Electrode coating slurry circulation system capable of circulating slurry when line stop occurs, and electrode coating slurry circulation method using same

Abstract

The present invention relates to an electrode coating slurry circulation system and an electrode coating slurry circulation method using same, the electrode coating slurry circulation system comprising: a double-layer slot coating die for applying electrode active-material slurry to an electrode top and an electrode bottom on a current collector; a first tank for supplying first electrode active-material slurry, which is to be applied to the electrode top, to the coating die; a second tank for supplying second electrode active-material slurry, which is to be applied to the electrode bottom, to the coating die; a first circulation pipe connecting the coating die to the first tank; and a second circulation pipe connecting the coating die to the second tank, wherein when a line is stopped, the slurry is circulated through the circulation pipes connecting the coating die and the tanks.

Description

A slurry circulation system for electrode coating capable of slurry circulation when line float occurs, and a slurry circulation method for electrode coating using the same

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0094694, filed July 20, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a slurry circulation system for electrode coating capable of slurry circulation even when line drift occurs, and a slurry circulation method for electrode coating using the same. Specifically, the present invention relates to a slurry circulation system for electrode coating capable of slurry circulation even when line drift occurs by changing the structure of a coating die, and a slurry circulation method for electrode coating using the same.

[0003] As the scope of secondary battery utilization expands from small portable electronic devices to medium and large electric vehicles (EVs), energy storage systems (ESS), and electric ships, the demand for lithium secondary batteries with high capacity, high energy density, and long lifespan is rapidly increasing.

[0004] The electrode manufacturing process for manufacturing the positive and negative electrodes, which are essential for manufacturing the secondary battery, typically involves coating an electrode slurry containing a mixture of an active material and a conductive material on a current collector, drying the coating, and performing the coating process using a coating die device for electrode manufacturing using the electrode active material slurry supplied from a tank. In addition, in the event of a line stop during the coating process, since there is no separate system for circulating the slurry, the slurry inside the die is discharged back to the supply tank through a return valve connected to the bottom of the die, thereby preventing the slurry from remaining inside the coating die.

[0005] However, when the residual slurry is discharged from the die through the return valve in the event of a line drift, the slurry does not circulate in the coating process system including the tank and coating die, so the slurry often coagulates. In particular, the slurry coagulates inside the coating die, causing powder or gelation. In addition, when coating the electrode after the line drift, surface defects such as pinholes or dents or line defects in which the slurry gets stuck between the C-roll and the coating die occur. Ultimately, this leads to a decline in the coating quality and the scrapping of electrodes that do not meet the standards, which lowers the yield of the electrode process and reduces the Overall Equipment Effectiveness (OEE).

[0006] For example, in the conventional secondary battery manufacturing electrode coating process, when a line stop occurs, the slurry remaining in the die is drained back into the tank (20) using a return valve as shown in Fig. 1, and there is no separate slurry circulation system directly connected from the coating die (10) to the tank (20), so there was a problem that the slurry in the coating die (10) was coagulated and became powdery or gelated. This ultimately led to a deterioration in the coating quality, and there was also a problem that electrodes that did not meet the quality standards were discarded after production, causing cost losses.

[0007] Specifically, when examining the inside of the coating die after floating as shown in Fig. 2, the slurry was clumped together or a large amount of electrode powder was visually observed, and problems such as surface defects such as pinholes or dents and line defects such as slurry getting stuck in the C-roll and coating die were pointed out.

[0008] In order to solve the above problems, as in Korean Patent Application No. 10-2022-0071892, a slurry circulation system for electrode coating was proposed in which the structure of the coating die is changed so that a circulation pipe can be connected to the coating die and the slurry can be circulated through at least one of the left side, right side, rear side, and lower side of the die, thereby circulating the slurry to the tank through the circulation pipe connected to at least one of the left side, right side, rear side, and lower side of the coating die even when floating.

[0009] However, despite the above invention, there is a need for a slurry circulation system for electrode coating that can be used without limitation on the coating direction of a vertical or horizontal structure and without limitation on Double Layer Slot Die Coating (DLD) or Single Layer Slot Die Coating (SLD).

[0010] (Patent Document 1) Korean Patent Publication No. 10-2022-0168566, “Slurry circulation system for electrode coating capable of slurry circulation when line float occurs and slurry circulation method for electrode coating using the same.”

