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

Abstract

Provided are: a transfer member for forming a negative electrode that ensures adhesion of a carbon-containing layer against handling when forming an electrode having a carbon-containing layer, and that has excellent transferability of the carbon-containing layer onto a solid electrolyte layer or a current collector as a transfer material; a negative electrode structure, an electrode, and a secondary battery using the transfer member; and a method for producing the same. The transfer member for forming a negative electrode is applied to a secondary battery, transfers a carbon-containing layer to a body to be transferred, and includes a substrate having a first linear expansion coefficient, and the carbon-containing layer that contains an electrically conductive carbon allotrope and that has a second linear expansion coefficient in which the absolute value of the difference with the first linear expansion coefficient is 10.0 × 10-6 K-1 or less.

Description

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

[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.

[0002] Generally, secondary batteries are composed 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. Such secondary batteries are used in a wide range of applications, from small devices such as mobile phones to large devices such as electric vehicles.

[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 a method for producing an electrode sheet in which a particle layer containing active material particles is laminated on a resin substrate by contacting a transfer plate, on which active material particles are arranged in a pattern, with the resin substrate having adhesive properties.

[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 the liquid 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.

[0005] JP 2019-137061 A JP 2017-143027 A

[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 such a transfer member is used, 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, or assembly. As a result, it has been found that the 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.

[0008] According to at least one aspect of the present disclosure, there is provided a transfer member for forming an anode that is applied to a secondary battery, the transfer member for forming an anode being configured to transfer a carbon-containing layer to a transferee, the transfer member comprising: a substrate having a first linear expansion coefficient; and a conductive carbon allotrope having a difference in absolute value between the first linear expansion coefficient and the substrate, the absolute value being 10.0 × 10 －６ K －１ and the carbon-containing layer having a second linear expansion coefficient that is:

[0009] According to at least one aspect of the present disclosure, there is provided an anode structure for forming an anode to be used in a secondary battery, the anode structure including the above-described anode-forming transfer member 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-described anode-forming transfer member, the anode structure, and methods for manufacturing an electrode and a secondary battery using them.

[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.

[0011] Fig. 1 is a diagram schematically showing the configuration of a transfer member. Fig. 2 is an image diagram showing a method for manufacturing a transfer member. Fig. 3 is a diagram schematically showing the configuration of a particle placement device. Fig. 4 is a diagram schematically showing the configuration of an electrode structure. Fig. 5 is an image diagram showing a method for manufacturing an electrode.

[0012] In the present disclosure, the expressions "XX or more and YY or less" and "XX to YY" representing a numerical range mean a numerical range including the endpoints, that is, the lower and upper limits, unless otherwise specified. 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, for example, 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 disposed 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 possible cause of the above-mentioned problem is that during the heat treatment of the carbon-containing layer during the electrode manufacturing process, 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 general inorganic particles, the particles separate when the resin is removed by heat treatment, and each particle moves in accordance with the thermal expansion of the substrate, so the above-mentioned problem due to differences in thermal expansion is unlikely to occur. However, if the layer formed on the substrate contains carbon particles, the flat-shaped carbon particles 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 have investigated a method for 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 is 10 × 10 －６ K －１ It was found that by transferring a 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 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 a carbon-containing layer is transferred using the transfer member, and the manufacturing method thereof are described in detail below. The transfer member of the present disclosure can be used in the manufacture of electrodes for secondary batteries. Specifically, it can be used as a transfer member that transfers carbon particles or active material particles to a current collector metal. While an example using a carbon-containing layer will be described below, the transfer member of the present disclosure can be used for both positive and negative electrodes.

[0018] The structure of the transfer member is shown in Figure 1. The transfer member 1 has a substrate 3 and a carbon-containing layer 2. That is, the transfer member 1 has a layer 2 containing carbon particles on the substrate 3. The carbon-containing layer 2 contains an electrically conductive carbon allotrope. 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 a 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 10.0×10 －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 having 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 between the first linear expansion coefficient and 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 x 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 the －６ K －１ Examples of substrates that can be used include metals such as invar, super invar, 42 invar, kovar, tungsten, platinum, etc., and ceramic materials such as silicon, sapphire, diamond, silicon carbide, aluminum nitride, silicon nitride, alumina, yttria, cermet, cordierite, etc. The above materials may be used alone or in combination.

[0022] When using a substrate in which the material is not uniform, such as a substrate in which different materials are bonded together, the linear expansion coefficient of each material is measured in advance, and the absolute value of the difference between the linear expansion coefficient of the carbon-containing layer and the linear expansion coefficient of the carbon-containing layer is determined to be 10.0 × 10 －６ K －１ You can verify that the following is true:

[0023] The first linear expansion coefficient of the substrate can be measured by an absolute measurement method such as optical interferometry or X-ray diffraction, or a comparative measurement method such as a push rod dilatometer or a thermomechanical analyzer (TMA). Measurement can be performed by any method described in JIS R 1618-2002 "Method for measuring thermal expansion of fine ceramics by thermomechanical analysis" and JIS Z 2285-2003 "Method for measuring the linear expansion coefficient of metallic materials," which are standards for measuring the linear expansion coefficient of various solid materials. Details of the measurement method will be described 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 －１When the absolute value is 5.0×10 or less, the adhesion between the substrate and the carbon-containing layer can be improved. －６ K －１ It is more preferable that the absolute value is 3.0 × 10 or less, since this can reduce wrinkles that occur in the carbon-containing layer after the degreasing step described below. In particular, when the carbon-containing layer is formed by arranging carbon particles and silicon particles in a pattern by 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 the resistance of the electrode. －６ K －１ It is even more preferable that:

[0025] (Carbon-Containing Layer) The carbon-containing layer contains a conductive carbon allotrope. Examples of conductive carbon allotropes include amorphous carbon, glassy carbon, graphite (carbon black, HOPG), diamond-like carbon, carbon nanofibers, graphite nanofibers, and graphene. Polycrystalline diamond, in which a portion of the sp3 bond framework constituting the crystalline structure is replaced with sp2 bonds, may also be included. Such conductive carbon allotropes form electron conduction paths due to the extension of pi bonds derived from sp2 bonds. This ensures conductivity without the introduction of external dopants such as phosphorus, nitrogen, and vanadium, thereby reducing the influence of dopants on other adjacent layers in a laminated structure. However, because carbon allotropes do not necessarily have a high affinity with other metal elements, some solution has been sought to improve the 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. The carbon-containing layer may also 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 －１Preferably, it is 3.0 × 10 or less. －６ K －１ It is more preferable that the linear expansion coefficient of the carbon-containing layer is not more than 1000 kJ / cm.sup.2. The linear expansion coefficient of the carbon-containing layer can be measured by the method described below.

[0027] (Carbon allotropes) The carbon allotropes are not particularly limited as long as they are electrically conductive, and known allotropes can be used. Examples include 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, highly oriented pyrolytic graphite (HOPG), etc. The linear expansion coefficient of carbon materials varies depending on the manufacturing method, orientation, etc., but is usually 1.0 × 10 －６ K －１ ~7.0 x 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] One example of a method for disposing carbon allotropes on a resin substrate is the method of arranging particles on a resin substrate, as described in JP 2019-137061 A. The resin substrate used in this case is a substrate formed from a material containing resin. Using a substrate formed from an organic material such as resin makes it easier to remove the substrate by heating in the manufacturing process of the electrode substrate, which will be described later. Details of the method for disposing carbon allotropes on a resin substrate will be described later.

[0030] The resin contained in the material of the resin substrate is not particularly limited, and examples thereof include polyesters such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), as well as polyamides such as nylon. Of 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 resin may be added as a binder to the carbon allotrope to form a carbon-containing layer. When applying carbon particles as a slurry, the slurry may contain, in addition to the carbon allotrope, a binder component, a dispersant, a solvent, and the like. Examples of binder components that can be used include polyvinyl butyral, polycarboxylic acid, polyacrylic acid, polymethacrylic acid, polycarboxylates, polyacrylates, polymethacrylates, polyvinyl alcohol, polyvinylpyrrolidone, and polyimides. Examples of dispersants that can be used include various anionic, cationic, and nonionic surfactants, and polycarboxylic acid polymer dispersants. For example, polyvinyl alcohol can be used as a dispersant. Examples of solvents 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 the above, NMP is preferred.

[0032] (Other Components) 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. For example, 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 can be used. 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 and SiB ４ , SiB ６ , Mg ２ Si, Ni２ Si, TiSi ２ , MoSi ２ , CoSi ２ , NiSi ２ , CaSi ２ , CrSi ２ , Cu ５ Si, FeSi ２ , MnSi ２ , NbSi2, TaSi ２ , VSi ２ , WSi ２ , ZnSi ２ , SiC, Si ３ N ４ , Si ２ N ２ O, SiO, SiO ２ , SnSiO ３ , LiSiO. These particles are preferred, and the particle size is preferably 1 μm or less in order to reduce the volume change that occurs 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% by mass or more and 30% by mass or less 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 other problems, making it difficult to use as a negative electrode.

[0035] <Method for Measuring Linear Expansion Coefficient> The linear expansion coefficient of the carbon-containing layer can be measured by a known linear expansion coefficient measurement method, preferably using a thermomechanical analyzer (TMA). Measurement standards such as JIS R 7222:2017, Method for Measuring Physical Properties of Graphite Materials, can be used. Specifically, the measurement can be performed by the following method. A 5 mm x 20 mm 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, measuring the elongation of the sample 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 corresponding to the first-order coefficient of the linear expansion change rate with 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. The linear expansion coefficient can also be calculated using a similar method when measuring the linear expansion coefficient of various substrates, including substrates made of different materials bonded together.

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

[0037] <Method for manufacturing transfer member> Hereinafter, an example of a method for manufacturing a transfer member will be described in detail with reference to the drawings. Note that a method using a resin substrate will be described in detail. The method for manufacturing a transfer member has the following steps: (1) a preparation step of preparing a resin substrate having an adhesive portion; (2) a first step of arranging first particles P1 on the surface of the adhesive portion (S101 in FIG. 2); (3) a second step of arranging second particles P2 on the surface of the adhesive portion (S102 in FIG. 2); (4) a third step of attaching the substrate 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 substrate 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 forming a carbon-containing layer by disposing a carbon allotrope on the adhesive portion, and a step of attaching the carbon-containing layer to 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 Step) In the preparation step, a resin substrate having an adhesive portion is prepared. In the present disclosure, "having an adhesive portion" means that an adhesive portion is provided on a part or the entire surface of the resin substrate. As the resin substrate, a substrate containing the above-mentioned resin can be used. Although the method for providing the adhesive portion is not particularly limited, a method of applying an adhesive to the surface of the resin substrate is preferred. In other words, 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 Step and Second Step) The first step is a step of arranging first particles P1 on the surface of the adhesive portion of the resin substrate. The second step is a step of arranging second particles P2 on the surface of the adhesive portion of the resin substrate where the first particles P1 are not arranged. Note that, although the second step (S102) is illustrated in FIG. 2 as following the first step (S101), the order of the first step and the second step is not particularly limited. In other words, the step of arranging the first particles P1 may be performed after the step of arranging the second particles P2 on the surface of the adhesive portion.

[0042] The first particles P1 are, for example, carbon particles. For example, the above-mentioned carbon allotrope can be used as the first particles P1. The second particles P2 are, for example, particles that can correspond to active material particles in the electrode substrate after manufacture. 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 step and the second step can also be described as 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 second particles P2 preferably have a cumulative 50% particle size in the volume-based particle size distribution of the primary particles of 0.01 to 10.0 μm, 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 P1 and the second particles P2 may be carbon particles.

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

[0046] 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 21 a for storing and supplying a first substrate 11 a, a first belt device 22 a for transporting the first substrate 11 a, and a pattern forming device 23 for forming a concave-convex pattern on the first substrate 11 a.

[0047] A substrate containing the resin described above 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 11 a.

[0048] The particle placement device includes 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 carrying particles P1 on their surfaces over 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 into the recesses.

[0049] The particle placement device includes 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 second substrate 11b may be a substrate containing the resin described above. The particle placement device includes a transfer unit 25a in which rollers 223 of the first belt device 22a and the 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 devices that are less relevant to explaining the effects of this invention, such as a peeling and recovery device for peeling and recovering the first substrate 11a from the first belt device 22a after transfer and various cleaning devices, will not be illustrated or described in detail.

[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 unit 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 unit that places the second particles P2 in areas on the second substrate 11b where the first particles P1 are not placed.

[0052] (Third Step) The third step is a step of attaching the base material on which the particles prepared in the second step are arranged onto a substrate. Thereafter, a step of improving the adhesion between the substrate of the transfer member and the electrode base material may be included. Specifically, a heating treatment or a pressure treatment step may be included. Heating and pressure application may be performed independently or simultaneously. The heating temperature depends on the type of resin component, but is preferably 30°C to 250°C. The pressure applied during pressure application is preferably 5 MPa to 500 MPa. As a pressure application method, it is preferable to apply pressure evenly to the entire transfer member. In order to prevent the particles from moving due to pressure and disrupting the arrangement, it is particularly preferable to use a means of isotropic pressure application.

[0053] (Fourth Step) The fourth step is a step of heat-treating the transfer substrate and the base material on which the particles are 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 part of the resin in the transfer member by heat treatment. As a heating means, a firing furnace used for firing ceramics etc. can be used. It may also be combined with a pressure means. As a pressure means, it may be possible to simply place a metal plate or a ceramic plate on the carbon-containing layer, but it may also be a hot press machine or the like. As the atmospheric gas for the fourth step, an oxidizing atmosphere (O ２ ), inert atmosphere (Ar, N ２ etc.) or reducing atmosphere (Ar-H ２ ) can be used, but sintering may also be carried out in air.

[0054] The heat treatment device preferably exhausts the released gas to the outside of the heating furnace using a pressure reducing means. The resin substrate can be burned and removed by creating an oxidizing atmosphere, i.e., an atmosphere containing oxygen gas such as air, inside the heating furnace using an atmospheric gas supplying means or the like. 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, an inert atmosphere (Ar, N ２ etc.) or reducing atmosphere (Ar-H ２ ) is preferably heated.

[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 preferably 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 even more preferably 400°C or higher and 550°C or lower. The upper limit temperature during heating is preferably maintained for 30 minutes or longer, more preferably 1 hour or longer.

[0056] The thermal decomposition temperature is the temperature at which the weight of a material begins to decrease 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 heating temperature is even higher than the thermal decomposition temperature of the substrate 11.

[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 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. This can shorten the time required to remove the resin substrate and increase the removal rate of the resin substrate.

[0059] When removing the substrate 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 substrate 11. That is, it is preferable that the thermal decomposition temperature of the substrate 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 typically in the range of 1400°C or higher and 3500°C or lower, and the thermal decomposition temperature of the carbon-containing layer is typically in the range of 600°C or higher and 900°C or lower. It is preferable that the thermal decomposition temperature of the substrate having the adhesive portion is, for example, 300°C or higher and 500°C or lower.

[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] <Method of Thermogravimetric Analysis> The thermogravimetric analysis can be performed using a simultaneous thermogravimetric and differential thermal analyzer (TG-DTA). 10 to 15 mg of a 1 mm square sheet-like 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 to measure the weight. The weight measurement is performed in a furnace containing an air atmosphere. The weight loss rate of the resin substrate can be determined 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 in an 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. When the resin substrate gasified by pyrolysis is released to the outside of the transfer member as a gas, it may push up the particle layer formed on the resin substrate, causing the shape to become distorted. Therefore, 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, of 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 having particles 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 with a BIB-SEM, determining the particle presence region (x, z) using image processing software, and determining the difference between the maximum and minimum values ​​of z, where x is the resin substrate surface and z is the lamination direction of the resin substrate.

[0067] The thickness of the resin substrate may be determined using a BIB-SEM, similar to 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 a method of 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 known methods can be used. For example, the slurry can be applied using an automatic coater or an applicator. The thickness of the coating is preferably 10 to 1000 μm. The substrate on which the slurry has been applied 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. Furthermore, pressure may be applied by CIP treatment or the like, as needed, and further heating may be performed after the pressure treatment.

[0070] A negative electrode structure, which is an electrode structure, can be obtained by contacting the transfer member with a current collector or a solid electrolyte. The configuration of the electrode structure is shown in FIG. 4. The electrode structure 5 has a structure 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 known materials can be used. 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 formed by solidifying solid electrolyte particles to a thickness that does not cause short circuits. 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] The sulfide-based solid electrolyte is Li ７ P ３ S １１ , Li ３ P.S. ４ , Li ８ P ２ S ９ , Li １３ GeP ３ S １６ , Li １０ GeP ２ S １２ The sulfide-based solid electrolyte can be made 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 (P.O. ４ ) ３ (LAGP), Li １＋ｘ Al ｘ Ti ２－ｘ (P.O. ４ ) ３ (LATP), and their substitution products. Garnet-type lithium lanthanum zirconate (Li) ７ La ３ Zr ２ O １２ and their substitution products, for example, Li ７－ｘ La ３ Zr ２－ｘ Ta ｘ O １２As the perovskite type, La ２／３－ｘ Li ３ｘ TiO ３ (LLTO), and their substitution products. ３ BO ３ (LBO), Li ６－ｘ R １－ｘ M ｘ (BO ３ ) ３ (R is Yb, Er, Ho, Tm, La, Nd, Sm, and M is Zr, Ce, 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 desirably 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 that 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 can be measured according to the Vickers hardness test method described in JIS Z 2244. It can also be measured using a nanoindenter measuring device or the like. Specifically, it can be measured by the following method. A plate made of the material to be measured and having a thickness of 0.5 mm or more is prepared, and a 15 mm x 15 mm test piece is prepared. The test piece is set in a Vickers hardness tester, and an indentation test is performed using a diamond indenter. The indentation test force is set to 49.03 N (HV5), and the surface area of ​​the indentation formed by the indentation is measured from the obtained image. The Vickers hardness Hv can be calculated from the measured value and the test force used for the indentation test.

[0077] <Electrode Manufacturing Method> An example of an electrode manufacturing method will now be described in detail with reference to the drawings. An electrode can be obtained by peeling off the substrate 3 from the electrode structure 5 shown in FIG. 4. The electrode manufacturing method 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) a step of pressing the electrode structure to transfer the carbon-containing layer to the current collector metal or the solid electrolyte layer (S202 in FIG. 5); and (III) a step of peeling off the substrate of the transfer member from the electrode structure to obtain an electrode (S203 in FIG. 5).

[0078] That is, the negative electrode can be manufactured by a manufacturing method including the steps of forming a transfer member, bringing a metal current collector or a solid electrolyte layer into contact with the transfer member so as to sandwich the carbon-containing layer on the transfer member 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 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] (Step I) Step I is a step of producing an electrode structure by bonding a transfer member and a current collector metal or a solid electrolyte layer. That is, the method for producing an anode structure includes a step of forming a transfer member by the above-mentioned 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] (Step II) Step II is a step of transferring the carbon-containing layer from the substrate of the transfer member to the current collector metal side or the solid electrolyte layer by pressing the electrode structure prepared in Step I. Pressurization is preferably performed by vacuum degassing, isostatic pressing, or by using a general hydraulic press or roller press. Of these, pressing by a combination of vacuum degassing and isostatic pressing is preferred. Pressurization is preferably performed at a pressure of 5 MPa to 500 MPa. This 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] (Step III) Step III is a step of peeling the transfer member substrate from the pressed electrode structure to obtain an electrode. The peeling method may be any method as long as it can peel the transfer member substrate 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] <Method for manufacturing secondary battery> 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-mentioned 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 material particles used for the positive electrode on a resin substrate using the particle arrangement device illustrated in Fig. 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, and a conductive additive. The positive electrode active material particles are not particularly limited and any known material can be used. For example, a composite oxide containing lithium can be used. Specifically, for example, LiCoO ２ Li-Co oxide active material particles such as LiMO ２ (M is an element selected from the group consisting of Ni, Mn, and Co), ４ Oxide-based active material particles, Si-based active material particles (Si, Si-C, etc.), graphite-based active material particles (graphite, graphene, carbon nanotubes, etc.), lithium vanadium compounds (Li ３ V ２ (P.O. ４ ) ３ , LiVOPO ４ ), olivine-type phosphate compounds (LiMPO ４ (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 positive electrode active material that does not contain lithium may be used as the positive electrode active material particles. Specifically, for example, a metal oxide (MnO ２ , V ２ O ５ etc.) and fluorides (FeF ３ , V.F. ３ When using a positive electrode active material that does not contain lithium, it can be used by discharging the negative electrode active material first, using metallic lithium containing lithium or a negative electrode active material doped with lithium ions.

[0089] The solid electrolyte particles are not particularly limited, and any ion-conductive solid electrolyte commonly used in all-solid-state batteries can be used. For example, Li-B oxide-based solid electrolyte particles, Li-Yb oxide-based solid electrolyte particles, Nasicon-type solid electrolyte particles (LiAlTi(PO ４ ) ３ , Li ２－ｘ Al ｘ Ge ２－ｘ (P.O. ４ ) ３ (LAGP), perovskite-type oxide solid electrolyte particles (Li ｘ La （１－ｘ）／３ TiO ３ , LixLa （１－ｘ）／３ NbO ３ etc.), garnet-type oxide solid electrolyte particles (Li ７ La ３ Zr ２ O １２ and their substitutes (e.g., Li ７－ｘ La ３ Zr ２－ｘ Ta ｘ O １２ (LLZT)), Li-P-O solid electrolyte particles (Li ３ P.O. ４ , LiPON (Li ３ P.O. ４ Examples of such particles include particles in which some of the O in the above-mentioned formula (II) is replaced with N.

