Double-slit mold coating machine, method for coating electrode active material slurry and electrode

Abstract

The dual-slit mold coating machine according to this disclosure includes a lower slit and an upper slit for extruding and coating an electrode active material slurry onto the surface of a continuously moving current collector through the lower slit and / or the upper slit. The dual-slit mold coating machine includes a lower plate, an intermediate plate located on the lower plate, and an upper plate located on the intermediate plate. The lower slit is formed between the lower plate and the intermediate plate, and the upper slit is formed between the intermediate plate and the upper plate. The lower plate, the intermediate plate, and the upper plate each have a lower mold lip, an intermediate mold lip, and an upper mold lip, respectively. Each of these forms a front end of the dual-slit mold coating machine relative to the current collector. The distance between the current collector and the lower mold lip is greater than the distance between the current collector and the upper mold lip and the distance between the current collector and the intermediate mold lip.

Description

Technical Field

[0001] This disclosure relates to a double-slit mold coating machine capable of simultaneously forming a double-layer structure, and a method for coating electrode active material slurry using the double-slit mold coating machine. More specifically, this disclosure relates to electrodes manufactured using the double-slit mold coating machine and methods for manufacturing electrodes. This application claims priority to Korean Patent Application No. 10-2020-0119918, filed with the Korean Intellectual Property Office on September 17, 2020, and Korean Patent Application No. 10-2021-0122022, filed with the Korean Intellectual Property Office on September 13, 2021, the disclosures of which are incorporated herein by reference. Background Technology

[0002] With the continuous development of technology and the increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Secondary batteries essentially consist of electrode assemblies that serve as power generation elements. These electrode assemblies include a positive electrode, a separator, and a negative electrode stacked at least once. The positive and negative electrodes are manufactured by coating and drying positive and negative active material slurries onto current collectors made of aluminum foil and copper foil, respectively. Typically, secondary batteries include positive active materials such as layered crystalline lithium cobalt oxide (LiCoO2), lithium manganese oxide, layered crystalline LiMnO2, spinel crystalline LiMn2O4, and lithium nickel oxide (LiNiO2). Furthermore, negative active materials primarily include carbon-based materials. Recently, with the increasing demand for high-energy lithium secondary batteries, a hybrid approach combining silicon-based and silicon oxide-based materials with at least 10 times higher effective capacity than carbon-based materials has been proposed. For uniform charge-discharge characteristics of the secondary battery, the positive and negative active material slurries need to be uniformly coated onto the current collector.

[0003] To improve the performance of secondary batteries, researchers are focusing on developing electrode structures with a double-layer active material layer on the current collector. To form this double-layer active material layer on the current collector, a dual-slit die coating machine capable of simultaneously coating two types of electrode active material slurries can be used.

[0004] Figure 1 This illustrates an example of a coating method using a double-slit die coating machine. Figure 2 yes Figure 1 Enlarged view of section A.

[0005] refer to Figure 1 and 2By simultaneously conveying two types of electrode active material slurries from the double-slit die coater 20 while moving the current collector 15 using the rotation of the coating roller 10, two electrode active material layers can be formed on the current collector 15. The electrode active material slurry conveyed from the double-slit die coater 20 is coated on one surface of the current collector 15 to form an electrode active material layer.

[0006] The dual-slit mold coating machine 20 is assembled from three mold blocks: a lower plate 25, a middle plate 30, and an upper plate 35. Slits are formed between the lower plate 25 and the middle plate 30, and between the middle plate 30 and the upper plate 35, for a total of two slits. Two types of electrode active material slurries are simultaneously conveyed through outlets 40 and 45. Each outlet 40 and 45 communicates with each slit, thus the first electrode active material slurry 50 is coated earlier, and an additional second electrode active material slurry 55 is continuously coated on top of the first electrode active material slurry 50 to obtain a double-layer structure. The ends of the lower plate 25, the middle plate 30, and the upper plate 35 are aligned in a straight line.

[0007] However, the coating method using a conventional dual-slit die coating machine 20 involves intermittent coating in the MD direction (corresponding to the longitudinal direction of movement of the current collector in continuous coating). Intermittent coating forms a pattern on the current collector 15 in the order of active material layer, uncoated area, active material layer, and uncoated area by repeatedly supplying and stopping the first electrode active material slurry 50 and the second electrode active material slurry 55 while moving the current collector 15.

[0008] Figure 3 This is a cross-sectional view of the electrode during ideal intermittent coating. The double-layered upper electrode active material slurry layer 50a and lower electrode active material slurry layer 55a are formed smoothly and horizontally, with the ends of the pattern almost perpendicular to the current collector 15, as shown. Figure 3 As shown.

[0009] However, in the case of a conventional double-slit die coating machine 20, when the supply of the electrode active material slurry stops, the loading stops smoothly, and as... Figure 4 As shown in the magnified image, the end B of the slurry layer exhibits a loading out phenomenon on the current collector 15, resulting in low coating quality at the end.

[0010] refer to Figure 4 The distance L from point Ps, where the thickness of the upper slurry layer 55a decreases due to the slurry delivery stopping, to the end point of the slurry delivery, i.e., the coating end point Pe, is the loading fading region. This loading fading region becomes a wasteful, redundant area, reducing process efficiency and increasing manufacturing costs.

[0011] Therefore, there is a need to develop a technology that minimizes the area wasted in the electrode active material slurry coating process when manufacturing electrodes with a double-layer active material layer. Summary of the Invention

[0012] Technical issues

[0013] This disclosure aims to solve the above-mentioned problems. Therefore, this disclosure aims to provide a double-slit mold coating machine for preventing load fading phenomenon and a method for coating electrode active material slurry using the double-slit mold coating machine.

[0014] This disclosure further relates to providing electrodes with a minimal load fading region using a dual-slit die coating machine.

[0015] However, the problems to be solved by this disclosure are not limited to those described above, and other problems will be clearly understood by those skilled in the art through the following detailed description.

[0016] Technical solution

[0017] To address the aforementioned issues, the dual-slit mold coating machine of this disclosure includes a lower slit and an upper slit for extruding and coating an electrode active material slurry onto the surface of a continuously moving current collector through the lower slit and / or the upper slit. The dual-slit mold coating machine includes a lower plate, an intermediate plate located on the lower plate, and an upper plate located on the intermediate plate. The lower slit is formed between the lower plate and the intermediate plate, and the upper slit is formed between the intermediate plate and the upper plate. The lower plate, the intermediate plate, and the upper plate each have a lower mold lip, an intermediate mold lip, and an upper mold lip, respectively. Each of these lips forms the front end of the dual-slit mold coating machine relative to the current collector, and the distance between the current collector and the lower mold lip is greater than the distance between the current collector and the upper mold lip and the distance between the current collector and the intermediate mold lip.

