Secondary batteries

Abstract

We propose a technology to suppress the generation of temperature gradients within laminated structures. [Solution] The secondary battery comprises a laminate composed of multiple stacked cells, a housing member composed of a film that houses the laminate, and a heat transfer material disposed inside the housing member and sandwiched between the side surface of the laminate and the housing member. Within the range of the length of the heat transfer material in the stacking direction of the laminate, the thermal resistance of the heat transfer material is lower than the thermal resistance of the housing member. In this secondary battery, within the range of the length of the heat transfer material in the stacking direction, the thermal resistance of the heat transfer material is lower than the thermal resistance of the housing member. Therefore, during use of the secondary battery, the heat transferred from the laminate to the heat transfer material is efficiently conducted in the stacking direction by the heat transfer material. As a result, the generation of a temperature gradient within the laminate can be suppressed.

Description

Technical Field

[0001] The technology disclosed in this specification relates to secondary batteries.

Background Art

[0002] Patent Document 1 discloses a battery pack in which secondary batteries and coolers are alternately stacked.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a secondary battery composed of a stack of a plurality of cells, heat is difficult to transfer in the stacking direction. Therefore, during use of the secondary battery, a temperature gradient is likely to occur in the stacking direction within the stack, and the inside of the stack is likely to become high temperature. As a result, deterioration of the secondary battery may occur, and the performance of the secondary battery may decrease. In this specification, a technique for suppressing the generation of a temperature gradient within the stack is proposed.

Means for Solving the Problems

[0005] (Aspect 1) The secondary battery disclosed in this specification includes a stack composed of a plurality of stacked cells, a housing member composed of a film and housing the stack, and a heat transfer material disposed inside the housing member and sandwiched between a side surface of the stack and the housing member. In the range of the length of the heat transfer material in the stacking direction of the stack, the thermal resistance of the heat transfer material is lower than the thermal resistance of the housing member.

[0006] In the secondary battery described above, within the range of the length of the heat transfer material in the stacking direction, the thermal resistance of the heat transfer material is lower than the thermal resistance of the housing component. Therefore, during the use of the secondary battery, the heat transferred from the stack to the heat transfer material is efficiently conducted in the stacking direction by the heat transfer material. As a result, the generation of a temperature gradient within the stack can be suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of the battery pack. [Figure 2] This is a schematic diagram of the secondary battery of Example 1. [Figure 3] This is an explanatory diagram of a laminate. [Figure 4] This is a schematic diagram of the secondary battery of Example 2. [Figure 5] This is a schematic diagram of the secondary battery of Example 3. [Modes for carrying out the invention]

[0008] Following the above description of Embodiment 1, additional configurations of the secondary battery disclosed herein will be described below. (Aspect 2) It further comprises a sealing member that is disposed inside the aforementioned housing member and covers the side surface of the laminate, The heat transfer material covers the side surface of the sealing member and the outer periphery of the electrode layer that constitutes the end face of the laminate. A secondary battery as described in Embodiment 1. (Aspect 3) A secondary battery according to embodiment 1 or 2, further comprising: a sealing member disposed inside the housing member and covering the side surface of the laminate; a metal plate disposed inside the housing member and in contact with the electrode layer constituting the end surface of the laminate and the end surface of the sealing member, wherein the heat transfer material covers the side surface of the sealing member, the metal plate is in contact with the heat transfer material, the housing member is disposed in a portion that overlaps with the electrode layer when viewed along the lamination direction and has a conductive film portion in contact with the metal plate, and an insulating film portion that covers the side surface of the heat transfer material and is connected to the conductive film portion. (Aspect 4) A secondary battery according to any one of embodiments 1 to 3, wherein the metal plate has a first portion that contacts the end face of the sealing member and a second portion that is curved convexly toward the end face of the electrode layer and connected to the first portion at a position away from the heat transfer material, and further comprises a conductive adhesive that adheres the second portion to the end face of the electrode layer. (Appendix 5) A secondary battery according to any one of embodiments 1 to 4, wherein the thermal conductivity of the heat transfer material is higher than the thermal conductivity of the laminate in the aforementioned stacking direction.

