JPH0210546B2 - - Google Patents

Description

[Detailed description of the invention]

This invention provides a molded anode in which a foamed metal having a specific solid volume and an anode mixture are integrally pressure-molded so that the anode mixture is also included in the voids on the surface of the foamed metal, with the foamed metal side serving as a separator. This invention relates to a button type battery housed in an anode can so as to be in contact with each other. Generally, in button-type batteries, the anode mixture, which is mainly composed of anode active materials such as silver oxide and manganese dioxide, is pressure-formed into a disk shape before being stored in the battery. By fixing a metal annular pedestal with an L-shaped cross section to the periphery of the mixture, storing it as it is inside the battery, and using the pedestal to stop the pressure applied during sealing, the molded anode can be prevented from deforming or collapsing due to the sealing pressure. We are trying to prevent this. However, such a molded anode with a pedestal is usually manufactured by placing an annular pedestal in a predetermined mold, filling it with an anode mixture, and press-molding it from above. When taken out from the mold, the anode mixture portion of the molded product tends to expand in the radial and thickness directions because it is released from the pressurizing force and the surrounding mold, causing a so-called springback phenomenon. In this case, the side to which the annular pedestal is fixed is prevented from expanding radially outward, and the side to which the annular pedestal is not fixed extends radially outward, so that the third
As shown in the figure, the center of the shaped anode 21 is curved,
If the thickness of the molded anode is thin, this curved part 21
There are problems such as cracks or fractures occurring in a, or the annular pedestal 22 separating from the molded anode. Such problems did not occur as much when the thickness of the molded anode was about 1.8 mm, as was the case in the past, so it was not a particular cause for concern, but in recent years, batteries have become thinner. It is also required to reduce the thickness of molded anodes, and when manufacturing such thin molded anodes, the above-mentioned problem frequently occurs. In molded alkaline batteries, the number of defects increases rapidly when the thickness of the molded anode becomes 0.6 mm or less, and for batteries with a thickness of 0.5 mm, the defect rate reaches 70%, which is a serious problem. It's summery. Therefore, in order to solve such problems, it was devised to manufacture a molded anode by integrally press-molding a foamed metal such as nickel or silver and an anode mixture, and this applicant proposed Although a patent application has already been filed for this, in the case of such a foamed metal, there is no vertical part in the metal annular pedestal, so even if spring back occurs in the molded product, it will not move outward in the radial direction. Since it does not strongly block the stretching force in the direction like a metal annular pedestal, there is no possibility of cracks or cracks occurring in the center of the formed anode, and the foamed metal is compressed after pressure forming. The foamed metal 2 can withstand the sealing pressure of the battery, thereby preventing the molded anode from deforming or collapsing due to the sealing pressure.As shown in FIG. Separator 4
Because it is in contact with the entire area of the anode mixture 3 on the side, the thickness of the foamed metal after pressure forming is too large, or the foamed metal is not compressed with the anode mixture included in its voids. This causes problems such as not being able to obtain the desired electrical capacity or increasing the internal resistance of the battery. In view of these circumstances, the inventor conducted various studies and found that a foamed metal with a solid volume of 1.43 to 8.00 μ/cm ² was used, and the foamed metal and anode mixture were integrally pressure-molded. When producing a molded anode in which the anode mixture is included in the voids on the surface of the metal, and storing the molded anode so that the foamed metal side contacts the separator, the thickness of the molded anode must be In addition to being able to suppress the occurrence of cracks or cracks even in extremely thin cases of 0.6 mm or less, it has the same or higher electric capacity than when using a metal annular pedestal, and has a lower internal resistance even at low temperatures. It was discovered that a small battery of 100 mL can be obtained, and based on this finding, the present invention was completed. That is, the solid volume of foam metal is 1.43~8.00μ
/cm ² range, more preferably 2.83-4.98μ/
cm ² range, a battery with large capacitance and low internal resistance can be obtained as mentioned above, but if the solid volume of the foam metal exceeds the above range, air will be released during the molding process. As a result, the amount of air remaining on the foamed metal side of the formed anode increases, reducing the amount of anode active material filled, and the force of repelling the electrolyte due to the oxide film on the foamed metal surface increases, and the metal solid on the anode surface increases. As the area of the anode becomes larger, the area of the holes that keep the electrolyte connected on the anode surface becomes smaller, making it difficult for the electrolyte to flow, making it impossible to obtain the desired discharge voltage and capacitance. In addition, since the foamed metal cannot be compressed while containing the anode mixture in the voids on its surface, polarization increases during battery discharge, and conversely, if the solid volume of the foamed metal is smaller than the above range, However, it is currently impossible to manufacture such foamed metal, and there are concerns that it will be difficult to withstand the pressure when sealing the battery. In addition, in this invention, when storing the molded anode in the anode can, it is stored in the anode can so that the foamed metal side can come into contact with the separator, but this is because the foamed metal is porous and electrolytic. This is to improve battery performance by bringing the anode mixture into contact with the electrolyte over a wide area by taking advantage of its excellent ability to retain liquid. Therefore, as mentioned above, a foam metal is used, which has a solid volume of 8.00 μ/cm ² or less, which is a small volume occupied by the metal solid on the surface. The foamed metal used in this invention is, for example, metal-plated on the entire surface of the net-like part of a polyurethane foam to form a continuous ternary network structure having communicating holes inside, and then heated to form a polyurethane foam. A metal foam produced by burning a part and subjecting it to a reduction process, usually nickel or silver foam, especially nickel foam, and usually has a porosity of 45
