JPH10241698A - Alkaline storage battery electrode and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the adhesion strength of core material and a porous body so as to suppress the pole plate deformation or the falling-out of the active material at an active material impregnation time and to enhance an efficiency discharge characteristic by forming fine recesses and protrusions of a specific diameter and depth on the surface layer of conductive core material. SOLUTION: Nickel porous bodies 2 contained in a nickel slurry are hooked with fine recesses and protrusions 1 on the core material surface of a bored steel plate 3, so that the contact area of the bored steel plate 3 and the nickel porous bodies 2 is increased. Therefore, substrate strength after sintering is enhanced, and the deformation of an pole plate or the falling-out of active material in respective processes such as active material impregnation, formation, battery group constitution can be suppressed. With respect to 2 to 3μm average particle diameter of the nickel porous bodies 2, when the diameter of the core material surface recesses and protrusions 1 is 0.01μm or less, a pore diameter is too small, and reversely, when the diameter is 10μm or more, the pore diameter is too large so that the nickel powder 2 cannot be efficiently hooked with the core material surface. Therefore, the diameter of the recesses and protrusions is set to be 0.01 to 10μm, and the depth, to be 0.1 to 5μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrode for an alkaline storage battery, and more particularly to a sintered electrode and a method for producing the same.

[0002]

2. Description of the Related Art Alkaline storage batteries have been expanding their market scale as portable devices such as communication devices, office automation equipment, and power tools have been developed. However, there is a strong demand for higher capacity and higher performance.

[0003] The shape of an electrode for an alkaline storage battery is roughly classified into two types according to the manufacturing method. A paste obtained by kneading a carbonyl nickel powder and a thickener on a core material of the electrode is applied to a substrate obtained by sintering the paste. A sintering method obtained by electrically and chemically impregnating a substance, and filling a paste containing an active material into a porous metal such as foamed metal or nickel nonwoven fabric or a two-dimensional core material such as punching metal or expanded metal. There is a paste type obtained by coating. The sintering method has a feature that the capacity is lower than that of the paste method, but the charge and discharge characteristics at a large current are excellent.

Attempts have been made to improve the porosity of sintered substrates in order to meet the demand for higher capacity in sintered substrates. However, when the porosity is increased, the adhesion between the core material and the porous body is reduced, and the deformation of the substrate in each step such as the active material impregnation step, the chemical conversion step, and the dropout of the nickel porous body and the active material become problems. .

Therefore, as an attempt to improve the adhesion between the core material and the porous body, Japanese Patent Application Laid-Open No.
A method has been proposed in which nickel is plated on an iron plate at a current density of 5 to 20 A / dm < ² >, and powdered nickel is attached to a core material having a coarse plating precipitate formed on the surface of the iron plate and sintered. Further, Japanese Patent Publication No. 60-41426 discloses that after a slurry composed of a metal powder for sintering having an average particle size of 0.1 μm or less and an adhesive is applied to a core material, the slurry is dried and sintered, and then this After applying a slurry comprising a metal powder for sintering having an average particle size of 1.5 to 4.5 μm and an adhesive on the surface of the sintered layer,
Drying and sintering methods have been proposed. Japanese Patent Application Laid-Open No. 55-97403 proposes a method in which nickel or nickel-plated metal fiber having a wire diameter of 20 μm or less is sintered in advance on a core material, and nickel powder is sintered thereon.

[0006]

In the above-mentioned method using a core material in which coarse plating deposits are formed on the surface of an iron plate, the adhesion between the porous body and the core material is small because the surface of the core material has small irregularities. Sex does not improve. In the method of sintering a metal powder for sintering of 0.1 μm or less or a metal fiber having a wire diameter of 20 μm or less, a sintered body layer having low substrate porosity is formed near the core material, and the porosity of the entire substrate is reduced. There is a problem that the battery capacity decreases due to the decrease.

The present invention solves the above-mentioned problems, and improves the adhesion strength between a core material and a porous body, thereby impregnating an active material, forming an active material, and forming an electrode plate when forming a battery group. It aims at suppressing deformation or falling off of the active material and further improving the efficiency discharge characteristics.

