JP2002252025A - Nickel/hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel/hydrogen secondary battery, which is suitable for having high capacity, has high production yield by preventing poor insertion of a spiral electrode group, and secures stabilized quality by preventing a poor short circuit and shortage of an electrode mixture agent. SOLUTION: At a beginning end part of winding of the spiral electrode group 5 contained in a sealed battery can with alkali electrolytic solution, has a structure where a beginning end part of winding 4a of the negative- electrode sheet 4 is arranged inside of a folded part 3a of the separator 3 folded in 2 sheets, and the beginning end part of winding 2a of the positive-electrode sheet 2 is arranged at the winding center 5B side of the spiral electrode group 5, which is near the folded part 3a. Preferably, a collector substrate of the positive-electrode sheet 2 consists of a sintered metal fine particles sheet formed by the powder rolling method, and has two or more openings. Further, the circumference edge parts of the openings, which adjoins mutually, form shorn parts, which project to opposite directions mutually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-hydrogen secondary battery, and more particularly, to a nickel-hydrogen secondary battery having a high capacity by reducing a dead space around a winding start end of a spiral electrode group. -It relates to a hydrogen secondary battery.

[0002]

2. Description of the Related Art In recent years, with the development of cordless, high-performance, miniaturized, and lightweight electronic devices such as mobile phones and portable notebook personal computers, a secondary battery as a power source has been required. The demand for higher capacity is increasing. Hitherto, nickel-cadmium secondary batteries have been mainly used as power supplies for these electronic devices. However, with the increasing demand for higher capacity described above, nickel-cadmium batteries are compatible and have higher capacities than nickel-cadmium batteries. Has begun to be used.

[0003] This nickel-hydrogen secondary battery is generally
A positive electrode sheet in which an electrode mixture containing a powder of nickel hydroxide, which is a positive electrode active material, is supported on a current collecting substrate having a three-dimensional network structure represented by a nickel foam; A non-woven fabric made of, for example, a polyolefin fiber that has been subjected to a hydrophilic treatment between an electrode mixture containing a powder of a hydrogen storage alloy that can be released and a negative electrode sheet supported on a current collecting substrate for a negative electrode such as punched metal. A spiral electrode group provided with a separator made of and an alkaline electrolyte are sealed in a battery can.

[0004] Such a spiral electrode group is manufactured as follows. First, as shown in FIG. 5A, a core 20 composed of two semi-cylindrical members is prepared, and
The separator 23 is sandwiched between 0. Then, as shown in FIG. 5B, the winding core 20 is rotated by 180 °, and the separator 23 is wound around the winding core in an S shape, and then the winding start end 24a of the negative electrode sheet 24 is turned into an S-shaped separator. It is arranged inside one curved portion, and furthermore, the winding start end portion 22a of the positive electrode sheet 22 is
It is arranged inside the other curved portion of the S-shaped separator 23.
Next, by rotating the core 20, the positive electrode sheet 22 and the negative electrode sheet 24 are separated from each other by the separator 23.
Is wound in a state in which is interposed. And finally core 2
0 is pulled out, and the spiral electrode group 25 is manufactured.

As shown in FIG. 6, the spiral electrode group 25 formed by the above-described method has a separator 23 located in the center of the spiral electrode group 25 in an S-shape as shown in FIG. Inside the two S-shaped curved portions, a winding start end 22a of the positive electrode sheet 22 and a winding start end 24a of the negative electrode sheet are arranged, respectively. Most of the inside of such a curved portion is formed into a semi-cylindrical space indicated by a virtual line due to the core being pulled out after winding. Such a void is a dead space from the viewpoint of increasing the capacity of the battery, since the positive electrode sheet and / or the negative electrode sheet is not disposed therein.

[0006]

The nickel-hydrogen secondary battery having the above-described structure has a higher capacity than a nickel-cadmium secondary battery, but still requires a higher capacity. . To achieve this, it is necessary to increase the capacity of the positive electrode sheet. That is, it is effective to increase the amount of the electrode mixture carried on the positive electrode sheet.

