JP2000277122A - Cylindrical battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylindrical battery reduced in an occurrence ratio of internal short circuit. SOLUTION: This cylindrical battery is provided with an electrode group 5 produced by winding positive and negative electrodes 2 and 4 through a separator 3. In the battery, at least one of the positive and negative electrodes 2 and 4 has 3-10 kgf of tensile strength in the wound direction as a collector and includes a conductive substrate of a three-dimensional structure having 2-8% of elongation in the wound direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cylindrical battery.

[0002]

2. Description of the Related Art A cylindrical alkaline secondary battery, which is an example of a cylindrical battery, has a structure in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween, and an alkaline electrolyte. Are housed in a container.

The positive electrode is manufactured, for example, by a method described below. First, a paste is prepared by kneading a nickel hydroxide powder, a conductive material and a binder in the presence of water. After filling the paste into a conductive substrate having a three-dimensional structure such as a foamed metal substrate, the paste is dried and pressed to produce the positive electrode.

As described above, the positive electrode using the conductive substrate having a three-dimensional structure as the current collector can increase the amount of active material per unit volume as compared with the sintered positive electrode, and can increase the capacity. Is advantageous.

[0005]

However, since the positive electrode using the conductive substrate having the three-dimensional structure has low flexibility, the positive electrode is spirally wound with a separator interposed between the positive electrode and the negative electrode. Breakage or breakage occurs when the electrode group is manufactured. As a result, the conductive substrate is exposed on the surface of the positive electrode, and the conductive substrate penetrates through the separator and contacts the negative electrode, thereby causing an internal short circuit.

For this reason, it has been proposed to increase the flexibility of the positive electrode by passing the positive electrode between a rubber roller and a metal roller having a diameter smaller than that of the rubber roller to perform softening. However, when the above-described softening process is performed on the positive electrode, the positive electrode often cracks or breaks, which causes a problem that the yield of the positive electrode decreases.

An object of the present invention is to provide a cylindrical battery having a reduced internal short-circuit occurrence rate.

[0008]

According to the present invention, there is provided a cylindrical battery including an electrode group manufactured by spirally winding a positive electrode and a negative electrode through a separator. At least one of the negative electrodes has a tensile strength in the winding direction of 3 to 3 as a current collector.
It is characterized by including a conductive substrate having a three-dimensional structure of 10 kgf and an elongation percentage in a winding direction of 2 to 8%.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A cylindrical alkaline secondary battery as an example of the cylindrical battery 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. The positive electrode tab 9 has one end connected to the positive electrode 2 and the other end connected to the lower surface of the sealing plate 7. The positive electrode terminal 10 having a hat shape is provided on the sealing plate 7 with the hole 6.
It is attached to cover. Rubber safety valve 11
Is disposed 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 with a protrusion of the positive electrode terminal 10.
Are arranged 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 positive electrode 2, the negative electrode 4, the separator 3
And the electrolyte will be described. 1) Positive electrode 2 The positive electrode 2 has a tensile strength in the winding direction of 3 to 10 kg.
f, and has a structure in which a mixture containing an active material is supported on a current collector made of a conductive substrate having a three-dimensional structure and having an elongation of 2 to 8% in a winding direction. In the above-described secondary battery having the structure shown in FIG. 1, since the positive electrode 2 is wound around an end perpendicular to the longitudinal direction as an axis, the winding direction of the positive electrode 2 is the same as the longitudinal direction of the positive electrode 2. Parallel.

The positive electrode 2 is manufactured by, for example, a method described below.

First, a paste is prepared by kneading a nickel hydroxide powder, a conductive material and a binder in the presence of water. The paste has a tensile strength in the longitudinal direction of 3 to
The positive electrode is obtained by filling or coating a current collector made of a conductive substrate having a three-dimensional structure of 10 kgf and a longitudinal elongation of 2 to 8%, followed by drying and rolling.

