JPH11250891A - Nickel-hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel-hydrogen secondary battery capable of discharging a large current five times or more in an hourly rate. SOLUTION: An electrode group A of a structure comprising a positive electrode 2 in which positive electrode mix mainly comprising nickel compound is carried on a collector sheet, and a negative electrode 1 in which negative electrode mix mainly comprising hydrogen storage alloy is carried on a collector sheet, alternately laminated or rolled through a separator 3, is contained in a battery can 5 with electrolyte, and an opening part of the battery can 5 is sealed with a sealing plate 8 provided with a positive electrode terminal 10. In this case, an end part 1A of the collector sheet of the negative electrode 1, at least, is continuous with the battery can 5 through a collector plate 6a disposed there by welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-metal hydride secondary battery, and more particularly, to a nickel-metal hydride secondary battery capable of extracting a larger current than a conventional nickel-metal hydride secondary battery because of its low internal resistance. It relates to a hydrogen secondary battery.

[0002]

2. Description of the Related Art Various electric tools and bicycles with electric assist,
In addition, various secondary batteries are used as drive power sources for electric vehicles and the like, which are being developed recently because they are chargeable / dischargeable and portable. A secondary battery suitable for the above-mentioned applications is required to have a characteristic of being capable of discharging a large current, and a nickel-cadmium secondary battery has been often used in the past. This is for the following reasons.

That is, a nickel-cadmium secondary battery has a low internal resistance, a large discharge current per hour rate (discharge rate), and causes deterioration of battery characteristics even when overcharged or overdischarged. This is because it has a characteristic of being difficult. On the other hand, as a drive power source for small electronic devices such as notebook computers and mobile phones, the nickel-
Nickel-metal hydride secondary batteries are more widely used than cadmium secondary batteries. This is for the following reason.

[0004] That is, a nickel-hydrogen secondary battery has a larger size than a nickel-cadmium secondary battery of the same size.
Although its internal resistance is high and its discharge rate is small, its discharge capacity is as large as 1.5 to 2 times. This is because it can be driven. This nickel
There are two types of hydrogen rechargeable batteries, cylindrical and square.
The outline of the cylindrical shape will be described below.

[0005] First, the production of a positive electrode and a negative electrode will be described. In the production of the positive electrode, a powder of a nickel compound such as nickel hydroxide, which is an active material, is mainly used.
A paste of a positive electrode mixture is prepared by kneading a binder such as TFE, a conductive material of a cobalt compound such as cobalt oxide or cobalt hydroxide, and water.

Next, a predetermined amount of the paste is filled into an alkali-resistant metal porous structure (current collector sheet) such as a sponge-like porous metal having a three-dimensional network structure or a metal fiber mat, and then dried. If necessary, pressure molding, cutting, or the like is performed to obtain a sheet-shaped positive electrode having a predetermined thickness and a predetermined planar shape. Therefore, the obtained positive electrode has a state in which the dried positive electrode mixture is supported on the internal voids and the surface of the current collector sheet. Then, a tab terminal made of, for example, nickel and having a small piece shape is attached to the upper end of the positive electrode.

On the other hand, in the production of the negative electrode, first, a paste of a negative electrode mixture mainly containing a powder of a hydrogen storage alloy and further containing a thickener such as carboxymethyl cellulose and a conductive material such as carbon powder. Is prepared. Then
A predetermined amount of the paste is applied to, for example, a nickel punching sheet (current collector sheet) having a predetermined opening ratio, dried, and then subjected to a rolling process, cutting, or the like, so as to have a predetermined thickness and a predetermined planar shape. A sheet-shaped negative electrode is used. Therefore, the obtained negative electrode is in a state where the dried negative electrode mixture is carried on the opening and the surface of the current collector sheet.

