Secondary battery

Abstract

To provide a highly reliable secondary battery.SOLUTION: A secondary battery includes a power generation element including a current collector, an electrode tab 3 welded to the current collector, an exterior material 4 including a pair of metal plates 4A and 4B having outer peripheral edges bonded to each other, in which the power generation element and at least a welded part 5 of the electrode tab 3 with the current collector are accommodated inside by sandwiching them between the pair of metal plates 4A and 4B, and a portion of the electrode tab 3 different from the welded part 5 is exposed to the outside, and a heat dissipation member 61 in contact with the exterior material 4 to dissipate heat of the welded part 5 to the exterior material 4.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] Conventionally, secondary batteries have been known that include a power generating element in which a positive electrode including a positive electrode current collector and a negative electrode including a negative electrode current collector are stacked with a solid electrolyte layer interposed therebetween, a positive electrode tab joined to the positive electrode current collector, and a negative electrode tab joined to the negative electrode current collector (see, for example, Patent Document 1). In such secondary batteries, the joint between the positive electrode tab and the positive electrode current collector and the joint between the negative electrode tab and the negative electrode current collector are sealed by a laminated outer casing, and a portion of the positive electrode tab and a portion of the negative electrode are extended to the outside of the laminated outer casing. In the secondary battery of Patent Document 1, the current collectors (positive electrode current collector, negative electrode current collector) and the tabs (positive electrode tab, negative electrode tab) are made of different metals, and an intermetallic compound is formed at the joint interface between these current collectors and tabs, and the maximum diameter of the intermetallic compound is less than 1 μm when observed with a transmission electron microscope. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-149801 Summary of the Invention [Problem to be solved by the invention]

[0004] However, electrical resistance is high at the joint between the positive electrode current collector and the positive electrode tab, and at the joint between the negative electrode current collector and the negative electrode tab. Therefore, as the output of the secondary battery increases during charging and discharging, the amount of heat generated at the joint increases. Conventional secondary batteries, such as those described in Patent Document 1, are unable to dissipate heat generated at the joint, which can lead to melting and damage, reducing the reliability of the secondary battery.

[0005] An object of the present invention is to provide a highly reliable secondary battery. [Means for solving the problem]

[0006] A secondary battery according to a first aspect of the present invention comprises: a power generating element including a current collector; an electrode tab welded to the current collector; and an exterior material made of a pair of metal plates with their outer edges joined together, the exterior material containing the power generating element and at least the welded portion of the electrode tab to the current collector by sandwiching it between the pair of metal plates, and exposing a portion of the electrode tab other than the welded portion to the outside; and a heat dissipation member in contact with the exterior material and dissipating heat from the welded portion to the exterior material. [Effects of the Invention]

[0007] In the present invention, the heat generated at the welded portion between the electrode tab and the current collector can be dissipated to the exterior material by the heat dissipation member, thereby preventing melting of the joint even when the joint generates heat during charging and discharging of the secondary battery. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a schematic configuration of a secondary battery according to a first embodiment; [Figure 2] FIG. 2 is a schematic cross-sectional view of the secondary battery taken along line AA in FIG. 1. [Figure 3] FIG. 4 is a plan view of the joining position between the positive electrode tab and the positive electrode current collector foil in the first embodiment, viewed from the Z direction. [Figure 4] FIG. 4 is a schematic cross-sectional view of the vicinity of the positive electrode tab taken along line BB in FIG. 3 . [Figure 5] FIG. 6 is a cross-sectional view showing a schematic configuration of the vicinity of an electrode tab (positive electrode tab) of a secondary battery according to a second embodiment. [Figure 6] FIG. 10 is a cross-sectional view showing a schematic configuration of the vicinity of an electrode tab (positive electrode tab) of a secondary battery according to a third embodiment. [Figure 7] FIG. 10 is a plan view of the joining position between the positive electrode tab and the positive electrode current collector foil of the secondary battery according to the fourth embodiment, as viewed from the Z direction. [Figure 8] 8 is a schematic cross-sectional view of the vicinity of the positive electrode tab taken along line CC in FIG. 7. [Figure 9] 10 is a cross-sectional view showing a schematic configuration of the vicinity of an electrode tab (positive electrode tab) of a secondary battery according to Modification 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] A secondary battery according to a first embodiment of the present invention will be described below. In this embodiment, a flat laminated type all-solid-state battery will be described as an example of the secondary battery. Fig. 1 is a perspective view showing a schematic configuration of a secondary battery 1 of a first embodiment. Fig. 2 is a schematic cross-sectional view of the secondary battery 1 taken along line AA in Fig. 1. The secondary battery 1 of this embodiment includes a power generating element 2 (see FIG. 2), electrode tabs 3, and an exterior material 4. The power generating element 2 and the electrode tabs 3 are electrically connected. The exterior material 4 houses the power generating element 2 and the electrode tabs 3 inside, with a portion of the electrode tabs 3 protruding (exposed) to the outside. 1 and 2, the electrode tabs 3 include a positive electrode tab 3A and a negative electrode tab 3B, and the direction from the positive electrode tab 3A to the negative electrode tab 3B is defined as the X direction. In the following description, when there is no need to distinguish between the positive electrode tab 3A and the negative electrode tab 3B, they will be referred to as the electrode tabs 3. 2, the power generating element 2 is configured by alternately stacking positive electrodes 2A and negative electrodes 2B with electrolyte layers 2C interposed therebetween, and the stacking direction of the positive electrodes 2A and negative electrodes 2B is defined as the Z direction. The Z direction is the thickness direction of the present disclosure and is perpendicular to the X direction. Furthermore, the direction perpendicular to the X direction and the Z direction is defined as the Y direction.

