JP2021068510A - Method for producing electrode sheet - Google Patents

Abstract

To provide a method for producing an electrode sheet, with which the binding strength between both ends of a mixture and a current collector foil can be increased.SOLUTION: A method for producing an electrode sheet includes: a film formation step (S2) of forming a current collector foil 9 with a membrane electrode mixture having a membrane electrode mixture 8 on the surface of a current collector foil 7; and a drying step (S3) of drying the membrane electrode mixture 8 of the current collector foil 9 with a membrane electrode mixture, thereby forming an electrode mixture layer 18 on the surface of the current collector foil 7. In the method for producing an electrode sheet, the film formation step (S2) includes a densification step of making the density of mixture both ends 8c, 8d that are located at both ends of the membrane electrode mixture 8 in a width direction WD higher than the density of a mixture intermediate part 8b that is located between the mixture both ends 8c, 8d in the width direction WD, in the membrane electrode mixture 8.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for manufacturing an electrode sheet constituting a battery. More specifically, the present invention relates to a method for producing an electrode sheet having an electrode mixture layer on the surface of a current collector foil.

Conventionally, as an electrode sheet (positive electrode sheet or negative electrode sheet), an electrode sheet having an electrode mixture layer on the surface of a current collector foil is known. As a method for producing such an electrode sheet, for example, a method disclosed in Patent Documents 1 and 2 is known. Specifically, first, an electrode mixture composed of a plurality of wet granulated materials obtained by mixing an electrode active material, a binder, and a solvent is produced.

Japanese Unexamined Patent Publication No. 2013-052353 Japanese Unexamined Patent Publication No. 2016-20740

Next, in the film forming step, the electrode mixture is made into a film while being compressed by passing the electrode mixture through the gap between the first roll and the second roll that rotate opposite to each other, and the electrode mixture is formed into a film. Adhere to the surface of the second roll. Further, the current collecting foil conveyed by the third roll, which rotates facing the second roll, is passed through the gap between the second roll and the third roll, so that the film is attached to the surface of the second roll. The electrode mixture of No. 1 is brought into contact with the surface of the current collector foil while being pressurized, and transferred onto the surface of the current collector foil. As a result, a current collector foil with a film-like electrode mixture having a film-like electrode mixture on the surface of the current collector foil is produced.

Then, in the drying step, the film-like electrode mixture of the current collector foil with the film-like electrode mixture is dried to form an electrode mixture layer on the surface of the current collector foil. As a result, an electrode sheet in which an electrode mixture layer is formed on the surface of the current collector foil is produced.

By the way, in the electrode sheet produced as described above (dried current collector foil with film-like electrode mixture), both ends in the width direction of the electrode mixture layer (dried film-like electrode mixture). The binding force between both ends of the mixture located at the portion and the surface of the current collector foil is weak (the bond between the intermediate portion of the mixture located between both ends of the mixture in the width direction and the surface of the current collector foil). It was weaker than the force of application), and both ends of the mixture were easily peeled off from the surface of the current collector foil. Therefore, there has been a demand for a method for manufacturing an electrode sheet capable of increasing the binding force between both ends of the mixture and the current collector foil.

The present invention has been made in view of the present situation, and an object of the present invention is to provide a method for manufacturing an electrode sheet capable of enhancing the binding force between both ends of a mixture and a current collector foil.

One aspect of the present invention is a method for producing an electrode sheet having an electrode mixture layer on the surface of a current collector foil, in which an electrode active material, a binder, and a solvent are mixed and granulated. By passing the electrode mixture composed of the plurality of wet granulated bodies in the gap between the first roll and the second roll rotating in opposition to each other, the electrode mixture is compressed and formed into a film to form a film. The electrode mixture is attached to the surface of the second roll, and the current collecting foil conveyed by the third roll that rotates in opposition to the second roll is combined with the second roll and the third roll. By passing it through the gap between the two rolls, the film-like electrode mixture, which is the film-like electrode mixture adhering to the surface of the second roll, is brought into contact with the surface of the current collector foil while being pressed. A film forming step of transferring onto the surface of the current collector foil to prepare a current collector foil with a film-like electrode mixture having the film-like electrode mixture on the surface of the current collector foil, and the film-like film. In a method for manufacturing an electrode sheet, which comprises a drying step of forming the electrode mixture layer on the surface of the current collector foil by drying the film-shaped electrode mixture of the current collector foil with the electrode mixture. In the film forming step, in the film-like electrode mixture, the densities of both ends of the mixture located at both ends of the film-like electrode mixture in the width direction are located between both ends of the mixture in the width direction. This is a method for manufacturing an electrode sheet, which includes a densification step in which the density is higher than the density of the intermediate portion of the mixed material.

In the above-mentioned method for producing an electrode sheet, in the film forming step, an electrode mixture composed of a plurality of wet granulated bodies obtained by mixing an electrode active material, a binder and a solvent is rotated to face each other. By passing it through the gap between the 1st roll and the 2nd roll, the electrode mixture is compressed and formed into a film, and the film-shaped electrode mixture is attached to the surface of the 2nd roll and faces the 2nd roll. By passing the current collecting foil conveyed by the rotating third roll through the gap between the second roll and the third roll, a film-like electrode mixture (film-like electrode) adhering to the surface of the second roll The mixture material) is brought into contact with the surface of the current collector foil while being pressurized, and transferred onto the surface of the current collector foil. As a result, a current collector foil with a film-like electrode mixture having a film-like electrode mixture on the surface of the current collector foil is produced.

Then, in the drying step, the film-like electrode mixture of the current collector foil with the film-like electrode mixture is dried to form an electrode mixture layer on the surface of the current collector foil. As a result, an electrode sheet in which an electrode mixture layer is formed on the surface of the current collector foil is produced.

In the electrode sheet thus produced (dried current collector foil with film-like electrode mixture), it is located at both ends in the width direction of the electrode mixture layer (dried film-like electrode mixture). The binding force between both ends of the mixture and the surface of the current collector foil is weak (weaker than the binding force between the intermediate portion of the mixture located between both ends of the mixture and the surface of the current collector foil in the width direction). ), Both ends of the mixture were easily peeled off from the surface of the collector foil.

