JP2001202944A - Alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline battery suitable for large current use by making the strength of porous metal substrate to be welded higher with respect to a current collector terminal of metal plate. SOLUTION: The alkaline battery is made by pacing a group of wound electrodes into a battery can. The wound electrode is made by winding a positive electrode, formed of a combined layer for positive electrode at least at a part of a substrate and a negative electrode, formed of a combined layer for negative electrode at least at a part of a substrate through the intermediary of a separator. For the substrate of the electrode of at least either of the positive or the negative electrode, a porous metal substrate is used of which width direction end part is filled with metal powder. The porous metal substrate is compressed, forming no combined layer for electrode at the width direction end part filled with metal powder and leaving it in imposed state. A current collector terminal is connected by means of welding at many points in the width direction end part of the porous metal substrate, filled with the metal powder and compressed, after forming a group of wound electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery, and more particularly, to an alkaline storage battery suitable for a large current application which can be charged and discharged with a large current of 10 C or more.

[0002]

2. Description of the Related Art Alkaline storage batteries are widely used as portable power supplies. Generally, these batteries connect a metal terminal to an exposed portion of a substrate at a widthwise end of a wound electrode group to extract current. For example, when this alkaline storage battery is used for a power tool, it must be used at a high current of 10 A or more, particularly when a large current is required, about 50 A, so that its internal resistance must be reduced. It is said. Therefore, in a nickel-cadmium battery, a metal plate current collector terminal is welded at many points to an exposed portion of a substrate at an end in a width direction of a wound body electrode group formed by winding a positive electrode and a negative electrode via a separator. To reduce the internal resistance. This is because the internal resistance is reduced while the resistance of each part of the electrode is made relatively uniform by providing a large number of current extraction sites along the winding direction of the electrode.

[0003]

In the above-mentioned nickel-cadmium battery, a punched metal is used for a substrate of a negative electrode, and a nickel electrode having a perforated steel plate as a substrate is used as a positive electrode for a positive electrode. Therefore, the widthwise end of the wound electrode group is made of punched metal on the negative electrode side and made of a perforated steel plate on the positive electrode side. There is no problem in strength.

However, recently, due to the demand for higher capacity of the battery, nickel-metal hydride storage batteries using a hydrogen storage alloy for the negative electrode have become the mainstream. In this nickel-metal hydride storage battery, a porous metal substrate is used as a substrate. A paste-type electrode using is widely used. In particular, when the positive electrode of the nickel-metal hydride storage battery is a paste-type nickel electrode, the conductivity of nickel hydroxide, which is an active material, is low.
In a nickel-metal hydride storage battery for a large current application, it is necessary to use a porous metal substrate as a substrate in order to increase the conductivity in the electrode. However, since the strength of the porous metal substrate is lower than that of the perforated steel plate, when the metal plate current collector terminal is to be welded to the exposed portion of the porous metal substrate at the widthwise end of the wound electrode group. , Destruction of the porous metal substrate,
Therefore, there was a problem that welding could not be performed reliably and internal resistance was likely to increase.

Therefore, in the case of a paste-type nickel electrode using a porous metal substrate, it is conceivable that a nickel thin plate is welded to the exposed portion of the porous metal substrate at the end in the width direction of the wound electrode group to reinforce it. In addition, the process becomes complicated, and the adhesion between the nickel thin plate and the porous metal substrate is poor, and there is a possibility that poor welding may occur. In the case of a paste-type nickel electrode using a porous metal substrate, the electrode is pressed and compressed in order to increase the amount of the active material filled in the battery can. When the nickel thin plate is welded to the width direction end of the porous metal substrate before the formation of the electrode mixture layer including the electrode mixture layer, the extension between the nickel thin plate and the portion where the electrode mixture layer is formed at the time of pressing the electrode. Because of the difference, the electrode pressing process becomes difficult, which causes a reduction in productivity. Furthermore, when the nickel thin plate is welded to the exposed portion at the width direction end of the porous metal substrate after the formation of the electrode mixture layer, the nickel thin plate adheres to the portion to be welded of the porous metal substrate during the formation of the electrode mixture layer. There is a problem that the welding process itself is difficult because sparks easily occur during welding due to the electrode mixture. In addition, these problems also occur in alkaline storage batteries other than nickel-metal hydride storage batteries to a greater or lesser extent.