~99% by volume is used. In this invention, the solid volume is the areal density, that is, the density of the plane of the plate-shaped foam metal divided by the specific gravity of the metal, and the area of the surface of the plate-shaped foam metal 1
It refers to the volume occupied by a metal solid per cm ^2. For example, in the case of foamed nickel, the solid volume range is expressed as an areal density of 12.6 to 70.8 mg/cm ² , preferably 21.5 to 44.1 mg/cm ^2. Become. This invention is suitably applied to molded anodes with a thickness of 0.85 mm or less, especially molded anodes with a thickness of 0.6 mm or less; however, it is suitable for molded anodes with a thickness of 0.85 mm or more. There is no harm in applying it to Furthermore, according to this invention, since the foamed metal is in contact with the anode mixture over a wide area, the conductivity of the anode mixture is improved, and therefore it is possible to reduce or eliminate the addition of conductive additives such as graphite. The amount of anode active material added can be increased accordingly. FIG. 1 is an explanatory cross-sectional view showing the state when manufacturing the molded anode used in the present invention, in which the foamed metal 2 is put into the mold 11 along the cylindrical frame 12 of the mold 11 and the underframe 13, and anode active materials such as first silver oxide, second silver oxide, manganese dioxide, mercury oxide, nickel peroxide, copper oxide, iron sulfide, and silver chloride are added as necessary. The anode mixture 3 made of a conductive additive such as graphite is charged from above the upper frame 14.
The molded anode 1 is manufactured by applying a pressure of 6480 kg/cm ² . The molded anode 1 is not actually a layered metal foam 2 and anode mixture 3 with a clear boundary line as shown in the drawing, but a part of the anode mixture is made of foam metal. enter the void,
It has a structure that is compressed under pressure. Moreover, the solid volume of the foam metal used is 1.43 ~
Since the volume occupied by the metal solid on the surface is small (8.00 μ/cm ^{2 )} ,
The anode mixture 3 is compressed to be contained in the gap up to the bottom surface, that is, the surface that will come into contact with the separator when assembled into a battery. FIG. 2 is a cross-sectional view of a button-type alkaline battery showing an embodiment of the present invention. The formed anode 1 made as described above is placed inside the anode can 6 so that the foamed metal 2 side is in contact with the separator 4. is stored in
The molded anode 1 is partially impregnated with an alkaline electrolyte such as caustic potash or caustic soda. The separator 4 is a stack of, for example, a hydrophilically treated microporous resin film, cellophane, and a liquid-absorbing layer made of vinylon-rayon mixed paper. 5 is a cathode material made by injecting most of the alkaline electrolyte into an amalgamated zinc active material. The anode can 6 is made of nickel-plated iron in which the molded anode 1 and the separator 4 are housed, and the cathode terminal plate 7 with the cathode agent 5 filled in the opening of the can is made of polyethylene, polypropylene, nylon, etc. An annular gasket 8 made of various resins or rubber and having an approximately L-shaped cross section is interposed and fitted,
The open end of the anode can 6 is tightened inward to create a sealed structure inside the battery. The cathode terminal plate 7 is made of a steel plate, with a nickel layer on the outer side to satisfy aesthetics and corrosion resistance, and a copper layer on the inner side to prevent the formation of local batteries with the zinc active material. , a clad plate consisting of a nickel layer and a copper layer is drawn into a shape having a peripheral folded part 9, or a steel plate is formed in advance by a similar method, and then the nickel layer and copper layer are formed by a plating method. was formed. Note that a liquid packing material such as asphalt pitch or fluorine-based oil is interposed between the annular gasket 8, anode can 6, and cathode terminal plate 7 at their contact surfaces. Figure 4 is a characteristic diagram showing the relationship between the solid volume of the foam metal and the amount of discharged electricity, and Figure 5 is a characteristic diagram showing the relationship between the solid volume of the foam metal and the battery's voltage at 5 seconds after the start of 2kΩ discharge and the internal resistance of the battery. It is a characteristic diagram showing a relationship. The battery used to obtain the characteristic diagrams shown in FIGS. 4 and 5 had the configuration shown in FIG.
wt%, manganese dioxide 3.0 wt% and graphite 0.5
% by weight and foamed nickel having various solid volumes were pressure-molded into a disk shape with a thickness of 0.44 mm at 5270 Kg/ ^cm2 , and the electrolyte was 5% by weight. 35% dissolved zinc oxide
A wt % caustic potassium aqueous solution was used. In addition, the amount of discharge electricity is data measured by a method of continuous discharge under a load of 2 kΩ. As shown in FIG. 5, the closed-circuit voltage of the battery increases as the solid volume increases, and then gradually decreases. On the other hand, the internal resistance of a battery once decreases and then gradually increases. Considering the balance between this closed circuit voltage and internal resistance, the solid volume of the foam metal is
It can be said that 1.43 to 8.00 μ/cm ² is preferable. As shown in Figure 4, the amount of discharged electricity gradually decreases as the solid volume increases, but even when the solid volume is 8.00μ/ ^cm2 , it still has a large amount of discharged electricity of about 36mAh. . Table 1 below shows the battery characteristics of a button-type alkaline battery A having the configuration as illustrated in FIG. 2 and a conventional button-type alkaline battery B. Battery A used a molded anode containing an anode mixture consisting of 96.5% by weight of silver oxide, 3.0% by weight of manganese dioxide, and 0.5% by weight of graphite, and foamed nickel (porosity: 94% by volume) with a solid volume of 4.3 μ/cm ² . Battery ^B uses the same anode mixture as Battery A, 0.13 mm thickness, and pedestal height. 0.37mm,
A stainless steel annular pedestal with an outer diameter of 10.75 mm and an inner diameter of 8.25 mm is combined with a circular pedestal of 5270 Kg/cm ² and a thickness of 0.44 mm (diameter
10.91 mm). In both batteries A and B, the electrolyte is
A 35% by weight aqueous solution of caustic potassium in which 5.0% by weight of zinc oxide was dissolved was used.

