JP3349619B2 - Alkaline secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline secondary battery having a paste type electrode, and more particularly to an alkaline secondary battery having an improved binder for the electrode.

[0002]

2. Description of the Related Art An alkaline secondary battery has a structure in which an electrode group and an alkaline electrolyte prepared by interposing a separator between a positive electrode and a negative electrode are housed in a container. Paste electrodes are used for the positive electrode and the negative electrode. The paste-type electrode is, for example, to prepare a paste containing an active material, a binder, and water, and after filling the paste into a conductive substrate such as a punched metal or a reticulated sintered fiber substrate, the paste is dried. , Formed by molding.

[0003] Since the paste is a water-dispersed system, the binder used has conventionally been methylcellulose (M
C), water-soluble cellulose derivatives represented by carboxymethylcellulose (CMC) or hydroxypropylmethylcellulose (HPMC), polyvinyl alcohol (PVA), polyacrylate, polyacrylamide (PA), polyvinylpyrrolidone (PVP), polyethylene oxide A water-soluble binder such as (PEO) is used.

However, such a water-soluble binder and nickel hydroxide particles (Ni (O
H) ₂ ) to produce a paste-type positive electrode and use this positive electrode in the secondary battery, there are the following problems.
Since the binder has a linear structure in which a single monomer is polymerized, the flexibility is poor, and the bonding force with the nickel hydroxide particles is weak, so that the nickel hydroxide particles are held on the conductive substrate. Power is low. Therefore, in such a secondary battery, there is a problem that the nickel hydroxide particles fall off from the positive electrode as the charge / discharge cycle progresses. This dropping also causes a problem that the nickel hydroxide particles come into contact with the negative electrode to cause an internal short circuit. Further, since the binder has a low viscosity, the nickel hydroxide particles cannot be stably dispersed in the paste. Further, since the binder has poor absorption capacity of the alkaline electrolyte,
The positive electrode has a reduced holding amount of the electrolyte. In particular, since the polyacrylate has an extremely low absorbency of a solution containing a salt such as an alkaline electrolyte, the positive electrode containing the polyacrylate has an extremely small amount of holding the electrolyte. As a result, in the charge / discharge reaction of the secondary battery, the oxidation-reduction reaction between nickel hydroxide and nickel oxyhydroxide (NiOOH), which is performed in the presence of an alkaline electrolyte, hardly occurs. Due to the above-described problems, the internal pressure of the secondary battery increases as the charge / discharge cycle progresses, and the charge / discharge cycle life decreases.

On the other hand, when a paste-type negative electrode is prepared using the above-described water-soluble binder and, for example, a hydrogen storage alloy powder as an active material, and this negative electrode is used in an alkaline secondary battery having the above-described structure, There is a problem shown. Since the binder swells when absorbing the alkaline electrolyte, the negative electrode swells as the charge / discharge cycle progresses, and the gas absorption performance decreases. Further, as described above, the binder has a weak force for holding the nickel hydroxide particles on the current collector, and the paste containing the binder has low dispersion stability. Therefore, in the negative electrode using an active material having a higher specific gravity than nickel hydroxide particles such as a hydrogen storage alloy powder, the amount of falling off with the progress of the charge / discharge cycle is further increased and the dispersion stability of the paste is remarkably reduced. Due to these problems, the internal pressure of the secondary battery increases as the charge / discharge cycle progresses, and the life of the charge / discharge cycle decreases.

Further, when a paste is prepared from a binder comprising the polyvinyl alcohol and the polyacrylate, the polyacrylate is dissolved in water, but the polyvinyl alcohol is a high molecular weight polymer which can be used as a binder. Because it has the property that it becomes difficult to dissolve in water when it becomes
These polymers do not mix well in the paste, making it difficult to stably disperse the active material in the paste. In an alkaline secondary battery provided with an electrode made of such a paste having poor dispersion stability, the active material falls off as the charge / discharge cycle proceeds, the internal pressure increases, and the charge / discharge cycle life is shortened.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the dispersion stability of an aqueous paste, to enable an active material to be firmly held on a conductive substrate, and to absorb an alkaline electrolyte. It is an object of the present invention to provide an alkaline secondary battery having improved charge / discharge cycle life by using a binder having high resistance and excellent swelling resistance when absorbing an alkaline electrolyte for a paste electrode.

[0008]

Means for Solving the Problems The present inventionPertaining to alkaline
Secondary batteryIs a positive electrode active material, a binder andwaterPaste containing
A positive electrode having a structure filled in a conductive substrate,Hydrogen storage
Including goldA negative electrode, interposed between the positive electrode and the negative electrode
Alkaline separator comprising a separator and an alkaline electrolyte.
In the following battery, the binder of the positive electrode has a COOX group
Copolymers of monomers and vinyl alcohol (provided that X
Is the group consisting of hydrogen, alkali metals and alkaline earth metals
Element selected from)particleIncludingThe copolymergrain
The cumulative 10% representative particle diameter D10 of the particles is 1 to 20 μm.
Both have a cumulative 50% representative particle size D50 of 5 to 50 μm.R
(However, D10 and D50 satisfy D10 <D50.
Add)The monomer having a COOX group is acrylic
Acid, maleic acid, fumaric acid, acrylate, maleic acid
Selected from the group consisting of salts and fumarate saltsFeatures
It is assumed that.

Another alkaline rechargeable battery according to the present invention comprises a positive electrode, a negative electrode having a structure in which a paste containing a hydrogen storage alloy , a binder and water is filled in a conductive substrate, and a negative electrode between the positive electrode and the negative electrode. In an alkaline secondary battery provided with a separator interposed in and an alkaline electrolyte, the binder for the negative electrode is a copolymer of a monomer having a COOX group and vinyl alcohol (where X is hydrogen, an alkali metal and Particles selected from the group consisting of alkaline earth metals), and a cumulative 10% representative particle diameter D10 of the copolymer particles
Is 1 to 20 μm and the cumulative 50% representative particle diameter D50
Ri 5~50μm Dare (provided that the said D10 D50
Satisfies D10 <D50) , and has the COOX group.
Monomers are acrylic acid, maleic acid, fumaric acid,
From the group consisting of lylate, maleate and fumarate
It is characterized by being selected .

[0010] Still another alkaline secondary battery according to the present invention includes a positive electrode having a structure in which a paste containing a positive electrode active material, a binder and water is filled in a conductive substrate, and a hydrogen storage alloy , a binder and water . a negative electrode having a paste was filled in a conductive substrate structure, and a separator interposed between the positive electrode and the negative electrode, the alkaline secondary with an alkaline electrolyte
In the following battery, the binder for the positive electrode and the binder for the negative electrode are a copolymer of a monomer having a COOX group and vinyl alcohol (where X is an element selected from the group consisting of hydrogen, alkali metal and alkaline earth metal). in a) comprises particles each said co 10% accumulated representative particle diameter D10 of the polymer particles is 50% cumulative representative particle diameter D50 with a 1~20μm is Ri 5~50μm der (provided that the said D10 D50 Satisfies D10 <D50) , and the COOX group is
Monomers having acrylic acid, maleic acid, fumaric
Acid, acrylate, maleate and fumarate
Selected from the group consisting of:

An example of an alkaline secondary battery (cylindrical alkaline secondary battery) according to the present invention will be described below with reference to FIG. The negative electrode 1 is spirally wound with a separator 3 interposed between the negative electrode 1 and the positive electrode 2, and is housed in a bottomed cylindrical container 4. The negative electrode 1 is arranged at the outermost periphery of the prepared electrode group and is in electrical contact with the container 4. The alkaline electrolyte is contained in the container 4. A circular sealing plate 6 having a hole 5 in the center is arranged at the upper opening of the container 4. Ring-shaped insulating gasket 7
Is disposed between the peripheral edge of the sealing plate 6 and the inner surface of the upper opening of the container 4, and the sealing plate 6 is connected to the container 4 via the gasket 7 by caulking to reduce the diameter of the upper opening inward. And airtightly fixed. One end of the positive electrode lead 8 is connected to the positive electrode 2, and the other end is connected to the lower surface of the sealing plate 6. A positive electrode terminal 9 having a hat shape is mounted on the sealing plate 6 so as to cover the hole 5. A rubber safety valve 10 is disposed in a space surrounded by the sealing plate 6 and the positive electrode terminal 9 so as to close the hole 5.

Next, the positive electrode 2, the negative electrode 1, the separator 3, and the electrolyte will be described. 1) Positive electrode 2 The positive electrode 2 is prepared, for example, by adding a conductive material and a binder to a positive electrode active material, kneading them in the presence of water to prepare a paste, filling the paste into a conductive substrate, After drying, it is manufactured by roller pressing.

