JP2003323914A - Nickel-hydrogen battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nickel - hydrogen battery improving discharge capacity during discharge at low loads. <P>SOLUTION: The nickel - hydrogen battery 100 comprises a cylindrical metal cell can 11 with a bottom, a hollow cylindrical positive electrode consisting of a positive electrode mix 12 disposed within the can 11 and a negative electrode consisting of a negative electrode mix 14 disposed at the center of the can 11 via a separator 13. By adding, to the negative electrode, polytetrafluoroethylene powder by 0.1 to 1 mass % of the total amount of the negative electrode mix 14, the positive and negative electrode active materials can be filled with high density and negative electrode elasticity is improved, so that, upon insertion of a collector pin 15 into the negative electrode, good electrical contact can be achieved between the collector pin 15 and a hydrogen absorbing alloy. As a result, discharge capacity during discharge at low loads is improved. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nickel-hydrogen battery using nickel hydroxide as a positive electrode active material and a hydrogen storage alloy as a negative electrode active material. Specifically, a hollow cylindrical positive electrode made of a positive electrode mixture is placed in a metal battery can having a bottomed cylindrical shape, and a structure in which a negative electrode made of a negative electrode mixture is placed in the center thereof through a separator is adopted. Then, by blending the negative electrode mixture with at least a blending ratio of polytetrafluoroethylene powder or nickel powder in a predetermined range, the positive electrode active material and the negative electrode active material are densely packed,
The present invention also relates to a nickel-hydrogen battery in which the battery conductivity is improved and the discharge capacity during light load discharge is improved.

[0002]

2. Description of the Related Art In recent years, electronic devices have been miniaturized and made portable, and the number of products driven by batteries has been increasing. In particular, recently, attention has been focused on nickel-hydrogen secondary batteries using a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen. The nickel-hydrogen secondary battery utilizes hydrogen storage alloy for mutual conversion of chemical energy and electric energy by electrochemically advancing hydrogen storage / desorption reaction.

Generally, a nickel-hydrogen battery, as shown in FIG. 5, has a strip-shaped positive electrode plate 1 in which nickel hydroxide is filled in a foamed nickel substrate and a strip-shaped negative electrode plate in which a hydrogen storage alloy is applied to a perforated steel plate. 2 has a structure in which the non-woven fabric separator 3 is spirally wound, inserted into a metal battery can (case), and is sealed with a sealing plate 5 on the upper part thereof via a positive electrode current collector 4. . With such a configuration, the electrode area can be increased, and the nickel-hydrogen battery 10 exhibits excellent heavy load discharge characteristics.

[0004]

However, as described above, the nickel-hydrogen secondary battery 1 using the hydrogen storage alloy is described.
No. 0 is excellent in heavy load characteristics, but conversely, under light load discharge, it is not possible to take out a large capacity as much as an alkaline dry battery. In particular, in recent years, the current consumption of various portable audio devices has been reduced, and the number of cases in which batteries are discharged under a relatively light load is increasing, and even hydrogen storage alloy batteries are expected to have increased capacity during light load discharge. Is becoming. The improvement of light load discharge characteristics has become an issue.

To increase the capacity during light load discharge,
The positive electrode active material and the negative electrode active material of the battery must be densely packed, but the structure in which the band-shaped positive electrode, band-shaped negative electrode, and band-shaped separator used in conventional hydrogen storage alloy batteries are wound directly It has a drawback that the separator, which is not involved, occupies a large volume in the battery container and therefore cannot be filled with a sufficient positive electrode active material and negative electrode active material.

Furthermore, as described above, in order to wind the positive electrode and the negative electrode, the electrode is required to have flexibility, and therefore the electrode density cannot be increased so much and the filling property is impaired.

