JP3158417B2 - Electrodes for alkaline storage batteries - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]

The present invention relates to an electrode plate for an alkaline storage battery,
In particular, the present invention relates to a so-called sintered metal type electrode plate for an alkaline storage battery.

[0002]

[Prior art]

A conventional sintered metal type alkaline storage battery electrode plate has a sintered metal layer formed using a perforated plate such as a mesh knitted with a nickel wire or a punched metal made of stainless steel as a core metal, and the sintered metal layer is activated. Substance is retained. Specifically, a slurry obtained by kneading nickel powder with a binder such as methylcellulose as a binder is collectively applied to a perforated plate via a slitter by a doctor blade method and dried, and then sintered in a reducing atmosphere such as hydrogen. Then, a sintered substrate is formed, and the sintered substrate is filled with an active material.

[0003] Sintering-type electrodes for alkaline storage batteries have conflicting demands to increase the holding amount of the active material and to improve the holding strength and current collecting characteristics of the active material. In order to increase the retention amount of the active material, the porosity (the volume of the sintered metal becomes smaller) by making the skeleton of the current collector network composed of the sintered metal layer thinner and increasing the pore size of the pores. It is necessary to increase the ratio to the total volume of the layer. However, if the porosity is too high, the mechanical strength of the sintered metal layer decreases, and the holding strength of the active material decreases. This is because the bonding strength between the perforated plate and the sintered metal layer depends on the size of the contact area and the degree of corrosion of the sintered metal layer near the perforated plate, and the skeleton of the current collector network is thin. As a result, the contact area decreases and the influence of corrosion increases.

On the other hand, in order to increase the holding strength of the active material and improve the current collection characteristics, the skeleton of the current collector network made of the sintered metal layer is made thicker, and the pore size of the pores is made smaller. Porosity must be reduced.

In order to increase only the porosity, for example, a pore-forming agent such as a microballoon is added to a slurry for forming a sintered metal layer, or a powder shape of nickel powder which is a material for forming the sintered metal layer. Can be dealt with by changing However, if the porosity of the sintered metal layer alone is simply increased, the holding strength of the active material (mechanical strength of the sintered metal layer) is reduced as described above, so that a cylindrical battery is formed during the production of the electrode plate. Of the active material is likely to occur in the winding process of the electrode plate, for example, and the short circuit (short circuit) between the electrodes or between the electrodes and the container is likely to occur after filling the container. .

[0006] Therefore, in order to increase the mechanical strength of the sintered metal layer, it has been considered to manufacture a sintered metal layer by mixing nickel fibers in a nickel slurry. However, since the specific surface area of the nickel fiber is smaller than the specific surface area of the nickel powder, there is a problem that the surface energy of the nickel fiber is small and sintering is difficult. To solve this problem, it has been considered that a large amount of heat is applied to form a sintered metal layer.
However, even if a sintered metal layer can be formed, since the nickel fibers protrude from the sintered metal layer, the protruding nickel fibers break the separator forming the electrode plate group, causing a short circuit in the battery. In addition, during the step of applying the slurry to the perforated plate via the slitter by the doctor blade method, a problem arises in that the nickel fibers cling to the slitter.

Therefore, a first sintered metal layer mainly made of nickel powder and a second sintered metal layer are laminated on a perforated plate to form a sintered metal layer, and a first sintered metal layer in contact with the perforated plate is formed. There is also proposed a method in which the porosity of the sintered metal layer is set lower than that of the second sintered metal layer, and the active material is retained in the second sintered metal layer having a high porosity existing on the surface.

[0008]

[Problems to be solved by the invention]

However, the first and second sintered metal layers are different in porosity.
The electrode plate for alkaline storage batteries formed of the sintered metal layer of
1. In order to change the porosity of the second sintered metal layer, the same nickel powder is used as the main raw material, and the mixing ratio of the binder solution is changed (Japanese Patent Laid-Open No. 48-7248). Since water-insoluble cellulose or microballoons have been added as an agent (Japanese Patent Application Laid-Open Nos. 48-8033 and 61-23706), the following problems have been encountered.

(A) Since the slurry contains water-insoluble cellulose and microballoons, it is easy to peel off from the perforated plate after drying.

(B) If water-insoluble cellulose or microballoons are added to the slurry, they are lifted up, the slurry viscosity is not stable, and the product tends to vary.

An object of the present invention is to stably form a sintered metal layer having a high bonding strength of a first sintered metal layer to a perforated plate and a large holding strength of an active material to a second sintered metal layer. An object of the present invention is to provide an electrode plate for an alkaline storage battery that can be configured.

