Double slot die coater

Abstract

This disclosure provides a dual-slit mold coating machine that facilitates easy alignment of the mold lip. The dual-slit mold coating machine of this disclosure includes a first slit and a second slit to deliver a coating solution in the opposite direction of gravity, and includes: a first mold block, which is mounted perpendicularly to and integrally formed with the base behind an upper surface of the base; a second mold block, positioned in front of the first mold block and contacting the base to form a first slit between the second mold block and the first mold block; and a third mold block, positioned in front of the second mold block and contacting the base to form a second slit between the third mold block and the second mold block.

Description

Technical Field

[0001] This disclosure relates to a double-slit mold coating machine capable of simultaneously forming two or more layers through wetting, and more specifically, to a vertical mold type double-slit mold coating machine for conveying the coating solution in the opposite direction of gravity. This application claims priority to Korean Patent Application No. 10-2021-0167687, filed in Korea on November 29, 2021, and Korean Patent Application No. 10-2022-0071278, filed in Korea on June 13, 2022, the disclosures of which are incorporated herein by reference. Background Technology

[0002] With the rapid development of technology and the increasing demand for mobile devices, the demand for secondary batteries as an energy source is increasing rapidly. These secondary batteries essentially consist of electrode assemblies that act as power-generating elements. The electrode assemblies include a positive electrode, a separator, and a negative electrode stacked at least once. The positive and negative electrodes are prepared separately by coating and drying positive and negative active material slurries onto current collectors made of aluminum foil and copper foil, respectively. For uniform charge / discharge characteristics of the secondary battery, it is necessary to uniformly coat the positive and negative active material slurries onto the current collector, and a slot die coating machine has been used.

[0003] Figure 1 This is a cross-sectional view showing a conventional slot die coating machine.

[0004] Reference Figure 1 The electrode manufacturing method using a conventional slit mold coating machine 30 includes: coating an active material slurry from the slit mold coating machine 30 onto a current collector 20 conveyed by a coating roller 10. The active material slurry from the slit mold coating machine 30 is coated onto one surface of the current collector 20 to form an active material layer. The slit mold coating machine 30 includes two mold blocks 31 and 32, and a slit 35 between the two mold blocks 31 and 32, and can convey an active material slurry of a certain type through an outlet 37 communicating with the slit 35 to form an electrode active material layer. Compared to rod coating or comma blade coating, the slit mold coating machine achieves high-speed coating, and due to this advantage, it is widely used from a high productivity perspective. Figure 1 The slot die coating machine shown is a vertical die type that delivers the active material slurry in the opposite direction of gravity.

[0005] To fabricate high-energy-density rechargeable batteries, the thickness of the active material layer has been gradually increased from approximately 130 μm to 300 μm. When forming a thick active material layer using a conventional slit-die coater 30, the migration of binders and conductive materials in the active material slurry becomes more severe during drying, resulting in an unevenly fabricated electrode. To address this issue, performing two coating processes—coating and drying the active material layer at a smaller thickness and repeating the process layer by layer on top of another—takes a considerable amount of time. To improve both electrode performance and productivity, a dual-slit-die coater capable of simultaneously coating two types of active material slurries is needed.

[0006] Because slot die coaters have slots on the mating surfaces of the die blocks, essentially three die blocks are needed to include two slots, similar to a double slot die coater. Since the active material slurry exits simultaneously from different outlets connected to the two slots, it is difficult to form individual active material layers of the desired thickness using a double slot die coater.

[0007] In particular, mold lip alignment at the front end of each mold block is important. Mold lip alignment is achieved by assembling and aligning the mold blocks using insert blocks or spacers or by adjusting their position with bolts. However, insert blocks or spacers require multiple conditions to match numerous contact surfaces for mold lip alignment, making it difficult to rely solely on probability. Adjusting with bolts is time-consuming and highly dependent on operator skill, resulting in low reproducibility.

[0008] Therefore, the relevant industries need dual-slit mold coating machines that allow for easier and more precise mold lip alignment. Summary of the Invention

[0009] Technical issues

[0010] This disclosure aims to solve the above-mentioned problems, and therefore aims to provide a double-slit mold coating machine that can easily align the mold lip.

[0011] However, the problems to be addressed by this disclosure are not limited to those described above, and those skilled in the art will clearly understand from the following description other problems not mentioned.

[0012] Technical solution

[0013] To address the aforementioned issues, the dual-slit mold coating machine of this disclosure includes a first slit and a second slit to deliver a coating solution in the opposite direction of gravity, and comprises: a first mold block, which is mounted perpendicularly to and integrally formed with the base behind the upper surface of the base; a second mold block, which is positioned in front of the first mold block and contacts the base to form the first slit between the second mold block and the first mold block; and a third mold block, which is positioned in front of the second mold block and contacts the base to form the second slit between the third mold block and the second mold block.

[0014] In one embodiment, the lower surfaces of the second mold block and the third mold block can be in overall contact with the base.

[0015] In another embodiment, the lower surfaces of the second mold block and the third mold block may be in intermittent contact with the base.

[0016] In this case, the pressing element can be connected to the bottom of the base.

[0017] The pressing element can be a servo motor.

[0018] In this disclosure, the dual-slit mold coating machine may further include: a first gasket located between the first mold block and the second mold block to form the first slit, and a second gasket located between the second mold block and the third mold block to form the second slit, wherein the first gasket and the second gasket have open portions cut at least in one region.

[0019] In this case, the region can be intermittently cut to form multiple open sections.

[0020] In a preferred embodiment, a reinforcing member may be provided on the lower surface of the second mold block for intermittent contact with the base, and a bending space may be formed between the reinforcing members. Similarly, a reinforcing member may be provided on the lower surface of the third mold block for intermittent contact with the base, and a bending space may be formed between the reinforcing members.

[0021] In this preferred example, a servo motor may be connected to the bottom of the base to deform the bending space. More preferably, the servo motor may be connected to the center of the bottom of the base.

[0022] Multiple reinforcing members may be located along the length of the dual-slit mold coating machine. Preferably, the multiple reinforcing members may be symmetrical along the length direction with reference to the center of the dual-slit mold coating machine. Preferably, the distance between the reinforcing members in the central region of the multiple reinforcing members may be greater than the distance between the other reinforcing members.

[0023] In this disclosure, the first mold block may include a first manifold that contains a first coating solution and communicates with the first slit, and the third mold block may include a second manifold that contains a second coating solution and communicates with the second slit.

[0024] In the double-slit mold coating machine according to this disclosure, bolts can be vertically installed into the contact surface between the base and the second mold block, and bolts can be vertically installed into the contact surface between the base and the third mold block.

[0025] The first slit may be perpendicular to the base.

[0026] The cross-section of the second mold block can be a right triangle.

[0027] The first mold block, the second mold block, and the third mold block may each include a first mold lip, a second mold lip, and a third mold lip forming the front end, and the first mold lip, the second mold lip, and the third mold lip may be arranged on the same straight line.

[0028] The thickness of the third mold lip is preferably greater than the thickness of the first mold lip and the thickness of the second mold lip.

[0029] The second outlet communicating with the second slit may be located between the third mold lip and the second mold lip, and the first outlet communicating with the first slit may be located between the second mold lip and the first mold lip. The second coating solution may be conveyed to the substrate through the second outlet. The first outlet may be separated from the second outlet on the downstream side of the coating direction, and the first coating solution may be conveyed to the substrate through the first outlet.

[0030] Beneficial effects

[0031] According to this disclosure, since the mold blocks are positioned to contact the base, the mold lip is easily aligned. Positional mismatch between mold blocks is prevented, and the distance between the mold lip and the substrate, i.e., the coating gap, is always maintained at the desired level. Uniform mold lip alignment can be achieved at each assembly point and maintained without change during the process, thereby preventing coating gap shift in the width direction perpendicular to the substrate's movement direction.

[0032] Therefore, according to this disclosure, when adjusting the coating gap or using auxiliary devices such as blocks or spacers, a uniform coating gap can always be maintained by a simple assembly operation of combining the mold blocks without disassembling and reassembling the mold blocks, which are structurally fragile due to their small thickness.

[0033] According to this disclosure, taking into account the deformation of the die block due to pressure when conveying the active material slurry, a uniform (±2%) coating gap can be maintained, thereby uniformly controlling the coating amount and the resulting coating quality. Therefore, by using a double-slit die coating machine with a uniform coating gap, coated products with uniform quality can be obtained, specifically, electrodes of secondary batteries.

[0034] According to one aspect of this disclosure, a dual-slit die coating machine with minimal assembly alignment requirements—that is, a single contact surface fastened and a structure that eliminates the need for bolt-based position adjustment—can be provided. Adjustment using bolts requires time, heavily relies on operator skill, and results in low reproducibility. According to this disclosure, die lip alignment can be achieved without bolt-based position adjustment, thereby eliminating the time required for adjustment and dependence on operator skill, and improving reproducibility.

