JPH10334899A - Manufacture of alkaline storage battery and its electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve charge/discharge characteristic using a base board formed by integrating a conductive core material which is composed of a porous material such as a metal board or a net with nickel fibers constituted of a core part, which is raised from the both surfaces of the core material and composed of carbon fibers, and a nickel layer covering its surface. SOLUTION: After a polyvinyl butyral-based adhesive has been applied on the both sides of a nickel plated steel punching metal 1 of numerical aperture 42%, rayon fibers are transplanted and the surfaces of the punching metal 1 and the rayon fibers are coated with nickel with a prescribed thickness. The rayon fibers are heated in a non-oxidizing atmosphere, so as to be formed into carbon fibers, the nickel applied on the punching metal 1 and rayon fiber surfaces, and the core material are burned, and the obtained base board is filled with an active material. That is to say, the base board formed by integrating the punching metal 1 with the nickel fibers and constituting the nickel fibers of a carbon fibers 2 and a nickel coating layer 3 is filled with the active material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art The market size of alkaline storage batteries has been expanding as portable devices such as communication devices and personal computers have been used. In these fields, the demand for lightweight and high-capacity batteries has been rapidly increasing recently. In addition, demands for alkaline storage batteries are increasing also in applications that require charging and discharging with a large current, such as power tools and auxiliary power.

The method of manufacturing an electrode for an alkaline storage battery is roughly classified into a method in which a paste obtained by kneading a nickel powder and a thickener on a conductive core material such as punching metal is applied, and a substrate obtained by sintering the paste is impregnated with an active material. And a paste type obtained by filling or applying a paste containing an active material to a porous metal such as foamed metal or nickel nonwoven fabric or a conductive core material such as punched metal or expanded metal. There is.

Japanese Patent Application Laid-Open No. 61-293618 proposes a substrate obtained by implanting fibrous nickel in a stainless steel mesh, rolling the sintered nickel, and sintering the same, similar to the electrode of the present invention. This is intended to solve the above-described disadvantages that the nickel plate sintered in the sintering type electrode plate has cracks and the thickness cannot be controlled.

Japanese Patent Application Laid-Open No. 8-144153 proposes a carbon fiber pile fabric comprising a thread-like base fabric layer containing carbon fibers and a flocking portion raised from the base fabric layer. This is used as electrode conductivity (substrate) for some secondary batteries, particularly for sodium-sulfur batteries, and was not suitable as an electrode substrate for alkaline storage batteries.

[0006]

As a substrate for a paste type electrode, a porous metal such as a foamed metal or a nickel nonwoven fabric is used for a nickel electrode having a low conductivity of an active material. These substrates have a longer current collection path from the active material to the electrode terminal as a current inlet / outlet compared to sintered substrates in which a conductive core material passes through the center of the substrate. Is inferior. Further, since the pore diameter of the substrate is generally larger than that of the sintered substrate, the substrate strength and the active material holding power are also inferior. In the nickel electrode, when charge and discharge are repeated, the volume of the active material changes greatly, and the electrode plate swells by absorbing the electrolytic solution. At this time, if the holding power of the active material is low, the contact between the substrate and the active material particles is likely to be reduced, and the current collecting ability is greatly deteriorated.

On the other hand, a cadmium electrode and a hydrogen storage alloy electrode having relatively high conductivity of the active material use a two-dimensional conductive core material such as a punching metal as a substrate, and further use carbon powder or a carbon powder to supplement the conductivity. 2. Description of the Related Art Electrodes to which a conductive material such as fiber, a binder for supplementing an active material holding power, and the like are added have been widely used. However, when charging and discharging with a large current by adding a conductive material, the current collecting ability is still insufficient.

In order to reduce the manufacturing cost of the nickel electrode, an electrode using a two-dimensional conductive core material such as a punched metal has been conventionally studied. Since no agent has been obtained, the charge / discharge characteristics and the charge / discharge repetition life characteristics are inferior, and thus have not yet been put to practical use.

