JP2002260630A - Connection structure and connection method of electrochemical cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a lead wire hard to be dropped off from an electrode made of aluminum of an electrochemical cell. SOLUTION: The lead wire 18, made of copper, is jointed to a tab part 14 of a collector 30 made of aluminum and projected from a cell body 12 of a lithium ion polymer secondary battery 10. A wire, in which a tin cover film is formed on a surface, is preferably the lead wire 18 made of copper. A heating press-contacting method is preferable as the jointing method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure and a connection method for an electrochemical cell, and more particularly, to an electrical structure in which lead wires for electrically connecting an electrochemical cell and an electric circuit are firmly joined. The present invention relates to a connection structure and a connection method of a chemical cell.

[0002]

2. Description of the Related Art A lithium ion polymer secondary battery having an electrolyte made of a gel polymer is used as a battery as a power source of various electric and electronic devices such as a portable telephone, a video camera, a notebook personal computer, etc., which have rapidly spread in recent years. The adoption of batteries is being considered. The reason for this is that the lithium ion polymer secondary battery has the advantage of being thin and lightweight since the exterior material is a laminate film. In addition, for this reason, the shape of the battery is not restricted as in the case of a cylindrical battery or a rectangular battery in which the exterior material is made of metal (battery can).

In a laminated film of this type of lithium ion polymer secondary battery, a positive electrode and a negative electrode face each other via a gel polymer electrolyte. Among these, the positive electrode is configured by supporting a positive electrode mixture layer on an aluminum current collector, while the negative electrode is configured by supporting a negative electrode mixture layer on a nickel current collector. ing.

The positive electrode mixture layer is made of, for example, Li which is a positive electrode material.
A powder of a lithium composite oxide such as NiO ₂ or LiMn ₂ O ₄ is bound together by a binder. Note that a conductive agent such as a carbon material powder such as carbon black or a metal powder such as copper, silver, or aluminum may be added to the positive electrode mixture layer as needed. Similarly for the negative electrode mixture layer,
For example, it is configured by binding a powder of a carbon material (anode material) such as graphite with a binder.

[0005] Then, outside the laminate film,
The tabs of the aluminum current collector and the nickel current collector protrude, and an external circuit is electrically connected to each of the tabs via a lead wire. As a result, current is supplied to the external circuit from the lithium ion polymer secondary battery.

[0006]

By the way, prior to the lithium ion polymer secondary battery, a battery in which an iron-based metal is an electrode is often used. In this case, a nickel lead is used for the electrode and the electric circuit. It was customary to be electrically connected to each other by wires. In this case, the electrode and the nickel lead wire were joined by welding.

For this reason, even at present, when adoption of a lithium ion polymer secondary battery is being studied, a nickel lead wire is used, and an aluminum current collector and a nickel lead wire are welded. Are joined together.

As a method for welding a nickel lead wire and a tab portion of an aluminum current collector, an ultrasonic welding method is mainly used. This is because the following inconveniences are caused when trying to weld nickel to aluminum by the spot welding method. That is, first, aluminum is picked up by the welding electrode during welding, so dressing of the welding electrode is required. Therefore, the nickel lead wire cannot be efficiently joined to the tab portion of the aluminum current collector. Also, in the spot welding method, the joining area is small, and aluminum undergoes recrystallization or deformation, so that it is not always possible to ensure good strength at the joining portion.

[0009] However, the ultrasonic welding method has a disadvantage that the ultrasonic welding apparatus itself is expensive and therefore expensive. In addition, reproducibility is poor,
Even if welding is performed under the same conditions, if the working days are different, there is a drawback that the joining can be easily performed and sometimes extremely difficult.

Therefore, a lead wire made of a nickel-aluminum clad material is sometimes used. The nickel-aluminum clad material is a joined body of a nickel thin plate and an aluminum thin plate. Therefore, nickel is exposed on one end surface and aluminum is exposed on the other end surface. In this case, by joining the tab portion of the aluminum current collector and the aluminum surface of the lead wire made of the nickel-aluminum clad material, the lead wire is less likely to fall off the tab portion. This is because aluminums are bonded to each other well.

