Method for manufacturing electrode for all-solid-state battery, and electrode for all-solid-state battery

Abstract

Provided is a means capable of reducing resistance in an electrode for an all-solid-state battery, said electrode having an active material layer that contains an active material, a solid electrolyte, a fibrous conductive assistant, and polytetrafluoroethylene and that has sufficient dispersibility. Provided is a method for producing an electrode for an all-solid-state battery having an active material layer containing an active material, a solid electrolyte, a fibrous conductive auxiliary agent, and polytetrafluoroethylene, the method comprising: a first stirring step in which the active material and the solid electrolyte are placed in a first container and stirred in the first container; stirring by using an acoustic resonance mixer; and a second stirring step for putting the mixture obtained in the first stirring step and the fibrous conductive auxiliary agent into a second container and stirring the mixture and the fibrous conductive auxiliary agent using an acoustic resonance mixer, the first stirring step and the second stirring step satisfying at least one of predetermined conditions (1)-(4).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an electrode for an all-solid-state battery and an electrode for an all-solid-state battery. Background Art

[0002] In recent years, research and development related to all-solid-state batteries using oxide-based and sulfide-based solid electrolytes has become popular. Solid electrolytes are materials composed mainly of ion conductors that can conduct ions in solids. Therefore, all-solid-state batteries have the advantage that, in principle, they do not have the various problems caused by flammable organic electrolytes that have occurred in previous liquid batteries using non-aqueous electrolytes. In addition, when high-potential / large-capacity positive electrode materials and large-capacity negative electrode materials are usually used, a significant increase in the power density and energy density of the battery can be achieved.

[0003] In all-solid-state batteries, in order to ensure good ion conduction paths and electron conduction paths in the active material layer, the active material layer may also contain a solid electrolyte and a fibrous conductive additive in addition to the active material. For example, Japanese Patent Publication No. 2016-58277 discloses a positive electrode mixture comprising positive electrode active material particles, a fibrous conductive material (fibrous conductive additive), a granular conductive material, and a solid electrolyte. The total number of positive electrode active material particles is set to 100%, and the number of positive electrode active material particles in contact with the fibrous conductive material via the granular conductive material is greater than 40%. According to Japanese Patent Publication No. 2016-58277, it is believed that using a positive electrode mixture with such a structure, while taking into account both ion conductivity and electron conductivity, a solid battery with excellent output characteristics can be obtained. In addition, Japanese Patent Publication No. 2016-58277 also discloses that the positive electrode mixture with the above structure may contain a binder such as polytetrafluoroethylene (PTFE). Summary of the Invention

[0004] Problems to be solved by the invention

[0005] However, studies by the present inventors have revealed that when PTFE is used in the positive electrode mixture described in Japanese Patent Application Laid-Open No. 2016-58277, the electrode may have high resistance.

[0006] Therefore, an object of the present invention is to provide a means for reducing resistance in an all-solid-state battery electrode having an active material layer containing an active material, a solid electrolyte, a fibrous conductive additive, and PTFE and having sufficient dispersibility.

[0007] Solutions for solving problems

[0008] The present inventors conducted intensive research to solve the above-mentioned problems and found that a two-stage stirring process using an acoustic resonance mixer as a method for dispersing the active material, solid electrolyte, and fibrous conductive additive can solve the above-mentioned problems, thereby completing the present invention.

[0009] Furthermore, analysis of the all-solid-state battery electrode produced by the above method revealed that the above-mentioned problem can be solved by including a fibrous conductive additive having a predetermined length at a predetermined ratio.

[0010] That is, a method for manufacturing an electrode for an all-solid-state battery according to one embodiment of the present invention is a method for manufacturing an electrode for an all-solid-state battery having an active material layer comprising an active material, a solid electrolyte, a fibrous conductive additive, and polytetrafluoroethylene, comprising: a first stirring step of placing the active material and the solid electrolyte into a first container and stirring them using an acoustic resonance mixer; and a second stirring step of placing the mixture obtained by the first stirring step and the fibrous conductive additive into a second container and stirring them using an acoustic resonance mixer. Furthermore, the manufacturing method is characterized in that the first stirring step and the second stirring step satisfy at least one of the following conditions (1) to (4): condition (1): a maximum distance D1 between inner walls of the first container parallel to the vibration direction of the acoustic resonance mixer in the first stirring step is shorter than a maximum distance D2 between inner walls of the second container parallel to the vibration direction of the acoustic resonance mixer in the second stirring step; condition (2): a frequency of the acoustic resonance mixer in the first stirring step is higher than a frequency of the acoustic resonance mixer in the second stirring step; condition (3): an acceleration of the acoustic resonance mixer in the first stirring step is higher than an acceleration of the acoustic resonance mixer in the second stirring step; and condition (4): a stirring time in the first stirring step is longer than a stirring time in the second stirring step.

[0011] In addition, as another embodiment of the present invention, an electrode for an all-solid-state battery is characterized in that it is an electrode for an all-solid-state battery having an active material layer comprising an active material, a solid electrolyte, a fibrous conductive aid and polytetrafluoroethylene, and the ratio of the number of fibrous conductive aids having a fiber length greater than twice the average particle size (D50) of the active material to the total number of the aforementioned fibrous conductive aids is greater than 40% and less than 90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [ Figure 1 ] Figure 1 It is a perspective view showing the appearance of a flat stacked all-solid-state lithium secondary battery as one embodiment of the all-solid-state battery of the present invention.

[0013] [ Figure 2 ] Figure 2 For the Figure 1 A cross-sectional view along line 2-2 is shown. DETAILED DESCRIPTION

[0014] <Method for manufacturing electrodes for all-solid-state batteries>

[0015] A method for manufacturing an electrode for an all-solid-state battery according to one embodiment of the present invention is a method for manufacturing an electrode for an all-solid-state battery having an active material layer comprising an active material, a solid electrolyte, a fibrous conductive additive, and polytetrafluoroethylene, comprising: a first stirring step of placing the active material and the solid electrolyte into a first container and stirring them using an acoustic resonance mixer; and a second stirring step of placing the mixture obtained by the first stirring step and the fibrous conductive additive into a second container and stirring them using an acoustic resonance mixer. Then, the manufacturing method is characterized in that the first stirring step and the second stirring step satisfy at least one of the following conditions (1) to (4): Condition (1): The maximum distance D1 between the inner walls of the first container parallel to the vibration direction of the acoustic resonance mixer in the first stirring step is shorter than the maximum distance D2 between the inner walls of the second container parallel to the vibration direction of the acoustic resonance mixer in the second stirring step; Condition (2): The frequency of the acoustic resonance mixer in the first stirring step is higher than the frequency of the acoustic resonance mixer in the second stirring step; Condition (3): The acceleration of the acoustic resonance mixer in the first stirring step is higher than the acceleration of the acoustic resonance mixer in the second stirring step; Condition (4): The stirring time in the first stirring step is longer than the stirring time in the second stirring step. According to the manufacturing method of this embodiment, the resistance of an electrode for an all-solid-state battery having an active material layer containing an active material, a solid electrolyte, a fibrous conductive additive and PTFE and having sufficient dispersibility can be reduced. The following describes each step in the manufacturing method of this embodiment.