[0035] According to another aspect of this disclosure, a bending space and a contact surface for fastening can be provided. Bending is achieved by deforming the alignment position. According to this disclosure, a pressing element for controlling coating uniformity in the width direction can be used to deform with high uniformity. As described above, according to this disclosure, the deformation of the die block can be controlled very uniformly, thereby directly improving coating uniformity.

[0036] As described above, according to this disclosure, even when conveying active material slurry under high pressure, although thin die blocks are used, the coating gap can still be maintained once the coating gap is adjusted. Specifically, vertical die types experience an increase in the distance between die blocks during slurry conveying, but this disclosure prevents this increase in the distance between die blocks, thereby ensuring coating operability and reproducibility.

[0037] Using a dual-slit mold coating machine, the coating layer, specifically the active material layer, can be uniformly coated to the desired thickness. Preferably, two types of active material slurries can be coated simultaneously, thereby improving performance and productivity.

[0038] As described above, when the dual-slit mold coating machine of this disclosure is used to coat the active material slurry on the current collector while moving the current collector to manufacture the electrode of the secondary battery, uniform coating can be achieved under high-speed or wide-scale coating conditions. Attached Figure Description

[0039] The accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with the following detailed description, are intended to provide a further understanding of the technical features of the present disclosure. Therefore, the present disclosure is not to be construed as limited to the drawings.

[0040] Figure 1 This is a schematic cross-sectional view of a double-slit mold coating machine based on relevant technologies.

[0041] Figure 2 This is a perspective view of a double-slit mold coating machine according to an embodiment of the present disclosure.

[0042] Figure 3 This is a cross-sectional view of a double-slit mold coating machine according to an embodiment of the present disclosure.

[0043] Figure 4 yes Figure 3 An enlarged view of part A in the image.

[0044] Figure 5 This is a perspective view of a double-slit mold coating machine according to another embodiment of the present disclosure.

[0045] Figure 6 It was taken from line VI-VI'. Figure 5 Cross-sectional view, Figure 7 It is a section taken along line VII-VII'. Figure 5 Cross-sectional view.

[0046] Figure 8 This is a flowchart of the assembly steps of a double-slit mold coating machine according to another embodiment of the present disclosure.

[0047] Figures 9 to 12 This is a diagram illustrating the assembly steps of a double-slit mold coating machine according to another embodiment of the present disclosure.

[0048] Figures 13 to 15 It is a diagram used to help understand the structure of the mold block.

[0049] Figure 16 This is a cross-sectional view of a double-slit mold coating machine based on a comparative example.

[0050] Figures 17 to 20 This is a diagram showing the assembly steps of a double-slit mold coating machine according to a comparative example.

[0051] Figure 21 The effect of reducing mold changeover time through simplified design of mold block structure / assembly is shown in another embodiment of this disclosure compared to a comparative example.

[0052] Figure 22The effect of improving electrode quality by improving assembly quality is shown in another embodiment of this disclosure compared to a comparative example.

[0053] Figure 23 This is a diagram used in a comparative example and another embodiment of the present disclosure to analyze the impact of bolted connection on the operation of the servo motor.

[0054] Figure 24 This is a graph showing a comparison (μm) of coating gap direction deformation according to the operation of the servo motor in a comparative example and another embodiment of the present disclosure. Detailed Implementation

[0055] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before description, it should be understood that the terms or words used in the specification and appended claims should not be construed as limited to their general or dictionary meanings, but rather interpreted based on their meanings and concepts corresponding to the technical aspects of the present disclosure, on the basis of the principle that allows the inventor to appropriately define terms for best interpretation. Therefore, the embodiments described herein and the examples in the drawings are merely exemplary embodiments of the present disclosure and do not fully describe the technical features of the present disclosure. It should be understood that various other equivalents and modifications may be made in lieu of such description when filing a patent application. The same reference numerals denote the same elements. Furthermore, in the drawings, the thickness, proportions, and dimensions of elements are exaggerated for the purpose of effectively describing the technical subject matter.

[0056] The dual-slit mold coating machine of this disclosure includes a first slit and a second slit to deliver a coating solution in opposite directions of gravity, and is configured to coat the coating solution onto a substrate in a bilayer. In the following description, "substrate" is a current collector, and "coating solution" is an active material slurry. Both the first coating solution and the second coating solution are active material slurries, and they may have the same or different components (types of active material, conductive material, and binder), amounts (amounts of each of the active material, conductive material, and binder), or properties. The dual-slit mold coating machine of this disclosure is best suited for electrodes manufactured by simultaneously coating two types of active material slurries, or by pattern coating of two types of active material slurries in an alternating manner. However, the scope of this disclosure is not limited thereto. For example, the substrate may be a porous substrate constituting a diaphragm, and the first and second coating solutions may be organic materials with different components or properties. That is, when thin-film coating is required, the substrate, the first coating solution, and the second coating solution are not limited to specific types.

[0057] Figure 2 This is a perspective view of a dual-slit mold coating machine according to an embodiment of the present disclosure. Figure 3This is a cross-sectional view of a double-slit mold coating machine according to an embodiment of the present disclosure. Figure 4 yes Figure 3 An enlarged view of part A in the image.

[0058] First, refer to Figure 2 and Figure 3 The dual-slit mold coating machine 100 according to embodiments of the present disclosure is configured to deliver a coating solution in the opposite direction of gravity and includes a first slit 101 and a second slit 102. The dual-slit mold coating machine 100 can simultaneously or alternately deliver and coat the same type of coating solution or two different types of coating solutions on a substrate 170 through the first slit 101 and the second slit 102.

[0059] For example, by moving the substrate 170 by rotating the rotatable coating roller 160 at the front of the double-slit die coating machine 100, the first coating solution 50, which is a first electrode active material slurry, and the second coating solution 60, which is a second electrode active material slurry, are continuously brought into contact with the surface of the substrate 170 to be coated. This allows the first coating solution 50, which is a first electrode active material slurry, and the second coating solution 60, which is a second electrode active material slurry, to be coated simultaneously on the substrate 170, both having a double-layer structure. The first coating solution 50 is coated on the substrate 170 to form a lower slurry layer, and almost simultaneously, the second coating solution 60 is coated on the lower slurry layer to form an upper slurry layer.

[0060] The dual-slit mold coating machine 100 is mounted such that the transport direction (X-direction) of the coating solution or active material slurry is almost perpendicular (almost: ±5°). In embodiments of this disclosure, the X-axis direction shown in the figures refers to the transport direction of the coating solution, the Z-axis refers to the length direction of the dual-slit mold coating machine 100, and the Y-axis direction refers to the horizontal direction perpendicular to the X-axis and Z-axis directions. Specifically, it represents the direction from the first mold block 110 of the dual-slit mold coating machine 100 toward the third mold block 130, and for convenience, it can be the front side of the dual-slit mold coating machine 100.

[0061] The dual-slit die coating machine 100 includes a base 90. A first die block 110 is integrally and vertically mounted to the rear of the upper surface of the base 90. The first die block 110 is a plate-shaped structure extending along its length. The first die block 110 is placed on the base 90 and assembled together. When the base 90 and the first die block 110 are placed together, they do not need to be aligned relative to the base 90, and they can be treated as a single unit for easy handling. The first die block 110, integrally formed with the base 90, may be referred to as a body block and may also be referred to as an upper plate. The XY cross-section of the first die block 110 may be approximately L-shaped.

[0062] The second mold block 120 is positioned to contact the base 90 in front of the first mold block 110 to form a first slit 101 between the second mold block 120 and the first mold block 110. To define the first slit 101, a first gasket 113 is located between the second mold block 120 and the first mold block 110.

[0063] A gap can be formed by a first gasket 113 between the second mold block 120 and the first mold block 110, which corresponds to a first slit 101 through which the coating solution flows. In this case, the thickness of the first gasket 113 determines the vertical width (slit gap) of the first slit 101. The first gasket 113 may be referred to as the upper gasket.

[0064] The first gasket 113 may have an open portion cut in at least one region and may be located on the remaining portion of the facing surface of each of the first mold block 110 and the second mold block 120, excluding one side in the edge region. Thus, a first outlet 101a for the coating solution to exit is formed only between the front end of the first mold block 110 and the front end of the second mold block 120.

[0065] like Figure 4 As shown, the front end of the first mold block 110 and the front end of the second mold block 120 are defined as the first mold lip 111 and the second mold lip 121, respectively. In other words, the first outlet 101a is formed by the gap between the first mold lip 111 and the second mold lip 121. The first mold lip 111 and the second mold lip 121 can be cuboids that extend along the length direction and have a flat upper surface.

[0066] For reference, the first gasket 113 serves as a gasket to prevent the coating solution from leaking through the gap between the first mold block 110 and the second mold block 120, except for the area where the first outlet 101a is formed, and is therefore preferably made of a material with sealing capabilities.

