JPH11138327A - Cutting method for battery electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a large burr of an electrode collector from generating on a cut surface by cutting a battery electrode in a heated condition at a specified temperature. SOLUTION: A battery electrode 1 provided with an electrode active material layer 3 on an electrode collector 2 is cut in a heated condition within a range of 60-135 deg.C, preferably 80-135 deg.C. When the heating temperature of the battery electrode 1 at the time of cutting is below 60 deg.C, the softening of a binder forming the electrode active material layer 3 is insufficient, and a cutting load from a cutting blade is dispersed by the electrode active material layer, and is not concentrated to the electrode collector 2 to cause elongation in the electrode collector 2, causing the large burr 5 of the electrode collector 2. While, when the heating temperature of the battery electrode 1 at the time of cutting exceeds 135 deg.C, the large burr 5 of the electrode collector 2 in a cut surface can be prevented, but another defect of separation of the electrode active material layer 3 from the electrode collector 2 is caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an electrode for a non-aqueous electrolyte battery, and more particularly to a method for cutting an electrode for a battery.

[0002]

2. Description of the Related Art An electrode for a nonaqueous electrolyte battery, for example, an electrode for a lithium ion secondary battery, is one in which an electrode active material layer is formed on both surfaces of a metal electrode current collector. The electrode active material layer is formed by a method in which a coating material in which the electrode active material is dispersed in a binder is applied to one surface of the electrode current collector and dried, and then applied to the other surface and dried. Or,
It is formed by a method in which the paint is simultaneously applied to both surfaces of the electrode current collector and dried. The battery electrode in which the electrode active material layers are formed on both surfaces of the electrode current collector as described above,
It is pressed, cut into desired dimensions, and used.

[0003] The above-mentioned cutting of the battery electrode generally includes a slitting step of forming the electrode into a predetermined width along the manufacturing flow direction and a cutting step of cutting the battery electrode having the predetermined width into a desired length. Become. The cutting of the battery electrode in the slitting step is performed by, for example, a shearing method, a ganging method, or the like. In the shear method, a rotating shaft equipped with multiple thin blades as round blades and a rotating shaft equipped with multiple thick lower blades as round blades are arranged in parallel. Each of the rotating shafts is rotated in a state of contact, and cutting is performed by shearing force. The gang method is a method of cutting by shearing force as in the shear method, and a round blade having a rectangular cross section is alternately and parallelly assembled for each slit on two rotating shafts. ) Is divided into two stages and emerges from the blade, so that they do not interfere with each other. Both the shearing method and the gang-type cutting means shear the object to be cut, and do not cut with a sharp blade.

[0004]

However, when the battery electrode in which the electrode active material layers are formed on both sides of the electrode current collector is cut by the above-described shearing force, burrs of the electrode current collector are formed on the cut surface. Occur. This is because the cutting load from the cutting blade is dispersed by the electrode active material layers present on both sides of the electrode current collector and does not concentrate on the electrode current collector. Since it is cut in the state, it is considered that burrs are generated. In particular, in the negative electrode for a lithium ion secondary battery, since rolled copper foil is used as an electrode current collector, generation of burrs of the electrode current collector on the cut surface as described above is observed. As such burrs of the electrode current collector, if there are large burrs that protrude from the cut surface to above the electrode active material layer, a problem such as breaking through the separator and short-circuiting the negative electrode and the positive electrode inside the battery occurs. There was a problem.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a cutting method capable of cutting a battery electrode without generating a large burr of an electrode current collector on a cut surface. Aim.

[0006]

In order to achieve the above object, the present invention provides a method for cutting a battery electrode in which an electrode active material layer is provided on an electrode current collector.
The configuration was such that cutting was performed in a state of being heated within a range of 135 ° C.

[0007] In the present invention, the battery electrode has 60 electrodes.
By being heated within the range of about 135 ° C., the cutting blade easily penetrates into the electrode active material layer, and the cutting is concentrated on the electrode current collector without dispersing the cutting load from the cutting blade.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

According to the method for cutting a battery electrode of the present invention, a battery electrode having an electrode active material layer provided on an electrode current collector is used for cutting a battery electrode of 60 to 13 times.
The cutting is carried out while heating at 5 ° C, preferably within the range of 80 to 135 ° C. If the heating temperature of the battery electrode at the time of cutting is lower than 60 ° C., the binder constituting the electrode active material layer is insufficiently softened, and the cutting load from the cutting blade is dispersed by the electrode active material layer, so that the electrode collection is not performed. Without being concentrated on the current collector, the electrode current collector is extended, and large burrs of the electrode current collector are generated on the cut surface. On the other hand, when the heating temperature of the battery electrode at the time of cutting exceeds 135 ° C., large burrs of the electrode current collector are prevented from being generated on the cut surface, but the electrode active material layer is separated from the electrode current collector. Another drawback occurs. In addition, 80-
By heating in the range of 135 ° C., the binder of the electrode active material layer is further softened, and the penetration of the cutting blade becomes easier.