[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 a relatively low temperature (700°C or lower), and therefore, reaction with the positive electrode active material particles during sintering can be suppressed, and ionic conductivity can be maintained.

[0091] The solid electrolyte particles may be commercially available products or may be prepared separately as materials. Examples of the Li-B oxide solid electrolyte particles include Li ３ BO ３ Ya, Li ３ BO ３Particles in which part of O is replaced with C can be used. In addition, as the Li-Yb oxide solid electrolyte particles, for example, compounds described in JP-A-2022-130301 can be used, for example, Li ５．９ Yb ０．８１ La ０．０９ Zr ０．１ (BO ３ ) ３ 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 obtained positive electrode substrate is laminated with a desired area on an aluminum foil that can also be used as a positive electrode current collector, and the resin component is degreased by heat treatment to obtain a positive electrode layer. If necessary, a pressure step may be provided between each step. The positive electrode layer can also be produced by a coating method using a general slurry. For example, the positive electrode layer can also be produced by coating and drying a slurry containing positive electrode active material particles.

[0094] The above-mentioned materials can be used for the solid electrolyte layer. The solid electrolyte layer needs only to insulate the electrodes and have ion conductivity. Furthermore, by providing an appropriate polymer electrolyte layer at the interface between the electrode and the solid electrolyte layer, the electrochemical reaction occurring between the electrode and the solid electrolyte can be suppressed.

[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.

[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 molded by the above-described method for preparing a carbon-containing layer. Specifically, a particle layer was formed on a resin substrate using the particle layer forming apparatus shown in FIG. 2. Particles P1 and P2 used in preparing the carbon-containing layer and the arrangement pattern of each particle are shown in Table 1. In Table 1, "P1 ratio" and "P2 ratio" indicate the mixing ratio of P1 and P2 on a mass basis.

[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 product 3N (manufactured by Japan NER Co., Ltd.)

[0099] The carbon-silicon mixed particles used to prepare 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 diameter of the primary particles of the carbon particles was 5.5 μm. The volume-based cumulative 50% particle diameter of the primary particles of the silicon particles was 1.2 μm.

[0100] (Preparation 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. N-methyl-2-pyrrolidone was added to the mixture so that the solid content was 50% by mass, and the mixture was stirred to prepare a slurry. Details of the materials used to prepare the carbon-containing layer 4 are as follows: 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 (manufactured by Kishida Chemical Co., Ltd.)

[0101] (Measurement of Linear Expansion Coefficient of 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). Measurements were 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 a single resin substrate. For carbon-containing layer 4, the above-mentioned slurry was applied to a PET separator film (manufactured by AS ONE Co., Ltd.) to create a sample for linear expansion coefficient measurement. The slurry was applied using an automatic coating machine ACL-mini+ (manufactured by Cortec Co., Ltd.) to a film thickness of 300 μm. The sample was then heated to 120°C in an electric furnace to remove the solvent, and isostatically pressed by CIP before being peeled off from the film and measured. The results are shown in 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 had been formed to a substrate described in Table 3. Thereafter, the resin substrate was removed from the transfer member by heating using an electric furnace. The heating temperature at this time is shown in Table 3. The heating time was one hour in all cases. After heating was completed, 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: A The carbon-containing layer peeled off when the substrate was turned upside down: B

[0103] Example 5 Five resin substrates on which carbon particle layers were formed 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 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 on which carbon particle layers were formed 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 temperature is 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.

[0105] Example 14 A carbon-containing slurry having 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, and the film was applied to a thickness of 75 μm. The film was then heated in an electric furnace at 120°C to remove the solvent. After applying pressure by CIP treatment, the film was again heated in an electric furnace at 510°C for 1 hour to remove the resin component from the transfer member. The obtained sample was used to perform evaluations similar to those in Examples 1 to 13 and Comparative Examples 1 to 4. The results are shown in 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 －１ In the following examples, the carbon-containing layer was not peeled off from the substrate even after the heat treatment, and was usable as a transfer member. －６ K －１ In the larger comparative example, the carbon-containing layer peeled off from the substrate after the heat treatment, and it was not possible to use it as a transfer member.

