JP2002280057A - Alkaline secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline secondary battery to prevent ignition of a negative electrode layer of a negative electrode by heat and explosion generated at the time of welding a current collecting plate of the negative electrode (especially, plain part) to an electric conductive member to make conduction with a container while maintaining high capacity. SOLUTION: This alkaline secondary battery is furnished with the container, an electrode group stored in this container and spirally winding the negative electrode having the negative electrode layer containing hydrogen storage alloy powder and a positive electrode having a positive electrode layer containing nickel hydroxide with a separator between them and an alkaline electrolytic solution stored in the container, the negative electrode has the current collecting plate made of a punching metal sheet having the plain part at least on one side end part, the plain part is connected to an inner surface of a bottom part of the container through the electrical conductive member of a belt type or a plate type similar to the container bottom part, and the negative electrode constitutes its characteristic feature of having a region of 0.1-5 mm wide and where the current collecting plate is actually exposed on an end part on the container bottom part side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkaline secondary battery having an improved negative electrode having a negative electrode layer containing a hydrogen storage alloy.

[0002]

2. Description of the Related Art Various electric tools and bicycles with electric assist,
Further, various secondary batteries have been used as drive power supplies for recently developed electric vehicles and the like because they can be charged and discharged and are portable.

[0003] As a secondary battery suitable for the above-mentioned applications, a nickel-cadmium secondary battery having a feature of being capable of discharging a large current is often used. This is because the nickel-cadmium secondary battery has a low internal resistance, a large discharge current (discharge rate) per time rate, and is unlikely to cause deterioration of battery characteristics even when overcharge / overdischarge is performed. This is due to having characteristics.

On the other hand, nickel-hydrogen secondary batteries are widely used as drive power supplies for small electronic devices such as notebook personal computers and mobile phones. This is because a nickel-hydrogen secondary battery has a higher internal resistance and a lower discharge rate than a nickel-cadmium secondary battery of the same size, but has a discharge capacity of 1.5 to 2 times as compared with the secondary battery. This is because an electronic device that can be driven with a small current can be driven over a long period of time even if the size is twice as large and the shape is small.

[0005] Further, the negative electrode containing a hydrogen storage alloy can increase the energy density per unit weight or unit volume as compared with cadmium, which is a material of a conventional representative negative electrode for an alkaline secondary battery. In addition to being able to increase the capacity, the battery has characteristics that it has a low risk of environmental pollution and also has excellent battery characteristics.

[0006] However, nickel-hydrogen secondary batteries which have been commercially available conventionally have a nominal capacity of not more than 1 to 3 times the hourly rate (when the full charge is discharged in 20 minutes to 1 hour). Therefore, although it is effective as a power source of the small electronic device that can be driven by a small current, it cannot be used as a power source of a power tool or an electric vehicle that requires a large current. Was.
For example, when a conventional nickel-hydrogen secondary battery is discharged with a large current that exceeds five times the hourly rate, that is, when the full charge is discharged in less than 12 minutes, the operating voltage is significantly reduced. In particular, in the case of a battery with a high capacity, the above-mentioned decrease in the operating voltage appears remarkably, and there has been a problem that not only the decrease in the operating voltage but also the cycle life is not practical.

For these reasons, Japanese Patent Application Laid-Open No. H11-2508 discloses
No. 91 discloses a negative electrode having a negative electrode layer containing a hydrogen storage alloy powder, a positive electrode having a positive electrode layer containing nickel hydroxide arranged with a separator interposed between the negative electrode, an alkaline electrolyte, and a housing containing these members. And a current collector plate made of a punched metal sheet having a solid portion on at least one side end as the negative electrode, and the solid portion has a band-like shape or a plate-like conductive shape similar to the container bottom portion. By using a structure connected to the inner surface of the container bottom through a member, the conventional problem can be solved, and nickel having a high capacity and capable of suppressing a decrease in operating voltage even when a large current discharge is performed. -A hydrogen secondary battery is disclosed.

