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

Abstract

A slot die coater for improving the profile of an edge portion of an electrode active-material layer is provided. The slot die coater according to the present invention comprises: a top die block, an intermediate die block and a bottom die block; an upper shim provided between the top die block and the intermediate die block so as to form an upper slot; and a lower shim provided between the intermediate die block and the bottom die block so as to form a lower slot, discharges a first coating liquid and applies same onto a substrate through an upper discharge port communicating with the upper slot thereto, and discharges a second coating liquid and applies same onto the substrate through a lower discharge port communicating with the lower slot, wherein 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, at the front end thereof adjacent to the lower discharge port, a section that has a smaller width than the first opening.

Description

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

[0001] The present invention relates to an apparatus and method for manufacturing an electrode plate for a secondary battery, and more particularly, 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 in a wet manner, and a method for manufacturing an electrode plate for a secondary battery using the same. This application claims priority to Korean Patent Application No. 10-2023-0093003, filed on July 18, 2023, and all contents disclosed in the specification and drawings of the said application are incorporated by reference herein.

[0002] With the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. These secondary batteries essentially include an electrode assembly, which is a power generation element. The electrode assembly has a structure in which a positive electrode, a separator, and an anode are laminated at least once. The positive and negative electrodes 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. To ensure uniform charge / discharge characteristics of the secondary battery, the positive active material slurry and negative active material slurry must be evenly coated onto the current collector, and a slot die coater has been conventionally used for this purpose.

[0003] Figure 1 is a schematic diagram showing an example of use of 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 on a current collector (20) using a slot die coater (10). In this method, an electrode active material slurry discharged from a slot die coater (10) is applied onto a current collector (20) that is conveyed 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 a core (60) is interposed between the two die blocks (40, 50) to form a slot, and an electrode active material slurry can be discharged through a discharge port (70) communicated 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 width of the slot. If a change in the coating width is required, various coating widths can be implemented by changing the shim (60) that determines the slot width. In particular, in order to ensure the safety of the electrode plate, the electrode active material slurry must be applied so that it can be evenly distributed on the current collector (20).

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

[0007] In the same core (60) as in Fig. 2, the spacing between the cores (61) is constant (W1=W2) regardless of the front or rear of the core (60), and the spacing between the cores (61) determines the coating width. By means of this core (60), an electrode active material layer can be formed on a current collector (20) along one 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, in which an electrode active material slurry is coated on one surface of the current collector, and illustrates a state in which sliding has occurred.

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

[0010] Such sliding can frequently occur at the ends of the retention section (both sides of the TD), where the electrode active material slurry is coated, and causes loading unevenness. Furthermore, sliding causes unevenness during rolling, and further results in the NP ratio, which is the ratio of the facing surfaces of the negative and positive active material layers, not satisfying the design conditions.

[0011] In particular, when a core (60) as illustrated in FIG. 2 is used, the discharge capacity ratio between the positive and negative electrodes in the flat section of the coating is maintained to be the same as the design value, but a sliding portion (S) is formed at the position where the edge of the coating layer of the positive plate and the edge of the coating layer of the negative plate face each other, causing the discharge capacity ratio to be distorted. In addition, since the risk increases when the positive electrode capacity is greater than the negative electrode capacity, there is also a problem that the position where the positive electrode flat portion and the negative electrode sliding portion (S) face each other becomes very vulnerable to stability. For this reason, it is necessary to control sliding in the electrode active material slurry coating process, and in particular, when coating a stripe pattern using multiple lanes, it is necessary to manage the shape control of the boundary surface (sliding portion), 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 a shape in which the thickness increases as the width distance from the point (Ps) where the coating portion starts, and then the thickness increase rate gradually decreases beyond a certain width distance, and the thickness has a flat shape with almost no increase and is close to a shape that 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 said to be the point where flattening starts in the electrode profile. For example, it can be said to be a point where the target coating layer thickness (H) is reached or close to within a certain % range.

[0013] However, in the method of manufacturing electrode plates for secondary batteries, in order to utilize both sides of the current collector, there are cases where an electrode active material layer is first coated on the top surface of the current collector and then on the back surface, which is called a sequential coating method. 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, the quality of the electrode on the top surface deteriorates, which is problematic. In addition, since the sliding of the edge of the top surface creates a part where the current collector is turned over when coating the back surface, the electrode active material slurry is concentrated on the edge when coating the back surface, and the side ring phenomenon in which the edge of the back surface protrudes upward after the process can be particularly problematic. Figure 3 also shows the electrode profile when a side ring (R) occurs in a dotted line. In particular, when the side flow rate is increased to manage the sliding length (SL) through shape control of the core (60), even if the increase in the side flow rate is severe, a side ring (R) occurs, limiting the improvement of the profile of the edge of the electrode active material layer.

[0014] The present invention has been created in consideration of the above-described problems, and the problem to be solved by the present invention is to provide a slot die coater for improving the edge profile of an electrode active material layer.

[0015] Another problem to be solved by the present invention is to provide a method for manufacturing an electrode plate for a secondary battery using such a slot die coater.

[0016] The slot die coater according to the present invention for solving the above technical problem is a slot die coater having a lower slot and an upper slot and applying a coating liquid by extruding it through the lower slot and the upper slot onto a continuously moving substrate surface.