[0016] [First stirring step]

[0017] In the first stirring step, the active material and the solid electrolyte among the materials constituting the active material layer are placed in a first container and stirred using an acoustic resonance mixer.

[0018] (Active substance)

[0019] The active material exchanges electrical energy by absorbing and releasing ions. When the electrode for an all-solid-state battery of this embodiment is a positive electrode, the active material is a positive electrode active material; when the electrode for an all-solid-state battery of this embodiment is a negative electrode, the active material is a negative electrode active material.

[0020] As a positive electrode active material, there is no particular limitation as long as it is a material that can release lithium ions during the charging process of the all-solid-state battery and can absorb lithium ions during the discharge process. As an example of such a positive electrode active material, there can be listed a material containing an M1 element and an O element, wherein the aforementioned M1 element contains at least one element selected from the group consisting of Li, Mn, Ni, Co, Cr, Fe and P. As such a positive electrode active material, for example, layered rock salt type active materials such as LiCoO2, LiMnO2, LiNiO2, Li(Ni-Mn-Co)O2, LiMn2O4, LiNi 0.5 Mn 1.5 O4 and other spinel active materials, LiFePO4, LiMnPO4 and other olivine active materials, Li2FeSiO4, Li2MnSiO4 and other Si-containing active materials, etc. In addition, as oxide active materials other than the above, for example, Li4Ti5O 12 、LiVO2.

[0021] Furthermore, the positive electrode active material may also contain elemental sulfur. As a positive electrode active material containing elemental sulfur, there is no particular limitation, and in addition to elemental sulfur (S), particles or films of organic sulfur compounds or inorganic sulfur compounds may also be listed, as long as it is a substance that can utilize the redox reaction of sulfur to release lithium ions during charging and absorb lithium ions during discharge. As organic sulfur compounds, disulfide compounds, sulfur-modified polyacrylonitrile, sulfur-modified polyisoprene, erythromycin (dithiooxamide), carbon polysulfide, etc. may be listed. Among them, disulfide compounds (disulfide compound) and sulfur-modified polyacrylonitrile, and erythromycin are preferred, and sulfur-modified polyacrylonitrile is particularly preferred. As disulfide compounds, dithiourea derivatives, substances having a thiourea group, a thiocyanate group, or a thioamide group are more preferred. On the other hand, inorganic sulfur compounds are preferred due to their excellent stability. Specific examples include elemental sulfur (S), S-carbon composites, Li2S, TiS2, TiS3, TiS4, NiS, NiS2, CuS, FeS2, MoS2, and MoS3. Among these, S, Li2S, S-carbon composites, TiS2, TiS3, TiS4, FeS2, and MoS2 are preferred. Elemental sulfur (S), Li2S, TiS2, and FeS2 are more preferred. From the perspective of high capacity, elemental sulfur (S) or Li2S are particularly preferred. It should be noted that as elemental sulfur (S), α-sulfur, β-sulfur, or γ-sulfur having an S8 structure can be used. These elemental sulfur (S) absorb lithium ions during discharge and exist in the positive electrode active material layer as lithium (poly)sulfides.

[0022] Depending on the situation, two or more positive electrode active materials may be used in combination. Of course, positive electrode active materials other than those listed above may also be used.

[0023] The shape of the positive electrode active material is preferably granular. When the positive electrode active material is granular, its average particle size (D50) is preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, further preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. It should be noted that in this specification, the value of the average particle size (D50) of the active material can be measured by laser diffraction scattering method.

[0024] The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but is preferably within a range of 30 to 99 mass %, more preferably within a range of 40 to 90 mass %, and even more preferably within a range of 50 to 85 mass %.

[0025] As the negative electrode active material, there is no particular limitation as long as it is a material that can absorb lithium ions during the charging process of the all-solid-state battery and release lithium ions during the discharging process. As an example of such a negative electrode active material, carbon materials, metal oxides and metal active materials can be listed. As carbon materials, for example, natural graphite, artificial graphite, mesophase carbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, soft carbon, etc. can be listed. In addition, as metal oxides, for example, Nb2O5, Li4Ti5O 12 etc. Furthermore, silicon-based negative electrode active materials and tin-based negative electrode active materials can also be used. Here, as the silicon-based negative electrode active material, it is preferred to use Si simple substance. In addition, it is also preferred to use SiO2 which is not uniform in the two phases of Si phase and silicon oxide phase. x (0.3≤x≤1.6) and other silicon oxides. At this time, the range of x is more preferably 0.5≤x≤1.5, and further preferably 0.7≤x≤1.2. Furthermore, alloys containing silicon (silicon-containing alloy-based negative electrode active materials) can also be used. On the other hand, as negative electrode active materials containing tin elements (tin-based negative electrode active materials), Sn simple substance, tin alloys (Cu-Sn alloys, Co-Sn alloys), amorphous tin oxides, tin silicon oxides, etc. can be listed. Among them, as amorphous tin oxides, SnB 0.4 P 0.6 O 3.1 . In addition, SnSiO3 can be exemplified as tin silicon oxide. In addition, a metal containing lithium can also be used as the negative electrode active material. There is no particular limitation on the negative electrode active material as long as it is an active material containing lithium. In addition to lithium metal, lithium-containing alloys can also be listed. There is no particular limitation on the lithium-containing alloy. For example, alloys of Li and at least one of In, Al, Si, Sn, Mg, Au, Ag and Zn can be listed.

[0026] Depending on the situation, two or more negative electrode active materials may be used in combination. Of course, negative electrode active materials other than those listed above may also be used.

[0027] The negative electrode active material is preferably in the form of particles. When the negative electrode active material is in the form of particles, its average particle size (D50) is preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, further preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm.

[0028] The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but is preferably within a range of 40 to 100% by mass, and more preferably within a range of 50 to 90% by mass.

[0029] (Solid Electrolyte)

[0030] Solid electrolyte refers to a material composed mainly of an ion conductor that can conduct ions in a solid, especially a material with a lithium ion conductivity of 1×10 -5 S / cm or higher, the lithium ion conductivity is preferably 1×10 -4 S / cm or more. Here, the value of ion conductivity can be measured by an AC impedance method. Examples of solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes.

