Stack case and secondary battery

Abstract

To solve the following problem: in conventional secondary batteries, cooling efficiency of a battery cell disposed near a termination part of a duct is low.SOLUTION: A stack case 10 of the present invention is a stack case for accommodating a first battery stack and a second battery stack. The stack case includes: a first duct 14 where either branched cooling air branched from cooling air supplied through one air blowing port flows in, the first duct distributing the cooling air into a plurality of spacers included in the first battery stack; and a second duct 15 where the other branched cooling air branched from cooling air supplied through the air blowing port flows in, the second duct distributing the cooling air into a plurality of spacers included in the second battery stack. The first duct 14 and the second duct 15 have a structure where a plurality of ribs 31 is formed so as to be alternate on left and right walls from the air blowing port toward a termination part located on the side opposite to the air blowing port.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a secondary battery in which a battery pack formed by combining a large number of non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries is housed in a stack case, and the stack case thereof.

Background Art

[0002] When constructing a battery pack formed by combining a large number of non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries, a battery stack in which a plurality of secondary batteries are stacked is constructed, and this battery stack is housed in a stack case. Further, in the battery pack, cooling air may be supplied into the stack case in order to cool each of the battery cells of the battery stack. Further, when performing cooling by such cooling air, a duct is provided in the stack case, and the cooling air is supplied to each battery cell through this duct. Therefore, an example of a technique related to the cooling of a battery pack is disclosed in Patent Documents 1 to 3.

[0003] The battery pack described in Patent Document 1 is a battery pack in which a plurality of batteries are arranged, and includes a cooling medium supply passage formed along one side surface of each of the arranged batteries for supplying a cooling medium between the batteries, and a first rectifying plate provided on one side surface of the battery for changing the flow direction of the cooling medium in the cooling medium supply passage, and a second rectifying plate provided on a surface facing one side surface of the arranged batteries for changing the flow direction of the cooling medium in the cooling medium supply passage, and the first rectifying plate and the second rectifying plate are alternately arranged in the cooling medium supply passage.

[0004] The battery cooling structure described in Patent Document 2 includes an assembled battery composed of a plurality of battery modules stacked in a predetermined direction, a plurality of refrigerant passages formed between the plurality of adjacent battery modules respectively through which refrigerant flows, a refrigerant suction passage that extends in the predetermined direction and communicates with the plurality of refrigerant passages and through which the refrigerant supplied to the plurality of refrigerant passages flows, and a refrigerant discharge passage that extends in the predetermined direction and communicates with the plurality of refrigerant passages and through which the refrigerant discharged from the plurality of refrigerant passages flows. In the refrigerant suction passage and the refrigerant discharge passage, the refrigerant flows in opposite directions along the predetermined direction. Further, a refrigerant flow changing member is provided in the refrigerant suction passage, which is disposed on the upstream side of the refrigerant flow in the refrigerant suction passage with respect to the position where the refrigerant suction passage communicates with the plurality of refrigerant passages, and changes the refrigerant flow direction to the side away from the assembled battery.

[0005] The assembled battery described in Patent Document 3 includes a first and a second single battery disposed adjacent to each other, and a spacer disposed between the first and the second single batteries for providing a cooling flow path through which a cooling medium passes. The spacer includes a first protruding portion that protrudes from the center in the thickness direction toward the first single battery and forms a gap functioning as the cooling flow path between the first and the second single batteries, and a second protruding portion that protrudes from the center in the thickness direction toward the second single battery and forms a gap functioning as the cooling flow path between the second and the first single batteries. The first protruding portion and the second protruding portion are alternately repeated in a direction intersecting the cooling flow path to form a first meandering portion. A second meandering portion is disposed adjacent to the first meandering portion in the direction of the cooling flow path, and the first and the second protruding portions are alternately repeated in a direction intersecting the cooling flow path with a phase different from that of the first meandering portion.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the air flow in the duct provided in the stack case becomes more rectified as it approaches the end. And due to the rectification of the air flow in the duct, near the end portion of the duct, the pressure loss of the cooling air flowing toward the spacer side increases, resulting in a problem that the cooling efficiency of the battery cells arranged near the end portion of the duct decreases. In Patent Documents 1-3, there is a problem that the decrease in cooling efficiency caused by the increase in this pressure loss cannot be solved.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to improve the cooling efficiency of the battery cells arranged near the end portion of the duct among the cooling efficiencies of the battery cells included in the battery stack.