[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 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 applied by ejecting it onto a substrate through an upper discharge port communicated with the upper slot, and a second coating liquid is applied by ejecting it onto the substrate through a lower discharge port communicated with the lower slot, wherein the upper shim includes at least one first opening, and the lower shim includes a second opening at a position corresponding to the first opening, wherein the second opening includes a section having a smaller width than the first opening at a front end adjacent to the lower discharge port.

[0018] Preferably, the upper core comprises a first portion that serves as a base 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 opening, and the width of the first opening being constant.

[0019] The lower core includes a third portion that serves as a base and at least two fourth portions that extend 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 opening, and a flow rate increasing portion that increases the flow rate of the second coating liquid by having a width greater than the width of the front end of the second opening may be formed on the inside of the lower core at the rear end of the second opening.

[0020] At this time, the width of the fourth portion may be configured differentially in the rear direction to form the flow rate increase portion.

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

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

[0023] And, the angle of the slope can be 25˚ to 70˚.

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

[0025] The width of the fourth portion may be linearly reduced from the front end of the second opening toward the rear end.

[0026] As another example, the lower core may include a third portion that serves as a base 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 opening, and a structure in which a protrusion is further formed on the front end of the second opening toward the side of the fourth portion.

[0027] The above protrusion may have a right triangle or right trapezoid shape.

[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 above intermediate 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.

[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 can form an angle of 30˚ to 60˚.

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

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

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

[0036] Another method for manufacturing an electrode plate for a secondary battery according to the present invention for solving the above-described other problem includes a 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 include a natural graphite active material and the first coating solution may include 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 at which the first coating liquid spreads can be adjusted to be larger than the width of the first opening and the width at which the second coating liquid spreads can be adjusted to be larger than the width of the second opening.

[0039] In electrode active material slurry coating using a slot die coater, sliding must be managed. Sliding can be detected by the widthwise thickness variation within the lane. To reliably achieve the target cell capacity, it is necessary to improve coating loading within the lane to reduce thickness variation.

[0040] According to one aspect of the present invention, a slot die coater is provided that includes a core capable of improving intra-lane loading deviation by more stably increasing loading at a desired location. The lower core 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 increasing the side flow rate by controlling the shape of the lower core to manage the sliding length, since the shape of the upper core is different from that of the lower core, the increase in the side flow rate does not overlap, so there is no concern about the occurrence of a side ring.

[0042] According to the present invention, by changing the shape of the lower core for the purpose of improving the coating deviation within the lane and providing a slot die coater that combines the shape of the lower core with an upper core of a different shape, the flow rate deviation of the electrode active material slurry, which is a coating liquid, is improved, and as a result, the coating liquid flow rate of the side portion within the lane is increased while not generating a side ring, thereby improving the edge portion 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 positive electrode does not exceed the discharge capacity of the negative electrode, thereby ensuring lithium deposition and cell safety.

[0044] According to the present invention, loading unevenness due to sliding can be prevented, and side ring occurrence can be reduced even when using a sequential coating method. That is, according to the present invention, in a sequential coating method where the back surface is coated after the top surface is coated, side ring occurrence 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 back surface is remarkably effective.

[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, both performance and productivity are excellent. 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 in that uniform application is possible even under high-speed or long-width application conditions.

[0046] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0047] Figure 1 is a schematic diagram showing an example of use of a slot die coater according to the prior art.

[0048] Figure 2 is a plan view of a heart according to the prior art.

[0049] Figure 3 shows a cross-section 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, and illustrates a state in which sliding has occurred.

[0050] Figure 4 is a schematic cross-sectional view of a slot die coater according to one embodiment of the present invention.

[0051] Figure 5 is a schematic exploded perspective view of a slot die coater according to one embodiment of the present invention.

[0052] 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.

[0053] FIG. 7 is a partially enlarged view of a lower core included in a slot die coater according to one embodiment of the present invention.

[0054] FIG. 8 is a partially enlarged view of another lower core included in a slot die coater according to one embodiment of the present invention.

[0055] Fig. 9 shows a cross-section of a TD direction electrode plate for a secondary battery when coating an electrode active material slurry using the lower core of Fig. 7.

[0056] Figure 10 is a cross-section in the TD direction of an electrode plate for a secondary battery manufactured according to the present invention.

[0057] 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.

[0058] 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.

[0059] Figure 13 shows the sliding length comparison results for samples #1 to #4.

[0060] Figure 14 shows the electrode profile comparison results for samples #1 to #4.

[0061] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, it should be noted that the terms and words used in this specification and claims should not be interpreted as limited to their typical or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of the term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only 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 modified examples may exist as of the time of this application.

[0062] 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 and coating a coating liquid in a double layer on a substrate. The 'substrate' described below is a current collector and the coating liquid is an 'electrode active material slurry'. The first coating liquid and the second coating liquid are both electrode active material slurries, and may refer to electrode active material slurries having the same or different compositions (types of active material, conductive material, and binder), contents (amounts of active material, conductive material, and binder) or physical properties. The slot die coater according to an embodiment of the present invention is optimized for manufacturing an electrode plate for a secondary battery by simultaneously or alternately applying 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 separator, and the first coating liquid and the second coating liquid may be organic materials having different compositions or physical properties. That is, if a thin film coating is required, the above-mentioned substrate and the first coating solution and the second coating solution may be any of them.

