Electrode manufacturing method

Abstract

To provide an electrode manufacturing method capable of preventing the electrode from peeling off from the current collecting foil.SOLUTION: The electrode manufacturing method includes: a coating step of obtaining a coating by dispersing the electrode material in a solvent and applying the resulting slurry over the current collecting foil; and a drying step of drying the coating while the current collecting foil on which the coating is formed is transported inside the drying oven. The coating has three regions divided along the transport direction, including a central portion disposed at the center in the width direction and edges on both sides of the central portion. In the drying step, each edge of the coating is dried with a low-energy-density heat source, and the center of the coating is dried by a high-energy-density heat source.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present application relates to a method for manufacturing an electrode. [Background technology]

[0002] Conventionally, a method for manufacturing an electrode has been known in which a slurry obtained by dispersing an electrode material in a solvent is applied onto a current collector foil to obtain a coating film, and then the coating film is dried in a drying furnace to obtain an electrode.

[0003] For example, Patent Document 1 discloses a method for manufacturing an electrode, in which a slurry for forming an electrode composite layer is applied to a web-shaped current collecting foil, and then the current collecting foil coated with the slurry is sent in one direction in a drying furnace while applying hot air to the coating film to dry the coating film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-084383 A Summary of the Invention [Problem to be solved by the invention]

[0005] The coating film formed on the current collector foil becomes thinner at its edges than at its center due to dripping caused by surface tension. As a result, the edges of the coating film tend to dry out more quickly than the center of the coating film. As a result, the edges of the electrode obtained by drying the coating film tend to peel off from the current collector foil, which may result in a decrease in battery performance.

[0006] Therefore, a main object of the present disclosure is to provide a manufacturing method for an electrode that can suppress peeling of the electrode from the current collecting foil. [Means for solving the problem]

[0007] The present disclosure provides at least the following aspects.

[0008] The first aspect is a method for manufacturing an electrode, comprising: a coating step of coating a current collecting foil with a slurry obtained by dispersing an electrode material in a solvent to obtain a coating film; and a drying step of drying the coating film while transporting the current collecting foil on which the coating film has been formed inside a drying furnace, wherein the coating film is divided into three regions along the transport direction, and has a central portion located in the center in the width direction and end portions located on either side of the central portion, and the drying step dries each end portion of the coating film with a low energy density heat source and dries the central portion of the coating film with a high energy density heat source.

[0009] A second aspect is the electrode manufacturing method according to the first aspect, wherein in the drying step, the heat source with low energy density is hot air or a laser, and the heat source with high energy density is a laser.

[0010] A third aspect is a method for producing an electrode according to the second aspect, in which EC / EE calculated based on the following formula is 1 or more and 4 or less, where EC is the sum of the average energy densities of the heat sources irradiated to a center part of the coating film and EE is the sum of the average energy densities of the heat sources irradiated to an edge part of the coating film. (Laser average energy density (W / cm 2 ))=(laser energy density (W / cm 2 ))÷(laser irradiation length in the transport direction (mm)) × (total length of drying oven in the transport direction (mm)) (Hot air average energy density (W / cm 2 ))=(Laser average energy density (W / cm 2 )) × (Time to dry the coating using only the laser (s)) ÷ (Time to dry the coating using only hot air (s))

[0011] A fourth aspect is a method for producing an electrode according to any one of the first to third aspects, wherein the end of the coating film is a region extending from the outermost end of the coating film in the width direction to a width of 3 to 18 mm inward from the starting point in the width direction.

[0012] A fifth aspect is the method for producing an electrode according to any one of the first to fourth aspects, wherein the length of the coating film in the width direction is 1000 mm or more and 1500 mm or less.