On the other hand, in the above-mentioned method for manufacturing an electrode sheet, in the film forming step, in the film-like electrode mixture, the density (per unit volume) of both ends of the mixture located at both ends in the width direction of the film-like electrode mixture. Includes a densification step that increases the density of the mixture in the width direction higher than the density (mass per unit volume) of the intermediate portion of the mixture located between both ends of the mixture. By performing this densification step, the density of the binder at both ends of the mixture (for example, the density of the binder at both ends of the mixture in contact with the current collector foil) can be increased. It is possible to increase the number of binders that come into contact with (bond) the current collector foil at both ends of the material. Therefore, it is possible to increase the bonding area between both ends of the mixture by the binder and the current collector foil.

As a result, in the current collector foil with the film-like electrode mixture, the binding force between both ends of the mixture and the current collector foil can be enhanced. Therefore, even in the electrode sheet obtained by drying the current collector foil with the film-like electrode mixture, the binding force between both ends of the mixture and the current collector foil can be enhanced. Therefore, both ends of the mixture are less likely to be peeled off from the surface of the current collector foil. Furthermore, the binding force between the electrode active materials via the binder can be increased even in both ends of the mixture (the electrode active material can be easily bound to the binder in both ends of the mixture). It is also possible to reduce the detachment (falling off) of a part of both ends of the mixture (for example, a portion of both ends of the mixture on the surface side).

As a step of increasing the density, for example, in the film-like electrode mixture, both ends of the mixture located at both ends in the width direction are more than the middle portion of the mixture located between both ends of the mixture in the width direction. A step of making the density of both ends of the mixture higher than the density of the middle portion of the mixture by compressing the material significantly in the thickness direction (increasing the compression ratio) can be mentioned. The densification step of this example also includes a case where only both ends of the mixture are compressed (consolidated) in the thickness direction without compressing the intermediate portion of the mixture.

Further, as the step of increasing the density, for example, a step of transferring the film-shaped electrode mixture to the surface of the current collector foil and at the same time increasing the density of both ends of the mixture to be higher than the density of the middle portion of the mixture can be mentioned. Specifically, the film-like electrode mixture is adhered to the surface of the second roll so that the thickness of both ends of the mixture is thicker than the thickness of the middle part of the mixture, and then this film is formed. When the shape electrode mixture passes through the gap between the second roll and the third roll and is transferred to the surface of the current collector foil while being compressed in the thickness direction (at the same time as the transfer), the film-like electrode Both ends of the mixture, which are thicker than the middle part of the mixture, are compressed in the thickness direction larger than the middle part of the mixture (by being compressed at a high compression ratio), so that both ends of the mixture are compressed. The step of making the density of the mixture higher than the density of the intermediate portion of the mixture can be mentioned.

In addition, as another step of increasing the density, before the film-like electrode mixture is transferred to the surface of the current collecting foil in the gap between the second roll and the third roll, the density of both ends of the mixture is adjusted to the intermediate portion of the mixture. The process of making the density higher than the density can be mentioned. Specifically, regarding the transport direction of the film-like electrode mixture, the fourth roll (consolidation) facing the second roll is located at a position upstream of the position where the second roll and the third roll face each other with a gap. A roll to perform the conversion) is provided. In this fourth roll, the outer diameter of the portion (outer peripheral surface) of the film-like electrode mixture facing both ends of the mixture is made larger than the outer diameter of the portion (outer peripheral surface) facing the intermediate portion of the mixture. There is. Therefore, in the gap between the second roll and the fourth roll, the gap dimension of the film-like electrode mixture at the position where both ends of the mixture pass is smaller than the gap dimension at the position where the intermediate portion of the mixture passes. There is. As a result, when the film-like electrode mixture that adheres to the surface (outer peripheral surface) of the second roll and is conveyed passes through the gap between the second roll and the fourth roll, the film-like electrode mixture is mixed. A step of increasing the density of both ends of the mixture to be higher than the density of the intermediate part of the mixture by compressing both ends of the material in the thickness direction (compressed at a high compression rate) larger than the middle part of the mixture. be able to.

The wet granulated material refers to a substance (granular material) in which the solvent is held (absorbed) by the particles of the electrode active material and the binder, and these are aggregated (bonded).

It is a side view schematic diagram of the electrode sheet manufacturing apparatus which concerns on embodiment. FIG. 5 is a sectional view taken along the line CC of FIG. It is a flowchart which shows the flow of the manufacturing method of the electrode sheet which concerns on embodiment. It is sectional drawing of the electrode sheet (negative electrode sheet). It is a top view of the electrode sheet (negative electrode sheet). It is a side view schematic diagram of the electrode sheet manufacturing apparatus which concerns on a deformed form. FIG. 6 is a cross-sectional view taken along the line DD of FIG. FIG. 6 is an H perspective plan view of FIG. It is a figure which shows the relationship between the density ratio B / A and the binding force of both ends of a mixture. It is a figure which shows the relationship between the density ratio B / A and the amount of the residual solvent at both ends of a mixture. It is a figure which compares the binding force of both ends of a mixture.

<Embodiment>
Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings. In this embodiment, the present invention is applied to the production of a negative electrode sheet (electrode sheet) of a lithium ion secondary battery. In the present embodiment, as the material of the negative electrode mixture (electrode mixture) for forming the negative electrode active material layer (electrode mixture layer) of the negative electrode sheet, a negative electrode active material (electrode active material), a binder, and a binder are used. Use with a solvent.

In this embodiment, a powdered carbon material (for example, graphite) is used as the negative electrode active material. Moreover, water is used as a solvent. Moreover, CMC (carboxymethyl cellulose) is used as a binder.

In the present embodiment, first, in the electrode mixture manufacturing step, each of the above materials is kneaded and granulated to produce a large number of wet granulated bodies 16, and a negative electrode mixture composed of a large number of wet granulated bodies 16. 6 is made. Next, in the film forming step, the negative electrode mixture 6 is adhered (coated) on the surface of the current collector foil 7 in the form of a film, so that the film-like negative electrode mixture 8 (film) is formed on the surface of the current collector foil 7. Form electrode mixture) is formed. However, in this film forming step, in the film-like negative electrode mixture 8 (film-like electrode mixture), the densities of both ends 8c and 8d of the mixture located at both ends of the film-like negative mixture 8 in the width direction WD ( A densification step is included in which the mass per unit volume) is made higher than the density (mass per unit volume) of the intermediate portion 8b of the mixture located between both ends 8c and 8d of the mixture in the width direction WD. ..

