Shim plate and slot die coater including same

Abstract

The present invention provides a shim plate and a slot die coater including the same, which can improve load difference in the width direction during electrode coating. The shim plate is disposed between a lower die block and an upper die block of a slot die coater to form a slot and to discharge a coating solution from a discharge port communicating with the slot. The shim plate includes a plurality of shim teeth that are intermittently cut in one region to provide a plurality of openings, and a plate membrane that partially fills spaces between the plurality of shim teeth.

Description

[Technical Field]

[0001] The present invention relates to a shim plate and a slot die coater including the same, and more particularly to a shim plate that can improve a load difference in the width direction during electrode coating and a slot die coater including the same.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0171222 filed on December 9, 2022, Korean Patent Application No. 10-2023-0008348 filed on January 19, 2023, and Korean Patent Application No. 10-2023-0097672 filed on July 26, 2023, and the contents disclosed in the specifications and drawings of those applications are incorporated herein in their entirety. [Background technology]

[0003] As technological development and demand for mobile devices continues to grow, demand for secondary batteries as energy sources is rapidly increasing. These secondary batteries essentially include an electrode assembly, which is a power-generating element. An electrode assembly has a structure in which a positive electrode, a separator, and a negative electrode are stacked at least once. The positive electrode and negative electrode are fabricated by coating and drying a positive electrode active material slurry and a negative electrode active material slurry on current collectors made of aluminum foil and copper foil, respectively. To ensure consistent charge / discharge characteristics of secondary batteries, the positive electrode active material slurry and the negative electrode active material slurry must be uniformly coated on the current collectors, and a slot die coater has traditionally been used for this purpose.

[0004] Figure 1 shows an example of a coating method using a conventional slot die coater. Figure 2 is a cross-sectional view taken along line II-II' in Figure 1, showing the slot die coater along the MD direction (the running direction of the current collector).

[0005] 1 and 2, in a method for manufacturing an electrode using a slot die coater 30, an electrode active material slurry is applied from the slot die coater 30 onto a current collector 20 transported by a coating roll 10. The electrode active material slurry is applied widely over one surface of the current collector 20 to form an electrode active material layer. The slot die coater 30 includes two die blocks 32 and 34, with a slot 36 formed between the two die blocks 32 and 34. A manifold 38 receives electrode active material slurry supplied from a feed unit (not shown), and the electrode active material slurry is discharged from a discharge port 40 communicating with the slot 36 to form an electrode active material layer. Reference numerals 42 and 44 denote die lips, which are the ends of the two die blocks 32 and 34, respectively.

[0006] The coating width of the electrode active material layer coated on the current collector 20 is determined by the width of the slot 36. If the coating width needs to be changed, various coating widths can be realized by changing the shim plate 50 that determines the inner space of the manifold 38 and the width of the slot 36.

[0007] The shim plate 50 is a sheet-like member having a thickness that defines the gap between the through slots. Figures 3a, 3b, and 3c show an example in which the coating width is adjusted by varying the size and pattern of the shim plate 50 inserted between the two die blocks 32 and 34.

[0008] 3a, a shim plate 50 has an opening 50a formed by cutting out one area, and is interposed in the remaining area except for one side of the edge area of ​​each of the opposing surfaces of the two die blocks 32 and 34. The width of the opening 50a of the shim plate 50 is designed to be a so that an electrode active material layer 60 having a coating width a is formed on the current collector 20, and uncoated areas 62 are formed on both sides of the electrode active material layer 60.

[0009] Referring to FIG. 3b, to form an electrode active material layer 60 having a coating width of b which is smaller than a on the current collector 20, the width of the opening 50a of the shim plate 50 is designed to be b (b < a).

[0010] If necessary, a stripe pattern-shaped electrode active material layer 60 may be formed on the current collector 20. In such a case, a shim plate 50 as shown in FIG. 3c is used. Referring to FIG. 3c, the shim plate 50 has a region intermittently cut open to provide a plurality of openings 50a, and the width of the opening 50a is c which is smaller than a or b (c < a, c < b). By using such a shim plate 50, a plurality of electrode active material layers 60 having a coating width of c are formed in a plurality of stripe pattern shapes corresponding to the number of the openings 50a on the current collector 20, and non-coated portions 62 are formed on both sides of the electrode active material layer 60.

[0011] However, in the slot die coater 30 using such a shim plate 50, since the injection direction of the coating liquid is the central portion of the die blocks 32 and 34 (the inlet of the slurry is located at the central portion of the manifold 38, and the electrode active material slurry in the manifold 38 is filled and discharged), the liquid coating amount at the central portion is larger than that at the side portion, and thus a non-uniform coating profile in the width direction (perpendicular to the MD direction) is obtained.

[0012] FIG. 4 is a diagram showing problems in the use of a conventional shim plate. What is shown in FIG. 4 is a cross-section of five electrode active material layers 60 formed on the current collector 20 in the shim plate 50 as shown in FIG. 3c, for example, when there are five openings 50a. As shown in the figure, when five patterns are formed, since the load amount at the central portion in the width direction is high, the one located at the central portion of the electrode active material layer 60 is thicker than the others, showing a non-uniform coating profile in the width direction. Thus, conventionally, there is an inevitable problem that a load difference according to the reference position (center - side) in the coating width direction occurs, and as a result, a high electrode processability cannot be ensured.

Summary of the Invention

[0013] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a shim plate that can improve the load difference in the width direction during electrode coating.

[0014] Another object of the present invention is to provide a slot die coater including such a shim plate.

[0015] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the description of the invention below. [Means for solving the problem]

[0016] To achieve the above object, the shim plate of the present invention is provided between a lower die block and an upper die block of a slot die coater to form a slot and to discharge a coating liquid from a discharge port communicating with the slot. The shim plate includes a plurality of shim teeth in which one area is intermittently cut to provide a plurality of openings, and includes a plate membrane that partially blocks the spaces between the plurality of shim teeth.