Examples of the positive electrode active material include nickel hydroxide, nickel oxide such as nickel oxide (NiO) and nickel hydroxide in which nickel hydroxide, zinc and cobalt are co-precipitated with metal nickel and contained as a solid solution. Nickel compounds can be mentioned. Among them, it is preferable to use nickel hydroxide in which zinc and cobalt are coprecipitated.

Examples of the conductive material include cobalt compounds such as cobalt oxide and cobalt hydroxide, and metallic cobalt. As the conductive substrate,
For example, mesh, sponge, fibrous, formed from nickel, stainless steel or nickel-plated metal
Alternatively, a felt-like porous metal body can be used. Above all, it is preferable to use a porous body having a structure in which metal fibers formed from the above-described types of metals are three-dimensionally arranged.

The binder comprises copolymer particles of a monomer having a COOX group and vinyl alcohol (where X is an element selected from hydrogen, an alkali metal, and an alkaline earth metal). The cumulative 10% representative particle size D10 is 1 to 20 μm, and the cumulative 50% representative particle size D50 is 5 to 50 μm. Alternatively, the binder comprises a mixture of the copolymer particles and another polymer.

Among the above X of the COOX group, hydrogen, sodium, potassium and lithium are particularly preferred. Among them, sodium is more preferred. In addition, the water absorption of the copolymer is controlled by introducing a crosslinked structure into the molecule by copolymerizing a small amount of a divalent or higher-valent monomer such as a divalent acrylate in the copolymer. Can be.

Examples of the monomer having a COOX group include acrylic acid, maleic acid, fumaric acid, acrylate, maleate, fumarate and the like. Above all, acrylates and maleic acid are preferred. In addition, the paste containing the copolymer particles of maleic acid and vinyl alcohol can maintain a stable viscosity during storage aging performed after preparation. The copolymer particles of acrylic acid or acrylate and vinyl alcohol can be produced by copolymerizing an acrylate and vinyl acetate and then saponifying the copolymer. Such copolymer particles are allowed to contain unreacted acrylate or vinyl acetate as a copolymer component.

The cumulative 10% representative particle size D10 is defined as a particle size distribution of the copolymer particles represented by a frequency distribution indicating how many particles are present in a certain particle size section as shown in FIG. The frequency is integrated from the smaller particle size, and the integrated particle occupies 10% of the total frequency. For example, in FIG.
m. The cumulative 50% representative particle size D50 is such that the ratio of the frequency integrated from the smaller particle size to the entire frequency is 5%.
It refers to the particle size reaching 0%. In addition, the D50
Corresponds to the average particle size of the copolymer particles. For example, in FIG. 2, the D50 is 50 μm.

FIG. 3 is a schematic diagram showing the relationship between D10 and D50 and the properties of the paste. The reason why D10 and D50 are limited to the above range will be described with reference to FIG. When D10 is less than 1 μm, the viscosity is reduced due to the low molecular weight copolymer, and the dispersion stability of the paste may be reduced. On the other hand, D10
If it exceeds 20 μm, the paste may gel because of the high molecular weight copolymer, and it may be difficult to uniformly apply the paste to the conductive substrate. If the D50 is less than 5 μm, the viscosity is reduced due to the low molecular weight copolymer, and the dispersion stability of the paste may be reduced. On the other hand, if the D50 exceeds 50 μm, the paste gels due to the high molecular weight copolymer, and it may be difficult to uniformly apply the paste to the conductive substrate. In particular, when D10 is 1.5 to 7
μm, the D50 is 8 to 20 μm, and D10 <D
It is preferable to use copolymer particles having a particle size distribution satisfying 50. The particle size of the copolymer particles is preferably measured by a laser diffraction scattering method.

The copolymer particles may be copolymerized with a small amount of a water-repellent monomer (for example, styrene or butadiene) for the purpose of adjusting hydrophilicity and strength. Among the copolymer particles, those having a straight-chain structure can enhance the fluidity of the paste. Examples of the copolymer particles having a linear structure include copolymer particles of acrylic acid or acrylate of Sumikagel L-5H manufactured by Sumitomo Chemical Co., Ltd. and vinyl alcohol, and the like. be able to. On the other hand, those having a three-dimensional cross-linked structure are inferior in solubility to water as compared with the linear type, but have high viscosity due to high water absorption of the alkaline electrolyte and structural viscosity. Such a copolymer particle can form a stable three-dimensional network structure in the paste due to its structural viscosity, so that the dispersion stability of the paste can be remarkably improved with a small amount. In addition, the binder containing the copolymer particles having the three-dimensional cross-linking structure can hold a larger amount of the alkaline electrolyte in the positive electrode than in the case where a linear type binder is used. As the copolymer particles having a three-dimensional cross-linked structure, Nippon Synthetic Chemical Industry Co., Ltd. has a trade name of a copolymer particle of maleic acid and vinyl alcohol of Aqua Reserve GP, a trade name of Sumitomo Chemical Co., Ltd. Is Sumikagel S-50, Sumikagel S-80, Sumikagel S-100, Sumikagel SP-
510, Sumikagel SP-520 copolymer particles of acrylic acid or acrylate and vinyl alcohol.

Among the copolymer particles having a three-dimensional crosslinked structure and having a particle size distribution as described above, it is preferable to use those having a water absorption capacity of 100 g / g to 800 g / g. A paste containing such a copolymer particle as a binder can have an optimum viscosity for coating and can uniformly disperse the positive electrode active material therein. As a result, a positive electrode having a structure in which the paste is uniformly filled in the conductive substrate and the positive electrode active material is uniformly dispersed in the paste can be produced. The holding force can be sufficiently exhibited. Further, the positive electrode can hold a large amount of an alkaline electrolyte therein. Therefore, by incorporating a positive electrode having such characteristics into an alkaline secondary battery, it is possible to suppress an increase in internal pressure and achieve a longer life.

The reason for limiting the above-described water absorption capacity to the above range is as follows. The water absorption capacity is 1
When it is less than 00 g / g, the viscosity of the paste is reduced and the fluidity becomes too high, so that it may be difficult to uniformly fill the conductive substrate with the paste. On the other hand, if the water absorption capacity exceeds 800 g / g, the paste gels, which may make it difficult to uniformly fill the conductive substrate with the paste. A more preferable range of the water absorption capacity is 300 g / g to 600 g / g.

Examples of the polymer used in combination with the copolymer particles having the above-mentioned particle size distribution include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, and rubber-based polymers (eg, styrene-butadiene rubber (SB)
R) latex, acrylonitrile butadiene rubber (NBR) latex, ethylene propylene diene monomer (EPDM) latex) and other hydrophobic polymers;
For example, hydrophilic polymers such as carboxymethylcellulose (CMC), methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), polyacrylate (eg, sodium polyacrylate (SPA)), polyvinyl alcohol (PVA), and polyethylene oxide; Can be mentioned. In particular, it is preferable to use a mixed polymer composed of the hydrophobic polymer and the hydrophilic polymer. Among these mixed polymers, polytetrafluoroethylene and carboxymethylcellulose,
It is more preferable to use one composed of at least one hydrophilic polymer selected from methylcellulose and polyvinyl alcohol. The polytetrafluoroethylene can improve the strength of the positive electrode. In addition, the carboxymethyl cellulose, the methyl cellulose, and the polyvinyl alcohol can control the fluidity of the paste. Among these, the carboxymethyl cellulose is preferable because it is an excellent paste flow regulator. In addition, the polyethylene, the polypropylene, and the polytetrafluoroethylene can be used in the form of a dispersion.

The binder comprising the copolymer particles alone is
It is desirable to add 0.2 to 10 parts by weight based on 100 parts by weight of the positive electrode active material. This is due to the following reasons. If the addition amount is less than 0.2 parts by weight, the force for holding the positive electrode active material on the conductive substrate may decrease, and the positive electrode active material may fall off as the charge / discharge cycle proceeds. On the other hand, if the addition amount exceeds 10 parts by weight, the paste may thicken,
It is necessary to increase the amount of water added to the paste, and the active material density of the positive electrode may decrease. In particular, the binder is 0.3 parts by weight to 100 parts by weight of the positive electrode active material.
It is more preferable to add 3 parts by weight.

