JP2017054680A - Method of manufacturing electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrode, configured to prevent transfer failure in a step of transferring a film formed of an active material paste to a foil.SOLUTION: The method includes: forming a film-like active material paste 6 to generate an active material film 7; conveying the active material film 7 by a B roll 2; performing corona discharge to the outer peripheral surface of the active material film 7 on the B roll 2 by a corona treatment device 4 so that a water contact angle may be equal to or less than 30 degrees; conveying a metal foil 9 by a C roll 3 facing the B roll 2; and bringing the metal foil 9 conveyed by the C roll 3 into contact with the outer peripheral surface of the active material film 7 subjected to corona discharge, to transfer the active material film 7 to the metal foil 9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a production method for producing an electrode for a battery by forming an active material layer on a surface of a foil.

  Conventionally, for example, in a lithium ion secondary battery, a sheet-like electrode in which an active material layer is formed on the surface of a metal foil is used. As a manufacturing method for manufacturing a sheet-like electrode, a paste containing an active material is formed into a film shape, adhered to a roll, conveyed, and brought into contact with the surface of a metal foil conveyed by another roll for transfer. There is a manufacturing method.

  For example, Patent Document 1 discloses a document that discloses a method for manufacturing an electrode. Patent Document 1 discloses a manufacturing method in which a discharge process using a corona discharger is performed on the surface of a rolling roll member that is in contact with the active material layer in the step of pressing while transporting the sheet electrode coated with the active material. Has been. In Patent Document 1, foreign matter attached to the surface of a rolling roll member is altered by corona discharge, and is easily removed by wiping with a waste cloth.

JP 2010-287545 A

  However, the conventional technique described above has the following problems. That is, when the active material formed into a film is transferred to a foil between rolls, a transfer failure may occur. The surface treatment by corona discharge is expected to be effective in suppressing transfer defects, but the above-mentioned patent document does not describe details of the treatment in the case of performing corona discharge to suppress transfer defects. . Even if corona discharge is simply performed, there is a high possibility that the effect of suppressing transfer defects cannot be sufficiently exhibited.

  The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide an electrode manufacturing method that suppresses transfer failure in a process of forming an active material paste and transferring it to a foil.

  An electrode manufacturing method for solving this problem is an electrode manufacturing method in which a layer of an active material paste is formed on the surface of a foil, and the active material paste is formed into a film to form an active material film. And a corona discharge so that the contact angle of water is 30 ° or less with respect to the outer peripheral surface of the active material film on the first roll, and the film forming step of conveying the active material film by the first roll. A corona treatment step to be performed; and the outer peripheral surface of the active material film on which the foil is conveyed by a second roll facing the first roll and subjected to corona discharge in the corona treatment step; and the second roll And a transfer step of bringing the active material film into the foil by bringing it into contact with the foil being conveyed in step (b).

  In the electrode manufacturing method according to the above aspect, after the active material paste is formed into an active material film, corona discharge is performed on the active material film. In particular, the corona discharge is set so that the contact angle of water in the treated active material film is 30 ° or less. This sufficiently increases the wettability of the outer peripheral surface of the active material film. Then, the outer peripheral surface of the active material film subjected to corona discharge is brought into contact with the foil. Therefore, the active material film can be easily transferred to the foil, and the transfer failure can be expected to be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode which suppresses the transfer defect in the process of forming an active material paste into a film and transferring to foil is implement | achieved.

It is explanatory drawing which shows the manufacturing apparatus of the electrode of this form. It is a graph which shows the change of the transfer defect rate by a contact angle. It is a graph which shows the relationship between a corona treatment amount and a contact angle.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a film forming apparatus used for manufacturing an electrode for a lithium ion secondary battery.

