Secondary batteries

Abstract

To effectively cool a battery while suppressing short-circuit of a bus bar or deterioration of metal.SOLUTION: A flat secondary battery 1 includes: an electrode body 10 including positive electrode collection foil parts and negative electrode collection foil parts at respective end parts in a horizontal direction; a case including a plurality of battery boxes 23 in which the electrode bodies 10 are aligned and accommodated individually so that the positive electrode collection foil parts and the negative electrode collection foil parts are disposed alternately; a plurality of bus bars 8 disposed in the case and connecting the positive electrode collection foil parts and the negative electrode collection foil parts accommodated in the adjacent battery boxes 23; and a lid body. The bus bar 8 airtightly seals the battery box 23 and is connected to the electrode body 10 in the battery box 23 disconnected from a vertical ventilation path 27. A part of the bus bar 8 is configured as a heat dissipation surface facing the vertical ventilation path 27 extending in a vertical direction communicating with the outside air along the bus bar. The vertical ventilation path 27 communicates with the outside air by a bottom part ventilation path at a lower part and an upper end thereof communicates with the outside air by an exhaust hole provided in the lid body.SELECTED DRAWING: Figure 33

Description

Technical Field

[0001] The present invention relates to a secondary battery, and more particularly to a secondary battery that effectively cools the battery while suppressing short circuits in the bus bar and deterioration of the metal.

Background Art

[0002] Conventionally, secondary batteries, such as non-aqueous electrolyte secondary batteries like lithium-ion secondary batteries and alkaline secondary batteries like nickel-metal hydride storage batteries, have a high energy density and are widely used as power sources for electric vehicles and hybrid vehicles, and as stationary power sources for homes and factories.

[0003] In such secondary batteries, conventionally, a plurality of battery cells each containing a wound body of an electrode body were connected in series in one battery case to form a battery pack that obtained a voltage suitable for the purpose.

[0004] Further, Patent Document 1 discloses a lead battery including a plurality of lead battery cells, an auxiliary battery including a plurality of power storage elements, and a composite battery that houses the lead battery and the auxiliary battery in one case whose interior is partitioned into a plurality of battery compartments.

[0005] In a configuration in which a general cell battery is stacked and combined in large numbers, or in a battery pack having a large number of battery compartments like the battery described in Patent Document 1, a high voltage can be obtained by combining a large number of single batteries in a compact configuration.

[0006] Here, in the lead battery, the energy density is also low, and there were no such problems with heat dissipation. However, in batteries with a high energy density, heat dissipation becomes a problem. In conventional battery packs, there was a type in which battery cells were stacked and externally connected terminals were electrically connected by a bus bar, and outside air was introduced here to cool the battery. With such a configuration, the battery could be efficiently cooled via the bus bar.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-175128 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, directly introducing outside air for cooling the busbars could cause short circuits or metal degradation due to dust and chemicals in the outside air. The problem that the secondary battery of the present invention aims to solve is to effectively cool the battery while suppressing busbar short circuits and metal degradation in the secondary battery. [Means for solving the problem]

[0009] To solve the above problems, the secondary battery of the present invention comprises a plurality of flat electrode bodies in which positive electrodes and negative electrodes are alternately stacked and each horizontal end has a positive electrode busbar connection portion and a negative electrode busbar connection portion; a case having an open top and a plurality of cells that individually house the plurality of flat electrode bodies, which are aligned such that the positive electrode busbar connection portions and the negative electrode busbar connection portions are alternately arranged in the thickness direction; a plurality of busbars that connect the positive electrode busbar connection portions and the negative electrode busbar connection portions of the electrode bodies housed in adjacent cells, and a lid that seals the cells of the case, wherein the busbars are arranged in the case and constitute the cell airtightness of the cell as part of the cell, and a part thereof is configured to dissipate heat to the outside of the cell as a heat dissipation surface.

[0010] The heat dissipation surface of the busbar may face a space that is in communication with the outside air. The space communicating with the outside air may be a vertical ventilation passage extending vertically along the busbar.

[0011] The heat dissipation surface of the busbar may be arranged along the inner circumferential surface of the vertical ventilation passage. A heat sink may be provided on the heat dissipation surface of the busbar.

[0012] The intake port at the lower end of the lead-through air passage may communicate with the outside air through an intake opening provided below the battery cell. A bottom air passage, which is a space communicating the intake opening and the intake port of the lead-through air passage, may be provided entirely below the electrode body housed in the battery cell of the case.

[0013] A fan for introducing outside air may be provided at the intake opening provided below the battery cell. The exhaust port at the upper end of the lead-through air passage may communicate with the outside air through an exhaust hole provided in the lid body.

Advantages of the Invention

[0014] According to the secondary battery of the present invention, it is to effectively cool the battery while suppressing a short circuit of the bus bar and deterioration of metal in the secondary battery.

Brief Description of the Drawings

[0015] [Figure 1] It is a perspective view of the appearance of the secondary battery. [Figure 2] It is a perspective view of the appearance of the secondary battery with the lid body removed. [Figure 3] It is a plan view of the appearance of the secondary battery. [Figure 4] It is a plan view of the appearance of the secondary battery with the lid body removed. [Figure 5] It is a front view of the appearance of the secondary battery. [ [Figure 6] It is a rear view of the appearance of the secondary battery. [Figure 7] It is a left side view of the appearance of the secondary battery. [Figure 8] It is a right side view of the appearance of the secondary battery. [Figure 9] It is a bottom view of the appearance of the secondary battery. [Figure 10] It is an exploded perspective view of the secondary battery. < / / [Figure 11] It is a perspective view of the electrode body. [Figure 12] It is a plan view of the electrode body. [Figure 13] It is a front view of the electrode body. [Figure 14] It is a rear view of the electrode body. [Figure 15] It is a partially developed view showing the configuration of the electrode body 10. [Figure 16] It is a schematic diagram showing the process of impregnating the electrode body 10 with a non-aqueous electrolyte. [Figure 17] It is a perspective view of the case. [Figure 18] It is a plan view of the case. [Figure 19] It is a partially enlarged view of the plan view of the case. [Figure 20] It is a bottom view of the case. [Figure 21] It is a perspective view showing the bus bar and the position for inserting the bus bar into the case. [Figure 22] It is a schematic diagram showing an example of the composition of the material of the bus bar of this embodiment. Fig. 22(a) is a view in plan view, and Fig. 22(b) is a view seen from the outside. [Figure 23] It is a schematic diagram showing another example of the composition of the material of the bus bar of this embodiment. [Figure 24] It is a perspective view of the flexible substrate. [Figure 25] It is a perspective view of the bus bar arranged in the case, the temperature / voltage detection part arranged here, and the flexible substrate connecting them. [Figure 26] It is an enlarged view of a part of the perspective view of the case shown in Fig. 17. [Figure 27] It is a view showing the part where the front plate and the lid are welded in Fig. 26. [Figure 28] It is an enlarged perspective view of a part of Fig. 25 showing the connection between the electrode body and the bus bar. [Figure 29] It is a perspective view of the state where the electrode body is attached to the bus bar shown in Fig. 25. [Figure 30] It is a view showing the state where the central part of the positive electrode current collector foil of the electrode body housed in the battery is pressed against the positive electrode connection surface of the bus bar by a clip and laser welding is performed. [Figure 31]Figure 25 is a plan view showing the busbar with the electrodes attached. [Figure 32] This is a perspective view of section 32-32 in Figure 5. [Figure 33] This is an enlarged view of a portion of section 32-32 in Figure 5. [Figure 34] This is a cross-sectional view of section 34-34 in Figure 4. [Figure 35] This is a cross-sectional view of section 35-35 in Figure 4. [Figure 36] This is a perspective view of the lid from below. [Figure 37] This is a front view of the lid. [Figure 38] This is a magnified perspective view of a portion of Figure 36. [Figure 39] This is a cross-sectional view of section 39-39 in Figure 3. [Figure 40] This is a perspective view showing an electrode body being welded to a busbar using a modified clip of the clip according to this embodiment. [Modes for carrying out the invention]

[0016] Hereinafter, the secondary battery of the present invention will be described with reference to Figures 1 to 40, using a secondary battery 1 consisting of a lithium-ion secondary battery pack according to one embodiment. (Configuration of this embodiment) <Appearance of secondary battery 1> Figure 1 is a perspective view of the external appearance of the secondary battery 1. Figure 3 is a top view of the external appearance of the secondary battery 1. Figure 5 is a front view of the external appearance of the secondary battery 1. Figure 6 is a rear view of the external appearance of the secondary battery 1. Figure 7 is a left side view of the external appearance of the secondary battery 1. Figure 8 is a right side view of the external appearance of the secondary battery 1. Figure 9 is a bottom view of the external appearance of the secondary battery 1.

[0017] The secondary battery 1 of this embodiment is configured as a battery pack comprising a plurality of battery cells (28 in this embodiment). As shown in Figure 1, the secondary battery 1 is roughly a rectangular prism overall, with a length along the length direction L, a width direction W perpendicular to the length direction L, which is approximately 30% of the length, and a height direction H, which is approximately 23% of the length. In Figure 1, the front left is referred to as the "front," the front right as the "right," and the top as the "top."

[0018] Figure 10 is an exploded perspective view of the secondary battery 1. As shown in Figures 1 and 8, the right side of the secondary battery 1 is covered by the rectangular right end plate 21R of case 2. Also, as shown in Figure 7, the left side of the secondary battery 1 is covered by the rectangular left end plate 21L of case 2. Case 2 is the framework of the secondary battery 1, which is generally rectangular as a whole, as shown in Figure 10.

[0019] As shown in Figures 1, 3, and 10, a rectangular lid 5 is positioned to cover the top 2U of case 2. As shown in Figures 1, 5, and 10, a rectangular front panel 7F, which constitutes the side panel 7, is positioned to cover the front 2F of case 2. As shown in Figures 6 and 10, a rectangular back panel 7B, which constitutes the side panel 7, is positioned to cover the rear 2B of case 2. As shown in Figure 9, a rectangular bottom panel 6 is positioned to cover the bottom 2D of case 2.