[0017] The plate membrane may be positioned in a portion to reduce the load of the coating liquid.

[0018] The shim plate includes a base first part and at least four second parts extending from the first part, the second parts being connected to the same side of the first part and extending in the same direction, the second parts being composed of two side second parts located on both sides and an inner second part located between the two side second parts, and the plate membrane can be located between the inner second parts.

[0019] The side second portion may have a width greater than the inner second portion.

[0020] The edge of the second side portion, on the side where the coating liquid is discharged, may be chamfered.

[0021] The chamfered edge portion may be one of a stepped surface with a constant cutting depth, an inclined surface with a cutting depth that varies toward the end of the shim plate, a convex curved surface, or a concave curved surface. The inclined surface may be formed at an angle of 10° to 80° with respect to the direction in which the coating liquid is discharged.

[0022] The plate membrane may be located between every two adjacent inner second portions.

[0023] The plate membrane may not be located between the side second portions and the inner second portions, and may be located only between the inner second portions.

[0024] The plate membrane may extend without being separated from the first portion.

[0025] The plate membrane may extend away from the first portion to define an open vent between the first portion and the plate membrane.

[0026] The end of the plate membrane that defines the vent portion may have a rounded cross section.

[0027] The length of the plate membrane is greater than the size of the vent portion.

[0028] In order to achieve the other object described above, the slot die coater of the present invention includes a lower die block and an upper die block, a shim plate disposed between the lower die block and the upper die block and forming a slot, and a manifold disposed in at least one of the upper die block and the lower die block and containing a coating liquid, and the coating liquid is discharged onto a substrate from a discharge port communicating with the slot to apply the coating liquid, wherein the shim plate includes a plurality of shim teeth that are intermittently cut in one area to provide a plurality of openings that determine a coating width of the coating layer applied to the substrate, and a plate membrane that partially blocks spaces between the plurality of shim teeth.

[0029] The manifold may include an upper manifold included in the upper die block and a lower manifold included in the lower die block, the upper manifold and the lower manifold facing each other, and the shim plate may be interposed between the upper manifold and the lower manifold.

[0030] A coating liquid inlet pipe for introducing the coating liquid may be connected to a coating liquid inlet hole formed in the center of the lower manifold.

[0031] The shim plate includes a base first part and at least four second parts extending from the first part, the second parts being connected to the same side of the first part and extending in the same direction, the second parts being composed of two side second parts located on both sides and an inner second part located between the two side second parts, and the plate membrane can be located between the inner second parts.

[0032] The plate membrane may extend away from the first portion, thereby defining an open vent between the first portion and the plate membrane.

[0033] In such a case, the coating liquid may flow from the lower manifold to the upper manifold through the vent.

[0034] The plate membrane may be formed in a shape that blocks at least a portion of the coating liquid inlet hole.

[0035] The orthogonal projection of the membrane does not deviate from the orthogonal projection of the manifold.

[0036] The front end of the plate membrane may be located rearward of the front end of the manifold.

[0037] A lower surface of the upper die block and an upper surface of the shim plate may be joined together without a gap at the rear and front of the manifold, and an upper surface of the lower die block and a lower surface of the shim plate may be joined together without a gap. [Effects of the Invention]

[0038] According to one aspect of the present invention, by including the shim plate, when the slot die coater is used, a coating layer having a stripe pattern can be formed on a substrate without load difference in the electrode coating width direction.

[0039] According to another aspect of the present invention, not only is the load difference between coating electrode positions improved, but the coating liquid in the center can be guided to the side without causing a vortex in the coating liquid.

[0040] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical concept of the present invention, so the present invention should not be interpreted as being limited to the matters described in the drawings. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a schematic diagram showing an example of use of a slot die coater according to the prior art. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II' in FIG. [Figure 3a] 1 shows various examples of the use of conventional shim plates. [Figure 3b] 1 shows various examples of the use of conventional shim plates. [Figure 3c] 1 shows various examples of the use of conventional shim plates. [Figure 4] The following shows the problems that arise when using conventional shim plates. [Figure 5] FIG. 1 is a cross-sectional view of a slot die coater according to one embodiment of the present invention. [Figure 6] FIG. 2 is a plan view of a shim plate included in a slot die coater according to one embodiment of the present invention. [Figure 7] This is a modified example of the shim plate shown in FIG. [Figure 8] 7 is another modification of the shim plate shown in FIG. 6. [Figure 9] 7 is a diagram showing yet another modification of the shim plate shown in FIG. 6. [Figure 10] 10A and 10B are diagrams illustrating the effect of using a shim plate according to an embodiment of the present invention. [Figure 11] 10 shows the flow of coating liquid using a shim plate of a comparative example. [Figure 12] 1 illustrates the flow of coating liquid through a shim plate according to one embodiment of the present invention. [Figure 13] 1 illustrates the flow of coating fluid in a slot die coater according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical ideas of the present invention, in accordance with the principle that the inventor himself can appropriately define the concepts of terms in order to best explain the invention. Therefore, it should be understood that the embodiment described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical ideas of the present invention, and therefore various equivalents and modifications that can be substituted therefor may exist at the time of filing this application.

[0043] In addition, the same reference numerals denote the same elements, and in the drawings, thickness, ratio, and size of elements may be exaggerated for the purpose of effectively explaining the technical contents.

[0044] The slot die coater of the present invention is a device equipped with a slot and configured to apply a coating liquid onto a substrate through the slot. In the following description, the "substrate" refers to a current collector, and the "coating liquid" refers to an electrode active material slurry. However, the scope of the present invention is not necessarily limited thereto. For example, the substrate may be a porous support that constitutes a separator, and the coating liquid may be an organic material. In other words, the substrate and coating liquid may be any material as long as a thin film coating is required. In this specification, "front" refers to the direction toward the discharge port, and "rear" refers to the opposite direction.

