Slot mold coater and method for manufacturing electrode plate for secondary battery using same

Abstract

A slot die coater is provided for improving the profile of an edge portion of an electrode active material layer. The slot die coater according to the present invention comprises: an upper die block, a middle die block, and a lower die block; the upper gasket is arranged between the upper mold block and the middle mold block to form an upper groove; and a lower gasket provided between the intermediate mold block and the lower mold block to form a lower groove, discharging a first coating liquid through an upper outlet communicating with the upper groove and applying the first coating liquid to a substrate, and discharging a second coating liquid through a lower outlet communicating with the lower groove and applying the second coating liquid to the substrate, the upper gasket comprises at least one first opening, the lower gasket comprises a second opening at the position corresponding to the first opening, and the second opening comprises a section with the width smaller than that of the first opening at the position close to the front end of the lower outlet.

Description

Technical Field

[0001] The present disclosure relates to an apparatus and method for manufacturing an electrode plate of a secondary battery, more specifically, the present disclosure relates to a slot die coater capable of coating an electrode active material slurry on a current collector, and also to a method for manufacturing an electrode plate of a secondary battery using a slot die coater. In particular, the present disclosure relates to a double slot die coater capable of simultaneously forming two or more layers in a wet manner, and also to a method for manufacturing an electrode plate of a secondary battery using the double slot die coater. This application claims priority to Korean Patent Application No. 10-2023-0093003 filed in Korea on July 18, 2023, the disclosure of which is incorporated herein by reference. Background Art

[0002] With the development of mobile device technology and the increase in demand for mobile devices, the demand for secondary batteries as energy sources is rapidly increasing, and these secondary batteries inevitably include electrode assemblies as power generation elements. The electrode assembly is configured so that the positive electrode, the separator, and the negative electrode are laminated at least once, and the positive electrode and the negative electrode are manufactured by coating and drying the positive electrode active material slurry and the negative electrode active material slurry on the current collector made of aluminum foil and copper foil, respectively. In order to make the charge / discharge characteristics of the secondary battery consistent, the positive electrode active material slurry and the negative electrode active material slurry must be uniformly coated on the current collector, so a slot die coater is traditionally used.

[0003] Figure 1 is a schematic diagram showing an embodiment using a slot die coater according to the prior art.

[0004] refer to Figure 1 , generally, an electrode plate is manufactured by coating an electrode active material slurry onto a current collector 20 using a slot die coater 10. In this method, the electrode active material slurry discharged from the slot die coater 10 is applied to the current collector 20 conveyed in the MD direction by a coating roller 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 mold blocks 40 and 50, and has a slot formed by inserting a gasket 60 between the two mold blocks 40 and 50, so that the electrode active material slurry can be discharged via an outlet 70 connected to the slot to form an electrode active material layer.

[0005] The TD directional coating width of the electrode active material layer coated on the current collector 20 is determined by the width of the groove. If the coating width needs to be changed, the spacer 60 that determines the groove width can be changed to implement various coating widths. In particular, in order to ensure the safety of the electrode plate, the electrode active material slurry must be applied to be evenly distributed on the current collector 20.

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

[0007] exist Figure 2 In the illustrated gasket 60, the spacing between the gasket fingers 61 is constant (W1=W2) regardless of the front or rear of the gasket 60, and the spacing between the gasket fingers 61 determines the coating width. With this gasket 60, an electrode active material layer can be formed on the current collector 20 along one channel formed between two gasket fingers 61. However, since the electrode active material slurry is a fluid, it has a property of flowing downward after coating, which is called sliding.

[0008] Figure 3 A cross section of a secondary battery electrode plate in which an electrode active material slurry is coated on one surface of a current collector in the TD direction is shown, and a state in which slip occurs is shown.

[0009] refer to Figure 3 , a portion of the electrode active material slurry flows downward from the edge of the electrode active material layer, resulting in a sliding phenomenon in which the thickness of the electrode active material layer gradually decreases toward the side. Reference symbol S indicates a portion where sliding occurs, that is, a sliding portion.

[0010] Such sliding may often occur at both ends in the width direction (TD direction) of the holding portion on which the electrode active material slurry is applied, resulting in uneven loading. In addition, the sliding causes unevenness during rolling and further causes the NP ratio, which is the surface ratio of the negative electrode active material layer to the positive electrode active material layer, to fail to meet the design requirements.

[0011] In particular, despite using Figure 2 The gasket 60 shown in FIG. 6 maintains the same discharge capacity ratio as the design value between the positive and negative electrodes in the flat coating section, but the sliding portion S may be formed at a 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, resulting in a distortion of the discharge capacity ratio. In addition, if the positive electrode capacity becomes greater than the negative electrode capacity, the risk increases, so the stability in the portion where the positive flat portion and the negative sliding portion S face each other is significantly deteriorated. For this reason, it is necessary to control the sliding during the coating process of the electrode active material slurry, and in particular, when multiple channels are used for stripe pattern coating, it is necessary to manage the shape control of the boundary surface (sliding portion), and in particular, the sliding length must be managed.

[0012] like Figure 3As shown in , the overall shape of the sliding portion S in the electrode profile shows that when the coating portion starts from the starting point Ps, the thickness increases with the increase of the lateral distance, and after exceeding a certain lateral distance, the increase rate of the thickness gradually decreases, so that the thickness converges to a certain value and no longer increases, forming a flat shape. The sliding length SL can be defined as the lateral distance from the starting point Ps of the coating portion to the point Pe where the sliding ends. The point Pe where the sliding ends may be the point where the electrode profile begins to flatten. For example, this may be a point where the thickness reaches the target coating thickness H or approaches the target coating thickness within a certain range.

[0013] However, in the method of manufacturing the electrode plate of the secondary battery, in order to utilize both sides of the current collector, a so-called sequential coating method is used, in which the electrode active material layer is first coated on the top surface of the current collector and then on the rear surface. In this case, the top surface tends to have a sliding length SL that is longer than the sliding length of the rear surface. Therefore, even if sequential coating is performed using a slot die coater including the same gasket, the quality of the electrode on the top surface may deteriorate. In addition, since the sliding in the edge of the top surface may produce a recessed portion of the current collector when the current collector is flipped to coat the rear surface, the electrode active material slurry may be concentrated on the edge during coating the rear surface, thereby causing a specific problem of the side ring phenomenon: the edge of the rear surface protrudes upward after the process is completed. Figure 3 The electrode profile when the side ring R appears is also shown in dotted lines. In particular, in the case where the flow rate in the side portion is increased in order to manage the sliding length SL by shape control of the gasket 60, the side ring R may appear even if the flow rate in the side portion is significantly increased, so there is a limit to the improvement of the profile of the edge of the electrode active material layer. Summary of the invention

[0014] Technical issues

[0015] The present disclosure is designed to solve the problems of the prior art, and thus the present disclosure is directed to providing a slot die coater for improving an edge profile of an electrode active material layer.

[0016] The present disclosure also aims to provide a method for manufacturing an electrode plate of a secondary battery using the slot die coater.

[0017] Technical Solution

[0018] According to one aspect of the present disclosure, there is provided a slot die coater including a lower slot and an upper slot, and applying a coating liquid by means of the lower slot and the upper slot and coating a surface of a continuously traveling substrate with the coating liquid.

