JPS5958754A - Manufacture of sealed battery - Google Patents

Abstract

PURPOSE:To prevent any collapses from being cuased on the bottom surface section of a sealed battery during sealing so as to realize sufficient sealing by making the hardness of the bottom surface section greater than that of the raised section by subjecting only the bottom surface section to cold working after the battery case is subjected to annealing treatment by being heated at a temperature within a limited range. CONSTITUTION:A battery case 1 is subjected to annealing treatment by being heated at 800-1,200 deg.C so as to remove the work hardening of the case 1. Next, a bottom surface section 1a is subjected to cold working by press thereby making the hardness of the bottom surface section 1a greater than that of a raised section 1b. Here, it is preferred that the hardness of the bottom surface section 1a is 2-3 times greater than that of the raised section 1b considering the ease of the cold working as well as prevention of the collapse of the bottom surface section 1a. Such a hardness can be obtained by appropriately adjusting work temperature and work rate, and the work hardening can be increased both by decreasing the work temperature and increasing the work rate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a sealed battery in which the opening of a battery container is tightened inward to seal it. There's a battery. In this battery, the bottom part 1a of the battery container 1 is the rising part 1b.
It has a larger area compared to the battery case 1, and a positive electrode mixture 3 surrounded by a cathode ring 2, a separator 4, and a negative electrode 5 made of metallic lithium are housed in order in a battery container 1, and a sealing plate 6
After covering the opening of the rising portion 1b, the opening of the rising portion 1b is tightened inward through the backing 7, thereby sealing the opening.

This battery container 1 is usually made of austenitic stainless steel, and is work-hardened due to processing. For this reason, it is difficult to seal the opening of the upright portion 1b when it is tightened inward, and springback occurs even after sealing, resulting in insufficient sealing. In particular, in the illustrated flat battery, since the rising portion 1b is low, there is a problem in that the force tightening the rising portion 1b escapes to the bottom portion 1a, causing a dent in the bottom portion 1a.

In order to solve this problem, a method has been proposed in which the battery container 1 is heat treated to remove work hardening. According to this method, the hardness of the upright portion lb is lowered, so that sealing is easier than in the above-mentioned method, and springback can also be prevented. However, since the entire battery container 1 is heat-treated, the bottom part 1a has the same hardness as the rising part lb, which solves the problem that the force during sealing escapes to the bottom part 1a and causes dents in the bottom part 1&. I couldn't.

The present invention has been made in view of the above circumstances, and its purpose is to provide a sealed battery that can prevent dents from being formed on the bottom surface during sealing and provide a sufficient seal. It is something to do.

In other words, the present invention provides a battery container made of austenitic stainless steel with an upright part formed around the bottom part.
After annealing by heating at 0 to 1200°C, only the bottom part is cold worked to make the hardness of the bottom part higher than the hardness of the rising part (preferably 2 to 3 times), and then the battery is processed. The trick is to house the electrode in a container, place a sealing plate on it, and tighten the opening of the rising part inward to seal it.

The present invention will be explained below with reference to the drawings.

First, a battery container 1 is prepared. This battery container 1 is 5US
It is made of austenitic stainless steel such as 304, and has a rising portion 1b around the bottom portion 1a. In the present invention, this battery container is annealed by heating at a temperature of 800 to 12,000 to remove work hardening. The reason why the annealing treatment temperature is set in the above range is that a sufficient annealing effect cannot be obtained at less than 80°C, and 1200°C is not suitable for over-elt annealing.
This is because the annealing effect is saturated.◎This annealing treatment is usually carried out for about 2 to 60 minutes, and is preferably performed in a non-oxidizing atmosphere such as a hydrogen stream. Then, by annealing, the battery container 1 has a 100 to 2
The hardness becomes about 00 Hv.

