JP6423267B2 - Horizontal type double-side coating equipment - Google Patents

Description

  The present invention relates to a horizontal double-side coating apparatus that simultaneously applies and dries a slurry-like mixture on both sides of a long sheet.

In recent years, midnight power storage systems, home-use distributed power storage systems based on solar power generation technology, and power storage systems for electric vehicles have attracted attention from the viewpoint of the effective use of energy aimed at preserving the global environment and conserving resources. Yes. Along with this, demand for new energy storage devices such as lithium ion batteries, electric double layer capacitors, and lithium ion capacitors is expected to grow.
Electrodes such as a positive electrode and a negative electrode of these energy storage devices generally include oxides and phosphate compounds containing lithium, carbon material powders containing graphite and activated carbon, active materials such as silicon and alloys, conductive assistants such as carbon black, PVDF Apply a slurry-like electrode mixture composed of a binder (such as polyvinylidene fluoride) or SBR (styrene-butadiene rubber), a solvent, etc. to both sides or one side of a current collector such as an aluminum foil or copper foil, and dry. It is manufactured by.

  In coating and drying, it is necessary to produce a high-performance electrode with high productivity. The electrode is formed by adhering a current collector and active material particles or active material particles to each other with a binder containing a conductive additive. It is necessary to improve the current collection performance of the electrode in order to improve the performance of the storage element. Therefore, the distribution of the binder is preferably uniform in the thickness direction of the electrode, and it is necessary to develop a network structure that connects the active materials. Necessary for a good electrode.

  In the drying of the electrode mixture, when the hot air temperature in the drying furnace is too high, or when the hot air speed is too strong, drying is performed exclusively from the electrode surface to which the electrode mixture is applied. For this reason, when the solvent moves to the electrode surface, the binder dissolved in the solvent also moves to the electrode surface, increasing the amount of binder on the electrode surface after drying, and conversely, the electrode mixture layer and the current collector The amount of binder at the interface may be low. In such a case, the current collection performance of the electrode is reduced, the resistance is increased, and the electrode mixture layer is easily peeled off from the current collector. There is also a problem that the production efficiency is lowered due to the occurrence of defects such as missing layers. Therefore, it is necessary to manufacture the electrode under appropriate drying conditions.

In order to improve the productivity of the electrode, it is preferable to apply and dry the mixture simultaneously on both sides of the current collector, rather than the method of coating one side at a time, and as a result, the manufacturing cost of the storage element can be reduced.
In order to apply both surfaces simultaneously, it is necessary to dry without contacting the roller or the like until at least the surface of the electrode in which the slurry electrode mixture is applied to the current collector is dried.
As an example of the drying method, a horizontal float drying method in which hot air is applied from above and below the electrode coated with the electrode mixture layer is often used so that the electrode does not contact the roller in the drying furnace.

Japanese Patent No. 4739711 JP2013-122332A JP 2014-11102 A

  However, in the horizontal float drying furnace as described above, it is necessary to increase the wind speed in order to float the electrode. For this reason, as described above, the solvent quickly evaporates from the electrode surface after coating. As a result, there is a problem that a large amount of the binder is distributed on the electrode surface and the peeling strength at the electrode mixture layer interface is insufficient due to a decrease in the binder present at the electrode mixture layer and current collector interface. The techniques shown in Patent Documents 1 to 3 listed above relate to a technique for solving the drying unevenness with respect to the horizontal float drying method. However, the uneven distribution and peeling strength of the binder in the electrode mixture layer as described above. There is no fundamental solution to the decline in

  The present invention has been made in view of the above-described conventional situation, and there is no uneven distribution of the binder in the coating layer or a decrease in peel strength, and it is possible to produce a coated body with good performance with high production efficiency. An object of the present invention is to provide a horizontal double-side coating apparatus.

As a result of intensive studies, the present inventors applied the coating agent simultaneously on both sides of the long sheet while supporting the long sheet substantially horizontally by the support roller that contacts the non-coated portion of the long sheet. It was conceived that it is possible to produce a coated body with good performance with high production efficiency by drying without bringing it into contact with a roller or the like.
That is, the present invention is as follows.

[1]
An unwinding section for unwinding the long sheet;
A winding unit for winding the long sheet;
A roller body disposed between the unwinding unit and the winding unit and rotatable in the conveying direction of the long sheet;
A pair of coating machines arranged to face both sides of the long sheet,
A horizontal-type double-side coating apparatus in which a coating part and a non-coating part are repeatedly formed in the width direction on both sides of the long sheet,
Each of the pair of coating machines has one or a plurality of coating heads arranged at predetermined intervals in the width direction of the long sheet,
The roller body is disposed at a position shifted from the coating head in a side view in the width direction of the long sheet, and the long peripheral sheet comes into contact with the non-coated portion of the long sheet. It has a support roller for supporting a substantially horizontal seat, and,
The horizontal double-side coating apparatus , wherein the position of the support roller is variable in the width direction of the long sheet corresponding to the position of the non-coating portion .
[2]
The horizontal double-side coating apparatus according to [ 1 ], wherein the support roller has a width of a peripheral surface that contacts the long sheet that is smaller than a width of the non-coated part.
[3]
The support roller includes a lower support roller in contact with the non-coated portion of the lower surface of the elongated sheet, and an upper support roller in contact with the non-coated portion of the upper surface of the long sheet,
The horizontal double-side coating apparatus according to [1] or [2] , wherein the upper support roller and the lower support roller are in positions shifted from each other in a top view.
[4]
The horizontal double-sided coating apparatus according to any one of [1] to [ 3 ], including a radiation-type drying device disposed to face both surfaces of the long sheet.
[5]
The roller body has a pair of guide rollers arranged on the outer side in the width direction of the long sheet than the support roller,
The distance between the pair of guide rollers is substantially equal to the width of the long sheet,
The horizontal double-side coating apparatus according to any one of [1] to [4], wherein both end portions of the long sheet are in contact with side surfaces of the guide roller.
[6]
An electrode mixture using a fluorine-containing resin as a binder is applied to both sides of a long current collector using the horizontal double-side coating apparatus according to any one of [1] to [ 5 ], In a method for producing an electrode having an electrode mixture layer formed by drying,
The concentration ratio of fluorine element between the surface of the electrode mixture layer and the peeled surface exposed in the peel test of the electrode mixture layer and the current collector: (fluorine content of the peeled surface / fluorine content of the surface) is It adjusts so that it may become the range of 0.7 to 1.2, The manufacturing method of the electrode which has an electrode mixture layer characterized by the above-mentioned.

  In the coating apparatus of the present invention, after coating the coating agent on both sides, drying without contact with the roller and the like, there is no uneven distribution of binder in the coating layer or a decrease in peel strength, etc. A good coated body can be produced with high production efficiency.

It is a schematic diagram which shows an example of the horizontal type | mold double-sided coating apparatus which concerns on this invention. It is a schematic diagram which shows an example of the horizontal type | mold double-sided coating apparatus which concerns on this invention. It is a side view which shows typically the positional relationship of a roller body, a elongate sheet | seat, and a coating head. It is a side view which shows typically the positional relationship of a roller body, a elongate sheet | seat, and a coating head. It is a figure which shows an example of a drying furnace typically. It is a figure which shows an example of a drying furnace typically. It is a figure which shows typically an example of the drying furnace in the conventional coating apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of a horizontal double-side coating apparatus according to the present invention, and FIG. 2 is a schematic diagram showing an example of a horizontal double-side coating apparatus of the present invention. FIG. 3 is a side view schematically showing the positional relationship among the roller body, the long sheet, and the coating head. FIG. 4 is a side view schematically showing the positional relationship among the roller body, the long sheet, and the coating head. 5-7 is a figure which shows the drying furnace used by the Example and the comparative example.
The horizontal double-side coating apparatus 1 of the present invention (hereinafter simply referred to as a coating apparatus 1) includes an unwinding section 3 for unwinding the long sheet 2, a winding section 4 for winding the long sheet 2, and a winding A roller body 8 disposed between the take-out unit 3 and the winding unit 4 and rotatable in the conveying direction of the long sheet 2, and a pair of coating machines disposed on both sides of the long sheet 2. 5 is provided. In this coating apparatus 1, the coating part 11a and the non-coating part 11b are repeatedly formed in the width direction on both surfaces of the long sheet 2 supported and transported substantially horizontally.
In the coating apparatus 1 according to the present invention, each of the pair of coating machines 5 includes a plurality of coating heads 5a arranged at predetermined intervals in the width direction of one or the long sheet 2. The roller body 8 is disposed at a position shifted from the coating head 5 a in a side view in the width direction of the long sheet 2, and the outer peripheral surface is brought into contact with the non-coated part 11 b of the long sheet 2 to increase the length. It has the support roller 9 which supports the scale sheet 2 substantially horizontally.

The coating apparatus 1 is a horizontal double-side coating apparatus that applies a coating agent to both sides of a long sheet 2 that is supported substantially horizontally and is conveyed in the longitudinal direction, and then dries. This coating apparatus 1 can be used, for example, for manufacturing electrodes for positive electrodes and negative electrodes for lithium ion secondary batteries, electric double layer capacitors, and lithium ion capacitors.
Specifically, for example, a slurry-like electrode mixture in which an active material, a conductive additive, a binder, a viscosity modifier, a solvent, and the like are mixed and dispersed is placed on a current collector such as an aluminum foil or a copper foil. An electrode mixture layer is formed by coating and drying.

The coating apparatus 1 applies a coating agent to the unwinding unit 3 for unwinding the long sheet 2 wound in a roll shape, the winding unit 4 for winding the long sheet 2 into a roll shape, and the long sheet 2. A coating machine 5, a drying furnace 6 that dries the applied coating layer, and a roller body 8 that supports the long sheet 2 are provided.
The long sheet 2 is unwound from the unwinding unit 3, and the long sheet 2 is unwound from the unwinding unit 3 by being wound by the winding unit 4 while being supported substantially horizontally by the roller body 8. It travels (conveys) in the longitudinal direction toward the winding unit 4.
Here, the long sheet 2 is, for example, a current collector, and the coating agent is, for example, an electrode mixture.

As shown in FIG. 3, the roller body 8 has one or a plurality of (three in the example shown in the figure) disk-shaped support rollers 9. The support roller 9 is arranged at a position shifted from the coating head 5 a in a side view in the width direction of the long sheet 2, and the outer peripheral surface is in contact with the non-coating portion 11 b of the long sheet 2. The length sheet 2 is supported substantially horizontally.
As will be described later, when the stripe-shaped coating layer 11 in which the coating portion 11a and the non-coating portion 11b are repeated in the width direction is formed in parallel with the rotation direction of the common rotation axis. In the roller body 8 having a plurality of support rollers 9, the support roller 9 is in contact with the non-coated portion 11b and supports the long sheet 2, so that the coating agent is applied to both sides of the long sheet 2, It can pass through the drying furnace 6 without a roller etc. touching the apply | coated part. Therefore, the drying oven 6 can be dried with the hot air speed reduced. Thereby, for example in an electrode, the binder which connects an active material can be made into a uniform state in the thickness direction of an electrode mixture layer.

The position of the support roller 9 is preferably variable in the width direction of the long sheet 2 corresponding to the position of the non-coated portion 11b. Since the position of the support roller 9 can be made variable, the degree of freedom in manufacturing the coating layer is increased, and the stripe-shaped coating layer 11 with various intervals can be formed.
Moreover, in the support roller 9, the width | variety of the surrounding surface which contacts the elongate sheet 2 is smaller than the width | variety of the non-coating part 11b. Thereby, it is prevented that the support roller 9 touches the non-drying coating layer immediately after coating.

As shown in FIG. 2, the support roller 9 includes a lower support roller 9 </ b> B that contacts the non-coated portion 11 b on the lower surface of the long sheet 2, and an upper support roller 9 </ b> A that contacts the non-coated portion 11 b on the upper surface of the long sheet 2. You may have. At this time, the upper support roller 9 </ b> A and the lower support roller 9 </ b> B are in positions shifted from each other in a top view.
By arranging the supporting rollers 9A and 9B in contact with the non-coated part 11b on the lower surface of the long sheet 2 and the non-coated part 11b on the upper surface by a plurality of supporting rollers 9 spaced apart from each other, the long sheet 2 is arranged. Appropriate tension can be applied and it can be conveyed stably. However, if the upper and lower support rollers 9A and 9B are in a position where they overlap each other in the top view (opposing via the long sheet 2), the long sheet 2 may be wrinkled or damaged. Therefore, the upper and lower support rollers 9 </ b> A and 9 </ b> B are arranged at positions shifted from each other (not opposed via the long sheet 2) when viewed from above. Thereby, it is possible to prevent the long sheet 2 from being wrinkled or damaged.
The roller body 8 may be disposed inside the drying furnace 6 as shown in FIG. 1, or may be disposed outside the drying furnace 6 as shown in FIG.

  Furthermore, as shown in FIG. 4, the roller body 8 preferably has a pair of guide rollers 10 arranged outside the support roller 9. The guide roller 10 has a disk shape larger in diameter than the support roller 9, the distance between the pair of guide rollers 10 is substantially equal to the width of the long sheet 2, and both end portions in the width direction of the long sheet 2 are Each is in contact with the side surface of the guide roller 10. By contacting the end of the long sheet 2 with the side surface of the guide roller 10, it is possible to prevent the long sheet 2 from shifting in the width direction due to fluttering caused by hot air during conveyance, coating, or drying. Can be transported stably. The guide roller 10 may be arranged on the upper side or the lower side of the long sheet 2.

The material of the roller body 8, the support roller 9, and the guide roller 10 is generally made of metal, but FRP (fiber reinforced plastic) can also be used. Since the long sheet 2 directly touches the support roller 9, the surface of the roller needs to be smooth.
Furthermore, it is preferable to provide a nip roller (not shown) between the unwinding unit 3 and the coating machine 5 and between the drying furnace 6 and the winding unit 4 to control the conveyance speed of the long sheet 2. . Moreover, it is preferable to install a tension control roller so that the tension of the long sheet 2 falls within an appropriate range.

The coating machine 5 is disposed to face both surfaces of the long sheet 2. Each of the pair of coating machines 5 includes one or a plurality of coating heads 5 a arranged at predetermined intervals in the width direction of the long sheet 2.
Since the coating machine 5 is disposed so as to face both surfaces of the long sheet 2, it can be applied simultaneously to both surfaces of the long sheet 2, and the production efficiency can be increased.
In addition, since the plurality of coating heads 5a are arranged at intervals, a plurality of coating portions 11a can be formed on the long sheet 2 at predetermined intervals. The portion where the coating head 5a is not disposed becomes the non-coated portion 11b. Thereby, the stripe-shaped coating layer 11 in which the coating part 11a and the non-coating part 11b are repeated in the width direction of the long sheet 2 can be formed.
Although the coating method in the coating machine 5 is not specifically limited, For example, a die method is preferable.

A coating layer 11 such as an electrode mixture layer is formed on the long sheet 2 by applying various coating agents such as an electrode mixture in the coating machine 5 and then drying in a drying furnace 6. Is done.
The drying furnace 6 is provided with a hot air blowing section and a discharge section (not shown), and the drying state is stabilized by controlling the temperature in the furnace and exhausting the vaporized solvent outside the furnace (FIG. 5). reference).
In the drying furnace 6, a structure in which hot air is not directly applied to the long sheet 2 from the outlet is preferable. Also, until the surface of the coating layer 11 applied to the long sheet 2 is dried, the hot air blowing speed is preferably 10 m / second or less, and more preferably 8 m / second or less. By installing a plurality of drying furnaces 6 and sequentially changing the drying temperature, the long sheet 2 can be dried in a short time without drying rapidly even in the same drying time.

Moreover, as shown in FIG.1 and FIG.2, the radiation-type drying apparatus 7 may be installed in the inside of the drying furnace 6 so that both surfaces of the elongate sheet | seat 2 may be opposed, respectively.
In the drying with hot air as described above, when hot air is applied from above and below the long sheet 2, the contact area between the support roller 9 and the long sheet 2 is small, causing sheet flapping and reducing coating accuracy. There is a risk of it. Therefore, the present invention includes not only hot air but also radiant heating as a drying means.

The radiation-type drying device 7 heats the long sheet 2 from the upper surface or the lower surface, or from the upper and lower surfaces. By drying not by hot air but by heating, efficient drying can be achieved even if the amount of hot air blown out is reduced, so that fluttering of the long sheet 2 can be suppressed and coating accuracy can be improved.
As the radiation type drying device 7, a heating device using far infrared rays can be used. In the far-infrared heating means, for example, far-infrared rays reach not only the surface of the electrode mixture layer coated with the electrode mixture but also the inside of the electrode mixture layer. Can do. That is, the evaporation of the solvent also proceeds from the inside of the mixture layer, and as a result, the distribution of the binder amount becomes uniform in the thickness direction of the electrode. As a result, the peel strength of the electrode is improved and the current collecting property becomes uniform, so that the electrode resistance is also reduced.
The long sheet 2 from which the coating layer 11 has been dried is wound up in a roll shape at the winding unit 4.

The coating apparatus 1 of the present invention as described above is preferably used for manufacturing various battery electrodes.
That is, the electrode of the present invention was formed by applying an electrode mixture using a fluorine-containing resin as a binder to both sides of a long current collector using the coating apparatus 1 and drying. In the electrode having the electrode mixture layer, the concentration ratio of the fluorine element on the current collector surface and the peeled surface exposed in the peel test of the electrode mixture layer and the current collector: (fluorine content on the peel surface / fluorine content on the surface) Amount) is in the range of 0.7 to 1.2.

The electrode mixture layer is formed by applying and drying the slurry-like electrode mixture on the current collector, and the electrode is produced.
The electrode mixture is not particularly limited, but is prepared, for example, by dispersing and mixing an active material, a conductive auxiliary agent, a binder, a solvent, and the like.
The active material is not particularly limited, and examples thereof include lithium-containing oxides, phosphate compounds, activated carbon, graphite, carbon, silicon, and alloys.
Although it does not specifically limit as a conductive support agent, For example, carbon black, a vapor growth carbon fiber (VGCF), a carbon nanotube (CNT) etc. are mentioned.
The binder is not particularly limited as long as it is a general one used in batteries and power storage elements, and examples thereof include PVDF (polyvinylidene fluoride), styrene butadiene latex, and acrylic latex.
The solvent is not particularly limited. For example, NMP is used when PVDF is used as a binder, and water is used when latex is used as a binder.

  These materials are dispersed and mixed to form a slurry-like electrode mixture, which is applied onto a current collector such as an aluminum foil or a copper foil. A current collector with an anchor coating applied may be used to improve conductivity. Further, a current collector having a hole may be used. The electrode mixture is applied by a general method, and the mixture layer is applied so that the thickness of the mixture layer is in the range of 30 μm to 300 μm.

The fact that the binder for adhering the active material is in a uniform state in the thickness direction of the electrode means that, for example, in the electrode in which a mixture layer using a fluorine-containing resin as a binder is applied and dried, It can be evaluated by measuring the concentration ratio of the fluorine element between the surface and the peeled surface exposed in the peel test of the electrode mixture layer and the current collector: (fluorine content on the peeled surface / fluorine content on the surface). it can.
In general, the site where peeling occurs in the peeling test can be regarded as the position where the amount of binder is the smallest. Therefore, when the fluorine content on the peeled surface is compared with the fluorine content on the surface, the value is close to 1. It can be judged that the binder is uniform in the thickness direction of the electrode. In order to obtain good peel strength, the concentration ratio needs to be in the range of 0.7 to 1.2.

  As described above, by using the coating apparatus of the present invention, it is possible to apply on both sides, so that the productivity is high and the wind speed is not excessively strong. Therefore, the binder distribution in the thickness direction in the electrode mixture layer is uniform, and the peel strength is strong. The electrode thus obtained develops a network structure that connects active materials and increases the current collecting property of the electrode, and the performance is improved by using this electrode for a storage element.

Hereinafter, the effects of the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited to these examples.
Using the coating apparatus of the present invention as described above, the electrode mixture layer was formed by applying the electrode mixture in stripes on both sides of the long sheet-like current collector and drying.
It was performed by changing the presence or absence of support by a roller during drying and the conditions of the drying method, and the deviation of the binder concentration and the peel strength of the obtained electrode mixture layer were evaluated.
First, commercially available activated carbon is used as an active material, commercially available carbon black is used as a conductive aid, PVDF is used as a binder, NMP is used as a solvent, and PVP (polyvinylpyrrolidone) is mixed as a viscosity adjusting agent at a predetermined ratio. % Slurry-like electrode mixture was prepared.

This electrode mixture was applied to an aluminum foil having a thickness of 15 μm and a width of 350 mm. In the coating, two coated portions having a width of 10 cm were used, and the width of the non-coated portion at both ends of the aluminum foil and the width of the non-coated portion between the two coated portions were 5 cm. The coating method was performed on both upper and lower surfaces by die coating, and the amount of slurry applied was adjusted so that the basis weight after drying was 30 g / m ² .

  The drying furnace has a total furnace length of 4 m and is divided into four zones (1st to 4th zones) every 1 m, individually set temperature, hot air blowing speed and direction of blowing, radiant heating means The specification which can change with / without is used. Regarding the quality of the coated electrode, the electrode peel strength was 0.1 N / cm or more and the drying condition was changed to produce an electrode.

  The peel strength was measured by adding a non-coated portion of 2.5 cm in the MD direction (longitudinal direction) to the coated portion 10 cm in the MD direction (longitudinal direction) and 2 cm at both ends on the both ends. The specimen was cut into a 14 cm rectangle. A cellophane tape having a width of 23 mm defined by JIS Z1522 was attached to the surface of the electrode mixture layer side. Using an autograph, the stress was measured when the cellophane tape and the aluminum foil were peeled off at a constant rate of 180 ° and a tensile rate of 50 mm / min. Specifically, the peel strength (N / cm) was calculated by averaging the stress at the 2.5 cm to 6.5 cm portion of the portion where the electrode mixture layer was formed. The measurement was performed 5 times, and the average value was obtained.

In addition, as a method for evaluating the uniformity of the PVDF binder distribution in the electrode, the relative sensitivity of XPS (X-ray photoelectron spectroscopy) is used to determine two locations on the surface of the electrode and the peeled surface exposed in the peel test. The element concentration of each element was measured, and the concentration ratio of fluorine element concentration: (fluorine element concentration on the peeled surface / fluorine element concentration on the surface) was determined. The material containing fluorine in the electrode mixture is only the PVDF binder in the material used this time, and the portion where the fluorine element concentration is high can be evaluated as indicating that the amount of PVDF binder is large.
The XPS measurement conditions are as follows.
Equipment: ESCALAB 250 type manufactured by Thermo Fisher X-ray source: Monochromatic Al Kα ray
Analysis area: Ellipse of about 1 mm Photoelectron extraction angle: 0 ° (perpendicular to sample surface)
Analyzer path energy: 20 eV
Moreover, the sensitivity coefficient shown below was used for calculation of relative element concentration.
C 1s: 1.00
O 1s: 2.72
N 1s: 1.68
F 1s: 4.67
Other elements: The relative sensitivity coefficient attached to the device is used as it is.

<Example 1>
From the first zone to the third zone of the drying furnace, a structure in which hot air does not directly hit the long sheet as shown in FIG. Three rollers having a diameter of 6 cm and a width of 4 cm were attached to the supporting roller so that the distance between the rollers (distance between the ends of the rollers) was 11 cm. Two rollers were installed in each zone of the drying furnace at intervals of 50 cm, and the rollers were arranged so that the lower surface of the non-coated part of the long sheet and the roller were in contact with each other. The hot air blowing port was set so that the hot air was not directly applied to the long sheet, and the wind velocity of the hot air was set to 8 m / second in each zone at the blowing port. On the other hand, the fourth zone was a hot air float type shown in FIG. Hot air outlets are installed in each zone at two locations, upper and lower, so that the hot air hits the long sheet substantially vertically. The set temperature of each zone was set to 70 ° C., 80 ° C., 110 ° C., and 160 ° C. from one zone, respectively. While keeping the electrode weight constant, the conveying speed of the long sheet was gradually increased, and the drying time was gradually shortened.

  As a result, the peel strength of the obtained electrode gradually decreased, and the target was 0.1 N / cm or more until the drying time was 5 minutes, but the peel strength could not be cleared below that. The peel strength when the drying speed was 5 minutes was 0.10 N / cm. The fluorine concentration ratio between the electrode surface and the interface between the electrode mixture layer and the current collector (fluorine concentration at the interface / fluorine concentration at the surface) was 0.88, and the binder concentration was approximately the same.

<Example 2>
A radiation type heat drying apparatus as shown in FIG. 6 was arranged from the first zone to the third zone of the drying furnace. The supporting rollers in the drying furnaces in the first to third zones, their positions, the direction of the hot air blowing port, and the wind speed were the same as in Example 1. Far infrared heaters were placed on the upper and lower surfaces of the long sheet. The heating temperature of the far infrared heater was set to 160 ° C.
On the other hand, the fourth zone was a hot air float type shown in FIG. Hot air outlets 20 are installed in each zone at two locations, upper and lower, so that the hot air hits the long sheet substantially vertically. The set temperature of each zone was set to 70 ° C., 80 ° C., 110 ° C., and 160 ° C. from one zone, respectively.

  As a result, when the conveyance time of the long sheet was increased to shorten the drying time, the peel strength was 0.10 N / cm or more, which was the target until the drying time was 3.5 minutes. When the long sheet was dried with a drying time of 5 minutes, the peel strength of the electrode was 0.15 N / cm. Further, the fluorine concentration ratio between the electrode surface and the interface between the electrode mixture layer and the current collector (fluorine concentration at the interface / fluorine concentration at the surface) was 1.01, and the binder concentration was equal between the surface and the interface. .

<Comparative example>
No roller in contact with the long sheet was disposed in the drying furnace, and drying was performed while the long sheet was floated by a conventional hot air float method in each zone as shown in FIG.
Hot air outlets are installed in each zone at two locations, upper and lower, so that the hot air hits the long sheet substantially vertically. The wind speed in each zone was 12 m / sec from the first zone to the third zone, and 20 m / sec in the fourth zone. The distance between the long sheet being dried and the hot air outlet was 3 mm to 15 mm. The set temperature of each zone was set to 70 ° C., 80 ° C., 110 ° C., and 160 ° C. from one zone, respectively.

  As a result, the drying time for obtaining the target peel strength was 7 minutes. When the drying time was shorter than that, the peel strength decreased and did not reach the target value. When the long sheet was dried with a drying time of 5 minutes, the peel strength of the electrode was 0.04. Further, the fluorine concentration ratio (interface fluorine concentration / surface fluorine concentration) between the electrode surface and the interface between the electrode mixture layer and the current collector was 0.33. Thus, in the conventional hot air float type drying, it was suggested that the concentration of the binder is remarkably high on the surface, the binder at the interface is small, and the binder concentration is uneven.

  For each Example and Comparative Example, the minimum drying time when the peel strength of the electrode layer exceeds the target value (0.1 N / cm), and the peel strength and fluorine ratio of the electrode layer when the drying time is 5 minutes, Table 1 summarizes the results.

  As can be seen from Table 1, by applying and drying using the coating machine of the present invention, the electrode strength with a high peel strength and a suppressed binder concentration can be achieved in a shorter time than in the past. It was found that an agent layer was obtained. In this case, when fluorine-containing resin was used as the binder, the fluorine content on the release surface / the fluorine content on the surface was in the range of 0.7 to 1.2.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be appropriately changed without departing from the spirit of the invention.
For example, in the above-described embodiment, the case where the electrode mixture is applied onto the current collector has been described as an example. However, the present invention is not limited thereto, and various coating agents can be used as long sheets. Widely applicable when applied on top.

  By using the coating machine according to the present invention, it becomes possible to produce a coating layer with good performance with little deviation in binder concentration, and can be widely used as a coating machine for electrode mixture coating. .

DESCRIPTION OF SYMBOLS 1 Horizontal type double-side coating apparatus 2 Long sheet 3 Unwinding part 4 Winding part 5 Coating machine 6 Drying furnace 7 Radiation-type drying apparatus 8 Roller body 9 Support roller 10 Guide roller 11a Coating part 11b Non-coating part

Claims (6)

An unwinding section for unwinding the long sheet;
A winding unit for winding the long sheet;
A roller body disposed between the unwinding unit and the winding unit and rotatable in the conveying direction of the long sheet;
A pair of coating machines arranged to face both sides of the long sheet,
A horizontal-type double-side coating apparatus in which a coating part and a non-coating part are repeatedly formed in the width direction on both sides of the long sheet,
Each of the pair of coating machines has one or a plurality of coating heads arranged at predetermined intervals in the width direction of the long sheet,
The roller body is disposed at a position shifted from the coating head in a side view in the width direction of the long sheet, and the long peripheral sheet comes into contact with the non-coated portion of the long sheet. Having a support roller for supporting the sheet substantially horizontally , and
The horizontal double-side coating apparatus , wherein the position of the support roller is variable in the width direction of the long sheet corresponding to the position of the non-coating portion . 2. The horizontal double-side coating apparatus according to claim 1 , wherein, in the support roller, a width of a peripheral surface contacting the long sheet is smaller than a width of the non-coated portion. The support roller includes a lower support roller in contact with the non-coated portion of the lower surface of the elongated sheet, and an upper support roller in contact with the non-coated portion of the upper surface of the long sheet,
The horizontal type double-side coating apparatus according to claim 1 or 2 , wherein the upper support roller and the lower support roller are in positions shifted from each other in a top view. The horizontal double-side coating apparatus according to any one of claims 1 to 3 , further comprising a radiation-type drying device arranged to face both surfaces of the long sheet. The roller body has a pair of guide rollers arranged on the outer side in the width direction of the long sheet than the support roller,
The distance between the pair of guide rollers is substantially equal to the width of the long sheet,
The horizontal type | mold double-sided coating apparatus as described in any one of Claims 1-4 with which the both ends of the said elongate sheet | seat contact the side surface of this guide roller, respectively. An electrode mixture using a fluorine-containing resin as a binder is applied to both sides of a long current collector using the horizontal double-side coating apparatus according to any one of claims 1 to 5 , In a method for producing an electrode having an electrode mixture layer formed by drying,
The concentration ratio of fluorine element between the surface of the electrode mixture layer and the peeled surface exposed in the peel test of the electrode mixture layer and the current collector: (fluorine content of the peeled surface / fluorine content of the surface) is It adjusts so that it may become the range of 0.7 to 1.2, The manufacturing method of the electrode which has an electrode mixture layer characterized by the above-mentioned.

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