JPS6249701B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to the improvement of alkaline batteries, and aims to improve leakage resistance. Generally, when sealing a battery, a gasket made of synthetic resin or rubber such as polyethylene, polypropylene, or nylon is placed in the opening of the anode can, and the gasket is connected to the cathode terminal by tightening the opening edge of the anode can inward. By pressing against a cathode current collector such as a plate or cathode lead body, the contact surfaces between the anode can, the gasket, and the cathode current collector are brought into close contact with each other, thereby preventing electrolyte from leaking from these contact surfaces. There is. However, batteries that use alkaline electrolytes such as caustic potash tend to have low leakage resistance despite the sealing methods described above, and for this reason, until now, the shape of the cathode terminal plate has been modified to improve leakage resistance. Many proposals have been made, such as improving the shape or interposing a liquid packing material such as asphalt pitch, fatty polyamide, or fluorine-based oil on the interface between the gasket, anode can, and cathode current collector. Even with these methods, a high degree of leakage resistance is not necessarily achieved. By the way, electrolyte leakage in alkaline batteries is generally more likely to occur from the contact surface between the cathode current collector and the gasket than from the contact surface between the anode can and the gasket. The reason for this is that most of the alkaline electrolyte is injected into the cathode side in order to improve the discharge characteristics, but it is thought to be mainly due to the creep phenomenon peculiar to the cathode current collector. In other words, when the electrolyte is electrochemically reduced and OH ^- is generated at the rising part of the cathode current collector from the cathode agent layer, that is, at the boundary where the contact between the cathode current collector and the cathode agent layer is broken, the alkali As the concentration locally increases, the surrounding electrolyte moves to the above-mentioned rising part due to the concentration difference, and appears as a creep phenomenon in which it creeps up over time along the surface of the cathode current collector. In addition, the cathode current collector is typically made of copper at least on the side that contacts the catholyte to prevent the formation of local batteries with amalgamated zinc powder, which is common as the cathode active material. Alternatively, it is made of a copper alloy, but the relatively large potential difference between this metal and the active material zinc is also a cause of the above-mentioned electrochemical creep phenomenon. In light of these circumstances, this invention was made with the aim of improving the leakage resistance of the battery as a whole by suppressing leakage of electrolyte from the contact surface between the cathode current collector and the gasket as much as possible. The general formula ( (In the formula, R ₁ is hydrogen, halogen or alkyl group,
R ₂ and R ₃ are hydrogen or an alkyl group, R ₂
and R ₃ may be the same or different)
By forming a film made of -aminomethyl derivatives, we succeeded in greatly improving the leakage resistance. That is, the N-aminomethyl derivative of the benzotriazole compound represented by the above general formula () has strong activity against copper, and the N=N bond in its structural formula is cleaved to form nitrogen ( N) forms a film that is chemically strongly and densely bonded to copper,
This prevents electrolyte leakage due to creep on the surface of the copper or copper alloy of the cathode current collector. Next, the present invention will be explained based on the drawings. FIG. 1 is a partial cross-sectional view of a button-type alkaline battery showing an embodiment of the present invention, in which 1 is a positive electrode active material such as ferrous oxide, manganese dioxide, ferric oxide, mercury oxide, or nickel oxide; An anode mixture containing a conductive additive such as carbon black or phosphorescent graphite and impregnated with a portion of an alkaline electrolyte; 2 is an anode mixture 1 and a metal annular pedestal 3 fixed to its periphery; is a separator that comes into contact with
The separator 2 is a stack of, for example, a hydrophilically treated microporous polypropylene film, cellophane, and vinylon-rayon mixed paper. 4
is a cathode material containing an amalgamated zinc active material and a gelling dispersant such as sodium polyacrylate, carboxymethylcellulose, or starch, into which most of the alkaline electrolyte is injected. Reference numeral 5 denotes an anode can made of a nickel-plated iron plate, and this anode can 5 is filled with an anode mixture 1 and a separator 2, and serves as a cathode current collector with a cathode agent 4 filled in the opening of the can. The cathode terminal plate 6 is fitted with an annular gasket 7 made of synthetic resin such as polyethylene, polypropylene, nylon, or rubber and having an L-shaped cross section interposed, and the opening edge of the anode can 5 is tightened inward to complete the battery. The inside has a sealed structure. As shown in FIG. 2, the cathode terminal plate 6 has a nickel layer 9 on the outer surface of a steel plate 8 that satisfies aesthetics and corrosion resistance, and a zinc active material on the inner surface to prevent the formation of local batteries. Usually, a clad plate consisting of a steel plate 8, a nickel layer 9 and a copper layer 10 is drawn into a shape having a peripheral folded part 11, or only the steel plate 8 is formed in advance. Molding was carried out using the same method, and then a nickel layer 9 and a copper layer 10 were formed using a plating method. On the surface 12 of the peripheral folded portion 11 of the cathode terminal plate 6 and the copper layer 10 in the vicinity thereof, the annular gasket 7 is brought into pressure contact via a liquid packing material.