[0008]

However, in the nickel-hydrogen secondary battery disclosed in the above publication, the current collector plate of the negative electrode, particularly, the uncoated portion is formed of a conductive member (for example, a plate-like material similar to the container bottom portion). The negative electrode layer formed in the uncoated part of the negative electrode is ignited or ignited by heat or explosion generated when welding to the conductive member), and as a result, the separator in the vicinity thereof undergoes heat shrinkage, and the positive and negative electrodes are separated from each other. There was a risk of internal short circuit. The present invention provides a negative electrode of the negative electrode, which is generated by heat or explosion generated when welding a current collector plate (particularly a plain portion) of the negative electrode to a conductive member in order to establish conduction with a container while maintaining high capacity. An object of the present invention is to provide an alkaline secondary battery in which a layer is prevented from firing or igniting.

[0009]

The alkaline secondary battery according to the present invention comprises a container, a negative electrode having a negative electrode layer containing a hydrogen storage alloy powder, and a positive electrode layer containing nickel hydroxide, which is contained in the container. An electrode group in which a positive electrode is spirally wound with a separator interposed therebetween, comprising an alkaline electrolyte contained in the container, wherein the negative electrode is formed from a punched metal sheet having a solid portion at at least one side end. A current collector plate, and the uncoated portion is connected to the inner surface of the container bottom via a strip-shaped or plate-like conductive member similar to the container bottom, and the negative electrode is an end on the container bottom side. And a region having a width of 0.1 to 5 mm where the current collector plate is substantially exposed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an alkaline secondary battery (cylindrical nickel-metal hydride secondary battery) according to the present invention will be described with reference to FIG.

An electrode group 2 is housed in a cylindrical container 1 having a bottom. As shown in FIGS. 1 to 3, the electrode group 2 has a current collector plate made of a punched metal sheet 4 having a solid portion 3 at a lower end, and a negative electrode layer 5 containing a hydrogen storage alloy on both surfaces. A strip-shaped negative electrode 6, a strip-shaped separator 7, and a strip-shaped positive electrode 11 in which a positive electrode layer 10 containing nickel hydroxide particles as an active material is formed on a conductive substrate 9 at an upper end portion, and a lead 8 a is attached to a plain portion 8. Are stacked so that the uncoated portion 3 of the negative electrode 6 is exposed on one side and the uncoated portion 8 of the positive electrode 11 is exposed on the opposite side, and the laminate is spirally wound. It is produced by The negative electrode 6
Has an area on the bottom side of the container 1 where the current collector plate is substantially exposed with a width of 0.1 to 5 mm.

The lower end of the uncoated portion 3 of the negative electrode 6 of the electrode group 2 is
It is spot-welded to a plate-like (eg, disk-shaped) conductive member 13 similar to the bottom of the container 1. This conductive member 13
As shown in FIG. 4, a large number of minute projections 12 are formed on the surface of the negative electrode 6 on which the lower end of the uncoated portion 3 contacts. After being accommodated in the container 1, the conductive member 13 is spot-welded near its center to the bottom surface of the container 1. The upper end of the lead 8a of the positive electrode 11 of the electrode group 2 is shown in FIG.
Disc-shaped conductive plate 1 having a hole 14 opened in the center as shown in FIG.
5 is spot-welded. The alkaline electrolyte is contained in the container 1.

A circular sealing plate 17 having a hole 16 in the center,
It is arranged at the upper opening of the container 1. 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 1, and the sealing plate is formed on the container 1 by caulking to reduce the diameter of the upper opening inward. 17 is hermetically fixed via the gasket 18. The positive electrode tab 19 has one end connected to the disc-shaped conductive plate 15 of the positive electrode 11 and the other end connected to the lower surface of the sealing plate 17.

A positive electrode terminal 21 having a hat shape having a plurality of gas vent holes 20 is provided on the sealing plate 17.
7 so as to cover the hole 16. The rubber safety valve 22 is disposed so as to close the hole 16 in a space surrounded by the sealing plate 17 and the positive electrode terminal 21.

Next, the negative electrode 6, the positive electrode 11, the separator 7, and the electrolyte will be described.

