JPH0810586B2 - Sealed battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nickel-plated steel battery container in which an open end of a nickel-plated steel battery container is fitted and a joint portion thereof is formed. The present invention relates to a sealed battery sealed by laser welding, and particularly to improvement of nickel plating thereof.

2. Description of the Related Art Batteries with excellent long-term reliability have been demanded due to transmission of electronic devices, and improvements have been made in battery sealing methods. Lithium batteries that require a high degree of airtightness, or
Instead of the conventional crimp-type sealing method for prismatic sealed alkaline batteries, there is a method in which a metallic lid is also fitted to the open end of a metallic battery container and the joints are welded and sealed. It is becoming established. As a welding method, in the case of a small sealed battery, a laser welding method capable of accurately welding a narrow width is often used. As a form of fitting the battery container and the lid in such a battery, as shown in the side sectional view of the main part of FIG. 4, the battery container 11 is in contact with the inner edge of the open end (see FIG. )), A cover 13 having a flat peripheral edge is fitted (FIG. 4 (B)), or Japanese Patent Publication No. 45-14217.
As disclosed in Japanese Laid-Open Patent Publication No. 61-119255 or Japanese Utility Model Laid-Open No. 61-119255, a battery container is used in which a rising portion provided on the peripheral edge of the lid is fitted in contact with the inner edge of the open end of the battery container. The lid was fitted and the joint was sealed by laser welding. In the case of small batteries, the latter method is generally used because of the accuracy of parts during mass production and the workability of assembly.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention With such a conventional configuration, when the battery container is sealed by laser welding, as disclosed in JP-A-57-74964 and the like, locally and instantaneously. Since it can be welded to the battery, it has very few thermal effects on the battery main body, and it has the advantage of being able to perform high-precision welding, but on the other hand, the laser beam has good straightness and the focal area is extremely small. Due to the influence of the shape, accuracy and material of the joint formed by the open end of the battery container, which is the welding surface, and the edge of the lid or the end face of the rising portion, incomplete welding results in a sufficiently sealed state. There was something I couldn't do. In laser welding, the material is a single metal such as iron, or JP-A-56-
As shown in Japanese Patent No. 107470, it is an iron-based alloy material such as stainless steel, and when welding between metal members of the same kind, there is no problem due to the freedom of material and easy welding, but the surface of the electronic container In order to prevent rusting and reduce the contact resistance inside and outside the battery, or when a material with good workability such as a prismatic battery container is required, form a steel material that has been used in conventional caulked sealed batteries. Then, it was necessary to use a battery container and a lid whose surface was nickel-plated. However, when the sealing method by laser welding is applied to the above structure, a minute crack of several tens of μm or less, which is considered to be caused by strain, is likely to be generated in the welded portion formed by welding the upper surface of the joint portion with laser light. There was a problem. The state of occurrence of this crack is slightly improved by improving the fitting shape and accuracy of the battery container and the lid, as described in the above-mentioned Japanese Unexamined Patent Publication No. 57-74964, etc. However, there is a problem in that leakage of the electrolytic solution and gas leakage are likely to occur when the battery is used because of insufficient sealing.

The present invention solves such problems, and by using the specified matte nickel electroplating as the plating layer applied to the battery container and the lid made of steel, fine cracks are generated in the welded portion. The purpose is to prevent.

Means for Solving the Problems In order to solve this problem, the present invention provides a battery container and a lid made of steel with a thickness of a plating layer of at least a welded portion of 2 to 10 μm, and It is used by applying a matte electric nickel plating with a Vickers hardness of Hv280 or less.

Action With this structure, the laser beam locally bonds the joint,
It is possible to suppress the distortion caused by the presence of the nickel plating layer when being instantly melted and cooled, and to form a weld portion in which no crack occurs.

