Method and apparatus for manufacturing electrode for energy storage device

Abstract

[Problem] To provide a method and an apparatus for manufacturing an electrode for an energy storage device whereby a more compact electrode coating apparatus, an improvement in electrode production speed, and a reduction in running costs can be achieved. [Solution] Provided is a method for manufacturing an electrode for an energy storage device, the method comprising: a step A for applying a slurry to a rolled current collector conveyed in one direction at a prescribed speed; a step B for heating the applied slurry to a temperature not below 30°C and not above the boiling point of a dispersant in the slurry; and a step C for irradiating the slurry applied to the current collector with laser light of a wavelength equal to or greater than 435 nm and less than 550 nm, or of a wavelength equal to or greater than 890 nm and less than 1100 nm, from a laser irradiation unit, wherein the slurry contains 0.1% by mass or more of carbon relative to the solid content of the slurry.

Description

Manufacturing method and manufacturing apparatus for electrodes for power storage devices

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

[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, lithium-ion batteries are a representative example of non-aqueous electrolyte secondary batteries, and demand for them is rapidly increasing due to their features of small size, light weight, high voltage, and no memory effect.

[0004] A nonaqueous 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 power storage device. Specific examples include lithium ion batteries, lithium polymer batteries, all-solid-state lithium 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 (storage case). 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, and lithium ion capacitors. Of these, lithium ion capacitors are electricity storage devices that use a non-aqueous electrolyte and an active material in which either the positive electrode material or the negative electrode material can absorb and release lithium ions, based on the basic principle of electric double layer capacitors.

[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] An electricity storage device, which is a component of an electrode, has a current collector and a composite layer (active material layer). For example, in a nickel-metal hydride battery, a 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 top of the current collector.

[0008] On the other hand, lithium ion batteries use aluminum foil or copper foil as a current collector and a composite layer containing lithium transition metal oxide, graphite, or other active materials as the main components, while lithium ion capacitors use aluminum foil or copper foil as a current collector and a composite layer containing activated carbon, graphite, or other active materials.

[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] Electrodes include positive electrodes, negative electrodes, reference electrodes, and bipolar electrodes. Each electrode can be fabricated using an active material, a conductive additive, a binder, and a current collector. In a typical electrode manufacturing process, a slurry (a paste-like, fluid mixture) is applied or filled onto a current collector. The dispersion medium contained in the slurry is evaporated (dried), and then the composite layer is pressurized using a roll press or similar. This slurry is composed of liquid and solid components. To manufacture an electrode, the active material, conductive additive, binder, and other components must be mixed with the dispersion medium to achieve a fluid state.

[0011] In the above-mentioned slurry drying process, if the slurry applied to the current collector is rapidly dried, a phenomenon in which the binder or thickener is unevenly distributed on the surface (surface layer) of the composite layer, i.e., migration, is observed. Electrodes that have undergone such migration have reduced adhesion between the current collector and the composite layer, resulting in the composite layer becoming more susceptible to detachment or peeling. Furthermore, when such electrodes are used in batteries, this can cause deterioration in cycle characteristics and increase in internal resistance.

[0012] One possible solution to this problem is to slow down the drying speed of the slurry, but this method reduces 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, increasing the length of the drying oven clearly requires larger equipment, which has the drawback of requiring a larger site area and increasing energy consumption.

[0013] The process of drying a 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 slowly 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.

[0014] JP 2015-185250 A

[0015] In addition to improving production speed, the above-mentioned energy storage devices also require reduced running costs. The current electrode production process mainly uses drying methods that utilize hot air or radiation. However, this method heats the air and peripheral equipment that are not being dried, resulting in a large amount of wasted energy.

[0016] The inventors focused on technology that uses lasers 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 wavelengths of light that can be used have increased. Furthermore, with the advent of fiber lasers, it is now possible to amplify the light of multiple semiconductor lasers using fibers, improving the convenience of high-power lasers.

[0017] There are various types of laser irradiation devices, including 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. Another key feature of lasers is the amplification of the generated light.

[0018] It was found that if the electrode slurry contains carbon materials such as graphite or amorphous carbon, the carbon absorbs energy when exposed to laser light, generating heat and evaporating the slurry's dispersion medium. This allows the slurry to be instantly heated only in the areas irradiated with the laser light, reducing the energy required to 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 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 of a series of drying processes. This means that rapid drying during the constant-rate drying period or an earlier stage (material preheating period) makes migration more likely to occur. However, when drying using a laser beam, migration is less likely to occur during the falling-rate drying period, but the amount of dispersion medium, which is a vaporizable component, is small, so the temperature rises suddenly, making temperature control difficult.

[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 manufacturing apparatus for manufacturing electrodes with high productivity without causing migration.

[0022] In order to achieve the above object, one aspect 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 being 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, making it 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 preferably 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, narrow laser light.

[0026] In addition, in this method for manufacturing an electrode for a power 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 where the slurry is applied with laser light, the temperature of the current collector is raised, which in turn raises the temperature of the slurry from the current collector side, contributing to drying and improving compatibility with the slurry.

[0028] In this method for manufacturing 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 electricity 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 a slurry, but when the laser light is irradiated onto the uncoated portion of the current collector with an output that can dry the slurry, the current collector is likely to oxidize, while low-output laser light adjusted to a level that does not oxidize the current collector may not sufficiently dry the slurry. Therefore, by overlapping the laser light irradiated onto the slurry, it is possible to sufficiently dry the slurry.

[0030] In this case, the overlapping area beams are characterized by irradiating the boundary between the coated and uncoated portions of the slurry.