1) Negative electrode 6 This negative electrode 6 has a current collector plate made of a punched metal sheet 4 having a solid portion 3 at the lower end as described above.
In addition, the negative electrode layer 5 including the hydrogen storage alloy is formed in the area of the punched metal sheet 4 excluding the uncoated portion within a range of 0.1 to 5 mm from the end on the bottom side of the container 1. The negative electrode layer is formed, for example, by adding a conductive material to a hydrogen storage alloy powder, kneading the mixture with a polymer binder and water, and forming a paste on a predetermined area of a punching metal sheet (current collector plate) having the above-described uncoated portion. , Dried, and then molded.

The hydrogen storage alloy is particularly limited.
Not electrochemically generated water in the electrolyte
Element can be occluded and the occluded hydrogen can be easily released during discharge
Anything that can be done is acceptable. As this hydrogen storage alloy,
For example, LaNi_Five, MmNi _Five(Mm; Mishmeta
L), LmNi_Five(Lm: lantern-enriched misch
Al), Mn, C
o, Ti, Cu, Zn, Zr, Cr, B
Substituted multi-element type, TiNi type, TiF
e-type ones can be mentioned. Among them, the general formula Lm
Ni_xMn_yA_z(However, A is selected from Al and Co
At least one metal, and the atomic ratios x, y, z are the sum of
The value is 4.8 ≦ x + y + z ≦ 5.4)
It is preferred to use

Examples of the polymer binder include carboxymethylcellulose, methylcellulose, sodium polyacrylate, polytetrafluoroethylene, styrene / butadiene rubber, and modified styrene / butadiene rubber.

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

The negative electrode is placed at an end on the bottom side of the container.
It is necessary to have a region having a width of 1 to 5 mm substantially exposing the current collector plate. When the width of the exposed portion of the current collector plate at the bottom end portion of the negative electrode is less than 0.1 mm, heat generated when spot-welding the uncoated portion of the current collector plate to the disc-shaped conductive member is reduced. The bomb blast may cause the negative electrode layer to ignite or ignite, resulting in thermal contraction of the nearby separator and an internal short circuit between the positive and negative electrodes. On the other hand, if the width of the exposed portion of the current collector plate at the end of the negative electrode on the bottom side of the container exceeds 5 mm, the area of the negative electrode layer occupying the negative electrode may decrease, which may cause a reduction in the capacity of the secondary battery. More preferably, the width of the exposed portion of the current collector plate at the end on the container bottom side in the negative electrode is 0.5 to 2.0 mm. 2) Positive Electrode 11 As described above, the positive electrode 11 is formed by forming the positive electrode layer 10 containing nickel hydroxide particles as an active material on the conductive substrate 9 having the uncoated portion 8 at the upper end, and forming a lead on the uncoated portion 8. 8a
Is attached by, for example, welding. This positive electrode layer, for example, after adding a conductive material to nickel hydroxide particles as an active material, kneading the mixture with a polymer binder and water, filling the conductive substrate described above, and drying, It is formed by molding.

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

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

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

Examples of the polymer binder include carboxymethylcellulose, methylcellulose, sodium polyacrylate, polytetrafluoroethylene and the like.

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

[0026] The positive electrode, exposed to the area except for the current collecting plate of the battery theoretical capacity (Ah) per 30 cm ² or more, i.e. 30 cm ² / Ah or more. This positive electrode area is 30 cm ²
If it is less than / Ah, large current discharge may be difficult. A more preferable positive electrode area is 38 cm ² / Ah or more. In order to increase the area of the positive electrode, if the outer diameter and height of the electrode group are constant, the thickness of the positive electrode can be reduced. This is because the length of the positive electrode wound by the electrode group increases, the number of positive electrodes increases, and the area occupied by the electrode group after the rotation increases. However, if the thickness of the positive electrode is made too thin, the strength of the positive electrode decreases, cracks and cracks occur at the time of fatigue, and not only the defect of the electrode group increases, but also the area of the separator in the electrode group increases. Causes a reduction in capacity. Therefore, the upper limit of the area of the positive electrode is preferably set to 100 cm ² / Ah. 3) Separator 7 Examples of the separator 7 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 disc-shaped conductive member is preferably made of a material which is not corroded by an alkaline electrolyte, has a low specific resistance, and is relatively inexpensive. For example, pure nickel, stainless steel, and a nickel-plated metal plate are preferable. As the thickness of the conductive member increases, the conductor resistance decreases and a large current easily flows. However, when the thickness is too large, the cost increases and the capacity of the secondary battery decreases (the bottom where the electrode group is housed). (Reduction in volume of the cylindrical container).
Therefore, the thickness of the conductive member is 0.15 to 2.0 mm
Is preferable. The present invention is not limited to the embodiment in which the disc-shaped conductive member is connected to the lower end of the uncoated portion of the negative electrode, but a plurality of strip-shaped conductive members are connected to the lower end of the uncoated portion of the negative electrode, and these strip-shaped conductive members are formed on the inner surface of the container bottom. The connection may be made by spot welding or the like.