In the case of the negative electrode, a tab terminal may be attached to the end, as in the case of the positive electrode. Next, an electrode group is manufactured using the positive electrode and the negative electrode manufactured as described above. As shown in FIG. 9 and FIG. 10 which is a cross-sectional view taken along line XX of FIG. 9, and FIG. 11 which is a cross-sectional view taken along line XI-XI of FIG. Sheet) 1a on which a negative electrode mixture 1b is supported, and a current collector sheet (nickel foam sheet) 2
a, a positive electrode mixture is carried, and one end has a tab terminal 2
The sheet laminate is formed by sandwiching a separator 3 having liquid retaining properties and electrical insulation properties, for example, a nonwoven fabric of polyolefin, between the positive electrodes 2 to which c is attached.

Then, after a winding core is disposed on the positive electrode 2 of the sheet laminate, the electrode is wound so that the negative electrode 1 is on the outside, thereby producing a spirally shaped electrode group having a predetermined outer diameter. Therefore, as shown in FIG. 12, the sectional structure of the electrode group has a laminated structure in which the negative electrode 1 and the positive electrode 2 are alternately laminated with the separator interposed therebetween, and the core is removed at the center thereof. A hole 4 remaining afterward is formed.

Then, the electrode group is inserted into a battery can having a predetermined inner diameter, and a predetermined alkaline electrolyte is injected,
The upper opening of the battery can is sealed with a sealing plate provided with a positive electrode terminal. At this time, since the negative electrode 1 of the electrode group contacts the inner wall of the battery can, the battery can functions as a negative electrode terminal. When the electrode group is inserted into the battery can, the tab terminal 2c of the positive electrode 2 is connected to the sealing plate.

In the case of an electrode group of a prismatic battery, a negative electrode and a positive electrode having a predetermined thickness by alternately stacking a plurality of negative electrodes and a positive electrode via a separator are used. Therefore, also in this case, the sectional structure of the electrode group is a laminated structure.

[0012]

Incidentally, in the above-mentioned nickel-cadmium secondary battery, although a large current can be taken out, cadmium in the electrode may adversely affect the environment. In recent years, it has begun to be avoided as a drive power source for the above-mentioned electric tool and the like, and it has been studied to replace it with a nickel-hydrogen secondary battery that is non-polluting and has a higher capacity than nickel-cadmium secondary batteries.

However, conventionally commercially available nickel-metal hydride secondary batteries can obtain a capacity corresponding to the nominal capacity only at the time of discharging at a rate of about 1 to 3 times an hour rate, and can be driven with a small current. Although effective as a power source for the small electronic device, there is a problem that it cannot be used practically as a power source for electric tools or electric vehicles that require a large current.

For example, in the case of a conventional nickel-hydrogen secondary battery, if it is discharged with a large current exceeding five times the hourly rate, the operating voltage is greatly reduced, and it is impossible to withstand practical use. It is in. The present invention solves the above-described problems in the conventional nickel-hydrogen secondary battery, and has a novel structure of a nickel-hydrogen secondary battery having a high capacity and capable of suppressing a decrease in operating voltage even when a large current is discharged. The purpose is to provide.

[0015]

Means for Solving the Problems The present inventors have made the following considerations in conducting research for achieving the above object. (1) Since nickel-hydrogen secondary batteries have a higher volumetric energy density than nickel-cadmium secondary batteries, when batteries of the same size are discharged at the same time rate,
The discharge current of the nickel-hydrogen secondary battery is larger.

Therefore, in order to prevent the operating voltage of the nickel-hydrogen secondary battery from lowering even when it is operated at a high discharge rate, it is necessary to reduce the internal resistance of the battery as much as possible. In the case of a conventional nickel-hydrogen secondary battery, the contact interface between the negative electrode and the inner wall of the battery can was one of the conduction paths. And when taking out a small current, the contact resistance does not cause a large voltage drop,
As the discharge current increases, the contact resistance has a large effect on the decrease in the operating voltage.

Accordingly, in order to realize a large current discharge in the nickel-hydrogen secondary battery, it is necessary to incorporate another low-resistance conduction path. (2) In the electrode group, when the facing area between the positive electrode and the negative electrode is increased, the current density of the current flowing between the two electrodes can be reduced, and a decrease in operating voltage can be suppressed.

Therefore, it is considered effective to increase the facing area between the positive electrode and the negative electrode, basically, the area of the portion supporting the positive electrode active material, for realizing a large current discharge. From the above viewpoints, the present inventors have conducted intensive research and have developed the nickel-hydrogen secondary battery of the present invention.

