing wall portion 51. As a result, as shown in the graph in Figure 8, the value of the bending moment M applied to the pressing wall portion 51 is maximum at the position of the fixing point 910, and decreases as it approaches the first restricting portion 56A or the second restricting portion 56B at both ends. In other words, in the example in Figure 8, there is no region where the value of the bending moment M is uniform in the Y direction. Therefore, in the example in Figure 8, if the positional relationship between the fracture-prone portion 60 and the fixing point 910 is misaligned, the fracture temperature at which the fracture-prone portion 60 fractures will differ accordingly. Furthermore, setting the positional relationship between the fracture-prone portion 60 and the fixing point 910 as designed requires the battery cells to be manufactured with high precision, resulting in a high-cost battery pack.

[0050] In contrast, with the configuration shown in Figure 7, if the portion 60 to be fractured is located within region D, it can be fractured at the target temperature as designed. This is because, within region D, the bending moment M applied to the pressing wall portion 51 is approximately constant at value M1. In other words, the battery cell 10 with the configuration shown in Figure 7 can fracture the portion 60 to be fractured at the designed fracture temperature, even if the actual position of the portion 60 to be fractured is slightly different from the designed position. That is, a battery pack 1 having a battery cell 10 that can fracture the portion 60 to be fractured at the designed fracture temperature can be manufactured at low cost.

[0051] As described above, the battery pack 1 according to the above embodiment comprises a plurality of battery cells 10. Each battery cell 10 has an electrode body 20, a case 30, and a pressing portion 100. The electrode body 20 is composed of a positive electrode plate 21 and a negative electrode plate 22. The electrode body 20 is a flattened, wound type. The case body 50 of the case 30 houses the electrode body 20 in an internal space 33. The pressing portion 100 is provided in the gap between the electrode body 20 and the case body 50 and presses against the electrode body 20. The pressing portion 100 also has a fixing point 110, a pressing surface 120, and a deformable portion 130. The fixing point 110 is a point fixed to the inner surface 54 of the pressing wall portion 51 of the case body 50. The pressing surface 120 is the surface that is pressed against the electrode body 20. The deformable portion 130 is located between the fixing point 110 and the pressing surface 120. Furthermore, the deformable portion 130 is made of a bimetal that deforms in a direction that moves the pressing surface 120 away from the pressing wall portion 51 as the temperature increases. The pressing portion 100 maintains a pressing state where the pressing surface 120 presses against the electrode body 20 within the normal temperature range. On the other hand, the pressing portion 100 releases the pressing state in the low temperature range, which is lower than the lower limit temperature of the normal temperature range. As a result, the battery pack 1 is easy to manufacture and prevents the movement of the electrode body 20 inside the case 30 during use.

[0052] Next, specific examples of the deformation portion of the pressing section will be explained with reference to Figures 9, 10, and 11. Figure 9 shows the deformation portion of the first embodiment. The deformation portion 130 of the first embodiment is the same as the one described in Figure 4 above. That is, the deformation portion 130 of the first embodiment is a bimetal composed of a first metal material P1 with a high coefficient of thermal expansion that constitutes the pressing wall portion 51 side and a second metal material P2 with a low coefficient of thermal expansion that constitutes the electrode body 20 side. Figure 9 shows the deformation amount E1 of the deformation portion 130. The deformation amount E1 indicates the distance traveled by the reference point that moves the most in response to temperature changes within the deformation portion 130. Specifically, the reference point is the point on the side of the deformation portion 130 opposite to the fixed point 110 side. Furthermore, the deformation amount E1 is the distance traveled by the reference point from a state in which the deformation portion 130 is shaped along the pressing wall portion 51 in the low temperature range, to a state in which it is curved away from the pressing wall portion 51 when the temperature is raised to a reference temperature within the normal temperature range.

[0053] Figure 10 shows a deformation section of a second embodiment, which differs from the first embodiment. In short, the second embodiment is a structure in which multiple deformation sections are connected by folding them back. In the second embodiment, the deformation section has a first deformation section 130 and a second deformation section 131. The first deformation section 130 is the same as the one described in Figure 9. That is, the first deformation section 130 in the second embodiment has a fixing point 110 on one end. However, the first deformation section 130 in the second embodiment has a connection point 111 for the second deformation section 131 on the opposite side of the fixing point 110. For example, welding, bonding, brazing, etc., can be used to form the connection point 111.

