JP2011100661A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack excellent in conductivity and intensity at a connection part between batteries, even if materials structuring a positive electrode and a negative electrode are a combination of dissimilar metal with high welding difficulty. <P>SOLUTION: The battery pack is provided with a connecting part 40 equipped with a plurality of cylindrical unit batteries, wherein in a major axis direction of at least two cylindrical unit batteries 20A, 20B, a positive electrode 30 of one of the unit batteries is connected with an negative electrode 29 of the other. In the connecting part in the major axis direction, an end part constituting the positive electrode of one of the unit batteries and an end part constituting the negative electrode of the other are connected with each other with intercalation of a connection member 100. Here, the connection member is integrally coupled by welding with the end part 29 of one of the unit batteries 20A out of the two, and is connected with the end part 30 of the other unit battery 20B by two coupling parts of a welding part 115 by welding and a coupling part 130 by mechanical coupling. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a battery pack having a structure in which a plurality of chargeable / dischargeable single cells (secondary cells) are included, and at least two of the cells are electrically connected in series in the long axis direction. .

Lithium secondary batteries and other secondary batteries are becoming increasingly important as power supplies for vehicles or as power supplies for personal computers and portable terminals. In particular, a lithium secondary battery (for example, a lithium ion battery) that is lightweight and obtains a high energy density is expected to be preferably used as a high-output power source for mounting on a vehicle.
By the way, in order to reduce the work of assembling the battery and the number of parts, it is an effective means to make the battery into an assembled battery. In particular, when used as a vehicle-mounted high-output power source, it is necessary to construct an assembled battery by connecting a plurality of single cells in series.
For example, when connecting cylindrical unit cells, in order to suppress an increase in contact resistance at the connection part between the unit cells, one positive electrode and the other negative electrode are welded between adjacent unit cells in the long axis direction. May be electrically connected. In Patent Document 1, as a technical document relating to the connection between cylindrical unit cells, a connecting member welded and fixed to the lid of one battery is fitted into a fitting groove formed at the lower part of the case of the other battery. A technique for fixing by welding is described.

JP 2008-103302 A

However, the material constituting the positive electrode (that is, the positive electrode terminal, typically a lid that closes the case opening of the unit cell) and the material constituting the negative electrode (that is, the negative electrode terminal, typically the case body of the unit cell). If they are different, welding of different materials (typically welding between dissimilar metals) is required, and there is a possibility that sufficient strength cannot be obtained at the connection portion when welding is not possible or welding is possible. In particular, when the material constituting the positive electrode is aluminum and the material constituting the negative electrode is copper as in a typical lithium secondary battery, the difficulty of welding is very high and the cost may increase. In addition, when the material constituting the negative electrode is iron, aluminum and iron are melted and mixed during welding to form a completely different substance (intermetallic compound), so that the connecting portion becomes brittle and mounted on the vehicle. There is a risk that it may not be able to withstand the use of a high output such as a power source. Furthermore, only mechanical connection such as connection with bolts and nuts provides sufficient strength at the connection part, but the contact resistance at the connection part increases, and there is a risk of heat generation at the connection part when current flows. is there.
Therefore, the present invention was created to solve the conventional problems associated with assembled batteries, and the object of the present invention is a combination of dissimilar metals with high welding difficulty in the materials constituting the positive electrode and the negative electrode. Another object of the present invention is to provide a battery pack having a connection structure that can maintain high connection strength and ensure sufficient electrical conductivity between connected cells.

According to the present invention, a plurality of cylindrical single cells (for example, a secondary battery such as a lithium secondary battery) are provided, and at least two cylindrical single cells have a positive electrode of one single cell in the major axis direction and the other An assembled battery having a connecting portion in the long axis direction connected to the negative electrode of the single battery is provided.
In the assembled battery disclosed herein, an end portion constituting the positive electrode of one unit cell and an end portion constituting the negative electrode of the other unit cell interpose a connecting member in the connecting portion in the long axis direction. Are connected to each other. Here, the connection member is integrally connected to the end portion of one of the two unit cells by welding, and the welded portion is welded to the end portion of the other unit cell. And a connection part by mechanical connection, and is connected by two kinds of connection parts.

  In this specification, the “single cell” is a term indicating individual power storage elements constituting an assembled battery, and includes batteries and capacitors of various compositions unless otherwise specified. The “secondary battery” generally refers to a battery that can be repeatedly charged, and includes a so-called storage battery such as a lithium secondary battery or a nickel metal hydride battery. The power storage element constituting the lithium secondary battery is a typical example included in the “unit cell” referred to herein, and a lithium secondary battery module including a plurality of such unit cells is disclosed herein. It is one typical example of an “assembled battery”.

