JP2007035650A - Welding method of battery container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding method of a battery container having larger welding intensity to a lead material even with low welding current and having less variations when a lead material is welded by a parallel type resistance welding method. <P>SOLUTION: In the welding method of a battery container, a lead material arranged on a surface of a plating layer of a battery container with a coating layer made of an Ni base alloy formed on a part or a whole of an outside surface, the lead material is pressed with a welding pressure of 22N by two welding electrodes, a parallel type resistance welding is proceeded by a welding current of 1.2kA to 1.6kA, and the lead material is welded to the battery container with a welding intensity of 53.5 to 75.3N. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery container welding method, and more particularly to a battery container welding method that exhibits high welding strength with a lead material when the lead material is resistance-welded.

  Along with the widespread use of various electric and electronic devices, there are increasing cases in which a plurality of batteries as drive sources are packaged and directly incorporated into the device. In that case, in order to charge or discharge the battery, it is necessary to electrically connect each battery or between the package terminal and the battery with a lead material. That is, it is necessary to fix the lead material to the outer surface of the battery, for example, a partial surface of the battery container such as a lid part or a bottom part.

The same situation is required for a battery pack in which one battery is packaged together with a charge / discharge control circuit.
Conventionally, a parallel resistance welding method as shown in FIG. 3 has been widely used to connect the battery container and the lead material. This method will be described below.
In FIG. 3, a lead material 2 is disposed on the surface 1 a of the positive electrode terminal of the battery container 1, and two welding electrodes 4 a and 4 b connected to the power source 3 are predetermined on the surface 2 a of the lead material 2. Are arranged in a parallel state with an interval of. Then, a predetermined pressure is applied to the welding electrodes 4a and 4b and the tip thereof is pressed against the surface 2a of the lead material 2, whereby the back surface 2b of the lead material 2 is pressed against the surface 1a of the positive electrode terminal.

  In this state, a predetermined value of current is supplied from the power source 3. For example, the current is input to the lead material 2 from one welding current 4a, a part of which is returned to the power source from the other welding electrode 4b through the lead material, and the rest is the lead material 2 positioned immediately below the welding electrode 4a. It flows to the surface 1a side of the positive electrode terminal through the vicinity of the positive electrode terminal, and then returns to the power source from the welding electrode 4b through the lead material from the vicinity of the lead material 2 located immediately below the other welding electrode 4b.

In this process, Joule heat is generated at the contact interface between the back surface 2b of the lead material located near the welding electrode and the surface 1a of the positive terminal, and both members near the contact interface melt to form a nugget. Both members are spot welded.
By the way, the surface of the lead material and the surface of the positive electrode terminal are both smooth surfaces when viewed macroscopically, but are complex uneven surfaces when viewed microscopically. Therefore, even if the lead material is arranged on the surface of the positive electrode terminal, the two are not in a uniform contact state. It is in contact with the surface. Then, a current is passed through the minute contact portion, Joule heat is generated at the portion, and nugget formation proceeds.

At this time, the influence on the contact state based on the minute deformation of the lead material 2 and the like due to the pressing and pressing of the welding electrodes 4a and 4b to the lead material 2 is added, and the welding behavior is further complicated.
In such a resistance welding method, in order to increase the welding strength between the battery container and the lead material and reduce the strength variation to make the spot welded portion stable, basically two welding A stable nugget may be formed by increasing the Joule heat generated immediately below the electrode.

In that case, the generated Joule heat is the magnitude of the current value from the power source, the specific resistance of the battery container and the lead material, the energization time, and the pressure applied to the lead material by the welding electrode, that is, the back surface of the lead material and the battery container Stipulated by the state of close contact with each other.
By the way, as a battery container, generally, a mild steel plate is plastically processed into a predetermined can shape, and for the purpose of rust prevention, the surface thereof is covered with, for example, a Ni plating layer having a desired thickness. The same applies to the lid member. Furthermore, as the lead material to be resistance-welded, a material obtained by applying Ni plating to a mild steel plate as in the case of a battery container is often used.