[Table] As shown in Table 1, the battery A of the present invention has higher open-circuit voltage and closed-circuit voltage and lower internal resistance than the conventional battery B, and the difference is particularly noticeable at low temperatures. Moreover, it has excellent battery performance with a long discharge duration. As described in detail above, the present invention can be used as a molded anode for a button battery with a solid volume of 1.43 to 8.00μ/
cm ² of foamed metal and an anode mixture are integrally pressure-molded, and the anode mixture is also included in the voids on the surface of the foamed metal. According to the present invention, the occurrence of cracks or fractures in the molded anode during the production of molded anodes is suppressed, and the mass production of thin molded anodes becomes possible. A battery with large capacity and low internal resistance even at low temperatures can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view showing the state of manufacturing the molded anode used in this invention;
Fig. 2 is a sectional view of a button-type alkaline battery showing an embodiment of the present invention, Fig. 3 is a sectional view showing a conventional battery in which the molded anode is bent due to spring back, and Fig. 4 is a sectional view of a button-type alkaline battery showing an embodiment of the present invention. FIG. 5 is a characteristic diagram showing the relationship between the solid volume of metal and the amount of discharged electricity, and FIG. 5 is a characteristic diagram showing the relationship between the solid volume of foam metal, internal resistance, and closed circuit voltage. 1... Molded anode, 2... Foamed metal, 3... Anode mixture, 4... Separator, 6... Anode can.

Claims (1)

[Claims] 1 Using a foamed metal with a solid volume of 1.43 to 8.00μ/cm ² , the foamed metal and anode mixture are integrally pressure-molded so that the anode mixture is included in the voids on the surface of the foamed metal. A button-type battery characterized in that a molded anode is housed in an anode can such that the foamed metal side is in contact with a separator.