JP2002231236A - Hydrogen storage alloy electrode, method of manufacturing the same, and alkaline battery with hydrogen storage alloy electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a hydrogen storage alloy electrode capable of inhibiting the impairing of the strength of a negative plate even when the hydrogen storage alloy powder of small average particle size is used to increase the filling density of an active material, whereby the dropping of the hydrogen storage alloy powder from a conductive core body can be prevented, and the alkaline battery of high quality can be provided. SOLUTION: This method comprises a coating process for coating the conductive core body with the active material slurry composed of the hydrogen storage alloy powder of average particle size <=60 μm, a binding agent and a solvent of the binding agent to obtain a coated pole plate, a drying process for drying the coated pole plate to obtain the dried pole plate, a pressing process for pressing the dried pole plate to obtain the pressed pole plate, and a solvent attaching process for attaching the solvent of the binding agent onto a surface of the pressed pole plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen storage alloy electrode in which a mixture containing at least a hydrogen storage alloy powder and a binder is adhered to a conductive core, a method for producing the same, and a method for manufacturing the hydrogen storage alloy powder. The present invention relates to an alkaline storage battery provided with an electrode group in which an attached negative electrode and positive electrode are laminated via a separator, in a metal outer can.

[0002]

2. Description of the Related Art In recent years, demand for secondary batteries (storage batteries) that can be charged and discharged has increased with the increase in small portable devices.
In particular, as devices become smaller, thinner, and more space efficient,
The demand for nickel-hydrogen storage batteries that can provide a large capacity has rapidly increased. This type of nickel-hydrogen storage battery is configured such that a positive electrode using nickel hydroxide as an active material and a negative electrode using a hydrogen storage alloy are stacked via a separator to form an electrode group,
The electrode group is housed in a metal outer can (battery case) together with an alkaline electrolyte and the metal outer can is sealed.

[0003] By the way, this type of nickel-hydrogen storage battery is required to have higher capacity and higher output, and it is indispensable to ensure a high energy density of the positive and negative electrodes. In order to ensure a high energy density of these positive and negative electrodes, it is necessary to make the active material filling density as high as possible. In particular, in the case of the negative electrode, it is necessary to make the filling density of 4.85 g / cm ³ or more. desirable. However, when producing a negative electrode having such a high packing density, if a hydrogen-absorbing alloy powder having a large average particle size is used, the obtained negative electrode may be wavy or wrinkled, and the obtained negative electrode There was a problem that the quality deteriorated.

In this method, after applying an active material paste using a hydrogen storage alloy powder having a large average particle size to a conductive core, a predetermined pressure is applied to the negative electrode to form a negative electrode having a high packing density. It is considered that when pressure is applied, the pressure is unevenly distributed due to the fact that the hydrogen storage alloy powder itself is not compressed and the volume other than the hydrogen storage alloy powder is large. In order to solve such a problem, various studies were made on a method for producing a negative electrode having a high packing density using a hydrogen storage alloy powder having a small average particle diameter.
It was found that the use of the following hydrogen storage alloy powder can suppress generation of waviness and wrinkles in the obtained negative electrode.

[0005]

However, when a hydrogen-absorbing alloy powder having an average particle diameter of 60 μm or less is used and packed at a high density, it is possible to suppress the occurrence of waving and wrinkles in the obtained negative electrode. On the other hand, there has been a problem that the mechanical strength of the negative electrode is reduced and the hydrogen storage alloy powder falls off the negative electrode. This is because the number of particles of the hydrogen storage alloy powder increases as the average particle diameter of the hydrogen storage alloy powder decreases, and the pressure applied to the negative electrode increases due to high density packing, and the particles of the hydrogen storage alloy powder increase. Cracks occur in the binder that is fixed between each other or between the hydrogen storage alloy powder and the conductive core body, and the particles of the hydrogen storage alloy powder fixed to this or between the hydrogen storage alloy powder and the conductive It is considered that a deviation occurred between the cores.

Here, if a deviation (crack of the binder) occurs between the particles of the hydrogen storage alloy powder or between the hydrogen storage alloy powder and the conductive core, the negative electrode is used to pass through a separator. When a positive electrode is laminated and formed into an electrode group, or when such an electrode group is inserted into a metal outer can, there has been a problem that the hydrogen storage alloy powder tends to fall off the negative electrode. In particular, in order to effectively use the space in the metal outer can to obtain a high-capacity battery, the negative electrode is exposed without coating the separator on the outer peripheral portion of the negative electrode arranged on the outermost side of the electrode group. In the battery in which the exposed negative electrode is brought into direct contact with the metal outer can, when the electrode group is inserted into the metal outer can, there is a problem that the hydrogen storage alloy powder is more likely to fall off from the negative electrode. occured.

Therefore, the present invention has been made to solve the above problems, and even if a hydrogen storage alloy powder having a small average particle diameter is used to increase the packing density of an active material,
It is an object of the present invention to provide a manufacturing method capable of suppressing a decrease in mechanical strength of a negative electrode, to prevent the hydrogen storage alloy powder from falling off the negative electrode, and to obtain a long-life, high-quality alkaline storage battery. .

