Heat absorbing member and battery pack

Abstract

A heat-absorbing member 50 comprises a heat-absorbing agent 51 and a sheath member 52 that accommodates the heat-absorbing agent 51. The sheath member 52 has a section 61 that contacts an object. The section 61 has a groove 64.

Description

[Technical Field]

[0001] The present disclosure relates to a heat absorption member and a battery pack. [Background technology]

[0002] Patent Document 1 discloses, as an example of a battery pack, a battery module including a heat-absorbing member and a plurality of cells. The heat-absorbing member includes a heat-absorbing agent and an exterior film containing the heat-absorbing agent. When the secondary battery generates abnormal heat, the exterior film tears open, and the heat-absorbing agent reduces the temperature of the secondary battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2010 / 098067 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable that the exterior film (exterior member) be easily torn when the secondary battery generates abnormal heat.

[0005] The present disclosure has been made in view of the above, and aims to provide a heat-absorbing member that easily splits when an object generates heat. [Means for solving the problem]

[0006] The heat-absorbing member of the present disclosure includes an absorbing agent and an exterior member that houses the absorbing agent, the exterior member having a first portion that contacts an object, and the first portion having a groove.

[0007] A battery pack according to the present disclosure includes the heat-absorbing member described above and a secondary battery, and the target object is the secondary battery. [Effects of the Invention]

[0008] According to the present disclosure, the heat-absorbing member can be easily cleaved when an object generates abnormal heat. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view of a battery pack according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is an exploded perspective view of the battery unit shown in FIG. [Figure 3] 3 is a vertical cross-sectional view of the secondary battery and lead plates shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the heat absorbing member. [Figure 5] FIG. 5 is an exploded perspective view of the exterior member. [Figure 6] FIG. 6 is a perspective view of the first exterior member as seen from the outer surface. [Figure 7] FIG. 7 is a partial cross-sectional view of the first exterior member. [Figure 8] FIG. 8 is a partially enlarged cross-sectional view of the first exterior member. [Figure 9] FIG. 9 is a schematic diagram showing a process of forming the first exterior member by injection molding. [Figure 10] FIG. 10 is a diagram showing the positions of convex portions according to another modified example of the first embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram showing the positions of convex portions according to another modified example of the first embodiment of the present disclosure. [Figure 12] FIG. 12 is a diagram showing the positions of convex portions according to another modified example of the first embodiment of the present disclosure. [Figure 13] FIG. 13 is an exploded perspective view of a battery unit according to a second embodiment of the present disclosure. [Figure 14] FIG. 14 is an exploded perspective view of the exterior member. [Figure 15] FIG. 15 is a perspective view of the first exterior member. [Figure 16] FIG. 16 is a cross-sectional view of the first exterior member taken along the line AA shown in FIG. [Figure 17]FIG. 17 is a cross-sectional view of the first exterior member taken along line BB shown in FIG. [Figure 18] FIG. 18 is a schematic diagram showing a process of forming the first exterior member by injection molding. [Figure 19] FIG. 19 is a diagram showing the positions of convex portions according to another modified example of the second embodiment of the present disclosure. [Figure 20] FIG. 20 is a diagram showing the positions of convex portions according to another modified example of the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings. Note that the present disclosure is not limited to these embodiments. Each embodiment is an example, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible.

[0011] First Embodiment <Battery pack 1> 1 is an exploded perspective view of a battery pack 1 according to a first embodiment of the present disclosure. The battery pack 1 can be used as a power source for external devices (not shown), such as electronic devices, electric vehicles, and power tools. The battery pack 1 includes an outer case 10, a connector 20, a control board 30, and a battery unit 40.

[0012] The exterior case 10 is box-shaped and houses the control board 30 and the battery unit 40. The exterior case 10 has a first case portion 11 and a second case portion 12.

[0013] The connector 20 is attached to the exterior case 10. The connector 20 electrically connects an external device and the battery unit 40 via the control board 30, and supplies (discharges) power from the battery unit 40 to the external device. The connector 20 also electrically connects a power source (e.g., a commercial power source) and the battery unit 40 via the control board 30, and supplies (charges) power from the power source to the battery unit 40. The control board 30 controls charging and discharging of the battery unit 40.

[0014] Fig. 2 is an exploded perspective view of the battery unit 40 shown in Fig. 1. The battery unit 40 includes a plurality of secondary batteries 41, a holder 42, a plurality of lead plates 43, and a plurality of heat absorbing members 50.

[0015] The secondary batteries 41 are, for example, lithium ion batteries. The secondary batteries 41 have a cylindrical shape. In the first embodiment, the number of secondary batteries 41 is ten, but it goes without saying that the number is not limited to ten.

[0016] The plurality of secondary batteries 41 are arranged in parallel. That is, the axes of the plurality of secondary batteries 41 are substantially parallel to one another. In the first embodiment, the plurality of secondary batteries 41 are arranged in two rows. The plurality of secondary batteries 41 are also arranged such that the positive electrode terminals 41a and the negative electrode terminals 41b are oriented in predetermined directions.

[0017] Fig. 3 is a longitudinal cross-sectional view of secondary battery 41 and lead plate 43 shown in Fig. 2. Holder 42 and heat absorption member 50 are not shown in Fig. 3. Secondary battery 41 includes electrode assembly 41c, can 41d, and lid 41e. Can 41d and lid 41e are made of, for example, iron, stainless steel, or aluminum, and are electrically conductive.

[0018] The electrode assembly 41c is formed by stacking a plurality of sheet-shaped positive electrodes (not shown) and a plurality of sheet-shaped negative electrodes (not shown) with separators (not shown) interposed therebetween and winding them up.

[0019] The can 41d is cylindrical and has an opening at one end. The can 41d is electrically connected to the negative electrode of the electrode assembly 41c via a current collector foil (not shown). The negative electrode terminal 41b of the secondary battery 41 is located at the center of the other end face of the can 41d.

[0020] Lid 41e is plate-shaped and covers the opening at one end of can 41d. Lid 41e and can 41d are electrically insulated from each other by an insulating member (not shown). Lid 41e is electrically connected to the positive electrode of electrode assembly 41c via a current collecting foil.

[0021] The lid 41e has a protrusion 41f and a split valve 41g. The protrusion 41f is located in the center of the lid 41e. The protruding end surface of the protrusion 41f is the positive electrode terminal 41a of the secondary battery 41. The protrusion 41f is also provided with a hole 41f1 that connects the inside and outside of the secondary battery 41. There may be multiple holes 41f1.

[0022] Split valve 41g is disposed inside protrusion 41f inside secondary battery 41. Specifically, split valve 41g is disposed at a position that separates the space communicating with hole 41f1 inside secondary battery 41 from the space in which electrode assembly 41c is located. Split valve 41g splits to enter an open state when the internal pressure of secondary battery 41 reaches or exceeds a predetermined value.

[0023] Furthermore, a battery thin-walled portion 41h is provided at the other end of the can 41d. The battery thin-walled portion 41h is a thinner portion at the other end of the can 41d. When the internal pressure of the secondary battery 41 increases, the portion at the other end of the can 41d splits open from the battery thin-walled portion 41h. For example, if the split valve 41g does not open even when the internal pressure of the secondary battery 41 reaches or exceeds a predetermined value, when the internal pressure of the secondary battery 41 further increases, the portion at the other end of the can 41d splits open from the battery thin-walled portion 41h.

[0024] 2 holds a plurality of secondary batteries 41. There are two holders 42, and they mainly hold the outer circumferential surfaces of the secondary batteries 41. Specifically, the holders 42 hold the positive electrode terminal 41a, the negative electrode terminal 41b, the protrusion 41f, and the portion of the can 41d where the battery thin-walled portion 41h is provided.

[0025] The lead plates 43 electrically connect the multiple secondary batteries 41 in series or parallel. The lead plates 43 also electrically connect the multiple secondary batteries 41 to the control board 30. The lead plates 43 include a first lead plate 43a and a second lead plate 43b. The first lead plate 43a electrically connects two secondary batteries 41. The second lead plate 43b electrically connects four secondary batteries 41. It goes without saying that the number of secondary batteries 41 electrically connected to the first lead plate 43a and the second lead plate 43b is not limited to the above number.

[0026] <Heat absorption member 50> The battery pack 1 includes two heat-absorbing members 50. The heat-absorbing members 50 are arranged between the secondary batteries 41 arranged in two rows. The heat-absorbing members 50 come into contact with an object. The object is the secondary batteries 41. The heat-absorbing members 50 come into contact with the secondary batteries 41 arranged in one row. It goes without saying that the number of heat-absorbing members 50 is not limited to two. Furthermore, the heat-absorbing members 50 may be arranged outside the secondary batteries 41 arranged in two rows.

[0027] FIG. 4 is a cross-sectional view of the heat-absorbing member 50. The first direction D1 and the second direction D2 shown in the drawing are straight and perpendicular to each other. FIG. 4 shows the cross-sectional shape of the heat-absorbing member 50 when the heat-absorbing member 50 is cut along a plane perpendicular to the first direction D1. In each of the first direction D1 and the second direction D2, the side indicated by the arrow is the positive side, and the side opposite the positive side is the negative side. The heat-absorbing member 50 absorbs heat from the secondary battery 41 (details will be described later). The heat-absorbing member 50 includes a heat-absorbing agent 51 and an exterior member 52 that accommodates the heat-absorbing agent 51.

[0028] The heat-absorbing agent 51 contains a substance that absorbs heat generated from the secondary battery 41. The main component of the heat-absorbing agent 51 is a liquid such as water. The heat-absorbing agent 51 may contain a gelling agent, a surfactant, and an antifreeze agent. The heat-absorbing agent 51 may or may not have fluidity.

