JP2004106059A - Aluminum-nickel clad member, manufacturing method thereof, and external terminal for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an external terminal for battery which exhibits stable weldability even when ultrasonic welding is applied, and less prone to cause defective shapes even when bending is performed, an aluminum-nickel clad member suitable for the external terminal, and a manufacturing method thereof. <P>SOLUTION: In the aluminum/nickel clad member, an aluminum layer 3 formed of pure aluminum and a nickel layer 2 formed of pure nickel are diffusion-bonded to each other so that the hardness of the nickel layer 2 amounts to Hv130 to 170. Excellent peeling strength is obtained in this clad member by performing the diffusion-bonding of the aluminum layer and the nickel layer to each other via an Al-Ni intermetallic compound layer of the thickness of 0.4 to 1.0 μm, preferably, 1.0 to 6.0 μm. <P>COPYRIGHT: (C)2004,JPO

Description

(4) The present invention relates to an external terminal joined to a battery outer can and an aluminum / nickel clad material that can be suitably used as a material for the external terminal.

小 Small electronic and electrical devices such as mobile phones and notebook computers are equipped with small batteries. Some of such small batteries have an outer can made of pure aluminum. Electricity generated by the battery is supplied to various electronic components via an external terminal attached to the pure aluminum outer can and a conductive member joined thereto. The conductive member is usually formed of pure nickel having excellent corrosion resistance and durability.

(4) The external terminal has a rectangular shape with a width of about 3 mm and a length of about 20 mm. For example, as described in JP-A-2001-6746, the external terminal is formed of pure aluminum in consideration of bondability with a pure aluminum outer can and a pure nickel conductive member. Some are formed of an aluminum / nickel clad material in which an aluminum layer and a nickel layer formed of pure nickel are joined.

Conventionally, this aluminum / nickel clad material is obtained by superimposing a nickel sheet formed of pure nickel and an aluminum sheet formed of pure aluminum, passing the superimposed sheet through a pair of rolls, and cold-pressing the laminated sheet. The press-bonded sheet is manufactured by performing diffusion annealing on the aluminum layer and the nickel layer by diffusion bonding. The rolling reduction in the cold pressure welding is set to about 60% or more so that the two sheets can be joined to such a degree that they are not separated in a later step. Further, it is considered that the diffusion annealing at a high temperature generates a fragile Al-Ni-based intermetallic compound at the interface between the aluminum layer and the nickel layer, thereby deteriorating the peel strength between the aluminum layer and the nickel layer. For this reason, the diffusion annealing is usually performed by holding at a low annealing temperature of about 400 ° C. or less for a short time so that the intermetallic compound is not generated. The battery external terminal is usually formed by slitting the aluminum / nickel clad material into a strip having the same width as the required external terminal width along the length direction, and further shearing the obtained strip to a required length. Manufactured by

(4) Conventionally, the external terminal has been joined to a battery outer can by spot welding (resistance welding). At the spot weld, aluminum and nickel of the clad material are melted and solidified to form an intermetallic compound, so that the electrical resistance increases at the weld and the efficiency of the battery decreases. For this reason, in recent years, the external terminals have been joined by ultrasonic welding. In the ultrasonic welding, since the aluminum layer is brought into pressure contact with the battery outer can without melting the welded portion, no intermetallic compound is generated, and a decrease in battery efficiency can be prevented.

However, when ultrasonic welding is performed using an external terminal for a battery manufactured using a conventional aluminum / nickel clad material joined by cold pressure welding, there is a problem that the joining strength varies greatly and the joining property is unstable. .

In recent years, external terminals having various bent shapes such as a Z-shape have been required. When the external terminal having such a form is formed of a conventional clad material, there is a problem that large springback is likely to occur during bending, and a shape defect is likely to occur.

The present invention has been made in view of such a problem, and a stable weld joint property is obtained even when ultrasonic welding is applied, and a shape defect hardly occurs even when subjected to bending, as a battery external terminal, and as a material thereof. An object is to provide a suitable aluminum / nickel clad material and a method for manufacturing the same.

