Carbon material and method for producing same, dispersion, composition for electrode, slurry for electrode, electrode, and lithium ion secondary battery

Abstract

The purpose is to provide a carbon material which exhibits a high oil absorption capability and therefore can exhibit excellent battery characteristics and the like. The carbon material has an oil absorption capability of 550 mL or more per 100 g as measured in accordance with JIS K5101-13-1:2004. This method for producing a carbon material involves a removal step for forming a carbon material precursor by removing, from a carbonaceous layer-covered mold material formed from a mold material and a carbonaceous layer, the mold material, wherein the mold material is an aggregate in which a plurality of primary particles is aggregated and connected like beads on a string, and the carbonaceous layer is formed so as to cover a surface of the mold material.

Description

Carbon material and its manufacturing method, dispersion, electrode composition, electrode slurry, electrode, and lithium ion secondary battery

[0001] The present invention relates to a carbon material, a method for producing the same, a dispersion, a composition for an electrode, a slurry for an electrode, an electrode, and a lithium ion secondary battery.

[0002] Carbon materials, including carbon black and graphite, have traditionally been used in a variety of applications. For example, conductive carbon and graphite are widely used in various fields, such as battery materials, carbon black as a reinforcing material for rubber materials, and activated carbon as an adsorbent. Since their creation, lithium-ion batteries have been used in a wide range of applications in everyday life, including smartphones and electric vehicles (EVs). Carbon materials are also widely used in these batteries. Recently, carbon materials for secondary batteries, including lithium-ion batteries, have been the subject of much research.

[0003] For example, Patent Document 1 discloses that in a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, flake graphite or carbon black is used as a conductive material, thereby improving high-rate discharge characteristics.

[0004] In general, the conductivity and reinforcing properties of carbon materials tend to increase as the continuous structure of aggregated carbon particles, known as a structure, develops. Carbon materials with a developed structure tend to have larger voids between the aggregates (also called primary aggregates or aggregates), which increases the oil absorption capacity. Therefore, conductive carbon materials with an oil absorption capacity of approximately 150 to 500 mL / 100 g, such as Ketjen Black, which has an oil absorption capacity of approximately 400 mL / 100 g, have been widely used. Even now, research is underway to develop carbon materials with high oil absorption capacity and use them as battery materials, etc.

[0005] For example, Patent Document 2 describes a method for producing a polymer having a BET specific surface area of ​​10 to 200 m ２It has been disclosed that when a carbon material having a partial graphite structure exhibiting the properties of a pore volume of 0.2 mL / g or more, a DBP absorption (oil absorption) of 150 mL / 100 g or more, for example, 210 to 220 mL / 100 g, is kneaded into a positive electrode, the electrolyte retention capacity and cycle characteristics are excellent.

[0006] Patent Document 3 discloses a lithium ion secondary battery that has excellent charge / discharge cycle characteristics and uses carbon black with a DBP absorption (oil absorption) of 240 mL / 100 g or more, with the maximum value in the examples being 343 mL / 100 g.

[0007] In addition to the above, new carbon materials are also being developed. For example, Patent Document 4 describes a carbon material having a BET specific surface area of ​​80 to 250 m ２ / g and an oxygen to carbon element ratio (O / C) measured by X-ray photoelectron spectroscopy of 0.09 to 0.3, has high dispersibility and ionic conductivity and is suitable for lithium ion secondary batteries.

[0008] Furthermore, Patent Document 5 discloses a method for producing a porous carbon material, which includes a coating step of forming a precursor containing graphene on the surface of a template made of alkaline earth metal oxide particles, and a separation and removal step of dissolving the template with a fluorine-free acid to separate the template from the precursor. The porous carbon material disclosed includes one containing graphene with 1.9 stacking layers and one containing graphene with 2.5 stacking layers, and suggests applications such as an electrode material for secondary batteries.

[0009] JP 2004-22177 A JP 2019-91587 A International Publication No. 2017 / 119428 JP 2020-100556 A JP 2021-84819 A

[0010] Although various carbon materials have been developed as described above, further improvements in their functionality are required. For example, the carbon materials described in the above-mentioned Patent Documents 1 to 5 have insufficient electrical conductivity, and secondary batteries using them may have insufficient physical properties such as rapid discharge capability and capacity characteristics.

[0011] The present invention has been made in view of the above circumstances, and aims to provide a carbon material that exhibits high oil absorption (oil absorption capacity) and can therefore exhibit various excellent functions. More specifically, the present invention provides a carbon material that can be used to form, for example, a highly conductive polymer composite due to its high oil absorption capacity and that can improve performance such as rapid discharge performance, battery capacity characteristics, and charge / discharge characteristics of lithium ion secondary batteries, a method for producing the same, a dispersion in which the carbon material is dispersed, an electrode composition, electrode slurry, electrode, and lithium ion secondary battery each containing the carbon material.

[0012] As a result of extensive research, the present inventors have succeeded in producing a new carbon material with high oil absorption, and have found that this carbon material can exhibit excellent functions, such as improving the capacity characteristics while maintaining the charge / discharge characteristics of a secondary battery, and significantly improving the rapid discharge characteristics.

[0013] The present inventors also prepared a carbonaceous layer-coated template material comprising a template material that is an agglomerate of multiple primary particles that are linked together like beads, and a carbonaceous layer that is formed so as to coat the surface of the template material. They then removed the template material from the carbonaceous layer-coated template material, and, if desired, subjected it to heat treatment, thereby obtaining a carbon material that has a connected structure with significantly increased oil absorption. They also discovered that when this carbon material is used, for example, as a material for a lithium-ion secondary battery, it has a high 2C retention rate (excellent rapid discharge capability), a high capacity, and excellent initial charge / discharge characteristics.

[0014] Based on these findings, the present inventors have completed the present invention, which provides the following (1) to (24):

[0015] (1) A carbon material having an oil absorption of 550 mL / 100 g or more as measured in accordance with JIS K5101-13-1:2004.

[0016] (2) The carbon material according to (1), wherein a plurality of hollow particulate portions, each formed by a surrounding wall made of a carbonaceous material including a graphene structure, define an internal space and include one or more connecting structures each having an elongated shape connected in a beaded shape, and pores are formed in the connecting structures.

[0017] The present inventors considered that a carbon material having a complex structure similar to that of highly conductive carbon black, with a hollow interior and a carbonaceous layer having a six-membered carbon ring structure, preferably a graphene structure, could be used to obtain a material with a high oil absorption capacity as described in (1) above. As a result of investigations involving structural design, the carbon material described in (2) above was obtained.

[0018] (3) Intensity of the 2D band in Raman spectroscopy (I ２Ｄ ) versus G band intensity (I Ｇ ) intensity ratio (I Ｇ / I ２Ｄ ) is in the range of 0.4 to 5.0.

[0019] The inventors have investigated the I in Raman measurements, which is an index of the number of graphene layers constituting a carbon material. Ｇ / I ２Ｄ It has been found that by setting the above to a specific range, pores of a specific pore diameter can be maintained, and the carbon material not only has excellent electron transport properties, but also retains an electrolyte solution, resulting in a material with excellent ionic conductivity, for example, of lithium ions.

[0020] (4) The carbon material according to any one of (1) to (3) above, wherein the mode pore diameter is in the range of 1 to 100 nm.

[0021] The present inventors have also found that by specifying the mode pore diameter, which indicates the size of the hollow portions of the hollow particle shapes in the continuous structure, the oil absorption capacity can be increased, and when used as a lithium ion secondary battery material, the rapid discharge performance, battery capacity characteristics, and charge / discharge characteristics can be further improved.

[0022] (5) The carbon material according to any one of (1) to (4) above, wherein the total pore volume is in the range of 0.1 to 20 cc / g.

[0023] (6) The carbon material according to (5) above, wherein the ratio of the macropore volume to the total pore volume is 5% or more.

[0024] (7) The carbon material according to any one of (1) to (6) above, having an apparent density of 2 g / cc or less.

[0025] (8) BET specific surface area is 100 to 2700 m ２The carbon material according to any one of (1) to (7), wherein the carbon content is in the range of / g.

[0026] (9) The carbon material according to any one of (1) to (8), wherein the crystallite size Lc(002) in the c-axis direction, as measured by X-ray diffraction (XRD), is in the range of 0.1 to 5 nm.

[0027] (10) The carbon material according to any one of (1) to (9), wherein the lattice spacing d002 of the (002) plane is 3 to 5 Å as measured by X-ray diffraction (XRD).

[0028] The present inventors have also found that by specifying the index Lc(002) of the number of crystalline graphene layers confirmed by XRD measurement, the value of the BET specific surface area, and the like, the oil absorption can be further increased, and that when the material is used as a lithium ion secondary battery material, for example, properties such as rapid dischargeability, battery capacity, and charge / discharge characteristics are well balanced.

[0029] (11) The carbon material according to any one of (1) to (10) above, having a median diameter D50 of 1 to 100 μm as measured by a laser diffraction / scattering method for particle size distribution.

[0030] (12) The carbon material according to any one of (1) to (11) above, wherein the ratio of D90 to D10 (D90 / D10 ratio) is 100 or less in particle size distribution measurement by a laser diffraction / scattering method.

[0031] (13) The carbon material according to any one of (1) to (12) above, wherein the ratio of D90 to the mode pore size M (D90 / M ratio) is 50,000 or less in particle size distribution measurement by a laser diffraction / scattering method.

[0032] The present inventors have also found that, for example, by specifying the median diameter D50 or (D90 / D10) ratio in particle size distribution measurement, which indicates the size of a continuous structure in which a plurality of hollow particles (hollow particulate portions) having an internal space are linked together, and an aggregate thereof (agglomerate: so-called secondary aggregate formed by aggregation of a carbon material), the oil absorption can be increased, and when used in a lithium ion secondary battery material, the rapid discharge property, battery capacity characteristics, and charge / discharge characteristics can be further improved.

[0033] (14) The carbon material according to any one of (1) to (13), wherein the carbon material is a graphene meso-sponge.

[0034] (15) The carbon material according to any one of (1) to (14) above, which is for use in a secondary battery.

[0035] (16) The method for producing a carbon material according to any one of (1) to (15) above, further comprising: a removing step of forming a carbon material precursor by removing the template material from a carbonaceous layer-coated template material, the template material being an aggregate of a plurality of primary particles aggregated and linked together like beads, and a carbonaceous layer formed so as to coat the surface of the template material.

[0036] (17) The method for producing a carbon material according to any one of (1) to (15) above, comprising: a removal step of forming a carbon material precursor by eluting and removing the template material from a carbonaceous layer-coated template material, the template material being an aggregate of a plurality of primary particles agglomerated and linked together in a beaded shape, and a carbonaceous layer formed so as to cover the surface of the template material, by an acid treatment; and a heating step of heat-treating the carbon material precursor to partition and form an internal space, thereby obtaining a carbon material in which a plurality of hollow particulate portions formed by surrounding walls made of carbonaceous material including a graphene structure have one or a plurality of connected structures having an elongated shape connected in a beaded shape, and the connected structures have pores.