[0029] FIG. 5 is an exploded perspective view of the exterior member 52. The exterior member 52 includes a first exterior member 60 and a second exterior member 70. The first exterior member 60 and the second exterior member 70 are made of an electrically insulating thermoplastic resin. The first exterior member 60 and the second exterior member 70 are made of, for example, polyethylene terephthalate alone. The first exterior member 60 and the second exterior member 70 may also be made of a synthetic resin containing at least one of polyethylene terephthalate, polypropylene, polyethylene, and polystyrene. The first exterior member 60 and the second exterior member 70 are formed by injection molding.

[0030] 4 and 5, the first exterior member 60 has a plurality of (specifically, three) portions 61, a plurality of (specifically, two) portions 62, and a plurality of (specifically, four) portions 63. The portion 61 corresponds to the "first portion." . Department Part 61, part 62 and part 63 are integral.

[0031] The portions 61 and 62 come into contact with the target object, the secondary battery 41. At least a portion of the portions 61 and 62 comes into contact with at least a portion of the outer circumferential surface of the secondary battery 41. It goes without saying that the number of the portions 61 is not limited to three, the number of the portions 62 is not limited to two, and the number of the portions 63 is not limited to four.

[0032] The portions 61 extend along the first direction D1. As shown in Fig. 4, the cross-sectional shape of each of the portions 61 when cut along a plane perpendicular to the first direction D1 is a concave shape that is recessed toward the inside of the exterior member 52. In other words, each of the portions 61 is recessed from the first exterior member 60 side toward the second exterior member 70 side. Specifically, the cross-sectional shape of the portion 61 shown in Fig. 4 is semicircular. In other words, the cross-sectional shape of the portion 61 being concave means that the cross-sectional shape of the portion 61 is semicircular.

[0033] The outer surface of portion 61, which is part of the outer surface of exterior member 52, is a curved surface that fits along the outer circumferential surface of secondary battery 41. The outer surface of portion 61 comes into contact with the outer circumferential surface of secondary battery 41, which has a cylindrical shape. This increases the contact area between portion 61 and secondary battery 41.

[0034] The three portions 61 are arranged in parallel along the second direction D2. This allows the heat-absorbing member 50 to be arranged between the multiple secondary batteries 41, thereby preventing the battery pack 1 from becoming larger.

[0035] The portion 62 extends along the first direction D1. As shown in FIG. 4, the cross-sectional shape of the portion 62 when cut along a plane perpendicular to the first direction D1 is a concave shape recessed toward the inside of the exterior member 52. In other words, the portion 62 is recessed from the first exterior member 60 side toward the second exterior member 70 side. Specifically, the cross-sectional shape of the portion 62 shown in FIG. 4 is a quadrant. In other words, the fact that the cross-sectional shape of the portion 62 is concave means that the cross-sectional shape of the portion 62 is a quadrant. It goes without saying that the cross-sectional shapes of the portions 61 and 62 are not limited to a concave shape.

[0036] The outer surface of the portion 62, which is part of the outer surface of the exterior member 52, is a curved surface that follows the outer peripheral surface of the secondary battery 41, which is the target. The outer surface of the portion 62 comes into contact with the outer peripheral surface of the cylindrical secondary battery 41. This increases the contact area between the portion 62 and the secondary battery 41. Furthermore, the two portions 62 are disposed on both sides of the three portions 61 in the second direction D2.

[0037] Fig. 6 is a perspective view of the first exterior member 60 as seen from the outer surface. As shown in Figs. 4 and 6, the portions 63 are arranged on both sides of the portion 61 in a direction perpendicular to the first direction D1 (i.e., the second direction D2), and are continuous with the portion 61. The portion 63 extends along the first direction D1. The portion 63 does not contact the outer peripheral surface of the cylindrical secondary battery 41. However, the portion 63 may contact the outer peripheral surface of the cylindrical secondary battery 41.

[0038] The portions 63 continuing from two portions 61 adjacent to each other in the second direction D2 are integral. That is, the portions 63 connect the two portions 61 adjacent to each other in the second direction D2. Furthermore, the portion 62 adjacent to the portion 61 in the second direction D2 is continuing from the portion 63. That is, the portion 63 connects the portions 61 and 62 adjacent to each other in the second direction D2.

[0039] Fig. 7 is a partial cross-sectional view of the first exterior member 60. As shown in Figs. 6 and 7, each of the four portions 63 has a protruding portion 63a. The protruding portion 63a is located in the center of the portion 63 in the first direction D1. Specifically, the protruding portion 63a is a gate mark.

[0040] 6, the portion 61 has a groove 64. The groove 64 is located in the center of the portion 61 in the second direction D2 and extends substantially along the first direction D1. The groove 64 is located in at least a portion of the portion 61 in the first direction D1, and the groove 64 is specifically a weld line.

[0041] 8 is a partially enlarged cross-sectional view of the first exterior member 60. The groove 64 is on the outer surface of the portion 61. The outer surface of the groove 64 does not come into contact with the secondary battery 41.

[0042] 5, the first exterior member 60 has a recess 60a and a flange 60b. The recess 60a is concave, with the inner surfaces of the portions 61, 62, and 63 as its bottom surface. The inner surfaces of the portions 61, 62, and 63 are part of the inner surface of the exterior member 52. The flange 60b is formed around the entire periphery of the recess 60a.

