Electrode and secondary battery, and method for manufacturing an electrode

Abstract

To provide an electrode that can mitigate volume fluctuations of the active material and suppress the desorption of the active material within the electrode. [Solution] An electrode for use in a secondary battery, characterized by comprising: an active material-containing layer containing an active material; and a carbon-containing layer having a layered porous body containing carbon, having a portion in contact with the active material-containing layer and extending in a direction intersecting the thickness direction of the active material-containing layer.

Description

[Technical Field]

[0001] This disclosure relates to electrodes and secondary batteries, as well as methods for manufacturing electrodes. [Background technology]

[0002] Generally, rechargeable batteries consist of electrodes (positive and negative electrodes) and an electrolyte, and charging and discharging occur through the movement of ions between the electrodes via the electrolyte. Such rechargeable batteries are used in a wide range of applications, from small devices such as mobile phones to large devices such as electric vehicles. Therefore, there is a demand for further improvements in the performance of rechargeable batteries.

[0003] In recent years, research and development of so-called all-solid-state batteries, which use inorganic solid electrolytes, has been progressing. By replacing conventional organic electrolytes with solid electrolytes, all-solid-state batteries are expected to improve the safety, capacity, and output of secondary batteries. On the other hand, all-solid-state batteries face challenges in ensuring proper contact between the active material particles and the solid electrolyte particles. This makes them prone to high resistance, which can limit their capacity and output. Patent Document 1 discloses a positive electrode consisting of positive electrode active material particles having protrusions. Patent Document 2 discloses an electrode using a porous aluminum material. In both cases, the contact between the active material particles and the solid electrolyte particles can be improved, the utilization rate of the active material particles can be increased, and the capacity and output can be improved.

[0004] Furthermore, in all-solid-state batteries, during the ion insertion and deinsertion process at the electrodes, the volume fluctuations of the active material particles easily disrupt the conduction paths of ions and electrons at various points in the electrodes, making it difficult to maintain stable capacity and output. Examples of disruption sites include between individual particles within the electrode, between the electrode and the current collector, and between the electrode and the electrolyte. Patent document 3 discloses an electrode having a concentration gradient of active material particles and conductive additives in the layer thickness direction. Conductive additives composed of secondary particles can mitigate volume fluctuations of the active material particles. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-088258 [Patent Document 2] Japanese Patent Publication No. 2014-234531 [Patent Document 3] Japanese Patent Publication No. 2021-039849 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, our research has shown that it can be difficult to achieve both improved capacity and output of secondary batteries and mitigation of volume fluctuations in the active material. As described in Patent Documents 1 and 2, improving the contact between active material particles and solid electrolyte particles makes the electrode more susceptible to volume fluctuations of the active material particles. On the other hand, as described in Patent Document 3, electrodes having a concentration gradient of active material particles and conductive additives in the layer thickness direction can mitigate volume fluctuations of the active material particles by deformation of secondary particles of the conductive additive, but this effect may be limited. Furthermore, it has been found that when the volume of the active material particles changes, the conductive additive (secondary particles) cannot hold the active material particles, causing the active material to desorb within the electrode, inhibiting ion conduction, and potentially reducing capacity and output.

[0007] According to one aspect of this disclosure, an electrode with excellent ion conductivity is provided that can mitigate volume fluctuations of the active material due to charging and discharging and suppress the desorption of the active material within the electrode. Furthermore, a secondary battery with high cycle life that can suppress the decrease in capacity and output is provided using the electrode. Furthermore, a method for manufacturing the electrode is provided. [Means for solving the problem]

[0008] According to at least one aspect of this disclosure, An electrode for use in secondary batteries, An active material-containing layer containing an active material, It has a portion in contact with the active material-containing layer and has a carbon-containing layered porous body extending in a direction intersecting the layer thickness direction of the active material-containing layer, a carbon-containing layer; An electrode characterized by including the above is provided.

Advantages of the Invention

[0009] According to one aspect of the present disclosure, an electrode excellent in ionic conductivity is provided, which can alleviate the volume fluctuation of the active material due to charge and discharge and suppress the detachment of the active material in the electrode. Further, a secondary battery with high cycle performance capable of suppressing a decrease in capacity and output using the above electrode is provided. Furthermore, a method for manufacturing the above electrode is provided.

Brief Description of the Drawings

[0010] [Figure 1] A diagram showing the manufacturing process of an electrode precursor [Figure 2] A diagram schematically showing the configuration of the particle arrangement device 1 [Figure 3] A diagram schematically showing the configuration of the filling device [Figure 4] A schematic diagram of the filler being conveyed on the first substrate [Figure 5] An enlarged view showing the vicinity of the surface of the first substrate [Figure 6] A schematic diagram of the configuration of the filling device using brush fibers as the carrier [Figure 7] A diagram schematically showing the configuration of the transfer part [Figure 8] An enlarged view showing the vicinity of the surface of the second substrate in the filling process [Figure 9] A diagram schematically showing the second substrate after arranging the first particle P1 and the second particle P2 [Figure 10] A diagram schematically showing the configuration of the particle arrangement device 2 [Figure 11] A diagram schematically showing the devices used in the third and fourth steps [Figure 12] A schematic diagram explaining the sedimentation of particles [Figure 13] A schematic diagram from above the substrate after the third step [Figure 14]Schematic diagram of the substrate from above after the fourth step. [Figure 15] A diagram showing an example of a simple device that does not use a belt system. [Figure 16] A schematic diagram illustrating the operation of the filling device. [Figure 17] Diagram showing the electrode manufacturing process [Figure 18] A schematic diagram showing the configuration of a laminate molding apparatus. [Figure 19] A schematic diagram showing the configuration of a sintering apparatus. [Figure 20] Cross-sectional SEM images of the electrode precursor stack before and after the heating process. [Figure 21] SEM-EDX mapping images for identifying each part of the electrode precursor stack. [Figure 22] SEM-EDX mapping images to identify each part of the electrode. [Figure 23] SEM-EDX mapping image showing electrode cross-section [Figure 24] STEM and mapping images showing electrode cross-sections. [Figure 25] Figure showing the results of EELS measurement of the carbon-containing layer. [Figure 26] Figure showing the X-ray diffraction spectrum of the electrode obtained by X-ray diffraction. [Figure 27] A schematic diagram showing the overall configuration of an additive manufacturing system. [Figure 28] SEM-EDX mapping image of the particle layer of cathode precursor 1 observed from above. [Figure 29] SEM-EDX mapping image of the particle layer of cathode precursor 1 observed in cross-section. [Figure 30] SEM-EDX mapping image obtained by cross-sectional observation of cathode precursor stack 1. [Figure 31] SEM-EDX mapping image obtained by cross-sectional observation of positive electrode 1. [Figure 32] Figure 31 shows a magnified view of the carbon-containing layer 11x. [Figure 33] Charge / discharge measurement results of all-solid-state battery 1 at output 1C [Figure 34] Cycle evaluation results of all-solid-state battery 1 at output 1C [Figure 35] Cross-sectional STEM image and mapping image of the positive electrode [Figure 36] EELS spectral image obtained by cooling EELS measurement of the region containing the carbon-containing layer 11x of positive electrode 1. [Figure 37] Enlarged view of the EELS spectrum of the region containing the carbon-containing layer 11x of positive electrode 1. [Figure 38] X-ray diffraction spectra of positive electrode 1 before and after cycle evaluation. [Figure 39] SEM-EDX mapping image of positive electrode 2 observed from above. [Figure 40] SEM-EDX mapping image of the cross-section of positive electrode 2 [Figure 41] Cross-sectional SEM-EDX mapping image of the positive electrode of Comparative Example 1 [Figure 42] Example of a cross-sectional SEM-EDX mapping image used to determine an extended carbon-containing layer. [Figure 43] Example of an image showing the electrode component cut out from Figure 42. [Figure 44] Example of a normalized image from Figure 43 [Figure 45] Diagram showing the results of determining the presence of carbon. [Figure 46] Figure 45 shows the results of the determination of region L. [Figure 47] Figure 45 shows the results of the determination of region N. [Modes for carrying out the invention]

[0011] 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, 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.

[0012] Furthermore, in this disclosure, any 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.

[0013] Our investigations have revealed that it is important to provide a carbon-containing layer, which is a layered porous material containing carbon, inside the electrode in order to mitigate volume fluctuations of the active material due to charging and discharging and to suppress the desorption of the active material within the electrode. It is important that the porous carbon-containing layer extends within the electrode in a direction intersecting the thickness direction of the active material-containing layer, so as to align with the region where the active material is present.

[0014] The carbon-containing layer functions as a relaxation layer that mitigates volume fluctuations of the active material during charging and discharging, while also facilitating the conduction of lithium ions and electrons within the electrode. Furthermore, the carbon-containing layer can hold the active material-containing layer in a predetermined position within the electrode, thereby suppressing the desorption of the active material within the electrode. In addition to the above, by configuring the carbon-containing layer to sandwich the active material-containing layer, the volume fluctuations of the active material-containing layer due to charging and discharging can be further mitigated by the deformation of the porous carbon-containing layer. Therefore, it is believed that an electrode with excellent ion conductivity can be provided that mitigates volume fluctuations of the active material due to charging and discharging and suppresses the desorption of the active material within the electrode.

[0015] The electrode includes an active material-containing layer containing an active material, and a carbon-containing layer which is a layered porous body containing carbon, having a portion in contact with the active material-containing layer and extending in a direction intersecting the thickness direction of the active material-containing layer. For example, by stacking multiple electrode precursors, each containing an active material on a resin substrate, and heating the electrode precursor laminate for a long time at a temperature that does not completely decompose the resin substrate while maintaining a reducing atmosphere, an electrode having an active material-containing layer and a carbon-containing layer extending in contact with the active material-containing layer is obtained. It can be manufactured.

[0016] One method for heating while maintaining a reducing atmosphere is to continuously supply a reducing gas at least during the heating process and throughout the heating time. The resin substrate generates reducing gas (CO) when it partially gasifies due to thermal decomposition. However, if heating continues and the resin substrate completely decomposes, the source of the reducing gas disappears and it becomes impossible to maintain a reducing atmosphere. On the other hand, by heating the electrode precursor for a long time at a temperature that does not completely decompose the resin substrate while maintaining a reducing atmosphere by supplying a reducing gas, a portion of the resin substrate gasifies due to thermal decomposition and is released to the outside as a gas, forming a carbon-containing layer having a porous carbon body. Details of the electrode manufacturing method will be described later.

[0017] In this disclosure, the mitigation of volume fluctuations is conveniently evaluated using an indicator called the "cycle characteristics" of the prototype battery, and the ion conductivity is conveniently evaluated using an indicator called the "output characteristics" of the prototype battery.

[0018] <Electrode> The electrode includes an active material-containing layer 12 containing an active material, and a carbon-containing layer 11x having a portion in contact with the active material-containing layer 12 and extending in a direction intersecting the thickness direction of the active material-containing layer. The carbon-containing layer has a layered porous body containing carbon (Figure 20B). The electrode can be applied to a secondary battery.

[0019] For example, by stacking multiple electrode precursors, each containing active material particles, on a resin substrate and heating them at a temperature of 650°C or higher while maintaining a reducing atmosphere to modify the resin substrate, a carbon-containing layer can be formed that has a porous body containing carbon extending in a direction intersecting the thickness direction of the active material-containing layer. The presence of a porous carbon material in the carbon-containing layer can be confirmed by observing the electrode cross-section using SEM-EDX and mapping the carbon components. Details of the carbon-containing layer formation method and SEM-EDX observation method will be described later.

[0020] By including a carbon-containing layer, which is a porous material containing carbon, extending so that the electrode has a portion in contact with the active material-containing layer, volume fluctuations of the active material during charging and discharging can be mitigated. That is, even if volume fluctuations occur in the active material-containing layer due to repeated charging and discharging, the deformation of the carbon-containing layer 11x reduces stress on the active material-containing layer. As a result, the cycle characteristics of the battery can be improved. Furthermore, since the active material-containing layer can be held in a predetermined position within the electrode, the desorption of the active material within the electrode can be suppressed. As a result, the ionic conductivity of the electrode is improved, and the capacity and output of the secondary battery can be increased.

[0021] The electrode preferably contains 1 to 100 layers of carbon-containing layer 11x, preferably 2 to 50 layers, and preferably 3 to 20 layers. It is preferable that the carbon-containing layer 11x is arranged to sandwich the active material-containing layer 12. It is preferable that the active material-containing layer 12 is sandwiched between the carbon-containing layers 11x such that it has a portion in contact with the carbon-containing layer 11x on both the front and back surfaces of the layer. It is preferable that the active material-containing layer 12 is sandwiched between two carbon-containing layers 11x. The active material-containing layer 12 may also be sandwiched between a single bent carbon-containing layer 11x. With such a configuration, the active material-containing layer 12 is held in a predetermined position by the carbon-containing layers 11x, making it easier to suppress the desorption of the active material within the electrode. As a result, the ionic conductivity of the electrode can be further improved.

[0022] The active material-containing layer preferably contains an active material and a solid electrolyte. The active material-containing layer preferably exhibits a mixed phase of the active material and the solid electrolyte. By having such a configuration, This can improve ionic conductivity, thereby increasing capacity and output. The carbon-containing layer may contain an active material. Preferably, the active material is contained within the pores of the porous material. Containing the active material within the pores of the porous material makes it easier to suppress its desorption. The presence of the active material within the pores of the porous material can be confirmed, for example, by observation using a scanning electron microscope (SEM).

[0023] The carbon-containing layer includes a configuration in which a first region containing carbon and a second region in which an active material may be contained exist as separate regions. This configuration includes electrodes incorporated into a secondary battery, electrodes incorporated into a semi-secondary battery, and electrodes not incorporated into a secondary battery. By having such first and second regions, the carbon-containing layer exhibits the function of a porous structure (porous framework) that can insert and remove the active material. In the carbon-containing layer, the existence of a first region containing carbon and a second region in which an active material may be contained as separate regions is equivalent to containing the active material in such a way that the first region containing carbon and the second region in which an active material may be contained are located at different positions.

[0024] Here, a simple and commonly used method for identifying the first region containing carbon and the second region where active material may be contained is to perform elemental mapping using SEM and EDX images. However, the macroscopic generation efficiency differs between secondary electrons, backscattered electrons, and excitation X-rays, which depend on the acceleration voltage of primary electrons. For this reason, EDX images typically have lower image resolution than SEM images. Considering this, in the first embodiment, the EDX image is obtained such that a region of mixed active material and carbon (including apparent mixing) exists between the active material-present region (e.g., the second region where Li contained in the active material is detected) and the carbon-present region (the first region where carbon is detected). In the second embodiment, the EDX image is obtained such that a region exhibiting a carbon concentration gradient changing from low to high concentration exists between the depletion region (e.g., the second region where carbon is not significantly detected) and the carbon-present region (the first region where carbon is significantly detected). In other words, both the first and second embodiments can be rephrased as the first and second regions appearing to be in close proximity and in different positions, separated by a transition region, in the EDX image.

[0025] Here, the first region containing carbon, that is, the first region where carbon is significantly detected, can be rephrased as the region where carbon is present at a high concentration compared to other elements in the observation system. Furthermore, the second region where active material may be present, that is, the second region where carbon is not significantly detected, can be rephrased as the region where the active material is held in an insertable and removable manner within the porous structure (porous framework) of carbon due to electrochemical phase changes (charge / discharge), thermal phase changes (thermal diffusion), etc.

[0026] In a carbon-containing layer, the first region containing carbon and the second region where active material may be contained exist as separate regions. This reduces the volume change of the electrode due to the intercalation of the active material during charging and discharging, thereby improving the charge-discharge cycle characteristics. Furthermore, if the carbon skeleton has double bonds due to the carbonization of the resin substrate, carrier exchange between electrons exchanged with the current collector and the active material held in the skeleton is more easily maintained, further improving the ionic conductivity of the electrode.

[0027] The active material and solid electrolyte contained in the active material-containing layer are preferably made of materials that are difficult to decompose by reduction even during sintering in a reducing atmosphere, and are not particularly limited. For example, the following materials can be used.

[0028] As the active material, either a positive electrode active material or a negative electrode active material can be used. The positive electrode active material preferably contains an olivine-based positive electrode active material. Including an olivine-based positive electrode active material allows for the formation of a highly safe electrode. This is because the strong bond between phosphorus and oxygen in the crystal makes it difficult for oxygen to be released due to overcharging or crystal structure breakdown at high temperatures. Furthermore, it exhibits small volume expansion and contraction and relatively high cycleability. By including an olivine-based cathode active material in the electrode active material, a secondary battery with superior safety and high cycle life can be obtained.

[0029] For example, the positive electrode active material preferably includes an olivine-based positive electrode active material such as lithium vanadium phosphate Li3V2(PO4)3(LVP) or lithium iron phosphate LiFePO4(LFP). In other words, the active material preferably contains at least one of lithium vanadium phosphate and lithium iron phosphate.

