JP2000164208A - Manufacture of electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing electrodes effective for restricting the projection of an active material layer at the edge of a foil-like collector. SOLUTION: A foil-like collector 1 is coated with an active material layer by coating a surface 10 with the paste-like active material so as to manufacture an electrode. An edge part 15 of the surface 10 to be coated of the collector 1 is formed more hydrophilic than a central area 17. Thereafter, the surface 10 to be coated is coated with the paste-like active material. The edge part 15 can be formed with a rugged part such as cutout and a hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing an electrode used in a battery.

[0002]

2. Description of the Related Art Conventionally, in manufacturing the above-mentioned electrode, as shown in FIG. 11, a paste-like active material is applied to a surface of a foil-shaped current collector 100 to be applied to a constant thickness, The active material layer 200 is to be covered. In this case, as shown in FIG.
0w and the foil-like current collector 100 is placed on the holding table 30.
The paste-like active material 200 </ b> X is applied to the current collector 100 together with the 0 mounting surface 300 w, and then the current collector 100 is peeled off from the holding table 300.

[0003]

However, as shown in FIG. 3, an edge 101 of the surface of the foil-shaped current collector 100 to be coated is used.
In, the swelling 202 tended to occur in the active material layer 200. It is presumed that the reasons are the effects of the water repellency of the current collector 100 itself and the surface tension of the paste-like active material.

As described above, the swelling 2 in the active material layer 200 occurs.
02, the foil-shaped current collector 10 is dried.
0 may be rounded. In this case, a crack or a crack may be generated in the active material layer 200 in a subsequent pressing step. The present invention has been made in view of the above-described circumstances, and it is a common object to provide a method for manufacturing an electrode that is advantageous in suppressing the rise of an active material layer at an edge of a foil-shaped current collector.

[0005]

Means for Solving the Problems The present inventor has proposed a method for suppressing the swelling of the active material layer at the edge of the foil-shaped current collector.
Development proceeded. The inventor of the present invention has found out that, by giving hydrophilicity to the edge of the foil-shaped current collector to be applied, where the bulge occurs, the bulge at the edge can be suppressed, and confirmed by a test, the first invention A method according to the present invention has been invented.

Further, the present inventor has found that by forming a cut or a hole in the edge of the surface of the current collector where the current is to be applied, where the bulge occurs, and forming irregularities on the edge, the bulge of the active material layer can be suppressed. Invented and confirmed by tests, and invented a method according to the second invention. That is, in the method for manufacturing an electrode according to the first invention, which corresponds to claim 1, the electrode is manufactured by coating the active material layer by applying a paste-like active material to an application surface of a foil-shaped current collector. The method is characterized in that an edge of a surface to be coated of a current collector is made more hydrophilic than a central region thereof, and thereafter, a paste-like active material is applied to a surface to be coated of the current collector. .

According to a third aspect of the present invention, there is provided a method for manufacturing an electrode, wherein a paste-like active material is applied to a surface of a foil-shaped current collector to be coated so as to cover the active material layer and manufacture the electrode. In this method, irregularities are formed on the edge of the surface of the current collector to be coated, and then the paste-like active material is applied to the surface of the current collector to be coated.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the method according to the first and second inventions, the thickness of the foil-shaped current collector can be appropriately selected.
It can be 50 μm, but is not limited to this.
The material of the current collector is selected according to the conductivity, the type of the electrolytic solution, and the like, and is typically an aluminum-based material, but is not limited thereto.

The paste-like active material to be applied can include activated carbon, a conductive material, a binder, and a solvent. Typical conductive materials include carbon black and graphite. A typical binder is methylcellulose (M
C), carboxymethyl cellulose (CMC) can be employed. Water and organic solvents can be used as the solvent. The thickness of the active material layer formed by applying the paste active material is 30.
で き る 100 μm, but is not limited to this. In the method of the present invention, a form in which the paste-like active material is applied to one side of the current collector may be used, or a form in which the paste-like active material is applied to both sides of the current collector may be used.

In the method according to the first invention, the edge of the surface to be coated of the electrode is made more hydrophilic than the central region, and then the paste is applied to the surface to be coated of the current collector (including the hydrophilic portion). Apply active material. As means for making the material hydrophilic, means for applying a material having hydrophilicity can be adopted. As a substance having hydrophilicity, a carboxylate, an amine salt, a polyhydric alcohol, or the like can be used.

The area and location where the hydrophilic substance is applied can be selected so as to correspond to the projected area of the site where a bulge occurs. In particular,
It can be applied to an area that is the same as or smaller than the projected area of the site where the bulge occurs. The function of preventing the swelling by imparting hydrophilicity is not always clear, but it is presumed that a change in the contact angle at the interface affects the surface tension of the paste.

[0012] In the method according to the second aspect of the present invention, irregularities are formed on the edge of the surface of the electrode to be coated, and then the paste-like active material is applied to the surface of the current collector (including the irregularities). The unevenness includes a form in which the entirety is formed by forming the concave, a form in which the entirety is formed by forming the convex, and a form in which the entirety is formed by forming the concave and convex.

Therefore, as the unevenness, a method of forming a notch at the edge of the surface to be coated with the electrode, a method of forming a hole at the edge of the surface to be coated with the electrode, and a surface roughness of the edge of the surface to be coated with the electrode Can be adopted, but the present invention is not limited thereto. The hole may be a through hole,
Non-through holes may be used. In the case of forming a hole, the current collecting area of the current collector is reduced. Therefore, it is preferable to select an appropriate hole area in order to secure a current collecting area.

The area and location of the area where the unevenness is formed can be selected so as to correspond to the projected area of the area where the bulge occurs. Specifically, in a region where a bulge occurs, irregularities can be formed in a region having an area equal to or smaller than the projected area of the region. The effect of preventing swelling due to the formation of irregularities is not always clear, but one of the
It appears to be hydrophilic.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment will be described below with reference to FIGS. This embodiment is a case where the present invention is applied to an electrode used for a battery. In this embodiment, a foil-shaped aluminum current collector 1 is used. The current collector 1 has a rectangular shape, and has long sides 1a and 1b facing each other and short sides 1e and 1d facing each other. The current collector 1 has a length A of about 100 mm, a width B of about 50 mm, and a thickness of about 20 μm. The current collector 1 has a surface 10 to be coated (size:
L1 × B).

Of the surface 10 to be coated on one side of the current collector 1,
A material having hydrophilicity was applied to the square frame-shaped edge 15 (the area indicated by hatching in FIG. 1). In this example, this substance was glycerin. In this embodiment, the edge 1
The width E of 5 was 3 mm. In the prior art shown in FIG. 13, the width EA at which the bulge occurs (see FIG. 13) is about 3
mm.

The edge 15 of the coating surface 10 of the current collector 1 is
No hydrophilic material was applied to the central region 17 surrounded by. Thereby, the edge 15 of the surface 10 to be coated of the current collector 1 was made more hydrophilic than the central region 17 thereof. Thereafter, the surface 10 to be coated of the current collector 1 (the edge 15, the central region 17).
Is coated with the paste-like active material 20X to form the active material layer 20. The basic composition of the paste active material 20X is as follows: activated carbon: conductive material: binder: water = 10: 1: 1: 60
(Weight ratio). The target thickness of the active material layer 20 in the central region 17 of the coating surface 10 was set to 70 μm.

As shown in FIG.
The measurement was performed by the doctor blade method in a state where the current collector 1 was mounted on the flat mounting surface 70 of the holding table 7. That is, the surface 10 to be coated of the current collector 1 placed on the mounting surface 70 of the holding table 7 is coated with the paste-like active material 20X, and then the excess paste-like active material is scraped off with a blade so as to have a uniform thickness. Was. next,
An arrow Y1 is attached to the current collector 1 coated with the paste active material 20X.
A force was applied in the direction (see FIG. 2), and peeled off from the holding table 7. The removed current collector 1 was dried to obtain the electrode 3 shown in FIG. The electrode 3 includes a current collector 1 and an active material layer 20 coated on the current collector 1.

FIG. 4 is a view taken along the line IV-IV in FIG. In this electrode 3, even if the swelling state of the active material layer 20 is observed, as can be understood from FIG. 4, the swelling of the active material layer 20 at the edge 15 of the coating surface 10 of the current collector 1 is substantially Was not recognized. (Second Embodiment) A second embodiment will be described below with reference to FIGS. In this embodiment, a current collector, a paste-like active material,
The application form of the paste-like active material was the same as in the first embodiment.

That is, in this embodiment, a foil-shaped aluminum current collector 1B is used. The current collector 1B has a rectangular shape, and has long sides 1a and 1b facing each other and short sides 1e and 1d facing each other. The current collector 1B has a length A of about 100 mm, a width B of about 50 mm, and a thickness of about 20 μm. The current collector 1B has an application surface 10B (size: L1 × B).

However, in this embodiment, instead of applying a hydrophilic substance, the surface 10 to be coated of the current collector 1B is not coated.
In B, a large number of small cuts 7 were formed at a predetermined pitch interval P1 in the frame-shaped edge 15B, and a cut group 70 was formed. As shown in FIG. 5, the cut group 70 including a large number of cuts 7 is arranged in a U-shape as a whole. The length L3 of the cut 7 was 1 mm. The ends 7a of the cuts 7 are located on the long sides 1a and 1b and the short side 1e. In this embodiment, the cut 7 is formed by cutting with a cutter knife.

Thereafter, a paste-like active material 20X was applied to the application surface 10B (including the cut 7 and the central region 17B) of the current collector 1B to form an active material layer 20B. The basic composition of the paste active material 20X was the same as in the first embodiment. The target thickness of the active material layer 20B was 70 μm. The application was performed by the doctor blade method in a state where the current collector was mounted on the flat mounting surface of the holding table, as in the first embodiment. Of course, the paste-like active material 20X was also applied to the edge 15B where the cut 7 was formed in the application surface 10B of the current collector 1B. Thereafter, the electrode 3B shown in FIG. 6 was formed after drying. The electrode 3B includes a current collector 1B and an active material layer 20B.

The pitch interval P1 of the above-mentioned cut 7 is set to 0.
The present inventor conducted a test for measuring the swelling of the edge 15B of the coated surface 10B of the current collector 1B by appropriately changing the thickness within a range of about 2.5 mm. The measurement was performed in a state where the current collector 1B was corrected to a correct posture, even if the current collector 1B was rounded. The test results are shown in FIG. The horizontal axis in FIG. 7 indicates the pitch interval P1 of the cut 7 and the vertical axis indicates the edge 1 of the current collector 1B.
The swelling at 5B is shown. The protrusion is 50% when the thickness of the active material layer 20B in the central region 17B of the coated surface 10B is 100%, and the protrusion is 50%, that is, the thickness is 150%. Means that.

As shown in the test results shown in FIG.
The effect of reducing swelling was recognized by forming. In other words, the pitch interval P1 of the cut 7
Became smaller, that is, as the number of cuts 7 increased, the swell decreased. When the cut 7 was not formed, the swell was about 50%.

In this test, the pitch P of the cut 7
When 1 was 2.5 mm, the swell was about 25%. Pitch interval P1 of cut 7 is 1.5 mm or more
At 2.0 mm, the swell was near 0%. When the pitch interval P1 of the cut 7 becomes further smaller,
The excitement was negative. When the pitch P1 of the cut 7 is 0.5 mm, the swell is -50%.
It was close to

The fact that the swell is negative means that the thickness of the active material layer 20B at the edge 15B
B means thinner than the thickness of the active material layer 20B. In this case, the active material layer 20 at the edge 15B
Although the thickness of B is reduced, even in this case, unlike the related art, cracks and cracks in the active material layer 20B can be effectively suppressed, which is preferable for securing battery performance.

If the thickness of the active material layer 20B at the edge 15B becomes excessive due to swelling as in the prior art, the frequency of cracks and cracks in the active material layer 20B increases, so that the battery performance is increased. It is not preferable to secure
In order to ensure the battery performance while taking the above test results into consideration, under the conditions according to the above embodiment, the upper limit value of the pitch P1 of the cut 7 is 3 mm, 2.5
mm, 2.0 mm, and the lower limit is 0.3 mm,
Although 0.5 mm can be adopted, it is not limited to these.

(Third Embodiment) Hereinafter, a third embodiment will be described with reference to FIGS.
This will be described with reference to FIG. In the present embodiment, the current collector, the paste-like active material, and the application form of the paste-like active material were the same as those in the above-described Example 1. However, in this embodiment,
Instead of applying a hydrophilic substance, a large number of fine holes 8 are equally formed on a rectangular frame-shaped edge 15C (width E3 = 3 mm) of a coating surface 10C of a foil-shaped current collector 1C. A hole group 80 was formed in a dispersed state. In this embodiment, the diameter of the hole 8 is 0.1 mm. The hole 8 was formed by a drilling tool so that the tip of the drilling tool penetrated.

After forming the holes 8, the paste active material 20X was applied to the application surface 10C of the current collector 1C. Of course, the paste-like active material 20X was also applied to the edge 15C of the coating surface 10C where the hole 8 was formed. After drying, an electrode 3C shown in FIG. 9 was obtained. The electrode 3C includes a current collector 1C and an active material layer 20C. Current collector 1
In the area of the edge 15C of C (width E3 = 3 mm), the hole 8
Change the area ratio occupied within the range of 0 to 50%,
The present inventor conducted a test for measuring the swelling of the active material layer 20C.

FIG. 10 shows the test results. The horizontal axis in FIG. 10 indicates the area ratio of the hole 8 to the area of the edge 15C of the current collector 1C, and the vertical axis indicates the swelling of the edge 15C of the current collector 1C. In this test, the area ratio of the holes 8 is [(total area of many holes 8) / (total area of edge 15C)] ×
It was determined at 100%. The area of one hole 8 was considered to be the hole area of the drilling tool. Then, the total area of the holes 8 was obtained based on the product of the hole area of the drilling tool and the total number of the holes 8.

As shown in the test results shown in FIG. 10, when the area ratio of the holes 8 was small, the swell was large. As the area ratio of the holes 8 increased, the swelling became smaller. Specifically, when the area ratio of the holes 8 was 0%, that is, when the holes 8 were not formed, the swell was about 50%. However, as the area ratio of the holes 8 increased, the swell sharply decreased. In this test, when the area ratio of the holes 8 was 10%, the swell was about -25%. Thereafter, even if the area ratio of the holes 8 increased, the swell did not change much. In consideration of the above test results and the securing of the current collecting area of the current collector, the lower limit of the area ratio of the hole 8 to the area of the edge 15C can be 3%, 5%, and 10%, and the upper limit is 3%. Can be adopted as 40%, 30%, and 20%, but is not limited thereto.

(Others) The present invention is not limited to the above-described embodiment, but can be implemented with appropriate modifications as needed. For example, the cut length, the cut pitch interval, the hole diameter, the hole area ratio, and the like are not limited to those described above, and can be appropriately selected as needed.

In the method of the present invention, the foil-shaped current collector may have both cuts and holes. Or,
It is good also as a form which has both a substance which has hydrophilicity and a cut. Alternatively, a form having both a hydrophilic substance and holes may be used.

[0034]

According to the first invention method and the second invention method,
This is advantageous in suppressing the rise of the active material layer at the edge of the foil-shaped current collector.

[Brief description of the drawings]

FIG. 1 is a plan view of a foil-like current collector according to a first embodiment.

FIG. 2 is a configuration diagram illustrating a process of manufacturing an electrode.

FIG. 3 is a perspective view of an electrode.

FIG. 4 is a view taken along line IV-IV in FIG. 3;

FIG. 5 is a plan view of a foil-shaped current collector according to the second embodiment.

FIG. 6 is a perspective view of an electrode.

FIG. 7 is a graph showing a relationship between a pitch interval of a cut and a swell.

FIG. 8 is a plan view of a foil-shaped current collector according to the third embodiment.

FIG. 9 is a perspective view of an electrode.

FIG. 10 is a graph showing a relationship between a hole area ratio and a swell.

FIG. 11 is a perspective view of an electrode according to the related art.

FIG. 12 is a configuration diagram illustrating a process of manufacturing an electrode.

FIG. 13 shows XI in FIG. 11 when a swell occurs
FIG. 3 is a cross-sectional view taken along line II-XIII.

[Explanation of symbols]

In the drawing, 1 is a current collector, 10 is a surface to be coated, 15 is an edge, 17
Denotes a central region, and 20 denotes an active material layer.

Claims (3)

[Claims] 1. A method for producing an electrode by coating a paste-like active material on a surface to be coated of a foil-like current collector to cover an active material layer, wherein the method comprises the steps of: A method for manufacturing an electrode, wherein an edge portion is made more hydrophilic than a central region thereof, and thereafter, a paste-like active material is applied to a surface to be applied of the current collector. 2. The method according to claim 1, wherein the means for rendering hydrophilic include:
A method for producing an electrode, characterized by applying a hydrophilic substance. 3. A method for producing an electrode by coating a paste-like active material on a surface to be coated of a foil-like current collector to cover the active material layer, wherein the method comprises the steps of: A method for manufacturing an electrode, comprising forming irregularities on an edge portion, and thereafter applying a paste-like active material to a surface to be applied of the current collector.