[0043] 5, the outer surface of the first exterior member 60 has a plurality of end faces S1. The plurality of end faces S1 are on the positive side of the first direction D1 of the portions 61, 62, and 63. The plurality of end faces S1 are aligned along the second direction D2. Note that the plurality of end faces S1 may be formed continuously to form a single end face S1.

[0044] As shown in FIG. 6, the outer surface of the first exterior member 60 has a plurality of end faces S2. The plurality of end faces S2 are on the negative side of the portions 61, 62, and 63 in the first direction D1. The plurality of end faces S2 are aligned along the second direction D2. The plurality of end faces S2 may be formed continuously to form a single end face S2. Each of the plurality of portions 63 is sandwiched between an end face S1 and an end face S2 in the first direction D1. The number of end faces S1 and the number of end faces S2 are equal to the number of portions 63.

[0045] The second exterior member 70 is in the form of a plate that covers the recess 60a of the first exterior member 60. The peripheral edge of the second exterior member 70 is joined to the flange portion 60b. Specifically, the peripheral edge of the second exterior member 70 and the flange portion 60b are joined by, for example, vibration welding or heat welding. As a result, the exterior member 52 accommodates the heat-absorbing agent 51 in a sealed state.

[0046] Next, a process for forming the grooves 64 in the first exterior member 60 will be described. Fig. 9 is a schematic diagram showing the process for forming the first exterior member 60 by injection molding. The arrows in Fig. 9 indicate the flow of the resin R, which is the material of the first exterior member 60, within the cavity of the mold for the first exterior member 60 during molding.

[0047] The gates of the mold for the first exterior member 60 are located at positions corresponding to the protrusions 63a of the first exterior member 60. In other words, there are four gates of the mold. The gates of the mold are so-called pin gates.

[0048] Resin R flows into the mold cavity from each of the four gates and flows from the gate (protrusion 63a) toward positions corresponding to both sides in the first direction D1 and positions corresponding to both sides in the second direction D2, as shown by the solid arrows in Figure 9. Furthermore, resin R flowing from each of two gates adjacent to each other in the second direction D2 hits a position corresponding to the center of portion 61. At this time, the temperature of resin R on the surface side of resin R is lower than that of the interior of resin R, and therefore solidification of resin R is progressing. Therefore, resin R does not fuse sufficiently on the surface side of resin R, and grooves 64 are formed on the surface of portion 61.

[0049] 9, the resin R flows toward positions corresponding to both sides of the first direction D1 and toward a position corresponding to the center of the portion 61 in the second direction D2. As the resin R further hits the position corresponding to the center of the portion 61 in the second direction D2, the groove 64 extends along the first direction D1.

[0050] When the first exterior member 60 is removed from the mold, the first exterior member 60 and the gate are separated, and convex portions 63a, which are gate marks, are formed on the first exterior member 60. In this way, by providing gates at positions corresponding to the convex portions 63a of the first exterior member 60, that is, positions corresponding to the centers in the first direction D1 of the portion 63 on both ends of the portion 61 in the second direction D2, it is possible to form grooves 64 in the portion 61.

[0051] Next, a description will be given of the operation of the battery pack 1 when abnormal heat is generated in the secondary battery 41. Abnormal heat generation in the secondary battery 41 occurs, for example, due to a short circuit in the secondary battery 41 or external heating.

[0052] The heat-absorbing member 50 is in contact with the secondary battery 41. Therefore, when the secondary battery 41 generates abnormal heat, the heat of the secondary battery 41 is transferred to the heat-absorbing member 50, causing the temperatures of the exterior member 52 and the heat-absorbing agent 51 to rise. The temperature rise of the heat-absorbing agent 51 causes the internal pressure of the heat-absorbing member 50 to rise.

[0053] Here, the thickness of the portion 61 where the groove 64 is formed is thinner than the thickness of other portions (see FIG. 8). Therefore, the strength of the portion 61 where the groove 64 is formed is weaker than the strength of other portions. Furthermore, the internal pressure of the heat-absorbing member 50 acts evenly on the inner surface of the portion 61.

[0054] Therefore, when the internal pressure of the heat-absorbing member 50 increases, the grooves 64 act as starting points to split the first exterior member 60. As a result, the heat-absorbing agent 51 leaks from the exterior member 52 and adheres to the secondary battery 41. Furthermore, the heat-absorbing agent 51 adhered to the secondary battery 41 evaporates, and the temperature of the secondary battery 41 drops.

[0055] In this way, the grooves 64 serve as starting points for splitting the first exterior member 60, so that the heat absorption member 50 can be easily split when the secondary battery 41 generates abnormal heat. Furthermore, when the secondary battery 41 generates abnormal heat, the portion 61 in contact with the secondary battery 41 is directly heated by the secondary battery 41 and softens. Therefore, the first exterior member 60 can be more easily split using the grooves 64 as starting points.