[0011] In order to solve the above problem, the present inventors intend to provide a slurry circulation system for electrode coating capable of slurry circulation when line drift occurs, and a slurry circulation method for electrode coating using the same, which can prevent the phenomenon of the slurry stagnating or coagulating in a die in advance by continuously circulating two electrode active material slurries throughout the coating process system when line drift occurs in a double layer process of applying electrode active material slurry to the upper and lower surfaces of a current collector, and minimize surface defects and line defects that may occur during electrode coating after line drift, thereby improving coating quality, process yield, and productivity.

[0012] According to the 'first aspect' of the present invention,

[0013] A double layer slot coating die for applying electrode active material slurry to the electrode top layer and electrode bottom layer on a current collector; a first tank for supplying a first electrode active material slurry to be coated on the electrode top layer to the coating die; a second tank for supplying a second electrode active material slurry to be coated on the electrode bottom layer to the coating die;

[0014] A slurry circulation system for electrode coating is provided, which comprises a first circulation pipe connecting the coating die and the first tank; and a second circulation pipe connecting the coating die and the second tank; and is a system in which slurry is circulated through the circulation pipes connecting the coating die and the tanks when the line is stopped.

[0015]

[0016] According to the 'second aspect' of the present invention,

[0017] A slurry circulation method for electrode coating using the above slurry circulation system is provided.

[0018] The slurry circulation system for electrode coating according to the present invention and the slurry circulation method for electrode coating using the same have the effect of improving productivity by minimizing coating quality defects during the coating process after the line stop by preventing the two electrode active material slurries from remaining in the die and continuously circulating throughout the entire process including the tank and the die, without causing the slurry of each electrode active material slurry to become powdery or gelled due to slurry agglomeration in the die, even when a line stop occurs during the coating process of a secondary battery, thereby preventing the slurry of each electrode active material slurry from becoming powdery or gelled.

[0019] In addition, the slurry circulation system for electrode coating according to the present invention and the slurry circulation method for electrode coating using the same provide a system in which two slurries can continuously circulate, so that even when line floating occurs, the process temperature within the coating die is maintained without fluctuation, and thus, there is an advantage in that the coating process can be effectively performed without a separate process even after line floating is performed.

[0020] In addition, the slurry circulation system for electrode coating according to the present invention and the slurry circulation method for electrode coating using the same are applicable to both positive and negative electrode coating processes, and have the advantage of being able to respond regardless of the current collector size in the coating process using a slot die.

[0021] Figure 1 is a schematic diagram showing the flow of slurry circulating and draining during the electrode coating process in the manufacture of secondary batteries when the line is floating.

[0022] Figure 2 shows (A) a photograph of the inside of the coating die when it is opened after floating, and (B) a photograph of surface defects that occurred during electrode coating after floating, when the slurry is only drained instead of circulated as in the past when floating occurs.

[0023] Figure 3 is a schematic diagram showing a double-layer slot coating process in the electrode coating process during secondary battery manufacturing.

[0024] Fig. 4 shows a specific example of a coating die of the slurry circulation system for electrode coating according to the present invention.

[0025] Fig. 5 shows another specific example of a coating die of the slurry circulation system for electrode coating of the present invention.

[0026] Figure 6 is a schematic diagram showing a structure in which a circulation pipe is connected to the lower surface of a coating die in one specific example of a slurry circulation system for electrode coating according to the present invention.

[0027] Figure 7 is a schematic diagram showing a structure in which a circulation pipe is connected to the lower surface of a coating die in one specific example of a slurry circulation system for electrode coating according to the present invention.

[0028] Figure 8 is a schematic diagram showing a structure in which a circulation pipe is connected to the lower surface of a coating die in one specific example of a slurry circulation system for electrode coating according to the present invention.

[0029] Figure 9 is a schematic diagram showing a structure in which a circulation pipe is connected to the lower surface of a coating die in one specific example of a slurry circulation system for electrode coating according to the present invention.

[0030] Figure 10 is a schematic diagram showing the flow of slurry circulating and draining during the electrode coating process in the manufacture of a secondary battery according to the present invention.

[0031] Figure 11 shows a specific example of a slurry circulation system for electrode coating according to the present invention.