[0063] In this specification, 'front' refers to the direction in which the outlet is facing (X direction, MD direction), and 'back' refers to the opposite direction. 'Left / right' refers to the direction perpendicular to the direction in which the outlet is facing, and refers to the width direction of the slot (Z direction, TD direction).

[0064] 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.

[0065] 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 simultaneously or alternately coating two types of coating liquids, the same or different, on a substrate (200) through the upper slot (101) and the lower slot (102).

[0066] Referring to FIGS. 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, 130) can be assembled to each other through bolts, which are fastening members.

[0067] In Fig. 4, the slot die coater (100) is installed so that the direction (X direction) in which the electrode active material slurry, which is a coating liquid, is discharged is almost horizontal (approximately: ± 5 degrees).

[0068] The intermediate die block (120) is a block located in the middle of the blocks constituting the slot die coater (100), and is a block placed 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 the present embodiment has a right-angled triangle cross-section, but is not necessarily limited to this shape, and for example, the cross-section may be formed as an isosceles triangle.

[0069] The first surface (120a) of the intermediate die block (120) facing the upper die block (110) is placed almost horizontally, and the opposite surface (110d, i.e., the surface forming the upper surface of the outer surface of the slot die coater (100)) of the surface (110b) of the upper die block (110) facing the first surface (120a) is also placed almost horizontally. In this way, the first surface (120a) and the opposite surface (110d) are made almost parallel. In addition, the opposite surface (130d, i.e., the surface forming the lower surface of the 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 placed almost horizontally, and this surface becomes the bottom surface (130d, XZ plane).

[0070] The surfaces opposite to the direction in which the electrode active material slurry is discharged from the upper die block (110), the middle die block (120), and the lower die block (130), i.e., the rear surfaces (110c, 120c, 130c), are positioned almost vertically (Y direction).

[0071] Among the surfaces forming the outer surface of the slot die coater (100) in the upper die block (110) and the lower die block (130), which are the outermost die blocks, the upper surface (110d) of the upper die block (110) and the bottom surface (130d) of the lower die block (130) can be manufactured to be almost perpendicular to the rear surface (110c, 130c). In addition, the first surface (120a) of the intermediate die block (120) can be manufactured to be almost perpendicular to the rear surface (120c). In these die blocks (110, 120, 130), since the edges formed by the surfaces are configured at right angles, a right-angled portion exists in the cross section, and a vertical or horizontal plane can be used as a reference surface, so that the manufacturing and handling thereof are easy and precision is guaranteed. In addition, the combined state of the upper die block (110), the middle die block (120), and the lower die block (130) has an overall roughly rectangular parallelepiped shape, and only the front portion (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 roughly similar to a slot die coater having a single slot (e.g., 10 in FIG. 1), and thus can share a slot die coater stand, etc.

[0072] The slot die coater (100) may further include two or more fixing parts (140) provided on the rear surface (110c, 120c, 130c). The fixing parts (140) are provided to fasten between the lower die block (130) and the intermediate die block (120), and to fasten between the intermediate die block (120) and the upper die block (110). A plurality of fixing parts (140) may be provided along the width direction of the slot die coater (100). Bolts are fastened to the fixing parts (140), through which the upper die block (110), the intermediate die block (120), and the lower die block (130) may be assembled to each other.

[0073] The upper die block (110), the middle die block (120), and the lower die block (130) are not necessarily limited to the forms exemplified above, and for example, they may be configured as vertical dies with the direction of discharging the electrode active material slurry upward (Y direction) and the rear surface (110c, 120c, 130c) as the bottom surface.

[0074] Die blocks (110, 120, 130) are made of, for example, SUS. Materials that are easy to process, 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 being able to be manufactured into a desired shape at low cost.

[0075] The upper die block (110) is arranged to face the first surface (120a), which is the upper surface of the intermediate die block (120) that is horizontal to the bottom surface. The upper slot (101) is formed between the intermediate die block (120) and the upper die block (110) where they face each other. An upper shim (300) may be interposed between the intermediate die block (120) and the upper die block (110) to provide a gap therebetween. This forms an upper slot (101) corresponding 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) 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 shim (300). The thickness of the upper core (300) may be approximately 1 mm. For example, when coating with a thickness of 70 µm to 300 µm by applying an electrode active material slurry containing 40-80% solid content, the thickness of the upper core (300) may be 0.5 mm to 1.5 mm.

[0076] As illustrated in FIG. 5, the upper core (300) has at least one area cut out to include at least one first opening (310), and is interposed only in the remaining portion except for one side of the edge area of ​​the opposing surfaces of each of the intermediate die block (120) and the upper die block (110). Accordingly, the circumferential direction except for the front of the upper slot (101) is blocked, and the upper discharge port (101a) is formed only between the front end of the upper die block (110) and the front end of the intermediate die block (120). The front end of the upper die block (110) and the front end 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).