Means for Solving the Problems

[0009] One aspect of the stack case according to the present invention is a stack case that houses a first battery stack and a second battery stack in which battery cells and spacers are alternately stacked, and one of the branched cooling air obtained by diverting the cooling air supplied from one air inlet flows in, and a first duct that distributes the cooling air to a plurality of the spacers included in the first battery stack, and the other of the branched cooling air obtained by diverting the cooling air supplied from the air inlet flows in, and a second duct that distributes the cooling air to a plurality of the spacers included in the second battery stack, and the first duct and the second duct have a structure in which a plurality of ribs are formed alternately on the left and right walls from the air inlet toward the end portion located on the side opposite to the air inlet.

[0010] One aspect of the secondary battery according to the present invention includes a first battery stack and a second battery stack in which battery cells and spacers are alternately stacked, and a stack case that houses the first battery stack and the second battery stack with a partition wall therebetween. The stack case has a first duct into which one of the branched cooling airflows obtained by diverting the cooling air supplied from one air inlet flows, and the cooling air is distributed to a plurality of the spacers included in the first battery stack, and a second duct into which the other of the branched cooling airflows obtained by diverting the cooling air supplied from the air inlet flows, and the cooling air is distributed to a plurality of the spacers included in the second battery stack. The first duct and the second duct have a structure in which a plurality of ribs are formed alternately on the left and right walls from the air inlet toward the end portion located on the side opposite to the air inlet.

Advantages of the Invention

[0011] According to the secondary battery of the present invention, it is possible to improve the cooling efficiency of the battery cells disposed near the end portion of the duct among the cooling efficiencies of the battery cells included in the battery stack.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 10

Figure 11

Figure 12

[0013] For clarity of explanation, the following descriptions and drawings are appropriately omitted and simplified. In each drawing, the same elements are denoted by the same reference numerals, and duplicate explanations are omitted as necessary. In the following description, the direction in which battery stacks are arranged in the stack case is defined as the width direction X, the direction in which battery cells and spacers are stacked when configuring the battery stack is defined as the stacking direction Y, and the direction orthogonal to the width direction X and the stacking direction Y and serving as the height of the battery stack is defined as the height direction Z. The width direction X and the stacking direction Y coincide with the horizontal direction when the battery stack is housed in the stack case, and the height direction Z coincides with the vertical direction. In the following description, the left and right directions may be referred to with respect to the width direction X, the up and down directions may be referred to with respect to the height direction Z, and the depth direction may be referred to with respect to the stacking direction. In the following description, the combination of the battery stack and the stack case may be referred to as a secondary battery.

[0014] Embodiment 1 FIG. 1 shows a schematic view of a battery stack 1 according to Embodiment 1. As shown in FIG. 1, in the battery stack 1 according to Embodiment 1, a plurality of battery cells 2 and spacers 3 are alternately stacked.

[0015] Next, the spacer 3 will be described in detail. Note that the shape of the ribs formed on the spacer to constitute the flow path shown below is an example and is not limited thereto.

[0016] Fig. 2 shows a diagram for explaining the cooling air flow path of the spacer 3 according to Embodiment 1. As shown in Fig. 2, the spacer 3 has an air supply port 5, a first exhaust port 6, and a second exhaust port 7. The air supply port 5 is provided on a first side facing a duct provided in the stack case, and cooling air blown through the duct is supplied. The first exhaust port 6 is provided on a second side orthogonal to the first side, and discharges the cooling air supplied from the air supply port 5. The second exhaust port 7 is provided on a third side orthogonal to the first side and facing the second side, and discharges the cooling air supplied from the air supply port 5. Further, in the spacer 3, a flow path of the cooling air connecting the air supply port 5 and the first exhaust port 6 or the second exhaust port 7 is constituted by ribs 8. The spacer 3 is symmetrically formed with a first flow path connecting the air supply port 5 and the first exhaust port 6 and a second flow path connecting the air supply port 5 to the second exhaust port 7.

