Battery pack and current-carrying member

Abstract

To provide a battery pack of which a bonding strength of an electric connection part between unit cells is high, and provide a current-carrying member of which the bonding strength is high.SOLUTION: According to an embodiment, the present invention provides a battery pack comprising a plurality of unit cells, and a structure body including a lamination structure. The plurality of unit cells includes a first electrode and a second electrode. The structure body includes: a first electrode lead that is electrically connected to the first electrode, and includes a hard metal; a second electrode lead that is electrically connected to the second electrode, and includes a soft metal having a hardness that is lower than that of the hard metal; and a plate including the hard metal. The lamination structure includes: an intermetallic compound layer of the hard metal and the soft metal; one part of the first electrode lead; and the plate material. The plurality of unit cells is electrically serially connected by the structure body.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a battery pack and an energizing member.

Background Art

[0002] In various fields, joining of dissimilar metals may be required. For example, as one method for increasing the capacity of a battery module (battery pack) including a plurality of single cells, a method of electrically connecting cells (single cells) in series within the module has been studied, and in that case, the positive electrode lead and the negative electrode lead may be joined. Since the operating potential and the properties of the electrode material are different between the positive electrode and the negative electrode, the metal materials forming each electrode lead may be different.

[0003] As a specific example, an aqueous electrolyte battery using an aqueous electrolyte containing water as a main component of a solvent can be mentioned. Since an aqueous electrolyte battery can be expected to have high safety as compared with a non-aqueous electrolyte battery using a non-aqueous electrolyte containing a flammable organic solvent as a main component of the solvent, development is underway for large-capacity stationary batteries. In an aqueous electrolyte battery, for example, titanium (Ti), which is a hard metal, is used for the current collector and lead of the positive electrode, and zinc (Zn), which is a soft metal, is used for the current collector and lead of the negative electrode. When performing series connection for increasing the capacity of a battery module using such an aqueous electrolyte battery, the positive electrode Ti lead and the negative electrode Zn lead are joined.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] An embodiment aims to provide a battery module having a high bonding strength at an electrical connection portion between single cells, and a current-carrying member having a high bonding strength.

MEANS FOR SOLVING THE PROBLEMS

[0006] According to an embodiment, a battery module is provided that includes a plurality of single cells and a structure including a laminated structure. The plurality of single cells each include a first electrode and a second electrode. The structure includes a first electrode lead that is electrically connected to the first electrode and includes a hard metal, a second electrode lead that is electrically connected to the second electrode and includes a soft metal having a hardness lower than that of the hard metal, and a plate member including the hard metal. The laminated structure includes a layer of an intermetallic compound of the hard metal and the soft metal, a part of the first electrode lead, and the plate member. The plurality of single cells are electrically connected in series by the structure.

[0007] According to another embodiment, a current-carrying member including a laminated structure is provided. The current-carrying member includes a first member including a hard metal, a second member including a soft metal having a hardness lower than that of the hard metal, and a plate member including the hard metal. The laminated structure includes a layer of an intermetallic compound of the hard metal and the soft metal, a part of the first member, and the plate member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]

Figure 1

Figure 2

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Figure 8

Figure 9

MODE FOR CARRYING OUT THE INVENTION

[0009] When series-connecting aqueous electrolyte batteries using a positive electrode Ti lead and a negative electrode Zn lead, for example, joining of a thin positive electrode Ti lead and a negative electrode Zn lead having a thickness of about 0.1 mm to 0.3 mm may be required. As a method applicable to joining of different metals of thin plates, fusion welding such as resistance welding, which has many application examples for small parts, mechanical fastening using rivets, etc., and solid-phase diffusion joining such as friction pressure welding and ultrasonic joining are known. However, in fusion welding, there is a possibility that the metal may evaporate and sublime, and voids may occur. In mechanical fastening, there is a concern about an increase in the weight and cost of the obtained structure. Also, there is a risk that the thin plate may be damaged during fastening. In friction pressure welding, there is a risk that the soft metal may break due to the load. Although ultrasonic joining is a method with a low risk of breakage because it has a low load (about 1 / 10) compared to friction pressure welding, there is still a possibility that the member may be thinned and the strength may be reduced due to the joining tool sinking in.

