Transfer member for forming negative electrode, negative electrode structure, and manufacturing method for the same

Abstract

To provide a transfer member for forming a negative electrode, a negative electrode structure using the transfer member, an electrode, a secondary battery, and a manufacturing method for the same, in which the adhesion of a carbon-containing layer is ensured during handling when forming an electrode having a carbon-containing layer, and the transferability of the carbon-containing layer onto a current collector or a solid electrolyte layer, which are transfer targets, is excellent.SOLUTION: A transfer member for forming a negative electrode for application to a secondary battery transfers a carbon-containing layer onto a transferred body. The transfer member for forming a negative electrode includes a substrate having a first linear expansion coefficient, and a carbon-containing layer including a conductive carbon allotrope and having a second linear expansion coefficient. The absolute value of the difference between the second linear expansion coefficient and the first linear expansion coefficient is 10.0×10-6K-1 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a transfer member for forming a negative electrode, a negative electrode structure, and a method for manufacturing the same. [Background technology]

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

[0003] A technique for forming an electrode sheet having a resin substrate as a sacrificial layer to form an electrode to be used in a secondary battery is known. Patent Document 1 discloses that a transfer plate, on which active material particles are arranged in a pattern on a transfer substrate, is brought into contact with an adhesive resin substrate to produce an electrode sheet in which a particle layer containing active material particles is laminated on a resin substrate.

[0004] Furthermore, a technique for producing a negative electrode for a secondary battery by applying a paste-like carbon-containing liquid containing graphite onto a metal current collector and curing it is known. Patent Document 2 discloses a method for producing a negative electrode sheet by adding carbon black, a binder resin, a dispersant, and N-methyl-2-pyrrolidone to a negative electrode active material to form a slurry, which is then applied to a current collector and dried. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-137061 [Patent Document 2] Patent Publication No. 2017-143027 Summary of the Invention [Problem to be solved by the invention]

[0006] In the preparation of the electrode sheet, a transfer member for forming the electrode sheet may be prepared by depositing a carbon thin film containing a conductive carbon allotrope, such as graphite, HOPG, or carbon black, on a metal sheet. However, when using such a transfer member, part or all of the carbon thin film may peel off from the metal sheet during handling in the electrode manufacturing process, such as gripping, transporting, and assembly. As a result, it has been found that such a transfer member may be difficult to handle as a transfer member for forming the electrode sheet.

[0007] According to at least one aspect of the present disclosure, there is provided a transfer member for forming an anode, which ensures adhesion of the carbon-containing layer during handling when forming an electrode having the carbon-containing layer and exhibits excellent transferability of the carbon-containing layer onto a current collector or solid electrolyte layer, which is a transfer target. There is also provided a negative electrode structure using the transfer member. Furthermore, there are provided methods for manufacturing the transfer member for forming an anode, the anode structure, and an electrode and a secondary battery using the transfer member and the anode structure. [Means for solving the problem]

[0008] According to at least one aspect of the present disclosure, A transfer member for forming a negative electrode applied to a secondary battery, the negative electrode forming transfer member transfers the carbon-containing layer to a transfer target, a substrate having a first linear expansion coefficient; The absolute value of the difference between the first and second linear expansion coefficients is 10.0 × 10 -6 K -1 and the carbon-containing layer having a second linear expansion coefficient that is:

[0009] Furthermore, according to at least one aspect of the present disclosure, there is provided an anode structure for forming an anode to be applied to a secondary battery, the anode structure including the above-described transfer member for forming an anode, and a current collector or a solid electrolyte layer in contact with a carbon-containing layer. Furthermore, according to at least one aspect of the present disclosure, there are provided the above-mentioned transfer member for forming a negative electrode, the above-mentioned negative electrode structure, and methods for manufacturing an electrode and a secondary battery using them. [Effects of the Invention]

[0010] According to at least one aspect of the present disclosure, there is provided a transfer member for forming an anode, which ensures adhesion of the carbon-containing layer during handling when forming an electrode having the carbon-containing layer and exhibits excellent transferability of the carbon-containing layer onto a current collector, which is a transfer target. There is also provided a negative electrode structure using the transfer member. Furthermore, there are provided methods for manufacturing the transfer member for forming an anode, the negative electrode structure, and an electrode and a secondary battery using the transfer member and the negative electrode structure. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram schematically illustrating the configuration of a transfer member. [Figure 2] 1A to 1C are conceptual diagrams illustrating a method for manufacturing a transfer member. [Figure 3] FIG. 1 is a diagram schematically illustrating the configuration of a particle placement device. [Figure 4] FIG. 2 is a diagram schematically illustrating the configuration of an electrode structure. [Figure 5] FIG. 1 is an image diagram showing a method for manufacturing an electrode. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this disclosure, unless otherwise specified, the expressions "XX to YY" and "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints. When a numerical range is described in stages, any combination of the upper and lower limits of each numerical range is also disclosed. Furthermore, in the present disclosure, a description such as "at least one selected from the group consisting of XX, YY, and ZZ" means any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ.

[0013] Carbon materials such as graphite are used as electrode materials due to their ability to repeatedly insert and extract Li ions between their layers. One example of a method for forming a carbon-based electrode is a method in which carbon particles are arranged on a resin substrate to form a thin film, as described in Patent Document 1. Another method, as described in Patent Document 2, involves mixing carbon black with a negative electrode active material and a binder resin in a solvent to form a slurry, which is then applied to a metal current collector.

[0014] These resin substrates and binder resins themselves are not necessary for the battery performance, so it is desirable to remove them. However, if the resin components are removed by heat treatment, the formed carbon-containing layer may peel off from the metal current collector.

[0015] One of the reasons for the above problem is thought to be that during the heat treatment of the carbon-containing layer in the process of manufacturing the electrode, stress is generated due to differences in the degree of change caused by thermal expansion between the carbon-containing layer and the substrate, resulting in peeling. If the layer formed on the substrate is composed of ordinary inorganic particles, the particles will separate when the resin is removed by heat treatment, and each particle will move in accordance with the thermal expansion of the substrate, so it is thought that the above-mentioned problems due to differences in thermal expansion will rarely occur. However, if the layer formed on the substrate contains carbon particles, the flat-shaped carbon particles will stack with adjacent carbon particles and behave like a single film, which is thought to significantly affect the difference in thermal expansion between the carbon-containing layer and the substrate.

[0016] In order to solve the above-mentioned problems, the present inventors investigated a method of forming an electrode by removing the resin component from a carbon-containing layer on a substrate different from the current collector, and then transferring the carbon-containing layer onto the current collector. As a result of the investigation, it was found that the absolute value of the difference in the linear expansion coefficient between the carbon-containing layer and the substrate was 10 × 10 -6 K -1 It has been found that by transferring the carbon-containing layer to a metal current collector using the following transfer member, the carbon-containing layer does not peel off from the substrate even when the resin component is removed, making it easy to handle. Furthermore, it was also found that by making the Vickers hardness of the substrate of the transfer member to which the carbon-containing layer is applied higher than the Vickers hardness of the metal used as the current collector, the carbon-containing layer can be easily transferred to the current collector and formed into an electrode.

[0017] The transfer member, the negative electrode structure and electrode to which the carbon-containing layer is transferred using the transfer member, and the method for producing the same will be described in detail below. The transfer member of the present disclosure can be used in the manufacture of electrodes for secondary batteries, specifically as a transfer member for transferring carbon particles or active material particles to a current collector metal. An example in which a carbon-containing layer is used will be described below, but the transfer member of the present disclosure can be used for either a positive electrode or a negative electrode.

[0018] The structure of the transfer member is shown in Fig. 1. The transfer member 1 has a substrate 3 and a carbon-containing layer 2. That is, the structure has a layer 2 containing carbon particles on a substrate 3. The carbon-containing layer 2 contains an electrically conductive allotrope of carbon. The transfer member 1 transfers the carbon-containing layer 2 to a current collector, which is a transfer target.

[0019] (Substrate of transfer member) The substrate has a first linear expansion coefficient. The first linear expansion coefficient corresponds to the linear expansion coefficient in a plane intersecting the thickness direction of the substrate in a temperature range of 25°C or higher and 100°C or lower. The absolute value of the difference between the first linear expansion coefficient and the linear expansion coefficient in a plane intersecting the thickness direction of a carbon-containing layer described below is 10.0 x 10 -6 K -1 The following is the result.

[0020] When a resin substrate is used in forming the carbon-containing layer, the resin substrate may be removed by heat treatment, so the substrate of the transfer member is preferably made of an inorganic material. Since the carbon material itself generally has a small linear expansion coefficient, a substrate with a low linear expansion coefficient is also selected. The first linear expansion coefficient is not particularly limited as long as the absolute value of the difference with the linear expansion coefficient of the carbon-containing layer satisfies the above-mentioned range, but is usually 0.1 × 10 -6 K -1 ~50.0×10-6 K -1 The range is.

