JP2002175833A - Alkali secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali secondary battery for large-current electrical discharge, using a collector substrate of superior holding capability with respect to an electrode composite. SOLUTION: In the alkali secondary battery, the collector substrate A made to hold the electrode composite, which consists of a porosity metal sheet 1, produced by powder rolling method and two or more openings 2 that have flash parts 3 are formed in its circumference edge part, is made into the cathode positive pole. Moreover, the area of holding the electrode composite in the above collector substrate 1 is 25 cm2 or more per theoretical capacity (Ah) of the above battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkaline secondary battery capable of discharging a large amount of current at a high capacity.
Since the volume occupied by the current collecting substrate used for the positive electrode in the battery is small, a large amount of the positive electrode mixture can be accommodated in the battery,
Since the current collecting substrate has excellent ability to carry a positive electrode mixture, the present invention relates to an alkaline secondary battery having a large capacity and capable of discharging a large current.

[0002]

2. Description of the Related Art Alkaline secondary batteries such as nickel-cadmium secondary batteries and nickel-hydrogen secondary batteries generally use a positive electrode carrying a nickel compound powder such as nickel hydroxide and a hydrogen storage alloy powder. An electrode group is formed by, for example, spirally winding a laminate formed by interposing an electrically insulating and liquid-retaining separator between the negative electrode to be supported and a separator, which is a battery, The battery can is housed in a can together with a predetermined alkaline electrolyte, and then the battery can is sealed.

As the above-mentioned positive electrode (nickel electrode), there are conventionally a sintered type and a paste type. Among them, the paste-type nickel electrode is generally manufactured as follows. First, nickel hydroxide particles as an active material, for example, a conductive material such as cobalt monoxide, which forms a conductive matrix in the process of initial charging after battery assembly and expresses conductivity, such as carboxymethylcellulose A binder is kneaded with water to prepare a paste mixture having a predetermined composition (hereinafter, referred to as an electrode mixture).

[0004] Then, the electrode mixture is directly applied or filled on the current collecting substrate, and then dried and further roll-rolled, for example, to adjust the thickness, and at the same time, to densify the dried electrode mixture and to form the current collecting substrate. To form a nickel electrode. In such a configuration, a porous foamed metal porous sheet in which communication holes are three-dimensionally formed therein, specifically, a foamed Ni porous sheet is generally used as the current collecting substrate. I have.

[0005] Since the electrode mixture is filled not only in the surface but also in the internal communication holes of the current collecting substrate made of such a foamed metal porous sheet, high-density packing becomes possible.
This is extremely advantageous for increasing the capacity of the battery. In addition, at the same time, the electrode mixture filled in the communication holes distributed intricately inside is securely secured in the communication holes, so that the electrode mixture is collected even when the electrodes are wound, for example. There is also an advantage that falling off from the substrate is prevented.

However, on the other hand, the current collecting substrate has the following problems. First, the first problem is that it is expensive. This means that when manufacturing a large battery capable of discharging a large amount of current, it is necessary to carry multiple electrode mixes on the current collecting substrate. Since the use amount of the body sheet inevitably increases, the manufacturing cost increases, and there is a problem in responding to recent low price competition.

When a large amount of the electrode mixture is carried on the current collecting substrate, the thickness of the current collecting substrate is inevitably increased. Therefore, when an electrode group having a predetermined outer diameter that matches the inner diameter of the battery can is manufactured, the volume occupied by the current collecting substrate in the volume of the electrode group increases, and as a result, the relative ratio of the electrode mixture becomes Since the battery capacity decreases, it becomes difficult to increase the capacity of the battery.

Second, the foamed Ni porous sheet is subjected to flexibility. Therefore, as described above, this foamed Ni
A nickel electrode manufactured using a porous sheet as a current collecting substrate,
For example, when laminating a hydrogen storage alloy negative electrode via a separator and then spirally winding to form an electrode group, the foamed Ni porous body sheet breaks and its broken end breaks through the separator and contacts the negative electrode, This may cause a short circuit.

