Manufacturing method and manufacturing apparatus for electrodes for power storage devices

Abstract

Provided is a manufacturing method and apparatus for electrodes for power storage devices, which can reduce the size of electrode coating equipment, improve the electrode production speed, and reduce running costs. [Solution] A method for manufacturing an electrode for an electricity storage device, comprising: step A of applying a slurry to a roll-shaped current collector transported in one direction at a predetermined speed; step B of heating the applied slurry to a temperature of 30°C or higher and lower than the boiling point of the dispersion medium in the slurry; and step C of irradiating the slurry applied to the current collector with laser light having a wavelength of 435 nm or more and less than 550 nm, or 890 nm or more and less than 1100 nm, from a laser irradiation unit, wherein the slurry contains 0.1 mass % or more of carbon relative to the solid content of the slurry.

Description

[Technical field]

[0001] The present invention relates to a method and an apparatus for manufacturing an electrode for an electricity storage device.

[0002] Energy storage devices play an important role in mobile vehicles such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles, as well as in power storage systems. These devices are increasingly being positioned as important key devices from the perspective of economic growth, and with the recent increase in demand, there is a strong demand for improving the productivity of energy storage devices. The main types of energy storage devices are secondary batteries and capacitors.

[0003] Commonly available general-purpose secondary batteries include lead-acid batteries, nickel-metal hydride (Ni-MH) batteries, nickel-cadmium (Ni-Cd) batteries, lithium-ion batteries, etc. In particular, the demand for lithium-ion batteries is rapidly increasing as a representative example of non-aqueous electrolyte secondary batteries due to their characteristics of small size, light weight, high voltage, and no memory effect.

[0004] A non-aqueous electrolyte secondary battery is a general term for a battery system that uses an electrolyte that does not contain water as a main component, and is a chargeable and dischargeable electricity storage device. Specific examples include lithium ion batteries, lithium polymer batteries, lithium solid-state batteries, lithium air batteries, lithium sulfur batteries, sodium ion batteries, sodium sulfur batteries, potassium ion batteries, multivalent ion batteries, and fluoride ion batteries. These batteries are composed of a positive electrode, a negative electrode, an electrolyte, and an exterior body (storage case), and when the electrolyte has fluidity, a separator is interposed between the positive electrode and the negative electrode.

[0005] Representative capacitors include aluminum electrolytic capacitors, ceramic capacitors, electric double layer capacitors, lithium ion capacitors, etc. Among these, lithium ion capacitors are electricity storage devices based on the basic principle of electric double layer capacitors, and use active materials in which either the positive or negative electrode material can absorb and release lithium ions, and a non-aqueous electrolyte.

[0006] In recent years, development of electricity storage devices using sodium ions, potassium ions, magnesium ions, calcium ions, etc. instead of lithium ions has also been progressing. Such ion capacitors are composed of a positive electrode, a negative electrode, a separator, an electrolytic solution or electrolyte, and an exterior body (also called a battery container, storage case, or casing).

[0007] In a power storage device as a component of an electrode, a current collector and a composite layer (active material layer) exist. For example, in a nickel-hydrogen battery, nickel steel foil or nickel foam is used as a current collector, and a composite layer containing an active material such as nickel hydroxide or a hydrogen storage alloy is provided on the current collector.

[0008] On the other hand, in lithium ion batteries, aluminum foil or copper foil is used as a current collector, and a composite layer containing lithium transition metal oxide, graphite, or other active material as a main component is provided, while in lithium ion capacitors, aluminum foil or copper foil is used as a current collector, and a composite layer containing activated carbon, graphite, or other active material is provided.

[0009] Such active materials are synthesized, for example, by a calcination method or a hydrothermal method. After synthesis, the particles are granulated to a particle size of about 5 to 30 μm using a technique such as spray drying, and then further subjected to a classification process for production.

[0010] There are various types of electrodes, including positive electrodes, negative electrodes, reference electrodes, and bipolar electrodes. All of them can be made using active materials, conductive assistants, binders, and current collectors. In a typical electrode manufacturing process, a slurry (a mixture with a paste-like fluidity) is applied or filled onto a current collector, and the dispersion medium contained in the slurry is evaporated and removed (dried), after which the composite layer is pressure-adjusted using a roll press or the like. This slurry is made up of liquid and solid components, and when manufacturing an electrode, it is necessary to mix the active materials, conductive assistants, binders, and the like with the dispersion medium to give it fluidity.

[0011] In the drying process of the slurry, if the slurry applied to the current collector is dried rapidly, a phenomenon in which the binder or thickener is unevenly distributed on the surface (surface layer) of the composite layer, that is, migration, is observed. In an electrode where such migration has occurred, the binding strength between the current collector and the composite layer is reduced, and as a result, the composite layer is easily removed or peeled off. Furthermore, when such an electrode is used as a battery, it causes a decrease in cycle characteristics and an increase in internal resistance.

[0012] One possible solution to this problem would be to slow down the drying speed of the slurry, but this would result in a drop in productivity. At electrode production sites, the length of the drying oven (the area where the electrodes are heated to vaporize and remove the dispersion medium) after coating is increased to increase the conveying speed and improve productivity. However, it is clear that increasing the length of the drying oven itself would require large-scale equipment, which would entail the drawbacks of requiring a large site area and increasing energy consumption.

[0013] Incidentally, the process of drying the slurry can be divided into three stages: a material preheating stage, a constant-rate drying stage, and a falling-rate drying stage. For example, Patent Document 1 describes the stage in which the surface of the coating film is heated to the evaporation temperature of the solvent as the "material preheating stage," the stage in which the solvent content in the coating film decreases almost linearly as the solvent evaporates from the surface of the coating film as the "constant-rate drying stage," and the stage in which the solvent evaporates gently from the fine gaps between the particles that make up the coating film as the "falling-rate drying stage." An electrode manufacturing method has been proposed in which the atmospheric pressure and drying temperature are set higher in the constant-rate drying stage than in the material preheating stage and the falling-rate drying stage. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] JP 2015-185250 A Summary of the Invention [Problem to be solved by the invention]

[0015] In the above-mentioned energy storage devices, not only is there a need to increase production speed, but there is also a need to reduce running costs. In the current electrode production process, the mainstream drying method is to use hot air or radiation. However, this method heats up the air and peripheral equipment that are not being dried, resulting in a lot of wasted energy.

[0016] The inventors focused on a technology that uses a laser in the drying process in order to reduce the energy consumed in the manufacturing process. In recent years, laser light irradiation devices have become smaller, and the wavelength of light that can be used has also increased. Furthermore, with the advent of fiber lasers, the light of multiple semiconductor lasers can be amplified by fiber, improving the convenience of high-power lasers.

[0017] There are various types of laser irradiation devices, such as solid-state lasers, gas lasers, fiber lasers, and semiconductor lasers. These lasers have in common that they store energy in a laser medium and generate light through the phenomenon of stimulated emission. In addition, amplification of the generated light is also one of the main features of lasers.

[0018] It was found that if the electrode slurry contains carbon materials such as graphite or amorphous carbon, the carbon absorbs energy and generates heat when exposed to laser light, which allows the dispersion medium in the slurry to evaporate. As a result, only the parts of the slurry irradiated with the laser light can be heated instantly, and the energy required is less than half that required by conventional drying methods using hot air or radiation. Furthermore, it is possible to shorten the length of the drying oven or increase the conveying speed, which is expected to improve electrode productivity.

[0019] However, as a result of the inventors' investigations, it was found that drying means using only laser light has the drawback that migration is likely to occur because the temperature of the slurry is momentarily increased.

[0020] According to Patent Document 1, migration is particularly likely to occur during the constant-rate drying period in a series of drying processes. In other words, migration is likely to occur if drying is rapid during the constant-rate drying period or an earlier stage (material preheating period). However, when drying is performed using laser light, migration is less likely to occur during the falling-rate drying period, but on the other hand, the amount of dispersion medium, which is a vaporized component, is small, so the temperature rises suddenly, making it difficult to control the temperature.

[0021] The present invention has been made in view of the above, and a main object of the present invention is to provide a manufacturing method and a manufacturing apparatus for manufacturing electrodes with high productivity without causing migration. [Means for solving the problem]

[0022] In order to achieve the above-mentioned object, one embodiment of the present invention provides a method for manufacturing an electrode for an electricity storage device, comprising: step A of applying a slurry to a current collector transported at a predetermined speed; step B of heating the applied slurry at a temperature of 30°C or higher and lower than the boiling point of the dispersion medium in the slurry; and step C of irradiating the slurry applied to the current collector with laser light having a wavelength of 435 nm or higher and lower than 550 nm, or 890 nm or higher and lower than 1100 nm, from a laser irradiation unit, wherein the slurry contains 0.1 mass % or more of carbon with respect to the solid content of the slurry.

[0023] According to this configuration, after the step B of heating the slurry, the step C of heating the slurry using a laser is performed, so that it is possible to manufacture electrodes with high productivity while suppressing the occurrence of migration.

[0024] In this method for manufacturing an electrode for an electricity storage device, the laser light is desirably an area beam having an irradiation length of 1 cm or more in the MD direction of the current collector.

[0025] According to this configuration, from the viewpoint of suppressing migration and producing a homogeneous electrode, it is desirable that the laser light be an area beam that can irradiate a certain area, rather than a spot beam that irradiates a pinpoint or a line beam that irradiates a long and narrow laser light.

[0026] In addition, in the method for producing an electrode for an electricity storage device, the laser light is an area beam that is irradiated onto a current collector on which no slurry has been applied in the TD direction of the current collector.

[0027] According to this configuration, by irradiating the current collector at the boundary portion where the slurry is applied with laser light, the temperature of the current collector is raised, and the temperature of the slurry is raised from the current collector side as well, which contributes to drying and improves compatibility with the slurry.

[0028] In this method for producing an electrode for an electricity storage device, the step C is characterized in that laser light is simultaneously irradiated from a plurality of laser irradiation units to form overlapping area beams.

[0029] According to this configuration, when the material of the current collector used in the electrode for the power storage device is a metal such as Al, Cu, Ni, Ti, Cr, Mo, Ru, W, or stainless steel, it has a property of reflecting laser light more easily than the slurry, but when the current collector, which is the uncoated portion, is irradiated with laser light at an output that can dry the slurry, the current collector is easily oxidized, while the slurry may not be sufficiently dried with a low-output laser light adjusted to a level where the current collector is not oxidized. Therefore, by overlapping the laser light irradiated to the slurry, it is possible to sufficiently dry the slurry.

[0030] In this case, the overlapping area beams are characterized in that they irradiate the boundary between the coated portion and the uncoated portion of the slurry.