[0010] As described above, the power generating element 2 is configured by stacking the positive electrodes 2A and the negative electrodes 2B with the electrolyte layer 2C interposed therebetween. There is no particular limitation on the number of stacked positive electrodes 2A and negative electrodes 2B in the power generating element 2.

[0011] The positive electrode 2A includes a flat positive electrode current collector 21A and a positive electrode active material layer 22A provided on at least one surface of the positive electrode current collector 21A. This positive electrode 2A can be formed, for example, by weighing and mixing predetermined amounts of a positive electrode active material, a sulfide solid electrolyte, a conductive additive, a binder, and xylene to prepare a slurry, applying this to one or both sides of a carbon-coated aluminum foil, and then drying it. Furthermore, a positive electrode current collector foil 23A that protrudes toward the positive electrode tab 3A is provided at one end of the positive electrode current collector 21A that is close to the positive electrode tab 3A. The positive electrode current collector foil 23A is welded to the positive electrode tab 3A, thereby electrically connecting the positive electrode current collector 21A and the positive electrode tab 3A. The positive electrode current collector foil 23A may be provided integrally with the positive electrode current collector 21A, or may be made of a conductive material separate from the positive electrode current collector 21A.

[0012] The negative electrode 2B includes a flat negative electrode current collector 21B and a negative electrode active material layer 22B provided on at least one surface of the negative electrode current collector 21B. This negative electrode 2B can be formed, for example, by weighing and mixing predetermined amounts of a negative electrode active material (including, for example, Ag and C), a binder, and NMP to prepare a slurry, applying the slurry to one or both sides of a SUS foil, and then drying the slurry. Furthermore, a negative electrode current collector foil 23B that protrudes toward the negative electrode tab 3B is provided at one end of the negative electrode current collector 21B that is close to the negative electrode tab 3B. The negative electrode current collector foil 23B is welded to the negative electrode tab 3B, thereby electrically connecting the negative electrode current collector 21B and the negative electrode tab 3B. The negative electrode current collector foil 23B may be provided integrally with the negative electrode current collector 21B, or may be made of a conductive material separate from the negative electrode current collector 21B.

[0013] The electrolyte layer 2C is configured to include a solid electrolyte. This electrolyte layer 2C can be formed, for example, by weighing and mixing predetermined amounts of a sulfide solid electrolyte, a binder, and xylene to prepare a slurry, applying this to both sides of a SUS foil, and then drying it.

[0014] In the following description, when there is no need to distinguish between the positive electrode current collector 21A and the negative electrode current collector 21B, they will be referred to as current collectors 21. Similarly, when there is no need to distinguish between the positive electrode current collector foil 23A and the negative electrode current collector foil 23B, they will be referred to as current collector foil 23.

[0015] As described above, the electrode tabs 3 include a positive electrode tab 3A and a negative electrode tab 3B. The positive electrode tab 3A and the negative electrode tab 3B are each made of a conductive material; for example, the positive electrode tab 3A is made of aluminum, and the negative electrode tab 3B is made of nickel. The positive electrode tab 3A is disposed on the −X side of the secondary battery 1, and inside the exterior packaging 4, the positive electrode current collector foil 23A is welded. The negative electrode tab 3B is disposed on the +X side of the secondary battery 1, and inside the exterior packaging 4, the negative electrode current collector foil 23B is welded.

[0016] The electrode tab 3 also has an upper surface 31 on the +Z side and a lower surface 32 on the -Z side, and these upper surface 31 and lower surface 32 are flat surfaces parallel to the XY plane. In this embodiment, as shown in FIG. 2 , the positive electrode current collector foil 23A is welded to the upper surface 31 side of the positive electrode tab 3A, and the negative electrode current collector foil 23B is welded to the lower surface 32 side of the negative electrode tab 3B. That is, in this embodiment, the upper surface 31 of the positive electrode tab 3A corresponds to the first surface of the present disclosure, and the lower surface 32 corresponds to the second surface of the present disclosure. Meanwhile, the lower surface 32 of the negative electrode tab 3B corresponds to the first surface of the present disclosure, and the upper surface 31 corresponds to the second surface of the present disclosure. It should be noted that whether the current collector foil 23 is welded to the upper surface 31 or the lower surface 32 of the electrode tab 3 is not limited to the above. For example, the positive current collector foil 23A may be welded to the lower surface 32 of the positive electrode tab 3A, and the negative current collector foil 23B may be welded to the upper surface 31 of the negative electrode tab 3B. Alternatively, the positive current collector foil 23A may be welded to both the upper surface 31 and the lower surface 32 of the positive electrode tab 3A, and the negative current collector foil 23B may be welded to both the upper surface 31 and the lower surface 32 of the negative electrode tab 3B. The detailed structure of the welded portion between the electrode tab 3 and the current collecting foil 23 and the heat dissipation structure of the welded portion will be described later.