[0017] Subsequently, Fig. 3 shows a schematic diagram of the stack case 10 according to Embodiment 1. The stack case 10 according to Embodiment 1 is configured to be able to accommodate two battery stacks 1 side by side. Therefore, in Fig. 3, a first battery stack 21 and a second battery stack 22 are shown as two battery stacks. Also, although not shown in Fig. 3, a duct connecting tube that guides cooling air supplied from one air supply port to the first duct 14 and the second duct 15 is connected to the stack case 10.

[0018] In Fig. 3, as ducts provided in the stack case 10, there are a first duct 14 corresponding to the first battery stack 21 and a second duct 15 corresponding to the second battery stack 22. In Fig. 3, in order to more clearly explain the duct structure, the stack case 10 is shown by a solid line, the first battery stack 21 and the second battery stack 22 are shown by a broken line, and the lid and the duct connecting tube 18 are not shown.

[0019] First, in the secondary battery according to Embodiment 1, as shown in FIG. 1, battery cells and spacers are alternately stacked to form a first battery stack 21 and a second battery stack 22. Then, the first battery stack 21 and the second battery stack 22 are respectively housed in the battery stack housing region of the stack case 10. And the stack case 10 guides cooling air to the ventilation paths provided in the spacers via a first duct 14 and a second duct 15. At this time, in the secondary battery according to Embodiment 1, one of the branched cooling air obtained by diverting the cooling air supplied from one air outlet flows into the first duct 14, and the cooling air is distributed to a plurality of spacers included in the first battery stack 21. Also, in the secondary battery according to Embodiment 1, the other of the branched cooling air obtained by diverting the cooling air supplied from the air outlet flows into the second battery stack 22, and the cooling air is distributed to a plurality of spacers included in the second battery stack 22.

[0020] As shown in FIG. 3, the stack case 10 houses the first battery stack 21 and the second battery stack 22 on the left and right sides with a partition wall 11 interposed therebetween. Also, in the stack case 10, a part of the bottoms of the first battery stack 21 and the second battery stack 22 in the left - right direction is fixed so as to be in contact with the battery contact surface 12. And the stack case 10 has the first duct 14 formed on the bottom side of the first battery stack 21 and the second duct 15 formed on the bottom side of the second battery stack 22. The surfaces of the first duct 14 and the second duct 15 in contact with the battery stack are formed to be open, and the air outlets for the cooling air of the spacer 3 of the battery stack are arranged at the openings of these ducts. Then, the first duct 14 and the second duct 15 distribute the cooling air to the spacer 3.

[0021] Cooling air is supplied to the first duct 14 and the second duct 15 from an air outlet provided in the air guide duct. At this time, the stack case 10 has a flow dividing structure portion 13 with a shape that tapers toward the air outlet side at a portion where the first duct 14 and the second duct 15 merge. Due to this flow dividing structure portion 13, the cooling air supplied from the air outlet is divided into branched cooling air flowing to the first duct 14 side and branched cooling air flowing to the second duct 15. Although it will be described in detail later, near the inlet of each duct, since the air pressure and air velocity of the branched cooling air are different on the left and right in the width direction X within the duct, a swirling airflow that swirls in a direction perpendicular to the stacking direction Y is generated.

[0022] Although not shown in FIG. 3, an air guide duct is connected to the stack case 10, and cooling air is supplied from an air outlet provided in this air guide duct to the first duct 14 and the second duct 15. One air outlet is provided for the two ducts. A blower for blowing the cooling air may be provided at the air outlet.

[0023] Also, as shown in FIG. 3, the stack case 10 according to Embodiment 1 has a structure in which a plurality of ribs 31 are formed alternately on the left and right walls from the air outlet toward the end portion located on the side opposite to the air outlet. In one example, this rib 31 has a tapered shape from the bottom surface toward the height direction Z of the duct. Hereinafter, the shape of this rib 31 will be described in detail.

[0024] FIG. 4 shows a diagram for explaining the shape of the rib 31 formed in the duct according to Embodiment 1. As shown in FIG. 4, the rib 31 is provided on both the first duct 14 and the second duct 15. Further, the rib 31 is provided in a region on the end portion side from the center of the stack storage region where the first battery stack 21 and the second battery stack 22 are stored. In Embodiment 1, the rib 31 has a triangular pyramid shape. And the bottom rib apex is set at a position where the distance from the wall is the greatest on the bottom surface, and the wall rib apex at the highest position is set on the wall.