[0045] Fig. 5 is a cross-sectional view of a slot die coater according to one embodiment of the present invention, and Fig. 6 is a plan view of a shim plate included in the slot die coater according to one embodiment of the present invention.

[0046] 5 and 6, a slot die coater 100 includes two die blocks 110 and 130, a lower die block and an upper die block, respectively. A shim plate 113 for forming a slot 101 is provided between the two die blocks 110 and 130. The number of die blocks may be two or more. In the following embodiment, a single slot die coater in which the slot 101 is defined between the two die blocks 110 and 130 will be described. However, the present invention may also be embodied as a dual slot die coater in which the die block includes an upper plate, a middle plate, and a lower plate and has a dual slot.

[0047] Most of the surfaces of the upper die block 130 and the lower die block 110 may be manufactured to be nearly vertical. In these upper die block 130 and lower die block 110, the edges between the surfaces are perpendicular, resulting in right-angled cross-sectional shapes. This allows for a vertical or horizontal reference plane, simplifying manufacturing and handling and ensuring precision. Furthermore, when the upper die block 130 and the lower die block 110 are assembled, the opposing surfaces support each other with high surface contact, providing excellent fastening and maintenance. The assembled upper die block 130 and the lower die block 110 have an approximately rectangular parallelepiped shape overall, with only the front portion, from which the coating liquid is discharged, tilting toward the substrate. The upper die block 130 and the lower die block 110 are made of, for example, stainless steel. Materials that are easy to process, such as SUS420J2, SUS630, SUS440C, SUS304, and SUS316L, may be used. SUS has the advantages of being easy to process, inexpensive, highly corrosion-resistant, and capable of being manufactured into a desired shape at low cost.

[0048] In Figure 5, the slot die coater 100 is installed with the direction (X direction) in which the electrode active material slurry, which is the coating liquid 150, is discharged almost horizontally (approximately ±5°). However, the present invention is not limited to this example configuration, and for example, the slot die coater may be configured with a vertical die in which the direction in which the electrode active material slurry is discharged is upward (Y direction). The Z direction is the width direction of the slot die coater 100.

[0049] The slot 101 is formed between the two die blocks 110 and 130 where they face each other. A shim plate 113 is interposed therebetween, providing a gap between them, thereby forming the slot 101, which serves as a passage through which the coating liquid 150 can flow. The thickness of the shim plate 113 determines the vertical width of the slot 101 (Y direction, slot gap).

[0050] 6, the shim plate 113 has a plurality of openings 113a formed by intermittently cutting one area, and may be disposed in the remaining area except for one side of the edge area of ​​the opposing surfaces of the die blocks 110 and 130. As a result, the discharge port 101a through which the coating liquid 150 is discharged to the outside is formed between the two die lips 111 and 131 at the ends of the die blocks 110 and 130. That is, the discharge port 101a is formed by separating the two die lips 111 and 131, and the end of the slot 101 becomes the discharge port 101a.

[0051] For reference, the shim plate 113 preferably is made of a material having sealing properties because it also functions as a gasket to prevent the coating liquid 150 from leaking from the gap between the two die blocks 110 and 130, except for the area where the discharge port 101a is formed. The shim plate 113 may be made of, for example, plastic or metal, but the present invention is not limited thereto. The shim plate 113 may be made of, for example, a resin sheet such as Teflon (registered trademark) or polyester, or a metal sheet such as copper or aluminum. The shim plate 113 may be connected and fixed to at least one of the two die blocks 110 and 130, for example, by screws, but the present invention is not limited thereto.

[0052] At least one of the die blocks 110 and 130 is provided with a manifold 112 having a predetermined depth and communicating with the slot 101. In this embodiment, the lower die block 110 is provided with the manifold 112 for containing the coating liquid. The manifold 112 is connected to an external coating liquid supply chamber (not shown) via a supply pipe to supply the coating liquid 150. When the manifold 112 is completely filled with the coating liquid 150, the coating liquid 150 is guided to flow along the slot 101 and is discharged to the outside through a discharge port 101a communicating with the slot 101.

[0053] According to the slot die coater 100 having such a configuration, a rotatable coating roll 180 is disposed in front of the slot die coater 100, and the coating roll 180 is rotated to move the substrate 190 to be coated, while the coating liquid 150 is continuously discharged and brought into contact with the surface of the substrate 190 to coat the substrate 190. Alternatively, the supply of the coating liquid 150 can be alternately started and stopped to form an intermittent pattern coating on the substrate 190.

[0054] The lower surface of the upper die block 130 and the upper surface of the shim plate 113 can be joined together without any gaps at the rear and front of the manifold 112, and the upper surface of the lower die block 110 and the lower surface of the shim plate 113 can be joined together without any gaps. This allows the coating liquid 150 to flow only within the slots 101 defined by the shim plate 113. By including such a shim plate 113, a coating layer 170 having a stripe pattern can be formed on the substrate 190 using the slot die coater 100.

[0055] In particular, the shim plate 113 shown in FIG. 6 may be cut intermittently in one area to provide a plurality of openings 113a, thereby forming a stripe-patterned coating layer (170 in FIG. 10) on the substrate 190.

[0056] The shim plate 113 is characterized in that it includes a plurality of shim teeth 115, with one area intermittently cut to provide a plurality of openings 113a to determine the coating width of the coating layer applied onto the substrate 190, and includes a plate membrane 117 that partially closes the spaces between the plurality of shim teeth 115.

[0057] Thus, the present invention proposes a coating that induces an improvement in the load difference at each coating electrode position by developing a novel shim plate 113 in the coating process. The shim plate 113 may be called an FIB shim (Flow-Induced Block Shim).

[0058] The plate membrane 117 may be positioned in a portion where it is desired to reduce the load of the coating liquid 150. For example, in the slot die coater 100, when the coating liquid 150 is injected from the outside toward the center of the die blocks 110 and 130, the liquid application amount (load amount) in the center portion may be greater than that in the side portions. In such a case, the plate membrane 117 may be included in the center portion of the shim plate 113 to reduce the load amount in the center portion.