[0013] A method for producing a battery, comprising: an electrode producing step of obtaining an electrode by using the electrode producing method according to any one of the first to fifth aspects; and a battery producing step of assembling a battery using the electrode. Effect of the Invention

[0014] According to the electrode manufacturing method of the present disclosure, it is possible to suppress peeling of the electrode from the current collecting foil, and according to the battery manufacturing method of the present disclosure, it is possible to suppress deterioration of battery performance due to electrode peeling. [Brief description of the drawings]

[0015] [Figure 1] 2 is a cross-sectional view of the drying furnace 30 cut along the transport direction X of the current collector foil 10. FIG. [Diagram 2] FIG. 2 is a plan view of the coating film 20. [Diagram 3] FIG. 2 is a side view of the coating film 20. [Figure 4] (A) Schematic diagram of pulsed irradiation in the transport direction X. (B) Schematic diagram of continuous irradiation in the transport direction X. [Diagram 5] 2 is a schematic diagram of a heat source device 132 which is an example of the heat source device 32. FIG. [Figure 6] 2 is a schematic diagram of a heat source device 232 which is an example of the heat source device 32. FIG. [Figure 7] 13 is an experimental result showing the relationship between the edge area of ​​a coating film and the residual moisture content after drying. [Figure 8] 13 is an experimental result showing the relationship between the coating position and the drying time. [Figure 9] 13 is an experimental result showing a laser energy density map. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] [Electrode manufacturing method] The method for producing an electrode according to the present disclosure will be described using one embodiment.

[0017] A manufacturing method of an electrode in one embodiment includes a coating step of coating a current collecting foil 10 with a slurry obtained by dispersing an electrode material in a solvent to obtain a coating film 20, and a drying step of drying the coating film 20 while transporting the current collecting foil 10 on which the coating film 20 has been formed inside a drying furnace 30.

[0018] <Coating process> The coating step is a step of coating a current collector foil 10 with a slurry obtained by dispersing an electrode material in a solvent to obtain a coating film 20. Such a coating step is well known. A typical example will be described below, but the present invention is not limited to this example.

[0019] The current collector foil 10 is not particularly limited as long as it is a sheet-shaped conductive member. For example, the current collector foil 10 may be a metal foil made of a metal such as stainless steel, copper, aluminum, titanium, or nickel. The metal foil may be made of an alloy containing two or more of these metals. The metal foil may also be subjected to a surface treatment such as plating. The current collector foil 10 may be made of two or more sheets of metal foil. In this case, the metal foils may be joined by an adhesive or the like, or may be joined by pressing or the like.

[0020] The electrode material includes at least an active material. The active material is a positive electrode active material or a negative electrode active material. The positive electrode active material is not particularly limited, and may be appropriately selected from known materials depending on the target battery performance. Examples include composite oxides, metallic lithium, and sulfur. The composition of the composite oxide includes, for example, at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. An example of the composite oxide is olivine-type lithium iron phosphate (LiFePO4). The negative electrode active material is not particularly limited, and may be appropriately selected from known materials depending on the target battery performance. Examples include carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, metal compounds, elements or compounds thereof that can be alloyed with lithium, and boron-added carbon. Examples of elements that can be alloyed with lithium include silicon and tin.

[0021] When the electrode material contains a positive electrode active material, the final electrode is a positive electrode, whereas when the electrode material contains a negative electrode material, the final electrode is a negative electrode.

[0022] The electrode material may optionally contain a conductive assistant. The conductive assistant is not particularly limited and may be appropriately selected from known materials depending on the intended battery performance. Examples of the conductive assistant include acetylene black, carbon black, graphite, etc.

[0023] The electrode material may optionally contain a binder. The binder is not particularly limited and may be appropriately selected from known materials according to the intended battery performance. For example, fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluorine rubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, acrylic resins such as poly(meth)acrylic acid, styrene-butadiene rubber (SBR), carboxymethyl cellulose, alginates such as sodium alginate and ammonium alginate, water-soluble cellulose ester crosslinked bodies, and starch-acrylic acid graft polymers can be mentioned.

[0024] The electrode material may optionally contain a solid electrolyte. The solid electrolyte is not particularly limited and may be appropriately selected from known materials depending on the intended battery performance. For example, oxide solid electrolytes and sulfide solid electrolytes may be mentioned.

[0025] The solvent is not particularly limited as long as it can disperse the electrode material appropriately. For example, water and organic solvents can be used. Examples of organic solvents include N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, methanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, and tetrahydrofuran. These solvents may be used alone or in combination of two or more.

[0026] The coating method is not particularly limited as long as the slurry can be applied in a thin film form to the current collector foil 10. For example, the slurry can be applied to the current collector foil 10 in any thickness using a known coating device.