  A schematic configuration of the film forming apparatus 100 of this embodiment is shown in FIG. The film forming apparatus 100 of this embodiment is an apparatus for manufacturing a laminated sheet 10 in which a paste layer containing an electrode active material is formed on the surface of a metal foil. For example, there is a lithium ion secondary battery in which a wound electrode body and an electrolytic solution are enclosed in a case. For example, a wound electrode body includes a sheet-like positive electrode in which a positive electrode active material layer is formed on an aluminum foil and a sheet-like negative electrode in which a negative electrode active material layer is formed on a copper foil, with a separator interposed therebetween. It is manufactured by winding with. The laminated sheet 10 manufactured by the film forming apparatus 100 according to the present embodiment becomes an electrode for such a secondary battery through processes such as drying and pressing.

  As shown in FIG. 1, the film forming apparatus 100 of this embodiment includes an A roll 1, a B roll 2, a C roll 3, and a corona treatment apparatus 4. The B roll 2 is an example of a first roll, and the C roll 3 is an example of a second roll. The film forming apparatus 100 according to this embodiment sequentially executes a film forming process, a corona treatment process, and a transfer process in this order.

  As shown in FIG. 1, the A roll 1, the B roll 2 and the C roll 3 are parallel to each other and arranged in this order. The A roll 1 and the B roll 2 face each other with a slight gap. Further, the B roll 2 and the C roll 3 face each other with a slight gap. The A roll 1 and the C roll 3 are not opposed to each other. The corona treatment device 4 includes a discharge electrode disposed in parallel with the B roll 2 at a lower position in the drawing of the B roll 2, and performs corona discharge toward the B roll 2.

  In addition, partition plates 5 are provided on both sides in the axial direction at the upper side in FIG. 1 between the A roll 1 and the B roll 2. As shown in FIG. 1, the active material paste 6 containing the material of the active material layer and kneaded with the solvent into a paste form is separated above the A roll 1 and the B roll 2 by the partition plates 5 on both sides. Supplied during.

  In the method for manufacturing a laminated sheet by the film forming apparatus 100, the rolls 1, 2, and 3 are rotated as indicated by arrows in FIG. The rotation direction of each roll is determined so as to rotate in the forward direction with respect to each other at the position where the two rolls face each other. That is, the A roll 1 and the C roll 3 rotate in the same rotation direction, and the B roll 2 rotates in the opposite direction to the A roll 1 and the C roll 3.

  Then, the active material paste 6 supplied between the partition plates 5 is pushed downward in FIG. 1 from the gap between the A roll 1 and the B roll 2 by the rotation of the A roll 1 and the B roll 2. It is. As a result, the active material paste 6 is defined by the distance between the partition plates 5 and the size of the gap between the A roll 1 and the B roll 2 at the position where the A roll 1 and the B roll 2 face each other. The active material film 7 is formed into a film having a continuous width and thickness. This process corresponds to a film forming process.

  As for the rotational speeds of the rolls 1, 2, and 3, the peripheral speed of the A roll 1 is the slowest, and the peripheral speed of the C roll 3 is the fastest. The peripheral speed of the B roll 2 is faster than the peripheral speed of the A roll 1 and slower than the peripheral speed of the C roll 3. And the active material film | membrane 7 shape | molded between A roll 1 and B roll 2 is carry | supported by the surface of B roll 2 whose peripheral speed is faster than A roll 1, and toward FIG. It is conveyed by the B roll 2.

  Further, the length in the axial direction of each member, that is, the length in the depth direction in FIG. 1 only needs to be larger than the width of the member carried by each member. For example, a partition plate in which the length of the A roll 1 in the axial direction, the length of the B roll 2 in the axial direction, and the length of the discharge electrode of the corona treatment device 4 are the width of the active material film 7 to be formed. It is longer than the interval of 5. Further, the axial length of the C roll 3 is longer than the width of the metal foil 9 described later. The width of the metal foil 9 is not less than the width of the active material film 7. From the viewpoint of energy saving, it is preferable that the length of the discharge electrode of the corona treatment device 4 is not more than the length of the B roll 2 in the axial direction. Further, the diameters of the rolls 1, 2, 3 are not necessarily equal.

