Electrode precursor, secondary battery, and method for producing same

Abstract

Provided is an electrode precursor that is for forming an electrode of an all-solid-state battery in which a garnet-type solid electrolyte is used as an electrolyte layer, the electrode precursor being useful for producing a secondary battery with excellent charge / discharge characteristics. The present invention is an electrode precursor for application to the production of an electrode of a secondary battery, wherein the electrode precursor includes: an active material layer precursor including a first resin base material and active material particles held by the first resin base material; and an interface bonding precursor that includes a second resin base material and first solid electrolyte particles held by the second resin base material and has a portion in contact with the active material layer precursor, said first solid electrolyte particles having a softening point temperature higher than the softening point temperature of each of the first resin base material and the second resin base material and lower than the softening point temperature of the active material particles.

Description

Electrode Precursor, Secondary Battery, and Method for Manufacturing the Same

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

[0002] Generally, a secondary battery is composed of electrodes (a positive electrode and a negative electrode) and an electrolyte, and charging and discharging are performed by the movement of ions through the electrolyte between the electrodes. 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 using an inorganic solid electrolyte as the electrolyte has been progressing. By replacing the conventional organic electrolyte with a solid electrolyte, all-solid-state batteries are expected to improve the safety and high-capacity, high-output performance of secondary batteries. In particular, oxide-based all-solid-state batteries using an oxide-based solid electrolyte are expected as next-generation secondary batteries due to their high safety and stability. Among them, garnet-type solid electrolytes (such as Li ７ La ３ Zr ２ O １２ (LLZ), etc.) are expected to be put into practical use due to their high lithium ion conductivity and stability against metallic lithium. On the other hand, it is difficult to ensure the solid-solid contact between active material particles and solid electrolyte particles in all-solid-state batteries. Therefore, the battery is likely to have a high resistance, and the capacity and output are likely to be limited.

[0004] Patent Document 1 discloses a method for manufacturing a battery having a three-dimensional structure in which particles are patterned in the plane direction and the stacking direction. The patterning can improve the solid-solid contact between active material particles and solid electrolyte particles. Patent Document 2 discloses an electrode sheet in which an active material particle and a solid electrolyte particle are filled in a sheet-like porous substrate. The electrode sheet is disclosed to suppress the dropout of electrode materials and surface cracks and to be excellent in ionic conductivity.

[0005] Japanese Unexamined Patent Application Publication No. 2019-137061, Japanese Unexamined Patent Application Publication No. 2015-153459

[0006] However, even when the solid-solid contact between the active material particles and the solid electrolyte particles is improved as in Patent Document 1, the ionic conductivity may decrease due to the interfacial resistance between the electrode and the electrolyte layer and the grain boundary resistance within the electrode. As a result, it has been found that the capacity and output of the battery may decrease. On the other hand, although the electrode sheet disclosed in Patent Document 2 can suppress the missing of the electrode material and the cracking of the surface, since it is un-sintered and the densification between the particles does not progress, it has been found that the resistance of the electrode sheet (the grain boundary resistance within the electrode sheet and the interfacial resistance between the electrode sheet and the electrolyte layer) tends to be difficult to decrease.

[0007] In addition, according to the studies of the present inventors, the electrode forming of all-solid-state batteries using garnet-type solid electrolytes as electrolyte layers can be very difficult. Especially for LLZ, which is a difficult-to-sinter material with low formability, it is easy to increase the resistance at the interface with the electrode and within the electrode due to high-temperature firing, and it is easy to cause decomposition of the material due to the high temperature during sintering. Therefore, it has been found that it is difficult to fabricate an electrode that makes use of the potential of LLZ.

[0008] According to one aspect of the present disclosure, there is provided an electrode precursor for forming an electrode of an all-solid-state battery using a garnet-type solid electrolyte as an electrolyte layer, which is useful for manufacturing a secondary battery having excellent charge-discharge characteristics. Further, according to another aspect of the present disclosure, there is provided a secondary battery manufactured using the electrode precursor. Furthermore, according to another aspect of the present disclosure, there are provided a method for manufacturing the electrode precursor, an electrode structure, and a secondary battery.

[0009] At least one aspect of the present disclosure is an electrode precursor applicable to the manufacture of an electrode of a secondary battery, including: an active material layer precursor including a first resin substrate and active material particles held by the first resin substrate; and an interface bonding precursor including a second resin substrate and first solid electrolyte particles held by the second resin substrate and having a portion in contact with the active material layer precursor, wherein the first solid electrolyte particles have a softening point temperature higher than the softening point temperatures of the first resin substrate and the second resin substrate and lower than the softening point temperature of the active material particles.

[0010] According to one aspect of this disclosure, an electrode precursor for forming electrodes of an all-solid-state battery using a garnet-type solid electrolyte as an electrolyte layer is provided, which is useful for manufacturing a secondary battery with excellent charge-discharge characteristics. According to another aspect of this disclosure, an electrode structure, an electrode, and a secondary battery manufactured using the electrode precursor are provided. Furthermore, according to yet another aspect of this disclosure, a method for manufacturing the electrode precursor, electrode structure, electrode, and secondary battery is provided.

[0011] Figure 1A is a schematic diagram showing the structure of the solid electrolyte layer and electrode precursor before firing. Figure 1B is a schematic diagram showing the electrode precursor after firing. Figures 2A and 2B show methods for manufacturing the interfacial bonding precursor and the active material layer precursor. Schematic diagram of the particle packing apparatus Schematic diagram illustrating the operation of the particle packing apparatus Enlarged view of the vicinity of the surface of the first substrate Schematic diagram of the particle transfer apparatus Schematic diagram of the transfer section Schematic diagram illustrating the operation of the particle packing apparatus Figures 9A and 9B are enlarged views of the vicinity of the surface of the second substrate. Schematic diagram of the particle sedimentation apparatus Figure 11A is a schematic diagram of the cross-section of the second substrate before the third process. Figure 11B is a schematic diagram of the cross-section of the second substrate after the third process. Schematic diagram showing the second substrate after the third process from above Schematic diagram showing the second substrate after the fourth process from above Figures 14A and 14B are schematic diagrams of the configuration of the packing apparatus when brush fibers are used as the support material. Figure 23A is an SEM image showing the pattern shape (line pattern) of the active material layer precursor. Figure 23B is an SEM image showing the pattern shape (uniform dispersion pattern) of the active material layer precursor. Figure 23C is an SEM image showing the pattern shape (uniform aggregation pattern) of the active material layer precursor. Figure 24A is an upper SEM image of the electrode structure of Example 4. Figure 24B is an EDX mapping image of Co. Figure 27A is an example of an FFT power spectrum in the pattern evaluation of the positive electrode. Figure 27A is a cross-sectional SEM image of the electrode precursor before pre-sintering. Figure 27A is an example of an SEM image. Figure 27B is an example of an EDX mapping image of Co. Figure 27D shows an example of an EDX mapping image of La. Figures 29A and 29B show an example of a charge-discharge curve of a secondary battery and are Cole-Cole plots of the example. Figures 30A and 30B show Cole-Cole plots of comparative examples. Figure 31A is a cross-sectional SEM image of the electrode precursor before calcination of Example 1. Figure 31B is a cross-sectional SEM image of the electrode structure after final calcination of Example 1. Figure 32A shows the charge-discharge curve of the secondary battery of Example 1. Figure 32B shows the Cole-Cole plot of the secondary battery of Example 1.Figure 33A shows the charge-discharge curve of the secondary battery of Comparative Example 1. Figure 33B shows the Cole-Cole plot of the secondary battery of Comparative Example 1. Figure 34A shows the charge-discharge curve of the secondary battery of Example 8. Figure 34B shows the Cole-Cole plot of the secondary battery of Example 8. Figure 35A shows the charge-discharge curve of the secondary battery of Comparative Example 3. Figure 35B shows the Cole-Cole plot of the secondary battery of Comparative Example 3. Cross-sectional SEM image of the electrode structure of Example 2. Figure 37A shows the charge-discharge curve of the secondary battery of Example 2. Figure 37B shows the Cole-Cole plot of the secondary battery of Example 2. Figure 38A shows the charge-discharge curve of the secondary battery of Comparative Example 2. Figure 38B shows the Cole-Cole plot of the secondary battery of Comparative Example 2. Figure 39A shows the charge-discharge curve of the secondary battery of Comparative Example 4. Figure 39B shows the Cole-Cole plot of the secondary battery of Comparative Example 4. Figure 40A shows the charge-discharge curve of the secondary battery of Example 3. Figure 40B shows the Cole-Cole plot of the secondary battery of Example 3. Figure 41A shows the charge-discharge curve of the secondary battery of Comparative Example 5. Figure 41B shows the Cole-Cole plot of the secondary battery of Comparative Example 5. Figure 42A is a schematic diagram showing the electrode precursor of Example 4 before firing. Figure 42B is a schematic diagram showing the electrode structure of Example 4 after firing. Figure 43A is an overhead SEM image of the electrode structure of Example 4. Figure 43B is an EDX mapping image of Co and La. Cross-sectional SEM image of the electrode structure of Example 4. Figure 45A is an enlarged view of the cross-sectional SEM image of the electrode structure of Example 4. Figure 45B is an EDX mapping image of Co. Figure 45C is an EDX mapping image of La. Figure 46A shows the charge-discharge curve of the secondary battery of Example 4. Figure 46B shows the Cole-Cole plot of the secondary battery of Example 4. Figure 47A shows the charge-discharge curve of the secondary battery of Comparative Example 6. Figure 47B shows the Cole-Cole plot of the secondary battery of Comparative Example 6. Figure 48A shows the charge-discharge curve of the secondary battery of Example 7. Figure 48B shows the Cole-Cole plot of the secondary battery of Example 7. Figure 49A shows the charge-discharge curve of the secondary battery of Comparative Example 7. Figure 49B shows the Cole-Cole plot of the secondary battery of Comparative Example 7.Figure 50A is a schematic diagram showing the arrangement pattern (uniform dispersion pattern) of particles in the active material layer precursor. Figure 50B is a schematic diagram showing the arrangement pattern (line pattern) of particles in the active material layer precursor. Figure 51A is an upper SEM image of the electrode structure of Example 5, and Figure 51B is an EDX mapping image. Cross-sectional SEM image of the electrode structure of Example 5. Figure 53A shows the charge-discharge curve of the secondary battery of Example 5. Figure 53B shows the Cole-Cole plot of the secondary battery of Example 5. Figure 54A shows the charge-discharge curve of the secondary battery of Comparative Example 8. Figure 54B shows the Cole-Cole plot of the secondary battery of Comparative Example 8. Figures 55-55D show the formation procedure of the interface evaluation model positive electrode (LCO solid film) and the three-dimensional structure positive electrode (Laminated film of LCO pattern). Figure 55A shows the interface evaluation model positive electrode (LCO solid film). Figure 55B shows a cross-sectional view of the interface evaluation model positive electrode. Figure 55C shows a three-dimensional structured cathode (a laminated film with an LCO pattern). Figure 55D shows a cross-sectional view of the three-dimensional structured cathode. Figures 56A to 56E are schematic diagrams showing the procedure for electrode molding (a model cathode for interface evaluation (a solid LCO film)). Figures 57A to 57F are schematic diagrams showing the procedure for precursor fabrication (interface bonding precursor, active material layer precursor). Figure 58A is a schematic diagram showing the sample of Comparative Example 2 before firing, and Figure 58B is a schematic diagram of the secondary battery of Comparative Example 2. Figure 59A shows the TG-DTA measurement results of LYbBO, and Figure 59B shows the sintering temperature dependence of ionic conductivity. Figures 60A to 60C are schematic diagrams of the XRD measurement samples in Example 2. Figure 60D shows the XRD results. Figure 61A is a schematic diagram of the secondary battery in Example 2, and Figure 61B is a schematic diagram showing the sample before firing. Figure 62A shows the correlation between firing temperature (800°C in Example 2) and charge / discharge capacity, and Figure 62B is a schematic diagram of the interfacial bonding layer. Figure 63A is a schematic diagram illustrating the increased resistance when using only the Bi-LLZT interfacial bonding precursor (solid) (one layer), and Figure 63B shows the relationship between firing temperature and charge / discharge capacity when the LBO interfacial bonding precursor (solid) is added. Figure 64A is a schematic diagram of the electrode precursor before firing in Example 4, and Figure 64B is a schematic diagram of the electrode structure after firing. Figure 65A is a schematic diagram showing the cross-section of the cross-sectional SEM image.Figure 65B is a cross-sectional SEM image of the precursor laminate of Example 4 before firing, cut at the above cross-section. Figure 65C is a cross-sectional SEM image of the electrode structure of Example 4 after firing, cut at the above cross-section.

[0012] In this disclosure, the expressions "XX or greater and YY or less" and "XX to YY" that represent numerical ranges mean numerical ranges that include the lower and upper limits, which are the endpoints, unless otherwise specified. When numerical ranges are described in steps, any combination of the upper and lower limits of each numerical range is also disclosed.

[0013] Furthermore, in this disclosure, a statement such as "at least one selected from the group consisting of XX, YY, and ZZ" means any of the following: XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ. Note that if XX is a group, multiple elements may be selected from XX, and the same applies to YY and ZZ.

[0014] Generally, electrode molding for oxide-based all-solid-state batteries requires the creation of a dense molded body and sintering at an appropriate temperature to promote densification and reduce grain boundary resistance. However, because garnet-type solid electrolytes have a high sintering temperature, in the manufacturing process of secondary batteries using garnet-type solid electrolytes, a resistance layer is easily formed by the reaction between the electrode active material and the solid electrolyte, and material decomposition is also likely to occur due to the high temperature during sintering. Therefore, it has become clear that there is a problem in that electrode molding is difficult when garnet-type solid electrolytes are used as the electrolyte layer in secondary batteries.

[0015] As a result of their research, the inventors have found that it is important to provide an interfacial junction layer between the electrode layer and the solid electrolyte layer in order to form the electrodes of an all-solid-state battery using a garnet-type solid electrolyte as the electrolyte layer. Furthermore, they have found that by ensuring close contact between the active material particles and solid electrolyte particles in the electrode layer, resistance is suppressed, and a secondary battery with excellent charge-discharge characteristics can be manufactured. The phenomenon in which a resistive layer is easily formed by the reaction between the electrode active material and the solid electrolyte can sometimes be rephrased as an increase in ion transport resistance between materials or a decrease in ionic conductivity as a side reaction.

[0016] Specifically, by using an electrode precursor (positive electrode precursor) which is a laminate of an interfacial bonding precursor having solid electrolyte particles arranged on a resin substrate and an active material layer precursor having active material particles and solid electrolyte particles arranged on a resin substrate, an interfacial bonding layer can be provided between the electrode layer and the solid electrolyte layer. As a result, even when a garnet-type solid electrolyte is used as the electrolyte layer, the electrodes of the secondary battery can be stably molded. Furthermore, by manufacturing electrodes and secondary batteries using an electrode precursor in which the active material particles and solid electrolyte particles are arranged in a pattern in the planar direction and the lamination direction, the active material particles and solid electrolyte particles can come into close contact within the electrode layer, resulting in a secondary battery with excellent charge-discharge characteristics.

[0017] Electrode precursors are applied to the manufacture of electrodes for secondary batteries. In particular, they are preferably applied to the manufacture of electrodes for all-solid-state batteries using a garnet-type solid electrolyte as the electrolyte layer. The electrode precursor has a structure in which an active material layer precursor and an interfacial bonding precursor are laminated. Figures 1A and 1B are schematic diagrams showing the structure of a solid electrolyte layer 50 containing a garnet-type solid electrolyte and an electrode precursor 15 laminated on the solid electrolyte layer. An electrode precursor 15, in which an interfacial bonding precursor 51 and an active material layer precursor 52 are laminated, is arranged on one surface of the solid electrolyte layer 50 (Figure 1A). Figure 1A is a schematic diagram showing the laminated state before firing, and Figure 1B is a schematic diagram showing the electrode precursor after firing. In Figure 1A, the direction indicated by the arrow is the lamination direction of the resin substrate and particle layer, and the direction perpendicular to the lamination direction, that is, the direction along the surface on which the particle layer is laminated in the resin substrate, is the surface direction of the resin substrate and particle layer.

[0018] The active material layer precursor and the interface bonding precursor have a configuration in which particles are arranged on a resin substrate. The active material layer precursor contains at least active material particles, and the interface bonding precursor contains solid electrolyte particles. The solid electrolyte particles contained in the interface bonding precursor have higher ionic conductivity than the active material particles and the resin substrate, and their softening point temperature is higher than the resin substrate and lower than that of the active material particles. In the manufacturing process of a secondary battery, by stacking the electrode precursor and the electrolyte layer so that the interface bonding precursor is in contact with the electrolyte layer and firing them, some or all of the solid electrolyte particles contained in the interface bonding precursor melt, and a good interface can be formed between the electrolyte layer and the active material layer containing the active material particles. Furthermore, because the solid electrolyte particles have high ionic conductivity, a good ion conduction path is formed between the electrolyte layer and the active material layer, which can improve the charge and discharge characteristics of the secondary battery. In addition, the softening point temperature of the solid electrolyte particles is higher than that of the resin substrate and lower than that of the active material particles. For example, the softening point temperature of the solid electrolyte particles contained in the interfacial bonding precursor is preferably 300°C or more higher than the softening point temperature of the resin substrate, and preferably 200°C or more lower than the softening point temperature of the active material particles. Therefore, by firing at a temperature above the melting point of the solid electrolyte particles, the resin substrate in each precursor is eliminated, and the densification of the electrode layer containing the interfacial bonding layer and active material particles can be promoted (Figure 1B). For these reasons, by using the above-described electrode precursor, electrodes for an all-solid-state battery that can operate at room temperature and uses a garnet-type solid electrolyte as the electrolyte layer can be formed. (Step 1, Figures 55A and 55B)

[0019] Furthermore, by using an electrode precursor (positive electrode precursor) in which an active material layer precursor and an interfacial bonding precursor are laminated, with active material particles and solid electrolyte particles arranged on a resin substrate, a three-dimensional positive electrode structure can be formed in which the active material particles and solid electrolyte particles are arranged in a pattern in the planar direction and the lamination direction. (Step 2, Figures 55C and 55D) In ​​this disclosure, the charge-discharge capacity, which is the charge-discharge characteristic (constant current charging, constant current discharging) of a prototype battery formed with a three-dimensional positive electrode structure, is used as an indicator for evaluation. The active material layer precursor and interfacial bonding precursor that constitute the electrode precursor will be described below.