[0030] Since olivine-based cathode active materials have low electronic conductivity, it is preferable to carbon-coate the particle surface using a known method. In other words, it is preferable that the active material includes olivine-based cathode active material whose surface is carbon-coated. Possible negative electrode active materials include lithium, graphite, and lithium titanate (Li4Ti5O). 12 (LTO), silicon, tin, aluminum, antimony, zinc, bismuth, silver, indium, etc. can be used as alloy-based anodes.

[0031] Solid electrolytes include lithium borate (Li3BO3) and Li 5.9 Yb 0.81 La 0.09 Zr 0.1 It is preferable to include a low-melting-point solid electrolyte such as (BO3)3(LYbBO). By including a low-melting-point solid electrolyte, side reactions between the active material and the solid electrolyte can be suppressed by low-temperature firing, while a good interface can be formed between the active material and the solid electrolyte, thereby further improving ionic conductivity.

[0032] The melting point of the solid electrolyte is preferably 900°C or lower, and more preferably 800°C or lower. The lower limit of the melting point of the solid electrolyte is not particularly limited, but is preferably 200°C or higher, and more preferably 400°C or higher. That is, the melting point of the solid electrolyte is preferably 200 to 900°C, and more preferably 400 to 800°C. In this disclosure, "melting point" refers to the melting point temperature measured by a differential thermogravimetric analyzer (TG-DTA) or a differential scanning calorimetry analyzer (DSC).

[0033] The active material and solid electrolyte contained in the active material-containing layer can be identified by performing elemental and compositional analysis of each material using SEM-EDX. The observation conditions for SEM-EDX will be described later. The electrode preferably contains 1 to 100 layers of the active material-containing layer 12, more preferably 2 to 50 layers, and more preferably 3 to 20 layers.

[0034] It is preferable that the carbon-containing layer 11x is sandwiched between the active material-containing layers 12. It is preferable that the carbon-containing layer is sandwiched between the active material-containing layers such that it has portions in contact with the active material-containing layers on both the front and back surfaces of the layer. It is preferable that the carbon-containing layer is sandwiched between two active material-containing layers. The carbon-containing layer may also be sandwiched between one bent active material-containing layer. That is, the electrode has at least two active material-containing layers 12, and it is preferable that the carbon-containing layer 11x is sandwiched between at least two active material-containing layers 12.

[0035] The electrode has at least two carbon-containing layers 11x and at least two active material-containing layers 12, and it is preferable that at least two carbon-containing layers 11x and at least two active material-containing layers 12 are alternately stacked. That is, it is preferable that the carbon-containing layers and active material-containing layers are alternately present inside the electrode, with the active material-containing layers 12 sandwiched between the carbon-containing layers 11x and the carbon-containing layers 11x sandwiched between the active material-containing layers 12. This configuration makes it easier to mitigate volume fluctuations of the active material, further improving cycle characteristics. Additionally, it makes it easier to suppress the desorption of the active material, further improving ionic conductivity. For example, by stacking three or more of the above-mentioned electrode precursors to form an electrode, the carbon-containing layer 11x A configuration can be provided in which an active material-containing layer 12 is sandwiched between the active material-containing layers 12, and a carbon-containing layer 11x is sandwiched between the active material-containing layers 12.

[0036] For the carbon-containing layer 11x to function as a relaxation layer, it is important that it has sufficient thickness while not inhibiting lithium ion and electronic conductivity. Therefore, the thickness of the carbon-containing layer is preferably 50 nm to 50 μm, and more preferably 100 nm to 10 μm. The thickness of the carbon-containing layer can be increased, for example, by increasing the thickness of the resin substrate, or decreased by decreasing the thickness of the resin substrate. Furthermore, the thickness of the carbon-containing layer can be controlled by the firing conditions (temperature, time) in the electrode manufacturing method described later. For example, by using a resin substrate with a thickness of 1 μm to 500 μm and firing it at 650 to 1000°C for 0.5 to 15 hours, the thickness of the carbon-containing layer can be within the above range. The thickness of the carbon-containing layer can be measured, for example, using a scanning transmission electron microscope (STEM).

[0037] The carbon-containing layer is preferably bulkier than the active material-containing layer. In this disclosure, "bulky" refers to a high bulk density. Because the carbon-containing layer is bulkier than the active material-containing layer, it can function as a mitigating layer that reduces volume fluctuations in the active material-containing layer. Furthermore, by reducing the weight of the carbon-containing layer, which does not function as a capacity component, the decrease in the gravimetric energy density of the battery can be suppressed. For example, by manufacturing electrodes using the manufacturing method described later, a carbon-containing layer bulkier than the active material-containing layer can be formed.

[0038] The ratio of the thickness of the carbon-containing layer to the thickness of the active material-containing layer (thickness of the carbon-containing layer (μm) / thickness of the active material-containing layer (μm)) is preferably 0.01 to 2. By keeping the ratio within this range, volume fluctuations in the active material-containing layer can be sufficiently mitigated. Furthermore, the volume of the carbon-containing layer, which does not function as a capacity component, can be suppressed, thereby preventing a decrease in the volumetric energy density of the battery. The layer thickness can be controlled within this range by controlling the particle size of the active material particles on the resin substrate, the particle layer thickness, and the thickness of the resin substrate.

[0039] The carbon-containing layer preferably has π bonds and σ bonds derived from carbon-carbon double bonds. It is believed that the presence of these bonds in the carbon-containing layer makes it easier for electrons to move within the electrode. When energetically stable, strong σ bonds and relatively weak π bonds coexist, the electrons on the π bonds (π electrons) do not remain localized but spread throughout the entire π-conjugated structure (delocalized), making them relatively more mobile. Therefore, it is thought that some of the π electrons are extracted during firing, creating partial holes. When holes are created, adjacent negative charges (π electrons) move to fill the positive charges, and holes are created in the places where the moved π electrons were. It is thought that this process is repeated, making it easier for electrons to move.

[0040] It is more preferable for the carbon-containing layer to further contain π bonds derived from the carbon-oxygen double bond. This is thought to allow the oxygen atom to contribute to the delocalization of π electrons, thereby making electrons more mobile. The presence of π bonds and σ bonds originating from carbon-carbon double bonds, as well as π bonds originating from carbon-oxygen double bonds, can be confirmed by analyzing electron energy loss spectroscopy (EELS) spectra. Details of the analysis method will be described later.

[0041] <Electrode precursor> The electrode precursor comprises a resin substrate and an active material disposed on the resin substrate. The resin substrate has an adhesive portion on at least one side. The active material is arranged in contact with the adhesive portion, and a particle layer is formed.

[0042] As the material constituting the resin substrate, known resin materials such as polyethylene (PE), polypropylene (PP), polyester such as polyethylene terephthalate (PET), and polyamide such as nylon can be used. Among these, PET is preferred from the viewpoint of decomposition temperature and the low toxicity of gases generated during thermal decomposition. The carbon-containing layer is preferably at least one sintered product selected from the group consisting of polyethylene (PE), polypropylene (PP), polyester such as polyethylene terephthalate (PET), and polyamide such as nylon.

[0043] The adhesive forming the adhesive portion may be an acrylic adhesive, a rubber adhesive, a silicone adhesive, or a thermoplastic resin or a photocurable resin whose adhesive strength changes due to external disturbances such as heat or light. Alternatively, known epoxy, acrylic, urethane, or two-component adhesives may also be used.

[0044] The particle layer contains at least an active material. Preferably, the particle layer contains active material particles and solid electrolyte particles. The active material particles and solid electrolyte particles constituting the particle layer are not particularly limited, but materials that are not easily reduced or decomposed even during sintering in a reducing atmosphere are preferred. The materials mentioned above can be used as the active material particles and solid electrolyte particles.

[0045] <Method for manufacturing electrode precursors> The following describes in detail an example of a method for manufacturing an electrode precursor, with reference to the drawings. The following explanation uses a positive electrode precursor using positive electrode active material particles as the active material, but the method described below can be used for manufacturing electrode precursors, regardless of whether they are positive or negative electrodes. A positive electrode precursor can be manufactured by using the above-mentioned positive electrode active material particles as the active material. Similarly, a negative electrode precursor can be manufactured by using the above-mentioned negative electrode active material particles as the active material.

[0046] The method for producing the cathode precursor comprises the following two steps (step 1 and step 2). (1) A first step (S101 in Figure 1) of placing first particles (positive electrode active material particles or first solid electrolyte particles) on a resin substrate equipped with an adhesive portion. (2) A second step (S102 in Figure 1) of placing second particles (first solid electrolyte particles or positive electrode active material particles) in the area on the resin substrate where the first particles are not placed.

[0047] After performing the above steps, the following third and fourth steps may be performed as needed. (3) A third step (S103 in Figure 1) to allow the first particles and the second particles (positive electrode active material particles and first solid electrolyte particles) to settle in the adhesive portion. (4) A fourth step (S104 in Figure 1) in which a third particle is placed in the area where the adhesive part has been exposed due to sedimentation.

[0048] (1st and 2nd steps) The first and second steps involve arranging positive electrode active material particles and, if necessary, first solid electrolyte particles on a resin substrate. In these steps, particles are arranged on the resin substrate using a particle arrangement device. The following describes two particle placement devices that can be used: Particle Placement Device 1 and Particle Placement Device 2.

[0049] [Particle placement device 1] Figure 2 is a schematic diagram showing the configuration of the particle placement device 1. Hereinafter, the first particle P1 and the second particle P2 refer to the positive electrode active material particles and the first solid electrolyte particles described above. At least one of the first particle P1 and the second particle P2 is a positive electrode active material particle. For example, the first particle P1 can be a positive electrode active material particle and the second particle P2 can be a first solid electrolyte particle. Alternatively, the first particle P1 can be a first solid electrolyte particle and the second particle P2 can be a positive electrode active material particle. Active material particles may be used. Furthermore, positive electrode active material particles may be used for both the first particle P1 and the second particle P2.

[0050] The particle placement 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, and a pattern forming device 23 for forming an uneven pattern on the first substrate 11a. The particle placement apparatus 1 also includes a first filling device 24a for placing first particles P1 in the recesses of the uneven pattern formed on the first substrate 11a. The particle placement apparatus 1 also includes 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.

[0051] The particle placement device 1 has a transfer section 25a where the rollers 223 of the first belt device 22a and the second belt device 22b face each other, and in the transfer section 25a, the first particles P1 are transferred from the first substrate 11a to the second substrate 11b. Furthermore, the particle placement device 1 has a second filling device 24b for placing the second particles P2 in the non-transfer areas on the second substrate 11b. Note that devices that are not relevant to explaining the effects of this invention, such as a peeling and recovery device for peeling and recovering the first substrate 11a after transfer from the first belt device 22a, and various cleaning devices, are not shown in the illustrations and detailed descriptions.

[0052] In the particle placement apparatus 1, the pattern forming apparatus 23, the first filling apparatus 24a, and the transfer section 25a correspond to the first placement means for arranging the first particles P1 in a pattern on the second substrate 11b. The second filling apparatus 24b corresponds to the second placement means for arranging the second particles P2 in areas on the second substrate 11b where the first particles P1 are not present. The following describes the method of placing particles on the substrate 11 using the particle placement device 1, following the flow of each process.

[0053] First, the first base material 11a is supplied from the first containment container 21a to the first belt device 22a by a supply means (not shown). When an ultraviolet-curable liquid is applied by the pattern forming apparatus 23, it is preferable that at least the surface material of the first substrate 11a is made of a material with high wettability to the ultraviolet-curable liquid. Furthermore, it is preferable that the surface of the first substrate 11a is smooth.

[0054] As the first substrate 11a, a resin sheet such as polyester that has been treated with a hydrophilic or lipophilic treatment according to the ultraviolet-curable liquid (water-based or oil-based) used can be used. The first substrate 11a may be a substrate that is cut individually like cut paper, a continuous substrate wound in a roll like roll paper, or a continuous substrate that is folded alternately like continuous paper.

[0055] The first belt device 22a transports the supplied first substrate 11a to the pattern forming position of the pattern forming device 23. The first belt device 22a includes drive rollers 221a, 222a, pressure roller 223a, and a belt-shaped transport member 224a suspended from them. At this time, the pressure roller 223a rotates by a driven motion.

[0056] The conveying member 224a is preferably made of resin or metal, for example, a polyimide resin belt can be used. The drive rollers 221a and 222a are preferably made of metal, for example, stainless steel metal rollers can be used. The pressure roller 223a is preferably made of soft roller having an elastic layer on its surface, for example, a soft roller with an elastic layer of silicone rubber on the surface of a stainless steel core can be used. Although the first belt device 22a is used as the conveying device for transporting the first base material 11a, a roller device can also be used instead of the belt device. The second belt device will be described later. The same applies to location 22b.

[0057] The pattern forming apparatus 23 forms a fine relief pattern on the first substrate 11a that has been transported to the pattern forming position. Known fine pattern forming methods such as UV imprinting, thermal imprinting, UV inkjet printing, and laser etching can be used to form the relief pattern.

[0058] When the pattern forming apparatus 23 forms an uneven pattern by UV imprinting, the pattern forming apparatus 23 has a coating means for applying an ultraviolet-curable liquid onto the first substrate 11a. The pattern forming apparatus 23 also has an imprinting means for imprinting a mold with an uneven pattern formed on its surface onto the ultraviolet-curable liquid on the first substrate 11a, and a light source for irradiating the ultraviolet-curable liquid with ultraviolet light. Typically, the ultraviolet-curable liquid is ultraviolet-curable liquid silicone rubber (PDMS) or resin, the mold is a quartz mold or film mold, and the light source is a UV lamp.

[0059] Furthermore, a rubber mold with an uneven surface pattern can also be used as the first base material 11a. For example, a UV-curable resin such as PDMS is coated onto a known resin substrate such as PET using a known coating method such as a bar coater. Then, the PDMS-coated surface of the substrate is brought into contact with the uneven surface of a quartz mold, and cured by UV irradiation to produce a rubber mold having an uneven pattern. The resulting rubber mold can be used as the first substrate 11a. The uneven pattern formed on the first substrate 11a is preferably a periodic pattern structure. The pattern structure is not particularly limited, but for example, a line pattern is preferred.

[0060] When the first particles P1 are filled into recesses on the first substrate 11a using a support material S1 bearing the first particles P1 with the first filling device 24a, it is preferable that the opening diameter of the recesses in the uneven pattern on the first substrate 11a is larger than the volume-based cumulative 50% particle size (median diameter) of the first particles P1. It is also preferable that the opening diameter of the recesses is smaller than the volume-based cumulative 50% particle size (median diameter) of the support material S1. Here, it is preferable that the opening diameter of the recesses in the uneven pattern is 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.

[0061] As a result, the first particles P1 can come into contact with the bottom and side surfaces (typically the bottom surface) of the recesses in the uneven pattern, while the support material S1 cannot come into contact with 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 the support material S1 cannot be captured by the uneven pattern. In other words, it is preferable that the first particles P1 can come into contact with the bottom and side surfaces of the recesses in the uneven pattern, while the first support material S1 cannot come into contact with the bottom and side surfaces of the recesses in the uneven pattern.

[0062] The pattern forming device 23 forms an uneven pattern on the first substrate 11a, but a substrate with an uneven pattern already formed on its surface may be used as the first substrate 11a. Alternatively, the pattern forming device 23 may directly form an uneven pattern on the surface of the conveying member 224a of the first belt device 22a, or a conveying member with an uneven pattern on its surface may be used as the conveying member 224a. In this case, considering durability, it is preferable to use a metal belt such as stainless steel or aluminum and to form an uneven pattern on its surface using microfabrication techniques such as laser etching, wet etching, or dry etching.

[0063] The first substrate 11a, which has an uneven surface pattern formed on it, is transported by the first belt device 22a to the filling position of the first filling device 24a. Figure 3 is a schematic diagram showing the configuration of the filling device. The configuration of the first filling device 24a will be described below. The first filling device 24a includes a filling container 242a for containing the filler 241a, a stirring screw member 243a for stirring and conveying the filler 241a, a recovery member 244a for recovering the filler, and a magnetic member 247a.

[0064] The filler 241a comprises 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. The filler 241a contained in the filling container 242a is thoroughly mixed when stirred and conveyed by the stirring screw member 243a. As a result, the first particles P1 are supported on the surface of the support material S1. The forces acting between the particles 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 of the first particles P1 that are not supported on the support material S1.

[0065] 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. Furthermore, even if the first particles P1 are small in size and tend to aggregate, the support material S1 plays a role in loosening them through stirring and conveying. For example, magnetic particles (standard carrier P02 manufactured by the Imaging Society of Japan) can be used as the support material S1.

[0066] The recovery member 244a includes a roller 245a that can rotate in the direction of arrow d2 in the figure, and a magnet 246a that is positioned inside the roller 245a and fixed to the filling container 242a. The magnetic member 247a is positioned opposite the filling container 242a via the transport member 224a and has a magnet 248a inside.

[0067] Magnet 246a has multiple north and south poles arranged alternately along the rotational direction of the retrieval member 244a. Magnet 248a has multiple north and south poles arranged alternately along the transport direction of the transport member 224a. Furthermore, magnet 246a has a pole of opposite polarity (N1 pole in Figure 3) at the position closest to and opposite to the downstream magnetic pole (S1 pole in Figure 3) of magnet 248a, and an N2 pole, which is the same polarity as N1 pole, is positioned at the downstream position.