Film 13 made of an N-aminomethyl derivative of a benzotriazole compound represented by the general formula ()
is formed, and the film 13 is chemically strongly and densely bonded to the surface of the copper layer 10 due to the strong activity of the benzotriazole compound toward copper, and leakage of the electrolyte due to the electrochemical creep phenomenon on the surface of the copper layer 10 is prevented. strongly prevents Note that a liquid packing material is interposed between the film 13 and the gasket 7, but this prevents leakage of the electrolyte due to creep on the surface of the cathode current collector such as the cathode terminal plate 6, as shown in the general formula () above. This can be prevented by using the film 13 made of an N-aminomethyl derivative of a benzotriazole compound. A liquid packing material is interposed between the film 13 and the gasket 7, and the fine gaps created between the film 13 and the gasket 7 are filled with the liquid packing material to prevent leakage of the electrolytic solution from between the film 13 and the gasket 7. This is because it is preferable to do so. The liquid packing material used for this purpose may be any material as long as it can fill the fine gaps between the film 13 and the gasket 7 and has alkali resistance and water repellency, such as asphalt pitch, fluorine-based packing material, etc. Oils, fatty polyamides, etc. are used. In the present invention, representative examples of the N-aminomethyl derivative of the benzotriazole compound represented by the general formula () used to form the film 13 as described above include, for example, N-dimethylaminomethylbenzotriazole, N- Examples include dioctylaminomethylbenzotriazole, and such N-aminomethyl derivatives increase the solubility in organic solvents such as petroleum ether while maintaining the strong activity of benzotriazole-based compounds toward copper. facilitates handling during formation. To form the film 13 on the cathode terminal plate 6, a treatment solution containing the N-aminomethyl derivative of the benzotriazole compound represented by the above general formula () is prepared, and the cathode terminal plate 6 is placed in the treatment solution. Alternatively, the treatment liquid may be applied or sprayed onto the cathode terminal plate 6. The treatment solution can usually be prepared by dissolving the N-aminomethyl derivative of the benzotriazole compound represented by the general formula () in a paraffinic solvent such as petroleum ether, and the concentration is usually 0.01 to 0.01. 1.0% by weight range,
Particularly preferred is a range of 0.1 to 0.5% by weight. If the concentration is in such a concentration range, by immersing the cathode terminal plate 6 in the treatment liquid for about 1 to 5 minutes, a film 13 having a desired thickness can be obtained after drying. Furthermore, a small amount of a nonionic surfactant such as polyoxyethylene alkyl ether may be added when preparing the treatment liquid. Note that when forming the film 13, the cathode terminal plate 6
The copper surface, especially the surface where the annular gasket 7 comes into pressure contact with the liquid packing material, is washed with alkali to remove oil and the like, and then chemically polished with a hydrogen peroxide-sulfuric acid polishing solution to activate the copper surface. In addition, if the surface is smoothed, the leakage resistance will be further improved. In this case, the surface roughness is preferably about 3 μm or less as a center line average roughness according to JIS B 0601. The following Table 1 shows the coating film made of N-dimethylaminomethylbenzotriazole when N-dimethylaminomethylbenzotriazole is used as an example of the N-aminomethyl derivative of the benzotriazole compound represented by the general formula (). In order to investigate the leakage prevention effect of the alkaline electrolyte, we conducted a copper rod peeling test prior to the battery mounting test.

