JP2000357510A - Manufacture of nickel-hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a nickel-hydrogen secondary battery with a high allowable current value, a high capacity, and a long cycle life. SOLUTION: In the manufacturing method of a nickel hydrogen secondary battery, a negative electrode is manufactured in such a way that paste containing a hydrogen storage alloy is applied to a conductive substrate having a thickness of 30-100 μm and many pores of 30-70% porosity, the coated substrate is dried, and then pressed with a roll to obtain the coated substrate with C/B 0.1-2 ton/mm. B is the width of the coated substrate in the direction of the shaft of the roll and C is the load applied with upper and lower rolls. The paste contains styrene-butadiene rubber or its derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a nickel-metal hydride secondary battery having an improved negative electrode containing a hydrogen storage alloy.

[0002]

2. Description of the Related Art A sealed nickel-metal hydride secondary battery is composed of a paste-type positive electrode containing nickel hydroxide as an active material and a paste-type negative electrode containing a hydrogen-absorbing alloy with an electrode group together with an alkaline electrolyte. It is housed in a container and has a closed structure. Generally, conduction of the secondary battery is ensured by welding the positive electrode with a sealing plate serving also as a positive electrode terminal and a lead, and bringing the negative electrode into contact with a container also serving as a negative electrode external terminal. Such sealed nickel-metal hydride secondary batteries have been widely put into practical use as operating power supplies for various electronic devices such as portable telephones and portable imaging devices.

In recent years, electric vehicles have attracted attention, and batteries used as power supplies are required to have larger allowable current values, unlike the above-described power supplies for operating electronic devices. As a secondary battery having a large allowable current value, a nickel cadmium secondary battery is known. However, nickel cadmium secondary batteries have a problem of low capacity.

Japanese Patent Application Laid-Open No. 3-261072 discloses that the porosity is 45 to 70% and the thickness is 0.05 to 0.1%.
A non-sintered hydrogen storage alloy electrode having a current collector made of a 15 mm punched metal is disclosed. Japanese Patent Publication No. 2572337 discloses a nickel-hydrogen secondary battery having a negative electrode sheet in which a hydrogen storage alloy is supported on a punched metal sheet having at least a surface made of nickel and having a porosity of 30 to 44%. Have been.

[0005]

However, it is difficult to improve the allowable current value only by using such a current collector.

The present invention has a high allowable current value, a high capacity,
Another object of the present invention is to provide a method for manufacturing a nickel-metal hydride secondary battery having excellent cycle life.

[0007]

According to the method of manufacturing a nickel-metal hydride secondary battery according to the present invention, a large number of holes having a thickness of 30 to 100 μm and a porosity of 30 to 70% are formed in a negative electrode. After applying a paste containing a hydrogen storage alloy to a conductive substrate having the coating and drying the obtained coated body, a roll press is performed on the coated body so that C / B is 0.1 to 2 ton / mm. It is a feature.

Here, B is the width of the coating body in the direction along the axis of the roll, and C is the rolling load by the upper and lower rolls.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A nickel hydride secondary battery (cylindrical nickel hydride secondary battery) manufactured by the method according to the present invention will be described below with reference to FIG.

An electrode group 5 formed by stacking a positive electrode 2, a separator 3, and a negative electrode 4 and winding them in a spiral shape is accommodated in a cylindrical container 1 having a bottom. The negative electrode 4 is arranged at the outermost periphery of the electrode group 5 and is in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. A circular first sealing plate 7 having a hole 6 in the center is arranged at the upper opening of the container 1. The ring-shaped insulating gasket 8 is
Is arranged between the periphery of the container and the inner surface of the upper opening of the container 1,
The sealing plate 7 is airtightly fixed to the container 1 via the gasket 8 by caulking to reduce the diameter of the upper opening inward. One end of the positive electrode lead 9 is connected to the positive electrode 2, and the other end is connected to the lower surface of the sealing plate 7. The positive electrode terminal 10 having a hat shape is attached on the sealing plate 7 so as to cover the hole 6. Rubber safety valve 1
1 is arranged so as to close the hole 6 in a space surrounded by the sealing plate 7 and the positive electrode terminal 10. A circular holding plate 12 made of an insulating material having a hole in the center is provided on the positive electrode terminal 10 so that a protrusion of the positive electrode terminal 10 is provided on the holding plate 1.
2 so as to protrude from the holes. The outer tube 13 covers the periphery of the holding plate 12, the side surface of the container 1, and the periphery of the bottom of the container 1.