In order to densely fill the positive electrode active material and the negative electrode active material of a battery, a hollow cylindrical positive electrode is placed in a cylindrical metal battery can with a bottom, which is adopted in alkaline dry batteries.
The structure in which the negative electrode is arranged in the center portion of the separator via the separator is excellent. However, simply nickel hydroxide on the positive electrode,
When a nickel-hydrogen battery having this structure is prepared by using a hydrogen storage alloy for the negative electrode, the hydrogen storage alloy has a certain degree of conductivity, but is insufficient to cause the expected battery reaction. Is. In addition, since the negative electrode mixture made of a hydrogen storage alloy lacks elastic force, when the negative electrode current collector pin is inserted into the negative electrode, the electrical contact between the current collector pin and the hydrogen storage alloy is weak and the current collection on the negative electrode side is poor. However, there is a problem that sufficient capacity cannot be taken out even with light load discharge.

Therefore, the present invention provides a nickel-hydrogen battery which can be filled with a positive electrode active material and a negative electrode active material at a high density, has improved battery conductivity, and has improved discharge capacity during light load discharge. With the goal.

[0009]

In the nickel-hydrogen battery according to the present invention, a hollow cylindrical positive electrode made of a positive electrode mixture is placed in a cylindrical metal battery can having a bottom, and the positive electrode is placed at the center of the positive electrode. A negative electrode made of a negative electrode mixture is arranged via a separator, the negative electrode mixture contains a hydrogen storage alloy and polytetrafluoroethylene powder, and the positive electrode mixture contains nickel hydroxide and graphite.

For example, the blending ratio of the polytetrafluoroethylene powder is set to 0.1 to 1 mass% with respect to the total amount of the hydrogen storage alloy and the polytetrafluoroethylene powder. Further, for example, the nickel powder has a filament shape or a spike shape. The compounding ratio is 1 to 10 mass% with respect to the total amount of the hydrogen storage alloy and the nickel powder.

In the present invention, a hollow cylindrical positive electrode made of a positive electrode mixture is placed in a cylindrical metal battery can having a bottom, and a negative electrode made of a negative electrode mixture is placed in the center thereof through a separator. By adopting the structure, the positive electrode active material and the negative electrode active material can be packed with high density. Then, by adding 0.1 to 1% by mass of polytetrafluoroethylene powder to the negative electrode, the negative electrode is highly elastic, and when the current collecting pin is inserted into the negative electrode, Sufficient electrical contact is obtained between the collector pin and the hydrogen storage alloy. In addition, for example, a nickel powder having a filament shape or a spike shape is added to the negative electrode as a conductive material, and the addition amount is 1 to 10 mass% with respect to the total amount of the hydrogen storage alloy and the nickel powder. It may improve the conductivity of the battery. As a result, it becomes possible to improve the discharge capacity during light load discharge.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A nickel-hydrogen battery 100 as a first embodiment of the present invention will be described below. FIG. 1 shows the configuration of a nickel-hydrogen battery 100 according to the first embodiment. This nickel-hydrogen battery 100 has a structure in which a hollow cylindrical positive electrode made of a positive electrode mixture is arranged in a metal battery can having a bottomed cylindrical shape, and a negative electrode made of a negative electrode mixture is arranged at a central portion thereof through a separator. A mixture containing nickel hydroxide and graphite as a positive electrode mixture and a mixture of a hydrogen storage alloy and polytetrafluoroethylene powder is used as a negative electrode mixture.

The nickel-hydrogen battery 100 shown in FIG.
The battery can 11, the positive electrode mixture 12, the separator 13, the negative electrode mixture 14, and the sealing unit 20. The sealing unit 20 is composed of a negative electrode collector pin 15, a negative electrode terminal plate 16, a sealing member 17, and a reinforcing member 18.

The battery can 11 is formed by pressing a nickel-plated metal plate, for example. This battery can 11 is a positive electrode terminal 1 of a nickel-hydrogen battery 100.
Also doubles as 1a.