[0008]

Means for Solving the Problems and Actions / Effects of the Invention In order to achieve the above object, the present invention provides a mixture comprising a conductive core containing at least a hydrogen storage alloy powder and a re-dissolvable binder. The hydrogen storage alloy electrode to which the hydrogen storage alloy powder has an average particle diameter of 60 μm or less, a packing density of the hydrogen storage alloy of 4.85 g / cm ³ or more, The hydrogen storage alloy powder and the conductive core are fixed by a binder that can be re-dissolved.

If a hydrogen storage alloy powder having an average particle size of 60 μm or less is applied at a packing density of 4.85 g / cm ³ or more, a high capacity hydrogen storage alloy electrode is obtained. When configuring an alkaline storage battery using the negative electrode,
Since the capacity ratio of the negative electrode increases and the reserve increases, it is possible to provide an alkaline storage battery having excellent charge-discharge cycle characteristics and a long life. In this case, if the hydrogen-absorbing alloy powders or the hydrogen-absorbing alloy powder and the conductive core are fixed by a remeltable binder, even if the remeltable binder has cracks, Since the binder is re-dissolved in the solvent of the binder (for example, pure water or water in the case of a water-soluble binder), the hydrogen-absorbing alloy powder is hardly peeled off and the hydrogen-absorbing alloy powder is prevented from falling off. become able to. If the average particle size of the hydrogen-absorbing alloy powder is too small, cracking of the alloy due to charge / discharge is less likely to occur and an active surface is less likely to occur, and the internal resistance due to contact resistance also increases. It is desirable that the lower limit of the average particle size of the hydrogen storage alloy powder is 20 μm.

The conductive core has an average particle size of 60 μm.
In order to improve the mechanical strength of the hydrogen storage alloy electrode even when the following hydrogen storage alloy powder is adhered at a packing density of 4.85 g / cm ³ or more, the method for producing a hydrogen storage alloy electrode according to the present invention comprises: An application step of applying an active material slurry composed of a hydrogen storage alloy powder having an average particle diameter of 60 μm or less, a binder capable of being re-dissolved, and a solvent of the binder to a core body to form a slurry application electrode A drying step of drying the slurry-coated electrode to form a dry electrode, a pressing step of pressing the dry electrode to form a pressing electrode, and a solvent attaching step of attaching a binder solvent to the surface of the pressing electrode. Process.

As in the present invention, when a solvent of a binder (for example, pure water or water in the case of a water-soluble binder) is allowed to adhere to the surface of the dry electrode, the binder Since the solvent permeates into the hydrogen storage alloy layer and the binder is re-dissolved, after the cracks generated in the binder during rolling are dissolved again, the dissolved binder solidifies, The particles of the hydrogen storage alloy powder and the conductive core and the hydrogen storage alloy powder are firmly fixed. This makes it difficult for the hydrogen storage alloy layer to peel off, thereby preventing the hydrogen storage alloy powder from falling off. When the electrode to which the solvent is attached is dried, the electrode to which the solvent is attached is desirably dried at a lower temperature (40 ° C. or lower) than the drying temperature in the drying step.

A binder application step of applying a binder solution comprising a binder which can be re-dissolved in the conductive core and a solvent of the binder; Coating an active material slurry containing a hydrogen-absorbing alloy powder having an average particle size of 60 μm or less on a conductive core to form a slurry-coated electrode, and drying the slurry-coated electrode to form a dry electrode Process, a pressurizing step of pressing the dry electrode into a pressurizing electrode, and a solvent adhering step of adhering a solvent of the binder onto the surface of the pressurizing electrode, Can be prevented. This is because when the active material slurry is applied to the conductive core coated with the re-dissolvable binder, the re-dissolvable binder diffuses into the active material slurry, and the hydrogen storage alloy powder This is because the particles and the conductive core and the hydrogen storage alloy powder are fixed to each other.

[0013] When the slurry-coated electrode is dried and rolled, a binder solvent is applied to the surface of the dried electrode and adhered to the dried electrode, and then dried, the surface of the hydrogen-absorbing alloy electrode becomes rough. occured. For this reason, for example, the hydrogen storage alloy electrode is spirally wound so as to be located at the outermost periphery, and when the winding tape is attached to the outermost periphery, the winding tape is attached to the outermost hydrogen storage alloy electrode. The problem that it was difficult to do it occurred. Therefore, in the present invention, the solvent of the binder is applied to the surface of the dry electrode, and repressurization is performed after drying at a low temperature. This makes it possible to suppress the occurrence of the roughness phenomenon that occurs when the solvent of the binder is attached to the electrode surface.