[0012]

[Means for Solving the Problems]

According to the present invention, a sintered metal layer is formed using a perforated plate as a core metal, and the sintered metal layer is formed on a perforated plate by a first sintered metal layer and a second sintered metal layer mainly composed of nickel powder. Are laminated with the first sintered metal layer adjacent to the perforated plate, the first sintered metal layer is set to have a lower porosity than the second sintered metal layer, and the second sintered metal layer is mainly It is intended for an alkaline storage battery electrode plate in which an active material is held in a layer.

In the electrode plate for an alkaline storage battery according to the present invention, the nickel powder forming the first sintered metal layer has an average particle diameter of 2 to 2.
8 μm, the bulk density is 1.0 to 3.0 g / ml, and the nickel powder for forming the second sintered metal layer 3 has an average particle size of 2 μm.
４4 μm and a bulk density of 0.4-1.0 g / ml.

[0014]

Effect of the Invention

As described above, as the nickel powder forming the first sintered metal layer, the average particle diameter is 2 to 8 μm, and the bulk density is 1.0.
~ 3.0 g / ml, the average particle diameter of the nickel powder forming the second sintered metal layer is 2-4 μm,
When the powder having a bulk density of 0.4 to 1.0 g / ml is used, the nickel powder forming the first sintered metal layer has a higher bulk density than the nickel powder forming the second sintered metal layer. In addition, there is no need to include water-insoluble cellulose or microballoons in the slurry, and the first sintered metal layer is less likely to peel off from the porous plate during drying. Further, since water-insoluble cellulose and microballoons are not added to the slurry, the slurry viscosity is stable, the product hardly varies, and a stable product can be obtained.

Further, since the sintered metal layer forms a first sintered metal layer made of a sintered body having a thick skeleton near the perforated plate using nickel powder having a large particle diameter, The contact area between the sintered metal layer and the perforated plate is large, and the first sintered metal layer adjacent to the perforated plate is less susceptible to corrosion, and the bonding strength of the sintered metal layer to the perforated plate can be increased. In addition, current collection performance can be improved. Also, since the bonding strength between the first sintered metal layer and the perforated plate can be increased, even if the porosity of the second sintered metal layer away from the perforated plate is increased to increase the amount of active material retained, The sintered metal layer holding the active material does not easily peel off from the perforated plate, and a high capacity of the battery can be achieved. Further, since no metal fiber or the like is mixed, the occurrence of a short circuit can be prevented.

[0016]

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a main part of an electrode plate for an alkaline storage battery according to one embodiment of the present invention. In the figure, 1 is a perforated plate made of low carbon steel as a core metal, 2 is a first sintered metal layer having low porosity formed in a portion adjacent to the perforated plate 1, and 3 is a first sintered metal layer. A second sintered metal layer having a high porosity laminated on the first sintered metal layer 2;
And the sintered metal layer 3 constitutes a sintered metal layer 4. The first and second sintered metal layers are formed using nickel powder as a main raw material. The nickel powder forming the first sintered metal layer 2 has a higher bulk density than the nickel powder forming the second sintered metal layer 3. That is, as the nickel powder forming the first sintered metal layer 2, the average particle diameter is 2 to 8 μm, and the bulk density is 1.
0 to 3.0 g / ml is used, and as the nickel powder forming the second sintered metal layer 3, the average particle diameter is 2 to 4 μm.
m, having a bulk density of 0.4 to 1.0 g / ml.
As a result, the first sintered metal layer 2 becomes the second sintered metal layer 3
The porosity is set lower. Note that the active material is mainly held by the second sintered metal layer 3.

Next, a method of manufacturing the electrode plate of the embodiment shown in FIG. 1 will be described. In this example, the sintered metal layer 4 was manufactured using two types of slurries. First, 100 g of water and 5 g of methylcellulose as an organic pressure-sensitive adhesive were added and kneaded to prepare a paste liquid composed of the organic pressure-sensitive adhesive. Next, 200 g of nickel powder of # 123 manufactured by International Nickel Corporation was added to the size liquid,
A first slurry (hereinafter, referred to as slurry A) was prepared by kneading under a reduced pressure of −700 mmHg or less.

