KR20220030756A - Method for evaluating the deviation of electrode dryness in real time and method for drying the electrode - Google Patents

Abstract

The present invention relates to a method for evaluating dryness deviation of an electrode in real time, including the steps of: transferring an electrode into an oven; obtaining an image or a video by photographing the surface state of the electrode in real time while drying the electrode; measuring a gray level value for the image or the video; and analyzing the dryness deviation in the width direction of the electrode from the gray level value.

Description

A method for evaluating the real-time dryness deviation of an electrode and a method for drying an electrode

The present invention relates to a method for evaluating the real-time dryness deviation of an electrode and a method for drying an electrode.

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.

In this case, during the drying process of the electrode, a difference may occur in the drying speed in the width direction of the electrode. This is due to the difference in the heat transfer degree of the substrate and the imbalance in the flow of hot air, and in general, both side portions of the electrode dry faster than the central portion. Due to the deviation in the dryness of the electrode in the width direction, deviation in thickness and adhesion of the electrode may occur. In addition, problems such as overdrying of the electrode, electrode detachment, wrinkles, and cracks may occur. In order to solve this problem, it is necessary to determine the difference in drying degree according to the width direction of the electrode during drying in real time and quantitatively.

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 real-time evaluation of dryness deviation of electrodes 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 dryness in real time during the drying process of the electrode, the change in the dryness of the electrode surface, the deviation in the dryness and the level of occurrence of surface defects are detailed. An object of the present invention is to provide a method for evaluating a real-time dryness deviation of an electrode that can be quantitatively evaluated for each drying time point, and a method for drying an electrode.

A method for evaluating the dryness deviation of an electrode in real time according to the present invention includes the steps of: transferring the electrode into an oven; obtaining an image or image by photographing the surface state of the electrode in real time while drying the electrode; measuring a gray level value for the image or image; and analyzing the dryness deviation in the width direction of the electrode from the gray level value.

In a specific example, the oven has a hot air nozzle and an infrared heater therein.

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 step of obtaining an image or an image by photographing the surface state of the electrode in real time is performed by a photographing unit including an illumination and an image sensor.

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

The oven 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, measuring the gray level value includes converting the image or the image to a gray scale and measuring a gray value 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 analyzing of the dryness deviation in the width direction of the electrode is a process of quantifying the dryness deviation in the width direction of the electrode at each drying time of the electrode and the defect level according to the dryness deviation from the gray value. includes

In addition, the present invention provides a method for drying an electrode. The method of drying the electrode includes: evaluating the deviation of the dryness between the electrode width directions according to the method for evaluating the dryness deviation of the electrode in real time as described above; and controlling the drying intensity of the electrode in each width direction by reflecting the dryness deviation.

In the present invention, by photographing the surface of the electrode in real time, converting the photographed image to gray scale and measuring the gray level, the change in electrode surface dryness, the level of surface defects, etc. can be evaluated for each detailed drying time point, Accordingly, in the drying process of the electrode, it is possible to quantitatively evaluate the dryness deviation along the width direction of the electrode in real time.

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 flowchart illustrating a procedure of a method for evaluating a real-time dryness deviation of an electrode according to the present invention.
4 is a block diagram showing the configuration of a real-time dryness deviation evaluation apparatus of an electrode according to the present invention.
5 is a schematic diagram showing the structure of an oven used in the method for evaluating the real-time dryness deviation of the electrode according to the present invention.
6 is a schematic diagram showing a specific structure of an oven according to an embodiment of the present invention.
7 is a schematic diagram showing a specific structure of an oven according to another embodiment of the present invention.
8 is a graph showing a photograph of an electrode surface image converted to a gray scale and a gray scale value accordingly.
9 is a photograph and a graph showing the dryness deviation along the width direction according to an embodiment of the present invention.
10 is a graph showing a change in the drying degree for each part of an electrode 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 flowchart illustrating a procedure of a method for evaluating a real-time dryness deviation of an electrode according to the present invention.

