Slot die coater, and method for manufacturing electrode plates for secondary batteries using the same

Abstract

A slot die coater is provided for improving the profile of the edge portion of the electrode active material layer. The slot die coater according to the present invention includes an upper die block, an intermediate die block, and a lower die block, an upper shim provided between the upper die block and the intermediate die block and forming an upper slot, and a lower shim provided between the intermediate die block and the lower die block and forming a lower slot, wherein a first coating liquid is discharged onto a substrate through an upper discharge port communicating with the upper slot and a second coating liquid is discharged onto the substrate through a lower discharge port communicating with the lower slot, the upper shim includes at least one first opening, the lower shim includes a second opening at a position corresponding to the first opening, and the second opening includes a section at its front end adjacent to the lower discharge port that is narrower than the first opening.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for manufacturing an electrode plate for a secondary battery. More specifically, the present invention relates to a slot die coater that can be used to coat an electrode active material slurry on a current collector, and a method for manufacturing an electrode plate for a secondary battery using such a slot die coater. The present invention particularly relates to a dual slot die coater that can simultaneously form two or more layers wet, and a method for manufacturing an electrode plate for a secondary battery using the same. This application claims priority based on Korean Patent Application No. 10-2023-0093003 filed on July 18, 2023, and all the contents disclosed in the specification and drawings of the application are incorporated into this application.

Background Art

[0002] With the increasing development and demand for mobile devices, the demand for secondary batteries as an energy source has been rapidly increasing. Such secondary batteries essentially include an electrode assembly as a power generation element. The electrode assembly has a form in which a positive electrode, a separator, and a negative electrode are laminated at least once or more. The positive electrode and the negative electrode are manufactured by applying and drying a positive electrode active material slurry and a negative electrode active material slurry, respectively, on current collectors made of aluminum foil and copper foil. In order to make the charge and discharge characteristics of the secondary battery uniform, such positive electrode active material slurry and negative electrode active material slurry must be uniformly coated on the current collector, and a slot die coater has been conventionally used.

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

[0004] Referring to Figure 1, conventionally, electrode plates are manufactured by coating a current collector 20 with an electrode active material slurry using a slot die coater 10. In this method, the electrode active material slurry discharged from the slot die coater 10 is applied to the current collector 20, which is being transported in the MD direction by a coating roll 30. The electrode active material slurry discharged from the slot die coater 10 is broadly applied to one surface of the current collector 20, forming an electrode active material layer. The slot die coater 10 includes two die blocks 40 and 50, with a shim 60 interposed between the two die blocks 40 and 50 to form a slot, and the electrode active material slurry can be discharged through an outlet 70 communicating with the slot to form an electrode active material layer.

[0005] The TD-direction coating width of the electrode active material layer coated on the current collector 20 is determined by the slot width. If it is necessary to change the coating width, various coating widths can be achieved by changing the shim 60 that determines the slot width. In particular, in order to ensure the safety of the electrode plate, it is essential that the electrode active material slurry is applied so that it is uniformly distributed on the current collector 20.

[0006] Figure 2 is a plan view of a shim relating to the conventional technology.

[0007] In the shim 60 shown in Figure 2, the spacing between the shim ribs 61 is constant regardless of whether they are in front of or behind the shim 60 (W1=W2), and the spacing between the shim ribs 61 determines the coating width. With such a shim 60, an electrode active material layer can be formed on the current collector 20 along a lane formed between two shim ribs 61. However, since the electrode active material slurry is a fluid, it has the property of flowing down after coating, and this flow of the electrode active material slurry is called sliding.

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

[0009] Referring to Figure 3, a sliding phenomenon is observed where a portion of the electrode active material slurry flows down at the edge of the electrode active material layer, causing the thickness of the electrode active material layer to gradually decrease towards the sides. Reference numeral S indicates the portion where sliding occurs, i.e., the sliding portion.

[0010] Such sliding can frequently occur at the edges of the surface area (both sides of the TD), which is the part coated with electrode active material slurry, and this sliding can cause uneven loading. Furthermore, sliding causes unevenness during rolling, resulting in the NP ratio (the ratio of the face-to-face ratio of the negative electrode active material layer to the positive electrode active material layer) not meeting the design requirements.

[0011] In particular, when using a shim 60 as shown in Figure 2, the ratio of discharge capacity between the positive and negative electrodes in the flat coating section is maintained as designed. However, at the point where the edge of the coating layer on the positive electrode plate and the edge of the coating layer on the negative electrode plate face each other, a sliding section S is formed, resulting in a different ratio of discharge capacity. Furthermore, since the risk increases when the positive electrode capacity is greater than the negative electrode capacity, a problem arises where the point where the flat positive electrode section and the sliding negative electrode section S face each other becomes extremely vulnerable to instability. For these reasons, it is necessary to control sliding in the electrode active material slurry coating process, and especially when coating a stripe pattern using multiple lanes, it is necessary to control the shape of the interface (sliding section), and in particular, to control the sliding length.

[0012] As shown in Figure 3, the general shape of the sliding portion S in the electrode profile is close to a shape that converges to a constant value, where the thickness increases as the width distance from the starting point Ps of the coating portion increases, and beyond a certain width distance the rate of thickness increase gradually decreases, resulting in a flat shape where the thickness hardly increases. The sliding length SL can be defined as the width distance from the starting point Ps of the coating portion to the ending point Pe of the sliding portion. The ending point Pe of the sliding portion can be said to be the point where flattening begins in the electrode profile. For example, it can be said to be the point where the thickness reaches the target coating layer H, or is close to a predetermined percentage range.

[0013] However, in the manufacturing method of electrode plates for secondary batteries, a so-called sequential coating method is sometimes used to utilize both sides of the current collector. This involves first coating the top surface of the current collector with the electrode active material layer, and then coating the back surface with the electrode active material layer. 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 shims, there is a problem of reduced electrode quality on the top surface. Furthermore, sliding at the edge of the top surface can cause the current collector to become concave when the back surface is covered during coating. This can lead to a concentration of electrode active material slurry at the edge during back surface coating, and a side ring phenomenon, where the edge of the back surface protrudes upward after the process is completed, can be particularly problematic. Figure 3 shows the electrode profile when side ring R occurs, indicated by a dotted line. In particular, if the flow rate in the side section is increased to control the sliding length SL through the control of the shape of the shim 60, side ring R will still occur even if the flow rate in the side section is significantly increased, thus limiting the improvement of the profile of the electrode active material layer at the edge. [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] This invention has been made in consideration of the above-mentioned problems, and the problem that this invention aims to solve is to provide a slot die coater for improving the profile of the edge portion of the electrode active material layer.