[0020] <Outline of the assembly of secondary battery 1> Next, with reference to Figure 10, the general assembly of the secondary battery 1 will be explained. Figure 21 is a perspective view showing the busbar 8 and the position in which the busbar 8 is inserted into the case 2. Figure 25 is a perspective view of the busbar 8 inserted and positioned in the case 2 shown in Figure 17, the temperature / voltage detection unit 91 positioned therein, and the flexible substrate 9 connecting them. First, as shown in Figures 21 and 25, the busbar 8 is inserted into a predetermined position in the case 2 during the molding process. The temperature / voltage detection unit 91 is provided on the busbar 8 positioned in this manner. Then, the flexible substrate 9 connecting these temperature / voltage detection units 91 is positioned around the case 2.

[0021] Figure 2 is a perspective view of the secondary battery 1 with the cover 5 removed. Figure 4 is a plan view of the secondary battery 1 with the cover 5 removed. As shown in Figure 4, 28 electrode bodies 10 are inserted into the battery case 23 of this case 2. The electrode bodies 10 inserted into the battery case 23 are welded to the busbar 8 and electrically connected.

[0022] Subsequently, the front panel 7F, which constitutes the side panel 7, is welded to the front part 2F of case 2 as shown in Figure 10. Also, the back panel 7B, which constitutes the side panel 7, is welded to the back part 2B of case 2. The bottom panel 6 is welded to the bottom part 2D of case 2.

[0023] Then, a lid 5 is welded to the top 2U of the case 2, which houses the electrode body 10. The side plate 7 and the lid 5 are welded to the case 2, forming an airtight battery case 23. Next, we will describe in detail the components of each secondary battery 1.

[0024] <Electrode body 10> Figure 11 is a perspective view of the electrode body 10, Figure 12 is a plan view of the electrode body 10, Figure 13 is a front view of the electrode body 10, and Figure 14 is a rear view of the electrode body 10.

[0025] As shown in Figure 11, the electrode body 10 is generally a plate-shaped member. As shown in the front view in Figure 13 and the rear view in Figure 14, the cross-sectional shape perpendicular to the width direction W, which is the longitudinal direction, is shaped like a vertically elongated track.

[0026] Here, Figure 15 is a partially unfolded view showing the configuration of the electrode body 10. The electrode body 10 is made up of a long positive electrode plate 12 and a negative electrode plate 13, laminated together via a separator 11. The positive electrode plate 12 has a positive electrode composite layer containing a positive electrode active material on a metal foil substrate such as Al, and its right end has a positive electrode foil collection portion 12a where the Al foil is exposed. This positive electrode foil collection portion 12a protrudes to the right in Figure 15. This positive electrode foil collection portion 12a is an example of the "positive electrode busbar connection portion" of the present invention. On the other hand, the negative electrode plate 13 has a negative electrode composite layer containing a negative electrode active material on a metal foil substrate such as Cu, and its left end has a negative electrode foil collection portion 13a where the Cu foil is exposed. This negative electrode foil collection portion 13a protrudes to the left in Figure 15. This negative electrode foil collection portion 13a is an example of the "negative electrode busbar connection portion" of the present invention. The stacked positive electrode plate 12, negative electrode plate 13, and separator 11 are then rolled up so that the separator 11 is on the outermost periphery, and pressed flat. As a result, as shown in the upper part of Figure 15, the cross-sectional shape perpendicular to the width direction W, which is the longitudinal direction, becomes a stacked section 10a with a shape resembling a vertically elongated racing track.

[0027] At this time, the central part 12c of the positive electrode foil collection section 12a, which is slightly above the center in the height direction H, is pressed thinly in the thickness direction of the electrode body 10. As a result, the upper part 12b of the positive electrode foil collection section at the top in the height direction H and the lower part 12d of the positive electrode foil collection section at the bottom in the height direction H are thicker than the central part 12c of the positive electrode foil collection section.

[0028] Similarly, the central part 13c of the negative electrode foil collection section 13a, which is slightly above the center in the height direction H, is thinned by pressing in the thickness direction of the electrode body 10. As a result, the upper part 13b of the negative electrode foil collection section at the top of the height direction H and the lower part 13d of the negative electrode foil collection section at the bottom of the height direction H are thicker than the central part 13c of the negative electrode foil collection section.

[0029] As shown in Figure 13, the electrode body 10 manufactured in this manner has a positive electrode foil collection section upper part 12b and a positive electrode foil collection section lower part 12d at the top of the height H, which are thicker than the central part 12c of the positive electrode foil collection section. Also, as shown in Figure 14, the negative electrode foil collection section upper part 13b and a negative electrode foil collection section lower part 13d at the bottom of the height H are thicker than the central part 13c of the negative electrode foil collection section.

[0030] <Impregnation of electrode body 10 with non-aqueous electrolyte> Figure 16 is a schematic diagram showing the process of impregnating the electrode body 10 with a non-aqueous electrolyte 14. In this embodiment, the electrode body 10 is impregnated with the non-aqueous electrolyte 14 before being housed in the battery case 23. Conventionally, the electrode body 10 was generally connected to an external electrode via a lid, with a current collector welded to it. The electrode body 10 assembled in this manner was housed in a battery case and sealed with a lid. The non-aqueous electrolyte 14 was then poured into the sealed battery case through an injection port.

[0031] However, impregnating the electrode body 10 with the non-aqueous electrolyte 14 using conventional methods requires a long time, and it is difficult to completely remove air and other particles that have entered the gaps of the stacked porous separator. Furthermore, in conventional secondary batteries, the electrode body, welded to the current collector, is housed in the battery case, and the electrolyte is poured in while the case is sealed with a lid.

[0032] On the other hand, in the secondary battery of this embodiment, the electrode body 10 is placed in the battery case 23 after being impregnated with a non-aqueous electrolyte 14 under vacuum. In this state, the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a of the electrode body 10 are foil-collected but not welded. Therefore, the non-aqueous electrolyte 14 penetrates more easily from the ends of the electrode body 10 than in the state after foil collection. Furthermore, if the electrode body 10 is impregnated with a non-aqueous electrolyte 14 in this way, the electrode body 10 is placed in the battery case 23 with an open connection hole 28, and before completely sealing it, the electrode body 10, which already contains the non-aqueous electrolyte 14, is welded to the busbar 8 through the connection hole 28. After that, the battery case 23 is sealed. The non-aqueous electrolyte 14 is impregnated into the electrode body 10 through this process. Therefore, compared to conventional methods of welding the positive electrode foil collecting portion 12a and the negative electrode foil collecting portion 13a to the current collecting member and then permeating the electrode body 10 with the non-aqueous electrolyte 14, this method allows for far more efficient permeation of the non-aqueous electrolyte 14 into the electrode body 10.

[0033] The procedure for impregnating the electrode body 10 with the non-aqueous electrolyte 14 is described below. <step1> First, the electrode body 10 is manufactured using the method described above. At this stage, the positive electrode foil collection section 12a and the negative electrode foil collection section 13a are not welded, allowing the non-aqueous electrolyte 14 to easily penetrate the separator 11 from the edges.

[0034] <step2> Next, the electrode body 10 is placed in a vacuum container 15. The vacuum container 15 has an airtight structure. The material of the vacuum container 15 is not limited; it may be a large rigid tank made of SUS material or similar material for processing large quantities, or it may be made of flexible bags that individually contain the electrode body 10. By using such bags, the electrode body 10 can be immersed in a small amount of non-aqueous electrolyte 14. The material of the bag can be, for example, a laminate material made by laminating resin and aluminum foil. Once the electrode body 10 is placed inside, the vacuum container 15 is sealed. After sealing the vacuum container 15, the air inside the vacuum container 15 is sucked out from the degassing valve of the vacuum container 15 using a vacuum pump 16. In this process, air and water vapor present in the porous separator 11 between the positive electrode plate 12 and the negative electrode plate 13 of the electrode body 10 are also discharged. At this time, heating may be used to vaporize and discharge any remaining moisture inside the electrode body 10.

[0035] <step3> Once the vacuum chamber 15 is evacuated, the non-aqueous electrolyte 14 is injected through the injection port while maintaining the vacuum state. At this time, because there is no air in the porous separator 11 between the positive electrode plate 12 and the negative electrode plate 13 of the electrode body 10, the non-aqueous electrolyte 14 rapidly penetrates into every corner of the porous separator 11 between the positive electrode plate 12 and the negative electrode plate 13 of the electrode body 10 without leaving any gaps.

[0036] <step4> Once the non-aqueous electrolyte 14 has sufficiently permeated the electrode body 10, the vacuum state is released and the vacuum container 15 is opened to remove the electrode body 10 from the vacuum container 15. In this state, the non-aqueous electrolyte 14 is retained in the porous separator 11 structure between the positive electrode plate 12 and the negative electrode plate 13 of the electrode body 10. If necessary, the non-aqueous electrolyte 14 on the outside of the electrode body 10 is removed by drying or wiping.

[0037] At this time, it is preferable to prevent the internal non-aqueous electrolyte 14 from decreasing. For example, at this stage, the positive electrode foil collection section 12a and the negative electrode foil collection section 13a may be collected and welded, or connecting metal plates or metal foils may be attached to tightly seal the ends.

[0038] Subsequently, an electrode housing step is performed in which the electrode body 10, which has been permeated with the non-aqueous electrolyte 14, is housed in the battery case 23, and a connection step is performed in which the positive and negative electrodes of the electrode body 10 are connected to the busbar 8. Through these steps, the electrode body 10, which has been immersed in the non-aqueous electrolyte 14, is housed in the individual battery cases 23 of the case 2 and connected to the busbar 8 by laser welding via the connection holes 28. After welding the electrode body 10 to the busbar 8, after welding the front plate 7F and the back plate 7B, and before welding the lid 5, the non-aqueous electrolyte 14 may be preemptively replenished in the battery case 23.

[0039] <Case 2> Figure 17 is a perspective view of Case 2. Figure 18 is a plan view of Case 2. Figure 19 is a partially enlarged view of the plan view of Case 2. Figure 20 is a bottom view of Case 2.

[0040] Next, we will explain Case 2 with reference to Figures 17 to 20. Case 2 in this embodiment is a component that forms the framework of the secondary battery 1, and is characterized by the fact that its complex and multi-functional configuration is manufactured as a single unit by resin molding. Case 2 has the following functions.

[0041] Furthermore, case 2 primarily serves as the framework for the shape of the secondary battery 1. Case 2 also constitutes multiple battery cases 23. Together with the lid 5, it has the function of firmly holding the electrode bodies 10 housed in each battery case 23.