[0031] As for the solid electrolyte, from the viewpoint of exhibiting excellent lithium ion conductivity and being able to follow the volume change of the active material accompanying charge and discharge, a sulfide solid electrolyte containing the S element is preferred, more preferably a sulfide solid electrolyte containing the Li element, the M element and the S element, wherein the M element contains at least one element selected from the group consisting of P, Si, Ge, Sn, Ti, Zr, Nb, Al, Sb, Br, Cl and I, and even more preferably a sulfide solid electrolyte containing the S element, the Li element and the P element.

[0032] The sulfide solid electrolyte may have a Li3PS4 skeleton, a Li4P2S7 skeleton, or a Li4P2S6 skeleton. Examples of sulfide solid electrolytes having a Li3PS4 skeleton include LiI-Li3PS4, LiI-LiBr-Li3PS4, and Li3PS4. In addition, examples of sulfide solid electrolytes having a Li4P2S7 skeleton include Li-PS-based solid electrolytes known as LPS. In addition, examples of sulfide solid electrolytes such as Li (4-x) Ge (1-x) P xS4 (x satisfies 0<x<1) LGPS etc. More specifically, examples thereof include LPS (Li2S-P2S5), Li7P3S 11 、Li 3.2 P 0.96 S. Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 Or Li6PS5X (where X is Cl, Br or I), etc. It should be noted that the description of "Li2S-P2S5" means a sulfide solid electrolyte formed using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions. Among them, from the perspective of having high ion conductivity and low bulk elastic modulus and thus being able to follow the volume change of the active material accompanying charge and discharge, the sulfide solid electrolyte is preferably selected from LPS (Li2S-P2S5), Li6PS5X (where X is Cl, Br or I), Li7P3S 11 、Li 3.2 P 0.96 A group composed of S and Li3PS4.

[0033] The shape of the solid electrolyte is preferably granular. When the solid electrolyte is granular, its average particle size (D50) is not particularly limited, and is preferably 0.01 μm or more and 40 μm or less, more preferably 0.01 μm or more and 20 μm or less, further preferably 0.1 μm or more and 10 μm or less, and further preferably 0.1 μm or more and 1 μm or less. It should be noted that in this specification, the average particle size (D50) of the solid electrolyte adopts the following value: a value calculated as the average value of the particle size of the solid electrolyte observed in several to dozens of fields of view using an observation means such as a scanning electron microscope (SEM) and a transmission electron microscope (TEM).

[0034] The content of the solid electrolyte in the active material layer is preferably 1% by mass or more and 60% by mass or less, and more preferably 10% by mass or more and 50% by mass or less.

[0035] (1st container)

[0036] The first container used in the first stirring step may be any known sealed container without limitation as long as it has airtightness, strength, durability, and the like that prevents the contents from leaking or the container from being damaged during stirring.

[0037] The raw material of the first container can be appropriately selected from synthetic resins, glass, metals, etc. As the raw material of the sealed container, synthetic resins are preferred from the perspective of visibility of the contents. Examples of synthetic resins include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc. Among them, PP and PE are preferred from the perspective of visibility of the contents and versatility.

[0038] The shape of the first container is not particularly limited as long as it can be installed in the acoustic resonance mixer, and examples thereof include polygonal prisms such as triangular prisms and quadrangular prisms (cubes, rectangular parallelepipeds), and cylindrical shapes.

[0039] From the perspective of the efficiency of dispersion caused by the collision of the contents against the inner wall and the collision of particles with each other, the filling rate of the active material and solid electrolyte in the first container is preferably 30 volume % or more and 80 volume % or less, more preferably 40 volume % or more and 60 volume % or less.

[0040] (Acoustic Resonance Mixer)

[0041] In this step, the active material (positive electrode active material or negative electrode active material) and the solid electrolyte are placed in a first container and sealed, and then stirred using an acoustic resonance mixer. Examples of acoustic resonance mixers include LabRAM I and LabRAM II manufactured by RESODYNACOUSTIC MIXERS, INC., but are not limited thereto.

[0042] The frequency of the acoustic resonance mixer is not particularly limited, but from the viewpoint of efficiently stirring the active material and the solid electrolyte, it is preferably 10 Hz to 200 Hz, more preferably 20 Hz to 150 Hz, further preferably 40 Hz to 100 Hz, and particularly preferably 50 Hz to 80 Hz.

[0043] The acceleration of the acoustic resonance mixer is not particularly limited. From the perspective of efficiently stirring the active material and the solid electrolyte, it is preferably 10 G or more and 200 G or less, more preferably 30 G or more and 180 G or less, further preferably 50 G or more and 150 G or less, and particularly preferably 80 G or more and 120 G or less.

[0044] From the viewpoint of sufficiently dispersing the active material and the solid electrolyte, the stirring time is preferably 1 minute to 120 minutes, more preferably 5 minutes to 60 minutes, and even more preferably 10 minutes to 30 minutes.

[0045] [Second stirring step]

[0046] In the second stirring step, the mixture obtained in the first stirring step and the fibrous conductive additive are placed in a second container and stirred using an acoustic resonance mixer.

[0047] (Fiber-shaped conductive additive)

[0048] The fibrous conductive agent can help improve the conductivity (reduce the resistance) in the active material layer. In this specification, the "fibrous conductive agent" refers to a conductive agent having an aspect ratio of 10 or greater and a minimum Feret diameter of 0.2 μm or less in an image observed using a scanning electron microscope (SEM). The electronic conductivity of the fibrous conductive agent is preferably 1 S / m or greater, more preferably 1×10 2 S / m or more, more preferably 1×10 4 S / m or more, more preferably 1×10 5 S / m or more. The upper limit of the electronic conductivity of the fibrous conductive additive is not particularly limited, but is usually 1×10 7 S / m or less.

[0049] As a fibrous conductive aid, from the aspect of being lightweight and having excellent electrical conductivity, conductive carbon is preferably used. As the type of fibrous carbon, as long as there is the above-mentioned shape, there is no particular limitation, and carbon fiber (carbon nanofiber), graphene, carbon nanotube (single-walled carbon nanotube and multi-walled carbon nanotube) can be listed. Among them, carbon fiber (carbon nanofiber) is preferred. Fibrous carbon can be used alone or in combination of two or more.

[0050] The content of the fibrous conductive additive in the active material layer is preferably 1 mass % or more and 10 mass % or less, and more preferably 2 mass % or more and 5 mass % or less.

[0051] (Second container)

[0052] The second container used in the second stirring step is not particularly limited; the same container as the first container used in the first stirring step can be used. The first and second containers may be different containers, but for ease of operation, they are preferably the same container. In this case, in the second stirring step, it is more preferred to place the fibrous conductive additive in the container containing the mixture obtained in the first stirring step and stir using an acoustic resonance mixer. This allows for the omission of steps such as removing and placing powder in the container between the first and second stirring steps.

[0053] From the perspective of the efficiency of dispersion caused by the impact of the contents on the inner wall, the filling rate of the mixture obtained by the first stirring step and the fibrous conductive aid in the second container is preferably greater than 30 volume % and less than 80 volume %, and more preferably greater than 40 volume % and less than 60 volume %.