In the electrode group 2 used in the alkaline secondary battery according to the present invention, as shown in FIG. 2 described above, from the end of the uncoated portion 3 located on the bottom side of the container 1 of the negative electrode 5 to the bottom side of the container 1 of the positive electrode 11 If the length to the end of the position (protruding length of the negative electrode and the separator) and h _1, h ₁ from the viewpoint the h ₁ is to prevent a short circuit between the conductive member 13 to be conductive positive electrode 11 and the negative electrode 6 is> Preferably, it is set to zero. In order to sufficiently secure the opposing area between the positive electrode 11 and the negative electrode 6, h ₁ <5 mm
Is preferable. That is, it is preferable that 0 <h ₁ <5 mm. Further, in the electrode group 2 used in the alkaline secondary battery according to the present invention, as shown in FIG. 2 described above, the separator 7 is located from the end of the uncoated portion 3 located on the bottom side of the container 1 to the cathode 11 on the bottom side of the container 1. If the length to the end (the protruding length of the separator) and h _2, the h ₂ is 0 <h
₂ <preferably satisfies the h _1. Number of minute protrusions formed on the disc-shaped conductive member surface, it is preferable that the height is the h ₁ below. The alkaline secondary battery according to the present invention described above (for example, a nickel-metal hydride secondary battery)
A container, an electrode group housed in the container, and a spirally wound negative electrode having a negative electrode layer containing a hydrogen storage alloy powder and a positive electrode having a positive electrode layer containing nickel hydroxide with a separator interposed therebetween; Wherein the negative electrode has a current collector plate made of a punched metal sheet having a solid portion at at least one side end, and the solid portion is strip-shaped or similar to the container bottom. Connected to the inner surface of the bottom of the container via a plate-shaped conductive member. In addition, the negative electrode has an area on the bottom side of the container where the current collector plate is substantially exposed and has a width of 0.1 to 5 mm.

In the secondary battery having such a configuration, it is possible to suppress a decrease in the operating voltage at the time of discharging a large current while maintaining a high capacity, and to weld a negative electrode current collector plate (particularly a plain portion) to a conductive member. It is possible to prevent a short circuit between the positive and negative electrodes due to ignition or ignition at the time. In other words, nickel-hydrogen secondary batteries generally have a higher internal resistance than nickel-cadmium secondary batteries, and especially when discharged at a high discharge rate,
The operating voltage is reduced.

In the above-described nickel-hydrogen secondary battery, it is necessary to reduce the internal resistance as much as possible to suppress or prevent a decrease in the battery operating voltage even when operated at a high discharge rate.

In view of the above, the present invention uses a negative electrode having a current collector made of a punched metal sheet having a non-colored portion at at least one side end, and the non-colored portion of the negative electrode is strip-shaped or similar to the container bottom. Since the contact resistance between the negative electrode and the container can be significantly reduced by connecting to the inner surface of the container bottom through the plate-shaped conductive member, it is possible to effectively suppress a decrease in the operating voltage at the time of large current discharge. Can be.

In addition, a high capacity is maintained by using a negative electrode having a structure in which the current collector plate is substantially exposed at a width of 0.1 to 5 mm at an end on the bottom side of the container. In addition, it is possible to prevent the negative electrode layer from being ignited or ignited by heat or explosion generated when spot-welding the uncoated end portion to, for example, a disk-shaped conductive member. As a result, thermal contraction of the separator due to ignition or ignition of the negative electrode layer can be prevented, and the problem of internal short circuit between the positive and negative electrodes can be avoided. In particular, by setting the area of the positive electrode excluding the exposed current collector plate to 30 cm ² or more per theoretical capacity (Ah) of the battery, the density of the current flowing between the positive and negative electrodes can be reduced. As a result, a large current discharge can be realized while suppressing a decrease in the operating voltage.