In addition, 70 g of # 255 nickel powder manufactured by International Nickel Corporation and 3 g of microballoons called F5C manufactured by Matsumoto Yushi Seiyaku Co., Ltd.
A second slurry (hereinafter referred to as slurry B) was prepared by adding 0.2 g of a defoamer made of Wako Pure Chemical Industries, Ltd. consisting of phosphoric acid-tri-n-butyl phosphate and kneading under reduced pressure of -700 mmHg or less.

Next, a perforated plate 1 composed of a perforated plate having holes formed in low carbon steel
Slurry A is applied to both sides using the doctor blade method.
20 μm was applied and dried at 150 ° C. for 20 minutes. After drying, slurry B was applied thereon using the doctor blade method,
Dry at 20 ° C. for 20 minutes. Next, the slurry A and B were sintered in a reducing atmosphere containing hydrogen at a temperature of 900 ° C. for 5 minutes to obtain a sintered substrate for an alkaline storage battery. In the completed electrode plate, the porosity of the first sintered metal layer 2 was 61%, and the porosity of the second sintered metal layer 3 was 86%.

The sintered substrate was filled with nickel hydroxide as an active material by a chemical impregnation method to obtain an anode plate. The filling rate of the active material in this example was 2.3 g / cc · vold.

The nickel powder for forming the first sintered metal layer 2 has an average particle diameter of 2 to 8 μm and a bulk density of 1.0 to 3.0.
g / ml powder, nickel powder for forming the second sintered metal layer 3 is nickel having an average particle diameter of 2 to 4 μm and a bulk density of the first sintered metal layer 2. A lower powder, 0.4-1.0 g / ml, was used.

Next, in order to compare various characteristics between the electrode plate of the present embodiment and a conventional electrode plate, electrode plates A to D shown in the following table were produced, and various experiments were performed.

The electrode plate A is the electrode plate of the above embodiment of the present invention.

The electrode plate B is an electrode plate having a sintered metal layer formed using the slurry B used for forming the second sintered metal layer 3 of the electrode plate of the above embodiment. Therefore, the sintered metal layer has the same porosity of 86% as the second sintered metal layer 3 of the above embodiment.

The electrode plate C was prepared by adding 100 g of # 255 nickel powder manufactured by International Nickel Corporation to 105 g of the adhesive liquid composed of the organic pressure-sensitive adhesive used in the above-described embodiment to form a slurry, and this was used as a porous plate. This is an electrode plate provided with a sintered metal layer having a porosity of 81% obtained by applying, drying and sintering.

The electrode D is an electrode having a porosity of 76% for the sintered metal layer manufactured using the same material as the electrode C. In the table below, data of various characteristics obtained in various experiments are also shown.

[0028] In the above table, the unit of the active material filling rate is “g / cc
ld ". Here, the capacity is calculated based on the product of the active material filling rate and the active material utilization rate. In the above table, the capacity of the electrode plate A is 1.0, and the capacity of each electrode plate is shown. Incidentally, the active material utilization rate of the electrode plate A was 83%, and the active material utilization rate of the electrode plate C was 85%. The peel strength was calculated based on the value obtained by measuring the adhesion between the sintered metal layer and the perforated plate using a Sebastian Tester manufactured by Qnad Group in the United States. Specifically, the measured value of the electrode plate A of the embodiment of the present invention is
The peel strength of each electrode plate is shown as 1.0. In addition, the short-circuit rate is a value indicating, as a percentage, how many batteries are short-circuited when 1,000 AA-type batteries are prepared using each electrode plate. Generally, the peel strength tends to decrease as the porosity increases. Incidentally, the peel strength of a 90% porosity electrode plate manufactured in the same manner as the electrode plate B is as follows.
0.52, and the short circuit rate was 0.022%.

When the electrode plate A and the electrode plate B are compared, the porosity of the portion holding the active material is the same, but the peel strength of the electrode plate is approximately equal to that of the electrode plate B of the present invention. It shows a high value of 1.67 times, and the short ratio shows a high value of 15 out of 1000 electrode plates B. This shows that even if the porosity of the portion holding the active material is the same, the use of the electrode plate of the present invention can significantly improve the peel strength and short-circuit rate of the electrode plate.

When the electrode plate A is compared with the electrode plates C and D, the values of the peel strength of the electrode plates are approximately similar, but the electrode plates A and C have the same capacity. About 1.15 times and about 1.
It shows a high value of 26 times. From the above, it can be seen that the capacity of the electrode plate of this embodiment is greatly improved as compared with the conventional electrode plate having substantially the same peel strength and short-circuit rate.