The positive electrode mixture 12 has a hollow cylindrical shape as shown in FIG. 1, and is arranged inside the battery can 11. The positive electrode mixture 12 is formed by mixing nickel hydroxide as a positive electrode active material, graphite as a conductive agent, and an alkaline aqueous solution as an electrolyte, and molding the mixture into a hollow cylindrical shape. As the alkaline aqueous solution, for example, an aqueous potassium hydroxide solution is used, but an aqueous solution of lithium hydroxide, sodium hydroxide or the like can also be used.

The positive electrode mixture 12 is manufactured as follows. First, nickel hydroxide, graphite and an aqueous potassium hydroxide solution are weighed at a weight ratio of 86: 8: 6 and mixed by a stirring method such as an impeller or a ball mill. Next, the mixed material is treated, for example, with an outer diameter of 13.2.
A positive electrode mixture 12 is obtained by pressure molding into a hollow cylindrical pellet having a diameter of 9 mm, an inner diameter of 9 mm, a height of 13.4 mm, and a mass of 3 g.
Three hollow cylindrical pellets are inserted into the battery can 11 to form a positive electrode.

The separator 13 has a cylindrical shape with a bottom and is arranged inside the positive electrode mixture 11. For example, the separator 13 is formed into a bottomed cylindrical shape by winding twice a polyolefin non-woven fabric having a thickness of 0.15 mm and bending the bottom portion inward.

The negative electrode mixture 14 is a hydrogen storage alloy and polytetrafluoroethylen powder.
e powder) and is filled in the separator 13. Hydrogen storage alloys include, for example, Co, Mn,
It is Al-containing LmNi5 (here, Lm means a lanthanum-enriched misch metal), and its average particle size is 20 μm.

Further, the sealing unit 20 of the nickel-hydrogen battery 100 includes a negative electrode collector pin 15 and a negative electrode terminal plate 16.
And a sealing member 17 and a reinforcing member 18. A negative electrode collector pin 15 made of, for example, brass is welded to the negative electrode terminal plate 16. The sealing unit 20 functions to seal the opening of the battery can 11.

The nickel-hydrogen battery 100 shown in FIG.
It is manufactured as follows. First, the positive electrode mixture 12 pressure-molded into a hollow cylinder is placed in the battery can 11. Next, the bottomed cylindrical separator 13 is inserted into the center of the positive electrode mixture 12, and the separator 13 is filled with the negative electrode mixture 14. Finally, the sealing unit 20 is inserted into the battery can 11, the edge of the opening of the battery can 11 is bent inside, and the sealing unit 20 is fixed. When inserting the sealing unit 20 into the battery can 11, the negative electrode current collector pin 15 welded to the negative electrode terminal plate 16 is inserted into the negative electrode mixture 14.

In the nickel-hydrogen battery 100 shown in FIG. 1, the current collection of the negative electrode is ensured by inserting the negative electrode current collecting pin 15 welded to the negative electrode terminal plate 16 into the negative electrode mixture 14. Further, the current collection of the positive electrode is ensured by connecting the positive electrode mixture 12 and the battery can 11. The outer peripheral surface of the battery can 11 is covered with an outer label 19 on which the manufacturer name, battery type, cautionary note, etc. are written.
Convex portion of the bottom of the battery can 11 (the nickel-hydrogen battery 10 shown
The positive electrode terminal 11a is located in the upper part of 0).

The discharge reaction and theoretical electromotive force in this nickel-hydrogen battery 100 are as follows. Charge / discharge reaction of negative electrode: MH + OH ⁻ ⇔ M + H ₂ O + e ⁻ Charge / discharge reaction of positive electrode: NiOOH + H ₂ O + e ⁻ ⇔ Ni (OH) ₂ + OH ⁻ Charge / discharge reaction of the entire battery: MH + NiOOH ⇔ M + Ni (OH) ₂

As described above, the nickel-hydrogen battery 100 utilizes the reaction of hydrogen in the solid phase (where MH is a metal hydrate). The theoretical electromotive force is about 1.32V, and the actual operating voltage is about 1.2V.