[0067] The second mold block 120 is a block disposed in the middle of the mold blocks of the double-slit mold coating machine 100, and is a plate inserted between the first mold block 110 and the third mold block 130 to form a double slit. In this embodiment, the cross-section of the second mold block 120 is a right-angled triangle, but its shape is not limited to this; for example, the cross-section of the second mold block 120 can be an isosceles triangle. When the cross-section of the second mold block 120 is a right-angled triangle, the first slit 101 is aligned almost perpendicularly with the substrate 170, making it easy to control the delivery of the coating solution through the first slit 101.

[0068] The second mold block 120 is a plate-shaped structure extending along its length. The first surface 120a of the second mold block 120, facing the first mold block 110, is placed almost perpendicular to the base 90. That is, the first surface 120a of the second mold block 120 is a vertical surface. The second surface 110b of the first mold block 110, facing the first surface 120a of the second mold block 120, and the opposing first surface 110a (i.e., the surface forming the rear surface of the outer peripheral surface of the double-slit mold coating machine 100) are placed almost perpendicular to the base 90. That is, the first surface 110a and the second surface 110b of the first mold block 110 are also vertical surfaces. Therefore, the first slit 101 is perpendicular to the base 90. The first surface 120a of the second mold block 120 is almost parallel to the first surface 110a and the second surface 110b of the first mold block 110, thus forming an overall stable and balanced structure. The first mold block 110 has an inclined surface 110a' on the upper part of the first surface 110a that is inclined toward the conveying direction. Therefore, the cross-section of the upper part of the first mold block 110 is almost triangular and gradually tapers toward the first mold lip 111. The second mold block 120 may be referred to as the inner mold and also as the intermediate plate.

[0069] The first mold block 110 includes a first manifold 112 having a predetermined depth on a second surface 110b, and the first manifold 112 communicates with a first slit 101. The first manifold 112 is a space from the second surface 110b of the first mold block 110 facing the second mold block 120 toward the first surface 110a opposite to the second surface 110b. The first manifold 112 is a recessed cavity in the first mold block 110 and contains a first coating solution. The first manifold 112 is connected to a first coating solution supply chamber (not shown) and a supply line disposed externally, and is supplied with the first coating solution. When the first manifold 112 is completely filled with the first coating solution, the flow of the first coating solution is guided along the first slit 101 and exits from the first outlet 101a.

[0070] The first mold block 110 may further include an vent (not shown) passing through it, and the vent may be connected to the first manifold 112. The vent is used to remove air bubbles included in the first coating solution within the first manifold 112. The vent may be formed by simply drilling a hole in the first mold block 110, or by inserting a hollow tube into the hole.

[0071] The third mold block 130 is positioned to contact the base 90 in front of the second mold block 120 to form a second slit 102 between the third mold block 130 and the second mold block 120. A second gasket 133 is located between the third mold block 130 and the second mold block 120 to define the second slit 102. The second slit 102 is formed in the contact area between the second mold block 120 and the third mold block 130. That is, the second slit 102 is formed by placing the third mold block 130 and the second mold block 120 together.

[0072] Similar to the first slit 101, a gap can be formed between the second mold block 120 and the third mold block 130 by a second gasket 133, which corresponds to the channel through which the coating solution flows in the second slit 102. In this case, the thickness of the second gasket 133 determines the vertical width (slit gap) of the second slit 102. The second gasket 133 may be referred to as the lower gasket.

[0073] Furthermore, the second gasket 133 has a similar structure to the first gasket 113, and has an open portion cut out in at least one region, located only on the remaining portion of the facing surfaces of each of the second mold block 120 and the third mold block 130, excluding one side of the edge region. Similarly, the outer peripheral direction is blocked except for the front side of the second slit 102, and the second outlet 102a is formed only between the front end of the second mold block 120 and the front end of the third mold block 130.

[0074] Reference Figure 4 The front end of the third mold block 130 is defined as the third mold lip 131. In other words, the second outlet 102a is formed by the gap between the second mold lip 121 and the third mold lip 131. The third mold lip 131 may also be a cuboid that extends along the length direction and has a flat upper surface.

[0075] As described above, the second outlet 102a, which communicates with the second slit 102, is located between the third mold lip 131 and the second mold lip 121, and the first outlet 101a, which communicates with the first slit 101, is located between the second mold lip 121 and the first mold lip 111. The second coating solution 60, which forms the lower slurry layer, is supplied to the substrate 170 through the second outlet 102a. The first outlet 101a is separated from the second outlet 102a on the downstream side of the coating direction, and the first coating solution 50, which forms the upper slurry layer, is supplied to the lower slurry layer on the substrate 170 through the first outlet 101a. When the first coating solution 50 and the second coating solution 60, such as an electrode active material slurry, are supplied while the substrate 170 moves from the third mold lip 131 toward the first mold lip 111, an electrode can be formed by forming the upper slurry layer on the lower slurry layer.

[0076] The third mold block 130 is also a plate-shaped structure extending along its length. Furthermore, the second surface 120b of the second mold block 120 facing the third mold block 130, the first surface 130a of the third mold block 130 facing the second surface 120b of the second mold block 120, and the opposing second surface 130b (i.e., the surface forming the front surface of the outer peripheral surface of the double-slit mold coating machine 100) are almost parallel to each other, forming a stable and balanced structure in shape. The third mold block 130 has an inclined surface 130b' above the second surface 130b, which slopes towards the conveying direction. The upper section of the third mold block 130 is almost triangular and gradually tapers towards the third mold lip 131. The surface 130b' below the second surface 130b in the third mold block 130 is placed almost perpendicular to the base 90. The third mold block 130 may be referred to as an outer mold and also as a lower plate.

[0077] Furthermore, the third mold block 130 includes a second manifold 132 having a predetermined depth on a first surface 130a facing the second mold block 120, and the second manifold 132 communicates with a second slit 102. The second manifold 132 is a space from the first surface 130a of the third mold block 130 facing the second mold block 120 toward a second surface 130b opposite to the first surface 130a. The second manifold 132 is a recessed cavity in the third mold block 130 and contains a second coating solution. Although not shown in the figures, the second manifold 132 is connected to a second coating solution supply chamber and supply line disposed externally, and is supplied with the second coating solution. When the second manifold 132 is completely filled with the second coating solution supplied from the outside along the tubular supply line, the flow of the second coating solution is guided along the second slit 102 communicating with the second manifold 132 and exits from the second outlet 102a.

[0078] The third mold block 130 may further include an vent (not shown) passing through it, and the vent may be connected to the second manifold 132. The vent is used to remove air bubbles included in the second coating solution within the second manifold 132. The vent may be formed by simply drilling a hole in the third mold block 130, or by inserting a hollow tube into the hole.

[0079] The second slit 102 and the first slit 101 form a predetermined angle, which can be approximately 20° to 70°. The second slit 102 and the first slit 101 intersect at a single point, and the second outlet 102a and the first outlet 101a can be located near the intersection point. Therefore, the first coating solution 50 and the second coating solution 60 can be delivered to almost only one point.

[0080] The angle θ between the second surface 120b of the second mold block 120 facing the third mold block 130 and the first surface 120a of the second mold block 120 facing the first mold block 110 is preferably within a range where turbulence is not formed immediately after the second coating solution 60 exits from the second outlet 102a and simultaneously the first coating solution 50 exits from the first outlet 101a. When the angle θ is too small, the second mold block 120 is too thin and therefore very easy to deform and twist. The angle θ determines the angle between the second slit 102 and the first slit 101, and can be approximately 20° to 70°. Preferably, the angle θ can be 25°. The angle between the second surface 110b and the inclined surface 110a' of the first mold block 110 can be 70°. The angle between the first surface 130a and the inclined surface 130b' of the third mold block 130 can be 60°. According to this structure, the assembled mold blocks 110, 120, and 130 have an overall generally rectangular shape, and only the front side from which the coating solution leaves is inclined toward the substrate 170, so that it is easy to handle when the coating solution flows downward. Moreover, the assembled shape is approximately the same as that of a slot coater with a single slit, so that the slot coater support can be shared.

[0081] The first manifold 112 and the second manifold 132 are formed in the first mold block 110 and the third mold block 130, respectively. This configuration can have a smaller impact on the deformation of the structurally most vulnerable second mold block 120. Furthermore, when the second mold block 120 is divided into a left mold block and a right mold block, wherein the left mold block is configured to move together with the first mold block 110 and the right mold block is configured to move together with the third mold block 130, the left mold block and the right mold block can slide at the interface between the left mold block and the right mold block, thereby making it easier to change the position of the first slit 101 and the second slit 102.

[0082] The surfaces, i.e., the lower surfaces, opposite to the direction of the coating solution transport in the first mold block 110, the second mold block 120, and the third mold block 130 are placed almost horizontally (YZ plane). Since the mold blocks 110, 120, and 130 have right-angled portions at the edges between the surfaces, right-angled portions exist in the cross-section, and the vertical or horizontal surfaces can be used as reference surfaces, thereby making them easy to manufacture or process and ensuring accuracy.