[0068] Magnets 246a and 248a may be composed of multiple magnets, and the types of magnets constituting magnets 246a and 248a are not particularly limited. For example, rare earth magnets such as ferrite magnets, neodymium magnets, and samarium cobalt magnets, permanent magnets such as plastic magnets, or means of generating a magnetic field such as electromagnets can be used. Magnet 248a may be configured to move in the transport direction of the first substrate 11a or in the opposite direction.

[0069] Furthermore, a restricting member for restricting the filler 241a on the first substrate 11a, or a recovery member for recovering any filler 241a that cannot be recovered by the recovery member 244a, may be provided upstream or downstream of the recovery member 224a in the conveying direction. As the recovery member for recovery, in addition to a member similar to the recovery member 244a, simpler members such as fixed magnets or restricting members, or recovery members that recover by air blowing, may be used.

[0070] Next, the process of filling the recesses on the first substrate 11a with the first particles P1 using the first filling device 24a will be explained with reference to Figures 3 to 5. As the first transport member 224a moves in the direction of arrow d1 in Figure 3, the first base material 11a, which is being carried by the first transport member 224a, is transported to the filling position of the first filling device 24a.

[0071] The stirring screw member 243a transports the filler 241a and supplies it onto the first substrate 11a (dotted line a in Figure 3). At this time, a magnetic field is formed by the magnetic member 247a and the recovery member 244a, and the filler 241a, which contains the magnetic particle support S1, forms multiple magnetic spikes on the first substrate 11a due to this magnetic field. The filler 241a supplied onto the first substrate 11a is transported on the first substrate 11a in the state of having formed magnetic spikes as the first substrate 11a moves (dotted line b in Figure 3).

[0072] Figure 4 is a schematic diagram of the filler 241a being transported on the first substrate 11a. For illustrative purposes, filler 241a other than the filler forming a single magnetic spike is omitted from the illustration. As described above, the filler 241a on the first substrate 11a forms magnetic spikes along the magnetic field lines of the formed magnetic field, and is transported while changing the shape of the magnetic spikes as the first substrate 11a moves, as shown in Figures 4A, 4B, and 4C. In this case, a particularly strong magnetic force acts near the magnet 248a, so the transport speed v2 of the filler 241a is smaller than the moving speed v1 of the first substrate 11a when the filler 241a moves away from the magnetic pole, and larger when it moves away from the magnetic pole. That is, the filler 241a on the first substrate 11a has a non-zero relative speed with respect to the first substrate 11a.

[0073] Figure 5 is an enlarged view of the vicinity of the surface of the first substrate 11a in Figure 4. Although not shown in Figure 4, a textured pattern 111a is formed on the first substrate 11a as shown in Figure 5. The filler 241a comes into contact with this textured pattern 111a and is transported together with the first substrate 11a while having a non-zero relative velocity to the first substrate 11a, while receiving a magnetic force (solid line Fm in the figure) in a direction perpendicular to the surface of the first substrate 11a.

[0074] As a result, the first particles P1 supported on the support material S1 are transported while being rubbed against the uneven pattern 111a on the surface of the first substrate 11a. At this time, the particle size of the first particles P1 is smaller than the opening diameter of the recesses in the uneven pattern 111a, and the particle size of the first support material S1 is larger than the opening diameter of the recesses. Therefore, the first particles P1 can come into contact with the bottom surface (bottom) and side surfaces of the recesses in the uneven pattern 111a, but the support material S1 cannot. In other words, only the first particles P1 selectively come into contact with the bottom surface and side surfaces of the recesses within the filler 241a.

[0075] 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 substrate 11a and the structural material constituting the uneven pattern 111a, and detaches from the support material S1. Note that, for illustrative purposes, Figure 5 shows the first particles P1 supported on the surface of the support material S1, but during the stirring, supply, and transport of the filler 241a, it is acceptable for the first particles P1 not to be supported on the support material S1 to be present.

[0076] Downstream of the magnetic member 247a, as shown in Figure 3, a recovery member 244a is positioned with a gap between it and the first transport member 224a. As the first substrate 11a moves, the filler 241a, which has been transported to the vicinity of the downstream magnetic pole (S1 pole) of the magnet 248a, is influenced by the magnetic field formed by the magnet 246a and moves from the first substrate 11a to the recovery member 244a, where it is recovered (dotted line c in Figure 3).

[0077] Furthermore, excess particles on the first substrate 11a can also be removed using magnetic particles. For example, the filler 241a can be replaced with a recovery agent containing only magnetic particles, or magnetic particles and a small amount of first particles P1, and the recovery agent can be transported in the same manner as described above, and the excess first particles P1 can be recovered by transporting it back and forth on the first substrate 11a. During the process in which the recovery agent is transported back and forth on the first substrate 11a, the magnetic particles recover excess first particles P1 and rearrange the first particles P1 that have filled the recesses to make them more dense. It can be filled. Removal of excess particles can be adjusted as appropriate, such as by combining the above methods or performing the process multiple times.

[0078] As described above, during the transport process (dotted lines a, b, and c in Figure 3), the recesses of the uneven surface pattern 111a on the first substrate 11a come into sufficient contact with the multiple fillers 241a. Therefore, after the fillers 241a are recovered by the recovery member 244a, the first particles P1 are selectively and densely arranged in the recesses of the uneven surface pattern 111a.

[0079] In Figures 4 and 5, the first particles P1 are all shown with the same particle size, but in reality, there is a particle size distribution, and depending on the material, aggregated secondary particles may also be formed. Furthermore, the first particles P1 are almost never spherical as shown in the figures. Even in such cases, only the particles that can contact the recesses of the aforementioned uneven pattern 111a are selectively and densely packed, so coarse powder and secondary particles contained in the filler 241a are excluded during the particle placement process, and only the first particles P1 can be selectively arranged in a pattern.

[0080] 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 the first particles P1 to be filled is determined by the depth of the recesses. For example, to obtain a thin layer (single layer) in which the 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 recess is made larger than the volume-based cumulative 50% particle size (median diameter) of the first particle P1, and smaller than the volume-based cumulative 50% particle size (median diameter) of the support material S1.

[0081] The first particle 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. By preventing the support material S1 from coming into contact with the bottom or sides of the recess, it is possible to suppress the support material S1 from being confined and filling the recess. When using brush fibers as described later as the support material, the "average particle size of the support material" in the above explanation becomes the "average fiber diameter of the support material".

[0082] The filler 241a recovered by the recovery member 244a is conveyed by the rotating roller 244a (dotted line d in Figure 3). The filler 241a conveyed by the roller 244a falls into the filling container 242a due to the magnetic field created by two adjacent, repelling magnetic poles of the same polarity (N1, N2) and the influence of gravity (dotted line e in Figure 3). Subsequently, it is agitated and conveyed again by the stirring screw member 243a, and this process is repeated thereafter.

[0083] The mixing ratio of the support material S1 and the first particles P1 is not particularly limited, but for example, the ratio of the mass of the first particles P1 to the mass of the filler (total mass of the support material S1 and the first particles P1) is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass. The weight ratio of the first particles P1 to the support material S1 in the filler 241a within the filling container 242a is determined by an inductance sensor that measures using magnetic permeability, which is common in electrophotographic devices, or by a patch density sensor that predicts the weight by measuring the reflectance density on a substrate, etc. Then, at least one of the first particles P1 and the support material S1 is replenished as needed by a replenishment means (not shown). This enables stable filling over a long period of time.

[0084] In this case, magnetic particles are used as a support material to form a so-called magnetic brush. A filling device that fills recesses with a material has been described, but the method of filling the device is not limited to this. Brush fibers can be used as the support material. Alternatively, an elastic material whose surface is composed of an elastic material can be used as the support material.

[0085] Figure 6A is a schematic diagram showing the configuration of the 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, or polyvinyl chloride. Surface treatment may be applied to the surface of the fibers for the purpose of adjusting their electrostatic properties or rigidity.

[0086] The filling device 24c has a supply member that supplies the filler 241a to the roller 2410. The filler 241a contains a powder composed of a plurality of first particles P1 and is contained in the filling container 242a. In this example, the filler 241a does not contain a support material S1 which is magnetic particles. The filler 241a is stirred and conveyed by the stirring screw member 243a and supplied to the supply member 249. The supply member 249 is a member that supplies the filler 241a to the roller 2410, and its configuration is not particularly limited. For example, the supply member 249 can be a roller in which at least the surface is made of an elastic, porous foam material. Typically, an elastic sponge roller can be used in which a relatively low-hardness polyurethane foam with a foamed skeletal structure is formed on a metal core. In addition to urethane, various rubber materials such as nitrile rubber, silicone rubber, acrylic rubber, hydrin rubber, and ethylene propylene rubber can be used as the material for the foam.

[0087] The supplied filler 241a is filled into the foam on the surface of the supply member 249 and transported to the supply section that contacts the roller 2410. In the supply section, the filler 241a filled into the foam becomes electrically charged by contact with the brush fibers of the roller 2410 and is supported by the brush fibers of the roller 2410. Furthermore, the supply member 249 may also have a function to remove and refresh any filler 241a remaining on the roller 2410. The filler 241a supplied to the roller 2410 comes into contact with the first substrate 11a due to the movement of the brush fibers.

[0088] In this configuration, the first particles P1 in the filler 241a can come into contact with the bottom and side surfaces of the recesses in the uneven pattern 111a on the surface of the first substrate 11a, but the brush fibers cannot. That is, the fiber diameter of the brush fibers is made larger than the opening width of the recesses in the uneven pattern 111a. This allows only the first particles P1 to be selectively arranged in a pattern.

[0089] The fiber diameter of the brush fibers can be measured by placing glass on the surface of the roller 2410 and obtaining an image of the brush fibers through the glass using an optical microscope. In this case, the fiber diameter of about 100 brush fibers is measured, and the average diameter calculated by measuring the distribution of fiber diameters is taken as the fiber diameter of the brush fibers. As the conveying member 224a moves and the roller 2410 rotates, the brush fibers of the roller 2410 are rubbed against the surface of the first substrate 11a. As a result, the first particles supported on the brush fibers are densely arranged in the recesses of the uneven pattern 111a on the surface of the first substrate 11a.

[0090] Figure 6B is a schematic diagram showing the configuration of the filling device 24d when an elastic material is used as the support material. The filling device 24d has the same configuration as the filling device 24c, but has brush fibers. It differs in that it uses roller 2411, which has an elastic material, instead of roller 2410. Roller 2411 is a roller with an elastic layer formed on its surface.

[0091] The elastic layer is formed from an elastic material such as rubber, silicone rubber, acrylic rubber, nitrile rubber, urethane rubber, or fluororubber. The surface shape of the elastic layer may be controlled by adding fine particles such as spherical resin. If the elastic layer has protrusions on its surface, the size of the protrusions of the elastic layer should be larger than the size of the recesses in the uneven pattern 111a. The size of the protrusions of the elastic layer can be measured in the same way as the fiber diameter of the brush fibers described above. As the transport member 224a moves and the roller 2411 rotates, the elastic material on the surface of the roller 2411 is rubbed against the surface of the first substrate 11a. As a result, the first particles supported on the elastic material are densely arranged in the recesses of the uneven pattern 111a on the surface of the first substrate 11a.

[0092] As shown in Figures 6A and 6B, by using brush fibers or elastic materials as the support material, it becomes unnecessary to include magnetic particles in the filler, and the configuration of the filling device can be simplified. On the other hand, when magnetic particles are used as the support material, as shown in Figure 3, there is greater freedom in the size and shape of the support material compared to the case of brush fibers or elastic materials. Also, in the case of magnetic particles, there is greater freedom in the movement of the support material on the substrate. For these reasons, when magnetic particles are used as the support material, particles such as the first particle P1 can be supplied to the substrate more efficiently, and the depressions on the substrate can be filled more efficiently. Furthermore, when a magnetic material is used as the support material, even if the support material deteriorates during the process, the support material can be replenished or replaced without stopping the process.

[0093] 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.

[0094] The first substrate 11a, in which the recesses of the uneven pattern 111a are filled with the first particles P1 by the first filling device 24a, is conveyed to the transfer section 25a by the first belt device 22a. Here, as shown in Figure 2, the second belt device 22b, like the first belt device 22a, has drive rollers 221b and 222b, a pressure roller 223b, and a belt-shaped conveying member 224b suspended from them. At this time, the pressure roller 223b is rotating by force. In the transfer section 25a, the pressure roller 223a of the first belt device 22a and the pressure roller 223b of the second belt device 22b face each other.

[0095] 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 2. The second base material 11b is transported in conjunction with the timing at which the first base material 11a is transported to the transfer unit 25a. In the transfer section 25a, the first particles P1 packed into the first substrate 11a are transferred to the second substrate 11b. In other words, the first substrate 11a can be called a transfer substrate for transferring the first particles P1 to the second substrate 11b. Furthermore, the uneven pattern formed on the surface of the first substrate 11a can be called a transfer uneven pattern.

[0096] The transcription process will be explained below with reference to Figure 7. Figure 7 is a schematic diagram showing the configuration of the transfer section 25a. The transfer section 25a consists of the pressure roller 223a and conveying member 224a of the first belt device 22a, and the pressure roller 223b and conveying member 224b of the second belt device 22b. As described above, the pressure rollers 223a and 223b rotate by force, and the two rollers are connected by the conveying members 224a and 224b. They are in contact. 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.

[0097] The first substrate 11a, which has been filled with first particles P1 by the first filling device 24a, and the second substrate 11b are transported at approximately constant speed by their respective transport 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 adhesion force to the first particle P1 is greater than the adhesion force to the first particle P1 on the first substrate 11a. In other words, the adhesion force of the first particle P1 to the second substrate 11b is greater than the adhesion force of the first particle P1 to the first substrate 11a. As a result, in the nip portion, the first particle P1 on the first substrate 11a is transferred to the second substrate 11b.

[0098] The material of the second substrate 11b is not particularly limited, and a substrate made of the same material as the first substrate 11a can be used. For example, the known resin materials described above can be used. The second base material 11b, like the first base material 11a, may be a base material that is individually separated, such as cut paper, or it may be a continuous base material wound in a roll, such as roll paper, or a continuous base material that is folded alternately, such as continuous paper.

[0099] The second substrate 11b is preferably surface-treated to enhance adhesion in order to transfer the first particles P1 that it comes into contact with. For example, the second substrate 11b is preferably adhesive, having an adhesive portion on its surface.

[0100] Furthermore, it is preferable that the back surface of the second substrate 11b (the surface to which the first particles P1 have not been transferred) also has an adhesive portion coated with the same adhesive as the surface, and that this surface is further covered with a protective film or the like. This prevents misalignment between substrates during lamination, as described later, and firmly fixes the positive electrode active material particles and solid electrolyte particles 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, and the desired electrode can be formed.

[0101] The adhesive may be an acrylic adhesive, a rubber adhesive, or a silicone adhesive, or it may be a thermoplastic resin or a photocurable resin whose adhesive strength changes due to external disturbances such as heat or light. In addition, known epoxy, acrylic, urethane, or two-component mixed adhesives may be used. The material layer forming apparatus 1 may also have a dispenser for applying the adhesive to the surface of the second substrate 11b while it is being transported, as well as known coating means such as an inkjet head or a bar coater.

[0102] 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, etc., but it is preferable that the adhesive strength of the adhesive is greater than that of the textured pattern 111a. The adhesive strength can be compared using a general method using a nanoindenter.

[0103] In the nip section, the first particle P1 is restrained by the adhesive force generated between it and the second substrate 11b. After passing the nip section, the two transport members 224a and 224b separate, and the first particle P1 that was placed on the first substrate 11a is transferred to the second substrate 11b.

[0104] In addition to the above-mentioned apparatus, existing pressurizing devices can also be used as a method for transferring particles. Uniaxial pressurizing devices and isotropic pressurizing devices (CIP / HIP) can be used. By applying pressure while the first substrate 11a and the second substrate 11b are in contact and then separating them, the first particles P1 can be transferred onto the surface of the second substrate 11b.

[0105] For example, a first substrate 11a, in which the recesses are filled with the first particles P1 using the method described above, and a second substrate 11b, which has an adhesive layer pre-applied to it, are prepared. The first substrate 11a and the adhesive layer of the second substrate 11b are bonded together so that the surface of the first substrate 11a with the uneven pattern is in contact with the adhesive layer of the second substrate 11b, then vacuum packaged and pressurized using a pressurizing device. After that, the bonded substrates are removed, and the second substrate 11b is released from the first substrate 11a, thereby transferring the first particles P1 onto the second substrate 11b. The method of vacuum packaging is not particularly limited, but for example, the bonded substrates can be packed into a vacuum bag (manufactured by Asahi Kasei Pax) and then vacuum packaged using a vacuum packaging machine (such as the V-307GII manufactured by Tosei). Vacuum packaging is possible. An isotropic pressurizer (manufactured by Nikkiso) can be used as the pressurizing device. The pressurizing conditions are not particularly limited and can be adjusted as appropriate depending on the material of the base material, but it is preferable to pressurize at, for example, 5 to 200 MPa. The pressurizing time can be adjusted as appropriate, but it is preferable to pressurize for, for example, 0.1 to 5 minutes.

