JP7197267B2 - Electrode sheet manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an electrode sheet that constitutes a battery. Specifically, the present invention relates to a method of manufacturing an electrode sheet having a structure in which an electrode mixture layer is formed on the surface of a current collector foil.

Conventionally, as an electrode sheet (positive electrode sheet or negative electrode sheet), an electrode sheet having a structure in which an electrode mixture layer is formed on the surface of a collector foil is known. As a method for manufacturing an electrode sheet having such a structure, for example, a method disclosed in Patent Document 1 is known. Specifically, first, an electrode composite material is produced, which is composed of a plurality of wet granules obtained by mixing and granulating an electrode active material, a binder, and a solvent. Next, this electrode mixture is passed through a gap between a pair of rolls facing each other to form a film, and the film-like electrode mixture is adhered onto the surface of the current collector foil.

JP 2013-77560 A

More specifically, in the roll forming process, the electrode mixture is passed through a gap between a pair of rolls consisting of a second roll for transferring the electrode mixture to the current collector foil and a first roll facing the second roll. By doing so, the electrode mixture is made into a film, and the film-shaped electrode mixture is adhered to the second roll. Thereafter, in the transfer step, the film-like electrode mixture adhering to the second roll is transferred (adhered) onto the surface of the current collector foil. Thereafter, in the electrode mixture layer forming step, the film-like electrode mixture adhered to the surface of the current collector foil is dried to form an electrode mixture layer on the surface of the current collector foil, thereby forming an electrode sheet. make.

In addition, in Patent Document 1, the peripheral speed of the second roll is faster than the peripheral speed of the first roll. As a result, the electrode mixture (wet granules) that has been compressed into a film between the first roll and the second roll passes through the gap between the first roll and the second roll. The contact area (liquid bridge area) with the second roll is larger than the contact area (liquid bridge area) with the roll. As a result, the film-like electrode mixture (wet granules) adheres to (is carried by) the surface of the second roll when passing through the gap between the first roll and the second roll.

By the way, when producing an electrode mixture made of wet granules, it is difficult to uniformly disperse the solvent over the entire electrode mixture. For this reason, in the electrode mixture, the solid content (in other words, solvent content) of the plurality of wet granules constituting the electrode mixture may vary greatly. That is, a wet granule with a high solid content (in other words, a low solvent content) and a wet granule with a low solid content (in other words, a high solvent content) are mixed in the electrode mixture. was sometimes mixed with In addition, the solid content (in other words, the solvent content) of each wet granule constituting the electrode mixture also varies greatly. That is, in one wet granule, a portion with a high solid content (in other words, a low solvent content) and a portion with a low solid content (in other words, a high solvent content) are mixed. I had something to do.

When the electrode mixture made of such wet granules passes through the gap between the first roll rotating oppositely and the second roll having a faster peripheral speed in the roll forming process, the electrode mixture Part of the wet granules sometimes adhered to the surface of the first roll without adhering to the surface of the second roll. For this reason, the film of the electrode mixture adhering to the surface of the second roll may have holes (or the thickness of the film may become extremely thin in some parts). As a result, in the transfer process, the film of the electrode mixture transferred from the surface of the second roll onto the surface of the current collector foil has holes (or the thickness of the film is partially extremely thin). ) Defects in film formation (defects in film formation) may occur. When there are many film-forming defects (film-forming defects), it may not be possible to use it appropriately as an electrode sheet constituting a battery.

The reason why such a problem occurs is considered as follows. Specifically, for example, in the wet granules, a site with a high solid content (in other words, a low solvent content) and a site with a low solid content (in other words, a high solvent content) In the case where the wet granules are mixed, when the wet granules pass through the gap between the first roll and the second roll that rotate in opposition, the solid content is high (in other words, the solvent content is When the portion with a low solid content (in other words, with a high solvent content) contacts the surface of the first roll, the wet granule and The liquid bridge force between the surface of the first roll is greater than the liquid bridge force between the wet granule and the surface of the second roll.

For this reason, the wet granules adhere to the surface of the first roll without adhering to the surface of the second roll when passing through the gap between the first roll and the second roll that rotate in opposition to each other. Sometimes I end up doing it. For this reason, in the film of the electrode mixture adhering to the surface of the second roll, holes may be formed at the sites where the wet granules are removed (or the thickness of the film may be extremely thin at those sites). be. As a result, in the transfer step, even in the film of the electrode mixture transferred from the surface of the second roll onto the surface of the current collector foil, holes are formed in the relevant portions (or the thickness of the film is extremely thin) film formation defects (film formation defects) are thought to occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing an electrode sheet in which film formation defects (film formation defects) are less likely to occur.

An electrode mixture consisting of a plurality of wet granules obtained by mixing and granulating an electrode active material, a binder, and a solvent is passed through a first roll rotating in opposition to a second roll having a higher peripheral speed than the first roll. A roll forming step of compressing the electrode mixture into a film by passing it through a gap and attaching the film-like electrode mixture to the surface of the second roll; A transfer step of transferring the film-like electrode mixture adhering to the surface of the current collector foil, and drying the film-like electrode mixture transferred on the surface of the current collector foil, and an electrode mixture layer forming step of forming an electrode mixture layer on the surface of the current collector foil, and manufacturing an electrode sheet having the electrode mixture layer on the surface of the current collector foil. In the method, in the roll forming step, the wet granules contained in the electrode mixture and the first roll when the electrode mixture passes through the gap between the first roll and the second roll. The average value F1 (kPa) of the liquid bridge force between the surface and the average value F2 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the second roll. is preferably a method for producing an electrode sheet that satisfies the relationship F1<F2.

In the above-described manufacturing method, in the roll forming step, when the electrode mixture passes through the gap between the first roll and the second roll, the wet granules contained in the electrode mixture and the surface of the first roll The average value F1 (kPa) of the liquid bridging force and the average value F2 (kPa) of the liquid bridging force between the wet granules contained in the electrode mixture and the surface of the second roll are such that F1 < F2 satisfy the relationship. In the manufacturing method described above, in the roll forming process, the peripheral speed of the second roll is made faster than the peripheral speed of the first roll, as in the conventional case.

More specifically, in the electrode mixture, even if there is variation in the solid content (in other words, solvent content) of the plurality of wet granules constituting the electrode mixture, the electrode Even if the solid content (in other words, solvent content) varies among the wet granules that make up the mixture, in the roll forming process, the electrode mixture is divided into the first roll and the second roll. The average value F1 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the first roll when passing through the gap, and the wet granules contained in the electrode mixture The average value F2 (kPa) of the liquid bridge force between the granules and the surface of the second roll satisfies the relationship of F1<F2.

By doing so, when the wet granules contained in the electrode mixture pass through the gap between the first roll and the second roll that rotate in opposition to each other, the first roll and the second roll are relatively It tends to adhere to the surface of the second roll, which has a relatively large liquid-bridging force.

For example, in wet granules, a portion with a high solid content (in other words, a low solvent content) and a portion with a low solid content (in other words, a high solvent content) are mixed. In the case where the wet granules pass through the gap between the first roll and the second roll that rotate in opposition, the portion with a high solid content (in other words, a low solvent content) is the first Even when the surface of the second roll is in contact with the surface of the second roll and the portion with a low solid content (in other words, a high solvent content) is in contact with the surface of the first roll, the wet granule and the surface of the second roll The liquid bridging force between the wet granules and the surface of the first roll becomes larger than the liquid bridging force between .

Therefore, in the above-described roll forming process, in the film of the electrode mixture adhering to the surface of the second roll, some wet granules contained in the electrode mixture adhere to the surface of the first roll. Holes (or extreme reduction in film thickness) are less likely to occur. As a result, in the subsequent transfer step, even in the film of the electrode mixture transferred from the surface of the second roll to the surface of the current collector foil, holes (or extreme reduction in film thickness) are less likely to occur, and the film is formed. Film defects (deposition defects) are less likely to occur.

As described above, the above-described manufacturing method is a method for manufacturing an electrode sheet in which poor film formation (defective film formation) is unlikely to occur.
Note that the wet granules refer to a substance (granules) in which a plurality of electrode active material particles and a binder are aggregated (bonded) in a state in which the solvent is held (absorbed).

Further, in the method for manufacturing the electrode sheet, in the roll forming step, air is blown onto the surface of the first roll to dry the surface of the first roll while forming the electrode mixture into the first roll. A method of manufacturing an electrode sheet is preferable in which the relationship of F1<F2 is satisfied by passing the electrode sheet through the gap between the first roll and the second roll.
In one aspect of the present invention, an electrode mixture producing step of producing an electrode mixture comprising a plurality of wet granules obtained by mixing and granulating an electrode active material, a binder, and a solvent; The material is passed through a gap between a first roll that rotates in opposition to the first roll and a second roll that rotates at a higher peripheral speed than the first roll, thereby compressing the electrode mixture into a film shape, thereby forming the electrode mixture in the form of a film. a roll forming step of adhering the material to the surface of the second roll; a transfer step of transferring the film-like electrode mixture adhering to the surface of the second roll onto the surface of the current collector foil; an electrode mixture layer forming step of forming an electrode mixture layer on the surface of the current collector foil by drying the film-like electrode mixture transferred onto the surface of the current collector foil; In the electrode sheet manufacturing method for manufacturing an electrode sheet having the electrode mixture layer on the surface of an electric foil, the electrode mixture preparation step comprises: the electrode active material and the binder without adding the solvent; A first mixing step of producing a mixed pre-mixture, and a second mixing step of stirring the pre-mixture and the solvent to produce the electrode mixture made of the wet granules, In the second mixing step, the stirring speed is set faster in the latter half of the step than in the first half, and in the roll forming step, the electrode mixture passes through the gap between the first roll and the second roll. The average value F1 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the first roll, and the wet granules contained in the electrode mixture when and the average value F2 (kPa) of the liquid bridge force between the surface of the second roll satisfies the relationship of F1<F2, and in the roll forming step, by blowing air onto the surface of the first roll and a method of manufacturing an electrode sheet in which the relationship F1<F2 is satisfied by passing the electrode mixture through the gap between the first roll and the second roll while drying the surface of the first roll. be.

In the above-described manufacturing method, in the roll forming process, the surface of the first roll is dried by blowing air onto the surface of the first roll, and the electrode mixture (wet granules) is formed between the first roll and the second roll. to satisfy the relationship F1<F2.

By drying the surface of the first roll by blowing air onto the surface of the first roll in this way, the moisture content of the surface of the first roll can be made smaller than the moisture content of the surface of the second roll. can. In other words, the water content on the surface of the second roll can be made larger than the water content on the surface of the first roll. Thereby, in the roll forming step, when the electrode mixture passes through the gap between the first roll and the second roll, a liquid bridge is formed between the wet granules contained in the electrode mixture and the surface of the first roll. The average value F1 (kPa) of the force and the average value F2 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the second roll satisfy the relationship of F1<F2. become.

By doing so, in the roll forming step, when the wet granules contained in the electrode mixture pass through the gap between the first roll and the second roll that rotate in opposition to each other, the first roll and the second roll Among the rolls, it becomes easier to adhere to the surface of the second roll, which has a relatively large liquid-bridging force. Therefore, in the film of the electrode mixture formed on the surface of the second roll, holes (or extreme reduction in film thickness) are less likely to occur, and even in the transfer process after the roll forming process, the surface of the second roll It becomes difficult for holes (or extreme reduction in film thickness) to occur in the film of the electrode mixture transferred from the surface of the collector foil. Therefore, according to the manufacturing method described above, film formation defects (film formation defects) are less likely to occur.

Further, in any one of the electrode sheet manufacturing methods described above, in the roll forming step, dry air having a dew point of −30° C. or less is used as the air to be blown onto the surface of the first roll. good to do

In the above manufacturing method, dry air with a dew point of -30°C or less is used as the air blown onto the surface of the first roll in the roll forming process. That is, in the roll forming step, dry air having a dew point of −30° C. or less is blown onto the surface of the first roll to dry the surface of the first roll, and the electrode mixture (wet granules) is formed on the first roll. and the second roll to satisfy the relationship of F1<F2.

In this way, the surface of the first roll is dried by blowing dry air with a dew point of −30° C. or less on the surface of the first roll, so that the moisture content on the surface of the first roll is changed to the moisture content on the surface of the second roll. Compared to the amount, it can be much less. In other words, the water content on the surface of the second roll can be made much larger than the water content on the surface of the first roll. This makes it possible to increase the difference between F1 and F2. That is, F2 can be made much larger than F1.

