JP6819586B2 - Electrode manufacturing method and electrodes - Google Patents

Description

One aspect of the present invention relates to an electrode manufacturing method and an electrode.

In the conventional electrode manufacturing process, the electrode is punched out from the strip-shaped electrode in which the active material layer is formed on the strip-shaped metal foil using a cutting tool, and the position of the end of the electrode is detected for use in the laminating process in the subsequent process. To do. Image recognition based on an image obtained by capturing an electrode with an imaging device is generally used for detecting this position (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-51035

When an electrode is imaged with an imaging device, a predetermined amount of light is required, so that illumination is applied. Therefore, in the case of a white electrode (for example, an electrode on which an active material layer made of a white active material is formed, an electrode having a protective layer made of white ceramic covering the active material layer), an image obtained by capturing this electrode. Then, the contrast between the electrode and the background decreases. Therefore, in the image recognition based on this image, the recognition accuracy of the end portion of the electrode is lowered.

Therefore, in one aspect of the present invention, it is an object of the present invention to propose an electrode manufacturing method and an electrode that improve the image recognition accuracy of the end portion of the electrode.

The method for manufacturing an electrode according to one aspect of the present invention is a method for manufacturing an electrode in which an active material layer is formed on a metal foil, and a band-shaped electrode in which an active material layer is formed on a band-shaped metal foil is laserized for each electrode. It includes a cutting step of cutting with light and an image recognition step of detecting the end of the electrode cut in the cutting step by image recognition. In the cutting step, the end of the electrode is cut by cutting the band-shaped electrode with laser light. Discolor.

In this electrode manufacturing method, energy from a laser beam is applied to a band-shaped electrode, and individual electrodes are cut from the band-shaped electrode by melting by heat. As a result, the cut surface (end portion) of the electrode undergoes evaporation of the surface substance due to heat, for example, and the color tone changes (discolors) due to the change in the surface state accompanying the evaporation. Here, the region where the hue has changed (discolored) is defined as the altered portion. The altered part is altered by burning or evaporating depending on the surface material. For example, in the case of the active material layer, it may be burnt, and in the case of the protective layer described later, it may evaporate. Therefore, in this electrode manufacturing method, when the end portion of the electrode is detected by image recognition, the contrast between the end portion of the electrode and the background in the image is increased, and the image recognition accuracy of the end portion of the electrode is improved.

In the cutting step of the method for manufacturing an electrode of one embodiment, the band-shaped electrode may be cut by a continuous wave laser beam. When a continuous wave laser beam is used, by continuously applying energy of a predetermined magnitude to the band-shaped electrode, a thick active material layer can be cut in a short time by melting by heat, and the cut surface of the active material layer is heated. Can be discolored with.

In the electrode manufacturing method of one embodiment, the strip-shaped electrode may be formed with a protective layer covering the active material layer. Even in the case of an electrode having a protective layer, the protective layer at the end of the electrode is melted by the heat generated by the laser beam, so that the contrast between the end of the electrode and the background in the image does not decrease.

In the method for manufacturing an electrode of one embodiment, the size of the discolored region of the end portion in the direction intersecting the extending direction of the end portion may be 100 μm or more.

In the electrode manufacturing method of one embodiment, in the image recognition step, the end portion is detected by image recognition for the image captured by the camera, and the dimension of the discolored region of the end portion in the direction intersecting the extending direction of the end portion. May be greater than or equal to the size of three pixels of the camera.

In these cases, the end portion of the electrode can be stably recognized in the image recognition step.

The electrode manufacturing method of one embodiment is a method of manufacturing an electrode in which an active material layer is formed on a metal foil, and a strip-shaped electrode having an active material layer formed on a strip-shaped metal foil is cut by laser light for each electrode. Including the cutting step, in the cutting step, the end of the electrode is discolored by cutting the band-shaped electrode with a laser beam, and the dimension of the discolored region of the end in the direction intersecting the extending direction of the end is 100 μm or more. Is.

The electrode of one embodiment is an electrode having an active material layer formed on a metal foil, and is manufactured by cutting a strip-shaped electrode having an active material layer formed on a strip-shaped metal foil, and is formed at an end portion formed by the cutting. Is formed, and the dimension of the discolored region of the end portion in the direction intersecting the extending direction of the end portion is 100 μm or more.

