JPS6138580B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a so-called hermetically sealed battery sealed with glass. In sealed batteries, the greatest concern is to prevent electrolyte leakage, but it is extremely difficult to prevent leakage, and the reality is that there is no perfect solution. This is due to the corrosive effect of the electrolyte inside the battery, and for this reason, sealing methods that have been used and are effective in other sealed electronic components do not work well in batteries, and leaks often occur. There was a time when something was going to happen.
For example, hermetic seals, which are often used in high-end electronic components, are less effective than other seals, such as those using organic sealants such as rubber.
It is said to be chemically and mechanically stable and able to maintain a reliable sealing effect over a long period of time. However, even such a hermetic seal does not necessarily provide a sufficient sealing effect when used to seal a sealed battery, and the electrolyte may leak out. Conventionally, when leakage occurs in hermetically sealed batteries, if there is a gap between the glass and the metal part, or if there is a crack in the glass, electrolysis can occur through the gap or tight crack. It is thought that the electrolyte will leak out to the outside, and therefore, in order to prevent electrolyte leakage, it is recommended to check for gaps and cracks in advance using, for example, a helium leak test method. was. However, even if the seal portion is subjected to a strict preliminary inspection using, for example, a helium leak inspection method, liquid leakage may still occur in the case of batteries. This invention was made against the above-mentioned background, and its objectives are, first, to provide a method for manufacturing a sealed battery with improved leakage resistance; It is an object of the present invention to provide a method for relatively easily manufacturing a sealed battery having high performance. Here, prior to completing this invention, the present inventors came to know the following important fact. In other words, in a sealed battery, the glass of the seal part that is welded to the battery terminal is
The chemical erosive action of the electrolyte inside the battery and the erosive action caused by the electrochemical reaction (O ₂ + 2H ₂ O + 4e ^- → 4OH ^- ) occurring at the cathode terminal in contact with the glass act synergistically. Therefore, it is important to note that the seal may gradually erode, and even if it is able to completely prevent leakage in the early stages, the sealing effect will weaken over time and leakage will eventually occur. I got it. For example, in a sealed alkaline battery using an alkaline electrolyte, in addition to the corrosive effect of the strong alkalinity of the alkaline electrolyte, nascent hydrogen, which is extremely chemically active, is generated by an electrochemical reaction on the cathode side. The corrosive action of the nascent hydrogen in the lever may act synergistically on the glass in the sealing part, and at this time, if there is a minute crack in the glass in the sealing part, especially in the part of the glass on the cathode terminal side, this crack will Gradual growth occurs due to the above-mentioned erosion, and as a result, even if the cracks are so small that they cannot be detected at first, they gradually grow larger over time, and eventually the electrolyte flows through the cracks that have grown. It was found that the liquid began to ooze out, causing so-called leakage. By the way, in order to prevent fluid leakage caused by such micro-cracks, it seems to be a good idea to conduct a preliminary inspection for the presence or absence of micro-cracks that are likely to cause the fluid leakage, but the problem is that As mentioned above, the micro cracks that cause liquid leakage are
This includes leaks that are so small that they cannot be detected even with a strict leak test such as the helium leak test method.
In addition, even if something does not leak at the time of inspection, it will grow to cause leakage afterwards, so it is actually impossible to eliminate these in advance by inspection. This invention was made based on the above-mentioned knowledge, but the present inventors have now come to an even more important knowledge. That is, as long as the leakage caused by the growth of minute cracks can be prevented from growing at least in the portion of the seal portion that is welded to the glass cathode side terminal, the leakage caused by the growth of microcracks as described above can be prevented. They learned that leakage caused by crack growth can be effectively prevented with a fairly high probability. Therefore, in this invention, a sealing part of a metal battery case that also serves as a terminal for one pole and a metal current collector that also serves as a terminal for the other pole and passes through the sealing part are sealed with glass. Accordingly, in the manufacturing method of a sealed battery in which the power generation element contained in the battery case is hermetically sealed, a thin layer of glass is preliminarily applied to the surface of the metal member that also serves as the cathode terminal to be welded to the glass. A preliminary process of welding,
It consists of a step of sealing with glass between the metal member on the cathode terminal side and the metal member on the counter electrode terminal side, on which a glass layer has been formed on the surface in this preliminary step, and the welding temperature when providing the glass layer in the preliminary step is By setting the welding temperature higher than the welding temperature during subsequent glass sealing, leakage due to the growth of cracks as described above can be effectively prevented by providing relatively simple additional means. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an example of a sealed battery manufactured by the method according to the present invention. The structure of the battery shown in FIG. The annular gap between the case 1 and the rod-shaped metal current collector lead 3 which is inserted and also serves as a terminal is sealed with a glass 4. Above battery case 1
The bottom case part 1a and the bottom case part 1b are welded together.
b is provided with a through hole through which the current collector lead 3 is loosely fitted, and an annular boss portion 1c is integrally formed along the inner peripheral edge of this through hole. The power generation element 2 is a stack of an anode mixture 2a containing silver oxide as a main ingredient, a separator 2b containing an alkaline electrolyte, and a cathode material 2c.