[0020] <Active material layer precursor> The active material layer precursor includes a first resin substrate and active material particles held on the first resin substrate. The active material layer precursor preferably further includes second solid electrolyte particles held on the resin A. That is, the active material layer precursor preferably has a particle layer including active material particles and second solid electrolyte particles.

[0021] The first resin substrate is a substrate formed of a material containing resin. As the material constituting the resin substrate, known resin materials such as polyethylene (PE), polypropylene (PP), polyesters such as polyethylene terephthalate (PET), and polyamides such as nylon can be used. Among them, from the viewpoints of decomposition temperature and low toxicity of the gas generated during thermal decomposition, it is preferable to use PET.

[0022] The active material particles are not particularly limited and known ones can be used. For example, composite oxides containing lithium can be used. Specifically, for example, Li-Co oxide-based active material particles such as lithium cobalt oxide (LiCoO ２ ), and ternary active material particles in which a part of Co is substituted, LiNi ｘ Mn ｙ Co ｚ O ２ (NMC) or LiNi ｘ Co ｙ Al ｚ O ２Examples include (NCA). Among the above positive electrode active material particles, Li-Co oxide-based active material particles are preferred. The active material layer precursor preferably contains lithium cobalt oxide (LCO) particles as active material particles. The softening point temperature of the active material particles varies depending on the particles used, but is preferably 900 to 1700°C, and more preferably 1000 to 1500°C. The softening point temperature of the active material particles is preferably 200°C or more higher than the softening point temperature of the first solid electrolyte particles contained in the interfacial bonding precursor, and more preferably 300°C or more higher. In this disclosure, "softening point temperature" refers to the softening point temperature measured by a thermomechanical analyzer (TMA). "Melting point" refers to the melting point temperature measured by a differential thermothermogravimetric analyzer (TG-DTA) or differential scanning calorimetry (DSC). If the positive electrode active material particles are uniformly mixed and the melting point can be clearly measured, the softening point temperature can be substituted with the melting point. The methods for measuring the softening point temperature and melting point will be described later.

[0023] The active material particles may be commercially available or prepared separately as a material. Examples of Li-Co oxide-based active material particles include Cellseed C-5H (trade name, manufactured by Nippon Chemical Industrial Co., Ltd., softening point temperature 1050°C, melting point 1130°C) (LiCoO ２ ) and the like can be used. The active material particles may be used individually or in combination of two or more types.

[0024] The second solid electrolyte particle is not particularly limited, and an ion-conducting solid commonly used in all-solid-state batteries can be used. For example, Li-B oxide-based solid electrolyte particles (such as LBO particles), Li-Yb oxide-based solid electrolyte particles (Li ５．９ Yb ０．８１ La ０．０９ Zr ０．１ (BO ３ ) ３ (LYbBO particles, etc.), garnet-type oxide-based solid electrolyte particles (Li ７ La ３ Zr ２ O １２ (LLZ), Li ７－ｘ La ３ Zr ２－ｘ Taｘ O １２ (LLZT), Li ６．７５ La ３ Zr １．７５ Nb ０．２５ O １２ Examples include (LLZNb), etc.

[0025] Among the above solid electrolyte particles, it is preferable to use Li-B oxide-based LBO particles, Li-Yb oxide-based LYbBO particles, garnet-type oxide-based LLZT particles, or Bi-doped LLZT particles (Bi-LLZT particles) in which Bi ions are doped into LLZT. Bi-LLZT particles are thought to have a lower sintering temperature compared to LLZT because low-melting-point Bi oxide (Li-Bi-O) is generated during sintering, and the melt promotes sintering (liquid-phase sintering). The softening point temperature of the second solid electrolyte particle is not particularly limited, but is preferably 900 to 1700°C, and more preferably 950 to 1200°C. The softening point temperature of the second solid electrolyte particle is preferably higher than the softening point temperature of the first solid electrolyte particle contained in the interfacial bonding precursor. For example, it is preferably 100°C or more higher than the softening point temperature of the first solid electrolyte particle, and more preferably 200°C or more higher.

[0026] The solid electrolyte particles may be used individually or in combination of two or more types. The active material layer precursor preferably contains at least one selected from the group consisting of LBO particles, LYbBO particles, LLZT particles, and Bi-LLZT particles as the second solid electrolyte particle.

[0027] In the active material layer precursor, it is preferable that the active material particles and the second solid electrolyte particles are arranged adjacent to each other on the first resin substrate. That is, it is preferable that the active material layer precursor includes second solid electrolyte particles in contact with the active material particles. For example, by arranging the particles in a pattern using the method described later, the active material particles and the second solid electrolyte particles can be arranged in contact with each other. By arranging them in this way, when the active material layer precursor is laminated, a three-dimensional electrode structure can be obtained in which the active material particles and solid electrolyte particles are densely arranged.

[0028] The content of active material particles in the active material layer precursor is preferably 30 to 90% by mass or 40 to 80% by mass, based on the total amount of particles contained in the particle layer (for example, the sum of active material particles and the second solid electrolyte).

[0029] It is preferable that the active material particles and the second solid electrolyte particles contained in the active material layer precursor are positioned at different locations on the surface facing the interfacial bonding precursor. That is, it is preferable that the active material particles and the second solid electrolyte particles are positioned on a common support surface such that when they are in contact with the interfacial bonding precursor and orthogonally projected onto the common support surface, the centers of gravity of each particle do not overlap. It is preferable that the active material particles and the second solid electrolyte particles are positioned at different locations on the first resin substrate. It is preferable that the second solid electrolyte particles in contact with the active material particles are present in the area where the region where the active material particles are located and the region where the second solid electrolyte is located are in contact. With this arrangement, when multiple active material layer precursors are laminated in the lamination process described later, the active material particles can easily come into contact with each other in the lamination direction, thereby improving the electron conductivity within the positive electrode.

[0030] The active material layer precursor may further contain third solid electrolyte particles that differ from the second solid electrolyte particles in at least one of the following: average particle size, composition, melting point, and softening point temperature. That is, it is preferable that the active material layer precursor further contains solid electrolyte particles that differ from the second solid electrolyte particles. It is preferable that the average particle size (median diameter (volume-based D50)) of the second solid electrolyte particles and the third solid electrolyte particles differ by 50% or more. Or, it is preferable that the softening point temperatures differ by 50°C or more. Or, it is preferable that the softening point temperatures differ by 50°C or more.

[0031] By including the third solid electrolyte particles as described above, when heated in the firing process described later, the third solid electrolyte particles melt and bond the particles together while maintaining the structure (particle layer) consisting of the active material particles and the second solid electrolyte particles, thereby forming a dense and high-strength electrode.

[0032] The particle size of the second solid electrolyte particle is not particularly limited, but is preferably, for example, an average particle size of 1 to 15 μm, and more preferably 2 to 10 μm. The melting point is not particularly limited, but is preferably, for example, 500 to 1200°C, and more preferably 600 to 1000°C. The softening point temperature is not particularly limited, but is preferably, for example, 400 to 1100°C, and more preferably 500 to 900°C.

[0033] The particle size of the third solid electrolyte particle is not particularly limited, but it is preferably, for example, an average particle size of 0.01 to 1 μm, and more preferably 0.05 to 0.5 μm. The melting point is not particularly limited, but it is preferably, for example, 500 to 1000°C, and more preferably 550 to 950°C. The softening point temperature is not particularly limited, but it is preferably, for example, 400 to 900°C, and more preferably 450 to 850°C. The average particle size is the median diameter (volume-based D50) calculated from the equivalent circle diameter of each particle (the diameter of the circle corresponding to the image area of ​​each particle) obtained from SEM images obtained by electron microscopy. For example, when LLZT is included as the second solid electrolyte particle, it is preferable to include Bi-LLZT, which has a softening point temperature 200°C different from LLZT, as the third solid electrolyte particle.

[0034] The active material layer precursor may be used as a single layer, or it may be used in a stacked configuration. Multiple identical active material layer precursors may be stacked, or multiple active material layer precursors with different materials and particle arrangements may be stacked. Generally, when prototyping a high-output battery, it is preferable to reduce the number of stacked active material precursors because it is necessary to lower the electrode resistance. When prototyping a high-capacity battery, it is preferable to increase the number of stacked active material precursors. The number of stacked layers is adjusted according to the battery specifications. The configuration of stacking multiple identical active material layer precursors includes configurations in which the materials and particle arrangements are common to the layers constituting each active material precursor.

[0035] When stacking active material layer precursors, active material layer precursors with different patterns may be used on the top and bottom, or they may be used in combination with active material layer precursors that have no pattern. Alternatively, active material layer precursors containing different active material particles may be used. As shown in Figure 1A, it is preferable to stack active material layer precursors having the same pattern structure alternately with the pattern orientation changed by 90°. This stacking method is preferable because it improves electronic conductivity by allowing active material particles to come into contact with each other in the stacking direction of the precursors, and also improves ionic conductivity by allowing solid electrolyte particles to come into contact with each other.

[0036] In the active material layer precursor, the arrangement of active material particles is preferably a pattern structure having periodicity in the planar direction within the particle layer. A periodic pattern structure refers to a pattern in which the same particle arrangement is repeated at regular intervals or periods.

[0037] Specifically, an SEM-EDX image of Co contained in the active material particles in the particle layer is acquired, the acquired image is binarized, and then a two-dimensional Fourier transform is performed to obtain an FFT power spectrum. When peak detection processing is performed on the obtained FFT power spectrum, if there is at least one peak other than the origin, it is determined that there is a periodic pattern structure.

[0038] The planar direction within the particle layer is the direction perpendicular to the lamination direction of the resin substrate and the particle layer. In other words, it is preferable that the active material particles have a periodic pattern structure in the SEM-EDX image of Co observed from the lamination direction on the outer surface of the particle layer of the active material layer precursor. The formation of a pattern structure in the planar direction within the particle layer makes it easier for the active material particles and the solid electrolyte particles placed between the active material particles to be adjacent, thus facilitating the formation of electron conduction paths and ion conduction paths. Furthermore, when the active material layer precursor is laminated, contact between active material particles and contact between solid electrolyte particles is ensured in the lamination direction, facilitating the formation of electron conduction paths and ion conduction paths in the lamination direction.

[0039] By arranging particles in a periodic pattern structure, a three-dimensional cathode structure can be formed in which active material particles and solid electrolyte particles are in close contact within the electrode layer. In other words, even when an electrode is obtained by stacking active material layer precursors, ion conduction and electron conduction paths can be formed between the upper and lower layers of the particle layer.

[0040] Examples of such periodic pattern structures include one-dimensional grid (line) patterns, zigzag patterns, two-dimensional grid patterns, staggered patterns, sea-island patterns, honeycomb patterns, and the like. The periodic pattern structure preferably includes at least one of a one-dimensional grid (line) pattern, a two-dimensional grid pattern, and a sea-island pattern, with a one-dimensional grid (line) pattern being preferred.

[0041] The pattern shape is preferably determined so that ion conduction and electron conduction paths can be connected to each particle, and further preferably so that the paths can properly contact each other when stacked. Moreover, it is preferable that the pattern allows paths to connect even without sufficient alignment during stacking. For example, in a line pattern, changing the angle at which the upper and lower layers are attached will always create a point where the lines meet, thus connecting the paths. Another example is a configuration in which the orientation of the pattern structure of adjacent layers differs by 90° in multiple particle layers. In a sea-island pattern as well, by appropriately designing the area ratio of the island portions, the island portions can always be made to contact each other vertically.

[0042] When peak detection processing is performed on the FFT power spectrum, examples of peaks in each pattern are shown below. In a one-dimensional grid (line) pattern, if the vertical lines are equally spaced with a width of 10 μm, for example, in the direction of an angle of 0° from the wavenumber (0,0), the horizontal component wavenumber (spatial frequency) is 10 μm. －1 A peak is observed at the position indicated. However, if there is some variation in the line pattern width, for example, if the variation is ±2 μm, then the peak will be 18-20 μm. －1 , and the multiple components are 16-24 μm －1 In some cases, two or more peaks spaced apart by a certain wavenumber (spatial frequency) may be observed.

[0043] Furthermore, if the image is acquired with the above line pattern tilted at 45°, the power spectrum will show, for example, a peak at a wavenumber of 10 μm for both the horizontal and vertical components, at an angle of 45° relative to the wavenumber (0,0).

[0044] In the case of a two-dimensional grid pattern consisting of equally spaced vertical lines with a width of 10 μm and equally spaced horizontal lines with a width of 5 μm, on the FFT two-dimensional power spectrum, the horizontal component has a wavenumber of 10 μm in the directions of angles 0°, 30°, and 90° relative to the wavenumber (0,0). －1 , 10 μm －1 , 0 μm －1 , wavenumber of the vertical component 0 μm －1 , 5 μm －1 , 5 μm －1 A peak is observed at the position indicated by ,.

[0045] In a sea-island pattern where a circle with a diameter of 10 μm is considered an island, and the origins of three adjacent circles form an equilateral triangle with side lengths of 12 μm, for example, the horizontal component wavenumbers at angles of 0°, 45°, and 90° relative to the wavenumber (0,0) are each 21 μm. －1 , 12 μm －1 , 0 μm －1 The wavenumber of the vertical component is 0 μm. －1 , 12 μm －1 , 21 μm －1 A peak is observed at the position indicated by ,.

[0046] The period of the periodic pattern structure is preferably, for example, 0.05 μm to 50 μm, 1 to 20 μm, or 5 to 15 μm. The period of the pattern structure corresponds to the -1 power of the wavenumber of the horizontal or vertical component relative to the peak when peak detection processing is performed on the FFT power spectrum.

[0047] The period of the pattern structure is preferably determined by the particle size of the active material particles used, and is preferably 1 to 10 times the volume-based median diameter D50, and more preferably 1 to 6 times. If the period of the pattern structure is 1 or more times the volume-based median diameter D50, the active material particles can be sufficiently packed, and the charge / discharge capacity can be more easily improved. Also, if the period of the pattern structure is 10 or less times the median diameter D50, it becomes easier to construct ion conduction and electron conduction paths in each particle, and the charge / discharge characteristics of the secondary battery can be further improved.

[0048] <Interfacial bonding precursor> The interfacial bonding precursor comprises a second resin substrate and first solid electrolyte particles held in the second resin substrate. The interfacial bonding precursor has a portion that contacts the active material layer precursor. Preferably, the entire surface of the interfacial bonding precursor is in contact with the active material layer precursor. The materials described above can be used as the material constituting the second resin substrate. The first resin substrate and the second resin substrate may be resin substrates with common physical properties and composition, or they may be resin substrates with different physical properties and composition. The softening point temperature of the first resin substrate and B varies depending on the material used, but is preferably, for example, 50 to 400°C. For example, when PET is used as the first and second resin substrates, both have a melting point of 260°C (softening point temperature of 80°C).

[0049] The interfacial bonding precursor includes first solid electrolyte particles held in the second resin substrate described above. The first solid electrolyte particles have a softening point temperature that is higher than the softening point temperatures of the first and second resin substrates, respectively, and lower than the softening point temperature of the active material particles. Preferably, the first solid electrolyte particles have higher ionic conductivity than the active material particles. The higher ionic conductivity of the first solid electrolyte particles compared to the active material particles allows for the formation of a good ionic conduction path between the electrolyte layer and the active material layer during the secondary battery manufacturing process. When operating as an electrode in a secondary battery, the solid electrolyte components can ensure a predetermined ionic conductivity (lower limit of ionic conductivity) regardless of the charge / discharge state for the active material that undergoes expansion and contraction (intercalation) in the electrode due to charging and discharging.

[0050] The ionic conductivity of the first solid electrolyte particle is not particularly limited, but for example, 1 × 10⁻⁶ －７ ~1 x 10 －３ It is preferable that the ionic conductivity of the active material particles is not particularly limited, but is 1 × 10⁻⁶. －８ The following is more preferable. The ionic conductivity (ionic conductivity) of the solid electrolyte particles and active material particles can be measured by the method described below.

[0051] Because the softening point temperature of the first solid electrolyte particles is higher than that of the resin substrate and lower than that of the active material particles, the resin substrate can be removed by heating during the secondary battery manufacturing process, and the first solid electrolyte particles can melt to form a good interface between the electrolyte layer and the active material layer.

[0052] The first solid electrolyte particles are not particularly limited as long as they satisfy the above requirements, and known solid electrolyte particles can be used. For example, the solid electrolyte particles described above can be used. The solid electrolyte particles may be used individually or in combination of two or more types. The first solid electrolyte particles and the second solid electrolyte particles may be particles with common physical properties and composition, or different particles may be used. A method for arranging the first solid electrolyte particles on a resin substrate will be described later.

[0053] The first solid electrolyte particles can be selected by combining them with the first resin substrate, the second resin substrate, and the active material particles in the active material layer precursor. For example, when PET is used as the first and second resin substrates and LCO particles are used as the active material particles, it is preferable that the first solid electrolyte particles include at least one selected from the group consisting of LBO particles, LYbBO particles, and Bi-LLZT particles.

[0054] The softening point temperature of the first solid electrolyte particles is preferably 400 to 950°C, and more preferably 450 to 900°C. The softening point temperature of the first solid electrolyte particles is preferably 300°C or more higher than the softening point temperature of the resin substrate, and more preferably 400°C or more higher. Furthermore, it is preferably 200°C or more lower than the softening point temperature of the active material particles, and more preferably 300°C or more lower. The methods for measuring the softening point temperatures of the solid electrolyte particles, active material particles, and resin substrate, as well as the ionic conductivity of the solid electrolyte particles and active material particles, will be described later.

[0055] The interfacial bonding precursor is preferably a laminate of one or more second resin substrates on which first solid electrolyte particles are arranged. Multiple identical interfacial bonding precursors may be laminated, or multiple interfacial bonding precursors with different materials and particle arrangements may be laminated and used. Interfacial bonding precursors with different patterns on the top and bottom may be used, or they may be used in combination with an interfacial bonding precursor without a pattern. Furthermore, interfacial bonding precursors containing different solid electrolyte particles may be used.

[0056] The interfacial bonding precursor preferably further contains the same particles as the second or third solid electrolyte particles contained in the active material layer precursor described above, and is particularly preferably the third solid electrolyte particle. That is, the interfacial bonding precursor preferably contains the first solid electrolyte particle held on the second resin substrate and the third solid electrolyte particle described above. The solid electrolyte particles on the interfacial bonding precursor can be identified by compositional analysis using FIB-SEMEDX or X-ray crystallography (XRD), as described later. As an example, schematic diagrams (Figures 60A to 60C) and measurement results (Figure 60D) of the XRD measurement sample in Example 2 (fired temperature dependent) are shown. Figure 60A shows the measurement sample before firing, Figure 60B shows the measurement sample after firing at 800°C, and Figure 60C shows the measurement sample after firing at 900°C.