[0031] According to this configuration, the boundary between the coated and uncoated portions of the slurry, i.e., the boundary between the slurry and the current collector, is irradiated with overlapping laser light, thereby thoroughly drying the slurry at the boundary, which is more likely to peel than other portions, and preventing the slurry from peeling.

[0032] Furthermore, in this method for manufacturing an electrode for an electricity storage device, 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 applied and uncoated areas.

[0033] This configuration allows the boundary between the coated and uncoated portions of the slurry, i.e., the boundary between the slurry and the current collector, to be irradiated with laser light multiple times, thereby thoroughly drying the slurry at the boundary. This ensures that the portion that is more susceptible to peeling than other portions can be dried reliably, preventing the slurry from peeling.

[0034] Moreover, this method for producing an electrode for a power 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 in which the slurry is further heated and dried 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, making it possible to manufacture electrodes with high productivity while suppressing the occurrence of migration.

[0037] In this method for manufacturing an electrode for an electricity storage device, the wavelength of the laser irradiation unit in step C is 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. With this configuration, it is possible to obtain a constant output and improve the drying rate while maintaining a wavelength that is capable of drying the slurry. Note that a wavelength of 890 nm or more and less than 950 nm is more preferable because a semiconductor laser can 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 as non-aqueous electrolyte secondary batteries, the inventors of the present application have found through testing and investigation that when a slurry containing sulfur or a sulfur-carbon composite is heated by laser light, the vapor pressure of the sulfur content increases, and evaporation and sublimation easily occur.

[0039] Furthermore, sulfur-based gases such as sulfur, hydrogen sulfide, and sulfur dioxide, even at low concentrations, can corrode metals and cause serious damage to metal components in electronic devices. In particular, in laser irradiation areas, not only do metal contacts and wiring corrode, but the adhesion of sulfur to optical components can also significantly reduce the laser output, luminous flux, and quality. Therefore, when 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] In this method for producing an electrode for a power storage device, the step C is characterized in that the laser beam is irradiated onto the slurry in a constant 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 rise 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, constant rate drying period, and decreasing 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 is 60% or more and 95% or less to make it into a slurry for the constant rate drying period.

[0042] In this method for manufacturing an electrode for an electricity storage device, it is preferable that step A be 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 shape be such that laser light can be easily irradiated not only to the applied slurry but also to the current collector.

[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 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 laser light in step C, migration during drying with laser light can be suppressed.

[0044] In this method for manufacturing an electrode for an electricity storage device, the step B is a step of drying the slurry using a heating device, and the heating device has a hot air nozzle or a heater. With this configuration, by heating the slurry using the heating device during the material preheating period before drying with a laser, migration can be prevented.

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

[0046] This method for manufacturing an electrode for an electricity storage device is characterized in that step C is a step of performing the laser irradiation in a constant drying rate period to produce a slurry for a falling drying rate period in which the temperature of the slurry rises rapidly. According to this configuration, by performing the laser irradiation in the constant drying rate period, the occurrence of migration is suppressed, and it is also possible to prevent unintended thermal decomposition or ignition of the composite layer, oxidation or melting of the current collector, etc., which would otherwise occur in the falling drying rate period due to a sudden rise in the temperature of the slurry, making temperature control difficult, if the temperature of the composite layer rises too much.

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

[0048] In this method for manufacturing an electrode for a power storage device, it is desirable 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 a power storage device, it is desirable that the active material or the active material precursor is a material composited with carbon.

[0050] In this method for manufacturing an electrode for an electricity storage device, it is desirable to interpose 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 object, one aspect of the present invention provides an apparatus for manufacturing electrodes for electricity storage devices, which comprises: a mechanism A that applies a slurry to a current collector that is being transported at a predetermined speed; a mechanism B that heats the applied slurry by maintaining the temperature inside a drying furnace at 30°C or higher and at most the boiling point of the dispersion medium in the slurry; and a mechanism C that irradiates 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 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 across the entire width of the slurry applied to the current collector, and a second laser irradiation unit is arranged so as to be able to irradiate the slurry including at the boundary between the applied and unapplied 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 laser.

[0057] This manufacturing apparatus for an electrode for a power storage device is characterized by further comprising a mechanism D for heating the applied slurry, located downstream of the mechanism C in the direction of transport of the current collector.

[0058] In this manufacturing apparatus for an electrode for a power storage device, 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 a wavelength of 890 nm or more and less than 950 nm.

[0059] In this manufacturing apparatus for electrodes for electricity storage devices, the mechanism B is arranged upstream of the mechanism C in the conveying direction of the current collector, at a position where the slurry can be dried during the material preheating period of the process of drying the slurry, which is a material preheating period, a constant rate drying period, and a decreasing rate drying period, 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 characterized by including 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 has a hot air nozzle or a heater.

[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 apparatus, improve the electrode production speed, and reduce running costs.

