JPH11288724A - Manufacture of electrode active material holding substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the connecting strength to prevent peeling in sintering by temporarily sintering a green sheet formed of a metal slurry obtained by mixing a foaming agent to a metal powder to form a temporarily sintered body, and sticking this temporarily sintered body to a reinforcing metal plate followed by main sintering to connect the both. SOLUTION: A mixed slurry 1 obtained by mixing nickel powder, a binder and a plasticizer to a solvent is formed into a sheet to form a green sheet 2, and the green sheet 2 is foamed to form a porous foamed sheet 3. The foamed sheet 3 is temporarily sintered at 800-900 deg.C to form a temporarily sintered body 4, which is then put on a reinforcing metal plate 5 to form an integrated base 6. A weight 7 is put thereon, and a main sintering is performed at 1,000-1,200 deg.C in 5% hydrogenous nitrogen. Consequently, the temporarily sintered body 4 is made into a porous sintered metal plate 8 and bonded to the reinforcing metal plate 5 to form an integrated active material holding substrate 9. According to this, the temporarily sintered body 4 is bonded to the reinforcing metal plate 5 by surface contact, and hardly peeled with a high bonding strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an active material holding substrate for an electrode of a storage battery, which is formed by laminating a porous sintered metal plate and a reinforcing metal plate.

[0002]

2. Description of the Related Art In recent years, alkaline storage batteries such as nickel-metal hydride batteries have attracted attention because they have recently been used in batteries of hybrid vehicles. As the anode of a nickel-metal hydride battery or the like, a nickel electrode containing an active material mainly containing nickel hydroxide is usually used.

[0003] The method of manufacturing the nickel electrode is roughly classified into a sintered type and a non-sintered type. The sintering method generally has the advantage of good electrical and thermal conductivity due to the use of a reinforcing metal plate, whereas the non-sintering method has a conductive nickel foam. Since a method of holding an active material mainly composed of nickel hydroxide having no conductivity on a base such as a body is employed, there is an advantage that the packing density of the active material can be increased.

Japanese Patent Application Laid-Open No. Hei 8-1069 has advantages of both the sintered and non-sintered production methods.
No. 06, a method of using an active material holding base formed by integrally sintering and forming a base such as a nickel foam for holding an active material and a reinforcing metal plate for reinforcing the base. There is. The active material holding substrate manufactured by this method can hold a large amount of the active material, so that a battery using the holding substrate has a large capacity, and has a high conductivity, so that a large current can flow. It has the feature of.

A conventional method of manufacturing an active material holding substrate (hereinafter, referred to as an integrated active material holding substrate) formed by integrally sintering and molding a substrate such as a nickel foam as described above and a reinforcing metal plate. Is shown. The production method includes: (1) a step of kneading a foamable resin to form a foamed resin pillar; (2) a step of slicing the foamed resin pillar to form a thin film; and (3) a process of forming a reinforcing metal plate into a core material. (4) a step of applying the nickel powder-containing solution to one or both sides of the reinforcing metal plate with an adhesive, applying a nickel powder-containing solution, and then baking and thermally decomposing the foamable resin, the adhesive, and the like; The steps of sintering the thin film and (5) removing the oxide on the surface of the thin film are the basic manufacturing procedures. In the integrated active material holding substrate manufactured by such a method, the packing density of the active material can be increased, and a large current can flow. Usually, in the production of an electrode, after the active material holding substrate is filled with an active material slurry, the filled substrate is dried, further rolled, and densified.

[0006]

Meanwhile, in the integrated active material holding substrate manufactured by the above-described method, the nickel foam is fired by applying a nickel powder-containing solution to the surface of a foamable resin. 6A, the portion occupied by the foamable resin becomes hollow by firing, and FIG.
As schematically shown in (b), the nickel foam 32 has a structure in which a hollow portion 31 is formed inside a nickel skeleton 30. For this reason, as schematically shown in an enlarged view of a joining portion between the nickel foam 32 and the reinforcing metal plate 33 in FIG. 6B, the joining portion P is in point contact, and The joining strength is reduced. In the sintering, the change in size due to the thermal expansion and contraction of the reinforcing metal plate 33 is negligible, while the nickel foam 32
Greatly shrinks. For this reason, there was a problem that the nickel foam 32 was easily separated from the reinforcing metal plate 33 during sintering.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method for manufacturing an active material holding substrate for an electrode, which is formed by bonding a porous sintered metal plate such as a nickel foam and a reinforcing metal plate. It is another object of the present invention to manufacture an integrated active material holding substrate having a high bonding strength, and to prevent the porous sintered metal plate from peeling from the reinforcing metal plate during sintering.