In the assembled battery having the above-described configuration, at least two unit cells are connected in the major axis direction with a connecting member between an end portion constituting the positive electrode of one unit cell and an end portion constituting the negative electrode of the other unit cell. ing. The connection member is integrally connected to the end of one of the two unit cells by welding, and the other end of the unit cell is welded and mechanically connected. They are connected by coupling means.
Thus, by joining the end of one of the two cells (typically the cell case of the cell) and the connecting member integrally by welding (for example, spot welding), The end and the connecting member are coupled. Then, by connecting the end of the other unit cell (typically a lid that closes the case opening of the unit cell) and the connection member by mechanical connection, the end and the connection member at the connection part Can be firmly connected. As a result, connection with a joining force equal to or higher than that in the case of welding is realized at the connection portion. Further, by joining the end of the other unit cell and the connection member by welding (for example, projection welding), a welded portion having a low electrical resistance and excellent conductivity performance is formed, and the end and the connection member are electrically connected. Connected. Thereby, when charging / discharging the assembled battery, a current flows between one unit cell and the other unit cell through a welded portion having a low electrical resistance. For this reason, in the connection part of the major axis direction between single cells, joining force is heightened by the connection part, and low electrical resistance is implement | achieved by a welding part.
Therefore, according to the present invention, when the assembled battery is constructed by electrically and mechanically connecting the cylindrical unit cells, the material constituting the positive electrode and the negative electrode is a combination of dissimilar metals having high welding difficulty. Even if it is a case, it is possible to flow a large amount of current through the welded portion with excellent conductivity without heat generation at the connected portion by welding and mechanical connection, and the connection portion reinforces the connection between the cells. Thus, an assembled battery having sufficient connection strength (bonding force) can be provided.

  In a preferred aspect of the assembled battery disclosed herein, the end of the unit cell on the side integrally joined by welding is composed of the same material. To do. Since they are made of the same material, welding is easy and the strength of the welded portion is higher than that between different metals.

  Further, in a preferred aspect of the assembled battery disclosed herein, a caulking projection is formed at an end of the unit cell on the side coupled by the two coupling portions, and the caulking The connecting portion between the end portion and the connection member is formed by caulking a protrusion with respect to the connection member. According to this aspect, mechanical connection (connection) between the end of the unit cell on the side coupled by the two coupling units and the connection member can be performed more reliably, Connection strength can be increased. There is also a cost advantage.

  Preferably, a bolt insertion hole is formed in each of the end portion of the unit cell and the connection member on the side joined by the two coupling portions, and the bolt passing through the bolt insertion hole and the bolt The connecting portion between the end portion and the connecting member is formed by a nut fastened to the bolt. As in this aspect, by using known fastening means such as bolts and nuts, mechanical connection between the end portion of the unit cell and the connection member on the side coupled by the two coupling portions (Connection) can be performed more reliably, and the connection strength between the cells can be increased.

  Further, in a preferred aspect of the assembled battery disclosed herein, the connecting portion between the connection member and the end of the unit cell on the side connected by the two connecting portions is mutually connected. It is characterized by being independently formed at least three places. In this way, the connection strength can be balanced in the connection portion by mechanically connecting the connection portions formed independently of each other at least three places.

  Further, in a preferred aspect of the assembled battery disclosed herein, the welded portion between the connection member and the end portion of the unit cell on the side coupled by the two coupling portions is mutually connected. It is characterized by being formed independently at least two places. Even if there is a case where stress is applied to one of the welded parts and it breaks due to being connected by at least two welded parts formed independently of each other, it remains without being broken. Since the current flows in the welded part, the reliability of the assembled battery is improved.

  Further, in a preferred aspect of the assembled battery disclosed herein, the connection member is a cap shape that can be fitted to an end of the unit cell that is integrally coupled to the connection member by the welding. A welded portion and a connecting portion are formed on the bottom surface of the connection member facing the end of the unit cell on the side joined by the two joining portions, The welded portion is formed in an inner region of the bottom surface, and the connecting portion is formed in an outer region of the bottom surface. According to this aspect, when a lateral stress (for example, stress perpendicular to the long axis direction) is applied to the single cells connected in the long axis direction from the outside, the outer side than the welded portion formed in the inner region of the bottom surface. Since the stress acts on the connecting portion formed in the region (that is, formed outside the welded portion) and the stress is not concentrated on the welded portion, the welded portion can be prevented from being broken.

  In a preferred embodiment of the assembled battery disclosed herein, the unit cell includes a positive electrode made of an aluminum material or an alloy thereof, and a negative electrode made of a copper material, an alloy thereof, an iron material, or an alloy thereof. It is characterized by that. Thus, when the material of the lid constituting the positive electrode is an aluminum material or an alloy thereof, and the material of the battery case constituting the negative electrode is a copper material, an iron material or an alloy thereof, both electrodes are directly connected by welding. Although it is difficult, an assembled battery can be easily constructed by interposing the connection member. A lithium secondary battery can be cited as a unit battery that is particularly preferably used.

  Moreover, according to this invention, a vehicle provided with one of the assembled batteries disclosed here is provided. The assembled battery provided by the present invention may exhibit a quality suitable as an assembled battery mounted on a vehicle (for example, the connecting portion of the single cells has a strength that can withstand a large current output). Therefore, the assembled battery can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile equipped with an electric motor such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle.