[0056] In addition, when the endothermic agent 51 has fluidity, the endothermic agent 51 flows along the outer surface of the secondary battery 41, thereby increasing the contact area between the endothermic agent 51 and the secondary battery 41 compared to when the endothermic agent 51 does not have fluidity, and the temperature of the secondary battery 41 can be reduced more quickly.

[0057] Furthermore, abnormal heat generation in the secondary battery 41 may cause the split valve 41g to open, and the exterior member 52 may be heated by gas and sparks ejected from the split valve 41g, causing the part of the exterior member 52 heated by the sparks to split open. The sparks may be generated from, for example, a part of the current collecting foil or an electrode.

[0058] <Modification of the first embodiment> For example, the groove 64 may be located in a position other than the center of the portion 61 in the second direction D2, and may extend along a direction that is inclined with respect to the first direction D1. The groove 64 may also be curved in a plan view of the first exterior member 60. Furthermore, the groove 64 may be located on the inner surface of the portion 61.

[0059] In the portion 61, the thickness of the portion where the groove 64 is formed is thinner than the thickness of other portions, regardless of the position of the groove 64. Therefore, in the portion 61, the strength of the portion where the groove 64 is formed is weaker than the strength of other portions. Furthermore, as described above, the internal pressure of the heat-absorbing member 50 acts evenly on the inner surface of the portion 61. Therefore, when the internal pressure of the heat-absorbing member 50 increases, the groove 64 becomes the starting point and the first exterior member 60 splits open, regardless of the position of the groove 64.

[0060] Alternatively, the groove 64 may be provided in the portion 62. In this case, the first exterior member 60 may further have a protrusion 63a on the opposite side of the portion 62 from the portion 63 in the second direction D2. In this case, the groove 64 is formed in the portion 62 as in the portion 61, and when the secondary battery 41 generates abnormal heat, the groove 64 becomes the starting point for cracking of the first exterior member 60 as in the first embodiment described above, and the heat absorption member 50 can easily crack when the secondary battery 41 generates abnormal heat.

[0061] Furthermore, the protrusion 63a may be located at a position other than the center of the portion 63 in the first direction D1, and one portion 63 may have a plurality of protrusions 63a.

[0062] Regardless of the position and number of the protrusions 63a in the portion 63, as long as there are protrusions 63a, the resin R flowing in from each gate (protrusion 63a) during molding of the first exterior member 60 hits the position corresponding to the portion 61. That is, a groove 64 is formed in the portion 61. As a result, the groove 64 becomes the starting point for splitting the first exterior member 60, as in the first embodiment described above.

[0063] 10 is a diagram showing the position of the protrusions 63a according to another modified example of the first embodiment of the present disclosure. In this modified example, the number of protrusions 63a is two. The protrusions 63a are arranged on the flange portion 60b. The two protrusions 63a are arranged on both sides of the portion 61 in the central portion in the second direction D2. In this case, the groove 64 is formed in the central portion of the first exterior member 60 in the first direction D1 so as to extend along the second direction D2.

[0064] 11 is a diagram showing the position of the protrusions 63a according to another modified example of the first embodiment of the present disclosure. In this modified example, the number of protrusions 63a is two. When the first exterior member 60 is viewed in the first direction D1, the two protrusions 63a overlap each other. When the first exterior member 60 is viewed in the first direction D1, the protrusions 63a are arranged on the end faces S1 and S2 that overlap each other. In this case, the groove 64 is formed in the center of the first exterior member 60 in the first direction D1 so as to extend along the second direction D2.

[0065] FIG. 12 is a diagram showing the positions of the protrusions 63a according to another modified example of the first embodiment of the present disclosure. In this modified example, the number of protrusions 63a is two. When the first exterior member 60 is viewed along the first direction D1, the two protrusions 63a are arranged in positions where they do not overlap. One protrusion 63a is arranged on the third end face S1 from the negative side in the second direction D2 among the multiple end faces S1. On the other hand, the other protrusion 63a is arranged on the second end face S2 from the negative side in the second direction D2. In this case, the grooves 64 are formed so as to extend from the positive side to the negative side in the first direction D1 as they extend from the negative side to the positive side in the second direction D2 in the first exterior member 60. In another variant shown in Figures 10, 11 and 12, when the secondary battery 41 generates abnormal heat, the groove 64 becomes the starting point for the cracking of the first exterior member 60, so that the heat absorption member 50 can easily crack when the secondary battery 41 generates abnormal heat.

[0066] Furthermore, the grooves 64 may be formed by convex shapes of a mold, rather than by weld lines. Even in the case of such grooves 64, when the secondary battery 41 generates abnormal heat, the grooves 64 become the starting points for cleavage of the first exterior member 60 as described above, and the heat absorption member 50 can easily cleave when the secondary battery 41 generates abnormal heat.

[0067] Second Embodiment Next, the battery pack 1 and the heat absorbing member 150 of the second embodiment will be described, focusing mainly on the differences from the heat absorbing member 150 of the first embodiment.