[0031] According to this configuration, the boundary between the coated and uncoated parts of the slurry, i.e., the boundary between the slurry and the current collector, is irradiated with overlapping laser light, so that the slurry at the boundary can be thoroughly dried. This allows the part that is more likely to peel off than other parts to be dried reliably, and peeling of the slurry can be prevented.

[0032] Moreover, in the manufacturing method of an electrode for an electricity storage device, the step C is characterized in that laser light is irradiated from a plurality of laser irradiation units, a first laser irradiation unit irradiates the laser light over the entire width direction of the slurry applied to the current collector, and a second laser irradiation unit irradiates the slurry applied to the current collector including at the boundary between the coated and uncoated areas.

[0033] According to this configuration, the boundary between the coated and uncoated parts of the slurry, i.e., the boundary between the slurry and the current collector, can be irradiated with the laser light multiple times, and the slurry at the boundary can be thoroughly dried. This allows the part that is more likely to peel off than other parts to be dried reliably, and peeling of the slurry can be prevented.

[0034] Moreover, the method for producing an electrode for an electricity storage device is characterized by further comprising, after step C, step D of heating the applied slurry.

[0035] According to this configuration, by providing a step D of further heating and drying the slurry after drying the slurry with the laser from the laser irradiation unit in the step C, the slurry can be dried more reliably.

[0036] According to this configuration, after the step B of heating the slurry, the step C of heating the slurry using a laser is performed, so that it is possible to manufacture electrodes with high productivity while suppressing the occurrence of migration.

[0037] This method for producing an electrode for a power storage device is characterized in that the wavelength of the laser irradiation unit in step C is a laser beam having a wavelength of 435 nm or more and less than 550 nm, or a wavelength of 890 nm or more and less than 950 nm. With this configuration, it is possible to obtain a certain output and improve the drying speed while using a wavelength that can dry the slurry. Note that a wavelength of 890 nm or more and less than 950 nm is more preferable because a semiconductor laser can be used to achieve high output and has high electrical efficiency.

[0038] According to this configuration, the slurry does not contain sulfur. Although there are secondary batteries using electrodes containing sulfur in non-aqueous electrolyte secondary batteries, the inventors of the present application have tested and studied the slurry containing sulfur or a sulfur-carbon composite, and have found that when the slurry contains sulfur or a sulfur-carbon composite, the vapor pressure of the sulfur increases and evaporation or sublimation easily occurs when the slurry contains sulfur or a sulfur-carbon composite.

[0039] In addition, sulfur, hydrogen sulfide, sulfur dioxide, and other sulfur-based gases can corrode metals even at low concentrations, and can cause serious damage to metal components in electronic devices. In particular, in laser irradiated areas, not only do metal contacts and wiring corrode, but also sulfur adheres to optical components, causing a significant decrease in the laser output, light flux, and quality. For this reason, in drying using laser light, it is desirable for the slurry to contain an active material that does not contain sulfur or sulfur-carbon composites.

[0040] This method for producing an electrode for a power storage device is characterized in that the step C irradiates the laser beam to the slurry in a constant-rate drying period when the solid content is 60% or more and 95% or less. According to this configuration, if the laser beam is irradiated during the initial drying period when the solid content is less than 60%, migration is likely to occur due to a sudden increase in temperature, but if the solid content is 60% or more, migration can be easily suppressed.

[0041] In this case, among the material preheating period, the constant rate drying period, and the falling rate drying period in the process of drying the slurry, the process B is characterized by comprising the material preheating period and a process of concentrating the solid content of the slurry so that the solid content rate is 60% or more and 95% or less, to obtain a slurry for the constant rate drying period.

[0042] In this method for producing an electrode for a power storage device, it is preferable that the step A is intermittent coating or stripe coating. According to this configuration, the step of applying the slurry is preferably intermittent coating or stripe coating, because it is preferable that the applied slurry has a coating shape that makes it easy to irradiate the current collector with laser light, not just the applied slurry.

[0043] This method for producing an electrode for an electricity storage device is characterized in that heating is performed for 10 seconds or more using hot air or radiation in the step B. According to this configuration, by drying the slurry by heating with hot air or radiation during a material preheating period or the like prior to drying with a laser beam in the step C, migration during drying with a laser beam can be suppressed.

[0044] In this method for producing an electrode for a power storage device, the step B is a step of drying the slurry by a heating device, and the heating device has a hot air nozzle or a heater. According to this configuration, the slurry is heated by the heating device during the material preheating period before drying by a laser, thereby making it possible to prevent migration.

[0045] In this method for producing an electrode for a power storage device, the step D is a step of drying the slurry by a heating device, and the heating device has a hot air nozzle or a heater. According to this configuration, the slurry can be dried more reliably by further heating the slurry by the heating device after drying the slurry by the laser.

[0046] This method for producing an electrode for an electricity storage device is characterized in that step C is performed in a constant drying rate period to produce a slurry in a falling drying rate period in which the temperature of the slurry rises rapidly. According to this configuration, by irradiating the laser light in the constant drying rate period, the occurrence of migration is suppressed, and in the falling drying rate period, the temperature of the slurry rises suddenly, making temperature control difficult, and if the temperature of the mixture layer rises too much, unintended thermal decomposition or ignition of the mixture layer, or oxidation or melting of the current collector, can be prevented.

[0047] In this method for producing an electrode for a power storage device, it is preferable that the slurry contains any one of polyimide, polyamide, polyamideimide, polyamic acid, silicate, silicate hydrate, phosphate, and phosphate hydrate.

[0048] In this method for producing an electrode for a power storage device, it is preferable that the slurry contains an active material precursor, and that the active material precursor is a material capable of undergoing a solid-phase reaction with a material contained in the mixture layer or a current collector.

[0049] In this method for producing an electrode for an electricity storage device, it is preferable that the active material or the active material precursor is a material composited with carbon.

[0050] In this method for producing an electrode for an electricity storage device, it is desirable to intervene a light-shielding filter between the mechanism for step A and the mechanism for step C.

[0051] In this method for producing an electrode for an electricity storage device, the electricity storage device is a battery that uses alkali metal ions as a carrier. The method can also be applied to a capacitor.

[0052] In order to achieve the above-mentioned object, an apparatus for manufacturing an electrode for an electricity storage device according to one embodiment of the present invention includes a mechanism A that applies a slurry to a current collector transported at a predetermined speed, a mechanism B that heats the applied slurry by setting the temperature inside a drying furnace to 30°C or higher and lower than the boiling point of the dispersion medium in the slurry, and a mechanism C that irradiates the slurry applied on the current collector with laser light having a wavelength of 435 nm or more and less than 550 nm, or 890 nm or more and less than 1100 nm, from a laser irradiation unit, and is characterized in that the laser irradiation unit is provided outside the drying furnace.

[0053] This manufacturing apparatus for electrodes for energy storage devices is characterized in that it has a plurality of the laser irradiation units, and the plurality of laser irradiation units are arranged so that when laser light is irradiated simultaneously from the plurality of laser irradiation units, there is an area where the laser light overlaps.

[0054] This manufacturing apparatus for electrodes for energy storage devices is characterized in that the multiple laser irradiation units are arranged so that the area where the multiple laser beams overlap irradiates the boundary between the coated and uncoated areas of the slurry.

[0055] In this manufacturing apparatus for electrodes for energy storage devices, the mechanism C is characterized in that it has a plurality of laser irradiation units, a first laser irradiation unit is arranged so as to be able to irradiate laser light over the entire width direction of the slurry applied to the current collector, and a second laser irradiation unit is arranged so as to be able to irradiate including the boundary between the coated and uncoated areas of the slurry applied to the current collector.

[0056] In this manufacturing apparatus for electrodes for energy storage devices, the mechanism A is capable of applying the slurry to the front and back of the current collector, and the mechanism C is characterized in that it has a plurality of the laser irradiation units, and the laser irradiation units are arranged in positions where they can irradiate the front and back of the current collector with a laser.

[0057] This manufacturing apparatus for an electrode for an electricity storage device is characterized in that it further comprises a mechanism D, downstream of the mechanism C in the transport direction of the current collector, for heating the applied slurry.

[0058] In this electricity storage device electrode manufacturing apparatus, the laser irradiation unit in the mechanism C emits laser light having a wavelength of 435 nm or more and less than 550 nm, or 890 nm or more and less than 950 nm.

[0059] In this manufacturing apparatus for electrodes for energy storage devices, the mechanism B is arranged upstream of the mechanism C in the transport direction of the current collector, at a position where the slurry can be dried during a material pre-heating period among a material pre-heating period, a constant rate drying period, and a falling rate drying period in the process of drying the slurry, and the mechanism C is arranged at a position where the slurry can be dried during the constant rate drying period.

[0060] In this manufacturing apparatus for an electrode for an electricity storage device, the mechanism B is equipped with a heating device, and the heating device has a hot air nozzle or a heater.

[0061] In this manufacturing apparatus for an electrode for an electricity storage device, the mechanism D is characterized by including a heating device, and the heating device having a hot air nozzle or a heater. Effect of the Invention

[0062] According to the manufacturing method or manufacturing apparatus of the present invention, the slurry at the irradiated area can be heated in a short time using laser light, thereby making it possible to reduce the size of the electrode coating device, increase the electrode production speed, and reduce running costs. [Brief description of the drawings]

[0063] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a manufacturing apparatus for a secondary battery electrode according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the arrangement of a laser irradiation unit of the manufacturing apparatus for electrodes for secondary batteries. [Diagram 3]FIG. 2 is a schematic diagram showing the arrangement of a laser irradiation unit of the manufacturing apparatus for electrodes for secondary batteries. [Figure 4A] FIG. 1 is a schematic diagram showing a configuration of a modified example of a manufacturing apparatus for a secondary battery electrode according to the present embodiment. [Figure 4B] FIG. 1 is a schematic diagram showing a configuration of a modified example of a manufacturing apparatus for a secondary battery electrode according to the present embodiment. [Diagram 5] Figure showing the appearance of electrodes manufactured by continuous coating, intermittent coating, and stripe coating [Figure 6] Diagram showing the different stages in the drying process of a slurry [Figure 7] FIG. 1 shows a Na element map of the electrode cross section in Example 1. [Figure 8] FIG. 13 is a diagram showing a Na element map of the electrode cross section in Example 2. [Figure 9] FIG. 1 is a diagram showing a Na element map of the electrode cross section of Comparative Example 1. [Figure 10] FIG. 1 shows cycle characteristics of electrodes according to Example 1, Example 2, and Comparative Example 1. [Figure 11] FIG. 1 shows a C element map of the electrode cross section of Reference Example 1. [Figure 12] FIG. 1 shows a C element map of the electrode cross section of Reference Example 2. [Figure 13] FIG. 13 is a C element map of the electrode cross section of Reference Example 3. [Figure 14] FIG. 13 is a C element map of the electrode cross section of Reference Example 4. [Figure 15] FIG. 13 is a C element map of the electrode cross section of Comparative Example 2. [Figure 16] FIG. 1 is a SEM image of a cross section of an electrode in Reference Example 1. [Figure 17] FIG. 1 shows an SEM image of a cross section of an electrode in Reference Example 2. [Figure 18] FIG. 13 is a SEM image of a cross section of an electrode in Reference Example 3. [Figure 19] FIG. 13 is a SEM image of a cross section of an electrode according to Reference Example 4. [Figure 20] FIG. 13 is a SEM image of a cross section of an electrode in Comparative Example 2. [Figure 21] FIG. 1 shows cycle characteristics of electrodes of Reference Examples 1 to 4 and Comparative Example 2. [Figure 22]A diagram showing how the applied slurry is dried by irradiating it with a laser beam. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The electrodes include a positive electrode, a negative electrode, a bipolar electrode, and a reference electrode. However, the electrodes are all manufactured using the same manufacturing apparatus and method, with only the current collector and active material being different.