[0054] (Acoustic Resonance Mixer)

[0055] In this step, the mixture obtained in the first stirring step and the fibrous conductive additive are placed in a sealed second container and stirred using an acoustic resonance mixer. The acoustic resonance mixer, frequency, acceleration, and stirring time in the second stirring step are not particularly limited and are the same as those in the first stirring step.

[0056] The method for producing an all-solid-state battery electrode of this embodiment is characterized in that the first stirring step and the second stirring step satisfy at least one of the following conditions (1) to (4).

[0057] Condition (1): The maximum distance D1 between the inner walls of the first container parallel to the vibration direction of the acoustic resonance mixer in the first stirring step is shorter than the maximum distance D2 between the inner walls of the second container parallel to the vibration direction of the acoustic resonance mixer in the second stirring step;

[0058] Condition (2): The frequency of the acoustic resonance mixer in the first stirring step is higher than the frequency of the acoustic resonance mixer in the second stirring step;

[0059] Condition (3): The acceleration of the acoustic resonance mixer in the first stirring step is higher than the acceleration of the acoustic resonance mixer in the second stirring step;

[0060] Condition (4): The stirring time in the first stirring step is longer than the stirring time in the second stirring step.

[0061] According to the manufacturing method of this embodiment, after the active material and the solid electrolyte are fully dispersed in the first stirring step, a fibrous conductive aid is added in the second stirring step. As a result, the fibrous conductive aid becomes easier to disperse in the mixture of the active material and the solid electrolyte, so even if the stirring is performed under milder conditions than before with the fibrous conductive aid added, a fully dispersed state can be obtained. In addition, by performing the first stirring step and the second stirring step in a manner that satisfies at least one of the above conditions (1) to (4), it becomes difficult to apply a large shear force during the stirring after the addition of the fibrous conductive aid. As a result, the cutting of the fibrous conductive aid can be suppressed, and a mixture containing the fibrous conductive aid with a sufficient fiber length can be obtained. In addition, by mixing the obtained mixture with PTFE in the mixing step described later, an active material layer in which the length of the fibrous conductive aid is maintained in a state longer than before can be obtained, thereby reducing the resistance of the electrode having the active material layer.

[0062] When condition (1) is satisfied, the ratio (D2 / D1) of the maximum distance D2 between the inner walls of the second container parallel to the vibration direction of the acoustic resonance mixer in the second stirring step to the maximum distance D1 between the inner walls of the first container parallel to the vibration direction of the acoustic resonance mixer in the first stirring step is preferably 1.2 or more and 4 or less, more preferably 1.5 or more and 3 or less, and even more preferably 2 or more and 2.5 or less. When condition (1) is not satisfied, the ratio (D2 / D1) is preferably 1.

[0063] When condition (2) is satisfied, the ratio (F1 / F2) of the frequency F1 of the acoustic resonance mixer in the first stirring step to the frequency F2 of the acoustic resonance mixer in the second stirring step is preferably 1.2 or more and 4 or less, more preferably 1.5 or more and 3 or less, and even more preferably 2 or more and 2.5 or less. When condition (2) is not satisfied, the ratio (F1 / F2) is preferably 1 (i.e., the frequency of the acoustic resonance mixer in the first stirring step is the same as the frequency of the acoustic resonance mixer in the second stirring step).

[0064] When condition (3) is satisfied, the ratio (A1 / A2) of the acceleration A1 of the acoustic resonance mixer in the first stirring step to the acceleration A2 of the acoustic resonance mixer in the second stirring step is preferably 1.2 or more and 4 or less, more preferably 1.5 or more and 3 or less, and even more preferably 2 or more and 2.5 or less. When condition (3) is not satisfied, the ratio (A1 / A2) is preferably 1 (i.e., the acceleration of the acoustic resonance mixer in the first stirring step is the same as the acceleration of the acoustic resonance mixer in the second stirring step).

[0065] When condition (4) is satisfied, the ratio (T1 / T2) of the stirring time T1 in the first stirring step to the stirring time T2 in the second stirring step is preferably 1.2 or more and 4 or less, more preferably 1.5 or more and 3 or less, and even more preferably 2 or more and 2.5 or less. When condition (4) is not satisfied, the ratio (T1 / T2) is 1 (i.e., the stirring time in the first stirring step is the same as the stirring time in the second stirring step).

[0066] According to a more preferred embodiment, the first stirring step and the second stirring step satisfy at least condition (1). According to a further preferred embodiment, the first stirring step and the second stirring step satisfy condition (1) and satisfy all of the following conditions (2') to (4'): condition (2'): the frequency of the acoustic resonance mixer in the first stirring step is the same as the frequency of the acoustic resonance mixer in the second stirring step (the ratio (F1 / F2) is 1), or higher than the frequency of the acoustic resonance mixer in the second stirring step; condition (3'): the acceleration of the acoustic resonance mixer in the first stirring step is the same as the acceleration of the acoustic resonance mixer in the second stirring step (the ratio (A1 / A2) is 1), or higher than the frequency of the acoustic resonance mixer in the second stirring step; condition (4'): the stirring time in the first stirring step is the same as the stirring time in the second stirring step (the ratio (T1 / T2)), or longer than the frequency of the acoustic resonance mixer in the second stirring step. In this way, sufficient stirring can be ensured in each of the first stirring step and the second stirring step. According to a particularly preferred embodiment, the first stirring step and the second stirring step satisfy condition (1), the above ratio (F1 / F2) is 1, the above ratio (A1 / A2) is 1, and the above ratio (T1 / T2) is 1. Furthermore, in these embodiments, from the perspective of ease of operation, the first container and the second container are the same container (that is, the same container is used for stirring in the first stirring step and the second stirring step). In this case, by changing the orientation of the container relative to the vibration direction of the acoustic resonance mixer, the maximum distance D1 between the inner walls and the maximum distance D2 between the inner walls are set in a manner that satisfies condition (1). According to this embodiment, the effect of the present invention can be achieved with simpler operation.

[0067] In this embodiment, from the viewpoint of further improving the dispersibility of the active material and the solid electrolyte and further suppressing the cutting of the fibrous conductive additive, it is also preferable to satisfy two or more, three or more, or four of the conditions (1) to (4).

[0068] In the first stirring step and / or the second stirring step, materials other than the aforementioned active material, solid electrolyte, and fibrous conductive additive (hereinafter referred to as "other materials") may be added and stirred as needed. Examples of other materials include non-fibrous conductive additives such as carbon blacks such as acetylene black, Ketjen Black (registered trademark), furnace black, channel black, and thermal black.

[0069] The first stirring step and the second stirring step are preferably carried out in the absence of a solvent. This eliminates the need to remove the solvent when forming the active material layer. Furthermore, the reaction between the solid electrolyte and the solvent can be prevented.