However, if the positive electrode sheet is simply made thicker or the positive electrode sheet and the negative electrode sheet are lengthened for the purpose of increasing the amount of the electrode mixture carried, the spiral electrode group formed by winding them is formed. Since the winding outer diameter is large, it becomes difficult to house the spiral electrode group in a battery can having a limited inner diameter. Further, even if such a spiral electrode group can be housed in the battery can, during the housing, the negative electrode sheet located on the outermost side of the electrode group rubs against the inner wall of the battery can. As a result, the electrode mixture containing the negative electrode active material carried thereon may fall off, or in the worst case, the current collector substrate of the negative electrode sheet may crack, resulting in short-circuit failure or active material The problem of deterioration of battery characteristics due to shortage occurs.

The present invention solves all of the above problems,
With the conventional spiral electrode group, an object is to provide a nickel-hydrogen secondary battery including an electrode group having a structure in which a positive electrode sheet and a negative electrode sheet can be arranged in the above-mentioned dead space formed in the center thereof. I do.

[0009]

In order to achieve the above-mentioned object, according to the present invention, a spiral electrode is formed by winding a laminated sheet having a separator interposed between a negative electrode sheet and a positive electrode sheet. In a nickel-hydrogen secondary battery in which a group is housed in a battery can together with an alkaline electrolyte, the winding start end of the spiral electrode group is located inside the folded portion of the folded separator, and the winding start end of the negative electrode sheet is The nickel-hydrogen secondary battery has a structure in which the winding portion of the positive electrode sheet is arranged near the bent portion and near the center of the winding of the spiral electrode group. Provided,
Preferably, the positive electrode sheet is one in which an active material mainly composed of nickel oxide is supported on a positive electrode current collecting substrate,
The positive electrode current collector substrate is made of a metal powder sintered body sheet formed by a powder rolling method, and the metal powder sintered body sheet has a plurality of openings formed therein. A nickel-hydrogen secondary battery having a burr portion projecting in the opposite direction is provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a structural example of a nickel-hydrogen secondary battery of the present invention. In this battery, a spiral electrode group 5 formed by winding a laminated sheet in which a separator 3 is interposed between a positive electrode sheet 2 and a negative electrode sheet 4 in a cylindrical battery can 1 having a bottom is formed by alkaline electrolysis. Liquid (not shown)
It is stored with. At this time, the negative electrode sheet 4
By being arranged on the outermost side of the electrode group 5, it is in electrical contact with the battery can 1.

A ring-shaped insulating gasket 8 is arranged inside the upper opening of the battery can 1, and a hole 6 is formed in the center with the peripheral edge biting into the insulating gasket 8.
Is disposed. At this time,
The sealing plate 7 hermetically seals the upper opening of the battery can 1 via the gasket 8 by caulking to reduce the diameter of the upper opening inward.

A positive electrode lead 9 is connected to the lower surface of the sealing plate 7, and the other end of the positive electrode lead 9 is connected to the positive electrode sheet 2.
It is connected to the. A safety valve 11 made of rubber is disposed so as to cover the hole 6 of the sealing plate 7, and a hat-shaped positive terminal 10 is welded to the sealing plate 7 so as to cover the same. In addition, on the upper part of the battery can 1 having the above structure,
A circular holding plate 12 made of an insulating material having a central hole
The outer tube 13 is arranged so that the projection of the positive electrode terminal 10 protrudes from the central hole, and covers the peripheral portion of the holding plate 12 and the side and bottom portions of the battery can 1.

As shown in FIG. 2, the spiral electrode group used in the nickel-metal hydride secondary battery of the present invention has a winding start end portion having a bent portion 3a of a separator 3 which is folded in half.
The winding start end 4a of the negative electrode sheet 4 is arranged inside the
The winding start end 2a of the positive electrode sheet 2 is near the bent portion 3a of the separator 3 and the winding center 5 of the spiral electrode group 5
The structure is such that it is located on the B side.

