Device for testing dryness of electrode and method for testing dryness of electrode

Abstract

The device for testing the dryness of an electrode according to the present invention comprises: a light-emitting unit comprising an electrode substrate having electrode slurry applied to a current collector, a standard sample, a light source, and bifurcated optical fibers connected to the light source, the light-emitting unit being configured to emit light selectively to one of the electrode substrate and the standard sample through one of the bifurcated optical fibers; a light-receiving unit comprising a spectrometer for selectively receiving and analyzing reflected light which has been reflected from one of the electrode substrate and the standard sample; and a control unit for correcting at least one of the light source and the spectrometer on the basis of the result of analysis by the spectrometer.

Description

Electrode dryness inspection device and electrode dryness inspection method

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0159514, filed November 16, 2023, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to an electrode dryness inspection device and an electrode dryness inspection method, and more particularly, to an electrode dryness inspection device and an electrode dryness inspection method capable of checking and correcting the dryness of an electrode inline during an electrode drying process.

[0004] As technological developments and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. In particular, secondary batteries are attracting significant attention as an energy source not only for mobile devices such as cell phones, digital cameras, laptops, and wearable devices, but also for powertrains such as electric bicycles, electric cars, and hybrid electric vehicles.

[0005] A secondary battery is manufactured by embedding an electrode assembly together with an electrolyte into a secondary battery case, and the electrode assembly is manufactured by stacking and / or winding a positive electrode, a separator, and a negative electrode.

[0006] At this time, electrodes such as positive and negative electrodes are manufactured by mixing materials such as active materials, conductive agents, and binders with a solvent to create a slurry, which is then applied to a current collector and dried. Here, drying is performed by passing the electrodes through multiple drying zones, and a measurement method utilizing the electrode's reflectivity is used to evaluate the degree of drying of each electrode.

[0007] Meanwhile, among the reflectivity measurement equipment of the electrode, the light source and spectrometer have a limited lifespan, so the light quantity and measurement performance may decrease over time, and it is essential to periodically check and correct this.

[0008] Figure 1 is a schematic diagram of a conventional electrode dryness inspection device.

[0009] Referring to FIG. 1, a conventional electrode dryness inspection device (10) includes a transfer unit (13) for transferring an electrode substrate (11) to an electrode drying zone (12), an optical fiber (15) and a collimating lens (16) for irradiating light from a light source (14) to the electrode substrate (11), a spectrometer (17) for analyzing reflected light reflected from the electrode substrate (11), a spectrometer hub (18) connected to the spectrometer (17), and a control unit (20) including a display device (19) for displaying the analysis results of the spectrometer (17).

[0010] In order to irradiate light from a light source to the electrode substrate (11), an optical fiber (15) and a collimating lens (16) are positioned above the electrode substrate (11), and the light is irradiated vertically to measure the reflectivity with a spectrometer (17). The standard sample is positioned in the same environment as the electrode substrate (11), i.e., in a drying oven. That is, in the past, the drying process in progress was stopped for correction work, and a person directly measured the reflectivity of the standard sample placed in the drying oven. In this case, there was a problem that loss occurred because the drying process was stopped, and there was a possibility of a safety accident occurring because a person directly entered the high-temperature drying oven.

[0011] Therefore, in order to solve this problem, it is necessary to develop a device and method that can position a standard sample outside a drying oven and measure the reflectivity of the standard sample independently of the drying process of the electrode substrate (11).

[0012] The present invention aims to solve the above-mentioned problem by positioning a standard sample outside a drying oven and measuring the reflectivity of the standard sample independently of the drying process of the electrode substrate. The present invention also provides an electrode dryness inspection device and method capable of calibrating reflectivity measurement equipment in real time.

[0013] The electrode dryness inspection device of the present invention comprises: an electrode substrate on which an electrode slurry is applied on a current collector; a standard sample; a light emitting unit including a light source and a bifurcated optical fiber connected to the light source, and selectively irradiating light to either the electrode substrate or the standard sample through one of the bifurcated optical fibers; a light receiving unit including a spectrometer that selectively receives reflected light reflected from either the electrode substrate or the standard sample and analyzes the reflected light; and a control unit that corrects at least one of the light source and the spectrometer based on an analysis result of the spectrometer.

