JP2021086683A - Secondary battery - Google Patents

Abstract

To provide a secondary battery in which conductivity of a caulking part is remarkably improved.SOLUTION: A secondary battery 1 comprises: an electrode body 30; a battery case 20 in which the electrode body 30 is accommodated, a terminal mounting hole 22a from the inside of the case to the outside being formed in a portion of the battery case; an internal terminal 12 which is a terminal member electrically connected with the electrode body 30, at least partially disposed inside of the case 20 and including a shank 12c penetrating the terminal mounting hole 22a; and an external terminal 11 which is disposed outside of the case 20 and in which a through hole 11b that the shank 12c penetrates is formed in a portion. A caulking part 15 in which at least the internal terminal 12 and the external terminal 11 are caulked and bonded is formed on a surface of the external terminal 11. A conduction path formed by wire bonding is formed between the internal terminal 12 constituting the caulking part 15 and the external terminal 11 around the caulking part.SELECTED DRAWING: Figure 2

Description

The present invention relates to a secondary battery. More specifically, the present invention relates to the structure of a caulking portion composed of an internal terminal and an external terminal in a secondary battery.

Secondary batteries such as lithium ion secondary batteries and nickel-metal hydride batteries are preferably used not only as so-called portable power sources such as personal computers and mobile terminals, but also as power sources for driving vehicles in recent years. In particular, lithium-ion secondary batteries, which are lightweight and have high energy density, are preferable as high-output power sources for driving vehicles such as electric vehicles (EV), plug-in hybrid vehicles (PHV), and hybrid vehicles (HV), and will continue to be used in the future. Demand is expected to grow.

As an example of a secondary battery for the above-mentioned applications, for example, a battery having an electrode body housed in a case body of a battery case having an opening and having the opening closed by a lid (sealing plate). Can be mentioned.
In such a secondary battery, for example, an internal terminal connected to the electrode body inside the battery case and an external terminal attached to the lid body outside the battery case are connected by forming a caulking portion. ing. In recent years, research and development on the caulking structure of a secondary battery has been energetically carried out, and Patent Document 1 discloses a technique for improving the caulking strength of a secondary battery by laser welding the caulked portion. ..

Patent No. 6117927

By the way, it is known that the contact portion between the internal terminal and the external terminal constituting the crimped portion is easily affected by the long-term use of the secondary battery. For example, if a foreign substance such as an oxide is generated at the contact portion, the conductivity at the portion may decrease. This is not preferable because it causes an increase in the resistance of the secondary battery. For example, when the internal terminal and the external terminal are welded in the portion, it is considered that the above-mentioned decrease in conductivity is suppressed to some extent.
However, when different metals are joined by welding means such as laser welding, an intermetallic compound may be produced. Since such an intermetallic compound is brittle, when it is produced, the welding strength between dissimilar metals may decrease. The internal terminal and the external terminal of the secondary battery may be made of different metals. For example, if an intermetallic compound is generated in the crimped portion, the mechanical strength of the crimped portion may decrease.

The secondary battery for vehicle use as described above is generally used as an assembled battery in which a plurality of single batteries are connected to each other, for example. Each cell is connected, for example, via a bus bar. The bus bar is welded to an external terminal, for example, as described in Patent Document 1 above. While the vehicle is in use, the assembled battery is always affected by an external force due to vibration or the like. Therefore, the decrease in mechanical strength in the crimped portion as described above promotes the decrease in the conductivity of the crimped portion, and may be a factor that hinders the proper use of the assembled battery.

Therefore, the present invention has been created in view of the above problems, and an object of the present invention is to provide a technique for remarkably improving the conductivity in the crimped portion of the secondary battery.

The present inventor has focused on performing wire bonding between the internal terminal and the external terminal in the caulked portion of the secondary battery. Then, they have found that the conductivity of the crimped portion is remarkably improved by this, and have completed the present invention.
The secondary battery disclosed here is an electrode body, a battery case accommodating the electrode body, and a battery case in which terminal mounting holes extending from the inside to the outside of the battery case are partially formed, and the above. An internal terminal that is a terminal member (collecting terminal) electrically connected to the electrode body, at least a part of which is arranged inside the battery case, and has a shaft portion penetrating the terminal mounting hole. It is provided with an external terminal that is arranged on the outside of the battery case and has a through hole through which the shaft portion penetrates, and at least the internal terminal and the external terminal are crimped and joined. The part is a secondary battery formed on the surface of the external terminal.
A conduction path is formed by wire bonding between the internal terminal constituting the crimped portion and the external terminal around the crimped portion.

