Electrode and solid-state battery

Abstract

To provide an electrode that is used for a solid-state battery and has a shape retaining property, especially, self-shape-retaining property even when contents of a binder are reduced.SOLUTION: An electrode includes a solid electrolyte, an active material, and carbon fiber. A content of the carbon fiber is more than 0.1 mass%. The content of the carbon fiber is preferably 1 mass% or more. The carbon fiber is preferably a carbon nanotube. The solid electrolyte is preferably a sulfide solid electrolyte. The sulfide solid electrolyte preferably contains a crystal phase having an argyrodite-type crystal structure.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an electrode and a solid-state battery. [Background technology]

[0002] In recent years, CO 2 Secondary batteries have been attracting attention as an effort to prevent global warming by reducing CO2 emissions. Among secondary batteries, solid-state batteries using a solid electrolyte instead of an electrolytic solution have been attracting attention from the viewpoints of energy density and safety. In contrast, the technology described in the following Patent Document 1 and Non-Patent Document 1 is intended for use as an electrode for a battery using an electrolytic solution, and no consideration has been given to the use of the technology in a solid-state battery. Patent Document 1 and Non-Patent Document 1 disclose an electrode manufactured using a slurry containing carbon nanotubes and an active material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-122593 A [Non-patent literature]

[0004] [Non-Patent Document 1] K. Hasegawa, et al., Journal of Power Sources, 2016, 321, 155-162. Summary of the Invention [Problem to be solved by the invention]

[0005] Electrodes used in batteries generally contain a binder to help them retain their shape, but because the binder in the electrode acts as a resistance component, there is a demand to reduce the amount of binder used. It is therefore an object of the present invention to provide an electrode for use in a solid-state battery, which has shape retention, in particular self-retaining properties, even when the binder content is reduced. [Means for solving the problem]

[0006] The present invention has achieved the above object by providing an electrode comprising a solid electrolyte, an active material, and carbon fibers, the carbon fibers being present in an amount of more than 0.1% by mass. Effect of the Invention

[0007] According to the present invention, it is possible to provide an electrode for use in a solid-state battery, which has shape retention, particularly self-retaining properties, even when the binder content is reduced. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention will be described below based on its preferred embodiments. The present invention relates to an electrode. The electrode of the present invention includes a solid electrolyte, an active material, and carbon fibers. Therefore, the electrode of the present invention is used in a solid-state battery. The electrode in this specification is a concept that does not include a current collector. In the following description, when the term "carbon fiber" is used, it may refer to an individual fiber or an aggregate of multiple fibers, depending on the context.

[0009] The electrode of the present invention is a fiber assembly in which carbon fibers are entangled with each other. In one embodiment, the electrode made of the fiber assembly may be in the form of a sheet. In the fiber assembly, the solid electrolyte and the active material are held in the spaces between the entangled carbon fibers.

[0010] Conventional electrodes can acquire shape retention by including a binder such as a polymer organic compound. On the other hand, since the binder can be a resistance component of a battery, it is becoming increasingly necessary to reduce the content of the binder or to eliminate the binder. As a result of intensive research by the present inventors into electrodes that have shape retention while reducing the content of the binder, it has been found that when the electrode contains a predetermined amount of carbon fibers, shape retention, particularly self-retaining properties, can be imparted to the electrode. Specifically, in an electrode that contains a predetermined amount of carbon fibers, the carbon fibers are entangled with each other and therefore shape retention is easily obtained, and it has been found that shape retention, particularly self-retaining properties, can be imparted to the electrode even when the content of the binder is reduced. In this specification, the term "self-supporting" refers to the ability of an electrode cut into a 10 cm square to be held together by two adjacent corners with tweezers and not broken by its own weight when lifted.

[0011] The electrode of the present invention preferably contains carbon fiber as one of its constituent materials. The carbon fiber is mainly composed of carbon element. In this specification, "mainly composed of carbon element" refers to a state in which the carbon element content in the carbon fiber is 80 mass% or more. From the viewpoint of improving the performance of the battery, the carbon element content in the carbon fiber is more preferably 90 mass% or more, and even more preferably 98 mass% or more. The carbon element content in the carbon fiber can be measured, for example, by Raman spectroscopy, TG-DTA, elemental analysis, etc.

[0012] The electrode of the present invention preferably contains a predetermined amount of carbon fiber. Specifically, from the viewpoint of easily imparting shape retention, particularly self-retaining property, to the electrode by generating entanglement between the carbon fibers, the content of carbon fiber in the electrode is preferably more than 0.1 mass%, more preferably 1 mass% or more, and even more preferably 3 mass% or more. In addition, from the viewpoint of improving the performance of the battery by ensuring the content of the solid electrolyte and active material in the electrode while maintaining the entanglement between the carbon fibers, the content of carbon fiber in the electrode is preferably 15 mass% or less, more preferably 9 mass% or less, and even more preferably 6 mass% or less.

[0013] Examples of carbon fibers include carbon nanotubes, vapor-grown carbon fibers, pitch-based carbon fibers, and bread-based carbon fibers. The carbon fibers can be used alone or in combination of two or more. From the viewpoint of improving the conductivity and improving the performance of the battery, it is more preferable to use carbon nanotubes or vapor-grown carbon fibers as the carbon fibers, and it is even more preferable to use carbon nanotubes.

[0014] Carbon nanotubes are substances in which a six-membered ring network (graphene sheet) composed of carbon is in the form of a single-layer or multi-layer coaxial tube. Examples of carbon nanotubes include single-wall carbon nanotubes (SWCNT) which are single-layered, and multi-wall carbon nanotubes (MWCNT) which are multi-layered. Among multi-layered nanotubes, those with two layers in particular are called double-walled carbon nanotubes (DWCNT). In the present invention, these may be used as carbon nanotubes, either alone or in combination of two or more. From the viewpoints of dispersibility and cost, it is preferable to use multi-walled carbon nanotubes. From the viewpoints of dispersibility and cost, the number of walls of the multi-walled carbon nanotube is preferably 2 or more, and more preferably 5 or more. On the other hand, the number of walls of the multi-walled carbon nanotube is, for example, preferably 50 or less, more preferably 30 or less, and even more preferably 10 or less. The number of walls of the multi-walled carbon nanotube can be measured, for example, by a transmission electron microscope.

[0015] When carbon nanotubes are used as the carbon fibers, for example, the carbon nanotubes may be long or short. The fiber diameter of the long carbon nanotubes may be, for example, 0.4 nm or more, 5 nm or more, or 7 nm or more. On the other hand, the fiber diameter of the long carbon nanotubes may be, for example, 20 nm or less, 15 nm or less, or 13 nm or less. In addition, the average length of the long carbon nanotubes may be, for example, 30 μm or more, 100 μm or more, or 200 μm or more. On the other hand, the average length of the long carbon nanotubes may be, for example, 600 μm or less, 500 μm or less, or 400 μm or less. The fiber diameter of the short carbon nanotubes may be, for example, 0.4 nm or more, 1 nm or more, or 3 nm or more. On the other hand, the fiber diameter of the short carbon nanotubes may be, for example, 100 nm or less, 80 nm or less, or 50 nm or less. Also, the average length of the short carbon nanotubes may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. On the other hand, the average length of the short carbon nanotubes may be, for example, 50 μm or less, 40 μm or less, or 30 μm or less. From the viewpoint of dispersibility, it is preferable to use short carbon nanotubes.

[0016] The fiber diameter of the carbon fibers may be, for example, 0.4 nm or more, 3 nm or more, or 5 nm or more. On the other hand, the fiber diameter of the carbon fibers may be, for example, 100 nm or less, 50 nm or less, or 20 nm or less. Also, the average length of the carbon fibers may be, for example, 10 nm or more, 50 nm or more, or 100 nm or more. On the other hand, the average length of the carbon fibers may be, for example, 600 μm or less, 300 μm or less, or 100 μm or less.

[0017] The carbon fibers preferably have a predetermined aspect ratio (length of carbon fiber [μm] / fiber diameter of carbon fiber [μm]) from the viewpoint of easily entangling the carbon fibers with each other and easily imparting shape retention, particularly self-retaining properties, to the electrode. Specifically, the aspect ratio of the carbon fibers may be, for example, 37.5 or more, 300 or more, or 3000 or more. From the same viewpoint, the aspect ratio of the carbon fibers may be, for example, 60000 or less, 6000 or less, 5000 or less, or 4000 or less.

[0018] In the present invention, the carbon fiber content in the electrode can be adjusted according to the type of carbon fiber in order to facilitate the entanglement of the carbon fibers and to facilitate the provision of shape retention, particularly self-retaining properties, to the electrode. For example, when carbon fibers having a large aspect ratio, such as long carbon nanotubes, are used, the content may be relatively small. On the other hand, when carbon fibers having a small aspect ratio, such as short carbon nanotubes, are used, the content is preferably relatively large. Also, when single-phase carbon nanotubes are used, the carbon fiber content can be reduced by using carbon fibers having a large aspect ratio. On the other hand, when carbon fibers having a small aspect ratio are used, it is preferable to increase the carbon fiber content.

[0019] The fiber diameter of the carbon fibers can be measured, for example, by the following method. For example, first, the electrode is observed by a scanning electron microscope (hereinafter also referred to as "SEM"). At this time, the observation is performed at a magnification of 500 times or more and 100,000 times or less so that the fiber diameter of the carbon fibers constituting the electrode can be easily measured. The fiber diameters of 10 carbon fibers other than the fibers that are intricately entangled with other carbon fibers and cannot be measured individually are measured. The fiber diameter of the carbon fibers is obtained by arithmetically averaging the measured values. Alternatively, for example, the fiber diameter can be obtained by measuring the dimensions of 10 carbon fibers randomly selected in an atomic force microscope image and taking the arithmetic mean of them.

[0020] The length of the carbon fibers can be measured, for example, by the following method. For example, first, the electrode is observed by SEM. At this time, the observation is performed at a magnification between 500 times and 100,000 times so that the length of the carbon fibers constituting the electrode can be easily measured. The length of 20 carbon fibers other than the fibers that are intricately entangled with other carbon fibers and cannot be measured individually is measured. The length of the carbon fibers is obtained by arithmetically averaging the measured values. Alternatively, for example, the length of the carbon fibers can be obtained by measuring the dimensions of 20 randomly selected carbon fibers in an atomic force microscope image and taking the arithmetic mean of them. The length of the carbon fibers on the order of mm that cannot be measured by an atomic force microscope may be measured using an image taken by a microscope.

[0021] The surface of the carbon fiber may be coated with a substance other than carbon element. Examples of the substance that can be coated on the carbon fiber include a sulfide solid electrolyte, an oxide solid electrolyte, a nitride solid electrolyte, and a halide solid electrolyte. The substance can be used alone or in combination of two or more. From the viewpoint of forming a good interface, it is preferable that the surface of the carbon fiber is coated with a sulfide solid electrolyte.

[0022] The electrode of the present invention preferably contains a solid electrolyte as one of its constituent materials. The solid electrolyte may be the same as a solid electrolyte used in a general solid-state battery. Examples of such a solid electrolyte include a sulfide solid electrolyte, an oxide solid electrolyte, a nitride solid electrolyte, and a halide solid electrolyte. Among them, it is preferable to use a sulfide solid electrolyte containing a sulfur (S) element.

[0023] The sulfide solid electrolyte may be, for example, one containing lithium (Li) and S elements and having lithium ion conductivity, or one containing Li, phosphorus (P) and S elements and having lithium ion conductivity. The sulfide solid electrolyte may be any of a crystalline material, glass ceramics, and glass. The sulfide solid electrolyte may include a crystalline phase having an argyrodite-type crystal structure. Examples of such sulfide solid electrolytes include Li 2 SP 2 S 5 , Li 2 SP 2 S 5 -LiX (where "X" represents one or more halogen elements), Li 2 SP 2 S 5 -P 2 O 5 , Li 2 S-Li 3 PO 4 -P 2 S 5 , Li 3 P.S. 4 , Li 4 P 2 S 6 , Li 10 GeP 2 S 12 , Li 3.25 Ge 0.25 P 0.75 S 4 , Li 7 P 3 S 11 , Li 3.25 P 0.95 S 4 , and Li 7-x P.S. 6-x Xx (Solid electrolytes containing a crystal phase having an argyrodite-type crystal structure, where "X" represents one or more halogen elements, and 0.2 < x < 2.0 or 0.2 < x < 1.8.) and the like can be mentioned.

[0024] The solid electrolyte has a volume cumulative particle size D at 50% by volume according to the laser diffraction scattering method for particle size distribution measurement 50 (Hereinafter, simply referred to as "particle size D" 50 "). It is also preferable that it is within a predetermined range. Specifically, from the viewpoint of suppressing an excessive increase in the surface area of the solid electrolyte and suppressing an increase in the resistance of the battery, and from the viewpoint of making it easier to impart shape retention, particularly self-retention, to the electrode, the particle size D of the solid electrolyte 50 is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. Also, from the viewpoint of increasing the contact points and contact area between the solid electrolyte and the active material particles and improving the performance of the battery, the particle size D of the solid electrolyte 50 is preferably 10 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. The measurement method of the particle size D of the solid electrolyte 50 will be described in the examples described later.

[0025] The electrode of the present invention preferably contains a predetermined amount of solid electrolyte. Specifically, from the viewpoint of improving the performance of the battery, the content of the solid electrolyte in the electrode is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Also, from the viewpoint of ensuring the content of carbon fiber in the electrode while improving the performance of the battery and making it easier to impart shape retention, particularly self-retention, to the electrode, the content of the solid electrolyte in the electrode is preferably 80% by mass or less, more preferably 50% by mass or less, and even more preferably 35% by mass or less.

[0026] The electrode of the present invention preferably contains an active material as one of its constituent materials. The active material may be a positive electrode active material or a negative electrode active material. In either case, the active material may be the same as the active material used in a general solid-state battery.

[0027] As the positive electrode active material constituting the positive electrode layer, for example, a positive electrode active material of a lithium ion battery can be appropriately used. As such a positive electrode active material, for example, a positive electrode active material containing lithium, specifically, a spinel type lithium transition metal oxide, a lithium metal oxide having a layered structure, and an olivine type active material can be mentioned, but is not limited thereto. By using a high voltage type positive electrode active material as the positive electrode active material, it is possible to improve the energy density of the battery.

[0028] As the negative electrode active material constituting the negative electrode layer, for example, a negative electrode active material of a lithium ion battery can be appropriately used. As such a negative electrode active material, for example, lithium metal or a negative potential comparable to lithium metal (about 0.1 V vs. Li + Carbon-based materials such as graphite, artificial graphite, natural graphite, and non-graphitizable carbon (hard carbon), which are materials that are charged and discharged with a current of 1000 V / Li, can be used. This can greatly improve the energy density of the battery. In addition, silicon or tin, which are promising high-capacity materials, can also be used as the negative electrode active material.

[0029] Regardless of whether the active material is a positive or negative electrode active material, the active material has a particle size D 50 Specifically, in order to increase the contact area between the active materials and improve the performance of the battery, it is also preferable that the particle diameter D of the active material is within a predetermined range. 50 is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 5 μm or more. 50 is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. Particle size of active material D50 The method for measuring this will be described in the Examples below.

[0030] The electrode of the present invention preferably contains a predetermined amount of active material. Specifically, from the viewpoint of improving the performance of the battery, the content of the active material in the electrode is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 80% by mass or more. In addition, from the viewpoint of improving the performance of the battery while ensuring the content of carbon fiber in the electrode and easily imparting shape retention, particularly self-retaining property, to the electrode, the content of the active material in the electrode is preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0031] The electrode of the present invention having the above-mentioned configuration has high shape retention, particularly high self-retention, due to the carbon fibers being entangled with each other. Furthermore, in the electrode of the present invention, a three-dimensional structure is formed by the entanglement of the carbon fibers with each other, which facilitates contact between the solid electrolyte and the active material, thereby improving the performance of the battery.

[0032] The electrode of the present invention preferably has a predetermined thickness. This effectively causes the carbon fibers to intertwine with each other, making it easier to impart shape retention, particularly self-retaining properties, to the electrode, while ensuring the contents of the solid electrolyte and active material in the electrode to improve the performance of the battery. The thickness of the electrode may be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, or 100 μm or more. From the same viewpoint, the thickness of the electrode may be 1 mm or less, 800 μm or less, or 700 μm or less.

[0033] The thickness of the electrode can be measured, for example, by an electron microscope or a micrometer.

[0034] The electrode of the present invention preferably does not contain a binder. As described above, the binder can be a resistance component of the battery. Since the electrode of the present invention does not contain a binder, the increase in the resistance of the battery can be suppressed more than in conventional electrodes. In this specification, "does not contain a binder" means that the electrode of the present invention does not contain any binder at all, and that the electrode of the present invention does not intentionally contain a binder, but the inevitable inclusion of a binder in the manufacturing process of the electrode is allowed. Specifically, even if the electrode of the present invention inevitably contains a binder, the content is preferably 0.5 mass% or less relative to the electrode.

[0035] The electrode of the present invention may contain other constituent materials in addition to the carbon fiber, solid electrolyte, and active material. Examples of the other constituent materials include a conductive assistant and a dispersant. These may be used alone or in combination of two or more. When the electrode of the present invention contains a conductive assistant and a dispersant, the content of these may be equivalent to the content of the conductive assistant and the dispersant contained in a general electrode. As the conductive assistant, for example, a conductive material made of a carbon material (excluding fibrous conductive carbon) may be used. However, it is preferable that the electrode of the present invention does not contain a conductive assistant. In this specification, "does not contain a conductive assistant" means both that the electrode of the present invention does not contain any conductive assistant at all, and that the electrode of the present invention is not intentionally made to contain a conductive assistant, but that the conductive assistant is allowed to be inevitably mixed in during the manufacturing process of the electrode. The content of the conductive assistant contained in the electrode of the present invention may be, for example, 3.5 mass% or less with respect to the electrode.

[0036] Next, a preferred method for producing the electrode of the present invention will be described. First, carbon fibers, which are one of the constituent materials of the electrode, are prepared. There is no particular limitation on the method of manufacturing the carbon fibers, and those manufactured by various methods can be used. When carbon nanotubes are used as the carbon fibers, those manufactured by, for example, an arc discharge method, a laser evaporation method, a chemical vapor deposition method, etc. can be used. If necessary, the surface of the carbon fiber may be pretreated by coating it with a substance other than elemental carbon, or by disintegrating aggregated carbon fibers by ultrasonic treatment.

[0037] A solid electrolyte, which is one of the constituent materials of the electrode, is prepared together with the carbon fibers. There is no particular limitation on the method for producing the solid electrolyte, and those produced by various methods can be used. An active material, which is one of the constituent materials of the electrode, is prepared. There is no particular limitation on the method for producing the active material, and active materials produced by various methods can be used. If necessary, the solid electrolyte or active material may be subjected to a pretreatment such as pulverization to adjust the particle size to a desired size.

[0038] In addition to the above-mentioned constituent materials, a conductive assistant may be prepared as necessary. As the conductive assistant, for example, acetylene black and ketjen black may be used. The conductive assistant may be used alone or in combination of two or more. From the viewpoint of effectively improving the conductivity of the battery, it is preferable to use acetylene black.

[0039] Furthermore, a solvent for dispersing the above-mentioned constituent materials is also prepared. The solvent is not particularly limited as long as it can be used, for example, in the manufacture of an electrode using a solid electrolyte. Examples of the solvent include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents. Examples of the aliphatic hydrocarbon solvent include toluene and heptane. Examples of the aromatic hydrocarbon solvent include ether solvents, and ester solvents such as butyl butyrate and ethyl benzoate.

[0040] Once the above constituent materials are prepared, they are mixed to obtain a dispersion liquid. There are no particular limitations on the mixing method, and mixing can be performed, for example, by stirring using a magnetic stirrer, mixing in a mortar, or mixing in a ball mill.

[0041] The concentration of the total solid content in the dispersion is, for example, preferably 3% or more, preferably 5% or more, and preferably 7% or more. On the other hand, the concentration of the total solid content in the dispersion is, for example, preferably 25% or less, preferably 20% or less, and preferably 15% or less. When the concentration of the total solid content in the dispersion is within the above range, the carbon fibers can be sufficiently dispersed, and the carbon fibers can be effectively entangled with each other.

[0042] After the preparation of the dispersion liquid is completed, the solvent is removed from the dispersion liquid to obtain an intermediate. The solvent can be removed by, for example, natural filtration, pressure filtration, vacuum filtration, natural drying, heating drying, heating and vacuum drying, or the like.

[0043] Next, the obtained intermediate is dried to remove the solvent that was not completely removed by the above-mentioned removal operation, thereby obtaining the electrode of the present invention. The drying temperature and drying time may be set to a level sufficient to remove the solvent from the intermediate. Specifically, the drying temperature is preferably 50° C. or higher, more preferably 100° C. or higher, and even more preferably 150° C. or higher. The drying temperature is preferably 400° C. or lower, more preferably 300° C. or lower, and even more preferably 200° C. or lower. The drying time is preferably 1 hour or more, more preferably 5 hours or more, and even more preferably 10 hours or more, and is preferably 24 hours or less, more preferably 20 hours or less, and even more preferably 15 hours or less.

[0044] Thereafter, if necessary, the electrode can be pressed in the thickness direction using a press, thereby making it possible to adjust the electrode thickness to the desired level. From the viewpoint of obtaining an electrode having a desired thickness, the pressure applied to the electrode is preferably 100 MPa or more, more preferably 300 MPa or more, and even more preferably 600 MPa or more. From the same viewpoint, the pressure applied to the electrode is preferably 1000 MPa or less, more preferably 800 MPa or less, and even more preferably 700 MPa or less. The resulting electrodes may then be cut to the desired size and / or shape.

[0045] By producing an electrode by the above-mentioned method, the carbon fibers are entangled with each other in the electrode, and the electrode can have shape retention, particularly self-retaining properties.

[0046] By using the electrode of the present invention, for example, a solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer can be produced. The electrode of the present invention can be used for either the positive electrode layer or the negative electrode layer, or for both.

[0047] In relation to the above embodiment, the following electrode and solid-state battery are further disclosed. [1] An electrode comprising a solid electrolyte, an active material, and carbon fibers, the carbon fibers being present in an amount exceeding 0.1% by mass.

[0048] [2] The electrode according to [1], wherein the carbon fiber content is 1% by mass or more. [3] The electrode according to [1] or [2], wherein the carbon fiber is a carbon nanotube. [4] The electrode according to any one of [1] to [3], wherein the solid electrolyte is a sulfide solid electrolyte. [5] The electrode according to [4], wherein the sulfide solid electrolyte includes a crystalline phase having an argyrodite-type crystal structure. [6] The electrode according to any one of [1] to [5], which has self-supporting properties.

[0049] [7] The electrode according to any one of [1] to [6], which does not contain a binder. [8] A solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein either the positive electrode layer or the negative electrode layer is made of the electrode according to any one of [1] to [7]. EXAMPLES

[0050] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "%" means "% by mass".

[0051] Example 1 (1) Preparation of dispersion As the carbon fiber, multi-walled carbon nanotubes (fiber diameter 10 nm, length 30-600 μm, aspect ratio 3000-60000, <10 layers, LL-CNT, manufactured by Microphase Co., Ltd.) were prepared. As the solid electrolyte, an argyrodite-type solid electrolyte (particle size D 50 0.7μm) was prepared. 0.5 Co 0.2 Mn 0.3 O 2 (Particle size D 50 5.5 μm) was prepared. The total amount of these 0.36 g and 3 g of ethyl benzoate were stirred using a magnetic stirrer to prepare a dispersion. The content ratio of each component material in the dispersion was as shown in Table 1.

[0052] (2) Removal of solvent The dispersion was filtered under reduced pressure using a filtration device to obtain an intermediate, which was then dried at 180° C. for 12 hours to obtain an electrode.

[0053] [Examples 2 to 10] In Example 1, the contents of the carbon nanotubes, solid electrolyte, and active material were changed to the values ​​shown in Table 1. Other than this, the same procedure as in Example 1 was carried out to obtain the intended electrode.

[0054] Comparative Example 1 Acetylene black was prepared as a conductive assistant instead of carbon nanotubes in Example 1. The content ratio of each component material in the dispersion was as shown in Table 1. Other than this, the target electrode was obtained in the same manner as in Example 1.

[0055] Comparative Example 2 No carbon nanotubes were used in Example 1. The content ratio of each component material in the dispersion was as shown in Table 1. Other than this, the same procedure as in Example 1 was carried out to obtain the target electrode.

[0056] Comparative Example 3 In Example 1, the contents of the carbon nanotubes, solid electrolyte, and active material were changed to the values ​​shown in Table 1. Other than this, the same procedure as in Example 1 was carried out to obtain the intended electrode.

[0057] [Examples 11 to 14] In Example 1, artificial graphite (particle size D 50 The content of each component material in the dispersion was as shown in Table 1. Other than this, the same procedure as in Example 1 was carried out to obtain the target electrode.

[0058] 〔evaluation〕 For the electrodes obtained in the examples and comparative examples, the thickness of the electrodes was measured by the method described above. The electrodes obtained in the Examples and Comparative Examples were evaluated for self-retention ability by the following method.

[0059] [Self-retention] The electrodes obtained in the examples and comparative examples were cut into 10 cm squares using a cutter to obtain cut pieces. Next, two adjacent corners of the cut pieces were picked up with tweezers and lifted to a height of 20 cm, and held in that state for 20 seconds. After that, the cut pieces were visually observed by five expert panelists, and the self-holding ability was evaluated according to the following evaluation criteria.

[0060] [Evaluation Criteria] ○: The cut piece was not broken. ×: The cut piece was destroyed.

[0061] [Table 1]

[0062] As is clear from the results shown in Table 1, the electrodes obtained in the Examples have improved shape retention, particularly self-retaining property, compared to the electrodes obtained in the Comparative Examples.

Claims

1. An electrode comprising a solid electrolyte, an active material, and carbon fibers, the carbon fibers being present in an amount of more than 0.1 mass%.

2. The electrode according to claim 1 , wherein the carbon fiber content is 1% by mass or more.

3. The electrode of claim 1 , wherein the carbon fibers are carbon nanotubes.

4. 2. The electrode of claim 1, wherein the solid electrolyte is a sulfide solid electrolyte.

5. 5. The electrode of claim 4, wherein the sulfide solid electrolyte comprises a crystalline phase having an argyrodite-type crystal structure.

6. The electrode of claim 1 which is self-supporting.

7. 10. The electrode of claim 1 which is binder-free.

8. A solid-state battery having a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer, wherein either the positive electrode layer or the negative electrode layer is made of the electrode according to claim 1.

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