In this case, it is necessary to prevent a deviation between the particles of the hydrogen-absorbing alloy powder and between the conductive core and the hydrogen-absorbing alloy powder due to the re-pressurization. With a pressure of, it is possible to maintain the effect of causing the solvent of the binder to adhere to the electrode surface, so that the pressure at the time of re-pressing is preferably within 10% of the predetermined thickness. . In addition, the hydrogen storage alloy electrode of the present invention can be applied to any type of alkaline storage battery.
It is effective to apply an electrode group in which a negative electrode coated with a hydrogen storage alloy powder and a positive electrode are laminated via a separator to an alkaline storage battery provided in a metal outer can.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below. 1. Preparation of hydrogen storage alloy powder Commercially available metal elements (Mm Ni _3.4 Co _0.8 Al _0.2 Mn _0.6 (Mm is a misch metal))
m, Ni, Co, Al, Mn) were weighed and mixed. This was put into a high-frequency melting furnace to be melted, poured into a mold, cooled, and cooled to MmNi _3.4 Co _0.8 Al _0.2 Mn _0.6.
(Ingot) of a hydrogen storage alloy composed of
The lump of the hydrogen storage alloy was roughly pulverized and then mechanically pulverized in an inert gas atmosphere to produce a hydrogen storage alloy powder. The hydrogen storage alloy powder mechanically pulverized until the average particle diameter became 30 μm (this average particle diameter is a value measured by a laser diffraction method) was used as the hydrogen storage alloy α. Similarly, the hydrogen storage alloy powder pulverized to an average particle size of 50 μm is referred to as a hydrogen storage alloy β, and the hydrogen storage alloy powder pulverized to an average particle size of 70 μm is referred to as a hydrogen storage alloy γ, and the average particle size is 90 μm The hydrogen storage alloy powder pulverized until the powder became a hydrogen storage alloy δ.

2. Production of Hydrogen Storage Alloy Electrode (1) Example 1 Hydrogen storage alloy α (hydrogen storage alloy powder having an average particle diameter of 30 μm) produced as described above was used. A polyethylene oxide (PEO) powder as a water-soluble binder is added and kneaded with 1% by mass based on the mass of the hydrogen-absorbing alloy powder and an appropriate amount of water (or pure water) as a solvent for the water-soluble binder. Thus, a hydrogen storage alloy slurry was prepared. Then, a hydrogen-absorbing alloy slurry was applied to both surfaces of a conductive core made of punched metal having a surface provided with nickel plating and having openings, thereby forming a slurry-coated electrode plate.

Thereafter, the electrode was dried at about 60 ° C. for 20 minutes to obtain a dried electrode plate, and the dried electrode plate was pressed to a predetermined thickness to prepare a dry-pressed electrode plate. Next, water or pure water (solvent of a water-soluble binder (PEO)) is applied (pure water treatment) to the entire surface of the obtained dry pressing electrode plate, so that the entire surface of the dry pressing electrode plate becomes wet. Water or pure water was adhered to some extent. After that, it is allowed to stand at room temperature (about 25 ° C.) for about 2 hours to be naturally dried, and then re-pressed with a pressing force to compress the thickness of the dry-pressed electrode plate by 5% to produce a re-pressed electrode plate. did. The amount of the hydrogen storage alloy slurry applied was adjusted so that the density of the hydrogen storage alloy after re-pressing was 5.10 g / cm ³ and the thickness was about 0.5 mm. This re-pressed electrode plate was cut into a predetermined size to produce a hydrogen storage alloy electrode a of Example 1.

(2) Example 2 A conductive core made of a punching metal having a surface plated with nickel and having openings is prepared by adding polyethylene oxide (PE) to a solvent (pure water or water) of a water-soluble binder.
O) The powder was immersed in a binder solution in which the powder was dissolved, and polyethylene oxide (PEO) was applied to both surfaces of the conductive core. Thereafter, the hydrogen storage alloy α (hydrogen storage alloy powder having an average particle diameter of 30 μm) was 99% by mass, and carboxymethyl cellulose (CMC) as a thickener was 1% by mass relative to the mass of the hydrogen storage alloy powder. An appropriate amount of water (or pure water) was added and kneaded as a solvent for the agent to prepare a hydrogen storage alloy slurry. Then, a hydrogen storage alloy slurry was applied to both sides of the conductive core coated with PEO to form a coated electrode plate.

Thereafter, the electrode was dried at about 60 ° C. for 20 minutes to obtain a dried electrode plate, and the dried electrode plate was pressed to a predetermined thickness to produce a dry pressed electrode plate. Next, water or pure water (solvent of a water-soluble binder (PEO)) is applied (pure water treatment) to the entire surface of the obtained dry pressing electrode plate, so that the entire surface of the dry pressing electrode plate becomes wet. Water or pure water was adhered to some extent. After that, it is allowed to stand at room temperature (about 25 ° C.) for about 2 hours to be naturally dried, and then re-pressed with a pressing force to compress the thickness of the dry-pressed electrode plate by 5% to produce a re-pressed electrode plate. did. The amount of the hydrogen storage alloy slurry applied was adjusted so that the density of the hydrogen storage alloy after re-pressurization was 5.10 g / cm ³ and the thickness was about 0.5 mm. This re-pressed electrode plate was cut into a predetermined size to produce a hydrogen storage alloy electrode b of Example 2.