[0018] In this disclosure, the dual-slit die coating machine may also include a control unit for linearly aligning the lower die lip, intermediate die lip, and upper die lip relative to the current collector and then individually moving the lower die lip backward.

[0019] In this disclosure, a lower outlet communicating with the lower slit can be formed between the lower mold lip and the intermediate mold lip, and an upper outlet communicating with the upper slit can be formed between the intermediate mold lip and the upper mold lip. A predetermined step is formed between the lower outlet and the upper outlet.

[0020] In this configuration, the lower outlet can transport the electrode active material slurry forming the lower slurry layer to the current collector, and the upper outlet can be spaced from the lower outlet downstream along the coating direction and transport the electrode active material slurry forming the upper slurry layer to the lower slurry layer on the current collector.

[0021] In this case, the predetermined step is preferably 20% to 70% of the sum of the average thickness of the lower slurry layer and the average thickness of the upper slurry layer.

[0022] Preferably, the lower slit and the upper slit form an angle of 30° to 60°.

[0023] In this disclosure, the double-slit mold coating machine may further include a first spacer disposed between the lower plate and the intermediate plate to adjust the width of the lower slit, and a second spacer disposed between the intermediate plate and the upper plate to adjust the width of the upper slit.

[0024] In this disclosure, the lower plate may include a first manifold communicating with the lower slit to receive a first electrode paste, and the upper plate may include a second manifold communicating with the upper slit to receive a second electrode paste.

[0025] This disclosure may also include a first valve for opening / closing the delivery through the lower outlet, a second valve for opening / closing the delivery through the upper outlet, and a valve control unit for controlling the opening / closing of the first and second valves.

[0026] To address the aforementioned problems, the coating method for electrode active material slurry according to this disclosure includes supplying electrode active material slurry on the current collector while moving the current collector from the lower die lip to the upper die lip using a double-slit die coating machine according to this disclosure, thereby forming an electrode active material slurry layer on the current collector.

[0027] To address the aforementioned issues, another coating method for electrode active material slurry according to this disclosure includes intermittently coating a layer of electrode active material slurry onto the current collector by repeatedly supplying and stopping the current collector while moving it from the lower die lip to the upper die lip using a dual-slit die coating machine.

[0028] To address the aforementioned problems, another coating method for electrode active material slurry according to this disclosure is a coating method using a dual-slit die coating machine. This dual-slit die coating machine includes a lower slit and an upper slit and is used to simultaneously extrude and coat two electrode active material slurries onto the surface of a continuously moving current collector through the lower and upper slits. The dual-slit die coating machine includes a lower plate, an intermediate plate located on the lower plate, and an upper plate located on the intermediate plate. The lower slit is formed between the lower plate and the intermediate plate, and the upper slit is formed between the intermediate plate and the upper plate. The lower plate, intermediate plate, and upper plate each have a lower die lip, an intermediate die lip, and an upper die lip, respectively, each forming a relative... The front end of the current collector and the distance between the current collector and the lower mold lip are greater than the distance between the current collector and the upper mold lip and the distance between the current collector and the intermediate mold lip. The method includes: simultaneously conveying two electrode active material slurries onto the current collector moving from the lower mold lip to the upper mold lip through a lower outlet and an upper outlet to form a double-layer structure including a lower slurry layer and an upper slurry layer coated on the lower slurry layer, wherein a lower outlet connected to the lower slit is formed between the lower mold lip and the intermediate mold lip, an upper outlet connected to the upper slit is formed between the intermediate mold lip and the upper mold lip, and the upper outlet is spaced apart from the lower outlet downstream along the coating direction.

[0029] Here, intermittent coating can be achieved by repeatedly and simultaneously feeding and stopping two electrode active material slurries.

[0030] A predetermined step can be formed between the lower outlet and the upper outlet, and the step can be 20% to 70% of the sum of the average thickness of the lower slurry layer and the average thickness of the upper slurry layer.

[0031] The ratio of the average thickness of the lower slurry layer to the average thickness of the upper slurry layer can be 1:3 to 3:1.

[0032] To address another issue, the electrode according to this disclosure includes a current collector and an electrode active material layer formed on the current collector. The electrode active material layer includes a lower active material layer disposed adjacent to the surface of the current collector and an upper active material layer disposed on the lower active material layer. The lower active material layer and the upper active material layer each have a flat portion and an inclined portion connected to the flat portion. The inclined portion has a smaller thickness toward the periphery. The end of the upper active material layer on the current collector matches the end of the lower active material layer or is disposed at a position further outward than the end of the lower active material layer.

[0033] The boundaries of the flat and inclined portions of the upper active material layer can be positioned further outward than the boundaries of the flat and inclined portions of the lower active material layer. The inclined portion of the upper active material layer can cover the inclined portion of the lower active material layer to prevent the inclined portion of the lower active material layer from being exposed. The distance from the boundaries of the flat and inclined portions of the upper active material layer to the end of the upper active material layer can be less than 4 mm.

[0034] Beneficial effects

[0035] According to one aspect of this disclosure, the lower die lip is positioned further back from the current collector than the upper die lip and the intermediate die lip. The step between the lips reduces the length of the load fading (without reduction) when the supply of the electrode active material slurry stops. Therefore, load fading can be prevented and the length of the load fading region reduced, thereby increasing the battery capacity. This disclosure does not degrade coating quality. In particular, this disclosure is highly effective in intermittent coating by alternating the supply and stopping of the electrode active material slurry.

[0036] This disclosure controls the step between the upper and lower outlets, and particularly controls the lower plate of the lower outlet, which is defined between the lower plate and the intermediate plate. This disclosure causes the lower mold lip, i.e., the lip of the lower plate, to be further rearward and away from the manifold than the lip of the upper plate / intermediate plate.

[0037] The dual-slit die coating machine and the method for coating electrode active material slurry using the dual-slit die coating machine disclosed herein can improve process efficiency and reduce defect rate when forming a double-layer active material layer on the current collector. Furthermore, by reducing the loading fading region, the wasted electrode area after the process can be reduced.

