Electrode base material, electrode base material laminate, electrode, secondary battery, and methods for manufacturing same

Abstract

The present invention provides: an electrode base material for secondary batteries with which it is possible to manufacture a secondary battery that has a low internal resistance; an electrode base material laminate; an electrode; a secondary battery; and methods for manufacturing the same. Disclosed is an electrode base material which is used for manufacturing an electrode, the electrode base material being characterized by comprising a resin base material and active material particles and solid electrolyte particles on the resin base material, wherein: a particle layer which contains the active material particles and the solid electrolyte particles is formed on the resin base material; when the particle layer is viewed through from a surface on the resin base material side or from the reverse surface side, the solid electrolyte particles are disposed so as to cover at least a part of the surfaces of the active material particles; and, in a cross-sectional observation of the particle layer, the difference between the area ratio of exposed surfaces of the active material particles on a surface of the particle layer on the side in contact with the resin base material, and the area ratio of exposed surfaces of the active material particles on the reverse side of the particle layer to the side in contact with the resin base material is 1 to 70 area%.

Description

Electrode substrate, electrode substrate laminate, electrode and secondary battery, and method for manufacturing the same

[0001] The present disclosure relates to an electrode substrate, an electrode substrate laminate, an electrode and a secondary battery, and a method for manufacturing the same.

[0002] Generally, secondary batteries are composed of electrodes (positive and negative electrodes) and an electrolyte, and charge and discharge occur through the movement of ions between the electrodes via the electrolyte. Such secondary batteries are used in a wide range of applications, from small devices such as mobile phones to large devices such as electric vehicles. Therefore, further improvement in the performance of secondary batteries is required.

[0003] In recent years, research and development of so-called all-solid-state batteries, which use inorganic solid electrolytes as the electrolyte, has progressed. By replacing conventional organic electrolytes with solid electrolytes, all-solid-state batteries are expected to improve the safety and capacity of secondary batteries, and to achieve high output. However, in all-solid-state batteries, both the active material and the solid electrolyte are solid, and interfaces are formed between solid particles, resulting in high interfacial resistance. As a result, the resistance inside the electrode increases, and the resulting battery output decreases. Therefore, technologies have been developed to reduce internal resistance.

[0004] Patent Document 1 discloses an electrode in which active material particles and solid electrolyte particles are arranged in a pattern to ensure smooth ion conduction between the active material and the solid electrolyte. Patent Document 2 discloses an electrode in which the concentration of active material particles is high and the concentration of solid electrolyte particles is low on the current collector side, while the concentration of active material is low and the concentration of solid electrolyte particles is high on the solid electrolyte layer side to ensure smooth ion conduction.

[0005] JP 2019-137060 A JP 2021-039848 A

[0006] However, according to the inventors' research, it has been found that because solid electrolytes and active materials are unsuitable for electronic conduction and ionic conduction, respectively, simply controlling the arrangement of each particle, as in Patent Document 1, may result in insufficient contact between the particles, and may not be able to sufficiently reduce the internal resistance. Furthermore, it has been found that when the concentration of each particle is graded within the electrode, as in Patent Document 2, there is insufficient contact between particles of the same type between low-concentration and high-concentration regions, resulting in areas where the ionic conduction paths and electronic conduction paths are not connected, and therefore, the internal resistance may not be sufficiently reduced. Therefore, there is a need to further reduce the internal resistance of electrodes and further improve the output of secondary batteries.

[0007] According to at least one aspect of the present disclosure, there are provided an electrode substrate for a secondary battery, an electrode substrate laminate, an electrode, and a secondary battery, which enable the production of a secondary battery having excellent electronic conductivity and ionic conductivity, low internal resistance, and high output. Also, according to at least one aspect of the present disclosure, there are provided methods for producing the electrode substrate, electrode substrate laminate, electrode, and secondary battery.

[0008] According to at least one aspect of the present disclosure, there is provided an electrode substrate used in manufacturing an electrode, the electrode substrate comprising: a resin substrate; and active material particles and solid electrolyte particles on the resin substrate; a particle layer containing the active material particles and the solid electrolyte particles is formed on the resin substrate; when the particle layer is viewed through the surface side in contact with the resin substrate or the surface side opposite to the surface in contact with the resin substrate, the solid electrolyte particles are arranged so as to cover at least a portion of the surface of the active material particles; and when a cross-section of the particle layer is observed with a scanning electron microscope (SEM), the difference between the area ratio of the exposed surface of the active material particles on the surface of the particle layer in contact with the resin substrate and the area ratio of the exposed surface of the active material particles on the surface opposite to the surface in contact with the resin substrate is 1 to 70 area %.

[0009] According to at least one embodiment of the present disclosure, there is provided an electrode substrate laminate in which a plurality of the electrode substrates are laminated.

[0010] According to at least one aspect of the present disclosure, there is provided an electrode for a secondary battery, the electrode being a sintered body of the above-described electrode base material, or an electrode being a sintered body of an electrode base material laminate in which a plurality of the above-described electrode base materials are laminated.

[0011] According to at least one embodiment of the present disclosure, there is provided a secondary battery comprising an electrode that is a sintered body of the electrode substrate, and an electrolyte layer adjacent to the electrode.

[0012] According to at least one aspect of the present disclosure, there is provided a method for producing the electrode base material used in producing an electrode, the method comprising the steps of: preparing the resin base material having an adhesive portion; arranging the active material particles on a surface of the adhesive portion; rubbing the surfaces of the active material particles arranged on the surface of the adhesive portion; and arranging the solid electrolyte particles on the surface of the adhesive portion and the rubbed surfaces of the active material particles.

[0013] According to at least one aspect of the present disclosure, there is provided a method for producing an electrode base material used in producing an electrode, the electrode base material comprising: a resin base material; and active material particles and solid electrolyte particles on the resin base material; a particle layer comprising the active material particles and the solid electrolyte particles is formed on the resin base material; and when the particle layer is viewed through from the surface side in contact with the resin base material or the surface side opposite to the surface in contact with the resin base material, the solid electrolyte particles are arranged so as to cover at least a portion of the surface of the active material particles, the production method comprising the steps of: preparing the resin base material having an adhesive portion; arranging the active material particles on the surface of the adhesive portion; rubbing the surfaces of the active material particles arranged on the surface of the adhesive portion; and arranging the solid electrolyte particles on the surface of the adhesive portion and the rubbed surfaces of the active material particles.

[0014] Furthermore, according to at least one aspect of the present disclosure, there is provided a method for manufacturing an electrode, comprising the steps of: stacking a plurality of the electrode base materials described above to form a laminate; removing the resin base material from the laminate to obtain a three-dimensional object; and applying pressure to the three-dimensional object to obtain an electrode.

[0015] Furthermore, according to at least one aspect of the present disclosure, there is provided a method for manufacturing a secondary battery, the method including: preparing an electrode by the above-described electrode manufacturing method; and laminating the electrode, a current collector, and an electrolyte.

[0016] According to at least one aspect of the present disclosure, there are provided an electrode substrate, an electrode, and a secondary battery that can produce a secondary battery that has excellent electronic conductivity and ionic conductivity, low internal resistance, and high output, as well as methods for producing the electrode substrate, the electrode, and the secondary battery.

[0017] FIG. 1 is a conceptual diagram showing an electrode substrate. FIG. 2 is a conceptual diagram showing a manufacturing method of an electrode substrate. FIG. 3 is a diagram schematically showing the configuration of a particle arrangement device 1. FIG. 4 is a diagram schematically showing the configuration of a filling device. FIGS. 5A to 5C are schematic diagrams showing the stages of the state of the filler being conveyed on a first substrate. FIG. 6 is an enlarged view of the vicinity of the surface of a first substrate. FIG. 7A is a diagram schematically showing the configuration of a filling device when brush fibers are used as the carrier material, and FIG. 7B is a diagram schematically showing the configuration of a filling device when an elastic material is used as the carrier material. FIG. 8 is a diagram schematically showing the configuration of a transfer unit. FIG. 9 is an enlarged view of the vicinity of the surface of a second substrate in a filling process using a second filling device. FIG. 10A is a diagram schematically showing the second substrate after the first particles P1 have been transferred, and FIG. 10B is a diagram schematically showing the second substrate after the second particles P2 have been transferred. FIG. 11 is a diagram schematically showing the configuration of a particle arrangement device 2. FIG. 12 is a diagram schematically showing each device in the second and third steps in the manufacturing method of an electrode base material. FIG. 13 is a diagram schematically showing a third filling device that does not use a belt device. FIG. 14 is a schematic diagram explaining the operation of the filling device. FIG. 15 is an image diagram showing the manufacturing method of an electrode. FIG. 16 is a diagram schematically showing the configuration of a laminate molding device. FIG. 17 is a diagram schematically showing the configuration of a sintering processing device. FIG. 18A is an SEM image of a cross section of a laminate after the first step of the manufacturing method of an electrode, FIG. 18B is an SEM image of a three-dimensional object after the second step, and FIG. 18C is an SEM image of an upper part of the three-dimensional object. FIG. 19 is a diagram schematically showing the overall configuration of an additive manufacturing system. FIG. 20A is an image diagram showing manufacturing method 1 of an electrode base material, FIG. 20B is an image diagram showing manufacturing method 2 of an electrode base material, FIG. 20C is an image diagram showing manufacturing method 3 of an electrode base material, and FIG. 20D is an image diagram showing manufacturing method 4 of an electrode base material. Fig. 21A is a diagram schematically showing the structure of the upper surface of a first substrate having a concave-convex pattern formed on its surface, and Fig. 21B is a cross-sectional view taken along the line A-A in Fig. 21A. Fig. 22A is an SEM image of the upper part of the electrode substrate of Example 1, and Fig. 22B is an SEM image of the cross section of the electrode substrate of Example 1. Fig. 23A is a diagram showing an example of an SEM image of the upper surface of the electrode substrate, and Fig. 23B is a diagram showing an example of a binarized image used to calculate the cover ratio.Fig. 24 is a diagram showing an example of a cross-sectional image of an electrode base material photographed with an electron microscope. Fig. 25A is an example of an image cut out to show only the particle layer from an SEM image used to calculate the area of ​​exposed surfaces of active material particles, Fig. 25B is an example of an image in which only active material particles are shown with white pixels, Fig. 25C is an example of an image in which both solid electrolyte particles and active material particles are shown with white pixels, and Fig. 25D is a diagram showing an example of an image after noise removal. Fig. 26 is a BIB-SEM image of the cross section of an electrode produced using the electrode base material of Example 1. Fig. 27A is a schematic diagram of an electrode base material laminate, and Fig. 27B is a schematic diagram of the cross section of an electrode produced using the electrode base material laminate.

[0018] In the present disclosure, the expressions "XX to YY" and "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. When a numerical range is described in stages, any combination of the upper and lower limits of each numerical range is also disclosed.

[0019] When an inorganic solid electrolyte is used as the electrolyte, the active material and the electrolyte come into contact in a solid-state state, making it difficult to obtain a sufficient contact area and establish a conductive path at the interface. In particular, if the active material aggregates, the aggregated active material becomes even less likely to contact the solid electrolyte, making it more likely to have a reduced ionic conductivity. This can increase the internal resistance of the battery and lead to a decrease in battery output.

[0020] To solve the above-mentioned problems, the inventors conducted detailed studies on the arrangement of active material particles and solid electrolyte particles inside an electrode. As a result of their studies, they found that both electronic conductivity and ionic conductivity can be improved by arranging the active material particles on the electrode surface so that the solid electrolyte particles cover at least a portion of the surface of the active material particles and controlling the area ratio of the exposed surface of the active material particles. Specifically, both electronic conductivity and ionic conductivity can be improved by setting the difference between the area ratio of the exposed active material particles on one surface of the electrode and the area ratio of the exposed active material particles on the other surface to 1 to 70 area percent. This means that a large portion of the surface of the active material particles is exposed on one surface of the electrode, while on the other surface, a portion of the surface of the active material particles is covered by the solid electrolyte particles, reducing the area ratio of the exposed active material particles.

[0021] In the present disclosure, the above-described configuration is realized by using an electrode substrate in which active material particles and solid electrolyte particles are disposed on a resin substrate having the characteristics of the present disclosure. A plurality of electrode substrates can be laminated to form an electrode substrate laminate. Furthermore, the electrode substrate and the electrode substrate laminate can be used as materials for electrodes.

[0022] In a secondary battery manufactured using an electrode having such a configuration, the active material particles are exposed in large amounts on one side of the electrode, thereby increasing the contact area between the active material, which has excellent electronic conductivity, and the current collector, and thus facilitating smooth electron transfer. Furthermore, on the side of the electrode opposite to the above-mentioned side, the exposed surface area of ​​the active material particles is reduced, thereby increasing the contact area between solid electrolyte particles and facilitating smooth ionic conduction. Smooth electronic and ionic conduction reduces the internal resistance of the electrode and improves the output of the secondary battery.

[0023] In order to produce an electrode having the above-described configuration, it is important to control the arrangement of the active material particles and solid electrolyte particles in the electrode substrate. Specifically, the solid electrolyte particles are arranged on the surface of the electrode substrate so that they cover at least a portion of the surface of the active material particles. Furthermore, the solid electrolyte particles are arranged so that they are unevenly distributed in the thickness direction of the electrode substrate. By arranging the active material particles and solid electrolyte particles in this manner, the area ratio of the exposed surface of the active material particles on one surface of the electrode substrate can be arranged so that it is sufficiently larger than the area ratio of the exposed surface of the active material particles on the other surface. As a result, an electrode substrate with excellent electronic conductivity and ionic conductivity can be obtained.

[0024] By manufacturing an electrode using the electrode base material having the above-described configuration, it is possible to improve the electronic conduction between the active material particles in the electrode, the electronic conduction from the active material particles to the current collector, and the ionic conduction from the active material particles to the electrolyte. Furthermore, in a secondary battery using such an electrode, the internal resistance can be reduced, and the output can be improved.

[0025] In this disclosure, the electronic conductivity and ionic conductivity are evaluated using an index called the "rate characteristic" of a prototype battery for convenience. The electrode substrate, electrode substrate laminate, electrode, and secondary battery using them, as well as a method for manufacturing the same, are described in detail below.

[0026] The electrode substrate of the present disclosure can be used in the manufacture of electrodes for secondary batteries. Hereinafter, a positive electrode substrate using positive electrode active material particles will be described as an example, but the electrode substrate of the present disclosure can be used for both positive and negative electrodes. The electrode substrate includes a resin substrate, and active material particles and solid electrolyte particles on the resin substrate. A particle layer including the active material particles and solid electrolyte particles is formed on the resin substrate.

[0027] The resin substrate is a substrate formed from a material containing resin. Using a substrate formed from an organic material such as resin as the substrate can facilitate removal of the substrate by heating in the manufacturing process of the electrode substrate, which will be described later. The resin contained in the material of the resin substrate is not particularly limited, but examples thereof include polyesters such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), as well as polyamides such as nylon. Among these, PET is preferably used from the viewpoints of its decomposition temperature and the low toxicity of gases generated during thermal decomposition.

[0028] The active material particles are not particularly limited and may be any known material. For example, a composite oxide containing lithium may be used. Specifically, for example, LiCoO ２ Li-Co oxide active material particles such as LiMO ２ (M is an element selected from the group consisting of Ni, Mn, and Co), ４ Oxide-based active material particles, Si-based active material particles (Si, Si-C, etc.), graphite-based active material particles (graphite, graphene, carbon nanotubes, etc.), lithium vanadium compounds (Li ３ V ２ (P.O. ４ ) ３ , LiVOPO ４ ), olivine-type phosphate compounds (LiMPO ４ (M is one or more elements selected from the group consisting of Co, Ni, Mn, Fe, Mg, V, Nb, Ti, Al, and Zr). A lithium-free positive electrode active material may also be used. Specifically, for example, a metal oxide (MnO ２ , V ２ O ５ etc.) and fluorides (FeF ３ , V.F. ３ When using a positive electrode active material that does not contain lithium, it can be used by discharging the negative electrode active material first, using metallic lithium containing lithium or a negative electrode active material doped with lithium ions.

[0029] The present inventors have revealed that, among the above positive electrode active material particles, the use of Li—Co oxide-based active material particles increases the surface area of ​​the positive electrode active material particles, thereby improving the output characteristics of the secondary battery (Japanese Patent Application Laid-Open No. 2020-198301). ４ Oxide-based active material particles are very stable because the covalent bond between P—O is strong and oxygen release is suppressed. Therefore, among the above positive electrode active material particles, Li—Co oxide-based active material particles, Li—PO ４ It is preferable that the active material contains oxide-based particles.

[0030] The active material particles may be commercially available products or may be prepared separately. Examples of the Li-Co oxide active material particles include Cellseed C-5H (trade name, manufactured by Nippon Chemical Industry Co., Ltd.) (LiCoO ２ ) can be used. ２ (M is an element selected from the group consisting of Ni, Mn, and Co) Cellseed NMC (trade name, manufactured by Nippon Chemical Industry Co., Ltd.) (LiNi （１－ｘ－ｙ） Mn ｘ Co ｙ O ２ ) and the like can be used. ４ The oxide-based active material particles include LiFePO ４ (Toshima Manufacturing Co., Ltd.) and Li ３ V ２ (P.O. ４ ) ３ (manufactured by Tokyo Chemical Industry Co., Ltd.) or the like can be used. ４ and Li ３ V ２ (P.O. ４ ) ３ When using active material particles having low electronic conductivity such as those described above, the particle surfaces may be coated with carbon by a general method before use. The active material particles may be used alone or in combination of two or more.