The inventor of the present invention has found that when ultrasonic welding is performed using an external terminal for a battery made of a conventional aluminum / nickel clad material, the bondability becomes unstable. As a result of intensive investigation on the cause of the susceptibility, it was found that the cause was that the nickel layer of the aluminum / nickel clad material was too hard. Conventionally, it has been considered that when an Al-Ni-based intermetallic compound is formed at the interface between an aluminum layer and a nickel layer during diffusion annealing, the peel strength between the aluminum layer and the nickel layer is deteriorated. It has been found that the peel strength is rather improved in a region where the thickness of the Ni-based intermetallic compound layer is particularly small. The present invention has been made based on such findings.
That is, in the aluminum / nickel clad material of the present invention, an aluminum layer formed of pure aluminum having an aluminum purity of 98 mass% or more and a nickel layer formed of pure nickel having a nickel purity of 98 mass% or more are diffusion bonded. And the hardness of the nickel layer is Hv130 to 170. The thickness of the aluminum layer is preferably 25 to 100 μm, and the thickness of the nickel layer is preferably 50 to 200 μm.

According to this aluminum / nickel clad material, the hardness of the nickel layer is Hv130 to 170, and the nickel layer is not excessively hard, so that ultrasonic vibration is generated at the ultrasonic vibration output end (the tip of the horn) during ultrasonic welding. , Is quickly transmitted to the aluminum layer via the nickel layer, so that stable weldability can be obtained. Also, since there is no excessive springback, good moldability can be obtained. On the other hand, since the nickel layer is not excessively soft, projections (burrs) are less likely to occur on the shearing edge of the processed piece when the processed piece such as the battery external terminal or its material is obtained by shearing the clad material. If there is a burr, the work piece does not adhere to the material to be welded, making it difficult to transmit ultrasonic vibration. In the clad material, since burrs are not easily generated on the work piece, ultrasonic vibration is quickly transmitted, and good ultrasonic weldability is obtained.

In the aluminum / nickel clad material, the aluminum layer and the nickel layer are diffusion-annealed through an Al-Ni intermetallic compound layer having a thickness of 0.4 to 10.0 μm, preferably 1.0 to 6.0 μm. It is desirable to be done. Although the Al-Ni-based intermetallic compound itself is brittle, the brittleness does not appear in the region near the boundary between the nickel layer or aluminum layer and the intermetallic compound layer. Bond well. When the thickness of the intermetallic compound layer is about 0.4 to 10.0 μm, the brittleness of the intermetallic compound layer itself hardly appears, so that the bondability between the aluminum layer and the nickel layer is relatively good. Further, by setting the thickness of the intermetallic compound layer to 1.0 to 6.0 μm, particularly excellent bonding properties can be obtained. For this reason, even if severe processing is performed on the clad material or its processed piece, the aluminum layer and the nickel layer are hardly peeled off, and excellent forming workability is obtained.

The aluminum / nickel clad material is suitable as a material for an external terminal for a battery, and the aluminum / nickel clad material can be easily manufactured by subjecting the aluminum / nickel clad material to shearing such as cutting or punching with a shear. it can.

The aluminum / nickel clad material heats a nickel sheet formed of pure nickel having a nickel purity of 98 mass% or more to 100 to 300 ° C., and heats the heated nickel sheet and pure aluminum having a purity of aluminum of 98 mass% or more. After the formed aluminum sheet is overlapped and pressed with a reduction rate of 10 to 17%, the obtained pressed sheet can be easily manufactured by diffusion annealing. The diffusion annealing is preferably performed in a temperature range of 500 to 600 ° C.

According to the aluminum / nickel clad material of the present invention, since the hardness of the nickel layer is adjusted to Hv130 to 170, stable weldability can be obtained at the time of ultrasonic welding, and excessive springback occurs. It is suppressed and has excellent bending workability. For this reason, it is suitable as a material for external terminals for batteries and the like. Further, according to the manufacturing method of the present invention, an aluminum / nickel clad material having a nickel layer having a predetermined hardness can be easily manufactured without requiring special equipment.

As shown in FIG. 1, the aluminum / nickel clad material 1 of the present invention has an aluminum layer 3 and a nickel layer 2 pressed and diffusion bonded, and the hardness of the nickel layer 2 after diffusion annealing is as follows. Hv 130 to 170.

ア ル ミ ニ ウ ム The aluminum layer 3 and the nickel layer 2 are made of pure aluminum and pure nickel, respectively. Although the purity of aluminum and nickel is preferably as high as possible, impurities of up to about 2 mass% are allowed in the present invention, and the purity of aluminum and nickel is 98 mass% or more, preferably 99 mass% or more, more preferably 99.9 mass% or more. Preferably, it is used.

