Application device

Abstract

According to the present invention, an application device comprises a die head 20 for applying a slurry 13. The die head 20 has a slit 21 that has an opening through which the slurry 13 is discharged. At the opening of the slit 21, the slit width W2 at both ends in the longitudinal direction of the slit 21 is up to 20% greater than the slit width W1 at the center in the longitudinal direction of the slit 21.

Description

Coating Equipment

[0001] The present disclosure relates to a coating device.

[0002] Die coating devices are used to manufacture battery electrode plates. For example, Patent Document 1 discloses a device that applies a coating material (electrode material) to a web (metal foil) using a die head with a slit. In this device, the slurry is applied by ejecting it from a slit of a fixed width provided in the die head.

[0003] Japanese Patent Application Laid-Open No. 2004-249261

[0004] When electrodes are manufactured by applying a slurry using a conventional die coating device, regions in the width direction of the electrode plate where the desired characteristics are not obtained are generated. These regions cannot be used as electrodes and must be discarded, which increases manufacturing costs.

[0005] In the present disclosure, a coating device that can apply slurry more uniformly up to near both ends of the coating width will be described.

[0006] The inventors of the present application have noticed that the cause of the above problem is that the amount of slurry discharged is small at both longitudinal ends of the opening of the slit, and have come up with the technique of the present disclosure.

[0007] The coating device of the present disclosure includes a die head for applying a slurry. The die head has a slit through which the slurry is discharged. At the slit opening, the slit width at both ends in the longitudinal direction of the slit is greater by 20% or less than the slit width at the center of the slit in the longitudinal direction.

[0008] According to the coating device of the present disclosure, the slit width is increased at both longitudinal ends of the slit, so that a desired amount of slurry can be applied to both ends as well. As a result, when used in the manufacture of electrode plates for lithium-ion batteries, for example, the amount of waste at the widthwise ends of the electrode plates can be reduced.

[0009] FIG. 1 is a diagram schematically illustrating application of a slurry by a die head of a coating apparatus according to the present disclosure. FIG. 2 is a perspective view schematically illustrating the die head of FIG. 1. FIG. 3 is a diagram schematically illustrating the die head and the slurry applied to a current collector by the die head. FIG. 4 is a diagram illustrating the shape of a slit provided at the tip of the die head. FIG. 5 is a diagram illustrating the shape of a slit in the die head according to the present disclosure and the cross-sectional shape of the slurry applied to a current collector sheet through the slit. FIG. 6 is a diagram illustrating the shape of a slit in a die head of a comparative example and the cross-sectional shape of the slurry applied to a current collector sheet through the slit. FIG. 7 is a diagram schematically illustrating the shape of a slit in a modified example of the present disclosure.

[0010] Hereinafter, embodiments will be described with reference to the accompanying drawings. The following description is merely an example and is not intended to be limiting. Furthermore, modifications can be made as appropriate within the scope of the present invention.

[0011] 1 is a diagram illustrating a main part of an exemplary coating device 10 according to an embodiment of the present disclosure. In this embodiment, the coating device 10 is used to coat a current collector with a slurry containing an active material in the manufacture of electrode plates for lithium-ion batteries.

[0012] The coating device 10 includes a roller 11 that conveys the current collector sheet 12, and a die head 20 that applies the slurry 13 to the current collector sheet 12 on the roller 11. Fig. 2 shows only the die head 20 as a schematic perspective view.

[0013] Die head 20 has a substantially pentagonal cross section with one side of a rectangle protruding into a triangle, and is provided with slit 21 so that the apex of the protruding triangle is open. The slurry supplied to die head 20 passes through slit 21 and is discharged from the opening, and is supplied onto current collector sheet 12. As current collector sheet 12 is transported by the rotation of roller 11, slurry 13 is applied to current collector sheet 12.

[0014] Fig. 3 is a plan view schematically showing a state in which the slurry 13 has been applied to the current collector sheet 12. The left-right direction in Fig. 3 corresponds to the direction perpendicular to the plane of the paper in Fig. 1. Fig. 4 is a diagram schematically showing the shape of the opening of the slit 21 provided in the die head 20, and corresponds to a view from above in Fig. 3. However, the shape of the slit 21 is shown with emphasis, and the aspect ratio in particular does not necessarily represent the actual shape.