[0077] For reference, the upper shim (300) may be made of a material having sealing properties, as it 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 for the area where the upper discharge port (101a) is formed. The upper shim (300) may be made of, for example, plastic or metal, but the present invention is not limited thereto. The upper shim (300) may be a resin sheet such as Teflon or polyester, or a metal sheet such as copper or aluminum. The upper shim (300) may also be made of SUS, the same material as the die blocks (110, 120, 130). The upper shim (300) may be fixedly joined to the upper die block (110) or the intermediate die block (120) using, for example, screws.

[0078] In addition, the intermediate die block (120) has a first manifold (155) having a predetermined depth on the first surface (120a) facing the upper die block (110) and communicating 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 through 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 first coating liquid (150) is induced to flow along the upper slot (101) communicating with the first manifold (155) and is discharged to the outside through the upper discharge port (101a) communicating with the upper slot (101). As another example, the first manifold (155) may be provided on a surface (110b) of the upper die block (110) facing the middle die block (120).

[0079] The lower die block (130) is the block located at the lowest position among the blocks constituting the slot die coater (100), and has a shape in which the surface (130b) facing the middle die block (120) is inclined at an angle of approximately 20˚ to 60˚ with respect to the bottom surface (130d).

[0080] The lower slot (102) may be formed between the lower die block (130) and the intermediate die block (120) where they face each other. A lower shim (400) may be interposed between the lower die block (130) and the intermediate die block (120) to form a gap therebetween, thereby forming a lower slot (102) corresponding to a passage through which the second coating liquid (160) may 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) may be about 1 mm. For example, when coating with a thickness of 70 µm to 300 µm by applying an electrode active material slurry containing 40-80% of solid content, the thickness of the lower core (400) may be 0.5 mm to 1.5 mm.

[0081] As illustrated in FIG. 5, the lower core (400) may also include at least one second opening (410) by cutting out at least one area, and may be interposed in the remaining portion except for one side of the edge area of ​​the opposing surfaces of each 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) may 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). The tip of the lower die block (130) is defined as the lower die lip (131), and in other words, the lower discharge port (102a) may be formed by spacing out the lower die lip (131) and the intermediate die lip (121).

[0082] Likewise, the lower shim (400) may be made of a material having sealing properties, as it 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 for the area where the lower discharge port (102a) is formed. The lower shim (400) may also be made of, for example, plastic or metal, but the present invention is not limited thereto. The lower shim (400) may be a resin sheet such as Teflon or polyester, or a metal sheet such as copper or aluminum. The lower shim (400) may also be made of SUS, the same material as the die blocks (110, 120, 130). The lower shim (400) may be fixedly joined to the intermediate die block (120) or the lower die block (130) using, for example, screws.

[0083] The lower die block (130) has a second manifold (165) having a predetermined depth and communicating with the lower slot (102) on the surface (130b) facing the intermediate die block (120). 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 coating liquid (160) is full inside the second manifold (165), 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) of the intermediate die block (120) facing the lower die block (130).

[0084] The upper slot (101) and the lower slot (102) form a certain angle, which may be approximately 30˚ to 60˚. The upper slot (101) and the lower slot (102) intersect each other 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 solution (150) and the second coating solution (160) may be concentrated at approximately one point. Through this, the lower coating layer by the second coating solution (160) and the upper coating layer by the first coating solution (150) may be aligned up, down, left, and right to form a double layer.

[0085] According to the slot die coater (100) having such a configuration, a coating roll (500) that is provided to be rotatable is placed 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 the first coating liquid (150) is applied by being sprayed onto the substrate (200) through the upper discharge port (101a), and the second coating liquid (160) is applied by being sprayed onto the substrate (200) through the lower discharge port (102a).

[0086] 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 viscosities of 4000 cps to 6000 cps. The first coating solution (150) and the second coating solution (160) may be electrode active material slurries.

[0087] Through the slot die coater (100), the second coating solution (160) and the first coating solution (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 stop of the second coating solution (160) and the supply and stop of the first coating solution (150) can be alternately performed to intermittently form a pattern coating on the substrate (200). Preferably, the second coating solution (160) and the first coating solution (150) are discharged simultaneously to coat in a double layer. In order to manufacture a high-energy-density secondary battery, the thickness of the electrode active material layer, which was about 130 μm, is gradually increasing to reach 300 μm. When a thick electrode active material layer is formed using the conventional slot die coater (10) illustrated in FIG. 1, migration of the binder and conductive material in the active material slurry becomes severe during drying, resulting in an uneven final electrode. To solve this problem, if a coating is performed twice, such as by applying a thin layer of electrode active material, drying it, and then applying it again on top and drying it, there is a disadvantage in 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 solution (160) and the first coating solution (150) can be discharged simultaneously, so that a thick layer of electrode active material can be formed at once, thereby improving both electrode performance and productivity.

[0088] In particular, the slot die coater (100) is characterized by having different shapes of the upper core (300) and the lower core (400), through which the profile of the edge of the electrode active material layer can be improved.

[0089] 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 partially 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.

[0090] 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 smaller width than the first opening (310) at a front end 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 a 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).