Although the sintered electrode has better charge / discharge characteristics at a large current than the paste type, it has a lower porosity and a thicker porous body than the substrate used in the paste type. The battery capacity per unit volume is lower than that of the paste type because it is difficult. Furthermore, since the pore diameter of the sintered substrate is smaller than that of the paste type, there is also a problem that the production method is complicated such that it is necessary to repeat the impregnation of the solution several times in order to fill the required amount of the active material.

[0010] The present invention solves the above-described problems, and is an excellent alkaline storage battery that maintains a battery capacity equivalent to that of a conventional paste-type electrode and has improved active material holding power and current collecting function. An object of the present invention is to provide an electrode having charge / discharge characteristics.

[0011]

According to the present invention, there is provided a conductive core made of a porous material such as a metal plate or a net, and nickel fibers brushed from both surfaces of the core. The present invention provides an electrode using a substrate composed of a core portion made of carbon fiber and a nickel layer covering the surface thereof, and an alkaline storage battery using the same.

Further, the method of manufacturing the electrode includes a step of applying an adhesive to both surfaces of the conductive core material and then implanting resin fibers by an electrostatic flocking method or the like; For example, a step of coating nickel to a desired thickness by electroless plating or electroplating, and a heat treatment in a non-oxidizing atmosphere to convert the resin fibers into carbon fibers and to form the surface of the conductive core material and the surface of the resin fibers. And a step of filling the substrate obtained from the step of sintering the nickel coating the core with the core material with an active material.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is directed to an alkaline storage battery, which is an alkaline storage battery comprising a positive electrode, a negative electrode, a separator and an alkaline electrolyte, wherein at least one of the positive and negative electrodes is provided. One electrode has a conductive core material and nickel fibers brushed from both surfaces of the conductive core material integrated with each other, and the nickel fiber is a carbon fiber core and a nickel covering the surface. The active material is filled in the substrate composed of the layers.

Claims 2 and 3 define the form of the nickel fiber.

[0015] The invention according to claim 4 specifies a method of manufacturing the electrode.

The resin fibers are planted by a static flocking method utilizing static electricity on the surface of a conductive core material such as a punching metal to which an adhesive is applied, in an upright structure at substantially equal intervals. The interval is regulated by the length and diameter of the fiber. As the spacing between the flocks becomes narrower, the density of nickel fibers formed after nickel coating increases, and the current collection path from the active material to the substrate becomes shorter, so that the charge / discharge characteristics as an electrode are improved.

However, in such a flocking structure in which nickel fibers are upright, the mechanical strength is low, so that the active material holding power as an electrode is insufficient. Therefore, after electrostatic flocking, the resin fiber surface is coated with nickel, and then heat-treated in a non-oxidizing atmosphere to convert the resin fiber into carbon fiber, and the surface of the conductive core material and the coated nickel and core are coated. By sintering the material, the mechanical strength of the planted portion can be increased, and the active material holding power of the electrode can be improved. Thereby, the influence of swelling of the active material when charge and discharge are repeated as an electrode can be suppressed. In addition, the contact property between the active material and the substrate is improved and the current collecting function is improved, so that the charge and discharge characteristics are also improved.

[0018]

【Example】

(Example) Polyvinyl butyral-based adhesive (solid content: 20%) on both surfaces of a nickel-plated iron punched metal having a thickness of 60 μm, a punching hole diameter of 1 mm, and a porosity of 42%.
Was spray-coated so that the coating amount was 50 g / m ² . Subsequently, before the adhesive dries, a diameter of 30 μm
m, a rayon fiber having a length of 2 mm is shaken off from a sieve provided with electrodes, and a voltage of 70 kV is applied between the electrode in the sieve and the punching metal to charge the rayon fiber, and the electrostatic force is applied to the punching metal side. Electrostatic flocking for suction was performed.