[0025] When the rib 31 takes the width direction X (hereinafter referred to as the stack adjacent direction) as the direction in which the first duct 14 and the second duct 15 are adjacent to each other, and the axis extending in the stack adjacent direction passing through the bottom rib vertex is taken as the symmetry axis, the rib 31 has a shape that is asymmetric left and right with respect to the symmetry axis. Specifically, when the vertex closest to the air outlet side among the vertices on the bottom surface side of the rib 31 is defined as the air outlet side vertex, and the vertex closest to the end portion side among the vertices on the bottom surface side of the rib 31 is defined as the end portion side vertex, the angle D formed by the side connecting the air outlet side vertex and the rib vertex and the symmetry axis is set to be smaller than the angle E formed by the side connecting the end portion side vertex and the rib vertex and the symmetry axis. Further, from another perspective, the rib 31 is formed such that the first distance between the air outlet side and the symmetry axis is shorter than the second distance between the end portion side vertex and the symmetry axis.

[0026] In addition, the plurality of ribs 31 are formed at the following pitch. When the vertex of the rib 31 formed on one wall (for example, the first rib) is defined as the first bottom rib vertex, the vertex of the rib 31 formed at the position closest to the first rib on the other wall (for example, the second rib) is defined as the second bottom rib vertex, and the vertex of the rib 31 formed at the position closest to the first rib on the same wall as the first rib (for example, the third rib) is defined as the third bottom rib vertex, the plurality of ribs 31 are arranged such that the first pitch A, which is the distance between the first bottom rib vertex and the second bottom rib vertex, is at a position that is half or less of the distance between the first bottom rib vertex and the third bottom rib vertex, which is the second pitch B. The first pitch A and the second pitch B are defined as the lengths along the direction from the air outlet of the duct to the end portion. Although it will be described in detail later, it is preferable that the first pitch A is set to 20% to 50% of the second pitch B.

[0027] Further, the rib 31 has a wall rib vertex at the highest position on the wall (for example, the highest position of the wall in the vertical direction Z), and the wall rib vertex is set at the middle position of the duct wall. Here, in FIG. 4, an angle F formed by the side connecting the bottom rib vertex and the wall rib vertex and the horizontal axis extending in the width direction X is shown. The angle F is preferably about 45 degrees. The angle H or the height of the wall rib vertex is preferably set to the above-mentioned value from the viewpoint of not hindering the flow of the cooling air toward the end portion side. In addition, although not necessarily required, by setting the wall rib vertex in the middle of the duct wall, it becomes possible to smoothly connect the duct wall and the rib 31, without hindering the air flow of the cooling air, or facilitating the molding of the duct.

[0028] Also, in FIG. 4, the distance between the wall surface and the bottom rib vertex is shown as the rib size C. The rib height C is preferably set so that, for example, the rib size C is about 1 / 3 to 1 / 2 times the width of the duct, from the viewpoint of not hindering the flow of the cooling air toward the end portion side.

[0029] Subsequently, the flow of the cooling air in the secondary battery according to the first embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 is a diagram for explaining the flow of the cooling air in the duct (for example, the first duct 14 and the second duct 15) according to the first embodiment. FIG. 6 is a diagram for explaining the flow of the cooling air branched from the duct to the spacer disposed between the battery cells housed in the stack case according to the first embodiment.

[0030] In addition, in Fig. 5, the arrows indicating the flow of the cooling air in the portion with high air pressure of the cooling air are made thick, and the arrows become thinner as the air pressure decreases. Further, in Fig. 6, the number of arrows in the portion with high air pressure of the vortex air flow is increased, and the number of arrows is decreased as the air pressure of the vortex air flow decreases. Further, in Fig. 6, the flow of the cooling air at three locations in the stack storage area where the first battery stack 21 and the second battery stack 22 are stored is schematically shown. Specifically, in Fig. 6, a schematic diagram of the flow of the cooling air at each of point α near the inlet of the duct in the stack storage area, point β near the bottom rib apex of the rib 31 formed at the position closest to the air outlet in the stack storage area, and point γ near the end portion of the stack storage area is shown.