[0021] The absolute value of the difference between the linear expansion coefficient of the carbon-containing layer and -6 K -1 Examples of substrates that can be used include metals such as invar, super invar, 42 invar, kovar, tungsten, and platinum, and ceramic materials such as silicon, sapphire, diamond, silicon carbide, aluminum nitride, silicon nitride, alumina, yttria, cermet, and cordierite. The above materials may be used alone or in combination.

[0022] When using a substrate with non-uniform materials, such as a substrate made of different materials bonded together, measure the linear expansion coefficient of each material in advance to ensure that the absolute value of the difference between the linear expansion coefficient of the carbon-containing layer and that of the carbon-containing layer is 10.0 × 10 -6 K -1 You can confirm that the following is true:

[0023] The first linear expansion coefficient of the substrate can be measured by absolute measurement methods such as optical interferometry and X-ray diffraction, or by comparative measurement methods such as a push rod dilatometer and a thermomechanical analyzer (TMA). JIS R 1618-2002 "Method for measuring thermal expansion of fine ceramics by thermomechanical analysis" and JIS Z 2285-2, which are standards for measuring the linear expansion coefficient of various solid materials, are also used. The linear expansion coefficient of a metal material can be measured by any method described in "Method for measuring the linear expansion coefficient of a metal material" in 2003. The measurement method will be described in detail later.

[0024] The absolute value of the difference between the first linear expansion coefficient of the substrate and the linear expansion coefficient of the carbon-containing layer described later is 10.0 × 10 -6 K -1 When the absolute value is 5.0×10 or less, the adhesion between the substrate and the carbon-containing layer can be improved. -6 K -1It is more preferable that the absolute value is 3.0 × 10 or less, since it can reduce wrinkles that occur in the carbon-containing layer after the degreasing step described below. In particular, when forming a carbon-containing layer by arranging carbon particles and silicon particles in a pattern using the method described below, it is thought that reducing the occurrence of wrinkles after the degreasing step can maintain the particle arrangement pattern during transfer, and can prevent an increase in electrode resistance. -6 K -1 It is even more preferable that:

[0025] (carbon-containing layer) The carbon-containing layer includes an allotrope of carbon that has electrical conductivity. Conductive carbon allotropes include amorphous carbon, glassy carbon, graphite (carbon black, HOPG), diamond-like carbon, carbon nanofibers, graphite nanofibers, graphene, etc. Polycrystalline diamonds may also be included, in which a portion of the sp3 bond framework constituting the crystalline structure is replaced with sp2 bonds. Such conductive carbon allotropes form electron conduction paths due to the extended pi bonds derived from sp2 bonds. This ensures conductivity without the introduction of external dopants such as phosphorus, nitrogen, or vanadium, thereby reducing the influence of dopants on adjacent layers in a laminated structure. However, carbon allotropes do not necessarily have a high affinity with other metal elements, and some solution has been sought to improve their affinity and adhesion with solid electrolytes containing active materials. The carbon-containing layer of the transfer member of this embodiment may contain a resin component, as described below. The carbon allotrope may be disposed on a resin substrate, as described below, or may form a layer containing a resin binder. Furthermore, the carbon-containing layer may contain active material particles in addition to the carbon allotrope.

[0026] The absolute value of the difference between the first linear expansion coefficient of the substrate and the linear expansion coefficient in a plane intersecting the thickness direction of the carbon-containing layer in a temperature range of 25°C or higher and 100°C or lower is 10.0 × 10 -6 K -1 The absolute value is 5.0×10 -6 K -1 Preferably, it is 3.0 x 10 or less. -6K -1 More preferably, it is: The linear expansion coefficient of the carbon-containing layer can be measured by the method described below.

[0027] (carbon allotrope) The carbon allotrope is not particularly limited as long as it has electrical conductivity, and known allotropes can be used, such as the above-mentioned amorphous carbon, glassy carbon, graphite (carbon black), diamond-like carbon, carbon nanofiber, graphite nanofiber, graphene, natural graphite, artificial graphite, non-graphitizable carbon, graphitizable carbon, cokes, graphites, glassy carbons, fired organic polymer compounds, carbon fibers, activated carbon, carbon nanotubes, carbon nanohorns, and highly oriented pyrolytic graphite (HOPG). The linear expansion coefficient of carbon materials varies depending on the manufacturing method, orientation, etc., but is usually 1.0 x 10 -6 K -1 ~7.0×10 -6 K -1 is.

[0028] The method for forming the carbon-containing layer on the substrate is not particularly limited, but examples thereof include a method in which a carbon allotrope is disposed on a resin substrate in advance, and the resin substrate is then disposed on the substrate. Alternatively, the carbon-containing layer can be formed by applying a slurry containing a carbon allotrope and a binder component to a current collector and drying the slurry.

[0029] As a method for disposing a carbon allotrope on a resin substrate, there is a method disclosed in JP 2019-137061 A. One example is a method of arranging particles on a resin substrate, as described in the report. The resin substrate used in this case is a substrate formed from a material containing resin. By using a substrate formed from an organic material such as resin, it is possible to easily remove the substrate by heating in the manufacturing process of the electrode substrate, which will be described later. The method of arranging carbon allotropes on a resin substrate will be described in detail later.

[0030] The resin contained in the material of the resin substrate is not particularly limited, but examples thereof include polyesters such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), as well as polyamides such as nylon, etc. Among these, it is preferable to use PET from the viewpoints of its decomposition temperature and the low toxicity of gases generated during thermal decomposition.

[0031] Alternatively, a carbon-containing layer may be formed by adding a resin as a binder to the carbon allotrope. When the carbon particles are applied as a slurry, the slurry may contain a binder component, a dispersant, a solvent, and the like in addition to the carbon allotrope. The binder component may be polyvinyl butyral, polycarboxylic acid, polyacrylic acid, polymethacrylic acid, polycarboxylate, polyacrylate, polymethacrylate, polyvinyl alcohol, polyvinylpyrrolidone, polyimide, or the like. As the dispersant, various anionic, cationic and nonionic surfactants, and polycarboxylic acid polymer dispersants can be used. For example, polyvinyl alcohol can be used as the dispersant. Examples of the solvent that can be used include organic solvents such as tetrahydrofuran, methyl ethyl ketone, dimethylformamide, dimethylacetamide, tetramethylurea, dimethyl sulfoxide, trimethyl phosphate, and N-methyl-2-pyrrolidone (NMP). Among these, NMP is preferred.

[0032] (Other ingredients) Other components that can be contained in the carbon-containing layer include materials used as negative electrode active materials. Examples of negative electrode active materials include materials that can be alloyed with lithium. Examples include materials containing Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, and Au. Only one type of negative electrode active material may be used, or two or more types may be used in combination. Among materials that can be alloyed with lithium, silicon-based materials containing Si are particularly preferred.

[0033] Examples of silicon-based materials include Si, SiB4, SiB6, Mg2Si, Ni2Si, TiSi2, MoSi2, CoSi2, NiSi2, CaSi2, CrSi2, Cu5Si, FeSi2, MnSi2, NbSi2, TaSi2, VSi2, WSi2, ZnSi2, SiC, Si3N4, Si2N2O, SiO, SiO2, SnSiO3, and LiSiO. These particles are preferred, and the particle size is preferably 1 μm or less to minimize the volume change associated with the insertion and desorption of Li.

[0034] The content of the negative electrode active material in the carbon-containing layer is preferably 0.01 to 30% by mass. When a silicon component is contained as the negative electrode active material, the carbon-containing layer preferably contains 0.01% to 30% by mass of the silicon component. If the content of the negative electrode active material is 0.01% by mass or less, the effect of adding the silicon component cannot be obtained. On the other hand, if the content exceeds 30% by mass, the volume change of the negative electrode active material used during charge and discharge becomes large, which can cause peeling and make it difficult to use as a negative electrode.

[0035] <Method for measuring the coefficient of linear expansion> The linear expansion coefficient of the carbon-containing layer can be measured by a known method for measuring the linear expansion coefficient. Measurement using a thermomechanical analyzer (TMA) is preferred. JIS R 7222:2017, Measurement Method for Physical Properties of Graphite Materials, can be used as a measurement standard. Specifically, measurement can be performed using the following method. A 5mm x 20mm test piece with the same composition as the carbon-containing layer used in the transfer member is prepared. The sample is placed in a thermomechanical analyzer, and measurements are performed in an air atmosphere. The sample elongation is measured at each temperature between 25°C and 150°C at a heating rate of 5°C / min. The elongation is measured with the low temperature side at 25°C and the high temperature side at 100°C, and the linear expansion coefficient, which corresponds to the first-order coefficient of the linear expansion rate with respect to temperature in that temperature range, is calculated. Alumina can be used as a reference test piece. Three identical samples are prepared, and the average of the measured values ​​is used as the linear expansion coefficient. Furthermore, the linear expansion coefficient of various substrates, including substrates made of different materials bonded together, can also be calculated using a similar method.

