Slot die coater and manufacturing method for electrode plate of secondary battery using the same

Abstract

A slot die coater for improving the edge profile of an electrode active material layer is provided. The slot die coater according to the present invention comprises: an upper die block, an intermediate die block, and a lower die block; an upper core provided between the upper die block and the intermediate die block to form an upper slot; and a lower core provided between the intermediate die block and the lower die block to form a lower slot. A first coating liquid is discharged and applied onto a substrate through an upper discharge port communicating with the upper slot, and a second coating liquid is discharged and applied onto the substrate through a lower discharge port communicating with the lower slot. The upper core comprises at least one first opening, and the lower core comprises a second opening at a position corresponding to the first opening, wherein the second opening comprises a section with a width smaller than that of the first opening in the shear adjacent to the lower discharge port.

Description

Technology Field

[0001] The present invention relates to an apparatus and method for manufacturing an electrode plate for a secondary battery, and more specifically, to a slot die coater that can be used to coat an electrode active material slurry onto a current collector, and a method for manufacturing an electrode plate for a secondary battery using such a slot die coater. In particular, the present invention relates to a dual slot die coater capable of simultaneously forming two or more layers in a wet manner, and a method for manufacturing an electrode plate for a secondary battery using such a dual slot die coater. Background Technology

[0002] As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and these secondary batteries necessarily include an electrode assembly as a power generation component. The electrode assembly has a form in which a positive electrode, a separator, and a negative electrode are stacked at least once, and the positive electrode and the negative electrode are manufactured by coating and drying a positive active material slurry and a negative active material slurry onto a current collector made of aluminum foil and copper foil, respectively. In order to make the charge and discharge characteristics of the secondary battery uniform, these positive active material slurries and negative active material slurries must be evenly coated onto the current collector, and a slot die coater has conventionally been used.

[0003] FIG. 1 is a schematic diagram illustrating an example of using a slot die coater according to the prior art.

[0004] Referring to FIG. 1, conventionally, an electrode plate is manufactured by coating an electrode active material slurry onto a current collector (20) using a slot die coater (10). In this method, an electrode active material slurry discharged from the slot die coater (10) is applied onto a current collector (20) that is transported in the MD direction by a coating roll (30). The electrode active material slurry discharged from the slot die coater (10) is widely applied to one surface of the current collector (20) to form an electrode active material layer. The slot die coater (10) includes two die blocks (40, 50) and forms a slot by interposing a core (60) between the two die blocks (40, 50), and can form an electrode active material layer by discharging the electrode active material slurry through a discharge port (70) that communicates with the slot.

[0005] The TD direction coating width of the electrode active material layer coated on the current collector (20) is determined by the width of the slot. If a change in the coating width is required, various coating widths can be achieved by changing the core (60) that determines the width of the slot. In particular, to ensure the safety of the electrode plate, the electrode active material slurry must be applied so that it is evenly distributed on the current collector (20).

[0006] Figure 2 is a plan view of a deliberation according to the prior art.

[0007] The spacing between the cores (61) in the core (60) as in FIG. 2 is constant regardless of whether it is in the front or rear of the core (60) (W1=W2), and the spacing between the cores (61) determines the coating width. With such a core (60), an electrode active material layer can be formed on the current collector (20) along a single lane formed between two cores (61). However, since the electrode active material slurry is a fluid, it has the property of flowing down after coating, and the flowing down of the electrode active material slurry is called sliding.

[0008] Figure 3 shows a cross-section in the TD direction of an electrode plate for a secondary battery coated with an electrode active material slurry on one side of a current collector, illustrating a state in which sliding occurs.

[0009] Referring to FIG. 3, a sliding phenomenon occurs in which a portion of the electrode active material slurry flows down from the edge portion of the electrode active material layer, causing the thickness of the electrode active material layer to gradually become thinner towards the side portion. Reference numeral S indicates the portion where sliding occurs, i.e., the sliding portion.

[0010] Such sliding can frequently occur at the ends of the retaining portion in the width direction (both sides of TD), where the electrode active material slurry is coated, and uneven loading occurs due to the sliding. Furthermore, sliding causes unevenness during rolling and, furthermore, results in the NP ratio, which is the ratio of the negative active material layer to the positive active material layer, failing to satisfy design conditions.

[0011] In particular, when using a shim (60) as shown in FIG. 2, the discharge capacity ratio between the anode and the cathode in the flat section of the coating is maintained at the same as the design value, but a sliding section (S) is formed at the position where the coating layer edge of the anode plate and the coating layer edge of the cathode plate face each other, causing the discharge capacity ratio to be distorted. In addition, if the anode capacity becomes larger than the cathode capacity, the risk increases, and a problem arises where the position where the anode flat section and the cathode sliding section (S) face each other becomes very vulnerable to instability. For this reason, it is necessary to control sliding in the electrode active material slurry coating process, and in particular, when using a stripe pattern coating with multiple lanes, management of the shape control of the boundary surface (sliding section) is required, and in particular, the sliding length must be managed.

[0012] As illustrated in FIG. 3, the general shape of the sliding portion (S) in the electrode profile is such that as the width distance from the point (Ps) where the coating portion starts increases, the thickness increases, but beyond a certain width distance, the rate of increase in thickness gradually decreases, resulting in a flat shape where the thickness hardly increases and converges to a constant value. The sliding length (SL) can be defined as the width distance from the point (Ps) where the coating portion starts to the point (Pe) where the sliding ends. The point (Pe) where the sliding ends can be described as the point where flattening begins in the electrode profile. For example, it can be described as the point where the target coating layer thickness (H) is reached or is close to a predetermined % range.

[0013] However, in the method for manufacturing electrode plates for secondary batteries, a so-called sequential coating method is sometimes used to utilize both sides of the current collector by first coating an electrode active material layer on the top surface of the current collector and then coating an electrode active material layer on the back surface. In this case, the sliding length (SL) of the top surface tends to be longer than that of the back surface. Therefore, even if sequential coating is performed using a slot die coater containing the same core, a degradation in the electrode quality of the top surface is induced, which becomes a problem. Furthermore, the sliding of the edge portion of the top surface creates a region where the current collector sinks when the current collector is flipped over during back surface coating. Consequently, the electrode active material slurry accumulates at the edge portion during back surface coating, and a side ring phenomenon, in which the edge portion of the back surface protrudes upward in a convex manner after the process is completed, can be a particular problem. In Figure 3, the electrode profile when the side ring (R) occurs is also illustrated with a dotted line. In particular, when an increase in the flow rate of the side portion is sought to manage the sliding length (SL) through shape control of the core (60), even if the increase in the flow rate of the side portion is severe, a side ring (R) occurs, which limits the improvement of the profile of the electrode active material layer edge portion. The problem to be solved

[0014] The present invention was conceived in consideration of the aforementioned problems, and the problem to be solved by the present invention is to provide a slot die coater for improving the edge profile of the electrode active material layer.

[0015] Another problem that the present invention aims to solve is to provide a method for manufacturing an electrode plate for a secondary battery using such a slot die coater. means of solving the problem

[0016] A slot die coater according to the present invention for solving the above technical problem is a slot die coater equipped with a lower slot and an upper slot, which extrudes and applies a coating liquid to a substrate surface that travels continuously through the lower slot and the upper slot.