[0008]

In order to achieve the above object, the present invention provides a method for manufacturing an active material holding substrate for an electrode, which is constituted by bonding a porous sintered metal plate and a reinforcing metal plate. A green sheet is formed from a metal slurry obtained by mixing a powder with a foaming agent, and the green sheet is temporarily sintered to form a temporarily sintered body. Then, the temporarily sintered body is bonded to a reinforcing metal plate. It is characterized in that both are joined by main sintering.

That is, since the calcined body is formed by foaming a metal slurry, the metal skeleton becomes solid,
Therefore, the joint portion with the reinforcing metal plate is also in surface contact, and has a higher joint strength and is less likely to peel off as compared with the conventional type which is a point contact.

Further, by pre-sintering only the green sheet to form a calcined body, the thermal expansion and contraction of the calcined body during the main sintering performed after the pre-sintering can be reduced. Therefore, the difference in thermal expansion and contraction between the calcined body and the metal plate for reinforcement, which is originally small in thermal expansion and contraction, is reduced, and peeling of the calcined body from the metal plate for reinforcement can be prevented. In this case, as long as nickel powder is used as the metal powder of the porous sintered metal plate,
The sintering temperature is 800 to 950 ° C, preferably 900 ° C,
Main sintering temperature is 1000-1200 ° C., preferably 110
By setting the temperature at 0 ° C., the shrinkage can be advanced by 90% or more during the preliminary sintering, and the shrinkage during the main sintering can be suppressed to 1% or less.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for manufacturing an active material holding substrate for an electrode according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an outline of a manufacturing process of an integrated active material holding substrate. First, a mixed slurry is prepared by mixing a metal powder, a binder, a plasticizer, and the like into a solvent. For example,
300 g of nickel powder having an average particle size of 2 μm, and hydroxypropyl methylcellulose 20 as a binder and thickener
g, glycerin 20 g as a plasticizer, and water 20 as a solvent.
A slurry having a composition of 0 g is kneaded with the slurry for 24 hours, and then deaerated under vacuum, and 50% of sodium dodecylbenzenesulfonate is used as a surfactant.
A mixed slurry 1 is prepared by mixing 20 g of the aqueous solution and then adding 8 g of hexane as a blowing agent.

Next, the mixture slurry 1 is formed into a sheet by a known doctor blade method, slip casting method, coating method or the like, as shown in FIG. . This green sheet 2
Specifically, foaming and sintering are performed in the following procedure. First, the green sheet 2 is set to a humidity of 95, for example.
% In a high humidity atmosphere at a temperature of 40 ° C. for 20 minutes for foaming, and as shown in FIG. The reason why this foaming step is performed while keeping the humidity high is to prevent cracking when the green sheet is foamed after drying. Hexane has a vapor pressure higher than that of water, so that it is easily vaporized to become a gas, and a large number of fine and sized air bubbles are generated, thereby forming a porous foam sheet.
Then, the foamed sheet 3 is dried by using far-infrared rays at an ambient temperature of 50 ° C. for 30 minutes. Furthermore, it is heated at 600 ° C. for 20 minutes in an air atmosphere to degrease it. At this time, the binder and the like are volatilized.

Next, the green sheet 2 is placed in a relatively low temperature range of 800 to 950 ° C.
Pre-sintering is performed at a temperature of 00 ° C. for 20 minutes to form a pre-sintered body 4 of a foamed sheet as shown in FIG.

Then, as shown in FIG. 1 (4), the calcined body 4 is placed on a reinforcing metal plate 5 to form an integral base 6. On this base 6, as shown in FIG. Is placed on a weight 7 made of aluminum oxide or the like to obtain a state shown in FIG. 1 (6).
The main sintering is performed by holding at a high temperature range of 00 ° C., for example, 1100 ° C. for 20 minutes. Thus, the calcined body is made into a porous sintered metal plate 8 and joined to the reinforcing metal plate 5.
An integrated active material holding substrate 9 as shown in (7) is completed.

