JPH05325978A - Nickel sintered substrate and manufacture thereof for alkaline storage battery - Google Patents

Abstract

PURPOSE:To provide a sintered substrate for an alkaline storage battery wherein peeling strength can be highly maintained even when porosity is improved by increasing mixing ratio of nickel powder of large mean grain size. CONSTITUTION:A sintered substrate is manufactured by using nickel slurry contained with mixed nickel powder of mixing the first nickel powder of 0.5 to 1.5mum Fischer grain size and o.4o to 0.65g/cm<3> bulk density with the second nickel powder of 2.5 to 4.0mum Fischer grain size and 0.30 to 0.52g/cm<3> bulk density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel sintered substrate for an alkaline storage battery and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, when manufacturing a nickel sintered substrate for an alkaline storage battery, a nickel slurry is prepared by mixing nickel powder, a binder and water, and nickel is used as a core material of nickel or a nickel-plated iron perforated plate. After applying the slurry, a sintered body is formed on the core material through the steps of drying and sintering. In the conventional manufacturing method, the bulk density is 0.50 to 0.
Fisher particle size is 2.2-2.8 μm at 65 g / cm ^3.
The nickel powder which consisted of the above powder was used. When this nickel powder was used to sinter nickel slurry at a temperature of 800 to 900 ° C. in a reducing atmosphere, the porosity of the sintered plate was 79 to 81%. Since the electrode active material is filled in the voids (porous portions) of the sintered substrate, the higher the porosity of the sintered substrate, the larger the capacity of the battery. Therefore, various methods for increasing the porosity of the sintered substrate have been conventionally proposed. For example, as a method of increasing the porosity of a sintered substrate, a method of lowering the sintering temperature and shortening the sintering time has been proposed. However, the sintered substrate obtained by this method has a problem of extremely low strength. In addition, a method of mixing a pore-forming agent with nickel slurry has been proposed (Japanese Patent Laid-Open No. 58-66267). As the pore-forming agent used in this method, a material made of a combustible and decomposable organic material such as cellulose or polystyrene is used, and the pore-forming agent decomposes and burns out during sintering. as a result,
The portion where the pore-forming agent is burnt out becomes pores, and the porosity of the substrate increases. However, in the method using this pore forming agent, there is a problem that the pore forming agent expands and decomposes in the drying stage before sintering, resulting in uneven porosity or insufficient increase in porosity.

Therefore, as a method for increasing the porosity without using a pore-forming agent, as disclosed in JP-A-2-139864, nickel powder having an average particle diameter of 2.2 to 2.8 μm and average particles are used. It has been proposed to manufacture a sintered substrate using mixed nickel powder mixed with nickel powder having a diameter of 3.0 to 4.0 μm. In the invention disclosed in this publication, nickel powders having different particle diameters are used for the following reasons. First, nickel powder with a large average particle size (3.0 to
If the sintered substrate is manufactured using only 4.0 μm), the porosity of the sintered substrate can be increased. However, there is a problem that the trunk of the sintered body becomes thick and the flexibility of the sintered substrate decreases, and the peeling strength of the sintered body from the core material decreases. On the contrary, when a sintered substrate is manufactured using only nickel powder (2.2 to 2.8 μm) having a small average particle size, the flexibility of the sintered substrate increases,
The peeling strength of the sintered body from the core material can be maintained high. However, since the trunk of the sintered body becomes thin, shrinkage easily progresses during sintering, and the porosity is likely to decrease. Therefore, in the invention disclosed in this publication, by using a mixed nickel powder in which both nickel powders are mixed, a problem that occurs when only each nickel powder is used is compensated for, the porosity is high, and the core material is peeled off. We are trying to obtain a sintered substrate with high strength. Specifically, the mixing ratio of both nickel powders is 1: 1. When a sintered substrate is manufactured using the mixed nickel powder having such a mixing ratio, a sintered portion having a porosity of about 80% formed by the nickel powder having an average particle diameter of 2.2 to 2.8 μm and an average A sintered portion having a porosity of about 88% formed of nickel powder having a particle diameter of 3.0 to 4.0 μm is dispersed and formed, and a sintered body having an average porosity of about 85% is obtained. be able to.

[0004]

However, in order to produce a sintered substrate having a porosity of 85% or more by the conventional method, the amount of nickel powder having an average particle size of 3.0 to 4.0 μm is changed to the average particle size. If the amount of nickel powder of 2.2 to 2.8 μm is increased, the peeling strength of the sintered substrate will decrease, and the sintered body will peel off from the core during the process of impregnation / formation and assembly of the active material. It was found that there is a problem that the active material falls off.