By doing so, in the roll forming process, when the wet granules contained in the electrode mixture pass through the gap between the first roll and the second roll that rotate in opposition to each other, the surface of the second roll It becomes much easier to adhere. Therefore, in the film of the electrode mixture formed on the surface of the second roll, holes (or extreme reduction in film thickness) are more difficult to occur, and even in the transfer process after the roll forming process, the current collector foil Holes (or extreme reduction in film thickness) are much less likely to occur in the film of the electrode mixture transferred onto the surface of the . Therefore, according to the manufacturing method described above, film formation defects (film formation defects) are much less likely to occur.

Further, in any one of the electrode sheet manufacturing methods described above, the roll forming step preferably satisfies the relationship F1≦2.8 kPa.

In the manufacturing method described above, the relationship F1≦2.8 kPa is satisfied in the roll forming process. Specifically, for example, in the roll forming step, the surface of the first roll is dried by blowing air onto the surface of the first roll so that F1≦2.8 kPa. In this way, by reducing the average value F1 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the first roll, the It becomes extremely difficult for the wet granules to adhere to the surface of the first roll. In other words, in the roll forming process, the wet granules contained in the electrode mixture are very likely to adhere to the surface of the second roll.

Therefore, in the film of the electrode mixture formed on the surface of the second roll, holes (or extreme reduction in film thickness) are extremely difficult to occur. It becomes extremely difficult for holes (or extreme reduction in film thickness) to occur in the film of the electrode composite material transferred onto the surface. Therefore, according to the manufacturing method described above, film formation defects (film formation defects) are extremely unlikely to occur.

Further, in any one of the electrode sheet manufacturing methods described above, in the roll forming step, the surface of the second roll is wetted by adhering a liquid to the surface of the second roll, and the electrode mixture is is passed through the gap between the first roll and the second roll to satisfy the relationship F1<F2.
In another aspect of the present invention, an electrode mixture producing step of producing an electrode mixture comprising a plurality of wet granules obtained by mixing and granulating an electrode active material, a binder, and a solvent; By passing the composite material through a gap between a first roll that rotates in opposition to the first roll and a second roll that rotates at a higher circumferential speed than the first roll, the electrode composite material is compressed and formed into a film, thereby forming the electrode into a film. a roll forming step of adhering the composite material to the surface of the second roll; a transfer step of transferring the film-like electrode composite material adhering to the surface of the second roll onto the surface of the current collector foil; an electrode mixture layer forming step of forming an electrode mixture layer on the surface of the current collector foil by drying the film-like electrode mixture transferred onto the surface of the current collector foil; In the electrode sheet manufacturing method for manufacturing the electrode sheet having the electrode mixture layer on the surface of the current collector foil, the electrode mixture preparation step comprises: the electrode active material and the binder without adding the solvent; and a second mixing step of stirring the preceding mixture and the solvent to prepare the electrode mixture made of the wet granules. , in the second mixing step, the stirring speed is faster in the latter half of the step than in the first half; and in the roll forming step, the electrode mixture passes through the gap between the first roll and the second roll. The average value F1 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the first roll, and the wet granules contained in the electrode mixture when The average value F2 (kPa) of the liquid bridge force between the body and the surface of the second roll satisfies the relationship of F1<F2, and in the roll forming step, the liquid is adhered to the surface of the second roll. By passing the electrode mixture through the gap between the first roll and the second roll while wetting the surface of the second roll, an electrode sheet is manufactured that satisfies the relationship F1<F2. The method.

In the above-described manufacturing method, in the roll forming step, the liquid is applied to the surface of the second roll to moisten (moisten) the surface of the second roll while the electrode mixture (wet granules) is formed into the second roll. The relation F1<F2 is satisfied by letting the film pass through the gap between the first roll and the second roll.

In this way, by moistening (moistening) the surface of the second roll by adhering the liquid to the surface of the second roll, the water content on the surface of the second roll is reduced from the water content on the surface of the first roll. can be more. Thereby, in the roll forming step, when the electrode mixture passes through the gap between the first roll and the second roll, a liquid bridge is formed between the wet granules contained in the electrode mixture and the surface of the first roll. The average value F1 (kPa) of the force and the average value F2 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the second roll satisfy the relationship of F1<F2. become.

By doing so, in the roll forming step, when the wet granules contained in the electrode mixture pass through the gap between the first roll and the second roll that rotate in opposition to each other, the first roll and the second roll Among the rolls, it becomes easier to adhere to the surface of the second roll, which has a relatively large liquid-bridging force. Therefore, in the film of the electrode mixture formed on the surface of the second roll, holes (or extreme reduction in film thickness) are less likely to occur, and even in the transfer process after the roll forming process, the surface of the current collector foil Holes (or extreme reduction in film thickness) are less likely to occur in the film of the electrode composite material that has been transferred thereon. Therefore, according to the manufacturing method described above, film formation defects (film formation defects) are less likely to occur.

Further, in any one of the electrode sheet manufacturing methods described above, in the roll forming step, a liquid equivalent to the solvent contained in the wet granules is used as the liquid to be adhered to the surface of the second roll. It is preferable to provide a method for manufacturing an electrode sheet that

In the manufacturing method described above, a liquid equivalent to the solvent contained in the wet granules is used as the liquid to be adhered to the surface of the second roll in the roll forming process. That is, in the roll forming step, the surface of the second roll is wetted by attaching a liquid equivalent to the solvent contained in the wet granules to the surface of the second roll.

In this way, by using a liquid equivalent to the solvent contained in the wet granules as the liquid to be adhered to the surface of the second roll, the wet granules contained in the electrode mixture and the surface of the second roll can be It is possible to appropriately increase the average value F2 (kPa) of the inter-liquid bridging force. Furthermore, even if the liquid adheres to the wet granules, problems such as deterioration of the electrode active material and the binder contained in the wet granules do not occur, which is preferable.

Further, in any one of the electrode sheet manufacturing methods described above, the roll forming step preferably satisfies the relationship F2≧12.4 kPa.

In the manufacturing method described above, the relationship F2≧12.4 kPa is satisfied in the roll forming process. Specifically, for example, in the roll forming step, the surface of the second roll is wetted by adhering a liquid to the surface of the second roll so that F2≧12.4 kPa.

Thus, by increasing the average value F2 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the second roll, The wet granules that are soaked are very likely to adhere to the surface of the second roll. Therefore, in the film of the electrode mixture formed on the surface of the second roll, holes (or extreme reduction in film thickness) are extremely difficult to occur. It becomes extremely difficult for holes (or extreme reduction in film thickness) to occur in the film of the electrode composite material transferred onto the surface. Therefore, according to the manufacturing method described above, film formation defects (film formation defects) are extremely unlikely to occur.

1 is a schematic perspective view of a roll film forming apparatus according to Examples 1 and 2; FIG. It is the side view schematic diagram of the same roll film-forming apparatus. It is the cross-sectional schematic of a negative electrode sheet and a positive electrode sheet. 4 is a flow chart showing the flow of a method for manufacturing a negative electrode sheet. 5 is a subroutine of the flowchart of FIG. 4; It is a figure which shows the production procedure of a negative electrode wet granule (negative electrode mixture). It is a figure which shows one aspect|mode of a wet granule. It is a figure explaining a roll forming process, and is equivalent to the A section enlarged view of FIG. It is another figure explaining a roll forming process, and is equivalent to the A section enlarged view of FIG. It is a flowchart which shows the flow of the manufacturing method of a positive electrode sheet. 11 is a subroutine of the flowchart of FIG. 10; FIG. 4 is a diagram showing a procedure for producing a positive electrode wet granule (positive electrode mixture). It is the perspective schematic diagram of the roll film-forming apparatus concerning Example 3,4. It is the side view schematic diagram of the same roll film-forming apparatus. It is the perspective schematic diagram of the roll film-forming apparatus concerning Example 5,6. It is the side view schematic diagram of the same roll film-forming apparatus. It is the perspective schematic diagram of the roll film-forming apparatus concerning Example 7,8. It is the side view schematic diagram of the same roll film-forming apparatus. It is a figure explaining the method of calculating|requiring liquid bridge|bridging force. FIG. 11 is another diagram for explaining a method of obtaining liquid bridge strength. It is a figure explaining the defect in a roll forming process. It is a figure explaining the film-forming defect (film-forming defect).

(Example 1)
EMBODIMENT OF THE INVENTION Hereafter, Embodiment 1 which actualized this invention is described in detail, referring drawings. In Example 1, the present invention is applied to manufacture of a negative electrode sheet (electrode sheet) for a lithium ion secondary battery. In Example 1, a negative electrode active material (electrode active material) and a binder are used as materials for a negative electrode mixture (electrode mixture) for forming a negative electrode mixture layer (electrode mixture layer) of a negative electrode sheet. , solvent and .

Note that in Example 1, a powdery carbon material (specifically, amorphous coated 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.
The negative electrode sheet 19 produced in Example 1 has a negative electrode collector foil 7 and a negative electrode mixture layer 18 laminated on the surface of the negative electrode collector foil 7, as shown in FIG.

Here, a method for manufacturing the electrode sheet (negative electrode sheet 19) according to Example 1 will be described in detail. FIG. 1 is a schematic perspective view of a roll film forming apparatus 20 according to Example 1. FIG. FIG. 2 is a schematic side view of the roll film forming apparatus 20. As shown in FIG. FIG. 4 is a flow chart showing the flow of the manufacturing method of the electrode sheet (negative electrode sheet 19) according to the first embodiment. FIG. 5 is a subroutine of the flowchart of FIG. FIG. 6 is a diagram showing a procedure for producing the negative electrode wet granules 16 (negative electrode mixture 6).

As shown in FIG. 4, first, in step S1 (electrode mixture preparation step), the negative electrode active material 13 (carbon material), the binder 14 (CMC), and the solvent 15 (water) are mixed and granulated. A large number of wet negative electrode granules 16 are produced by the above method, and a negative electrode composite material 6 composed of the large number of wet negative electrode granules 16 is produced. Specifically, as shown in FIG. 5, in step S11 (first mixing step), the negative electrode active material 13 and the binder 14 are mixed to prepare a pre-mixed body 6A. In Example 1, the negative electrode active material 13 and the binder 14 are put into a known stirring granulator (not shown) and stirred to mix (mix) the negative electrode active material 13 and the binder 14 ( dispersion) to form a pre-mixture 6A (see FIG. 6).

Next, in step S12 (second mixing step), the preceding mixture 6A obtained by mixing the negative electrode active material 13 and the binder 14 is mixed with water as the solvent 15 to obtain a negative electrode wet granule. 16 is produced, and a negative electrode composite material 6 composed of a large number of negative electrode wet granules 16 is produced. Specifically, water, which is the solvent 15, is added to the above-described stirring granulator containing the preceding mixture 6A obtained by mixing the negative electrode active material 13 and the binder 14, and the mixture is stirred. A large number of negative electrode wet granules 16 are formed. In the mixing in step S12 (second mixing step), all the components constituting the negative electrode wet granules 16 are mixed. By performing this mixing of all the components, the negative electrode composite material 6 composed of a large number of negative electrode wet granules 16 is obtained.

Further, in step S12 (second mixing step) of the first embodiment, the rotating speed of stirring is changed between the first half and the second half of the step. Specifically, in the first half, the rotation is at a low speed, and the preceding mixture 6A obtained by mixing the negative electrode active material 13 and the binder 14 and the water as the solvent 15 are stirred (mixed). As a result, the negative electrode active material 13 and the binder 14 can be appropriately granulated while absorbing (retaining) the solvent 15 (water) to prepare a wet granule. However, the wet granules obtained by stirring at low speed rotation have too large particle diameters and cannot be appropriately formed into a film in step S2 (roll forming step) described later. For this reason, in the second half of step S12 (second mixing step), the wet granules are stirred at high speed to make the wet granules finer, and the negative electrode wet granules having a particle size that can be appropriately formed into a film in step S2 (roll forming step). It is considered as granules 16 (see FIG. 6).

As shown in FIG. 7, the negative electrode wet granules 16 are formed in a state in which water, which is the solvent 15, is held (absorbed) by the plurality of particles of the negative electrode active material 13 and the binder 14 (not shown). , and these are aggregated (combined) substances (granules). The negative electrode mixture 6 is an aggregate of such wet negative electrode granules 16 .

Moreover, in the first embodiment, the compounding ratio of each component to be mixed in step S11 (first mixing step) and step S12 (second mixing step) is as follows. In step S11 (first mixing step), the mixing ratio (mixing ratio) of the negative electrode active material 13 and the binder 14 is set to 99:1 by weight. Further, in step S12 (second mixing step), the solvent 15 (water) is blended so that the NV (solid content) of the negative electrode wet granules 16 is 71% by weight. Specifically, components other than the solvent 15 (water), that is, the negative electrode active material 13 and the binder 14 are solid contents (nonvolatile components), and the total weight of these is the total weight of the negative electrode wet granule 16 ( The total weight of the negative electrode active material 13, the binder 14, and the solvent 15) is 71 wt%.