[0031] The solid electrolyte particles are not particularly limited, and ion-conductive solids that are commonly used in all-solid-state batteries can be used. For example, Li-B oxide-based solid electrolyte particles, Li-Yb oxide-based solid electrolyte particles, Nasicon-type oxide-based solid electrolyte particles (LiAlTi(PO ４ ) ３ , LiAlGe (PO ４ ) ３ etc.), perovskite-type oxide solid electrolyte particles (Li ｘ La （１－ｘ）／３ TiO ３ , Li ｘ La （１－ｘ）／３ NbO ３ etc.), garnet-type oxide solid electrolyte particles (Li ７ La ３ Zr ２ O １２ , etc.), Li-P-O based solid electrolyte particles (Li ３ P.O. ４ , LiPON (Li ３ P.O. ４ Examples of the solid electrolyte particles include Li-B oxide-based solid electrolyte particles and Li-Yb oxide-based solid electrolyte particles, which can be sintered at relatively low temperatures (700°C or lower), thereby suppressing reaction with the positive electrode active material particles during sintering and maintaining ionic conductivity. For this reason, among the solid electrolyte particles, it is preferable to include Li-B oxide-based solid electrolyte particles and Li-Yb oxide-based solid electrolyte particles.

[0032] The solid electrolyte particles may be commercially available products or may be prepared separately as materials. Examples of the Li-B oxide solid electrolyte particles include Li ３ BO ３ (Toshima Manufacturing Co., Ltd.) and Li ３ BO ３ Particles in which part of O is replaced with C can be used. In addition, as the Li-Yb oxide solid electrolyte particles, for example, compounds described in JP-A-2022-130301 can be used, for example, Li ５．９ Yb ０．８１ La ０．０９ Zr ０．１ (BO３ ) ３ These solid electrolyte particles may be made amorphous in advance by planetary ball milling or the like.

[0033] The area ratio of the exposed surface of the active material particles to the surface of the particle layer is determined by processing a cross section with a broad ion beam (BIB) of Ar and obtaining a two-dimensional image of the cross section using a scanning electron microscope. Hereinafter, the above-mentioned method for observing two-dimensional images will be referred to as BIB-SEM. The details of the measurement method will be described later.

[0034] The electrode substrate has a particle layer containing active material particles and solid electrolyte particles formed on a resin substrate. When the particle layer is viewed through the surface in contact with the resin substrate or the surface opposite to the surface in contact with the resin substrate, the solid electrolyte particles are arranged so as to cover at least a portion of the surface of the active material particles. This arrangement provides a uniformly dense portion of the active material particles and the solid electrolyte particles, allowing sufficient contact between the active material particles and the solid electrolyte particles. As a result, ionic conductivity can be improved.

[0035] The active material particles are preferably arranged at the same height on the resin substrate. Whether the active material particles are arranged at the same height can be determined from the cross-sectional SEM image. In the present disclosure, the height of the active material particles refers to the height from the surface of the resin substrate on which the active material particles are arranged to the position of the top surface of the active material particles. The height of the active material particles can be measured using the method described below. The active material particles may be arranged so as to have irregularities, but the height of the protrusions is preferably three times or less the average height of the active material particles. The height of the protrusions is the height of the active material particles with the highest height among the active material particles in the cross-sectional SEM image. The average height of the active material particles is determined by dividing the cross-sectional SEM image into columns with a width of one pixel, determining the height of the active material particles from the surface of the resin substrate in each column, and averaging the heights of the active material particles in all columns. The average height of the active material particles can be measured using the method described below. When the height of the protrusions is three times or less the average height of the active material particles, the arrangement density of the active material particles becomes uniform, allowing for sufficient contact between the active material particles and between the active material particles and the solid electrolyte particles.

[0036] There may be regions on the resin substrate where no active material particles are disposed. Other particles, such as solid electrolyte particles or graphite particles, are disposed in these regions. The average height of the active material particles from the surface of the resin substrate is preferably 1 to 50 μm, more preferably 2 to 10 μm. An average height of less than 1 μm makes it difficult to uniformly arrange the active material particles on the resin substrate. This makes it difficult to achieve smooth electronic and ionic conduction. On the other hand, for example, when using small-diameter active material particles (up to 10 μm), if the average height is greater than 50 μm, the active material particles will be stacked across the entire region and arranged in multiple layers, making it difficult to establish internal electronic and ionic conduction paths. Furthermore, when using large-diameter active material particles (10 μm or more), if the average height is greater than 50 μm, the interparticle voids will be large, making it difficult to achieve smooth electronic and ionic conduction. In other words, by setting the average height of the active material particles from the surface of the resin substrate to 1 to 50 μm, the paths of electronic and ionic conduction can be effectively controlled. The active material particles may be arranged on the resin substrate so that a plurality of active material particles are stacked on top of each other. When the active material particles are arranged so as to be stacked, the maximum height of the active material particles can be appropriately adjusted depending on the particle size, etc., but is preferably, for example, about 1 to 10 times the average particle size of the active material particles.

[0037] In cross-sectional observation of the particle layer of the electrode substrate using a scanning electron microscope (SEM), the difference between the area ratio of the exposed surface of the active material particles on the surface of the particle layer that contacts the resin substrate and the area ratio of the exposed surface of the active material particles on the surface opposite to the side that contacts the resin substrate is 1 to 70 area %. That is, the electrode substrate of the present disclosure has a configuration in which the area ratio of the exposed surface of the active material particles on one surface of the particle layer is significantly different from the area ratio of the exposed surface of the active material particles on the other surface of the particle layer. The area ratio of the exposed active material particles on the surface of the particle layer and the difference can be calculated by the method described below.

[0038] The difference between the area ratio of the exposed surface of the active material particles on the surface of the particle layer that contacts the resin substrate and the area ratio of the exposed surface of the active material particles on the surface opposite to the surface that contacts the resin substrate being 1 to 70 area % indicates that the resin substrate has a surface with a large surface area of ​​active material particles that are excellent in electronic conductivity and a surface with a large surface area of ​​solid electrolyte particles that are excellent in ionic conductivity. The area ratio of the exposed surface of the active material particles can be controlled by controlling the arrangement of the active material particles and solid electrolyte particles on the resin substrate. Specifically, the area ratio of the exposed surface of the active material particles can be controlled by arranging the active material particles and solid electrolyte particles using the method described below. Furthermore, by manufacturing an electrode using an electrode substrate in which the active material particles and solid electrolyte particles are arranged in the above-described configuration, an electrode can be obtained that has a configuration in which the surface area of ​​the active material particles is large on one surface and the surface area of ​​the solid electrolyte particles is large on the other surface. A secondary battery is produced using an electrode having the above-described configuration, and the surface of the active material particles having a larger surface area is arranged on the current collector side, and the surface of the solid electrolyte particles having a larger surface area is arranged on the electrolyte layer side, thereby enabling smooth electron conduction and ion conduction, and resulting in a secondary battery with reduced internal resistance of the electrode.

[0039] The difference between the area ratio of the exposed surface of the active material particles on the surface of the particle layer that comes into contact with the resin substrate and the area ratio of the exposed surface of the active material particles on the surface of the particle layer opposite to the side that comes into contact with the resin substrate is 1 to 70 area %, preferably 5 to 60 area %, more preferably 10 to 50 area %.

[0040] When the difference is 1 area % or more, electronic conduction and ionic conduction can be smoothly achieved. Furthermore, when the difference is 70 area % or less, when the electrode base materials are stacked to form an electrode, active material particles that contact each other in the stacking direction can be in sufficient contact with each other, and high efficiency of electronic conduction can be maintained. When the difference is 1 to 70 area %, ionic conductivity and electronic conductivity can be improved and internal resistance can be further suppressed.

[0041] The area ratio of the exposed surface of the active material particles on the surface of the particle layer is preferably 10 to 80 area%, more preferably 20 to 75 area%, and even more preferably 25 to 70 area%. In the particle layer, the surface on which the exposed surface of the active material particles is greater may be either the upper or lower surface of the particle layer. That is, it may be the surface on the side in contact with the resin substrate, or the surface opposite to the side in contact with the resin substrate. It is preferable that the area ratio of the exposed surface of the active material particles on the surface on the side in contact with the resin substrate of the particle layer is greater than the area ratio of the exposed surface of the active material particles on the surface opposite to the side in contact with the resin substrate of the particle layer. In this case, the difference is the value obtained by subtracting the area ratio of the exposed surface of the active material particles on the surface opposite to the side in contact with the resin substrate from the area ratio of the exposed surface of the active material particles on the surface on the side in contact with the resin substrate of the particle layer.

[0042] For example, by a method described below, first particles P1 as active material particles and second particles P2 as solid electrolyte particles are arranged on a resin substrate as a material for the electrode substrate. This allows the active material particles and the solid electrolyte particles to be controlled so as to be arranged adjacently in the electrode substrate. Furthermore, when the particle layer is viewed through from the surface side in contact with the resin substrate or the surface side opposite to the surface in contact with the resin substrate, the solid electrolyte particles are arranged so as to cover part of the surface of the active material particles. The formation of a particle layer in the electrode substrate, the adjacent arrangement of the active material particles and the solid electrolyte particles, and the arrangement of the solid electrolyte particles so as to cover the surface of the active material particles can be confirmed, for example, by observation using an SEM.

[0043] For example, when the electrode substrate is observed from a cross section, the resin substrate, active material particles, and solid electrolyte particles are arranged in this order from the lower side of the electrode substrate (the side on which no particle layer is formed). On the surface of the upper side of the electrode substrate (the side opposite to the resin substrate), the solid electrolyte particles are arranged so as to cover at least a portion of the surface of the active material particles. Furthermore, the solid electrolyte particles are arranged in the portions of the resin substrate on which no active material particles are arranged.

[0044] That is, in the particle layer in the electrode substrate, the solid electrolyte particles are densely arranged on the side in contact with the resin substrate or on the surface opposite to the resin substrate side, and the active material particles are arranged in large numbers on the surface opposite to the above-mentioned surface. With this configuration, electron conduction is smooth on the surface where the active material particles are arranged in large numbers, and ion conduction is smooth on the surface where the solid electrolyte particles are arranged in large numbers.

[0045] In the present disclosure, the active material particles and solid electrolyte particles present on the resin substrate are identified in an SEM image of a cross section of the electrode substrate, and the area ratio of the exposed active material particles on the resin substrate side is compared with that on the opposite side to calculate the difference. The method for identifying the active material particles and the solid electrolyte particles and the method for calculating the area ratio will be described later.

[0046] A schematic diagram of an electrode substrate in the present disclosure is shown in Figure 1. For the sake of explanation, particles P1 and P2 are depicted as spherical and having the same particle size. Particles P1 represent active material particles, and particles P2 represent solid electrolyte particles. Solid electrolyte particles P2 are disposed in areas on the resin substrate where active material particles P1 are not disposed. Solid electrolyte particles P2 are also disposed so as to cover part of the surface of active material particles P1 on the surface of the particle layer opposite the resin substrate side. In Figure 1, the surface of the particle layer facing the resin substrate has a large exposed area, while the surface of the active material particles has a small exposed area on the surface opposite the resin substrate side.

[0047] Active material particles often have higher electronic conductivity than solid electrolyte particles, and the degree of contact between active material particles is likely to affect electronic conductivity within the electrode. Therefore, when electrode substrates are stacked using the method described below, sufficient contact can be achieved without impeding contact between the active material particles and solid electrolyte particles, between active material particles, or between solid electrolyte particles in the stacking direction of the electrode substrates. This maintains high ionic conductivity of the secondary battery and improves rate characteristics. Furthermore, since more active material particles can be arranged on the electrode substrate, a battery with a high volumetric energy density can be manufactured.

[0048] <Method for manufacturing electrode substrate> Hereinafter, an example of a method for manufacturing an electrode substrate will be described in detail with reference to the drawings. Although the description will be made using a positive electrode substrate using positive electrode active material particles as an example, the manufacturing method described below can be used as a method for manufacturing an electrode substrate for both positive and negative electrodes.

[0049] The method for manufacturing an electrode substrate includes the following steps: (1) a preparation step of preparing a resin substrate having an adhesive portion; (2) a first step of arranging first particles P1 on the surface of the adhesive portion (S101 in FIG. 2); (3) a second step of rubbing the surface of the first particles P1 arranged on the surface of the adhesive portion (S102 in FIG. 2); and (4) a third step of arranging second particles P2 on the surface of the adhesive portion and the rubbed surfaces of the active material particles (S103 in FIG. 2).

[0050] (Preparation Step) In the preparation step, a resin substrate having an adhesive portion is prepared. In the present disclosure, "having an adhesive portion" means that an adhesive portion is provided on a part or the entire surface of the resin substrate. As the resin substrate, a substrate containing the above-mentioned resin can be used. Although there is no particular limitation on the method for providing the adhesive portion, a method of applying an adhesive to the surface of the resin substrate is preferred. The adhesive is not particularly limited, and known adhesives can be used. For example, it may be an acrylic adhesive, a rubber adhesive, or a silicone adhesive, or it may be a thermoplastic resin or a photocurable resin whose adhesive strength changes in response to external disturbances such as heat or light.

[0051] (Step 1, Step 2, and Step 3) Step 1 is a step of arranging active material particles on the surface of the adhesive portion of the resin substrate. Step 2 is a step of rubbing the surfaces of the active material particles arranged on the surface of the adhesive portion. Step 3 is a step of arranging second particles P2 on the surface of the adhesive portion where no active material particles are arranged and on the surfaces of the rubbed active material particles. In this disclosure, "rubbing" refers to contacting the surface of the active material particles with magnetic particles or a member of a rubbing device described below, and moving the member while applying pressure to rub the surface of the active material particles. As described below, a rubbing step may be further performed after the arrangement of the second particles P2. In this case, magnetic particles or the member may be contacted with the surfaces of the active material particles and the second particles P2, and the surface of the active material particles and the second particles P2 may be rubbed by moving the member while applying pressure. The rubbing is preferably performed using magnetic particles. In other words, the rubbing step preferably includes a step of rubbing the surface of the active material particles with magnetic particles.

[0052] The first particles P1 are active material particles. For example, the above-described active material particles can be used as the first particles P1. The particle size of the primary particles of the first particles P1 is not particularly limited, but for example, the cumulative 10% particle size (r10) in the volume-based particle size distribution is preferably 0.1 to 10.0 μm, and more preferably 1.0 to 7.0 μm. Furthermore, the cumulative 50% particle size (r50) in the volume-based particle size distribution is preferably 0.5 to 20.0 μm, and more preferably 2.0 to 10.0 μm. Furthermore, the cumulative 90% particle size (r90) in the volume-based particle size distribution is preferably 2.0 to 20.0 μm, and more preferably 3.0 to 15.0 μm.

[0053] The second particles P2 are solid electrolyte particles. For example, the above-described solid electrolyte particles can be used as the second particles P2. The particle size of the primary particles of the second particles P2 is not particularly limited. For example, the primary particles of the second particles P2 preferably have a cumulative 10% particle size (r10) in a volume-based particle size distribution of 0.5 to 10.0 μm, more preferably 1.0 to 7.0 μm. The primary particles of the second particles P2 preferably have a cumulative 50% particle size (r50) in a volume-based particle size distribution of 1.0 to 20.0 μm, more preferably 5.0 to 15.0 μm. The primary particles of the second particles P2 preferably have a cumulative 90% particle size (r90) in a volume-based particle size distribution of 5.0 to 50.0 μm, more preferably 10.0 to 30.0 μm.

[0054] The ratio of the particle size of the primary particles of the first particles P1 to the particle size of the primary particles of the second particles P2 is not particularly limited. For example, the ratio {(r50(P1)) / (r50(P2))} of the cumulative 50% particle size (r50(P2)) in the volume-based particle size distribution of the primary particles of the first particles P1 to the cumulative 50% particle size (r50(P2)) in the volume-based particle size distribution of the primary particles of the second particles P2 is preferably 0.05 to 20.0, and more preferably 0.1 to 2.0.

[0055] As described above, the first particles P1 are active material particles. The second particles P2 are solid electrolyte particles. In other words, in the method for producing an electrode substrate, the first and third steps can be described as steps of arranging active material particles and solid electrolyte particles on the surface of the adhesive portion. By inserting the second step between the first and third steps, a denser and more uniform particle layer can be formed.

[0056] Further, additional steps may be provided between each step or after the third step. Examples include a step of arranging third particles P3 and a step of rubbing the arranged third particles P3. Examples of the third particles P3 include graphite particles, active material particles, and solid electrolyte particles. In the first and third steps, particles are arranged on the adhesive portion of the resin substrate using a particle arrangement device. Below, particle arrangement device 1 and particle arrangement device 2 that can be used will be described in order.

[0057] 3 is a diagram schematically illustrating the configuration of the particle arrangement device 1. The particle arrangement device 1 has a first storage container 21 a that stores and supplies the first base material 11 a, a first belt device 22 a that transports the first base material 11 a, and a pattern forming device 23 that forms a concave-convex pattern on the first base material 11 a.

[0058] The particle placement device 1 has a first filling device 24a that places first particles P1 in recesses of a concave-convex pattern formed on a first substrate 11a. The particle placement device 1 also has a second storage container 21b that stores and supplies a second substrate 11b, and a second belt device 22b that transports the second substrate 11b. The particle placement device 1 also has a transfer unit 25a in which rollers 223 of the first belt device 22a and the second belt device 22b face each other, and the first particles P1 are transferred from the first substrate 11a to the second substrate 11b in the transfer unit 25a.

[0059] The particle placement device 1 has a rubbing device 30 that rubs the surface of the first particles P1 transferred onto the first substrate 11b. Furthermore, the particle placement device 1 has a second filling device 24b that places second particles P2 in non-transfer areas on the second substrate 11b. Note that devices that are less relevant to explaining the effects of this invention, such as a peeling and recovery device that peels and recovers the first substrate 11a from the first belt device 22a after transfer and various cleaning devices, are not shown or described in detail.