That is, the nickel-hydrogen secondary battery of the present invention has a positive electrode in which a current collector sheet carries a positive electrode mixture mainly composed of a nickel compound, and a current collector sheet mainly containing a hydrogen storage alloy. An electrode group having a structure in which a negative electrode carrying a negative electrode mixture is alternately laminated or wound via a separator is accommodated in a battery can together with an electrolytic solution, and the opening of the battery can is provided with a positive electrode terminal. In a nickel-hydrogen secondary battery sealed with a sealing plate provided with, at least the end portion of the current collector sheet of the negative electrode, the sealing plate through the current collector plate disposed by welding there. The battery can is electrically connected to each other. In particular, in the present invention, a current collector plate is also provided at the end of the positive electrode current collector sheet,
Further, there is provided a nickel-hydrogen secondary battery in which an area of a portion of the battery group where the positive electrode mixture of the positive electrode is supported is 30 cm ² or more per theoretical capacity (unit: Ah) of the battery.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a nickel-hydrogen secondary battery of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a preferred example of a cylindrical nickel-metal hydride secondary battery of the present invention in which current collectors are provided at both the lower end and the upper end of an electrode group. In FIG. 1, a battery can 5 accommodates an electrode group A formed by spirally winding a sheet stack of a negative electrode 1, a separator 3, and a positive electrode 2 together with an alkaline electrolyte (not shown).

A disk-shaped current collector plate 6a having a predetermined diameter is welded to the bottom of the battery can 5, and the electrode group A is provided thereon. A is connected to a lead 7 welded to a sealing plate 8 provided with a positive electrode terminal 10, and a current collecting plate 6 b having a predetermined diameter is arranged on A, and the sealing plate 8 is connected via a gasket 9 to the battery can 5. Is fitted into the upper opening, and a caulking process is performed on the upper opening to form a completely closed structure.

Here, the above-mentioned current collector plates 6a and 6b are both means for lowering the internal resistance of the battery, and these are arranged on the lower end face and the upper end face of the electrode group A, respectively. This is a feature of the battery of the invention. In the battery of the present invention, the current collector plate 6a is provided on the lower end face of the electrode group A.
Is an essential requirement, and the current collector 6
The arrangement of b is not always necessary. Then, instead of disposing the current collector plate 6b on the upper end surface of the electrode group A, for example, a plurality of tab terminals may be attached to the upper end during the manufacture of the positive electrode. However, as compared with the case of mounting a plurality of tab terminals, as shown in FIG.
The arrangement of the current collecting plate 6b also on the upper end surface of the electrode group A is advantageous in that the internal resistance of the battery is reduced, and
This is preferable because the battery assembling operation is also facilitated.

First, the negative electrode 1 and the positive electrode 2 in the above-mentioned electrode group A have the following structure. First, in the case of the negative electrode 1, as shown in FIG. 2 and FIG. 3, which is a cross-sectional view taken along the line III-III of FIG.
A (the lower end in the figure) does not carry the negative electrode mixture 1b, and the end 1A is in a state where the current collector sheet 1a is exposed in a band shape. In the case of the positive electrode 2, as shown in FIG. 4 and FIG. 5, which is a cross-sectional view taken along line VV in FIG.
One end 2A (upper end in the figure) of the current collector sheet 2a is compressed in the thickness direction and is in a densified state, and the end 2A is in a state where the positive electrode mixture 2b is not carried thereon. Appears in a band.

At the time of manufacturing the electrode group A, the negative electrode 1 and the positive electrode 2 are overlapped so that the end 1A and the end 2A face in opposite directions, and then the negative electrode 1 is wound outside. I do. Therefore, the obtained electrode group A is provided on one end face (lower end face) of the end portion 1A of the negative electrode current collector sheet 1a.
Are formed in a spiral shape, and the end 2A of the positive electrode current collector sheet 2a is also formed in a spiral shape on the other end surface (upper surface).