[0054] The second deformable portion 131 is connected to a connection point 111 on the opposite end of the first deformable portion 130, which is opposite to the fixing point 110 on one end. The second deformable portion 131 is also provided so as to fold back relative to the first deformable portion 130. The size and material of the second deformable portion 131 are the same as those of the first deformable portion 130. In other words, the second deformable portion 131 is also a bimetal composed of a first metal material P1 with a high coefficient of thermal expansion and a second metal material P2 with a low coefficient of thermal expansion. The second deformable portion 131 deforms in a direction that moves away from the pressing wall portion 51 on the side opposite to the connection point 111 as the temperature increases.

[0055] The deformation amount E2 is also shown for the second embodiment, which has a first deformation portion 130 and a second deformation portion 131. The deformation amount E2 represents the distance traveled by the reference point that moves the most in response to temperature changes among the first deformation portion 130 and the second deformation portion 131. Specifically, the reference point is the part of the second deformation portion 131 opposite to the connection point 111. Furthermore, the deformation amount E2 in the second embodiment is twice the deformation amount E1 in the first embodiment.

[0056] In other words, by connecting multiple deformable parts so that adjacent parts fold over each other, the amount of deformation can be increased by the number of deformable parts that are provided to fold over each other. Furthermore, a configuration with folds as in the second embodiment can increase the distance the pressing surface moves in response to temperature changes within a certain temperature range. For this reason, it can be used, for example, when it is desired to ensure a sufficient gap between the electrode body 20 and the pressing surface 120 when housing the electrode body 20 in the case body 50. The deformable parts that are adjacent to each other due to the folding should be configured to face each other on sides that have the same thermal expansion coefficient. In the example of the second embodiment shown in Figure 10, the first deformable part 130 and the second deformable part 131 that are adjacent to each other due to the folding are configured to face each other on sides of the second metal material P2.

[0057] Furthermore, even if a second embodiment having a first deformation section 130 and a second deformation section 131 is adopted, the pressing load is the same as in the first embodiment having only the deformation section 130. In other words, by connecting multiple deformation sections in a folded manner to form a pressing section, the amount of deformation can be increased by the number of deformation sections connected in a folded manner while maintaining a constant pressing load.

[0058] Figure 11 shows a deformation section of a third embodiment, which is different from both the first and second embodiments. In short, the deformation section of the third embodiment is made up of multiple bimetals stacked together. It is constructed by stacking two deformation sections 130 of the first embodiment shown in Figure 9, and is made up of two stacked bimetals. Therefore, in the deformation section 132 of the third embodiment, the first metal material P1, the second metal material P2, the first metal material P1, and the second metal material P2 are stacked in order from the pressing wall 51 side.

[0059] The deformation amount E3 is also shown for the deformation portion 132 of the third embodiment. The deformation amount E3 indicates the distance traveled by the reference point in the deformation portion 132 that moves the most in response to temperature changes. Specifically, the reference point is the part of the deformation portion 132 opposite to the fixed point 110. Furthermore, the deformation amount E3 is the same as the deformation amount E1 of the deformation portion 130 in the first embodiment. In other words, even if the number of stacked bimetals in the deformation portion is changed, the deformation amount can be kept constant. On the other hand, by adopting the deformation portion 132 of the third embodiment, the pressing load can be doubled compared to the deformation portion 130 of the first embodiment. In other words, by constructing the deformation portion by stacking multiple bimetals, the pressing load can be increased by the number of stacked bimetals while maintaining a constant deformation amount. Furthermore, a configuration having a stacked bimetal structure like the third embodiment can significantly change the load applied by the pressing surface in response to temperature changes within a certain temperature range. For this reason, it can be adopted, for example, when it is desired to increase the holding force of the electrode body 20 by the pressing portion in the normal temperature range. Furthermore, for example, this method can be used when it is desired to significantly change the load applied to the pressing wall portion 51 by the pressing portion in a high-temperature range in order to reliably break the portion 60 intended to break.

[0060] As described above, the amount of deformation of the pressing section can be adjusted by providing multiple deformable sections that are folded back. Furthermore, the pressing load of the pressing section 100 can be adjusted by stacking multiple bimetals to form the deformable section. The number of folds in the deformable section and the number of stacked bimetals can be determined according to the amount of deformation and pressing load required for the pressing section. Specifically, for example, if it is desired to triple the amount of deformation and double the pressing load for a pressing section 100 that uses only one deformable section made of a single bimetal, the pressing section 200 can be configured as shown in Figures 12 and 13. Figure 12 shows the pressing section 200 in the low temperature range. Figure 13 shows the pressing section 200 in the normal temperature range.