[0015] Another problem that the present invention aims to solve is to provide a method for manufacturing electrode plates for secondary batteries using such a slot die coater. [Means for solving the problem]

[0016] To solve the above technical problems, the slot die coater according to the present invention has a lower slot and an upper slot, and is a slot die coater that applies a coating liquid by pressurizing it through the lower slot and the upper slot to the surface of a continuously moving substrate.

[0017] The slot die coater according to the present invention includes an upper die block, an intermediate die block, and a lower die block, an upper shim provided between the upper die block and the intermediate die block to form an upper slot, and a lower shim provided between the intermediate die block and the lower die block to form a lower slot, wherein a first coating liquid is discharged onto a substrate through an upper discharge port communicating with the upper slot and a second coating liquid is discharged onto the substrate through a lower discharge port communicating with the lower slot, the upper shim includes at least one first opening, the lower shim includes a second opening at a position corresponding to the first opening, and the second opening includes a section at its front end adjacent to the lower discharge port that is narrower than the first opening.

[0018] Preferably, the upper shim includes a base first portion and at least two second portions extending from the first portion, the second portions being connected to the same side of the first portion and extending in the same direction, the space between the second portions being defined as the first open portion, the width of which is constant.

[0019] The lower shim includes a third part serving as a base and at least two fourth parts extending from the third part. 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 part, and the width of the second opening part is wider than the width of the front end thereof. A flow rate increasing part where the flow rate of the second coating liquid increases may be formed inside the lower shim at the rear end of the second opening part.

[0020] At this time, in order to form the flow rate increasing part, the width of the fourth part may be configured to change in the direction of the rear end.

[0021] In order to form the flow rate increasing part, the side surface of the fourth part may be formed in a taper shape.

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

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

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

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

[0026] As another example, the lower shim includes a third part serving as a base and at least two fourth parts extending from the third part. 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 part, and a structure may be formed in which a protrusion is further formed on the side surface of the fourth part at the front end of the second opening part.

[0027] The 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 liquid and the second coating liquid may have a viscosity of 4000 cps to 6000 cps.

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

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

[0032] The lower slot and the upper slot can form an angle between 30° and 60°.

[0033] The method for manufacturing an electrode plate for a secondary battery according to the present invention includes the steps of increasing the flow rate of the side portion and forming a lower coating layer on a substrate with a second coating liquid, and simultaneously forming an upper coating layer on the substrate with a first coating liquid on the lower coating layer and pressing the portion where the flow rate of the side portion has increased.

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

[0035] Such a method for manufacturing electrode plates for secondary batteries can be easily carried out using the slot die coater according to the present invention.

[0036] A method for manufacturing an electrode plate for a secondary battery according to the present invention, which solves the above-mentioned other problems, includes the steps of forming a lower coating layer on a substrate with a second coating liquid using a slot die coater according to the present invention, and simultaneously forming an upper coating layer on the substrate with a first coating liquid on the lower coating layer.

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

[0038] Furthermore, by adjusting the distance between the upper slot of the slot die coater and the substrate, and the distance between the lower slot of the slot die coater and the substrate, the width to which the first coating liquid spreads beyond the width of the first opening, and the width to 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, controlling sliding is essential, and the presence or absence of sliding can be confirmed by the thickness deviation in the width direction within the lane. To stably achieve the target cell capacity, it is necessary to improve the coating loading within the lane and reduce the thickness deviation.

[0040] According to one aspect of the present invention, a slot die coater is provided that includes a shim that can improve loading deviations within a lane by more stably increasing loading at a desired location. The lower layer shim included in the slot die coater of the present invention enables a technique that allows control of the amount of loading along the width direction when coating an electrode active material slurry.

[0041] Furthermore, according to the present invention, the sliding length is controlled by controlling the shape of the lower shim, and the flow rate in the side portion is increased. Since the upper shim has a different shape from the lower shim, the increase in flow rate in the side portion does not overlap, and there is no risk of side ring formation.

[0042] According to the present invention, in order to improve coating deviation within the lane, a slot die coater is provided that changes the shape of the lower shim and combines it with an upper shim that has a different shape from the lower shim. As a result of improving the flow rate deviation of the electrode active material slurry, which is the coating liquid, the flow rate of the coating liquid in the side part of the lane is increased without the occurrence of side rings, and the profile of the edge part of the electrode active material layer can be improved. In particular, the profile of the sliding part can be improved.

[0043] By using the slot die coater according to the present invention, sliding can be improved, the discharge capacity of the positive electrode will not exceed the discharge capacity of the negative electrode, and the safety of lithium deposition and the cell can be ensured.

[0044] According to the present invention, loading inconsistencies caused by sliding can be prevented, and the occurrence of side rings can be reduced even when using a sequential coating method. In other words, according to the present invention, in a sequential coating method in which the back surface is coated after the top surface, the occurrence of side rings on the back surface can be prevented by controlling the sliding of the top surface. Therefore, simultaneous management of the top and back surfaces is extremely effective.

[0045] According to the present invention, a coating layer, particularly an electrode active material layer, can be formed uniformly with a desired thickness, and simultaneous coating of two or more electrode active material slurries is possible, resulting in excellent performance and productivity. When using the slot die coater of the present invention, uniform coating is possible even under high-speed coating or long-width coating conditions when manufacturing electrode plates for secondary batteries by coating an electrode active material slurry onto a current collector.

[0046] The following drawings accompanying this specification illustrate preferred embodiments of the invention and, together with the detailed description of the invention, serve to further illustrate the technical idea of ​​the invention; therefore, the invention should not be construed as being limited solely to what is shown in the drawings. [Brief explanation of the drawing]

[0047] [Figure 1] This is a schematic diagram illustrating an example of the use of a slot die coater according to conventional technology. [Figure 2] This is a plan view of a shim related to the conventional technology. [Figure 3] This shows a cross-section in the TD direction of an electrode plate for a secondary battery, in which one surface of the current collector is coated with an electrode active material slurry, illustrating the state in which sliding has occurred. [Figure 4] This is a schematic cross-sectional view of a slot die coater according to one embodiment of the present invention. [Figure 5] This is a schematic exploded perspective view of a slot die coater according to one embodiment of the present invention. [Figure 6] This is a plan view of the upper and lower shims included in a slot die coater according to one embodiment of the present invention. [Figure 7] This is a magnified view of a lower layer shim included in a slot die coater according to one embodiment of the present invention. [Figure 8] This is a magnified view of a portion of another lower layer shim included in a slot die coater according to one embodiment of the present invention. [Figure 9] The cross-section of the electrode plate for the secondary battery in the TD direction is shown when the electrode active material slurry is coated using the lower layer shim in Figure 7. [Figure 10] This is a cross-section in the TD direction of an electrode plate for a secondary battery manufactured according to the present invention. [Figure 11] This shows a cross-sectional view in the TD direction of an electrode plate for a secondary battery coated with an electrode active material slurry using the slot die coater according to the present invention. [Figure 12]This shows a cross-sectional view 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] This shows the results of comparing the sliding lengths for samples #1 to #4. [Figure 14] This shows the results of comparing the electrode profiles for samples #1 to #4. [Modes for carrying out the invention]

[0048] Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and in the claims are not to be interpreted in their usual and dictionary sense, but rather in accordance with the technical ideas of the present invention, in accordance with the principle that the inventor himself may appropriately define the concepts of terms in order to best describe the invention. Therefore, it should be understood that the configurations shown in the embodiments described herein represent only one of the most preferred embodiments of the present invention and do not represent the entirety of the technical ideas of the present invention, and that there may be a variety of equivalents and modifications that can be substituted for them at the time of this application.