[0017] A slot die coater according to the present invention comprises: an upper die block, an intermediate die block, and a lower die block; an upper core provided between the upper die block and the intermediate die block to form an upper slot; and a lower core provided between the intermediate die block and the lower die block to form a lower slot; wherein a first coating liquid is discharged and applied onto a substrate through an upper discharge port communicating with the upper slot, and a second coating liquid is discharged and applied onto the substrate through a lower discharge port communicating with the lower slot; wherein the upper core includes at least one first opening, and the lower core includes a second opening at a position corresponding to the first opening, wherein the second opening includes a section with a width smaller than that of the first opening in the shear adjacent to the lower discharge port.

[0018] Preferably, the upper core comprises a first part that serves as a base and at least two second parts extending from the first part, wherein the second parts are connected to the same side of the first part and extend in the same direction, the space between the second parts is defined as the first opening, and the width of the first opening is constant.

[0019] The lower core comprises a third part that serves as a base and at least two fourth parts extending from the third part, wherein the fourth parts are connected to the same side of the third part and extend in the same direction, and the space between the fourth parts is defined as the second opening, and a flow rate increasing part may be formed on the inner side of the lower core at the rear end of the second opening, such that the width of the second opening is greater than the width of the front end of the second opening, thereby increasing the flow rate of the second coating liquid.

[0020] At this time, the width of the fourth part may be configured differentially in the rear direction to form the above-mentioned flow rate increasing part.

[0021] A taper shape may be applied to the side of the fourth part to form the above-mentioned flow rate increasing part.

[0022] The width of the fourth part may be constant at a first width from the front end of the second opening to a first position in the rear end direction, and decrease to a second width by the inclined surface to a second position in the rear end direction, and remain constant at the second width up to the third part.

[0023] Also, the angle of the above inclined surface may be 25˚ to 70˚.

[0024] At this time, the width of the second part may be constant as the second width.

[0025] The width of the fourth part may decrease linearly from the front end of the second opening in the direction of the rear end.

[0026] As another example, the lower core may include a third part serving as a base and at least two fourth parts extending from the third part, wherein the fourth parts are connected to the same side of the third part and extend in the same direction, the space between the fourth parts is defined as the second opening, and the structure may further have a protrusion formed on the side of the fourth part at the front end of the second opening.

[0027] The above protrusion may be in the shape of a right triangle or a right trapezoid.

[0028] The first coating solution and the second coating solution may be different types of coating solutions.

[0029] The first coating solution and the second coating solution may have a viscosity of 4000 cps to 6000 cps.

[0030] The above intermediate die block may have a first manifold that receives the first coating liquid and communicates with the upper slot, and the above lower die block may have a second manifold that receives the second coating liquid and communicates with the lower slot.

[0031] The upper die block may have a first manifold that receives the first coating liquid and communicates with the upper slot, and the lower die block may have a second manifold that receives the second coating liquid and communicates with the lower slot.

[0032] The lower slot and the upper slot may form an angle of 30˚ to 60˚.

[0033] A method for manufacturing an electrode plate for a secondary battery according to the present invention comprises the steps of: forming a lower coating layer on a substrate with a second coating solution by increasing the flow rate of the side portion; and simultaneously forming an upper coating layer on the lower coating layer with a first coating solution on the substrate to press the portion with the increased flow rate of the side portion.

[0034] Here, the first coating solution and the second coating solution may be electrode active material slurries having different types of active materials or binder contents.

[0035] Such a method for manufacturing an electrode plate for a secondary battery can be easily performed using a slot die coater according to the present invention.

[0036] A method for manufacturing another electrode plate for a secondary battery according to the present invention for solving the above other problems includes the step of forming a lower coating layer on a substrate with a second coating solution and simultaneously forming an upper coating layer on the lower coating layer with a first coating solution on the substrate using a slot die coater according to the present invention.

[0037] The second coating solution may contain a natural graphite active material, and the first coating solution may contain an artificial graphite active material.

[0038] In addition, by adjusting the gap between the upper slot of the slot die coater and the substrate and the gap between the lower slot of the slot die coater and the substrate, the width by which the first coating liquid spreads beyond the width of the first opening and the width by which the second coating liquid spreads beyond the width of the second opening can be adjusted. Effects of the invention

[0039] In electrode active material slurry coating using a slot die coater, sliding must be managed, and whether sliding occurs can be identified by the thickness variation in the width direction within the lane. To stably achieve the target cell capacity, it is necessary to improve the thickness variation by improving the coating loading within the lane.

[0040] According to one aspect of the present invention, a slot die coater is provided that includes a shim capable of improving loading deviation within a lane by more stably increasing the loading of a desired area. The lower layer shim included in the slot die coater of the present invention realizes a technology capable of controlling the loading amount along the width direction during electrode active material slurry coating.

[0041] Furthermore, according to the present invention, while aiming to increase the flow rate of the side portion by managing the sliding length through shape control of the lower core, the upper core has a different shape from the lower core, so the increase in the flow rate of the side portion does not overlap, and there is no concern about the occurrence of a side ring.

[0042] According to the present invention, by providing a slot die coater that modifies the shape of a lower core for the purpose of improving coating deviation within a lane and combines an upper core with a shape different from that of the lower core, the flow rate deviation of the electrode active material slurry, which is the coating liquid, is improved. As a result, the flow rate of the coating liquid in the side portion of the lane is increased without generating a side ring, thereby improving the edge profile of the electrode active material layer. In particular, the sliding portion profile can be improved.

[0043] By using the slot die coater according to the present invention, sliding can be improved so that the discharge capacity of the anode does not exceed the discharge capacity of the cathode, thereby ensuring lithium deposition and the safety of the cell.

[0044] According to the present invention, uneven loading caused by sliding can be prevented, and the occurrence of side rings can be reduced even when using a sequential coating method. That is, according to the present invention, in a sequential coating method in which the back surface is coated after the top surface is coated, the occurrence of side rings on the back surface can be prevented as a result of controlling the sliding of the top surface. Therefore, simultaneous management of the top surface and the back surface has an excellent effect.