In the secondary battery having such a configuration, the conductivity in the crimped portion is remarkably improved, and the increase in resistance is remarkably suppressed even when used for a long period of time.

It is sectional drawing which shows typically the structure of the secondary battery which concerns on one Embodiment. It is sectional drawing of the main part schematically showing the structure around the current collector terminal connection structure which concerns on one Embodiment. It is a schematic diagram explaining the action and effect of this invention.

Hereinafter, the secondary battery according to the embodiment of the present invention will be described with reference to the drawings. In the following drawings, members and parts that perform the same action are described with the same reference numerals. The dimensional relationships (length, width, thickness, etc.) in FIGS. 1 and 2 do not reflect the actual dimensional relationships. In FIGS. 1 to 3, U, D, R, and L indicate top, bottom, right, and left, respectively. In the present specification, the numerical ranges A to B indicate A or more and B or less. Matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention (for example, general techniques for constructing a secondary battery such as the composition and manufacturing method of an electrode body and an electrolyte) are , Can be grasped as a design matter of a person skilled in the art based on the prior art in the field.
In the following embodiments, a lithium ion secondary battery (hereinafter, also simply referred to as “secondary battery”) will be described as an example to which the present invention is applied.

First, the overall structure of the secondary battery disclosed herein will be described in detail with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the structure of the secondary battery according to the embodiment.
As shown in FIG. 1, the secondary battery 1 disclosed here includes a battery case 20, an electrode body 30, and an electrolytic solution (not shown).
The electrode body 30 is, for example, a wound electrode body in which a long sheet-shaped positive electrode 32 and a long sheet-shaped negative electrode 34 are laminated with a separator 36 interposed therebetween and wound in the winding axis direction. is there. The positive electrode 32 is formed with a positive electrode active material layer 32b on one side or both sides of the positive electrode current collector 32a. The negative electrode 34 is formed with a negative electrode active material layer 34b on one side or both sides of the negative electrode current collector 34a. Since the electrode body 30 itself does not characterize the present invention, detailed description thereof will be omitted.
The electrolyte can be, for example, a non-aqueous electrolyte containing a lithium salt. The electrolytic solution is not particularly limited, but for example, a carbonate-based non-aqueous solvent such as ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) contains a lithium salt. There is something wrong with it.

The battery case 20 houses and seals the electrode body 30 and the electrolytic solution. The battery case 20 includes a case main body 21 having an opening at one end, and a lid 22 that closes the opening. The case body 21 may have, for example, a flat rectangular parallelepiped shape, and the lid 22 may have, for example, a rectangular flat plate shape. The case body 21 and the lid 22 can be integrated by welding, for example. Further, as the material of the battery case 2, for example, a lightweight metal material having good thermal conductivity such as aluminum can be mentioned.

A current collecting terminal connection structure 10 is provided at both ends of the lid 22 in the horizontal direction (that is, the X direction). A positive electrode current collecting terminal connection structure is provided at the end on the L side, and a negative electrode current collecting terminal connection structure is provided at the R side end. The positive electrode current collecting terminal connection structure and the negative electrode current collecting terminal connection structure are arranged substantially symmetrically with respect to the center in the X direction of the lid 22.
The current collector terminal connection structure 10 includes an external terminal 11 and an internal terminal 12. For example, the positive electrode current collecting terminal connection structure includes a positive electrode external terminal and a positive electrode internal terminal, and the negative electrode current collecting terminal connection structure includes a negative electrode external terminal and a negative electrode internal terminal.
The positive electrode external terminal and the negative electrode external terminal and the positive electrode internal terminal and the negative electrode internal terminal are each formed to have substantially the same shape. The current collecting terminal connection structure of the positive electrode and the current collecting terminal connection structure of the negative electrode are substantially the same structure. Therefore, in the following description, when the members constituting the current collector terminal connection structure are not particularly distinguished between positive and negative, they are simply referred to as the current collector terminal connection structure, the external terminal, and the internal terminal as described above. When it is necessary to distinguish between positive and negative in these explanations, either "positive electrode" or "negative electrode" is added to distinguish them.

