A slurry circulation system for electrode coatings that enables slurry circulation when a line stops, and a method for circulating an electrode coating slurry using the same.

Abstract

The present invention relates to a slurry circulation system for electrode coating and a method for circulating a slurry for electrode coating using the same, comprising: a double-layer slot coating die for applying an electrode active material slurry to the upper and lower layers of an electrode on a 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, wherein the slurry circulates through the circulation pipe connecting the coating die and the tank when the line is stopped.

Description

Technical Field

[0001] The present invention claims the benefit of priority based on Korean Patent Application No. 10-2023-0094694 filed on July 20, 2023, and all the contents disclosed in the document of the Korean patent application are included as part of this specification.

[0002] The present invention relates to a slurry circulation system for electrode coating that enables slurry circulation during line stops and a method for circulating slurry for electrode coating using the same. Specifically, it relates to a slurry circulation system for electrode coating that enables slurry circulation even during line stops due to a structural change in the coating die and a method for circulating slurry for electrode coating using the same.

Background Art

[0003] The range in which secondary batteries are utilized has expanded from small portable electronic devices to medium and large electric vehicles (EVs), energy storage systems (ESSs), electric ships, etc., and the demand for high-capacity, high-energy-density, and long-life lithium secondary batteries has increased rapidly.

[0004] In the electrode manufacturing process for manufacturing positive and negative electrodes, which is inevitably involved in the manufacture of secondary batteries, usually, after applying an electrode slurry in which an active material and a conductive material are mixed onto a current collector and drying it for coating, the electrode active material slurry supplied from a tank can be coated using a coating die device for electrode manufacturing. Also, when a line stop occurs where the coating process is interrupted, since there is no other system capable of circulating the slurry, the slurry in the die is re-discharged to the supply tank through a return valve connected to the lower part of the die to prevent the slurry from remaining in the coating die.

[0005] However, when residual slurry is discharged from the die through the return valve during line stoppages, the slurry does not circulate within the coating process system, including the tank and coating die, leading to frequent slurry aggregation. In particular, slurry aggregation and solidification or gelation occurred within the coating die, resulting in surface defects such as pinholes and dents, as well as line defects such as slurry getting stuck between the C-roll and the coating die during electrode coating after line stoppages. Ultimately, this leads to a decrease in coating quality and the disposal of electrodes that do not meet standards, resulting in a decrease in electrode process yield and overall equipment effectiveness (OEE).

[0006] For example, in the electrode coating process for conventional secondary battery manufacturing, when a line stoppage occurs, as shown in Figure 1, the slurry remaining in the die is simply drained back into the tank (20) using a return valve. Since there is no separate slurry circulation system directly connected from the coating die (10) to the tank (20), there was a problem of the slurry in the coating die (10) solidifying or gelling due to aggregation. This ultimately led to a decrease in coating quality, and electrodes that did not meet quality standards were discarded after production, resulting in cost losses.

[0007] Specifically, as shown in Figure 2, an examination of the inside of the coating die after stopping revealed that the slurry had agglomerated, and numerous electrode particles were visible to the naked eye. This indicated surface defects such as pinholes and dents, as well as line defects where slurry became trapped between the C-roll and the coating die.

[0008] To solve the above-mentioned problems, a circulation system for electrode coating slurry has been proposed, as described in Korean Published Patent No. 10-2022-0168566, "A circulation system for electrode coating slurry that enables slurry circulation when a line stops, and a method for circulating electrode coating slurry using the same," which modifies the structure of the coating die 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, back, and bottom surfaces of the die, thereby enabling the slurry to be circulated to a tank via a circulation pipe connected to at least one of the left side, right side, back, and bottom surfaces of the coating die even when the line stops.