[0042] On the other hand, since each electrode body 10 is held by being sandwiched from above and below, the thickness direction (length direction L) of the electrode body 10 does not need to be constrained, and even if the electrode body 10 expands, the partition wall 25 of case 2 has the function of absorbing bending stress.

[0043] Furthermore, by inserting the busbar 8 into the case 2 and integrally molding it with resin, the busbar 8 is utilized as part of the wall of the airtight battery case 23. With this configuration, the busbar 8 functions as a heat sink that efficiently dissipates the heat from the electrode body 10 to the outside of the battery case 23 while maintaining the airtightness of the battery case 23.

[0044] Furthermore, the heat radiated from the battery case 23 is efficiently released into the atmosphere through the vertical air passage 27 formed by the case 2, thus providing a heat dissipation function. In addition, Case 2, together with the bottom plate 6, forms a bottom ventilation passage 24, which sends sufficient cold air from the intake opening 24a into the vertical ventilation passage 27, and the bottom ventilation passage 24 itself has the function of cooling the electrode body 10 housed in the battery case 23 from below.

[0045] Furthermore, although not shown in the illustration, the secondary battery 1 can also be directly attached to structural members such as vehicle members using the legs 26 shown in Figure 17, without needing to be housed in a battery pack or similar device.

[0046] <Overall structure of Case 2> As shown in Figure 17, the case 2 has a lower frame 2Fa of the front section 2F and a lower frame 2Ba of the rear section 2B at the lower ends of both ends in the width direction W, extending in a rod shape in the length direction L. The upper ends of each end are integrally connected to a thick, plate-shaped right end plate 21R and a left end plate 21L. These parts function as structural members that maintain the overall strength of the secondary battery 1.

[0047] <Legs 26> As shown in Figures 7 and 8, the lower surface of the lower frame 2Fa of the front section 2F and the lower surface of the lower frame 2Ba of the rear section 2B are flat surfaces formed flush with the bottom plate 6.

[0048] As shown in Figure 18, plate-shaped legs 26 are provided flush with the bottom 2D so as to protrude in the width direction W from the front 2F and rear 2B. The legs 26 consist of six parts: the right end, left end, and approximately the center of the front lower frame 2Fa that protrude in the width direction W, and the right end, left end, and approximately the center of the rear lower frame 2Ba that protrude in the width direction W. To prevent interference between the front legs 26 and the rear legs 26 when the secondary batteries 1 are aligned in the width direction W, the rear legs 26 have both ends offset inward in the length direction L, and the central leg 26 is offset to the right.

[0049] Figure 26 is an enlarged view of a portion of the perspective view of Case 2 shown in Figure 17. As shown in Figure 26, the leg portion 26 comprises a base portion 26a having parallel ends that protrude perpendicularly from the lower frames 2Fa and 2Ba, a tip portion 26b having an arc-shaped contour that is continuous with the base portion 26a, and a screw hole 26c for fastening that is concentric with the center of the arc.

[0050] A rubber bushing 26d is fitted into this screw hole 26c. Therefore, when the secondary battery 1 is installed in a location using the leg portion 26, the rubber bushing 26d absorbs vibrations and torsional stresses from the installation location, suppressing deformation of the secondary battery 1.

[0051] <End Plate> As shown in Figure 8, the right end plate 21R is a plate-like portion that covers the right side of the secondary battery 1, and the lower part has an intake opening 24a of the bottom ventilation passage 24. The lower end of this intake opening 24a is welded to the bottom plate 6 to form the bottom ventilation passage 24. Approximately two-thirds of the upper part of the right end plate 21R functions as an end plate that sandwiches multiple battery cells. For this reason, sufficient thickness is ensured to withstand the stress caused by the expansion of the battery cells. In addition, ribs 21Rb are formed on the right end plate 21R to increase strength in the horizontal, vertical, and two diagonal directions, centered on its center. At the same time, the other parts are made lighter by forming recesses 21Ra. Furthermore, a negative electrode external terminal 31 is provided on the upper rear side.

[0052] As shown in Figure 7, the left end plate 21L is a plate-shaped portion that covers the left side of the secondary battery 1, and its lower part is formed as a flat plate-shaped portion. A flexible circuit board external connector 32 is provided on the rear side of the lower part of the left end plate 21L for extracting temperature data and voltage data acquired by the flexible circuit board 9 to the outside. From here, temperature data and voltage data can be extracted to the outside of the secondary battery 1.

[0053] The upper two-thirds of the left end plate 21L has a similar configuration to the right end plate 21R, and its thickness is ensured to serve as an end plate that can withstand the stress caused by the expansion of the battery cell. In addition, the left end plate 21L also has ribs 21Lb formed around its center to increase strength in the horizontal, vertical, and two diagonal directions. The rest of the plate is made lighter by forming recesses 21La. Furthermore, a negative electrode external terminal 31 is provided on the upper rear side.

[0054] <Battery container 23> As shown in Figure 18, 28 battery cases 23 are formed inside the case 2. Each battery case 23 forms a space that accommodates each electrode body 10 without any excess or deficiency. As shown in Figure 4, the electrode bodies 10 housed in the battery cases 23 are aligned so as to be stacked in the thickness direction (length direction L) via the partition walls 25 of the battery cases 23. The electrode bodies 10 are arranged so that the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a are staggered.

[0055] As shown in Figure 20, the lower end of the battery case 23 is isolated by a bottom partition wall 23a that horizontally seals the entire battery case 23. An air intake port 27D is provided in the bottom partition wall 23a for communication with each vertical air passage 27.

[0056] Figure 39 is a cross-sectional view of section 39-39 of Figure 3. As can be seen from the cross-sectional view along the length L of the bottom partition wall 23a of the battery case as shown in Figure 39, the upper surface of the bottom partition wall 23a of the battery case is provided with a lower holding portion 23b that holds the lower end of each electrode body 10 housed in the battery case 23. The lower holding portion 23b has a recess that conforms to the shape of the lower part of the housed electrode body 10. Therefore, the lower part of the electrode body 10 housed in the battery case 23 is fitted into the lower holding portion 23b, and its movement in the length L (stacking direction) is restricted by the lower holding portion 23b together with the partition wall 25.

[0057] The lower end of the bulkhead 25 is connected to the bulkhead 23a at the bottom of the battery case, creating an airtight seal. Furthermore, the bulkhead 25 is airtightly isolated from the adjacent battery case 23. Furthermore, as shown in Figures 18 and 26, the partition wall 25 has a relatively thin wall portion 25a and five rib-shaped support portions 25b, which are thicker than the wall portion 25a, provided on both sides at roughly equal intervals. The wall portion 25a has a gap with the contained electrode body 10, and the support portions 25b contact the electrode body 10 to support it in the thickness direction. As a result, the electrode body 10 is constrained in the stacking direction. However, there may be a slight gap between the electrode body 10 and the support portions 25b, and since the partition wall 25 is made of elastic resin, the wall portion 25a flexes, allowing displacement in the length direction L (stacking direction) due to expansion of the electrode body 10, etc.

[0058] One end of the partition wall 25 extends to the end of the case 2 in the width direction W, and this portion becomes the electrode foil collection section insertion portion 25d. One side of the electrode foil collection section insertion portion 25d is into which the positive electrode foil collection section 12a is inserted, and the other side is into which the negative electrode foil collection section 13a is inserted. In addition, rib-shaped fixing ribs 25c that protrude in the thickness direction of the partition wall 25 are provided on both sides of the wall portion 25a at the base end of the electrode foil collection section insertion portion 25d. When the electrode body 10 is inserted, the fixing ribs 25c contact the stepped portion 12e of the positive electrode or the stepped portion 13e of the negative electrode shown in Figure 12, thereby restricting the movement of the electrode body 10 in the width direction W and positioning it.

[0059] The other end of the partition wall 25 is integrally constructed and airtight, with a shape that abuts against the inner part 27I of the vertical air passage 27 provided at the widthwise end W of the case 2. When the electrode body 10 is inserted into the battery case 23, the stepped portion 12e of the positive electrode or the stepped portion 13e of the negative electrode shown in Figure 12 abuts against the inner part 27I (Figure 26) of the vertical air passage 27, thereby restricting the movement of the electrode body 10 in the widthwise direction W, and positioning it together with the fixing rib 25c.

[0060] <Vertical ventilation duct 27> As shown in Figure 18, the vertical ventilation passages 27 are located at approximately equal intervals along the length L at the width W end of the front side of the case 2, with 15 openings. The vertical ventilation passages 27 are positioned at the ends of every other partition wall 25. On the other hand, on the rear side of the case 2, there are 16 vertical ventilation passages located at approximately equal intervals along the length L. In this case, the vertical ventilation passages 27 on the front side and the vertical ventilation passages 27 on the rear side are positioned at the positions of staggered partition walls 25. Furthermore, the vertical ventilation passage 27 at the right end of the length L on the rear side is located on the inner surface of the right end plate 21R, not on the partition wall 25. Similarly, the vertical ventilation passage 27 at the left end of the length L on the rear side is located on the inner surface of the left end plate 21L, not on the partition wall 25.

[0061] At the top 2U of the case 2, an exhaust port 27U is formed at the upper end surface of each vertical air passage 27. At the lower end surface of each vertical air passage 27, an intake port 27D (Figure 20) is formed at the bottom partition wall 23a of the case 2. These intake ports 27D and exhaust ports 27U are connected by the vertical air passage 27.

[0062] As shown in Figure 19, each vertical ventilation passage 27 is a pipe-shaped section with a rectangular cross-section when viewed from above. Each vertical ventilation passage 27 consists of four planar plate-like sections: an inner section 27I located inside the case 2, an outer section 27O located outside the case 2, and a pair of opposing, orthogonal side sections 27S, 27S located on both the left and right sides of these sections, connecting their ends.

[0063] As shown in Figure 26, the inner section 27I, located inside the case 2, is connected to the partition wall 25 in its center. The outer section 27O, located outside the case 2, has a detection hole 29, which is a rectangular cutout at its lower part, with dimensions corresponding to approximately 40% of the vertical dimension and approximately 80% of the horizontal dimension. The detection hole 29 is used to measure the temperature and voltage of the busbar 8. The inner section 27I and the outer section 27O also have a pair of orthogonal, opposing side sections 27S, 27S that connect their respective vertical ends. Each side section 27S has a connection hole 28, which is a rectangular window, opening in the upper outer part of the side section, with dimensions corresponding to approximately 85% of the vertical dimension and approximately 55% of the horizontal dimension. The connection hole 28 is an opening used for welding the busbar 8 to the electrode body 10.

