Power storage device

Abstract

To provide a power storage device in which lithium deposition is suppressed.SOLUTION: A power storage device includes a first storage cell 2A, a second storage cell arranged at a distance from the first storage cell 2A in a stacking direction L1, and an inter-cell separator 3A arranged between the first storage cell 2A and the second storage cell, the inter-cell separator 3A includes a first main surface 46 and a second main surface 47 arranged in the stacking direction L1 and a plurality of protrusions 41 formed on the first main surface 46 and the second main surface 47, and the plurality of protrusions 41 are arranged at intervals in a first direction perpendicular to the stacking direction L1 and also arranged at intervals in a second direction perpendicular to the stacking direction L1 and the first direction.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a power storage device.

Background Art

[0002] Conventionally, various power storage devices have been proposed. For example, the assembled battery described in Japanese Unexamined Patent Application Publication No. 2020-057597 includes a plurality of power storage cells, an inter-cell separator disposed between the power storage cells, a first end plate and a second end plate, and a restraint band. The plurality of power storage cells are arranged at intervals in the stacking direction.

[0003] The inter-cell separator includes a first main surface and a second main surface arranged in the stacking direction, and a plurality of ribs formed to be long in the left-right direction are formed on the first main surface. Each rib is formed at intervals in the up-down direction.

[0004] In the above power storage device, each rib is formed to be long in the left-right direction, and each rib is arranged at intervals in the up-down direction. Therefore, a cooling passage is formed between each rib. Then, the power storage cells are cooled by the cooling air passing through the cooling passage.

[0005] The plurality of power storage cells and the inter-cell separator are disposed between the first end plate and the second end plate, and the plurality of power storage cells and the inter-cell separator are fixed by the restraining force applied from the first end plate and the second end plate.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the above-described power storage device, a load is applied to the power storage cells from the ribs of the inter-cell separator by the restraining force from each end plate. The power storage cell includes an electrode body and a housing case that houses the electrode body. Then, a load from the rib is applied to the electrode body through the housing case.

[0008] Here, since each rib is formed to be long in the left-right direction and the ribs are arranged at intervals in the up-down direction, the load applied to the electrode body through the housing case is likely to be non-uniform.

[0009] In this way, when the electrode body is charged and discharged in a state where the load applied to the electrode body is non-uniform, lithium precipitation is likely to occur in the electrode body.

[0010] The present disclosure has been made in view of the above problems, and an object thereof is to provide a power storage device in which lithium precipitation is suppressed.

Means for Solving the Problems

[0011] The power storage device according to the present disclosure includes a first power storage cell, a second power storage cell arranged at an interval in the stacking direction with respect to the first power storage cell, and an inter-cell separator arranged between the first power storage cell and the second power storage cell. The inter-cell separator includes a first main surface and a second main surface arranged in the stacking direction, and a plurality of protrusions formed on the first main surface. The plurality of protrusions are arranged at intervals in a first direction orthogonal to the stacking direction, and are arranged at intervals in a second direction orthogonal to the stacking direction and the first direction.

[0012] Each of the plurality of protrusions is formed in a columnar shape. The above-described inter-cell separator includes a first strip portion formed on the first main surface and formed to extend in the second direction, and a second strip portion formed on the first main surface, spaced apart from the first strip portion in the second direction, and formed to extend in the second direction. The plurality of protrusions are arranged between the first strip portion and the second strip portion in the first direction. The first direction is the vertical direction, and the second direction is the width direction of the inter-cell separator.

[0013] The above-described power storage device includes a first end plate, a second end plate, and a restraint plate. The first end plate is disposed at one end of the power storage device in the stacking direction, the second end plate is disposed at the other end of the power storage device in the stacking direction, and the restraint plate is provided to connect the first end plate and the second end plate.

Advantages of the Invention

[0014] According to the power storage device according to the present disclosure, it is possible to suppress lithium precipitation.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

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Figure 4

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Figure 8

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Figure 10

Embodiments for Carrying Out the Invention

[0016] Embodiments of the present disclosure will be described with reference to the drawings. In the drawings referred to below, the same or corresponding members are given the same reference numerals.

[0017] FIG. 1 is a perspective view showing a power storage device 1 according to the present embodiment. The power storage device 1 includes a plurality of storage cells 2, a plurality of inter-cell separators 3, an end plate 4, an end plate 5, a restraint plate 6, a restraint plate 7, and a plurality of bus bars 8.

[0018] The plurality of storage cells 2 includes a storage cell (first storage cell) 2A and a storage cell (second storage cell) 2B. The plurality of storage cells 2 are arranged at intervals in the stacking direction L1, and the storage cell 2A and the storage cell 2B are arranged at intervals in the stacking direction L1.