[Table] In the above test, a copper rod with a diameter of 2.6 mm was chemically polished with a hydrogen peroxide-sulfuric acid-based polishing solution, and after pickling, the treatment solution was
After dipping for a minute and drying to form a film with a thickness of about 50 to 100 Å on the surface of the copper rod, about 1/5 of the length of the copper rod was immersed in a 35% by weight aqueous potassium hydroxide solution in a test tube. was brought into contact with amalgamated zinc powder and left at 60°C and 90% relative humidity for 10 days, and the height at which caustic potash climbed above the liquid level onto the copper rod was measured. Note that chemical polishing was also performed on the sample used for comparison without forming a film of N-dimethylaminomethylbenzotriazole. The following Table 2 has the configuration shown in Figures 1 and 2, with silver oxide as the anode active material, amalgamated zinc powder as the cathode active material, and zinc oxide as the electrolytic solution of 5% by weight. The leakage resistance of the button-type alkaline battery A of the present invention using a 35% by weight aqueous solution of caustic potassium is shown in comparison with that of a conventional button-type alkaline battery B.

[Table] In the battery A of the present invention used in the above test, the coating 13 was formed of N-dimethylaminomethylbenzotriazole, and a liquid packing material made of asphalt pitch was interposed between the coating 13 and the gasket 7. It is something that Battery B used for comparison did not form such a film of N-dimethylaminomethylbenzotriazole on the contact surface of the cathode terminal plate with the gasket, but instead formed an asphalt pitch between the cathode terminal plate and the gasket. Only a liquid packing material is used. The values in Table 2 indicate the number of batteries in which electrolyte leakage was observed when 100 batteries were stored in an atmosphere of 45°C and 90% relative humidity for a specified period of time. As is clear from Table 2, the battery A of the present invention has better leakage resistance than the conventional battery B. As described above, the excellent electrolyte leakage prevention function of the alkaline battery of the present invention is due to the cathode terminal plate 6.
The peripheral folded portion 11 and the copper layer 1 in its vicinity
The annular gasket 7 on the 0 surface is formed on the surface 12 which is pressed into contact with the N-
The dimethylaminomethylbenzotriazole film 13 is chemically bonded strongly and densely to the copper surface of the cathode terminal plate 6 due to its strong activity towards copper,
In addition, in order to prevent the formation of an oxide film on the surface of the copper layer 10 before or after battery assembly due to the film-forming ability of the N-dimethylaminomethylbenzotriazole, leakage of the electrolyte based on the creep phenomenon on the surface of the copper layer is prevented. This is because it was effectively suppressed. Such an excellent leakage prevention effect is different from the coating 13 of the present invention, and is also shown in Table 2 above, depending on a general water-repellent coating made of asphalt pitch, silicone resin, polyamide resin, etc. It is something that cannot be obtained at all. This is because such a film is merely physically applied and does not form a chemical bond with the copper, and therefore, compared to the film 13 of the present invention, the cathode terminal plate is The adhesion to the copper surface is poor, and due to this poor adhesion and lack of strong film-forming ability, oxidation of the copper layer surface cannot be substantially prevented, resulting in a non-uniform oxide film. This is because the surface condition is likely to be damaged by the formation of , and the effect of preventing electrolyte leakage due to electrochemical creep phenomenon is reduced. FIGS. 3 and 4 show other embodiments of the present invention, in which the surface of the cathode terminal plate 6 as a cathode current collector in a button-type alkaline battery is pressed into contact with the gasket 7 through a liquid packing material. 1