The nickel-hydrogen battery 100 shown in FIG.
The discharge capacity during light load discharge was measured under the following test conditions.
The discharge capacity during light load discharge was measured by first charging the battery at 100 mA for 25 hours in order to stabilize it, and then measuring 100
Discharging to 1.0 V with mA was repeated twice. Then, after charging at 100 mA for 25 hours, 1.0 mA at 100 mA was added to check the discharge capacity after stabilization.
It was discharged to V. A test was performed on five nickel-hydrogen batteries 100 to measure the average discharge capacity.

Here, the nickel-hydrogen batteries 100 of Examples 1 to 3 and the nickel-hydrogen batteries of Comparative Examples 1 to 3 below were examined. Example 1 is 86 mass% nickel hydroxide
And 8% by mass of graphite and 6% by mass of potassium hydroxide aqueous solution having a concentration of 37% by mass, a positive electrode mixture 12 having an outer diameter of 13.2 mm, an inner diameter of 9 mm, a height of 13.4 mm, and a mass of 3
g into hollow cylindrical pellets and press
The individual pieces were inserted into the battery can 11 to make positive electrodes. Next, two hollow polyolefin nonwoven fabrics having a thickness of 0.15 mm are wound in the hollow portion of the positive electrode mixture 12 and the bottom portion is bent inward so that the separator 13 having a bottomed cylindrical shape is brought into contact with the positive electrode mixture 12. Inserted in. Then, 1 g of an aqueous potassium hydroxide solution having a concentration of 37% by mass was injected into the separator 13. A hydrogen storage alloy of 99.5% by mass and a filamentary nickel powder of 0.5% by mass were mixed therein, and 0.1% by mass of polytetrafluoroethylene powder was added to this mixture, followed by thorough mixing and stirring. Then, 8 g of this was filled as the negative electrode mixture 14. The hydrogen storage alloy used at this time was LmNi5 containing Co, Mn, and Al, and the average particle size was 20 μm. In this negative electrode mixture 14,
A battery was prepared by adding 0.5 g of an aqueous potassium hydroxide solution having a concentration of 37% by mass and following the procedure for preparing the nickel-hydrogen battery 100 described above.

In Example 2, as the negative electrode mixture 14, 99.5 mass% of hydrogen storage alloy and 0.5 mass% of filamentary nickel powder were mixed, and polytetrafluoroethylene powder was added to this mixture in an amount of 0. A battery was produced by the same production method as in Example 1 except that 5% by mass was used.

In Example 3, as the negative electrode mixture 14, 99.5 mass% of hydrogen storage alloy and 0.5 mass% of filamentary nickel powder were mixed, and 1 mass of polytetrafluoroethylene powder was mixed with this mixture. A battery was prepared by the same manufacturing method as in Example 1 except that the battery containing 0.1% was used.

In Comparative Example 1, 70% by mass of nickel hydroxide powder, 7% by mass of graphite, and 23% by mass of an aqueous solution of carboxymethylcellulose (Carboxymethylcellulose) having a concentration of 1% by mass were filled into a foamed nickel plate. It was dried and rolled by a roller press to obtain a positive electrode plate. Further, a mixture of 60 mass% of hydrogen storage alloy and 40 mass% of carboxymethylcellulose aqueous solution having a concentration of 1 mass% was applied on a punching metal, dried, and rolled by a roller press to obtain a negative electrode plate. these,
It was wound through a non-woven fabric separator to obtain an electrode element. This is inserted into a hollow cylindrical metal battery can having an opening, a potassium hydroxide aqueous solution is injected as an electrolytic solution, and the opening is sealed to obtain a nickel-hydrogen battery 10 shown in FIG. It was made.

In Comparative Example 2, a battery was manufactured by the same manufacturing method as in Example 1 except that the negative electrode mixture 14 was made of 100% hydrogen storage alloy.