Next, proceeding to step S2 (roll forming step), the negative electrode mixture 6 (negative electrode wet granules 16) produced in step S1 (electrode mixture producing step) is placed against the first roll 1 rotating in opposition. By passing through the gap with the second roll 2, the negative electrode mixture 6 is compressed and formed into a film, and the film-shaped negative electrode mixture 6 is adhered to the surface 2b of the second roll 2 (FIGS. 1 and 2). reference). Then, in step S3 (transfer step), the film-like negative electrode mixture material 6 attached to the surface 2b of the second roll 2 (referred to as the film-like negative electrode mixture material 8) is transferred onto the surface of the negative electrode current collector foil 7. to be transcribed. In addition, in the present Example 1, step S2 (roll forming process) and step S3 (transfer process) are continuously performed using the roll film-forming apparatus 20 shown in FIG.1 and FIG.2.

The roll deposition apparatus 20 has three rolls, a first roll 1, a second roll 2 and a third roll 3, as shown in FIGS. These three rolls 1, 2, 3 are horizontally arranged in a line and provided parallel to each other. Also, the first roll 1 and the second roll 2 face each other with a slight gap therebetween. Similarly, the second roll 2 and the third roll 3 are also facing each other with a slight gap. Furthermore, partition plates 4 and 5 are spaced apart in the width direction of the rolls (the axial direction, the direction perpendicular to the paper surface in FIG. 2) above the portion where the first roll 1 and the second roll 2 face each other. ing.

Further, the directions of rotation of these three rolls 1 to 3 are such that the directions of rotation of two adjacent (facing) rolls are opposite to each other, as indicated by the arrows in FIGS. The two rolls are set to rotate in the forward direction with respect to each other. At the position where the first roll 1 and the second roll 2 face each other, the surfaces of these rolls move downward as they rotate. In addition, at the locations where the second roll 2 and the third roll 3 face each other, the surfaces of these rolls move upward as they rotate.

In addition, the peripheral speed of the rolls (moving speed of the surface of the rolls due to rotation) is set to be the slowest for the first roll 1, the fastest for the third roll 3, and the middle for the second roll 2. . Therefore, in step S2 (roll forming step), the peripheral speed of the second roll 2 is made faster than the peripheral speed of the first roll 1 .

In such a roll film forming apparatus 20, step S1 (electrode mixture manufacturing step) is placed 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 composite material 6 (negative electrode wet granules 16) prepared in 1. is introduced. Further, a negative electrode current collector foil 7 is stretched over the third roll 3 . The negative electrode current collector foil 7 is a metal foil (copper foil), and along with the rotation of the third roll 3 , passes through the facing portion between the second roll 2 and the third roll 3 to move from the lower right to the upper right of the third roll 3 . It is designed to be transported to Further, in a state where the negative electrode current collector foil 7 is passed between the second roll 2 and the third roll 3, there is a slight gap between the second roll 2 and the negative electrode current collector foil 7. It is supposed to be. That is, the gap between the second roll 2 and the third roll 3 (the gap when the negative electrode current collector foil 7 is not present) is slightly wider than the thickness of the negative electrode current collector foil 7 .

In step S<b>2 (roll forming step), first, the negative electrode mixture 6 is put into the accommodation space between the partition plates 4 and 5 of the roll film forming apparatus 20 . Then, the charged negative electrode mixture 6 is supplied into the gap between the first roll 1 and the second roll 2, and the rotation of the first roll 1 and the second roll 2 causes the gap between the rolls to close. and become a film (see FIGS. 1, 2, and 8). At this time, since the peripheral speed of the second roll 2 is higher than that of the first roll 1, as shown in FIG. The surface 2b of the second roll 2 is stretched more than the surface 1b of the first roll 1, and the contact area (liquid bridge area) on the surface 2b of the second roll 2 is larger than the surface 1b of the first roll 1, so that the second roll 2 is attached (carried) to the surface 2b of the . 8 is an enlarged view of part A in FIG.

The film-like negative electrode mixture material 6 (film-like negative electrode mixture material 8) adhering to the surface 2b of the second roll 2 is conveyed as the second roll 2 rotates (see FIGS. 1 and 2). After that, the negative electrode current collector foil 7 and the film-like negative electrode mixture 8 meet at the place where the second roll 2 and the third roll 3 face each other.
Then, in step S3 (transfer step), the filmy negative electrode mixture material 8 is transferred from the second roll 2 onto the surface of the negative electrode current collector foil 7 rotating together with the third roll 3 moving at a higher speed. (adhere to). As a result, a current collector foil 9 with a filmy negative electrode mixture is obtained in which the filmy negative electrode mixture 8 is formed on the negative electrode current collector foil 7 .

By the way, when the negative electrode mixture 6 composed of the negative electrode wet granules 16 is prepared in step S<b>1 (electrode mixture preparation step), it is difficult to uniformly disperse the solvent 15 over the entire negative electrode mixture 6 . Therefore, in the negative electrode mixture 6 , the solid content (in other words, the solvent content) of the plurality of wet negative electrode granules 16 constituting the negative electrode mixture 6 may vary greatly. That is, the negative electrode wet granules 16 with a high solid content (in other words, a low solvent content) and the wet negative electrode granules 16 with a low solid content (in other words, a high solvent content) are It was mixed in the negative electrode composite material 6 in some cases.

Further, in each negative electrode wet granule 16 that constitutes the negative electrode mixture 6, the solid content rate (in other words, the solvent content rate) may vary greatly. That is, in one negative electrode wet granule 16, a region with a high solid content (in other words, a low solvent content) and a region with a low solid content (in other words, a high solvent content) were sometimes mixed. For example, in the negative electrode wet granule 16B shown in FIG. The second portion 16B2 has a relatively low solid content (in other words, a high solvent content). are very different.

Conventionally, when the negative electrode composite material 6 composed of such negative electrode wet granules 16 passes through the gap between the first roll 1 and the second roll 2 that rotate facing each other in step S2 (roll forming step), A part of the negative electrode wet granules 16 in the negative electrode mixture 6 sometimes did not adhere to the surface 2b of the second roll 2 but adhered to the surface 1b of the first roll 1 . For this reason, the film of the negative electrode mixture 6 adhering to the surface 2b of the second roll 2 may have holes (or the thickness of the film may be extremely thin). As a result, in step S3 (transfer step), holes were formed in the film of the negative electrode mixture 6 (film-like negative electrode mixture 8) transferred from the surface 2b of the second roll 2 onto the surface of the negative electrode current collector foil 7. In some cases, film formation failure (film formation defect) occurs (or the thickness of the film becomes extremely thin). When there are many film formation defects (film formation defects), the negative electrode sheet 19 constituting the battery cannot be used appropriately.

The reason why such a problem occurs is considered as follows. Specifically, for example, as shown in FIG. ) As shown in FIG. 8, the negative electrode wet granule 16B having the second portion 16B2 is formed by forming a gap between the first roll 1 and the second roll 2 that rotate facing each other in step S2 (roll forming step). When passing through, when the first portion 16B1 contacts the surface 2b of the second roll 2 and the second portion 16B2 contacts the surface 1b of the first roll 1, the negative electrode wet granule 16B and the first The liquid bridge force between the surface 1b of the roll 1 and the surface 1b of the second roll 2 tends to be greater than the liquid bridge force between the negative electrode wet granule 16B and the surface 2b of the second roll 2.

For this reason, when the negative electrode wet granules 16B pass through the gap between the first roll 1 and the second roll 2 that rotate facing each other in step S2 (roll forming step), as shown in FIG. In addition, it may adhere to the surface 1 b of the first roll 1 instead of the surface 2 b of the second roll 2 . For this reason, in the film of the negative electrode mixture 6 (film-like negative electrode mixture 8) attached to the surface 2b of the second roll 2, holes are formed at sites where the negative electrode wet granules 16B are removed (or The thickness of the film may be extremely thin at the site). As a result, in the film of the negative electrode mixture 6 (film-like negative electrode mixture 8) transferred from the surface 2b of the second roll 2 onto the surface of the negative electrode current collector foil 7 in step S3 (transfer step), as shown in FIG. As shown in , it is considered that a hole H is formed in the relevant portion (or the thickness of the film becomes extremely thin at the relevant portion), and film formation failure (film formation defect) occurs.

On the other hand, in the present Example 1, the drying apparatus 60 is provided in the roll film-forming apparatus 20. FIG. The drying device 60 includes an air nozzle 61 having an air outlet 61b for blowing out air AR (see FIGS. 1 and 2). The air nozzle 61 is arranged such that the air outlet 61b faces the surface 1b of the first roll 1. As shown in FIG. In the roll forming process of the first embodiment, the air AR is blown from the air nozzle 61 of the drying device 60 to the surface 1b of the first roll 1 to dry the surface 1b of the first roll 1 while the negative electrode mixture 6 ( The negative electrode wet granules 16) are passed through the gap between the first roll 1 and the second roll 2. As shown in FIG.

In this way, by drying the surface 1b of the first roll 1 by blowing air AR (atmosphere) onto the surface 1b of the first roll 1, the moisture content of the surface 1b of the first roll 1 is reduced to that of the second roll 2. can be less than the water content of the surface 2b. In other words, the water content of the surface 2b of the second roll 2 can be made larger than the water content of the surface 1b of the first roll 1. As a result, in step S2 (roll forming step), when the negative electrode mixture 6 passes through the gap between the first roll 1 and the second roll 2, the negative electrode wet granules 16 contained in the negative electrode mixture 6 and the second The average value F1 (kPa) of the liquid bridge force between the surface 1b of the first roll 1 and the liquid bridge force between the negative electrode wet granules 16 contained in the negative electrode mixture 6 and the surface 2b of the second roll 2 and the average value F2 (kPa) satisfy the relationship F1<F2.

By doing so, in step S2 (roll forming step), the negative electrode wet granules 16 contained in the negative electrode mixture 6 pass through the gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. When doing so, it becomes easier to adhere to the surface 2b of the second roll 2, which has a relatively large liquid-bridging force, out of the first roll 1 and the second roll 2. Therefore, in the film of the negative electrode mixture (film-shaped negative electrode mixture 8) formed on the surface 2b of the second roll 2, holes (or extreme reduction in the film thickness) are less likely to occur, and the subsequent step S3 ( In the transfer step), the film of the negative electrode mixture 6 (film-shaped negative electrode mixture 8) transferred onto the surface of the negative electrode current collecting foil 7 is also less likely to have holes (or an extreme decrease in film thickness). That is, film formation defects (film formation defects) are less likely to occur.

Specifically, for example, as shown in FIG. ) As shown in FIG. 8, the negative electrode wet granule 16B having the second portion 16B2 is formed by forming a gap between the first roll 1 and the second roll 2 that rotate facing each other in step S2 (roll forming step). Even when the first portion 16B1 contacts the surface 2b of the second roll 2 and the second portion 16B2 contacts the surface 1b of the first roll 1 when passing through, the negative electrode wet granules 16B and the second roll 2 can be greater than the liquid bridge force between the negative electrode wet granules 16B and the surface 1b of the first roll 1. Moreover, since the peripheral speed of the second roll 2 is higher than that of the first roll 1, as shown in FIG. The surface 2b is stretched more, and the contact area (liquid bridge area) on the surface 2b of the second roll 2 becomes larger than that on the surface 1b of the first roll 1. This enables the negative electrode wet granules 16B to adhere to the surface 2b of the second roll 2, as shown in FIG.

Therefore, in the roll forming step (step S2) of the first embodiment, the film of the negative electrode mixture 6 (the film-like negative electrode mixture 8) attached to the surface 2b of the second roll 2 is Holes (or extreme reduction in film thickness) due to adhesion of the negative electrode wet granules 16 to the surface 1b of the first roll 1 are less likely to occur. As a result, in the subsequent transfer step (step S3), the film of the negative electrode mixture 6 (film-shaped negative electrode mixture 8) transferred from the surface 2b of the second roll 2 onto the surface of the negative electrode current collector foil 7 also has holes. (or an extreme decrease in film thickness) is less likely to occur, and film formation defects (deposition defects) are less likely to occur.

After that, the process proceeds to step S4 (electrode mixture layer forming step), and the current collector foil 9 with the filmy negative electrode mixture is dried in a drying oven (not shown) (the filmy negative electrode transferred onto the surface of the negative electrode current collector foil 7 is dried). drying the mixture 8). As a result, the solvent 15 (water) absorbed (held) in the film-like negative electrode mixture 8 (negative electrode wet granules 16) is removed (evaporated), and the film-like negative electrode mixture 8 becomes a negative electrode mixture. It becomes the layer 18 (electrode mixture layer) (see FIG. 2). As a result, the negative electrode sheet 19 (see FIG. 3) having the negative electrode mixture layer 18 on the surface of the negative electrode current collector foil 7 is obtained.