As described above, in recent large batteries for large current discharge, the above foamed N
Instead of the i-porous sheet, a so-called coated electrode in which an inexpensive and thin two-dimensional sheet such as Ni punched metal or Ni expanded metal is used and an electrode mixture is applied to the surface thereof has been studied. ing. This coated electrode has 2
It can be manufactured by simply applying the electrode mixture to the surface of the three-dimensional sheet at a predetermined thickness, and then drying and rolling, so that the manufacturing cost can be reduced as compared with the case of using the porous metal sheet described above. is there.

However, the coated electrode using the two-dimensional sheet as a current collecting substrate also has the following problems. First, since the current collecting substrate is a two-dimensional sheet, the adhesion between the electrode mixture and the current collecting substrate is weak, and the electrode mixture is easily peeled off from the surface of the current collecting substrate. As a result, a decrease in the capacity of the electrode and an increase in the electric resistance occur, and as a result, the discharge capacity and the discharge voltage of the assembled battery are reduced.

Second, when the active material in the electrode mixture is nickel hydroxide particles, the nickel hydroxide particles are non-conductive, so that the electrode mixture layer formed on the surface of the current collecting substrate is not electrically conductive. There is a problem that the electron conductivity between the nickel hydroxide particles existing at a position distant from the current collecting substrate in the thickness direction and the current collecting substrate is reduced. Therefore, a reduction in the utilization rate of the active material, a reduction in the current collection efficiency, an increase in the electrical resistance as an electrode, and a reduction in a discharge voltage and a discharge capacity are caused.

This problem can be solved to some extent by increasing the ratio of the conductive material in the electrode mixture. However, conventionally used conductive materials such as cobalt oxide and cobalt hydroxide are themselves non-conductive materials like nickel hydroxide particles, and during the initial charging process after battery assembly. Since these are materials forming a conductive matrix, the prerequisite for using them as a conductive material is that the electrode mixture does not fall off the current collecting substrate.

Further, the current collecting substrate formed of a two-dimensional sheet is higher in strength than the current collecting substrate of a porous metal foam sheet, so that it is possible to reduce the basis weight of the substrate with respect to the required strength as an electrode. In a secondary battery, since the current collecting substrate is a material that does not contribute to the battery capacity, if the basis weight of the substrate can be reduced in this way, voids in the battery increase, the amount of active material increases, and the amount of electrolyte solution increases. Since the amount can be increased, it is extremely effective for increasing the capacity of the battery.

In view of the above points, the current collecting substrate formed of a two-dimensional sheet has an advantage as a current collecting substrate of a battery for large current discharge as compared with a current collecting substrate of a porous metal foam sheet. Nevertheless, there are difficulties in terms of the ability to carry the electrode mixture and a reduction in the utilization of the active material.

[0015]

SUMMARY OF THE INVENTION The present invention provides a positive electrode mixture by using a current collecting substrate which solves the above-mentioned problems in an alkaline secondary battery using a two-dimensional sheet as a positive electrode current collecting substrate. It is an object of the present invention to provide an alkaline secondary battery having improved cycle life characteristics and high current discharge characteristics as a result.

[0016]

In order to achieve the above-mentioned object, in the present invention, a positive electrode, a negative electrode facing the positive electrode via a separator, and an alkaline electrolyte are contained in a container. The positive electrode is manufactured by a powder rolling method, and the electrode mixture is supported on a current collecting substrate made of a porous metal sheet having a plurality of openings having burrs at a peripheral portion. And
The area where the current collecting substrate carries the electrode mixture (hereinafter simply referred to as the carrying area) is 25% of the theoretical capacity (Ah) of the battery.
alkaline secondary battery, characterized by cm ^{2 or} more is provided.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an example of the structure of an alkaline secondary battery of the present invention is shown in FIG. In the figure, a metal battery can 15, which is also a negative electrode terminal, contains an electrode group 12 described later and a predetermined alkaline electrolyte (not shown).
The electrode group 12 includes, for example, a positive electrode 1 formed by supporting an electrode mixture containing, for example, nickel hydroxide powder as a main component on a current collecting substrate described later.
2a and an electrode mixture mainly composed of a hydrogen storage alloy powder and a separator 12c interposed between a negative electrode 12b supported on a current collecting substrate, which will be described later, and spirally wound. .