[0065] Fig. 1 is a diagram showing a schematic configuration of a manufacturing apparatus for a secondary battery electrode according to the present embodiment. Fig. 2 is a schematic diagram showing the arrangement of a laser irradiation unit of the manufacturing apparatus for a secondary battery electrode from the front side. Fig. 3 is a schematic diagram showing the arrangement of a laser irradiation unit of the manufacturing apparatus for a secondary battery electrode from the top side.

[0066] As shown in FIG. 1, the manufacturing apparatus 10 for electrodes for secondary batteries according to this embodiment mainly comprises an unwinding mechanism 11 for unwinding a roll-shaped current collector 100, a winding mechanism 12 for winding up the current collector 100 in a state in which the current collector 100 has been coated with a slurry 200, a drying furnace 20 for drying the slurry 200 coated on the current collector 100, a heater 21, and a laser irradiation unit 30.

[0067] The manufacturing apparatus 10 for electrodes for electricity storage devices also includes a slot die 13 that ejects a slurry 200 to be applied to the current collector 100 unwound from the unwinding mechanism 11, a plurality of support rolls 14 that support the transport of the current collector 100 coated with the slurry 200 as it passes through the drying furnace 20, and a back roll 17 that contacts the back surface of the current collector to support the coated surface.

[0068] In addition, in the drying furnace 20, a plurality of heaters 21 for heating and drying the slurry 200 applied to the current collector 100 are provided above and below the passing current collector 100. The heaters 21 are an example of the heating device of this embodiment, and a heating device using a hot air nozzle or the like may be used. It is also possible to use a heating device using a low-output laser or the like.

[0069] In addition, the drying furnace 20 is connected to an air supply pipe 15 for supplying outside air and an exhaust pipe 16 for exhausting the supplied air and gas generated in the drying furnace 20 to the outside. In addition, the manufacturing apparatus 10 for an electrode for an electricity storage device is provided with a plurality of laser irradiation units 30 that irradiate a laser downstream of the heater 21 in the transport direction of the current collector 100.

[0070] The laser irradiation unit 30 is disposed outside the drying furnace 20, and a transmission window 22 is disposed in a wall portion of the drying furnace 20 through which the irradiated laser passes. This transmission window 22 allows the laser from the laser irradiation unit 30 to be irradiated into the drying furnace 20 from outside the drying furnace 20. In addition, a light-shielding filter 40 is disposed outside the drying furnace 20, and in this embodiment, the laser irradiation unit 30 is disposed outside the drying furnace 20 and inside the light-shielding filter 40.

[0071] As shown in FIG. 2(a), three laser irradiation units 30 are arranged as an example of this embodiment, with one laser irradiation unit 30A arranged in the center of the width direction of the current collector 100 and one laser irradiation unit 30B arranged on each side. The central laser irradiation unit 30A is a laser (L1) that irradiates the entire slurry 200 applied to the current collector 100, and the laser irradiation units 30B on both sides are lasers (L2) that irradiate the boundary between the current collector 100 and the slurry 200. When the boundary between the current collector 100 and the slurry 200 is only on one side, it is also possible to configure the laser irradiation unit 30A and the laser irradiation unit 30B as shown in FIG. 2(b).

[0072] The laser irradiation unit 30A and the laser irradiation unit 30B may be arranged so that the laser (L1) from the laser irradiation unit 30A and the laser (L2) from the laser irradiation unit 30B overlap at the same time as shown in Fig. 3(a), or so that the laser L1 and the laser L2 partially overlap as shown in Fig. 3(b), or so that they overlap with a time lag, that is, so that the boundary portion is irradiated multiple times as shown in Fig. 3(c). In either case, the boundary portion between the current collector 100 and the slurry 200 is irradiated with more laser than other portions, so that the boundary portion where the slurry is likely to peel off can be thoroughly dried.

[0073] 4A, the manufacturing apparatus 10 of this embodiment can also be configured to further include a heater 21 downstream of the multiple laser irradiation units 30. In this case, the slurry 200 is first dried by the heater 21, then dried by the laser of the laser irradiation unit 30, and then further dried by the heater 21. In this way, the slurry can be dried more reliably.

[0074] 4B, the manufacturing apparatus 10 of this embodiment can also be configured to apply the slurry 200 to both sides of the current collector 100. In this case, it is preferable that at least the support roll 14 before the laser irradiation is, for example, an air support 18 using air, or that support rolls are provided only on both sides of the current collector where the slurry is not applied, or that the support roll itself is eliminated. Also, the support roll may be made of a material to which the slurry does not adhere. This is because if a normal support roll is used for the undried slurry applied to the current collector, the undried slurry may adhere to the support roll.

[0075] A method for manufacturing an electrode using manufacturing apparatus 10 having the above-described configuration includes the steps of applying a slurry to a roll-shaped current collector transported in one direction at a predetermined speed, heating the slurry to a temperature of 30°C or higher and lower than the boiling point of the dispersion medium in the slurry, and then irradiating the slurry with laser light having a wavelength of 435 nm or more and less than 550 nm, or 890 nm or more and less than 1100 nm, from a laser irradiation unit to vaporize and remove the dispersion medium in the slurry, thereby forming a composite layer on the current collector.

[0076] For example, a metal foil with a thickness of 10 μm wound into a roll is prepared as a current collector, and an electrode slurry is produced on one side. The electrode slurry is then applied to the surface of the metal foil and dried with a laser beam of the above wavelength to obtain an electrode. When applying the slurry to both sides of the metal foil, it can be applied simultaneously or one side at a time as shown in Figure 4.

[0077] By applying this embodiment to a method for manufacturing electrodes for lithium ion batteries, the slurry at the location irradiated with the laser light is instantly heated, so that a highly productive manufacturing method can be provided. Specifically, compared to conventional drying methods, it is possible to shorten the drying time, reduce the energy consumption in the drying process, shorten the length of the drying oven, and significantly reduce the installation space without deteriorating the performance of the electrode. In other words, with the same space, it is possible to improve the production capacity compared to conventional drying methods.

[0078] An example in which this embodiment is applied to an electrode for a lithium ion battery will be described in detail below, but various additions, modifications, and omissions can be made without departing from the spirit of the present invention.

[0079] There is no limitation on the method of applying the slurry. In other words, any known coating pattern such as continuous coating, intermittent coating, stripe coating, etc. may be selected. Electrodes manufactured by continuous coating, intermittent coating, and stripe coating will have an appearance as shown in Figure 5.

[0080] As an example, there is a method in which a slurry is discharged from a coating head in a uniform thickness and coated onto the surface of a current collector that is transported in one direction at a predetermined speed. As the coating head, a known head such as a bar coater, knife coater, comma coater, lip coater, gravure coater, die coater, air knife, lip coater, reverse coater, doctor coater, etc. After coating, the dispersion medium contained in the slurry is evaporated and removed (dried), thereby forming an electrode mixture layer on the surface of the current collector.

[0081] The coating method can be broadly divided into pre-metering and post-metering. The pre-metering method is characterized by the fact that a slurry that has been adjusted in advance to the desired coating amount is applied to the substrate, so that a coating film is formed along the shape of the substrate, and it is easy to obtain a consistent coating thickness. The post-metering method is characterized by the fact that an excess amount of slurry is applied first, and then the coating amount is adjusted by removing the slurry to the desired coating amount, so that a smooth coating surface is formed regardless of the shape of the substrate, and the total thickness (the total thickness of the substrate and coating film) is easy to obtain. Either method can be used to produce electrodes without any problems, but the post-metering method is preferred from the viewpoint of ease of coating with a high basis weight.

[0082] Examples of post-metering types include bar coaters, knife coaters, comma coaters, lip coaters, die coaters, air knives, lip coaters, and doctor coaters.

[0083] The current collector can be transported by known methods such as the roll-to-roll method, the belt conveyor method, the chain conveyor method, the roller conveyor method, and the lifting method. The roll-to-roll method is a method in which one roll-shaped current collector is unwound while the slurry is applied to the current collector, and the other current collector is wound up again in a roll shape. The belt conveyor method is a method in which the current collector is placed on a flat belt, transported by the movement of the belt, and coated. The chain conveyor method is a method in which the current collector is placed on a platform attached to a chain, transported, and coated. The roller conveyor method is a method in which the current collector is placed on multiple rollers lined up, transported by the rotation of the rollers, and coated. The lifting method is a method in which the current collector is hung from above and coated while being pulled up. Of these, the roll-to-roll method is preferred because it is easy to mass-produce and can be continuously produced at high speed under the same conditions.

[0084] If the current collector is not transported, the coating head must move to coat the current collector with the slurry, which is disadvantageous for producing electrodes with a large area.

[0085] When the current collector is transported, the current collector is supported by a back roll or a support roll, and the tension is adjusted as necessary, so that the slurry can be uniformly applied onto the current collector.

[0086] Here, the back roll is a roller located near where the slurry is applied, contacting the back surface of the current collector to support the coated surface. This allows the current collector to receive the slurry evenly. The support roll is a roller provided between the unwinding mechanism and the winding mechanism, and can support the current collector with multiple rollers. The back roll or support roll may be provided with a heating mechanism.

[0087] In the drying process of the slurry, the dispersion medium can be vaporized and removed by irradiating the applied slurry with a laser beam. This makes it possible to manufacture electrodes. However, when irradiating a laser beam on a slurry in the material preheating stage (more specifically, a slurry with a temperature of 30°C or less), it is very difficult to adjust the laser output. Specifically, if the laser output is even slightly low, the slurry will not dry sufficiently, and if it is even slightly high, the slurry will boil and a dense composite layer will not be obtained. Furthermore, if the material is dried without a sufficient material preheating period, components such as binders and thickeners will easily precipitate on the surface of the composite layer.