[0009] However, despite the inventions described above, there is a need for a circulating system for electrode coating slurry that can be used without limitation in the coating direction of a vertical or horizontal structure and can be used without limitation in double-layer slot die coating (DLD) or single-layer slot die coating (SLD). [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Korean Published Patent Publication No. 10-2022-0168566 [Overview of the project] [Problems that the invention aims to solve]

[0011] To solve the above-mentioned problems, the present inventors provide a slurry circulation system for electrode coating that enables slurry circulation when a line stop occurs, and a method for circulating a slurry for electrode coating using the same, which prevents the two electrode active material slurries from stagnating and agglomerating in the die during a double-layer process in which electrode active material slurry is applied to the upper and lower surfaces of a current collector, and minimizes surface defects and line defects that may occur during electrode coating after a line stop, thereby improving coating quality, process yield, and productivity. [Means for solving the problem]

[0012] According to the "first aspect" of the present invention, A double-layer slot coating die for applying electrode active material slurry to the upper (Top) and lower (Bottom) layers of electrodes on a current collector, A first tank supplies a first electrode active material slurry, which is to be coated on the upper layer of the electrode, to a double-layer slot coating die, A second tank supplies a second electrode active material slurry, which is to be coated on the lower layer of the electrode, to the double-layer slot coating die, A first circulation pipe connecting the double-layer slot-coated die and the first tank, It includes a second circulation pipe connecting a double-layer slot-coated die and a second tank, This invention provides a slurry circulation system for electrode coating, in which the slurry circulates through circulation piping connecting the double-layer slot coating die and the tank when the line is stopped.

[0013] According to a "second aspect" of the present invention, a method for circulating an electrode coating slurry using an electrode coating slurry circulation system is provided. [Effects of the Invention]

[0014] The electrode coating slurry circulation system and electrode coating slurry circulation method according to the present invention have the effect of minimizing coating quality defects during the coating process after line stoppage, and improving productivity, as the two electrode active material slurries do not remain in the die even when the secondary battery coating process is interrupted due to line stoppage, and the entire process including the tank and die is continuously circulated through the system, preventing solidification or gelation phenomena due to slurry aggregation in the die, and thus preventing the respective electrode active material slurries from occurring.

[0015] Furthermore, the electrode coating slurry circulation system and electrode coating slurry circulation method using the present invention provide a system in which two slurries can be continuously circulated, maintaining the process temperature inside the coating die without fluctuation even when a line stop occurs, and enabling the coating process to be effectively carried out without any additional steps after the line stop.

[0016] Furthermore, the electrode coating slurry circulation system and electrode coating slurry circulation method according to the present invention have the advantage of being applicable to both positive electrode and negative electrode coating processes, and can be used regardless of the current collector size in the slot die coating process. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram illustrating the flow of slurry during line stoppage in the electrode coating process during secondary battery manufacturing. [Figure 2] When a stoppage occurs, instead of circulating the slurry as in the conventional method, only draining is performed. The images show (A) a photograph of the inside of the coating die after it has been opened following the stoppage, and (B) a photograph of surface defects that occurred during electrode coating after the stoppage. [Figure 3] This is a schematic diagram of the double-layer slot coating process in the electrode coating process during the manufacturing of secondary batteries. [Figure 4]It is a diagram showing an embodiment of a coating die of a circulation system for a slurry for electrode coating in the present invention. [Figure 5] It is a diagram showing another embodiment of a coating die of a circulation system for a slurry for electrode coating in the present invention. [Figure 6] In one embodiment of a circulation system for a slurry for electrode coating in the present invention, it is a schematic diagram of a structure in which a circulation pipe is connected to the lower surface of a coating die. [Figure 7] In one embodiment of a circulation system for a slurry for electrode coating in the present invention, it is a schematic diagram of a structure in which a circulation pipe is connected to the lower surface of a coating die. [Figure 8] In one embodiment of a circulation system for a slurry for electrode coating in the present invention, it is a schematic diagram of a structure in which a circulation pipe is connected to the lower surface of a coating die. [Figure 9] In one embodiment of a circulation system for a slurry for electrode coating in the present invention, it is a schematic diagram of a structure in which a circulation pipe is connected to the lower surface of a coating die. [Figure 10] In the electrode coating process during the manufacture of a secondary battery, it is a schematic diagram of the flow in which the slurry is circulated and drained at the time of stopping in the present invention. [Figure 11] It is a diagram showing an embodiment of a circulation system for a slurry for electrode coating in the present invention. [Figure 12] It is a diagram showing an embodiment of a circulation system for a slurry for electrode coating in the present invention. [Figure 13] It is a diagram showing the structure of a lip guard provided on a coating die in the present invention. [Figure 14] It is a diagram showing the opening and closing structure of a lip guard provided on a coating die in the present invention. [Figure 15] In the present invention, it is a diagram showing an enlarged structure in which a lip guard provided on a coating die abuts on a discharge part.