However, in the case of the materials described above, there is a problem that when both are resistance-welded, the welding strength between the two is not necessarily increased, and the variation in strength increases. In particular, this tendency becomes large in the case of the bottom portion where the welding width becomes wide.
Therefore, for example, the current value to be energized is set high, or the energized Joule heat is increased by increasing the energization time. It may be fused with the surface, making it impossible to set up a smooth welding process. Furthermore, due to excessive heat generation, the surface of the positive electrode terminal and the melt dust of the metal material constituting the lead material may be generated, and the welding strength may be reduced.

  The present invention solves the above-mentioned problems when the battery container and the lead material are welded by the parallel resistance welding method, and is a low current value that does not easily cause fusion and does not generate melt dust. Even if it exists, it aims at provision of the welding method of a battery container which weld strength becomes high and also the dispersion | variation becomes small.

  In order to achieve the above object, in the present invention, a lead material is arranged on the surface of the plating layer of the battery container in which a plating layer made of a Ni-based alloy is formed on a part or all of the outer surface. The lead material is pressed with two welding electrodes at a pressure of 22 N, and parallel resistance welding is performed at a welding current of 1.2 kA to 1.6 kA. The lead material is welded at a welding strength of 53.5 to 75.3 N. A battery container welding method is provided, wherein the battery container is welded to the battery container. In particular, there is provided a battery container welding method in which the Ni-based alloy of the plating layer is a Ni—Fe alloy having an Fe content of 50 atomic% or less, and the plating layer has a thickness of 5 μm at most. .

  As is clear from the above description, the surface of the battery container of the present invention is coated with a Ni-based alloy having a large specific resistance, preferably a Ni-Fe alloy. When welding, even with a lower welding current than before, the welding strength between the battery container and the lead material is increased, and the variation is reduced, and the industrial value is great.

  FIG. 1 shows an example of the battery container of the present invention. FIG. 1 is a partially cutaway cross-sectional view of a lid 1 that also serves as a positive electrode terminal constituting a battery container. The lid 1 is formed by, for example, plastically processing a base material 1b made of a mild steel plate into a shape as shown in FIG. 1 and covering the surface with a plating layer 1c made of a Ni-based alloy described later.

The plating layer 1c may be formed so as to cover the entire surface of the base material 1b, but may be formed so as to partially cover at least a portion where a lead material which is a counterpart material is welded.
In addition, although the lid | cover was illustrated as a battery container in FIG. 1, the battery container in this invention is not limited to a lid | cover, It is the other party material of the said lid | cover, and is a battery can which accommodates an electric power generation element and electrolyte solution inside. There may be.

The plating layer 1c is, for example, a Ni—Fe alloy, but may be composed of any one of Ni-based alloys such as a Ni—Co alloy, a Ni—Zn alloy, and a Ni—Fe—Co alloy. The surface of the lid 1 is formed by electroplating.
Each of the above-described Ni-based alloys formed by electroplating is composed of a single phase in which other elements such as Fe, Co, Zn, etc. are dissolved in a Ni crystal lattice, or a combination of a plurality of phases. In general, the specific resistance is larger than that of Ni alone or other elements alone. When the parallel resistance welding method described above is applied to the battery capacity having these Ni-based alloy plating layers, it is possible to form a stable nugget even when a current smaller than that of a conventional one is passed, and to improve the welding strength. One possible reason for this is the high electrical resistance of the Ni-based alloy plating layer.

In particular, the Ni—Fe alloy is effective in that the welding strength can be increased even with a small current.
In that case, if the Fe content is too high, the surface of the battery container tends to rust when exposed to a high temperature and high humidity environment, so the content is 50 atomic% or less, preferably 45. It is preferable to regulate so as to be at most atomic%.

Such regulation of the Fe content can be easily achieved, for example, by adjusting the concentration of the Fe source in the plating bath used in electroplating.
In the case of a Ni—Co alloy, the Co content is preferably regulated to 5 to 50 atomic%, and in the case of a Ni—Zn alloy, the Zn content is preferably regulated to 5 to 30 atomic%. Furthermore, in the case of a Ni-Fe-Co alloy, it is preferable to regulate to more than Fe: 0 to 50 atomic% and Co: 5 to 50 atomic%. However, the sum of atomic percent of Fe and Co is 50 atomic percent or less.

