Method for manufacturing electrodes, and method for manufacturing energy storage devices

Abstract

The present invention provides a method for manufacturing electrodes and energy storage devices that can suppress cracking of the active material layer. [Solution] In the manufacturing method of the bipolar electrode 20, in the drying step in which a slurry coated on the current collector 21 is radiantly heated to form a positive electrode active material layer 22 and a negative electrode active material layer 23, air is blown in such a way that the humidity of the uncoated region T2 of the current collector 21, where the slurry is not coated, becomes higher than the humidity of the coated region T1 of the current collector 21 where the slurry is coated.

Description

【Technical Field】 【0001】 The present invention relates to a method for manufacturing an electrode and a method for manufacturing a power storage device. 【Background Art】 【0002】 Patent Document 1 discloses a technique of irradiating a coating film with far-infrared rays having a wavelength with high absorbency to an organic solvent to evaporate the organic solvent from the entire layer of the coating film and lead the coating film to a dry state. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Laid-Open No. 6-63495 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 By the way, in an electrode and a power storage device, it is preferable to suppress cracking of the active material layer. 【0005】 An object of the present invention is to provide a method for manufacturing an electrode and a power storage device capable of suppressing cracking of the active material layer. 【Means for Solving the Problems】 【0006】 In the drying step of forming an active material layer by heating a slurry coated on a current collector, while drying the slurry, air is blown so that the humidity of the uncoated region of the current collector where the slurry is not coated is higher than the humidity of the coated region of the current collector where the slurry is coated. 【0007】 In the electrode manufacturing method according to claim 1, the humidity of the uncoated region of the current collector, where the slurry is not applied, is made higher than the humidity of the coated region of the current collector, thereby resulting in a higher humidity in the uncoated region of the current collector compared to the coated region. As a result, drying of the slurry at the edges of the coated region is suppressed. Consequently, cracking of the active material layer can be suppressed. 【0008】 The electrode manufacturing method according to claim 2 is the electrode manufacturing method according to claim 1, wherein in the drying step, air is blown from a first blower to the coated area, and air with a higher humidity than the air blown from the first blower is blown from a second blower to the uncoated area. 【0009】 In the electrode manufacturing method according to claim 2, by blowing air at a higher humidity than the coated region onto the uncoated region of the current collector, the uncoated region of the current collector is made to have a higher humidity than the coated region. As a result, drying of the slurry at the edge of the coated region is suppressed. Consequently, cracking of the active material layer can be suppressed. 【0010】 The electrode manufacturing method according to claim 3 is the electrode manufacturing method according to claim 2, wherein the coated area is set in the center in the width direction of the current collector, the uncoated area is set at the end in the width direction of the current collector, and the air blown from the second blower to the uncoated area is exhausted by an exhaust device located on the outside in the width direction of the current collector. 【0011】 In the electrode manufacturing method according to claim 3, the air blown to the uncoated area is exhausted to the side of the current collector, thereby suppressing the flow of air blown to the uncoated area into the coated area. As a result, a balance is maintained between the drying rate of the slurry at the edge of the coated area and the drying rate of the slurry in the center of the coated area. Consequently, cracking of the active material layer can be suppressed. 【0012】 A method for manufacturing an energy storage device according to claim 4 includes a cutting step of cutting an electrode manufactured by the manufacturing method described in any one of claims 1 to 3, a sealing step of sealing the periphery of the cut electrode, and a welding step of stacking the sealed electrodes and welding the outer surface. 【0013】 The method for manufacturing an energy storage device according to claim 4 makes it possible to manufacture an energy storage device that can suppress cracking of the active material layer. [Effects of the Invention] 【0014】 As described above, according to the method for manufacturing electrodes and energy storage devices of the present invention, cracking of the active material layer can be suppressed. [Brief explanation of the drawing] 【0015】 [Figure 1] This is a schematic cross-sectional view showing an energy storage device according to an embodiment. [Figure 2] This is a schematic perspective view showing an electrode manufacturing apparatus according to an embodiment. [Figure 3] This is a schematic cross-sectional view showing the electrode manufacturing apparatus according to the embodiment, and shows the AA section of Figure 2. [Figure 4] This is a flowchart showing a method for manufacturing an energy storage device according