[0057] Furthermore, it is preferable that the first solid electrolyte particles have the same composition as the second or third solid electrolyte particles. That is, it is preferable that the first solid electrolyte particles contained in the interfacial bonding precursor and the second or third solid electrolyte particles contained in the active material layer precursor are particles with the same physical properties and composition. It is preferable that the first solid electrolyte particles and the second or third solid electrolyte particles are particles with the same physical properties and composition because it suppresses the side reactions during firing described later and facilitates the formation of a good interface between the active material layer precursor and the interfacial bonding precursor.

[0058] It is preferable that at least one of the first, second, and third solid electrolyte particles contained in the interfacial bonding precursor contains at least one selected from the group consisting of Bi and Ca. It is more preferable that at least one of the first, second, and third solid electrolyte particles contains Bi. For example, it is more preferable to use Bi-LLZT particles as at least one of the first, second, and third solid electrolyte particles. Whether Bi and Ca are contained in the solid electrolyte particles on the interfacial bonding precursor can be determined by compositional analysis by FIB-SEM as described later.

[0059] It is preferable that at least one of the first solid electrolyte particles, the second solid electrolyte particles, and the third solid electrolyte particles includes at least one selected from the group consisting of Bi and Ca, because the Bi and / or Ca oxides generated during firing become liquid phase at low temperatures, allowing for the formation of a better interface at low temperatures through liquid-phase sintering.

[0060] <Method for Measuring Ion Conductivity> The ionic conductivity of active material particles and solid electrolyte particles can be measured by the following method. Ion conductivity (ionic conductivity) can be measured by impedance measurement using an electrochemical measuring device (manufactured by Solartron). For solid electrolytes, electrodes (gold) are placed on both sides of the calcined sample, and an electrochemical measuring device is connected to the electrodes (two electrodes). The AC amplitude is set to 10 mV and the frequency (sweep) to 0.1 to 1 MHz, and impedance measurement is performed. The resistance (S) and electrode area (cm²) obtained from the Cole-Cole plot are then measured. ２ It can be determined by calculating the ionic conductivity (S / cm) from the sample thickness (cm) and the sample temperature (°C).

[0061] A method for preparing samples for measuring the ion conductivity of solid electrolyte particles is described. Multiple interfacial bonding precursors are stacked on a gold plate, and the first and second heating steps are performed using the method described later. Gold foil is stacked on the surface of the resulting sample opposite the gold plate (solid electrolyte) so as to be in contact with it, and two electrodes are provided so as to be in contact with the gold foil and gold plate. The sample is then packaged in an aluminum laminate film to prepare a sample for measuring ion conductivity. If the solid electrolyte particles are identified, these solid electrolyte particles may be prepared, pelletized using a known method, and after firing the pellets, both sides may be sputtered with gold (Φ8 mm) using a sputtering apparatus (manufactured by Vacuum Devices) to provide two electrodes. The sample thickness can be determined from a thickness gauge or cross-sectional SEM image.

[0062] Furthermore, the ionic conductivity of the active material particles can also be measured by a similar method. The method for preparing a sample for measuring the ionic conductivity of active material particles will be described below. Multiple active material layer precursors containing only active material particles are stacked on an ion conductor (LLZT sintered body, Φ10 mm / d1 mm, manufactured by Toyoshima Seisakusho) whose ionic conductivity is known in advance, and the first and second heating steps are performed using the method described later. Gold foil (Φ8 mm, d50 μm) is stacked on both sides of the obtained sample so as to be in contact with it, and an extraction electrode is provided so as to be in contact with the gold foil, and the sample is packaged in an aluminum laminate film. The same procedure is followed for subsequent samples.

[0063] <Method for Measuring Softening Point and Melting Point> The softening point of active material particles, solid electrolyte particles, and resin substrates can be measured by the following method. The softening point can be measured using a thermomechanical analyzer (manufactured by Hitachi High-Tech). A sample is placed inside a heater, and a probe connected to the displacement detection unit and load generation unit is applied to the sample. While applying a load to the sample via the probe, the sample temperature is changed by the heater. The amount of displacement (TMA curve) associated with the deformation of the sample due to softening is measured. The softening point is defined as the temperature at the intersection of the extension of the straight portion of the TMA curve on the lower temperature side of probe penetration and the tangent to the portion with the maximum penetration velocity.

[0064] By using the resin substrate to be measured as the sample described above, the softening point temperature of the resin substrate can be measured. The method for preparing samples other than resin substrates will be described below. For measuring active material particles, multiple active material layer precursors containing only active material particles are stacked on a gold plate, and then calcined and pressurized using the method described later. For measuring solid electrolyte particles, multiple interfacial bonding precursors consisting only of solid electrolytes are stacked on a gold plate, and then calcined and pressurized using the method described later. If the strength of the sample is low, it may be carried out up to the final calcination stage. If the active material particles or solid electrolyte particles are identified, pellet-shaped samples made from the same material (powder) using a known method may be used.

[0065] The softening point temperature of active material particles and solid electrolyte particles can also be determined from the temperature dependence of their relative density. Using the sample preparation method described above, a precursor consisting only of active material particles or only of solid electrolyte particles is laminated on a substrate, and a laminate is prepared by calcination and pressurization processes. Next, the final calcination is performed, and the density of the sample (g / cm³) is determined. ３ The relative density is calculated by determining the ) and plotting the temperature dependence of the relative density by varying the firing temperature and setting the temperature at which the relative density reaches 80% as the softening point temperature. If the active material particles or solid electrolyte particles are identified, the same material (powder) may be prepared and a pellet-shaped sample formed by a known method may be used.

[0066] If the sample is homogeneous and its melting point can be measured, the softening point temperature can be substituted for the melting point. The melting point can be measured by the following methods: The melting point can be measured using a thermogravimetric-differential thermal analyzer (TG-DTA). The sample is placed in an alumina sample pan and the sample temperature is changed. The TG curve and DTA curve are measured as the sample temperature changes, and the melting point can be determined.

[0067] <Method for Identifying Interfacial Bonding Precursors and Active Material Layer Precursors> The presence of interfacial bonding precursors and active material layer precursors can be confirmed by compositional analysis using FIB-SEM and EDX. Specifically, by obtaining a cross-sectional SEM image of the electrode precursor using FIB-SEM, and obtaining EDX mapping images of the elements contained in the interfacial bonding precursor and the elements contained in the active material layer precursor in the cross-section, the interfacial bonding precursor and the active material layer precursor can be identified. For example, by detecting La, Zr, Yb, and B as elements contained in the interfacial bonding precursor and Co as an element contained in the active material layer precursor, each precursor can be identified. Detailed methods for compositional analysis using FIB-SEM and EDX will be described later.

[0068] <Method for Manufacturing Electrode Precursors> An electrode precursor is a laminate in which an interfacial bonding precursor and an active material layer precursor are stacked. An electrode precursor can be manufactured by stacking the interfacial bonding precursor and the active material layer precursor. An example of a method for manufacturing the interfacial bonding precursor and the active material layer precursor will be described in detail below with reference to the drawings.

[0069] <Method for manufacturing interface bonding precursor and active material layer precursor> The method for manufacturing the interface bonding precursor and active material layer precursor comprises at least the following two steps (first step and second step): (1) A first step (S101 in Figures 2A and 2B) in which first particles P1 are placed on a resin substrate having an adhesive portion. (2) A second step (S102 in Figures 2A and 2B) in which second particles P2 are placed in an area on the resin substrate where the first particles P1 are not placed.

[0070] Furthermore, the method for producing the interfacial bonding precursor and the active material layer precursor may further include the following third and fourth steps: (3) A third step (S103 in Figure 2B) in which the first particle P1 and the second particle P2 are settled in the adhesive portion; (4) A fourth step (S104 in Figure 2B) in which, after the third step, the third particle P3 is placed in the area where the adhesive portion is exposed.

[0071] When producing an active material layer precursor, active material particles and, if necessary, solid electrolyte particles (second solid electrolyte particles) are used as the first particle P1, second particle P2, and third particle P3. That is, in the production process of the active material layer precursor, the first particle P1, second particle P2, and third particle P3 each contain at least active material particles. Preferably, the first particle P1, second particle P2, and third particle P3 each contain at least active material particles and second solid electrolyte particles. When producing an interfacial bonding precursor, solid electrolyte particles (first solid electrolyte particles) are used as the first particle P1, second particle P2, and third particle P3.

[0072] In the following description of the manufacturing method, an example using positive electrode active material particles as the active material particles for the active material layer precursor will be given. However, the electrode precursor of this disclosure can also be used as a negative electrode precursor. That is, regardless of whether it is a positive or negative electrode, the manufacturing method described below can be used as a method for manufacturing the active material layer precursor.

[0073] The following describes the first to fourth steps in detail. (First Step) The first step is to place the first particles P1 on a resin substrate for particle transfer. Specifically, this involves placing particles on the first substrate using a particle filling device, and then transferring the particles onto a second substrate (the first resin substrate or the second resin substrate) using a particle transfer device. The particle filling device and particle transfer device that can be used in the present invention will be described below.

[0074] [Particle Packing Apparatus] Figure 3 shows an example of a particle packing apparatus. In the following description, when producing a positive electrode active material layer precursor, positive electrode active material particles or second solid electrolyte particles are used as the first particle P1 and second particle P2. When producing an interfacial bonding precursor, first solid electrolyte particles are used as the first particle P1 and second particle P2.

[0075] The particle filling device 24 includes a filling container 242, a stirring screw member 243, a magnet conveying member 247, a magnet 248 fixed to the magnet conveying member, and a regulating member 249. The magnet 248 can be a ferrite magnet, a neodymium magnet, a rare earth magnet such as a samarium cobalt magnet, a permanent magnet such as a plastic magnet, or a means of generating a magnetic field such as an electromagnet. The filling container 242 contains a filler 241a. 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 a plurality of first particles P1 and a powder composed of a plurality of support materials S1.

[0076] Furthermore, the particle filling device 24 is configured to allow the attachment and detachment of a holder 110 for fixing a pre-prepared first substrate 11a for particle transfer. The first substrate 11a has a fine uneven pattern 111a formed on its surface (Figure 57A). As a means for forming the uneven pattern, known fine pattern formation methods such as UV imprinting, thermal imprinting, UV inkjet, printing, and laser etching can be used. For example, it is preferable to use a resin substrate as the first substrate 11a, which has an uneven pattern 111a formed by curing ultraviolet-curable liquid silicone rubber (polydimethylsiloxane PDMS) using a UV imprinting method on a master mold (quartz) on which a fine pattern has been formed on its surface using photolithography technology. The master mold is made using known microfabrication techniques, such as photolithography or physical processing techniques such as cutting, machining, and laser processing. The uneven pattern can be selected from the periodic pattern structures described above. The recesses should be formed so that the first particles P1 fill the periodic pattern structure described above. The uneven pattern 111a is preferably a line pattern or a sea-island pattern (a uniform dispersion pattern described later).

[0077] Figure 4 is a schematic diagram illustrating the operation of the particle filling apparatus. The filler 241a contained in the filling container 242 is thoroughly mixed when stirred and conveyed by the stirring screw member 243. As a result, the first particles P1 are supported on the surface of the support material S1. The forces acting between the particles during this support include not only electrostatic forces due to triboelectric charging, but also van der Waals forces and liquid bridging forces. Note that there may be particles among the first particles P1 that are not supported on the support material S1.

[0078] The support material S1 is magnetic particles. Preferably, the support material S1 is a particle in which the surface of ferrite core particles or resin particles in which magnetic material is dispersed is coated with a resin composition. 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 and conveyed. Furthermore, even if the first particles P1 are small in size and prone to agglomeration, the agglomeration of the first particles P1 can be loosened by stirring and conveying them with the support material S1. The filler 241a, which has been sufficiently stirred by the stirring screw member 243, is supplied in an appropriate amount by the regulation of the magnet conveying member 247 regulating member 249, which has moved from the home position in the direction of arrow a in Figure 4. The supplied filler 241a is rubbed on the first substrate 11a as the magnet conveying member 247 moves back and forth (arrow b in Figure 4).

[0079] Figure 5 is an enlarged view of the vicinity of the surface of the first substrate 11a in Figure 4. Multiple magnetic spikes (multiple magnetic particles arranged in a spike-like manner) exist on the first substrate 11a along the magnetic field lines of the magnetic field formed by the magnet 248 and the magnetic material containing magnetic particles. For explanatory purposes, all but one magnetic particle S1 and the multiple first particles P1 supported on it are omitted from the illustration.

[0080] As shown in Figure 5, a textured pattern 111a is formed on the first substrate 11a. Preferably, the opening diameter of the recesses in the textured pattern 111a is larger than the cumulative 50% particle size (median diameter) based on the volume of the first particle P1. Also, preferably, the opening diameter of the recesses is smaller than the cumulative 50% particle size (median diameter) based on the volume of the support material S1. Here, the opening diameter of the recesses in the textured pattern is preferably the opening diameter in the short-side direction of the recess, and more preferably the maximum opening diameter in the short-side direction of the recess.

[0081] By controlling the opening diameter of the recess as described above, the first particles P1 can contact the bottom and side surfaces (typically the bottom surface) of the recesses in the uneven pattern, while the support material S1 cannot contact the bottom and side surfaces of the recesses. This allows the first particles P1 that come into contact with the bottom and side surfaces of the recesses to be captured by the uneven pattern, while preventing the support material S1 from being captured by the uneven pattern. In other words, it is preferable that the first particles P1 can contact the bottom and side surfaces of the recesses in the uneven pattern, while the first support material S1 cannot contact the bottom and side surfaces of the recesses in the uneven pattern. Furthermore, it is preferable that the opening diameter of the recess is three times or less the cumulative 50% particle size (median diameter) of the first particles P1 based on volume. By setting the opening diameter of the recess as described above, it is preferable that the particles can be arranged so that the first particles P1 and the second particles P2, which will be placed in a later process, are adjacent to each other.

[0082] The filler 241a comes into contact with the uneven pattern 111a and is transported while reciprocating with a relative velocity v to the first substrate 11a, while receiving a magnetic force (arrow Fm in Figure 5) perpendicular to the surface of the first substrate 11a. At this time, the first particles P1 supported on the carrier S1 are transported while being rubbed against the uneven pattern 111a on the surface of the first substrate 11a (Figure 57B).

[0083] As described above, the particle size of the first particle P1 is smaller than the opening diameter of the recess in the uneven pattern 111a, and the particle size of the first carrier S1 is larger than the opening diameter of the recess. As a result, the first particle P1 can come into contact with the bottom surface (bottom) and side surface of the recess in the uneven pattern 111a, but the carrier S1 cannot. In other words, only the first particle P1 contained in the filler 241a selectively comes into contact with the bottom surface and side surface of the recess. The first particle P1 that comes into contact with the recess is strongly restrained by the physical restraining force due to the structure of the uneven pattern 111a, and by non-electrostatic adhesive forces such as electrostatic adhesion and adhesive force with the first base material 11a and the structural material constituting the uneven pattern 111a, and detaches from the carrier S1. Although Figure 5 shows the first particles P1 supported on the surface of the support material S1 for illustrative purposes, it is acceptable for the first particles P1 not to be supported on the support material S1 to be present during the stirring, supply, and transport of the filler 241a.

[0084] After the desired number of round trips, the magnetic transport member 247 moves in the direction of arrow c in Figure 4 to a distant home position where the magnetic force acting on the filler 241a is sufficiently weakened. The transported filler 241a falls downward due to gravity and is collected in a collection container (not shown). Any remaining filler may be recovered by air blowing, vibration, or magnets.

[0085] After the transport, filling, and recovery of the filler 241a described above, the first particles P1 are densely packed into the recesses on the first substrate 11a (Figure 57C). The thickness of the layer of packed particles can be controlled by adjusting the depth of the recesses in the uneven pattern 111a of the first substrate 11a. When the first particles P1 are arranged in a thin layer (approximately a single layer), the depth of the recesses should be set to be less than or equal to the particle size of the first particles P1.

[0086] In Figure 5, the first particles P1 are all shown as perfectly spherical with a common particle size, but in reality, there is a particle size distribution, and in some materials, they may aggregate to form secondary particles. Also, the first particles P1 are almost never spherical as shown in the figure. Even in such cases, according to the method described above, only the particles that can contact the recesses of the uneven pattern 111a are selectively and densely packed, so that coarse powder and secondary particles contained in the filler 241a are excluded during the particle arrangement process, and only the first particles P1 can be selectively arranged in a pattern.

[0087] After recovering the filler 241a, it is preferable to further remove any excess particles on the first substrate 11a. Methods for removing excess particles include using air blowing or vibration, or using magnetic particles. The method using magnetic particles will be described below. The filler 241a of the particle filling apparatus is replaced with a recovery agent containing only magnetic particles, or magnetic particles and a small amount of first particles P1, and the recovery agent is transported in the same manner as described above and transported back and forth on the first substrate 11a. During the process of the recovery agent being transported back and forth on the first substrate 11a, the magnetic particles recover any excess first particles P1 and rearrange the first particles P1 that have been filled in the recesses, allowing for more dense filling. The removal of excess particles can be adjusted as appropriate by combining the above methods or performing the process multiple times. In the filling apparatus shown in Figures 3 and 4, friction is performed on an inclined surface for recovery, but friction may also be performed on a flat surface.

[0088] As described above, the amount of first particles P1 filling the recesses of the uneven pattern 111a can be controlled by the size (area, width, depth) of the recesses and the particle size of the first particles P1. Specifically, the area (volume) of the recesses becomes approximately the filling area (volume), and the thickness of the layer of first particles P1 to be filled is determined by the depth of the recesses. For example, to obtain a thin layer (approximately a single layer) in which first particles P1 are filled in an area of ​​50% of the substrate area, the area ratio of the recesses (the area ratio of the area where the recesses are formed to the total area of ​​the area where the uneven pattern is formed) should be set to 50%, and the depth of the recesses should be controlled to be less than or equal to the particle size of the first particles P1. In this case, the opening width of the recesses should be larger than the cumulative 50% particle size (median diameter) based on the volume of the first particles P1, and smaller than the cumulative 50% particle size (median diameter) based on the volume of the support material S1.

[0089] The first particles P1 may have a broad particle size distribution, but the support material S1 preferably has a narrow particle size distribution, and more preferably is monodisperse. This makes it easier to control the support material S1 so that it does not come into contact with the bottom (or bottom surface) or sides of the recess.

