JP2021125460A - Electrode manufacturing method - Google Patents

Abstract

To provide an electrode manufacturing method capable of improving performance.SOLUTION: In a press step S2, since a molded body 22 is formed on a carrier foil 21 instead of a current collection foil 2, the molded body 22 can be formed under a thick and high-density manufacturing condition while avoiding the influence on the current collection foil 2. In a transfer step S4, the carrier foil 21 is pressed against the current collection foil 2 so as to join the molded body 22 and an adhesive layer 4 to each other, so that the molded body 22 can be transferred onto the current collection foil 2 via the adhesive layer 4. It is possible to form an active material layer 3 in a state where the performance as the electrode 1 is enhanced with respect to the current collection foil 2. Here, the adhesive layer 4 contains at least one of materials constituting the active material layer 3. Therefore, since the adhesive layer 4 can also function as a part of the active material layer, it is possible to prevent the performance of the electrode 1 from deteriorating at the position of the adhesive layer 4.SELECTED DRAWING: Figure 4

Description

The present invention relates to an electrode manufacturing method.

Conventionally, as a method for manufacturing a current collector foil and an electrode having an active material layer formed on the current collector foil, the one described in Patent Document 1 is known. In this manufacturing method, the powder of the active material layer is placed on the current collector foil and hot-pressed to form the active material layer on the current collector foil. As a result, the active material layer can be made thicker than when the slurry is applied to the current collector foil.

Japanese Unexamined Patent Publication No. 11-149918

In the above-mentioned electrode manufacturing method, pressing is performed at a high pressure in order to increase the density of the active material layer. However, when the strength of the current collector foil is low, there is a problem that the current collector foil is deformed by pressing at a high pressure. On the other hand, there is a method of suppressing deformation of the current collector foil by forming a thick and high-density active material layer precursor on the carrier foil and then transferring the active material layer precursor to the current collector foil. .. At this time, it is difficult to directly transfer the active material layer precursor to the current collector foil only by heat or pressure. On the other hand, when the transfer is performed using a general resin-based adhesive or the like, there is a problem that the performance of the electrode is affected by the mixing of unnecessary materials in the electrode.

An object of the present invention is to provide a method for manufacturing an electrode capable of improving performance.

The method for manufacturing an electrode according to one aspect of the present invention is a method for manufacturing an electrode including a current collector foil and an active material layer, in which a first active material layer precursor of the active material layer is formed on a carrier foil. An active material layer forming step to be formed, an adhesive layer forming step of forming an adhesive layer precursor of an adhesive layer for adhering the active material layer to the current collecting foil on the current collecting foil, and a first active material layer. The adhesive layer comprises a transfer step of transferring the first active material layer precursor to the current collector foil by pressing the carrier foil against the current collector foil so as to bond the precursor and the adhesive layer precursor. , At least one of the materials constituting the active material layer.

This electrode manufacturing method includes an active material layer forming step of forming a first active material layer precursor on a carrier foil. In the active material layer forming step, since the first active material layer precursor is formed on the carrier foil instead of the current collecting foil, the production conditions are thick and high density while avoiding the influence on the current collecting foil. The first active material layer precursor can be formed at. Then, in the transfer step, the carrier foil is pressed against the current collector foil so as to bond the first active material layer precursor and the adhesive layer, so that the first active material is passed through the adhesive layer to the current collector foil. The layer precursor can be transcribed. In this way, it is possible to form an active material layer in a state where the performance as an electrode is enhanced with respect to the current collector foil. Here, the adhesive layer contains at least one of the materials constituting the active material layer. Therefore, since the adhesive layer can also function as a part of the active material layer, it is possible to suppress deterioration of the electrode performance at the position of the adhesive layer. From the above, it is possible to manufacture an electrode having improved performance.

The active material layer may contain carbon as an additive and the adhesive layer may contain a carbon coat. As a result, the first active material layer precursor is adhered to the current collector foil at low pressure and low temperature.

The adhesive layer precursor may be composed of a second active material layer precursor of the active material layer. In this case, since the adhesive layer functions as the active material layer, the thickness of the active material layer as the entire electrode can be increased.

In the adhesive layer forming step, the adhesive layer precursor is formed by gravure coating or die head, and in the active material layer forming step, the first active material layer precursor is formed by extrusion molding or compression molding. May be formed. In this case, in the active material layer forming step, a sufficiently thickened first active material layer precursor can be formed. On the other hand, in the adhesive layer forming step, a paste-like adhesive layer can be formed.

In the transfer step, a plurality of first active material layer precursors formed as separate bodies from each other are transferred to the current collector foil so as to be arranged in the width direction of the current collector foil, and the plurality of first active material layers are transferred. The precursors may be transferred to the current collector foil at different times. This method can suppress the occurrence of wrinkles in the current collector foil as compared with the case of transferring one large first active material layer precursor. In addition, this method can suppress the occurrence of wrinkles in the current collector foil in the gaps between the first active material layer precursors, as compared with the case where a plurality of first active material layer precursors are transferred at one time. can.

In the transfer step, the laminate of the carrier foil, the first active material layer precursor, the adhesive layer precursor, and the current collector foil is pressed by a roller, and in the transfer step, the first active material of one of the laminates is pressed. For the first transfer step of pressing with a roller in a state where the press plate is laminated on the portion corresponding to the layer precursor, and for the portion of the laminate corresponding to the other first active material layer precursor. It may have a second transfer step of pressing with a roller at a timing different from that of the first transfer step in a state where the press plates are laminated. In this case, by using individual press plates for the plurality of first active material layers, the precursors of the respective first active material layers are collected regardless of the shape of the rollers and the uneven thickness of the laminated body. It can be evenly attached to the electric foil.

