JP2001266840A - Bonding method of battery wiring material and sealed battery using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joining method capable of reliably welding an aluminum outer can and an aluminum wiring member with a small number of steps and a normal welding device, and a sealed battery manufactured by the method. SOLUTION: A wiring member 13 is formed using an aluminum plate 14 and a clad material of a metal plate 15 having a higher melting point than the aluminum plate 14 and a small thickness. And welding is performed by resistance welding so that only the outer can 1 and the aluminum plate 14 are fused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for joining an outer can or lid of a secondary battery to a wiring material of a battery pack (hereinafter, also simply referred to as "wiring material"). BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining technique for joining aluminum wiring members to an outer can or a lid in a battery using aluminum, and a sealed battery manufactured by the joining technique.

[0002]

2. Description of the Related Art Generally, the following is known as a sealed structure of a sealed battery, taking a rectangular sealed battery as an example.

[0003] Inside a bottomed cylindrical aluminum alloy outer can,
The positive electrode and the negative electrode, which are power generating elements, are opposed to each other with the separator interposed therebetween, and the electrode body coil formed by pressing after winding is loaded, and each lead tab connected from the positive / negative current collector of the electrode body coil is connected to the outer can. In this case, a positive electrode aluminum lead tab is welded to the aluminum alloy outer can by an ultrasonic welding method or the like. From the viewpoint of manufacturability, a method of welding to a lid of aluminum or an aluminum alloy is generally used. The negative electrode lead tab is connected to, for example, a negative electrode terminal formed in the lid and insulated by a hermetic seal. Normally, a nickel material or the like is generally used as the negative electrode lead tab, and a method of connecting the negative electrode terminal portion to a negative electrode terminal portion obtained by applying nickel plating on nickel or iron by resistance welding is used.

As described above, the lid connected to the positive and negative electrodes is joined to the outer can, and the joint is seam-welded by a method such as laser welding. The lid or the outer can is provided with a hole, for example, having a diameter of about 1 mm for injecting the electrolyte. First, after the water in the internal electrodes and the like is evaporated from the injection port to reduce the water content to a predetermined amount or less by a drying step, an electrolytic solution is injected from the injection port. A sealed secondary battery is assembled by immediately closing and sealing the injection port after injecting the electrolyte. After completion of the above assembling process, the process waits for a time until the electrolyte is impregnated, and then performs processing in a predetermined charging / discharging process to manufacture a sealed secondary battery.

[0005] Usually, these sealed secondary batteries are not handled as bare bodies when mounted on devices such as various types of information equipment, but are built into a resin case and lid to be used as batteries. A battery pack is formed, and the battery pack is handled as one unit.

In particular, the energy density of a lithium ion battery is high, and if it is short-circuited when handled naked,
There is a danger of fire, and a battery pack is necessary for handling.

The electrodes of the secondary battery in the battery pack are not only electrically connected to the wiring members of the battery pack, but also mechanically so that they do not fall off when the mounted equipment is handled. Must be joined with sufficient strength.

[0008] Normally, a secondary battery using aluminum for an outer can and a wiring member of a battery pack are joined together. Generally, nickel is mainly used as a wiring member used inside a battery pack. The intermediate nickel plate is joined to the aluminum portion of the outer can by laser welding, and the nickel wiring material of the battery pack is joined to the nickel plate by resistance welding.

As another method, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-3290565, a cladding material of nickel and aluminum is used for a wiring material.
Ultrasonic welding is performed on the aluminum side as the side connected to the outer can.

[0010]

However, in each of the above-described methods, when the outer can of the secondary battery is made of aluminum, the nickel wiring member of the battery pack cannot be directly resistance-welded to the aluminum portion. The intermediate nickel wiring material was joined to the aluminum part by ultrasonic welding.

[0011] Therefore, it is necessary to prepare the laser welding machine and the ultrasonic welding machine used in this welding method with very expensive equipment while the welding process is performed twice.

In the method of laser welding a nickel positive electrode wiring material, an intermetallic compound of nickel and aluminum or an aluminum alloy is formed in a molten portion. This intermetallic compound is generally brittle, and therefore, it is difficult to obtain a welding fixation strength between the nickel positive electrode wiring member and the outer can. For this reason, it is inevitable to take measures such as increasing the strength by welding at multiple points.

Further, for example, since the thickness of the outer can is reduced by reducing the size and weight of the lithium ion secondary battery, if the laser input energy is increased to obtain welding strength, the outer can is likely to be perforated.