Referring to FIG. 3 , the method for evaluating the dryness deviation of an electrode in real time according to the present invention includes: transferring the electrode into an oven (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 analyzing the dryness deviation in the width direction of the electrode from the gray level value (S40).

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, in the present invention, by photographing the surface of the electrode in real time, converting the photographed image to gray scale and measuring the gray level, it is possible to evaluate the change in the dryness of the electrode surface, the level of surface defects, etc. for each detailed drying time point, Accordingly, in the drying process of the electrode, it is possible to quantitatively evaluate the deviation of the drying degree along the width direction of the electrode in real time.

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.

<Production of electrode>

4 is a block diagram showing the configuration of a real-time dryness deviation evaluation apparatus of an electrode according to the present invention. 5 is a schematic diagram showing the structure of an oven used in the method for evaluating the real-time dryness deviation of the electrode according to the present invention. 6 is a schematic diagram showing a specific structure of an oven according to an embodiment of the present invention.

4 to 6 together with FIG. 3 , an electrode is first manufactured. The electrode 110 may have a structure in which an electrode active material layer 112 is formed by coating an electrode slurry including an electrode active material on a current collector 111 . The electrode slurry may be applied to at least one surface of the current collector 111 .

In this case, the current collector 111 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 and includes 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 = and F, S, or N, and -0.5≤x≤+0.5, 0≤y≤0.5, 0≤z≤0.1), and the like).

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.

<Drying the electrode and photographing the surface condition of the electrode>

3 to 6 , the method for evaluating the real-time dryness deviation of the electrode according to the present invention may be performed by the apparatus 100 for evaluating the real-time dryness deviation of the electrode shown in FIG. 4 . Referring to FIG. 4 , the real-time dryness deviation evaluation apparatus 100 of an electrode includes an oven 120 , a photographing unit 130 , a measuring unit 140 , and a determining unit 150 .

The electrode manufactured by the method as described above is put into the oven 120 and dried. The oven 120 has a chamber shape and provides a space in which the electrode 110 is dried, so that the electrode 110 to be dried is temporarily accommodated in the drying process, and internal heat escapes to the outside for drying. can be prevented

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.

At this time, while drying the electrode, the step of obtaining an image or image by photographing the surface state of the electrode in real time is performed. This may be performed by the photographing unit 130 .

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 oven 120 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

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

Referring to FIG. 7 , 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 , when an image or an image is obtained, a gray value of the image or image is measured. This is performed by the measurement unit 140 .

8 is a graph showing a photograph of an electrode surface image converted to a gray scale and a gray scale value accordingly.

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. Conversion to gray scale is to form a black-and-white image by designating each pixel on a color image the 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 an image or image obtained by photographing the surface state of an electrode into a 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. 8 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 the width direction of the electrode 110 .

Specifically, as shown in (a) of FIG. 8 , 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 (a) of FIG. 8 , 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, as shown in FIG. 8(b) , the change in gray level values for predetermined points (eg, A to F) located on the virtual line may be represented with time.

Meanwhile, referring to FIG. 3 , when the gray level value is measured, the step of analyzing the dryness deviation in the width direction of the electrode from the gray level value is performed. This may be performed by the determination unit 150 .

Specifically, the step of analyzing the dryness deviation in the width direction of the electrode is the surface according to the dryness deviation and the dryness deviation in the width direction of the electrode for each part of the electrode 110 or for each drying time from the gray value. Quantify the occurrence of defects. Here, as the type of surface defect, a crater or crack generated on the electrode surface may be mentioned. 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, in the step of analyzing the dryness deviation in the width direction of the electrode, the dryness deviation in the width direction of the electrode may be compared by comparing the difference in gray level values along the width direction.

At this time, when the gray level value is 140 or more, it may be determined that drying is complete. In addition, when the gray value is less than 140, the electrode can be determined to be in an undried state, and among them, when the gray value is 30 to 80, the electrode is wet by the solvent, and when the gray value is 90 to 140 It can be determined that the electrode is drying.