However, the nickel-aluminum clad material is very expensive, and the use of this lead wire causes a problem that the price of electric equipment such as a cellular phone rises.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a connection structure and a connection method for an electrochemical cell in which a lead wire is not easily dropped from an aluminum current collector.

[0013]

According to the present invention, there is provided a connection structure for an electrochemical cell having an aluminum electrode, wherein the aluminum electrode includes an electric circuit and the electrochemical cell. A copper lead wire for electrically connecting the cells to each other is joined. Note that an electrochemical cell in this specification refers to a cell in which an oxidation reaction occurs on one electrode and a reduction reaction occurs on the other electrode to generate an electromotive force.

Aluminum and copper bond well to each other. That is, the copper lead wire does not easily fall off the aluminum electrode. Also, since copper has excellent flexibility,
The joining of the copper lead to the electrochemical cell or circuit is not difficult.

A preferred example of the electrochemical cell is a battery. Specifically, a lithium ion polymer secondary battery comprising a gel polymer electrolyte and at least one of a positive electrode material and a negative electrode material occluding or releasing lithium ions, wherein the aluminum electrode is Is a current collector carrying the compound.

Alternatively, the battery may have an aluminum electrode exposed on at least one end.

Another preferred example of the electrochemical cell is an electric double layer capacitor.

In any case, it is preferable that a metal film made of a metal having a lower melting point than copper is formed on the copper lead wire. In this case, the copper lead wire is more firmly joined to the aluminum electrode.

A preferred example of the metal film is tin.

The present invention also relates to a method for connecting an electrochemical cell having an aluminum electrode and an electric circuit to each other with a copper lead wire, wherein the aluminum electrode and the copper lead are connected to each other. The wire and the wire are joined together by heating and pressing.

As described above, the aluminum electrode and the copper lead are firmly joined to each other by heating and pressing the aluminum electrode and the copper lead (hereinafter, collectively referred to as heating and pressing). be able to. Further, since the apparatus for performing the pressure welding is inexpensive and the reproducibility of the pressure welding itself is good, it is also possible to connect the aluminum electrode and the copper lead wire at low cost.

Before the heat welding, a metal film made of a metal having a lower melting point than copper is preferably formed on the surface of the copper lead wire. This, as described above,
This is because the bonding strength between the aluminum electrode and the copper lead wire is improved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a connection structure and a connection method for an electrochemical cell according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic overall perspective view of a lithium ion polymer secondary battery (electrochemical cell) 10 according to the present embodiment. This lithium ion polymer secondary battery 10
Has a cell body 12 and two tab portions 14 and 16 protruding from the cell body 12, a copper lead wire 18 is joined to the tab portion 14, and a nickel lead wire is connected to the tab portion 16. 20 are joined.

The cell body 12 is formed by laminating a positive electrode 22 and a negative electrode 24 shown in FIG. 2 and a gel polymer electrolyte (not shown) interposed between the electrodes 22 and 24 in a laminated state. (See FIG. 1).

The positive electrode 22 (see FIG. 2) is made of a positive electrode material made of a lithium composite oxide such as LiNiO ₂ or LiMn ₂ O ₄ , a binder, and carbon black, copper, silver, aluminum, etc. added as necessary. The positive electrode mixture layer 28 made of such a conductive agent is supported on an aluminum current collector 30. On the other hand, the negative electrode 24
Is formed by supporting a negative electrode mixture layer 32 composed of a negative electrode material such as a carbon material and a binder on a nickel current collector 34. Positive electrode mixture layer 28 and negative electrode mixture layer 32
Are disposed so as to face each other via the gel polymer electrolyte in the laminate film 26. Note that metallic lithium itself may be used as the negative electrode material.

As can be understood from FIG. 2, each of the aluminum current collector 30 and the nickel current collector 34 has a quadrangular portion having one end face on which the positive electrode mixture layer 28 or the negative electrode mixture layer 32 is supported. 36, 38 and the quadrangular portions 36, 38
And tab portions 14 and 16 protruding from the thin plate. In the lithium ion polymer secondary battery 10,
These tab portions 14 and 16 serve as electrode terminals for the cell body 12.
(See FIG. 1). One end of the copper lead wire 18 is connected to the tab portion 14 of the aluminum current collector 30.
On the other hand, one end of the nickel lead wire 20 is joined to the tab portion 16 of the nickel current collector 34.