[0107] XRD measurements were performed on the carbon-containing layers produced in Examples 2 and 3. <XRD Measurement Method> Measurements were performed using an X-ray diffraction measurement device X'pertPRO (manufactured by PANalytical) by the parallel beam method. The measurement conditions are as follows: Measurement conditions: Cu tube, 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, it was confirmed that in Example 2, only the peaks of the carbon particles and the Super Invar used in the substrate were visible, and the resin substrate had disappeared due to heating. On the other hand, in Example 3, peaks derived from the resin substrate remained, suggesting that the resin substrate had not completely disappeared. Thermal analysis using TG-DTA also showed that the weight loss rate of the resin substrate was about 45% at 400°C, suggesting that the resin substrate remained.

[0109] (Examples 15 to 27) Electrode structures were produced using the transfer members produced in the examples. Using the transfer members, current collector metals, or solid electrolytes (transfer recipients) shown in Table 4, the carbon-containing layer on the transfer member was sandwiched between the current collector metals or solid electrolytes, and pressed at 196 MPa using a cold isostatic pressing device (manufactured by Nikkiso Co., Ltd.), and the carbon-containing layer on the transfer member was transferred to the current collector metal side or solid electrolyte side. The transfer was evaluated visually according to the following evaluation criteria. The results are shown in Table 4. The carbon-containing layer was transferred to the current collector metal side or solid electrolyte side: A The carbon-containing layer was transferred to the current collector metal side or solid electrolyte side, but a portion remained on the transfer member: B The carbon-containing layer was not transferred to the current collector metal side or solid electrolyte side: C The solid electrolyte layer pellets in Table 4 were as follows: LAGP pellets: Li １．５ Al ０．５ Ge １．５ (P.O. ４ ) ３ Φ10mm, 0.3mmt Toshima Manufacturing Co., Ltd. LLZT pellets: Li ６．６ La ３ Zr １．６ Ta ０．４ O １２ Φ10mm, 1mmt, manufactured by Toshima Manufacturing Co., Ltd. "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 transfer recipient. 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] As in Example 21, when the same material was used for both the transfer-side substrate and the current collector metal of the transferee, part of the carbon-containing layer was transferred, and part was separated onto the transfer member substrate side. Furthermore, as in Reference Example 1, the carbon-containing layer was not successfully transferred to SUS304, which has a higher Vickers hardness than the transfer member-side substrate. From the above, it was confirmed that the carbon-containing layer is more easily transferred and has excellent transferability when the transfer member-side substrate has a higher Vickers hardness than the transfer member-side current collector metal.

[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 pressing device (manufactured by Nikkiso Co., Ltd.) was used to pressurize the copper foil 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. A sintered LAGP body was used as the solid electrolyte layer. LAGP powder (Li １．５ Al ０．５ Ge １．５ (P.O. ４ ) ３0.04 g of LAGP (manufactured by Toshima Manufacturing Co., Ltd.) was filled into a Φ11 mm mold and uniaxially pressed at 40 MPa to obtain a pellet. The resulting pellet was sintered in air at 850°C for 12 hours to obtain a Φ10 mm, 270 μm thick LAGP sintered body. Next, 8 parts of polyoxyethylene-polypropylene oxide polymer and 2 parts of lithium bis(trifluoromethanesulfonyl)imide were added and dissolved in 70 parts of ethanol. This solution was used to form a 500 μm thick film on a PET sheet using a bar coater, and the solvent was thoroughly dried at 80°C to obtain a polymer electrolyte. The dried polymer electrolyte had a thickness of 30 μm. 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, LAGP sintered body, polymer electrolyte, negative electrode, and copper foil current collector were stacked in this order, vacuum-packed in aluminum laminate film, and cold isostatically pressed to obtain a half-cell. The above battery assembly was performed in a low humidity environment. The obtained half-cell was evaluated at 0.025 C and room temperature 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 battery could be charged and discharged at a capacity of 200 mAh / g and functioned as a battery. As described above, the negative electrode prepared using this transfer member was also capable of charging and discharging, and it was possible to prepare an electrode containing carbon.

[0113] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to clarify the scope of the present disclosure. This application claims priority based on Japanese Patent Application No. 2024-045559, filed March 21, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A transfer member for forming a negative electrode used in a secondary battery, the transfer member for forming a negative electrode being used to transfer a carbon-containing layer to a transferee, the transfer member having a first linear expansion coefficient and a conductive carbon allotrope containing a carbon-containing layer, the absolute value of the difference between the first linear expansion coefficient and the first linear expansion coefficient being 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 transfer member for forming a negative electrode according to claim 1, wherein the transfer member for forming a negative electrode includes a base material having an adhesive portion, and 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. The transfer member for forming a negative electrode according to claim 1 or 2, wherein the substrate is made of an inorganic material.