[0090] [Particle Transfer Apparatus] Figure 6 shows an example of a particle transfer apparatus. The particle transfer apparatus 1 includes a first storage container 21a for storing and supplying a first substrate 11a, a first belt device 22a for transporting the first substrate 11a, a second storage container 21b for storing and supplying a second substrate 11b, and a second belt device 22b for transporting the second substrate 11b. The first belt device 22a and the second belt device 22b each include drive rollers 221a, 222a, 221b, and 222b, pressure rollers 223a and 223b, and belt-shaped transport members 224a and 224b suspended therefrom. At this time, the pressure roller 223b is rotating in a driven manner.

[0091] The conveying members 224a and 224b are preferably made of resin or metal, for example, a polyimide resin belt can be used. The drive rollers 221a, 222a, 221b, and 222b are preferably made of metal, for example, a stainless steel metal roller can be used. The pressure rollers 223a and 223b are preferably made of soft rollers having an elastic layer on the surface, for example, a soft roller with an elastic layer of silicone rubber on the surface of a stainless steel core can be used.

[0092] The second belt device 22b receives the second base material 11b from the second storage container 21b and is transported in the direction of the arrow in Figure 6. Meanwhile, the first belt device 22a receives the first base material 11a from the first storage container 21a and is transported toward the transfer unit 25a. The first particles P1, which have been filled in the manner described above, are arranged in a pattern on the surface of the supplied first base material 11a. The second base material 11b is transported in conjunction with the timing at which the first base material 11a is transported toward the transfer unit 25a.

[0093] The particle transfer apparatus 1 has a transfer section 25a where the pressure rollers 223a and 223b of the first belt apparatus 22a and the second belt apparatus 22b face each other. In the transfer section 25a, the first particles P1 are transferred from the first substrate 11a to the second substrate 11b, and a particle layer 12 is placed on the second substrate 11b (Figure 57D).

[0094] The second substrate 11b is the first resin substrate in the active material layer precursor and the second resin substrate in the interfacial bonding precursor. Note that devices less relevant to explaining the effects of this disclosure, such as peeling and recovery devices for peeling and recovering the substrates 11a and 11b from the belt device after transfer, and various cleaning devices, are not shown in detail.

[0095] Figure 7 is a schematic diagram showing the configuration of the transfer section 25a. The pressure rollers 223a and 223b rotate under driven motion, and the two rollers are in contact 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 portion is formed where the two rollers are in contact.

[0096] The first substrate 11a and the second substrate 11b, which are filled with the first particles P1 by the particle filling device 24, are conveyed at approximately constant speed by their respective conveying members (224a, 224b) and enter the nip portion formed by the contact of the pressure rollers 223a, 223b. In the nip portion, 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. The second substrate 11b is a substrate whose adhesive force to the first particles P1 is greater than the adhesive force to the first particles P1 on the first substrate 11a. In other words, the adhesive force of the first particles P1 on the second substrate 11b is greater than the adhesive force of the first particles P1 on the first substrate 11a. As a result, in the nip portion, the first particles P1 on the first substrate 11a are transferred onto the second substrate 11b.

[0097] The material of the second substrate 11b is a resin substrate whose weight decreases upon thermal decomposition. The materials described above can be used as the materials constituting the resin substrate. Preferably, the second substrate 11b is surface-treated to enhance adhesion in order to transfer the first particles P1 that it comes into contact with. For example, it is preferable that the second substrate 11b has an adhesive portion on its surface to which an adhesive is applied. In addition to acrylic adhesives, the adhesive may be any known adhesive such as rubber adhesives, silicone adhesives, urethane adhesives, epoxy adhesives, or polyvinyl ether adhesives, or it may be a thermoplastic resin or a photocurable resin whose adhesive strength changes due to disturbances such as heat or light. Furthermore, known epoxy, acrylic, urethane, or two-component mixed adhesives may also be used. In addition, 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 on which the same adhesive as the surface is applied, and that its surface is further covered with a protective film or the like. This prevents misalignment between substrates during the lamination process described later, and firmly fixes the positive electrode active material particles and solid electrolyte particles placed between the substrates by sandwiching them between the upper and lower surfaces (in the lamination direction). As a result, particle movement is suppressed during lamination, storage of the laminate, heat treatment, and pressurization, enabling the formation of desired active material layer precursors, interface bonding precursors, and electrode precursors.

[0098] In addition to the two-layer configuration of the resin substrate and the adhesive portion, a single-layer configuration utilizing the adhesive force (electrostatic / non-electrostatic adhesive force) of the substrate itself is also acceptable. Furthermore, a multi-layer configuration in which two or more adhesive portions are formed on the surface of the resin substrate is also acceptable. Moreover, a resin substrate with adhesive pre-applied may be used, or the adhesive may be applied to the surface of the second substrate 11b during transport by a known application method (not shown). Known application methods include dispensers, inkjet heads, and bar coaters.

[0099] The type and amount of adhesive applied are adjusted as appropriate depending on the shape and material of the textured pattern used, the particle size and material of the first particle P1 and the second particle P2, but it is preferable that the adhesive strength is greater than that of the textured pattern 111a. The adhesive strength can be compared using a general method using a nanoindenter.

[0100] The first base material 11a and the second base material 11b may be individual base materials, such as cut paper, or they may be continuous base materials wound in a roll, such as roll paper, or continuous base materials folded alternately, such as continuous paper.

[0101] Furthermore, the particle transfer device can use existing pressurizing devices in addition to the aforementioned device. As the pressurizing device, a uniaxial pressurizing device or an isotropic pressurizing device (CIP / HIP) can be used. By pressing the first substrate 11a and the second substrate 11b in contact and then separating them, the first particles P1 can be transferred onto the surface of the second substrate 11b.

[0102] (Second step) The second step is to place the second particles P2 in areas on the second substrate 11b where the first particles P1 are not present. The second particles P2 can be placed on the second substrate 11b in the same manner as the first step, in which the first particles P1 were placed on the first substrate 11a using a particle packing device.

[0103] Figure 8 is a schematic diagram illustrating the operation of the particle filling apparatus. In the particle filling apparatus (Figure 3) used in the first step, a second base material 11b on which the first particles P1 are arranged in a pattern is set in place of the first base material 11a. The filler 241b comprises second particles P2 and a support material S2 (magnetic particles) that supports the second particles P2. The filler 241b is a mixture of multiple powders, including powder composed of multiple second particles P2 and powder composed of multiple support materials S2.

[0104] Figure 9 is an enlarged view of the vicinity of the surface of the second substrate 11b. Similar to Figure 5, for illustrative purposes, only one magnetic particle S2 and the plurality of second particles P2 supported thereon are shown. The adhesive portion 13 described above is formed on the second substrate 11b, and an uneven pattern is formed having convex portions formed by the placement of the first particles P1 and concave portions where the adhesive portion 13 is exposed and the first particles P1 are not placed (Figure 9A).

[0105] The filler 241b comes into contact with this uneven pattern and is transported with a relative velocity v to the second substrate 11b while receiving a magnetic force (arrow Fm in Figures 9A and 9B) perpendicular to the surface of the second substrate 11b. As a result, the second particles P2 supported on the support S2 are transported while being rubbed against the uneven pattern on the surface of the second substrate 11b (Figure 57E).

[0106] In this case, the opening width of the recesses in the uneven pattern formed on the second substrate 11b is set to a size that allows the second particles P2 to contact the recesses, but the support material S2 cannot. For example, when the first particles P1 are arranged in a line on the second substrate 11b, it is preferable that the line width of the region where the first particles P1 are not arranged is larger than the volume-based cumulative 50% particle size (median diameter) of the second particles P2, and smaller than the average size (volume-based cumulative 50% particle size (median diameter)) of the support material S2. By controlling the opening width of the recesses in the uneven pattern as described above, only the second particles P2 can selectively contact the recesses within the filler 241b.

[0107] The second particle P2, upon contact with the recess, is strongly restrained by the adhesive force of the adhesive portion 13 of the second substrate 11b, the physical restraining force due to the structure of the uneven pattern, and the electrostatic and non-electrostatic adhesive forces with the structural material constituting the uneven pattern (in this case, the first particle P1), and detaches from the support material S2.

[0108] In Figures 9A and 9B, for illustrative purposes, the second particles P2 are shown to be supported on the surface of the support material S2. However, during the stirring, supply, and transport of the filler 241b, it is acceptable for particles P2 not to be supported on the support material S2 to be present.

[0109] After the desired number of round trips, the magnetic transport member 247 moves in the direction of arrow c in Figure 8 to a distant home position where the magnetic force acting on the filler 241b is sufficiently weakened. The transported filler 241b falls downward due to gravity and is collected in a collection container (not shown). Any remaining filler may be recovered by air blowing, vibration, or magnets.

[0110] After the transport, filling, and recovery of the filler 241b described above, the first particles P1 and the second particles P2 are densely arranged on the second substrate 11b (Figure 57F). The thickness of the layer of the filling second particles P2 can be controlled by adjusting the depth of the recesses in the second substrate 11b (i.e., the particle size of the first particles P1) and the particle size of the second particles P2. When the second particles P2 are arranged in multiple layers, the particle size of the second particles P2 (cumulative 50% particle size by volume (median diameter)) should be set to 50% or less of the particle size of the first particles P1 (cumulative 50% particle size by volume (median diameter)). When the second particles P2 are arranged in approximately a single layer, the particle size of the second particles P2 (median diameter) should be set to be larger than 50% of the particle size of the first particles P1 (median diameter).

[0111] In Figures 9A and 9B, the second particles P2 are all shown as perfectly spherical with a common particle size, but in reality, there is a particle size distribution, and furthermore, depending on the material, the second particles P2 may aggregate to form secondary particles. Also, the second particles P2 are almost never spherical as shown in the figures. Even in such cases, according to the method described above, only the particles that can contact the recesses of the uneven pattern are selectively and densely packed, so coarse powder and secondary particles contained in the filler 241b are excluded in the particle placement process, and only the second particles P2 are selectively pattern-arranged in areas of the substrate surface where the first particles P1 are not placed, thereby forming a dense, thin particle layer. It is preferable to remove excess particles from the second substrate 11b after recovering the filler 241b. The excess particles can be removed using the same method as described above for removing excess particles from the first substrate 11a.

[0112] The amount of second particles P2 filling into the recesses (regions where the first particles P1 are not placed) on the second substrate 11b can be controlled by the size (area, width, depth) of the recesses and the particle size of the second particles P2. Specifically, the area (volume) of the recesses becomes approximately the filling area (volume), and the thickness of the filled layer of second particles P2 is determined by the depth of the recesses (the particle size of the pre-placed first particles P1). For example, to obtain a thin layer (approximately a single layer) in which second particles P2 are filled in an area of ​​50% of the substrate area, the area ratio of the recesses (the area ratio of the region where the first particles P1 are not placed relative to the total area of ​​the substrate) should be controlled to 50%, and the depth of the recesses (the median diameter of the pre-placed first particles P1) should be controlled to be less than or equal to the particle size (median diameter) of the second particles P2. In this case, it is preferable that the opening width of the recess (the width of the area on the substrate where the first particle P1 is not placed) is greater than the volume-based cumulative 50% particle size (median diameter) of the second particle P2, and smaller than the volume-based cumulative 50% particle size (median diameter) of the support material S2.

[0113] The second particle P2 may have a broad particle size distribution, but the support material S2 preferably has a narrow particle size distribution, and more preferably is monodisperse. This makes it easier to control the support material S2 so that it does not come into contact with the bottom (or bottom surface) or sides of the recess.

[0114] As described above, the interfacial bonding precursor is manufactured in the first and second steps (S101 and S102 in Figures 2A and 2B) by using solid electrolyte particles (first solid electrolyte particles) as the first particle P1 and the second particle P2. The solid electrolyte particles used for the first particle P1 and the second particle P2 may be of the same type or different types.

[0115] On the other hand, the active material layer precursor is manufactured in the first and second steps by using active material particles or solid electrolyte particles (second solid electrolyte particles) as the first particle P1 and the second particle P2. Alternatively, active material particles may be used as the first and second particles without using a fixed electrolyte. In this case, the active material particles used for the first and second particles may be of the same type or different types. That is, when manufacturing the active material layer precursor, the first particle P1 and the second particle P2 are each active material particles or solid electrolyte particles, and at least one of the first particle P1 and the second particle P2 is an active material particle.

[0116] Furthermore, in the manufacturing process of the interfacial bonding precursor and the active material layer precursor, the following third and fourth steps (S103 and S104 in Figures 2A and 2B) can be carried out in addition to the first and second steps described above to arrange a third particle.

[0117] (Third Step) The third step is to allow the first particles P1 and the second particles P2, which were placed in the first and second steps, to settle on the adhesive portion 13 of the second substrate 11b. Figure 10 is a schematic diagram of the particle settling device used in the third step. The second substrate 11b, on which a particle layer 12 with the first particles P1 and the second particles P2 has been formed by the first and second steps, is transferred to the belt device 24 shown in Figure 10. The belt device 24 is equipped with a particle settling device 25 and drive rollers 221 and 222.

[0118] The particle sedimentation device 25 has pressure rollers 223c and 223d, with the pressure roller 223d rotating by a driven force. Preferably, at least one of the pressure rollers 223c and 223d is a soft roller having an elastic layer on its surface. For example, a soft roller can be used in which an elastic layer of silicone rubber or fluororubber is provided on the surface of a stainless steel core. In addition, a heating element (not shown) may be built inside at least one of the pressure rollers 223c and 223d.

[0119] The second substrate 11b is conveyed by the belt device 24 to the pressurized section 25 between the pressure rollers 223c and 223d. When pressurized by the pressure rollers 223c and 223d, the first particles P1 and the second particles P2 on the substrate settle into the adhesive portion on the substrate. As the first particles P1 and the second particles P2 settle into the adhesive portion 13, the adhesive portion 13 is exposed to the surface through the gaps between the particles. At this time, the settling of the particles may be accelerated by heating the adhesive portion with the heating heater. Alternatively, a heating source may be provided upstream of the particle settling device 25 to heat the adhesive portion.

[0120] The pressure roller 223c comes into contact with the particle layer 12 on the substrate. Therefore, it is preferable to coat the surface of the pressure roller with a material that has good release properties, such as fluorine, in order to suppress particle adhesion. Alternatively, a cleaning mechanism may be provided to remove particles that have adhered to the pressure roller 223c.

[0121] To suppress particle adhesion to the pressure roller, it is more preferable to pressurize the particle layer 12 while it is covered with a protective material (not shown). In this case, the protective material covering the particle layer 12 is preferably made of a material with good release properties, and can be made of resin or metal. For example, if it is made of resin, it is preferable to cover the particle layer with a fluorine sheet, and if it is made of metal, it is preferable to cover it with nichrome foil. When a protective material is used, a removal mechanism (not shown) for removing the protective material is provided downstream of the particle settling device 25.

[0122] The particle sedimentation device 25 may be any known pressurizing or heating device other than the device described above. For example, an isotropic pressurizing device (CIP / HIP), a uniaxial pressurizing device, or even a weight or magnet may be used to apply pressure. Also, if the specific gravity of the particles is high, the particles may be allowed to settle by their own weight. In this case, it is preferable to promote the settling of particles by their own weight under heating conditions such as an oven. The temperature and storage time are adjusted as appropriate according to the physical properties of the particles and adhesive (shape, particle size and specific gravity, adhesiveness and viscoelasticity). If the temperature or storage time is insufficient, the particles will not settle sufficiently, and the adhesive portion will not be exposed on the surface through the gaps between the particles. On the other hand, if the temperature or storage time is excessive, the particles will move in the planar direction on the surface of the substrate along with the settling of the particles, and the density of the particle arrangement tends to decrease.

[0123] In addition to known pressurizing devices and the methods described above, the particles may be pressed by vacuum packaging or by rubbing the magnetic particles to cause them to settle. The rubbing of the magnetic particles can be performed using the particle filling device, while also removing excess particles.

[0124] Figures 11A and 11B are schematic cross-sectional diagrams of the substrate 11b to illustrate the sedimentation of particles on the second substrate 11b by the particle sedimentation device 25. Figure 11A shows the state before the third step in which the first particle P1 and the second particle P2 are sedimented in the adhesive portion 13 on the substrate 11b, and Figure 11B shows the state after the third step. For explanatory purposes, particles P1 and P2 are represented as perfectly spherical in shape and are described as having the same particle size. As shown in Figure 11A, before the third step, particle sedimentation is limited, and the first particle P1 and the second particle P2 are positioned on the adhesive portion 13 without sedimenting much. After the third step, as shown in Figure 11B, the sedimentation of the first and second particles into the adhesive portion 13 progresses, and the adhesive portion 13, which has been pushed out by the sedimentation of the particles, is exposed on the surface through the gaps between the particles.

[0125] Figure 12 is a schematic diagram of the substrate 11b after the third step, viewed from above (the side where the first particle P1 and the second particle P2 are located). As the first particle P1 and the second particle P2 settle into the adhesive portion 13, the adhesive portion 13 is exposed on the surface through the gaps between the particles. This creates tiny recesses (for example, A in Figure 12) between the particles, each having an adhesive portion 13 at its bottom.

[0126] (Fourth Step) The fourth step is to place the third particles P3 in the minute recesses where the adhesive portion is exposed. The third particles P3 can be placed in the same manner as the second particles P2 were placed in the second step using a particle filling device. In the fourth step, a filler 241c is used that contains the third particles P3 that can contact the minute recesses and their carrier S3 (magnetic particles). Figure 13 is a schematic diagram of the substrate 11b from above after the fourth step. The third particles P3 are placed in the minute recesses where the adhesive portion 13 is exposed. For the purposes of this explanation, the third particles P3 are represented as perfectly spherical and described with the same particle size, but multiple irregularly shaped third particles P3 can be placed to match the openings of the minute recesses. By performing the third and fourth steps, a denser particle layer can be formed.

[0127] Furthermore, the particle sedimentation and arrangement process may be repeated in the fourth step and beyond, and multiple particles such as the fourth, fifth, etc., P4, P5, etc., may be arranged. The particles can be sedimented and arranged using the particle sedimentation device described above used in the third step and the particle filling device described above used in the fourth step. Furthermore, conductive particles as conductive additives, resin particles as binder resins, and other functional particles may be used as the third particle P3 and beyond.

[0128] When manufacturing an interfacial bonding precursor by steps 1 to 4, solid electrolyte particles are used as the first particle P1, the second particle P2, and the third particle P3. The solid electrolyte particles used for the first, second, and third particles may be of the same type or different types. When manufacturing an active material layer precursor by steps 1 to 4, the first particle P1, the second particle P2, and the third particle P3 are each active material particles or solid electrolytes, and at least one of the first particle P1, the second particle P2, and the third particle P3 is an active material particle.