The copper lead 18 and the nickel lead 20 are connected to the lithium ion polymer secondary battery 10.
And an electric circuit which constitutes an electric device such as a mobile phone (not shown). That is, the copper lead 18 and the nickel lead 20
Is joined to the terminal joint of the electric circuit as described above.

Copper bonds better with aluminum than nickel. Therefore, the copper lead wire 18
When the other end is joined to the electric device, it is hard to fall off from the tab portion 14 of the aluminum current collector 30. That is, the lithium ion polymer secondary battery 10 is
0 can be reliably connected to an electric circuit.

Moreover, since copper is excellent in flexibility, when joining the copper lead wire 18 to an electric circuit, the copper lead wire 18 can be bent or bent as required. That is, joining the copper lead wire 18 to the tab portion 14 of the aluminum current collector 30 does not make it difficult to join the lithium ion polymer secondary battery 10 to the electric circuit.

The copper lead wire 18 may be a thin plate made of copper, but the surface of the thin plate made of copper is coated with a film having a melting point lower than that of copper, such as tin. Preferably, there is. In the latter case, the bonding strength of the aluminum current collector 30 to the tab portion 14 is improved as compared with the former.

Note that nickel is well bonded to nickel. That is, the tab portion 1 of the nickel current collector 34
6 and the nickel lead wire 20 are satisfactorily joined to each other. Accordingly, on the negative electrode 24 side, it is not particularly necessary to use the copper lead wire 18 instead of the nickel lead wire 20, but it is a matter of course that the copper lead wire 18 may be used.

When the lithium ion polymer secondary battery 10 electrically connected to the electric circuit by these lead wires 18 and 20 is charged, lithium in the lithium composite oxide serving as a positive electrode material is ionized. Lithium ions and electrons are generated. Of these, lithium ions move to the negative electrode 24 via the gel polymer electrolyte and are occluded by the carbon material as the negative electrode material. That is, the carbon material is a layered substance, and lithium ions are inserted between the layers (intercalation reaction). On the other hand, electrons are transferred from the aluminum current collector 30 constituting the positive electrode 22 to the negative electrode 24 via a charger.
And finally reaches the carbon material. Then, they recombine with lithium ions to become metallic lithium.

When an electric device is used, a discharge reaction occurs in the lithium ion polymer secondary battery 10. That is,
Metal lithium inserted between carbon material layers is ionized into electrons and lithium ions, and is released from the layers (deintercalation reaction). Lithium ions move to the positive electrode 22 through the gel polymer electrolyte. Here, the lithium composite oxide, which is a positive electrode material, is also a layered substance, and therefore, an intercalation reaction also occurs in the positive electrode 22. Then, the electrons emitted from the nickel current collector 34 act as electric energy for driving an electric device, reach the positive electrode material via the aluminum current collector 30, and recombined with lithium ions, It becomes lithium constituting the lithium composite oxide.

When the negative electrode material is metallic lithium,
In the negative electrode 24, lithium is ionized during discharging, and metallic lithium is precipitated during charging. On the other hand, in the positive electrode 22, the above-described intercalation reaction and deintercalation reaction occur.

Thereafter, the lithium ion polymer secondary battery 1
By performing charging / discharging on 0, the electric device can be used repeatedly.

Next, the lithium ion polymer secondary battery 1
A method of connecting the copper lead wire 18 to the 0 tab portions 14 and 16 will be described.

First, a copper lead wire 18 is manufactured by forming a metal film such as tin on a thin film made of copper. The means for forming the metal film is not particularly limited, but a plating method is preferable because the metal film can be formed quickly and at low cost. As the plating method, an electroplating method or an electroless plating method may be used.

Next, the copper lead wire 18 is joined to the tab portion 14 of the aluminum current collector 30 projecting from the cell body 12, while the nickel lead wire is connected to the tab portion 16 of the nickel current collector 34. Join the wires 20.