[0014] In one embodiment, the light receiving unit may include a multiplexer to selectively receive the reflected light of either the electrode substrate or the standard sample.

[0015] In one embodiment, the light emitting portion further comprises a collimating lens connected to the branched optical fiber, wherein the collimating lens is capable of converting the light into parallel light.

[0016] In one embodiment, the diameter of the collimating lens may be greater than or equal to 5 mm and less than or equal to 50 mm, and may be spaced from the electrode substrate or the standard sample by greater than or equal to 30 mm and less than or equal to 100 mm.

[0017] In one embodiment, the collimating lens may be coated with an anti-reflective material.

[0018] In one embodiment, the light source may emit light of 680 nm or more and 1050 nm or less.

[0019] In one embodiment, the standard sample may have a reflectivity of greater than or equal to 98%.

[0020] In one embodiment, the average diameter of the branched optical fiber may be greater than or equal to 200 μm and less than or equal to 800 μm.

[0021] The electrode dryness inspection method of the present invention comprises the steps of: irradiating light to the electrode substrate through one of the branched optical fibers in the electrode dryness inspection device, and analyzing the first reflected light reflected from the surface of the electrode substrate to monitor the dryness of the electrode substrate; and calibrating at least one of the light source and the spectrometer by irradiating light to the standard sample through another of the branched optical fibers, and analyzing the second reflected light reflected from the surface of the standard sample.

[0022] In one embodiment, the correcting step may further consider, in addition to the analysis results of the second reflected light, the analysis results of noise light measured in a state where no light is provided from the light source.

[0023] In one embodiment, the correcting step may be performed periodically during the progress of the monitoring step.

[0024] The electrode dryness inspection device according to the present invention can check the reflectivity of a standard sample inline during the drying process and calibrate the reflectivity measuring device.

[0025] Accordingly, the electrode dryness inspection device of the present invention can reliably inspect the reflectivity of the electrode.

[0026] Figure 1 is a schematic diagram of a conventional electrode dryness inspection device.

[0027] Fig. 2 is a schematic diagram of an electrode dryness inspection device according to one embodiment.

[0028] Fig. 3 is a schematic diagram of a portion of the electrode dryness inspection device of Fig. 2.

[0029] Fig. 4 is a schematic diagram of a portion of the electrode dryness inspection device of Fig. 2.

[0030] Fig. 5 is a schematic diagram of a portion of the electrode dryness inspection device of Fig. 2.

[0031] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0032] In order to clearly explain the present invention, parts that are not related to the description are omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0033] Furthermore, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to the illustrated components. In the drawings, the thicknesses are enlarged to clearly represent various layers and regions. Furthermore, in the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0034] Furthermore, when we say that a layer, membrane, region, plate, or other part is "on" or "over" another part, this includes not only cases where it is "directly on" the other part, but also cases where there are other parts in between. When we say that a part is "directly on" another part, we mean that there are no other parts in between. Furthermore, when we say that a part is "on" or "over" a reference part, we mean that it is located above or below the reference part, and we do not necessarily mean that it is located "above" or "over" the reference part in the opposite direction of gravity.

[0035] Additionally, throughout the specification, whenever a part is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0036] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0037]

[0038] According to one embodiment of the present invention, an electrode dryness inspection device,

[0039] An electrode substrate in which an electrode slurry is applied on a current collector,

[0040] standard sample,

[0041] A light emitting unit including a light source and a bifurcated optical fiber connected to the light source, and selectively irradiating light to one of the electrode substrate and the standard sample through one of the bifurcated optical fibers;

[0042] A light receiving unit including a spectrometer that selectively receives and analyzes reflected light reflected from one of the electrode substrate and the standard sample, and

[0043] An electrode dryness inspection device is provided, including a control unit that corrects at least one of the light source and the spectrometer based on the analysis results of the spectrometer.

[0044]

[0045] Hereinafter, the electrode dryness inspection device of the present invention will be described with reference to FIGS. 2 to 4.

[0046] Fig. 2 is a schematic diagram of an electrode dryness inspection device according to one embodiment.