[0010] Here, the burr in the present invention is, as shown in FIG. 1, a cut surface 4 of a battery electrode 1 having electrode active material layers 3, 3 on both sides of an electrode current collector 2. The burr 5 protrudes from the current collector 2.

In the electrode active material layer heated within the above temperature range, the binder is softened and the cutting blade is easily penetrated, and the cutting load from the cutting blade is concentrated on the electrode current collector without being dispersed. The electrode can be cut in a state where the electrode current collector hardly extends. Thus, the battery electrode can be cut without causing large burrs of the electrode current collector on the cut surface. Here, the large burr is a burr that satisfies the relationship h ≧ t between the height h of the burr 5 and the thickness t of the electrode active material layer 3 in FIG. Such large burrs protrude from the cut surface to above the electrode active material layer, break through the separator, and cause problems such as a short circuit between the negative electrode and the positive electrode inside the battery.

As the cutting means used in the method for cutting a battery electrode of the present invention, any cutting means conventionally used for slitting or cutting a battery electrode can be used. Examples of the cutting means in the slit include a shear method, a score method, a gang method, and the like. The shape of the cutting blade to be used is not particularly limited, and any conventionally used cutting blade, for example, a Goebel type, a right angle type, or the like can be used.

In the present invention, the method for heating the battery electrode in the range of 60 to 135 ° C. at the time of cutting is as follows.
There is no particular limitation, and examples thereof include a method of heating with an infrared image furnace, a method of blowing hot air, and a method of heating with a furnace using a heating wire such as a panel heater.

Next, a battery electrode to which the cutting method of the present invention is applied will be described.

The battery electrode to which the cutting method of the present invention is applied is a battery electrode in which an electrode active material layer is provided on an electrode current collector.

As the above-mentioned electrode current collector, a metal foil or a punching metal is preferably used. The metal material of the electrode current collector is not particularly limited, as long as it is conventionally used for the electrode current collector. Specific examples of such a metal material include copper, aluminum, stainless steel, nickel, iron and the like.

The electrode active material layer includes at least an electrode active material,
A method of applying a coating containing a binder and a solvent to one surface of the electrode current collector and drying, and then applying and drying the other surface to the other surface of the electrode current collector. It is formed by a drying method.

The electrode active material is not particularly limited as long as it has been conventionally used as an electrode active material. The material of the electrode active material may differ depending on whether it is used as a negative electrode or a positive electrode.

As the negative electrode active material, a carbonaceous material is usually used. As the carbonaceous material, any conventionally used carbonaceous material can be used without any particular limitation.For example, amorphous carbon, acetylene black, petroleum coke, coal coke, artificial graphite, graphite-based carbon fiber And non-graphitizable carbon.

On the other hand, the positive electrode active material can be used without any particular limitation as long as it has been conventionally used. As such a positive electrode active material, for example, various positive electrode active materials such as lithium cobaltate and lithium manganate can be used.

As the binder constituting the electrode active material layer, any conventionally used binder can be used without particular limitation. Specifically, polyacrylonitrile (PAN), polyethylene terephthalate, polyvinylidene fluoride (PVDF), polyvinyl fluoride, or the like can be used. Such a binder is usually 1 to 40 parts by weight based on 100 parts by weight of the electrode active material.
Parts by weight, preferably 2 to 25 parts by weight, particularly preferably 5 parts by weight.
Used in an amount of １５15 parts by weight.

The solvent used in the paint for the electrode active material layer is
Any solvent conventionally used for this purpose can be used without particular limitation. As such a solvent, for example, N-methylpyrrolidone (NMP), pyrrolidone, N-methylthiopyrrolidone, dimethylformamide (DMF), dimethylacetamide, hexamethylphosphamide, or the like can be used alone or in combination. . Such a solvent usually has a solid content (non-volatile content) in the coating material for the electrode active material layer of 10 to 60% by weight,
Preferably 30 to 50% by weight, particularly preferably 35 to 4%.
It can be used in a range of 5% by weight.

The coating of the above-mentioned material onto the electrode current collector can be applied by a conventionally known method, for example, extrusion coating, gravure coating, reverse roll coating, dip coating, kiss coating, doctor coating, knife coating, curtain coating. It can be performed by a coating method such as coating or screen printing.

[0024]

Next, the present invention will be described in more detail with reference to examples. Preparation of Battery Electrode A slurry-like negative electrode paint having the following composition was prepared.

(Composition of negative electrode paint) Graphite (negative electrode active material) 100 parts by weight Acetylene black (conductive agent) 5 parts by weight Polyvinylidene fluoride (PVDF) (binder) 10 parts by weight N-methyl Pyrrolidone (NMP) (solvent) ... 115 parts by weight-Oxalic acid dihydrate (additive) ... 1 part by weight To prepare the above slurry-like negative electrode coating material, first, 10 parts by weight of a binder was reduced to 50 parts by weight of a solvent. Dissolve and Lacquer 6
0 parts by weight were produced. Next, 10 parts by weight of the lacquer was added to 5 parts by weight of acetylene black and kneaded. The remaining 50 parts by weight of the lacquer and 65 parts by weight of the solvent were added to the kneaded material and mixed well. After mixing, 1 part by weight of oxalic acid dihydrate was added to obtain a negative electrode paint.

Next, the above-mentioned negative electrode paint is applied to one surface of an electrode current collector made of a copper foil having a thickness of 18 μm by extrusion coating, and then dried in a drying oven at 110 ° C. to form an electrode active material layer. did. Thereafter, the same coating operation was performed on the other surface of the copper foil to form an electrode active material layer. The electrode current collector having the electrode active material layers formed on both sides as described above was compression-molded by applying a roller press. Thus, a battery electrode in which the thickness t of the electrode active material layer on one side was 100 mm was obtained. Cutting of battery electrode Next, the above-mentioned battery electrode was cut into 60 pieces using a panel heater.
While heating to ℃, it was cut (slit) with a shear type right angle type blade to obtain a cut battery electrode (sample 1).

The heating temperature of the battery electrode was 9
Except that the temperature was set at 0 ° C., 120 ° C., and 135 ° C., cutting (slitting) was performed in the same manner as in Sample 1 described above to obtain cut battery electrodes (Samples 2 to 4).

On the other hand, for comparison, a cut (slit) was performed in the same manner as in Sample 1 except that the battery electrode was not heated to obtain a cut battery electrode (Comparative Sample 1).

Further, the heating temperature of the battery electrode is set to 140 ° C.
Was cut (slit) in the same manner as in the above-mentioned sample 1 except that the sample was set to, and a cut battery electrode (comparative sample 2) was obtained. Evaluation of cut surface The cut surface of each battery electrode (samples 1 to 4 and comparative samples 1 and 2) cut (slit) as described above was evaluated by the following method, and the results are shown in Table 1 below. .

(Evaluation Method of Cut Surface) A total of 6 sections of the upper blade section and the lower blade section of the battery electrode, 25 mm per section
Was observed with a projector, and the number of burrs of the electrode current collector (copper foil) satisfying the following conditions was obtained.

Condition A: The height of the burr is equal to or greater than the thickness of the electrode active material layer (the relationship h ≧ t is established between the height h of the burr and the thickness t of the electrode active material layer shown in FIG. 1). Condition B: The height of the burr is smaller than the thickness of the electrode active material layer (the height h of the burr and the thickness t of the electrode active material layer shown in FIG. 1).
And the relationship h <t holds.)

[0032]

[Table 1] As shown in Table 1, all of the samples 1 to 4 cut (slit) by the cutting method of the present invention have no large burrs (burrs under the condition A) on the cut surface. In addition, although small burrs (burrs under the condition B) exist on the cut surfaces of the samples 1 to 4, such burrs break through the separator and cause problems such as a short circuit between the negative electrode and the positive electrode inside the battery. There is no. In Samples 1 to 4, the number of small burrs (burrs under the condition B) was reduced as the heating temperature at the time of cutting was increased.
It was confirmed that heating the battery electrode to a higher temperature within the range of 135 ° C. was effective for preventing burr generation.

On the other hand, in Comparative Sample 1 in which the battery electrode was not heated at the time of cutting, large burrs (condition A
And a large number of such burrs were present and could not be used as a battery electrode. In Comparative Sample 2 in which the battery electrode was heated to 140 ° C. at the time of cutting, the electrode active material layer was separated from the electrode current collector, and the battery electrode could not be cut.

[0034]

As described in detail above, according to the present invention, a battery electrode having an electrode active material layer provided on an electrode current collector can be used in a range of 60 to 60.
Since cutting is performed in a state of being heated within the range of 135 ° C., the binder is softened in the electrode active material layer, so that the cutting blade easily penetrates, and the cutting load from the cutting blade is dispersed by the presence of the electrode active material layer. Therefore, it is possible to cut the electrode current collector in a state where the electrode current collector is hardly stretched, thereby preventing large burrs of the electrode current collector on the cut surface.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an example of a battery electrode and burrs applied to a cutting method of the present invention.

[Description of Signs] 1 ... Battery electrode 2 ... Electrode current collector 3 ... Electrode active material layer 4 ... Cutting surface 5 ... Burr h ... Burr height t ... Thickness of electrode active material layer

Claims (1)

[Claims] 1. A method for cutting a battery electrode in which an electrode active material layer is provided on an electrode current collector, comprising:
A method for cutting an electrode for a battery, characterized in that the electrode is cut while being heated within a range of 5 ° C.