The electrode of one embodiment may be manufactured by cutting the strip-shaped electrode with a laser beam. Further, the laser light may be a continuous wave laser light.

According to one aspect of the present invention, the image recognition accuracy of the end portion of the electrode is improved.

It is a figure which shows typically a part of the electrode manufacturing lines to which the electrode manufacturing method which concerns on one Embodiment is applied. (A) is a plan view of the strip-shaped electrode before cutting, (b) is a cross-sectional view of the strip-shaped electrode of (a) along the line II-II, and (c) is a plan view of the electrode after cutting. is there. It is an enlarged cross-sectional view of the end portion of an electrode after cutting. (A) is a diagram schematically showing a state in which a positive electrode is placed on a strip-shaped separator, and (b) is a diagram schematically showing a state in which a positive electrode is wrapped with two separators. It is a schematic diagram of an electrode cut by using a cutting tool. It is a figure which shows the relationship between an electrode and a pixel of a camera. It is a schematic diagram of an electrode cut by using a laser beam. It is a figure which shows the relationship between an electrode and a pixel of a camera. It is a figure which shows the relationship between an electrode and a pixel of a camera, and the relationship of light intensity.

Hereinafter, the method for manufacturing the electrode and the electrode according to the embodiment of one aspect of the present invention will be described with reference to the drawings. In each figure, the same or corresponding elements are designated by the same reference numerals, and duplicate description will be omitted.

In one embodiment, it is applied to an electrode manufacturing method including a cutting step of cutting an electrode from a band-shaped electrode with a laser beam and an image recognition step of detecting an end portion of the electrode for each cut electrode by image recognition. This cutting process and image recognition process are incorporated as part of the electrode production line. As a post-process using the information on the end of the electrode, an example is a mounting process in which the positive electrode is placed on the band-shaped separator, which is one step when the positive electrode (electrode) wrapped in the bag-shaped separator is manufactured. To do. This post-process is incorporated after the image recognition process on the production line. The manufactured electrodes are used, for example, in a power storage device such as a secondary battery or an electric double layer capacitor. The secondary battery is, for example, a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery. In this embodiment, it is assumed that an electrode used for a lithium ion secondary battery is manufactured.

An electrode manufacturing line 1 to which the electrode manufacturing method according to the embodiment is applied will be described with reference to FIGS. 1 to 4. FIG. 1 is a diagram schematically showing a part of an electrode manufacturing line to which the electrode manufacturing method according to the embodiment is applied. 2 (a) is a plan view of the strip-shaped electrode before cutting, FIG. 2 (b) is a cross-sectional view of the strip-shaped electrode of FIG. 2 (a) along the line II-II, and FIG. 2 (c) is a cross-sectional view. It is a top view of the electrode after cutting. FIG. 3 is an enlarged cross-sectional view of the end portion of the electrode after cutting. FIG. 4A is a diagram schematically showing a state in which the positive electrode is placed on the strip-shaped separator, and FIG. 4B is a diagram schematically showing a state in which the positive electrode is wrapped with two separators. is there.

Before explaining the production line 1, the electrodes will be described. The electrode is coated with an electrode paste on at least one surface of a metal foil to form an active material layer, and a protective paste is applied so as to cover the active material layer to form a protective layer. The protective layer is a layer that protects the active material layer, and secures the insulating property, heat resistance, etc. of the active material layer. The protective layer is a thinner layer than the active material layer. The electrode has a tab on which no active material layer is formed at the end of the metal foil.

The metal foil is, for example, an aluminum foil in the case of a positive electrode, and a copper foil or a nickel foil in the case of a negative electrode. The electrode paste is in the form of a slurry having a predetermined viscosity and contains an active material, a binder, a solvent and the like. The active material is a positive electrode active material or a negative electrode active material. The positive electrode active material is, for example, a composite oxide or a sulfur-based material. The composite oxide contains at least one of manganese, nickel, cobalt and aluminum and lithium. The negative electrode active material includes, for example, graphite, highly oriented graphite, mesocarbon microbeads, carbon such as hard carbon and soft carbon, alkali metals such as lithium and sodium, metal compounds, and SiOx (0.5 ≦ x ≦ 1.5). ) And other metal oxides and boron-added carbon. The binder is, for example, a fluororesin such as polyvinylidene fluoride, polytetrafluoroethylene or fluororubber, a thermoplastic resin such as polypropylene or polyethylene, an imide resin such as polyimide or polyamideimide, or an alkoxysilyl group-containing resin. The solvent is, for example, an organic solvent such as NMP (N-methylpyrrolidone), methanol, or methyl isobutyl ketone. Further, the electrode paste may contain a conductive auxiliary agent such as carbon black, graphite, acetylene black, and Ketjen black (registered trademark). In addition, the electrode paste may contain a thickener such as carboxymethyl cellulose (CMC).