[0060] In the particle placement device 1, the pattern forming device 23, the first filling device 24a, and the transfer unit 25a correspond to a first placement means that places the first particles P1 in a pattern on the second substrate 11b. The rubbing device 30 corresponds to a means for rubbing the first particles. The second filling device 24b corresponds to a second placement means that places the second particles P2 in areas on the second substrate 11b where the first particles P1 are not placed. Below, the method for placing particles on the substrate 11 using the particle placement device 1 will be explained in the following process flow.

[0061] First, a supply means (not shown) supplies the first substrate 11a from the first storage container 21a to the first belt device 22a. When a UV-curable liquid is applied by a pattern forming device 23 (described later), it is preferable that at least the surface of the first substrate 11a be made of a material that is highly wettable by the UV-curable liquid. Furthermore, it is preferable that the surface of the first substrate 11a be smooth. The first substrate 11a may be a sheet made of a resin such as polyester that has been subjected to a hydrophilic or lipophilic treatment in accordance with the UV-curable liquid (water-based or oil-based) to be used. The first substrate 11a may be a substrate that is individually cut, such as cut paper, a continuous substrate wound into a roll, such as roll paper, or a continuous substrate that is alternately folded, such as continuous paper.

[0062] The first belt device 22a transports the supplied first substrate 11a to a pattern formation position of the pattern forming device 23. The first belt device 22a has drive rollers 221a and 222a, a pressure roller 223a, and a belt-like transport member 224a suspended between them. At this time, the pressure roller 223a is rotated by being driven.

[0063] The conveying member 224a is preferably made of a material selected from resin or metal, and for example, a polyimide resin belt can be used. The drive rollers 221a and 222a are preferably made of metal rollers, and for example, stainless steel metal rollers can be used. The pressure roller 223a is preferably made of a soft roller having an elastic layer on its surface, and for example, a soft roller having a silicone rubber elastic layer on the surface of a stainless steel core can be used. Note that in FIG. 3, the first belt device 22a is used as the conveying device for conveying the first substrate 11a, but a roller device can also be used instead of the belt device. The same applies to the second belt device 22b described below.

[0064] The pattern forming device 23 forms a fine concave-convex pattern on the first substrate 11a that has been transported to the pattern forming position. Methods for forming the concave-convex pattern include UV imprinting, thermal imprinting, UV inkjet printing, printing, and laser etching.

[0065] When the pattern forming device 23 forms a concave-convex pattern using a UV imprinting method, the pattern forming device 23 has a coating means for coating a UV-curable liquid onto the first substrate 11a. The UV-curable liquid can be, for example, a UV-curable resin such as UV-curable liquid silicone rubber. The pattern forming device 23 also has an imprinting means for imprinting a mold having a concave-convex pattern formed on its surface onto the UV-curable liquid on the first substrate 11a, and a light source for irradiating the UV-curable liquid with UV rays. Typically, UV-curable liquid silicone rubber (PDMS) or resin is used as the UV-curable liquid, a film mold is used as the mold, and a UV lamp is used as the light source.

[0066] When the first filling device 24a fills the recesses on the substrate 11a with the first particles P1 using the support material S1 carrying the first particles P1, the opening diameter (width) of the recesses in the uneven pattern on the first substrate 11a is preferably larger than the cumulative 50% particle diameter (median diameter) of the first particles P1 on a volume basis. Furthermore, the opening diameter (width) of the recesses is preferably smaller than the average size of the support material S1. Here, the opening diameter of the recesses in the uneven pattern is preferably the opening diameter in the short-side direction of the recesses, and more preferably the maximum opening diameter in the short-side direction of the recesses.

[0067] The width of the recess can be adjusted appropriately depending on the particle sizes of the first particles P1 and the support material S1, etc. The width of the recess is not particularly limited, but is preferably 0.2 to 30 μm, and more preferably 2 to 15 μm, for example.

[0068] By setting the opening diameter of the recesses of the concave-convex pattern as described above, the first particles P1 can contact the bottoms and side surfaces (typically the bottom surfaces) of the recesses of the concave-convex pattern. On the other hand, the support material S1 cannot contact the bottoms and side surfaces of the recesses. This allows the first particles P1 that contact the bottoms and side surfaces of the recesses to be captured by the concave-convex pattern, while preventing the support material S1 from being captured by the concave-convex pattern. In other words, it is preferable that the first particles P1 can contact the bottoms and side surfaces of the recesses of the concave-convex pattern, and that the first support material S1 cannot contact the bottoms and side surfaces of the recesses of the concave-convex pattern.

[0069] Although the pattern forming device 23 forms a concave-convex pattern on the first substrate 11a, a substrate with a concave-convex pattern pre-formed on its surface may be used as the first substrate 11a. Alternatively, the pattern forming device 23 may form a concave-convex pattern directly on the surface of the conveying member 224a of the first belt device 22a, or a conveying member having a concave-convex pattern on its surface may be used as the conveying member 224a. In this case, in consideration of durability, it is preferable to use a metal belt made of stainless steel, aluminum, or the like, and form the concave-convex pattern on its surface using a microfabrication technique such as laser etching, wet etching, or dry etching. The first substrate 11a with the concave-convex pattern formed on its surface is transported by the first belt device 22a to the filling position of the first filling device 24a.

[0070] 4 is a diagram showing a schematic configuration of the filling device. The configuration of the first filling device 24a will be described below, but the second filling device 24b is similar. The first filling device 24a has a filling container 242a that stores a filler 241a, a stirring screw member 243a that stirs and conveys the filler 241a, a recovery member 244a that recovers the filler, and a magnetic member 247a.

[0071] The filler 241a includes first particles P1 and a support material S1 that supports the first particles P1. The filler 241a is a mixture of multiple powders, including a powder composed of multiple first particles P1 and a powder composed of multiple support materials S1. The filler 241a contained in the filling container 242a is thoroughly mixed when stirred and transported by the stirring screw member 243a. As a result, the first particles P1 are supported on the surface of the support material S1. The forces acting between the particles when supported include electrostatic forces due to frictional charging and the like, as well as van der Waals forces and liquid bridging forces.

[0072] The support material S1 is a magnetic particle. The support material S1 is preferably a particle in which the surface of a resin particle in which ferrite core particles or a magnetic material is dispersed is coated with a resin composition. For example, a standard carrier (Standard Carrier P02 manufactured by the Japan Imaging Society), which is a magnetic particle, can be used. The particle size and material of the support material S1 are appropriately selected according to the particle size and material of the first particles P1. This allows the first particles P1 to be stably supported. Furthermore, even if the first particles P1 are small in particle size and prone to agglomeration, the support material S1 plays a role in loosening the particles by stirring and transporting them with the support material S1. The particle size of the support material S1 can be appropriately adjusted by the size (area, width, depth) of the recess. For example, the cumulative 50% particle size (median diameter) based on volume is preferably 50 to 100 μm.

[0073] Recovery member 244a has roller 245a that can rotate in the direction of arrow d2 in the figure, and magnet 246a that is arranged inside roller 245a and fixed to filling container 242a. Magnetic member 247a is arranged opposite filling container 242a across transport member 224a, and has magnet 248a inside.

[0074] Magnet 246a has a plurality of N and S poles alternately arranged along the rotation direction of collection member 244a. Magnet 248a has a plurality of N and S poles alternately arranged along the transport direction of transport member 224a. Magnet 246a also has a magnetic pole (N1 pole in FIG. 4) of a different polarity at a position closest to and facing the most downstream magnetic pole (S1 pole in FIG. 4) of magnet 248a, and an N2 pole of the same polarity as N1 pole is arranged at the most downstream position.

[0075] The magnet 246a and the magnet 248a may be composed of a plurality of magnets, and the type of magnet constituting the magnet 246a and the magnet 248a is not particularly limited. For example, a permanent magnet such as a rare earth magnet, a ferrite magnet, a neodymium magnet, or a samarium-cobalt magnet, or a plastic magnet, or a means for generating a magnetic field such as an electromagnet can be used. The magnet 248a may be configured to be movable in the transport direction of the first substrate 11a or in the opposite direction.

[0076] Note that a regulating member for regulating the filler 241 a on the first base material 11 a or a collecting member for re-collecting the filler 241 a that cannot be collected by the collecting member 244 a may be provided upstream or downstream of the collecting member 244 a in the transport direction of the transport member 224 a. The collecting member for re-collecting the filler 241 a may be a member similar to the collecting member 244 a, or may be a simple member such as a fixed magnet or a regulating member, or a collecting member that performs collection by air blowing.

[0077] Next, the process of filling the recesses on the first substrate 11a with the first particles P1 by the first filling device 24a will be described with reference to Figures 4 to 6. The first substrate 11a carried and transported by the first transport member 224a is transported to the loading position of the first filling device 24a by the first transport member 224a moving in the direction of the solid arrow d1 in Figure 4.

[0078] The filler 241a is transported by the stirring screw member 243a and supplied onto the first substrate 11a (dotted line a in FIG. 4). At this time, a magnetic field is formed by the magnetic member 247a and the recovery member 244a, and the filler 241a containing the magnetic particle carrier material S1 forms multiple magnetic chains on the first substrate 11a due to the magnetic field. The filler 241a supplied onto the first substrate 11a is transported on the first substrate 11a while forming magnetic chains as the first substrate 11a moves (dotted line b in FIG. 4).

[0079] Figures 5A, 5B, and 5C are schematic diagrams of filler 241a being transported on the first substrate 11a. For illustrative purposes, filler 241a other than the filler forming a single magnetic strand are omitted from the illustration. As described above, the filler 241a on the first substrate 11a forms magnetic strands along the magnetic field lines of the generated magnetic field. As the first substrate 11a moves, the magnetic strands change shape as they are transported, as shown in Figures 5A, 5B, and 5C. Because a particularly strong magnetic force acts near the magnet 248a, the transport speed v2 of the filler 241a is smaller than the movement speed v1 of the first substrate 11a when the filler 241a moves away from the magnetic pole, and is larger when the filler 241a moves away from the magnetic pole. In other words, the filler 241a on the first substrate 11a has a non-zero relative speed with respect to the first substrate 11a.

[0080] Fig. 6 is an enlarged view of the vicinity of the surface of the first base material 11a in Fig. 5A to C. Although not shown in Fig. 5A to C, a concave-convex pattern 111a is formed on the first base material 11a as shown in Fig. 6. The concave-convex pattern can be formed as a desired pattern such as a honeycomb pattern or a line pattern.

[0081] The filler 241a comes into contact with the concave-convex pattern 111a, and is transported together with the first substrate 11a at a non-zero relative speed with respect to the first substrate 11a while being subjected to a magnetic force (solid line Fm in the figure) in a direction perpendicular to the surface of the first substrate 11a. As a result, the first particles P1 carried on the support material S1 are transported while being rubbed against the concave-convex pattern 111a on the surface of the first substrate 11a.

[0082] At this time, the particle size of the first particles P1 is smaller than the opening diameter of the recesses of the uneven pattern 111a, and the particle size of the first support material S1 is larger than the opening diameter of the recesses, so the first particles P1 can contact the bottom surfaces (bottoms) and side surfaces of the recesses of the uneven pattern 111a, but the support material S1 cannot. In other words, only the first particles P1 in the filler 241a selectively contact the bottom surfaces and side surfaces of the recesses.

[0083] The first particles P1 that come into contact with the recesses are strongly restrained by the physical restraining force due to the structure of the concave-convex pattern 111a and by non-electrostatic adhesive forces such as electrostatic adhesive forces and adhesive forces with the structural materials that make up the first base material 11a and the concave-convex pattern 111a, and are detached from the support material S1. Note that, for the sake of explanation, in Fig. 6 the first particles P1 are supported on the surface of the support material S1, but it is acceptable for there to be first particles P1 that are not supported on the support material S1 during the agitation, supply, or transport of the filler 241a.

[0084] As shown in Fig. 4, downstream of the magnetic member 247a, a recovery member 244a is disposed with a gap between it and the first transport member 224a. As the first base material 11a moves, the filler 241a is transported to the vicinity of the most downstream magnetic pole (pole S1) of the magnet 248a. Under the influence of the magnetic field formed by the magnet 246a, the filler 241a moves from the first base material 11a to the recovery member 244a and is recovered (dotted line c in Fig. 4).

[0085] As described above, during the transport process (dotted lines a, b, and c in FIG. 4), the recesses of the concave-convex pattern 111a on the surface of the first base material 11a are in sufficient contact with the plurality of fillers 241a. Therefore, after the fillers 241a are collected by the collection member 244a, the first particles P1 are selectively and densely arranged in the recesses of the concave-convex pattern 111a.

[0086] 5A to 5C and 6, the first particles P1 are all shown with the same particle size, but in reality there is a particle size distribution, and depending on the material, the particles may form aggregated secondary particles. Furthermore, the particles may not have the spherical shape shown in the figure. Even in such cases, only particles that can contact the recesses of the uneven pattern 111a are selectively and densely packed, so that coarse powder and secondary particles that may adversely affect the particle placement process are easily excluded.

[0087] In this way, the amount of the first particles P1 filled into the recesses of the concave-convex pattern 111a can be controlled by the size (area, width, height) of the concave-convex pattern and the particle size of the first particles P1. Specifically, the area of ​​the recesses is approximately the filling area, and the layer thickness of the filled first particles P1 is determined by the height of the protrusions.

[0088] The pitch of the convex portions is not particularly limited, but is preferably, for example, 1.0 to 20 μm, and more preferably 2.0 to 15 μm. The height of the convex portions is not particularly limited, but is preferably, for example, 0.1 to 20.0 μm, and more preferably 1.0 to 10.0 μm. The area ratio of the concave portions (the ratio of the concave portions to the area of ​​the concave-convex pattern) is not particularly limited, but is preferably, for example, 50% or more, and more preferably 70% or more.

[0089] For example, to obtain a thin layer (single layer) that accounts for 50% of the area of ​​the substrate, the area ratio of the recesses (the area ratio of the recesses to the entire concave-convex pattern) should be 50%, and the depth of the recesses should be equal to or less than the particle size of the first particles P1. In this case, the opening width of the recesses should be larger than the median diameter of the first particles P1 and smaller than the average size (here, the average particle size) of the support material S1.

[0090] Although the first particles P1 may have a wide particle size distribution (broad particle size distribution), the support material S1 preferably has a narrow particle size distribution, and is more preferably monodisperse. This makes it easier to prevent the support material S1 from contacting the bottom (or bottom surface) or side surface of the recess. If the support material S1 can contact the bottom or side surface of the recess, there is a risk that the support material S1 will also be restrained and filled into the recess.

[0091] Furthermore, the opening width of the recesses of the uneven pattern 111a is preferably smaller than four times the particle diameter of the first particles P1. By making the opening width smaller than four times the particle diameter of the first particles P1, the probability that the first particles P1 will contact two points, the bottom and side surfaces of the recesses of the uneven pattern 111a, can be increased. In this way, the first particles P1 that make multiple contacts with the recesses of the uneven pattern 111a are strongly constrained by the uneven pattern 111a, thereby increasing the efficiency of filling the uneven pattern 111a with the first particles P1. The same applies to the particle diameter of the second particles P2 (described later) and the size of the recesses of the uneven pattern formed by the first particles P1 on the second substrate. Furthermore, when brush fibers are used as the carrier material, the "average particle diameter of the carrier material" in the above description becomes the "average fiber diameter of the carrier material."

[0092] The filler 241a collected by the collecting member 244a is transported by the rotating collecting member, roller 244a (dotted line d in FIG. 4). The filler 241a transported by roller 244a falls into filling container 242a (dotted line e in FIG. 4) due to the magnetic field generated by two adjacent, repelling magnetic poles of the same polarity (N1, N2) and the influence of gravity. Thereafter, the filler 241a is again stirred and transported by stirring screw member 243a, and this process is repeated thereafter.

[0093] The mass ratio of the first particles P1 to the support material S1 in the filler 241a in the filling container 242a is determined by an inductance sensor that measures magnetic permeability, a patch density sensor that measures and predicts the reflection density on a substrate, or the like, which are common in electrophotographic devices. At least one of the first particles P1 and the support material S1 is replenished by a replenishment means (not shown) as needed. This allows stable filling over a long period of time.

[0094] The mass % of the first particles P1 in the filler 241a (the ratio of the mass of the first particles P1 to the total mass of the filler 241a) is expressed by the following formula (1) using the coverage S1 of the supported first particles P1 to the surface area of ​​the magnetic particles (support material). The coverage S1 indicates the ratio of the total cross-sectional area of ​​the first particles P1 to the surface area of ​​the magnetic particles (support material). Mass % of the first particles P1 in the filler 241a = (400 × ρＰ１ ×r Ｐ１ × S1) / (100×ρ ｃ ×r ｃ +4×ρ Ｐ１ ×r Ｐ１ ×S1) Equation (1) (The symbols in equation (1) represent the following: ρ Ｐ１ : true density of the first particle P1, r Ｐ１ : particle size (r50) of the first particle P1, ρ ｃ : true density of magnetic particles, r ｃ : particle size of the magnetic particle (r50), S1: coverage rate of the first particle P1 relative to the surface area of ​​the magnetic particle)

[0095] The mass % of the first particles P1 in the filler 241a is not particularly limited, but is preferably in the range of 5 to 40 mass %, or 10 to 30 mass %. Furthermore, the coverage S1 in the above formula (1) is preferably adjusted to 30 to 200 area %, and more preferably adjusted to 50 to 100 area %. The particle diameters (r50) of the first particles P1 and the magnetic particles (support material) can be determined by laser diffraction / scattering particle size distribution measurement. Furthermore, the true density of the first particles P1 and the magnetic particles (support material) can be determined by a pycnometer method.