The first active material layer precursor and the adhesive layer precursor contain a binder soluble in a solvent of the same system, and the method for producing the electrode is that of the first active material layer precursor in the pre-stage of the transfer step. A solvent application step of applying a solvent to at least one of the bonding surface and the bonding surface of the adhesive layer precursor may be further provided. In this case, the bondability between the first active material layer precursor and the adhesive layer precursor can be improved. Therefore, transfer with a low load and high speed becomes possible. Further, since the elongation of the current collector foil and the first active material layer precursor can be suppressed, the deflection of the electrode can be suppressed. In addition, the floating of the first active material layer precursor can be locally suppressed.

In the solvent application step, the solvent may be applied to the bonding surface of the first active material layer precursor. In this case, the range of application of the solvent can be limited to the required range. For example, if the solvent remains on the bonding surface of the adhesive layer precursor that does not bond with the first active material layer precursor, the adhesive layer precursor may be transferred to a roller for pressing. However, such a problem can be suppressed by applying a solvent to the bonding surface of the first active material layer precursor.

In the solvent application step, the solvent may be applied to the bonding surface of the adhesive layer precursor including a region where the elongation of the first active material layer precursor is expected at the time of transfer. In this way, by applying the solvent in consideration of the elongation of the first active material layer precursor at the time of transfer, the bondability between the first active material layer precursor and the adhesive layer precursor can be improved. can.

According to the present invention, it is possible to provide a method for manufacturing an electrode capable of improving performance.

It is sectional drawing of the electrode manufactured by the manufacturing method of the electrode which concerns on embodiment of this invention. It is the schematic of the manufacturing apparatus which manufactures an electrode. It is a process drawing which shows the manufacturing method of the electrode which concerns on embodiment of this invention. It is a conceptual diagram which shows the manufacturing method of the electrode which concerns on this embodiment. It is a figure which shows the experimental result about the electrode manufactured by the manufacturing method which concerns on Example and Comparative Example. It is a process drawing which shows the manufacturing method of the electrode which concerns on the modification. It is a figure which shows the current collector foil corresponding to one electrode, the adhesive layer precursor, and the laminated body of a molded body. It is a figure which shows the state of the solvent application process. It is a figure which shows the state of the solvent application process. It is a schematic plan view which shows the state of the 1st transfer process and the 2nd transfer process. It is a schematic side view which shows the state of the 1st transfer process and the 2nd transfer process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicate description will be omitted.

First, the configuration of the electrode 1 will be described with reference to FIG. FIG. 1 is a cross-sectional view of the electrode 1 manufactured by the method for manufacturing the electrode 1 according to the present embodiment. As shown in FIG. 1, the electrode 1 includes a current collecting foil 2, an active material layer 3, and an adhesive layer 4. In the example shown in FIG. 1, the electrode 1 has an active material layer 3 and an adhesive layer 4 on both sides of the current collecting foil 2, but the active material layer 3 is provided only on one side of the current collecting foil 2. And may have an adhesive layer 4.

The current collector foil 2 is a member that extracts electricity generated by the electrode 1. The current collector foil 2 is made of an aluminum foil, a copper foil, or the like. For example, when the electrode 1 is an electrode used in a lithium ion secondary battery, either a positive electrode active material or a negative electrode active material is adopted as the active material forming the active material layer 3. Examples of the positive electrode active material include composite oxides, metallic lithium, sulfur and the like. Composite oxides include, for example, at least one of manganese, nickel, cobalt and aluminum and lithium. Examples of the negative electrode active material include 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 or boron-added carbon and the like.

The adhesive layer 4 is a layer for adhering the active material layer 3 to the main surface of the current collector foil 2. A detailed description of the adhesive layer 4 will be described later together with a description of the manufacturing method.

Next, a method for manufacturing the electrode 1 according to the present embodiment will be described with reference to FIGS. 2 to 4. FIG. 2 is a schematic view of a manufacturing apparatus 100 for manufacturing the electrode 1. FIG. 3 is a process diagram showing a method for manufacturing the electrode 1 according to the present embodiment. FIG. 4 is a conceptual diagram showing a method of manufacturing the electrode 1 according to the present embodiment.

First, the manufacturing apparatus 100 will be described with reference to FIG. As shown in FIG. 2, the manufacturing apparatus 100 includes a press unit 11 and a transfer unit 12. The press portion 11 and the transfer portion 12 are arranged so as to be aligned horizontally with each other. Here, assuming that the transport direction of the molded body 22 is the “convey direction D1”, the press portion 11 is arranged on the upstream side in the transport direction D1, and the transfer portion 12 is arranged on the downstream side in the transport direction D1.

The press portion 11 is a portion on which the material of the active material layer 3 is pressed onto the carrier foil 21 to form the molded product 22 (first active material layer precursor). The press portion 11 receives the strip-shaped carrier foil 21 flowing from the upstream side in the transport direction D1. The strip-shaped carrier foil 21 has a precursor 23 of the molded body 22 on the upper surface thereof. The precursor 23 of the molded body 22 is formed by pre-molding the material of the active material layer 3 in advance. The precursor 23 of the molded body 22 is provided in a state of being arranged at predetermined intervals along the longitudinal direction of the carrier foil 21.