[0045] According to the present invention, a coating layer, particularly an electrode active material layer, can be uniformly formed with a desired thickness, and since simultaneous coating of two or more types of electrode active material slurries is possible, there is an effect of excellent performance and productivity. When using the slot die coater of the present invention to manufacture an electrode plate for a secondary battery by applying an electrode active material slurry onto a current collector, there is an advantage that uniform coating is possible even under high-speed or wide-width coating conditions. Brief explanation of the drawing

[0046] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. FIG. 1 is a schematic diagram illustrating an example of using a slot die coater according to the prior art. Figure 2 is a plan view of a deliberation according to the prior art. Figure 3 shows a cross-section in the TD direction of an electrode plate for a secondary battery coated with an electrode active material slurry on one side of a current collector, illustrating a state in which sliding occurs. FIG. 4 is a schematic cross-sectional view of a slot die coater according to one embodiment of the present invention. FIG. 5 is a schematic exploded perspective view of a slot die coater according to one embodiment of the present invention. FIG. 6 is a plan view of an upper core and a lower core included in a slot die coater according to one embodiment of the present invention. FIG. 7 is a partial enlarged view of a lower layer core included in a slot die coater according to one embodiment of the present invention. FIG. 8 is a partial enlarged view of another lower layer core included in a slot die coater according to one embodiment of the present invention. Figure 9 shows a cross-section in the TD direction of an electrode plate for a secondary battery when an electrode active material slurry is coated using the lower layer core of Figure 7. FIG. 10 is a cross-sectional view in the TD direction of an electrode plate for a secondary battery manufactured according to the present invention. FIG. 11 shows a cross-section in the TD direction of an electrode plate for a secondary battery coated with an electrode active material slurry using a slot die coater according to the present invention. Figure 12 shows a cross-section in the TD direction of an electrode plate for a secondary battery coated with an electrode active material slurry using a slot die coater according to a comparative example. Figure 13 shows the sliding length comparison results for samples #1 to #4. Figure 14 shows the results of electrode profile comparison for samples #1 to #4. Specific details for implementing the invention

[0047] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0048] A slot die coater according to an embodiment of the present invention may have two or more slots. Basically, it is a device equipped with a lower slot and an upper slot that coats a coating solution onto a substrate in a double layer. The "substrate" described below is a current collector, and the coating solution is an "electrode active material slurry." Both the first coating solution and the second coating solution are electrode active material slurries, and may refer to electrode active material slurries that are identical or different in composition (type of active material, conductive material, binder), content (amount of active material, conductive material, binder), or physical properties. The slot die coater according to an embodiment of the present invention is optimized for manufacturing electrode plates for secondary batteries by applying two or more types of electrode active material slurries simultaneously or alternately. However, the scope of the rights of the present invention is not necessarily limited thereto. For example, the above substrate may be a porous support constituting a separator, and the first coating solution and the second coating solution may be organic materials with different compositions or physical properties. That is, if thin film coating is required, the above substrate, the first coating solution, and the second coating solution may be any of them.

[0049] In this specification, 'front' refers to the direction in which the discharge port faces (X direction, MD direction), and 'back' refers to the opposite direction. 'Left / Right' refers to the direction perpendicular to the direction in which the discharge port faces, in the width direction of the slot (Z direction, TD direction).

[0050] FIG. 4 is a schematic cross-sectional view of a slot die coater according to one embodiment of the present invention, and FIG. 5 is a schematic exploded perspective view of a slot die coater according to one embodiment of the present invention.

[0051] A slot die coater (100) according to one embodiment of the present invention is a device having an upper slot (101) and a lower slot (102) and capable of coating two types of coating liquids that are the same or different from each other on a substrate (200) simultaneously or alternately through the upper slot (101) and the lower slot (102).

[0052] Referring to FIGS. 4 and 5, the slot die coater (100) comprises an upper die block (110), an intermediate die block (120), and a lower die block (130). The upper die block (110) is positioned on top of the intermediate die block (120), and the intermediate die block (120) is positioned on top of the lower die block (130). The die blocks (110, 120, 130) can be assembled together through bolts which are fastening members.

[0053] In FIG. 4, the slot die coater (100) is installed so that the direction (X direction) for discharging the electrode active material slurry, which is the coating liquid, is nearly horizontal (nearly ± 5 degrees).

[0054] The intermediate die block (120) is a block located in the middle among the blocks constituting the slot die coater (100), and is a block positioned between the upper die block (110) and the lower die block (130) to form a double slot. The intermediate die block (120) included in the slot die coater (100) of this embodiment has a cross-section of a right triangle, but it is not necessarily limited to this shape; for example, the cross-section may be provided as an isosceles triangle.

[0055] The first surface (120a) of the intermediate die block (120) facing the upper die block (110) is positioned nearly horizontally, and the opposite surface (110d, i.e., the surface forming the upper outer surface of the slot die coater (100)) of the surface (110b) facing the first surface (120a) of the upper die block (110) is also positioned nearly horizontally. In this way, the first surface (120a) and the opposite surface (110d) are positioned nearly parallel. Furthermore, the opposite surface (130d, i.e., the surface forming the lower outer surface of the slot die coater (100)) of the surface (130b) of the lower die block (130) facing the intermediate die block (120) is also positioned nearly horizontally, and this surface becomes the bottom surface (130d, XZ plane).

[0056] The side opposite to the direction in which the electrode active material slurry is discharged from the upper die block (110), middle die block (120), and lower die block (130), i.e., the rear side (110c, 120c, 130c), is positioned nearly vertically (in the Y direction).

[0057] Among the surfaces forming the outer surface of the slot die coater (100) in the outermost die blocks, the upper die block (110) and the lower die block (130) may be manufactured such that the upper surface (110d) of the upper die block (110) and the bottom surface (130d) of the lower die block (130) are nearly perpendicular to the rear surface (110c, 130c). Also, the first surface (120a) of the intermediate die block (120) may be manufactured such that it is nearly perpendicular to the rear surface (120c). In these die blocks (110, 120, 130), the edges formed by the surfaces are configured at right angles, so there is a right angle in the cross-section, and since the vertical or horizontal plane can be used as a reference surface, the manufacturing and handling are easy and precision is guaranteed. In addition, the combined state of the upper die block (110), middle die block (120), and lower die block (130) has an overall shape of a rectangular prism, and only the front part (110a, 130a) from which the coating liquid is discharged has an oblique shape toward the substrate (200). This has the advantage that the shape after assembly is approximately similar to a slot die coater having a single slot (e.g., 10 of FIG. 1), allowing the slot die coater base and the like to be shared.

[0058] The slot die coater (100) may further include two or more fixing parts (140) provided on its rear surface (110c, 120c, 130c). The fixing parts (140) are provided to connect the lower die block (130) and the middle die block (120), and to connect the middle die block (120) and the upper die block (110). Multiple fixing parts (140) may be provided along the width direction of the slot die coater (100). Bolts are fastened to the fixing parts (140), and through this, the upper die block (110), the middle die block (120), and the lower die block (130) may be assembled together.

[0059] The upper die block (110), middle die block (120), and lower die block (130) are not necessarily limited to the form exemplified above, and, for example, may be configured as a vertical die with the direction for discharging the electrode active material slurry upward (Y direction) and the rear surface (110c, 120c, 130c) as the bottom surface.

[0060] The die blocks (110, 120, 130) are made of, for example, SUS material. Easy-to-process materials such as SUS420J2, SUS630, SUS440C, SUS304, and SUS316L can be used. SUS has the advantages of being easy to process, inexpensive, having high corrosion resistance, and being able to be manufactured into desired shapes at low cost.

[0061] The upper die block (110) is positioned to face the first surface (120a), which is the upper surface of the intermediate die block (120) that is horizontal with respect to the bottom surface. The upper slot (101) is formed between the intermediate die block (120) and the upper die block (110) in this manner. An upper core (300) may be interposed between the intermediate die block (120) and the upper die block (110) to create a gap between them. This forms an upper slot (101) that serves as a passage through which the first coating liquid (150) can flow. In other words, the upper core (300) is provided between the upper die block (110) and the intermediate die block (120) to form the upper slot (101). In this case, the vertical width (Y direction, slot gap) of the upper slot (101) is determined by the thickness of the upper core (300). The thickness of the upper core (300) may be approximately 1 mm. For example, when an electrode active material slurry containing 40-80% solid content is applied to coat the upper core (300) to a thickness of 70 µm to 300 µm, the thickness of the upper core (300) may be 0.5 mm to 1.5 mm.

