JPS6238824B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a sealed alkaline battery. For example, as shown in FIG. 1, a sealed alkaline battery is constructed by arranging an anode active material 2a, a separator 2b containing an alkaline electrolyte, and a cathode active material 2c in layers in a metal battery case 1 that also serves as a terminal. While the power generation element 2 is loaded, the battery case 1
is sealed with a sealing material 3, and the sealing material 3 is electrically insulating, and the anode terminal side and the cathode terminal side are insulated and isolated from each other by the sealing material 3. In such a sealed alkaline battery, the most important issue is how to stably confine the electrolyte contained in the power generation element 2 sealed inside and prevent it from leaking outside. . In particular, in small flat sealed alkaline batteries like the one shown in the figure, in order to achieve the goal of miniaturization, the seal structure must be simple to prevent leakage of alkaline electrolyte. do not have. However, as is well known, the alkaline electrolyte used there has an extremely strong leaching power.
It also has strong chemical and electrochemical corrosive power, and tends to cause creep, especially along the metal surface on the cathode side. For this reason, conventionally, a layer 3a of, for example, epoxy resin or bituminous material is disposed at the interface between the sealing material 3 and the cathode metal portion 4 in contact with the sealing material 3, thereby preventing the alkaline electrolyte from creeping. It was. However, epoxy resins and bituminous materials are not necessarily stable over time, and at least when they are arranged in a layered manner at the interface, they cannot reliably prevent the occurrence of creep caused by the alkaline electrolyte over a long period of time. Also,
When the sealant 3 is made of glass, ceramics, etc., it is naturally impossible to provide the epoxy resin or bituminous substance at the interface between the sealant and the metal part due to considerations such as sealing temperature. That is, it is impossible to apply it to a hermetic seal type sealed alkaline battery. Here, even if the sealing material 3 is of a so-called hermetic type using glass or ceramics, the alkaline electrolyte still creeps along the interface between the sealing material 3 and the metal part. This causes liquid leakage. In addition, in the sealed alkaline battery as described above, nascent hydrogen is often generated by electrochemical reactions within the battery case 1, and this nascent hydrogen is generated at the interface between the sealing material 3 and the metal part. This often causes alkaline electrolyte leakage. Further, the hydrogen generated within the battery increases the internal pressure of the battery and destroys the adhesion between the sealing material 3 and the metal parts in contact with it, which may cause liquid leakage. Furthermore, most alkaline batteries use zinc chloride as the cathode material 2c, but this zinc chloride causes the interface between the sealing material 3 and the metal part to become opaque, and as a result of this opacity, The above-mentioned creep also progresses. In view of the above, in a relatively small sealed battery as shown in Figure 1, leakage of electrolyte can be ensured within its extremely limited volume without impairing the effective power generation capacity. It is extremely difficult to prevent this from occurring. The purpose of this invention is to prevent electrolyte leakage caused by the various factors mentioned above.