[0059] The load amount is determined by the position and area (size) of the plate membrane 117, and the position and area can be adjusted depending on the degree to which the flow rate of the coating liquid 150 in the width direction is desired. This allows the flow rate of the liquid in the width direction inside the die blocks 110 and 130 to be adjusted, thereby improving the coating uniformity in the width direction.

[0060] Using the slot die coater 100 including the shim plate 113 of the present invention, it is possible to form a coating layer, particularly an electrode active material layer, uniformly to a desired thickness and shape. The coating liquid 150 is discharged between two adjacent shim teeth 115. According to the present invention, the coating liquid 150 is not discharged directly from the manifold 112 between the two shim teeth 115, but rather hits the plate film 117 between the two shim teeth 115, where its flow stops temporarily, and then is discharged. When the plate film 117 is located particularly in the center of the shim plate 113, the coating liquid 150 is guided along the slot 101 between the two shim teeth 115 with a smaller flow rate difference in the width direction than in the past, and is discharged to the outside from the discharge port 101a, thereby significantly improving the difference in the width direction.

[0061] The shim plate 113 may be a seamless, one-piece structure. That is, even if the plate membrane 117 is included between two shim teeth 115, the portion where the plate membrane 117 and the shim teeth 115 are connected may be continuous without a seam. The shim plate 113 may have a flat upper surface and a flat lower surface. That is, it may be a sheet-like member.

[0062] The shim plate 113 can be formed as an integral part from the beginning during the manufacture of the shim plate 113, rather than by additionally stacking or adhering the plate membrane 117 made of a separate component. This has the advantages of not complicating the manufacturing process, eliminating the need to consider and manage the bonding strength with the shim plate, which would be necessary if the plate membrane 117 were a separate structure, and providing a robust structure. It also prevents the problem of the coating liquid 150 getting caught between the connecting portions.

[0063] Since the upper surface of the shim plate 113 is flat and the lower surface of the shim plate 113 is also flat, the shim plate 113 can be formed in a substantially plate-like shape.

[0064] 6, the shim plate 113 includes a first portion 114 serving as a base and at least four second portions 115 extending from the first portion 114, the second portions 115 being connected to the same side of the first portion 114 and extending in the same direction. Here, the second portions 115 become the shim teeth 115.

[0065] The first portion 114 extends along the width direction. The first portion 114 forms the rear portion of the shim plate 113. The second portions 115 each extend forward from the first portion 114. The end of the second portion 115 forms the front end portion of the shim plate 113. The second portions 115 are arranged spaced apart from each other in the width direction. An open portion 113a is defined between two adjacent second portions 115.

[0066] The second portion 115 includes side second portions 115a located on both sides and inner second portions 115b located between the side second portions 115a. In this embodiment, the number of inner second portions 115b is four. The number of inner second portions 115b may vary (at least two). When the number of second portions 115 is N, the number of side second portions 115a is two, and the number of inner second portions 115b is N-2 (N is at least 4). The shim plate 113 includes N-1 openings 113a, and each opening 113a becomes a lane that forms a pattern, forming N-1 stripe-shaped coating layers.

[0067] The plate membrane 117 may be positioned between the inner second portions 115b. In this embodiment, the plate membrane 117 is positioned between every two adjacent inner second portions 115b. In this case, the shape of the shim that forcibly closes the space within the manifold 112 can guide the flow of the coating liquid 150 from the center portion to the side portion.

[0068] The plate membrane 117 is not located between the side second portion 115a and the inner second portion 115b, but is located only between the inner second portions 115b. That is, the plate membrane 117 is located in the center, not in the side portions. As the coating liquid 150 strikes and accumulates against the plate membrane 117 located in the center, a portion of the coating liquid 150 that flows into the center is sent to both side portions. This prevents the coating liquid 150 from concentrating in the center, and therefore, by using the slot die coater 100 of the present invention, it is possible to form a coating layer, particularly an electrode active material layer in a stripe pattern, uniformly along the width direction to the desired thickness and shape.

[0069] The first portion 114 and the second portion 115 may be integrally formed. That is, there is no gap or separation between the first portion 114 and the second portion 115. Therefore, unnecessary flow of the coating liquid 150 between the first portion 114 and the second portion 115 can be prevented. In addition, as described above, since the shim plate 113 is integrally formed from the beginning during manufacture, the plate film 117 can also be integrally formed with the first portion 114 and the second portion 115. The first portion 114, the second portion 115, and the plate film 117 can have the same thickness. Therefore, the shim plate 113 is disposed between the two die blocks 110 and 130 without any gap between the top and bottom, thereby preventing the flow of the coating liquid 150.

[0070] In this embodiment, six second portions 115 are included. The first portion 114 is a portion of the shim plate 113 that is placed behind the lower die block 110. At least two second portions 115 are required so that the shim plate 113 can be interposed between the edge regions of the opposing surfaces of the upper die block 130 and the lower die block 110 except for one side. A larger number of second portions 115 are required to coat a stripe pattern. The second portions 115 extend toward the discharge port 101a. The second portions 115 connect to the same side of the first portion 114 and extend in the same direction, and an opening 113a is defined between two adjacent second portions 115. The second portions 115 are portions of the shim plate 113 that extend toward the front of the lower die block 110. Increasing the number of second portions 115 allows more patterns to be formed side by side on the substrate 190. That is, coating in a stripe pattern can be performed. However, the present invention is not limited by the number of second portions 115.

[0071] The side second portion 115a may have a width greater than that of the inner second portion 115b. For example, if the width of the side second portion 115a is d and the width of the inner second portion 115b is e, then d may be greater than e. Making the side second portion 115a wider than the inner second portion 115b can strengthen the overall structure of the shim plate 113.

