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 in cooling efficiency of battery cells included in a battery stack is low.SOLUTION: A stack case of the present invention is a stack case for accommodating a first battery stack including battery cells and spacers 31 alternately stacked and a second battery stack including battery cells and spacers 32 alternately stacked. The stack case includes: a first duct 14 where either branched cooling air branched from cooling air supplied through one air supply port flows in, the first duct distributing the cooling air into the plurality of spacers 31 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 supply port flows in, the second duct distributing the cooling air into the plurality of spacers 32 included in the second battery stack. The first duct 14 and the second duct 15 have a structure where the left-right asymmetry of a cross-sectional shape of a flow path gradually increases from the air supply port toward a termination part located on the side opposite to the air supply port.SELECTED DRAWING: Figure 4

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 cell stack in which a plurality of secondary batteries are stacked is constructed, and this cell 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 cell 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 a duct is disclosed in Patent Document 1.

[0003] The duct structure described in Patent Document 1 is a duct structure in which an intake opening and an exhaust opening are formed in a container having a chamber formed therein, and a swirling flow regulating surface along the opening direction of the exhaust opening is provided at a position inside the chamber on the inner side of the exhaust opening container, and a swirling flow regulating member for regulating the generation of a swirling flow at the exhaust opening is provided.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the duct structure described in Patent Document 1, by arranging a swirling flow regulating member that regulates the generation of a swirling flow around the exhaust opening of the duct, the airflow around the exhaust opening of the duct is rectified. However, when distributing the airflow to a plurality of airflow distribution destinations according to the flow path, rectifying the airflow increases the pressure loss near the end portion of the flow path, resulting in a problem that the cooling efficiency of the battery cell disposed near the end portion of the duct decreases.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to improve the cooling efficiency of a battery cell disposed near the end portion of a duct among the cooling efficiencies of the battery cells included in a battery stack.

Means for Solving the Problems

[0007] 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 supply port flows in, 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 supply port flows in, 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 duct have a structure in which the left-right asymmetry of the cross-sectional shape of the flow path gradually increases toward the end portion located on the side opposite to the air supply port from the air supply port.

[0008] 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 air streams 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 air streams 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 duct have a structure in which the left-right asymmetry of the cross-sectional shape of the flow path gradually increases toward the end portion located on the side opposite to the air inlet from the air inlet.

Advantages of the Invention

[0009] According to the secondary battery of the present invention, it is possible to improve the cooling efficiency of the battery cells included in the battery stack, particularly the battery cells arranged near the end portion of the duct.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0011] For the sake of clarity of explanation, the following descriptions and drawings are appropriately omitted and simplified. In each drawing, the same reference numerals are assigned to the same elements, and duplicate explanations are omitted as necessary. Also, in the following description, the direction in which battery stacks are arranged within the stack case is defined as the width direction X, the direction in which battery cells and spacers are stacked when constructing the battery stack is defined as the stacking direction Y, which is orthogonal to the width direction X and the stacking direction Y, and the direction that becomes the height of the battery stack is defined as the height direction Z. And 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. Also, in the following description, the left - right direction may be referred to with respect to the width direction X, the up - down direction 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.

[0012] Embodiment 1 FIG. 1 shows a schematic diagram of a secondary battery 1 according to Embodiment 1. Also, FIG. 2 shows a schematic view of the duct portion of the stack case according to Embodiment 1 as seen from the outside. The secondary battery 1 according to Embodiment 1 includes a stack case 10, a lid, a first battery stack 21, a second battery stack 22, and an air duct 18.

[0013] In FIG. 1, to more clearly explain the structures of the first duct 14 and the second duct 15 provided in the stack case 10, 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 dashed line, and the lid and the air duct 18 are not shown.

[0014] Also, in FIG. 2, only the spacer 31 incorporated in the first battery stack 21, the spacer 32 incorporated in the second battery stack 22, the first duct 14, and the second duct 15 are shown, and other members are omitted for the sake of explanation.

[0015] First, in the secondary battery 1 according to Embodiment 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 regions of the stack case 10. And the stack case 10 guides cooling air to the ventilation paths provided in the spacers via the first duct 14 and the second duct 15. At this time, in the secondary battery 1 according to Embodiment 1, one of the branched cooling air obtained by diverting the cooling air supplied from one air supply port 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 1 according to Embodiment 1, the other of the branched cooling air obtained by diverting the cooling air supplied from the air supply port flows into the second duct 15, and the cooling air is distributed to a plurality of spacers included in the second battery stack 22. Here, in the secondary battery 1 according to Embodiment 1, the first duct 14 and the second duct 15 have a structure in which the left - right asymmetry of the cross - sectional shape of the flow path gradually increases toward the end portion located on the side opposite to the air supply port from the air supply port.