Note that, in Example 1, an example in which the film-like negative electrode mixture 8 (negative electrode mixture layer 18) is formed only on one side of the negative electrode current collector foil 7 (that is, a single-sided coated negative electrode sheet is manufactured) is shown. However, it may be formed on both sides of the negative electrode current collector foil 7 (that is, a negative electrode sheet coated on both sides may be manufactured). When the negative electrode mixture layer 18 is formed on both sides of the negative electrode current collector foil 7, after manufacturing a single-sided coated negative electrode sheet in which the negative electrode mixture layer 18 is formed on one side of the negative electrode current collector foil 7, the single-sided coating is performed. Steps S2, S3, and S4 may be performed on the surface of the negative electrode collector foil 7 of the negative electrode sheet on which the negative electrode mixture layer 18 is not formed.

The produced negative electrode sheet 19 is then combined with a positive electrode sheet 49 and a separator, which will be described later, to form an electrode body. Next, after attaching a terminal member to the electrode body, the electrode body and the electrolytic solution are accommodated in the battery case. This completes the lithium ion secondary battery.

(Example 2)
Next, Embodiment 2 of the present invention will be described in detail with reference to the drawings. In Example 2, the present invention is applied to manufacture of a positive electrode sheet (electrode sheet) for a lithium ion secondary battery. In Example 2, a positive electrode active material (electrode active material) and a binder are used as materials for a positive electrode mixture (electrode mixture) for forming a positive electrode mixture layer (electrode mixture layer) of a positive electrode sheet. , a conductive material, and a solvent.

In addition, in the present Example 2, nickel cobalt lithium aluminum oxide is used as a positive electrode active material. Also, acetylene black is used as the conductive material. Also, polyvinylidene fluoride (hereinafter also referred to as PVdF) is used as a binder. In addition, N-methylpyrrolidone (hereinafter also referred to as NMP) is used as a solvent.
The positive electrode sheet 49 manufactured in Example 2 has, as shown in FIG.

Here, a method for manufacturing the electrode sheet (positive electrode sheet 49) according to the second embodiment will be described in detail. FIG. 10 is a flow chart showing the flow of the manufacturing method of the electrode sheet (positive electrode sheet 49) according to the second embodiment. FIG. 11 is a subroutine of the flow chart of FIG. 10 and is a flow chart showing the flow of the manufacturing method of the positive electrode composite material 36 . FIG. 12 is a diagram showing a procedure for producing the positive electrode wet granules 56 (the positive electrode mixture 36). In the second embodiment, as in the first embodiment, step T2 (roll forming process) and step T3 (transfer process), which will be described later, are performed using the roll film forming apparatus 20 shown in FIGS.

As shown in FIG. 10, first, in step T1 (electrode mixture preparation step), the positive electrode active material 33, the conductive material 44, the binder 34, and the solvent 35 are mixed and granulated to form a large number of positive electrode wet granules. The granules 56 are produced, and the positive electrode composite material 36 composed of a large number of wet positive electrode granules 56 is produced. Specifically, as shown in FIG. 11, in step T11 (first mixing step), the positive electrode active material 33 and the conductive material 44 are mixed using a known stirring granulator (not shown), and pre-mixed. A body 36A is produced. (See FIG. 12).

Next, proceeding to step T12 (second mixing step), the preceding mixture 36A obtained by mixing the positive electrode active material 33 and the conductive material 44, the binder 34 and the solvent 35 are mixed, and the positive electrode wet granulation is performed. The body 56 is produced, and the positive electrode composite material 36 composed of a large number of positive electrode wet granules 56 is produced. Specifically, a liquid mixture of a binder 34 and a solvent 35 is added to a stirring granulator containing a preceding mixture 36A obtained by mixing a positive electrode active material 33 and a conductive material 44, A large number of positive electrode wet granules 56 are obtained by stirring. In the mixing in step T12 (second mixing step), all components constituting the positive electrode wet granules 56 are mixed. By performing this mixing of all components, the positive electrode mixture 36 composed of a large number of wet positive electrode granules 56 is obtained.

In the positive electrode wet granules 56, as shown in FIG. 7, NMP, which is the solvent 35, contains a plurality of particles of the positive electrode active material 33, particles of the conductive material 44 (not shown), and the binder 34 (not shown). ) are held (absorbed) in a state in which they are aggregated (bonded) (particulate matter). The positive electrode composite material 36 is an aggregate of such wet positive electrode granules 56 .

Moreover, in the first embodiment, the compounding ratio of each component to be mixed in step T11 (first mixing step) and step T12 (second mixing step) is as follows. The mixing ratio (compounding ratio) of the positive electrode active material 33, which is a solid content, the conductive material 44, and the binder 34 is 94.4:4.1:1.5 in terms of weight ratio. Further, in step T12 (second mixing step), the solvent 35 is blended so that the NV (solid content ratio) of the positive electrode wet granules 56 is 81% by weight.

Next, proceeding to step T2 (roll forming step), the positive electrode mixture 36 (positive electrode wet granules 56) produced in step T1 (electrode mixture producing step) is placed against the first roll 1 rotating in opposition. By passing it through the gap between the second roll 2 and compressing the positive electrode mixture 36 into a film, the film-shaped positive electrode mixture 36 is adhered to the surface 2b of the second roll 2 (FIGS. 1 and 2). reference). After that, in step T3 (transfer step), the film-like positive electrode mixture 36 attached to the surface 2b of the second roll 2 (referred to as the film-like positive electrode mixture 38) is transferred onto the surface of the positive electrode current collector foil 37. to be transcribed. As a result, a current collector foil 39 with a positive electrode mixture film is obtained in which the positive electrode mixture film 38 is formed on the positive electrode current collector foil 37 .

By the way, also in the second embodiment, the drying device 60 is provided in the roll film forming apparatus 20 as in the first embodiment. In the roll forming process of the second embodiment, as in the roll forming process of the first embodiment, the air AR is blown from the air nozzle 61 of the drying device 60 to the surface 1b of the first roll 1, so that the surface of the first roll 1 While drying 1b, the positive electrode composite material 36 (positive electrode wet granules 56) is passed through the gap between the first roll 1 and the second roll 2 (see FIGS. 1 and 2).

In this way, by drying the surface 1b of the first roll 1 by blowing air AR (atmosphere) onto the surface 1b of the first roll 1, the moisture content of the surface 1b of the first roll 1 is reduced to that of the second roll 2. can be less than the water content of the surface 2b. In other words, the water content of the surface 2b of the second roll 2 can be made larger than the water content of the surface 1b of the first roll 1. As a result, in step T2 (roll forming step), when the positive electrode mixture 36 passes through the gap between the first roll 1 and the second roll 2, the positive electrode wet granules 56 contained in the positive electrode mixture 36 and the second The average value F1 (kPa) of the liquid bridge force between the surface 1b of the first roll 1 and the liquid bridge force between the positive electrode wet granules 56 contained in the positive electrode mixture 36 and the surface 2b of the second roll 2 and the average value F2 (kPa) satisfy the relationship F1<F2.

By doing so, in step T2 (roll forming step), the positive electrode wet granules 56 contained in the positive electrode mixture 36 pass through the gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. When doing so, it becomes easier to adhere to the surface 2b of the second roll 2, which has a relatively large liquid-bridging force, out of the first roll 1 and the second roll 2. Therefore, in the film of the positive electrode mixture 36 (the film-shaped positive electrode mixture 38) formed on the surface 2b of the second roll 2, holes (or extreme reduction in film thickness) are less likely to occur, and the following step T3 is performed. In the (transfer step), the film of the positive electrode mixture 36 (membrane positive electrode mixture 38) transferred onto the surface of the positive electrode current collector foil 37 is also less likely to have holes (or an extreme reduction in film thickness). That is, film formation defects (film formation defects) are less likely to occur.

Specifically, for example, as shown in FIG. ) As shown in FIG. 8, the positive electrode wet granule 56B having the second portion 56B2 is formed in step T2 (roll forming step) by forming a gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. Even when the first portion 56B1 contacts the surface 2b of the second roll 2 and the second portion 56B2 contacts the surface 1b of the first roll 1 when passing through, the positive electrode wet granules 56B and the second roll 2 can be greater than the liquid bridge force between the positive electrode wet granule 56B and the surface 1b of the first roll 1 . Moreover, since the peripheral speed of the second roll 2 is higher than that of the first roll 1, as shown in FIG. The surface 2b is stretched more, and the contact area (liquid bridge area) on the surface 2b of the second roll 2 becomes larger than that on the surface 1b of the first roll 1. This enables the positive electrode wet granules 56B to adhere to the surface 2b of the second roll 2, as shown in FIG.

Thereafter, the process proceeds to step T4 (electrode mixture layer forming step), in which the current collector foil 39 with the positive electrode mixture is dried in a drying oven (not shown) (the positive electrode film transferred onto the surface of the positive electrode current collector foil 37 is dried). drying the composite 38). As a result, the solvent 35 absorbed (held) in the film-like positive electrode mixture 38 (positive wet granules 56) is removed (evaporated), and the film-like positive electrode mixture 38 becomes the positive electrode mixture layer 48 ( electrode mixture layer) (see FIG. 2). As a result, the positive electrode sheet 49 (see FIG. 3) having the positive electrode mixture layer 48 on the surface of the positive electrode collector foil 37 is obtained.

The second embodiment shows an example in which the film-like positive electrode mixture 38 (positive electrode mixture layer 48) is formed only on one side of the positive electrode current collector foil 37 (that is, a positive electrode sheet coated on one side is manufactured). However, it may be formed on both sides of the positive electrode current collector foil 37 (that is, a positive electrode sheet coated on both sides may be manufactured). When the positive electrode mixture layer 48 is formed on both sides of the positive electrode current collector foil 37, after manufacturing a single-sided coated positive electrode sheet in which the positive electrode mixture layer 48 is formed on one side of the positive electrode current collector foil 37, the single-sided coating is applied. Steps T2, T3, and T4 may be performed on the surface of the positive current collector foil 37 of the positive electrode sheet on which the positive electrode mixture layer 48 is not formed.

(Example 3)
Next, Embodiment 3 of the present invention will be described in detail with reference to the drawings. It should be noted that Example 3 differs from Example 1 only in the roll film forming apparatus used for performing Step S2 (roll forming step) and Step S3 (transfer step), and the rest is the same. . Therefore, here, the points different from the first embodiment will be mainly described, and the description of the same points will be omitted or simplified.

In Example 3, as in Example 1, the present invention is applied to manufacture of the negative electrode sheet 19 (electrode sheet) of a lithium ion secondary battery. In Example 3, as in Example 1, the negative electrode active material 13 was used as the material of the negative electrode mixture 6 (electrode mixture) for forming the negative electrode mixture layer 18 (electrode mixture layer) of the negative electrode sheet 19 . (electrode active material), binder 14 and solvent 15 are used. A method for manufacturing the electrode sheet (negative electrode sheet 19) according to Example 3 will be described in detail below.

As shown in FIG. 4, first, in step S1 (electrode mixture preparation step), the negative electrode active material 13 (carbon material), the binder 14 (CMC), and the solvent 15 (water) are mixed and granulated. A large number of wet negative electrode granules 16 are produced by the above method, and a negative electrode composite material 6 composed of the large number of wet negative electrode granules 16 is produced. That is, a negative electrode mixture 6 equivalent to that of Example 1 is produced.

Next, in step S2 (roll forming step), the negative electrode mixture 6 (negative electrode wet granules 16) produced in step S1 (electrode mixture production step) is placed between the first roll 1 and the first roll 1 rotating in opposition to each other. By passing it through the gap between the second roll 2, the negative electrode mixture 6 is compressed and made into a film, and the film-shaped negative electrode mixture 6 is adhered to the surface 2b of the second roll 2 (see FIGS. 13 and 14). ). Then, in step S3 (transfer step), the film-like negative electrode mixture material 6 attached to the surface 2b of the second roll 2 (referred to as the film-like negative electrode mixture material 8) is transferred onto the surface of the negative electrode current collector foil 7. to be transcribed.

Note that, unlike the first embodiment, in the third embodiment, the roll film forming apparatus 120 shown in FIGS. 13 and 14 is used to perform step S2 (roll forming process) and step S3 (transfer process).
As shown in FIGS. 13 and 14, the roll film forming apparatus 120 of Example 3 differs from the roll film forming apparatus 20 of Example 1 only in that the drying device 60 is changed to a drying device 160. , and so on.