[0070] (Mixing process)

[0071] In the manufacturing method of this mode, preferably after the second stirring process, there is further a mixing process in which the mixture obtained by the second stirring process is mixed with polytetrafluoroethylene (PTFE). Here, there is no particular restriction on the timing of adding polytetrafluoroethylene (PTFE), and it can be when the active material and the solid electrolyte are placed in the first container in the first stirring process, when the fibrous conductive additive is placed in the second container in the second stirring process, or after the second stirring process and between the mixing processes. Wherein, polytetrafluoroethylene (PTFE) is preferably added after the second stirring process and before the mixing process, thereby, the cutting of the fibrous conductive additive can be further suppressed. That is, according to a preferred embodiment, the mixing process adds the aforementioned polytetrafluoroethylene to the mixture obtained by the aforementioned second stirring process, and the mixture obtained by the second stirring process is mixed with polytetrafluoroethylene (PTFE).

[0072] Polytetrafluoroethylene (PTFE) is the polymer of tetrafluoroethylene, and by applying the shearing force brought by mixing, fibrillation (fibrillation) can take place.Active material, solid electrolyte and fibrous conductive aid are wound around and maintained in the fibrous tissue of fibrillated PTFE.It should be noted that polytetrafluoroethylene (PTFE) can comprise the material that a part for end or side chain is replaced (modified) by other substituents.In the case of the form that a part for end or side chain is replaced (modified) by other substituents, the structural unit that end or side chain is replaced (modified) by other substituents, the shared ratio in whole structural units 100 mol % is preferably below 10 mol %, more preferably below 5 mol %.

[0073] The kneading apparatus used for kneading is not particularly limited as long as it can apply shearing force to PTFE, and an extruder, a Banbury mixer, a roll, a kneader, etc. can be appropriately used. Alternatively, kneading can be performed using a mortar.

[0074] Through the above steps, a mixture containing an active material, a solid electrolyte, a fibrous conductive additive, and PTFE is obtained. In addition, the mixture is formed into a sheet using a roller or the like and cut into a desired size to obtain an active material layer. The thickness of the active material layer also varies depending on the configuration of the target all-solid-state battery, for example, preferably within the range of 0.1 to 1000 μm, more preferably 40 to 100 μm.

[0075] <Electrodes for all-solid-state batteries>

[0076] According to the above-mentioned manufacturing method, the active material, solid electrolyte and fibrous conductive aid are dispersed by a predetermined two-stage stirring process, so that the fiber length of the fibrous conductive aid in the active material layer can be maintained longer. Therefore, according to another embodiment of the present invention, there is provided an all-solid-state battery electrode, which is an all-solid-state battery electrode having an active material layer comprising an active material, a solid electrolyte, a fibrous conductive aid and polytetrafluoroethylene, and relative to the total number of the above-mentioned fibrous conductive aids, the ratio of the number of fibrous conductive aids having a fiber length of more than 2 times the average particle size (D50) of the above-mentioned active material is more than 40% and less than 90%. According to the above-mentioned structure, the electron conduction path between the active materials is well formed, so the resistance of the electrode can be reduced. It should be noted that, in this specification, the fiber length of the fibrous conductive aid is obtained by the method described in the examples described later.

[0077] The ratio of the number of fibrous conductive agents having a fiber length that is at least twice the average particle size (D50) of the active material relative to the total number of the fibrous conductive agents must be 40% to 90%, preferably 50% to 80%, and more preferably 50% to 70%. If this ratio is less than 40%, there is a concern that the electron conduction path between the active materials becomes insufficient, increasing the resistance of the electrode. In addition, if this ratio exceeds 90%, there is a concern that the proportion of short fibrous conductive agents becomes relatively small, thereby reducing the contact points between the active material and the fibrous conductive agents, and thus increasing the resistance of the electrode.

[0078] In this embodiment, to further reduce electrode resistance, the fiber length distribution of the fibrous conductive additive preferably has at least two peaks. More preferably, the fiber length distribution has two peaks. This configuration further enhances electron conduction paths between the active materials and contact points with the active materials. As a result, electrode resistance can be further reduced.

[0079] All-solid-state batteries

[0080] The electrode obtained by the aforementioned method for manufacturing an electrode for an all-solid-state battery can reduce resistance, and therefore, by applying it to an all-solid-state battery, the output and input characteristics of the battery can be improved. Therefore, according to yet another embodiment of the present invention, an all-solid-state battery is provided, comprising an electrode obtained by the aforementioned method for manufacturing an electrode for an all-solid-state battery. In the all-solid-state battery of this embodiment, the aforementioned electrode is preferably a positive electrode.

[0081] The present invention is described below with reference to the accompanying drawings. The technical scope of the present invention should be determined based on the description of the claims and is not limited to the following embodiments. It should be noted that the dimensional ratios in the drawings are exaggerated for the sake of convenience and may differ from the actual ratios.

[0082] Figure 1 It is a perspective view showing the appearance of a flat laminated all-solid-state lithium secondary battery as one embodiment of the present invention. Figure 2 For the Figure 1 The cross-sectional view of line 2-2 is shown. By making a stacked type, the battery can be made compact and have a high capacity. Figure 1 and Figure 2 The flat stacked non-bipolar all-solid-state lithium secondary battery (hereinafter referred to as a "stacked secondary battery") is described in detail as an example. However, from the perspective of the internal electrical connection form (electrode structure) of the secondary battery of this embodiment, it is applicable to both non-bipolar (internal parallel) batteries and bipolar (internal series) batteries.

[0083] like Figure 1 As shown, the stacked secondary battery 10a has a flat rectangular shape, with a negative electrode collector plate 25 and a positive electrode collector plate 27 extending from both sides thereof for extracting electricity. The power generation element 21 is wrapped with the battery casing material (laminated film 29) of the stacked secondary battery 10a, and heat-welded around it. The power generation element 21 is sealed with the negative electrode collector plate 25 and the positive electrode collector plate 27 extending to the outside. It should be noted that Figure 1 The collector plates (25, 27) shown in the figure can be taken out by leading the negative collector plate 25 and the positive collector plate 27 from the same side, or by dividing the negative collector plate 25 and the positive collector plate 27 into multiple pieces and taking them out from each side, etc. Figure 1 shown.

[0084] like Figure 2 As shown, the power generation element 21 of the stacked secondary battery 10a of this embodiment has the following structure during charging: a negative electrode having a negative electrode active material layer 13 containing lithium metal arranged on both sides of a negative electrode collector 11', a solid electrolyte layer 17, and a positive electrode having a positive electrode active material layer 15 containing a lithium transition metal composite oxide arranged on both sides of a positive electrode collector 11". Specifically, one negative electrode active material layer 13 and the adjacent positive electrode active material layer 15 are placed opposite to each other with the solid electrolyte layer 17 interposed therebetween, and the negative electrode, the solid electrolyte layer and the positive electrode are stacked in this order. Thus, the adjacent negative electrode, the solid electrolyte layer and the positive electrode constitute a single cell layer 19. Therefore, it can also be said that Figure 2 The stacked secondary battery 10 a shown has a structure in which a plurality of single cell layers 19 are stacked and electrically connected in parallel.