[0017] The exterior material 4 is composed of a pair of metal plates 4A and 4B with high thermal conductivity. The exterior material 4 sandwiches the power generating element 2 and parts of the electrode tabs 3 in the Z direction between 4A, which is located on the +Z side, and metal plate 4B, which is located on the -Z side. This allows the exterior material 4 to house parts of the electrode tabs 3 and the power generating element 2. The specific material of the metal plates 4A, 4B is not particularly limited, and any material may be used as long as it can dissipate heat to the exterior material 4 to an extent that does not cause melting of the welded portion between the electrode tab 3 and the current collecting foil 23, in response to the amount of heat generated at the welded portion between the electrode tab 3 and the current collecting foil 23. For example, the material may have a thermal conductivity of 1 W / (m·K) or more.

[0018] As shown in Figures 1 and 2, the metal plates 4A and 4B that make up the exterior material 4 have an outer peripheral edge portion 41 (see Figure 1), a storage portion 42, and a tab lead-out portion 43 provided in a part of the outer peripheral edge portion 41. The outer peripheral edge portion 41 has a flat surface parallel to the XY plane and is provided along the outer peripheral edges of the metal plates 4A and 4B. By joining the opposing outer peripheral edge portions 41 of the pair of metal plates 4A and 4B together, the exterior material 4 is configured to maintain an airtight interior.

[0019] The storage section 42 is provided in the center of the metal plates 4A and 4B surrounded by the outer peripheral edge 41, and is formed concave in the Z direction from the outer peripheral edge 41. The storage section 42 of the metal plate 4A is concave on the +Z side, and the storage section 42 of the metal plate 4B is concave on the -Z side. This leaves a space of a predetermined height between the storage section 42 of the metal plate 4A and the storage section 42 of the metal plate 4B, and the power generating element 2 is placed in this space. The storage section 42 may be provided on one of the pair of metal plates 4A, 4B, and not on the other.

[0020] The tab leading-out portion 43 is a portion where the electrode tab 3 is disposed. In this embodiment, the positive electrode tab 3A is led out to the −X side, and the negative electrode tab 3B is led out to the +X side, so the tab leading-out portions 43 are provided at the +X side end and the −X side end of the outer circumferential edge portion 41, respectively. Similar to the storage section 42, the tab derivation section 43 is a groove recessed in the Z direction from the outer peripheral edge section 41, and is provided from the storage section 42 to the outer peripheral edges of the metal plates 4A and 4B. The groove depth of the tab derivation section 43 is shallower than the depth of the recess of the storage section 42, and it is sufficient if the electrode tab 3 can be disposed between the opposing tab derivation sections 43 of the pair of metal plates 4A and 4B. An insulating sealant 431 may be filled between the electrode tab 3 and the tab derivation section 43, thereby maintaining the inside of the exterior material 4 airtight. In addition, in this embodiment, since the metal plates 4A and 4B are used as the exterior material 4, the insulating sealant 431 can insulate the electrode tab 3 from the exterior material 4. The tab lead-out portion 43 may be provided on one of the pair of metal plates 4A, 4B, and not on the other.

[0021] (heat dissipation structure) Next, the welding of the electrode tab 3 and the current collecting foil 23 and the heat dissipation configuration will be described. Fig. 3 is a plan view of the joint position between the positive electrode tab 3A and the positive electrode current collector foil 23A as viewed from the Z direction. Fig. 4 is a schematic cross-sectional view of the vicinity of the positive electrode tab 3A taken along line BB in Fig. 3. Note that, although the heat dissipation configuration will be described here using the welding position between the positive electrode tab 3A and the positive electrode current collector foil 23A, the negative electrode tab 3B and the negative electrode current collector foil 23B have the same configuration and are therefore not shown.

[0022] The electrode tab 3 and the current collector foil 23 are welded together at multiple locations, as shown in Fig. 3, for example. The portions where the electrode tab 3 and the current collector foil 23 are welded together are hereinafter referred to as welds 5. In this embodiment, as shown in Fig. 3, multiple welds 5 (three in the example of Figs. 3 and 4) that are elongated in the Y direction are arranged in parallel in the X direction. The positions and sizes of the welds 5 are not particularly limited. For example, the welds 5 may be arranged at equal intervals in the X and Y directions, or welds that are elongated in the X direction may be arranged in parallel in the Y direction.