[0088] On the other hand, when the laser light is irradiated from the falling-rate drying period, the temperature rises suddenly because there is little dispersion medium, which is the vaporized component, making it difficult to control the temperature. If the temperature of the composite layer rises too much, it may cause unintended thermal decomposition or ignition of the composite layer, or oxidation or melting of the current collector.

[0089] It is preferable to irradiate the slurry in the constant drying rate period with the laser beam because the above problems are less likely to occur. In addition, by irradiating the slurry in the constant drying rate period with the laser beam, it is possible to shorten the length of the drying furnace or increase the conveying speed, thereby improving the productivity of the electrode. As shown in Figure 6, the process of drying the slurry is divided into three stages: material preheating period, constant rate drying period, and falling rate drying period.

[0090] The material preheating period is a period during which the temperature of the applied slurry rises to near the evaporation temperature of the dispersion medium, although there is a small amount of evaporation of the dispersion medium from the slurry, and is shorter in time than the constant rate drying period and the falling rate drying period. In addition, during this period, there is little change in the solid content of the slurry, and the generation of internal stress is hardly observed.

[0091] The constant rate drying period is the drying period that occurs after the material preheating period, and at this point, the entire surface of the slurry is covered with a liquid film of the dispersion medium. During this period, the drying process is similar to evaporation from the free water surface, and the temperature of the material is roughly constant, and the evaporation rate is also roughly constant. This period is also called the constant rate drying period, and its characteristics are that the temperature distribution in the thickness direction of the applied slurry is kept constant, and the evaporation rate is proportional to the difference between the saturated water vapor pressure corresponding to the surface temperature and the partial pressure of water vapor in the air. Here, the free water surface means the liquid surface that is subjected to atmospheric pressure. Also, during this period, the volume of the slurry shrinks as the drying progresses, and a rapid increase in internal stress occurs. After the constant rate drying period, it transitions to the falling rate drying period.

[0092] The falling drying period is a period in which the evaporation rate of the slurry decreases as the slurry dries. The surface temperature of the slurry starts to rise rapidly, and the slurry in the thickness direction rises in accordance with the surface temperature, and then the surface temperature of the slurry rises until it approaches the heat source temperature.

[0093] The material pre-heating period, constant rate drying period, and falling rate drying period can be determined by placing the current collector coated with the slurry in an environment with a temperature close to the boiling point of the dispersion medium and observing the temperature and weight changes of the slurry. For example, the period from the start of heating when almost no weight loss is observed corresponds to the material pre-heating period. The period after the material pre-heating period when there is almost no change in the temperature of the slurry and the rate of weight loss is proportional to time corresponds to the constant rate drying period. The period after the constant rate drying period when the temperature of the slurry rises rapidly, or the period from when the rate of weight loss is no longer proportional to time until the dispersion medium runs out and the solid content ratio reaches equilibrium corresponds to the falling rate drying period.

[0094] In order to suppress the migration of binders, thickeners, etc. and produce a homogeneous electrode, it is preferable to provide a material pre-heating period in which the applied slurry is heated in advance. Specifically, the temperature of the slurry is kept at 30°C or higher and below the boiling point of the dispersion medium, and the laser light is irradiated in that state. In this material pre-heating period, there is also a method of adjusting the output of the laser light to a low level in order to keep the temperature of the slurry on the current collector within the above range.

[0095] Furthermore, when the slurry is applied after being preheated to a predetermined temperature, the drying process does not require a material preheating stage.

[0096] Regardless of the heating method, the material preheating period is preferably set to 10 seconds or more and 600 seconds or less. If it is less than 10 seconds, the preheating may be insufficient or the temperature may be uneven. Even during the material preheating period, there is a small amount of evaporation of the dispersion medium from the slurry, so if it exceeds 600 seconds, the solid content ratio is likely to be high.

[0097] Although it is possible to use a laser beam during the material preheating stage to warm the slurry, if the applied slurry is a thick film, only the surface of the slurry is heated, and the temperature of the slurry near the current collector tends to remain low. In order to improve the energy density of the electricity storage device, it is effective to increase the film thickness of the composite layer, but the use of a laser beam during the material preheating stage is not very suitable.

[0098] For these reasons, it is preferable to use a heating means such as hot air or radiation during the material preheating stage to warm the slurry. In particular, radiation heating using near infrared rays or far infrared rays, or microwave heating, is preferable because it reduces temperature unevenness in the thickness direction of the slurry. Such radiation heating is direct heating by radiant energy and does not require an intermediate medium such as air convection heat, so it has better drying efficiency than hot air.

[0099] The light source of the laser light preferably has a wavelength of 435 nm or more and less than 1100 nm, and more preferably is a semiconductor laser with a wavelength of 435 nm or more and less than 550 nm, or a wavelength of 890 nm or more and less than 1100 nm. In particular, a semiconductor laser with a wavelength of 900 to 1080 nm is more preferable because it can achieve high output and has high electrical efficiency.

[0100] Here, a semiconductor laser is a laser that is generated by applying a voltage to a circuit element made from a semiconductor material. Generally, the intensity of laser light is expressed in terms of output. Output here refers to the amount of energy (W) that the laser can output per unit time. The higher the laser output, the higher the temperature can be, and the shorter the drying time can be.

[0101] From the viewpoint of suppressing migration and producing a homogeneous electrode, the laser light is preferably an area beam capable of irradiating a certain area, rather than a spot beam for pinpoint irradiation or a line beam for irradiating a long and narrow laser beam. This area beam preferably has an irradiation area with an irradiation length of 1 cm or more in the MD direction of the current collector. As the irradiation length in the MD direction becomes longer, binder migration tends to be less likely to occur. More preferably, the area beam is 2 cm or more, and desirably 5 cm or more in the MD direction of the current collector.

[0102] In the TD direction, it is preferable to irradiate the laser light in a range exceeding the coating width of the slurry. In other words, it is preferable to use an area beam that can irradiate not only the coated slurry but also the current collector with the laser light. In particular, the length exceeding the coating width of the slurry is preferably 0.1 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more.

[0103] By irradiating the laser beam over a range that exceeds the coating width of the slurry, it is possible to suppress dripping of the slurry after coating and to suppress unevenness in the thickness of the composite layer, thereby reducing deviations in the basis weight. In addition, the coating layer can be dried uniformly.

[0104] Here, the MD direction means the direction in which the current collector is transported, and the TD direction means the direction perpendicular to the MD direction, i.e., the width direction of the current collector.

[0105] The step of applying the slurry is preferably intermittent coating or stripe coating because the applied shape allows easy irradiation of the laser beam not only to the applied slurry but also to the current collector. Also, intermittent coating and stripe coating may be combined.

[0106] Intermittent coating is a method of intermittently coating a current collector with slurry while it is being transported. Specifically, the slurry is supplied to a coating head during coating and applied to the current collector, and when coating is not performed, the supply of the slurry to the coating head is stopped. By repeating this operation, multiple intermittent portions can be created on the current collector in the MD direction.

[0107] Stripe coating is a coating method that forms coated and uncoated areas in the TD direction of the current collector. For example, when using a die coater, this can be achieved by applying the coating with a shim plate sandwiched between the slurry outlet of the die coater.

[0108] The materials of the current collectors used in the electrodes for electricity storage devices are metals such as Al, Cu, Ni, Ti, Cr, Mo, Ru, W, and stainless steel, and have the property of reflecting laser light more easily than slurries, but when the current collector, which is an uncoated portion, is irradiated with laser light at an output that can dry the slurry, the current collector is easily oxidized, while the slurry does not dry sufficiently with low-output laser light adjusted to a level where the current collector is not oxidized. For these reasons, it is desirable to overlap the laser light.

[0109] However, in this method, there is a possibility that the laser light may scatter, and there is a risk that the laser light may be irradiated to an operator or an unintended location. In order to improve safety, it is desirable to provide a light-shielding filter between the mechanism for applying the slurry and the mechanism for drying with the laser light.

[0110] The light-shielding filter may be a plate, film, curtain, or the like, made of a material such as ceramics, glass, metal, or resin, and having a highly light-shielding color corresponding to the wavelength of the laser light.

[0111] In addition, a series of drying steps including the material preheating period, the constant rate drying period, and the falling rate drying period are preferably carried out in a drying furnace equipped with an air inlet and an exhaust port. By providing a mechanism for introducing air into the furnace from the air inlet using a fan or blower and exhausting the air from the furnace from the exhaust port, the vaporized gas released from the slurry can be effectively removed. In addition, when an organic solvent is used as the dispersion medium for the slurry, it is preferable to provide the drying furnace with an explosion-proof mechanism for safety reasons. Furthermore, the drying furnace may be provided with a door or an opening for removing the current collector and the laser irradiation unit.

[0112] A plurality of the above-mentioned laser irradiation units may be provided, and laser light may be simultaneously emitted from each of the laser irradiation units, so that there may be overlapping irradiation areas. In order to obtain high-power laser light, a large-sized laser oscillator is generally required, but this has the drawback of requiring large-scale equipment. However, by installing a plurality of small and versatile laser irradiation units and making the laser light emitted from these oscillators overlap in a specific area, it is possible to obtain high-power laser light without the need for a large-sized laser oscillator.

[0113] The laser irradiation unit is preferably provided outside the drying furnace so as to face the coating surface. In this case, a transmission window through which the laser can pass may be provided on the wall of the drying furnace. If it is necessary to provide the laser irradiation unit inside the drying furnace, the lens surface of the laser irradiation unit may be contaminated by gas generated during the hardening of the slurry, so it is preferable to use an air curtain or the like to prevent the generated gas from adhering to the lens surface.

[0114] The laser irradiation unit is preferably installed at a distance of 5 cm to 300 cm from the current collector, more preferably 10 cm to 200 cm. If the distance between the laser irradiation unit and the current collector is too close, it becomes difficult to ensure a sufficient beam area. Conversely, if the distance is too far, the laser output must be increased to reach the required temperature, which is inefficient.

[0115] The conveying speed of the current collector may be appropriately set within the range of 0.1 m / min to 5000 m / min depending on the composition of the slurry, the solid content ratio, the coating amount, the laser output, and the like.

[0116] The slurry is a mixture of an active material, a conductive additive, a binder, and a dispersion medium. However, when drying is performed by irradiating a laser beam, it is preferable that the slurry contains carbon. Specifically, it is preferable that the slurry contains 0.1 mass% or more of carbon based on the solid content. If the amount of carbon is less than 0.1 mass%, the slurry is unlikely to generate heat even when irradiated with a laser beam, so high laser output is required and drying takes a long time. It is preferable that the amount of carbon is 0.2 mass% or more, and it is desirable that the amount of carbon is 0.5 mass% or more.