The protective paste is in the form of a slurry having a predetermined viscosity and contains a ceramic, a binder and a solvent. The ceramic may have excellent insulating properties and heat resistance, and is, for example, aluminum oxide (alumina). The color of aluminum oxide is white. The binder is exemplified as, for example, a binder for an electrode paste. The solvent is exemplified as a solvent for the electrode paste, for example. As the substance forming the protective layer, a substance other than ceramic may be used, and a substance having excellent insulating properties and heat resistance may be used.

The separator separates the positive electrode and the negative electrode, and allows lithium ions to pass through while preventing a short circuit due to contact between the two electrodes. In particular, since the two separators wrap the portion other than the tab of the positive electrode, the ends of the two separators are joined by welding to form a bag-shaped separator. The separator has a substantially rectangular shape. The separator is, for example, a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), a woven fabric made of polypropylene, polyethylene terephthalate (PET), methyl cellulose or the like, or a non-woven fabric.

When the electrode is manufactured, a step of applying the electrode paste to the strip-shaped metal foil and a step of drying the coated electrode paste are performed, and an active material layer is formed on the strip-shaped metal foil. After the formation of the active material layer, a step of applying a protective paste so as to cover the entire active material layer and a step of drying the applied protective paste are performed to form a protective layer covering the active material layer. .. As a result, as shown in FIGS. 2A and 2B, a strip-shaped electrode ZE in which the active material layer A is formed on the strip-shaped metal foil M and the protective layer P covering the active material layer A is formed is generated. Will be done. In this embodiment, a strip-shaped electrode ZE in which the active material layer A and the protective layer P are formed by continuous coating on both sides of the metal foil M is used, and two electrodes are arranged in the width direction of the strip-shaped electrode ZE. And. In the cutting step, the electrode E shown in FIG. 2C is cut from the strip-shaped electrode ZE. In the image recognition step, the position and inclination of the end portion of the cut electrode E are detected by image recognition. When manufacturing an electrode, in addition to the above-mentioned steps, there are steps such as pressing, baking, and inspection.

As shown in FIG. 2B, the strip-shaped electrode ZE is composed of a portion composed of only the metal foil M, a portion composed of the metal foil M and the protective layer P, and the metal foil M, the active material layer A, and the protective layer P. Has a part. The thickness of the metal foil M is, for example, several tens of μm. The thickness of the active material layer A is, for example, several hundred μm. The thickness of the protective layer P is, for example, several tens of μm. Therefore, the portion composed of the metal foil M, the active material layer A, and the protective layer P is thicker than the other portions. In the image recognition step, the end portion of the portion composed of the metal foil M, the active material layer A, and the protective layer P is detected. The strip-shaped electrode ZE shown in FIG. 2A shows a line CL cut by a cutting device by a long-dotted chain line. This cutting line CL is a virtual line, and the line is not actually drawn.

Now, the production line 1 will be described. In the production line 1, the strip-shaped electrode ZE being conveyed is cut by the cutting device 10 for each electrode E (cutting step), and the position and inclination of the end portion of the electrode E are detected for each electrode E by the image recognition device 20 (image). Recognition step), the electrode E (positive electrode) is placed on the strip-shaped separator S (placement step). The production line 1 is provided with transfer devices 30, 40, and 50 in each process, and transfer devices 60 and 70 are provided between each process. Each of the devices 10, 20, 30, 40, 50, 60, 70 is controlled by a control device (not shown) of the production line 1.

The cutting device 10 is a device that cuts the strip-shaped electrode ZE using a laser beam. The cutting device 10 irradiates the laser beam L from above the strip-shaped electrode ZE being conveyed. Further, the cutting device 10 moves the center of the spot of the laser beam L along the cutting line CL corresponding to the outer shape of the electrode E to irradiate. The cutting device 10 includes a laser light oscillator 11 and a scanner 12.