[0019] The slot die coater according to the present disclosure includes: an upper die block, an intermediate die block and a lower die block; an upper gasket, which is arranged between the upper die block and the intermediate die block to form an upper slot; and a lower gasket, which is arranged between the intermediate die block and the lower die block to form a lower slot, wherein a first coating liquid is discharged through an upper outlet connected to the upper slot and applied to a substrate, and a second coating liquid is discharged through a lower outlet connected to the lower slot and applied to the substrate, wherein the upper gasket includes at least one first opening, wherein the lower gasket includes a second opening at a position corresponding to the first opening, and wherein the second opening includes a section having a smaller width than the first opening at a front end adjacent to the lower outlet.

[0020] Preferably, the upper gasket includes a first portion configured to serve 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, and the space between the second portions is defined as the first opening, and the width of the first opening is constant.

[0021] The lower gasket may include a third portion configured to serve as a base and at least two fourth portions extending from the third portion, the fourth portions may be connected to the same side of the third portion and extend in the same direction, the space between the fourth portions may be defined as the second opening, and a flow increase portion may be formed on the inner side of the lower gasket at the rear end of the second opening, the width of the flow increase portion being greater than the width of the front end of the second opening to increase the flow of the second coating liquid.

[0022] In this case, the width of the fourth portion may be differently configured in a direction toward the rear end to form the flow rate increasing portion.

[0023] A side surface of the fourth portion may apply a tapered shape to form the flow increasing portion.

[0024] The width of the fourth portion may be constant at a first width from the front end toward the rear end to a first position of the second opening, may decrease to a second width toward the rear end to a second position with an inclined surface, and may be constant at the second width until a third portion.

[0025] Furthermore, the angle of the inclined surface may be 25 degrees to 70 degrees.

[0026] In this case, the width of the second portion may be constant to the second width.

[0027] The width of the fourth portion may linearly decrease from the front end toward the rear end of the second opening.

[0028] As another embodiment, the lower gasket may include a third part configured to serve as a base and at least two fourth parts extending from the third part, and the fourth parts may be connected to the same side of the third part and extend in the same direction, the space between the fourth parts may be defined as the second opening, and a protrusion may also be formed on the side surface of the fourth part at the front end of the second opening.

[0029] The protrusion may have a right triangle or a right trapezoid shape.

[0030] The first coating liquid and the second coating liquid may be different types of coating liquids.

[0031] The first coating liquid and the second coating liquid may have a viscosity of 4000 cps to 6000 cps.

[0032] The middle mold block may have a first manifold receiving the first coating liquid and communicating with the upper tank, and the lower mold block may have a second manifold receiving the second coating liquid and communicating with the lower tank.

[0033] The upper mold block may have a first manifold receiving the first coating liquid and communicating with the upper tank, and the lower mold block may have a second manifold receiving the second coating liquid and communicating with the lower tank.

[0034] The lower groove and the upper groove may form an angle of 30 to 60 degrees.

[0035] According to the present disclosure, a method for manufacturing an electrode plate of a secondary battery may include: forming a lower coating layer on a substrate with a second coating liquid by increasing the flow rate in a side portion; and simultaneously forming an upper coating layer on the lower coating layer with a first coating liquid on the substrate to press the flow increase portion in the side portion.

[0036] Here, the first coating liquid and the second coating liquid may be electrode active material slurries having different types of active materials or contents of binders from each other.

[0037] The above-described method for manufacturing an electrode plate of a secondary battery may be easily performed using the slot die coater according to the present disclosure.

[0038] According to another aspect of the present disclosure, the above-mentioned method for manufacturing an electrode plate of a secondary battery includes using the slot die coater described in the present disclosure to form a lower coating layer on a substrate using a second coating liquid, and simultaneously forming an upper coating layer on the lower coating layer on the substrate using a first coating liquid.

[0039] The second coating liquid may include a natural graphite active material, and the first coating liquid may include an artificial graphite active material.

[0040] In addition, 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 can be adjusted to control the first coating liquid to spread to a width exceeding the width of the first opening and the second coating liquid to spread to a width exceeding the width of the second opening.

[0041] Beneficial Effects

[0042] Slippage must be managed in the coating of electrode active material slurry using a slot die coater, and whether slippage occurs can be identified by the thickness unevenness in the width direction in the channel. In order to stably implement the target battery capacity, it is necessary to improve the thickness unevenness by improving the coating loading in the channel.

[0043] According to one aspect of the present invention, a slot die coater including a gasket is provided, which can improve the loading non-uniformity in the channel by more stably increasing the loading in the desired area. The lower gasket included in the slot die coater of the present disclosure realizes a technology capable of controlling the loading amount in the width direction during the coating of the electrode active material slurry.

[0044] Furthermore, according to the present disclosure, while increasing the flow rate in the side portion to manage the sliding length by controlling the shape of the lower gasket, the upper gasket has a different shape from the lower gasket, so the increase in the flow rate in the side portion does not overlap, thereby eliminating the possibility of the occurrence of a side ring.

[0045] According to the present disclosure, a slot die coater is provided in which the shape of a lower gasket is changed and in which the shape of an upper gasket is different from that of a lower gasket, for the purpose of improving coating unevenness in a channel, so that the flow difference of an electrode active material slurry as a coating liquid can be improved, thereby increasing the flow of the coating liquid in the side portion of the channel without the occurrence of a side ring, and thus the profile of the edge of the electrode active material layer can be improved. In particular, the profile of the sliding portion can be improved.

[0046] Using the slot die coater according to the present disclosure, sliding can be improved so that the discharge capacity of the positive electrode does not exceed the discharge capacity of the negative electrode, thereby preventing lithium deposition and ensuring battery safety.

[0047] According to the present disclosure, it is possible to prevent uneven loading due to sliding, and to reduce the occurrence of side rings even in a sequential coating method. That is, according to the present disclosure, in a sequential coating method of coating the top surface and then coating the rear surface, sliding on the top surface is controlled so that the occurrence of side rings on the rear surface can be prevented. Therefore, it is very effective to manage both the top surface and the rear surface.

[0048] According to the present disclosure, the coating layer (especially the electrode active material layer) can be uniformly formed to have a desired thickness, and since two or more electrode active material slurries can be coated simultaneously, excellent effects are achieved in terms of performance and productivity. The slot die coater of the present disclosure is used to manufacture an electrode plate of a secondary battery by applying an electrode active material slurry on a current collector, and uniform coating can be performed even under high-speed or long-width coating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the detailed description of the present invention, are used to provide further understanding of the technical idea of ​​the present disclosure; therefore, the present disclosure is not to be construed as being limited to the accompanying drawings.

[0050] Figure 1 is a schematic diagram showing an embodiment using a slot die coater according to the prior art.

[0051] Figure 2 is a plan view of a gasket according to the prior art.

[0052] Figure 3 A cross section of a secondary battery electrode plate in which an electrode active material slurry is coated on one surface of a current collector in the TD direction is shown and a state in which slip occurs is shown.

[0053] Figure 4 is a schematic cross-sectional view of a slot die coater according to an embodiment of the present disclosure.

