JPH1140146A - Paste-type electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the flexibility and the property suitable for rolling by providing a three dimensional substrate and an active material mix held in the substrate, forming notch parts in the rim part regions at right angles to the longitudinal direction along the direction of the regions, and making the number of the notches in one side lower than that of the notches in the other side. SOLUTION: Notch parts 23 vertical to the longitudinal direction of rolling are formed at equal intervals in the side of a paste-type nickel positive electrode 21, which forms the outer circumference when being rolled, except for the region where a lead tab 2 is formed. Each notch part 23 has a V shape, and the interval L of the notch bottom parts is controlled to be 0. 1 mm, the depth H of each notch to be 0.05 mm, and the angle α of the notch bottom part to be 30 degrees. Notch parts are formed also in the rear side, and the interval L is controlled to be 0.5 mm and other sizes and the angle are made equal to those of the notches in the front side. Consequently, the number of the notches in the side, which becomes the inner circumference when being rolled, is equivalent to 20% of the number of the notches formed in the side which becomes the outer circumference. As a result, the curving width can be narrowed as compared with a positive electrode having no notch and warping can be avoided, even in the case the paste-filling density is increased for heightening capacity and flexibility is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paste type electrode.

[0002]

2. Description of the Related Art In recent years, as electric appliances have become portable and portable personal computers (PCs) and mobile phones have become widespread, it has been demanded to increase the capacity of a battery as a main power source and to improve the volumetric efficiency. . As a battery used as a main power supply of such a device, for example, there is an alkaline secondary battery.

[0003] In this alkaline secondary battery, in order to satisfy the above-mentioned demands, it is necessary to improve the capacity of a positive electrode which is an electrode for regulating the capacity of the secondary battery. As a positive electrode for an alkaline secondary battery, a sintered nickel positive electrode has been conventionally known. However, in this sintered positive electrode, the ratio occupied by the substrate was as high as about 30%, and a higher capacity could not be expected.

Accordingly, a paste-type positive electrode formed by filling a paste containing an active material into a three-dimensional substrate such as a nickel sponge-like substrate has been developed, and this type of positive electrode is currently the mainstream. . This paste-type positive electrode is advantageous in increasing the capacity since the ratio occupied by the substrate is as low as about 10%. The positive electrode is formed into a paste by kneading, for example, nickel hydroxide, a cobalt compound as a conductive additive, a binder, and water.
It can be manufactured by filling a three-dimensional substrate, drying, and forming into a desired thickness by rolling.

In order to increase the capacity of such a paste-type positive electrode, it is necessary to increase the amount of paste filled in the three-dimensional substrate. However, when the paste filling amount is increased, the thickness of the positive electrode and the paste filling density are increased, which causes a problem that the flexibility of the positive electrode is reduced. As a result, when the spiral electrode group is manufactured by winding the positive electrode and the negative electrode with a separator interposed therebetween, large cracks are generated non-uniformly in the positive electrode, particularly in the winding start portion, and the obtained electrode group The diameter increases, and it may not be stored in the can. Further, there is a problem that a three-dimensional substrate broken during winding or broken due to cracks penetrates through the separator and comes into contact with the negative electrode, thereby causing an internal short circuit.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a paste-type electrode having improved flexibility and winding properties by forming grooves on the surface.

[0007]

According to the present invention, there is provided a three-dimensional substrate, and an active material mixture held on the substrate, wherein at least an end region perpendicular to the longitudinal direction has a direction perpendicular to the longitudinal direction. Is provided, and the number of grooves on one surface is smaller than the number of grooves on the other surface.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The paste-type electrode according to the present invention includes a three-dimensional substrate and an active material mixture held on the substrate, and at least in an end region of the surface orthogonal to the longitudinal direction, along a direction orthogonal to the longitudinal direction. It has a groove, and the number of grooves on one surface is smaller than the number of grooves on the other surface.

An example in which the electrode according to the present invention is applied to a paste-type positive electrode for an alkaline secondary battery will be described. For the positive electrode, for example, a paste containing nickel hydroxide as a main component as an active material, a conductive agent, a binder and water was prepared, and the paste was filled in a three-dimensional substrate except for a band-shaped tab forming region. Thereafter, it can be manufactured by drying and rolling, and forming the above-described grooves on both surfaces with a roller with a cutter, for example.

Examples of the nickel hydroxide particles include nickel hydroxide particles and nickel hydroxide particles in which zinc and / or cobalt are coprecipitated. The positive electrode containing the latter nickel hydroxide particles,
It is possible to further improve the charging efficiency in a high temperature state.