[0015] 3 also shows the die head 20, and the slurry 13 is applied to a width corresponding to the width of the die head 20. More precisely, the slurry is applied according to the dimensions of the slit 21 provided in the die head 20. Here, for the slit 21 shown in FIG. 4, the dimension in the longitudinal direction (left-right direction in FIG. 4) is the "length" of the slit, and the dimension in the lateral direction (up-down direction in FIG. 4) is the "width." Therefore, in FIG. 3, the slurry 13 is applied to a width corresponding to the "length" of the slit 21.

[0016] 4, the slit 21 has portions at both longitudinal ends that are wider than the central portion. By using such slits 21, a sufficient amount of slurry 13 can be applied to the ends, thereby reducing the amount of waste in the manufactured electrode plates.

[0017] This will be explained with reference to Figures 5 and 6. Figure 5 is a diagram showing the shape of the slits 21 in the die head 20 of this embodiment and the cross-sectional shape of the slurry 13 applied to the current collector sheet 12 using the die head 20. Figure 6 shows a comparative example to be compared with Figure 5. The slits 21a of the comparative example have the same width throughout the entire longitudinal direction. Figure 5 also shows the slurry 13 applied using the die head having the slits 21a.

[0018] In the comparative example, the opening shape of the slit 21a is a simple rectangle with a length L1 and a width W1, and the width (short dimension) is the same throughout the longitudinal direction. Because the slurry 13 has fluidity, the slurry 13 applied using the slit 21a is applied to a width slightly wider than the length of the slit 21a. As a result, the amount of slurry 13 applied is insufficient at both ends in the width direction of the slurry 13, resulting in defective portions 13a that do not exhibit the desired characteristics as an electrode plate. Therefore, the width A2 of the portion that can be used as an electrode plate is smaller than the length L1 of the slit 21a.

[0019] In contrast, the slit 21 in this embodiment shown in FIG. 5 has wider portions at both longitudinal ends. More specifically, the length of the slit 21 is L1, the same as the slit 21a in FIG. 6. The width W1 of the central portion of the slit 21 is the same as the width W1 of the slit 21a. However, the slit 21 has wide portions at both longitudinal ends, which are wider than W1, within the range of the length L2. This allows a larger amount of slurry 13 to be discharged at both ends of the slit 21 than at the center. As a result, the amount of slurry 13 applied to the current collector sheet 12 is reduced even at both widthwise ends, and defective portions 13a are reduced. Therefore, the width A1 of the portion usable as an electrode plate is larger than the width A2 in the comparative example and is closer to the length L1 of the slit 21. Fewer defective portions 13a are discarded, improving raw material utilization efficiency.

[0020] (Dimensions of Slit) The dimensions of each part of the slit 21 will be further described.

[0021] There is no particular limitation on the overall length L1 of the slit 21, but in the case of manufacturing electrode plates for lithium ion batteries, it is, for example, 100 mm to 2000 mm, and may be 300 mm, 600 mm, 1200 mm, or the like.

[0022] The longitudinal dimension L2 of the wide portions (wide portions) at both ends of the slit 21 is preferably 3 mm or more, and more preferably 5 mm or more. With such a dimension, the effect of increasing the amount of slurry 13 discharged at the ends and reducing defective portions 13a is appropriately achieved. Furthermore, L2 is preferably 20 mm or less, and more preferably 15 mm or less. In order to adjust the amount of slurry 13 discharged near the longitudinal ends, it is preferable to provide a difference in width between the regions near the ends and the center. The occurrence of defective portions 13a occurs when the slurry discharged from the slit 21 spreads beyond the length of the slit 21, and the length L1 of the slit 21 has little effect on the desirable value of L2.

[0023] In the central portion, which is located inside the wide portion (the range of L2) in the longitudinal direction, it is preferable that the width W1 is uniform. This is because the coating amount is equal in each portion in the longitudinal direction in order to obtain a uniform coating thickness in the central portion. However, this does not exclude the width being varied in the central portion for other process reasons.

[0024] The width W1 of the central portion of the slit 21 is, for example, 0.3 mm or more, preferably 0.5 mm or more, and more preferably 1.0 mm or more, and is, for example, 5.0 mm or less, preferably 4.0 mm or less, and more preferably 3.0 mm or less.

[0025] The width W2 of each longitudinal end of the slit 21 is preferably 1% or more, more preferably 3% or more, larger than the width W1 of the central portion. The width W2 is preferably 20% or less, more preferably 10% or less, larger than the width W1.