In Comparative Example 3, as the negative electrode mixture 14, 99.5 mass% of hydrogen storage alloy and 0.5 mass% of filamentary nickel powder were mixed, and 2 mass% of polytetrafluoroethylene powder was mixed with this mixture. A battery was manufactured by the same manufacturing method as in Example 1 except that the battery with the addition of 100% was used.

Table 1 shows the results of measuring the discharge capacities of Examples 1 to 3 and Comparative Examples 1 to 3 under the above-mentioned test conditions.

[0032]

[Table 1]

From the measurement results shown in Table 1, the nickel-hydrogen batteries 100 of Examples 1 to 3 have a discharge capacity of 1400 mAh.
In contrast to the above high capacities, the nickel-metal hydride batteries of Comparative Examples 1 to 3 were all 1400 mAh or less. In particular, when the wound element shown in Comparative Example 1 is used, if a large amount of the positive electrode mixture is filled into the foamed nickel plate in order to increase the packing density, the positive electrode is broken during winding and the discharge capacity becomes low. I got it. In Comparative Example 2, since the polytetrafluoroethylene powder was not contained, it is judged that the current collection of the negative electrode was bad. In Comparative Example 3, since the blending amount of the water-repellent polytetrafluoroethylene powder was excessive, the electrolytic solution on the negative electrode side became insufficient, and the discharge capacity decreased. For these Comparative Examples 1 to 3, the polytetrafluoroethylene powder blending amount is 0.1 to 1% by mass.
In the nickel-hydrogen batteries 100 of Examples 1 to 3, which have been described above, the negative electrode has good current collecting ability and shows a large capacity.

As described above, in the nickel-hydrogen battery 100, the hollow cylindrical positive electrode made of the positive electrode mixture 12 is arranged in the cylindrical metal battery can 11 having a bottom, and the negative electrode via the separator 13 at the center thereof. By adopting the structure in which the negative electrode made of the mixture 14 is arranged, the positive electrode active material and the negative electrode active material can be packed at high density. Then, the negative electrode mixture 14
By adding 0.1 to 1% by mass of polytetrafluoroethylene powder to the total amount of the negative electrode, the negative electrode has a high elasticity, and when the current collecting pin 15 is inserted into the negative electrode, the current collecting pin 15 and the hydrogen storage alloy are Sufficient electrical contact is obtained with. As a result, the discharge capacity during light load discharge can be improved.

Next, a nickel-hydrogen battery 200 as a second embodiment of the present invention will be described. FIG. 2 shows the configuration of a nickel-hydrogen battery 200 according to the second embodiment. In FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

In this nickel-hydrogen battery 200, a hollow cylindrical positive electrode made of a positive electrode mixture is placed in a metal battery can having a bottomed cylindrical shape, and a negative electrode made of a negative electrode mixture is placed in the center thereof through a separator. Is adopted, nickel hydroxide and graphite are contained as a positive electrode mixture, and a mixture of hydrogen storage alloy and nickel powder is contained as a negative electrode mixture.

The nickel-hydrogen battery 200 shown in FIG.
It is composed of a battery can 11, a positive electrode mixture 12, a separator 13, a negative electrode mixture 14A, and a sealing unit 20. The sealing unit 20 is composed of a negative electrode collector pin 15, a negative electrode terminal plate 16, a sealing member 17, and a reinforcing member 18.

As the negative electrode mixture 14A, a mixture of hydrogen storage alloy as a negative electrode active material and nickel powder as a conductive agent to which polytetrafluoroethylene powder is added is used. To be done.
Hydrogen storage alloys as negative electrode active materials include, for example, Co, M
LmNi5 containing n and Al (here, Lm means lanthanum-enriched misch metal), and its average particle size is 20 μm. Further, as the nickel powder as the conductive agent, for example, filament-like nickel powder and spike-like nickel powder are used.
FIG. 3 is a photograph of filamentary nickel powder. FIG. 4 is a photograph of spiked nickel powder.

