KR20220037364A - Dual slot die coater, electrode active material slurry coating method using the same and an electrode using the same - Google Patents

Abstract

The present invention relates to a dual slot die coater capable of improving a loading-off phenomenon and an electrode active material slurry coating method using the same. The dual slot die coater, according to the present invention has a lower slot and an upper slot, and extrudes and coats an electrode active material slurry through at least one of the lower slot and the upper slot on a surface of a current collector which continuously runs. The dual slot die coater comprises: a lower plate; a middle plate disposed above the lower plate and forming the lower slot interposed between the middle plate and the lower plate; and an upper plate disposed above the middle plate and forming the upper slot between the upper plate and the middle plate. Each of the lower plate, the middle plate, and the upper plate includes: a lower die lip; a middle die lip; and an upper die lip, which form a front end part of the current collector. 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 middle die lip.

Description

Dual slot die coater, electrode active material slurry coating method using the same and an electrode using the same

The present invention relates to a dual slot die coater capable of simultaneously forming a two-layer structure and a method for coating an electrode active material slurry using the same. The present invention also relates to an electrode using a dual slot die coater and a method for manufacturing the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and such secondary batteries essentially include an electrode assembly, which is a power generation element. The electrode assembly has a form in which a positive electrode, a separator, and a negative electrode are laminated at least once, and the positive electrode and the negative electrode are prepared by coating and drying a positive electrode active material slurry and a negative electrode active material slurry on a current collector made of aluminum foil and copper foil, respectively. Such secondary batteries are positive electrode active materials, lithium-containing manganese oxides such as lithium-containing cobalt oxide (LiCoO ₂ ) having a layered crystal structure, LiMnO ₂ having a layered crystal structure, and LiMn ₂ O ₄ having a spinel crystal structure, and lithium-containing nickel oxide (LiNiO). ₂ ) is generally used. In addition, a carbon-based material is mainly used as an anode active material, and in recent years, due to an increase in demand for high-energy lithium secondary batteries, a silicon-based material having an effective capacity of 10 times or more than that of a carbon-based material, mixed use with a silicon oxide-based material is being considered. . In order to make the charging/discharging characteristics of the secondary battery uniform, the positive electrode active material slurry and the negative electrode active material slurry should be uniformly coated on the current collector.

In order to improve the performance of a secondary battery, the development of an electrode structure in which an active material layer having a two-layer structure is formed on a current collector is attracting attention. In order to form the active material layer having such a two-layer structure on the current collector, a dual slot die coater capable of simultaneously coating two types of electrode active material slurries may be used.

FIG. 1 shows an example of a coating method using a dual slot die coater, and FIG. 2 is an enlarged view of area A of FIG. 1 .

Referring to FIGS. 1 and 2 , two types of electrode active material slurries are discharged from the dual slot die coater 20 while the current collector 15 is driven by rotating the coating roll 10 , and the 2 It is possible to simultaneously form the electrode active material layers of the layers. The electrode active material slurry discharged from the dual slot die coater 20 is widely coated on one surface of the current collector 15 to form an electrode active material layer.

The dual slot die coater 20 is configured by assembling three die blocks, that is, the lower plate 25 , the middle plate 30 , and the upper plate 35 . Since slots are formed between the lower plate 25 and the middle plate 30 and between the middle plate 30 and the upper plate 35, two slots are formed, and through the outlets 40 and 45 communicating with each slot, two types By simultaneously discharging the electrode active material slurry of the first electrode active material slurry 50, an additional second electrode active material slurry 55 can be continuously coated on the first coated electrode active material slurry 50, thereby obtaining a two-layer structure. Ends of the lower plate 25 , the middle plate 30 , and the upper plate 35 are positioned on the same straight line.

However, in the conventional coating method using the dual slot die coater 20, there is a case of intermittent coating in the MD direction (longitudinal direction corresponding to the running direction of the current collector during continuous coating). In the intermittent coating, supply, stop, supply, and stop of the first and second electrode active material slurries 50 and 55 are repeated while the current collector 15 is driven, and the active material layer, the uncoated region, and the active material layer are formed on the current collector 15 . , to form a pattern in the order of the uncoated area.

3 is a cross-sectional view of an electrode when intermittent coating is ideally performed. What we want to achieve is that, as shown in Fig. 3, the electrode active material slurry layers 50a and 55a of the upper and lower two layers are smoothly horizontally formed, and the end, where the pattern ends, is almost perpendicular to the current collector 15. .

However, in the case of using the conventional dual slot die coater 20, when the electrode active material slurry supply is stopped, the loading is gently cut off, and in fact, the loading is off on the current collector 15 as shown in an enlarged view of the end B of the slurry layer in FIG. 4 . It is easy to deteriorate the coating quality of the edge part, such as a phenomenon occurring.

Referring to FIG. 4 , the distance (L) from the point (Ps) at which the thickness of the upper slurry layer (55a) is reduced by stopping the discharge of the slurry to the distal end of the discharged slurry, that is, the coating end point (Pe) (L) is the loading off section am. The loading off section acts as a surplus part to be discarded, which leads to a decrease in process efficiency and an increase in manufacturing cost.

Therefore, there is a need to develop a technology capable of minimizing the area wasted in the electrode active material slurry coating process when manufacturing an electrode having a two-layer structure of an active material layer.

The present invention has been devised in consideration of the above problems, and an object of the present invention is to provide a dual slot die coater capable of improving the loading off phenomenon and a method for coating an electrode active material slurry using the same.

Another problem to be solved by the present invention is to provide an electrode having a minimized loading off period by using such a dual slot die coater.

However, the technical problems to be solved by the present invention are not limited to the above problems, and other problems not mentioned will be clearly understood by those skilled in the art from the description of the invention described below.