[0010] The assembled battery according to the embodiment includes a plurality of single cells and the following structure. The plurality of single cells are electrically connected in series by the structure.

[0011] Each of the plurality of single cells includes a first electrode and a second electrode. The first electrode and the second electrode are, for example, the positive electrode and the negative electrode of the single cell, respectively, or the first electrode and the second electrode are the negative electrode and the positive electrode of the single cell, respectively. That is, the first electrode and the second electrode are in a counter electrode relationship with each other. The single cell is, for example, a secondary battery. Specific examples of the secondary battery include a non-aqueous electrolyte battery and an aqueous electrolyte battery. Further, the secondary battery is, for example, a lithium ion battery.

[0012] The structure included in the battery pack includes a first electrode lead containing a hard metal, a second electrode lead containing a soft metal, and a plate material containing a hard metal. "Hard metal" and "soft metal" are relative expressions, meaning that the hardness of the first metal, which is the main constituent in the first electrode lead and the plate material, is higher than the hardness of the second metal, which is the main constituent in the second electrode lead. The hardness can be represented by, for example, Vickers hardness (unit: HV). That is, the soft metal included in the second electrode lead has a lower hardness than the hard metals of the first electrode lead and the plate material. The hard metal included in the plate material is the same as the hard metal included in the first electrode lead. The structure includes a laminated structure including a layer of an intermetallic compound of the hard metal and the soft metal, a part of the first electrode lead, and the plate material. The structure is a joined body of the first electrode lead, the second electrode lead, and the plate material.

[0013] The first electrode lead is electrically connected to the first electrode included in one of the plurality of single cells included in the battery pack. The second electrode lead is electrically connected to the second electrode included in another single cell included in the battery pack. In this way, the plurality of single cells are electrically connected in series via a structure that functions as a conductor.

[0014] An example of the assembled battery according to the embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is a perspective view schematically showing an example of the assembled battery. The illustrated assembled battery (battery module) 200 includes a plurality of single cells (battery cells) 100. FIG. 2 is a partially cutaway plan view schematically showing an example of the single cell included in such an assembled battery, and represents, for example, the single cell 100 located on the far right in FIG. 1. Each single cell 100 includes an electrode group 1 and a container 2 as an exterior member that houses the electrode group 1. Each of FIGS. 3 and 4 is an enlarged cross-sectional view schematically showing an example of part A shown in FIG. 1.

[0015] The electrode group 1 includes a first electrode 3 and a second electrode 4. In the electrode group 1, a separator 5 is interposed between the first electrode 3 and the second electrode 4. In the electrode group 1, the separator 5 is formed of a material having electrical insulation properties and electrically insulates the first electrode 3 from the second electrode 4.

[0016] The first electrode 3 includes, for example, a first current collector such as a foil containing a hard metal (both not shown), and a first active material-containing layer supported on the surface of the first current collector. The first current collector is not limited to these, but is, for example, a titanium foil, a titanium alloy foil, or a copper foil, etc., and has a thickness of about 5 μm to 20 μm. The first active material-containing layer includes a first active material and may optionally contain a binder and a conductive agent. The first electrode 3 can be either the positive electrode or the negative electrode described later.

[0017] The second electrode 4 includes a second current collector such as a foil containing a soft metal (both not shown), and a second active material-containing layer supported on the surface of the second current collector. The second current collector is not limited to these, but is, for example, a zinc foil, a zinc alloy foil, an aluminum foil, or an aluminum alloy foil, etc., and has a thickness of about 5 μm to 20 μm. The second active material-containing layer includes a second active material and may optionally contain a binder and a conductive agent. The second electrode 4 can be the other of the positive electrode or the negative electrode described later.

[0018] In the illustrated example, the electrode group 1 has a structure in which the first electrode 3 and the second electrode 4 are wound in a spiral shape so as to have a flat shape with a separator 5 interposed therebetween. The electrode group may have a stack structure in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with a separator interposed therebetween. For the electrode group 1, a folded single separator 5 may be used, or a plurality of separators 5 may be used.