Next, in the drying step, the film-like negative electrode mixture 8 (film of the negative electrode mixture 6) on the surface of the current collector foil 7 is dried, and the negative electrode mixture layer 18 (electrode combination) is placed on the surface of the current collector foil 7. Material layer) is formed. As a result, the negative electrode sheet 19 having the negative electrode mixture layer 18 on the surface of the current collector foil 7 is manufactured.

Here, the method of manufacturing the electrode sheet (negative electrode sheet 19) according to the present embodiment will be described in detail. FIG. 1 is a schematic side view of the electrode sheet manufacturing apparatus 10 according to the embodiment. FIG. 2 is a cross-sectional view taken along the line CC of FIG. FIG. 3 is a flowchart showing the flow of the manufacturing method of the electrode sheet (negative electrode sheet 19) according to the embodiment.

As shown in FIG. 1, the electrode sheet manufacturing apparatus 10 used in the present embodiment includes a roll film forming apparatus 20, a drying apparatus (not shown), and a winding apparatus (not shown). Although the drying device and the winding device are not shown in FIG. 1, the drying device is downstream of the roll film forming device 20 with respect to the transport direction CD of the current collector foil 9 with the film-like negative electrode mixture. Is located in. Further, the winding device is a device that winds the manufactured negative electrode sheet 19 by arranging the collecting foil 9 (negative electrode sheet 19) with the film-like negative electrode mixture in the transport direction CD downstream from the drying device. is there.

As shown in FIG. 3, first, in step S1 (electrode mixture manufacturing step), a large number of particles are granulated while mixing the negative electrode active material (carbon material), the binder (CMC), and the solvent (water). A wet granulated body 16 is produced, and a negative electrode mixture 6 composed of a large number of wet granulated bodies 16 is produced. In the present embodiment, the negative electrode active material, the binder and the solvent are mixed (dispersed) by putting the negative electrode active material, the binder and the solvent into a known stirring granulator (not shown) and stirring the mixture. While granulating, a large number of wet granulated bodies 16 are formed. As a result, the negative electrode mixture 6 composed of a large number of wet granulated materials 16 can be obtained.

The wet granulated material 16 is a substance (granular material) in which water, which is a solvent, is held (absorbed) by a plurality of negative electrode active material particles and a binder, and these are aggregated (bonded). .. The negative electrode mixture 6 is an aggregate of such wet granulated materials 16. Further, in the present embodiment, the negative electrode active material, the binder, and the solvent are mixed so that the solid content of the negative electrode mixture 6 (wet granulated material 16) is 70 wt% or more (for example, 78 wt%). There is.

Next, the process proceeds to step S2 (deposition step), the negative electrode mixture 6 produced in step S1 (electrode mixture production step) is made into a film, and the film-like negative electrode mixture 6 is formed on the surface of the current collector foil 7. Adhere on top. In this embodiment, step S2 (deposition step) is performed using the roll film forming apparatus 20 shown in FIGS. 1 and 2.

As shown in FIG. 1, the roll film forming apparatus 20 has three rolls, a first roll 1, a second roll 2, and a third roll 3. The first roll 1 and the second roll 2 are arranged side by side in the horizontal direction (horizontal direction in FIG. 1). On the other hand, the second roll 2 and the third roll 3 are arranged side by side in the vertical direction (vertical direction in FIG. 1). Further, the first roll 1 and the second roll 2 face each other (opposite) with a slight interval between them. Similarly, both the second roll 2 and the third roll 3 face each other with a slight interval. Further, partition plates 4 and 5 are arranged on the upper side of the facing portion between the first roll 1 and the second roll 2 so as to be separated from each other in the width direction of the roll (axial direction, direction orthogonal to the paper surface in FIG. 1). ing.

Further, the rotation directions of these three rolls 1 to 3 are such that the rotation directions of the two adjacent (facing) rolls are opposite to each other, that is, the two facing each other, as shown by the arrows in FIG. The rolls are set to rotate forward with each other. Then, at the points where the first roll 1 and the second roll 2 face each other, the surfaces of these rolls are set to move downward by rotation. Further, at the points where the second roll 2 and the third roll 3 face each other, the surfaces of these rolls are set to move to the right by rotation. Further, regarding the rotation speed, the moving speed of the surface of the roll due to rotation is set to be the slowest in the first roll 1, the fastest in the third roll 3, and intermediate between them in the second roll 2.

In such a roll film forming apparatus 20, step S1 (electrode mixture manufacturing step) is performed in the accommodation space between the partition plates 4 and 5 located above the facing portions of the first roll 1 and the second roll 2. The negative electrode mixture 6 produced in 1 above is charged. Further, a current collecting foil 7 is hung on the third roll 3.

The current collector foil 7 is a metal foil (copper foil) and has a thickness of about 10 μm. The current collecting foil 7 is conveyed from the lower right to the upper right of the third roll 3 through the facing portion (gap G2) between the second roll 2 and the third roll 3 together with the rotation of the third roll 3. It has become like. Further, in a state where the current collecting foil 7 is passed through the facing portion (gap G2) between the second roll 2 and the third roll 3, a slight amount of space is further between the second roll 2 and the current collecting foil 7. There is a gap. That is, the gap between the second roll 2 and the third roll 3 (the gap in the absence of the current collector foil 7) is slightly wider than the thickness of the current collector foil 7.

In this step S2 (deposition step), the negative electrode mixture 6 is passed through the gap G1 between the first roll 1 and the second roll 2 which rotate opposite to each other to form a film while compressing the negative electrode mixture 6. The film-shaped negative electrode mixture 6 is attached to the surface of the second roll 2. At the same time, the current collecting foil 7 conveyed by the third roll 3 that rotates in opposition to the second roll 2 is passed through the gap G2 between the second roll 2 and the third roll 3 to form the second roll 2. The film-like negative electrode mixture 6 adhering to the surface is brought into contact with the surface of the current collector foil 7 while being pressed, and transferred onto the surface of the current collector foil 7.

More specifically, first, the negative electrode mixture 6 produced in step S1 (electrode mixture production step) is put into the accommodation space between the partition plates 4 and 5 of the roll film forming apparatus 20. The charged negative electrode mixture 6 is supplied into the gap G1 at the position where the first roll 1 and the second roll 2 rotate so as to face each other, and both rolls are rotated by the rotation of the first roll 1 and the second roll 2. It passes through the gap G1 between 1 and 2 to form a film (see FIGS. 1 and 2). At this time, since the rotation speed of the second roll 2 is faster than that of the first roll 1, the negative electrode mixture 6 (wet granulated material 16) is supported on the surface of the second roll 2 in the form of a film (the surface of the second roll 2). Adhere to). Here, the film-like negative electrode mixture 6 supported (attached) on the surface of the second roll 2 is referred to as the film-like negative electrode mixture 8.