[0062] As illustrated in FIG. 5, the upper core (300) is cut in at least one area to include at least one first opening (310), and is interposed only in the remaining portion excluding one side of the edge area of ​​the opposing surfaces of the intermediate die block (120) and the upper die block (110). Accordingly, the circumferential direction excluding the front of the upper slot (101) is blocked, and an upper discharge port (101a) is formed only between the tip of the upper die block (110) and the tip of the intermediate die block (120). The tip of the upper die block (110) and the tip of the intermediate die block (120) are defined as the upper die lip (111) and the intermediate die lip (121), respectively; in other words, the upper discharge port (101a) can be said to be a place formed by the separation between the upper die lip (111) and the intermediate die lip (121).

[0063] For reference, the upper core (300) may be made of a sealing material as it also functions as a gasket to prevent the first coating liquid (150) from leaking through the gap between the upper die block (110) and the intermediate die block (120), except for the area where the upper discharge port (101a) is formed. The upper core (300) may be made of plastic or metal, for example, but the present invention is not limited thereto. The upper core (300) may be a resin sheet such as Teflon or polyester, or a metal sheet such as copper or aluminum. The upper core (300) may be made of SUS material, just like the die blocks (110, 120, 130). The upper core (300) may be fixed to the upper die block (110) or the intermediate die block (120) by means of screws, for example.

[0064] Additionally, the intermediate die block (120) has a first manifold (155) that has a predetermined depth on the first surface (120a), which is the surface facing the upper die block (110), and communicates with the upper slot (101). Although not shown in the drawing, this first manifold (155) is connected to a first coating liquid (150) supply chamber installed externally via a supply pipe to receive the first coating liquid (150). When the first coating liquid (150) is supplied from the outside along the pipe-shaped supply pipe and fills the first manifold (155), the flow of the first coating liquid (150) is induced along the upper slot (101) that communicates with the first manifold (155), and is discharged to the outside through the upper discharge port (101a) that communicates with the upper slot (101). As another example, the first manifold (155) may be provided on the surface (110b) facing the intermediate die block (120) in the upper die block (110).

[0065] The lower die block (130) is the lowest block among the blocks constituting the slot die coater (100), and has a slanted shape such that the surface (130b) facing the middle die block (120) forms an angle of approximately 20˚ to 60˚ with respect to the bottom surface (130d).

[0066] A lower slot (102) can be formed between the lower die block (130) and the middle die block (120) where they face each other. A lower core (400) is interposed between the lower die block (130) and the middle die block (120) to create a gap between them, thereby forming a lower slot (102) that serves as a passage through which the second coating liquid (160) can flow. In other words, the lower core (400) is provided between the middle die block (120) and the lower die block (130) to form the lower slot (102). In this case, the thickness of the lower core (400) determines the vertical width (Y direction, slot gap) of the lower slot (102). The thickness of the lower core (400) may be approximately 1 mm. For example, when an electrode active material slurry containing 40-80% solid content is applied to coat the material to a thickness of 70㎛-300㎛, the thickness of the lower core (400) may be 0.5mm-1.5mm.

[0067] As shown in FIG. 5, the lower core (400) is cut in at least one area to include at least one second opening (410) and may be interposed in the remaining portion excluding one side of the edge area of ​​the opposing surfaces of the lower die block (130) and the intermediate die block (120). Accordingly, the lower discharge port (102a), through which the second coating liquid (160) can be discharged to the outside, is formed only between the tip of the lower die block (130) and the tip of the intermediate die block (120). If the tip of the lower die block (130) is defined as the lower die lip (131), then the lower discharge port (102a) can be said to be a place formed by the gap between the lower die lip (131) and the intermediate die lip (121).

[0068] Likewise, the lower core (400) may be made of a sealing material as it also functions as a gasket to prevent the second coating liquid (160) from leaking through the gap between the lower die block (130) and the intermediate die block (120), except for the area where the lower discharge port (102a) is formed. The lower core (400) may also be made of plastic or metal, for example, but the present invention is not limited thereto. The lower core (400) may be a resin sheet such as Teflon or polyester, or a metal sheet such as copper or aluminum. The lower core (400) may also be made of SUS material, just like the die blocks (110, 120, 130). The lower core (400) may be fixed to the intermediate die block (120) or the lower die block (130), for example, through a screw.

[0069] The lower die block (130) is provided with a second manifold (165) having a predetermined depth on the surface (130b) facing the intermediate die block (120) and communicating with the lower slot (102). Although not shown in the drawing, this second manifold (165) is connected to a second coating liquid supply chamber (not shown) installed externally via a supply pipe to receive the second coating liquid (160). When the second manifold (165) is filled with the second coating liquid (160), the second coating liquid (160) is induced to flow along the lower slot (102) and is discharged to the outside through the lower discharge port (102a) communicating with the lower slot (102). As another example, the second manifold (165) may be provided on the surface (120b) facing the lower die block (130) of the intermediate die block (120).

[0070] The upper slot (101) and the lower slot (102) form a certain angle, which may be approximately 30° to 60°. These upper slot (101) and lower slot (102) intersect at one point, and an upper discharge port (101a) and a lower discharge port (102a) may be provided near the intersection point. Accordingly, the discharge points of the first coating liquid (150) and the second coating liquid (160) can be concentrated at approximately one point. Through this, the lower coating layer formed by the second coating liquid (160) and the upper coating layer formed by the first coating liquid (150) can be aligned vertically and horizontally to form a double layer.

[0071] According to the slot die coater (100) having such a configuration, a coating roll (500) that is rotatably arranged is positioned in front of the slot die coater (100), and by rotating the coating roll (500), the substrate (200) to be coated is driven in the MD direction, and a first coating liquid (150) is discharged and applied onto the substrate (200) through an upper discharge port (101a), and a second coating liquid (160) is discharged and applied onto the substrate (200) through a lower discharge port (102a).

[0072] The first coating solution (150) and the second coating solution (160) may be different types of coating solutions. The first coating solution (150) and the second coating solution (160) may have a viscosity of 4000 cps to 6000 cps. The first coating solution (150) and the second coating solution (160) may be electrode active material slurries.

[0073] Through a slot die coater (100), the second coating liquid (160) and the first coating liquid (150) can be continuously brought into contact with the surface of the substrate (200) to coat the substrate (200) in a double layer. Alternatively, the supply and interruption of the second coating liquid (160) and the supply and interruption of the first coating liquid (150) can be alternately performed to form a pattern coating on the substrate (200) intermittently. Preferably, the second coating liquid (160) and the first coating liquid (150) are discharged simultaneously to form a double layer. In order to manufacture a secondary battery with high energy density, the thickness of the electrode active material layer, which was about 130 μm, is gradually increased to reach 300 μm. When a thick electrode active material layer is formed using a conventional slot die coater (10) as shown in FIG. 1, migration of the binder and conductive material within the active material slurry intensifies during drying, resulting in the final electrode being manufactured unevenly. If the electrode active material layer is coated in two steps to solve this problem, such as by applying a thin layer and drying it, and then applying it again and drying it, there is a disadvantage that it takes a long time. According to the present invention, if a slot die coater (100) having two slots is used, the second coating liquid (160) and the first coating liquid (150) can be discharged simultaneously to form a thick electrode active material layer at once, thereby improving electrode performance and productivity at the same time.