[0023] However, these welded portions 5 have high electrical resistance, and therefore generate a large amount of heat during charging and discharging of the secondary battery 1. For this reason, in this embodiment, a heat dissipation member 61 is provided for each welded portion 5 as a heat dissipation configuration for these welded portions 5. For example, in the example of Fig. 3, multiple heat dissipation members 61 (three in the example of Fig. 3) are arranged in the Y direction for the welded portion 5 that is elongated in the Y direction. In this embodiment, since the exterior material 4 is made of the metal plates 4A and 4B, it is preferable to use an insulating material for the heat dissipation member 61. More specifically, an insulating material with thermal conductivity of 1 W / (m K) or more is used as the heat dissipation member 61. Examples of such a material include ceramics such as Al2O3, SiO2, and SiC. Alternatively, a resin material to which a filler powder of highly thermally conductive ceramic is added may be used. These heat dissipation members 61 are in contact with both the welded portion 5 and the inner surface of the exterior material 4 (in the example of FIG. 3, the -Z side surface of the metal plate 4A).

[0024] Furthermore, second heat dissipation members 62 are provided on the side of the electrode tab 3 opposite to the welded portion 5 (the second surface side of the present disclosure) at XY positions corresponding to the respective heat dissipation members 61. In other words, the electrode tab 3 and the welded portion 5 are sandwiched between the heat dissipation members 61 and the second heat dissipation members 62. Similar to the heat dissipation members 61, these second heat dissipation members 62 can be made of an insulating, highly heat-conductive material with a thermal conductivity of 1 W / (m K) or more, such as ceramics such as Al2O3, SiO2, and SiC. Furthermore, these second heat dissipation members 62 are in contact with the electrode tab 3 and the inner surface of the exterior material 4 (the +Z side surface of the metal plate 4B in the example of FIG. 3).

[0025] In this embodiment, the current collecting foil 23 is welded to either the upper surface 31 or the lower surface 32 of the electrode tab 3, but if the current collecting foil 23 is welded to both the upper surface 31 and the lower surface 32 of the electrode tab 3, the second heat dissipation member 62, like the heat dissipation member 61, may be positioned between the welded portion 5 and the metal plate 4B so as to abut against both the welded portion 5 and the metal plate 4B. Grease with high thermal conductivity may be applied between the heat dissipation member 61 and the metal plate 4A, between the heat dissipation member 61 and the welded portion 5, between the second heat dissipation member 62 and the metal plate 4B, and between the second heat dissipation member 62 and the electrode tab 3. In this case, by filling the irregularities on the surfaces of the heat dissipation member 61, the welded portion 5, and the exterior material 4 with grease, it is possible to further improve the heat dissipation efficiency.

[0026] Furthermore, in this embodiment, each welded portion 5 is provided with a first through hole 71 penetrating in the Z direction, and the electrode tab 3 is provided with a second through hole 72 that is coaxial with the first through hole 71. In this embodiment, the first through hole 71 and the second through hole 72 have the same diameter. The heat dissipation member 61 and the second heat dissipation member 62 are connected by a shaft 63 that passes through the first through hole 71 and the second through hole 72. The shaft 63 has the same diameter as the first through hole 71 and the second through hole 72, which prevents the heat dissipation member 61 and the second heat dissipation member 62 from shifting in position. Similarly to the heat dissipation member 61 and the second heat dissipation member 62, the shaft 63 can be made of an insulating, highly heat-conductive material with a thermal conductivity of 1 W / (m·K) or more, such as ceramics such as Al2O3, SiO2, or SiC. As a result, by the shaft 63 being in contact with the welded portion 5 at the first through hole 71, the heat of the welded portion 5 can be released from the shaft 63 to the exterior material 4 via the heat dissipation member 61 and the second heat dissipation member 62.

[0027] The shank 63 is preferably formed integrally with either the heat dissipation member 61 or the second heat dissipation member 62. For example, the heat dissipation member 61 and the shank 63 may be formed integrally to form a rivet. In this case, as shown in FIG. 4 , the second heat dissipation member 62 is preferably provided with a pinhole 621 into which the shank 63 is press-fitted. In this case, the shank 63 is inserted through the first through hole 71 and the second through hole 72, and the tip of the shank 63 is press-fitted into the pinhole 621 of the second heat dissipation member 62. This makes it possible to easily fix the heat dissipation member 61 and the second heat dissipation member 62 to each welded portion 5.

[0028] Alternatively, the heat dissipation member 61 and the shaft 63 may be integrally formed to form a bolt, and a male thread may be provided on the shaft 63. In this case, a nut having a female thread is used as the second heat dissipation member 62, and the male thread of the shaft 63 is screwed into the female thread of the second heat dissipation member 62, thereby fixing the heat dissipation member 61 and the second heat dissipation member 62 to the welded portion 5.