However, in the present embodiment, the portions of the first roll 1 that come into contact with the negative electrode mixture 6 are located at both ends 1c and 1d in the width direction (roll axis direction, vertical direction in FIG. 2, and the same direction as the width direction WD). The outer diameter is made smaller than the outer diameter of the intermediate portion 1b located between the both end portions 1c and 1d (see FIG. 2). The both end portions 1c and 1d of the first roll 1 are the portions forming the mixture end portions 8c and 8d located at both end portions of the film-like negative electrode mixture 8 with the second roll 2. On the other hand, the intermediate portion 1b of the first roll 1 is connected to the second roll 2 with the intermediate portion 8b of the mixed material of the film-like negative electrode mixture 8 (of the film-like negative electrode mixture 8, both ends 8c and 8d of the mixture). It is a part that forms (a part located between). On the other hand, the outer diameter of the portion of the second roll 2 that comes into contact with the negative electrode mixture 6 is constant (that is, it has a right cylindrical shape, see FIG. 2).

Therefore, in the gap G1 between the first roll 1 and the second roll 2, as shown in FIG. 2, the gap G12 at the portion where both ends 8c and 8d of the mixture located at both ends of the film-like negative electrode mixture 8 is formed. , G13 (radial dimension, left-right dimension in FIG. 2) is the dimension of the gap G11 (diametrical dimension, left-right direction in FIG. 2) at the portion forming the mixture intermediate portion 8b of the film-like negative electrode mixture 8. Dimension) is larger than. As a result, in the present embodiment, in the film-like negative electrode mixture 8 adhering to the surface (outer peripheral surface) of the second roll 2, the thickness of both ends 8c and 8d of the mixture becomes thicker than the thickness of the intermediate portion 8b of the mixture. (See FIG. 2). As described above, in the present embodiment, the film-like negative electrode is formed on the surface of the second roll 2 so that the thickness of both ends 8c and 8d of the film-like negative electrode mixture 8 is thicker than the thickness of the intermediate portion 8b of the mixture. The mixture 8 is attached.

Then, the film-like negative electrode mixture 8 supported (attached) on the surface of the second roll 2 is conveyed with the rotation of the second roll 2 (see FIG. 1). Then, at the point where the second roll 2 and the third roll 3 face each other, the surface of the current collector foil 7 and the film-like negative electrode mixture 8 meet, and the current collector foil is between the second roll 2 and the third roll 3. 7 and the film-like negative electrode mixture 8 are sandwiched. The dimensions (minimum gap dimensions) of the gap G2 at the positions facing the second roll 2 and the third roll 3 are the thickness of the current collector foil 7 and the thickness of the film-like negative electrode mixture 8 (details will be described later). It is made smaller than the sum with the thickness of the intermediate portion 8b).

Therefore, when the current collector foil 7 and the film-like negative electrode mixture 8 are sandwiched between the second roll 2 and the third roll 3, the film-like negative electrode mixture 8 is collected from the surface of the second roll 2. A pressing load is applied toward the surface of the electric foil 7. As a result, the film-like negative electrode mixture 8 adhering to the surface of the second roll 2 can be brought into contact with the surface of the current collector foil 7 while being pressed, so that the film-like negative electrode mixture 8 is the second. It is transferred (adhered) from the roll 2 onto the surface of the current collector foil 7 that is rotating together with the third roll 3. As a result, the current collector foil 9 with the film-like negative electrode mixture is obtained, in which the film-like negative electrode mixture 8 is formed on the surface of the current collector foil 7.

In the present embodiment, as described above, with respect to the film-like negative electrode mixture 8 that adheres to the surface of the second roll 2 and is conveyed toward the gap G2, the thicknesses of both ends 8c and 8d of the mixture are combined. It is thicker than the thickness of the material intermediate portion 8b (see FIG. 2). Further, the dimension of the gap G2 between the second roll 2 and the third roll 3 is constant. Therefore, when the film-like negative electrode mixture 8 is sandwiched between the second roll 2 and the third roll 3 and transferred to the surface of the current collector foil 7 while being compressed in the thickness direction (transferred). (At the same time), of the film-like negative electrode mixture 8, both ends 8c and 8d of the mixture, which are thicker than the intermediate portion 8b of the mixture, are compressed in the thickness direction more than the intermediate portion 8b of the mixture (at a high compression ratio). To be compressed). As a result, the density of both ends 8c and 8d of the mixture (mass per unit volume) can be made higher than the density of the intermediate portion 8b of the mixture (mass per unit volume).

The step of increasing the density of both ends 8c and 8d of the mixed material to be higher than the density of the intermediate portion 8b of the mixed material is called a densification step. As described above, in the present embodiment, the film forming step (step S2) includes a densification step. In the film forming step (step S2) of the present embodiment, the film-like negative electrode mixture 8 is transferred (formed) to the surface of the current collecting foil 7, and at the same time, the densities of both ends 8c and 8d of the mixture are set in the middle of the mixture. It is higher (higher density) than the density of part 8b. As a result, in the film forming step of the present embodiment, the current collection with the film-like negative electrode mixture having the film-like negative electrode mixture 8 in which the densities of both ends 8c and 8d of the mixture are higher than the density of the mixture intermediate 8b. The foil 9 is formed.

In the present embodiment, the film-like negative electrode mixture 8 is not formed on the surfaces of both ends (first end 7b and second end 7c) of the current collector foil 7 in the width direction WD. (See FIG. 2). The first end portion 7b and the second end portion 7c of the current collector foil 7 are used as parts for connecting to the terminal member of the battery.

Then, as shown in FIG. 3, the process proceeds to step S3 (drying step), and the current collecting foil 9 with the film-like negative electrode mixture is dried (the film-like negative electrode mixture 8 is dried). Specifically, the film-shaped negative electrode mixture 8 (membrane) transferred to the surface of the current collecting foil 7 by passing the current collecting foil 9 with the film-shaped negative electrode mixture through the inside of a drying device (drying furnace) (not shown). The negative electrode mixture 6) is dried. As a result, the solvent (water) absorbed (retained) in the film-like negative electrode mixture 8 (wet granulated body 16) is removed (evaporated), and the film-like negative electrode mixture 8 becomes the negative electrode mixture layer 18. (Electrode mixture layer). As a result, the negative electrode sheet 19 (see FIG. 4) in which the negative electrode mixture layer 18 is formed on the surface of the current collector foil 7 is produced. Of the negative electrode mixture layer 18, the portions located at both ends of the WD in the width direction are defined as the ends 18c and 18d of the mixture (the ends 8c and 8d of the mixture are dried), and the mixture is WD in the width direction. The portion located between the both end portions 18c and 18d is defined as the mixed material intermediate portion 18b (the mixed material intermediate portion 8b is dried) (see FIG. 5).