[0031] As shown in Fig. 5, in the stack case 10 according to the first embodiment, the cooling air blown in from the air outlet is separated into the branched cooling air flowing into the first duct 14 and the branched cooling air flowing into the second duct 15 by the flow dividing structure portion 13. At this time, near the flow dividing structure portion 13, that is, near the inlet of each duct (for example, point α), the air pressure near the inner side of the stack case 10 is high, and the air pressure near the outer side is low.

[0032] Then, due to this difference in air pressure, as shown in Fig. 6, a strong vortex air flow is generated. This vortex air flow rotates clockwise on the first duct 14 side and counterclockwise on the second duct 15 side. Then, due to this vortex air flow, the cooling air flowing into the spacer 3 becomes more than the cooling air flowing in the outer direction of the stack case 10 flowing in the inner direction.

[0033] Next, in the stack case 10 according to Embodiment 1, in the region where the rib 31 is formed, the cooling air is meandered by the rib 31. Further, since the rib 31 has a triangular pyramid shape, the rib 31 meanders the cooling air and generates a pressure difference in the left - right direction of the duct to generate a vortex flow. Therefore, at point β, although the wind pressure of the cooling air in the duct is lower than that at point α, a wind pressure difference occurs between the left and right sides of the duct, generating a vortex flow. Note that the wind pressure of the vortex flow at point β is lower than that at point α. And at point β, due to the vortex flow, similar to point α, the cooling air flowing into the spacer 3 is more than the cooling air flowing from the outer direction to the inner direction of the stack case 10.

[0034] In the stack case 10 according to Embodiment 1, the rib 31 is also formed at point C. Thereby, similar to point β, a vortex flow is generated in the cooling air. And due to this vortex flow, the cooling air smoothly flows in the spacer direction even at the terminal end of the duct, suppressing the pressure loss at the terminal end of the duct.

[0035] Here, as a comparative example, an example in which the rib 31 is not provided in the stack case will be described with reference to FIGS. 7 and 8. FIG. 7 is a diagram for explaining the flow of the cooling air in the duct according to the comparative example. FIG. 8 is a diagram for explaining the flow of the cooling air branched from the duct to the spacer disposed between the battery cells housed in the stack case according to the comparative example.

[0036] As shown in FIGS. 7 and 8, regarding point α in the duct according to the comparative example, the airflow is almost the same as that in the duct according to Embodiment 1. On the other hand, at points β and γ, which are regions from the central part to the end part of the ducts with different rib 31 configurations, the airflow is different between the comparative example and Embodiment 1. Specifically, in the duct according to the comparative example, at point β, since the cooling air does not meander, although vortical airflow is generated, the wind pressure of the vortical airflow is lower than that of the stack case 10 according to Embodiment 1, and the air volume of the cooling air flowing toward the spacer 3 side decreases. Also, at point γ, although vortical airflow is not generated, a swirling vortex is generated in which the cooling air that has reached a dead end at the end part swirls in a top view. Further, in the comparative example, at point γ, vortical airflow is not generated, and the air volumes of the airflow flowing outside the stack case and the airflow flowing inside via the spacer 3 are almost the same and decrease. The generation of the swirling flow in the comparative example is due to the fact that the wind pressure of the cooling air discharged via the spacer 3, that is, the pressure loss, is smaller than that of the duct according to Embodiment 1.

[0037] Here, the effect of reducing the pressure loss at the end portion of the duct by providing the rib 31 will be described in detail. First, FIG. 9 shows a graph for explaining the difference in pressure loss caused by the difference in the asymmetry of the ribs in the stack case 10 according to the first embodiment. In FIG. 9, the comparative example is the one described in FIGS. 7 and 8. In the stack case 10 according to the first embodiment, it has been found by the verification of the inventors that when the shape on the air outlet side and the shape on the end portion side are targeted with the symmetry axis passing through the bottom rib apex of the rib 31 as the axis of line symmetry, a phenomenon occurs in which the pressure loss becomes higher than that of the comparative example. As shown in FIG. 4, the rib 31 has an asymmetrical shape on the left and right such that the angle D formed around the symmetry axis is larger than the angle E, whereby the effect of reducing the pressure loss shown in FIG. 9 can be obtained. FIG. 9 is a verification result based on an example in which the angle D is set to 60° and the angle E is set to 75°. As shown in FIG. 9, by setting the angle D to 60° and the angle E to 75°, in the stack case 10 according to the first embodiment, it becomes possible to reduce the pressure loss compared to the comparative example. Thus, by making the inclination of the rib 31 on the end portion side of the duct gentler than the inclination of the rib 31 on the air outlet side, it becomes possible to reduce the swirling airflow generated on the end portion side rather than the bottom rib apex.

