JP2001076712A - Coating method of electrode paste for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method of electrode paste for a battery capable of applying the electrode paste to a current collector, with less generation of stripe defects and with smooth surface. SOLUTION: In the coating method of a roll coater type using two rolls of a backup roll 10 and a measuring roll 20, and a reverse roll coater type using three rolls of the backup roll 10, an application roll 30, and the measuring roll 20, the measuring roll 20 is formed in a column shape, rotated in the same direction as the backup roll 10 or the application roll 30, and electrode paste 2 is applied to a current collector 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrode sheet constituting a battery, and more particularly to a method for applying an electrode paste containing an active material to the surface of a current collector.

[0002]

2. Description of the Related Art Batteries are widely used in various fields, and in recent years, high energy density batteries such as lithium secondary batteries have been used. For example, a lithium secondary battery or the like employs a configuration in which two sheet-like electrodes, a positive electrode and a negative electrode, are wound or laminated. Such a sheet-like electrode is formed by forming an electrode mixture containing an active material, a binder and the like in a layer on the surface of a current collector made of metal foil.

[0003] In general, a sheet-like electrode (hereinafter, referred to as an electrode sheet) is formed by combining an electrode mixture (hereinafter, referred to as an electrode paste) made into a paste by adding a solvent (dispersion medium) into a band-like collection. It is applied to the surface of the electric conductor, and then dried to evaporate the solvent, and if necessary, the density of the electrode mixture is increased by a press or the like, and the electrode is cut into an appropriate size.

[0004] The application of the electrode paste to the current collector is generally performed using a coating machine called a coater because of its excellent productivity and uniformity of the thickness of the electrode mixture. The coater supports and conveys the current collector by a roll, and arranges a comma roll, a knife blade, etc. with a small gap between the supported current collector and the electrode paste from the near side in the conveying direction of the current collector. Is applied to apply the electrode paste oozing out of the gap to the surface of the current collector (see FIG. 4). Coma rolls, knife blades, and the like can change the thickness of the electrode paste applied to the current collector by changing the size of the gap, and serve as a measuring instrument in the coater. It has become.

[0005]

When an electrode paste is applied using a conventional coater, defects such as streaks, spots, and lumps often occur on the surface of the applied electrode paste. Since the electrode paste is a mixture of a particulate active material with a binder or the like, it contains coarse particles and aggregates, and is a defect caused by these. Such coarse particles and aggregates are removed using a filter or the like before coating, but cannot be completely removed, and aggregates may be generated even after passing through the filter. Therefore, the above-described defect cannot be avoided by means of a filter.

A streak defect is a defect caused by clogging of a gap between a current collector with a comma roll, a knife blade, or the like with coarse particles, agglomerates, and the like. This is especially the case. In a battery, an electrode sheet having a thin electrode mixture layer and a large area may be preferred for the purpose of improving the output density or the like. Therefore, particularly when the electrode paste is applied thinly, it is strongly desired to suppress generation of streak defects. In the case of a thin coating, not only streak defects but also coarse particles, agglomerates, and the like may be clogged in gaps, leading to a risk that the current collector may be damaged.

The inventor of the present invention has found that a conventional comma roll, knife blade, or the like, which functions as a measuring instrument, is fixed. Was found to be easy to pass through. The present invention is based on this finding, and it is an object of the present invention to provide a method of applying an electrode paste with few defects such as streaks by improving the function of a portion of a measuring device constituting a gap.

[0008]

According to the method of applying the electrode paste for a battery of the present invention, a column-shaped current collector is supported on a side surface of the column, and the current collector is conveyed by rotating. A backup roll, formed in a columnar shape, and positioned in parallel with the backup roll on the opposite side of the backup roll with the current collector interposed therebetween with a gap from a portion of the current collector supported by the backup roll; Measuring roll, and the electrode paste in a state where the gap between the current collector portion and the measuring roll is located on the near side in the transport direction of the current collector and is in contact with the current collector and the measuring roll. Using a roll coater having a paste reservoir for storing the electrode paste, and applying the electrode paste exuding from the gap between the current collector portion and the measuring roll to the surface of the current collector. A cloth method, the metering roll, and wherein the rotating small peripheral speed than the peripheral speed of the backup roll in the same direction as the rotation direction of the backup roll.

In other words, the method of applying the electrode paste for a battery according to the present invention relates to a method of applying a roll coater system using two cylindrical rolls, and a measuring method capable of changing an applied thickness by adjusting a gap. The roll is rotated in the same direction as the backup roll, that is, in the direction opposite to the direction in which the current collector is transported. By generating a flow away from the gap between the current collector and the measuring roll in the electrode paste present in the paste reservoir, coarse particles and agglomerates contained in the electrode paste are efficiently moved away from the gap and pass through the gap. Alternatively, it efficiently controls clogging in gaps,
The surface where the occurrence of streak defects or the like is small enables the electrode paste to be applied with a smooth surface.

Another method of applying the electrode paste for a battery according to the present invention is a backup roll which has a cylindrical shape, supports a belt-shaped current collector on the side surface of the cylinder, and conveys the current collector by rotating. The backup roll is located in parallel with the backup roll on the opposite side of the current collector of the backup roll in a state close to the portion of the current collector supported by the backup roll. An application roll that rotates in the same direction as the rotation direction of the roll at a peripheral speed smaller than the peripheral speed of the backup roll; and a measuring roll that has a cylindrical shape and is positioned parallel to the application roll with a gap from the application roll. And the rotation direction of the application roll in the gap between the application roll and the measuring roll. Using a reverse roll coater, which is located in front of the application roll and has a paste reservoir for storing an electrode paste in contact with the application roll and the measurement roll, exuding from the gap between the application roll and the measurement roll. The above electrode paste,
A method for applying an electrode paste for a battery, comprising supplying the electrode paste in the form of a film on the surface of the cylindrical side surface of the application roll and transferring the supplied electrode paste to the surface of the current collector. Is rotated at a peripheral speed smaller than the peripheral speed of the application roll in the same direction as the rotation direction of the application roll.

That is, the application method of the battery electrode paste of the present invention in this aspect relates to a reverse roll coater type application method using three cylindrical rolls. The current collector is rotated so as to be in the opposite direction to the transport direction. As in the application method of the above aspect, by applying a flow away from the gap between the application roll and the measuring roll to the electrode paste present in the paste reservoir, the application of the electrode paste having a good surface state is performed similarly to the application method. Making it possible.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the method for applying a battery electrode paste of the present invention will be described in detail with reference to the drawings. The description will first be made on a current collector, an electrode paste, and the like in the case of a lithium secondary battery, which is one of the batteries to which the present application method can be applied, and then a roll coater type application method using two rolls. A reverse roll coating method using a book roll and other application examples are respectively performed.

<Current Collector, Electrode Paste, etc. for Lithium Secondary Battery> As one example of an electrode to which the coating method of the present invention can be applied, an electrode of a lithium secondary battery is taken up, and the current collector and the electrode paste are taken up. Will be described. However, the application method of the present invention is not limited to the application of the electrode to a lithium secondary battery electrode, has a foil-shaped or plate-shaped current collector, the electrode mixture on the surface of the current collector Any type of battery electrode can be used as long as it is a layer or film type electrode.

For the positive electrode of the lithium secondary battery, an aluminum foil or the like is used as a current collector in consideration of electrochemical stability. When an aluminum foil is used for the current collector, the thickness is generally 15 to 20 μm. The size can be arbitrarily determined according to the area of the electrode, the performance of the coater, and the like.

The positive electrode mixture formed on the surface of the positive electrode current collector includes:
It is composed of a particulate active material and a conductive material, and a binder for binding them. The positive electrode active material includes LiCoO ₂ , LiNi
Particle powder such as O ₂ and LiMn ₂ O ₄ can be used. As the conductive material, carbonaceous powder particles such as graphite, carbon black, and acetylene black can be used. As the binder, a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, or a thermoplastic resin such as polypropylene or polyethylene can be used. The particle size of the active material is 5 to 3 in average particle size.
Generally, a coating having a thickness of 0 μm is used, and the coating method of the present invention may be followed. Note that the conductive material particles are preferably smaller than the active material particles,
The average particle size of the secondary particles in which the primary particles are aggregated is 5 to 2
What is necessary is just to use a thing of 0 μm.

The positive electrode is formed by forming the positive electrode mixture into a paste and applying the positive electrode paste to the surface of the positive electrode current collector by a coating method of the present invention described later. For the positive electrode paste, the active material, the conductive material, and the binder diluted with the solvent are sufficiently kneaded using a ball mill, a medium stirring mill, or the like, and the active material particles and the conductive material particles are uniformly dispersed in the binder. Adjust by doing. As the solvent,
An organic solvent such as N-methyl-2-pyrrolidone can be used.

The viscosity of the positive electrode paste is preferably 8000 to 15000 mPa · s when measured using an E-type viscometer at a rotational speed of the rotating disk of 0.5 rpm. The viscosity may be adjusted so as to have a relatively high viscosity when applied thickly, and to be relatively low when applied thinly. The viscosity may be adjusted by adjusting the amount of the solvent added.

Among lithium secondary batteries, in the case of a so-called lithium ion secondary battery using a carbon material for the negative electrode, the negative electrode can be formed in the same manner as the positive electrode. In that case, a copper foil or the like is used as the current collector. When a copper foil is used for the current collector, the thickness is generally 10 to 20 μm.

The negative electrode mixture formed on the surface of the negative electrode current collector is:
It is composed of a particulate active material and a binder for binding the active material. As the negative electrode active material, natural or artificial graphite, coke, or powdery particles of a carbon material such as non-graphitizable amorphous carbon can be used. As the binder, as in the case of the positive electrode, a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, or a thermoplastic resin such as polypropylene or polyethylene can be used. The particle diameter of the negative electrode active material is generally 10 to 30 μm in average particle diameter, and the coating method of the present invention may follow this.

As in the case of the positive electrode, the negative electrode is formed by forming the negative electrode mixture into a paste and applying the negative electrode paste to the surface of the negative electrode current collector by a coating method of the present invention described later. . The negative electrode paste is prepared by sufficiently kneading the active material and the binder diluted with the solvent using a medium stirring mill or the like, and uniformly dispersing the active material particles in the binder. As a solvent, an organic solvent such as N-methyl-2-pyrrolidone can be used.

As in the case of the positive electrode paste, the viscosity of the negative electrode paste was 8000 to 1 when measured using an E-type viscometer at a rotation speed of the rotating disk of 0.5 rpm.
The pressure is preferably set to 2000 mPa · s. As in the case of the positive electrode, the viscosity may be adjusted so as to have a relatively high viscosity when applied thickly, and to be relatively low when applied thinly.

<Roll Coater Coating Method> Among the coating methods of the present invention in which the electrode paste is coated on the current collector surface, a roll coating method using two rolls will be described. FIG. 1 schematically shows a roll-type coater (coating apparatus) that can realize the coating method of the present invention. FIG. 2 shows a cross section of the coater shown in FIG.

The illustrated coater has a columnar shape, and supports the band-shaped current collector 1 on the side surface 11 of the cylinder, and a backup roll 10 that conveys the current collector 1 by rotating, and a columnar-shaped backup roll. The backup roll 1 is separated from the portion of the current collector 1 supported by the roll 10 with a gap.
Backup roll 10 on the opposite side of the current collector 1
And the measuring roll 20 which is positioned in parallel with the current collector 1 and is located on the near side in the transport direction of the current collector 1 in the gap 25 between the portion of the current collector 1 and the measuring roll 20 and contacts the current collector 1 and the measuring roll 20. Paste 40 for storing the electrode paste 2 in a state where
And The measuring roll 20 rotates at a peripheral speed smaller than the peripheral speed of the backup roll 10 in the same direction as the rotation direction of the backup roll 10. In order to make the peripheral speed ratio between the two rolls appropriate, it is desirable to perform synchronous control. Therefore, in the illustrated coater, the measuring roll 20 and the backup roll 10 are synchronously controlled.

The current collector 1 has longitudinal ends connected to an unwinding roll and a winding roll, respectively, which are not shown. The sheet is conveyed in a stretched state by the rotational driving force. The supply of the electrode paste 2 to the paste reservoir 40 is performed by a pump (not shown), a filter is provided in the middle of the supply path, and remarkable coarse particles and aggregated particles are removed by the filter.

The electrode paste 2 oozes out of the gap 25, and the current collector 1 is conveyed, so that the electrode paste 2 is applied to the surface of the current collector 1. In other words, the current collector 1 is transported in the paste reservoir 40 in contact with the electrode paste 2,
The electrode paste 2 adhering to the surface of the electrode paste 2 passes through the gap 25 which is an outlet from the space, and is formed into a layered material having a predetermined thickness according to the size of the gap 25.

The length of the gap 25 communicating with the paste reservoir 40 can be adjusted according to the width of the current collector 1 so that the electrode paste 20 can be applied over the entire width of the current collector 1. Has become. Furthermore, the paste reservoir 40
A paste scraping blade 50 (omitted in FIG. 1) is provided at a position above the measuring roll 20 in contact with the cylindrical surface 21 of the measuring roll 20, and the electrode paste 2 adhered to the measuring roll 20 is rotated by the rotation thereof. To prevent the electrode paste 2 from passing through the gap 25, that is, overlapping the surface of the electrode paste 2 after application.

The electrode paste 2 in the paste reservoir 40 is
By moving the current collector 1 and rotating the measuring roll 20,
The flow is generated in the direction of the arrow shown in FIG. Due to the action of the flow of the electrode paste 2, coarse particles and aggregated particles are prevented from passing through the gap 25 and from trying to clog the gap 25. Therefore, the electrode paste 2 applied to the surface of the current collector 1 through the gap 25 has few defects such as bumps and lumps due to the presence of coarse particles and aggregated particles, and has a small number of defects such as streaks due to clogging. Less, good surface condition. In particular, when it is desired to form the electrode mixture layer thinly, the gap 25 must be applied with a small size. However, in the case of a battery paste containing coarse particles or the like, the problem of clogging of the gap 25 is serious in this case. Becomes Therefore,
The coating method of the present invention is a particularly effective technique when it is desired to form an electrode mixture thin.

Here, to form the electrode mixture thinly means
It does not mean only the applied thickness of the electrode paste immediately after the application. The electrode paste contains a solvent, and the applied thickness changes due to evaporation of the solvent. Normally, if the size of the gap is reduced, the thickness of the formed electrode mixture layer is reduced, but the gap amount and the thickness of the mixture layer do not have a linear relationship. In order to increase the density of the mixture by pressing after drying, etc., in order to form the electrode mixture layer thinly, the amount of the electrode mixture excluding the solvent per unit area (basis weight)
Is desirably reduced.

When the coating is performed using a roll coater type apparatus, the diameter of the measuring roll is desirably substantially the same as or smaller than the diameter of the backup roll.
This is because if the diameter of the measuring roll is too large, the distance of the narrow gap portion in the gap 25 becomes too long, and the gap 25
This is because there is an increased possibility that coarse-grained material and the like may be clogged before the minimum gap interval.

It is desirable that the peripheral speed of the measuring roll is not more than 1/2 of the peripheral speed of the backup roll. This is because if the peripheral speed of the measuring roll is too high, the possibility that coarse particles and the like pass through the gap 25 increases. It has been found through experiments that the peripheral speed of the measuring roll is set to 0.3 to 0.45 with respect to the peripheral speed of the backup roll, so that the surface condition of the applied electrode paste is improved. Is more desirable.

The thickness of the electrode paste applied to the current collector surface is as follows:
By changing the size of the gap between the above-mentioned measuring roll and the portion of the current collector supported by the backup roll, any one can be obtained. In the case of a lithium secondary battery, the electrode paste is applied in a thickness of 50 to 70 μm (the thickness after drying). In such a case, the size of the gap may vary depending on the viscosity of the electrode paste or the like.
m.

The electrode paste applied to the current collector is conveyed to a drying oven, and the solvent contained therein is evaporated, whereby the thickness of the electrode paste is reduced and the electrode paste is tightly bound to the current collector. Further, if necessary, the density of the electrode mixture is increased by compression using a roll press or the like, and the battery is cut into a predetermined size to complete a sheet-like electrode.

<Reverse Roll Coating Method> A reverse roll coating method using three rolls of the coating method of the present invention when the electrode paste is coated on the current collector surface will be described. . FIG. 3 schematically shows a reverse roll type coater capable of realizing the coating method of the present invention.

The illustrated coater has a columnar shape, and supports the band-shaped current collector 1 on the side surface 11 of the column, and a backup roll 10 that conveys the current collector 1 by rotating, and a columnar-shaped backup roll. The backup roll 10 is positioned parallel to the backup roll 10 on the opposite side of the current collector 1 of the backup roll 10 in a state close to the portion of the current collector 1 supported by the roll 10, in the same direction as the rotation direction of the backup roll 10. An application roll 30 that rotates at a peripheral speed smaller than the peripheral speed of the backup roll 10; a measuring roll 20 that has a cylindrical shape and is positioned parallel to the application roll 30 with a gap 25 between the application roll 30; Of the gap 25 between the application roll 30 and the measuring roll in the rotation direction of the application roll 30 Located in, formed by a paste reservoir 40 for reserving the electrode paste 2 in a state in contact with the application roll 30 and metering roll 20. And
The measuring roll 20 rotates at a peripheral speed smaller than the peripheral speed of the application roll 30 in the same direction as the rotation direction of the application roll 30. In order to make the peripheral speed ratio between the two rolls appropriate, it is desirable to perform synchronous control. Therefore, in the illustrated coater, the measuring roll 20 and the application roll 30 are synchronously controlled.

The relationship between the current collector 1 and the unwinding and winding rolls (not shown), the supply of the electrode paste 2 to the paste reservoir 40, and the like are the same as in the case of the roll coater.

The electrode paste 2 oozes out of the gap 25. When the application roll 30 rotates, the electrode paste 2 is supplied to the cylindrical side surface 31 of the application roll 30 in a film form. In other words, the cylindrical side 31 of the application roll 30
Moves in the paste reservoir 40 in contact with the electrode paste 2, and a gap 25 which is an outlet from the paste reservoir 40.
, The electrode paste 2 attached to the cylindrical side surface 31 is formed into a layer having a predetermined thickness according to the size of the gap 25. Next, the application role 30
Paste 2 supplied to the backup roll 1
The coating is applied so as to be transferred to the surface of the current collector 1 at a position close to the portion of the current collector 1 supported by the zero.

The length of the gap 25 is such that it is impossible over the entire width of the current collector 1 as in the case of the roll coater. Further, similarly to the case of the above-mentioned roll coater, a paste scraping blade is provided at a position above the paste reservoir 40 in contact with the cylindrical surface 21 of the measuring roll 20, and although not shown, On the back of the application roll 30, another paste scraping blade for contacting the cylindrical side surface 31 of the application roll and removing the electrode paste 2 remaining without being transferred is provided.

The flow of the electrode paste 2 in the paste reservoir 40 due to the rotation of the application roll 30 and the measuring roll 20 is in the same state as in the case of the roll coater shown in FIG. This prevents passage and clogging of the gap 25. Therefore, the electrode paste 2 supplied to the cylindrical side surface 31 of the application roll 30 through the gap 25 has almost no coarse particles or aggregated particles, and hardly any streaks due to clogging. The surface condition of the electrode paste applied to the surface of the conductor 1 is also good.

When coating is performed using a reverse roll coater type apparatus, the diameter of the measuring roll is desirably substantially the same as or smaller than the diameter of the application roll for the same reason as in the case of the roll coater type. . It is desirable that the backup roll has substantially the same diameter as the application roll.

For the same reason as in the case of the above-mentioned roll coater system, it is desirable that the peripheral speed of the measuring roll is not more than 1/2 of the peripheral speed of the application roll. More preferably, it is set to 0.3 to 0.45 with respect to the speed.

The thickness of the electrode paste applied to the current collector surface;
The relationship between the gap between the measuring roll and the application roll is the same as in the case of the roll coater method.
The current collector supported by the backup roll and the application roll are brought close to each other, but the interval is preferably as close as possible to 0 in order to perform smooth transfer. The current collector and the applied electrode paste are subjected to the same process as in the case of the roll coater method, and a sheet-like electrode is completed.

<Other Applications> The present invention has a cylindrical measuring roll, and the measuring roll is rotated in the same direction as the rotation method of the backup roll or the application roll to collect coarse particles and aggregated particles. Although the application to the electric body is suppressed, the operation of the measuring roll may be an embodiment which is interesting for the reverse hand. In this embodiment, the measuring roll is intermittently rotated.

By providing a period in which the measuring roll is rotated in the same direction as the backup roll or the application roll, and a period in which the measuring roll is not rotated or reversed, the electrode paste applied to the current collector intermittently becomes coarse particles and agglomerates. It has a section containing grains or a section where streaks are formed intermittently. By roughening a part of the surface of the electrode sheet, for example, it is possible to secure a passage of gas generated on the electrode surface during overcharge or the like, and to easily discharge gas generated inside the electrode body to the outside of the electrode body. And a battery with excellent safety.

Further, as shown in FIG. 2, the coater includes a paste scraping blade 50 which comes into contact with the measuring roll 20. Measuring roll 2 of this paste scraping blade 50
0, the electrode paste 2 containing the coarse particles and the aggregated particles does not pass through the gap 25,
The electrode paste 2 having passed through the gap 25 by the rotation of 0
Will be further adhered to the surface. As described above, the fact that the coarse particles and the aggregated particles can be applied to the current collector surface without passing through the gap 25 allows the coarse particles and the aggregated particles to be efficiently applied without causing the clogging of the coarse particles and the aggregated particles. It is possible to apply the electrode paste with good yield.

Further, by gradually increasing the gap between the paste scraping blade 50 and the measuring roll 20, it is possible to produce an electrode sheet in which the thickness of the electrode mixture gradually increases. By intermittently bringing the paste scraping blade 50 into contact with the measuring roll 20, an electrode sheet in which the thickness of the electrode mixture changes intermittently can be produced.

[0046]

EXAMPLE Based on the above embodiment, an electrode paste was actually applied using a roll coater. This is described below as an example. In addition, the application of the electrode paste without rotating the measuring roll and the application of the electrode paste using a conventional comma roll are listed as comparative examples, and the surface condition of each applied electrode paste after drying is compared. Then, the coating method of the present invention was evaluated.

Example 1 A negative electrode paste for a lithium ion secondary battery was used as an electrode paste. In this electrode paste, graphitized mesophase microspheres (MCMB) having an average particle diameter of 25 μm are used as an active material, polyvinylidene fluoride (PVDF) is used as a binder, and N-methyl-2-vinyl is used as a solvent.
Each of pyrrolidone (NMP) was kneaded sufficiently with a twin-screw kneader and adjusted. The mixing ratio of MCMB and PVDF was 92: 8 by weight, and the viscosity of the paste was 112.
It is adjusted by adding NMP so as to be 00 mPa · s. The current collector has a thickness of 10 μm and a width of 200 μm.
mm copper foil was used.

The coater was of the type shown in FIGS. 1 and 2 and had a steel backup roll having a diameter of 120 mmφ and a steel measuring roll having a diameter of 90 mmφ. 3m / mi peripheral speed of backup roll
n, the peripheral speed of the measuring roll was 1 m / min, and the peripheral speed ratio of the measuring roll to the backup roll was 0.33. The gap between the portion of the current collector supported by the backup roll and the measuring roll is 123 μm and 100 μm, respectively.
m and 30 μm were applied.

<Example 2> Electrode paste and current collector,
The same roll coater as in Example 1 was used.
The peripheral speed of the backup roll was 3 m / min, the peripheral speed of the measuring roll was 1.3 m / min, and the peripheral speed ratio of the measuring roll to the backup roll was 0.43. The electrode paste was applied with a gap of 123 μm between the portion of the current collector supported by the backup roll and the measuring roll.

<Example 3> Electrode paste and current collector,
The same roll coater as in Example 1 was used.
The peripheral speed of the backup roll was 3 m / min, the peripheral speed of the measuring roll was 0.3 m / min, and the peripheral speed ratio of the measuring roll to the backup roll was 0.1. The electrode paste was applied with a gap of 123 μm between the portion of the current collector supported by the backup roll and the measuring roll.

<Comparative Example 1> Coating was performed using the same roll coater as in Example 1, except that the measuring roll was not rotated. The electrode paste and the current collector were the same as those in Example 1. The electrode paste was applied with a gap of 123 μm between the portion of the current collector supported by the backup roll and the measuring roll.

<Comparative Example 2> Instead of a cylindrical measuring roll,
The electrode paste was applied using a conventional coater using a comma roll (see FIG. 4B). Coma roll does not rotate. In addition, the comma roll has an outer diameter of 90 mmφ as in the case of the measuring roll in Example 1.
Was used. The gap between the current collector portion supported by the backup roll and the comma roll is 80 μm each.
m and 60 μm, and electrode paste was applied.

<Evaluation> Table 1 below shows the results of applying the electrode paste in each of the examples and comparative examples. As a result, Table 1 shows the type of the coater, the ratio of the peripheral speed of the measuring roll to the peripheral speed of the backup roll, the size of the gap, the thickness of the electrode mixture layer after coating and drying, and the electrode mixture per unit area, respectively. The material amount (weight per unit area), the electrode mixture layer density, the state of the electrode mixture surface, and the judgment are listed.

[0054]

[Table 1]

As is clear from Table 1, in the examples in which the coating by the roll coater method in which the measuring roll is rotated is performed, no streak defect occurs in any case, and a relatively good coated surface is obtained. You can see that.

However, in the case of Example 3 in which the peripheral speed ratio of the measuring roll to the peripheral speed of the backup roll was 0.1, a part of the coating surface was wavy. This is presumably because the peripheral speed of the measuring roll was low, and the rotation of both rolls was affected by the imbalance. From this,
It can be confirmed that the peripheral speed of the measuring roll is more appropriately set to 0.3 to 0.45 of the peripheral speed of the backup roll.

On the other hand, in the case of Comparative Example 1 in which the measuring roll was not rotated, a streak-like defect occurred. Therefore, it can be confirmed from this that the rotating action of the measuring roll is essential.

In the case of Comparative Example 2 using a comma roll, when the thickness of the mixture layer was small and the basis weight was small, streak defects occurred. Therefore, it can be confirmed that the comma roll is an unsuitable coating method when the electrode mixture layer is formed to be thin or when the coating is performed so as to reduce the basis weight.

[0059]

The method for applying the electrode paste for a battery according to the present invention includes a roll coating method using two rolls and a reverse roll coating method using three rolls. Are cylindrical, and the electrode paste is applied by rotating the measuring roll in the same direction as the backup roll or the application roll.

By employing such a method, the coating method of the present invention allows the coarse particles and agglomerates contained in the electrode paste to be collected and collected by the measuring roll even when the electrode mixture layer is formed thin. Efficiently preventing passage through the gap between the body and the application roll and clogging of the gap, it is possible to apply the electrode paste with a smooth surface with little occurrence of streak defects or the like.