In the present invention, the winding start end of the spiral electrode group 5 is defined as the winding start end 2a of the positive electrode sheet 2.
It refers to a portion including the winding start end 4a of the negative electrode sheet 4 and the location of the separator 3 covering those ends. The winding center 5B of the spiral electrode group 5 refers to the center point of the spiral. Since the winding start end of the spiral electrode group 5 has such a structure, the dead space, which has conventionally been wound by using a core and then inevitably exists to pull out the core after winding, is used. Is not formed around the winding start end of the spiral electrode group 5. Therefore, the conventional dead space can be effectively used. For example, even in the case where the capacity of the electrode mixture is increased and the capacity of the battery is increased, the positive electrode sheet 2 or the negative electrode sheet 4 supporting the active material is also arranged in the dead space. Therefore, a desired capacity can be secured without increasing the outer diameter of the entire electrode group 5. Therefore, even when the high-capacity spiral electrode group 5 is housed in the battery can 1, the outer diameter of the spiral electrode group 5 is kept constant, so that the occurrence of poor insertion is prevented, and the outermost negative electrode sheet 4 is located. Is prevented from rubbing against the inner wall of the battery can 1, the current collecting substrate of the negative electrode sheet 4 is not broken, and the negative electrode active material carried on the negative electrode sheet 4 does not fall off. It is possible to suppress a decrease in battery characteristics due to shortage.

The above spiral electrode group can be manufactured, for example, by the following method. First, as shown in FIG. 3A, the positive electrode sheet 2, the negative electrode sheet 4, and the separator 3 are disposed inside the winding start end 2 a of the positive electrode sheet 2 and the folded portion 3 a of the folded separator 3. Laminated sheet 5A is formed by arranging so that winding start end 4a of negative electrode sheet 4 is aligned. And this laminated sheet 5A
Is folded once to the positive electrode sheet 2 side at a position about 1 to 3 mm behind the winding start end 2 a of the positive electrode sheet, and once again, the same as described above at a position about 1 to 3 mm behind the bent point By bending in the direction, a key portion is formed at the end of the laminated sheet 5A. Thereafter, the key portion is sandwiched between a pair of vertically movable rollers 14A and 14B (FIG. 3B), and the pair of rollers 14A and
At 4B, the tail of the laminated sheet 5A is sequentially wound around the key by rotating the key as shown by the arrow in FIG. 3B while pressing the key (FIG. 3C). Then, the spirally wound electrode group 5 as shown in FIG. 2 is manufactured by winding the positive electrode sheet 2, the negative electrode sheet 4, and the end of the separator 3.

In this embodiment, the end of the laminated sheet 5A is bent to form a key-shaped portion, but the dimensions are substantially the same as the key-shaped portion, and the laminated sheet 5A can be wound there. The shape may be any shape, and may be a semi-cylindrical portion or a cylindrical portion. Nickel with the above structure
The positive electrode sheet 2 incorporated in the hydrogen secondary battery has a structure in which an electrode mixture containing a positive electrode active material is supported on a current collecting substrate. In this case, the positive electrode sheet 2 includes, for example, a positive electrode active material,
A paste-like electrode mixture is prepared by mixing and kneading a binder and, if necessary, a conductive agent and water, and after filling this mixture into a positive electrode current collector substrate, a drying process is performed. It is manufactured by rolling.

As the positive electrode active material, a powdery metal oxide, for example, a material mainly containing nickel hydroxide can be used. Examples of the conductive agent include metal cobalt;
Cobalt compounds such as cobalt hydroxide, cobalt monoxide and dicobalt trioxide can be mentioned. As the positive electrode binder, for example, polytetrafluoroethylene (P
Examples include fluorocarbon resins such as TFE), carboxymethylcellulose (CMC), methylcellulose, for example, polyacrylates such as sodium polyacrylate, hydroxymethylcellulose, and polyvinyl alcohol.