When the binder comprises a mixture of the copolymer particles and another polymer, the copolymer particles are added in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of the positive electrode active material,
Preferably, the polymer is added in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the positive electrode active material. This is due to the following reasons. When the addition amount of the copolymer particles is less than 0.05 parts by weight, there is a possibility that the force for holding the positive electrode active material on the conductive substrate is reduced. On the other hand, if the amount of the copolymer particles exceeds 5 parts by weight, the active material density in the positive electrode may decrease, and battery performance such as battery capacity may deteriorate. If the amount of the polymer is less than 0.1 part by weight, the fluidity and stability of the paste may be reduced. On the other hand, if the amount of the polymer exceeds 5 parts by weight, there is a possibility that the battery performance may be seriously affected, such as the internal pressure characteristics of the secondary battery being reduced. Particularly, the copolymer particles are added in an amount of 0.1 part by weight to 2.0 parts by weight based on 100 parts by weight of the positive electrode active material, and the polymer is added in an amount of 0.3 parts by weight to 100 parts by weight of the positive electrode active material. It is more preferable to add 3 parts by weight.

Copolymer particles of a monomer having a COOX group and vinyl alcohol (where X is an element selected from hydrogen, alkali metal and alkaline earth metal), and a cumulative 10% of the particles are representative particles Diameter D10 is 1-2
0 μm and a cumulative 50% representative particle size D50 of 5 to 5
When a binder having a thickness of 0 μm is used as a binder for the negative electrode, the positive electrode is allowed to contain the following binder in place of the binder described above.

Examples of such a binder include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, rubber-based polymers (eg, styrene butadiene rubber (SBR) latex, acrylonitrile butadiene rubber (NBR) latex, ethylene propylene diene monomer (EPDM) latex); for example, carboxymethylcellulose (CM
C), hydrophilic polymers such as methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), polyacrylates (eg, sodium polyacrylate (SPA)), polyvinyl alcohol (PVA), and polyethylene oxide; .

2) Negative Electrode 1 The negative electrode 1 is manufactured by preparing a paste containing a negative electrode active material, a binder and water, filling the paste into a conductive substrate, drying, and then molding.

As the active material, a material directly involved in the charge / discharge reaction or a material directly involved in the charge / discharge reaction is stored.
Emitting substances can be used. Examples of the former include powders of cadmium compounds such as metal cadmium and cadmium hydroxide. Examples of the latter include, for example, a hydrogen storage alloy powder that stores and releases hydrogen. Among them, a secondary battery provided with a negative electrode containing the above-mentioned hydrogen storage alloy powder is preferable because it can discharge at a higher current and has less risk of environmental pollution than a nickel cadmium secondary battery.

The hydrogen storage alloy is not particularly limited, and may be any alloy capable of storing hydrogen electrochemically generated in an electrolyte and easily releasing the stored hydrogen during discharge. . For example, LaNi ₅ , MmNi
₅ (Mm means a misch metal which is a mixture of lanthanide elements such as La, Ce, Pr, Nd, Sm), LnNi ₅ (Ln; lanthanum-enriched misch metal), and one of these Nis Parts are Al, Mn, Co,
Examples thereof include a multi-element-based material substituted with an element such as Ti, Cu, Zn, Zr, Cr, and B, or a TiNi-based or TiFe-based material. In particular, the general formula LnNi _x M
n _y A _z (However, Ln is La, Nd, Ce, misch metal consisting of Pr, A is Al, at least one metal selected from Co, the atomic ratio x, y, z is the total value is 4.8 ≦ x + y + z ≦ 5.4) It is desirable to use a multi-element hydrogen storage alloy represented by the following formula: Since the negative electrode containing such a hydrogen storage alloy can suppress the pulverization accompanying the progress of the charge / discharge cycle, the charge / discharge cycle life of the secondary battery can be improved.

When a hydrogen storage alloy is used as the negative electrode active material, a conductive material can be added to the paste. Examples of such a conductive material include nickel powder, cobalt oxide, titanium oxide, and carbon black. In particular, it is preferable to use the carbon black as a conductive material.

Examples of the conductive substrate include those having a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and those having a three-dimensional structure such as foamed metal and reticulated sintered metal fibers. Especially, it is preferable to use the above-mentioned punched metal.

The binder comprises copolymer particles of a monomer having a COOX group and vinyl alcohol (where X is an element selected from hydrogen, an alkali metal and an alkaline earth metal). The cumulative 10% representative particle size D10 is 1 to 20 μm, and the cumulative 50% representative particle size D50 is 5 to 50 μm. Alternatively, the binder comprises a mixture of the copolymer particles and another polymer.

Among the above X of the COOX group, it is preferable to use hydrogen, sodium, potassium and lithium. Among them, sodium is more preferred. In addition, the water absorption of the copolymer is controlled by introducing a crosslinked structure into the molecule by copolymerizing a small amount of a divalent or higher-valent monomer such as a divalent acrylate in the copolymer. Can be.

Examples of the monomer having a COOX group include acrylic acid, maleic acid, fumaric acid, acrylate, maleate and fumarate. Above all, acrylates and maleic acid are preferred. In addition, the paste containing the copolymer particles of maleic acid and vinyl alcohol can maintain a stable viscosity during storage aging performed after preparation. The copolymer particles of acrylic acid or acrylate and vinyl alcohol can be produced by copolymerizing an acrylate and vinyl acetate and then saponifying the copolymer. Such copolymer particles are allowed to contain unreacted acrylate or vinyl acetate as a copolymer component.

The reason why D10 and D50 are limited to the above range will be described with reference to FIG. Said D
If 10 is less than 1 μm, the viscosity is reduced due to the low molecular weight copolymer, and the dispersion stability of the paste may be reduced. On the other hand, when D10 exceeds 20 μm,
The paste gels due to the high molecular weight copolymer,
It may be difficult to apply the paste uniformly to the conductive substrate. Further, when the D50 is less than 5 μm, the viscosity is reduced due to the low molecular weight copolymer,
The dispersion stability of the paste may be reduced. On the other hand, if the D50 exceeds 50 μm, the paste gels due to the high molecular weight copolymer, and it may be difficult to uniformly apply the paste to the conductive substrate. Particularly, the D10 is 1.5 to 7 μm, and the D50 is 8 to
It is preferable to use copolymer particles having a particle size distribution of 20 μm and satisfying D10 <D50. The particle size of the copolymer particles is preferably measured by a laser diffraction scattering method.

A small amount of a water-repellent monomer (such as styrene or butadiene) may be copolymerized with the copolymer particles for the purpose of adjusting hydrophilicity and strength. Among the copolymer particles, those having a straight-chain structure can enhance the fluidity of the paste. Examples of the copolymer particles having a linear structure include copolymer particles of acrylic acid or acrylate of Sumikagel L-5H manufactured by Sumitomo Chemical Co., Ltd. and vinyl alcohol, and the like. be able to. On the other hand, those having a three-dimensional cross-linked structure are inferior in solubility to water as compared with the linear type, but have high viscosity due to high water absorption of the alkaline electrolyte and structural viscosity. Such a copolymer particle can form a stable three-dimensional network structure in the paste due to its structural viscosity, so that the dispersion stability of the paste can be remarkably improved with a small amount. In addition, the binder containing the copolymer particles having the three-dimensional cross-linking structure has a stronger force to hold the negative electrode active material on the conductive substrate than when using a linear type binder. As the copolymer particles, Nippon Synthetic Chemical Industry Co., Ltd. has a trade name of a copolymer of maleic acid and vinyl alcohol of Aqua Reserve GP, and Sumitomo Chemical Co., Ltd. has a trade name of Sumikagel S-50. Sumikagel S-80, Sumikagel S-10
0, Sumikagel SP-510, Sumikagel SP-520
Copolymer particles of acrylic acid or acrylate and vinyl alcohol.

Of the copolymer particles having a three-dimensional crosslinked structure and having the above-mentioned particle size distribution, it is preferable to use those having a water absorption capacity of 100 g / g to 800 g / g. The paste containing such copolymer particles as a binder can have an optimum viscosity for coating and can uniformly disperse the negative electrode active material therein. As a result, a negative electrode having a structure in which the paste is uniformly filled in the conductive substrate and in which the negative electrode active material is uniformly dispersed in the paste can be produced. The holding power and the swelling resistance can be sufficiently exhibited. In addition, in order to ensure excellent battery characteristics, the negative electrode needs to hold a certain amount of an alkaline electrolyte therein. By using the above-described copolymer particles having a water absorbing ability as a binder, an appropriate amount of an alkaline electrolyte can be held in the negative electrode. Therefore, by incorporating a negative electrode having such excellent characteristics into an alkaline secondary battery, it is possible to suppress an increase in internal pressure and achieve a long life.

The above-mentioned water absorption capacity is limited to the above range for the following reason. The water absorption capacity is 1
When it is less than 00 g / g, the viscosity of the paste is reduced and the fluidity becomes too high, so that it may be difficult to uniformly fill the conductive substrate with the paste. On the other hand, if the water absorption capacity exceeds 800 g / g, the paste gels, which may make it difficult to uniformly fill the conductive substrate with the paste. A more preferable range of the water absorption capacity is 300 g / g to 600 g / g.