In the case of this battery, the end 13a of the negative electrode 12b of the electrode group 12 is attached, for example, by welding, to the negative electrode current collector 14a, and the negative electrode current collector 14a is further connected via the lead 14b. It is electrically connected to the battery can 15. The end 13b of the positive electrode 12b of the electrode group 12 is attached to the current collector 16a on the positive electrode side, for example, by welding, and the positive electrode current collector 16a is electrically connected to a sealing plate 17 described later via a lead 16b. It is connected to the.

The sealing plate 17 is disposed at the upper opening of the battery can 15 via a gasket 18 made of an electrically insulating material.
An airtight structure is formed at that location by, for example, crimping. A small hole 17a is formed at the center of the sealing plate 17, and a valve body 19 having rubber elasticity is arranged so as to close the small hole 17a. 20 is arranged as a positive electrode terminal, and the space between the positive electrode cap 20 and the sealing plate 17 is, for example, welded.

In the case of this battery, gas is generated inside the battery when it is driven by a large current discharge or when overcharged,
In some cases, the internal pressure of the battery may be increased. In this case, the gas pressure opens the valve body 19 and the generated gas is discharged out of the battery can 15, thereby ensuring the safety of the battery. In the battery of the present invention, the positive electrode 1
The current collecting substrate used in 2a is as described below, and the area of the current collecting substrate carrying the electrode mixture is 25 cm ² or more per theoretical capacity (Ah) of the battery. And Further, it is preferable that the current collecting substrate used for the negative electrode 12b is a punched metal sheet whose end is a non-opening portion, and the non-opening portion is welded to the negative electrode-side current collecting plate 13a. .

Next, the positive electrode current collector substrate, which is a main part of the alkaline secondary battery of the present invention, will be described in detail. FIG.
FIG. 3 is a plan view showing an example A of the current collector substrate of the present invention, FIG. 3 is a cross-sectional view along the line III-III in FIG. 2, and FIG. 4 is an enlarged view of a region B surrounded by a circle in FIG. is there. First, in FIG.
The current collecting substrate A is entirely composed of a metal porous sheet 1 described later, and a plurality of openings 2 are formed in the surface thereof.

Here, the metal porous sheet 1 as a constituent material of the current collecting substrate A is manufactured by a so-called powder rolling method. Specifically, for example, a metal powder having a predetermined particle size is continuously sprayed on a conveying sheet made of, for example, stainless steel, and the metal powder is pressed by the rolling rolls by passing the metal powder between a pair of rolling rolls. Roll. At this time, by adjusting the pressure of the rolling roll to an appropriate value, the metal powder becomes a green compact sheet in a state of point contact or line contact with each other.

Thereafter, the green compact sheet is introduced and heated in a baking furnace in an inert gas atmosphere adjusted to a temperature at which melting and sintering of the metal powder do not occur. To As a result of this heat treatment, as shown in the enlarged view of FIG.
The metal powders 1a constituting the green compact sheet are partially thermally fused at the contact portions 1b without melting or sintering as a whole. Therefore, holes (communication holes) 1c that are three-dimensionally distributed in a complicated shape are formed between the metal powders 1a.

Finally, the metal porous sheet 1 which is a material of the current collecting substrate A of the present invention is obtained by taking out from the baking furnace and peeling off from the conveying sheet. In this series of manufacturing steps, the properties such as the porosity and mechanical strength (for example, tensile strength) of the porous metal sheet 1 are determined by appropriately selecting the above-described pressing force of the rolling roll, the temperature during firing, and the like. Can be changed.