When inserting the obtained electrode group A into the battery can 5, first, a current collector plate 6 a, which will be described later, is disposed on the end 1 A of the spirally projecting negative electrode current collector sheet 1 a. After the current collector plate is brought into contact with the end face 1B of the end portion 1A, a plurality of portions of the contact portion are welded to integrate the electrode group A and the current collector plate 6a. Then, the electrode group A is inserted into the battery can 5 with the welded current collector plate 6a side down, and the current collector plate 6a and the bottom of the battery can 5 are brought into contact. Then, an upper welding electrode (not shown) is formed from the hole 4 of the electrode group A.
Is inserted to press the current collector plate 6a, and a lower welding electrode (not shown) is disposed outside the battery
The current collector plate 6a is welded to the can bottom of the battery can 5 by pressurizing the bottom of the can upward and applying a welding current between both electrodes.
It is preferable to form a small projection or the like at the center of the lower surface of the current collector plate 6a, because the reliability of the above-described welding is enhanced.

Then, the end 2A of the positive electrode current collector sheet 2a
A current collecting plate 6b is disposed on the current collecting plate and the end 2A.
After that, the electrode group A and the current collecting plate 6b are integrated by welding a plurality of portions of the contact portion. In the battery shown in FIG. 1 assembled as described above, the positive electrode terminal 10 {the sealing plate 8} the lead 7} the upper current collector 6 b {the end portion 2A of the positive electrode current collector sheet} the positive electrode 2, the negative electrode 1} and the negative electrode A conduction path is formed between the end portion 1A of the current collector sheet, the lower current collector plate 6a, and the battery can 5, through which charging / discharging current flows.

The diameter of each of the current collector plates 6a and 6b is smaller than the inner diameter of the battery can 1, so that the surface thereof can be reliably brought into contact with the end portions 1A and 2A. The current collector 6
a, 6b, the end portion 1A of the negative electrode current collector sheet,
If minute projections are formed on the surface of the positive electrode current collector sheet that is in contact with the end 2A, the minute projections may be attached to each of the current collectors when the above-described contact with each end or spot welding is performed. Since the state is such that the sheet bites into the end face of the end of the sheet, the contact resistance when a welding current flows is reduced, and the strength of the welding point after welding is preferably increased.

As the material forming the current collector plates 6a and 6b, a material which is not eroded by the alkaline electrolyte, has a low specific resistance, and can be obtained at a relatively low cost is selected. For example, a plate made of pure Ni, stainless steel, Ni-plated metal, or the like is preferable. Further, assuming that the inner diameter of the battery can 5 is constant, the thicker the current collector plates 6a and 6b, the lower the conductor resistance as a whole, so that a large current easily flows. However, if the thickness is too large, the cost and the capacity of the battery are reduced.
It is preferable to set it to about 5 to 2.0 mm.

When the current collector plate and the end of each current collector sheet are spot-welded, for example, the number of spot-welded points, that is, the number of weld points, is an important factor in reducing the internal resistance of the battery. Become. For example, in the electrode group A, when the lower current collector plate 6a is welded to the end 1A of the negative electrode current collector sheet at four places, if this negative electrode 1 is developed, as shown in FIG. At one end 1A, four welding points B1, B
2, B3 and B4 exist. And the negative electrode 1
The electron transfer reaction based on the battery reaction that occurs on the entire surface of
It is realized via these welding points B1, B2, B3, B4. That is, the negative electrode 1 shown in FIG.
This is the same as the state in which four tab terminals are attached to 2, B3 and B4, respectively. Therefore, the greater the number of welding points, the greater the number of tab terminals attached to the negative electrode 1, which is equivalent to the following:
For the electron transfer reaction at all points of the negative electrode 1,
This means that the negative electrode 1 has a low resistance as a whole.

The increase in the number of welding points is as follows.
This is effective in reducing the apparent resistance of the negative electrode 1 (similarly in the case of the positive electrode 2), and thereby reducing the internal resistance of the entire battery. However, if the number of welding points is too large, in the actual manufacturing process, many spot welding operations with the current collector plate are performed, which causes an increase in manufacturing cost.