Next, the negative electrode 4, the positive electrode 2, the separator 3
And the electrolyte will be described.

1) Negative electrode 4 The negative electrode 4 is prepared by adding a hydrophilic polymer, a binder, and a conductive material to a hydrogen storage alloy powder and kneading the mixture with water to prepare a paste. After coating on a conductive substrate having a large number of holes of 100 μm and having a porosity of 30 to 70%, and drying the obtained coated body, C is applied to the coated body.
It is manufactured by rolling by performing roll pressing so that / B is 0.1 to 2 ton / mm. Here, B is the width in the direction along the axis of the roll of the width of the application body, and C is the rolling load by the upper and lower rolls. In the production method according to the present invention, cutting can be performed after drying or after roll pressing as necessary.

As the hydrogen storage alloy, for example, La
Ni _5, MmNi ₅ (Mm is misch metal), LmN
i ₅ (Lm is a La-enriched misch metal), and a multi-element alloy in which a part of Ni of these alloys is substituted by at least Al and Mn. The above-described multi-element hydrogen storage alloy has Al and Mn as substitution elements for Ni.
In addition, at least one element selected from Co, Ti, Cu, Zn, Zr, Cr and B may be included.
Above all, the general formula _{LnNi w Co x Al y Mn z} ( However, Ln is a rare earth element, the atomic ratio w, x, y, z respectively 3.30 ≦ w ≦ 4.50,0.50 ≦ x ≦ 1.10 ,
0.20 ≦ y ≦ 0.50, 0.05 ≦ z ≦ 0.20,
And the total value is 4.90 ≦ w + x + y + z ≦ 5.50
Is preferably used. More preferable values of the atomic ratio w, x, y, z are 3.80 ≦ w ≦ 4.20, 0.70 ≦ x ≦ 0.90, respectively.
0.30 ≦ y ≦ 0.40, 0.08 ≦ z ≦ 0.13,
And the total value is 5.00 ≦ w + x + y + z ≦ 5.20
It is.

Examples of the conductive substrate having a large number of holes include a punching metal and a conductive substrate obtained by a powder rolling method.

It is preferable that the conductive substrate having a large number of holes has at least a surface having a material having high alkali resistance and high conductivity. Examples of such a material include nickel.

The reason why the thickness of the conductive substrate having a large number of holes is defined within the above range is as follows. When the thickness is less than 30 μm, the strength is reduced, so that the conductive substrate may be broken at the time of manufacturing the negative electrode (for example, a coating step, a drying step or a rolling step). on the other hand,
When the thickness exceeds 100 μm, the volume occupied by the conductive substrate becomes large, so that the negative electrode becomes bulky, the voids in the battery decrease, and it becomes difficult to accommodate a desired amount of the alkaline electrolyte. As a result, the internal resistance increases with the progress of the charge / discharge cycle, and the cycle life decreases. A more preferable range of the thickness is 35 to 80 μm.

The reason why the porosity of the conductive substrate having a large number of holes is defined in the above range is as follows. When the porosity is less than 30%, the volume occupied by the conductive substrate is increased, so that the voids in the negative electrode are reduced, making it difficult to accommodate a desired amount of the alkaline electrolyte. As a result, the internal resistance increases with the progress of the charge / discharge cycle, and the cycle life decreases. On the other hand, if the porosity exceeds 70%, the strength is reduced, and the conductive substrate may be broken during the production of the negative electrode. A more preferred range of the porosity is 40 to 65%.