[0032] Figure 12 shows a specific example of a slurry circulation system for electrode coating according to the present invention.

[0033] Fig. 13 shows the structure of a lip guard provided in a coating die according to the present invention.

[0034] Fig. 14 shows the opening and closing structure of the lip guard provided in the coating die in the present invention.

[0035] Figure 15 is an enlarged view showing the structure in which the lip guard and the discharge portion provided in the coating die of the present invention are in contact.

[0036] According to the 'first aspect' of the present invention,

[0037] A double layer slot coating die for applying electrode active material slurry to the electrode top layer and electrode bottom layer on a current collector; a first tank for supplying a first electrode active material slurry to be coated on the electrode top layer to the coating die; a second tank for supplying a second electrode active material slurry to be coated on the electrode bottom layer to the coating die;

[0038] A slurry circulation system for electrode coating is provided, which comprises a first circulation pipe connecting the coating die and the first tank; and a second circulation pipe connecting the coating die and the second tank; and is a system in which slurry is circulated through the circulation pipes connecting the coating die and the tanks when the line is stopped.

[0039]

[0040] In one specific example of the present invention, the coating die provides a slurry circulation system for electrode coating, which includes two manifold sections for discharging slurry to the top layer of the electrode and the bottom layer of the electrode on the current collector inside the die.

[0041]

[0042] In one specific example of the present invention, a slurry circulation system for electrode coating is provided, wherein the circulation RPM of the second circulation pipe is different from the circulation RPM of the first circulation pipe.

[0043]

[0044] In one specific example of the present invention, a slurry circulation system for electrode coating is provided, wherein the circulation RPM of the second circulation pipe is 1 / 3 to 2 / 3 of the circulation RPM of the first circulation pipe.

[0045]

[0046] In one specific example of the present invention, the coating die has a discharge portion through which slurry for electrode coating is discharged and a lip guard that can block and open the discharge portion.

[0047] The above lip guard provides a slurry circulation system for electrode coating including a Teflon-based material.

[0048]

[0049] In one specific example of the present invention, the slurry circulation system for electrode coating is provided as a system in which slurry is circulated through the circulation pipes connected from the rear of the coating die to the tanks when the line is floating.

[0050]

[0051] In one specific example of the present invention, the slurry circulation system for electrode coating is provided as a system in which slurry is circulated through respective circulation pipes connected from the left and right sides of the coating die to the tanks when the line is floating.

[0052]

[0053] In one specific example of the present invention, slurry supply holes connected to manifold parts inside the die are located on the lower surface of the coating die,

[0054] The above manifolds each have a first flow path including a hollow portion formed in an upper surface direction from the slurry supply hole; and a second flow path including a hollow portion formed in a side direction on both sides centered on one end of the first flow path. A slurry circulation system for electrode coating is provided.

[0055]

[0056] In one specific example of the present invention, a connection hole for connecting a circulation pipe is located on at least one of the left side, right side, rear side and lower side of the coating die,

[0057] When the line is floating, the electrode active material slurry supplied through the slurry supply hole moves in both lateral directions inside the coating die through the slurry movement path, and is circulated to the tanks through each of the circulation pipes connected to the connection hole, thereby providing a slurry circulation system for electrode coating.

[0058]

[0059] In one specific embodiment of the present invention, the slurry circulation system for electrode coating further includes a pump for supplying slurry from each tank to the coating die; a filter; and a valve connected to the slurry supply hole.

[0060]

[0061] In one specific embodiment of the present invention, the slurry circulation system for electrode coating further includes a return valve; and a drain pipe connecting the return valve and each tank; and when the line is floating, the return valve is opened to discharge a portion of the electrode active material slurry supplied from each tank to each tank through the drain pipe.

[0062]

[0063] According to the 'second aspect' of the present invention,

[0064] A slurry circulation method for electrode coating using the slurry circulation system of any one of claims 1 to 11 is provided.

[0065] Although preferred embodiments are presented to help understand the present invention, the following embodiments are provided only to make it easier to understand the present invention and the present invention is not limited thereto.

[0066]

[0067] In addition, the size and shape of components illustrated in the drawings may be exaggerated for clarity and convenience of explanation, and terms specifically defined in consideration of the configuration and operation of the present invention may vary depending on the intention or custom of the user or operator, and the definitions of these terms should be made based on the contents throughout this specification.