硬度 The hardness of the nickel layer 2 is important in the present invention, and is set to Hv130 to 170 in Vickers hardness. The hardness of the nickel layer 2 has a great effect on ultrasonic weldability, formability and the like. When the hardness exceeds Hv 170, the shape defect due to springback tends to be excessive during molding, and the ultrasonic wave during ultrasonic welding. Is difficult to transmit from the nickel layer 2 to the aluminum layer 3, the welding between the aluminum layer 3 and the battery outer can becomes unstable, and stable weldability cannot be obtained. On the other hand, if it is less than Hv130, the strength is reduced, and large burrs are generated at the end of the cut surface when shearing a slit or the like. When burrs occur on the outer peripheral edge of the external terminal, a gap is generated between the battery outer can and the ultrasonic vibration output end of the ultrasonic welding device, and it is difficult to adhere, so that ultrasonic vibration is difficult to transmit, This may cause poor welding. Therefore, in the present invention, the hardness of the nickel layer 2 is set to Hv130 to 170, preferably Hv140 to 160.

The aluminum layer and the nickel layer are diffusion-bonded by diffusion annealing. With this diffusion bonding, an Al-Ni intermetallic compound may be generated at the bonding interface. Since the Al-Ni intermetallic compound itself is fragile, it has been considered that the peel strength between the aluminum layer and the nickel layer is reduced. However, it was found that the bonding strength did not decrease in a region where the thickness of the Al-Ni-based intermetallic compound layer formed at the interface between the aluminum layer and the nickel layer was extremely small, but rather improved in some cases. When the thickness of the intermetallic compound layer is about 0.4 to 10.0 μm, the peel strength is practically sufficient. In particular, by setting the thickness of the intermetallic compound layer to about 1.0 to 6.0 μm, the peel strength becomes extremely high, as will be apparent from the examples described later, and it is sufficiently applicable to severe molding. Will be able to

ア ル ミ ニ ウ ム The thickness of the aluminum layer 3 is preferably 25 to 100 µm. If the aluminum layer 3 is too thin, it will be difficult to press the nickel layer 2 in the manufacturing process, while if it is too thick, it will be difficult to ultrasonically weld to the battery outer can. Therefore, the thickness is preferably 25 to 100 μm, and more preferably about 30 to 70 μm. The thickness of the nickel layer 2 is preferably 50 μm or more in order to ensure ultrasonic weldability and durability, but if it is too thick, it will only increase the cost, so it is 200 μm or less, preferably 150 μm or less. Good.

Next, a method for manufacturing the aluminum / nickel clad material of the present invention will be described.
The aluminum / nickel clad material prepares an aluminum sheet formed of pure aluminum and a nickel sheet formed of pure nickel, heats the nickel sheet to 100 to 300 ° C., and heats the heated nickel sheet with the aluminum sheet. It is manufactured by superimposing and pressing rolls at a rolling reduction of 10 to 17% through a gap between a pair of rolls, and diffusion-annealing a press-bonded sheet obtained by joining the aluminum layer and the nickel layer. The rolling reduction (%) is calculated by (thickness reduced by rolling) / (original total thickness) × 100.

加熱 By heating the nickel sheet to 100 to 300 ° C., it is possible to obtain a pressure contact sheet having a sufficient bonding strength of about 2 N / mm or more even under a low pressure of 10 to 17%. When the heating temperature of the nickel sheet is lower than 100 ° C., the bonding strength with the aluminum sheet is insufficient even when the roll is pressed at a rolling reduction of 17%, and the nickel sheet may be peeled off in a process after the pressing. On the other hand, if the temperature is higher than 300 ° C., lubrication of the roll at the time of pressure welding becomes severe, and poor lubrication occurs, making pressure welding difficult. For this reason, the heating temperature of the nickel sheet is set to 100 to 300 ° C, preferably 150 to 250 ° C. After the nickel sheet is heated to a predetermined temperature, it is desirable to press the roll with the aluminum sheet as quickly as possible, and it is recommended to press the nickel sheet with the aluminum sheet within 5 seconds, preferably within 3 seconds after the heating.