[0037] (18) The method for producing a carbon material according to (16) or (17), wherein the template material is made of one or more types of particles selected from the group consisting of ceramic particles and carbonate particles.

[0038] The present inventors have also found that the carbon materials described in (1) to (14) and (15) above can be easily produced by using a specific template material, forming a carbonaceous layer such as a graphene layer on the surface of the template, and then removing the template material. The present inventors have further found that when forming a carbonaceous layer on the surface of a template material by a CVD reaction, the number of deposited carbonaceous layers can be adjusted by the type of template material, etc.

[0039] (19) A dispersion liquid obtained by dispersing any one of the carbon materials (1) to (15) above in a dispersion medium.

[0040] (20) An electrode composition comprising the carbon material according to any one of (1) to (15) above, an active material, and a binder.

[0041] (21) A slurry for an electrode obtained by dispersing the electrode composition according to (20) above in a solvent.

[0042] (22) An electrode comprising the carbon material according to any one of (1) to (15) above.

[0043] (23) A lithium ion secondary battery comprising the carbon material according to any one of (1) to (15) above.

[0044] The present invention provides a carbon material that has a high oil absorption capacity and can therefore be used to form, for example, a highly conductive polymer composite, thereby exhibiting excellent battery characteristics. The invention also provides a carbon material that can significantly improve the rapid discharge performance, battery capacity characteristics, and charge / discharge characteristics of a lithium ion secondary battery, a method for producing the same, a dispersion in which the carbon material is dispersed, an electrode composition containing the carbon material, an electrode slurry, an electrode, and a lithium ion secondary battery.

[0045] FIG. 1 is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention, measured at an accelerating voltage of 80 kV. FIG. 2 is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention, measured at an accelerating voltage of 100 kV. FIG. 3 is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention, measured at an accelerating voltage of 100 kV. FIG. 4 is a diagram showing an example of a Raman spectrum measured for a carbon material according to one embodiment of the present invention. FIG. 5 is a diagram illustrating an ultra-high sensitivity vacuum TPD device used for thermal desorption analysis.

[0046] The present invention will be described in detail below based on embodiments, but the present invention is not limited to these embodiments.

[0047] <<Carbon Material>> The carbon material of this embodiment is characterized by having an oil absorption of 550 mL / 100 g or more. Here, the oil absorption is the oil absorption of refined linseed oil measured in accordance with JIS K5101-13-1:2004 (Pigment Testing Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method). Carbon materials with such high oil absorption can be used, for example, in electrodes and can exhibit excellent battery characteristics. In particular, they can significantly improve the rapid discharge characteristics, battery capacity characteristics, charge / discharge characteristics, etc. of lithium-ion secondary batteries and the like.

[0048] <Oil Absorption> The oil absorption of the carbon material of this embodiment is 550 mL / 100 g or more as described above, but is preferably 600 mL / 100 g or more, more preferably 800 mL / 100 g or more, even more preferably 900 mL / 100 g or more, even more preferably 1000 mL / 100 g or more, and particularly preferably 1400 mL / 100 g or more. Such a high oil absorption allows the carbon material to retain a large amount of electrolyte when used, for example, as a battery material, and reduces delays in ion supply even during rapid battery reactions, thereby preventing a decrease in discharge capacity. It is also possible to further improve battery characteristics such as 2C retention. Furthermore, the carbon material can exhibit excellent reinforcing properties for polymers such as rubber.

[0049] The upper limit of the oil absorption is not particularly limited, but from the viewpoint of facilitating maintenance of the structure of the carbon material and facilitating control of the amount of electrolyte retained, the oil absorption may be 5000 mL / 100 g or less, preferably 4000 mL / 100 g or less, more preferably 3500 mL / 100 g or less, even more preferably 3000 mL / 100 g or less, and particularly preferably 2500 mL / 100 g or less.

[0050] The oil absorption of the carbon material of this embodiment may be, for example, 550 to 5000 mL / 100g, or 600 to 4500 mL / 100g, or 700 to 4000 mL / 100g, or even 900 to 3500 mL / 100g, or even 1000 to 3000 mL / 100g, and particularly 1400 to 2500 mL / 100g, from the viewpoint of balancing physical properties and ease of control. Carbon materials with oil absorptions according to the purpose can be prepared or used. For example, when used as a material for a battery with a high 2C retention rate and excellent rapid discharge performance, the oil absorption of the carbon material is preferably about 550 to 1500 mL / 100g, particularly about 700 to 1300 mL / 100g.

[0051] <Structure of Carbon Material> The carbon material of this embodiment is not particularly limited in its structure, as long as it has an oil absorption of 550 mL / 100 g or more. Preferably, the carbon material has a structure in which a plurality of hollow particulate portions formed by a surrounding wall made of carbonaceous material containing a graphene structure, which partitions an internal space, have one or more connected structures having an elongated shape connected like beads, and pores are formed in the connected structures, but is not limited to this form. For example, the entire surrounding wall does not need to have a graphene (crystal) structure, and a carbon-based substance having another structure may be mixed in.

[0052] Fig. 1 shows an example of a TEM image of the carbon material of this embodiment observed at an accelerating voltage of 80 kV using a transmission electron microscope (TEM: JEM-ARM300F, manufactured by JEOL Ltd.). Graphene is a sheet-like substance of sp2-bonded carbon, and as shown in Fig. 1, six-membered carbon ring structures are connected to form a honeycomb-like hexagonal lattice structure. The carbon material of this embodiment may be a graphene meso sponge (GMS) or a carbon meso sponge (CMS), which will be described later.

[0053] 2 shows a TEM image of an example of the carbon material according to this embodiment, observed using a transmission electron microscope (TEM: H-7650, manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 100 kV and a magnification of 15,000 times. The degree of particle transmission in FIG. 2 also shows that the interior of the particle is hollow. It is also clear that the carbon material according to this embodiment has a connected structure in which particle shapes, each having a pore surrounded by a carbonaceous shell, are intricately connected together by the shell.

[0054] A constriction may be provided at the joining portion where adjacent hollow particulate portions (shell-shaped bodies) having surrounding walls are adjacent. For example, when two hollow particulate portions are joined, the shape becomes like a peanut shell or a dumbbell. A plurality of such particle shapes are combined to form a connected structure (shell-shaped body), and these may also be connected to form a structure. Figure 2 shows an example of the carbon material of this embodiment, and the connected structure has a complex structure that does not have a fixed shape.

[0055] The carbon material of this embodiment preferably has a plurality of hollow particulate portions (granular objects) that are long and connected in multiple directions, with the voids being interconnected, as shown in FIG. 2 . Such a plurality of long hollow particulate portions connected together will have a continuous shape, for example, resembling an underground ant's nest. Furthermore, such shell-like bodies are more preferably those with multiple branched structures. When a plurality of hollow particulate portions are connected and extend in multiple directions, they may have a shape resembling, for example, ginger root, an edible vegetable. Furthermore, when the connected structure has a long connected shape, one end and the other end may be ring-shaped. Alternatively, the tips of the branches that branch out into multiple branches may be ring-shaped. The tips of such ring shapes may or may not be connected to each other.

[0056] Here, the size (pore diameter) of the pores (internal spaces) surrounded by the surrounding walls (shell portions) of the connected structure may be, for example, 0.1 to 100 nm, preferably 1 to 100 nm, or 1 to 80 nm, particularly 5 to 50 nm. The length of the connected structure (the shell-like body having the pores) is, for example, 0.01 to 100 μm, preferably 0.05 to 80 μm, and more preferably 0.1 to 50 μm. The average particle size (average outer diameter) of the hollow particulate portions in the connected structure may be, for example, 0.05 to 50 μm, and preferably 0.05 μm to 6 μm, 0.1 to 10 μm, 0.1 μm to 5 μm, or 0.5 to 5 μm.

[0057] The size of the internal space (pore diameter, inner diameter) can be determined as the mode pore diameter, for example, by nitrogen adsorption / desorption measurement, as described below. The average particle diameter (average outer diameter) of the hollow particulate portions can be determined, for example, by adding twice the product of the average stacking number n and the average interplanar spacing determined from the 002 diffraction line to the mode pore diameter, as described below. The average particle diameter (average outer diameter) may also be determined by image analysis of TEM images.

[0058] As described above, the carbon material of this embodiment preferably has a connected structure in which a plurality of hollow particulate portions formed by surrounding walls are connected in an elongated shape like a rosary. The term "structure of a carbon material" is used to describe the complex structure of carbon black, and refers to an aggregate structure in which primary particles are connected with multiple branching points. That is, a particularly preferred carbon material of this embodiment can be said to have a structure in which the interiors of highly conductive carbon black primary particles are hollow and the outer surrounding walls have a graphene crystal structure, with the aggregates having spaces that communicate with each other.

[0059] The carbon material of this embodiment may have an agglomerate-like structure in which a plurality of the above-described continuous structures are aggregated or connected, i.e., a structure composed of a plurality of connected connected structures. Fig. 3 is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention, measured using a transmission electron microscope (TEM: JEM-2100Plus model, manufactured by JEOL Ltd.) at an acceleration voltage of 100 kV and a magnification of 40,000 times. When such continuous structures, which are porous carbon materials, aggregate, gaps (pores) are formed between the plurality of continuous structures, thereby further increasing the oil absorption capacity.

[0060] <Characteristics of Carbon Material> The oil absorption capacity of the carbon material of this embodiment is significantly higher than that of carbon black, which is commonly used as a conductive material for lithium-ion secondary batteries and a reinforcing agent for rubber. Therefore, it can exhibit high conductivity and reinforcing properties. In particular, when the carbon material has a structure such as the above-mentioned connected structure or agglomerate, voids are formed not only in the internal space of the connected structure, but also in the areas surrounded by the bead-like connected surrounding walls and between multiple continuous structures. This makes it possible to retain an extremely large amount of oil in these voids (pores).

[0061] Such carbon materials with high oil absorption generally have a large total surface area and high electronic conductivity. In particular, when mixed with polymers, they are likely to form composites with excellent conductivity. High-oil-absorption carbon materials can also retain a large amount of electrolyte when used as battery materials, enabling, for example, a stable supply of lithium ions, which can contribute to the rapid charging, charge / discharge characteristics, and battery capacity of lithium-ion batteries.

[0062] Carbon materials having such interconnected structures exhibit a large elastic deformation workload, i.e., they may recover without plastic deformation under weak stress. Carbon materials typically consist of an elastically deformable structure and a plastically deformable structure. The plastically deformable structure exhibits high strength against stress, but once deformed, it cannot recover even when unloaded. In the particularly preferred carbon material of this embodiment, the graphene portion, which accounts for the majority, exhibits elastic deformability, and therefore may exhibit good properties against stress deformation. On the other hand, materials with a large number of graphene layers, such as graphite, maintain elastic deformability within a certain stress range, but suddenly undergo plastic deformation when a certain stress threshold is exceeded, destroying the particle shape and interconnected shape. The degree of elastic deformation and plastic deformation of carbon materials can be measured by an ultra-small load-unload test.