[0054] Figure 5 is a schematic exploded perspective view of a slot die coater according to an embodiment of the present disclosure.

[0055] Figure 6 is a plan view of an upper shim and a lower shim included in a slot die coater according to an embodiment of the present disclosure.

[0056] Figure 7 is a partial enlarged view of a lower gasket included in a slot die coater according to an embodiment of the present disclosure.

[0057] Figure 8 is an enlarged partial view of another subshim included in a slot die coater according to an embodiment of the present disclosure.

[0058] Fig. 9 Shown in use Figure 7 Cross-section of a secondary battery electrode plate in the TD direction in the case where the lower gasket is coated with electrode active material slurry.

[0059] Fig.10A cross section in the TD direction of a secondary battery electrode plate manufactured according to the present disclosure is shown.

[0060] Fig.11 A cross section in the TD direction of a secondary battery electrode plate coated with an electrode active material slurry using a slot die coater according to the present disclosure is shown.

[0061] Fig.12 A cross section in the TD direction of a secondary battery electrode plate coated with an electrode active material slurry using a slot die coater according to a comparative example is shown.

[0062] Fig.13 Results comparing the sliding lengths between samples #1 to #4 are shown.

[0063] Fig.14 Results comparing electrode profiles between samples #1 to #4 are shown. DETAILED DESCRIPTION

[0064] Hereinafter, the preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be interpreted as limited to the general meaning and dictionary meaning, but are interpreted based on the meaning and concept corresponding to the technical aspects of the present disclosure based on the principle of allowing the inventor to appropriately define the terms for the best interpretation. Therefore, the configurations proposed in the embodiments of this specification and the accompanying drawings only indicate the most preferred embodiments of the present disclosure and do not represent all the technical ideas of the present disclosure, so it should be understood that various equivalent examples and variant examples can be made when submitting this application.

[0065] The slot die coater according to an embodiment of the present disclosure may have two or more slots. Mainly, the device has a lower slot and an upper slot, and the coating liquid is coated on the substrate in a double-layer manner. 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 with the same or different components (types of active materials, conductive materials and binders), contents (active materials, conductive materials and binders) or properties. The slot die coater according to an embodiment of the present disclosure is optimized for manufacturing electrode plates for secondary batteries by applying two or more types of electrode active material slurries simultaneously or alternately. However, the scope of the present disclosure is not necessarily limited thereto. For example, the substrate may be a porous carrier constituting a diaphragm, and the first coating liquid and the second coating liquid may be organic substances with different components or properties. That is, if thin film coating is required, any substance may be used for the substrate and the first coating liquid and the second coating liquid.

[0066] In this specification, "front" refers to the direction in which the outlet faces (X-axis direction or MD direction), and "rear" refers to the opposite direction. "Left and right" refers to the direction perpendicular to the direction in which the outlet faces and indicates the width direction of the slot (Z-axis direction or TD direction).

[0067] Figure 4 is a schematic cross-sectional view of a slot die coater according to an embodiment of the present disclosure, and Figure 5 is a schematic exploded perspective view of a slot die coater according to an embodiment of the present disclosure.

[0068] The slot die coater 100 according to an embodiment of the present disclosure is an apparatus having an upper slot 101 and a lower slot 102 , and is capable of simultaneously or alternately coating the same or different two types of coating liquids on a substrate 200 by means of the upper slot 101 and the lower slot 102 .

[0069] refer to Figure 4 and Figure 5 , the slot die coater 100 includes an upper mold block 110, a middle mold block 120, and a lower mold block 130. The upper mold block 110 is disposed on the middle mold block 120, and the middle mold block 120 is disposed on the lower mold block 130. The mold blocks 110, 120, and 130 may be assembled to each other by means of bolts as fastening members.

[0070] exist Figure 4 , the slot die coater 100 is installed so that the direction (X-axis direction) in which the electrode active material slurry (which is a coating liquid) is discharged is almost horizontal (about ±5 degrees).

[0071] The middle mold block 120 is disposed in the middle of the mold blocks constituting the slot die coater 100 and is disposed between the upper mold block 110 and the lower mold block 130 to form a double slot. Although the cross section of the middle mold block 120 included in the slot die coater 100 of the present embodiment is a right triangle, it is not necessarily limited thereto, and for example, the cross section may be configured as an isosceles triangle.

[0072] The first surface 120a of the middle mold block 120 facing the upper mold block 110 is arranged almost horizontally, and the opposite surface 110d of the surface 110b of the upper mold block 110 facing the first surface 120a (i.e., the upper outer surface of the slot die coater 100) is also arranged almost horizontally. As described above, the first surface 120a and the opposite surface 110d are almost parallel. In addition, the opposite surface 130d of the surface 130b of the lower mold block 130 facing the middle mold block 120 (i.e., the lower outer surface of the slot die coater 100) is also arranged almost horizontally, and this surface becomes the bottom surface 130d (XZ plane).

[0073] Surfaces of the upper mold block 110 , the middle mold block 120 , and the lower mold block 130 facing the direction opposite to the discharge direction of the electrode active material slurry (ie, rear surfaces 110 c , 120 c , and 130 c ) are disposed almost vertically (Y-axis direction).

[0074] In the upper mold block 110 and the lower mold block 130 which are the outermost mold blocks, among the surfaces constituting the outer surface of the slot die coater 100, the top surface 110d of the upper mold block 110 and the bottom surface 130d of the lower mold block 130 can be configured to be almost perpendicular to the rear surfaces 110c and 130c. In addition, the first surface 120a of the middle mold block 120 can be configured to be almost perpendicular to the rear surface 120c. Since the corners formed by the surfaces are configured at right angles in the mold blocks 110, 120 and 130, there is a right angle section in the cross section, and since a vertical or horizontal surface can be used as a reference surface, its manufacture or processing is easy and the accuracy is guaranteed. In addition, the assembly of the upper mold block 110, the middle mold block 120 and the lower mold block 130 has a rectangular parallelepiped shape as a whole, and is inclined toward the substrate 200 only from the front parts 110a and 130a from which the coating liquid is discharged. The assembled shape of the above-mentioned slot die coater is roughly similar to that of a slot die coater having a single slot (for example, Figure 1 The assembly shape of 10) in FIG. 1 can thus be shared by a slot die coater bracket and the like.

[0075] The slot die coater 100 may further include two or more fixing portions 140 disposed on the rear surfaces 110c, 120c, and 130c thereof. The fixing portions 140 are respectively provided to fasten the lower mold block 130 and the middle mold block 120 to each other and to fasten the middle mold block 120 and the upper mold block 110 to each other. A plurality of fixing portions 140 may be provided along the width direction of the slot die coater 100. Bolts may be engaged with the fixing portions 140 so that the upper mold block 110, the middle mold block 120, and the lower mold block 130 are assembled to each other.

[0076] The upper mold block 110, the middle mold block 120 and the lower mold block 130 are not necessarily limited to the above configuration. For example, they can be configured as vertical molds that discharge the electrode active material slurry upward (in the Y-axis direction) and have the rear surfaces 110c, 120c and 130c as the bottom surface.

[0077] The mold blocks 110, 120 and 130 are made of, for example, SUS material. Materials that are easy to process, such as SUS420J2, SUS630, SUS440C, SUS304 or 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.

[0078] The upper mold block 110 is arranged to contact the first surface 120a, which is the top surface of the intermediate mold block 120 parallel to the bottom surface. The upper groove 101 is formed in the portion where the intermediate mold block 120 and the upper mold block 110 contact each other. The upper gasket 300 is inserted between the intermediate mold block 120 and the upper mold block 110 to form a gap therebetween. Therefore, the upper groove 101 corresponding to the channel through which the first coating liquid 150 flows is formed. That is, the upper gasket 300 is arranged between the upper mold block 110 and the intermediate mold block 120 to form the upper groove 101. In this case, the vertical width (in the Y-axis direction) (groove gap) of the upper groove 101 is determined by the thickness of the upper gasket 300. The thickness of the upper gasket 300 may be about 1 mm. For example, when coated with an electrode active material slurry including a solid content of 40% to 80% to have a thickness of 70 μm to 300 μm, the thickness of the upper gasket 300 may be 0.5 mm to 1.5 mm.

[0079] like Figure 5 As shown in , the upper gasket 300 includes at least one first opening 310 formed by cutting at least one area, and is interposed between the middle mold block 120 and the upper mold block 110 only in the remaining portion of the boundary area on the opposite surfaces of the middle mold block 120 and the upper mold block 110 except one side. Therefore, the peripheral portion of the upper groove 101 except the front portion is closed, and the upper outlet 101a is formed only between the front edge of the upper mold block 110 and the front edge of the middle mold block 120. The front edge of the upper mold block 110 and the front edge of the middle mold block 120 are defined as the upper mold lip 111 and the middle mold lip 121, respectively, and thus the upper outlet 101a can be formed by means of the interval between the upper mold lip 111 and the middle mold lip 121.

[0080] For reference, the upper gasket 300 can be used as a gasket to prevent the first coating liquid 150 from leaking through the gap between the upper mold block 110 and the middle mold block 120 (except for the area where the upper outlet 101a is formed), and therefore can be made of a material with sealing properties. The upper gasket 300 can be made of, for example, plastic or metal, but the present disclosure is not limited thereto. The upper gasket 300 can be made of, for example, a resin sheet (such as Teflon or polyester) or a metal sheet (such as copper or aluminum). Similar to the mold blocks 110, 120 and 130, the upper gasket 300 can also be made of SUS. The upper gasket 300 can be connected and fixed to the upper mold block 110 or the middle mold block 120 by means of, for example, screws.

[0081] In addition, the middle mold block 120 has a first manifold 155 formed on a first surface 120a facing the upper mold block 110 to have a predetermined depth and communicate with the upper tank 101. Although not shown in the figure, the first manifold 155 is connected to a first coating liquid supply chamber installed outside via a supply pipe to receive the first coating liquid 150. If the first coating liquid 150 is supplied from the outside via the supply pipe so that the first manifold 155 is filled with the first coating liquid, the first coating liquid 150 is guided to flow along the upper tank 101 communicated with the first manifold 155, and is discharged to the outside via the upper outlet 101a communicated with the upper tank 101. As another embodiment, the first manifold 155 may be provided on a surface 110b of the upper mold block 110 facing the middle mold block 120.

[0082] The lower mold block 130 is disposed at the lowest position among the blocks constituting the slot die coater 100, and a surface 130b thereof facing the middle mold block 120 is inclined at an angle of about 20 to 60 degrees with respect to a bottom surface 130d.

[0083] The lower groove 102 may be formed in a portion where the lower mold block 130 and the intermediate mold block 120 contact each other. A lower gasket 400 may be inserted between the lower mold block 130 and the intermediate mold block 120 to form a gap therebetween, thereby forming the lower groove 102 corresponding to the channel through which the second coating liquid 160 flows. That is, the lower gasket 400 is disposed between the intermediate mold block 120 and the lower mold block 130 to form the lower groove 102. In this case, the thickness of the lower gasket 400 determines the vertical width (in the Y-axis direction) (groove gap) of the lower groove 102. The thickness of the lower gasket 400 may be about 1 mm. For example, when coated with an electrode active material slurry including a solid content of 40% to 80% to have a thickness of 70 μm to 300 μm, the thickness of the lower gasket 400 may be 0.5 mm to 1.5 mm.

[0084] like Figure 5 As shown in , the lower gasket 400 may include at least one second opening 410 formed by cutting at least one area, and is interposed between the lower mold block 130 and the middle mold block 120 only in the remaining portion of the boundary area on the opposite surfaces of the lower mold block 130 and the middle mold block 120 except for one side. Therefore, the lower outlet 102a is formed only between the front edge of the lower mold block 130 and the front edge of the middle mold block 120, and the second coating liquid 160 is discharged to the outside through the lower outlet. The front edge of the lower mold block 130 is defined as the lower mold lip 131, so the lower outlet 102a can be formed by the interval between the lower mold lip 131 and the middle mold lip 121.

[0085] Similarly, the lower gasket 400 can be used as a gasket to prevent the second coating liquid 160 from leaking through the gap between the lower mold block 130 and the intermediate mold block 120 (except for the area where the lower outlet 102a is formed), and therefore can be made of a material with sealing properties. The lower gasket 400 can also be made of, for example, plastic or metal, but the present disclosure is not limited thereto. The lower gasket 400 can be made of, for example, a resin sheet (such as Teflon or polyester) or a metal sheet (such as copper or aluminum). Similar to mold blocks 110, 120 and 130, the lower gasket 400 can also be made of SUS. The lower gasket 400 can be connected and fixed to the intermediate mold block 120 or the lower mold block 130 by means of, for example, screws.

[0086] The lower mold block 130 has a second manifold 165 formed on a surface 130b facing the middle mold block 120 to have a predetermined depth and communicate with the lower tank 102. Although not shown in the figure, the second manifold 165 is connected to a second coating liquid supply chamber (not shown) installed outside via a supply pipe to receive the second coating liquid 160. If the second manifold 165 is filled with the second coating liquid 160, the second coating liquid 160 is guided to flow along the lower tank 102 and discharged to the outside via the lower outlet 102a communicated with the lower tank 102. As another embodiment, the second manifold 165 may be provided on the surface 120b of the middle mold block 120 facing the lower mold block 130.

[0087] A certain angle may be formed between the upper groove 101 and the lower groove 102, and the angle may be about 30 to 60 degrees. The upper groove 101 and the lower groove 102 may intersect each other at one point, and the upper outlet 101a and the lower outlet 102a may be arranged near the intersection. Therefore, the discharge points of the first coating liquid 150 and the second coating liquid 160 may be concentrated at approximately one point. Thus, the lower coating layer of the second coating liquid 160 and the upper coating layer of the first coating liquid 150 may be aligned upward, downward, leftward, and rightward to form a double layer.

[0088] According to the slot die coater 100 having the above configuration, the coating roller 500 may be configured to be rotatable in front of the slot die coater 100, and by rotating the coating roller 500, the substrate 200 to be coated may travel in the MD direction, so that the first coating liquid 150 may be discharged through the upper outlet 101a and applied to the substrate 200, and so that the second coating liquid 160 may be discharged through the lower outlet 102a and applied to the substrate 200.