[0029] [Effects of this embodiment] The secondary battery 1 of this embodiment comprises a power generating element 2 including a current collector 21, an electrode tab 3 to which a current collecting foil 23 of the current collector 21 is welded, and an exterior material 4 made of a pair of metal plates 4A and 4B with their outer edges joined together, where the power generating element 2 and at least the welded portion 5 of the electrode tab 3 are sandwiched between the pair of metal plates 4A and 4B to house the exterior material 4 and expose a portion of the electrode tab 3 other than the welded portion 5 to the outside, and a heat dissipation member 61 in contact with the exterior material 4 and dissipating heat from the welded portion 5 to the exterior material 4. As a result, in the secondary battery 1 of this embodiment, heat from the welded portion 5 can be dissipated by heat dissipation from the heat dissipation member 61 to the exterior material 4. Therefore, even if the welded portion 5 generates heat during charging and discharging, melting damage to the welded portion 5 due to the heat can be suppressed, and the reliability of the secondary battery 1 can be improved.

[0030] In this embodiment, the heat dissipation member 61 is disposed between the pair of metal plates 4A, 4B and is in contact with both the welded portion 5 and the inner surface of the exterior material 4. As a result, heat generated at the welded portion 5 is dissipated to the heat dissipation member 61, and further dissipated from the heat dissipation member 61 to the exterior material 4. As a result, the heat at the welded portion 5 can be effectively dissipated and cooled.

[0031] In this embodiment, a second heat dissipation member 62 is further provided which abuts against a second surface (lower surface 32 in the example of Figures 3 and 4) opposite to the first surface to which the current collecting foil 23 is joined by the welded portion 5 of the electrode tab 3, and against the exterior material 4. This allows the heat transferred from the welded portion 5 to the electrode tab 3 to be dissipated to the exterior material 4 via the second heat dissipation member 62, thereby further improving the heat dissipation efficiency of the secondary battery 1.

[0032] In this embodiment, the welded portion 5 has a first through hole 71 that penetrates in the Z direction, and the electrode tab 3 has a second through hole 72 that penetrates in the Z direction and is coaxial with the first through hole 71. The heat dissipation member 61 and the second heat dissipation member 62 are connected by a shaft portion 63 that is inserted into the first through hole 71 and the second through hole 72. As a result, the positions of the heat dissipation member 61 and the second heat dissipation member 62 are determined by the shaft portion 63, thereby preventing misalignment of the heat dissipation member 61 and the second heat dissipation member 62. Furthermore, by making the shaft portion 63 out of a highly thermally conductive material, it is also possible to dissipate heat from the welded portion 5 to the exterior material 4 from the shaft portion 63 via the heat dissipation member 61 and the second heat dissipation member 62.

[0033] In this embodiment, the heat dissipation member 61 is a rivet integrally formed with the shank 63, and the second heat dissipation member 62 has a pinhole 621 through which the shank 63 is inserted. This makes it possible to easily attach the heat dissipation member 61 and the second heat dissipation member 62 to the position of the welded portion 5 by press-fitting the shank 63 of the rivet into the pinhole 621 .

[0034] In this embodiment, the heat dissipation member 61 may be a bolt integrally formed with the shaft portion 63 and having a male threaded portion formed on the shaft portion 63, and the second heat dissipation member 62 may be a nut having a female threaded portion into which the male threaded portion is screwed. Even in this case, the heat dissipation member 61 and the second heat dissipation member 62 can be easily attached to the position of the welded portion 5 by screwing the bolts into the nuts.

[0035] [Second embodiment] Next, a second embodiment will be described. In the first embodiment, the surface of the exterior packaging material 4 facing the heat dissipation member 61 is a flat surface parallel to the XY plane, and the surface of the heat dissipation member 61 facing the exterior packaging material 4 is also a flat surface parallel to the XY plane. In contrast, since the electrode tabs 3 are arranged on the outer periphery of the secondary battery 1, the exterior material 4 may not be flat, but may have a shape that is inclined toward the outer periphery. The second embodiment differs from the first embodiment in that the heat dissipation member 61 and the second heat dissipation member 62 are configured to be able to abut the entire side opposite the electrode tab 3 even with such a shape of the outer casing material 4. In the following description, the same components will be denoted by the same reference numerals, and their description will be omitted or simplified.

[0036] FIG. 5 is a cross-sectional view showing a schematic configuration of the vicinity of the electrode tab 3 (positive electrode tab 3A) of the secondary battery 1A of the second embodiment. In this embodiment, the pair of metal plates 4A, 4B that make up the exterior packaging material 4 are inclined in directions that draw closer to each other as they approach the outer periphery. For example, in the example of Fig. 5, the metal plate 4A on the +Z side is formed in a tapered shape that inclines toward the metal plate 4B side (-Z side) as it approaches the -X side. Similarly, the metal plate 4B on the -Z side is formed in a tapered shape that inclines toward the metal plate 4A side (+Z side) as it approaches the -X side.