[0063] <Graphene Crystal Structure> The carbon material of this embodiment preferably has a surrounding wall having a graphene crystal structure as described above. Such a crystal structure can be obtained by, for example, measuring the intensity ratio I between the G band and the 2D band in Raman spectroscopy. Ｇ / I ２Ｄ This can also be confirmed by the fact that is 0.2 or more.

[0064] An example of the Raman spectrum measured for the carbon material of this embodiment is shown in FIG. 4. The Raman spectrum shows a peak at wavenumber 1593 cm －１ The peak in the region around 1356 cm in the Raman spectrum is called the G band, which indicates the sp2 bond (C=C stretching motion of the aromatic ring) of the carbon material. －１ The peak present around the wavenumber 2680 cm in the Raman spectrum is called the D band, which indicates the sp3 bond (C-H stretching motion) of the carbon material, and increases when the sp2 bond in the carbon six-membered ring structure of the carbonaceous layer is broken to form an sp3 bond. －１ The peak present in the region nearby is called the 2D band, which is a band indicating secondary phonon scattering (C—H stretching motion) and indicates the number of stacked graphene layers that make up the carbon material.

[0065] Intensity ratio I between the G band and the 2D band of carbon materials Ｇ / I ２Ｄis said to reflect the stacking state of the graphene layers (D. Graf, et al., NANO LETTERS, 7, 238-242; (2007)). Ｇ / I ２Ｄ is sometimes called the "stacking index." In this paper, it is stated that the number of graphene layers becomes one when the (G / 2D) intensity ratio is 0.2.

[0066] The intensity ratio of the G band to the 2D band in the carbon material of this embodiment (I Ｇ / I ２Ｄ ) is preferably in the range of 0.4 to 5.0, and may further be in the range of 1.00 to 4.50, 1.10 to 4.00, 1.20 to 3.57, 1.30 to 3.00, 1.40 to 2.50, or 1.43 to 2.08. Ｇ / I ２Ｄ When the value of is within this range, the strength characteristics and elastic deformability that maintain the hollow structure (internal space) of the carbon material are well balanced, and when the carbon material is used as a conductive material for, for example, a lithium ion secondary battery, desired characteristics such as rapid discharge characteristics, capacity characteristics, and durability can be highly improved.

[0067] In addition, the G band intensity (I Ｇ ) to the intensity ratio of the D band intensity (I Ｄ / I Ｇ ) is preferably in the range of 0.1 to 10, more preferably in the range of 0.5 to 5, even more preferably in the range of 1 to 3, still more preferably in the range of 1.2 to 2.5, and particularly preferably in the range of 1.4 to 2. Ｄ / I Ｇ When the carbon material has a molecular weight of 1.0 or 2.0, the sp2 orbital and the sp3 orbital are in an optimal state, the electron conduction path and the ion conduction path are highly balanced, and the rapid discharge property, capacity characteristic, and charge / discharge characteristic of, for example, a lithium ion secondary battery can be further improved. Ｄ / I Ｇ Hereinafter, this may be referred to as the "amorphous index."

[0068] The carbon material of this embodiment also preferably has a crystallite size Lc(002) in the c-axis direction measured by X-ray diffraction (XRD) in the range of 0.1 to 5 nm. The degree of crystallinity of a carbon material can be evaluated by the Lc(002) of the

[002] plane. When Lc(002) is in the range of 0.1 to 5 nm, large mesopores and macropores tend to form easily. The Lc(002) value may alternatively be 0.3 nm or more, 0.5 nm or more, 1.0 nm or more, or 1.1 nm or more, or may be 3 nm or less, 2.5 nm or less, 2.0 nm or less, 1.9 nm or less, 1.5 nm or less, 1.25 nm or less, or 1.21 nm or less. Lc(002) is more preferably in the range of 0.3 to 3 nm, 0.5 to 2.5 nm, 1.0 to 2.0 nm, or 1.1 to 1.9 nm.

[0069] In the carbon material of this embodiment, the crystallite size La(10) of the

[10] plane in the a-axis direction measured by X-ray diffraction (XRD) is not particularly limited. It is preferably 0.1 nm or more, or alternatively, 0.5 nm or more, 1.0 nm or more, 1.5 nm or more, or 1.8 nm or more. The upper limit is preferably 10 nm or less, or alternatively, 5.0 nm or less, 4.5 nm or less, 4.0 nm or less, or 3.8 nm or less.

[0070] The carbon material of this embodiment preferably has a lattice spacing d002 of the

[002] plane measured by X-ray diffraction (XRD) of 3 to 5 Å, more preferably 3.3 to 4.5 Å, even more preferably 3.3 to 4.0 Å, still more preferably 3.3 to 3.9 Å, and particularly preferably 3.3 to 3.8 Å.

[0071] <Surface State of Carbon Material> The surface state of the carbon material of this embodiment is not particularly limited, but preferably has a large surface area for achieving high oil absorption. It also preferably has a large number of voids of various sizes. Hereinafter, these voids may be collectively referred to as "pores," which includes not only the "pores" in the continuous structure of the porous carbon material described above, but also, for example, the internal space of the continuous structure.

[0072] (Specific Surface Area) The BET specific surface area of ​​the carbon material of this embodiment is a specific surface area calculated from nitrogen adsorption as specified in JIS Z8830, and is preferably 100 to 2700 m ２ / g, or 300 to 2500 m ２ / g, 500-2000m ２ / g, 600-1800m ２ / g, 800-1200m ２ / g. The theoretical value of the specific surface area of ​​single-layer graphene is 2627 m ２ / g, it can be said that the closer the specific surface area is to this value, the more ideal the carbon conductive material is. ２ / g (which may exceed the theoretical value if pores are present), the oil absorption and electrical conductivity are highly increased, which is preferable.

[0073] (Pores) The carbon material of this embodiment preferably has pores of various sizes. The International Union of Pure and Applied Chemistry (IUPAC) defines micropores as pores with a diameter of less than 2 nm, mesopores as pores with a diameter of 2 to 50 nm, and macropores as pores with a diameter of more than 50 nm. In a particularly preferred carbon material of this embodiment, mesopores are the internal spaces of connected structures in which hollow particulate portions are linked together like beads. Macropores are the spaces at the branched portions of continuous structures, or the external spaces partitioned by multiple continuous structures when the continuous structures aggregate, or the external spaces partitioned by a single continuous structure extending in a ring shape. Micropores are presumably the gaps formed between carbon surrounding walls where the continuous structures branch in complex ways or where there are large depressions, or the through-holes present in the surrounding walls themselves due to defects or the like. However, the surface state of the carbon material of this embodiment is not limited to these forms.

[0074] The average pore diameter of the carbon material of this embodiment may preferably be 1 to 500 nm. Alternatively, it is also preferable that the average pore diameter is in the range of 5 to 100 nm, 10 to 75 nm, 12 to 60 nm, 15 to 50 nm, or 20 to 40 nm. When the average pore diameter is in this range, the carbon material exhibits a higher oil absorption capacity, which can result in higher ionic conductivity and electronic conductivity. The pore diameter and pore volume can be obtained, for example, by analyzing the adsorption behavior of various gases. Furthermore, information such as the bulk density and void volume (described below) can be obtained from pore volume measurements calculated by compressing the powder or by using a mercury porosimeter.

[0075] The mode pore diameter (M) in the pore distribution of the carbon material of this embodiment is the peak-top value in the pore distribution curve, and is preferably in the range of 1 to 100 nm. Alternatively, it is preferably in the range of 5 to 100 nm, 10 to 50 nm, 15 to 40 nm, or 15 to 30 nm. When the peak-top pore diameter of the pore distribution is in such a range, the carbon material exhibits a higher oil absorption, which can result in higher ionic conductivity and electronic conductivity.

[0076] The total pore volume of the carbon material of this embodiment, as measured by, for example, nitrogen adsorption / desorption measurement, is preferably in the range of 0.1 to 20 cc / g. If the total pore volume is 0.1 cc / g or more, it becomes easy to retain a sufficient amount of electrolyte in the carbon material when used, for example, as a battery material. The total pore volume may be 1 cc / g or more, 1.5 cc / g or more, 2 cc / g or more, or 2.95 cc / g or more. Furthermore, if the total pore volume is 20 cc / g or less, the skeleton of the pore structure, for example, the above-mentioned connecting structure, retains its strength and is more likely to maintain its shape.

[0077] Here, the "total pore volume" refers to a value including not only the volume of pores, etc., but also the volume of voids (all pores including micropores, mesopores, and macropores), such as the internal space of the continuous structure and the external space surrounded by the surrounding wall. The total pore volume of the carbon material of this embodiment may also be within a range of 1 to 15 cc / g, 2 to 10 cc / g, 2 to 8 cc / g, 2.95 to 6.1 cc / g, 2.95 to 5.7 cc / g, etc.

[0078] The micropore volume of the carbon material of this embodiment, i.e., the volume of pores with a pore diameter of less than 2 nm, is preferably, for example, 5 cc / g or less, or 2 cc / g or less, 1 cc / g or less, 0.5 cc / g or less, or 0.4 cc / g or less. It is also preferably 0.01 cc / g or more, or 0.05 cc / g or more, 0.1 cc / g or more, 0.2 cc / g or more, or 0.3 cc / g or more. If the micropore volume of the carbon material is excessively large, the ionic conductivity may be poor, and conversely, if it is excessively small, the strength characteristics may be poor.

[0079] The micropore volume ratio in the carbon material of this embodiment, i.e., the ratio of the volume of pores with a diameter of less than 2 nm to the total pore volume, is not particularly limited. For example, it is preferably 20% or less, or 15% or less, 12% or less, 10% or less, or 9% or less. The lower limit is preferably 5% or more. If the micropore volume ratio of the carbon material is too large, the ionic conductivity may be poor, and conversely, if it is too small, the strength characteristics may be poor.

[0080] The mesopore volume of the carbon material of this embodiment, i.e., the volume of pores with a pore diameter of 2 to 50 nm, is not particularly limited. For example, it may be 0.1 cc / g or more, or 0.5 cc / g or more, 1 cc / g or more, 1.5 cc / g or more, or 2 cc / g or more. It may also be, for example, 15 cc / g or less, or 10 cc / g or less, 5 cc / g or less, 4 cc / g or less, or 3.5 cc / g or less. If the mesopore volume of the carbon material is within this range, ionic conductivity and strength characteristics are likely to be well balanced, which is preferable.