Further, when welding with a YAG laser is used for joining, if heat is input to such an extent that nickel and aluminum are fused, the laser light absorptivity of the melted portion increases, and the melted portion enlarges rapidly. It is very difficult to control a proper fusion state because of the tendency to perform the fusion. For this reason, welding by the YAG laser is a method which is not suitable for securing the welding strength without causing a hole in the thinned aluminum outer can.

In the method of ultrasonically welding a clad material of nickel and aluminum, the uneven shape engraved on the horn or anvil of ultrasonic welding is transferred to the surface of the clad material, and the portion is not suitable for mounting a lead tap for mounting. Becomes As a result, the welding area of the mounting lead terminals is reduced, or it is necessary to use an extra-sized wiring material in anticipation of the reduced area, and particularly as a wiring material for a lightweight and small lithium ion secondary battery. Is not preferred because of large restrictions on the arrangement.

The present invention has been made based on these circumstances, and a joining method capable of reliably welding an aluminum outer can or lid and an aluminum wiring material with a small number of steps and a normal welding device. And a sealed battery manufactured by the same.

[0017]

According to the first aspect of the present invention, there is provided a method for bonding a wiring member for a battery, wherein the wiring member is bonded to an outer surface of an aluminum outer can or a lid forming a sealed battery. The wiring member is formed by using an aluminum plate and a clad material of a metal plate having a higher melting point than the aluminum plate and a small thickness, and placing the aluminum plate side on the outer can or the lid to reduce the resistance. A method of joining battery wiring members, wherein welding is performed so that only the outer can and the aluminum plate are fused by welding.

According to the second aspect of the present invention,
The thin metal plate is made of nickel or a nickel-based alloy.

According to the third aspect of the present invention,
The thickness of the outer can _{d 1} and its specific resistivity _{p 1,} the thickness _{d 2} and the resistivity _{p 2} of the aluminum plate, the thickness _{d 3} of the metal plate
Relationship between the specific resistance _{p 3} and is a bonding method for a battery wiring member, which is a _{d 1 / p 1> d 2} / p 2 + d 3 / p 3.

Further, according to the means of the present invention,
In a sealed battery in which a wiring material is bonded to the outer surface of an outer can or a lid, the wiring material is formed of a clad material of a metal plate having a higher melting point than an aluminum plate and this aluminum plate, and having a small plate thickness, and The sealed battery is characterized in that the aluminum plate side is placed on the outer can or the lid and only the joined outer can and the aluminum plate are welded by resistance welding so as to fuse together.

According to the fifth aspect of the present invention,
The sealed battery is characterized in that the thin metal plate is a nickel plate.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

First, the structure of a secondary battery according to the present invention will be described in detail with reference to FIG. 1 using a rectangular sealed battery as an example. FIG. 1 is a perspective view showing a sealed battery according to the present invention, for example, a rectangular sealed lithium ion secondary battery. here,
The square shape means that the cross-sectional shape when the outer can 1 is cut along the surface including the power generating element is rectangular, but also includes the case where each corner is formed in a round shape.

That is, the outer case 1 having a rectangular shape with a bottom and made of aluminum or an aluminum-based alloy also serves as a positive electrode terminal. An insulating film 2 is disposed on the inner surface of the bottom of the outer can 1.

The electrode body 3 as a power generation element is housed inside the outer can 1. The electrode body 3 is composed of the negative electrode 4 and the separator 5
The positive electrode 6 and the positive electrode 6 are formed by spirally winding the positive electrode 6 so as to be positioned at the outermost periphery, and then press-molding into a flat shape. A spacer 7 made of, for example, a synthetic resin and having a lead extraction hole near the center is arranged on the electrode body 3 inside the outer can 1. A lid 8 made of aluminum or an aluminum-based alloy and provided with a liquid injection hole 10 and a hole 9 for taking out a negative electrode terminal is hermetically joined to an upper end opening of the outer can 1 by, for example, laser welding. After the electrolyte is injected into the outer can 1, the plug (not shown) made of aluminum or an aluminum alloy inserted into the injection hole 10 is welded to the lid 8 by a pulse laser. The injection hole 10 is sealed.

The purity of aluminum is 9
9.3% or more of pure aluminum is used, or JIS standard A3003 (M
When the content of n is 1.0 to 1.5% by weight and the content of Si is 0.6% by weight or less), laser welding defects can be suppressed.

The negative electrode terminal 11 is hermetically sealed in the take-out hole 9 of the lid 8 via an insulator 12 made of glass or resin. Further, a wiring member 13 of the battery pack is joined to the outside of the bottom surface of the outer can 1.