[0089] The first coating liquid 150 and the second coating liquid 160 may be different types of coating liquids. The first coating liquid 150 and the second coating liquid 160 may have a viscosity of 4000 cps to 6000 cps. The first coating liquid 150 and the second coating liquid 160 may be electrode active material slurries.

[0090] The second coating liquid 160 and the first coating liquid 150 may be continuously applied to the surface of the substrate 200 by means of the slot die coater 100, thereby coating the substrate 200 with a double layer. Alternatively, the supply and stop of the second coating liquid 160 and the supply and stop of the first coating liquid 150 may be alternately performed to intermittently form a coating pattern on the substrate 200. Preferably, the second coating liquid 160 and the first coating liquid 150 are discharged simultaneously to form a double-layer coating. In order to manufacture a secondary battery with a high energy density, the thickness of the electrode active material layer is gradually increased from about 130 μm to 300 μm. If used Figure 1 If the conventional slot die coater 10 shown in forms a thick electrode active material layer, the migration of the binder and the conductive material deteriorates in the active material slurry during drying, thereby producing an uneven final electrode. In order to solve the above problem, two coatings can be performed so that the electrode active material layer is thinly coated and dried, and then another electrode active material layer is coated and dried thereon, but the time required is long. According to the present disclosure, if a slot die coater 100 having two slots is used, the second coating liquid 160 and the first coating liquid 150 can be discharged simultaneously to form a thick electrode active material layer at one time, thereby improving both electrode performance and productivity.

[0091] In particular, the slot die coater 100 has the upper gasket 300 and the lower gasket 400 having different shapes, which can improve the profile of the edge of the electrode active material layer.

[0092] Figure 6 is a plan view of an upper shim and a lower shim included in a slot die coater according to an embodiment of the present disclosure, and Figure 7 is a partial enlarged view of a lower gasket included in a slot die coater according to an embodiment of the present disclosure, which enlarges Figure 6 Area A in .

[0093] First, refer to Figure 6 , the upper gasket 300 includes at least one first opening 310, and the lower gasket 400 includes a second opening 410 at a position corresponding to the first opening 310. The second opening 410 includes a section SA having a smaller width than the first opening 310 at a front end adjacent to the lower outlet 102a. For example, the first opening 310 has a width D1, and the second opening 410 includes a section SA having a width D2 less than D1. The section SA having a width D2 less than D1 may be a portion 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.

[0094] The upper shim 300 and the lower shim 400 determine the coating width of the coating layer applied to the substrate 200, and the number of the first openings 310 and the second openings 410 may determine the number of channels (i.e., the number of patterns), and the sizes of the first openings 310 and the second openings 410 may affect the coating width. Although the illustrated embodiment shows one first opening 310 and one second opening 410, a plurality of first openings 310 and second openings 410 may be included to form a coating layer in a stripe pattern on the substrate 200.

[0095] More specifically, the upper gasket 300 includes a first portion 320 serving as a base and at least two second portions 330 extending from the first portion 320, and the second portions 330 are connected to the same side of the first portion 320 and extend in the same direction (X-axis direction), and the space between the second portions 330 is defined as the first opening 310. In particular, in the present 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.

[0096] The first portion 320 and the second portion 330 may be formed as a single piece. That is, there is no gap or interval between the first portion 320 and the second portion 330. Therefore, the first coating liquid 150 may be prevented from flowing between the first portion 320 and the second portion 330 unnecessarily.

[0097] The first portion 320 of the upper gasket 300 is disposed in the rear portion of the upper mold block 110. In order for the upper gasket 300 to be interposed between the remaining portions of the edge regions on the opposing surfaces of the upper and middle mold blocks 110 and 120 except for one side, at least two second portions 330 are required.

[0098] The second portion 330 extends toward the upper outlet 101a (i.e., in the X-axis direction). That is, the second portion 330 extends from the upper gasket 300 toward the front portion of the upper mold block 110. If the number of the second portions 330 increases, more channels can be generated for discharging the first coating liquid 150 on the substrate 200, thereby forming more patterns side by side at one time. That is, stripe pattern coating can be performed. However, the present disclosure is not limited to a specific number of the second portions 330. The second portions 330 correspond to Figure 2 The shim fingers 61 of the conventional shim 60 in FIG.

[0099] The lower gasket 400 includes a third portion 420 serving as a base and at least two fourth portions 430 extending from the third portion 420, and the fourth portions 430 are connected to the same side of the third portion 420 and extend in the same direction (X-axis direction), and a space between the fourth portions 430 is defined as a second opening 410. In addition, the shape of the lower gasket 400 is different from that of the upper gasket 300, and a flow increase portion 440 is formed at the rear end of the second opening 410 on the inner side of the lower gasket 400, in which the flow of the second coating liquid 160 is increased due to the width D1 of the second opening 410 being greater than the front width D2. The second coating liquid 160 can be discharged through the second opening 410, and due to the flow increase portion 440, the load in the side portion can be increased.

[0100] The third portion 420 and the fourth portion 430 may be formed as a single piece. That is, there is no gap or interval between the third portion 420 and the fourth portion 430. Therefore, the second coating liquid 160 may be prevented from flowing between the third portion 420 and the fourth portion 430 unnecessarily.

[0101] The third portion 420 of the lower gasket 400 is disposed in the rear portion of the lower mold block 130. In order for the lower gasket 400 to be interposed between the remaining portions of the edge regions on the opposing surfaces of the lower mold block 130 and the middle mold block 120 except one side, at least two fourth portions 430 are required.

[0102] The fourth portion 430 extends toward the lower outlet 102a (i.e., in the X-axis direction). That is, the fourth portion 430 extends from the lower gasket 400 toward the front portion of the lower mold block 130. If the number of the fourth portions 430 increases, more channels can be generated to discharge the second coating liquid 160 on the substrate 200, and more patterns can be formed side by side at one time. That is, stripe pattern coating can be performed. However, the present disclosure is not limited to a specific number of the fourth portions 430. The fourth portion 430 corresponds to Figure 2 The shim fingers 61 of the conventional shim 60 in FIG.

[0103] The width L of the fourth portion 430 may be configured differently toward the rear end to form the flow increase portion 440 in the lower gasket 400. For example, a tapered shape may be applied to the side surface of the fourth portion 430 to form the flow increase portion 440. In this case, the tapered shape may be various and may be a curve, a straight line, a step shape, a combination thereof, etc., and may be, for example, Figure 7 and Figure 8 as shown in .

[0104] First, refer to Figure 7The width of the fourth portion 430 may be constant as a first width (a) from the front end toward the rear end to the first position AA of the second opening 410, and may decrease to a second width (b) along the inclined surface 435 toward the rear end to the second position BB, and may be constant as the second width (b) thereafter. The length from the front end of the lower gasket 400 to the first position AA is "c", and the length from the first position AA to the second position BB is represented as "d".

[0105] exist Figure 7 In the illustrated embodiment, the inclined surface 435 is formed to protrude a width (ab) in the width direction and extend a length (d) toward the lower outlet 102a. If (ab) and (d) are the same, the angle α of the inclined surface 435 becomes 45 degrees. The angle α of the inclined surface 435 is adjustable to improve uneven loading, and (ab), (c) or (d) can also be adjusted to improve sliding. In addition, the determination of (ab), (c) or (d) can be a trade-off between improving sliding improvement and paying attention to the appearance of fat edges.