An object of the present invention is to provide a sintered substrate for an alkaline storage battery which can maintain high peeling strength and a method for producing the same even if the porosity is increased by increasing the mixing ratio of nickel powder having a large average particle size. That is.

[0006]

According to a first aspect of the invention, a bulk density of 0.40 to 0.65 is intended for a nickel sintered substrate for an alkaline storage battery obtained by sintering a nickel slurry.
First nickel powder with g / cm ³ and Fisher particle size of 0.5-1.5 μm, and bulk density of 0.30-0.52 g / cm
^In No. ³ , a nickel slurry containing a mixed nickel powder mixed with a second nickel powder having a Fisher particle size of 2.5 to 4.0 μm is used. The Fischer particle size is a particle size measured by Subsieve Sizer (trademark) manufactured by Fischer Co., as is well known.

According to the second aspect of the invention, the content of the first nickel powder in the mixed nickel powder is 5 to 20% by weight.

According to the third aspect of the present invention, a slurry producing step of producing a nickel slurry by mixing nickel powder, a binder and water, and a step of applying the nickel slurry to a core material and drying the nickel slurry are performed. A method for producing a nickel sintered substrate for an alkaline storage battery, which comprises a sintering step of sintering, with a bulk density of 0.40 to 0.65 g / cm ³ and a Fisher particle size of 0.5 to 1.5 μm. The first nickel powder subjected to the agglomeration prevention treatment and the bulk density of 0.30
Fisher particle size is 0.5-4.0 at 0.52 g / cm ^3.
A mixed nickel powder mixed with a second nickel powder of μm is used as the nickel powder.

[0009]

The first nickel powder having a bulk density of 0.40 to 0.65 g / cm ³ and a Fischer particle size of 0.5 to 1.5 μm, and a bulk density of 0.30 to 0.52 g / cm ³ When mixed with a second nickel powder having a Fischer particle diameter of 2.5 to 4.0 μm, secondary particles are formed in which the first nickel powder and the second nickel powder are connected to each other. And this 2
The secondary particles can be formed even if the amount of the first nickel powder is decreased and the amount of the second nickel powder is increased within the range of the above requirements. Therefore, according to the first aspect of the present invention, it is possible to obtain a sintered substrate in which the peeling strength can be maintained high even if the mixing ratio of the second nickel powder is increased and the porosity is increased as compared with the prior art. Further, since the first nickel powder can be sintered at a low temperature and in a short time, the present invention also has an advantage of improving sinterability.

When the content of the first nickel powder is 5 to 20% by weight as in the second aspect of the present invention, a porosity of 85% or more is obtained within a range in which the peel strength can be maintained sufficiently high. You can

According to the third aspect of the present invention, since the first nickel powder subjected to the agglomeration prevention treatment is used,
The first nickel powder can be mixed with the second nickel powder almost uniformly. Therefore, the porosity is high,
A sintered substrate with high peel strength can be obtained. Moreover, since the first nickel powder is mixed almost uniformly with the second nickel powder, the present invention has an advantage that the sinterability is improved.

[0012]