[0096] Although the filling device described here uses magnetic particles as a carrier material to form a magnetic brush, filling the recesses with the particulate material, the filling device method is not limited to this. Brush fibers can also be used as the carrier material. Alternatively, an elastic material, at least the surface of which is made of an elastic body, can also be used as the carrier material.

[0097] 7A is a diagram schematically illustrating the configuration of a filling device 24c when brush fibers are used as the carrier material. The filling device 24c has a roller 2410 with brush fibers on its surface. The roller 2410 is a so-called brush roller, with brush fibers planted on its surface. The brush fibers of the roller 2410 may be made of, for example, nylon, rayon, acrylic, vinylon, polyester, or vinyl chloride. The surface of the fiber may be subjected to a surface treatment in order to adjust the chargeability or rigidity.

[0098] The filling device 24c has a supply member that supplies the filler 241a to the roller 2410. The filler 241a contains powder including the first particles P1 and is stored in a filling container 242a. In this example, the filler 241a does not contain the carrier material S1, which is a magnetic particle. The filler 241a is stirred and transported by a stirring screw member 243a and supplied to a supply member 249.

[0099] The supply member 249 supplies the filler 241a to the roller 2410, and its configuration is not particularly limited. For example, the supply member 249 can be a roller whose surface is made of an elastic, porous foam material. Typically, an elastic sponge roller having a foamed skeleton structure and a relatively low-hardness polyurethane foam formed on a core metal can be used. Note that, in addition to urethane, various rubber materials such as nitrile rubber, silicone rubber, acrylic rubber, hydrin rubber, and ethylene propylene rubber can be used as the foam material.

[0100] The supplied filler 241a is filled into the foam material on the surface of the supply member 249 and is transported to a supply section that comes into contact with the roller 2410. In the supply section, the filler 241a filled into the foam material is charged by contact with the brush fibers of the roller 2410 and is carried by the brush fibers of the roller 2410. Furthermore, the supply member 249 may also have a function of stripping off and refreshing the filler 241a remaining on the roller 2410. The filler 241a supplied to the roller 2410 comes into contact with the first substrate 11a as the brush fibers move.

[0101] At this time, the first particles P1 in the filler 241a can contact the bottom and side surfaces of the recesses of the uneven pattern 111a on the surface of the first substrate 11a, but the brush fibers cannot. That is, the fiber diameter of the brush fibers is set to be larger than the opening width of the recesses of the uneven pattern 111a. The fiber diameter of the brush fibers can be measured by placing glass on the surface of the roller 2410 and taking an image of the brush fibers through the glass using an optical microscope. At this time, the fiber diameters of approximately 100 brush fibers are measured, the fiber diameter distribution is measured, and the average diameter is calculated.

[0102] The movement of the transport member 224a and the rotation of the roller 2410 cause the brush fibers of the roller 2410 to rub against the surface of the first substrate 11a, so that the first particles carried by the brush fibers are densely arranged in the recesses of the uneven pattern 111a on the surface of the first substrate 11a.

[0103] 7B is a diagram showing a schematic configuration of a filling device 24d when an elastic material is used as the carrier material. The filling device 24d has a similar configuration to the filling device 24c, but differs in that a roller 2411 having an elastic material is used instead of the roller 2410 having brush fibers. The roller 2411 is a roller having an elastic layer formed on its surface.

[0104] The elastic layer is formed of an elastic material such as a rubber material, such as silicone rubber, acrylic rubber, nitrile rubber, urethane rubber, or fluororubber. The surface shape of the elastic layer may be controlled by adding spherical resin particles or other fine particles. If the elastic layer has convex portions on its surface, the size of the convex portions of the elastic layer is set larger than the size of the concave portions of the concave-convex pattern 111a. The size of the convex portions of the elastic layer can be measured in the same manner as the fiber diameter of the brush fibers described above.

[0105] The movement of the transport member 224a and the rotation of the roller 2411 causes the elastic material on the surface of the roller 2411 to rub against the surface of the first base material 11a, thereby causing the first particles carried by the elastic material to be densely arranged in the recesses of the concave-convex pattern 111a on the surface of the first base material 11a.

[0106] By using brush fibers or elastic material as the carrier material as shown in Figures 7A and 7B, it is not necessary to include magnetic particles in the filler. Furthermore, the configuration of the filling device can be simplified. On the other hand, when magnetic particles are used as the carrier material as shown in Figure 4, there is greater freedom in the size and shape of the carrier material than when using brush fibers or elastic material. Furthermore, magnetic particles allow for greater freedom in the movement of the carrier material on the substrate.

[0107] For these reasons, when magnetic particles are used as the support material, particles such as the first particles P1 can be more efficiently supplied onto the substrate, and recesses on the substrate can be more efficiently filled. Also, when a magnetic material is used as the support material, even if the support material deteriorates during the process, it can be replenished or replaced without stopping the process.

[0108] The method of filling the recesses with particles by rubbing a support material carrying the particles allows a larger amount of dispersed particles to be supplied to the recesses, and allows for stable and dense filling, compared to a filling method using a restricting member such as a blade. This advantage is more pronounced as the particle size of the particles to be filled becomes smaller, since the particles tend to aggregate more easily.

[0109] The first substrate 11a, in which the recesses of the concave-convex pattern 111a have been filled with the first particles P1 by the first filling device 24a, is transported to the transfer unit 25a by the first belt device 22a. Here, the second belt device 22b, like the first belt device 22a, has drive rollers 221b and 222b, a pressure roller 223b, and a belt-like transport member 224b suspended therebetween, as shown in FIG. 4 . At this time, the pressure roller 223b is driven to rotate. In the transfer unit 25a, the pressure roller 223a of the first belt device 22a and the pressure roller 223b of the second belt device 22b face each other.

[0110] The second substrate 11b is supplied from the second storage container 21b to the second belt device 22b and transported in the direction of the arrow in Fig. 4. The supplied second substrate 11b is transported in synchronization with the transport of the first substrate 11a to the transfer unit 25a. In the transfer unit 25a, the first particles P1 filled in the first substrate 11a are transferred to the second substrate 11b.

[0111] That is, the first substrate 11a can also be referred to as a transfer substrate for transferring the first particles P1 to the second substrate 11b. The concave-convex pattern formed on the surface of the first substrate 11a can also be referred to as a transfer concave-convex pattern. This transfer process will be described below with reference to FIG. 8.

[0112] 8 is a diagram showing a schematic configuration of the transfer unit 25a. The transfer unit 25a is composed of the pressure roller 223a and the conveying member 224a of the first belt device 22a, and the pressure roller 223b and the conveying member 224b of the second belt device 22b. As described above, the pressure rollers 223a and 223b rotate drivenly, and the two rollers are in contact with each other via the conveying members 224a and 224b. At least one of the pressure rollers 223a and 223b is a soft roller having an elastic layer on its surface, and a nip is formed where the two rollers contact each other.

[0113] The first substrate 11a and the second substrate 11b, which have been filled with the first particles P1 by the first filling device 24a, are transported at approximately the same speed by their respective transport members (224a and 224b) and enter a nip formed by contact between the pressure rollers 223a and 223b. In the nip, the first particles P1 on the first substrate 11a come into contact with the second substrate 11b and are transferred onto the second substrate 11b.

[0114] The second substrate 11b has a stronger adhesive force to the first particles P1 than the first substrate 11a has to the first particles P1. In other words, the adhesive force of the first particles P1 to the second substrate 11b is stronger than the adhesive force of the first particles P1 to the first substrate 11a. As a result, the first particles P1 on the first substrate 11a are transferred to the second substrate 11b at the nip portion.

[0115] The material of the second substrate 11b is not particularly limited, and a substrate of the same material as the first substrate 11a can be used. Note that, like the first substrate 11a, the second substrate 11b may be a substrate that is individually cut like cut paper, a continuous substrate that is wound into a roll like roll paper, or a continuous substrate that is alternately folded like continuous paper.

[0116] The second substrate 11b is preferably subjected to a surface treatment to enhance adhesive strength in order to transfer the contacted first particles P1. For example, the second substrate 11b preferably has an adhesive portion on its surface where an adhesive is applied. As a preparation step for preparing a resin substrate having an adhesive portion, for example, the second substrate 11b is prepared. The thickness of the second substrate is not particularly limited, but is preferably, for example, 1 to 10 μm. Furthermore, the thickness of the adhesive portion is not particularly limited, but is preferably, for example, 0.1 μm or more, and more preferably 0.5 μm or more.

[0117] Furthermore, it is preferable that the back surface of the second substrate 11b (the surface to which the first particles P1 are not transferred) also has an adhesive portion coated with the same adhesive as the front surface, and that the front surface is further covered with a protective film, etc. This prevents the substrates from shifting when stacked as described below, and also sandwiches and firmly fixes the active material particles and solid electrolyte particles between the substrates between the upper and lower surfaces (stacking direction).As a result, particle movement is suppressed when stacking the electrode substrates, storing the stack, heat treating, or applying pressure, and a desired electrode can be formed.

[0118] The adhesive is not particularly limited, and the adhesives described above can be used. The particle placement device 1 may also have an application means, such as a dispenser, inkjet head, spin coater, or bar coater, that applies the adhesive to the surface of the second substrate 11b during transport. The type and amount of adhesive applied are adjusted appropriately depending on the shape and material of the concave-convex pattern used, the particle size and material of the first particles P1 and the second particles P2, and the like, but it is preferable that the adhesive has a greater adhesive strength than the concave-convex pattern 111a. Comparison of adhesive strength can be measured by a common method using a nanoindenter.

[0119] At the nip portion, the first particles P1 are restrained by the adhesive force generated between the first particles P1 and the second substrate 11b. When the conveying members 224a and 224b pass through the nip portion and are separated from each other, the first particles P1 on the first substrate 11a are transferred to the second substrate 11b.

[0120] The second substrate 11b that has passed through the transfer unit 25a has first particles P1 disposed on it, but the adhesive portion is exposed in the area where the first particles P1 are not disposed. In the second step, the first particles P1 disposed on the resin substrate are rubbed with magnetic particles having a particle diameter larger than the width of the exposed adhesive portion on the resin substrate. The second substrate 11b onto which the first particles P1 have been transferred is transported to the rubbing device 30 by the transport member 224b. The rubbing device 24 has the same configuration and function as the first filling device 24a, except that the filling container 242a contains a filler having a carrier material S3 instead of the filler 241a having the first particles P1 and the carrier material S1.

[0121] The rubbing device 30 rubs the first particles P1 arranged on the resin substrate using a support material S3, which is magnetic particles with no particles attached, using the same mechanism as when the first particles P1 were filled. In the above-described filling device, a magnetic material is used as a filler, and the surface of the resin substrate on which the first particles P1 are arranged can be rubbed by contacting the magnetic material with the surface of the resin substrate on which the first particles P1 are arranged. The support material S3 is not particularly limited as long as it is magnetic, but is preferably the same as the support material S1 described above. For example, a standard carrier (Standard Carrier P02, manufactured by the Japan Imaging Society), which is a magnetic particle, can be used. The particle size and material of the support material S3 are appropriately selected according to the particle size and material of the first particles P1. The particle size of the support material S3 is preferably larger than the width of the portion of the resin substrate on which the active material particles are not arranged. For example, the volume-based cumulative 50% particle size (median diameter) is preferably 50 to 100 μm. By doing so, the carrier material S3 has a particle size that does not come into contact with the adhesive portion exposed on the resin substrate, and therefore can rub only the first particles P1 arranged on the substrate.

[0122] By rubbing the surface of the first particles P1 transferred onto the substrate 11b, the first particles P1 can be more firmly fixed to the adhesive portion on the substrate 11b, preventing particle damage and shifting in subsequent processes. Furthermore, the packing density of the transferred first particles P1 increases, resulting in an electrode substrate with very dense particle packing even after the subsequently applied second particles P2 are applied. Furthermore, rubbing the first particles P1 makes it easier for the second particles P2 to mount on the surface of the first particles P1. That is, rubbing makes the surface of the first particles P1 have a gently convex shape, increasing the area that can contact the second particles P2. Furthermore, the second particles P2, which are arranged in the process described below, are arranged to a height approximately equal to the top surface of the first particles P1. Therefore, rubbing the first particles P1 makes it easier for the second particles P2 to be arranged on the first particles P1.

[0123] This makes it easier to achieve a configuration in which the second particles P2 cover at least a part of the surface of the first particles P1 on one surface of the particle layer, increasing the area ratio of the second particles P2, i.e., a difference is easily created between the area ratio of the exposed surface of the active material particles on one surface of the particle layer and the area ratio of the exposed surface of the active material particles on the other surface.

[0124] The second substrate 11b that has been rubbed is transported by a transport member 224b to a loading position of a second loading device 24b. The second loading device 24b has the same configuration and function as the first loading device 24a, except that a loading container 242a contains a loading agent 241b having second particles P2 and a carrier material S2 instead of the loading agent 241a having first particles P1 and a carrier material S1.

[0125] The second filling device 24b fills the second particles P2 into the portions of the second substrate 11b where the first particles P1 are not placed. As described above, the first particles P1 are placed on the second substrate 11b that has passed through the transfer unit 25a, but the adhesive portions are exposed in the portions where the first particles P1 are not placed, forming recesses, so to speak. The second filling device 24b fills the recesses (adhesive portions) with the second particles P2 using the same process as the first filling device 24a.

[0126] In this way, the second particles P2 that can be filled are selectively filled into the gaps on the second substrate 11b where the first particles P1 are not placed, thereby improving the coverage of the substrate by the particles. The second particles P2 preferably have a median diameter equal to or smaller than the opening width of the gaps between the first particles P1. Note that, although the case where magnetic particles are used as the carrier material will be described here, brush fibers or elastic materials may also be used as the carrier material, as in the first filling device 24a.

[0127] The filler 241b includes second particles P2 and a support material S2 that supports the second particles P2. The filler 241b is a mixture of multiple powders including a powder composed of multiple second particles P2 and a powder composed of multiple support materials S2. The support material S2 may be the same as or different from the support material S1. The support material S2 is selected appropriately depending on the particle size and material of the second particles P2 and the opening width of the voids described above.

[0128] 9 is an enlarged view of the surface of the second substrate 11b during the filling process using the second filling device 24b. A concave-convex pattern is formed on the second substrate 11b, including protrusions formed by the first particles P1 and recesses where the first particles P1 are not disposed. The adhesive portions 13b are exposed in the recesses on the second substrate 11b where the first particles P1 are not disposed. During the filling process using the second filling device 24b, the second particles P2 are disposed on the adhesive portions 13b on the surface of the second substrate 11b. After the filling process using the second filling device 24b, the first particles P1 and the second particles P2 are disposed adjacent to each other on the surface of the adhesive portion of the second substrate 11b. That is, by disposing the second particles P2 in the portions of the second substrate 11b where the first particles P1 are not disposed, the first particles P1 and the second particles P2 can be disposed adjacent to each other. Furthermore, it is not necessary that the second particles P2 are disposed adjacent to all of the first particles P1, and the first particles P1 or the second particles P2 may be adjacent to each other.

[0129] The filler 241b comes into contact with this uneven pattern, and is transported together with the second substrate 11b at a non-zero relative speed with respect to the second substrate 11b while being subjected to a magnetic force (solid line Fm in the figure) in a direction perpendicular to the surface of the second substrate 11b. As a result, the second particles P2 carried on the support material S2 are transported while being rubbed against the uneven pattern on the surface of the second substrate 11b. The mass % of the second particles P2 in the filler 241b (the ratio of the mass of the second particles P2 to the total mass of the filler 241b) is expressed by the following formula (2) using the coverage S2 of the carried second particles P2 with respect to the surface area of ​​the magnetic particles (support material). The coverage S2 indicates the ratio of the total cross-sectional area of ​​the second particles P2 to the surface area of ​​the magnetic particles (support material). Mass % of the second particles P2 in the filler 241b = (400 x ρ Ｐ２ ×r Ｐ２ × S2) / (100 × ρ ｃ ×r ｃ +4×ρ Ｐ２ ×r Ｐ２ ×S2) Equation (2) (The symbols in equation (2) represent the following: ρ Ｐ２ : true density of the second particle P2, r Ｐ２ : particle size (r50) of the second particle P2, ρ ｃ : true density of magnetic particles, r ｃ : particle size of the magnetic particle (r50), S2: coverage rate of the second particles P2 relative to the surface area of ​​the magnetic particle)

[0130] The mass % of the second particles P2 in the filler 241b is not particularly limited, but is preferably in the range of 5 to 40 mass %, or 10 to 30 mass %. Furthermore, the coverage S2 in the above formula (2) is preferably adjusted to 30 to 200 area %, and more preferably adjusted to 50 to 100 area %. The particle diameters (r50) of the second particles P2 and the magnetic particles (support material) can be determined by laser diffraction / scattering particle size distribution measurement. Furthermore, the true density of the second particles P2 and the magnetic particles (support material) can be determined by pycnometer method.

[0131] At this time, the opening width of the recesses of the uneven pattern is set to a size that allows the second particles P2 to contact the recesses but prevents the support material S2 from contacting them. That is, the opening diameter of the recesses of the uneven pattern on the second substrate 11b is preferably larger than the cumulative 50% particle size (median diameter) of the second particles P2 in the volume-based particle size distribution. Furthermore, the opening diameter of the recesses is preferably smaller than the average size of the support material S2. Here, the opening diameter of the recesses of the uneven pattern is preferably the opening diameter in the short direction of the recesses, and more preferably the maximum opening diameter in the short direction of the recesses. This allows only the second particles P2 in the filler 241b to selectively contact the recesses.