Embodiments for Carrying Out the Invention

[0018] According to the "first aspect" of the present invention, A double-layer slot coating die for applying electrode active material slurry to the upper and lower layers of electrodes on a current collector, A first tank supplies a first electrode active material slurry, which is to be coated on the upper layer of the electrode, to a double-layer slot coating die, A second tank supplies a second electrode active material slurry, which is to be coated on the lower layer of the electrode, to the double-layer slot coating die, A first circulation pipe connecting the double-layer slot-coated die and the first tank, It includes a second circulation pipe connecting a double-layer slot-coated die and a second tank, This invention provides a slurry circulation system for electrode coating, in which the slurry circulates through circulation piping connecting the double-layer slot coating die and the tank when the line is stopped.

[0019] In one embodiment of the present invention, the double-layer slot coating die provides a slurry circulation system for electrode coating, which includes two manifold sections inside the die that discharge slurry onto the upper and lower layers of electrodes on a current collector.

[0020] In one embodiment of the present invention, a circulating system for electrode coating slurry is provided, characterized in that the circulating RPM (revolutions per minute) (rotations per minute) of the second circulating pipe is different from the circulating RPM of the first circulating pipe.

[0021] In one embodiment of the present invention, a circulating system for electrode coating slurry is provided, characterized in that the circulating RPM of the second circulating pipe is 1 / 3 to 2 / 3 (one-third to two-thirds) of the circulating RPM of the first circulating pipe.

[0022] In one embodiment of the present invention, the double-layer slot coating die includes a discharge section from which an electrode coating slurry is discharged and a lip guard that can be opened and closed on the discharge section. LipGuard provides a circulation system for electrode coating slurries containing Teflon®-based materials.

[0023] One embodiment of the present invention provides a slurry circulation system for electrode coating, in which the slurry circulates through circulation piping connected from the back of a double-layer slot coating die to a tank when the line is stopped.

[0024] In one embodiment of the present invention, a slurry circulation system for electrode coating is provided, in which, when the line is stopped, the slurry circulates through circulation pipes connected from the left and right sides of the double-layer slot coating die to a tank.

[0025] In one embodiment of the present invention, a slurry supply hole connected to a manifold inside the die is provided on the lower surface of the double-layer slot coating die. The manifold section is a structure that includes a first flow path including a hollow section formed upward from a slurry supply hole, and a second flow path including a hollow section formed laterally from one end of the first flow path, providing a circulating system for electrode coating slurry.

[0026] In one embodiment of the present invention, at least one of the left side, right side, back, and bottom surfaces of the double-layer slot coating die is provided with a connecting hole for circulating piping. This system provides a slurry circulation system for electrode coating, in which, when the line is stopped, the electrode active material slurry supplied through the slurry supply hole moves laterally inside the double-layer slot coating die through the slurry movement path and circulates to the tank through each circulation pipe connected to the circulation pipe connection hole.

[0027] One embodiment of the present invention provides a slurry circulation system for electrode coating, further comprising a pump for supplying slurry from each tank to a double-layer slot coating die, a filter, and a valve connected to a slurry supply hole.

[0028] One embodiment of the present invention further includes a return valve and drain piping connecting the return valve to each tank, This system provides a circulation system for electrode coating slurry, which opens a return valve when the line is stopped, allowing a portion of the electrode active material slurry supplied from each tank to be discharged back into the tank through a drain pipe.

[0029] According to the "second aspect" of the present invention, The present invention provides a method for circulating an electrode coating slurry using the electrode coating slurry circulation system described in any one of claims 1 to 11.