[0019] As shown in FIG. 2, strip-shaped first current collector tabs 6 are provided at a plurality of locations at the end of the first electrode 3 located on the end face of the electrode group 1. Each of the first current collector tabs 6 has conductivity and is formed of, for example, the same material as the first current collector. Each of the first current collector tabs 6 may be integrally formed with one corresponding to the first current collector, or may be formed separately from the first current collector. A first electrode lead 8 having conductivity is electrically connected to the first electrode 3. The first electrode lead 8 is electrically connected to the first electrode 3 via, for example, the first current collector tab 6. For example, as shown in FIGS. 3 and 4, the first electrode lead 8 is connected to a plurality of first current collector tabs 6 bundled together. Alternatively, the first electrode lead 8 may be connected to the first electrode 3 without passing through the first current collector tab 6. In that case, the first current collector tab 6 may be omitted. The first electrode lead 8 contains a hard metal and includes, for example, titanium, a titanium alloy, or copper. The first electrode lead 8 is preferably formed of the same material as the first current collector tab 6 or the first current collector. The first electrode lead 8 is, for example, a plate containing a hard metal having a strip shape. The first electrode lead 8 may have a shape obtained by bending such a plate. The thickness of the first electrode lead 8 can be, for example, about 0.1 mm to 0.3 mm.

[0020] The first current collector tab 6 can be either a positive electrode current collector tab or a negative electrode current collector tab. For example, when the first electrode 3 is a positive electrode, the first current collector tab 6 is a positive electrode current collector tab, and when the first electrode 3 is a negative electrode, the first current collector tab 6 is a negative electrode current collector tab. Similarly, the first electrode lead 8 can be a positive electrode lead or a negative electrode lead according to the first electrode 3 and the first current collector tab 6.

[0021] A plurality of strip-shaped second current collecting tabs 7 are provided at respective multiple locations of the end portions of the second electrode 4 located on the end face of the electrode group 1 (see FIG. 2). Each of the second current collecting tabs 7 has conductivity and is formed of, for example, the same material as the second current collector. Each of the second current collecting tabs 7 may be integrally formed with one corresponding to the second current collector, or may be formed separately from the second current collector. A second electrode lead 9 having conductivity is electrically connected to the second electrode 4. The second electrode lead 9 is electrically connected to the second electrode 4 via, for example, the second current collecting tab 7. For example, as shown in FIGS. 3 and 4, the second electrode lead 9 is connected to the plurality of second current collecting tabs 7 bundled together. Alternatively, the second electrode lead 9 may be connected to the second electrode 4 without passing through the second current collecting tab 7. In that case, the second current collecting tab 7 may be omitted. The second electrode lead 9 contains a soft metal and includes, for example, zinc, a zinc alloy, aluminum, or an aluminum alloy. The second electrode lead 9 is preferably formed of the same material as the second current collecting tab 7 or the second current collector. The second electrode lead 9 is, for example, a plate containing a soft metal having a strip shape. The second electrode lead 9 may have a shape obtained by bending such a plate. The thickness of the second electrode lead 9 can be, for example, about 0.1 mm to 0.3 mm.

[0022] The second current collecting tab 7 can be either a negative electrode current collecting tab or a positive electrode current collecting tab. For example, when the second electrode 4 is a negative electrode, the first current collecting tab 6 is used as the negative electrode current collecting tab, and when the second electrode 4 is a positive electrode, the second current collecting tab 7 is used as the positive electrode current collecting tab. Similarly, the second electrode lead 9 can be a negative electrode lead or a positive electrode lead according to the second electrode 4 and the second current collecting tab 7.

[0023] The first electrode lead 8 and the second electrode lead 9 extend outside the container 2. A part of the first electrode lead 8 forms a structure together with the second electrode lead 9 and the plate material 10 that another single cell 100 has, as opposed to the corresponding single cell 100. A part of the second electrode lead 9 forms a structure together with the first electrode lead 8 and the plate material 10 that another single cell 100 has, as opposed to the corresponding single cell 100. By the structure including the first electrode lead 8, the second electrode lead 9, and the plate material 10, the single cells 100 are electrically connected in series in the assembled battery 200.