Next, in the present invention, the bottom part 1a is cold-worked in a press to make the hardness of the bottom part 1a higher than that of the upright part 1b. In this case, considering the ease of cold working and the prevention of denting of the bottom surface part 1a, the hardness of the bottom surface '8151a is adjusted to the rising edge part 1b.
The hardness is preferably 2 to 3 times higher than that of . In order to obtain such hardness, it is possible to appropriately set the processing temperature and processing rate, and work hardening can be increased both when the processing temperature is lowered and when the processing rate is increased.

To obtain the hardness of the present invention, for example, 2O in the thickness direction at room temperature.
4. Made by cold working.

Then, the positive electrode mixture 3 surrounded by the cathode ring 2, the separator 4, and the negative electrode 5 such as metal lithium are placed in the battery container 1 obtained in this way, and the sealing plate 6 is covered. The opening of the portion 1b is sealed by tightening the opening inward through the sleeve 7.

In this sealing process, since the hardness of the rising portion 1b is low, sealing becomes easy and springback can also be prevented. Moreover, the bottom part 1a has higher hardness than the rising part 1b, so
The force that tightens the upright portion 1b does not escape to the bottom portion 1a, and denting of the bottom portion 1a can be prevented.

This was confirmed in the following examples.

EXAMPLE A battery container (as shown in FIG. 1) made of SUS 304 stainless steel was placed in a hydrogen stream.

After heating at .degree. C. for 5 minutes, the battery container was rapidly cooled to room temperature, and the bottom portion of the battery container was cold-worked at room temperature in the thickness direction by 2O4 to effect work hardening. The hardness distribution is shown in Figure 2.

Then, using the battery container obtained in this way, a battery of IEC standard CR2016 (the battery shown in FIG. 1) was assembled,
The incidence of dents on the bottom and the incidence of leakage when stored at 60°C-90% H were investigated and the results are shown in Tables 1 and 2.

For comparison, a battery container made of SUS 304 stainless steel was heated at 1100°C for 5 minutes in a hydrogen stream and then rapidly cooled to room temperature.The hardness distribution is shown in Figure 3. Note that the numbers on the horizontal axis in FIGS. 2 and 3 correspond to numbers P1 to P15 indicating the positions of the battery container 1 shown in the figures.

A battery conforming to IEC standard CR2016 was assembled using this 'battery container, and the dent occurrence rate and leakage rate were investigated in the same manner as in the example. The results are listed in Tables 1 and 2.

As can be seen from Table 1 and Table 2, according to the present invention, the dents on the bottom surface during date sealing can be completely eliminated, and the leakage resistance is also improved.

As is clear from the above results, according to the present invention, only the bottom part is cold-worked, which improves the workability when working with Japan, and prevents the sealing pressure from escaping to the bottom part, making the seal completely sufficient. 0 with remarkable effects

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a sealed battery, FIG. 2 is a diagram showing an example of the hardness distribution of a battery container treated by the method of the present invention, and FIG. 3 is a diagram showing an example of the hardness distribution of a battery container treated by the method of the present invention. Figure 4 is an explanatory diagram showing fixed points of the hardness distribution measured in Figures 2 and 3.
...Battery container, 1a...Bottom part, 1b...Vertical lily part, 2...Cathode ring, 3...Positive electrode mixture, 4
... Se/grator, 5... Negative 4k, 6... Sealing board, 7... Nozo, Tsuking. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 e Miya, 2;, Kame I, 20 letters! Figure 4

Claims (2)

[Claims] (1) A battery container made of austenitic stainless steel with a rising part formed around the bottom part.
After heating and annealing at ℃, only the bottom part is cold worked to make the hardness of the bottom part higher than the hardness of the rising part.
A method for producing a sealed battery, which comprises the steps of: Next, placing an electrode plate in a battery container, placing a sealing plate on the battery container, and sealing the opening of the rising portion by tightening the opening inward. (2) Claim 1, characterized in that only the bottom part of the annealed battery container is cold worked to make the hardness of the bottom part 2 to 3 times higher than the hardness of the rising part. 2. Method for manufacturing a sealed battery as described in .