[0106] The angle α of the inclined surface 435 relative to the side surface of the fourth portion 430 or the discharge direction (opposite to the X-axis direction) may be 25 to 70 degrees. If the angle α of the inclined surface 435 is less than 25 degrees, the length of the flow increase portion 440 may be shortened, thereby reducing the sliding improvement effect. If the angle α of the inclined surface 435 is greater than 70 degrees, a rapid change in flow may occur on the surface leading to the inclined surface 435, thereby affecting the discharge pressure, which is undesirable.

[0107] Furthermore, in response to the lower gasket 400 , the width of the second portion 330 in the upper gasket 300 may be constant to the second width (b).

[0108] Figure 7 The structure in FIG. 4 shows that a protrusion 450 is further formed on the side surface of the fourth portion 430 at the front end of the second opening 410. In addition, the protrusion 450 may be configured in a straight trapezoidal shape.

[0109] Next, if Figure 8 As shown in , the width of the fourth portion 430 may also decrease linearly from the front end toward the rear end of the second opening 410. The fourth portion 430 may have a first width (a) at the front end of the second opening 410, and the first width (a) may decrease to a second width (b) along the inclined surface 435 toward the rear end to the second position BB, and thereafter may be constant to the second width (b). Figure 8 The structure in FIG. 4 also shows that a protrusion 455 is further formed on the side surface of the fourth portion 430 at the front end of the second opening 410. In addition, the protrusion 455 may be configured in a right triangle shape.

[0110] The sliding improvement effect can be controlled by adjusting the shape and size of the protrusion 450 or 455. As the size of the protrusion 450 or 455 increases, the influence on the profile of the electrode active material layer will increase. In order to achieve a given coating width, the size of the protrusion 450 or 455 cannot be simply increased, and the size of the protrusion 450 or 455 can be adjusted by further considering the properties of the coating liquid.

[0111] Fig. 9 Shown in use Figure 7 A cross section of a secondary battery electrode plate in the TD direction when the lower gasket 400 is coated with an electrode active material slurry.

[0112] refer to Fig. 9 , the increase in flow rate in the side portion may result in an increase in thickness of the edge of the electrode active material layer, the edge (such as the side ring R') being thicker than the center.

[0113] When using Figure 6 When the upper gasket 300 shown in FIG. 1 is coated with the electrode active material slurry, the cross section of the secondary battery electrode plate in the TD direction may be similar to Figure 3 .

[0114] The present disclosure also provides a method for manufacturing an electrode plate of a secondary battery, the method comprising the following steps: using a slot die coater 100, forming a lower coating layer 160a on a substrate 200 using a second coating liquid 160, and simultaneously forming an upper coating layer 150a on the substrate 200 using a first coating liquid 150, the upper coating layer 150a being located on the lower coating layer 160a.

[0115] The first coating liquid 150 and the second coating liquid 160 may be electrode active material slurries having different types of active materials or contents of binders. For example, the second coating liquid 160 may include a natural graphite active material, and the first coating liquid 150 may include an artificial graphite active material.

[0116] In this case, by adjusting the gap between the upper slot 101 of the slot die coater 100 and the substrate 200 and the gap between the lower slot 102 of the slot die coater 100 and the substrate 200, the width (spreading width) of the first coating liquid 150 can be adjusted to spread larger than the width D1 of the first opening 310 and the width of the second coating liquid 160 can be adjusted to spread larger than the width D2 of the second opening 410. If the gap is narrow, the spreading width increases, and if the gap is large, the spreading width decreases.

[0117] Fig.10 FIG. 4 shows a cross section of a secondary battery electrode plate manufactured according to the present disclosure in the TD direction. Fig.10, an electrode active material layer 600 is formed on a substrate 200, and the electrode active material layer 600 includes an undercoat layer 160a and an overcoat layer 150a.

[0118] Since the slot die coater 100 of the present disclosure coats the electrode active material layer 600 using both the upper gasket 300 and the lower gasket 400, the cross-section of the electrode active material layer 600 formed on the substrate 200 in the TD direction can be improved, as Fig.11 shown.

[0119] Fig.11 The cross-section in the TD direction of a secondary battery electrode plate coated with an electrode active material paste using a slot die coater according to the present disclosure is shown.

[0120] Referring to Fig.11 , if the electrode active material layer 600 is coated on the substrate 200 using both the upper gasket 300 and the lower gasket 400 by means of the slot die coater 100 of the present disclosure, the cross-section of the electrode active material layer 600 in the TD direction can be identified. As a result of combining the cross-sectional profile in the TD direction of the upper gasket 300 (for example, the profile showing slippage as shown in Figure 3 ) and the cross-sectional profile in the TD direction of the lower gasket 400 (for example, the profile showing side loops as shown in Fig. 9 ), it can be seen that, compared with the conventional profile shown in Figure 3 , the slippage of the thickness profile of the electrode active material layer 600 shown in Fig.11 is significantly improved.

[0121] According to the present disclosure, the electrode active material layer 600 is coated using both the upper gasket 300 and the lower gasket 400 by means of the slot die coater 100, such that the undercoat layer 160a is formed on the substrate 200 by increasing the flow rate in the side portion using the second coating liquid 160, and the overcoat layer 150a (the overcoat layer 150a is located on the undercoat layer 160a) is formed on the substrate 200 using the first coating liquid 150, thereby pressing the portion where the flow rate increases in the side portion. Therefore, compared with the prior art, the thickness profile of the electrode active material layer 600 can be improved.

[0122] In particular, by using the lower gasket 400 having a flow rate increasing portion 440 formed thereon, the sliding length SL' of the electrode active material layer 600 applied to the substrate 200 becomes shorter than the conventional sliding length SL (SL' < SL). In addition, as shown in Figure 3 , compared with the thickness at the point where the thickness change starts to flatten in the sliding portion S of the conventional electrode active material layer, the thickness at the point where the thickness change starts to flatten in the sliding portion S' of the electrode active material layer 600 applied to the substrate 200 increases. Therefore, the profile of the sliding portion S' is improved.

[0123] According to the present disclosure, using the upper gasket 300 and the lower gasket 400 of different shapes, the contours of the edge of the electrode active material layer 600 can complement each other. The second opening 410 of the lower gasket 400 includes a section SA at the front end adjacent to the lower outlet 102a, and the section SA has a smaller width than the first opening 310 of the upper gasket 300. The lower gasket 400 includes a flow increase portion 440 on the inner side of the second opening 410. Since the lower gasket 400 can increase the flow of the second coating liquid 160 in the side portion, if the lower gasket 400 is used alone, it is possible to obtain a contour that forms a side ring R' at the edge. The upper gasket 300 can form an upper coating layer 150a, which can press and cover the lower coating layer 160a formed by the lower gasket 400 from above. If only the upper gasket 300 is used, it is possible to obtain a contour that causes sliding at the edge. However, the complementary combination of the sliding of the upper gasket 300 and the side ring R' of the lower gasket 400 enables the formation of a sliding portion S' having a reduced sliding length SL' compared to a conventional sliding portion at the edge where the upper coating layer 150a is formed on the lower coating layer 160a in the electrode active material layer 600. In addition, no side ring appears in the electrode active material layer 600.