A drying device 160 provided in the roll film forming apparatus 120 of Example 3 includes an air nozzle 161 having an air outlet 161b for blowing dry air DAR to the outside (see FIGS. 13 and 14). The air nozzle 161 is arranged such that the air outlet 161b faces the surface 1b of the first roll 1. As shown in FIG. In the roll forming process of Example 3, the surface 1b of the first roll 1 is dried by blowing dry air DAR from the air nozzle 161 of the drying device 160 onto the surface 1b of the first roll 1, and the negative electrode mixture 6 ( The negative electrode wet granules 16) are passed through the gap between the first roll 1 and the second roll 2. As shown in FIG. In the third embodiment, the surface 1b of the first roll 1 is blown with dry air DAR having a dew point of -30.degree.

In the present embodiment 3, the surface 1b of the first roll 1 is dried by blowing the dry air DAR onto the surface 1b of the first roll 1 as described above. The moisture content of the surface 1b can be made much smaller than the moisture content of the surface 2b of the second roll 2. In other words, compared with Example 1, the moisture content of the surface 2b of the second roll 2 can be made much larger than the moisture content of the surface 1b of the first roll 1.

As a result, in the third embodiment, in step S2 (roll forming step), when the negative electrode mixture 6 passes through the gap between the first roll 1 and the second roll 2, the negative electrode wettability contained in the negative electrode mixture 6 is reduced. The average value F1 (kPa) of the liquid bridge force between the granules 16 and the surface 1b of the first roll 1, and the surface 2b of the negative electrode wet granules 16 and the second roll 2 included in the negative electrode mixture 6 and the average value F2 (kPa) of the liquid bridge force between , satisfies the relationship of F1<F2. Specifically, in the third embodiment, compared with the first embodiment, the difference between F1 and F2 can be increased. That is, F2 can be made much larger than F1.

By doing so, in step S2 (roll forming step), the negative electrode wet granules 16 contained in the negative electrode mixture 6 pass through the gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. When doing so, it becomes even easier to adhere to the surface 2b of the second roll 2, which has a relatively large liquid-bridging force, of the first roll 1 and the second roll 2. Therefore, in the film of the negative electrode mixture (film-like negative electrode mixture 8) formed on the surface 2b of the second roll 2, holes (or extreme reduction in film thickness) are more difficult to occur, and the subsequent steps In S3 (transfer step), the film of the negative electrode mixture 6 (the film-like negative electrode mixture 8) transferred onto the surface of the negative electrode current collector foil 7 is much less likely to have holes (or an extreme decrease in film thickness). Become. That is, film formation defects (film formation defects) are much less likely to occur.

After that, the process proceeds to step S4 (electrode mixture layer forming step), and the current collector foil 9 with the filmy negative electrode mixture is dried in a drying oven (not shown) (the filmy negative electrode transferred onto the surface of the negative electrode current collector foil 7 is dried). drying the mixture 8). As a result, the solvent 15 (water) absorbed (held) in the film-like negative electrode mixture 8 (negative electrode wet granules 16) is removed (evaporated), and the film-like negative electrode mixture 8 becomes a negative electrode mixture. It becomes the layer 18 (electrode mixture layer) (see FIG. 2). As a result, the negative electrode sheet 19 (see FIG. 3) having the negative electrode mixture layer 18 on the surface of the negative electrode current collector foil 7 is obtained.

(Example 4)
Next, Embodiment 4 of the present invention will be described in detail with reference to the drawings. It should be noted that Example 4 differs from Example 2 only in the roll film forming apparatus used for performing step T2 (roll forming step) and step T3 (transfer step), and the rest is the same. . Therefore, here, the points different from the second embodiment will be mainly described, and the description of the same points will be omitted or simplified.

In Example 4, as in Example 2, the present invention is applied to manufacture of a positive electrode sheet 49 (electrode sheet) for a lithium ion secondary battery. In Example 4, as in Example 2, the positive electrode active material 33 was used as the material of the positive electrode mixture 36 (electrode mixture) for forming the positive electrode mixture layer 48 (electrode mixture layer) of the positive electrode sheet 49 . (electrode active material), a binder 34, a conductive material 44, and a solvent 35 are used. A method for manufacturing the electrode sheet (positive electrode sheet 49) according to Example 4 will be described in detail below.

As shown in FIG. 10, first, in step T1 (electrode mixture preparation step), the positive electrode active material 33, the conductive material 44, the binder 34, and the solvent 35 are mixed and granulated to form a large number of positive electrode wet granules. The granules 56 are produced, and the positive electrode composite material 36 composed of a large number of wet positive electrode granules 56 is produced. That is, a positive electrode composite material 36 equivalent to that of Example 2 is produced.

Next, proceeding to step T2 (roll forming step), the positive electrode mixture 36 (positive electrode wet granules 56) produced in step T1 (electrode mixture producing step) is placed against the first roll 1 rotating in opposition. By passing it through the gap between the second roll 2 and compressing the positive electrode mixture 36 into a film, the film-shaped positive electrode mixture 36 is adhered to the surface 2b of the second roll 2 (FIGS. 13 and 14). reference). After that, in step T3 (transfer step), the film-like positive electrode mixture 36 attached to the surface 2b of the second roll 2 (referred to as the film-like positive electrode mixture 38) is transferred onto the surface of the positive electrode current collector foil 37. to be transcribed.

Note that in the fourth embodiment, unlike the second embodiment, the roll film forming apparatus 120 shown in FIGS. 13 and 14 is used to perform step T2 (roll forming process) and step S3 (transfer process). That is, as in the third embodiment, the roll film forming apparatus 120 including the drying device 160 is used as the roll film forming apparatus. Therefore, in the roll forming process of the fourth embodiment, by blowing dry air DAR having a dew point of −30° C. or less from the air nozzle 161 of the drying device 160 onto the surface 1b of the first roll 1, the surface 1b of the first roll 1 While drying, the positive electrode mixture 36 (positive wet granules 56) is passed through the gap between the first roll 1 and the second roll 2.

As a result, in the fourth embodiment, in step T2 (roll forming step), the positive electrode wettability contained in the positive electrode mixture 36 when the positive electrode mixture 36 passes through the gap between the first roll 1 and the second roll 2 The average value F1 (kPa) of the liquid bridge force between the granules 56 and the surface 1b of the first roll 1, and the surface 2b of the positive electrode wet granules 56 and the second roll 2 included in the positive electrode mixture 36 and the average value F2 (kPa) of the liquid bridge force between , satisfies the relationship of F1<F2. Specifically, in the fourth embodiment, the difference between F1 and F2 can be increased compared to the third embodiment. That is, F2 can be made much larger than F1.

By doing so, in step T2 (roll forming step), the positive electrode wet granules 56 contained in the positive electrode mixture 36 pass through the gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. When doing so, it becomes even easier to adhere to the surface 2b of the second roll 2, which has a relatively large liquid-bridging force, of the first roll 1 and the second roll 2. Therefore, in the positive electrode composite material film (film-like positive electrode composite material 38) formed on the surface 2b of the second roll 2, holes (or extreme reduction in film thickness) are much less likely to occur, and the subsequent steps In T3 (transfer step), the film of the positive electrode mixture 36 (membrane positive electrode mixture 38) transferred onto the surface of the positive electrode current collector foil 37 is much less likely to have holes (or an extreme decrease in film thickness). Become. That is, film formation defects (film formation defects) are much less likely to occur.

Thereafter, the process proceeds to step T4 (electrode mixture layer forming step), in which the current collector foil 39 with the positive electrode mixture is dried in a drying oven (not shown) (the positive electrode film transferred onto the surface of the positive electrode current collector foil 37 is dried). drying the composite 38). As a result, the solvent 35 absorbed (held) in the film-like positive electrode mixture 38 (positive wet granules 56) is removed (evaporated), and the film-like positive electrode mixture 38 becomes the positive electrode mixture layer 48 ( electrode mixture layer) (see FIG. 2). As a result, the positive electrode sheet 49 (see FIG. 3) having the positive electrode mixture layer 48 on the surface of the positive electrode collector foil 37 is obtained.

(Example 5)
Next, Embodiment 5 of the present invention will be described in detail with reference to the drawings. It should be noted that Example 5 differs from Example 1 only in the roll film forming apparatus used for performing Step S2 (roll forming step) and Step S3 (transfer step), and the rest is the same. . Therefore, here, the points different from the first embodiment will be mainly described, and the description of the same points will be omitted or simplified.

As shown in FIG. 4, first, in step S1 (electrode mixture preparation step), the negative electrode active material 13 (carbon material), the binder 14 (CMC), and the solvent 15 (water) are mixed and granulated. A large number of wet negative electrode granules 16 are produced by the above method, and a negative electrode composite material 6 composed of the large number of wet negative electrode granules 16 is produced. That is, a negative electrode mixture 6 equivalent to that of Example 1 is produced.

Next, in step S2 (roll forming step), the negative electrode mixture 6 (negative electrode wet granules 16) produced in step S1 (electrode mixture production step) is placed between the first roll 1 and the first roll 1 rotating in opposition to each other. By passing it through the gap between the second roll 2, the negative electrode mixture 6 is compressed and made into a film, and the film-shaped negative electrode mixture 6 is adhered to the surface 2b of the second roll 2 (see FIGS. 15 and 16). ). Then, in step S3 (transfer step), the film-like negative electrode mixture material 6 attached to the surface 2b of the second roll 2 (referred to as the film-like negative electrode mixture material 8) is transferred onto the surface of the negative electrode current collector foil 7. to be transcribed.

Note that, in the fifth embodiment, unlike the first embodiment, the roll film forming apparatus 220 shown in FIGS. 15 and 16 is used to perform step S2 (roll forming process) and step S3 (transfer process).
As shown in FIGS. 15 and 16, the roll film forming apparatus 220 of Example 5 does not have the drying device 60, but has a moistening device 260, unlike the roll film forming device 20 of Example 1. Only the points are different, and the others are the same.

The wetting device 260 provided in the roll film forming apparatus 220 of the fifth embodiment includes a nonwoven fabric 261 arranged on the surface 2b of the second roll 2 and the nonwoven fabric 261 on the surface 2b of the second roll 2. and pressing means (not shown) for pressing (see FIGS. 15 and 16). Of these, the nonwoven fabric 261 is impregnated with a liquid L1 (that is, water) that is equivalent to the solvent 15 contained in the negative electrode mixture 6 . Therefore, in the roll forming process of the fifth embodiment, the nonwoven fabric 261 is pressed against the surface 2b of the rotating second roll 2 by the pressing means (not shown) of the wetting device 260, whereby the liquid L1 contained in the nonwoven fabric 261 is is attached to the surface 2b of the second roll 2. As a result, the negative electrode mixture 6 (negative electrode wet granules 16) is passed through the gap between the first roll 1 and the second roll 2 while the surface 2b of the second roll 2 is moistened.

In the present embodiment 5, the surface 2b of the second roll 2 is thus wetted by adhering the liquid L1 to the surface 2b of the second roll 2, so that the water content of the surface 2b of the second roll 2 is It can be made larger than the moisture content of the surface 1 b of the first roll 1 . As a result, in the present Example 5, in step S2 (roll forming step), the negative electrode wettability contained in the negative electrode mixture 6 when the negative electrode mixture 6 passes through the gap between the first roll 1 and the second roll 2 The average value F1 (kPa) of the liquid bridge force between the granules 16 and the surface 1b of the first roll 1, and the surface 2b of the negative electrode wet granules 16 and the second roll 2 included in the negative electrode mixture 6 and the average value F2 (kPa) of the liquid bridge force between , satisfies the relationship of F1<F2.

By doing so, in step S2 (roll forming step), the negative electrode wet granules 16 contained in the negative electrode mixture 6 pass through the gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. When doing so, it becomes easier to adhere to the surface 2b of the second roll 2, which has a relatively large liquid-bridging force, out of the first roll 1 and the second roll 2. Therefore, in the film of the negative electrode mixture (film-shaped negative electrode mixture 8) formed on the surface 2b of the second roll 2, holes (or extreme reduction in the film thickness) are less likely to occur, and the subsequent step S3 ( transfer step), the film of the negative electrode mixture 6 (the film-like negative electrode mixture 8) transferred onto the surface of the negative electrode current collecting foil 7 is less likely to have holes (or an extreme decrease in film thickness). That is, film formation defects (film formation defects) are less likely to occur.

After that, the process proceeds to step S4 (electrode mixture layer forming step), and the current collector foil 9 with the filmy negative electrode mixture is dried in a drying oven (not shown) (the filmy negative electrode transferred onto the surface of the negative electrode current collector foil 7 is dried). drying the mixture 8). As a result, the solvent 15 (water) absorbed (held) in the film-like negative electrode mixture 8 (negative electrode wet granules 16) is removed (evaporated), and the film-like negative electrode mixture 8 becomes a negative electrode mixture. It becomes the layer 18 (electrode mixture layer) (see FIG. 2). As a result, the negative electrode sheet 19 (see FIG. 3) having the negative electrode mixture layer 18 on the surface of the negative electrode current collector foil 7 is obtained.