[0091] 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 first openings (310) and second openings (410) determine 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 a plurality of first openings (310) and second openings (410) may be included to form a coating layer in the shape of a stripe pattern on the substrate (200).

[0092] More specifically, the upper core (300) includes a first portion (320) that serves as a base and at least two second portions (330) that extend 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 a first opening (310). In particular, in the present embodiment, the width of the first opening (310) is constant as D1. The first coating liquid (150) can be discharged through the first opening (310).

[0093] The first part (320) and the second part (330) may be formed integrally. That is, there is no gap or separation between the first part (320) and the second part (330). Accordingly, unnecessary flow of the first coating liquid (150) between the first part (320) and the second part (330) can be prevented.

[0094] The first part (320) is a part that is placed on the rear side 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 except for one side of the edge area of ​​the opposing surfaces of each of the upper die block (110) and the middle die block (120), at least two second parts (330) are required.

[0095] The second part (330) extends in the direction toward the upper discharge port (101a), i.e., in the X direction. That is, the second part (330) is a part that extends from the upper core (300) toward the front of the upper die block (110). If the number of second parts (330) increases, more lanes for discharging the first coating liquid (150) on the substrate (200) can be created, and more patterns can be formed side by side at once. That is, stripe pattern coating can be performed. However, the present invention is not limited by the number of second parts (330). The second part (330) corresponds to the core (61) of the conventional core (60) of FIG. 3.

[0096] The lower core (400) includes a third part (420) that serves as a base and at least two fourth parts (430) that extend from the third part (420), and the fourth parts (430) are connected to the same side of the third part (420) and extend in the same direction (X direction), and a space between the fourth parts (430) is defined as a second opening (410), and a flow rate increasing part (440) that increases the flow rate of the second coating liquid (160) by having a width (D1) greater than the width (D2) of the front end of the second opening (410) is formed on the inside of the lower core (400) at the rear end of the second opening (410), so that 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 since there is a flow rate increasing portion (440), the loading of the side portion can be increased.

[0097] The third part (420) and the fourth part (430) may be formed integrally. That is, there is no gap or separation between the third part (420) and the fourth part (430). Accordingly, unnecessary flow of the second coating liquid (160) between the third part (420) and the fourth part (430) can be prevented.

[0098] The third part (420) is a part that is placed on the rear side of the lower die block (130) in the lower core (400). In order for the lower core (400) to be interposed in the remaining part except for one side of the edge area of ​​the opposing surfaces of each of the lower die block (130) and the middle die block (120), at least two fourth parts (430) are required.

[0099] The fourth part (430) extends in the direction toward the lower discharge port (102a), that is, in the X direction. That is, the fourth part (430) is a part that extends toward the front of the lower die block (130) even in the lower core (400). If the number of fourth parts (430) increases, more lanes for discharging the second coating liquid (160) on the substrate (200) can be created, and more patterns can be formed side by side at once. That is, stripe pattern coating can be performed. However, the present invention is not limited by the number of fourth parts (430). The fourth part (430) corresponds to the core (61) of the conventional core (60) of FIG. 3.

[0100] The width (L) of the fourth portion (430) may be configured differentially in the rearward direction to form a flow rate increasing portion (440) in the lower core (400). For example, a tapered shape may be applied to the side surface of the fourth portion (430) to form the flow rate increasing portion (440). At this time, 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 illustrated in FIGS. 7 and 8, for example.

[0101] First, referring to FIG. 7, the width of the fourth portion (430) is constant as the first width (a) from the front end of the second opening (410) to the first position (AA) in the rearward direction, and decreases to the second width (b) in the rearward direction by the inclined surface (435) to the second position (BB), and may be constant as the second width (b) therebelow. The length from the front end of the lower core (400) to the first position (AA) is represented by c, and the length from the first position (AA) to the second position (BB) is represented by d.

[0102] In the example illustrated in Fig. 7, the inclined surface (435) is formed in a section that protrudes in the width direction by a width (ab) and advances in the direction of the lower discharge port (102a) by a length (d). If (ab) and d are the same, the angle (α) of the inclined surface (435) becomes 45° in this case. The angle (α) of the inclined surface (435) is an adjustable portion for improving loading deviation, and ab, c, d, etc. can also be adjusted to improve sliding. In addition, ab, c, d, etc. can be determined between the sliding improvement effect and the concern about the occurrence of a fat edge.

[0103] The angle (α) of the inclined surface (435) may be 25° to 70° with respect to the side surface of the fourth portion (430) or in the discharge direction (opposite to X). If the angle (α) of the inclined surface (435) is less than 25°, the length of the flow rate increasing portion (440) may be shortened, thereby reducing the sliding improvement effect. If the angle (α) of the inclined surface (435) is greater than 70°, a rapid change in flow rate may occur on the surface connected to the inclined surface (435), which may affect the discharge pressure, which is not preferable.

[0104] And in response to this lower core (400), the width of the second portion (330) in the upper core (300) can be constant as the second width (b).

[0105] The structure of Fig. 7 can be viewed as a structure in which a protrusion (450) is further formed on the side of the fourth portion (430) at the front end of the second opening (410). And the protrusion (450) can be said to have a right-angled trapezoidal shape.