The dual slot die coater according to the present invention for solving the above technical problem is a dual slot die coater having a lower slot and an upper slot, and through at least one of the lower slot and the upper slot on the surface of the current collector that continuously travels. The electrode active material slurry is extruded and coated, and the dual slot die coater includes a lower plate, a middle plate disposed on the lower plate to form the lower slot between the lower plate and the middle plate, and the middle plate disposed on the middle plate and an upper plate forming the upper slot between the crown and the upper plate, wherein the lower plate, the middle plate, and the upper plate each have a lower die lip, a middle die lip and an upper die lip forming a tip portion thereof with respect to the current collector; It is characterized in that the distance between the current collector and the lower die lip is greater than the distance between the whole and the upper die lip and the distance between the current collector and the middle die lip.

In the present invention, after aligning the lower die lip, the middle die lip, and the upper die lip with respect to the current collector, a control unit for individually moving the lower die lip may be further included.

In the present invention, a lower discharge port communicating with the lower slot is formed between the lower die lip and the middle die lip, and an upper discharge port communicating with the upper slot is formed between the middle die lip and the upper die lip, and the A predetermined step may be formed between the lower outlet and the upper outlet.

At this time, the lower discharge port discharges the slurry forming the lower slurry layer onto the current collector, the upper discharge port is spaced apart from the lower discharge port in the downstream direction in the coating direction, and the slurry forming the upper slurry layer is discharged It can be discharged on the lower slurry layer on the current collector.

In this case, the step difference is preferably in the range of 20 to 70% of the sum of the average thickness of the lower slurry layer and the average thickness of the upper slurry layer.

Preferably, the lower slot and the upper slot form an angle of 30 to 60 degrees.

In the present invention, further comprising: a first spacer interposed between the lower plate and the middle plate to adjust the width of the lower slot; and a second spacer interposed between the middle plate and the upper plate to adjust the width of the upper slot. can do.

In the present invention, the lower plate includes a first manifold for accommodating the first electrode slurry and communicating with the lower slot, and the upper plate includes a second manifold for receiving the second electrode slurry and communicating with the upper slot. can be provided

The present invention may further include a first valve that opens and closes the discharge of the lower discharge port, a second valve that opens and closes the discharge of the upper discharge port, and a valve control unit that controls opening and closing of the first and second valves.

The electrode active material slurry coating method according to the present invention for solving the above problems uses the dual slot die coater according to the present invention, while driving the current collector from the lower die lip to the upper die lip, supplying the electrode active material slurry to the current collector to form an electrode active material slurry layer.

Another electrode active material slurry coating method according to the present invention for solving the above problems is to repeat the supply and stop of the electrode active material slurry while driving the current collector in the direction from the lower die lip to the upper die lip using a dual slot die coater to collect the collector. Intermittent coating of the electrode active material slurry layer on the entire surface.

Another electrode active material slurry coating method according to the present invention for solving the above problems, as a dual slot die coater having a lower slot and an upper slot, through the lower slot and the upper slot on the surface of the current collector continuously traveling 2 Simultaneous coating by extruding a slurry of an electrode active material of a species, wherein the dual slot die coater is disposed on a lower plate, a middle plate disposed on the upper part of the lower plate to form the lower slot between the lower plate, and an upper part of the middle plate and an upper plate forming the upper slot between the middle plate and the lower plate, the middle plate and the upper plate each having a lower die lip, a middle die lip and an upper die lip forming a tip portion thereof with respect to the current collector, A coating method using a dual slot die coater, characterized in that the distance between the current collector and the lower die lip is greater than the distance between the current collector and the upper die lip and the distance between the current collector and the middle die lip, and the A lower discharge port communicating with the lower slot is formed between the lower die lip and the middle die lip, an upper discharge port communicating with the upper slot is formed between the middle die lip and the upper die lip, and the upper discharge port is the lower discharge port and the two kinds of electrode active material slurries are simultaneously discharged through the lower outlet and the upper outlet on the current collector running in the direction from the lower die lip to the upper die lip, the lower slurry layer and the lower To form a two-layer structure including an upper slurry layer applied on the slurry layer.

Here, the electrode active material slurry may be discharged and stopped at the same time to repeatedly perform intermittent coating.

A predetermined step is formed between the lower outlet and the upper outlet, and the step may be in the range of 20 to 70% of the sum of the average thickness of the lower slurry layer and the average thickness of the upper slurry layer.

A ratio of the average thickness of the lower slurry layer to the average thickness of the upper slurry layer may be 1:3 to 3:1.

An electrode according to the present invention for solving the other problem, the current collector; and an electrode active material layer formed on the current collector, wherein 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, wherein the The lower active material layer and the upper active material layer each have a flat portion and an inclined portion that is connected to the flat portion and becomes thinner toward the outer periphery, and the end of the upper active material layer on the current collector coincides with the end of the lower active material layer Or it is characterized in that it is located more outward.

A boundary between the flat portion and the inclined portion of the upper active material layer may be located further outward than a boundary between the flat portion and the inclined portion of the lower active material layer. The inclined portion of the upper active material layer may cover the inclined portion of the lower active material layer so that the inclined portion of the lower active material layer is not exposed to the outside. A distance from the boundary of the flat portion and the inclined portion of the upper active material layer to the end of the upper active material layer may be within 4 mm.

According to one aspect of the present invention, the lower die lip is positioned more rearward than the upper die lip and the middle die lip with respect to the current collector. Due to the lip step, the loading does not break smoothly when the electrode active material slurry supply is stopped, and the length of the loading is shortened. Accordingly, the loading-off phenomenon is improved and the length of the loading-off section is shortened, thereby increasing the cell capacity. When the present invention is used, there is no problem of deterioration of coating quality. In particular, the effect is excellent during intermittent coating, which alternates between supplying and stopping the electrode active material slurry.

The present invention corresponds to a configuration for controlling a step difference between an upper discharge port and a lower discharge section, particularly a method for controlling a lower plate defining a lower discharge port between the middle plate and the middle plate. This is a lower plate lip backwards method in which the lower die lip, which is the lip of the lower plate, is positioned further back than the lip of the upper/middle plate to move away from the current collector.

The dual slot die coater and the electrode active material slurry coating method using the same according to the present invention can increase process efficiency and lower the defect rate when forming the active material layer having a two-layer structure on the current collector. In addition, by reducing the loading off period, it is possible to reduce the electrode area discarded after the process.