In the case of a battery having a small discharge capacity,
Although the number of the above-mentioned welding points may be small, when the discharge capacity becomes large, the electron transfer reaction in the negative electrode 1 also increases. Therefore, it is necessary to increase the number of the above-mentioned welding points to correspond to the number. come. For this reason, in the battery structure of the present invention, the number of welding points is selected in relation to the battery capacity to be manufactured. In particular,
It is preferable to set the number to 4 or more per theoretical capacity (unit: Ah) of the battery.

The current collector plate needs to have a lower resistance than the current collector sheet as a whole. However, in order to perform spot welding between the current collector plate and the end of each current collector sheet well, It is necessary that the resistance value of the current collector plate at the portion to be welded is higher than the resistance value of the end portion of the current collector sheet. In the opposite case, since the welding current does not flow across the contact interface between the two, the formation of a nugget at the contact interface is unlikely to occur, that is, a good welding condition is not realized. This can be achieved by forming slits, holes, and the like in the current collector used.

In order to lower the internal resistance of the battery,
It is effective to increase the facing area between the positive electrode 2 and the negative electrode 1 in the electrode group A. Specifically, the area of the positive electrode 2 supporting the active material is increased. This reduces the current density even for a large current based on a high discharge rate, and further allows the large current discharge to be allowed in combination with the above-described effect of reducing the internal resistance due to the arrangement of the current collector plate. Because.

Specifically, the area of the positive electrode 2 wound around the electrode group A is determined by the theoretical capacity (C _T : Ah) of the battery to be manufactured.
It is preferable that the pressure is 30 cm ² or more, that is, 30 cm ² / Ah or more. More preferably, it is at least 38 cm ² / Ah. In order to increase the area of the positive electrode 2, for example, if the outer diameter and the height of the electrode group A are constant, the thickness of the positive electrode 2 may be reduced. This is because the length of the positive electrode 2 wound around the electrode group A increases, and as a result, the number of layers of the positive electrode after winding increases, and the area of the positive electrode in the electrode group A increases. However, if the thickness is too small, the strength of the positive electrode decreases, and cracks and cracks occur during winding and the number of defective electrodes in the electrode group A increases. Therefore, it is preferable to set the upper limit of the thickness to 100 cm ² / Ah. .

The positive electrode 2 may be either of a sintered type or a paste type, but the paste type can carry a larger amount of the positive electrode mixture, and can be used for increasing the capacity of the battery. Is effective. The positive electrode mixture supported on the paste-type positive electrode is mainly composed of a single powder of nickel hydroxide, which is an active material, or a powder produced by co-precipitating nickel with zinc, cobalt, bismuth, copper, and the like. It is prepared by blending a conductive material and a binder. At this time, the amount of the active material is determined in relation to the theoretical capacity of the battery to be manufactured, and the amounts of the conductive material and the binder are adjusted accordingly.

The case where the active material is the latter is preferable because the charging efficiency of the assembled battery in a high temperature state can be increased. Nickel hydroxide used as an active material has a peak half-value width of (101) plane of 0.8 ° / 2θ (Cu-Cu) measured by X-ray powder diffraction.
Kα) or more, especially 0.9 to 1.0 ° / 2θ (Cu-K
α) is preferable because the utilization factor and the life can be improved.

As the conductive material, one or more powders selected from a cobalt compound and metallic cobalt are used. Examples of the cobalt compound include cobalt hydroxide and cobalt monoxide. In particular, cobalt hydroxide or cobalt monoxide or a mixture of both is preferable because it can increase the utilization factor of the positive electrode. Examples of the binder include carboxymethylcellulose, methylcellulose, sodium polyacrylate, polyvinyl alcohol, a copolymer of vinyl alcohol and sodium acrylate, and polytetrafluoroethylene.

The current collector sheet for supporting the positive electrode mixture having the above-mentioned composition is made of nickel, stainless steel, or nickel-plated metal, and has a net-like, sponge-like, fibrous, or felt-like shape. A porous structure can be used. As the negative electrode of the nickel-metal hydride secondary battery, a sintered type and a paste type are known as in the case of the positive electrode. Of these,
The sintered negative electrode is disadvantageous for increasing the capacity of the battery, and has a problem that the manufacturing process is complicated and the cost is increased. The paste-type negative electrode is advantageous in that the capacity of the battery can be increased and that the production is easy and the production cost is low.