Examples of the current collecting substrate include a nickel plate, a stainless steel plate, and a net-like, sponge-like, fibrous, or felt-like conductive substrate made of a nickel-plated alkali-resistant resin material. Among these substrates, as shown in FIG. 4, it is composed of a metal powder sintered body sheet 2A formed by a powder rolling method, and a plurality of openings 2B are perforated in the metal powder sintered body sheet and adjacent to each other. The peripheral portion of the opening 2B is a burr portion 2 projecting in the opposite direction.
Those having C are preferred. By using such a substrate, even when the end portion of the positive electrode sheet is bent at the time of producing a spiral electrode group to be described later, the current collector substrate is prevented from cracking at that end, and a short circuit failure in the assembled battery is prevented. Can be prevented.

The negative electrode sheet 4 has a structure in which an electrode mixture containing a negative electrode active material is supported on a current collecting substrate. In this case, the negative electrode sheet 4 serves as, for example, a host for hydrogen as a negative electrode active material.
A paste-like electrode mixture is prepared by mixing and kneading a matrix, a conductive material for a negative electrode, a binder, and water, and then filling the mixture into a current collecting substrate for a negative electrode and performing a drying process.
It is manufactured by molding.

As the host matrix of hydrogen, for example, a hydrogen storage alloy can be used. The hydrogen storage alloy is not particularly limited, and may be any alloy capable of storing hydrogen electrochemically generated in an electrolyte and releasing the stored hydrogen at the time of discharge. Examples of such a hydrogen storage alloy include LaNi ₅ , MmNi
₅ (Mm is misch metal), LmNi ₅ (Lm is La-rich misch metal), and a part of Ni of these alloys is converted to A1, Mn, Co, Ti, Cu, Zn, Zr, Cr, B
Or a multi-element system substituted with an element such as TiN
i-type and TiFe-type ones can be mentioned. In particular,
The following formula: LmNiwCoxMnyAlz (w, x, y, z
Represents an atomic ratio satisfying 5.00 ≦ w + x + y + z ≦ 5.50. The hydrogen storage alloy having the composition represented by the formula (1) is preferable in that the pulverization accompanying the progress of the charge / discharge cycle is suppressed and the life of the charge / discharge cycle can be improved.

Examples of the conductive material for the negative electrode include carbon black and graphite. Examples of the binder for the negative electrode include polyacrylates such as sodium polyacrylate and potassium polyacrylate, fluorine-based resins such as polytetrafluoroethylene (PTFE), and carboxymethyl cellulose (CMC). .

Examples of the current collecting substrate for the negative electrode include a two-dimensional substrate such as a punched metal sheet, an expanded metal sheet, a perforated rigid plate, and a nickel net, and a tertiary material such as a felt-like metal porous body and a sponge-like metal porous body. The original substrate can be mentioned. The separator 3 can be formed from, for example, a nonwoven fabric made of a polyolefin fiber or a nylon fiber, a woven fabric made of the same, or a composite sheet in which the nonwoven fabric and the woven fabric are combined. When the separator 3 is made of a polyolefin fiber, it is preferable to perform a hydrophilic treatment. As the hydrophilic treatment, for example, application of a surfactant, graft copolymerization of a vinyl monomer having a hydrophilic group, or the like can be employed.

In particular, the separator 3 is desirably formed from a sheet-like material containing a polyolefin-based synthetic resin, which is obtained by graft-copolymerizing a vinyl monomer having a carboxylalkyl group. As the polyolefin-based synthetic resin, a fiber composed of one kind of polyolefin; a conjugate fiber having a core-sheath structure in which a certain polyolefin fiber is coated with a polyolefin fiber having a different surface; a division in which different kinds of polyolefin fibers are joined in a circular shape And the like. Examples of these polyolefins include polyethylene and polypropylene.