[0129] When manufacturing the active material layer precursor, for example, an active material particle can be used as the first particle P1, and a second solid electrolyte particle as the second particle P2. Alternatively, a second solid electrolyte particle can be used as the first particle P1, an active material particle as the second particle P2, and a third solid electrolyte particle as the third particle P3. Furthermore, active material particles may be used as the first particle P1 and the second particle P2, and a second solid electrolyte particle as the third particle P3. In this case, the active material particles used for the first particle P1 and the second particle P2 may be of the same type or different types.

[0130] In the first, second, and fourth steps described above, a particle filling apparatus was described in which a magnetic head is formed using magnetic particles as a support material to fill the depressions on the surface of the substrate with particle material. However, the method of particle filling apparatus is not limited to this. Brush fibers can also be used as the support material. Alternatively, an elastic material whose surface is composed of an elastic material can also be used as the support material.

[0131] Figure 14(a)A schematically shows the configuration of a filling device 24c when brush fibers are used as the support material. The filling device 24c has a roller 2410 having brush fibers on its surface. The roller 2410 is a so-called brush roller, with brush fibers implanted on its surface. The material of the fibers constituting the brush fibers of the roller 2410 can be, for example, nylon, rayon, acrylic, vinylon, polyester, polyvinyl chloride, etc. Surface treatment may be applied to the surface of the fibers for the purpose of adjusting the electrostatic properties and rigidity.

[0132] As shown in Figures 14A and 14B, using brush fibers or elastic materials as the support eliminates the need to include magnetic particles in the filler and simplifies the configuration of the filling device. On the other hand, when magnetic particles are used as the support, there is greater freedom in the size and shape of the support than when using brush fibers or elastic materials. Also, in the case of magnetic particles, there is greater freedom in the movement of the support on the substrate. For these reasons, when magnetic particles are used as the support, particles such as the first particle P1 can be supplied to the substrate more efficiently, and the recesses on the substrate can be filled more efficiently. Furthermore, when a magnetic material is used as the support, even if the support deteriorates during the process, the support can be replenished or replaced without stopping the process.

[0133] In a method of filling recesses by rubbing a support material on which particles are carried, it is possible to supply more dispersed particles to the recesses compared to filling methods using regulating members such as blades, resulting in stable and dense filling. This advantage becomes more pronounced as the particle size of the particles being filled decreases, as the particles tend to aggregate more easily.

[0134] After arranging the particles in the manner described above, the particle coverage rate on the second substrate 11b (the ratio of the area of ​​the region where the particles are arranged to the total area of ​​the second substrate 11b) is preferably 60 area % or more, more preferably 70 area % or more, and even more preferably 80 area % or more.

[0135] In other words, the ratio of the area of ​​the region where the active material particles and / or the second solid electrolyte particles are located to the first resin substrate of the active material layer precursor is preferably 60 area % or more, more preferably 70 area % or more, and even more preferably 80 area % or more. Similarly, the ratio of the area of ​​the region where the first solid electrolyte particles are located to the second resin substrate of the interfacial bonding precursor is preferably 60 area % or more, more preferably 70 area % or more, and even more preferably 80 area % or more. The particle coverage rate can be measured by photographing the region where the particle layer is formed from the vertical direction of the substrate with an optical microscope and calculating the area ratio of the particles within that region using image processing software.

[0136] In addition to the particle placement technique described above, the first particles P1 may be placed on the second substrate 11b using a known particle placement technique, and the second particles P2 may be placed using the particle packing apparatus. Here, as a known particle placement technique, for example, electrophotography can be used. The particle placement technique described above and the known particle placement technique may be combined, or particles may be placed using only one of them.

[0137] <Method for Manufacturing Electrode Precursors> The electrode precursor is formed by laminating the active material layer precursor and the interfacial bonding precursor. The electrode precursor is manufactured by laminating the interfacial bonding precursor and the active material layer precursor prepared by the method described above. When laminating the interfacial bonding precursor and the active material layer precursor, it is preferable to laminate the active material layer precursor on top of the interfacial bonding precursor. Alternatively, the interfacial bonding precursor can also be laminated on top of the active material layer precursor. The interfacial bonding precursor and the active material layer precursor are laminated such that the interfacial bonding precursor is in contact with the electrolyte layer.

[0138] In other words, the method for manufacturing the electrode precursor preferably includes the following steps: (1) A step of forming an active material layer precursor by holding active material particles on a first resin substrate via a first adhesive portion; (2) A step of forming an interfacial bonding precursor by holding first solid electrolyte particles on a second resin substrate via a second adhesive portion; (3) A step of laminating the active material layer precursor and the interfacial bonding precursor so that they are in contact with each other.

[0139] Figure 15 is a schematic diagram showing the configuration of a laminate molding apparatus for manufacturing electrode precursors. The laminate molding apparatus includes transport devices 31 and 33 for transporting a substrate 11b (interfacial bonding precursor or active material layer precursor) on which a particle layer 12 is formed, and a stage 32 that can move vertically (in the direction indicated by the arrow in Figure 15) by an actuator (not shown). An electrode precursor can be manufactured by laminating an interfacial bonding precursor and an active material layer precursor on the stage 32.

[0140] Furthermore, as shown in Figure 15, a substrate 50 for stacking electrode precursors may be set in the stage 32 in advance, and electrode precursors can also be manufactured by stacking each precursor on the substrate 50. The substrate 50 is a garnet-type solid electrolyte sintered body Li, which is made by pre-sintering pellets formed by pressure molding solid electrolyte particles. ６．６ La ３ Zr １．６ Ta ０．４ O １２ Metal foils or metal plates that also serve as current collectors (LLZT) can be used. Known current collectors such as Al foil, SUS foil, platinum, or gold foil can be used as current collectors. Alternatively, an electrolyte precursor consisting only of solid electrolyte particles arranged on a resin substrate similar to that of the interfacial bonding precursor may be used.

[0141] The substrate 50 is preferably an electrolyte layer containing a solid electrolyte. When a solid electrolyte sintered body is used as the substrate 50, an interfacial bonding precursor is laminated on the solid electrolyte sintered body, and an active material layer precursor is laminated on the interfacial bonding precursor. That is, the solid electrolyte sintered body as the substrate and the interfacial bonding precursor are laminated in contact with each other. In other words, the electrode precursor is in contact with the interfacial bonding precursor and preferably further has an electrolyte layer containing a solid electrolyte. The electrolyte layer preferably contains solid electrolyte particles that have the same physical properties and composition as the first solid electrolyte contained in the interfacial bonding precursor.

[0142] Furthermore, the solid electrolyte sintered body and electrolyte precursor may have a negative electrode or negative electrode precursor formed on the side opposite to the side on which the electrode precursor is stacked. The electrolyte precursor and negative electrode precursor can be manufactured by the same process as the first and second steps described above, and optionally the third and fourth steps.

[0143] The following describes a method for manufacturing electrode precursors, using a garnet-type solid electrolyte sintered body (LLZT) as the substrate 50 and stacking each precursor on the substrate as an example. The transport device 31 transports the substrate 11b having a particle layer 12 formed using a particle placement device to the stage 32. Examples of transport devices 31 capable of transporting the substrate 11b include a belt conveyor, rollers, and a robotic arm.

[0144] A garnet-type solid electrolyte sintered body (LLZT) is pre-placed on the stage 32 as the substrate 50. When the substrate 11b is transported to the stage 32 by the transport device 31, the stage 32 moves vertically (downward) by the thickness of the substrate 11b and the particle layer 12. By repeating the transport by the transport device 31 and the movement of the stage 32, multiple substrates 11b with the particle layer 12 formed on them are stacked on the substrate 50.

[0145] At this time, the electrode precursor 15 is formed by stacking interfacial bonding precursors and then stacking active material layer precursors on top of the interfacial bonding precursors. The number of interfacial bonding precursors and active material layer precursors is adjusted and stacked according to the active material particles, solid electrolyte particles, and desired electrode capacity used. In other words, an electrode precursor can be formed by stacking multiple interfacial bonding precursors and then stacking multiple active material layer precursors.

[0146] As described above, it is preferable that the base material 11b also has an adhesive portion on the back surface of the surface on which the particle layer 12 is formed. This adhesive portion allows the base materials to adhere to each other, increasing the strength of the laminate and suppressing displacement between the base materials. Furthermore, the particle layers 12 between the base materials are sandwiched between the upper and lower adhesive portions, which suppresses displacement during each process and during storage of the laminate. In other words, it is preferable that the interfacial bonding precursors adhere to each other, the active material layer precursors adhere to each other, and the interfacial bonding precursors adhere to the active material layer precursors via the adhesive portion of the resin base material. Furthermore, it is preferable that the electrode precursor, which consists of the interfacial bonding precursor and the active material layer precursor, and the substrate 50 adhere to each other via the adhesive portion of the resin base material.

[0147] The adhesive portion can be formed by applying an adhesive using a coating apparatus (not shown) before lamination. Alternatively, a substrate may be used in which an adhesive has been applied to the surface in advance and the coated surface has been covered with a protective film, and the protective film may be peeled off before lamination.

[0148] Furthermore, the electrode precursor may include a holding portion for maintaining the stacked state of the active material layer precursor and the interfacial bonding precursor. For example, a holding portion can be formed by vacuum-packaging the electrode precursor, which consists of a stacked active material layer precursor and an interfacial bonding precursor, in a laminate film. By providing a holding portion in the electrode precursor, displacement between the substrates of each stacked precursor can be prevented, and the active material particles and solid electrolyte particles are sandwiched in the stacking direction and firmly fixed. This makes it possible to obtain an electrode with a three-dimensional structure in which the active material particles and solid electrolyte particles are densely arranged. Also, as described above, the stacked state of the electrode precursor can be maintained by forming adhesive portions on the back surfaces of the first resin substrate and the second resin substrate. In this case, the adhesive portion functions as a holding portion.

[0149] The interface bonding precursor and the active material layer precursor may be stacked by inverting the substrate 11b, as shown in Figure 16. That is, the particle layer 12 may be positioned below the substrate 11b before stacking each precursor. Furthermore, a portion of the stack may be inverted. That is, a portion of the stack formed by stacking the interface bonding precursor and the active material layer precursor may have parts where the substrates 11b are in contact with each other, or parts where the particle layers are in contact with each other.

[0150] Furthermore, it is preferable to perform an electrostatic discharge process on the interfacial bonding precursor and the active material layer precursor immediately before lamination. The substrate 11b is easily charged, and electrostatic repulsion and adsorption forces are generated between the substrates when lamination occurs. As a result, the substrates may peel off or gaps and wrinkles may form between the substrates when lamination occurs. Therefore, by performing an electrostatic discharge process in advance, the substrates can be closely adhered to each other, and the lamination can be performed while maintaining the density of the particle arrangement pattern.

[0151] In the static elimination process, it is preferable to eliminate static electricity non-contact using an electrostatic elimination blower or the like. Furthermore, after all the precursors are stacked and the electrode precursor 15 is formed, it is preferable to have a degassing process to reduce the gaps between the substrates. In the degassing process, it is preferable to degas using a vacuum device or a vacuum packaging machine.

[0152] The electrode precursor described above can also be used to manufacture electrode structures applied to secondary batteries. The electrode structure comprises an electrolyte layer, an active material layer, and an interfacial bonding layer formed between the electrolyte layer and the active material layer. That is, the electrode structure is a structure obtained by firing the electrode precursor having the electrolyte layer described above and removing the resin substrate. The electrolyte layer contains a solid electrolyte. A garnet-type solid electrolyte is preferred as the solid electrolyte, and LLZT is more preferred.

[0153] The active material layer contains active material particles. Preferably, the active material particles include the active material particles contained in the active material layer precursor described above. Furthermore, the active material layer preferably contains solid electrolyte particles. Preferably, the solid electrolyte particles include the second solid electrolyte particles contained in the active material layer precursor described above. That is, the active material layer preferably contains active material particles and second solid electrolyte particles. More preferably, the active material layer contains LCO as the active material particles. Furthermore, it is preferable that the second solid electrolyte particles include at least one selected from the group consisting of LLZT, Bi-LLZT, LYbBO, and LBO. The active material particles and the second solid electrolyte particles contained in the active material layer are arranged so that they are in contact with the interfacial bonding layer.

[0154] The interfacial bonding layer formed between the electrolyte layer and the electrode layer is preferably less thick than the electrolyte layer. The thickness of the interfacial bonding layer is less than or equal to the thickness of the particles contained in the interfacial bonding precursor. If solid electrolyte particles are arranged in approximately a single layer on the interfacial bonding precursor, the thickness of the interfacial bonding layer is less than or equal to the particle size (median diameter by volume) of the solid electrolyte particles. The thickness of the interfacial bonding layer is preferably 5 μm or less, and more preferably 1 μm or less.

[0155] The thickness of the electrolyte layer is not particularly limited, but is preferably 10 to 500 μm. The thickness of the active material layer is not particularly limited, but is preferably 1 to 100 μm. The thickness of the active material layer is the thickness of the particles contained in the active material layer precursor. When the active material particles and solid electrolyte particles are arranged in approximately a single layer on the active material layer precursor, the particle size (volume-based median diameter) of the active material particles and solid electrolyte particles becomes the thickness of the active material layer. The interface bonding layer preferably contains a solid electrolyte with a lower softening point temperature than the solid electrolyte contained in the electrolyte layer. For example, when LLZT is used as the solid electrolyte X, the interface bonding layer preferably contains Bi-LLZT.

[0156] The active material layer in the electrode structure is preferably formed as a particle layer. That is, the electrode structure preferably has at least one particle layer. There may be multiple particle layers. For example, the number of particle layers can be 1 to 50. It is particularly preferable that all particle layers have a periodic pattern structure.

[0157] The active material layer of the electrode structure manufactured by the method described above preferably has a pattern structure with periodicity in a predetermined direction, corresponding to the in-layer arrangement of the active material particles and the second solid electrolyte particles within the particle layer. The predetermined direction within the particle layer is not particularly limited. The predetermined direction within the particle layer is, for example, one direction within the particle layer. The predetermined direction may be, for example, the stacking direction of the electrode precursor and the particle layer, or it may be a direction perpendicular to the stacking direction. If a pattern structure is formed in the predetermined direction within the particle layer, the active material particles and the solid electrolyte particles are more likely to be adjacent to each other, and electron conduction paths and ion conduction paths are more likely to be formed, so a secondary battery with excellent charge-discharge characteristics can be obtained. The predetermined direction within the particle layer is preferably a direction perpendicular to the stacking direction of the electrode precursor and the particle layer.

[0158] The above periodic pattern structure preferably includes at least one of a sea-island pattern, a houndstooth pattern, a two-dimensional grid pattern, or a one-dimensional grid pattern (line pattern). The pattern structure is more preferably a line pattern or a sea-island pattern.

[0159] <Method for Manufacturing an Electrode Structure> An example of a method for manufacturing an electrode structure will be described in detail below with reference to the drawings. The method for manufacturing an electrode structure has the following four steps (Step I, Step II, Step III, Step IV): (1) Lamination step (Step I) (T100 in Figure 17) in which the electrolyte layer and the electrode precursor are laminated so that the interfacial bonding precursor is in contact with the electrolyte layer (2) First heating step (Step II) (T101 in Figure 17) in which the laminate of the electrolyte layer and the electrode precursor is heated to a temperature above the thermal decomposition temperature of the resin substrate to form a calcined body (3) Pressurization step (Step III) (T102 in Figure 17) in which the calcined body is pressurized at least in the lamination direction (4) Second heating step (Step IV) (T103 in Figure 17) in which the calcined body is heated to a temperature above the softening point temperature of the first solid electrolyte particles. Steps I to IV will be described in detail below with reference to Figure 18.

[0160] (Step I) Step I is a lamination step in which the above-mentioned electrode precursor is laminated on an electrolyte layer containing a solid electrolyte such that the interfacial bonding precursor is in contact with the electrolyte layer. The substrate 50 is a solid electrolyte layer containing a solid electrolyte. The substrate 50 is, for example, a sintered body of a garnet-type solid electrolyte. For example, by using a sintered body of a garnet-type solid electrolyte as a substrate in the above-mentioned method for manufacturing the electrode precursor, the electrode precursor 15 can be laminated on an electrolyte layer, which is a substrate 50 containing a solid electrolyte, such that the interfacial bonding precursor is in contact with the electrolyte layer.

[0161] (Step II) Step II is a step in which the substrate 50 and electrode precursor laminated in Step I are calcined using a sintering apparatus to remove the resin substrate contained in the electrode precursor. Step II is a first heating step in which the laminate of the electrolyte layer containing a solid electrolyte and the electrode precursor is heated to a temperature above the thermal decomposition temperature of the first resin substrate and the second resin substrate to form a calcined body having an electrolyte layer 50, an interface bonding particle layer 51 and an active material particle layer 52. In Step II, the first resin substrate is removed from the active material layer precursor and an active material particle layer 52 containing active material particles is formed. The active material particle layer 52 may also contain second solid electrolyte particles. Similarly, the second resin substrate is removed from the interface bonding precursor and an interface bonding particle layer 51 containing first solid electrolyte particles is formed.

[0162] Figure 18 is a schematic diagram showing the configuration of a sintering apparatus. The sintering apparatus includes a transport device 41 for transporting electrode precursors 15 laminated on a substrate 50, and a heating furnace 42 for heating the electrode precursors 15. The transport device 41 transports the substrate 50 and electrode precursors 15 from the laminate molding apparatus to the heating furnace 42. The transport device 41 is preferably a device capable of transporting electrode precursors 15, similar to the transport device 31. Examples of devices capable of transporting electrode precursors 15 include belt conveyors, rollers, and robot arms.

[0163] The heating furnace 42 is a furnace for heating the substrate 50 and the electrode precursor 15. The heating furnace 42 includes a heating means 421, a pressurizing means 422, and an atmosphere adjustment means 423. As the heating furnace 42, a firing furnace or tubular furnace used for firing ceramics can be used. The pressurizing means 422 pressurizes the substrate 50 and the electrode precursor 15 being heated in the heating furnace 42, or pressurizes the substrate 50 and the electrode precursor 15 before and after heating. Preferably, the pressurizing part of the pressurizing means 422 that pressurizes the electrode precursor 15 is made of a porous material that allows gas to pass through easily. The atmosphere adjustment means 423 includes an atmosphere gas supply means 423a and a depressurizing means 423b, and adjusts the atmosphere gas in the processing space of the heating furnace 42.

[0164] The atmospheric gas in the processing space of the heating furnace 42 is an oxidizing atmosphere in order to remove the resin substrate. In particular, heating with pure oxygen or purified air with a low dew point is preferred. This is because the garnet-type solid electrolyte reacts with moisture and forms a high-resistance lithium carbonate layer (Li) on the surface. ２ CO ３ This is to prevent the formation of spores. The dew point should be adjusted to -20°C or lower, preferably -40°C or lower, and more preferably -70°C or lower.

[0165] Figure 19 shows the results of thermogravimetric analysis (TG) of PET with an adhesive surface that can be used as a second resin substrate in the manufacture of an electrode precursor. Weight loss (thermal decomposition) begins around 300°C, which is above the melting point of the resin substrate (approximately 260°C). In the first heating step, it is preferable to heat the electrode precursor 15 at a temperature above the thermal decomposition temperature of the resin substrate, and to heat it at a temperature below the thermal decomposition temperature of each particle layer in the electrode precursor 15.

[0166] In a sintering apparatus, when thermogravimetric analysis is performed by raising the temperature from room temperature (25°C) at a rate of 5°C / min under the heating atmosphere (typically pure oxygen), it is preferable to heat the second resin substrate to a temperature above the temperature at which its weight becomes 70% of its initial weight. Specifically, for example, when PET is used as the resin substrate, it is preferable that the heating temperature in the first heating step be 385°C or higher. More preferably, it is preferable to heat the second resin substrate to a temperature above the temperature at which its weight becomes 50% of its initial weight, and even more preferably to heat it to a temperature above the temperature at which its weight becomes 20% of its initial weight. Specifically, for example, it is preferable to heat it to 400°C or higher, and more preferably to 450°C or higher. This makes it possible to shorten the time required to remove the resin substrate and to increase the removal rate of the resin substrate.

[0167] Thus, when removing the resin substrate by heating using a sintering apparatus, it is preferable that the active material particles and solid electrolyte particles contained in the electrode precursor have a higher thermal decomposition temperature than the resin substrate. By firing at a temperature above the thermal decomposition temperature of the resin substrate, only the first resin substrate can be removed from the active material layer precursor to form an active material particle layer 52 containing active material particles, and only the second resin substrate can be removed from the interface bonding precursor to form an interface bonding particle layer 51 containing solid electrolyte particles. Generally, inorganic materials tend to have higher thermal decomposition temperatures than organic materials, so it is preferable that the active material particles and solid electrolyte particles are inorganic materials, and the material of the resin substrate is an organic material such as resin. Furthermore, when removing the resin substrate by heating using a sintering apparatus, it is preferable that the active material particles are made of a material that has a softening point temperature higher than the thermal decomposition temperature of the resin substrate.

[0168] In the sintering apparatus, it is preferable to remove 90% or more by weight of the resin substrate in the electrode precursor 15 by heating, more preferably 95% or more by weight, and even more preferably 97% or more by weight. In this case, it is preferable that the resin substrate is burned or gasified and released to the outside as a gas. At this time, when the resin substrate gasified by thermal decomposition is released to the outside of the laminate as a gas, it may push up the particle layer formed on the resin substrate and disrupt its shape. In that case, it is preferable to reduce the heating rate or reduce the thickness of the resin substrate used for the electrode precursor to reduce the effect on the particle layer.

[0169] Specifically, the thickness (μm) of the resin substrate used for the electrode precursor is preferably 20 times or less the thickness of the particle layer on the resin substrate, more preferably 10 times or less, and even more preferably 5 times or less. The thickness of the resin substrate is preferably 1 to 30 μm, and more preferably 2 to 15 μm. 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 exists, when the resin substrate surface is (x, y) and the lamination direction of the resin substrate is (z).

[0170] The thickness of the particle layer on the resin substrate and the resin substrate itself are calculated by observing the cross-section of the electrode precursor 15 using a FIB-SEM, determining the particle location (x, z) using image processing software, and finding the difference between the maximum and minimum values ​​of z, with the resin substrate surface as x and the layering direction of the resin substrate as z. Methods for identifying the active material particles, solid electrolyte particles, resin substrate, and adhesive portion during SEM observation using a FIB-SEM include elemental composition analysis using EDS. The FIB-SEM imaging conditions, required image area, and image processing methods will be described later. In addition to FIB-SEM, the thickness of the particle layer and resin substrate may also be measured using a digital thickness gauge or the like.

[0171] In the first heating step, the temperature at which the electrode precursor 15 is heated is preferably 200°C to 1000°C, more preferably 300°C to 800°C, and even more preferably 400°C to 700°C. As mentioned above, when PET is used as the resin substrate, it is preferable to heat it to 385°C or higher. The heating time in the first heating step (the time at which the temperature is maintained) is preferably 30 minutes or more, and more preferably 1 hour or more. There is no particular upper limit, but it may be, for example, 3 hours or less, or 2 hours or less. For example, it is preferable to maintain the temperature at the above temperature for 30 minutes to 3 hours, and more preferably 1 hour to 2 hours.

[0172] The thermal decomposition temperature is the temperature at which the weight of a material begins to decrease when the temperature is gradually increased under the heating atmosphere in a sintering apparatus. Therefore, by heating the electrode precursor 15 at a temperature above the thermal decomposition temperature of the resin substrate, the resin substrate in the electrode precursor 15 can be decomposed and its weight reduced, allowing the resin substrate to be removed from the electrode precursor 15 and a calcined body to be formed.

[0173] (Step III) Step III is a pressurizing step in which the calcined body formed in Step II is pressurized. Step III fills the voids created by the removal of the resin substrate with a particle layer, densifying the particle layer and increasing its strength. Figure 20 is a schematic diagram showing the structure of a calcined body containing an electrolyte layer 50, an interfacial bonding particle layer 51, and an active material particle layer 52, which is pressurized by an isotropic pressurizing device.

[0174] A release plate 53 is laminated onto the active material particle layer 52 of the calcined body to form a laminate. The laminate is then wrapped in a laminate film 54 and vacuum-packed. By pressurizing the vacuum-packed laminate with an isotropic pressurizing device, the particle layer can be densified and its strength improved. The material of the laminate film is not particularly limited, but it is preferable to use, for example, nylon, polyethylene, or an aluminum laminate film made by laminating polyethylene or the like onto an aluminum foil or aluminum vapor-deposited film as a base material. For example, Copack (product name) manufactured by Asahi Kasei Pax can be used as the laminate film.

[0175] The release plate 53 is placed between the active material particle layer and the laminate film to prevent adhesion between the active material particle layer and the laminate film. Alternatively, the pre-fired body may be packaged in the laminate film and vacuum-sealed without using the release plate 53. It is preferable to select a material for the release plate 53 that has low adhesion to the active material particle layer. For example, nichrome foil can be used. Pressurization using an isotropic pressurizing device is performed at 100 MPa or more, more preferably 150 MPa or more, for 1 to 3 minutes. After pressurization, the laminate film 54 is opened and the pre-fired body is removed.

[0176] In addition, in step III, existing pressurizing devices other than isotropic pressurizing devices can be used. For example, a uniaxial pressurizing device, a roller pressurizing device, or the pressurizing means 422 of a sintering processing device may be used. The pressurizing means 422 pressurizes the electrode precursor from above. Even when using the pressurizing means 422, it is preferable to form the laminate as described above and pressurize after vacuum packaging. In other words, step III is a pressurizing step in which the calcined body is pressed at least in the stacking direction. The stacking direction corresponds to the direction in which the electrolyte layer and the electrode precursor are stacked in the stacking step (step I).

[0177] (Step IV) Step IV is a step in which a laminate 55 consisting of an interfacial bonding particle layer 51 and an active material particle layer 52 laminated on the electrolyte layer 50 is fired using a sintering apparatus. The above laminate is a pre-fired body that has been removed from the laminate film after the pressurizing step and the release plate has been removed. That is, Step IV is a second heating step in which the pre-fired body is heated to a temperature above the softening point temperature of the first solid electrolyte particles. The sintering apparatus may be the same as that used in Step II, or a different sintering apparatus may be used. The following explanation will use an example where the same sintering apparatus as in Step II is used.

[0178] Figure 21 is a schematic diagram showing the configuration of the sintering apparatus. The sintering apparatus includes a conveying device 41 for conveying the calcined body 55 after the pressurizing process, and a heating furnace 42 for heating the electrode precursor 15. The conveying device 41 conveys the calcined body 55 from the pressurizing device in process III to the heating furnace 42 described above. The conveying device 41 is preferably a device capable of conveying the calcined body 55, similar to the conveying device 31. Examples of devices capable of conveying the calcined body 55 include a belt conveyor, rollers, and a robotic arm. After that, the main firing is performed using the same heating furnace 42 as in process II described above.

[0179] In the second heating step, the heating temperature when heating the calcined body 55 is a temperature equal to or higher than the softening point temperature of the solid electrolyte contained in the interfacial bonding particle layer (solid electrolyte particles contained in the interfacial bonding precursor). Here, the softening point temperature of the solid electrolyte refers to some or all of the solid electrolyte particles contained in the interfacial bonding precursor. Step IV is a step of heating the calcined body after the pressurizing step at a temperature equal to or higher than the softening point temperature of the second solid electrolyte particles.

[0180] By setting the heating temperature in the second heating step to a temperature above the softening point of the solid electrolyte constituting the interfacial bonding particle layer, some or all of the solid electrolyte particles contained in the interfacial bonding particle layer melt, and a good interface can be formed between the substrate and the active material particle layer. There is no particular upper limit, but it is preferable that the temperature is below the temperature at which the active material particles or solid electrolyte particles decompose or react with each other to form a highly resistant reaction layer. In other words, it is preferable that some or all of the solid electrolyte particles contained in the interfacial bonding particle layer melt in the second heating step. By melting the solid electrolyte particles, an interfacial bonding layer 51' can be formed between the substrate and the active material particle layer.

[0181] Specifically, the heating temperature in the second heating step is preferably, for example, 550°C to 1200°C. More preferably, it is preferably 650°C to 1000°C, and even more preferably 750°C to 950°C. The heating time in the second heating step (the time at which the heating temperature is maintained) is preferably 30 minutes or more, and even more preferably 1 hour or more. There is no particular upper limit, but it may be, for example, 15 hours or less, or 10 hours or less. For example, it is preferable to maintain the temperature at the above temperature for 30 minutes to 15 hours or 1 hour to 10 hours.

[0182] In the second heating step, a thin interfacial bonding layer 51' is formed at the interface between the substrate 50 and the active material particle layer 52 in the laminate 55. At the same time, some or all of the second solid electrolyte particles contained in the active material particle layer 52 melt, forming an active material layer 52'. As a result, an electrode layer 56 can be formed in which the active material particles and solid electrolyte particles are in close contact. That is, the electrode layer 56 has an interfacial bonding layer 51' and an active material layer 52'.

[0183] The active material layer can be used as a positive electrode layer if it contains a positive electrode active material, and as a negative electrode layer if it contains a negative electrode active material. By the manufacturing method described above, an electrode structure can be manufactured having an electrolyte layer, a positive electrode layer or a negative electrode layer (electrode layer), and an interfacial bonding layer formed between the electrolyte layer and the electrode layer.

[0184] In addition to the manufacturing method described above, it is also possible to manufacture an electrode structure by firing only the electrode precursor to form an electrode, stacking the electrode on a solid electrolyte layer, and re-firing it to join the interface. However, from the viewpoint of productivity and other factors, it is preferable to manufacture the electrode structure by the above-described steps I to IV.

[0185] <Method for Manufacturing Secondary Batteries> There are no particular limitations on the method for manufacturing secondary batteries, and several methods are possible, but a few examples will be given. In the method for manufacturing the electrode structure, the case in which a positive electrode layer 56 is formed on a solid electrolyte sintered body SE (LLZT) as a substrate 50 will be explained as an example. In the above case, the secondary battery is manufactured in a glove box or dry room with a dew point of -60°C or lower.

[0186] Figure 22 shows an example of a secondary battery configuration. The active material layer 52' ​​of the positive electrode layer 56 manufactured by the method described above is laminated on the positive electrode current collector 61 so as to be in contact with it, and the negative electrode 62 is laminated on the side of the substrate 50 opposite to the side on which the positive electrode layer 56 is laminated. The negative electrode current collector 63 is laminated on the side of the negative electrode 62 opposite to the side that is in contact with the substrate 50. The secondary battery can be manufactured using an electrode structure having an electrolyte layer, an electrode layer, and an interfacial junction layer formed between the electrolyte layer and the electrode layer, manufactured by the method described above. The secondary battery has at least the electrode structure, a positive electrode current collector, a negative electrode, and a negative electrode current collector. Figure 61A shows an evaluation system for reducing the effects of external disturbances such as atmosphere and ambient light on the prototype secondary battery. Figure 61B shows a schematic configuration of the electrode precursor before it is incorporated into the prototype secondary battery shown in Figure 61A.

[0187] A method for manufacturing a secondary battery includes (1) the step of electrically connecting a positive electrode current collector and an electrode structure manufactured by the method described above; (2) the step of electrically connecting the electrode structure and a negative electrode containing a negative electrode active material on the side having the electrolyte layer; and (3) the step of electrically connecting the negative electrode and the negative electrode current collector.

[0188] To reduce the interfacial resistance between the substrate 50 and the negative electrode 62, the substrate 50 may be subjected to a known pretreatment beforehand. For example, one method is to polish the surface of the substrate 50 opposite to the side in contact with the positive electrode layer 56 with abrasive paper and form an Au layer by a vacuum process such as sputtering. That is, an interfacial bonding layer (not shown) to reduce interfacial resistance may be provided between the electrolyte layer 50 and the negative electrode 62. As the interfacial bonding layer, a metal that alloys with lithium is preferred, and materials containing Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, and Au are preferred.

[0189] The negative electrode 62 may be formed on the surface of the substrate 50 opposite to the side in contact with the positive electrode layer 56 in the same manner as the positive electrode layer. Alternatively, the negative electrode may be laminated on the negative electrode current collector 63 as a substrate, formed in the same manner as the positive electrode layer. That is, the negative electrode 62 may be manufactured from a negative electrode precursor having a negative electrode active material layer precursor and an interfacial bonding precursor. Furthermore, the negative electrode may be formed by known means such as a coating process or a vacuum process.

[0190] The following explanation will describe an example in which metallic Li foil is used as the negative electrode 62. As described above, the positive electrode current collector 61, positive electrode layer 56 (active material layer 52' ​​and interface bonding layer 51'), substrate 50, Au layer as interface bonding layer, metallic Li foil as the negative electrode 62, and negative electrode current collector 63 are laminated in that order.

[0191] Subsequently, the laminate-type secondary battery can be manufactured by vacuum-packing the aluminum laminate film so that the extraction electrodes (tabs) that have been previously welded to each current collector are positioned outside the aluminum laminate film, and then pressurizing it with an isostatic pressurizing device. The pressurizing with the isostatic pressurizing device is performed at 100 MPa or more, more preferably 150 MPa or more, for about 1 minute.

[0192] Similarly, a coin-type secondary battery can be manufactured by packaging the positive electrode current collector, positive electrode layer, substrate, negative electrode, and negative electrode current collector inside a coin case. In addition to metallic Li foil, the negative electrode 62 can be made of indium, tin, aluminum, or other metal foils that alloy with lithium. The negative electrode 62 may also be directly molded onto the surface of the current collector or electrolyte sintered body by a vacuum process such as sputtering.

[0193] <Secondary Battery> The secondary battery manufactured by the above-described manufacturing method comprises at least an electrolyte layer, a positive electrode layer in contact with one side of the electrolyte layer, and a negative electrode layer in contact with the other side of the electrolyte layer opposite to the aforementioned side. The positive electrode layer includes a positive electrode active material layer 52' ​​and an interfacial bonding layer 51', and the interfacial bonding layer is arranged in contact with one side of the electrolyte layer. As described above, the negative electrode layer may similarly include a negative electrode active material layer 52' ​​and an interfacial bonding layer 51'. In such a case, the interfacial bonding layer of the negative electrode is arranged in contact with the other side of the electrolyte layer.

[0194] The secondary battery may include a current collector as needed. The current collector is positioned to contact the side of the electrode (positive electrode layer, negative electrode layer) opposite to the side that contacts the electrolyte layer. If the electrode has an active material layer 52' ​​and an interfacial bonding layer 51', the current collector is positioned to contact the active material layer 52'.

[0195] The present invention will be described in more detail below using examples, but this disclosure is not limited to these examples. In the following examples, unless otherwise specified, parts are given in parts by mass. Figures 56A to 56E are schematic diagrams of the electrode molding method. Figures 57A to 57F are schematic diagrams of the precursor preparation method. Details will be described below.

[0196] Table 2 shows the manufacturing conditions for the electrode precursor in each example. The substrate 50 is a garnet-type solid electrolyte Li ６．６ La ３ Zr １．６ Ta ０．４ O １２ This is a pellet-shaped ion conductor made by sintering (LLZT) (LLZT sintered body manufactured by Toyoshima Seisakusho, Φ10 mm / d1 mm).

[0197] An electrode precursor was molded using the electrode precursor manufacturing method described above. Specifically, active material particles and / or solid electrolyte particles were placed on a resin substrate using the particle filling apparatus shown in Figure 3 and the particle transfer apparatus shown in Figure 6 to produce an interface bonding precursor 51 and an active material layer precursor 52, respectively (Figure 56A). Using the apparatus shown in Figure 15, the interface bonding precursor 51 was laminated on the substrate 50, and then the active material layer precursor 52 was laminated on the interface bonding electrode precursor 51 to produce an electrode precursor on the substrate 50 (Figure 56B).

[0198] A surface textured pattern 111a was formed on the surface of the first substrate 11a used in the first step. Line patterns, uniform dispersion patterns (sea-island patterns), and uniform aggregation patterns (sea-island patterns) were formed as the surface textured patterns.

[0199] Figure 23 is an SEM image of the active material layer precursor. The line pattern shows active material particles (first particles P1) and solid electrolyte particles (second particles P2) arranged adjacent to each other in a line (Figure 23A). The uniform dispersion pattern is a sea-island pattern, where the active material particles (first particles P1) are uniformly dispersed (islands), and solid electrolyte particles (second particles P2) are arranged around them (sea) (Figure 23B). The uniform aggregation pattern is similarly a sea-island pattern, but the active material particles (first particles P1) are uniformly aggregated (islands) (Figure 23C).

[0200] The line pattern is formed so that the line width (opening width of the recess) is 7 μm, and the number of active material particles (first particles P1) is 3 or less per line width. The uniform dispersion pattern is formed so that the hole diameter (opening width of the recess) is 6 μm, and approximately 3 active material particles (first particles P1) are uniformly dispersed. The uniform aggregation pattern is formed so that the hole diameter (opening width of the recess) is 15 μm, and 8 or more active material particles (first particles P1) are uniformly aggregated.