[0037] When such an exterior material 4 is used, even if a heat dissipation member 61 or a second heat dissipation member 62 having the same shape as in the first embodiment is provided at the welded portion 5, the contact area between the heat dissipation member 61 or the second heat dissipation member 62 and the exterior material 4 cannot be sufficiently secured, and the heat dissipation effect is reduced. Therefore, in this embodiment, a heat dissipation member 61A and a second heat dissipation member 62A are used that have shapes corresponding to the shape of the inner circumferential surface of the exterior packaging material 4. For example, in the example of FIG. 5 , the surface of the heat dissipation member 61A opposite the electrode tab 3 has a tapered shape in which the thickness in the Z direction decreases toward the -X side, and is formed at the same inclination angle as the metal plate 4A. Furthermore, the thickness in the Z direction of the heat dissipation member 61A varies depending on the position of the heat dissipation member 61A in the X direction. For example, the heat dissipation member 61A on the +X side is formed to be thicker than the heat dissipation member 61A on the -X side. As a result, the +Z side surface of the heat dissipation member 61A abuts against the -Z side surface of the metal plate 4A of the exterior packaging material 4. 5, the surface of the second heat dissipation member 62A opposite the electrode tab 3 is tapered so that the thickness in the Z direction decreases toward the -X side, and is formed at the same inclination angle as the metal plate 4B. The thickness in the Z direction of the second heat dissipation member 62A varies depending on the position in the X direction of the second heat dissipation member 62A. For example, the second heat dissipation member 62A on the +X side is formed to be thicker than the second heat dissipation member 62A on the -X side. As a result, the -Z side surface of the second heat dissipation member 62A abuts against the +Z side surface of the metal plate 4B of the exterior packaging 4.

[0038] [Effects of this embodiment] In the secondary battery 1A of this embodiment, the surface of the heat dissipation member 61A facing the exterior packaging material 4 is formed in the same shape as the surface of the exterior packaging material 4 facing the heat dissipation member 61A. This allows the heat dissipation member 61A to be brought into contact with the inner surface of the exterior packaging material 4 regardless of the shape of the inner surface of the exterior packaging material 4, and allows the heat of the welded joint 5 to be dissipated to the exterior packaging material 4 via the heat dissipation member 61A. Furthermore, compared to when only a portion of the surface of the heat dissipation member 61A facing the exterior packaging material 4 is in contact with the exterior packaging material 4, the entire surface of the heat dissipation member 61A facing the exterior packaging material 4 can be brought into contact with the exterior packaging material 4, thereby improving heat dissipation efficiency.

[0039] [Third embodiment] Next, a third embodiment will be described. In the first embodiment, the first through hole 71 provided in the welded portion 5 and the second through hole 72 provided in the electrode tab 3 have the same diameter and are in contact with the shaft portion 63. In contrast, the third embodiment differs from the first embodiment in that the first through hole 71 and the second through hole 72 have different diameters.

[0040] FIG. 6 is a cross-sectional view showing a schematic configuration of the vicinity of the electrode tab 3 (positive electrode tab 3A) of a secondary battery 1B of the third embodiment. In this embodiment, the first through hole 71A provided in the welded portion 5 has a larger diameter than the second through hole 72 provided in the electrode tab 3. Note that the second through hole 72 is formed to have the same diameter as the shaft portion 63, similar to the first embodiment.

[0041] In this configuration, the hole diameter of the second through hole 72 and the shaft diameter of the shaft portion 63 are the same diameter, so as in the first embodiment, the position of the shaft portion 63 is fixed, and positional deviation of the heat dissipation member 61 and the second heat dissipation member 62 can be suppressed. Furthermore, because the hole diameter of the first through hole 71A is larger than the shaft diameter of the shaft portion 63, a gap is generated between the first through hole 71A and the shaft portion 63. As a result, even if thermal expansion of the welded portion 5 occurs, the welded portion 5 expands toward the gap between the first through hole 71A and the shaft portion 63. This makes it possible to suppress pressure loss of the shaft portion 63 due to the welded portion 5, separation of the electrode tab 3 due to thermal expansion of the welded portion 5, and generation of a gap between the heat dissipation member 61 and the welded portion 5.

[0042] [Effects of this embodiment] In the secondary battery 1B of this embodiment, the diameter of the first through-hole 71A is larger than the shaft diameter of the shaft portion 63, and the diameter of the second through-hole 72 is the same as the shaft diameter of the shaft portion 63. As a result, the heat dissipation member 61 and the second heat dissipation member 62 can be positioned by inserting the shaft portion 63 into the second through hole 72. Furthermore, even if the welded portion 5 thermally expands, the stress caused by the thermal expansion can be released into the gap between the first through hole 71A and the shaft portion 63. This makes it possible to prevent damage to the welded portion 5 and the inconvenience of a gap occurring between the welded portion 5 and the heat dissipation member 61 due to expansion of the welded portion 5 in the Z direction.