[0038] According to this disclosure, an electrode with a minimized load fading region can be provided. Because the load fading region is reduced, wasted excess area can be decreased, thereby improving process efficiency and reducing manufacturing costs. Attached Figure Description

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

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

[0041] Figure 2 yes Figure 1 Enlarged view of section A.

[0042] Figure 3 This is a cross-sectional view of the electrode during ideal intermittent coating.

[0043] Figure 4 This is a schematic cross-sectional view of an electrode manufactured using a conventional method for coating an electrode active material slurry.

[0044] Figure 5 This is a schematic cross-sectional view of a double-slit mold coating machine according to an embodiment of the present disclosure.

[0045] Figure 6 This is a schematic exploded perspective view of a double-slit mold coating machine according to an embodiment of the present disclosure.

[0046] Figure 7 yes Figure 5 The enlarged view in section C shows the electrode active material slurry coating process using a dual-slit mold coating machine according to an embodiment of the present disclosure.

[0047] Figure 8a and 8b This is a schematic cross-sectional view of an electrode manufactured by an electrode active material slurry coating method according to an embodiment of the present disclosure.

[0048] Figure 9 and Figure 10 This is a width-thickness diagram of the electrode cross-section based on the comparative example and the embodiment. Detailed Implementation

[0049] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Before description, it should be understood that the terminology used in the specification and appended claims should not be construed as limited to its general and dictionary meaning, but rather interpreted based on its meaning and concept corresponding to the technical aspects of the present disclosure, based on the principle of allowing the inventor to appropriately define the terminology to obtain the best interpretation. Therefore, the embodiments described herein and the descriptions in the accompanying drawings are merely some preferred embodiments of the present disclosure and do not fully describe the technical features of the present disclosure. It should be understood that various other equivalents and variations of the present disclosure are possible at the time of filing a patent application.

[0050] The dual-slit mold coating machine disclosed herein is an apparatus comprising a lower slit and an upper slit to coat a coating solution onto a substrate in a double-layer form. The “substrate” described below refers to a current collector, and the coating solution is an “electrode active material slurry.” The slurry conveyed through the lower slit and the slurry conveyed through the upper slit can be electrode active material slurries having the same or different compositions (types of active material, conductive material, and binder), amounts (quantities of active material, conductive material, and binder), or properties. The dual-slit mold coating machine of this disclosure is optimized for electrodes manufactured by simultaneously coating two types of electrode active material slurries, or by patterned coating (alternating coating of two types of electrode active material slurries), or by intermittent coating (alternating supply and stop of two types of electrode active material slurries). However, the scope of this disclosure is not necessarily limited thereto.

[0051] In traditional intermittent coating, when the paste supply is stopped during pattern formation, the following occurs: Figure 4The invention describes the phenomena of insufficient loading and gradual loading decay. The inventors discovered that the loading decay phenomenon occurs when residual slurry forming menisci or beads is coated on the current collector when the slurry supply is stopped to form the end. Therefore, the inventors investigated a structure for minimizing the slurry residue remaining between the dual-slit die coater and the current collector, and proposed a dual-slit die coater according to this disclosure.

[0052] Figure 5 This is a schematic cross-sectional view of a double-slit mold coating machine according to an embodiment of the present disclosure. Figure 6 This is a schematic exploded perspective view of a double-slit mold coating machine according to an embodiment of the present disclosure. Figure 7 yes Figure 5 The enlarged view in section C shows the electrode active material slurry coating process using a dual-slit mold coating machine according to an embodiment of the present disclosure.

[0053] refer to Figures 5 to 7 The dual-slit mold coating machine 100 disclosed herein includes a lower slit 101 and an upper slit 102, and is a device capable of simultaneously, alternately or intermittently coating the same electrode active material slurry or two different electrode active material slurries on the current collector 300 through the lower slit 101 and the upper slit 102.

[0054] The dual-slit die coating machine 100 includes a lower plate 110, an intermediate plate 120 located on the lower plate 110, and an upper plate 130 located on the intermediate plate 120. The lower plate 110, intermediate plate 120, and upper plate 130 are assembled together by fasteners such as bolts. The lower plate 110 is the lowest block in the dual-slit die coating machine 100, and its surface facing the intermediate plate 120 is inclined at approximately 30 degrees relative to the bottom surface (XZ plane). ° Angles up to 60°.

[0055] The lower slit 101 can be formed at a position where the lower plate 110 and the intermediate plate 120 face each other. For example, a first spacer 113 is inserted between the lower plate 110 and the intermediate plate 120 to form a gap, and the lower slit 101 can be formed corresponding to a channel for the flow of the first electrode active material slurry 150. In this case, the thickness of the first spacer 113 determines the vertical width of the lower slit 101 (Y-axis direction, slit gap).

[0056] like Figure 6As shown, the first spacer 113 has a first opening 113a, which is cut in one area and can be inserted into the remaining portion of the edge region of the respective opposing surfaces of the lower plate 110 and the intermediate plate 120, except for one side. Therefore, a lower outlet 101a for discharging the first electrode active material slurry 150 is formed only between the front ends of the lower plate 110 and the intermediate plate 120. The front ends of the lower plate 110 and the intermediate plate 120 are defined as the lower mold lip 111 and the intermediate mold lip 121, respectively; in other words, the lower outlet 101a is formed by the gap between the lower mold lip 111 and the intermediate mold lip 121.

[0057] For reference, the first spacer 113 serves as a gasket to prevent the first electrode active material slurry 150 from leaking through the gap between the lower plate 110 and the intermediate plate 120, except for the area where the lower outlet 101a is formed. Therefore, the first spacer 113 is preferably made of a material with sealing capabilities.

[0058] The lower plate 110 includes a first manifold 112 having a predetermined depth on its surface facing the intermediate plate 120, and the first manifold 112 communicates with the lower slit 101. Although not shown in the figure, the first manifold 112 is connected via a supply pipe to an externally mounted first electrode active material slurry supply chamber (not shown) and is supplied with first electrode active material slurry 150. When the first manifold 112 is completely filled with the first electrode active material slurry 150, the flow of the first electrode active material slurry 150 is guided along the lower slit 101 and flows out from the lower outlet 101a.

[0059] The intermediate plate 120 is a block disposed in the middle of the mold block of the double-slit mold coating machine 100, and is located between the lower plate 110 and the upper plate 130 to form a double slit. In this embodiment, the cross-section of the intermediate plate 120 is a right-angled triangle, but it is not limited to this. For example, the cross-section of the intermediate plate 120 may be an isosceles triangle.