[0026] Table 1 shows the width W1 of the central portion and the width W2 of the edge portion for Examples 1 to 9 and Comparative Examples 1 and 2. In Table 1, "slit width difference" indicates, in percentage, how much the width W2 of the edge portion is larger than the width W1 of the central portion. Furthermore, "edge coating thickness" indicates, in percentage, the ratio of the thickness of the applied slurry 13 at the center in the width direction to the thickness at the edge portion (more precisely, at a position 2 mm from the edge of the slurry 13 in the width direction). Therefore, when the thickness at the edge portion is smaller than the thickness at the center, the value is 100 or less. When this value is close to 100%, it means that the coating thickness of the slurry 13 at the center and the edge portion are similar values, and there are few defective portions 13a at the edge portion.

[0027]

[0028] In Table 1, Comparative Example 1 has a width W1 of the center portion of 2.0 mm and a slit width difference of 0% (i.e., the width is the same throughout the entire length of the slit as shown in Figure 5). In this case, the coating thickness at the edge is 92.3%, which is 7.7% thinner than the coating thickness at the center.

[0029] In contrast, in Example 3, the width W1 of the central portion is 2.0 mm, the same as in the comparative example, and the difference in slit width is 10%. In this case, the edge coating thickness is 97.9%, which is an improvement of 5.6 points over the comparative example.

[0030] In addition, in all of Examples 1 to 5, the difference in slit width was 10% (i.e., the width W2 of the end portion was 2.2 mm), and the width W1 of the central portion was a value ranging from 0.5 mm to 4.0 mm. In all of Examples 1 to 5, the edge coating thickness was greater than in Comparative Example 1, and the uniformity of the coating thickness of the slurry 13 at the edge portions was improved. In particular, a remarkable effect was observed in Examples 1 to 4, in which the width W1 of the central portion was 0.5 mm to 3.0 mm.

[0031] Furthermore, in Examples 6 to 9 and Comparative Example 2, the width W1 of the central portion is 2.0 mm, the same as in Comparative Example 1, and the differences in slit width are 1% to 20% and 30%. In all cases, the edge coating thickness is greater than in Comparative Example 1, eliminating the insufficient coating thickness at the edges. In particular, significant effects are seen in Examples 7 to 9, where the difference in slit width is 3% to 20%. In Comparative Example 2, where the difference in slit width is 30, the edge coating thickness exceeds 100%, making the edges thicker than the center. Therefore, it is preferable that the difference in slit width be up to about 20%.

[0032] (Modification) In the slit 21 shown in FIG. 5, the width of the slit 21 is increased in a triangular shape on both sides of the slit 21 in the short direction within the range of the length L2 at the longitudinal end. However, this is not limited to this. For example, as shown in FIG. 7, the width may increase in a smoothly connecting curve from the center. However, in order to make the coating thickness of the slurry 13 uniform at the end, it is preferable that the position where the width of the slit 21 is widest is the extreme end of the slit 21 in the long direction. Furthermore, it is preferable that there is no difference in width between the range of the length L2 where the width is increased and the central portion further toward the center. This allows the coating thickness of the slurry 13 to be more uniform to both ends in the width direction.

[0033] The above-described embodiments may be modified in form and detail without departing from the spirit of the claims. Furthermore, the contents of the embodiments may be combined and substituted as appropriate as long as the functions of the subject matter of the present disclosure are not impaired.

[0034] The coating device of the present disclosure can improve the uniformity of the coating thickness up to the vicinity of the ends of the die head in the width direction, and is therefore useful in, for example, producing electrode plates for lithium-ion batteries.

[0035] REFERENCE SIGNS LIST 10 Coating device 11 Roller 12 Current collector sheet 13 Slurry 13a Defective portion 20 Die head 21 Slit 21a Slit

Claims

1. A coating device comprising a die head for applying a slurry, the die head having a slit through which the slurry is discharged, and wherein the width of the slit opening at both ends in the longitudinal direction of the slit is greater than the width of the slit at the center in the longitudinal direction of the slit by no more than 20%.

2. A coating device according to claim 1, wherein the slit width at the central portion is 0.5 mm or more and 3.0 mm or less, and the slit width at each end is 3% or more and 20% or less wider than the slit width at the central portion.

3. The coating device according to claim 1, wherein the length of each of the two end portions is 15 mm or less.

4. The coating device according to claim 1, wherein the width of the central portion is constant.

5. A coating device according to claim 1, wherein the width of each of the opposite ends of the slit is the same as that of the central portion of the slit, and the width of each of the opposite ends of the slit increases toward the opposite ends of the slit.

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