Further, as shown in FIG.
A disk-shaped conductive member 15 having a hole 14 opened in the center is spot-welded to the upper end of the lead 8a of the positive electrode 11 and connected to a sealing plate 17 functioning as a positive electrode terminal through a positive electrode tab 19 connected to the conductive member 15. In this case, the internal resistance of the battery can be further reduced, and further, the interaction with the structure in which the lower end of the uncoated portion 3 of the negative electrode 6 is connected to the disk-shaped conductive member 13 allows the shape of the spirally wound electrode group 2 to be stabilized. Since the performance can be improved, the battery can be easily assembled.

Further, as shown in FIG. 4, if a disc-shaped conductive member 13 having a structure in which a large number of minute projections 12 are formed on the surface where the lower end of the negative electrode 6 uncoated portion 3 is in contact is used, When the lower end is abutted against the surface of the disc-shaped conductive member and welded, a large number of minute projections on the surface of the conductive member are pressed into contact with the end surface of the lower end of the uncoated portion, so that welding current is reduced. The contact resistance when flowing can be reduced, and the strength of the welding point after welding can be improved.

[0036]

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

[0037] (Examples 1 to 5 and Comparative Examples 1 to 6) <Preparation of Negative Electrode>Lm; was prepared (Lm lanthanum enriched misch _{metal) Ni 3.6 Co 0.8 Mn 0.3 Al} 0.3 of the hydrogen storage alloy. These alloys were heat-treated in an argon atmosphere at 1000 ° C. for 10 hours to homogenize the alloy compositions. Subsequently, the hydrogen storage alloy was mechanically pulverized and sieved to obtain a powder of 25 to 75 μm. To 100 parts by mass of the obtained hydrogen storage alloy powder, 0.3 parts by mass of sodium polyacrylate and carboxymethyl cellulose (CM
C) 0.1 parts by mass, 0.5 parts by mass of carboxy-modified styrene / butadiene rubber, 0.5 parts by mass of carbon black as a conductive material and 0.5 parts by mass of nickel flake are added, and mixed with 30 parts by mass of water. Thus, a paste was prepared. Subsequently, a punched metal sheet having a thickness of 0.06 mm, a lower end formed as a solid portion over a width of 1 mm, and an opening having a diameter of 1 mm punched at an opening ratio of 45% is prepared. The paste was applied, dried at a temperature of 80 ° C. for 1 hour, and then rolled by a roller press to form a negative electrode layer. Thereafter, a part of the negative electrode layer is removed and cut to a desired size, thereby obtaining a 5 m from the lower end shown in FIGS. 2 and 3 described above.
A negative electrode was produced by exposing a region having a height of m.

<Preparation of Positive Electrode> A mixed powder comprising 90 parts by mass of nickel hydroxide powder and 10 parts by mass of cobalt monoxide powder was mixed with 0.3 part of carboxymethyl cellulose (CMC).
A paste was prepared by adding 0.5 parts by mass of a dispersion of polytetrafluoroethylene (specific gravity: 1.5, solid content: 60% by mass) in terms of solid content and mixing with 45 parts by mass of pure water. .

Further, the upper end of the nickel foam sheet has a width of 2 mm.
By pressing in the length direction over the length of 1 mm to densify, a plain portion having a thickness of 1/5 of that before the pressing was formed over the width of 2 mm at the upper end. Subsequently, the paste was filled in a nickel foam sheet excluding the uncoated portion, and
After drying at a temperature of 0 ° C., rolling was performed with a roller press to form a positive electrode layer, and a lead made of nickel-plated stainless steel having a thickness of 0.08 mm and a width of 3 mm was welded to the uncoated portion to a desired size. By cutting, a positive electrode having a lead at the upper end was produced.