[0027] <Drying process> The drying step is a step of drying the coating film 20 while transporting the current collector foil 10 on which the coating film 20 has been formed inside a drying furnace 30. An electrode is obtained by the drying step. A schematic diagram for explaining the drying step is shown in Fig. 1. Fig. 1 is a cross-sectional view of the drying furnace 30 cut along the transport direction X of the current collector foil 10.

[0028] 1, the current collector foil 10 on which the coating film 20 has been formed is transported using a plurality of transport rollers 31 installed inside a drying furnace 30. During this process, the coating film 20 is dried by a heat source device 32 installed above the coating film 20. Typically, a plurality of heat source devices 32 are installed along the transport direction of the current collector foil 10. The transport speed is not particularly limited, but is, for example, in the range of 1 to 10 m / sec.

[0029] The heat source device 32 is a device that irradiates a heat source to the coating film 20. In Fig. 1, multiple heat source devices 32 are installed in the drying furnace 30, so the coating film 20 is irradiated with the heat source multiple times. However, the number of heat source devices 32 may be changed appropriately depending on the purpose, and at least one is sufficient. In other words, the drying process requires that the heat source be irradiated to the coating film 20 at least once.

[0030] Here, the coating film 20 formed on the current collecting foil 10 is conveniently divided into three regions. Fig. 2 shows a plan view of the coating film 20. As shown in Fig. 2, the coating film 20 is divided into three regions along the transport direction X, and has a central portion 21 disposed at the center in the width direction Y, and end portions 22 disposed on both sides of the central portion 21. The width direction Y is the surface direction of the coating film 20, and is a direction perpendicular to the transport direction. The reason for dividing the coating film 20 into three regions in this way is as follows.

[0031] FIG. 3 shows a side view of the coating film 20. The coating film 20 formed on the current collector foil 10 has a thinner film thickness at its end portion 22 than at its central portion 21 due to dripping caused by surface tension. As a result, the end portion 22 of the coating film 20 dries more easily than the central portion 21 of the coating film 20. In addition, drying also progresses from the side surfaces of the coating film 20, so from this viewpoint as well, the end portion 22 of the coating film 20 dries more easily than the central portion 21 of the coating film 20. Therefore, the end portion of the electrode obtained by drying the coating film 20 is likely to peel off from the current collector foil 10, which may result in a decrease in battery performance. This problem becomes more pronounced when a laser is used as the heat source.

[0032] To address these issues, the drying process of one embodiment is characterized in that each end 22 of the coating film 20 is dried with a low energy density heat source, and the central portion 21 of the coating film 20 is dried with a high energy density heat source.

[0033] This allows the drying time of each end 22 and the central portion 21 to be adjusted to be the same, and the end of the obtained electrode can be prevented from peeling off from the current collector foil 10. "The same drying time" means that the drying completion time of the central portion 21 and each end 22 of the coating film 20 is the same in the drying furnace 30, but this does not mean that they are completely simultaneous, but rather that they have a certain time span. In addition, by making the drying time of the central portion 21 and each end 22 of the coating film 20 the same, there is an advantage that high-speed drying is possible while downsizing the equipment. Furthermore, it is also possible to reduce the amount of binder added in the electrode material, and the battery performance can be improved.

[0034] A high energy density heat source is one with an average energy density of 1W / cm 2 The heat source is, for example, a laser. Specific examples of the laser include a semiconductor laser, a direct laser, and a VCSEL laser. The laser may be one with high light-focusing properties. The frequency of laser irradiation in the transport direction may be pulsed irradiation or continuous irradiation. For reference, FIG. 4(A) shows a schematic diagram of pulsed irradiation in the transport direction X, and FIG. 4(B) shows a schematic diagram of continuous irradiation in the transport direction X.