[0060] The upper plate 130 is positioned so that its top surface faces the middle plate 120 and is parallel to its bottom surface. As described above, the upper slit 102 is formed at a position where the middle plate 120 and the upper plate 130 face each other.

[0061] Similar to the lower slit 101 described above, the second spacer 133 can be inserted between the intermediate plate 120 and the upper plate 130 to form a gap between them. Thus, an upper slit 102 is formed opposite to the channel for the flow of the second electrode active material slurry 160. In this case, the vertical width (Y-axis direction, slit gap) of the upper slit 102 is determined by the second spacer 133.

[0062] Furthermore, the second spacer 133, having a structure similar to the first spacer 113, has a second opening 133a, which is cut in one region and inserted into the remaining portion of the edge region of the respective opposing surfaces of the intermediate plate 120 and the upper plate 130, except for one side. Similarly, the upper slit 102 is blocked circumferentially except on its front side, and the upper outlet 102a is formed only between the front ends of the intermediate plate 120 and the upper plate 130. The front end of the upper plate 130 is defined as the upper mold lip 131; in other words, the upper outlet 102a is formed by the gap between the intermediate mold lip 121 and the upper mold lip 131.

[0063] Furthermore, the upper plate 130 includes a second manifold 132 having a predetermined depth on its surface facing the intermediate plate 120, and the second manifold 132 communicates with the upper slit 102. Although not shown in the figure, the second manifold 132 is connected via a supply pipe to an externally mounted supply chamber for a second electrode active material slurry 160, and is supplied with the second electrode active material slurry 160. When the second electrode active material slurry 160 is supplied from an external source along the supply pipe, and the second manifold 132 is completely filled with the second electrode active material slurry 160, the flow of the second electrode active material slurry 160 is guided along the upper slit 102 communicating with the second manifold 132 and flows out from the upper outlet 102a.

[0064] The upper slit 102 and the lower slit 101 form an angle, and this angle can be approximately 30° to 60°. ° The upper slit 102 and the lower slit 101 may intersect at a single point, and the upper outlet 102a and the lower outlet 101a may be located near the intersection point. Therefore, the locations of the first electrode active material slurry 150 and the second electrode active material slurry 160 may be concentrated at approximately one point.

[0065] The first manifold 112 and the second manifold 132 are formed in the lower plate 110 and the upper plate 130, respectively. In this case, the structurally most vulnerable intermediate plate 120 may be less affected.

[0066] Meanwhile, the double slit mold coating machine 100 may also include a first valve for opening / closing the conveying through the lower outlet 101a, a second valve for opening / closing the conveying through the upper outlet 102a, and a valve control unit for controlling the opening / closing of the first and second valves.

[0067] According to the dual-slit mold coating machine 100 having the above-described structure, a rotatable coating roller 200 is located at the front of the dual-slit mold coating machine 100, and the coating roller 200 is rotatable to move the current collector 300 to be coated, while the first electrode active material slurry 150 and the second electrode active material slurry 160 are continuously in contact with the surface of the current collector 300, so that the current collector 300 can be coated into a double-layer structure simultaneously. Alternatively, the first valve and the second valve can be controlled to close / open by a valve control unit to alternately perform the supply and stop of the first electrode active material slurry 150 and the supply and stop of the second electrode active material slurry 160, thereby intermittently forming a patterned coating on the current collector 300.

[0068] refer to Figure 7 The structure of the mold lip of the dual-slit mold coating machine according to embodiments of the present disclosure and the method for coating electrode active material slurry using the dual-slit mold coating machine will be described in detail. The dual-slit mold coating machine 100 according to the present disclosure has lip steps of upper / middle / lower plates.

[0069] The distance H3 between the current collector 300 and the lower mold lip 111 is greater than the distance H1 between the current collector 300 and the upper mold lip 131, and the distance H2 between the current collector 300 and the intermediate mold lip 121. This distance difference is achieved by moving the lower mold lip 111 (which is the lip of the lower plate 110) further back from the current collector 300 in the opposite direction to the conveying direction than the upper mold lip 131 (which is the lip of the upper plate 130) and the intermediate mold lip 121 (which is the lip of the intermediate plate 120), thus forming a lip step. This lip step reduces the load fading area. The distance H1 between the current collector 300 and the upper mold lip 131 can be equal to the distance H2 between the current collector 300 and the intermediate mold lip 121.

[0070] To form the lip step, the dual-slit die coating machine 100 may also include a control unit to individually rearward move the lower die lip 111 after the lower die lip 111, the intermediate die lip 121, and the upper die lip 131 are linearly aligned relative to the collector 300. In this configuration, the lower die lip 111 is positioned further away from the collector 300 than the upper die lip 131 and the intermediate die lip 121.

[0071] Therefore, a predetermined step D' is formed between the lower outlet 101a and the upper outlet 102a. Step D' is the result of subtracting the distance H1 between the current collector 300 and the upper mold lip 131 from the distance H3 between the current collector 300 and the lower mold lip 111. The lower outlet 101a and the upper outlet 102a are horizontally separated by step D', thereby preventing the second electrode active material slurry 160 exiting from the upper outlet 102a from entering the lower outlet 101a, or preventing the first electrode active material slurry 150 exiting from the lower outlet 101a from entering the upper outlet 102a. A feature of this disclosure is that the intermediate plate 120 and the lower plate 110 forming the lower outlet 101a are spaced apart from each other.

[0072] As shown in the figure, when the lip position is set, the upper outlet 102a is spaced apart from the lower outlet 101a downstream in the coating direction. By simultaneously conveying the first electrode active material slurry 150 and the second electrode active material 160 through the lower outlet 101a and the upper outlet 102a, respectively, while moving the current collector 300 from the lower mold lip 111 to the upper mold lip 131, an active material layer with a double-layer structure can be formed on the current collector 300.

[0073] This disclosure is based solely on the lower layer slurry, namely, the first electrode active material slurry 150 flowing out from the lower outlet 101a, which moves the lower layer upstream away from the current collector 300. In other words, this disclosure moves the lower plate 110 away from the current collector 300 to create a height difference between the intermediate plate 120 and the lower plate 110, i.e., the two plates forming the lower outlet 101a. Whether upstream or downstream, it is different from the movement of the outlet itself.