[0068] 13 is an exploded perspective view of a battery unit 40 according to a second embodiment of the present disclosure. The battery unit 40 of the second embodiment has four secondary batteries 41 arranged in two rows and three heat-absorbing members 150.

[0069] 14 is an exploded perspective view of the exterior member 152. The exterior member 152 has a hollow columnar shape extending along the first direction D1. A central axis 152a of the exterior member 152 extends along the first direction D1. A third direction D3 around the central axis 152a of the exterior member 152 shown in FIG. 14 corresponds to the circumferential direction of the exterior member 152.

[0070] The first exterior member 160 is cylindrical and has a portion 165 that intersects with the first direction D1 at the first end side in the first direction D1, a plurality of (specifically, four) portions 161 that extend along the first direction D1, and a plurality of (specifically, four) portions 166 that extend along the first direction D1. 2 Part 161 corresponds to the "first part." Part 166 corresponds to the "second part." 3 The portion 165, the plurality of portions 161 and the plurality of portions 166 are integral. The first exterior member 160 has an opening on the second end side in the first direction D1.

[0071] Fig. 15 is a perspective view of the first exterior member 160. Fig. 16 is a cross-sectional view of the first exterior member 160 taken along line AA shown in Fig. 15. Fig. 16 shows the cross-sectional shape of the first exterior member 160 when cut along a plane perpendicular to the first direction D1. As shown in Figs. 15 and 16, the four portions 161 are arranged continuously from the portion 165 and are aligned along the circumferential direction (third direction D3) of the exterior member 152. This allows the heat-absorbing member 150 to be arranged between the multiple secondary batteries 41 (see Fig. 13), thereby preventing the battery pack 1 from becoming larger.

[0072] 14 to 16, in the second embodiment, the cross-sectional shape of each portion 161 when cut along a plane perpendicular to the first direction D1 is a concave shape that is concave toward the inside of the first exterior member 160. In other words, each portion 161 is concave toward the central axis 152a of the exterior member 152. The cross-sectional shape of each portion 161 when cut along a plane perpendicular to the first direction D1 is a quadrant.

[0073] Furthermore, the central portion of the portion 161 in the circumferential direction of the exterior member 152 has a groove 164 which is a weld line extending substantially along the first direction D1.

[0074] The portions 166 are arranged on both sides of the portion 161 in the circumferential direction of the exterior member 152, and are continuous from the portion 161. The portions 166 that are continuous from two portions 161 that are adjacent to each other in the circumferential direction of the exterior member 152 are integral. In other words, the portions 166 connect the two portions 161 that are adjacent to each other in the circumferential direction of the exterior member 152 to each other. The thickness of the portions 166 is greater than the thickness of the portions 161.

[0075] The four portions 166 are arranged continuously from the portion 165. The portions 166 do not contact the outer peripheral surface of the cylindrical secondary battery 41. However, the portions 166 may contact the outer peripheral surface of the cylindrical secondary battery 41.

[0076] Fig. 17 is a cross-sectional view of the first exterior member 160 taken along line BB shown in Fig. 16. As shown in Figs. 16 and 17, the portion 165 integrally has a protrusion 163a, a base 165a, and a connecting portion 165b. The protrusion 163a is a gate mark and is located on the outer surface S3 of the portion 165 facing the positive side in the first direction D1. The protrusion 163a is located in the center of the portion 165 in a plan view of the portion 165. The base 165a is connected to an end of the portion 161 on the first end side in the first direction D1.

[0077] The thickness of the connecting portion 165b is greater than the thickness of the base portion 165a. The inner surface of the connecting portion 165b is located more inside the first exterior member 160 than the inner surface of the base portion 165a.

[0078] The connecting portion 165b connects the four portions 166 and the protruding portion 163a. ​​Specifically, as shown in Fig. 16, the connecting portion 165b connects two of the four portions 166 that face each other in a plan view of the portion 165, and overlaps with two diagonal lines L that intersect with each other. In other words, the connecting portion 165b is X-shaped in a plan view of the portion 165. Furthermore, the protruding portion 163a overlaps with an intersection P of the two diagonal lines L in a plan view of the portion 165.

[0079] 14, the second exterior member 170 is plate-shaped and covers the opening of the first exterior member 160. The peripheral edge of the second exterior member 170 is joined to the end of the first exterior member 160 on the second end side in the first direction D1. Specifically, the peripheral edge of the second exterior member 170 and the end of the first exterior member 160 are joined by, for example, vibration welding and heat welding. This seals in the heat-absorbing agent 51.

[0080] Next, the process of forming the grooves 164 in the first exterior member 160 will be described. Fig. 18 is a schematic diagram showing the process of forming the first exterior member 160 by injection molding. The arrows in Fig. 18 indicate the flow of resin R, which is the material of the first exterior member 160, within the cavity of the mold for the first exterior member 160 during molding. The gate of the mold for the first exterior member 160 is located at a position corresponding to the protrusion 163a of the first exterior member 160. That is, in this second embodiment, there is one gate of the mold.