[0132] The second particles P2 that come into contact with the recesses are strongly restrained by the physical restraining force due to the structure of the concave-convex pattern, and by the electrostatic adhesion and adhesive force with the second substrate 11b and the structural material that constitutes the concave-convex pattern (here, the first particles P1), and are detached from the support material S2. Note that, for the sake of explanation, in Figure 9, the second particles P2 are supported on the surface of the support material S2, but it is also acceptable for there to be second particles P2 that are not supported on the support material S2 during the agitation, supply, or transport of the filler 241b.

[0133] 10A is a diagram schematically illustrating the second substrate 11b after the first particles P1 have been transferred by the transfer unit 25a, as viewed from a direction perpendicular to the substrate surface. As shown in FIG. 10A, a honeycomb pattern is formed on the second substrate 11b, in which the first particles P1 are arranged in regular hexagonal arrangement regions.

[0134] The first particles P1 are densely arranged within this regular hexagonal region, and the other areas (white areas in FIG. 10A ) are free of the first particles P1, leaving the adhesive portion of the surface of the second substrate 11b exposed. The regular hexagonal region in which the first particles P1 are held is referred to as the first pattern portion. The honeycomb pattern region in which the second particles P2 are held and which corresponds to the gaps in the first pattern portion is referred to as the second pattern portion.

[0135] 10B is a schematic diagram of the second substrate 11b after the second particles P2 have been filled by the second filling device 24b, viewed from a direction perpendicular to the substrate surface. As shown in FIG. 10B, the second particles P2 are densely arranged in the areas where the first particles P1 were not arranged and the adhesive portion was exposed. Furthermore, the first particles P1 and the second particles P2 are densely arranged at the boundary between the area where the first particles P1 are arranged and the area where the second particles P2 are arranged. Note that particles can also be filled in the small gaps between the first particles P1 using a similar method. In this case, it is possible to fill the gaps between the first particles P1 using a filler containing particles with a particle size corresponding to the gaps between the first particles P1 using the same method as described above, thereby forming an even denser thin film.

[0136] 11 is a diagram schematically illustrating the configuration of the particle arrangement device 2. The particle arrangement device 2 is a device that forms a particle layer 12 on a substrate 11, and includes a storage container 21 that stores and supplies the substrate 11, and a belt device 22 that transports the substrate 11. The particle arrangement device 2 may also include a liquid application device 201 that applies a liquid for providing adhesive portions on the substrate 11. In this case, in order to densely arrange the particles on the substrate 11, it is preferable to apply the liquid in a pattern on the substrate 11.

[0137] The liquid applying device 201 may be a device that ejects liquid by an inkjet method or a device that applies liquid, but a plate-based method such as a flexographic printing method may also be used. Of these, it is preferable to use a device that ejects liquid by an inkjet method as the liquid applying device. Devices that eject liquid by an inkjet method may be devices using various ejection methods, such as a thermal type, a piezo type, an electrostatic type, or a continuous type.

[0138] The liquid applied by the liquid application device 201 may be water-based or oil-based, as long as it contains a material to which the first particles P1 can be attached. A material that does not react with the first particles P1 can be selected as appropriate. The liquid application device 201 may also form the pattern L1 using a plurality of types of liquid. For example, the liquid application device 201 may apply two types of liquid that react with each other on the substrate 11 to increase adhesion. Examples of materials to which the first particles P1 can be attached include resins such as acrylic resins.

[0139] The powder application device 202 applies powder containing the first particles P1 to the substrate 11 on which the liquid has been arranged in a pattern, thereby fixing the first particles P1 by the material on the substrate 11 in a pattern corresponding to the pattern L1.

[0140] The means for applying the powder by the powder applying device 202 may be a means for spraying or sprinkling the powder toward the substrate 11. The powder applying device 202 may further include a means for removing the first particles P1 that have not been fixed to the substrate 11 by means of vibration, centrifugation, air blowing, suction, or the like.

[0141] The particle arrangement device 2 may further include a drying device that evaporates at least a portion of the liquid applied by the liquid application device 201 to control the amount of material on the substrate 11, the thickness of the pattern L1, and the like. This drying device may be provided downstream of the liquid application device 201 and upstream of the powder application device 202. The material on the substrate after drying may be a liquid, a liquid containing solids, or only solids.

[0142] In the manufacturing method of the electrode substrate, the second step can be described as a particle rubbing step in which the first particles P1 arranged on the surface of the adhesive portion are fixed by rubbing. In the particle rubbing step, the first particles P1 are rubbed using the above-mentioned support material S3. The manufacturing method of the electrode substrate may include the above-mentioned steps, and the order of each step can be changed as appropriate. For example, after the step of arranging the first particles P1 on the resin substrate, a step of rubbing the surfaces of the first particles P1 is performed. After the rubbing step, a step of arranging the second particles P2 on the resin substrate is performed. Furthermore, a step of rubbing the first particles P1 and the second particles P2 may be performed. In other words, the particle rubbing step may include a step of rubbing the first particles P1 and the second particles P2 arranged on the resin substrate.

[0143] FIG. 12 is a schematic diagram showing the devices for the second and third steps. The substrate 11 on which the first particles P1 are disposed is transferred to the belt device shown in FIG. 12. The belt device is provided with a particle rubbing device 25 on the upstream side and a filling device 24b downstream thereof for disposing the second particles P2. The particle rubbing device 25 has pressure rollers 223c and 223d, and the pressure roller 223d rotates in a driven manner. At least one of the pressure rollers 223c and 223d is preferably a soft roller having an elastic layer on its surface. For example, a soft roller having an elastic layer of silicone rubber or fluororubber on the surface of a stainless steel core can be used. In addition, a heater (not shown) may be built into at least one of the pressure rollers 223c and 223d.

[0144] The substrate 11 is transported by a belt device to a pressure section between the pressure rollers 223c and 223d. When the substrate 11 is pressed by the pressure rollers 223c and 223d, the first particles P1 arranged on the surface of the adhesive portion on the substrate settle into the adhesive portion on the substrate. At this time, the above-mentioned heater may be used to facilitate rearrangement of the particles in the adhesive portion on the substrate. Furthermore, a heat source may be provided upstream of the particle rubbing device 25 to heat the adhesive portion on the substrate.

[0145] Since the pressure roller 223c comes into contact with the particle layer 12 on the substrate, it is preferable to coat the surface with a material with good releasability, such as fluorine, to prevent particles from adhering to the pressure roller 223c. A cleaning mechanism for removing particles adhering to the pressure roller 223c may also be provided. It is even more preferable to apply pressure to the particle layer 12 while it is covered with a protective material (not shown). In this case, the protective material used is preferably a material with good releasability, such as a fluorine sheet if it is a resin, or nichrome foil if it is a metal. When a protective material is used, a removal mechanism (not shown) for removing the protective material is provided downstream of the particle rubbing device 25 and upstream of the second filling device 24b.

[0146] The particle rubbing device 25 may be any other known pressure device, such as an isostatic pressure device (CIP / HIP), a uniaxial pressure device, or a device that uses a weight or a magnet.

[0147] After rubbing and fixing the first particles P1 arranged on the substrate 11, a liquid may be applied by a liquid application device 203 to provide adhesive portions at least in areas where the first particles P1 were not arranged. The liquid application device 203 has the same function as the liquid application device 201. A removal mechanism (not shown) for removing excess solvent from the applied liquid may also be provided. Using a second filling device 24, second particles P2 are arranged on the surface of the substrate 11 to which the liquid has been applied by the liquid application device 203. As a result, a dense particle layer 12 is formed on the substrate 11.

[0148] Furthermore, like the particle arrangement device 1, the particle arrangement device 2 may have a transfer unit. In this case, the transfer unit is provided downstream of the powder application device 202. The first particles P1 are transferred from the substrate 11 to another substrate having an adhesive portion. In the substrate to which the first particles P1 have been transferred, the second particles P2 can be arranged using the second filling device 24 in areas where the first particles P1 are not arranged and the adhesive portion is exposed. This makes it possible to arrange the first particles P1 and the second particles P2 densely on the adhesive portion of the resin substrate.

[0149] Using the above-mentioned particle placement device 1 or particle placement device 2, first particles P1 are placed on the adhesive portion of the resin substrate in the first step (S101 in FIG. 2), the first particles P1 are rubbed and fixed in place in the second step (S103 in FIG. 2), and second particles P2 are placed on the adhesive portion of the resin substrate in the third step (S103 in FIG. 2).

[0150] The first and second filling devices 24 may be simple devices that do not use a belt device. FIG. 13 shows an example of such a device. The third filling device 24 includes a filling container 242, a stirring screw member 243, a magnetic member 247, a magnet 248, and a regulating member 250. FIG. 14 is a schematic diagram illustrating the operation of the filling device. The filler 241 sufficiently stirred by the stirring screw member 243 is supplied in an appropriate amount by the magnetic member 247 (arrow a in the figure) that has moved from its home position and the regulating member 250. The supplied filler 241 is rubbed on the substrate 11 as the magnetic member 247 moves back and forth (arrow b in FIG. 14). After rubbing the desired number of times, the magnetic member 247 moves to a distant home position where the magnetic force acting on the filler 241 on the substrate is sufficiently weakened (arrow c in FIG. 14). The filler 241 on the substrate falls downward due to gravity and is collected in a collection container (not shown). At this time, it is more preferable to use air blowing or vibration. Also, instead of rubbing on an inclined surface as shown in the figure, rubbing on a flat surface may be performed to collect the filler 241, and then the filler 241 remaining on the substrate may be collected again by reciprocating the magnetic member 247. At this time, it is more preferable to use air blowing or vibration during each collection.

[0151] In the preparation of the electrode substrate, additional processes may be performed between the above-described processes or after the third process. That is, a process of arranging third particles P3 and a process of rubbing the arranged third particles P3 may be performed. For example, after the process of arranging first particles P1 on the resin substrate, a process of rubbing the surfaces of the first particles P1 is performed. After the rubbing process, a process of arranging second particles P2 on the resin substrate is performed. Then, a process of arranging third particles P3 on the first particles P1 and the second particles P2 may be performed. Furthermore, a process of rubbing the surfaces of the third particles P3 may be performed. When the third particles P3 are applied, they can be applied in the same manner as the filling devices 24a and 24b described in the particle arrangement device 1 or the mechanism described in the particle arrangement device 2. The rubbing process can also be performed after the arrangement of each particle using the magnetic particles or rubbing device described above.

[0152] In the electrode substrate, the coverage of the resin substrate surface by the active material particles and solid electrolyte particles is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. In the present disclosure, the coverage of the resin substrate surface refers to the ratio (area %) of the area covered by the active material particles and solid electrolyte particles to the total area of ​​the resin substrate surface. The coverage of the substrate surface by the active material particles and solid electrolyte particles can be measured by photographing the area where the particle layer is formed using an optical microscope from the direction perpendicular to the substrate and calculating the area ratio of the area covered by the active material particles and solid electrolyte particles using image processing software. Details of the measurement method will be described later.

[0153] The upper limit of the coverage is not particularly limited, but is preferably 99% or less, and more preferably 98% or less. For example, the coverage of the resin substrate surface by the active material particles and solid electrolyte particles is preferably in the range of 60 to 99%, 70 to 99%, 80 to 99%, 60 to 98%, 70 to 98%, or 80 to 98%. When the coverage is in the above range, a dense particle layer is formed on the substrate, improving the density of the particles in the electrode. As a result, ionic conductivity can be improved.

[0154] <Electrode Manufacturing Method> An example of an electrode manufacturing method will be described in detail below with reference to the drawings. The following description will be given taking a positive electrode using positive electrode active material particles as an example, but the manufacturing method described below can be used to manufacture electrodes regardless of whether they are positive electrodes or negative electrodes.

[0155] The method for manufacturing an electrode includes the following three steps (steps 1, 2, and 3): (1) step 1 of stacking a plurality of electrode base materials to form a laminate (S201 in FIG. 15), (2) step 2 of removing the resin base material from the laminate to obtain a three-dimensional object (S202 in FIG. 15), and (3) step 3 of pressurizing the three-dimensional object to obtain an electrode (S203 in FIG. 15).

[0156] That is, the electrode is manufactured by a manufacturing method including the steps of stacking a plurality of electrode base materials and forming a laminate, removing the resin base material from the laminate to obtain a three-dimensional object, and applying pressure to the three-dimensional object. For example, a sintered body of the above-mentioned electrode base material can be used as the electrode. Each step of the electrode manufacturing method will be described in detail below.

[0157] (First Step) The first step is a step of stacking a plurality of electrode base materials to form a laminate. The number of layers is not particularly limited and is determined according to the desired electrode capacity. For example, it is preferable to stack three or more of the above-mentioned electrode base materials. Furthermore, the electrode base materials to be stacked may be the same, or different electrode base materials may be stacked.

[0158] That is, the electrode substrate can also be used as an electrode substrate laminate in which a plurality of electrode substrates are stacked. As described above, the electrode substrate has a resin substrate and a particle layer formed on the resin substrate. When stacking electrode substrates, it is preferable to stack them so that the electrode substrate laminate has resin substrates and particle layers alternately. That is, it is preferable that the electrode substrate laminate has a configuration in which resin substrates and particle layers alternate in the cross section of the electrode substrate laminate. Such a configuration allows sufficient contact between active material particles, between active material particles and solid electrolyte particles, and between solid electrolyte particles, thereby further improving ionic conductivity and electronic conductivity. For example, a sintered body of the electrode substrate laminate can be used as an electrode. Alternatively, a sintered body obtained by sintering an electrode substrate, in which at least a portion of the resin substrate in the electrode substrate has been removed, may be used as an electrode.

[0159] Furthermore, the laminate is preferably formed on an electrode current collector as a substrate. That is, it is preferable that the electrode has a substrate. As the electrode current collector, known current collectors such as Al foil, SUS foil, Cu foil, Cu—Ni foil, platinum foil, and gold foil can be used. An electrolyte may also be used as the substrate. As described above, smooth electron transfer can be achieved by increasing the contact area between the active material particles, which have excellent electronic conductivity, and the current collector. Therefore, it is preferable that the surface of the electrode substrate on which the active material particles are more exposed is provided on the current collector side. That is, when forming the laminate on the electrode current collector, it is preferable to laminate the electrode substrate so that the surface of the electrode substrate on the resin substrate side is provided on the current collector side.

[0160] In this case, the electrolyte may be a separately prepared solid electrolyte sheet or an electrolyte substrate consisting of only solid electrolyte particles on a similar substrate. That is, a solid electrolyte can be used as the electrolyte. Furthermore, the solid electrolyte sheet or electrolyte substrate may have a negative electrode or a negative electrode substrate formed on the opposite side from the stacking surface of the positive electrode substrate.

[0161] 16 is a diagram showing a schematic configuration of a laminate forming apparatus. The laminate forming apparatus includes a conveying device 31 that conveys a substrate 11 on which a particle layer 12 is formed, and a stage 32 that can be moved back and forth in the vertical direction by an actuator (not shown).

[0162] The conveying device 31 receives the substrate 11 having the particle layer 12 formed using the particle placement device, and conveys it to the stage 32. Examples of the conveying device 31 that can convey the substrate 11 include a belt conveyor, a roller, and a robot arm. When the substrate 11 is conveyed to the stage 32 by the conveying device 31, the stage 32 moves in the vertical direction by an amount corresponding to the thickness of the substrate 11 and the particle layer 12. By repeating the conveying by the conveying device 31 and the movement of the stage 32, multiple substrates 11 each having a particle layer 12 formed thereon are stacked, and the laminate 15 is formed.

[0163] In this case, it is preferable that the back surface of the substrate 11 on which the particle layer 12 is formed has an adhesive portion. This adhesive portion allows the substrates to adhere to each other, increasing the strength of the laminate and preventing misalignment between the substrates even after the first step. Furthermore, the particle layer 12 between the substrates is sandwiched between the upper and lower adhesive portions, preventing misalignment during processing or storage of the laminate. The adhesive portion may be applied by a coating device (not shown) before lamination, or a pre-coated substrate may be used and the protective film coated on the coated surface may be peeled off before lamination.

[0164] It is preferable to have a de-electrification step of de-electrifying the substrate immediately before the laminate 15 is formed. The particle layer 12 and the substrate 11 formed using the particle placement device are easily charged, and electrostatic repulsion occurs between the substrates during lamination. Therefore, when laminating in the first step, the substrates tend to peel off or gaps tend to form between the substrates. In the de-electrification step, it is preferable to perform non-contact de-electrification using an electrostatic de-electrification blower or the like. Furthermore, it is preferable to have a de-aeration step of de-aerating the laminate after the laminate 15 is formed in order to reduce gaps between the substrates. In the de-aeration step, it is preferable to perform de-aeration using a vacuum packaging machine or the like.

[0165] (Second Step) The second step is a step of sintering the laminate to remove the resin base material from the laminate. Fig. 17 is a diagram showing a schematic configuration of a sintering treatment apparatus. The sintering treatment apparatus has a conveying device 41 that conveys the laminate 15 and a heating furnace 42 that heats the laminate 15.

[0166] The conveying device 41 receives the laminate 15 from the laminate forming device and conveys it to the heating furnace 42. Similar to the conveying device 31, the conveying device 41 is preferably a device capable of conveying the laminate 15. Examples of devices capable of conveying the laminate 15 include a belt conveyor, a roller, and a robot arm.

[0167] The heating furnace 42 is a furnace that heats the laminate 15. The heating furnace 42 has a heating means 421, a pressurizing means 422, and an atmosphere adjusting means 423. A firing furnace used for firing ceramics or the like can be used as the heating furnace 42. The pressurizing means 422 pressurizes the laminate 15 being heated in the heating furnace 42, and pressurizes the laminate 15 before and after heating.