On the other hand, the aluminum sheet does not need to be heated in principle and can be kept at room temperature. Even when heating, it is preferable to keep the temperature at 200 ° C. or less. Since a low rolling reduction is adopted as the rolling reduction in the roll pressing, the thickness of the aluminum sheet before the rolling is necessarily reduced. For example, when the thickness of the aluminum layer of the clad material is 25 to 100 μm, the thickness of the aluminum sheet is 28 to 111 μm. When the aluminum sheet having a thickness of about 25 to 120 μm is roll-welded, if the aluminum sheet is heated to more than 200 ° C., the strength of the sheet is reduced by heating. It becomes impossible to withstand the applied tension, causing problems such as partial elongation and breakage in severe cases.

圧 The rolling reduction in the roll pressing must be in a very narrow range of 10 to 17% as described above. If it is less than 5%, even when the nickel is heated to 300 ° C., the bonding strength between the aluminum sheet and the nickel sheet will be about 2 N / mm or less, and sufficient bonding strength will not be obtained, possibly causing peeling. Further, if it is 5% or more and less than 10%, burrs are increased, and ultrasonic weldability is reduced. On the other hand, when the nickel sheet is reduced by more than 17%, the hardness after the reduction exceeds Hv170 even when the nickel sheet is heated to 300 ° C., which causes problems in the formability and ultrasonic weldability. Therefore, the rolling reduction is set to 10 to 17%, preferably 11 to 15%.

(4) The pressure-bonded sheet bonded by roll pressure bonding becomes a clad material by diffusion bonding of the aluminum layer and the nickel layer by diffusion annealing. Although the peel strength between the aluminum layer and the nickel layer in the clad material varies depending on the diffusion annealing conditions, the peel strength of the clad material may be practically about 4.0 N / mm or more. In particular, when severe processing is performed on the clad material, it is preferable to have a sufficient peel strength of about 8.0 N / mm or more, more preferably about 10.0 N / mm or more. In order to select a sufficient peel strength in a relatively short time, it is preferable to perform diffusion annealing at a temperature of 500 to 600 ° C. Diffusion annealing can be performed even at 400 to 450 ° C., but in order to obtain a sufficient peel strength, an annealing time of 1 hr or more is required, and productivity is significantly reduced. On the other hand, sufficient peeling strength can be obtained in a relatively short time of about 3 to 20 minutes in annealing at 500 ° C and about 1 to 5 minutes at 600 ° C. The hardness of the nickel layer tends to slightly decrease due to the diffusion annealing, but the degree increases as the annealing temperature increases and the annealing time increases.

接合 The bonding strength of the press-contact sheet and the peel strength of the same sheet (clad sheet) after diffusion annealing are measured in the following manner. As shown in FIG. 2, the aluminum layer 13 and the nickel layer 12 were partially peeled off at the end of the test piece 11 taken from the press-contact sheet, the peeled portion was bent vertically, and the end was pulled by a tensile tester. Then, the peeling force required for peeling is determined. The value is divided by the width of the test piece to determine the peeling force per unit width as the bonding strength. In the clad sheet in which the aluminum layer and the nickel layer are diffusion-bonded by diffusion annealing, since it is difficult to peel off each layer at the end of the test piece, before the diffusion annealing, peel off the end of the press-contact sheet in advance. After the diffusion annealing, the peeled-off portion that has been peeled off in advance is vertically bent, and the peeling force per unit width is obtained in the same manner as above, and this is defined as the peeling strength.

The aluminum / nickel clad material manufactured as described above is slit into a strip having an appropriate width, for example, the same width as the width of the external terminal. The external terminal is manufactured by shearing a strip slit to a terminal width to a required external terminal length, or by punching a strip slit to a width wider than the terminal width. Further, the flat plate-like processed piece thus processed is subjected to a forming process such as a bending process as required, and is processed into a desired shape.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not construed as being limited to such Examples.

Various samples of the clad material were manufactured in the following manner.
A nickel sheet having a width of 60 mm and a thickness of 50 μm of pure nickel (nickel purity of 99.9% or more) and an aluminum sheet of the same width and a thickness of 50 μm of pure aluminum (aluminum purity of 99.9% or more) were prepared. After heating the nickel sheet in a tunnel furnace, the sheet was overlapped with the aluminum sheet within about 2 seconds after exiting the tunnel furnace, and passed through a pair of reduction rolls to be pressed. Table 1 shows the heating temperature of the nickel sheet of each sample and the rolling reduction during roll pressing.