[0019] The plurality of inter-cell separators 3 are arranged between the respective storage cells 2. The plurality of inter-cell separators 3 includes an inter-cell separator 3A arranged between the storage cell 2A and the storage cell 2B.

[0020] The end plate 4 is arranged at one end of the power storage device 1 in the stacking direction L1, and the end plate 5 is arranged at the other end of the power storage device 1 in the stacking direction L1. The restraint plates 6 and 7 are provided so as to connect the end plate 4 and the end plate 5.

[0021] The plurality of power storage cells 2 and the plurality of inter-cell separators 3 are disposed between the end plates 4 and 5. The plurality of power storage cells 2 and the plurality of inter-cell separators 3 are fixed between the end plates 4 and 5 by the load applied from the end plates 4 and 5. The bus bar 8 is disposed so as to electrically connect the power storage cells 2 adjacent to each other in the stacking direction L1.

[0022] FIG. 2 is a cross-sectional view showing the power storage cell 2A. The power storage cell 2A is a lithium-ion battery. The power storage cell 2A includes an electrode body 20 and a housing case 21. The electrode body 20 and the electrolytic solution are housed in the housing case 21.

[0023] The electrode body 20 includes a positive electrode sheet 25, a negative electrode sheet 26, and separators 27 and 28. In the example shown in FIG. 2, the electrode body 20 is formed by winding the positive electrode sheet 25, the negative electrode sheet 26, and the separators 27 and 28. On the other hand, the electrode body 20 may be formed by sequentially laminating a plurality of positive electrode sheets, a plurality of separators, and a plurality of negative electrode sheets.

[0024] FIG. 3 is a perspective view showing the housing case 21 of the power storage cell 2A. The housing case 21 includes a top plate 30, a bottom plate 31, main walls 32 and 33, and side walls 34 and 35.

[0025] The top plate 30 and the bottom plate 31 are arranged in the vertical direction (first direction) D1. The vertical direction D1 is orthogonal to the stacking direction L1. The side walls 34 and 35 are arranged in the width direction (second direction) D2. The width direction D2 is orthogonal to the stacking direction L1 and the vertical direction D1. The main walls 32 and 33 are arranged in the stacking direction L1.

[0026] FIG. 4 is a perspective view showing the power storage cell 2A, the power storage cell 2B, and the inter-cell separator 3A. The inter-cell separator 3A is formed of an insulating member such as resin. The inter-cell separator 3A is formed in a plate shape. The inter-cell separator 3A includes a main body plate 40, a plurality of protrusions 41, a strip portion 42, and a strip portion 43.

[0027] The main body plate 40 is formed in a plate shape. The main body plate 40 includes an upper surface 44, a lower surface 45, a main surface 46, a main surface 47, a side surface 48, and a side surface 49.

[0028] The main surfaces 46 and 47 are arranged in the stacking direction L1. The side surfaces 48 and 49 are arranged in the width direction D2. The plurality of protrusions 41, the strip portion 42, and the strip portion 43 are formed on the main surface 46. The plurality of protrusions 41, the strip portion 42, and the strip portion 43 are formed so as to protrude in the stacking direction L1. Note that a plurality of protrusions and strip portions are also formed on the main surface 47 in the same manner as the main surface 46. Note that the protruding directions of the plurality of protrusions and the plurality of strip portions formed on the main surface 47 are opposite to the protruding directions of the plurality of protrusions 41, the strip portion 42, and the strip portion 43 formed on the main surface 46.

[0029] FIG. 5 is a front view showing the inter-cell separator 3A. The strip portion 42 and the strip portion 43 are arranged at intervals in the vertical direction D1. The strip portion 42 and the strip portion 43 are formed so as to extend long in the width direction D2. The strip portion 42 and the strip portion 43 are formed so as to extend from the side surface 48 side to the side surface 49 side. The strip portion 42 is arranged on the upper surface 44 side, and the strip portion 43 is arranged on the lower surface 45 side. In the vertical direction D1, the width of the strip portion 42 is larger than the width of the strip portion 43.

[0030] The plurality of protrusions 41 are arranged between the strip portion 42 and the strip portion 43 in the vertical direction D1. The plurality of protrusions 41 are formed at intervals in the vertical direction D1 and at intervals in the width direction D2. Each protrusion 41 is formed in a columnar shape.

[0031] Thus, since the protrusions 41 are formed at intervals, a refrigerant passage 50 is formed between the belt portion 42 and the belt portion 43. Then, a refrigerant such as cooling air can flow through the refrigerant passage 50.

