Patent Publication Number: US-2023158538-A1

Title: Slot Die Coating Device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2021/005580, filed on May 4, 2021, which claims priority from Korean Patent Application No. 10-2020-0064320 filed on May 28, 2020, with the Korean Intellectual Property Office, the disclosures of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a slot die coating device, and more particularly, to a slot die coating device for electrode production. 
     BACKGROUND 
     As energy prices are increasing due to the depletion of fossil fuels and increasing attention is being paid to environmental pollution, the demand for environmentally-friendly alternative energy sources acts as an essential factor for future life. Thus, research into techniques for generating various kinds of power, such as nuclear energy, solar energy, wind energy, and tidal power, is underway, and power storage apparatuses for more efficient use of the generated energy are also drawing much attention. 
     Moreover, the demand for batteries as energy sources is rapidly increasing as mobile device technology continues to develop and the demand for such mobile devices continues to increase. Accordingly, much research on batteries capable of satisfying various needs has been carried out. In particular, in terms of the material for batteries, the demand for lithium secondary batteries, such as lithium ion batteries and lithium ion polymer batteries, which have advantages such as high energy density, discharge voltage, and output stability, is very high. 
     A secondary battery includes an electrode assembly having a structure, in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are stacked, and the electrode assemblies are received in a pouch case, a cylindrical can, a prismatic case, and the like depending on the purpose of use to manufacture the battery. 
     The positive electrode and the negative electrode are manufactured by coating a positive electrode slurry and a negative electrode slurry onto an electrode current collector formed of an aluminum foil and a copper foil, and drying the slurry. In order to make the charge and discharge characteristics of the secondary battery uniform, a positive electrode active material slurry and a negative electrode active material slurry have to be uniformly coated onto the current collector, and for this purpose, a slot die coating process may be commonly performed. 
     The slot die coating device for the slot die coating process may include a slot die coater as an equipment for coating the electrode slurry onto the electrode current collector. 
     The slot die coater refers to a device that supplies a liquid fluid with fluidity (slurry, adhesive, hard coating agent, ceramic, etc.) between the upper and lower slot dies via a pulsation-free pump or a piston pump, and coats a material on an object to be coated such as fabric, film, glass plate, and sheet moving in one direction with a certain thickness. 
     The slot die coater for electrode production refers to a configuration in which a slot die coater is applied for electrode production, and an electrode slurry, which is a supply fluid, is coated onto an electrode current collector in order to make an electrode of a secondary battery. 
     The flow rate distribution in the width direction of the electrode slurry may differ depending on the process conditions and the shape of the slot die. Thus, in order to obtain a coating layer having a uniform thickness, it is necessary to properly design the shape of each part of the slot die coater for electrode production. 
     In order to shorten the time required for the drying process and secure the productivity of the electrode, an active material and a conductive material are mixed with the electrode slurry in a high ratio, so that the electrode slurry has a high viscosity. 
     Depending on the shape of the flow path in all sections from a mixing tank that stores and supplies the electrode slurry to the slot die coater, the electrode slurry can be stagnant or have a very low flow rate. 
     The width of the electrode slurry coated varies depending on the model of the electrode to be manufactured, and the internal pressure of the slot die coater may increase when manufacturing the electrode having a small width of the electrode slurry. As the internal pressure of the slot die coater increases, a problem may occur in which the amount of electrode slurry to be coated is not uniform in the width direction, or the electrode slurry is leaked. 
     Therefore, there is a need to develop a slot die coating device having an improved structure capable of solving these problems. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problem 
     It is an object of the present disclosure to provide a slot die coating device that can reduce the pressure inside the slot die coater to uniformly coat an electrode slurry and can prevent leakage of electrode slurry. 
     However, the problem to be solved by the embodiments of the present disclosure is not limited to the above-described problems, and can be variously expanded within the scope of the technical idea included in the present disclosure. 
     Technical Solution 
     According to one embodiment of the present disclosure, there is provided a slot die coating device comprising: a slot die coater configured to form an internal space for housing the electrode slurry and a discharge passage connected to the internal space to discharge the electrode slurry; and a block located in the internal space, wherein a distance between the first inside portion and the second inside portion forming the internal space is formed longer than a distance between the first discharge inside portion and the second discharge inside portion forming the discharge passage, and wherein the block comprises a first block facing the first inside portion and a second block facing the second inside portion. 
     A distance between the first block and the second block may be equal to or longer than a distance between the first discharge inside portion and the second discharge inside portion. 
     One surface of the first block may face the first inside portion, and the other surface of the first block may form a surface parallel to the first discharge inside portion. 
     One surface of the second block may face the second inside portion, and the other surface of the second block may form a surface parallel to the second discharge inside portion. 
     The first block may be in contact with the first inside portion, and the second block may be in contact with the second inside portion. 
     The block may include at least one of MC nylon (Mono cast nylon) and Teflon (Polytetrafluoroethylene, PTFE). 
     The slot die coater may include an upper die, a lower die, and a plate-shaped shim portion located between the upper die and the lower die. 
     The shim portion may include a first side portion and a second side portion connected in parallel to each other; a central portion that connects the first side portion and the second side portion; and a first protrusion portion and a second protrusion portion each protruding from one end of the first side portion and one end of the second side portion in opposite directions in a direction facing each other, wherein the first protrusion portion and the second protrusion portion may form the discharge passage. 
     The first side portion may form at least a part of the first inside portion, and the second side portion may form at least a part of the second inside portion. 
     The discharge passage may be connected up to an outer surface of the slot die coater to form a discharge port. 
     The slot die coating device may further include a roller that moves in one direction the electrode current collector on which the electrode slurry is coated. 
     Advantageous Effects 
     According to embodiments of the present disclosure, both the pressure and the pressure deviation inside the slot die coater can be reduced through a block disposed inside the slot die coater. Therefore, the electrode slurry can be uniformly coated, and leakage of the electrode slurry can be prevented. 
     The effects of the present disclosure are not limited to the effects mentioned above and additional other effects not described above will be clearly understood from the description of the appended claims by those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a slot die coater according to an embodiment of the present disclosure; 
         FIG.  2    is an exploded perspective view of the slot die coater of  FIG.  1   ; 
         FIG.  3    is a cross-sectional view taken along the cutting line A-A′ of  FIG.  1   ; 
         FIG.  4    is a perspective view of a slot die coater according to a comparative example of the present disclosure; 
         FIG.  5    is a cross-sectional view taken along the cutting line B-B′ of  FIG.  4   ; and 
         FIG.  6    is a plan view of a slot die coater and a roller according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement them. The present disclosure can be modified in various different ways, and is not limited to the embodiments set forth herein. 
     Portions that are irrelevant to the description will be omitted to clearly describe the present disclosure, and like reference numerals designate like elements throughout the specification. 
     Further, in the drawings, the size and thickness of each element are arbitrarily illustrated for convenience of description, and the present disclosure is not necessarily limited to those illustrated in the drawings. In the drawings, the thickness of layers, regions, etc. are exaggerated for clarity. In the drawings, for convenience of description, the thicknesses of some layers and regions are shown to be exaggerated. 
     Further, it will be understood that when an element such as a layer, film, region, or plate is referred to as being “on” or “above” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, it means that other intervening elements are not present. Further, the word “on” or “above” means disposed on or below a reference portion, and does not necessarily mean being disposed on the upper end of the reference portion toward the opposite direction of gravity. 
     Further, throughout the specification, when a portion is referred to as “including” a certain component, it means that the portion can further include other components, without excluding the other components, unless otherwise stated. 
     Further, throughout the specification, when referred to as “planar”, it means when a target portion is viewed from the upper side, and when referred to as “cross-sectional”, it means when a target portion is viewed from the side of a cross section cut vertically. 
       FIG.  1    is a perspective view of a slot die coater according to an embodiment of the present disclosure.  FIG.  2    is an exploded perspective view of the slot die coater of  FIG.  1   .  FIG.  3    is a cross-sectional view taken along the cutting line A-A′ of  FIG.  1   . 
     Referring to  FIGS.  1  to  3   , the slot die coating device according to the embodiment of the present disclosure includes a slot die coater  100  configured to form an internal space  110  for housing the electrode slurry and a discharge passage  120  connected to the internal space  110  to discharge the electrode slurry; and a block  500  located in the internal space  110 . A distance dl between the first inside portion  111  and the second inside portion  112  forming the internal space  110  is formed longer than a distance d 2  between the first discharge inside portion  121  and the second discharge inside portion  122  forming the discharge passage  120 , and the block  500  includes a first block  510  facing the first inside portion  111  and a second block  520  facing the second inside portion  112 . 
     Here, the first inside portion  111  and the second inside portion  112  may mean internal side surfaces perpendicular to the y-axis in the internal space  110 , and the first discharge inside portion  121  and the second discharge inside portion  122  may mean internal side surfaces perpendicular to the y-axis in the discharge passage  120 . Meanwhile, the internal space  110  may mean a manifold, that is, a volume space occupied by the coating solution of the electrode slurry inside the slot die coater  100  in the slot die coating process. 
     The slot die coater  100  may include an upper die  200 , a lower die  300 , and a plate-shaped shim portion  400  located between the upper die  200  and the lower die  300 . 
     The upper die  200  and the lower die  300  may be coupled to each other to form an internal space  110  in which the electrode slurry is housed. The lower die  300  is provided with a supply port H 1  connected to the internal space  110  of the slot die coater  100 . The liquid electrode slurry may pass through the supply port H 1  via a pulsation-free pump, a piston pump, or the like and move to the internal space  110 . 
     The shim portion  400  is configured to determine the internal space  110  of the slot die coater  100  and the width of the coating, and may include a first side portion  410  and a second side portion  420  connected in parallel to each other; a central portion  430  that connects the first side portion  410  and the second side portion  420 ; and a first protrusion portion  410 P and a second protrusion portion  420 P each protruding from one end of the first side portion  410  and one end of the second side portion  420  in opposite directions facing each other. The coating width of various electrode slurries can be realized by changing the size design value of the shim portion  400 . 
     Specifically, the discharge passage  120  connected to the internal space  110  may be connected up to the outer surface of the slot die coater  100  to form the discharge port H 2 , and the electrode slurry may be discharged onto the electrode current collector via the discharge port H 2 . At this time, the first side portion  410  of the shim portion  400  forms at least a part of the first inside portion  111  of the internal space  110 , and the second side portion  420  of the shim portion  400  may form at least a part of the second inside portion  112  of the internal space  110 . Further, the first protrusion portion  410 P and the second protrusion portion  420 P may form the discharge passage  120 . The distance between the first protrusion portion  410 P and the second protrusion portion  420 P determines the width of the discharge passage  120  and the discharge port H 2 . That is, the width of the discharge passage  120  and the discharge port H 2  may be set by adjusting the distance between the first protrusion portion  410 P and the second protrusion portion  420 P of the shim portion  400 . Therefore, the width of the electrode slurry coated on the electrode current collector may be changed by replacing the shim portion  400  between the upper die  200  and the lower die  300  according to the electrode model to be manufactured. 
     Thereby, as described above, the distance dl between the first inside portion  111  and the second inside portion  112  forming the internal space  110  is formed longer than the distance d 2  between the first discharge inside portion  121  and the second discharge inside portion  122  forming the discharge passage  120 . Here, the distance d 2  between the first discharge inside portion  121  and the second discharge inside portion  122  may correspond to the distance between the first protrusion portion  410 P and the second protrusion portion  420 P of the shim portion  400 . 
     As described above, the slot die coating device according to the present embodiment includes a block  500  located in the internal space  110  of the slot die coater  100 , and the block  500  includes a first block  510  facing the first inside portion  111  and a second block  520  facing the second inside portion  112 . The first block  510  and the second block  520  may be a rectangular parallelepiped—shaped structure having a constant volume. 
     Specifically, the distance d 3  between the first block  510  and the second block  520  may be equal to or longer than the distance d 2  between the first discharge inside portion  121  and the second discharge inside portion  122 . Specifically, the distance d 3  between the first block  510  and the second block  520  may be 1 to 1.2 times the distance d 2  between the first discharge inside portion  121  and the second discharge inside portion  122 . When the distance d 3  between the first block  510  and the second block  520  is shorter than the distance d 2  between the first discharge inside portion  121  and the second discharge inside portion  122 , the electrode slurry is likely to be coated with a width smaller than the coating width of the designed electrode slurry, which is thus not preferable. Further, when the distance d 3  between the first block  510  and the second block  520  exceeds 1.2 times the distance d 2  between the first discharge inside portion  121  and the second discharge inside portion  122 , the pressure inside the slot die coater  100  is not sufficiently reduced. Therefore, it is not possible to effectively prevent leakage of electrode slurry or improve wear of the slot die coater  100 , which will be described later. 
     On the other hand, the two distances d 2  and d 3  are formed to be identical, so that one surface of the first block  510  faces the first inside portion  111 , the other surface of the first block  510  may form a surface parallel to the first discharge internal portion  121 , one surface of the second block  520  faces the second inside portion  112 , and the other surface of the second block  520  may form a surface parallel to the second discharge inside portion  122 . 
     Hereinafter, the slot die coater  100  including the block  500  according to the present embodiment will be described in comparison with the slot die coater  10  according to the comparative example of the present disclosure shown in  FIGS.  4  and  5   . 
       FIG.  4    is a perspective view of a slot die coater according to a comparative example of the present disclosure.  FIG.  5    is a cross-sectional view taken along the cutting line B-B′ of  FIG.  4   . 
     Referring to  FIGS.  4  and  5   , the slot die coater  10  according to the present comparative example includes a supply port h 1 , an internal space  11 , a discharge passage  12 , and a discharge port h 2 . The electrode slurry that flows into the internal space  11  of the slot die coater  10  via the supply port h 1  is coated onto the electrode current collector via the discharge passage  12  and the discharge port h 2 . 
     At this time, the distance d 4  between both inside portions of the internal space  11  may be longer than the distance d 5  between both inside portions of the discharge passage  12 . A distance d 4  between both inside portions of the internal space  11  corresponds to a distance d 1  between the first inside portion  111  and the second inside portion  112  in the present embodiment, and a distance d 5  between both inside portions of the discharge passage  12  corresponds to a distance d 2  between the first discharge inside portion  121  and the second discharge inside portion  122 . 
     In the slot die coater  10  according to the present comparative example, the distance d 4  between both inside portions of the internal space  11  is formed to be long, so that the internal space  11  is formed to be relatively large. Thereby, the space occupied by the electrode slurry in the slot die coater  10  increases, and the pressure inside the slot die coater  10  increases. The increased pressure may cause problems such as leakage of the electrode slurry or wear of the slot die coater  10 . Further, due to the difference in length between the distance d 4  between both inside portions of the internal space  11  and the distance d 5  between the both inside portions of the discharge passage  12 , a pressure deviation may occur at both end portions and the central portion of the discharge passage  12  in the width direction (y-axis direction), and the electrode slurry may be non-uniformly coated onto the electrode current collector with reference to the width direction (y-axis direction). 
     On the other hand, the slot die coater  100  according to the present embodiment can physically reduce the space occupied by the electrode slurry in the internal space  110  by the block  500 , and the pressure inside the slot die coater  100  can be reduced. Thereby, leakage of the electrode slurry can be prevented to reduce the loss of the electrode slurry, and the wear of the slot die coater  100  due to the pressure of the electrode slurry can be improved. 
     Further, the pressure deviation of the discharged electrode slurry can be reduced, so that the electrode slurry can be uniformly coated, which can lead to improved performance of the manufactured electrode. 
     Meanwhile, the first block  510  may be in contact with the first inside portion  111 , and the second block  520  may be in contact with the second insider portion  112 . That is, the first block  510  can be in contact with the first inside portion  111  in a state of being fitted into the first protrusion portion  410 P, the first side portion  410  and the central portion  430 , and the second block  520  may be in contact with the second inside portion  112  in a state of being fitted into the second protrusion portion  420 P, the second side portion  420 , and the central portion  430 , so that the first block  510  and the second block  520  are stably fixed at predetermined positions in the internal space  110 . 
     Meanwhile, the block  500  according to the present embodiment may include at least one of MC nylon (mono cast nylon) and Teflon (polytetrafluoroethylene, PTFE) in order to improve chemical resistance. 
       FIG.  6    is a plan view of a slot die coater and a roller according to an embodiment of the present disclosure. 
     Referring to  FIG.  6   , the slot die coating device according to the present embodiment includes a slot die coater  100  including an upper die  200  and a lower die  300 , and a roller  600  that moves in one direction the electrode current collector  700  on which the electrode slurry is coated. 
     The electrode slurry is discharged through the discharge port H 2  of the slot die coater  100 , and the electrode slurry can be coated to a constant thickness onto the electrode current collector  700  moving in one direction by the rotating roller  600 . 
     Even though the terms representing directions such as front, rear, left, right, upper and lower directions are used herein, it is obvious to those skilled in the art that these merely represent for convenience in explanation, and may differ depending on a position of an observer, a position of an object, or the like. 
     Although preferred embodiments of the present disclosure have been described in detail above, the scope of the present disclosure is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts of the present disclosure, which are defined in the appended claims, also belong to the scope of the present disclosure. 
     DESCRIPTION OF REFERENCE NUMERALS 
       100 : slot die coater 
       200 : upper die 
       300 : lower die 
       400 : shim portion 
       500 : block 
       510 : first block 
       520 : second block