[0068] Hereinafter, the present invention will be described in detail with reference to the attached drawings.

[0069]

[0070] The present inventors have invented a slurry circulation system for electrode coating and a slurry circulation method for electrode coating using the same, comprising: a double layer slot coating die for applying electrode active material slurry to an electrode top layer and an electrode bottom layer on a current collector; a first tank for supplying a first electrode active material slurry to be coated on the electrode top layer to the coating die; a second tank for supplying a second electrode active material slurry to be coated on the electrode bottom layer to the coating die; a first circulation pipe connecting the coating die and the first tank; and a second circulation pipe connecting the coating die and the second tank; wherein, when the line is stopped, the slurry is circulated through the circulation pipes connecting the coating die and the tanks.

[0071]

[0072] According to one embodiment of the present invention, a slurry circulation system for electrode coating includes a double layer slot coating die for applying electrode active material slurry to an electrode top layer and an electrode bottom layer on a current collector; a first tank for supplying a first electrode active material slurry to be coated on the electrode top layer to the coating die; a second tank for supplying a second electrode active material slurry to be coated on the electrode bottom layer to the coating die; a first circulation pipe connecting the coating die and the first tank; and a second circulation pipe connecting the coating die and the second tank; and when the line is stopped, the slurry is circulated through the circulation pipes connecting the coating die and the tanks.

[0073]

[0074] In this specification, line stop refers to all situations in which the electrode coating process is stopped for a certain reason during secondary battery manufacturing.

[0075]

[0076] In this specification, the left side, right side, rear side and lower side of the coating die (10) can be defined as the left side, right side, rear side and lower side when looking at the lip end from which slurry is discharged from the coating die.

[0077]

[0078] In one embodiment of the present invention, the slurry circulation system for electrode coating includes a double layer slot coating die (10) that applies electrode active material slurry to the electrode top layer and electrode bottom layer on a current collector. This double layer slot coating die is shown in FIG. 3. According to FIG. 3, the electrode coating process using the double layer slot coating die is a coating die that can use two types of slurry and has the advantage of being able to strengthen the electrode while selectively imparting functions to the electrode top layer and electrode bottom layer depending on the purpose. In the electrode coating process, when applying the electrode active material slurry to the electrode top layer and electrode bottom layer on the current collector, the electrode can be coated through a process in which a plurality of electrode active material slurries are supplied to the coating die (10) and then discharged to apply them to the electrode top layer and electrode bottom layer of the current collector.

[0079]

[0080] In one embodiment of the present invention, in order to enable circulation of slurry for electrode coating even when line floating occurs, the coating die (10) may be configured to have a structure in which the internal slurry movement path structure of the coating die (10) is changed and a circulation pipe (30) is connected to at least one of the left side, right side, rear side, and lower side of the coating die.

[0081] In one embodiment of the present invention, as shown in FIGS. 4 and 5, the coating die (10) may include a manifold section (11) inside the die. In particular, two manifold sections for circulating the active material slurry may be used. The coating die of the present invention includes two manifold sections inside the die for discharging the slurry to the upper and lower surfaces of the current collector, thereby discharging the slurry to the upper layer (Top) of the electrode and the lower layer (Bottom) of the electrode on the current collector without changing the separate coating process conditions, thereby performing double-layer coating, thereby having the effect of reducing costs.

[0082] In one embodiment of the present invention, it can be applied not only to a horizontal double layer slot coating as in FIG. 4, but also to a vertical double layer slot coating as in FIG. 5.

[0083] In one embodiment of the present invention, a slurry supply hole (12) connected to one manifold part (11) inside the die is positioned on the lower surface of the coating die (10), and the manifold part (11) may have a structure including a first flow path including a hollow part formed in the upper surface direction from the slurry supply hole (12); and a second flow path including a hollow part formed in the lateral direction centered on one end of the first flow path.

[0084] According to one embodiment of the present invention, since there are separate tanks and circulation pipes connected to each of the two electrode active material slurries, there are also separate manifolds connected to each of the electrode active material slurries. Two such manifolds are formed in the coating die, and there are two discharge portions through which each slurry is discharged from these two manifolds through the coating die.

[0085] If we look at each manifold section and the movement path of the slurry below, it can be as follows.