[0049] A slot die coater according to an embodiment of the present invention may have two or more slots. Basically, it is a device having a lower slot and an upper slot, which coats a substrate with a coating liquid in a double layer. The "substrate" described below is a current collector, and the coating liquid is an "electrode active material slurry." Both the first coating liquid and the second coating liquid are electrode active material slurries, and may mean electrode active material slurries that are identical or different in composition (type of active material, conductive material, and binder), content (amount of active material, conductive material, and binder), and physical properties. A slot die coater according to an embodiment of the present invention is optimized for manufacturing electrode plates for secondary batteries by simultaneously or alternately coating two or more types of electrode active material slurries. However, the scope of the present invention is not necessarily limited thereto. For example, the substrate may be a porous support constituting a separation membrane, and the first coating liquid and the second coating liquid may be organic substances with different compositions and physical properties. That is, if a thin film coating is required, the substrate, the first coating liquid, and the second coating liquid can be any of the above.

[0050] In this specification, "front" refers to the direction the discharge port is facing (X direction, MD direction), and "rear" refers to the opposite direction. "Left / right" refers to the direction perpendicular to the direction the discharge port is facing, and to the width direction of the slot (Z direction, TD direction).

[0051] Figure 4 is a schematic cross-sectional view of a slot die coater according to one embodiment of the present invention, and Figure 5 is a schematic exploded perspective view of a slot die coater according to one embodiment of the present invention.

[0052] A slot die coater 100 according to one embodiment of the present invention has an upper slot 101 and a lower slot 102, and is a device that can simultaneously or alternately coat two types of coating liquids, which may be the same or different from each other, onto a substrate 200 via the upper slot 101 and the lower slot 102.

[0053] Referring to Figures 4 and 5, the slot die coater 100 includes an upper die block 110, an intermediate die block 120, and a lower die block 130. The upper die block 110 is positioned above the intermediate die block 120, and the intermediate die block 120 is positioned above the lower die block 130. The die blocks 110, 120, and 130 can be assembled together by bolts, which are fastening members.

[0054] In Figure 4, the slot die coater 100 is positioned so that the direction (X direction) from which the electrode active material slurry, which is the coating liquid, is discharged is almost horizontal (approximately ±5 degrees).

[0055] The intermediate die block 120 is a block located in the middle of the blocks that make up the slot die coater 100, and is 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 right-angled triangular cross-section, but is not necessarily limited to this shape, and for example, the cross-section may be formed as an isosceles triangle.

[0056] The first surface 120a of the intermediate die block 120, which faces the upper die block 110, is positioned almost horizontally, and the opposite surface 110d of the upper die block 110 (i.e., the surface that forms the upper surface of the outer periphery of the slot die coater 100), which faces the first surface 120a, is also positioned almost horizontally. In this way, the first surface 120a and the opposite surface 110d are almost parallel. Furthermore, the opposite surface 130d of the lower die block 130 (i.e., the surface that forms the lower surface of the outer periphery of the slot die coater 100), which faces the intermediate die block 120, is also positioned almost horizontally, and this surface becomes the bottom surface 130d (XZ plane).

[0057] In the upper die block 110, the intermediate die block 120, and the lower die block 130, the surfaces opposite to the direction in which the electrode active material slurry is discharged, i.e., the rear surfaces 110c, 120c, and 130c, are positioned almost vertically (in the Y direction).

[0058] In the outermost die blocks, the upper die block 110 and the lower die block 130, the upper surface 110d of the upper die block 110 and the bottom surface 130d of the lower die block 130, which form the outer circumferential surface of the slot die coater 100, can be manufactured so that they are approximately perpendicular to the rear surfaces 110c and 130c. Similarly, the first surface 120a of the intermediate die block 120 can be manufactured so that it is approximately perpendicular to the rear surface 120c. In such die blocks 110, 120, and 130, the angles between the surfaces are right angles, resulting in right-angle sections in the cross-section. This allows for the use of vertical or horizontal planes as reference surfaces, making manufacturing and handling easier and ensuring accuracy. Furthermore, the combined upper die block 110, intermediate die block 120, and lower die block 130 form a roughly rectangular parallelepiped shape overall, with only the front sections 110a and 130a, where the coating liquid is discharged, having a shape that is inclined toward the substrate 200. This has advantages such as the fact that the assembled shape is approximately similar to that of a slot die coater with a single slot (for example, 10 in Figure 1), and that the stand and other components of the slot die coater can be shared.

[0059] The slot die coater 100 may further include two or more fixing parts 140 provided on its rear surfaces 110c, 120c, and 130c. The fixing parts 140 may include those that fasten the lower die block 130 to the intermediate die block 120 and those that fasten the intermediate die block 120 to 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, thereby allowing the upper die block 110, the intermediate die block 120, and the lower die block 130 to be assembled together.

[0060] The upper die block 110, the intermediate die block 120, and the lower die block 130 are not necessarily limited to the embodiments described above. For example, they can also be configured as vertical dies with the direction of discharge of the electrode active material slurry upward (Y direction) and the rear surfaces 110c, 120c, and 130c as the bottom surfaces.

[0061] Die blocks 110, 120, and 130 are made from materials such as SUS. Easily processed materials such as SUS420J2, SUS630, SUS440C, SUS304, and SUS316L can be used. SUS has the advantages of being easy to process, inexpensive, highly corrosion-resistant, and able to be manufactured in desired shapes at low cost.

[0062] The upper die block 110 is positioned to face the first surface 120a, which is the upper surface of the intermediate die block 120, which is horizontal to the bottom surface. The upper slot 101 is formed between the intermediate die block 120 and the upper die block 110 at the point where they face each other. An upper shim 300 may be interposed between the intermediate die block 120 and the upper die block 110, creating a gap between them. This forms the upper slot 101, which corresponds to a passage through which the first coating liquid 150 can flow. In other words, the upper shim 300 is provided between the upper die block 110 and the intermediate die block 120, forming 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 shim 300. The thickness of the upper shim 300 can be approximately 1 mm. For example, when coating an electrode active material slurry containing 40-80% solid content to a thickness of 70-300 μm, the thickness of the upper shim 300 can be 0.5 mm to 1.5 mm.

