Battery module

Abstract

To provide a battery module with suppressed lithium deposition.SOLUTION: A battery module comprises a plurality of battery cells 2 and a plurality of elastic bodies 3 alternately arranged in one direction. The battery cells 2 each comprise: electrode bodies 25 and 26; current collector foils 22 and 23 drawn from edge parts of the electrode bodies 25 and 26; and a battery case 21 that accommodates the electrode bodies 25 and 26 and the current collector foils 22 and 23. The electrode bodies 25, 26 each comprise: a first region E1 which includes an edge part with the current collector foil 22, 23 being drawn therefrom, and in which current is concentrated when charged; and a second region E2 which is located at an opposite side to the current collector foil 22, 23 across the first region E1, and in which less current is concentrated when charged compared with the first region E1. The elastic bodies 3 each comprise: a first rib 31 opposed to the first region E1 across the battery case 21; and a plurality of second ribs 32 and 33 opposed to the second region E2 across the battery case 21. A contact area between the first rib 31 and the battery case 21 is larger than that between the largest rib 33 of the plurality of second ribs 32 and 33 and the battery case 21.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to the structure of a battery module.

Background Art

[0002] In recent years, rechargeable batteries that have become popular for automotive applications are generally assembled batteries in which a plurality of single cells are connected to increase the capacity. In particular, rechargeable batteries for electric vehicle applications require high output, and thus lithium-ion secondary batteries having a high energy density are used.

[0003] Patent Document 1 discloses an assembled battery having both overcharge resistance and high-rate resistance. The assembled battery is formed by alternately arranging single cells and an elastic body as a single unit. The single cell includes an electrode body having a positive electrode and a negative electrode, and a battery case that houses the electrode body and has a pair of long side surfaces facing the elastic body. The elastic body includes a pressing portion that presses a part of the reaction portion in the arrangement direction against the surface facing the long side surface of the single cell. The pressing portion presses only a specific region and is configured to avoid excessive pressing.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A lithium-ion secondary battery used as a battery for an electric vehicle needs to have a certain cooling performance from the viewpoint of safety. For this purpose, the lithium-ion secondary battery is provided with an elastic body in which a cooling passage for flowing cooling air is formed between single cells constituting the battery, and is designed to maintain the cooling performance. However, a lithium-ion secondary battery for electric vehicle applications has a high external restraint force on the single cells in order to achieve a high density of capacity, and has a structure in which a high pressure is applied to the single cells depending on the structure of the elastic body. Therefore, the electrode distance between the positive electrode and the negative electrode constituting the single cell becomes locally small, and current concentration may occur. Current concentration causes precipitation of lithium inside the single cell, and the precipitated lithium may cause an internal short circuit.

[0006] An object of the present disclosure is to provide a battery module that suppresses lithium precipitation inside the battery due to external restraint.

Means for Solving the Problems

[0007] A first aspect of the present disclosure relates to a battery module. In a battery module including a plurality of battery cells and a plurality of elastic bodies alternately arranged in one direction, The battery cell includes an electrode body, a current collector foil drawn out from an edge of the electrode body, and a battery case that houses the electrode body and the current collector foil. The electrode body includes a first region that includes an edge from which the current collector foil is drawn out and where current concentrates during charging, and a second region that is located on the opposite side of the current collector foil with the first region interposed therebetween and where the current concentration during charging is smaller than that in the first region. The elastic body includes a first rib facing the first region with the battery case interposed therebetween, and a plurality of second ribs facing the second region with the battery case interposed therebetween. The contact area between the first rib and the battery case is larger than the contact area between the largest rib among the plurality of second ribs and the battery case.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to provide a battery module that suppresses lithium precipitation inside the battery due to external restraint.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0010] Figure 1 is an overall view of the battery module in the present embodiment.

[0011] The battery module 1 includes a plurality of battery cells 2 and a plurality of elastic bodies 3 that are alternately arranged in one direction. Further, the battery module 1 includes an end plate 4, a terminal connection portion 5, a restraint plate 6, and a cover 7.

[0012] The battery cell 2 is sandwiched from both sides by the elastic body 3. Specifically, one battery cell 2 has a pair of long side surfaces in the arrangement direction, and is sandwiched by two elastic bodies 3 from both sides of the long side surfaces.

[0013] The elastic body 3 sandwiches the battery cell 2 from both sides in the arrangement direction. Specifically, one elastic body 3 contacts two different battery cells 2 on both sides.

[0014] The end plate 4 is arranged at both ends in the arrangement direction so as to sandwich the plurality of battery cells 2 and the plurality of elastic bodies 3 from both sides in the arrangement direction. The end plate 4 contacts the battery cell 2 at both ends in the arrangement direction. The end plate 4 is in contact with the restraint plate 6, and receives a force from the restraint plate 6 in the direction in which the battery cell 2 and the elastic body 3 are arranged.