Examples of the sheet-like material containing polyolefin-based synthetic resin fibers include a nonwoven fabric made of the above-mentioned polyolefin-based synthetic resin, a woven fabric made of the same fibers, or a composite sheet in which these nonwoven fabrics and woven fabrics are composited. it can. The nonwoven fabric is produced by, for example, a dry method, a wet method, a spun bond method, a melt flow method, or the like.

The average fiber diameter of the polyolefin synthetic resin fibers is preferably in the range of 1 to 20 μm from the viewpoint of mechanical strength and prevention of short circuit between the positive electrode sheet and the negative electrode sheet. A more preferable range of the average fiber diameter is 3 to 1
5 μm. Examples of the vinyl monomer having a carboxyl group include acrylic acid, methacrylic acid, esters of acrylic acid and methacrylic acid, and the like. Acrylic acid is preferred among the vinyl monomers.

Examples of the alkaline electrolyte include a mixture of potassium hydroxide, sodium hydroxide and lithium hydroxide, a mixture of potassium hydroxide and lithium hydroxide, and a mixture of sodium hydroxide and lithium hydroxide. Can be. In the nickel-hydrogen secondary battery of the present invention, after the above-mentioned spiral electrode group 5 is housed in the battery can 1, an alkaline electrolyte is injected into the battery can to connect the spiral electrode group 5 to an external terminal. After that, the opening of the battery can 1 is sealed with a sealing body 7 or the like to manufacture the battery can.

[0027]

Embodiment (Embodiment 1) Preparation of Positive Electrode A dispersion of 0.3 parts by mass of carboxymethyl cellulose and a dispersion of polytetrafluoroethylene (specific gravity: 1.5, solid content: 60 parts by mass) was mixed with 100 parts by mass of a mixed powder composed of 90% by mass of nickel hydroxide and 10% by mass of cobalt monoxide.
% By mass) and 45 parts by mass of distilled water were added and kneaded to prepare a paste-like electrode mixture. This mixture is a substrate made of a metal powder sintered body sheet formed by a powder rolling method, in which a plurality of openings are formed by pressing, and the peripheral portions of the openings adjacent to each other are in opposite directions. After filling into the burr portion that protrudes from the substrate, a drying treatment was performed, and a roller was pressed to produce a paste-type nickel positive electrode sheet.

2. Preparation of Negative Electrode A hydrogen storage alloy having a composition of LmNi _4.0 Co _0.4 Mn _0.3 Al _0.3 was mechanically pulverized, and this was made into a powder under 200 mesh (Tyler sieve). For 100 parts by mass of the alloy powder, 0.5 part by mass of sodium polyacrylate, 0.125 part by mass of carboxymethylcellulose, and a dispersion of polytetrafluoroethylene (specific gravity 1.5, solid content 60 mass%) were converted to solid content. , 2.5 parts by mass of carbon powder, 1.0 part by mass of carbon powder and 50 parts by mass of water were added and kneaded to prepare a paste-like electrode mixture. Thereafter, the mixture was applied to a punched metal, subjected to a drying treatment, and subjected to pressure molding to produce a paste-type hydrogen storage alloy negative electrode sheet.

3. 1. Preparation of Electrode Group First, a separator 3 prepared by graft bonding acrylic acid monomer to a nonwoven fabric having a basis weight of 55 g / m ² and a thickness of 0.20 mm, which was prepared from a polypropylene fiber having a fiber diameter of 10 μm by a spun bond method. Was prepared. Then, the negative electrode sheet 4 is provided at a predetermined position of the separator 3 to be the bent portion 3a.
The negative electrode sheet 4 was disposed on the upper surface of the separator 3 such that the winding start end 4a of the negative electrode was positioned. Then, the negative electrode sheet 4
By bending the portion of the separator 3 where no
The sheet was folded to form a bent portion 3a. At this time, the length of the portion of the separator 3 described above was shorter than the length of the portion of the separator 3 located on the lower side by a length corresponding to substantially the outermost circumference of the electrode group 5 to be formed.