[0061] As shown in Figures 12 and 13, the pressing portion 200 has a fixing point 210 to the pressing wall portion 51 and a pressing surface 220 that is pressed against the electrode body 20. The pressing portion 200 also has a deformable portion located between the fixing point 210 and the pressing surface 220, which is a first deformable portion 230, a second deformable portion 231, and a third deformable portion 232.

[0062] A fixing point 210 is provided at one end of the first deformable section 230. A connection point 211 for the second deformable section 231 is provided at the other end of the first deformable section 230, opposite to the fixing point 110. The second deformable section 231 is connected to the first deformable section 230 at the connection point 211 and is positioned to fold back relative to the first deformable section 230. A connection point 212 for the third deformable section 232 is provided on the opposite side of the connection point 211 of the second deformable section 231. The third deformable section 232 is connected to the second deformable section 231 at the connection point 212 and is positioned to fold back relative to the second deformable section 231.

[0063] The first deformation section 230, the second deformation section 231, and the third deformation section 232 are all constructed by alternately stacking two first metal material P1 and two second metal material P2. In other words, the first deformation section 230, the second deformation section 231, and the third deformation section 232 are all constructed by stacking two bimetallic strips.

[0064] A pressure pad 221 is provided on the electrode body 20 side of the third deformation portion 232. The pressure surface 220 of the pressure portion 200 is formed by the pressure pad 221. The pressure pad 221 can be made of, for example, metal, resin, rubber, etc.

[0065] As described above, the pressing section 200 has three deformable sections connected in a folded manner. Therefore, the amount of deformation of the pressing section 200 is three times that of the case with one deformable section. In addition, each deformable section of the pressing section 200 is constructed by stacking two bimetals. Therefore, the pressing load of the pressing section 200 is twice that of the case where the deformable section is constructed with one bimetal. In this way, the amount of deformation and the pressing load can be appropriately adjusted by appropriately adjusting the number of deformable sections provided in a folded manner and the number of stacked bimetals that make up the deformable section.

[0066] Alternatively, adjacent battery cells in a battery pack may share the case wall, as shown in Figure 14. The battery pack 9 shown in Figure 14 has multiple battery cells 19 in the thickness direction. The case body 150 of the case 39 of the battery cells 19 is for multiple battery cells 19, and adjacent battery cells 19 share a wall portion 53, which is a side wall. That is, the case body 150 has a pressing wall portion 151 that constitutes the upper wall portion and a wall portion 152 that constitutes the lower portion, and also has a partition wall 153 that divides the space between the pressing wall portion 151 and the wall portion 152 in the thickness direction of the electrode body 20. As a result, one case body 150 has an internal space 33 equal to the number of battery cells 19 arranged in the thickness direction. For this reason, in the battery pack 9, there is only one partition wall 153 between the electrode bodies 20 of adjacent battery cells 19. This configuration eliminates the situation where two side walls of the battery cell cases are present between the electrode bodies of adjacent battery cells.

[0067] In recent years, battery packs have undergone integration and omission of various parts in order to improve energy density. The shape of the battery cell 19 case body 150 can be modified to improve the energy density of the battery pack 9 by omitting part of the wall. Furthermore, the structure of the battery pack 9 can be adopted in a method called cell-to-pack (CTP), which omits the modularization of battery cells and directly houses the battery cells in the battery pack.

[0068] However, in a battery pack 9 with the structure shown in Figure 14, it is difficult to hold the electrode body 20 inside the case 39 by applying a restraining load to each battery cell 19 in the thickness direction from the outside of the case 39. However, in the battery pack 9 shown in Figure 14, a pressing portion 100 (first pressing portion 100A, second pressing portion 100B) is provided for each battery cell 19. Each pressing portion 100 for each battery cell 19 is provided on the pressing wall portion 151, which is the upper wall portion of the case body 150. And even in a battery pack 9 with the structure shown in Figure 14, the electrode body 20 can be properly held because each battery cell 19 is provided with a pressing portion 100.

[0069] The embodiments described above are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can naturally be improved and modified in various ways without departing from its essence.