The thickness of the plating layer 1c is preferably 5 μm or less. When the thickness is thicker than 5 μm, the variation in welding strength with the lead material tends to increase.
In addition, when the plating layer 1c consists of a Ni-Fe alloy, it is more preferable to regulate the thickness to 4.5 micrometers or less. The reason is not clear, but if the plating thickness is thicker than 4.5 μm, a large variation is observed in the welding strength with the lead material.

  The thickness of the plating layer 1c can be easily adjusted by a method such as adjusting the time for performing electroplating or the current density.

Examples 1-6
A battery can and lid for AA size batteries were prepared. These materials are all mild steel plates.
A plating bath for a Ni-Fe alloy composed of ferrous chloride, nickel chloride, and calcium chloride was constructed. At this time, various plating baths having different Fe concentrations, such as ferrous chloride concentration: 210-380 g / L, nickel chloride concentration: 30-80 g / L, calcium chloride concentration: 150-180 g / L were prepared. If necessary, thiourea was added at a concentration of 1 g / L or less.

Using these plating baths, the above-described battery can and the lid were electroplated to form Ni-Fe alloy plating layers having different Fe contents on the surfaces of the battery can and the lid. As plating conditions, suitable conditions are selected within the range of pH 0.9 to 1.5, bath temperature 60 to 90 ° C., current density 3 to 5 / dm ² , and the plating time is 3 μm in thickness of the plating layer. It set so that it might become.
The plating bath and plating conditions are not limited to those described above. For example, a sulfate bath, a sulfate-chloride bath, a citric acid bath, a pyrophosphate bath, and the like can be selected.

An AA size nickel metal hydride secondary battery was assembled using the obtained battery can and lid, and the lead material made of Ni-plated mild steel sheet with a thickness of 0.15 mm and a width of 5 mm is shown in Table 1 on the bottom surface of the battery. Welded by applying parallel resistance welding method under different conditions. Note that the pressure applied to the lead material by the welding electrode was 22 N in all cases.
However, the value of the applied pressure is the sum of the forces applied to the two welding electrodes, and the forces applied to the respective welding electrodes are set to be substantially equal.

  Subsequently, a welding strength measurement test was performed as shown in FIG. That is, this is a test in which one end 2 c of the lead material 2 welded to the bottom surface of the battery 5 is held by the chuck 6, and the chuck 6 is pulled up by the tensile tester 7 to peel off the lead material 2. At this time, the lead material 2 is pulled up approximately in the direction of the central axis of the battery can, and the tester 7 pulls the chuck 6 so that the strength of the chuck 6 increases at a substantially constant speed. The tensile strength when the material 2 was completely peeled off from the bottom surface of the battery 5 was taken as the welding strength. The results are collectively shown in Table 1 as an average value of 30 battery containers.

From Table 1, the following is clear.
(1) In each of the examples and comparative examples, the welding strength increases as the welding current increases.
(2) When the welding conditions at the time of resistance welding are the same, the welding strength between the battery container whose surface is coated with the plating layer of the present invention and the lead material is a battery made of only a conventional Ni-plated mild steel sheet. It is larger than the welding strength between the container and the lead material.
This means that when the battery container of the present invention is used when obtaining an equivalent welding strength, the welding current can be reduced as compared with the conventional case.

  (3) In addition, in the Ni-Fe alloy constituting the plating layer, the welding strength increases as the Fe content increases, but conversely, if the Fe content increases excessively, the welding strength increases. A decline is happening. For this reason, when the plating layer is made of a Ni—Fe alloy, the Fe content is preferably 50 atomic% or less, more preferably about 10 to 45 atomic%, including rusting problems.

