JPH10334900A - Manufacture of alkaline storage batter and its electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve charge/discharge characteristic by using a base board formed by integrating a conductive core material, composed of a porous material such as a metal board or a net, netted nickel fibers arranged on the both surfaces of the conductive core material, and nickel fibers raised between the netted nickel fibers with each other. SOLUTION: After a phenol-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 so as to be stuck to the surface of the punching metal 1 into a net state and then raised outwards from between the netted rayon fibers. After the surfaces of the punching metal 1 and the rayon fibers have been coated with nickel to a prescribed thickness, the rayon fibers and the adhesive are thermally decomposed and removed, and the surface nickel and the core material are burned. Then the base board obtained is filled with an active material. In this case, most of nickel fibers 3 raised from between the netted nickel fibers 2 are combined together adjacent to the tip by bundles each with a plural fibers.

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 divided 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 conductive core material such as a porous metal such as foamed metal or nickel non-woven fabric or a punching metal or expanded metal. There is.

[0004] As a device similar to the present invention, Japanese Patent Application Laid-Open No. 61-293618 published earlier discloses a substrate in which fibrous nickel is implanted in a stainless steel net, which is rolled and sintered. ing. This solves the inconvenience of cracking of the nickel substrate sintered in the sintered electrode plate as described above and the inability to control the thickness of the substrate.

Further, Japanese Patent Application Laid-Open No. 8-144153 proposes a carbon fiber pile fabric comprising a base fabric layer made of a thread containing carbon fibers and a raised portion raised from the base fabric layer. This is intended to be used as an electrode conductive material (substrate) of a secondary battery, particularly a sodium-sulfur battery, and is not suitable as a substrate for an alkaline storage battery.

[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-absorbing alloy electrode having relatively high conductivity of the active material use a two-dimensional conductive core material such as a punched metal as a substrate, and further use carbon powder or metal 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 even by adding a conductive material, the current collecting ability is 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. Battery capacity per unit volume is lower than that of the paste type. Furthermore, since the pore diameter of the sintered type is smaller than that of the paste type, there is also a problem that the production method is complicated, for example, 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 a mesh formed on both surfaces of the conductive core. It is an object of the present invention to provide an electrode using a substrate in which nickel fibers and nickel fibers raised from between the mesh nickel fibers are integrated, and an alkaline storage battery using the same.

[0012] Further, the method of manufacturing the electrode is such that an adhesive is applied to both surfaces of the conductive core material, and then the resin fibers are adhered to the surface of the conductive core material in a net-like manner. A step of planting the resin fibers in a state of being raised outward from between the mesh-like resin fibers, and coating the surface of the conductive core material and the resin fibers with nickel to a desired thickness by, for example, electroless plating or electroplating. The active material is filled in the substrate obtained from the step of sintering the core material with nickel, which covers the surface of the conductive core material and the resin fiber surface, by thermally decomposing and removing the resin fiber and the adhesive. And the step of performing

[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 of the electrodes has a conductive core material, a reticulated nickel fiber disposed on both surfaces of the conductive core material, and a nickel fiber raised from between the reticulated nickel fibers integrated with the conductive core material. Most of the nickel fibers thus obtained are those in which the active material is filled in a substrate connected in plurals near the tip thereof.

The length of the nickel fibers constituting the reticulated nickel fibers is preferably longer than the length of the nickel fibers raised between the reticulated nickel fibers because the nickel fibers are more closely entangled with each other, and It is preferable from the viewpoint of reinforcing the base and from the standpoint of the current collecting path.

[0015] The invention according to claim 3 specifies a method of manufacturing the electrode.

According to the electrostatic flocking method utilizing static electricity, the resin fibers are planted in a vertically upright structure at substantially equal intervals on the surface of a conductive core material such as a punching metal to which an adhesive is applied. 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.

In such a structure in which the flocking portion is upright, a current collecting path exists only in the vertical direction of the conductive core material. However, in order to more efficiently improve the current collecting property of the substrate, the conductive core material has It is better that the fibers are located in a diagonal or parallel direction so that a current collecting path exists. Therefore, if a net-like nickel fiber is entangled with the root of the fiber which is planted upright from the conductive core material and is entangled with the fiber, the resistance of the whole substrate is greatly reduced and the charge / discharge characteristics are improved.

Furthermore, the active material holding power of the substrate, especially in the vicinity of the conductive core material, is improved, and the effect of the volume change of the active material when charge and discharge are repeated is suppressed, so that the cycle life characteristics are also improved.