[0072] Furthermore, the length d' of the second side portion 115a at the end of the shim plate 113 may be greater than the width d of the second side portion 115a. In other words, the portion of the second side portion 115a adjacent to the discharge port 101a may extend further toward the inner second portion 115b. By adjusting the extent of this extension, the width of the opening 113a can be adjusted, and thus the coating width can be adjusted.

[0073] The edge of the second side portion 115a, on the side where the coating liquid 150 is discharged, may be chamfered. The chamfered edge portion T may be one of a stepped surface with a constant cutting depth, an inclined surface where the cutting depth changes toward the end of the shim plate 113, a convex curved surface, or a concave curved surface. The illustrated example shows an inclined surface. The inclined surface may be formed at an angle α of 10° to 80° with respect to the direction in which the coating liquid 150 is discharged. If the angle is outside this range, the flow of the coating liquid 150 may become unnatural or it may be difficult to form a stable boundary surface shape at the end.

[0074] In the illustrated example, the cutting depth gradually decreases toward the end of the shim plate 113; in other words, the cutting depth gradually increases toward the inside of the manifold 112. The length of the second side portion 115a at the end of the shim plate 113 is d', and the length is maintained up to an inner depth h, after which the cutting depth increases to a width d, forming a slope. By including such a chamfer on the surface of the second portion 115a corresponding to the inside of the outlet 101a, i.e., the inner edge of the second side portion 115a, sliding of both edges of the pattern can be adjusted. The depth h at which cutting begins can be appropriately determined taking into account the flow of the coating liquid 150. The chamfered portion T can also be provided on the inner second portion 115b.

[0075] Conversely, the cutting depth may gradually increase toward the end of the shim plate 113. In this case, the discharge opening 101a located on the side gradually expands in width as it approaches the outside. In other words, the discharge opening 101a may be configured to gradually expand in the rotation direction (or MD) of the coating roll 180. This distributes the pressure of the discharged coating liquid 150, preventing it from scattering to other areas. This allows a stable interface to be formed between the coated and non-coated areas, improving the coating quality of the product. By forming a chamfered portion in this way, the coating liquid 150 can reach the substrate 190 from the die lips 111 and 131 only after it has sufficiently expanded from the end of the second portion 113b, i.e., after a certain amount of the discharge pressure has been released, preventing the coating liquid 150 from scattering. Furthermore, a stable interface can be formed between the active material pattern and the non-coated area. The shim plate 113 may include a vent portion V. Since the plate membrane 117 extends away from the first portion 114, an open vent portion V may be defined between the first portion 114 and the plate membrane 117. In designing a type 2 die (a manifold consisting of both an upper die block and a lower die block, which will be described in a later embodiment), the vent portion V may be formed by partially opening the space at the lower end to prevent vortex flow of the coating liquid 150.

[0076] Specifically, in the shim plate 113 of FIG. 6, the distance FD between the front end 112F of the manifold 112 and the front end 117F of the plate membrane 117 may be approximately 3 mm. For example, the distance FD may be 2 to 4 mm. In this manner, the front end 117F of the plate membrane 117 may be positioned further rearward than the front end 112F of the manifold 112. A predetermined offset is provided between the front end 112F of the manifold 112 and the front end 117F of the plate membrane 117 so that the coating liquid 150 in the manifold 112 can be stably discharged through the space between the second portions 113b. In this manner, the plate membrane 117 is not formed on the land portion outside the manifold 112. The plate membrane 117 does not obstruct the flow of the coating liquid 150 passing over the land portion. The plate membrane 117 covers the upper portion of the manifold 112. In other words, the orthographic projection of the plate membrane 117 does not deviate from the orthographic projection of the manifold 112. The plate membrane 117 is located only in the inner region of the manifold 112 .

[0077] The rear end 112R of the manifold 120 and the front end 114F of the first portion 114 may be aligned on the same line in the vertical direction. The inner edge 115S of the second side portion 115a may be aligned on the same line in the vertical direction with both ends 112S on the left and right sides of the manifold 112. In this manner, the first portion 114 and the second side portion 115a are arranged along the periphery of the manifold 112, and while most of the area of ​​the manifold 112 is exposed by the shim plate 113, a portion of the center may be blocked by the plate membrane 117.

[0078] The size VD of the open vent portion V may be approximately 5 mm. The size VD can be the exposed length from the rear to the front. For example, the size VD can be 3 to 8 mm. The three-dimensional shape of the vent portion V may be a semi-cylindrical shape. For example, if the size VD of the vent portion V is 5 mm, the open vent portion V may be formed in the shape of a semi-cylindrical cylinder with a radius of 2.5 mm to prevent vortex phenomena. In other words, the end of the plate membrane 117 defining the vent portion V may be rounded (rounded) so that the cross section has a rounded shape. By rounding the portion that the coating liquid 150, which receives an upward force from the bottom surface of the manifold 112, comes into contact with as it flows out of the vent portion V, the generation of vortexes can be suppressed and the flow of the coating liquid 150 can be made smooth.

[0079] The vent portion V is thus positioned rearward on the shim plate 113. The area of ​​the shim plate 113 occupied by the vent portion V is smaller than the area of ​​the plate membrane 117. For example, if the length from the front end 117F to the rear end 117R of the plate membrane 117 is SD, the length SD of the plate membrane 117 is larger than the size VD of the vent portion V. Therefore, most of the area in the central part of the manifold 112 is covered by the plate membrane 117, and only a narrower portion is exposed to the vent portion V. By positioning the vent portion V rearward on the shim plate 113, the coating liquid 150 flowing out from the vent portion V can pass over a wide area of ​​the upper surface of the plate membrane 117 and be guided toward the discharge port 101a.