[0201] PET (thickness: 2 μm) was used as the resin substrate 11b for the interfacial bonding precursor and the active material layer precursor. The softening point temperature of the resin substrate was 80°C and the melting point was 260°C. An acrylic adhesive was applied to the surface of the resin substrate to form an adhesive layer.

[0202] The first particle P1 and the second particle P2 (first solid electrolyte particle) used as the interfacial bonding precursor are lithium borate LBO (LBO particles manufactured by Toyoshima Seisakusho), Li ５．９ Yb ０．８１ La ０．０９ Zr ０．１ (BO ３ ) ３ (Our own LYbBO particles) and Bi-doped LLZT (NIMS-made Bi-LLZT particles) are produced by doping LLZT with Bi ions to lower the sintering temperature of the LLZT. When different particles are used in combination as the first particle P1 and the second particle P2, they are arranged in a line pattern.

[0203] In the production of the active material layer precursor, positive electrode active material particles and / or solid electrolyte particles (second solid electrolyte particles, third solid electrolyte particles) were used as the first particle P1, second particle P2, and third particle P3 in the combination shown in Table 2. Furthermore, these particles were arranged on the first resin substrate so that the LCO density was as shown in Table 2. The LCO density was calculated using the following formula: LCO density (mg / cm³) ２ ) = (Mass of LCO particles arranged on one active material layer precursor (mg)) / (Area of ​​the region on the first resin substrate where the particles are arranged (cm²)) ２ ))

[0204] Lithium cobalt oxide LCO (LCO particles) (Cellseed C-5H, manufactured by Nippon Chemical Industrial Co., Ltd.) was used as the positive electrode active material particles. The following solid electrolyte particles were used: LBO particles (manufactured by Toyoshima Seisakusho), LYbBO particles (manufactured in-house), LLZT (LLZT particles, manufactured by Toyoshima Seisakusho), and Bi-LLZT particles (manufactured by NIMS). As an example, a figure showing the sintering temperature dependence of TG-DTA (Figure 59A) and ionic conductivity (Figure 59B) of LYbBO is shown. The ionic conductivity and softening point temperature of the active material particles and solid electrolyte particles are as shown in Table 1. The softening point temperature of the resin substrate (PET) was 80°C and the melting point was 260°C.

[0205] The active material layer precursor was manufactured using the first substrate 11a having the aforementioned uneven pattern, with the arrangement pattern changed as shown in Table 2. When the same particles were used as the first particle P1, second particle P2, and third particle P3, the same particles were arranged on the surface of the active material layer precursor, and therefore no particle pattern was observed (indicated as "solid" in Table 2).

[0206] The interfacial bonding precursor was used individually or by stacking multiple interfacial bonding precursors with different particle arrangements. The active material layer precursor was used by stacking one to three layers. Both the interfacial bonding precursor and the active material layer precursor underwent a static elimination process and a degassing process before stacking. As shown in Table 2, the interfacial bonding precursor and the active material layer precursor were stacked on the substrate 50 (LLZT) in the order of interfacial bonding precursor 1, interfacial bonding precursor 2, and active material layer precursor to produce an electrode precursor having an electrolyte layer containing LLZT. In the table, the coverage rate indicates the ratio of the area where particles are placed to the total area of ​​the resin substrate. In Examples 1 to 8 and Comparative Examples 1 to 8, the substrate used was the aforementioned LLZT (thickness 1 mm). All line patterns were formed so that the line width was 7 μm.

[0207] <Method for Manufacturing Electrode Structures> Using the substrate and electrode precursor manufactured by the method described above, electrode structures were manufactured by the method described above. In step II, the electrode precursor and substrate were calcined to remove the resin substrate. The calcination temperature was 510°C and the calcination time was 1 hour, and the calcination was carried out in a pure oxygen atmosphere (Figure 56C). Subsequently, step III was performed to pressurize the calcined electrode precursor. For the substrate (LLZT) on which the interfacial bonding particle layer BPL and the active material particle layer APL were formed by calcination, a release plate RP (Nichrome foil manufactured by Nilaco) was laminated onto the active material particle layer APL. Subsequently, the substrate, interfacial bonding particle layer, active material particle layer and release plate were packaged using a laminate film LF (Copack manufactured by Asahi Kasei Pax) and vacuum packaged using a vacuum packaging machine (manufactured by Tosei). After vacuum packaging, the entire structure was pressurized at 196 MPa for 1 minute using an isotropic pressurizing device (CIP manufactured by Nikkiso) (Figure 56D). After step III, the final firing (step IV) was performed using a sintering apparatus to obtain an electrode structure in which the electrode (positive electrode) and electrolyte layer were integrated (Figure 56E). Table 3 shows the conditions for the final firing of the electrode structure in each example.

[0208]

[0209] <Method for Manufacturing Secondary Batteries> Secondary batteries were manufactured using the manufactured electrode structures. Table 4 shows the configuration of secondary batteries in each example. The positive electrode current collector was aluminum foil (Niraco, d20μm), the negative electrode was Li foil (Honjo Metal, Φ8mm, d50μm), and the negative electrode current collector was copper foil (Niraco, d20μm). The constituent materials of the secondary battery were laminated in the order of positive electrode current collector, electrode structure, negative electrode, and negative electrode current collector. The laminated materials were packed in aluminum laminate film (Hosen) and vacuum-packed using a vacuum packaging machine (Tosei). The vacuum-packed aluminum laminate film was pressurized at 196 MPa for 1 minute using an isotropic pressurizing device (Nikkiso CIP) to obtain a secondary battery.

[0210] In examples where LYbBO and LBO were used as interfacial bonding precursors, it was confirmed that the thickness of the interfacial bonding layer was approximately 300 nm. Furthermore, it was confirmed that in all examples, the thickness of the interfacial bonding layer was thinner than that of the electrolyte layer.

[0211] Table 5 shows the pattern evaluation results of the active material layer precursor, the evaluation results of the presence or absence of the interfacial bonding precursor, and the charge / discharge measurement results of the secondary battery (charge capacity and discharge capacity for each rate) and evaluation results for each example.

[0212] In Table 5, regarding the pattern evaluation of the active material layer precursor, "○" indicates that a pattern structure was confirmed. Note that pattern evaluation was not performed for examples and comparative examples that were composed of a common group of particles and where it was clear that no pattern structure was formed. "-" indicates that evaluation was not performed. Regarding the evaluation of the presence or absence of an interfacial bonding precursor, "○" indicates that the interfacial bonding precursor was identified, and "×" indicates that the interfacial bonding precursor was not identified.

[0213] The evaluation methods for the examples and comparative examples are described below. <Pattern evaluation method for the active material layer precursor> The pattern evaluation of the active material layer precursor was performed by evaluating the presence or absence of a periodic pattern structure, and the determination was made as follows. First, an EDX mapping image of Co in the positive electrode active material LCO was obtained based on an SEM image taken from above the active material layer precursor using the method described later. If a peak was detected when the obtained image was subjected to a two-dimensional Fourier transform, it was determined that the particle arrangement had a periodic structure, and therefore a pattern structure was present. On the other hand, if no peak was observed and the pattern was uniform, it was determined that there was no pattern structure.

[0214] (SEM-EDX Observation of Electrode Precursors and Electrode Structures) The method for SEM-EDX measurement of the surfaces of electrode precursors and electrode structures is described below. Surface observation of electrode precursors and electrode structures was performed using a scanning electron microscope (SEM), and the surface of the particle layer was photographed from the stacking direction. The electron microscope used was a Carl Zeiss ULTRA55, and images were taken under the following conditions. The imaging area was the area in which the particle layer could be observed. Detector: SE2 (secondary electron image) Observation conditions: Acceleration voltage 10kV Magnification: 1000x Next, elemental and compositional analysis of each particle was performed using SEM-EDX (Bruker XFlash Detector 630M), and an EDX mapping image of Co in the positive electrode active material LCO of the active material layer precursor was obtained.

[0215] The pattern evaluation of the three-dimensional structure cathode can also be determined using a similar method. Specifically, the determination of the three-dimensional structure cathode was performed as follows. The EDX mapping image of Co was used for determination. The image size was set to 256 x 200 pixels. Figure 24 shows the upper SEM image of the three-dimensional structure cathode of Example 4 (Figure 24A) and the EDX mapping image of Co (Figure 24B).

[0216] Image processing of the SEM-EDX images of Co was performed using OpenCV. After converting the images to grayscale, the scale and other parts were cut off. The resulting images were normalized to have an average brightness of 100 and a standard deviation of ±45. Next, the images were binarized with a brightness of 105 as the threshold, resulting in images where the Co portion was represented by white pixels. A two-dimensional Fourier transform was performed on the binarized images to obtain the FFT power spectrum. An example of the obtained FFT power spectrum is shown in Figure 25.

[0217] Next, peak detection processing was performed on the obtained FFT power spectrum. The peak detection process was carried out in the following steps: After applying a 3x3 maximum value filter to the power spectrum, elements other than pixels with the same value as the original image were set to 0, and the peaks were detected. Subsequently, intensity peaks with a value of 50% or less of the maximum peak were removed as noise, and these were used as the final peaks.

[0218] The surface of the active material layer precursor was evenly divided into 10 sections, and one SEM-EDX image of Co was obtained from each of the 10 sections, for a total of 10 SEM-EDX images. Peak detection processing was performed on all 10 SEM-EDX images using FFT power spectra, and if at least one peak other than the origin was found in 8 or more images, it was determined that the measured active material layer precursor had a periodic pattern structure.

[0219] In the active material layer precursor with particles arranged in a line pattern, a peak was observed at an angle of 0° and a distance of 6.6 μm. This indicates that the pattern structure has a line-like periodicity at intervals of approximately 7 μm. When evaluating the positive electrode of a secondary battery, the secondary battery is disassembled, the positive electrode current collector is removed, and the pattern structure is evaluated. If the upper surface of the positive electrode is damaged during disassembly, the positive electrode surface may be processed using known processing methods such as FIB (Focused Ion Beam) or BIB (Broad Ion Beam) before observation.

[0220] <Method for Evaluating the Presence or Absence of Interfacial Bonding Precursors> The presence or absence of interfacial bonding precursors was evaluated by compositional analysis using FIB-SEM and EDX. Figure 26 is an example of a cross-sectional SEM image of an electrode precursor before calcination. An electrode precursor 15 consisting of two interfacial bonding precursors 51 and one active material layer precursor 52 is stacked on top of the electrolyte sintered body 50. Figure 27 is an example of an EDX mapping image (Figure 27A is the SEM image, Figure 27B is Co, Figure 27C is Zr, and Figure 27D is La). If a precursor is present between the active material layer precursor 52 and the electrolyte sintered body 50, and if the precursor further contains solid electrolyte particles, the precursor is identified as an interfacial bonding precursor 51.

[0221] Here, we will explain the method for identifying the active material layer precursor 52. Identifying the active material layer precursor 52 requires identifying the positive electrode active material particles. To this end, the electrode precursor is compositionally analyzed by X-ray diffraction (XRD) or the like to identify the materials constituting the electrode. Then, specific elements (e.g., Co in LCO) contained in the positive electrode active material particles and solid electrolyte particles are detected and identified by SEM-EDX using the method described above. The precursor containing the particles identified as positive electrode active material particles was identified as the active material layer precursor 52. Similarly, the interface junction precursor was identified by detecting and identifying specific elements (e.g., La in LLZT) contained in the solid electrolyte particles contained in the interface junction precursor using SEM-EDX using the method described above. In addition to the above-described X-ray diffraction, the materials constituting the electrode precursor can also be identified by electron energy loss spectroscopy (EELS) in TEM. Furthermore, identification can also be performed by Raman spectroscopy or TOF-SIMS, and the materials constituting the electrode precursor may be identified by combining the above-described analytical methods.

[0222] <FIB-SEM and EDX Conditions> After applying a Pt-Pd coating film to the sample surface, cross-sectional observation by FIB-SEM and EDX analysis were performed. The Pt-Pd coating film was applied to a thickness of 10 nm using a coating device (Hitachi High-Tech). FIB-SEM was performed using a FIB-SEM device (Carl Zeiss, Crossbeam 350) ＋ Processing was performed at 30kV, and observation was conducted at an acceleration voltage of 3kV. EDX analysis was performed using an EDX device (Brker XFlash6160) at an acceleration voltage of 10kV.

[0223] <Method for Measuring the Particle Size of Active Material and Solid Electrolyte on a Precursor> SEM-EDX measurements were performed on the surface of the precursor, and particles for particle size measurement were identified from the SEM and EDX images. The particle sizes of 100 or more particles randomly selected from the identified particles were measured. The particle size was determined by calculating the equivalent diameter of a circle (the diameter of a circle with the same area) from the area (px) of the SEM image of the identified particle. The median diameter (volume-based D50) was determined from the obtained particle size distribution and was defined as the particle size. Alternatively, the precursor may be calcined to extract and measure only the particles. Surface observation was performed using a scanning electron microscope (SEM), and the surface of the particle layer was photographed from the stacking direction. The electron microscope used was a Carl Zeiss ULTRA55, and images were taken under the following conditions. The imaging area was the area in which the particle layer could be observed. Detector: ESB (backscattered electron image) Observation conditions: Acceleration voltage 3kV Magnification: 2000x

[0224] <Evaluation Method for Secondary Batteries> Secondary batteries were evaluated by performing charge and discharge measurements in constant current mode, and the calculated charge and discharge capacities were used. The constant current value can be determined for each rate from the total mass of the active material particles in the positive electrode, assuming the actual capacity of the LCO is 120 mAh / g. The total mass of the active material particles in the positive electrode is the mass of active material particles per unit area of ​​the active material layer precursor M (g / cm³). ２ The total mass of the active material particles in the positive electrode can be calculated from the positive electrode diameter (Φ8 mm) using the following formula: Total mass of active material particles in the positive electrode = (Mass of active material particles M × Number of layers of active material precursors × Positive electrode area (cm²) ２ ))

[0225] The mass of active material particles M per unit area of ​​the active material layer precursor is determined as follows. In the production of the active material layer precursor, the weight of the first substrate 11a (PDMS type) was measured after filling it with first particles P1 (LCO) using the particle filling device 24. Next, the weight of the first substrate 11a (PDMS type) was measured after transferring the first particles P1 to the second substrate 11b (resin substrate) using the particle filling device. The difference was calculated to determine the mass of the first particles P1 (LCO) transferred onto the second substrate 11b (resin substrate). Then, the mass of the first particles P1 was divided by the transfer area to determine the mass of active material particles M per unit area of ​​the active material layer precursor.

[0226] Another calculation method involves using ICP emission spectroscopy. The active material particle mass M (g / cm³) per unit area is calculated beforehand using the aforementioned method. ２ Three levels of a second substrate 11b (resin substrate) on which a particle layer has been identified is prepared. These resin substrates are dissolved by microwave acid decomposition (ETHOS PRO), and the acid decomposition solution is diluted with ultrapure water. Then, ICP-AES measurement (CIROS CCD) is performed to quantify the element Co, and the active material particle mass M (g / cm³) per unit area is obtained relative to the elemental concentration. ２ A calibration curve is obtained. From the calibration curve, the mass of active material particles M (g / cm³) per unit area of ​​the resin substrate on which the particle layer to be measured is formed can be obtained. ２ ) can be calculated.

[0227] Charge and discharge measurements were performed at room temperature (without pressure) using a charge and discharge measurement device (manufactured by Biologic). Current values ​​for current rates of 0.01C and 0.02C were determined using the method described above, and charge and discharge measurements (constant current charging / constant current discharging) were performed sequentially from the lowest current rate. Figure 28 shows an example of the measured charge and discharge curve. The vertical axis represents the battery cell voltage (V vs. Li). ＋ The graph shows the capacity (mAh / g) of the battery cell, with the horizontal axis representing the capacity per unit mass of the positive electrode active material. The actual capacity of the LCO was set to 120 mAh / g, and the cutoff voltage (relative to Li) was set to 4.2V (charging) / 2.6V (discharging).

[0228] For charge / discharge evaluation, a rating of "○" was given if the charging and discharging capacities were confirmed (>0 mAh / g) at both current rates of 0.01C and 0.02C. A rating of "△" was given if the charging and discharging capacities were confirmed (>0 mAh / g) at only 0.01C. A rating of "×" was given if the charging and discharging capacities could not be confirmed (>0 mAh / g) at both 0.01C and 0.02C. The evaluation results are shown in Table 5.

[0229] <Impedance Measurement of Secondary Batteries> The impedance of secondary batteries was measured at room temperature (without pressure) using an electrochemical measuring device (manufactured by Solartron) after the charge-discharge measurements described above. The measurement was performed using the two-terminal method (positive electrode and negative electrode), with an AC amplitude of 10 mV and a frequency (sweep) of 0.1 to 1 MHz. Under the above conditions, impedance measurements were performed for each example and comparative example, and Cole-Cole plots were obtained. The results are shown in Figure 29 (Examples 2, 3 and 4 (Figure 29A), Examples 1, 5, 7 and 8 (Figure 29B)) and Figure 30 (Comparative Examples 2 to 5 (Figure 30A), Comparative Examples 6 to 8 (Figure 30B)). Note that Example 6 is the same as Example 5, and Comparative Example 1 is the same as Comparative Example 2, so they are omitted.

[0230] Figure 31 shows cross-sectional SEM images of the electrode precursor before firing and the electrode structure after firing in Example 1. Figure 31A shows the cross-section before pre-firing, and Figure 31B shows the cross-section after main firing. After main firing, a nearly single layer of LCO particles was densely arranged on the substrate 50 (LLZT sintered body), and the LCO particle layer was bonded to the substrate 50.

[0231] Figure 32A shows the charge-discharge curve obtained from the charge-discharge measurement of Example 1, and Figure 32B is the Cole-Cole plot obtained from the impedance measurement. Figure 33A shows the charge-discharge curve obtained from the charge-discharge measurement of Comparative Example 1, and Figure 33B is the Cole-Cole plot obtained from the impedance measurement. In Example 1, which was manufactured using an interfacial bonding precursor, the battery resistance decreased, and the operation (charge-discharge) of the secondary battery at room temperature was confirmed. On the other hand, in Comparative Example 1, which was manufactured under the same conditions as Example 1 without using an interfacial bonding precursor, the battery resistance was high, and the operation (charge-discharge) of the secondary battery at room temperature could not be confirmed. Figure 63A is a schematic diagram illustrating the increase in resistance due to interfacial delamination when only Bi-LLZT interfacial bonding precursor (solid) (one layer) is used, and Figure 63B is a diagram showing the relationship between firing temperature and charge-discharge capacity when LBO interfacial bonding precursor (solid) is added and laminated to prevent interfacial delamination.