[0032] In FIG. 4, the plurality of protrusions 41 of the inter-cell separator 3A, the belt portion 42, and the belt portion 43 are in contact with the main wall 33 of the power storage cell 2A. Then, when the cooling air passes through the refrigerant passage 50, the power storage cell 2A is cooled.

[0033] A load is applied to the power storage cell 2A and the inter-cell separator 3A by the end plates 4 and 5.

[0034] Specifically, a load is applied to the electrode body 20 of the power storage cell 2A from the plurality of protrusions 41, the belt portion 42, and the belt portion 43 through the main wall 33 of the housing case 21.

[0035] At this time, the plurality of protrusions 41 are arranged at intervals in the vertical direction D1 and the width direction D2. Therefore, the load applied to the electrode body 20 through the main wall 33 is equalized.

[0036] Thereby, it is suppressed that the distance between the positive electrode sheet 25 and the negative electrode sheet 26 of the electrode body 20 becomes locally small. And when the electrode body 20 is charged and discharged, it is possible to suppress the occurrence of lithium precipitation.

[0037] Using FIG. 6 and the like, the power storage device 61 according to the comparative example will be described. FIG. 6 is a perspective view showing the power storage device 61. The configuration of the inter-cell separator 63 of the power storage device 61 is different from that of the inter-cell separator 3 of the power storage device 1. The configuration of the power storage device 61 other than the inter-cell separator is substantially the same as that of the power storage device 1.

[0038] The power storage device 61 includes a plurality of power storage cells 62 arranged in the stacking direction L1 and an inter-cell separator 63 disposed between the power storage cells 62.

[0039] Note that, similar to the power storage cell 2, the power storage cell 62 includes an electrode body 70 and a housing case 71 that houses the electrode body 70 and the electrolytic solution. The electrode body 70 of the power storage cell 62 also includes a positive electrode sheet 75, a negative electrode sheet 76, and a separator, and is formed by winding each sheet.

[0040] FIG. 7 is a front view showing the inter-cell separator 63. The inter-cell separator 63 includes a main body plate 40, a plurality of ribs 11, a central rib 12, a strip portion 42, and a strip portion 43.

[0041] The plurality of ribs 11, the central rib 12, the strip portion 42, and the strip portion 43 are formed on the main surface 46 of the main body plate 40.

[0042] The plurality of ribs 11 and the central rib 12 are formed so as to extend in the width direction D2. The plurality of ribs 11 and the central rib 12 are formed between the strip portion 42 and the strip portion 43. The plurality of ribs 11 and the central rib 12 are formed at intervals in the vertical direction D1. Note that the width of the central rib 12 in the vertical direction D1 is longer than the width of the rib 11 in the vertical direction D1.

[0043] And also in the inter-cell separator 63, a refrigerant passage 64 is formed between the strip portion 42 and the strip portion 43.

[0044] When the power storage device 1 and the power storage device 61 configured as described above are overcharged, metallic lithium may precipitate on the surface of the negative electrode sheet. In FIGS. 8 and 9, the power storage devices 1 and 61 were charged under the same charging conditions.

[0045] FIG. 8 is a developed view of the negative electrode sheets 26A and 26B of the power storage cells 2A and 2B of the power storage device 1. FIG. 9 is a developed view of the negative electrode sheets 76A and 76B of the power storage cells 62A and 62B of the power storage device 61.

[0046] The negative electrode sheets 26A and 26B are formed in a long shape in the longitudinal direction L3. The negative electrode sheets 26A and 26B include a starting end portion 53 located at one end in the longitudinal direction L3 and an ending end portion 54 located at the other end. The starting end portion 53 is located on the winding center side of the electrode body 20, and the ending end portion 54 is located at the winding end of the electrode body 20. The negative electrode sheets 26A and 26B include a metal foil 51 formed in a long shape in the longitudinal direction L3 and a plurality of negative electrode composite layers 52 formed on the metal foil 51. The negative electrode composite layers 52 are formed at intervals in the longitudinal direction L3. The metal foil 51 includes a pair of long sides, and a plurality of tabs 55 are formed at intervals on one long side of the metal foil 51. The metal foil 51 is formed of, for example, copper or the like.

[0047] In FIG. 9, the negative electrode sheets 76A and 76B are also formed in a long shape in the longitudinal direction L3. The negative electrode sheets 76A and 76B include a starting end portion 83 and an ending end portion 84. The negative electrode sheets 76A and 76B include a metal foil 81 and a plurality of negative electrode composite layers 82 formed on the metal foil 81. The negative electrode composite layers 82 are formed at intervals in the longitudinal direction L3. A plurality of tabs 85 are formed at intervals on one long side of the metal foil 81.