[0035] A low energy density heat source is one that has a lower average energy density than a high energy density heat source. For example, a heat source with an average energy density of 1 W / cm 2 The heat source is less than 100°C. For example, it is hot air or laser. The temperature of the hot air is not particularly limited, but is, for example, in the range of 100°C to 120°C. The wind speed of the hot air is not particularly limited, but is, for example, 3 m / s to 50 m / s. The hot air may be irradiated only to each end 22, but may be irradiated to the entire coating film 20. By irradiating the hot air, a large amount of gaseous solvent generated in the drying furnace 30 can be discharged to the outside of the furnace. This effect is exhibited even in a form in which the hot air is irradiated only to each end 22, but is more pronounced in a form in which the hot air is irradiated to the entire coating film 20. Specific examples of the laser include a fiber laser, a direct laser, and a VCSFL laser. The laser may be a laser with high light concentration. The frequency of laser irradiation in the transport direction may be pulse irradiation or continuous irradiation (see FIG. 4).

[0036] In this way, the drying step of one embodiment can be carried out by combining a high energy density heat source and a low energy density heat source. The mechanism of simultaneously drying the coating film 20 using these heat sources is as follows. First, the central portion 21 of the coating film 20 can be dried by irradiating a high energy density heat source to the central portion 21. In addition, each end portion 22 can be dried by heat conduction from the central portion 21 to each end portion 22. Furthermore, by irradiating each end portion 22 with a low energy density heat source, combined with residual heat from the central portion 21, each end portion 22 can be dried simultaneously with the central portion 21. This allows the drying time of the central portion 21 and each end portion 22 of the coating film 20 to be adjusted to be the same.

[0037] Here, the formula for calculating the average energy density of the laser and hot air is shown below. (Laser average energy density (W / cm 2 ))=(laser energy density (W / cm 2))÷(laser irradiation length in the transport direction (mm)) × (total length of drying oven in the transport direction (mm)) (Hot air average energy density (W / cm 2 ))=(Laser average energy density (W / cm 2 )) × (Time to dry the coating using only the laser (s)) ÷ (Time to dry the coating using only hot air (s))

[0038] "Time to dry the coating film using only a laser" refers to the time it takes to dry the coating film by irradiating the entire coating film with only a laser. "Time to dry the coating film using only hot air" refers to the time it takes to dry the coating film by irradiating the entire coating film with only hot air.

[0039] When the sum of the average energy densities of the heat sources irradiated to the center 21 of the coating film 20 is EC and the sum of the average energy densities of the heat sources irradiated to the edge 22 of the coating film 20 is EE, EC / EE may be 1 or more and 4 or less. The reason for "the sum of the average energy densities of the heat sources irradiated to the center 21 of the coating film 20 is EC" is that the center 21 of the coating film 20 may be irradiated with other heat sources in addition to the high energy density heat source. For example, as shown in FIG. 5 described later, the center 21 may be irradiated with a laser and hot air. In this case, EC is the sum of the average energy densities of the laser and hot air. The same is true for EE. That is, in addition to the low energy density heat source, other heat sources may be irradiated to the edge 22 of the coating film 20. This means that the edge 22 is irradiated with multiple low energy density heat sources. For example, the edge 22 may be irradiated with a laser and hot air. In this case, EE is the sum of the average energy densities of the laser and hot air. Typically, however, end 22 is irradiated with a single low energy density heat source.

[0040] If EC / EE is less than 1, the energy density of the laser irradiated to each end 22 will be too high, and the drying time of the end 22 will be shorter than that of the central portion 21, and there is a risk that cracking or peeling of the end will not be suppressed. If EC / EE exceeds 4, the energy density of the laser irradiated to each end 22 will be too low, and there is a risk that drying of the end 22 will not be completed. From the viewpoint of further improving the effect, EC / EE may be 2 or more and 4 or less.

[0041] Here, the coating film 20 will be further described. As described above, each end 22 of the coating film 20 is dried by heat conduction from the central portion 21 irradiated with a high energy density heat source in addition to irradiation with a low energy density heat source, and is dried simultaneously with the central portion 21. For this reason, the range of each end 22 is set so that it is dried simultaneously with the central portion 21, taking into consideration the above mechanism. Therefore, the specific range of the end 22 of the coating film 20 is not particularly limited, and varies depending on the type of high energy density heat source and low energy density heat source and the average energy density. For example, when the end 22 of the coating film 20 is set as the starting point at the end in the width direction of the coating film 20, the end 22 of the coating film 20 may be a region of 3 to 18 mm from the starting point toward the inside in the width direction (i.e., the width direction length of the end 22 of the coating film 20 may be 3 to 18 mm). In addition, the end 22 of the coating film 20 may be a region of 5 to 18 mm from the starting point toward the inside in the width direction (i.e., the width direction length of the end 22 of the coating film 20 may be 5 to 18 mm).