[0086] First, through the manifold section (11), the slurry supplied from the slurry supply hole (12) moves toward the upper surface through the first flow path, and then the slurry circulates from one end of the first flow path toward both sides through the second flow path, so that the process temperature inside the coating die can be maintained even when the line is floating, and the phenomenon of the slurry stagnating and coagulating inside the coating die can be prevented. For example, the manifold section (11) may have a structure in which a T-shaped slurry movement path is formed inside.

[0087] In this specification, the ‘void section’ may be defined as an empty space formed inside the first and second flow paths of the manifold section (11) for the slurry to move.

[0088] In one embodiment of the present invention, FIGS. 6 to 9 illustrate a movement structure of one of two electrode active material slurries, wherein a connection hole (13) for connection to a circulation pipe may be positioned on at least one of the left side, right side, rear side, and lower side of the coating die. The connection hole (13) is configured to allow a circulation pipe (30) leading to a tank (20) to be connected to the coating die (10), and its shape is not particularly limited as long as it can be connected to the circulation pipe (30). The diameter of the connection hole (13) for connection to the circulation pipe may preferably be the same as the diameter of the slurry supply hole (12), but is not particularly limited thereto.

[0089]

[0090] In one embodiment of the present invention, the slurry circulation system for electrode coating includes a first tank for supplying a first electrode active material slurry to be coated on the upper surface of the current collector to the coating die; and a second tank for supplying a second electrode active material slurry to be coated on the lower surface of the current collector to the coating die.

[0091] As illustrated in FIG. 12, in one embodiment of the present invention, the tanks (20-1, 20-2) store and supply electrode active material slurry, and are not particularly limited in the present invention as long as they are tanks that can store the electrode active material slurry circulated from the coating die when the line is floating, and may be conventional tanks known in the art, but may include two tanks that are connected to the two manifold sections and supply two electrode active material slurries to the coating die, and specifically, may include a first tank (20-1) that supplies a first electrode active material slurry to be coated on the upper surface of the current collector to the coating die, and a second tank (20-2) that supplies a second electrode active material slurry to be coated on the lower surface of the current collector to the coating die.

[0092]

[0093] In one embodiment of the present invention, the slurry circulation system for electrode coating includes a first circulation pipe (30-1) connecting the coating die (10) and the first tank (20-1); and a second circulation pipe (30-2) connecting the coating die (10) and the second tank (20-2).

[0094] As shown in Fig. 10, the slurry circulation system for the electrode coating can continuously circulate the slurry through each circulation pipe (30) even when floating by connecting each circulation pipe (30) from the coating die (10) to each tank (20). The circulation pipe (30) is configured to be connected to the connection hole (13) in the coating die (10) and may be a pipe that can be easily attached and detached to the connection hole (13). Since it may include a first tank and a second tank that are connected to two manifold parts and supply two electrode active material slurries to the coating die, it may include a first circulation pipe that connects the coating die and the first tank and a second circulation pipe that connects the coating die and the second tank. Since Fig. 10 illustrates the circulation process of one slurry, only one tank, a pump, a filter, a valve, and a return valve are illustrated.

[0095]

[0096] In one embodiment of the present invention, the slurry circulation system for electrode coating includes a circulation pipe (30) as shown in FIG. 11. Since FIG. 11 illustrates the circulation process of one slurry, only one tank, one pump, one filter, one valve, and one return valve are illustrated. The circulation pipe (30) may be a flexible pipe. Specifically, when the line is floating, the gap between the die and the C-roll widens. In this case, when a fixed circulation pipe is used, a problem of the pipe being separated or deformed may occur. To prevent this, a flexible pipe that can be freely bent may be used instead of a fixed circulation pipe.

[0097] The above circulation pipe (30) has a larger diameter, which is more effective in the flow of slurry. Therefore, a circulation pipe with a larger diameter can be used within a range that does not interfere with the die's fastening portion.

[0098]

[0099] As illustrated in FIG. 12, in one embodiment of the present invention, each of the first circulation pipe (30-1) and the second circulation pipe (30-2) may further include a valve (60-1, 60-2) before being connected to the tank (20-1, 20-2). In one embodiment of the present invention, the circulation pipe (30-1, 30-2) may further include a pump (40-1, 40-2) for transporting the slurry before being connected to the tank (20-1, 20-2). The valve (60-1, 60-2) or the pump (40-1, 40-2) located on the circulation pipe is not particularly limited in the present invention, and may be a conventional valve or pump known in the art. In one embodiment of the present invention, since there are two tanks (first tank, second tank) and two circulation pipes (first circulation pipe, second circulation pipe), it goes without saying that two valves and pumps can also be provided accordingly.

[0100] In one embodiment of the present invention, the pump (40-1, 40-2) is not particularly limited in the present invention as long as it can transport the electrode active material slurry, and may be a conventional pump known in the art. In one embodiment of the present invention, the filter (50-1, 50-2) is not particularly limited in the present invention as long as it can filter the slurry when the electrode active material slurry is circulated, and may be a conventional pump known in the art. In one embodiment of the present invention, the valve (60-1, 60-2) is not particularly limited in the present invention as long as it has a configuration that can control the circulation of the electrode active material slurry by opening and closing, and may be a conventional pump known in the art.

[0101]

[0102] In one embodiment of the present invention, the slurry circulation system for electrode coating further includes a return valve (70-1, 70-2); and a drain pipe (80-1, 80-2) connecting the return valve and the tank, and when the line is floating, the return valve (70-1, 70-2) is opened so that a portion of the electrode active material slurry supplied from the tank (20-1, 20-2) can be discharged into the tank (20-1, 20-2) through the drain pipe (80-1, 80-2). A portion of the electrode active material slurry can also be drained through the return valve (70-1, 70-2) and drain pipe (80-1, 80-2) located at the bottom of the coating die (10) separately from the circulation pipe (30-1, 30-2) when the line is floating. This can have the effect of preventing the slurry from leaking from the lip end of the coating die. In one embodiment of the present invention, since each tank and circulation pipe is provided with two, the return valves (70-1, 70-2) and drain pipes (80-1, 80-2) can also be provided with two.

[0103]

[0104] In one embodiment of the present invention, the circulation RPM of the second circulation pipe may be different from the circulation RPM of the first circulation pipe. When different slurries are used, the speed of circulating the slurries must be different so that the viscosity and physical properties of each slurry can be controlled, and therefore, the circulation RPM is adjusted differently from the first circulation pipe. In particular, when coating a secondary battery, when proceeding with double layer slot coating, the content of binder included in the slurry of the lower layer of the electrode is increased compared to the slurry of the upper layer of the electrode to increase the adhesive strength of the coated electrode. At this time, since the binder bond is broken when the circulation RPM increases, a difference is made between the circulation RPM of the first circulation pipe and the circulation RPM of the second circulation pipe.

[0105] In one embodiment of the present invention, the circulation RPM of the second circulation pipe can be adjusted to 1 / 3 to 2 / 3 of the circulation RPM of the first circulation pipe. When coating a secondary battery, if double layer slot coating is performed, the content of the binder contained in the slurry of the lower layer of the electrode is further increased, so the circulation RPM of the second circulation pipe circulating the slurry of the lower layer of the electrode can be adjusted to 1 / 3 to 2 / 3 of the circulation RPM of the first circulation pipe. When this range is satisfied, there is an advantage in that the bonding of the binder contained in the slurry is not easily broken.

[0106]

[0107] In one embodiment of the present invention, the slurry circulation system for electrode coating is a system in which, when the line stops as illustrated in FIG. 12, slurry is circulated through a circulation pipe (30) of either the first circulation pipe or the second circulation pipe connected from at least one of the left side, the right side, the rear side, and the lower side of the coating die (10) to either the first tank or the second tank, the tank (20). Unlike the left side, the right side, the rear side, and the lower side of the coating die (10), when the circulation pipe (30) is connected to the upper side of the coating die (10), the flow direction of the slurry is formed from a direction with low potential energy to a direction with high potential energy, so that it is relatively difficult to form a smooth slurry circulation flow due to the resistance of gravity, and there is a problem in that the slurry leaks from the lip end of the die.

[0108]

[0109] In one embodiment of the present invention, the slurry circulation system for electrode coating can circulate the slurry by connecting a circulation pipe to at least one of the left side, right side, rear side, and bottom side of the coating die in order to minimize interference phenomenon of the fastening parts according to the position of the fastening parts used for fastening the upper and lower plates of the die during the manufacturing process of the coating die (10). For example, the circulation pipe can be connected to both the left side and the right side of the coating die, can be connected to only the lower side, or can be connected to only the rear side.