Embodiment FIG. 1 and FIG. 2 are longitudinal sectional views showing a welded portion between a battery container and a lid of a sealed battery according to an embodiment of the present invention and a main portion of a battery side surface. 1 and 2, the battery fuser 1
And, the lid 3 having the rising portion 3a on the periphery is formed by forming a cold-rolled steel plate (JIS SPC steel plate) into a predetermined shape, and then applying matte electric nickel plating having the contents described below, and 1a, 3 respectively.
Battery container 1 using the nickel plated layer b
The nickel-cadmium-based or lithium-based power generating element 2 is housed in the battery case 1, and the terminal portion 8 is formed by fixing the terminal pin 8a to the lid 3 via the insulating ring 8b. Laser light from above the joining portion 4 which is fitted to the end and is formed by the upper end of the rising portion 3a of the lid 3 and the inner edge of the opening end of the battery container 1 by using a YAG laser device or the like as shown in FIG. 5, the upper portion of the joint 4 is welded and integrated, and a weld 6 is formed to seal the joint.

Next, the matte electric nickel plating layers 1a and 3b provided on the battery container 1 and the lid 3 described above will be described in detail.

For nickel plating applied to the present invention, a brightening agent such as a commonly used organic substance-based agent is not added, and a pH buffering agent, for example, a dull nickel plating solution consisting of boric acid and a relatively high concentration nickel salt solution is used, By controlling the electrolytic deposition conditions, the hardness of the plating layer is Hv280 or less in Vickers hardness, and matte electric nickel plating having a thickness of 2 to 10 μm is used. With the combination of the plated battery container 1 and lid 3, the welding speed was 1 to 20 mm / sec and the laser beam 5 was irradiated as shown in FIG. Was not seen. According to the findings obtained by the present inventors from the results of a comparative study of various nickel plating, the present invention has excellent weldability.
It is thought to be due to the following reasons. FIG. 3 is an enlarged view of a main part of FIG. 1 showing a welding state at the time of layer welding. In the drawing, 1 is an open end portion of a battery container, 3a is a rising portion of a lid 3, and a joint portion where both are in contact with each other. As you can see from the figure, there is usually a slight gap (about 0.05 to 0.2 mm) in 4, but
As described above, when the laser light 5 is irradiated from above the joining portion 4, the contact portions of the battery container 1 and the rising portions 3a of the lid 3 which are in contact with each other including the respective plating layers 1a and 3b are melted and integrated. It becomes (solid solution), and a welded portion is formed and sealed as shown in FIG. In laser welding, the laser light spots are welded linearly in a connected state, but during melting, the steel material of the vessel 1, the lid 3 and the plating layers 1a, 3b each undergo thermal expansion in response to a temperature rise. According to the coefficient, it expands in the direction that the gap of the joint becomes narrower as shown by the dotted arrow in the figure,
At the time of cooling, it contracts outward as shown by the solid arrow to generate tensile stress. The melted welded portion 6 is cooled from the outer periphery toward the central portion. However, since the vicinity of the portion indicated by the arrow C in the figure is cooled last in time, the portion of the welded portion 6 is also pulled in this portion as indicated by the arrow during cooling. Stress acts. Therefore, as a whole, the portion indicated by arrow C has a factor that causes a crack due to tensile stress immediately before cooling. As described above, in the case of an alloy such as stainless steel, the composition and the crystalline state are stable during melting and cooling, and practically withstand stress and do not cause cracks. ,
Nickel and its additives diffuse into the steel during melting. However, since the melting-cooling time is very short, the composition,
It is considered that the crystalline state becomes non-uniform, the internal strain increases, the strength decreases, and cracks easily occur. In a small battery, the plate thickness of the battery container 1 and the lid 3 shown in FIG. 3 is about 0.3 to 0.6 mm, the welding width W is 0.4 to 1 mm, and the welding depth d is about 0.1 to 0.3 mm. It is a thing. Therefore,
The thickness of the plating layers 1a and 3b and the physical properties thereof greatly affect when the weld 6 is cooled. According to the results of applying various nickel plating methods that have been commonly used in the past, it was found that cracks tend to occur when a plating layer with a large internal stress before welding is used. It has been found that the hardness is almost proportional to the hardness, and that the Vickers hardness of Hv 280 or less (the range of Hv is about 150 to 280) is effective in preventing the occurrence of cracks. However, the stability of the welded portion is still insufficient only by optimizing the hardness, and the welding depth d is comparatively shallow as described above.
It has been found that the thickness of the nickel plating layer affects when the weld is cooled. This is because there are some differences in the physical properties of steel and nickel, that is, the thermal expansion coefficient, melting point, heat of fusion, etc., and if the nickel plating layer is thick, the thermal strain of the joint becomes large, and the solid solution composition at the weld It is considered that an increase in internal strain due to an increase in non-uniformity of the cracks leads to cracks. According to the examination results, it was confirmed that cracks were not generated at a normal laser welding speed by using nickel plating having a Vickers hardness of Hv280 or less as described above and 10 μm or less. An example of the plating conditions that meet the above conditions is as follows.