[0106] The second substrate 11b onto which the first particle P1 has been transferred is transported by the transport member 224b to the filling position of the second filling device 24b. The second filling device 24b has the same configuration and function as the first filling device 24a, except that the filling container 242a contains a filling material 241b having second particles P2 and a supporting material S2 instead of a filling material 241a having first particles P1 and a supporting material S1.

[0107] The second filling device 24b fills the portions of the second substrate 11b where the first particles P1 are not present with the second particles P2. As described above, the first particles P1 are present on the second substrate 11b after it has passed through the transfer section 25a, but recesses are formed in the portions where the first particles P1 are not present. The second filling device 24b fills these recesses with the second particles P2 using the same process as the first filling device 24a. In this way, the second particles P2, which can fill the voids on the second substrate 11b where the first particles P1 are not present, are selectively filled, thereby improving the coverage rate of the substrate by the particles. Coverage rate is the ratio of the particle area to the substrate area when the substrate is observed from above.

[0108] The second particle P2 preferably has a median diameter less than or equal to the opening width of the void between the first particles P1 arranged on the second substrate 11b. Although the case in which magnetic particles are used as the support material is described here, brush fibers or elastic materials may also be used as the support material, similar to the first filling device 24a.

[0109] The filler 241b comprises second particles P2 and a support material S2 that supports the second particles P2. The filler 241b is a mixture of multiple powders, including a powder composed of multiple second particles P2 and a powder composed of multiple support materials S2. The support material S2 may be the same as or different from the support material S1. It is appropriately selected according to the particle size and material of the second particles P2 and the opening width of the void described above. The mixing ratio of the support material S2 and the second particles P2 is not particularly limited, but for example, the ratio of the mass of the second particles P2 to the mass of the filler (total mass of the support material S2 and the second particles P2) is preferably 1 to 30% by mass, and more preferably 1 to 15% by mass.

[0110] Figure 8 is an enlarged view of the vicinity of the surface of the second substrate 11b during the filling process by the second filling device 24b. The second substrate 11b has an uneven surface pattern formed thereon, which includes convex portions formed by the placement of the first particles P1 and concave portions where the first particles P1 are not placed. The filler 241b comes into contact with this uneven pattern and is transported together with the second substrate 11b while having a non-zero relative velocity to the second substrate 11b, while receiving a magnetic force (arrow Fm in Figure 8) 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.

[0111] At this time, 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. Here, the opening width of the recesses is the width of the region on the second substrate 11b where the first particles P1 are not placed. In other words, the median diameter of the second particles P2 is controlled to be smaller than the opening width of the recesses, and the median diameter of the support material S2 is controlled to be larger than the opening width of the recesses. As a result, only the second particles P2 can selectively contact the recesses within the filler 241b.

[0112] The second particle P2, upon contact with the recess, is strongly restrained by the physical restraining force due to the structure of the uneven pattern, as well as by the electrostatic adhesion and adhesive force with the second substrate 11b and the structural material constituting the uneven pattern (in this case, the first particle P1), and detaches from the support material S2. Note that, for illustrative purposes, Figure 8 shows the second particles P2 supported on the surface of the support material S2, but it is acceptable for particles P2 not to be supported on the support material S2 to be present during the stirring, supply, and transport of the packing agent 241b.

[0113] Figure 9A is a schematic diagram showing the second substrate 11b after the first particles P1 have been transferred by the transfer unit 25a or the pressurizing device described above, and is a view of the second substrate 11b from a direction perpendicular to the substrate surface. As shown in Figure 9A, a honeycomb pattern is formed on the second substrate 11b, in which arrangement regions in which the first particles P1 are arranged in a regular hexagonal shape are aligned. Within this hexagonal region, the first particles P1 are densely arranged, while in the other areas (the white areas in Figure 9A), the first particles P1 are not present, and the surface of the second substrate 11b is exposed. The hexagonal region where the first particles P1 are held can be described as the first pattern section, and the honeycomb pattern region where the second particles P2 are held, corresponding to the gaps in the first pattern section, can be described as the second pattern section.

[0114] Figure 9B is a schematic diagram showing the second substrate 11b after it has been filled with the second particles P2 by the second filling device 24b, and is a view of the second substrate 11b from a direction perpendicular to the substrate surface. As shown in Figure 9B, the second particles P2 are densely arranged in the areas where the first particles P1 were not previously placed. Furthermore, the first particles P1 and the second particles P2 are densely arranged at the boundary between the area where the first particles P1 are placed and the area where the second particles P2 are placed. Furthermore, particles can be used to fill even the small gaps between the first particles P1 in the same manner. In this case, it is possible to fill the gaps between the first particles P1 using a filler containing particles of a size corresponding to the gaps between the first particles P1 in the same manner as described above, thereby forming an even denser thin film.

[0115] [Particle placement device 2] In addition to the above-mentioned apparatus, the following particle placement apparatus 2 can also be used. Figure 10 is a schematic diagram showing the configuration of the particle placement apparatus 2. The particle placement apparatus 2 is an apparatus for forming a particle layer 12 on a substrate 11, and includes a storage container 21 for storing and supplying the substrate 11, and a belt device 22 for transporting the substrate 11. As the substrate 11, a known resin substrate such as PET can be used.

[0116] Furthermore, the particle placement device 2 includes a liquid application device 201 for placing liquid on the substrate 11. In this case, in order to densely place the first particles P1 on the substrate 11, it is preferable to place the liquid on the substrate 11 in a pattern. As the liquid application device 201, an inkjet-type device that ejects liquid or a liquid coating device can be used, but a plate-based method such as a flexographic plate can also be used. Among these, it is preferable to use an inkjet-type device that ejects liquid as the liquid application device. Inkjet-type liquid ejection devices can utilize various ejection methods, such as thermal, piezo, electrostatic, and continuous types.

[0117] The liquid dispensed by the liquid dispenser 201 may be water-based or oil-based, as long as it contains a material to which the first particles P1 can adhere. The liquid may be appropriately selected, such as by selecting a material that does not react with the first particles P1. Examples of materials to which the first particles P1 can adhere include resins such as acrylic resin. Furthermore, the liquid application device 201 may form the pattern L1 using multiple types of liquids. For example, the liquid application device 201 may apply two types of liquids that react on the substrate 11 to increase its viscosity. The pattern L1 is preferably a line pattern, for example.

[0118] The powder dispensing device 202 dispenses powder containing the first particles P1 onto the substrate 11, which is arranged so that the liquid forms a pattern L1. As a result, the first particles P1 are fixed on the substrate 11 in a pattern corresponding to pattern L1. The means by which the powder is applied by the powder application device 202 are not particularly limited, and for example, means of blowing or sprinkling the powder toward the substrate 11 can be used. The powder application device 202 may further include means for removing first particles P1 that are not fixed to the substrate 11 by means of vibration, centrifugation, air blowing, suction, etc.

[0119] The particle distribution device 2 may further include a drying device that evaporates at least a portion of the liquid applied by the liquid application device 201 to control the amount of material on the substrate 11, the thickness of the pattern L1, and so on. This drying device may be installed downstream of the liquid application device 201 and upstream of the powder application device 202. The material on the substrate after drying may be liquid, liquid containing solids, or solids only.

[0120] After the first particles P1 are fixedly placed on the substrate 11, the liquid dispensing device 203 further dispenses the above-mentioned liquid into areas where at least the first particles P1 were not placed. The liquid dispensing device 203 has the same function as the liquid dispensing device 201. In areas of the substrate 11 to which the liquid has been applied by the liquid application device 203, where the first particles P1 are not present, the second particles P2 are placed using the second filling device 24. As a result, a dense particle layer 12 is formed on the substrate 11.

[0121] Furthermore, the particle distribution device 2 may also have a transfer section, similar to the particle distribution device 1. In this case, the transfer section is provided downstream of the powder dispensing device 202. The first particles P1 can be transferred from the base material 11 to another base material having an adhesive portion, and the second particles P2 can be placed in the areas of the base material to which the first particles P1 have been transferred that were not previously placed, using the second filling device 24. This makes it possible to densely arrange the particles on the base material.

[0122] After transferring the particles using particle placement devices 1 and 2, the coverage rate of the substrate by the first particles P1 and the second particles P2 (the ratio of the area of ​​the region where the particles are placed 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. There is no particular upper limit to the coverage rate, and it is usually 100% or less. For example, the coverage rate of the substrate surface by the first particle P1 and the second particle P2 is preferably 60 to 100%. The range is 70-100% area and 80-100% area.

[0123] By ensuring the coverage is within the above range, a dense particle layer is formed on the substrate, improving the density of particles within the electrode. As a result, ion conductivity can be improved. The coverage rate of the substrate by the first particle P1 and the second particle P2 can be measured by photographing the region where the particle layer is formed from the vertical direction of the substrate using an optical microscope, and calculating the area ratio of the region where the first particle P1 and the second particle P2 are located within that region using image processing software. If the particle size is small and measurement is difficult, images taken with an electron microscope may be used. Using a mapping image obtained with SEM-EDX, the first and second particles can be identified, and the area ratio of the region where the first and second particles are located within that region can be calculated.

[0124] Using the particle placement apparatus 1 or particle placement apparatus 2 described above, the first particle P1, which is the positive electrode active material particle, is placed on the resin substrate in the first step (S101 in Figure 1). Subsequently, if necessary, the second particle P2, which is the first solid electrolyte particle, can be placed on the same resin substrate in the second step (S102 in Figure 1). In addition to the particle placement devices 1 and 2, the first particles P1 may be placed on the substrate 11 using known particle placement techniques or transfer techniques, and the second particles P2 may be placed using the filling device 24. Here, as a known particle placement technique, for example, electrophotography can be used. Alternatively, the first particles P1 and the second particles P2 may be placed on the substrate 11 using electrophotography.

[0125] (3rd and 4th steps) After arranging the first particles P1 and the second particles P2 described above on the resin substrate, a third particle P3 may be further arranged. For example, solid electrolyte particles can be used as the third particle P3. If the first particle P1 or the second particle P2 is a solid electrolyte particle, the third particle P3 may be the same solid electrolyte particle as the first particle P1 or the second particle P2, or a different solid electrolyte particle may be used. At least one of the first particle P1, the second particle P2, and the third particle P3 is an active material particle. The third particle P3 may be anything other than a solid electrolyte particle, such as an active material particle, a conductive additive, or a resin particle like a binder resin.

[0126] The third and fourth steps involve settling the first particles P1 and the second particles P2 into the adhesive portion on the resin substrate, and then placing the third particles P3 into the newly exposed adhesive portion on the surface. The following describes the steps in order.

[0127] Figure 11 is a schematic diagram showing the apparatus for the third and fourth processes. In the following description, the first particle P1 refers to positive electrode active material particles, the second particle P2 refers to first solid electrolyte particles, and the third particle P3 refers to second solid electrolyte particles, but is not limited to these. The substrate 11, on which the particle layer 12 has been formed by the particle placement device 1 or particle placement device 2, is transferred to the belt device shown in Figure 11. The belt device is equipped with a particle settling device 25 on the upstream side and a third filling device 24 downstream thereof for placing third particles P3.

[0128] The particle sedimentation device 25 includes 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 into at least one of the pressure rollers 223c and 223d.

[0129] The substrate 11 is conveyed by a belt device to the pressurized section between the pressure rollers 223c and 223d. When pressurized by the pressure rollers 223c and 223d, the first particles P1 and second particles P2 on the substrate settle into the adhesive section on the substrate. As the first particles P1 and second particles P2 settle into the adhesive section 13, the adhesive section 13 is exposed to the surface through the gaps between the particles. In this case, the aforementioned heating element may be used to facilitate the settling of particles into the adhesive portion on the substrate. Alternatively, a heating source may be provided upstream of the particle settling device 25 to heat the adhesive portion on the substrate. 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.

[0130] To suppress particle adhesion to the pressure roller, it is even 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 and upstream of the third filling device 24.

[0131] The particle sedimentation device 25 may be any other known pressurizing or heating device. For example, an isotropic pressurizing device (CIP / HIP), a uniaxial pressurizing device, or even a device that uses weights or magnets to apply pressure may be used. Furthermore, if the specific gravity of the particles is high, they may settle due to their own weight. In this case, it is preferable to promote particle settling by storing the substrate under heating, such as in an oven. The temperature and storage time should be adjusted appropriately according to the physical properties of the particles and adhesive (shape, particle size, specific gravity, tackiness, 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, along with particle settling, the particles will also move in the planar direction on the surface of the substrate, and the density of the particle arrangement tends to decrease.

[0132] In addition to known pressurizing devices and the methods described above, the particles may be pressed and settled by friction with magnetic particles. In this case, a fourth filling device 24 having the same configuration as the first filling device 24a described above can be used as the particle settling device 25. The fourth filling device contains only magnetic particles instead of filler. With the fourth filling device, the magnetic particles rub against the substrate 11, causing the first particles P1 and the second particles P2 on the substrate to settle in the adhesive portion of the substrate.

[0133] Furthermore, by using the fourth filling device 24 described above to settle the particles, there is also the effect of rearranging the first particles P1 and the second particles P2 on the substrate by the magnetic particles. Rearranging refers to the process of placing or removing excess particles that are not fixed to the adhesive part on the substrate into the gaps between particles, or moving or rotating particles that are unstablely fixed to the adhesive part, thereby fixing the particles more stably and increasing the density of the particle arrangement on the substrate. Furthermore, when arranging particles using the particle arrangement device 1 described above, a fourth filling device for the purpose of rearrangement may also be used. In this case, the fourth filling device is placed downstream of the first filling device 24a and the second filling device 24b. This makes it possible to rearrange the first particles P1 and the second particles P2 on the substrate.

[0134] Figure 12 is a schematic diagram of a cross-section of the substrate 11 to illustrate the sedimentation of particles on the substrate 11 by the particle sedimentation device 25. Figure 12A 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 11, and Figure 12B shows the state after the third step. For explanatory purposes, the first The first particle P1 and the second particle P2 are described as spherical and having the same particle size. As shown in Figure 12A, 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 with almost no sedimentation. On the other hand, after the third step, as shown in Figure 12B, the sedimentation of the first particle P1 and the second particle P2 into the adhesive portion 13 progresses significantly, and the adhesive portion 13, which has been pushed out by particle sedimentation, is exposed on the surface through the gaps between the particles.

[0135] Figure 13 is a schematic diagram of the substrate 11 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 upper surface through the gaps between the particles, and tiny recesses (for example, A in Figure 13) with adhesive portions on their bottom surfaces are created between the particles.

[0136] The fourth step is to place the third particle P3 in the minute recess where the adhesive portion is exposed. The third particle P3 can be placed in the same manner as the second particle P2 was placed using a particle filling device in the second step. After the third step, the substrate 11 is transported by a belt device to the filling position of the third filling device 24 for placing the third particles P3, as the fourth step. The third filling device 24 is a filling device that, like the first and second filling devices, uses magnetic particles, brush fibers, or elastic materials as a support material for filling. The following description will focus on a configuration using magnetic particles as the support material.

[0137] The filler contained in the third filling device consists of third particles P3 and a support material S3 that supports the third particles P3. For example, the third particles P3 are solid electrolyte particles. The third particles P3 have a smaller average circular equivalent diameter than the second particles P2. Therefore, the third particles P3 are selectively filled into the aforementioned minute recesses by friction of the filler. At this time, the support material S3 is not filled because it is sufficiently large compared to the opening width of the aforementioned minute recesses. Figure 14 is a schematic diagram of the substrate 11 from above after the fourth step. The third particles P3 are placed in the minute recesses described above. For explanatory purposes, the third particles P3 are described as spherical and having the same particle size, but multiple irregularly shaped third particles P3 can be placed to match the openings of the recesses.

[0138] As the third filling device 24, a simple device that does not use a belt system can also be used. Figure 15 shows an example of the apparatus. The third filling apparatus 24 shown in Figure 15 includes a filling container 242, a stirring screw member 243, a magnetic member 247, a magnet 248, and a regulating member 249. Figure 16 is a schematic diagram illustrating the operation of the filling apparatus. The filler 241, which has been thoroughly stirred by the stirring screw member 243, is supplied in an appropriate amount by the magnetic member 247 (arrow a in Figure 16) and the regulating member 249, which have moved from their home positions. The supplied filler 241 is rubbed on the substrate 11 as the magnetic member 247 moves back and forth (arrow b in Figure 16). After a desired number of rubbings, the magnetic member 247 moves to a distant home position where the magnetic force acting on the filler 241 on the substrate is sufficiently weakened (arrow c in Figure 16).

[0139] The filler 241 on the substrate falls downward due to gravity and is collected in a collection container (not shown). Using air blowing or vibration is even more preferable at this stage. While the collection is performed by rubbing on an inclined surface, it may also be performed on a flat surface. Furthermore, the first particles P1 and the second particles P2 may be arranged similarly using the same simple apparatus. That is, the first and second steps described above can also be performed using the apparatus shown in Figure 16. Note that the third and fourth steps are not essential and may be omitted.

[0140] <Method of manufacturing electrodes> The following describes in detail an example of an electrode manufacturing method with reference to the drawings. The method for manufacturing electrodes comprises the following two steps (the first step and the second step). (1) A first step (S201 in Figure 17) to fix the active material onto the resin substrate via the adhesive portion and form a first laminate. (2) A second step (S202 in Figure 17) in which the laminate is heated in a reducing atmosphere to form electrodes. The following explanation will use a positive electrode using positive electrode active material particles as an example, but the manufacturing method described below can be used for both positive and negative electrodes.

[0141] (First step) The first step is to fix the active material to the resin substrate via an adhesive portion to form a first laminate. In other words, the first step is to form a first laminate in which a resin substrate and a layer containing the active material disposed on the resin substrate are laminated together. The first laminate may be a laminate in which multiple resin substrates to which the active material is fixed via an adhesive portion are laminated together, and the number of laminates is determined according to the desired electrode capacity. Preferably, the first laminate is a laminate in which three or more resin substrates to which the active material is fixed via an adhesive portion are laminated together. Preferably, the first laminate is formed such that the particle layer containing the active material narrows the resin substrate.

[0142] For example, the active material can be fixed to the resin substrate via the adhesive portion by a method such as the one using the particle placement apparatus described above. The active material described above can be used as the active material used in the first step. The active material preferably contains an olivine-based cathode active material, and preferably contains at least one of lithium vanadium phosphate (LVP) and lithium iron phosphate (LFP). In other words, the first step is preferably carried out to fix an active material containing an olivine-based cathode active material onto a resin substrate, and more preferably to fix an active material containing at least one of lithium vanadium phosphate (LVP) and lithium iron phosphate (LFP) onto a resin substrate.

[0143] Furthermore, a solid electrolyte may be further fixed on the resin substrate. That is, the first step may be a step of fixing the active material and the solid electrolyte on the resin substrate via an adhesive portion to form a first laminate. Preferably, the first step is carried out by further fixing the solid electrolyte on the resin substrate so that the first laminate includes the solid electrolyte that comes into contact with the active material.

[0144] As the resin base material on which the active material is fixed, the electrode precursor manufactured by the above method can be used. That is, the first laminate may be a laminate of the electrode precursors manufactured by the above method. The first laminate may include a plurality of the above electrode precursors. The number of laminations is determined according to the desired electrode capacity. The number of laminations is not particularly limited, but it is preferably one or more, and more preferably three or more.

[0145] In addition, the first laminate is preferably formed on a positive electrode current collector as a base. As the positive electrode current collector, known current collectors such as Al foil, SUS foil, platinum (Pt foil), and gold foil can be used. As the base, an electrolyte may be used, but care must be taken regarding the reaction of the electrolyte in the second step described later.

[0146] At this time, as the electrolyte as the base, a separately manufactured solid electrolyte sheet, an electrolyte precursor in which only solid electrolyte particles are arranged on the resin base material by the above method, or the like can be used. Further, the solid electrolyte sheet or the electrolyte precursor may have a negative electrode or a negative electrode precursor formed on the surface opposite to the surface on which the positive electrode precursor is laminated. The solid electrolyte sheet can be formed, for example, by pelletizing a powder of solid electrolyte particles and sintering in air in an electric furnace. As the solid electrolyte particles, Li 1.5 Al 0.5 Ge 1.5 P3O 12 (LAGP) When used, the electrolyte sheet can be formed by sintering in air at 850 °C for 12 hours.

[0147] FIG. 18 is a diagram schematically showing the configuration of a laminate forming apparatus. The laminate forming apparatus includes transport devices 31 and 33 that transport a base material 11b (positive electrode precursor 17) on which a particle layer 12 formed using a particle placement device is formed, and a stage 32 that can move relative to the vertical direction (the direction indicated by the arrow in FIG. 18) by an actuator (not shown). The conveying device 31 receives the positive electrode precursor 17 and conveys it to the stage 32. Examples of conveying devices 31 capable of conveying the positive electrode precursor 17 include a belt conveyor, rollers, and a robotic arm.

[0148] When the positive electrode precursor 17 is transported to the stage 32 by the transport device 31, the stage 32 moves vertically (downward) by the thickness of the positive electrode precursor 17. By repeating the transport by the transport device 31 and the movement of the stage 32, the positive electrode precursor is stacked and the first laminate 15 is formed.

[0149] In this case, it is preferable that the positive electrode precursor 17 has an adhesive portion on the back surface of the base material 11b (the surface opposite to the surface on which the particle layer 12 is formed). This adhesive portion causes the positive electrode precursors to adhere to each other between the base materials, increasing the strength of the laminate and suppressing displacement between the base materials even after the first step. Furthermore, the particle layer 12 between the base materials is sandwiched between the upper and lower adhesive portions, which suppresses displacement during the manufacturing process and storage of the laminate. The adhesive portion can be formed by applying an adhesive using a coating apparatus (not shown) before lamination. Alternatively, a base material 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.

[0150] Furthermore, it is preferable to have a static elimination step to eliminate the positive electrode precursor immediately before the first laminate 15 is formed. The particle layer 12 and substrate 11b formed using the particle placement device are easily charged, and electrostatic repulsion and adsorption forces occur between the substrates when laminating. As a result, when laminating in the first step, the substrates tend to peel off or gaps and wrinkles tend to form between the substrates. By performing a static elimination step in advance, the substrates can be closely adhered to each other, and lamination can be performed while maintaining the density of the particle placement 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 the first laminate 15 is formed, it is preferable to have a degassing process to remove air from the laminate in order to reduce the gaps between the substrates. The degassing process is preferably carried out using a vacuum device or a vacuum packaging machine. For example, it is preferable to pack the multiple electrode precursors stacked by the method described above into a vacuum bag (manufactured by Asahi Kasei Pax), and then vacuum-pack them using a vacuum packaging machine (manufactured by Tosei) to degas and pressurize them. After pressurization, the first stacked body 15 is removed from the vacuum bag and the second step described below is performed.

[0152] (Second step) The second step involves heating the first laminate under a reducing atmosphere to promote the sintering of the particle layer 12, while simultaneously thermally decomposing a portion of the resin substrate and transforming the resin substrate 11 into a carbon-containing layer. In other words, the second step is to heat the first laminate under a reducing atmosphere to sinter the active material and form an active material-containing layer, and to thermally decompose a part of the resin substrate to form a carbon-containing layer. The second step makes it possible to form an electrode having an active material-containing layer containing an active material, and a carbon-containing layer which is a layered porous body containing carbon, having a portion in contact with the active material-containing layer and extending in a direction intersecting the thickness direction of the active material-containing layer.

[0153] Figure 19 is a schematic diagram showing the configuration of a sintering apparatus. The sintering apparatus includes a transport device 41 for transporting the laminate 15 and a heating furnace 42 for heating the laminate 15. The conveying device 41 receives the laminate 15 from the laminate forming device and conveys it to the heating furnace 42. The conveying device 41 is preferably a device capable of conveying the laminate 15, similar to the conveying device 31. Examples of devices capable of conveying the laminate 15 include belt conveyors, rollers, and robotic arms.

[0154] The heating furnace 42 is a furnace for heating the laminate 15. The heating furnace 42 has 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 and the like can be used. The pressurizing means 422 pressurizes the laminate 15 being heated in the heating furnace 42, or pressurizes the laminate 15 before and after heating. Preferably, the pressurizing part of the pressurizing means 422 that pressurizes the laminate 15 is made of a porous material that allows gas to pass through easily. The atmosphere adjustment means 423 has 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.

[0155] Here, when sintering the laminate, it is preferable to heat it for a long time at a temperature that does not cause the resin substrate to completely decompose while maintaining a reducing atmosphere, in order to make the substrate 11b function as an extended porous body. As a method of heating while maintaining a reducing atmosphere, for example, a method of continuously supplying reducing gas at least during the temperature rise and throughout the heating time can be mentioned. When the electrode precursor is heated in a reducing atmosphere, a portion of the resin substrate is gasified by thermal decomposition and released to the outside as a gas. At this time, if the resin substrate is completely thermally decomposed, the source of the reducing gas disappears, and it becomes impossible to maintain the reducing atmosphere. On the other hand, by maintaining a reducing atmosphere through the supply of reducing gas, etc., and heating the electrode precursor for a long period of time at a temperature at which the resin substrate does not completely thermally decompose, a portion of the resin substrate is gasified by thermal decomposition and released to the outside as a gas, thereby forming a carbon-containing layer having a porous carbon structure. In other words, by heating the electrode precursor laminate for a long time in the temperature range described later while maintaining a reducing atmosphere, the resin substrate in the electrode precursor can be transformed into a carbon-containing layer, which is a layered porous material containing carbon.

[0156] Common reducing gases used as atmospheric gases when sintering laminates include hydrogen (H2), carbon monoxide (Co), and hydrocarbon gases (CH4, C3H8, C4H2). 10It is preferable to use gases such as argon (Ar-H2) or argon-hydrogen gas. Argon-hydrogen gas is particularly preferable because it has little effect on the material. It is also possible to use carbon monoxide (Co) generated when heating the laminate 15. In this case, argon (Ar) or the like may be used as the atmospheric gas.

[0157] For example, before sintering the laminate, it is preferable to first release the gas inside the sintering apparatus using the depressurization means 423b, then fill it with the aforementioned atmospheric gas using the atmospheric gas supply means 423a, and repeat this several times. After that, it is preferable to supply the desired atmospheric gas using the atmospheric gas supply means 423a, open an outlet valve (not shown), adjust the inside of the sintering apparatus to a reducing atmosphere, and then sinter. In the second step, it is preferable to maintain a reducing atmosphere, and it is preferable to supply a reducing gas to maintain the reducing atmosphere, at least during the heating and sintering time.

[0158] The temperature at which the laminate 15 is heated is preferably below the thermal decomposition temperature of the particles constituting the particle layer 12. If the particle layer 12 contains only active material particles, it is preferable to heat it at a temperature below the thermal decomposition temperature of the active material. The thermal decomposition temperature referred to here is the temperature at which, when the temperature is gradually increased under the atmosphere during heating in a sintering apparatus, a weight decrease of 10% compared to the weight before the decrease is observed.

[0159] In the second step, the first laminate is heated at a temperature below the thermal decomposition temperature of the active material, but at a temperature in which the resin substrate does not completely decompose. The temperature for heating the laminate is preferably 650°C to 1000°C, more preferably 700°C to 900°C, and even more preferably 750°C to 800°C. By heating the electrode precursor laminate within the above temperature range while maintaining a reducing atmosphere, the resin substrate in the electrode precursor can be transformed into a carbon-containing layer, which is a layered porous material containing carbon.

[0160] The heating time in the second step can be appropriately changed depending on the material of the electrode precursor and the heating temperature. Preferably, the heating time is such that the weight of the resin substrate after heating is 1% to 70% by weight of the weight before heating, more preferably 2% to 60% by weight, and even more preferably 3% to 40% by weight.

[0161] By ensuring that the weight of the resin substrate after heating is 1% or more of its weight before heating, the carbon-containing layer can be more easily made strong enough to withstand the insertion and removal (movement) of the active material. Furthermore, by keeping the weight at 70% or less, the carbon-containing layer can adequately hold the active material, thereby further improving battery capacity. For example, when using PET as the resin substrate material and heating within the above temperature range, the heating time is preferably 1 to 15 hours, more preferably 5 to 12 hours, and even more preferably 7 to 12 hours.

[0162] Figure 20 shows cross-sectional SEM images of the laminate 15 before and after the second process. The cross-sectional processing method and SEM observation conditions will be described later. Figure 20A is a cross-sectional SEM image of the laminate 15 before the second process. The laminate 15 consists of three layers of substrate 11b (electrode precursor 17), each with a particle layer 12 positioned and fixed by an adhesive portion 13, laminated on a Pt foil acting as a current collector 14. It can be confirmed that at least two of the substrate 11b layers are positioned so that their front and back surfaces are in contact with the particle layer.

[0163] Figure 20B is a cross-sectional SEM image of the first laminate 15 after the second process. As the sintering of the particle layer 12 progresses, the shape of the substrate 11b changes significantly and extends to hold the particle layer 12 within the positive electrode. In other words, the heating process transforms the particle layer 12 into an active material-containing layer, and the substrate 11b is modified to become a carbon-containing layer having a porous carbon material. Furthermore, the modification of the substrate 11b, which was positioned so that its front and back surfaces were in contact with the particle layer in the cross-sectional SEM image before heating, results in a configuration where the active material-containing layer is sandwiched between the carbon-containing layers. As a result, the active material contained in the active material-containing layer is held within the electrode by the extending porous carbon-containing layer 11x, and desorption is suppressed. In other words, in the electrode manufacturing process, by stacking three or more electrode precursors such that the substrate 11b and particle layer 12 are alternately present, an electrode can be obtained in which the active material-containing layer is sandwiched between carbon-containing layers, and the carbon-containing layer is sandwiched between active material-containing layers.

[0164] In the electrode after the second step, the active material-containing layer preferably includes a sintered body of the active material extending along the carbon-containing layer. This allows the carbon-containing layer 11x to come into contact with the active material, which is thought to facilitate the diffusion of lithium ions and the conduction of electrons within the positive electrode, thereby enabling high capacity and output.

[0165] Figures 21 and 22 are EDX mapping images used to identify each part of the laminate 15. Figure 21A is a cross-sectional SEM image of the first laminate 15 before the second process, Figure 21B is a mapping image of the carbon (C) component, and Figure 21C is a mapping image of the phosphorus (P) component. In the examples shown in Figures 21 and 22, lithium vanadium phosphate is used as the positive electrode active material and lithium borate is used as the solid electrolyte. Therefore, the phosphorus contained in the positive electrode active material ( The positive electrode active material (P1) can be identified by the P) component. In addition, the substrate 11b and the adhesive portions 13 formed on its upper and lower surfaces can be identified by the carbon (C) component.

[0166] Figure 22A is a cross-sectional SEM image of the electrode after the second step, Figure 22B is a mapping image of the carbon (C) component, and Figure 22C is a mapping image of the phosphorus (P) component. As described above, in the example shown in Figure 22, lithium vanadium phosphate is used as the positive electrode active material and lithium borate is used as the solid electrolyte, so the positive electrode active material (P1) can be identified by the phosphorus (P) component contained in the positive electrode active material. In addition, the carbon (C) component can be used to identify the extended carbon-containing layer 11x that has been modified from the substrate 11b. The carbon-containing layers 11x extend in multiple layers horizontally in Figure 22B, with some carbon-containing portions connecting the carbon-containing layers. This is thought to be due to carbon components that were trapped in the particle layer and remained when the resin substrate was partially gasified by thermal decomposition and released outside the positive electrode.

[0167] Figure 23A is a cross-sectional SEM image of the electrode after the second step, Figure 23B is a mapping image of the carbon (C) component, and Figure 23C is a mapping image of the boron (B) component. The carbon-containing layer 11x extends to hold the active material-containing layer, and its porous nature, consisting of numerous voids, can be confirmed from the cross-sectional SEM image (Figure 23A). Furthermore, it can be seen that the carbon-containing layer 11x deforms to conform to the shapes of the upper and lower active material-containing layers. Thus, both the upper and lower surfaces of the carbon-containing layer 11x extend to contact the active material-containing layer, and the carbon-containing layer 11x is positioned to sandwich the active material-containing layer. As a result, the carbon-containing layer 11x deforms to follow volume fluctuations in the active material-containing layer, functioning as a relaxation layer. Moreover, the carbon-containing layer 11x holds the active material-containing layer in a predetermined position, preventing desorption. Consequently, ion conductivity can be improved, and capacity and output can be enhanced.

[0168] Figures 24A and 24B show scanning transmission electron microscope (STEM) images of the cross-section of the electrode after the second step. Figure 24A is a HAADF-STEM image, and Figure 24B is a carbon mapping image. Figure 25 shows the results of EELS measurement in the carbon-containing layer 11x. The TEM observation conditions will be described later. By using HAADF-STEM and EELS in combination, the elements constituting the electrode can be identified. Figure 25A shows the measurement position (area 1) of the EELS measurement in the electrode cross-section, and Figure 25B shows the analysis result of the EELS spectrum at the above measurement position (CK end). A peak of π bonds originating from the carbon-carbon double bond can be seen around 286 eV, and a peak of σ bonds originating from the carbon-carbon double bond can be seen around 294 eV. In other words, it can be confirmed that the carbon-containing layer of the electrode has π bonds and σ bonds originating from the carbon-carbon double bond.

[0169] Figure 26 shows the X-ray diffraction spectrum of the electrode after the second step. The conditions for the X-ray diffraction analysis will be described later. In addition to the main peak of lithium vanadium phosphate (● in the figure), the main peak of lithium borate (〇 in the figure), and the peak of Pt, there are also lithium-carbon compounds (LiC6 and LiC6). 12 A peak can be observed. This indicates that the carbon-containing layer 11x contains a Li-containing compound.

[0170] As described above, when a carbon-containing layer is formed by modifying the substrate 11 using a sintering apparatus, it is preferable that the active material and solid electrolyte are made of materials having a higher thermal decomposition temperature than the substrate 11. Generally, inorganic materials tend to have higher thermal decomposition temperatures than organic materials, so it is preferable that the positive electrode active material and solid electrolyte are inorganic materials, and the material of the substrate 11 is an organic material such as resin.