It is a front view which shows the assembled battery which concerns on one Embodiment. It is a side view which shows the assembled battery which concerns on one Embodiment. It is sectional drawing which shows the structure of the lithium secondary battery (unit cell) which comprises the assembled battery which concerns on one Embodiment. It is a principal part expanded sectional view which expands and shows the enclosure part shown by the dotted line I in FIG. It is a disassembled perspective view which shows typically the structure of the cover body and connection member which concern on one Embodiment. It is a perspective view which shows the state which fitted the cover body and connection member which concern on one Embodiment. It is a perspective view which shows the state which connected the cover body and connection member which concern on one Embodiment. It is a top view which shows typically the connection member which concerns on other one Embodiment. It is a top view which shows typically the connection member which concerns on other one Embodiment. It is sectional drawing which shows the connection part of the connection member which concerns on other one Embodiment, and a cover body. It is a graph which shows tensile strength. It is a graph which shows the synthetic resistance value of a welding part and a connection part. It is a side view which shows typically the vehicle (automobile) provided with the assembled battery which concerns on this invention.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings. The matters necessary for the implementation of the present invention other than the matters specifically mentioned in the present specification (for example, the connection portion between the single cells) are the design matters of those skilled in the art based on the prior art in the relevant field. Can be grasped as. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  The assembled battery according to the present invention uses a rechargeable secondary battery as a unit cell, and a plurality of such unit cells are connected in series (typically at least two unit cells are connected in series in the major axis direction). The assembled battery is not particularly limited. Although not intended to be particularly limited, the present invention will be described in more detail below by taking as an example the case where the present invention is mainly applied to a lithium secondary battery. In addition, in the following drawings, the same code | symbol is attached | subjected to the member and site | part which show | plays the same effect | action, and the overlapping description may be abbreviate | omitted. Moreover, the dimensional relationship (length, width, thickness, etc.) in each drawing does not necessarily reflect the actual dimensional relationship.

FIG. 1 is a front view schematically showing an assembled battery 10 according to an embodiment. FIG. 2 is a side view schematically showing the assembled battery 10 according to one embodiment. FIG. 3 is a cross-sectional view schematically showing the structure of a lithium secondary battery (unit cell) 20A constituting the assembled battery 10 according to the embodiment. The lithium secondary batteries 20A, 20B, 20C, and 20D have the same configuration.
As shown in FIG. 1, the assembled battery 10 according to the present embodiment (first embodiment) includes a plurality (typically 10 or more, preferably about 10 to 30; four in the present embodiment). Chargeable / dischargeable cylindrical lithium secondary batteries (unit cells) 20A, 20B, 20C, and 20D are connected in series. The lithium secondary batteries 20 </ b> A to 20 </ b> D constituting the assembled battery 10 according to the present embodiment typically have a predetermined electrode constituent material (positive and negative electrode current collectors) in the same manner as the single battery constituting the conventional assembled battery. A wound electrode body 50 having sheet-like electrodes, separators, etc. each holding positive and negative active materials, and a cylinder (including a prism) containing the electrode body 50 and an appropriate liquid electrolyte (electrolyte) For example, a cylindrical battery case).

As shown in FIG. 1, a plurality of lithium secondary batteries 20A to 20D having the same shape are formed by projecting portions (negative electrodes) of a case body 27, which will be described later, which are end portions constituting negative electrodes of one of the lithium secondary batteries 20A and 20C. Terminal) 29 and a lid (positive electrode terminal) 30, which will be described later, which constitutes the positive electrode of the other lithium secondary battery 20B, 20D, has a connecting member 100 interposed in the long axis direction at the connecting portion 40, respectively. And are arranged to connect to each other. 1 and 2, the protrusion (negative electrode terminal) 29 of the lithium secondary battery 20B and the lid (positive electrode terminal) 30 of the lithium secondary battery 20C are electrically and electrically connected by a conductive bus bar 90. Mechanically connected. Moreover, as shown in FIG. 1, the assembled battery positive electrode terminal 12 is attached to the lid (positive electrode terminal) 30 of the lithium secondary battery 20A. On the other hand, the assembled battery negative electrode terminal 14 is attached to the protrusion (negative electrode terminal) 29 of the lithium secondary battery 20D. Each connection portion 40 is provided with a ring-shaped holding member 16 made of rubber such as EPDM or insulating resin in order to hold each connection portion 40.
Thus, the assembled battery 10 which has a desired voltage is constructed | assembled by connecting each lithium secondary battery 20A-20D in series. The connection portion 40 between the lid (positive electrode terminal) 30, the connection member 100, and the protruding portion (negative electrode terminal) 29 of the case body 27 will be described in detail later.

Next, a configuration of a lithium secondary battery 20A suitable for configuring the assembled battery 10 according to the present embodiment will be described with reference to the drawings. In addition, since the lithium secondary batteries 20B, 20C, and 20D have the same configuration as that of 20A, redundant description is omitted.
As shown in FIG. 3, the battery case 25 includes a cylindrical case main body 27 in which one surface of the cylindrical shape is an opening 45, and a lid 30 that closes the opening 45. A projecting portion 29 having a circular cross-sectional shape projecting outward (downward in FIG. 3) of the case main body 27 is integrally formed at the bottom end portion of the case main body 27 according to the present embodiment. Yes. As a material constituting the case main body 27, the same material as that used in a general lithium secondary battery can be appropriately used, and there is no particular limitation. From the viewpoint of reducing the weight of the assembled battery 10 itself, for example, a case body 27 made of metal (for example, a copper material or an alloy thereof, an iron material or an alloy thereof) or a synthetic resin can be preferably used. In this embodiment, it is formed of an iron material (for example, a nickel-plated steel plate). Further, the case main body 27 according to this embodiment is connected to a negative electrode current collector 70 of the electrode body 50 described later to constitute an external negative electrode terminal.