[0110]

[0111] As illustrated in FIG. 12, in one embodiment of the present invention, the slurry circulation system for electrode coating may be a system in which, when the line is stopped, the slurry is circulated through a circulation pipe (30) of either the first circulation pipe or the second circulation pipe connected from at least one of the left and right sides of the coating die (10) to either the first tank or the second tank (20). Since FIG. 12 illustrates the circulation process of either slurry, only one tank, pump, filter, valve, and return valve are illustrated.

[0112] As illustrated in FIGS. 6 and 7, in one embodiment of the present invention, the slurry circulation system for electrode coating may be a system in which slurry is circulated through a circulation pipe (30) of either the first circulation pipe or the second circulation pipe connected from the left and right sides of the coating die (10) to either the first tank or the second tank (20) when the line is floating. Specifically, when the line is floating, the electrode active material slurry supplied through the slurry supply hole (12) may be a system in which each slurry movement path moves in the direction of two different manifold parts inside the coating die, and circulates to each tank (20) through each circulation pipe (30) connected to the connection hole (13).

[0113] In one embodiment of the present invention, after two electrode active material slurries move through two manifold parts (11) inside the coating die (10), the electrode active material slurries can be circulated to one of the first tank and the second tank (20) through one of the circulation pipes (30) of the first circulation pipe and the second circulation pipe connected thereto. Through this, even though two different active material slurries are used, there is an effect of preventing a deterioration in coating quality after line floating, and evenly performing a coating process on the upper and lower surfaces of the current collector, and a thermometer, a flow meter, or a pressure gauge can be installed in the circulating pipe to check the circulation status.

[0114]

[0115] As illustrated in FIG. 8, in one embodiment of the present invention, the slurry circulation system for electrode coating may be a system in which slurry is circulated through a circulation pipe (30) of either the first circulation pipe or the second circulation pipe connected from the rear of the coating die (10) to either the first tank or the second tank (20) when the line is floating. In the case of circulating the slurry through the circulation pipe (30) connected from the rear of the coating die (10) to the tank (20), there is an advantage in that the influence of interference phenomena caused by bolts fastening the upper and lower plates of the die can be reduced compared to the case in which a circulation valve is connected to the other surface of the coating die.

[0116]

[0117] As illustrated in FIG. 9, in one embodiment of the present invention, the slurry circulation system for electrode coating may be a system in which slurry is circulated through a circulation pipe (30) of either the first circulation pipe or the second circulation pipe connected from the lower surface of the coating die (10) to either the first tank or the second tank (20) when the line is floating.

[0118]

[0119] As illustrated in FIG. 13, in one embodiment of the present invention, the coating die (10) may be provided with a discharge portion (14) through which slurry for electrode coating is discharged, and a lip guard (15) capable of blocking or opening the discharge portion (14) may be provided on the discharge portion (14). The lip guard (15) is positioned at one end of a lip cover (16) to block or open the discharge portion (14), and the lip cover (16) is connected to a lip cutter shaft (17) and can be operated to block or open the discharge portion (14) by operating a handle (18). There are no particular limitations on the lip cover (16) or the lip cutter shaft (17) as long as it has enough rigidity to move the lip guard (15) and sufficiently block the discharge portion, and is made of a material that does not easily corrode, but preferably, a pad made of a Teflon-based material or a silicone foam pad can be used.

[0120] Specifically, when the slurry for electrode coating is not discharged, the lip guard (15) may block the discharge portion (14) as shown in (a) of Fig. 14. This not only prevents leakage of the slurry for electrode coating, but also prevents the overall circulation of the slurry for electrode coating from being obstructed. In addition, when the slurry for electrode coating is discharged, the lip guard (15) must not block the discharge portion (14) as shown in (b) of Fig. 14. To this end, the lip guard (15) may be provided with a lip guard contact portion (15-1) that directly contacts the discharge portion (14) to prevent discharge of the slurry for electrode coating, as shown in Fig. 15, and a lip guard fixing portion (15-2) that fixes the lip guard contact portion (15-1). The above lip guard contact portion (15-1) may be made of an elastic material to completely block the discharge portion (14), but is not necessarily limited thereto. The above lip guard fixing portion (15-2) may also be made of, for example, plastic, which can fix the above lip guard contact portion (15-1), but is not necessarily limited thereto.