[0081] The mesopore volume ratio in the carbon material of this embodiment, i.e., the ratio of the volume of pores with pore diameters in the range of 2 to 50 nm to the total pore volume, is not particularly limited. For example, it may be 10% or more, or 20% or more, 30% or more, 40% or more, or 50% or more. It may also be, for example, 90% or less, or 85% or less, 80% or less, 75% or less, or 70% or less. When the mesopore volume ratio of the carbon material is within this range, the particle shape has appropriate strength, which contributes to the stability of the particle shape and makes it easier to maintain the shape. This makes it easier to maintain a good balance between electronic conductivity and the supply of ions held in the pores.

[0082] The macropore volume of the carbon material of this embodiment, i.e., the volume of pores with a pore diameter of more than 50 nm, is not particularly limited. For example, it may be 0.01 cc / g or more, or 0.05 cc / g or more, 0.1 cc / g or more, 0.48 cc / g or more, or 1 cc / g or more. It may also be, for example, 15 cc / g or less, or 10 cc / g or less, 5 cc / g or less, 3 cc / g or less, or 2.57 cc / g or less. When the macropore volume of the carbon material is within this range, the particle shape has appropriate strength, which contributes to the stability of the particle shape and makes it easier to maintain the shape. This makes it easier to maintain a good balance between electronic conductivity and the supply of ions held in the pores.

[0083] The macropore volume ratio of the carbon material of this embodiment, i.e., the ratio of the volume of pores with a pore diameter greater than 50 nm to the total pore volume, is not particularly limited. Preferably, the macropore volume ratio is 5% or more. When the macropore volume ratio is 5% or more, the carbon material exhibits superior ionic conductivity. The macropore volume ratio may be 10% or more, 15% or more, 20% or more, or 25% or more. It may also be 80% or less, 70% or less, 60% or less, 50% or less, or 45% or less. When the macropore volume ratio is equal to or less than these values, the carbon material tends to exhibit higher strength. The macropore volume ratio may be, for example, 5 to 80%, 10 to 70%, 15 to 60%, 20 to 50%, or 25 to 45%.

[0084] <Particle Size of Carbon Material> The carbon material of this embodiment may have any particle size (particle diameter), and its average value and distribution (particle size) are not particularly limited. In this embodiment, unless otherwise specified, the term "particle size" refers to the length in the extension direction of the agglomerates (so-called secondary aggregates formed by agglomeration of the carbon material), i.e., the longest size. The particle size distribution curve can be obtained, for example, through measurement using a particle size distribution measuring device based on a laser diffraction / scattering method, such as the MT3300EX II manufactured by Microtrac-Bell Corporation. The particle size distribution measurement may also be performed, for example, after immersing the unpulverized material in a solvent for 9 minutes. Since this immersion treatment partially or completely dissociates agglomerates with low cohesive strength, the cohesive strength of the linked structure can also be estimated from the particle size distribution curve.

[0085] The median diameter D50 of the carbon material of this embodiment, i.e., the diameter at which half of the particles exist in the particle size distribution curve, is not particularly limited, but is preferably 1 to 100 μm. If the median diameter D50 is within this range, the carbon material will have superior electronic conductivity and ionic conductivity. The median diameter D50 may also be 5 to 90 μm, 10 to 80 μm, 15 to 60 μm, 20 to 50 μm, 25 to 45 μm, or 30 to 40 μm.

[0086] The particle diameter D10 of the carbon material of this embodiment, i.e., the particle diameter at which 10% of the particles exist in a particle size distribution curve, is not particularly limited and may be, for example, 0.1 to 100 μm, 0.5 to 50 μm, 1 to 50 μm, 5 to 30 μm, or 10 to 15 μm.

[0087] The particle diameter D90 of the carbon material of this embodiment, i.e., the particle diameter at which 90% of the particles exist in a density distribution curve, is not particularly limited. For example, it may be 5 to 250 μm, 10 to 150 μm, 20 to 100 μm, 30 to 70 μm, 45 to 65 μm, 45 to 55 μm, or 40 to 60 μm. If the D90 is within this range, the carbon material can exhibit better electrical conductivity.

[0088] The ratio of D90 to D10 (D90 / D10 ratio) in the carbon material of this embodiment is not particularly limited. Preferably, the D90 / D10 ratio is 100 or less, or 50 or less, 10 or less, or 5 or less. If the (D90 / D10) ratio of the carbon material is too large, the carbon material tends to aggregate and not disperse well, which tends to result in insufficient conductivity of the lithium ion secondary battery.

[0089] In the carbon material of this embodiment, the ratio of D90 to the mode pore diameter M (D90 / M ratio) is also not particularly limited. D90 / M is a value obtained by converting the D90 value from μm units to a value in nm units by multiplying it by 1000, and then dividing the converted D90 value (nm) by the mode pore diameter M value (nm). For example, D90 / M may be in any range of 50,000 or less, 20,000 or less, 10,000 or less, 6,000 or less, 5,000 or less, or 4,000 or less. In particular, it is preferable that the ratio is 10,000 or less. Carbon materials with an excessively large (D90 / M) ratio have strong cohesion and poor dispersibility, which may result in insufficient conductivity in lithium-ion secondary batteries.

[0090] The carbon material of this embodiment may have a low apparent density or bulk density, which is advantageous for achieving a high oil absorption amount, or which is due to the above-described complex structure.

[0091] The apparent density of the carbon material of this embodiment is not particularly limited, but is preferably 2 g / cc or less. Alternatively, any of the ranges of 1.5 g / cc or less, 1 g / cc or less, 0.5 g / cc or less, or 0.3 g / cc or less is also preferred, and any of the ranges of 0.05 g / cc or more, 0.1 g / cc or more, or 0.15 g / cc or more is also preferred. When the apparent density is in such a range, the hollow structure in the carbon material is easily maintained, making it more suitable for use as a carbon material for batteries.

[0092] The apparent density can be calculated, for example, from the total pore volume and true density according to the following formula: apparent density (g / cc) = 1 / (total pore volume + (1 / true density)) The total pore volume (cc / g) can be a value calculated at a relative pressure of 0.99, and the true density can be the value of graphite, 2.2 g / cc.

[0093] The bulk density of the carbon material of this embodiment is preferably 0.01 to 1000 g / L, or preferably any of the ranges of 0.1 to 100 g / L, 0.5 to 50 g / L, or 1 to 25 g / L. When the bulk density of the carbon material is in this range, high oil absorption and electrical conductivity are likely to be exhibited, and the carbon material is suitable because it is easy for an electrolyte to permeate into the carbon material.

[0094] The bulk density is the mass per unit volume of a carbon material filled in a container of a certain volume under certain conditions. The bulk density can be measured, for example, according to JIS K6219-2.

[0095] The number density of the carbon material of this embodiment is a value calculated by the method described below, and is preferably 5×10 １４ ~1 x 10 ２０ pieces / g, or 1×10 １６ ~1 x 10 １９ pieces / g, 5×10 １６ ~5 x 10 １８ pieces / g, 1×10 １７ ~1 x 10 １８ pieces / g, 3×10 １７ ~7 x 10 １７ It is also preferable that the number density of the carbon material is in any of the ranges of 1000 / 10000 particles / g. When the number density of the carbon material is in this range, the oil absorption becomes optimal, which is preferable.

[0096] The number density N ｐ (particles / g) is the ratio of the specific surface area SA of the primary particles to the inner diameter D of the primary particles. ０ and outer diameter D １ Therefore, it can be calculated using the following formula: ｐ = SA / (πD １ ２ +πD ０ ２ ) SA is the BET specific surface area, D ０ The mode pore diameter described above can be used for D. １ is D ０ The average number of layers n is multiplied by the interplanar spacing of the (002) plane, and the resulting value is doubled and added to the mode diameter. １ may be determined by TEM image analysis or the like. In addition, in the case of a solid carbon material, D ０For example, the known DENKA BLACK Li-100 has a particle outer diameter (D １ ) with an average particle size of 35 nm, D ０ = 0.

[0097] (Graphene Meso Sponge) The carbon material of this embodiment may be a graphene meso sponge (GMS). Graphene meso sponge is a porous carbon material or a porous carbon material having a graphene crystal structure. Because of its large specific surface area, it tends to exhibit high oil absorption. In particular, GMS having the above-described interconnected structure is likely to exhibit extremely high oil absorption. The average number N of stacked graphene layers is, for example, 0.9 to 5.0, preferably 1.0 to 4.0, and particularly preferably 1.5 to 2.0. The fewer the stacks of the graphene crystal structure, the larger the specific surface area of ​​the porous carbon material. GMS also has a particularly large elastic deformation work load and is likely to exhibit the property of recovering its original state without plastic deformation under weak stress.

[0098] (Carbon Meso Sponge) The carbon material of this embodiment may also be carbon meso sponge (CMS). CMS is a porous carbon material similar to GMS, except that the surrounding walls constituting the sponge do not have, or have little to no, graphene crystal structure. Therefore, although CMS does not necessarily exhibit the same level of electrical conductivity as GMS, it can exhibit high oil absorption properties similar to GMS.

[0099] <Components in Carbon Material> The carbon content of the carbon material of this embodiment is preferably 95% by mass or more, or also preferably 97% by mass or more, 98% by mass or more, 99% by mass or more, or 99.3% by mass or more.

[0100] The carbon content can be determined by temperature programmed desorption mass spectrometry (TPD-MS) measurement using, for example, an ultra-high sensitivity vacuum thermal desorption mass spectrometer 50 (developed at Tohoku University, see T. Ishii et al., CARBON 80, 2014, pp. 135-145) shown in FIG. 5. The thermal desorption mass spectrometer 50 includes a radioactive thermometer 41, a quartz reactor including a sample holder 42 and a high-frequency induction coil 43, and a detection unit connected to the quartz reactor. The detection unit includes, for example, a gas reservoir, a turbomolecular pump TMP, a rotary pump RP, a cold cathode Pirani gauge P1, and a capacitance gauge P2.

[0101] The oxygen-containing functional groups and hydrogen-terminated edge sites can also be accurately qualitatively and quantitatively analyzed by the ultra-high sensitivity vacuum thermal desorption mass spectrometer 50. Specifically, 1 to 3 mg of each carbon material is placed on a graphite sample stage, heated in vacuum to 1800°C at a heating rate of 10°C / min, and the gas released during heating is analyzed by the mass spectrometer, thereby enabling accurate qualitative and quantitative analysis of the oxygen-containing functional groups and hydrogen-terminated edge sites.

[0102] The oxygen content of the carbon material of this embodiment can be measured by, for example, H ２ O, CO and CO ２ The oxygen content of the carbon material is preferably 5% by mass or less, 3% by mass or less, 2% by mass or less, 1% by mass or less, or 0.6% by mass or less, as calculated from the amount of released oxygen. When the oxygen content of the carbon material is within these ranges, the stability of the lithium ion secondary battery is further improved, which can contribute to higher performance.