According to the present invention, an electrode having a minimized loading off period is provided. According to the present invention, since the loading off section is shortened, the surplus part to be discarded is reduced, resulting in an increase in process efficiency and a reduction in manufacturing cost.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the detailed description of the present invention to be described later, so that the present invention is described in such drawings should not be construed as being limited only to
1 is a schematic cross-sectional view of a dual slot die coater according to the prior art.
FIG. 2 is an enlarged view of area A of FIG. 1 .
3 is a cross-sectional view of an electrode when intermittent coating is ideally performed.
4 is a schematic view showing a cross-section of an electrode manufactured according to a conventional electrode active material slurry coating method.
5 is a schematic cross-sectional view of a dual slot die coater according to an embodiment of the present invention.
6 is a schematic exploded perspective view of a dual slot die coater according to an embodiment of the present invention.
7 is an enlarged view of region C of FIG. 5 , and is a schematic diagram illustrating a process of coating an electrode active material slurry using a dual slot die coater according to an embodiment of the present invention.
8A and 8B are schematic diagrams illustrating a cross-section of an electrode manufactured according to a method for coating an electrode active material slurry according to an embodiment of the present invention.
9 and 10 are graphs of width versus thickness in cross-sections of electrodes according to Comparative Examples and Examples.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical idea of the present invention. Accordingly, the embodiments described in the present specification and the configurations shown in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. It should be understood that there may be equivalents and variations.

The dual slot die coater of the present invention is an apparatus having a lower slot and an upper slot and coating a coating solution in a double layer on a substrate. The 'substrate' described below is the current collector and the coating solution is the 'electrode active material slurry'. The slurry discharged through the lower slot and the slurry discharged through the upper slot have the same or different composition (type of active material, conductive material, binder), content (amount of active material, conductive material, binder), or physical properties of the electrode active material slurry can be The dual slot die coater of the present invention coats two types of electrode active material slurries simultaneously or pattern-coats while alternately coating two types of electrode active material slurries, or intermittently coats the two types of electrode active material slurries while alternately supplying and stopping the two types of electrode active material slurries Optimized for manufacturing. However, the scope of the present invention is not necessarily limited thereto.

For the conventional intermittent coating, if the slurry supply is stopped during pattern formation, the loading is cut off gently, and the loading off phenomenon as described in FIG. 4 occurs. The present inventors found that when this loading off phenomenon stops the supply of the slurry to form the end, the residual slurry that forms a bead or forms a meniscus between the dual slot die coater and the current collector is even coated on the current collector. was found to be a phenomenon. Accordingly, a structure capable of minimizing residual slurries between the dual slot die coater and the current collector was studied to propose a dual slot die coater according to the present invention.

5 is a schematic cross-sectional view of a dual slot die coater according to an embodiment of the present invention. 6 is a schematic exploded perspective view of a dual slot die coater according to an embodiment of the present invention. 7 is an enlarged view of region C of FIG. 5 , and is a schematic diagram illustrating a process of coating an electrode active material slurry using a dual slot die coater according to an embodiment of the present invention.

5 to 7 , the dual slot die coater 100 according to the present invention has a lower slot 101 and an upper slot 102 and is identical to each other through the lower slot 101 and the upper slot 102 . or two different types of electrode active material slurries simultaneously, alternately, or intermittently coated on the current collector 300 .

The dual slot die coater 100 includes a lower plate 110 , a middle plate 120 disposed on the lower plate 110 , and an upper plate 130 disposed on the middle plate 120 . The lower plate, the middle plate, and the upper plate 110 , 120 , 130 are assembled to each other through fastening members such as bolts. The lower plate 110 is a block located at the bottom of the blocks constituting the dual slot die coater 100, and the side facing the middle plate 120 is at an angle of about 30 to 60 degrees with respect to the bottom surface (XZ plane). It has an inclined shape to achieve

The lower slot 101 may be formed between the lower plate 110 and the middle plate 120 facing each other. For example, the first spacer 113 is interposed between the lower plate 110 and the middle plate 120 to provide a gap therebetween, so that the lower slot 101 corresponds to a passage through which the first electrode active material slurry 150 can flow. ) can be formed. In this case, the thickness of the first spacer 113 determines the vertical width (Y-axis direction, slot gap) of the lower slot 101 .

As shown in FIG. 6 , one area of the first spacer 113 is cut to have a first opening 113a, and one of the edge areas of the opposite surfaces of the lower plate 110 and the middle plate 120 , respectively. It may be interposed in the remaining part except for the side. Accordingly, the lower discharge port 101a through which the first electrode active material slurry 150 can be discharged to the outside is formed only between the front end of the lower plate 110 and the front end of the middle plate 120 . The distal end of the lower plate 110 and the distal end of the middle plate 120 are defined as a lower die lip 111 and an intermediate die lip, respectively. It can be said that it is a place formed by the separation between (121).

For reference, the first spacer 113 prevents the first electrode active material slurry 150 from leaking through the gap between the lower plate 110 and the middle plate 120 except for the region where the lower discharge port 101a is formed. It is preferable that it is made of a material having sealing properties as it functions as a gasket.

The lower plate 110 has a predetermined depth on a surface facing the middle plate 120 and includes a first manifold 112 communicating with the lower slot 101 . Although not shown in the drawings, the first manifold 112 is connected to a first electrode active material slurry supply chamber (not shown) installed outside through a supply pipe to receive the first electrode active material slurry 150 . When the first electrode active material slurry 150 is filled in the first manifold 112 , the flow of the first electrode active material slurry 150 is induced along the lower slot 101 and through the lower outlet 101a. will be discharged to the outside.

The middle plate 120 is a block located in the middle among the die blocks constituting the dual slot die coater 100 , and is disposed between the lower plate 110 and the upper plate 130 to form a double slot. Although the cross section of the middle plate 120 of this embodiment is a right triangle, this shape is not necessarily limited thereto. For example, the cross section may be provided as an isosceles triangle.