Even in a relatively small-sized sealed alkaline battery as shown in FIG. 1, the objective is to ensure that the effective power generation capacity can be prevented without any loss and even with a simple sealing structure. The sealed alkaline battery according to the present invention has a chromium oxide layer provided at least along the cathode side interface between the sealing material made of glass or ceramics bonded with glass and the metal part in contact with the sealing material. First, mechanically, a strong and stable bond is obtained between the oxide layer and the metal part, and chemically and electrochemically, it is bonded to the alkaline electrolyte and the electrode materials in the battery. It is also extremely stable, has a sufficiently high hydrogen overvoltage, is sufficiently stable against hydrogen during its generation, and is extremely resistant to oxidation, thereby ensuring that alkaline electrolyte does not leak due to the various factors mentioned above. It was designed so that it could be prevented. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 2 shows an embodiment of a sealed alkaline battery according to the present invention. The battery shown in the figure uses an alkaline aqueous solution as an electrolyte, and is of almost the same type as the conventional battery shown in Figure 1. Anode active material 2
a, a power generation element 2 consisting of a separator 2b containing an alkaline electrolyte and a cathode active material 2c is loaded, and a metal current collector lead 4 which also serves as a cathode terminal passes through the upper center of the case 1, and the case 1 and the lead 4 An annular gap 5 between the two terminals is sealed with a sealing material 3 made of glass, and both terminal sides are electrically insulated from each other. Then, a metal portion in contact with the glass sealing material 3, that is, the sealing material 3
A chromium oxide layer 6 is formed at the contact interface between the current collector lead 4 and the current collector lead 4 . This chromium oxide layer 6
In the embodiment, is formed in advance on the side of the current collector lead 4, which is a metal part. This oxide layer 6 is provided along at least the portion in contact with the sealing material 3. Furthermore, the oxide layer 6 is
It must be provided at least on the metal part on the cathode terminal side. However, it is desirable to provide the chromium oxide layer 6 also on the anode terminal side. Here, in order to form the chromium oxide layer 6, at least the surface portion of the metal portion in contact with the sealing material 3 is formed of chromium or an alloy containing chromium, and the surface of the metal portion is further oxidized. good. At this time, in order to form at least the surface of the current collector lead 4 or, if necessary, the case 1 with chromium or an alloy containing chromium, the current collector lead 4 and the entire case 1 contain chromium or contain chromium. It may be made of an alloy, or its leads 4 and case 1 may be made of a metal other than chromium, and the necessary surface portions thereof may be coated with chromium or an alloy containing chromium by plating or the like. As the chromium oxide layer 6 formed on the surface of the metal portion in contact with the sealing material 3, Cr ₂ O ₃ is suitable, but CrO, CrO ₂ , Cr ₂ O ₅ , CrO ₃ and the like may also be used. Now, as described above, the chromium oxide layer 6 is formed along the interface between the sealing material 3 and the metal part in contact with it.
As mentioned above, this oxide layer 6 exhibits a very strong and stable bond with the metal part on which it is formed, and as a result, the oxide layer 6 exhibits a very strong and stable bonding state along the surface of the metal part. Progressing creep caused by the alkaline electrolyte is prevented.
In addition, the chromium oxide layer 6
is stable against alkaline electrolytes and very stable against nascent hydrogen, which is often generated in batteries, and can exhibit a sufficiently high hydrogen overvoltage, making it highly stable against chemical Also, leakage of alkaline electrolyte caused by electrochemical erosion can be reliably prevented. Furthermore, the chromium oxide layer 6 very conveniently has the property of being extremely difficult to be oxidized. Therefore, in an alkaline battery using zinc oxide as the cathode material 2c, Even if the zinc chloride were to come into direct contact with the edge of the interface between the sealing material and the metal part, this would not cause the alkaline electrolyte to leak. As described above, leakage of alkaline electrolyte can be ensured without making the seal part too complicated, without impairing the effective power generation capacity of the battery, and with an extremely simple seal structure. It will be possible to prevent this from happening. Here, FIG. 3 shows a test method for examining the creep rate of an alkaline electrolyte outside the battery system. In the method shown in the figure, zinc chloride 7 and alkaline electrolyte 8 are used as cathode materials.
A metal rod 10 is placed in a container 9 containing a metal rod. Above this metal rod 10, a sealing material 3 is encircled in an annular shape and tightly attached, similar to when forming the seal structure of an actual battery. A creep-resistant material layer 11 is provided at the interface between the sealing material 3 and the metal rod 10 to prevent creep caused by the alkaline electrolyte. Here, the sealing material 3
The types of the creep-resistant material layer 11 were varied, and the time required for the alkaline electrolyte to appear on the upper side of the creep-resistant material layer 11 was measured for each combination of types, as shown in the table below. I got good results.

[Table] However, the distance l1 from the liquid level of the alkaline electrolyte to the upper side of the sealant 3 is 20 mm, and the length l2 of the sealant 3 and the creep-resistant material layer 11 are the same. The width was 5 mm in both cases. The test conditions are normal temperature and normal humidity. As is clear from the above test results, sealing material 3
The chromium oxide layer provided along the interface between the metal part and the metal part in contact with this has a much better ability to prevent creep caused by alkaline electrolytes than conventional products using epoxy or bituminous materials. . Even when an actual battery system is configured, the sealed alkaline battery according to the present invention is susceptible to various causes of leakage occurring only within the battery system, such as battery leakage, as is clear from the test results described below. against electrochemical corrosion within the system, and against nascent hydrogen that often occurs within batteries.
