JPS6235256Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a so-called hermetically sealed alkaline battery sealed with glass. Sealed alkaline batteries must have particularly tight seals to prevent leakage of the alkaline electrolyte used therein. For this reason, it has been conventional practice to seal sealed alkaline batteries using glass sealants that are often used in high-end electronic components.
This is because glass is chemically and mechanically stable compared to other sealing materials, such as organic sealing materials such as rubber, and is expected to provide a reliable sealing effect over a long period of time. However, this sealing effect with glass is an exception for batteries, especially alkaline batteries; in the case of sealed alkaline batteries,
Even if glass was used for the seal, leakage could not be suppressed. Conventionally, the cause of this liquid leakage is often unknown. For example, even if the presence or absence of leakage at the glass seal part is rigorously inspected using helium leak detection methods during the manufacturing stage, it is still difficult to prevent the occurrence of liquid leakage. I couldn't. Regarding the occurrence of such leakage, the present inventors have learned that the major causes of leakage of sealed alkaline batteries sealed with glass are as follows. . That is, in a sealed alkaline battery, nascent hydrogen with extremely high chemical activity may be generated due to an electrochemical reaction inside the battery. At this time, if there are minute cracks in the glass of the sealing part, the hydrogen in the generation stage erodes the glass along the cracks in the presence of a strongly alkaline electrolyte, thereby causing the cracks to grow. As a result, cracks that are so small that they cannot be detected at first gradually grow larger over time, and eventually the electrolyte begins to leak from these growing cracks. In order to prevent fluid leakage caused by such micro-cracks, it seems to be sufficient to conduct a preliminary inspection for the presence or absence of micro-cracks that are likely to cause fluid leakage. As mentioned above, the micro cracks that result in cracks include cracks that are so small that they cannot be detected even by helium leak testing methods, etc., and even those that do not cause any leakage at the time of inspection may cause leakage later. Because they grow like this, it is actually impossible to eliminate them in advance through inspection. Here, the inventors of the present invention came to an even more important knowledge when conceiving this invention.
That is, the knowledge is that the growth of micro-cracks in the glass of the sealing part due to nascent hydrogen etc. as described above is caused by the use of glass in the sealing part containing zirconic acid (hereinafter referred to as ZrO ₂ ). This means that it can be suppressed quite effectively. In particular, when glass containing 2 to 10% by weight of ZrO ₂ is used in the above sealed alkaline battery,
It has been learned that the occurrence of liquid leakage due to the growth of microcracks due to the corrosive action of the nascent hydrogen can be almost suppressed. This invention was made based on the above knowledge. In other words, the purpose of this idea is to
In the presence of an alkaline electrolyte inside a sealed alkaline battery, the growth of microcracks due to nascent hydrogen generated inside the battery is suppressed, thereby preventing leakage of the glass-sealed sealed alkaline battery. There is a particular thing. In the sealed alkaline battery according to this invention, the gap between the metal battery case, which also serves as the terminal of one pole, and the through-type metal current collector lead, which also serves as the terminal of the other pole, is sealed with glass. Contains 2-10% by weight of _ZrO2 . Hereinafter, embodiments of this invention will be described with reference to the accompanying drawings. The figure shows an embodiment of a sealed alkaline battery according to this invention. In the figure, a power generating element 2 is first placed inside a flat metal battery case 1, and a terminal An annular gap between the rod-shaped metal current collector lead 3 that also serves as a
It is sealed with glass 4 containing ZrO ₂ . The battery case 1 is made by welding together a sealed bottom case part 1a and a sealed case part 1b, and the sealed case part 1b is provided with a through hole through which the current collector lead 3 is loosely fitted. Further, a boss portion 1c as an annular member is integrally formed along the inner peripheral edge of the through hole. The power generation element 2 is made by laminating, for example, an anode mixture 2a containing silver oxide as a main ingredient, a separator 2b containing an alkaline electrolyte, and a cathode material 2c. Direct contact and also cathode material 2c
The current collecting lead 3 is connected to the current collecting lead 3 via the dish-shaped current collecting plate 3a.
electrically connected to. 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. More specifically, the glass 4 allows the sealing side case part 1 to
After the lead 3 and the current collector plate 3a are integrated, electricity is applied between the lead 3 and the current collector plate 3a in a press-contact state, and the heat generated by this energization causes the leads 3 and the current collector plate 3a 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, and between the current collector plate 3a and the battery case 1, for example, polyethylene, polypropylene, etc. A dish-shaped insulating packing 5 made of flexible and elastic material such as polyamide is interposed. Furthermore, in the sealed alkaline battery of the embodiment, the annular metal member surrounding the glass 4, that is, the sealing side case portion 1b here, is formed of a material having a larger coefficient of thermal expansion than the glass 4. The glass 4 is constantly compressed by the residual thermal stress of the annular boss portion 1c of the sealing side case portion 1b after welding. A so-called compression type seal structure is formed. Here, regarding the above-mentioned glass 4, this glass 4 is a borosilicate glass containing SiO ₂ as a main component and B ₂ O ₃ as a subcomponent, and an example of the composition is 79% SiO ₂ , B ₂ O ₃ 8%, Al ₂ O ₃ 2.8%, CaO
0.2%, Na ₂ O 6%, ZrO ₂ 4%, etc. According to what the present inventors have learned, the content of ZrO ₂ contained in this glass 4 may be 2% by weight or more. Below that, the effect is weak, and the growth phenomenon of minute cracks becomes noticeable due to the above-mentioned nascent hydrogen. Furthermore, from another point of view, the content of ZrO ₂ is desirably 10% by weight or less. I mean,
As the content of ZrO ₂ increases, the melting temperature of the glass increases, which requires higher working temperatures during sealing, shortens the life of melting furnaces, carbon jigs, etc., and reduces the risk of damage to other parts, such as those mentioned above. This is because it causes disadvantages such as increasing the thermal influence on the current collecting lead and the case 1, and worsening the welding state with the current collecting lead and the case 1. As described above, by containing 2 to 10% by weight of ZrO ₂ in the glass 4 of the sealing part, the growth of microcracks in the glass caused by the nascent hydrogen generated inside the sealed alkaline battery is suppressed. As a result, leakage of the electrolyte can be effectively prevented, as will be shown in the test examples described later. Incidentally, in the embodiment, the current collecting lead 3 and the current collecting plate 3a are joined by electric welding, but in such a case, this invention brings about even greater effects. That is, when the current collecting lead 3 and the current collecting plate 3a are welded together, the thermal expansion of the current collecting lead 3 during welding causes the gap between the current collecting lead 3 and the sealing side case portion 1b to be Minute cracks are likely to form in the sealed glass, and in the conventional case, there was a great risk of liquid leakage due to the growth of these microscopic cracks. However, if the glass is a glass containing ZrO ₂ as in the case of the above-mentioned embodiment, even if minute cracks enter the glass when welding and joining the current collector lead 3 and the current collector plate 3a, Since the growth of cracks is suppressed, there is no fear of leakage. Further, in the embodiment, the sealing portion made of the glass 4 is a so-called compression seal, but even in the case of this compression seal structure, the present invention can produce even better effects. This is because in the case of a compression seal type, the glass is always in a compressed state, making it susceptible to minute cracks. Therefore, in the past, the compression seal type had the opposite effect of causing more leakage, but this product eliminates the cause of leakage caused by such minute cracks. In this invention, there is no fear of increased leakage due to the compression seal structure, but rather the inherent characteristics of the compression seal structure are effectively utilized, resulting in even better leakage resistance. Next, the results of a comparative test of the leakage rate between the sealed alkaline battery (JIS "SR 1130") shown in the example and a conventional sealed battery of the same type will be shown. In this case, the test included A case where the seal part was sealed with normal glass that does not contain any _ZrO2 , and a case where the seal part was sealed with glass containing 2% by weight, 4% by weight, and 10% by weight of _ZrO2 , respectively. The same number of B1, B2, and B3 (n=50) were used. Test method Each battery was stored in an atmosphere with a temperature of 80°C and humidity of 90%, and leakage was observed. Results Number of leaks in n = 50