As the negative electrode 1 incorporated in the battery of the present invention,
Either a sintering type or a paste type can be used, but a high capacity can be achieved by using a paste type negative electrode carrying a negative electrode mixture prepared as described below. It is preferable because it can be performed. That is, the above-mentioned negative electrode mixture is obtained by adding polytetrafluoroethylene or styrene-butadiene rubber or modified styrene-butadiene rubber as a binder and carbon powder or / and nickel powder as a conductive material to a hydrogen storage alloy powder. This is a blended paste.

The current collector sheet for supporting the negative electrode mixture is made of nickel, stainless steel, or nickel-plated metal, and has a net shape, a sponge shape, a fibrous shape, or the like.
Alternatively, a felt-like porous structure or foil, a punching metal having a desired aperture ratio, and the like can be given. Among these, punched metal is preferred in terms of strength and cost, and good coating properties of the negative electrode mixture paste.

Here, when the current collector sheet to be used is a punching metal, it is preferable to adopt the following mode. That is, in the negative electrode 1 shown in FIGS. 2 and 3, the current collector sheet (punched metal) 1a
It is preferable to use an end 1A having no opening. This is because the resistance between the welding points with the current collector plate 6a can be reduced.

Even if an opening exists at the end 1A, the opening ratio at the end 1A only needs to be smaller than the opening ratio at other portions where the negative electrode mixture is carried. Also in this case, the resistance between the welding points is relatively lower than at other portions where the negative electrode mixture is carried. As shown in FIG. 7, the current collector sheet 1a
The end 1A is a non-opening part, and the negative electrode mixture 1b is carried on the end 1A, and then the negative electrode mixture adhered to the end face 1B of the end 1A. For example, by grinding to expose only the end face 1B,
Here, it is preferable to weld the current collecting plate 6a.

In this case, the capacity of the negative electrode is larger than that of the negative electrode shown in FIG. 2, since the negative electrode mixture 1b is also supported at the end 1A which is a non-opening portion. Because. Further, after the negative electrode mixture is carried on the entire surface of the current collector sheet including the non-opening portion, when a part of the non-opening portion is cut and removed, the end face of the current collector sheet can be easily exposed. Therefore, it is preferable in manufacturing.

[0044]

EXAMPLES Examples 1 to 5 and Comparative Examples 1 to 3 A cylindrical nickel-hydrogen secondary battery having a size of 4/5 A shown in FIG. 1 was manufactured as follows. The inner diameter of this battery can is 16.1 mm. (1) Production of Positive Electrode A Ni foam sheet is prepared as a current collector sheet 2a, and its upper end is pressed in the length direction over a width of 2 mm to densify it, thereby obtaining the end portion shown in FIGS. 2A was provided. The thickness of the end 2A is 1/5 of the total thickness of the Ni foam sheet.

Next, the Ni excluding the end 2A
The foam sheet was filled with the positive electrode mixture paste 2b mainly composed of nickel hydroxide powder, dried at a temperature of 100 ° C. for 1 hour, and then rolled to produce the positive electrode 2 shown in FIG. At this time, by changing the filling amount and the thickness of the positive electrode mixture, the amount of the positive electrode mixture was kept constant, and a positive electrode having an area as shown in Table 1 when the electrode group A was assembled was obtained.

[0046]

[Table 1]

(2) Production of Negative Electrode For 100 parts by weight of the hydrogen storage alloy powder, 0.3 part by weight of a copolymer of sodium acrylate and vinyl alcohol, carboxylated styrene / butadiene rubber (toluene insoluble content: 60% by weight) Parts by weight, 1 part by weight of carbon black,
Nickel powder was mixed at a ratio of 1 part by weight, and 50 parts by weight of water was added thereto and stirred to prepare a negative electrode mixture paste.