[0232] Figure 34A shows the charge-discharge curve obtained from the charge-discharge measurement in Example 8, and Figure 34B shows the Cole-Cole plot obtained from the impedance measurement. In Example 8, the Bi-LLZT particles used in the interfacial bonding precursor 1 of Example 1 and the LBO particles used in the interfacial bonding precursor 2 were arranged in a pattern on the same resin substrate. The same effect as in Example 1 was confirmed even when the interfacial bonding precursor was a single sheet in which the Bi-LLZT particles and LBO particles were arranged in a pattern. That is, the battery resistance decreased, and the operation (charge and discharge) of the secondary battery at room temperature was confirmed.

[0233] Figure 35A shows the charge-discharge curve obtained from the charge-discharge measurement of Comparative Example 3, and Figure 35B shows the Cole-Cole plot obtained from the impedance measurement. It was confirmed that even under the conditions of production using the interfacial bonding precursor, if the main firing temperature was set to a temperature lower than the melting point of the solid electrolyte (Bi-LLZT particles and LBO particles) of the interfacial bonding precursor, the battery resistance increased and the battery's charge-discharge characteristics deteriorated.

[0234] Figure 36 is a cross-sectional SEM image of the electrode structure after firing in Example 2. After firing, an interfacial bonding layer of approximately 300 nm thickness, attributed to LYbBO particles, was formed between the substrate SE (LLZT sintered body) and the nearly single-layer LCO particle layer, and the substrate and the active material layer were bonded by this interfacial bonding layer. Figures 61A and 61B are schematic diagrams of Example 2 before firing and a schematic diagram of the secondary battery.

[0235] Figure 37A shows the charge-discharge curve obtained from the charge-discharge measurement of Example 2, and Figure 37B shows the Cole-Cole plot obtained from the impedance measurement. Figure 38A shows the charge-discharge curve obtained from the charge-discharge measurement of Comparative Example 2, and Figure 38B shows the Cole-Cole plot obtained from the impedance measurement. Figure 58B is a schematic diagram of the prototype battery of Comparative Example 2. Figure 58A is a schematic diagram showing the sample of Comparative Example 2 before firing. Figure 62A shows the correlation between firing temperature (800°C for Example 2) and charge-discharge capacity, and Figure 62B is a schematic diagram of the interfacial bonding layer. In Example 2, which was manufactured using an interfacial bonding precursor, the battery resistance decreased, and the operation of the secondary battery (charge-discharge) at room temperature was confirmed. On the other hand, in Comparative Example 2, which was manufactured under the same conditions as Example 2 without using an interfacial bonding precursor, the battery resistance was high, and the operation of the secondary battery (charge-discharge) at room temperature could not be confirmed.

[0236] Figure 39A shows the charge-discharge curve obtained from the charge-discharge measurement of Comparative Example 4, and Figure 39B shows the Cole-Cole plot obtained from the impedance measurement. It was confirmed that even under the conditions of production using the interfacial bonding precursor, if the main firing temperature was set to a temperature lower than the melting point of the solid electrolyte (LybBO particles) of the interfacial bonding precursor, the battery resistance increased and the battery's charge-discharge characteristics deteriorated.

[0237] Figure 40A shows the charge-discharge curve obtained from the charge-discharge measurement in Example 3, and Figure 40B shows the Cole-Cole plot obtained from the impedance measurement. In Example 3, which was manufactured using an interfacial junction precursor, the battery resistance decreased, and the operation (charge-discharge) of the secondary battery at room temperature was confirmed. On the other hand, in Comparative Example 2, which was manufactured under the same conditions as Example 3 without using an interfacial junction precursor, the battery resistance was high, and the operation (charge-discharge) of the secondary battery at room temperature could not be confirmed.

[0238] Figure 41A shows the charge-discharge curve obtained from the charge-discharge measurement of Comparative Example 5, and Figure 41B shows the Cole-Cole plot obtained from the impedance measurement. It was confirmed that even under the conditions of production using the interfacial bonding precursor, if the main firing temperature was set to a temperature lower than the melting point of the solid electrolyte (LBO particles) of the interfacial bonding precursor, the battery resistance increased and the battery's charge-discharge characteristics deteriorated.

[0239] Figures 42A and 42B are schematic diagrams of Example 4 before and after firing. Figure 42A shows a schematic diagram before firing, and Figure 42B shows a schematic diagram after firing. An electrode precursor 15 consisting of an interfacial bonding precursor 51 and an active material layer precursor 52 is laminated on a substrate 50 (LLZT sintered body). The active material layer precursor 52 includes positive electrode active material particles (LCO particles) which are first particles P1, solid electrolyte particles (LLZT particles) which are second particles P2, and solid electrolyte particles (Bi-LLZT particles) (not shown) which are third particles P3. After arranging the first particles P1 and the second particles P2 in a line, the first particles P1 and the second particles P2 were allowed to settle, and then the third particles P3 (not shown) were placed. Figure 64A is a schematic diagram showing the configuration of Example 4 before firing. Figure 64B is a schematic diagram showing the electrode structure of Example 4 after firing.

[0240] In Example 4, three active material layer precursors were stacked. The three active material layer precursors 52 were stacked such that the second layer intersected (approximately 90 degrees) with the other layers to ensure excellent electronic and ionic conductivity (Figure 42A). By stacking in this manner, the LCO particles in the active material layer precursors come into contact with each other in the stacking direction, improving electronic conductivity, and the LLZT particles come into contact with each other, improving ionic conductivity. As a result, the charge and discharge characteristics of the secondary battery can be further improved.

[0241] The following FIB-SEM cross-sectional observations were performed on a cross-section cut by a plane approximately perpendicular to the line direction of the first particle in the uppermost layer of the positive electrode layer, as shown in Figure 42B (FIB cross-section).

[0242] Figure 43A is an overhead SEM image taken from above the cathode layer after firing in Example 4, and Figure 43B is an EDX mapping image of Co and La. In Figure 43B, the dark areas indicate the presence of Co, and the bright areas indicate the presence of La. That is, it was confirmed that the LCO particles were arranged in groups of three or fewer relative to the line width of the line pattern, and that the LCO particles were arranged in contact with adjacent LLZT particles.

[0243] Figure 44 is a cross-sectional SEM image of the electrode structure of Example 4 after firing, cut at the above cross-section. Figure 65B is a cross-sectional SEM image of the precursor laminate of Example 4 before firing, cut at the above cross-section (Figure 65A). Figure 65C is a cross-sectional SEM image of the electrode structure of Example 4 after firing, cut at the above cross-section (Figure 65A). Figure 45A is an enlarged image of Figure 44. Figures 45B and 45C are EDX mapping images, showing Co (Figure 45B) and La (Figure 45C), respectively. In the electrode of Example 4, the particle arrangement of the active material layer precursor was maintained even after firing, and a three-dimensional positive electrode structure was formed in which linearly arranged LCO particles and LLZT particles were stacked so as to intersect. Furthermore, it was confirmed that the interface between the active material layer containing LCO particles and the substrate 50 (LLZT sintered body) was bonded.

[0244] Example 4 includes Bi-LLZT particles, in which both the interfacial bonding precursor and the active material layer precursor have lower melting points compared to LLZT particles. By stacking the above interfacial bonding precursor and active material layer precursor and molding them at a melting point above that of the Bi-LLZT particles, the effect of liquid-phase sintering is produced. As a result, it is considered that a good interfacial layer is formed between particles in the positive electrode and between the positive electrode layer and the substrate at the interfacial bonding portion.

[0245] Figure 46A shows the charge-discharge curve obtained from the charge-discharge measurement of Example 4, and Figure 46B shows the Cole-Cole plot obtained from the impedance measurement. Example 4 has three layers of active material precursor containing LCO particles stacked together, and despite the weight of the LCO particles being approximately twice that of Example 1 (Figures 32A and 32B), the resistance increase was suppressed and good charge-discharge characteristics were confirmed.

[0246] This is because the interfacial bonding between the positive electrode layer and the substrate 50 (LLZT sintered body) by the interfacial bonding precursor creates a good interface between the positive electrode layer and the substrate. Furthermore, the three-dimensional structure positive electrode, in which the positive electrode active material LCO particles, high-melting-point solid electrolyte LLZT particles, and low-melting-point solid electrolyte Bi-LLZT particles contained in the active material layer precursor are arranged as described above, also creates interfacial bonding between the LCO particles and LLZT particles. As a result, a positive electrode with good lithium-ion conductivity and electronic conductivity can be formed. A key feature of this manufacturing method is that it can simultaneously form the interfacial bonding layer and the three-dimensional structure positive electrode.

[0247] Figure 47A shows the charge-discharge curve obtained from the charge-discharge measurement of Comparative Example 6, and Figure 47B shows the Cole-Cole plot obtained from the impedance measurement of Comparative Example 6. It was confirmed that in Comparative Example 6, because the active material layer precursor does not contain Bi-LLZT particles, the interfacial bonding between LCO particles and LLZT particles in the three-dimensional cathode structure decreases, the battery resistance increases, and the battery's charge-discharge characteristics deteriorate.

[0248] Figure 48A shows the charge-discharge curve obtained from the charge-discharge measurement of Example 7, and Figure 48B shows the Cole-Cole plot obtained from the impedance measurement of Example 7. In Example 7, the active material particles and solid electrolyte particles were arranged in the above-described uniform dispersion pattern in the active material layer precursor. Similar to Example 4 (Figures 46A and 46B), despite the weight of the LCO particles being approximately twice that of Example 1 (Figures 32A and 32B), the resistance increase was suppressed and good charge-discharge characteristics were confirmed.

[0249] Figure 49A shows the charge-discharge curve obtained from the charge-discharge measurement of Comparative Example 7, and Figure 49B shows the Cole-Cole plot obtained from the impedance measurement of Comparative Example 7.

[0250] Comparative Example 7 was manufactured under the same conditions as Example 7, except that the arrangement pattern of the active material layer precursor particles was changed. Specifically, Comparative Example 7 used an active material layer precursor in which LCO particles (approximately 8 LCO particles) were uniformly and low-density dispersed, arranged to deliberately aggregate using the uniform aggregation pattern described above. It was confirmed that Comparative Example 7 had higher battery resistance and lower battery charge / discharge characteristics compared to Example 7.

[0251] The reason for the decrease in battery performance is presumed to be as follows. Figures 50A and 50B are schematic diagrams showing the arrangement pattern of particles in the active material layer precursor. In the active material layer precursor in which particles are arranged in a line pattern as shown in Figure 50B, the LCO particles are arranged such that there are, for example, three or fewer LCO particles relative to the line width, and they are arranged to be in contact with adjacent LLZT particles. Therefore, the number of LCO particles that cannot contact LLZT particles within the plane of the active material layer precursor can be suppressed. Furthermore, by stacking multiple active material layer precursors so that they intersect with each other, contact between LCO particles and contact between LLZT particles is ensured in the stacking direction. Electronic conductivity is easily improved when LCO particles are in contact with each other, and ionic conductivity is easily improved when LLZT particles are in contact with each other. As a result, LCO particles that cannot contribute to lithium ion intercalation are suppressed (high capacity mAh / g), and a three-dimensional cathode with good lithium ion conductivity and electronic conductivity can be manufactured.

[0252] On the other hand, in the active material layer precursor with particles arranged in a hole-like pattern, as shown in the uniform dispersion (sea-island) pattern in Figure 50A, if eight or more LCO particles aggregate, some aggregated LCO particles will be unable to contact the surrounding LLZT particles within the plane of the active material layer precursor. Furthermore, when stacking the active material layer precursor without adjusting the stacking direction or position of each layer, in order to ensure contact (electron conduction) between LCO particles in the stacking direction, the geometric area ratio (density) of LCO particles in the active material layer precursor needs to exceed 30 area percent. For this reason, it is thought that the battery performance of Comparative Example 7 deteriorated due to the aggregation of LCO particles and poor contact between LCO particles in the stacking direction.

[0253] Furthermore, the area ratio of LCO particles in the active material layer precursor can be calculated by identifying the LCO particles in the EDX mapping image (above) of the active material layer precursor, determining the area (px) occupied by the LCO particles using image processing software (Adobe Photoshop®), and expressing it as an area ratio % relative to the total area (px).

[0254] Figure 51A is an overhead SEM image taken from above the cathode layer after firing in Example 5, and Figure 51B is an EDX mapping image. In the cathode layer of Example 5, it was confirmed that the LCO particles were arranged in groups of three or fewer relative to the line width and were positioned in contact with adjacent LYbBO particles.

[0255] Figure 52 shows a cross-sectional SEM image of the electrode after firing in Example 5. LCO particles and LYbBO particles were identified by an EDX mapping image (not shown). The particle arrangement of the active material layer precursor was maintained even after firing, and a three-dimensional cathode structure was formed in which linearly arranged LCO particles and LLZT particles were stacked so as to intersect. However, because the same type of solid electrolyte particles as those contained in the interfacial bonding precursor were used in the active material layer precursor, it was confirmed that some of the solid electrolyte dissolved from within the cathode due to molding above its melting point, resulting in noticeable voids.

[0256] Figure 53A shows the charge-discharge curve obtained from the charge-discharge measurement of Example 5, and Figure 53B shows the Cole-Cole plot obtained from the impedance measurement of Example 5. As described above, Example 5 has air gaps and low density of the positive electrode, so it was confirmed that the battery resistance increased and the battery charge-discharge characteristics deteriorated.

[0257] Figure 54A shows the charge-discharge curve obtained from the charge-discharge measurement of Comparative Example 8, and Figure 54B shows the Cole-Cole plot obtained from the impedance measurement of Comparative Example 8. In Comparative Example 8, the electrode was manufactured by process I (first heating process) and process IV (second heating process) without performing process III (pressurization process) in the electrode manufacturing method.

[0258] In the electrode manufacturing method, it was confirmed that in Comparative Example 8, the battery resistance increased and the battery's charge / discharge characteristics deteriorated compared to Example 2 (Figures 37A and 37B) in which steps I, III, and IV were carried out. In other words, in the electrode manufacturing method, it is preferable to carry out the pressurization step after the first heating step and before the second heating step.

[0259] This disclosure is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are attached to make the scope of this disclosure public. This application claims priority based on Japanese Patent Application No. 2024-201200, filed on 18 November 2024, the entire contents of which are incorporated herein by reference.

Claims

An electrode precursor applied to the manufacture of electrodes for secondary batteries, An active material layer precursor comprising a first resin substrate and active material particles held in the first resin substrate, An interfacial bonding precursor comprising a second resin substrate and first solid electrolyte particles held on the second resin substrate, having a portion in contact with the active material layer precursor, Includes, The first solid electrolyte particles are an electrode precursor having a softening point temperature higher than the softening point temperatures of the first resin substrate and the second resin substrate, respectively, and lower than the softening point temperature of the active material particles. 　 The electrode precursor according to claim 1, wherein the active material layer precursor further comprises second solid electrolyte particles held on the first resin substrate. 　 The electrode precursor according to claim 2, wherein the active material layer precursor includes the second solid electrolyte particles in contact with the active material particles. 　 The electrode precursor according to claim 2 or 3, wherein the active material particles and the second solid electrolyte particles are arranged at different positions in the plane facing the interfacial bonding precursor. 　 The electrode precursor according to any one of claims 2 to 4, wherein the active material layer precursor comprises the second solid electrolyte particles and a third solid electrolyte particle having at least one of the average particle size, composition, melting point, and softening point temperature. 　 The electrode precursor according to claim 5, wherein the interfacial bonding precursor comprises the third solid electrolyte particle. 　 The electrode precursor according to claim 5 or 6, wherein the first solid electrolyte particle and the second solid electrolyte particle or the third solid electrolyte particle have at least one of the physical properties and composition in common. 　 The electrode precursor according to any one of claims 5 to 7, wherein at least one of the first solid electrolyte particles and the third solid electrolyte particles comprises at least one selected from the group consisting of Bi and Ca. 　 The electrode precursor according to any one of claims 2 to 8, wherein the active material layer precursor has a pattern structure that is periodic in a predetermined direction, corresponding to the arrangement of the active material particles and the second solid electrolyte particles within the layer. 　 The electrode precursor according to any one of claims 1 to 9, wherein the active material layer precursor comprises a holding portion that maintains a stacked state with the interfacial bonding precursor. 　 The electrode precursor according to any one of claims 1 to 10, wherein the interfacial bonding precursor comprises a plurality of second resin substrates on which the first solid electrolyte particles are arranged. 　 The electrode precursor according to any one of claims 1 to 11, wherein the first solid electrolyte particles have higher ionic conductivity than the active material particles. 　 The electrode precursor according to any one of claims 1 to 12, further comprising an electrolyte layer containing a solid electrolyte, which is in contact with the interfacial bonding precursor. 　 The electrode precursor according to claim 13, wherein the solid electrolyte is the same solid electrolyte particle as the first solid electrolyte particle. 　 The electrode precursor according to claim 14, wherein the pattern structure includes at least one of a sea-island pattern, a houndstooth pattern, a two-dimensional grid pattern, and a one-dimensional grid pattern. 　 A step of forming an active material layer precursor by holding active material particles on a first resin substrate via a first adhesive portion, A step of forming an interfacial bonding precursor by holding first solid electrolyte particles on a second resin substrate via a second adhesive portion, A step of stacking the active material layer precursor and the interface bonding precursor so that they are in contact, Includes, A method for producing an electrode precursor, characterized in that the first solid electrolyte particles have a softening point temperature higher than the softening point temperature of the first resin substrate and the second resin substrate, and lower than the softening point temperature of the active material particles. 　 A lamination step of laminating an electrolyte layer containing a solid electrolyte and an electrode precursor according to any one of claims 1 to 15 such that the interfacial bonding precursor is in contact with the electrolyte layer, A first heating step involves heating the laminate of the electrolyte layer and the electrode precursor to a temperature above the thermal decomposition temperature of the first resin substrate and the second resin substrate to form a calcined body. A pressurizing step of pressurizing the calcined body in at least the stacking direction, A second heating step involves heating the calcined body to a temperature above the softening point temperature of the first solid electrolyte particles, A method for manufacturing an electrode structure having the following characteristics. 　 The method for manufacturing an electrode structure according to claim 17, wherein the lamination direction corresponds to the direction in which the electrolyte layer and the electrode precursor are laminated in the lamination process. 　 A step of electrically connecting a positive electrode current collector and an electrode structure manufactured by the manufacturing method described in claim 17 or 18, A step of electrically connecting the electrode structure and the negative electrode containing the negative electrode active material on the side having the electrolyte layer, A step of electrically connecting the negative electrode and the negative electrode current collector, A method for manufacturing a secondary battery, including the battery itself.

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