[0042] In addition, the width direction length of the coating film 20 is not particularly limited, but the drying process of one embodiment is suitable for a coating film 20 having a long width direction length. This is because the longer the width direction length of the coating film 20, the more likely it is that uneven drying will occur. For example, the width direction length of the coating film 20 may be 1000 mm or more and 1500 mm or less.

[0043] Next, a description will be given of a heat source device 32 capable of carrying out the drying step of one embodiment. The heat source device 32 can be realized by combining a high energy density heat source device capable of irradiating a center portion 21 of the coating film 20 with a high energy density heat source and a low energy density heat source device capable of irradiating each end portion 22 of the coating film 20 with a low energy density heat source.

[0044] FIG. 5 shows a heat source device 132, which is an example of the heat source device 32. The heat source device 132 is a combination of a laser irradiation device 133, which is a high energy density heat source device, and a hot air irradiation device 134, which is a low energy density heat source device. As shown in FIG. 5, the laser irradiation device 133 has a plurality of laser irradiation units 133a arranged in the width direction, and can irradiate the center part 21 of the coating film 20 with a laser. The range indicated by L in FIG. 5 is the laser irradiation range. The number of the laser irradiation units 133a is not particularly limited, and it is sufficient that the entire width direction of the center part 21 can be set as the laser irradiation range. FIG. 5 shows an example of a laser irradiation device 133 equipped with three laser irradiation units 133a. The hot air irradiation device 134 has a length equal to or greater than the width direction of the coating film 20, and is arranged across the width direction of the coating film 20. Then, hot air can be irradiated to the entire width direction of the coating film 20. The range indicated by W in FIG. 5 is the hot air irradiation range. By using such a heat source device 132, the drying step of one embodiment can be performed, and the drying time can be adjusted to be the same for the center and ends of the coating film 20. The hot air irradiating devices 134 are not limited to being disposed across the width of the coating film 20 as shown in Fig. 5, but may be disposed on the outer side in the width direction of the laser irradiating devices 233, respectively, and may irradiate hot air to each end 22 of the coating film 20.

[0045] FIG. 6 shows a heat source device 232, which is another example of the heat source device 32. The heat source device 232 is a combination of a laser irradiation device (high energy density laser irradiation device) 233, which is a high energy density heat source device, and laser irradiation devices (low energy density laser irradiation devices) 234, 234, which are low energy density heat source devices. The average energy density of the laser irradiated from the high energy density laser irradiation device 233 is set higher than the average energy density of the laser irradiated from the low energy density laser irradiation devices 234, 234. As shown in FIG. 6, the high energy density laser irradiation device 233 is exemplified by one having a structure similar to that of the laser irradiation device 133 in FIG. 5. As shown in FIG. 6, the range indicated by L1 is the irradiation range of the high energy density laser. The low energy density laser irradiation devices 234, 234 are each disposed outside the laser irradiation device 233 in the width direction, and can irradiate the entire width direction of each end 22 of the coating film 20 with a laser. As shown in FIG. 6, the range indicated by L2 is the irradiation range of the low energy density laser. In FIG. 6, the low energy density laser irradiation devices 234, 234 are provided with one laser irradiation unit, but are not limited to this form and may be provided with a plurality of laser irradiation units.

[0046] The method for manufacturing an electrode according to the present disclosure has been described above using one embodiment. According to the method for manufacturing an electrode according to the present disclosure, peeling of the electrode from the current collecting foil can be suppressed.

[0047] [Battery manufacturing method] The manufacturing method of the battery of the present disclosure will be described using one embodiment.

[0048] One embodiment is a method for producing a battery, comprising: an electrode production step of obtaining an electrode by using the above-mentioned electrode production method; and a battery production step of assembling a battery using the electrode. Since the electrode production step has been described above, the battery production step will be described below.