[0019]

【Example】

(Example) 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 hole opening ratio of 42% so that the coating amount was 50 g / m ^2. Was applied by spraying.
Subsequently, before the adhesive dries, the diameter is 30 μm and the length is 4 μm.
mm rayon fiber was sprinkled and attached to both surfaces of the conductive core material to form a net-like structure. The fiber amount at this time is 3
g / m ² . Then, while shaking rayon fibers having a diameter of 30 μm and a length of 2 mm from the sieve provided with the electrodes, 70 k between the electrodes in the sieve and the punching metal.
A voltage of V was applied to charge the rayon fibers, and electrostatic flocking was performed. At this time, the fiber amount was 50 g / m ² .

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 0.5 μm thick nickel-phosphorus alloy by electroless plating. Thereafter, electro-nickel plating was performed in a watt bath for electro-plating at a current density of 10 A / dm ² and a nickel plating weight of 300 g / m ² .

Then, the phenolic adhesive and the rayon fiber are removed by thermal decomposition at 700 ° C.
For 5 minutes. Subsequently, the punched metal and the nickel fiber were sintered at 1000 ° C. in a nitrogen-hydrogen stream to produce a substrate a according to the present invention. The thickness of the obtained substrate a was about 4 mm.

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 net-like nickel fiber which is hollow due to thermal decomposition of rayon fiber, and 3 is a brushed fiber which is hollow when the rayon fiber as a core is thermally decomposed. Shows nickel fibers.

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 alloy electrode 5.

A nonwoven fabric separator 6 made of sulfonated polypropylene was interposed between the nickel electrode 4 and the hydrogen storage alloy electrode 5 and spirally wound, and housed in a battery case 7 of 4/5 A 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 A phenolic adhesive (solid content: 20%) was applied to both sides 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 applied by spraying so that the applied amount was 50 g / m ² . Subsequently, before the adhesive dries, the diameter 3
While shaking rayon fibers having a length of 0 μm and 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 to perform electrostatic flocking. The fiber amount at this time is 50
g / m ² . Thereafter, a substrate b for comparison was manufactured through a nickel coating and a heat treatment process in the same manner as in the example. Using this substrate b, battery B
Was prepared.

Next, the discharge characteristics of the batteries A and B were evaluated. 1
After charging with CmA for 72 minutes, the discharge current was increased to 0.2 Cm
Table 1 shows the discharge capacities of the respective batteries when discharged to 1.0 V at A, 1 CmA, and 3 CmA.

[0029]

[Table 1]

As shown in the results in Table 1, the battery A according to the example had improved discharge capacity and average discharge voltage as compared with the battery B. This is because both the holding power of the active material and the current collecting function have been improved.

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).

[0032]

[Table 2]

As shown in the results of Table 2, the battery A according to the example had significantly improved charge / discharge cycle life characteristics as compared with the battery B. This is also due to the good holding power of the active material and the current collecting function of the substrate.

Although the punching metal is used as the conductive core material in the embodiment, a similar effect can be obtained by using a metal plate, a metal net, an expanded metal, etc. having no holes. Resin fibers such as acrylic and nylon may be used in addition to rayon fibers.

Further, in the embodiment, the case where the flocking type substrate is used for the nickel electrode has been described. However, similar effects can be obtained when the flocking type substrate is used for the negative electrode such as the cadmium electrode and the hydrogen storage alloy electrode.

[0036]

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

[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 Reticulated nickel fiber 3 Brushed nickel fiber 4 Nickel electrode 5 Hydrogen storage alloy electrode 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 (3)

[Claims] 1. A positive electrode, a negative electrode, a separator, and an alkaline electrolyte. At least one of the positive and negative electrodes has a conductive core made of a porous material such as a metal plate or a net. An alkaline storage battery in which an active material is filled in a substrate in which mesh nickel fibers arranged on both surfaces of a core material and nickel fibers raised from between the mesh nickel fibers are integrated. 2. The alkaline storage battery according to claim 1, wherein the length of the nickel fibers constituting the mesh nickel fibers is longer than the length of the nickel fibers raised from between the mesh nickel fibers. 3. 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 net. An active material is filled in a substrate in which mesh nickel fibers arranged on both surfaces of the core material and nickel fibers raised from between the mesh nickel fibers are integrated with each other. A step of applying an adhesive to both surfaces of the core material and then attaching the resin fibers to the surface of the conductive core material in a net-like manner; and a step of planting the resin fibers in a state where the resin fibers are raised from between the net-like resin fibers. And then covering the surfaces of the conductive core material and the resin fibers with nickel of a desired thickness,
The resin fiber and the adhesive are thermally decomposed and removed, and the substrate obtained from the step of sintering the conductive core material and nickel covering the surface of the resin fiber and the conductive core material is filled with an active material. A method for producing an electrode for an alkaline storage battery obtained by the above method.