[0080] With the lengths of both left and right ends 112S of manifold 112 fixed to predetermined values, shim plate 113 can be designed to satisfy predetermined dimensional relationships among the distance FD between front end 112F of manifold 112 and front end 117F of plate membrane 117, the length SD of plate membrane 117, and the size VD of vent portion V. For example, the ratio of distance FD:length SD:size VD may be 2-4:47-51:4-6. Desirably, the ratio of distance FD:length SD:size VD may be 3:49:5. The distance FD may be smaller than the size VD. The length SD may be 7.8 times or more the size VD. Desirably, the length SD is 9.8 times the size VD. As a result, most of the area in the center of manifold 112 is covered by plate membrane 117, and only a narrower portion is exposed to vent portion V. If the size VD of the vent portion V is made too small, when the coating liquid 150 receives an upward force from the bottom surface of the manifold 112 and flows out of the vent portion V, the pressure applied to the coating liquid 150 becomes too large, which is undesirable. On the other hand, if the size VD of the vent portion V is made too large, the length SD of the plate membrane 117 becomes small, which may reduce the degree to which the coating liquid 150 is guided to the side portion. Therefore, the size VD of the vent portion V must be determined organically with the length SD of the plate membrane 117 taking these points into consideration.

[0081] As described above, the edge portion from which the coating liquid 150 is discharged may be chamfered. For example, the chamfered shape may be cut obliquely from a portion 20 mm deep (h) from the end of the shim plate 113 inward to the inside of the edge. For example, the chamfered shape may be cut obliquely up to the front end 112F of the manifold 112. This allows for further guidance of the flow rate at the side portion and control of the sliding shape.

[0082] FIG. 7 shows a modification of the shim plate shown in FIG.

[0083] In the shim plate 113 of Fig. 6, a plate film 117 is located between every two adjacent inner second portions 115b. In the shim plate 113 of Fig. 7, a plate film 117 is located only between two central inner second portions 115b among the four inner second portions 115b. In this way, the plate film 117 is located between the inner second portions 115b, but can be selectively located only in areas where it is desired to reduce the load amount of the coating liquid 150.

[0084] FIG. 8 shows another modification of the shim plate shown in FIG.

[0085] 8 does not include the vent portion V, unlike the shim plate 113 shown in Figures 6 and 7. In this manner, the plate membrane 117 can extend without being separated from the first portion 114.

[0086] FIG. 9 shows yet another modification of the shim plate shown in FIG.

[0087] In the illustrated example, the second portion 115 comprises two side second portions 115a and two inner second portions 115b. This shim plate 113 defines three openings 113a. The plate membrane 117 is positioned between the inner second portions 115b. The number of inner second portions 115b can vary depending on the number of coating layers to be formed. The widths of the side second portions 115a and the inner second portions 115b can also differ from those of the shim plate 113 shown in FIG. 6. To form a coating layer of a desired width, the width of the openings 113a can be fixed, while the widths of the side second portions 115a and the inner second portions 115b can be varied. FIG. 10 is a diagram illustrating the effect of using a shim plate according to one embodiment of the present invention.

[0088] FIG. 10 shows a cross section of five coating layers 170 formed on a substrate 190 when there are five openings 113a, as in the shim plate 113 of FIG. 6. Five patterns are formed, showing a uniform coating profile in the width direction. As described above, according to the present invention, there is no difference in load between positions (center to side) based on the width direction of the coating, thereby ensuring high electrode process performance. The thickness CD of the coating layer along the width direction of the substrate 190 can be made uniform regardless of position. Therefore, according to the present invention, coating layers, particularly electrode active material layers, can be stably formed without generating pattern defects.

[0089] Hereinafter, the present invention will be described in more detail by explaining experimental examples.

[0090] The shim plate of the present invention, which has an FD of 3 mm, a VD of 5 mm, and a h of 20 mm, was compared with a comparative example, which is a shim plate that does not have these dimensions, to measure the load difference in the width direction. The comparative example is a shim plate 113 according to the present invention, which does not have a plate membrane 117 and does not have a chamfered edge on the side where the coating liquid 150 is discharged (see 113' in Figure 11).

[0091] Looking at the load amount, the cell is 5.56 mg / 25 cm in the comparative example. 2 has been measured, and in the example of the present invention, it is 5.37 mg / 25 cm 2 The load difference in the width direction was reduced by 3.5%. In particular, in the center of the width direction, the load difference in the comparative example was 9.12 mg / 25 cm. 2 is measured, and in the example of the present invention, it is 3.22 mg / 25 cm 2 From the measurements, it was confirmed that the example of the present invention had the effect of reducing the load difference in the width direction by 183.2%.

[0092] The improvement in process capability due to the present invention was also confirmed.

[0093] Currently, after forming a stripe-patterned electrode active material layer on a current collector, notches are made in the non-coated areas between the electrode active material layers to serve as individual electrode plates. In this process, the positions near the shim teeth of the shim plate that form the non-coated areas are formed as tabs during the notching process in the assembly process following the electrode process. Because the coated electrode positions near these tabs are the coating areas actually included in the cell, samples were taken from these areas for loading measurement, and these positions are hereinafter referred to as "cells." For coated electrodes, samples were also taken from the center region of each coating lane for loading measurement, and these positions are hereinafter referred to as "centers."

[0094] The index used to confirm process capability is Cpk (process capability index), which is used as a numerical value to confirm how close a product is to the target within the product specifications in a statistical sense and how consistent performance it exhibits. For example, the more values ​​in the measured data are close to the target, the higher the Cpk will be, and the greater the dispersion of data within the specifications, the lower the Cpk will be.

[0095] When the Cpk of the loading measurement data at the sampling position labeled "cell" is defined as "cell_Cpk" and the Cpk of the loading measurement data at the sampling position labeled "center" is defined as "center_Cpk," in the comparative example, cell_Cpk was 2.09, center_Cpk was 0.71, and cell_Cpk + center_Cpk was 1.05, while in the example of the present invention, cell_Cpk was 2.81, center_Cpk was 3.04, and cell_Cpk + center_Cpk was 1.94.

[0096] As shown, the Cell_Cpk, Center_Cpk, and Cell_Cpk + Center_Cpk values ​​for the present invention are all higher than those for the comparative example. Therefore, it can be seen that the loadings at the positions marked "Cell" and "Center" are all within specifications and close to the target, with a small degree of dispersion. This confirms that the present invention has improved process capability compared to the comparative example.