(Example 6)
Next, Embodiment 6 of the present invention will be described in detail with reference to the drawings. It should be noted that Example 6 differs from Example 2 only in the roll film forming apparatus used for performing step T2 (roll forming step) and step T3 (transfer step), and the rest is the same. . Therefore, here, the points different from the second embodiment will be mainly described, and the description of the same points will be omitted or simplified.

As shown in FIG. 10, first, in step T1 (electrode mixture preparation step), the positive electrode active material 33, the conductive material 44, the binder 34, and the solvent 35 are mixed and granulated to form a large number of positive electrode wet granules. The granules 56 are produced, and the positive electrode composite material 36 composed of a large number of wet positive electrode granules 56 is produced. That is, a positive electrode composite material 36 equivalent to that of Example 2 is produced.

Next, proceeding to step T2 (roll forming step), the positive electrode mixture 36 (positive electrode wet granules 56) produced in step T1 (electrode mixture producing step) is placed against the first roll 1 rotating in opposition. By passing it through the gap between the second roll 2 and compressing the positive electrode mixture 36 into a film, the film-shaped positive electrode mixture 36 is adhered to the surface 2b of the second roll 2 (FIGS. 15 and 16). reference). After that, in step T3 (transfer step), the film-like positive electrode mixture 36 attached to the surface 2b of the second roll 2 (referred to as the film-like positive electrode mixture 38) is transferred onto the surface of the positive electrode current collector foil 37. to be transcribed.

In addition, in the sixth embodiment, unlike the second embodiment, the roll film forming apparatus 220 shown in FIGS. 15 and 16 is used to perform step S2 (roll forming process) and step S3 (transfer process). That is, as in Example 5, the roll film forming apparatus 220 including the wetting device 260 is used as the roll film forming apparatus. However, in the sixth embodiment, unlike the fifth embodiment, the nonwoven fabric 261 of the wetting device 260 is impregnated with the liquid L2 (that is, NMP) equivalent to the solvent 35 contained in the positive electrode mixture 36 .

In the roll forming process of Example 6, similarly to Example 5, the liquid L2 contained in the nonwoven fabric 261 is removed by pressing the nonwoven fabric 261 of the wetting device 260 against the surface 2b of the rotating second roll 2. By adhering to the surface 2b of the second roll 2, the surface 2b of the second roll 2 is moistened, and the positive electrode composite material 36 (positive wet granules 56) is placed in the gap between the first roll 1 and the second roll 2. I'm going through

As a result, in the sixth embodiment, in step T2 (roll forming step), the positive electrode wettability contained in the positive electrode mixture 36 when the positive electrode mixture 36 passes through the gap between the first roll 1 and the second roll 2 The average value F1 (kPa) of the liquid bridge force between the granules 56 and the surface 1b of the first roll 1, and the surface 2b of the positive electrode wet granules 56 and the second roll 2 included in the positive electrode mixture 36 and the average value F2 (kPa) of the liquid bridge force between , satisfies the relationship of F1<F2.

By doing so, in step T2 (roll forming step), the positive electrode wet granules 56 contained in the positive electrode mixture 36 pass through the gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. When doing so, it becomes easier to adhere to the surface 2b of the second roll 2, which has a relatively large liquid-bridging force, out of the first roll 1 and the second roll 2. Therefore, in the positive electrode composite material film (film-like positive electrode composite material 38) formed on the surface 2b of the second roll 2, holes (or extreme reduction in film thickness) are less likely to occur, and the following step T3 ( In the transfer step), the film of the positive electrode mixture 36 (membrane positive electrode mixture 38) transferred onto the surface of the positive electrode current collecting foil 37 is less likely to have holes (or an extreme decrease in film thickness). That is, film formation defects (film formation defects) are less likely to occur.

Thereafter, the process proceeds to step T4 (electrode mixture layer forming step), in which the current collector foil 39 with the positive electrode mixture is dried in a drying oven (not shown) (the positive electrode film transferred onto the surface of the positive electrode current collector foil 37 is dried). drying the composite 38). As a result, the solvent 35 absorbed (held) in the film-like positive electrode mixture 38 (positive wet granules 56) is removed (evaporated), and the film-like positive electrode mixture 38 becomes the positive electrode mixture layer 48 ( electrode mixture layer) (see FIG. 2). As a result, the positive electrode sheet 49 (see FIG. 3) having the positive electrode mixture layer 48 on the surface of the positive electrode collector foil 37 is obtained.

(Example 7)
Next, Embodiment 7 of the present invention will be described in detail with reference to the drawings. It should be noted that Example 7 differs from Example 5 only in the roll film forming apparatus used for performing Step S2 (roll forming step) and Step S3 (transfer step), and the rest is the same. . Therefore, here, the points different from the first embodiment will be mainly described, and the description of the same points will be omitted or simplified.

As shown in FIG. 4, first, in step S1 (electrode mixture preparation step), the negative electrode active material 13 (carbon material), the binder 14 (CMC), and the solvent 15 (water) are mixed and granulated. A large number of wet negative electrode granules 16 are produced by the above method, and a negative electrode composite material 6 composed of the large number of wet negative electrode granules 16 is produced. That is, a negative electrode mixture 6 equivalent to that of Example 1 is produced.

Next, in step S2 (roll forming step), the negative electrode mixture 6 (negative electrode wet granules 16) produced in step S1 (electrode mixture production step) is placed between the first roll 1 and the first roll 1 rotating in opposition to each other. By passing it through the gap between the second roll 2, the negative electrode mixture 6 is compressed and formed into a film, and the film-shaped negative electrode mixture 6 is adhered to the surface 2b of the second roll 2 (see FIGS. 17 and 18). ). Then, in step S3 (transfer step), the film-like negative electrode mixture material 6 attached to the surface 2b of the second roll 2 (referred to as the film-like negative electrode mixture material 8) is transferred onto the surface of the negative electrode current collector foil 7. to be transcribed.

Note that, in the seventh embodiment, unlike the fifth embodiment, the roll film forming apparatus 320 shown in FIGS. 17 and 18 is used to perform step S2 (roll forming process) and step S3 (transfer process).
As shown in FIGS. 17 and 18, the roll film forming apparatus 320 of Example 7 is different from the roll film forming apparatus 220 of Example 5 only in that a wetting device 360 is provided instead of the wetting device 260. are different and otherwise similar.

The wetting device 360 provided in the roll film forming apparatus 320 of the seventh embodiment includes a plurality of spray nozzles 361 arranged above the second roll 2 and a liquid supply unit (not shown) that supplies liquid to the spray nozzles 361. and (see FIGS. 17 and 18). In addition, in Example 7, as the liquid supplied to the spray nozzle 361, the liquid L1 (that is, water), which is equivalent to the solvent 15 contained in the negative electrode mixture 6, is used. Therefore, in the roll forming process of the seventh embodiment, the liquid L1 sprayed downward from the spray nozzle 361 is adhered to the surface 2b of the second roll 2, thereby moistening the surface 2b of the second roll 2. The negative electrode composite material 6 (negative electrode wet granules 16) is passed through the gap between the first roll 1 and the second roll 2. As shown in FIG.

In the present embodiment 7, the surface 2b of the second roll 2 is thus wetted by adhering the liquid L1 to the surface 2b of the second roll 2, so that the water content of the surface 2b of the second roll 2 is reduced to It can be made larger than the moisture content of the surface 1 b of the first roll 1 . As a result, in Example 7, in step S2 (roll forming step), when the negative electrode mixture 6 passes through the gap between the first roll 1 and the second roll 2, the negative electrode wettability contained in the negative electrode mixture 6 is reduced. The average value F1 (kPa) of the liquid bridge force between the granules 16 and the surface 1b of the first roll 1, and the surface 2b of the negative electrode wet granules 16 and the second roll 2 included in the negative electrode mixture 6 and the average value F2 (kPa) of the liquid bridge force between , satisfies the relationship of F1<F2.

By doing so, in step S2 (roll forming step), the negative electrode wet granules 16 contained in the negative electrode mixture 6 pass through the gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. When doing so, it becomes easier to adhere to the surface 2b of the second roll 2, which has a relatively large liquid-bridging force, out of the first roll 1 and the second roll 2. Therefore, in the film of the negative electrode mixture (film-shaped negative electrode mixture 8) formed on the surface 2b of the second roll 2, holes (or extreme reduction in the film thickness) are less likely to occur, and the subsequent step S3 ( transfer step), the film of the negative electrode mixture 6 (the film-like negative electrode mixture 8) transferred onto the surface of the negative electrode current collecting foil 7 is less likely to have holes (or an extreme decrease in film thickness). That is, film formation defects (film formation defects) are less likely to occur.

After that, the process proceeds to step S4 (electrode mixture layer forming step), and the current collector foil 9 with the filmy negative electrode mixture is dried in a drying oven (not shown) (the filmy negative electrode transferred onto the surface of the negative electrode current collector foil 7 is dried). drying the mixture 8). As a result, the solvent 15 (water) absorbed (held) in the film-like negative electrode mixture 8 (negative electrode wet granules 16) is removed (evaporated), and the film-like negative electrode mixture 8 becomes a negative electrode mixture. It becomes the layer 18 (electrode mixture layer) (see FIG. 2). As a result, the negative electrode sheet 19 (see FIG. 3) having the negative electrode mixture layer 18 on the surface of the negative electrode current collector foil 7 is obtained.

(Example 8)
Next, Embodiment 8 of the present invention will be described in detail with reference to the drawings. It should be noted that Example 8 differs from Example 6 only in the roll film forming apparatus used for performing step T2 (roll forming step) and step T3 (transfer step), and the rest is the same. . Therefore, here, the points different from the sixth embodiment will be mainly described, and the description of the same points will be omitted or simplified.

As shown in FIG. 10, first, in step T1 (electrode mixture preparation step), the positive electrode active material 33, the conductive material 44, the binder 34, and the solvent 35 are mixed and granulated to form a large number of positive electrode wet granules. The granules 56 are produced, and the positive electrode composite material 36 composed of a large number of wet positive electrode granules 56 is produced. That is, a positive electrode composite material 36 equivalent to that of Example 2 is produced.

Next, proceeding to step T2 (roll forming step), the positive electrode mixture 36 (positive electrode wet granules 56) produced in step T1 (electrode mixture producing step) is placed against the first roll 1 rotating in opposition. By passing it through the gap between the second roll 2 and compressing the positive electrode mixture 36 into a film, the film-shaped positive electrode mixture 36 is adhered to the surface 2b of the second roll 2 (FIGS. 17 and 18). reference). After that, in step T3 (transfer step), the film-like positive electrode mixture 36 attached to the surface 2b of the second roll 2 (referred to as the film-like positive electrode mixture 38) is transferred onto the surface of the positive electrode current collector foil 37. to be transcribed.

In addition, in the eighth embodiment, unlike the sixth embodiment, the roll film forming apparatus 320 shown in FIGS. 17 and 18 is used to perform step S2 (roll forming process) and step S3 (transfer process). That is, as in Example 7, the roll film forming apparatus 320 including the wetting device 360 is used as the roll film forming apparatus. However, in the eighth embodiment, unlike the seventh embodiment, as the liquid supplied to the spray nozzle 361, the same liquid L2 as the solvent 35 contained in the positive electrode mixture 36 (that is, NMP) is used.

In the roll forming process of Example 8, similarly to Example 7, the liquid L2 sprayed downward from the spray nozzle 361 is caused to adhere to the surface 2b of the second roll 2, so that the surface 2b of the second roll 2 The positive electrode mixture 36 (positive wet granules 56) is passed through the gap between the first roll 1 and the second roll 2 while wetting the positive electrode mixture.

As a result, in the eighth embodiment, in step T2 (roll forming step), the positive electrode wettability contained in the positive electrode mixture 36 when the positive electrode mixture 36 passes through the gap between the first roll 1 and the second roll 2 The average value F1 (kPa) of the liquid bridge force between the granules 56 and the surface 1b of the first roll 1, and the surface 2b of the positive electrode wet granules 56 and the second roll 2 included in the positive electrode mixture 36 and the average value F2 (kPa) of the liquid bridge force between , satisfies the relationship of F1<F2.

By doing so, in step T2 (roll forming step), the positive electrode wet granules 56 contained in the positive electrode mixture 36 pass through the gap between the first roll 1 and the second roll 2 that rotate in opposition to each other. When doing so, it becomes easier to adhere to the surface 2b of the second roll 2, which has a relatively large liquid-bridging force, out of the first roll 1 and the second roll 2. Therefore, in the positive electrode composite material film (film-like positive electrode composite material 38) formed on the surface 2b of the second roll 2, holes (or extreme reduction in film thickness) are less likely to occur, and the following step T3 ( In the transfer step), the film of the positive electrode mixture 36 (membrane positive electrode mixture 38) transferred onto the surface of the positive electrode current collecting foil 37 is less likely to have holes (or an extreme decrease in film thickness). That is, film formation defects (film formation defects) are less likely to occur.