The reinforcing metal plate in the above-described embodiment is a metal plate obtained by plating an iron plate with nickel and having an aperture ratio of, for example, 60%. Reference numeral 5a in FIG. 2 indicates the hole. Also, a track A shown on the reinforcing metal plate 5 in FIG. 1 (4) indicates the width of the battery, and the reinforcing metal plate 5 in this figure has tracks for two batteries. The calcined bodies 4 are stacked so as to cover the respective tracks A. Since the reinforcing metal plate 5 is used for the purpose of reinforcing the entire substrate 9 and improving the conductivity, any metal material having a different material and a different aperture ratio can be used as long as it can exhibit these functions. It is also possible to use

By being manufactured as described above,
Separation between the porous sintered metal plate and the reinforcing metal plate is reliably prevented. That is, since the calcined body is formed by foaming a metal slurry, FIGS. 2 (a) and 2 (b)
As shown in the above, the metal skeleton 21 has a solid shape, and therefore, the joint Q with the reinforcing metal plate 5 also comes into surface contact, and the joint strength is lower than that of the conventional type which is a point contact. It will be higher.

On the other hand, FIG. 3 shows the state of the characteristic of shrinkage of the green sheet with respect to the sintering temperature. When the sintering temperature is increased, the green sheet starts to shrink greatly from around 700 ° C., and the shrinkage rate near 900 ° C. is 25%.
%, Which indicates that at this temperature, shrinkage of 90% or more, which is already 27%, which is the critical shrinkage ratio of the green sheet, is achieved. On the other hand, although not shown, the change in size due to sintering of the reinforcing metal plate is negligibly small as compared with the green sheet. That is, as usual, the green sheet and the reinforcing metal plate
When sintering is performed at around 00 ° C., the green sheet shrinks by about 27%, whereas the reinforcing metal plate has a negligible change in size due to thermal expansion and contraction. The large difference causes peeling of the green sheet from the reinforcing metal plate during sintering.

Therefore, in the production method of the present invention, first, the green sheet is pre-sintered at around 900 ° C. and shrunk to near the critical shrinkage to produce a calcined body of the green sheet. Then, since the shrinkage of the calcined body in the main sintering is less than 1%, after the pre-sintering, the calcined body is bonded to the reinforcing metal plate, and the main sintering is performed. After that, the difference in size change due to thermal expansion and contraction between the two becomes small, and peeling becomes difficult.

In the production method described in JP-A-8-291304, which is the same as the production method of the present invention except that the step of the preliminary sintering is not included, the green sheet before the sintering has a high strength. Because of low brittleness, during the main sintering, the green sheet is easily crushed by the weight of the reinforcing metal plate, and it is difficult to perform continuous sintering with a long length, but in the case of the manufacturing method according to the present invention, By performing sintering, the green sheet is sintered to form a calcined body, whereby the strength is increased, and continuous sintering with a long length can be performed. Therefore, the production method of the present invention is suitable for mass production, and the production cost can be reduced by mass production.

FIG. 4 and FIG. 5 schematically show a joining step in mass-producing the above-mentioned active material holding substrate. FIG. 4 shows the calcined body 4 shown in FIG. 1 (3) on both surfaces of the unrolled portion of the reinforcing metal plate 5 while rewinding the reinforcing metal plate 5 wound in a roll shape. 2 shows an example of a joining step in which a step of performing main sintering and joining through a sintering furnace 11 while pressing with a load belt 10 after joining is performed continuously. FIG. 5 shows a case where the calcined body is rolled, and the calcined body 4 and the reinforcing metal plate 5 are rewound at the same speed, and are bonded to both sides of the reinforcing metal plate 5 as in the case of FIG. Sintering furnace 1 while pressing with a load belt 10
1 and perform main sintering and joining. Through such a process, the active material holding substrate can be mass-produced.