The cathode material 2c is electrically connected to the current collecting lead 3 via a dish-shaped current collecting plate 3a. As a result, the case 1 serves as an anode terminal, and the current collection lead 3 serves as a cathode terminal. Here, the current collector lead 3 and the current collector plate 3a are joined by spot welding. To explain in more detail, the above glass 4
The sealing side case part 1b and the current collecting lead 3
After these are integrated, electricity is applied between the leads 3 and the current collector plate 3a in a press-contact state, and the heat generated by this electricity flow causes them to be welded together. The current collector plate 3a is formed in a dish shape so as to cover the cathode material 2c along the inner surface of the case 1,
Furthermore, a flexible and elastic dish-shaped insulating packing 5 made of, for example, polyethylene, polypropylene, or polyamide resin is interposed between the current collector plate 3a and the battery case 1. Now, in manufacturing the sealed battery having the above-mentioned structure, the current collector lead 3, the glass 4, and the sealing side case part 1b are integrated in advance to form the sealing part 6. The sealing part 6 is formed by fixing the sealing side case part 1b and the current collecting lead 3 in respective predetermined positions using an appropriate jig. In other words, in the case of the battery shown in FIG. The current collecting lead 3 is fixed in a penetrating state along the central axis of the case part 1b, and in this state, the current collecting lead 3 and the sealing side case part 1b are welded with the glass 4. Prior to forming such a sealing portion 6, in the present invention, a preliminary step is performed in which a thin layer of glass is welded to the surface 3b of the current collector lead 3 to be welded to the glass 4. FIGS. 2a, b, c, and d show one embodiment of the process in order. First, the glass welding surface 3b of the cylindrical current collector lead 3 as shown in FIG. Then, as shown in Figure b, glass powder 4 is added.
Apply a. Then, the applied glass powder 4a is heated and softened, and is evenly welded to the glass welding surface 3b of the current collecting lead 3 to form a thin glass layer 4b, as shown in FIG. In this way, the glass layer 4b is attached to the glass welding surface 3b.
As described above, the current collecting lead 3 with the welded and formed current collector lead 3 is positioned in the central through hole of the sealing side case part 1b, and the space between them is welded and sealed with the sealing glass 4, as shown in FIG. 2d. A sealing portion 6 like this is formed. In this way, if the preliminary process of forming a thin glass layer 4 on the current collector lead 3 is performed in advance, the subsequent sealing process of the glass 4 will not only be performed very easily, but also the pairing of the current collector lead 3 can be made in advance. By welding the glass layer 4b to the glass welding surface 3b, it is possible to ensure the welding state between the current collector lead 3, which is a metal member, and the glass portion, so that the current collector lead 3 is connected to the cathode terminal. In this case, the generation of cracks that may cause liquid leakage in the future along the interface between the lead 3 and the glass is prevented, and therefore the effect of preventing liquid leakage is great. . What should be noted here is that when the glass 4 is used to seal between the current collector lead 3 and the sealing side case part 1b, if the welding temperature is increased when the glass 4 is welded, the glass 4 The viscosity of the glass decreases, causing the glass to drip from between the jigs during welding or escape from the sealing area, making it impossible to seal properly. Therefore, a sufficient welding condition could not be obtained at the welding interface with the current collector lead, which is a metal member, and this was a cause of leakage. However, by providing the preliminary process as described above, , the glass welding surface 3b of the current collector lead 3
The welding temperature when forming the glass layer 4b and the welding temperature of the glass 4 can now be set separately and independently.This allows the welding of the current collector lead 3, which is a metal member, to the glass 4. At the interface,
It is possible to easily obtain a good welding state. This eliminates the cause of liquid leakage due to crack formation as described above, and makes it possible to reliably reduce the occurrence of liquid leakage. In addition, the current collector lead 3 and the glass 4 are metal members.
In order to obtain a sufficient welding condition at the welding interface of As mentioned above, the seal may sag or escape from the sealing area, making it impossible to seal properly. However, in this invention, the glass layer 4b
When providing the glass layer 4b, since the glass layer 4b itself is a thin layer, even if the welding temperature is increased, the glass layer 4b will not sag from the surface and a sufficient welded state can be obtained. Therefore, in this invention, the glass layer 4
The welding temperature when providing b is the same as that of the subsequent glass 4
The welding temperature is set higher than the welding temperature during sealing. Here, if it becomes possible to increase the welding temperature when providing the glass layer 4b, it is possible to make the coefficient of thermal expansion of the glass forming the glass layer 4b smaller than that of the glass of the sealing part. become. In general, it has been difficult to use glass with a low coefficient of thermal expansion because its welding temperature tends to be too high, but in the present invention, the glass layer 4b is made of glass with a low coefficient of thermal expansion. This can be easily done, and the thermal expansion coefficient of the glass forming the glass layer 4b can be adjusted to the glass 4 of the sealing part.