[0015] The terminal connection part 5 connects the positive electrode terminal led out to the outside of the battery cell 2 and the negative electrode terminal led out to the outside of another battery cell 2. In the present embodiment, a plurality of terminal connection parts 5 are provided to continuously electrically connect a plurality of battery cells 2.

[0016] The restraint plate 6 sandwiches a plurality of battery cells 2 arranged in one direction, a plurality of elastic bodies 3, and the end plates 4. Two restraint plates 6 are arranged so as to face each other in a direction perpendicular to the arrangement direction.

[0017] The cover 7 covers the plurality of battery cells 2, the plurality of elastic bodies 3, and the end plates 4 from above the terminal connection part 5.

[0018] FIG. 2 is a schematic diagram showing a part of the internal structure of the battery cell 2.

[0019] The battery cell 2 includes a battery case 21, a positive electrode body 25, a negative electrode body 26, a positive electrode current collector foil 22, a negative electrode current collector foil 23, and a separator 24 disposed between the positive electrode body 25 and the negative electrode body 26.

[0020] The battery case 21 is a case having a pair of long side surfaces facing each other in the direction in which the battery cells 2 are arranged, and a plurality of positive electrode bodies 25, separators 24, and negative electrode bodies 26 are arranged inside.

[0021] The positive electrode current collector foil 22 is connected to the positive electrode body 25, and the negative electrode current collector foil 23 is connected to the negative electrode body 26. The positive electrode current collector foil 22 and the negative electrode current collector foil 23 are connected to the positive electrode body 25 and the negative electrode body 26, respectively, for the purpose of taking out current to the outside of the electrode body.

[0022] The negative electrode body 26 can be divided into a first region E1 including the edge portion from which the negative electrode current collector foil 23 is drawn out and a second region E2 located on the side opposite to the negative electrode current collector foil 23 with the first region E1 interposed therebetween. In the negative electrode body 26, during charging, current tends to concentrate near the edge portion from which the negative electrode current collector foil 23 is drawn out. That is, the first region E1 is a region where current concentration during charging is larger than that in the second region E2.

[0023] Current concentration in the negative electrode body 26 causes lithium precipitation, leading to a decrease in charge and discharge efficiency. The elastic body 3 described below is devised to mitigate current concentration in the negative electrode body 26, particularly power concentration in the first region E1.

[0024] FIG. 3 is a diagram showing the structure of the elastic body 3.

[0025] The elastic body 3 has a first rib 31 and a plurality of second ribs 32. The first rib 31 and the second ribs 32 are provided so as to face both sides of the elastic body center 34. The first rib 31 and the second ribs 32 are each in contact with a different battery cell 2.

[0026] The elastic body 3 further has a sealing portion 35. A refrigerant for cooling the battery cell 2 flows between the ribs provided on the elastic body 3. In the present embodiment, the refrigerant is air, and air flows between the ribs. The sealing portion 35 is a member provided to prevent the refrigerant from leaking to the outside. The sealing portion 35 is provided so as to face both sides of the elastic body center 34, similar to the first rib 31 and the second ribs 32.

[0027] The first rib 31 faces the first region E1 of the negative electrode body 26 in the arrangement direction with the battery case 21 interposed therebetween. The largest second rib 33 faces the second region E2 of the negative electrode body 26 in the arrangement direction with the battery case 21 interposed therebetween.

[0028] The measure for mitigating power concentration in the first region E1 lies in the size of the first rib 31. The first rib 31 has the largest size among all the ribs. More specifically, the contact area between the first rib 31 and the battery case 21 is larger than the contact area between the largest second rib 33 among the second ribs 32 and the battery case 21.

[0029] The second rib 33 is larger than the other second ribs 32 in order to ensure the strength of the elastic body 3. Also, by being disposed at the center, the largest second rib 33 contributes to further improving the strength.

[0030] Figure 4 is a schematic diagram showing the flow of current inside the battery cell.

[0031] In the battery cell 2, the positive electrode body 25 and the negative electrode body 26 face each other with the separator 24 interposed therebetween. The positive electrode body 25 is connected to the positive current collector foil 22, and the negative electrode body is connected to the negative current collector foil 23.

[0032] During charging, current flows from the positive electrode body 25 to the negative electrode body 26 in the battery cell 2. Specifically, current flows from an external power source to the positive current collector foil 22, and then flows between the electrode bodies through the positive electrode body 25. Between the electrode bodies, the current flows through the separator 24 to the negative electrode body 26. The current flowing into the negative electrode body 26 passes through the negative current collector foil 23 and flows into the external circuit.