[0097] FIG. 11 shows the flow of the coating liquid using the shim plate of the comparative example.

[0098] As shown in Figure 11, in contrast to the present invention, the prior art shim plate 113' has open spaces between the shim teeth. With this type of shim plate 113', the manifold 112 is filled with coating liquid without any blocked spaces, and the coating liquid is discharged in the direction of the arrow. The length of the arrow indicates the amount of coating liquid discharged, and as mentioned above, there is a problem of loading concentrating in the center.

[0099] FIG. 12 illustrates the flow of coating liquid through a shim plate according to one embodiment of the present invention.

[0100] Compared to Figure 11, the shim plate 113 of the present invention closes the gap between the shim teeth and guides the flow of coating liquid from the center to the side. As a result, the amount of coating liquid discharged from the center and side is similar. In the figure, it can be seen that the lengths of the arrows are the same. This results in an electrode coating profile like that shown in Figure 10.

[0101] The shape of the manifold is unlikely to be changed after the initial molding. According to the present invention, there is an advantage that the loading of the slot die coater 100 can be controlled using the shape of the shim plate 113 without changing the manifold.

[0102] FIG. 13 shows the flow of coating liquid in a slot die coater according to another embodiment of the present invention.

[0103] 13, the manifold 112 may include an upper manifold 112a included in the upper die block 130 and a lower manifold 112b included in the lower die block 110. In other words, the manifold 112 exists in both the upper die block 130 and the lower die block 110. The shim plate 113 may be interposed between the upper manifold 112a and the lower manifold 112b.

[0104] A coating liquid inlet pipe 152 for introducing a coating liquid 150 may be connected to a coating liquid inlet hole 154 formed in the center of the lower manifold 112b.

[0105] 6 and 12, the plate membrane 117 may be formed to block at least a portion of the coating liquid inlet hole 154. In contrast, in the comparative example shim plate 113′ shown in FIG. 11, the coating liquid inlet hole 154 is not blocked.

[0106] The shim plate 113 includes a vent portion V, and the coating liquid 150 can flow from the lower manifold 112b to the upper manifold 112a through the open vent portion V. That is, the design of the type 2 die prevents vortex flow of the coating liquid 150. The flow of the coating liquid 150 is as indicated by the arrows. The coating liquid 150 flows through a coating liquid inlet hole 154 formed in the center of the bottom surface of the lower manifold 112b and receives an upward force. The coating liquid 150 impinges on the plate membrane 117 of the shim plate 113 and remains there. A portion of the coating liquid 150 flows into the upper manifold 112a through the vent portion V. The coating liquid 150 is steadily discharged through the space between the front end of the lower manifold 112b and the front end of the plate membrane 117, and is then guided by the second portion 115 and discharged from the discharge port 101a.

[0107] The slot die coaters 100 and 200 and their modifications described above can be used to stably form an electrode active material layer. For example, the slot die coaters can be applied to the manufacture of a positive electrode for a secondary battery by coating a positive electrode active material slurry.

[0108] In particular, according to the present invention, by forming the positive electrode active material layer and the negative electrode active material layer with uniform thickness, when a positive electrode including a positive electrode active material layer and a negative electrode including a negative electrode active material layer are opposed to each other, it is possible to face them with an accurate target load amount, which is highly desirable. In the case of electrodes that exhibit loading-off, loss occurs, but according to the present invention, loading-off can be prevented, thereby achieving a loss reduction effect. Furthermore, when electrodes with high positive electrode loading and low negative electrode loading are opposed to each other, the incidence of lithium deposition increases. However, according to the present invention, it is possible to manufacture electrodes with a well-balanced positive electrode loading and negative electrode loading, which is expected to prevent lithium deposition.

[0109] The positive electrode includes a current collector and a positive electrode active material layer formed on the current collector. The current collector may be made of an electrically conductive material such as Al or Cu, and may be selected based on the polarity of a current collector electrode known in the field of secondary batteries. The positive electrode active material layer may further include one or more of a plurality of positive electrode active material particles, a conductive material, and a binder. The positive electrode may further include various additives to complement or improve electrochemical properties.

[0110] The active material is not limited to a specific component as long as it can be used as a positive electrode active material for lithium-ion secondary batteries. Non-limiting examples include layered compounds such as lithium manganese composite oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; 1+x Mn 2-xO4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and the chemical formula LiNi 1-x M x Ni-site lithium nickel oxide represented by the chemical formula LiMnO2 (where M=Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3). 2-x M x The positive electrode may contain one or a mixture of two or more of the following solid electrolyte materials: lithium manganese composite oxides represented by LiMnO2 (where M=Co, Ni, Fe, Cr, Zn, or Ta, and x=0.01 to 0.1) or Li2Mn3MO8 (where M=Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3. In the present invention, the positive electrode may contain one or more of a polymer-based solid electrolyte, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte as the solid electrolyte material.

[0111] The conductive material is typically added in an amount of 1 wt% to 20 wt% based on the total weight of the mixture containing the active material. There are no particular limitations on the conductive material, as long as it does not induce chemical changes in the battery and is conductive. For example, the conductive material may include one or a mixture of two or more conductive materials selected from the following: graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers, such as carbon fiber or metal fiber; metal powders, such as carbon fluoride, aluminum, and nickel powder; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and polyphenylene derivatives.

[0112] The binder is not particularly limited as long as it is a component that helps bind the active material and conductive material and the current collector. Examples include polyvinylidene fluoride (PVF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers. The binder is typically included in an amount of 1 wt% to 30 wt% or 1 wt% to 10 wt% relative to 100 wt% of the electrode layer.

[0113] The slot die coaters 100 and 200 of the present invention can be used to coat negative electrode active material slurry and manufacture a negative electrode for a secondary battery. The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector. The negative electrode active material layer may further include one or more of a plurality of negative electrode active material particles, a conductive material, and a binder. The negative electrode may also include various additives to complement or improve electrochemical properties.