[0124] at the same time, Figure 3 The electrode profile of the slot die coater 10 using the conventional shim 60 is shown, and if two identical conventional shims 60 are applied to the upper and lower shims in the case of the configuration of the double slot die coater as disclosed herein, the electrode profile becomes worse. Therefore, in the case of the double slot die coater according to the disclosure, the effect of combining the upper shim 300 and the lower shim 400 having different shapes is significant.

[0125] Fig.12 A cross section in the TD direction of a secondary battery electrode plate coated with an electrode active material slurry using a slot die coater according to a comparative example is shown.

[0126] Fig.12 2 shows an electrode profile in the case where, for example, two identical conventional gaskets 60 are applied to an upper gasket and a lower gasket to form an electrode active material layer 80 on a current collector 20. Figure 3 As shown in FIG. 1 , according to the conventional gasket 60, a sliding portion S or a side ring R is generated, and if the upper and lower gaskets of the same shape are used, the same shape is added, so the electrode profile will result in the following: Fig.12 (a) shows very severe slip or Fig.12 In particular, if the gasket for increasing the flow rate of the side portion is applied to both the upper gasket and the lower gasket, the side ring problem will be worse, such as Fig.12 As shown in (b).

[0127] As mentioned above, it is completely understandable: Fig.12 Compared to the electrode profile in FIG. 1 , due to the application of different shaped gaskets to the features of the dual slot die coater of the present disclosure, the electrode profile can be as Fig.11 The improvement is shown in .

[0128] The electrode active material layer can be stably formed using the slot die coater 100 including the upper gasket 300 and the lower gasket 400 described above. According to the present disclosure, since the coating width, loading amount and sliding can be controlled, the quality of the coating layer and the electrode active material layer formed according to the present disclosure is very excellent. For example, regardless of the position, the thickness of the coating layer in the width direction of the substrate 200 can be uniform, and the sliding section can be formed into a desired shape. Therefore, according to the present disclosure, a coating layer, especially an electrode active material layer, can be stably formed without causing pattern defects.

[0129] For example, coating of the positive active material slurry using the slot die coater 100 may be applied to manufacturing of a positive electrode plate of a secondary battery.

[0130] The positive electrode plate includes a current collector and a positive active material layer formed on a surface of the current collector. According to the present disclosure, the positive active material layer may be formed on one surface of the current collector, or on the top surface and the rear surface by sequential coating.

[0131] The current collector exhibits electrical conductivity, such as Al, Cu, etc., and an appropriate current collector can be used according to the polarity of the current collector electrode known in the field of secondary batteries. The positive electrode active material slurry may also include one or more of a plurality of positive electrode active material particles, a conductive material, and a binder. In addition, the positive electrode active material slurry may also include various additives for the purpose of supplementing or improving electrochemical properties.

[0132] The active material is not limited to a specific composition, as long as it can be used as a positive electrode active material for a lithium ion secondary battery. Non-limiting examples of the active material may include: a layered compound such as lithium manganese oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a compound having a chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as LiMnO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2Cu O2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; 1-x M xNi-site lithium nickel oxide represented by O2 (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); represented by the chemical formula LiMn 2-x M x Lithium manganese composite oxide represented by Li2Mn3MO8 (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 portion of Li in the chemical formula is replaced by alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3; and mixtures thereof. In the present disclosure, 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.

[0133] Generally, the conductive material may be added 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 does not cause chemical changes in the battery and has conductivity, and may include, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives; or mixtures thereof.

[0134] The binder is not particularly limited as long as it can contribute to the combination of the active material and the conductive material and the combination with the current collector, and can be, for example, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber and various copolymers. Relative to 100wt% of the electrode layer, the binder can be included in an amount ranging from 1wt% to 30wt% or from 1wt% to 10wt%.

[0135] The negative electrode plate of the secondary battery can also be manufactured by coating the negative electrode active material slurry using the slot die coater 100 of the present disclosure. 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 rear surface of the current collector. The negative electrode active material slurry may also include one or more of a plurality of negative electrode active material particles, a conductive material, and a binder. In addition, the negative electrode active material slurry may also include various additives for the purpose of supplementing or improving electrochemical characteristics.

[0136] The negative electrode active material can be: a carbon material such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube or carbon nanohorn; a lithium metal material; an alloy material such as silicon or tin; an oxide material such as Nb2O5, Li5Ti4O 12 or TiO2); or a composite thereof. The description of the conductive material, binder and current collector for the positive electrode is also applicable to the negative electrode.

[0137] In particular, as described above, by making the types of active materials or the contents of binders of the first coating liquid 150 and the second coating liquid 160 different from each other, a negative plate having desired characteristics can be manufactured or the characteristics of the negative plate can be controlled. If the content of the binder is different between the first coating liquid 150 and the second coating liquid 160, while maintaining the same solid content, the content of the active material can also be different between the first coating liquid 150 and the second coating liquid 160. For example, by making the binder content of the second coating liquid 160 higher and the binder content of the first coating liquid 150 lower, the lower coating layer 160a can be well attached to the substrate 200 and the upper coating layer 150a can be formed on the lower coating layer 160a. The upper coating layer 150a can contain a higher active material content than the lower coating layer 160a, thereby further increasing the capacity of the secondary battery. In addition, the second coating liquid 160 can contain a natural graphite active material, and the first coating liquid 150 can contain an artificial graphite active material, thereby controlling the characteristics of the negative plate and appropriately utilizing the unique characteristics of the corresponding active materials.

[0138] The slot die coater 100 of the present disclosure can be used to improve sliding so that the discharge capacity of the positive electrode does not exceed the discharge capacity of the negative electrode, thereby preventing lithium deposition and ensuring battery safety. In addition, the electrode plate manufactured using the method for manufacturing a secondary battery electrode plate according to the present disclosure can generate an electrode assembly and be included in a cylindrical secondary battery. In particular, this cylindrical secondary battery can be manufactured as a large cylindrical secondary battery with a form factor of 4680 or more. The size of the electrode plate can be changed according to the size of the roll-type electrode assembly to be manufactured (i.e., the size of the cylindrical secondary battery to be manufactured). The size of the electrode plate included in the large cylindrical secondary battery with a shape factor of 4680 must be larger than the size of the electrode plate included in the small cylindrical secondary battery with a shape factor of 1865 or 2170. The slot die coater 100 of the present disclosure is suitable for manufacturing such large electrode plates.

[0139] Here, the form factor is a value indicating the diameter and height of a cylindrical secondary battery. A cylindrical secondary battery that can be manufactured by the slot die coater 100 according to the present disclosure may be, for example, a 4611 battery cell, a 4875 battery cell, a 4811 battery cell, a 4880 battery cell, or a 4680 battery cell. In the numerical value indicating the form factor, the first two digits indicate the diameter of the battery cell, and the next two digits indicate the height of the battery cell. The last digit "0" is added to indicate that the cross section of the battery cell is circular.