[0083] Mold blocks 110, 120, and 130 are made of, for example, SUS material. Easily machinable materials such as SUS420J2, SUS630, SUS440C, SUS304, and SUS316L can be used. SUS is easy to machinable, inexpensive, and highly corrosion-resistant, and can be formed into desired shapes at low cost.

[0084] Bolt 141 can be vertically installed into the contact surface between the base 90 and the second mold block 120, and bolt 142 can be vertically installed into the contact surface between the base 90 and the third mold block 130. Furthermore, the first mold block 110 and the second mold block 120 can be held together by bolts (not shown). The second mold block 120 and the third mold block 130 can also be held together by bolts (not shown). When the combination of the first mold block 110, the second mold block 120, and the third mold block 130 is held together by bolts 141 and 142, their facing portions can be supported to a high degree of contact with each other, thereby being secured and held very well by fastening.

[0085] As described above, the dual-slit die coating machine 100 can be made of SUS material. Typically, SUS components are prone to liquid leakage at the mating surfaces, and to suppress leakage, rubber rings or any other flexible material are placed between the structures to create a seal. However, this sealing method is not suitable for controlling uniform assembly (e.g., assembly deviations of less than 10 μm), and therefore difficult to use in the dual-slit die coating machine 100.

[0086] For this reason, in the double-slit die coating machine 100, the die blocks 110, 120, and 130, machined with very high precision (straightness, flatness ±5μm), are assembled by bolt connection. To prevent liquid leakage, a high pressure of approximately 200N to 350N is desired for the bolt connection.

[0087] According to this disclosure, assembly methods can be improved. Since the bolts used for fastening are all non-adjustable fasteners, there is no time loss due to adjustment, it is not dependent on the operator's skill, and high reproducibility can be achieved.

[0088] According to this disclosure, the mold blocks 110, 120, and 130 are structurally modified compared to related technologies. The lower surfaces of the second mold block 120 and the third mold block 130 are in integral contact with the base 90. There is no gap between the second mold block 120 and the base 90. Therefore, even if torque is generated due to the internal pressure of the double-slit mold coating machine 100, the contact surface between the first mold block 110 and the second mold block 120 can be supported by inserting a first shim 113 between the first mold block 110 and the second mold block 120. In other words, the widening of the first slit 101 can be prevented. Similarly, there is no gap between the third mold block 130 and the base 90. Therefore, even if torque is generated due to the internal pressure of the double-slit mold coating machine 100, the contact surface between the second mold block 120 and the third mold block 130 can be supported by inserting a second shim 133 between the second mold block 120 and the third mold block 130. That is, the widening of the second slit 102 can be prevented.

[0089] Conventional vertical-die slit coating machines experience increased distance between die blocks due to pressure during coating solution delivery. In the dual-slit coating machine 100 of this disclosure, the lower surfaces of the second die block 120 and the third die block 130 are integrally contacted with the base 90, thus fixing the second die block 120 and the third die block 130 to prevent the first slit 101 and the second slit 102 from widening. With increased distance between die blocks and feeding of active material slurry, uncoated areas are intermittently contaminated by the active material slurry, leading to surface defects. However, using the dual-slit coating machine 100 according to this disclosure, electrodes without surface defects can be formed.

[0090] Furthermore, according to this disclosure, since the second mold block 120 and the third mold block 130 are in contact with the base 90, it is not necessary to align the mold blocks 110, 120, and 130 individually, and alignment is very easy. Because the second mold block 120 and the third mold block 130 are always in contact with the base 90, and there is no gap between them, the positions of the mold lips 111, 121, and 131 are fixed during assembly. Therefore, mold lip alignment is simple and precise, and does not depend on the operator.

[0091] The vertical lengths of mold blocks 110, 120, and 130 can be equal. Vertical length refers to the vertical distance from the lower surface of each mold block to the mold lip. When the vertical lengths of mold blocks 110, 120, and 130 are equal, such as... Figure 4 As shown, by simply assembling them, the first mold lip 111, the second mold lip 121 and the third mold lip 131 can be arranged on the same straight line.

[0092] As described above, according to this disclosure, the need for individually manipulating the mold lip alignment can be eliminated. This disclosure provides assembly alignment with minimal requirements, namely, one contact surface is secured (the upper surface of base 90 and the lower surface of the second mold block 120, and the upper surface of base 90 and the lower surface of the third mold block 130), and no adjustment function is needed. Furthermore, the alignment is excellent during assembly.

[0093] The coating process using a dual-slit die coater 100 needs to prevent problems such as leakage and side rings caused by the simultaneous exit of the first coating solution 50 and the second coating solution 60 from different outlets 101a and 102a. Leakage refers to the loss of a portion of the coating solution on the upstream side outside the die lip, resulting in instability. This is a loss of pre-metered coating solution, and the final coating thickness cannot be predicted. Due to leakage, the coating solution may remain for an extended period and solidify, or it may cause coating thickness deviations in the width direction. In particular, leakage as described above becomes more severe when the coating solution is delivered under high pressure at a coating gap of several hundred μm for thin film coating or to reduce the width-direction thickness deviation of the coating layer.

[0094] The optimal coating area (window margin) lies between the leakage area and the edge ring area. A wider window margin results in higher productivity. The coating gap significantly affects the size and shape of the coating droplets between the substrate 170 and the die lips 111, 121, 131, as well as the position of the dynamic contact line during the coating process. According to this disclosure, the coating gap can be uniformly maintained by aligning the die lips 111, 121, 131, and the initial conditions, such as the characteristics of the coating solution and its flow rate and velocity, can be adjusted by increasing the window margin through adjusting the dimensions of the die lips 111, 121, 131, thereby allowing for more flexible setting of initial conditions to prevent leakage.

[0095] Preferably, the thickness D3 of the third mold lip is greater than the thickness D2 of the second mold lip and the thickness D1 of the first mold lip. Therefore, the thickness D3 of the third mold lip is greater than the average thickness of the thickness D1 of the first mold lip and the thickness D2 of the second mold lip. As mentioned above, the thickness D3 of the third mold lip is the largest (D3>D2, D3>D1, D3>(D1+D2) / 2). Furthermore, the thickness D2 of the second mold lip and the thickness D1 of the first mold lip can be equal.

[0096] The ratio of the third mold lip thickness D3 to the first mold lip thickness D1 can be 1.2:1 or greater. That is, the third mold lip thickness D3 can be at least 1.2 times greater than the first mold lip thickness D1. While a window margin can be increased when the third mold lip thickness D3 is simply greater than the first mold lip thickness D1, a leak-proof effect is improved when the third mold lip thickness D3 is at least 1.2 times greater than the first mold lip thickness D1. Leakage occurs when the third mold lip thickness D3 is equal to the first mold lip thickness D1 or when the first mold lip thickness D1 is greater than the third mold lip thickness D3.

[0097] The ratio of the third mold lip thickness D3 to the second mold lip thickness D2 can be 1.2:1 or greater. That is, the third mold lip thickness D3 can be at least 1.2 times greater than the second mold lip thickness D2. When the third mold lip thickness D3 is simply greater than the second mold lip thickness D2, the window margin can be increased; however, when the third mold lip thickness D3 is at least 1.2 times greater than the second mold lip thickness D2, the leak-proof effect can be improved. When the third mold lip thickness D3 is equal to the second mold lip thickness D2, leakage occurs. When the second mold lip thickness D2 is greater than the third mold lip thickness D3, no leakage occurs, but pattern defects are produced.

[0098] According to the above example, the thickness D3 of the third die lip is greater than the thickness D2 of the second die lip and the thickness D1 of the first die lip. The thickness D3 of the third die lip is the largest. The inventors have discovered that as the thickness D3 of the third die lip increases, the window margin increases. Therefore, the coating gap or initial conditions can be controlled more flexibly. Therefore, according to this configuration, productivity can be improved, and dynamic contact lines can be used at different positions during the coating process according to the target coated product and quality. According to this disclosure, leakage limitations can be overcome due to the increased window margin. In addition, the edge ring area can be reduced. As the coating gap decreases, leakage occurs above a predetermined level when the dynamic contact line moves in the opposite direction to the coating. According to this configuration, leakage can be suppressed by increasing the thickness D3 of the third die lip. The electrode active material slurry does not leave and is retained more in the third die lip 131. According to this disclosure, leakage can be reduced when the coating gap is insufficient or when a large amount of slurry is fed relative to the moving speed of the substrate 170.