[0168] It is preferable that the pressurizing means 422 has a pressurizing portion that pressurizes the laminate 15 and is made of a porous material that allows gas to easily pass through. The atmosphere adjusting means 423 has an atmosphere gas supplying means 423a and a pressure reducing means 423b, and adjusts the atmosphere gas in the processing space of the heating furnace 42. The atmosphere gas may be an oxidizing atmosphere (O ２ ), inert atmosphere (Ar, N ２ etc.) or reducing atmosphere (Ar-H ２ ) can be used, but sintering may also be carried out in air.

[0169] When sintering the laminate, it is preferable to heat the laminate at a temperature equal to or higher than the thermal decomposition temperature of the substrate 11 in the laminate 15, and preferably at a temperature lower than the thermal decomposition temperature of each particle layer in the laminate 15. The temperature to which the laminate is heated is preferably 200°C or higher and 1000°C or lower, more preferably 400°C or higher and 800°C or lower. It is preferable to maintain the sintering temperature for 30 minutes or longer, and more preferably for 1 hour or longer. The thermal decomposition temperature is the temperature at which the weight of the material begins to decrease when the temperature is gradually increased in the heating atmosphere in the sintering treatment device. Therefore, by heating the laminate at a temperature equal to or higher than the thermal decomposition temperature of the substrate 11, the substrate 11 in the laminate can be decomposed to reduce its weight, and the resin substrate can be removed from the laminate.

[0170] The heating temperature is preferably equal to or higher than the thermal decomposition temperature of the base material 11, but is preferably even higher than the thermal decomposition temperature. Specifically, when the temperature is increased from room temperature (25°C) at a rate of 5°C / min in an atmosphere (typically air) during heating in a sintering treatment device and thermogravimetric analysis is performed, the heating temperature is preferably equal to or higher than the temperature at which the mass is reduced to 70% by mass of the initial mass. Specifically, for example, 385°C or higher is preferable.

[0171] Similarly, when thermogravimetric analysis is performed, it is more preferable to heat at a temperature equal to or higher than the temperature at which the mass is reduced to 50% by mass of the initial mass, and even more preferable to heat at a temperature equal to or higher than the temperature at which the mass is reduced to 20% by mass of the initial mass. Specifically, for example, 400°C or higher is preferable, and 450°C or higher is more preferable. This can shorten the time required to remove the resin substrate and increase the removal rate of the resin substrate.

[0172] In this way, when the sintering treatment apparatus removes the substrate 11 by heating, it is preferable that the active material particles and the solid electrolyte particles have a higher thermal decomposition temperature than the substrate 11. In general, inorganic materials tend to have higher thermal decomposition temperatures than organic materials, so it is preferable that the active material particles and the solid electrolyte particles are inorganic materials and the substrate 11 is made of an organic material such as a resin. Furthermore, when the sintering treatment apparatus removes the substrate 11 by heating, it is preferable that the active material particles have a softening point temperature higher than the thermal decomposition temperature of the substrate 11.

[0173] The sintering treatment device is required to remove at least a portion of the resin substrate in the laminate 15 by heating, thereby providing a portion where the particles of the upper and lower layers of the laminate come into contact. It is preferable to remove 90% by mass or more of the resin substrate in the laminate 15, more preferably 95% by mass or more, and even more preferably 97% by mass or more. In this process, the resin substrate is preferably burned or gasified and released to the outside as a gas. When the resin substrate gasified by pyrolysis is released to the outside of the laminate as a gas, it may push up the particle layer formed on the resin substrate, causing the shape to become distorted. Therefore, it is preferable to reduce the thickness of the resin substrate to reduce the impact on the particle layer.

[0174] Specifically, the thickness (μm) of the resin substrate is preferably 10 times or less, more preferably 5 times or less, and even more preferably 2 times or less, the thickness of the particle layer on the resin substrate. Here, the thickness of the particle layer refers to the difference between the maximum and minimum values ​​of z in the region (x, y, z) where each particle arranged on the resin substrate is present, when the resin substrate surface is (x, y) and the lamination direction of the resin substrate is (z) in the electrode substrate. The thickness of the resin substrate is preferably 1 μm or more and 1 mm or less. The thickness of the particle layer is preferably 0.1 μm or more and 100 μm or less.

[0175] The thickness of the particle layer on the resin substrate is calculated by observing the cross section of the laminate 15 with a BIB-SEM, determining the particle presence area (x, z) using image processing software, where x is the resin substrate surface and z is the lamination direction of the resin substrate, and then calculating the difference between the maximum and minimum values ​​of z. Here, the BIB-SEM imaging conditions, the required image area, and the image processing method are the same as those described above.

[0176] The thickness of the resin substrate may be determined by BIB-SEM, as with the particle diameter of the active material particles, or may be measured using a digital thickness gauge, etc. In addition, in SEM observation using BIB-SEM, methods for identifying the active material particles, solid electrolyte particles, substrate, and adhesive portion, include a method of elemental composition analysis by EDS.

[0177] The sintering treatment device preferably exhausts the released gas to the outside of the heating furnace 42 using the pressure reducing means 423b. By creating an oxidizing atmosphere, i.e., an atmosphere containing oxygen gas such as air, inside the heating furnace 42 using the atmospheric gas supplying means 423a or the like, the resin base material can be burned and removed. However, depending on the active material particles and solid electrolyte particles used, sintering in an oxidizing atmosphere may cause decomposition or composition changes. In such cases, it is recommended to use an inert atmosphere (Ar, N ２ etc.) or reducing atmosphere (Ar-H ２ ) is preferably sintered.

[0178] As described above, when the resin substrate is gasified by pyrolysis from the laminate 15 and released as a gas, the particle layers in the laminate 15 may be pushed up and deformed. Therefore, when heating in the heating furnace 42, the laminate 15 may be pressurized by the pressurizing means 422 before or during heating.

[0179] FIG. 18A is a BIB-SEM image of the cross section of the laminate after the first step. The laminate 15 is formed by stacking six second substrates 11b, each having a particle layer 12 formed thereon, on a base 14. FIG. 18B is a BIB-SEM image of a three-dimensional object 16 (positive electrode) after the second step. The resin substrate has been removed from the laminate 15, resulting in a three-dimensional object 16 consisting of six particle layers. FIG. 18C is an SEM image of the top of the three-dimensional object 16. The first particles P1 and second particles P2 periodically arranged on the second substrate 11b in the first step are maintained even after the second step.

[0180] (Third Step) The third step is a step of pressurizing the three-dimensional object 16 from which the resin base material has been removed. As a method of pressurizing, the three-dimensional object 16 can be pressurized by a pressurizing means 422 during cooling or heat dissipation after heating. Alternatively, after the resin base material is removed by a sintering treatment device, pressure can be applied by a separate pressurizing device. Specific pressing methods are preferably vacuum degassing, isostatic pressing, or a general hydraulic press or roller press. Among these, pressing by a combination of vacuum degassing and isostatic pressing is preferred.

[0181] The pressure is preferably 5 MPa to 500 MPa. This fills the voids in the three-dimensional object from which the resin substrate has been removed, improving the density and strength of the three-dimensional object. After the third step, the three-dimensional object may be heated again in a sintering treatment device for sintering. Alternatively, the laminate may be impregnated with a solution in which a conductive additive, a binder resin, etc. are dispersed in a solvent, thereby dispersing each material within the laminate.

[0182] An electrode can be manufactured by a manufacturing method including the above-described steps. The electrode preferably has a substrate and a particle layer containing active material particles and solid electrolyte particles. It is also preferable that voids exist in the particle layer. This configuration can improve ionic conductivity within the electrode and mitigate volume fluctuations of the active material particles.

[0183] 19 is a diagram schematically illustrating the overall configuration of an additive manufacturing system 100. The additive manufacturing system 100 includes a control unit U1, a particle layer forming unit U2, a stacking unit U3, a removal unit U4, and a post-processing unit U5.

[0184] The control unit U1 is responsible for controlling each component of the additive manufacturing system 100. The particle layer formation unit U2 forms a particle layer 12 on a substrate 11 using the particle placement device (FIG. 3) described above. The lamination unit U3 uses the laminate molding device (FIG. 16) described above to stack multiple substrates 11, each with a particle layer 12 formed in the particle layer formation unit U2, to form a laminate 15 including multiple particle layers 12 and multiple substrates 11. The removal unit U4 uses the sintering treatment device (FIG. 17) described above to remove the substrate 11 from the laminate 15 formed in the lamination unit U3 to form a three-dimensional object 16 (electrode). The post-processing unit U5 performs post-processing of the three-dimensional object 16 formed in the removal unit U4. Note that the unit configuration shown in FIG. 19 is merely an example, and other configurations may be adopted. The configuration and operation of each unit are described below.

[0185] [Control Unit] The control unit U1 controls each part of the additive manufacturing system 100, specifically the particle layer formation unit U2, the stacking unit U3, the removal unit U4, and the post-processing unit U5. The control unit U1 may include a three-dimensional shape data input unit that accepts input of three-dimensional shape data of a three-dimensional object (hereinafter, sometimes referred to as a "modeling target") to be formed by the additive manufacturing system 100 from an external device (e.g., a personal computer). The three-dimensional shape data can be data created and output using a three-dimensional CAD system, a three-dimensional modeler, a three-dimensional scanner, or the like. While the file format is not critical, for example, the STL (StereoLithography) file format is preferably used.

[0186] The control unit U1 may be equipped with a slice data calculation section that slices the three-dimensional shape data at a predetermined pitch to calculate the cross-sectional shape of each layer, and generates image data (referred to as "slice data") to be used for image formation in the particle layer forming unit U2 based on the cross-sectional shape.

[0187] As will be described in more detail below, the particle layer forming unit U2 of this embodiment can use multiple types of materials to form material layers in which each material is patterned. Therefore, slice data corresponding to images of each material may be generated. The slice data file format can be, for example, multi-value image data (each value representing a type of material) or multi-plane image data (each plane corresponding to a type of material).

[0188] Although not shown, the control unit U1 also includes an operation unit, a display unit, and a memory unit. The operation unit has a function to accept instructions from the user. For example, it is possible to input instructions such as turning the power on / off, various settings of the device, and operation instructions. The display unit has a function to present information to the user. For example, it is possible to present various setting screens, error messages, operation status, etc. The memory unit has a function to store three-dimensional shape data, slice data, various setting values, etc.

[0189] In terms of hardware, the control unit U1 can be configured as a computer equipped with a CPU (Central Processing Unit), memory, auxiliary storage device (hard disk, flash memory, etc.), input device, display device, and various I / Fs. Each of the above-mentioned functions is realized by the CPU reading and executing a program stored in the auxiliary storage device or the like and controlling the necessary devices. However, some or all of the above-mentioned functions may be configured with circuits such as ASIC or FPGA, or may be executed by another computer using technologies such as cloud computing or grid computing.

[0190] [Particle Layer Formation Unit] The particle layer formation unit U2 is a unit that forms a particle layer 12 on the substrate 11. The particle placement device (FIG. 3) described above can be used as the particle layer formation unit U2. The particle layer formation unit may have a particle filling unit and a rubbing unit. The additive manufacturing system 100 may have multiple particle layer formation units U2. This allows the particle layer 12 to be formed on the substrate 11 simultaneously and in parallel, further improving the throughput of the formation of laminates and three-dimensional objects. Furthermore, when there are many types of materials that make up the three-dimensional object, providing a particle layer formation unit U2 for each material type or group of material types can eliminate the need to switch material types or processes within the particle layer formation unit U2. This allows the continuous production of three-dimensional objects.

[0191] [Lamination Unit] The lamination unit U3 is a unit that laminates multiple substrates 11, each having a particle layer 12 formed thereon in the particle layer forming unit U2, to form a laminate 15 including multiple particle layers 12 and multiple substrates 11. The laminate molding apparatus described above ( FIG. 16 ) can be used. The lamination unit U3 may further include a conveying device 33 that conveys the formed laminate 15 to the removal unit U4 or the like, and a pressure device (not shown) that pressurizes the laminate 15 in the stacking direction. The conveying device 33 may have a configuration similar to that of the conveying device 31.

[0192] [Removing Unit] The removing unit U4 is a unit that removes the base material 11 from the laminate 15 formed in the laminating unit U3 to form a three-dimensional object 16. The above-described sintering treatment device (FIG. 17) can be used.

[0193] [Post-processing unit] The post-processing unit U5 is a unit that performs post-processing of the three-dimensional object 16 formed by the removal unit U4. The type of post-processing performed by the post-processing unit U5 is not particularly limited, but examples include a process of further heating and sintering the three-dimensional object 16. Note that when the post-processing unit U5 performs a heat treatment as a post-processing, the removal unit U4 may also perform that function. By sintering the three-dimensional object 16, particles within and between particle layers can be sintered.

[0194] Furthermore, reducing gases such as carbon monoxide generated when the resin substrate is removed may change the composition and reduce ionic conductivity depending on the active material particles and solid electrolyte particles used. In this case, the composition can be changed again by sintering (oxidation) in the post-treatment unit U5, thereby improving ionic conductivity. Of course, in sintering in the post-treatment unit U5, in addition to an oxidizing atmosphere with a controlled oxygen concentration, Ar or N ２ or ArH ２ It is also possible to sinter in a reducing atmosphere such as

[0195] An example of post-treatment other than sintering is a process in which the laminate is impregnated with a solution in which a conductive additive, a binder resin, etc. are dispersed in a solvent, thereby dispersing each material within the laminate. After dispersion, a drying process or a pressurizing process may be included to volatilize the solvent and fix the binder.

[0196] A secondary battery has electrodes (positive and negative electrodes), an electrolyte layer adjacent to the electrodes, and, if necessary, a current collector. For example, an electrode manufactured using the above-mentioned electrode substrate can be used as the positive electrode. The electrode can be manufactured, for example, by the above-mentioned method. Furthermore, known materials can be used as the negative electrode without any particular limitation. Examples of such materials include negative electrodes containing metal foils that form a lithium alloy layer, such as lithium metal, indium, tin, aluminum, zinc, and magnesium, graphite particles (graphite, hard carbon, soft carbon, etc.), silicone particles, and lithium titanate particles.

[0197] The electrolyte layer is not particularly limited and any known material can be used. For example, Li １．５ Al０．５ Ge １．５ P ３ O １２ (hereinafter also referred to as LAGP), Li １．３ Al ０．３ Ti １．７ P ３ O １２ (hereinafter also referred to as LATP), Li ５．９ Yb ０．８１ La ０．０９ Zr ０．１ (BO ３ ) ３ (hereinafter also referred to as LYbBO), Li ３ BO ３ (hereinafter also referred to as LBO), Li ６．２５ La ３ Zr ２ Al ０．２５ O １２ (hereinafter also referred to as LLZ), Li ０．３３ La ０．５５ TiO ３ (hereinafter also referred to as LLT), etc. can be used. Furthermore, the electrolyte may be an electrolyte sheet obtained by pelletizing a material using a pressure device or the like and sintering it. The current collector is not particularly limited, and known materials can be used. For example, aluminum, stainless steel, platinum, gold, etc. can be used as a positive electrode current collector. Furthermore, copper, copper-nickel, platinum, gold, etc. can be used as a negative electrode current collector. The above metals that can be used as current collectors may also be used as metal foils.

[0198] <Method for manufacturing secondary batteries> There are multiple possible methods for manufacturing secondary batteries using the above-described additive manufacturing system 100, but several examples will be given below. A case where the system is used to manufacture a positive electrode or a negative electrode will be described. Using a current collector or an electrolyte formed by a separate means as a base, the system can manufacture a positive electrode, a negative electrode, or both electrodes.

[0199] A secondary battery can be manufactured by laminating an electrode, a current collector, and an electrolyte, optionally packaging the laminate with an aluminum laminate film or the like, and then molding and pressurizing the laminate. That is, a method for manufacturing a secondary battery may include a step of laminating an electrode, a current collector, and an electrolyte. The electrode may be the electrode described above. Also, a method for manufacturing a secondary battery may include a step of preparing an electrode by the electrode manufacturing method described above and a step of providing a solid electrolyte adjacent to the electrode. Also, a method for manufacturing a secondary battery may include a step of simultaneously providing the electrode and the solid electrolyte adjacent to the electrode. That is, the electrode and the solid electrolyte may be prepared separately in separate steps, or may be prepared simultaneously in the same step.

[0200] Here, the alternative means for forming the electrolyte is a known means, such as pelletizing solid electrolyte particles using a uniaxial press or the like and sintering them in an electric furnace or the like. The electrolyte may be an electrolyte sheet or the like. By stacking the produced components in the order of positive electrode current collector, positive electrode, electrolyte, negative electrode, and negative electrode current collector, a laminated secondary battery packed in a laminate film or a coin-type secondary battery packed in a coin case can be produced.

[0201] The particles constituting the positive electrode, electrolyte, and negative electrode may differ in the appropriate temperature and atmosphere during sintering. When handling such materials, it is preferable to separately manufacture the positive electrode, electrolyte, and negative electrode components and assemble them into a battery. Furthermore, when lithium metal or indium is used as the negative electrode, it is preferable to use the negative electrode as a metal foil or to form it into a current collector or electrolyte by a vacuum process such as sputtering. Because lithium metal has a strong reducing power, it is easily decomposed depending on the type of solid electrolyte. In this case, a buffer layer may be provided between the electrode and the electrolyte. It is preferable to use a polymer electrolyte or the like as the buffer layer.

[0202] The above example is an example in which a positive electrode or negative electrode laminate is formed using the additive manufacturing system 100 to manufacture an electrode, but it is also possible to form a laminate containing two or more of the main components of a secondary battery, namely a positive electrode collector, a positive electrode, an electrolyte, a negative electrode, and a negative electrode collector, and manufacture it as a three-dimensional object.