The present invention solves the above-mentioned problems in the prior art, improves the strength of the width direction end of a porous metal substrate to be welded to a current collector terminal of a metal plate, and provides an alkali suitable for a large current application. It is intended to provide a storage battery.

[0007]

SUMMARY OF THE INVENTION The present invention provides a separator comprising a positive electrode having a positive electrode mixture layer formed on at least a part of a substrate and a negative electrode having a negative electrode mixture layer formed on at least a part of the substrate. In an alkaline storage battery containing a wound body electrode group manufactured by winding through a battery can, a positive electrode, a metal porous substrate is used as a substrate of at least one electrode of a negative electrode,
Fill the metal porous material at the width direction end of the porous metal substrate,
At the width direction end of the porous metal substrate filled with the metal powder, an electrode mixture layer is not formed and pressed and compressed in a state where the porous metal substrate is exposed, and after producing a wound electrode group, A metal plate current collecting terminal is connected at a number of points to the width direction end of the metal porous material substrate which is filled and compressed with metal powder, thereby forming a connection portion with the metal plate current collecting terminal. It is an object of the present invention to solve the above problems by providing an alkaline storage battery suitable for large-current charging and discharging by improving the strength of an end portion in a width direction and reducing welding defects.

That is, according to the present invention, the widthwise end of the porous metal substrate is filled with metal powder and then pressed (compressed) and compressed to form an electrode mixture layer on the widthwise end of the porous metal substrate. The ratio of the metal was increased from that of the portion, thereby increasing the strength at the widthwise end of the porous metal substrate serving as a portion to be welded to the metal plate current collecting terminal. Also, by filling the metal powder, there is no difference in elongation at the time of pressing the electrode as in the case of welding a nickel thin plate, it is possible to reduce the defective rate in the pressing process,
Further, since the nickel thin plate is not welded, there is no spark at the time of welding as in the past.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a porous metal substrate used as an electrode substrate in the present invention will be described in detail.

In the present invention, various substrates can be used as the porous metal substrate. In particular, a metal foam or a metal plate or a perforated metal plate provided with a metal foam layer on one or both sides thereof is preferably used. Used. As a typical method of manufacturing a metal foam, a resin foam such as urethane foam is subjected to metal plating such as nickel plating, and then the resin foam forming the skeleton is removed by heating and burning. Then, a method of annealing is given. That is, by removing the resin foam constituting the skeleton portion by burning as described above, only the metal portion formed in a porous state on the resin foam remains, and a metal foam is obtained. Further, a porous metal substrate provided with a metal foam layer on one or both sides of a metal plate or a perforated metal plate,
For example, a resin foam such as urethane foam is subjected to metal plating such as nickel plating, and the plated resin foam is disposed on one surface of a base metal plate or a perforated metal plate, or the plating is performed. It is obtained by sandwiching a metal plate as a base material or a perforated metal plate with the applied resin foam, heating the resin foam to remove it by burning, and further sintering.

In the present invention, as the metal porous substrate, a metal foam or a metal plate or a perforated metal plate provided with a metal foam layer on one or both sides is preferably used. The porous metal substrate will be described in detail with the body as the main object. Examples of the material include nickel, iron (with nickel plating), copper and the like, and nickel is particularly suitable. Further, examples of the material of the metal powder include nickel, copper, gold, platinum, and the like. Further, an alloy that maintains a stable state in an alkaline electrolyte at the operating potential of the electrode may be used.

[0012] The porous metal substrate having a portion in which the width direction end is filled with metal powder and then pressed and compressed can be used as either a positive electrode or a negative electrode. The positive electrode of the alkaline storage battery for the application is
Since it is composed of a paste-type nickel electrode having poor conductivity, it is preferably used as a substrate for a positive electrode, and may be used as a substrate for a positive electrode and a negative electrode.

