Method for manufacturing an electrode active material layer, and method for manufacturing a battery

Abstract

This disclosure provides a method for manufacturing an electrode active material layer that can suppress overheating and prolonged drying, and a method for manufacturing a battery that includes manufacturing an electrode active material layer in this manner. [Solution] The present disclosure method for manufacturing an electrode active material layer includes the following steps: conveying a long sheet-like preliminary electrode active material layer 110 with a transport roller 20; laser heating the preliminary electrode active material layer in a reduced-pressure environment; measuring the surface temperature at one or more locations on the preliminary electrode active material layer; and feedback-controlling the laser output so that the surface temperature does not exceed a predetermined temperature. The present disclosure method for manufacturing a battery includes manufacturing an electrode active material layer by the present disclosure method.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an electrode active material layer and a method for manufacturing a battery.

Background Art

[0002] As disclosed in Patent Documents 1 to 4, a technique for drying an electrode active material layer is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present inventors have found that when the electrode active material layer is heated and dried at a high temperature such as 180°C or higher in order to reduce the moisture in the electrode active material layer to a target value or less, the binder contained in the electrode active material layer becomes brittle, and thereby the flexibility of the binder may deteriorate.

[0005] Therefore, in order to suppress such deterioration of the flexibility of the binder, it is desirable to suppress overheating.

[0006] On the other hand, when the electrode active material layer is dried at a low temperature in order to suppress such deterioration of the flexibility of the binder, another problem occurs in that the drying time becomes longer as the drying temperature decreases.

[0007] The present disclosure aims to provide a method for manufacturing an electrode active material layer that can suppress overheating and prolonged drying, and a method for manufacturing a battery that includes manufacturing an electrode active material layer in this manner. [Means for solving the problem]

[0008] The Disclosing Party has found that the above-mentioned problems can be solved by the following means. <Aspect 1> A method for producing an electrode active material layer, including the following steps: The long, sheet-like preliminary electrode active material layer is transported by rollers using a transport roller. The aforementioned preliminary electrode active material layer is laser-heated under reduced pressure. Measuring the surface temperature at one or more locations in the aforementioned preliminary electrode active material layer, and The laser output is feedback-controlled so that the surface temperature does not exceed a predetermined temperature. <Aspect 2> The method according to embodiment 1, wherein the surface temperature is measured with a radiation thermometer. <Aspect 3> The method according to embodiment 1 or 2, wherein the predetermined temperature is a temperature selected from temperatures of 180°C or lower. <Aspect 4> The method according to any one of embodiments 1 to 3, further comprising pressing the preliminary electrode active material layer before the laser heating. <Aspect 5> A method for manufacturing a battery, comprising manufacturing an electrode active material layer by the method described in any one of embodiments 1 to 4. [Effects of the Invention]

[0009] According to the method for manufacturing the electrode active material layer of this disclosure, it is possible to suppress overheating and prolonged drying of the electrode active material layer.

[0010] The method for manufacturing a battery according to this disclosure provides a battery containing an electrode active material layer in which overheating and prolonged drying are suppressed. [Brief explanation of the drawing]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing an example of the method of the present disclosure for manufacturing an electrode active material layer. [Figure 2] FIG. 2 is a schematic diagram showing an example of the method of the present disclosure for manufacturing an electrode active material layer. [Figure 3] FIG. 3 is a graph showing the relationship between the laser irradiation time and the irradiation energy density in the examples. [Figure 4] FIG. 4 is a graph showing the relationship between the drying time and the surface temperature of the preliminary electrode active material layer in the examples.

MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the disclosure.

[0013] <<Method for Manufacturing Electrode Active Material Layer>> The method of the present disclosure for manufacturing an electrode active material layer includes the following steps: roller-conveying a long sheet-like preliminary electrode active material layer with a conveying roller, laser-heating the preliminary electrode active material layer in a reduced-pressure environment, measuring the surface temperature at one or more locations of the preliminary electrode active material layer, and feedback-controlling the laser output so that the surface temperature does not exceed a predetermined temperature.

[0014] The present inventors have found that it is difficult to uniformly heat the preliminary electrode active material layer by heating with hot air, radiant heat, etc., and thus local overheating may occur.