The average diameter of the conductive substrate having a large number of holes is preferably in the range of 0.5 to 2.5 mm. This is due to the following reasons. When the average hole diameter is less than 0.5 mm, the gap between the holes of the conductive substrate becomes small and the conductive substrate is easily broken. On the other hand, the average pore size is 2.
If it exceeds 5 mm, the distance between the conductive substrate and the alloy in the hole becomes large, the conductivity decreases, and it may be difficult to increase the allowable current value of the nickel-metal hydride secondary battery. A more preferable range of the average pore diameter is 1.0 to 2.0 mm.

Examples of the hydrophilic polymer include carboxymethylcellulose, methylcellulose, sodium polyacrylate, polyvinyl alcohol, and sodium acrylate-vinyl alcohol copolymer.

Examples of the binder include a fluororesin such as polytetrafluoroethylene, styrene-butadiene rubber and derivatives thereof. Among them, derivatives of styrene-butadiene rubber are preferred.
As the derivative, those having a carboxyl group are preferable because of their high adhesion to the alloy surface. The derivative desirably has a toluene-insoluble content of 60% or more. If the toluene insoluble content is less than 60%, the cycle life may be reduced. A more preferable range of the toluene insoluble content is
70-90%.

In particular, it is preferable to use carboxymethylcellulose, sodium acrylate-vinyl alcohol copolymer and styrene-butadiene rubber derivatives as the hydrophilic polymer and the binder.

As the conductive material, for example, carbon black, flake-shaped conductive material, metal fiber such as nickel fiber, or the like can be used. In particular, it is preferable to use both carbon black and a flake-shaped conductive material.

The flake-shaped conductive material is, for example,
It is obtained by pressing the metal particles so as to have a flat shape. Such a conductive material desirably has alkali resistance, and can be formed of, for example, nickel.

The flake-shaped conductive material has an average diameter of 15 to 20 μm and an average thickness of 1.0 to 1.1.
It is preferable to set it to μm. The flake-shaped conductive material having such an average diameter and an average thickness can improve the conductive path of the negative electrode without reducing the amount of the hydrogen storage alloy of the negative electrode.

The reason why the above-mentioned coated body is rolled by applying a roll press so that C / B is within the above range is as follows. The value represented by C / B is 0.1 ton
If it is less than / mm, it is difficult to increase the density of the negative electrode and improve the allowable current value of the secondary battery. In addition, since it cannot be rolled to a sufficient thickness, it may hinder the increase in capacity of the secondary battery. On the other hand, when the value of C / B is 2.
If it exceeds 0 ton / mm, the hydrogen storage alloy is pulverized at the time of rolling to increase the surface area of the alloy and accelerate the corrosion, so that the cycle life decreases. A more preferred range of C / B is 0.
It is 3 to 1.5 ton / mm.

The diameter of the roll used in the roll pressing is preferably in the range of 35 to 1000 mm. This is due to the following reasons. If the diameter of the roll is less than 35 mm, it may be difficult to sufficiently increase the density of the negative electrode, so that the allowable current value of the secondary battery may be reduced. In addition, since it cannot be rolled to a sufficient thickness, it may hinder the increase in capacity of the secondary battery. Furthermore, since the conductive substrate filled or applied with the paste is easily stretched, the negative electrode may be distorted (curved) or broken by rolling. on the other hand,
If the diameter of the roll exceeds 1000 mm, the contact area between the rolling object and the roll increases, so that the rolling load increases, and it may be substantially difficult to sufficiently increase the density of the negative electrode. The allowable current value of the secondary battery may decrease. In addition, since it cannot be rolled to a sufficient thickness, it may hinder the increase in capacity of the secondary battery. A more preferred range for the diameter of the roll is 150-60.
0 mm.