Then, after drying at 120 ° C. for 10 minutes to cure the adhesive, the surface of the rayon fiber and the punching metal was coated with a nickel-phosphorus alloy having a thickness of 0.5 μm by electroless plating. Thereafter, electroplating was performed using a watt bath for electroplating at a current density of 10 A / dm ² and a nickel plating weight of 300 g / m ² .

Thereafter, a rayon fiber and a conductive core material coated with a polyvinyl butyral-based adhesive and nickel are heat-treated at 1000 ° C. in a nitrogen-hydrogen stream to sinter the punched metal and nickel fibers, Was made into carbon fiber to produce a substrate a according to the present invention. The thickness of the obtained substrate a was about 4 mm.

Incidentally, the polyvinyl butyral adhesive was decomposed by heat treatment.

FIG. 1 is an enlarged schematic view of the substrate a. In the figure, 1 is a nickel-plated iron punching metal, 2 is a rayon fiber as a carbon fiber core, and 3 is a nickel layer coated. In the process of nickel plating, if there is a pinhole or the like in a part of the nickel plating, carbon fiber is exposed in this part, but if it is a small amount, it can be used without any trouble because it is covered in contact with the active material. .

Next, the obtained substrate a is pressed to a thickness of 1.4.
After adjusting the thickness to mm, a lead attachment portion not filled with the active material was formed at a predetermined position by compressing to a thickness of about 0.2 mm with a 5 mm square mold.

Subsequently, 90 parts of commercially available nickel hydroxide and 10 parts of cobalt hydroxide were mixed with water in such an amount that the water content of the paste became 30%, and the mixture was kneaded and filled into a substrate a.
After drying at 0 ° C. for 30 minutes, the pressure was adjusted to 0.7 mm in thickness. The nickel electrode obtained in this way was
It was cut into 5 mm and 110 mm in length. The capacity of this nickel electrode is about 1600 mAh. Then, a nickel lead plate was spot-welded to a predetermined position where the active material was not filled to form a nickel electrode 4.

A hydrogen storage alloy electrode was used as the negative electrode. This provides the following powder 50μm by pulverizing a hydrogen absorbing alloy having a composition consisting of _{MmNi 3.55 Mn 0.4 Al 0.3 Co 0.} 75, put 1 hour it in 31% KOH aqueous solution of 80 ° C., the alloy powder surface An activation treatment for removing the oxide film was performed. A paste obtained by adding a 1.5 wt% carboxymethylcellulose aqueous solution to this powder was filled in a foamed nickel plate, and
After drying at 30 ° C. for 30 minutes, the pressure was adjusted to 0.4 mm in thickness. After that, it is coated with a 5 wt% fluororesin dispersion, dried, and then has a width of 35 mm and a length of 14 mm.
It was cut to 5 mm to obtain a hydrogen storage alloy electrode 5.

Between the nickel electrode 4 and the hydrogen-absorbing alloy 5, a separator non-woven fabric separator 6 made of sulfonated polypropylene was interposed and spirally wound, and stored in a battery case 7 of 4 / 5A size. Thereafter, a predetermined amount of an electrolytic solution obtained by dissolving 30 g / l of lithium hydroxide in a potassium hydroxide aqueous solution having a specific gravity of 1.30 was injected, and the opening of the case was closed with a sealing plate 8 to which the positive electrode terminal was fixed, as shown in FIG. Such a sealed nickel-hydrogen storage battery was constructed. Thus, Battery A of the present invention was produced.

Comparative Example 1 A phenolic adhesive (solid content: 20%) was applied to both surfaces of a nickel-plated iron punched metal having a thickness of 60 μm, a punching hole diameter of 1 mm, and a porosity of 42%.
%) Was spray-coated so that the coating amount was 50 g / m ² . Subsequently, before the adhesive dries, the diameter is 30 μm,
While shaking the rayon fiber having a length of 2 mm from the sieve provided with the electrodes, a voltage of 70 kV was applied between the electrodes in the sieve and the punching metal to charge the rayon fibers, thereby performing electrostatic flocking.