The lid 30 is a circle having a predetermined diameter corresponding to the opening 45 from a metal material (for example, an iron material, a nickel-plated steel plate, an aluminum material or an alloy thereof, in the present embodiment, an aluminum material plate). It is molded into a plate shape. The lid body 30 is connected to a positive electrode current collector 60 of an electrode body 50 described later to constitute an external positive electrode terminal.
Further, like the conventional battery case, the lid 30 has a safety valve (not shown) for discharging gas generated inside the case body 27 to the outside of the case body 27 (for example, more than the body portion of the lid 30). A structure in which a thin portion is cleaved as the pressure in the case body 27 increases is provided. The safety valve can be used without any limitation as long as it has a mechanism for opening the valve and discharging the gas inside the case body 27 to the outside when the pressure inside the case body 27 rises above a predetermined level.
The lid 30 is attached to the opening 45 of the case body 27 via a gasket (rubber or insulating resin such as EPDM) 80. Specifically, the lid 30 is clamped and fixed to the opening 45 of the case body 27 so as to sandwich the lid 30 with the gasket 80. By caulking through the gasket 80 in this way, the lid (positive electrode terminal) 30 and the case main body (negative electrode terminal) 27 are insulated and the gap between the two is closed to construct a battery sealing structure. .

The material and members themselves that constitute the wound electrode body 50 according to the present embodiment may be the same as those of the electrode body of the conventional lithium secondary battery, and are not particularly limited. For example, the positive electrode sheet can be formed by applying a positive electrode active material layer for a lithium secondary battery (hereinafter referred to as a positive electrode active material layer) on a long positive electrode current collector. For the positive electrode current collector, an aluminum foil (this embodiment) or other metal foil suitable for the positive electrode is preferably used. As the positive electrode active material, one kind or two or more kinds of substances conventionally used in lithium secondary batteries can be used without any particular limitation. Preferable examples include a composite oxide containing lithium and at least one transition metal element such as LiMn ₂ O ₄ , LiCoO ₂ , and LiNiO ₂ .

On the other hand, the negative electrode sheet can be formed by applying a negative electrode active material layer for a lithium secondary battery (hereinafter referred to as a negative electrode active material layer) on a long negative electrode current collector. For the negative electrode current collector, a copper foil (this embodiment) or other metal foil suitable for the negative electrode is preferably used. As the negative electrode active material, one or two or more kinds of materials conventionally used in lithium secondary batteries can be used without any particular limitation. Preferred examples include carbon materials such as graphite (graphite), oxide materials such as lithium-titanium oxide (Li ₄ Ti ₅ O ₁₂ ), tin (Sn), aluminum (Al), zinc (Zn), silicon (Si ) And other alloy materials.

  Moreover, as a suitable long sheet-like separator used between a positive electrode sheet and a negative electrode sheet, the separator similar to the past can be used. For example, a porous sheet (porous film) made of a polyolefin resin can be used. Alternatively, a polymer solid electrolyte can be used as a separator.

As the electrolyte accommodated in the case body 27 together with the wound electrode body 50, the same electrolyte as a non-aqueous electrolyte (typically, an electrolytic solution) conventionally used for a lithium secondary battery is used without particular limitation. Can do. For example, a lithium salt such as LiPF ₆ can be used. An appropriate amount (for example, concentration 1M) of lithium salt such as LiPF ₆ is dissolved in a non-aqueous solvent such as a mixed solvent of diethyl carbonate and ethylene carbonate (for example, a mass ratio of 1: 1) and used as a non-aqueous electrolyte. Can do.

  As shown in FIG. 3, in the wound electrode body 50 according to the present embodiment, a positive electrode active material layer is formed on the surface of a long sheet-like positive electrode current collector 60, similarly to the electrode body of a normal lithium secondary battery. The positive electrode sheet (positive electrode) and the negative electrode sheet (negative electrode) having a negative electrode active material layer formed on the surface of the long sheet-like negative electrode current collector 70 are laminated together with two long sheet-like separators, Further, the wound electrode body 50 is obtained by winding the positive electrode sheet and the negative electrode sheet while slightly shifting in the width direction (winding axis direction). Moreover, in the wound positive electrode sheet, the positive electrode current collector 60 is exposed without forming the positive electrode active material layer at one end portion along the longitudinal direction, while the wound negative electrode sheet However, the negative electrode current collector 70 is exposed at one end portion along the longitudinal direction without forming the negative electrode active material layer. Then, one end of the lead member 65 is joined (for example, welded) to the exposed end portion of the positive electrode current collector 60 (the upper end of the electrode body 50 in FIG. 3), and the other end of the lead member 65 is the lid body 30. As a result, the positive electrode sheet and the lid (positive electrode terminal) 30 are electrically connected. Similarly, the exposed end of the negative electrode current collector 70 (the lower end of the electrode body 50 in FIG. 3) is electrically connected to the case body (negative electrode terminal) 27. The connection (welding) of the electrode body 50 to the lid body (positive electrode terminal) 30 and the case body (negative electrode terminal) 27 may be the same as that of a conventional lithium secondary battery having the same shape, and does not characterize the present invention. Therefore, detailed description is omitted.