[0009] According to embodiment 2, heat is easily transferred from the electrode layer to the heat transfer material, thus improving heat dissipation.

[0010] According to embodiment 3, heat is easily transferred from the heat transfer material to the conductive film portion via the metal plate, thus improving heat dissipation.

[0011] According to embodiment 4, when the conductive adhesive softens due to the heat generated by the laminate, the second portion deforms in a direction away from the laminate, and the connection between the second portion and the laminate is released. As a result, the current in the laminate can be stopped.

[0012] (Example 1) The battery pack 200 shown in Figure 1 is mounted, for example, in an electric vehicle. The battery pack 200 has a plurality of secondary batteries 100 stacked in the z direction. The plurality of secondary batteries 100 are stacked in the z direction via a cooler 50 and a current collector plate 52. The cooler 50 and the current collector plate 52 are arranged alternately in the z direction. The cooler 50 is sandwiched above and below by two secondary batteries 100. The current collector plate 52 is sandwiched above and below by two secondary batteries 100. Therefore, each secondary battery 100 is in contact with the cooler 50 on one of its upper and lower surfaces, and in contact with the current collector plate 52 on the other of its upper and lower surfaces. The cooler 50 is provided with a flow path for a coolant. The cooler 50 cools adjacent secondary batteries 100. The cooler 50 is made of a conductor and electrically connects the upper and lower secondary batteries 100. The current collector plate 52 is made of a conductive material and electrically connects the upper and lower secondary batteries 100. The current collector plate 52 can be made of, for example, aluminum or copper.

[0013] Each secondary battery 100 has a laminate 12. As shown in Figure 2, the laminate 12 is composed of a plurality of cells 10 stacked in the z direction. Each cell 10 has a roughly plate-like shape extending in the x and y directions and is a rechargeable secondary battery cell. Each cell 10 is, for example, a lithium-ion battery cell or an all-solid-state battery cell.

[0014] As shown in Figure 3, each cell 10 has multiple electrode layers 14 and a cell body 16. The electrode layers 14 are the electrodes of the secondary battery cell. Although not shown, the cell body 16 has a separator, electrolyte, etc. The cell body 16 is sandwiched between two electrode layers 14. Adjacent cells 10 share an electrode layer 14. The surface of a cell 10 located at the end is made up of an electrode layer 14. Therefore, the upper surface 12b and lower surface 12c of the laminate 12 shown in Figure 2 are made up of electrode layers 14. Multiple cells 10 are connected in series. As a result, the laminate 12 outputs a high voltage between the upper surface 12b and the lower surface 12c.

[0015] As shown in FIG. 2, the secondary battery 100 includes a seal member 22, a heat transfer material 20, and a housing member 30. The housing member 30 houses the laminate 12, the seal member 22, and the heat transfer material 20. That is, the laminate 12, the seal member 22, and the heat transfer material 20 are disposed inside the housing member 30.

[0016] The seal member 22 is made of a resin material. The seal member 22 covers the outer peripheral edge of the laminate 12. That is, the seal member 22 covers the side surface 12a of the laminate 12.