[0074] Figure 8a and Figure 8b This is a diagram showing a cross-section of an electrode manufactured by a coating method for an electrode active material slurry according to an embodiment of the present disclosure. Figure 8a It is a cross-section after the electrode active material slurry is coated. Figure 8b The cross-section is shown after coating and drying.

[0075] like Figure 8a As shown, a first electrode active material slurry 150 flowing from the lower outlet 101a is coated onto the current collector 300 to form a lower slurry layer 150a, while a second electrode active material slurry 160 flowing from the upper outlet 102a is coated onto it to form an upper slurry layer 160a. Using the dual-slit die coating machine 100 of this disclosure, a double-layer structure including the upper slurry layer 160a on the lower slurry layer 150a can be formed. Specifically, when the supply of the first electrode active material slurry 150 and the second electrode active material slurry 160 stops simultaneously, a lip step of the dual-slit die coating machine 100 can be used to obtain… Figure 8aThe pattern shown at the end, and can be obtained after drying or further rolling. Figure 8b The pattern shown at the end. Roll forming is an optional step that can be performed to adjust the thickness.

[0076] The ratio of the average thickness D1 of the lower slurry layer 150a formed by the first electrode active material slurry 150 flowing out from the lower outlet 101a to the average thickness D2 of the upper slurry layer 160a formed by the second electrode active material slurry 160 flowing out from the upper outlet 102a is in the range of 1:3 to 3:1 (D1:D2). The thickness ratio is a relative representation of the average length in the thickness direction of each layer. Furthermore, the average thickness D1 of the lower slurry layer 150a and the average thickness D2 of the upper slurry layer 160a can each be from 40 to 200 μm.

[0077] The thicknesses of the upper slurry layer 150a and the lower slurry layer 160a correspond to the pressure of the slurry to be supplied. When the pressure of the second electrode active material slurry 160 is three times higher than the pressure of the first electrode active material slurry 150, resulting in a thickness ratio of the lower slurry layer 150a to the upper slurry layer 160a of 1:3 or greater, the pressure of the upper layer is greater than that of the lower layer. Therefore, the first electrode active material slurry 150 is pushed back in the opposite direction to the coating direction, increasing the likelihood of leakage. Furthermore, due to the high pressure of the second electrode active material slurry 160, the first electrode active material slurry 150 cannot be supplied adequately. Additionally, the high pressure of the second electrode active material slurry 160 leads to uneven supply of the first electrode active material slurry 150, making it difficult to uniformly form the lower slurry layer 150a.

[0078] Meanwhile, when the pressure of the second electrode active material slurry 160 is 3 times higher than that of the first electrode active material slurry 150, resulting in a thickness ratio of the lower slurry layer 150a to the upper slurry layer 160a of 1:3 or greater, the second electrode active material slurry 160 may not be supplied properly, or the second electrode active material slurry 160 may not be uniformly coated in the coating direction, resulting in an uneven coating solution surface.

[0079] The range of step D' is preferably between 20% and 70% of the sum of the average thickness D1 of the lower slurry layer 150a and the average thickness D2 of the upper slurry layer 160a. When it is below 20%, the effect of reducing the loading ebb-off length when the slurry supply stops is poor. When it is above 70%, the entire area of ​​the space where the slurry resides before coating, i.e., the space between the lower mold lip 111, the intermediate mold lip 121, and the lower slurry layer 150a, is very small compared to the amount of slurry, so that the first electrode active material slurry 150 being supplied is not coated and it leaks back. Leakage refers to the instability caused by the loss of some slurry from upstream of the lower mold lip. This refers to the loss of pre-metered slurry and the inability to estimate the final coating thickness.

[0080] Traditionally, for intermittent coating, when the paste supply is stopped during pattern formation, the loading decreases and a gradual decline in loading occurs. Returning to the existing display technology... Figure 2 The inventors discovered that the loading fading phenomenon occurs when residual first electrode active material slurry 50 and second electrode active material slurry 55, forming menisci or beads, are coated on the current collector 15 between the double-slit mold coater 20 and the current collector 15 when the slurry supply stops to form an end. Specifically, it was found that the length S from the front end of the upper plate 35 to the meniscus of the first electrode active material slurry 50 is related to the length of the loading fading region.

[0081] Due to such Figure 7 As shown, the lower plate 110 moves rearward, and this disclosure reduces the amount of residual slurry forming menisci or beads between the dual-slit die coater 100 and the current collector 300. This is because the length S' of the meniscus from the upper die lip 131 at the front end of the upper plate 130 to the first electrode active material slurry 150 is greater than... Figure 2 The length S is short. Therefore, it is possible to reduce the loading decay length where the loading does not decrease when the slurry supply stops. Therefore, it is possible to ideally form pattern ends, such as... Figure 8a and 8b As shown.

[0082] like Figure 8a As shown, a lower slurry layer 150a and an upper slurry layer 160a are formed on the current collector 300 by coating almost sequentially along the movement direction of the current collector. In this disclosure, the distance L' from point Ps', where the thickness of the upper slurry layer 160a begins to decrease due to the slurry delivery stopping, to the end of slurry delivery, i.e., the coating endpoint Pe', is the loading fading region, which is much smaller than that in the prior art. Figure 4The distance L of the loading fading region. The loading fading region acts as a wasted remaining area, which reduces process efficiency and increases manufacturing costs. According to this disclosure, as the loading fading region is reduced, the wasted remaining area can be reduced, thereby improving process efficiency and reducing manufacturing costs.

[0083] Normally, Figure 4 The distance L of the fading zone is generally 5.5 mm or more. However, using the double-slit die coating machine 100 according to this disclosure, the distance L' of the remaining area, i.e., from point Ps' where the thickness of the upper slurry layer 160a begins to decrease due to the slurry delivery stopping, to the end of slurry delivery, i.e., the coating endpoint Pe', can be adjusted to less than 4 mm. When the length of the remaining area exceeds 4 mm, the wasted area increases, resulting in low economic efficiency.

[0084] For example, the coating method for the electrode active material slurry disclosed herein can be applied to the manufacture of the positive electrode of a secondary battery. The positive electrode includes a positive electrode active material layer formed on the surface of a current collector and a current collector. The current collector can include any material exhibiting conductivity, such as Al or Cu, and appropriate materials can be used according to the polarity of the current collector in electrodes well known in the field of secondary batteries. The positive electrode active material layer may also include at least one of positive electrode active material particles, a conductive material, or a binder. Furthermore, the positive electrode may include various additives to enhance or improve its electrical and chemical properties.