  The wound electrode body 50 produced above is housed in the case body 27 in the winding axis direction, and the electrolyte is injected into the case body 27, and then the lid body 30 is attached to the opening 45 and sealed. Thus, the lithium secondary battery 20A of the present embodiment can be constructed.

  Hereinafter, the connection portion 40 between the lid (positive electrode terminal) 30, the connection member 100, and the protruding portion (negative electrode terminal) 29 of the case body 27 according to the present embodiment will be described in detail. FIG. 4 is an enlarged cross-sectional view of a main part showing an enlarged encircled portion indicated by a dotted line I in FIG. FIG. 5 is an exploded perspective view schematically showing the structure of the lid 30 and the connection member 100 according to one embodiment (first embodiment). FIG. 6 is a perspective view illustrating a state in which the connection member 100 is fitted to the lid body 30 according to the first embodiment. FIG. 7 is a perspective view showing a state in which the lid 30 and the connection member 100 according to the first embodiment are connected.

As shown in FIG. 4, the protrusion (negative electrode terminal) 29 of one unit cell 20 </ b> A and the lid (positive electrode terminal) 30 of the other unit cell 20 </ b> B according to the present embodiment interpose the connection member 100 at the connection unit 40. And electrically and mechanically connected. As shown in FIG. 5, the connection member 100 according to the present embodiment includes a circular bottom surface (bottom surface) 105 corresponding to the cross-sectional shape of the protruding portion 29 of the unit cell 20 </ b> A and an outer peripheral edge of the bottom surface portion 105. It forms in the shape of a cap provided with the side part 110 which stood up in the direction. The inner diameter of the connecting member 100 is slightly larger than the outer diameter of the protruding portion 29 of the case main body 27 and is formed into a shape that can be fitted to the protruding portion 29, that is, a shape that allows the protruding portion 29 to be fitted into the connecting member 100. The length in the vertical direction of the side portion 110 of the connecting member 100 is not particularly limited as long as at least a part of the protruding portion 29 can be fitted. In the present embodiment, approximately the bottom half of the protruding portion 29 is fitted into the connecting member 100.
Moreover, as a material which comprises a connection member, a metal material with favorable electroconductivity can be used preferably. From the viewpoint of ease of processing and cost, it is preferable to use iron (for example, a nickel-plated steel plate). More preferably, it is formed from the same material as the case main body (negative electrode terminal) 27. The protruding portion (negative electrode terminal) 29 of the case body 27 and the connecting member 100 are joined by welding as will be described later. However, welding is easy when the materials constituting each are the same.

As shown in FIG. 5, welding projections 120 are pressed on the lower surface side of the bottom surface portion 105 of the connection member 100 (see FIG. 4) on the same circumference centering on the center point of the bottom surface portion 105 of the connection member 100. A plurality of locations (in this embodiment, 4 locations at equal intervals) are formed independently by molding or the like. The welding projections 120 may be formed at only one location as long as a current-carrying area of a welded portion 115 described later can be secured, but it is preferable to form the welding projections 120 independently at least at two locations from the viewpoint of improving reliability.
Further, as shown in FIG. 5, the bottom surface portion 105 of the connection member 100 has a through-hole 125 that penetrates the bottom surface portion 105 in the vertical direction on the same circumference around the center point of the bottom surface portion 105 of the connection member 100. Are formed in the same number and at the same interval as the caulking projections 35 formed on the lid body 30 described later (in this embodiment, four locations are equally spaced). The through holes 125 and the welding protrusions 120 according to the present embodiment are alternately formed on the same circumference around the center point of the bottom surface portion 105 of the connection member 100.

  As shown in FIG. 4, when lithium secondary batteries 20 </ b> A and 20 </ b> B are connected to each other in the major axis direction through the connection member 100 according to the present embodiment, the lithium secondary battery mechanically coupled to the connection member 100 is used. On the lid (positive electrode terminal) 30 of the secondary battery 20B, a plurality of caulking projections 35 are formed on the same circumference centering on the center point of the lid 30 (see FIG. 5). As shown in FIG. 5, the caulking protrusion 35 has a shape that can be inserted into the through-hole 125 formed in the connection member 100. The caulking protrusions 35 are preferably formed at least at three positions from the viewpoint of improving the strength balance (for example, the caulking protrusions 35 are formed at equal intervals on the same circumference centered on the center point of the lid 30. ).