[0099] The average thickness of the lower slurry layer formed by the second coating solution 60 exiting the second outlet 102a and the average thickness of the upper slurry layer formed by the first coating solution 50 exiting the first outlet 101a can each be 60 μm or greater. Each average thickness can be 200 μm or less. Typically, the average particle size of the active material in a secondary battery is approximately 10 μm, but since the particle size follows a normal distribution, d(90) or d(max) is usually greater than 10 μm. Due to the inclusion of active material, it is difficult to form a slurry layer with a thickness less than 40 μm. When the thickness of the slurry layer is 60 μm or greater, it can be coated smoothly while preventing the active material from getting stuck in the normally maintained coating gaps. Furthermore, when the thickness of the slurry layer is 200 μm or greater, it is desirable but not practically possible. Using a coating thickness greater than 200 μm in a secondary battery is practically difficult.

[0100] For example, the method of coating electrode active material slurry using the dual-slit die coating machine 100 of this disclosure is applied to the manufacture of the positive electrode of a secondary battery. The positive electrode has a structure in which a lower active material layer and an upper active material layer of a lower slurry layer are stacked sequentially on a current collector. The lower active material layer contains a large amount of conductive material, and the upper active material layer contains a small amount of conductive material. In this case, the amount of conductive material in the lower active material layer can be adjusted in the range of 0.5 to 5 wt%. When the amount of conductive material in the upper active material layer is reduced, the amount of active material on the electrode surface can be increased and the conductivity can be reduced to a predetermined level or less. In particular, when the amount of conductive material in the upper active material layer is controlled at a very low level of 0.02 wt% or less, the exothermic reaction during an internal short circuit in the battery can be reduced.

[0101] In another example, the average particle size P1 of the active material forming the lower active material layer is in the range of 50% to 95% of the average particle size P2 of the active material forming the upper active material layer. In this case, an active material with a smaller particle size is applied to the lower active material layer. An active material with a larger particle size is applied to the upper active material layer to improve the wettability of the electrolyte solution and induce smooth movement of ions or holes.

[0102] Here, the flow rate ratio of the first coating solution 50 and the second coating solution 60 can be 1:1. The viscosity of the first coating solution 50 and the second coating solution 60 can be 1000 cps or greater. Because a coating solution with a viscosity of 1000 cps or greater must be coated, the structure of the dual-slit die coating machine 100 of this disclosure differs from that of devices used for coating any other coating solutions with lower viscosity (e.g., common resin solutions, such as photosensitive emulsions, magnetic solutions, anti-reflective or anti-glare solutions, widening-field solutions, and pigment solutions for color filters), and cannot be obtained through design modifications. The first coating solution 50 and the second coating solution 60 may include graphite, conductive materials, CMC, and adhesives.

[0103] Under the above coating conditions, the most preferred ratio is 3:1:1 for the thickness of the third mold lip D3, the thickness of the second mold lip D2, and the thickness of the first mold lip D1. Using the double-slit mold coating machine 100 can improve the process efficiency of forming a double-layer active material layer on the current collector and reduce the defect rate.

[0104] Figure 5 This is a perspective view of a double-slit mold coating machine according to another embodiment of the present disclosure. Figure 6 It was taken from line VI-VI'. Figure 5 Cross-sectional view, Figure 7 It is a section taken along line VII-VII'. Figure 5 Cross-sectional view.

[0105] Figures 5 to 7 The double slit mold coating machine 200 shown is compared with the reference. Figures 2 to 4 The difference in the described dual-slit die coating machine 100 is that the lower surfaces of the second die block 120' and the third die block 130' are in intermittent contact with the base 90. In the dual-slit die coating machine 200, elements similar to those in the dual-slit die coating machine 100 are given similar reference numerals in the drawings, and repeated descriptions are omitted.

[0106] In the aforementioned dual-slit die coating machine 100, the second die block 120 and the third die block 130, extending along their entire vertical length, contact the base 90. Due to the overall contact with the base 90, the supporting force increases with the increase in contact area. Compared to the dual-slit die coating machine 100, the dual-slit die coating machine 200 of this embodiment includes a second die block 120' and a third die block 130' whose lower surfaces are locally reinforced. That is, the second die block 120' and the third die block 130' intermittently contact the base 90, and reinforcement members RR are intermittently added to the bottom of each die block. Multiple reinforcement members RR can be provided on the lower surfaces of the second die block 120' and the third die block 130' along their length. In the second die block 120', there can be blank spaces between the reinforcement members RR. Similarly, in the third die block 130', there can be blank spaces between the reinforcement members RR. According to this structure, the contact area with the base 90 is smaller than the contact area of ​​the double slit mold coating machine 100, but the stress can be reduced by the blank space.

[0107] The reinforcing member RR of the second mold block 120' is not separate from the second mold block 120', and the reinforcing member RR of the third mold block 130' is not separate from the third mold block 130'. Each of the second mold block 120' including the reinforcing member RR and the third mold block 130' including the reinforcing member RR is a monolithic component. That is, it is a seamless, one-piece component. Therefore, due to its structural robustness, it is highly stable against external impacts during operation and handling. In cases where the reinforcing member RR is not included in each mold block, but rather comprises two or more corresponding components, the alignment of each component must be considered during installation, and the total tolerance increases after assembling the components.

[0108] Additionally, the blank spaces between the reinforcing members RR in the second mold block 120' and the third mold block 130' can be bending spaces. For this purpose, a pressing element 190 can be connected to the bottom of the base 90. Preferably, the pressing element 190 can be a servo motor. The pressing element 190 can preferably be located in the center of the base 90. If desired, the pressing element 190 can be placed closer to the second mold block 120' or the third mold block 130'. The closer it is to the pressing element 190, the greater the force it can withstand and the more it can bend. The pressing element 190 can push the second mold block 120' and the third mold block 130' in the conveying direction, or pull the second mold block 120' and the third mold block 130' in the opposite direction to the conveying direction.

[0109] Multiple reinforcing members RR can be provided along the length of the double-slit die coating machine 200. According to this configuration, bending spaces divided at multiple locations can be formed along the length of the double-slit die coating machine 200, thereby achieving uniform bending.

[0110] Preferably, the multiple reinforcing members RR can be symmetrical in the length direction with reference to the center in the length direction of the double slit mold coating machine 200. According to this configuration, it is helpful to bend evenly on both sides with reference to the center in the length direction of the double slit mold coating machine 200, thereby avoiding alignment deviation between the left and right sides, and applying uniform fastening force to the left and right sides through the fastening on the contact surfaces.

[0111] Preferably, the distance between the reinforcing members RR in the central region among the plurality of reinforcing members RR can be greater than the distance between the other reinforcing members RR. According to this configuration, the coating gap in the central region can be better controlled by increasing the curvature in the central region.

[0112] Because the coating solution is injected into the center of the mold blocks 110, 120', and 130', the amount of liquid coated at the center is greater than that at the sides. Therefore, the dual-slit mold coating machine 200 can have a non-uniform coating profile in the width direction (perpendicular to the MD direction) of the substrate 170. In other words, the load of the coating solution is concentrated in the center of the width direction of the first slit 101 and the second slit 102. In this case, the coating gap and thus the load distribution can be adjusted by pushing or pulling the second mold block 120' and the third mold block 130' with the pressing element 190 to deform the second mold lip 121 and the third mold lip 131. When the pressing element 190 pushes each mold block 120', 130' in the conveying direction, the coating gap at the center can be reduced. Conversely, when the pressing element 190 pulls each mold block 120', 130' in the opposite direction to the conveying direction, the coating gap at the center can be increased.

[0113] According to this disclosure, since the second mold block 120' and the third mold block 130' remain in contact with the base 90 while deforming each mold block 120', 130' through a bending space defined as the space between the reinforcing members RR, a pressing element 190 for controlling the coating uniformity in the width direction can be used to allow deformation with high uniformity.

[0114] As described above, the dual-slit die coating machine 200 has minimal assembly alignment requirements, namely, one contact surface fastening, and no adjustment function is needed. Furthermore, the dual-slit die coating machine 200 is a die structure with a bending space. As described above, according to this disclosure, a bending space and one contact surface fastening are provided. Bending is achieved by deforming the alignment position, and according to this disclosure, the deformation of each plate of the second die block 120' and the third die block 130' can be controlled very uniformly.

[0115] Therefore, according to this disclosure, high coating uniformity can be easily achieved in a direct manner. As a result, electrode quality / productivity / utilization can be improved according to this disclosure.

[0116] Figure 8 This is a flowchart of the assembly steps of a double-slit mold coating machine according to another embodiment of the present disclosure. Figures 9 to 12 This is a diagram illustrating the assembly steps of a double-slit mold coating machine according to another embodiment of the present disclosure. Figures 9 to 12 The assembly steps will follow as follows Figure 8 The flowchart shown. Figures 13 to 15 It is a diagram used to help understand the structure of the mold block.

[0117] exist Figures 9 to 12 In the double slit mold coating machine 300, elements similar to those in the previously described double slit mold coating machines 100 and 200 are given similar reference numerals, and repeated descriptions are omitted.