[0036] The carbon-containing layer may be formed on a substrate in a single layer or in multiple layers. The number of layers is not particularly limited and is determined according to the desired electrode capacity. For example, it is preferable to stack three or more resin substrates on which a carbon-containing layer is formed. The resin substrates on which the carbon-containing layer is formed may be the same, or different substrates may be stacked.

[0037] <Method of manufacturing transfer member> An example of a method for producing a transfer member will be described in detail below with reference to the drawings. Here, a method using a resin substrate will be described in detail. The method for producing the transfer member includes the following steps. (1) A preparation step of preparing a resin substrate with an adhesive portion. (2) A first step of disposing first particles P1 on the surface of the adhesive portion (S101 in FIG. 2). (3) A second step of disposing second particles P2 on the surface of the adhesive portion (S102 in FIG. 2). (4) a third step of attaching the base material on which the particles are arranged onto a transfer substrate (S103 in FIG. 2); and (5) a fourth step of heat-treating the transfer substrate and the base material on which the particles are arranged and attached to the substrate (S104 in FIG. 2).

[0038] That is, the method for manufacturing a transfer member for forming a negative electrode includes a preparation step of preparing a resin substrate having an adhesive portion, a step of arranging a carbon allotrope on the adhesive portion to form a carbon-containing layer, and a step of attaching the carbon-containing layer onto a substrate. In the step of attaching the carbon-containing layer to the substrate, the absolute value of the difference in linear expansion coefficient between the substrate and the carbon-containing layer is 10.0 × 10 -6 K -1 It is preferable that the linear expansion coefficient is equal to or less than 1000 .mu.m.

[0039] (preparation process) In the preparation step, a resin substrate having an adhesive portion is prepared. In the present disclosure, the term "having an adhesive portion" means that an adhesive portion is provided on a part or the entire surface of the resin substrate. The resin substrate may be a substrate containing the resin described above. The method for providing the adhesive portion is not particularly limited, but a method of applying an adhesive to the surface of the resin substrate is preferred. That is, the transfer member may contain an adhesive or may include a substrate having an adhesive portion.

[0040] The adhesive is not particularly limited, and known adhesives can be used, such as acrylic adhesives, rubber adhesives, and silicone adhesives, as well as thermoplastic resins and photocurable resins whose adhesive strength changes in response to external disturbances such as heat and light.

[0041] (First and second steps) The first step is a step of disposing first particles P1 on the surface of the adhesive part of the resin substrate. The second step is a step of disposing second particles P2 on the surface of the adhesive part of the resin substrate where the first particles P1 are not disposed. 2, the second step (S102) is illustrated as following the first step (S101), but the order of the first and second steps is not particularly limited. That is, the step of arranging the second particles P2 on the surface of the adhesive portion may be performed after the step of arranging the first particles P1.

[0042] The first particles P1 are, for example, carbon particles. For example, the above-mentioned carbon allotropes can be used as the first particles P1. The second particles P2 are particles that can correspond to active material particles in the electrode substrate after manufacture, for example. For example, the above-mentioned negative electrode active material can be used as the second particles P2. That is, in the method for manufacturing the electrode substrate, the first and second steps can be said to be steps of arranging carbon particles and active material particles on the surface of the adhesive portion.

[0043] The particle size of the primary particles of the first particles P1 is not particularly limited, but for example, the cumulative 50% particle size in the volume-based particle size distribution is preferably 0.01 to 10.0 μm, and more preferably 0.05 to 7.0 μm.

[0044] The particle size of the primary particles of the second particles P2 is not particularly limited. For example, the cumulative 50% particle size in the volume-based particle size distribution of the primary particles of the second particles P2 is preferably 0.01 to 10.0 μm, and more preferably 0.05.0 to 7.0 μm. The ratio of the particle size of the primary particles of the first particles P1 to the particle size of the primary particles of the second particles P2 is not particularly limited. The first particles P1 and the second particles P2 may be interchangeable, or the same particles may be used. That is, the first particles P1 may be particles that can correspond to active material particles, and the second particles P2 may be carbon particles. Alternatively, both the first particles and the second particles may be carbon particles.

[0045] In addition, additional steps may be added between the steps, such as a step of applying third particles P3 and a step of rubbing particles. The third particles P3 include graphite particles, other active material particles, and solid electrolyte particles.

[0046] FIG. 3 is a diagram showing a schematic configuration of a particle placement device for placing particles on a resin substrate. The particle placement device includes a first storage container 21a that stores and supplies a first substrate 11a, a first belt device 22a that transports the first substrate 11a, and a pattern forming device 23 that forms a concave-convex pattern on the first substrate 11a.

[0047] A substrate containing the above-mentioned resin can be used as the first substrate a. Methods for forming the concave-convex pattern using the pattern forming device 23 include UV imprinting, thermal imprinting, UV inkjet printing, printing, and laser etching. Note that a substrate on which a concave-convex pattern has been previously formed may also be used as the first substrate 11a.

[0048] The particle placement device has a first filling device 24a that places first particles P1 in the recesses of the concave-convex pattern formed on the first substrate 11a. The filling device 24a is a device that fills the recesses with the first particles P1 by rubbing magnetic particles, each having particles P1 carried on its surface, on the substrate 11a using magnetic force. By making the particle size of the magnetic particles used here larger than the period of the concave-convex pattern formed on the substrate 11a, only the particles to be placed are filled in the recesses.

[0049] The particle placement device has a second storage container 21b that stores and supplies the second substrate 11b, and a second belt device 22b that transports the second substrate 11b. The particle placement device has a transfer unit 25a where rollers 223 of a first belt device 22a and a second belt device 22b face each other, and the first particles P1 are transferred from the first substrate 11a to the second substrate 11b in the transfer unit 25a.

[0050] Furthermore, the particle placement device has a second filling device 24b that places second particles P2 on the second substrate 11b in areas where the first particles P1 have not been transferred. The filling device 24b also fills the second particles P2 using a mechanism similar to that of the filling device 24a. Note that illustrations and detailed descriptions of devices that are less relevant to explaining the effects of the present invention, such as a peeling and recovery device that peels and recovers the first substrate 11a from the first belt device 22a after transfer and various cleaning devices, will be omitted.

[0051] In the particle placement device, the pattern forming device 23, the first filling device 24a, and the transfer unit 25a correspond to a first placement means that places the first particles P1 in a pattern on the first substrate 11a, and the second filling device 24b corresponds to a second placement means that places the second particles P2 in areas on the second substrate 11b where the first particles P1 are not placed.

[0052] (3rd step) The third step is a step of attaching the base material on which the particles produced in the first two steps are arranged onto a substrate. Thereafter, a process for improving the adhesion between the substrate of the transfer member and the electrode base material may be included. Specifically, a heating process or a pressure process may be included. Heating and pressure application may be performed independently or simultaneously. The heating temperature is preferably 30°C to 250°C, depending on the type of resin component. The pressure applied during pressure application is preferably 5 MPa to 500 MPa. A pressure application method that applies pressure evenly to the entire transfer member is preferred. In order to prevent particles from moving due to pressure and disrupting their arrangement, a means for applying isotropic pressure is particularly preferred.

[0053] (4th step) The fourth step is a step of heat-treating the transfer substrate and the base material on which the particles are arranged and attached to the substrate. That is, the method for manufacturing a transfer member may include a heating step of heating the transfer member. The fourth step is a step of degreasing at least a portion of the resin in the transfer member by heat treatment. A firing furnace used for firing ceramics or the like can be used as a heating means. This may also be combined with a pressure means. The pressure means may simply be a metal or ceramic plate placed on the carbon-containing layer, or a hot press or the like may also be used. As the atmospheric gas for the fourth step, an oxidizing atmosphere (O2), an inert atmosphere (Ar, N2, etc.) or a reducing atmosphere (Ar-H2) can be used, but sintering may also be carried out in air.

[0054] The heat treatment device preferably uses a pressure reducing means to exhaust the released gas to the outside of the heating furnace. By creating an oxidizing atmosphere, i.e., an atmosphere containing oxygen gas such as air, inside the heating furnace using an atmospheric gas supply means, the resin substrate can be burned and removed. However, depending on the active material particles and solid electrolyte particles used, heating in an oxidizing atmosphere may cause decomposition or composition changes. In such cases, heating in an inert atmosphere (Ar, N, etc.) or a reducing atmosphere (Ar-H) is preferred.

[0055] When the carbon-containing layer is degreased, it is preferably heated at a temperature equal to or higher than the thermal decomposition temperature of the substrate having the adhesive portion in the carbon-containing layer, and is preferably heated at a temperature lower than the thermal decomposition temperature of each particle in the carbon-containing layer. The temperature at which the carbon-containing layer is heated is preferably 200°C or higher and 700°C or lower, more preferably 300°C or higher and 600°C or lower, and more preferably 400°C or lower. It is more preferable that the upper limit temperature during heating is maintained for 30 minutes or more, and more preferably for 1 hour or more.

[0056] The thermal decomposition temperature is the temperature at which a material begins to lose weight when the temperature is gradually increased in a heating atmosphere in a heat treatment device. Therefore, by heating the carbon-containing layer at a temperature equal to or higher than the thermal decomposition temperature of the substrate 11, the substrate 11 in the carbon-containing layer can be decomposed to reduce its weight, and the resin substrate can be removed from the carbon-containing layer. The heating temperature is preferably equal to or higher than the thermal decomposition temperature of the substrate 11, and more preferably, the substrate 11 is heated at a temperature even higher than the thermal decomposition temperature.

[0057] Specifically, when thermogravimetric analysis is performed by increasing the temperature from room temperature (25°C) at a rate of 5°C / min in an atmosphere (typically air) during heating in a heat treatment device, it is preferable to heat the substrate 11 to a temperature equal to or higher than the temperature at which the mass of the substrate 11 becomes 70% by mass of the initial mass. Specifically, for example, 385°C or higher is preferable.

[0058] Similarly, when thermogravimetric analysis is performed, it is more preferable to heat the substrate 11 at a temperature equal to or higher than the temperature at which the mass of the substrate 11 is reduced to 50% by mass of its initial mass, and it is even more preferable to heat the substrate 11 at a temperature equal to or higher than the temperature at which the mass of the substrate 11 is reduced to 20% by mass of its initial mass. Specifically, for example, the temperature is preferably 400° C. or higher, and more preferably 450° C. or higher, which can shorten the time required to remove the resin substrate and increase the removal rate of the resin substrate.

[0059] When removing the base material 11 by heating in a heat treatment device in this way, it is preferable that the carbon allotrope, active material particles, and solid electrolyte particles in the carbon-containing layer have a higher thermal decomposition temperature than the base material 11. In other words, it is preferable that the thermal decomposition temperature of the base material having the adhesive portion is lower than the thermal decomposition temperature or melting point of the substrate of the transfer member and the thermal decomposition temperature of the carbon-containing layer. For example, the thermal decomposition temperature or melting point of the substrate is usually in the range of 1400° C. to 3500° C., and the thermal decomposition temperature of the carbon-containing layer is usually in the range of 600° C. to 900° C. The thermal decomposition temperature of the base material having the adhesive portion is preferably, for example, 300° C. to 500° C.

[0060] In general, inorganic materials tend to have higher thermal decomposition temperatures than organic materials, so it is preferable that the active material particles and solid electrolyte particles are inorganic materials and that the material of the substrate 11 is an organic material such as a resin. It is also preferable that the active material particles have a softening point temperature higher than the thermal decomposition temperature of the substrate 11.

[0061] By the above-mentioned heat treatment, it is preferable to remove 50% by mass or more of the resin substrate in the carbon-containing layer, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0062] <Thermogravimetric analysis method> The above thermogravimetric analysis can be carried out using a simultaneous thermogravimetry and differential thermal analyzer (TG-DTA). 10-15 mg of a 1 mm square sheet of resin substrate is placed on a platinum heat-resistant pan, and the temperature is raised from room temperature to 1000°C at a rate of 5°C / min, followed by weight measurement. Weight measurement is carried out in a furnace with an air atmosphere introduced. The weight loss rate of the resin substrate can be calculated by measuring the change in weight due to the temperature increase and determining the amount of change from the weight before heating.

[0063] Alternatively, the resin may be heated at a temperature and atmosphere that removes components other than the C element from the resin component, i.e., carbonizes the resin. In this case, the resin substrate is preferably burned or gasified and released to the outside as a gas. In this case, the resin substrate gasified by thermal decomposition is transferred to the transfer member as a gas. When the particles are released to the outside, they may push up the particle layer formed on the resin substrate, causing the shape to become distorted. For this reason, it is preferable to reduce the thickness of the resin substrate to reduce the impact on the particle layer.

[0064] Specifically, the thickness (μm) of the resin substrate is preferably 10 times or less, more preferably 5 times or less, and even more preferably 2 times or less, the thickness of the particle layer on the resin substrate. Here, the thickness of the particle layer refers to the difference between the maximum and minimum values ​​of z in the region (x, y, z) where each particle arranged on the resin substrate exists, when the surface direction of the resin substrate is (x, y) and the stacking direction of the resin substrate is (z) in an electrode substrate in which particles are arranged on the resin substrate.

[0065] The thickness of the resin substrate is preferably 1 μm or more and 1 mm or less, and the thickness of the particle layer is preferably 0.1 μm or more and 100 μm or less.

[0066] The thickness of the particle layer on the resin substrate is calculated by observing the cross section of the carbon-containing layer using a BIB-SEM, determining the particle presence area (x, z) using image processing software, where x is the resin substrate surface and z is the lamination direction of the resin substrate, and then determining the difference between the maximum and minimum values ​​of z.

[0067] The thickness of the resin substrate may be determined using a BIB-SEM, as with the particle size of the active material particles, or may be measured using a digital thickness gauge, etc. In addition, in SEM observation using a BIB-SEM, methods for identifying the carbon particles, active material particles, solid electrolyte particles, substrate, and adhesive portion include elemental composition analysis using EDS.

[0068] As described above, a transfer member having a carbon-containing layer can also be produced by applying and drying a slurry containing a carbon allotrope and a binder component. For example, a transfer member can be formed by applying a slurry containing a carbon allotrope, a binder resin, a dispersant, and a solvent to a substrate. The carbon allotrope, the binder resin, the dispersant, and the solvent can be the same materials as those described above.

[0069] The method for applying the slurry is not particularly limited, and any known method can be used. For example, the slurry can be applied using an automatic coater or an applicator. The thickness of the applied slurry is preferably 10 to 1000 μm. The substrate coated with the slurry is then heated in an electric furnace to remove the solvent. The heating temperature and heating time are not particularly limited, but it is preferable to heat the substrate at 30 to 300°C for 0.5 to 24 hours. If necessary, pressure may be applied by CIP treatment or the like, and further heating may be performed after the pressure treatment.

[0070] By bringing the transfer member into contact with a current collector or a solid electrolyte, a negative electrode structure, which is an electrode structure, can be obtained. The configuration of the electrode structure is shown in Figure 4. The electrode structure 5 has a configuration in which a member 4 is disposed so as to be in contact with the carbon-containing layer 2 of the transfer member 1. The member 4 is a current collector metal or a solid electrolyte layer. The electrode structure can also be formed as an electrode sheet. An electrode sheet refers to an electrode structure that extends in a sheet shape. The transport form of the electrode sheet may include a stretched form in which it is pulled by a highly rigid structure, or a roll form in which it is wound around a core structure.

[0071] (current collector metal) The current collector metal is not particularly limited and may be any known material. For example, aluminum, stainless steel, platinum, gold, copper, copper-nickel, nickel, tungsten, etc. The above metals that can be used as the current collector may be used in the form of a metal foil or mesh.

[0072] (Solid electrolyte layer) The solid electrolyte layer is made by solidifying solid electrolyte particles to a thickness that does not short-circuit the electrolyte. As the solid electrolyte, either a sulfide-based solid electrolyte or an oxide-based solid electrolyte can be used as long as it has electrical insulation and ionic conductivity.

[0073] Sulfide-based solid electrolytes include Li7P3S 11 , Li3PS4, Li8P2S9, Li 13 GeP3S 16 , Li 10 GeP2S 12 etc. The sulfide-based solid electrolyte can be formed into a solid electrolyte layer by cold pressing the powder to remove the bonds between the particles.

[0074] As oxide-based solid electrolytes, Nasicon type Li 2-x Al x Ge 2-x (PO4)3(LAGP), Li 1+x Al x Ti 2-x (PO4)3(LATP) and their substitution products. Garnet-type lithium lanthanum zirconate, Li7La3Zr2O 12 and their substitution products, for example, Li 7-x La3Zr 2-x Ta x O 12 (LLZT). Perovskite-type 2 / 3-x Li 3x TiO3 (LLTO) and their substitution products. Boric acid-based compounds include Li3BO3 (LBO), Li 6-x R 1-x M x Examples include (BO3)3 (R is Yb, Er, Ho, Tm, La, Nd, or Sm, and M is Zr, Ce, or Sn), and substitution products thereof. The oxide-based solid electrolyte powder is pressed into pellets, which are then sintered at a predetermined temperature to obtain a solid electrolyte layer.

[0075] The Vickers hardness of the current collector metal or the solid electrolyte layer is preferably lower than that of the substrate of the transfer member. That is, the Vickers hardness of the substrate of the transfer member is preferably higher than that of the current collector. Also, the Vickers hardness of the substrate of the transfer member is preferably higher than that of the solid electrolyte layer. In this case, the difference in Vickers hardness is preferably 10 HV or more. That is, the Vickers hardness of the substrate of the transfer member is preferably 10 HV or more higher than the Vickers hardness of the current collector or the solid electrolyte layer. When the difference in Vickers hardness is within the above range, it becomes possible to easily transfer the carbon-containing layer from the substrate of the transfer member to the current collector metal.

[0076] Vickers hardness is measured according to the Vickers hardness test method specified in JIS Z 2244. It can be measured by a test method. It can also be measured by a nanoindenter measuring device or the like. Specifically, it can be measured by the following method. Prepare a plate made of the material to be measured that is 0.5 mm thick or more, and prepare a 15 mm x 15 mm test piece. Set the test piece in a Vickers hardness tester and perform an indentation test using a diamond indenter. The indentation test force was set to 49.03 N (HV5), and the surface area of ​​the indentation formed by the indentation was measured from the obtained image. The Vickers hardness Hv can then be calculated from the measured value and the test force used in the indentation test.

[0077] <Electrode manufacturing method> An example of a method for producing an electrode will be described in detail below with reference to the drawings. The electrode can be obtained by peeling off the substrate 3 from the electrode structure 5 shown in FIG. The method for producing an electrode includes the following three steps (Step I, Step II, and Step III). (I) A step of bonding a transfer member and a current collector metal or a solid electrolyte layer to obtain an electrode structure (S201 in FIG. 5). (II) Pressing the electrode structure to transfer the carbon-containing layer to a current collector metal or a solid electrolyte layer. Step (S202 in Figure 5) (III) A step of peeling off the substrate of the transfer member from the electrode structure to obtain an electrode (5 in the figure, S203).

[0078] That is, the negative electrode can be produced by a production method including the steps of: forming a transfer member; bringing a metal current collector or a solid electrolyte layer on the transfer member into contact with the transfer member so as to sandwich the carbon-containing layer therebetween to obtain a negative electrode structure; applying pressure to the negative electrode structure to transfer the carbon-containing layer from the transfer member to the current collector metal or the solid electrolyte layer; and peeling off the substrate of the transfer member from the negative electrode structure. Each step of the electrode manufacturing method will be described in detail below.

[0079] (Process I) Step I is a step of bonding a transfer member and a current collector metal or a solid electrolyte layer to prepare an electrode structure. That is, the method for producing an anode structure includes a step of forming a transfer member by the above-described production method and a step of bringing the current collector or the solid electrolyte layer into contact with the transfer member.

[0080] The contacting step includes either electrically bonding the current collector and the carbon-containing layer or bonding the electrolyte layer and the carbon-containing layer in a manner capable of exchanging ions. For example, the current collector and the carbon-containing layer can be electrically bonded by bonding the carbon-containing layer on the transfer member so that the current collector metal is in contact with the current collector. Furthermore, the electrolyte layer and the carbon-containing layer can be bonded in a manner capable of exchanging ions by bonding the carbon-containing layer on the transfer member so that the solid electrolyte layer is in contact with the current collector.

[0081] That is, the electrode structure is laminated so that the metal substrate or solid electrolyte layer of the current collector metal is in contact with the carbon-containing layer of the transfer member. The electrode structure includes the transfer member, and the current collector or solid electrolyte layer in contact with the carbon-containing layer of the transfer member.

[0082] (Process II) Step II is a step of transferring the carbon-containing layer from the substrate of the transfer member to the metal collector side or the solid electrolyte layer by applying pressure to the electrode structure prepared in step I. The pressing method is preferably vacuum degassing, isostatic pressing, or a general hydraulic press or roller press, and is particularly preferably a combination of vacuum degassing and isostatic pressing. The pressure is preferably 5 MPa to 500 MPa, which allows the carbon-containing layer to be transferred from the substrate of the transfer member to the current collector metal side or the solid electrolyte layer side.

[0083] (Process III) Step III is a step of peeling the substrate of the transfer member from the pressed electrode structure to obtain an electrode. The peeling method may be any method that can peel the substrate of the transfer member from the current collector metal or the solid electrolyte layer, but it is desirable that the method does not destroy the carbon-containing layer during peeling. For example, peeling can be achieved by fixing the current collector or solid electrolyte layer side and slowly lifting the substrate from one side with tweezers or the like. Furthermore, after step II and / or step III, a step of heating again in a heat treatment device may be included.

[0084] <Secondary battery manufacturing method> A secondary battery can be manufactured by using, as a negative electrode, an electrode in which a carbon-containing layer is formed on the above-described current collector metal or solid electrolyte layer. Here, a method for manufacturing a secondary battery using an electrode in which a carbon-containing layer is formed on a current collector metal will be described in detail.

[0085] In addition to the electrodes manufactured as described above, the cathode layer, cathode current collector, anode current collector, and solid electrolyte layer necessary for the secondary battery are prepared. The cathode current collector, cathode layer, solid electrolyte layer, anode, and anode current collector are stacked in this order, and vacuum-packed in an aluminum laminate film to form a secondary battery. The above-described anode structure can be used as the anode and anode current collector or the solid electrolyte layer and anode.

[0086] The positive electrode layer can be obtained by arranging the material particles used for the positive electrode on a resin substrate using the particle arrangement device shown in Figure 3, followed by lamination and heating and degreasing. At this time, the positive electrode layer can be produced by using particles P1 as the positive electrode active material and particles P2 as solid electrolyte particles.

[0087] Examples of material particles used in the positive electrode include a positive electrode active material, a solid electrolyte, a conductive additive, etc. The positive electrode active material particles are not particularly limited, and known particles can be used. For example, a composite oxide containing lithium can be used. Specific examples include Li-Co oxide active material particles such as LiCoO2, LiMO2 (wherein M is one element selected from the group consisting of Ni, Mn, and Co), Li-PO4 oxide active material particles, Si active material particles (Si, Si-C, etc.), graphite active material particles (graphite, graphene, carbon nanotubes, etc.), lithium vanadium compounds (Li3V2(PO4)3, LiVOPO4), and olivine-type phosphate compounds (LiMPO4 (wherein M is one or more elements selected from the group consisting of Co, Ni, Mn, Fe, Mg, V, Nb, Ti, Al, and Zr)).

[0088] Furthermore, a lithium-free positive electrode active material may be used as the positive electrode active material particles. Specific examples include metal oxides (MnO2, V2O5, etc.) and fluorides (FeF3, VF3, etc.). When using a lithium-free positive electrode active material, metallic lithium containing lithium or a lithium ion-doped negative electrode active material is placed as the negative electrode active material, and the battery can be used by starting with discharge.

[0089] The solid electrolyte particles are not particularly limited, and any ion-conductive solid electrolyte that is commonly used in all-solid-state batteries can be used. For example, Li-B oxide solid electrolyte particles, Li-Yb oxide solid electrolyte particles, Nasicon type solid electrolyte particles (LiAlTi(PO4)3, Li 2-x Al x Ge 2-x(PO4)3(LAGP), etc.), perovskite-type oxide solid electrolyte particles (Li x La (1-x) / 3 TiO3, LixLa (1-x) / 3 NbO3, etc.), garnet-type oxide solid electrolyte particles (Li7La3Zr2O 12 and their substituted derivatives (e.g., Li 7-x La3Zr 2-x Ta x O 12 (LLZT), etc.), and Li-PO solid electrolyte particles (Li3PO4, LiPON (particles in which part of the O in Li3PO4 is replaced with N), etc.).

[0090] Among the above solid electrolyte particles, Li-B oxide-based solid electrolyte particles and Li-Yb oxide-based solid electrolyte particles can be sintered at relatively low temperatures (700°C or lower), which makes it possible to suppress reaction with the positive electrode active material particles during sintering and maintain ionic conductivity.

[0091] The solid electrolyte particles may be commercially available products or may be separately prepared as materials. As the Li-B oxide-based solid electrolyte particles, for example, Li3BO3 or particles in which part of the O in Li3BO3 is replaced with C can be used. Furthermore, as the Li-Yb oxide-based solid electrolyte particles, for example, the compound described in JP-A-2022-130301 can be used. For example, Li 5.9 Yb 0.81 La 0.09 Zr 0.1 (BO3)3, etc. These solid electrolyte particles may be made amorphous in advance by planetary ball milling or the like.

[0092] The method for disposing the positive electrode material particles on the resin substrate can be the same as the method for disposing the negative electrode particles on the resin substrate in the above-mentioned method for manufacturing a transfer member. That is, in Figure 3, by using the first particles P1 as the positive electrode active material and the second particles P2 as the solid electrolyte, a positive electrode substrate in which the positive electrode material particles are disposed on the resin substrate can be obtained.

[0093] For example, the positive electrode layer can be obtained by laminating the obtained positive electrode substrate in a desired area on an aluminum foil that can also be used as a positive electrode current collector, and then degreasing the resin component by heat treatment. If necessary, a pressure application step may be performed between each step. Alternatively, the positive electrode layer can be formed by a coating method using a general slurry. For example, the positive electrode layer can be formed by coating a slurry containing positive electrode active material particles and drying the slurry.

[0094] The solid electrolyte layer can be made of any of the materials described above, as long as it provides insulation between the electrodes and has ion conductivity. Furthermore, by providing an appropriate polymer electrolyte layer at the interface between the electrode and the solid electrolyte layer, it is possible to suppress the electrochemical reaction that occurs between the electrode and the solid electrolyte.

[0095] When an electrode having a carbon-containing layer formed on a solid electrolyte is used as a negative electrode, a secondary battery can be manufactured in the same manner as described above. In this case, a negative electrode current collector, a positive electrode layer, and a positive electrode current collector are prepared, and the positive electrode current collector, positive electrode layer, solid electrolyte layer, negative electrode, and negative electrode current collector are laminated in this order as described above, and the resulting structure is vacuum-packed in an aluminum laminate film to form a secondary battery. The negative electrode structure described above can be used as the negative electrode and negative electrode current collector or the solid electrolyte layer and negative electrode. [Example]

[0096] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, the number of parts is based on parts by mass.

[0097] (Preparation of Carbon-Containing Layers 1 to 3) A transfer member for forming a negative electrode was formed by the above-described method for producing a carbon-containing layer. Specifically, a particle layer was formed on a resin substrate using the particle layer forming apparatus shown in Figure 2. Table 1 shows the particles P1 and P2 used in producing the carbon-containing layer and the arrangement pattern of each particle. [Table 1] In Table 1, "P1 ratio" and "P2 ratio" indicate the mass-based mixing ratio of P1 and P2.

[0098] The materials in Table 1 are as follows: Resin substrate: PET substrate ultra-thin 5 μm double-sided tape No. 5600 (manufactured by Nitto Denko) Carbon particles: SGP-5 (manufactured by SEC Carbon Co., Ltd.) Silicon particles: Si powder, particle size (D50) 1.0 μm, 3N (manufactured by NER Japan)

[0099] The carbon-silicon mixed particles used in the preparation of the carbon-containing layer 3 were prepared by adding and mixing the silicon particles so that the amount of silicon particles added to the carbon-containing layer was 10 mass %. The volume-based cumulative 50% particle size of the primary particles of the carbon particles was 5.5 μm, and the volume-based cumulative 50% particle size of the primary particles of the silicon particles was 1.2 μm.

[0100] (Fabrication of carbon-containing layer 4) A mixture of 96 parts by mass of carbon particles, 3 parts by mass of polyvinyl butyral resin as a binder, and 1 part by mass of polyvinyl alcohol as a dispersant was used as the solid content, and N-methyl-2-pyrrolidone was added to the mixture so that the solid content was 50% by mass, followed by stirring to prepare a slurry. Details of the materials used to prepare the carbon-containing layer 4 are given below. Carbon particles: SGP-5 (manufactured by SEC Carbon Co., Ltd.) Binder resin: S-LEC BM-1 (manufactured by Sekisui Chemical Co., Ltd.) Dispersant: Kuraray Poval PVA-205 (manufactured by Kuraray Co., Ltd.) Solvent: N-methyl-2-pyrrolidone (Kishida Chemical)

[0101] (Measurement of the linear expansion coefficient of the carbon-containing layer) The linear expansion coefficient in a plane intersecting the thickness direction of each carbon-containing layer was measured using a thermomechanical measuring device TMA8310 (manufactured by Rigaku Corporation). The measurement was performed between 25°C and 150°C, and the linear expansion coefficient was calculated from data up to 100°C. Carbon-containing layers 1 to 3 were measured using one resin substrate on which they were formed. The carbon-containing layer 4 was prepared by applying the above-described slurry to a PET separator film (manufactured by AS ONE Co., Ltd.) to prepare a sample for measuring the linear expansion coefficient. The slurry was applied using an automatic coating machine ACL-mini+ (manufactured by Cortec Co., Ltd.) to a film thickness of 300 μm. The layer was then heated at 120°C in an electric furnace to remove the solvent, and the layer was isostatically pressed by CIP, after which it was peeled off from the film and measured. The results are shown in Table 2. [Table 2]

[0102] (Examples 1 to 4, 6 to 9, and 11 to 13 and Comparative Examples 1 to 4) A transfer member was formed by attaching one resin substrate on which a carbon particle layer was formed to a substrate shown in Table 3. The resin substrate was then removed from the transfer member by heating in an electric furnace. The heating temperature is shown in Table 3. The heating time was 1 hour in all cases. After heating, the adhesion of the carbon-containing layer to the substrate was evaluated according to the following criteria. The transfer member was inverted so that the substrate was on top and the carbon-containing layer was on the bottom, and the presence or absence of peeling of the carbon-containing layer was visually confirmed. In the following criteria, peeling of the carbon-containing layer means that the carbon-containing layer was completely peeled off from the substrate. The evaluation results are shown in Table 3. The carbon-containing layer did not peel off even when the substrate was turned upside down: 〇 When the substrate was turned upside down, the carbon-containing layer peeled off: ×

[0103] Example 5 Five resin substrates with carbon particle layers formed on them were stacked and attached to a substrate to form a transfer member. Thereafter, the resin substrate was removed from the transfer member by heating in an electric furnace. The heating temperatures are shown in Table 3. The heating time was 1 hour in all cases. The obtained samples were evaluated in the same manner as in Examples 1 to 4, 6 to 9, and 11 to 13 and Comparative Examples 1 to 4. The results are shown in Table 3.

[0104] Example 10 Ten resin substrates with carbon particle layers formed thereon were stacked and attached to a substrate to form a transfer member. The resin substrates were then heated and removed from the transfer member in an electric furnace. The heating temperatures are shown in Table 3. The heating time was one hour in all cases. The obtained samples were evaluated in the same manner as in Examples 1 to 4, 6 to 9, and 11 to 13 and Comparative Examples 1 to 4. The results are shown in Table 3.

[0105] Example 14 A carbon-containing slurry with the same composition as the slurry prepared for carbon-containing layer 4 was applied to a Super Invar foil to form a transfer member. A doctor blade film applicator (manufactured by TP Giken) was used to apply the slurry to a film thickness of 75 μm. The foil was then heated at 120°C in an electric furnace to remove the solvent. After applying pressure by CIP treatment, the foil was again heated at 510°C in an electric furnace for 1 hour to remove the resin component from the transfer member. The obtained samples were evaluated in the same manner as in Examples 1 to 13 and Comparative Examples 1 to 4. The results are shown in Table 3. [Table 3] In Table 3, "Number of layers" indicates the number of layers of the resin substrate on which the carbon particle layer is formed. "Difference from carbon-containing layer" indicates the absolute value of the difference between the linear expansion coefficient of the substrate in the in-plane direction and the linear expansion coefficient of the carbon-containing layer in the in-plane direction at 25 to 100°C.

[0106] The absolute value of the difference in the linear expansion coefficient between the carbon-containing layer and the substrate is 10 × 10 -6 K -1In the following examples, the carbon-containing layer was retained without peeling off from the substrate even after the heat treatment and could be used as a transfer member. On the other hand, in the comparative example where the absolute value of the difference in the linear expansion coefficient between the carbon-containing layer and the base material was greater than 10×10 -6 K -1 after the heat treatment, the carbon-containing layer peeled off from the substrate and could not be used as a transfer member.

[0107] XRD measurement was performed on the carbon-containing layers prepared in Example 2 and Example 3. <XRD measurement method> Using an X-ray diffractometer X’pertPRO (manufactured by PANalytical), measurement was performed by the parallel beam method. The measurement conditions are shown below. Measurement conditions: tube target Cu, 45 kV 40 mA, D.S. = 1 / 2°, B.M. = 10 mm, soller slit = 0.04 rad., 2θ: 20 to 40°, step = 0.02°, exposure time 4 seconds

[0108] From the spectrum results, for Example 2, only the peaks of the carbon particles and the Super Invar used for the substrate were visible, and it was confirmed that the resin base material disappeared due to heating. On the other hand, for Example 3, the peak derived from the resin base material remained, and it was considered that the resin base material did not completely disappear. Also in the thermal analysis by TG-DTA, since the weight loss rate of the resin base material was about 45% at 400°C, it was considered that the resin base material remained.

[0109] (Examples 15 to 27) An electrode structure was fabricated using the transfer member prepared in the example. Using the transfer member, current collector metal or solid electrolyte (transfer target) shown in Table 4, the carbon-containing layer on the transfer member was sandwiched between the current collector metal or solid electrolyte, and pressurized at 196 MPa with a cold isostatic pressure press device (manufactured by Nikkiso Co., Ltd.), and the carbon-containing layer on the transfer member was transferred to the current collector metal side or the solid electrolyte side. The feasibility of the transfer was visually evaluated according to the following evaluation criteria. The results are shown in Table 4. ​The carbon-containing layer was transferred to the metal side of the current collector or the solid electrolyte side: Yes The carbon-containing layer was transferred to the metal side of the current collector or the solid electrolyte side, but part of it remained on the transfer member: △ The carbon-containing layer was not transferred to the metal side of the current collector or the solid electrolyte side: × The solid electrolyte layer pellets in Table 4 were as follows: LAGP pellets: Li 1.5 Al 0.5 Ge 1.5 (PO4) 3Φ10mm, 0.3mmt, manufactured by Toshima Manufacturing Co., Ltd. LLZT pellets: Li 6.6 La3Zr 1.6 Ta 0.4 O 12 Φ10mm, 1mmt, manufactured by Toshima Manufacturing Co., Ltd. [Table 4] "Hardness (Hv)" in Table 4 represents Vickers hardness. "Difference in Hv" represents the value obtained by subtracting the Vickers hardness of the current collector metal, which is the transferred body, from the Vickers hardness of the substrate of the transferring member.

[0110] In Examples 15 to 27, the carbon-containing layer was transferred from the substrate of the transfer member on the transfer side to the current collector metal, which was the transferee. This was also the case in Example 16, which used a transfer member with a remaining resin substrate. Furthermore, even when multiple carbon-containing layers were laminated as in Examples 18 and 25, the layers were transferred without any problems.

[0111] When the same material was used for both the transfer-side substrate and the current collector metal of the transferee, as in Example 21, part of the carbon-containing layer was transferred, and part was separated onto the substrate side of the transfer member. Also, as in Reference Example 1, the carbon-containing layer was not successfully transferred to SUS304, which has a higher Vickers hardness than the substrate on the transfer member side. From the above, it was confirmed that the carbon-containing layer is more easily transferred to the substrate on the transfer member side when the substrate has a Vickers hardness greater than that of the current collector metal of the transferee, and that this results in excellent transferability.

[0112] Example 28 Two carbon-containing layers 1 were laminated on tungsten foil and heated at 510°C for 1 hour to prepare a transfer member. The prepared transfer member was placed on copper foil so that the carbon-containing layer 1 was in contact with the copper foil, and a cold isostatic press (manufactured by Nikkiso Co., Ltd.) was used to apply pressure at 196 MPa to obtain a negative electrode structure. The substrate was peeled off from the obtained negative electrode structure to form a negative electrode in which the carbon-containing layer 1 was transferred onto the copper foil. The sintered LAGP powder (Li 1.5 Al 0.5 Ge 1.5 0.04 g of (PO4)3 (manufactured by Toshima Manufacturing Co., Ltd.) was packed into a Φ11 mm mold and uniaxially pressed at 40 MPa to obtain pellets. The obtained pellets were sintered in air at 850 °C for 12 hours to obtain LAGP sintered compacts with a Φ10 mm and a thickness of 270 μm. Next, 8 parts of polyoxyethylene-polypropylene oxide polymer and 2 parts of lithium bis(trifluoromethanesulfonyl)imide were added to 70 parts of ethanol and dissolved. This solution was used to form a film of 500 μm thickness on a PET sheet using a bar coater, and the solvent was then thoroughly dried at 80°C to obtain a polymer electrolyte. The thickness of the polymer electrolyte after drying was 30 μm. A lithium foil (Φ8 mm, 50 μm thick, manufactured by Honjo Chemical Co., Ltd.) was used as the positive electrode. A copper foil current collector, lithium foil, polymer electrolyte, sintered LAGP, polymer electrolyte, negative electrode, and copper foil current collector were stacked in this order, and then vacuum-packed in aluminum laminate film and cold isostatically pressed to obtain a half-cell. The battery assembly was carried out in a low-humidity environment. The resulting half-cell was evaluated at room temperature and 0.025 C using a charge-discharge device (manufactured by Biologic). The C rate was calculated from the amount of carbon particles added to the negative electrode. It was confirmed that the cell could be charged and discharged at a capacity of 200 mAh / g, and functioned as a battery. As described above, charging and discharging were possible even with the negative electrode prepared using this transfer member, and it was possible to prepare an electrode containing carbon.

[0113] The present disclosure relates to the following configurations and methods. (Configuration 1) A transfer member for forming a negative electrode applied to a secondary battery, the negative electrode forming transfer member transfers the carbon-containing layer to a transfer target, a substrate having a first linear expansion coefficient; The absolute value of the difference between the first and second linear expansion coefficients is 10.0 × 10 -6 K -1 and the carbon-containing layer has a second linear expansion coefficient that is equal to or less than 1000 kJ / cm.sup.2. (Configuration 2) the transfer member includes a substrate having an adhesive portion; 2. The transfer member for forming a negative electrode according to claim 1, wherein the thermal decomposition temperature of the base material is lower than the thermal decomposition temperature of the substrate and the thermal decomposition temperature of the carbon-containing layer. (Configuration 3) 3. The transfer member for forming a negative electrode according to claim 1, wherein the substrate is made of an inorganic material. (Configuration 4) The absolute value of the difference in the linear expansion coefficient is 5.0 × 10 -6 K -1 4. A transfer member for forming a negative electrode according to any one of Configurations 1 to 3, which is as follows: (Configuration 5) 5. The transfer member for forming a negative electrode according to any one of configurations 1 to 4, wherein the carbon-containing layer contains 0.01% by mass or more and 30% by mass or less of a silicon component. (Configuration 6) the first linear expansion coefficient corresponds to a linear expansion coefficient in a plane intersecting a thickness direction of the substrate, 6. The transfer member for forming a negative electrode according to any one of configurations 1 to 5, wherein the second linear expansion coefficient corresponds to a linear expansion coefficient in a plane intersecting the thickness direction of the carbon-containing layer. (Configuration 7) the first linear expansion coefficient corresponds to an average value in an azimuthal direction of linear expansion coefficients in a plane intersecting a thickness direction of the substrate, 7. The transfer member for forming a negative electrode according to any one of configurations 1 to 6, wherein the second linear expansion coefficient corresponds to an average value in an azimuthal direction of the linear expansion coefficient in a plane intersecting the thickness direction of the carbon-containing layer. (Configuration 8) 8. The transfer member for forming a negative electrode according to any one of Configurations 1 to 7, wherein the first linear expansion coefficient and the second linear expansion coefficient correspond to first-order coefficients with respect to temperature in a temperature range of 25°C or higher and 100°C or lower. (Configuration 9) A negative electrode structure for forming a negative electrode applied to a secondary battery, A transfer member for forming a negative electrode according to any one of configurations 1 to 8, a current collector in contact with the carbon-containing layer. (Configuration 10) 10. The negative electrode structure of claim 9, wherein the substrate has a Vickers hardness greater than the Vickers hardness of the current collector. (Configuration 11) 10. The negative electrode structure of claim 9, wherein the substrate has a Vickers hardness that is at least 10 times higher than the Vickers hardness of the current collector. (Configuration 12) An electrode structure for forming a negative electrode applied to a secondary battery, A transfer member for forming a negative electrode according to any one of configurations 1 to 8, a solid electrolyte layer in contact with the carbon-containing layer. (Configuration 13) 13. The anode structure of claim 12, wherein the substrate has a Vickers hardness greater than the Vickers hardness of the solid electrolyte layer. (Configuration 14) 13. The negative electrode structure according to claim 12, wherein the substrate has a Vickers hardness that is at least 10 times higher than the Vickers hardness of the solid electrolyte layer. (Method 15) A method for manufacturing a transfer member for forming a negative electrode that is applied to a secondary battery, comprising: a preparation step of preparing a substrate having an adhesive portion; disposing a carbon allotrope on the adhesive portion to form a carbon-containing layer; The absolute value of the difference in linear expansion coefficient from the carbon-containing layer is 10.0 × 10 -6 K -1 a substrate having a linear expansion coefficient of less than or equal to 1000 nm; The method for producing a transfer member for forming a negative electrode includes the steps of: (Method 16) 16. The method for producing a transfer member for forming a negative electrode according to Method 15, further comprising a heating step of heating the transfer member for forming a negative electrode. (Method 17) the linear expansion coefficient of the substrate corresponds to the linear expansion coefficient in a plane intersecting the thickness direction of the substrate; 17. The method for producing a transfer member for forming a negative electrode according to Method 15 or 16, wherein the linear expansion coefficient of the carbon-containing layer corresponds to the linear expansion coefficient in a plane intersecting the thickness direction of the carbon-containing layer. (Method 18) the linear expansion coefficient of the substrate corresponds to an average value of the linear expansion coefficient in an azimuthal direction in a plane intersecting the thickness direction of the substrate, 18. The method for producing a transfer member for forming a negative electrode according to any one of Methods 15 to 17, wherein the linear expansion coefficient of the carbon-containing layer corresponds to an average value in an azimuthal direction of the linear expansion coefficient in a plane intersecting with the layer thickness direction of the carbon-containing layer. (Method 19) 19. The method for producing a transfer member for forming a negative electrode according to any one of Methods 15 to 18, wherein the linear expansion coefficient of the substrate and the linear expansion coefficient of the carbon-containing layer correspond to a first-order coefficient with respect to temperature in a temperature range of 25°C or higher and 100°C or lower. (Method 20) forming a transfer member for forming a negative electrode by the manufacturing method described in any one of Methods 15 to 19; and bringing a current collector or a solid electrolyte layer into contact with the transfer member for forming the negative electrode. (Method 21) 21. The manufacturing method according to Method 20, wherein the contacting step includes either electrically coupling the current collector and the carbon-containing layer or ionically coupling the electrolyte layer and the carbon-containing layer. (Method 22) 22. The method according to claim 20 or 21, wherein the substrate has a Vickers hardness higher than the Vickers hardness of the current collector. (Method 23) 22. The method of claim 20 or 21, wherein the substrate has a Vickers hardness greater than the Vickers hardness of the electrolyte layer. (Method 24) forming a transfer member for forming a negative electrode by the manufacturing method described in any one of Methods 15 to 19; a step of contacting a current collector with the transfer member for forming a negative electrode to obtain a negative electrode structure; a transfer step of pressing the negative electrode structure to transfer the carbon-containing layer to a current collector; peeling the substrate from the negative electrode structure; A method for producing a negative electrode, comprising: (Method 25) forming a transfer member for forming a negative electrode by the manufacturing method described in any one of Methods 15 to 19; a step of contacting a solid electrolyte with the transfer member for forming a negative electrode to obtain a negative electrode structure; a transfer step of pressing the negative electrode structure to transfer the carbon-containing layer to a solid electrolyte; peeling the substrate from the negative electrode structure; A method for producing a negative electrode, comprising: (Method 26) preparing a negative electrode by the method described in Method 24; disposing a solid electrolyte layer in contact with the carbon-containing layer of the negative electrode; disposing a positive electrode layer in contact with the solid electrolyte layer; providing a positive electrode current collector in contact with the positive electrode layer; A method for manufacturing a secondary battery, comprising: (Method 27) preparing a negative electrode by the method described in Method 25; disposing a current collector in contact with the carbon-containing layer of the negative electrode; disposing a positive electrode layer in contact with the solid electrolyte layer; providing a positive electrode current collector in contact with the positive electrode layer; A method for manufacturing a secondary battery comprising:

Claims

1. A transfer member for forming a negative electrode applied to a secondary battery, the negative electrode forming transfer member transfers the carbon-containing layer to a transfer target, a substrate having a first linear expansion coefficient; The absolute value of the difference between the first and second linear expansion coefficients is 10.0 × 10 －６ K －１ and the carbon-containing layer has a second linear expansion coefficient that is equal to or less than 0.

05.

2. the negative electrode forming transfer member includes a substrate having an adhesive portion, The transfer member for forming a negative electrode according to claim 1 , wherein the thermal decomposition temperature of the base material is lower than the thermal decomposition temperature of the substrate and the thermal decomposition temperature of the carbon-containing layer.

3. 3. The transfer member for forming a negative electrode according to claim 1, wherein the substrate is made of an inorganic material.

4. The absolute value of the difference is 5.0 × 10 －６ K －１ The transfer member for forming a negative electrode according to claim 1 or 2, wherein:

5. 3. The transfer member for forming a negative electrode according to claim 1, wherein the carbon-containing layer contains 0.01% by mass or more and 30% by mass or less of a silicon component.

6. the first linear expansion coefficient corresponds to a linear expansion coefficient in a plane intersecting a thickness direction of the substrate; 3 . The transfer member for forming a negative electrode according to claim 1 , wherein the second linear expansion coefficient corresponds to a linear expansion coefficient in a plane intersecting a thickness direction of the carbon-containing layer.

7. the first linear expansion coefficient corresponds to an average value in an azimuthal direction of linear expansion coefficients in a plane intersecting a thickness direction of the substrate; 3 . The transfer member for forming a negative electrode according to claim 1 , wherein the second linear expansion coefficient corresponds to an average value in an azimuthal direction of linear expansion coefficients in a plane intersecting a thickness direction of the carbon-containing layer.

8. 3. The transfer member for forming a negative electrode according to claim 1, wherein the first linear expansion coefficient and the second linear expansion coefficient correspond to a first-order coefficient of a linear expansion change rate with respect to temperature in a temperature range of 25°C or higher and 100°C or lower.

9. A negative electrode structure for forming a negative electrode applied to a secondary battery, The transfer member for forming a negative electrode according to claim 1 or 2, a current collector in contact with the carbon-containing layer.

10. 10. The negative electrode structure of claim 9, wherein the substrate has a Vickers hardness higher than that of the current collector.

11. 10. The negative electrode structure according to claim 9, wherein the Vickers hardness of the substrate is at least 10 HV higher than the Vickers hardness of the current collector.

12. An electrode structure for forming a negative electrode applied to a secondary battery, The transfer member for forming a negative electrode according to claim 1 or 2, a solid electrolyte layer in contact with the carbon-containing layer.

13. 2. The method of claim 1, wherein the Vickers hardness of the substrate is higher than the Vickers hardness of the solid electrolyte layer.

3. The negative electrode structure according to claim 2.

14. 13. The negative electrode structure according to claim 12, wherein the Vickers hardness of the substrate is at least 10 HV higher than the Vickers hardness of the solid electrolyte layer.

15. A method for manufacturing a transfer member for forming a negative electrode that is applied to a secondary battery, comprising: a preparation step of preparing a substrate having an adhesive portion; disposing a carbon allotrope on the adhesive portion to form a carbon-containing layer; The absolute value of the difference in linear expansion coefficient from the carbon-containing layer is 10.0 × 10 －６ K －１ a substrate having a linear expansion coefficient of less than or equal to 1000 nm; The method for producing a transfer member for forming a negative electrode includes the steps of:

16. The method for producing a transfer member for negative electrode formation according to claim 15 , further comprising a heating step of heating the transfer member for negative electrode formation.

17. the linear expansion coefficient of the substrate corresponds to the linear expansion coefficient in a plane intersecting the thickness direction of the substrate; The method for producing a transfer member for forming a negative electrode according to claim 15 or 16, wherein the linear expansion coefficient of the carbon-containing layer corresponds to the linear expansion coefficient in a plane intersecting a layer thickness direction of the carbon-containing layer.

18. the linear expansion coefficient of the substrate corresponds to an average value of the linear expansion coefficient in an azimuthal direction in a plane intersecting the thickness direction of the substrate, 17. The method for producing a transfer member for forming a negative electrode according to claim 15, wherein the linear expansion coefficient of the carbon-containing layer corresponds to an average value in an azimuthal direction of the linear expansion coefficient in a plane intersecting a layer thickness direction of the carbon-containing layer.

19. 17. The method for manufacturing a transfer member for forming a negative electrode according to claim 15 or 16, wherein the linear expansion coefficient of the substrate and the linear expansion coefficient of the carbon-containing layer correspond to a first-order coefficient of a linear expansion change rate with temperature in a temperature range of 25°C or higher and 100°C or lower.

20. forming a transfer member for forming a negative electrode by the manufacturing method according to claim 15; and bringing a current collector or a solid electrolyte layer into contact with the transfer member for forming the negative electrode.

21. 21. The method for manufacturing a negative electrode structure according to claim 20, wherein the contacting step includes either being performed so as to electrically bond the current collector and the carbon-containing layer together, or being performed so as to bond the solid electrolyte layer and the carbon-containing layer together in an ion-transferable manner.

22. The method for manufacturing a negative electrode structure according to claim 20 or 21, wherein the Vickers hardness of the substrate is higher than the Vickers hardness of the current collector.

23. 22. The method for manufacturing an anode structure according to claim 20, wherein the Vickers hardness of the substrate is higher than the Vickers hardness of the solid electrolyte layer.

24. forming a transfer member for forming a negative electrode by the manufacturing method according to claim 15 or 16; a step of contacting a current collector with the transfer member for forming a negative electrode to obtain a negative electrode structure; a transfer step of pressing the negative electrode structure to transfer the carbon-containing layer to the current collector; peeling the substrate from the negative electrode structure; A method for producing a negative electrode, comprising:

25. forming a transfer member for forming a negative electrode by the manufacturing method according to claim 15 or 16; a step of contacting a solid electrolyte layer with the transfer member for forming an anode to obtain an anode structure; a transfer step of pressing the negative electrode structure to transfer the carbon-containing layer to the solid electrolyte layer; peeling the substrate from the negative electrode structure; A method for producing a negative electrode, comprising:

26. producing a negative electrode according to the method of claim 24; disposing a solid electrolyte layer in contact with the carbon-containing layer of the negative electrode; disposing a positive electrode layer in contact with the solid electrolyte layer; providing a positive electrode current collector in contact with the positive electrode layer; A method for manufacturing a secondary battery, comprising:

27. producing a negative electrode according to the method of claim 25; disposing a current collector in contact with the carbon-containing layer of the negative electrode; disposing a positive electrode layer in contact with the solid electrolyte layer; providing a positive electrode current collector in contact with the positive electrode layer; A method for manufacturing a secondary battery comprising the steps of:

Images