Further, the configuration of the above-mentioned current collector terminal connection structure will be described in detail with reference to FIGS. 1 and 2. FIG. 2 is a cross-sectional view of a main part schematically showing a structure around a current collecting terminal connection structure according to an embodiment.
The internal terminal 12 is connected to the electrode body 30 inside the battery case 20. The internal terminal 12 has a lead portion 12a, a base portion 12b, and a shaft portion 12c.
The lead portion 12a is plate-shaped (strip-shaped), and its tip 12a1 (lower end 12a1) is welded (for example, ultrasonically welded) to a current collector of the same electrode in the electrode body 30. The lead portion 12a extends substantially vertically from the tip 12a1 toward the lid 22 (that is, in the U direction) and is connected to a plate-shaped (for example, substantially rectangular or substantially disc-shaped) base portion 12b. The base portion 12b bends at a substantially right angle (from the back side to the front side in the drawings in FIGS. 1 and 2) from the connection portion with the lead portion and spreads substantially parallel to the inner surface of the lid 22 to spread the sealing material 14. It is attached to the lid 22 via. The base portion 12b is provided with a columnar (for example, columnar) shaft portion 12c extending substantially vertically from the base portion 12b. The shaft portion 12c penetrates the through hole 14b (terminal mounting hole 22a), the through hole 13b, and the through hole 11b from the base portion 12b, and its tip 12c1 (upper end 12c1) protrudes from the surface of the external terminal 11. .. The tip 12c1 is crimped, and the internal terminal 12 and the external terminal 11 are connected (fastened) (formation of the crimped portion 15).

The internal terminal 12 is made of metal, and is preferably selected as appropriate depending on the material to be connected, conductivity, strength, material cost, and the like. For example, the internal terminal 12 is preferably made of the same type of metal as the current collector to be connected from the viewpoint of achieving good welding strength.
For example, in a typical lithium ion secondary battery, the positive electrode current collector 32a may be made of aluminum, an aluminum alloy, or the like, and the negative electrode current collector 34a may be made of copper, a copper alloy, or the like. As the positive electrode internal terminal, for example, an internal terminal made of aluminum or copper can be used. As the negative electrode internal terminal, for example, an internal terminal made of aluminum or copper can be used.

The external terminal 11 is a plate-shaped metal member, and has a flat plate portion 11a and a through hole 11b.
The external terminal 11 extends substantially parallel to the outer surface of the lid 22 and is attached to the lid 22 via the insulating member 13. As described above, the shaft portion 12c penetrates through the through hole 11b, and the caulking portion 15 is formed on the surface of the external terminal 11.
The external terminal 11 is made of metal and is not particularly limited, but is preferably made of aluminum, for example.

As shown in the figure, in the crimped portion 15, the tip 12c1 of the crimped shaft portion 12c and the external terminal 11 around the crimped portion 15 are connected by a wire 16.
The wire 16 is attached, for example, by wire bonding. The number of wires 16 in the crimped portion 15 is not particularly limited as long as the number of wires 16 is sufficient to improve the conductivity in the crimped portion 15. The number may be, for example, 1 or more and 50 or less, and preferably at least 5 or more. The number of wires 16 may be 30 or less, 20 or less, and 10 or less. The number of wires 16 may be, for example, 5 or more and 10 or less.
The length of the wire 16 is not particularly limited as long as the internal terminal 12 (shaft portion 12c) and the external terminal 11 can be connected and good conductivity in the crimped portion can be realized. Further, the diameter of the wire 16 is not particularly limited.

Although not particularly limited, the wire 16 is either a case where the external terminal 11 and the internal terminal 12 are made of the same metal, or a case where the external terminal 11 and the internal terminal 12 are made of different metals. May be attached.
The wire 16 is preferably attached, for example, when the external terminal 11 and the internal terminal 12 are made of different metals. In such a case, the combination of metals constituting the external terminal 11 and the internal terminal 12 may be, for example, aluminum and copper. Welding (eg, laser welding) of aluminum and copper, which are different metals, can produce hard and brittle intermetallic compounds. Even when the two metals to be bonded are in such a combination, the formation of the intermetallic compound can be reduced by wire bonding. The wire 16 can be preferably attached, for example, when the negative electrode external terminal is made of aluminum and the negative electrode internal terminal is made of copper.
The "intermetallic compound" is a solid substance composed of at least two or more metal elements, and means a compound having a structure and properties clearly different from those of the constituent metals. Examples of the intermetallic compound that can be produced by aluminum and copper include CuAl ₂ .