  The active material film 7 transported by the B roll 2 passes through a position facing the corona treatment device 4 as shown in FIG. The corona treatment device 4 continuously performs corona discharge at a predetermined discharge power on the active material film 7 that passes through the facing position at a constant speed. The wettability of the outer peripheral surface of the active material film 7 which is the surface facing the corona treatment device 4 is improved by corona discharge. Specifically, the outer peripheral surface of the active material film 7 is activated by receiving corona discharge energy. Further, a hydrophilic polar group is formed on the surface of the resin component of the active material film 7. In the film forming apparatus 100 of this embodiment, the output of the corona treatment apparatus 4 is set so that the contact angle of water on the outer peripheral surface of the active material film 7 after treatment is 30 ° or less. This process corresponds to a corona treatment process.

  On the other hand, the metal foil 9 is wound around the C roll 3 as shown in FIG. The metal foil 9 is drawn from a supply source such as a supply roll, and is wound around the C roll 3 on the upstream side of the C roll 3 facing the B roll 2. And the metal foil 9 is conveyed to the location facing the B roll 2 by the rotation of the C roll 3.

  The active material film 7 transported to the B roll 2 and the metal foil 9 transported to the C roll 3 come into contact with each other at a position where the C roll 3 and the B roll 2 face each other. That is, the size of the gap between the C roll 3 and the B roll 2 is smaller than the sum of the thickness of the metal foil 9 and the thickness of the active material film 7. Then, the active material film 7 moves to the C roll 3 having a faster peripheral speed at the location where the C roll 3 and the B roll 2 face each other, and is transferred to the metal foil 9. This process corresponds to a transfer process.

  Of the active material film 7, the outer peripheral surface that contacts the metal foil 9 at the location where the C roll 3 and the B roll 2 face each other is a surface whose wettability is improved by corona discharge. The transfer to 9 is performed well. Thereby, the laminated sheet 10 in which the layer of the active material film 7 is formed on the metal foil 9 is obtained. The manufactured laminated sheet 10 is conveyed by the C roll 3 and sent to the next process.

  Next, details of the corona treatment process will be described. The inventor of the present application investigated the difference in transfer failure rate depending on the output level of the corona treatment device 4 in the step of transferring the active material film for the negative electrode to the copper foil by the film forming device 100. The inventor further investigated the contact angle of water on the surface of the active material film 7 after the treatment with respect to the magnitude of the output of the corona treatment device 4. From these results, the inventor found that there is a certain relationship between the contact angle of water on the surface of the active material film 7 and the degree of occurrence of transfer failure. In other words, it has been found that a sufficient effect of suppressing transfer failure of the active material film 7 to the metal foil 9 can be obtained by performing corona discharge to make the contact angle of the active material film 7 equal to or less than a predetermined value.

  FIG. 2 shows the relationship between the contact angle of the active material film after the treatment and the degree of change in the transfer defect rate. This figure shows the size of the contact angle after processing and the ratio of the transfer failure rate after processing to the transfer failure rate during non-processing, assuming that the transfer failure rate during non-processing when corona discharge is not performed is 100. , Is shown in a graph. As shown in FIG. 2, if the contact angle of the active material film after corona discharge is 30 ° or less, the transfer failure rate becomes 1/10 or less of that during non-processing, and transfer failure is caused. It turned out that it can suppress appropriately.

  In addition, the inventor prepared an active material film obtained by molding an active material paste for a negative electrode for an experiment, performed corona discharge at a five-step treatment amount, and measured the contact angle after the treatment. Note that the active material paste for the negative electrode includes a carbon material such as graphite and a binder. As a result of this experiment, the results shown in FIG. 3 were obtained for the relationship between the throughput of the corona treatment apparatus and the contact angle of the active material film after treatment. That is, as shown in FIG. 3, the contact angle of the active material film after the corona discharge is smaller as the treatment amount of the corona treatment device is larger.