[0064] <Configuration of busbar 8> The busbar 8 shown in Figure 21 is a U-shaped member whose horizontal cross-section consists of three planes connected at right angles to each other. The busbar 8 has the function of electrically connecting the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a of the electrode body 10. In the secondary battery 1 of this embodiment, as shown in Figure 21, it is insert-molded at a predetermined position in the case 2 and integrated as part of the wall of the airtight battery case 23. Furthermore, it has the function of dissipating heat from the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a of the electrode body 10 to the outside of the secondary battery 1 from the inner circumference heat dissipation surface 8d.

[0065] As shown in Figure 21, the outside of the case 2 of the busbar 8 is provided with a vertically elongated rectangular connecting portion 8c, and from both horizontal ends of the connecting portion, a foil collection welding surface 8a and a foil collection welding surface 8b are provided facing each other at a right angle toward the inside of the case 2. The upper part of the connecting portion 8c becomes an adhesive surface 8f that is in close contact with the inner surface of the outer part 27O of the vertical ventilation passage 27 of the case 2. The lower part of the connecting portion 8c becomes a detection surface 8e, which is the area to which the temperature / voltage detection unit 91 is attached.

[0066] Furthermore, the busbar 8 is positioned along the inner circumferential surface of the vertical air passage 27. Therefore, the inner surface of the busbar 8 becomes a heat dissipation surface 8d that dissipates heat from the busbar 8 into the vertical air passage 27. <Material of busbar 8> The busbar 8 has the function of electrically connecting the positive electrode foil collector portion 12a and the negative electrode foil collector portion 13a of the electrode body 10. Welding is preferable for a simple and reliable electrical connection. In the lithium-ion secondary battery illustrated in this embodiment, Al foil is used as the positive electrode current collector. Cu foil is used as the negative electrode current collector. When joining Cu, which has high thermal conductivity and melting point, and Al, which has opposite properties, by welding, the joint surface may become weak, or contact corrosion may occur due to the potential difference.

[0067] The busbar 8 needs to be reliably electrically and mechanically connected to both Cu and Al. Therefore, the busbar 8 in this embodiment has the following configuration. Figure 22 is a schematic diagram showing an example of the material composition of the busbar 8 in this embodiment. Figure 22(a) is a plan view, and Figure 22(b) is an external view. As shown in Figures 22(a) and (b), the foil collection welding surface 8a is made of Al, and the foil collection welding surface 8b is made of Cu. Here, the ends of an aluminum plate and a copper plate of the same thickness are connected. However, the detection surface 8e in the lower center of the connecting part 8c is made of Al. This is because if the detection surface 8e were made of dissimilar metals, Al and Cu, the measurement of the temperature sensor and voltage sensor of the temperature / voltage detection unit 91 attached to the detection surface 8e may become unstable.

[0068] Furthermore, the detection surface 8e at the lower center of the connecting portion 8c may be made of Cu material. Figure 23 is a schematic diagram showing another example of the material configuration of the busbar 8 in this embodiment. In the busbar 8 shown in Figure 22, an aluminum plate and a copper plate of the same thickness are connected at the ends, but in this alternative example of the busbar 8, the aluminum plate and the copper plate are connected across the surface at the connecting portion 8c. This configuration allows for a larger joining surface area. In this case as well, the configuration may be such that Al is on the inside and Cu is on the outside, rather than Al being on the outside and Cu on the inside.

[0069] <Manufacturing method for bus bar 8> The busbar 8 shown in Figure 22 can be joined in the following way, for example. As mentioned above, there were problems with conventional welding of Al and Cu. Therefore, the manufacturing method of the busbar 8 in this embodiment includes a busbar forming step in which dissimilar metals are joined together.

[0070] First, the process includes a "component formation process" which involves cutting aluminum and copper plates into predetermined shapes and performing necessary bending steps. Next, Al and Cu undergo solid-phase diffusion bonding. However, Al is extremely easily oxidized, and its oxide film is very strong. Therefore, a "pretreatment step" is included as a preliminary step, in which the oxide film is broken down by friction between Al and Cu, for example, using ultrasonic vibrations.

[0071] Furthermore, it includes a "solid-phase diffusion bonding process" that performs solid-phase diffusion bonding of Al and Cu. Here, "solid-phase diffusion bonding" refers to a method of directly joining materials to be bonded together. By heating and pressurizing the materials to be joined, atomic movement at the bonding interface is promoted, resulting in bonding. By joining the materials while they are still solid, without melting them, eutectic bonding is achieved, eliminating the joint surface. As a result, electrical resistance can be made extremely low. Furthermore, the bonded portion has extremely high strength, equivalent to that of the main body.

[0072] The procedure involves, for example, maintaining a low temperature of 30-50% of the base material's melting point while the joining surfaces are pressed together, allowing atoms to diffuse and join, thereby creating a bond that shares atoms while suppressing the formation of intermetallic compounds.

[0073] <Manufacturing method for Case 2> Case 2 is manufactured entirely from, for example, molten PP (polypropylene) by injection molding using a mold. Case 2 is integrally molded using a single mold, but at that time, the busbar 8 is insert-molded at the position shown in Figure 21. By insert-molding the busbar 8, the busbar 8 is hermetically integrated into the predetermined position. As a result, the battery case 23, right end plate 21R, left end plate 21L, vertical ventilation passage 27, etc., which constitute Case 2, are formed integrally and indivisibly.

[0074] <Lid 5 components> Figure 36 is a perspective view of the lid 5 from below. Figure 37 is a front view of the lid 5. Figure 38 is an enlarged perspective view of a portion of Figure 36.

[0075] Figure 27 shows the area where the front section 2F and the lid 5 are welded together in Figure 26. As shown in Figures 1 and 10, the lid 5 is attached to the top section 2U of the case 2 and seals the top of the secondary battery 1. The lid 5 is a plate-shaped member made of the same material as the case 2 and is welded to the top section 2U of the case 2. More specifically, as shown in Figure 27, it is welded to the top welding section 20U, which is located on the same horizontal plane as the top of the right end plate 21R, the left end plate 21L, the vertical ventilation passage 27, and the partition wall 25.

[0076] <Upper holding part 52> As shown in Figures 36 to 38, the lower inner surface 5b of the lid 5 is provided with an upper holding portion 52. The upper holding portion 52 is positioned to correspond to the upper position of the electrode body 10 housed in the battery case 23. The upper holding portion 52 has a recess 52b at the lower end of a rib-shaped base portion 52a that protrudes downward from the inner surface 5b of the lid 5, and this recess conforms to the shape of the upper part of the electrode body 10. In addition, the side portions 52c at both widthwise ends of the base portion 52a are provided with ribs 52d that protrude horizontally and extend in the height direction H. When the lid 5 is placed over the top portion 2U of the case 2, the ribs 52d of the side portions 52c face each other at positions corresponding to the wall portion 25a of the partition wall 25. The portion of the side portion 52c without ribs 52d faces each other at positions corresponding to the support portion 25b of the partition wall 25. In other words, a partition wall 25 is inserted between the upper holding portions 52 of the lid 5, and its uneven shape is designed to nest inside each other, preventing large gaps from forming. It also suppresses movement of the lid 5 in the width direction W.

[0077] <Exhaust section 51> As shown in Figure 3, exhaust sections 51, which are roughly square in plan view, are provided at both ends of the width W of the lid 5. Fourteen exhaust sections 51 are provided at equal intervals at the front end. In addition, fifteen exhaust sections 51 are provided at equal intervals at the rear end. As shown in Figure 18, the exhaust sections 51 are positioned in a location corresponding to the exhaust port 27U of the vertical air passage 27. That is, the air discharged from the exhaust port 27U of the vertical air passage 27 is released into the atmosphere through the lid 5 via the exhaust sections 51.

[0078] As shown in Figure 1, the exhaust section 51 has a protrusion 51a that projects upward on the outer surface 5a of the cover 5, and as shown in Figure 38, its interior is hollow. Furthermore, as shown in Figure 1, each exhaust section 51 has an exhaust port 51b that opens outward in the width direction W. This exhaust port 51b is in communication with the exhaust port 27U of the vertical air passage 27. As a result, the air heated by the heat radiated from the busbar 8 becomes lighter and rises from the vertical air passage 27, and is discharged into the atmosphere through this exhaust port 51b. In other words, convection is generated by the chimney effect, efficiently releasing heat from inside the secondary battery 1.

[0079] <Composition of base plate 6> Figure 34 is a cross-sectional view of the 34-34 portion of the plan view of the secondary battery 1, with the lid 5 of Figure 4 omitted. Figure 35 is a cross-sectional view of the 35-35 portion of Figure 4.

[0080] As shown in Figures 1 and 10, the bottom plate 6 is a rectangular plate-shaped member formed from the same material as the case 2, and is welded to the bottom welding portion 20D shown in Figure 18 so as to cover the bottom 2D of the case 2. Then, as shown in Figures 39, 34, and 35, the bottom ventilation passage 24 is formed by the lower part of the front part 2F of the case 2, the lower part of the rear part 2B, the bottom partition wall 23a of the battery case bottom, and the bottom plate 6. Also, as shown in Figure 6, the bottom plate 6 and the bottom surfaces of the lower frames 2Fa, 2Ba, and the legs 26 are flush.

[0081] As shown in Figure 8, the bottom ventilation passage 24 can introduce outside air through the intake opening 24a opened in the right end plate 21R. As shown in Figures 34 and 35, the intake port 27D of the vertical ventilation passage 27 is in communication with the bottom ventilation passage 24. As mentioned above, heat dissipation from the busbar 8 creates an upward airflow in the vertical ventilation passage 27, resulting in a chimney effect. Therefore, an airflow is generated from the bottom ventilation passage 24 to the vertical ventilation passage 27. In other words, the air entering through the intake opening 24a, along with the heat dissipated from the busbar 8, passes through the vertical ventilation passage 27 and is efficiently discharged from the exhaust port 51b of the lid 5.