By the way, in the electrode sheet (for example, the negative electrode sheet) manufactured by the conventional manufacturing method (for example, Patent Documents 1 and 2), the electrode sheet is located at both ends in the width direction of the electrode mixture layer (for example, the negative electrode mixture layer). The binding force between both ends of the mixture and the surface of the current collector foil is weak (weaker than the binding force between the intermediate portion of the mixture located between both ends of the mixture and the surface of the current collector foil in the width direction). ), Both ends of the mixture were easily peeled off from the surface of the collector foil. Therefore, for example, when a terminal member is bonded (for example, ultrasonic welding) to an electrode sheet (for example, a negative electrode sheet), both ends of the mixture are peeled off from the surface of the current collector foil due to the influence of vibration generated during bonding. There was a risk of dropping out.

On the other hand, in the manufacturing method of the present embodiment, as described above, the film forming step (step S2) is located at both ends of the film-like negative electrode mixture 8 (film-like electrode mixture) in the width direction WD. It includes a densification step of increasing the density of both ends 8c and 8d of the material to be higher than the density of the intermediate portion 8b of the mixture located between both ends 8c and 8d of the mixture in the width direction WD. By performing this densification step, the density of the binder at both ends 8c and 8d of the mixture can be increased, so that the surfaces of the current collector foil 7 are contacted (bonded) at both ends 8c and 8d of the mixture. The number of binders to be used can be increased. Therefore, it is possible to increase the bonding area between both ends 8c and 8d of the mixture by the binder and the surface of the current collector foil 7.

As a result, in the current collector foil 9 with the film-like negative electrode mixture (the current collector foil with the film-like electrode mixture), both ends 8c and 8d of the mixture (the first end 8c of the mixture and the second end 8d of the mixture). It is possible to increase the binding force between the current collector foil 7 and the surface of the current collector foil 7. Therefore, in the current collector foil 9 with the film-like electrode mixture, both ends 8c and 8d of the mixture are less likely to be peeled off from the surface of the current collector foil 7. Further, also in the negative electrode sheet 19 (electrode sheet) obtained by drying the current collector foil 9 with the film-like negative electrode mixture, both ends 18c and 18d of the mixture (the first end 18c of the mixture and the second end 18d of the mixture 18d). ) And the surface of the current collector foil 7 can be enhanced. Therefore, in the negative electrode sheet 19 (electrode sheet), both ends 18c and 18d of the mixture material are less likely to be peeled off from the surface of the current collector foil 7.

Further, the binding force between the negative electrode active materials (electrode active materials) via the binder can be enhanced in both ends 8c, 8d, 18c, 18d of the mixture (both ends 8c, 8d, 18c of the mixture). , The negative electrode active material tends to bind to the binder within 18d). As a result, it is possible to reduce the detachment (falling off) of a part of both ends 8c, 8d, 18c, 18d of the mixture (for example, the surface side portion of the ends 8c, 8d, 18c, 18d of the mixture). Can be done.

The negative electrode mixture layer 18 may be formed on only one side of the current collector foil 7 (that is, a single-sided coated negative electrode sheet is manufactured), or may be formed on both sides (that is, a double-sided coated negative electrode sheet). May be manufactured). When the negative electrode mixture layer 18 is formed on both sides of the current collector foil 7, a single-sided coated negative electrode sheet having the negative electrode mixture layer 18 formed on one side of the current collector foil 7 is manufactured, and then the single-sided coated negative electrode sheet is used. The treatments of steps S2 and S3 may be sequentially performed on the surface of the current collector foil 7 on which the negative electrode mixture layer 18 is not formed.

The produced negative electrode sheet 19 can be used, for example, as a negative electrode sheet for a lithium ion secondary battery. Specifically, for example, the negative electrode sheet 19 is cut at the center position in the width direction of the negative electrode sheet 19 and then cut to a predetermined length to form the first end portion 18c of the mixture or the second end 18d of the mixture. It is a negative electrode sheet having a predetermined shape. This negative electrode sheet is combined with the positive electrode sheet and the separator to form an electrode body. Next, after attaching the terminal members to the positive electrode sheet and the negative electrode sheet of the electrode body, respectively, the electrode body and the electrolytic solution are housed in the battery case. This completes the lithium ion secondary battery.

By the way, ultrasonic welding may be used as a method of attaching a terminal member to a negative electrode sheet of an electrode body. When a terminal member is bonded to a negative electrode sheet by ultrasonic welding, vibration is transmitted to the first end portion 18c of the mixture material or the second end portion 18d of the mixture material of the negative electrode sheet. Since the bonding force between both ends 18c and 18d (first end 18c of the composite material and 18d of the second end of the mixture) and the surface of the current collector foil 7 is enhanced, the influence of propagated vibration during ultrasonic welding is increased. Therefore, it is possible to prevent the first end portion 18c of the mixed material or the second end portion 18d of the mixed material from peeling off from the surface of the current collecting foil 7 and falling off.

(Examples 1 to 4)
As the first roll 1, four types of first rolls 1 (Examples 1 to 4) having the same outer diameter of the intermediate portion 1b but different outer diameters of both end portions 1c and 1d are prepared, and the first rolls 1 of each are prepared. Four types (Examples 1 to 4) of negative electrode sheets 19 were produced using four types of electrode sheet manufacturing devices 10 provided with rolls 1 (Examples 1 to 4). In the electrode sheet manufacturing apparatus 10 (roll film forming apparatus 20) of Examples 1 to 4, since the outer diameters of both ends 1c and 1d of the first roll 1 are different, the gap G1 between the first roll 1 and the second roll 2 is different. Of these, the dimensions (see FIG. 2) of the gaps G12 and G13 at the locations where both ends 8c and 8d of the film-like negative electrode mixture 8 are formed are different.