to an embodiment. [Modes for carrying out the invention] 【0016】 The following description of the energy storage device according to the embodiment will be made with reference to the drawings. The energy storage device according to the embodiment is mounted on a vehicle such as an electric vehicle or a hybrid vehicle and used as an on-board power source. In each figure, the arrow UP indicates the upper side of the energy storage device 10 in the vertical direction, the arrow LH indicates the left side of the energy storage device 10 in the horizontal direction, the arrow W indicates the width direction W of the bipolar electrode 20, and the arrow R indicates the transport direction R of the current collector 21. Also, the upper side of the energy storage device 10 coincides with the upper side of the vehicle on which the energy storage device 10 is mounted. 【0017】 [Configuration of the energy storage device 10] As shown in FIG. 1, the power storage device 10 is formed in a rectangular plate shape with the vehicle up-and-down direction as the plate thickness direction. The power storage device 10 is a so-called bipolar battery, and is, for example, a secondary battery such as a nickel-hydrogen secondary battery or a lithium-ion secondary battery. 【0018】 The power storage device 10 includes a laminate 12, a sealing body 28, and an electrolytic solution (not shown). The laminate 12 has a plurality of bipolar electrodes (an example of an electrode) 20 and a plurality of separators 25 laminated in a lamination direction D. 【0019】 (Bipolar electrode 20) The bipolar electrode 20 includes a current collector 21, a positive electrode active material layer 22, and a negative electrode active material layer 23. 【0020】 The current collector 21 is formed in a rectangular plate shape with the vehicle up-and-down direction as the plate thickness direction. The current collector 21 is, for example, a metal foil made of copper, aluminum, or the like. 【0021】 The positive electrode active material layer 22 is formed in a rectangular plate shape with the vehicle up-and-down direction as the plate thickness direction. The positive electrode active material layer 22 is formed by coating one surface (the upper surface) in the up-and-down direction of the current collector 21. The positive electrode active material layer 22 is formed inside the outer edge of the current collector 21. The positive electrode active material layer 22 is configured to include a positive electrode active material (for example, a lithium-containing composite oxide) that can occlude and release charge carriers such as lithium ions. 【0022】 The negative electrode active material layer 23 is formed in a rectangular plate shape with the vehicle up-and-down direction as the plate thickness direction. The negative electrode active material layer 23 is formed by coating the other surface (the lower surface) in the up-and-down direction of the current collector 21. The negative electrode active material layer 23 is formed inside the outer edge of the current collector 21. The negative electrode active material layer 23 is configured to include a negative electrode active material (for example, a carbon-based active material such as graphite or hard carbon) that can occlude and release charge carriers such as lithium ions. 【0023】 (Separator 25) The separator 25 is formed in the shape of a rectangular plate with the vehicle's vertical direction as the plate thickness direction. The separator 25 is positioned between adjacent bipolar electrodes 20 in the stacking direction D. The separator 25 prevents electrical short circuits between electrodes by isolating adjacent bipolar electrodes 20. The positive electrode active material layer 22 and the negative electrode active material layer 23 are impregnated with electrolyte. 【0024】 (Sealing body 28) The sealing body 28 is formed in a frame shape so as to surround the periphery of the laminate 12. The sealing body 28 can be formed in a frame shape by, for example, placing molten thermoplastic resin around the periphery of the laminate 12 and cooling it. The sealing body 28 holds the periphery of the bipolar electrode 20 and the separator 25, and seals the space S formed between the bipolar electrode 20. 【0025】 [Manufacturing method for the energy storage device 10] As shown in Figure 2, the energy storage device 10 is manufactured by including an electrode manufacturing process, a lamination process, and a welding process. The electrode manufacturing process includes a coating process, a drying process, a cutting process, and a sealing process. 【0026】 The coating and drying processes will be described in the following manner: forming the positive electrode active material layer 22 on one surface of the current collector 21 in the vertical direction. The method for forming the negative electrode active material layer 23 on the other surface of the current collector 21 in the vertical direction can be the same as the method for forming the positive electrode active material layer 22. 【0027】 (Coating process) In the coating process of step S101, as shown in Figure 3, the current collector 21, which is formed in a long strip shape, is unfurled in the longitudinal direction and transported in the transport direction R. Then, a slurry that forms the positive electrode active material layer 22 is supplied from the slurry supply device 31 to one surface of the transported current collector 21 in the vertical direction. 