(3) Example 3 A dry pressurized electrode plate was prepared in the same manner as in Example 1 described above, and water or pure water (water-soluble binder) was applied to the entire surface of the obtained dry pressurized electrode plate. (PEO) solvent) (pure water treatment)
Then, water or pure water was adhered to such an extent that the entire surface of the dry pressure electrode plate became wet. Then, after allowing to dry naturally at room temperature (about 25 ° C.) for about 2 hours, the thickness of the dry pressing electrode
% To obtain a re-pressed electrode plate. The amount of the hydrogen storage alloy slurry applied was adjusted so that the density of the hydrogen storage alloy after re-rolling was 5.10 g / cm ³ and the thickness was about 0.5 mm. This re-pressed electrode plate was cut into a predetermined size to produce a hydrogen storage alloy electrode c of Example 3.

In each of the above-described embodiments, an appropriate method such as a coating method using a brush, a coating method using a spray, or a coating method using a roll is adopted in consideration of productivity and the like when performing pure water treatment. Then, water or pure water may be allowed to adhere to the entire surface of the dry pressure electrode plate.

(4) Comparative Example 1 A dry pressurized electrode plate was prepared in the same manner as in Example 1 described above, and water or pure water (water-soluble binder (PEO ) Was cut to a predetermined size without applying the solvent) to produce a hydrogen storage alloy electrode r of Comparative Example 1. The coating amount of the hydrogen storage alloy slurry was such that the density of the hydrogen storage alloy after pressurization was 5.10 g / cm ³ and the thickness was about 0.5.
mm.

(5) Comparative Example 2 A dry pressurized electrode plate was prepared in the same manner as in Example 2 described above, and water or pure water (water-soluble binder (PEO ) Was cut into a predetermined size without applying the solvent) to produce a hydrogen storage alloy electrode s of Comparative Example 2. The coating amount of the hydrogen storage alloy slurry was such that the density of the hydrogen storage alloy after pressurization was 5.10 g / cm ³ and the thickness was about 0.5.
mm.

(6) Comparative Example 3 A dry pressurized electrode plate was prepared in the same manner as in Example 1 described above, and water or pure water (water-soluble binder (PEO ) Was cut to a predetermined size without applying the solvent) to produce a hydrogen storage alloy electrode t of Comparative Example 3. The coating amount of the hydrogen storage alloy slurry was such that the density of the hydrogen storage alloy after pressurization was 4.85 g / cm ³ and the thickness was about 0.5.
mm.

(7) Comparative Example 4 Using the hydrogen storage alloy β (hydrogen storage alloy powder having an average particle diameter of 50 μm) prepared as described above, the above-mentioned Example 1 was used.
In the same manner as described above, after preparing a dry pressing electrode plate, water or pure water (water-soluble binder (PEO)
Without applying the solvent), and cut into a predetermined size to produce a hydrogen storage alloy electrode t of Comparative Example 4. The coating amount of the hydrogen storage alloy slurry was adjusted so that the density of the hydrogen storage alloy after pressurization was 4.85 g / cm ³ and the thickness was about 0.5 mm.

(8) Comparative Example 5 Using the hydrogen storage alloy γ (hydrogen storage alloy powder having an average particle diameter of 70 μm) produced as described above, the above-mentioned Example 1 was used.
In the same manner as described above, after preparing a dry pressing electrode plate, water or pure water (water-soluble binder (PEO)
) Was cut into a predetermined size without applying the solvent, and a hydrogen storage alloy electrode u of Comparative Example 5 was produced. The coating amount of the hydrogen storage alloy slurry was adjusted so that the density of the hydrogen storage alloy after pressurization was 4.85 g / cm ³ and the thickness was about 0.5 mm.

(9) Comparative Example 6 Using the hydrogen storage alloy δ (hydrogen storage alloy powder having an average particle size of 90 μm) produced as described above, the above-mentioned Example 1 was used.
In the same manner as described above, after preparing a dry pressing electrode plate, water or pure water (water-soluble binder (PEO)
(Solvent) was applied and cut into a predetermined size to produce a hydrogen storage alloy electrode v of Comparative Example 6. The coating amount of the hydrogen storage alloy slurry was adjusted so that the density of the hydrogen storage alloy after pressurization was 4.85 g / cm ³ and the thickness was about 0.5 mm.

(10) Comparative Example 7 Using the hydrogen storage alloy β (hydrogen storage alloy powder having an average particle size of 50 μm) prepared as described above, the above-mentioned Example 1 was used.
In the same manner as described above, after preparing a dry pressing electrode plate, water or pure water (water-soluble binder (PEO)
) Was cut to a predetermined size without applying the solvent, and a hydrogen storage alloy electrode x of Comparative Example 7 was produced. The coating amount of the hydrogen storage alloy slurry was adjusted so that the density of the hydrogen storage alloy after pressurization was 5.10 g / cm ³ and the thickness was about 0.5 mm.