[0047] Referring to FIG. 2, the electrode dryness inspection device (100) includes an electrode substrate (101) to be dried, a light source (120), a branched optical fiber (121), a spectrometer (131), a control unit (140), and a standard sample (151).

[0048] The electrode substrate (101) is a current collector coated with an electrode slurry. In one embodiment, the electrode slurry may be prepared by mixing an active material, a binder, and optionally a conductive material in an organic solvent. The mixed electrode slurry may be coated on a current collector and dried to form an electrode composite layer, thereby preparing a positive or negative electrode. For the negative electrode, copper may be used as the electrode current collector, and for the positive electrode, aluminum may be primarily used.

[0049] The active material may be a positive electrode active material or a negative electrode active material, and as a positive electrode active material, any compound known in the art that allows reversible intercalation and deintercalation of lithium may be used without limitation. Specifically, the positive electrode active material may be a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum.

[0050] A binder is used to bind the active material and the conductive material and to bind the slurry and the current collector. Non-limiting examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethacrylic acid (PMA), polymethyl methacrylate (PMMA), polyacrylamide (PAM), polymethacrylamide, polyacrylonitrile (PAN), polymethacrylonitrile, polyimide (PI), alginic acid, alginate, chitosan, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluoroelastomer, and various copolymers thereof.

[0051] Conductive materials are used to further improve the conductivity of electrode active materials, and are not particularly limited as long as they have electrical conductivity without causing chemical changes 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 fiber or metal fiber, metal powders such as fluorocarbon, aluminum, and nickel powder, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and polyphenylene derivatives can be used.

[0052] In this specification, the electrode substrate (101) is in a state where electrode slurry is applied to a current collector, and can pass through the electrode dryness inspection device (100) of the present invention to perform a drying process. In the drying process, the solvent component of the slurry is removed, and it is important that the slurry is dried to an appropriate degree to improve battery characteristics. If the drying is insufficient, there may be a problem in that the solvent is not sufficiently removed, and if the drying is excessive, the drying quality of the slurry may deteriorate.

[0053] The electrode substrate (101) sequentially passes through the drying zone (102) by the conveying unit (110). A plurality of drying zones (102) may be provided along the conveying direction of the electrode substrate (101), and as an example, FIG. 2 illustrates that nine drying zones (102) are provided, designated as zones #2 to #9. In each drying zone (102), the electrode substrate (101) is positioned within a drying oven, and the drying oven can have a temperature of up to 150 degrees Celsius. In order to determine the degree of drying each time the electrode substrate (101) passes through the drying zone (102), a light-receiving unit and a light-emitting unit, which will be described later, are provided in each drying zone (102).

[0054] In addition, the electrode substrate (101) is sequentially dried while passing through a number of drying zones. For example, the electrode substrate (101) may be dried in five stages: from a wet state, to a state in which the surface is dried, to a state in which surface drying is complete, to a state in which the interior is dried, and to a state in which interior drying is complete.

[0055] Meanwhile, the electrode dryness test device (100) includes a standard sample (151) positioned independently from the electrode substrate (101). Specifically, the standard sample (151) is positioned outside the drying oven and is positioned independently from the electrode substrate (101). For example, the standard sample (151) may be positioned within a dark box configured with the same environment as the drying oven.

[0056] The standard sample (151) may have a reflectance of 98% or more. That is, the standard sample (151) may provide a white standard reflectance. Specifically, the standard sample (151) may have a reflectance of 98% or more for light of 880 nm or more and 980 nm or less. The standard sample (151) may be made of PTFE (Polytetrafluoroethylene).

[0057] The electrode dryness inspection device (100) includes a light source (120) and a light emitting unit including a bifurcated optical fiber (121) connected to the light source (120). This will be described below with reference to FIG. 3.

[0058] Fig. 3 is a schematic diagram of a portion of the electrode dryness inspection device of Fig. 2. Specifically, Fig. 3 is an enlarged view of the T region of Fig. 2.

[0059] Referring to FIGS. 2 and 3 together, the light of the light source (120) may have a wavelength of 680 nm to 1050 nm. The wavelength corresponds to near infrared, and more preferably, it may have a wavelength of 880 nm to 980 nm. The power of the light source varies depending on the device, and may have a power of, for example, 5 W to 200 W. The lifespan is preferably 2000 hours or more. For example, a halogen lamp of 4.5 W or more may be used as the light source (120). However, the type, power, and wavelength of the light source of the present invention are not limited to the above.

[0060] The branched optical fiber (121) may include a first optical fiber (121A) directed toward the electrode substrate (101) through the a channel and a second optical fiber (121B) directed toward the standard sample (151) through the b channel. Fiber connectors (121C) may be arranged between the a channel and the first optical fiber (121A) and between the b channel and the second optical fiber (121B), respectively. The electrode dryness inspection device (100) may selectively irradiate light to one of the electrode substrate (101) and the standard sample (151) through the branched optical fiber (121). Specifically, the light source (120) may be placed in a room temperature environment, and the branched optical fiber (121) may selectively irradiate light to the electrode substrate (101) and the standard sample (151) located in a high-temperature oven box or dark box. The first optical fiber (121A) and the second optical fiber (121B) can distribute the light from the light source (120) at a ratio of 1:9 to 9:1, and preferably at a ratio of 5:5.

[0061] In addition, the light emitting unit may further include a collimator lens (122). The collimator lens (122) is positioned at one end of the branched optical fiber (121) and can convert light spreading from the light source (120) into parallel light. Accordingly, light can be intensively irradiated to an irradiation target spaced apart from the branched optical fiber (121) and the collimator lens (122). The collimator lens (122) may include a first collimator lens (122A) positioned at one end of the first optical fiber (121A) and a second collimator lens (122B) positioned at one end of the second optical fiber (121B). The first collimator lens (122A) is positioned on the electrode substrate (101), and the second collimator lens (122B) is positioned on the standard sample (151). Referring to Fig. 4, the irradiation of light through a branched optical fiber (121) and a collimating lens (122) will be described in more detail.

[0062] Fig. 4 is a schematic diagram of a portion of the electrode dryness inspection device of Fig. 2. Specifically, it is a schematic diagram showing an enlarged view of the first optical fiber (121A), the first collimating lens (122A), and the electrode substrate (101) in the electrode dryness inspection device (100).

[0063] Referring to FIG. 4, an electrode dryness inspection device (100) of one embodiment may utilize regular reflection. Accordingly, the first collimating lens (122A) irradiates light perpendicularly to the surface of the electrode substrate (101) based on the transport direction of the electrode substrate (101). The first collimating lens (122A) may have a separation distance (H) in the vertical direction from the electrode substrate (101). The separation distance (H) may be 30 mm or more and 100 mm or less, specifically 30 mm or more and 80 mm or less, and even more specifically 40 mm or more and 60 mm or less, and most preferably 50 mm. If the separation distance (H) is too close outside the above range, physical interference with the electrode substrate (101) being processed may occur, which may cause problems such as breakage, and if it is too far, the irradiation range of the light may become wide, making it difficult to accurately irradiate the irradiation target, which is not preferable.

[0064] The diameter (R) of the first collimating lens (122A) may be 5 mm or more and 50 mm or less, specifically 10 mm or more and 40 mm or less, and even more specifically 10 mm or more and 20 mm or less. If the diameter (R) is smaller than the above range, the amount of light is small, making it difficult to accurately measure the reflectivity of the electrode. If it is larger, the light source irradiation range may become too wide, which is not desirable.

[0065] Additionally, the first collimating lens (122A) may be coated with an anti-reflection material. Accordingly, the reflectivity of the first collimating lens (122A) may be 0.5% or less on average.

[0066] The first optical fiber (121A) that irradiates light through the first collimating lens (122A) may have an average diameter of 200 μm or more and 800 μm or less, specifically, 400 μm or more and 800 μm or less, and even more specifically, 400 μm or more and 600 μm or less. If the average diameter is small beyond the above range, the amount of light may be too small to measure reflectivity, and if it is too large, manufacturing and efficiency may be problematic.

[0067] Meanwhile, the above-described explanation can be equally applied to the relationship between the second optical fiber (121B), the second collimating lens (122B), and the standard sample (151).

[0068] Referring again to FIGS. 2 and 3, the electrode dryness inspection device (100) includes a light receiving unit (130) including a spectrometer (131) and a spectrometer hub (132). The spectrometer (131) selectively receives and analyzes reflected light reflected from either the electrode substrate (101) or a standard sample (151). For example, the spectrometer (131) may analyze the intensity or spectrum of the reflected light. The spectrometer hub (132) transmits the analysis results obtained from the spectrometers (131) of the drying zone (102) to the control unit (140).

[0069] The light receiving unit (130) includes a multiplexer (133) connected to a spectrometer (131), and can selectively receive reflected light reflected from either the electrode substrate (101) or the standard sample (151). The multiplexer (133) can be replaced with a TTL switch, and the following description of the multiplexer (133) can be equally applied to the TTL switch.

[0070] The light receiving unit (130) can receive light reflected from the surface of the electrode substrate (101) through the c channel of the multiplexer (133), or can receive light reflected from the surface of the standard sample (151) through the d channel of the multiplexer (133).

[0071] The analyzer (131) may analyze the reflected light of the electrode substrate (101) or standard sample (151) passed through the multiplexer (133).

[0072]

[0073] Meanwhile, in another embodiment of the present invention, the branched optical fiber (121) included in the light-emitting unit and the multiplexer (133) included in the light-receiving unit (130) may be replaced with one multiplexer.

[0074] Fig. 5 is a schematic diagram of a portion of the electrode dryness inspection device of Fig. 2.

[0075] Referring to FIG. 5, the branched optical fiber (121) and multiplexer (133) described in FIG. 3 may be replaced with a single multiplexer (121 '). The multiplexer (121 ') may function as the branched optical fiber (121) and multiplexer (133) of FIG. 3, including e, f, g, and h channels.

[0076] Specifically, the light source (120) can irradiate light to the electrode substrate (101) through the g channel and the first collimating lens (122A). Light reflected from the electrode substrate (101) can be transmitted to the spectrometer (131) through the h channel. In addition, the light source (120) can irradiate light to the standard sample (151) through the e channel and the second collimating lens (122B). Light reflected from the standard sample (151) can be transmitted to the spectrometer (131) through the f channel.

[0077]

[0078] The control unit (140) includes a display device (141) connected to the spectrometer hub (132). The display device (141) displays data values ​​obtained from the spectrometer hub (132), and the control unit (140) corrects at least one of the light source (120) and the spectrometer (131) based on the analysis results of the spectrometer (131). The correction may be performed, for example, by adjusting the intensity of the light source (120) or correcting the analysis results of the spectrometer (131). The correction will be described in detail in the electrode dryness inspection method described below.

[0079]

[0080] According to another embodiment of the present invention, a method for inspecting electrode dryness using the above electrode dryness inspecting device is provided.

[0081]

[0082] According to one embodiment of the present invention,

[0083] In the above electrode dryness inspection device,

[0084] A step of irradiating light onto the electrode substrate through one of the branched optical fibers and analyzing the first reflected light reflected from the surface of the electrode substrate to monitor the dryness of the electrode substrate; and

[0085] A method for inspecting electrode dryness is provided, comprising: a step of irradiating light to the standard sample through another optical fiber among the branched optical fibers, analyzing the second reflected light reflected from the surface of the standard sample, and correcting at least one of the light amount of the light source and the analysis result of the spectrometer;

[0086] Hereinafter, the electrode dryness inspection method of the present invention will be described with reference to FIGS. 2 to 4. Meanwhile, the description of the aforementioned components of the electrode dryness inspection device (10) applies equally to the following.

[0087] The step of monitoring the dryness of the electrode substrate is a step of irradiating light from a light source (120) onto the surface of the electrode substrate (101) through a first optical fiber (121A) and a first collimating lens (122A), and then analyzing the first reflected light, which is light reflected from the surface of the electrode substrate (101). That is, the step of monitoring the dryness of the electrode substrate is a step of irradiating and analyzing light from the light emitting unit and light receiving unit (130) of the electrode dryness inspection device (10) onto the electrode substrate (101), and displaying the result value on a display device (141).

[0088] The step of correcting includes a step of irradiating light from a light source (120) onto the surface of a standard sample (151) through a second optical fiber (121B) and a second collimating lens (122B), and then analyzing the second reflected light, which is light reflected from the surface of the standard sample (151). That is, in order to confirm the necessity of correction, light is irradiated and analyzed from the light emitting unit and light receiving unit (130) of the electrode dryness inspection device (10) onto the standard sample (151).

[0089] At this time, in addition to the analysis results of the second reflected light, the analysis results of noise light measured in a state where no light is provided from the light source (120) are additionally considered. Specifically, noise light refers to light from the surrounding environment rather than the light source, and may be, for example, a fluorescent lamp. For accurate correction, the analysis results of noise light in a state where no light source is provided are also considered during the correction step.

[0090] In this way, in the correction step, at least one of the light source (120) and the spectrometer (130) is corrected by taking into account the analysis results of the second reflected light and the analysis results of the noise light. For example, at least one of the light quantity of the light source (120) and the analysis results of the spectrometer (130) may be corrected as needed.

[0091] In addition, the calibration step can be performed independently from the monitoring step, as it can be used to check whether calibration is necessary through an external standard sample (151) without stopping the drying process of the electrode substrate (101). Accordingly, the calibration step can be performed periodically during the progress of the monitoring step.

[0092] Therefore, the electrode dryness inspection device and electrode dryness inspection method of the present invention can position a standard sample outside a drying oven and measure the reflectivity of the standard sample independently of the drying process of the electrode substrate. This provides an electrode dryness inspection device and method capable of real-time calibration of reflectivity measurement equipment, enabling reliable inspection of electrode dryness.

[0093]

[0094] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. An electrode substrate on which an electrode slurry is applied on a current collector; standard sample; A light emitting unit including a light source and a bifurcated optical fiber connected to the light source, and selectively irradiating light to one of the electrode substrate and the standard sample through one of the bifurcated optical fibers; A light receiving unit including a spectrometer that selectively receives reflected light reflected from one of the electrode substrate and the standard sample and analyzes the reflected light; and An electrode dryness inspection device comprising a control unit that corrects at least one of the light source and the spectrometer based on the analysis results of the spectrometer.

2. In paragraph 1, An electrode dryness inspection device, wherein the light receiving unit includes a multiplexer to selectively receive the reflected light of one of the electrode substrate and the standard sample.

3. In paragraph 1, The above light emitting portion further includes a collimating lens connected to the branched optical fiber, The above collimating lens is an electrode dryness inspection device that converts the light into parallel light.

4. In paragraph 3, An electrode dryness inspection device wherein the diameter of the collimating lens is 5 mm or more and 50 mm or less and is spaced 30 mm or more and 100 mm or less from the electrode substrate or the standard sample.

5. In paragraph 3, An electrode dryness inspection device wherein the above-mentioned collimating lens is coated with an anti-reflection material.

6. In paragraph 1, An electrode dryness inspection device wherein the light source emits light of 680 nm or more and 1050 nm or less.

7. In paragraph 1, An electrode dryness test device wherein the above standard sample has a reflectivity of 98% or more.

8. In paragraph 1, An electrode dryness inspection device wherein the average diameter of the above branched optical fiber is 200㎛ or more and 800㎛ or less.

9. In the electrode dryness inspection device according to the above paragraph 1, A step of irradiating light onto the electrode substrate through one of the branched optical fibers and analyzing the first reflected light reflected from the surface of the electrode substrate to monitor the dryness of the electrode substrate; and A method for inspecting electrode dryness, comprising: a step of irradiating light to the standard sample through another optical fiber among the branched optical fibers, analyzing second reflected light reflected from the surface of the standard sample, and calibrating at least one of the light source and the spectrometer; 10. In Article 9, A method for inspecting electrode dryness, wherein the above-mentioned correcting step additionally considers, in addition to the analysis results of the second reflected light, the analysis results of noise light measured in a state where no light is provided from the light source.

11. In Article 9, The above correction step is a method for inspecting electrode dryness that is periodically performed during the progress of the above monitoring step.

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