[0015] On the other hand, the present inventors have found that laser heating in a reduced-pressure environment makes it easy to uniformly heat the preliminary electrode active material layer at a relatively low temperature. Also, in order to suppress overheating of the electrode active material layer, it has been found that it is easy to feedback-control the laser output based on the surface temperature at one or more locations of the preliminary electrode active material layer due to the high responsiveness of the laser.

[0016] In this disclosure, "preliminary electrode active material layer" refers to the layer formed from the electrode mixture before and during the laser heating process, as described later. In this disclosure, "electrode active material layer" refers to the layer formed from the electrode mixture after the laser heating process.

[0017] In this disclosure, “electrode mixture” means a composition that can constitute an electrode active material layer, either as is or by further containing other components. In this disclosure, “electrode mixture slurry” means a slurry that includes a dispersion medium in addition to the “electrode mixture,” and thereby can be applied and dried to form an electrode active material layer.

[0018] The "electrode active material layer" may be a positive electrode active material layer or a negative electrode active material layer, and may be a positive electrode active material layer in particular.

[0019] The preliminary electrode active material layer may be formed on the current collector layer. Therefore, the preliminary electrode active material layer may together with the current collector layer constitute a preliminary electrode laminate, and the electrode active material layer may together with the current collector layer constitute an electrode laminate. In this case, the electrode laminate may be a bipolar electrode laminate. In the context of this disclosure, "bipolar electrode laminate" means an electrode laminate having a positive electrode active material layer, a current collector layer, and a negative electrode active material layer in this order.

[0020] The method for manufacturing the electrode active material layer according to this disclosure will be described below with reference to the drawings as appropriate. Note that the dimensions shown in the drawings do not reflect the actual dimensions.

[0021] <Roller conveying process> As illustrated in Figure 1, the method of this disclosure includes conveying a long sheet-like preliminary electrode active material layer 110 using a conveyor roller 20. Figure 1 is a schematic diagram illustrating how the preliminary electrode active material layer 110 is wound onto a winding reel 32 after being heated (dried) by a laser irradiation device 10 and conveyed by the conveyor roller 20 from an unwinding reel 31.

[0022] <Laser heating process> The method disclosed herein includes laser heating of the preliminary electrode active material layer 110 under reduced pressure.

[0023] Laser heating allows for uniform heating of the preliminary electrode active material layer 110. Furthermore, the high responsiveness of the laser enables effective feedback control, as described later. On the other hand, performing this process under reduced pressure allows for drying of the preliminary electrode active material layer 110 at a relatively low temperature. Therefore, overheating and prolonged drying of the preliminary electrode active material layer 110 can be suppressed.

[0024] As illustrated in Figure 2, laser heating may be performed by the laser irradiation device 10. Figure 2 is a schematic, enlarged view of the laser irradiation device 10 and its surroundings in Figure 1.

[0025] Laser irradiation may be pulsed irradiation; that is, laser irradiation may be performed intermittently. The laser irradiation time and irradiation energy density, the non-irradiation time, and the number of repetitions of laser irradiation and non-irradiation are not particularly limited and can be set appropriately considering the ease with which the preliminary electrode active material layer heats up, the target heating temperature, etc. For example, an irradiation energy density of 2.0 W / cm² over 1.6 seconds. 2 The preliminary electrode active material layer 110 may be heated by repeating laser irradiation and periods of 3.7 seconds without laser irradiation three times.

[0026] The wavelength range of the laser is not particularly limited, but for example, if the preliminary electrode active material layer 110 is black, it may be in the near-infrared region.

[0027] The laser can be a semiconductor laser.

[0028] When using laser heating, a fan may be used in conjunction. The fan may be hot air.

[0029] The reduced pressure environment is not particularly limited and may be, for example, a vacuum environment. Specifically, the pressure in the reduced pressure environment may be 0.01 atmospheres or more, 0.02 atmospheres or more, or 0.03 atmospheres or more, and may also be 0.06 atmospheres or less, 0.05 atmospheres or less, 0.04 atmospheres or less, or 0.03 atmospheres or less.

[0030] As illustrated in Figure 2, the inside of the laser irradiation device 10 may be depressurized, for example, by a vacuum pump 50. An exhaust mechanism 60 may also be provided at the end of the vacuum pump 50.

[0031] <Surface temperature measurement process> The method disclosed herein includes measuring the surface temperature of the preliminary electrode active material layer 110.