The present invention also provides a method for drying an electrode.

The method for drying an electrode according to the present invention includes the steps of: evaluating the difference in dryness between the electrode width directions according to the method for evaluating the dryness deviation in real time of the electrode as described above; and controlling the drying intensity of the electrode in each width direction by reflecting the dryness deviation. In this case, the drying intensity of the electrode in each width direction may be controlled according to the difference in the previously measured gray level values.

There are various methods of controlling the drying intensity for each width direction 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, if a shield for blocking infrared and hot air is installed between the infrared heater or hot air nozzle, the number of shields to block the position of the shield along the width direction or the application of infrared rays and hot air to a specific part of the electrode can be adjusted to control the area where the electrode is exposed to hot air or infrared rays. For example, when the dryness of the side part is greater than that of the central part, a shield may be placed on the side part to block infrared rays and hot air.

In addition, the present invention provides an electrode real-time dryness deviation evaluation apparatus for performing the method for evaluating the real-time dryness deviation of the electrode as described above.

4, the real-time dryness deviation evaluation apparatus of the electrode according to the present invention provides a space in which the electrode 110 is dried, and an oven having a hot air nozzle 124 and an infrared heater 125 therein. 120); 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 analyzes the dryness deviation in the width direction of the electrode 110 from the gray level value.

In the present invention, by photographing the surface of the electrode in real time, converting the photographed image to gray scale and measuring the gray level, the change in electrode surface dryness, the level of surface defects, etc. can be evaluated for each detailed drying time point, Accordingly, in the drying process of the electrode, it is possible to quantitatively evaluate the dryness deviation along the width direction of the electrode in real time.

The description of the oven 120 and the photographing unit 130 is the same as described above.

Specifically, the electrode manufactured by the method as described above is put into the oven 120 and dried. The oven 120 has a chamber shape, and provides a space in which the electrode 110 is dried. The oven 120 is provided with a hot air nozzle 124 and an infrared heater 125 for drying the electrode 110 therein, and the hot air nozzle 124 and the infrared heater 125 move the electrode 110 . It may be arranged alternately along the direction. The oven 120 may be divided into a plurality of drying zones.

In addition, the photographing unit 130 includes an illumination (not shown) and an image sensor, and obtains an image or an image by photographing the surface state of the electrode 110 in real time. The photographing unit may be located between the drying zones.

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

In another example, the photographing unit 130 may be located outside the oven 120 , and in this case, a viewing window 132 is formed on the outer wall of the oven 120 , and the photographing unit 130 is the The surface state of the electrode 110 in the oven 120 is photographed through the observation window 132 .

Also, the oven 120 may include a cooling device 131 for cooling the photographing unit 130 .

Meanwhile, the measurement unit 140 converts the image or image to gray scale, and measures a gray value of the converted image. In this case, the measurement unit 140 may measure a gray level value in the width direction of the electrode 110 .

On the other hand, the determination unit 150 quantifies the occurrence of surface defects according to the dryness deviation and the dryness deviation in the width direction of the electrode for each part of the electrode 110 or for each drying time 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 may determine that drying is completed when the gray level value is 140 or more. In addition, when the gray value is less than 140, the electrode can be determined to be in an undried state, and among them, when the gray value is 30 to 80, the electrode is wet by the solvent, and when the gray value is 90 to 140 It can be determined that the electrode is drying.

In addition, the present invention provides an electrode drying apparatus, the electrode drying apparatus comprising: a real-time dryness deviation evaluation apparatus of the electrode as described above; and a control unit controlling the drying intensity of the electrodes in each width direction by reflecting the dryness deviation.

The control unit may, for example, adjust 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 , and when the shield is installed, the position of the shield along the width direction Alternatively, the area to which the electrode is exposed to hot air or infrared light can be controlled by adjusting the number of shielding frames for blocking the application of infrared and hot air to a specific portion of the electrode.

Hereinafter, to help the understanding of the present invention, examples will 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, and 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 serving 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.

An image was obtained by photographing the surface of the electrode through a camera positioned between the drying zones according to time while the cathode was put into an oven and dried. This is shown in FIG. 9 . At this time, in the photo of FIG. 9 , the right side corresponds to a side portion in the width direction of the electrode, and the left side corresponds to the center portion of the electrode.

The image was converted into gray scale through image analysis software in the measurement unit, and the gray scale value along the width direction of the electrode was measured. This is shown graphically as in FIG. 9 . In the graph of FIG. 9 , the horizontal axis is a position along the width direction of the electrode, which means a distance away from the center of the electrode.

In addition, with respect to the specific portion of the central portion and the side portion based on the width direction of the electrode, the change in the gray value according to the drying time is shown in FIG. 10 .

Referring to FIG. 9 , 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 the 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, as drying continues, the drying speed of the side portion is faster than that of the central portion in the width direction, and thus, it can be confirmed that the drying degree deviation between the width directions occurs. 9 , it can be seen that the portion corresponding to the central portion in the width direction of the electrode (the left portion of each photograph) has more dark areas than the portion corresponding to the side of the electrode (the right portion of each photograph). In addition, it can be seen from the graph that the gray value increases from the side portion in the width direction of the electrode as drying proceeds.

This phenomenon can also be confirmed in FIG. 10 . Referring to FIG. 10 , it can be seen that the gray value of the side portion in the width direction of the electrode is larger than that of the central portion until 450 seconds after drying. However, after 468 seconds after drying, it can be seen that the gray value of the side part and the gray value of the center part become similar.

In the present invention, by photographing the surface of the electrode in real time, converting the photographed image to gray scale and measuring the gray level, the change in the dryness of the electrode surface and the level of surface defects can be evaluated for each detailed drying time point, Accordingly, in the drying process of the electrode, it is possible to quantitatively evaluate the dryness deviation along the width direction of the electrode 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

Claims (12)

transferring the electrode into an oven;
obtaining an image or image by photographing the surface state of the electrode in real time while drying the electrode;
measuring a gray level value for the image or image; and
and analyzing the dryness deviation in the width direction of the electrode from the gray level value.
According to claim 1,
The oven is a real-time dryness deviation evaluation method of the electrode having a hot air nozzle and an infrared heater therein.
3. The method of claim 2,
in the oven,
The hot air nozzle and the infrared heater are alternately arranged along the moving direction of the electrode, the real-time dryness deviation evaluation method of the electrode.
According to claim 1,
The step of obtaining an image or image by photographing the surface state of the electrode in real time,
A real-time dryness deviation evaluation method of electrodes performed by a photographing unit including a lighting and an image sensor.
5. The method of claim 4,
The oven is divided into a plurality of drying zones,
The photographing unit is a real-time dryness deviation evaluation method of electrodes positioned between drying zones.
5. The method of claim 4,
The oven, the real-time dryness deviation evaluation method of the electrode further comprising a cooling device for cooling the photographing unit.
5. The method of claim 4,
The real-time dryness deviation evaluation method of the electrode in which the photographing unit is located in the oven to directly photograph the surface state of the electrode.
5. The method of claim 4,
The photographing unit is located on the outside of the oven, and a real-time dryness deviation evaluation method of the electrode for photographing the surface state of the electrode through a viewing window formed on the outer wall of the oven.
According to claim 1,
Measuring the gray level value comprises:
and converting the image or image into gray scale and measuring a gray value of the converted image.
According to claim 1,
The gray level value is a real-time dryness deviation evaluation method of an electrode measured in a width direction of the electrode.
According to claim 1,
The step of analyzing the dryness deviation in the width direction of the electrode is,
and quantifying the dryness deviation in the width direction of the electrode at each drying time of the electrode and the defect level according to the dryness deviation from the gray level value.
evaluating the dryness deviation between the electrode width directions according to the real-time dryness deviation evaluation method of the electrode according to claim 1; and
and controlling the drying intensity of the electrode in each width direction by reflecting the drying degree deviation.

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