[0081] The resin R flows into the cavity of the mold through one gate. Because the thickness of the connecting portion 165b is greater than the thickness of the base portion 165a, in the region corresponding to the portion 165, the flow rate (flow rate per unit time; the same applies below) of the resin R flowing from the gate (the protruding portion 163a) to the positions corresponding to the four portions 166 is greater than the flow rate of the resin R flowing from the gate to the positions corresponding to the central portions of the portions 161 in the circumferential direction of the exterior member 152.

[0082] Furthermore, because the thickness of portion 166 is greater than the thickness of portion 161, the flow rate of resin R flowing through the portion corresponding to portion 166 is greater than the flow rate of resin R flowing through the portion corresponding to portion 161, and resin R flows through the portion corresponding to portion 166 before the portion corresponding to portion 161. As a result, as shown by the arrow in Fig. 18, a flow of resin R occurs from the portion corresponding to portion 166 toward a position corresponding to the center of portion 161 in the third direction D3. Therefore, resin R flowing from the portion corresponding to portion 166 hits the portion corresponding to the center of portion 161 in the third direction D3, creating a groove 164 along the first direction D1.

[0083] As described above, the thickness of connecting portion 165b is greater than the thickness of base portion 165a, and the thickness of portion 166 is greater than the thickness of portion 161, so that the flow of resin R is adjusted and groove 164 is formed along first direction D1 in the central portion of portion 161 in the third direction D3. Furthermore, as described above, when portion 165 is viewed in plan, intersection P of two diagonal lines L that overlap with connecting portion 165b overlaps with protruding portion 163a, so that the flow rate of resin R flowing from the gate (protruding portion 163a) toward four portions 166 can be made uniform and groove 164 can be formed in the central portion of portion 161 in the third direction D3.

[0084] In the exterior member 152 of this second embodiment, when the secondary battery 41 generates abnormal heat, the groove 164 becomes the starting point for cracking of the first exterior member 60, so that the heat absorption member 50 can easily crack when the secondary battery 41 generates abnormal heat.

[0085] <Modification of the second embodiment> For example, it goes without saying that the number of the portions 161 and the portions 166 in the first exterior member 160 is not limited to four.

[0086] Furthermore, the protrusion 163a may be located at a position other than the position overlapping with the intersection P in a planar view of the portion 165 (for example, a position where the protrusion 163a overlaps with the connecting portion 165b in a planar view). The connecting portion 165b may have a shape (for example, a linear or T-shape) that connects at least one portion 166 and the protrusion 163a. ​​Even in these cases, when the first exterior member 160 is molded, the flow rate of the resin R flowing from the gate (the protrusion 163a) to a position corresponding to the portion 166 is greater than the flow rate of the resin R flowing from the gate to a position corresponding to the center of the portion 161 in the circumferential direction of the exterior member 152. Therefore, as in the second embodiment described above, the groove 164 is formed in the portion 161. However, if the timing at which the resin R arrives at each of the four portions 166 differs, the groove 164 may be formed in a portion of the portion 161 other than the center of the portion 161 in the third direction D3.

[0087] Furthermore, the connecting portion 165b may have a shape that protrudes from the outer surface S3 toward the outside of the first exterior member 160. In this case, as in the second embodiment described above, when the first exterior member 160 is molded, in the region corresponding to the portion 165, the flow rate of the resin R that flows from the gate (the protruding portion 163a) to the position corresponding to the four portions 166 is greater than the flow rate of the resin R that flows from the gate to the position corresponding to the center of the portion 161 in the circumferential direction of the exterior member 152. Therefore, as in the second embodiment described above, the groove 164 is formed in the portion 161.

[0088] Furthermore, the first exterior member 160 does not need to include the connecting portion 165b. In this case, the thickness of the portion 165 is constant. In this case, as in the second embodiment described above, the thickness of the portion 166 is greater than the thickness of the portion 161, and therefore the flow rate of the resin R flowing through the portion corresponding to the portion 166 is greater than the flow rate of the resin R flowing through the portion corresponding to the portion 161, and the resin R flows through the portion corresponding to the portion 166 before the portion corresponding to the portion 161. As a result, as shown by the arrow in FIG. 18 , a flow of the resin R occurs from the portion corresponding to the portion 166 toward a position corresponding to the center of the portion 161 in the third direction D3. Therefore, the groove 164 is formed by the resin R that has flowed from the portion corresponding to the portion 166.

[0089] FIG. 19 is a diagram showing the positions of the protrusions 163a according to another modification of the second embodiment of the present disclosure. In this modification, the number of protrusions 163a is four. The four protrusions 163a are arranged on the outer surface S3. When the first exterior member 160 is viewed in the first direction D1, the protrusions 163a overlap with the portion 166. In this case, as in the second embodiment, the groove 164 is formed in each of the four portions 161 so as to extend along the first direction D1 at the center of the third direction D3. The groove 164 is also formed in the portion 165. When the first exterior member 160 is viewed in the first direction D1, the grooves 164 of the two portions 161 that are opposite each other are connected to each other via the groove 164 of the portion 165. When the first exterior member 160 is viewed in the first direction D1, the groove 164 of the portion 165 is X-shaped.