Further, the metal porous sheet 1 preferably has a porosity of 5 to 15%. If the porosity is less than 5%, the material is too dense, so that cracks frequently occur during the punching process described below, which tends to be defective. If the porosity is more than 15%, the strength characteristics are not sufficient, and damage during handling is caused. Is likely to occur frequently.

The opening 2 formed in the plane of the metal porous sheet 1 has a polygonal shape (square in the figure) in plan view. Each of the sides 2a of the opening 2 is formed with four triangular burrs 3 having the side 2a as a base and protruding in the same direction as a punching direction by a mold described later. The burr portions 3 are formed so as to protrude from both the front surface 1A and the back surface 1B alternately at the opening position.
Each of the burrs 3 warps and expands in the direction of the surface 1A or 1B of the porous metal sheet 1 (FIG. 3).

The warpage of the burr portion 3 has the following function and effect. That is, when the electrode mixture 4 is applied to both surfaces of the metal porous sheet 1 as shown by the imaginary lines in FIG. 3, the burr portions 3 warped to the surface 1A side and the surface 1B side are formed. Exerts an anchor effect on as a result,
The carrying capacity of the current collecting substrate A on the electrode mixture 4 is improved.

The burrs 3 are disposed in the electrode mixture in such a manner as to bite in the thickness direction of the applied electrode mixture. The function of ensuring the electron conductivity of the active material existing far from 1B, that is, the function as a conductive path is also exhibited. Such burrs 3 can be formed as follows. That is, as shown in FIG. 5, the metal porous sheet 1 is subjected to a punching process in a direction indicated by an arrow by a punching die or a punch 5 having a quadrangular pyramid-shaped tip 5a. The portion of the metal porous sheet 1 punched at the tip 5a is, as shown in FIG.
The burr portion 3 is torn into four triangular shapes corresponding to the shape of a and protrudes in a direction substantially perpendicular to the surface 1A (surface 1B) or slightly warped toward the surface 1A (surface 1B). . Then, the whole is passed, for example, between a pair of rolling rolls and pressurized. These burrs 3 are pressed toward the surface 1A (surface 1B), and as a result, the burrs 3 are warped toward the surface 1A (surface 1B) as shown in FIG.

At this time, the degree of the warpage in the burr section 3 can be made by adjusting the skin path between the rolling rolls, that is, by adjusting the pressing force of the rolling rolls. This is because the smaller the skin pass, the smaller the warp angle, and the larger the skin pass, the larger the warp angle. FIG. 6 shows another example of the burr section 3 in the present invention. In the case of this burr part 3,
At the side 2a of the opening 2, it protrudes in a substantially vertical direction, but only the tip 3a is warped toward the surface 1A. Although not shown, the same applies to the surface 1B. Such burrs 3 also
The tip 3a exerts an anchor effect on the electrode mixture applied.

The burr portion 3 shown in FIG. 6 is formed by adjusting the skin pass of the rolling roll when the metal porous sheet 1 is relatively thick and the strength of the base of the burr portion 3 is relatively strong. Can be. The current collecting substrate A shown in FIG. 2 is a case where the burr portions 3 of the openings 2 alternately protrude from the front surface 1A and the rear surface 1B of the porous metal sheet 1, but the current collecting substrate A used in the present invention. Is not limited to this embodiment.
May have a structure in which the burr portions 3 protrude in the same direction.

The opening 2 is not limited to a square as shown in FIG. 2, but may be any polygon such as a triangle or a pentagon or a circle. For example, in the case of a triangle,
Three burrs are formed, and they exert an anchoring effect on the coated electrode mixture. An electrode mixture is applied to the current collecting substrate, dried, and then roll-rolled to adjust the thickness, whereby the positive electrode 12a used in the present invention is manufactured.