[0117] It is preferable that the carbon that generates heat by the laser beam also serves as an active material or a conductive additive. For example, in the case of a capacitor electrode, activated carbon is included as an active material, so that the active material itself can be made to generate heat by the laser beam. However, Li 4 Ti 5 O 12 In the case of the negative electrode, Li is included as an active material. 4 Ti 5 O 12 Since the active material is white, it does not generate much heat. In such cases, add a carbon-based conductive agent to the slurry or use Li 4 Ti 5 O 12 It is preferable to use an active material in which carbon is composited with carbon.

[0118] Here, the term "composite" is a different concept from "mixture." A mixed powder is a collection of particles consisting of two or more components, whereas a composite powder contains two or more components in one particle. Specifically, Li 4 Ti 5 O 12 When the particle surface of Li is completely covered with carbon, 4 Ti 5 O 12 When the particle surface of Li is partially covered (in other words, supported) by carbon, 4 Ti5 O 12 The carbon is dispersed in the matrix of Li 4 Ti 5 O 12 When the surface of the particles is partially exposed, the powder is a composite powder.

[0119] When applying a slurry to a current collector, the slurry must have fluidity. Although this differs depending on the type of application method used, it is preferable that the solid content of the slurry is adjusted to between 30wt% and 70wt%, and that the viscosity (at 25°C) is between 100mPa·s and 20,000mPa·s.

[0120] On the other hand, the solid content of the slurry to be irradiated with the laser light is preferably adjusted to 55 wt % or more and 95 wt % or less, more preferably 57 wt % or more and 90 wt % or less, and even more preferably 60 wt % or more and 85 wt % or less.

[0121] When the solid content of the slurry to be applied is less than 55 wt%, it is preferable to evaporate the dispersion medium by heating and adjust the solid content to within the above range, and then dry the slurry by irradiating it with a laser beam. This also applies to the case where the slurry contains precursors of the active material, binder, and conductive additive described later.

[0122] By adjusting the solid content rate within the above range, migration due to the laser light is unlikely to occur, and excessive heat generation of the electrode can be suppressed. For example, when a slurry with a solid content rate of less than 55 wt% is irradiated with laser light, the slurry boils and the composite layer foams, not only making it impossible to obtain a dense composite layer, but also making it easy for components such as binders and thickeners to precipitate on the surface of the composite layer. In the case of a slurry with a solid content rate of more than 95 wt%, the amount of dispersion medium is small, so the temperature of the composite layer rises immediately, making it difficult to control the temperature of the electrode. If the temperature of the composite layer rises too much, unintended thermal decomposition of the composite layer, ignition, melting of the current collector, etc. may occur. For example, in the case of LiCoO with a solid content of 98 wt%, 2 When the slurry containing the metal oxide is placed on an aluminum foil and is continuously irradiated with laser light, a thermite reaction occurs, which may result in a violent exothermic reaction.

[0123] The active material can be any known material used in lithium ion batteries. In other words, a material capable of electrochemically absorbing and releasing lithium ions, which act as carriers, can be used. For example, LiCoO 2 , Li(Ni 0.33 Co 0.33 Mn 0.33 )O 2 , Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 , Li(Ni 0.6 Co 0.2 Mn 0.2 )O 2 , Li(Ni 0.7 Co 0.1 Mn 0.2 )O 2 , Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 , LiNiO 2 , Li(Ni 0.8 Co 0.15 Al 0.05 )O 2 , Li(Ni 0.87 Co 0.1 Al 0.03 )O 2 , Li(Ni 0.91 Co 0.05 Al 0.04 )O 2 , LiMn 2 O 4 , LiMn 1.5 Ni 0.5 O 4 , LiFePO 4 , Life 0.2 Mn 0.8 PO 4 , LiMnPO 4 , Li 5 Fe 5 (P 2 O 7 ) 4 , Li 2 MnO 3 Li(Co-Mn)O 2 , Li 2 FeSiO 4, Li 2 MnSiO 4 For the negative electrode active material, carbon-based materials such as graphite, hard carbon, and soft carbon, and Li 4 Ti 5 O 12 , TiNb 2 O 7 , Sn, Sn alloys, Al, Si, SiO, Si alloys, Ge, Sb, Bi, etc. These may be used alone or in combination of two or more. They may also be composited with carbon.

[0124] As described in paragraph 0004, there is a secondary battery using an electrode containing sulfur as a nonaqueous electrolyte secondary battery. However, the inventors of the present application have found that, when a slurry containing sulfur or a sulfur-carbon composite is heated by a laser beam, the vapor pressure of the sulfur increases, and evaporation or sublimation easily occurs.

[0125] In addition, sulfur, hydrogen sulfide, sulfur dioxide, and other sulfur-based gases, even at low concentrations, can corrode metals and cause serious damage to metal components in electronic devices. In particular, in the laser irradiated area, not only corrosion of metal contacts and wiring occurs, but also the sulfur content adheres to optical components, causing a significant decrease in the laser output, light flux, and quality. Therefore, it is undesirable to use an active material containing sulfur or a sulfur-carbon composite. That is, it is preferable that the object to be irradiated with the laser light does not contain sulfur. Specifically, it is preferable that the sulfur content in the slurry is 100 ppm or less. The amount of sulfur can be accurately determined by using inductively coupled plasma emission spectrometry.

[0126] For applications such as sodium ion batteries, potassium ion batteries, sodium ion capacitors, and potassium ion capacitors, the Li element can be replaced with the same element as the ions (carriers) responsible for electrical conduction.

[0127] The binder may be a resin-based (organic) binder or an inorganic binder. Examples of the resin-based binder include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamideimide, aramid, polyacrylic, styrene butadiene rubber (SBR), ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butylene-styrene copolymer (SEBS), carboxymethyl cellulose (CMC), carboxymethyl cellulose salts (CMC-Li, CMC-Na, CMC-K, CMC-NH4, etc.), xanthan gum, polyvinyl alcohol (PVA), ethylene vinyl alcohol, polyvinyl butyral (PVB), ethylene vinyl alcohol, polyethylene (PE), polypropylene (PP), polyacrylic acid, lithium polyacrylate, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, methyl polyacrylate, ethyl polyacrylate, etc. Organic materials such as cellulose, polyamine polyacrylate, polyacrylic ester, epoxy resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), nylon, vinyl chloride, silicone rubber, nitrile rubber, cyanoacrylate, urea resin, melamine resin, phenolic resin, latex, polyurethane, silylated urethane, nitrocellulose, dextrin, polyvinylpyrrolidone, vinyl acetate, polystyrene, chloropropylene, resorcinol resin, polyaromatic, modified silicone, methacrylic resin, polybutene, butyl rubber, 2-propenoic acid, cyanoacrylic acid, methyl methacrylate, glycidyl methacrylate, acrylic oligomer, 2-hydroxyethyl acrylate, alginic acid, starch, lacquer, sucrose, glue, casein, and cellulose nanofibers may be used alone or in combination of two or more kinds.

[0128] The inorganic binder may be, for example, a silicate-based or phosphate-based binder as described in patent documents (Japanese Patent No. 6149147, Japanese Patent Publication No. 2018-063912), or a sol-based or cement-based binder. For example, lithium silicate, sodium silicate, potassium silicate, cesium silicate, guanidine silicate, ammonium silicate, silicofluoride, borate, lithium aluminate, sodium aluminate, potassium aluminate, aluminosilicate, lithium aluminate, sodium aluminate, potassium aluminate, polyaluminum chloride, aluminum nitrate, ammonium alum, lithium alum, sodium alum, potassium alum, chrome alum, iron alum, manganese alum, diatomaceous earth, polyzirconoxane, polytitanium taloxane, mullite, white carbon, silica sol, colloidal silica, fumed silica, alumina sol, colloidal alumina, fumed alumina, zirconia sol, colloidal zirconia, fumed di Inorganic materials such as luconia, magnesia sol, colloidal magnesia, fumed magnesia, calcia sol, colloidal calcia, fumed calcia, titania sol, colloidal titania, fumed titania, zeolite, silicoaluminophosphate zeolite, sepiolite, montmorillonite, kaolin, saponite, aluminum phosphate, magnesium phosphate, calcium phosphate, iron phosphate, copper phosphate, zinc phosphate, titanium phosphate, manganese phosphate, barium phosphate, tin phosphate, low melting point glass, plaster, gypsum, magnesium cement, litharge cement, Portland cement, blast furnace cement, fly ash cement, silica cement, phosphate cement, concrete, and solid electrolytes may be used alone or in combination of two or more.

[0129] As for the inorganic binder, in the case of a slurry containing sulfur or a sulfur-carbon composite, similarly to the active material, when heated by a laser beam, the vapor pressure of the sulfur increases, and evaporation or sublimation easily occurs. Therefore, it is not desirable to use an inorganic binder containing sulfur or a sulfur-carbon composite.

[0130] The conductive assistant is not particularly limited as long as it has electronic conductivity, and examples thereof include metals, carbon materials, conductive polymers, conductive glass, etc., but carbon materials are preferred from the viewpoint of high electronic conductivity and oxidation resistance, and because they are prone to heat generation by laser light.Specific examples include acetylene black (AB), ketjen black (KB), furnace black (FB), thermal black, lamp black, channel black, roller black, disc black, carbon black (CB), carbon fiber (for example, vapor-grown carbon fiber named VGCF, which is a registered trademark), carbon nanotubes (CNT), carbon nanohorns, graphite, graphene, glassy carbon, amorphous carbon, etc., and it is preferable to use one or more of these.

[0131] Furthermore, when the slurry contains precursors of the active material, binder, and conductive assistant, it is preferable that the carbon material is contained at 1% by mass or more relative to the solid content of the slurry. If it is less than 1% by mass, heat generation for reacting the precursors is unlikely to occur even when irradiated with laser light, and unreacted precursors may remain in the electrode. It is preferable that the carbon material is contained at 2% by mass or more, and it is desirable that the carbon material is contained at 3% by mass or more. In this case, the carbon material should have a median diameter (D 50 It is preferable that the particles have a particle size of 0.1 μm or less and are present in the binder matrix.

[0132] The carbon material that generates heat upon receiving the laser light may be any carbon material that is commonly used in batteries, such as acetylene black (AB), furnace black, carbon nanotubes (CNT), carbon fiber, graphene, graphite, activated carbon, etc. In other words, any common carbon-based conductive assistant can be used.