Therefore, in Examples 1 to 4, the thicknesses of both ends 8c and 8d of the mixed material are different with respect to the film-like negative electrode mixed material 8 that adheres to the surface of the second roll 2 and is conveyed toward the gap G2. On the other hand, in Examples 1 to 4, the dimensions of the gap G2 between the second roll 2 and the third roll 3 are the same. Therefore, in Examples 1 to 4, the film-like negative electrode mixture 8 is sandwiched between the second roll 2 and the third roll 3, and is transferred to the surface of the current collector foil 7 while being compressed in the thickness direction. At this time, the compression rates of the intermediate parts 8b of the mixed material are the same, but the compression rates of both ends 8c and 8d of the mixed material are different. Therefore, in Examples 1 to 4, in the current collector foil 9 with the film-like negative electrode mixture, the ratio of the density of the mixture intermediate portion 8b to the density of both ends 8c and 8d of the mixture is different, and further, the negative electrode sheet 19 The value of the ratio (B / A) of the density A of the intermediate portion 18b of the mixed material and the density B of both ends 18c and 18d of the mixed material is also different. In this way, the negative electrode sheets 19 of Examples 1 to 4 having different density ratio B / A values were produced.

For the negative electrode mixture layer 18 of the negative electrode sheet 19 of each example, the density of the mixture intermediate portion 18b and the densities of both ends 18c and 18d of the mixture were measured, and the value of the density ratio B / A of each example was calculated. .. As a result, in Example 1, B / A = 1.02. Further, in Example 2, B / A = 1.06. Further, in Example 3, B / A = 1.12. Further, in Example 4, B / A = 1.17.

The ratio of the density E of the intermediate portion 8b of the mixed material to the density F of both ends 8c and 8d of the mixed material in the film-shaped negative electrode mixture 8 of the current collector foil 9 with the film-like negative electrode mixture produced by the film forming step (F). / E) is the ratio (B / E) of the density A of the intermediate portion 18b of the mixed material and the density B of both ends 18c and 18d of the mixed material in the negative electrode mixture layer 18 of the negative electrode sheet 19 produced by performing the subsequent drying step. It can be regarded as equivalent to A).

Therefore, in Example 1, it can be said that the film forming step (specifically, the densifying step) is performed so that the value of the density ratio F / E is 1.02. Further, in Example 2, it can be said that the film forming step (specifically, the densifying step) is performed so that the value of the density ratio F / E is 1.06. Further, in Example 3, it can be said that the film forming step (specifically, the densifying step) is performed so that the value of the density ratio F / E is 1.12. Further, in Example 4, it can be said that the film forming step (specifically, the densifying step) is performed so that the value of the density ratio F / E is 1.17.

Then, with respect to the negative electrode sheets 19 of Examples 1 to 4, the both ends 18c and 18d of the mixture were peeled off from the current collector foil 7 using a known 90 ° peeling tester, and the ends 18c and 18d of the mixture were tied. The adhesive force (N / cm) was measured. This test is conducted in accordance with JIS K6854-1: 1999. As a result, in Example 1, the binding force of both ends 18c and 18d of the mixed material was 1.38 N / cm. Further, in Example 2, the binding force of both ends 18c and 18d of the mixed material was 1.50 N / cm. Further, in Example 3, the binding force of both ends 18c and 18d of the mixed material was 1.53 N / cm. Further, in Example 4, the binding force of both ends 18c and 18d of the mixed material was 1.54 N / cm.

Further, as a comparative form, a current collecting foil with a film-like negative electrode mixture was produced by performing a film forming step not including a densification step as in the conventional case. Specifically, the outer diameter of the first roll 1 is made constant as compared with the electrode sheet manufacturing apparatus 10 of the embodiment (the outer diameters of both ends 1c and 1d are set to the intermediate portion of the first roll 1 of the embodiment. A current collecting foil with a film-like negative electrode mixture and a negative electrode sheet were produced using an electrode sheet manufacturing apparatus different only in the points (equal to the outer diameter of 1b). Therefore, in the comparative form, the density ratio B / A = F / E = 1. It became 0.

The results of Examples 1 to 4 and the comparative embodiments described above are shown in FIG. 9 as the relationship between the value of the density ratio B / A and the binding force of both ends 18c and 18d of the mixture. From FIG. 9, it can be seen that as the value of the density ratio B / A increases, the binding force of both ends 18c and 18d of the mixed material increases. From this result, the film forming step (step S2) includes a densification step of increasing the density of both ends 8c and 8d of the mixture to be higher than the density of the intermediate portion 8b of the mixture, so that the film-like negative electrode mixture is attached. In the current collector foil 9, the binding force between both ends 8c and 8d of the mixture and the surface of the current collector foil 7 can be enhanced, and as a result, in the negative electrode sheet 19, both ends 18c and 18d of the mixture and current collection. It can be said that the binding force with the surface of the foil 7 can be enhanced.

As shown in FIG. 9, by making the B / A value larger than 1.0, the binding force between both ends 18c and 18d of the mixture and the surface of the current collector foil 7 can be enhanced. It can be seen that even if the value of B / A is made larger than 1.1, the binding force between both ends 18c and 18d of the mixture and the surface of the current collector foil 7 is not so large. Even if the B / A value is made larger than 1.1, the effect of increasing the binding force between both ends 18c and 18d of the mixture and the surface of the current collector foil 7 is small, so 1.0 <(B / A). ) It can be said that it is more preferable to set it within the range of ≦ 1.1.

Further, with respect to the negative electrode sheets 19 of Examples 1 to 4 and the negative electrode sheets of the comparative form, the residual solvent amounts (ppm) at both ends 18c and 18d of the mixture were measured. As a result, in Example 1, the amount of residual solvent was 240 ppm. Further, in Example 2, the amount of residual solvent was 250 ppm. Further, in Example 3, the amount of residual solvent was 320 ppm. Further, in Example 4, the amount of residual solvent was 490 ppm. In the comparative form, the amount of residual solvent was 235 ppm. These results are shown in FIG. 10 as the relationship between the value of the density ratio B / A and the amount of residual solvent.

As shown in FIG. 10, as the value of the density ratio B / A increases, the amount of residual solvent at both ends 18c and 18d of the negative electrode mixture layer 18 tends to increase. In particular, when the value of the density ratio B / A is larger than 1.1, the amount of residual solvent tends to increase sharply. The larger the amount of residual solvent, the higher the internal resistance of the battery tends to be. Therefore, from the viewpoint of the amount of residual solvent, it can be said that the value of the density ratio B / A is preferably 1.1 or less. Therefore, it can be said that it is preferable to set it within the range of 1.0 <(B / A) ≦ 1.1.