[0103] For example, to improve the performance and extend the life of lithium-ion batteries, a highly efficient battery reaction without a decrease in efficiency due to side reactions is required, and the carbon material in the electrode must have electrochemical stability, i.e., oxidation resistance and corrosion resistance. Electrochemical side reactions such as oxidation are believed to originate from oxygen-containing functional groups and edge faces of carbon materials. To improve the oxidation resistance of carbon materials, it is effective to reduce the number of oxygen-containing functional groups and edge faces with low oxidation resistance.

[0104] In the oxygen content measurement by TPD-MS, H released from the carbon material ２ , H ２ O, CO and CO ２ The amount of oxygen-containing gases measured is derived from oxygen-containing functional groups such as hydroxyl groups (including phenolic groups), carbonyl groups (including quinones), ethers, acid anhydrides, carboxyl groups, and lactones at the edge terminals of the carbon material. Therefore, a high amount of oxygen-containing functional groups in the carbon material means a high amount of oxygen-containing functional groups and edges present in the carbon material structure, which can lead to reduced durability and become a barrier to extending the life and improving the performance of lithium-ion secondary batteries. The amount of oxygen-containing functional groups and edges in the carbon material can be adjusted by the CVD conditions and heat treatment temperature.

[0105] The ratio of the oxygen content to the carbon content of the carbon material of this embodiment, expressed as an O / C ratio, is preferably 1 or less, or preferably 0.5 or less, 0.1 or less, 0.05 or less, or 0.01 or less. When the O / C ratio of the carbon material is within this range, the lithium ion secondary battery is more likely to exhibit a longer life and higher performance.

[0106] In this embodiment, the gas amount is preferably 5000 μmol / g or less, or may be any of 3000 μmol / g or less, 1000 μmol / g or less, 750 μmol / g or less, and 500 μmol / g or less. The gas amount is measured, for example, by TPD-MS measurement. When the amount of gas generated from the carbon material is within this range, it can contribute to extending the life and improving the performance of lithium-ion secondary batteries.

[0107] The edge amount of the carbon material of this embodiment is a value calculated from the amount of gas measured by, for example, TPD-MS measurement, and is preferably 500 m ２ / g or less, or 300m ２ / g or less, 100m ２ / g or less, 50m ２ / g or less, 30m ２ / g or less is also preferable. Alternatively, the edge amount of the carbon material of this embodiment is also preferably either 750 μmol / g or less or 500 μmol / g or less. When the edge amount of the carbon material is in this range, the durability is excellent, and the stability and high performance of the lithium ion secondary battery are more likely to be achieved.

[0108] The ash content of the carbon material of this embodiment is preferably 10,000 ppm or less, or preferably 5,000 ppm or less, 4,000 ppm or less, 3,500 ppm or less, or 3,000 ppm or less. When the ash content of the carbon material is in this range, the stability of the electrolyte is further improved, and the durability and performance of the lithium ion secondary battery can be further improved.

[0109] <Physical Properties of Carbon Material> The carbon material of this embodiment often exhibits high electrical conductivity along with high oil absorption. In particular, the above-described linked structure, particularly GMS, has a graphene structure extending in the plane direction, and therefore is likely to exhibit particularly high electrical conductivity. Therefore, it is useful as a carbon material for electrodes in batteries and the like.

[0110] For example, carbon materials contained in electrodes of lithium-ion batteries preferably have high electrical conductivity. Because electron migration in carbon occurs through the transfer of π electrons, forming an ideal conductive path within an electrode using a carbon material requires a mesh-like arrangement of single-layer graphene, in which carbon atoms are bonded in the planar direction. Furthermore, when a conductive material such as a carbon material is filled into a non-conductive material such as a positive electrode material, a low filling rate of the conductive material can make it difficult to achieve electrical conductivity. At a certain filling rate, conductive material paths are formed within the compound, causing a sudden increase in electronic conductivity, which then stabilizes. The lower the threshold filling rate at which electronic conductivity increases, the more suitable the conductive material is. For example, in the above-mentioned interconnected structure, the in-plane electrical conductivity and the path-formed electrical conductivity are highly balanced, potentially resulting in high electrical conductivity.

[0111] The electrical conductivity of carbon materials can be evaluated, for example, by measuring the electrical conductivity of powder using lateral constrained uniaxial compression as described below. In this measurement method, a dry sample is filled into a cylindrical container consisting of an insulating cylinder and a negative electrode. A positive electrode is inserted into the insulating cylindrical container filled with the sample, and the sample is sandwiched between the negative and positive electrodes and placed on a force gauge stand. A spring-loaded force gauge attached to the force gauge stand is lowered to apply force to the sample inside the cylindrical container, compressing it. While measuring the compressive force and sample height with a length measuring instrument, the resistance of the sample is measured with a digital multimeter connected to the positive and negative electrodes. The conductivity of the powder during compression is calculated from the obtained resistance value, the packed cross-sectional area of ​​the sample, and the packed height.

[0112] The electrical conductivity of the carbon material of this embodiment is preferably 1 to 100 S / cm, or preferably any of the ranges of 5 to 70 S / cm, 10 to 50 S / cm, and 20 to 30 S / cm, as measured under a pressure of 10 MPa. The electrical conductivity of a carbon material is calculated as the reciprocal of its electrical resistivity. The electrical resistivity of a carbon material can be measured, for example, according to JIS K1469.

[0113] The pH of the carbon material of this embodiment is preferably 5 to 10, or preferably any of the ranges of 5.5 to 9.5, 6 to 9, 6.5 to 8.5, and 7 to 8. When the pH of the carbon material is in this range, the stability is further improved, which is preferable.

[0114] The combustion temperature of the carbon material of this embodiment is preferably 300° C. or higher, or preferably any of 400° C. or higher, 450° C. or higher, 500° C. or higher, 550° C. or higher, and 600° C. or higher. The combustion temperature test of the carbon material is carried out as a simple test of corrosion resistance, and a higher combustion temperature tends to increase the electrochemical stability in the electrode.

[0115] The carbon material of this embodiment exhibits high oil absorption, and therefore exhibits a high reinforcing effect on, for example, polymers. Furthermore, when used as an electrode material for, for example, a lithium-ion battery, electrolyte solution containing dissolved lithium ions is easily permeated and retained, resulting in excellent ion supply during the reaction. In particular, when the carbon material has a graphene crystal structure, it also exhibits excellent electron transfer, and can favorably support secondary battery reactions. Therefore, the carbon material of this embodiment is suitable for secondary batteries.

[0116] <<Method for Producing Carbon Material>> The carbon material as described above can be produced, for example, by the production method shown below. Hereinafter, the method for producing a carbon material of the present invention will be described in detail based on a typical embodiment.

[0117] One aspect of the method for producing a carbon material according to the present embodiment includes a step of removing the template material from a carbonaceous layer-coated template material, which is an aggregate of multiple primary particles clustered together in a beaded pattern, and a carbonaceous layer formed to coat the surface of the template material, to form a carbon material precursor. This production method can produce, for example, carbon materials that form the carbon meso sponge (CMS) or CMS aggregates described above.

[0118] Another aspect of the method for producing a carbon material according to the present embodiment includes the steps of: (1) forming a carbon material precursor by eluting and removing the template material from a carbonaceous layer-coated template material, the template material being an aggregate of multiple primary particles linked together in a beaded pattern, and a carbonaceous layer covering the surface of the template material; and (2) heat-treating the carbon material precursor to form a carbon material having an internal space, the carbon material precursor comprising a plurality of hollow particulate portions formed by surrounding walls made of graphene-containing carbonaceous material, each of which has one or more interconnected structures having an elongated shape connected in a beaded pattern, and the interconnected structures having pores. This production method can produce, for example, the graphene meso sponge (GMS) described above, or the interconnected structures that form GMS aggregates.

[0119] The method for producing a carbon material according to this embodiment may also include, prior to the above steps, a step of forming a carbonaceous layer on the surface of the template material. More specifically, prior to the removal step, the method may include a step of placing the template material in a reaction vessel, a step of heating the reaction vessel and introducing a carbon-containing source gas into the reaction vessel, and a step of depositing a product of thermal decomposition of the source gas on the surface of the template material by chemical vapor deposition (CVD) to form a carbonaceous layer-coated template material that covers the surface.

[0120] That is, the method for producing a carbon material according to the present embodiment may include, for example, the steps of placing a template material in a reaction vessel, heating the reaction vessel, and introducing a source gas containing carbon into the reaction vessel, depositing a product obtained by thermally decomposing the source gas on the surface of the template material by chemical vapor deposition (CVD) to form a carbonaceous layer-coated template material covering the surface, eluting and removing the template material from the carbonaceous layer-coated template material by acid treatment to form a carbon material precursor, and heating the carbon material precursor to partition and form an internal space, thereby obtaining a carbon material in which a plurality of hollow particulate portions formed by surrounding walls made of carbonaceous material including a graphene structure have one or a plurality of connected structures having an elongated shape connected in a beaded pattern, and pores are formed in the connected structures.

[0121] According to this production method, a carbon material having an oil absorption of 550 mL / 100 g or more, particularly a carbon material having a connected structure having an elongated shape in which a plurality of hollow particulate portions are connected in a beaded shape, can be efficiently obtained. Below, each step of this embodiment and the raw materials used, etc. will be described in detail.

[0122] <Manufacturing Process of Carbonaceous Layer-Coated Mold Material> The carbonaceous layer-coated mold material can be manufactured, for example, by placing the mold material in a reaction vessel, heating it, and then introducing a carbon-containing source gas into the reaction vessel. For example, a CVD method is used to deposit pyrolysis products of the carbon-containing source gas on the surface of the mold material, thereby obtaining a carbonaceous layer-coated mold material whose surface is coated with a carbonaceous layer. This method is also sometimes called a template chemical vapor deposition method (T-CVD method).

[0123] (Template Material) The template material used in this embodiment is preferably one that can realize a complex, elongated, and highly structured carbon material having interconnected internal spaces. For example, a template material having an aggregate structure in which primary particles are strung together in a beaded pattern with multiple branched structures can be used.

[0124] The primary particle diameter of the template material used in this embodiment is preferably 1 to 150 nm, more preferably 5 to 100 nm, even more preferably 10 to 60 nm, even more preferably 15 to 50 nm, and particularly preferably 20 to 40 nm. When the primary particle diameter of the template material is within this range, it is preferable because, for example, a continuous structure with a large mesopore volume is easily formed, and the oil absorption capacity of the produced carbon material can be significantly increased. Furthermore, when the primary particle diameter of the template material is within this range, it is easy to handle and has good permeability to the raw material gas that serves as the carbon source for the carbonaceous layer, facilitating uniform carbon coating.

[0125] The BET specific surface area of ​​the mold material used in this embodiment is, for example, 1 to 1000 m ２ / g, preferably 10 to 500m ２ / g, more preferably 20 to 200 m ２ / g, more preferably 40 to 160 m ２ / g, particularly preferably 50 to 120 m ２ When the BET specific surface area of ​​the template material is in this range, the oil absorption capacity and mesopore volume of the produced carbon material can be significantly increased, which is preferable.