[0171] When the substrate 11 in the laminate 15 is modified by sintering, the resin substrate is partially gasified by thermal decomposition and released to the outside as a gas. At this time, the particle layer 12 formed on the substrate 11 may be disturbed. For this reason, the thickness of the resin substrate used as the electrode precursor is reduced, and the particles It is preferable to minimize the impact on the layer. Specifically, the thickness (μm) of the resin substrate is preferably 1 μm or more and 500 μm or less, and more preferably 3 μm or more and 100 μm or less. The thickness of the substrate can be measured using a cross-sectional SEM image or a digital thickness gauge.

[0172] Furthermore, the known resin materials described above can be used as the material constituting the base material 11. Among these, PET is preferred from the viewpoint of decomposition temperature and the low toxicity of the gases generated during thermal decomposition. The active material and solid electrolyte are preferably materials that do not easily decompose by reduction even during sintering in a reducing atmosphere, and are not particularly limited. The materials mentioned above can be used as the active material and solid electrolyte.

[0173] <Electrode Vinyl Laminate> The electrode precursor laminate is a laminate of electrode precursors manufactured by the method described above (Figure 20A). Preferably, the electrode precursor laminate is a laminate in which three or more electrode precursors are stacked. In this case, it is preferable to have an adhesive portion on the opposite side of the resin substrate of the electrode precursor from where the active material is located, in order to increase the shift resistance and strength of the laminate. That is, it is preferable to manufacture the electrode precursor using a resin substrate that has adhesive portions on both sides. In this case, it is preferable to protect the adhesive portion on the side where the active material is not located with a film, and then peel off the film when manufacturing the electrode precursor laminate to expose the adhesive portion and laminate it. This further strengthens the fixation of the particle layers between the resin substrates and suppresses the disorder of the molded body before and after sintering.

[0174] As described above, in the manufacturing process of the electrode precursor, the active material particles and solid electrolyte particles can be arranged in a pattern due to the uneven pattern of the first substrate 11a. When stacking electrode precursors in a line pattern, it is preferable to stack them so that the orientations of the particle arrangement patterns intersect. For example, when active material particles and solid electrolyte particles are arranged in a line pattern, it is preferable to stack electrode precursors having the same line pattern alternately, with the orientation of the pattern changed by 90°. By stacking in this manner, the line pattern formed by the active material particles and solid electrolyte particles can come into contact with multiple line patterns above and below in the stacking direction of the electrode precursors, thereby improving the diffusivity and electronic conductivity of lithium ions within the positive electrode.

[0175] <Manufacturing method for secondary batteries> There are several possible methods for manufacturing secondary batteries, but here are a few examples. Electrodes manufactured by the above method can be used as electrodes for secondary batteries. A positive electrode, a negative electrode, or both electrodes can be manufactured using the above-described electrode precursor method, based on an electrolyte formed by a current collector or other means. Here, the other means for forming the electrolyte are known means and are not particularly limited, but examples include pelletizing solid electrolyte particles using a uniaxial press or the like and sintering them in an electric furnace or the like.

[0176] A laminated battery can be manufactured by stacking a positive electrode current collector, a positive electrode, an electrolyte layer, a negative electrode, and a negative electrode current collector in that order, and then packaging them in a laminate film. Alternatively, a coin-type battery can be manufactured by packaging the materials stacked in the above order inside a coin case. For example, when manufacturing a laminate-type battery, the positive electrode current collector, positive electrode, electrolyte sheet, negative electrode, and negative electrode current collector are stacked in that order, and the tab leads for the extraction electrodes, which are welded to the current collectors in advance, are placed on the outside of the laminate. These are then packaged in an aluminum laminate film, formed into a laminate cell using a vacuum packaging machine, and pressurized with an isostatic pressurizing device to manufacture an all-solid-state secondary battery.

[0177] The secondary battery includes the above-mentioned electrodes as at least one of the positive and negative electrodes. It is preferable that the secondary battery includes the above-mentioned electrode as the positive electrode. It is also preferable that an electrolyte layer is provided between the positive electrode and the negative electrode. The electrolyte layer is preferably a solid electrolyte layer made of a solid electrolyte. In the electrode manufacturing method described above, by using a positive electrode active material as the active material, an electrode having a positive electrode active material-containing layer can be manufactured. It is preferable that the secondary battery has a positive electrode current collector electrically connected to the positive electrode active material layer. As the positive electrode current collector, known current collectors such as the above-mentioned Al foil, SUS foil, platinum (Pt foil), and gold foil can be used.

[0178] In the electrode manufacturing method described above, an electrode having a negative electrode active material layer can be manufactured by using a negative electrode active material as the active material. The secondary battery preferably has a negative electrode current collector electrically connected to the negative electrode active material layer. It is preferable to use known current collectors such as copper, nickel, copper-nickel, SUS, or carbon as the negative electrode current collector. For example, a metal foil containing the above-mentioned metal can be used as the negative electrode. Alternatively, the negative electrode can be directly formed on the negative electrode current collector or electrolyte layer by a vacuum process such as sputtering.

[0179] The particles constituting the positive electrode, electrolyte, and negative electrode may have different optimal temperatures and atmospheres during sintering. When handling such materials, it is preferable to manufacture each component—the positive electrode, electrolyte layer, and negative electrode—separately and then assemble them into a battery. Furthermore, a laminate containing two or more of the positive electrode current collector, positive electrode, electrolyte layer, negative electrode, and negative electrode current collector can be formed using the method described above with the electrode precursors, and manufactured as a three-dimensional object (half-cell structure). For example, a three-dimensional object can be manufactured by producing two or more of the positive electrode current collector precursor, positive electrode precursor, electrolyte precursor, negative electrode precursor, and negative electrode current collector precursor using the particle arrangement apparatus described above.

[0180] The positive electrode precursor may have a particle layer containing multiple types of particles, or it may have a particle layer containing a single type of particle. Examples of particles contained in the particle layer of the positive electrode precursor include positive electrode active material particles, solid electrolyte particles, and conductive additives, but the particle layer contains at least one type of positive electrode active material particle.

[0181] The electrolyte precursor consists of a particle layer containing at least one type of solid electrolyte particle. Two or more different types of solid electrolyte particles may be used as the solid electrolyte particles contained in the electrolyte precursor. Furthermore, multiple electrolyte precursors containing different types of solid electrolyte particles may be manufactured and then stacked.

[0182] The negative electrode precursor may have a particle layer containing multiple types of particles, or it may have a particle layer containing a single type of particle. Examples of particles contained in the particle layer of the negative electrode precursor include negative electrode active material particles, solid electrolyte particles, and conductive additives, but the particle layer contains at least one type of negative electrode active material particle.

[0183] When the particle layers of the positive electrode and / or negative electrode contain only one type of particle, a dense particle layer of the single type of active material particle can be formed on the substrate by using the same type of filler in the filling devices 24a and 24b. Alternatively, multiple electrode precursors may be formed using two or more different types of active material particles, and then the resulting electrode precursors may be stacked and used. The current collector precursor contains at least one type of conductive particle. The current collector precursor can be formed by arranging the conductive particles on a resin substrate using the method described above.

[0184] Figure 27 is a schematic diagram showing the overall configuration of the additive manufacturing system. The additive manufacturing system 100 includes a control unit U1, a particle layer formation unit U2, a layering unit U3, a modification unit U4, and a post-processing unit U5.

[0185] The control unit U1 is responsible for controlling various parts of the additive manufacturing system 100. The particle layer formation unit U2 forms a particle layer 12 on the substrate 11 using the particle placement device (Figure 2) described above. The lamination unit U3 uses the above-described laminate molding apparatus (Figure 18) to laminate a plurality of substrates 11, each having a particle layer 12 formed in the particle layer formation unit U2, to form a laminate 15 containing a plurality of particle layers 12 and a plurality of substrates 11. The modification unit U4 uses the sintering apparatus described above (Figure 19) to modify the substrate 11 from the laminate 15 formed by the laminate unit U3, thereby forming an electrode with a carbon-containing layer made of a porous carbon material extending inside the electrode. The post-processing unit U5 performs post-processing on the three-dimensional object (electrode) 16 formed by the modification unit U4. Note that the unit configuration shown in Figure 27 is merely an example, and other configurations may be used. The configuration and operation of each unit will be described below.

[0186] [Control Unit] The control unit U1 is responsible for controlling various parts of the additive manufacturing system 100, specifically the particle layer formation unit U2, the additive manufacturing unit U3, the modification unit U4, and the post-processing unit U5. The control unit U1 may include a 3D shape data input unit that accepts input of 3D shape data of a three-dimensional object (hereinafter sometimes referred to as "object to be manufactured") to be formed by the additive manufacturing system 100 from an external device (e.g., a personal computer). As 3D shape data, data created and output by 3D CAD, 3D modeler, 3D scanner, etc., can be used. The file format is not limited, but for example, the STL (StereoLithography) file format can be preferably used.

[0187] The control unit U1 may include a slice data calculation unit that slices the 3D shape data at a predetermined pitch to calculate the cross-sectional shape of each layer, and generates image data (referred to as "slice data") used for image formation by the particle layer formation unit U2 based on that cross-sectional shape. As will be described in more detail later, the particle layer formation unit U2 of this embodiment can use multiple types of materials to form material layers patterned with each material. Therefore, slice data corresponding to the image of each material may be generated. As for the file format of the slice data, for example, multi-level image data (each value representing the type of material) or multi-plane image data (each plane corresponding to the type of material) can be used.

[0188] Furthermore, the control unit U1 may include an operation unit, a display unit, and a storage unit (not shown). The operation unit is a function that receives instructions from the user. For example, it can input power on / off, various device settings, and operation instructions. The display unit is a function that presents information to the user. For example, it can display various setting screens, error messages, and operating status. The storage unit is a function that stores 3D shape data, slice data, various setting values, etc.

[0189] The control unit U1 can be configured, in hardware terms, as a computer equipped with a CPU (Central Processing Unit), memory, auxiliary storage devices (hard disk, flash memory, etc.), input devices, display devices, and various interfaces. Each of the above functions is realized by the CPU reading and executing programs stored in auxiliary storage devices, etc., and controlling the necessary devices. However, some or all of the above functions may be configured with circuits such as ASICs or FPGAs, or they may be executed by other computers using technologies such as cloud computing or grid computing.

[0190] [Particle layer formation unit] The particle layer forming unit U2 is a unit that forms a particle layer 12 on the substrate 11. The particle arrangement device described above (Figure 2) can be used as the layer formation unit U2. The additive manufacturing system 100 may have multiple particle layer formation units U2. This allows for the simultaneous formation of particle layers 12 on the substrate 11, further improving the throughput of forming the laminate and the three-dimensional object. Furthermore, when there are many types of materials constituting the three-dimensional object, a particle layer formation unit U2 can be provided for each material type or group of material types, eliminating the need to switch between material types or processes within the particle layer formation unit U2. This enables the continuous manufacturing of three-dimensional objects.

[0191] [Laminated Unit] The lamination unit U3 is a unit that stacks multiple substrates 11, each having a particle layer 12 formed on it by the particle layer formation unit U2, to form a laminate 15 containing multiple particle layers 12 and multiple substrates 11. The laminate molding apparatus described above (Figure 18) can be used. The lamination unit U3 may further include a transport device 33 for transporting the formed laminate 15 to a modification unit U4 or the like, and a pressurizing device (not shown) for pressurizing the laminate 15 in the lamination direction. Alternatively, it may transport and laminate components (such as electrolyte sheets or current collectors) formed by other methods. The transport device 33 may have the same configuration as the transport device 31.

[0192] [Modification Unit] The modification unit U4 is a unit that modifies the substrate 11 from the laminate 15 formed by the laminate unit U3 to form an electrode 16 having a carbon-containing layer made of a porous carbon material extending inside the electrode. The sintering apparatus described above (Figure 19) can be used as the modification unit.

[0193] [Post-processing unit] The post-processing unit U5 is a unit that performs post-processing on the electrode 16 formed by the modification unit U4. The type of post-processing performed by the post-processing unit U5 is not particularly limited, but one example is a process of heating the electrode 16 to adjust the compositional changes of the material. This process can adjust for compositional deviations of the active material and solid electrolyte caused by firing in a reducing atmosphere. Another example is a process in which a solution in which a conductive additive, binder resin, and electrolyte (polymer electrolyte or inorganic solid electrolyte) is dispersed in a solvent is impregnated into the laminate to disperse each material within the laminate. This process allows the solution to penetrate into the interconnected pores of the carbon-containing layer and the pores of the active material-containing layer within the electrode, thereby promoting ion conduction and electron conduction. After dispersion, heating and pressurizing steps may be included to allow the solvent to volatilize and the binder to set.

[0194] <Secondary battery> The secondary battery manufactured by the method described above includes at least the electrodes described above. That is, it is preferable that at least one of the positive electrode and the negative electrode is an electrode manufactured by the method described above using an electrode precursor. The secondary battery is not particularly limited as long as it satisfies the above, and for example, it may be a laminated battery in which a positive electrode current collector, a positive electrode, an electrolyte layer, a negative electrode, and a negative electrode current collector are laminated in this order and packaged in a laminate film, or it may be a coin-type battery in which the materials laminated in the above order are packaged in a coin case.

Example

[0195] Hereinafter, the present invention will be described in more detail using examples, but the present disclosure is not limited to these examples. In the following examples, unless otherwise specified, the number of parts is based on mass parts.

[0196] (Example 1) The positive electrode was formed using the above-described laminated shaping system 100. Specifically, a positive electrode precursor having a particle layer formed on a substrate 11 was produced using the particle layer forming unit U2 shown in FIG. 27, and the positive electrode precursor was laminated (number of laminations: 3) on a current collector (Pt foil) using the lamination unit U3. Then, the substrate 11 was modified using the modification unit U4 to form a positive electrode provided with a carbon-containing layer composed of a porous body of carbon extending inside the electrode. The sintering atmosphere in the modification unit U4 was an Ar-H2 gas, and the carbon-containing layer was formed by heating at a sintering temperature of 750° C. for 10 hours. As the electrolyte, Li 1.5 Al 0.5 Ge 1.5 P3O 12 (LAGP) powder was pelletized with a uniaxial pressing device and an electrolyte sheet (thickness: 260 μm) was formed by sintering in air (850° C. / 12 h) in an electric furnace. The negative electrode used indium foil (thickness: 50 μm, hereinafter also referred to as In).

[0197] In an environment with a temperature of 25°C and a humidity of 50%, stack the positive current collector (Al foil with a thickness of 20 μm), the positive electrode (on a Pt foil), the electrolyte sheet, the negative electrode (In), and the negative current collector (Cu foil with a thickness of 20 μm) in this order. Place the tab leads for the extraction electrode, which are pre-welded to the current collector, outside the laminate, and package them in an aluminum laminate film. Then, form them into a laminate cell using a vacuum packaging machine (manufactured by TOSEI), and pressurize them (196 MPa) with an isostatic pressure pressurizing device (manufactured by Nikkiso Co., Ltd.) to fabricate an all-solid-state secondary battery.

[0198] <Fabrication of the Positive Electrode Precursor 1> The forming process of the positive electrode will be described in order. First, the method for fabricating the positive electrode precursor will be described. The formation of the particle layer used the third filling device 24 in FIG. 15. Instead of the base material 11, a rubber mold with a linearly formed concavo-convex pattern on its surface, which was separately fabricated, was placed and fixed.

[0199] The method for fabricating the rubber mold will be described. A master mold with a reverse pattern of the desired concavo-convex pattern was prepared. The master mold was fabricated by known microfabrication techniques, such as typical photolithography techniques and physical processing techniques such as cutting, machining, and laser processing. The master mold used was a quartz mold having a line pattern with a line width of 7 μm, a pitch width of 14 μm (concavo-convex ratio 50 area%), and a depth of 5 μm by photolithography techniques.

[0200] Next, a rubber mold with a reverse pattern of the quartz mold was fabricated by UV nanoimprint technology. An ultraviolet curable resin (ultraviolet curable liquid silicone rubber, PDMS, manufactured by Shin-Etsu Chemical Co., Ltd.) was coated on a resin substrate (PET) using a bar coater, and the concavo-convex surface of the above-mentioned quartz mold was brought into contact with the PDMS surface and cured by UV irradiation to fabricate the rubber mold.

[0201] The filler 241 used a powder prepared by mixing the first particle P1, which is lithium vanadium phosphate Li3V2(PO4)3 (LVP) (manufactured by Tokyo Chemical Industry Co., Ltd.), and the support material S1, which is magnetic particles (standard carrier P02 manufactured by the Image Society of Japan), such that the ratio of the mass of LVP particles to the mass of the filler was 17% by mass. The cumulative 50% particle size (median diameter) in the volume-based particle size distribution of LVP particles was 3.3 μm, and the thermal decomposition temperature was 1500°C. The cumulative 50% particle size (median diameter) in the volume-based particle size distribution of standard carrier P02 was 81 μm.