【0028】 In this case, the area to which the slurry is supplied is defined as the coated area T1, and the area to which the slurry is not supplied is defined as the uncoated area T2. In this embodiment, the coated area T1 is defined as the area including the center in the width direction W of the current collector 21, and the uncoated area T2 is defined as the areas at both ends (edges) of the width direction W of the current collector 21. 【0029】 Alternatively, the slurry may be supplied intermittently in the longitudinal direction of the current collector 21 to form a coated region and an uncoated region aligned in the longitudinal direction of the current collector 21. 【0030】 (drying process) In the drying step S102, the current collector 21 supplied with the slurry for forming the positive electrode active material layer 22 is transported in the transport direction R. Then, the current collector 21 being transported is dried by the drying device 32 using radiant heating (for example, by irradiating it with laser light or an infrared heater) to form the positive electrode active material layer 22. 【0031】 In this process, as shown in Figure 4, the blower 40 supplies air to the coated area T1 and the uncoated area T2. In other words, the current collector 21 on which the slurry is placed is heated by radiation from the drying device 32, and air is supplied from the blower 40. 【0032】 Furthermore, air may be supplied by the blower 40 before the current collector 21 to which the slurry is supplied is radiantly heated by the drying device 32, or air may be supplied by the blower 40 after the current collector 21 to which the slurry is supplied has been radiantly heated by the drying device 32. 【0033】 Here, the blower 40 includes a first blower 41 and a second blower 42. The first blower 41 is located in the center of the width direction W of the current collector 21. The first blower 41 is configured to supply air with lower humidity than the second blower 42. 【0034】 The second blower 42 is positioned at both ends of the current collector 21 in the width direction W. The second blower 42 is configured to supply air with a higher humidity than the first blower 41. As a result, the uncoated area T2 is supplied with air at a higher humidity than the coated area T1. Therefore, the humidity in the uncoated area T2 is higher than the humidity in the coated area T1. 【0035】 Furthermore, the air supplied by the blower 40 is exhausted by the exhaust device 50. Here, the exhaust device 50 includes a first exhaust device 51 and a second exhaust device 52. 【0036】 The first exhaust device 51 is located in approximately the same position as the blower 40 in the longitudinal direction of the current collector 21, and is positioned outside the width direction W of the current collector 21. The first exhaust device 51 exhausts the air supplied by the blower 40 to the outside (side) of the width direction W of the current collector 21. 【0037】 The second exhaust device 52 is located below the current collector 21, in approximately the same position as the blower 40 in the longitudinal direction of the current collector 21. The second exhaust device 52 exhausts the air that has been exhausted to the outside (side) in the width direction W of the current collector 21 to the bottom of the current collector 21. The air exhausted by the second exhaust device 52 may be supplied to the blower 40. 【0038】 (cutting process) In step S103, the cutting process, the current collector 21 on which the positive electrode active material layer 22 and the negative electrode active material layer 23 are formed is cut in the width direction W to form individual sheets. 【0039】 (Sealing process) In the sealing step S104, the periphery of the cut current collector 21 is sealed with, for example, a thermoplastic resin. This forms the bipolar electrode 20. 【0040】 (Lamination process) In the lamination process of step S105, the bipolar electrodes 20 and separators 25 are alternately stacked in the lamination direction D to form a laminate 12. 【0041】 (Welding process) In the welding process of step S106, for example, molten thermoplastic resin is placed on the periphery of the laminate 12 and heat-welded to form a sealant 28. In other words, in the welding process, the outer surface of the laminate 12 is heat-welded to form a sealant 28. This forms the energy storage device 10. 【0042】 [Effect] Incidentally, during the drying process, when the slurry coated on the current collector 21 is radiantly heated, the uncoated region T2, where the slurry is not applied, becomes overheated. The heat from the overheated uncoated region T2 is transferred to the coated region T1 of the current collector 21. As a result, the slurry at the edges of the coated region T1 dries faster than the slurry in the center of the coated region T1. When the slurry dries rapidly, vapor escapes violently from the pores (micropores) formed in the positive electrode active material layer 22 and the negative electrode active material layer 23. Consequently, cracks may occur in the positive electrode active material layer 22 and the negative electrode active material layer 23 formed at the edges of the coated region T1. 【0043】 In the manufacturing method of the bipolar electrode 20 according to the embodiment, in the drying step in which a slurry coated on the current collector 21 is radiantly heated to form a positive electrode active material layer 22 and a negative electrode active material layer 23, the humidity of the uncoated region T2 on the current collector 21 where the slurry is not coated is made higher than the humidity of the coated region T1 on the current collector 21 where the slurry is coated (see Figure 4). 