[0085] It has the following structure: a negative electrode collector plate 25 and a positive electrode collector plate 27 that are conductive with each electrode (negative electrode and positive electrode) are respectively installed on the negative electrode collector 11' and the positive electrode collector 11", so that they are clamped at the end of the laminate film 29 and led out to the outside of the laminate film 29. The negative electrode collector plate 25 and the positive electrode collector plate 27 can be respectively installed on the negative electrode collector 11' and the positive electrode collector 11" of each electrode by ultrasonic welding, resistance welding, etc. with the help of a negative terminal lead and a positive terminal lead (not shown) as needed.

[0086] The laminated secondary battery 10a of this embodiment is preferably formed by connecting the Figure 1 The power generation element 21 sealed by the laminated film 29 shown is clamped with the power generation element 21 sealed by the laminated film 29, and then fastened using a fastening member. Thus, the above-mentioned plate-like member and the fastening member function as a pressure member that pressurizes (constrains) the power generation element 21 in its stacking direction. Examples of the plate-like member include metal plates, resin plates, and the like. In addition, examples of the fastening member include bolts and nuts. However, there is no particular limitation on the pressure member as long as it is a member that can pressurize the power generation element 21 in its stacking direction. As a pressure member, typically, a combination of a plate formed of a rigid material such as a plate-like member and the above-mentioned fastening member can be used. In addition, as the fastening member, not only bolts and nuts can be used, but also tension plates that fix the ends of the plate-like member in a manner that constrains the power generation element 21 in its stacking direction can be used. It should be noted that the lower limit of the load applied to the power generation element 21 (the restraining pressure in the stacking direction of the power generation element) is, for example, 0.1 MPa or more, preferably 1 MPa or more, more preferably 3 MPa or more, and even more preferably 5 MPa or more. The upper limit of the restraining pressure in the stacking direction of the power generation element is, for example, 100 MPa or less, preferably 70 MPa or less, more preferably 40 MPa or less, and even more preferably 10 MPa or less.

[0087] Hereinafter, main components of the stacked secondary battery 10 a will be described.

[0088] [Current Collector]

[0089] The current collector (negative electrode current collector 11 ′ and positive electrode current collector 11 ″) is a conductive member that functions as a flow path for electrons released from the positive electrode to an external load or flowing from the power supply to the positive electrode as the battery reaction (charge and discharge reaction) proceeds. The material constituting the current collector is not particularly limited, and for example, metals and conductive resins can be used.

[0090] Specifically, examples of metals include aluminum, nickel, iron, stainless steel, titanium, and copper. Furthermore, cladding materials of nickel and aluminum, or cladding materials of copper and aluminum, can also be used. Furthermore, a foil formed by coating aluminum on the metal surface can also be used. Among these, aluminum, stainless steel, copper, and nickel are preferred from the perspectives of electronic conductivity, battery operating potential, and adhesion of active materials.

[0091] Examples of the latter conductive resin include a conductive polymer material or a non-conductive polymer material to which a conductive filler is added as needed.

[0092] It should be noted that the current collector can be a single-layer structure formed by a single material, or can be a stacked structure formed by appropriately combining layers formed by these materials. From the perspective of lightweighting the current collector, it is preferred that it at least contain a conductive resin layer formed by a conductive resin. In addition, from the perspective of cutting off the movement of lithium ions between single cell layers, a metal layer can also be provided on a part of the current collector. Furthermore, as long as the aforementioned negative electrode active material layer and positive electrode active material layer themselves have conductivity and can perform the current collection function, a current collector as a component independent of these active material layers may not be used. In this way, the aforementioned negative electrode active material layer directly constitutes the negative electrode, and the aforementioned positive electrode active material layer directly constitutes the positive electrode.

[0093] [Solid electrolyte layer]

[0094] Figure 1 and Figure 2 In the laminated secondary battery of the illustrated embodiment, the solid electrolyte layer 17 is sandwiched between the positive electrode active material layer and the negative electrode active material layer and contains a solid electrolyte (generally as a main component). The specific form of the solid electrolyte contained in the solid electrolyte layer is not particularly limited, and the solid electrolytes and their preferred forms exemplified in the first stirring step section of the aforementioned all-solid-state battery manufacturing method can be similarly used.

[0095] The content of the solid electrolyte in the solid electrolyte layer is, for example, preferably 10 to 100 mass %, more preferably 50 to 100 mass %, and even more preferably 90 to 100 mass %, relative to the total mass of the solid electrolyte layer.

[0096] The solid electrolyte layer may further contain a binder in addition to the above-mentioned solid electrolyte.

[0097] The thickness of the solid electrolyte layer also varies depending on the configuration of the target all-solid-state battery, but is preferably within the range of 0.1 to 1000 μm, and more preferably 10 to 40 μm, for example.

[0098] [Positive electrode collector plate and negative electrode collector plate]

[0099] The material constituting the collector plates (25, 27) is not particularly limited, and known highly conductive materials that have been used as collector plates for secondary batteries can be used. As the constituent material of the collector plates, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferred. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferred, and aluminum is particularly preferred. It should be noted that the positive collector plate 27 and the negative collector plate 25 may be made of the same material or different materials.

[0100] [Positive lead and negative lead]

[0101] In addition, although the figure is omitted, the collector and the collector plate can also be electrically connected by means of a positive lead and a negative lead. As the constituent materials of the positive and negative leads, materials that can be used in known secondary batteries can be used in the same manner. It should be noted that the portion removed from the outer shell is preferably covered with a heat-resistant insulating heat shrink tube or the like to prevent it from contacting with peripheral equipment, wiring, etc. and leaking electricity, or affecting products (such as automotive parts, particularly electronic equipment, etc.).

[0102] [Battery casing material]

[0103] As battery casing materials, in addition to the well-known metal can shells, other materials such as Figure 1 and Figure 2 The bag-shaped housing shown is a laminate film 29 containing aluminum that can cover the power generation element. The laminate film can be, for example, a three-layer structure formed by laminating PP, aluminum, and nylon in this order, but is not limited to these. From the perspective of high output, excellent cooling performance, and suitability for large-scale equipment batteries for EVs and HEVs, the laminate film is ideal. In addition, from the perspective of being able to easily adjust the group pressure applied to the power generation element from the outside, the outer shell is more preferably a laminate film containing aluminum.