Examples of the polymer used in combination with the copolymer particles having the particle size distribution include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, and rubber-based polymers (eg, styrene-butadiene rubber (SB)
R) latex, acrylonitrile butadiene rubber (NBR) latex, ethylene propylene diene monomer (EPDM) latex) and other hydrophobic polymers;
For example, hydrophilic polymers such as carboxymethylcellulose (CMC), methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), polyacrylate (eg, sodium polyacrylate (SPA)), polyvinyl alcohol (PVA), and polyethylene oxide; Can be mentioned. Among such combined polymers, it is preferable to use one or more selected from carboxymethylcellulose, methylcellulose and polyvinyl alcohol. The carboxymethyl cellulose, the methyl cellulose, and the polyvinyl alcohol can control the fluidity of the paste. Among these, the carboxymethyl cellulose is preferable because it is an excellent fluidity regulator. The polyethylene,
The polypropylene and the polytetrafluoroethylene can be used in the form of a dispersion.

The binder consisting of the copolymer particles alone is
It is desirable to add 0.5 to 2.0 parts by weight to 100 parts by weight of the negative electrode active material. This is due to the following reasons. When the addition amount is less than 0.5 parts by weight,
There is a possibility that the force for holding the negative electrode active material on the conductive substrate may be reduced. On the other hand, if the amount exceeds 2.0 parts by weight,
The dispersion stability of the paste may be reduced. In particular, when a negative electrode active material having a large specific gravity such as a hydrogen storage alloy is used, the hydrogen storage alloy may aggregate in the paste. The binder is more preferably added in an amount of 0.5 to 1.0 part by weight based on 100 parts by weight of the negative electrode active material.

When the binder comprises a mixture of the copolymer particles and another polymer, the copolymer particles are added in an amount of 0.05 to 2.0 parts by weight based on 100 parts by weight of the negative electrode active material. It is desirable that the polymer be added in an amount of 0.1 to 3.0 parts by weight based on 100 parts by weight of the negative electrode active material. This is due to the following reasons. If the amount of the copolymer particles is less than 0.05 parts by weight, the dispersion stability of the paste may be reduced, and the negative electrode may swell with the progress of the charge / discharge cycle. On the other hand, if the amount of the copolymer particles exceeds 2.0 parts by weight, the capacity of the negative electrode may decrease and the internal pressure may increase. If the amount of the polymer is less than 0.1 part by weight, the fluidity of the paste may be insufficient and the application to the conductive substrate may be difficult. On the other hand, if the amount of the polymer exceeds 3.0 parts by weight, the internal pressure may increase. In particular, in order to improve the dispersion stability of the paste, and to prevent swelling due to the progress of the charge and discharge cycle of the negative electrode, 0.2 to 0.5 parts by weight of the copolymer particles is added, It is more preferable to add 0.1 to 0.125 parts by weight of the polymer.

Copolymer particles of a monomer having a COOX group and vinyl alcohol (where X is an element selected from hydrogen, alkali metal and alkaline earth metal), and a cumulative 10% representative particle of the particles Diameter D10 is 1-2
0 μm and a cumulative 50% representative particle size D50 of 5 to 5
When a binder having a thickness of 0 μm is used as a binder for the positive electrode, the negative electrode is allowed to contain the following binder in place of the binder described above.

Examples of the binder include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, rubber-based polymers (eg, styrene butadiene rubber (SBR) latex, acrylonitrile butadiene rubber (NBR) latex, ethylene propylene diene monomer (EPDM) latex); for example, carboxymethylcellulose (CM
C), hydrophilic polymers such as methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), polyacrylates (eg, sodium polyacrylate (SPA)), polyvinyl alcohol (PVA), and polyethylene oxide; . 3) Separator 3 As the separator 3, for example, a non-woven fabric made of an ethylene-vinyl alcohol copolymer fiber or a non-woven fabric made of a polyolefin fiber (for example, a non-woven fabric made of a polyethylene fiber or a non-woven fabric made of a polypropylene fiber) is provided with a hydrophilic functional group. Examples thereof include nonwoven fabrics made of polyamide fibers such as nylon 6,6. Examples of a method for imparting a hydrophilic functional group to the polyolefin fiber nonwoven fabric include a corona discharge treatment, a sulfonation treatment, a graft copolymerization, and the application of a surfactant or a hydrophilic resin. 4) Alkaline Electrolyte Solution As the alkali electrolyte solution, a potassium hydroxide solution or a mixed solution obtained by adding one or both of sodium hydroxide and lithium hydroxide to potassium hydroxide can be used.

[0045]

The binder for the paste-type positive electrode of the alkaline secondary battery according to the present invention contains copolymer particles of a monomer having a COOX group and vinyl alcohol, and the cumulative 10% representative particle diameter D10 of the particles is 1%. And the cumulative 50% representative particle size D50 is 5 to 50 μm.

Since the paste containing the copolymer particles has excellent dispersion stability and optimum viscosity for coating, the positive electrode prepared from the paste can uniformly disperse the active material therein.

The copolymer particles are more flexible than conventional binders composed of a polymer of a single monomer, so that they can wrap and hold the active material. In addition, since the copolymer particles have an OH group and a COOX group in vinyl alcohol, the number of types of adsorptive functional groups can be increased as compared with a conventional binder. Since the locations where these adsorptive functional groups are adsorbed to the positive electrode active material are different from each other, the number of bonding points between the copolymer particles and the positive electrode active material can be increased. Therefore, since the paste-type positive electrode made from the binder containing the copolymer particles can firmly hold the positive electrode active material on the conductive substrate, the alkaline secondary battery including the positive electrode has a charge / discharge cycle. It is possible to prevent the active material from falling off from the positive electrode as the process proceeds.

Further, since the copolymer particles have a high ability to absorb the alkaline electrolyte, the positive electrode containing the copolymer particles can hold a large amount of the alkaline electrolyte required for the charge / discharge reaction.

As described above, by providing the positive electrode manufactured using the binder containing the copolymer particles,
A uniform dispersion of the positive electrode active material, a reduction in the amount of the positive electrode active material falling off with the progress of the charge / discharge cycle, and the retention of a large amount of the alkaline electrolyte can be achieved, so that the internal pressure rises with the progress of the charge / discharge cycle. Can be provided, and an alkaline secondary battery having an improved charge / discharge cycle life can be provided.

Another alkaline secondary battery according to the present invention uses the above-mentioned copolymer particles as a binder for a paste type negative electrode. Since the paste containing the copolymer particles has excellent dispersion stability and an optimum viscosity for coating, the negative electrode prepared from the paste can uniformly disperse the active material therein. In addition, the adsorptive functional group of the copolymer particles can be adsorbed to various portions of the negative electrode active material, and the copolymer particles can wrap the negative electrode active material, so that the copolymer A negative electrode made of a binder containing particles can firmly hold a negative electrode active material on a conductive substrate. In particular, by using a binder containing the copolymer particles in a paste containing a negative electrode active material having a large specific gravity such as a hydrogen storage alloy, the dispersion stability of the paste can be significantly improved, and The amount of the negative electrode active material falling off as the discharge cycle progresses can be drastically reduced.

Further, since the copolymer particles hardly swell when absorbing the alkaline electrolyte, it is necessary to prevent the negative electrode containing the copolymer particles from swelling as the charge / discharge cycle progresses in the secondary battery. Can be prevented. as a result,
The negative electrode can maintain high gas absorption performance for a long time.

As described above, the provision of the negative electrode produced by using the binder containing the copolymer particles enables uniform dispersion of the negative electrode active material and dropping of the negative electrode active material as the charge / discharge cycle progresses. To provide an alkaline secondary battery in which the internal pressure is suppressed from increasing due to a charge / discharge cycle, and the charge / discharge cycle life is improved, because the amount can be reduced and the gas absorption performance can be improved. Can be.

In still another alkaline secondary battery according to the present invention, a binder containing the copolymer particles is used for both a positive electrode and a negative electrode. The paste-type positive electrode including the copolymer particles and the paste-type negative electrode including the copolymer particles have excellent characteristics as described above. For this reason, an alkaline secondary battery equipped with such a positive electrode and a negative electrode can prevent the internal pressure from rising due to the progress of the charge / discharge cycle, keep the internal pressure low for a long period of time, and greatly improve the charge / discharge cycle life. can do.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. (1) Copolymer particles of a monomer having a COOX group and vinyl alcohol are contained as a binder, and the particles have a cumulative 10% representative particle diameter D10 of 1 to 20 μm and a cumulative 50% representative particle diameter D50 of 5%. An alkaline secondary battery including a negative electrode having a thickness of about 50 μm. Examples 1 to 4 and Reference Examples 1 and 2 <Preparation of Paste Type Negative Electrode> Ln (Ln is a misch metal composed of 50% by weight of La, 4% by weight of Ce, 11% by weight of Pr, and 35% by weight of Nd) And Ni, Co, Mn,
A hydrogen storage alloy represented by the formula Ln _w Ni _4.0 Co _0.4 Mn _0.3 Al _0.3 was prepared from Al and pulverized. A paste was prepared by kneading 100 parts by weight of the obtained hydrogen storage alloy powder, 1.0 part by weight of carbon black, 50 parts by weight of water, and 0.5 part by weight of a binder. This paste was applied to a punched metal serving as a conductive substrate, dried, molded by a roller press, and cut into a desired size to produce a negative electrode.