From the viewpoint of improving the charge / discharge efficiency of the alkaline secondary battery, the nickel hydroxide has a peak half-value width of the (101) plane determined by an X-ray powder diffraction method of 0.8 ° / 2θ (Cu
-Kα) or more. A more preferable range of the peak half width is 0.9 to 1.0 °.

The particles mainly composed of nickel hydroxide have an average particle diameter of 5 to 30 μm and a tap density of 1.8 g / g.
cm ³ or more and a specific surface area of 1 to ²⁰ m ² / g.

It is preferable that the particles mainly composed of nickel hydroxide have a spherical shape or a shape similar thereto. As the conductive agent, for example, metal cobalt,
Cobalt hydroxide (Co (OH) ₂ ), cobalt monoxide (CoO), and the like can be given. Among them, cobalt hydroxide and cobalt monoxide are preferred. However, this conductive agent is allowed to contain trace amounts of dicobalt trioxide and tricobalt tetroxide. Further, the conductive agent may be present in the form of particles in the positive electrode, or may be present in the form of a layer on the surface of the particles containing nickel hydroxide as a main component.

Examples of the binder include carboxymethylcellulose, polyacrylate, and fluororesin. The three-dimensional substrate can be formed of, for example, nickel or iron. Examples of the three-dimensional substrate include a nickel sponge-like substrate, a nickel fibrous substrate, and a nickel felt-like substrate. Above all, the nickel sponge-like substrate has a high electrode strength, so that forming a groove as in the present invention can greatly improve the flexibility.

[0015] The groove is formed at least in a winding start end region on the surface of the positive electrode so as to extend along a direction orthogonal to the longitudinal direction of the positive electrode. Here, to form the groove portion along a direction orthogonal to the longitudinal direction of the positive electrode,
In addition to forming the groove perpendicular to the longitudinal direction of the positive electrode, the angle between the groove and the longitudinal direction of the positive electrode is 90 ° ± 1.
This means that the groove is formed so as to be 0 °. By forming the groove in such a direction, the positive electrode is formed into a groove-forming end of the ends orthogonal to the longitudinal direction as a winding start end, and preferentially when spirally wound together with the negative electrode and the separator. Fine cracks can be generated along the groove, and large cracks such as breakage of the substrate at the winding start end of the positive electrode and uneven cracks can be avoided.

The grooves are formed on both surfaces of the positive electrode, and the number of grooves formed on one surface is smaller than the number of grooves formed on the other surface. In the positive electrode,
At the time of winding, the number of grooves formed on the surface located on the inner peripheral side is made smaller than the number of grooves formed on the surface located on the outer peripheral side. If the groove is formed only on one side of the positive electrode, only this surface extends, and the positive electrode warps. When the positive electrode is warped, there are inconveniences such as cracks occurring in the positive electrode at a position deviating from the groove when the spiral electrode group is manufactured, and difficulty in handling during manufacturing. In the positive electrode, it is preferable that the number of grooves formed on the surface located on the inner peripheral side during winding be 10% or more and less than 100% of the number of grooves formed on the surface located on the outer peripheral side. This is due to the following reasons. When the number of grooves on the inner peripheral side is less than 10% of the number of grooves on the outer peripheral side, the positive electrode is easily warped. On the other hand, as the number of grooves on the inner peripheral side increases, the flexibility of the positive electrode improves, but the amount of active material and the strength of the positive electrode decrease. If the number of grooves on the inner peripheral side exceeds 50% of the number of grooves on the outer peripheral side, a decrease in the positive electrode capacity and the positive electrode strength may become apparent. It is more preferable that the number of grooves on the inner peripheral side be 20% or more and 50% or less of the number of grooves on the outer peripheral side.

On the surface located on the outer peripheral side at the time of winding, the groove forming region is at least 20% of the length of the positive electrode (the length of the positive electrode is 1%) from the end (winding start end) orthogonal to the longitudinal direction of this surface.
It is preferable that a portion corresponding to (00%) exists. The length of the groove forming region on the outer peripheral surface is set to 20% or more from the end perpendicular to the longitudinal direction, and the positive electrode and the negative electrode are interposed with a separator therebetween so that the groove forming region becomes a winding start portion. By spirally winding the three-dimensional substrate to form an electrode group, it is possible to suppress occurrence of irregular cracks at the beginning of winding of the three-dimensional substrate,
The occurrence rate of insulation failure can be greatly reduced. In addition, on the surface located on the inner peripheral side at the time of winding, a groove may be formed so as to avoid warpage of the positive electrode,
The groove forming region may be less than the range described above.

