Method for measuring intensity distribution of laser beam radiated for drying electrode material layer applied on collector sheet in manufacturing electrode sheet

Abstract

To inspect an intensity distribution of a laser beam L radiated to the entire area in the width direction of an electrode material layer 2 on a collector sheet 1 in manufacturing an electrode sheet, without removing a laser beam radiating facility 3 from an installation place.SOLUTION: In a method for measuring the intensity distribution of the laser beam radiated over the entire area in the width direction of the collector sheet, for drying the electrode material layer applied on the collector sheet, while conveying the collector sheet constituting the electrode sheet in its longitudinal direction, an imaging apparatus 4 for imaging an irradiation area with the laser beam on the collector sheet is prepared, a sheet-like member 5 for scattering or irregularly reflecting the laser beam to the irradiation area with the laser beam is arranged, the sheet-like member arranged in the irradiation area and irradiated with the laser beam is imaged by the imaging apparatus, and luminance distribution in an image of the irradiation area with the laser beam on the sheet-like member imaged by the imaging apparatus is measured as the intensity distribution of the laser beam.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a manufacturing technique for electrode sheets of batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and Na-ion batteries. More specifically, it relates to a method for measuring the intensity distribution of laser light irradiated onto an electrode material layer coated on a current collector sheet during the drying of the electrode sheet in the manufacture of the electrode sheet.

Background Art

[0002] As one method for manufacturing electrode sheets of lithium-ion secondary batteries, nickel-metal hydride batteries, Na-ion batteries, etc., while transporting a long current collector sheet made of a metal foil such as aluminum or copper with a roller or the like, an electrode material containing a slurry-like active material is coated thereon in layers, and a configuration that uses laser light irradiation for drying the electrode material layer is known. For example, in Patent Document 1, it is proposed to irradiate laser light to the edge of the electrode material layer coated on the current collector sheet to rapidly dry the area and suppress sagging at the edge of the coating part and the dropout of the conductive material from the edge. Note that Patent Document 2 discloses using a laser for measuring the amount of elongation or elongation rate after pressing of each of the non-coated part and the coated part in a configuration where the electrode material layer coated on the current collector sheet is pressed and fixed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, in the method of manufacturing an electrode sheet by coating a slurry-like electrode material on a long current collector sheet while transporting it and then drying it, the inventors of the present invention have developed a process of irradiating a laser beam over the entire width direction of the electrode material layer coated and stretched on the current collector sheet to dry and fix the electrode material layer. In such a process, since the state of the electrode material layer after drying changes depending on the intensity of the laser beam hitting the electrode material layer, it is preferable that the intensity distribution of the laser beam irradiated over the entire width direction of the electrode material layer can be inspected in a timely manner. In that case, it is advantageous that the intensity distribution of the laser beam can be inspected while the laser beam is being irradiated onto the current collector sheet without removing the equipment (laser light source, optical system device) for irradiating the laser beam onto the current collector sheet from their installation locations.

[0005] Thus, the main problem of the present invention is to provide a method capable of inspecting the intensity distribution of the laser beam irradiated over the entire width direction of the electrode material layer on the current collector sheet in the manufacture of the electrode sheet without removing the laser beam irradiation equipment from its installation location.

Means for Solving the Problem

[0006] According to the present invention, the above problem is solved by a method of measuring the intensity distribution of a laser beam irradiated over the entire width direction of a current collector sheet while transporting the current collector sheet constituting the electrode sheet in its longitudinal direction, the method comprising: a process of preparing an imaging device for imaging the laser beam irradiation area on the current collector sheet; a process of arranging a sheet-like member that scatters or diffusely reflects the laser beam in the laser beam irradiation area; a process of imaging the sheet-like member arranged in the irradiation area and irradiated with the laser beam using the imaging device; a process of measuring the luminance distribution in the image of the laser beam irradiation area on the sheet-like member imaged by the imaging device as the intensity distribution of the laser beam and is achieved by a method including these steps.