[0104] An embodiment of the all-solid-state battery of the present invention has been described above. However, the present invention is not limited to the configuration described in the above embodiment, and can be modified appropriately based on the description of the claims.

[0105] It should be noted that the following embodiments are also included in the scope of the present invention: the manufacturing method according to claim 1 having the features of claim 2; the manufacturing method according to claim 1 or 2 having the features of claim 3; the manufacturing method according to any one of claims 1 to 3 having the features of claim 4; the manufacturing method according to any one of claims 1 to 4 having the features of claim 5; and the electrode for an all-solid-state battery according to claim 6 having the features of claim 7.

[0106] Example

[0107] The present invention will be further described in detail below through examples. However, the technical scope of the present invention is not limited to the following examples. It should be noted that the following instruments and equipment used in the glove box must be thoroughly dried beforehand.

[0108] <Example of Preparation of a Mixture of a Positive Electrode Active Material, a Solid Electrolyte, and a Fibrous Conductive Aid>

[0109] [Comparative Production Example 1]

[0110] (First stirring step)

[0111] The NMC composite oxide (LiNi) as the positive electrode active material was weighed in an argon atmosphere glove box with a dew point below -68°C. 0.6 Mn 0.2 Co 0.2 80g of O2 (NMC622), average particle size (D50): 10μm), and 15g of argyrodite-type sulfide solid electrolyte (Li6PS5Cl, average particle size (D50): 1μm) as a solid electrolyte. These materials are placed in a polypropylene (PP) container with a lid as the first container (a cylindrical container with an internal diameter of 65mm and an internal height of 100mm), and the container is installed in a low-frequency acoustic resonance mixer (LabRAMII, manufactured by RESODYN ACOUSTIC MIXERS, INC., the same applies below). At this time, the low-frequency acoustic resonance mixer is installed in a manner parallel to the height direction of the container. Stir for 10 minutes under the conditions of acceleration 100G and frequency 60Hz to obtain a mixture of the positive electrode active material and the solid electrolyte.

[0112] (Second stirring step)

[0113] In a glove box with an argon atmosphere at a dew point below -68°C, 3 g of carbon nanofibers (CNF) (aspect ratio: 60, average fiber diameter: about 150 nm, average fiber length: about 63 μm) as a fibrous conductive aid were weighed. The mixture obtained by the first stirring step and the above-mentioned fibrous conductive aid were placed in a polypropylene (PP) container with a lid as a second container (a cylindrical container with an internal diameter of 65 mm and an internal height of 100 mm), and the container was installed in a low-frequency acoustic resonance mixer. At this time, the low-frequency acoustic resonance mixer was installed in a manner parallel to the height direction of the container. Stirring for 10 minutes under the conditions of acceleration 100G and frequency 60 Hz, a mixture of positive electrode active material, solid electrolyte and fibrous conductive aid was obtained.

[0114] [Comparative Production Example 2]

[0115] In the first stirring step, a polypropylene (PP) container with a lid (a cylindrical container with an inner diameter of 65 mm and an inner height of 50 mm) was used as the first container. Furthermore, in the second stirring step, a polypropylene (PP) container with a lid (a cylindrical container with an inner diameter of 65 mm and an inner height of 50 mm) was used as the second container. Otherwise, the mixture of this comparative manufacturing example was obtained by the same method as in comparative manufacturing example 1.

[0116] [Production Example 1]

[0117] In the first stirring step, a polypropylene (PP) container with a lid (a cylindrical container having an inner diameter of 65 mm and an inner height of 50 mm) was used as the first container. In addition, the mixture of this manufacturing example was obtained by the same method as in Comparative Manufacturing Example 1.

[0118] [Comparative Production Example 3]

[0119] In the second stirring step, a polypropylene (PP) container with a lid (a cylindrical container having an inner diameter of 65 mm and an inner height of 50 mm) was used as the second container. In addition, the mixture of this comparative manufacturing example was obtained by the same method as in comparative manufacturing example 1.

[0120] <Dispersibility of mixture>

[0121] For the mixture of the positive electrode active material, solid electrolyte and fibrous conductive aid obtained by the above-mentioned manufacturing example and comparative manufacturing example, the dispersibility of the fibrous conductive aid was evaluated by the following method. First, an image of the mixture was taken at a magnification of 1000 times under the condition of an accelerating voltage of 5kV using a scanning electron microscope (SEM). The obtained image was 2-valued to determine the portion of the fibrous conductive aid. The image was divided into 16 parts, and for each divided area, the ratio of the area occupied by the fibrous conductive aid relative to the area of ​​1 area was calculated. The standard deviation (σ) and the average value (μ) of the 16 values ​​obtained were calculated respectively, and the value (σ / μ) obtained by dividing the standard deviation (σ) by the average value (μ) was used as an index of the dispersibility of the fibrous conductive aid. The case where the value (σ / μ) exceeded 0.40 was evaluated as × (poor), the case where it was 0.25 or more and less than 0.40 was evaluated as △ (acceptable), and the case where it was less than 0.25 was evaluated as ○ (good). The results are shown in Table 1 below.

[0122] <Resistance of the mixture>

[0123] The resistance of the mixture of the positive electrode active material, solid electrolyte and fibrous conductive aid obtained by the above-mentioned manufacturing example and comparative manufacturing example was evaluated by the following method. First, in a glove box with an argon atmosphere at a dew point of -68°C or less, a SUS cylindrical convex punch (diameter 10.2 mm) was inserted into one side of a cylindrical tube fixture made of MACOR (tube inner diameter 10.2 mm, outer diameter 23 mm, height 20 mm), and 200 mg of the mixture was placed from the upper side of the cylindrical tube fixture. Then, another SUS cylindrical convex punch was inserted to clamp the mixture and press it at a pressure of 100 MPa to make a closed unit consisting of SUS / mixture / SUS laminated. Next, the impedance of the unit was measured. The measurement was carried out at 25°C and pressurized to 100 MPa, and the impedance at 100 kHz was taken as the resistance value (Ω). Furthermore, the volume resistivity (Ω·cm) was calculated as an indicator of the resistance of the mixture according to the formula: Volume resistivity (Ω·cm) = Resistance value (Ω) × Cross-sectional area (0.5 cm × 0.5 cm × 3.14) / Thickness (cm). The results are shown in Table 1 below.

[0124] <Example of Preparation of Positive Electrode Active Material Layer>

[0125] [Comparative Example 1]

[0126] In a glove box with an argon atmosphere at a dew point of -68°C or less, the mixture obtained in Comparative Manufacturing Example 1 and polytetrafluoroethylene (PTFE) were weighed to a mass ratio of 98:2 and kneaded for 30 minutes using an agate mortar (kneading step). After confirming that the PTFE was fibrillated by this kneading step, the obtained mixture was formed into a sheet by hand roll and punched into a circular shape with a diameter of 10 mm to obtain the positive electrode active material layer (thickness 80 μm) of this comparative example.

