JPS6138579B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to alkaline batteries such as silver oxide batteries and manganese dioxide batteries that use an alkaline electrolyte as an electrolyte. Generally, when sealing a battery, a gasket made of synthetic resin such as polyamide, polyethylene, polypropylene, or rubber is placed in the anode opening, and this gasket is tightened inward of the anode can to seal the cathode lead body or cathode terminal plate. The contact surfaces between the anode can, the gasket and the cathode current collector are brought into close contact with each other by pressing against the cathode current collector, thereby preventing leakage of the electrolyte from these contact surfaces. However, batteries that use alkaline electrolytes such as caustic potash tend to have low leakage resistance despite the sealing method 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 gasket, interposing liquid packing such as pitch or fluorine oil on the interface between the gasket, anode can, and cathode current collector. However, the high degree of leakage resistance required for use in wristwatches, electronic exposure meters, etc. cannot necessarily be 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 to improve discharge characteristics, but it is thought to be mainly due to the electrochemical creep phenomenon unique to the cathode current collector. ing. In other words, when the electrolyte is electrochemically reduced to produce OH ^- at the rising edge from the cathode agent layer in the cathode current collector, that is, at the boundary where the contact between the current collector and the cathode agent layer is broken, the alkali concentration increases. becomes locally high, and the surrounding electrolyte migrates to the above-mentioned rising part due to the concentration difference, but as a result of this migration being influenced by electrochemistry, it rises over time along the current collector surface. It appears as a creep phenomenon. In addition, the cathode current collector is usually made of copper or copper at least on the side of the current collector that comes into contact with the cathode agent, to prevent the formation of local batteries with amalgamated zinc powder, which is common as a cathode active material. Although it is composed of an alloy, 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 the above circumstances, it is an object of this invention to improve the leakage resistance of the battery as a whole by suppressing leakage of electrolyte from the surfaces of the cathode current collector and gasket as much as possible. The inventors of the present invention have conducted intensive studies for this purpose and found that when a specific coating is formed on the surface of the copper or copper alloy of the cathode current collector, the leakage resistance is greatly improved. It is. An embodiment of the present invention will be described below based on the drawings. In FIGS. 1 and 2, numeral 1 is a positive electrode active material such as ferrous oxide, manganese dioxide, ferric oxide, or mercury oxide, and carbon black. , a conductive additive such as phosphorescent graphite, and an anode mixture which is impregnated with a portion of an alkaline electrolyte; 2 is an anode mixture 1 and a metal annular pedestal 3 fixed to the periphery of the mixture; A separator 7 is composed of, for example, a hydrophilically treated microporous film 4, a cellophane film 5, and a liquid absorbing layer 6 such as vinylon-rayon mixed paper, which is in contact with the amalgamated zinc active material and polyester. This is a cathode material that contains sodium acrylate, carboxymethyl cellulose, and a glue such as starch, into which most of the alkaline electrolyte is poured. 8 is an anode can such as a nickel-plated iron can in which an anode mixture 1 and a separator 2 are filled, and a cathode terminal plate 9 as a cathode current collector with a cathode agent 7 filled in the opening of the can is made of polyamide. ,polyethylene,
An annular gasket 10 with an L-shaped cross section made of various resins such as polypropylene or rubber is interposed and fitted, and the anode can 8 is tightened inward to form a sealed structure inside the battery. The cathode terminal plate 9 consists of a copper plate 11, with a nickel layer 12 on the outer surface that satisfies aesthetics and corrosion resistance, and a copper layer 13 on the inner surface to prevent the formation of local batteries with the zinc active material. , usually copper plate 1
1. A clad plate consisting of a nickel layer 12 and a copper layer 13 is drawn into a shape having a peripheral folded part 14, or only the copper plate 11 is formed in advance by a similar method, and then nickel is formed by a plating method. A layer 12 and a copper layer 13 are formed. A coating 16 formed by coating and drying a solution of naphthotriazole or a derivative thereof is provided on the surface 15 of the peripheral folded portion 14 of the terminal plate 9 and the copper layer 13 in the vicinity thereof, which is in contact with the annular gasket 10. This coating 16 is chemically and firmly bonded to the surface of the copper layer 13 due to the strong activity of naphthotriazole or its derivatives toward copper. Here, naphthotriazole has the following structure.