Sufficient durability could be confirmed. In particular, in actual battery systems, the electrochemical action within the battery system accelerates the leakage of the alkaline electrolyte, and moreover, it occurs concentratedly along the surface of the metal part on the cathode side. There was a tendency, but
In the battery according to the present invention, leakage of alkaline electrolyte at the cathode side can be reliably prevented. An example of test results within the battery system will be shown below. The test was conducted on the flat type sealed alkaline batteries shown in Figure 1 or Figure 2, respectively.
Various changes were made to the type of sealing material, the type of leak-proofing material provided along the interface between the sealing material and the metal part, etc. The test was carried out by storing in an environment at a temperature of 60°C and a humidity of 90%, and the results were as shown in the table below.

[Table] As is clear from the above table, the sample battery constructed according to the present invention is different from the conventionally constructed battery (No. 1).
The leakage resistance has been significantly improved compared to the previous model. This is done by providing a chromium oxide layer 6 along the interface between the sealing material 3 and the metal parts in contact with it, especially the metal parts on the cathode side. In addition, when glass is used as the sealing material 3, the chromium oxide layer 6 can form a good adhesive state with the glass, and also has a stable mechanical bond with the metal part. By being strong, it is now possible to reliably prevent alkaline electrolyte leakage caused by cracks in the glass. In addition, in the case where glass is used as the sealing material 3, in the so-called compression type, in which the glass is constantly compressed from the metal part side, distortion is constantly generated in the glass due to the compression. It becomes easier for cracks to enter or grow, but
In such a compression type glass, it has been confirmed that the oxide layer 6 also has the function of preventing cracks from forming in the glass, or from growing large cracks that have already occurred. . As described above, the sealed battery according to the present invention is
Even with a relatively simple configuration, it has become possible to improve leakage resistance, etc., especially in sealed batteries whose structure has been unavoidably simplified for miniaturization.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a conventional sealed alkaline battery, Fig. 2 is a sectional view showing an example of a sealed alkaline battery according to the present invention, and Fig. 3 is a sectional view of a conventional battery and a battery according to the present invention. FIG. 3 is a cross-sectional view showing an example of a test method for comparing the performance of seal structures of FIG. 1...Metal battery case, 2...Power generation element, 3
... Sealing material, 4... Current collection lead, 6... Chromium oxide layer.

Claims (1)

[Scope of Claims] 1. A power generation element is loaded into a metal battery case that also serves as a terminal, and the battery case is sealed with a sealing material, and the sealing material is electrically insulating and the sealing material is electrically insulating. In a sealed battery in which the anode terminal side and the cathode terminal side are insulated and isolated from each other, the sealing material is composed of glass or ceramics bonded with glass, and the sealing material is made of glass or ceramics bonded with glass, and at least the cathode side A sealed alkaline battery characterized by having a chromium oxide layer along the interface. 2. The sealed alkaline battery according to claim 1, wherein the chromium oxide layer is provided only at the interface between the sealing material and the metal portion on the cathode terminal side. 3. The sealed alkaline battery according to claim 1, wherein the chromium oxide layer is provided on both the cathode side metal part and the anode side metal part. 4. The sealed alkaline battery according to claim 1, 2, or 3, wherein the chromium oxide layer is integrally formed on the surface of a metal portion that is in contact with the sealing material. 5. The patent states that the chromium oxide layer is formed by forming at least the surface portion of the metal portion in contact with the sealing material with chromium or an alloy containing chromium, and further oxidizing the surface of this metal portion. A sealed alkaline battery according to claim 1, 2, 3, or 4. 6. Claims 1, 2, 3, and 4, wherein the chromium oxide layer is an oxidized chromium plating layer formed on the surface of the metal part. Or the sealed alkaline battery described in item 5. 7. Claim 1, wherein the power generating element is characterized in that its cathode material is mainly made of zinc chloride.
The sealed alkaline battery according to any one of Items 1 to 8.