[0063] As shown in Figure 5, the upper shim 300 has at least one region cut open and includes at least one first opening 310, and the intermediate die block 120 and the upper die block 110 are interposed only in the remaining portion of the edge regions of each opposing surface, excluding one side. As a result, the circumferential direction is blocked except in front of the upper slot 101, and the 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 is the area formed by the separation between the upper die lip 111 and the intermediate die lip 121.

[0064] For reference, the upper shim 300 can also be made of a sealing material, as it also functions as a gasket to prevent the first coating liquid 150 from leaking into the gap between the upper die block 110 and the intermediate die block 120, except in the area where the upper discharge port 101a is formed. The upper shim 300 is made of plastic or metal, for example, but the present invention is not limited thereto. The upper shim 300 is made of resin sheets such as Teflon® or polyester, or metal sheets such as copper or aluminum. The upper shim 300 can also be made of SUS material, similar to the die blocks 110, 120, and 130. The upper shim 300 can be fixed to the upper die block 110 or the intermediate die block 120 by screw, for example.

[0065] Furthermore, the intermediate die block 120 has a first manifold 155 with a predetermined depth on its first surface 120a, which is the surface facing the upper die block 110, and which communicates with the upper slot 101. Although not shown in the figures, such a first manifold 155 is connected to an externally provided first coating liquid 150 supply chamber and supply pipe to receive the first coating liquid 150. The first coating liquid 150 is supplied from the outside along a pipe-shaped supply pipe, and once the first manifold 155 is completely filled, the flow of the first coating liquid 150 is guided along the upper slot 101 which communicates with the first manifold 155, and discharged to the outside through an upper discharge port 101a which communicates with the upper slot 101. In another example, the first manifold 155 may be provided on the surface 110b of the upper die block 110 that faces the intermediate die block 120.

[0066] The lower die block 130 is the lowest block among the blocks that make up the slot die coater 100, and has a shape inclined such that the surface 130b facing the intermediate die block 120 is inclined at an angle of approximately 20° to 60° with respect to the bottom surface 130d.

[0067] The lower slot 102 can be formed between the lower die block 130 and the intermediate die block 120 at the points where they face each other. By interposing a lower shim 400 between the lower die block 130 and the intermediate die block 120, a gap is created between them, thereby forming the lower slot 102, which corresponds to a passage through which the second coating liquid 160 can flow. In other words, the lower shim 400 is provided between the intermediate die block 120 and the lower die block 130 to form the lower slot 102. In this case, the thickness of the lower shim 400 determines the vertical width (Y direction, slot gap) of the lower slot 102. The thickness of the lower shim 400 can be approximately 1 mm. For example, when coating with an electrode active material slurry containing 40-80% solid content to a thickness of 70 μm-300 μm, the thickness of the lower shim 400 may be 0.5 mm-1.5 mm.

[0068] As shown in Figure 5, the lower shim 400 may also be interposed in the remaining portion of the edge regions of the opposing faces of the lower die block 130 and the intermediate die block 120, excluding one side, with at least one region cut open and containing at least one second opening 410. As a result, the lower discharge port 102a, from 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 we define the tip of the lower die block 130 as the lower die lip 131, in other words, the lower discharge port 102a can be said to be the area formed by the separation between the lower die lip 131 and the intermediate die lip 121.

[0069] Similarly, the lower shim 400 can also be made of a sealing material, as it also functions as a gasket to prevent the second coating liquid 160 from leaking into the gap between the lower die block 130 and the intermediate die block 120, except in the area where the lower discharge port 102a is formed. The lower shim 400 can also be made of plastic or metal, for example, but the present invention is not limited thereto. The lower shim 400 can be, for example, a resin sheet such as Teflon® or polyester, or a metal sheet such as copper or aluminum. The lower shim 400 can also be made of SUS material, similar to the die blocks 110, 120, and 130. The lower shim 400 can be fixed to the intermediate die block 120 or the lower die block 130 by screw, for example.

[0070] The lower die block 130 has a second manifold 165 with a predetermined depth on the surface 130b facing the intermediate die block 120 and communicating with the lower slot 102. Although not shown, such a second manifold 165 is connected by a supply pipe to an externally provided second coating liquid supply chamber (not shown) to receive the second coating liquid 160. When the second manifold 165 is completely filled with the second coating liquid 160, the flow of the second coating liquid 160 is guided along the lower slot 102 and discharged to the outside through a lower discharge port 102a communicating with the lower slot 102. In another example, the second manifold 165 may be provided on the surface 120b of the intermediate die block 120 facing the lower die block 130.

[0071] The upper slot 101 and the lower slot 102 are at a certain angle, which is approximately 30° to 60°. The upper slot 101 and the lower slot 102 intersect at one point, and the upper discharge port 101a and the lower discharge port 102a can be provided near this intersection point. This allows the discharge points of the first coating liquid 150 and the second coating liquid 160 to be concentrated at approximately one point. As a result, 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.

[0072] With a slot die coater 100 having such a configuration, a rotatable coating roll 500 is positioned in front of the slot die coater 100, and by rotating the coating roll 500, the substrate 200 to be coated is moved in the MD direction, and the first coating liquid 150 is discharged onto the substrate 200 through the upper discharge port 101a and applied, and the second coating liquid 160 is discharged onto the substrate 200 through the lower discharge port 102a and applied.

[0073] 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.

[0074] The slot die coater 100 allows the second coating liquid 160 and the first coating liquid 150 to be continuously brought into contact with the surface of the substrate 200, thereby coating the substrate 200 in a double layer. Alternatively, by alternately supplying and interrupting the second coating liquid 160 and the first coating liquid 150, a pattern coating can be formed intermittently on the substrate 200. Preferably, the second coating liquid 160 and the first coating liquid 150 are discharged simultaneously to coat in a double layer. In order to manufacture high-energy-density secondary batteries, the thickness of the electrode active material layer, which was about 130 μm, has gradually increased to 300 μm. When a thick electrode active material layer is formed using a conventional slot die coater 10 as shown in Figure 1, the migration of the binder and conductive material in the active material slurry deteriorates during drying, resulting in the production of an uneven final electrode. To solve this problem, coating is performed twice, by applying a thin layer of the electrode active material layer and drying it, and then applying another layer and drying it again, but this has the disadvantage of taking a long time. According to the present invention, by using a slot die coater 100 having two slots, the second coating liquid 160 and the first coating liquid 150 can be discharged simultaneously, and a thick electrode active material layer can be formed at once, thereby improving both electrode performance and productivity.