[0024] The plate material 10 contains the same hard metal as the first electrode lead 8. The plate material 10 contains, for example, titanium, a titanium alloy, copper, or the like. The plate material 10 may contain the hard metal at least on its surface, and the internal material may be different. For example, by using a plate material 10 having a structure in which a member of an inexpensive metal such as aluminum is used as a core material and a surface layer of a hard metal is provided around it, cost reduction can be achieved. The entire plate material 10 may be made of a material containing a hard metal.

[0025] The structure includes a laminated structure 11 that includes at least an intermetallic compound layer 20, a first electrode lead 8, and a plate material 10. The laminated structure 11 may have a three-layer structure of the first electrode lead 8, the intermetallic compound layer 20, and the plate material 10, for example, as shown in FIG. 3. Specifically, the intermetallic compound layer 20 is located between the portion of the first electrode lead 8 included in the laminated structure 11 and the plate material 10. The intermetallic compound layer 20 includes an intermetallic compound of the hard metal of the first electrode lead 8 and the plate material 10 and the soft metal of the second electrode lead 9. Alternatively, the laminated structure 11 may have a five-layer structure as shown in FIG. 4. Specifically, the laminated structure 11 shown in FIG. 4 further includes a first layer 21 of a soft metal, and the intermetallic compound layer includes a second layer 22 between the first layer 21 and a part of the first electrode lead 8, and a third layer 23 between the first layer 21 and the plate material 10. The first layer 21 of the soft metal may have the same composition as the second electrode lead 9. The first layer 21 may be the portion of the second electrode lead 9 included in the laminated structure 11. The second layer 22 of the intermetallic compound includes an intermetallic compound of the hard metal of the first electrode lead 8 and the soft metal of the second electrode lead 9. The third layer 23 of the intermetallic compound includes an intermetallic compound of the hard metal of the plate material 10 and the soft metal of the second electrode lead 9. The compositions of the second layer 22 and the third layer 23 of the intermetallic compound may be the same.

[0026] Regarding both the three-layer structure and the five-layer structure, the laminated structure 11 has a layer of a metal compound of a hard metal and a soft metal. Since the laminated structure 11 has a sufficient thickness due to the plate material 10 acting as a protective plate, the strength of the structure including the laminated structure 11 is high. Therefore, the bonding strength between the first electrode lead 8 and the second electrode lead 9 in the battery pack 200 is high. The first electrode lead 8 and the second electrode lead 9 are electrically connected and can be energized through the structure. In this way, the single cells 100 are electrically connected in series.

[0027] The container 2 can be, for example, a metal container, a laminated film container, or a resin container. As the metal container, a metal can made of nickel, iron, stainless steel, etc. can be used. Examples of the laminated film include, for example, a multilayer film in which a metal layer is coated with a resin layer. Examples of the metal layer include stainless steel foil, aluminum foil, and aluminum alloy foil. For the resin layer, polymers such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used. As the resin container, a container made of PP or PE, etc. can be used.

[0028] Each single battery 100 may further contain an electrolyte. The electrolyte can be, for example, a liquid electrolyte or a gel electrolyte. The liquid electrolyte is prepared by dissolving an electrolyte salt as a solute in a solution as a solvent. The gel electrolyte is prepared by complexing a liquid electrolyte and a polymer material. The electrolyte can be a non-aqueous electrolyte using an organic solvent as the solvent, or an aqueous electrolyte using an aqueous solvent as the solvent. Examples of the electrolyte salt include alkali salts such as lithium salts. Alternatively, as the electrolyte, in addition to the liquid electrolyte and the gel electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, etc. may be used. The liquid electrolyte, the gel electrolyte, and the room temperature molten salt can be held in the electrode group 1. The solid electrolyte can be interposed between the first electrode 3 and the second electrode 4 instead of the separator 5. In this case, in the electrode group 1, the first electrode 3 is electrically insulated from the second electrode 4 by the solid electrolyte.