[0063] FIG. 1 is a diagram showing a schematic configuration of an apparatus for manufacturing an electrode for a secondary battery according to the present embodiment; FIG. 2 is a diagram showing a schematic arrangement of a laser irradiation unit of the apparatus for manufacturing an electrode for a secondary battery according to the present embodiment; FIG. 3 is a diagram showing a schematic arrangement of a laser irradiation unit of the apparatus for manufacturing an electrode for a secondary battery according to the present embodiment; FIG. 4 is a diagram showing a schematic arrangement of a modified example of the apparatus for manufacturing an electrode for a secondary battery according to the present embodiment; FIG. 5 is a diagram showing the appearance of an electrode manufactured by continuous coating, intermittent coating, and stripe coating; FIG. 6 is a diagram showing each stage of the drying process of the slurry; FIG. 7 is a diagram showing a Na element map of the cross section of the electrode of Example 1; FIG. 8 is a diagram showing a Na element map of the cross section of the electrode of Example 2; FIG. 1 shows the cycle characteristics of the electrodes of Example 1, Example 2, and Comparative Example 1. FIG. 2 shows a C element map of the cross section of the electrode of Reference Example 1. FIG. 3 shows a C element map of the cross section of the electrode of Reference Example 2. FIG. 4 shows a C element map of the cross section of the electrode of Reference Example 3. FIG. 5 shows a C element map of the cross section of the electrode of Reference Example 4. FIG. 6 shows a C element map of the cross section of the electrode of Comparative Example 2. FIG. 7 shows an SEM image of the cross section of the electrode of Reference Example 1. FIG. 8 shows an SEM image of the cross section of the electrode of Reference Example 2. FIG. 9 shows an SEM image of the cross section of the electrode of Reference Example 3. FIG. 10 shows an SEM image of the cross section of the electrode of Reference Example 4. FIG. 11 shows an SEM image of the cross section of the electrode of Comparative Example 2. FIG. 12 shows the cycle characteristics of the electrodes of Reference Examples 1 to 4 and Comparative Example 2. FIG. 13 shows the state in which the applied slurry is irradiated with laser light and dried.

[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 only difference between the electrodes is the current collector and the active material, and the manufacturing apparatus and manufacturing method are the same.

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

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

[0067] The manufacturing apparatus 10 for electrodes for energy 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] Furthermore, within 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 current collector 100 as they pass through. The heaters 21 are an example of a heating device in this embodiment, and a heating device using a hot air nozzle may also be used. It is also possible to use a heating device using a low-power laser.

[0069] The drying furnace 20 is also connected to an air supply pipe 15 that supplies outside air and an exhaust pipe 16 that exhausts the supplied air and gas generated in the drying furnace 20 to the outside. The manufacturing apparatus 10 for an electrode for an electricity storage device is also provided with a plurality of laser irradiation units 30 that irradiate with a laser downstream of the heater 21 in the conveyance 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 the 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] 2(a), three laser irradiation units 30 are arranged in one 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 of it. 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. Note that when the boundary between the current collector 100 and the slurry 200 is on only one side, it is also possible to configure the current collector 100 with two laser irradiation units, ie, the laser irradiation unit 30A and the laser irradiation unit 30B, as shown in FIG. 2(b).

[0072] The laser irradiation units 30A and 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 simultaneously, as shown in Fig. 3(a), or so that the lasers L1 and L2 partially overlap, as shown in Fig. 3(b), or so that the lasers overlap with a time lag, i.e., 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 light than other portions, and therefore the boundary portion, where peeling of the slurry is likely to occur, can be thoroughly dried.

[0073] 4A, the manufacturing apparatus 10 of this embodiment may further include a heater 21 downstream of the plurality of 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 the front and back surfaces of the current collector 100. In this case, it is desirable that at least the support roll 14 before laser irradiation be, for example, an air support 18 using air, or that support rolls be provided only on both sides of the current collector in the portion not coated with the slurry, or that the support roll be eliminated entirely. The support roll may also 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 that is 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 higher and lower than 550 nm, or 890 nm or higher and lower 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 10 μm-thick metal foil 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 the slurry is applied to both sides of the metal foil, it can be applied simultaneously or one side at a time as shown in FIG. 4.

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

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

[0080] One example is a method in which a coating head dispenses a slurry at a uniform thickness onto the surface of a current collector being transported in one direction at a predetermined speed. Known coating heads such as a bar coater, knife coater, comma coater, lip coater, gravure coater, die coater, air knife, lip coater, reverse coater, and doctor coater can be used. 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 a pre-metering method and a post-metering method. The pre-metering method involves applying a slurry that has been adjusted in advance to the desired coating amount to the substrate, so that the coating film conforms to the shape of the substrate, making it easier to obtain a consistent coating thickness. The post-metering method involves first applying an excess amount of slurry, and then removing the slurry to adjust the coating amount to the desired coating amount, so that a smooth coating surface is formed regardless of the shape of the substrate, making it easier to obtain a consistent total thickness (the total thickness of the substrate and the coating film). While either method can be used to produce electrodes without any problems, the post-metering method is preferred from the perspective of facilitating high-basis-weight coating.

[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, belt conveyor method, chain conveyor method, roller conveyor method, and lifting method. The roll-to-roll method involves unwinding one roll of the current collector, coating the current collector with a slurry, and then rewinding the other roll. The belt conveyor method involves placing the current collector on a flat belt, transporting it by the belt's movement, and coating it. The chain conveyor method involves placing the current collector on a platform attached to a chain, transporting it, and coating it. The roller conveyor method involves placing the current collector on a series of rollers, transporting it by the rotation of the rollers, and coating it. The lifting method involves suspending the current collector from above and lifting it up while coating it. Of these, the roll-to-roll method is preferred because it facilitates mass production and allows for continuous production at high speed and under consistent conditions.

[0084] If the current collector is not transported, the coating head must move to apply the slurry to the current collector, 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 the area where the slurry is applied, which contacts 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 multiple rollers can support the current collector. 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 allows for the production of electrodes. However, when irradiating a slurry during the material preheating period (more specifically, a slurry at a temperature of 30°C or less) with a laser beam, it is extremely 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, preventing the formation of a dense composite layer. Furthermore, if the material is dried without a sufficient preheating period, components such as binders and thickeners will easily precipitate on the surface of the composite layer.