As the binder, a 10% cumulative representative particle size D10 determined by a laser diffraction scattering method and a 50% cumulative representative particle size D50 of sodium acrylate and vinyl alcohol having the values shown in Table 1 below are used. Polymer particles were used.

As the copolymer particles, Sumikagel SP520, a product of Sumitomo Chemical Co., Ltd., was used. The water absorption capacity of the copolymer particles is 500 g / g.
Met. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles, the viscosity of the aqueous solution was 1500 c.
p. <Preparation of Paste-Type Positive Electrode> 90 parts by weight of nickel hydroxide powder, 10 parts by weight of cobalt monoxide, 3.5 parts by weight of polytetrafluoroethylene as a binder, 0.15 parts by weight of carboxymethyl cellulose, and polyacrylic acid 0.175 parts by weight of soda was added. To this, 60 parts by weight of pure water was added and kneaded to prepare a paste. After filling the paste into a porous metal body made of nickel-plated fiber as a conductive substrate, the paste is further applied to both surfaces thereof, dried, and rolled by a roller press to have a thickness of 0.6 mm. A positive electrode having a capacity per unit volume of 670 mAH / cc was produced.

An electrode group was formed by spirally winding the obtained negative electrode and positive electrode through a separator made of a nonwoven fabric made of polyamide fiber via a separator. The electrode group was housed in a cylindrical container having an AA size, an electrolyte consisting of 7N KOH and 1N LiOH was injected, sealed, and the capacity was set to 1000 mAh.
The cylindrical alkaline secondary battery having the structure shown in FIG. 1 described above was assembled.

The obtained secondary batteries of Examples 1 to 4 and Reference Examples 1 and 2 were aged at 45 ° C. for 24 hours, and were then charged for the first time and then used in. Example 1 with first charging
-4 and the secondary batteries of Reference Examples 1 and 2, 15 at 1C
After charging at 0%, the charge-discharge cycle in which the cut-off voltage was 1 V and the battery was discharged at 1 C was repeated seven times. Further, after charging these secondary batteries at 480% at 1 C, the charge / discharge cycle of discharging at 1 C with the cutoff voltage at 1 V is 10 cycles.
The internal pressure, the discharge capacity and the battery voltage at the 10th cycle were measured, and the results are shown in Table 2.

The charge / discharge cycle in which the secondary batteries of Examples 1 to 4 and Reference Examples 1 and 2 that were initially charged were charged at 150% at 1 C, and then discharged at 1 C with a cutoff voltage of 1 V. , And the number of cycles required for the capacity to become 800 mA or less was measured. The results are also shown in Table 2.

The dispersibility and stability of the pastes of the negative electrodes of Examples 1 to 4 and Reference Examples 1 and 2 (observation of changes in appearance after standing overnight) and film strength (conductivity of the paste coated with the paste) Affixing an adhesive tape to the substrate and judging by the amount of the paste peeled off from the substrate with the adhesive tape).
Shown in

On the other hand, the negative electrodes of Examples 1 to 4 and Reference Examples 1 and 2 were immersed in ion-exchanged water for 60 minutes, and their surfaces were lightly wiped with water-absorbing paper five times and weighed to determine the water absorption ( The rate of increase in weight before inundation) was determined, and the results are also shown in Table 3 below. Furthermore, the state of swelling of the negative electrode after water absorption was evaluated relatively in five steps from the appearance, and the results are also shown in Table 3 below.

After the operation of spirally winding the negative electrodes of Examples 1 to 4 and Reference Examples 1 and 2 was repeated five times, these negative electrodes were weighed and the weight was reduced as compared with that before the winding. The strength of the negative electrode was measured by determining whether it was performed. The results are shown in Table 3 below.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

As is clear from Table 2, the secondary batteries of Examples 1 to 4 have a high capacity and a high voltage, have lower battery internal pressures than those of Reference Examples 1 and 2, and have a longer charge / discharge cycle life. It turns out that it is long.

As is clear from Table 3, the negative electrodes of Examples 1 to 4 have high water absorption, can suppress swelling during water absorption, and have high strength. Further, it can be seen that the pastes of Examples 1 to 4 are superior in the dispersion stability and the coating film strength as compared with the pastes of Reference Examples 1 and 2. Therefore, to suppress the internal pressure rise with the progress of the charge and discharge cycle, and to achieve long life, excellent dispersion stability, high coating film strength, high water absorption, and excellent swelling resistance, strong A binder which simultaneously satisfies the active material holding power, that is, contains a copolymer particle of sodium acrylate and vinyl alcohol, and has a cumulative 1
The 0% representative particle size D10 is 1 to 20 μm and the cumulative 5%.
It is understood that it is important to use a binder having a 0% representative particle diameter D50 of 5 to 50 μm. Examples 5 to 19 As the binder, copolymer particles of sodium acrylate and vinyl alcohol were used alone at the compounding ratio shown in Table 4 below, or the copolymer particles were mixed with carboxymethyl cellulose (CMC) and methyl cellulose. Examples 1 to 4 except that at least one selected from (MC), hydroxypropylmethylcellulose (HPMC), polyvinyl alcohol (PVA), and sodium polyacrylate (SPA) was used in a mixing ratio shown in Table 4 below. A cylindrical alkaline secondary battery having the structure shown in FIG.

As the copolymer particles, Sumikagel SP520 manufactured by Sumitomo Chemical Co., Ltd. was used. The copolymer particles have a cumulative 10% representative particle size D10 determined by a laser diffraction scattering method of 5 μm and a cumulative 50%.
% Representative particle diameter D50 was 12 μm. The water absorption capacity of the copolymer particles was 500 g / g. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles,
The viscosity of the aqueous solution was 1500 cp. Comparative Examples 1 to 4 Examples 1 to 4 except that sodium polyacrylate and one or more kinds selected from carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose and polyvinyl alcohol were used as binders in the mixing ratio shown in Table 4 below. 4, a cylindrical alkaline secondary battery having the structure shown in FIG. 1 described above was assembled.

The obtained Examples 5 to 19 and Comparative Examples 1 to 4
After aging at 45 ° C. for 24 hours, the secondary battery was charged for the first time and then used in. Example 5 with first charging
-19 and the secondary batteries of Comparative Examples 1-4, the internal pressure, the discharge capacity, the battery voltage,
The cycle life was measured, and the results are shown in Table 5 below.

The dispersibility, stability and coating strength of the pastes of the negative electrodes of Examples 5 to 19 and Comparative Examples 1 to 4 were relatively evaluated by the same method as described above.
The results are shown in Table 6 below.

On the other hand, for the negative electrodes of Examples 5 to 19 and Comparative Examples 1 to 4, the water absorption and
The swelling state and the strength were relatively evaluated in five steps, and the results are shown in Table 6 below.

[0072]

[Table 4]

[0073]

[Table 5]

[0074]

[Table 6]

As is clear from Table 5, Examples 5 to 19
It can be seen that the secondary battery has a high capacity, a high battery voltage, can suppress an increase in the internal pressure as the charge / discharge cycle progresses, and has a longer charge / discharge cycle life than Comparative Examples 1 to 4.

As is clear from Table 6, Examples 5-19
It can be seen that the paste No. has excellent dispersion stability and high coating film strength. Further, it can be seen that the negative electrodes manufactured from these pastes have a high water absorption rate, are unlikely to swell after absorbing water, and can firmly hold the active material on the conductive substrate.

On the other hand, it can be seen that the paste of Comparative Example 1 has good dispersion stability and coating strength as in Examples 5 to 19. However, it can be seen that the negative electrode produced from the paste swells when absorbing water, and the amount of the active material dropped off is larger than in Examples 5 to 19. Comparative Example 2
It can be seen that the pastes Nos. 4 to 4 have poor dispersion stability and low coating film strength. Examples 20 to 24 and Reference Examples 3 and 4 Copolymer particles of maleic acid and vinyl alcohol having the D10 and D50 shown in Table 7 below as a binder for the negative electrode were used, and the blending amount was 0.5 wt. A cylindrical alkaline secondary battery having the structure shown in FIG. 1 described above was assembled in the same configuration as in Examples 1 to 4, except for the parts.