[0016] In the secondary battery 1 according to Embodiment 1, when the first duct 14 and the second duct 15 are formed in such a shape, a swirling airflow that swirls in a direction perpendicular to the stacking direction Y of the battery stack is created around the end portion of the duct. And by generating this swirling airflow, the pressure loss around the end portion of the duct is reduced. Hereinafter, mainly the structure of the duct will be described in detail with reference to the drawings.

[0017] As shown in FIGS. 1 and 2, the stack case 10 stores the first battery stack 21 and the second battery stack 22 on the left and right sides with the partition wall 11 interposed therebetween. Further, 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 to be in contact with the battery contact surface 12. And, the stack case 10 has a first duct 14 formed on the bottom side of the first battery stack 21 and a 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 that contact the battery stack are formed to be open, and the air supply ports for the cooling air of the spacers 31 and 32 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 spacers 31 and 32.

[0018] The cooling air is supplied to the first duct 14 and the second duct 15 from the air supply port provided in the air guide pipe 18. At this time, the stack case 10 has a flow - dividing structure portion 13 with a shape that tapers toward the air supply port side at the portion where the first duct 14 and the second duct 15 merge. The cooling air supplied from the air supply port is divided into the branched cooling air flowing to the first duct 14 side and the branched cooling air flowing to the second duct 15 by this flow - dividing structure portion 13. Although it will be described in detail later, near the inlet of each duct, since the air pressure and the air velocity of the branched cooling air are different on the left and right in the width direction X in the duct, a swirling air flow that swirls in a direction perpendicular to the stacking direction Y is generated.

[0019] And, the first duct 14 and the second duct 15 have a slope surface 16 and a slope surface 17. In the stack case 10 according to Embodiment 1, the slope surface 16 and the slope surface 17 make the left - right asymmetry of the cross - sectional shape of the flow path gradually increase from the air supply port toward the terminal portion located on the side opposite to the air supply port.

[0020] More specifically, the bottom surface of each duct is inclined obliquely. Here, in the stack case 10, the slope surfaces 16 and 17 are formed such that the length of the inclined surface becomes longer toward the terminal end of the duct. Further, the slope surfaces 16 and 17 are provided on the bottom surface along the outer sides of the first duct 14 and the second duct 15 on the outer peripheral side of the stack case 10. The slope surfaces 16 and 17 are provided in a region on the terminal side from the center of the stack storage region where the first battery stack and the second battery stack are stored. With such a structure, the first duct 14 and the second duct 15 have a bilaterally symmetric cross-sectional shape orthogonal to the entering direction of the cooling air on the air supply port side, and a bilaterally asymmetric cross-sectional shape orthogonal to the entering direction of the cooling air on the terminal end side. Here, the cross-sectional shape is defined based on a cross-section parallel to the width direction X of the stack case 10.

[0021] As shown in FIG. 2, an air guide duct 18 is connected to the stack case 10, and cooling air is supplied from an air supply port provided in the air guide duct 18 to the first duct 14 and the second duct 15. One air supply port is provided for the two ducts. A blower for blowing the cooling air may be provided at the air supply port.

[0022] Subsequently, the flow of the cooling air in the secondary battery 1 according to the first embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram for explaining the flow of the cooling air in the ducts (for example, the first duct 14 and the second duct 15) according to the first embodiment. FIG. 4 is a diagram for explaining the flow of the cooling air branched from the ducts to the spacers disposed between the battery cells stored in the stack case according to the first embodiment.

[0023] In addition, in FIG. 3, 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 are made thinner as the air pressure becomes lower. Further, in FIG. 4, 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 becomes lower. Further, in FIG. 4, 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. 4, schematic diagrams of the flow of the cooling air at point A near the inlet of the duct in the stack storage area, point B near the center of the stack storage area, and point C near the end portion of the stack storage area are shown respectively.

[0024] As shown in FIG. 3, in the stack case 10 according to the first embodiment, the cooling air blown from the air supply port is separated into the branched cooling air flowing into the first duct 14 and the branched cooling air flowing into the second duct 15 in 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 A), the air pressure near the inside of the stack case 10 is high, and the air pressure near the outside is low.

[0025] Then, due to this difference in air pressure, as shown in FIG. 4, a strong vortex air flow is generated. This vortex air flow is 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 spacers 31 and 32 is more than the cooling air flowing in the inner direction of the cooling air flowing in the outer direction of the stack case 10.

[0026] Subsequently, at point B, since the air pressure of the cooling air in the duct is lower than that at point A, the air pressure difference between the left and right of the duct is also lower than that at point A. As a result, at point B, the air pressure of the vortex air flow is lower than that at point A. However, at point B, since the vortex air flow is generated, the cooling air flowing into the spacers 31 and 32 is more than the cooling air flowing in the inner direction of the cooling air flowing in the outer direction of the stack case 10, similar to point A.