Preferably, the positive electrode has been subjected to a softening process. The softening is performed using, for example, a flexibility adding device shown in FIG. That is,
As shown in FIG. 2, the flexibility adding device comprises a roller 20 having a flexible surface, such as a rubber roller, opposed to the rubber roller 20 with a desired gap.
Hard roller having a diameter smaller than 0 (for example, a metal roller)
21 are provided. The three pressing mechanisms are aligned at equal intervals. In such an apparatus, fine cracks are formed on the surface of the positive electrode 22 by passing the positive electrode 22 between the rubber roller 20 and the metal roller 21 of each pressing mechanism, and softening is performed.

As the nickel hydroxide powder, for example, a single nickel hydroxide powder or a nickel hydroxide powder 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 powder can further improve the charging efficiency in a high-temperature state.

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

Examples of the binder include polyacrylates such as sodium polyacrylate and potassium polyacrylate, and fluorine resins such as polytetrafluoroethylene.
Alternatively, carboxymethyl cellulose and the like can be mentioned.

Examples of the conductive substrate having the three-dimensional structure include a foamed metal substrate, a metal fiber substrate, and a felt-shaped metal substrate. It is preferable that at least the surface of the conductive substrate is made of nickel.
The conductive substrate is preferably a foamed metal substrate.

The reason why the tensile strength of the conductive substrate in the winding direction is defined in the above range is as follows. If the tensile strength is less than 3 kgf, the mechanical strength of the positive electrode decreases, so that when the positive electrode and the negative electrode are spirally wound with a separator interposed therebetween to form an electrode group, the positive electrode breaks. Further, it becomes difficult to suppress the occurrence of cracks. Further, when the softening is performed, cracks and breaks often occur in the positive electrode. On the other hand, when the tensile strength exceeds 10 kgf, the amount of the mixture held on the conductive substrate is insufficient, and the discharge capacity is reduced. A more preferred range of the tensile strength is 4
５5 kgf.

The reason why the elongation percentage of the conductive substrate in the winding direction is defined in the above range is as follows.
When the elongation is less than 2%, the flexibility of the positive electrode is reduced, so that it is difficult to prevent the positive electrode from being broken or cracked when a spiral electrode group is manufactured. Further, when the softening is performed, cracks and breaks often occur in the positive electrode. On the other hand, if the elongation exceeds 8%, the current collector filled or applied with the paste in the rolling step at the time of manufacturing the positive electrode meanders, and the yield of the positive electrode decreases. A more preferable range of the elongation is 5 to 7%.

In the conductive substrate, the average skeleton diameter of the surface layer portion and the internal average skeleton diameter are equal, and the average skeleton diameter is 40 to 40.
It is desirable to have a structure that is in the range of 80 μm.
This is due to the following reasons. If the average skeleton diameter of the surface layer portion and the average skeleton diameter of the inside are different, the mechanical strength of the conductive substrate is uneven, so that the positive electrode breaks when producing a spiral electrode group and when performing softening. In addition, breakage is likely to occur. The average skeleton diameter is 40 μ
When it is less than m, the mechanical strength of the conductive substrate is not uneven, but the mechanical strength of the substrate itself may be insufficient. On the other hand, if the average skeleton diameter exceeds 80 μm, there is a possibility that the mixture holding amount of the conductive substrate may be insufficient, so that a high discharge capacity may not be obtained. A more preferable range of the average skeleton diameter is 50 to 60 μm. However, the surface layer of the conductive substrate has a thickness corresponding to 5 to 10% of the thickness of the conductive substrate.

The current collector has a tensile strength in the winding direction of 3 to 10 kgf and an elongation in the winding direction of 2 to 8 kgf.
%, A conductive substrate having a two-dimensional structure such as punched metal, expanded metal, or wire mesh as a current collector of the positive electrode, or the two-dimensional negative electrode is used as a current collector for the positive electrode. It is allowed to use a conductive substrate having a structure having irregularities on the periphery of the hole.