In this case, the electrode mixture is applied so that the area where the current collecting substrate A carries the electrode mixture is 25 cm ² or more with respect to the theoretical capacity (Ah) of the target battery. It is necessary to The carrying area mentioned above is 25 cm ²
If it is smaller than / Ah, sufficient discharge characteristics cannot be exhibited, and the utilization rate of the active material cannot be sufficiently increased.

When the electrode to be manufactured is a nickel electrode using nickel hydroxide particles as an active material, the active material may be nickel hydroxide particles such as those proposed in Japanese Patent No. 3040760. It is preferable to use composite nickel hydroxide particles in which the surfaces of conductive nickel hydroxide particles are coated with a higher oxide of cobalt having conductivity. Alternatively, nickel hydroxide particles whose surfaces are coated with a cobalt compound such as cobalt hydroxide or cobalt monoxide may be used. Further, both may be used in a mixed state. When these active materials are used, a state in which the electron conductivity is secured even if the active material exists far away from the surface of the current collecting substrate is formed. This is because the utilization rate is improved.

On the other hand, as a negative electrode to be combined with this positive electrode, for example, as shown in FIG.
A sheet in which a negative electrode mixture 11 mainly containing a hydrogen storage alloy powder is supported on a sheet 10 is used. In particular, in the case of an alkaline secondary battery for large current discharge, it is preferable to form a non-coating portion (non-opening portion) 10a that does not support the negative electrode mixture 11 on at least one end of the punched Ni sheet 10 constituting the negative electrode. This is because the current collection efficiency during large current discharge can be increased.

Example (1) Production of Current Collector Substrate A Ni porous sheet was produced as follows by a powder rolling method using an apparatus schematically shown in FIG. First, a traveling speed of 1 m is drawn by drawing an endless track between the rolls 20a and 20b.
Hopper 22 on a belt conveyor 21 rotating at
After continuously supplying Ni powder 23 having an average particle diameter of 2 to 3 μm contained therein and conveying it downstream, and forming a powder layer having a thickness of 300 μm with a doctor blade 24 arranged downstream, the roll diameter is the same. A pair of rolling rolls 25, 25
, And was rolled from above and below with a pressing force of about 2940 N / mm to form a dust layer.

Then, the Ni porous sheet 1 was introduced into a baking furnace 26 in an Ar atmosphere and heated at a temperature of 950 ° C. for 10 minutes to form a Ni porous sheet 1, which was peeled off from the belt conveyor 21 and continuously wound up. The thickness of the obtained Ni porous sheet 1 is 30 μm on average, and its porosity is 7 μm on average.
%, And the basis weight was 300 g / m ² .

Next, the Ni porous sheet 1 was subjected to a punching process to form a square opening 2 having a side 2a of 400 μm in a grid at a ratio of 204 per unit area (1 cm ² ) (total of both sides). It was formed in a shape. at this point,
When each burr portion 3 was visually observed, it was found that the burr portion 3 generally protruded in a direction substantially perpendicular to the surfaces 1A and 1B (slightly warped toward the surface 1A or 1B).

Next, the punched sheet was passed between a pair of rolling rolls to warp the entire burr portion 3 toward the surface 1A or 1B as shown in FIG. In addition,
For comparison, a foamed Ni sheet (1.3 mm thick) having communicating holes with an average pore diameter of 500 μm, a porosity of 96%, and a basis weight of 420 g / m ² was prepared.

(2) Production of Nickel Positive Electrode First, particles containing nickel hydroxide as a main component and particles of a cobalt compound were stirred and mixed while being subjected to a heat treatment in a closed mixer in the presence of oxygen and an aqueous alkali solution. Thus, composite nickel hydroxide particles having an average particle size of about 12 μm were prepared. In the composite nickel hydroxide particles, the surface of the nickel hydroxide particles is coated with a higher oxide of cobalt having conductivity.