[0038] Further, FIG. 10 shows a graph for explaining the difference in pressure loss caused by the difference in the pitch of the ribs in the stack case 10 according to the first embodiment. The example shown in FIG. 10 is a graph (the left curve of the graph) in which the pressure loss is calculated when the first pitch A is changed to 50 mm, 86 mm, and 100 mm with the second pitch B fixed at 173 mm, for example, and a graph (the right curve of the graph) in which the pressure loss is calculated when the second pitch B is changed to 150 mm, 173 mm, and 200 mm with the first pitch A fixed at 86 mm, for example.

[0039] As shown in FIG. 10, the changes in the first pitch A and the second pitch B cause a change in pressure loss along a parabola that is generally a quadratic curve. And, as shown in FIG. 10, it can be seen from FIG. 10 that the relationship between the first pitch A and the second pitch B that can reduce the pressure loss compared to the comparative example is a region where the first pitch A is in the range of 20% to 50% of the second pitch B. It should be easily understood by those skilled in the art that the absolute values of the first pitch A and the second pitch B vary depending on the cross-sectional area of the cross-section that can recognize the height and width of the duct, and the length of the duct.

[0040] From the above description, in the stack case 10 according to Embodiment 1, by providing the rib 31 in the region from near the center of the duct toward the end portion, a swirling airflow is generated also in the latter half portion of the duct. Thereby, the stack case 10 according to Embodiment 1 can enhance the efficiency of sending the cooling air to the spacer 3 and reduce the pressure loss at the end portion of the duct. And, by using the stack case 10 according to Embodiment 1, it becomes possible to enhance the cooling efficiency of the battery cell disposed near the end portion of the duct. Further, since the shape of the rib 31 has a tapered shape in the height direction of the duct, the generation efficiency of the swirling airflow on the rear end portion side of the duct can be enhanced. Here, the generation efficiency refers to the degree to which the strength of the swirling airflow weakens toward the rear end portion side of the duct, and the higher the generation efficiency of the swirling airflow, the faster the flow velocity of the swirling airflow on the rear end portion side of the duct.

[0041] Also, in the stack case 10 according to Embodiment 1, since integral molding by a molding die such as die casting is possible, it becomes possible to suppress the labor required for parts management to be equivalent to that of the stack case according to the comparative example.

[0042] Embodiment 2 In Embodiment 2, a stack case 40 which is another form of the stack case 10 according to Embodiment 1 will be described. In the description of Embodiment 2, the same components as those described in Embodiment 1 are denoted by the same reference numerals as those in Embodiment 1, and the description thereof is omitted.

[0043] FIG. 11 shows a diagram for explaining the duct according to the second embodiment. As shown in FIG. 11, in the stack case 40 according to the second embodiment, it has ribs 41 instead of the ribs 31. The rib 41 has a semi-conical shape that tapers in the height direction of the duct from the bottom surface. And in the stack case 40, a plurality of ribs 41 are formed such that they alternate on the left and right walls from the air outlet toward the end portion located on the side opposite to the air outlet.

[0044] Subsequently, FIG. 12 shows a diagram for explaining the shape of the rib formed on the duct according to the second embodiment. As shown in FIG. 12, the rib 41 is obtained by dividing an elliptical cone in half from the apex toward the bottom surface. And when the direction in which the first duct 14 and the second duct 15 are adjacent to each other is defined as the stack adjacent direction, and the axis extending in the stack adjacent direction passing through the apex of the bottom rib is defined as the symmetry axis, the first distance G between the apex on the air outlet side and the symmetry axis is formed shorter than the second distance H between the apex on the end portion side and the symmetry axis. Note that for the rib 41, the first pitch A, the second pitch B, the rib size C, and the included angle F are set the same as those of the rib 31.