Thereafter, the process proceeds to step T4 (electrode mixture layer forming step), in which the current collector foil 39 with the positive electrode mixture is dried in a drying oven (not shown) (the positive electrode film transferred onto the surface of the positive electrode current collector foil 37 is dried). drying the composite 38). As a result, the solvent 35 absorbed (held) in the film-like positive electrode mixture 38 (positive wet granules 56) is removed (evaporated), and the film-like positive electrode mixture 38 becomes the positive electrode mixture layer 48 ( electrode mixture layer) (see FIG. 2). As a result, the positive electrode sheet 49 (see FIG. 3) having the positive electrode mixture layer 48 on the surface of the positive electrode collector foil 37 is obtained.

(Evaluation test of manufacturing method)
Next, tests were conducted to evaluate the manufacturing methods of Examples 1-4. Specifically, using the roll film forming apparatuses 20 and 120 of each example, a current collector foil 9 with a film-like negative electrode mixture or a current collector foil 39 with a film-like positive electrode mixture having a length of 100 m was produced. Then, for the collector foil 9 with the filmy negative electrode mixture or the collector foil 39 with the filmy positive electrode mixture of each example, the number of film formation failures (film formation defects) occurring in a length of 100 m was determined. investigated. Table 1 shows the results.

Further, as Comparative Example 1, a 100-m-long film-like negative electrode mixture material was prepared using a roll film-forming apparatus that was different from the roll film-forming apparatus 20 of Example 1 only in that the drying device 60 was not provided. A current collector foil 9 with Furthermore, as Comparative Example 2, a positive electrode mixture film having a length of 100 m was prepared using a roll film forming apparatus that was different from the roll film forming apparatus 20 of Example 1 only in that the drying device 60 was not provided. A current-collecting foil 39 was produced. Also for these, the number of film formation failures (film formation defects) occurring in a length of 100 m was investigated. Table 1 shows the results.

Further, in the roll forming process of Examples 1 to 4 and Comparative Examples 1 and 2, "When the negative electrode mixture 6 passes through the gap between the first roll 1 and the second roll 2, The average value F1 (kPa) of the liquid bridge force between the negative electrode wet granule 16 and the surface 1b of the first roll 1”, or “the gap between the positive electrode mixture 36 and the first roll 1 and the second roll 2 The average value F1 (kPa) of the liquid bridge force between the positive electrode wet granules 56 contained in the positive electrode mixture 36 and the surface 1b of the first roll 1 when passing through the roller was investigated. In addition, in this test, the average value F1 (kPa) of the liquid bridge force is obtained as follows.

Specifically, the average value F1 (kPa) of the liquid bridge force was obtained using a known powder layer shear force measuring device 90 (see FIG. 19). The powder layer shear force measuring device 90 includes a flat plate 91 having a surface 91b (equal in surface roughness and the like) to the surface 1b of the first roll 1, and a cylindrical body placed on the surface 91b of the flat plate 91. 93 and a columnar piston 95 capable of moving up and down inside the cylindrical body 93 .

For example, the average value F1 (kPa) of the liquid bridge force in step S2 (roll forming step) of Example 1 is obtained as follows. First, by housing the negative electrode mixture 6 (negative electrode wet granules 16 ) inside the cylinder 93 , the negative electrode wet granules 16 constituting the negative electrode mixture 6 are brought into contact with the surface 91 b of the flat plate 91 . After that, the negative electrode composite material 6 is pressed vertically downward by the piston 95 to apply a predetermined vertical stress (kPa) to the negative electrode wet granules 16 constituting the negative electrode composite material 6 . In this state, by moving the flat plate 91 in the horizontal direction (right direction in FIG. 19), a shear stress is applied to the negative electrode wet granules 16 constituting the negative electrode mixture 6, and the shear stress ( kPa) was measured.

However, similarly to the roll film forming apparatus 20 of Example 1, by blowing the air AR from the air nozzle 61 of the drying device 60 to the surface 91b of the flat plate 91, the surface 91b of the flat plate 91 is dried, and the above measurement test is performed. Is going. That is, similarly to the surface 1b of the first roll 1 in the roll forming process of Example 1, the shear stress (kPa) is measured in a state where the surface 91b of the flat plate 91 is dried. Further, the vertical stress (kPa) applied to the negative electrode wet granules 16 constituting the negative electrode mixture 6 by the piston 95 was varied, and the shear stress (kPa) at each vertical stress (kPa) was measured. The same applies to the measurement of shear stress (kPa) according to Example 2, which will be described later.

Then, as shown in FIG. 20, these measurement data are plotted on a coordinate plane with normal stress (kPa) on the horizontal axis and shear stress (kPa) on the vertical axis. Then, these plotted data were linearly approximated using the method of least squares to obtain a relational expression (linear expression) between normal stress (kPa) and shear stress (kPa) as shown by a straight line in FIG. The y-intercept of this linear expression (straight line) (that is, the value of the shear stress when the value of the normal stress is 0) is taken as "the negative electrode mixture 6 is the first roll 1 and the second roll 2, the average value F1 (kPa) of the liquid bridge force between the negative electrode wet granules 16 contained in the negative electrode mixture 6 and the surface 1b of the first roll 1" considered.

Similarly, in the roll forming process of Examples 2 to 4 and Comparative Examples 1 and 2, "When the negative electrode mixture 6 passes through the gap between the first roll 1 and the second roll 2, the negative electrode mixture 6 The average value F1 (kPa) of the liquid bridge force between the negative electrode wet granules 16 and the surface 1 b of the first roll 1 contained in the “positive electrode mixture 36 is the first roll 1 and the second roll 2 The average value F1 (kPa) of the liquid bridge force between the positive electrode wet granules 56 contained in the positive electrode mixture 36 and the surface 1b of the first roll 1 when passing through the gap between . These results are shown in Table 1.

However, when obtaining the average value F1 (kPa) of the liquid bridge force in Examples 3 and 4, the surface of the flat plate 91 from the air nozzle 161 of the drying device 160 is The measurement test described above is performed while drying the surface 91b of the flat plate 91 by blowing the dry air DAR onto the flat plate 91b. That is, similarly to the surface 1b of the first roll 1 in the roll forming process of Examples 3 and 4, the surface 91b of the flat plate 91 is dried and the shear stress (kPa) is measured. In this measurement test, a dry air DAR with a dew point of −30° C. is used as the dry air DAR.
Further, when obtaining the average value F1 (kPa) of the liquid bridging force applied to Comparative Examples 1 and 2, the above-described measurement test is performed without blowing air or the like to the surface 91b of the flat plate 91 .

Furthermore, tests were conducted to evaluate the manufacturing methods of Examples 5-8. Specifically, using the roll film forming apparatuses 220 and 320 of each example, a current collector foil 9 with a film-like negative electrode mixture or a current collector foil 39 with a film-like positive electrode mixture having a length of 100 m was produced. Then, for the collector foil 9 with the filmy negative electrode mixture or the collector foil 39 with the filmy positive electrode mixture of each example, the number of film formation failures (film formation defects) occurring in a length of 100 m was determined. investigated. Table 2 shows the results.

In addition, as Comparative Example 3, a film-like negative electrode mixture material having a length of 100 m was prepared using a roll film forming apparatus that was different from the roll film forming apparatus 220 of Example 5 only in that the wetting device 260 was not provided. A current collector foil 9 with Furthermore, as Comparative Example 4, a positive electrode composite film having a length of 100 m was prepared by using a roll film forming apparatus that was different from the roll film forming apparatus 220 of Example 5 only in that the wetting device 260 was not provided. A current-collecting foil 39 was produced. Also for these, the number of film formation failures (film formation defects) occurring in a length of 100 m was investigated. Table 2 shows the results.

Further, in the roll forming process of Examples 5 to 8 and Comparative Examples 3 and 4, "When the negative electrode mixture 6 passes through the gap between the first roll 1 and the second roll 2, Average value F2 (kPa) of the liquid bridge force between the negative electrode wet granules 16 and the surface 2b of the second roll 2”, or “the gap between the positive electrode mixture 36 and the first roll 1 and the second roll 2 The average value F2 (kPa) of the liquid bridge force between the positive electrode wet granules 56 contained in the positive electrode mixture 36 and the surface 2b of the second roll 2 when passing through the roller was investigated. In addition, in this test, the average value F2 (kPa) of the liquid bridge force is obtained as follows.

Specifically, similarly to the average value F1 (kPa) of the liquid bridge force according to Example 1 and the like described above, using the powder layer shear force measuring device 90 (see FIG. 19), the average value of the liquid bridge force F2 (kPa) was obtained. In addition, since the surface 1b of the first roll 1 and the surface 2b of the second roll 2 are equivalent surfaces (surface roughness etc. are equivalent), in this test, the surface 1b of the first roll 1 and the surface 2b of the second roll 2 The surface 91b of the flat plate 91 is commonly used as a substitute for the surface 2b of the plate.

However, when obtaining the average value F2 (kPa) of the liquid bridge force according to Examples 5 and 6, the liquids L1 and L2 contained in the nonwoven fabric 261 are is adhered to the surface 91b of the flat plate 91 to wet the surface 91b of the flat plate 91 while performing the above measurement test. That is, similarly to the surface 2b of the second roll 2 in the roll forming process of Examples 5 and 6, the shear stress (kPa) is measured while the surface 91b of the flat plate 91 is wet.

Further, when obtaining the average value F2 (kPa) of the liquid bridge force according to Examples 7 and 8, the liquids L1 and L2 sprayed from the spray nozzle 361 are is adhered to the surface 91b of the flat plate 91 to wet the surface 91b of the flat plate 91 while performing the above measurement test. That is, similarly to the surface 2b of the second roll 2 in the roll forming process of Examples 7 and 8, the shear stress (kPa) is measured with the surface 91b of the flat plate 91 wet.
Further, when obtaining the average value F2 (kPa) of the liquid bridging force applied to Comparative Examples 3 and 4, the above-described measurement test is performed without the liquid adhering to the surface 91 b of the flat plate 91 .

After that, in the same manner as the average value F1 (kPa) of the liquid bridge force described above, for each example and comparative example, the vertical stress (kPa) was plotted on the horizontal axis, and the shear stress (kPa) was plotted on the vertical axis. Plot in the coordinate plane (see Figure 20). Then, these plotted data were linearly approximated using the method of least squares to obtain a relational expression (linear expression) between normal stress (kPa) and shear stress (kPa) as shown by a straight line in FIG. The y-intercept of this linear expression (straight line) (that is, the value of shear stress when the value of normal stress is 0) is the average value F2 of the liquid bridge force in step S2 (roll forming process) of each example and comparative example (kPa). These results are shown in Table 2.

Here, the results shown in Tables 1 and 2 are examined.
First, the results of Examples 1 to 4 and Comparative Examples 1 and 2 shown in Table 1 are examined. In Comparative Example 1, the average value F1 of the liquid bridge force was 9.3 kPa, and there were 213 film formation defects (film formation defects). Further, in Comparative Example 2, the average value F1 of the liquid bridge force was 6.2 kPa, and there were 168 film formation defects (film formation defects).

On the other hand, in Example 1, the average value F1 of the liquid bridge force was as small as 2.8 kPa, and the number of film formation defects (film formation defects) was reduced to nine. In addition, in Example 2, the average value F1 of the liquid bridge force was as small as 1.6 kPa, and the film formation defects (film formation defects) were reduced to 7 locations. Furthermore, in Example 3, the average value F1 of the liquid bridging force was extremely small, at 0.4 kPa, and the film formation defects (film formation defects) were extremely small at two locations. Furthermore, in Example 4, the average value F1 of the liquid bridging force was extremely small, at 0.2 kPa, and the film formation defects (film formation defects) were extremely small at two locations.

As described above, in Examples 1 to 4, compared with Comparative Examples 1 and 2, film formation defects (film formation defects) could be significantly reduced. The reason for this is that in Examples 1 to 4, compared with Comparative Examples 1 and 2, the average value F1 of the liquid bridging force could be significantly reduced.

Specifically, in Examples 1 and 2, the surface 1b of the first roll 1 is dried by blowing air AR from the air nozzle 61 of the drying device 60 to the surface 1b of the first roll 1 in the roll forming process. At the same time, the negative electrode composite material 6 (negative electrode wet granules 16) or the positive electrode composite material 36 (positive electrode wet granules 56) is passed through the gap between the first roll 1 and the second roll 2, thereby forming a liquid bridge. This is because the average force value F1 is reduced to satisfy the relationship F1<F2 (see FIGS. 1 and 2).