[0029] The positive electrode includes, for example, a positive electrode current collector such as a positive electrode current collector foil, and a positive electrode active material-containing layer supported on the surface of the positive electrode current collector. The positive electrode current collector is not limited to these, but is, for example, a titanium foil, a titanium alloy foil, an aluminum foil, or an aluminum alloy foil, etc., and has a thickness of about 5 μm to 20 μm. The positive electrode active material-containing layer includes a positive electrode active material and may optionally contain a binder and a conductive agent. Examples of the positive electrode active material include, but are not limited to, oxides, sulfides, and polymers that can occlude and release lithium ions.

[0030] The negative electrode includes a negative electrode current collector such as a negative electrode current collector foil, and a negative electrode active material-containing layer supported on the surface of the negative electrode current collector. The negative electrode current collector is not limited to these, and examples thereof include a zinc foil, a zinc alloy foil, or a copper foil, etc., and the thickness is about 5 μm to 20 μm. The negative electrode active material-containing layer includes a negative electrode active material and may optionally contain a binder and a conductive agent. The negative electrode active material is not particularly limited, and examples thereof include metal oxides, metal sulfides, metal nitrides, and carbon materials that can occlude and release lithium ions.

[0031] The assembled battery 200 can be accommodated by, for example, an accommodation container 201 and its lid 202 as shown in FIG. 5 to constitute a battery pack. In one example, a pair of external terminals 203 and 204 are provided on the lid 202, and the first electrode lead 8 and the second electrode lead 9 are electrically connected to the external terminals 203 and 204, respectively. The supply of power to the single battery 100 included in the assembled battery 200 and the output of power from the single battery 100 can be performed via the external terminals 203 and 204. The positions of the external terminals 203 and 204 for energization are not limited to the lid 202, and for example, the external terminals 203 and 204 may be provided on the side surface of the accommodation container 201. The battery pack may include, in addition to the assembled battery 200, for example, a charge and discharge control device such as a protection circuit.

[0032] As described above, an application example of the structure as a connecting member for electrically connecting the single batteries 100 to each other has been described, but the application location of the structure is not limited to the battery. The structure included in the assembled battery 200 as a connecting member is a specific example including the first electrode lead 8 and the second electrode lead 9 as the first member and the second member, respectively. The first member and the second member are not limited to electrode leads and may be, for example, other conductive members.

[0033] The structure according to the embodiment includes a first member containing a hard metal, a second member containing a soft metal, and a plate material containing a hard metal. The soft metal contained in the second member has a lower hardness than the hard metals of the first member and the plate material. The hard metal contained in the plate material is the same as the hard metal contained in the first member. The structure includes a laminated structure including a layer of an intermetallic compound between the hard metal and the soft metal, a part of the first member, and the plate material. By including the laminated structure having the above configuration, the bonding strength between the first member and the second member is high.

[0034] An example of the structure according to the embodiment will be described with reference to FIGS. 6 and 7. FIGS. 6 and 7 are schematic cross-sectional views each showing an example of the structure according to the embodiment.

[0035] FIG. 6 shows an example of a structure including a laminated structure 11 having a three-layer structure. The illustrated structure includes a first member 18 containing a hard metal, a second member 19 containing a soft metal, and a plate material 10 containing a hard metal. The structure in FIG. 6 includes a laminated structure 11 having a three-layer structure of the first member 18, a layer 20 of an intermetallic compound, and the plate material 10. Specifically, the layer 20 of the intermetallic compound is located between the portion of the first member 18 included in the laminated structure 11 and the plate material 10. It is sufficient that the layer 20 of the intermetallic compound is provided on at least a part of the plate material 10. For example, the layer 20 of the intermetallic compound may be formed on a part of the surface of the plate material 10, or may be formed on the entire surface of the plate material 10. The layer 20 of the intermetallic compound contains an intermetallic compound of the hard metals of the first member 18 and the plate material 10 and the soft metal of the second member 19.