As shown in FIGS. 6 and 7, the caulking protrusion 35 formed on the lid 30 of the lithium secondary battery 20 </ b> B is inserted into the through hole 125 (see FIG. 5) formed in the connecting member 100, thereby connecting the connecting member. In the state where 100 and the lid 30 are overlapped in the vertical direction, the caulking protrusion 35 protruding upward from the connecting member 100 is caulked (for example, the caulking protrusion 35 is crushed in the vertical direction) to thereby form a connecting portion (coupling portion). 130 is formed, and the connecting member 100 and the lid 30 are mechanically connected by the connecting portion 130. Further, a large current is passed through the welding projection 120 in contact with the lid 30, and heat is applied by the resistance heat generated at the welded portion 115 where the lid 30 and the welding projection 120 are in contact to apply pressure. In this way (projection welding), the lid body 30 and the welding projection 120 are welded, and the lid body 30 and the connection member 100 are coupled at a welded portion (joint portion) 115.
As a result, the connecting portion of the connecting member 100 and the lid body 30 connected by the two connecting portions of the connecting portion 130 and the welded portion 115 has a connection strength equal to or higher than that of the welded portion 115. The connection strength is increased by the mechanical connection at, and the electrical connection excellent in the conductive performance with low electrical resistance is realized by the welding at the welded portion 115.
Then, the connecting member 100 is fitted into the protruding portion 29 of the case body 27 of the other lithium secondary battery 20A, and the contact portion between the side portion 110 of the connecting member 100 and the protruding portion 29 is welded (for example, spot welding) (FIG. 4). In the present embodiment, since the material constituting the connection member 100 and the material constituting the case main body 27 are the same, the connection member 100 and the protruding portion 29 can be easily welded.
According to such a configuration, the case body 27 is made of an iron material (for example, a nickel-plated steel plate) and the lid 30 is made of an aluminum material as in this embodiment, and it is difficult to connect the two metals by welding. Even so, the connection strength between the lithium secondary batteries 20 </ b> A and 20 </ b> B is increased at the connection portion 130 by interposing the connection member 100 according to the present embodiment, and the large capacity is obtained via the welded portion 115 having excellent conductivity. Current can flow.
In addition, the connection by welding of the connection member 100 and the cover body 30 is not restricted to the said projection welding, A conventionally well-known general welding method can be used suitably.

In the embodiment described above, the through-holes 125 and the welding projections 120 formed in the connection member 100 are alternately formed on the same circumference around the center point of the bottom surface portion 105 of the connection member 100. It is not limited to such a form. Hereinafter, a suitable example of the connection member according to the second embodiment will be described with reference to the drawings. FIG. 8 is a plan view of the connection member 300 according to the second embodiment.
As shown in FIG. 8, the connection member 300 according to the second embodiment includes a bottom surface (bottom surface) 305 and side portions 310. In the inner region on the lower surface side of the bottom surface portion 305, the welding projections 420 are formed on the same circumference centered on the center point of the bottom surface portion 305 at a plurality of locations by press molding or the like (4 locations at equal intervals in this embodiment). It is formed independently. Further, in the outer region of the bottom surface portion 305 of the connection member 300, there is a penetrating through the bottom surface portion 305 in the vertical direction on the same circumference centering on the center point of the bottom surface portion 305 and outside the welding projection 420. A plurality of holes 325 (in this embodiment, four places at equal intervals) are formed independently. When connecting the lithium secondary batteries with the connection member 300 having such a configuration interposed therebetween, the connecting portion having a connection strength equal to or higher than that of the welded portion is more than the welded portion formed in the inner region of the bottom surface portion 305. Since it is formed on the outside, even if an external force (for example, a force perpendicular to the major axis direction of the lithium secondary battery) is applied to the connection portion, stress is not concentrated on the welded portion, thereby preventing the welded portion from being broken. be able to.

In the various embodiments described above, the through hole into which the caulking protrusion can be inserted is formed in the connection member, but the present invention is not limited to such a form. Hereinafter, a suitable example of the connection member according to the third embodiment will be described with reference to the drawings. FIG. 9 is a plan view of a connection member 500 according to the third embodiment.
As shown in FIG. 9, the connection member 500 according to the third embodiment includes a bottom surface portion 505 and a side portion 510. A through hole 550 is formed in the central portion of the bottom surface portion 505. Further, on the inner side of the bottom surface portion 505 (that is, the portion where the through hole 550 is formed), there are a plurality of caulking notch portions 560 that are notched with the bottom surface portion 505 facing outward (four locations at equal intervals in this embodiment). ) Is formed. Further, on the lower surface side of the bottom surface portion 505 of the connection member 500, welding projections 620 are formed on the same circumference centered on the center point of the bottom surface portion 505 by a plurality of locations (in this embodiment, four at regular intervals). Locations) are formed independently.
When connecting the lithium secondary batteries with the connection member 500 having such a configuration interposed therebetween, the caulking protrusion formed on the lid body in a state where the connection member 500 and the lid body are overlapped in the vertical direction is notched for caulking. The caulking protrusion is disposed inside (that is, in the center direction of the bottom surface portion 505) from one end portion (that is, the inner peripheral edge of the bottom surface portion 505) of the portion 560 (arranged in a portion indicated by a two-dot chain line in FIG. 9). ), And the caulking protrusion is caulked to the caulking notch portion 560 (typically, the caulking protrusion is crushed horizontally, that is, outside the bottom surface portion 505) to form a coupling portion. The connection member 500 and the lid are mechanically connected by the portion. Further, the welding projection 620 and the lid are coupled in the same manner as described above. Thereby, the effect similar to the said embodiment is acquired.