[0008]

In order to solve the above-mentioned problems, in the present invention, the surface layer of the conductive core material has a diameter of 0.01 to 1 mm.
An electrode for an alkaline storage battery using a sintered substrate provided with fine irregularities of 0 μm and a depth of 0.1 to 5 μm is used.
The nickel powder contained in the nickel slurry is caught by the fine irregularities on the surface of the core material, and the contact area between the core material and the nickel powder increases. Therefore, the strength of the substrate after sintering is improved, and deformation of the electrode plate or falling off of the active material in each step such as impregnation of the active material can be suppressed. When the average particle diameter of the nickel powder is 2 to 3 μm and the diameter of the irregularities on the surface of the core material is 0.01 μm or less, the pore diameter is too small.
If it is more than μm, it is too large, so that the nickel powder cannot be efficiently anchored on the surface of the core material.

Further, since the shape of the irregularities on the surface of the conductive core material is maintained after sintering, the irregularities are filled with the active material. Therefore, it is possible to secure an active material filling amount substantially equal to that of the conventional sintered substrate.

The method for producing the electrode of the present invention is as follows.
The conductive core material is electroplated using a plating solution to which a water-soluble polymer has been added, and both surfaces of the conductive core material are covered with a eutectoid plating film in which a water-soluble polymer and nickel coexist. Thereafter, baking is performed to remove the water-soluble polymer from the plating film to form fine irregularities on the surface of the core material. Subsequently, a nickel slurry composed of a nickel powder and a thickener is applied to both surfaces of the core material, followed by drying and sintering steps to obtain a sintered substrate. An electrode for an alkaline storage battery is obtained by impregnating the sintered substrate with an active material by an electric or chemical method.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is directed to an electrode for an alkaline storage battery, and is applied to a sintered substrate composed of a conductive core material and a nickel porous body disposed at the center of the substrate. An electrode filled with a substance, wherein the surface layer of the conductive core material has a diameter of 0.01 to 10 μm and a depth of 0.1 to 5 μm.
Thus, an electrode for an alkaline storage battery using a sintered substrate provided with m fine irregularities is obtained.

According to a third aspect of the present invention, there is provided a method for manufacturing an electrode for an alkaline storage battery according to the first aspect, wherein the adhesion between the core material and the nickel porous body is improved without reducing the substrate porosity. As a result, the current collection efficiency of the substrate is improved. As a result, the charge / discharge characteristics of the battery using this substrate at high current are improved.

[0013]

EXAMPLE A thickness of 60 μm, an opening diameter of 1 mm, and an opening ratio of 1
2.0 μm nickel plating was applied to both sides of an 8% perforated steel plate. Further, both surfaces were covered with a 2.0 μm thick nickel-water-soluble polymer composite plating film by electrolytic plating. Electroplating conditions were bath composition: nickel sulfate hexahydrate 240 g / l, nickel chloride hexahydrate 45 g /
1, boric acid 35 g / l, polyetheramine 25 g /
1, bath temperature: 50 ° C., current density: 10 A / dm ² . A slurry obtained by kneading 100 parts of carbonyl nickel powder (Type 255) manufactured by INCO and 100 parts of a 3 wt% concentration aqueous methylcellulose solution was applied to both surfaces of the core material so that the total thickness was 1.3 mm, and 100 ° C.
For 10 minutes. This was sintered at 900 ° C. for 5 minutes in a nitrogen-hydrogen atmosphere to produce a sintered substrate a. FIG. 1 shows an enlarged schematic view of the cross section of the substrate. In the figure, reference numeral 1 denotes an unevenness on the surface of a core material formed by nickel-water-soluble polymer composite plating and firing, 2 denotes a nickel porous body, and 3 denotes a perforated steel plate which mainly forms the core material. Next, the obtained substrate a was treated with a nickel nitrate / cobalt aqueous solution (pH:
2.0, liquid temperature: 80 ° C.) for 10 minutes.
After drying at 0 ° C. for 10 minutes, a cycle of immersion in an aqueous solution of sodium hydroxide (specific gravity: 1.2 g / cc, liquid temperature: 80 ° C.) for 20 minutes was repeated eight times to impregnate nickel hydroxide as an active material. The nickel electrode thus obtained was cut into a width of 35 mm and a length of 200 mm, and a lead plate was spot-welded to a part thereof to obtain a nickel electrode 4. The capacity of the nickel electrode 4 is 1600 mAh.