[0082] <Configuration of side panel 7> As shown in Figure 10, the side panel 7 is composed of a front panel 7F and a back panel 7B. The side panel 7 is a plate-shaped member made of the same material as the case 2, and a bulge 71 extending horizontally from the bottom is provided to increase strength. Furthermore, as shown in Figure 34, this bulge 71 forms a space for the wiring of the flexible circuit board 9, which is wired into the flexible circuit board wiring groove 33 of the case 2.

[0083] The side plate 7 is welded to the side of the case 2 (front section 2F and rear section 2B) so as to cover it. Specifically, for example, on the front section 2F, it is welded to the front welding section 20F, which is formed as a vertical, flat surface on the front side end of the front section 2F of the case 2 as shown in Figure 27. By welding the side plate 7 to the case 2, the open portion on the side of the battery case 23 of the case 2 is sealed. In other words, the side plate 7 is a part that constitutes a part of the battery case 23. Before welding the side plate 7, the opening for welding the electrode body 10 and the busbar 8 inside the battery case 23 is exposed, and the battery case 23 is hermetically sealed by welding the side plate 7 to the case 2.

[0084] <Temperature / voltage detection unit 91 and flexible substrate 9> Figure 24 is a perspective view of the flexible circuit board 9. Figure 25 is a perspective view of the busbar 8 located in the case 2, the temperature / voltage detection unit 91 located therein, and the flexible circuit board 9 connecting them. As shown in Figure 25, the flexible circuit board 9 shown in Figure 24 is connected to each of the 29 temperature / voltage detection units 91.

[0085] The temperature / voltage detection unit 91 incorporates a temperature sensor, such as a thermocouple, and a terminal for measuring potential. The temperature / voltage detection unit 91 is attached to each busbar 8 at the detection hole 29 so as to be in close contact with it. The substrate converts the temperature [°C] of the busbar 8 detected by the temperature / voltage detection unit 91 and the battery voltage [V] calculated from the difference in potential [V] between the pair of temperature / voltage detection units 91 sandwiching the electrode body 10 into an electrical signal, which is then output. The converted electrical signal is processed by a circuit built into the flexible substrate 9 and sent out. The sent electrical signal is connected to an externally provided control device (not shown) via the flexible substrate 9 to the flexible substrate external connector 32 of the case 2, and the control device monitors the battery temperature [°C] and each cell voltage [V]. Since the battery temperature [°C] is detected from each busbar 8, the average temperature of the pair of cell batteries connected to the busbar 8 is detected, rather than the temperature of each individual cell battery. Unlike conventional methods that measure the cooling effect of a specific secondary battery 1 by measuring the temperature inside the battery case using a temperature sensor placed inside the cell, this embodiment aims to measure the temperature of the electrode body 10 outside the battery case 23 by measuring the busbar 8 almost directly. This makes wiring using a flexible circuit board 9 easier.

[0086] The flexible circuit board 9 is composed of what is known as a "flexible printed circuit board (FPC)". The flexible circuit board referred to here is a printed circuit board with a structure that can be bent, using a material with high heat resistance, high mechanical strength and insulation (for example, polyimide film) and copper foil densely printed on it. In this embodiment, a detailed explanation of the structure is omitted, but by arranging electronic components, it has the same function as a rigid circuit board that processes signals from the temperature / voltage detection unit 91, which is a sensor located on the busbar 8, as shown in Figure 25. The flexible circuit board 9 is also arranged so as to surround the case 2 with its front part 9a, back part 9b, and left side part 9d. Taking advantage of its thinness, it has the function of a cable that transports multiple data from 29 temperature / voltage detection units 91 (in this case, 29 temperature data and 29 voltage data) in parallel to the flexible circuit board external connector 32, each individually.

[0087] The signal processing may be performed inside the temperature / voltage detection unit 91 instead of the flexible circuit board 9, or it may be performed on a rigid circuit board located near the external connector 32 of the flexible circuit board.

[0088] <Assembly of secondary battery 1> Next, we will describe the assembly of the secondary battery 1 having the configuration described above. <Assembly of electrode body 10> As shown in Figure 15, the electrode body 10 is formed by creating a positive electrode plate 12 with a positive electrode foil collection portion 12a (positive electrode busbar connection portion) by forming a positive electrode composite material layer in a predetermined area of ​​a positive electrode current collector (positive electrode substrate) made of Al foil. Similarly, a negative electrode plate 13 with a negative electrode foil collection portion 13a (negative electrode busbar connection portion) is formed by forming a negative electrode composite material layer in a predetermined area of ​​a negative electrode current collector (negative electrode substrate) made of Cu foil. These are then laminated via a separator 11. This laminate is wound to form a wound body, and then press-molded to a predetermined thickness to form a flat electrode body 10. At each horizontal end of this electrode body 10, a positive electrode foil collection portion 12a, which serves as the positive electrode busbar connection portion, and a negative electrode foil collection portion 13a, which serves as the negative electrode busbar connection portion, are formed. At this time, the thickness of the laminated portion 10a of the electrode body 10 is slightly smaller than the inner dimension in the thickness direction (length direction L) of the battery case 23.

[0089] <Impregnation of the electrode body 10 with non-aqueous electrolyte 14> After the completed electrode body 10 has been dried in a drying process to remove moisture and other contaminants, the non-aqueous electrolyte 14 is impregnated into the electrode body 10 under a vacuum atmosphere according to the procedure shown in Figure 16.

[0090] <Molding of Case 2> As shown in Figure 21, the busbar 8 is inserted in a predetermined position to integrally mold the case 2. Molten PP, which is the raw material, is injected into the cavity of the mold to integrally form the entire case 2, and the busbar 8 becomes one with the case 2 and forms part of the airtight battery case 23.

[0091] <Housing of electrode body 10 in case 2> In the battery case 23 of case 2, the electrode bodies 10 are arranged in the thickness direction (length direction L) such that the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a are alternately arranged, as shown in Figure 31, and then individually housed as shown in Figure 4.

[0092] <Welding of electrode body 10 and busbar 8> Figure 28 is an enlarged perspective view of a portion of Figure 25 showing the connection between the electrode body 10 and the busbar 8. In Figure 28, the resin portion of the case 2 is omitted to show the relationship between the connection between the electrode body 10 and the busbar 8. As shown in Figure 13, the central part 12c of the positive electrode foil collection section of the electrode body 10 housed in the battery case 23 is pressed and shaped to be thin. The central part 12c of the positive electrode foil collection section of the electrode body 10 is in close contact with the foil collection section welding surface 8a on the left outer surface in the longitudinal direction L of the front busbar 8. Also, as shown in Figure 14, the central part 13c of the negative electrode foil collection section of the electrode body 10 housed in the battery case 23 is pressed and shaped to be thin. The central part 13c of the negative electrode foil collection section of the electrode body 10 is in close contact with the foil collection section welding surface 8b on the right outer surface in the longitudinal direction L of the back busbar 8.

[0093] Figure 30 shows the state in which the central part 12c of the positive electrode foil collection section of the electrode body 10 housed in the battery case 23 is pressed against the welding surface 8a of the foil collection section of the busbar 8 by a clip 100 to perform laser welding.

[0094] As shown in Figure 28, the central part 13c of the negative electrode foil collection section must be brought into close contact with the foil collection section welding surface 8a facing the right side of the busbar 8, and the central part 13c of the negative electrode foil collection section must be brought into close contact with the foil collection section welding surface 8b on the right outer surface of the busbar 8 and welded. Similarly, the central part 12c of the positive electrode foil collection section must be brought into close contact with the foil collection section welding surface 8b facing the left side of the busbar 8, and the central part 12c of the positive electrode foil collection section must be brought into close contact with the foil collection section welding surface 8a on the left outer surface of the busbar 8 and welded. To achieve this, simply inserting the electrode body 10 into the battery case 23 is not enough to bring them into close contact. Therefore, as shown in Figure 30, welding is performed using a jig called a clip 100. Here, the clip 100 is a bifurcated tweezers-shaped elastic metal (for example, SUS) with the upper part 100a connected, and the pressing parts 100b in the center in the height direction H are curved so that they separate from each other. The width of the pressing portion 100b of the clip 100 is wider than the distance between adjacent busbars 8, 8. As shown in Figure 30, the pair of electrode bodies 10 housed in the battery case 23 adjacent to each other in the longitudinal direction L are inserted so that the central portion 12c of the positive electrode foil collection section 12c and the central portion 13c of the negative electrode foil collection section 13c are each inserted up to the electrode foil collection section insertion section 25d. The clip 100 is inserted between the central portion 12c of the positive electrode foil collection section 12c and the central portion 13c of the negative electrode foil collection section 13c, while reducing its width (in the longitudinal direction L). When the force that reduces the pressing portion 100b of the clip 100 in the width direction (in the longitudinal direction L) is released, it expands in the longitudinal direction L, and the pressing portions 100b, 100b of the clip 100 press against the central portion 12c of the positive electrode foil collection section 12c and the central portion 13c of the negative electrode foil collection section 13c, pushing them apart. Therefore, the central part 12c of the positive electrode foil collection section is in close contact with the foil collection section welding surface 8a on the left outer surface in the longitudinal direction L of the busbar 8. Also, the central part 13c of the negative electrode foil collection section is in close contact with the foil collection section welding surface 8b on the right outer surface.

[0095] In this state, a laser beam is shone from the outside of case 2 onto the central part 12c of the positive electrode foil collection section, welding the central part 12c of the positive electrode foil collection section to the foil collection section welding surface 8a. Similarly, a laser beam is shone from the outside of case 2 onto the central part 13c of the negative electrode foil collection section, welding the central part 13c of the negative electrode foil collection section to the foil collection section welding surface 8b. Of course, the shape of the jig is not limited to the example shown.

[0096] Figure 32 is a perspective view of section 32-32 of Figure 5. Figure 33 is an enlarged view of a part of Figure 32. As shown in Figure 32, the secondary battery 1 is considered to have a horizontal cross-section at approximately the center height. As shown in Figure 33, the central part 12c of the positive electrode foil collection section of the electrode body 10 is welded to the busbar 8 so as to be in close contact with it. Similarly, the central part 13c of the negative electrode foil collection section of the electrode body 10 is also welded to be in close contact with the busbar 8.