In the above-described embodiment, the connection member 100 and the lid body 30 are mechanically coupled by caulking the caulking projections 35 formed on the lid body 30, but are not limited to such an embodiment. Hereinafter, as a fourth embodiment, a preferred example in the case where the connection member 700 and the lid 630 are connected to each other by a bolt and a nut will be described with reference to the drawings. FIG. 10 schematically shows a connection portion 640 between the connection member 700 and the lid body 630 according to the fourth embodiment, and is an enlarged cross-sectional view of the main part corresponding to the encircled portion indicated by the dotted line I in FIG. It is.
As shown in FIG. 10, the connection member 700 is formed with a bolt insertion hole 725 that penetrates a part of the connection member 700 in the vertical direction. The lid 630 is formed with a bolt insertion hole 675 that penetrates a part of the lid 630 in the vertical direction. These bolt insertion holes 675 and 725 are formed so as to communicate with each other when the connecting member 700 and the lid 630 are overlapped with each other, and are formed in a shape into which the leg portion 750 of the bolt 740 can be inserted. The connecting member 700 and the lid 630 are overlapped in the vertical direction, and the leg portion 750 of the bolt 740 is inserted into the bolt insertion holes 675 and 725 and the leg portion 750 protruding upward from the connecting member 700 is fastened with the nut 760. Thus, a connecting portion (joining portion) 730 is formed, and the connecting member 700 and the lid 630 are mechanically connected to each other by the connecting portion 730. Further, similarly to the above embodiment, the connection member 700 is formed with a welding projection (not shown), and the welding projection and the lid 630 are coupled at a welding portion (coupling portion) 715. With this configuration, the same effect as in the first embodiment can be obtained.

  In order to confirm that an assembled battery having low electrical resistance and high connection strength can be constructed by connecting lithium secondary batteries to each other using the connection member, the connection portion is excellent in conductivity and connection strength. The following experiment was conducted as an example. It should be noted that the present invention is not intended to be limited to those shown in the specific examples.

[Construction of battery pack according to Examples 1 to 7]
In Examples 1 to 7, lithium secondary batteries (unit cells) having a diameter of 29 mm and a height of 150 mm were produced. The case body of the lithium secondary battery is made of a nickel-plated iron material. As the lid of the lithium secondary battery, a lid made of an aluminum material (A1070) and having a diameter of 27.5 mm and a thickness of 3.5 mm was used. On the lid coupled to the connecting member, caulking protrusions (see FIG. 5) having a diameter of 2.0 mm are formed at four locations. Moreover, the connection member comprised in the shape shown in FIG. 9 from the iron material plated with nickel was used. The connecting member has dimensions of 33.2 mm in diameter, 8 mm in height, and 0.4 mm in thickness, and four notches having a width of 2.0 mm and a length of 3.0 mm are formed on the bottom surface of the connecting member. And four welding projections with a diameter of 1.5 mm are formed.
Then, with a 600 N electrode pressure applied to the welded portion between the welding projection and the lid, the current was increased to 30 kA with an upslope time of 20 milliseconds and energized for 50 milliseconds with a constant current of 30 kA. The connecting member and the lid were connected by welding (projection welding). In addition, with 1600 N (163 kgf) of applied pressure applied to the caulking projection, the current is increased to 30 kA with an upslope time of 20 ms, and the caulking projection is connected by energizing at a constant current of 30 kA for 50 ms. It crimped to the notch part of the member. Thereafter, the connecting member was integrally bonded to the case body of the other lithium secondary battery by spot welding to construct an assembled battery.

[Reference Example 1]
In the assembled battery of Reference Example 1, with an electrode pressurization force of 600 N applied to the welded portion between the welding projection and the lid, the current was increased to 25 kA with an upslope time of 20 milliseconds, and the constant current was 25 kA. Except that the connection member and the lid were welded and joined by energizing for 30 milliseconds and the connection member and the lid were not mechanically coupled by caulking, the same as in Examples 1 to 7. An assembled battery was constructed.

[Reference Example 2]
In the assembled battery of Reference Example 2, an assembled battery was constructed in the same manner as Reference Example 1 except that the current was increased to 20 kA.

[Tensile test]
Using a commercially available tensile testing machine, the tensile strength of the welded part and the connected part of Example 1 was evaluated. One unit cell constituting the assembled battery according to the above-described example was fixed, and the other unit cell connected in the long axis direction was pulled by 0.2 mm / sec vertically upward with a tension jig to break. The tensile strength (tensile load) [N] was measured. The result is shown in FIG. In FIG. 11, the horizontal axis represents the displacement (mm), and the vertical axis represents the tensile force (N).
As shown in FIG. 11, the tensile strength of the welded portion of Example 1 is stable at 545N, and the tensile strength of the connecting portion is substantially the same as 450N. Since the welded part is vulnerable to cold heat and impact fracture, the effect of forming a connecting part having the same strength in terms of not concentrating stress on the welded part was confirmed.
Although detailed data is not shown, the caulking projection is caulked to the connecting member having the through hole as shown in FIG. 4 shown in the previous embodiment, so that the connecting member having the notch is formed. Higher mechanical strength can be obtained.