Then, the winding start end 2a of the positive electrode sheet 2
The negative electrode sheet 4 covered by the separator 3 is disposed on the upper surface of the positive electrode sheet 2 so that the winding start end 4a of the negative electrode sheet 4 located inside the bent portion 3a of the separator 3 is aligned. 5A was formed (FIG. 3a). Next, the laminated sheet 5A is folded at a position 3 mm from the winding start end 2a of the positive electrode sheet 2 using a bending jig.
It was folded to the side, and again once again in the same direction as described above at a position 3 mm from the bent point to form a key-like portion. Then, as shown in FIG. 3B, the key-shaped portion of the laminated sheet 5A was disposed so as to be sandwiched between a pair of rollers 14A and 14B each having a diameter of about 10 mm and capable of moving up and down. Thereafter, these rollers 14A, 14A
B is rotated at a speed of about 300 revolutions / minute in the direction shown in FIG. 3B while pressing the laminated sheet 15A at 1 to 500 N / m ² , and the tail part of the laminated sheet is sequentially wound around the key portion. (FIG. 3c). At this time, the interval between these rollers widened as the laminated sheet 5A was wound. Thus, the spiral electrode group 5 was produced by winding up to the end of the laminated sheet 5A. The outermost side of the electrode group 5 is the negative electrode sheet 4.

4. Battery assembly The electrode group was housed in a cylindrical metal can with a bottom. Then, an alkaline electrolyte composed of 7N potassium hydroxide and 1N lithium hydroxide was injected into the battery can, and each member such as a sealing member was used in a 4 / 3A size having a rated capacity of 40%.
A 00 mAh cylindrical nickel-metal hydride secondary battery was assembled.

Example 2 A cylindrical nickel-metal hydride secondary battery was assembled in the same manner as in Example 1 except that a nickel-plated fiber substrate was used for the positive electrode sheet. (Comparative Example 1) A cylindrical nickel-hydrogen secondary battery was assembled in the same manner as in Example 1 except that the electrode group was prepared as follows.

First, as shown in FIGS. 5A and 5B, the separator is wound 180 ° in a state where the separator is sandwiched between cores having a diameter of about 3.5 mm to form an S-shaped separator.
The winding start end of the positive electrode sheet and the winding start end of the negative electrode sheet were respectively arranged inside the two curved portions having the letter shape. Thereafter, by rotating the winding core, the positive electrode sheet and the negative electrode sheet were wound with the separator interposed therebetween, thereby producing a spiral electrode group. The outermost side of the electrode group was made to be a negative electrode sheet, and the core was pulled out after the preparation of the electrode group.

(Comparative Example 2) A cylindrical nickel alloy was produced in the same manner as in Example 2 except that the electrode group was produced in the same manner as in Comparative Example 1.
A hydrogen secondary battery was assembled. In the manufacturing processes of Examples 1 and 2 and Comparative Examples 1 and 2 described above, the average value (out of 1000) of the spiral outer diameters of the formed spiral electrode groups, and each electrode group was made of metal having a bottomed cylindrical shape The insertion failure rate (out of 1,000) of the electrode group that occurred when the electrode group was housed in the battery can was determined. The results are shown in Table 1 together with the method of winding the spiral electrode group and the current collecting substrate for the positive electrode used.

Further, after each electrode group is housed in a bottomed cylindrical metal battery can, if the resistance between the electrodes is 10 MΩ or less when a voltage of 500 V is applied by a leak tester, a short-circuit failure occurs. A short-circuit inspection was performed and the short-circuit defect rate (10
(Out of 00 pieces). The results are also shown in Table 1.

[0036]

[Table 1]

As can be seen from Table 1, the winding outer diameter of the spiral electrode group is smaller in Examples 1 and 2 than in Comparative Examples 1 and 2, and poor insertion of the electrode group is obtained in Examples 1 and 2. No. 2 did not occur. From this, it can be seen that the structure of the winding start end of the spiral electrode group of the present invention is effective for reducing the winding outer diameter, thereby preventing poor insertion.