[0075] In particular, the slot die coater 100 is characterized by the fact that the shapes of the upper shim 300 and the lower shim 400 are different from each other, which makes it possible to improve the profile of the edge portion of the electrode active material layer.

[0076] Figure 6 is a plan view of the upper and lower shims included in a slot die coater according to one embodiment of the present invention, and Figure 7 is a partially enlarged view of the lower shim included in the slot die coater according to one embodiment of the present invention, which is an enlargement of part A in Figure 6.

[0077] First, referring to Figure 6, the upper shim 300 includes at least one first opening 310, and the lower shim 400 includes a second opening 410 in a position corresponding to the first opening 310. The second opening 410 includes a section SA at its front end adjacent to the lower discharge port 102a that is narrower than the first opening 310. 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 narrower than D1. The section SA with a width D2 that is narrower than D1 is part of the second opening 410, and the width of the remaining section of the second opening 410 is D1, which may be the same as the width of the first opening 310.

[0078] The upper shim 300 and the lower shim 400 determine the coating width of the coating layer applied on the substrate 200, the number of first openings 310 and second openings 410 determines the number of lanes, i.e., the number of patterns, and the size of the first openings 310 and second openings 410 can affect the coating width. In the illustrated example, there is one first opening 310 and one second opening 410, but by including multiple first openings 310 and second openings 410, a striped pattern coating layer can also be formed on the substrate 200.

[0079] More specifically, the upper shim 300 includes a base first portion 320 and at least two second portions 330 extending from the first portion 320, the second portions 330 being connected to the same side of the first portion 320 and extending in the same direction (X direction), and the space between the second portions 330 is defined as the first opening 310. In particular, in this embodiment, the width of the first opening 310 is constant at D1. The first coating liquid 150 can be discharged through the first opening 310.

[0080] The first part 320 and the second part 330 can be formed as a single unit. That is, there are no gaps or separations between the first part 320 and the second part 330. Therefore, it is possible to prevent unwanted flow of the first coating liquid 150 between the first part 320 and the second part 330.

[0081] The first part 320 is the portion of the upper shim 300 that is located at the rear of the upper die block 110. At least two second parts 330 are required to interpose the upper shim 300 in the remaining portion of the edge regions of the opposing surfaces of the upper die block 110 and the intermediate die block 120, excluding one side.

[0082] The second portion 330 extends toward the upper discharge port 101a, i.e., in the X direction. That is, the second portion 330 is also the portion of the upper shim 300 that extends toward the front part of the upper die block 110. If the number of second portions 330 is further increased, more lanes can be created on the substrate 200 to which the first coating liquid 150 can be discharged, and more patterns can be arranged and formed at once. That is, stripe pattern coating can be performed. However, the present invention is not limited by the number of second portions 330. The second portion 330 corresponds to the shim rib 61 of the conventional shim 60 in Figure 3.

[0083] The lower shim 400 includes a base third portion 420 and at least two fourth portions 430 extending from the third portion 420, the fourth portions 430 being connected to the same side of the third portion 420 and extending in the same direction (X direction), the space between the fourth portions 430 being defined as a second opening 410, and a flow rate increasing portion 440 being formed inside the lower shim 400 at the rear end of the second opening 410, having a width D1 greater than the width D2 of the front end of the second opening 410, thereby increasing the flow rate of the second coating liquid 160, and having a different shape from the upper shim 300. The second coating liquid 160 can be discharged through the second opening 410, and the side loading can be increased due to the presence of the flow rate increasing portion 440.

[0084] The third portion 420 and the fourth portion 430 can be formed integrally. That is, there is no gap or separation between the third portion 420 and the fourth portion 430. Therefore, it is possible to prevent the flow of unwanted second coating liquid 160 between the third portion 420 and the fourth portion 430.

[0085] The third portion 420 is the portion of the lower shim 400 that is located at the rear of the lower die block 130. At least two fourth portions 430 are required to interpose the lower shim 400 in the remaining portion of the edge regions of the opposing faces of the lower die block 130 and the intermediate die block 120, excluding one side.

[0086] The fourth portion 430 extends toward the lower discharge port 102a, i.e., in the X direction. That is, the fourth portion 430 is also the portion of the lower shim 400 that extends toward the front part of the lower die block 130. If the number of fourth portions 430 is further increased, more lanes can be created on the substrate 200 to which the second coating liquid 160 can be discharged, and more patterns can be arranged and formed at once. That is, stripe pattern coating can be performed. However, the present invention is not limited by the number of fourth portions 430. The fourth portion 430 corresponds to the shim rib 61 of the conventional shim 60 in Figure 3.

[0087] In order to form a flow rate increasing section 440 in the lower shim 400, the width L of the fourth section 430 can be configured to change toward the rear end. For example, in order to form the flow rate increasing section 440, the side surface of the fourth section 430 can be formed in a tapered shape. In this case, the tapered shape can be of various shapes, such as curved, straight, stepped, or a combination thereof, as shown in Figures 7 and 8, for example.

[0088] First, referring to Figure 7, the width of the fourth section 430 is constant at a first width a from the front end to the rear end of the second opening 410 up to the first position AA, then decreases to a second width b from the inclined surface 435 down to the second position BB, and below that, it may be constant at the second width b. The length from the front end of the lower shim 400 to the first position AA is c, and the length from the first position AA to the second position BB is shown as d.

[0089] In the example shown in Figure 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 the same, the angle (α) of the inclined surface 435 becomes 45°. The angle (α) of such an inclined surface 435 is an adjustable part to improve the loading deviation, and sliding can also be improved by adjusting ab, c, d, etc. Furthermore, ab, c, d, etc. can be determined by considering the sliding improvement effect and the risk of fat edge formation.

[0090] The angle (α) of the inclined surface 435 can be 25° to 70° with respect to the side of the fourth section 430 or the discharge direction (X direction). If the angle (α) of the inclined surface 435 is less than 25°, the length of the flow rate increasing section 440 will be shortened, which may reduce the sliding improvement effect. If the angle (α) of the inclined surface 435 is greater than 70°, it is undesirable because it may cause abrupt flow rate changes on the surface connected to the inclined surface 435, which may affect the discharge pressure.

[0091] Furthermore, in correspondence with such a lower shim 400, the width of the second portion 330 in the upper shim 300 may be constant at the second width b.

[0092] The structure in Figure 7 can be considered as a structure in which a projection 450 is further formed on the side surface of the fourth portion 430 at the front end of the second opening 410. Furthermore, the projection 450 can be said to have a right-angled trapezoidal shape (a shape combining a rectangle and a right-angled triangle).