The upper plate 130 is disposed to face the upper surface of the middle plate 120 that is horizontal with respect to the bottom surface. The upper slot 102 is formed between the place where the middle plate 120 and the upper plate 130 face each other in this way.

Like the lower slot 101 described above, the second spacer 133 may be interposed between the middle plate 120 and the upper plate 130 to provide a gap therebetween. Accordingly, an upper slot 102 corresponding to a passage through which the second electrode active material slurry 160 can flow is formed. In this case, the vertical width (Y-axis direction, slot gap) of the upper slot 102 is determined by the second spacer 133 .

In addition, the second spacer 133 also has a structure similar to that of the above-described first spacer 113 , and has a second opening 133a in which one region is cut, and opposite surfaces of the middle plate 120 and the upper plate 130 , respectively. It is interposed only in the remaining part except for one side of the border area of . Similarly, the circumferential direction except for the front of the upper slot 102 is blocked, and the upper discharge port 102a is formed only between the front end of the middle plate 120 and the front end of the upper plate 130 . The front end of the upper plate 130 is defined as the upper die lip 131 , in other words, the upper discharge port 102a is formed by separating the intermediate die lip 121 and the upper die lip 131 from each other. .

In addition, the upper plate 130 has a predetermined depth on a surface facing the middle plate 120 and includes a second manifold 132 communicating with the upper slot 102 . Although not shown in the drawings, the second manifold 132 is connected to the second electrode active material slurry 160 supply chamber and the supply pipe installed outside to receive the second electrode active material slurry 160 . When the second electrode active material slurry 160 is supplied from the outside along the pipe-shaped supply pipe and fills the second manifold 132 , the second electrode active material slurry 160 communicates with the second manifold 132 . The flow is induced along the upper slot 102 and is discharged to the outside through the upper discharge port 102a.

The upper slot 102 and the lower slot 101 form a constant angle, and the angle may be approximately 30 degrees to 60 degrees. The upper slot 102 and the lower slot 101 intersect each other in one place, and the upper discharge port 102a and the lower discharge port 101a may be provided near the intersection point. Accordingly, the discharge points of the first electrode active material slurry 150 and the second electrode active material slurry 160 may be concentrated in approximately one place.

The first and second manifolds 112 and 132 are respectively formed on the lower plate 110 and the upper plate 130 . By doing this, it is possible to less influence the deformation of the structurally weakest middle plate 120 .

On the other hand, it may further include a first valve for opening and closing the discharge of the lower discharge port (101a), a second valve for opening and closing the discharge of the upper discharge port (102a), and a valve control unit for controlling the opening and closing of the first and second valves there is.

According to the dual slot die coater 100 having this configuration, a rotatably provided coating roll 200 is disposed in front of the dual slot die coater 100, and the house to be coated by rotating the coating roll 200 While driving the entire 300, the first electrode active material slurry 150 and the second electrode active material slurry 160 are continuously brought into contact with the surface of the current collector 300 to form a two-layer structure on the current collector 300 Simultaneous coating is possible. Alternatively, supply and interruption of the first electrode active material slurry 150 and supply and interruption of the second electrode active material slurry 160 are alternately performed while controlling the opening and closing of the first and second valves through the valve control unit, so that the current collector ( 300), it is possible to form a pattern coating intermittently.

With further reference to FIG. 7 , the structure of the die lip portion of the dual slot die coater according to an embodiment of the present invention and the electrode active material slurry coating method using the dual slot die coater will be described in detail. In the dual slot die coater 100 according to the present invention, the lip step of the upper/middle/lower plate is formed.

The current collector 300 and the lower die lip 111 than the distance H1 between the current collector 300 and the upper die lip 131 and the distance H2 between the current collector 300 and the middle die lip 121 The distance H3 between them is greater. The position of the lower die lip 111, which is the lip of the lower plate 110, is pulled back in the opposite direction to the discharge direction than the upper die 131, which is the lip of the upper plate 130, and the middle die lip 121, which is the lip of the middle plate 120. By locating it away from the entire 300, such a distance difference can be generated to form a lip step. Through the step between the ribs, it is possible to achieve the relief of the loading off section. The distance H1 between the current collector 300 and the upper die lip 131 and the distance H2 between the current collector 300 and the middle die lip 121 may be equal to each other.

In order to form a lip step, the lower die lip 111, the middle die lip 121, and the upper die lip 131 are aligned with the current collector 300 and then the lower die lip 111 is individually moved backward. may further include. By configuring in this way, the lower die lip 111 is located further back from the current collector 300 than the upper die 131 and the middle die lip 121 .

Accordingly, a predetermined step D' is formed between the lower discharge port 101a and the upper discharge port 102a. This step D' is equal to the distance H3 between the current collector 300 and the lower die lip 111 minus the distance H1 between the current collector 300 and the upper die lip 131 . As the lower discharge port 101a and the upper discharge port 102a are disposed at positions spaced apart from each other in the horizontal direction by this step D', the second electrode active material slurry 160 discharged from the upper discharge port 102a is There is no fear that the first electrode active material slurry 150 introduced into the lower outlet 101a or discharged from the lower outlet 101a flows into the upper outlet 102a. The present invention is characterized in that the middle plate 120 and the lower plate 110 forming the lower discharge port 101a are spaced apart from each other.

As shown, in a state in which the lip positions are set, the upper discharge port 102a is spaced apart from the lower discharge port 101a in the downstream direction in the coating direction. When the slurries 150 and 160 are simultaneously discharged through the lower discharge port 101a and the upper discharge port 102a while the current collector 300 is driven in the direction from the lower die lip 111 to the upper die lip 131, the current collector 300 ), it is possible to form an active material layer on the two-layer structure.

In the present invention, based on the lower layer slurry, that is, the first electrode active material slurry 150 discharged from the lower discharge port 101a, only the lower layer upstream is spaced apart from the current collector 300 in a farther direction. In other words, while generating a height difference between the two plates, the middle plate 120 and the lower plate 110 , which form the lower discharge port 101a , the lower plate 110 is moved further away from the current collector 300 . . It is different from the case where only the movement of the outlet itself is used without distinction between the upstream and the downstream.