[0106] Next, as illustrated in FIG. 8, the width of the fourth portion (430) may also linearly decrease from the front end of the second opening (410) toward the rear end. The width of the fourth portion (430) may be a first width (a) at the front end of the second opening (410), and may decrease to a second width (b) toward the rear end by the inclined surface (435) to a second position (BB), and may be constant at the second width (b) thereafter. The structural diagram of FIG. 8 can also be viewed as a structure in which a protrusion (455) is further formed on the side of the fourth portion (430) at the front end of the second opening (410). And here, the protrusion (455) may be said to have a right-angled triangle shape.

[0107] The sliding improvement effect can be controlled by adjusting the shape and size of the protrusions (450, 455). As the size of the protrusions (450, 455) increases, the influence on the electrode active material layer profile will increase. In order to implement a given coating width, the size of the protrusions (450, 455) cannot be simply increased, and the size of the protrusions (450, 455) can be controlled by taking into account the properties of the coating solution, etc.

[0108] Fig. 9 shows a cross-section of a TD direction of an electrode plate for a secondary battery when coating an electrode active material slurry using the lower core (400) of Fig. 7.

[0109] Referring to Fig. 9, the thickness of the edge portion of the electrode active material layer may increase more than that of the center portion, such as the side ring (R'), due to the increase in the flow rate of the side portion.

[0110] When coating an electrode active material slurry using an upper layer core (300) as illustrated in FIG. 6, the TD direction cross-section of the electrode plate for a secondary battery may be similar to FIG. 3.

[0111] In the present invention, a method for manufacturing an electrode plate for a secondary battery is also proposed, which includes a step of forming a lower coating layer (160a) on a substrate (200) with a second coating liquid (160) and simultaneously forming an upper coating layer (150a) on the lower coating layer (160a) on the substrate (200) with a first coating liquid (150), using a slot die coater (100).

[0112] 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 contents. For example, the second coating solution (160) may include a natural graphite active material, and the first coating solution (150) may include an artificial graphite active material.

[0113] 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. When the gap is narrow, the spreading width increases, and when the gap is large, the spreading width decreases.

[0114] 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).

[0115] 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.

[0116] 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.

[0117] 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 confirmed. As a result of combining the TD direction cross-section profile by the upper core (300) (for example, a shape in which sliding occurs as in FIG. 3) and the TD direction cross-section profile by the lower core (400) (for example, 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 as compared to the conventional profile as in FIG. 3.

[0118] 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 the slot die coater (100), and the side flow rate is increased to form the lower coating layer (160a) on the substrate (200) with the second coating liquid (160), and at the same time, the upper coating layer (150a) is formed on the lower coating layer (160a) with the first coating liquid (150) on the substrate (200), thereby performing the step of pressing the portion where the side flow rate is increased, so that the thickness profile of the electrode active material layer (600) can be improved compared to the prior art.

[0119] In particular, by using the lower core (400) in which the flow rate increasing portion (440) is formed, the sliding length (SL') of the electrode active material layer (600) applied 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.

[0120] According to the present invention, the edge shape of the electrode active material layer (600) can be complemented by using the upper core (300) and the lower core (400) of different shapes. The second opening (410) of the lower core (400) includes a section (SA) with a smaller width than the first opening (310) of the upper core (300) at the front end adjacent to the lower discharge port (102a). The inside of the second opening (410) of the lower core (400) includes a flow rate increasing section (440). The lower core (400) can increase the side flow rate of the second coating solution (160), so that if only the lower core (400) is used, a shape that generates a side ring (R') at the edge will be created. The upper core (300) can form an upper coating layer (150a) that can press down and cover the lower coating layer (160a) formed by the lower core (400). If only the upper core (300) is used, a mold that causes sliding at the edge can be created. However, as a result of the sliding by the upper core (300) and the side ring (R') by the lower core (400) complementing each other, 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') compared to the prior art can be formed at the edge. In addition, no side ring occurs in the electrode active material layer (600).

[0121] Meanwhile, Fig. 3 is an electrode profile by a slot die coater (10) using a conventional shim (60). If two identical conventional shims (60) are applied to the upper and lower shims while configuring a dual slot die coater like the present invention, the resulting electrode profile becomes worse. Therefore, in the case of a dual slot die coater like the present invention, the effect is remarkable when the upper shim (300) and the lower shim (400) are combined in different shapes.

[0122] 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.

[0123] FIG. 12 illustrates an electrode profile when, for example, two identical conventional cores (60) are applied to the upper and lower cores to form an electrode active material layer (80) on a current collector (20). As described in FIG. 3, according to the conventional core (60), a sliding portion (S) or a side ring (R) occurs, and if the upper and lower cores of the same shape are used, the same shape is added, so the electrode profile will result in very severe sliding as in FIG. 12 (a) or side rings as in FIG. 12 (b). In particular, if a core for the purpose of increasing side flow rate is applied to both the upper and lower cores, side rings will seriously occur as in FIG. 12 (b).

[0124] As such, it will be fully understood that the electrode profile of FIG. 11 can be significantly improved compared to the electrode profile of FIG. 12 due to the high degree of specificity of the present invention in applying different shaped cores to the dual slot die coater.