[0121] Additionally, in one embodiment of the present invention, a protective film may be additionally formed over the lip guard (15) to prevent it from being affected by solvents such as NMP. There are no particular limitations on the protective film as long as it is not affected by solvents such as NMP, but for example, Teflon film or Teflon tape may be used.

[0122]

[0123] In one embodiment of the present invention, the slurry circulation method for electrode coating uses the slurry circulation system described above. In one embodiment of the present invention, the slurry circulation method for electrode coating can circulate the slurry to each tank (20) through the circulation pipe (30) of any one of the first circulation pipe and the second circulation pipe connected from at least one of the left side, the right side, the rear side and the lower side of the coating die (10) of the slurry circulation system to the first tank and the second tank tank (20) when the line is floating. Accordingly, there is an effect of maintaining the internal temperature of the coating die (10) constant without the slurry stagnating in a specific area within the coating die (10) and coagulating or gelling, thereby minimizing surface defects or line defects after the line is floating, thereby improving the coating quality and improving the productivity of the process.

[0124]

[0125] All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

Claims

1. Double Layer Slot Coating Die for applying electrode active material slurry to the electrode top layer and electrode bottom layer on the current collector; A first tank for supplying a first electrode active material slurry to be coated on the upper layer of the electrode to the coating die; A second tank for supplying a second electrode active material slurry to be coated on the lower layer of the electrode to the coating die; A first circulation pipe connecting the coating die and the first tank; and A second circulation pipe connecting the coating die and the second tank; A slurry circulation system for electrode coating, which is a system in which slurry circulates through the circulation pipes connecting the coating die and the tanks when the line stops.

2. In paragraph 1, The above coating die is a slurry circulation system for electrode coating, which includes two manifold sections for discharging slurry to the upper layer (Top) of the electrode and the lower layer (Bottom) of the electrode on the current collector inside the die.

3. In paragraph 1, A slurry circulation system for electrode coating, wherein the circulation RPM of the second circulation pipe is different from the circulation RPM of the first circulation pipe.

4. In paragraph 1, A slurry circulation system for electrode coating, wherein the circulation RPM of the second circulation pipe is 1 / 3 to 2 / 3 of the circulation RPM of the first circulation pipe.

5. In paragraph 1, The above coating die has a discharge portion through which slurry for electrode coating is discharged and a lip guard that can block and open the discharge portion. The above lip guard is a slurry circulation system for electrode coating containing a Teflon-based material.

6. In paragraph 1, The above slurry circulation system for electrode coating is a system in which slurry is circulated through the circulation pipes connected from the rear of the coating die to the tanks when the line is floating.

7. In paragraph 1, The above slurry circulation system for electrode coating is a system in which slurry is circulated through respective circulation pipes connected from the left and right sides of the coating die to the tanks when the line is floating.

8. In paragraph 1, On the lower surface of the above coating die, slurry supply holes are located that are connected to the manifold parts inside the die, A slurry circulation system for electrode coating, wherein the manifold sections each have a first flow path including a hollow portion formed in an upper surface direction from the slurry supply hole; and a second flow path including a hollow portion formed in a side direction centered on one end of the first flow path.

9. In paragraph 8, At least one of the left, right, rear and lower surfaces of the above coating die has a connecting hole for connecting a circulation pipe, A slurry circulation system for electrode coating, wherein, when the line is floating, the electrode active material slurry supplied through the slurry supply hole moves in both lateral directions inside the coating die through the slurry movement path and circulates to the tanks through each of the circulation pipes connected to the connection hole.

10. In paragraph 1, The slurry circulation system for electrode coating further comprises a pump for supplying slurry from each tank to the coating die; a filter; and a valve connected to the slurry supply hole.

11. In paragraph 10, The slurry circulation system for the electrode coating further includes a return valve; and a drain pipe connecting the return valve and each of the tanks; A slurry circulation system for electrode coating, which opens the return valve when the line is floating, and discharges a portion of the electrode active material slurry supplied from each tank to each tank through the drain pipe.

12. A slurry circulation method for electrode coating using the slurry circulation system of any one of claims 1 to 11.

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