[0017] The heat transfer material 20 is made of an insulating material having a high thermal conductivity. The heat transfer material 20 is composed of, for example, an acrylic resin, a silicone resin, a polyolefin resin, or the like. Note that the heat transfer material 20 may contain a ceramic filler or a metal filler. Also, the heat transfer material 20 may be of a filled type or a sheet type. The heat transfer material 20 covers the outer side surface 22a of the seal member 22 in a range extending across a plurality of cells 10. The outer side surface of the heat transfer material 20 is in contact with the housing member 30. That is, the heat transfer material 20 is sandwiched between the side surface 22a and the housing member 30. The heat transfer material 20 covers the upper surface 22b and the lower surface 22c of the seal member 22. The heat transfer material 20 covers the outer peripheral portion 14a of the upper surface 12b of the laminate 12. That is, the heat transfer material 20 covers the outer peripheral portion 14a of the electrode layer 14 that constitutes the upper surface 12b. Similarly, the heat transfer material 20 covers the outer peripheral portion 14b of the lower surface 12c of the laminate 12. That is, the heat transfer material 20 covers the outer peripheral portion 14b of the electrode layer 14 that constitutes the lower surface 12c. In the range L1 of the length of the heat transfer material 20 in the z direction, the thermal conductivity of the heat transfer material 20 is higher than the thermal conductivity of the laminate 12.

[0018] The housing member 30 includes a conductor film portion 34a, a conductor film portion 34b, and an insulating film portion 36. The conductor film portions 34a and 34b are made of a conductive material. Examples of the conductive material of the conductor film portions 34a and 34b include aluminum, copper, and the like. The insulating film portion 36 has a structure in which a conductive film 36c (such as aluminum) is laminated with an insulating film 36d.

[0019] When viewed along the z direction, the conductor film portion 34a is disposed at a portion overlapping with the upper surface 12b (i.e., the electrode layer 14). The conductor film portion 34a is in contact with the electrode layer 14. In other words, the conductor film portion 34a is in contact with the upper surface 12b of the laminate 12. The conductor film portion 34a is electrically connected to the laminate 12.

[0020] When viewed along the z direction, the conductor film portion 34b is disposed at a portion overlapping with the lower surface 12c (i.e., the electrode layer 14). The conductor film portion 34b is in contact with the electrode layer 14. In other words, the conductor film portion 34b is in contact with the lower surface 12c of the laminate 12. The conductor film portion 34b is electrically connected to the laminate 12.

[0021] The insulating film portion 36 has an upper insulating film portion 36a and a lower insulating film portion 36b. The upper insulating film portion 36a is connected to the outer peripheral edge of the conductor film portion 34a. The upper insulating film portion 36a is insulated from the conductor film portion 34a. The upper insulating film portion 36a is in contact with the upper surface and the outer side surface of the heat transfer member 20. The lower insulating film portion 36b is connected to the outer peripheral edge of the conductor film portion 34b. The lower insulating film portion 36b is insulated from the conductor film portion 34b. The lower insulating film portion 36b is in contact with the lower surface and the outer side surface of the heat transfer member 20. The outer peripheral edge of the lower insulating film portion 36b is welded to the outer peripheral edge of the upper insulating film portion 36a on the side of the heat transfer member 20. Therefore, the heat transfer member 20 is sandwiched between the insulating film portion 36 and the side surface 22a of the seal member 22.

[0022] In the range L1 of the length of the heat transfer member 20 in the z direction, the thermal resistance of the heat transfer member 20 is lower than the thermal resistance of the housing member 30 (here, the insulating film portion 36). Also, in the z direction, the thermal conductivity of the heat transfer member 20 is higher than the thermal conductivity of the laminate 12.

[0023] During charging and discharging of the secondary battery 100, heat is generated in the laminate 12. A cooler 50 is in contact with one end face of the secondary battery 100. Therefore, the portion of the laminate 12 on the side of the cooler 50 is cooled by the cooler 50. Also, because the thermal conductivity of the laminate 12 in the z direction is low, heat is not easily transferred in the z direction inside the laminate 12. For this reason, if there is no heat transfer material 20, a temperature gradient in the z direction will be generated inside the laminate 12. That is, the portion of the laminate 12 on the side of the current collector plate 52 (the portion opposite to the cooler 50) is not easily cooled and becomes hot. In contrast, the secondary battery 100 of Example 1 has a heat transfer material 20 that extends from the outer periphery 14a of the upper surface 12b to the outer periphery 14b of the lower surface 12c. In the z direction, the thermal conductivity of the heat transfer material 20 is higher than that of the laminate 12. Furthermore, within the length range L1 of the heat transfer material 20 in the z direction, the thermal resistance of the heat transfer material 20 is lower than that of the housing member 30 (in this case, the insulating film portion 36). Therefore, the heat generated in the laminate 12 is efficiently conducted in the z direction to the cooler 50 by the heat transfer material 20. As a result, the generation of a temperature gradient within the laminate 12 can be suppressed, and the temperature rise of the portion of the laminate 12 on the current collector plate 52 side can be suppressed.