[0074] In particular, the slot die coater (100) is characterized by having different shapes for the upper core (300) and the lower core (400), which allows for the improvement of the profile of the electrode active material layer edge portion.

[0075] FIG. 6 is a plan view of an upper core and a lower core included in a slot die coater according to one embodiment of the present invention, and FIG. 7 is a partial enlarged view of a lower core included in a slot die coater according to one embodiment of the present invention, which is an enlarged view of part A of FIG. 6.

[0076] First, referring to FIG. 6, the upper core (300) includes at least one first opening (310), and the lower core (400) includes a second opening (410) at a position corresponding to the first opening (310). The second opening (410) includes a section (SA) with a width smaller than that of the first opening (310) in the front section adjacent to the lower discharge port (102a). For example, the width of the first opening (310) is D1, and the second opening (410) includes a section (SA) with a width D2 that is smaller than D1. The section (SA) with a width D2 that is smaller than D1 may be part of the second opening (410), and the width of the remaining section of the second opening (410) may be D1, which is the same as the width of the first opening (310).

[0077] The upper core (300) and the lower core (400) determine the coating width of the coating layer applied on the substrate (200), and the number of the first opening (310) and the second opening (410) determines the number of lanes, i.e., the number of patterns, and the size of the first opening (310) and the second opening (410) may affect the coating width. In the illustrated example, there is one first opening (310) and one second opening (410), but a plurality of first openings (310) and second openings (410) may be included to form a stripe pattern-shaped coating layer on the substrate (200).

[0078] More specifically, the upper core (300) includes a first part (320) that serves as a base and at least two second parts (330) that extend from the first part (320), the second parts (330) are connected to the same side of the first part (320) and extend in the same direction (X direction), and the space between the second parts (330) is defined as a first opening (310). In particular, in this embodiment, the width of the first opening (310) is constant at D1. A first coating liquid (150) can be discharged through the first opening (310).

[0079] The first part (320) and the second part (330) may be formed as a single unit. That is, there is no gap or separation between the first part (320) and the second part (330). Therefore, unnecessary flow of the first coating liquid (150) between the first part (320) and the second part (330) can be prevented.

[0080] The first part (320) is a part that is placed at the rear of the upper die block (110) in the upper core (300). In order for the upper core (300) to be interposed in the remaining part excluding one side of the edge area of ​​the opposing surfaces of the upper die block (110) and the intermediate die block (120), at least two second parts (330) are required.

[0081] The second part (330) extends in the direction toward the upper discharge port (101a), that is, in the X direction. In other words, the second part (330) is a part that extends toward the front part of the upper die block (110) even in the upper layer core (300). If the number of the second part (330) is increased, more lanes can be created to discharge the first coating liquid (150) on the substrate (200), and more patterns can be formed side by side at once. That is, a stripe pattern coating can be performed. However, the present invention is not limited by the number of the second part (330). The second part (330) is a part corresponding to the core (61) of the conventional core (60) of FIG. 3.

[0082] The lower core (400) includes a third part (420) that serves as a base and at least two fourth parts (430) extending from the third part (420). The fourth parts (430) are connected to the same side of the third part (420) and extend in the same direction (X direction). The space between the fourth parts (430) is defined as a second opening (410). A flow rate increasing part (440) is formed on the inner side of the lower core (400) at the rear end of the second opening (410), such that the width (D1) of the second opening (410) is larger than the width (D2) of the front end of the second opening (410), thereby increasing the flow rate of the second coating liquid (160). The shape is different from that of the upper core (300). The second coating liquid (160) can be discharged through the second opening (410), and the loading of the side part can be increased because there is a flow rate increasing part (440).

[0083] The third part (420) and the fourth part (430) may be formed as a single unit. That is, there is no gap or separation between the third part (420) and the fourth part (430). Therefore, unnecessary flow of the second coating liquid (160) between the third part (420) and the fourth part (430) can be prevented.

[0084] The third part (420) is a part that is placed in the rear portion of the lower die block (130) in the lower core (400). In order for the lower core (400) to be interposed in the remaining portion excluding one side of the edge area of ​​the opposing surfaces of the lower die block (130) and the intermediate die block (120), at least two fourth parts (430) are required.

[0085] The fourth part (430) extends in the direction toward the lower discharge port (102a), that is, in the X direction. In other words, the fourth part (430) is a part that extends toward the front part of the lower die block (130) even in the lower core (400). If the number of the fourth part (430) is increased, more lanes can be created to discharge the second coating liquid (160) on the substrate (200), and more patterns can be formed side by side at once. That is, a stripe pattern coating can be performed. However, the present invention is not limited by the number of the fourth part (430). The fourth part (430) is a part corresponding to the core (61) of the conventional core (60) of FIG. 3.

[0086] The width (L) of the fourth part (430) may be differentially configured in the rearward direction to form a flow rate increase section (440) in the lower core (400). For example, a tapered shape may be applied to the side of the fourth part (430) to form a flow rate increase section (440). In this case, the tapered shape may be various and may be a curve, a straight line, a step shape, a combination thereof, etc., and may be as shown in FIGS. 7 and FIGS. 8, for example.

[0087] First, referring to FIG. 7, the width of the fourth part (430) is constant as a first width (a) from the front end of the second opening (410) to the rear end direction to the first position (AA), and decreases to a second width (b) in the rear end direction to the second position (BB) by the inclined surface (435), and below that, it can be constant as a second width (b). The length from the front end of the lower core (400) to the first position (AA) is c, and the length from the first position (AA) to the second position (BB) is d.

[0088] In the example illustrated in FIG. 7, the inclined surface (435) is formed in a section that protrudes by a width (ab) in the width direction and extends by a length (d) in the direction of the lower discharge port (102a). If (ab) and d are equal, the angle (α) of the inclined surface (435) in this case becomes 45˚. The angle (α) of such an inclined surface (435) is adjustable to improve loading deviation, and sliding can be improved by adjusting ab, c, d, etc. Additionally, ab, c, d, etc. can be determined between the sliding improvement effect and the concern regarding the occurrence of a fat edge.

[0089] The angle (α) of the inclined surface (435) may be 25° to 70° with respect to the side of the fourth part (430) or in the discharge direction (opposite to X). If the angle (α) of the inclined surface (435) becomes smaller than 25°, the length of the flow rate increase section (440) is shortened, and the sliding improvement effect may be reduced. If the angle (α) of the inclined surface (435) becomes larger than 70°, a sudden change in flow rate occurs on the surface following the inclined surface (435), which may affect the discharge pressure and is therefore undesirable.