[Resistance measurement]
Using a digital multimeter, the voltage drop of the four welding parts of the said Examples 1-7 was measured, and the synthetic resistance value of the welding part was calculated | required. Similarly, the resistance value of the four connection parts of the said Examples 1-7 was measured, and the synthetic resistance value of the connection part was calculated | required. Moreover, the resistance value of the four welding parts of the said reference examples 1 and 2 was measured, and the synthetic resistance value of the welding part was calculated | required. The obtained result is shown in FIG. In addition, the vertical axis | shaft in FIG. 12 represents each combined resistance value (mohm) of a welding part and a connection part.
As shown in FIG. 12, according to Examples 1 to 7, it was confirmed that the combined resistance value of the welded portion was a low resistance value of 0.0010 mΩ or less. Moreover, it has confirmed that all the combined resistance values of the joint part which consists of a welding part and a connection part were 0.035 m (ohm) or less.
When the above measurement result was put together, it was shown that the electrical connection excellent in the electroconductive performance with low electrical resistance was implement | achieved in the connection part of the lithium secondary batteries of the assembled battery which concerns on an Example. Moreover, it was shown that the connection strength is enhanced at the connection portion by mechanical coupling between the lithium secondary batteries.

As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible. For example, the lid of each lithium secondary battery constituting the assembled battery may constitute an external negative electrode terminal, and the case main body may constitute an external positive electrode terminal. In each of the above embodiments, the connecting member is fitted into the projecting portion of the case body and integrally joined by welding. However, even if the case body does not include the projecting portion, the lower end of the case body The connecting member may be fitted into the part and integrally connected by welding.
Moreover, the welding part and the connection part do not need to be formed on the same circumference centering on the center point of the bottom face part of a connection member.

  Since the assembled battery according to the present invention can output a large current, it can be suitably used as a power source for a motor (electric motor) mounted on a vehicle such as an automobile. That is, as shown in FIG. 11, a vehicle 1 (typically an automobile equipped with an electric motor such as an automobile, particularly a hybrid automobile, an electric automobile, or a fuel cell automobile) provided with the assembled battery 10 according to the embodiment as a power source is provided. can do.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Assembly battery 12 Assembly battery positive electrode terminal 14 Assembly battery negative electrode terminal 16 Holding member 20A, 20B, 20C, 20D Lithium secondary battery (single cell)
25 Battery case 27 Case body (negative electrode terminal)
29 Protrusion (negative electrode terminal)
30 Lid (positive terminal)
35 Caulking projection 40 Connection portion 45 Opening portion 50 Winding electrode body 60 Positive electrode current collector 65 Lead member 70 Negative electrode current collector 80 Gasket 90 Bus bar 100 Connection member 105 Bottom surface (bottom surface)
110 Side 115 Welded part (joint part)
120 Welding projection 125 Through-hole 130 Connection part (joint part)
300 Connecting member 305 Bottom surface (bottom surface)
310 Side 325 Through-hole 420 Welding projection 500 Connection member 505 Bottom (bottom)
510 Side part 550 Through hole 560 Caulking notch 620 Welding protrusion 630 Lid 640 Connection part 675 Bolt insertion hole 700 Connection member 715 Welded part (joint part)
725 Bolt insertion hole 730 Connection part (joint part)
740 Bolt 750 Leg 760 Nut

Claims (10)

An assembled battery comprising a plurality of cylindrical unit cells, and at least two cylindrical unit cells having a connection portion in which the positive electrode of one unit cell and the negative electrode of the other unit cell are connected in the major axis direction. There,
In the connecting portion in the long axis direction, an end portion constituting the positive electrode of one unit cell and an end portion constituting the negative electrode of the other unit cell are connected to each other with a connecting member interposed therebetween,
Here, the connection member is integrally connected to the end portion of one of the two unit cells by welding, and the welded portion is welded to the end portion of the other unit cell. A battery pack characterized by being connected by two types of joints between a mechanically coupled part and a mechanically coupled part.   2. The assembled battery according to claim 1, wherein the connecting member and an end portion of the unit cell on the side integrally connected by the welding are made of the same material.   A caulking projection is formed at an end of the unit cell on the side coupled by the two coupling portions, and the caulking projection is caulked against the connecting member to The assembled battery according to claim 1, wherein the connection portion with the connection member is formed.   Bolt insertion holes are respectively formed in the end portions of the unit cells on the side joined by the two coupling portions and the connection member, and the bolts passing through the bolt insertion holes and the bolts are fastened. The assembled battery according to claim 1, wherein the connecting portion between the end portion and the connection member is formed by a nut to be formed.   The connection portion between the connection member and the end portion of the unit cell on the side connected by the two connection portions is formed at least three locations independently of each other. Item 5. The assembled battery according to any one of Items 1 to 4.   The welded portion between the connection member and the end portion of the unit cell on the side joined by the two coupling portions is formed at least two locations independently of each other. Item 6. The assembled battery according to any one of Items 1 to 5. The connecting member is formed in a cap shape that can be fitted to the end of the unit cell that is integrally connected to the connecting member by welding, and is connected by the two connecting portions. A welded portion and a connecting portion are formed on the bottom surface of the connecting member facing the end of the unit cell on the side where
The welded portion is formed in an inner region of the bottom surface, and the connecting portion is formed in an outer region of the bottom surface. Battery pack.   The unit cell according to any one of claims 1 to 7, wherein the positive electrode is made of an aluminum material or an alloy thereof, and the negative electrode is made of a copper material or an alloy thereof, or an iron material or an alloy thereof. The assembled battery as described.   The assembled battery according to claim 8, wherein the single battery is a lithium secondary battery.   A vehicle provided with the assembled battery as described in any one of Claims 1-9.

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