[0097] It can be seen that the vertical ventilation passage 27, together with the busbar 8, forms a space isolated from the battery case 23. It can also be seen that it forms a space isolated from the outside air. Figure 29 is a perspective view showing the electrode bodies 10 mounted on the busbar 8 shown in Figure 25, with the temperature / voltage detection unit 91 and flexible substrate 9 mounted. Figure 31 is a plan view showing the electrode bodies 10 mounted on the busbar 8 shown in Figure 25. In this figure as well, the resin portion of the case 2 is omitted. As shown in Figure 29, multiple flat electrode bodies 10 are aligned so that the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a are arranged alternately in the thickness direction. The busbar 8 located in the case 2 connects the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a of the electrode bodies 10 housed in adjacent battery cells 23 of the case 2, respectively. Therefore, all 28 electrode bodies 10 are connected in series.

[0098] As shown in Figures 25 and 29, among the busbars 8 located on the rear side, the busbar located at the right end is formed in an L-shape extending to the right in a plan view and is configured as a negative electrode terminal busbar 81 that is connected only to the negative electrode foil collection portion 13a of the electrode body 10. The negative electrode terminal busbar 81 is connected to the negative electrode external terminal 31 shown in Figures 1 and 8, and becomes the negative electrode external terminal of the secondary battery 1, which is a battery pack.

[0099] Furthermore, of the busbars 8 located on the rear side, the busbar located at the left end is formed in an L-shape extending to the left in a plan view, and is configured as a positive electrode terminal busbar 82 that is connected only to the positive electrode foil collection portion 12a of the electrode body 10. The positive electrode terminal busbar 82 is connected to the positive electrode external terminal 30 shown in Figure 7, and becomes the positive electrode external terminal of the secondary battery 1, which is a battery pack.

[0100] <Mounting of temperature / voltage detection unit 91 and flexible circuit board 9> Once the welding of the electrode body 10 and the busbars 8 is complete, the temperature / voltage detection unit 91 is attached to the detection surface 8e of each busbar 8 through the detection hole 29. For attachment, for example, a silicone-containing adhesive with high thermal conductivity is used. After the temperature / voltage detection unit 91 is attached to the detection surface 8e of each busbar 8, the lead portion 9c of the flexible substrate 9 and the connection terminal of the temperature / voltage detection unit 91 are connected to the temperature / voltage detection unit 91 as shown in Figure 25. At the same time, the front portion 9a of the flexible substrate 9 is placed in the space formed by the flexible substrate wiring groove 33 and bulge portion 71 formed at the bottom of the front portion 2F of the case 2 as shown in Figures 17 and 34. The left side portion 9d of the flexible substrate 9 is placed in the flexible substrate wiring groove (not shown) formed at the bottom of the inside of the left end plate 21L of the case 2. The back portion 9b of the flexible substrate 9 is placed in the space formed by the flexible substrate wiring groove 33 and bulge portion 71 formed at the bottom of the rear portion 2B of the case 2. As shown in Figure 24, there is a connection part 9e on the left side portion 9d of the flexible circuit board 9, and the connection part 9e is connected to a flexible circuit board external connector 32 provided on the left end plate 21L of the case 2.

[0101] <Welding of side plate 7> Once the welding of the electrode body 10 is complete, the side plates 7, namely the front plate 7F and the back plate 7B, are welded to the side of the case 2. As shown in Figure 10, the front plate 7F is welded to the front portion 2F of the case 2. As shown in Figure 27, it is welded to the front welding portion 20F, which is a horizontal, flat area on the same plane provided on the front portion 2F of the case 2. Although detailed illustrations are omitted, the back plate 7B is welded to the back portion 2B of the case 2 in the same way as the front. It is welded to the back welding portion, which is a horizontal, flat area on the same plane provided on the back portion 2B of the case 2. Before welding the front plate 7F, the central portion 12c of the positive electrode foil collection section and the central portion 13c of the negative electrode foil collection section could be welded to the welding surfaces 8a and 8b of the foil collection section of the busbar 8 through the connection hole 28 from the opening of the battery case 23. By welding the front panel 7F to the front section 2F of case 2, the opening on the side of the battery case 23 is sealed and airtight. Similarly, by welding the back panel 7B to the rear section 2B of case 2, the opening on the side of the battery case 23 is sealed and airtight.

[0102] <Welding of lid 5> As shown in Figure 10, the lid 5 is welded to the top 2U of the case 2. As shown in Figure 27, the lid 5 is welded to the top welding portion 20U, which is a horizontal flat portion on the same plane as the top of the right end plate 21R, the left end plate 21L, the vertical ventilation passage 27, and the partition wall 25. At this time, the area around the exhaust portion 51 of the lid 5 and the exhaust port 27U of the vertical ventilation passage 27 of the case 2 are airtightly welded together, and the exhaust portion 51 of the lid 5 and the vertical ventilation passage 27 of the case 2 are in communication.

[0103] Furthermore, the area around the upper retaining portion 52 of the lid 5 and the top of the partition wall 25 of the case 2 are airtightly welded together. In addition, the front side end of the lid 5 and the upper end of the front plate 7F, which is the side plate 7, are also airtightly welded together.

[0104] Furthermore, both ends of the lid 5 in the longitudinal direction L are also airtightly welded to the top surfaces of the right end plate 21R and the left end plate 21L. As a result, the battery case 23 becomes completely airtight, preventing the non-aqueous electrolyte 14 from leaking out.

[0105] Furthermore, the connection between the front section 2F and the rear section 2B of case 2 enhances the strength of the secondary battery 1. <Welding of base plate 6> As shown in Figure 10, the bottom plate 6 is welded to the bottom 2D of the case 2. As shown in Figure 20, it is welded to the bottom welding portion 20D provided on the bottom 2D of the case 2. The bottom welding portion 20D is a stepped portion provided on the bottom 2D of the case 2 at a position offset inward in the width direction W and the length direction L. The bottom plate 6 is formed to the same thickness as this step. Therefore, by welding the bottom plate 6 to this bottom welding portion 20D, the bottom 2D of the case 2 becomes a flush surface. This then forms the bottom of the bottom ventilation passage 24, and the bottom ventilation passage 24 becomes airtight except for the intake opening 24a and the communication opening 24b.

[0106] Furthermore, the connection between the front section 2F and the rear section 2B of case 2 enhances the strength of the secondary battery 1. (Operation of this embodiment) The secondary battery 1 of this embodiment has the above configuration and therefore performs the following functions.

[0107] <Function of the skeletal structure of secondary battery 1> The structure of the secondary battery 1 exhibits high durability against vibration and torsional stress due to its high mechanical strength. The case 2 has high strength because it connects the thick plate right end plate 21R and left end plate 21L with a structural member made of integrally molded resin consisting of a thick rod-shaped lower frame 2Fa of the front part 2F and a lower frame 2Ba of the rear part 2B. Therefore, even when the electrode body 10 housed in the battery case 23 surrounded by these structural members expands, the case 2 has high mechanical strength and a strong structure that will not break due to its elasticity.

[0108] Furthermore, the strength is further enhanced by welding the lid 5, bottom plate 6, and side plates 7 together. The legs 26 are integrally provided with the lower frame 2Fa of the thick, rod-shaped front section 2F and the lower frame 2Ba of the rear section 2B. The legs 26 firmly fix the secondary battery 1 to its installation location. Rubber bushings 26d, disposed in the screw holes 26c of the legs 26, absorb vibrations and torsional stresses from the installation location, thereby suppressing deformation of the secondary battery 1.

[0109] <Function of the support structure of electrode body 10> The secondary battery 1 has the function of supporting the electrode body 10 in a stable state even when there is vibration. Each battery case 23 of the case 2 is equipped with a lower holding portion 23b that holds the lower end of each of the multiple electrode bodies 10. The lid 5 is equipped with an upper holding portion 52 that holds the upper part of each of the multiple electrode bodies 10 inserted into the battery case 23 of the case 2. Each electrode body 10 is held between the lower holding portion 23b and the upper holding portion 52 from above and below.

[0110] The electrode body 10 is held between a recess in the lower holding portion 23b that conforms to the lower shape of the electrode body 10 and a recess 52b in the upper holding portion 52 that conforms to the upper shape of the electrode body 10, thereby restricting the movement of the electrode body 10 in the longitudinal direction L.

[0111] Furthermore, a fixing rib 25c is provided on the partition wall 25 of the battery case 23. This fixing rib 25c fixes the stepped portion 13e of the electrode body 10 and restricts the movement of the electrode body 10 in the width direction W. Furthermore, the electrode body 10 is supported by welding its positive electrode foil collection portion 12a (positive electrode busbar connection portion) and negative electrode foil collection portion 13a (negative electrode busbar connection portion) at both ends to a busbar 8 which is integrally incorporated into the case 2.

[0112] With the above structure, the electrode body 10 is restricted from moving in any direction (height H, length L, width W), ensuring stable retention even when subjected to external vibrations. Furthermore, except for the upper and lower portions and both ends of the electrode body 10, the electrode body 10 is not constrained in the thickness direction (length direction L). Therefore, even if the electrode body 10 expands, there is dimensional clearance, and the resin partition wall 25 can also bend, thus mitigating the stress on the battery case 23 due to the expansion of the electrode body 10.

[0113] <Function of the structure of the battery case 23> In this embodiment, the battery case 23 of the secondary battery 1 has the function of stably supporting the electrode body 10 and keeping it airtight. The battery case 23 seals the electrode body 10 together with the non-aqueous electrolyte 14, and electricity is extracted from the electrode body 10 by the busbar 8. In this embodiment, the battery case 23 is not made up of individual components, but is formed by dividing a single case 2 with partition walls 25. In the conventional technology, a large number of cell batteries, each with an individual metal case, were stacked and restrained by a restraining member to form a battery pack, which was then housed in a resin case. Compared to such conventional technology, the number of components in the secondary battery 1 can be reduced, and the manufacturing process can be simplified. Furthermore, the secondary battery 1 can be made significantly more compact and lighter.

[0114] The battery case 23 is formed by the airtight welding of the bottom partition wall 23a and partition wall 25 of the case 2, the busbar 8 which is insert-molded into the case 2, the front plate 7F and back plate 7B which constitute the side plate 7, and the lid 5. Since all of these are made of resin (e.g., PP) and metal (Al, Cu) that do not allow non-aqueous electrolyte 14 or hydrogen to pass through, the deterioration of the secondary battery 1 due to the decrease in non-aqueous electrolyte 14 or hydrogen can be suppressed.