[0090] And corresponding to this lower core (400), the width of the second part (330) in the upper core (300) can be constant as the second width (b).

[0091] The structure of FIG. 7 can be seen as a structure in which a protrusion (450) is further formed on the side of the fourth part (430) at the front of the second opening (410). The protrusion (450) can be said to have a right-angled trapezoidal shape.

[0092] Next, as illustrated in FIG. 8, the width of the fourth part (430) may decrease linearly from the front end of the second opening (410) toward the rear end. The width of the fourth part (430) is a first width (a) at the front end of the second opening (410), decreases to a second width (b) toward the second position (BB) toward the rear end by the inclined surface (435), and remains constant at the second width (b) below. The structure of FIG. 8 can be seen as a structure in which a protrusion (455) is further formed on the side of the fourth part (430) at the front end of the second opening (410). And here, the protrusion (455) can be said to have the shape of a right triangle.

[0093] The sliding improvement effect can be controlled by adjusting the shape and size of the protrusions (450, 455). If the size of the protrusions (450, 455) increases, the effect on the electrode active material layer profile will increase. In order to achieve a fixed coating width, the size of the protrusions (450, 455) cannot be made indefinitely large, and the size of the protrusions (450, 455) can be adjusted by further considering the physical properties of the coating liquid.

[0094] FIG. 9 shows a cross-section in the TD direction of an electrode plate for a secondary battery when an electrode active material slurry is coated using the lower layer core (400) of FIG. 7.

[0095] Referring to Fig. 9, the thickness at the edge of the electrode active material layer may increase more than the center portion, such as the side ring (R'), through an increase in flow rate at the side portion.

[0096] When coating an electrode active material slurry using an upper layer core (300) as shown in FIG. 6, the TD direction cross-section of the electrode plate for a secondary battery may be similar to FIG. 3.

[0097] In the present invention, a method for manufacturing an electrode plate for a secondary battery is also proposed, comprising the step of forming a lower coating layer (160a) on a substrate (200) using a slot die coater (100) with a second coating liquid (160) and simultaneously forming an upper coating layer (150a) on the lower coating layer (160a) using a first coating liquid (150) on the substrate (200).

[0098] The first coating solution (150) and the second coating solution (160) may be electrode active material slurries with different types of active materials or binder contents. For example, the second coating solution (160) may contain natural graphite active material and the first coating solution (150) may contain artificial graphite active material.

[0099] At this time, by adjusting the gap between the upper slot (101a) of the slot die coater (100) and the substrate (200) and the gap between the lower slot (102a) of the slot die coater (100) and the substrate (200), the width (spreading width) of the first coating liquid (150) spreading more than the width (D1) of the first opening (310) and the width (D2) of the second coating liquid (160) spreading more than the width (D2) of the second opening (410) can be adjusted. If the gap is narrow, the spreading width increases, and if the gap is large, the spreading width decreases.

[0100] FIG. 10 is a cross-sectional view in the TD direction of an electrode plate for a secondary battery manufactured according to the present invention. Referring to FIG. 10, an electrode active material layer (600) is formed on a substrate (200), and the electrode active material layer (600) includes a lower coating layer (160a) and an upper coating layer (150a).

[0101] Since the slot die coater (100) of the present invention coats the electrode active material layer (600) using both the upper core (300) and the lower core (400), the TD direction cross-section of the electrode active material layer (600) formed on the substrate (200) can be improved as shown in FIG. 11.

[0102] FIG. 11 shows a cross-section in the TD direction of an electrode plate for a secondary battery coated with an electrode active material slurry using a slot die coater according to the present invention.

[0103] Referring to FIG. 11, when an electrode active material layer (600) is coated on a substrate (200) using both an upper core (300) and a lower core (400) through a slot die coater (100) according to the present invention, the TD direction cross-section of the electrode active material layer (600) can be observed. As a result of combining the TD direction cross-section profile by the upper core (300) (e.g., a shape in which sliding occurs as in FIG. 3) and the TD direction cross-section profile by the lower core (400) (e.g., a shape in which a side ring occurs as in FIG. 9), it can be seen that the thickness profile of the electrode active material layer (600) as in FIG. 11 has significantly improved sliding compared to the conventional profile as in FIG. 3.

[0104] According to the present invention, the electrode active material layer (600) is coated using both the upper core (300) and the lower core (400) through a slot die coater (100). By increasing the side flow rate, a lower coating layer (160a) is formed on the substrate (200) using the second coating liquid (160), and at the same time, an upper coating layer (150a) is formed on the lower coating layer (160a) using the first coating liquid (150) on the substrate (200), thereby performing a step of pressing the part with increased side flow rate, so that the thickness profile of the electrode active material layer (600) can be improved compared to the conventional one.

[0105] In particular, by using a lower core (400) in which a flow rate increasing portion (440) is formed, the sliding length (SL') of the electrode active material layer (600) coated on the substrate (200) becomes shorter than the conventional sliding length (SL'). <SL). 나아가, 도 3에 도시한 것과 같은 종래 전극 활물질층의 슬라이딩부(S)에서 두께 변화가 완만해지기 시작하는 지점에서의 두께에 비하여, 기재(200) 상에 도포된 전극 활물질층(600)의 슬라이딩부(S')에서 두께 변화가 완만해지기 시작하는 지점에서의 두께가 증가한다. 따라서, 슬라이딩부(S')의 프로파일이 개선된다.

[0106] As such, according to the present invention, the shape of the edge portion of the electrode active material layer (600) can be mutually complemented by using an upper core (300) and a lower core (400) of different shapes. The second opening (410) of the lower core (400) includes a section (SA) that is narrower than the first opening (310) of the upper core (300) in the front portion adjacent to the lower discharge port (102a). A flow rate increasing portion (440) is included inside the second opening (410) of the lower core (400). The lower core (400) can increase the side portion flow rate of the second coating liquid (160), so if the lower core (400) is used alone, it will create a shape that generates a side ring (R') at the edge portion. The upper core (300) can form an upper coating layer (150a) that can press down on and cover the lower coating layer (160a) formed by the lower core (400). If only the upper core (300) is used alone, a shape that causes sliding at the edge can be created. However, as a result of the sliding caused by the upper core (300) and the side ring (R') caused by the lower core (400) complementing each other, the electrode active material layer (600) formed up to the upper coating layer (150a) on the lower coating layer (160a) can form a sliding portion (S') at the edge with a reduced sliding length (SL') compared to the conventional one. Additionally, no side ring is generated in the electrode active material layer (600).

[0107] Meanwhile, FIG. 3 shows an electrode profile of a slot die coater (10) using a conventional core (60). If two identical conventional cores (60) are applied to the upper core and the lower core while configuring a dual slot die coater as in the present invention, the electrode profile is further deteriorated. Therefore, in the case of a dual slot die coater like the present invention, the effect of combining the upper core (300) and the lower core (400) in different shapes is significant.

[0108] Figure 12 shows a cross-section in the TD direction of an electrode plate for a secondary battery coated with an electrode active material slurry using a slot die coater according to a comparative example.