[0118] First, prepare the first mold block 110, which is integrally formed with the base 90, and according to... Figure 8 Step S1 and Figure 9 The first gasket 113' is assembled onto the first mold block 110. Figure 13 This is a front view of the first mold block 110 as viewed from the Y-axis direction. The first gasket 113' is placed on the first manifold 112.

[0119] Reference Figure 9 The first gasket 113' may have a rough approximation. The shape defines the first outlet 101a. Specifically, the first gasket 113' has a plurality of open portions that are intermittently cut in a region. The first gasket 113' included in the dual slit mold coating machine 300 of this embodiment has two open portions, so that the coating layer can be formed on the substrate 170 as a pattern of two parallel stripes.

[0120] Bolts (not shown) can be used to assemble the first washer 113' and the first mold block 110. Figure 9 and Figure 13 The first washer 113' and the first mold block 110 are illustrated by way of example, and can have bolt holes H1 for bolted connections. Bolts can be inserted into each bolt hole H1, and the total number of bolts can be, for example, 13. The bolts are of a non-adjustable fixing type and are independent of operator skill. Bolts can be selected based on mechanical properties defined according to the required strength (tensile strength). The strength varies depending on the material; for example, the use of SUS304 can provide 700 N / mm². 2 The tensile strength. Further consideration of corrosion resistance allows for the specification and selection of materials with suitable properties.

[0121] The bolt can be of a suitable size depending on the bolt tension required for the corresponding fastening position. Bolt tension is a value obtained by multiplying the bolt's tensile strength by the bolt's effective cross-sectional area, which varies depending on the thread shape (calculated by those skilled in the art, taking into account the inner diameter of the screw as the diameter at the groove between the threads, the outer diameter of the screw as the diameter at the screw shaft, and the effective diameter corresponding to a value between them). In embodiments of this disclosure, the bolts used to assemble the first washer 113' and the first mold block 110 may include, for example, M5 to M16.

[0122] in addition, Figure 9 An offset block mounting portion 114 is shown, which includes a first shim offset block (not shown) for mounting. The offset block mounting portion 114 can be mounted in multiple locations. The first shim offset block is configured to adjust the offset or distance between the end of the mold lip and the end of the first shim 113' by pulling the first shim 113' in the opposite direction to the mold lip. The coating width can be changed by adjusting the offset. The smaller the offset, the shorter the landing length of the coating solution on it, and therefore the smaller the coating width.

[0123] Subsequently, according to Figure 8 Step S2 and Figure 10 The second mold block 120' is assembled onto the first gasket 113'. Figure 14 This is a front view of the second mold block 120' as viewed from the Y-axis direction.

[0124] The second mold block 120' can be assembled onto the first mold block 110. Bolts (not shown) can be used to assemble the second mold block 120' and the first mold block 110. Figure 10 and Figure 14 The second mold block 120' is illustrated by way of example, and may have bolt holes H2 for bolted connections. Bolts can be inserted into each bolt hole H2, and the total number of bolts may be, for example, 22. The bolts are of a non-adjustable, fixed type.

[0125] Reference Figure 10 and Figure 14 As described above, the second mold block 120' has reinforcing members RR for intermittent contact between the lower surface and the base 90 and for the bending space between the reinforcing members RR. Multiple reinforcing members RR are arranged along the length of the double-slit mold coating machine 300. The reinforcing members RR can be symmetrical along the length direction with a center point as a reference. The distance L1 between the reinforcing members RR in the central region among the multiple reinforcing members RR can be greater than the distance L2 between the other reinforcing members RR. According to this configuration, the coating gap at the center can be better controlled by increasing the bending at the center.

[0126] Bolts (not shown) can be vertically installed into the contact surface between the second mold block 120' and the base 90. Since the contact surface is formed at the reinforcement RR, the bolts can be installed into the reinforcement RR. Figure 9 By way of example, the base 90 corresponding to the reinforcement RR can have bolt holes HR for bolt connection.

[0127] Subsequently, according to Figure 8 Step S3 and Figure 11 The second gasket 133' is assembled onto the second mold block 120'.

[0128] The second gasket 133' may have a rough approximation. The shape defines the second outlet 102a. Specifically, the second gasket 133' has a plurality of open portions that are intermittently cut in one area. The second gasket 133' included in the dual-slit die coating machine 300 of this embodiment has two open portions, thus the coating layer can be formed into two parallel pattern shapes. The open portions of the first gasket 113' and the second gasket 133' are aligned with each other. Therefore, the upper slurry layer can be aligned and formed on the lower slurry layer.

[0129] Bolts (not shown) can be used to assemble the second washer 133' and the second mold block 120'. Figure 11The second washer 133' is illustrated by way of example, and may have bolt holes H3 for bolt fastening. Bolts can be inserted into each bolt hole H3, and the total number of bolts may be, for example, 13. The bolts are of a non-adjustable fastening type.

[0130] A second shim offset block (not shown) may also be installed. The second shim offset block may be installed between the reinforcing members RR of the second mold block 120'. The second offset block is configured to adjust the offset or distance between the mold lip and the end of the second shim 133' by pulling the second shim 133' in the opposite direction to the mold lip.

[0131] Subsequently, according to Figure 8 Step S4 and Figure 12 The assembly of the double slit mold coating machine 300 is completed by assembling the third mold block 130' onto the second gasket 133'. Figure 15 This is a front view of the third mold block 130' as viewed from the Y-axis direction.

[0132] The third mold block 130' can be assembled with the second mold block 120'. Bolts (not shown) can be used to assemble the third mold block 130' and the second mold block 120'. Figure 12 and Figure 15 The third mold block 130' is illustrated by way of example, and may have bolt holes H4 for bolted connections. Bolts can be inserted into each bolt hole H4, and the total number of bolts may be, for example, 22. The bolts are also of a non-adjustable, fixed type. All bolts used in the double-slit mold coating machine 300 of this disclosure are of a non-adjustable, fixed type.

[0133] As described above, the third mold block 130' also has reinforcing members RR for intermittent contact between its lower surface and the base 90. Similarly, multiple reinforcing members RR are arranged along the length of the double-slit mold coating machine 300. The reinforcing members RR can be symmetrical along the length direction with a center point as a reference. The distance L1 between the reinforcing members RR in the central region among the multiple reinforcing members RR can be greater than the distance L2 between the other reinforcing members RR. According to this configuration, the coating gap at the center can be better controlled by increasing the curvature at the center.

[0134] Bolts (not shown) can be vertically installed into the contact surface between the third mold block 130' and the base 90. Since the contact surface is formed at the reinforcement RR, the bolts can be installed into the reinforcement RR. Figures 9 to 11 As shown, the base 90 corresponding to the reinforcing member RR may have bolt holes HR' for bolt connection.

[0135] Subsequently, according to Figure 8 Step S5 determines the assembly state. When an assembly defect is detected ( Figure 8 If no), the method returns to the first step to adjust assembly defect items (in the negative). Figure 8 (S6 in the present disclosure). However, in the double slit die coating machine 300, since all bolts are of the fixed type and the die lips 111, 121, 131 are automatically aligned by simply assembling the first die block 110, the second die block 120', and the third die block 130', assembly defects can be avoided. Figure 8 (The one in the middle) and completes the final assembly through a single assembly ( Figure 8 Step S7 in the process.

[0136] Because the dual-slit die coating machine 300 of this disclosure uses a single contact surface for fixing, it can be assembled by simple manual operation and does not require adjustment based on operator skill. The use of a fixed fastener improves assembly quality and reproducibility. Furthermore, a bending space is formed between the reinforcing members RR.

[0137] According to the dual-slit mold coating machines 100, 200, and 300 of this disclosure having this structure, a double-layer coating can be formed on the substrate 170 by, for example, moving the substrate 170 by rotating the rotatable coating roller 160 clockwise on the top of the dual-slit mold coating machine 100, 200, and 300, and continuously contacting the first coating solution 50 and the second coating solution 60 with the surface of the substrate 170 to be coated. Alternatively, pattern coating can be intermittently formed on the substrate 170 by alternately supplying and stopping the first coating solution 50 and the second coating solution 60.

[0138] In specific examples, the slit mold coating machines 100, 200, and 300 of this disclosure can be used to coat a positive electrode active material slurry to manufacture the positive electrode of a secondary battery. The positive electrode includes a current collector and a layer of positive electrode active material on the surface of the current collector. The current collector may include conductive materials, such as Al and Cu, and suitable materials may be used depending on the polarity of the current collector electrode known in the field of secondary batteries. The positive electrode active material layer may further include at least one of various positive electrode active material particles, conductive materials, or binders. Furthermore, the positive electrode may further include various types of additives to supplement or enhance its electrochemical properties.