2) Positive Electrode 2 The positive electrode 2 has a structure in which a positive electrode material containing nickel hydroxide particles as an active material, a conductive material and a binder is supported on a conductive substrate.

As the nickel hydroxide particles, for example, single nickel hydroxide particles or nickel hydroxide particles in which a metal such as zinc, cobalt, bismuth or copper is eutectic can be used. In particular, the latter positive electrode containing nickel hydroxide particles can further improve the charging efficiency in a high-temperature state.

The nickel hydroxide particles have a peak half-value width of the (101) plane determined by an X-ray powder diffraction method of 0.8 ° / 2θ.
(Cu-Kα) or more is preferable. More preferable peak half width of the nickel hydroxide particles is 0.9 to 1.0.
゜ / 2θ (Cu-Kα).

Examples of the conductive material include metal cobalt, cobalt oxide, cobalt hydroxide and the like.

Examples of the binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, polytetrafluoroethylene and the like.

Examples of the conductive substrate include a mesh-like, sponge-like, fiber-like, or felt-like porous metal body made of nickel, stainless steel, or nickel-plated metal.

The positive electrode 2 is prepared, for example, by adding a conductive material to nickel hydroxide particles as an active material, kneading the mixture with a binder and water to prepare a paste, filling the paste into a conductive substrate, and drying the paste. Thereafter, it is manufactured by molding.

3) Separator 3 Examples of the separator 3 include a nonwoven fabric made of polyamide fiber, a nonwoven fabric made of polyolefin fiber such as polyethylene and polypropylene, or a nonwoven fabric provided with a hydrophilic functional group.

4) Alkaline Electrolyte As the alkaline electrolyte, for example, a mixed solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH),
A mixture of potassium hydroxide (KOH) and LiOH, KOH
And a mixed solution of LiOH and NaOH.

The nickel-hydrogen secondary battery manufactured by the method according to the present invention is characterized in that (a) a current collector is welded to the bottom of the electrode group so as to ensure electrical connection with only the negative electrode, and this current collector is It is preferable to weld to the bottom of the container, or (b) to make the end of the conductive substrate of the negative electrode in contact with the bottom of the container a non-porous region. With the configuration of (a) and / or (b), the conductivity of the negative electrode can be further improved, so that the allowable current value and the cycle life can be further improved.

The method of manufacturing a nickel-metal hydride secondary battery according to the present invention described above has a thickness of 30
A paste containing a hydrogen-absorbing alloy is applied to a conductive substrate having a large number of holes having a pore ratio of 30 to 70% and a pore ratio of 30 to 70%, and the obtained coated body is dried.
The roll press is performed so that B is 0.1 to 2 ton / mm. Here, B is the width in the direction along the roll axis of the width of the coating body, and C is the rolling load by the upper and lower rolls. According to such a method, it is possible to manufacture a nickel-metal hydride secondary battery in which a practical charge / discharge cycle life and discharge capacity are secured and an allowable current value is improved.

Further, by including styrene-butadiene rubber or a derivative thereof in the paste for the negative electrode, the charge / discharge cycle life can be improved.
That is, when polytetrafluoroethylene is used as a binder for the negative electrode, the polytetrafluoroethylene is fiberized mainly by using the rolling of the negative electrode, and the conductive substrate is formed by the fiberized polytetrafluoroethylene. Captures hydrogen storage alloy. For this reason, it is necessary to increase the press pressure during roll pressing. Therefore, when a paste containing polytetrafluoroethylene as a binder is applied to the above-described conductive substrate, dried, and then roll-pressed so that C / B satisfies the above range, to produce a negative electrode, In some cases, polytetrafluoroethylene cannot be sufficiently fiberized. If the fiberization is not sufficiently performed, the ability of the polytetrafluoroethylene to capture the alloy decreases, so that the alloy falls off the negative electrode as the charge / discharge cycle progresses, leading to a reduction in cycle life. Styrene-
Butadiene rubber or a derivative thereof can capture the hydrogen-absorbing alloy on the conductive substrate by elasticity and adhesiveness, so that the strength can be ensured even when the pressing pressure during roll pressing is low. Therefore, a paste containing styrene-butadiene rubber or a derivative thereof as a binder is applied to the above-described conductive substrate, dried, and then dried.
When a negative electrode is produced by performing roll pressing so that B satisfies the above range, the alloy can be prevented from falling off from the negative electrode as the charge / discharge cycle progresses, so that the cycle life can be improved. it can.