The basis weight of the porous metal substrate is as follows.
The weight per unit area of the porous metal substrate is 350 g / m ^2.
It is preferably at least 600 g / m ² ,
More preferably, it is 0 g / m ² or more and 500 g / m ² or less.

In order to increase the filling amount of the electrode mixture-containing paste, the porosity of the porous metal substrate is preferably 90% or more, more preferably 95% or more and 99% or less, and the pore size is 100 PPI [ No. of holes per 25.4 mm (1 inch)] or less, and more preferably 110 PPI or less. In addition, all the percentages related to the porosity are volume percentages.

Here, an example of the porous metal substrate used in the present invention will be described with reference to FIG. 1. The porous metal substrate 1 is used in the form of a strip, and a metal powder is applied to an end 1a in the width direction. It is filled and pressed and compressed after filling of the metal powder. However, the compression by this press is not necessarily performed subsequent to the filling of the metal powder,
Other parts as shown below (parts other than width direction end 1a)
The compression may be performed simultaneously with the compression of the electrode mixture layer formed as described above. That is, the electrode mixture-containing paste is not applied and filled on the width direction end 1a filled with the metal powder, and the other portion 1b of the metal porous substrate 1 (that is, the width direction end 1a filled with the metal powder) is not applied.
The electrode mixture-containing paste is applied, filled, and dried to form an electrode mixture layer. Accordingly, the width direction end portion 1a of the porous metal substrate 1 filled with the metal powder.
No electrode mixture layer is formed, and the metal porous body substrate is exposed at the width direction end 1a.

After the electrode mixture layer is formed as described above, it is pressed and compressed. At that time, the porous metal substrate 1 is also compressed in the width direction end 1a filled with the metal powder together with the other portion 1b on which the electrode mixture layer is formed. Therefore, it is not always necessary to press and compress the width direction end 1a of the porous metal substrate after the filling of the metal powder, and after forming the electrode mixture layer on the other portion 1b, the electrode mixture layer is formed. It is sufficient to press and compress together with the other portion 1b on which the electrode mixture layer is formed, and in such a case, only one pressing step is required, which is more efficient. However, it goes without saying that pressing and compression may be performed subsequent to filling of the metal powder.

The electrode manufactured as described above will be described with reference to FIG. 2. The electrode 2 is composed of a porous metal substrate and an electrode mixture layer 3.
It is composed of However, when the electrode 2 is formed, the porous metal substrate can be seen only in the width direction end 1a, and the width direction end 1a is pressed and compressed after filling the metal powder as described above. The electrode mixture layer 3 is formed by applying and filling the electrode mixture-containing paste on the other portion of the porous metal substrate (that is, the portion other than the width direction end 1a), and then drying. It is formed by pressing and compressing. In FIG. 2, dots are provided in the electrode mixture layer 3 to facilitate identification.

Using the porous metal substrate, the electrode fabricated as described above and the counter electrode are wound through a separator to form a wound electrode group, and the wound electrode group is fabricated. The width direction end of the porous metal substrate at the width direction end (that is, the portion where the inside is filled with metal powder and then compressed to improve the strength, and the metal porous substrate itself is exposed to the outside. Are connected to the metal plate current collector terminal by welding at many points.

[0019]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only those illustrated in the embodiments. In the following, "part"
The term “parts” means “parts by weight”, and “%” indicating the concentration of a solution or dispersion means “% by weight” unless the unit is specified.

Example 1 100 parts of nickel powder was mixed with 10 parts of a 2% aqueous solution of carboxymethyl cellulose to form a paste.

As a substrate, a porous metal substrate made of a nickel foam having a basis weight of 400 g / m ² , a length of 680 mm and a width of 33 mm was prepared. The paste was applied over a width of 2 mm, filled, and dried. The porosity of the nickel foam was 98%, and the average pore size was 100 PPI.