The wire 16 is made of metal. Examples of the metal include gold (Au), copper (Cu), aluminum (Al), and silver (Ag), which can be appropriately selected depending on the constituent materials of the external terminal 11 and the internal terminal 12.
Although not particularly limited, for example, when the external terminal 11 and the internal terminal 12 are made of the same metal, the wire 16 is the same metal as the metal and a metal having a Young's modulus smaller than that of the metal. Is preferable.
For example, when the external terminal 11 and the internal terminal 12 are made of different metals, the wire 16 is preferably made of a metal having a smaller Young's modulus than an intermetallic compound that can be produced by the different metals. For example, when the dissimilar metals are aluminum and copper, the wire 16 is preferably made of a metal having a lower Young ratio than an intermetal compound that can be produced by aluminum and copper, for example, either aluminum or copper. It may consist of copper.

The Young's modulus E (GPa) of the metal that can form the wire 16 is as follows. For example, gold (Au) is 79, copper (Cu) is 128, aluminum (Al) is 71, and silver is 82.7.

The sealing material 14 is arranged between the lid 22 and the internal terminal 12 (base portion 12b). The sealing material 14 has a flange portion 14a, a through hole 14b, and a tubular portion 14c. The collar portion 14a extends substantially parallel to the inner surface of the lid body 22 and is arranged so as to be sandwiched between the lid body 22 and the base portion 12b. The tubular portion 14c extends substantially vertically from the flange portion 14a, is arranged between the shaft portion 12c penetrating the terminal mounting hole 22a and the terminal mounting hole 22a, and reaches the outside of the lid 22. The sealing material 14 insulates between the shaft portion 12c and the terminal mounting hole 22a and between the internal terminal 12 and the lid body 22.
The sealing material 14 is formed of a material having elasticity, insulating property, and electrolytic solution resistance. Examples of the material include a fluororesin material such as a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA).

The battery case 2 (lid body 22) has a terminal mounting hole 22a extending from the inside to the outside of the battery case 20. The shaft portion 12c is passed through the terminal mounting hole 22a.

The insulating member 13 is arranged between the external terminal 11 and the lid 22 on the outside of the battery case 20. The insulating member 13 has a recessed portion 13a and a through hole 13b. The recessed portion 13a extends substantially parallel to the inner surface of the lid 22. An external terminal 11 (flat plate portion 11a) is arranged here. The shaft portion 12c penetrates through the through hole 13b. The insulating member 13 is a member that insulates the external terminal 11 and the lid 22.
The insulating member 13 is formed of an insulating material, and examples of the material include polyolefins such as polypropylene (PP) and polyethylene (PE), and resin materials such as polyphenylene sulfide resin (PPS).

Next, a method for manufacturing the secondary battery disclosed here will be described.
Roughly speaking, the secondary battery 1 disclosed here is constructed by attaching the internal terminal 12 and the external terminal 11 to form the crimped portion 15, and attaching the internal terminal 12 to the electrode body 30.

Regarding the formation of the caulking portion 15, the base portion 12b and the external terminal 11 are sandwiched between a pair of pressurizing portions (not shown) of the press device, and these are pressed in a direction in which they approach each other (Z direction). Then, a caulking member (not shown) presses against the tip 12c1 and crushes the tip 12c1, whereby the caulking portion 15 is formed.

Next, wire bonding is performed on the internal terminal 12 constituting the crimped portion 15 and the external terminal 11 around the crimped portion 15. Specifically, a desired number of wires 16 are joined to the portion.
As an apparatus for performing wire bonding, a commercially available wire bonding apparatus can be used without particular limitation. Further, the wire bonding means may be solid-phase bonding such as ultrasonic welding and resistance welding, and is not particularly limited. The conditions for performing wire bonding (for example, bonding temperature, bonding speed, bond load, output amount from the wire bonding apparatus, etc.) are not particularly limited, and can be appropriately adjusted as necessary.

Next, the lead portion 12a (tip 12a1) is attached to the electrode body 30. The method of constructing the electrode body 30 and the method of attaching the terminals may be the same as those in the prior art and do not characterize the present invention, and thus detailed description thereof will be omitted.
Then, the electrode body 30 is housed in the battery case 20, and the lid body 22 is welded. The electrolytic solution is poured into the battery case 20 to seal the opening of the battery case. Then, a secondary battery in a usable state is constructed by performing initial activation and aging treatment under predetermined conditions.

In the secondary battery disclosed here, in a caulking portion composed of an internal terminal and an external terminal, wire bonding is performed between the internal terminal constituting the caulking portion and the external terminal around the caulking portion. By being connected, a good conduction path is formed. As a result, the conductivity in the crimped portion is remarkably improved. Therefore, even if the secondary battery is used for a long period of time, it is possible to suppress a decrease in conductivity at the crimped portion, and thus an increase in resistance of the secondary battery.