(11) Comparative Example 8 Using the hydrogen storage alloy γ (hydrogen storage alloy powder having an average particle diameter of 70 μm) prepared as described above, the above-mentioned Example 1 was used.
In the same manner as described above, after preparing a dry pressing electrode plate, water or pure water (water-soluble binder (PEO)
Without coating), and cut into predetermined dimensions to produce a hydrogen storage alloy electrode y of Comparative Example 8. The coating amount of the hydrogen storage alloy slurry was adjusted so that the density of the hydrogen storage alloy after pressurization was 5.10 g / cm ³ and the thickness was about 0.5 mm.

(12) Comparative Example 9 Using the hydrogen storage alloy δ (hydrogen storage alloy powder having an average particle size of 90 μm) prepared as described above, the above-mentioned Example 1 was used.
In the same manner as described above, after preparing a dry pressing electrode plate, water or pure water (water-soluble binder (PEO)
Without applying the solvent), and cut into a predetermined size to produce a hydrogen storage alloy electrode z of Comparative Example 9. The coating amount of the hydrogen storage alloy slurry was adjusted so that the density of the hydrogen storage alloy after pressurization was 5.10 g / cm ³ and the thickness was about 0.5 mm.

3. Production of Nickel-Hydrogen Storage Battery Next, using the respective hydrogen storage alloy electrodes a to c of Examples 1 to 3 and the respective hydrogen storage alloy electrodes r to z of Comparative Examples 1 to 9 prepared as described above, The hydrogen storage alloy electrode and a well-known non-sintered nickel positive electrode were wound via a separator made of an alkali-resistant nylon nonwoven fabric.
At this time, the spirally wound electrode group was produced by spirally winding the hydrogen storage alloy electrode so that the electrode was on the outside. After each of the spirally wound electrode groups thus manufactured is inserted into a bottomed cylindrical metal outer can, potassium hydroxide (KOH) and lithium hydroxide (LiO2) are respectively inserted into each metal outer can.
H) and sodium hydroxide (NaOH), and a three-component electrolyte solution is injected thereinto and sealed to obtain a nominal capacity of 17%.
Nickel-metal hydride batteries A, B, C, R, S, T, U, V, W, X, Y, and Z having a size of 4/5 A of 00 mAh were produced, respectively.

Here, a battery using the hydrogen storage alloy electrode a is referred to as a battery A, a battery using the hydrogen storage alloy electrode b is referred to as a battery B, and a battery using the hydrogen storage alloy electrode c is referred to as a battery C. The battery R using the alloy electrode r was used as the battery R, the battery using the hydrogen storage alloy electrode s was used as the battery S, the battery using the hydrogen storage alloy electrode t was used as the battery T, and the battery using the hydrogen storage alloy electrode u was used. A battery U, a battery V using the hydrogen storage alloy electrode v, a battery W using the hydrogen storage alloy electrode w, a battery X using a hydrogen storage alloy electrode x, and a hydrogen storage alloy electrode battery using battery y
A battery using the hydrogen storage alloy electrode z was designated as a battery Z.

4. Measurement of number of active material falling off and number of winding deviations As described above, each of the nickel-hydrogen storage batteries A to C and R to
When manufacturing 100 pieces of Z each, when manufacturing the spiral electrode group, each electrode a, b, c, r, s, t, u, v,
When the number of electrode groups in which the hydrogen storage alloy powder was dropped from w, x, y, and z and the number of spirally displaced spiral electrode groups were measured, the results shown in Tables 1 to 4 below were obtained. Was.

(1) Relationship between the average particle size of the hydrogen storage alloy powder and the number of falling and winding deviations of the active material Here, the packing density of the active material was set equal to 4.85 g / cm ³ , The average particle size is 30 μm (hydrogen storage alloy electrode t), 50 μm (hydrogen storage alloy electrode u), 7
When the number of active materials that had fallen off and the number of winding deviations was changed to 0 μm (hydrogen storage alloy electrode v) and 90 μm (hydrogen storage alloy electrode w), the results shown in Table 1 below were obtained.

[0035]

[Table 1]

As is clear from the results shown in Table 1, when producing a hydrogen storage alloy electrode having a hydrogen storage alloy powder packing density of 4.85 g / cm ³ , the larger the average particle size of the hydrogen storage alloy powder used, the larger the average particle size of the hydrogen storage alloy powder used. While the number of active materials falling off decreases, the number of occurrences of winding deviation increases. Conversely, the smaller the average particle diameter of the hydrogen storage alloy powder, the more the number of active materials falling off increases, but the number of winding deviations increases. It can be seen that the number decreases. This is because the smaller the average particle size of the hydrogen storage alloy powder, the more the hydrogen storage alloy powder is fixed when the packing density is increased to 4.85 g / cm ³ , or the more the hydrogen storage alloy powder becomes conductive. It is considered that a crack was generated in the binder that fixes the core body, and the active material was easily dropped off. On the other hand, as the average particle diameter of the hydrogen storage alloy powder increases, the hydrogen storage alloy electrode pressed to a packing density of 4.85 g / cm ³ has more waves and wrinkles.

