Apparatus for drying electrode slurry of secondary battery

Abstract

The present invention relates to an apparatus for drying electrode slurry of a secondary battery, the apparatus including a nozzle plate having a plurality of perforations formed therein. The objective of the present invention is to uniformly dry electrode slurry on a substrate. To this end, the present invention provides a drying apparatus comprising: a nozzle for spraying gas for drying electrode slurry including a solvent applied onto a substrate for a drying process; and a nozzle plate provided at an outlet of the nozzle and having a plurality of perforations for discharging the gas sprayed from the nozzle toward the substrate, wherein the number of perforations is determined on the basis of the amount of undried solvent on the substrate after the drying process.

Description

Secondary battery electrode slurry drying device

[0001] The present invention relates to an electrode slurry drying device for a secondary battery including a nozzle plate having a plurality of perforations formed therein.

[0002] Secondary batteries, unlike non-rechargeable primary batteries, are rechargeable and dischargeable. Low-capacity secondary batteries are used in small, portable electronic devices such as smartphones, feature phones, laptops, digital cameras, and camcorders, while large-capacity secondary batteries are widely used as power sources for motor drives and power storage in hybrid and electric vehicles. These secondary batteries include an electrode assembly comprising a positive and negative electrode, a case housing the electrode assembly, and electrode terminals connected to the electrode assembly.

[0003] Secondary batteries are manufactured through a variety of processes. In particular, during the electrode process, a slurry containing active materials is coated onto a substrate and then dried to produce the positive and negative electrodes of the secondary battery. Typically, the slurry coated onto the substrate passes through a drying unit, where the solvent that makes up part of the slurry evaporates, resulting in drying.

[0004] At this time, if the slurry dries unevenly depending on its location on the substrate, binder migration can degrade the quality of the secondary battery. This uneven drying of the slurry can be caused by the internal structure and airflow distribution within the drying unit, depending on the circulation method, which can slow down the electrode process. Therefore, a drying device design that addresses these issues is required.

[0005] The above-described information disclosed in the background technology of this invention is only intended to improve understanding of the background of the present invention, and therefore may include information that does not constitute prior art.

[0006] The present invention relates to a device for drying electrode slurry of a secondary battery to solve the above-mentioned problem.

[0007] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0008] In a secondary battery electrode slurry drying device for solving a technical problem, the device comprises a nozzle for injecting gas for drying electrode slurry including a solvent applied on a substrate for a drying process, and a nozzle plate provided at an outlet of the nozzle and having a plurality of perforations formed therein for discharging gas injected from the nozzle toward the substrate, wherein the number of perforations is determined based on the amount of undried solvent on the substrate after the drying process.

[0009] In one embodiment of the present disclosure, the nozzle plate includes a plate region having a plurality of plate sub-regions, and the number of perforations formed on the plate sub-regions is proportional to the amount of undried solvent present in the substrate region corresponding to the plate sub-region.

[0010] In one embodiment of the present disclosure, the number of perforations is determined by applying a ratio proportional to the amount of undried solvent to the total number of candidate perforations within the plate sub-region.

[0011] In one embodiment of the present disclosure, the position of the punching is determined to be a position selected so as to maintain a constant spacing between the punchings.

[0012] In one embodiment of the present disclosure, the electrode slurry is coated on the substrate in a stripe coating manner, and no perforations are formed on the nozzle plate corresponding to the substrate area where the electrode slurry is not positioned.

[0013] In one embodiment of the present disclosure, the positions of the perforations have a pattern of linear symmetry.

[0014] In one embodiment of the present disclosure, the number of perforations formed in a plate sub-region corresponding to the central portion of the substrate is greater than the number of perforations formed in a plate sub-region corresponding to the edge portion of the substrate.

[0015] In one embodiment of the present disclosure, the amount of undried solvent is calculated by a density meter based on the area-wise change in density of the slurry formed on the substrate before and after the drying process.

[0016] In one embodiment of the present disclosure, the density meter corresponds to a radiation type sensor.

[0017] In one embodiment of the present disclosure, a chamber is further provided, in which an inlet for introducing a substrate and an outlet for withdrawing the substrate are formed, and an electrode slurry is dried inside the chamber, a nozzle is connected to the chamber and injects gas into the interior of the chamber, and an amount of undried solvent is determined based on the substrate withdrawn from the outlet.

[0018] In one embodiment of the present disclosure, the nozzle plate includes a plate region having a plurality of plate sub-regions, and an area of ​​a perforation formed on the plate sub-region is proportional to an amount of undried solvent present in a substrate region corresponding to the plate sub-region.

[0019] In one embodiment of the present disclosure, the device further comprises a plurality of supply pipes for supplying gas to the nozzle, each of the plurality of supply pipes supplying gas according to a different heat source.

[0020] A method for drying electrode slurry of a secondary battery for solving a technical problem comprises the steps of: injecting gas for drying electrode slurry including a solvent applied on a substrate through a nozzle plate provided at an outlet of a nozzle; measuring the amount of undried solvent on the substrate; and determining the arrangement of holes formed on the nozzle plate based on the amount of undried solvent.

[0021] In one embodiment of the present disclosure, the step of measuring the amount of undried solvent includes the step of measuring by a density meter based on the amount of change in the area-wise density of the slurry formed on the substrate.

[0022] In one embodiment of the present disclosure, the method further comprises the steps of replacing the nozzle plate with a new nozzle plate having a determined number of perforations formed therein, and drying an electrode slurry including a solvent applied on a substrate using a nozzle having the new nozzle plate.

[0023] In one embodiment of the present disclosure, the nozzle plate includes a plate region having a plurality of plate sub-regions, and the step of determining the arrangement of the perforations includes a step of determining the number of perforations formed on the plate sub-regions to be proportional to the amount of undried solvent present in a substrate region corresponding to the plate sub-regions.

[0024] In one embodiment of the present disclosure, the step of determining the arrangement of the perforations includes the step of determining the number of perforations by applying a ratio proportional to the amount of undried solvent to the total number of candidate perforations within the plate sub-region.

[0025] In one embodiment of the present disclosure, the step of determining the arrangement of the perforations includes the step of determining the positions of the perforations to be positions selected so as to maintain a constant spacing between the perforations.

[0026] In one embodiment of the present disclosure, the step of injecting includes a step of injecting gas supplied from at least one of a plurality of supply pipes, each of which supplies gas according to a different heat source, through a nozzle plate.

[0027] According to the present invention, the electrode slurry coated on the substrate can be uniformly dried in the width direction.

[0028] According to an embodiment of the present disclosure, by controlling the gas flow inside the drying section, there is an effect of uniformly drying the solvent over the entire area of ​​the substrate.

[0029] According to an embodiment of the present disclosure, the number of perforations can be easily controlled by applying a ratio proportional to the amount of undried solvent to the total number of candidate perforations in the plate sub-region.

[0030] According to the present invention, the number of perforations per unit area is formed differently between plate sub-areas, thereby easily controlling the flow rate of gas discharged toward the substrate.

[0031] According to the present invention, by not forming a perforation on a specific sub-area of ​​the nozzle plate, it is possible to prevent the phenomenon of substrate folding due to thermal shrinkage from becoming worse due to a large amount of heat being applied to an area where electrode slurry is not applied.

[0032] However, the effects that can be obtained through the present invention are not limited to the effects described above, and other technical effects that are not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0033] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0034] FIG. 1 is a drawing showing a cross-section of an electrode slurry drying device for a secondary battery according to one embodiment of the present disclosure.

[0035] FIG. 2 is a drawing showing a nozzle plate according to one embodiment of the present disclosure.

[0036] Figure 3 is a drawing showing the flow of gas discharged toward the substrate from a nozzle having the nozzle plate of Figure 2.

[0037] Fig. 4 is a drawing showing the degree of drying of a dried substrate using a nozzle having the nozzle plate of Fig. 2.

[0038] FIG. 5 is a drawing showing a graph showing the area-specific density of a slurry on a dried substrate measured using a nozzle equipped with the nozzle plate of FIG. 2.

[0039] FIG. 6 is a drawing showing a nozzle plate according to one embodiment of the present disclosure.

[0040] FIG. 7 is a drawing showing a method for determining the number of holes in a nozzle plate according to one embodiment of the present disclosure.

[0041] Figure 8 is a drawing showing the flow of gas discharged toward the substrate from a nozzle having the nozzle plate of Figure 6.

[0042] Figure 9 is a drawing showing a graph measuring the area-specific density of slurry on a substrate according to the type of nozzle plate.

[0043] Figure 10 is a drawing showing a color map associated with the area-specific density of slurry on a substrate according to the type of nozzle plate.

[0044] FIG. 11 is a flowchart showing a method for drying electrode slurry of a secondary battery according to one embodiment of the present disclosure.

[0045] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms or words used in this specification and claims should not be interpreted as limited to their typical or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of a term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as substitutes for them at the time of filing this application.

[0046] Additionally, when used herein, the terms "comprise", "include" and / or "comprising", "including" specify the presence of stated features, numbers, steps, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, elements and / or groups thereof.

[0047] Additionally, to facilitate understanding of the invention, the attached drawings are not drawn to scale and some components may be exaggerated in size. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0048] The statement that two compared objects are "identical" means "substantially identical." Therefore, "substantially identical" may include deviations considered low in the art, such as deviations of less than 5%. Furthermore, uniformity of a parameter over a given region may imply uniformity on average.

[0049] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless otherwise specified, a "first" component may also be a "second" component.

[0050] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0051] Any configuration being placed "on (or under)" or "above (or below)" a component may mean not only that any configuration is placed in contact with the upper surface (or lower surface) of said component, but also that other configurations may intervene between said component and any configuration placed on (or below) said component.

[0052] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component. Furthermore, when it is said that a part is electrically coupled to another part, this includes not only cases where they are directly connected, but also cases where they are connected with another element in between.

[0053] When reference is made throughout the specification to "A and / or B," this means A, B, or A and B, unless otherwise stated. In other words, "and / or" includes all or any combination of the listed items. When reference is made to "C through D," this means C or more and D or less, unless otherwise stated.

[0054] The terminology used herein is for the purpose of describing embodiments of the present disclosure and is not intended to be limiting of the present disclosure.

[0055] In the present disclosure, 'areal density' may refer to the mass of a material applied / coated on a substrate per unit area of ​​the substrate. For example, the areal density may be mg / cm 2 It can be calculated in units.

[0056] FIG. 1 is a drawing showing a cross-section of an electrode slurry drying device (100) for a secondary battery according to one embodiment of the present disclosure. Referring to FIG. 1, the electrode slurry drying device (100) may include a drying unit (110), a chamber (112), a nozzle (114), a discharge unit (116), a supply pipe (122, 124), a roller (150), and a density meter (160). The drying device (100) is not limited thereto, and may further include other components, or some components may be omitted.

[0057] The substrate (130) coated with electrode slurry (142) can be introduced into the drying section (110) through the drying section inlet (110a), dried, and then taken out of the drying section (110) through the drying section outlet (110b). The drying section (110) can be formed of various materials and in various shapes such as rectangular, cylindrical, and multilayered, depending on the purpose, and is not limited to the shape illustrated in FIG. 1.

[0058] The substrate (130) can be introduced into or withdrawn from the drying unit (110) while moving using a roller (150). The direction of movement of the substrate (130) may correspond to the +y direction. The roller (150) may rotate at a constant speed to continuously introduce or withdraw the substrate (130) into or out of the drying unit (110). The roller (150) may rotate for a first time period to move the substrate (130) and then stop for a second time period. The substrate can be dried in a moving state during the first time period and in a stopped state during the second time period. Alternatively, the roller (150) may continuously rotate without stopping. When the roller (150) continuously rotates without stopping, the rotation speed of the roller (150) may be relatively low compared to when there is a stop time, and the substrate (130) can be dried in a continuously moving state.

[0059] Before the substrate (130) is introduced into the drying section (110) through the drying section inlet (110a), electrode slurry (142) may be applied / coated on the substrate (130) in the coating section (140). At this time, the electrode slurry (142) may be coated on the substrate (130) in a stripe coating manner in the direction of substrate movement.

[0060] The electrode slurry (142) coated on the substrate (130) can be manufactured by mixing an active material, a binder, and a conductive material using a solvent. The active material included in the electrode slurry (142) can vary depending on the type of electrode being manufactured. For example, the electrode slurry for manufacturing a positive electrode can include a positive electrode active material such as lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), ternary lithium metal oxide (NCM), spinel compound, etc., and the electrode slurry for manufacturing a negative electrode can include a negative electrode active material such as graphite, carbon fiber, etc.

[0061] A variety of materials can be used as binders, including polyvinylidene fluoride (PVDF), polymethylmethacrylate, polyacrylonitrile, polyethylene, and related polymers or copolymers.

[0062] N-methyl-2-pyrrolidone (NMP), water, etc. can be used as a solvent. The electrode slurry (142) is not limited to the materials described and may include various types of materials. For example, the solvent may correspond to a material that can be dried by a heated gas.

[0063] The drying unit (110) can perform a drying process for drying the electrode slurry (142) by removing the solvent within the electrode slurry (142). The drying unit (110) can be designed to allow the substrate to slide through the interior.

[0064] Specifically, inside the drying unit (110), an inlet (112a) through which a substrate (130) is introduced and an outlet (112b) through which the substrate (130) is withdrawn are formed, and a chamber (112) in which electrode slurry (142) is dried inside, a nozzle (114) connected to the chamber (112) for injecting gas for drying the electrode slurry (142) into the interior of the chamber (112), a nozzle plate (not shown) provided at the outlet of the nozzle (114) and having a plurality of perforations formed for discharging the gas injected from the nozzle (114) toward the substrate (130) (or the electrode slurry (142)), and an exhaust unit (116) for discharging the gas used for drying the electrode slurry to the outside of the chamber (112) may be provided.

[0065] The drying unit (110) is not limited to that illustrated in FIG. 1, and any number of chambers, nozzles, discharge ports, etc. may be provided at any location. In addition, a nozzle plate provided at the outlet of the nozzle and having a plurality of perforations formed therein will be described in detail later with reference to FIGS. 2, 6, and 7.

[0066] In one embodiment, the discharge portion (116) may be positioned to face the nozzle (114) with the substrate (130) as the center. That is, the discharge portion (116) may be positioned facing the nozzle (114) and spaced apart from the substrate (130).

[0067] For example, when the nozzle (114) is positioned on the upper side (+z direction) of the substrate (130), the discharge unit (116) may be positioned on the lower side (-z direction) of the substrate (130), and when the nozzle (114) is positioned on the lower side (-z direction) of the substrate (130), the discharge unit (116) may be positioned on the upper side (+z direction) of the substrate (130). Since the nozzle (114) and the discharge unit (116) are positioned opposite each other with the substrate as the center, the flow of gas can be controlled more precisely, and thereby the drying amount of the solvent can be controlled precisely.

[0068] In another embodiment, the nozzle (114) and the discharge portion (116) may be positioned in the same direction (e.g., above the substrate (130)) with respect to the substrate (130).

[0069] The supply pipes (122, 124) can supply gas to the nozzles (114). In FIG. 1, two supply pipes (122, 124) are shown for each nozzle, but this is not limited thereto, and any number of supply pipes can be connected to each nozzle.

[0070] The supply pipes (122, 124) can be connected to a gas generating device (e.g., a hot air generating device) for drying the electrode slurry, and the amount of gas transferred to the supply pipes (122, 124) and / or the amount of gas supplied to the nozzle (114) can be controlled using a pump, a fan, a valve, etc. Each of the supply pipes (122, 124) can supply gas (e.g., hot air, steam, etc.) according to a different heat source.

[0071] The density meter (160) can measure the density of the slurry on the substrate (130) by area after the drying process. In one embodiment, the density meter (160) can be provided in the direction of the drying unit outlet (110b) and can be a radiation type sensor (e.g., a B-ray sensor). The density of the slurry by area can be measured for the entirety or part of the substrate (130). For example, the substrate (130) can be sequentially divided based on the stripe area, and the density of the slurry can be measured by stripe area. For example, when six stripe areas are formed (see FIG. 4), each stripe area can be sequentially defined as area 1 to area 6, and the density of each slurry by area can be measured. The density by area can be measured in real time or at regular intervals.

[0072] After the drying process, the amount of dried solvent evaporated from the electrode slurry (142) and the amount of undried solvent that has not been evaporated can be determined using a density meter (160). The amount of dried solvent and the amount of undried solvent can be determined based on the density of each region on the substrate of the electrode slurry before and after the drying process. At this time, the region on the substrate where the density is measured can be a region that vertically divides the width direction (x-axis direction) of the substrate (130) into a certain length (e.g., a region in the form of a stripe formed in the substrate transport direction).

[0073] For example, the area-wise density of the electrode slurry (142) on the substrate before the drying process can be directly measured using a separate density meter at the drying section inlet (110a), or can be determined from the constituent materials and mixing ratio of the electrode slurry. Then, the area-wise density of the electrode slurry (142) on the substrate can be measured using a density meter (160) after the drying process. Thereafter, based on the amount of change in the area-wise density of the electrode slurry (142) on the substrate measured / determined before and after the drying process, the area-wise dried solvent amount and the undried solvent amount can be determined based on the substrate (130) withdrawn from the drying section outlet (110b).

[0074] Alternatively, the amount of dried or undried solvent per area may be measured by thickness measurement, spectroscopic analysis, etc. before and after the drying process.

[0075] Thereafter, the solvent of the electrode slurry (142) can be uniformly dried on the substrate (130) as the number of holes on the nozzle plate is determined based on the amount of undried solvent per area. This will be described in detail later using FIGS. 6 to 10.

[0076] FIG. 2 is a drawing showing a nozzle plate (200) according to one embodiment of the present disclosure, and FIG. 3 is a drawing showing a flow of gas discharged from a nozzle (114) having the nozzle plate (200) of FIG. 2 toward an electrode slurry (142) on a substrate (130). The nozzle plate (200) may be provided at the outlet of the nozzle (114), and a plurality of perforations indicated by dark dots may be formed in a specific pattern on the nozzle plate (200). The nozzle plate (200) may be installed by being inserted into the outlet of the nozzle (114) as shown in FIG. 3, or may be installed at the outlet end of the nozzle (114) so ​​that at least a portion of the nozzle plate (200) is exposed to the outside.

[0077] As illustrated in FIG. 2, the nozzle plate (200) may be formed with holes such that the number of holes per unit area is constant. Accordingly, as illustrated in FIG. 3, the gas discharged toward the substrate (130) may be discharged at a constant flow rate per unit area. The size of the arrows illustrated in FIG. 3 indicates the gas flow rate, and arrows of the same size indicate that the same flow rate of gas is discharged per unit area.

[0078] As can be seen from the multiple arrows indicated in the width direction (x-axis) of the substrate, the gas discharged from the nozzle plate (200) in the width direction (x-axis) collides with the slurry (142) on the substrate (130) and then moves to the edges on both sides of the center of the substrate (130) or the slurry (142). In this process, it can be seen that the gas flow rate increases at the edges in the width direction. That is, it can be seen that arrows of the same size overlap at the edges in the width direction in FIG. 3 (see dotted line). Accordingly, the slurry applied to the center of the substrate may not be sufficiently dried compared to the edges in the width direction of the substrate, which may result in a deterioration in the performance of the battery cell due to binder migration imbalance.

[0079] In particular, it is important to ensure solvent drying uniformity during the process of uniformly applying the cathode slurry manufactured in the mixing process onto a substrate (e.g., Cu Foil) and evaporating the solvent while passing the substrate through a drying unit. If there is a difference in the solvent drying uniformity in the width direction of the substrate, quality (peel strength) deterioration and cell performance differences due to binder migration imbalance may occur. The internal airflow distribution and drying efficiency vary depending on various factors such as the internal circulation structure of the drying unit, the location of the exhaust port, the coating method, and the overall width of the substrate. This causes drying deviation in the width direction of the substrate and reduces the process margin or coating speed. Even if the solvent drying deviation is controlled as a production condition, there is bound to be a limitation due to the difference in the level of substrate folding caused by the substrate thermal deformation distribution and stress that occur in the width direction of the substrate. According to an embodiment of the present disclosure, by controlling the gas flow inside the drying unit by the arrangement of the perforations (e.g., see the arrows illustrated in FIG. 9), the solvent is uniformly dried over the entire area of ​​the substrate. In the present disclosure, the arrangement of perforations is used as a concept that includes the location of the perforations, the size of the perforations, the number of the perforations, etc.

[0080] Fig. 4 is a drawing showing the drying degree of a substrate (400) dried using a nozzle (114) equipped with a nozzle plate (200) of Fig. 2. The substrate (400) can be dried in a drying unit (110) and then withdrawn from a drying unit outlet (110b). At this time, the slurry-free area on the substrate (400) corresponds to a slurry-free area resulting from the stripe coating method.

[0081] As illustrated and described in FIG. 3, as the flow of gas is deflected toward the edges in the width direction on the substrate (130), the amount of undried solvent in the central portion (410) may be large (indicated by a dark color) and the amount of undried solvent in the edges (420) may be small (indicated by a light color). That is, a problem arises in which the amount of dried solvent contained in the slurry varies depending on the position where the slurry is placed on the substrate. Such a problem does not occur only in the stripe coating method illustrated in FIG. 4, but may occur in various coating methods.

[0082] Fig. 5 is a drawing showing a graph (500) in which the density of a slurry on a dried substrate is measured by area using a nozzle (114) equipped with a nozzle plate (200) of Fig. 2. In the graph (500), an area without density data in the density measurement corresponds to an area where slurry is not applied.

[0083] As shown, the density (mg / cm2) of the slurry decreases toward the edges in the width direction of the substrate and increases toward the center in the width direction. That is, it can be confirmed that the amount of undried solvent is smaller toward the edges in the width direction of the substrate and larger toward the center in the width direction.

[0084] For example, density can be measured using a coating weight measurement system. This system can indirectly measure the difference in quantity before and after coating (weight = weight after application - weight before application). A B-ray sensor capable of measuring both the object and the surrounding air layer can be used to calculate coating weight, and a servo motor can perform high-speed scanning in the TD direction with a positional resolution of 1 / 1000 mm.

[0085] Fig. 6 is a drawing showing a nozzle plate (600) according to one embodiment of the present disclosure. The nozzle plate (600) may be provided at the outlet of the nozzle (114), and a plurality of perforations may be formed in a specific pattern on the nozzle plate (600).

[0086] In one embodiment, the plate area of ​​the nozzle plate (600) may have a plate sub-area having a boundary line in the direction of movement of the substrate or in the longitudinal direction (y-axis direction) (see FIG. 7).

[0087] In one embodiment, as illustrated in FIG. 6, the number of perforations formed in a plate sub-region corresponding to the widthwise central portion of the substrate may be greater than the number of perforations formed in a plate sub-region corresponding to the widthwise edge portion of the substrate. This allows the amount of gas discharged toward the center of the substrate to increase and the amount of gas discharged toward the edge portion of the substrate to decrease, compared to a case where the same number of perforations are formed per unit area in all regions. This prevents the problem of the amount of undried solvent in the center of the substrate being greater than the amount of undried solvent in the edge portion of the substrate after the drying process, and reduces the regional variation in the amount of undried solvent.

[0088] Additionally or alternatively, to prevent the problem that the amount of undried solvent in the central portion of the substrate after the drying process is greater than the amount of undried solvent in the edge portion of the substrate, the size of the perforations formed in the plate area corresponding to the widthwise central portion of the substrate may be larger than the size of the perforations formed in the plate area corresponding to the widthwise edge portion of the substrate.

[0089] In one embodiment, the perforations formed in the nozzle plate (600) may be positioned in a pattern of linear symmetry. For example, the perforations may be formed in a pattern of linear symmetry centered around the x-axis or y-axis centerline of the nozzle plate (600).

[0090] The nozzle plate (600) illustrated and described in FIG. 6 may be determined based on the amount of undried solvent on the substrate after the drying process. For example, the number of perforations formed on each plate region may be proportional to the amount of undried solvent present in the substrate region corresponding to each plate sub-region.

[0091] FIG. 7 is a drawing showing a method for determining the number of holes in a nozzle plate (720) according to one embodiment of the present disclosure.

[0092] Table (710) of Fig. 7 illustrates an example in which the number of holes per plate sub-region of the nozzle plate (720) is determined based on the amount of undried solvent per substrate region corresponding to the plate sub-region after drying the electrode slurry using an existing nozzle plate having the same number of holes per plate sub-region. The amount of undried solvent can be calculated by a densitometer based on the amount of change in the density per region of the slurry formed on the substrate before and after the drying process.

[0093] In one embodiment, the number of perforations can be determined by applying a ratio proportional to the amount of undried solvent to the total number of candidate perforations within the plate sub-region.

[0094] For example, one plate region may have twelve plate sub-regions (the first plate sub-region to the twelfth plate sub-region). The slurry dryness level may be measured for the substrate region corresponding to each plate sub-region. For example, the plate sub-regions may correspond to stripe regions of the substrate. For example, two plate sub-regions may be combined to correspond to one stripe region, and the twelve plate sub-regions may each correspond to a total of six stripe regions. Alternatively, one plate sub-region may correspond to one stripe region, in which case the twelve plate sub-regions may each correspond to a total of twelve stripe regions. Alternatively, six plate sub-regions may correspond to one stripe region, in which case the twelve plate sub-regions may correspond to two stripe regions. In this way, the plate sub-regions and the stripe regions may have a 1:1 or N:1 correspondence relationship (N is a natural number).

[0095] As illustrated in FIG. 7, since the undried solvent level of the 6th plate sub-region and the 7th plate sub-region is the highest at 10%, the number of perforations of the 6th plate sub-region and the 7th plate sub-region can correspond to 100% (32) of the total number of candidate perforations.

[0096] Thereafter, the number of holes can be determined in the same manner for sub-regions different from the amount of undried solvent in the 6th plate sub-region and the 7th plate sub-region.

[0097] For example, the undried solvent level of the fifth plate sub-region is 8%, which corresponds to 80% of the undried solvent level of the sixth plate sub-region. Therefore, the number of perforations in the fifth plate sub-region can be determined to be 80% of the number of perforations in the sixth plate sub-region (i.e., 24 or 25, which corresponds to approximately 80% of the total number of candidate perforations).

[0098] Additionally, the level of the undried solvent in the fourth plate sub-region is 6%, which corresponds to 60% of the level of the undried solvent in the sixth plate sub-region. Therefore, the number of perforations in the fourth plate sub-region can be determined to be 60% of the number of perforations in the sixth plate sub-region (i.e., 19 or 20, which corresponds to approximately 60% of the total number of candidate perforations). The number of perforations in other plate sub-regions of the nozzle plate (720) can also be determined in the same manner.

[0099] Alternatively, the size of the perforations may be determined by applying a ratio proportional to the amount of undried solvent to the area of ​​the candidate perforations within the plate area. For example, the number of perforations in each area of ​​the nozzle plate (720) may be the same, the total perforation area of ​​the fourth plate sub-area of ​​the nozzle plate (720) may be determined to be 60% of the total perforation area of ​​the sixth plate sub-area, and the perforation positions may be the same.

[0100] The number and area of ​​the regions can be determined arbitrarily. In Fig. 7, 12 plate sub-regions within the plate are distinguished, the amount of undried solvent is measured, and the number of perforations for the plate sub-regions is determined, but this is not limited thereto.

[0101] The location of the perforations can be determined at a position selected to maintain a constant spacing between the perforations. This allows the gas to be evenly sprayed over the entire area of ​​the substrate.

[0102] In one embodiment, since the electrode slurry is coated on the substrate in a stripe coating manner, a sub-region of the nozzle plate (720) corresponding to a substrate area (non-coated area) where the electrode slurry is not positioned may be separately created, and no perforations may be formed in the sub-region. This can prevent the substrate from folding due to thermal shrinkage from being aggravated by applying a large amount of heat to the area where the electrode slurry is not applied.

[0103] For example, the non-porous sub-region (722) of the nozzle plate (720) may correspond to a portion of the substrate where the electrode slurry is not positioned. That is, the substrate corresponding to the nozzle plate (720) may be coated with the electrode slurry in two stripes. In another example, when the electrode slurry is coated in six stripes as in FIG. 4, five non-porous sub-regions where no holes are formed may be formed in the nozzle plate (720).

[0104] After the number of perforations in each sub-area is determined, the existing nozzle plate can be replaced with a new nozzle plate, i.e., nozzle plate (720). The process of measuring the amount of undried solvent and replacing the nozzle plate based on the measured amount can be performed at predetermined intervals or as needed.

[0105] FIG. 8 is a drawing showing the flow of gas discharged from a nozzle (114) equipped with a nozzle plate (600) of FIG. 6 toward a substrate (130).

[0106] As the number of perforations formed in the plate area corresponding to the widthwise central portion of the substrate is formed to be greater than the number of perforations formed in the plate area corresponding to the widthwise edge portion of the substrate, the gas discharged toward the substrate (130) can be discharged at a greater flow rate in the widthwise central portion of the substrate compared to the widthwise edge portion of the substrate.

[0107] As shown in Figure 8, it can be confirmed that the size (width) of the arrow proportional to the flow rate of gas discharged toward the center of the width direction of the substrate is larger than the size (width) of the arrow proportional to the flow rate of gas discharged toward the edge of the width direction of the substrate.

[0108] Through this, even if the gas discharged toward the center of the nozzle plate in the width direction (x-axis) collides with the center of the electrode slurry (142) formed on the substrate (130) in the width direction and then moves to the edge portions on both sides of the center portion, the total flow rate of the gas moving to the edge portions can be reduced compared to the flow rate shown in FIG. 3. Accordingly, the electrode slurry (142) can be uniformly dried in the width direction.

[0109] Fig. 9 is a drawing showing a graph (900) measuring the area-specific density of slurry on a substrate according to the type of nozzle plate.

[0110] In the graph (900), the areas where there is no density data or where the density is 0 correspond to areas where slurry is not applied due to the stripe coating method. When the stripe coating method is used, the density of the slurry by area may correspond to the density of the slurry by each stripe area. In the case of Fig. 9, the slurry density measured for four stripe areas is shown, but the number of stripe areas may be changed. As in Fig. 4, six stripe areas may be formed, and the slurry density for each of the six stripe areas may be measured. In this case, the slurry density graph by area may be displayed as six.

[0111] The area-specific density measurement of the slurry can be measured to correspond to the plate sub-areas. For example, if there are 12 plate sub-areas as shown in Fig. 7, the slurry density can be measured for the substrate area corresponding to the plate sub-areas. In this case, the area-specific density graph of the slurry can be displayed as 12.

[0112] In the case of a substrate dried using a nozzle (114) equipped with a nozzle plate (200) of FIG. 2 (before changing the number of holes), it can be confirmed that the difference in density of the slurry in the central and edge areas in the width direction of the substrate is relatively large, resulting in a large difference in the degree of drying of the solvent in each stripe area.

[0113] On the other hand, in the case of a substrate dried using a nozzle (114) equipped with a nozzle plate (600) of FIG. 6 (after changing the number of holes), it can be confirmed that the difference in density of the slurry by region in the central and edge portions of the width direction of the substrate is relatively small, and thus the difference in the degree of drying of the solvent by region is significantly reduced.

[0114] Figure 10 is a drawing showing a color map (1010, 1020) associated with the area-specific density of slurry on the substrate according to the type of nozzle plate.

[0115] In the first color map (1010) associated with the substrate dried using the nozzle (114) having the nozzle plate (200) of FIG. 2, it can be confirmed that there is a large difference in the density of the slurry between the central and edge portions of the width direction of the substrate. That is, there is a large difference between the density of the slurry corresponding to the inner stripe region and the density of the slurry corresponding to the outer stripe region. This can be confirmed from the large difference between the colors representing the two inner stripe regions and the colors representing the two outer stripe regions in the color map.

[0116] On the other hand, in the second color map (1020) associated with the substrate dried using the nozzle (114) having the nozzle plate (600) of FIG. 6, it can be confirmed that the difference in the density of the slurry between the central and edge portions of the width direction of the substrate is reduced. That is, the difference between the density of the slurry corresponding to the inner stripe region and the density of the slurry corresponding to the outer stripe region is small. This can be confirmed from the small difference between the colors representing the two inner stripe regions and the colors representing the two outer stripe regions in the color map.

[0117] FIG. 11 is a flowchart illustrating a method (1100) for drying electrode slurry of a secondary battery according to one embodiment of the present disclosure. The electrode slurry drying method (1100) can be performed by the electrode slurry drying device described above. It can be initiated by injecting gas for drying electrode slurry including a solvent applied on a substrate through a nozzle plate provided at an outlet of the nozzle (S1110). In one embodiment, gas supplied from at least one of a plurality of supply pipes, each supplying gas according to a different heat source, can be injected through the nozzle plate.

[0118] Thereafter, the amount of undried solvent on the substrate can be measured (S1120). In one embodiment, the amount of undried solvent can be measured using a densitometer based on the area-specific density change of the slurry formed on the substrate. The densitometer used to measure the amount of undried solvent can correspond to a radiation-type sensor.

[0119] Thereafter, the arrangement of the perforations formed on the nozzle plate can be determined based on the amount of undried solvent (S1130).

[0120] In one embodiment, the number of perforations formed on a plate sub-region may be determined to be proportional to the amount of undried solvent present in the substrate region corresponding to the plate sub-region. For example, the number of perforations may be determined by applying a ratio proportional to the amount of undried solvent to the total number of candidate perforations within the plate sub-region.

[0121] In one embodiment, no perforations may be formed on the nozzle plate corresponding to a region of the substrate where the electrode slurry coated on the substrate in the stripe coating manner is not located.

[0122] In one embodiment, the location of the punches can be determined at a location selected to maintain a constant spacing between the punches.

[0123] Thereafter, the nozzle plate may be replaced with a new nozzle plate having an adjusted number and / or position of perforations, depending on the determined number and / or position of perforations. The electrode slurry including the solvent applied on the substrate may be dried using a nozzle equipped with the new nozzle plate.

[0124] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. In a secondary battery electrode slurry drying device, A nozzle for spraying gas to dry the electrode slurry including the solvent applied on the substrate for the drying process; and A nozzle plate provided at the outlet of the nozzle and having a plurality of perforations formed therein for discharging gas sprayed from the nozzle toward the substrate. Including, A drying device, wherein the number of perforations is determined based on the amount of undried solvent on the substrate after the drying process.

2. In paragraph 1, The above nozzle plate includes a plate area having a plurality of plate sub-areas, A drying device, wherein the number of perforations formed on the plate sub-area is proportional to the amount of undried solvent present in the substrate area corresponding to the plate sub-area.

3. In paragraph 2, A drying device wherein the number of the above perforations is determined by applying a ratio proportional to the amount of undried solvent to the total number of candidate perforations within the plate sub-area.

4. In paragraph 1, A drying device in which the position of the above punching is determined to be a position selected so as to maintain a constant interval between the punchings.

5. In paragraph 1, The above electrode slurry is coated on the substrate in a stripe coating manner, A drying device in which no perforations are formed on the nozzle plate corresponding to a substrate area where the electrode slurry is not located.

6. In paragraph 1, A drying device in which the positions of the above perforations have a pattern of linear symmetry.

7. In paragraph 2, A drying device in which the number of perforations formed in a plate sub-region corresponding to the central portion of the above-mentioned substrate is greater than the number of perforations formed in a plate sub-region corresponding to the edge portion of the above-mentioned substrate.

8. In paragraph 1, The above amount of undried solvent is, A drying device, which is calculated by a density meter based on the change in the density of each area of ​​the slurry formed on the substrate before and after the above drying process.

9. In paragraph 8, The above density meter is a drying device corresponding to a radiation type sensor.

10. In paragraph 1, It further includes a chamber in which an inlet for introducing the above-mentioned material and an outlet for withdrawing the above-mentioned material are formed and in which the electrode slurry is dried. The above nozzle is connected to the chamber and sprays gas into the interior of the chamber, A drying device wherein the above-mentioned amount of undried solvent is determined based on the substrate withdrawn from the outlet.

11. In paragraph 1, The above nozzle plate includes a plate area having a plurality of plate sub-areas, A drying device, wherein the area of ​​the perforation formed on the plate sub-area is proportional to the amount of undried solvent present in the substrate area corresponding to the plate sub-area.

12. In paragraph 1, Further comprising a plurality of supply pipes for supplying gas to the above nozzle, A drying device, wherein each of the plurality of supply pipes supplies gas according to a different heat source.

13. In a method for drying electrode slurry of a secondary battery, A step of injecting gas for drying an electrode slurry including a solvent applied on a substrate through a nozzle plate provided at the outlet of the nozzle; A step of measuring the amount of undried solvent in the above description; A step of determining the arrangement of perforations formed on the nozzle plate based on the amount of the above-mentioned undried solvent. A drying method comprising:

14. In paragraph 13, The step of measuring the amount of the above-mentioned undried solvent is: A drying method comprising a step of measuring by a density meter based on the amount of change in the density of each area of ​​the slurry formed on the above substrate.

15. In paragraph 14, The above density meter corresponds to a radiation type sensor, a drying method.

16. In paragraph 13, A step of replacing the above nozzle plate with a new nozzle plate having the determined number of perforations formed; and A step of drying an electrode slurry including a solvent applied on a substrate using a nozzle equipped with the above-mentioned new nozzle plate. A drying method further comprising:

17. In paragraph 13, The above nozzle plate includes a plate area having a plurality of plate sub-areas, The step of determining the arrangement of the above punching holes is: A drying method, comprising a step of determining the number of perforations formed on the plate sub-region to be proportional to the amount of undried solvent present in a substrate region corresponding to the plate sub-region.

18. In paragraph 17, The step of determining the arrangement of the above punching holes is: A drying method comprising a step of determining the number of perforations by applying a ratio proportional to the amount of undried solvent to the total number of candidate perforations within the plate sub-area.

19. In paragraph 13, The step of determining the arrangement of the above punching holes is: A drying method comprising a step of determining the position of the perforation to be a position selected so as to maintain a constant interval between the perforations.

20. In paragraph 13, The above spraying step is, A step of injecting gas supplied from at least one of a plurality of supply pipes each supplying gas according to a different heat source through the nozzle plate. A drying method comprising:

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