[0032] As illustrated in Figure 2, in the method of this disclosure, the surface temperature of one or more locations may be measured with a radiation thermometer 40. Due to the high responsiveness of the radiation thermometer 40, feedback control described later can be effectively performed, which makes it easier to suppress overheating of the preliminary electrode active material layer 110. Although Figure 2 illustrates the case in which two radiation thermometers 40 are used, the number of radiation thermometers 40 is not limited to this, and there may be one or more.

[0033] Furthermore, when the preliminary electrode active material layer 110 is heated by a laser, heat can be selectively applied to the irradiated area, and therefore no excess heat is generated in the surrounding area. As a result, the surface temperature of the preliminary electrode active material layer 110 can be appropriately measured even when using a non-contact radiation thermometer 40.

[0034] In contrast, when heating is performed using, for example, hot air or radiant heat, not only the surface of the preliminary electrode active material layer 110 but also its surroundings become hot. Therefore, in this case, a non-contact radiation thermometer 40 cannot properly measure the surface temperature of the preliminary electrode active material layer 110.

[0035] <Feedback control process> The method disclosed herein includes feedback control of the laser output so that the surface temperature of the preliminary electrode active material layer 110 does not exceed a predetermined temperature. This makes it easier to suppress overheating of the preliminary electrode active material layer 110.

[0036] In the method of this disclosure, the predetermined temperature may be a temperature selected from temperatures of 180°C or lower. This temperature may be, for example, 50°C or higher, 75°C or higher, 100°C or higher, 120°C or higher, 140°C or higher, 150°C or higher, or 160°C or higher, and may also be 180°C or lower, 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, 120°C or lower, or 100°C or lower. The higher this temperature, the more effectively the drying time of the preliminary electrode active material layer 110 can be suppressed. The lower this temperature, the easier it is to suppress overheating of the preliminary electrode active material layer 110.

[0037] There are no particular limitations on the method of feedback-controlling the laser output so that the surface temperature of the preliminary electrode active material layer 110 does not exceed a predetermined temperature. For example, when a radiation thermometer 40 is used to measure the surface temperature of the preliminary electrode active material layer 110, the control can be performed as follows. First, the temperature information of the preliminary electrode active material layer 110 measured by the radiation thermometer 40 is output to the laser irradiation device 10. Next, the laser irradiation device 10 compares the temperature information input from the radiation thermometer 40 with information of a preset temperature that is n°C lower than the predetermined temperature. At this time, if the temperature information input from the radiation thermometer 40 is higher than the information of the preset temperature, the laser output to the preliminary electrode active material layer 110 is stopped by turning off the power of the laser irradiation device 10. n is not particularly limited and may be, for example, 20, 15, 10, 5, 3, 1, or 0. On the other hand, if the temperature information input from the radiation thermometer 40 is lower than the information of the preset temperature, the laser output to the preliminary electrode active material layer 110 is continued. These controls may be performed by a control unit that is not shown.

[0038] By using the laser and radiation thermometer 40 in combination in this way, their high responsiveness allows for effective feedback control, and therefore makes it easier to suppress overheating of the preliminary electrode active material layer 110.

[0039] <Pressing Process> Although not shown in the figures, the method of this disclosure may further include pressing the preliminary electrode active material layer 110 before laser heating.

[0040] If the preliminary electrode active material layer 110 contains a binder, it is thought that the binder is compressed in the preliminary electrode active material layer 110 after pressing, and therefore the flexibility is reduced. Based on this assumption, applying the method of this disclosure to the preliminary electrode active material layer 110 after pressing is particularly effective.

[0041] If the electrode active material layer 110 constitutes a bipolar electrode stack, the binder may be contained in a preliminary electrode active material layer that serves as the counter electrode to the preliminary electrode active material layer 110 that is irradiated with a laser, and the method of this disclosure may suppress the decrease in the flexibility of the preliminary electrode active material layer that serves as the counter electrode.

[0042] The pressing method is not particularly limited, and a conventional method can be used.

[0043] The pressing pressure is not particularly limited and can be set as appropriate so that the density of the preliminary electrode active material layer reaches the desired value.