[0127] [Comparative Example 2]

[0128] A positive electrode active material layer of this comparative example was obtained by the same method as in Comparative Example 1, except that the mixture obtained in Comparative Example 2 was used instead of the mixture obtained in Comparative Example 1.

[0129] [Example 1]

[0130] A positive electrode active material layer of this example was obtained by the same method as in Comparative Example 1 except that the mixture obtained in Production Example 1 was used instead of the mixture obtained in Comparative Production Example 1.

[0131] [Comparative Example 3]

[0132] A positive electrode active material layer of this comparative example was obtained by the same method as in Comparative Example 1, except that the mixture obtained in Comparative Example 3 was used instead of the mixture obtained in Comparative Example 1.

[0133] <Observation of the positive electrode active material layer>

[0134] The fibrous conductive aid contained in the positive electrode active material layer obtained in the above-mentioned embodiments and comparative examples was observed by the following method. First, the cross section of the positive electrode active material layer was exposed by FIB (focused ion beam) processing. Using a scanning electron microscope (SEM), 5 images of the cross section of the positive electrode active material layer were taken at a magnification of 1000 times under the condition of an accelerating voltage of 5kV. Using image analysis software, the fiber length of all the fibrous conductive aids observed in the 5 images was measured. In addition, the horizontal axis was set to the fiber length of the fibrous conductive aid and the vertical axis was set to the number of fibrous conductive aids, and a graph of the fiber length distribution was prepared to find the number of peaks present in the graph and the fiber length of the peak top. In addition, using image analysis software, the particle size of all the positive electrode active materials observed in each image was measured, and the average particle size (D50) was calculated. The results confirmed that it was 10μm in all embodiments and comparative examples. Furthermore, the ratio of the number of fibrous conductive agents having a fiber length longer than twice the average particle size (D50) of the positive electrode active material (20 μm) was calculated relative to the total number of fibrous conductive agents observed in the five images (referred to as "ratio of long fibers" in Table 1 below). The results are shown in Table 1 below.

[0135] <Resistance of the positive electrode active material layer>

[0136] The resistance of the positive electrode active material layer obtained in the above-mentioned embodiment and comparative example was evaluated by the following method. First, in a glove box with an argon atmosphere at a dew point below -68°C, a SUS cylindrical convex punch (10 mm diameter) was inserted into one side of a cylindrical tube fixture (tube inner diameter 10 mm, outer diameter 23 mm, height 20 mm) made of MACOR, and the positive electrode active material layer was placed from the upper side of the cylindrical tube fixture. Then, another SUS cylindrical convex punch was inserted to clamp the positive electrode active material layer, and a hydraulic press was used to press at a pressure of 100 MPa for 3 minutes to produce a closed unit consisting of SUS / positive electrode active material layer / SUS laminated. Next, the impedance of the cell was measured. The measurement was carried out at 25°C and pressurized to 100 MPa, and the impedance at 100 kHz was taken as the resistance value (Ω). Furthermore, the volume resistivity (Ω·cm) was calculated using the formula: Volume resistivity (Ω·cm) = Resistance value (Ω) × Cross-sectional area (0.5 cm × 0.5 cm × 3.14) / Thickness (cm) to serve as an indicator of the resistance of the positive electrode active material layer. The results confirmed that the resistance of the positive electrode active material layer is correlated with the resistance of the mixture.

[0137] [Table 1]

[0138] Table 1

[0139]

[0140] The results shown in Table 1 show that the present invention can reduce the resistance of an all-solid-state battery electrode having an active material layer containing an active material, a solid electrolyte, a fibrous conductive additive, and PTFE and having sufficient dispersibility.

[0141] Description of Reference Numerals

[0142] 10a stacked battery,

[0143] 11' negative electrode collector,

[0144] 11" positive electrode collector,

[0145] 13 negative electrode active material layer,

[0146] 15 positive electrode active material layer,

[0147] 17 solid electrolyte layer,

[0148] 19 single cell layers,

[0149] 21 Power generation elements,

[0150] 25 negative electrode collector plate,

[0151] 27 positive electrode collector plate,

[0152] 29Laminating film.

Claims

1. A method for producing an electrode for an all-solid-state battery, comprising: a first stirring step of placing the active material and the solid electrolyte into a first container and stirring them using an acoustic resonance mixer; and In the second stirring step, the mixture obtained in the first stirring step and the fibrous conductive additive are placed in a second container and stirred using an acoustic resonance mixer. The first stirring step and the second stirring step satisfy at least one of the following conditions (1) to (4): Condition (1): The maximum distance D1 between the inner walls of the first container parallel to the vibration direction of the acoustic resonance mixer in the first stirring step is shorter than the maximum distance D2 between the inner walls of the second container parallel to the vibration direction of the acoustic resonance mixer in the second stirring step; Condition (2): The frequency of the acoustic resonance mixer in the first stirring step is higher than the frequency of the acoustic resonance mixer in the second stirring step; Condition (3): The acceleration of the acoustic resonance mixer in the first stirring step is higher than the acceleration of the acoustic resonance mixer in the second stirring step; Condition (4): The stirring time in the first stirring step is longer than the stirring time in the second stirring step.

2. The method for producing an electrode for an all-solid-state battery according to claim 1, wherein: The first stirring step and the second stirring step satisfy the condition (1), And all the following conditions (2') to (4') are met, Condition (2'): The frequency of the acoustic resonance mixer in the first stirring step is the same as or higher than the frequency of the acoustic resonance mixer in the second stirring step; Condition (3'): The acceleration of the acoustic resonance mixer in the first stirring step is the same as the acceleration of the acoustic resonance mixer in the second stirring step, or is higher than the frequency of the acoustic resonance mixer in the second stirring step; Condition (4'): The stirring time in the first stirring step is the same as the stirring time in the second stirring step, or is longer than the frequency of the acoustic resonance mixer in the second stirring step.

3. The method for producing an electrode for an all-solid-state battery according to claim 1, wherein: The first container and the second container are the same container.

4. The method for producing an electrode for an all-solid-state battery according to claim 1, wherein: The first stirring step and the second stirring step are performed in the absence of a solvent.

5. The method for manufacturing an electrode for an all-solid-state battery according to claim 1, further comprising: In the kneading step, the mixture obtained in the second stirring step is kneaded with the polytetrafluoroethylene.

6. An electrode for an all-solid-state battery, comprising an active material layer, the active material layer comprising an active material, a solid electrolyte, a fibrous conductive additive, and polytetrafluoroethylene, The ratio of the number of the fibrous conductive additives having a fiber length that is twice or more the average particle size (D50) of the active material to the total number of the fibrous conductive additives is 40% to 90%.

7. The all-solid-state battery electrode according to claim 6, wherein: The fiber length distribution of the fibrous conductive additive has at least two peaks.

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