In particular, a toluene-insoluble content of 60 as a binder is used.
% Or more, and using a styrene-butadiene rubber derivative having a carboxyl group, the derivative has excellent adhesion to a metal, so that the bonding force between alloys and between the alloy and the conductive substrate can be increased. As a result, the negative electrode can further reduce the amount of the hydrogen storage alloy that has fallen off and can improve the conductive path, so that the allowable current value and cycle life of the secondary battery can be further improved. it can.

Further, in the manufacturing method according to the present invention, by adding a flake-shaped conductive material as a conductive material to the paste of the negative electrode, the conductive path in the negative electrode can be converted to a negative electrode containing carbon black or metal fiber as the conductive material. Thus, the allowable current value of the secondary battery can be further increased. Further, by adding styrene-butadiene rubber or a derivative thereof as a binder to the paste of such a negative electrode, the strength of the negative electrode can be improved, and the flake-shaped conductive material and the hydrogen storage alloy fall off. , The charge / discharge cycle life of the secondary battery can be further improved. In particular, by using a styrene-butadiene rubber derivative having a toluene insoluble content of 60% or more and having a carboxyl group as a binder for the negative electrode, the bonding of the alloy, the flake-shaped conductive material, and the conductive substrate is performed. Can improve the condition,
The conductive path in the negative electrode can be further improved, and the alloy and the flake-shaped conductive material can be greatly reduced from falling off. As a result, the charge / discharge cycle life and allowable current value of the secondary battery can be significantly improved.

In the manufacturing method according to the present invention, by including both carbon black and a flake-like conductive material as a conductive material in the paste of the negative electrode, the gas absorption performance of the negative electrode can be ensured by the carbon black. At the same time, since the conductive path in the negative electrode can be improved by the flake-shaped conductive material, the allowable current value can be improved, and the increase in the internal pressure accompanying the progress of the charge / discharge cycle is suppressed, thereby improving the cycle life. be able to.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

(Examples 1-3 and Comparative Examples 1-2) <Preparation of Negative Electrode> A mixture of rare earth metals such as Mm, Ni,
Co, put Mn and Al in the arc melting furnace 10 ^-4 to 1
After evacuating to 0 ^-5 torr, arc discharge was performed in an argon gas atmosphere, and the mixture was heated and melted.
The _{mNi 3.8 Co 0.8 Mn 0.1 Al 0} .4 hydrogen absorbing alloy of the composition of was prepared. This alloy was heat-treated in an argon atmosphere at 1050 ° C. for 6 hours to homogenize the alloy composition. Subsequently, the alloy was roughly pulverized, and further pulverized with a ball mill to prepare a hydrogen storage alloy powder having an average particle diameter of 37 μm. Sodium acrylate-vinyl alcohol copolymer 0.5 part by weight, carboxymethyl cellulose (CMC) 0.1 part by weight, carboxylated styrene having a carboxyl group in the copolymer was added to 100 parts by weight of the obtained hydrogen storage alloy powder. 0.5 part by weight of a butadiene rubber derivative emulsion (solid content 50% by weight, toluene insoluble content 80%, butadiene polymerization ratio 40% by weight) in terms of solid content,
0.5 parts by weight of carbon black and flake-like nickel powder (trade name of Novamet HCA-
1, the thickness is about 1 μm, and the screen analysis value is +3.
25: trace, -400: 98%).
A paste was prepared by mixing with 0 parts by weight. This paste is used as a conductive substrate, and the surface thereof is plated with nickel. The paste is perforated in a staggered pattern except for an end portion connected to a current collector plate described later.
The negative electrode was formed by applying and drying a punching metal having an average pore diameter of 2 mm and a thickness of 60 μm, and applying a roll press with a roll having a diameter of 200 mm so that the above-mentioned C / B becomes a value shown in Table 1 below. Produced.