Embodiments of the present invention will be described in detail with reference to the drawings. In the example, the sintered substrate was manufactured as follows. First, the bulk density in the distribution range of A in FIG.
Fisher particle size is 0.5 to 1.5 at 0.65 g / cm ^3.
1 μm of the first nickel powder and a second nickel powder having a bulk density of 0.30 to 0.52 g / cm ³ and a Fischer particle diameter of 2.5 to 4.0 μm in the distribution range of FIG. 1B. Was mixed so that the content of the first nickel powder was 5 to 20% by weight to prepare a mixed nickel powder. As can be seen from the states of the first nickel powder and the second nickel powder shown in FIGS. 2 (A) and 2 (B), the primary particles A1 and B1 are aggregated to form the secondary particles A2. B2 is formed. It is preferable that the first nickel powder used in this example has a minimum agglomeration rate. Therefore, in the present embodiment, as the first nickel powder, one subjected to a coagulation prevention treatment was used. The aggregation prevention treatment was performed as follows.
First, a mixed solution is prepared by adding a predetermined amount of the first nickel powder to an aqueous solution of polytetrafluoroethylene (PTFE) disversion (trade name: D-1) (0.1 wt% in PTFE solid content), and the mixed solution Was sonicated for 30 minutes. Next, this mixed solution was filtered to extract the first nickel powder, and after sufficiently removing water from the first nickel powder, it was sufficiently dried at a temperature of 100 ° C. to complete the aggregation prevention treatment. .. When mixing the first nickel powder subjected to the agglomeration prevention treatment with the second nickel powder, the first nickel powder is passed through a sieve and sprinkled on the second nickel powder to mix. The reason for sieving is that the first nickel powder is dispersed as much as possible and mixed with the second nickel powder. The amount of PTFE attached to the first nickel powder is extremely small, and it decomposes and disappears during sintering. Needless to say, a sieve may be used for the first nickel powder that has not been subjected to the aggregation prevention treatment. In that case, the first nickel powder is sprinkled on the second nickel powder through the sieve in the same manner as described above to mix the first nickel powder and the second nickel powder. If the first nickel powder is dispersed while eliminating particles that have agglomerated and increased in size by passing through a sieve, the first nickel powder and the second nickel powder can be mixed when the first nickel powder is mixed. Although the nickel powder may partly aggregate, it can be put to practical use. FIG. 3 is a schematic diagram showing particles of the mixed nickel powder of the first nickel powder and the second nickel powder thus mixed. As shown in this figure, the mixed nickel powder is formed by the secondary particles C in which the primary particles A1 of the first nickel powder and the primary particles B1 of the second nickel powder are connected to each other.

The thus-prepared mixed nickel powder is kneaded with an appropriate binder aqueous solution in which a binder and water are mixed to prepare a nickel slurry, which is burned by a production line having a configuration schematically shown in FIG. A bonded substrate was manufactured. More specifically, first, the sheet-shaped perforated plate 1 was immersed in a tank 2 containing nickel slurry. Next, while pulling up the perforated plate 1 from the tank 2, the excess nickel slurry was cut off by the slits 3 to adjust the thickness of the slurry on both surfaces of the perforated plate 1. After that, the slurry was dried through a drier 4, and then the dried slurry was sintered in a sintering furnace 5 having a furnace temperature of 700 to 1000 ° C. in a reducing atmosphere to manufacture a sintered substrate.

Next, two types of SC type batteries D and E were made in order to investigate the characteristics of the sintered substrate of this example manufactured as described above. Battery D was manufactured by using a mixed nickel powder in which the first nickel powder and the second nickel powder were mixed so that the content of the first nickel powder was 20% by weight. It is a battery made using the sintered substrate of. Battery E was manufactured using a mixed nickel powder prepared by mixing nickel powder having an average particle diameter of 2.2 to 2.8 μm and nickel powder having an average particle diameter of 3.0 to 4.0 μm in a weight ratio of 1: 1. It is a battery made using the sintered substrate of. The batteries D and E were repeatedly charged and discharged, and the discharge characteristics (discharge current 5C) at the 200th cycle were examined. FIG. 5 shows the measurement result. From this figure, it is understood that the battery D using the sintered substrate of this example has higher discharge capacity and discharge voltage than the battery E using the conventional sintered substrate.

Next, the relationship between the content of the first nickel powder in the mixed nickel powder and the porosity and strength of the sintered substrate was investigated. FIG. 6 shows the measurement result. In the figure, curves F1 and F2 represent changes in porosity of the sintered substrate and changes in peel strength of the sintered body from the core material, respectively, produced by changing the content of the first nickel powder in the mixed nickel powder. Shows. The curves G1 and G2 are
The changes in the porosity of the sintered substrate and the changes in the peeling strength from the core material of the sintered body produced by changing the content of the first nickel powder not subjected to the agglomeration prevention treatment in the mixed nickel powder are respectively shown. There is. The sintered substrate used in this test was burned in this example except that the first nickel powder was subjected to a coagulation prevention treatment and the content of the first nickel powder in the mixed nickel powder was changed. It was manufactured in the same manner as the bonded substrate. Further, the porosity P was obtained by the method of substituting the pores with water and calculated by the following formula.

P = (I−H) / {(H−J) / K + (I−H)} In the above formula, H is the weight of the dried sintered substrate, and I
Is the weight of the sintered substrate with pores replaced with water. J is the weight of the perforated plate and K is the true density of metallic nickel. In addition, the peel strength is measured by Quad Group in the United States.
It was measured by a Sebastian type I tester manufactured by p.