[0126] The specific surface area of ​​the produced carbon material depends on the specific surface area of ​​the template. The smaller the particle diameter, the greater the ratio of particle volume to surface area, so the smaller the particle diameter, the greater the surface area per volume, i.e., the surface area per unit mass. Therefore, using particles with a small primary particle diameter for the template material makes it easier to obtain a carbon material with a high specific surface area.

[0127] The template material used in this embodiment has an aggregate structure in which the primary particles are strung together in a beaded pattern with multiple branches, similar to the structure of carbon black.

[0128] The average primary particle size of the template material (aggregates) in this embodiment may be, for example, 1 to 100 nm, or may be in the range of 2 to 50 nm, 4 to 50 nm, or 3 to 30 nm. The length of the aggregate structure is, for example, in the range of 0.01 to 100 μm, preferably 0.05 to 10 μm, and preferably 0.1 to 5 μm. The average particle size of the aggregate structure is, for example, in the range of 0.05 to 10 μm, and preferably 0.1 to 5 μm.

[0129] The bulk density of the template material used in this embodiment is, for example, in the range of 0.1 to 500 g / L, preferably 0.5 to 250 g / L, more preferably 1 to 200 g / L, even more preferably 10 to 100 g / L, and particularly preferably 30 to 70 g / L. When the bulk density of the template material is in this range, the electrical conductivity of the produced carbon material can be increased and the oil absorption and mesopore volume can be significantly increased, which is preferable.

[0130] The template material used in this embodiment is preferably basic or acidic. Examples of suitable basic compounds include magnesium oxide and calcium carbonate. Examples of acidic compounds include aluminum oxide and silanol-containing silica compounds. The acidic pH, measured in 4% water, is, for example, 7 or less, preferably 6.5 or less, more preferably 6 or less, even more preferably 5.5 or less, and particularly preferably 5 or less. The lower limit is, for example, 1 or more, preferably 2 or more, more preferably 3 or more, even more preferably 3.5 or more, and particularly preferably 4 or more.

[0131] The template material used in this embodiment may be any material having an aggregate structure in which primary particles are strung together in a beaded pattern with multiple branches, and is preferably a compound that has catalytic activity for the carbon deposition reaction. Examples of template materials include metal compounds, metalloid compounds, and nonmetallic compounds, and are preferably ceramic particles and / or carbonate particles.

[0132] Examples of ceramic particles include glass, cement, fine ceramics, and more specifically, particles of silica (silicon dioxide), alumina, magnesia (magnesium oxide), and the like.

[0133] Alumina has acidic sites on its surface and functions as a solid acid. When the acidic sites in the solid acid come into contact with hydrocarbons, the acidic sites act as a catalyst for the hydrocarbon reforming reaction. Furthermore, when the acidic sites come into contact with hydrocarbons, a carbon deposition reaction occurs, and carbon can be deposited on the surface of the solid acid. This function is called a solid acid catalyst function, and by utilizing this function, it is possible to decompose the source gas, which is the source of the carbonaceous layer, polymerize the decomposition product, carbon radicals, and deposit a carbonaceous layer, even at temperatures below the decomposition temperature of the source gas.

[0134] Examples of carbonate particles include, but are not limited to, particles of calcium carbonate, magnesium carbonate, dolomite, barium carbonate, lithium carbonate, sodium carbonate, potassium carbonate, etc. In particular, particles of calcium carbonate and / or magnesium carbonate are preferred.

[0135] Examples of template materials for metal compounds other than carbonate particles include monovalent metal compounds and polyvalent metal compounds, with polyvalent metal compounds being preferred. Examples of monovalent metal compounds include chlorides, sulfates, nitrates, and phosphates of alkali metals such as sodium and potassium. Examples of polyvalent metal compounds include alkaline earth metal compounds such as calcium and magnesium, and trivalent metal compounds such as aluminum, with calcium compounds, magnesium compounds, and aluminum compounds being preferred. Examples of compounds of calcium, magnesium, and aluminum include chlorides, sulfates, nitrates, phosphates, and oxides, with oxides being preferred.

[0136] Examples of metalloid (semimetal) compounds include compounds of boron, silicon, germanium, antimony, etc., with silicon compounds being preferred. Examples of silicon-based template materials include silicon monoxide, silicon dioxide, silicon nitride, silicon carbide, silicon, etc., with silicon dioxide being preferred, and these are classified as ceramic particles.

[0137] Furthermore, fumed compounds (particulate compounds in an aerosol state) can be suitably used as template materials because they form an aggregate structure in which primary particles have multiple branched structures and are strung together like beads. Examples of fumed compounds include compounds obtained by flame hydrolysis, which is one of the dry production methods for inorganic materials.

[0138] A typical example of a fumed compound is fumed silicon dioxide. Fumed silicon dioxide produced by flame hydrolysis does not undergo a liquid phase process during production, and therefore agglomeration is gentle. For this reason, fumed silicon dioxide has excellent dispersibility in the liquid phase or compound (solid phase). Fumed silicon dioxide is produced by high-temperature gas phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame, accompanied by hydrochloric acid as a by-product. By changing production conditions such as the flame temperature, oxygen and hydrogen supply ratio, raw material supply amount, and residence time, it is possible to produce fumed silicon dioxide with an average particle size of 7 to 40 nm and a specific surface area of ​​50 to 380 m, for example. ２ / g of silicon dioxide particles are obtained.

[0139] Other examples of fumed compounds produced by flame hydrolysis include fumed alumina, fumed titania, and fumed zirconia. Other fumed metal compounds include chlorides of Na, Ba, or Sr, sulfates of K, Na, Sr, or Mg, nitrates of Na or K, phosphates of Na or K, carbonates of Na, K, Ca, or Mg, and metal oxides of Na, K, Ca, or Ba. The mold material is preferably in the form of a fumed form.

[0140] Precipitated silica can also be used as the template material. Precipitated silica is obtained by reacting a sodium silicate solution with an acid in the liquid phase, followed by precipitation, filtration, washing, drying, and pulverization. By adjusting the reaction conditions, precipitates with an average particle size of about 7 to 140 nm and a specific surface area of ​​about 20 to 400 m can be obtained. ２ / g of silicon dioxide particles are obtained.

[0141] The water content of the mold material used in this embodiment is, for example, 5% by mass or less, preferably 3% by mass or less, more preferably 1.5% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less.

[0142] The carbon content of the mold material used in this embodiment may be, for example, 0.0001% by mass or more, preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and particularly preferably 0.5% by mass or more, with the upper limit being, for example, 5% by mass or less, preferably 4% by mass or less, more preferably 3% by mass or less, even more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. When the carbon content of the mold material is in this range, it is preferable because it facilitates the formation of a carbonaceous layer on the mold surface.

[0143] In this embodiment, a carbonaceous layer can be formed on the mold surface by, for example, chemical vapor deposition (CVD), as described below. In this case, the amount of carbon deposited on the mold surface is greatly affected by the CVD reaction conditions, such as the source gas species, source gas concentration, flow rate, reaction temperature, and reaction time, as well as the surface of the mold material.

[0144] Compounds having a suitable surface for carbon deposition by CVD include, for example, compounds containing oxygen atoms. In the CVD reaction, carbon in the source gas is replaced by oxygen atoms, which act as the starting point for carbon deposition. Examples of oxygen-containing compounds include the metal oxides and metal carbonates described above. Among these compounds, acidic or basic compounds are particularly suitable. Examples of basic oxygen-containing compounds include magnesium oxide and calcium carbonate.

[0145] Furthermore, surfaces suitable for forming a carbonaceous layer by CVD include those having a hydrocarbon as a carbon source. Hydrocarbons are compounds that can be used as source gases, as described below, such as compounds having a methyl group or a carbon-carbon unsaturated bond. Suitable template materials are inorganic compounds having a hydrocarbon on their surface.

[0146] As the inorganic compound having a hydrocarbon on its surface, for example, an inorganic material surface-treated with a silane coupling agent, particularly a silica compound, is suitable. The silane coupling agent may be one that is commonly used as a surface treatment agent, such as a methoxy-type silane coupling agent, an ethoxy-type silane coupling agent, a vinyl-type silane coupling agent, a dialkoxy-type silane coupling agent, or a trialkoxy-type silane coupling agent. Among these, a trialkoxy-type silane coupling agent having a large number of methyl groups per molecule is preferred, and a trimethoxysilane compound is particularly preferred.

[0147] The amount of silane coupling agent is appropriately selected depending on the intended use, but is expressed as the amount of hydrocarbon in the inorganic material, and is, for example, in the range of 0.01 to 10 mass%, preferably 0.02 to 8 mass%, more preferably 0.05 to 5 mass%, even more preferably 0.1 to 3 mass%, and particularly preferably 0.5 to 1.5 mass%. When the amount of silane coupling agent (hydrocarbon amount) in the inorganic compound is within this range, the amount of carbon on the template surface can be easily adjusted, which is preferable.

[0148] The above-mentioned template materials can be used alone or in combination of two or more. Particularly preferred are silica compounds such as fumed silicon dioxide and carbonate compounds such as calcium carbonate.

[0149] (Carbonous Layer Formation and Carbonization Step) In this embodiment, the carbonous layer can be formed on the surface of the template material by, for example, contacting the template material with an organic substance that serves as a carbon source and performing a carbonization heat treatment. The contact with the carbon source and the carbonization heat treatment can be performed simultaneously or separately. The template material is contacted with the carbon source at a temperature ranging from room temperature to approximately 1000°C, for example.

[0150] Methods for contacting a carbon source with a template material are roughly divided into liquid-phase contacting and gas-phase contacting, with the gas-phase contacting being preferred. The liquid-phase contacting method is, for example, a method in which the template material is immersed in an organic liquid. The gas-phase contacting method is, for example, a method in which an organic vapor is introduced at high temperature and brought into contact with the template material, which is a so-called CVD method.

[0151] In this embodiment, it is preferable to use a chemical vapor deposition (CVD) method as the vapor phase contact method. CVD is preferably carried out in a temperature range where a dehydrogenation reaction can proceed, in order to bring an organic compound as a carbon source into contact with a template material and to strongly bond the carbon source and the template material.

[0152] The organic compound used as a carbon source in the gas-phase contact method may be appropriately selected depending on the intended use, but hydrocarbons such as saturated hydrocarbons, unsaturated hydrocarbons having double and / or triple bonds, alicyclic hydrocarbons, and aromatic hydrocarbons are preferably used. Saturated hydrocarbons may be either linear or branched, and examples thereof include methane, ethane, and propane. Unsaturated hydrocarbons may be either linear or branched, and examples thereof include ethylene, propylene, isoprene, and acetylene. Alicyclic hydrocarbons include cyclopropane and cyclohexane. Aromatic hydrocarbons include benzene and toluene.