【0044】 By making the humidity of the uncoated region T2 of the current collector 21, where the slurry is not applied, higher than the humidity of the coated region T1 of the current collector 21, the uncoated region T2 of the current collector 21 has a higher humidity than the coated region T1. As a result, drying of the slurry at the edge of the coated region T1 is suppressed. Consequently, cracking of the positive electrode active material layer 22 and the negative electrode active material layer 23 can be suppressed. 【0045】 In the manufacturing method of the bipolar electrode 20 according to the embodiment, during the drying process, air is blown to the uncoated region T2 at a higher humidity than the coated region T1 (see Figure 4). 【0046】 By blowing air at a higher humidity than the coated area T1 onto the uncoated area T2, the uncoated area T2 of the current collector 21 becomes more humid than the coated area T1. As a result, drying of the slurry at the edge of the coated area T1 is suppressed. Consequently, cracking of the positive electrode active material layer 22 and the negative electrode active material layer 23 can be suppressed. 【0047】 In the manufacturing method of the bipolar electrode 20 according to this embodiment, the air blown to the uncoated region T2 is exhausted to the side of the current collector 21 (see Figure 4). 【0048】 By exhausting the airflow directed towards the uncoated area T2 to the side of the current collector 21, the airflow directed towards the uncoated area T2 is suppressed from flowing into the coated area T1. As a result, a balance is maintained between the drying rate of the slurry at the edge of the coated area T1 and the drying rate of the slurry in the center of the coated area T1. Consequently, cracking of the positive electrode active material layer 22 and the negative electrode active material layer 23 can be suppressed. 【0049】 The manufacturing method for the energy storage device 10 according to this embodiment includes a cutting step of cutting the bipolar electrode 20, a sealing step of sealing the periphery of the cut bipolar electrode 20, and a welding step of stacking the sealed bipolar electrode 20 and welding the outer surface (see Figure 2). 【0050】 This makes it possible to manufacture an energy storage device 10 that can suppress cracking of the positive electrode active material layer 22 and the negative electrode active material layer 23. 【0051】 The manufacturing methods for electrodes and energy storage devices have been described above based on embodiments. However, the specific configuration is not limited to these embodiments, and design changes are permitted as long as they do not deviate from the gist of the invention as described in each claim of the patent. 【0052】 In this embodiment, the uncoated area T2 is blown with air at a higher humidity than the coated area T1, resulting in a higher humidity in the uncoated area T2 than in the coated area T1. However, the humidity in the uncoated area T2 may also be made higher than that of the coated area T1 by providing an enclosure around the uncoated area T2. Alternatively, the uncoated area T2 may be blown with air at a higher humidity than the coated area T1, and an enclosure may also be provided around the uncoated area T2. 【0053】 In this embodiment, an example was shown in which the electrode is a bipolar electrode 20. However, the electrode is not limited to this embodiment and may also be a monopolar electrode. 【0054】 In this embodiment, an example was shown in which an electrolyte solution is contained inside the energy storage device 10. However, the energy storage device may also be an all-solid-state battery. [Explanation of Symbols] 【0055】 10 Energy storage device 20. Bipolar electrodes (an example of an electrode) 21 Current collector 22 Positive electrode active material layer (active material layer) 23 Negative electrode active material layer (active material layer) T1 Coating Area T2 Unpainted Area

Claims

[Claim 1] In a drying process in which a slurry coated on a current collector is heated to form an active material layer, While the slurry is drying, air is blown in such a way that the humidity of the uncoated area of ​​the current collector where the slurry is not applied is higher than the humidity of the coated area of ​​the current collector where the slurry is applied. A method for manufacturing electrodes. [Claim 2] In the drying process, Air is supplied from the first blower to the coating area. The method for manufacturing an electrode according to claim 1, wherein a second blower blows air with a higher humidity than the air blown from the first blower blows air to the uncoated area. [Claim 3] The coated area is located in the center of the current collector in the width direction, and the uncoated area is located at the end of the current collector in the width direction. The air blown from the second blower to the uncoated area is exhausted by an exhaust device located on the outside in the width direction of the current collector. The method for manufacturing an electrode according to claim 2. [Claim 4] A cutting step of cutting an electrode manufactured by the manufacturing method described in any one of claims 1 to 3, A sealing step of sealing the periphery of the cut electrode, A welding step involves stacking the sealed electrodes and welding the outer surface, A method for manufacturing an energy storage device that includes [a specific component].

Images