Examples 7-11
Using a plating bath whose bath composition was adjusted so that the Fe content in the plating layer was 20 atomic%, a plating layer having a plating thickness as shown in Table 2 was formed on the battery container by changing the plating time. Next, 30 batteries were assembled using each battery container, the lead material described above was placed on the bottom surface, and a welding current of 1.5 kA was applied while applying a pressure of 22 N with the welding electrode, and both were connected. Resistance welded.

Here, the value of the applied pressure is the sum of the forces applied to the two welding electrodes, and the forces applied to the respective welding electrodes at that time are set to be substantially equal.
And welding strength was measured by the same specification as the case of Examples 1-6. Table 2 shows the maximum value, the minimum value, and the average value of 30 weld strengths.

  As apparent from Table 2, when the thickness of the plating layer is thicker than 5 μm, not only does the tendency of the welding strength decrease, but also the variation in the welding strength increases. For this reason, the thickness of the plating layer is preferably 5 μm or less. In particular, when the thickness is about 3 μm, the welding strength is large and the variation is very small, which is preferable in terms of realizing stable quality control.

Example 12
The surface of the mild steel plate was covered with a 2.0 μm thick Ni plating layer made of a Ni-25% Fe alloy to form a 0.3 mm thick plated steel plate, which was plastic processed to obtain a battery lid.
A soft steel lead material having a thickness of 0.3 mm on which a Ni-plating layer having a thickness of 2.0 μm is formed is placed on the surface of 100 lids and pressed with a pressure of 22 N. The welding current shown in Table 3 Resistance welding was performed for about 5 ms.

Here, the value of the applied pressure has the same meaning as in Examples 1 to 6 and Examples 7 to 11.
Subsequently, the welding strength was measured in the same manner as in Examples 1-11. The results are shown in Table 3. In addition, when the lead material was peeled off, the number of cases where two nuggets remained on the lid was measured and is also shown in Table 3. The larger the number, the more stable the nugget is formed during resistance welding.

  For comparison, the same resistance welding was performed when a lid having a Ni plating layer having the same thickness was used instead of the Ni-25% Fe alloy plating layer, and the results are also shown in Table 3.

As is apparent from Table 3, in the case of resistance welding to a lid (comparative example) that is not plated with a Ni-25% Fe alloy, only two nuggets remain when the welding current is 1.6 kA. Is recognized. On the other hand, in the case of the lid of the present invention, even when the welding current is 1.2 kA, two nuggets are reliably generated, and the welding strength is also compared with a comparative example with a welding current of 1.6 kA. It is equivalent to.
That is, the lid of the present invention enables high welding strength even with a small welding current.

It is a partially cutaway sectional view showing an example of a battery container of the present invention. It is the schematic for demonstrating the measuring method of welding strength. It is the schematic for demonstrating a parallel type resistance welding method.

Explanation of symbols

1 Battery container (lid that also serves as a positive terminal)
DESCRIPTION OF SYMBOLS 1a The surface of the battery container 1 1b Base material 1c Plating layer 2 Lead material 2a The surface of the lead material 2b The back surface of the lead material 2 3 Power supply 4a, 4b Welding electrode 5 Battery 6 Chuck 7 Tensile tester

Claims (5)

  A lead material is arranged on the surface of the plating layer of the battery container in which a plating layer made of a Ni-based alloy is formed on a part or all of the outer surface, and the lead material is applied with a pressure of 22 N by two welding electrodes. The battery container is characterized in that the lead material is welded to the battery container at a welding strength of 53.5 to 75.3 N by performing parallel resistance welding at a welding current of 1.2 kA to 1.6 kA. Welding method.   The battery container welding method according to claim 1, wherein the Ni-based alloy is any one of a Ni—Fe alloy, a Ni—Co alloy, a Ni—Zn alloy, and a Ni—Fe—Co alloy.   The battery container welding method according to claim 2, wherein the Ni-based alloy is a Ni—Fe alloy having an Fe content of 50 atomic% or less.   The battery container welding method according to claim 1, wherein the plating layer has a thickness of 5 μm at most.   The battery container welding method according to claim 3, wherein the plating layer has a thickness of 4.5 μm at most.

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