Method for measuring the intensity distribution of laser light irradiated for drying an electrode material layer coated on a current collector sheet during the manufacturing of an 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 for drying on an electrode material layer coated on a current collector sheet in the manufacture of an 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 layer by layer thereon, 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 that area and suppress sagging at the edge of the coating part and 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 a method for manufacturing an electrode sheet by transporting a long current collector sheet and coating it with a slurry-like electrode material, then drying it, the inventors of the present invention have developed a step in which laser light is irradiated over the entire width of the electrode material layer coated and stretched on the current collector sheet to dry and fix the electrode material layer. In this step, the state of the electrode material layer after drying changes depending on the intensity of the laser light that strikes the electrode material layer, so it is preferable to be able to inspect in a timely manner whether the intensity distribution of the laser light irradiated over the entire width of the electrode material layer is as intended. In that case, it is advantageous if the intensity distribution of the laser light can be inspected while the laser light is still being irradiated onto the current collector sheet, without removing the equipment (laser light source, optical system) for irradiating the current collector sheet from its installation location.

[0005] Thus, the main objective of the present invention is to provide a method for inspecting the intensity distribution of laser light irradiated over the entire widthwise region of the electrode material layer on a current collector sheet during the manufacturing of an electrode sheet, without removing the laser light 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 for measuring the intensity distribution of laser light irradiated over the entire width of a current collector sheet for drying an electrode material layer coated on the current collector sheet, while the current collector sheet constituting the electrode sheet is transported in its longitudinal direction, The process of preparing an imaging device for imaging the irradiation area of ​​the laser beam on the current collector sheet, A process of arranging a sheet-like member that scatters or diffusely reflects the laser light in the irradiation area of ​​the laser light, The process of imaging the sheet-like member, which is placed in the irradiation area and irradiated with the laser light, using the imaging device, A process of measuring the brightness distribution in the image of the irradiation area of ​​the laser light on the sheet-like member captured by the imaging device as the intensity distribution of the laser light. This is achieved by a method that includes [a specific method].

[0007] In the above configuration, the "electrode sheet" may be an electrode sheet in the usual form that constitutes a lithium-ion secondary battery or other battery, and more specifically, it may be a configuration in which an electrode material layer is fixed on a current collector sheet such as copper foil or aluminum foil. In particular, the electrode sheet to which the present invention pertains is manufactured as described above by conveying the current collector sheet in its longitudinal direction, coating a slurry-like electrode material in layers, and irradiating the coated electrode material layer with laser light over its entire width to dry and fix the electrode material layer. The "electrode material" may be a material commonly used in this field as the positive or 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 CMOS camera that detects the intensity of light from each part in the field of view as brightness for each pixel, and in the method of the present invention, as described in the later section on embodiments, it is installed so that the entire irradiation area of ​​the laser light irradiated onto the current collector sheet is within the field of view. The "sheet-like member" is a sheet made of any material such as paper or cloth, and may be any member that scatters or diffusely reflects incident light substantially uniformly in all directions without specular reflection.

[0008] In the above configuration, during the manufacturing process of an electrode sheet in which an electrode material layer is coated onto a current collector sheet while it is being transported in its longitudinal direction 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 placed in the laser light irradiation area, and the sheet-like member irradiated with laser light is imaged by an imaging device. With this configuration, the laser light is scattered or diffusely reflected by the sheet-like member rather than specularly reflected, so light with an intensity roughly proportional to the intensity of the laser light irradiated thereon enters the imaging device from each part of the sheet-like member, and the brightness distribution of the image of the sheet-like member on the imaging device corresponds to the intensity distribution of the irradiated laser light. Therefore, the intensity distribution of the laser light can be obtained by measuring the brightness distribution in the image of the laser light irradiation area on the sheet-like member. With this configuration, the laser beam intensity distribution can be obtained without removing the equipment for irradiating the current collector sheet from its installation location, while the laser beam is still being irradiated onto the current collector sheet. This allows for verification of whether the laser beam intensity distribution is as expected.

[0009] In the method of the present invention described above, the electrode material to be coated is in a slurry state before drying. Therefore, if a sheet-like member is placed on it, the slurry of the electrode material will adhere to the sheet-like member, resulting in an undesirable situation. For this reason, when inspecting the intensity distribution of the laser light, it is preferable to place the sheet-like member on a current collector sheet that is not coated with the electrode material, and to capture an image of the laser light irradiation area above it. It should be noted that when inspecting the intensity distribution of the laser light, the current collector sheet does not need to be present in the laser light irradiation area, and this case also falls within the scope of the present invention.

[0010] In the above configuration, if there is image distortion within the captured field of view or unevenness in detection sensitivity depending on the part of the image in the imaging device, the image distortion and / or unevenness in detection sensitivity may be corrected by any method. [Effects of the Invention]

[0011] Thus, according to the method of the present invention, inspection of the distribution of laser light irradiation intensity for drying the electrode material layer coated on the current collector sheet can be performed simply by placing a sheet-like member in the irradiation area and taking an image of it, while the laser irradiation equipment remains installed in a state where it irradiates the current collector sheet with laser light. This eliminates the need for troublesome procedures such as removing the laser irradiation equipment, which is advantageous. Furthermore, since the inspection of the distribution of laser light irradiation intensity by the method of the present invention can be performed as appropriate during the manufacturing of the electrode sheet, it is expected to be useful in quality control without significantly impairing productivity.

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

[0013] [Figure 1] Figure 1(A) is a schematic diagram of the process of coating an electrode material layer onto a current collector sheet to which this embodiment is applied and drying it. Figure 1(B) is a schematic diagram of the process of measuring the intensity distribution of laser light irradiated on the current collector sheet according to this embodiment for drying the electrode material layer. [Figure 2] Figure 2(A) is a diagram illustrating the path of light when laser light is directly shone onto the current collector sheet, and a schematic brightness distribution diagram of the image of the shone area captured by the camera in that case. Figure 2(B) is a diagram illustrating the path of light when laser light is shone onto the current collector sheet with a sheet-like member placed on top, and a schematic brightness distribution diagram of the image of the shone area captured by the camera in that case. [Figure 3] Figure 3 shows an example of an image captured by a camera when a laser beam is shone on a sheet-like member placed on a current collector sheet. [Explanation of symbols]

[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] While referring to the attached 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] Electrode sheet manufacturing process 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 the laser beam L from the laser irradiation device 3 is irradiated across the entire width of the electrode material layer 2, so that the electrode material layer 2 is dried and fixed. 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 of 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 commonly 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 beam L extending across its entire width, and the entire area of the electrode material layer 2 is irradiated with the laser beam and dried. The wavelength and power of the laser beam 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 up by a winding roller (not shown) or the like and used as an electrode sheet in the next manufacturing process.

[0017] Measurement of light intensity distribution in the laser beam irradiation area 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 is 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 that 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 is executed in a timely manner. Regarding this point, 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 of a commercially available beam profiler. However, in that case, 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 light of the above situation, this embodiment proposes a novel method for measuring the laser light intensity distribution in the irradiation area S of the laser light irradiated from the laser irradiation device 3 to the current collector sheet 1, while the laser irradiation device 3 remains installed at its location. Specifically, first, as schematically depicted in Figure 1(B), a camera 4 (imaging device) is installed to image the entire irradiation area S, and the camera 4 captures an image of the irradiation area S while the laser light is irradiated. At that time, the current collector sheet 1 is usually made of metal foil, and as schematically depicted in Figure 2(A), if the laser light L is directly incident on the current collector sheet 1, even if the intensity of the light incident on the irradiation area S is uniform, specular reflection occurs on the current collector sheet 1, so the intensity of the reflected light from the irradiation area S that reaches the light-receiving surface (not shown) of the camera 4 is not uniform (as shown in the lower part of Figure 2(A), the brightness is higher from the part where the angle of incidence and the angle of reflection are equal in the camera image).

[0020] Therefore, in this embodiment, as shown in Figure 1(B), when measuring the laser light intensity distribution, a sheet-like member 5 that causes almost no specular reflection is arranged to cover the entire irradiation area S, and in this state, laser light is irradiated, and an image of the irradiation area S is captured by the camera 4. With this configuration, as schematically shown in Figure 2(B), when laser light strikes the sheet-like member 5, light is emitted or reflected in substantially all directions due to scattering or diffuse reflection of light at each part. Therefore, if the intensity of the light incident on the irradiation area S is uniform, it is expected that the intensity of the reflected light from the irradiation area S that reaches the light-receiving surface (not shown) of the camera 4 will be substantially uniform (see the lower part of Figure 2(B)). Furthermore, the higher the laser light intensity irradiated to each part of the irradiation area S, the higher the brightness of the corresponding part in the image of the irradiation area S captured by the camera 4. Thus, the brightness distribution of the image of the irradiation area S captured by the camera 4 can be measured as the laser light intensity distribution of the irradiation area S.

[0021] The sheet-like member 5 may be paper or cloth, but preferably, a flame-retardant material (flame-retardant cloth) may be used when irradiated with laser light. Furthermore, if the sheet-like member 5 is placed on the current collector sheet 1 while a slurry-like electrode material layer is coated on it, the electrode material may adhere to the sheet-like member 5, making subsequent processing troublesome. Therefore, when measuring the intensity distribution of the laser light, an area without the electrode material layer may be provided on the current collector sheet 1, the sheet-like member 5 may be placed on that area, and imaging with the camera may be performed. Note that the transport of the current collector sheet 1 may be stopped when imaging with the camera. Also, if the sheet-like member 5 can be placed in the irradiation area S, imaging with the camera may be performed even when the current collector sheet 1 is not in the irradiation area S.

[0022] As described above, when the camera 4 captures an image of the illumination area S, distortion of the image shape and unevenness in brightness due to uneven detection sensitivity within the image may occur depending on the positional relationship between the camera 4 and the illumination area S. In such cases, distortion correction and sensitivity unevenness correction of the camera 4 may be performed by any method. Specifically, for example, a calibration object whose shape and dimensions are known may be placed in the illumination area S, and the image obtained there may be used to correct the image so that the dimensions and shape of the calibration object can be reproduced. Similarly, a calibration object whose brightness is known may be placed in the illumination area S, and the image obtained there may be used to correct the sensitivity unevenness for each pixel. Alternatively, an image of the illumination area S with the illumination light intensity distribution adjusted to a desired state may be captured in advance, and that image may be used as a reference to compare with images of the illumination area obtained at appropriate times during the manufacturing process to check whether the illumination light intensity distribution matches the desired state.

[0023] Figure 3 is a photograph of the irradiation area when laser light is shone onto a sheet-like member according to the method of this embodiment. As can be seen from the figure, by arranging the sheet-like member, the brightness across the entire irradiation area becomes almost uniform. (In the illustrated example, paper was used as the sheet-like member.)

[0024] Thus, in the method of this embodiment, inspection of the distribution of laser light irradiation intensity for drying the electrode material layer coated on the current collector sheet can be performed at any time while the laser irradiation equipment remains set up to irradiate the current collector sheet with laser light. As a result, inspection of the distribution of laser light irradiation intensity can be performed as needed during the manufacturing of the electrode sheet, saving production time and facilitating quality control.

[0025] While the above description is made in relation to embodiments of the present invention, many modifications and changes are readily possible for those skilled in the art, and it will be clear that the present invention is not limited to the embodiments illustrated above, but 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 of a current collector sheet for drying an electrode material layer coated on the current collector sheet, while transporting the current collector sheet in its longitudinal direction, The process of preparing an imaging device for imaging the irradiation area of ​​the laser beam on the current collector sheet, A process of arranging a sheet-like member that scatters or diffusely reflects the laser light in the irradiation area of ​​the laser light, The process of imaging the sheet-like member, which is placed in the irradiation area and irradiated with the laser light, using the imaging device, A process of measuring the brightness distribution in the image of the irradiation area of ​​the laser light on the sheet-like member captured by the imaging device as the intensity distribution of the laser light. A method that includes this.

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