[0140] Preferably, the shape factor of the secondary battery that can be produced is 4680, and the electrode plate obtained as described above can be included in the core-wound electrode assembly included in the cylindrical secondary battery, and the width of one electrode plate can be 60mm to 110mm, and the length can be 3m to 5m. The upper gasket 300 and the lower gasket 400 can have a size that can manufacture an electrode plate having the above-mentioned size. In addition, the number of the second part 330 and the fourth part 430 corresponding to the gasket finger-shaped portion can be increased so that the electrode active material layer pattern is formed into strips on a substrate 200 along multiple channels side by side at the same time, and then cut along the uncoated area between two adjacent electrode active material layer patterns, so that each electrode active material layer pattern is used as an electrode plate.

[0141] Hereinafter, comparison results of electrode plates manufactured according to an embodiment of the present disclosure and a comparative example will be described.

[0142] Measure the electrode profile and compare it to Sample #1 (where Figure 6 The lower gasket 400 shown in FIG. 1 is applied to both the upper and lower gaskets), sample #2 (with Fig.12 Same situation) (where, Figure 6 The upper gasket 300 shown in FIG. 1 is applied to both the upper gasket and the lower gasket), sample #3 (corresponding to an embodiment of the present disclosure) (wherein, Figure 6 The upper gasket 300 in the embodiment is applied to the upper gasket and Figure 6 The lower gasket 400 in is applied to the lower gasket) and sample #4 (wherein, Figure 6 The lower gasket 40 in the embodiment is applied to the upper gasket and Figure 6 The upper gasket 300 is applied to the sliding length of the lower gasket (the positions of the upper gasket / lower gasket are opposite to those in the embodiment of the present disclosure).

[0143] The coating width is designed to be 230mm and the loading is 367mg / 25cm 2, the upper spreading width is 3mm, and the lower spreading width is 3mm. The lower gasket 400 has a protrusion 450. In this case, (ab) is 4mm, (c) is 2mm, and the angle α is 45 degrees. The first coating liquid 150 and the second coating liquid 160 are electrode active material slurries including 53% solid content. The thickness of the lower gasket 400 and the upper gasket 300 is 0.6mm respectively. The length from the front end to the rear end of the upper gasket 300 and the lower gasket 400 is 169.9mm respectively, and the length from the left end to the right end of the upper gasket 300 and the lower gasket 400 is 449mm respectively.

[0144] Fig.13 Results comparing the sliding lengths between samples #1 to #4 are shown.

[0145] The sliding length of sample #1 was 2.4 mm, which showed an improved result compared to the sliding length of 3.2 mm in sample #2, but according to an embodiment of the present disclosure, the sliding length of sample #1 was longer than the sliding length of 2.1 mm in sample #3. The sliding length of sample #4, in which the positions of the upper shim / lower shim are opposite to those in the embodiment of the present disclosure, was as long as that of sample #2. The sliding length of sample #3 was reduced by 34% compared to sample #2. Sample #3 showed the most favorable results in terms of sliding length.

[0146] Fig.14 The results of comparing the electrode profiles between samples #1 to #4 are shown. Sample #3 shows an advantage in the shape of the sliding portion compared to samples #1 and #4. In particular, sample #3 is significantly advantageous in that no side rings appear even when the spread width is 3 mm.

[0147] As described above, although the present disclosure has been described through limited embodiments and drawings, the present disclosure is not limited thereto, and it is obvious that a person skilled in the art to which the present disclosure belongs can make various modifications and changes within the scope of the technical idea of ​​the present disclosure and the equivalent scope of the claims to be described below.

[0148] [Explanation of Reference Numerals]

[0149] 100: Slot die coater 101: Upper slot

[0150] 102: Lower slot 110: Upper mold block

[0151] 120: Middle mold block 130: Lower mold block

[0152] 200: Base material 300: Upper gasket

[0153] 310: first opening 320: first part

[0154] 330: Second part 400: Lower gasket

[0155] 410: Second opening 420: Third part

[0156] 430: Part 4 435: Inclined Surface

[0157] 440: flow increase part 450, 455: protrusion

[0158] 600: Electrode active material layer

Claims

1. A slot die coater, comprising: an upper mold block, a middle mold block, and a lower mold block; an upper gasket, the upper gasket being disposed between the upper mold block and the middle mold block to form an upper groove; as well as a lower gasket, the lower gasket being disposed between the middle mold block and the lower mold block to form a lower groove, wherein the first coating liquid is discharged through an upper outlet connected to the upper tank and applied to the substrate, and the second coating liquid is discharged through a lower outlet connected to the lower tank and applied to the substrate, Wherein, the upper gasket comprises at least one first opening, wherein the lower gasket includes a second opening at a position corresponding to the first opening, and The second opening includes a section having a smaller width than that of the first opening at a front end adjacent to the lower outlet.

2. The slot die coater of claim 1, wherein: The upper gasket includes a first portion configured to serve as a base and at least two second portions extending from the first portion, wherein the second portions are connected to the same side of the first portion and extend in the same direction, wherein a space between the second portions is defined as the first opening, and wherein a width of the first opening is constant.

3. The slot die coater of claim 2, wherein: The lower gasket includes a third part configured to serve as a base and at least two fourth parts extending from the third part, wherein the fourth parts are connected to the same side of the third part and extend in the same direction, wherein the space between the fourth parts is defined as the second opening, wherein a flow increase part is formed on the inner side of the lower gasket at the rear end of the second opening, and the width of the flow increase part is greater than the width of the front end of the second opening to increase the flow of the second coating liquid.

4. The slot die coater of claim 3, wherein: The width of the fourth portion is differently configured in a direction toward the rear end to form the flow rate increasing portion.

5. The slot die coater of claim 3, wherein: A side surface of the fourth portion applies a tapered shape to form the flow increasing portion.

6. The slot die coater of claim 3, wherein: The width of the fourth portion is constant at a first width from the front end toward the rear end of the second opening to a first position, decreases to a second width toward the rear end to a second position with an inclined surface, and is constant at the second width until a third portion.

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

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

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

10. The slot die coater of claim 1, wherein: The lower gasket includes a third portion configured to serve as a base and at least two fourth portions extending from the third portion, wherein the fourth portions are connected to the same side of the third portion and extend in the same direction, wherein the space between the fourth portions is defined as the second opening, and wherein a protrusion is further formed on the side surface of the fourth portion at the front end of the second opening.

11. The slot die coater of claim 10, wherein: The protrusion has a right triangle or a right trapezoid shape.

12. The slot die coater of claim 1, wherein: The first coating liquid and the second coating liquid are coating liquids of different types from each other.

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

14. A method for manufacturing an electrode plate of a secondary battery, the method comprising: forming a lower coating layer on the substrate with a second coating liquid by increasing the flow rate in the side portion; as well as At the same time, an upper coating layer is formed on the lower coating layer on the substrate using a first coating liquid to press the flow increase portion in the side portion.

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 materials or contents of binders from each other.

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

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

18. The method for manufacturing an electrode plate for a secondary battery according to claim 16, wherein: The gap between the upper slot of the slot die coater and the substrate and the gap between the lower slot of the slot die coater and the substrate are adjusted to control the first coating liquid to spread to a width exceeding the width of the first opening and the second coating liquid to spread to a width exceeding the width of the second opening.

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