[0043] [Fourth embodiment] Next, a fourth embodiment will be described. In the fourth embodiment, the size of the heat dissipation member 61 relative to the welded portion 5 is different from that in the first embodiment. 7 is a plan view of the joint position between the positive electrode tab 3A and the positive electrode current collector foil 23A of a secondary battery 1C of the fourth embodiment, as viewed from the Z direction. FIG. 8 is a schematic cross-sectional view of the vicinity of the positive electrode tab 3A along the line CC in FIG. As shown in Figures 7 and 8, in the secondary battery 1C of this embodiment, when the area of ​​the welded portion 5 viewed from the Z direction is taken as the welded area, the area of ​​the heat dissipation member 61B viewed from the Z direction is larger than the welded area, and the outer edge of the welded portion 5 is located inside the outer edge of the heat dissipation member 61B. That is, in this embodiment, the heat dissipation member 61B is disposed so as to cover the entire welded portion 5, and the contact area of ​​the heat dissipation member 61B with the exterior material 4 is larger than the welded area.

[0044] 8, the second heat dissipation member 62 and the shaft 63 are integrally formed. The shaft 63 is inserted through the first through-hole 71 and the second through-hole 72 and engaged with an engaging portion 611 provided on the heat dissipation member 61B. For example, the second heat dissipation member 62 and the shaft 63 may be integrally formed as a rivet. In this case, the shaft 63 is press-fitted into the engaging portion 611 provided on the heat dissipation member 61B. The second heat dissipation member 62 and the shaft 63 may also be integrally formed as a bolt. In this case, a female screw hole is provided in the engaging portion 611 of the heat dissipation member 61B, and the shaft 63 is screwed into the bolt. This allows the heat dissipation member 61B and the second heat dissipation member 62 to be positioned relative to the welded portion 5.

[0045] [Effects of this embodiment] In the secondary battery 1C of this embodiment, the contact area between the heat dissipation member 61B and the exterior material is larger than the area of ​​the welded portion. In this configuration, the area of ​​contact between heat dissipation member 61B and exterior material 4 is larger than the area of ​​contact between heat dissipation member 61B and welded portion 5. Therefore, heat dissipation member 61B can efficiently dissipate heat radiated from welded portion 5 to exterior material 4, which is in contact with heat dissipation member 61B over a larger area, thereby improving heat dissipation efficiency.

[0046] [Variations] The present invention is not limited to the above-described embodiment, but also includes the following modifications within the scope of achieving the object of the present invention.

[0047] [Variation 1] In the above embodiment, the heat dissipation member 61 is disposed between the metal plate 4A of the exterior packaging material 4 and the welded portion 5, but may be disposed outside the exterior packaging material 4. FIG. 9 is a cross-sectional view showing a schematic configuration of the vicinity of the electrode tab 3 (positive electrode tab 3A) of a secondary battery 1D according to the first modification. In the secondary battery 1D shown in FIG. 9 , the heat dissipation member 61C and the shaft 63 are integrally formed as a bolt, and the shaft 63 is screwed into a female screw hole provided in the second heat dissipation member 62 and tightened. This allows the heat dissipation member 61C to press the inner surface of the exterior material 4 (metal plate 4A) against the welded portion 5 and bring them into contact. In this configuration, the heat dissipation member 61C itself is not in direct contact with the welded portion 5, but by contacting the exterior material 4 and pressing the exterior material 4 against the welded portion 5, heat from the welded portion 5 can be released to the exterior material 4. Furthermore, the heat dissipation member 61C may be provided with heat dissipation fins or the like. In this case, heat transferred from the exterior material 4 can be dissipated into the air from the heat dissipation fins.

[0048] [Variation 2] In the second embodiment, an example has been shown in which the surface of the exterior material 4 facing the electrode tab 3 is tapered, and the surfaces of the heat dissipation member 61A and the second heat dissipation member 62A facing the exterior material 4 are correspondingly tapered, but this is not limiting. The shapes of the heat dissipation member 61A and the second heat dissipation member 62A may be formed into shapes that allow contact with the exterior material 4 over a wide contact surface. For example, if the surface of the exterior material 4 facing the electrode tab 3 is uneven, the surfaces of the heat dissipation member 61A and the second heat dissipation member 62A facing the exterior material 4 are configured to have unevenness of the same shape as the unevenness of the exterior material 4. By engaging the convex portions of the heat dissipation member 61A and the second heat dissipation member 62A with the concave portions of the exterior material 4 and by engaging the concave portions of the heat dissipation member 61A and the second heat dissipation member 62A with the convex portions of the exterior material 4, the contact area between the heat dissipation member 61A and the second heat dissipation member 62A and the exterior material 4 is increased, thereby further improving the heat dissipation effect.

[0049] [Variation 3] In the first embodiment, an example was shown in which the heat dissipation member 61 and the second heat dissipation member 62 are made of an insulating, highly thermally conductive material such as ceramic, but metal may also be used for the heat dissipation member 61 and the second heat dissipation member 62. In this case, it is preferable to form a film of highly thermally conductive resin on at least the surface of the exterior material 4 that faces the electrode tab 3. As the highly thermally conductive resin, for example, a resin material such as epoxy to which filler powder of ceramics such as Al2O3, SiO2, or BN has been added can be used. Such highly thermally conductive resin has high thermal conductivity and electrical insulation properties. Alternatively, although a pair of metal plates 4A and 4B is exemplified as the exterior material 4, other ceramic materials such as alumina, silica, and boron nitride, which have high thermal conductivity, may also be used.