[0049] The battery preparation process is a process of assembling a battery using the electrode obtained in the electrode preparation process. Such a battery preparation process is publicly known. Below, a typical example in which the electrode obtained in the electrode preparation process is a positive electrode will be described, but the present invention is not limited to this form.

[0050] When the electrode obtained in the electrode preparation step is a positive electrode, a battery is prepared using a separately prepared negative electrode and electrolyte layer.

[0051] When the electrolyte is a liquid electrolyte, a separator is placed between the positive electrode and the negative electrode, and then an electrolytic solution is supplied to the separator to fabricate a battery. The separator is mainly a polyolefin-based porous sheet. The electrolytic solution is a non-aqueous solvent in which a supporting salt is dissolved. Examples of the non-aqueous solvent include carbonates, ethers, and esters. Examples of the supporting salt include LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethane)sulfonimide (LiTFSI).

[0052] When the electrolyte is a solid electrolyte, a battery can be fabricated by disposing a solid electrolyte layer between a positive electrode and a negative electrode. The solid electrolyte layer includes a solid electrolyte. The solid electrolyte layer may also include a binder. The solid electrolyte and the binder may be appropriately selected from the solid electrolytes and binders described above.

[0053] The manufacturing method of the battery of the present disclosure has been described above using one embodiment. Since the manufacturing method of the battery of the present disclosure manufactures the electrodes based on the manufacturing method of the electrodes, peeling of the electrodes from the current collecting foil is suppressed. Therefore, the manufacturing method of the battery of the present disclosure can suppress the deterioration of the battery performance due to the peeling of the electrodes. EXAMPLES

[0054] [Relationship between the edge area of ​​the coating film and the residual moisture content after drying] A slurry obtained by dispersing the electrode material in a solvent was applied onto the current collector foil to obtain a coating film, and the current collector foil with the coating film formed thereon was then introduced into a drying furnace to dry the coating film. The width of the coating film was adjusted to 1160 mm.

[0055] The heat source device of the drying furnace was constructed following the configuration shown in Fig. 5. That is, a heat source device combining a laser irradiation device and a hot air irradiation device was used. The average energy density of the laser irradiated from the laser irradiation device was 0.44 W / cm 2 The average energy density of the hot air irradiated from the hot air irradiator was set to 0.19 W / cm. 2 The EC / EE ratio was calculated from these values ​​to be 2.32. The width of the hot air irradiation device was set to 1160 mm.

[0056] Here, the width of each end of the coating was changed to 5 mm, 10 mm, 18 mm, and 20 mm, i.e., the width of the center of the coating (laser irradiation range) was changed to 1150 mm, 1140 mm, 1124 mm, and 1120 mm, and the moisture remaining rate in the electrode end after drying was measured. The moisture remaining rate was calculated by cutting a piece of the electrode and calculating the weight ratio of the piece before and after drying. The results are shown in Figure 7.

[0057] As shown in Figure 7, when the width direction length of each end of the coating film was set to 5 mm, 10 mm, or 18 mm, the moisture remaining rate in the electrode end was 0%, and the electrode end was completely dry. On the other hand, when the width direction length of each end of the coating film was set to 20 mm, the moisture remaining rate in the electrode end was 0.16%, and the electrode end was not completely dry. From this result, it is considered desirable to set the width direction length of each end of the coating film to 18 mm or less.

[0058] [Relationship between coating position and drying time] A coating was obtained by dispersing the electrode material in a solvent and applying a slurry onto the current collector foil, and then the current collector foil with the coating was placed in a drying furnace to dry the coating. The width of the coating was adjusted to 1000 mm.

[0059] The heat source device of the drying oven was constructed following the form of Fig. 8. That is, a heat source device combining a laser irradiation device and a hot air irradiation device was used. Then, after the coating film was stopped at a predetermined position in the drying oven, the coating film was dried using a laser and hot air.

[0060] The laser irradiation device and hot air irradiation device used in the examples and comparative examples are as follows. Example: Laser average energy density 1.2 W / cm 2 A laser irradiation device capable of irradiating a laser with a width of 960 mm was used. Laser was not irradiated to the edge. In addition, a hot air irradiation device capable of irradiating hot air with a width of 1100 mm and a wind speed of 10 m / s was used. Comparative example: Laser average energy density 1.2 W / cm 2 A laser irradiation device capable of irradiating a laser with a width of 1100 mm was used. Also, a hot air irradiation device capable of irradiating hot air with a wind speed of 10 m / s and a width of 1100 mm was used.