[0088] On the other hand, when laser light is applied during the falling-rate drying period, the temperature rises suddenly because there is little dispersion medium, which is the vaporizing component, making temperature control difficult. 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 with a laser beam during the constant drying period because the above problems are minimized. Furthermore, irradiating the slurry with a laser beam during the constant drying period makes it possible to shorten the length of the drying oven or increase the conveying speed, thereby improving electrode productivity. As shown in Figure 6, the process of drying the slurry is divided into three stages: a material preheating period, a constant drying period, and a falling 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 some 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. Also, 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 occurs after the material preheating period, during which 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, with the material temperature and evaporation rate remaining roughly constant. This period is also called the constant-rate drying period, and is characterized by the fact that the temperature distribution in the thickness direction of the applied slurry remains 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 refers to the liquid surface subjected to atmospheric pressure. During this period, the volume of the slurry shrinks as drying progresses, resulting in a rapid increase in internal stress. After the constant-rate drying period, the slurry transitions to the falling-rate drying period.

[0092] The falling-rate drying period is the period during which the evaporation rate decreases as the slurry dries. The surface temperature of the slurry begins to rise rapidly, and the slurry in the thickness direction rises in line with the surface temperature, after which the surface temperature of the slurry rises until it approaches the heat source temperature.

[0093] The material preheating period, constant-rate drying period, and falling-rate drying period can be determined by placing a current collector coated with 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 preheating period. The period after the material preheating period when almost no change in the temperature of the slurry occurs and the rate of weight loss becomes 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 sharply, or the period from when the rate of weight loss becomes no longer proportional to time until the dispersion medium is used up and the solids ratio reaches equilibrium corresponds to the falling-rate drying period.

[0094] In order to suppress migration of binders, thickeners, etc. and produce a homogeneous electrode, it is preferable to provide a material preheating period in which the applied slurry is heated in advance. Specifically, the temperature of the slurry is maintained at 30°C or higher and below the boiling point of the dispersion medium, and the laser beam is irradiated in this state. In this material preheating period, one method is to adjust the output of the laser beam to a low level in order to maintain 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, 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 laser light can be used in 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. Increasing the film thickness of the composite layer is effective in improving the energy density of the electricity storage device, but using laser light in the material preheating stage is not very suitable.

[0098] For these reasons, it is preferable to use heating means such as hot air or radiation during the material preheating stage to warm the slurry. In particular, radiation heating using near-infrared or far-infrared rays or microwave heating is preferable because it minimizes temperature unevenness in the thickness direction of the slurry. Such radiation heating is direct heating using 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 is preferably a semiconductor laser 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. In particular, a wavelength of 900 to 1080 nm is more preferable because semiconductor lasers can achieve high output and have high electrical efficiency.

[0100] Here, a semiconductor laser is a laser that is generated by applying voltage to a circuit element made from a semiconductor material. Generally, the intensity of laser light is expressed in terms of output. Here, output refers to the energy (W) that the laser can emit 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 that can irradiate a fixed area, rather than a spot beam that irradiates a pinpoint or a line beam that irradiates a long, 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 increases, binder migration tends to become less likely to occur. More preferably, an area beam with an irradiation length of 2 cm or more, preferably 5 cm or more in the MD direction of the current collector is preferable.

[0102] In the TD direction, it is preferable to irradiate the laser beam in a range exceeding the coating width of the slurry. That is, it is preferable to use an area beam that can irradiate not only the coated slurry but also the current collector with the laser beam. 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 exceeding the width of the slurry coating, it is possible to prevent dripping of the slurry after coating and to prevent unevenness in the thickness of the composite layer, thereby reducing deviations in the basis weight. In addition, it is possible to dry the coating layer 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 coating shape allows easy irradiation of the laser beam not only to the applied slurry but also to the current collector. Alternatively, intermittent coating and stripe coating may be combined.

[0106] Intermittent coating is a method of intermittently applying a slurry to a current collector during transportation. Specifically, the slurry is supplied to a coating head and applied to the current collector during coating, and the supply of the slurry to the coating head is stopped when coating is not being performed. 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 current collectors used in electrodes for electricity storage devices are made of 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. However, when laser light is irradiated onto the uncoated portion of the current collector with an output that dries the slurry, the current collector is prone to oxidation, whereas low-output laser light adjusted to prevent oxidation of the current collector does not sufficiently dry the slurry. For these reasons, it is desirable to overlap the laser light.

[0109] However, with this method, there is a risk that the laser light may scatter, irradiating workers or unintended locations. To improve safety, it is desirable to install a light-shielding filter between the mechanism that applies the slurry and the mechanism that dries it with laser light.

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

[0111] Furthermore, the series of drying processes, including the material preheating period, constant-rate drying period, and 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 through the air inlet using a fan or blower and exhausting the air from the furnace through the exhaust port, vaporized gases released from the slurry can be effectively removed. Furthermore, 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 equipped with a door or opening for removing the current collector and laser irradiation unit.

[0112] A plurality of the above laser irradiation units may be provided, and laser light may be emitted from each laser irradiation unit simultaneously, resulting in overlapping irradiation areas. Obtaining high-power laser light generally requires a large laser oscillator, which has the drawback of requiring large-scale equipment. However, by installing a plurality of small, versatile laser irradiation units and allowing the laser light emitted from these oscillators to overlap in specific areas, it is possible to obtain high-power laser light without the need for a large 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 the laser irradiation unit needs to be provided inside the drying furnace, the lens surface of the laser irradiation unit may be contaminated by gases generated during the curing of the slurry, so it is preferable to use an air curtain or the like to block the adhesion of the generated gas to the lens surface.