[0093] Next, as shown in Figure 8, the width of the fourth portion 430 can decrease linearly from the front end to the rear end of the second opening 410. The width of the fourth portion 430 is a first width a at the front end of the second opening 410, decreases to a second width b by the inclined surface 435 towards the rear end up to a second position BB, and can remain constant at the second width b thereafter. The structure in Figure 8 can also be considered as a structure in which a projection 455 is further formed on the side surface of the fourth portion 430 at the front end of the second opening 410. Furthermore, it can be said that the projection 455 has a right-angled triangular shape.

[0094] The sliding improvement effect can be adjusted by adjusting the shape and size of the protrusions 450 and 455. Increasing the size of the protrusions 450 and 455 will increase their impact on the electrode active material layer profile. To achieve a specified coating width, simply increasing the size of the protrusions 450 and 455 is not sufficient; the size of the protrusions 450 and 455 must be adjusted while further considering the physical properties of the coating solution.

[0095] Figure 9 shows a cross-section of the electrode plate for a secondary battery in the TD direction when the electrode active material slurry is coated using the lower layer shim 400 shown in Figure 7.

[0096] Referring to Figure 9, an increase in flow rate in the side portion can cause the edge portion of the electrode active material layer to exhibit a further increase in thickness compared to the center portion, similar to the side ring R'.

[0097] When coating the electrode active material slurry using the upper layer shim 300 as shown in Figure 6, the cross-section of the secondary battery electrode plate in the TD direction may be the same as that shown in Figure 3.

[0098] The present invention also proposes a method for manufacturing an electrode plate for a secondary battery, which includes 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 substrate 200 on the lower coating layer 160a using a first coating liquid 150.

[0099] The first coating solution 150 and the second coating solution 160 may be electrode active material slurries having different types of active materials or binder content. 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.

[0100] At this time, by adjusting the spacing between the upper slot 101a of the slot die coater 100 and the substrate 200, and the spacing between the lower slot 102a of the slot die coater 100 and the substrate 200, the width (expanded width) of the first coating liquid 150, which is wider than the width D1 of the first opening 310, and the width of the second coating liquid 160, which is wider than the width D2 of the second opening 410, can be adjusted. A narrower spacing results in a wider expanded width, and a wider spacing results in a narrower expanded width.

[0101] Figure 10 shows a cross-section in the TD direction of an electrode plate for a secondary battery manufactured according to the present invention. Referring to Figure 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.

[0102] Since the slot die coater 100 of the present invention coats the electrode active material layer 600 using both an upper shim 300 and a lower shim 400, the cross-section of the electrode active material layer 600 formed on the substrate 200 in the TD direction can be improved as shown in Figure 11.

[0103] Figure 11 shows a cross-sectional view in the TD direction of an electrode plate for a secondary battery coated with an electrode active material slurry using the slot die coater according to the present invention.

[0104] Referring to FIG. 11, when the electrode active material layer 600 is coated on the substrate 200 using both the upper shim 300 and the lower shim 400 by the slot die coater 100 according to the present invention, the cross-section of the electrode active material layer 600 in the TD direction can be confirmed. As a result of combining the cross-section profile in the TD direction by the upper shim 300 (for example, the schematic of sliding as shown in FIG. 3) and the cross-section profile in the TD direction by the lower shim 400 (the schematic of side ringing as shown in FIG. 9), as shown in FIG. 11, it can be seen that the thickness profile of the electrode active material layer 600 has been significantly improved in sliding compared to the conventional profile as shown in FIG. 3.

[0105] According to the present invention, since the electrode active material layer 600 is coated using both the upper shim 300 and the lower shim 400 by the slot die coater 100, the flow rate of the side portion is increased, and while the lower coating layer 160a is formed on the substrate 200 by the second coating liquid 160, an upper coating layer 150a is formed on the lower coating layer 160a by the first coating liquid 150 on the substrate 200, and as a result, the step of pushing the portion where the flow rate of the side portion has increased is performed, so that the thickness profile of the electrode active material layer 600 can be improved compared to the conventional one.

[0106] Particularly, by using the lower shim 400 in which the 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' < SL). Further, compared to the thickness at the point where the thickness change starts to become gentle in the sliding portion S of the conventional electrode active material layer as shown in FIG. 3, the thickness at the point where the thickness change starts to become gentle in the sliding portion S' of the electrode active material layer 600 coated on the substrate 200 increases. Therefore, the profile of the sliding portion S' is improved.

[0107] Thus, according to the present invention, by using an upper shim 300 and a lower shim 400 of different shapes, the general shape of the edge portion of the electrode active material layer 600 can be complemented by each other. The second opening 410 of the lower shim 400 includes a section SA at its front end adjacent to the lower discharge port 102a, which is narrower than the first opening 310 of the upper shim 300. Inside the second opening 410 of the lower shim 400 is a flow rate increasing section 440. The lower shim 400 increases the flow rate of the side portion of the second coating liquid 160, so if only the lower shim 400 is used, a general shape will be formed that creates a side ring R' at the end. The upper shim 300 can form an upper coating layer 150a that can press down on and cover the lower coating layer 160a formed by the lower shim 400. When only the upper shim 300 is used, a general shape that causes sliding at the edges is formed. However, as a result of the mutual complementarity of the sliding caused by the upper shim 300 and the side ring R' caused by the lower shim 400, in the electrode active material layer 600 formed up to the upper coating layer 150a on the lower coating layer 160a, a sliding portion S' with a reduced sliding length SL' at the edge can be formed compared to the conventional method. Furthermore, no side rings are generated in the electrode active material layer 600.

[0108] On the other hand, Figure 3 shows the electrode profile of a slot die coater 10 using a conventional shim 60. If two identical conventional shims 60 were used as the upper and lower shims when configuring a dual slot die coater as in the present invention, the electrode profile would be further deteriorated. Therefore, in the case of a dual slot die coater like the present invention, the effect of using a combination of upper shim 300 and lower shim 400 having different shapes becomes significant.

[0109] Figure 12 shows a cross-sectional view 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.

[0110] Figure 12 shows the electrode profile when, for example, two identical conventional shims 60 are applied to the upper and lower shims, and an electrode active material layer 80 is formed on the current collector 20. As explained in Figure 3, with conventional shims 60, sliding sections S and side rings R are generated, and if upper and lower shims of the same shape are used, the same general shape is added, resulting in an electrode profile that is either very sliding as shown in Figure 12(a) or side rings as shown in Figure 12(b). In particular, if shims to increase side flow are applied to both the upper and lower shims, side rings will be severely generated as shown in Figure 12(b).

[0111] Thus, it should be fully understood that, due to the highly specialized nature of this invention, which applies shims of different shapes to a dual-slot die coater, the electrode profile can be significantly improved compared to the electrode profile in Figure 12, as shown in Figure 11.