  The throughput of the corona treatment device is the amount of discharge power per unit area and unit time, and is obtained by dividing the discharge power (W) by the product of the discharge width (m) and the conveyance speed (m / min). Value. In the film forming apparatus 100, the discharge width corresponds to, for example, the width in the depth direction of the active material film 7 in FIG. 1 or the length of the discharge electrode of the corona treatment apparatus 4. Further, the transport speed is a relative speed between the corona treatment apparatus and the object to be treated. In the film forming apparatus 100, for example, the transport speed of the active material film 7 or the active material film 7 on the B roll 2 is measured. Corresponds to the peripheral speed of the surface.

  In this experiment, the amount of corona treatment was changed by changing the conveying speed of the active material film, and the water contact angle of the active material film after treatment at each treatment amount was measured. In the experiment, corona discharge was performed with a discharge power of a maximum output of 4 kW using a ceramic electrode type corona treatment apparatus with a discharge width of 0.25 m. At this time, the processing speed at each transport speed was calculated by changing the transport speed of the active material film. Furthermore, the contact angle of water was measured at three locations on the surface of the treated active material film, and the average value was calculated. The contact angle of water was measured using a general measuring device using image processing. The difference in contact angle depending on the measurement location was small.

As shown in FIG. 3, the contact angle of the active material film before the corona discharge was about 42 °. It was found that the contact angle after the treatment could be 30 ° or less if the treatment amount of the corona treatment device was 250 W · min / m ² or more. As described above, 30 ° is a good contact angle at which the transfer failure rate can be reduced to 1/10 or less of that during non-processing.

Therefore, in the film forming apparatus 100 of this embodiment, the use conditions of the corona treatment apparatus 4 are set so that the contact angle of water in the processed active material film 7 is 30 ° or less. This use condition is satisfied by setting the combination of discharge power, discharge width, and conveyance speed so that the processing amount of the corona treatment device 4 becomes a predetermined value of 250 W · min / m ² or more. Therefore, it can be expected that the transfer failure is about 1/10 compared to the case where the corona discharge by the corona treatment device 4 is not performed.

  As described in detail above, according to the electrode manufacturing method of the present embodiment, the active material paste 6 is formed into a film shape by the A roll 1 and the B roll 2 in the film forming apparatus 100, and the active material film 7. Then, the active material film 7 is conveyed by the B roll 2. Further, the outer peripheral surface of the active material film 7 on the B roll 2 is treated by corona discharge so that the contact angle of water is 30 ° or less. Then, the active material film 7 is transferred to the metal foil 9 by bringing the outer peripheral surface treated by corona discharge into contact with the metal foil 9 conveyed by the C roll 3. Since the active material film 7 whose wettability is improved so that the contact angle is 30 ° or less and the metal foil 9 are brought into contact with each other, transfer defects can be suppressed in the process of forming the active material paste and transferring it to the foil. I can expect.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.

  For example, the present invention can also be applied to a positive electrode. In addition, the manufacturing method for forming a sheet-like electrode by forming a layer of an active material paste on a metal plate can be applied not only to an electrode for a lithium ion secondary battery but also to an electrode manufacturing method for various batteries. It is. Further, for example, the film forming method for forming the active material paste into a film shape is not limited to the method using the gap of the roll.

2 B roll 3 C roll 4 Corona treatment device 6 Active material paste 7 Active material film 9 Metal foil

Claims (1)

An electrode manufacturing method for forming an active material paste layer on a surface of a foil, comprising:
A film forming step of forming the active material paste into a film to form an active material film, and transporting the active material film by a first roll;
A corona treatment step of performing corona discharge so that the contact angle of water is 30 ° or less with respect to the outer peripheral surface of the active material film on the first roll;
The foil is transported by the second roll facing the first roll, and is transported by the outer peripheral surface of the active material film subjected to corona discharge in the corona treatment step, and by the second roll. A transfer step of contacting the foil and transferring the active material film to the foil;
A method for producing an electrode, comprising:

Images