The laser light oscillator 11 is an oscillator that oscillates a continuous wave laser light L. The laser light oscillator 11 outputs the oscillated laser light L to the scanner 12. The wavelength of the laser beam L is, for example, 1000 to 1100 nm. The output of the laser beam L is, for example, 500 W. In the laser optical oscillator 11, the output can be changed within a predetermined range.

The scanner 12 is a device that moves the laser beam L with respect to the strip-shaped electrode ZE being conveyed along the cutting line CL corresponding to the outer shape of the electrode E. The scanner 12 is arranged above the band-shaped electrode ZE transported by the transport device 30, and irradiates the laser beam L toward the band-shaped electrode ZE below. The scanner 12 has, for example, two mirrors, two driving devices for changing the three-dimensional angle of each mirror (that is, rotating each mirror three-dimensionally), and a condenser lens. There is. In the scanner 12, the angle of each mirror is changed by each driving device, and the laser beam L is reflected by the two mirrors to change the irradiation direction. The cutting speed of the laser beam L changes according to the speed at which the angle of each mirror is changed by each driving device. The cutting speed is, for example, 20 to 50 m / min. The cutting speed is set independently of the transport speed of the strip-shaped electrode ZE transported by the transport device 30. The pattern for changing the angle of each mirror in each drive device and the speed at which the angle is changed are preset for each transfer speed and stored in the scanner 12. In the scanner 12, the laser beam L reflected by the two mirrors is incident on the condenser lens, and the laser beam L condensed by the condenser lens is irradiated toward the band-shaped electrode ZE being conveyed. The spot diameter of the laser beam L is, for example, 100 μm.

In the cutting device 10, the assist gas may be sprayed onto the strip-shaped electrode ZE at a portion where the laser beam L is irradiated. Further, the cutting device 10 may be a laser beam other than the continuous wave laser beam, and may be, for example, a pulse wave laser beam.

The image recognition device 20 is a device that detects the position and inclination (angle) of the end portion of the electrode E by image recognition for each electrode E. In the image recognition device 20, for example, as shown in FIG. 2C, the reference position BC and the reference line BL are stored in advance, and the corner portion C (active material layer A is formed) as the position of the end portion of the electrode E. The corner portion of the portion to be chamfered, which may be a chamfered shape) is detected relative to the reference position BC, and the end portion (the portion where the active material layer A is formed) is detected as the inclination of the end portion of the electrode E. The relative angle of the line EL along the reference line BL to the reference line BL is detected. The reference position BC and the reference line BL are set based on the position where the electrode E is placed on the strip-shaped separator S and the like. The image recognition device 20 includes a camera 21 and an image processing unit 22.

The camera 21 is a camera that captures the electrode E. The camera 21 is arranged above the electrode E transported by the transport device 40, and images the lower electrode E. When the camera 21 takes an image of the electrode E, the transfer of the electrode E by the transfer device 40 is temporarily stopped. The camera 21 outputs the captured image to the image processing unit 22. Since an appropriate amount of light is required when taking an image with the camera 21, the portion where the electrode E is taken with the camera 21 is illuminated. For example, a lighting device is incorporated in the transport device 40, and lighting is applied from below the electrode E. Therefore, the portion where the electrode E is imaged by the camera 21 is bright and whitish. Note that this inspection (for example, imaging of the electrode E) may be performed while transporting the electrode E without stopping the transport of the electrode E.

The image processing unit 22 is an image processing unit that detects the position and inclination of the end portion of the electrode E by image recognition of the image captured by the camera 21. An example of the image recognition method in the image processing unit 22 will be described. First, by detecting the edge from the brightness difference between the pixels using the brightness value of each pixel of the image, the line along the end (cut surface) of the electrode E is detected and the outline of the electrode E is acquired. .. Then, the corner portion C to be detected and the line EL along the end portion are extracted from the outer line of the electrode E, the relative position of the corner portion C with respect to the reference position BC is obtained, and the line EL along the end portion is relative to the reference line BL. Find the relative angle. The relative position and the relative angle are used as a correction amount when the electrode E is placed on the band-shaped separator S.

The transport device 30 is a device that transports the strip-shaped electrode ZE and the electrode E after cutting. The transport device 30 continuously transports the strip-shaped electrode ZE and the electrode E after cutting. The scanner 12 of the cutting device 10 is arranged at a predetermined position above the transport device 30. During transportation, a predetermined tension is applied to the strip-shaped electrode ZE.

The transport device 40 is a device that transports the electrode E transferred from the transport device 30. The transport device 40 is arranged on the downstream side of the transport device 30 in the transport direction D. In the transport device 40, each time the electrode E reaches directly under the camera 21 of the image recognition device 20, the transport of the electrode E is stopped for a predetermined time. A camera 21 is arranged at a predetermined position above the transport device 40.

The transport device 50 is a device that transports the strip-shaped separator S. In the transport device 50, the strip-shaped separator S may be continuously transported, or the transport may be temporarily stopped when the electrode E is placed on the strip-shaped separator S. During transportation, a predetermined tension is applied to the strip-shaped separator S.

The transfer device 60 is a device for transferring the electrode E on the transfer device 30 onto the transfer device 40. The transfer device 60 includes, for example, a robot arm 61 and a plurality of suction pads 62 attached to one end side of the robot arm 61. In the transfer device 60, the robot arm 61 moves a plurality of suction pads 62 above the electrodes E transported to one end of the transfer device 30, and the plurality of suction pads 62 suck the electrodes E. Then, in the transfer device 60, the electrodes E adsorbed on the plurality of suction pads 62 by the robot arm 61 are moved above one end of the transfer device 40, and the adsorption by the plurality of suction pads 62 is stopped and transferred. The electrode E is placed on the device 40. Note that FIG. 1 shows only a part of the robot arm 61.

The transfer device 70 is a device for transferring the electrode E on the transfer device 40 onto the strip-shaped separator S transported by the transfer device 50. Like the transfer device 60, the transfer device 70 includes, for example, a robot arm 71 and a plurality of suction pads 72 attached to one end side of the robot arm 71. In the transfer device 70, the robot arm 71 moves the plurality of suction pads 72 above the electrodes E stopped at the other end of the transfer device 40 (directly below the camera 21), and the plurality of suction pads 72 are used. Adsorb electrode E. Then, in the transfer device 70, the electrodes E adsorbed on the plurality of suction pads 72 by the robot arm 71 are moved above the strip-shaped separator S transported by the transfer device 50, and the electrodes E are adsorbed by the plurality of suction pads 72. Is stopped and the electrode E is placed on the strip-shaped separator S (see FIG. 4). Note that FIG. 1 shows only a part of the robot arm 71.

In the transfer device 70, when the electrode E is transferred onto the strip-shaped separator S by the robot arm 71, the corner portion C of the electrode E detected by the image recognition device 20 is located at a relative position and an end portion with respect to the reference position BC. The position and inclination of the electrode E are corrected and placed on the strip-shaped separator S with the relative angle of the line EL along the reference line BL as the correction amount. As a result, a welding region having an appropriate width is secured around the electrode E, and the electrode E is placed on the strip-shaped separator S. If a welding region having an appropriate width is not secured, a part of the electrode E (positive electrode) may be welded together with the separator when the two separators are welded to each other.

The cutting process, the image processing process, and the mounting process performed on the production line 1 will be described. First, the cutting process will be described. The transport device 30 transports the strip-shaped electrode ZE at a predetermined transport speed. While the band-shaped electrode ZE is being conveyed, the laser light oscillator 11 of the cutting device 10 oscillates the laser light L and outputs the laser light L to the scanner 12. In the scanner 12, the angle of each mirror is changed by each drive device in synchronization with the transfer of the strip-shaped electrode ZE. Then, in the scanner 12, the input laser light L is sequentially reflected by the two mirrors to change the irradiation direction, and the laser light L is focused by the condenser lens and directed toward the lower band-shaped electrode ZE. Irradiate. The irradiated laser beam L moves on the cutting line CL of the strip-shaped electrode ZE being conveyed. As a result, the electrode E is cut from the strip-shaped electrode ZE.

High energy is continuously applied to the portion of the band-shaped electrode ZE that is irradiated with the continuous wave laser beam L. As a result, the portion irradiated with the laser beam L is cut off by the continuously applied high-energy heat. At this time, a part of the protective layer P (ceramic or the like), the active material layer A (active material or the like), the metal leaf M or the like is melted and deteriorated by heat. The degree of melting and the degree of alteration can be increased by increasing the output of the laser beam L or reducing the cutting speed.

FIG. 3 shows a cross section of the cut portion of the electrode E. Since the amount of heat received by the laser beam L increases toward the upper side of the electrode E, the amount of melting of the active material or the like increases. Therefore, as shown in FIG. 3, the cut surface F of the electrode E is largely chipped toward the upper side, and a part of the upper protective layer P is removed. Further, the cut surface F of the electrode E is deteriorated and becomes blackish. In this way, a part of the white protective layer P is removed from the cut surface F of the electrode E, and the cut surface F is larger toward the upper side of the active material layer A, so that the active material layer A is exposed when viewed from above. Become. Therefore, when the electrode E is viewed from above, the cut surface F (end portion) of the electrode E looks blackish due to deterioration. Further, even if there is a portion where the altered portion is not formed, if the active material of the active material layer A is a black material (for example, carbon of the negative electrode active material and a composite oxide of the positive electrode active material), the electrode E The cut surface F looks blackish.

Further, in the case of cutting by melting using a continuous wave laser beam L, the thick active material layer A can also be cut in a short irradiation time. Therefore, in the cutting using the continuous wave laser beam L, the strip-shaped electrode ZE can be cut even if the transport speed and the cutting speed are set to high speeds. By increasing the transport speed and the cutting speed, the production amount of the electrode E per unit time increases, and the production efficiency becomes high.

Next, the image recognition process will be described. When the electrode E reaches a predetermined position at the end of the transfer device 30, the transfer device 60 sucks the electrodes E on the transfer device 30 with a plurality of suction pads 62. Then, in the transfer device 60, the electrode E is moved to a predetermined position of the transfer device 40 by the robot arm 61, and the electrode E is placed on the transfer device 40. The transport device 40 transports the electrode E and stops the electrode E for a predetermined time when the electrode E reaches directly under the camera 21 of the image recognition device 20. The camera 21 images the lower electrode E and outputs the captured image to the image processing unit 22. The image processing unit 22 extracts the outline of the electrode E from the image by image recognition, detects the relative position of the corner portion C of the electrode E with respect to the reference position BC, and detects the reference line BL of the line EL along the end portion of the electrode E. Detects the relative angle to.

Since the cut surface F (particularly the portion where the active material layer A is formed) which is the end portion of the electrode E is black when viewed from above, the contrast between the end portion of the electrode E and the background shown in the image. (For example, the difference in brightness) is large. Therefore, the image recognition device 20 can extract the outer line along the end portion (cut surface F) of the electrode E with high accuracy, and raises the relative position of the corner portion C of the electrode E and the relative angle of the line EL along the end portion. Can be obtained with accuracy.

Finally, the mounting process will be described. When the image recognition of the electrode E by the image recognition device 20 is completed, the transfer device 70 sucks the electrodes E on the transfer device 40 by the plurality of suction pads 72. Then, in the transfer device 70, the electrode E is conveyed by the transfer device 50 while correcting the position and inclination of the electrode E so that the relative positions and the relative angles detected by the image recognition device 20 by the robot arm 71 become zero, respectively. The band-shaped separator S inside is moved to a predetermined position, and the electrode E is placed on the band-shaped separator S.

As shown in FIG. 4A, electrodes E are sequentially placed on the strip-shaped separator S at substantially constant intervals. The line EL along the end of the electrode E placed on the strip-shaped separator S is substantially parallel to the line SL along the end of the strip-shaped separator S. By placing each electrode E on the strip-shaped separator S in this way, a welding region having an appropriate width is secured around the electrode E.

After the electrode E is placed on the strip-shaped separator S, another strip-shaped separator is placed on the electrode E. Then, for example, a welding device (not shown) sequentially moves the welding head for each electrode E to the welding region of the separator to weld the two separators to each other. Further, for example, a cutting device (not shown) cuts each electrode E wrapped in two separators. As a result, the electrode E (positive electrode) wrapped in the two welded separators S shown in FIG. 4B is produced. A welded portion W is formed on the two separators so as to surround the electrode E except for the tab T portion.

In the electrode manufacturing method including each of the above steps, the electrode E is cut from the band-shaped electrode ZE by the laser beam L, so that the contrast between the end portion (cut surface) of the electrode E and the background in the image obtained by capturing the electrode E is increased. The size is increased, and the image recognition accuracy of the end portion of the electrode E is improved. Therefore, the position and inclination of the end portion of the electrode E can be obtained with high accuracy. As a result, for example, the positive electrode E can be placed at a predetermined position on the strip-shaped separator S with high accuracy, and an appropriate welding region can be secured. This makes it possible to prevent the electrode E (positive electrode) from entering the welded portion W when the two separators are welded to each other.

Further, in the electrode manufacturing method, by using a continuous wave laser beam L, energy of a predetermined magnitude is continuously applied to the band-shaped electrode ZE, so that a thick active material layer A can be melted by heat in a short time. It can be cut and the cut surface F of the active material layer A can be discolored by heat. Since the thick active material layer A can also be cut in a short time, the transport speed and the cutting speed of the strip-shaped electrode ZE can be set high, and the production efficiency of the electrode E can be improved.

Although the embodiment of one aspect of the present invention has been described above, the embodiment is not limited to the above embodiment and may be implemented in various forms.

For example, in the above embodiment, it is applied to an electrode having a protective layer covering the active material layer, but it can also be applied to an electrode having no protective layer. In the case of an electrode without a protective layer, for example, even if the electrode has an active material layer containing a white active material (tin oxide of the negative electrode active material), the end portion of the active material layer turns black when cut by laser light. , The image recognition accuracy of the end of the electrode is improved.

Further, in the above embodiment, the step of placing the electrode (positive electrode) on the separator is shown as an example of the post-step using the position and inclination of the end of the electrode detected in the image recognition step, but other than this, the electrode Post-processes using the position and inclination of the end include, for example, a step of laminating the positive electrode and the negative electrode wrapped in the separator, a configuration of laminating only the positive electrode, and a step of laminating only the negative electrode.

Further, in the above embodiment, the position of the corner portion (position relative to the reference position) and the inclination of the end portion (angle with respect to the reference line) are detected as the information of the end portion of the electrode, but the information of the end portion of the electrode is the position. Either one of the above and the inclination may be detected, or the information at the other end may be detected.

Here, FIG. 5 is a schematic view of an electrode cut by using a cutting tool. (A) and (b) of FIG. 5 are a positive electrode Ep and a negative electrode En cut by punching using a punching die, respectively. (C) and (d) of FIG. 5 are a positive electrode Ep and a negative electrode En cut by using a roller cutter, respectively. As shown in FIG. 5, the active material layer A is exposed on the cut surface F according to the angle of the blade at the ends of the electrodes E (positive electrode Ep and negative electrode En) even when the cutting tool is used. , Discolored region AR occurs. However, the dimensions (dimensions in the direction intersecting the extending direction of the ends) Wa of the discolored region AR are all about 90 μm or less. That is, when a cutting tool is used, the size of the discolored region AR is generally less than 100 μm. This is smaller than when laser light is used, as will be described later.

Therefore, as shown in FIG. 6A, for example, when the dimension Xa of the pixel X of the camera 21 is about 50 μm, one row of pixels X is used for recognizing the discolored region AR. It will be. Therefore, it is difficult to stably recognize the end portion (region AR) of the electrode E. On the other hand, as shown in FIG. 6B, if a camera 21 having a larger number of pixels such that the dimension Xb of the pixel X is, for example, 30 μm is used, the pixels X for a plurality of rows can be used. Becomes possible. Therefore, the end portion of the electrode E can be stably recognized. However, in this case, the camera 21 becomes expensive.

On the other hand, according to the method according to the present embodiment, it is possible to stably recognize the end portion of the electrode E while avoiding the cost of the camera 21. This will be described more specifically. FIG. 7 is a schematic view of an electrode cut by using a laser beam. (A) and (b) of FIG. 7 are a positive electrode Ep and a negative electrode En cut by using a laser beam L which is a continuous wave, respectively. 7 (c) and 7 (d) are positive electrode Ep and negative electrode En cut by using the laser beam L which is a pulse wave, respectively. As shown in FIG. 7, when the laser beam L is used, the dimension Wb of the discolored region AR is larger than the dimension Wa when the cutting tool is used, for example, 100 μm or more. In particular, when the laser beam L, which is a continuous wave, is used ((a), (b) in FIG. 7), the dimension Wb is 300 μm or more.

Therefore, as shown in FIG. 8, for example, even when the dimension Xa of the pixel X of the camera 21 is about 50 μm, the pixels for a plurality of rows (for example, 4 rows) are recognized with respect to the recognition of the discolored region AR. It is possible to use X. Therefore, the end portion (region AR) of the electrode E can be stably recognized, and it is not necessary to use an expensive camera having a large number of pixels. As described above, the discolored region AR when the laser beam L is used is the region where the active material layer A different from the color of the surface layer (for example, the protective layer P) of the electrode E is exposed, and / or the surface layer and This is the region where the alteration of the active material layer A has occurred.

This action / effect will be described in more detail with reference to FIG. As shown in FIG. 9A, the discolored region AR is relatively small in the electrode E cut by using the cutting tool. Therefore, for example, pixels X for one row of the camera 21 are used for recognizing the end portion of the electrode E. Therefore, where the electrode E is in focus on the camera 21 (here, the focus is on the transport surface of the transport device 40), a sufficient contrast between the end of the electrode E and the background can occur. That is, a signal with clear contrast can be obtained. On the other hand, in a place where the electrode E is deviated from the focal point of the camera 21 due to a cause such as warpage of the electrode E, sufficient contrast may not be generated.

In other words, when a cutting tool is used, in the pixel X of one row used for recognizing the end portion of the electrode E, the pixel X whose light intensity I exceeds a predetermined threshold value TH and the pixel X which does not exceed a predetermined threshold value are Occurs. Therefore, it is difficult to stably recognize the end portion of the electrode E. When the discoloration is black, the light intensity I exceeding the threshold value means that the light intensity I becomes smaller than the threshold value.

On the other hand, as shown in FIG. 9B, the discolored region AR is relatively large in the electrode E cut by using the laser beam L. Therefore, in recognizing the end portion of the electrode E, pixels X for a plurality of rows (for example, four rows) of the camera 21 are used. Therefore, even if the contrast is lowered in the pixels X in both ends of the plurality of rows, a signal having a clear contrast can be obtained in the pixels X in the center row. In this example, even if the contrast is lowered in the pixels X in the two rows at both ends of the four rows, a signal with a clear contrast can be obtained in the pixels X in the central two rows. Therefore, the end portion of the electrode E can be reliably recognized by using the signal.

In consideration of the above points, in the cutting step, when the end of the electrode E is discolored by cutting the band-shaped electrode ZE with the laser beam L, the extending direction of the end of the electrode E (the extending direction of the cutting line CL). The size of the discolored region RA of the end portion in the direction intersecting with) can be 100 μm or more. Alternatively, in the cutting step, when the end portion of the electrode E is discolored by cutting the band-shaped electrode ZE with the laser beam L, the discolored region RA of the end portion in the direction intersecting the extending direction of the end portion of the electrode E. Can be set to be equal to or larger than the size of three pixels of the camera 21.

The above image processing may be applied to an inspection step (for example, a foreign matter inspection step) after alignment using edges, or a width after slitting the electrode in a long shape like a wound electrode. May be applied to the process of inspecting.

According to one aspect of the present invention, it is possible to provide an electrode manufacturing method and an electrode in which the image recognition accuracy of the end portion of the electrode is improved.

1 ... Production line, 10 ... Cutting device, 11 ... Laser light oscillator, 12 ... Scanner, 20 ... Image recognition device, 21 ... Camera, 22 ... Image processing unit, 30, 40, 50 ... Transfer device, 60, 70 ... Transfer Mounting device, 61, 71 ... Robot arm, 62, 72 ... Suction pad.

Claims (3)

A method for manufacturing an electrode in which an active material layer is formed on a metal foil.
A cutting process in which a strip-shaped electrode having an active material layer formed on a strip-shaped metal foil is cut by a laser beam for each electrode.
An image recognition step of detecting the end of the electrode cut in the cutting step by image recognition,
Including
Prior to the cutting step, a step of forming a protective layer for protecting the active material layer so as to cover the active material layer of the strip-shaped electrode is further included.
Wherein in the cutting step, by cutting the strip electrodes by the laser beam of a continuous wave, by removing a portion of the protective layer at the end portion of the electrode to expose the active material layer, before Symbol electrode A method for manufacturing an electrode, which discolors the end portion. The dimension of the discolored region of the end in the direction intersecting the extending direction of the end is 300 μm or more.
The method for manufacturing an electrode according to claim 1 . In the image recognition step, the end portion is detected by image recognition of the image captured by the camera.
The dimension of the discolored region of the end in the direction intersecting the extending direction of the end is equal to or larger than the dimension of three pixels of the camera.
The method for manufacturing an electrode according to claim 1 or 2 .