<Preparation of Positive Electrode> A mixed powder comprising 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide powder was mixed with 0.3 parts of carboxymethyl cellulose (CMC).
A paste was prepared by adding 0.5 parts by weight of a polytetrafluoroethylene dispersion (specific gravity 1.5, solid content 60% by weight) in terms of solid content and mixing with 45 parts by weight of pure water. . Subsequently, the paste was filled in a foamed nickel substrate, dried, and then rolled by roller pressing to produce a positive electrode.

Then, the design capacity ratio of each of the negative electrodes (the design capacity of the positive electrode is set to 1) is set to 1.3, and a separator made of a nonwoven fabric made of a polypropylene fiber which has been graft-polymerized between such positive and negative electrodes is used. It was interposed and spirally wound to produce an electrode group. After welding a circular current collector made of nickel to the non-perforated end of the punched metal of the negative electrode exposed on the bottom surface of such an electrode group, these were collected in a bottomed cylindrical container, and the bottom surface in the container was removed. The current collector was welded.
Subsequently, an alkaline electrolyte of specific gravity 1.30 composed of 7N potassium hydroxide and 1N lithium hydroxide was accommodated in the container, and the container was sealed, as shown in FIG.
A sealed cylindrical nickel-metal hydride secondary battery having a nominal capacity of 1700 mAh and a regulated positive electrode capacity was assembled, and a predetermined activation was performed to obtain a battery.

The obtained secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2 were charged at a current of 1 C to 120%,
The discharge capacity was measured when the battery was discharged to a voltage of 0.3 V with the current A, and the results are shown in Table 1 below.

Further, the secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2 were charged at a current of 1 C at 120% and charged at 1 C.
The charge / discharge cycle of discharging the battery to a voltage of 1.0 V throughout the current was repeated at 25 ° C. In such charge and discharge, the number of charge and discharge cycles when the discharge capacity became 80% or less of the initial value was determined. The results are shown in Table 1 below.

[0048]

[Table 1]

As is apparent from Table 1, the thickness is 60
A paste containing a hydrogen-absorbing alloy is applied to a punching metal having a pore size of 60% with a pore size of 60 μm, dried, and then dried.
Examples 1 to 3 provided with a negative electrode produced by performing roll pressing so that / B is 0.1 to 2 ton / mm.
It can be seen that the secondary battery of No. 3 is superior in discharge capacity and cycle life when discharged with a large current of 30 A as compared with the secondary battery of Comparative Example 1 in which C / B is less than 0.1 ton / mm. . Further, the secondary batteries of Examples 1 to 3 have C / B of 2t.
It can be seen that the cycle life is superior to that of the secondary battery of Comparative Example 2 exceeding on / mm. Regarding the secondary battery of Comparative Example 1, the density of the negative electrode was low, so that the
It is presumed that the resistance between the punching metals increases and the discharge capacity under a large current decreases. It is considered that the reason why the cycle life of the secondary battery of Comparative Example 1 was inferior was that the strength was low and the hydrogen storage alloy fell off as the charge / discharge cycle progressed. On the other hand, it is considered that the cycle life of the secondary battery of Comparative Example 2 was shortened because the hydrogen storage alloy was pulverized by the roll press.

(Examples 4 to 5 and Comparative Examples 3 and 4) The same procedures as in Examples 1 to 3 were carried out except that the negative electrode described below was used.
A sealed cylindrical nickel-metal hydride secondary battery was manufactured in the same manner as described above.