[0114] The laser irradiation unit is preferably installed at a distance of 5 cm to 300 cm, more preferably 10 cm to 200 cm, from the current collector. 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 by irradiating with laser light, it is preferable that carbon is contained. Specifically, it is preferable that the carbon content of the slurry is 0.1% by mass or more. If the carbon content is less than 0.1% by mass, it is difficult to generate heat even when irradiated with laser light, so a high laser output is required and drying takes a long time. It is preferable that the carbon content be 0.2% by mass or more, and it is desirable that the carbon content be 0.5% by mass or more.

[0117] It is preferable that the carbon that generates heat when exposed to laser light 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 when exposed to laser light. However, Li ４ Ti ５ O １２ In the case of the negative electrode, Li is contained as an active material. ４ Ti ５ O １２ In such cases, a carbon-based conductive additive is added to the slurry, or Li ４ Ti ５ O １２ It is preferable to use an active material in which carbon is composited with silicon.

[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 Ti ５ O １２ The carbon is dispersed in the matrix of Li ４ Ti ５ O １２ If the surface of the particles is partially exposed, the powder is a composite powder.

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

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

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

[0122] By adjusting the solid content within the above range, migration due to 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 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 exceeding 95 wt%, the 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, when a LiCoO ２ When the slurry containing the metal oxide is applied to an aluminum foil and is continuously irradiated with laser light, a thermite reaction occurs, which may cause a violent exothermic reaction.

[0123] The active material can be any known material used in lithium ion batteries. That is, a material capable of electrochemically absorbing and releasing lithium ions, which act as carriers, can be used. For example, the positive electrode active material can be LiCoO ２ , Li(Ni ０．３３ Co ０．３３ Mn ０．３３ ) O２ , 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 P.O. 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 The negative electrode active material includes carbon 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 are secondary batteries using electrodes containing sulfur as nonaqueous electrolyte secondary batteries. However, the inventors of the present application have conducted tests and studies and found that when a slurry containing sulfur or a sulfur-carbon composite is heated by a laser beam, the vapor pressure of the sulfur content increases, and evaporation or sublimation easily occurs.

[0125] Furthermore, sulfur-based gases such as sulfur, hydrogen sulfide, and sulfur dioxide, even at low concentrations, can corrode metals and cause serious damage to metal components in electronic devices. In particular, in laser irradiation areas, not only do metal contacts and wiring corrode, but the adhesion of sulfur to optical components can also significantly reduce the laser output, luminous flux, and quality. Therefore, it is undesirable to use active materials containing sulfur or sulfur-carbon composites. In other words, it is preferable that the object to be irradiated with laser light does not contain sulfur. Specifically, it is preferable that the sulfur content in the slurry be 100 ppm or less. Sulfur can be accurately determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0126] When the battery is used for a sodium ion battery, a potassium ion battery, a sodium ion capacitor, or a potassium ion capacitor, the Li element can be replaced with the same element as the ion (carrier) 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, and ethyl polyacrylate.

[0039] Organic materials such as cellulose ether, polyamine polyacrylate, polyacrylic acid 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.

[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 Application Laid-Open 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 zirconia 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 salts, magnesium phosphate salts, calcium phosphate salts, iron phosphate salts, copper phosphate salts, zinc phosphate salts, titanium phosphate salts, manganese phosphate salts, barium phosphate salts, tin phosphate salts, 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, similarly to the active material, when a slurry containing sulfur or a sulfur-carbon composite is heated by laser light, 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 additive 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 additive, it is preferable that the carbon material is contained in an amount of 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 precursor is unlikely to occur even when irradiated with laser light, and unreacted precursor may remain in the electrode. It is preferable that it is contained in an amount of 2% by mass or more, and it is desirable that it is contained in an amount of 3% by mass or more. In this case, the carbon material should have a median diameter (D ５０ ) It is preferable that the particle diameter is 0.1 μm or less and that the particle diameter is present in the binder matrix.

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

[0133] For example, when manufacturing a Sn—Cu alloy negative electrode for a lithium-ion battery, a copper foil is coated with a slurry containing Sn as an active material precursor, AB as a conductive additive, and an acrylic resin as a binder, and then the coated material is irradiated with laser light so that the surface temperature of the coated material reaches 150°C or higher and 300°C or lower. The carbon material contained in the coated material generates heat, and the Sn in the coated material and the copper of the current collector undergo an alloying reaction, resulting in a Sn—Cu alloy. In this case, since oxidation of Sn and Cu occurs in the atmosphere, to suppress oxidation, the laser light can be irradiated in an inert gas environment 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 preferable to add a carbon-based conductive additive. For example, a slurry containing Si as the active material, polyamic acid as the binder precursor, and AB as the conductive additive can be applied to a stainless steel foil, and then irradiated with laser light in the air or in an inert gas environment so that the surface temperature of the coated object is between 150°C and 400°C. The conductive additive contained in the coated object generates heat, causing the polyamic acid to be imidized.

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

[0136] In addition, from the precursor of the active material, LiCoO ２ When manufacturing a positive electrode, it is also advisable to use a carbon-based conductive additive. For example, after a slurry consisting of an active material precursor made of lithium carbonate and cobalt hydroxide, a silicate-based inorganic binder, and AB is applied to a stainless steel foil, the coated material is irradiated with laser light so that the surface temperature of the coated material is 700°C or higher and 1000°C or lower. The conductive additive contained in the coated material generates heat, and the cobalt hydroxide and lithium carbonate react to form LiCoO２ It is possible to synthesize LiCoO ２ Since the synthesis of (I) requires a temperature of 700° C. or higher, it is necessary to select materials for the current collector and binder that are excellent in heat resistance and oxidation resistance.