As a joining method, a heating pressure welding method can be adopted. The heating pressure welding method has an advantage that the copper lead wire 18 can be joined at low cost because the apparatus itself is inexpensive.

Specifically, as shown in FIG. 3, the tab portion 14 of the aluminum current collector 30 is placed on a back bar 39 made of an electrical insulator and having heat resistance.
A copper lead wire 18 is placed on the tab portion 14. Then, after the first electrode chip 40 and the second electrode chip 42 of the heating and pressing device (not shown) are pressed against the copper lead wire 18, the first electrode chip 40 and the second electrode chip 42 are pressed from the first electrode chip 40 via the copper lead wire 18 and the tab portion 14. The current i is made to flow toward the second electrode tip 42. In this case, the current i does not flow through the back bar 39 because the back bar 39 is an electrical insulator. Therefore, both the copper lead wire 18 and the tab portion 14 are efficiently heated, and eventually, the copper lead wire 18 and the tab portion 14 are satisfactorily joined to each other.

Similarly, by joining the nickel lead wire 20 to the tab portion 16 of the nickel current collector 34, the lithium ion polymer secondary battery 10 is obtained.

Since the reproducibility of the heating pressure welding method is remarkably good as compared with the ultrasonic welding, the joining yield between the tab portions 14 and 16 of the lithium ion polymer secondary battery 10 and the copper lead wire 18 is improved. Therefore, the joining cost of the copper lead wire 18 can be further reduced.

As described above, in the connection method according to the present embodiment, since the copper lead wire 18 made of copper which can be satisfactorily bonded to aluminum is joined by the heating and pressure welding method, the copper lead wire 18 is used. It is difficult for the aluminum current collector 30 to fall off the tab portion 14.

In the above embodiment, the lithium ion polymer secondary battery 10 is used as an electrochemical cell.
However, the present invention is not particularly limited to this, and any device having an aluminum electrode may be used. For example, a battery in which an aluminum electrode is exposed at least on one end surface of the cell body may be used. Further, instead of a battery, an electric double layer capacitor may be used.

In this embodiment, an aluminum current collector which does not participate in the charge / discharge reaction is described as an example. However, an aluminum electrode which participates in the charge / discharge reaction may be used.

Further, the tab portions 14, 16 and the copper lead wire 18 may be joined to each other by an ultrasonic welding method.

[0048]

EXAMPLE On a back bar 39 made of zirconia, a tab portion 14 of an aluminum current collector 30 having a thickness of 0.07 mm and a width of 5 mm protruding from the cell body 12 and a thickness of 0.1 mm having a tin film formed by plating. After placing a copper lead wire 18 having a width of 1 mm and a width of 5 mm in this order, the first electrode tip 40 and the second electrode tip 42 of the heating and pressing device were pressed against the copper lead wire 18 at 0.35 MPa. The first electrode tip 40 and the second electrode tip 42 were separated from each other with an interval of 4 mm.

In this state, a voltage of 2.5 to 3.0 V is applied to the first electrode tip 40 and the second electrode tip 42, so that 2.2 to 2.5 V is applied between the two electrode tips 40 and 42.
A current i of kA was passed to join the tab portion 14 and the copper lead wire 18. The energization time was 3 to 5 milliseconds.

Further, the tab portion 14 and the copper lead 1
8, the first electrode tip 40 and the second electrode tip 42 are moved in parallel, and then heated and pressed in the same manner as described above. As shown in FIG. The wire 18 was joined at four places. During the joining, sticking to the first electrode tip 40 and the second electrode tip 42 was not recognized.

Next, a peeling test was performed at the joint. That is, after the copper lead wire 18 is heated and pressed against the tab portion 14 in the state shown in FIG. 5, the end of the copper lead wire 18 on the cell body 12 side is gripped and pulled upward, and the copper lead wire 18 and the tab portion 14 When the load at the time of peeling was measured for a plurality of samples, all were within the range of 0.05 to 0.06 N.