In this example, a film 13 for preventing electrolyte leakage made of N-dimethylaminomethylbenzotriazole was formed on 2, whereas in this example, an alloy of copper and zinc was used as a cathode current collector in a cylindrical alkaline battery. On the surface 12 of the brass cathode lead body 14 to which the gasket 7 is pressed via a liquid packing material,
Film 13 made of an N-aminomethyl derivative of a benzotriazole compound represented by the general formula ()
was formed. In the figure, 15 is a resin tube and 16 is an outer can, and parts having the same configuration or function as those illustrated in FIGS. 1 and 2 are given the same reference numerals. Generally, regarding electrolyte leakage in cylindrical alkaline batteries, the cathode lead body 1 as a cathode current collector
It is said that the surface 12 where the gasket 7 of No. 4 is brought into pressure contact through the liquid packing material is also important, and the surface 12 where the gasket 7 is brought into pressure contact through the liquid packing material has benzotriazole represented by the general formula (). By forming the film 13 made of the N-aminomethyl derivative of the system compound,
Leakage of the electrolyte due to the electrochemical creep phenomenon along the surface of the cathode lead body 14 can be effectively suppressed for the same reason as in the case of the button-type alkaline battery described above. Table 3 below has a configuration similar to that shown in Figures 3 and 4, with manganese dioxide as the anode active material, amalgamated zinc powder as the cathode active material, and zinc oxide as the electrolyte. The leakage resistance of the cylindrical alkaline battery C of the present invention using a 35% by weight aqueous caustic potassium solution is shown in comparison with that of a conventional cylindrical alkaline battery D.

[Table] Battery C of the present invention used in the above test uses N-dimethylaminomethylbenzotriazole as the N-aminomethyl derivative of the benzotriazole compound represented by the general formula (), and the gasket of the cathode lead body 14 is A film 13 made of N-dimethylaminomethylbenzotriazole is formed on the surface 12 to which 7 is brought into pressure contact via a liquid packing material. This battery C has a film 13
A liquid packing material made of asphalt pitch is interposed between the gasket 7 and the gasket 7. Battery D used for comparison did not have such an N-dimethylaminomethylbenzotriazole film on the surface of the cathode lead body in contact with the gasket, but instead had an asphalt pitch between the cathode lead body and the gasket. Only a liquid packing material is used. The values in Table 3 indicate the number of batteries in which electrolyte leakage was observed when 100 batteries were stored in an atmosphere of 45° C. and 90% relative humidity for a specified period of time. As is clear from Table 3, the battery C of the present invention has better leakage resistance than the conventional battery D. As described in detail above, the present invention applies N of a benzotriazole compound represented by the general formula ( - By forming a film made of an aminomethyl derivative, leakage of the electrolyte from between the cathode current collector and the gasket is prevented,
It has improved leakage resistance.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a button-type alkaline battery showing one embodiment of the present invention, Fig. 2 is an enlarged view of the main part of Fig. 1, and Fig. 3 is a cylindrical alkaline battery showing another embodiment of the invention. A partial sectional view of the battery, FIG. 4 is an enlarged view of the main part of FIG. 3. 6, 14... cathode current collector, 7... gasket,
12... Surface to which the gasket is pressed into contact via the liquid packing material, 13... Film.

Claims (1)

[Claims] 1. The surface 12 of the copper or copper alloy surface of the cathode current collectors 6, 14 to which at least the gasket 7 is pressed through a liquid packing material is formed by the general formula (). (In the formula, R ₁ is hydrogen, halogen or alkyl group,
R ₂ and R ₃ are hydrogen or an alkyl group, R ₂
and R ₃ may be the same or different)
- An alkaline battery characterized in that a film 13 made of an aminomethyl derivative is formed, and a liquid packing material is interposed between the film 13 and the gasket 7.