From this figure, the first in the mixed nickel powder
It can be seen that when the content of the nickel powder is 5 to 20% by weight, a sintered substrate having high porosity can be obtained within a range in which the peeling strength can be maintained sufficiently high. By the way, when the content of the first nickel powder in the mixed nickel powder is 20% by weight, the sintered substrate shown by the curves G1 and G2 has a porosity of 86.8% and a peel strength of 1.5.
It becomes MPa. The peeling strength is a peeling strength that can sufficiently endure winding. The peeling strength is the same as the porosity (86.
8%) has a peel strength of 5 times or more that of a sintered substrate,
Same porosity (86.8) using conventional mixed nickel powder
%), Which is twice the peel strength of the sintered substrate.

[0018]

According to the first aspect of the present invention, it is possible to obtain a sintered substrate capable of maintaining high peeling strength even when the second nickel powder is mixed at a high mixing ratio to increase the porosity as compared with the prior art. You can Therefore, when the sintered substrate of the present invention is used, a battery having a large discharge capacity and a high battery voltage can be obtained. Further, since the first nickel powder can be sintered at a low temperature and in a short time, the present invention also has an advantage of improving sinterability.

According to the invention of claim 2, since the content of the first nickel powder is 5 to 20% by weight, a porosity of 85% or more is obtained within a range in which the peel strength can be maintained sufficiently high. be able to.

According to the third aspect of the present invention, the first nickel powder is subjected to the coagulation preventing treatment, so that the first nickel powder can be mixed with the second nickel powder almost uniformly. Therefore, a sintered substrate having high porosity and high peel strength can be obtained. Moreover, since the first nickel powder is mixed almost uniformly with the second nickel powder, the present invention has an advantage that the sinterability is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing distribution ranges of Fischer particle size and bulk density of particles of each nickel powder used for a sintered substrate of the present invention.

FIG. 2A is a schematic diagram showing particles of a first nickel powder, and FIG. 2B is a schematic diagram showing particles of a second nickel powder.

FIG. 3 is a schematic diagram showing particles of a mixed nickel powder used for the sintered substrate of the present invention.

FIG. 4 is a schematic view showing a part of a process line for producing a sintered substrate of the present invention.

FIG. 5 is a diagram showing discharge characteristics of a battery used in a test in which charging and discharging are repeated.

FIG. 6 is a diagram showing the relationship between the content of the first nickel powder in the mixed nickel powder and the porosity and strength of the sintered substrate.

[Explanation of symbols]

 1 Perforated Plate 2 Tank 3 Slit 4 Dryer 5 Sintering Furnace

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Tsunoda 1-1-1, Nishishinjuku, Shinjuku-ku, Tokyo Inside Shin-Kindo Electric Co., Ltd. (72) Mitsuru Koseki 1-2-1, Nishishinjuku, Shinjuku-ku, Tokyo No. 1 Shinjin To Denki Co., Ltd.

Claims (3)

[Claims] 1. A nickel sintered substrate for an alkaline storage battery, which is obtained by sintering a nickel slurry, wherein the nickel slurry has a bulk density of 0.40 to 0.65 g / cm ³ and a Fisher particle size of 0.5. Mixed nickel powder in which a first nickel powder having a particle size of ˜1.5 μm and a second nickel powder having a bulk density of 0.30 to 0.52 g / cm ³ and a Fischer particle size of 2.5 to 4.0 μm are mixed. A nickel sintered substrate for an alkaline storage battery, which comprises: 2. The first in the mixed nickel powder
The nickel sintered substrate for alkaline storage batteries according to claim 1, wherein the content of said nickel powder is 5 to 20% by weight. 3. A slurry manufacturing step of manufacturing a nickel slurry by mixing nickel powder, a binder and water, and applying the nickel slurry to a core material and drying it, and then sintering the nickel slurry. A method for producing a nickel sintered substrate for an alkaline storage battery, comprising a sintering step, wherein the nickel powder has a bulk density of 0.40 to 0.65.
The first nickel powder having a Fischer particle size of 0.5 to 1.5 μm at g / cm ³ and an anti-agglomeration treatment, and a bulk density of 0.30 to 0.52 g / cm ³ at a Fisher particle size of 2 ．
A method for manufacturing a nickel sintered substrate for an alkaline storage battery, which comprises using a mixed nickel powder mixed with a second nickel powder having a size of 5 to 4.0 μm.