8A and 8B are schematic diagrams illustrating a cross-section of an electrode manufactured according to a method for coating an electrode active material slurry according to an embodiment of the present invention. 8A is a cross-section after coating the electrode active material slurry, and FIG. 8B is a cross-section after coating and drying.

As shown in FIG. 8A , the first electrode active material slurry 150 discharged from the lower discharge port 101a is first applied on the current collector 300 to form a lower slurry layer 150a, and the upper discharge port 102a is formed thereon. ), the second electrode active material slurry 160 is simultaneously applied to form an upper slurry layer 160a. As described above, when the dual slot die coater 100 of the present invention is used, a two-layer structure including the upper slurry layer 160a can be formed on the lower slurry layer 150a. In particular, if the supply of the first electrode active material slurry 150 and the second electrode active material slurry 160 is stopped at the same time, the pattern end as shown in FIG. 8A can be obtained due to the lip step of the dual slot die coater 100 . and after drying it, or after proceeding to roll press, the end of the pattern as shown in FIG. 8B can be obtained. Roll press is an optional step that can be further performed for thickness control.

The average thickness D1 of the lower slurry layer 150a formed by the first electrode active material slurry 150 discharged through the lower discharge port 101a and the second electrode active material slurry 160 discharged through the upper discharge port 102a The ratio of the average thickness D2 of the upper slurry layer 160a formed by The thickness ratio is a relative indication of the average value of the lengths in the thickness direction of each layer. In addition, each of the average thicknesses D1 and D2 of the lower slurry layer 150a and the upper slurry layer 160a may be 40 to 200 μm.

The thickness of the slurry layers 150a and 160a as described above can be viewed as the pressure of the slurry to be supplied. The pressure of the second electrode active material slurry 160 is more than 3 times the pressure of the first electrode active material slurry 150 so that the thickness ratio of the lower slurry layer 150a and the upper slurry layer 160a is 1:3 or more. In this case, since the upper layer has a stronger pressure than the lower layer, the possibility of leaking increases by pushing the first electrode active material slurry 150 backward, which is the opposite direction of the coating progress direction, and the first electrode active material slurry 150 is the second electrode active material Due to the strong pressure of the slurry 160, it may not be properly supplied. In addition, since the supply of the first electrode active material slurry 150 is not uniform due to the high pressure of the second electrode active material slurry 160 , it is difficult to form the lower slurry layer 150a uniformly.

Meanwhile, the pressure of the second electrode active material slurry 160 exceeds that of the first electrode active material slurry 150 by 3 times so that the thickness ratio of the lower slurry layer 150a and the upper slurry layer 160a is 3:1 or more. In the case of supplying with the , there is a problem that the supply of the second electrode active material slurry 160 is difficult, or the coating of the second electrode active material slurry 160 is pushed in the coating progress direction, and the surface of the coating solution may be non-uniform.

The step D' is preferably in the range of 20 to 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. If the range is less than 20%, there is little effect of shortening the loading length when the slurry supply is stopped. When the range exceeds 70%, compared to the amount of the slurry, the total area of the space where the slurry stays to be coated, that is, the space between the die ribs 111 and 121 and the lower slurry layer 150a, is insufficient. The first electrode active material slurry 150 is not coated and leaking back occurs. Leaking refers to the instability that a portion of the slurry is lost out of the lower die lip to the upstream side. This means loss of pre-metered slurry, which makes the final coating thickness unpredictable.

For intermittent coating, if the supply of the slurry is stopped during pattern formation, the loading is cut off gently and the loading off phenomenon occurs. Referring back to FIG. 2 related to the prior art, the present inventors found that this loading off phenomenon forms a meniscus between the dual slot die coater 20 and the current collector 15 when the slurry supply is stopped to form an end. It was found that this is a phenomenon in which the remaining slurries 50 and 55 remaining in the form of beads are coated even on the current collector 15 . In particular, 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 off section.

In the present invention, since the lower plate 110 is pulled back as shown in FIG. 7 , a meniscus is formed between the dual slot die coater 100 and the current collector 300 or the amount of the residual slurry remaining while forming a bead is increased. less This is because the length (S′) from the upper die lip 131 , which is the front end of the upper plate 130 , to the meniscus of the first electrode active material slurry 150 is shorter than the length S of FIG. 2 . Accordingly, when the slurry is stopped, the loading is not gently cut off and the length of the loading is short. Accordingly, it is possible to ideally form the end of the pattern as shown in FIGS. 8A and 8B.

Referring to FIG. 8A , a case in which the lower slurry layer 150a and the upper slurry layer 160a are coated almost sequentially on the current collector 300 along the current collector traveling direction is shown. In the present invention, the distance (L') from the time point (Ps') at which the thickness of the upper slurry layer (160a) is reduced by stopping the discharge of the slurry to the distal end of the discharged slurry, that is, the coating end point (Pe'), is off loading section, which is very short compared to the loading off section distance L of FIG. 4 related to the prior art. The loading off section acts as a surplus part to be discarded, which leads to a decrease in process efficiency and an increase in manufacturing cost. According to the present invention, since the loading off section is shortened, the surplus part to be discarded is reduced, resulting in an increase in process efficiency and a reduction in manufacturing cost.

Conventionally, the loading off section distance (L) of FIG. 4 is typically 5.5 mm or more. However, when the dual slot die coater 100 according to the present invention is used, the surplus, that is, the distal end of the discharged slurry from the time point (Ps') at which the thickness of the upper slurry layer 160a is reduced by stopping the discharge of the slurry, that is, the end of the coating The distance L' to the point Pe' can be adjusted to be within 4 mm. This is because, when the length of the surplus portion exceeds 4 mm as described above, the discarded area increases and it is not economical.