[0112] By using the slot die coater 100 including the upper shim 300 and lower shim 400 described above, the electrode active material layer can be formed stably. According to the present invention, the coating width, loading amount, and sliding can be controlled, resulting in excellent quality for the coating layer and electrode active material layer formed by the present invention. For example, the thickness of the coating layer along the width direction of the substrate 200 becomes uniform regardless of position, and the sliding section can be formed into a desired shape. As a result, according to the present invention, the coating layer, and especially the electrode active material layer, can be formed stably without causing pattern defects.

[0113] For example, by coating a positive electrode active material slurry using a slot die coater 100, this can be applied to the manufacture of a positive electrode plate for a secondary battery.

[0114] The positive electrode plate includes a current collector and a positive electrode active material layer formed on the surface of the current collector. According to the present invention, the positive electrode active material layer can be formed on one surface of the current collector, or on the top and back surfaces by sequential coating.

[0115] The current collector is made of an electrically conductive material such as Al or Cu, and can be an appropriate material depending on the polarity of the current collector electrode known in the field of secondary batteries. The positive electrode active material slurry may further contain one or more of a plurality of positive electrode active material particles, a conductive material, and a binder. The positive electrode active material slurry may also further contain various additives for the purpose of complementing or improving the electrochemical properties.

[0116] The active material is not limited to a specific composition as long as it can be used as the positive electrode active material for lithium-ion secondary batteries. Non-limiting examples include layered compounds such as lithium manganese composite oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), and lithium nickel oxide (LiNiO2), as well as compounds substituted with one or more transition metals and compounds with the chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, lithium copper oxide (Li2CuO2), vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, and 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 to 0.3), and the chemical formula LiMn 2-x M xThe present invention 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 part of the Li in the chemical formula is replaced with an alkaline earth metal ion, a disulfide compound, and a mixture of one or more of Fe2(MoO4)3. In the present invention, the positive electrode may include one or more polymer-based solid electrolytes, oxide-based solid electrolytes, and sulfide-based solid electrolytes as the solid electrolyte material.

[0117] Conductive materials can 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 materials are not particularly limited as long as they are conductive without causing a chemical change in the battery, and may include, for example, a mixture of one or more conductive materials selected from graphite such as natural graphite or artificial graphite, carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black, conductive fibers such as carbon fibers and metal fibers, metal powders such as carbon fluoride, aluminum, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive materials such as polyphenylene derivatives.

[0118] The binder is not particularly limited as long as it is a component that contributes to the bonding of the active material to the conductive material and 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 binder is usually included in an amount of 1 wt% to 30 wt%, or 1 wt% to 10 wt%, per 100 wt% of the electrode layer.

[0119] The negative electrode plate of a secondary battery can also be manufactured by coating a negative electrode active material slurry using the slot die coater 100 of the present invention. The negative electrode plate includes a current collector and a negative electrode active material layer formed on one surface or the top and back surfaces 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, conductive materials, and binders. The negative electrode active material slurry may also further include various additives for the purpose of complementing or improving electrochemical properties.

[0120] The negative electrode active material is a carbon material such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotubes, carbon nanohorns, lithium metal material, alloy materials such as silicon and tin, Nb2O5, Li5Ti4O 12 Oxide-based materials such as TiO2, or composites thereof, can be used. For the negative electrode, the conductive material, binder, and current collector can be referenced from the information provided for the positive electrode.

[0121] In particular, as described above, by making the type of active material or the binder content of the first coating liquid 150 and the second coating liquid 160 different from each other, it is possible to manufacture a negative electrode plate with desired characteristics or to control the characteristics of the negative electrode plate. If the binder content differs between the first coating liquid 150 and the second coating liquid 160 while maintaining the same solid content, the active material content can also be made different between the first coating liquid 150 and the second coating liquid 160. For example, by increasing the binder content of the second coating liquid 160 and decreasing the binder content of the first coating liquid 150, the lower coating layer 160a can be well adhered to the substrate 200, and the upper coating layer 150a can be formed on top of it. Since the upper coating layer 150a can contain a higher amount of active material than the lower coating layer 160a, the capacity of the secondary battery can be further increased. Furthermore, by making the second coating solution 160 contain natural graphite active material and the first coating solution 150 contain artificial graphite active material, the characteristics of the negative electrode plate can be adjusted to appropriately utilize the unique properties of each active material.

[0122] By using the slot die coater 100 of the present invention, sliding can be improved, preventing the discharge capacity of the positive electrode from exceeding the discharge capacity of the negative electrode, and ensuring lithium deposition and cell safety. Furthermore, electrode plates manufactured using the method for manufacturing electrode plates for secondary batteries according to the present invention can be manufactured as electrode assemblies and incorporated into cylindrical secondary batteries. In particular, such cylindrical secondary batteries can be manufactured as large cylindrical secondary batteries with a form factor of 4680 or more. The size of the electrode plates can be varied according to the size of the jelly roll type electrode assembly to be manufactured, and consequently, the size of the cylindrical secondary battery to be manufactured. The size of the electrode plates included in a large cylindrical secondary battery with a form factor of 4680 must be larger than the size of the electrode plates 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 manufacturing such large electrode plates.

[0123] Here, form factor refers to a value representing the diameter and height of a cylindrical secondary battery. Examples of cylindrical secondary batteries that can be manufactured by the slot die coater 100 according to the present invention include 4611 cells, 4875 cells, 4811 cells, 4880 cells, and 4680 cells. In the numerical value indicating 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 cell's cross-section is circular.

[0124] Preferably, the form factor of the cylindrical secondary battery that can be manufactured is 4680, and the electrode plates obtained as described above are included in a jelly roll type electrode assembly contained in such a cylindrical secondary battery, with a width of 60-110 mm and a length of 3-5 m for one electrode plate. The upper shim 300 and lower shim 400 can have dimensions that allow for the manufacture of electrode plates of such size. Furthermore, by further increasing the number of second parts 330 and fourth parts 430 corresponding to shim ribs, electrode active material layer patterns can be simultaneously arranged in a stripe pattern along multiple lanes on a single substrate 200, and then each can be utilized as an electrode plate by slitting along the blank area between two adjacent electrode active material layer patterns.

[0125] The following describes the manufacturing of electrode plates according to the embodiments and comparative examples of the present invention, and the results of comparing them.

[0126] Sample #1 was the case where the lower shim 400 as shown in Figure 6 was applied to both the upper and lower shims; Sample #2 was the case where the upper shim 300 as shown in Figure 6 was applied to both the upper and lower shims (same as Figure 12); Sample #3 was the case where the upper shim 300 from Figure 6 was applied to the upper shim and the lower shim 400 from Figure 6 was applied to the lower shim (corresponding to an embodiment of the present invention); and Sample #4 was the case where the lower shim 400 from Figure 6 was applied to the upper shim and the upper shim 300 from Figure 6 was applied to the lower shim (the upper / lower shim positions are reversed from the embodiment of the present invention). The electrode profiles were measured and the sliding lengths were compared.