試 験 A test piece having a width of 10 mm and a length of 100 mm was sampled from a pressure-welded sheet in which the aluminum layer and the nickel layer were pressed by roll pressing, and the bonding strength between the aluminum layer and the nickel layer was measured according to the measurement procedure described above. The bonding strength needs to be about 2 N / mm or more in order to process the subsequent steps without any problem.

Next, the press-bonded sheet was subjected to diffusion annealing under the annealing conditions shown in the same table to obtain a clad material in which an aluminum layer and a nickel layer were diffusion-bonded. The peel strength of the clad material and the hardness of the nickel layer were measured. The peel strength was measured using a test piece having a width of 10 mm and a length of 100 mm according to the above-described measurement procedure, and the hardness was measured with a Vickers hardness meter by applying a load of 0.2 kgf (1.96 N).

断面 Further, a cross-section observation test piece was collected from the clad material, and the average thickness of the Al-Ni-based intermetallic compound layer formed between the aluminum layer and the nickel layer of the clad material was measured in the following manner. The cross-section observation test piece is embedded in a synthetic resin so that a cross section along the plate thickness direction (plate thickness cross section) is set as an observation surface, and the embedded test piece is polished so that the plate thickness cross section is exposed. The cross section was observed at 4,000 times with a scanning electron microscope. The measurement results are also shown in Table 1. The observed intermetallic compound layer was subjected to elemental analysis by EPMA, and it was confirmed that the layer was formed of an Al—Ni-based intermetallic compound.

(4) The clad material was supplied to a slitter so that the nickel layer was on the lower side, and cut to obtain a strip having a width of 3 mm. The slitter has a plurality of cutting portions including a pair of upper and lower rotary blades, and the rotary blades cut the clad material by rotating and approaching each other so as to cross each other. For this reason, burrs were formed at the lower end of the nickel layer on one cut surface of the cut strip, and burrs were formed at the upper end of the aluminum layer on the other cut surface. The height (μm) of burrs formed at the ends of the nickel layer and the aluminum layer was measured by a surface roughness meter. If the burr height exceeds 10 μm, the ultrasonic weldability will be adversely affected. Therefore, a burr height of 10 μm or less is considered acceptable.

The aluminum / nickel clad strip thus obtained was sheared to a length of 20 mm to obtain a welded test piece. The aluminum layer side surface of the welding test piece was brought into contact with a 0.5 mm pure aluminum plate (5 mm wide × 30 mm long), and the center in the width direction was ultrasonically welded. The welding conditions are as follows.
Ultrasonic welding machine: Ultrasonic Industry Co., Ltd., model USW-2410Z15S
Pressure: 200N
Application time: 0.3 seconds Peak power: 250 W
Energy: 63J
After the ultrasonic welding, the joining strength of the weld was measured. As shown in FIG. 3, the measurement procedure is such that the welded test piece 21 and the pure aluminum plate 22 after welding are each vertically bent in an L-shape at the end of the welded portion W, and the ends are pulled to separate the joint. Was measured as the joining force. Such measurement was performed at five points for each sample, and the difference ΔF between the maximum value and the minimum value of the bonding force was obtained. It is important that a stable welded joint is obtained at the joint. If ΔF exceeds 0.5 kgf (4.9 N), the joining stability of ultrasonic welding becomes a problem. Therefore, regarding ultrasonic weldability, ΔF ≦ 4.9N is accepted.

Also, a bending test piece S having a length of 50 mm was collected from the strip, and the stiffness tester (manufactured by PCA, Model 719) was used to open the 60 ° open angle so that springback could be easily observed. The bent specimen was bent into a V-shape having a bending radius of 0.38 mm), the opening angle θ ° of the V-shaped part of the processed test piece was measured, and the springback amount Δθ = θ−60 was obtained. When Δθ exceeds 20 °, the bending accuracy in which the angle between two adjacent sides is bent to 90 ° is significantly deteriorated when performing bending, so that Δθ ≦ 20 ° is acceptable for bending workability. . Table 1 also shows the results of these measurements.

１８０ In addition, a 180 ° bending test was performed using the bending test piece S in the following manner. As shown in FIG. 4, the test piece S was bent by 180 ° around the center in the longitudinal direction so that the aluminum layer was on the inside, and then folded back together. The state of occurrence of local peeling from the layer was visually observed. The observation results are shown in Table 1 together with AA where no local peeling occurred, A where slight local peeling occurred, and B where clear local peeling occurred.