[0022]

[Experimental example] When an electrode is actually manufactured, the active material holding substrate manufactured in the above-described process is filled with an active material slurry, followed by drying and rolling. Therefore, for the active material holding substrate manufactured by the method according to the present invention, the effectiveness in preventing the porous sintered metal plate such as the calcined body or the nickel foam from being peeled off from the reinforcing metal plate is evaluated. For the purpose of investigation, an active material holding substrate by the manufacturing method according to the present invention and a conventional method (Japanese Patent Laid-Open No. 8-106)
No. 906) was used to compare the state of peeling when an electrode was actually manufactured using the active material holding substrate.

The active material slurry has an average particle size of 10 μm.
m nickel hydroxide powder 50 g, Teflon dispersion solution 5 g,
What mixed 10 g of water was used. The electrode was manufactured by including the active material slurry on the active material holding substrate, drying at 100 ° C. for 30 minutes, and then rolling at a reduction of 50%. As a result, when the active material holding substrate manufactured by the conventional method was used, peeling of the nickel foam from the reinforcing metal plate was confirmed, whereas the active material holding substrate according to the manufacturing method of the present invention was used. In this case, peeling of the calcined body was not confirmed.

From the above experimental results, the active material holding substrate manufactured by the manufacturing method of the present invention is used as a method for preventing peeling of the porous sintered metal plate from the reinforcing metal plate during sintering. Was confirmed to be effective.

[0025]

As described above in detail, according to the method for manufacturing an active material holding substrate for an electrode according to the present invention, the following effects can be obtained.

(1) Since the calcined body is formed by foaming a metal slurry, its metal skeleton is solid, and therefore, the joint with the reinforcing metal plate is also in surface contact and is in point contact. Compared with the conventional type, the bonding strength is high and it is hard to peel off.

(2) Before laminating the green sheet and the reinforcing metal plate and performing main sintering, only the green sheet is preliminarily sintered to form a calcined body, so that both of the green sheet and the reinforcing metal plate during the main sintering are formed. It is possible to prevent the calcined body from peeling off from the reinforcing metal plate due to the difference in thermal expansion and contraction rate.

(3) By performing the preliminary sintering, the green sheet is sintered and becomes a calcined body, the strength is increased, and it is possible to perform continuous sintering in a long length. Therefore, the production method of the present invention is suitable for mass production, and the production cost can be reduced by mass production.

(4) Nickel is used as the metal powder of the metal slurry.
When the temperature is set at around 100 ° C., the contraction rate of the porous sintered metal plate at the time of the main sintering can be made 1% or less, the bonding strength with the reinforcing metal plate is high, and the porous metal plate does not easily peel off.

[Brief description of the drawings]

FIG. 1 is a schematic process chart of an embodiment according to a production method of the present invention.

FIG. 2 (a) is a schematic view of a joint portion between a porous sintered metal plate and a reinforcing metal plate when manufactured by the manufacturing method of the present invention. (B) It is the schematic diagram which expanded the joining site | part.

FIG. 3 is a graph showing shrinkage characteristics with respect to a sintering temperature of a green sheet.

FIG. 4 is a schematic view showing a step of joining a porous sintered metal plate while continuously supplying a reinforcing metal plate.

FIG. 5 is a schematic view showing a joining step in which a calcined body is rolled and joined while being supplied to a reinforcing metal plate.

FIG. 6A is a schematic view of a joint portion between a porous sintered metal plate and a reinforcing metal plate when manufactured by a conventional manufacturing method. (B) It is the schematic diagram which expanded the joining site | part.

[Explanation of symbols]

 2 green sheet 4 calcined body 5 reinforcing metal plate 7 weight 8 porous sintered metal plate 9 integrated active material holding substrate 10 load belt P joint Q joint

Claims (2)

[Claims] 1. A method for manufacturing an active material holding substrate for an electrode, comprising bonding a porous sintered metal plate and a reinforcing metal plate, wherein a green sheet is prepared by mixing a metal powder with a foaming agent. And forming a calcined body by calcining the green sheet to form a calcined body, then superimposing the calcined body on a reinforcing metal plate, and sintering the two to join them together. A method for manufacturing an active material holding substrate for an electrode. 2. The active material for an electrode according to claim 1, wherein the metal powder is a nickel powder, and the temperature of the preliminary sintering is set to 800 to 950 ° C. and the temperature of the main sintering is set to 1000 to 1200 ° C. Manufacturing method of holding substrate.