The production of a secondary battery having these structures is as follows.
An insulating paper 2 is placed on the bottom surface of a rectangular bottomed outer can 1 made of metal, and a power generating element (for example, a positive electrode 6 and a negative
Is spirally wound with the separator 5 interposed therebetween, and the flat electrode body 3) is stored. In the case of a rechargeable secondary battery, a rechargeable power generation element is used.

Next, a spacer 7 having a lead extraction hole near the center is arranged on the electrode body 3 in the outer can 1, and the electrode terminal (hermetically sealed) via the insulating material 12 is formed. A negative electrode terminal 11) and a lid 8 made of aluminum or an aluminum-based alloy having a liquid injection port 10 having a columnar shape or a truncated conical shape having a narrowing in the depth direction are attached to the upper end opening of the outer can 1, for example. Airtight joining by laser welding.

Next, a predetermined amount of an electrolytic solution (not shown) is accurately injected into the outer can 1 through a liquid inlet 10 of the lid 8 by a liquid injector (not shown). The electrolyte is a non-aqueous electrolyte,
For example, an electrolyte such as lithium hexafluoride is dissolved in an organic solvent such as ethylene carbonate or propylene carbonate. As the electrolyte, for example, Li
ClO ₄ , LiPF ₆ , LiAsF ₆ , LiBF ₄ Li
C, F ₃ FO ₃ , LiB (C ₆ H ₅ ) ₄ , LiCl, L
One or more lithium salts selected from iBr and LiCH ₃ SO ₃ are used.

Examples of the organic solvent include, for example, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, γ-butyl lactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, sulfolane, acetonitrile, diethylene carbonate, dipropylene One or a mixture of two or more kinds selected from bill carbonate is used. The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.5 to 1.55 mol / l. A stopper (not shown) is press-fitted into the outer can 1 into which the predetermined amount of the electrolyte has been injected.

Next, a joining method for joining the wiring member 13 of the battery pack to the bottom portion of the outer can 1 will be described. As shown in FIG. 2, the wiring member 13 is formed of a clad material of an aluminum plate 14 and a nickel plate 15 having a higher melting point than the aluminum plate 14. The thickness of the aluminum plate 1
4 is 0.1 mm, and the nickel plate 15 is 0.05 mm thinner. The size is rectangular and each side is 3mm
× 10 mm. The thickness of the bottom of the outer can 1 is about 0.5 mm.

As shown in FIG. 3, the outer can 1 and the wiring material 13
Is performed using resistance welding. Resistance welding is performed by a generally used resistance welding machine (not shown).
By flowing a large current between the electrodes for a short period (several cycles), resistive heat is generated at the contact surface between the exterior can 1 and the wiring member 13 to be joined. At that time, the heat at the contact surface of the electrodes passes through the electrodes. However, the contact surface between the outer can 1 and the wiring member 13 to be joined reaches a molten state, so that a nugget (point weld metal) is formed by applying pressure at this time.

The portion of the bottom surface of the outer can 1 to be welded and the wiring member 13 are thoroughly cleaned and cleaned beforehand. Then, the wiring member 13 formed of a clad material is placed on the bottom of the outer can 1 by aluminum. The plate 14 is placed so that the surface of the plate 14 is on the bottom side of the outer can 1, and two electrode rods 17a and 17b of a resistance welding machine (not shown) are lowered onto the nickel plate 15 of the wiring member 13 so as to be in close contact with each other and resistance welding I do. The electrode rods 17a and 17b use electrode rods of alumina-dispersed copper having a tip diameter of φ1.3 mm,
Two series weldings are performed twice to perform a total of 4p welding points.

The processing conditions at that time are as shown in FIG.
The processing conditions for one shot are sequentially raised in a straight line up to 0.85 V in 5 ms, the state of 0.85 V is maintained for 3 ms, and
It falls linearly to 0 V in ms.

FIG. 5 is a schematic cross-sectional view showing the result of observation of the cross-section of a welding location by these weldings. Only the aluminum plate 14 of the wiring member 13 formed of the clad material and the aluminum alloy of the outer can 1 are fused to form a fused portion 16a.
On the other hand, the nickel plate 15 of the wiring member 13 did not show any trace of melting.

After these welding processes, as shown in FIG. 6, a nickel tab 20 for a tensile test is attached on the welded wiring member (positive terminal plate) 13 by resistance welding, and the wiring member 13 and the outer can 1 are connected. The joining strength was measured. As a result, it was confirmed that a tensile strength of 2 kgf or more was easily obtained.

Although the above-mentioned joining is performed by joining the wiring member to the outer can, the same can be applied to joining the wiring member to the lid.