[0070] For example, the configuration of the pressing portion shown in the above embodiment is merely one example. That is, for example, the number of pressing portions for one battery cell can be one or three or more. Also, for example, a restricting portion that restricts the pressing of the electrode body by the pressing portion can be provided in correspondence with the pressing portion. That is, for example, if there is one pressing portion, one restricting portion is sufficient. Also, for example, the portion of the electrode body pressed by the pressing portion is not limited to a curved surface, but can be a flat surface, for example. Also, for example, a restricting portion that restricts the pressing of the electrode body by the pressing portion, and a portion intended to break when pressed by the pressing portion are not necessarily required. Also, for example, the form of the restricting portion is not limited to a protrusion as shown in the above embodiment. Also, for example, as a combination of the first metal material and the second metal material constituting the bimetal, for example, a combination of Ni-Mn-Fe alloy and Ni-Fe alloy can be given. However, the combination of the first metal material and the second metal material is only required so that the deformable portion constituting the bimetal can deform in accordance with temperature changes, and of course, other combinations of metal materials can be used. Furthermore, for example, the application of the above embodiment is not particularly limited in terms of battery type (such as nickel-metal hydride batteries or lithium-ion batteries). Also, the technology disclosed in the above embodiment can be implemented in various forms, such as a method for manufacturing battery packs.

[0071] Furthermore, the disclosed technology described above includes the following means 1 to means 9. [Means 1] A battery pack comprising multiple battery cells, The aforementioned battery cell is A flattened, wound electrode body containing positive and negative electrode plates, A case for housing the electrode body inside, It has a pressing portion provided in the gap between the electrode body and the case, which presses the electrode body, The pressing portion is, The fixing points are fixed to the inner surface of the wall portion of the aforementioned case, A pressing surface that is pressed against the electrode body, It has a deformable part made of bimetal, located between the fixed point and the pressing surface, which deforms in a direction that moves the pressing surface away from the wall of the case as the temperature increases. A battery pack that, within a predetermined normal temperature range for using the battery cell by charging or discharging, maintains a pressed state in which the electrode body is pressed by the pressing surface, and releases the pressed state in a low temperature range lower than the lower limit temperature of the normal temperature range.

[0072] [Means 2] The battery pack described in method 1, A battery pack provided on the inner surface of the wall of the case, which is in contact with the pressing portion in the pressed state and which restricts the pressing surface from moving any further away from the wall of the case.

[0073] [Means 3] The battery pack described in method 2, In the wall portion of the case, the pressing wall portion to which the fixing point of the pressing portion is fixed on the inner surface is provided with a portion intended to break. The aforementioned fracture-prone portion is a battery pack in which, in a high-temperature range higher than the upper limit temperature of the normal temperature range, the pressing wall portion deforms when pressed from the inside by the pressing portion.

[0074] [Means 4] The battery pack described in means 3, The pressing portion has a first pressing portion and a second pressing portion. The first pressing portion and the second pressing portion are fixed to the inner surface of the pressing wall portion, with a gap between them at the fixing points. The portion scheduled to break is a battery pack provided in the pressing wall portion in the region between the fixing point of the first pressing portion and the fixing point of the second pressing portion.

[0075] [Means 5] A battery pack according to any of the means 1 to means 4, The electrode body is A planar portion in which two circumferential surfaces facing each other in the thickness direction are both flat, It has two curved portions located at both ends of the aforementioned flat portion, the outer surfaces of which are curved. The two curved portions are housed inside the case, with their respective sides facing upwards and downwards. The fixing point of the pressing part is fixed to the inner surface of the wall portion located on the upper side of the wall portion of the case. The pressing surface of the pressing portion presses against the upper curved portion, which is the curved portion located on the upper side of the electrode body, in this battery pack.

[0076] [Means 6] The battery pack described in means 5, The pressing portion is, Of the upper curved portion, a first pressing portion presses one side of the electrode body in the thickness direction from the center with the pressing surface, The upper curved portion has a second pressing portion which presses the other side opposite to the one mentioned above with the pressing surface, A battery pack in which the direction of pressure applied to the upper curved surface by the pressing surface of the first pressing portion and the direction of pressure applied to the upper curved surface by the pressing surface of the second pressing portion intersect each other.

[0077] [Means 7] A battery pack according to means 5 or means 6, The battery pack wherein the pressing surface of the pressing portion has a curved shape that conforms to the location on the outer circumferential surface of the upper curved portion where the pressing surface makes contact.