[0133] For example, in the case of manufacturing a Sn-Cu alloy negative electrode for a lithium ion battery, a slurry consisting of Sn as an active material precursor, AB as a conductive assistant, and acrylic resin as a binder is applied to a copper foil, and then the surface temperature of the coating is irradiated with a laser beam so that the surface temperature of the coating is 150°C to 300°C. The carbon material contained in the coating generates heat, and the Sn in the coating and the copper of the current collector undergo an alloying reaction to obtain a Sn-Cu alloy. In this case, since oxidation of Sn and Cu occurs in the atmosphere, in order to suppress oxidation, it is recommended to irradiate the laser beam in an environment of an inert gas such as argon gas or nitrogen gas, in a reduced pressure environment, or while spraying an inert gas onto the composite layer.

[0134] Even when polyamic acid (polyamic acid) is used as the binder precursor, it is advisable to include a carbon-based conductive assistant. For example, a slurry using Si as the active material, polyamic acid as the binder precursor, and AB as the conductive assistant may be applied to a stainless steel foil, and then the coated material may be irradiated with laser light in the air or in an inert gas environment so that the surface temperature of the coated material is 150°C to 400°C. The conductive assistant contained in the coated material generates heat, and the polyamic acid can be imidized.

[0135] Even when copper formate or nickel formate is used as the conductive assistant precursor, it is advisable to add a carbon-based conductive assistant. For example, a slurry containing SiO as the active material, acrylic resin as the binder, copper formate as the conductive assistant precursor, and AB as the conductive assistant is applied to a stainless steel foil, and then laser light is irradiated to the surface of the coating in an inert gas environment so that the surface temperature of the coating is 150°C to 300°C. The conductive assistant contained in the coating generates heat, and the copper formate can be converted to copper and the nickel formate can be converted to nickel.

[0136] In addition, from the precursor of the active material, LiCoO 2A carbon-based conductive assistant may also be used when manufacturing a positive electrode. For example, a slurry consisting of an active material precursor made of lithium carbonate and cobalt hydroxide, a silicate-based inorganic binder, and AB may be applied to a stainless steel foil, and then the coated material may be irradiated with laser light so that the surface temperature of the coated material is 700°C to 1000°C. The conductive assistant contained in the coated material generates heat, and the cobalt hydroxide and lithium carbonate react to form LiCoO 2 It is possible to synthesize LiCoO 2 Since the synthesis of requires temperatures of 700°C or higher, it is necessary to select materials with excellent heat resistance and oxidation resistance for the current collector and binder.

[0137] Examples of binders with high heat resistance include polyamide, polyimide, polyamideimide, and inorganic binders. That is, when the precursor is reacted with laser light, it is preferable to use these binders, especially inorganic binders.

[0138] The current collector is not particularly limited as long as it is a material that has electronic conductivity and can pass current through the electrode material it holds. The shape of the current collector may be linear, rod-like, plate-like, foil-like, or porous. Examples of porous current collectors include mesh, woven fabric, nonwoven fabric, embossed body, punched body, perforated body, expanded body, and foamed body.

[0139] Various electrodes can be manufactured by selecting an appropriate binder and current collector based on the surface temperature of the coating. That is, when manufacturing an electrode using a laser beam, it is required to adjust the surface temperature below the heat resistance temperature of the material. Specifically, it is necessary to adjust the surface temperature below the melting point of the current collector and below the carbonization temperature of the binder. In addition, if oxidation of the electrode may occur at a certain temperature, it is preferable to irradiate the laser beam in a vacuum or inert gas environment, or while spraying inert gas onto the coating. More specifically, when using Al foil as the current collector, the surface temperature needs to be 660°C or less, when using Cu foil, it needs to be 1085°C or less, and when using stainless steel, it needs to be 1500°C or less.

[0140] When PVdF or SBR is used as the binder, the temperature should be 220°C or less, when an acrylic resin is used, the temperature should be 300°C or less, and when a polyimide, polyamide, or polyamideimide is used, the temperature should be 400°C or less. Note that there is no upper limit for inorganic binders such as silicates and phosphates, as they do not carbonize.

[0141] Since the surface temperature is highly dependent on the material being processed, when dealing with an unknown slurry, it is difficult to know the surface temperature accurately using only the laser output. Therefore, a method is needed to confirm whether the processing surface has reached the desired temperature. Contact or non-contact (radiation) temperature measuring devices can be used to measure the surface temperature. However, in the case of contact types, heat transfer due to the temperature difference between the object and the sensor can affect the measurement. Also, it is difficult to measure the temperature of a moving object.

[0142] For these reasons, it is preferable to use a non-contact temperature measuring device. An example of a non-contact type is an infrared radiation thermometer (for example, model number: AD-5616, manufactured by A&D). This radiation thermometer is not suitable for measuring the temperature of highly glossy metals, but is effective for measuring the surface temperature of coatings such as slurries and composite layers.

[0143] Although it varies depending on the laser output, the composition of the slurry, the solid content ratio, the film thickness, etc., the laser light irradiation time is preferably 2 seconds to 900 seconds, more preferably 6 seconds to 300 seconds. By increasing the laser output, the time can be shortened, but if it is less than 2 seconds, the composite layer may not be dried or may be burned. If it exceeds 900 seconds, the composite layer may deteriorate or the collector may be oxidized, resulting in poor charge and discharge efficiency.

[0144] The shapes of the above-mentioned active materials, active material precursors, and conductive assistants are not particularly limited, and may be spherical, elliptical, faceted, strip-like, fibrous, flake-like, doughnut-like, or hollow powders, and these may be single particles or granules.

[0145] The dispersion medium contained in the slurry can be a known dispersion medium used in electrode slurries for lithium ion batteries. That is, a fluid capable of dispersing powdered active materials or active material precursors is used. For example, water, N-methyl-2-pyrrolidone (NMP), alcohols, ketones, and solvents used in electrolytes can be used.

[0146] The electrodes obtained by the above manufacturing method can be used as a positive electrode, a negative electrode, or a reference electrode. When manufacturing a bipolar electrode, it can be realized by providing different composite layers on the front and back. For example, an electrode may be provided with a positive electrode composite layer on the front side and a negative electrode composite layer on the back side.

[0147] The power storage device can be manufactured by using the above-mentioned electrodes as the positive electrode and / or negative electrode, interposing a separator between the positive electrode and the negative electrode, and adding an electrolyte. When the above-mentioned electrode is used as a reference electrode, it may be interposed between the positive electrode and the negative electrode, or may be provided in the vicinity of the positive electrode or the negative electrode. When the above-mentioned electrode is a bipolar electrode, it may be configured by stacking the electrodes with a separator interposed between them so that the positive electrode surface and the negative electrode surface face each other. Note that a solid electrolyte may be used instead of the separator.

[0148] For example, in the case of a lithium ion battery using the above-mentioned electrodes (positive or negative electrodes), a battery structure in which the positive and negative electrodes are joined via a separator and sealed in a state of being immersed in an electrolyte solution is conceivable. Note that the battery structure is not limited to this, and the present invention can be applied to existing battery forms and structures such as stacked batteries and wound batteries.

[0149] The electrolyte used in this battery may be a liquid or solid that can move alkali metal ions from the positive electrode to the negative electrode or from the negative electrode to the positive electrode, and may be the same as the electrolyte used in known nonaqueous electrolyte secondary batteries and ion capacitors. Examples include electrolytic solution, gel electrolyte, solid electrolyte, ionic liquid, and molten salt. Here, the electrolytic solution refers to an electrolyte dissolved in a solvent.

[0150] The electrolyte is not particularly limited as long as it is used in non-aqueous electrolyte secondary batteries and ion capacitors, but alkali metal salts such as lithium salts, sodium salts, and potassium salts are preferred.

[0151] Examples of the electrolyte solvent include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (GBL), methyl-γ-butyrolactone, methyl lactone, 2-methyltetrahydrofuran, 1,3-dioxolane (DOL), 4-methyl-1,3-dioxolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, diethyl ether, furan, dimethylfuran, tetrahydrofuran (THF), methyltetrahydrofuran (MeTHF), tetrahydrofuran (THP), dioxane (DIOX), crown ether, dimethoxymethane (DMM), Dimethoxyethane (DME), diglyme, triglyme, tetraglyme, methyl acetate (MA), ethyl acetate (EA), propyl acetate, isopropyl acetate, butyl acetate, methyl fluoroacetate, ethyl trifluoroacetate, methyl propionate, ethyl propionate, propyl propionate, methyl formate, ethyl formate, propyl formate, ethyl butyrate, propyl butyrate, methyl propyl butyrate, vinyl acetate, methyl cyanoacetate, gamma-valerolactone, sigma-valerolactone, epsilon-caprolactone, gamma-hexalactone, gamma-undecalactone, trimethyl phosphate (TMP), triethyl phosphate (TEP), tri-n-propyl phosphate, trioctyl phosphate, triphenyl phosphate, N,N-Dimethylformamide (DMF), ethylenediamine, pyridine, N-methylimidazole, dimethyl sulfate, dimethyl sulfite, dipropyl sulfite, ethylene sulfite, dimethyl sulfone, ethyl methyl sulfone, diphenyl sulfone, sulfolane, methyl sulfolane, methyl methanesulfonate, methyl benzenesulfonate, methyl trifluoromethanesulfonate, propanesulfone, butanesulfone, dimethylsulfoxide, diphenyl disulfide, dimethyl sulfide, diethyl sulfide, acetonitrile, propanenitrile, adiponitrile, valeronitrile, glutaniline At least one selected from the group consisting of butyl ether, malononitrile, succinonitrile, pimelonitrile, suberonitrile, isobutyronitrile, biphenyl, succinic anhydride, t-butylbenzene, naphthalene, cyclohexylbenzene, benzotriazole, thiophene, toluene, methyl ethyl ketone, benzene, fluorobenzene, hexafluorobenzene, nitromethane, N,N-dimethylformamide, dimethyl sulfoxide, vinylene carbonate (VC), vinyl ethylene carbonate (EVC), fluoroethylene carbonate (FEC), and ethylene sulfite (ES) can be used.

[0152] Ionic liquids and molten salts are classified by the type of cation (positive ion), such as pyridine, alicyclic amine, and aliphatic amine. By selecting the type of anion (negative ion) to be combined with this, a variety of ionic liquids and molten salts can be synthesized. Examples of cations include ammonium ions such as imidazolium salts and pyridinium salts, phosphonium ions, and inorganic ions, while examples of anions include halogen ions such as bromide ions and triflates, boron ions such as tetraphenylborate, and phosphorus ions such as hexafluorophosphate.