[0109] FIG. 12 illustrates an electrode profile in which, for example, two identical conventional cores (60) are applied to the upper core and the lower core to form an electrode active material layer (80) on the current collector (20). As described in FIG. 3, according to the conventional core (60), a sliding portion (S) or a side ring (R) occurs. If the upper core and the lower core of the same shape are used, the same shape is added, resulting in the electrode profile becoming very sliding as in FIG. 12 (a) or having a side ring as in FIG. 12 (b). In particular, if a core intended to increase side flow is applied to both the upper core and the lower core, a severe side ring occurs as in FIG. 12 (b).

[0110] As such, it will be fully understood that due to the high specialization of the present invention in applying shims of different shapes to a dual slot die coater, the electrode profile can be significantly improved as shown in Fig. 11 compared to the electrode profile in Fig. 12.

[0111] An electrode active material layer can be stably formed using a slot die coater (100) including the upper layer core (300) and lower layer core (400) described above. According to the present invention, since the coating width, loading amount, and sliding control are possible, the quality of the coating layer and electrode active material layer formed according to the present invention is excellent. For example, the thickness of the coating layer along the width direction of the substrate (200) can be uniform regardless of the position, and the sliding section can be formed in a desired shape. Accordingly, according to the present invention, a coating layer, particularly an electrode active material layer, can be stably formed without causing pattern defects.

[0112] For example, it can be applied to the manufacture of a positive plate of a secondary battery by coating a positive active material slurry using a slot die coater (100).

[0113] The positive plate comprises a current collector and a positive active material layer formed on the surface of the current collector. According to the present invention, a positive active material layer can be formed on one surface of the current collector, or on the top surface and the back surface by sequential coating.

[0114] The above current collector may be one that exhibits electrical conductivity, such as Al or Cu, and may be appropriate depending on the polarity of the current collector electrode known in the field of secondary batteries. The positive active material slurry may further include one or more of a plurality of positive active material particles, a conductive material, and a binder. In addition, the positive active material slurry may further include various additives for the purpose of supplementing or improving electrochemical properties.

[0115] The active material is not limited to specific components as long as it can be used as a positive electrode active material for a lithium-ion secondary battery. Non-limiting examples include layered compounds such as lithium manganese complex oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; chemical formula Li 1+x Mn2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 ~ 0.3); chemical formula LiMn 2-x M x It may include a lithium manganese composite oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of the Li in the chemical formula is substituted with alkaline earth metal ions; a disulfide compound; and a mixture of two or more of Fe2(MoO4)3. In the present invention, the anode may include one or more of a polymer-based solid electrolyte, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte as a solid electrolyte material.

[0116] The conductive material may typically be added in an amount of 1 wt% to 20 wt% based on the total weight of the mixture containing the active material. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and may include, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or one or more mixtures selected from conductive materials such as polyphenylene derivatives.

[0117] The above binder is not particularly limited as long as it is a component that assists in the bonding of the active material and the conductive material, and the bonding to the current collector, and examples include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers. The above binder may typically be included in a range of 1 wt% to 30 wt% or 1 wt% to 10 wt% relative to 100 wt% of the electrode layer.

[0118] A negative electrode plate of a secondary battery may be manufactured by coating a negative electrode active material slurry using the slot die coater (100) of the present invention. The negative electrode plate comprises a current collector and a negative electrode active material layer formed on one side or on the top and back sides of the current collector. The negative electrode active material slurry may further include one or more of a plurality of negative electrode active material particles, a conductive material, and a binder. Additionally, the negative electrode active material slurry may further include various additives for the purpose of supplementing or improving electrochemical properties.

[0119] The above-mentioned negative electrode active material is a carbon material such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotubes, carbon nanohorns, etc., a lithium metal material, an alloy-based material such as silicon or tin, Nb2O5, Li5Ti4O. 12 Oxide-based materials such as TiO2, or composites thereof, may be used. For the cathode, the conductive material, binder, and current collector may be described in the section on the anode.

[0120] In particular, as previously mentioned, the type of active material or the binder content of the first coating solution (150) and the second coating solution (160) can be made different to manufacture a negative electrode plate with desired characteristics or to control the characteristics of the negative electrode plate. By making the binder content of the first coating solution (150) and the second coating solution (160) different while maintaining the same solid content, the active material content of the first coating solution (150) and the second coating solution (160) can also be different. For example, the binder content of the second coating solution (160) can be made higher and the binder content of the first coating solution (150) less, so that the lower coating layer (160a) is well attached to the substrate (200) and the upper coating layer (150a) is formed thereon. The upper coating layer (150a) can contain an active material at a higher content than the lower coating layer (160a), thereby further increasing the capacity of the secondary battery. In addition, the second coating solution (160) may contain a natural graphite active material and the first coating solution (150) may contain an artificial graphite active material, thereby allowing the unique characteristics of each active material to be appropriately utilized while controlling the characteristics of the negative electrode plate.

[0121] By using the slot die coater (100) of the present invention, sliding can be improved so that the discharge capacity of the positive electrode does not exceed the discharge capacity of the negative electrode, thereby ensuring lithium deposition and cell safety. Furthermore, the electrode plate manufactured using the method for manufacturing an electrode plate for a secondary battery according to the present invention can be manufactured into an electrode assembly and included in a cylindrical secondary battery. In particular, such a cylindrical secondary battery can be manufactured as a large cylindrical secondary battery with a form factor of 4680 or more. The size of the electrode plate may vary depending on the size of the jelly-roll type electrode assembly to be manufactured, and ultimately the size of the cylindrical secondary battery to be manufactured. The size of the electrode plate included in a large cylindrical secondary battery with a form factor of 4680 must be larger than the size of the electrode plate included in a small cylindrical secondary battery with a form factor of 1865 or 2170. The slot die coater (100) of the present invention is suitable for use in manufacturing such large electrode plates.

[0122] Here, the form factor refers to a value representing the diameter and height of a cylindrical secondary battery. The cylindrical secondary battery that can be manufactured by the slot die coater (100) according to the present invention may be, for example, a 4611 cell, a 4875 cell, a 4811 cell, a 4880 cell, or a 4680 cell. In the numerical value representing the form factor, the first two digits represent the diameter of the cell, and the next two digits represent the height of the cell. A final digit 0 may be added to indicate that the cross-section of the cell is circular.

[0123] Preferably, the form factor of the cylindrical secondary battery that can be manufactured is 4680, and the electrode plate obtained as described above is included in a jelly-roll type electrode assembly included in such a cylindrical secondary battery, and the width of one electrode plate can be 60-110 mm and the length can be 3-5 m. The upper core (300) and the lower core (400) can have dimensions that allow for the manufacture of electrode plates of these sizes. Additionally, by increasing the number of the second part (330) and the fourth part (430) corresponding to the core, electrode active material layer patterns can be formed simultaneously in a stripe shape along multiple lanes on a single substrate (200), and then slitting can be performed along the unstriped portion between two adjacent electrode active material layer patterns to utilize each as an electrode plate.

[0124] The results of manufacturing electrode plates according to the embodiments and comparative examples of the present invention and comparing them will be explained below.