[0061] The measurement sites 1 to 5 shown in Figure 8 will now be described. Measurement sites 1 and 5 are the edges of the coating film, and sites 2 to 4 are the measurement positions when the central part is divided into three. The drying time at each measurement site was measured from the temperatures of the front and back surfaces. The surface temperature was measured using a thermoviewer. The back surface temperature was measured using a thermocouple. The results are shown in Figure 8.

[0062] As shown in Fig. 8, in the comparative example, the drying time of the edge was shorter than that of the center, while in the example, the drying time of the center and edge was the same. From this result, it is considered that the drying time of the center and edge can be adjusted to be the same by adjusting the average energy density of the heat source irradiated to the center and edge.

[0063] [Laser energy density map] As shown in Figure 9, three laser irradiation devices 1 to 3 with different energy densities were installed. The irradiation width of each laser irradiation device was set to 400 mm. The average energy density of the laser irradiated from the laser irradiation device is as follows: Laser irradiation device 1:1W / cm2 Laser irradiation device 2: 2.5W / cm 2 Laser irradiation device 3:1W / cm 2

[0064] The laser energy density map (temperature distribution) was obtained by irradiating each laser onto a heat-resistant block and measuring the block surface with a thermoviewer. The results are shown in Figure 9.

[0065] 9, the temperature of the part irradiated by the laser irradiation device 2 was high, while the temperatures of the parts irradiated by the laser irradiation devices 1 and 3 were low. This result also suggests that the drying time of the center and the edges can be adjusted to be the same by adjusting the average energy density of the heat source irradiated to the center and edges. [Explanation of symbols]

[0066] 10 Current collecting foil 20 Coating 21 Central part 22 End 30 Drying oven 31 Transport roller 32, 132, 232 Heat source equipment 133 Laser irradiation device 134 Hot air irradiation device 233 High Energy Density Laser Irradiation Device 234 Low Energy Density Laser Irradiation Device

Claims

1. a coating step of coating a slurry obtained by dispersing an electrode material in a solvent onto a current collector foil to obtain a coating film; a drying step of drying the coating film while transporting the current collecting foil on which the coating film has been formed in a drying furnace, The coating film is divided into three regions along the transport direction, and has a central portion disposed at the center in the width direction and end portions disposed on both sides of the central portion, The drying step includes drying each of the ends of the coating film with a heat source having a low energy density and drying a central portion of the coating film with a heat source having a high energy density. A method for manufacturing an electrode.

2. 2. The electrode manufacturing method according to claim 1, wherein in the drying step, the heat source of low energy density is hot air or a laser, and the heat source of high energy density is a laser.

3. 3. The method for producing an electrode according to claim 2, wherein EC / EE calculated based on the following formula is 1 or more and 4 or less, where EC is a sum of average energy densities of the heat sources irradiated to a central portion of the coating film and EE is a sum of average energy densities of the heat sources irradiated to an end portion of the coating film. (Laser average energy density (W / cm ２ ))=(laser energy density (W / cm ２ ) ÷ (laser irradiation length in the transport direction (mm)) × (total length of the drying oven in the transport direction (mm)) (Hot air average energy density (W / cm ２ ))=(laser average energy density (W / cm ２ ) × (Time (s) to dry the coating using only a laser) ÷ (Time (s) to dry the coating using only hot air)

4. The method for producing an electrode according to any one of claims 1 to 3, wherein the end of the coating film is a region extending from an end of the coating film in a width direction thereof to an inner side of the coating film in a width direction of 3 to 18 mm from the end of the coating film in a width direction thereof.

5. The method for producing an electrode according to any one of claims 1 to 3, wherein the length of the coating film in the width direction is 1000 mm or more and 1500 mm or less.

6. An electrode preparation step of obtaining an electrode by using the electrode production method according to any one of claims 1 to 3; A battery fabrication step of assembling a battery using the electrode. How batteries are manufactured.

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