As described above, the density E of the intermediate portion 8b of the mixed material and the ends 8c of the mixed material in the film-like negative electrode mixture 8 of the current collector foil 9 with the film-like negative electrode mixture produced by the film forming step (step S2) of the embodiment. The ratio (F / E) of 8d to the density F is the density A of the mixture intermediate portion 18b and both ends 18c of the mixture in the negative electrode mixture layer 18 of the negative electrode sheet 19 produced by performing the subsequent drying step. It can be considered to be equivalent to the ratio (B / A) of 18d to the density B. Therefore, in the film forming step of the embodiment, it can be said that it is preferable to prepare the current collector foil with the film-like electrode mixture so as to satisfy the relationship of 1.0 <(F / E) ≦ 1.1. Specifically, in the densification step of the embodiment, the density F of both ends 8c and 8d of the mixture is set to the density of the intermediate portion 8b of the mixture so as to satisfy the relationship of 1.0 <(F / E) ≤ 1.1. It can be said that it is preferable to make it higher than E.

<Transformation form>
Next, a modified form of the present invention will be described. The manufacturing method of this modified embodiment is different from the manufacturing method of the embodiment only in the film forming step (step S2), and is the same except for the manufacturing method. Further, the electrode sheet manufacturing apparatus 110 (see FIG. 6) of the present modified embodiment has a different roll film forming apparatus as compared with the electrode sheet manufacturing apparatus 10 of the embodiment, and the others are the same. Therefore, here, the points different from those of the embodiment will be mainly described, and the description of the same points will be omitted or simplified.

Unlike the roll film forming apparatus 20 of the embodiment, the roll film forming apparatus 120 of the present modification has a constant outer diameter (specifically, the outer diameters of both ends are set to the intermediate portion of the first roll 1 of the embodiment. It has a first roll 101 (similar to the outer diameter of 1b) (see FIG. 6). Therefore, in the roll film forming apparatus 120 of the present modified form, the gap G101 between the first roll 101 and the second roll 2 is constant in the width direction WD (the direction orthogonal to the paper surface in FIG. 6). Therefore, in the roll film forming apparatus 120 of this modified form, the thickness of the film-like negative electrode mixture 108 adhering to the surface (outer peripheral surface) of the second roll 2 is constant in the width direction WD.

Further, unlike the roll film forming apparatus 20 of the embodiment, the roll film forming apparatus 120 of this modified form has a gap G101 between the first roll 101 and the second roll 2 in the transport direction of the film-like negative electrode mixture 108. Between the position where the second roll 2 and the third roll 3 face each other with a gap G2 (the position on the downstream side of the gap G101 and the position on the upstream side of the gap G2). A fourth roll 40 (a roll for compaction) facing the second roll 2 is provided with a gap G103 (see FIG. 6). As shown in FIG. 7, the fourth roll 40 is a portion of the film-like negative electrode mixture 108 facing both ends 108c and 108d of the mixture (the first end 108c of the mixture and the second end 108d of the mixture). The outer diameter of (both ends 40c and 40d) is made larger than the outer diameter of the portion (intermediate portion 40b) facing the intermediate portion 108b of the mixed material. Note that FIG. 7 is a cross-sectional view taken along the line DD of FIG. 6 showing only the cut surface of the DD.

Therefore, the gap G103 between the second roll 2 and the fourth roll 40 is the dimension (diametrical direction) of the gaps G1032 and G1033 at positions where both ends 108c and 108d of the film-like negative electrode mixture 108 pass (sandwich). The dimension (the dimension in the left-right direction in FIG. 7) is smaller than the dimension of the gap G1031 (the dimension in the radial direction, the dimension in the left-right direction in FIG. 7) at the position where the intermediate portion 108b of the mixture passes. As a result, when the film-like negative electrode mixture 108 adhering to the surface (outer peripheral surface) of the second roll 2 and being conveyed passes through the gap G103 between the second roll 2 and the fourth roll 40 in the film forming step. In addition, of the film-like negative electrode mixture 108, both ends 108c and 108d of the mixture are compressed in the thickness direction more than the intermediate portion 108b of the mixture (compressed at a high compression rate). As a result, the densities of both ends 108c and 108d of the mixture can be made higher than the density of the intermediate portion 108b of the mixture.

In this modified form, with respect to the film-like negative electrode mixture 108 that adheres to the surface (outer peripheral surface) of the second roll 2 and is conveyed toward the gap G2, both ends of the mixture are formed by the fourth roll 40 as described above. The step of increasing the density of 108c and 108d to be higher than the density of the intermediate portion 108b of the mixture is the step of increasing the density. In this modified form, the film-like negative electrode mixture 108 is subjected to a densification step before being transferred to the surface of the current collecting foil 7 in the gap between the second roll 2 and the third roll 3, and both ends of the mixture 108c. , 108d is made higher than the density of the intermediate portion 108b of the mixture.

After that, when the film-like negative electrode mixture 108 passes through the gap G2 between the second roll 2 and the third roll 3, the film-like negative electrode mixture 108 is rotated from the second roll 2 together with the third roll 3. It is transferred (adhered) to the surface of the electric foil 7. As a result, the current collector foil 109 with the film-like negative electrode mixture is obtained, in which the film-like negative electrode mixture 108 is formed on the surface of the current collector foil 7. Then, in the drying step, the current collecting foil 9 with the film-like negative electrode mixture is dried (the film-like negative electrode mixture 8 is dried), so that the negative electrode mixture layer 118 is formed on the surface of the current collector foil 7. Sheet 119 (see FIG. 5) is made. Of the negative electrode mixture layer 118, the portions located at both ends of the WD in the width direction are the ends 118c and 118d of the mixture (the first end 118c of the mixture and the second end 118d of the mixture), and the WD in the width direction. The portion located between both ends 118c and 118d of the mixed material is referred to as the intermediate part 118b of the mixed material (see FIG. 5).