[0027] Subsequently, at point C, the slope surfaces 16 and 17 create a difference in the left and right areas of the duct, and due to this area difference, a pressure difference occurs between the left and right sides of the duct. Then, in the stack case 10 according to the first embodiment, a vortex airflow is generated even at the end of the duct due to the pressure difference between the left and right sides of the duct. And due to this vortex airflow, more cooling air flowing in the outer direction of the stack case 10 becomes more than the cooling air flowing in the inner direction.

[0028] Here, as a comparative example, the airflow when the slope surfaces 16 and 17 are not provided will be described with reference to FIGS. 5 and 6. FIG. 5 is a diagram for explaining the flow of cooling air in the duct according to the comparative example. FIG. 6 is a diagram for explaining the flow of cooling air branched from the duct to the spacers arranged between the battery cells housed in the stack case according to the comparative example.

[0029] As shown in FIGS. 5 and 6, regarding points A and B in the duct according to the comparative example, the airflow is almost the same as that in the duct according to the first embodiment. On the other hand, at point C, which is the end of the duct where the presence or absence of the slope surface is different, the airflow is different between the comparative example and the first embodiment. Specifically, in the duct according to the comparative example, at point C, no vortex airflow is generated, but a swirling vortex is generated in which the cooling air that has reached a dead end at the end forms a swirling flow when viewed from above. Also, in the comparative example, at point C, no vortex airflow is generated, and the air volumes of the airflow flowing outside and inside the stack case through the spacers 31 and 32 are almost the same. The generation of the swirling flow in the comparative example is due to the fact that the pressure drop of the cooling air discharged through the spacers 31 and 32, that is, the pressure loss, is smaller than that in the duct according to the first embodiment.

[0030] Therefore, Fig. 7 shows a graph comparing a comparative example and Embodiment 1 with respect to pressure loss. Fig. 7 shows the magnitude of the pressure loss at point C. As shown in Fig. 7, in the duct according to the decimal form 1, the pressure loss at the end portion of the duct has decreased to less than half of the duct according to the comparative example. Such a decrease in pressure loss is caused by the increased efficiency of the cooling air flowing toward the spacers 31 and 32 due to the swirling air flow.

[0031] From the above description, in the stack case 10 according to Embodiment 1, by reducing the pressure loss at the end portion of the duct, the efficiency of delivering the cooling air to the spacers 31 and 32 at the end portion can be increased. Thereby, in the secondary battery 1 according to Embodiment 1, it becomes possible to increase the cooling efficiency of the battery cells arranged near the end portion of the duct.

[0032] Note that the present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the spirit thereof.

Description of Reference Numerals

[0033] 1 Secondary battery 10 Stack case 11 Partition wall 12 Battery contact surface 13 Flow splitting structure portion 14 First duct 15 Second duct 16 Slope surface 17 Slope surface 18 Air guide duct 21 First battery stack 22 Second battery stack 31 Spacer 32 Spacer

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 inlet flows, and distributing the cooling air to the plurality of 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 inlet flows, and distributing the cooling air to the plurality of spacers included in the second battery stack, wherein the first duct and the second duct have a structure in which the left-right asymmetry of the cross-sectional shape of the flow path gradually increases toward the end portion located on the side opposite to the air inlet.

2. The stack case according to claim 1, wherein the first duct and the second duct have a slope surface that obliquely inclines the bottom surface of the duct, and the slope surface is formed such that the length of the inclined surface increases toward the end portion.

3. The stack case according to claim 2, wherein the slope surface is provided on the bottom surface along the outer sides of the first duct and the second duct on the outer peripheral side of the stack case.

4. The stack case according to claim 2, wherein the slope surface is provided in a region on the end portion side from the center of the stack storage region in which the first battery stack and the second battery stack are stored.

5. The stack case according to claim 1, wherein the first duct and the second duct have a left-right symmetric cross-sectional shape orthogonal to the entering direction of the cooling air on the air inlet side, and a left-right asymmetric cross-sectional shape orthogonal to the entering direction of the cooling air on the end portion side.

6. The stack case according to claim 1, having a flow diversion structure portion with a shape that tapers toward the air inlet side at a portion where the first duct and the second duct merge.

7. 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 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 inlet flows, and that distributes 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 inlet flows, and that distributes the cooling air to a plurality of the spacers included in the second battery stack. The first duct and the second duct have a structure in which the left - right asymmetry of the cross - sectional shape of the flow path gradually increases toward the end portion located on the side opposite to the air inlet from the air inlet. A secondary battery.

Images