[0125] An electrode active material layer can be stably formed using a slot die coater (100) including the upper core (300) and lower core (400) described above. According to the present invention, since the coating width, loading amount, and sliding can be controlled, the quality of the coating layer and electrode active material layer formed according to the present invention is very excellent. For example, the thickness of the coating layer along the width direction of the substrate (200) can be made 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.

[0126] For example, it can be applied to the manufacture of a positive electrode plate of a secondary battery by coating a positive electrode active material slurry using a slot die coater (100).

[0127] 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, a positive electrode 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.

[0128] The above current collector exhibits electrical conductivity, such as Al, Cu, etc., and can be used appropriately depending on the polarity of current collector electrodes known in the secondary battery field. The cathode active material slurry may further include one or more of a plurality of cathode active material particles, a conductive agent, and a binder. In addition, the cathode active material slurry may further include various additives for the purpose of supplementing or improving electrochemical properties.

[0129] The active material is not limited to a specific component as long as it can be used as a positive electrode active material of a lithium ion secondary battery. Non-limiting examples thereof include layered compounds such as lithium manganese oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), 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; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; 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 to 0.3); chemical formula LiMn 2-x M x A lithium manganese composite oxide represented by O2 (wherein M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a part of the Li in the chemical formula is replaced with an alkaline earth metal ion; a disulfide compound; and Fe2(MoO4)3 may include one or a mixture of two or more thereof. In the present invention, the positive electrode may include at least one of a polymer-based solid electrolyte, an oxide-based solid electrolyte and a sulfide-based solid electrolyte as a solid electrolyte material.

[0130] The conductive material can be added typically in an amount of 1 wt% to 20 wt% based on the total weight of the mixture including the active material. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, it may include one or a mixture of two or more selected from the following conductive materials: 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 summer black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorinated carbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0131] 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 thereof include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers. The binder may typically be included in an amount of 1 wt% to 30 wt%, or 1 wt% to 10 wt%, relative to 100 wt% of the electrode layer.

[0132] A 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 surface and the back surface 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 agent, and a binder. In addition, the negative electrode active material slurry may further include various additives for the purpose of supplementing or improving electrochemical characteristics.

[0133] The above negative active material is a carbon material such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, carbon nanohorn, lithium metal material, alloy material such as silicon or tin, Nb2O5, Li5Ti4O 12 , oxide materials such as TiO2, or their composites can be used. For the negative electrode, the conductive material, binder, and current collector, refer to the content described for the positive electrode.

[0134] In particular, as mentioned above, by making the types of active materials or the binder contents of the first coating solution (150) and the second coating solution (160) different from each other, it is possible to manufacture a negative electrode plate having desired characteristics or to control the characteristics of the negative electrode plate. By making the binder contents of the first coating solution (150) and the second coating solution (160) different while maintaining the solid content the same, the active material contents of the first coating solution (150) and the second coating solution (160) can also be different. For example, by making the binder content of the second coating solution (160) higher and the binder content of the first coating solution (150) lower, the lower coating layer (160a) can be well attached to the substrate (200) and the upper coating layer (150a) can be formed thereon. The upper coating layer (150a) can contain a higher content of active material than the lower coating layer (160a), thereby further increasing the capacity of the secondary battery. In addition, the second coating solution (160) may include a natural graphite active material and the first coating solution (150) may include an artificial graphite active material, thereby controlling the characteristics of the negative electrode plate and appropriately utilizing the unique characteristics of each active material.

[0135] 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 precipitation and cell safety. In addition, 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 into a large cylindrical secondary battery having 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 having a form factor of 4680 should be larger than the size of the electrode plate included in a small cylindrical secondary battery having 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.

[0136] Here, the form factor refers to a value indicating 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, 4611 cells, 4875 cells, 4811 cells, 4880 cells, and 4680 cells. In the numerical value indicating the form factor, the first two numbers indicate the diameter of the cell, and the next two numbers indicate the height of the cell. The last number 0 is added to indicate that the cross-section of the cell is circular.

[0137] Preferably, the form factor of the cylindrical secondary battery that can be manufactured is 4680, and the electrode plate that can be 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 can manufacture an electrode plate of such a size. In addition, the number of the second part (330) and the fourth part (430) corresponding to the core can be further increased, and the electrode active material layer patterns can be simultaneously formed in a stripe shape along several lanes in parallel on one substrate (200), and then slitting can be performed along the non-coated portion between two adjacent electrode active material layer patterns, so that each can be utilized as an electrode plate.

[0138] Hereinafter, the results of manufacturing electrode plates according to the examples and comparative examples of the present invention and comparing them with each other will be described.

[0139] The case where the lower core (400) as shown in FIG. 6 was applied to both the upper core and the lower core was Sample #1, the case where the upper core (300) as shown in FIG. 6 was applied to both the upper core and the lower core was Sample #2 (same case as FIG. 12), the case where the upper core (300) of FIG. 6 was applied to the upper core and the lower core (400) of FIG. 6 was applied to the lower core was Sample #3 (corresponding to the embodiment of the present invention), and the case where the lower core (400) of FIG. 6 was applied to the upper core and the upper core (300) of FIG. 6 was applied to the lower core was Sample #4 (the upper core / lower core positions are opposite to those of the embodiment of the present invention) were used, and the electrode profiles were measured and the sliding lengths were compared.