For example, the electrode active material slurry coating method of the present invention may be applied to the manufacture of a positive electrode of a secondary battery. The positive electrode includes a current collector and a positive electrode active material layer formed on a surface of the current collector. The current collector may be used according to the polarity of the current collector electrode known in the field of secondary batteries as showing electrical conductivity such as Al, Cu, and the like. The positive active material layer may further include one or more of a plurality of positive active material particles, a conductive material, and a binder. In addition, the positive electrode may further include various additives for the purpose of supplementing or improving electrochemical properties.

The active material is not limited to a specific component as long as it can be used as a positive active material of a lithium ion secondary battery. Non-limiting examples thereof include layered compounds such as lithium manganese composite oxide (LiMn ₂ O ₄ , LiMnO ₂ , etc.), lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or substituted with one or more transition metals. compound; Lithium manganese oxides such as Formula Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiV ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site-type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _2-x M _x O ₂ (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, lithium manganese composite oxide represented by Ni, Cu or Zn; LiMn ₂ O ₄ in which a part of Li in the formula is substituted with an alkaline earth metal ion; disulfide compounds; One or a mixture of two or more of Fe ₂ (MoO ₄ ) ₃ may be included. In the present invention, the positive electrode may include at least one of a polymer-based solid electrolyte, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte as a solid electrolyte material.

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 electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. 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, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; One or a mixture of two or more selected from conductive materials such as polyphenylene derivatives may be included.

The binder is not particularly limited as long as it is a component that assists in bonding the active material and the conductive material and bonding to the current collector, for example, polyvinylidene fluoride polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxy Propylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers and the like. The binder may be included in an amount of 1 wt% to 30 wt%, or 1 wt% to 10 wt% compared to 100 wt% of the electrode layer.

The electrode may be a cathode. The negative electrode includes a current collector and an anode active material layer formed on a surface of the current collector. The negative active material layer may further include at least one of a plurality of negative active material particles, a conductive material, and a binder. In addition, the negative electrode may further include various additives for the purpose of supplementing or improving electrochemical properties.

The negative active material is a carbon material such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, or carbon nanohorn, a lithium metal material, an alloy-based material such as silicon or tin, Nb ₂ O ₅ , Li ₅ Ti ₄ O ₁₂ , an oxide-based material such as TiO ₂ , or a composite thereof may be used. For the negative electrode, the conductive material, the binder, and the current collector may refer to the description of the positive electrode. In particular, the electrode produced according to the present invention is preferably a negative electrode.

When the resultant having the coating state as in FIG. 8A is dried, an electrode as shown in FIG. 8B can be manufactured.

Referring to FIG. 8B , the electrode according to an embodiment of the present invention includes a current collector 300 and an electrode active material layer formed on the current collector 300 . In particular, the electrode active material layer includes a lower active material layer 150b disposed adjacent to the surface of the current collector 300 and an upper active material layer 160b disposed 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 a dried lower slurry layer 150a, and the upper active material layer 160b is a dried upper slurry layer 160a.

For example, the lower active material layer 150b may contain a high content of the conductive material, and the upper active material layer 160b may contain a relatively low content of the conductive material. In this case, the content of the conductive material in the lower active material layer 150b can be adjusted in the range of 0.5 to 5 wt%. The upper active material layer 160b may reduce the content of the conductive material, thereby increasing the content of the active material on the electrode surface and lowering the electrical conductivity to a certain level. In particular, when the content of the conductive material in the upper active material layer 160b is controlled to a very low level of 0.02 wt% or less, exothermic reaction during a short circuit inside the cell can be reduced.

In another example, the average particle diameter P1 of the active material forming the lower active material layer 150b is in the range of 50 to 95% of the average particle diameter P2 of the active material forming the upper active material layer 160b. In this case, an active material having a relatively small particle diameter is applied to the lower active material layer 150b. By applying an active material having a relatively large particle diameter to the upper active material layer 160b, it is possible to easily impregnate the electrolyte and induce smooth movement of ions or holes.

In the illustrated example, the lower active material layer 150b and the upper active material layer 160b are connected to the flat portions 151 and 161 and the flat portions 151 and 161, respectively, and the inclined portion ( 153, 163). The boundary between the flat portions 151 and 161 and the inclined portions 153 and 163 is the point 152 and 162 where the thickness of each layer starts to decrease, the flat portions 151 and 161 are terminated and the inclined portion 153 is formed. , 163) also means the starting point.

The end 164 of the upper active material layer 160b and the end 154 of the lower active material layer 150b, that is, the point at which the thickness of each layer becomes 0, is the end where the pattern ends, as shown in FIG. 3, the current collector ( It is preferable that they are aligned and matched with each other at a position almost perpendicular to 300) or coincide with each other on the current collector 300, but as shown, the ends 164 of the upper active material layer 160b on the current collector 300 are The lower active material layer 150b may be positioned 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 coincide with the end 154 of the lower active material layer 150b.

The points 152 and 162 at which the thickness of each layer starts to decrease may also be aligned and coincide with each other at a position almost perpendicular to the current collector 300, but as shown, the thickness of the upper active material layer 160b starts to decrease. The point 162 at which the lower active material layer 150b starts to decrease in thickness may be located further outward than the point 152 at which the thickness of the lower active material layer 150b starts to decrease.

The inclined portion 163 of the upper active material layer 160b and the inclined portion 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 is the lower active material layer 150b. It is possible to achieve a gentle or steep slope without a step while covering the slope 153 of the. As shown in FIG. 4 , the step shape that appears while the slopes of each floor are connected to each other is not shown. In the case of FIG. 4 , the upper end is located further inside than the lower end, and a part of the lower slope is exposed to the outside, thereby representing a step shape. In the electrode according to the present invention, when the slurry is stopped, the length at which the loading of the lower slurry layer is removed is shortened. As a result, the end 164 of the upper active material layer 160b and the end 154 of the lower active material layer 150b coincide or the upper While the end 164 of the active material layer 160b is positioned more outward than the end 154 of the lower active material layer 150b, the lower inclined portion is not exposed to the outside.