Further, the packing density of the active material was increased to increase the packing density of 5.1.
0 g / cm ³ and the average particle size of the hydrogen storage alloy is 3
0 μm (hydrogen storage alloy electrode r), 50 μm (hydrogen storage alloy electrode x), 70 μm (hydrogen storage alloy electrode y), 90 μm
m (hydrogen storage alloy electrode z), the number of the active materials that had fallen off and the winding had shifted was obtained. The results are shown in Table 2 below.

[0038]

[Table 2]

As is evident from the results in Table 2, even when a hydrogen storage alloy electrode having a packing density of 5.10 g / cm ³ is prepared, the average particle size of the hydrogen storage alloy powder used is small. It can be seen that the smaller the number is, the more the number of active materials falling off, while the number of occurrences of winding deviation decreases. Also, as is clear from the results of Tables 1 and 2,
Even if the average particle size of the hydrogen storage alloy powder is the same, the packing density of the hydrogen storage alloy powder is from 4.85 g / cm ³ to 5.1.
It can be seen that, when it is increased to 0 g / cm ³ , the number of active materials falling off and the number of occurrences of winding deviation increase. This is because when the hydrogen storage alloy powder having a small average particle diameter is filled at a high density, the number of hydrogen storage alloy powder particles per unit volume increases, and the rolling load increases to increase the packing density. The binder that fixes the hydrogen storage alloy powders together or bonds the hydrogen storage alloy powder and the conductive core easily cracks, and the hydrogen storage alloy powders and the hydrogen storage alloy powder and the conductive core are It is considered that the gap between them became easier to shift.

(2) Relationship between Pure Water Treatment and Number of Drops and Number of Windings of Active Material Further, using a hydrogen storage alloy powder having an average particle diameter of 30 μm, the packing density of the active material was set to 5.10 g / cm ³ . Hydrogen storage alloy electrode a (equalized and subjected to pure water treatment) (binder contained in slurry and repressurization of 5%), b
(The binder is applied to the core and the re-pressurization is 5%), c
(A slurry containing a binder and a re-pressurization of 10%) and a hydrogen storage alloy electrode r not subjected to pure water treatment.
Table 3 shows the numbers of the active materials (with the binder contained in the slurry) and s (with the binder applied to the core) in which the active material was dropped and the winding was displaced. The result was as follows.

[0041]

[Table 3]

As is evident from the results shown in Table 3, the number of active material drops of the hydrogen-absorbing alloy electrodes r and s in which the dry pressurized electrode plate was not subjected to the pure water treatment was 78/100 or 82/1.
00, the number of active material falling off of the hydrogen storage alloy electrodes a, b, and c obtained by subjecting the dry pressure electrode to pure water treatment is 2
It can be seen that the number has sharply decreased to / 100, 2/100 and 9/100.

This is because, when pure water or water is applied to and adhered to the surface of the dry electrode plate, the pure water or water penetrates into the hydrogen storage alloy layer and the water-soluble binder (PEO) is re-used. Since it becomes soluble, cracks generated in the water-soluble binder at the time of pressurization dissolve again, and after that, when dried at a lower temperature (preferably 40 ° C. or lower) than the drying step, the dissolved water-soluble binder is dissolved. It is considered that the agent was solidified and the hydrogen storage alloy powder and the conductive core and the hydrogen storage alloy powder were firmly adhered to each other. This makes it difficult for the hydrogen storage alloy layer to be peeled off, thereby preventing the hydrogen storage alloy powder from falling off.

A hydrogen-absorbing alloy electrode a (or hydrogen-absorbing alloy electrode r) containing a water-soluble binder in a slurry and a hydrogen-absorbing alloy electrode b having a binder coated on a conductive core in advance. (Or hydrogen storage alloy electrode s), it can be seen that the number of active material drops is not so different.
This is because even when the binder is preliminarily applied to the conductive core, the water-soluble binder dissolves in the slurry when the slurry is applied, and the hydrogen storage alloy powder and the conductive core and the conductive core are absorbed in hydrogen. It is considered that the alloy powder was strongly bonded.

When pure water or water was allowed to adhere to the surface of the drying and pressing electrode plate and then dried, the surface of the hydrogen storage alloy electrode became rough. Therefore, such a hydrogen storage alloy electrode is spirally wound so as to be located at the outermost periphery, and when the winding tape is attached to the outermost periphery, the winding tape is attached to the outermost hydrogen storage alloy electrode. The problem that it is difficult to wear was caused. Therefore, in the present invention, pure water or water is applied to the surface of the drying electrode plate, and repressurization is performed after drying at low temperature. This makes it possible to suppress the occurrence of the roughening phenomenon that occurs after the pure water treatment.