[0085] The active material is not limited to a specific type and may include any material that can be used as a positive electrode active material for lithium-ion secondary batteries. Non-limiting examples may include at least one of layered compounds or compounds having one or more transition metal substitutions, such as lithium manganese composite oxides (LiMn2O4, LiMnO2), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2); lithium manganese oxide, chemical formula Li 1+x Mn 2-x O4 (x is 0-0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxide, such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; and LiNi 1-x M x Ni-site lithium nickel oxide represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01–0.3); LiMn 2-x M xLithium manganese composite oxides represented by O2 (M = Co, Ni, Fe, Cr, Zn or Ta, x = 0.01 to 0.1) or Li2Mn3MO8 (M = Fe, Co, Ni, Cu or Zn); LiMn2O4, wherein Li in the chemical formula is partially replaced by an alkaline earth metal ion; disulfide; or Fe2(MoO4)3. In this disclosure, the positive electrode may include a solid electrolyte material, such as at least one of polymeric solid electrolytes, oxide solid electrolytes, or sulfide solid electrolytes.

[0086] Based on the total weight of the mixture containing electrode active materials, the amount of conductive material added is typically from 1 wt% to 20 wt%. The conductive material is not limited to a specific type and can include any material that has conductive properties and does not cause any chemical change to the corresponding battery, such as at least one selected from the following: graphite, such as natural or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lampblack, and thermally cracked black; conductive fibers, such as carbon fibers or metal fibers; metal powders, such as fluorinated carbon, aluminum, and nickel powders; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive materials, such as polystyrene derivatives.

[0087] The adhesive is not limited to a specific type, but can include any material that facilitates bonding of the active material to the conductive material and to the current collector, such as polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers thereof. Based on 100% by weight of the electrode layer, the adhesive can typically range from 1% by weight to 30% by weight or from 1% by weight to 10% by weight.

[0088] The electrode can be a negative electrode. The negative electrode includes a current collector and a layer of negative electrode active material formed on the surface of the current collector. The negative electrode active material layer may also include at least one of negative electrode active material particles, a conductive material, or a binder. Furthermore, the negative electrode may include various additives to enhance or improve its electrical and chemical properties.

[0089] Negative electrode active materials can include carbon materials, such as graphite, amorphous carbon, diamond-phase carbon, fullerenes, carbon nanotubes and carbon nanohorns, lithium metal materials, alloy-based materials, such as silicon or tin alloy-based materials, and oxide-based materials, such as Nb₂O₅ and Li₅Ti₄O₂. 12 TiO2 or a composite thereof. The conductive material, binder, and current collector of the negative electrode can be the same as those of the positive electrode. In particular, the electrode manufactured according to this disclosure is preferably a negative electrode.

[0090] It can be dried, such as Figure 8a The coating results shown are used to manufacture Figure 8b The electrodes.

[0091] refer to Figure 8b According to embodiments of the present disclosure, the electrode includes a current collector 300 and an electrode active material layer formed on the current collector 300. Specifically, the electrode active material layer includes a lower active material layer 150b positioned adjacent to the surface of the current collector 300 and an upper active material layer 160b located on the lower active material layer 150b. That is, the electrode active material layer has a structure in which the upper active material layer 160b is sequentially stacked on the lower active material layer 150b. The lower active material layer 150b is the result of drying the lower slurry layer 150a, and the upper active material layer 160b is the result of drying the upper slurry layer 160a.

[0092] For example, the lower active material layer 150b contains a larger amount of conductive material, while the upper active material layer 160b may contain a smaller amount of conductive material. In this case, the amount of conductive material in the lower active material layer 150b can be adjusted to a range of 0.5 to 5% by weight. By reducing the amount of conductive material in the upper active material layer 160b, the amount of active material on the electrode surface can be increased, and the conductivity can be reduced to a predetermined level. In particular, when the amount of conductive material in the upper active material layer 160b is controlled at a very low level of less than 0.02% by weight, the heat generation reaction in the event of an internal short circuit in the battery can be reduced.

[0093] In another example, the average particle size P1 of the active material forming the lower active material layer 150b is in the range of 50% to 95% of the average particle size P2 of the active material forming the upper active material layer 160b. In this case, the smaller particle size active material is coated onto the lower active material layer 150b, while the larger particle size active material is coated onto the upper active material layer 160b, which makes the electrolyte easy to wet and induces smooth movement of ions or holes.

[0094] In the illustrated example, the lower active material layer 150b and the upper active material layer 160b have flat portions 151 and 161 and inclined portions 153 and 163 respectively connected to the flat portions 151 and 161. The thickness of the inclined portions 153 and 163 decreases towards the periphery. The boundaries of the flat portions 151 and 161 and the inclined portions 153 and 163 are points 152 and 162 where the thickness of each layer begins to decrease, indicating the position where the flat portions 151 and 161 end and the inclined portions 153 and 163 begin.

[0095] Preferably, the ends 164 of the upper active material layer 160b and the ends 154 of the lower active material layer 150b (each layer having a thickness of 0 at the ends) are aligned and matched at positions almost perpendicular to the current collector 300 at the ends of the pattern, such as... Figure 3As shown; or they may be matched on the current collector 300, but as shown, the end 164 of the upper active material layer 160b may be positioned on the current collector 300 at a position further outward than the end 154 of the lower active material layer 150b. The end 164 of the upper active material layer 160b on the current collector 300 may match the end 154 of the lower active material layer 150b.

[0096] Points 152 and 162 where the thickness of each layer begins to decrease can be aligned and matched with the current collector 300 in an almost vertical position. However, as shown in the figure, point 162 where the thickness of the upper active material layer 160b begins to decrease can be set at a position further outward than point 152 where the thickness of the lower active material layer 150b begins to decrease.

[0097] The inclined portions 163 of the upper active material layer 160b and the inclined portions 153 of the lower active material layer 150b are not connected to each other, and the inclined portion 163 of the upper active material layer 160b covers the inclined portion 153 of the upper active material layer 150b to form a gentle or steep slope without steps. Figure 4 As shown, the connected sloping sections of each layer do not form steps. Figure 4 The upper layer end is positioned further inward than the lower layer end, and a portion of the inclined portion of the lower layer is exposed to the outside, forming a step. In the electrode according to this disclosure, in particular, since the loading decay length of the lower slurry layer is reduced when the slurry supply stops, the end 164 of the upper active material layer 160b matches the end 154 of the lower active material layer 150b, or the end 164 of the upper active material layer 160b is positioned further outward than the end 154 of the lower active material layer 150b, so that the inclined portion of the lower layer is not exposed to the outside.