As described above, when the dual slot die coater 100 according to the present invention is used, the surplus, that is, the distal end of the discharged slurry from the time point (Ps') at which the thickness of the upper slurry layer 160a is reduced by stopping the slurry discharge, That is, it is possible to adjust the distance (L') to the coating end point (Pe') to be within 4mm. 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 may be within 4 mm.

As described above, according to the present invention, an electrode having a minimized loading off period is provided. According to the present invention, since the loading off section is shortened, the surplus part to be discarded is reduced, resulting in an increase in process efficiency and a reduction in manufacturing cost.

The electrode according to the present invention may be manufactured as a secondary battery. The electrode according to the present invention may be an anode or a cathode. A separator is placed between the anode and the cathode to insulate the anode and the cathode. It is preferable to make the width of the anode shorter than the width of the cathode and make the N/P ratio 100 to 115%. In the above, the width of the positive electrode and the width of the negative electrode do not mean the width of the current collector, but mean the end of each electrode to which the electrode active material is applied. That is, it means the boundary between the non-coated part and the maintained part. For example, the outermost end of the positive electrode may be shorter than 1.0 +/- 0.6 mm than the outermost end of the negative electrode. By designing the width of the anode and the anode in this way, the anode can accommodate lithium ions moving from the anode to the maximum (up to 100%).

The separator is used in the field of secondary batteries and can be used as long as it can insulate the positive electrode and the negative electrode and provide an ion movement path. For example, the separation membrane is mainly composed of a resin porous membrane, woven fabric, nonwoven fabric, etc., and as the resin component, for example, a polyolefin resin such as polypropylene or polyethylene, a polyester resin, an acrylic resin, a styrene resin, or a nylon resin etc. can be used. In particular, a polyolefin-based microporous membrane is preferable because it has excellent ion permeability and the ability to physically isolate an anode and a cathode. In addition, if necessary, the separator may form a coating layer containing inorganic particles, and the inorganic particles may include insulating oxides, nitrides, sulfides, carbides, etc. Among them, TiO ₂ or Al ₂ O ₃ It is preferable.

The secondary battery further includes an electrolyte. Examples of the electrolyte include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dipropyl carbonate (DPC). One type, or a mixture of two or more types of organic solvents such as chain carbonates such as chain carbonates, aliphatic carboxylic acid esters, γ-lactones such as γ-butyrolactone, chain ethers, cyclic ethers, etc. can be used. . In addition, lithium salts can be dissolved in these organic solvents.

Hereinafter, the present invention will be described in more detail through experimental examples.

(Comparative example)

A slurry layer having a two-layer structure was coated on the current collector using a conventional dual slot die coater 20 as shown in FIG. 2 . The ends of the lower plate 25 , the middle plate 30 , and the upper plate 35 were positioned on the same straight line, and the distance from the current collector was 150 μm. The moving speed of the current collector was 50 m/min. 9 is a graph of width versus thickness in a cross-section of an electrode according to a comparative example. The overall average thickness of the two-layered slurry layer coated through the comparative example was about 121.7 μm. The loading off start point (Ps in FIG. 4 ) was determined as a point corresponding to 95% of the average coating thickness in the x-coordinate of the graph of FIG. 9 . That spot was 47mm. The end point (Pe of FIG. 4) at which the coating was terminated was 53 mm, with a coating amount of 0 (thickness of 0) in the x-coordinate of the graph of FIG. 9 . Since the loading off section (L in FIG. 4) is calculated as 53mm-47mm, a result of 6mm was obtained.

(Example 1)

A slurry layer having a two-layer structure was coated on the current collector using the dual slot die coater 100 as shown in FIG. 7 . The lower die lip 111 is moved backward from the middle die lip 121 or the upper die lip 131 . The distance between the middle die lip 121 and the upper die lip 131 and the current collector was 150 μm, the same as in the comparative example, and the step D′ between the upper slot 102 and the lower slot 101 was 60 μm. made to be The moving speed of the current collector was 50 m/min.

10 is a graph of width versus thickness in a cross-section of an electrode according to an embodiment. The overall average thickness of the slurry bilayer coated through the examples was about 121.3 μm, which was almost similar to the comparative examples. The loading off start point (Ps' in FIG. 8) was a point corresponding to 95% of the average thickness of the coating in the x-coordinate of the graph of FIG. 10, and was 47.8 mm. The end point (Pe' of FIG. 8) at which the coating was terminated was 51.6 mm with a coating amount of 0 (thickness of 0) in the x-coordinate of the graph of FIG. 10 . The loading off section (L' in FIG. 8) was obtained from 51.6mm-47.8mm to 3.8mm.

As such, when the electrode active material slurry layer is coated according to the present embodiment, the waste portion is saved by reducing the length of the surplus, thereby increasing the efficiency in the process.

(Example 2)

A slurry layer having a two-layer structure was coated on the current collector using the dual slot die coater 100 as shown in FIG. 7 . The lower die lip 111 is moved backward from the middle die lip 121 or the upper die lip 131 . The distance between the middle die lip 121 and the upper die lip 131 and the current collector was 150 μm, the same as in the comparative example, and the step D′ between the upper slot 102 and the lower slot 101 was 60 μm. made to be The moving speed of the current collector was 40 m/min.

Earthen natural graphite, carbon black, carboxymethyl cellulose (CMC), and styrene-butathiene rubber (SBR) having an average particle diameter (D ₅₀ ) of 11 μm were mixed with water in a weight ratio of 94:1.5:2:2.5 to obtain water. A second electrode active material slurry 160 having a concentration of 50 wt% of the remaining components was prepared. Earthen natural graphite, carbon black, carboxymethyl cellulose (CMC), and styrene-butathiene rubber (SBR) having an average particle diameter (D ₅₀ ) of 8 μm were mixed with water in a weight ratio of 94:1.5:2:2.5 to add water. A first electrode active material slurry 150 having a concentration of 50 wt% of the remaining components was prepared.