<Preparation of Negative Electrode> A paste having the same composition as that described in Examples 1 to 3 was used as a conductive substrate, and the surface thereof was nickel-plated. Except for a zigzag pattern, the hole opening ratio is the value shown in Table 2 below, the average hole diameter is 2 mm, and the thickness is 60 μm.
Coated on a punching metal, dried,
The above-mentioned C / B with a roll of 0 mm is 0.7 ton / mm
A negative electrode was produced by applying a roll press so as to obtain a negative electrode. In Comparative Example 4 in which the porosity was more than 70%, the negative electrode could not be manufactured because the punched metal coated with the paste was broken during roll pressing.

With respect to the obtained secondary batteries of Examples 4 to 5 and Comparative Example 3, the discharge capacity and the cycle life at 30 A were measured in the same manner as described above, and the results are shown in Table 2 below. Table 2 also shows the results of Example 2.

[0053]

[Table 2]

As is clear from Table 2, the thickness is 60
A paste containing a hydrogen storage alloy is applied to a punching metal having a pore size of 30 to 70% and dried and then roll-pressed so that the above-mentioned C / B becomes 0.7 ton / mm. It can be seen that the cycle life of the secondary batteries of Examples 2, 4, and 5 including the manufactured negative electrode is superior to that of the secondary battery of Comparative Example 3 in which the porosity is less than 30%.

(Examples 6 to 7 and Comparative Examples 5 and 6) Except for using the negative electrode described below,
A sealed cylindrical nickel-metal hydride secondary battery was manufactured in the same manner as described in 3.

<Preparation of Negative Electrode> A paste having the same composition as that described in Examples 1 to 3 was used as a conductive substrate, and the surface thereof was plated with nickel. Except for the staggered grid pattern, the opening rate is 60
%, The average pore diameter is 2 mm, and the thickness is as shown in Table 3 below.
A negative electrode was produced by applying a roll press so that the above-mentioned C / B becomes 0.7 ton / mm with a roll of mm. In Comparative Example 5 in which the thickness of the punched metal was less than 30 μm, the negative electrode could not be produced because the punched metal to which the paste was applied was broken during roll pressing.

With respect to the obtained secondary batteries of Examples 6 to 7 and Comparative Example 6, the discharge capacity and cycle life at 30 A were measured in the same manner as described above, and the results are shown in Table 3 below. Table 3 also shows the results of Example 2.

[0058]

[Table 3]

As is apparent from Table 3, the thickness is 30
A paste containing a hydrogen-absorbing alloy is applied to a punching metal having a porosity of about 100 μm and a porosity of 60%, dried, and then roll-pressed so that the above-mentioned C / B becomes 0.7 ton / mm. It can be seen that the secondary batteries of Examples 2, 6, and 7 provided with the negative electrodes thus obtained have a superior cycle life as compared with the secondary batteries of Comparative Example 6 whose thickness exceeds 100 μm.

Examples 8 to 11 Sealed cylindrical nickel-metal hydride secondary batteries were produced in the same manner as in Examples 1 to 3 except that the negative electrode described below was used.

<Preparation of Negative Electrode> Nickel plating is applied to the surface of a paste having the same composition as that described in Examples 1 to 3 above as a conductive substrate. Except for the staggered grid pattern, the opening rate is 60
%, The average pore diameter is the value shown in Table 4 below, and the thickness is 60 μm.
Coated on a punching metal, dried,
The above-mentioned C / B with a roll of 0 mm is 0.7 ton / mm
A negative electrode was produced by applying a roll press so as to obtain a negative electrode.

With respect to the obtained secondary batteries of Examples 8 to 11, the discharge capacity at 30 A and the cycle life were measured in the same manner as described above, and the results are shown in Table 4 below. Table 4 also shows the results of Example 2.