Further, 100 parts of nickel hydroxide powder (cobalt solid solution amount: 1.2% by weight) coated with 4.7% by weight of cobalt hydroxide on the particle surface was added with cobalt monoxide powder as a cobalt-based conductive additive. 2.9 parts, 10 parts of a 2% carboxymethylcellulose aqueous solution and 2 parts of a 60% polytetrafluoroethylene dispersion were added and mixed to prepare a positive electrode mixture-containing paste. This positive electrode mixture-containing paste is applied to one of the widthwise ends of the porous metal substrate (that is,
Except for the nickel powder-filled portion), coated and filled on both sides and dried to form a positive electrode mixture layer, pressed, compressed and cut into a predetermined length to produce a sheet-shaped positive electrode . By pressing after the formation of the positive electrode mixture, a portion filled with nickel powder at one widthwise end of the porous metal substrate is also compressed.

Apart from the above, the composition is MmNi _4.05 Co
_0.45 Mn _0.5 Al _0.3 Mo _0.35 (Mm composition is La:
0.32 atomic%, Ce: 0.48 atomic%, Nd: 0.1
5 atomic%, Pr: 0.04 atomic%, N
i, Co, Mn, and Al are 5.35 in total), and nickel powder 2
Then, an appropriate amount of an aqueous carboxymethylcellulose solution and a polytetrafluoroethylene dispersion were added and mixed to prepare a negative electrode mixture-containing paste. This negative electrode mixture-containing paste is applied to both sides of a substrate made of perforated iron-nickel plated steel plate except for one widthwise end portion, filled and dried to form a negative electrode mixture layer, and then pressed and compressed. Thereafter, the sheet was cut to produce a sheet-shaped negative electrode.

Next, the positive electrode and the negative electrode were passed through a polypropylene separator obtained by sulfonating the positive electrode and the negative electrode,
Positional relationship in which the negative electrode is shifted from the widthwise end (that is, positional relationship in which one widthwise end of the positive electrode protrudes above the upper end of the negative electrode and one widthwise end of the negative electrode protrudes below the lower end of the positive electrode) ), Spirally wind while facing each other,
100 wound electrode groups for a battery were manufactured.

The widthwise end of the porous metal substrate in the positive electrode of the group of 100 wound electrodes thus produced (that is, in Example 1, the inside was filled with nickel powder and then compressed to reduce the strength. Using a resistance welding machine, a 0.2 mm thick circular metal plate current collecting terminal was applied to the welded terminal with a head pressure of 49 N (5 kgf) on the improved portion (exposed portion where the porous metal substrate was exposed on the outer surface side). ) / Cm ² , welding at 15 points, and a short-circuit occurring at the time of welding is regarded as poor welding.
When the defect occurrence rate was examined, no welding defect occurred. The results are shown in Table 1 below together with the defect occurrence rate during welding in Comparative Example 1 described later.

After the metal plate current collector terminal was welded, the wound electrode group was inserted into the battery can, the positive and negative terminals were welded to the sealing body and the battery can, respectively, and then zinc oxide was added to a 30% aqueous potassium hydroxide solution. Was dissolved in 33 g / liter, and a predetermined amount of an electrolytic solution was injected and sealed, thereby producing a sealed nickel-metal hydride battery. This nickel-metal hydride battery is
Hold for 25 hours, cool to 25 ° C, and then
The charging for 0.2 hours and discharging at 0.2 CA (final voltage 1.0 V) were repeated for 5 cycles, followed by charging for 7 hours at 0.2 CA and discharging at 10 CA (final voltage 1.0 V), and
Ratio of CA discharge capacity to 0.2 CA discharge capacity [(1
0 CA discharge capacity / 0.2 CA discharge capacity) × 100]. The results are shown in Table 2 below as 10 CA discharge capacity (%).

Comparative Example 1 A porous metal substrate similar to that of Example 1 was used as a substrate except that the nickel powder was not filled in the widthwise end portion, and except that the porous metal substrate was used. Example 1
100 wound electrode groups were produced in the same manner as described above.