As for the short-circuit defect rate, Example 1 and Comparative Example 1 using the same positive electrode current collecting substrate were compared with Example 2 using the same positive electrode current collector substrate.
When the comparison was made between Comparative Example 2 and Comparative Example 2, the Example was lower than the Comparative Example. This is because the spiral outer diameter of the spiral electrode group can be reduced by the structure of the spiral start end portion of the spiral electrode group of the present invention. This is presumably because the negative electrode sheet rubbed against the battery can only slightly when it was housed inside, preventing the negative electrode mixture from falling off and the negative electrode current collecting substrate from cracking.

Further, when comparing Example 1 and Example 2 using different current collecting substrates for the positive electrode, Example 1 using the positive electrode sheet having the burr portion has a shorter short-circuit failure rate than Example 2. Was low. This is composed of a metal powder sintered body sheet formed by a powder rolling method, a plurality of openings are perforated in the metal powder sintered body sheet, and peripheral portions of openings adjacent to each other project in opposite directions. It is considered that the use of the positive electrode current collecting substrate serving as the burr portion for the positive electrode sheet did not cause the positive electrode current collecting substrate to break even when the positive electrode sheet was bent when forming the spiral electrode group.

[0040]

As is apparent from the above description, according to the nickel-metal hydride secondary battery of the present invention, it is possible to use a thick positive electrode sheet inside, thereby achieving high capacity. it can. Also in this case, the production yield is good and stable quality can be ensured.

Further, according to the nickel-metal hydride battery of the present invention, it is composed of a metal powder sintered body sheet formed by a powder rolling method, and a plurality of openings are formed in the metal powder sintered body sheet so as to be adjacent to each other. A more stable quality can be ensured by using a positive electrode current collector substrate in which the peripheral portion of the opening is a burr portion protruding in the opposite direction to the positive electrode sheet.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an example of a nickel-hydrogen secondary battery according to the present invention.

FIG. 2 is a top view showing an example of a spiral electrode group according to the present invention.

FIG. 3 is a process chart showing an example of a method for forming a spiral electrode group according to the present invention.

FIG. 4 is a perspective view showing an example of a positive electrode current collecting substrate according to the present invention.

FIG. 5 is a process chart showing a conventional method for forming a spiral electrode group.

FIG. 6 is a top view showing a conventional spiral electrode group.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery can 2 Positive electrode sheet 2a End of winding start of positive electrode sheet 2A Sintered metal powder sheet 2B Opening 2C Burr 3 Separator 3a Bend of separator 4 Negative sheet 4a End of winding start of negative electrode sheet 5 Spiral electrode group 5A Laminated sheet 5B Winding center 6 Hole 7 Sealing body 8 Insulating gasket 9 Positive electrode lead 10 Positive electrode terminal 11 Safety valve 12 Holding plate 13 Outer tube 14A, 14B Roller

Claims (2)

[Claims] 1. A nickel-hydrogen secondary battery comprising a spirally wound electrode group formed by winding a laminated sheet having a separator interposed between a negative electrode sheet and a positive electrode sheet and contained in a battery can together with an alkaline electrolyte. In the battery, the winding start end of the spiral electrode group is such that the winding start end of the negative electrode sheet is disposed inside a folded portion of the separator that is folded in half, and the spiral electrode near the bent portion is disposed. A nickel-hydrogen secondary battery having a structure in which a winding start end of the positive electrode sheet is arranged on a winding center side of a group. 2. The positive electrode sheet according to claim 1, wherein the current collector substrate for a positive electrode carries an active material containing nickel oxide as a main component, and the current collector substrate for a positive electrode is formed of a metal formed by a powder rolling method. A plurality of openings are formed in the metal powder sintered body sheet, and peripheral edges of the openings adjacent to each other are burr parts projecting in opposite directions. Item 6. The nickel-metal hydride secondary battery according to Item 1.