As described above, also in the manufacturing method of this modified form, the film forming step is performed on both ends 108c and 108d of the mixture located at both ends of the film-like negative electrode mixture 108 (film-like electrode mixture) in the width direction WD. It includes a densification step in which the density is made higher than the density of the mixture intermediate portion 108b located between the both ends 108c and 108d of the mixture in the width direction WD. By performing this densification step, the density of the binder at both ends 108c and 108d of the mixture can be increased, so that when the film-like negative electrode mixture 108 is transferred to the surface of the current collector foil 7, the mixture is used. At both ends 108c and 108d, the number of binders that come into contact with (bond) to the surface of the current collector foil 7 can be increased. Therefore, it is possible to increase the bonding area between both ends 8c and 8d of the mixture by the binder and the surface of the current collector foil 7.

As a result, even in the current collector foil 109 with the film-like negative electrode mixture (collection foil with the film-like electrode mixture, see FIG. 8) manufactured by the manufacturing method of this modified form, both ends 108c and 108d of the mixture are collected. The binding force between the electric foil 7 and the surface of the electric foil 7 can be enhanced. Therefore, in the current collector foil 109 with the film-like electrode mixture, both ends 108c and 108d of the mixture are less likely to be peeled off from the surface of the current collector foil 7.
Further, also in the negative electrode sheet 119 (electrode sheet, see FIG. 5) obtained by drying the current collector foil 109 with the film-like negative electrode mixture, both ends of the mixture of the negative electrode mixture layer 118 (electrode mixture layer) 118c, 118d. Since the binding force between the collector foil 7 and the surface of the current collector foil 7 can be increased, in the negative electrode sheet 119 (electrode sheet), both ends 118c and 118d of the mixture material are less likely to be peeled off from the surface of the current collector foil 7.

Further, the binding force between the negative electrode active materials (electrode active materials) via the binder can be enhanced in both ends 108c, 108d, 118c, 118d of the mixture (both ends 108c, 108d, 118c of the mixture). , 118d makes it easier for the negative electrode active material to bind to the binder). As a result, it is possible to reduce the detachment (falling off) of a part of both ends 108c, 108d, 118c, 118d of the mixture (for example, the surface side portion of the ends 108c, 108d, 118c, 118d of the mixture). Can be done.

With respect to the negative electrode sheet 119 manufactured by the manufacturing method of this modified form, both ends 118c and 118d of the mixture are peeled off from the current collector foil 7 using a known 90 ° peeling tester as in the embodiment and the comparative embodiment. Then, the binding force (N / cm) of both ends 118c and 118d of the mixed material was measured. This test is conducted in accordance with JIS K6854-1: 1999. As a result, in the negative electrode sheet 119 of the present modified form, the binding force between both ends 118c and 118d of the mixture and the surface of the current collector foil 7 was 1.4 N / cm. Here, the binding force between both ends of the mixture and the surface of the current collector foil in the negative electrode sheets of the present modification, the embodiment (Example 2), and the comparative embodiment is shown in comparison with FIG.

As shown in FIG. 11, in the embodiment and the modified form, the binding force between both ends of the mixture and the surface of the current collector foil is larger than that in the comparative form. As described above, in the comparative form, a film-forming step that does not include the densification step is performed to produce a current collecting foil with a film-like negative electrode mixture, and the density of both ends of the mixture and the intermediate portion of the mixture are obtained. The density is equivalent. On the other hand, in the embodiment and the modified form, the current collecting foils 9 and 109 with the film-like negative electrode mixture are produced by performing the film forming process including the densification step, and the both ends 8c, 8d, 108c and 108d of the mixture are produced. The density is made higher than the densities of the intermediate parts 8b and 108b of the mixture.

From this result, the film forming process includes a high density step of increasing the density of both ends of the mixture to be higher than the density of the middle part of the mixture. It can be said that the binding force between the portion and the surface of the current collecting foil can be increased, and as a result, the binding force between both ends of the mixture and the surface of the current collecting foil can be enhanced in the negative electrode sheet. As a result, in the negative electrode sheet (electrode sheet), it can be said that both ends of the mixture are less likely to peel off from the surface of the current collector foil.

In the above, the present invention has been described in accordance with the embodiments and modifications, but the present invention is not limited to the above-described embodiments and the like, and it is said that the present invention can be appropriately modified and applied without departing from the gist thereof. Not to mention. For example, in the embodiment, as a method for manufacturing an electrode sheet according to the present invention, a method for manufacturing a negative electrode sheet has been exemplified. However, the present invention may be applied to a method for producing a positive electrode sheet.

1,101 1st roll 2 2nd roll 3 3rd roll 6 Negative electrode mixture (electrode mixture)
7 Current collector foil 8,108 Membrane-like negative electrode mixture (film-like electrode mixture)
8c, 8d, 108c, 108d Both ends of the mixture 8b, 108b Intermediate part of the mixture 9,109 Current collector foil with film-like negative electrode mixture (current collector foil with film-like electrode mixture)
10,110 Electrode sheet manufacturing equipment 16 Wet granulated material 18,118 Negative electrode mixture layer (electrode mixture layer)
18c, 18d, 118c, 118d Both ends of the mixture 18b, 118b Intermediate part 19,119 Negative sheet (electrode sheet)
20,120 Roll film forming apparatus CD Transport direction WD Width direction S1 Electrode mixture manufacturing process S2 Film forming process S3 Drying process

Claims (1)

It is a method of manufacturing an electrode sheet for manufacturing an electrode sheet having an electrode mixture layer on the surface of a current collector foil.
An electrode mixture composed of a plurality of wet granulated bodies obtained by mixing an electrode active material, a binder, and a solvent is passed through a gap between a first roll and a second roll that rotate in opposition to each other. The electrode mixture is compressed into a film, and the film-shaped electrode mixture is attached to the surface of the second roll and is conveyed by a third roll that rotates in opposition to the second roll. By passing the current collecting foil through the gap between the second roll and the third roll, the film-like electrode mixture, which is the film-like electrode mixture adhering to the surface of the second roll, is formed. A film-like electrode combination having the film-like electrode mixture on the surface of the current-collecting foil is transferred onto the surface of the current-collecting foil by contacting the surface of the current-collecting foil with pressure. The film formation process for producing the current collector foil with material, and
Manufacture of an electrode sheet comprising a drying step of forming the electrode mixture layer on the surface of the current collector foil by drying the film-like electrode mixture of the current collector foil with the film-like electrode mixture. In the method
In the film forming step, in the film-like electrode mixture, the densities of both ends of the mixture located at both ends of the film-like electrode mixture in the width direction are located between both ends of the mixture in the width direction. A method for manufacturing an electrode sheet, which includes a densification step in which the density is higher than the density of the intermediate portion of the mixed material.

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