From Table 1, the examples (sample Nos. 4 to 6, 10 to 13, 15 to 19, 21, 22) in which the hardness of the nickel layer is Hv 130 to 170 have good ultrasonic weldability and bending workability. I understand. On the other hand, Sample Nos. 1, 7, 8, and 23 in which the hardness of the nickel layer exceeds Hv 170 have problems in both ultrasonic weldability and bending workability. Further, since the rolling reduction is low, in Sample No. 3 in which the hardness of the nickel layer is Hv120, the burr height on the aluminum layer side exceeds 10 μm, and the weldability is reduced. For Samples Nos. 2 and 9, diffusion annealing should be performed because the peeling strength of the pressure contact sheet was too low because the rolling reduction or the heating temperature of the nickel sheet was inappropriate, and the nickel layer and the aluminum layer peeled off during handling. Could not be done. Sample No. 14 could not be pressed because the heating temperature of the nickel sheet was too high and poor lubrication occurred.

On the other hand, in Examples (Sample Nos. 4 to 6, 10 to 13, 15, 18, and 21) in which the average thickness of the Al—Ni intermetallic compound layer was 1.0 to 6.0 μm, the peeling after diffusion annealing was performed. Excellent diffusion bonding properties with a strength of 8 N / mm or more are obtained. Sample No. 17 having an average thickness of 0.4 μm and Sample No. 19 having a 9.8 μm thickness had a peeling strength of about 5 N / mm, which was slightly low, but local peeling was slight in a 180 ° bending test. It has molding processability that does not cause any practical problems. On the other hand, in Sample No. 16 in which the intermetallic compound layer was not formed and Sample No. 22 having an excessive thickness, although the ultrasonic weldability and bending workability were good, the peel strength was reduced. The degree of local peeling is large. For this reason, the clad materials of these samples are not very suitable for applications in which severe forming is performed. In sample No. 20, since the annealing time was too long at the annealing temperature of 550 ° C., the generation of the intermetallic compound was excessive, and the measurement of the peel strength was impossible. Sample No. 23 corresponds to a conventional clad material, and has a high rolling reduction at the time of pressure welding, so that good peel strength was obtained even at a diffusion annealing temperature of 350 ° C., but the hardness of the nickel layer was high. The deterioration of ultrasonic weldability and bending workability is remarkable.

It is a cross section of an aluminum / nickel clad material concerning the present invention. FIG. 4 is an explanatory view of a procedure for measuring the bonding strength of a press-contact sheet and the peel strength of a clad sheet after diffusion annealing. It is a bending test procedure explanatory drawing of an aluminum / nickel clad material test piece. It is a 180 degree bending test procedure explanatory drawing of an aluminum / nickel clad material test piece.

Explanation of reference numerals

1 Aluminum / nickel clad material 2 Nickel layer 3 Aluminum layer

Claims (8)

An aluminum / nickel clad material in which an aluminum layer formed of pure aluminum having an aluminum purity of 98 mass% or more and a nickel layer formed of pure nickel having a nickel purity of 98 mass% or more are diffusion-bonded,
An aluminum / nickel clad material in which the hardness of the nickel layer is Hv130 to 170. The aluminum / nickel clad material according to claim 1, wherein the aluminum layer and the nickel layer are diffusion-annealed through an Al-Ni-based intermetallic compound layer having a thickness of 0.4 to 10.0 µm. The aluminum / nickel clad material according to claim 1, wherein the aluminum layer and the nickel layer are diffusion-annealed via an Al-Ni-based intermetallic compound layer having a thickness of 1.0 to 6.0 µm. The aluminum / nickel clad material according to any one of claims 1 to 3, wherein the aluminum layer has a thickness of 25 to 100 µm. The aluminum / nickel clad material according to any one of claims 1 to 4, wherein the nickel layer has a thickness of 50 to 200 µm. A battery external terminal formed of the aluminum / nickel clad material according to any one of claims 1 to 5. A heating step of heating a nickel sheet made of pure nickel having a purity of 98 mass% or more to 100 to 300 ° C., and a heated nickel sheet and an aluminum sheet made of pure aluminum having a purity of 98 mass% or more. And a method of producing an aluminum / nickel clad material, comprising: a pressing step of obtaining a pressed sheet by pressing the sheets at a rolling reduction of 10 to 17%; and a diffusion annealing step of diffusing and annealing the pressed sheet. The method according to claim 7, wherein the diffusion annealing is performed in a temperature range of 500 to 600C.

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