[0078] [Means 8] A battery pack according to any of the means 1 to means 7, The pressing portion is, as the deformed portion, A first deformed portion having the aforementioned fixing point on one end, A battery pack having a second deformable portion connected to the other end of the first deformable portion opposite to the one end of the first deformable portion, and provided so as to fold back relative to the first deformable portion.

[0079] [Means 9] A battery pack according to any of the means 1 to means 8, The deformed portion of the pressing portion is a battery pack formed by stacking multiple bimetallic strips. [Explanation of Symbols]

[0080] 1. 9: Battery pack 10, 19: Battery cells 20: Electrode body 21: Positive plate 22: Negative plate 30, 39: Case 40: Flat part 41: Upper curved surface part 42: Lower curved surface part 51, 151: Pressing wall portion 56A: First Regulatory Section 57A: Second Regulatory Department 60: Part where fracture is expected 100, 200: Pressing part 100A, 900A: First pressing section 100B, 900B: Second pressing section 110, 210, 910: Fixing points 120, 220, 920: Pressing surface 130, 132, 930: Deformed part 130, 230: First deformation section 131, 231: Second deformation section

Claims

1. A battery pack comprising multiple battery cells, The aforementioned battery cell is A flattened, wound electrode body containing positive and negative electrode plates, A case for housing the electrode body inside, It has a pressing portion provided in the gap between the electrode body and the case, which presses the electrode body, The pressing portion is, The fixing points are fixed to the inner surface of the wall portion of the aforementioned case, A pressing surface that is pressed against the electrode body, It has a deformable part made of bimetal, located between the fixed point and the pressing surface, which deforms in a direction that moves the pressing surface away from the wall of the case as the temperature increases. A battery pack that, within a predetermined normal temperature range for using the battery cell by charging or discharging, maintains a pressed state in which the electrode body is pressed by the pressing surface, and releases the pressed state in a low temperature range lower than the lower limit temperature of the normal temperature range.

2. A battery pack according to claim 1, A battery pack provided on the inner surface of the wall of the case, which is in contact with the pressing portion in the pressed state and which restricts the pressing surface from moving any further away from the wall of the case.

3. The battery pack according to claim 2, In the wall portion of the case, the pressing wall portion to which the fixing point of the pressing portion is fixed on the inner surface is provided with a portion intended to break. The aforementioned fracture-prone portion is a battery pack in which, in a high-temperature range higher than the upper limit temperature of the normal temperature range, the pressing wall portion deforms when pressed from the inside by the pressing portion.

4. The battery pack according to claim 3, The pressing portion comprises a first pressing portion and a second pressing portion. The first pressing portion and the second pressing portion are fixed to the inner surface of the pressing wall portion, with a gap between them at the fixing points. The portion scheduled to break is a battery pack provided in the pressing wall portion in the region between the fixing point of the first pressing portion and the fixing point of the second pressing portion.

5. A battery pack according to claim 1, The electrode body is A planar portion in which two circumferential surfaces facing each other in the thickness direction are both flat, It has two curved portions located at both ends of the aforementioned flat portion, the outer surfaces of which are curved. The two curved portions are housed inside the case, with their respective sides facing upwards and downwards. The fixing point of the pressing part is fixed to the inner surface of the wall portion located on the upper side of the wall portion of the case. The pressing surface of the pressing portion presses against the upper curved portion, which is the curved portion located on the upper side of the electrode body, in this battery pack.

6. The battery pack according to claim 5, The pressing portion is, Of the upper curved portion, a first pressing portion presses one side of the electrode body in the thickness direction from the center with the pressing surface, The upper curved portion has a second pressing portion which presses the other side opposite to the one mentioned above with the pressing surface, A battery pack in which the direction of pressure applied to the upper curved surface by the pressing surface of the first pressing portion and the direction of pressure applied to the upper curved surface by the pressing surface of the second pressing portion intersect each other.

7. A battery pack according to claim 5 or claim 6, The battery pack wherein the pressing surface of the pressing portion has a curved shape that conforms to the location on the outer circumferential surface of the upper curved portion where the pressing surface makes contact.

8. A battery pack according to any one of claims 1 to 6, The pressing portion is, as the deformed portion, A first deformed portion having the aforementioned fixing point on one end, A battery pack having a second deformable portion connected to the other end of the first deformable portion opposite to the one end of the first deformable portion, and provided so as to fold back relative to the first deformable portion.

9. A battery pack according to any one of claims 1 to 6, The deformed portion of the pressing portion is a battery pack formed by stacking multiple bimetallic strips.

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