Further, in Examples 3 and 4, in the roll forming process, the surface 1b of the first roll 1 was dried by blowing dry air DAR from the air nozzle 161 of the drying device 160 onto the surface 1b of the first roll 1, and the negative electrode was formed. By passing the composite material 6 (negative electrode wet granules 16) or the positive electrode composite material 36 (positive electrode wet granules 56) through the gap between the first roll 1 and the second roll 2, the average liquid bridge force This is because the value F1 is significantly reduced to satisfy the relationship F1<F2 (see FIGS. 13 and 14).

It can be said that the value of F2 in Examples 1 and 3 and Comparative Example 1 is equivalent to the value of F2 in Comparative Example 3. That is, it can be said that F2=9.3 (kPa).
In addition, it can be said that the F2 value in Examples 2 and 4 and Comparative Example 2 is equivalent to the F2 value in Comparative Example 4. That is, it can be said that F2=6.2 (kPa).

By doing so, in Examples 1 to 4, the negative electrode wet granules 16 contained in the negative electrode mixture 6 or the positive electrode wet granules 56 contained in the positive electrode mixture 36 faced each other in the roll forming step. When passing through the gap between the first roll 1 and the second roll 2 that rotate with the As a result, it can be said that film formation defects (film formation defects) are less likely to occur.

From the above results, it can be said that film formation defects (film formation defects) are less likely to occur by drying the surface 1b of the first roll 1 and satisfying the relationship F1<F2 in the roll forming process. Furthermore, in the roll forming process, in addition to satisfying the relationship of F1 < F2, by satisfying the relationship of F1 ≤ 2.8 kPa, film formation defects (film formation defects) are extremely difficult to occur. It can be said that

The reason why Examples 3 and 4 were able to reduce film formation defects (film formation defects) as compared with Examples 1 and 2 is considered as follows. Specifically, in Examples 1 and 2, air AR (atmosphere) is blown onto the surface 1b of the first roll 1, whereas in Examples 3 and 4, the dew point is −30° C. or less (the above-mentioned In the test, dry air DAR of −30° C.) was blown, so compared to Examples 1 and 2, it can be said that the surface 1b of the first roll 1 was able to be further dried. As a result, in Examples 3 and 4, compared to Examples 1 and 2, F1 becomes even smaller, and the negative electrode wet granules 16 contained in the negative electrode mixture 6 or the positive electrode wet granules contained in the positive electrode mixture It can be said that the granules 56 are more likely to adhere to the surface 2b of the second roll 2, and as a result, film formation defects (film formation defects) are less likely to occur.

Next, the results of Examples 5 to 8 and Comparative Examples 3 and 4 shown in Table 2 are examined. In Comparative Example 3, the average value F2 of the liquid bridge force was 9.3 kPa, and there were 213 film formation defects (film formation defects). Further, in Comparative Example 4, the average value F1 of the liquid bridge force was 6.2 kPa, and there were 168 film formation defects (film formation defects).

On the other hand, in Example 5, the average value F2 of the liquid bridging force was as large as 29.1 kPa, and the film formation defects (film formation defects) were very few at three locations. In Example 6, the average value F2 of the liquid bridging force was as large as 13.6 kPa, and the number of defective film formations (defects in film formation) was extremely small at 5 locations. Furthermore, in Example 7, the average value F2 of the liquid bridging force increased to 19.1 kPa, and the film formation defects (film formation defects) decreased to 13 locations. Furthermore, in Example 8, the average value F2 of the liquid bridging force increased to 12.4 kPa, and the film formation defects (film formation defects) decreased to 19 locations.

As described above, in Examples 5 to 8, as compared with Comparative Examples 3 and 4, film formation defects (film formation defects) could be significantly reduced. The reason for this is that in Examples 5 to 8, compared with Comparative Examples 3 and 4, the average value F2 of the liquid bridging force was able to be increased.

Specifically, in Examples 5 and 6, the surface 2b of the second roll 2 was made to adhere to the surface 2b of the second roll 2 using the wetting device 260 in the roll forming process. By passing the negative electrode composite material 6 (negative electrode wet granules 16) or the positive electrode composite material 36 (positive electrode wet granules 56) through the gap between the first roll 1 and the second roll 2 while wetting, This is because the average value F2 of the liquid bridge force is increased to satisfy the relationship F1<F2 (see FIGS. 15 and 16).

Further, in Examples 7 and 8, in the roll forming process, the wetting device 360 is used to adhere the liquid L1 or L2 to the surface 2b of the second roll 2, thereby moistening the surface 2b of the second roll 2. , the negative electrode composite material 6 (the wet negative electrode granules 16) or the positive electrode composite material 36 (the wet positive electrode granules 56) is passed through the gap between the first roll 1 and the second roll 2, so that the liquid bridge force This is because the average value F2 of is increased to satisfy the relationship F1<F2 (see FIGS. 17 and 18).

It can be said that the value of F1 in Examples 5 and 7 and Comparative Example 3 is equivalent to the value of F1 in Comparative Example 1. That is, it can be said that F1=9.3 (kPa).
In addition, it can be said that the F1 value in Examples 6 and 8 and Comparative Example 4 is equivalent to the F1 value in Comparative Example 2. That is, it can be said that F1=6.2 (kPa).

By doing so, in Examples 5 to 8, the negative electrode wet granules 16 contained in the negative electrode mixture 6 or the positive electrode wet granules 56 contained in the positive electrode mixture 36 faced each other in the roll forming step. When passing through the gap between the first roll 1 and the second roll 2 that rotate with the As a result, it can be said that film formation defects (film formation defects) are less likely to occur.

From the above results, it can be said that film formation defects (film formation defects) are less likely to occur by moistening the surface 2b of the second roll 2 and satisfying the relationship F1<F2 in the roll forming process. Furthermore, in the roll forming process, in addition to satisfying the relationship of F1 < F2, by satisfying the relationship of F2 ≥ 12.4 kPa, film formation defects (film formation defects) are extremely difficult to occur. It can be said that

The reason why Examples 5 and 6 were able to reduce film formation defects (film formation defects) as compared with Examples 7 and 8 is considered as follows. Specifically, in Examples 7 and 8, the liquids L1 and L2 sprayed from the spray nozzle 361 are adhered to the surface 2b of the second roll 2, whereas in Examples 5 and 6, the nonwoven fabric 261 is applied to the surface 2b of the second roll 2. The liquids L1 and L2 contained in the nonwoven fabric 261 are adhered to the surface 2b of the second roll 2 by pressing the second roll 2 against the surface 2b.

Therefore, in Examples 5 and 6, compared with Examples 7 and 8, it can be said that the surface 2b of the second roll 2 could be more uniformly wetted. Thus, in Examples 5 and 6, as compared with Examples 7 and 8, the negative electrode wet granules 16 contained in the negative electrode mixture 6 or the positive electrode wet granules 56 contained in the positive electrode mixture 36 It can be said that it became easy to adhere over the whole surface 2b of the roll 2, and as a result, it became difficult to produce the film-forming defect (film-forming defect).

In the above, the present invention has been described in accordance with Examples 1 to 8, but the present invention is not limited to Examples 1 to 8, and can be appropriately modified and applied without departing from the gist thereof. Needless to say.

For example, in Examples 5 to 8, the liquid to be adhered to the surface 2b of the second roll 2 is the liquid L1 equivalent to the solvent 15 contained in the negative electrode mixture 6, or the liquid L1 contained in the positive electrode mixture 36. Liquid L2 equivalent to solvent 35 was used. However, the liquid to be adhered to the surface 2b of the second roll 2 is not limited to a liquid equivalent to the solvent contained in the electrode mixture, and any liquid that does not cause a chemical reaction with the substance contained in the electrode mixture. Any liquid may be used.

1 first roll 1b surface 2 second roll 2b surface 6 negative electrode mixture (electrode mixture)
7 negative electrode current collector foil 8 filmy negative electrode mixture 9 current collector foil with filmy negative electrode mixture 13 negative electrode active material (electrode active material)
14, 34 binders 15, 35 solvents 16, 16B negative electrode wet granules 18 negative electrode mixture layer (electrode mixture layer)
19 negative electrode sheet (electrode sheet)
20, 120, 220, 320 Roll deposition device 33 Positive electrode active material (electrode active material)
36 positive electrode mixture (electrode mixture)
37 positive electrode current collector foil 38 film positive electrode mixture 39 current collector foil with film positive electrode mixture 48 positive electrode mixture layer (electrode mixture layer)
49 positive electrode sheet (electrode sheet)
56, 56B Wet positive electrode granules 60, 160 Drying device 260, 360 Wetting device AR Air DAR Dry air L1, L2 Liquid S1, T1 Electrode mixture preparation steps S2, T2 Roll forming steps S3, T3 Transfer steps S4, T4 Electrode combination Material layer forming process

Claims (6)

an electrode mixture producing step of producing an electrode mixture comprising a plurality of wet granules obtained by mixing and granulating an electrode active material, a binder, and a solvent;
By passing the electrode mixture through a gap between a first roll that rotates in opposition to the first roll and a second roll that rotates at a faster peripheral speed than the first roll, the electrode mixture is compressed and made into a film. a roll forming step of adhering the electrode mixture to the surface of the second roll;
a transfer step of transferring the film-like electrode mixture adhering to the surface of the second roll onto the surface of the current collector foil;
an electrode mixture layer forming step of forming an electrode mixture layer on the surface of the current collector foil by drying the film-like electrode mixture transferred onto the surface of the current collector foil;
In the electrode sheet manufacturing method for manufacturing an electrode sheet having the electrode mixture layer on the surface of the current collector foil,
The electrode mixture preparation step includes:
a first mixing step of preparing a preliminary mixture by mixing the electrode active material and the binder without adding the solvent;
a second mixing step of stirring the preceding mixture and the solvent to prepare the electrode mixture made of the wet granules,
In the second mixing step, the stirring speed is faster in the latter half of the step than in the first half,
In the roll forming step,
Liquid bridge force between the wet granules contained in the electrode mixture and the surface of the first roll when the electrode mixture passes through the gap between the first roll and the second roll The average value F1 (kPa) and the average value F2 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the second roll satisfy the relationship of F1<F2. fill,
In the roll forming step,
By blowing air onto the surface of the first roll to dry the surface of the first roll, and passing the electrode mixture through the gap between the first roll and the second roll, it is possible to satisfy F1<F2. A method of manufacturing an electroded sheet that satisfies the relationship. A method for manufacturing the electrode sheet according to claim 1,
A method for manufacturing an electrode sheet, wherein in the roll forming step, dry air having a dew point of −30° C. or lower is used as the air to be blown onto the surface of the first roll. A method for manufacturing the electrode sheet according to claim 1 or 2,
In the roll forming step, the method for producing an electrode sheet satisfying the relationship of F1≦2.8 kPa. an electrode mixture producing step of producing an electrode mixture comprising a plurality of wet granules obtained by mixing and granulating an electrode active material, a binder, and a solvent;
By passing the electrode mixture through a gap between a first roll that rotates in opposition to the first roll and a second roll that rotates at a faster peripheral speed than the first roll, the electrode mixture is compressed and made into a film. a roll forming step of adhering the electrode mixture to the surface of the second roll;
a transfer step of transferring the film-like electrode mixture adhering to the surface of the second roll onto the surface of the current collector foil;
an electrode mixture layer forming step of forming an electrode mixture layer on the surface of the current collector foil by drying the film-like electrode mixture transferred onto the surface of the current collector foil;
In the electrode sheet manufacturing method for manufacturing an electrode sheet having the electrode mixture layer on the surface of the current collector foil,
The electrode mixture preparation step includes:
a first mixing step of preparing a preliminary mixture by mixing the electrode active material and the binder without adding the solvent;
a second mixing step of stirring the preceding mixture and the solvent to prepare the electrode mixture made of the wet granules,
In the second mixing step, the stirring speed is faster in the latter half of the step than in the first half,
In the roll forming step,
Liquid bridge force between the wet granules contained in the electrode mixture and the surface of the first roll when the electrode mixture passes through the gap between the first roll and the second roll The average value F1 (kPa) and the average value F2 (kPa) of the liquid bridge force between the wet granules contained in the electrode mixture and the surface of the second roll satisfy the relationship of F1<F2. fill,
In the roll forming step,
F1 < F2 by passing the electrode mixture through the gap between the first roll and the second roll while moistening the surface of the second roll by attaching a liquid to the surface of the second roll. A method of manufacturing an electrode sheet that satisfies the relationship of A method for manufacturing the electrode sheet according to claim 4,
In the roll forming step, as the liquid to be adhered to the surface of the second roll, a liquid equivalent to the solvent contained in the wet granules is used. A method for manufacturing the electrode sheet according to claim 4 or 5,
In the roll forming step, the method for producing an electrode sheet satisfying the relationship of F2≧12.4 kPa.

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