On the other hand, a nickel punched sheet having a thickness of 0.06 mm and an opening having a diameter of 1 mm and an opening ratio of 45% was prepared as a current collector sheet 1a. The above-mentioned negative electrode mixture paste was applied to this nickel punched sheet, dried at a temperature of 80 ° C. for 1 hour, and then rolled to produce negative electrodes 1 to 3 as shown in Table 2. Then, the dry mixture adhering to the end of each negative electrode was removed, and as shown in FIG. 2, the end 1A having a width of 2 mm was exposed.

Further, a negative electrode was manufactured in the same manner as in the case of the negative electrode 3 in Table 2 using a nickel punched sheet having a non-opening portion having a width of 2 mm at the end, and this was used as a negative electrode 4.

[0050]

[Table 2]

(3) Production of Electrode Group A Each positive electrode shown in Table 1 and each negative electrode shown in Table 2 were combined as shown in Table 3, and a sheet of polyolefin nonwoven fabric having a thickness of 0.12 mm was sandwiched therebetween as a separator. A laminate was obtained.
At this time, the end 2A of the positive electrode 2 and the end 1A of the negative electrode 1 are arranged to be opposite to each other.

This sheet laminate was wound using a winding core having a diameter of 4 mm so that the negative electrode was on the outside, so that the outer diameter was 16 mm.
Four kinds of electrode groups A as shown in Table 3 having holes 4 having a diameter of 4 mm in the center were manufactured.

[0053]

[Table 3]

(4) Assembling of Battery At the time of assembling the battery, conduction paths as shown in Table 4 were designed.

[0055]

[Table 4]

The arrangement of the current collecting plate on the negative electrode among the current collecting means from the negative electrode in Table 4 was performed as follows. That is, after a nickel current collector plate 6a having a diameter of 15.5 mm is brought into contact with the end face 1B of the end portion 1A of each electrode group, 20
The spots are welded together to integrate them, and then the current collector plate 6a
The electrode group A was inserted into the battery can 5 with the electrode facing downward, and the current collecting plate 6a was brought into contact with the current collecting plate and then welded.

The arrangement of the current collecting plate on the positive electrode among the current collecting means from the positive electrode was performed as follows. That is, a nickel current collector plate 6b having a diameter of 15.5 mm is arranged on the electrode group A, and spot welding is performed at 20 locations. Further, a nickel lead 7 is welded to the current collector plate 6b, and then a sealing plate 8 is also formed. The lead 7
Was welded.

The conduction paths 2, 3, and 4 in Table 4 were formed as follows. First, in the case where a tab terminal is disposed on the positive electrode in the table, the positive electrode 1 (in the case of the conduction path 2) or the positive electrode 2 (in the case of the conduction path 4) shown in Table 1 is used as the positive electrode, and its end 2A 2mm wide, 0.2mm thick, 15mm long
(In the case of the conduction path 2) or four (in the case of the conduction path 4) of the nickel tab terminals of FIG.
Connected to. In the table, the negative electrode in contact with the inner wall of the battery can is the negative electrode 1 (in the case of the conductive path 2) or the negative electrode 2 (in the case of the conductive path 4) shown in Table 2 and the end 1A thereof. Also, an electrode group was manufactured using a material carrying a negative electrode mixture, an insulating plate was disposed on the bottom of the battery can, and the electrode group was disposed thereon.

That is, in the case of the conduction paths 1 and 4 of the batteries obtained in this case, since the current collector is not provided on the negative electrode, the conduction path is formed at the contact interface between the negative electrode and the battery can. become. Table 5 shows the batteries assembled by the above method.

[0060]

[Table 5]

(5) Battery Characteristics Each of the above batteries was discharged for 1.2 hours at an hourly rate, and after a pause of 30 minutes, discharged at a current 10 times the hourly rate. The operating voltage of the battery was measured. The results are shown in FIG. 6 as a relationship between discharge capacity / nominal capacity and operating voltage. The following is clear from FIG.

1. In each of the batteries of Examples, stable discharge was realized even at the above-described high discharge rate. However, the operating voltage of the battery of the comparative example sharply decreased. This is because in the example battery, the internal resistance of the battery is reduced by disposing the current collecting plates 6a and 6b. 2. In addition, in the same example battery as well, as the area of the positive electrode in the electrode group increases, the operating voltage does not decrease even when a large current is discharged.