[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 conduct electricity to the electrode material it holds. The shape of the current collector may be wire, rod, plate, foil, or porous. Examples of porous current collectors include mesh, woven fabric, nonwoven fabric, embossed material, punched material, perforated material, expanded material, and foamed material.

[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 laser light, it is necessary to adjust the surface temperature below the heat resistance temperature of the material. Specifically, the surface temperature needs to be adjusted below the melting point of the current collector and below the carbonization temperature of the binder. Furthermore, if oxidation of the electrode may occur at a predetermined temperature, it is preferable to irradiate the electrode with laser light in a vacuum or inert gas environment, or while spraying inert gas onto the coating. More specifically, when using an Al foil as the current collector, the surface temperature needs to be 660°C or less, when using a 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 is 220°C or lower, when an acrylic resin is used, 300°C or lower, and when polyimide, polyamide, or polyamideimide, 400°C or lower. Note that no upper limit is set for inorganic binders such as silicates and phosphates, as they do not carbonize.

[0141] Because surface temperature is highly dependent on the material being processed, it is difficult to accurately determine the surface temperature using only the laser output when dealing with unknown slurries. Therefore, a method is needed to confirm whether the processing surface has reached the desired temperature. Contact and non-contact (radiation) temperature measurement devices can be used to measure surface temperature. However, with contact devices, heat transfer due to the temperature difference between the object and the sensor can affect the measurement. In addition, 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 surface temperature of highly glossy metals, but is effective for measuring the surface temperature of coated objects such as slurries and composite layers.

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

[0144] The shapes of the above-mentioned active materials, active material precursors, and conductive additives are not particularly limited, and may be spherical, elliptical, faceted, strip-shaped, fibrous, flake-shaped, doughnut-shaped, 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 material or active material precursor is used. For example, water, N-methyl-2-pyrrolidone (NMP), alcohols, ketones, solvents used in electrolytes, etc. 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. To manufacture a bipolar electrode, different composite layers can be provided on the front and back sides. 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] An electricity 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 solution. When the above-mentioned electrode is used as a reference electrode, it may be interposed between the positive electrode and the negative electrode, or provided near 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 electrode or negative electrode), a battery structure in which the positive electrode and the negative electrode are joined via a separator and sealed in a state immersed in an electrolyte solution is conceivable. However, 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 any liquid or solid that can transfer alkali metal ions from the positive electrode to the negative electrode or from the negative electrode to the positive electrode, and the same electrolytes used in known nonaqueous electrolyte secondary batteries and ion capacitors can be used. Examples include electrolytic solutions, gel electrolytes, solid electrolytes, ionic liquids, and molten salts. Here, the electrolytic solution refers to an electrolyte dissolved in a solvent.

[0150] The electrolyte is not particularly limited as long as it is one that can be 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, methylpropyl butyrate, vinyl acetate, methyl cyanoacetate, γ-valerolactone, σ-valerolactone, ε-caprolactone, γ-hexalactone, γ-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, propane sulfone, butane sulfone, dimethyl sulfoxide, diphenyl disulfide, dimethyl sulfide, diethyl sulfide, acetonitrile, propanenitrile, adiponitrile, valeronitrile, glutanitrile At least one selected from the group consisting of methyl acrylate, 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), vinylethylene 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, or aliphatic amine. By selecting the type of anion (negative ion) to be combined with this cation, a variety of ionic liquids or molten salts can be synthesized. Examples of cations include ammonium ions such as imidazolium salts and pyridinium salts, phosphonium ions, and inorganic ions. 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 － , (CF ３ SO ２) ２ N － , C.F. ３ SO ３ － , FeCl ４ － The ionic liquid or molten salt can function as an electrolytic solution without adding an electrolyte.

[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, although the examples will be described using an electrode for a lithium ion battery as an example, the present invention is not limited thereto.

[0155] [Graphite electrode] (Example 1) Artificial graphite (median diameter D ５０ = 20 μm), sodium carboxymethylcellulose (2260, manufactured by Daicel Corporation), SBR (TDR2001, manufactured by JSR Corporation), AB (Denka Black, manufactured by Denka Company Ltd.), and water were mixed to prepare a slurry (solid ratio 95:2:1:2 mass%, solid content ratio 54%) 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] The slurry was then preheated (solid content: 60%) by contacting it with a hot plate heater set to 80°C for 10 seconds, 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 reached 80 to 150°C, thereby drying the slurry 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 was 42 x 42 mm ２ The above steps were carried out in an atmospheric environment at a temperature of 24°C ± 2°C and a humidity of 60% ± 10%, unless otherwise specified.

[0159] Example 2 The electrodes of Example 2 were the same as those of Example 1, except that they were preheated by contacting them with a hot plate heater set at 80° C. for 60 seconds (solid content: 65%).

[0160] Comparative Example 1 The electrode of Comparative Example 1 was prepared in the same manner as Example 1, except that it was not preheated.

[0161] (Distribution of Na Element in Electrode Cross Section) In order to confirm whether migration had occurred in the composite layer, the distribution of Na element 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 of Example 1 (white areas indicate 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 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 locations where Na elements are present).

[0165] As is clear from Figures 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. Examples 1, 2, and Comparative Example 1 all use carboxymethyl cellulose as a thickener, which contains Na elements. This suggests that migration of the thickener occurs in the electrode of Comparative Example 1.