【formula】

【formula】 Naphthotriazole derivatives have the general formula

【formula】

[Formula] (where R represents a halogen, an alkyl group, an amino group, a hydroxyl group, a phenyl group, or a mercapto group); typical examples thereof include methylnaphthotriazole and chlornaphthotriazole. And so on. These naphthotriazoles or their derivatives are usually dissolved in an alcoholic solvent such as methanol or ethanol or water to a concentration of about 0.005 to 2% by weight, preferably about 0.05 to 0.2% by weight, and dissolved in the peripheral folded portion of the cathode terminal plate 9. 14 and the adjacent surface 15 of the copper layer 13 in contact with the annular gasket 10 and dried, it is possible to easily adhere to the copper layer 13 and form a strong coating. In addition, in forming this film, after removing oil and the like from the surface of the surface 15, it is smoothed by chemical polishing or the like in advance, and then a film is formed on this smooth surface to further improve leakage resistance. The surface roughness can be further improved.
The centerline average roughness according to JISB0601 is preferably about 3μ or less, usually 0.5 to 3μ. In the embodiment described above, the coating 16 made of the naphthotriazole or its derivative is provided on the peripheral folded portion 14 of the cathode terminal plate 9 and the surface 15 in contact with the annular gasket 10 of the copper layer 13 in the vicinity thereof.
When formed, the coating 16 improves the adhesion between the terminal plate 9 and the gasket 10, and further improves water repellency and adhesion to the contact surface 15 due to the chemical bond between the naphthotriazole or its derivative and the copper layer 13. The effect of increasing the strength, further preventing the formation of an oxide film on the surface of the copper layer 13, and suppressing leakage of electrolyte from the contact surface 15 mainly due to electrochemical creep phenomenon due to the synergistic effect of these factors. shows. Such a leakage prevention effect cannot be achieved with general water-repellent resins such as fluorine resins, silicone resins, and polyamide resins, which are simply physically applied to the surface of the copper or copper alloy to be coated. It is something that cannot be done. Table 1 shows the contact surface 15 of the cathode terminal plate 9 with the gasket 10 of an alkaline battery in which silver oxide is used as the anode active material, amalgamated zinc powder is used as the cathode active material, and a caustic potassium aqueous solution is used as the electrolyte. 1H-naphtho [1,2-] as naphthotriazole
d] Button battery coated with triazole
A. Leakage resistance of button battery B using 7-methyl-naphtho[2.3-d]triazole as a naphthotriazole derivative at a temperature of 45℃ and a relative humidity of 90℃.
The results are shown in comparison with button-type batteries C and D, which have different configurations from those of the present invention.

[Table] Note that battery C has a water-repellent resin coating 16 made of fluororesin formed on the contact surface 15 of the cathode terminal plate 9 with the gasket 10, and battery D has no coating formed on the contact surface 15 at all. The numbers in the table are the number of batteries in which electrolyte leakage was observed when 100 batteries were tested. From this table, it can be clearly seen that batteries A and B of the present invention are superior in leakage resistance compared to other batteries C and D. 3 and 4 show other embodiments of the present invention, in which a coating 16 was formed on the contact surface 15 of the cathode terminal plate 9 with the gasket 10 in a button type battery. On the other hand, in a cylindrical battery, a coating 16 made of naphthotriazole or its derivative is formed on the surface 15 in contact with the gasket 10 of the cathode lead body 17 made of brass, which is an alloy of copper and zinc. In the figure, parts having the same composition or function as the previous example are given the same numbers, and the anode can 8 is composed of an inner can 8a and an outer can 8b. Further, the cathode lead body 17 is welded to a cathode plate 18, and this cathode plate 18 functions as an external terminal. Generally, it is said that the contact surface 15 of the cathode lead body 17 with the gasket 10 is important for electrolyte leakage in a cylindrical alkaline battery, but by forming a coating 16 on this contact surface 15, the lead Leakage of the electrolyte mainly due to electrochemical creep along the body 17 can be effectively suppressed for the same reason as in the case of the button-type battery described above. Table 2 shows the contact surface 15 of the cathode lead body 17 with the gasket 10 of an alkaline battery in which manganese dioxide is used as the anode active material, agalgamized zinc powder is used as the cathode active material, and a caustic potassium aqueous solution is used as the electrolyte.
A cylindrical alkaline battery E with a coating of 1H-naphtho[1,2-d]triazole as a naphthotriazole, and a cylindrical alkaline battery with a coating of 7-methyl-naphtho[2,3-d]triazole as a naphthotriazole derivative. The results of testing the leakage resistance of type alkaline battery F under conditions of a temperature of 45°C and relative humidity of 90% are shown in comparison with cylindrical alkaline battery G having a different configuration from that of the present invention.

[Table] Battery G has gasket 1 of cathode lead body 17.
No film was formed on the surface 15 in contact with 0, and the numbers in the table are the number of batteries in which electrolyte leakage was observed when 100 batteries were tested. As detailed above, the present invention is such that a coating made of the naphthotriazole or its derivative is formed on at least the surface of the copper or copper alloy surface of the cathode current collector that is in contact with the gasket. Since leakage of the electrolyte from the contact surface between the cathode current collector and the gasket can be prevented, the leakage resistance of the battery as a whole is greatly improved. Further, in the present invention, if a liquid packing such as pitch or silicone oil is further interposed between the coating and the gasket, the leakage resistance can be further improved.

[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 part in Fig. 1, and Fig. 3 is a cylindrical alkaline battery showing another embodiment of the invention. FIG. 4 is an enlarged view of the middle part of FIG. 8... Anode can, 9, 17... Cathode current collector, 10... Gasket, 15... Surface to be brought into contact, 16... Coating.

Claims (1)

[Claims] 1. In an alkaline battery in which the anode can 8 and the cathode current collectors 9, 17 are sealed via a gasket 10, at least the gasket 10 is brought into contact with the copper or copper alloy surface of the cathode current collectors 9, 17. An alkaline battery characterized in that a coating 16 made of naphthotriazole or a derivative thereof is formed on a surface 15.