As the copolymer particles, Aqua Reserve GP, a product of Nippon Synthetic Chemical Co., Ltd., was used. The water absorption capacity of the copolymer particles was 500 g / g. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles, the viscosity of the aqueous solution was 1500 cp.
Met.

The obtained Examples 20 to 24 and Reference Example 3,
After the secondary battery of No. 4 was aged at 45 ° C. for 24 hours, it was charged for the first time, and the battery was used. The internal pressure, the discharge capacity, the battery voltage, and the cycle life of the secondary batteries of Examples 20 to 24 and Reference Examples 3 and 4 subjected to the initial charge were measured by the same method as described above. Is shown in Table 8.

Examples 20 to 24 and Reference Examples 3 and 4
With respect to the negative electrode paste, dispersibility, stability and coating film strength were relatively evaluated in five steps by the same method as described above, and the results are shown in Table 9 below.

On the other hand, Examples 20 to 24 and Reference Examples 3 and 4
With respect to the negative electrode, the water absorption, the swelling state, and the strength were relatively evaluated in five steps by the same method as described above, and the results are also shown in Table 9 below.

[0082]

[Table 7]

[0083]

[Table 8]

[0084]

[Table 9]

As is clear from Table 8, Examples 20 to 2
The secondary battery of No. 4 has a high capacity and a high voltage.
4, the internal pressure of the battery is lower and the charge / discharge cycle life is longer.

As is clear from Table 9, Examples 20 to 2
The negative electrode of No. 4 has high water absorption and can suppress swelling at the time of water absorption,
It can be seen that the strength is high. Further, it can be seen that the pastes of Examples 20 to 24 are superior in the dispersion stability and the coating film strength as compared with the pastes of Reference Examples 3 and 4. Therefore, in order to suppress the increase in internal pressure due to the progress of the charge and discharge cycle and to achieve long life, excellent dispersion stability, high coating film strength,
It contains a binder that simultaneously satisfies both high water absorption, excellent swelling resistance, and strong active material holding power, that is, a copolymer particle of maleic acid and vinyl alcohol, and the cumulative amount of the particle
The 0% representative particle size D10 is 1 to 20 μm and the cumulative 5%.
It is understood that it is important to use a binder having a 0% representative particle diameter D50 of 5 to 50 μm. Examples 25 to 39 As the binder, a copolymer particle of maleic acid and vinyl alcohol was used alone in the compounding ratio shown in Table 10 below, or the copolymer particles were combined with carboxymethylcellulose, methylcellulose, and hydroxypropylmethylcellulose. A negative electrode was manufactured in the same manner as in Examples 1 to 4, except that at least one selected from the group consisting of styrene, polyvinyl alcohol and sodium polyacrylate was used in the mixing ratio shown in Table 10 below.

As the copolymer particles, Aqua Reserve GP, a product of Nippon Synthetic Chemical Co., Ltd., was used. The copolymer particles have a 10% cumulative representative particle size D10 determined by a laser diffraction scattering method, 5 μm, and a 50% cumulative particle size.
The representative particle size D50 was 12 μm. The water absorption capacity of the copolymer particles was 500 g / g. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles, the viscosity of the aqueous solution was 1500 cp.

An electrode group was fabricated by spirally winding the obtained negative electrode and the same positive electrode as in Examples 1 to 4 through the same separator as in Examples 1 to 4. The electrode group is housed in a cylindrical container of AA size, the same alkaline electrolyte as in Examples 1 to 4 is injected, sealed, and the capacity is 1000 mAh. The cylindrical alkaline secondary battery having the structure shown in FIG. Was assembled.

The obtained secondary batteries of Examples 25 to 39 were aged at 45 ° C. for 24 hours, and were then charged for the first time and then used in. The internal pressure, the discharge capacity, the battery voltage, and the cycle life of the secondary batteries of Examples 25 to 39, which were initially charged, were measured in the same manner as described above, and the results are shown in Table 11.

The negative electrode pastes of Examples 25 to 39 were evaluated for dispersibility, stability and coating film strength in five steps in the same manner as described above, and the results are shown in Table 12 below.

On the other hand, with respect to the negative electrodes of Examples 25 to 39,
The water absorption, the swelling state, and the strength were relatively evaluated in five steps by the same method as described above, and the results are also shown in Table 12 below. Tables 11 and 12 show Comparative Examples 1-4.
The data of is also described.

[0092]

[Table 10]

[0093]

[Table 11]

[0094]

[Table 12]

As apparent from Table 11, Examples 25 to
The secondary battery of No. 39 has a high capacity, a high battery voltage, and can suppress an increase in internal pressure due to the progress of a charge / discharge cycle.
It can be seen that the charge / discharge cycle life is longer than in Comparative Examples 1 to 4.

As is clear from Table 12, Examples 25 to
It can be seen that the paste No. 39 has excellent dispersion stability and high coating film strength. Further, it can be seen that the negative electrodes manufactured from these pastes have a high water absorption rate, are unlikely to swell after absorbing water, and can firmly hold the active material on the conductive substrate.

(2) Copolymer particles of a monomer having a COOX group and vinyl alcohol as a binder, and a 10% cumulative particle diameter D10 of the particles is 1 to 20 μm.
And the cumulative 50% representative particle size D50 is 5 to 50 μm.
Alkaline secondary battery comprising the positive electrode. Examples 40 to 43 and Reference Examples 5 and 6 <Preparation of Paste-Type Positive Electrode> 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide were mixed with 0.5 part by weight of a binder and 60 parts by weight of pure water. The mixture was added and kneaded to prepare a paste. After filling the paste into a porous metal body made of nickel-plated fiber as a conductive core, the paste is further applied to both surfaces thereof, dried, and rolled by a roller press to a thickness of 0.6 mm. ,
A positive electrode having a capacity per unit volume of 670 mAH / cc was produced.

As the binder, copolymer particles of sodium acrylate and vinyl alcohol having D10 and D50 shown in Table 13 below were used. In addition, Sumikagel SP520, a product of Sumitomo Chemical Co., Ltd., was used as the copolymer particles. The water absorption capacity of the copolymer particles was 500 g / g. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles, the viscosity of the aqueous solution was 1500 cp. <Preparation of paste type negative electrode> 0.5 part by weight of sodium polyacrylate, 0.125 part by weight of carboxymethylcellulose, and 100 parts by weight of hydrogen storage alloy powder having the same composition as in Examples 1 to 4 A paste was prepared by mixing 1.0 part by weight of the dispersion (specific gravity 1.5, solid content 60 wt%) in terms of solid content and 1.0 part by weight of carbon black as a conductive material together with 50 parts by weight of water. This paste was applied to punched metal, dried, and then formed by a roller press to produce a hydrogen storage alloy negative electrode.

Examples 1 to 4 were provided between the obtained positive electrode and negative electrode.
An electrode group was produced by spirally winding through a separator similar to that described above. The electrode group is housed in a cylindrical container of AA size, the same alkaline electrolyte as in Examples 1 to 4 is injected, sealed, and the capacity is 1000 mAh. The cylindrical alkaline secondary battery having the structure shown in FIG. Was assembled.

The obtained Examples 40 to 43 and Reference Example 5,
After the secondary battery of No. 6 was aged at 45 ° C. for 24 hours, the battery was charged for the first time and was habituated. The internal pressure, discharge capacity, battery voltage, and cycle life of the secondary batteries of Examples 40 to 43 and Reference Examples 5 and 6 subjected to the initial charge were measured by the same method as described above. Are shown in Table 14.

Examples 40 to 43 and Reference Examples 5 and 6
The positive electrode paste was evaluated for dispersibility, stability, and coating film strength in five steps in the same manner as described above, and the results are shown in Table 15 below.

On the other hand, Examples 40 to 43 and Reference Examples 5 and 6
With respect to the positive electrode, the water absorption, the swelling state, and the strength were relatively evaluated in five steps by the same method as described above, and the results are also shown in Table 15 below.

[0103]

[Table 13]

[0104]

[Table 14]

[0105]

[Table 15]

As is clear from Table 14, Examples 40 to
It can be seen that the secondary battery of No. 43 has a high capacity and a high voltage, a longer charge / discharge cycle life, and a lower internal pressure than the secondary batteries of Reference Examples 5 and 6.