[0203] For example, each substrate is produced by the particle layer forming unit U2. That is, a positive electrode current collector substrate, a positive electrode substrate, an electrolyte substrate, a negative electrode substrate, and a negative electrode current collector substrate. Each substrate may contain multiple types of particles (positive electrode active material particles and solid electrolyte particles) like the positive electrode substrate, or may contain only a single type of particle. When only a single type of particle is contained, a dense particle layer containing only a single type of particle can be formed on the substrate by filling the filling devices 24a and 24b with the same type of filler.

[0204] The electrolyte base material is formed of a particle layer containing at least solid electrolyte particles. The negative electrode base material is formed of a particle layer containing at least negative electrode active material particles. The current collector base material is formed of a particle layer containing at least conductive particles. These base materials are stacked in the following order: positive electrode current collector base material, positive electrode base material, electrolyte base material, negative electrode base material, and negative electrode current collector base material using the stacking unit U3 to produce a laminate, and a secondary battery can be manufactured using the removal unit U4 and post-processing unit U5. Furthermore, a bipolar secondary battery can also be manufactured by stacking electrode base materials on both sides of the current collector base material.

[0205] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, the number of parts is based on parts by mass.

[0206] The positive electrode of a secondary battery was formed using the above-described additive manufacturing system 100. Specifically, a particle layer was formed on a resin substrate using the particle layer formation unit U2 shown in FIG. 19, and the substrate on which the particle layer was formed was laminated (three layers) on a current collector (Al foil) using the lamination unit U3 to form a laminate. The method of applying particles using the particle layer formation unit U2 was selected from methods 1 to 4 shown in FIG. 20 and used as described in Table 1 below. Then, using the removal unit U4, the resin substrate was removed from the laminate by heating, and a three-dimensional positive electrode was formed by applying pressure. The sintering atmosphere and sintering temperature (maintained for 1 hour) are as shown in Table 5 below.

[0207] The electrolyte is Li １．５ Al ０．５ Ge １．５ P ３ O１２ The electrolyte sheet (260 μm thick) was formed by pelletizing the LAGP (hereinafter also referred to as LAGP) powder using a uniaxial press and sintering it in an electric furnace (850°C / 12h). An indium foil (50 μm thick) was used as the negative electrode. Aluminum foil (20 μm thick) was used as the positive electrode current collector. Copper foil (20 μm thick) was used as the negative electrode current collector. The above materials were stacked in the order of positive electrode current collector, positive electrode, electrolyte, negative electrode, and negative electrode current collector. The stack was then packaged in an aluminum laminate film so that the tab lead for the extraction electrode, previously welded to the current collector, was positioned outside the laminate. The stack was then molded into a laminate cell shape using a vacuum packaging machine and pressurized (196 MPa) using an isostatic press to produce an all-solid-state secondary battery.

[0208] A polyester (PET) sheet was used as the first substrate 11a. A honeycomb-shaped concave-convex pattern was formed on the first substrate 11a using a pattern forming device 23. First, an ultraviolet-curable resin (ultraviolet-curable liquid silicone rubber, PDMS, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the first substrate 11a. Then, a film mold (standard mold, manufactured by Soken Chemical & Engineering Co., Ltd.) having a honeycomb-shaped concave-convex pattern on its surface corresponding to the desired concave-convex pattern was pressed against the ultraviolet-curable resin on the first substrate 11a. With the film mold pressed against the first substrate 11a, ultraviolet light was irradiated from a UV lamp to cure the ultraviolet-curable resin, and the film mold was then released.

[0209] The structure of a first substrate 11a having a concave-convex pattern 111a formed on its surface is shown in Figures 21A and 21B. Figure 21A is a top view of the first substrate 11a, and Figure 21B is a cross-sectional view taken along the line A-A in Figure 21A. As shown in Figures 21A and 21B, a honeycomb-shaped concave-convex pattern having hexagonal frame-shaped convex portions is formed on the surface of the first substrate 11a. Here, as shown in Figure 21B, the width of adjacent convex portions is k (μm), the pitch between adjacent convex portions is s (μm), and the height of the convex portions is d (μm). In the following examples, the shape of the concave-convex pattern was measured using a non-contact surface / layer cross-sectional shape measurement system (VertScan 2.0, manufactured by Ryoka Systems Co., Ltd.).

[0210] The second substrate 11b was a polyester (PET) sheet coated with an acrylic adhesive on both sides. The thickness of the second substrate 11b used was 3 μm. The acrylic adhesive was coated on both sides of the second substrate 11b to form an adhesive portion. The thickness of the formed adhesive portion was 1 μm.

[0211] The first particles P1 are active material particles of LiCoO ２ (hereinafter also referred to as LCO), LiMO ２ (M is an element selected from the group consisting of Ni, Mn, and Co. Hereinafter, also referred to as NMC), LiFePO ４ (hereinafter also referred to as LFP), Li ３ V ２ (P.O. ４ ) ３ (hereinafter also referred to as LVP) was used. ３ BO ３ (hereinafter also referred to as LBO), Li ５．９ Yb ０．８１ La ０．０９ Zr ０．１ (BO ３ ) ３ (manufactured by our company; hereinafter also referred to as LYbBO). LCO is manufactured by Nippon Chemical Industry Co., Ltd. (Cellseed C-5H), NMC is manufactured by Nippon Chemical Industry Co., Ltd. (Cellseed NMC), LFP is manufactured by Toshima Manufacturing Co., Ltd., LVP is manufactured by Tokyo Chemical Industry Co., Ltd., Li ３ BO ３ The product used was manufactured by Toshima Manufacturing Co., Ltd.

[0212] The carrier material S1 for the first particles P1, the carrier material S2 for the second particles P2, the carrier material S3 for the third particles P3, and the particles S0 used for rubbing were all magnetic particles, and standard carriers (Standard Carrier P02 manufactured by the Imaging Society of Japan) were used. The cumulative 50% particle size (median diameter) in the volume-based particle size distribution of the standard carrier was 81 μm.

[0213] <Method for manufacturing electrode substrate 1> LCO (first particles P1) and LBO (second particles P2) were mixed at a volume fraction of 7:3 to obtain a mixed powder. The obtained mixed powder and a standard carrier (support material S1) were stirred and mixed to obtain a filler 241a. Note that the above volume fraction was equivalent to the ratio of LCO to LBO applied to the electrode substrate 2 used in Example 1 below. The particle layer was formed using Method 1 shown in FIG. 20A. Using the obtained filler 241a, a particle layer 1 was formed on a resin substrate by a particle layer forming unit U2 to obtain an electrode substrate 1. That is, an electrode substrate 1 was obtained in which the LCO and LBO contained in the above mixed powder were arranged on a resin substrate as the first particles P1 and the second particles P2. At this time, the concave-convex pattern 111a on the first substrate 11a was controlled so that the width k of the concave portions was 6.0 μm, the pitch s of the convex portions was 7.5 μm, and the height d of the convex portions was 5.5 μm. The obtained electrode substrate 1 was used as Comparative Example 1.

[0214] <Method for manufacturing electrode substrate 2> LCO (first particles P1) and a standard carrier (support material S1) were stirred and mixed to obtain filler 241a. Using a similar method, LBO (second particles P2) and a standard carrier (support material S2) were stirred and mixed to obtain filler 241b. Using the obtained fillers 241a and b, a particle layer 2 was formed on a resin substrate by a particle layer forming unit U2 to obtain an electrode substrate 2. The particle layer was formed using method 1 shown in FIG. 20A. That is, first particles P1 were arranged on a resin substrate using the obtained filler 241a, and then second particles P2 were arranged on the resin substrate using the obtained filler 241b to form a particle layer 2. The concave-convex pattern 111a on the first substrate 11a was controlled so that the width k of the recesses was 6.0 μm, the pitch s of the protrusions was 7.5 μm, and the height d of the protrusions was 5.5 μm. The obtained electrode substrate 2 was designated Example 1.

[0215] <Method for manufacturing electrode substrate 3> The fillers used were the same fillers 241a and 241b as those used to form the particle layer 2 on the electrode substrate 2. The particle layer was formed using method 2 shown in FIG. 20B . That is, first particles P1 were arranged on the resin substrate using the filler 241a, and then the first particles P1 were rubbed with particles S0. Thereafter, second particles P2 were arranged on the resin substrate using the filler 241b, forming a particle layer 3 and obtaining an electrode substrate 3. The obtained electrode substrate 3 was designated Example 2.

[0216] <Method for manufacturing electrode substrate 4> The fillers used were the same fillers 241a and 241b as those used to form the particle layer 2 on the electrode substrate 2. Method 3 shown in FIG. 20C was used as the particle layer formation method. That is, first particles P1 were arranged on the resin substrate using the filler 241a, and then the first particles P1 were rubbed with particles S0. Then, second particles P2 were arranged on the resin substrate using the filler 241b. The first particles P1 and the second particles P2 were rubbed with particles S0 using the rubbing unit of the particle layer formation unit U2 to form a particle layer 4, thereby obtaining an electrode substrate 4. The obtained electrode substrate 4 was designated Example 3.

[0217] <Method for manufacturing electrode substrate 5> The fillers used were the same fillers 241a and 241b as those used to form the particle layer 2 on the electrode substrate 2. The particle layer was formed using Method 4 shown in FIG. 20D . That is, first particles P1 were arranged on the resin substrate using the filler 241a, and then the first particles P1 were rubbed with particles S0. Then, second particles P2 were arranged on the resin substrate using the filler 241b. Then, solid electrolyte particles P3 (LBO) were applied using the particle filling unit of the particle layer formation unit U2 to form a particle layer 5, thereby obtaining an electrode substrate 5. The cumulative 50% particle diameter of the solid electrolyte particles P3 was 1.2 μm, which was smaller than the cumulative 50% particle diameter (11 μm) of the solid electrolyte particles P2. The obtained electrode substrate 5 was designated Example 4.

[0218] <Method for manufacturing electrode substrates 6 and 7> Particle layers 6 and 7 were formed under the same conditions as for particle layer 3, except that the first particles P1 and the second particles P2 were changed as shown in Table 1, to obtain electrode substrates 6 and 7. The obtained electrode substrates 6 and 7 were designated as Examples 5 and 6.

[0219] <Method for manufacturing electrode substrates 8 to 10> The arrangement pattern of the first particles P1 and the second particles P2 on the resin substrate was changed as shown in Table 1, but otherwise particle layers 8 to 10 were formed under the same conditions as particle layer 2, thereby obtaining electrode substrates 8 to 10. The obtained electrode substrates 8 to 10 were designated Examples 7 to 9. <Method for manufacturing electrode substrate 11> The same fillers 241a and 241b used in forming particle layer 7 on electrode substrate 7 were used as fillers. The particle layer was formed using Method 4 shown in FIG. 20D . That is, first particles P1 were arranged on the resin substrate using filler 241a, and then the first particles P1 were rubbed with particles S0. Then, second particles P2 were arranged on the resin substrate using filler 241b. Thereafter, solid electrolyte particles P3 (LBO) were applied using the particle filling unit of the particle layer forming unit U2 to form particle layer 11, thereby obtaining electrode substrate 11. The cumulative 50% particle diameter of the solid electrolyte particles P3 was 1.2 μm, which was smaller than the cumulative 50% particle diameter (11 μm) of the solid electrolyte particles P2.

[0220] In the manufacturing process of electrode substrates 1 to 11, the compositions of fillers 241a, 241b, and 241c used when forming a particle layer on a resin substrate using particle layer forming unit U2, and the shape of the concave-convex pattern 111a on the first substrate 11a are shown in Tables 1 and 2. The carrier material S1 in filler 241a, the carrier material S2 in filler 241b, the carrier material S3 in filler 241c, and the carrier material (particles S0) used for rubbing were all the same as the standard carrier. In the table, the mass percentage of particles indicates the mass percentage of each particle in each filler.

[0221] Table 3 shows the particle size of the primary particles of each particle in fillers 241a-c. The particle sizes shown in Table 3 are the particle sizes of the material contained in the filler before the particle layer is formed. The particle sizes (r10, r50, r90) of each particle are the particle sizes of the cumulative distribution in the volume-based particle size distribution of the primary particles, with r10 being the particle size at 10% cumulative, r50 being the particle size at 50% cumulative, and r90 being the particle size at 90% cumulative. In other words, r50 is the median diameter. The particle sizes were measured using a laser diffraction / scattering particle size distribution measuring device (LA-960, manufactured by Horiba, Ltd.). The support materials S1 to S3 and the standard carrier used as the rubbing particles had r10 of 60 μm, r50 of 81 μm, and r90 of 113 μm.

[0222] 22A is an SEM image of the upper side (the side on which the particle layer is formed) of the electrode substrate 2 of Example 1. LCO particles P1 are periodically dispersed and arranged within the surface of the electrode substrate, and LBO particles P2 are arranged between the LCO particles. That is, in FIGS. 22A and 22B, P1 indicates the active material particles of the electrode substrate, and P2 indicates the solid electrolyte particles of the electrode substrate.

[0223] 22B is a BIB-SEM image of a cross section of the electrode substrate 2 of Example 1. A particle layer containing particles P1 and particles P2 was formed on the resin substrate (second substrate 11b) of the electrode substrate 2. In addition, in the particle layer, solid electrolyte particles LBO, which are particles P2, were arranged adjacent to LCO, which are particles P1. Particles P2 were arranged so as to cover part of the surface of particles P1.

[0224] Table 4 shows the evaluation results of Comparative Example 1 and Examples 1 to 9. The evaluation methods will be described later. In the table, "coverage" refers to the coverage of the surface of the resin substrate by the active material particles and solid electrolyte particles. "Active material particle area ratio" refers to the area ratio of the exposed surface of the active material particles on the surface of the particle layer. "Top surface" refers to the surface opposite to the side of the particle layer that comes into contact with the resin substrate. "Bottom surface" refers to the surface of the particle layer that comes into contact with the resin substrate. "Difference" refers to the difference between the area ratio of the exposed surface of the active material particles on the bottom surface and the area ratio of the exposed surface of the active material particles on the top surface. For "evaluation," a good result was given when the difference was within the range of 1 to 70 area percent, and an unsatisfactory result was given when the difference was outside the range.

[0225] Below, the methods for evaluating the electrode substrate and calculating each index are described. <Coverage> Images for calculating the coverage were obtained by SEM observation. For SEM observation, an electron microscope (S-4800: manufactured by Hitachi) was used to photograph the top surface of the electrode substrate (the side on which the particle layer was formed) from the vertical direction. An example of the photographed SEM image is shown in Figure 23A. The photograph was taken under the following conditions: Detector: ESB (backscattered electron image) Observation conditions: accelerating voltage 2 kV Magnification: 1000x Filter: bias of 1500 V applied to ESB filter

[0226] Next, elemental and compositional analysis of each particle on the resin substrate was performed using SEM-EDX (PV77-47190ME, manufactured by AMETEK Corporation) to identify the active material particles and the solid electrolyte particles. In FIG. 23A , the active material particles are shown as white particles (P1), and the solid electrolyte particles are shown as gray particles (P2). The active material particles and the solid electrolyte particles were specifically identified using the following method. The resin substrate was analyzed using X-ray diffraction (XRD) to identify the materials constituting the resin substrate. Then, the specific elements contained in the active material particles and the solid electrolyte particles could be detected and identified using SEM-EDX. When LCO was used as the first particles P1, which were active material particles, and LBO was used as the second particles P2 and the third particles P3, which were solid electrolyte particles, the active material particles were identified by detecting Co using SEM-EDX, and the solid electrolyte particles were identified by detecting B using SEM-EDX.

[0227] The coverage ratio was calculated by determining the proportion of the area where particles existed in the entire screen of the SEM image obtained by the above-mentioned method. Specifically, it was calculated by the following image processing. OpenCV was used for image processing, and analysis was performed using Python. The obtained SEM image was normalized to an average brightness of 100 and a standard deviation of ±30. The normalized image was binarized using a brightness of 50 as a threshold, and an image in which all particles were represented by white pixels was prepared. An example of the prepared image is shown in Figure 23B. The proportion of white pixels among all pixels making up the image was analyzed and calculated as the particle coverage ratio. For example, the coverage ratio in Figure 23A is 97%.

[0228] <BIB-SEM Imaging Method> The area ratio of exposed active material particles on the surface of the particle layer was calculated using BIB-SEM images. The BIB-SEM imaging conditions are explained below. Three resin substrates were stacked on a substrate (Al foil), vacuum-packed, and isostatically pressed to prepare a sample. The sample was cut in the stacking direction with a wire saw (DWS3400 / wire diameter 170 μm, diamond diameter 30 μm), and the cut surface was cross-sectionally processed with a broad ion beam of Ar (JEOL SM-09010 Cross Section Polisher). The cross-sectional processing conditions were a voltage of 6 kV and a current of 150 to 200 mA. A cross section of the resin substrate and the particle layer in the stacking direction was obtained as a BIB-SEM image, and the cross section was observed.

[0229] The cross section was photographed using an electron microscope (ULTRA55) under the following conditions. Five images were taken from the center of the cross section, with 100 active material particles counted per image, using the method described below, so that a total of 500 active material particles were counted. An example of the photographed image is shown in Figure 24. Detector: ESB (backscattered electron image) Observation conditions: accelerating voltage 3 kV Magnification: 1000x Filter: bias of 1500 V applied to ESB filter

[0230] Next, elemental and compositional analysis of each particle on the resin substrate was performed using SEM-EDX (XFlash Detector 630M manufactured by Bruker Corporation), and the active material particles and solid electrolyte particles were identified. The active material particles and solid electrolyte particles were identified using the method described above. The resin substrate was analyzed using X-ray diffraction (XRD) to identify the materials that make up the resin substrate. Thereafter, the specific elements contained in the active material particles and solid electrolyte particles were detected and identified using SEM-EDX using the method described above.