Other structures are the same as those of the nickel-hydrogen battery 100 shown in FIG. 1 and are manufactured in the same manner.

Also in the nickel-hydrogen battery 200, the current collection of the negative electrode is ensured by inserting the negative electrode current collecting pin 15 welded to the negative electrode terminal plate 16 into the negative electrode mixture 14A. Further, the current collection of the positive electrode is performed by the positive electrode mixture 12 and the battery can 11.
It is secured by connecting and.

Further, the nickel-hydrogen battery 20 shown in FIG.
For 0, the discharge capacity at light load discharge was measured under the same test conditions as the nickel-hydrogen battery 100 of the first embodiment described above.

Here, the nickel-hydrogen batteries 200 of the following Examples 4 to 9 and the nickel-hydrogen batteries of Comparative Examples 4 to 7 were examined.

In Example 4, 86% by mass of nickel hydroxide was used.
And 8% by mass of graphite and 6% by mass of potassium hydroxide aqueous solution having a concentration of 37% by mass, a positive electrode mixture 12 having an outer diameter of 13.2 mm, an inner diameter of 9 mm, a height of 13.4 mm, and a mass of 3
g into hollow cylindrical pellets and press
The individual pieces were inserted into the battery can 11 to make positive electrodes. Next, two 0.15 mm-thick polyolefin nonwoven fabrics are wound in the hollow portion of the positive electrode mixture 12 and the bottom portion is bent inward so that the separator 13 having a bottomed cylindrical shape is brought into contact with the positive electrode mixture 12. Inserted in. Then, 1 g of an aqueous potassium hydroxide solution having a concentration of 37% by mass was injected into the separator 13. 8 g of a negative electrode mixture 14A composed of a mixture of 99% by mass of hydrogen storage alloy and 1% by mass of filamentary nickel powder, and 0.5% by mass of polytetrafluoroethylene powder was added to the mixture. did. The hydrogen storage alloy used at this time was LmNi5 containing Co, Mn, and Al, and the average particle size was 20 μm. Filamentous nickel powder is available from IN
It was manufactured by CO and had an average particle size of 2 μm. This negative electrode mixture 1
To 4A, 0.5 g of 37% aqueous potassium hydroxide solution
Nickel-Hydrogen Battery 10 Added and And Above
A battery was manufactured according to the manufacturing procedure of No. 0.

In Example 5, 95 mass% of hydrogen storage alloy and 5 mass% of filamentary nickel powder were mixed as the negative electrode mixture 14A, and 0.5 mass% of polytetrafluoroethylene powder was added to this mixture. A battery was manufactured in the same manufacturing method as in Example 4 except that the above-mentioned one was used.

In Example 6, as the negative electrode mixture 14A, 90% by mass of a hydrogen storage alloy and a filamentary nickel powder 10 were used.
A battery was produced by the same manufacturing method as in Example 4, except that the mixture was used at a mass% ratio, and 0.5% by mass of polytetrafluoroethylene powder was added to this mixture.

In Example 7, as the negative electrode mixture 14A, 99% by mass of a hydrogen storage alloy and 1% by mass of spiked nickel powder manufactured by INCO, USA were mixed, and polytetrafluoroethylene powder was added to the mixture in an amount of 0. A battery was made in the same manufacturing method as in Example 4, except that the battery containing 5% by mass was used.

In Example 8, as the negative electrode mixture 14A, 95% by mass of a hydrogen storage alloy and 5% by mass of spike-shaped nickel powder manufactured by INCO, USA were mixed, and polytetrafluoroethylene powder was added to the mixture in an amount of 0. A battery was made in the same manufacturing method as in Example 4, except that the battery containing 5% by mass was used.

In Example 9, 90% by mass of hydrogen storage alloy and 10% by mass of spiked nickel powder manufactured by INCO, USA were mixed as the negative electrode mixture 14A, and polytetrafluoroethylene powder was added to this mixture in an amount of 0. A battery was made in the same manufacturing method as in Example 4, except that the battery containing 5% by mass was used.