By making it smaller than that, the following effects can be obtained. That is, as shown in FIG. 3, if the coefficient of thermal expansion of the glass layer 4b is smaller than that of the surrounding sealing glass layer 4, the amount of thermal contraction accompanying cooling of the glass 4 after the welding operation will be less than that of the glass layer 4b. The glass 4 in the sealing portion is larger than the layer 4b, and therefore, after cooling, the glass layer 4b is constantly compressed along its surface direction, as indicated by the arrow in FIG. A certain amount of stress will remain. Due to the constant application of such compressive force, it becomes difficult for cracks to form in the glass layer 4b, and even if cracks occur, their growth is suppressed, further reducing the probability of leakage. You will be able to do this. Therefore, it is more preferable that the thermal expansion coefficient of the glass layer 4b is at least lower than that of the glass 4 of the sealed portion. Further, in another embodiment of the present invention, the glass layer 4b may be formed of glass containing direconium, and the glass 4 may be formed of, for example, commonly used cobalt glass. Glass containing zirconium has alkali-resistant properties and is therefore a preferred material for preventing alkaline electrolyte leakage, but as the inventors have learned, for example, It has been found that the use of glass containing 2% by weight or more of ZrO ₂ in the glass layer 4b is highly effective in inhibiting the growth of microcracks due to electrochemical corrosion as described above. This _ZrO2
Glass containing glass has not traditionally been used for sealing parts of sealed batteries due to problems such as high welding temperatures, but by providing the preliminary process described above, it can be easily used for sealed batteries. It became possible to do this. In addition, since the coefficient of thermal expansion of glass containing zirconium differs depending on the composition and composition ratio as with general glass, the glass containing zirconium that forms the glass layer 4b is selected to have a coefficient of thermal expansion smaller than that of glass 4. It is more preferable to do so. Regarding the formation of the glass layer 4b, in addition to the method of applying glass powder and heat welding as described above, for example, a pre-formed glass tube may be placed over the current collector lead and this may be heat welded. It can be done even if it is twisted. Further, the glass layer is preferably provided not only on the metal member on the cathode side but also on the metal member on the anode side. Here, the results of a comparative test of the leakage rate of a sealed battery manufactured by the method according to the present invention and a conventional sealed battery of the same type will be shown. In this case, the test was conducted on a type of silver oxide battery of the JIS "SR1130" type. Further, in the battery according to the present invention, the glass layer 4b and the glass 4 of the sealing part are made of the same glass A1, and the coefficient of thermal expansion of the glass of the glass layer 4b is smaller than that of the glass 4 of the sealing part. The same number of samples A2 and A3, in which the glass of the glass layer 4b contains zirconium, were prepared and compared with sample B manufactured by the conventional method. In addition, in the battery manufactured by the method of the present invention, the glass welding temperature during the preliminary step was set higher than the glass welding temperature during sealing. Test method: Each battery A1, A2, A3, B was tested at a temperature of 80℃ and humidity.
I saw a leakage of liquid stored in a 90% atmosphere.

[Table] Also, each battery A1, A2, A3, B is
Temperature 60℃ while in overcharged state due to 1.85V constant voltage.
When we looked at leakage when left in an atmosphere with 90% humidity, we found the following:

[Table] As is clear from the above results, battery A of the present invention
1, A2, and A3 all have improved leakage resistance performance than conventional battery B, and the same glass is used, but the glass layer 4b and the glass 4 of the sealing part are simply welded in separate processes with different welding temperatures. It was confirmed that the leakage resistance of Natsuta A1 was also significantly improved compared to conventional batteries. As described above, according to the method for manufacturing a sealed battery according to the present invention, a sealed battery with a hermetically sealed structure with reliably improved leakage resistance can be obtained by simply providing a relatively simple additional process. be able to.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a sealed battery produced by the method of the present invention, and FIGS. The cross-sectional view and FIG. 3 are enlarged cross-sectional views of the main parts in which the method of the invention was carried out. DESCRIPTION OF SYMBOLS 1... Battery case, 2... Power generation element, 3... Current collection lead, 3b... Glass welding surface, 4... Sealing glass, 4b... Glass layer, 6... Sealing part.

Claims (1)

[Scope of Claims] 1. By sealing with glass between the sealing part of the metal battery case that also serves as the terminal of one pole and the metal current collector that penetrates the sealing part and also serves as the terminal of the other pole, In a method for manufacturing a sealed battery in which a power generation element contained in a battery case is hermetically sealed, a preliminary step of welding a thin layer of glass to the surface of the metal member that also serves as a cathode terminal to be welded to the glass; It consists of a step of sealing with glass between the cathode terminal side metal member and the counter electrode terminal side metal member on whose surfaces a glass layer has been formed in this preliminary step, and the welding temperature at which the glass layer is provided is adjusted after that. A method for producing a sealed battery, characterized in that the welding temperature is higher than the welding temperature during glass sealing. 2. The method for manufacturing a sealed battery according to claim 1, characterized in that the coefficient of thermal expansion of the glass forming the glass layer is smaller than that of the glass of the sealed portion. 3. Claim 1, wherein the glass layer is made of alkali-resistant glass containing zirconium, and the glass is made of cobalt glass.
The method for manufacturing a sealed battery according to any one of Items 1 and 2.