[0024] Furthermore, in the secondary battery 100, the corners of the housing member 30 are reinforced with the heat transfer material 20, so cracks can be suppressed at the corners.

[0025] (Example 2) Figure 4 shows the secondary battery 102 of Example 2. In Figure 4, parts common to Figure 3 are denoted by the same reference numerals. The secondary battery 102 of Example 2 differs from Example 1 in that it has metal plates 60a and 60b. Also, the shape of the heat transfer material 20 differs from that of Example 1. Otherwise, the secondary battery 102 of Example 2 is the same as that of Example 1.

[0026] In the secondary battery 102 of Example 2, the heat transfer material 20 does not cover the outer periphery 14a and 14b. However, the heat transfer material 20 of the secondary battery 102 may cover the outer periphery 14a and 14b.

[0027] The metal plates 60a and 60b are arranged inside the housing member 30. The metal plates 60a and 60b have a substantially plate shape that extends in the x and y directions.

[0028] The metal plate 60a is in contact with the upper surface 12b of the laminate 12 (i.e., the electrode layer 14). The metal plate 60a is in contact with the conductive film portion 34a. The metal plate 60a is in contact with the upper surface 22b of the sealing member 22. The end of the metal plate 60a is embedded in the heat transfer material 20. The area around the end of the metal plate 60a is covered by the heat transfer material 20. Note that the metal plate 60a only needs to be in contact with the heat transfer material 20.

[0029] The metal plate 60b is in contact with the lower surface 12c of the laminate 12 (i.e., the electrode layer 14). The metal plate 60b is in contact with the conductive film portion 34b. The metal plate 60b is in contact with the lower surface 22c of the sealing member 22. The end of the metal plate 60b is embedded in the heat transfer material 20. The area around the end of the metal plate 60b is covered by the heat transfer material 20. Note that the metal plate 60b only needs to be in contact with the heat transfer material 20.

[0030] During the charging and discharging of the secondary battery 102, heat is generated in the laminated structure 12. In the secondary battery 102, heat is easily transferred from the heat transfer material 20 to the conductive film portion 34a via the metal plate 60a. Furthermore, in the secondary battery 102, heat is easily transferred from the heat transfer material 20 to the conductive film portion 34b via the metal plate 60b. Therefore, the heat generated in the laminated structure 12 is dissipated more efficiently.

[0031] (Example 3) The secondary battery 104 of Example 3 shown in Figure 5 differs from that of Example 2 in the structure of the metal plate. The other components of the secondary battery 104 of Example 3 are the same as those of Example 2.

[0032] In the secondary battery 104, the metal plate 60a has a first portion 66a and a second portion 68a. The first portion 66a is located on the upper part of the sealing member 22. The first portion 66a extends in the z direction. The lower end of the first portion 66a is in contact with the upper surface 22b of the sealing member 22. The second portion 68a is located on the upper part of the laminate 12 (i.e., on the upper part of the electrode layer 14). The second portion 68a has a plate shape that extends in the x and y directions. The second portion 68a is connected to the upper end of the first portion 66a. The second portion 68a is curved convexly downward (i.e., toward the upper surface 12b of the laminate 12). In other words, the second portion 68a is curved convexly toward the electrode layer 14. The second portion 68a is curved by elastic deformation and is bonded to the upper surface 12b of the laminate 12, i.e., the electrode layer 14, by conductive adhesive 70a. The upper surface of the second portion 68a is bonded to the conductive film portion 34a with a conductive adhesive 70b. The conductive adhesives 70a and 70b are, for example, epoxy-based, acrylic-based, rubber-based, ethylene vinyl acetate copolymer (EVA)-based, or polyolefin-based adhesives. The softening point of the conductive adhesives 70a and 70b is preferably 100°C or lower.

[0033] During the charging and discharging of the secondary battery 104, heat is generated in the laminate 12. When the conductive adhesive 70a softens due to the heat generated in the laminate 12, the stress in the curved portion of the second portion 68a is released, and the second portion 68a deforms in a direction away from the laminate 12. As a result, the electrical connection between the second portion 68a and the laminate 12 is released. Therefore, the current to the laminate 12 can be stopped. This prevents the laminate 12 from overheating. Also, if the conductive adhesive 70c softens due to heat, the second portion 68b of the metal plate 60b deforms in a direction away from the laminate 12 (i.e., the electrode layer 14), and the electrical connection between the second portion 68b and the laminate 12 is released.

[0034] The upper surface 12b and lower surface 12c of the laminate 12 are examples of "end faces of the laminate". The upper surface 22b and lower surface 22c of the sealing member 22 are examples of "end faces of the sealing member".

[0035] Although embodiments have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness. [Explanation of Symbols]

[0036] 10: Cell, 12: Laminate, 12a: Side, 12b: Top, 12c: Bottom, 14: Electrode layer, 14a, 14b: Outer periphery, 20: Heat transfer material, 22: Sealing member, 22a: Side, 22b: Top, 22c: Bottom, 30: Housing member, 34a: Conductive film part, 34b: Conductive film part, 36: Insulating film part, 60a, 60b: Metal plate, 66a: First part, 68a, 68b: Second part, 70a, 70b, 70c: Conductive adhesive, 100, 102, 104: Secondary battery, L1: Range

Claims

1. It is a secondary battery, A laminate composed of multiple stacked cells, It is made of film and includes a housing member that houses the laminate, A heat transfer material is disposed inside the aforementioned housing member and sandwiched between the side surface of the laminate and the housing member, Equipped with, Within the range of the length of the heat transfer material in the stacking direction of the laminate, the thermal resistance of the heat transfer material is lower than the thermal resistance of the housing member. Secondary battery.

2. It further comprises a sealing member that is disposed inside the aforementioned housing member and covers the side surface of the laminate, The secondary battery according to claim 1, wherein the heat transfer material covers the side surface of the sealing member and the outer periphery of the electrode layer that constitutes the end face of the laminate.

3. A sealing member is disposed inside the aforementioned housing member and covers the side surface of the laminate, A metal plate is disposed inside the housing member and is in contact with the electrode layer that constitutes the end face of the laminate and the end face of the sealing member. It further possesses, The heat transfer material covers the side surface of the sealing member, The aforementioned metal plate is in contact with the heat transfer material, The aforementioned housing member, It is arranged in the portion that overlaps with the electrode layer when viewed along the aforementioned stacking direction, and comprises a conductive film portion that is in contact with the metal plate, An insulating film portion covers the side surface of the heat transfer material and is connected to the conductive film portion, Having, The secondary battery according to claim 1.

4. The aforementioned metal plate, The first portion of the sealing member that contacts the end face, The electrode layer is curved convexly toward the end face, and the second portion is connected to the first portion at a position away from the heat transfer material, It has, The present invention further comprises a conductive adhesive that adheres the second portion to the end face of the electrode layer, The secondary battery according to claim 3.

5. The secondary battery according to any one of claims 1 to 4, wherein the thermal conductivity of the heat transfer material is higher than the thermal conductivity of the laminate in the aforementioned stacking direction.

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