[0007] In the above configuration, the "electrode sheet" may be an electrode sheet in a normal form constituting a lithium-ion secondary battery or other battery. More specifically, it may have a configuration in which an electrode material layer is fixed on a current collector sheet such as a copper foil or an aluminum foil. In particular, as described above, the electrode sheet targeted by the present invention is manufactured by coating a slurry-like electrode material in layers while transporting the current collector sheet in its longitudinal direction, and irradiating the entire width direction of the coated electrode material layer with laser light to dry and fix the electrode material layer. The "electrode material" may be a material commonly used in this field as a positive electrode or a negative electrode of a battery, including an active material appropriately selected according to the type of battery to be manufactured. The "imaging device" may be a camera such as a CCD camera or a CMOS camera that detects the intensity of light from each part within the field of view as the luminance for each pixel. In the method of the present invention, as described in the column of later embodiments, it is installed so that the entire irradiation area of the laser light irradiated on the current collector sheet falls within the field of view. The "sheet-like member" may be a sheet made of any material such as paper or cloth, and may be any member that does not specularly reflect and scatters or diffusely reflects incident light almost evenly in all directions.

[0008] In the above-described configuration, in the manufacturing process of the electrode sheet in which the current collector sheet is conveyed in its longitudinal direction, the electrode material layer is applied, and then dried with laser light, when measuring the intensity distribution of the laser light irradiation area on the current collector sheet, the above-mentioned "sheet-like member" is arranged in the laser light irradiation area, and the sheet-like member irradiated with the laser light is imaged by the imaging device. According to such a configuration, since the laser light is scattered or diffusely reflected rather than specularly reflected by the sheet-like member, light having an intensity approximately proportional to the intensity of the laser light irradiated thereon enters the imaging device from each part of the sheet-like member, and the luminance distribution of the image of the sheet-like member of the imaging device corresponds to the intensity distribution of the irradiated laser light. Therefore, by measuring the luminance distribution in the image of the laser light irradiation area on the sheet-like member, the intensity distribution of the laser light can be obtained. According to such a configuration, the intensity distribution of the laser light can be obtained in the state when the laser light is irradiated on the current collector sheet without removing the equipment for irradiating the laser light on the current collector sheet from its installation location, and it is possible to confirm whether the intensity distribution of the laser light is the intended distribution.

[0009] In the method of the present invention described above, since the electrode material to be applied is in a slurry state before drying, if a sheet-like member is arranged thereon, it becomes a troublesome state such as the slurry of the electrode material adhering to the sheet-like member. Therefore, when inspecting the intensity distribution of the laser light, it is preferable that the sheet-like member is arranged on the current collector sheet in a state where the electrode material is not applied, and the image of the laser light irradiation area thereon is imaged. Note that when inspecting the intensity distribution of the laser light, the current collector sheet may not be present in the laser light irradiation area, and this case also belongs to the scope of the present invention.

[0010] In the above-described configuration, in the imaging device, when there are image distortions in the field of view to be imaged and unevenness in detection sensitivity depending on the part within the image, the image distortions and / or the unevenness in detection sensitivity may be corrected by any method.

Advantages of the Invention

[0011] Thus, according to the method of the present invention, inspection of the distribution of the irradiation intensity of the laser light for drying the electrode material layer coated on the current collector sheet can be performed simply by placing the sheet-like member in the irradiation area and imaging it while the laser light irradiation equipment is still installed in the state of irradiating the current collector sheet with the laser light. Therefore, troublesome procedures such as removing the laser light irradiation equipment are not required, which is advantageous. Further, inspection of the distribution of the irradiation intensity of the laser light according to the method of the present invention can be appropriately performed during the production of the electrode sheet. Therefore, it is expected to be useful for quality control without significantly impairing productivity.

[0012] Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments of the present invention.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Explanation of Reference Numerals

[0014] 1... Current collector sheet, 2... Electrode material layer, 3... Laser irradiation device, 4... Camera, 5... Sheet-like member, L... Laser light

Best Mode for Carrying Out the Invention

[0015] With reference to the accompanying drawings below, the present invention will be described in detail with respect to several preferred embodiments. In the drawings, the same reference numerals indicate the same parts.

[0016] Manufacturing process of the electrode sheet In the manufacturing process of an electrode sheet of a battery that uses a laser beam whose intensity distribution is measured by the method according to this embodiment, as schematically depicted in FIG. 1(A), while conveying a long current collector sheet 1 in its longitudinal direction Y using a roller (not shown), a slurry-like electrode material layer 2 is coated on the current collector sheet 1, and laser light L from a laser irradiation device 3 is irradiated over the entire width of the electrode material layer 2, thereby drying and fixing the electrode material layer 2. In this process, the electrode sheet may be for any type of battery such as a lithium-ion secondary battery. More specifically, the current collector sheet 1 may be, for example, a metal foil such as aluminum, copper, SUS, nickel, etc. with a thickness of 0.1 to 100 μm. The electrode material coated as the electrode material layer 2 may be a slurry-like material that is usually used as a positive electrode material, negative electrode material, or bipolar material in this field, including an active material, electrolyte, conductive material, and binder selected according to the type of battery. In the manufacturing process, specifically, the electrode material layer 2 is extended while being discharged from a horizontally long nozzle (not shown) with a width of, for example, 300 to 1500 mm and a thickness of several mm onto the conveyed current collector sheet 1, and is coated. Thereafter, as the current collector sheet 1 is conveyed, the electrode material layer 2 passes through the irradiation region S of the laser light L extending over its entire width, and the entire region of the electrode material layer 2 is irradiated with the laser light and dried. The wavelength and power of the laser light may be appropriately selected according to the material of the electrode material layer 2. For example, as the energy density, it may be on the order of 0.1 to 3.0 W / cm 2 or so. Thus, when the electrode material layer 2 is fixed on the current collector sheet 1, the current collector sheet 1 may be wound around a winding roller (not shown) or the like and used as an electrode sheet in the next manufacturing process.

[0017] Measurement of the light intensity distribution in the irradiation area of the laser beam As already mentioned, since the state of the electrode material layer 2 dried on the current collector sheet 1 changes depending on the irradiation intensity of the laser light, it is preferable that the laser light in the irradiation region S be irradiated with a planned light intensity distribution. Usually, since the electrode material layer 2 is assumed to be in a homogeneous state on the current collector sheet 1, in the irradiation region S, the intensity distribution of the laser light may be adjusted so that the irradiation light intensity is as uniform as possible. However, in reality, the thickness may be different between the central region and the edge region of the electrode material layer 2, or the ease of drying may be different. Therefore, through experiments and the like, a preferable intensity distribution is explored, and the optical system of the laser irradiation device 3 may be adjusted so as to obtain the intensity distribution.

[0018] As described above, the intensity of the irradiation light in the irradiation region S of the laser light is adjusted so as to obtain a planned light intensity distribution. However, during the manufacturing process of the electrode sheet, the irradiation light intensity distribution may change due to some factors. Therefore, it is preferable that the inspection of the light intensity distribution in the irradiation region S be performed in a timely manner. In this regard, conventionally, for observing the manufacturing process of the electrode sheet, for example, an IR viewer installed so as to be able to overlook the entire electrode sheet during manufacturing may be used. However, it is difficult to measure the light intensity distribution in the irradiation region S with such an IR viewer. Also, the intensity distribution of the laser light emitted from the laser irradiation device 3 can be measured using a dedicated measuring instrument for a commercially available beam profiler. In that case, however, troublesome operations such as temporarily removing the laser irradiation device 3 from its installation location above the current collector sheet are required. Also, the area where the intensity distribution can be measured at one time is considerably smaller than the irradiation region S, so the intensity distribution of the entire irradiation region S cannot be measured at one time.

[0019] In view of the above situation, in the present embodiment, a novel method for measuring the laser light intensity distribution in the irradiation region S of the laser light irradiated from the laser irradiation device 3 to the current collector sheet 1 is proposed while the laser irradiation device 3 is installed at its installation location. Specifically, first, as schematically depicted in FIG. 1(B), a camera 4 (imaging device) for imaging the entire irradiation region S is installed, and an image of the irradiation region S is captured by the camera 4 in a state where the laser light is irradiated. At this time, the current collector sheet 1 is usually formed of a metal foil. As schematically depicted in FIG. 2(A), when the laser light L directly enters the current collector sheet 1, even if the intensity of the light incident on the irradiation region S is uniform, since it is specularly reflected on the current collector sheet 1, the intensity of the reflected light from the irradiation region S reaching the light receiving surface (not shown) of the camera 4 is not uniform (as shown in the lower figure of FIG. 2(A), in the image of the camera, the luminance is higher at the site where the incident angle and the reflection angle are equal).

[0020] Therefore, in the present embodiment, as depicted in FIG. 1(B), when measuring the laser light intensity distribution, a sheet-like member 5 that hardly causes specular reflection is arranged so as to cover the entire irradiation region S. In this state, the laser light is irradiated, and an image of the irradiation region S is captured by the camera 4. According to such a configuration, as schematically depicted in FIG. 2(B), in the sheet-like member 5, when the laser light hits, due to light scattering or diffuse reflection (diffuse reflection) at each site, light is emitted or reflected substantially in all directions. Therefore, if the intensity of the light incident on the irradiation region S is uniform, it is expected that the intensity of the reflected light from the irradiation region S reaching the light receiving surface (not shown) of the camera 4 will be substantially uniform (see the lower figure of FIG. 2(B)). And the higher the intensity of the laser light irradiated to each site of the irradiation region S, the higher the luminance of the corresponding site of the image of the irradiation region S captured by the camera 4. Thus, the luminance distribution of the image of the irradiation region S captured by the camera 4 can be measured as the laser light intensity distribution of the irradiation region S.

[0021] The above-described sheet-like member 5 may be paper or cloth, but preferably, a member made of a flame-retardant material (flame-retardant cloth) may be adopted by irradiating laser light. Also, when the sheet-like member 5 is placed on the current collector sheet 1 with a slurry-like electrode material layer coated thereon, the electrode material may adhere to the sheet-like member 5, etc., making subsequent processing troublesome. Therefore, when measuring the intensity distribution of the laser light, an area where the electrode material layer is not coated is provided on the current collector sheet 1, and the sheet-like member 5 is disposed thereon, and imaging by a camera may be performed. Note that the conveyance of the current collector sheet 1 may be stopped during imaging by the camera. Also, if the sheet-like member 5 can be disposed in the irradiation area S, imaging by the camera may be performed with the current collector sheet 1 not in the irradiation area S.

[0022] As described above, when imaging the image of the irradiation area S with the camera 4, depending on the positional relationship between the camera 4 and the irradiation area S, distortion of the image shape and luminance unevenness due to uneven detection sensitivity within the image may occur. In such a case, correction of the distortion of the camera 4 and correction of the sensitivity unevenness may be performed by any method. Specifically, for example, a calibration object with known shape and dimensions is placed in the irradiation area S, and using the image obtained there, correction of the image captured so that the dimensions and shape of the calibration object can be reproduced may be performed. Similarly, a calibration object with known luminance is placed in the irradiation area S, and using the image obtained there, correction of the sensitivity unevenness for each pixel may be performed. Alternatively, an image of the irradiation area S with the irradiation light intensity distribution adjusted to a desired state may be captured in advance, and based on that image, comparison is made with the image of the irradiation area obtained in a timely manner during the manufacturing process, and it may be inspected whether the irradiation light intensity distribution matches the desired state.

[0023] FIG. 3 is a photograph of an image of an irradiation area in a state where a laser beam is irradiated onto a sheet-like member according to the method of the present embodiment. As can be understood from the figure, it is understood that by disposing the sheet-like member, the luminance across the entire irradiation area becomes substantially uniform. (In the illustrated example, paper was used for the sheet-like member.)

[0024] Thus, in the method of the present embodiment, inspection of the distribution of the irradiation intensity of the laser light for drying the electrode material layer coated on the current collector sheet can be carried out as appropriate while the laser light irradiation equipment is installed in a state where the laser light is irradiated onto the current collector sheet. As a result, the inspection of the distribution of the irradiation intensity of the laser light can be appropriately carried out during the production of the electrode sheet, saving the time required for production and facilitating quality control.

[0025] The above description has been made in relation to the embodiments of the present invention, but many modifications and changes are easily possible for those skilled in the art, and the present invention is not limited to only the embodiments exemplified above, and it will be obvious that it can be applied to various devices without departing from the concept of the present invention.

Claims

【Claim 1】 A method for measuring the intensity distribution of laser light irradiated over the entire width direction of a current collector sheet for drying an electrode material layer coated on the current collector sheet while transporting the current collector sheet constituting the electrode sheet in its longitudinal direction, comprising: a process of preparing an imaging device for imaging an irradiation area of the laser light on the current collector sheet; a process of disposing a sheet-like member that scatters or diffusely reflects the laser light in the irradiation area of the laser light; a process of imaging the sheet-like member disposed in the irradiation area and irradiated with the laser light by the imaging device; a process of measuring, as the intensity distribution of the laser light, the luminance distribution in an image of the irradiation area of the laser light on the sheet-like member imaged by the imaging device and a method including the above.

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