[0114] The negative electrode active material may be a carbon material such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, or carbon nanohorn, a lithium metal material, an alloy material such as silicon or tin, Nb2O5, or Li5Ti4O 12 For the negative electrode, the conductive material, binder, and current collector may be referred to the contents related to the positive electrode.

[0115] Active material slurries containing such positive or negative active materials have very high viscosities. For example, the viscosity may be 1,000 cps or more. The viscosity of active material slurries used to form electrodes for secondary batteries may be 2,000 cps to 30,000 cps. For example, the viscosity of negative active material slurries may be 2,000 cps to 4,000 cps. The viscosity of positive active material slurries may be 8,000 cps to 30,000 cps. Because the slot die coaters 100 and 200 of the present invention must be capable of coating coating liquids with viscosities of 1,000 cps or more, they differ from, and are not a substitute for, conventional resin liquids used to coat coating liquids with lower viscosities, such as photosensitive emulsions, magnetic fluids, liquids that provide anti-reflection or anti-glare properties, liquids that provide a widening effect on the viewing angle, and pigment liquids for color filters. The slot die coaters 100 and 200 of the present invention are designed to coat active material slurries that may contain active material particles with an average particle size of approximately 10 μm, and therefore differ in structure from those used to coat other coating liquids that do not contain particles of this size, and are not devices that can be achieved by modifying them. The slot die coaters 100 and 200 of the present invention are optimized for use as coaters for producing electrodes.

[0116] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is of course possible for a person having ordinary skill in the art to which the present invention pertains to make various modifications and variations within the scope of the technical concept of the present invention and the scope of the claims.

[0117] Although terms indicating directions such as up, down, left, and right are used in this specification, it will be obvious to those skilled in the art that these terms indicate relative positions and are used only for convenience of explanation, and may vary depending on the position of the object in question, the position of the observer, etc. [Explanation of symbols]

[0118] 100, 200 slot die coater 101 Slots 101a Discharge port 110 Lower die block 111, 131 Dielip 112 Manifold 113 Shim plate 115 Shim Teeth 117 Plate membrane 130 Upper die block 150 coating liquid 152 Coating liquid inlet piping 154 Coating liquid inlet 170 coating layer 180 coating roll 190 Base material V vent

Claims

1. A shim plate provided between a lower die block and an upper die block of a slot die coater to form a slot and to discharge a coating liquid from a discharge port communicating with the slot, The shim plate includes a plurality of shim teeth that are intermittently cut in one area to provide a plurality of openings, and includes a plate membrane that partially fills spaces between the plurality of shim teeth.

2. The shim plate according to claim 1 , wherein the plate membrane is located at a portion for reducing the load of the coating liquid.

3. 2. The shim plate according to claim 1, wherein the shim plate includes a base first portion and at least four second portions extending from the first portion, the second portions being connected to the same side of the first portion and extending in the same direction, the second portions being composed of two side second portions located on both sides and an inner second portion located between the two side second portions, and the plate membrane being located between the inner second portions.

4. The shim plate according to claim 3 , wherein the plate membrane is located between every two adjacent inner second portions.

5. The shim plate according to claim 3 , wherein the sheet membrane is not positioned between the side second portion and the inner second portion, and the sheet membrane is positioned only between the inner second portions.

6. The shim plate according to claim 3 , wherein the plate membrane extends without being spaced apart from the first portion.

7. The shim plate of claim 3 , wherein the plate membrane extends away from the first portion to define an open vent between the first portion and the plate membrane.

8. The shim plate according to claim 7 , wherein the end of the membrane that defines the vent portion has a rounded cross section.

9. The shim plate according to claim 7 , wherein the length of the plate membrane is greater than the size of the vent portion.

10. A slot die coater including a lower die block, an upper die block, a shim plate provided between the lower die block and the upper die block to form a slot, and a manifold provided in at least one of the upper die block and the lower die block to accommodate a coating liquid, wherein the coating liquid is applied by being discharged onto a substrate from a discharge port communicating with the slot, The slot die coater includes a shim plate having a plurality of shim teeth that are intermittently cut in one area to provide a plurality of openings so as to determine the coating width of the coating layer applied to the substrate, and a plate membrane that partially fills the spaces between the plurality of shim teeth.

11. 11. The slot die coater of claim 10, wherein the manifold comprises an upper manifold included in the upper die block and a lower manifold included in the lower die block, the upper manifold and the lower manifold facing each other, and the shim plate being interposed between the upper manifold and the lower manifold.

12. The slot die coater according to claim 11, wherein a coating liquid inlet pipe for introducing the coating liquid is connected to a coating liquid inlet hole formed in a central portion of the lower manifold.

13. 13. The slot die coater of claim 12, wherein the shim plate includes a base first portion and at least four second portions extending from the first portion, the second portions connecting to the same side of the first portion and extending in the same direction, the second portions being composed of two side second portions located on both sides and an inner second portion located between the two side second portions, and the plate membrane being located between the inner second portions.

14. The slot die coater of claim 13 , wherein the plate film extends away from the first portion, thereby defining an open vent portion between the first portion and the plate film.

15. 15. The slot die coater of claim 14, wherein the coating fluid flows from the lower manifold to the upper manifold through the vent.

16. The slot die coater according to claim 14 , wherein the end of the plate film that defines the vent portion has a rounded cross section.

17. The slot die coater according to claim 14 , wherein the length of the plate film is greater than the size of the vent portion.

18. The slot die coater according to claim 12 , wherein the plate membrane is formed in a shape that blocks at least a part of the coating liquid inlet hole.

19. The slot die coater of claim 10 , wherein an orthogonal projection of the plate film does not deviate from an orthogonal projection of the manifold.

20. The slot die coater according to claim 10 , wherein a front end of the sheet membrane is located rearward of a front end of the manifold.

Images