[0045] By forming the rib 41 as a semi-elliptical cone in this way and making the first distance G smaller than the second distance H, it becomes possible to reduce the recirculation airflow generated on the end portion side of the apex of the bottom rib compared to the rib 31.

[0046] Note that the present invention is not limited to the above-described embodiments, and can be appropriately modified without departing from the gist thereof.

Explanation of Reference Numerals

[0047] 1 Battery stack 2 Battery cell 3 Spacer 5 Air supply port 6 First exhaust port 7 Second exhaust port 8 Rib 10, 40 Stack case 11 Partition wall 12 Battery contact surface 13 Shunt structure part 14 First duct 15 Second duct 21 First battery stack 22 Second battery stack 31, 41 Ribs

Claims

1. A stack case for housing a first battery stack and a second battery stack in which battery cells and spacers are alternately stacked, having a first duct into which one of the branched cooling air obtained by diverting the cooling air supplied from one air outlet flows, and distributing the cooling air to a plurality of the spacers included in the first battery stack; and a second duct into which the other of the branched cooling air obtained by diverting the cooling air supplied from the air outlet flows, and distributing the cooling air to a plurality of the spacers included in the second battery stack, wherein the first duct and the second duct have a structure in which a plurality of ribs are formed alternately on left and right walls from the air outlet toward a terminal end portion located on the side opposite to the air outlet.

2. The stack case according to claim 1, wherein the rib has a triangular pyramid shape or a semi-cone shape that tapers in the height direction of the duct from the bottom surface of the duct.

3. The rib has a bottom rib apex at a position on the bottom surface of the duct that is the farthest from the wall, and when the direction in which the first duct and the second duct are adjacent to each other is defined as the stack adjacent direction, and an axis extending in the stack adjacent direction passing through the bottom rib apex is defined as the symmetry axis, the stack case according to claim 1 or 2 has a left-right asymmetric shape with respect to the symmetry axis.

4. The rib has a bottom rib apex at a position on the bottom surface of the duct that is the farthest from the wall, and when the direction in which the first duct and the second duct are adjacent to each other is defined as the stack adjacent direction, and an axis extending in the stack adjacent direction passing through the bottom rib apex is defined as the symmetry axis, a first distance between a vertex on the bottom surface on the air outlet side and the symmetry axis is formed shorter than a second distance between a vertex on the bottom surface on the terminal end portion side and the symmetry axis, the stack case according to claim 1 or 2.

5. The rib has a wall rib apex that is the highest position on the wall, and the wall rib apex is set at an intermediate position of the wall of the duct. The stack case according to claim 1 or 2.

6. The rib has a bottom rib apex at a position that is the farthest distance from the wall on the bottom surface of the duct. When the apex of the first rib formed on one wall is the first bottom rib apex, the apex of the second rib formed at the position closest to the first rib on the other wall is the second bottom rib apex, and the apex of the third rib formed at the position closest to the first rib on the same wall as the first rib is the third bottom rib apex, the first pitch, which is the distance between the first bottom rib apex and the second bottom rib apex in the direction from the air supply port to the end portion of the duct, is set to 20% to 50% of the second pitch, which is the distance between the first bottom rib apex and the third bottom rib apex in the direction from the air supply port to the end portion of the duct. The stack case according to claim 1 or 2.

7. The rib is provided in a region on the end portion side from the center of the stack storage region where the first battery stack and the second battery stack are stored. The stack case according to claim 1 or 2.

8. A first battery stack and a second battery stack in which battery cells and spacers are alternately stacked. A stack case that houses the first battery stack and the second battery stack with a partition wall therebetween. The stack case includes: A first duct into which one of the branched cooling air obtained by diverting the cooling air supplied from one air supply port flows, and the cooling air is distributed to a plurality of the spacers included in the first battery stack. A second duct into which the other of the branched cooling air obtained by diverting the cooling air supplied from the air supply port flows, and the cooling air is distributed to a plurality of the spacers included in the second battery stack. The first duct and the second duct have a structure in which a plurality of ribs are formed alternately on the left and right walls from the air outlet toward the end portion located on the side opposite to the air outlet in a secondary battery.

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