2) Negative electrode 4 The negative electrode 4 has a tensile strength in the winding direction of 3 to 10 kg.
f, and has a structure in which a mixture containing an active material is supported on a current collector made of a conductive substrate having a three-dimensional structure and having an elongation of 2 to 8% in a winding direction. In the above-described secondary battery having the structure shown in FIG. 1, since the negative electrode 4 is wound around an end perpendicular to the longitudinal direction as an axis, the winding direction of the negative electrode 4 is the same as the longitudinal direction of the negative electrode 4. Parallel.

The negative electrode 4 includes, for example, an active material, a conductive agent,
The paste is prepared by kneading with a binder and water to prepare a paste, filling the paste into the conductive substrate, drying, and then press-molding.

Examples of the active material include cadmium compounds such as metal cadmium and cadmium hydroxide, and hydrogen. Examples of the host matrix of hydrogen include a hydrogen storage alloy.

In particular, the hydrogen storage alloy is the cadmium
The capacity of the secondary battery can be improved
This is preferable. The hydrogen storage alloy is specially restricted
Instead of hydrogen generated electrochemically in the electrolyte.
Can store and release the stored hydrogen easily when released
Anything can be used. For example, LaNi_Five, MmNi _Five
(Mm is misch metal), LmNi_Five(Lm is La wealth
Misched metal), and a small amount of Ni in these alloys
At least multi-elements substituted with Al and Mn
Can be The multi-element hydrogen storage alloy described above is
In addition to Al and Mn as replacement elements for Ni, Co, T
i, Cu, Zn, Zr, Cr and at least one selected from B
Both may contain one kind of element. Among them, the general formula L
nNi_wCo_xAl_yMn_z(However, Ln is a rare earth element
Element and atomic ratio w, x, y, z are 3.30 ≦ w ≦
4.50, 0.50 ≦ x ≦ 1.10, 0.20 ≦ y ≦
0.50, 0.05 ≦ z ≦ 0.20 and their total value
Represents 4.90 ≦ w + x + y + z ≦ 5.50)
This is what you want.

Examples of the conductive agent include carbon black and graphite.

Examples of the binder include polyacrylates such as sodium polyacrylate and potassium polyacrylate, and fluorine resins such as polytetrafluoroethylene.
Alternatively, carboxymethyl cellulose and the like can be mentioned.

Examples of the conductive substrate having the three-dimensional structure include a foamed metal substrate, a metal fiber substrate, a felted metal substrate, and the like. It is preferable that at least the surface of the conductive substrate is made of nickel.
The conductive substrate is preferably a foamed metal substrate.

The reason why the tensile strength of the conductive substrate in the winding direction is defined in the above range is as follows. When the tensile strength is less than 3 kgf, the mechanical strength of the negative electrode is reduced, so that the negative electrode is broken when the electrode group is manufactured by spirally winding the positive electrode and the negative electrode with a separator interposed therebetween. Further, it becomes difficult to suppress the occurrence of cracks. On the other hand, when the tensile strength exceeds 10 kgf, the amount of the mixture held on the conductive substrate becomes insufficient, and the capacity of the negative electrode decreases. A more preferable range of the tensile strength is 4 to 5 kgf.

The reason why the elongation percentage in the winding direction of the conductive substrate is defined in the above range is as follows.
If the elongation is less than 2%, the flexibility of the negative electrode is reduced, so that it is difficult to prevent the negative electrode from being broken or cracked when a spiral electrode group is manufactured. On the other hand, if the elongation exceeds 8%, the current collector filled or applied with the paste in the rolling step at the time of manufacturing the negative electrode meanders, so that the yield of the negative electrode decreases. A more preferable range of the elongation is 5 to 7%.

