JPS62126543A - Manufacture of sealed battery - Google Patents

Abstract

PURPOSE:To remove a defective container before it is used for battery by using eddy current test equipment which detects a defect of battery container by the variation of impedance of battery container placed close to a coil in which alternating current or pulse wave of megaheltzs flows. CONSTITUTION:A battery container 1a for a sealed thionyl chloride battery is formed by deep drawing of austenite stainless steel in a cylindrical form. The cylindrical container 1a is brought close to a coil 20 in which alternating current or pulse wave of megaheltzs flows, and the coil 20 or the container 1a is rotated to scan the whole surface of the container 1a. The variation of impedance or voltage is measured with a bridge 21 to detect the defect of the container 1a. If the defect exists, a selector 21 removes the container. The container 1a having cracks or scratches is surely removed before it is used for battery. Therefore, the battery which is free from electrolyte leakage and has high reliability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting defects such as cracks and scratches in battery containers.

[Conventional technology]

In recent years, lithium batteries using thionyl chloride as an electrolyte have been developed and commercialized. Applications include computer backup power supplies, various telemeter power supplies, and other fields that require high reliability. Self-deterioration rate is 1 year
It is an extremely reliable battery with a rating of about 10% over 10 years. Therefore, instead of the conventional mechanical seal, glass sealing, metallized sealing, etc. are used for the sealing part, and the fitting part is completely sealed by laser welding.

Figure 2 shows the configuration of a triple-base thionyl chloride battery. 1 in the figure is a battery container made of austenitic stainless steel with an open top surface that also serves as a negative electrode terminal, and a cylindrical negative electrode active material 2 made of metallic lithium is crimped onto the inner surface of this battery container 1. There is.

A positive electrode 3 is provided inside the negative electrode active material 2 with a separator 4 made of a nonwoven glass fiber fabric disposed on the inner surface of the negative electrode active material 2 . The positive electrode 3 includes a cylindrical porous carbon body 5 made of carbon black using polytetrafluoroethylene as a binder, and a metal collection consisting of a cylindrical wire mesh placed inside the hollow part of the porous carbon body 5. It is composed of an electric body 6. Further, an insulating paper 7 supported by the separator 4 is provided in the battery container 1 above the positive electrode 3. A metal top 8 is sealed to the upper opening of the battery container 1 by laser welding or the like. A through hole 9 is opened in the center of the metal top 8, and a positive terminal rod 10 is fixed to the through hole 9 while being insulated from the glass sealing material 11. This positive terminal rod 10
is connected to the metal current collector 6 of the positive electrode 3 via a lead wire 12 attached to its lower end. Further, the hollow portion of the metal current collector 6 is filled with an electrolyte solution of thionyl chloride as a liquid positive electrode active material, which also serves as an electrolyte.

[Problem that the invention seeks to solve]

The battery container 1 is obtained by deep drawing austenitic stainless steel having a diameter of 14 mm and a height of 50 mm. The drawing process requires several processing steps, but if there is a defect in the material, cracks or scratches may occur in the drawn body of the battery container 1. In general, stainless steel is processed from melting the material to rolling, and if inclusions such as non-metallic manganese and silicon are poorly dispersed and concentrated, inclusion cracking or cracking caused by gas blowing will be induced during the drawing process. Although some of these cracks are large enough to be seen with the naked eye, there are also cracks that are so small that they cannot be seen with the naked eye, or cracks that do not even reach the surface. When a container with such cracks is incorporated into a battery, thionyl chloride, an electrolyte, leaks from the cracked portion, causing damage to the container equipment, which poses a serious problem. Therefore, all items are checked during the assembly process or shipping inspection stage, but some of these cracks do not necessarily penetrate from the outer surface to the inner surface of the container, and the cracks stop in the middle. In some cases, it may not be possible to confirm this during the inspection process. There was a problem in that such cracks progressed after being shipped, causing leakage of the electrolyte.

The present invention provides a highly reliable sealed battery in which the battery container is checked for cracks, scratches, etc. using a flaw detector in advance, and all defects are removed and problems are solved.

[Means for solving problems]

As described above, the purpose of the present invention is to check all defective parts such as cracks and scratches leading to cracks that occur during the press drawing process of the battery container 1 using a flaw detector and remove defective products. In a broad sense, this method is called an induced electromagnetic test method, but because it utilizes the induced currents and eddy currents that occur in conductors, a method also called an eddy current test is used. This test method involves passing an alternating current of several megahertz or less through a coil, placing the coil close to a battery container, and detecting changes in the impedance of the coil when it hits defects such as cracks or scratches on the container, or
Defects can be detected by detecting voltage changes induced in the coil. Some use pulse waves instead of alternating current, and others use Hall elements instead of detection coils. Defects such as cracks and scratches do not conduct current, so they affect the distribution and size of eddy currents, which appear as defect indicators. By installing the tester for 100% inspection during the production process, cracked and defective battery containers can be detected and sorted in advance.

[Effect]

Defects such as cracks in the battery container were detected visually or by checking for leakage of electrolyte after battery assembly.
Problems such as small cracks being overlooked, or cracks that do not penetrate to the outer or inner surface of the container cannot be sorted out, are assembled into batteries and discovered after shipping.

The present invention can detect and sort out these defective products in advance using a crack detector, and can also handle mass production by automating the process by installing an automatic feeding device.

This testing method prevents thionyl chloride, the battery's electrolyte, from leaking out during manufacturing or storage, causing deterioration in discharge performance and storage performance, and prevents damage to the equipment used.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

First, austenitic stainless steel (S[JS304
) A material having a thickness of 9.3 mm is subjected to 7 to 8 press drawing steps to form the battery container 1a shown in FIG. 1. Next, wash this battery container with a solvent such as Triclean to thoroughly remove squeeze oil and dirt. Further, the battery container is automatically brought close to the coil 20 of the feed crack flaw detector using a feeding device such as a parts feeder device, and a current of several megahertz is applied while rotating the coil or the container and scanning the entire outer surface of the battery container, and its change is detected. Watch on Bridge 21. If there is no defect in the battery container, there will be no change in the coil impedance, but
If there is a defect such as a crack, the impedance will change, so the defective battery container 1b passes through a crack detector and then passes through a sorter 2.
By 2, υ is thrown out.

In this way, by continuously inspecting a large number of battery containers, sorting out defective products, and sending only good products to the battery assembly process, it is possible to reduce the number of batteries that were produced in the past, from about 5 to 10 out of every 100,000. In the present invention, there were no defective products that leaked electrolyte due to container cracking, and high reliability, which is a characteristic of the battery, could be obtained.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented in other battery systems without departing from the spirit of the invention.

For example, similar effects can be expected when the battery container is made of iron and nickel plated, as in the case of sealed batteries such as alkaline batteries and non-aqueous solvent batteries.

〔Effect of the invention〕

As described above, the present invention uses a crack detector to screen out and remove defective products with cracks or scratches on the battery case, thereby creating an excellent sealed battery that is highly reliable and free from electrolyte leakage. You can get batteries.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of a battery container crack detector according to an embodiment of the present invention, and FIG. 2 is a longitudinal cross-sectional view of a lithium thionyl chloride battery, which is a sealed battery. 1a...Battery container 1b.Defective battery container 20.
・Coil 21 ・Bridge 22...Sorting machine

Claims (1)

[Claims] Defects in the battery container are removed before battery assembly using an eddy current flaw detector that places a coil that passes several megahertz alternating current or pulse waves close to the battery container and detects changes in impedance or voltage at the defective part. A method for manufacturing a sealed battery characterized by: