KR20220030748A - Device for evaluating the real-time surface drying condition of electrodes and electrode device for drying electrode including the same - Google Patents

Abstract

The present invention relates to an apparatus for evaluating real-time dray condition of an electrode surface, comprising: an oven which providing a space for drying an electrode, and having a hot air nozzle and an infrared heater therein; a photographing unit obtaining an image or a video by photographing a dry condition of the electrode surface in real time; a measurement unit measuring a gray value of the image or the video; and a determination unit determining the dry condition of the electrode surface from the gray value. The apparatus evaluates dry condition of the electrode surface in real time to quantitatively evaluate dryness, dryness completion, dryness deviation, surface defect occurrence level, and the like of the electrode surface for each detailed drying time.

Description

DEVICE FOR EVALUATING THE REAL-TIME SURFACE DRYING CONDITION OF ELECTRODES AND ELECTRODE DEVICE FOR DRYING ELECTRODE INCLUDING THE SAME

The present invention relates to a real-time surface dry state evaluation apparatus of an electrode and a drying apparatus including the same.

Recently, rechargeable batteries capable of charging and discharging have been widely used as energy sources for wireless mobile devices. In addition, the secondary battery is attracting attention as an energy source for electric vehicles, hybrid electric vehicles, etc., which have been proposed as a way to solve air pollution of conventional gasoline vehicles and diesel vehicles using fossil fuels. Accordingly, the types of applications using secondary batteries are diversifying due to the advantages of secondary batteries, and it is expected that secondary batteries will be applied to more fields and products in the future than now.

These secondary batteries are sometimes classified into lithium ion batteries, lithium ion polymer batteries, lithium polymer batteries, etc. depending on the composition of the electrode and electrolyte. is increasing In general, secondary batteries, depending on the shape of the battery case, a cylindrical battery and a prismatic battery in which the electrode assembly is built in a cylindrical or prismatic metal can, and a pouch-type battery in which the electrode assembly is built in a pouch-type case of an aluminum laminate sheet The electrode assembly built into the battery case consists of a positive electrode, a negative electrode, and a separator structure interposed between the positive electrode and the negative electrode, and is a power generating element capable of charging and discharging. It is classified into a jelly-roll type wound with a separator interposed therebetween, and a stack type in which a plurality of positive and negative electrodes of a predetermined size are sequentially stacked with a separator interposed therebetween.

The positive electrode and the negative electrode are formed by applying a positive electrode slurry containing a positive electrode active material and a negative electrode slurry containing a negative electrode active material to a positive electrode current collector and a negative electrode current collector, respectively to form a positive electrode active material layer and a negative electrode active material layer, followed by drying and rolling them do.

At this time, it is essential to compare and determine the degree of drying of the electrode and the time of completion of drying to control the physical properties of the electrode, prevent non-drying or overdrying and drying deviation, surface defects, and roll contamination. The quality of the electrode is determined depending on the drying conditions. If the amount of drying heat is excessive, a significant amount of the binder in the electrode slurry moves to the surface during the drying process, reducing the adhesion of the electrode. This is because it causes contamination of the rolls in the process.

On the other hand, conventionally, a method in which an operator observes the surface of the electrode with the naked eye, or observes the surface of the electrode using an infrared temperature thickness or a thermal imaging camera has been used.

1 is a photograph showing a method by a conventional visual evaluation, Figure 2 is a schematic diagram showing a method using a conventional infrared thermometer.

Referring to FIG. 1 , in the case of the drying evaluation method by visual evaluation, it is possible to distinguish only three stages of drying, such as the initial stage of drying, the middle of drying, and the stage of completion of drying, so the classification of the degree of drying by drying time is limited, and the drying conditions and solvent types are limited. The problem is that the results vary depending on the

In addition, referring to FIG. 2 , in the case of the drying evaluation method by an infrared thermometer, the drying step is divided only into the temperature increase drying step, the constant rate drying step, and the decreasing rate drying step. In addition, only after measuring the temperature of the electrode surface, step classification is possible, and it is impossible to identify defects and change process conditions through real-time evaluation.

Therefore, there is a need to develop a technology for evaluating the dry state of the surface of the electrode that can solve the above problems.

Korean Patent Registration No. 10-1735034

The present invention has been devised to solve the above problems, and by evaluating the surface dry state in real time during the drying process of the electrode, the change in the surface dryness of the electrode, whether the drying is completed, the dryness deviation and the level of occurrence of surface defects, etc. in detail An object of the present invention is to provide a real-time surface dry state evaluation device for an electrode capable of quantitatively evaluating each drying time point, and an electrode drying device including the same.

A real-time surface dry state evaluation apparatus of an electrode according to the present invention provides a space in which the electrode is dried, and includes an oven having a hot air nozzle and an infrared heater therein; a photographing unit to obtain an image or an image by photographing the surface state of the electrode in real time; and a measuring unit measuring a gray value of the image or the image. and a determination unit for determining the dry state of the electrode surface from the gray level value.

In a specific example, in the oven, the hot air nozzle and the infrared heater are alternately arranged along the traveling direction of the electrode.

In a specific example, the oven is divided into a plurality of drying zones, and the photographing unit is located between the drying zones.

In addition, the real-time surface dry state evaluation apparatus of the electrode according to the present invention further includes a cooling device for cooling the photographing unit.

In one example, the photographing unit is located in the oven to directly photograph the surface state of the electrode.

In another example, the photographing unit is located outside the oven, and photographs the surface state of the electrode through a viewing window formed on the outer wall of the oven.

In a specific example, the measurement unit converts the image or image into gray scale, and measures a gray value of the converted image.

In this case, the gray level value is measured in the width direction of the electrode.

In a specific example, the determination unit quantifies a change in dryness for each part of the electrode or for each drying time point, whether drying is completed, a deviation in dryness between width directions, and whether a surface defect occurs from the gray level value.

In a specific example, the determination unit determines that drying is complete when there is no change in the gray level value.

In addition, the present invention provides an electrode drying apparatus, the electrode drying apparatus, the real-time surface condition evaluation apparatus of the electrode as described above; and a control unit controlling the drying intensity of the electrode according to the dry state of the electrode surface.

The present invention captures the surface of the electrode in real time, converts the photographed image to gray scale and measures the gray level, so that the change in the dryness of the electrode surface, whether the drying is complete, the dryness deviation and the level of surface defects, etc. are dried in detail. It can be evaluated for each time point, and thus, it is possible to quantitatively evaluate the surface dry state in real time during the drying process of the electrode.

1 is a photograph showing a method by a conventional visual evaluation.
2 is a schematic diagram showing a method using a conventional infrared thermometer.
3 is a block diagram showing the configuration of a real-time surface condition evaluation apparatus of an electrode according to the present invention.
4 is a schematic diagram showing the structure of an oven in the real-time surface condition evaluation apparatus of an electrode according to the present invention.
5 is a schematic diagram showing a specific structure of an oven according to an embodiment of the present invention.
6 is a schematic diagram showing a specific structure of an oven according to another embodiment of the present invention.
FIG. 7 is a graph showing a photograph obtained by converting an image of an electrode surface into a gray scale and a gray level value thereof.
8 is a block diagram showing the configuration of an electrode drying apparatus according to the present invention.
9 is a flowchart illustrating a procedure of a method for real-time surface condition evaluation of an electrode according to the present invention.
10 is a photograph and graph showing a real-time electrode surface dry state measurement result according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined in

In the present application, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or a combination thereof described in the specification exists, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. Also, when a part of a layer, film, region, plate, etc. is said to be “on” another part, it includes not only the case where the other part is “directly on” but also the case where there is another part in between. Conversely, when a part of a layer, film, region, plate, etc. is said to be “under” another part, it includes not only cases where it is “directly under” another part, but also cases where another part is in between. In addition, in the present application, “on” may include the case of being disposed not only on the upper part but also on the lower part.

Hereinafter, the present invention will be described in detail.

3 is a block diagram showing the configuration of a real-time surface condition evaluation apparatus of an electrode according to the present invention. 4 is a schematic diagram showing the structure of an oven in the real-time surface condition evaluation apparatus of an electrode according to the present invention, and FIG. 5 is a schematic diagram showing a specific structure of the oven according to an embodiment of the present invention.

3 to 5, the real-time surface dry state evaluation apparatus 100 of the electrode according to the present invention provides a space in which the electrode 110 is dried, and a hot air nozzle 124 and an infrared heater 125 therein. Oven 120 having; a photographing unit 130 for obtaining an image or an image by photographing the surface state of the electrode 110 in real time; and a measuring unit 140 for measuring a gray value of the image or the image. and a determination unit 150 that determines the dry state of the surface of the electrode 110 from the gray level value.

As described above, the drying evaluation method by the naked eye or by an infrared thermometer is limited in the classification of dryness by drying time, and the temperature measurement result is different depending on the drying conditions and the solvent to be evaporated, so the utility is limited. In particular, in the case of the evaluation method using an infrared thermometer, it is possible to classify the stages only after measuring the temperature of the electrode surface, and it is impossible to identify defects and change the process conditions through real-time evaluation.

Accordingly, the present invention captures the surface of the electrode in real time, converts the photographed image to gray scale, and measures the gray level, so that the change in the dryness of the electrode surface, whether the drying is completed, the dryness deviation and the level of surface defects, etc. in detail It can be evaluated for each drying time, and accordingly, the surface drying state can be quantitatively evaluated in real time during the drying process of the electrode.

On the other hand, in the specification of the present invention, the width direction of the electrode means a direction perpendicular to the transport direction of the electrode in the electrode surface.

Hereinafter, the configuration of the real-time surface dry state evaluation apparatus of the electrode according to the present invention will be described in detail.

3 to 5 , the apparatus 100 for evaluating a real-time surface dry state of an electrode according to the present invention includes an oven 120 . The oven 120 has a chamber shape and provides a space in which the electrode 110 is dried, so that the electrode to be dried is temporarily accommodated in the drying process, and heat from the inside can be prevented from escaping to the outside for drying. there is.

Meanwhile, the electrode may have a structure in which an electrode active material layer is formed by coating an electrode slurry containing an electrode active material on a current collector. The electrode slurry may be applied to at least one surface of the current collector.

In this case, the current collector may be a positive electrode current collector or a negative electrode current collector, and the electrode active material may be a positive electrode active material or a negative electrode active material. In addition, the electrode slurry may further include a conductive material and a binder in addition to the electrode active material.

In the present invention, the positive electrode current collector is generally made to have a thickness of 3 to 500 μm. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel. Carbon, nickel, titanium, silver, etc. surface-treated on the surface of the can be used. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on the surface thereof, and various forms such as a film, sheet, foil, net, porous body, foam body, and non-woven body are possible.

In the case of a sheet for a negative electrode current collector, it is generally made to a thickness of 3 to 500 μm. Such a negative current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. Carbon, nickel, titanium, a surface-treated material such as silver, aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven body, and the like.

In the present invention, the positive active material is a material capable of causing an electrochemical reaction, as a lithium transition metal oxide, containing two or more transition metals, for example, lithium cobalt oxide (LiCoO ₂ ) substituted with one or more transition metals. ), layered compounds such as lithium nickel oxide (LiNiO ₂ ); lithium manganese oxide substituted with one or more transition metals; Formula LiNi _1-y M _y O ₂ (wherein M = Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn or Ga, including at least one of the above elements, 0.01≤y≤0.7) Lithium nickel-based oxide represented by; Li _1+z Ni _1/3 Co _1/3 Mn _1/3 O ₂ , Li _1+z Ni _0.4 Mn _0.4 Co _0.2 O ₂ , etc. Li _1+z Ni _b Mn _c Co _{1-(b+c+d )} M _d O _(2-e) A _e (where -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2, 0≤e≤0.2, b+c+d <1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl) a lithium nickel cobalt manganese composite oxide; Formula Li _1+x M _1-y M' _y PO _4-z X _z where M = transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S, or N, and -0.5≤x≤+0.5, 0≤y≤0.5, 0≤z≤0.1 olivine-based lithium metal phosphate represented by), but is not limited thereto.

The negative electrode active material includes, for example, carbon such as non-graphitizable carbon and graphitic carbon; Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me' : metal composite oxides such as Al, B, P, Si, elements of Groups 1, 2, and 3 of the periodic table, halogen; 0<x≤1;1≤y≤3;1≤z≤8); lithium metal; lithium alloy; silicon-based alloys; tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , metal oxides such as Bi ₂ O ₅ ; conductive polymers such as polyacetylene; A Li-Co-Ni-based material or the like can be used.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The binder is a component that assists in bonding between the active material and the conductive material and bonding to the current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly propylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butyrene rubber, fluororubber, various copolymers, and the like.

Meanwhile, such an electrode slurry may be prepared by dissolving an electrode active material, a conductive material, a binder, and the like in a solvent. The solvent is not particularly limited in its kind as long as it can disperse the electrode active material and the like, and either an aqueous solvent or a non-aqueous solvent may be used. For example, as the solvent, the solvent may be a solvent generally used in the art, dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP) ), acetone, or water, and any one of them or a mixture of two or more thereof may be used. The amount of the solvent used is not particularly limited, as long as it can be adjusted so that the slurry has an appropriate viscosity in consideration of the application thickness of the slurry, production yield, workability, and the like.

The oven 120 includes a hot air nozzle 124 and an infrared heater 125 for drying the electrode 110 therein. 4 and 5 , the hot air nozzle 124 and the infrared heater 125 may be spaced apart from each other at regular intervals along the transfer direction (MD direction) of the electrode 110 and are perpendicular to the electrode 110 . Apply hot air or infrared rays in one direction. In FIGS. 4 and 5 , the hot air nozzle 124 and the infrared heater 125 are shown as being positioned above the electrode 110 , that is, on the lower surface of the ceiling of the oven 120 , but the electrode active material layers are formed on both sides of the current collector. In this case, the hot air nozzle 124 and the infrared heater 125 may be located both above and below the electrode 110 .

On the other hand, the hot air nozzle 124 includes a body portion and a spraying portion. The main body constitutes the body of the hot air nozzle, and the hot air nozzle 124 is fixed to the ceiling of the oven. In addition, the inside of the main body is empty, and the hot air transmitted from a hot air supply source (not shown) is transferred to the injection unit. On the other hand, the lower surface of the main body is provided with a spraying unit. The injection unit communicates with the main body, and the injection port through which the hot air is injected is formed on the lower surface of the injection unit. The injection hole may have a structure in which a plurality of pores are arranged at regular intervals.

On the other hand, the infrared heater 125 may include an infrared lamp for irradiating infrared rays to the electrode, and a holder for supporting or mounting the infrared lamp. The shape of the infrared lamp is not particularly limited, and, for example, a rod-shaped lamp may be arranged in parallel along the transport direction of the electrode while extending in the width direction of the electrode.

The hot air nozzle 124 and the infrared heater 125 may be alternately arranged along the moving direction of the electrode 110 in order to evenly supply hot air and infrared light to the surface of the electrode 110 . However, there is no particular limitation on the arrangement form, and a person skilled in the art can appropriately design and change the arrangement method of the hot air nozzle 124 and the infrared heater 125 according to drying conditions.

In addition, the oven 120 may include a transfer roller 126 for transferring the electrode. A plurality of the conveying rollers 126 may be disposed to be spaced apart from each other at regular intervals along the conveying direction of the electrode 110 , and support the electrode 110 during the drying process, and the dried electrode 110 may be heated in the oven 120 . ) is transferred to the outside.

The oven 120 may be divided into a plurality of drying zones. When an overdrying or non-drying situation occurs in the drying process of the electrode 110 , it is necessary to appropriately dry the electrode 110 while changing the drying intensity. By dividing the oven 120 into a plurality of drying zones, each drying zone Drying conditions can be controlled independently. 3, the oven 120 is shown in a shape partitioned into three drying zones, and in the specification of the present invention, the three drying zones are a first drying zone 121, a second drying zone along the transport direction of the electrode 110. The second drying zone 122 and the third drying zone 123 are named. In this case, for example, when the electrode is sufficiently dried in the first drying zone 121 and the second drying zone 122 , the drying strength of the electrode is reduced in the third drying zone 123 so that the degree of drying of the electrode is appropriate. can do.

In this case, the first drying zone 121 , the second drying zone 122 , and the third drying zone 123 may be spaces physically partitioned by actually installing an inner wall between the drying zones, and in the drying zone It may be an abstractly partitioned space depending on the drying conditions to be performed.

In addition, the real-time surface condition evaluation apparatus 100 of the electrode according to the present invention includes a photographing unit 130 that obtains an image or an image by photographing the surface condition of the electrode 110 in real time.

In one example, the photographing unit 130 may be located inside the oven 120 to directly photograph the surface state of the electrode 110 .

The photographing unit 130 includes a lighting (not shown) and an image sensor. The illumination irradiates light to the portion to be photographed so that the image sensor can smoothly photograph the image of the surface of the electrode 110 . For the illumination, for example, an LED light source may be used. The image sensor is to obtain an image or image by photographing the surface of the electrode 110, for example, may be a camera. The lighting and image sensors constituting the photographing unit 130 may be disposed through the outer wall of the oven.

On the other hand, the photographing unit 130 can perform the photographing process smoothly, and in order to prevent the lighting and the camera constituting the photographing unit 130 from being exposed to excessively high temperature, a relatively low temperature in the oven 120 . It is preferable to place In addition, it is preferable that the photographing unit 130 is positioned where the photographing field of view is not blocked by the hot air nozzle 124 and the infrared heater 125 in the oven 120 . Therefore, the photographing unit 130 may be located in a place where the hot air nozzle 124 and the infrared heater 125 are not disposed, and specifically may be located between the drying zones. Referring to FIG. 3 , the photographing unit 130 is located in the area between the first drying zone 121 and the second drying zone 122 and in the area between the second drying zone 122 and the third drying zone 123 . All can be located. In addition, although the photographing unit 130 is illustrated as being located on the upper portion of the electrode 110 in FIGS. 4 and 5 , when the electrode active material layers are formed on both sides of the current collector, the photographing unit 130 is positioned above and below the electrode. can all be located in

In addition, the real-time surface dry state evaluation apparatus 100 of the electrode according to the present invention further includes a cooling device 131 for cooling the photographing unit 130 . The cooling device 131 prevents the photographing unit 130 from being damaged by the high-temperature environment in the oven 120 to enable continuous shooting. The cooling device 131 may be fastened or attached to the photographing unit 130 from the outside of the oven 120 to prevent a temperature change inside the oven 120 . The cooling device 131 is not particularly limited in its shape as long as it can cool the photographing unit 130, for example, it is a cooling jacket that surrounds the photographing unit 130 and contains a refrigerant or the like therein. can

6 is a schematic diagram showing a specific structure of an oven according to another embodiment of the present invention.

Referring to FIG. 6 , in another example, the photographing unit 130 may be located outside the oven 120 . Through this, it is possible to prevent the photographing unit 130 from being damaged by the high temperature environment in the oven 120 . In this case, the viewing window 132 is formed on the outer wall of the oven 120 , and the photographing unit 130 takes a picture of the surface state of the electrode 110 in the oven 120 through the viewing window 132 . The viewing window 132 may be made of a transparent and heat-resistant material. In addition, even when the photographing unit 130 is outside the oven 120 , the photographing unit 130 may be damaged due to the high-temperature heat transmitted through the outer wall of the oven 120 . A cooling device 131 for cooling may be installed.

Meanwhile, referring to FIG. 3 , the apparatus for drying the real-time surface state of an electrode according to the present invention includes a measuring unit 140 for measuring the gray value of the image or the image. In addition, FIG. 7 is a graph showing a photograph obtained by converting an image of an electrode surface into a gray scale and a gray level value accordingly.

The measuring unit 140 converts the image or image to gray scale, and measures a gray value of the converted image. Conversion to gray scale is to form a black-and-white image by designating each pixel on a color image with contrast or density of black and white instead of color. Specifically, each pixel constituting a color image has a pixel value representing the brightness of each of the three primary colors, R (Red), G (Green), and B (Blue). In each pixel, the average value of the values representing the brightness of each of the three primary colors can be designated as a gray level. However, there may be various methods for converting to gray scale, and the present invention is not limited thereto.

According to the present invention, the dry state of the electrode surface can be intuitively recognized by converting the image or image photographed by the photographing unit 130 into gray scale and uniformly checking the contrast displayed on the image or image. In addition, it is possible to quantitatively evaluate the dry state of the electrode surface through conversion to gray scale.

Referring to FIG. 7 together with FIGS. 3 and 4 , the gray level value may be measured in the width direction of the electrode 110 . This is to observe the occurrence of a deviation in the degree of drying according to the width direction of the electrode 110 . In general, the side portion based on the width direction of the electrode 110 overlaps the heat emitted from the hot air nozzle 124 or the infrared heater 125, so the drying rate is faster than the drying rate of the central portion, so this dryness deviation occurs. will do In the present invention, by measuring the gray level value in the width direction of the electrode 110 , it is possible to check the dryness deviation for each drying time point and each part of the electrode 110 .

Specifically, as shown in FIG. 7 , a point to be measured is selected on the image converted to gray scale, and an imaginary line formed parallel to the width direction is drawn. With respect to a pixel at a point located on the virtual line, a gray level value represented by the pixel may be represented as a graph. In the graph of FIG. 7 , the horizontal axis is a position along the width direction of the electrode, which means a distance away from the center of the electrode (A is the center, and F indicates a point closer to the side). Then, while drying the electrode, a change in the gray level value for a predetermined point located on the virtual line may be plotted with time.

Meanwhile, referring to FIG. 3 , the determination unit 150 determines the dry state of the electrode surface from the gray level value. The determination unit 150 is connected to the measurement unit 140 in a network, so that the gray level value stored in the measurement unit may be received and analyzed.

Specifically, the determination unit 150 quantifies the change in dryness for each part of the electrode 110 or for each drying time point, whether drying is completed, the dryness deviation between the width directions, and whether surface defects are generated from the gray level value. In the present invention, unlike the method for evaluating the surface dry state by the naked eye or an infrared thermometer, the dry state can be quantitatively evaluated through a gray level value.

For example, the determination unit 150 may evaluate the dryness of the electrode based on the gray level value. The gray level value may vary depending on the material composition of the electrode, image capturing method, image conversion method, etc., but gradually increases as drying continues, and the increase in gray level value stops when drying is completed. That is, in the present invention, the determination unit quantifies the gray level value according to the material composition of the electrode and the photographing/conversion condition of the image, and may utilize the change pattern of the gray level value according to the drying time to the dryness evaluation. In addition, when the amount of change in the gray value according to the drying time is less than a predetermined value, it can be determined that drying is complete, and more specifically, when there is no change in the gray value, it is determined that drying is complete.

The present invention also provides an electrode drying device.

8 is a block diagram showing the configuration of an electrode drying apparatus according to the present invention.

Referring to FIG. 8 together with FIGS. 3 and 4 , the electrode drying apparatus 200 includes an electrode real-time surface condition evaluation apparatus 100 as described above; and a control unit 160 for controlling the drying intensity of the electrode according to the dry state of the electrode surface.

The control unit 160 controls the drying intensity of the electrode according to the drying state determined by the determination unit 150 . More specifically, the controller 160 may adjust the drying intensity of the electrode according to the gray level value.

There are various methods of controlling the drying intensity of the electrode, for example, there is a method of controlling the temperature of the hot air sprayed from the hot air nozzle 124 , the flow rate of the hot air and the output of the infrared heater 125 .

In addition, when a shield for blocking infrared and hot air is installed between the infrared heater or hot air nozzle, the area where the electrode is exposed to hot air or infrared can be adjusted by adjusting the position of the shield or the number of shielding frames.

In addition, the present invention provides a real-time surface state evaluation method of an electrode using the real-time surface state evaluation apparatus of the electrode as described above.

9 is a flowchart illustrating a procedure of a method for real-time surface condition evaluation of an electrode according to the present invention.

Referring to FIG. 9 , the method for evaluating a real-time surface dry state of an electrode according to the present invention includes: transferring the electrode into an oven according to the real-time surface dry state evaluation apparatus of the electrode as described above (S10); While drying the electrode, obtaining an image or image by photographing the surface state of the electrode in real time (S20); measuring a gray level value for the image or image (S30); and determining the dry state of the electrode surface from the gray level value (S40).

The present invention captures the surface of the electrode in real time, converts the photographed image to gray scale and measures the gray level, so that the change in the dryness of the electrode surface, whether the drying is complete, the dryness deviation and the level of surface defects, etc. are dried in detail. It can be evaluated for each time point, and thus, it is possible to quantitatively evaluate the surface dry state in real time during the drying process of the electrode.

Hereinafter, each step of the method for evaluating the real-time surface state of an electrode according to the present invention will be described in detail.

<Production of electrode>

First, an electrode is manufactured by forming an electrode active material layer including an electrode active material on a current collector. Specific details regarding the electrode are the same as described above. When the electrode is put in, the electrode is put into the oven as described above to start drying.

<Drying the electrode and shooting the dry state of the electrode>

When the electrode is put into the oven, an image or image is obtained by photographing the surface state of the electrode in real time while drying the electrode through an infrared heater and a hot air nozzle. This may be performed by the photographing unit as described above.

The photographing unit includes a lighting and an image sensor, and is located between the drying zones partitioned in the oven. In addition, the photographing unit may be located inside the oven to directly photograph the surface state of the electrode, or located outside the oven may photograph the surface state of the electrode through a viewing window formed on the outer wall of the oven. In this case, the process of cooling the photographing unit may be performed to prevent the photographing unit from being damaged by the high temperature environment in the oven and to keep the photographing unit running.

<Conversion of the captured image or video>

When an image or image of the electrode surface is captured through the photographing unit, a gray level value is measured for the image or image. Specifically, the step of measuring the gray scale value includes converting the image or the image to a gray scale and measuring a gray value of the converted image.

According to the present invention, the dry state of the electrode surface can be intuitively recognized by converting the image or image photographed by the photographing unit into gray scale and uniformly checking the contrast displayed on the image or image. In addition, it is possible to quantitatively evaluate the dry state of the electrode surface through conversion to gray scale.

In this case, the gray level value may be measured in the width direction of the electrode. As described above, on the grayscale-converted image, a point to be measured is selected, and an imaginary line formed parallel to the width direction is drawn. Subsequently, with respect to a pixel located on the virtual line, a gray level value indicated by the pixel may be represented as a graph. Through this, it is possible to check the degree of deviation of the dryness according to the width direction of the electrode.

<Determination of the dry state of the surface>

When the gray level value for the electrode surface is measured, the dry state of the electrode surface is determined from this. Specifically, it is possible to quantify the change in dryness for each part of the electrode or for each drying time point, whether drying is completed, the deviation of dryness between width directions, and whether surface defects are generated from the gray level value. This may be performed by the judging unit.

In this case, the dryness of the electrode may be evaluated based on the gray value. That is, the gray level value can be quantified according to the material composition of the electrode and the photographing/conversion conditions of the image, and the change in the gray level value according to the drying time can be used for the dryness evaluation. In addition, when the amount of change in the gray value according to the drying time is less than a predetermined value, it can be determined that drying is complete, and more specifically, when there is no change in the gray value, it is determined that drying is complete.

On the other hand, in the present invention, the drying intensity of the electrode can be controlled from the drying state measurement result as described above, and specifically, the drying intensity of the electrode can be adjusted according to the gray level value.

Hereinafter, examples will be given to help the understanding of the present invention be described in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the following examples. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

Example

97.6 parts by weight of artificial graphite and natural graphite (weight ratio: 90:10) functioning as an anode active material, 1.2 parts by weight of styrene-butadiene rubber (SBR) functioning as a binder, 1.2 parts by weight of carboxymethyl cellulose (CMC) , a negative electrode mixture was prepared. A negative electrode slurry was prepared by dispersing this negative electrode mixture in ion-exchanged water functioning as a solvent. This slurry was coated on both sides of a copper foil having a thickness of 20 μm and dried to prepare a negative electrode.

While the cathode was put into an oven and dried, an image was obtained by photographing the surface of the electrode through a camera positioned between the drying zones. This is shown in FIG. 10 . At this time, in the photo of FIG. 10 , the right side corresponds to the width direction side portion of the electrode, and the left side corresponds to the center portion of the electrode.

The image was converted to gray scale through image analysis software in the measurement unit, and the gray scale value was measured. At this time, as shown in FIG. 7 , the gray level value along the width direction of a specific point was measured.

This process was repeated at predetermined time intervals based on the drying start time to obtain a gray value along the width direction of the electrode. The results are shown in FIG. 10 . In the graph of FIG. 10 , the horizontal axis is a position along the width direction of the electrode, which means a distance away from the center of the electrode.

Referring to FIG. 10 , it can be seen that the surface of the electrode converted to gray scale is relatively dark at the time point (180 seconds after drying) not long after drying is started, since drying is not yet completed. Also, the gray value at this point is 80 or less, indicating that the electrode still maintains a wet state. However, as drying continues, as the solvent in the electrode evaporates, the surface of the electrode gradually becomes brighter, and it can be seen that the gray value gradually increases.

In particular, it can be seen that as drying is continued, the drying speed of the side part is faster than the central part in the width direction, and this causes a deviation in the drying degree between the width directions.

On the other hand, it can be seen that after 468 seconds have elapsed after drying, there is almost no change in grayness according to the drying time, indicating that drying has been completed.

That is, in the present invention, by measuring the gray level, it is possible to evaluate the change in the surface dryness of the electrode, whether drying is complete, the dryness deviation and the level of occurrence of surface defects, etc. for each detailed drying time point, and thus the surface dry state during the drying process of the electrode can be evaluated. It can be quantitatively evaluated in real time.

The above description is merely illustrative of the technical spirit of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains. Accordingly, the drawings disclosed in the present invention are for explanation rather than limiting the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these drawings. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Meanwhile, in this specification, terms indicating directions such as up, down, left, right, front, and back are used, but these terms are for convenience of explanation only, and may vary depending on the location of the object or the position of the observer. It is self-evident that

100: Real-time surface condition evaluation device of the electrode
110: electrode
111: current collector
112: electrode active material layer
120: oven
121: first drying zone
122: second drying zone
123: third drying zone
124: hot air nozzle
125: infrared heater
126: conveying roller
130: shooting department
131: cooling device
132: observation window
140: measurement unit
150: judgment unit
200: electrode drying device

Claims (11)

an oven providing a space in which the electrode is dried, and having a hot air nozzle and an infrared heater therein;
a photographing unit to obtain an image or an image by photographing the surface dry state of the electrode in real time; and
a measuring unit measuring a gray value of the image or the image; and
A real-time surface dry state evaluation apparatus of an electrode comprising a determination unit that determines a dry state of the electrode surface from the gray level value.
According to claim 1,
in the oven,
The hot air nozzle and the infrared heater are alternately arranged along the moving direction of the electrode, real-time surface dry state evaluation device of the electrode.
According to claim 1,
The oven is divided into a plurality of drying zones,
The photographing unit is a real-time surface dry state evaluation device of the electrode located between the drying zone.
According to claim 1,
Real-time surface dry state evaluation device of the electrode further comprising a cooling device for cooling the photographing unit.
According to claim 1,
The photographing unit is located in the oven to directly photograph the surface dry state of the electrode in real-time surface dry state evaluation device.
According to claim 1,
The photographing unit is located on the outside of the oven, and a real-time surface dry state evaluation device of the electrode for photographing the surface dry state of the electrode through a viewing window formed on the outer wall of the oven.
According to claim 1,
The measuring unit converts the image or image into gray scale, and measures a gray value of the converted image.
According to claim 1,
The gray level value is a real-time surface dry state evaluation device of the electrode measured in the width direction of the electrode.
According to claim 1,
The determination unit is an electrode real-time surface dry state evaluation device for quantifying the change in dryness for each part of the electrode or for each drying time point, whether drying is completed, the dryness deviation between the width directions, and whether surface defects occur from the gray level value.
10. The method of claim 9,
The determination unit, a real-time surface dry state evaluation device of the electrode that determines that the drying is completed when there is no change in the gray level value.
The real-time surface dry state evaluation device of the electrode according to claim 1; and
Electrode drying apparatus including a control unit for controlling the drying intensity of the electrode according to the dry state of the electrode surface.

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