[0044] <Atmospheric pressure drying process> The method of this disclosure may further include drying the preliminary electrode active material layer 110 under atmospheric pressure before pressing. The drying temperature in this step may be 50°C or higher, 60°C or higher, 80°C or higher, 90°C or higher, or 100°C or higher, and may be 140°C or lower, 130°C or lower, 120°C or lower, 110°C or lower, or 100°C or lower. The drying in this step may be mainly for the purpose of drying and removing the dispersion medium in the electrode mixture slurry for forming the preliminary electrode active material layer 110. In contrast, the drying in the laser heating step may be for the purpose of drying and removing moisture in the preliminary electrode active material layer 110.

[0045] <<Electrode active material layer>> The electrode active material layer 110 produced by the method of this disclosure comprises an electrode active material and may optionally include a binder, a conductive additive, and other components.

[0046] The thickness of the electrode active material layer is not particularly limited. The thickness of the electrode active material layer may be 10 μm or more and 500 μm or less, 100 μm or more and 450 μm or less, or 200 μm or more and 400 μm or less.

[0047] The size of the electrode active material layer is not particularly limited and can be set appropriately, for example, taking into consideration the desired battery capacity.

[0048] The shape of the electrode active material layer is not particularly limited, but may be a rectangle or other quadrilateral, for example.

[0049] <Electrode active material> The electrode active material is not particularly limited. For example, in this disclosure, if the electrode active material layer is a positive electrode active material layer, the electrode active material layer may contain a positive electrode active material. Also, for example, if the electrode active material layer is a negative electrode active material layer, the electrode active material layer may contain a negative electrode active material.

[0050] The positive electrode active material is not particularly limited as long as it has a noble potential compared to the negative electrode active material. When the electrode active material layer produced by the method of this disclosure is an electrode active material layer for a lithium-ion secondary battery, the positive electrode active material may be, for example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), solid solution oxide (Li2MnO3-LiMO2 (M=Co, Ni, etc.)), lithium nickel manganese oxide (LiNi 1 / 2 Mn 1 / 2 O2), lithium nickel-cobalt manganese oxide (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 Composite oxides such as O2, olivine-type lithium phosphate oxide (LiFePO4); conductive polymers such as polyaniline and polypyrrole; sulfide-based positive electrode active materials such as Li2S, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, Li-Mo-S compounds, Li-Ti-S compounds, and Li-VS compounds; materials using sulfur as an active material, such as sulfur-impregnated acetylene black, sulfur-impregnated porous carbon, and mixed powders of sulfur and carbon; etc. These positive electrode active materials may be used individually or in combination of two or more.

[0051] The content of positive electrode active material in the positive electrode composite material is not particularly limited and can be set appropriately considering the desired battery capacity, etc.

[0052] The shape of the positive electrode active material may be, for example, particulate.

[0053] The negative electrode active material is not particularly limited as long as it has a lower potential compared to the positive electrode active material. When the electrode active material layer produced by the method of this disclosure is an electrode active material layer for a lithium-ion secondary battery, the negative electrode active material may be, for example, carbonaceous materials such as graphite (artificial graphite, natural graphite), resin carbon, carbon fiber, activated carbon, hard carbon, soft carbon; metallic materials mainly consisting of tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, aluminum alloys, etc.; conductive polymers such as polyacene, polyacetylene, and polypyrrole; metallic lithium; Li4Ti5O 12 Examples include lithium titanium composite oxides such as Li-Si alloys, Li-Sn alloys, Li-Al alloys, Li-Ga alloys, Li-Mg alloys, and Li-In alloys; and lithium alloys such as Li-Si alloys, Li-Sn alloys, Li-Al alloys, Li-Ga alloys, Li-Mg alloys, and Li-In alloys. These negative electrode active materials may be used individually or in combination of two or more.

[0054] The content of the negative electrode active material in the negative electrode mixture as an electrode mixture is not particularly limited and can be set appropriately considering the desired battery capacity, etc.

[0055] The negative electrode active material may be in the form of particulate matter, for example.

[0056] <Binder> While not particularly limited, examples of binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamide-imide, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polymethyl polyacrylate, polyethyl polyacrylate, polyhexyl polyacrylate, polymethacrylic acid, polymethyl polymethacrylate, polyethyl polymethacrylate, polyhexyl polymethacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene, styrene-butadiene rubber, carboxymethylcellulose, and the like, especially when the battery of this disclosure is a lithium-ion secondary battery.

[0057] The binder content in the electrode mixture is not particularly limited and can be set appropriately considering the desired binding properties, etc.