The obtained positive electrode has a positive electrode layer area
38cm per theoretical capacity of battery^TwoThat is, 3
8cm^Two/ Ah. <Assembly of nickel-hydrogen secondary battery> The negative electrode, thickness
Separate made of 0.13mm polypropylene non-woven fabric
The positive electrode and the positive electrode are connected to the negative electrode as shown in FIG.
6 uncovered portion 3 is exposed to the lower side, and the lead of the positive electrode 11
8a are shifted from each other so as to be exposed on the upper side,
This laminate is spirally wound to form an outer diameter of 16 m.
m, electrode group having a hollow part with a diameter of 4 mm at the center
did. The lower end of the separator and the lower part of the negative electrode
The ends are each 1.
0 mm (h in FIG. 2) _Two), 2.0 mm (in FIG. 2)
h₁). Then, on the surface 1.0mm height
Nickel with a diameter of 15.5mm on which a large number of microprojections are formed
Prepare a disk-shaped conductive member made of
The uncoated uncoated portion of the negative electrode of the electrode group is formed on the surface where
Approximately 20 parts are abutted by pressing and spot welding.
Forming a nugget in place and integrating the electrode group and conductive members
Was. Subsequently, the electrode group is placed in a bottomed cylindrical container.
The disc-shaped conductive member integrated with the electrode group is located
The conductive member is inserted so as to be placed on the inner bottom of the container.
Surface. Continue to attach the upper welding electrode to the electrode
Insert through the central cavity of the group and at its welding electrode tip
The conductive member is pressurized and simultaneously placed on the outer bottom surface of the container.
The container was pressurized upward with the placed lower welding electrode
After that, a current is applied to both welding electrodes to
The conductive member was welded to the inner bottom surface of the container. Then
The lead of the positive electrode protruding from the upper end of the electrode group in the container is
Place a nickel-plated disc-shaped conductive member and spot weld 20 places
After that, one end of the nickel positive electrode tab is connected to the conductive member.
Welded. Subsequently, potassium hydroxide is mainly contained in the container.
An electrolyte to be a body was injected. Next, the positive electrode tab
Was welded to a sealing plate having holes. After this,
Insert a rubber safety valve into the sealing plate to cover the hole in the sealing plate
Arrange the cap shape with a vent hole on this sealing plate
After placing the positive electrode terminal around the safety valve,
Contacted Opening the sealing plate to the upper end opening of the bottomed cylindrical container
Into the mold via a gasket and mold clamping
4 / 5A size having the structure shown in FIG.
A cylindrical nickel-metal hydride secondary battery was assembled.

Example 2 A view similar to that of Example 1, except that a region having a height of 0.1 mm from the lower end of the punched metal sheet is exposed, and a negative electrode in which a negative electrode layer is formed in other regions is not used. A 4 / 5A cylindrical nickel-metal hydride secondary battery having the structure shown in FIG. 1 was assembled.

(Example 3) A view similar to that of Example 1 except that a region having a height of 0.5 mm from the lower end of the punched metal sheet is exposed, and a negative electrode having a negative electrode layer formed in other regions is not used. A 4 / 5A cylindrical nickel-metal hydride secondary battery having the structure shown in FIG. 1 was assembled.

(Example 4) As shown in FIG. 1 similar to Example 1, except that a region having a height of 2 mm from the lower end of the punched metal sheet was exposed, and a negative electrode layer in the other region was not used. A 4 / 5A size cylindrical nickel-metal hydride secondary battery having the structure shown was assembled.

(Example 5) As shown in FIG. 1 similar to Example 1, except that a region having a height of 3 mm from the lower end of the punched metal sheet was exposed and a negative electrode layer was formed in other regions. A 4 / 5A size cylindrical nickel-metal hydride secondary battery having the structure shown was assembled.

(Example 6) FIG. 1 is similar to Example 1 except that a region having a height of 5 mm from the lower end of the punched metal sheet is exposed and a negative electrode layer in the other region is used. A 4 / 5A size cylindrical nickel-metal hydride secondary battery having the structure shown was assembled.

(Comparative Example 1) A cylindrical nickel-metal hydride secondary battery of 4 / 5A size similar to that of Example 1 except that the lower end of the punched metal sheet is not exposed and a negative electrode having a negative electrode layer formed on the entire surface is desired to be used. Was assembled.