[0127] The coating width is designed to be 230mm, and the loading is 367mg / 25cm. 2 The upper layer's expansion width was set to 3 mm, and the lower layer's expansion width was also set to 3 mm. The lower layer shim 400 had a protrusion 450. At this time, ab was 4 mm, c was 2 mm, and the angle (α) was 45°. The first coating liquid 150 and the second coating liquid 160 were electrode active material slurries containing 53% solid content. The thickness of the lower layer shim 400 and the upper layer shim 300 was set to 0.6 mm. The length from the front end to the rear end of the upper layer shim 300 and the lower layer shim 400 was 169.9 mm, and the length from the left end to the right end of the upper layer shim 300 and the lower layer shim 400 was 449 mm.

[0128] Figure 13 shows the results of comparing the sliding lengths for samples #1 to #4.

[0129] In the case of sample #1, the sliding length was 2.4 mm, which was an improvement compared to the sliding length of 3.2 mm in sample #2, but still larger than the sliding length of 2.1 mm in sample #3, which is an embodiment of the present invention. In the case of sample #4, where the positions of the upper and lower shims are reversed compared to the embodiment of the present invention, the sliding length is long, similar to that of sample #2. Sample #3 showed a 34% reduction in sliding length compared to sample #2. Sample #3 showed the most favorable result in terms of sliding length.

[0130] Figure 14 shows a comparison of electrode profiles for samples #1 to #4. Sample #3 shows superiority in the shape of the sliding section compared to samples #1 and #4. In particular, sample #3 is significant because it does not produce side rings despite having an expansion width of 3 mm.

[0131] Although the present invention has been described above with reference to limited embodiments and drawings, it goes without saying that the present invention is not limited thereto, and various modifications and variations are possible within the equivalent scope of the technical idea of ​​the present invention and the claims described below by persons with ordinary skill in the art to which the present invention pertains. [Explanation of Symbols]

[0132] 100: Slot die coater 101: Top slot 102: Lower slot 110: Upper Die Block 120: Intermediate die block 130: Lower die block 200: Base material 300: Upper-level Sim 310: 1st opening 320: Part 1 330:Second part 400: Lower-level Sim 410:Second open section 420: 3rd part 430: 4th part 435: Inclined surface 440: Flow rate increasing section 450, 455: Protrusion 600: Electrode active material layer

Claims

1. Upper die block, middle die block, and lower die block, An upper shim is provided between the upper die block and the intermediate die block, forming an upper slot, Includes a lower shim provided between the intermediate die block and the lower die block, forming a lower slot, A slot die coater that dispenses and applies a first coating liquid onto a substrate through an upper discharge port communicating with the upper slot, and dispenses and applies a second coating liquid onto the substrate through a lower discharge port communicating with the lower slot, The upper shim includes at least one first open portion, A slot die coater in which the lower shim includes a second opening at a position corresponding to the first opening, and the second opening includes a section at its front end adjacent to the lower discharge port that is narrower than the first opening.

2. The slot die coater according to claim 1, wherein the upper shim includes a base first portion and at least two second portions extending from the first portion, the second portions being connected to the same side of the first portion and extending in the same direction, the space between the second portions being defined as the first open portion, and the width of the first open portion being constant.

3. The slot die coater according to claim 2, wherein the lower shim includes a base third portion and at least two fourth portions extending from the third portion, the fourth portions being connected to the same side of the third portion and extending in the same direction, the space between the fourth portions being defined as the second open portion, which is wider than the width of the front end of the second open portion, and a flow rate increasing portion being formed inside the lower shim at the rear end of the second open portion for increasing the flow rate of the second coating liquid.

4. The slot die coater according to claim 3, wherein the width of the fourth portion is configured to change toward the rear end toward the rear end of the second opening in order to form the flow rate increasing portion.

5. The slot die coater according to claim 3, wherein the side surface of the fourth portion is tapered in order to form the flow rate increasing portion.

6. The slot die coater according to claim 3, wherein the width of the fourth portion is constant as a first width from the front end of the second opening toward the rear end of the second opening to a first position, decreases to a second width by the inclined surface toward the rear end to a second position, and remains constant as the second width up to the third portion.

7. The slot die coater according to claim 6, wherein the angle of the inclined surface is 25° to 70°.

8. The slot die coater according to claim 7, wherein the width of the second portion is constant at the second width.

9. The slot die coater according to claim 3, wherein the width of the fourth portion decreases linearly in the direction toward the rear end from the front end of the second opening toward the rear end of the second opening.

10. The slot die coater according to claim 1, wherein the lower shim includes a base third portion and at least two fourth portions extending from the third portion, the fourth portions being connected to the same side of the third portion and extending in the same direction, the space between the fourth portions being defined as the second open portion, and the front end of the second open portion having a projection formed on the side of the fourth portion.

11. The slot die coater according to claim 10, wherein the protruding portion is in the shape of a right triangle or a right trapezoid.

12. The slot die coater according to claim 1, wherein the first coating liquid and the second coating liquid are different types of coating liquids.

13. The slot die coater according to claim 1, wherein the first coating liquid and the second coating liquid have a viscosity of 4000 cps to 6000 cps.

14. The steps include increasing the flow rate in the side section and forming a lower coating layer on the substrate with the second coating liquid, A method for manufacturing an electrode plate for a secondary battery, comprising the steps of simultaneously forming an upper coating layer on the lower coating layer on the substrate with a first coating liquid and pressing the portion where the flow rate of the side portion has increased.

15. The method for manufacturing an electrode plate for a secondary battery according to claim 14, wherein the first coating liquid and the second coating liquid are electrode active material slurries having different types of active material or binder content from each other.

16. A method for manufacturing an electrode plate for a secondary battery, comprising the steps of forming a lower coating layer on a substrate with a second coating liquid using a slot die coater according to any one of claims 1 to 13, and simultaneously forming an upper coating layer on the substrate with a first coating liquid on the lower coating layer.

17. The method for manufacturing an electrode plate for a secondary battery according to claim 16, wherein the second coating solution contains a natural graphite active material and the first coating solution contains an artificial graphite active material.

18. A method for manufacturing an electrode plate for a secondary battery according to claim 16, wherein the distance between the upper slot of the slot die coater and the substrate, and the distance between the lower slot of the slot die coater and the substrate are adjusted to adjust the width to which the first coating liquid spreads beyond the width of the first opening, and the width to which the second coating liquid spreads beyond the width of the second opening.

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