[0033] As disclosed in FIG. 4, inside the negative electrode body 26, since the current flows toward the negative current collector foil 23, current concentration occurs in the region immediately below the negative current collector foil 23 (the first region E1) including the edge where the negative current collector foil 23 is drawn out.

[0034] Figure 5 is a diagram showing the contact state between the battery cell and the elastic body.

[0035] The elastic body 3 is arranged such that the first rib 31 and the second rib 32 provided on the elastic body 3 are in contact with the battery case 21.

[0036] The battery cell 2 is pressed by the elastic body 3, and stress concentration regions are generated in the battery case 21 due to the pressure received from each rib. Two stress concentration regions 28 and 29 are shown in FIG. 5 as representatives. The stress concentration region 28 is a region generated by the pressure received from the first rib 31. The stress concentration region 29 is a region generated by the pressure received from the largest second rib 33.

[0037] The stress concentration region 28 has a region overlapping with the first region E1. Also, the stress concentration region 29 has a region overlapping with the second region E2. The stress concentration regions caused by the other second ribs 32 also have regions overlapping with the second region E2. However, none of the stress concentration regions caused by any of the second ribs 32 have regions overlapping with the first region E1.

[0038] The contact area between the first rib 31 and the battery case 21 is larger than the contact area between the largest second rib 33 and the battery case 21. This means that the pressure received by the battery cell 2 from the first rib 31 is smaller than the pressure received by the battery cell 2 from the largest second rib 33. Therefore, the stress applied to the stress concentration region 28 is smaller than the stress applied to any of the stress concentration regions caused by the second ribs 32 including the stress concentration region 29.

[0039] The stress applied to the first region E1 is affected by the stress applied to the stress concentration region 28. Since the stress applied to the stress concentration region 28 is smaller than the stress applied to any other stress concentration region, the stress applied to the first region E1 is smaller than the stress applied to any part of the second region E2. According to this embodiment, since the stress applied to the first region E1 is relaxed compared to the stress applied to other regions, the distance between the positive electrode body 25 and the negative electrode body 26 is ensured. Therefore, lithium precipitation is suppressed in the first region E1 where current concentration occurs.

[0040] However, if the first rib 31 is made too large, the passage through which the refrigerant flows will be narrowed, which will have an adverse effect on the cooling performance. Therefore, an upper limit is set for the size of the first rib 31. Specifically, the contact area between the first rib 31 and the battery case 21 is made smaller than the total contact area between the second ribs 32 and the battery case 21.

[0041] Specifically, when the contact area between the first rib 31 and the battery case 21 is set with the total contact area where the elastic body 3 contacts one battery case 21 being 100%, it may occupy 5 to 15%. The total contact area between the elastic body 3 and the battery case 21 includes the contact area between the sealing portion 35 and the battery case 21. By setting the contact area between the first rib 31 and the battery case 21 within the above range, it is possible to suppress lithium precipitation due to current concentration while satisfying the requirements regarding cooling performance.

[0042] In the present embodiment, in order to reduce the stress applied to the first region E1, the contact area between the first rib 31 facing the first region E1 and the battery case 21 is increased. Instead of or in addition to this, the first rib 31 may be formed of a material softer than other ribs. The softer material means a material with a small Vickers hardness.

Explanation of Reference Numerals

[0043] 1 Battery module, 2 Battery cell, 3 Elastic body, 4 End plate, 5 Terminal connection portion, 6 Restraining plate, 7 Cover, 21 Battery case, 22 Positive current collector foil, 23 Negative current collector foil, 24 Separator, 25 Positive electrode body, 26 Negative electrode body, 28 Stress concentration region, 29 Stress concentration region, 31 First rib, 32 Second rib, 33 Largest second rib, 34 Elastic body center, 35 Sealing portion, E1 First region, E2 Second region

Claims

1. In a battery module comprising a plurality of battery cells and a plurality of elastic bodies alternately arranged in one direction, the battery cell includes: an electrode body; a current collecting foil drawn out from an edge of the electrode body; a battery case for housing the electrode body and the current collecting foil; and the electrode body includes: a first region including the edge from which the current collecting foil is drawn out and where current concentrates during charging; a second region located on the opposite side of the current collecting foil with the first region interposed therebetween and having less current concentration during charging compared to the first region; and the elastic body includes: a first rib facing the first region with the battery case interposed therebetween; a plurality of second ribs facing the second region with the battery case interposed therebetween; and the contact area between the first rib and the battery case is larger than the maximum contact area among the contact areas between each of the plurality of second ribs and the battery case, and the total contact area between the plurality of second ribs and the battery case is larger than the contact area between the first rib and the battery case. A battery module characterized by this.

2. The battery module according to claim 1, wherein the contact area between the first rib and the battery case occupies 5 to 15% of the total contact area between all the ribs including the first rib and the plurality of second ribs and the battery case.

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