[0139] The active material is not limited to a specific type; it can be any active material that can be used as a positive electrode active material in lithium-ion secondary batteries. Non-limiting examples may include: at least one of layered compounds or compounds substituted with one or more transition metals, such as lithium manganese composite oxides (LiMn2O4, LiMnO2), lithium cobalt oxide (LiCoO2), and lithium nickel oxide (LiNiO2); [The text abruptly ends here, so the translation stops as well.] 1+x Mn2-x Lithium manganese oxides such as O4 (x is 0-0.33), LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxides (Li2CuO2); vanadium oxides, such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; and those with the chemical formula LiNi 1-x M x Lithium nickel oxides with Ni sites represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, x = 0.01–0.3); LiMn 2-x M x Lithium manganese composite oxides represented by O2 (M = Co, Ni, Fe, Cr, Zn, or Ta, x = 0.01–0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu, or Zn); LiMn2O4 having Li in the chemical formula partially replaced by alkaline earth metal ions; disulfide compounds; or Fe2(MoO4)3. In this disclosure, the positive electrode may include a solid electrolyte material, for example, at least one of polymer-based solid electrolytes, oxide-based solid electrolytes, or sulfide-based solid electrolytes.

[0140] Conductive materials are typically added in amounts ranging from 1 wt% to 20 wt% based on the total weight of the mixture, including the active material. The conductive material is not limited to a specific type and may include any material that has conductive properties without causing any chemical change in the corresponding battery, such as at least one selected from: graphite, for example, natural or artificial graphite; carbon black, for example, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers, for example, carbon fibers or metal fibers; metal powders, for example, fluorinated carbon powder, aluminum powder, and nickel powder; conductive whiskers, for example, zinc oxide and potassium titanate; conductive metal oxides, for example, titanium oxide; and conductive materials, for example, polyphenylene derivatives.

[0141] The adhesive is not limited to a specific type and may include any material that helps to bond the active and conductive materials together and adhere them to the current collector, such as polyvinylidene fluoride, 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 thereof. The adhesive may typically be included in the range of 1 wt% to 30 wt% or 1 wt% to 10 wt% based on 100 wt% of the electrode layer.

[0142] The slit mold coating machines 100, 200, and 300 disclosed herein can be used to coat negative electrode active material slurry to manufacture the negative electrode of a secondary battery. The negative electrode includes a current collector and a layer of negative electrode active material on the surface of the current collector. The negative electrode active material layer may further include at least one of various negative electrode active material particles, conductive materials, or binders. Furthermore, the negative electrode may further include various additives to enhance or improve its electrochemical properties.

[0143] Negative electrode active materials may include: carbon materials, such as graphite, amorphous carbon, diamond-like carbon, fullerenes, carbon nanotubes, and carbon nanohorns; lithium metal materials; alloy-based materials, such as silicon or tin alloy-based materials; and oxide-based materials, such as Nb₂O₅ and Li₅Ti₄O₂. 12 TiO2, or composites thereof. For details on the conductive materials, binders, and current collectors for the negative electrode, please refer to the description of the positive electrode.

[0144] Active material slurries, including positive or negative electrode active materials, have very high viscosity. For example, the viscosity can be 1000 cps or greater. The viscosity of active material slurries used to form electrodes for secondary batteries can be from 2000 cps to 30000 cps. For example, the viscosity of negative electrode active material slurries can be from 2000 cps to 4000 cps. The viscosity of positive electrode active material slurries can be from 8000 cps to 30000 cps. Because coating solutions with a viscosity of 1200 cps or greater must be applied, the structure of the slot die coating machines 100, 200, and 300 of this disclosure differs from that of devices used for coating any other coating solutions with lower viscosity (e.g., common resin solutions, such as photosensitive emulsions, magnetic solutions, anti-reflective or anti-glare solutions, widening-field-of-view solutions, and pigment solutions for color filters), and cannot be obtained through design modifications. Because the slit mold coating machines 100, 200, and 300 of this disclosure are designed, for example, to coat active material slurries, which may include active materials having an average particle size of approximately 10 μm, their structure differs from that of devices used for coating any other coating solution (excluding particles having the aforementioned particle size) and cannot be obtained through design modifications. The slit mold coating machines 100, 200, and 300 of this disclosure are optimal for manufacturing electrodes.

[0145] Figure 16 This is a cross-sectional view of the dual-slit die coating machine used in the comparative example. Figures 17 to 20 This is a diagram showing the assembly steps of a double-slit mold coating machine according to a comparative example.

[0146] Reference Figure 16In the comparative example of the dual-slit die coating machine 400, the vertical lengths of the second die block 120” and the third die block 130” are shorter than the vertical length of the first die block 110. In this state, when the front end of the second die block 120” is aligned with the front end of the first die block 110, the lower surface of the second die block 120” is separated from the upper surface of the base 90, forming a blank space between them. This space is formed such that the upper surface is formed by the lower surface of the second die block 120”, the bottom by the upper surface of the base 90, the front surface is open, the rear surface is formed by the front surface of the first die block 110, and the left and right sides are open. That is, in the comparative example, the second die block 120” and the third die block 130” are not in contact with the base 90.

[0147] The comparative example requires a bending space based on the characteristics of the bending die, and in order to form this space, two of the three die blocks 110”, 120”, and 130” need to have space in the alignment direction, so the resulting suspension structure adversely affects the alignment.

[0148] For this reason, the comparative example further includes a mold lip adjusting bolt 410 for mold block alignment. The mold lip adjusting bolt 410 is a push / pull bolt and requires care due to its dependence on operator skill and the risk of deformation.

[0149] In order to compare it with the contents of this disclosure, reference will be made to Figures 17 to 20 Description based on Figure 8 The flowchart shows the assembly of a comparative example of a double-slit mold coating machine 400.

[0150] Prepare a first mold block 110 to be integrally formed with the base 90, and according to Figure 8 Step S1 and Figure 17 The first gasket 113” is assembled onto the first mold block 110.

[0151] Bolts (not shown) are used to assemble the first washer 113” and the first mold block 110. The accompanying drawings illustrate, by way of example, that the first washer 113” may have bolt holes H1” for bolted connections. Bolts can be inserted into each bolt hole H1”, and the total number of bolts may be, for example, 22. However, contrary to this disclosure, the bolts are of an adjustable type that requires adjustment.

[0152] Subsequently, according to Figure 8 Step S2 and Figure 18 The second mold block 120” is assembled onto the first gasket 113”.

[0153] The second mold block 120” can be assembled with the first mold block 110. Bolts (not shown) can be used to assemble the second mold block 120” and the first mold block 110. The total number of bolts can be, for example, 22. However, contrary to the present disclosure, the bolts are adjustable types that require adjustment. The second mold block 120” does not contact the base 90 and has a suspension structure.

[0154] Subsequently, according to Figure 8 Step S3 and Figure 19 The second washer 133” is assembled onto the second mold block 120”. Bolts (not shown) are used to assemble the second washer 133” and the second mold block 120”. The accompanying drawings illustrate by way of example that the second washer 125” may have bolt holes H3” for bolting. Bolts can be inserted into each bolt hole H3”, and the total number of bolts may be, for example, 19. Contrary to this disclosure, the bolts are of an adjustable type that requires adjustment. Furthermore, contrary to this disclosure, a mold lip adjusting bolt 410 is required.

[0155] Subsequently, according to Figure 8 Step S4 and Figure 20 Assemble the third mold block 130” onto the second gasket 133”.

[0156] The third mold block 130” can be assembled with the second mold block 120”. Bolts (not shown) can be used to assemble the third mold block 130” and the second mold block 120”. The accompanying drawings illustrate, by way of example, that the third mold block 130” may have bolt holes H4” for bolted connections. The total number of bolts may be, for example, 20. Contrary to the present disclosure, the bolts are of an adjustable type that requires adjustment. The third mold block 130” does not contact the base 90 and has a suspension structure.

[0157] Subsequently, according to Figure 8 Step S5 determines the assembly state. When an assembly defect is detected, the method returns to the first step to determine the assembly state based on... Figure 8 Step S6 is to adjust assembly defect items.

[0158] In the case of the comparative example of the double-slit die coating machine 400, when according to Figure 8 During the assembly of the flowchart, an average of one or two assembly defects occur. Adjusting each assembly defect item takes 120 minutes. The dual-slit mold coating machine 300 of this disclosure is ultimately assembled in only one step, but the assembly time is relatively long.

[0159] Figure 21 The effect of reducing mold changeover time through simplified design of mold block structure / assembly is shown in another embodiment of this disclosure compared to a comparative example.

[0160] According to Figure 8 The flowchart above describes the mold block assembly process. Figures 17 to 20 As described, 22 bolts are used in the assembly of the first gasket 113” in the comparative example, 22 bolts are used in the assembly of the second mold block 120”, 19 bolts are used in the assembly of the second gasket 133”, and 20 bolts are used in the assembly of the third mold block 130”. Therefore, a total of 83 bolts are required, and the wrench is switched 6 times. All bolts are of the adjustable type described above. When adjusting the state in case of assembly defects, the mold assembly time is 120 minutes, and the mold changeover time is 12 hours.