The loading amount of the lower slurry layer 150a and the upper slurry layer 160a was 8 mg/cm ² based on the electrode area. The length of the loading off section after coating was measured to be 3 mm. The current collector coated with the electrode active material slurry was dried by passing it through a hot air oven having a length of 60 m, and the temperature of the oven was adjusted to maintain 130°C. Thereafter, the target thickness was set to 180 μm, and roll pressing was performed to obtain a negative electrode. The obtained negative electrode includes a lower active material layer 150b and an upper active material layer 160b, and the inclined portion 163 of the upper active material layer 160b covers the inclined portion 153 of the lower active material layer 150b and has a step difference. As a result of achieving a constant inclination without the absence of a constant inclination, a cross-sectional profile similar to that of FIGS. 8B and 10 was obtained.

As described above, although the present invention has been described with reference to limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following by those skilled in the art to which the present invention pertains. It goes without saying that various modifications and variations are possible within the scope of equivalents of the claims to be described.

Meanwhile, although terms indicating directions such as up, down, left, and right are used in the present specification, these terms are only for convenience of description and may vary depending on the location of the object or the location of the observer. It is apparent to those skilled in the art of

100: dual slot die coater 101: lower slot
102: upper slot 110: lower plate
111: lower die lip 112: first manifold
113: first spacer 120: middle plate
121: middle die lip 130: top plate
131: upper die lip 132: second manifold
133: second spacer 150: first electrode active material slurry
160: second electrode active material slurry 200: coating roll
300: current collector

Claims (15)

A dual slot die coater having a lower slot and an upper slot, wherein the electrode active material slurry is extruded and coated through at least one of the lower slot and the upper slot on the surface of the current collector running continuously, wherein the dual slot die coater comprises: ,
a lower plate, a middle plate disposed on the lower plate to form the lower slot with the lower plate, and an upper plate disposed on the middle plate to form the upper slot between the middle plate and the middle plate;
The lower plate, the middle plate, and the upper plate each have a lower die lip, a middle die lip and an upper die lip forming a tip portion thereof with respect to the current collector,
The dual slot die coater, characterized in that the distance between the current collector and the lower die lip is greater than the distance between the current collector and the upper die lip and the distance between the current collector and the middle die lip. The dual slot die coater according to claim 1, further comprising: a controller for individually reversing the lower die lip after aligning the lower die lip, the middle die lip, and the upper die lip with respect to the current collector. The method of claim 1, wherein a lower outlet communicating with the lower slot is formed between the lower die lip and the middle die lip, and an upper outlet communicating with the upper slot is formed between the middle die lip and the upper die lip, A dual slot die coater, characterized in that a predetermined step is formed between the lower discharge port and the upper discharge port. The method of claim 3, wherein the lower discharge port discharges the slurry forming the lower slurry layer onto the current collector, and the upper discharge port is spaced apart from the lower discharge port in a coating direction downstream from the lower discharge port, and forms an upper slurry layer A dual slot die coater, characterized in that the slurry is discharged onto the lower slurry layer on the current collector. 5. The dual slot die coater of claim 4, wherein the step is in the range of 20 to 70% of the sum of the average thickness of the lower slurry layer and the average thickness of the upper slurry layer. Using the dual slot die coater according to any one of claims 1 to 5,
An electrode active material slurry coating method, characterized in that the electrode active material slurry layer is formed on the current collector by supplying the electrode active material slurry while driving the current collector from the lower die lip to the upper die lip. Using the dual slot die coater according to any one of claims 1 to 5,
An electrode active material slurry coating method, characterized in that the electrode active material slurry layer is intermittently coated on the current collector by repeatedly supplying and stopping the electrode active material slurry while driving the current collector from the lower die lip to the upper die lip. A dual slot die coater having a lower slot and an upper slot, wherein the two types of electrode active material slurries are extruded through the lower slot and the upper slot to the surface of a current collector that is continuously running and coated at the same time, the dual slot die coater comprising: A lower plate comprising: a lower plate; a middle plate disposed on the lower plate to form the lower slot with the lower plate; and an upper plate disposed on the middle plate to form the upper slot with the middle plate; , the middle plate and the upper plate each have a lower die lip, a middle die lip and an upper die lip forming a tip portion thereof with respect to the current collector, and a distance between the current collector and the upper die lip and between the current collector and the middle die lip An electrode active material slurry coating method using a dual slot die coater, characterized in that the distance between the current collector and the lower die lip is greater than the distance of
A lower discharge port communicating with the lower slot is formed between the lower die lip and the middle die lip, an upper discharge port communicating with the upper slot is formed between the middle die lip and the upper die lip, and the upper discharge port is the lower It is spaced apart from the outlet and downstream in the coating direction,
On the current collector traveling from the lower die lip to the upper die lip, two kinds of electrode active material slurries are simultaneously discharged through the lower outlet and the upper outlet to form a lower slurry layer and an upper slurry layer coated on the lower slurry layer. Electrode active material slurry coating method, characterized in that to form a two-layer structure comprising a. [Claim 9] The method of claim 8, wherein the electrode active material slurry is discharged and stopped at the same time to perform intermittent coating. The method of claim 8, wherein a predetermined step is formed between the lower outlet and the upper outlet, and the step is in the range of 20 to 70% of the sum of the average thickness of the lower slurry layer and the average thickness of the upper slurry layer. Electrode active material slurry coating method characterized in that. The method of claim 8, wherein a 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. current collector; and
Including; 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 that is connected to the flat portion and becomes thinner toward the outer periphery,
An electrode, characterized in that the end of the upper active material layer on the current collector coincides with the end of the lower active material layer or is positioned further outward. The electrode according to claim 12, wherein a boundary between the flat portion and the inclined portion of the upper active material layer is located further outward than a boundary between the flat portion and the inclined portion of the lower active material layer. The electrode according to claim 12, wherein the inclined portion of the upper active material layer covers the inclined portion of the lower active material layer so that the inclined portion of the lower active material layer is not exposed to the outside. The electrode according to claim 12, wherein a distance from the boundary of the flat portion and the inclined portion of the upper active material layer to the end of the upper active material layer is within 4 mm.

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