[0153] Ionic liquids and molten salts are, for example, cations such as imidazolinium and Br - , Cl - , B.F. 4 - , P.F. 6 - , (CF3 SO 2 ) 2 N - , C.F. 3 SO 3 - , FeCl 4 - The electrolyte can be obtained by a known synthesis method such as combining with an anion such as the above. If it is an ionic liquid or a molten salt, it can function as an electrolyte without adding an electrolyte. EXAMPLES

[0154] Examples of the present invention will be described in more detail below, but the present invention is not limited to these examples. In particular, the examples will be described using an electrode for a lithium ion battery as an example, but the present invention is not limited thereto.

[0155] [Graphite electrode] Example 1 Artificial graphite (median diameter D 50 A slurry consisting of cellulose acetate (Daicel, 2260), SBR (JSR, TDR2001), AB (Denka, Denka Black), and water (solid ratio 95:2:1:2 by mass, solid content ratio 54%) was prepared using a planetary mixer (Thinky Corporation, Awatori Rentaro, ARE-310, rotation speed 2000 rpm, mixing time 10 minutes).

[0156] Next, the graphite slurry was continuously applied (coating width: 10 cm) to one side of the current collector using an electrode coater (comma coater).

[0157] After that, the slurry was preheated by contacting it with a hot plate heater set at 80°C for 10 seconds (solid content ratio 60%), and then irradiated with laser light (laser output 13 W, peak output 50 W, irradiation time 40 seconds) so that the surface temperature of the applied slurry became 80 to 150°C, and the slurry was dried to prepare an electrode. An electrolytic copper foil (Type A, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) with a thickness of 10 μm was used as the current collector.

[0158] The weight of the composite layer per unit area is 8 to 16 mg / cm 2 The laser irradiation size is 42 x 42 mm. 2 The above steps were carried out in an atmospheric environment at a temperature of 24°C ± 2 and a humidity of 60% ± 10 unless otherwise specified.

[0159] Example 2 The electrodes of Example 2 were preheated by contacting them with a hot plate heater set at 80° C. for 60 seconds (solids ratio 65%), but were otherwise similar to Example 1.

[0160] Comparative Example 1 The electrode of Comparative Example 1 was prepared similarly to Example 1, except that it was not preheated.

[0161] (Distribution of Na elements on electrode cross section) To check whether migration had occurred in the composite layer, the distribution of Na elements in the cross section of each electrode was observed by EPMA.

[0162] FIG. 7 shows a Na element map of the cross section of the electrode in Example 1 (white areas indicate the locations where Na elements are present).

[0163] FIG. 8 shows a Na element map of the cross section of the electrode of Example 2 (white areas indicate the locations where Na elements are present).

[0164] FIG. 9 shows a Na element map of the cross section of the electrode of Comparative Example 1 (white areas indicate the locations where Na elements are present).

[0165] As is clear from Figs. 7 to 9, Na elements are unevenly distributed in large amounts in the surface layer of the composite layer of Comparative Example 1. In contrast, such surface uneven distribution is not observed in Examples 1 and 2. All of Examples 1, 2, and Comparative Example 1 use carboxymethyl cellulose as a thickener, and this component contains Na elements. This suggests that migration of the thickener occurs in the electrode of Comparative Example 1.

[0166] (Battery characteristics) The electrodes of Example 1, Example 2, and Comparative Example 1 were used as test electrodes, and metallic Li (lithium foil made by this metal, 500 μm thick) was used as the counter electrode, and 1M LiPF was used as the electrolyte. 6 An R2032-type coin cell was produced in a dry environment with a dew point of -60°C or less using a mixture of EC:DEC = 1:1 vol. (Kishida Chemical Co., Ltd.) and a polypropylene (PP) / polyethylene (PE) / polypropylene (PP) three-layer microporous membrane (Celgard, 2325) and a glass filter (Advantec, GA-100) stacked as a separator.

[0167] To confirm the effect of the drying method of the slurry on the cycle characteristics, five cycles of charge / discharge at a 0.1C rate (cutoff voltage 0.0 to 1.5 V) were performed in a 30°C environment, and then charge / discharge at a 0.2C rate was repeated.

[0168] FIG. 10 shows the cycle characteristics of the electrodes of Example 1, Example 2 and Comparative Example 1. As is clear from FIG. 10, compared to Comparative Example 1, Examples 1 and 2 exhibited stable discharge capacity for a long period of time, and thus had a long life.

[0169] [SiO electrode] (Reference example 1) Si (Elkem, median diameter D 50 A slurry (solid ratio 79:3:18 mass%, solid content ratio 54%) consisting of SiO2 (Si = 3 μm), polyamic acid (IST, Dream Bond), acetylene black (Denka, Denka Black), and NMP was prepared using a planetary mixer (Thinky, Awatori Rentaro, ARE-310, rotation speed 2000 rpm, mixing time 10 minutes). Next, the above-mentioned Si slurry was continuously applied (coating width 10 cm) to one side of the current collector using an electrode coater (comma coater).

[0170] Thereafter, without preheating, the applied slurry was irradiated with laser light (laser output 13 W, peak output 50 W, irradiation time 10 seconds) so that the surface temperature of the slurry reached 170°C, drying the slurry and imidizing the polyamic acid to produce an electrode. A 10 μm thick Ni-plated steel foil (Nippon Steel Sumitomo Metal Corporation, Super Nickel) was used as the current collector. The weight of the composite layer per unit area was 1.6 to 1.8 mg / cm. 2 The laser irradiation size is 42 x 42 mm. 2 The above steps were carried out in an atmospheric environment at a temperature of 24°C ± 2 and a humidity of 60% ± 10 unless otherwise specified.

[0171] (Reference example 2) The electrode of Reference Example 2 was prepared in the same manner as Reference Example 1, except that the electrode was prepared by irradiating the applied slurry with laser light (laser output 18 W, peak output 50 W, irradiation time 10 seconds) so that the surface temperature of the slurry reached 200°C, drying the slurry, and imidizing the polyamic acid.

[0172] (Reference example 3) The electrode of Reference Example 3 was prepared in the same manner as Reference Example 1, except that the electrode was prepared by irradiating the applied slurry with laser light (laser output 34 W, peak output 50 W, irradiation time 10 seconds) so that the surface temperature of the applied slurry reached 320°C, drying the slurry, and imidizing the polyamic acid.

[0173] (Reference example 4) The electrode of Reference Example 4 was prepared in the same manner as Reference Example 1, except that the electrode was prepared by irradiating the applied slurry with laser light (laser output 100 W, peak output 150 W, irradiation time 10 seconds) so that the surface temperature of the applied slurry exceeded 500°C, drying the slurry, and imidizing the polyamic acid.

[0174] Comparative Example 2 The electrode of Comparative Example 2 was prepared in the same manner as in Example 3, except that the electrode was prepared by contacting the electrode with a hot plate heater set at 80°C for 60 seconds to adjust the solid content of the applied slurry to 96%, and then irradiating the applied slurry with laser light (laser output 27 W, peak output 50 W, irradiation time 10 seconds) so that the surface temperature of the applied slurry reached 280°C, thereby drying the slurry and imidizing the polyamic acid.

[0175] (Dryness of the mixture layer) In the mixture layers of Reference Examples 1 to 3, only the surfaces were dry, and the insides were not dry, and therefore, they were determined to have been insufficiently dried. The mixture layers of Reference Example 4 and Comparative Example 2 were dry.

[0176] (Distribution of C element on electrode cross section and SEM image) In order to confirm whether migration occurred in the composite layer, the distribution of C element in the cross section of each electrode was observed by EPMA. Note that, since the composite layers of Reference Examples 1 to 3 were not dried properly, they were again exposed to hot air at 80°C for 30 minutes for drying treatment.

[0177] FIG. 11 shows a C element map of the cross section of the electrode of Reference Example 1 (white areas indicate the locations where C elements are present).

[0178] FIG. 12 shows a C element map of the cross section of the electrode of Reference Example 2 (white areas indicate the locations where C elements are present).

[0179] FIG. 13 shows a C element map of the electrode cross section of Reference Example 3 (white areas indicate the locations where C elements are present).

[0180] FIG. 14 shows a C element map of the electrode cross section of Reference Example 4 (white areas indicate the locations where C elements are present).

[0181] FIG. 15 shows a C element map of the cross section of the electrode of Comparative Example 2 (white areas indicate the locations where C elements are present).

[0182] FIG. 16 shows an SEM image of a cross section of the electrode of Reference Example 1.

[0183] FIG. 17 shows an SEM image of a cross section of the electrode of Reference Example 2.

[0184] FIG. 18 shows an SEM image of a cross section of the electrode of Reference Example 3.

[0185] FIG. 19 shows an SEM image of a cross section of the electrode of Reference Example 4.

[0186] FIG. 20 shows an SEM image of a cross section of the electrode of Comparative Example 2.

[0187] As is clear from Figs. 11 to 15, the C element was unevenly distributed in large amounts on the surface of the composite layer of Reference Example 3, which was prepared so that the surface temperature was 320°C. This is thought to be C element derived from polyimide and conductive additives. On the other hand, such surface unevenness was not observed in Reference Examples 1 and 2, which were dried again with hot air at 80°C. Moreover, in Comparative Example 2, in which the solid content ratio of the slurry was adjusted to 96% in advance and then laser light was irradiated, such surface unevenness was not observed.

[0188] 16 to 20, multiple large voids were found inside the composite layer of Reference Example 4, which was produced at a temperature exceeding 500° C., but no large voids were found in Reference Examples 1 and 2, which were dried again with hot air at 80° C. Moreover, no voids were found in Comparative Example 2, in which the solid content ratio of the slurry was adjusted to 96% beforehand and then laser light was irradiated.

[0189] (Battery characteristics) The electrodes of Reference Examples 1 to 4 and Comparative Example 2 were used as test electrodes, and metal Li (500 μm thick lithium foil manufactured by Honjo Metals Co., Ltd.) was used as the counter electrode, and 1M LiPF 6 An R2032-type coin cell was produced in a dry environment with a dew point of -60°C or less using a 1:1 vol. / EC:DEC (Kishida Chemical Co., Ltd.) separator with a PP / PE / PP three-layer microporous membrane (Celgard, 2325) and a glass filter (Advantec, GA-100) stacked on top of each other.

[0190] In addition, since the mixture layers of Reference Examples 1 to 3 were insufficiently dried, they were again exposed to hot air at 80° C. for 30 minutes for drying treatment before use.

[0191] To confirm the effect of the drying method of the slurry on the cycle characteristics, five cycles of charge / discharge at a 0.1C rate (cutoff voltage 0.0 to 1.5 V) were performed in a 30°C environment, and then charge / discharge at a 0.2C rate was repeated.

[0192] FIG. 21 shows the cycle characteristics of the electrodes of Reference Examples 1 to 4 and Comparative Example 2. 21, Reference Examples 1 to 4 have larger discharge capacities than Comparative Example 2. Among these, Reference Example 2 maintains the highest and most stable capacity.