In this case, it is necessary to prevent deviation between the hydrogen storage alloy powders and between the conductive core and the hydrogen storage alloy powder due to the re-pressurization. If the pressure is within 10% of the predetermined thickness, the effect of the pure water treatment can be maintained. Therefore, the pressure at the time of re-pressurization should be within 10% of the predetermined thickness. desirable.

5. Measurement of Strength of Hydrogen Storage Alloy Electrodes Next, the hydrogen storage alloy electrodes a and b of Examples 1 and 2 and the hydrogen storage alloy electrodes r and s of Comparative Examples 1 and 2 prepared as described above were used, respectively. The adhesion strength of the hydrogen storage alloy electrode was measured. In this strength measurement,
As shown in FIG. 1, each of these electrode plates 10 (this electrode plate 10 has a hydrogen storage alloy layer 12,
After the surface of the hydrogen-absorbing alloy layer 12 on one side (on which the surface 13 is formed) was cut, the cut surface was lightly rubbed with a rag to remove cutting debris on the surface. Thereafter, after holding a cutter (not shown) at an angle of about 30 degrees with respect to the surface of the hydrogen storage alloy layer 12 of each of the electrode plates 10, 25
A load of about 0 g is applied to the hydrogen storage alloy layer 1
The kerfs x and y were drawn so as to cut two. In addition, each kerf x,
The interval of y is 1 mm, and each kerf x, y is 1
Each of them was drawn so as to cross each other at right angles.

Next, ten kerfs x and y are drawn so as to intersect at right angles at a time, thereby forming 10 kerfs in a grid pattern.
Zero cells were formed. Then, using 10 electrode plates 10 each having 100 grids formed in a grid pattern, the hydrogen storage alloy layers 12 and 13 are vertically set, and the height is raised to a position of about 100 mm. After that, each electrode plate 10 was freely dropped. After this drop test was repeated three times, the number of squares dropped on each electrode plate 10 was counted, and the average value was obtained. The results shown in Table 4 below were obtained.

[0049]

[Table 4]

As is clear from the results shown in Table 4, the number of active material drops of the hydrogen-absorbing alloy electrodes r and s in which the dry pressurized electrode plate was not subjected to the pure water treatment was 65/100 or 68/1.
00, the number of active material drops of the hydrogen-absorbing alloy electrodes a and b obtained by subjecting the dried and pressed electrode plates to pure water treatment was 1/1.
It can be seen that the number has sharply decreased to 00 and 2/100. This is because if pure water or water is applied to the surface of the dry pressing electrode plate and adheres, the pure water or water permeates the hydrogen storage alloy layer and the water-soluble binder is re-dissolved. To become
The cracks generated in the binder at the time of pressurization are dissolved again, and thereafter, when the binder is dried at a lower temperature than the drying step (preferably 40 ° C. or less), the dissolved water-soluble binder is solidified and hydrogen storage is performed. It is considered that the alloy powders and the conductive core and the hydrogen storage alloy powder were strongly bonded. This makes it difficult for the hydrogen storage alloy layer to peel off, thereby preventing the hydrogen storage alloy powder from falling off.

As described above, in the present invention, since pure water or water is applied to and adhered to the surface of the dry pressing electrode plate, the hydrogen storage alloy powder having an average particle size of 60 μm or less is used. Even if the hydrogen storage alloy layer is adhered to the conductive core at a high packing density of 0.85 g / cm ³ or more, the hydrogen storage alloy layer is hardly peeled off, and the hydrogen storage alloy powder can be prevented from falling off. As a result, a high-capacity hydrogen-absorbing alloy electrode is formed.If an alkaline storage battery is formed using such a high-capacity hydrogen-absorbing alloy electrode, the capacity ratio of the negative electrode increases and the reserve amount increases. It is possible to provide an alkaline storage battery having excellent cycle characteristics and a long life.

[0052] In the embodiment described above, description has been made of an example of using the _{MmNi 3.4 Co 0 .8 Al 0.2 Mn} 0.6 as the hydrogen storage alloy, the hydrogen storage alloy M
not limited to _{mNi 3.4 Co 0.8 Al 0.2 Mn 0.6} , Mm a Ni b
Co _c Al _d Mn _e (However, in the case of a = 1, 4.5 ≦ b
+ C + d + e ≦ 5.5) may be used. In this case, M
_{m a Ni b Co c Al d} Mn part of Ni represented by _e C
hydrogen storage alloy substituted with o, Mn, Al, or Ni
May be used as a hydrogen storage alloy in which a part of Co is replaced with Co, Cu, Fe, Cr, Si, Mo, or the like.

[0053] _{Further, Mm a Ni b Co c Al} d Mn e in other AB ₅ type rare earth hydrogen storage alloy other than hydrogen absorbing alloy represented, for example, a portion of the Ni Co and A in LaNi ₅ type
A hydrogen storage alloy substituted with l, W, etc. may be used. Further, in the above-described embodiment, the example in which the mechanically pulverized hydrogen storage alloy is used has been described.
A hydrogen storage alloy prepared by an atomizing method or a mixed powder obtained by mixing a pulverized alloy with the hydrogen storage alloy may be used.