[0058] <Conductive additive> The conductive additives are not particularly limited, but in the case of a lithium-ion secondary battery, examples include graphites such as natural graphite and artificial graphite; carbon blacks such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers such as carbon nanotubes and metal fibers; metal powders such as aluminum powder; conductive whiskers such as zinc oxide whiskers and conductive potassium titanate whiskers; conductive metal oxides such as titanium oxide; and organic conductive materials such as phenylene derivatives. These conductive additives may be used individually or in combination of two or more.

[0059] The content of the conductive additive in the electrode mixture is not particularly limited and can be set as appropriate, taking into consideration the desired conductivity, etc.

[0060] <Other ingredients> The electrode mixture may contain components other than those listed above. Examples of such components include solid electrolytes and dispersants.

[0061] <<Battery manufacturing method>> The method for manufacturing a battery according to this disclosure includes manufacturing an electrode active material layer by the method of this disclosure. A method for manufacturing an electrode active material layer by the method of this disclosure can be found in the description above.

[0062] A battery manufactured by the method of manufacturing a battery according to this disclosure includes an electrode active material layer 110 in which overheating and prolonged drying are suppressed.

[0063] In the method for manufacturing the electrode active material layer 110 according to this disclosure, for example, if the electrode active material layer 110 is a positive electrode active material layer and together with the current collector layer 120 and the negative electrode active material layer constitutes a bipolar electrode stack 100, the battery may have a bipolar electrode stack having the positive electrode active material layer, the current collector layer, and the negative electrode active material layer in that order, and an electrolyte layer.

[0064] The battery may be a liquid-based battery or a solid-state battery. In this disclosure, "solid-state battery" means a battery that uses at least a solid electrolyte as its electrolyte, and therefore a solid-state battery may use a combination of a solid electrolyte and a liquid electrolyte as its electrolyte. Furthermore, a solid-state battery may be an all-solid-state battery, i.e., a battery that uses only a solid electrolyte as its electrolyte.

[0065] The battery may be a primary battery or a secondary battery. In particular, it may be a lithium-ion secondary battery.

[0066] For details regarding the electrode active material layer, please refer to the description above.

[0067] As the current collector layer and electrolyte layer, those known as the current collector layer and electrolyte layer of a battery can be used. [Examples]

[0068] Using the equipment shown in Figure 2, an irradiation energy density of 2.0 W / cm² was applied to the preliminary electrode active material layer for 1.6 seconds under 0.03 atmospheres. 2 Laser heating was performed by repeating laser irradiation and 3.7-second periods of no laser irradiation three times. The laser irradiation profile for one set is shown in Figure 3. The target temperature for laser heating was 160°C. As shown in Figure 2, the surface temperature of the preliminary electrode active material layer was measured at two locations, points A and B, using a radiation thermometer. The measurement results of the surface temperature of the preliminary electrode active material layer are shown in Figure 4.

[0069] As shown in Figure 4, equivalent temperature profiles were observed at points A and B. This suggests that laser heating uniformly heats the pre-electrode active material layer, and therefore localized overheating is unlikely to occur.

[0070] Under the above conditions, laser heating confirmed that the moisture content of the electrode active material layer was below the specified value using a Karl Fischer moisture meter. The drying time was approximately 20 seconds, demonstrating that the drying time could not be prolonged. [Explanation of Symbols]

[0071] 10 Laser irradiation device 20 Conveyor rollers 31. Reel for unwinding 32 Reel for winding 40 Radiation thermometer 50 Vacuum pump 60 Exhaust mechanism 100 (Spare) Electrode Laminate 110 (Reserve) Electrode Active Material Layer 120 Current collector layer

Claims

1. A method for manufacturing an electrode active material layer, including the following steps: The long, sheet-like preliminary electrode active material layer is transported by rollers using a transport roller. The aforementioned preliminary electrode active material layer is laser-heated under reduced pressure. Measuring the surface temperature at one or more locations in the preliminary electrode active material layer, and The laser output is feedback-controlled so that the surface temperature does not exceed a predetermined temperature.

2. The method according to claim 1, wherein the surface temperature is measured with a radiation thermometer.

3. The method according to claim 1, wherein the predetermined temperature is a temperature selected from temperatures of 180°C or lower.

4. The method according to claim 1, further comprising pressing the preliminary electrode active material layer before the laser heating.

5. A method for manufacturing a battery, comprising manufacturing an electrode active material layer by the method according to any one of claims 1 to 4.

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