As is clear from Table 15, Examples 40 to
It is understood that the positive electrode of No. 43 has high water absorption, can suppress swelling at the time of water absorption, and has high strength. Examples 40 to 43
It can be seen that the paste No. has excellent dispersion stability and coating strength as compared with the pastes of Reference Examples 5 and 6. Therefore,
In order to suppress the rise in internal pressure due to the progress of the charge / discharge cycle and achieve long life, excellent dispersion stability, high coating film strength, high water absorption, excellent swelling resistance, and a strong active material It contains a binder that simultaneously satisfies the holding power, ie, copolymer particles of sodium acrylate and vinyl alcohol, and has a cumulative 10% representative particle size D10 of 1 to 20 μm and a cumulative 50% representative particle size. It turns out that it is important to use a binder having a D50 of 5 to 50 μm. Examples 44 to 57 As the binder for the positive electrode, a copolymer particle of sodium acrylate and vinyl alcohol was used alone at the compounding ratio shown in Table 16 below, or the copolymer particles were mixed with polytetrafluoroethylene. (PTFE), sodium polyacrylate (SPA), carboxymethyl cellulose (CM)
C), with the same configuration as in Examples 40 to 43, except that at least one selected from the group consisting of methylcellulose (MC) and polyvinyl alcohol (PVA) is used in the mixing ratio shown in Table 16 below. A cylindrical alkaline secondary battery having a structure was assembled.

As the copolymer particles, Sumikagel SP520, a product of Sumitomo Chemical Co., Ltd., was used. The copolymer particles have a cumulative 10% representative particle size D10 determined by a laser diffraction scattering method of 5 μm and a cumulative 50%.
% Representative particle diameter D50 was 12 μm. The water absorption capacity of the copolymer particles was 500 g / g. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles,
The viscosity of the aqueous solution was 1500 cp. Comparative Examples 11 to 15 As a binder for the positive electrode, one or more polymers selected from sodium polyacrylate, polytetrafluoroethylene, carboxymethylcellulose, methylcellulose, and polyvinyl alcohol, trade names of which are manufactured by Nippon Pure Chemical Co., Ltd. 1 except that the compounding ratio shown in FIG. 16 was used.
A cylindrical alkaline secondary battery having the structure shown in FIG.

The obtained Examples 44 to 57 and Comparative Example 11
After aging the secondary batteries of Nos. To 15 at 45 ° C. for 24 hours, the batteries were charged for the first time and then hammered. For the secondary batteries of Examples 44 to 57 and Comparative Examples 11 to 15 that were initially charged, the internal pressure, the discharge capacity,
The battery voltage and the cycle life were measured, and the results are shown in Table 17 below.

Examples 44 to 57 and Comparative Examples 11 to
With respect to the 15 positive electrode pastes, dispersibility, stability and coating film strength were relatively evaluated in five steps by the same method as described above, and the results are shown in Table 18 below.

On the other hand, Examples 44 to 57 and Comparative Examples 11 to
With respect to the 15 positive electrodes, the water absorption, the swelling state, and the strength were relatively evaluated in five steps in the same manner as described above, and the results are also shown in Table 18 below.

[0112]

[Table 16]

[0113]

[Table 17]

[0114]

[Table 18]

As is clear from Table 17, Examples 44 to
The secondary battery No. 57 has a high capacity, a high battery voltage, a low internal pressure, and a long charge / discharge cycle life as compared with Comparative Examples 11 to 15.

As is clear from Table 18, Examples 44 to
It can be seen that the paste No. 57 has excellent dispersion stability and high coating film strength. Further, it can be seen that the positive electrodes manufactured from these pastes have a high water absorption rate, are unlikely to swell after absorbing water, and can firmly hold the active material on the conductive substrate.

On the other hand, it can be seen that the pastes of Comparative Examples 11 and 14 have good dispersion stability and coating strength. However, it can be seen that the positive electrode produced from the paste swells when absorbing water and also has a larger amount of active material falling off than in Examples 44 to 57. Comparative Example 1
It can be seen that the pastes Nos. 2, 13, and 15 have poor dispersion stability and low coating film strength. It can be seen that the positive electrodes produced from these pastes swell when absorbing water and have a large amount of active material falling off. Examples 60 to 63 and Reference Examples 7 and 8 Copolymer particles of maleic acid and vinyl alcohol having the above-mentioned D10 and D50 shown in Table 19 below were used as binders for the positive electrode. 1 except that the parts shown in FIG.
A cylindrical alkaline secondary battery having the structure shown in FIG.

Further, Aqua Reserve GP, a product of Nippon Synthetic Chemical Co., Ltd., was used as the copolymer particles. The water absorption capacity of the copolymer particles was 500 g / g. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles, the viscosity of the aqueous solution was 1500 cp.
Met.

The obtained Examples 60 to 63 and Reference Example 7,
After the secondary battery of No. 8 was aged at 45 ° C. for 24 hours, the battery was charged for the first time, and the battery was conditioned. For the secondary batteries of Examples 60 to 63 and Reference Examples 7 and 8 that were initially charged, the internal pressure, discharge capacity, battery voltage, and cycle life were measured by the same method as described above. Are shown in Table 20.

Examples 60 to 63 and Reference Examples 7 and 8
For the negative electrode paste, dispersibility, stability, and coating film strength were relatively evaluated in five steps by the same method as described above, and the results are shown in Table 21 below.

On the other hand, Examples 60 to 63 and Reference Examples 7 and 8
With respect to the negative electrode, the water absorption, the swelling state, and the strength were relatively evaluated in five steps by the same method as described above, and the results are also shown in Table 21 below.

[0122]

[Table 19]

[0123]

[Table 20]

[0124]

[Table 21]

As is clear from Table 20, Examples 60 to
It can be seen that the secondary battery of No. 63 has a high capacity and a high voltage, and has a longer charge / discharge cycle life and a lower internal pressure than the secondary batteries of Reference Examples 7 and 8.

As is clear from Table 21, Examples 60 to
It can be seen that the positive electrode of No. 63 has high water absorption, can suppress swelling at the time of water absorption, and has high strength. Examples 60 to 63
It can be seen that the paste No. has excellent dispersion stability and coating strength as compared with the pastes of Reference Examples 7 and 8. Therefore,
In order to suppress the rise in internal pressure due to the progress of the charge / discharge cycle and achieve long life, excellent dispersion stability, high coating film strength, high water absorption, excellent swelling resistance, and a strong active material It contains a binder that simultaneously satisfies the holding power, that is, copolymer particles of maleic acid and vinyl alcohol, and the particles have a cumulative 10% representative particle size D10 of 1 to 20 μm and a cumulative 50% representative particle size D50. Is important to use a binder having a particle size of 5 to 50 μm. Examples 64 to 76 As the binder, a copolymer particle of maleic acid and vinyl alcohol was used alone at a blending ratio shown in Table 22 below, or the copolymer particle was mixed with polytetrafluoroethylene and polyacrylic acid. Except that at least one selected from soda, carboxymethylcellulose, methylcellulose, and polyvinyl alcohol was used in a mixing ratio shown in Table 22 below, positive electrodes were produced in the same configurations as in Examples 40 to 43.

As the copolymer particles, Aqua Reserve GP, a product of Nippon Synthetic Chemical Co., Ltd., was used. The copolymer particles have a 10% cumulative representative particle size D10 determined by a laser diffraction scattering method, 5 μm, and a 50% cumulative particle size.
The representative particle size D50 was 12 μm. The water absorption capacity of the copolymer particles was 500 g / g. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles, the viscosity of the aqueous solution was 1500 cp.

An electrode group was produced by spirally winding the obtained positive electrode and a negative electrode similar to those of Examples 40 to 43 with a separator similar to that of Examples 1 to 4 interposed therebetween. The electrode group is AA
It was stored in a cylindrical container having a size, and the same alkaline electrolyte solution as in Examples 1 to 4 was injected and sealed, and the capacity was 1000 mAh.
The cylindrical alkaline secondary battery having the structure shown in FIG. 1 described above was assembled.

The obtained secondary batteries of Examples 64 to 76 were aged at 45 ° C. for 24 hours, and were then charged for the first time, and were then habituated. The internal pressure, discharge capacity, battery voltage, and cycle life of the secondary batteries of Examples 64 to 76 to which the initial charge was applied were measured in the same manner as described above, and the results are shown in Table 23 below. .

The positive electrode pastes of Examples 64 to 76 were evaluated for dispersibility, stability and coating film strength in five steps in the same manner as described above. The results are shown in Table 24 below.

On the other hand, for the positive electrodes of Examples 64 to 76,
The water absorption, the swelling state, and the strength were relatively evaluated in five steps by the same method as described above, and the results are also shown in Table 24 below. Tables 23 and 24 show Comparative Examples 11 to
15 data are also shown.