[0090] 20 is a diagram showing the position of the protrusion 163a according to another modification of the second embodiment of the present disclosure. In this modification, the number of protrusions 163a is two. The two protrusions 163a are located in one of the four portions 166 and are spaced apart from each other in the first direction D1. In this case, the groove 164 is formed to extend between the two protrusions 163a along the third direction D3. In the other modification shown in FIGS. 19 and 20 , when the secondary battery 41 generates abnormal heat, the groove 164 becomes the starting point for tearing of the first exterior member 160, and the heat absorption member 150 can easily tear when the secondary battery 41 generates abnormal heat.

[0091] The above-described embodiments and modifications are intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. The present disclosure may be modified or improved without departing from the spirit thereof, and equivalents thereof are also included in the present disclosure.

[0092] <Configuration Example of the Present Disclosure> The present disclosure may also be implemented as a combination of the following configurations.

[0093] (1) An endothermic agent; an exterior member that accommodates the heat-absorbing agent; the exterior member has a first portion that contacts an object, The first portion has a groove. Heat absorbing material.

[0094] (2) the first portion extends along a first direction; The cross-sectional shape of the first portion when cut along a plane perpendicular to the first direction is concave. The heat-absorbing member according to (1).

[0095] (3) the exterior member further includes second portions that are arranged on both sides of the first portion in a direction perpendicular to the first direction and are continuous with the first portion, The second portion has a protrusion. The heat-absorbing member according to (2).

[0096] (4) The first portion is plural, The plurality of first portions are arranged in parallel along a direction perpendicular to the first direction. The heat-absorbing member according to (2) or (3).

[0097] (5) the exterior member has a columnar shape extending along the first direction and further has a third portion intersecting the first direction at a first end side in the first direction, the first portion is disposed contiguously with the third portion; The third portion has a protrusion. The heat-absorbing member according to (2).

[0098] (6) the exterior member further includes fourth portions disposed on both sides of the first portion in the circumferential direction of the exterior member and continuing from the first portion, The thickness of the fourth portion is greater than the thickness of the first portion. The heat-absorbing member according to (5).

[0099] (7) The third portion is A base and a connecting portion that connects the fourth portion and the protruding portion, The thickness of the connecting portion is greater than the thickness of the base portion. The heat-absorbing member according to (6).

[0100] (8) the exterior member has four of the first portions and four of the fourth portions arranged in parallel along the circumferential direction of the exterior member, the fourth portion connects two of the first portions that are adjacent to each other in the circumferential direction of the exterior member, the connecting portion connects two of the four fourth portions that are opposed to each other in a plan view of the third portion, and overlaps with two diagonal lines that intersect with each other; The convex portion overlaps with an intersection of the two diagonal lines in the plan view. The heat-absorbing member according to (7).

[0101] (9) The convex portion is a gate mark. A heat-absorbing member according to any one of (3) and (5) to (8).

[0102] (10) The groove is a weld line. A heat-absorbing member according to any one of (1) to (9).

[0103] (11) A heat-absorbing member according to any one of (1) to (10), a secondary battery; the target object is the secondary battery, Battery pack. [Explanation of symbols]

[0104] 1 battery pack 41 Secondary battery 50 Heat absorption member 51 Endothermic agent 52 Exterior materials 60 First exterior member 61 Part (First Part) 62 parts 63 copies minutes 63a Convex part 64 Groove 70 Second exterior member 165 Part (Chapter 165) 2 part) 165a base 165b Connection section 166 Part (Chapter 166) 3 part) D1 1st direction L diagonal P intersection

Claims

1. An endothermic agent; an exterior member having a columnar shape extending along a first direction and accommodating the heat-absorbing agent; The exterior member is a first portion extending along the first direction and contacting an object; a second portion intersecting the first direction on a first end side in the first direction; a third portion disposed on each side of the first portion in the circumferential direction of the exterior member and continuing from the first portion; a cross-sectional shape of the first portion when cut along a plane perpendicular to the first direction is concave, the first portion has a groove and is disposed continuously from the second portion; The second portion is A base and A convex portion, a connecting portion that connects the third portion and the protrusion, The thickness of the connecting portion is greater than the thickness of the base portion, The thickness of the third portion is greater than the thickness of the first portion. Heat absorbing material.

2. the exterior member has four of the first portions and four of the third portions arranged in parallel along a circumferential direction of the exterior member, the third portion connects two of the first portions that are adjacent to each other in the circumferential direction of the exterior member, the connecting portion connects two of the four third portions that are opposed to each other in a plan view of the second portion, and overlaps with two diagonal lines that intersect with each other; The convex portion overlaps with an intersection of the two diagonal lines in the plan view. The heat absorbing member according to claim 1 .

3. The convex portion is a gate mark. The heat absorbing member according to claim 1 or 2.

4. The groove is a weld line. The heat absorbing member according to claim 1 or 2.

5. The heat absorbing member according to claim 1 or 2; a secondary battery; the target object is the secondary battery, Battery pack.

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