[0036] FIG. 7 shows an example of a structure including a laminated structure 11 having a five-layer structure. The illustrated structure includes a first member 18 containing a hard metal, a second member 19 containing a soft metal, and a plate member 10 containing a hard metal. The laminated structure 11 in FIG. 7 further includes a first layer 21 of a soft metal, and the intermetallic compound layer is divided into a second layer 22 between the first layer 21 and a part of the first member 18 and a third layer 23 between the first layer 21 and the plate member 10. The first layer 21 of the soft metal may have the same composition as the second member 19. The first layer 21 may be a part of the second member 19 included in the laminated structure 11. It is only necessary that the second layer 22 is provided on at least a part of the first member 18. For example, the second layer 22 may be formed on a part of the surface of the first member 18, or the second layer 22 may be formed on the entire surface of the first member 18. Similarly, it is only necessary that the third layer 23 is provided on at least a part of the plate member 10. For example, the third layer 23 may be formed on a part of the surface of the plate member 10, or the third layer 23 may be formed on the entire surface of the plate member 10. The second layer 22 of the intermetallic compound contains an intermetallic compound of the hard metal of the first member 18 and the soft metal of the second member 19. The third layer 23 of the intermetallic compound contains an intermetallic compound of the plate member 10 and the soft metal of the second member 19.

[0037] Regarding both the three-layer structure and the five-layer structure, the laminated structure 11 has a layer of a metal compound of a hard metal and a soft metal. Since the laminated structure 11 has a sufficient thickness due to the plate member 10 as a protective plate, the strength of the structure including the laminated structure 11 is high. Therefore, the bonding strength between the first member 18 and the second member 19 is high. The first member 18 and the second member 19 may each independently be a component member included in the object to be joined, or may be a member independent of the object to be joined. The first member 18 and the second member 19 are electrically connected and can be energized through the structure. That is, such a structure can be used, for example, as an energizing member.

[0038] The structure according to the embodiment can be manufactured by a method including ultrasonic bonding. An example of the manufacturing will be described with reference to FIGS. 8 and 9. Each of FIGS. 8 and 9 is a schematic cross-sectional view showing a part of the manufacturing of the structure according to the embodiment.

[0039] As shown in Fig. 8, a first member 18 containing a hard metal and a second member 19 containing a soft metal are stacked on a plate material 10 containing a hard metal. At this time, the stacking order of the materials is in the order of hard metal / soft metal / hard metal. Therefore, as shown in the drawing, from the bottom, the plate material 10, the second member 19, and the first member 18 are in this order.

[0040] A bonding tool 99 for ultrasonic bonding is brought into contact with the first member 18 made of a hard metal. Ultrasonic vibration is transmitted from the bonding tool 99 to the first member 18, the second member 19, and the plate material 10, and an alloy of the hard metal and the soft metal is formed, thereby promoting the bonding between these members. As shown in Fig. 9, during ultrasonic bonding, the bonding tool 99 sinks into the first member 18 from the contact surface, and at the same time, each member deforms at a location corresponding to the sinking of the bonding tool 99. Due to the deformation, a portion where the total thickness of the first member 18 and the second member 19 becomes thinner is generated. The plate material 10 is placed as a protective plate on the surface of the second member 19 on the back side of the first member 18, and this plate material 10 is also bonded to the second member 19 by ultrasonic bonding. Also, the plate material 10 is deformed by the sinking of the bonding tool 99. The thickness of the entire resulting laminated structure 11 is sufficient even at the location deformed by the sinking of the bonding tool 99, and a decrease in strength due to the thinning of each member is suppressed.

[0041] The total thickness T of the first member 18 and the second member 19 stacked together 1 With respect to this, a plate material 10 having a thickness of 25% or more of the thickness T 2 is used (T 2 / T 1 ×100%≥25%), and the second member 19 and the first member 18 are stacked thereon and ultrasonic bonding is performed. When the bonding is performed with a sinking depth D by the bonding tool 99 being 25% or more and 50% or less with respect to the total thickness T 1 of the first member 18 and the second member 19, each member can be bonded. The plate material 10 having a thickness T 2 equal to or greater than the above sinking amount is not torn by the deformation caused by the above sinking amount. The thickness T 2 of the plate material 10 is at least 25% with respect to the total thickness T 1 of the first member 18 and the second member 19, and for example, the total thickness T1 can be 50% or more with respect to

[0042] In addition, when the lamination order of the materials is soft metal / hard metal / soft metal, even if ultrasonic waves are applied until the depth D of the sinking of the joining tool 99 reaches 50%, the respective members cannot be joined.