Low hardness Hv by controlling pH 3.5-4.5 and bath temperature 40-55 ℃ using the above plating bath and adding no brightener
160-250 is obtained. In this case, if the nickel plating thickness is less than 2 μm, rust may occur after plating, causing problems such as causing pinholes during welding, or causing iron rust to appear on the surface of the welded portion and cause rusting. Because it ’s easy
It must be 2 μm or more. Table 1 shows the results of comparison between the example of the present invention described above and another plating method including the thickness of the plating layer. From this table, it can be seen that the present invention is effective in preventing the occurrence of cracks.

The electroless plated product has a high crack occurrence rate, but this is partly evaporated during welding due to the low melting point of the plating layer, or added P (phosphorus), B (boron)
Etc. are thought to have an adverse effect on welding. The semi-bright electronickel plating containing the organic brightener has finer crystals, but cracks are thought to occur due to increased internal stress and residual brightener.
Even in matte electro-nickel plating, the bath temperature is increased and the current density is adjusted to increase the productivity for reasons such as generally improving productivity, but this causes a crystal state with large internal stress and a decrease in weldability. It is thought to have been done. As described above, the present invention prevents the occurrence of cracks in the welded portion by using the steel battery container provided with the specified nickel plating layer and the lid.

EFFECTS OF THE INVENTION As described above, according to the present invention, the steel battery container and the lid body are subjected to matte electric nickel plating with a Vickers hardness of Hv280 or less and a thickness of at least 2 to 10 μm in a welded portion. By using such a material, it is possible to prevent the generation of fine cracks in the welded portion during laser welding, and to provide a sealed battery with high long-term reliability.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part showing a laser welded portion of a sealed battery according to an embodiment of the present invention, FIG. 2 is a sectional view of an essential part of a side surface of the battery, and FIG. 3 shows a welding condition at the time of laser welding. FIG. 4 is an enlarged view of a main part of a side surface of a welded portion, and FIG. 4 is a cross-sectional view of a main part showing a structure of a conventional battery. 1 ... Battery container, 1a ... Nickel plated layer, 2 ... Power generating element, 3 ... Lid, 3a ... Rising part, 3b ... Nickel plated layer, 4 ... Junction part, 5 ... Laser beam, 6 ... Welded part, 8 ... Terminal part.

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-58-46658 (JP, A) JP-A-59-51457 (JP, A) JP-B-53-39374 (JP, B2) Edited by Japan Plating Technology Association “Practical plating for field engineers (▲ I ▼)” Showa 53-9-25 Maki Shoten P. 144

Claims (1)

[Claims] 1. A battery in which a lid is fitted to an open end of a battery container accommodating a power-generating element, and a joint portion thereof is sealed by laser welding, wherein the battery container and the lid are made of steel,
At least the thickness of the plating layer to be welded is 2 to 10μ
A sealed battery characterized in that it is m and has a hardness of Vvickers hardness Hv280 or less and is plated with matte electric nickel.