[0050] [Variation 4] In the first embodiment, a configuration is exemplified in which a heat dissipation member 61 is provided on the upper surface 31 side of the electrode tab 3 and a second heat dissipation member 62 is provided on the lower surface 32 side, but a configuration may also be adopted in which the second heat dissipation member 62 is not provided and the heat from the welded portion 5 is dissipated to the exterior material 4 using only the heat dissipation member 61.

[0051] [Variation 5] In the first embodiment, a configuration in which the heat dissipation member 61 and the second heat dissipation member 62 are connected by an axis portion 63 is exemplified, but the axis portion 63 may not be provided and the heat dissipation member 61 and the second heat dissipation member 62 may be provided independently of each other.

[0052] [Variation 6] In the first embodiment, the heat dissipation member 61 and the shaft portion 63 are integrally formed and are configured to engage with an engagement hole (e.g., a pinhole 621 or a female screw hole) provided in the second heat dissipation member 62, but this is not limited to this. For example, the second heat dissipation member 62 and the shaft portion 63 may be integrally configured, and the shaft portion 63 may be engaged with an engagement hole provided in the heat dissipation member 61 . Alternatively, the heat dissipation member 61, the shaft 63, and the second heat dissipation member 62 may be configured as separate bodies. In this case, engagement holes may be provided in both the heat dissipation member 61 and the second heat dissipation member 62, and the shaft 63 may be configured to engage with the engagement hole of the heat dissipation member 61 and the engagement hole of the second heat dissipation member 62. [Explanation of symbols]

[0053] DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C, 1D... Secondary battery, 2... Power generating element, 2A... Positive electrode, 2B... Negative electrode, 2C... Electrolyte layer, 3... Electrode tab, 3A... Positive electrode tab, 3B... Negative electrode tab, 4... Exterior material, 4A... Metal plate, 4B... Metal plate, 5... Welded portion, 21... Current collector, 21A... Positive electrode current collector, 21B... Negative electrode current collector, 22A... Positive electrode active material layer, 22B... Negative electrode active material layer, 23... Current collector foil, 23A... Positive electrode current collector foil, 23B... Negative electrode current collector foil, 41... Outer peripheral edge portion, 42... Storage portion, 43... Tab lead-out portion, 61, 61A, 61B, 61C... Heat dissipation member, 62, 62A... Second heat dissipation member, 63... Shaft portion, 71, 71A... First through hole, 72... Second through hole.

Claims

1. a power generating element including a current collector; an electrode tab welded to the current collector; an exterior material made of a pair of metal plates whose outer peripheries are joined together, the exterior material containing the power-generating element and at least the welded portion of the electrode tab to the current collector by sandwiching the welded portion between the pair of metal plates, and exposing a part of the electrode tab other than the welded portion to the outside; a heat dissipation member that is in contact with the exterior material and dissipates heat from the welded portion to the exterior material; A secondary battery comprising:

2. The heat dissipation member is disposed between the pair of metal plates and abuts against both the welded portion and the inner surface of the exterior material. The secondary battery according to claim 1 .

3. the electrode tab has a first surface joined to the current collector by the weld and a second surface opposite to the first surface, a second heat dissipation member that contacts the second surface of the electrode tab and the exterior material; The secondary battery according to claim 1 .

4. The direction from the first surface to the second surface is defined as the thickness direction. The welded portion includes a first through hole that penetrates in the thickness direction, the electrode tab has a second through-hole that penetrates in the thickness direction and is coaxial with the first through-hole; the heat dissipation member and the second heat dissipation member are connected by a shaft portion inserted through the first through hole and the second through hole, The secondary battery according to claim 3 .

5. one of the heat dissipation member and the second heat dissipation member is a rivet integrally formed with the shank, the other of the heat dissipation member and the second heat dissipation member has a pinhole through which the shaft portion is inserted. The secondary battery according to claim 4 .

6. one of the heat dissipation member and the second heat dissipation member is a bolt that is integrally formed with the shank and has a male thread portion formed on the shank, the other of the heat dissipation member and the second heat dissipation member is a nut provided with a female thread portion into which the male thread portion is screwed. The secondary battery according to claim 4 .

7. The hole diameter of the first through hole is larger than the shaft diameter of the shaft portion, The hole diameter of the second through hole is the same as the shaft diameter of the shaft portion. The secondary battery according to claim 4 .

8. The contact area between the heat dissipation member and the exterior material is larger than the area of ​​the welded portion. The secondary battery according to claim 1 .

9. a surface of the heat dissipation member facing the exterior material having the same surface shape as a surface of the exterior material facing the heat dissipation member; The secondary battery according to claim 1 .

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