Example 1 was formed at the widthwise end of the porous metal substrate (that is, the portion where the porous metal substrate was exposed) at the positive electrode of the 100 wound electrode groups manufactured as described above.
The same metal plate current collector terminal as in Example 1 was welded under the same conditions as in Example 1 and the occurrence rate of defects at the time of welding was examined. As a result, the occurrence rate of defects was 97%.

A sealed nickel-metal hydride storage battery was manufactured in the same manner as in Example 1 except that a wound electrode group in which welding failure did not occur when the above-mentioned metal plate current collecting terminal was welded was used. As in Example 1, a 10CA discharge capacity of 0.
Ratio to 2CA discharge capacity [(10CA discharge capacity /
0.2 CA discharge capacity) × 100]. The results are shown in Table 2 below as 10 CA discharge capacity (%).

As described above, first, Table 1 shows a defect occurrence rate when the metal plate current collecting terminals of Example 1 and Comparative Example 1 were welded to the wound electrode group.

[0031]

[Table 1]

As is evident from the results shown in Table 1, in Example 1, compared to Comparative Example 1, welding of the width direction end of the porous metal substrate and the metal plate current collecting terminal in the wound electrode group was performed. The failure occurrence rate at the time is significantly reduced. From this,
The positive electrode in the wound electrode group, the metal porous body substrate of at least one electrode of the negative electrode, by filling the metal powder at the width direction end portion as in the present invention, by compressing,
It is clear that the strength of the end of the wound metal electrode group in the width direction of the porous metal substrate can be improved, and the strength sufficient to withstand the head pressure during welding can be secured. Therefore, according to the present invention, it is possible to manufacture an alkaline storage battery suitable for a large current application that needs to be connected to the metal plate current collector terminal at many points in order to reduce the internal resistance.

Next, the 10CA discharge capacity (%) of the sealed nickel-metal hydride storage batteries of Example 1 and Comparative Example 1, that is, the ratio of 10CA discharge capacity to 0.2CA discharge capacity [(10CA discharge capacity / 0.2CA discharge capacity) Capacity) × 10
0] is shown in Table 2.

[0034]

[Table 2]

As is clear from the results shown in Table 2, the battery of Example 1 exhibited excellent discharge characteristics even at a large current discharge of 10 CA. On the other hand, the 10 CA discharge capacity (%) of the battery of Comparative Example 1 was low because the wound electrode group in which no short circuit occurred when the metal plate current collecting terminal was welded was used. As in Example 1, the metal plate collector terminal was not securely welded to the widthwise end of the porous metal substrate in the positive electrode of the wound electrode group, and the connection was unstable. it is conceivable that.

[0036]

As described above, according to the present invention,
An alkaline storage battery suitable for high current applications could be provided.

[Brief description of the drawings]

FIG. 1 is a front view schematically showing an example of a porous metal substrate used in the present invention.

FIG. 2 is a front view schematically showing an example of an electrode according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Porous metal substrate 1a End in width direction 1b Other part 2 Electrode 3 Electrode mixture layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H017 AA02 BB06 BB13 CC25 5H022 AA04 AA18 BB01 CC08 CC12 CC16 CC21 5H028 AA05 BB04 BB05 BB07 CC13

Claims (1)

[Claims] 1. A winding formed by winding a positive electrode having a positive electrode mixture layer formed on at least a part of a substrate and a negative electrode having a negative electrode mixture layer formed on at least a part of a substrate via a separator. In an alkaline storage battery accommodating the circulating electrode group in a battery can, a positive electrode, a porous metal substrate is used as a substrate of at least one electrode of the negative electrode, and a metal powder is filled into a width direction end of the porous metal substrate, At the width direction end of the porous metal substrate filled with the metal powder, an electrode mixture layer is not formed and pressed and compressed in a state where the porous metal substrate is exposed, and after producing a wound electrode group, An alkaline storage battery characterized in that a metal plate current collector terminal is connected at a number of points to an end portion in the width direction of a porous metal substrate filled with metal powder and compressed.