With respect to 100 parts by mass of the composite nickel hydroxide particles, 0.1 part by mass of carboxymethyl cellulose,
0.1 part by mass of sodium polyacrylate, 1 part by mass of polytetrafluoroethylene, and 30 parts by mass of water were mixed and kneaded to form a paste. Next, the electrode mixture is applied to the current collecting substrate obtained above, and dried at a temperature of 160 ° C. for 10 minutes, and then roll-rolled at a pressure of 4900 N / mm to a thickness of about 0.35 mm. did. The theoretical capacity of each of these nickel positive electrodes was adjusted so as to be about 1700 mAh, and as shown in Table 1, the loading area of the positive electrode mixture per theoretical capacity on the current collecting substrate was changed variously to obtain several types. Was produced.

(3) Assembly of Battery First, a hydrogen storage alloy having a composition of LmNi _4.0 Co _0.4 Al _0.3 was mechanically pulverized into an alloy powder having an average particle diameter of 35 μm. 0.1 parts by mass, carboxymethyl cellulose 0.1
Parts by mass, polytetrafluoroethylene dispersion 1.0 parts by mass (solid content conversion), carbon black 1.
After mixing 0 parts by mass and 35 parts by mass of water, the mixture was kneaded to prepare a negative electrode mixture paste.
8% punched Ni sheet, dried at 160 ° C for 10 minutes, and roll-rolled under a load of about 2940 N / mm with a load applied to the unit work width. An alloy negative electrode was manufactured.

A polypropylene nonwoven fabric which has been subjected to a hydrophilizing treatment is disposed between the hydrogen storage alloy negative electrode and each of the nickel positive electrodes having variously changed areas for supporting the positive electrode mixture, and then wound to form an electrode group. The electrode group is housed in a battery can,
Further, an electrolytic solution mainly composed of an aqueous solution of potassium hydroxide was injected and sealed, and a cylindrical nickel-hydrogen secondary battery of 4 / 5A size (nominal capacity 1700 mAh) as shown in FIG. 1 was assembled.

(4) Evaluation of Battery Characteristics First, each battery was charged at a temperature of 25 ° C. at a current of 0.5 C at 150%, and further discharged at a current of 0.5 C until the voltage reached 1 V. Then, at a current of 0.1 C, 150
After discharging at a depth of 0.2%, the battery is discharged at a current of 0.2 C until the voltage becomes 1 V. The discharge capacity at this time is measured, and the utilization rate (%) of the active material is calculated from the ratio of the value to the theoretical capacity. The results are shown in Table 1.

In addition, these batteries are 1.2 C at 1 C.
After charging the battery for 30 minutes, the battery was left for 30 minutes, followed by discharging a large current at 10 C, observing the change over time of the voltage, and comparing the result with FIG.
It was shown to. Further, in order to examine the charge / discharge cycle characteristics of these batteries, charging was performed at a temperature of 45 ° C. with a current of 2C for 45 minutes, and charge / discharge was repeated with 1 cycle of 2C and 1V cut, and the discharge capacity was initialized. Table 1 shows the number of cycles when the value became 80% or less of the value. In addition, the manufacturing cost of the current collecting substrate of the nickel positive electrode of each of the above-described batteries was calculated, and the calculated value is shown in Table 1 as a relative value when the manufacturing cost of the current collecting substrate (foamed Ni) of Comparative Example 1 was 100. Was.

[0045]

[Table 1]

The following is clear from Table 1. (1) First, the batteries using the current collecting substrate of the present invention for the nickel electrode were compared when they had the same positive electrode mixture carrying area per theoretical capacity (Example 1 and Comparative Examples 1 and 2). And Comparative Example 2), although the utilization was inferior, the discharge cycle characteristics,
Both cost ratios show the same or better performance than the battery using the conventional foamed Ni. This is attributable to an improvement in cycle characteristics due to an increase in voids in the battery.