Next, after drying at 120 ° C. for 10 minutes to cure the adhesive, the surface of the rayon fiber and the punching metal was coated with a 0.5 μm thick nickel-phosphorus alloy by electroless plating. Thereafter, electroplating was performed using a watt bath for electroplating at a current density of 10 A / dm ² and a nickel plating weight of 300 g / m ² .

Thereafter, firing was performed at 700 ° C. for 5 minutes in the air to remove the phenolic adhesive and rayon fiber at the time of flocking. Subsequently, the punched metal and the nickel fiber were sintered at 1000 ° C. in a nitrogen-hydrogen stream to prepare a substrate b for comparison. Using this, a battery B was produced in the same manner as in the example.

[0030]

[Table 1]

As shown in the results in Table 1, the discharge capacity and the average discharge voltage of the battery A of the example were improved as compared with the batteries B and C of the comparative example. This is because the current collecting property and the active material holding power in the nickel fiber portion were increased.

Next, for each of the three cells A and B,
Charge at 0.5 CmA for 3 hours at 0 ° C. and 0.9 at 1 CmA
A cycle life test for discharging to V was performed, and the number of cycles when the discharge capacity was reduced to 60% of the initial capacity is shown in (Table 2).

[0033]

[Table 2]

As shown in the results of Table 2, the battery A of the example had improved charge / discharge cycle life characteristics as compared with the battery B.

Although a punching metal is used as the conductive core material in the embodiment, a similar effect can be obtained by using a metal plate having no holes, a wire net, an expanded metal, or the like. Further, in the embodiment, the same effect can be obtained also when the flocking type substrate is used for the nickel electrode.

[0036]

According to the present invention, in the alkaline storage battery and its electrode, the current collecting property of the substrate is improved, the charge / discharge characteristics are improved, and the active material holding power as an electrode is also improved, so that the charge / discharge cycle life characteristics are also improved. improves.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic 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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nickel-plated iron punching metal 2 Carbon fiber 3 Nickel coating layer 4 Nickel electrode 5 Hydrogen storage alloy 6 Separator 7 Battery case 8 Sealing plate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuhiro Okamoto, Inventor 1006 Oaza Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A conductive core comprising a positive electrode, a negative electrode, a separator, and an alkaline electrolyte, at least one of the positive electrode and the negative electrode has a conductive core material made of a porous material such as a metal plate or a wire mesh, and the conductive core material. A substrate in which nickel fibers that are raised from both surfaces are integrated with an active material,
An alkaline storage battery in which the nickel fibers include a core made of carbon fiber and a nickel layer covering the surface thereof. 2. The alkaline storage battery according to claim 1, wherein the nickel fibers have carbon fibers exposed on a part of the nickel surface layer. 3. The alkaline storage battery according to claim 1, wherein the nickel fiber has a variation in diameter and / or a variation in irregularities in the fiber surface layer. 4. A positive electrode, a negative electrode, a separator, and an alkaline electrolyte, wherein at least one of the positive and negative electrodes has a conductive core material made of a porous material such as a metal plate or a wire mesh, and the conductive core material. The active material is filled into a substrate in which nickel fibers which are raised vertically from both surfaces are integrated, and the nickel fibers are composed of a core portion made of carbon fibers and a nickel layer covering the surface. The electrode is coated with an adhesive on both sides of the conductive core material and then planted with resin fibers. The electrode is bonded from the resin fibers raised from both surfaces of the conductive core material. A step of spray-coating an agent, a step of coating the surface of the conductive core material and the resin fiber with nickel by electroless plating, and a step of coating nickel by electroplating on the surface of the nickel coating layer. Heat-treating the resin fibers into carbon fibers in a non-oxidizing atmosphere, and sintering the nickel and the core material covering the surfaces of the carbon fibers and the core material; and A method for producing an electrode for an alkaline storage battery, wherein the substrate is filled with an active material.