[0153] Among these hydrocarbons, it is desirable to use methane, ethane, acetylene, ethylene, propylene, benzene, etc., and from the viewpoint of depositing highly crystalline carbon, methane, propylene, and benzene are preferred. In particular, methane is preferably used from the viewpoint of having a high thermal decomposition temperature and being able to obtain highly crystalline carbon.

[0154] As the organic compound used in the gas phase contact method, alcohols such as methanol, ethanol, propanol, butanol, etc., and nitrogen-containing compounds such as acetonitrile, acrylonitrile, etc. can also be used.

[0155] The reaction temperature during CVD is appropriately selected depending on the decomposition temperature of the organic compound used as the carbon source, and may be, for example, in the range of 400 to 1000°C, preferably 600 to 950°C, and more preferably 800 to 900°C.

[0156] The reaction time during CVD (CVD treatment time at a predetermined heating temperature) is appropriately selected depending on the type of template material, the type of organic compound used as the carbon source, or the number of carbonaceous layers to be deposited, but may be, for example, in the range of 0.1 to 10 hours, preferably 0.5 to 5 hours, and more preferably 1 to 3 hours. Furthermore, the analytical method disclosed herein can be applied to analyze the product, and the time required for sufficient carbon deposition can be appropriately set based on the results.

[0157] The CVD reaction can be carried out under an inert gas atmosphere, if necessary. Examples of inert gases include nitrogen, helium, neon, and argon, with argon being preferred. In the CVD method, carbon can be easily adsorbed or deposited on the template material in the gas phase by heating a gaseous organic compound together with a carrier gas while flowing the compound in contact with the template material. The type, flow rate, flow rate, and heating temperature of the carrier gas can be adjusted appropriately depending on the type of organic compound used. Examples of the carrier gas include the inert gases listed above, but they may also be mixtures with oxygen gas or hydrogen gas.

[0158] The number of carbonaceous layers introduced onto the template material can be appropriately selected depending on the CVD reaction time, but to form thin graphene layers, the flow rate of the carrier gas is preferably adjusted to 0.05 to 5 m / min, more preferably 0.1 to 1 m / min, even more preferably 0.2 to 0.8 m / min, and particularly preferably 0.32 to 0.64 m / min. Furthermore, to form an optimal number of carbonaceous layers, particularly graphene layers, the amount of organic compound introduced is preferably adjusted to a range of 1 to 70 vol%, more preferably 5 to 50 vol%, even more preferably 10 to 40 vol%, and particularly preferably 15 to 35 vol%, based on the total amount of carrier gas and organic compound.

[0159] In the method for producing a carbon material according to this embodiment, the number of carbonaceous layers is appropriately selected depending on the intended use, and is, for example, 1 or more, preferably 1.2 or more, more preferably 1.5 or more, even more preferably 2 or more, and particularly preferably 2.2 or more, with an upper limit of, for example, 15 or less, preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 5 or less. When the number of carbonaceous layers, particularly the number of graphene layers constituting the carbonaceous layers, is within this range, the carbon material tends to be excellent in strength characteristics and elastic deformation, and to easily maintain a hollow structure. Here, the number of carbonaceous layers can be determined, for example, by laminating the carbonaceous layers on template particles, calculating the weight of the carbonaceous layers using thermogravimetric analysis (TG), calculating the weight of the carbonaceous layers per template area from the weight of the carbonaceous layers and the surface area of ​​the template particles, and then multiplying this by the weight of the carbonaceous layers per area of ​​single-layer graphene (7.61 × 10 －４ g / m ２ ) can be calculated by dividing by

[0160] Since a carbonization reaction can also proceed during the CVD reaction, there is no need to carry out a separate carbonization treatment, but carbonization can be carried out if desired.

[0161] (Liquid-Phase Contact Method) In the liquid-phase contact method, an organic compound having a functional group reactive with the functional groups on the template surface, specifically a hydroxyl group, is preferably used, particularly a benzene-based hydrocarbon compound having a functional group reactive with a hydroxyl group. Among these, benzene-based aromatic hydrocarbon compounds having a hydroxyl group and / or a carboxyl group are preferred, with phenol, hydronaphthalene, and dihydronaphthalene being more preferred. This is because when an organic compound having a functional group reactive with the functional group on the template surface is used, a strong bond such as an ester bond is formed between the template material and the organic compound, which makes it easy to carbonize the organic compound in situ without volatilizing during the carbonization heat treatment.

[0162] In the liquid-phase contact method, for example, an organic compound serving as a carbon source is dissolved in a solvent and then contacted with a template material by impregnation at room temperature. To strongly bond the organic material to the template material, the temperature is preferably maintained at 250 to 600°C for a certain period of time. This causes a dehydration condensation reaction, such as an esterification reaction, between the hydroxyl groups on the template material surface and the organic material, resulting in fixation through bonds such as ester bonds, making it easier to obtain a carbonaceous layer with a graphene sheet structure. The temperature is then lowered, and excess organic material that has not reacted with the template material can be washed away with a solvent or the like.

[0163] Next, a heat treatment is performed to carbonize the organic compound that serves as a carbon source and has been brought into contact with the template material. This heat treatment causes a dehydrogenation reaction or the like in the organic material, such as hydrocarbon, and converts it into carbon with a graphene sheet structure or the like. The heat treatment temperature is, for example, 600°C or higher, preferably 600 to 1500°C, more preferably 750 to 1500°C, and particularly preferably 800 to 1000°C. Note that the heat treatment may be performed at 1500°C or higher as long as the template material does not collapse or melt.

[0164] <Template Removal Step> The template of the carbonaceous layer-coated template material formed as described above is subsequently removed in a template removal step to form a carbon material precursor. The template removal step of this embodiment may be any method that removes the template and leaves the formed carbonaceous layer. Examples include dissolution methods using acids or alkalis, and acid dissolution methods are preferred.

[0165] The acid used in this embodiment is appropriately selected depending on the type of template material, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, and hydrofluoric acid, with hydrochloric acid and hydrofluoric acid being preferred. The concentration of the acid used is appropriately adjusted to a range that allows the template to be dissolved and removed. The amount of acid used is not particularly limited as long as it allows the template material to be dissolved and removed, but may be, for example, 30 times or more the stoichiometric ratio relative to the template material, or 50 times or more the stoichiometric ratio.

[0166] The temperature for dissolving and removing the template material is, for example, in the range of 5 to 100°C, preferably 10 to 50°C, and more preferably 20 to 30°C. The step of dissolving and removing the template material may be carried out while adding stirring, vibration, and other operations. The time required for the removal step is appropriately selected within a range that allows the template to be dissolved and removed.

[0167] The carbon material after template removal can be recovered, for example, by filtration, and then washed with pure water. Washing conditions can be selected appropriately, but it is preferable to end the washing process after confirming that the pH of the washing solution has become neutral.

[0168] The carbon material after removal of the template material may be washed as desired and then dried by vacuum heat drying, etc. The conditions for vacuum heat drying are not particularly limited, but may be, for example, a temperature of 100 to 200° C. for 1 to 10 hours.

[0169] <Heating Step> Through the steps described above, a carbon material such as CMS or a precursor of the carbonaceous layer constituting GMS can be produced. The obtained carbon material may be further subjected to heat treatment. Heat treatment is particularly preferable for carbon material precursors. Heat treatment (heating step) increases the crystallinity of carbon, forming and stabilizing, for example, a graphene crystal structure, making it possible to produce a carbon material with higher levels of electrical conductivity, corrosion resistance, and / or a large specific surface area. It is also possible to produce larger aggregates.

[0170] The conditions for the heating step are not particularly limited as long as they enhance the crystallinity of carbon. For example, the holding temperature may be set to a range of 1000 to 3000°C, preferably 1300 to 2500°C, more preferably 1500 to 2000°C, even more preferably 1600 to 1900°C, and particularly preferably 1750 to 1850°C. A heat treatment temperature within this range is advantageous because it allows for the production of a carbon material with higher levels of electrical conductivity, corrosion resistance, and / or a large specific surface area. The heat treatment time (holding time at a predetermined heat treatment temperature) can be, for example, 0.1 to 10 hours, preferably 0.2 to 5 hours, and more preferably 0.5 to 5 hours. The atmospheric pressure in the heat treatment step is preferably atmospheric pressure or reduced pressure.

[0171] Furthermore, during the heating process, functional groups (mainly oxygen-containing functional groups) bound to carbon and carbon chains that do not form six-membered rings are detached at temperatures above 1000°C, which can result in the formation of dangling bonds. If the dangling bonds that are formed bond with other nearby carbons, the surface of the carbon material becomes a state in which functional groups are less likely to bond. Therefore, by performing a heat treatment at, for example, 1500°C or higher, preferably 1600°C or higher, it is possible to make the carbon material more electron conductive and more likely to maintain internal space.

[0172] During the heating process, structural defects in the graphene and non-graphene components of the carbonaceous layer may be adjusted. These structural defects include voids formed within the aggregate structure due to dissolution of the template material and infiltration pores formed in the outer shell formed from the carbonaceous layer. By changing the reaction conditions, such as the heat treatment temperature and heat treatment time, the extent of these structural defects can be adjusted. In other words, the size of the voids present within the carbon material and the size of the infiltration pores that allow oil or electrolyte to penetrate into the particles can be adjusted.

[0173] By the above-described production method, the carbon material of the present invention, for example, CMS or GMS, can be easily produced.

[0174] <<Uses of Carbon Materials>> Due to their high oil absorption, the above-described carbon materials can be incorporated into, for example, polymer composites to exhibit excellent reinforcing effects and high conductivity. Therefore, they are suitable for use in conductive composites, particularly secondary batteries. The present invention also encompasses a dispersion in which the above-described carbon materials are dispersed, an electrode composition containing the carbon material, an electrode slurry containing the carbon material, methods for producing the same, and an electrode and a lithium-ion battery. These embodiments are outlined below.

[0175] <Dispersion> This embodiment relates to a dispersion obtained by dispersing the above-described carbon material in a dispersion medium. As the dispersion medium, a polar solvent is preferable, particularly when the dispersion is used for manufacturing a lithium ion battery. From the viewpoint of affinity with the binder polymer, N,N-dimethylformamide, N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and water are preferable, and N-methylpyrrolidone (NMP) is particularly preferable. Furthermore, for carbon materials containing graphene, N-methylpyrrolidone (NMP) is suitable as a dispersion medium.

[0176] <Electrode Composition> This embodiment is an electrode composition containing the above-described carbon material, an active material, and a binder.

[0177] (Active Material) The active material used in this embodiment may be, for example, an active material used in a normal positive electrode or negative electrode. The ratio of the active material to the carbon material is appropriately selected depending on the intended use, and is, for example, in the range of 0.005 to 20 parts by mass, preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, even more preferably 0.1 to 2 parts by mass, and particularly preferably 0.5 to 1 part by mass, in terms of the ratio of the carbon material to 100 parts by mass of the active material.