For comparison, the nickel lead wire 20 and the tab portion 14 of the aluminum current collector 30 were heated and pressed against each other in accordance with the above, and a peeling test was performed on a plurality of the joints. . As a result, 0.06
Although some exceeded N, most were less than 0.05 N, and the variation was large. In some cases, sticking to the first electrode tip 40 or the second electrode tip 42 may occur during the joining.

Further, as shown in FIG.
8 was pulled in the direction of arrow X to perform a tensile test on the joint between the copper lead wire 18 and the tab portion 14 of the aluminum current collector 30.
The tab portion 14 was broken at 5N. That is,
The joint did not break. From this result, it is clear that the copper lead wire 18 and the tab portion 14 are firmly joined to each other.

[0054]

As described above, according to the electrochemical cell connection structure of the present invention, since a copper lead wire is joined to an aluminum electrode, the lead wire falls off the aluminum electrode. hard. Therefore, the effect that the electrochemical cell can be reliably connected to an electric circuit constituting an electric device such as a mobile phone is achieved.

Further, since the copper lead wire is excellent in flexibility, the copper lead wire can be easily joined to an electrochemical cell or an electric circuit.

Further, according to the method of connecting an electrochemical cell according to the present invention, a copper lead wire is joined to an aluminum electrode by a heating and pressure welding method. For this reason, the effect of being able to join the copper lead wire to the aluminum electrode at low cost, with good reproducibility and robustly is achieved.

[Brief description of the drawings]

FIG. 1 shows a lithium ion polymer 2 according to the present embodiment.
It is a general | schematic whole perspective view which shows the joining structure of a secondary battery (electrochemical cell).

FIG. 2 is a schematic overall perspective view of a positive electrode and a negative electrode included in the lithium ion polymer secondary battery of FIG.

FIG. 3 is a schematic front view showing a state in which a tab portion of the aluminum current collector and a copper lead wire are joined to each other by a heating and pressure welding method.

FIG. 4 is an enlarged plan view of a main part showing a joint portion between a tab part of the aluminum current collector and the copper lead wire.

FIG. 5 is a schematic front view showing a state in which a peeling test is being performed on the tab portion of the aluminum current collector and the copper lead wire that have been joined.

FIG. 6 is a schematic front view showing a state in which a tensile test is being performed on a tab portion of the aluminum current collector and the copper lead wire that have been joined.

[Explanation of symbols]

10 Lithium-ion polymer secondary battery (electrochemical cell) 12 Cell body 14, 16
Tab part 18 Copper lead 20 Nickel lead 22 Positive electrode 24 Negative electrode 26 Laminate film 30 Aluminum current collector 34 Nickel current collector 39 Back bar 40 First electrode chip 42 First 2-electrode tip i ... Current

Claims (9)

[Claims] 1. A connection structure for an electrochemical cell including an aluminum electrode, wherein a copper lead wire for electrically connecting an electric circuit and the electrochemical cell to each other is joined to the aluminum electrode. A connection structure for an electrochemical cell. 2. The connection structure for an electrochemical cell according to claim 1, wherein said electrochemical cell is a battery. 3. The connection structure according to claim 2, wherein the battery includes a gel polymer electrolyte, and at least one of a positive electrode material and a negative electrode material absorbs or releases lithium ions. A connection structure for an electrochemical cell, wherein the battery is a battery, and the aluminum electrode is a current collector supporting the positive electrode material. 4. The connection structure for an electrochemical cell according to claim 2, wherein the battery has the aluminum electrode exposed on at least one end surface of the battery. 5. The connection structure for an electrochemical cell according to claim 1, wherein said electrochemical cell is an electric double-layer capacitor. 6. The connection structure according to claim 1, wherein a metal film made of a metal having a melting point lower than that of copper is formed on the copper lead wire. And the connection structure of the electrochemical cell. 7. The connection structure for an electrochemical cell according to claim 6, wherein said metal film is made of tin. 8. A method for connecting an electrochemical cell having an aluminum electrode and an electric circuit to each other by a copper lead wire, wherein the aluminum electrode and the copper lead wire are heated. And connecting the cells by applying pressure. 9. The electrochemical cell according to claim 8, wherein a metal film made of a metal having a lower melting point than copper is formed on the surface of the copper lead wire before joining. Connection method.