[Table] In the above test, 50 pieces of glass with a ZrO ₂ content of 1% by weight and 50 pieces of glass with a ZrO 2 content of 12% by weight were made and tested under the above test conditions. The number of leaks was 7 and 2, and the number of leaks after 40 days was 14 and 8, and the best results were obtained when the ZrO ₂ content was in the range of 2 to 10% by weight. As described above, in the sealed battery according to this invention, the gap between the metal battery case, which also serves as the terminal of one pole, and the through-type metal current collector lead, which also serves as the terminal of the other pole, is sealed with glass. 2~
By including 10% by weight of ZrO ₂ , the growth of microcracks due to the corrosive action caused by the nascent hydrogen generated inside the battery is suppressed, effectively preventing liquid leakage at the glass seal part. can do.

[Brief explanation of drawings]

The figure is a sectional view showing an embodiment of a sealed alkaline battery according to this invention. 1... Battery case, 1c... Annular boss portion, 2...
...Power generation element, 3... Current collector lead, 3a... Current collector plate, 4... Glass containing ZrO ₂ .

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A metal battery case that also serves as a terminal for one pole and contains a power generation element containing a polar material, and a ring-shaped metal member of the metal battery case that also serves as a terminal for the other pole. In a sealed alkaline battery, the gap between the current collector and the fixed metal current collector lead is sealed with glass.
The glass consists of borosilicate glass, and
A sealed alkaline battery characterized by containing 2 to 10% by weight of _ZrO2 . (2) The sealed alkaline battery according to claim 1, wherein the glass is constantly compressed by residual thermal stress of the annular metal member surrounding the glass. (3) The current collecting lead is welded to the current collector that contacts one pole material of the power generation element by heat generated when current is passed between the current collecting lead and the current collector. A sealed alkaline battery according to claim 1 or 2 of the utility model registration claim, characterized in that: