JP2002279964A - Alkaline secondary battery and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a alkaline secondary battery, improved in strength of connecting a conductive base with a current collector, in a method for directly welding the current collector on the conductive base of a positive electrode. SOLUTION: This battery comprises the conductive base 6 having a three- dimensional structure, a current collector welding region positioned at the surface of the base 6, an active material containing mixture 3 held on the base 6 excepting at least the current collector welding region, the current collector 2 welded on the current collector welding region apart from the active material containing mixture holding region, a conductive base exposing part positioned between the current collector 2 and the active material containing mixture holding the region 3, the positive electrode 12 including conductive reinforcing material 5 covering at least the conductive base exposing part and a negative electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an alkaline secondary battery and a method for producing the same.

[0002]

2. Description of the Related Art A sealed alkaline storage battery typified by a nickel cadmium storage battery or a nickel hydrogen storage battery is frequently used as a power supply for a portable electronic device. The positive electrode of this sealed alkaline storage battery includes a conductive substrate having a three-dimensional structure such as a nickel foam substrate, and a mixture held on the conductive substrate and containing nickel hydroxide as an active material. It is.

[0003] As a method for collecting the current of the positive electrode, the following two methods are known.

The first method is to weld a strip-shaped lead along one side of a conductive substrate and weld a current collector to the strip-shaped lead. According to this method, the connection strength between the positive electrode and the current collector is increased, and the current collection efficiency is excellent, but sufficient capacity cannot be maintained at the position where the strip-shaped lead is welded because the mixture cannot be held. There is a problem that it cannot be obtained.

In the second method, after the mixture is held on the conductive substrate, a part of the mixture is removed by a physical method such as ultrasonic vibration, and the current collector plate is placed on the exposed conductive substrate. Welding method. 6 and 7 show an example of the positive electrode obtained by the second method. This positive electrode has a conductive substrate, a current collector welding region 31 present on both surfaces of the conductive substrate, a mixture 32 held on the conductive substrate except for at least the current collector welding region 31, A current collector 33 welded to the current collector welding area 31 and made of a strip-shaped metal plate.

According to the second method, the ratio of the current collector welding region 31 to the conductive substrate, that is, the ratio of the mixture non-holding region to the positive electrode, can be reduced as compared with the first method. In addition, it is possible to increase the active material filling amount of the positive electrode, and to increase the capacity of the secondary battery.

[0007]

However, the ultrasonic vibration elimination performed to form the current collector welding region 31 damages the conductive substrate such as causing cracks and the like. The connection strength with the electrical body decreases,
As illustrated in FIG. 8, the positive electrode may be cut off from the current collector welding region 31 due to handling or the like when manufacturing the alkaline secondary battery. In particular, when the basis weight of the conductive substrate is reduced to increase the active material filling density of the positive electrode, the connection strength is significantly reduced.

An object of the present invention is to provide an alkaline secondary battery having an improved connection strength between a conductive substrate and a current collector in a method in which a current collector is directly welded to a positive electrode conductive substrate, and a method of manufacturing the same. Is what you do.

[0009]

According to the present invention, there is provided an alkaline secondary battery comprising: a conductive substrate having a three-dimensional structure; a current collector welding region present on a surface of the conductive substrate; An active material-containing mixture held except for the current collector welding region; a current collector welded to the current collector welding region in a state separated from the active material containing mixture holding region; and the current collector And a conductive substrate exposed portion present between the active material-containing mixture holding region, a positive electrode including at least a conductive reinforcing material that covers the conductive substrate exposed portion, and a negative electrode. It is a feature.

The method of manufacturing an alkaline secondary battery according to the present invention is the method of manufacturing an alkaline secondary battery having a positive electrode and a negative electrode, wherein the active material-containing mixture is held on a conductive substrate having a three-dimensional structure. Step of obtaining an agent holding substrate, removing a part of the active material-containing mixture of the mixture holding substrate by ultrasonic vibration, forming a current collector welding region on the surface of the mixture holding substrate, Welding the current collector to the current collector welding area in a state where a current collector is separated from the mixture holding area and a conductive substrate exposed portion is provided between the current collector and the mixture holding area; Covering the exposed portion of the substrate with a conductive reinforcing material.

[0011]

DETAILED DESCRIPTION OF THE INVENTION An alkaline secondary battery according to the present invention includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an alkaline electrolyte.

Hereinafter, the positive electrode, the negative electrode, the separator and the alkaline electrolyte will be described.

1) Positive Electrode This positive electrode has a three-dimensional structure except for a conductive substrate, current collector welding regions existing on both sides of the conductive substrate, and at least the current collector welding region on the conductive substrate. An active material-containing mixture to be retained, a current collector welded to one of the current collector welding regions in a state separated from the active material-containing mixture holding region, and the current collector and the active material-containing mixture holding An exposed portion of the conductive substrate existing between the region and a conductive reinforcing material covering at least the exposed portion of the conductive substrate.

[0014] The other current collector welding area can be used as an installation surface of a welding electrode used for resistance welding of the current collector.

Examples of the conductive substrate having the three-dimensional structure include a conductive substrate having holes arranged three-dimensionally, such as a sintered metal fiber substrate, a substrate having a foamed shape, and a substrate having a felt shape. Can be mentioned. The conductive substrate having a three-dimensional structure can be formed from, for example, nickel, stainless steel, or nickel-plated metal.

The basis weight of the conductive substrate having a three-dimensional structure is desirably 400 g / m ² or less. If the basis weight exceeds 400 g / m ² , a high active material packing density may not be obtained. Although the smaller the basis weight is, the higher the active material filling density can be easily obtained, the conductive substrate tends to be greatly damaged when the mixture is removed from the mixture holding substrate by, for example, ultrasonic vibration. Even if the exposed portion of the substrate is covered with a reinforcing material, there is a possibility that improvement in welding strength and reduction in internal impedance cannot be achieved.
Therefore, the basis weight is more preferably in the range of 300 to 400 g / m ² .

The porosity of the conductive substrate having a three-dimensional structure is
It is preferable to be within the range of 96 to 98%.

As the active material, for example, particles containing nickel hydroxide can be used. As the nickel hydroxide-containing particles, nickel hydroxide particles in which one or more metals selected from zinc and cobalt are eutectic,
Alternatively, non-eutectic nickel hydroxide particles can be used.

The active material-containing mixture may contain a binder. Examples of the binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, polytetrafluoroethylene, and polyvinyl alcohol.

The current collector preferably has at least the surface formed of nickel. Examples of such a current collector include a nickel plate and a steel plate (NPS plate) plated with nickel.

Even when only the exposed portion of the conductive substrate is covered with the conductive reinforcing material, the connection strength between the conductive substrate and the current collector can be improved and the impedance can be reduced. It is preferable that at least a part of the other current collector welding region is covered with a conductive reinforcing material together with the substrate exposed portion. With such a configuration, the connection strength can be further improved, and the impedance can be further reduced.

The conductive reinforcing material is at least one selected from the group consisting of metals, carbon materials, alloys, and conductive resins.
It is desirable to include various types of conductive components. Examples of the metal include aluminum, copper, and nickel. Examples of the carbon material include carbon black and graphite. On the other hand, examples of the alloy include a low melting point alloy such as solder.
In particular, a metal or a carbon material is preferable as the conductive component. The conductive reinforcing material containing at least one of a metal and a carbon material has a higher thermal effect on the positive electrode when coating the exposed portion of the conductive substrate than the conductive reinforcing material containing solder, and has a higher charge-discharge reaction. It is possible to reduce side reactions during the reaction.

The conductive reinforcing material containing at least one of a metal and a carbon material is formed, for example, by the method described in the following (a) or (b).

(A) A conductive powder of at least one of a metal powder and a carbon material powder is dispersed in a molten thermoplastic resin, and the obtained slurry is applied to at least an exposed portion of the conductive substrate, and then solidified. By the conversion, at least the exposed portion of the conductive substrate is covered with the conductive reinforcing material.

(B) An adhesive or a resin is dissolved in a solvent, and at least one of a metal powder and a carbon material powder is dispersed in the obtained solution. Then, by drying, at least the exposed portion of the conductive substrate is covered with a conductive reinforcing material.

According to the method (a) described above, since the slurry contains no solvent, a drying step for evaporating the solvent can be eliminated. Therefore, it is possible to easily form the reinforcing material, and it is possible to solve the problem of the side reaction due to the remaining solvent.

It is desirable that the resin contained in the reinforcing material does not have an amino group and a nitro group. This is because a resin having an amino group or a nitro group is likely to cause a side reaction, and may promote self-discharge. Further, it is preferable that the resin is insoluble in water, has durability against strong alkali, and hardly swells in an aqueous alkali solution. Examples of the type of the resin include thermoplasticity and thermosetting. As the thermoplastic resin, solid paraffin and low density polyethylene are desirable. Further, the melting point of the thermoplastic resin is preferably low. On the other hand, a phenolic epoxy resin is preferable as the thermosetting resin.

The average particle size (D ₅₀ ) of the conductive powder is 10 μm.
It is preferable to set it within the range of not less than m and less than 50 μm.
This is due to the following reasons. Average particle size is 1
If the thickness is less than 0 μm, the contact area between the reinforcing material and the conductive substrate may be insufficient, and the fixing strength between the reinforcing material and the conductive substrate may be reduced. On the other hand, when the average particle size is 50 μm or more,
Insufficient specific surface area of the conductive powder may make it difficult to sufficiently lower the internal impedance. A more preferable range of the average particle size is 20 to 40 μm.

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

(First Step) A paste containing nickel hydroxide-containing particles, a binder, and water is prepared, and the paste is filled in a conductive substrate having a three-dimensional structure. An active material-containing mixture is held on a conductive substrate having an original structure to obtain a mixture holding substrate.

This paste can contain a conductive material. As the conductive material, for example metallic cobalt, cobalt compounds (e.g., cobalt oxide such as CoO, cobalt hydroxide such as Co (OH) _2), and the like. As the conductive material,
One or two or more selected from the types described above can be used. The conductive material can be added to the paste in the form of a powder or a layered material covering the surface of the nickel hydroxide-containing particles. Both nickel hydroxide-containing particles whose surfaces are coated with a conductive material and powder of a conductive material may be added to the paste.

On the surface of the nickel hydroxide-containing particles, a conductive layer containing cobalt oxyhydroxide (CoOOH) can be formed. When a conductive layer is formed, a conductive material need not be added to the paste.

(Second Step) A part of the active material-containing mixture held on the mixture holding substrate is removed, and current collector welding regions are formed on both surfaces of the mixture holding substrate.

As a method for removing the mixture, for example, removal by ultrasonic vibration may be mentioned.

(Third Step) A current collector is separated from the mixture holding region in one current collector welding region, and a conductive substrate exposed portion is provided between the current collector and the mixture holding region. Weld.

As the welding method, for example, resistance welding can be adopted.

The reason why the exposed portion of the conductive substrate is provided is to avoid the occurrence of splash due to the presence of the active material-containing mixture during welding.

(Fourth Step) A positive electrode is obtained by coating at least the exposed portion of the conductive substrate with a conductive reinforcing material.

2) Negative electrode As the negative electrode, for example, a cadmium electrode or a hydrogen storage alloy electrode can be used. Among them, it is preferable to use one containing a hydrogen storage alloy.

A negative electrode containing a hydrogen storage alloy is prepared by, for example, kneading a hydrogen storage alloy powder, a conductive material and a binder in the presence of water to prepare a paste, filling the paste into a conductive substrate, and drying the paste. After that, it is produced by applying a press.

It is preferable that the hydrogen storage alloy contains at least a rare earth element and nickel. One or more kinds of rare earth elements can be used. Among them, rare earth elements include La, Pr, Ce,
One or more elements selected from Nd and Sm are preferred.

Examples of the hydrogen storage alloy containing at least a rare earth element and nickel include LaNi ₅ , MmNi
₅ (Mm is misch metal), LmNi ₅ (Lm is La
Enriched misch metal), and multi-element materials in which part of Ni of these alloys is replaced with at least one element selected from Al, Mn, Co, Ti, Cu, Zn, Zr, Cr and B be able to. Among them, the general formula LmN
_{i v Co w Mn x Al y} Zr z ( However, Lm is at least one more rare earth elements, the atomic ratio v, w, x, y and z
Are expressed as 5.0 ≦ v + w + x + y + z ≦ 5.4). In particular, L
m preferably contains La. Among them, La, P
Those containing r, Ce and Nd are preferred.

The average particle diameter of the hydrogen storage alloy powder is 20
It is preferable to set the range to 70 μm.

Examples of the binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, polytetrafluoroethylene, polyvinyl alcohol (PVA), and styrene butadiene rubber (SB).
R) and the like.

As the conductive material, for example, graphite, carbon black or the like can be used.

Examples of the conductive substrate include a two-dimensional substrate such as a punched metal, an expanded metal, and a nickel net.

3) Separator Examples of the separator include a nonwoven fabric made of a polyamide fiber, a nonwoven fabric made of a 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 above-described alkaline secondary battery according to the present invention includes a conductive substrate having a three-dimensional structure, a current collector welding region present on one surface of the conductive substrate, An active material-containing mixture held except for the current collector welding region; a current collector welded to the current collector welding region in a state separated from the active material containing mixture holding region; and the current collector A positive electrode including a conductive substrate exposed portion existing between the active material-containing mixture holding region and the active material-containing mixture holding region; and a conductive reinforcing material covering at least the conductive substrate exposed portion.

According to such a secondary battery, even if the conductive substrate is damaged by cracking or the like due to the removal of the mixture for forming the current collector welding region, at least the conductive substrate exposed portion has a reinforcing material. The connection between the current collector and the conductive substrate can be improved because it is reinforced by welding, and the current collector welding of the conductive substrate is performed when tension is applied to the current collector due to battery manufacture or dropping. It is possible to prevent the current collector from coming off the positive electrode due to the region being broken.

In addition, since the electron conductivity of the exposed portion of the conductive substrate can be supplemented by the reinforcing material, the current collection efficiency of the positive electrode can be improved, the internal impedance of the battery can be reduced, and a large current discharge can be achieved. The characteristics can be improved.

Further, if the basis weight of the conductive substrate is set to 400 g / m ² or less in order to improve the active material filling density, the damage to the substrate due to the removal of the mixture becomes larger, but at least the exposed portion of the conductive substrate becomes conductive. By coating with a conductive reinforcing material, the connection strength between the conductive substrate and the current collector can be improved and the impedance can be reduced, so that the connection strength between the conductive substrate and the current collector is high, and the impedance is low and high. A large capacity alkaline secondary battery can be realized.

In the secondary battery according to the present invention, the reinforcing material is formed by applying a slurry containing a conductive powder and a molten thermoplastic resin to at least the exposed portion of the conductive substrate to form the reinforcing material. This can be easily performed and side reactions due to the reinforcing material can be reduced.

In the secondary battery according to the present invention, the reinforcing material contains a conductive powder having an average particle diameter (D ₅₀ ) of 10 μm or more and less than 50 μm, so that the fixing strength between the reinforcing material and the conductive substrate is improved. In addition, both conductivity of the reinforcing material can be satisfied.

According to the method of manufacturing an alkaline secondary battery of the present invention, a step of obtaining a mixture holding substrate by holding an active material-containing mixture on a conductive substrate having a three-dimensional structure; Removing a part of the active material-containing mixture by ultrasonic vibration to form a current collector welding region on one surface of the mixture holding substrate; and forming a current collector in the current collector welding region. A step of welding away from the mixture holding region and providing a conductive substrate exposed portion between the current collector and the mixture holding region; and covering at least the conductive substrate exposed portion with a conductive reinforcing material. The positive electrode is manufactured by a method including the steps of:

According to such a manufacturing method, an alkaline secondary battery having low internal impedance and improved connection strength between the positive electrode conductive substrate and the current collector can be manufactured with high mass productivity.

[0057]

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

FIG. 1 is a perspective view showing a current collector welding region in the positive electrode of the alkaline secondary battery of Example 1, and FIG. 2 is a current collector welding process in the production of the positive electrode of the alkaline secondary battery of Example 1. FIG. 3 is a front view showing the positive electrode of the alkaline secondary battery of Example 1, and FIG. 4 is a cross-sectional view obtained when the positive electrode of FIG. 3 is cut along the longitudinal direction. FIG.
1 is a partially cutaway perspective view showing an alkaline secondary battery of Example 1. FIG.

Example 1 <Preparation of Paste-Type Positive Electrode> A mixed powder composed of 90 mass% of nickel hydroxide powder and 10 mass% of cobalt monoxide powder was mixed with 3 mass% of carboxymethyl cellulose (CMC) and polytetrafluoroethylene. A paste was prepared by adding 5% by mass, adding 45% by mass of water to these, and kneading. Subsequently, the paste is filled into a nickel foam substrate having a basis weight of 370 g / m ² and a porosity of 96% as a conductive substrate having a three-dimensional structure, dried, and then roll-pressed by roller pressing. Thus, a conductive substrate filled with the active material-containing mixture was obtained. The mixture-filled substrate was cut into a predetermined size.

Next, a horn was arranged on one side of the mixture-filled substrate, and an anvil was arranged on the other side. Ultrasonic vibration is applied to the mixture-filled substrate with a horn to pulverize the mixture, and ultrasonic vibration removal is performed by suctioning the pulverized material of the mixture with the anvil.
The mixture existing on the surface and inside of the mx 5 mm portion was removed, and as shown in Fig. 1, the current collector welding areas 1a, 1b of 5mm x 5mm were formed on both sides of the longitudinal end of the mixture holding substrate. Was formed.

Next, as shown in FIG.
A current collector 2 made of a strip-shaped nickel plate having a width of 3 mm is placed on the current collector welding area 1a on one side of
m apart. As a result of this arrangement, the current collector 2
The exposed portion of the conductive substrate was provided between and the mixture holding region 3. The reason for providing the conductive substrate exposed portion is to avoid the occurrence of splash during resistance welding. A pair of welding electrodes 4a and 4b are prepared, one welding electrode 4a is arranged on the current collector 2 side, and the other welding electrode 4b is arranged on the current collector welding area 1b on the other surface side of the conductive substrate. Then, resistance welding was performed.

Subsequently, the average particle size (D ₅₀ ) was 10 μm.
Was dispersed in an acetone solution of solid paraffin to prepare a slurry. The obtained slurry is applied to the exposed portion of the conductive substrate and the current collector welding area 1b, dried and evaporated to form a conductive reinforcing layer 5 as shown in FIGS. A positive electrode of the formula was obtained.

<Preparation of Paste Type Hydrogen Storage Alloy Negative Electrode> 100% by mass of hydrogen storage alloy powder, 0.5% by mass of sodium polyacrylate, and carboxymethyl cellulose (CM
C) 0.12% by mass, polytetrafluoroethylene
5% by mass and 1% by mass of carbon black,
A paste was prepared by kneading with 0% by mass. This paste was applied on both sides of a punched metal as a conductive substrate, dried, and then roll-formed by a roller press to produce a negative electrode.

Next, a separator made of a polyolefin nonwoven fabric subjected to a hydrophilic treatment was interposed between the positive electrode and the negative electrode and spirally wound to form an electrode group. Such an electrode group was housed in a bottomed cylindrical metal container also serving as a negative electrode terminal. Next, KOH is placed in the container.
By injecting an alkaline electrolyte mainly composed of, for example, and performing sealing treatment, an AAA size cylindrical nickel-metal hydride secondary battery having the structure shown in FIG. 5 was manufactured.

That is, in the bottomed cylindrical container 11,
An electrode group 15 produced by laminating the positive electrode 12, the separator 13, and the negative electrode 14 and winding the same spirally is accommodated. The negative electrode 14 is arranged at the outermost periphery of the electrode group 15 and is in electrical contact with the container 11. The alkaline electrolyte is contained in the container 11. A circular sealing plate 17 having a hole 16 in the center is arranged at the upper opening of the container 11. The ring-shaped insulating gasket 18 is disposed between the peripheral edge of the sealing plate 17 and the inner surface of the upper opening of the container 11, and the sealing plate is formed on the container 11 by caulking to reduce the diameter of the upper opening inward. 17 is hermetically fixed via the gasket 18. The tip of the positive electrode tab 2 is connected to the lower surface of the sealing plate 17. A hat-shaped positive electrode terminal 19 is attached on the sealing plate 17 so as to cover the hole 16. A rubber safety valve 20 is disposed in a space surrounded by the sealing plate 17 and the positive electrode terminal 19 so as to close the hole 16. A circular holding plate 21 made of an insulating material having a hole in the center is arranged on the positive electrode terminal 19 such that a projection of the positive terminal 19 projects from the hole of the holding plate 21. The outer tube 22 covers the periphery of the holding plate 21, the side surface of the container 11, and the bottom periphery of the container 11.

[0066] (Examples 2-4) conductive reinforcing layer average particle diameter conductive powder contained in (D ₅₀₎ is 10μm of copper powder, the average particle diameter (D ₅₀₎ 10μm of nickel powder, average A cylindrical nickel-metal hydride secondary battery having the same configuration as that described in Example 1 was manufactured except that the carbon black powder having a particle size (D ₅₀ ) of 10 μm was changed.

Example 5 A cylindrical nickel-metal hydride secondary battery having the same structure as that described in Example 1 was manufactured except that a conductive reinforcing layer was formed by the method described below. .

That is, aluminum powder having an average particle size (D ₅₀ ) of 10 μm was dispersed in molten solid paraffin to prepare a slurry. The obtained slurry was applied to the exposed portion of the conductive substrate and the current collector welding region 1b, and was converted into a solid by leaving it at room temperature to form a conductive reinforcing layer.

[0069] (Example 6-8) conducting an average particle size of the conductive powder contained in the reinforcing layer (D ₅₀₎ is 10μm of copper powder, the average particle diameter (D ₅₀₎ 10μm of nickel powder, average A cylindrical nickel-metal hydride secondary battery having the same configuration as that described in Example 5 above was manufactured except that the carbon black powder having a particle size (D ₅₀ ) of 10 μm was changed.

Example 9 A cylindrical nickel-metal hydride secondary battery having the same structure as that described in Example 1 was manufactured except that a conductive reinforcing layer was formed by the method described below. .

That is, bisphenol A9 is used as a solvent.
An aluminum powder having an average particle diameter (D ₅₀ ) of 10 μm was dispersed in a solution comprising 0 parts by weight and 10 parts by weight of a modified aliphatic polyamine as a curing agent to prepare a slurry. The obtained slurry is applied to the conductive substrate exposed portion and the current collector welding region 1
b) and dried in a constant temperature room at 25 ° C. and a humidity of 30% for 24 hours to form a conductive reinforcing layer containing a phenolic epoxy resin and aluminum particles.

[0072] (Examples 10 to 12) conducting an average particle size of the conductive powder contained in the reinforcing layer (D ₅₀₎ is 10μm of copper powder, the average particle diameter (D ₅₀₎ 10μm of nickel powder, average A cylindrical nickel-metal hydride secondary battery having the same configuration as that described in Example 9 was manufactured except that the carbon black powder having a particle size (D ₅₀ ) of 10 μm was changed.

Example 13 A cylindrical nickel-metal hydride secondary battery having the same structure as that described in Example 1 was manufactured except that a conductive reinforcing layer was formed by the method described below. .

That is, the molten Pb-Sn alloy was applied to the exposed portion of the conductive substrate and the current collector welding region 1b to form a conductive reinforcing layer.

Example 14 A cylindrical nickel-metal hydride secondary battery having the same structure as that described in Example 1 was manufactured except that a conductive reinforcing layer was formed by the method described below. .

That is, aluminum powder having an average particle size (D ₅₀ ) of 50 μm was dispersed in molten solid paraffin to prepare a slurry. The obtained slurry was applied to the exposed portion of the conductive substrate and the current collector welding region 1b, and was converted into a solid by leaving it at room temperature to form a conductive reinforcing layer.

[0077] (Examples 15 to 17) conductive reinforcing layer average particle diameter conductive powder contained in (D ₅₀₎ is 50μm of copper powder, the average particle diameter (D ₅₀₎ 50μm of nickel powder, average A cylindrical nickel-metal hydride secondary battery having the same configuration as that described in Example 14 described above was manufactured except that the carbon black powder having a particle size (D ₅₀ ) of 50 μm was used.

Comparative Example A cylindrical nickel-metal hydride battery having the same structure as that described in the first embodiment except that no conductive reinforcing layer was formed on the exposed portion of the conductive substrate and the current collector welding region 1b. A secondary battery was manufactured.

With respect to the obtained secondary batteries of Examples 1 to 17 and Comparative Example, the impedance after charging at 150% at 0.2 C was measured.

Further, with respect to the positive electrodes of Examples 1 to 17 and Comparative Example, the tip of the current collector was pulled, and the tensile force (current collector) when the current collector welding area was cut off and the current collector came off from the positive electrode. Was measured, and the results are shown in Table 1 below.

[0081]

[Table 1]

As is clear from Table 1, Examples 1 to 17
It can be seen that the secondary battery has a higher tensile strength of the current collector at the positive electrode than the comparative example. In particular, the secondary batteries of Examples 1 to 12 using a reinforcing material containing a conductive powder having an average particle diameter (D ₅₀ ) of 10 μm or more and less than 50 μm, and the secondary batteries of Example 13 using a reinforcing material containing solder Indicates that the impedance can be made lower than that of the comparative example.

In the above-described embodiment, an example in which the present invention is applied to a cylindrical alkaline secondary battery has been described, but the battery according to the present invention is not limited to such a structure. For example, the present invention can be similarly applied to a rectangular alkaline secondary battery in which a laminate including a positive electrode and a negative electrode and a separator disposed between the positive electrode and the negative electrode is housed in a bottomed rectangular cylindrical container.

[0084]

As described above, according to the alkaline secondary battery and the method of manufacturing the same according to the present invention, the connection between the conductive substrate and the current collector in a method in which the current collector is welded to the positive electrode conductive substrate. There is a remarkable effect that the strength can be improved and the capacity can be increased.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a current collector welding region in a positive electrode of an alkaline secondary battery of Example 1.

FIG. 2 is a cross-sectional view showing a current collector welding step in manufacturing a positive electrode of the alkaline secondary battery of Example 1.

FIG. 3 is a front view showing a positive electrode of the alkaline secondary battery of Example 1.

FIG. 4 is a cross-sectional view obtained when the positive electrode of FIG. 3 is cut along a longitudinal direction.

FIG. 5 is a partially cutaway perspective view showing the alkaline secondary battery of Example 1.

FIG. 6 is a plan view showing a positive electrode included in a conventional alkaline secondary battery.

7 is a cross-sectional view obtained when the positive electrode of FIG. 6 is cut along the longitudinal direction.

FIG. 8 is a schematic diagram for explaining a problem of the positive electrode in FIG. 6;

[Explanation of symbols]

 1a, 1b ... current collector welding area, 2 ... current collector, 3 ... mixture holding area, 4a, 4b ... welding electrode 5 ... conductive reinforcing layer, 6 ... conductive substrate, 11 ... container, 12 ... positive electrode Reference numeral 13: negative electrode, 14: separator, 15: electrode group, 17: sealing plate, 18: insulating gasket.

Continued on the front page F-term (reference) 5H022 AA04 AA18 BB11 BB21 BB22 CC02 CC17 CC30 EE03 EE06 5H028 BB02 BB03 BB05 CC05 CC07 CC10 CC12 EE01 EE04 EE06 EE10 5H050 BA13 BA14 CA03 CB16 DA02 DA10 EA02 EA03 EA03 EA03 EA03 GA22

Claims (3)

[Claims] 1. A conductive substrate having a three-dimensional structure, a current collector welding region existing on a surface of the conductive substrate, and an active material held on the conductive substrate except for at least the current collector welding region. And a current collector that is welded to the current collector welding region in a state separated from the active material-containing mixture holding region, and is present between the current collector and the active material-containing mixture holding region. An alkaline secondary battery, comprising: a positive electrode including a conductive substrate exposed portion to be formed, a conductive reinforcing material covering at least the conductive substrate exposed portion, and a negative electrode. 2. The alkaline secondary battery according to claim 1, wherein the reinforcing material is obtained by applying a slurry containing a conductive powder and a molten thermoplastic resin to at least the exposed portion of the conductive substrate. battery. 3. A method of manufacturing an alkaline secondary battery including a positive electrode and a negative electrode, wherein a step of holding an active material-containing mixture on a conductive substrate having a three-dimensional structure to obtain a mixture holding substrate; Removing a part of the active material-containing mixture of the holding substrate by ultrasonic vibration to form a current collector welding region on the surface of the mixture holding substrate; and forming a current collector in the current collector welding region. Separate from the mixture holding area,
Welding with a conductive substrate exposed portion provided between the current collector and the mixture holding region; and covering at least the conductive substrate exposed portion with a conductive reinforcing material. A method for manufacturing an alkaline secondary battery, wherein the positive electrode is manufactured by the following method.