JPH10154506A - Battery electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent battery electrode by winding into a nearly complete round without applying stress at the winding of an electrode, and preventing electrode cracks and separator cutting in the spirally wound battery electrode. SOLUTION: An electrode is made of a belt-like metal porous body having three-dimensional continuous space, and active material filled in the space, and formed into a spiraliy wound electrode. The electrode is provided with plural stripe slits 4, 5 of 1/10 to 1/3 depth of electrode thickness along longitudinal directions on both faces, front and back, at equal intervals of 0.5 to 2.0mm, and the phases of the electrode front face side stripe slits 4 and the back face side stripe slits 5 are different so as to form the battery electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an electrode for a battery, particularly an electrode wound in a spiral shape.

[0002]

2. Description of the Related Art Battery electrodes are roughly classified into paste electrodes, sintered electrodes, pocket electrodes, and the like. recent years,
As a new electrode for an alkaline storage battery, particularly a nickel electrode, a band-shaped porous metal body having a three-dimensionally connected space, or a paste-type electrode in which a paste-like kneaded material is filled in a base made of a nonwoven fabric of nickel fiber is adopted. ing. Since these metal supports have a porosity of about 95% and a pore diameter of a space portion of a maximum of several hundred μm, they can be filled with a paste-like active material or active material powder at a high density.

In order to increase the capacity of a battery with the above configuration, it is necessary to make the electrodes thicker. However, when the electrode is made thicker, when the electrode group is formed by spirally winding the electrode together with the separator, the inner peripheral side of the electrode, which is the core side, is compressed and the outer side is elongated, so that cracks or cracks may be formed on the electrode. Occurs. There has been a problem that the tips of the cracks or the like may cause a decrease in the discharge capacity of the battery or the penetration of a relatively weak separator to cause an internal short circuit of the battery.

To solve this problem, Japanese Unexamined Patent Publication (Kokai) No. 5-41211 proposes providing a streak-shaped concave portion in the electrode so that the electrode can be wound smoothly.

[0005]

However, when the electrode is spirally wound, the inner side of the electrode is compressed and the outer side is elongated, so that the degree of force applied between the inner side and the outer side is different. For this purpose, it is not sufficient to provide streak-shaped concave portions in the electrode at equal intervals at the same depth.

[0006] When the inside (winding core side) and the outside (winding end side) of the spiral electrode are compared, since the radius of curvature is different, the inner side of the electrode group becomes an acute angle, so that the force applied to the electrode is increased. On the other hand, the outer side has a gentle winding radius and the force applied to the electrode is weak. For this reason, as the electrode is spirally wound, the winding force becomes different between the inside and the outside, so that winding deviation occurs. Furthermore, since the inside (the core side) of the electrode group is compressed more than the outside, and the outside is elongated, there is a problem that the electrode paste is cracked or the separator is cut off by the winding stress.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a spirally winding metal comprising a three-dimensionally continuous metal porous body and an active material filled in the space. The electrode is a plurality of stripes having a depth of 1/10 to 1/3 of the thickness of the electrode at equal intervals of 0.5 to 2.0 mm along the longitudinal direction on both front and back surfaces. This is a battery electrode having a groove, in which the streaks on the surface of the electrode are different in phase from those on the back side.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 comprises a metal porous body having a three-dimensionally continuous space, and an active material filled in the space, and is spirally wound. An electrode having a length of 0.5
1 / 10th of the electrode thickness at equal intervals of ~ 2.0mm
The battery electrode has a plurality of streaks having a depth of 1/3, and the streaks on the front surface of the electrode are different in phase from those on the back surface.

In this case, the electrode has streaks at equal intervals on both the front and back surfaces, and since this electrode has a different phase from the streaks on the front side and that on the back side, the electrode is always in the form of an electrode. Since it can be wound firmly and securely along either of the grooves on the front and back, it can be wound close to a perfect circle smoothly. This also prevents excessive force due to the winding from being applied to the electrode, and prevents cracking of the electrode and breakage of the separator.

The grooves are preferably formed at regular intervals of 0.5 to 2.0 mm along the longitudinal direction of both the front and back surfaces. Easy to crack by inward compression. On the other hand, if it is larger than 2.0 mm, the effect of winding the electrode along the groove is diminished. Also, this muscle groove is 1/10 to 1 of the thickness of the electrode.
When the depth is smaller than 1/10 of the thickness of the electrode, the effect of winding the electrode along the groove is lost, and when the electrode is formed deeper than 1/3 of the thickness of the electrode, the electrode becomes thinner. It will be easy to crack.

According to a second aspect of the present invention, the outer surface of the spirally wound electrode has a shallower depth than the inwardly facing groove, and the pitch between the grooves is smaller than that of the inner surface. It is longer than that of the groove.

In this case, the groove facing the outside of the electrode is shallower than the groove facing the inside, and the pitch between the grooves is longer than that facing the inside. Even if the elongating force acts more strongly on the outside than on the inside, it can cope with this, so that cracks on the outside of the electrode caused by extension of the electrode can be prevented.

According to a third aspect of the present invention, the groove facing the inside of the spirally wound electrode is deeper than the groove facing the outside, and the pitch at which the grooves are formed is set to the surface facing the outside. The groove is shorter than that of the groove.

In this case, the groove facing the inside of the electrode is deeper than the groove facing the outside, and the pitch between the grooves is shorter than that of the groove facing the outside. During the winding, the compression force is more strongly applied to the inside than the outside of the electrode, and the force pushed by the electrode around the groove can be absorbed, and cracks inside the electrode caused by compression of the electrode can be prevented. .

According to a fourth aspect of the present invention, the pitch of the groove formed on both the front and back surfaces of the spirally wound electrode is gradually increased from the winding start to the winding end. Out.

In this case, at the beginning of the winding of the electrode, the separator may be excessively pulled by the electrode wound usually with an angle and may be cut off. By narrowing and forming a large number of grooves in the winding start portion, the electrode can be wound closer to a perfect circle along the muscle groove, and an excessive force such as pulling the separator can be prevented. Further, the radius of curvature from the winding core increases as the winding proceeds from the winding start to the winding end, and the angle of winding of the electrode increases. Therefore, by gradually increasing the groove formation pitch from the winding start part to the winding end part, the outward extension of the electrode can be absorbed, and cracking can be prevented.

[0017]

Next, specific examples of the present invention will be described.

FIG. 1 shows a cross-sectional shape of a positive electrode 1 according to an embodiment of the present invention, and this configuration will be described below.

A mixture of 85% by weight of nickel hydroxide powder, 10% by weight of cobalt hydroxide powder and 5% by weight of nickel metal is added, and a 2% aqueous solution of carboxymethyl cellulose is added as a dispersion medium to prepare a paste-like positive electrode mixture 2. Spongy nickel having a porosity of 95%, an average pore diameter of 150 μm, and a thickness of 1.2 mm is sprayed and filled into a core material 3 having a base material, and pressurized by two rolls with ribs to form a groove 4 on the surface side.
After the thickness was adjusted to 0.7 mm while forming the groove 5 on the back surface side, it was dried at 90 ° C. for 2 hours and cut into a predetermined size to form a positive electrode 1 of the present invention.

In the positive electrode 1, the grooves 4 are formed on the surface side at equal intervals of 1.2 mm and at a depth of 0.08 mm.
Rib grooves 5 on the back side are spaced apart at equal intervals of 0.6 mm and 0.15
mm. In other words, muscle grooves 4 and 5
The front and back sides are out of phase.

The positive electrode 1 and a hydrogen storage alloy 6 as a negative electrode
Were spirally wound through a polypropylene separator 7 to form an electrode A of the present invention. The positive electrode 1 here is
The front side was outside the electrode A. FIG. 2 shows a cross-sectional view of the electrode A.

Next, a conventional positive electrode 8 was constructed in the same configuration as described above. In the positive electrode 8, stripe grooves 9 are formed on both the front and back surfaces at an equal interval of 1.2 mm with a depth of 0.08 mm. In other words, the streaks have the same phase on both front and back surfaces. FIG. 3 shows a cross-sectional view of the positive electrode 8.

A conventional electrode B was formed by spirally winding the positive electrode 8 and the hydrogen storage alloy 6 of the negative electrode through a polypropylene separator 7. FIG. 4 is a sectional view of the electrode B.
Shown in

Each of the spiral electrodes A and B is connected to 100
Table 1 shows the results of comparing the states of the zero-constituting device.

[0025]

[Table 1]

The electrode A has no defect caused by cracking of the spirally wound electrode or breakage of the separator.

This is because the streaks 4 on the front side (outside the electrode) and the streaks 5 on the back side (inside the electrode) of the positive electrode 1 are out of phase with each other. It is possible to wind the electrode tightly and regularly, and there is no stress of winding and the electrode can be wound closer to a perfect circle,
No cracks in the electrodes and no breaks in the separator. Further, in this electrode, since the positive electrode 1 has a formation pitch of the inner muscle groove 5 shorter than that of the outer muscle groove 4, and the inner muscle groove 5 has a greater depth than the outer muscle groove 4, Because it can be wound while absorbing the inward compressive force applied when forming a spiral electrode,
No cracks in the electrodes and no breaks in the separator.

However, when the electrode B is spirally wound, the number of cracks in the electrode is 10 and the number of breaks in the separator is 7 as a defect.

This is because the positive electrode 8 has a groove 9 on both the front side and the back side.
Are in the same phase, so that the creases 9 are formed at opposing positions on both the front and back surfaces, so that the creases cannot be formed sufficiently between the creases 9 and a winding stress is applied, thereby causing the separator to be cut. is there. Furthermore, the inner and outer groove 9 of the positive electrode 8
Has the same formation pitch and the same depth, it cannot sufficiently absorb the inward compression force and the outward expansion force applied when spirally winding the electrode, and cracks in the electrode and breakage of the separator may occur. What happens.

In the embodiment of the present invention, the one in which the groove is formed in the positive electrode is used. However, the one in which the groove is formed only in the negative electrode or the one in which the groove is formed in both the positive electrode and the negative electrode is similarly used. The effect of is obtained.

[0031]

As described above, when the electrode of the present invention is used, when the electrode is spirally wound, the phase of the groove formed on the electrode is different, so that any one of the stripes on the front and back surfaces can be used. It can be wound regularly along the groove, can be wound close to a perfect circle with no winding stress, and can provide a good battery electrode without cracking of the electrode or breakage of the separator.

[Brief description of the drawings]

FIG. 1 is a sectional view of a positive electrode according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a spiral electrode A according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional positive electrode.

FIG. 4 is a cross-sectional view of a conventional spiral electrode B.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Positive electrode mixture 3 Core material 4 Front surface side groove | channel of a positive electrode 5 Back surface side groove of a positive electrode 6 Hydrogen storage alloy 7 Separator

Claims (4)

[Claims] 1. A spirally wound electrode comprising a strip-shaped porous metal body having a three-dimensionally continuous space and an active material filled in the space, wherein the electrode is formed on both front and back surfaces. A plurality of grooves having a depth of 1/10 to 1/3 of the thickness of the electrode at regular intervals of 0.5 to 2.0 mm along the longitudinal direction, and a groove on the surface of the electrode. The battery electrode has a different phase from that of the back side. 2. A spirally wound electrode, wherein the outwardly facing groove is shallower in depth than the inwardly facing groove and the pitch between the grooves is longer than that of the inwardly facing groove. The battery electrode according to claim 1. 3. The spirally wound electrode, wherein the inwardly facing groove is deeper than the outwardly facing groove and the pitch between the grooves is shorter than that of the outwardly facing groove. The battery electrode according to claim 1. 4. The battery electrode according to claim 1, wherein the spirally wound electrode has a pitch of the groove formed on both the front and back surfaces of the electrode gradually increasing from the winding start portion to the winding end portion.