A cadmium electrode 5 was used as the negative electrode. The cadmium electrode 5 was spirally wound with a nylon nonwoven fabric separator 6 interposed between the nickel electrode 4 and the cadmium electrode 5 and housed in an SC type battery case 7. Thereafter, a predetermined amount of an alkaline electrolyte obtained by dissolving 30 g / l of lithium hydroxide monohydrate in potassium hydroxide having a specific gravity of 1.30 was injected, and the case opening was sealed with a sealing plate 8 to which the positive electrode terminal was fixed. A sealed nickel-cadmium storage battery A as shown in FIG. 2 was constructed.

The following substrates and batteries were prepared as comparative examples. Thickness 60 μm, opening diameter 1 mm, opening ratio 1
3.0 μm nickel plating was applied to both sides of an 8% perforated steel plate. Nickel slurry was applied to both surfaces of this core material in the same manner as in the example, dried and sintered to produce a sintered substrate b, and a battery B was produced using this substrate b.

The following tests were performed on the obtained sintered substrates a and b to evaluate the adhesion strength between the core material and the nickel porous body.

(Test 1) Substrates a and b are 10 × 100 mm
This was repeatedly wound ten times while being shifted to an iron wire having a diameter of 2 mm. The weight reduction ratio before and after the test was 3% for the substrate a and 10% for the substrate b. From this result, it can be understood that the substrate a has improved adhesion strength between the core material and the nickel porous body as compared with the substrate b.

(Test 2) Substrates a and b according to the grid test
Was cut into 50 × 50 mm, and a grid-shaped cut having a width of 2 mm was made in the nickel porous body on one side of the substrate. In this case, peeling of the nickel porous body was not observed for both the substrates a and b. Next, sticking and peeling of a gum tape were repeated three times. The weight reduction rate at this time was 0.1% for the substrate a and 30% for the substrate b. This also indicates that the substrate a has improved adhesion strength between the core material and the nickel porous body as compared with the substrate b.

Next, the discharge characteristics of the batteries A and B were evaluated. After charging for 72 minutes at 1 CmA, 0.8 V at 10 A
FIG. 3 shows a discharge curve when the battery was discharged to the maximum. From this result, it can be seen that in the battery A, the adhesion between the core material and the nickel porous body was improved, so that the current collecting function was enhanced, and the discharge characteristics were improved as compared with the battery B.

[0020]

According to the present invention, the strength of the substrate is improved by improving the adhesion between the conductive core material and the nickel porous body without lowering the porosity of the substrate as compared with the conventional sintered type substrate. As a result, an electrode for an alkaline storage battery having excellent high-rate discharge characteristics can be obtained while suppressing exfoliation of the nickel porous body during production of the electrode plate.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic cross-sectional view of a substrate according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the battery in the example.

FIG. 3 is a discharge curve diagram of the battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unevenness of core material surface 2 Nickel porous body 3 Perforated steel plate 4 Nickel electrode 5 Cadmium electrode 6 Separator 7 Battery case 8 Sealing plate

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hideo Kaiya 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] An electrode in which a sintered substrate composed of a conductive core material and a nickel porous body disposed at a central portion of a substrate is filled with an active material, and a surface layer of the conductive core material has a diameter of 0.1 mm. 01-1
An electrode for an alkaline storage battery using a sintered substrate provided with fine irregularities of 0 μm and a depth of 0.1 to 5 μm. 2. The alkaline storage battery according to claim 1, wherein said conductive core material is one of a flat plate made of metallic nickel, a flat plate made of iron coated with metallic nickel, and a member perforated therethrough. Electrodes. 3. A method for producing an electrode in which an active material is filled in a sintered substrate comprising a conductive core material and a nickel porous body disposed in a central portion of a substrate, wherein nickel and a water-soluble polymer are electroplated. Eutectoid metal nickel, an iron flat plate coated with metal nickel, or a step of coating the surface of a conductive core material that is one of members perforated therein, and firing the conductive core material. Applying a slurry comprising nickel powder and a thickener to both surfaces of a porous nickel-coated core material having undergone a step of desorbing a water-soluble polymer, and sintering the slurry at 800 to 1100 ° C. in a reducing atmosphere. A method for producing an electrode for an alkaline storage battery, comprising forming a sintered substrate from the steps and filling the sintered substrate with an active material.