In Comparative Example 4, a mixture of 70% by mass of nickel hydroxide powder, 7% by mass of graphite and 23% by mass of a carboxymethylcellulose aqueous solution having a concentration of 1% by mass was filled in a foamed nickel plate and then dried. This was rolled with a roller press to obtain a positive electrode plate. Also hydrogen storage alloy 6
A mixture of 0% by mass and 40% by mass of a carboxymethylcellulose aqueous solution having a concentration of 1% by mass was applied to a punching metal, dried, and rolled by a roller press to obtain a negative electrode plate. These were wound via a non-woven fabric separator to obtain an electrode element. This is inserted into a hollow cylindrical metal battery can having an opening, a potassium hydroxide aqueous solution is injected as an electrolytic solution, and the opening is sealed to obtain a nickel-hydrogen battery 10 shown in FIG. It was made.

Comparative Example 5 is the same as Example 4 except that as the negative electrode mixture 14A, a hydrogen storage alloy and 0.5% by mass of polytetrafluoroethylene powder added to this hydrogen storage alloy were used. A battery was manufactured by the manufacturing method described in 1.

In Comparative Example 6, as the negative electrode mixture 14A, 99.5 mass% of hydrogen storage alloy and 0.5 mass% of filamentary nickel powder were mixed, and polytetrafluoroethylene powder was added to this mixture in an amount of 0. A cylindrical hydrogen storage alloy battery was prepared by the same manufacturing method as in Example 4, except that the battery containing 5% by mass was used.

In Comparative Example 7, as the negative electrode mixture 14A, 84.5 mass% of hydrogen storage alloy and 15.5 mass% of filamentary nickel powder were mixed, and polytetrafluoroethylene powder was added to this mixture in an amount of 0. Table 2 shows the results obtained by measuring the batteries of Examples 4 to 9 and Comparative Examples 4 to 7 in which batteries were manufactured by the same manufacturing method as that of Example 4 except that 5% by mass was added under the above-mentioned test conditions. Shown in.

[0053]

[Table 2]

From the measurement results shown in Table 2, the nickel-hydrogen batteries 200 of Examples 4 to 9 have a discharge capacity of 1500 mAh.
The above high capacity was exhibited. On the other hand, in the nickel-hydrogen batteries of Comparative Examples 4 to 7, all were 1500 mAh or less. In particular, when the wound element shown in Comparative Example 4 is used, if a large amount of the positive electrode material is filled in the foamed nickel plate in order to increase the packing density, the positive electrode is broken during winding and the discharge capacity becomes low. Oops. In Comparative Example 5, since the nickel powder as the conductive material was not contained, it is judged that the discharge reaction was not performed promptly. In Comparative Example 6,
Although nickel powder as a conductive material was contained, the amount of addition was not sufficient, so that the discharge reaction did not proceed to a satisfactory level. In Comparative Example 7, since the amount of nickel powder added was excessive, the amount of hydrogen storage alloy directly involved in the reaction was reduced, and the discharge capacity was reduced.

In contrast to these Comparative Examples 4 to 7, in the nickel-hydrogen batteries 200 of Examples 4 to 9 in which the addition amount of nickel powder was optimized, the discharge reaction at the negative electrode was swiftly performed and the capacity was large. . In particular, the nickel powder having a filament shape showed a large capacity. This is because the filamentary nickel powder is bulkier than the spiked nickel powder (see FIGS. 3 and 4), and is more easily entangled,
It is thought that this is because it is easier to form a conductive network. Therefore, as the conductive material of the negative electrode, the shape of the nickel powder is preferably filamentous, and the compounding ratio thereof is based on the total amount of the hydrogen storage alloy and the nickel powder.
It is preferably 1% by mass to 10% by mass.