In the conductive substrate, the average skeleton diameter of the surface layer portion and the internal average skeleton diameter are equal, and the average skeleton diameter is 40 to 40.
It is desirable to have a structure that is in the range of 80 μm.
This is due to the following reasons. When the average skeleton diameter of the surface layer portion and the average skeleton diameter of the inside are different, the mechanical strength of the conductive substrate is uneven, so that when forming the spiral electrode group, the negative electrode is likely to be broken or broken. . When the average skeleton diameter is less than 40 μm, the mechanical strength of the conductive substrate is not uneven, but the mechanical strength of the substrate itself may be reduced. On the other hand, when the average skeleton diameter exceeds 80 μm, there is a possibility that the mixture holding amount of the conductive substrate may be insufficient, so that a high negative electrode capacity may not be obtained. A more preferable range of the average skeleton diameter is 50 to 60 μm. However, the surface layer of the conductive substrate has a thickness corresponding to 5 to 10% of the thickness of the conductive substrate.

The current collector has a tensile strength in the winding direction of 3 to 10 kgf and an elongation of 2 to 8 in the winding direction.
%, A conductive substrate having a two-dimensional structure such as a punched metal, an expanded metal, or a wire mesh as a current collector of the negative electrode, or the positive electrode including a conductive substrate having a three-dimensional structure. It is allowed to use a conductive substrate having a structure having irregularities on the periphery of the hole.

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.

According to the above-described cylindrical battery according to the present invention, when a conductive substrate having a three-dimensional structure is used as a current collector of at least one of the positive electrode and the negative electrode, By using a material having a tensile strength in the winding direction of 3 to 10 kgf and an elongation percentage of 2 to 8% in the winding direction, it is possible to improve the flexibility and strength for the winding without impairing the electrode capacity. it can. As a result, when the electrode group is manufactured by spirally winding the positive electrode and the negative electrode with a separator interposed therebetween, the electrode can follow the deformation at the time of winding. And breakage can be suppressed. Therefore, it is possible to provide a cylindrical battery having a practical discharge capacity and a reduced internal short-circuit occurrence rate.

Further, a conductive substrate having a three-dimensional structure in which the tensile strength and the elongation in the winding direction are within the above-mentioned specific ranges is used for the current collector of the positive electrode, and the paste containing an active material is used as the positive electrode. Filling or coating on a functional substrate, drying,
After rolling, when produced by passing between a hard roller and a roller having a flexible surface and performing softening, the positive electrode is hardly damaged at the time of softening. The flexibility at the time can be further improved. Accordingly, it is possible to greatly reduce the internal short-circuit occurrence rate when a spiral electrode group is manufactured using a positive electrode including a conductive substrate having a three-dimensional structure as a current collector.

On the other hand, by making the average skeleton diameter of the surface layer portion of the conductive substrate having the three-dimensional structure equal to the average skeleton diameter of the inside thereof and making the average skeleton diameter in the range of 40 to 80 μm, The mechanical strength of the substrate can be made uniform, and the mechanical strength can be increased without impairing the electrode capacity. As a result, it is possible to greatly reduce the internal short-circuit occurrence rate when fabricating the spiral electrode group while maintaining a practical discharge capacity. Further, using such a conductive substrate as a positive electrode, filling or applying the paste containing the active material to the conductive substrate, drying and rolling, the hard roller and the roller having a flexible surface. In this case, the positive electrode is hardly damaged during the softening process, so that the flexibility at the time of winding the positive electrode can be further improved. Accordingly, it is possible to greatly reduce the internal short-circuit occurrence rate when a spiral electrode group is manufactured using a positive electrode including a conductive substrate having a three-dimensional structure as a current collector.

[0039]

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

(Examples 1 to 4 and Comparative Examples 1 and 2) <Preparation of Positive Electrode> As shown in FIG. 3, a foamed nickel plate having a structure in which hollow nickel fibers 23 are arranged in a three-dimensional stitch is used. Prepared. The nickel foam plate has a width of 5
00 mm, have an areal density of 370 g / m ² and a thickness of 1.2
mm. Further, the tensile strength in the winding direction, the elongation percentage in the winding direction, and the average skeleton diameter of the surface layer portion and the inside were the values shown in Table 1 below. However, the average skeleton diameter of the foamed nickel plate means the average diameter of the hollow nickel fibers. Further, the thickness of the surface layer portion of the nickel foam plate is equivalent to 7% of the thickness of the nickel foam plate. The tensile strength in the winding direction of the nickel foam plate was 20 × 50 so that the winding direction of the nickel foam plate corresponded to the longitudinal direction of the test piece.
mm, and the obtained test piece was measured along a longitudinal direction at a tensile speed of 20 mm / min using a tensile tester.