Further characteristics deteriorate when carrying area is less than 25 cm ² / Ah, although greater than foam substrate utilization in consideration of the relative value of the production cost, and the cycle characteristics are better than the foam substrate. (2) Since the manufacturing cost of the current collecting substrate is greatly reduced (about 1/3) as compared with the conventional foamed Ni, the use of this current collecting substrate allows the cost to be significantly lower than the conventional one. A battery can be manufactured without deteriorating characteristics.

[0048]

As is evident from the above description, the current collecting substrate of the present invention is excellent in the carrying capacity of the electrode mixture and the current collecting efficiency for the active material despite being a two-dimensional sheet. Therefore, by using this current collecting substrate, it is possible to achieve an improvement in the utilization rate of the active material, and in particular, an improvement in the discharge characteristics of the battery for large current discharge.

Since the current collecting substrate is manufactured by the powder rolling method, the manufacturing cost is extremely low and the flexibility is high as compared with the case of the conventional porous metal foam, so that the current collecting substrate is manufactured at the time of manufacturing. Short-circuit accidents are less likely to occur, and batteries having characteristics comparable to conventional batteries can be manufactured at low cost, and their industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structural example of an alkaline secondary battery of the present invention.

FIG. 2 is a plan view showing an example A of a current collecting substrate of the present invention.

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

FIG. 4 is an enlarged view of a region B in FIG. 2;

FIG. 5 is an explanatory diagram showing a state in which a punching process is performed on a metal porous sheet.

FIG. 6 is a sectional view showing another burr portion.

FIG. 7 is a plan view of a punched Ni sheet constituting a negative electrode of the alkaline secondary battery of the present invention.

FIG. 8 is a schematic view showing a production line for a porous metal sheet.

FIG. 9 is a graph showing a change with time of a voltage at the time of discharging a large current of a battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal porous sheet 1a Metal powder 1b Contact part between metal powders 1a 1c Void (communication hole) 1A Surface of metal porous sheet 1 Opening 2a Side of opening 2 3 Burr part 3a Tip part of burr part 4 4 Mixture 5 Punching die (punch) 5a Tip of punching die 10 Negative electrode 10a No opening of punched Ni sheet 11 Negative electrode mixture 12 Electrode group 12a Positive electrode 12b Negative electrode 12c Separator 13a Negative end 13b Positive end 14a Negative electrode side Current collector 14b Lead 15 Battery can 16a Positive side current collector 16b Lead 17 Sealing plate 18 Gasket 19 Valve element 20 Positive electrode cap

Continued on the front page F-term (reference) 5H017 AA02 AS01 BB01 BB06 CC03 CC05 DD08 EE01 EE04 EE09 HH02 HH04 5H028 AA07 BB04 CC10 HH01 HH06 5H050 AA02 AA08 AA19 BA14 CA03 CB16 DA04 EA10 EA23 GA10 FA10

Claims (5)

[Claims] 1. An alkaline secondary battery comprising a positive electrode, a negative electrode facing the positive electrode with a separator interposed therebetween, and an alkaline electrolyte contained in a container, wherein the positive electrode is produced by a powder rolling method, An electrode mixture is carried on a current collecting substrate formed of a porous metal sheet having a plurality of openings having burrs at a peripheral portion, and the current collecting substrate carries the electrode mixture. An alkaline secondary battery having an area of 25 cm ² or more per theoretical capacity (Ah) of the battery. 2. The alkaline secondary battery according to claim 1, wherein at least a tip portion of a burr portion formed on the current collector substrate of the positive electrode is warped in the direction of the surface of the porous metal sheet. 3. The porosity of the porous metal sheet is 5-1.
3. The alkaline secondary battery according to claim 1, wherein the content is 5%. 4. The alkaline secondary battery according to claim 1, wherein the negative electrode contains a hydrogen storage alloy powder. 5. The negative electrode current collector substrate is made of a metal punched sheet, a non-opening portion is formed at an end of the punched sheet, and the non-opening portion is connected to the container bottom via a current collector plate. The alkaline secondary battery according to claim 1, wherein