(Comparative Example 2) As shown in FIG. 1 similar to that of Example 1, except that a region having a height of 8 mm from the lower end of the punched metal sheet was exposed and a negative electrode layer was formed in other regions. A 4 / 5A size cylindrical nickel-metal hydride secondary battery having the structure shown was assembled.

The obtained Examples 1 to 6 and Comparative Examples 1 and 2
After assembling, 10000 secondary batteries were allowed to stand at 25 ° C. for 24 hours after assembly, and the voltage was measured. In this measurement,
A secondary battery having a battery voltage of 1 mV or less was determined to have poor insulation, and the number of defective batteries was examined. The results are shown in Table 1 below. Also,
After the predetermined initial activation was performed on 100 secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2, after the initial activation, 1.
The battery was charged for 2 hours, paused for 30 minutes, discharged at a current rate of 1 hour, and the discharge capacity when the voltage was dropped to 0.7 V was measured and calculated as an average value of 100 batteries. The results are shown in Table 1 below.

[Table 1]

As is apparent from Table 1, a punched metal sheet region in a range of 0.1 to 5 mm from the end on the container bottom side was exposed, and the negative electrode layer was formed on the punched metal sheet excluding this region. In the secondary batteries of Examples 1 to 6, the number of defective insulations out of 10,000 was at most one,
It can be seen that the battery has high discharge capacity. In contrast,
The secondary battery of Comparative Example 1 in which the punched metal sheet was not exposed from the end on the container bottom side, and the negative electrode layer was formed on the entire surface,
It can be seen that although having a high discharge capacity, 20 out of 1000 insulation failures occur. Further, a secondary battery of Comparative Example 2 in which a punched metal sheet region was exposed in a range of 10 mm from the end on the container bottom side and a negative electrode layer was formed on the punched metal sheet excluding this region, was 10000.
It can be seen that although the number of insulation failures in each cell is 0, the discharge capacity is reduced.

[0050]

As described above, according to the present invention, it is possible to suppress a decrease in the operating voltage at the time of high-capacity and large-current discharge, and to use a negative electrode current collector plate (particularly, a plain portion). The heat generated when welding to the conductive member to establish conduction with the container prevents the negative electrode layer of the negative electrode from igniting, so that the positive and negative electrodes due to the heat shrinkage of the separator can avoid an internal short circuit, and various electric motors can be used. Bicycles with tools and electric assistance,
An alkaline secondary battery useful as a driving power source for an electric vehicle or the like can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a nickel-metal hydride secondary battery according to the present invention.

FIG. 2 is a developed view of an electrode group incorporated in the secondary battery of FIG.

FIG. 3 is a developed view of the electrode group of FIG. 2 when viewed from the back.

FIG. 4 is a plan view showing a disc-shaped conductive member disposed on the inner surface of the bottom of the container of the secondary battery of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... container, 2 ... electrode group, 3, 8 ... uncoated part, 6 ... negative electrode, 7 ... separator, 11 ... positive electrode, 13 ... conductive member, 17 ... sealing plate, 18 ... insulating gasket.

Continued on the front page (72) Inventor Koji Taguchi 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation F-term (reference) 5H022 AA04 AA18 BB16 CC13 CC20 CC23 EE01 5H028 AA01 AA05 BB05 BB07 CC05 CC10 CC12 EE01 HH06 HH10

Claims (2)

[Claims] 1. An electrode group in which a container, a negative electrode having a negative electrode layer containing hydrogen storage alloy powder, and a positive electrode having a positive electrode layer containing nickel hydroxide, which are housed in the container, are spirally wound with a separator interposed therebetween. And an alkaline electrolyte accommodated in the container, wherein the negative electrode has a current collector plate made of a punched metal sheet having a solid portion at at least one side end, and the solid portion is band-shaped. Alternatively, the negative electrode is connected to the inner surface of the container bottom through a plate-shaped conductive member similar to the container bottom, and the negative electrode has a width of 0.1 to 5 mm at the end on the container bottom side. An alkaline secondary battery having a region where an electric plate is exposed. 2. The alkaline secondary battery according to claim 1, wherein the positive electrode layer of the positive electrode incorporated in the electrode group has an area of 30 cm ² or more per theoretical capacity of the battery.