[0043] By ultrasonic bonding, the eutectic reaction between the hard metal and the soft metal can be utilized, so welding at a low temperature becomes possible. Therefore, for example, it is not necessary to heat up to the melting point of the constituent materials. In one example of a specific combination, the hard metal contains titanium (Ti) and the soft metal contains zinc (Zn). In this combination, for example, a Ti-Zn alloy can be formed as an intermetallic compound. In another example of a combination, the hard metal contains copper (Cu) and the soft metal contains aluminum (Al). In this combination, for example, a Cu-Al alloy can be formed as an intermetallic compound. The hardness of titanium is from 830 HV to 3420 HV in terms of Vickers hardness, and the hardness of zinc is about 30 HV to 50 HV. The hardness of copper is about 343 HV to 369 HV, and the hardness of aluminum is about 160 HV to 350 HV.

[0044] According to at least one embodiment described above, a battery pack including a plurality of single cells electrically connected in series is provided. A structure connecting the plurality of single cells in series includes a laminated structure including a layer of an intermetallic compound of a hard metal and a soft metal respectively included in the first and second electrode leads, a part of the first electrode lead, and a plate material. Since the above-described laminated structure includes a plate material that is a protective plate, the joint between the respective members in the laminated structure has a sufficient thickness and is integrated, so that the joint strength is high. Thereby, a battery pack with high reliability at the joint between the single cells can be provided. In addition, an energizing member having the configuration of the above-described structure is provided. The reliability of the energizing member is high for the above reasons.

[0045] Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0046] 1... Electrode group, 2... Container, 3... First electrode, 4... Second electrode, 5... Separator, 6... First current collector tab, 7... Second current collector tab, 8... First electrode lead, 9... Second electrode lead, 10... Plate material, 11... Laminated structure, 18... First member, 19... Second member, 20... Layer of intermetallic compound, 21... First layer of soft metal, 22... Second layer of intermetallic compound, 23... Third layer of intermetallic compound, 99... Joining tool, Single cell... 100, Battery pack... 200, 201... Containing container, 202... Lid, 203, 204... External terminal.

Claims

1. A plurality of single cells each including a first electrode and a second electrode, a first electrode lead electrically connected to the first electrode and including a hard metal, a second electrode lead electrically connected to the second electrode and including a soft metal having a hardness lower than that of the hard metal, and a plate material including the hard metal, and a structure including a laminated structure including a layer of an intermetallic compound between the hard metal and the soft metal, a part of the first electrode lead, and the plate material provided, wherein the plurality of single cells are electrically connected in series by the structure to form a battery pack.

2. The battery pack according to claim 1, wherein the layer of the intermetallic compound is located between a part of the first electrode lead included in the laminated structure and the plate material.

3. The battery pack according to claim 2, wherein the laminated structure further includes a first layer of the soft metal, and the layer of the intermetallic compound includes a second layer between the first layer and a part of the first electrode lead, and a third layer between the first layer and the plate material.

4. The battery pack according to any one of claims 1 to 3, wherein the plate material includes the hard metal at least on its surface.

5. The battery pack according to any one of claims 1 to 3, wherein the hard metal includes titanium and the soft metal includes zinc.

6. a first member including a hard metal, a second member including a soft metal having a hardness lower than that of the hard metal, and a plate material including the hard metal including a current-carrying member including a laminated structure including a layer of an intermetallic compound between the hard metal and the soft metal, a part of the first member, and the plate material.

7. The current-carrying member according to claim 6, wherein the layer of the intermetallic compound is located between a part of the first member included in the laminated structure and the plate material.

8. The current-carrying member according to claim 6, wherein the laminated structure further includes a first layer of the soft metal, and the layer of the intermetallic compound includes a second layer between the first layer and a part of the first member, and a third layer between the first layer and the plate material.

9. The current-carrying member according to any one of claims 6 to 8, wherein the plate material includes the hard metal at least on its surface.

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