By welding the internal terminal and the external terminal in the crimped portion as described above as in the conventional case, the decrease in the conductivity of the crimped portion can be suppressed to some extent. However, if the internal and external terminals are made of different metals, welding may produce brittle intermetallic compounds in the caulked portion.

Here, a part of the action and effect of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram illustrating the action and effect of the present invention.
For example, the secondary battery can be a cell that constitutes an assembled battery. In this case, one cell may be connected to another cell (not shown) via a bus bar 40, which can be welded to, for example, an external terminal 11. For example, due to vibration or the like, an external force P is input in the L direction in the long side direction (that is, the X direction) of the bus bar 40 with respect to the secondary battery as a single battery, and the external terminal 11 is subjected to an external force centering on the caulking portion 15. It is assumed that P is displaced counterclockwise by d. At this time, the caulking portion 15, may take the reaction force F ₁ in the external force P in the opposite direction (R direction).

The magnitude of the _{reaction force F 1 that} can be applied to the crimped portion 15 is
The following equation (1):
F ₁ = 3E ₁ Id / (L ₁ ) ³ (1)
Can be represented by. In the above formula, E ₁ is the Young's modulus of the metal constituting the wire 16, I is the moment of inertia of area, d is the displacement amount of the external terminal, and L ₁ is the length of the wire 16.
On the other hand, in the case where the crimped portion is welded as in the conventional case, when the external force P is input to the secondary battery as described above, the crimped portion becomes the center, and the external terminal is displaced counterclockwise by d due to the external force, the crimped portion The magnitude of the _{reaction force F 2 that} can be applied to
The following equation (2):
F ₂ = 3E ₂ Id / (L ₂ ) ³ (2)
Can be represented by. In the above formula, E ₂ is the Young's modulus of the intermetallic compound produced by welding, I is the moment of inertia of area, d is the displacement amount of the external terminal, and L ₂ is the major axis of the produced intermetallic compound.

Since a metal having a Young's modulus smaller than that of an intermetallic compound compound that can be produced by welding is used as the constituent material of the wire 16, E _{1 in the} formula (1) can be smaller than _{E 2 in the} formula (2). Since the wire 16 has a predetermined length, L ₁ of the equation (1) can be larger than _{L 2} of the equation (2). Therefore, the reaction force F ₁ can be smaller than the reaction force F _2.
In the secondary battery according to the present invention, by arranging the wire 16 on the crimped portion 15 by wire bonding as described above, the load applied to the crimped portion 15 by the external force P is reduced, and the mechanical strength of the crimped portion 15 is lowered. Can be suppressed. INDUSTRIAL APPLICABILITY According to the present invention, the continuity of the caulked portion in the secondary battery can be improved as compared with the conventional case.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.
For example, the secondary battery disclosed herein is not limited to a lithium ion secondary battery, and may be, for example, a nickel hydrogen battery, a sodium ion secondary battery, a magnesium ion secondary battery, or the like.

1 Rechargeable battery 10 Current collection terminal connection structure 11 External terminal 11a Flat plate portion 11b Through hole 12 Internal terminal 12a Lead portion 12a 1 Tip 12b Base 12c Shaft 12c 1 Tip 13 Insulating member 13a Depression 13b Through hole 14 Sealing material 14a 14b Through hole 14c Cylinder part 15 Caulking part 16 Wire 20 Battery case 21 Case body 22 Lid 22a Terminal mounting hole 30 Electrode body 32 Positive electrode 32a Positive electrode current collector 32b Positive electrode active material layer 34 Negative electrode 34a Negative electrode current collector 34b Negative electrode active material Layer 36 Separator 40 Bus bar P External force

Claims (1)

An electrode body, a battery case accommodating the electrode body, a battery case in which a terminal mounting hole extending from the inside to the outside of the battery case is partially formed, and a terminal electrically connected to the electrode body. An internal terminal which is a member and has a shaft portion which is arranged inside the battery case and has a shaft portion penetrating the terminal mounting hole, and a shaft portion which is arranged outside the battery case and has a shaft portion. With an external terminal in which a through hole is partially formed,
A secondary battery in which at least the crimped portion in which the internal terminal and the external terminal are crimped and joined is formed on the surface of the external terminal.
A secondary battery, characterized in that a conduction path is formed by wire bonding between the internal terminal constituting the crimped portion and the external terminal around the crimped portion.

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