[0231] <Method for calculating the area ratio of exposed active material particles on the surface of the particle layer> Active material particles and solid electrolyte particles were detected and identified from BIB-SEM images taken under the above conditions. OpenCV was used for image processing, and analysis was performed using Python. The BIB-SEM images were normalized to an average brightness of 100 and a standard deviation of ±30. In order to count the active material particles on the resin substrate, an image representing only the particle layer on the resin substrate was cut out from the normalized image so as to include all particles in the particle layer. An example of an image cut out from the normalized image so as to include all particles in the particle layer is shown in Figure 25A.

[0232] An image extracted from the normalized image so as to include all particles in the particle layer was binarized using a brightness threshold of 120, resulting in an image in which only the active material particles were represented by white pixels. For the purpose of noise removal, the area surrounded by white pixels was filled with white, and then a morphological transformation opening process was performed with a kernel size of 3 × 3 pixels to obtain a noise-removed image. Figure 25B shows an example of an image after noise removal from an image in which only the active material particles were represented by white pixels. Figure 25B shows an image of 55 × 1024 pixels. Next, the noise-removed image was divided into columns with a width of 1 pixel. For example, in Figure 25B, 1024 columns of 55 × 1 pixel were obtained. For each column with a width of 1 pixel after division, the top and bottom positions of the white pixels were determined. The top and bottom positions of the white pixels were recorded by determining the distance (number of pixels) from the bottom of the column to the top and bottom of the white pixels. The obtained values ​​were designated as the value (P1-A) indicating the position of the uppermost surface of the active material particle in each row, and the value (P1-B) indicating the position of the lowermost surface of the active material particle.

[0233] Next, an image extracted from the normalized image so as to include all particles in the particle layer was binarized using a brightness threshold of 90, resulting in an image in which both the solid electrolyte particles and the active material particles were represented by white pixels. An example of an image in which both the solid electrolyte particles and the active material particles were represented by white pixels is shown in Figure 25C. By subtracting the white pixel portion of the image in which only the active material particles were represented by white pixels from the image in which both the solid electrolyte particles and the active material particles were represented by white pixels, an image in which only the solid electrolyte particles were represented by white pixels was obtained. For the purpose of noise removal, the obtained image was filled with white pixels, and then subjected to a morphological transformation opening process with a kernel size of 3 x 3 pixels to obtain a noise-removed image. An example of the noise-removed image is shown in Figure 25D. Next, the noise-removed image was divided into columns with a width of 1 pixel. For each divided column with a width of 1 pixel, the top and bottom positions of the white pixels were determined and recorded using the method described above. The obtained values ​​were taken as the position of the uppermost surface of the solid electrolyte particles (P2-A) and the position of the lowermost surface of the solid electrolyte particles (P2-B) in each row.

[0234] For each column, the obtained value (P1-A) of the position of the top surface of the active material particles was compared with the value (P2-A) of the position of the top surface of the solid electrolyte particles. The number of columns in which the value (P1-A) of the position of the top surface of the active material particles was greater than the value (P2-A) of the position of the top surface of the solid electrolyte particles was recorded. That is, when the value (P1-A) of the position of the top surface of the active material particles was greater than the value (P2-A) of the top surface of the solid electrolyte particles, it was determined that the active material particles were present at the top surface of the particle layer on the side opposite to the side in contact with the resin substrate. As described above, each column is a column with a width of one pixel in the cross-sectional observation image of the particle layer. Therefore, the number of columns in which the value (P1-A) of the position of the top surface of the active material particles was greater than the value (P2-A) of the position of the top surface of the solid electrolyte particles can be considered to correspond to the number of pixels in which the active material particles were present at the top surface of the particle layer when the surface of the particle layer was observed vertically.

[0235] The ratio of the number of rows in which the value (P1-A) of the position of the top surface of the active material particles was greater than the value (P2-A) of the position of the top surface of the solid electrolyte particles was calculated relative to the total number of rows in the image. The obtained value was evaluated as the area ratio of the exposed surface of the active material particles on the surface (upper surface) opposite the side of the particle layer that contacts the resin substrate. Similarly, for each row with a width of 1 pixel, the value (P1-B) of the position of the bottom surface of the active material particles was compared with the value (P2-B) of the position of the bottom surface of the solid electrolyte particles. Then, the number of rows in which the value (P2-A) of the position of the bottom surface of the active material particles was smaller than the value (P2-B) of the position of the top surface of the solid electrolyte particles was recorded. In other words, when the value (P2-A) of the position of the bottom surface of the active material particles was smaller than the value (P2-B) of the position of the top surface of the solid electrolyte particles, it was determined that the active material particles were exposed on the top surface of the side of the particle layer that contacts the resin substrate. The ratio of the number of rows in which the value (P1-B) at the position of the lowest surface of the active material particles was smaller than the value (P2-B) at the position of the lowest surface of the solid electrolyte particles was calculated relative to the total number of rows in the image, and the obtained value was evaluated as the ratio of the exposed area of ​​the active material particle surface on the surface (lower surface) of the particle layer that contacts the resin substrate.

[0236] The difference between the area ratio of the exposed surface of the active material particles on the surface of the particle layer that contacts the resin substrate, calculated by the above-mentioned method, and the area ratio of the exposed surface of the active material particles on the other surface of the particle layer, i.e., the surface opposite to the side that contacts the resin substrate, was determined. This process was performed on 103 active material particles observed on an SEM image of three particle layers of the same electrode base material. Specifically, the above-mentioned process was performed on each of the three particle layers shown in Figure 24.

[0237] Based on the above evaluation, a difference of 1% or more and 70% or less was judged as ◯, and a difference not satisfying the requirement of 1% or more and 70% or less was judged as X. That is, in Table 4, a judgment of "◯" indicates that the difference between the proportion of active material particles appearing on the outermost surface on the surface of the particle layer that contacts the resin substrate and the proportion of active material particles appearing on the outermost surface on the surface opposite to the surface that contacts the resin substrate is 1 to 70 area %.

[0238] <Method for Calculating the Average Height of Active Material Particles> Active material particles and solid electrolyte particles were detected and identified using the method described above from the BIB-SEM image captured under the above conditions. An image for one layer was cropped to include the resin substrate portion, and used as an image for calculating the average height of the active material particles. Using the method described above, noise was removed from an image in which only the active material particles were represented by white pixels to obtain an image ( FIG. 25B ). The resulting image was divided into rows with a width of one pixel, and the position of the top surface of the active material particles (P1-A) was recorded using the method described above. In the row in which the active material particles were present, the difference (distance) between P1-A and the top surface of the resin substrate was calculated. The average of the obtained values ​​was calculated. The length per pixel of the SEM image was determined using the scale in the image, and the actual average height of the active material particles was calculated by multiplying this average value. For example, in FIG. 25B, the length of one pixel = 0.11 μm, and the average value of the top surface of the active material particles was 40.3 pixels, so the average height of the active material particles was calculated to be 4.4 μm. The same processing was performed on three SEM images taken in different fields of the same electrode substrate, and the overall average value was taken as the average height of the active material particles from the resin substrate.

[0239] Electrodes (cathode) were prepared from the electrode substrates of Examples 1 to 10, and all-solid-state batteries were assembled by the method described above. The results of evaluating the rate characteristics of all-solid-state batteries 1 to 10 manufactured using the electrode substrates of Examples 1 to 10 are shown below. The method for measuring the rate characteristics will be described later. In the table, "Air" indicates that sintering was carried out in air. ２ " refers to a reducing atmosphere (Ar-H ２ ) indicates that sintering was performed under the following conditions. In the rate characteristic evaluation of Examples 1 to 9 and Comparative Example 1, the actual capacity of each positive electrode active material was 120 mAh / g for LCO, 130 mAh / g for NMC, and 150 mAh / g for LFP and LVP. The cutoff voltage was 4.2 V / 2.6 V for LCO, 4.2 V / 2.6 V for NMC, and 3.8 V / 2.5 V for LFP and LVP.

[0240] The method for evaluating rate characteristics will be described below. <Rate characteristics> The mass M (g / cm) of active material particles per unit area of ​​the electrode substrate ２) to calculate the active material particle mass of the electrode (M × number of layers × electrode area (cm ２ )) is calculated to determine the current rate. The active material particle mass M per unit area is calculated as follows. The weight of the first substrate 11a is measured after the first particles P1 are filled using the first filling device. Next, the weight of the first substrate 11a is measured after the particles P1 on the first substrate 11a are transferred to the second substrate 11b. The difference is measured and divided by the area of ​​the first substrate 11a (area of ​​the concave-convex region) to calculate the active material particle mass M. In the present disclosure, the active material particle mass M per unit area is calculated using the above method. As another calculation method, ICP atomic emission spectroscopy may be used. The active material particle mass M per unit area (g / cm) is calculated in advance using the above method or the like. ２ Three levels of first substrates 11a are prepared, with the Co element quantified. These first substrates 11a are dissolved by microwave acid decomposition (ETHOS PRO), and the acid decomposition solution is diluted with ultrapure water and subjected to ICP-AES measurement (CIROS CCD), and the Co element is quantified. The active material particle mass per unit area M (g / cm) relative to the obtained element concentration is calculated. ２ From the calibration curve, the active material particle mass M (g / cm ２ ) can be obtained.

[0241] The actual capacity of the LCO was 120 mAh / g, and the cutoff voltage (vs. Li) was 4.2 V (charge) / 2.6 V (discharge). Charge / discharge measurements (constant current mode) were performed at each rate using a charge / discharge device (manufactured by Biologic Inc.), and the capacity retention rate (discharge capacity / charge capacity × 100%) was measured. The maximum value R at the rate at which the capacity retention rate was 80% or higher was determined. Based on the obtained maximum value R at the rate, the rate characteristics were evaluated using the following evaluation criteria: A: R≧0.3C B: 0.3C>R When the rate characteristics evaluation was A, it was determined that the electrode had excellent electronic conductivity and ionic conductivity, and that the internal resistance of the electrode was sufficiently suppressed. As a result, the rate characteristics evaluation was A in Examples 1 to 9, confirming that the internal resistance of the electrode was sufficiently suppressed.

[0242] FIG. 26 is a BIB-SEM image of the cross section of an electrode manufactured using electrode substrate 2 of Example 1. The substrate has been removed by sintering, and sintering of the particles has progressed. It can be seen that first particles P1 (LCO) and second particles P2 (LBO) are arranged on the positive electrode current collector (Al foil) of substrate 14, with a large amount of LCO in contact with substrate 14. It can also be seen that the same particles of both LCO and LBO are connected to each other in the z direction in the figure. This indicates that electron and ion conduction can occur uninterrupted in the stacking direction, i.e., the z direction. This structure is achieved by regularly arranging particles on the electrode substrate, which is the electrode precursor.

[0243] FIG. 27A is a schematic diagram of an electrode substrate laminate produced by stacking electrode substrates 1 of Example 1. For the sake of explanation, particles P1 and P2 are depicted as spherical and having the same particle diameter. As described above, in the electrode substrate 1 of Example 1, the second solid electrolyte particles are in contact with the active material particles on the side opposite the substrate, forming a dense region. On the other hand, the surface area of ​​the active material particles P1 is largely exposed and uniformly distributed on the substrate side. Even when the substrates are removed from the electrode substrate laminate by sintering, the particle arrangement structure of each substrate is maintained, and a structure like that shown in FIG. 27B is thought to be realized. Therefore, even in the electrode after the resin substrate is removed by sintering, the stacked particle layer structure is maintained, and active material particles capable of effective electronic conduction and solid electrolyte particles capable of effective ionic conduction are in contact with each other in the thickness direction of the stacked particle layers. Therefore, it is thought that both electronic conduction and ionic conduction are smoothly performed within the electrode produced by stacking electrode substrates, thereby suppressing internal resistance.

[0244] Although a laminate in which three identical positive electrode substrates were stacked was used in Examples 1 to 10, a laminate in which multiple types of positive electrode substrates having the configuration of the present disclosure are stacked may also be used. In addition, the electrode substrate may be used as a material for a coating process (including a multilayer capacitor (MLCC) manufacturing technique) or a powder pressing process, which are conventionally known manufacturing methods.

[0245] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to clarify the scope of the present disclosure. This application claims priority based on Japanese Patent Application No. 2023-136586, filed on August 24, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. An electrode substrate used in the manufacture of an electrode, the electrode substrate comprising: a resin substrate; and active material particles and solid electrolyte particles on the resin substrate; a particle layer comprising the active material particles and the solid electrolyte particles formed on the resin substrate; when the particle layer is viewed through from the surface side in contact with the resin substrate or the surface side opposite to the surface in contact with the resin substrate, the solid electrolyte particles are arranged so as to cover at least a part of the surface of the active material particles; and when a cross-sectional observation of the particle layer with a scanning electron microscope (SEM) is performed, the difference between the area ratio of the exposed surface of the active material particles on the surface of the particle layer in contact with the resin substrate and the area ratio of the exposed surface of the active material particles on the surface of the particle layer opposite to the surface in contact with the resin substrate is 1 to 70 area %.

2. The electrode substrate according to claim 1, wherein the average height of the active material particles from the surface of the resin substrate is 1 to 50 μm.

3. The electrode substrate according to claim 1 or 2, wherein the difference is 5 to 60 area %.

4. The electrode substrate according to claim 1 or 2, wherein the difference is 10 to 50 area %.

5. The electrode substrate according to any one of claims 1 to 4, wherein the solid electrolyte particles include at least one selected from the group consisting of Li-B oxide-based, Nasicon-type oxide-based, Perovskite-type oxide-based, and Garnet-type oxide-based electrolyte particles, and the active material particles include Li-Co oxide-based active material particles.

6. The solid electrolyte particles include at least one selected from the group consisting of electrolyte particles of Li-B oxide system, Nasicon type oxide system, Perovskite type oxide system, and Garnet type oxide system, and the active material particles include Li-PO ４ The electrode substrate according to any one of claims 1 to 4, comprising oxide-based active material particles.

7. The electrode substrate according to any one of claims 1 to 4, wherein the solid electrolyte particles include at least one selected from the group consisting of Li-B oxide-based, Nasicon-type oxide-based, perovskite-type oxide-based, and garnet-type oxide-based electrolyte particles, and the active material particles include Si-based active material particles.

8. The electrode substrate according to any one of claims 1 to 4, wherein the solid electrolyte particles include at least one selected from the group consisting of Li-B oxide-based, Nasicon-type oxide-based, perovskite-type oxide-based, and garnet-type oxide-based electrolyte particles, and the active material particles include graphite-based active material particles.

9. The electrode substrate according to any one of claims 1 to 8, wherein a coverage rate of the surface of the resin substrate by the active material particles and the solid electrolyte particles is 60% or more and 99% or less.

10. An electrode substrate laminate comprising a plurality of electrode substrates according to any one of claims 1 to 9 laminated together.

11. The electrode substrate laminate according to claim 10, wherein the resin substrate and the particle layer are present alternately in a cross section of the electrode substrate laminate.

12. An electrode for a secondary battery, the electrode being a sintered body of the electrode substrate according to any one of claims 1 to 9.

13. An electrode, which is a sintered body of the electrode substrate according to any one of claims 1 to 9, wherein at least a part of the resin substrate in the electrode substrate has been removed.

14. A secondary battery comprising the electrode according to claim 12 or 13 and an electrolyte layer adjacent to said electrode.

15. A method for producing an electrode substrate according to any one of claims 1 to 9, which is used in the production of an electrode, comprising the steps of: preparing the resin substrate having an adhesive portion; arranging the active material particles on a surface of the adhesive portion; rubbing the surfaces of the active material particles arranged on the surface of the adhesive portion; and arranging the solid electrolyte particles on the surface of the adhesive portion and the rubbed surfaces of the active material particles.

16. The method for producing an electrode substrate according to claim 15, wherein the rubbing step includes a step of rubbing the surfaces of the active material particles with magnetic particles.

17. A method for producing an electrode base material used in the production of an electrode, the electrode base material comprising a resin base material, and active material particles and solid electrolyte particles on the resin base material, a particle layer comprising the active material particles and the solid electrolyte particles is formed on the resin base material, and when the particle layer is viewed through from the surface side in contact with the resin base material or the surface side opposite to the surface side in contact with the resin base material, the solid electrolyte particles are arranged so as to cover at least a part of the surface of the active material particles, the production method comprising the steps of: preparing the resin base material having an adhesive portion; arranging the active material particles on the surface of the adhesive portion; rubbing the surfaces of the active material particles arranged on the surface of the adhesive portion; and arranging the solid electrolyte particles on the surface of the adhesive portion and the rubbed surfaces of the active material particles.

18. The method for producing an electrode substrate according to claim 17, wherein the rubbing step includes a step of rubbing the surfaces of the active material particles with magnetic particles.

19. A method for manufacturing an electrode, comprising the steps of stacking a plurality of electrode substrates according to any one of claims 1 to 9 to form a laminate; removing the resin substrate from the laminate to obtain a three-dimensional object; and applying pressure to the three-dimensional object to obtain an electrode.

20. A method for manufacturing a secondary battery, comprising the steps of: preparing an electrode by the electrode manufacturing method according to claim 19; and laminating the electrode, a current collector, and an electrolyte.

21. A method for manufacturing a secondary battery, comprising the steps of: preparing an electrode by the electrode manufacturing method according to claim 19; and providing a solid electrolyte adjacent to the electrode.

22. A method for manufacturing a secondary battery, comprising the steps of stacking a plurality of electrode substrates according to any one of claims 1 to 9 to form a laminate; providing adjacent solid electrolytes in a lump on the laminate; removing the resin substrate from the laminate to obtain a three-dimensional object; pressurizing the three-dimensional object; and stacking a current collector on the pressurized three-dimensional object.

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