[0030] Preferred embodiments are shown to aid in understanding the present invention, but the following embodiments are provided to make the present invention easier to understand, and the present invention is not limited thereto.

[0031] Furthermore, the size and shape of the constituent elements shown in the drawings may be exaggerated for clarity and convenience of explanation, and terms specifically defined in consideration of the structure and operation of the present invention may vary depending on the intent or custom of the user or operator, and the definitions of these terms should be determined based on the overall content of this specification.

[0032] The present invention will be described in detail below with reference to the attached drawings.

[0033] The present inventors have invented a slurry circulation system for electrode coating and a method for circulating a slurry for electrode coating using the same, comprising: a double-layer slot coating die for applying an electrode active material slurry to the upper and lower layers of an electrode on a 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 double-layer slot 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 double-layer slot coating die; a first circulation pipe connecting the double-layer slot coating die and the first tank; and a second circulation pipe connecting the double-layer slot coating die and the second tank, wherein when the line is stopped, the slurry circulates through the circulation pipe connecting the double-layer slot coating die and the tank.

[0034] A slurry circulation system for electrode coating according to one embodiment of the present invention includes a double-layer slot coating die for applying electrode active material slurry to the upper and lower layers of electrodes on a current collector, a first tank for supplying a first electrode active material slurry to be coated on the upper layer of electrodes to the double-layer slot coating die, a second tank for supplying a second electrode active material slurry to be coated on the lower layer of electrodes to the double-layer slot coating die, a first circulation pipe connecting the double-layer slot coating die and the first tank, and a second circulation pipe connecting the double-layer slot coating die and the second tank, wherein when the line is stopped, the slurry circulates through the circulation pipe connecting the double-layer slot coating die and the tank.

[0035] In this specification, line stoppage means all situations in the electrode coating process during secondary battery manufacturing where the coating process is interrupted for certain reasons.

[0036] In this specification, the left side, right side, back, and bottom of the coating die (10) are defined as the left side, right side, back, and bottom, respectively, based on the view from the front of the lip end from which the slurry is discharged from the coating die.

[0037] In one embodiment of the present invention, the electrode coating slurry circulation system includes a double-layer slot coating die for applying electrode active material slurry to the upper and lower electrode layers on a current collector. Such a double-layer slot coating die is shown in Figure 3. According to Figure 3, the electrode coating process using the double-layer slot coating die may use two types of slurry, and the coating die has the advantage of being able to strengthen the electrodes while selectively imparting functions to the upper and lower electrode layers according to the purpose. In the electrode coating process, when applying electrode active material slurry to the upper and lower electrode layers on a current collector, the electrodes can be coated through a process in which multiple electrode active material slurries are supplied to the coating die (10), discharged, and applied to the upper and lower electrode layers of the current collector.

[0038] In one embodiment of the present invention, the coating die (10) may be modified to allow the circulation of the electrode coating slurry even when a line stop occurs, by modifying the internal slurry movement path structure of the coating die (10) and forming a structure in which a circulation pipe (30) is connected to at least one of the left side, right side, back, and bottom surfaces of the coating die.

[0039] In one embodiment of the present invention, as shown in Figures 4 and 5, the coating die (10) may include a manifold section (11) inside the die. In particular, two manifold sections may be used for circulating the active substance slurry. The coating die of the present invention includes two manifold sections inside the die that discharge slurry to the upper and lower surfaces of the current collector, thereby discharging slurry to the upper and lower layers of the electrodes on the current collector and performing a double-layer coating without changing other coating process conditions, thus reducing costs.

[0040] In one embodiment of the present invention, it can be applied not only to horizontal double-layer slot coating as shown in Figure 4, but also to vertical double-layer slot coating as shown in Figure 5.

[0041] In one embodiment of the present invention, a slurry supply hole (12) is provided on the lower surface of the coating die (10) and communicates with one of the manifold sections (11) inside the die. The manifold section (11) may have a structure that includes a first flow path including a hollow section formed upward from the slurry supply hole (12), and a second flow path including hollow sections formed in the lateral directions around one end of the first flow path.