[0193] Although no migration occurred in Comparative Example 2, when drying was performed using laser light, the solids ratio of the slurry was high and the amount of the dispersion medium (NMP), which is a vaporized component, was small, which is thought to have caused the temperature of the electrode to rise and the current collector to oxidize.

[0194] [Laser area considerations] (Reference example 5) Artificial graphite (median diameter D 50 A slurry (solid ratio 95:2:1:2 mass%, solid content ratio 51%) consisting of graphite (fiber size 0.05 mm, thickness 0.05 mm, diameter 0.05 mm, thickness ...

[0195] The applied slurry was then irradiated with a laser beam at a laser output of 113 W for an irradiation time of 4.8 seconds to dry the slurry and produce an electrode. The laser beam was irradiated so that each side exceeded the applied width of the slurry by 11 mm. An electrolytic copper foil (Type A, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) with a thickness of 10 μm was used as the current collector. The weight of the composite layer per unit area was 16 to 18 mg / cm. 2The laser irradiation size is 42 x 42 mm. 2 It was decided.

[0196] (Reference example 6) The electrode of Reference Example 6 was the same as Reference Example 5, except that the graphite slurry was continuously applied (application width 42 mm) and laser light was irradiated so as not to exceed the application width of the slurry and so that no part of the slurry was left unirradiated.

[0197] (Reference example 7) The electrode of Reference Example 7 was continuously coated with the graphite slurry (coating width 60 mm) and irradiated with laser light within the coating width of the slurry. The electrode was the same as Reference Example 5, except that there was 9 mm of slurry on each side that was not irradiated with laser light.

[0198] (Dryness of the coating) FIG. 22 shows the process of drying the applied slurry by irradiating it with laser light (the diagonal areas in the figure are areas that were not sufficiently dried).

[0199] In Reference Example 5, the slurry on the entire surface irradiated with the laser light was sufficiently dried. However, in Reference Example 6, the slurry irradiated with the laser light was not sufficiently dried in the adjacent uncoated areas. In Reference Example 7, the slurry irradiated with the laser light was not sufficiently dried in the adjacent uncoated areas.

[0200] The reason why drying was more insufficient in Reference Example 7 than in Reference Example 6 is believed to be because the undried slurry had the effect of replenishing the dispersion medium to the dried composite layer.

[0201] As described above, the preferred embodiment of the present invention has been described with reference to the drawings, but various additions, modifications, and deletions are possible without departing from the spirit of the present invention. For example, the above embodiment has been described mainly with a lithium ion battery as an example, but the present invention is not limited to lithium ion batteries, and can also be applied to other non-aqueous electrolyte secondary batteries such as sodium ion batteries and potassium ion batteries. Therefore, such batteries are also included in the scope of the present invention. [Explanation of symbols]

[0202] 10. Electrode manufacturing equipment 11 Unwinding mechanism 12 Winding mechanism 13 Slot die 14 Support Roll 15 Intake pipe 16 Exhaust pipe 17 Back Roll 18 Air Support 20 Drying oven 21 Heater 30 Laser irradiation unit 40 Light-shielding filter 100 Current collector 200 Slurry L1 Laser L2 Laser

Claims

1. A method for manufacturing an electrode, comprising the steps of: A step A of applying a slurry to a current collector transported at a predetermined speed; A step B of heating the applied slurry at a temperature of 30° C. or higher and a boiling point of the dispersion medium in the slurry or lower so that the solid content is 60% or higher and 95% or lower; and a step C of irradiating the slurry applied onto the current collector with a laser beam having a wavelength of 435 nm or more and less than 550 nm, or a wavelength of 890 nm or more and less than 1100 nm, from a laser irradiation unit, The slurry contains carbon in an amount of 0.1% by mass or more based on the solid content of the slurry, The step C is an area beam in which laser light is simultaneously irradiated from a plurality of laser irradiation units and overlaps with each other, and the area beam in which the plurality of laser light beams overlap irradiates a boundary between a coated portion and an uncoated portion of the slurry. A method for producing an electrode for an electricity storage device.

2. A method for manufacturing an electrode, comprising the steps of: A step A of applying a slurry to a current collector transported at a predetermined speed; A step B of heating the applied slurry at a temperature of 30° C. or higher and a boiling point of the dispersion medium in the slurry or lower so that the solid content is 60% or higher and 95% or lower; and a step C of irradiating the slurry applied onto the current collector with a laser beam having a wavelength of 435 nm or more and less than 550 nm, or a wavelength of 890 nm or more and less than 1100 nm, from a laser irradiation unit, The slurry contains carbon in an amount of 0.1% by mass or more based on the solid content of the slurry, The step C irradiates the current collector with laser light from a plurality of laser irradiation units, a first laser irradiation unit irradiates the current collector with laser light over the entire width direction of the slurry applied thereto, and a second laser irradiation unit irradiates the current collector with laser light including at the boundary between the applied portion and the uncoated portion of the slurry applied thereto. A method for producing an electrode for an electricity storage device.

3. The laser light is an area beam having an irradiation length of 1 cm or more in the MD direction of the current collector. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

4. The laser light is an area beam that is irradiated to a current collector on which the slurry is not applied in the TD direction of the current collector. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

5. After the step C, the method further includes a step D of heating the applied slurry. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

6. The wavelength of the laser irradiation unit in the step C is a laser light having a wavelength of 435 nm or more and less than 550 nm, or a wavelength of 890 nm or more and less than 950 nm. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

7. The slurry is characterized in that it does not contain sulfur. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

8. The step A is intermittent coating or stripe coating. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

9. In the process of drying the slurry, among the material preheating period, the constant rate drying period, and the falling rate drying period, The step B is a step of concentrating the solid content of the slurry so that the solid content rate is 60% or more and 95% or less during the material preheating period, and forming a slurry for a fixed rate drying period. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

10. The step B heats the substrate for 10 seconds or more using hot air or radiation. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

11. The step B is a step of drying the slurry using a heating device, The heating device has a hot air nozzle or a heater. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

12. The step D is a step of drying the slurry using a heating device, The heating device has a hot air nozzle or a heater. The method for producing an electrode for an electricity storage device according to claim 5 .

13. The step C is carried out during a constant drying period, This is a process of making the slurry into a slurry during the falling rate drying period, during which the temperature of the slurry rises rapidly. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

14. The slurry contains any one of polyimide, polyamide, polyamideimide, polyamic acid, silicate, silicate hydrate, phosphate, and phosphate hydrate; The method for producing the electrode for an electricity storage device according to claim 1 or 2.

15. the slurry comprises an active material precursor; The active material precursor is a material capable of undergoing a solid-phase reaction with a material contained in a mixture layer or a current collector. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

16. The active material or active material precursor is It is composited with carbon. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

17. a light-shielding filter is interposed between an area where the step A is performed and an area where the step C is performed; The method for producing the electrode for an electricity storage device according to claim 1 or 2.

18. The electricity storage device is a battery or a capacitor using an alkali metal ion as a carrier. The method for producing the electrode for an electricity storage device according to claim 1 or 2.

19. An apparatus for manufacturing an electrode for an electricity storage device, comprising: a mechanism A for applying a slurry to a current collector transported at a predetermined speed; a mechanism B for heating the applied slurry to a solid content of 60% to 95% by setting the temperature inside the drying furnace to 30° C. or higher and the boiling point of the dispersion medium in the slurry or lower; a mechanism C that is located downstream of the mechanism B in the conveying direction of the current collector and that irradiates the slurry coated on the current collector with a laser beam having a wavelength of 435 nm or more and less than 550 nm, or a wavelength of 890 nm or more and less than 1100 nm, from a laser irradiation unit; The laser irradiation unit is provided outside the drying furnace, The laser irradiation unit includes a plurality of the laser irradiation units, and the plurality of laser irradiation units are arranged so that when laser light is simultaneously irradiated from the plurality of laser irradiation units, there is an area where the laser light overlaps, and the plurality of laser irradiation units are arranged so that the area where the plurality of laser light overlaps irradiates a boundary between a coated portion and an uncoated portion of the slurry. Manufacturing equipment for electrodes for power storage devices.

20. An apparatus for manufacturing an electrode for an electricity storage device, comprising: a mechanism A for applying a slurry to a current collector transported at a predetermined speed; a mechanism B for heating the applied slurry to a solid content of 60% to 95% by setting the temperature inside the drying furnace to 30° C. or higher and the boiling point of the dispersion medium in the slurry or lower; a mechanism C that is located downstream of the mechanism B in the conveying direction of the current collector and that irradiates the slurry coated on the current collector with a laser beam having a wavelength of 435 nm or more and less than 550 nm, or a wavelength of 890 nm or more and less than 1100 nm, from a laser irradiation unit; The laser irradiation unit is provided outside the drying furnace, the mechanism C includes a plurality of laser irradiation units, a first laser irradiation unit is arranged so as to be able to irradiate a laser beam over the entire width direction of the slurry applied to the current collector, and a second laser irradiation unit is arranged so as to be able to irradiate a boundary between a coated portion and an uncoated portion of the slurry applied to the current collector. Manufacturing equipment for electrodes for power storage devices.

21. The mechanism A is capable of applying the slurry to the front and back surfaces of the current collector, The mechanism C includes a plurality of the laser irradiation units, The laser irradiation unit is disposed at a position where the laser irradiation unit can irradiate the front and back surfaces of the current collector. An apparatus for manufacturing an electrode for an electricity storage device according to claim 19 or 20.

22. The current collector further includes a mechanism D for heating the applied slurry, the mechanism D being disposed downstream of the mechanism C in the conveying direction of the current collector. An apparatus for manufacturing an electrode for an electricity storage device according to claim 19 or 20.

23. The wavelength of the laser irradiation unit in the mechanism C is a laser beam having a wavelength of 435 nm or more and less than 550 nm, or a wavelength of 890 nm or more and less than 950 nm. An apparatus for manufacturing an electrode for an electricity storage device according to claim 19 or 20.

24. the mechanism B is disposed upstream of the mechanism C in the conveying direction of the current collector, at a position where the slurry can be dried in a material pre-heating period among a material pre-heating period, a constant rate drying period, and a falling rate drying period in a step of drying the slurry, The mechanism C is disposed at a position capable of drying the slurry during a fixed rate drying period. An apparatus for manufacturing an electrode for an electricity storage device according to claim 19 or 20.

25. The mechanism B includes a heating device, The heating device has a hot air nozzle or a heater. An apparatus for manufacturing an electrode for an electricity storage device according to claim 19 or 20.

26. The mechanism D includes a heating device, The heating device has a hot air nozzle or a heater. An apparatus for manufacturing an electrode for an electricity storage device according to claim 22.