[0132]

[Table 22]

[0133]

[Table 23]

[0134]

[Table 24]

As is clear from Table 23, Examples 64 to
It can be seen that the secondary battery of No. 76 has a high capacity, a high battery voltage, a low internal pressure and a long charge / discharge cycle life as compared with Comparative Examples 11 to 15.

As is clear from Table 24, Examples 64 to
It can be seen that the paste No. 76 has excellent dispersion stability and high film strength. Further, it can be seen that the positive electrodes manufactured from these pastes have a high water absorption rate, are unlikely to swell after absorbing water, and can firmly hold the active material on the conductive substrate. (3) It contains copolymer particles of a monomer having a COOX group and vinyl alcohol as a binder, and the particles have a cumulative 10% representative particle size D10 of 1 to 20 μm and a cumulative 50% representative particle size D50 of 5%. And a copolymer particle of a monomer having a COOX group as a binder and vinyl alcohol, and a cumulative 10% representative particle diameter D10 of the particles is 1 to 20 μm and a cumulative 50% representative particle. An alkaline secondary battery including a positive electrode having a diameter D50 of 5 to 50 μm. Examples 90 to 93 <Preparation of Paste-Type Positive Electrode> To 90 parts by weight of nickel hydroxide powder, 10 parts by weight of cobalt monoxide and binders of the types and mixing ratios shown in Table 25 below were added. Pure water 6
0 parts by weight were added and kneaded to prepare a paste. After filling the paste into a porous metal body made of nickel-plated fiber as a conductive substrate, the paste is further applied to both surfaces thereof, dried, and rolled by a roller press to have a thickness of 0.6 mm. A positive electrode having a capacity per unit volume of 670 mAH / cc was produced.

As the copolymer of acrylate and vinyl alcohol, copolymer particles of sodium acrylate and vinyl alcohol, trade name of Sumikagel SP520, manufactured by Sumitomo Chemical Co., Ltd. were used. The copolymer particles,
Cumulative 10% representative particle size D1 determined by laser diffraction scattering method
0 was 5 μm, and the cumulative 50% representative particle diameter D50 was 12 μm. The water absorption capacity of the copolymer particles is 500 g / g.
Met. Further, when a 1% by weight aqueous solution was prepared from the copolymer particles, the viscosity of the aqueous solution was 1500 c.
p.

As the copolymer of maleic acid and vinyl alcohol, a copolymer particle of maleic acid and vinyl alcohol having a trade name of AQUA RESERVE GP manufactured by Nippon Synthetic Chemical Co., Ltd. was used. The copolymer particles have a cumulative 10% representative particle diameter D10 of 5 μm determined by a laser diffraction scattering method.
The cumulative 50% representative particle diameter D50 was 12 μm. The water absorption capacity of the copolymer particles was 500 g / g.
Further, when a 1% by weight aqueous solution was prepared from the copolymer particles, the viscosity of the aqueous solution was 1500 cp. <Preparation of Paste-Type Negative Electrode> 100 parts by weight of a hydrogen storage alloy powder having the same composition as in Examples 1 to 15, 1.0 part by weight of carbon black, 50 parts by weight of water, and the types and mixing ratios shown in Table 25 below And a binder were kneaded to prepare a paste. This paste was applied to a punched metal serving as a conductive substrate, dried, molded by a roller press, and cut into a desired size to produce a negative electrode.

As the copolymer of acrylate and vinyl alcohol and the copolymer of maleic acid and vinyl alcohol, the same copolymers as those used in the above-mentioned positive electrode were used.

Examples 1 to 4 were provided between the obtained positive and negative electrodes.
An electrode group was produced by spirally winding through a separator similar to that described above. The electrode group is housed in a cylindrical container of AA size, the same alkaline electrolyte as in Examples 1 to 4 is injected, sealed, and the capacity is 1000 mAh. The cylindrical alkaline secondary battery having the structure shown in FIG. Was assembled.

The obtained secondary batteries of Examples 90 to 93 were aged at 45 ° C. for 24 hours, and were then charged for the first time and then used in. The internal pressure, the discharge capacity, the battery voltage, and the cycle life were measured for the secondary batteries of Examples 90 to 93 that were initially charged by the same method as described above, and the results are shown in Table 26 below. .

[0142]

[Table 25]

[0143]

[Table 26]

As is clear from Table 26, the results of Examples 90 to 90 are as follows.
The secondary battery of 93 has high capacity and voltage, low internal pressure,
It can be seen that the cycle life is longer than in Examples 1 to 76. This is because copolymer particles of a monomer having a COOX group as a binder for both the positive electrode and the negative electrode and vinyl alcohol (accumulated 10% representative particle diameter D10 is 1 to 20 μm
And the cumulative 50% representative particle size D50 is 5 to 50 μm.
Is used).

In the above embodiment, an example in which the present invention is applied to a cylindrical alkaline secondary battery is described. However, the present invention can be similarly applied to a rectangular alkaline secondary battery. Further, the electrode group housed in the battery container is not limited to the spiral shape, but may be a form in which a plurality of positive electrodes, separators, and negative electrodes are stacked in this order.

[0146]

As described above in detail, according to the present invention, it is possible to provide an alkaline secondary battery that suppresses an increase in internal pressure as the charge / discharge cycle progresses and that achieves a longer life. It works.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an alkaline secondary battery according to the present invention.

FIG. 2 is a characteristic diagram showing an example of a particle size distribution of a copolymer particle of a monomer having a COOX group and vinyl alcohol.

FIG. 3 is a characteristic diagram showing the relationship between the paste properties and the cumulative 10% representative particle diameter D10 and the cumulative 50% representative particle diameter D50.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Negative electrode, 2 ... Positive electrode, 3 ... Separator, 4 ... Container, 6 ...
Sealing plate, 7 ... insulating gasket.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/62 H01M 10/24

Claims (6)

(57) [Claims] 1. A positive electrode active material, a positive electrode having a structure filled in a conductive substrate a paste comprising a binder and water, the hydrogen absorption
An alkaline secondary battery comprising a negative electrode containing a storage alloy, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte, wherein the binder of the positive electrode is a monomer having a COOX group and vinyl alcohol. copolymers of (where, X is hydrogen, an alkali metal and an element selected from the group consisting of alkaline earth metals) comprises particles, 10% accumulated representative particle diameter D10 of the copolymer particles is 1~20μm 50% cumulative representative particle diameter D50 with it is Ri 5~50μm der, the COOX groups
Monomers having acrylic acid, maleic acid, fumaric
Acid, acrylate, maleate and fumarate
An alkaline secondary battery selected from the group consisting of : 2. A positive electrode, a negative electrode having a structure in which a paste containing a hydrogen storage alloy , a binder, and water is filled in a conductive substrate; a separator interposed between the positive electrode and the negative electrode; Wherein the binder for the negative electrode is a copolymer of a monomer having a COOX group and vinyl alcohol (where X is selected from the group consisting of hydrogen, an alkali metal, and an alkaline earth metal). includes an element in which) particles, 10% accumulated representative particle diameter D10 of the copolymer particles is 50% cumulative representative particle diameter D50 with a 1~20μm is Ri 5~50μm der, the COOX groups
Monomers having acrylic acid, maleic acid, fumaric
Acid, acrylate, maleate and fumarate
An alkaline secondary battery selected from the group consisting of : 3. A positive electrode having a structure in which a paste containing a positive electrode active material, a binder and water is filled in a conductive substrate, and a hydrogen absorbing material.
Rechargeable battery including a negative electrode having a structure in which a paste containing a storage alloy , a binder and water is filled in a conductive substrate, a separator interposed between the positive electrode and the negative electrode, and an alkaline electrolyte In the above, the binder for the positive electrode and the binder for the negative electrode are a copolymer of a monomer having a COOX group and vinyl alcohol (where X is an element selected from the group consisting of hydrogen, alkali metal and alkaline earth metal). ) Each containing particles
The cumulative 10% representative particle size D10 of the copolymer particles is 1 to 2
0 μm and a cumulative 50% representative particle size D50 of 5 to 5
0μm der is, a monomer having a COOX group, A
Crilic acid, maleic acid, fumaric acid, acrylate, male
An alkaline secondary battery selected from the group consisting of a phosphate and a fumarate . 4. The cumulative 10% representative particle size D10 is 1.5.
And the cumulative 50% representative particle size D50 is 8 to
4. The method according to claim 1, wherein the thickness is 20 [mu] m.
2. The alkaline secondary battery according to claim 1. 5. The copolymer particles have a three-dimensional crosslinked structure.
The method according to any one of claims 1 to 4, wherein
Alkaline secondary batteries. 6. The copolymer particles have a water absorption capacity of 100.
g / g to 800 g / g.
The alkaline secondary battery according to claim 1.