[0115] The busbar 8 is integrated into the case 2 by insert molding, and the joint is airtightly sealed. The positive electrode foil collection portion 12a (positive electrode busbar connection portion) of the electrode body 10 and the negative electrode foil collection portion 13a (negative electrode busbar connection portion) of the adjacent electrode body 10 are electrically connected by welding to the foil collection portion welding surface 8a of one busbar 8 and the foil collection portion welding surface 8b opposite to it. In this way, since both ends of each electrode body 10 in the width direction W are welded to the busbar 8, the electrode body 10 is stably held between itself and the busbar 8 even when installed in a vehicle or the like and subjected to severe vibrations.

[0116] <Function of heat dissipation structure> In this embodiment, the heat generated in the electrode body 10 can be efficiently dissipated to the outside of the secondary battery 1. The heat generated in the electrode body 10 is conducted to the Al foil of the positive electrode plate 12 and the Cu foil of the negative electrode plate 13, which have high thermal conductivity. Conventionally, the heat from the electrode body 10, which was wrapped in an insulator (e.g., PP), was dissipated through this insulator to the surface of the metal battery case. In contrast, in this embodiment, the heat from the electrode body 10 that has been conducted to the Al foil of the positive electrode plate 12 and the Cu foil of the negative electrode plate 13 is then directly conducted to the busbar 8 via the shortest distance, and dissipated through the busbar 8.

[0117] The busbars 8 welded to the positive electrode foil collection section 12a (positive electrode busbar connection section) and the negative electrode foil collection section 13a (negative electrode busbar connection section) conduct heat from the electrode body 10 with high thermal conductivity. The busbar 8 faces the vertical air passage 27. The vertical air passage 27 communicates with the bottom air passage 24, which has an intake opening 24a at its lower end that is open to the outside. The vertical air passage 27 also communicates with the exhaust section 51, which has an exhaust hole 51b at its upper end that is open to the outside of the cover 5. The busbar 8 dissipates heat from the electrode body 10 into the vertical air passage 27. As a result, the air heated by this heat becomes less dense and lighter, rising up the vertical air passage 27 and being discharged through the exhaust hole 51b of the cover 5. Meanwhile, the vertical air passage 27 is replenished with cooler air from the bottom air passage 24. In other words, heat convection occurs due to the chimney effect, promoting heat dissipation from the busbar 8. Therefore, heat can be efficiently dissipated from the busbar 8 without the need for an electric fan or the like.

[0118] Furthermore, the vertical ventilation passage 27 communicates with the bottom ventilation passage 24 and the exhaust section 51 of the cover 5 to introduce and exhaust outside air. In this case, the airflow is completely isolated from the inside of the battery case 23. Therefore, even if the outside air contains dust or chemical substances, the dust or chemical substances never come into contact with the foil collection welding surfaces 8a and 8b of the busbar 8. For this reason, deterioration of the electrical connections of the busbar 8 due to dust or chemical substances in the atmosphere can never occur.

[0119] <Function of the electrical structure of secondary battery 1> As shown in Figure 31, the 28 electrode bodies 10 are electrically connected in series by busbars 8 to the positive electrode foil collection portion (positive electrode busbar connection portion) 12a and the negative electrode foil collection portion (negative electrode busbar connection portion) of adjacent electrode bodies 10. Because the busbars 8 directly electrically connect the positive electrode foil collection portion (positive electrode busbar connection portion) 12a and the negative electrode foil collection portion (negative electrode busbar connection portion) of adjacent electrode bodies 10 by welding, the connection is made without disconnection and with low electrical resistance.

[0120] The positive terminal busbar 82 at the left end is connected to the positive external terminal 30 of the entire secondary battery 1. The negative terminal busbar 81 at the right end is connected to the negative external terminal 31 of the entire secondary battery 1. Therefore, by connecting to the positive external terminal 30 and the negative external terminal 31 from the outside, the secondary battery 1 can be treated as a single battery. Such a secondary battery 1 has the function of being able to obtain the required voltage [V] and battery capacity [Wh] by connecting them in series or parallel as needed.

[0121] <Operation of the control structure of secondary battery 1> In this embodiment, the secondary battery 1 has the effect of accurately measuring the temperature and voltage of each electrode body using the temperature / voltage detection unit 91. Furthermore, the measured data is transmitted individually to the 28 busbars 8 via the flexible cable of the flexible circuit board 9, enabling appropriate control and maintenance based on this data.

[0122] The busbar 8 is equipped with a temperature / voltage detection unit 91 that has a temperature sensor, allowing for direct measurement of the temperature of the busbar 8, which accurately reflects the heat generated by the two adjacent electrode bodies 10. The busbar 8 conducts heat from the electrode bodies 10 within the battery case 23. The temperature / voltage detection unit 91 can directly measure the temperature of this busbar 8 from outside the battery case 23. Therefore, the temperature measured by the temperature / voltage detection unit 91 can be output as an electrical signal from outside the secondary battery 1 via a flexible circuit board 9 outside the battery case 23, using a flexible circuit board external connector 32. This electrical signal can be processed by an external control device (not shown). The control device, for example, converts the analog voltage corresponding to the temperature into a digital signal using AD conversion and stores it along with the time. From this data, the accurate temperature history of the secondary battery can be determined, allowing for estimation of its degradation state. Furthermore, the temperature of a specific busbar 8 can be individually compared with a threshold using a comparator or similar device to detect abnormalities.

[0123] Furthermore, the temperature / voltage detection unit 91 located on the busbar 8 is equipped with a voltage sensor. Therefore, the battery voltage [V] of all 28 electrode bodies 10 housed in the secondary battery 1 can be measured individually. By measuring these battery voltages [V], the overcharge and over-discharge states of each battery cell can be determined. Based on this data, the input and output of the entire secondary battery 1 can be appropriately controlled to suppress battery degradation.

[0124] (Effects of this embodiment) (1) The secondary battery of this embodiment has the effect of effectively cooling the battery while suppressing busbar short circuits and metal degradation.

[0125] (2) The multiple flat electrode bodies 10 are arranged with positive and negative electrodes stacked alternately, and each end in the horizontal direction is provided with a positive electrode foil collection portion 12a (positive electrode busbar connection portion) and a negative electrode foil collection portion 13a (negative electrode busbar connection portion). The case 2 is open at the top and comprises multiple battery cases 23 that individually house the multiple flat electrode bodies 10, which are arranged in the thickness direction such that the positive electrode foil collection portions 12a and negative electrode foil collection portions 13a are alternately arranged. The busbars 8 connect the positive electrode foil collection portions 12a and negative electrode foil collection portions 13a of the electrode bodies 10 housed in adjacent battery cases 23, respectively. The lid 5 seals the battery cases 23 of the case 2. The busbars 8 are positioned in the case 2 and constitute the battery cases 23 as part of the battery cases 23, making them airtight. A portion of the busbars 8 is configured to dissipate heat to the outside of the battery cases 23 as a heat dissipation surface 8d. Therefore, the heat generated from the electrode body 10 is efficiently conducted to the positive electrode foil collection section 12a and the negative electrode foil collection section 13a, which have high thermal conductivity, and then conducted from there to the busbar 8, which also has high thermal conductivity. This has the effect of effectively dissipating heat to the outside of the secondary battery 1 from the heat dissipation surface 8d on the outside of the battery case 23.

[0126] (3) Furthermore, the heat dissipation surface 8d of the busbar 8 in this embodiment faces a space that is in communication with the outside air. Therefore, there is an effect that heat can be dissipated more effectively from the heat dissipation surface 8d to the outside of the secondary battery 1.

[0127] (4) Furthermore, this space that is in communication with the outside air is a vertical ventilation passage 27 that extends vertically along the bus bar 8. As a result, the air that has been heated from the bus bar 8 circulates due to the chimney effect, so that heat can be autonomously released to the outside air without the need for fans or anything like that.

[0128] (5) The heat dissipation surface 8d of the busbar 8 is positioned along the inner surface of the vertical air passage 27. Therefore, the heat from the busbar 8 is efficiently discharged to the outside of the secondary battery 1 by the air passing through the vertical air passage 27 in a chimney effect.

[0129] (6) If a heat sink is provided on the heat dissipation surface 8d of the bus bar 8, the heat from the bus bar 8 will be efficiently discharged to the outside of the secondary battery 1 by the air passing through the vertical air passage 27 via the chimney effect caused by the heat sink.

[0130] (7) The air intake port 27D at the lower end of the vertical air passage 27 is in communication with the outside air through an air intake opening 24a located below the battery case 23. Therefore, by supplying outside air to the vertical air passage 27 and passing through it due to the chimney effect, the air is efficiently discharged to the outside of the secondary battery 1.

[0131] (8) A bottom ventilation passage 24 is provided in the entire area below the electrode body 10 housed in the battery case 23 of case 2, and is a space that communicates with the intake opening 24a and the intake port 27D of the vertical ventilation passage 27. This has the effect of supplying outside air to the vertical ventilation passage 27 and efficiently discharging it to the outside of the secondary battery 1 by the air passing through it due to the chimney effect. Furthermore, the bottom ventilation passage 24 itself has the effect of dissipating heat from the battery case 23 by the outside air flowing through it.

[0132] (9) A fan for introducing outside air can be installed in the intake opening 24a located below the battery case 23. This configuration has the effect of more efficiently discharging the convection caused by the chimney effect to the outside of the secondary battery 1.

[0133] (10) The exhaust port 27U at the upper end of the vertical air passage 27 is in communication with the outside air through the exhaust hole 51b provided in the cover 5. Therefore, the heated and lighter air inside the vertical air passage 27 can be naturally and effectively released into the outside air through the exhaust hole 27U.

[0134] (Another example) The present invention is not limited to the above embodiments and can also be implemented as follows. ○This embodiment is just one example of how the present invention can be implemented, and the numerical values ​​and ranges described are examples only and are not limited to these.

[0135] This embodiment describes a lithium-ion secondary battery as an example of the secondary battery 1 to be used, but it can also be applied to other types of non-aqueous electrolyte secondary batteries. It can also be applied to alkaline batteries such as nickel-metal hydride batteries.