The interval between the grooves formed on the positive electrode surface located on the outer peripheral side during winding is preferably in the range of 0.1 mm to 10 mm. This is due to the following reasons. If the distance is less than 0.1 mm, it may be difficult to form the groove. On the other hand, when the interval is 10
If it exceeds mm, a number of cracks will be generated at locations off the groove, and there is a possibility that insulation failure will frequently occur. A more preferable range of the interval between the groove portions is 0.5 mm to 5 mm. Further, the intervals between the grooves may not be equal, and, for example, an end region (winding start region) perpendicular to the longitudinal direction may be narrowed and other regions may be widened. Note that a groove may be formed on the positive electrode surface located on the inner peripheral side at the time of winding so as to avoid warpage of the positive electrode, and the interval between grooves on this surface may exceed 10 mm.

The depths of the grooves on the inner and outer peripheral surfaces are preferably in the range of 0.01 mm to 0.4 mm. This is due to the following reasons.
If the depth is less than 0.01 mm, it may be difficult to form the groove. On the other hand, when the depth of the groove portion exceeds 0.4 mm, there is a possibility that the strength of the positive electrode is reduced and the positive electrode is broken or the like.

The shape of the groove can be, for example, V-shaped, key-shaped, semi-circular, or the like. Especially, it is preferable to make it V-shaped. When the shape of the groove is V-shaped, it is preferable that the angle of the groove (the angle between surfaces forming the groove) is 45 ° or less. If the angle exceeds 45 °, interference between the grooves tends to occur. In addition, the amount of active material reduced due to the formation of the groove increases,
There is a possibility that the capacity may be reduced.

An example of an alkaline secondary battery incorporating the above-described paste type positive electrode for an alkaline secondary battery will be described in detail with reference to FIG. An electrode group 5 produced by spirally winding the above-mentioned paste-type positive electrode 2 and negative electrode 4 with a separator 3 interposed therebetween is accommodated in a bottomed cylindrical container 1. The negative electrode 4
Are arranged at the outermost periphery of the electrode group 5 and are in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. A circular first sealing plate 7 having a hole 6 in the center is arranged at the upper opening of the container 1.
The ring-shaped insulating gasket 8 is disposed between the peripheral edge of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the container 1 is formed by caulking to reduce the diameter of the upper opening inward.
The sealing plate 7 is hermetically fixed via the gasket 8. One end of the positive electrode lead 9 is connected to the positive electrode 2,
The other end is connected to the lower surface of the sealing plate 7. The positive electrode terminal 10 having a hat shape is attached on the sealing plate 7 so as to cover the hole 6. The rubber safety valve 11
The hole 6 is disposed in a space surrounded by the sealing plate 7 and the positive electrode terminal 10 so as to close the hole 6. The circular holding plate 12 made of an insulating material having a hole in the center is
The projecting portion of the positive electrode terminal 10 is disposed on the reference numeral 0 so as to project from the hole of the holding plate 12. The outer tube 13 covers the periphery of the holding plate 12, the side surface of the container 1, and the periphery of the bottom of the container 1.

Next, the negative electrode 4, the separator 3, and the alkaline electrolyte will be described in detail. 1) Negative Electrode The negative electrode 4 is, for example, a hydrogen storage alloy negative electrode including hydrogen storage alloy particles that store and release hydrogen. Such a negative electrode has a structure in which a mixture having a composition including the hydrogen storage alloy powder, a conductive agent and a binder is fixed to a conductive core serving as a current collector.

Examples of the hydrogen storage alloy compounded in the mixture of the negative electrode 1 include LaNi ₅ , MmNi ₅ (Mm;
Misch metal), LmNi ₅ (Lm; lanthanum-enriched misch metal), and a part of Ni of these alloys is A
l, Mn, Co, Ti, Cu, Zn, Zr, Cr, a multi-element system substituted with elements such as B, or TiNi
And TiFe-based ones. In particular, the general formula _{LmNi w Co x Mn y Al z} ( atomic ratio w, x,
(The total value of y and z is 5.00 ≦ w + x + y + z ≦ 5.5.) A hydrogen storage alloy having a composition represented by the following formula: It is.

Examples of the conductive agent include carbon black and graphite. Examples of the binder include polyacrylates such as sodium polyacrylate and potassium polyacrylate, fluororesins such as polytetrafluoroethylene, and carboxymethyl cellulose. Such a binder is preferably blended in an amount of 0.1 to 5% by weight based on the hydrogen storage alloy.

Examples of the conductive core include those having a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and those having a three-dimensional structure such as a nickel sponge-like substrate, a nickel fiber-like substrate, and a nickel felt-like substrate. And a composite substrate combining a three-dimensional structure and a two-dimensional structure. When a three-dimensional substrate is used as the conductive core, a configuration having a groove similar to that described for the paste electrode described above can be employed. 2) Separator Examples of the separator 3 include a polyolefin nonwoven fabric such as polypropylene and polyethylene, a nylon nonwoven fabric, and a mixture of these fibers. Further, those subjected to a hydrophilic treatment as necessary can be applied. In particular, a polypropylene nonwoven fabric whose fiber surface has been hydrophilized is suitable as the separator 3. 3) Alkaline Electrolyte Examples of the alkaline electrolyte include a mixed aqueous solution of sodium hydroxide and lithium hydroxide, a mixed aqueous solution of potassium hydroxide and lithium hydroxide, or a mixed aqueous solution of sodium hydroxide, potassium hydroxide, and lithium hydroxide. Can be used.

As described above, the paste-type electrode according to the present invention includes the three-dimensional substrate and the active material mixture held on the substrate, and has at least an end region orthogonal to the longitudinal direction. It is characterized by having grooves along the direction orthogonal to each other, wherein the number of grooves on one surface is smaller than the number of grooves on the other surface. Such a paste-type electrode can improve flexibility while avoiding warpage even when the active material is densely packed for high capacity. As a result, among the ends orthogonal to the longitudinal direction of the electrode, the end where the groove is formed is set as the winding start end, and the electrode and the other electrode are wound with a separator interposed therebetween to form a spiral electrode group. When manufacturing the electrode, it is possible to suppress or prevent the occurrence of irregular cracks near the winding start end of the electrode, and to reduce the defect that the electrode group cannot be stored in the container and the occurrence rate of insulation failure. Can be. As a result, a high-capacity battery can be provided with a high yield.

In the above paste type electrode, the interval between grooves formed on the electrode surface located on the outer peripheral side at the time of winding is set to 0.1.
By making the range from 10 mm to 10 mm,
It is possible to avoid the occurrence of a large crack in the vicinity of the winding start end of the substrate, and it is possible to significantly reduce the problem that the electrode group cannot be accommodated in the container and the rate of occurrence of insulation failure.

Further, the depth of the groove on both sides of the electrode is set to 0.
By setting the thickness in the range of 01 mm to 0.4 mm, it is possible to effectively reduce the crack generation rate and to suppress a decrease in the active material filling amount and a decrease in the electrode strength.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail. (Example 1) 0.2 parts of carboxymethylcellulose and 40 parts of water were added to a mixture consisting of 90 parts of nickel hydroxide powder and 10 parts of cobalt monoxide, and kneaded to prepare a paste. The paste was filled in a sponge-like nickel substrate except for a lead tab mounting area, dried, and subjected to pressure molding by a roller press. Then
A groove as shown in FIG. 2 was formed on both sides of the roll with a V-shaped cutter, and a lead tab made of nickel was attached to the active material mixture non-holding area, and the paste filling density was 650 mAh /
cc, thickness 0.65mm, length 70mm, capacity 1
A 200 mAh paste-type nickel positive electrode was manufactured.

As shown in FIG. 2, the lead tab 22 is attached to an end (upper end) of the positive electrode 21 along the longitudinal direction. The positive electrode 21 has grooves (notches) 23 perpendicular to the winding direction (longitudinal direction) formed at equal intervals except for a lead tab formation region on a surface (upper surface in FIG. 2) located on the outer peripheral side during winding. It is formed apart. Each notch 23 has a V-shape as shown in FIGS. The interval (L) between the notches 23 is 0.1 mm. The depth (H) of each notch 23 is 0.05 mm.
It is. Further, the angle α of each notch 23 is 30 °. V-shaped notches having the same angle and depth as the front surface are formed at equal intervals on the entire back surface (the surface located on the inner peripheral side during winding) of the positive electrode. The distance (L) between the notches is 0.5 mm. The number of notches on the surface located on the inner peripheral side during winding corresponds to 20% of the number of notches located on the outer peripheral side during winding. (Example 2) The notch interval on the surface located on the outer peripheral side during winding is set to 0.3 mm, the notch interval on the surface located on the inner peripheral side during winding is set at 1.5 mm, and the notch interval is set on the inner peripheral side during winding. A paste-type nickel positive electrode was produced in the same manner as in Example 1, except that the number of notches on the surface to be formed was set to 20% of the number of notches located on the outer peripheral side during winding. (Example 3) The notch interval of the surface located on the outer peripheral side during winding is set to 0.5 mm, the notch interval of the surface located on the inner peripheral side during winding is set to 2.5 mm, and the notch interval is set at the inner peripheral side during winding. A paste-type nickel positive electrode was produced in the same manner as in Example 1, except that the number of notches on the surface to be formed was set to 20% of the number of notches located on the outer peripheral side during winding. (Example 4) The notch interval of the surface located on the outer peripheral side during winding is set to 1.0 mm, the notch interval of the surface located on the inner peripheral side during winding is set to 5 mm, and the surface located on the inner peripheral side during winding is set. A paste-type nickel positive electrode was produced in the same manner as in Example 1 except that the number of notches was 20% of the number of notches located on the outer peripheral side during winding. (Example 5) The notch interval of the surface located on the outer peripheral side during winding is set to 2.5 mm, the notch interval of the surface located on the inner peripheral side during winding is set to 12.5 mm, and the notch interval is set on the inner peripheral side during winding. 20% of the number of notches located on the outer peripheral side during winding
A paste-type nickel positive electrode similar to that of Example 1 was prepared except that the above method was adopted. (Example 6) The notch interval of the surface located on the outer peripheral side during winding is set to 5.0 mm, the notch interval of the surface located on the inner peripheral side during winding is set to 25 mm, and the surface located on the inner peripheral side during winding is set. A paste-type nickel positive electrode was produced in the same manner as in Example 1 except that the number of notches was 20% of the number of notches located on the outer peripheral side during winding. (Example 7) The notch interval of the surface located on the outer peripheral side during winding is 10 mm, the notch interval of the surface located on the inner peripheral side during winding is 20 mm, and the notch on the inner peripheral side during winding is set. A paste-type nickel positive electrode similar to that of Example 1 was produced except that the number was set to 50% of the number of notches located on the outer peripheral side at the time of winding. (Embodiment 8) The notch interval of the surface located on the outer peripheral side during winding is 15 mm, the notch interval of the surface located on the inner peripheral side during winding is 30 mm, and the notch interval on the inner peripheral side during winding is set. A paste-type nickel positive electrode similar to that of Example 1 was produced except that the number was set to 50% of the number of notches located on the outer peripheral side at the time of winding. (Example 9) The notch interval of the surface located on the outer peripheral side at the time of winding is set to 17 mm, the notch interval of the surface located at the inner peripheral side at the time of winding is 35 mm, and the notch at the inner peripheral side is set at the time of winding. A paste-type nickel positive electrode similar to that of Example 1 was produced except that the number was set to 50% of the number of notches located on the outer peripheral side at the time of winding. (Comparative Example 1) A paste-type nickel positive electrode was produced in the same manner as in Example 1, except that no notch was formed on both surfaces.

The obtained positive electrodes of Examples 1 to 9 and Comparative Example 1 were subjected to an insulation failure evaluation test. Each positive electrode and a hydrogen storage alloy negative electrode having a thickness of 0.3 mm are made of a nonwoven fabric made of polyolefin that has been subjected to a hydrophilic treatment between the negative electrodes and has a thickness of 0.2 mm.
The electrode group was manufactured by spirally winding the electrode with the above separator interposed therebetween. The obtained electrode group was accommodated in a container for AA size, an alkaline electrolyte was accommodated, and a nickel-metal hydride secondary battery for test was assembled by sealing.

Fifty pieces of the obtained secondary batteries of Examples 1 to 9 and Comparative Example 1 were prepared. For each secondary battery, the voltage was measured, the number of defective batteries whose voltage dropped to 0 V due to an internal short circuit was measured, and the defective insulation rate was obtained. The results are shown in FIG.

As is apparent from FIG. 5, the secondary batteries provided with the positive electrodes of Examples 1 to 9 can reduce the rate of occurrence of insulation failure as compared with Comparative Example 1. When these secondary batteries were disassembled and the positive electrode surface near the beginning of winding was observed, it was found that cracks occurred along the notches, that is, the cracks were formed uniformly. From this, Examples 1 to
It can be seen that the secondary battery provided with the positive electrode of No. 9 can suppress the winding deviation at the time of winding and the burr generated due to the non-uniform crack, so that the insulation failure rate can be reduced. Also, it can be seen that the insulation failure rate may increase as the notch interval increases. The notch width is 0.1mm
If it is less than 1, notches interfere with each other, and it is somewhat difficult to form the notch. (Examples 10 to 17) In the positive electrode of Example 1 described above, the notch depth (H) was 0.01 mm (Example 10).
0.03 mm (Example 11), 0.1 mm (Example 12),
0.2 mm (Example 13), 0.25 mm (Example 14),
0.3 mm (Example 15), 0.4 mm (Example 16),
A total of eight types of positive electrodes were prepared, different from 0.45 mm (Example 17).

With respect to the obtained positive electrodes of Examples 10 to 17, an insulation failure evaluation test was performed by the same method as described above, and the results are shown in FIG. FIG. 6 also shows the results of Comparative Example 1 and Example 1 described above.

As is clear from FIG.
It can be seen that the secondary batteries having the positive electrodes of Nos. 1 to 17 can reduce the insulation failure rate as compared with Comparative Example 1. Also, it can be seen that as the depth of the notch increases, cracks occur uniformly along the notch, and the insulation failure rate tends to decrease. However, when the depth of the notch exceeds 0.4 mm, the positive electrode may be broken at the time of manufacturing the electrode group, so that the insulation failure rate tends to be slightly higher. If the depth of the notch is less than 0.01 mm, it is somewhat difficult to form a notch having a desired shape.

Next, for the positive electrode of Example 4 described above and the positive electrodes of Example 18 and Comparative Example 2 described below, the bending width (degree of warpage) was measured. (Example 18) The notch interval of the surface located on the outer peripheral side during winding is 1.0 mm, the notch interval of the surface located on the inner peripheral side during winding is 20 mm, and the surface located on the inner peripheral side during winding A paste-type nickel positive electrode was produced in the same manner as in Example 1, except that the number of notches was 5% of the number of notches located on the outer peripheral side during winding. (Comparative Example 2) Example 1 except that no notch was formed on the surface located on the inner peripheral side during winding, that is, the number of notches on this surface was set to 0% of the number of notches located on the outer peripheral side during winding. A paste-type nickel positive electrode similar to that described above was produced.

The positive electrodes obtained in Examples 4 and 18 and Comparative Example 2 were placed on a horizontal surface with the surface located on the inner peripheral side facing down when wound, and between the surface and each positive electrode. The maximum value of the formed gap was measured as the bending width, and the result was shown in Table 1 below.
Shown in

[0038] As is clear from Table 1, the positive electrodes of Examples 4 and 18 in which notches are present on the surface located on the inner peripheral side during winding are compared with the positive electrodes of Comparative Example 2 in which notches are not formed on the inner peripheral surface side. Thus, the bending width can be reduced, and the occurrence of warpage can be prevented.

[0039]

As described above in detail, according to the paste-type electrode of the present invention, even when the paste filling density is improved for higher capacity, the flexibility is improved while avoiding warpage. This makes it possible to produce a high-capacity alkaline secondary battery at a high yield.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an example of an alkaline secondary battery into which a paste electrode according to the present invention is incorporated.

FIG. 2 is a perspective view showing a paste-type positive electrode of Examples 1 to 18 of the present invention.

FIG. 3 is a partial sectional view showing a positive electrode of FIG. 2;

FIG. 4 is a partial cross-sectional view showing the positive electrode of FIG.

FIG. 5 is a characteristic diagram showing the relationship between the interval between grooves and the insulation failure rate in the paste-type positive electrodes of Examples 1 to 9 of the present invention and the paste-type positive electrode of Comparative Example 1.

FIG. 6 is a characteristic diagram showing the relationship between the depth of the groove and the insulation failure rate in the paste-type positive electrodes of Examples 10 to 17 of the present invention and the paste-type positive electrode of Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 4 ... Negative electrode, 5 ... Electrode group, 7 ... Sealing plate.

Claims (3)

[Claims] 1. A paste electrode comprising a three-dimensional substrate and an active material mixture held on the substrate, wherein at least an end region orthogonal to the longitudinal direction has a groove along a direction orthogonal to the longitudinal direction. Wherein the number of grooves on one surface is smaller than the number of grooves on the other surface. 2. The interval between the grooves on the other surface is:
The paste-type electrode according to claim 1, wherein the thickness is from 0.1 mm to 10 mm. 3. The paste electrode according to claim 1, wherein the depth of the groove on the one surface and the other surface is 0.01 mm to 0.4 mm, respectively.