[0161] In contrast, according to Figure 8 During the mold assembly process, as referred above... Figures 9 to 12 As described, 13 bolts (ea) are used to assemble the first gasket 113' of a double-slit mold coating machine 300 according to another embodiment of this disclosure, 22 bolts are used to assemble the second mold block 120', 13 bolts are used to assemble the second gasket 133', and 22 bolts are used to assemble the third mold block 130'. Therefore, the total number of bolts is 70, and the number of wrench changes required is 4. Compared to the comparative example, the number of bolts and the number of wrench changes are reduced. In the embodiments of this disclosure, all bolts are of the fixed type. Therefore, compared to the comparative example, there is no time loss due to adjustment, it is not dependent on the operator's skill, and reproducibility is not reduced.

[0162] Since there are no assembly defects in this embodiment, the mold assembly time is 30 minutes. The mold changeover time is 8 hours. As described above, compared with the comparative example, the embodiment reduces the mold block assembly time by 75% and the mold changeover time by 25%.

[0163] Figure 22 The effect of improving electrode quality by improving assembly quality is shown in another embodiment of this disclosure compared to a comparative example.

[0164] In the case of the dual-slit die coating machine 300 according to another embodiment of the present disclosure, it was found that the die lip alignment was good, but in the comparative example, the alignment level was found to be low. For this reason, according to the comparative example, there were load distribution defects and uneven coating width. However, according to the embodiment of the present disclosure, when the die assembly quality is improved, the load distribution is good and close to the design value, thereby leading to improved electrode quality.

[0165] Figure 23 This is a diagram used in a comparative example and another embodiment of the present disclosure to analyze the impact of bolted connection on the operation of the servo motor.

[0166] The evaluation was conducted by connecting a servo motor, which serves as a pressing element 190, to the bottom of the base 90 of the dual slit mold coating machine 400 according to the comparative example and the dual slit mold coating machine 300 according to the present disclosure.

[0167] The comparative example of the dual-slit die coating machine 400 has a structure in which the second die block 120” and the third die block 130” are suspended, and the die bending is caused by a servo motor. The dual-slit die coating machine 300 of this disclosure embodiment has a bending space or a space between the reinforcing members RR of the second die block 120” and the third die block 130”, and the die bending is caused by a servo motor. The workload of the servo motor is 4.5 kN in the comparative example and 6 kN in the example (when moving 40 μm).

[0168] Figure 24 This is a graph showing a comparison (μm) of coating gap direction deformation based on the operation of the servo motor in a comparative example and another embodiment of this disclosure.

[0169] In the implementation and comparative examples, the amount of movement of the servo motor was reflected. After bolting, the deformation in the coating gap direction at the center of the length direction was negative, and the deformation in the coating gap direction increased to a positive value as the working length of the servo motor increased. When the deformation deviation of each mold block was small after bolting, it was determined that using a servo motor would easily correct the gap deviation.

[0170] In the comparative example, the deformation caused by the servo motor is more severe in the third mold block 130” than in the first mold block 110 and the second mold block 120”. This is because the third mold block 130” does not contact the base 90 and has a suspension structure.

[0171] However, in the embodiments of this disclosure, the deformation caused by the servo motor is almost identical across all mold blocks 110, 120', and 130'. That is, it can be seen that during mold bending for width-direction load control, the deformation of each of the first to third mold blocks in this embodiment is more uniform than in the comparative example. Since the second mold block 120' and the third mold block 130' remain in contact with the base 90 while allowing each mold block 110, 120', and 130' to deform through the bending space, deformation with high uniformity is permitted.

[0172] Additionally, while this embodiment describes applying two layers of coating solution or patterned coating by supplying the coating solution in an alternating manner, it will be apparent that this disclosure may include three or more slits to apply three or more layers simultaneously.

[0173] Although this disclosure has been described with respect to a limited number of embodiments and drawings, it is not limited thereto, and it will be apparent to those skilled in the art that various changes and modifications may be made to the technical aspects of this disclosure and to the appended claims and their equivalents.

[0174] In addition, terms indicating direction, such as front, back, up, down, left and right, are used herein, but these terms are for the convenience of description and it will be apparent to those skilled in the art that these terms may change depending on the position of the element or the observer.

[0175] [Reference Label Explanation]

[0176] 50: First coating solution; 60: Second coating solution

[0177] 90: Base; 100, 200, 300: Double slit mold coating machine 101: First slit; 101a: First exit

[0178] 102: Second slit; 102a: Second exit

[0179] 110: First mold block; 111: First mold lip

[0180] 112: First manifold; 113, 113': First gasket

[0181] 120, 120': Second mold block; 121: Second mold lip

[0182] 130, 130': Third mold block; 131: Third mold lip

[0183] 132: Second manifold; 133, 133': Second gasket

[0184] 141, 142: Bolts; 160: Coating roller

[0185] 170: Substrate; 190: Pressing element

[0186] RR: Reinforcing component.

Claims

1. A double-slit mold coating machine, the double-slit mold coating machine comprising a first slit and a second slit to deliver a coating solution in the opposite direction of gravity, the double-slit mold coating machine comprising: The first mold block is installed perpendicularly to the base and integrally formed behind the upper surface of the base; The second mold block is positioned in front of the first mold block and contacts the base integrally formed with the first mold block to form the first slit between the second mold block and the first mold block; as well as A third mold block is positioned in front of the second mold block and contacts the base integrally formed with the first mold block to form the second slit between the third mold block and the second mold block. The lower surfaces of the second mold block and the third mold block are in overall contact with the base.

2. A double-slit mold coating machine, the double-slit mold coating machine comprising a first slit and a second slit to deliver a coating solution in the opposite direction of gravity, the double-slit mold coating machine comprising: The first mold block is installed perpendicularly to the base and integrally formed behind the upper surface of the base; The second mold block is positioned in front of the first mold block and contacts the base integrally formed with the first mold block to form the first slit between the second mold block and the first mold block; as well as A third mold block is positioned in front of the second mold block and contacts the base integrally formed with the first mold block to form the second slit between the third mold block and the second mold block. The lower surfaces of the second mold block and the third mold block are in intermittent contact with the base.

3. The double slit mold coating machine according to claim 2, wherein the pressing element is connected to the bottom of the base.

4. The double-slit mold coating machine according to claim 3, wherein the pressing element is a servo motor.

5. The double-slit mold coating machine according to claim 1 or 2, further comprising: A first gasket located between the first mold block and the second mold block to form the first slit, and a second gasket located between the second mold block and the third mold block to form the second slit, wherein the first gasket and the second gasket have open portions cut at least in one region.

6. The double-slit mold coating machine according to claim 2, wherein a reinforcing member is provided on the lower surface of the second mold block for intermittent contact with the base, and a bending space is formed between the reinforcing members.

7. The double-slit mold coating machine according to claim 6, wherein a reinforcing member is provided on the lower surface of the third mold block for intermittent contact with the base, and a bending space is formed between the reinforcing members.

8. The double slit mold coating machine according to claim 7, wherein a servo motor is connected to the center of the bottom of the base to deform the bending space.

9. The double-slit mold coating machine according to claim 7, wherein a plurality of reinforcing members are located in the longitudinal direction of the double-slit mold coating machine.

10. The double-slit mold coating machine according to claim 9, wherein the plurality of reinforcing members are symmetrical about the center of the double-slit mold coating machine in the length direction.

11. The double slit mold coating machine according to claim 10, wherein the distance between the reinforcing members in the central region of the plurality of reinforcing members is greater than the distance between the other reinforcing members.

12. The dual-slit mold coating machine according to claim 1 or 2, wherein the first mold block includes a first manifold containing a first coating solution and communicating with the first slit, and the third mold block includes a second manifold containing a second coating solution and communicating with the second slit.

13. The double-slit mold coating machine according to claim 1 or 2, wherein the bolts are vertically installed in the contact surface between the base and the second mold block, and the bolts are vertically installed in the contact surface between the base and the third mold block.

14. The double-slit mold coating machine according to claim 1 or 2, wherein the first slit is perpendicular to the base.

15. The double-slit mold coating machine according to claim 1 or 2, wherein the cross-section of the second mold block is a right-angled triangle.

16. The double-slit mold coating machine according to claim 1 or 2, wherein the first mold block, the second mold block and the third mold block respectively include a first mold lip, a second mold lip and a third mold lip forming the front end, and the first mold lip, the second mold lip and the third mold lip are arranged on the same straight line.

17. The double-slit mold coating machine according to claim 16, wherein the thickness of the third mold lip is greater than the thickness of the first mold lip and the thickness of the second mold lip.

18. The dual-slit die coating machine of claim 17, wherein a second outlet communicating with the second slit is located between the third die lip and the second die lip, a first outlet communicating with the first slit is located between the second die lip and the first die lip, a second coating solution is conveyed to a substrate through the second outlet, the first outlet is separated from the second outlet on a downstream side in the coating direction, and a first coating solution is conveyed to the substrate through the first outlet.

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