[0202] The magnetic member 247 and the supply member 249 provided a fixed amount of filler 241. The magnetic member 247 reciprocated along its inclined surface (60 reciprocations) to transport the filler 241 back and forth onto the rubber mold. The filler 241 was transported by the magnetic force of the magnetic member 247, rubbing against the surface (unevenness) of the rubber mold, and LVP particles filled the recesses of the rubber mold. Next, a packing material 241 consisting solely of magnetic particles was used as a recovery agent and similarly transported back and forth on the rubber mold (60 reciprocations). This operation recovered excess LVP particles while removing them from the recesses. The LVP particles were rearranged and densely packed into the rubber-shaped recesses.

[0203] Next, the LVP particles filled in the recesses of the rubber mold were transferred to the substrate 11. The base material 11 consisted of a 3 μm thick PET film with a 1 μm thick adhesive layer (acrylic adhesive) formed on both the front and back surfaces, and the adhesive layer on the back surface covered with a film. The uneven surface of a rubber mold filled with LVP particles was bonded to the surface (adhesive layer) of the base material 11, and the pieces were packed into a vacuum bag (manufactured by Asahi Kasei Pax) and vacuum-packed using a vacuum packaging machine (manufactured by Tosei). The vacuum bag was pressurized (20 MPa) using an isostatic pressurizing device (manufactured by Nikkiso), and the base material 11 was released from the rubber mold after being removed from the vacuum bag, thereby transferring the LVP particles to the surface of the base material 11.

[0204] Next, the substrate 11 onto which the LVP particles were transferred was placed and fixed in the third filling apparatus 24 in Figure 15. The filler 241 is lithium borate Li3BO3 (manufactured by Toyoshima Seisakusho), which is the second particle P2. A powder was used, which consisted of magnetic particles (standard carrier P02, manufactured by the Imaging Society of Japan) as the support material S1, mixed so that the mass of LBO particles was 8% by mass relative to the mass of the packing material. The cumulative 50% particle size (median diameter) in the volume-based particle size distribution of the LBO particles was 4.2 μm.

[0205] The magnetic member 247 and the supply member 249 provided a fixed amount of filler 241, and the magnetic member 247 reciprocated along its inclined surface (60 reciprocations) to transport the filler 241 onto the substrate 11. The filler 241 was transported by the magnetic force of the magnetic member 247, rubbing against the surface of the substrate 11 (unevenness due to the presence or absence of LVP particles), and LBO particles filled the non-transferable areas of the substrate 11, in other words, the recesses of the substrate 11. Next, a packing agent 241 consisting solely of magnetic particles was used as a recovery agent and transported back and forth (60 times) on the substrate 11. Through this operation, excess LBO particles were recovered while the particles were rearranged, forming a particle layer 12 on the substrate 11 and creating a positive electrode precursor 1.

[0206] Figure 28A is an SEM image of the particle layer 12 of the positive electrode precursor 1 observed from above, and Figure 28B is an EDX mapping image of phosphorus. In Example 1, the particle layer 12 had LVP particles arranged in a linear pattern, with LBO particles arranged in a linear pattern to fill the gaps between the lines. Figure 29A is an SEM image of a cross-section of the particle layer 12 of the positive electrode precursor 1, and Figure 29B is an EDX mapping image of phosphorus. By mapping phosphorus, LVP particles can be identified. The sample for cross-sectional observation was processed so that the cross-section was perpendicular to the direction of the lines of the particle arrangement pattern (line pattern shown in Figure 28B). In the positive electrode precursor of Example 1, the LVP particles formed a multilayer particle layer in a linear shape, and the LBO particles formed a particle layer filling the spaces between these lines. Furthermore, the coverage rate of the resin substrate by LVP particles and LBO particles in positive electrode precursor 1 was 80%.

[0207] <Fabrication of Cathode Precursor Stack 1> Next, we will explain the method for fabricating the positive electrode precursor stack. Using the lamination unit U3, a positive electrode precursor laminate 1 was fabricated by laminating three positive electrode precursors 1 (Φ8mm) onto a Pt foil (d20μm). At this time, the film on the side (back side) where the particle layer 12 of the positive electrode precursor 1 was not formed was released to expose the adhesive layer, and the positive electrode precursors were sequentially laminated and fixed so that the line directions of the particle arrangement patterns of each positive electrode precursor intersected. That is, the positive electrode precursors were laminated alternately with the direction of the line pattern changed by 90°. This is to improve the diffusivity and electronic conductivity of lithium ions in the positive electrode by having lines made of LVP particles and LBO particles come into contact with multiple lines made of LVP particles and LBO particles above and below during electrode molding. The laminated positive electrode precursors were packed into a vacuum bag (manufactured by Asahi Kasei Pax) and vacuum-packed using a vacuum packaging machine (manufactured by TOSEI) to degas and pressurize. After pressurization, the material was removed from the vacuum bag to obtain the cathode precursor laminate 1.

[0208] Figure 30A is a cross-sectional SEM image of the cathode precursor stack 1, and Figure 30B is an EDX mapping image of phosphorus. In the first and third layers, phosphorus (LVP particles) are present at intervals, while in the second layer, phosphorus (LVP particles) are present in a linear pattern, confirming that the layers are stacked so that the linear directions of each precursor intersect.

[0209] <Fabrication of positive electrode 1> Next, the substrate 11 of the positive electrode precursor laminate 1 was modified to produce the positive electrode 1. The production method will be described below. The obtained cathode precursor laminate 1 was treated with a modification unit U4 to modify the substrate. The modification unit U4 was heated using the sintering apparatus shown in Figure 19. Before sintering the positive electrode precursor laminate, the sintering apparatus was first depressurized by the depressurization means 423b to release sufficient gas from inside the apparatus, and then filled with Ar gas by the atmosphere gas supply means 423a. This process was repeated three times. Subsequently, the atmosphere gas supply means 423a was started to supply Ar-H2 gas (2.9%) (0.1 Nl / min), and an outlet valve (not shown) was opened to prevent the inside from becoming positive pressure, adjusting the inside of the sintering apparatus to a reducing atmosphere, and then heating was started. During heating, the supply of Ar-H2 gas was continued to maintain the reducing atmosphere. The heating temperature was 750°C, and the heating time was 10 hours. By heating, the substrate was transformed into a carbon-containing layer consisting of a porous carbon material, and positive electrode 1 was fabricated.

[0210] Figure 31A is a cross-sectional SEM image of the positive electrode 1, and Figure 31B is an EDX mapping image of carbon. Three carbon-containing layers 11x corresponding to three substrates 11 were identified within the positive electrode 1. The carbon-containing layers 11x extended in a manner that sandwiched the active material-containing layer containing the active material. Furthermore, they deformed to conform to the active material-containing layer and were in good contact with the active material-containing layer. Figure 32 is an enlarged view of the carbon-containing layer 11x shown in Figure 31. The substrate 11 became porous due to thermal decomposition, and the carbon-containing layer 11x was formed as a porous body extending in layers.

[0211] Using the fabricated positive electrode 1, an all-solid-state battery 1 was constructed using the method described above, and its charge-discharge characteristics and cycle characteristics were evaluated. The detailed conditions for the charge-discharge characteristics and cycle characteristics evaluation will be described later. Figure 33 shows the charge / discharge measurement results of all-solid-state battery 1 at an output of 1C. Good charge / discharge characteristics were confirmed even at high output. Figure 34 shows the cycle evaluation results of all-solid-state battery 1 at an output of 1C. A high capacity retention rate (discharge capacity / charge capacity × 100%) was maintained even after 100 cycles, confirming both high output and good cycleability.

[0212] Next, the all-solid-state battery 1 was disassembled after the cycle evaluation, and the positive electrode 1 was removed and observed in cross-section. Figure 35 is a cross-sectional STEM image of the extracted positive electrode. Figure 35A is a HAADF-STEM image, and Figure 35B is a carbon mapping image. Note that Figures 24A and 24B are cross-sectional STEM observation images of the positive electrode 1 before performing charge-discharge characteristic evaluation and cycle characteristic evaluation, which were fabricated under the same conditions. For the positive electrode 1 before the above evaluation, three carbon-containing layers 11x corresponding to three base materials 11 were confirmed, and the thickness of each carbon-containing layer 11x was 1 to 2 μm.

[0213] Regarding the positive electrode 1 taken out by disassembling the prototype battery after the above evaluation, it was also confirmed that three carbon-containing layers 11x corresponding to three base materials 11 were extending, and they were deformed so as to wrap the active material-containing layer that repeated volume fluctuations, and it was confirmed that they were holding the active material-containing layer (Figure 35A). On the other hand, the thickness of each carbon-containing layer 11x had become thinner than 1 μm (Figure 35B). That is, it is considered that due to the carbon-containing layer 11x being a porous body, the thickness of the carbon-containing layer 11x changes according to the volume fluctuation of the active material-containing layer. It is considered that the thickness of the carbon-containing layer 11x changes according to the volume fluctuation of the active material-containing layer.

[0214] From the above, the reason why the electrode having the configuration of the present disclosure achieves both high output and cycle performance is that the carbon-containing layer 11x contacts and holds the active material-containing layer in the positive electrode, thereby being responsible for the diffusion of lithium ions and the conduction of electrons in the positive electrode, and it is considered that high capacity and output can be obtained. Also, even if the volume of the active material-containing layer fluctuates due to repeated charge and discharge, the porous carbon-containing layer 11x is deformed and further changes in thickness, making it difficult for stress to be applied to the active material-containing layer. Furthermore, since the carbon-containing layer 11x holds the active material-containing layer in the positive electrode so as to sandwich it, it is considered that it is difficult for the active material to desorb in the electrode, suppressing the decrease in capacity and output, and obtaining high cycle performance.

[0215] Figure 36 is an EELS spectrum obtained by cooling EELS measurement at -170 °C of the area of the carbon-containing layer 11x of the positive electrode 1 taken out by disassembling the prototype battery after cycle evaluation. By performing cooling EELS measurement, the positive electrode can be analyzed while suppressing damage caused by electron beam irradiation. Figure 36A shows the EELS spectrum at the Li-K end, and Figure 36B shows the EELS spectrum at the CK end. Arrow A in Figure 36A indicates the peak position of Li (around 60 eV), and arrow B in Figure 36B indicates the peak position of C (around 285-295 eV). After disassembling the prototype battery following cycle evaluation, it was confirmed that the carbon-containing layer 11x of the positive electrode 1 contained a compound composed of lithium and carbon.

[0216] Figure 37 is an enlarged view of Figure 36B. A peak representing a π bond originating from a carbon-carbon double bond was observed around 286 eV, a peak representing a σ bond originating from a carbon-carbon double bond was observed around 292-294 eV, and a peak representing a π bond originating from a carbon-oxygen double bond was observed around 288 eV. In other words, it was confirmed that the carbon-containing layer 11x of positive electrode 1 has π bonds and σ bonds originating from carbon-carbon double bonds, as well as π bonds originating from carbon-oxygen double bonds.

[0217] Figure 38 shows the X-ray diffraction spectra of positive electrode 1 before and after the above evaluation. The dashed line in Figure 38 represents the X-ray diffraction spectrum of positive electrode 1 before the battery was assembled, and the solid line represents the X-ray diffraction spectrum of positive electrode 1 extracted from the prototype battery after 50 charge-discharge cycles. By comparing the dashed and dotted lines, the above evaluation can be performed to determine LiC6 and LiC 12 The peak intensity has been shown to have changed. These results suggest that the carbon-containing layer 11x of the positive electrode is responsible for lithium ion diffusion.

[0218] (Example 2) LYbBO particles were used as the solid electrolyte (second particle P2) for the electrode precursor, and a positive electrode 2 and an all-solid-state battery 2 were fabricated under the same conditions as in Example 1, with a sintering temperature of 650°C and a sintering time of 1 hour. The cumulative 50% particle size (median diameter) in the volume-based particle size distribution of the LYbBO particles was 2.7 μm.

[0219] Figure 39A is an SEM image of cathode 2 observed from above, Figure 39B is an EDX mapping image of phosphorus, and Figure 39C is an EDX mapping image of ytterbium. By mapping phosphorus, LVP particles can be identified, and by mapping ytterbium, LYbBO particles can be identified. In cathode 2, LVP particles were arranged in a linear pattern, and LYbBO particles were arranged in a linear pattern filling the gaps between the lines.

[0220] Figure 40A is a cross-sectional SEM image of the positive electrode 2 removed from the disassembled all-solid-state battery 2, and Figure 40B is a mapping image of the carbon C component. Similar to positive electrode 1 in Example 1 (Figures 31A and 31B), a carbon-containing layer 11x was confirmed within positive electrode 2. In Figures 40A and 40B, the upper side of the image is the side that was in contact with the electrode's current collector (Pt foil), and the lower side of the image is the solid electrolyte sheet. (LAGP) exists.

[0221] (Example 3) A solid-state battery was fabricated using the same conditions as in Example 1, but with only one layer of positive electrode precursor stacked on top.

[0222] (Example 4) A solid-state battery was fabricated using the same conditions as in Example 2, but with only one layer of positive electrode precursor stacked on top.

[0223] (Example 5) An all-solid-state battery was fabricated using LFP particles as the positive electrode active material for the electrode precursor, with a sintering temperature of 700°C and a sintering time of 1 hour, and all other conditions being the same as in Example 1. The cumulative 50% particle size (median diameter) in the volume-based particle size distribution of the LFP particles was 1.6 μm, and the thermal decomposition temperature was 750°C.

[0224] (Example 6) An all-solid-state battery was fabricated using LFP particles as the positive electrode active material for the electrode precursor, with all other conditions being the same as in Example 2.

[0225] (Example 7) A solid-state battery was fabricated using the same conditions as in Example 5, but with only one layer of positive electrode precursor stacked on top.

[0226] (Example 8) A solid-state battery was fabricated using the same conditions as in Example 6, but with only one layer of positive electrode precursor stacked on top.

[0227] (Example 9) An all-solid-state battery was fabricated using Ar as the sintering atmosphere gas in the electrode manufacturing process, with all other conditions being the same as in Example 1.

[0228] (Example 10) An all-solid-state battery was fabricated using Ar as the sintering atmosphere gas in the electrode manufacturing process, with all other conditions being the same as in Example 5.

[0229] (Comparative Example 1) Before sintering with Ar-H2 at 750°C for 10 hours, pre-sintering was performed with Air at 510°C for 1 hour. All other conditions were the same as in Example 1 to fabricate the all-solid-state battery. Figure 41A is a cross-sectional SEM image of the positive electrode of the all-solid-state battery of Comparative Example 1, and Figure 41B is a mapping image of the carbon C component. The carbon-containing layer 11x was not observed within the positive electrode of Comparative Example 1.

[0230] (Comparative Example 2) Before sintering with Ar-H2 at 750°C for 10 hours, pre-sintering was performed with Air at 510°C for 1 hour. All other conditions were the same as in Example 3 to fabricate the all-solid-state battery.

[0231] (Comparative Example 3) Pre-sintering was performed using Air at 510°C for 1 hour before sintering with Ar-H2 at 700°C for 1 hour. All other conditions were the same as in Example 5 to fabricate an all-solid-state battery.

[0232] (Comparative Example 4) Before sintering with Ar-H2 / 700℃ / 1h, pre-sintering with Air / 510℃ / 1h was performed. All other conditions were the same as in Example 7 to fabricate the all-solid-state battery. Table 1 shows the manufacturing conditions and evaluation results for all-solid-state batteries in Examples 1-10 and Comparative Examples 1-4.

[0233] [Table 1] In the table, the number of layers indicates the number of layers of positive electrode precursor. The sintering atmosphere, sintering temperature, and sintering time indicate the sintering atmosphere, sintering temperature, and sintering time when sintering the positive electrode precursor laminate in the modification unit U4. A cycle count of "≧100" indicates that the number of cycles, as evaluated later, was 100 or more. "Present" indicates that an extended carbon-containing layer was present within the electrode. "Absent" indicates that an extended carbon-containing layer was not present within the electrode.

[0234] <Method for determining the presence of an extended carbon-containing layer> The presence or absence of an extended carbon-containing layer was determined for the positive electrodes of the all-solid-state batteries in Examples 1-10 and Comparative Examples 1-4. The determination method was defined as follows. First, the cross-sections of each cathode were observed using SEM-EDX, and EDX images with carbon (C) mapped were obtained. Figure 42A shows an example of a cross-sectional SEM image of a cathode, and Figure 42B shows an example of an EDX image with carbon (C) mapped.

[0235] In the EDX image of carbon C from the above cross-sectional SEM, regions where the carbon distribution is uneven in one direction (y-direction shown in Figure 42B) are extracted and designated as candidates for carbon-containing layers. At this time, the determination of uneven carbon distribution was made by measuring the number of pixels corresponding to the region where carbon is present, one pixel at a time in the y-direction. That is, for regions where the y-direction is 1 pixel and the x-direction matches the width of the image, the number of pixels corresponding to carbon was measured relative to the number of pixels in one column in the x-direction. When more than 50% of the number of pixels in one column in the x-direction correspond to carbon, that column in the x-direction was determined to be a region with uneven carbon distribution. This process was performed for all columns, one pixel at a time in the y-direction, and regions where the uneven carbon distribution was continuous were designated as continuous regions with uneven carbon distribution.