[0063]

[Table 4]

As is apparent from Table 4, the thickness is 60
μm, porosity 60%, average pore size 0.5-2.5
After applying a paste containing a hydrogen storage alloy to a punching metal having a thickness of 0.2 mm and drying, the aforementioned C / B is 0.7 ton.
The secondary batteries of Examples 2, 9, and 10 each having a negative electrode produced by performing a roll press so that the
It can be seen that the cycle life is superior to the secondary battery of Example 8 in which the average pore diameter is less than 0.5 mm. Further, the secondary batteries of Examples 2, 9, and 10 were 30 times smaller than the secondary batteries of Example 11 in which the average pore diameter exceeded 2.5 mm.
It can be seen that the discharge capacity when discharging with a large current of A is high.

Example 12 A sealed cylindrical nickel-metal hydride secondary battery was manufactured in the same manner as described in Examples 1 to 3, except that the negative electrode described below was used.

<Preparation of Negative Electrode> A sodium polyacrylate-vinyl alcohol copolymer was added to 100 parts by weight of the same hydrogen storage alloy powder as described in Examples 1 to 3 above.
5 parts by weight, carboxymethylcellulose (CMC)
1 part by weight, 0.5 parts by weight of polytetrafluoroethylene dispersion (specific gravity 1.5, solids content 60% by weight) in terms of solids, 0.5 parts by weight of carbon black, and described in Examples 1 to 3 The same flaky nickel powder as above was added and mixed with 50 parts by weight of water to prepare a paste. This paste is used as a conductive substrate, and the surface thereof is plated with nickel. Except for the end connected to the current collector, the paste is perforated in a houndstooth check pattern.
0%, an average pore diameter of 2 mm, a thickness of 60 μm, and a punching metal having a thickness of 60 μm, which is dried and then roll-pressed with a roll having a diameter of 200 mm so that the C / B becomes 0.7 ton / mm. To produce a negative electrode.

With respect to the obtained secondary battery of Example 12,
The discharge capacity and cycle life at 30 A were measured in the same manner as described above, and the results are shown in Table 5 below. Table 5 also shows the results of Example 2.

[0068]

[Table 5]

As is apparent from Table 5, the secondary battery of Example 2 provided with the negative electrode containing a styrene-butadiene rubber derivative having a carboxyl group as a binder contains polytetrafluoroethylene as a binder. It can be seen that the discharge capacity at 30 A is higher and the cycle life is longer than the secondary battery of Example 12 including the negative electrode.

In the above-described embodiment, the separator is interposed between the positive electrode and the negative electrode and spirally wound and accommodated in a cylindrical container having a bottom. It is not limited to a simple structure. For example, the present invention is similarly applicable to a square nickel-metal hydride secondary battery in which a separator is interposed between a positive electrode and a negative electrode, and a laminate of a plurality of the separators is housed in a bottomed rectangular cylindrical container.

[0071]

As described above, according to the present invention, it is possible to provide a method of manufacturing a nickel-metal hydride secondary battery having a high allowable current value, a high capacity, and excellent life characteristics.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a nickel-metal hydride secondary battery manufactured by a method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 3 ... Separator, 4 ... Negative electrode, 5 ... Electrode group, 7 ... Sealing plate, 8 ... Insulating gasket.

 ──────────────────────────────────────────────────続 き Continuing on the front page F-term (reference)

Claims (3)

[Claims] 1. The method for producing a negative electrode, wherein the thickness is 30 to 10
0 μm, a paste containing a hydrogen storage alloy is applied to a conductive substrate having a large number of holes having a porosity of 30 to 70%,
A method for producing a nickel-metal hydride secondary battery, comprising drying the obtained coated body and subjecting the coated body to roll pressing so that C / B is 0.1 to 2 ton / mm.
Here, B is the width in the direction along the roll axis of the width of the coating body, and C is the rolling load by the upper and lower rolls. 2. The method according to claim 1, wherein the paste contains styrene-butadiene rubber or a derivative thereof. 3. The paste according to claim 1, wherein the paste contains a flake-shaped conductive material.
The method for producing a nickel-metal hydride secondary battery according to the above item.