Also, the nickel lead for pack mounting can be connected to the entire surface of the wiring material, and the welding strength of the lead is not limited to the welding strength between the wiring material and the outer can, regardless of the welded portion and the non-welded portion. It was confirmed that a level comparable to that of the original could be maintained.

As described above, in the sealed battery of the present invention, the following effects can be obtained by using the melting point difference between the two metals constituting the clad material and the resistance welding method for the wiring material. .

That is, since the outer metal, for example, nickel for welding the lead tab for mounting wiring has a higher melting point than the metal on the side to be welded to the aluminum outer can, for example, aluminum or an aluminum alloy, nickel is completely eliminated. The aluminum of the outer can and the aluminum of the wiring material can be fused without melting.

The condition for realizing such a state is a range where the following inequality is satisfied.

D ₁ / p ₁ > d ₂ / p ₂ + d ₃ / p ₃ where d ₁ is the thickness of the outer can and its specific resistance p ₁ , and the thickness d ₂ of the metal of the wiring material to be joined to the outer can. And its specific resistance p
_2, the thickness d ₃ of the high melting point of the wiring metal material and its specific resistivity p
_{3 In} other words, as the ratio of the welding current flowing into the outer can at the time of series resistance welding becomes larger than the welding current flowing at the wiring material side, the condition under which the aluminum of the outer can and the aluminum of the wiring material are fused. Therefore, the nickel of the wiring material is less likely to be melted.

As described above, according to the method of the present invention, the wiring member (the positive electrode terminal plate) can be easily and easily joined without making a hole in the thin and thin outer can. The wiring member can be joined to the outer can in a state where the metal disposed outside the wiring member formed of the clad material is not melted. Therefore, when the outer can is flat and the lead tab for mounting is welded to the outer can, it can be applied to substantially the entire surface of the outer can.

[0045]

According to the present invention, the wiring member and the outer can can be easily and reliably welded, and even in the case of a thin outer can, the occurrence of perforation during welding is suppressed and sufficient welding is performed. Strength can be obtained.

Further, since almost the entire surface of the wiring member can be used as a lead welding area for mounting wiring, necessary functions can be secured with a minimum area and lightest wiring member as a sealed battery.

Further, a sealed battery provided with an aluminum or aluminum alloy outer can to which the wiring material has been joined by these weldings can be lightweight and small and can have high reliability.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a sealed battery according to the present invention, for example, a rectangular sealed lithium ion secondary battery.

FIG. 2 is a perspective view of a wiring member.

FIG. 3 is a schematic view of resistance welding.

FIG. 4 is a graph of applied voltage of resistance welding.

FIG. 5 is an explanatory sectional view of a welded portion by resistance welding.

FIG. 6 is a schematic diagram of a strength test of a resistance weld.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exterior can, 13 ... Wiring material, 14 ... Aluminum plate, 1
5 ... Nickel plate

Continuation of the front page (72) Inventor Masahiro Kato 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo F-term in AT Battery Co., Ltd. 5H022 AA02 AA04 AA09 CC10 EE03 EE04 5H040 AA03 AA22 AS22 AT02 DD07 JJ03 LL01

Claims (5)

[Claims] 1. A method for bonding a wiring member for a battery, wherein the wiring member is bonded to an outer surface of an aluminum outer can or a lid forming a sealed battery, wherein the wiring member has an aluminum plate and a melting point higher than that of the aluminum plate. And, the plate thickness is formed using a thin metal plate clad material, the aluminum plate side is placed on the outer can or the lid, and only the outer can and the aluminum plate are fused by resistance welding. A method for joining battery wiring members, characterized by welding. 2. The method according to claim 1, wherein the thin metal plate is made of nickel or a nickel-based alloy. Wherein the thickness d ₁ and its specific resistance p ₁ of the outer _can, the thickness d ₂ and the resistivity p ₂ of the aluminum _plate, the relationship between the thickness d ₃ and the resistivity p ₃ of the metal plate, d _{2. The method according to claim 1, wherein 1} / p ₁ > d ₂ / p ₂ + d ₃ / p _{3. 3} . 4. A sealed battery in which a wiring material is joined to an outer surface of an outer can or a lid, wherein the wiring material is an aluminum plate and a clad material of a metal plate having a higher melting point and a smaller thickness than the aluminum plate. A sealed battery formed, wherein the aluminum plate side is placed on the outer can or the lid, and the joined outer can and the aluminum plate alone are welded by resistance welding so as to fuse together. 5. The sealed battery according to claim 4, wherein the thin metal plate is a nickel plate.