[0125] Sample #1 is a case where the lower core (400) as shown in FIG. 6 is applied to both the upper core and the lower core; Sample #2 is a case where the upper core (300) as shown in FIG. 6 is applied to both the upper core and the lower core (same as FIG. 12); Sample #3 is a case where the upper core (300) of FIG. 6 is applied to the upper core and the lower core (400) of FIG. 6 is applied to the lower core (same as the embodiment of the present invention); and Sample #4 is a case where the upper core (400) of FIG. 6 is applied to the lower core and the upper core (300) of FIG. 6 is applied to the lower core (same as the embodiment of the present invention) is applied to the lower core (same as the upper core / lower core position is opposite to that of the embodiment of the present invention. The electrode profiles were measured and the sliding lengths were compared.

[0126] The coating width is designed to be 230mm, and the loading is 367mg / 25cm 2The upper layer spreading width was set to 3mm, and the lower layer spreading width was set to 3mm. The lower layer core (400) was made to have a protrusion (450). At this time, ab was set to 4mm, c to 2mm, and the angle (α) to 45˚. The first coating liquid (150) and the second coating liquid (160) were described as electrode active material slurries containing 53% solid content. The thickness of the lower layer core (400) and the upper layer core (300) was set to 0.6mm. The length from the front end to the rear end of the upper layer core (300) and the lower layer core (400) was set to 169.9mm, and the length from the left end to the right end of the upper layer core (300) and the lower layer core (400) was set to 449mm.

[0127] Figure 13 shows the sliding length comparison results for samples #1 to #4.

[0128] In the case of Sample #1, the sliding length is 2.4 mm, which shows an improved result compared to the sliding length of Sample #2 (3.2 mm), but is larger than the sliding length of Sample #3 (2.1 mm) according to the embodiment of the present invention. In the case of Sample #4, where the upper core / lower core positions are reversed compared to the embodiment of the present invention, the sliding length is as long as that of Sample #2. Sample #3 showed a result in which the sliding length was reduced by 34% compared to Sample #2. Sample #3 showed the most favorable result in terms of sliding length.

[0129] Figure 14 shows the results of comparing electrode profiles for samples #1 to #4. Sample #3 shows superiority in the shape of the sliding part compared to samples #1 and #4. In particular, Sample #3 is significant because no side ring occurs even when the spreading width is set to 3mm.

[0130] As described above, although the present invention has been explained by limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs. Explanation of the symbols

[0131] 100: Slot die coater 101: Upper slot 102: Lower slot 110: Upper die block 120: Middle die block 130: Lower die block 200 : Material 300 : Upper layer core 310: First opening 320: First part 330 : Part 2 400 : Lower layer 410: Second opening 420: Third part 430: Part 4 435: Inclined surface 440: Flow rate increasing section 450, 455: Protrusions 600: Electrode active material layer

Claims

Claim 1 A slot die coater comprising: an upper die block, a middle die block, and a lower die block; an upper core provided between the upper die block and the middle die block to form an upper slot; and a lower core provided between the middle die block and the lower die block to form a lower slot; wherein a first coating liquid is discharged and applied onto a substrate through an upper discharge port communicating with the upper slot, and a second coating liquid is discharged and applied onto the substrate through a lower discharge port communicating with the lower slot, wherein the upper core includes at least one first opening, and the lower core includes a second opening at a position corresponding to the first opening, wherein the second opening includes a section with a width smaller than that of the first opening in the shear adjacent to the lower discharge port, and the width of the remaining section of the second opening is the same as the width of the first opening. Claim 2 A slot die coater according to claim 1, wherein the upper layer core comprises a first part serving as a base and at least two second parts extending from the first part, wherein the second parts are connected to the same side of the first part and extend in the same direction, the space between the second parts is defined as the first opening, and the width of the first opening is constant. Claim 3 A slot die coater according to claim 2, wherein the lower core comprises a third part serving as a base and at least two fourth parts extending from the third part, wherein the fourth parts are connected to the same side of the third part and extend in the same direction, the space between the fourth parts is defined as the second opening, and a flow rate increasing part is formed on the inner side of the lower core at the rear end of the second opening, such that the width of the second opening is greater than the width of the front end of the second opening, thereby increasing the flow rate of the second coating liquid. Claim 4 A slot die coater characterized in that, in paragraph 3, the width of the fourth part is differentially configured in the rear end direction to form the flow rate increasing part. Claim 5 A slot die coater according to claim 3, characterized in that a tapered shape is applied to the side of the fourth part to form the flow rate increasing part. Claim 6 A slot die coater characterized in that, in paragraph 3, the width of the fourth part is constant at a first width from the front end of the second opening to a first position in the rear end direction, decreases to a second width by an inclined surface to a second position in the rear end direction, and remains constant at the second width up to the third part. Claim 7 A slot die coater according to claim 6, characterized in that the angle of the inclined surface is 25˚ to 70˚. Claim 8 A slot die coater characterized in that, in claim 7, the width of the second part is constant as the second width. Claim 9 A slot die coater according to paragraph 3, characterized in that the width of the fourth portion decreases linearly from the front end of the second opening in the rear end direction. Claim 10 A slot die coater according to claim 1, wherein the lower core comprises a third part serving as a base and at least two fourth parts extending from the third part, wherein the fourth parts are connected to the same side of the third part and extend in the same direction, the space between the fourth parts is defined as the second opening, and a protrusion is further formed on the side of the fourth part at the front end of the second opening. Claim 11 A slot die coater according to claim 10, characterized in that the above-mentioned protrusion is in the shape of a right triangle or a right trapezoid. Claim 12 A slot die coater according to claim 1, characterized in that the first coating solution and the second coating solution are different types of coating solutions. Claim 13 A slot die coater according to claim 1, characterized in that the first coating solution and the second coating solution have a viscosity of 4000 cps to 6000 cps. Claim 14 A method for manufacturing an electrode plate for a secondary battery, comprising: a step of forming a lower coating layer on a substrate with a second coating liquid by increasing the flow rate of the side portion corresponding to the edge portion of the coating layer in the TD direction cross-section on a substrate being transported in the MD direction; and a step of simultaneously forming an upper coating layer on the lower coating layer with a first coating liquid on the substrate and pressing the portion with increased flow rate of the side portion. Claim 15 A method for manufacturing an electrode plate for a secondary battery according to claim 14, wherein the first coating solution and the second coating solution are electrode active material slurries having different types of active materials or binder contents. Claim 16 A method for manufacturing an electrode plate for a secondary battery, comprising the step of forming a lower coating layer on a substrate with a second coating solution and simultaneously forming an upper coating layer on the lower coating layer with a first coating solution on the substrate using a slot die coater according to any one of claims 1 to 13. Claim 17 A method for manufacturing an electrode plate for a secondary battery according to claim 16, wherein the second coating solution comprises a natural graphite active material and the first coating solution comprises an artificial graphite active material. Claim 18 A method for manufacturing an electrode plate for a secondary battery according to claim 16, wherein the gap between the upper slot of the slot die coater and the substrate and the gap between the lower slot of the slot die coater and the substrate are adjusted such that the width of the first coating liquid spreading is greater than the width of the first opening and the width of the second coating liquid spreading is greater than the width of the second opening, wherein the spreading width increases when the gap is narrow and decreases when the gap is wide.

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