[0098] Using the dual-slit die coating machine 100 according to the present disclosure as described above, the remaining area, i.e., the distance L' from point Ps' where the thickness of the upper slurry layer 160a begins to decrease due to the slurry delivery stopping, to the end of slurry delivery, i.e., the coating endpoint Pe', can be adjusted to 4 mm or less. As a result, the distance from the boundary between the flat portion 161 and the inclined portion 163 of the upper active material layer 160b to the end 164 of the upper active material layer 160b can be 4 mm or less.

[0099] As described above, according to this disclosure, there exists an electrode with a minimized loading fading region. According to this disclosure, since the loading fading region is reduced, wasted remaining area can be reduced, thereby improving process efficiency and reducing manufacturing costs.

[0100] The electrodes according to this disclosure can be used to manufacture secondary batteries. The electrodes according to this disclosure can be either positive or negative electrodes. A separator is inserted between the positive and negative electrodes to separate them. Preferably, the width of the positive electrode is smaller than the width of the negative electrode, and the N / P ratio is 100% to 115%. The positive and negative electrode widths do not refer to the width of the current collector, but rather to the outermost end of each electrode coated with the electrode active material. That is, it is the boundary between the uncoated and coated areas. For example, the outermost end of the positive electrode can be 1.0 + / - 0.6 mm shorter than the outermost end of the negative electrode. The positive and negative electrode widths are designed such that the negative electrode can accommodate lithium ions moving from the positive electrode to the maximum extent (up to 100%).

[0101] The separator can include any type of separator commonly used in the field of secondary batteries to separate the positive and negative electrodes and provide ion movement channels. For example, the separator can typically include porous membranes, woven fabrics, and nonwoven fabrics made of resin, and the resin can include, for example, polyolefin resins such as polypropylene or polyethylene, polyester resins, acrylic resins, styrene resins, or nylon resins. In particular, polyolefin-based microporous membranes are preferred due to their good ion permeability and physical separation of the positive and negative electrodes. Furthermore, if desired, the separator can have a coating including inorganic particles, and the inorganic particles can include insulating oxides, nitrides, sulfides, and carbides, preferably TiO2 or Al2O3.

[0102] The secondary battery also includes an electrolyte solution. The electrolyte solution may include at least one of the following organic solvents: cyclic carbonates, including ethylene carbonate, propylene carbonate, vinylene carbonate, and butyl carbonate; chain carbonates, including ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dipropyl carbonate (DPC); aliphatic carboxylic acid esters; γ-lactones, including γ-butyrolactone; chain ethers; or cyclic ethers. Additionally, lithium salts may be dissolved in these organic solvents.

[0103] The present disclosure will be described in more detail below with examples.

[0104] (Comparative Example)

[0105] use Figure 2 The conventional double-slit mold coating machine 20 shown applies a double-layer slurry layer to the current collector. The ends of the lower plate 25, the middle plate 30, and the upper plate 35 are aligned in a straight line, with a distance of 150 μm from the current collector. The current collector moves at a speed of 50 m / min. Figure 9 This is a width-thickness curve of the electrode cross-section for the comparative example. The total average thickness of the two-layer slurry layer coated by the comparative example is approximately 121.7 μm. Loading fading initiation point ( Figure 4 Ps in the middle were determined to correspond to the Ps in the middle. Figure 9The point on the x-axis of the curve represents 95% of the average coating thickness. The point is 47 mm. (Coating endpoint) Figure 4 Pe) is in Figure 9 The x-coordinate of the curve shows a coating amount of 0 (thickness of 0), which is 53mm. (Load fading area) Figure 4 The L in the calculation is 53mm–47mm, so the result is 6mm.

[0106] (Example 1)

[0107] use Figure 7 The dual-slit die coating machine 100 shown applies a double-layer slurry layer to the current collector. The lower die lip 111 is further rearward than the intermediate die lip 121 or the upper die lip 131. The distance between the intermediate die lip 121 and the upper die lip 131 and the current collector 150 is 150 μm, which is the same as in the comparative example. The step D' between the upper slit 102 and the lower slit 101 is 60 μm. The current collector moves at a speed of 50 m / min.

[0108] Figure 10 This is a width-thickness diagram in the cross-section of an exemplary electrode. The total average thickness of the slurry bilayer coated in the example is approximately 121.3 μm, almost identical to that of the comparative example. The loading fading start point (Ps' in Figure 8) corresponds to the... Figure 10 The position on the x-axis of the curve is 95% of the average coating thickness, which is 47.8 mm. The coating endpoint (Pe' in Figure 8) is at... Figure 10 The area where the coating amount (thickness) is 0 at the x-axis of the curve is 51.6 mm. The results show that the fading loading region (L' in Figure 8) is 51.6 mm - 47.8 mm, which is equal to 3.8 mm.

[0109] As described above, the coating of the electrode active material slurry layer in this embodiment reduces the length of the remaining area, thus reducing wasted areas and improving process efficiency.

[0110] (Example 2)

[0111] use Figure 7 The dual-slit die coating machine 100 shown applies a double-layer slurry layer to the current collector. The lower die lip 111 is further rearward than the intermediate die lip 121 or the upper die lip 131. The distance between the intermediate die lip 121 and the upper die lip 131 and the current collector is 150 μm, which is the same as in the comparative example. The step D' between the upper slit 102 and the lower slit 101 is 60 μm. The current collector moves at a speed of 40 m / min.

[0112] With an average particle size D 50A second electrode active material slurry 160 was prepared by mixing 11 μm natural graphite, carbon black, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) with water at a weight ratio of 94:1.5:2:2.5, with the remaining components excluding water having a concentration of 50 wt%. The slurry had an average particle size D... 50 A first electrode active material slurry 150 is prepared by mixing 8μm natural graphite, carbon black, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) with water in a weight ratio of 94:1.5:2:2.5, with the remaining components having a concentration of 50wt% except for water.