[0140] The coating width is designed to be 230mm and the loading is 367mg / 25cm. 2, the upper layer spreading width was 3 mm, and the lower layer spreading width was 3 mm. The lower layer core (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 solution (150) and the second coating solution (160) were electrode active material slurries containing 53% solid content. The thicknesses of the lower layer core (400) and the upper layer core (300) were 0.6 mm. Each length from the front end to the rear end of the upper layer core (300) and the lower layer core (400) was 169.9 mm, and each length from the left end to the right end of the upper layer core (300) and the lower layer core (400) was 449 mm.

[0141] Figure 13 shows the sliding length comparison results for samples #1 to #4.

[0142] In the case of sample #1, the sliding length is 2.4 mm, which is an improved result compared to the sliding length of 3.2 mm of sample #2, but is longer than the sliding length of 2.1 mm of sample #3 according to the embodiment of the present invention. In the case of sample #4, which has the upper and lower core positions opposite to those of the embodiment of the present invention, the sliding length is as long as 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 advantageous result in terms of sliding length.

[0143] Figure 14 shows the results of a comparison of electrode profiles for Samples #1 to #4. Compared to Samples #1 and #4, Sample #3 exhibits superiority in sliding section shape. In particular, Sample #3 is significant in that no side ring occurs even though the spread width is 3 mm.

[0144] As described above, although the present invention has been described 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 idea of ​​the present invention and the equivalent scope of the claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0145] [Explanation of symbols]

[0146] 100: Slot die coater 101: Upper slot

[0147] 102: Lower slot 110: Upper die block

[0148] 120: Middle die block 130: Lower die block

[0149] 200: Base 300: Upper core

[0150] 310: First opening 320: First section

[0151] 330: Part 2 400: Lower layer

[0152] 410: Second opening 420: Third section

[0153] 430: Part 4 435: Slope

[0154] 440: Flow increase section 450, 455: Protrusion

[0155] 600: Electrode active material layer

Claims

1. Upper die block, middle die block and lower die block; An upper core formed between the upper die block and the middle die block to form an upper slot; and A lower core is provided between the middle die block and the lower die block to form a lower slot; A slot die coater that applies a first coating liquid onto a substrate by discharging it through an upper discharge port connected to the upper slot, and applies a second coating liquid onto the substrate by discharging it through a lower discharge port connected to the lower slot. The upper layer comprises at least one first opening, A slot die coater characterized in that the lower core includes a second opening at a position corresponding to the first opening, and the second opening includes a section having a smaller width than the first opening at a front end adjacent to the lower discharge port.

2. A slot die coater according to claim 1, wherein the upper core comprises a first portion that serves as a base 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 opening, and the width of the first opening being constant.

3. In the second paragraph, the lower core includes a third portion that serves as a base 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 opening, and a flow rate increasing portion having a width greater than the width of the front end of the second opening portion and increasing the flow rate of the second coating liquid is formed on the inside of the lower core at the rear end of the second opening portion. A slot die coater.

4. A slot die coater characterized in that the width of the fourth portion is differentially configured in the rear direction to form the flow rate increase portion in the third paragraph.

5. A slot die coater characterized in that a tapered shape is applied to the side of the fourth portion to form the flow rate increase portion in the third paragraph.

6. In the third paragraph, the width of the fourth portion is a slot die coater characterized in that it is constant at the first width from the front end of the second opening to the first position in the rear end direction, and decreases to the second width in the rear end direction by the inclined surface to the second position, and is constant at the second width up to the third portion.

7. A slot die coater according to claim 6, characterized in that the angle of the inclined surface is 25˚ to 70˚.

8. A slot die coater according to claim 7, characterized in that the width of the second portion is constant as the second width.

9. A slot die coater, characterized in that in the third paragraph, the width of the fourth portion linearly decreases from the front end of the second opening toward the rear end.

10. A slot die coater characterized in that in the first paragraph, the lower core includes a third portion that serves as a base 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 opening, and a protrusion is further formed on the front end of the second opening toward the side of the fourth portion.

11. A slot die coater according to claim 10, characterized in that the protrusion has a right triangle or right trapezoidal shape.

12. A slot die coater according to claim 1, characterized in that the first coating liquid and the second coating liquid are different types of coating liquids.

13. A 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. A step of forming a lower coating layer on the substrate with a second coating liquid by increasing the side flow rate; and A method for manufacturing an electrode plate for a secondary battery, comprising the 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 where the side flow rate is increased.

15. A method for manufacturing an electrode plate for a secondary battery, characterized in that in claim 14, the first coating solution and the second coating solution are electrode active material slurries having different types of active materials or different binder contents.

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 and simultaneously forming an upper coating layer on the lower coating layer with a first coating liquid on the substrate using a slot die coater according to any one of claims 1 to 13.

17. A method for manufacturing an electrode plate for a secondary battery, characterized in that in claim 16, 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, characterized in that, in the 16th paragraph, 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 to control the width at which the first coating liquid spreads more than the width of the first opening and the width at which the second coating liquid spreads more than the width of the second opening.

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