[Brief description of the drawings]

FIG. 1 shows a state in which an electrode paste is applied to the surface of a current collector by a roll coater type coating method of the present invention using two rolls of a measuring roll and a backup roll.

FIG. 2 is a cross-sectional view showing the state of application shown in FIG.

FIG. 3 shows how an electrode paste is applied to the surface of a current collector by a reverse roll coater type application method of the present invention using three rolls of a measuring roll, an application roll, and a backup roll.

FIG. 4 shows a conventional method of applying an electrode paste using a knife blade and a comma roll.

[Explanation of symbols]

 1: current collector 2: electrode paste 10: backup roll 11: cylindrical side surface 20: measuring roll 21: cylindrical side surface 25: gap 30: application roll 31: cylindrical side surface 40: paste reservoir 50: knife blade 60: comma roll

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasuaki Kawai 41-Cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory, Inc. (72) Inventor Toshihiko Inoue 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Kiwa Adachi 1-1-1, Showacho, Kariya City, Aichi Prefecture Address F-term in Denso Co., Ltd. (reference) 4D075 AC26 AC28 AC29 AC34 AC94 DA03 DC19 EA31 4F040 AA02 AB05 AC01 BA24 CB16 CB21 CB26 CB33 5H014 AA04 BB05 BB08 BB17 CC01 HH00 HH06

Claims (4)

[Claims] 1. A backup roll that has a cylindrical shape, supports a band-shaped current collector on its side surface, and conveys the current collector by rotating; and a backup roll that has a cylindrical shape and is supported by the backup roll. A measuring roll positioned in parallel with the backup roll on the opposite side of the backup roll across the current collector with a gap between the current collector portion; and the current collector portion and the measuring roll. Using a roll coater, which is located on the front side of the gap in the conveying direction of the current collector and has a paste reservoir for storing an electrode paste in a state of being in contact with the current collector and the measuring roll; A method for applying an electrode paste for a battery, wherein the electrode paste that oozes out of the gap between a portion of a current collector and the measuring roll is applied to a surface of the current collector, wherein the measuring roll includes a backup. The method of applying battery electrode paste, characterized in that rotating in the same direction as the rotation direction of Lumpur smaller peripheral speed than the peripheral speed of the backup roll. 2. The method according to claim 1, wherein the measuring roll has a diameter substantially equal to or smaller than the backup roll, and a peripheral speed of the measuring roll is equal to or less than １ ／ of a peripheral speed of the backup roll. Item 6. A method for applying the electrode paste for a battery according to Item 1. 3. A backup roll which has a cylindrical shape, supports a band-shaped current collector on the side surface of the cylinder, and conveys the current collector by rotating, and a backup roll which has a cylindrical shape and is supported by the backup roll. The backup roll is positioned parallel to the backup roll on the opposite side of the backup roll across the current collector in a state close to the current collector portion, and has a peripheral speed of the backup roll in the same direction as the rotation direction of the backup roll. An application roll that rotates at a smaller peripheral speed, a measuring roll that has a cylindrical shape and is positioned in parallel with the application roll with a gap from the application roll, and a gap between the application roll and the measuring roll. The application roll is located on the near side in the rotation direction of the application roll, and A reverse roll coater provided with a paste reservoir for storing an electrode paste in contact with an amount roll, wherein the electrode paste that oozes out of the gap between the application roll and the measuring roll is applied to a cylindrical side surface of the application roll. A method of applying a battery electrode paste for supplying the supplied electrode paste to the surface of the current collector so as to transfer the supplied electrode paste to the surface of the current collector. A method for applying an electrode paste for a battery, characterized in that the application roll is rotated at a peripheral speed smaller than the peripheral speed of the application roll in the same direction as the rotation direction. 4. The measuring roll has substantially the same diameter as the application roll or has a smaller diameter than the application roll, and a peripheral speed of the measuring roll is equal to or less than の of a peripheral speed of the application roll. Item 4. A method for applying the battery electrode paste according to Item 3.