[0236] Next, within the continuous region where the carbon distribution is uneven, the number of pixels corresponding to carbon is measured one pixel at a time in the direction perpendicular to the y-direction (the x-direction shown in Figure 42B) using the method described above. The region where the number of pixels corresponding to carbon accounts for 90% or more of the total number of pixels was determined to be a carbon-containing layer. Image processing and pixel count measurement can be performed using image processing software (such as OpenCV). The image processing methods will be described later. Observations using SEM-EDX were performed under the conditions described below. The measurement area size was set to 1024 × 1365 pixels.

[0237] In other words, a carbon-containing layer was defined as a region where carbon is unevenly distributed in the y-direction, and where carbon is continuously present in the x-direction within the unevenly distributed y-direction region. If at least one carbon-containing layer is found within the electrode using the above determination method, it was determined that a carbon-containing layer exists.

[0238] The following is an example of a method for determining the presence or absence of an extended carbon-containing layer from the EDX image of carbon C in a cross-sectional SEM of the electrode shown in Figure 42A (Figure 42B). First, from the EDX image in which carbon was detected (Figure 42B), only the portion containing the electrode components—carbon, active material, and solid electrolyte—is extracted. An example of the extracted image is shown in Figure 43. The extracted images described above are normalized to have an average brightness of 100 and a standard deviation of ±45. An example of a normalized image is shown in Figure 44A. Next, the normalized image is binarized with a brightness threshold of 125 to obtain an image in which the areas containing carbon are represented by white pixels. An example of an image in which the areas containing carbon are represented by white pixels is shown in Figure 44B.

[0239] For the binarized image, regions with uneven carbon distribution were extracted using the method described above. Figure 45 shows a binarized image with the number of white pixels counted per pixel in the y-direction, and a graph of the measured number of white pixels. In the graph, the vertical axis indicates the measurement position in the y-direction, and the horizontal axis represents the count value of the number of white pixels. The number of pixels in the x-direction of the measured image was 1300. Regions where the count value of white pixels was more than half of the total number of pixels (1300), i.e., more than half were carbon, were extracted and designated as candidates for extended carbon-containing layers (areas L and N, indicated by dashed lines in Figure 45). Next, the region corresponding to the candidate carbon-containing layer was divided into 1300 measurement areas of 1 pixel each in the x-direction, and the ratio of the number of white pixels to the total number of pixels was calculated for each measurement area. Figure 46 shows the results for region L shown in Figure 45, and Figure 47 shows the results for region N shown in Figure 45. In the graphs, the vertical axis represents the count value of the number of white pixels, and the horizontal axis represents the measurement position in the x-direction. In Figure 46, 97.8% (1271 regions) of the total number of measurement regions on the horizontal axis (1300 regions) had 90% or more white pixels. In Figure 47, 99.6% (1295 regions) had 90% or more white pixels. Specifically, in region L shown in Figure 46 and region N shown in Figure 47, it was confirmed that the carbon portion exists seamlessly in the x-direction. Based on the above, it was determined that regions L and N in the cross-sectional SEM image of Figure 42A are extended carbon-containing layers.

[0240] <Method for evaluating output characteristics> The output characteristics of the secondary battery were evaluated by performing charge and discharge measurements (constant current charging / constant current discharging) at specific output currents, and the highest current value at which the capacity retention rate exceeded 80% was used as the output value. To determine the output current value (constant current value), it is necessary to determine the weight (g) of the active material in the positive electrode. The weight of the active material is the mass M (g / cm³) of the active material particles arranged per unit area of ​​the substrate of the positive electrode precursor. 2 ) can be calculated using the following formula. Mass of active material particles = M × Number of stacked positive electrode precursors × Transfer area (cm²) 2 )

[0241] The mass M (g / cm³) of active material particles arranged per unit area of ​​the positive electrode precursor substrate. 2 The positive electrode active material particle area can be determined from the difference obtained by measuring the weight (initial weight) of the rubber mold filled with positive electrode active material particles in the manufacturing process of the positive electrode precursor, and subtracting the weight of the rubber mold after the positive electrode active material particle has been transferred from the rubber mold to the substrate 11 (post-transfer weight) from the initial weight, and from the transfer area of ​​the positive electrode active material particle.

[0242] Another calculation method involves using ICP emission spectroscopy. The mass M (g / cm³) of active material particles per unit area is determined beforehand using the methods described above. 2 Three levels of resin substrates are prepared, each containing a particle layer whose properties have been identified. 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 element V (in the case of LVP). The mass M (g / cm³) of active material particles per unit area relative to the obtained elemental concentration is calculated. 2 A calibration curve is obtained. From the calibration curve, the mass M (g / cm³) of active material particles per unit area of ​​the resin substrate on which the particle layer to be measured is formed can be determined. 2 ) can be calculated.

[0243] In this disclosure, the weight M (g / cm³) of the active material is obtained by subtracting the initial weight from the weight after transfer as described above. 2 ) was calculated. Based on the calculated weight (g) of the active material of the positive electrode and the actual capacity (LVP: 130 mAh / g, LFP: 150 mAh / g), the output current value corresponding to the C-rate is determined. Specifically, the product of the calculated weight (g) of the active material in the positive electrode and the actual capacity is the current value (mA) for charging (or discharging) in 1 hour, which is defined as 1C. 0.5C is the current value for charging (or discharging) in 2 hours, and 0.1C is the current value for charging (or discharging) in 10 hours. Charge-discharge measurement (constant current charging / constant current discharging) was performed at the determined output current (0.05C to 1C), and the capacity retention rate (discharge capacity (mAh / g) / charge capacity (mAh / g) × 100%) was obtained. The highest current value at which the capacity retention rate was 80% or more was taken as the output. In the present disclosure, it was determined that the output characteristics were good when the output was 0.4C or more.

[0244] <Evaluation method of cycle characteristics> Cycle evaluation (repeated charge-discharge measurement in constant current mode) was performed at the current value in the above output. The capacity retention rate was obtained for each charge-discharge cycle, and the maximum number of cycles at which the capacity retention rate was 80% or more was taken as the cycle number. For example, a cycle number of 100 or more indicates that the capacity retention rate was maintained at 80% or more even after 100 or more charge-discharges. On the other hand, a cycle number of 3 indicates that the capacity retention rate was maintained at 80% or more at the time of 3 charge-discharges, and the capacity retention rate became less than 80% at the time of the 4th charge-discharge.

[0245] <SEM measurement conditions> (Pretreatment method) The sample was cut with a wire saw (DWS3400 / wire diameter 170 μm · diamond diameter 30 μm) so as to obtain a cut surface that can observe a cross section perpendicular to the surface direction of the positive electrode precursor laminate and the positive electrode. The cross section was processed with a broad ion beam of Ar (JEOL SM-09010 Cross Section Polisher). The conditions for cross section processing were a voltage of 6 kV and a current of 150 - 200 mA. Instead of using a broad ion beam (BIB), a fine ion beam (FIB) with variable ion particle intensity and beam diameter in the beam can also be used.

[0246] (Observation and EDX measurement conditions) Cross-sectional observations of the cathode precursor laminate and the cathode were performed using an electron microscope. The cross-section obtained by the above method was photographed using an electron microscope (ULTRA55 manufactured by Carl Zeiss) under the following conditions. Observation conditions: acceleration voltage 2 - 10 kV (2 kV for detecting carbon C and boron B, 10 kV for detecting phosphorus P, vanadium V, and iron Fe) Magnification: 7000 times Next, SEM-EDX (XFlash Detector 630M manufactured by Bruker) was used to perform elemental and compositional analysis of the cathode precursor laminate and the cathode, and to identify the cathode active material, solid electrolyte, resin substrate, and carbon-containing layer.

[0247] The method for identifying the cathode active material and the carbon-containing layer will be described. The cathode active material was analyzed by X-ray diffraction (XRD) etc. of the cathode to identify the substances constituting the cathode. Then, specific elements contained in each of the cathode active material and the solid electrolyte were detected and identified by SEM-EDX by the above method. For example, the composition P was identified as an element for identifying the cathode active materials LVP and LFP. The carbon-containing layer was detected by SEM-EDX by the above method, and the composition C was identified.

[0248] The above method for determining the extending carbon-containing layer used an image with an acceleration voltage of 2 kV and a magnification of 7000 times. In addition to the above X-ray diffraction, the identification of the substances constituting the cathode can also be performed by electron energy loss spectroscopy (EELS) in TEM. It can also be identified by Raman spectroscopy or TOF-SIMS, and the substances constituting the laminate may be identified by combining the above analysis methods.

[0249] <STEM measurement conditions> (Pretreatment method) A Pt-Pd film was deposited on the sample, and Pt deposition and fragmentation were performed using a FIB-SEM device (Crossbeam350 manufactured by ZEISS) (30 kV, Ga+). (Observation and cooling EELS measurement conditions) Observation was carried out at an acceleration voltage of 200 kV using a transmission electron microscope device (Talos F200 manufactured by FEI). For the cooling EELS measurement, the sample was cooled to -170 °C with liquid nitrogen using a cryo holder and then measured.

[0250] (XRD measurement conditions) (Pretreatment method) As a sample for XRD measurement, a cathode precursor was laminated on a Si wafer (d 500 μm), and sintering was performed at a heating temperature of 750 °C for 10 hours in an Ar-H2 gas atmosphere and then pressurized (isostatic pressure pressurization device manufactured by Nikkiso Co., Ltd., 196 MPa) in the same manner as in Example 1. At this time, the surface of the sample (cathode) was pressurized so as to be covered with a nichrome foil (d 50 μm manufactured by Nilaco) and then released after pressurization. (XRD measurement conditions) The X-ray tube (Cu), tube voltage and current were set to 45 kV and 200 mA, the incident optical system was a CBO mirror (parallel beam optical system), the solar slit was 2.5°, the beam mask was 5 mm, and the light receiving optical system was PSA 0.5° and the solar slit was 2.5° (detector Hypix3000).

[0251] The present disclosure relates to the following configurations and methods. (Configuration 1) An electrode applicable to a secondary battery, An active material-containing layer containing an active material, A carbon-containing layer having a portion in contact with the active material-containing layer and having a carbon-containing layered porous body extending in a direction intersecting the layer thickness direction of the active material-containing layer, An electrode, characterized by comprising the above. (Configuration 2) The electrode according to Configuration 1, wherein the active material contains an olivine-based cathode active material. (Configuration 3) The electrode according to configuration 1 or 2, wherein the active material comprises at least one of lithium vanadium phosphate and lithium iron phosphate. (Composition 4) The electrode according to any one of configurations 1 to 3, wherein the carbon-containing layer contains the active material such that the region containing the carbon and the region where the active material may be contained are located at different positions. (Composition 5) The active material is the electrode described in configuration 4, which is contained in the pores of the porous body. (Composition 6) The active material-containing layer includes a solid electrolyte, The active material-containing layer exhibits a mixed phase of the active material and the solid electrolyte. An electrode as described in any of configurations 1 to 5. (Composition 7) The electrode according to any one of configurations 1 to 6, wherein the active material-containing layer is sandwiched between the carbon-containing layers such that each of the front and back surfaces of the layer has a portion in contact with the carbon-containing layer. (Composition 8) The electrode according to any one of configurations 1 to 7, wherein the carbon-containing layer is sandwiched between the active material-containing layers such that each of the front and back surfaces of the layer has a portion in contact with the active material-containing layer. (Composition 9) An electrode according to any one of configurations 1 to 8, wherein the carbon-containing layer and the active material-containing layer are alternately stacked. (Composition 10) The electrode according to any one of configurations 1 to 9, wherein the carbon-containing layer has π bonds and σ bonds derived from carbon-carbon double bonds. (Composition 11) The electrode according to configuration 10, wherein the carbon-containing layer further has π bonds derived from carbon-oxygen double bonds. (Composition 12) The electrode according to any one of configurations 1 to 11, wherein the active material-containing layer includes a sintered body of the active material. (Composition 13) A secondary battery comprising at least one of the electrodes described in any of configurations 1 to 12 as the positive electrode and the negative electrode. (Composition 14) A secondary battery having one of the electrodes described in configurations 1 to 12 as the positive electrode. (Composition 15) A secondary battery according to configuration 13, comprising an electrolyte layer between the positive electrode and the negative electrode. (Method 1) A method for manufacturing electrodes applied to secondary batteries, A first step involves fixing an active material onto a resin substrate via an adhesive portion to form a first laminate, A second step involves heating the first laminate under a reducing atmosphere to sinter the active material and thermally decompose a portion of the resin substrate, thereby forming a layered porous body containing carbon and extending in a direction intersecting the lamination direction of the first laminate. A method for manufacturing electrodes, having the following characteristics. (Method 2) The method for manufacturing an electrode according to Method 1, wherein the second step involves heating the active material at a temperature below its thermal decomposition temperature, and the heating is performed for a period of time such that the weight of the resin substrate after heating is 1% by weight or more and 70% by weight or less of the weight of the resin substrate before heating. (Method 3) The method for manufacturing an electrode according to method 1 or 2, wherein the first step is to fix the active material, which includes an olivine-based cathode active material, onto the resin substrate. (Method 4) The first step involves using lithium vanadium phosphate (LVP) and lithium iron phosphate (LF). A method for manufacturing an electrode according to method 1 or 2, wherein the active material comprising at least one of P) is fixed onto the resin substrate. (Method 5) The method for manufacturing an electrode according to any one of methods 1 to 4, wherein the first step is to further fix a solid electrolyte on the resin substrate so that the first laminate contains the solid electrolyte that is in contact with the active material. (Method 6) The method for manufacturing an electrode according to any one of methods 1 to 5, wherein the first step is performed to form a first laminate on the resin substrate such that the particle layer containing the active material is narrowed.

Claims

1. An electrode for use in secondary batteries, An active material-containing layer containing an active material, A carbon-containing layer having a layered porous body containing carbon, having a portion in contact with the active material-containing layer and extending in a direction intersecting the thickness direction of the active material-containing layer, An electrode characterized by containing [something].

2. The electrode according to claim 1, wherein the active material comprises an olivine-based cathode active material.

3. The electrode according to claim 1 or 2, wherein the active material comprises at least one of lithium vanadium phosphate and lithium iron phosphate.

4. The electrode according to claim 1 or 2, wherein the carbon-containing layer contains the active material such that the region containing the carbon and the region in which the active material may be contained are located at different positions.

5. The electrode according to claim 4, wherein the active material is contained in the pores of the porous body.

6. The active material-containing layer includes a solid electrolyte, The active material-containing layer exhibits a mixed phase of the active material and the solid electrolyte. The electrode according to claim 1 or 2.

7. The electrode according to claim 1 or 2, wherein the active material-containing layer is sandwiched between the carbon-containing layers such that each of the front and back surfaces of the layer has a portion in contact with the carbon-containing layer.

8. The electrode according to claim 1 or 2, wherein the carbon-containing layer is sandwiched between the active material-containing layers such that each of the front and back surfaces of the layer has a portion in contact with the active material-containing layer.

9. The electrode according to claim 1 or 2, wherein the carbon-containing layer and the active material-containing layer are alternately stacked.

10. The electrode according to claim 1 or 2, wherein the carbon-containing layer has π bonds and σ bonds derived from carbon-carbon double bonds.

11. The electrode according to claim 10, wherein the carbon-containing layer further has π bonds derived from carbon-oxygen double bonds.

12. The electrode according to claim 1 or 2, wherein the active material-containing layer includes a sintered body of the active material.

13. A secondary battery comprising at least one of the electrodes described in claim 1 or claim 2 as the positive electrode and the negative electrode.

14. A secondary battery comprising the electrode described in claim 1 or claim 2 as the positive electrode.

15. The secondary battery according to claim 13, further comprising an electrolyte layer between the positive electrode and the negative electrode.

16. A method for manufacturing electrodes applied to secondary batteries, A first step involves fixing an active material onto a resin substrate via an adhesive portion to form a first laminate, The first laminate is heated in a reducing atmosphere to sinter the active material and to thermally decompose a portion of the resin substrate, thereby producing carbon-containing material that extends in a direction intersecting the lamination direction of the first laminate. A second step involves forming a layered porous body, A method for manufacturing electrodes, having the following characteristics.

17. The second step involves heating the active material at a temperature below its thermal decomposition temperature, and the heating is performed for a duration such that the weight of the resin substrate after heating is 1% by weight or more and 70% by weight or less of the weight of the resin substrate before heating. The method for manufacturing an electrode according to claim 16.

18. The method for manufacturing an electrode according to claim 16 or 17, wherein the first step is performed to fix the active material, which includes an olivine-based cathode active material, onto the resin substrate.

19. The method for manufacturing an electrode according to claim 16 or 17, wherein the first step is to fix the active material, which comprises at least one of lithium vanadium phosphate (LVP) and lithium iron phosphate (LFP), onto the resin substrate.

20. The first step is carried out to further fix a solid electrolyte on the resin substrate so that the first laminate includes the solid electrolyte that comes into contact with the active material. A method for manufacturing an electrode according to claim 16 or 17.

21. The first step is carried out to form the first laminate on the resin substrate such that the particle layer containing the active material is narrowed. A method for manufacturing an electrode according to claim 16 or 17.

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