FIGS. 2A and 2B are SEM photographs of the electrode plate A of the present embodiment and the conventional electrode plate B near the perforated plate, respectively. From these photographs, it can be seen that the conventional electrode plate B has a thinner metal portion of the sintered metal layer than the electrode plate A of the present embodiment, and corrosion due to chemical impregnation has also progressed. It is considered that the difference between the peel strength and the short-circuit rate in the above table is sufficiently affected by the difference in the corrosion state.

In the above-described embodiment, the first and second sintered metal layers 2 and 3 are formed by one sintering using two types of slurries having different materials, but are formed of a single material. It is also possible to form two sintered metal layers having different porosity by using a slurry.
In this case, the slurry is applied to the perforated plate, dried and sintered once to form a first sintered metal layer, and then the same slurry is applied again on the first sintered metal layer. And dry,
The second sintered metal layer may be formed by sintering with less heat than the previous sintering. This method requires two sinterings, which increases the manufacturing cost. Further, as the porous plate, a plate obtained by plating nickel on low carbon steel is generally used, but there is a problem that the corrosion resistance of the nickel plating layer is deteriorated by sintering twice. Therefore, when comparing the method used in the above embodiment with this method, it can be said that the method used in the above embodiment is superior. Whichever method is used, the doctor blade method can be used as a slurry application method, and the amount of heat during sintering is larger than that of a sintered substrate made by mixing metal fibers etc. in the slurry. There is an advantage that there is no need to perform the process and that the breakthrough of the separator, the short-circuit rate, and the like can be reduced.

[0033]

【The invention's effect】

In the sintered metal layer used in the electrode plate for an alkaline storage battery according to the present invention, as the nickel powder forming the first sintered metal layer, the average particle diameter is 2 to 8 μm, and the bulk density is 1.0.
~ 3.0 g / ml, the average particle diameter of the nickel powder forming the second sintered metal layer is 2-4 μm,
Since the powder having a bulk density of 0.4 to 1.0 g / ml is used, the nickel powder forming the first sintered metal layer has a higher bulk density than the nickel powder forming the second sintered metal layer. And there is no need to include water-insoluble cellulose or microballoons in the slurry, and there is an advantage that the first sintered metal layer hardly peels off from the porous plate during drying. Further, since water-insoluble cellulose and microballoons are not added to the slurry, the slurry viscosity is stable, the product hardly varies, and a stable product can be obtained.

Further, since this sintered metal layer forms a first sintered metal layer composed of a sintered body having a thick skeleton near the perforated plate using nickel powder having a large particle diameter, The contact area between the sintered metal layer and the perforated plate is large, and the first sintered metal layer adjacent to the perforated plate is less susceptible to corrosion, and the bonding strength of the sintered metal layer to the perforated plate can be increased. In addition, current collection performance can be improved. Also, since the bonding strength between the first sintered metal layer and the perforated plate can be increased, even if the porosity of the second sintered metal layer away from the perforated plate is increased to increase the amount of active material retained, The sintered metal layer holding the active material does not easily peel off from the perforated plate, and a high capacity of the battery can be achieved. Further, since no metal fiber or the like is mixed, the occurrence of a short circuit can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of an electrode plate for an alkaline storage battery according to one embodiment of the present invention.

FIGS. 2 (A) and (B) are photographs of a metal structure for showing the corrosion state due to chemical impregnation for the product of the present invention and the conventional product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Perforated plate 2 ... 1st sintered metal layer 3 ... 2nd sintered metal layer 4 ... sintered metal layer

Continuation of the front page (56) References JP-A-48-7248 (JP, A) JP-A-48-8033 (JP, A) JP-A-61-23706 (JP, A) JP-A-62-55869 (JP) , A) JP-A-1-143149 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/80

Claims (1)

(57) [Claims] 1. A sintered metal layer is formed by using a perforated plate as a core metal, and said sintered metal layer is formed on said perforated plate by a first sintered metal layer mainly made of nickel powder and a second sintered metal layer. Layers are laminated with the first sintered metal layer adjacent to the perforated plate, and the first sintered metal layer has a lower porosity than the second sintered metal layer, and is mainly In the electrode plate for an alkaline storage battery in which an active material is held in the second sintered metal layer, the nickel powder forming the first sintered metal layer has an average particle diameter of 2 to 8 μm and a bulk density of Is 1.0 to 3.0 g / ml, and the nickel powder for forming the second sintered metal layer 3 has an average particle diameter of 2 to 4 μm and a bulk density of 0.4 to 1.0.
An electrode plate for an alkaline storage battery, which is g / ml.