The press portion 11 includes a pair of rollers 11A and 11B. The rollers 11A and 11B are arranged so as to face each other in the vertical direction with a gap thereof. Further, the rollers 11A and 11B have rotation axes that are parallel to the horizontal direction and extend in a direction orthogonal to the transport direction D1. The carrier foil 21 and the precursor 23 of the molded product 22 are supplied to the gap between the rollers 11A and the rollers 11B. The roller 11A presses the upper surface of the precursor 23 of the molded body 22, and the roller 11B presses the lower surface of the carrier foil 21. As a result, the press unit 11 transfers the precursor 23 in the transfer direction D1 while pressing the precursor 23 with the rollers 11A and 11B. As a result, the precursor 23 on the carrier foil 21 is pressed to become a high-density molded body 22.

The transfer unit 12 is a portion that transfers the molded body 22 formed by the press unit 11 to the band-shaped current collector foil 2. The transfer portion 12 receives the strip-shaped carrier foil 21 and the molded body 22 flowing from the press portion 11 on the upstream side in the transport direction D1. Further, the transfer unit 12 receives the band-shaped current collecting foil 2 which is on the upstream side in the transport direction D1 and flows from an angle different from that of the carrier foil 21. The band-shaped current collecting foil 2 has an adhesive layer precursor 27 of an adhesive layer 4 on the lower surface. The adhesive layer precursor 27 is intermittently coated so as to be arranged at a position corresponding to the molded body 22.

The transfer unit 12 includes a pair of rollers 12A and 12B. The rollers 12A and 12B are arranged so as to face each other in the vertical direction with a gap thereof. Further, the rollers 12A and 12B have rotation axes that are parallel to the horizontal direction and extend in a direction orthogonal to the transport direction D1. A carrier foil 21 on which the molded body 22 is formed and a current collecting foil 2 on which the adhesive layer precursor 27 is formed are supplied to the gap between the roller 12A and the roller 12B. The current collecting foil 2 is supplied from diagonally above the roller 12A, and is supplied to the gap between the rollers 12A and 12B while being guided by the outer peripheral surface of the roller 12A. The roller 12A presses the upper surface of the current collecting foil 2, and the roller 12B presses the lower surface of the carrier foil 21. At this time, the adhesive layer precursor 27 is pressed against the upper surface of the molded body 22. Further, since at least one of the rollers 12A and 12B has a heater, the adhesive layer precursor 27 can be pressed against the molded body 22 while being heated. By curing the adhesive layer precursor 27, the molded body 22 is fixed to the current collector foil 2. As a result, the transfer unit 12 transfers the molded body 22 to the current collecting foil 2 by pressing the carrier foil 21 against the current collecting foil 2 so as to bond the molded body 22 and the adhesive layer precursor 27.

After transferring the molded body 22 to the current collecting foil 2, the transfer unit 12 transfers the current collecting foil 2 to which the molded body 22 is adhered in the transport direction D1. On the other hand, the transfer unit 12 guides the carrier foil 21 peeled off from the molded body 22 on the outer peripheral surface of the roller 12B, and conveys the carrier foil 21 on the downstream side of the conveying direction D1 diagonally downward.

The press unit 11 and the transfer unit 12 are arranged on a straight line along the transport direction D1. The roller 11B of the press portion 11 and the roller 12B of the transfer portion 12 are arranged so as to face each other in the horizontal direction, and their upper ends are arranged at the same height position. Therefore, the carrier foil 21 and the precursor 23 pass through the gap between the rollers 11A and 11B in a horizontally extended state without being bent at the position of the press portion 11. Further, the carrier foil 21 and the molded body 22 move from the press portion 11 to the transfer portion 12 in a horizontally extended state without being bent. Further, the molded body 22 passes through the gap between the rollers 12A and 12B in a horizontally extended state without being bent at the position of the transfer portion 12.

Next, with reference to FIG. 3, the process flow of the method for manufacturing the electrode 1 according to the present embodiment will be described. As shown in FIG. 3, the manufacturing method of the electrode 1 includes a preforming step S1, a pressing step S2 (active material layer forming step), an adhesive layer forming step S3, a transfer step S4, and a cutting step S5. Be prepared.

The preforming step S1 is a step of forming the precursor 23 of the molded body 22 in the stage prior to the pressing step S2. In the preforming step S1, the powder of the material of the active material layer 3 is solidified into a desired shape. As a result, as shown in “A” of FIG. 4, the precursor 23 formed in a plate shape is arranged on the carrier foil 21. The precursor 23 contains the material P of the active material layer 3.

As an example of the preforming step S1, a method of forming the precursor 23 of the molded body 22 by extrusion molding and arranging it on the carrier foil 21 can be mentioned. In the molding method, the material of the active material layer 3 is put into the extrusion molding machine and extruded from the inside of the extrusion molding machine with a screw or the like to form the precursor 23, and the precursor 23 is arranged on the carrier foil 21.

Further, as an example of the preforming step S1, a method of forming the precursor 23 of the molded body 22 on the carrier foil 21 by compression molding using the frame body can be mentioned. In the molding method, the precursor 23 is formed by providing a frame on the carrier foil 21, putting the material of the active material layer 3 in the frame, and compression-molding the material in the frame. The carrier foil 21 itself may be provided with a groove corresponding to the shape of the precursor 23, and a material may be put in the groove and pressed.

The pressing step S2 is a step of pressing the material of the active material layer 3 (here, the preformed precursor 23) on the carrier foil 21 to form the molded body 22. As shown in “A” of FIG. 4, the precursor 23 arranged on the carrier foil 21 is pressed by the roller 11A. Specifically, in the pressing step S2, the pressing portion 11 shown in FIG. 2 presses the molded body 22 by the rollers 11A and 11B. The method for forming the molded body 22 does not include a method for forming the active material layer precursor by applying the slurry using a die head or the like. However, in the present invention, the method of forming the active material layer precursor on the carrier foil 21 is not necessarily limited to the method of molding using a press.

Here, the carrier foil 21 is a material having higher strength than the current collector foil 2. Specifically, the carrier foil 21 is made of stainless steel or the like, and the elongation due to the load during pressing is suppressed as compared with the current collector foil 2. When the molded body 22 is pressed together with the foil, the foil is stretched in the horizontal direction due to the load in the region where the molded body 22 overlaps with the molded body 22 of the foil. This extension increases in the transport direction. On the other hand, in the region that does not overlap with the molded body 22 of the foil, no load is applied and no elongation occurs. When the difference in elongation becomes large, the foil and the molded body 22 are deformed in the vertical direction such as waviness starting from the boundary between the two regions. As described above, the carrier foil 21 has less elongation than the current collector foil 2, whereby deformation of the carrier foil 21 and the molded body 22 is suppressed.

The adhesive layer forming step S3 is a step of forming the adhesive layer precursor 27 of the adhesive layer 4 that adheres the molded body 22 to the current collecting foil 2 on the current collecting foil 2. In the adhesive layer forming step S3, as shown in “B” of FIG. 4, the adhesive layer precursor of the adhesive layer 4 is placed on the current collector foil 2 at a place different from the place where the pressing is performed in the pressing step S2. 27 is formed. In the adhesive layer forming step S3, the adhesive layer precursor 27 is formed by gravure coating or using a die head. As a result, the paste-like adhesive layer precursor 27 is applied onto the current collector foil 2.

Here, the adhesive layer 4 contains at least one of the materials constituting the active material layer 3. For example, when the active material layer 3 contains carbon as an additive (conductive auxiliary), the adhesive layer 4 may contain a carbon coat. That is, as the adhesive layer precursor 27, a carbon-coated adhesive is applied to the surface of the current collector foil 2. The ratio of the thickness of the adhesive layer precursor 27 to the thickness of the molded body 22 is not particularly limited and can be appropriately set in the range of 0.1% to 10%.

Further, the adhesive layer precursor 27 may be composed of the active material layer precursor (second active material layer precursor) of the active material layer 3. When the active material layer precursor is formed on the current collector foil 2 as the adhesive layer precursor 27, a paste-like active material layer precursor in a semi-dry state is used. Although the active material layer precursor has undergone a drying step, it is not in an absolutely dry state, but is in an absolutely dry state after the molded product 22 is adhered. Therefore, the adhesive layer precursor 27 is not formed by extrusion molding or compression molding like the precursor 23 of the molded body 22, but is applied to the current collector foil 2 so that the adhesive layer precursor 27 is formed on the current collector foil 2. Is formed in. The thickness of the active material layer precursor coated on the current collector foil 2 as the adhesive layer precursor 27 is thinner than the thickness of the molded body 22. For example, the ratio of the thickness of the adhesive layer precursor 27 to the thickness of the molded body 22 is set to about 20%. However, the range of the thickness ratio is not particularly limited, and can be appropriately set in the range of 5% to 100%.

The transfer step S4 is a step of transferring the molded body 22 formed in the press step S2 to the current collector foil 2. That is, in the transfer step S4, the carrier foil 21 is pressed against the current collecting foil 2 so as to bond the molded body 22 which is the active material layer precursor and the adhesive layer precursor 27, so that the molded body is formed on the current collecting foil 2. 22 is transcribed. In the transfer step S4, as shown in “C” of FIG. 4, the molded body 22 is in a state of facing the adhesive layer precursor 27 on the current collecting foil 2, and as shown in “D”, the roller 12A is a molded body. 22 is pressed against the current collecting foil 2 via the adhesive layer precursor 27. As a result, the molded body 22 is transferred to the current collecting foil 2. Specifically, in the transfer step S4, the transfer unit 12 shown in FIG. 2 transfers the molded body 22 from the carrier foil 21 to the current collector foil 2 by the rollers 12A and 12B.

The cutting step S5 is a step of cutting the current collecting foils 2 connected in a strip shape to the size of each electrode 1. For example, as shown in FIG. 2, a gap is provided between the molded bodies 22 on the downstream side in the transport direction D1 from the transfer unit 12. In the cutting step S5, the current collecting foil 2 is cut at a gap between the molded bodies 22. In the cutting step S5, a rotary cutter, a laser cutting device, or the like is used.

Next, the action / effect of the method for manufacturing the electrode 1 according to the present embodiment will be described.

First, a method for manufacturing an electrode according to a comparative example will be described. As a method for producing an electrode according to a comparative example, a method of forming an active material layer by applying a slurry of an active material to a current collector foil 2 can be mentioned. When the thickness of the active material layer is to be increased by this production method, it is necessary to apply a thick coating of the active material slurry. However, when the slurry of the active material is thickly coated, there arises a problem that the active material layer is cracked or the like.

As a method for producing an electrode according to another comparative example, there is a method of forming an active material layer on the current collecting foil by arranging powder of the active material layer on the current collecting foil and hot pressing. According to this manufacturing method, the active material layer can be made thicker than when the slurry is applied to the current collector foil 2. In this manufacturing method, pressing is performed at high pressure in order to increase the density of the active material layer. However, when the current collector foil 2 is made of aluminum or the like and the strength of the current collector foil 2 is low, there is a problem that the current collector foil 2 is deformed by pressing at a high pressure.

As a method for producing an electrode according to still another modification, a thick and high-density active material layer precursor is formed on the carrier foil 21, and then the active material layer precursor is transferred to the current collector foil 2 to collect the active material layer. Examples thereof include a method of suppressing deformation of the electric foil 2. At this time, it is difficult to directly transfer the active material layer precursor to the current collector foil 2 only by heat or pressure. On the other hand, when the transfer is performed using an adhesive or the like, there is a problem that unnecessary materials are mixed in the electrode, which affects the performance of the electrode.

On the other hand, the method for manufacturing the electrode 1 according to the present embodiment includes a pressing step S2 (active material layer forming step) for forming the molded body 22 which is the active material layer precursor on the carrier foil 21. In the press step S2, since the molded body 22 is formed on the carrier foil 21 instead of the current collector foil 2, the molded body 22 is molded under thick and high-density manufacturing conditions while avoiding the influence on the current collector foil 2. Body 22 can be formed. Then, in the transfer step S4, the carrier foil 21 is pressed against the current collecting foil 2 so as to join the molded body 22 and the adhesive layer 4, so that the molded body 22 is pressed against the current collecting foil 2 via the adhesive layer 4. Can be transferred. In this way, it is possible to form the active material layer 3 in a state where the performance as the electrode 1 is enhanced with respect to the current collecting foil 2. Here, the adhesive layer 4 contains at least one of the materials constituting the active material layer 3. Therefore, since the adhesive layer 4 can also function as a part of the active material layer, it is possible to prevent the performance of the electrode 1 from deteriorating at the position of the adhesive layer 4. From the above, the electrode 1 having improved performance can be manufactured.

The active material layer 3 may contain carbon as an additive, and the adhesive layer 4 may contain a carbon coat. As a result, the molded body 22 is adhered to the current collector foil 2 at a low pressure and a low temperature.

The adhesive layer precursor 27 may be composed of the active material layer precursor (second active material layer precursor) of the active material layer 3. In this case, since the adhesive layer 4 functions as the active material layer, the thickness of the active material layer as a whole of the electrode 1 can be increased.

In this regard, with reference to FIG. 5, it will be described that even when the active material layer is bonded using the adhesive layer 4 made of the active material layer precursor, the deterioration of the battery characteristics is suppressed. .. The electrode on the left side of FIG. 5A shows an electrode manufactured by the manufacturing method according to the comparative example. The electrode according to the comparative example has a thick active material layer 53 by applying a slurry of the active material to the current collecting foil 2. The electrode on the right side of FIG. 5A shows an electrode manufactured by the manufacturing method according to the embodiment. The adhesive layer 4 of the electrode is formed by applying a slurry of the active material. The active material layer 3 is obtained by adhering the above-mentioned molded body 22 to the current collector foil 2 using the slurry as an adhesive layer precursor. The thickness of the current collecting foil 2 is equal to each other in the electrode according to the comparative example and the electrode according to the embodiment. Further, the sum of the thickness of the adhesive layer 4 of the electrode and the thickness of the active material layer 3 according to the embodiment is equal to the thickness of the active material layer 53 of the electrode according to the comparative example. The other conditions of the electrodes according to the comparative examples and the examples are the same. Specifically, "LCP420B", which was a positive electrode active material, is used as the active material (LFP / AB / PVdF = 85 / 7.5 / 7.5 wt%). The basis weight was 60 mg / cm ² . In addition, a battery was prepared using the electrodes according to the comparative examples and the examples. Lithium was used as the opposite electrode of these batteries. A single PE film was used as the separator. "TICU-08" was used as the electrolytic solution. The potential range was 4.1 to 2.0 V.

The battery characteristics of the above-mentioned batteries were measured. FIG. 5B is a graph showing the measurement result of the discharge curve. The solid line graph shows the results of the examples, and the dashed line graph shows the results of the comparative examples. As shown in FIG. 5B, the discharge curve of the battery using the electrodes according to the example was substantially equal to the discharge curve of the battery using the electrodes according to the comparative example. Further, FIG. 5C is a graph showing rate characteristics. As shown in FIG. 5C, the rate characteristics of the battery using the electrodes according to the examples were substantially equal to the rate characteristics of the batteries using the electrodes according to the comparative example. From the above, it can be understood that the electrode produced by laminating the active material layers has substantially the same performance as the electrode produced by single coating of the active material.

In the adhesive layer forming step S3, the adhesive layer precursor 27 is formed by using gravure coating or a die head, and in the preforming step S1, the precursor 23 of the molded body 22 is formed by extrusion molding or compression molding. May be formed. In this case, in the pressing step S2, the molded body 22 having a sufficiently increased thickness can be formed. On the other hand, in the adhesive layer forming step S3, a paste-like adhesive layer can be formed.

The method for manufacturing the electrode 1 according to the present embodiment includes a pressing step S2 in which the material of the active material layer 3 is pressed to form the molded body 22. By molding the molded body 22 by pressing in this way, a thick and high-density active material layer 3 can be obtained. Here, in the pressing step S2, pressing is performed on the carrier foil 21 having a higher strength than the current collecting foil 2. Since the carrier foil 21 as a base during pressing has high strength, deformation is suppressed. Then, in the transfer step S4, the molded body 22 is transferred to the current collector foil 2. Therefore, the current collector foil 2 is joined to the molded body 22 without being affected by the pressure at the time of pressing. From the above, it is possible to obtain a thick and high-density active material layer 3 while suppressing deformation of the current collector foil 2.

The carrier foil 21 may be made of stainless steel foil. In this case, the strength of the carrier foil 21 with respect to the press can be increased, and the peelability of the molded body 22 from the carrier foil 21 can be enhanced. Further, by increasing the thickness of the stainless steel foil to some extent, it can be reused as the carrier foil 21.

The press unit 11 that executes the press step S2 and the transfer unit 12 that executes the transfer step S4 may be arranged linearly along the transport direction D1 of the molded body 22. In this case, the thick and high-density molded body 22 is conveyed between the press portion 11 and the transfer portion 12 without being bent.

A pre-molding step S1 in which the precursor 23 of the molded body 22 is formed by extrusion molding and placed on the carrier foil 21 in the pre-stage of the pressing step S2 may be further provided. In this case, the shape of the molded body 22 can be adjusted before the pressing step S2.

A pre-molding step S1 in which the precursor 23 of the molded body 22 is formed on the carrier foil 21 using the frame body may be further provided in the step before the pressing step S2. In this case, the shape of the molded body 22 can be adjusted before the pressing step S2.

The present invention is not limited to the above-described embodiment.

For example, the electrode may be manufactured by the process as shown in the process diagram of FIG. The production method shown in FIG. 6 is different from the production method shown in FIG. 3 in that the solvent application step S10 is provided. Further, the manufacturing method shown in FIG. 6 is different from the manufacturing method shown in FIG. 3 in that the transfer step S4 includes the first transfer step S4A and the second transfer step S4B.

7 (a) and 7 (b) are views showing a laminated body of the current collecting foil 2, the adhesive layer precursor 27, and the molded body 22 corresponding to each electrode 1. FIG. 7A shows a plan view, and FIG. 7B shows a side view. A plurality of (here, two) molded bodies 22A and 22B, which are formed as separate bodies from each other, are transferred to the current collecting foil 2 corresponding to each electrode 1. Assuming that the direction orthogonal to the above-mentioned transport direction D1 is the width direction D2, the molded bodies 22A and 22B are formed so as to be aligned with the width direction D2. The state in which the molded bodies 22A and 22B are configured as separate bodies indicates a state in which the molded bodies 22A and 22B are separated from each other in the width direction D2, and the space between the two is an uncoated portion. Therefore, as shown in FIG. 7A, the current collector foil 2 has uncoated portions 2a and 2a on both sides in the width direction D2 as uncoated portions in which the molded bodies 22A and 22B are not formed. It has uncoated portions 2b and 2b on both sides of the transport direction D1 and uncoated portions 2c between the molded bodies 22A and 22B. In the preforming step S1 and the pressing step S2, the molded bodies 22A and 22B as described above are formed on the carrier foil 21.

The solvent application step S10 shown in FIG. 6 will be described. The solvent application step S10 is a step executed before the transfer step S4. In FIG. 6, the solvent application step S10 is executed after the adhesive layer forming step S3. Molds 22A and 22B and the adhesive layer precursor 27 contain a binder soluble in the same solvent (aqueous or organic solvent system). On the other hand, as shown in FIGS. 8A and 8B, in the solvent application step S10, the solvent 30 is applied to at least one of the bonding surface 22a of the molded bodies 22A and 22B and the bonding surface 27a of the adhesive layer precursor 27. do.

FIG. 8A shows how the solvent was applied to the joint surfaces 22a of the molded bodies 22A and 22B in the solvent application step S10. The joint surface 22a is a main surface opposite to the carrier foil 21. As shown in FIG. 9A, the solvent 30 is applied to the entire surface of the joint surface 22a of the molded bodies 22A and 22B. Although only the molded body 22B is shown in FIG. 9A, the same applies to the molded body 22A. In this case, in the transfer step S4, when the molded bodies 22A and 22B are pressed against the adhesive layer precursor 27, the solvent 30 adheres to the bonding surface 27a of the adhesive layer precursor 27. Note that FIG. 9A shows the molded product 22B before being pressed in the transfer step S4. When pressed in the transfer step S4, the molded body 22B is stretched by being pressed. The outer shape of the molded bodies 22A and 22B before transfer is defined as the outer shape SP1. The outer shape of the molded bodies 22A and 22B after transfer is defined as the outer shape SP2. In FIG. 9A, the post-transcriptional stretched outer shape SP2 is shown by a virtual line.