[0136] ○Although the electrode body 10 in this embodiment is exemplified as a flat, wound electrode body, the present invention can also be applied to cylindrical electrode bodies that are not molded to be flat, for example. Furthermore, it can also be applied to secondary batteries in which a large number of separate sheet-like positive and negative electrode plates are stacked planarly with separators in between.

[0137] ○In this embodiment, a configuration in which there is a slight gap between the electrode body 10 and the partition wall 25 is illustrated, but a gap is not necessarily required. Conversely, the electrode body 10 and the partition wall 25 may be in contact with each other and the right end plate 21R and the left end plate 21L may be restrained by a restraining member (for example, a belt made of thin metal plate) that pulls them together.

[0138] In this embodiment, case 2, lid 5, bottom plate 6, and side plate 7 were molded by injecting molten resin (PP) into a mold, but the material is not limited to PP; other resins such as PE (polyethylene) can also be used.

[0139] Alternatively, Case 2 may be divided into two or more blocks, molded, and then assembled into a single unit after molding. Furthermore, high-strength metal can be insert-molded to serve as a core material for reinforcing the lower frames 2Fa, 2Ba, the right end plate 21R, the left end plate 21L, etc.

[0140] Furthermore, by using a highly thermally conductive material such as metal for the bottom partition wall 23a of the battery case, or by inserting an insert, heat dissipation from the bottom ventilation passage 24 can also be promoted. Case 2, lid 5, bottom plate 6, and side plates 7 are welded together, but they could also be joined by adhesive or screws, for example.

[0141] Furthermore, all or part of the case 2, lid 5, bottom plate 6, and side plate 7 of this embodiment can be made of metal such as Al. However, in this case, measures such as insulation of the busbar 8 will be necessary.

[0142] ○In this embodiment, the lower part of the entire battery case 23 is used as the bottom ventilation passage 24, but an air intake port for introducing outside air may be provided for each vertical ventilation passage 27. ○In the vertical ventilation passage 27, a heat sink may be provided on the bus bar 8 to enhance the heat dissipation effect.

[0143] ○Although the busbar 8 has a U-shape with horizontal cross-sections connected at right angles, it may also have a rectangular cylindrical shape with a horizontal cross-section along the inner surface of the vertical air passage 27. ○In this embodiment, the busbar 8 and the positive electrode foil collection section 12a and the negative electrode foil collection section 13a are welded by laser welding, but this can also be done by spot welding or other methods.

[0144] ○In this embodiment, when welding the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a of the electrode body 10 to the busbar 8, the procedure was as shown in Figure 30. That is, the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a were fixed by pressing them against a pair of adjacent busbars 8 using the force of pressing against the outside of the pressing portion 100b of the clip 100.

[0145] Figure 40 is a perspective view showing the electrode body 10 being welded to the busbar 8 using clip 101, which is a modified version of clip 100. In the modified clip 101, the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a are fixed by pressing them against a single busbar, sandwiching it from both sides.

[0146] Here, as shown in Figure 40, the clip 101 is a bifurcated, tweezers-shaped, elastic metal with its upper part 101a connected, and the pressing parts 101b in the center in the height direction H are curved so that they approach each other. The width of the pressing parts 101b of the clip 101 is narrower than the width of one busbar 8. As shown in Figure 40, the pair of electrode bodies 10 housed in the battery case 23 adjacent to each other in the length direction L are inserted so that the central part 12c of the positive electrode foil collection section 12c and the central part 13c of the negative electrode foil collection section 13c are each inserted up to the electrode foil collection section insertion section 25d. The clip 101 is inserted between the central part 12c of the positive electrode foil collection section 12c and the central part 13c of the negative electrode foil collection section 13c, while expanding it in width (length direction L). When the force that expands the pressing portion 101b of the inserted clip 101 in the width direction (length direction L) is released, it approaches in the length direction L, and the pressing portions 101b, 101b of the clip 101 press against the central portion 12c of the positive electrode foil collection section and the central portion 13c of the negative electrode foil collection section, sandwiching them between them. As a result, the central portion 12c of the positive electrode foil collection section comes into close contact with the foil collection section welding surface 8a on the left outer surface of the busbar 8 in the length direction L. Also, the central portion 13c of the negative electrode foil collection section comes into close contact with the foil collection section welding surface 8b on the right outer surface.

[0147] In this invention, essentially, it is sufficient to fix and weld the positive electrode foil collection portion 12a and the negative electrode foil collection portion 13a of the electrode body 10 to the appropriate position on the busbar 8. Instead of metal clips 100 and 101, resin or other materials with elasticity may be used. Furthermore, although individual illustrations are omitted, the components may be fixed with screws or ratchet mechanisms, or dynamically pressed by power such as a motor in a robot.

[0148] ○The temperature sensor in the temperature / voltage detection unit 91 is exemplified as a thermocouple, but any type of sensor, such as a side-edge resistor or thermistor, is acceptable. Furthermore, the format of the electrical signal from the temperature / voltage detection unit 91 does not matter; ultimately, it is sufficient that it can be output as data to an external control device via the flexible circuit board external connector 32.

[0149] ○The signal processing for this purpose (for example, converting analog data to digital data) may be performed by the temperature / voltage detection unit 91 itself. Alternatively, a board having an electronic circuit for data processing may be provided near the lead portion 9c of the flexible board 9 within the flexible board 9, or near the flexible board external connector 32. Furthermore, such a board for signal processing may be provided on the flexible board external connector 32.

[0150] ○An intake fan or the like can also be installed in the intake opening 24a of the bottom ventilation passage 24. ○In this embodiment, the flexible circuit board 9 is wired in the flexible circuit board wiring groove 33 provided on the side of the case 2, but the location of the wiring is not limited.

[0151] ○The order of assembly of the secondary battery 1 is not limited to the order illustrated in the embodiment. The present invention is not limited to the above embodiments, and it goes without saying that those skilled in the art can implement it by adding, deleting, or substituting its configuration without departing from the scope of the claims. [Explanation of Symbols]

[0152] L...Length direction W...Width direction H...height direction 1…Secondary battery 10...Electrode body 10a...Laminated section 11... Separator 12…Positive plate 12a... Positive electrode foil collection section (positive electrode busbar connection section) 12b... Upper part of the positive electrode foil collection section 12c...Central part of positive electrode foil collecting section 12d…Bottom part of positive electrode foil collecting section 12e... Step section 13… Negative electrode plate 13a... Negative electrode foil collection section (negative electrode busbar connection section) 13b...Negative electrode foil collecting section upper part 13c...Central part of negative electrode foil collecting section 13d…lower part of negative electrode foil collecting section 13e... Step section 14...Nonaqueous electrolyte 15...Vacuum container 16… Vacuum pump 2…case 2F...Front section 2Fa…Lower frame 2B…Back part 2Ba…Lower frame 2U…Top 2D…Bottom 20F...Front welding part 20B…Back welding part 20U…Top welding part 20D…Bottom welding part 21R…Right end plate 21Ra…recess 21Rb... Rib 21L…Left end plate 23...Electron cell 23a…Bottom partition wall of battery case 23b…Lower holding part 24...Bottom ventilation channel 24a... Intake opening 24b…Communication port 25...Bulkhead 25a...Wall part 25b…Support part 25c…Fixed ribs 25d... Electrode body foil insertion part 26...legs 26a...Base 26b...Tip 26c... screw hole 26d... Rubber bushing 27…Vertical ventilation 27S... Side 27I…Inner part 27O...outer part 27D...Air intake 27U... Exhaust port 28…Connection holes 29…Detection hole 30…Positive external terminal 31... Negative external terminal 32... Flexible PCB external connector 33… Flexible circuit board wiring groove 5... Lid 5a…External surface 5b...Inner self 51... Exhaust section 51a... protruding part 51b... Exhaust port 52...Upper holding part 52a...Base 52b…recess 52c...side 52d... Rib 6…Bottom plate 7... Side panel 7F…Front plate (side plate) 7B…Back plate (side plate) 71...bulge 72...Welded part 8... Bus bar 8a...Welding surface of the foil collection section 8b... Welding surface of the foil collection section 8c...Connection part 8d…heat radiation surface 8e...Detection surface 8f…Adhesive surface 81... Negative terminal busbar 82... Positive terminal busbar 9… Flexible circuit board 9a...Front section 9b…Back part 9c... Lead section 9d…Left side part 9e...Connection part 91...Temperature / voltage detection unit 100, 101... clip

Claims

1. Multiple flat electrode bodies are arranged with alternating positive and negative electrodes, each having a positive electrode busbar connection and a negative electrode busbar connection at its horizontal end, A case having an open top, in which the plurality of flat electrode bodies are arranged such that the positive electrode busbar connection portion and the negative electrode busbar connection portion are alternately arranged in the thickness direction, and which is individually housed in a plurality of battery cases, A plurality of busbars connecting the positive electrode busbar connection portion and the negative electrode busbar connection portion of the electrode body housed in an adjacent battery case, respectively. A lid that seals the battery case of the aforementioned case and Equipped with, The busbar is arranged in the case and constitutes part of the battery case, making the battery case airtight, and a part of it is configured to dissipate heat to the outside of the battery case as a heat dissipation surface.

2. The secondary battery according to claim 1, characterized in that the heat dissipation surface of the busbar faces a space that communicates with the outside air.

3. The secondary battery according to claim 2, characterized in that the space communicating with the outside air is a vertical ventilation passage extending vertically along the busbar.

4. The secondary battery according to claim 3, characterized in that the heat dissipation surface of the busbar is arranged along the inner circumferential surface of the vertical ventilation passage.

5. The secondary battery according to claim 1, characterized in that a heat sink is provided on the heat dissipation surface of the busbar.

6. The secondary battery according to claim 3, characterized in that the air intake at the lower end of the vertical ventilation passage is in communication with the outside air through an air intake opening provided below the battery case.

7. A bottom ventilation passage is provided in the entire area below the electrode body housed in the battery case of the aforementioned case, and this passage is a space that communicates with the intake opening and the intake port of the vertical ventilation passage. The secondary battery according to claim 6.

8. The secondary battery according to claim 6, characterized in that a fan for introducing outside air is provided at the intake opening located below the battery case.

9. The secondary battery according to claim 3, characterized in that the exhaust port at the upper end of the vertical ventilation passage is in communication with the outside air through an exhaust hole provided in the cover.

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