[0042] 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 manifold sections connected to each electrode active material slurry. Two such manifold sections are formed on the coating die, and there are two discharge sections from which the respective slurries are discharged through the coating die.

[0043] The manifold sections and the slurry flow paths are as follows:

[0044] First, the slurry supplied from the slurry supply hole (12) through the manifold section (11) moves upward through the first flow path. Then, the slurry circulates through the second flow path from one end of the first flow path in both lateral directions, thereby maintaining the process temperature inside the coating die even when the line is stopped, and preventing the slurry from stagnating and agglomerating inside the coating die. For example, the manifold section (11) may have a structure in which a T-shaped slurry movement path is formed inside.

[0045] In this specification, "void section" can be defined as an unoccupied space formed inside the first and second flow paths of the manifold section (11) for the slurry to move.

[0046] In one embodiment of the present invention, Figures 6 to 9 show the movement structure of one of the two electrode active material slurries. However, a connecting hole (13) for circulating piping may be provided on at least one of the left side, right side, back, and bottom surfaces of the coating die. The connecting hole (13) is configured to allow circulating piping (30) connected 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 circulating piping (30). The diameter of the connecting hole (13) for circulating piping may preferably be the same as the diameter of the slurry supply hole (12), but is not particularly limited thereto.

[0047] In one embodiment of the present invention, the electrode coating slurry circulation system includes a first tank for supplying a first electrode active material slurry to be coated on the upper surface of a current collector to a coating die, and a second tank for supplying a second electrode active material slurry to be coated on the lower surface of a current collector to the coating die.

[0048] As shown in Figure 12, in one embodiment of the present invention, the tanks (20-1, 20-2) are not particularly limited in the present invention and may be ordinary tanks known in the industry, as long as they are tanks that store and supply electrode active material slurry and can store electrode active material slurry circulated from the coating die again when the line is stopped. However, they may also include two tanks connected to two manifold sections and supplying two electrode active material slurries to the coating die. Specifically, they may include a first tank (20-1) that supplies a first electrode active material slurry to the coating die to be coated on the upper surface of the current collector, and a second tank (20-2) that supplies a second electrode active material slurry to the coating die to be coated on the lower surface of the current collector.

[0049] In one embodiment of the present invention, the electrode coating slurry circulation system includes a first circulation pipe (30-1) connecting a coating die (10) and a first tank (20-1), and a second circulation pipe (30-2) connecting a coating die (10) and a second tank (20-2).

[0050] As shown in Figure 10, the electrode coating slurry circulation system connects each circulation pipe (30) from the coating die (10) to each tank (20), allowing for continuous circulation of the slurry even when the system is stopped. The circulation pipe (30) is configured to be connected to a connecting hole (13) in the coating die (10), and may be a pipe that can be easily attached to and detached from the connecting hole (13). It may include a first tank and a second tank connected to two manifold sections to supply two electrode active material slurries to the coating die, and may also include 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. In Figure 10, since the circulation process of any one slurry is shown, only one tank, pump, filter, valve, and return valve are shown.

[0051] In one embodiment of the present invention, the circulation system for electrode coating slurry includes circulation piping (30), as shown in Figure 11. Since Figure 11 shows the circulation process of one slurry, only one tank, pump, filter, valve, and return valve are shown. The circulation piping (30) may be in a flexible form. Specifically, when the line is stopped, the gap between the die and the C-roll widens. In this case, if fixed circulation piping is used, problems such as the piping separating or deforming may occur. To prevent this, flexible piping that can be bent freely may be used instead of fixed circulation piping.

[0052] From the viewpoint that a larger diameter is more effective for the flow of slurry, it is preferable to use a circulation pipe (30) with a larger diameter, provided that it does not interfere with the fastening portion of the die.

[0053] As shown in Figure 12, in one embodiment of the present invention, each of the first circulation pipes (30-1) and the second circulation pipes (30-2) may further include valves (60-1, 60-2) before being connected to the tanks (20-1, 20-2). In one embodiment of the present invention, the circulation pipes (30-1, 30-2) may further include pumps (40-1, 40-2) for transferring slurry before being connected to the tanks (20-1, 20-2). The valves (60-1, 60-2) or pumps (40-1, 40-2) located on the circulation pipes are not particularly limited in the present invention and may be ordinary valves or pumps known in the industry. 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), there are naturally two valves and two pumps associated with them.

[0054] In one embodiment of the present invention, the pumps (40-1, 40-2) are not particularly limited in the present invention and may be ordinary pumps known in the industry, as long as they are capable of transferring the electrode active material slurry. In one embodiment of the present invention, the filters (50-1, 50-2) are not particularly limited in the present invention and may be ordinary pumps known in the industry, as long as they are capable of filtering the slurry during the circulation of the electrode active material slurry. In one embodiment of the present invention, the valves (60-1, 60-2) are not particularly limited in the present invention and may be ordinary pumps known in the industry, as long as they are configured to control the circulation of the electrode active material slurry by opening and closing.

[0055] In one embodiment of the present invention, the electrode coating slurry circulation system further includes return valves (70-1, 70-2) and drain pipes (80-1, 80-2) connecting the return valves to a tank, and when the line is stopped, the return valves (70-1, 70-2) can be opened to discharge a portion of the electrode active material slurry supplied from the tanks (20-1, 20-2) to the tanks (20-1, 20-2) via the drain pipes (80-1, 80-2). In addition to the circulation pipes (30-1, 30-2), a portion of the electrode active material slurry can also be drained when the line is stopped through the return valves (70-1, 70-2) and drain pipes (80-1, 80-2) located at the bottom of the coating die (10). This prevents slurry leakage at the lip end of the coating die. In one embodiment of the present invention, since there are two tanks and two circulation pipes, there can also be two return valves (70-1, 70-2) and two drain pipes (80-1, 80-2).

[0056] In one embodiment of the present invention, the circulation RPM of the second circulation pipe may differ from that of the first circulation pipe. When different slurries are used, the viscosity and physical properties of each slurry can be adjusted by changing the circulation speed of the slurries. Therefore, the circulation RPM of the second circulation pipe is adjusted to differ from that of the first circulation pipe. In particular, when performing double-layer slot coating for secondary battery coating, the binder content in the slurry of the lower electrode layer is made higher than that of the slurry of the upper electrode layer to increase the adhesion strength of the coated electrode. At this time, if the circulation RPM is too high, the binder bonds will break, so a difference is made between the circulation RPM of the first circulation pipe and the circulation RPM of the second circulation pipe.

[0057] 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 performing double-layer slot coating during secondary battery coating, the circulation RPM of the second circulation pipe that circulates the slurry in the lower electrode layer can be adjusted to 1 / 3 to 2 / 3 of the circulation RPM of the first circulation pipe in order to increase the binder content in the slurry in the lower electrode layer. When this range is met, there is an advantage that the binder bonds in the slurry are less likely to break easily.

[0058] In one embodiment of the present invention, as shown in Figure 12, the slurry circulation system for electrode coating is a system in which, when the line is stopped, the slurry circulates through a first circulation pipe and a second circulation pipe (30) connected from at least one of the left side, right side, back and bottom surfaces of the coating die (10) to one of the first and second tanks (20). Unlike the left side, right side, back and bottom surfaces of the coating die (10), when the circulation pipe (30) is connected to the top surface of the coating die (10), the slurry flow direction is formed from a direction with low potential energy to a direction with high potential energy, and the smooth circulation flow of the slurry is relatively difficult to form due to the resistance of gravity, resulting in the problem of slurry leaking from the lip end of the die.

[0059] In one embodiment of the present invention, the electrode coating slurry circulation system can circulate the slurry by connecting the circulation piping to at least one of the left side, right side, back and bottom surfaces of the coating die in order to minimize interference phenomena of fastening parts due to the position of 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 piping may be connected to both the left and right sides of the coating die, to the bottom surface only, or to the back surface only.

[0060] As shown in Figure 12, in one embodiment of the present invention, the electrode coating slurry circulation system may be a system in which, when the line is stopped, the slurry circulates through either the first circulation pipe or the second circulation pipe (30) 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). In Figure 12, since the circulation process of either one of the slurry is shown, only one tank, pump, filter, valve, and return valve are shown.

[0061] As shown in Figures 6 and 7, in one embodiment of the present invention, the electrode coating slurry circulation system may be a system in which, when the line is stopped, the slurry circulates through either the first circulation pipe or the second circulation pipe (30) connected from the left and right sides of the coating die (10) to either the first tank or the second tank (20). Specifically, when the line is stopped, the electrode active material slurry supplied through the slurry supply hole (12) may move from inside the coating die towards two different manifold sections through their respective slurry movement paths and circulate to each tank (20) through their respective circulation pipes (30) connected to the connecting hole (13).

[0062] In one embodiment of the present invention, after two electrode active material slurries move through two manifold sections (11) inside the coating die (10), the electrode active material slurry can be circulated to either the first tank or the second tank (20) through one of the circulation pipes (30) connected thereto, either the first or the second circulation pipe. This has the effect of preventing a decrease in coating quality after line shutdown, even though two different active material slurries are used, and allowing the coating process to proceed uniformly on the upper and lower surfaces of the current collector. Furthermore, a thermometer, flow meter, or pressure gauge can be installed in the circulating pipe to check the circulation state.

[0063] As shown in Figure 8, in one embodiment of the present invention, the electrode coating slurry circulation system may be a system in which, when the line is stopped, the slurry circulates through either the first circulation pipe or the second circulation pipe (30) connected from the back of the coating die (10) to either the first tank or the second tank (20). When the slurry is circulated through the circulation pipe (30) connected from the back of the coating die (10) to the tank (20), there is an advantage in that it is less affected by interference phenomena caused by bolts fastening the upper and lower plates of the die, compared to when a circulation valve is connected to the other side of the coating die.

[0064] As shown in Figure 9, in one embodiment of the present invention, the electrode coating slurry circulation system may be a system in which, when the line is stopped, the slurry circulates from the bottom surface of the coating die (10) through either the first circulation pipe or the second circulation pipe (30) connected to either the first tank or the second tank (20).

[0065] As shown in Figure 13, in one embodiment of the present invention, the coating die (10) may be provided with a discharge section (14) from which an electrode coating slurry is discharged, and a lip guard (15) that can open and close the discharge section (14) may be provided on the discharge section (14). The lip guard (15) is located at one end of a lip cover (16) and can open and close the discharge section (14). Such a lip cover (16) is connected to a lip cutter shaft (17) and can be operated by a handle (18) to open and close the discharge section (14). The lip cover (16) and lip cutter shaft (17) are not particularly limited as long as they have sufficient rigidity to move the lip guard (15) and sufficiently close the discharge section and are made of a material that does not corrode easily, but preferably a Teflon®-based pad or a silicone foam pad may be used.

[0066] Specifically, when the electrode coating slurry is not being discharged, the lip guard (15) may block the discharge section (14), as shown in Figure 14(a). This not only prevents leakage of the electrode coating slurry but also prevents obstruction of the overall circulation of the electrode coating slurry. Furthermore, when the electrode coating slurry is being discharged, the lip guard (15) must not block the discharge section (14), as shown in Figure 14(b). For this reason, the lip guard (15) may include a lip guard contact section (15-1) that directly contacts the discharge section (14) to prevent the discharge of the electrode coating slurry, as shown in Figure 15, and a lip guard fixing section (15-2) that fixes such a lip guard contact section (15-1). The lip guard contact section (15-1) may be made of an elastic material to completely block the discharge section (14), but is not necessarily limited to this. The lip guard fixing part (15-2) is also capable of fixing the lip guard contact part (15-1), and may be made of plastic, for example, but is not necessarily limited to this.

[0067] Furthermore, in one embodiment of the present invention, a protective film can be further formed on the lip guard (15) to prevent it from being affected by solvents such as NMP (N-methylpyrrolidone, N-methyl-2-pyrrolidone). The protective film is not particularly limited as long as it is not affected by solvents such as NMP, but for example, Teflon® film or Teflon® tape may be used.

[0068] In one embodiment of the present invention, a slurry circulation system is used as the method for circulating the slurry for electrode coating. In one embodiment of the present invention, when the line is stopped, the slurry for electrode coating can be circulated to each tank (20) via either the first circulation pipe or the second circulation pipe (30) which is connected from at least one of the left side, right side, back and bottom surfaces of the coating die (10) of the slurry circulation system to the first tank and the second tank (20). This prevents the slurry from stagnating and agglomerating or gelling in specific areas within the coating die (10), and maintains a constant internal temperature of the coating die (10). This minimizes surface defects and line defects after the line is stopped, thereby improving coating quality and increasing process productivity.

[0069] Any mere modification or alteration of the present invention falls within the scope of the present invention, and the specific scope of protection of the present invention is made clear by the appended claims.

Claims

1. A double-layer slot coating die for applying electrode active material slurry to the upper and lower layers of electrodes on a 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 double-layer slot coating die, A second tank for supplying a second electrode active material slurry, which is to be coated on the lower layer of the electrode, to the double-layer slot coating die, A first circulation pipe connecting the double-layer slot coating die and the first tank, Includes a second circulation pipe connecting the double-layer slot coating die and the second tank, A slurry circulation system for electrode coating, wherein the slurry circulates through a circulation pipe connecting the double-layer slot coating die and the tank when the line is stopped.

2. The electrode coating slurry circulation system according to claim 1, characterized in that the double-layer slot coating die includes two manifold sections inside the die that discharge slurry to the upper and lower layers of the electrode on the current collector.

3. The electrode coating slurry circulation system according to claim 1 or 2, characterized in that the circulation RPM of the second circulation pipe is different from the circulation RPM of the first circulation pipe.

4. The electrode coating slurry circulation system according to claim 1 or 2, characterized in that the circulation RPM of the second circulation pipe is 1 / 3 to 2 / 3 of the circulation RPM of the first circulation pipe.

5. The double-layer slot coating die includes a discharge section from which an electrode coating slurry is discharged and a lip guard that can open and close the discharge section. The electrode coating slurry circulation system according to claim 1 or 2, characterized in that the lip guard includes a Teflon®-based material.

6. A slurry circulation system for electrode coating according to claim 1 or 2, wherein when the line is stopped, the slurry circulates through a circulation pipe connected from the back of the double-layer slot coating die to the tank.

7. A slurry circulation system for electrode coating according to claim 1 or 2, wherein when the line is stopped, the slurry circulates through circulation pipes connected from the left and right sides of the double-layer slot coating die to the tank.

8. A slurry supply hole, which is connected to the manifold inside the die, is located on the lower surface of the double-layer slot-coated die. The electrode coating slurry circulation system according to claim 1 or 2, wherein each manifold section is a structure including a first flow path including a hollow portion formed upward from the slurry supply hole, and a second flow path including a hollow portion formed laterally from one end of the first flow path.

9. A connecting hole for circulating piping is located on at least one of the left side, right side, back, and bottom surfaces of the double-layer slot-coated die. The electrode coating slurry circulation system according to claim 8, wherein when the line is stopped, the electrode active material slurry supplied from the slurry supply hole moves laterally inside the double-layer slot coating die via the slurry movement path and circulates to the tank via each circulation pipe connected to the circulation pipe connection hole.

10. The electrode coating slurry circulation system according to claim 1 or 2, further comprising a pump for supplying slurry from each tank to the double-layer slot coating die, a filter, and a valve communicating with a slurry supply hole.

11. The system further includes a return valve and drain piping connecting the return valve to each tank, The electrode coating slurry circulation system according to claim 10, characterized in that when the line is stopped, the return valve is opened and a portion of the electrode active material slurry supplied from each tank is discharged to each tank via the drain pipe.

12. A method for circulating an electrode coating slurry using the electrode coating slurry circulation system described in claim 1 or 2.

Images