4. The absolute value of the difference is 5.0 x 10 －６ K －１ The transfer member for forming a negative electrode according to any one of claims 1 to 3, wherein:

5. The transfer member for forming a negative electrode according to any one of claims 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.

6. A transfer member for forming a negative electrode according to any one of claims 1 to 5, wherein the first linear expansion coefficient corresponds to a linear expansion coefficient in a plane intersecting the thickness direction of the substrate, and the second linear expansion coefficient corresponds to a linear expansion coefficient in a plane intersecting the thickness direction of the carbon-containing layer.

7. A transfer member for forming a negative electrode according to any one of claims 1 to 6, wherein the first linear expansion coefficient corresponds to an average value in the azimuthal direction of the linear expansion coefficient in a plane intersecting the thickness direction of the substrate, and the second linear expansion coefficient corresponds to an average value in the azimuthal direction of the linear expansion coefficient in a plane intersecting the thickness direction of the carbon-containing layer.

8. A transfer member for forming a negative electrode according to any one of claims 1 to 7, wherein the first linear expansion coefficient and the second linear expansion coefficient correspond to a first-order coefficient of the rate of change of linear expansion with respect to temperature in a temperature range of 25°C or higher and 100°C or lower.

9. An anode structure for forming an anode to be applied to a secondary battery, comprising: a transfer member for forming an anode according to any one of claims 1 to 8; and a current collector in contact with the carbon-containing layer.

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

11. 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 an anode applied to a secondary battery, comprising: a transfer member for forming an anode according to any one of claims 1 to 8; and a solid electrolyte layer in contact with the carbon-containing layer.

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

14. 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 to be used in a secondary battery, comprising: a preparation step of preparing a substrate having an adhesive portion; a step of forming a carbon-containing layer by arranging a carbon allotrope on the adhesive portion; and a step of forming a carbon-containing layer by disposing an allotrope of carbon on the adhesive portion such that the absolute value of the difference in linear expansion coefficient between the carbon-containing layer and the substrate is 10.0 × 10 －６ K －１ and attaching the carbon-containing layer onto a substrate having a linear expansion coefficient of 0.1 to 1.0 μm.

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

17. A 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 corresponds to the linear expansion coefficient in a plane intersecting the thickness direction of the substrate, and 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.

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

19. A method for manufacturing a transfer member for forming a negative electrode according to any one of claims 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 of the rate of change of linear expansion with respect to temperature in a temperature range of 25°C or higher and 100°C or lower.

20. A method for manufacturing an anode structure, comprising: forming a transfer member for forming an anode by the manufacturing method according to any one of claims 15 to 19; and bringing a current collector or a solid electrolyte layer into contact with the transfer member for forming an anode.

21. The method for producing a negative electrode structure according to claim 20, wherein the contacting step includes either electrically bonding the current collector and the carbon-containing layer, or bonding the solid electrolyte layer and the carbon-containing layer 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. 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 solid electrolyte layer.

24. A method for manufacturing a negative electrode, comprising: a step of forming a transfer member for forming a negative electrode by the manufacturing method according to any one of claims 15 to 19; a step of bringing a current collector into contact 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; and a step of peeling the substrate from the negative electrode structure.

25. A method for manufacturing an anode, comprising: forming a transfer member for forming an anode by the manufacturing method according to any one of claims 15 to 19; bringing a solid electrolyte layer into contact with the transfer member for forming an anode to obtain an anode structure; applying pressure to the anode structure to transfer the carbon-containing layer to the solid electrolyte layer; and peeling the substrate from the anode structure.

26. A method for manufacturing a secondary battery, comprising: a step of manufacturing a negative electrode by the method according to claim 24; a step of arranging a solid electrolyte layer so as to be in contact with the carbon-containing layer of the negative electrode; a step of arranging a positive electrode layer so as to be in contact with the solid electrolyte layer; and a step of providing a positive electrode current collector so as to be in contact with the positive electrode layer.

27. A method for manufacturing a secondary battery, comprising: a step of manufacturing a negative electrode by the method according to claim 25; a step of arranging a current collector so as to be in contact with the carbon-containing layer of the negative electrode; a step of arranging a positive electrode layer so as to be in contact with the solid electrolyte layer; and a step of providing a positive electrode current collector so as to be in contact with the positive electrode layer.

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