[0063]

As is apparent from the above description, the nickel-hydrogen secondary battery of the present invention has a high capacity and a large current discharge which cannot be realized by a conventional nickel-hydrogen secondary battery. That is, a discharge exceeding 5 times the hourly rate is also possible. Therefore, this battery has great industrial value as a drive source for electric tools and electric vehicles.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a nickel-hydrogen secondary battery of the present invention.

FIG. 2 is a plan view showing one example of a negative electrode.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a plan view showing one example of a positive electrode.

FIG. 5 is a sectional view taken along line VV in FIG. 4;

FIG. 6 is a development view of a negative electrode to which a current collector plate is spot-welded.

FIG. 7 is a cross-sectional view showing a preferred arrangement state of a current collector plate on a negative electrode.

FIG. 8 is a graph showing the relationship between discharge capacity / nominal capacity and operating voltage.

FIG. 9 is a perspective view showing a state in which a negative electrode, a separator, and a positive electrode are overlaid.

FIG. 10 is a sectional view taken along line XX in FIG. 9;

FIG. 11 is a sectional view taken along the line XI-XI in FIG. 9;

FIG. 12 is a cross-sectional view showing a cross-sectional structure of a conventional electrode group.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Negative electrode 1a Current collector sheet 1A End of current collector sheet 1a 1b Negative electrode mixture 1B End face of end 1A 2 Positive electrode 2a Current collector sheet 2A End of current collector sheet 2a 2b Positive electrode mixture 2c Tab terminal 3 Separator 4 Hole 5 Battery can 6a, 6b Current collector 7 Lead 8 Sealing plate 9 Gasket 10 Positive electrode terminal

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[Procedure amendment]

[Submission date] April 16, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0061

[Correction method] Change

[Correction contents]

[0061] (5) for each cell of the above characteristics of the battery was charged 1.2 hours at 1-hour rate, after a 30 minute pause, discharging at 10 times the current of 1 hour rate, at that time The operating voltage of the battery was measured. The results are shown in FIG. 6 as a relationship between discharge capacity / nominal capacity and operating voltage. The following is clear from FIG.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuta Takeno 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation

Claims (7)

[Claims] A positive electrode in which a current collector sheet carries a positive electrode mixture mainly composed of a nickel compound, and a negative electrode in which a current collector sheet carries a negative electrode mixture mainly composed of a hydrogen storage alloy. An electrode group having a structure formed by alternately stacking or winding via a separator is housed in a battery can together with an electrolytic solution, and the opening of the battery can is sealed with a sealing plate having a positive electrode terminal. In the hydrogen secondary battery, at least an end portion of the current collector sheet of the negative electrode is electrically connected to the battery can through a current collector plate provided by welding therewith. Hydrogen secondary battery. 2. The nickel-hydrogen secondary battery according to claim 1, wherein the positive electrode current collector sheet is electrically connected to the sealing plate via a current collector plate provided by welding. 3. The nickel-hydrogen battery according to claim 1, wherein an area of a portion of the battery group where the positive electrode mixture of the positive electrode is supported is 30 cm ² or more per theoretical capacity (unit: Ah) of the battery. Next battery. 4. The current collector plate has a plurality of minute projections formed on a surface facing an end portion of the current collector sheet, and the current collector plate and an end of the current collector plate sheet are formed. The nickel-metal hydride secondary battery according to any one of claims 1 to 3, wherein the portion is spot-welded. 5. The nickel-hydrogen secondary battery according to claim 1, wherein the current collector sheet of the negative electrode is a punched metal. 6. The nickel-hydrogen secondary battery according to claim 5, wherein the current collector sheet of the negative electrode is a punched metal having a non-opening portion at an end, and the current collector plate is welded to the non-opening portion. battery. 7. The negative electrode has a negative electrode mixture carried on the entire surface of a punched metal, and only the end face of the punched metal facing the current collector is exposed, and the current collector is welded to the end face. The nickel-metal hydride secondary battery according to claim 5 or 6, wherein: