JP7111577B2 - Electrode sheet manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an electrode sheet having a structure in which an active material layer is formed on the surface of current collecting foil. More specifically, the present invention relates to a method of manufacturing an electrode sheet, in which the presence of hard magnetic foreign matter in the formed active material layer is also inspected.

Conventionally, as electrode sheets for batteries, those having a structure in which an active material layer is formed on the surface of a conductive collector foil have been used. An electrode sheet having such a structure is manufactured by forming an active material layer on the surface of a current collecting foil. Here, foreign substances, particularly foreign substances of hard magnetic material such as metal, may be mixed into the active material layer to be formed. Inclusion of such hard magnetic foreign matter is naturally a factor of deteriorating the quality of the electrode sheet. Therefore, it is necessary to check whether or not such hard magnetic foreign matter is mixed in by inspection.

As a technique for performing an inspection for that purpose, the technique described in Patent Document 1 can be cited. In the technique of the document, an electrode sheet (12) composed of a collector foil and an active material layer is conveyed by a magnetized first support roller (100). As a result, if hard magnetic foreign matter (P) is mixed in the active material layer, the foreign matter is magnetized. A magnetic force detection sensor (400) is arranged at a position downstream of the first support roller. As a result, the presence of a magnetized hard magnetic foreign object can be detected. The above is disclosed in [0030] to [0033] of Patent Document 1 and FIG.

Japanese Patent Application Laid-Open No. 2018-091646

However, the conventional techniques described above have the following problems. The accuracy of detection of hard magnetic foreign matter is not necessarily high. The reason for this is that hard magnetic particles move within the active material layer. The reason why the hard magnetic foreign matter can move is that the active material layer immediately after being formed is a fluid material obtained by kneading a powdery solid component and a liquid component. Therefore, when a hard magnetic foreign matter passes through the magnetic field of the first support roller, it is attracted by the magnetic force and moves toward the first support roller. This means that the hard magnetic foreign matter tends to concentrate at the position near the current collecting foil.

On the other hand, the magnetic force detection sensor is arranged on the active material layer side of the electrode sheet, not on the collector foil side. This is because the hard magnetic foreign matter in the active material layer to be detected is detected directly, not through the current collecting foil. For this reason, the hard magnetic foreign matter located closer to the current collector foil in the active material layer is located at a location not very close to the magnetic force detection sensor. For this reason, the detection accuracy does not increase so much.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art described above. That is, the object is to provide an electrode sheet manufacturing method capable of manufacturing an electrode sheet while detecting the presence of hard magnetic foreign matter with high accuracy.

In the method for producing an electrode sheet according to the first aspect or the second aspect of the present invention, in producing an electrode sheet having a structure in which an active material layer is formed on the surface of the current collector foil, A film formation process for forming an active material layer, and a magnetization process for magnetizing hard magnetic foreign matter that may be mixed in the active material layer by placing the magnetized roll facing the active material layer. and a detection step of detecting the presence of the magnetized hard magnetic foreign matter in the active material layer by facing the active material layer side surface of the electrode sheet conveyed in the magnetization step to the magnetic sensor. As a raw material for the active material layer in the film process, a wet mixture containing a solid component and a liquid component and having a weight ratio of the solid component of 70% or more and 90% or less is used.

In the electrode sheet manufacturing method of the above aspect, a wet mixture containing a solid component and a liquid component is used as a raw material for the active material layer. That is, an active material layer is formed on the surface of the collector foil in the film forming process using this raw material. In addition, the magnetization process magnetizes hard magnetic foreign matter that may be mixed in the active material layer. The electrode sheet is then subjected to a detection step in which the surface on the side of the active material layer faces the magnetic sensor. As a result, hard magnetic foreign matter is detected. Here, in the film formation step, a wet composite material in which the solid component accounts for 70% or more by weight is used. Therefore, the hard magnetic foreign matter does not move away from the magnetic sensor during the magnetization process. Therefore, it is possible to manufacture the electrode sheet while detecting the hard magnetic foreign matter with high detection accuracy. The magnetization process may be performed together with the film formation process, or may be performed later. In the magnetization step, the magnetizing roll may face the active material layer without interposing the current collecting foil, or may face the active material layer through the current collecting foil.

The method for manufacturing an electrode sheet according to the first aspect further comprises a first roll, a second roll facing the first roll, and a third roll facing the second roll but not the first roll. Using a film forming apparatus in which one or more of the first roll, the second roll, and the third roll are magnetized rolls, the film forming process is performed by wet bonding in the gap between the first roll and the second roll. A film forming step of forming an active material layer on the surface of the second roll by passing the material, and passing the current collector foil between the second roll and the third roll without contacting the first roll. Thus, the magnetization process is performed together with the film formation process or the transfer process .

In this way, the wet mixture forms a film-like active material layer on the surface of the second roll when passing through the gap between the first roll and the second roll (film forming step). Then, the active material layer is transferred onto the collector foil when passing between the second roll and the third roll (transfer step). In this manner, the film forming process is performed by the film forming apparatus having a three-roll structure. A magnetization process is also performed together with the film formation process or the transfer process. A film forming apparatus with a three-roll structure can form a film without any problem even with a wet mixture having a high solid content.

In the electrode sheet manufacturing method using a three-roll film forming apparatus, it is desirable that the third roll is a magnetizing roll, and that the magnetizing process is performed together with the transfer process. In this case, if the solid content of the wet mixture is low, the hard magnetic foreign matter will move away from the magnetic sensor during the magnetization process. However, in this embodiment, since the wet mixture having a high solid content is used, there is no such problem.

Further , in the method of manufacturing the electrode sheet of the second embodiment, the magnetization step is performed by arranging a soft magnetic roll made of a soft magnetic material at a position facing the magnetization roll with the collector foil interposed therebetween. In this way, the soft magnetic roll acts as a yoke for the magnetic field of the magnetized roll. For this reason, the magnetic flux density is high at the location where the hard magnetic foreign matter in the active material layer is magnetized, and the detection accuracy is correspondingly high. When the film-forming apparatus has the three-roll configuration described above and the third roll is a magnetized roll, the second roll is a soft magnetic roll.

In any of the above methods of manufacturing an electrode sheet, it is desirable to use a magnetized roll having a surface magnetic flux density of 0.5 T or more. If the magnetic force of the magnetized roll is too weak, the magnetization of the hard magnetic foreign matter may be weak and the detection accuracy may not be improved so much.

In the method of manufacturing the electrode sheet in which the magnetized roll faces the active material layer through the current collector foil in the magnetization step, the magnetized roll is supported and transported during the magnetization step. It is desirable to apply tension to the current collecting foil with a tension member. When the current collecting foil is under tension, the distance between the magnetizing roll and the active material layer is short during the magnetizing process. Therefore, magnetization of the hard magnetic foreign matter can be performed more reliably.

In any of the above methods of manufacturing an electrode sheet, it is desirable to further carry out a marking step of marking on the electrode sheet the location where the presence of the hard magnetic foreign matter is detected in the detection step. As a result, it is possible to easily recognize and eliminate the location where the hard magnetic foreign matter exists in the post-process.

In the case of the embodiment in which the marking process is performed, in the marking process, it is desirable to mark the non-coated area where the current collecting foil is exposed outside the width direction range where the active material layer is formed in the electrode sheet. . This is because marking itself is easier in the non-coated area than in the active material layer area, and the marking is easier to recognize in the subsequent process.

According to this configuration, there is provided a method of manufacturing an electrode sheet that can manufacture an electrode sheet while detecting the presence of hard magnetic foreign matter with high accuracy.

1 is a cross-sectional view showing the configuration of an electrode sheet manufacturing apparatus used in an embodiment; FIG. FIG. 5 is a cross-sectional view schematically showing that the positions of hard magnetic foreign matter are random even after the magnetization process. (Comparative example) FIG. 10 is a cross-sectional view schematically showing a situation in which hard magnetic foreign matter is concentrated on the collector foil side after the magnetization process. FIG. 4 is a perspective view showing the arrangement relationship between an electrode sheet and a magnetic sensor; 7 is a graph (part 1) showing an example of detection of a hard magnetic foreign object by a magnetic sensor; FIG. 10 is a perspective view showing a state where a position where a hard magnetic foreign object is detected is marked; 4 is a graph showing the results of testing the relationship between the magnetic flux density on the surface of the magnetized roll and the signal detected by the magnetic sensor. FIG. 11 is a graph (part 2) showing an example of detection of a hard magnetic foreign object by a magnetic sensor; FIG. It is a graph which shows the relationship between the distance from the surface of a magnet, and magnetic flux density.

Embodiments embodying the present invention will be described in detail below with reference to the accompanying drawings. This embodiment embodies the present invention as a method of manufacturing an electrode sheet 11 using a manufacturing apparatus 20 configured as shown in FIG. A manufacturing apparatus 20 in FIG. 1 has a film forming apparatus 1, a magnetic sensor 2, and a laser irradiator 3. Foreign matter is detected by the magnetic sensor 2 on the electrode sheet 11 formed by the film forming apparatus 1, and the location of the detected foreign matter is marked by the laser irradiator 3. FIG.

First, the film forming apparatus 1 will be described. A film forming apparatus 1 shown in FIG. All of these rolls rotate about their respective axes and are arranged parallel to each other. The yoke roll 5 is arranged close to both the film forming roll 4 and the magnetizing roll 6 with a gap therebetween. However, the film forming roll 4 and the magnetizing roll 6 are not close to each other. The rotation of the film forming roll 4 and the rotation of the yoke roll 5 are in the forward direction, and the rotation of the yoke roll 5 and the rotation of the magnetizing roll 6 are also in the forward direction.

In the film forming apparatus 1 of FIG. 1 configured as described above, the metal foil 10 is hung on the magnetizing roll 6 . The metal foil 10 does not pass through the gap between the film forming roll 4 and the yoke roll 5 but passes through the gap between the yoke roll 5 and the magnetizing roll 6 . That is, the metal foil 10 does not contact the film forming roll 4 . As a result, the metal foil 10 is conveyed as the magnetizing roll 6 rotates. A tension roll 7 is provided upstream of the magnetized roll 6 . A constant tension is applied to the metal foil 10 by the tension roll 7 . Also, the metal foil 10 on the magnetized roll 6 is brought into contact with the magnetized roll 6 without fail.

Then, the film forming material 13 is supplied to the gap between the film forming roll 4 and the yoke roll 5 from the upstream side of the rotation of the film forming roll 4 and the yoke roll 5 (arrow A). Thus, the electrode sheet 11 is obtained. The electrode sheet 11 is formed by forming an active material layer 14 on the surface of the metal foil 10 . The electrode sheet 11 is sent out from the gap between the yoke roll 5 and the magnetized roll 6 toward the downstream side of the rotation of the yoke roll 5 and the magnetized roll 6 .

Here, two processes, a film forming process and a transfer process, are performed until the film forming material 13 supplied as indicated by arrow A becomes the active material layer 14 on the surface of the metal foil 10 . The film forming process is a process in which the film forming material 13 is formed into a thin layer by passing through the gap between the film forming roll 4 and the yoke roll 5 . This thin layered film-forming material 13 is the active material layer 14 . The transfer process is a process of transferring the active material layer 14 from the surface of the yoke roll 5 to the surface of the metal foil 10 . A transfer process is performed when the active material layer 14 passes through the gap between the yoke roll 5 and the magnetization roll 6 . The film formation process and the transfer process constitute a film formation process for forming the active material layer 14 on the surface of the metal foil 10 . The electrode sheet 11 is thus manufactured. The metal foil 10 in the manufactured electrode sheet 11 functions as a collector foil in the battery.

In the film forming apparatus 1 of FIG. 1, the surface speed of the film forming roll 4, the yoke roll 5, and the magnetizing roll 6 is faster than that of the film forming roll 4. The setting is such that the magnetized roll 6 is faster. As a result, the active material layer 14 after the film forming process is placed not on the film forming roll 4 but on the surface of the faster yoke roll 5 . In addition, the active material layer 14 on the downstream side of the gap (transfer step) between the yoke roll 5 and the magnetizing roll 6 is not placed on the yoke roll 5 but on the surface of the metal foil 10 which is faster. ing.

The film-forming material 13 in the above is a wet mixture containing the electrode active material powder and the volatile liquid. Volatile liquids are liquids, such as water and alcohol, which are removed during the subsequent drying process and hardly remain in the active material layer 14 in the end. As a solid component in the film-forming material 13, an appropriate additive may be included in addition to the powder of the electrode active material. Additives include, for example, binders, thickeners, and conductive aids.

The mixing ratio of the solid components in the film-forming material 13, that is, the solid content ratio, is considerably higher than that of pastes, slurries, and the like. In other words, the content of the volatile liquid in the film forming material 13 is rather small. In this embodiment, the solid content rate of the film forming material 13 is set within the range of 70 to 90% by weight. This facilitates the subsequent drying process. The film-forming material 13, which is a wet mixture, is put into the film-forming apparatus 1 in the form of granules that have been thoroughly mixed in a granulator. In the film-forming apparatus 1 having a three-roll configuration as shown in FIG. 1, film formation can be performed without problems even with such a wet mixture having a high solid content.

In the film forming apparatus 1 of this embodiment, the magnetizing roll 6 is used as the third roll of the three-roll configuration as described above. The magnetized roll 6 incorporates a permanent magnet or an electromagnetic coil. Therefore, a magnetic field is formed on the surface of the magnetized roll 6 . The purpose of using the magnetizing roll 6 is to magnetize hard magnetic foreign matter such as iron powder that may be mixed in the active material layer 14 . That is, if hard magnetic foreign matter exists, the hard magnetic foreign matter is magnetized by the magnetic field of the magnetizing roll 6 when the active material layer 14 passes through the gap between the yoke roll 5 and the magnetizing roll 6. . Thereafter, the hard magnetic foreign matter is conveyed downstream while being magnetized. As described above, in the present embodiment, the magnetization step of magnetizing the hard magnetic foreign matter while conveying the electrode sheet 11 is performed together with the transfer step. The magnetic flux density on the surface of the magnetizing roll 6 is desirably 0.5 T or more, as will be described later.

The yoke roll 5, which is the second roll in the three-roll configuration in the film forming apparatus 1 of this embodiment, is preferably a soft magnetic roll made of a soft magnetic material. That is, the yoke roll 5 is desirably made of a material considered to have high magnetic permeability, such as low carbon steel, silicon steel, permalloy, or the like. If the material of the yoke roll 5 is such, most of the magnetic flux of the magnetized roll 6 will pass through the yoke roll 5 intensively. Therefore, the magnetic flux density in the gap between the yoke roll 5 and the magnetizing roll 6, that is, the portion where the transfer process is performed, is correspondingly high. Therefore, it is possible to more reliably magnetize the hard magnetic foreign matter passing through this portion.

Here, in the present embodiment, as described above, a wet mixture having a high solid content is used as the film-forming material 13 . This means that the active material layer 14 subjected to the magnetization process also has a high solid content. Therefore, the fluidity of the active material layer 14 is low. In other words, there is no possibility that the hard magnetic foreign matter moves within the active material layer 14 during the magnetization process. Therefore, even after the magnetization process, as shown in FIG. 2, the positions of the hard magnetic particles P in the active material layer 14 in the depth direction are random.

If a material with a low solid content and high fluidity is used as the film-forming material 13, hard magnetic foreign matter may move within the active material layer 14 during the magnetization process. The direction of movement is the direction in which the hard magnetic foreign matter is attracted to the magnetized roll 6 . Therefore, in this case, as shown in FIG. 3, the hard magnetic foreign matter P is concentrated at the position near the metal foil 10 due to the magnetization process. This poses a problem during detection, which will be described later. In contrast, in this embodiment, the hard magnetic foreign matter P is prevented from moving by using the film forming material 13 having a high solid content. 2 and 3 are for the sole purpose of schematically showing the distribution of the positions of the hard magnetic foreign matter P, and a large number of hard magnetic foreign matter P are concentrated on the actual electrode sheet 11 in this manner. It does not indicate that it is mixed with

Returning to FIG. 1, the electrode sheet 11 formed by the film forming apparatus 1 as described above is conveyed while being supported by the free rolls 8 and 9, faces the magnetic sensor 2, and then faces the laser irradiator 3. Face to face.

The magnetic sensor 2 is for detecting the existence of a hard magnetic foreign matter P that may be mixed in the active material layer 14 of the electrode sheet 11 . In the electrode sheet 11 that has reached the position facing the magnetic sensor 2 , if a hard magnetic foreign matter P is mixed, it is magnetized by the magnetizing roll 6 . Therefore, the presence of the hard magnetic foreign matter P can be detected by the magnetic sensor 2 . As the magnetic sensor 2, for example, a flux gate (FG) sensor can be used. Alternatively, a superconducting quantum interference device (SQUID) sensor or magnetoimpedance (MI) sensor can be used. The magnetic sensor 2 is provided not on the metal foil 10 side but on the active material layer 14 side with respect to the electrode sheet 11 . This is because the hard magnetic foreign matter P in the active material layer 14 is detected not through the metal foil 10 but directly.

Here, in this embodiment, as shown in FIG. 2 described above, the hard magnetic particles P in the active material layer 14 are randomly distributed without concentrating at positions near the metal foil 10 . Therefore, since the distance between the magnetic sensor 2 and the hard magnetic foreign matter P is relatively small, detection accuracy is high. If a material with a low solid content and high fluidity is used as the film forming material 13, the state shown in FIG. far away. Therefore, detection accuracy is low. In this embodiment, by using the film forming material 13 having a high solid content, high detection accuracy is obtained.

As shown in FIG. 4, the magnetic sensor 2 is provided so as to cover at least the entire formation width of the active material layer 14 on the electrode sheet 11 . Therefore, the presence of the magnetized hard magnetic foreign matter P can be detected by the magnetic sensor 2 regardless of the position within the range of the width direction W of the active material layer 14 . Assume here that a hard magnetic foreign matter P is mixed in the active material layer 14 . At this time, the output value of the magnetic sensor 2 traces the course as shown in FIG. In other words, although the noise level is generally constant at normal times, it fluctuates greatly for a moment (K in FIG. 5). Of course, this occurs when a hard magnetic foreign object P passes directly below the magnetic sensor 2 . As a result, the existence of the hard magnetic foreign matter P is detected.

The electrode sheet 11 detected by the magnetic sensor 2 further moves toward the position of the laser irradiator 3 in FIG. The laser irradiator 3 is for applying a marking to the electrode sheet 11 indicating that the hard magnetic foreign matter P has been detected. Therefore, the laser irradiator 3 irradiates the non-coated portion of the electrode sheet 11 in the width direction W, that is, the portion where the active material layer 14 is not formed and the metal foil 10 is exposed. to form an irradiation mark. The traces of irradiation may be limited to discoloration as long as they are clear, but they may be through-holes. However, through holes are more advantageous in that they can be recognized even from the back side. If the through-hole to be formed has a diameter of about 20 μm, it can be detected by an appropriate optical means in a post-process.

The timing at which the laser irradiator 3 irradiates the laser light is the timing at which the hard magnetic foreign matter P in the active material layer 14 passes through the position where the laser irradiator 3 is provided in the conveying direction of the electrode sheet 11. . This timing is calculated from the timing at which K in FIG. As a result, as shown in FIG. 6, a marking M indicating the existence of the detected hard magnetic foreign matter P is formed. Therefore, in the post-process, the existence of the hard magnetic foreign matter P can be recognized by the marking M, and the location can be excluded from the target of use.

As described above, in this embodiment, the position of the hard magnetic foreign matter P in the width direction W is not detected by the magnetic sensor 2 and is not reflected in the formation position of the marking M. However, if the electrode sheet 11 is then cut into cards and laminated together with other electrodes and separators, this is sufficient. If a magnetic sensor 2 having a positional resolution in the width direction W is used, information on the position of the hard magnetic foreign matter P in the width direction can be obtained. Using the information, the laser irradiator 3 may be configured to form the marking M at the position of the hard magnetic foreign matter P itself.

Next, the results of confirmation tests conducted by the present inventors regarding the usefulness of this embodiment will be described. This verification test was performed under the following conditions.
Type of electrode active material: Metal oxide-based lithium salt Type of additive: Binder (PVdF)
Liquid component: water solid content: 80% by weight (based on weight values measured by a precision electronic balance before and after drying)
Type of collector foil: Aluminum foil (thickness 100 μm)
Film forming device and granulator: Ricks magnetic sensor: FG sensor

In this test, SUS304 stainless steel powder having a nominal average particle size of 200 μm was intentionally added to the film forming material 13 as a hard magnetic foreign matter. This steel type itself is austenitic, but the powdery material added in this test is partly martensitic due to wear and pitting stress received during powderization. Therefore, it can be magnetized by the magnetic field of the magnetizing roll 6 .

FIG. 7 shows the relationship between the magnetic flux density on the surface of the magnetized roll 6 and the detection signal from the magnetic sensor 2. As shown in FIG. The detection signal here means the fluctuation range of the output value due to the presence of hard magnetic foreign matter, as indicated by K in the graph of FIG. As shown in FIG. 7, when the magnetic flux density on the surface of the magnetized roll 6 is less than 0.5 T (average), the detection signal is only about 40 mV. In this case, the fluctuation is not so conspicuous with respect to the noise level (see K in FIG. 8), so the improvement in detection accuracy is not so large.

On the other hand, if the magnetic flux density is 0.5 T or more on average, a detection signal of 60 mV or more is obtained as shown in FIG. This results in noticeable runout as indicated by K in FIG. Therefore, it is desirable that the magnetic flux density on the surface of the magnetizing roll 6 is 0.5 T or more. It can also be seen from FIG. 7 that even if the magnetic flux density on the surface of the magnetized roll 6 is increased steadily beyond 0.5 T, the detection signal does not increase accordingly. This is thought to be due to the magnetic susceptibility of hard magnetic foreign matter being limited. However, it is not the case that the magnetic flux density of the magnetized roll 6 is too high and the detection is hindered.

Shown in FIG. 9 is a graph showing the magnetic flux density measured for each distance from the magnetic pole surface of the magnet. In the measurement of FIG. 9, a permanent magnet with a surface magnetic flux density of 0.9 T was used. It can be seen from FIG. 9 that the magnetic flux density decreases exponentially as the distance from the surface of the magnetic pole increases. From this, it can be seen that the smaller the distance of the active material layer 14 from the surface of the magnetizing roll 6 in the magnetization process (transfer process) in the film forming apparatus 1 of FIG. 1, the better. For this reason, in the film forming apparatus 1 shown in FIG. is good. The above is the explanation of the confirmation test.

As described in detail above, according to the present embodiment, when forming the active material layer 14 on the surface of the metal foil 10 to obtain the electrode sheet 11, the film forming material 13 is wet We are going to use composite material. This prevents the hard magnetic foreign matter from moving toward the metal foil 10 when the hard magnetic foreign matter is also magnetized by the magnetizing roll 6 in the transfer process. In this way, a manufacturing method capable of manufacturing the electrode sheet 11 while detecting a hard magnetic foreign object with high precision using the magnetic sensor 2 is realized.

It should be noted that the present embodiment is merely an example, and does not limit the present invention in any way. Therefore, the present invention can naturally be improved and modified in various ways without departing from the scope of the invention. For example, the target electrode sheet 11 may be of any type. Although the example shown as the confirmation test described above is for the positive electrode of a lithium ion secondary battery, the present invention is not limited to this, and any type of battery may be used, and the positive electrode or negative electrode may be used. Also, the method of this embodiment can be applied when forming the active material layer 14 on the back surface of the electrode sheet 11 as well.

Also, the configuration of the film forming apparatus 1 may be modified. In the film forming apparatus 1 in the above embodiment, the magnetized roll 6 is used as the third roll in the three roll configuration for film formation. However, the structure is not limited to such a structure, and a structure using a magnetized roll as the first roll or the second roll in the three-roll structure may be used. It is also possible to arrange a separate magnetizing roll 6 downstream from the three-roll film forming apparatus. In that case, the yoke roll 5 is also separately arranged downstream from the three-roll film forming apparatus so as to face the magnetizing roll 6 . In that case, either the yoke roll 5 or the magnetizing roll 6 may be on the active material layer 14 side. Furthermore, the three-roll configuration itself is not essential.

Further, the provision of the tension roll 7 and the fact that the yoke roll 5 is a soft magnetic roll in the embodiment are more advantageous, but are not essential. It is not essential that the magnetic flux density on the surface of the magnetizing roll 6 is 0.5 T or more. Also, the laser irradiator 3 downstream of the magnetic sensor 2 is not essential. For example, instead of the laser irradiator 3, a small press machine may be provided to locally plastically deform the electrode sheet 11 or mechanically perforate the electrode sheet 11 for marking. A configuration in which marking is performed by adhering is also possible. Alternatively, it is also possible to provide only the information on the detection position of the hard magnetic foreign matter to the post-process without marking itself.

1 film forming device 2 magnetic sensor 4 film forming roll (first roll)
5 Yoke roll (2nd roll)
6 magnetized roll (third roll)
10 Metal foil (current collector foil)
11 Electrode sheet 13 Film-forming material (wet mixture)
14 active material layer

Claims (4)

A method for manufacturing an electrode sheet having a structure in which an active material layer is formed on the surface of a current collecting foil, comprising:
Having a first roll, a second roll facing the first roll, and a third roll facing the second roll without facing the first roll, the first roll and the second roll Using a film forming apparatus in which one or more of the third roll is the magnetized roll,
a film forming step of forming an active material layer on the surface of the current collecting foil;
a magnetizing step of causing a magnetized roll to face the active material layer to magnetize hard magnetic foreign matter that may be mixed in the active material layer;
a detection step of detecting the presence of the magnetized hard magnetic foreign matter in the active material layer by facing the active material layer side surface of the electrode sheet transported in the magnetizing step to a magnetic sensor; ，
The film formation step,
a film forming step of forming the active material layer on the surface of the second roll by passing the raw material of the active material layer through the gap between the first roll and the second roll;
transferring the active material layer onto the surface of the current collecting foil by passing the current collecting foil between the second roll and the third roll without contacting the first roll; performed by the process,
performing the magnetization step together with the film formation step or the transfer step;
A wet mixture containing a solid component and a liquid component in which the weight ratio of the solid component is 70% or more and 90% or less is used as a raw material of the active material layer in the film forming step. A method for manufacturing an electrode sheet. A method for manufacturing an electrode sheet having a structure in which an active material layer is formed on the surface of a current collector foil, comprising: a film forming step of forming an active material layer on the surface of the current collector foil;
a magnetizing step of causing a magnetized roll to face the active material layer to magnetize hard magnetic foreign matter that may be mixed in the active material layer;
a detection step of detecting the presence of the magnetized hard magnetic foreign matter in the active material layer by facing the active material layer side surface of the electrode sheet transported in the magnetizing step to a magnetic sensor;
As a raw material for the active material layer in the film forming step, using a wet composite material containing a solid component and a liquid component and having a weight ratio of the solid component of 70% or more and 90% or less,
A method of manufacturing an electrode sheet, wherein the magnetizing step is performed by arranging a soft magnetic roll made of a soft magnetic material at a position facing the magnetizing roll with the current collecting foil interposed therebetween. A method for manufacturing the electrode sheet according to claim 1,
A method of manufacturing an electrode sheet, wherein the magnetizing step is performed by arranging a soft magnetic roll made of a soft magnetic material at a position facing the magnetizing roll with the current collecting foil interposed therebetween. A method for manufacturing the electrode sheet according to claim 1 or claim 3,
The third roll is the magnetized roll,
A method for manufacturing an electrode sheet, wherein the magnetization step is performed together with the transfer step.

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