JPH0568063B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a prismatic sealed battery using a steel plate as a battery container material. BACKGROUND ART In recent years, as electronic devices have become wireless, smaller, and thinner, the demand for prismatic sealed batteries that are easy to store has increased dramatically. As prismatic sealed batteries for mobile devices, alkaline storage batteries that use nickel hydroxide for the positive electrode and cadmium, zinc, hydrogen storage alloys, etc. for the negative electrode are suitable because they can be completely sealed, have high energy density, and are highly reliable. It is considered the most suitable battery. Generally, the container for this type of prismatic sealed battery has a structure as shown in FIG. 1 is a square case, and 2 is a lid equipped with a terminal 3 that also serves as a safety valve. A prismatic sealed battery using a metal case is generally manufactured by the process shown below. A square case and lid are made by forming a steel plate into a specified shape. Nickel plating is applied to the square case and lid. The power generation element and electrolyte are housed in a square case. A lid is fitted into a square case, and the fitted part is sealed using laser welding, which is suitable for precision welding. Regarding the plating applied to the square case and lid, it is desirable to use high-purity matte nickel plating on the inside of the case from the viewpoint of battery performance. Therefore, the method initially used was to form a steel plate into a predetermined shape and then apply matte nickel plating using fishing plating or barrel plating, but the thickness of the plating was often uneven, and the inner surface of the case was often coated with matte nickel plating. In the worst case, there was a problem that rust occurred. In order to solve these plating problems, there is a method of forming a steel plate into a predetermined shape using a steel plate that has been previously coated with matte nickel plating on both sides. If this method is used, it is possible to prevent uneven plating and the occurrence of rust, which is preferable in terms of battery performance. Problems to be Solved by the Invention A schematic diagram of a general drawing process is shown in FIG. As the male die 5 is pressed in the direction of the arrow 8, the steel plate 10 is squeezed between the male die 5 and the female die 6, and the steel plate 10 is formed into a predetermined shape. At this time, as the drawing progresses, a strong frictional force acts between the surface of the steel plate 10 that becomes the outer side of the case and the inner side 9 of the female die. In other words, when a rectangular case is made by drawing from a steel plate that has been previously coated with matte nickel plating, the outside of the mold, which is subjected to frictional force against the outside of the case, is subject to severe wear, and its lifespan is longer than that of the unplated steel plate. There is a problem that the length is significantly shorter than when machining. The reason for this is that the surface of matte nickel plating is minutely uneven, and the mold surface is worn out by friction during processing. In addition, in terms of the appearance of the battery, when the outer plating of the battery case or the like is matte nickel plating, it tends to discolor, which is not desirable as a product image. Means for Solving the Problems As mentioned above, the present invention solves the manufacturing problems in the conventional case and lid made of a matte nickel-plated steel plate, and also solves the manufacturing problems in the conventional case and lid. The method is to obtain a rectangular sealed battery, and the method is to use the materials for the rectangular case and lid.
The battery is characterized by a rectangular case and lid made of a steel plate with glossy nickel plating on one side and matte nickel plating on the other side, with matte nickel plating on the inside of the battery and glossy nickel plating on the outside. do. EXAMPLES The present invention will be explained below using preferred examples. [Battery A] (Example of the present invention) A hoop-shaped material with 3 μm bright nickel plating on one side of a cold rolled steel plate and 2 μm matte nickel plating on the other side was used, and each of the length x width x height was used. A case with outer diameter dimensions of 5.6 x 16.4 x 67 mm was formed by drawing. The lid was made from the same material and had an outer diameter of 4.8 x 15.6 mm so that it was inscribed in the sealing part of the case. Next, a terminal 3, which also served as a safety valve, was attached to the case 1, which contained a power generation element consisting of a positive electrode mainly composed of nickel hydroxide, a negative electrode mainly composed of cadmium, a separator, etc., and an alkaline aqueous solution used as the electrolytic solution. The lid 2 was fitted, and the fitted portion was welded and sealed using a YAG laser welding machine, as shown in FIG. 2, to produce various types of sealed nickel-cadmium storage batteries A according to the present invention. [Battery B] (Conventional Example) For comparison, various types of sealed nickel-cadmium storage batteries B were manufactured using conventional methods in the same manner as Battery A except that steel plates with matte nickel plating on both sides were used. [Battery C] (Conventional Example) A sealed prismatic nickel-cadmium storage battery C was manufactured in the same manner as Battery A, except that a case and a lid that had been preformed and then matt nickel plated were used in the same manner as Battery A. Next, for Battery A of the present invention and conventional batteries B and C, the durability of the mold for drawing the case and the quality of the welded parts of the case and lid were examined. The results are shown in Table 1.

[Table] As can be seen from Table 1, the lifespan of a molding die is
It can be seen that battery A according to the present invention is not only significantly improved over battery B, which has matte nickel plating on both sides, but also superior to battery C, which is formed using an unplated steel plate. . This is thought to be due to the fact that the outer surface, which is subject to strong wear such as ironing during drawing, is made of smooth glossy nickel plating, which reduces mold wear and improves processing life. Next, when we compare the defectiveness rate of welded parts, battery A according to the present invention has a low rate of 0.1% or less;
In battery B, the dimensional accuracy and shape of the molded case are poor in proportion to the severe wear of the molding die, which causes an increase in the incidence of defects after welding. Furthermore, battery C has an even higher failure rate. If plating is applied after forming the case and lid,
It is difficult to control the plating thickness, and the plating layer becomes extremely thick due to the so-called edge effect, especially in the welded parts of square cases and lids, which causes poor airtightness due to poor fitting and welding defects. It is. Note that gloss plating may be general gloss nickel plating performed by adding a brightening agent to a wax bath, etc., or gloss nickel plating, which is performed by applying matte nickel plating and then applying a glossy finish using a method such as buffing. Effects can be obtained. In addition, in the example, the thickness of the plating was 3 μm and
The thickness of the plating was 1 μm on both sides.
The thickness is preferably about 5 μm. Effects of the Invention As described above, the present invention extends the processing life of the molding die and reduces the molding cost. Furthermore, since the plating thickness and processing accuracy are stable, it is possible to obtain a rectangular sealed battery with a highly reliable welded part.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a prismatic case constituting a prismatic sealed battery and a lid provided with a terminal. FIG. 2 is a diagram showing the structure of a prismatic sealed battery according to the present invention. FIG. 3 is a schematic diagram of a typical drawing process. 1a, 2a...Glossy nickel plating surface, 1b,
2b... Matte nickel plated surface.

Claims (1)

[Claims] 1. Using a steel plate with bright nickel plating on one side and matte nickel plating on the other side, fabricate a square case and lid by molding so that the bright nickel plated side faces the outside of the battery, and then place the plate inside the square case. 1. A method of manufacturing a prismatic sealed battery, which comprises fitting the lid to the prismatic case after storing a power generating element and an electrolyte, and sealing the fitting portion by laser welding.