In the above-described embodiment, an example in which polyethylene oxide (PEO) is used as the water-soluble binder has been described. However, the water-soluble binder is not limited to polyethylene oxide (PEO), but may be other water-soluble binders. Binders such as hydroxypropylcellulose (HP
C), unsaturated polyester resin (Aerosil), methylcellulose (MC), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyacrylic acid, polyacrylamide, crosslinked starch, sodium acrylate, sodium alginate , Sodium silicate or the like may be used. Further, the binder is not limited to the water-soluble binder, and another binder may be used. However, in this case, it is necessary to attach the solvent of the binder used in place of the pure water treatment to the dry pressurized electrode plate.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a state in which cross-cut grooves are formed in an active material layer in order to measure the adhesive strength of the active material.

[Explanation of symbols]

10: hydrogen storage alloy electrode, 11: conductive core (punched metal), 12, 13: hydrogen storage alloy layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Teruhito Nagae 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Kousuke Satoguchi 2 Keihanhondori, Moriguchi-shi, Osaka 5-5-5 Sanyo Electric Co., Ltd. (72) Inventor Seiji Wada 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5H028 AA05 BB03 BB04 BB05 BB08 CC08 CC12 CC13 HH01 HH03 HH05 HH08 5H050 AA07 BA14 CA03 CB17 DA04 DA11 FA05 FA17 GA02 GA10 GA22 GA27 HA05 HA08 HA15

Claims (8)

[Claims] 1. A hydrogen storage alloy electrode having a mixture containing at least a hydrogen storage alloy powder and a re-dissolvable binder attached to a conductive core, wherein the average particle size of the hydrogen storage alloy powder is The diameter is 60 μm or less, the packing density of the hydrogen storage alloy is 4.85 g / cm ³ or more, and the hydrogen storage alloy powders and the hydrogen storage alloy powder and the conductive core can be re-dissolved. A hydrogen storage alloy electrode which is fixed by a suitable binder. 2. A method for producing a hydrogen-absorbing alloy electrode in which an active material slurry containing at least a hydrogen-absorbing alloy powder is attached to a conductive core, wherein the conductive core has an average particle diameter of 60 μm or less. An application step of applying an active material slurry composed of the resorbable binder powder, a remeltable binder and a solvent of the binder to form a slurry-coated electrode, and drying the slurry-coated electrode. A drying step of forming a drying electrode, a pressing step of pressing the drying electrode to form a pressing electrode, and a solvent adhering step of adhering a solvent of the binder to the surface of the pressing electrode; 4.85 g / cm of hydrogen storage alloy powder on the conductive core
^A method for manufacturing a hydrogen storage alloy electrode, wherein the electrode is attached at a packing density of ³ or more. 3. A method for producing a hydrogen storage alloy electrode in which an active material slurry containing at least a hydrogen storage alloy powder is attached to a conductive core, wherein the binder is capable of being re-dissolved in the conductive core. And a binder application step of applying a binder solution comprising the solvent of the binder, and an average particle diameter of 60 μm on the conductive core coated with the binder.
m, a coating step of applying an active material slurry containing a hydrogen storage alloy powder of m or less to form a slurry-coated electrode; a drying step of drying the slurry-coated electrode to form a dry electrode; A pressurizing step of pressurizing the pressurized electrode; and a solvent adhering step of adhering a solvent of the binder to the surface of the pressurized electrode, wherein 4.85 g of the hydrogen storage alloy powder is applied to the conductive core. / Cm
^A method for manufacturing a hydrogen storage alloy electrode, wherein the electrode is attached at a packing density of ³ or more. 4. The method according to claim 2, further comprising, after the solvent attaching step, a low-temperature drying step of drying the electrode to which the solvent is attached at a lower temperature than the drying temperature in the drying step. Item 4. The method for producing a hydrogen storage alloy electrode according to Item 3. 5. The method for producing a hydrogen storage alloy electrode according to claim 4, further comprising, after the low-temperature drying step, a re-pressurizing step of re-pressing the low-temperature dried electrode. 6. The method for manufacturing a hydrogen storage alloy electrode according to claim 5, wherein the pressing force in the re-pressurizing step is a pressing force that compresses the thickness by 10% or less than a predetermined thickness. 7. An alkaline storage battery provided with an electrode group in which a negative electrode coated with a hydrogen storage alloy powder and a positive electrode are laminated via a separator in a metal outer can, wherein the negative electrode is a conductive core. An alkaline storage battery, characterized in that hydrogen storage alloy powder having an average particle size of 60 μm or less is attached at a packing density of 4.85 g / cm ³ or more. 8. The alkaline storage battery according to claim 7, wherein the negative electrode is disposed on the outermost side of the electrode group, and the negative electrode is in contact with the inner surface of the metal outer can.