[0048] In FIGS. 8 and 9, the precipitation regions R1, R2, and R3 indicate regions where lithium is precipitated. Note that the precipitation region R3 indicates a region where the precipitation amount is larger than that in the precipitation region R2. The precipitation region R2 indicates a region where the precipitation amount is larger than that in the precipitation region R1.

[0049] As is apparent from FIGS. 8 and 9, it can be seen that the amount of lithium precipitation occurring in the negative electrode sheets 26A and 26B is less than the amount of lithium precipitation occurring in the negative electrode sheets 76A and 76B.

[0050] In FIG. 5, the flow path cross-sectional area of the refrigerant passage 50 of the inter-cell separator 3 is smaller than the flow path cross-sectional area of the refrigerant passage 64 of the inter-cell separator 63 shown in FIG. 7. For example, the flow path cross-sectional area of the inter-cell separator 3 is about 80% of the flow path cross-sectional area of the inter-cell separator 63. Note that the flow path cross-sectional areas of the refrigerant passages 50 and 64 are the cross-sectional areas in the width direction D2 through which the refrigerant can actually flow.

[0051] Figure 10 is a graph schematically showing the cooling performance of the inter-cell separator 3 and the inter-cell separator 63. The vertical axis of the graph indicates the cooling performance (cooling performance: W). Graph 90 shows the cooling performance of the inter-cell separator 63, and graph 91 shows the cooling performance of the inter-cell separator 3.

[0052] As shown in Figure 10, the cooling performance of the inter-cell separator 3 is lower than that of the inter-cell separator 63. For example, the cooling performance of the inter-cell separator 3 is about 8% to 10% lower than that of the inter-cell separator 63.

[0053] Thus, while the flow path cross-sectional area S1 of the inter-cell separator 3 is about 20% smaller than the flow path cross-sectional area S2 of the inter-cell separator 63, the cooling performance of the inter-cell separator 3 is only about 8% to 10% lower than that of the inter-cell separator 63.

[0054] In Figure 10, the allowable value L4 indicates the allowable value for the cooling performance of the inter-cell separator. The cooling performance of the inter-cell separator 3 is higher than the allowable value L4. Thus, the inter-cell separator 3 sufficiently ensures the cooling performance.

[0055] And, as shown in FIG. 8 and the like above, the power storage device 1 can suppress the occurrence of lithium precipitation more than the power storage device 61.

[0056] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is shown by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of reference numerals

[0057] 1,61 Energy storage device, 2,2A,2B,62 Energy storage cell, 3,3A,63 Inter-cell separator, 4,5 End plate, 6,7 Constraint plate, 8 Bus bar, 11 Rib, 12 Central rib, 20,70 Electrode body, 21,71 Housing case, 25,75 Positive electrode sheet, 26,76 Negative electrode sheet, 27,28 Separator, 30 Top plate, 31 Bottom plate, 32,33 Main wall, 34,35 Side wall, 40 Body plate, 41 Protrusion, 42,43 Band portion, 44 Upper surface, 45 Lower surface, 46,47 Main surface, 48,49 Side surface, 50 Refrigerant passage, 51,81 Metal foil, 52,82 Negative electrode composite layer, 53,83 Starting end portion, 54,84 Ending end portion, 55,85 Tab, 90,91 Graph, D1 Vertical direction, D2 Width direction, L1 Laminating direction, L3 Longitudinal direction, L4 Allowable value, R1,R2,R3 Precipitation region.

Claims

1. a first power storage cell; a second power storage cell disposed at an interval in the stacking direction with respect to the first power storage cell; and a cell separator disposed between the first power storage cell and the second power storage cell, wherein the cell separator includes a first main surface and a second main surface arranged in the stacking direction, and a plurality of protrusions formed on the first main surface, wherein the plurality of protrusions are arranged at intervals in a first direction orthogonal to the stacking direction and are also arranged at intervals in a second direction orthogonal to the stacking direction and the first direction, a power storage device.

2. Each of the plurality of protrusions is formed in a columnar shape, the power storage device according to claim 1.

3. The cell separator, includes a first band portion formed on the first main surface and formed to extend in the second direction, and a second band portion formed on the first main surface, arranged at an interval from the first band portion in the second direction, and formed to extend in the second direction, wherein the plurality of protrusions are arranged between the first band portion and the second band portion in the first direction, the power storage device according to claim 1 or claim 2.

4. The first direction is the vertical direction, and the second direction is the width direction of the cell separator, the power storage device according to claim 1 or claim 2.

5. The power storage device includes a first end plate, a second end plate, and a restraint plate, wherein the first end plate is disposed at one end of the power storage device in the stacking direction, the second end plate is disposed at the other end of the power storage device in the stacking direction, and the restraint plate is provided to connect the first end plate and the second end plate, the power storage device according to claim 1.

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