[0113] Based on the electrode area, the loading amount of the lower slurry layer 150a and the upper slurry layer 160a is 8 mg / cm². 2 The measured length of the fading region after coating is 3 mm. The current collector coated with the electrode active material slurry is dried simultaneously in a 60 m long hot air oven at a temperature of 130 °C. Subsequently, it is rolled to a target thickness of 180 μm to obtain the negative electrode. The obtained negative electrode comprises a lower active material layer 150b and an upper active material layer 160b. Because the inclined portion 163 of the upper active material layer 160b covers the inclined portion 153 of the lower active material layer 150b while forming a uniform slope without steps, it obtains a electrode with... Figure 8b and Figure 10 Similar cross-sectional profiles.

[0114] Although this disclosure has been described in detail with reference to a limited number of embodiments and accompanying drawings, it is not limited thereto, and it will be apparent to those skilled in the art that various changes and modifications may be made to it in all respects and the scope of the appended claims and their equivalents.

[0115] Although terms indicating directions such as up, down, left, and right are used herein, these terms are for descriptive convenience only, and it will be apparent to those skilled in the art that these terms may vary depending on the position of the target object or the observer.

Claims

1. A double slit die coater comprising a lower slit and an upper slit for extruding an electrode active material slurry through the lower slit and / or the upper slit on a surface of a current collector moving continuously, the double slit die coater comprising: a lower plate, an intermediate plate on the lower plate, and an upper plate on the intermediate plate, the lower slit being formed between the lower plate and the intermediate plate, and the upper slit being formed between the intermediate plate and the upper plate, wherein the lower plate, the intermediate plate, and the upper plate have a lower die lip, an intermediate die lip, and an upper die lip, respectively, each of which forms a front end of the double slit die coater with respect to the current collector, and a distance between the current collector and the lower die lip is greater than a distance between the current collector and the upper die lip and a distance between the current collector and the intermediate die lip, wherein a lower outlet communicating with the lower slit is formed between the lower die lip and the intermediate die lip, an upper outlet communicating with the upper slit is formed between the intermediate die lip and the upper die lip, and a predetermined step is formed between the lower outlet and the upper outlet, wherein the lower outlet delivers an electrode active material slurry forming a lower slurry layer onto the current collector, and the upper outlet is spaced apart from the lower outlet downstream in a coating direction and delivers an electrode active material slurry forming an upper slurry layer onto the lower slurry layer on the current collector, and wherein the predetermined step is 20% to 70% of a sum of an average thickness of the lower slurry layer and an average thickness of the upper slurry layer, and the predetermined step is a result of subtracting the distance between the current collector and the upper die lip from the distance between the current collector and the lower die lip. 2.The double slit die coater of claim 1, further comprising: a control unit linearly aligning the lower die lip, the intermediate die lip, and the upper die lip with respect to the current collector and then moving the lower die lip backward alone. 3.A coating method for an electrode active material slurry, comprising: forming an electrode active material slurry layer on a current collector by supplying an electrode active material slurry while moving the current collector from the lower die lip to the upper die lip using the double slit die coater according to any one of claims 1 to 2. 4.A coating method for an electrode active material slurry, comprising: intermittently coating an electrode active material slurry layer on a current collector by repeatedly supplying and stopping an electrode active material slurry while moving the current collector from the lower die lip to the upper die lip using the double slit die coater according to any one of claims 1 to 2.

5. A method of coating electrode active material slurries using a dual slot die coater comprising a lower slot and an upper slot and used to simultaneously extrude coating two electrode active material slurries through the lower slot and the upper slot on the surface of a continuously moving current collector, the dual slot die coater comprising a lower plate, an intermediate plate located on the lower plate, and an upper plate located on the intermediate plate, the lower slot formed between the lower plate and the intermediate plate, the upper slot formed between the intermediate plate and the upper plate, wherein, the lower plate, the intermediate plate, and the upper plate having a lower die lip, an intermediate die lip, and an upper die lip, respectively, each of which forms a front end with respect to the current collector, and a distance between the current collector and the lower die lip being greater than a distance between the current collector and the upper die lip and a distance between the current collector and the intermediate die lip, the method comprising: simultaneously delivering the two kinds of electrode active material slurries on the current collector moving from the lower die lip to the upper die lip direction through the lower outlet and the upper outlet to form a double layer structure including a lower slurry layer and an upper slurry layer coated on the lower slurry layer, wherein the lower outlet communicating with the lower slit is formed between the lower die lip and the intermediate die lip, the upper outlet communicating with the upper slit is formed between the intermediate die lip and the upper die lip, and the upper outlet is spaced apart from the lower outlet downstream in the coating direction, wherein a predetermined step is formed between the lower outlet and the upper outlet, and the predetermined step is 20% to 70% of the sum of the average thickness of the lower slurry layer and the average thickness of the upper slurry layer, and the predetermined step is the result of subtracting the distance between the current collector and the upper die lip from the distance between the current collector and the lower die lip.

6. The method of coating an electrode active material slurry using a double- slit die coater according to claim 5, wherein, intermittent coating is performed by repeating the simultaneous delivery and the simultaneous stop of the two kinds of electrode active material slurries.

7. The method of coating an electrode active material slurry using a double- slit die coater according to claim 5, wherein, the ratio of the average thickness of the lower slurry layer to the average thickness of the upper slurry layer is 1:3 to 3:

1.

8. An electrode comprising: a current collector; and an electrode active material layer formed on the current collector by the double slit die coater according to any one of claims 1-2, the coating method for electrode active material slurry according to any one of claims 3-4, or the method of coating electrode active material slurry using a double slit die coater according to any one of claims 5-7, wherein the electrode active material layer includes a lower active material layer disposed adjacent to a surface of the current collector and an upper active material layer located on the lower active material layer, the lower active material layer and the upper active material layer each have a flat portion and a sloped portion connected to the flat portion, the sloped portion has a smaller thickness toward the periphery, and an end of the upper active material layer on the current collector is aligned with an end of the lower active material layer, or is disposed more outward than the end of the lower active material layer.

9. The electrode of claim 8, wherein, a boundary of the flat portion and the sloped portion of the upper active material layer is disposed more outward than a boundary of the flat portion and the sloped portion of the lower active material layer.

10. The electrode of claim 8, wherein, the sloped portion of the upper active material layer covers the sloped portion of the lower active material layer to prevent the sloped portion of the lower active material layer from being exposed to the outside.

11. The electrode of claim 8, wherein, a distance from a boundary of the flat portion and the sloped portion of the upper active material layer to an end of the upper active material layer is 4 mm or less.

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