A method of using nickel powder as a conductive material for the positive electrode mixture 12 is also conceivable, but in this case, the moldability of the positive electrode mixture 12 deteriorates and the high-density filling property is impaired. It is preferable to use graphite as the conductive material of the positive electrode.

Thus, the nickel-hydrogen battery 200
Has a structure in which a hollow cylindrical positive electrode made of the positive electrode mixture 12 is arranged in a metal battery can 11 having a bottomed cylindrical shape, and a negative electrode made of the negative electrode mixture 14A is arranged in the center thereof through a separator 13. By being adopted, the positive electrode active material and the negative electrode active material can be packed with high density. Then, for the negative electrode, a mixture of a hydrogen storage alloy and nickel powder is used as the negative electrode mixture 14A, so that the conductivity of the negative electrode is improved. As a result, the discharge capacity during light load discharge can be improved.

In the above embodiment, the nickel-hydrogen battery 1 in which nickel powder and polytetrafluoroethylene powder are added to the negative electrode having the hydrogen storage alloy.
However, only nickel powder may be added to the negative electrode having the hydrogen storage alloy. Also in this case, the conductivity of the battery can be improved and the discharge capacity at the time of light load discharge can be improved.

[0059]

According to the nickel-hydrogen battery of the present invention, a hollow cylindrical positive electrode made of a positive electrode mixture is placed in a bottomed cylindrical metal battery can, and a separator is provided in the center thereof. A structure in which a negative electrode made of a negative electrode mixture is arranged is adopted, and the positive electrode active material and the negative electrode active material can be packed in high density. Then, by adding 0.1 to 1% by mass of polytetrafluoroethylene powder to the negative electrode, the negative electrode is highly elastic, and when the current collecting pin is inserted into the negative electrode, Sufficient electrical contact is obtained between the collector pin and the hydrogen storage alloy. In addition, for example, a nickel powder having a filament shape or a spike shape is added to the negative electrode as a conductive material, and the addition amount is 1 to 10 mass% with respect to the total amount of the hydrogen storage alloy and the nickel powder. The conductivity of the battery is improved. as a result,
The discharge capacity at the time of light load discharge can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a nickel-hydrogen battery as a first embodiment.

FIG. 2 is a diagram showing a configuration of a nickel-hydrogen battery as a second embodiment.

FIG. 3 is a micrograph of filamentary nickel powder.

FIG. 4 is a micrograph of spiked nickel powder.

FIG. 5 is a diagram showing a configuration of a conventional nickel hydrogen battery.

[Explanation of symbols]

10, 100, 200 ... Nickel-hydrogen battery, 11
... Battery can, 11a ... Positive electrode terminal, 12 ... Positive electrode mixture, 13 ... Separator, 14, 14A ... Negative electrode mixture, 15 ... Negative electrode current collecting pin, 16 ... Negative electrode terminal plate, 17 ... Sealing member, 18 ... Reinforcing member, 19.
..Exterior label, 20 ... Sealing unit

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Claims (4)

[Claims] 1. A hollow cylindrical positive electrode made of a positive electrode mixture is placed in a bottomed cylindrical metal battery can, and a negative electrode made of a negative electrode mixture is placed in the center of the positive electrode through a separator. The nickel-hydrogen battery, wherein the negative electrode mixture contains a hydrogen storage alloy and at least polytetrafluoroethylene powder or nickel powder, and the positive electrode mixture contains nickel hydroxide and graphite. 2. The blending ratio of the polytetrafluoroethylene powder is 0.1 to 1 mass% with respect to the total amount of the hydrogen storage alloy and the polytetrafluoroethylene powder. Nickel-hydrogen battery. 3. The nickel-hydrogen battery according to claim 1, wherein the mixing ratio of the nickel powder is 1 to 10 mass% with respect to the total amount of the hydrogen storage alloy and the nickel powder. 4. The nickel-hydrogen battery according to claim 1, wherein the nickel powder has a filament shape or a spike shape.