On the other hand, a mixed powder consisting of 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide powder was added to
A paste is prepared by adding a binder (0.2 parts by weight of sodium polyacrylate powder and 1.5 parts by weight of polytetrafluoroethylene dispersion in terms of solid content) and mixing with 28 parts by weight of water. did. Subsequently, this paste was filled into each of the foamed nickel plates,
After being dried, six types of positive electrodes were produced by forming into a thickness of 0.6 mm by roll rolling. Then, fine cracks were formed on the surfaces of the respective positive electrodes by passing the respective positive electrodes between the rubber roller and the metal roller of each pressing mechanism of the above-described flexibility adding device shown in FIG.

<Preparation of Negative Electrode> A binder made of polytetrafluoroethylene, sodium polyacrylate, and carboxymethylcellulose, carbon black as a conductive agent, and water are added to the hydrogen storage alloy powder and kneaded. A paste was prepared. This paste was applied to punched metal, dried, and then pressed to form a negative electrode.

Next, a separator made of a nonwoven fabric made of polypropylene fiber subjected to hydrophilic treatment was interposed between the positive electrode and the negative electrode, and spirally wound to form an electrode group. After accommodating this electrode group in a cylindrical container having a bottom, an alkaline electrolyte is accommodated in the container, and the container is sealed and the like, thereby assembling the cylindrical nickel-metal hydride secondary battery having the structure shown in FIG. Was.

With respect to the secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2, when 1000 positive electrodes were manufactured, the number of the positive electrodes that were broken or broken was measured. Also shown in Table 1.

For the secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2, the number of internal short-circuits was measured when 1,000 electrode groups were produced, and the results are shown in Table 1 below. .

[0046]

[Table 1]

As is apparent from Table 1, a positive electrode including a three-dimensionally structured conductive substrate having a tensile strength in the winding direction of 3 to 10 kgf and an elongation of 2 to 8% in the winding direction is provided. The secondary batteries of Examples 1 to 4 have more flexibility than the secondary batteries of Comparative Example 1 including a positive electrode including a conductive substrate having a three-dimensional structure with a tensile strength in the winding direction smaller than the above range. It is possible to suppress the damage of the positive electrode during the process, and to reduce the internal short circuit at the time of manufacturing the electrode group.
In addition, the secondary battery of Comparative Example 2 including the positive electrode including the conductive substrate having a three-dimensional structure in which the tensile strength and the elongation in the winding direction exceed the above ranges has a high volume ratio of the conductive substrate in the positive electrode. In addition, the paste filling amount was reduced, and a positive electrode having a predetermined capacity could not be obtained.

[0048]

As described above, according to the present invention, it is possible to provide a cylindrical battery having a reduced rate of occurrence of insulation failure while maintaining a practical discharge capacity.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an example of a cylindrical battery according to the present invention.

FIG. 2 is a side view showing a flexibility adding device used for producing a positive electrode incorporated in the cylindrical battery of FIG. 1;

FIG. 3 is a schematic diagram showing a main part of a foamed nickel plate used for a positive electrode of the cylindrical nickel-metal hydride secondary battery of Example 1.

[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.

Claims (2)

[Claims] 1. A cylindrical battery provided with an electrode group produced by spirally winding a positive electrode and a negative electrode via a separator, wherein at least one of the positive electrode and the negative electrode has:
As a current collector, the tensile strength in the winding direction is 3 to 10 kgf
And a conductive battery having a three-dimensional structure having an elongation percentage in the winding direction of 2 to 8%. 2. The conductive substrate having a three-dimensional structure, wherein an average skeleton diameter of a surface layer portion and an average inner skeleton diameter are equal, and the average skeleton diameter is in a range of 40 to 80 μm. 2. The cylindrical battery according to 1.