[0166] (Battery Characteristics) Each of the electrodes of Example 1, Example 2, and Comparative Example 1 was used as a test electrode, and metal Li (a lithium foil made by this metal, 500 μm thick) was used as a counter electrode. 1M LiPF ６ An R2032-type coin cell was fabricated in a dry environment with a dew point of −60°C or lower using 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 on cycle characteristics, five cycles of charge / discharge at 0.1 C rate (cutoff voltage 0.0 to 1.5 V) were performed in a 30°C environment, followed by repeated charge / discharge at 0.2 C rate.

[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, demonstrating a long life.

[0169] [SiO electrode] (Reference Example 1) Si (manufactured by Elkem, median diameter D ５０ = 3 μm), polyamic acid (Dream Bond, manufactured by IST Corporation), acetylene black (Denka Black, manufactured by Denka Company Ltd.), and a slurry consisting of NMP (solid ratio 79:3:18 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). Next, using an electrode coater (comma coater), the above Si slurry was continuously applied (coating width 10 cm) to one side of a current collector.

[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 applied 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 was 42 x 42 mm ２ The above steps were carried out in an atmospheric environment at a temperature of 24°C ± 2°C 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 applied 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 applied slurry 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 composite layer) The composite layers of Reference Examples 1 to 3 were determined to be poorly dried because only the surface was dry and the interior was not. The composite layers of Reference Example 4 and Comparative Example 2 were dry.

[0176] (Distribution of C element in electrode cross section and SEM image) To check whether migration had 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 subjected to drying treatment by exposing them to hot air at 80°C for 30 minutes.

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

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

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

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

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

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

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

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

[0187] As is clear from Figures 11 to 15, a large amount of C element was unevenly distributed 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 the polyimide and conductive additive. 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. Furthermore, such surface unevenness was not observed in Comparative Example 2, in which the solid content ratio of the slurry was adjusted to 96% beforehand and then laser light was irradiated.

[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 the occurrence of such large voids was not found in Reference Examples 1 and 2, which were dried again with hot air at 80° C. Furthermore, the occurrence of such voids was not 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) Each of the electrodes of Reference Examples 1 to 4 and Comparative Example 2 was used as a test electrode, and metal Li (500 μm thick lithium foil manufactured by Honjo Metals Co., Ltd.) was used as a counter electrode. 1M LiPF ６An R2032-type coin cell was fabricated in a dry environment with a dew point of −60°C or lower using a PE / EC / DEC mixture (Kishida Chemical Co., Ltd.) with a PP / PE / PP three-layer microporous membrane (Celgard, 2325) and a glass filter (Advantec, GA-100) stacked as a separator.

[0190] In addition, since the composite layers of Reference Examples 1 to 3 were not sufficiently 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 on cycle characteristics, five cycles of charge / discharge at 0.1 C rate (cutoff voltage 0.0 to 1.5 V) were performed in a 30°C environment, followed by repeated charge / discharge at 0.2 C rate.

[0192] Fig. 21 shows the cycle characteristics of the electrodes of Reference Examples 1 to 4 and Comparative Example 2. As is clear from Fig. 21, Reference Examples 1 to 4 have larger discharge capacities than Comparative Example 2. Of 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 solid content of the slurry was high and the amount of the dispersion medium (NMP), which is a vaporizable 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 Study] (Reference Example 5) Artificial graphite (median diameter D ５０ A slurry (solid ratio 95:2:1:2 mass%, solid content 51%) consisting of graphite (20 μm), carboxymethyl cellulose (2260, manufactured by Daicel Corporation), SBR (TDR2001, manufactured by JSR), and acetylene black (Denka Black, manufactured by Denka Company Ltd.) was prepared. Next, the graphite slurry was continuously applied (coating width 20 mm) to one side of a current collector using an electrode coater (comma coater).

[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, producing an electrode. The laser beam was irradiated so that each side exceeded the applied width of the slurry by 11 mm. A 10 μm-thick electrolytic copper foil (Type A, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) was used as the current collector. The weight of the composite layer per unit area was 16 to 18 mg / cm. ２ The laser irradiation size was 42 x 42 mm ２ It was decided.

[0196] (Reference Example 6) The electrode of Reference Example 6 was the same as that of 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 prepared by continuously applying the graphite slurry (application width: 60 mm) and irradiating the electrode with laser light so as to fit within the application width of the slurry. The electrode was the same as Reference Example 5 except that there was a 9 mm area of ​​slurry on each side that was not irradiated with laser light.

[0198] (Dryness of Coating Film) FIG. 22 shows the state in which the applied slurry is irradiated with laser light and dried (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, even with the slurry irradiated with the laser light, the composite layer in the vicinity of the uncoated area was insufficiently dried. In Reference Example 7, even with the slurry irradiated with the laser light, the composite layer in the vicinity of the unirradiated area was insufficiently dried.

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

[0201] As described above, preferred embodiments of the present invention have been described with reference to the drawings, but various additions, modifications, and omissions are possible without departing from the spirit of the present invention. For example, while the above embodiments have been described mainly using lithium ion batteries as examples, 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 within the scope of the present invention.

[0202] REFERENCE SIGNS LIST 10 Electrode manufacturing device 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 furnace 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: Step A of applying a slurry to a current collector conveyed at a predetermined speed; Step B of heating the applied slurry at a temperature of 30°C or higher and below the boiling point of the dispersion medium in the slurry; Step C of irradiating the slurry applied on the current collector with 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 1100 nm from a laser irradiation unit; The method for manufacturing an electrode for a power storage device, wherein the slurry contains 0.1% by mass or more of carbon based on the solid content of the slurry.

2. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the laser light is an area beam having an irradiation length of 1 cm or more with respect to the MD direction of the current collector.

3. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the laser light is an area beam that irradiates the current collector where the slurry is not applied with respect to the TD direction of the current collector.

4. The method for manufacturing an electrode for a power storage device according to claim 1, wherein Step C is to simultaneously irradiate laser light from a plurality of laser irradiation units to form an overlapping area beam.

5. The method for manufacturing an electrode for a power storage device according to claim 4, wherein the overlapping area beam of the plurality of laser lights irradiates the boundary between the applied portion and the non-applied portion of the slurry.

6. The method for manufacturing an electrode for a power storage device according to claim 1, wherein Step C irradiates laser light from a plurality of laser irradiation units. The first laser irradiation unit irradiates the entire width direction of the slurry applied to the current collector with laser light, and the second laser irradiation unit irradiates the boundary between the applied portion and the non-applied portion of the slurry applied to the current collector with laser light.

7. The method for manufacturing an electrode for a power storage device according to claim 1, further comprising Step D of heating the applied slurry after Step C.

8. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the wavelength of the laser irradiation unit in Step C is 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.

9. The method for manufacturing an electrode for a power storage device according to claim 1, characterized in that the slurry does not contain sulfur.

10. The method for manufacturing an electrode for a power storage device according to claim 1, wherein Step C irradiates the slurry in a constant rate drying period with a solid content ratio of 60% or more and 95% or less with the laser light.

11. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the step A is intermittent coating or stripe coating.

12. The method for manufacturing an electrode for a power storage device according to claim 1, wherein in the step 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 preheating the material and further concentrating the solid content of the slurry so that the solid content ratio is 60% or more and 95% or less to obtain a slurry for the constant rate drying period.

13. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the step B is heating for 10 seconds or more using hot air or radiation.

14. The method for manufacturing an electrode for a power storage device according to claim 1, wherein 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.

15. The method for manufacturing an electrode for a power storage device according to claim 7, wherein 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.

16. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the step C is performed during the constant rate drying period to obtain a slurry for the falling rate drying period in which the temperature of the slurry rises rapidly.

17. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the slurry contains any one of polyimide, polyamide, polyamideimide, polyamic acid, silicate, silicate hydrate, phosphate, and phosphate hydrate.

18. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the slurry contains an active material precursor, and the active material precursor is a material that can undergo a solid-phase reaction with a material contained in the composite layer or a current collector.

19. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the active material or the active material precursor is complexed with carbon.

20. The method for manufacturing an electrode for a power storage device according to claim 1, wherein a light-shielding filter is interposed between the area where the step A is performed and the area where the step C is performed.

21. The method for manufacturing an electrode for a power storage device according to claim 1, wherein the power storage device is a battery or a capacitor using an alkali metal ion as a carrier.

22. A manufacturing apparatus for an electrode for a power storage device, comprising: a mechanism A for applying a slurry to a current collector conveyed at a predetermined speed; a mechanism B for heating the applied slurry with the temperature inside a drying furnace being 30°C or higher and lower than the boiling point of a dispersion medium in the slurry; and a mechanism C for irradiating the slurry applied on the current collector with 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 1100 nm, on the downstream side of the current collector in the conveyance direction from the mechanism B, wherein the laser irradiation unit is provided outside the drying furnace, and it is a manufacturing apparatus for an electrode for a power storage device.

23. The manufacturing apparatus for an electrode for a power storage device according to claim 22, comprising a plurality of the laser irradiation units, wherein the plurality of laser irradiation units are arranged such that when laser light is simultaneously irradiated from the plurality of laser irradiation units, there is an area where the laser light overlaps.

24. The manufacturing apparatus for an electrode for a power storage device according to claim 23, wherein the plurality of laser irradiation units are arranged such that the area where the plurality of laser lights overlap irradiates the boundary between the applied portion and the unapplied portion of the slurry.

25. The manufacturing apparatus for an electrode for a power storage device according to claim 22, wherein the mechanism C comprises a plurality of laser irradiation units, the first laser irradiation unit is arranged to be able to irradiate laser light over the entire width direction of the slurry applied to the current collector, and the second laser irradiation unit is arranged to be able to irradiate including the boundary between the applied portion and the unapplied portion of the slurry applied to the current collector.

26. The manufacturing apparatus for an electrode for a power storage device according to claim 22, wherein the mechanism A is capable of applying the slurry to the front and back surfaces of the current collector, the mechanism C comprises a plurality of the laser irradiation units, and the laser irradiation units are arranged at positions where laser irradiation is possible on the front and back surfaces of the current collector.

27. The manufacturing apparatus for an electrode for a power storage device according to claim 22, further comprising a mechanism D for heating the applied slurry on the downstream side of the current collector in the conveyance direction from the mechanism C.

28. The manufacturing apparatus for an electrode for a power storage device according to claim 22, wherein the wavelength of the laser irradiation unit in the mechanism C is 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.

29. The mechanism B is arranged at a position where the slurry can be dried during the material preheating stage among the material preheating stage, the constant rate drying stage, and the falling rate drying stage in the process of drying the slurry, upstream of the mechanism C in the conveyance direction of the current collector. The mechanism C is arranged at a position where the slurry can be dried during the constant rate drying stage. The manufacturing apparatus for an electrode for a power storage device according to claim 22.

30. The mechanism B includes a heating device, and the heating device has a hot air nozzle or a heater. The manufacturing apparatus for an electrode for a power storage device according to claim 22.

31. The mechanism D includes a heating device, and the heating device has a hot air nozzle or a heater. The manufacturing apparatus for an electrode for a power storage device according to claim 27.

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