FIG. 8B shows how the solvent was applied to the bonding surface 27a of the adhesive layer precursor 27 in the solvent application step S10. The joint surface 27a is the main surface on the opposite side of the current collector foil 2. As shown in FIG. 9B, in the solvent application step S10, the solvent 30 is added to the bonding surface 27a of the adhesive layer precursor 27 including the region EX in which the molded products 22A and 22B are expected to grow during transfer. May be given. The solvent 30 is applied in a shape corresponding to the outer shape SP2 of the molded bodies 22A and 22B after the transfer and stretching. The region EX is a region between the outer shape SP1 of the molded bodies 22A and 22B before stretching and the outer shape SP2 of the molded bodies 22A and 22B after stretching after transfer. The solvent 30 is applied to the entire inner peripheral side of the outer shape SP1 and the region including the region EX. After applying the solvent 30 to the joint surface 27a, the solvent 30 that has not soaked into the adhesive layer precursor 27 is wiped off. After the wiping, the transfer step S4 is executed. In the transfer step S4, the molded bodies 22A and 22B are pressed against the region of the bonding surface 27a to which the solvent 30 is applied.

The method of applying the solvent to the joint surfaces 22a and 27a is not particularly limited, and the solvent may be applied by spraying the solvent or by applying the solvent.

Next, the transfer step S4 will be described with reference to FIGS. 10 and 11. In the transfer step S4, the two molded bodies 22A and 22B, which are formed as separate bodies from each other, are transferred to the current collector foil 2 so as to line up in the width direction D2 of the current collector foil 2. Further, the two molded bodies 22A and 22B are transferred to the current collector foil 2 at different timings from each other.

Specifically, in the transfer step S4, the carrier foil 21, the molded bodies 22A and 22B, the adhesive layer precursor 27, and the laminated body 50 of the current collecting foil 2 are the rollers 112A and 112B of the transfer unit 112 and the rollers of the transfer unit 212. Pressed at 212A and 212B. The transfer step S4 includes a first transfer step S4A for transferring at the transfer unit 112 and a second transfer step S4B for transferring at the transfer unit 212 (see FIG. 6). In addition, in FIGS. 10 and 11, only the portion of the laminated body 50 in the vicinity of the transfer portions 112 and 212 is shown, but since the carrier foil 21 and the current collector foil 2 have not been cut yet, the same as in FIG. Similarly, it is continuous in a band shape.

In the first transfer step S4A, the press plates 40A are laminated with the rollers 112A and 112B on the portion corresponding to one molded body 22A of the laminated body 50. In the second transfer step S4B, the press plate 40B is laminated on the portion of the laminated body 50 corresponding to the other molded body 22B, and the timing is different from that of the first transfer step S4A (here, the first transfer step S4B). After the transfer step S4A), the rollers 212A and 212B are used for pressing. In FIG. 10, the rollers of the transfer portions 112 and 212 are arranged only at locations necessary for pressing, and have a narrow configuration. As a result, the effect of reducing the equipment area and cost by reducing the roller width can be obtained. However, the length of the rollers of the transfer portions 112 and 212 is not particularly limited, and may have a length that reaches the entire width direction D2 of the laminated body 50. Further, the press plates 40A and 40B were arranged so that the laminated body 50 was pressed from the lower surface side (lower surface side of the current collector foil 2), but the laminated body 50 was pressed from the upper surface side (upper surface side of the carrier foil 21). It may be arranged to press from.

Next, the actions and effects of the electrode manufacturing method according to the modified examples shown in FIGS. 6 to 11 will be described.

In the transfer step S4, a plurality of molded bodies 22A and 22B configured as separate bodies from each other are transferred to the current collecting foil 2 so as to line up in the width direction D2 of the current collecting foil 2, and the plurality of molded bodies 22A and 22B are transferred. May be transferred to the current collector foil 2 at different timings. This method can suppress the occurrence of wrinkles in the current collector foil 2 in the uncoated portions 2a and 2b (see FIG. 7) as compared with the case of transferring one large molded body 22. Further, in this method, as compared with the case where a plurality of molded bodies 22A and 22B are transferred at one time, the wrinkles of the current collecting foil 2 in the uncoated portion 2c (see FIG. 7) in the gap between the molded bodies 22A and 22B are formed. Occurrence can be suppressed. Therefore, it is possible to improve the quality and yield of the post-process (sealability, foil tearing, etc.).

In the transfer step S4, the laminate 50 of the carrier foil 21, the molded bodies 22A and 22B, the adhesive layer precursor 27, and the current collecting foil 2 is pressed by the rollers of the transfer portions 112 and 212, and in the transfer step S4, the laminate 50 Among the first transfer steps S4A in which the press plate 40A is laminated on the portion corresponding to one molded body 22A and pressed by the roller of the transfer unit 112, and the other molded body 22B of the laminated body 50. The second transfer step S4B, in which the press plate 40B is laminated on the portion corresponding to the above, is pressed by the roller of the transfer unit 212 at a timing different from that of the first transfer step S4B. For example, when a roll press is performed at the transfer portion, the load is not uniformly applied due to the electrode thickness and the deflection of the roller, and the electrode is swelled too much and a floating part is generated due to insufficient sticking. In some cases. On the other hand, by using the individual press plates 40A and 40B for the plurality of molded bodies 22A and 22B, the respective molded bodies 22A and 22B can be collected regardless of the shape of the rollers and the uneven thickness of the laminated body. It can be evenly attached to the electric foil 2. It is also possible to make the rollers narrower. In this way, it is possible to obtain the effects of reducing the required load, reducing the equipment area by reducing the roller width, and reducing the cost.

The molded bodies 22A and 22B and the adhesive layer precursor 27 contain a binder soluble in the solvent 30 of the same system, and the method for producing the electrode is the bonding surface 22a of the molded bodies 22A and 22B in the pre-stage of the transfer step S4. Further, a solvent applying step S10 for applying the solvent 30 to at least one of the bonding surfaces 27a of the adhesive layer precursor 27 may be further provided. In this case, the bondability between the molded bodies 22A and 22B and the adhesive layer precursor 27 can be improved. Therefore, transfer with a low load and high speed becomes possible. Further, since the elongation of the current collecting foil 2 and the molded bodies 22A and 22B can be suppressed, the deflection of the electrode 1 can be suppressed. In addition, the floating of the molded bodies 22A and 22B can be locally suppressed.

In the solvent application step S10, the solvent 30 may be applied to the joint surface 22a of the molded bodies 22A and 22B. In this case, the range of application of the solvent 30 can be limited to the required range. For example, if the solvent 30 remains on the bonding surface 27a of the adhesive layer precursor 27 where it is not bonded to the molded bodies 22A and 22B, the adhesive layer precursor 27 may be transferred to the press roller. However, such a problem can be suppressed by applying a solvent to the joint surfaces 22a of the molded bodies 22A and 22B.

In the solvent application step S10, the solvent 30 may be applied to the bonding surface 27a of the adhesive layer precursor 27 including the region EX in which the molded products 22A and 22B are expected to grow during transfer. As described above, by applying the solvent 30 in consideration of the elongation of the molded bodies 22A and 22B at the time of transfer, the bondability between the molded bodies 22A and 22B and the adhesive layer precursor 27 can be improved.

The solvent application step S10 and the transfer steps S4A and S4B added in the process diagram of FIG. 6 do not have to be performed at the same time, and at least one of them may be performed. For example, the solvent 30 may be applied to the molded product 22 as shown in FIG. 4, which is not configured as a separate body.

For example, the electrode 1 manufactured by the manufacturing method of the present invention is not limited to the electrode of a lithium ion secondary battery, and may be an electrode used in a battery such as a nickel hydrogen secondary battery. In this case, the material of the active material layer may be changed as appropriate according to the type of battery.

The manufacturing apparatus is not limited to that shown in FIG. 2, and may be appropriately changed as long as the manufacturing method of the present invention can be carried out.

In the production method of the present invention, a step of drying the adhesive layer precursor 27 may be provided before the cutting step S5.

The method for forming the active material layer precursor of the active material layer on the carrier foil is not limited to the method by the combination of the extrusion molding, the compression molding, and the pressing process as described above.

1 ... Electrode, 2 ... Current collector foil, 3 ... Active material layer, 4 ... Adhesive layer, 21 ... Carrier foil, 22 ... Molded body (first active material layer precursor), 23 ... Precursor (first active material layer) Material layer precursor), 27 ... Adhesive layer precursor.

Claims (9)

A method for manufacturing an electrode having a current collector foil and an active material layer.
An active material layer forming step of forming a first active material layer precursor of the active material layer on the carrier foil, and
An adhesive layer forming step of forming an adhesive layer precursor of an adhesive layer that adheres the active material layer to the current collector foil on the current collector foil.
By pressing the carrier foil against the current collector foil so as to bond the first active material layer precursor and the adhesive layer precursor, the first active material layer precursor is applied to the current collector foil. With a transfer process to transfer,
A method for manufacturing an electrode, wherein the adhesive layer contains at least one of the materials constituting the active material layer. The active material layer contains carbon as an additive and contains carbon.
The method for manufacturing an electrode according to claim 1, wherein the adhesive layer contains a carbon coat. The method for producing an electrode according to claim 1 or 2, wherein the adhesive layer precursor is composed of a second active material layer precursor of the active material layer. In the adhesive layer forming step, the adhesive layer precursor is formed by gravure coating or using a die head.
The method for producing an electrode according to any one of claims 1 to 3, wherein in the active material layer forming step, the first active material layer precursor is formed by extrusion molding or compression molding. In the transfer step, a plurality of the first active material layer precursors configured as separate bodies from each other are transferred to the current collector foil so as to be arranged in the width direction of the current collector foil, and the plurality of the first active material layer precursors are transferred. The method for producing an electrode according to any one of claims 1 to 4, wherein the active material layer precursor of 1 is transferred to the current collector foil at different timings from each other. In the transfer step, the carrier foil, the first active material layer precursor, the adhesive layer precursor, and the laminate of the current collector foil are pressed by a roller.
The transfer step is
A first transfer step of laminating a press plate on a portion of the laminated body corresponding to one first active material layer precursor and pressing with a roller.
A second layer of the laminated body, in which the press plate is laminated on the portion corresponding to the other first active material layer precursor, is pressed by a roller at a timing different from that of the first transfer step. The method for manufacturing an electrode according to claim 5, further comprising a transfer step. The first active material layer precursor and the adhesive layer precursor contain a binder soluble in a solvent of the same system, and contain a binder.
Claims 1 to further include a solvent application step of applying the solvent to at least one of the bonding surface of the first active material layer precursor and the bonding surface of the adhesive layer precursor in a step prior to the transfer step. The method for manufacturing an electrode according to any one of 6. The method for producing an electrode according to claim 7, wherein in the solvent applying step, the solvent is applied to the bonding surface of the first active material layer precursor. In the solvent application step, the solvent is applied to the bonding surface of the adhesive layer precursor including a region where the elongation of the first active material layer precursor is expected at the time of transfer. 8. The method for manufacturing an electrode according to 8.

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