[0178] (Binder) The binder used in this embodiment may be, for example, a binder used in a normal positive electrode or negative electrode. The amount of binder used is appropriately selected depending on the intended use, and is, for example, in the range of 0.05 to 10 parts by mass, preferably 0.1 to 8 parts by mass, more preferably 0.5 to 6 parts by mass, even more preferably 1 to 5 parts by mass, and particularly preferably 2 to 4 parts by mass, relative to 100 parts by mass of the active material.

[0179] (Other Additives) In addition to the carbon material, active material, and binder described above, other additives may be added to the electrode composition of this embodiment as desired. The other additives may be any additives that are commonly used in battery electrode compositions, and the amount used is, for example, 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 2 parts by mass or less, relative to 100 parts by mass of the active material.

[0180] <Slurry for Electrode> This embodiment is an electrode slurry obtained by dispersing the above-described electrode composition in a solvent. The solvent may be any solvent capable of dissolving or dispersing the binder, and may be a solvent typically used for positive or negative electrodes, a dispersion medium used in the above-described carbon material dispersion liquid, or the like. The amount of solvent used may be an appropriate amount, and is adjusted so that the viscosity of the electrode slurry in the next step can be applied to a current collector.

[0181] <Electrode> This embodiment relates to an electrode comprising the carbon material described above. The electrode of this embodiment may be either a negative electrode or a positive electrode, and can be obtained, for example, by applying the electrode slurry described above onto a current collector and then drying it. The current collector may be any of those used in ordinary positive or negative electrodes.

[0182] <Lithium-ion secondary battery> This embodiment is a lithium-ion secondary battery containing the above-described carbon material. Specifically, the battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and at least one of the positive electrode and the negative electrode uses the above-described electrode (positive electrode and / or negative electrode). One of the positive electrode or the negative electrode may be an electrode not containing the above-described carbon material. In addition, any separator and electrolyte used in a typical lithium-ion secondary battery may be used. The lithium-ion secondary battery of this embodiment may also optionally further include a battery container that houses an electrode assembly consisting of the positive electrode, negative electrode, and separator, a sealing member that seals the battery container, and the like.

[0183] <Other Applications> The carbon material of the present invention can exhibit its functionality and be effectively used in any electrochemical device other than the lithium ion secondary battery. Specifically, it can function as an intra-electrode conductive path when electrons are exchanged in a device reaction, or as a reinforcement when an electrode or the like is physically deformed. Depending on the embodiment of the carbon material, the durability of the graphene structure can be utilized to prevent a third material (such as a catalyst) from directly contacting a reaction material when the reaction material is in an oxidized or reduced state.

[0184] Examples of devices that can be used other than lithium ion secondary batteries include nonaqueous electrolyte batteries such as lithium ion batteries, sodium ion batteries, potassium ion batteries, magnesium ion batteries, calcium ion batteries, aluminum ion batteries, lithium-sulfur batteries, and lithium-air batteries; inorganic solid electrolyte batteries such as sulfide-based solid electrolytes and oxide-based solid electrolytes; polymer solid electrolyte batteries such as polyethylene oxide-based batteries; and semi-solid batteries typified by polymer gel electrolyte batteries in which an electrolyte is impregnated in PVDF or the like.

[0185] In these devices, as the negative electrode active material, graphitizable carbon, non-graphitizable carbon, graphite, lithium alloy-based materials such as silicon and tin, and other metal-based materials such as lithium are used, and as the positive electrode active material, lithium-containing metal oxides, particularly lithium-containing transition metal oxides having a layered structure, spinel structure, or olivine structure, lithium-free metal oxides, organic positive electrode materials, charge transfer complex positive electrode materials, sulfur, fluoride-based materials, etc. are used, but the carbon material of the present invention can effectively increase the conductivity of any active material. In addition, the carbon material of the present invention is also suitable as a material for lithium-sulfur batteries and the like described in WO2018 / 225619, JP2023-501679A, JP2019-517116A, JP2022-191280A, etc.

[0186] The carbon material of the present invention can also be suitably used in organic electrolyte capacitors, aqueous electrolyte capacitors, and aqueous electrolyte batteries. It can be used in fuel cells such as PEFC, SOFC, and DMPC, and in particular can be used as a support for redox catalysts in addition to providing electrical conductivity to electrodes.

[0187] The carbon material of the present invention can also be used in applications other than electrochemical devices. For example, it is suitable for use in electronic devices such as graphene-based sensors, electromagnetic interference suppression materials, antenna modules, heat dissipation substrates, heat exchangers, separation membranes, reverse osmosis membranes, transparent electrode materials, structural materials utilizing mechanical flexibility, conductive inks and pastes, etc. Furthermore, as the need for lightweight automobile bodies increases, which directly contributes to reducing carbon dioxide emissions and energy conservation, the carbon material can also be used in applications that utilize hollow shapes to reduce weight, such as reinforcing agents for various rubbers including tires, paints, coloring pigments, conductive fillers for various polymers, and additives for magnetic recording media. Because the carbon material of the present invention exhibits high oil absorption, it is also suitable as a filler for polymers, including the rubber reinforcing agents described above.

[0188] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples except as defined above. In the following, the units "%", "ppm" and "parts" that represent amounts are by mass unless otherwise specified.

[0189] Experiment 1: Preparation of carbon materials and polymer composites and evaluation of their physical properties

[0190] Example 1 (Production of Carbon Material) - CVD Reaction: Formation of Carbonaceous Layer on Template Material - Fumed silicon dioxide (SiO ２ / AEROSIL (registered trademark) NX90G, particle size 38 nm, BET specific surface area 71 m ２Approximately 1 g of carbon nanotubes (1000 kJ / g, carbon content 0.5-1.5%, manufactured by Nippon Aerosil Co., Ltd.) was spread on a quartz boat and placed in the center of a quartz reaction tube of a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). While flowing argon gas at a flow rate of 400 mL / min into the reaction tube, the reaction tube was heated to 900 °C at a temperature increase rate of 10 °C / min and held for 30 minutes. While maintaining the temperature at 900 °C, argon gas was flowed at a flow rate of 320 mL / min, while methane gas was flowed at a flow rate of 80 mL / min (raw material gas concentration: 20 vol%), and the temperature was held for 90 minutes. Subsequently, while flowing argon gas at a flow rate of 400 mL / min, the reaction tube was cooled to room temperature, the quartz boat was removed, and a carbonaceous layer-coated template material was obtained, in which the surface of the template material was coated with a carbonaceous layer. Furthermore, it was confirmed by electron microscopy that the template material was an aggregate of multiple primary particles linked together in a beaded pattern with multiple branched structures.

[0191] -Removal of Template Material- Next, the template material was removed from the obtained carbonaceous layer-coated template material by the following procedure, to obtain a carbon material precursor.

[0192] (1) The carbonaceous layer-coated mold material was placed in a 100 ml PFA beaker, and ultrapure water was added to wet the entire carbonaceous layer-coated mold material. (2) 46% hydrofluoric acid was added, followed by stirring with a stirrer for 2 hours. (3) After stirring was stopped, the sample was allowed to stand until it settled. (4) Using a PTFE membrane filter (47 mm diameter, 0.1 μm pore size), the supernatant was filtered by suction. (5) The sample on the filter paper was washed with approximately 39 mL of ultrapure water and then filtered by suction. This procedure was repeated three times. (6) The sample on the filter paper was returned to the original PFA beaker. (7) The above procedures (2) to (6) were repeated again. (8) Approximately 40 mL of ultrapure water was added, and the mixture was stirred with a stirrer for 1 hour. (9) After stirring was stopped, the sample was allowed to stand until it settled. (10) The supernatant was discarded, and 5% caustic soda was added. The mixture was stirred for 12 hours while being heated to 80°C. (11) After stopping the stirring, the mixture was left to stand until the sample settled. (12) A PTFE membrane filter (47 mmφ, pore size 0.1 μm) was used to suction-filter the supernatant. (13) The sample on the filter paper was washed with ultrapure water and suction-filtered. This procedure was repeated until the filtrate became neutral. (14) The sample on the filter paper was collected in a petri dish and dried in a dryer at 110°C for 8 hours.

[0193] - Heat Treatment - The carbon material precursor obtained above was placed in a square high-temperature heating furnace (manufactured by Izumi Tech Co., Ltd.) and heated under reduced pressure (10 －１ After adjusting the pressure to the order of Pa, the mixture was heated to 1800°C at a temperature increase rate of 15°C / min under an argon gas flow (10 mL / min) and maintained at that temperature for 1 hour for firing. Thereafter, the mixture was cooled to room temperature to obtain carbon material A.

[0194] (Method for measuring oil absorption of carbon material) The oil absorption of the obtained carbon material A was measured in accordance with "JIS K5101-13-1 Pigment testing methods - Part 13: Oil absorption - Section 1: Refined linseed oil method." The results are shown in Table 1 below.

[0195] (Transmission Electron Microscope Observation) The shape of the obtained carbon material A was observed. FIG. 2 is an enlarged TEM image of the carbon material A of Example 1 observed using a transmission electron microscope (TEM: H-7650, manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 100 kV and a magnification of 15,000 times. FIG. 3 is a TEM image of the carbon material A of Example 1 observed using a transmission electron microscope (TEM: JEM-2100Plus, manufactured by JEOL Ltd.) at an acceleration voltage of 100 kV and a magnification of 40,000 times. As shown in FIGS. 2 and 3 , it was confirmed that the surrounding wall of the carbon material A had a graphene structure consisting of a six-membered carbon ring structure. It was also confirmed that the carbon material A of Example 1 had a connected structure in which a plurality of hollow particulate portions were connected together, each of which was composed of a surrounding wall having a plurality of pores.

[0196] (Nitrogen Adsorption / Desorption Measurement) Nitrogen adsorption / desorption measurement was performed on the obtained carbon material A using an automatic specific surface area / pore size distribution measurement device (BELSORP MINI, manufactured by Microtrac-BEL Co., Ltd.). Prior to the measurement, the measurement sample was dried under reduced pressure at 150°C for 6 hours using a BEL pre. From the obtained adsorption isotherm, the BET specific surface area was determined using the BET method. The applicable range of the BET method was a relative pressure of 0.05 to 0.3. Furthermore, based on the obtained adsorption / desorption isotherm, the total pore volume was measured by converting the amount of nitrogen adsorbed at -196°C and a relative pressure of 0.99 into a volume at the density of liquid nitrogen. The results are shown in Table 1. The pore size distribution was determined using the BJH method.

[0197] (Raman Spectroscopic Measurement) Raman spectroscopy was performed on the obtained carbon material A using a micro-Raman device (LabRAM HR-800, manufactured by Horiba, Ltd.). A 532 nm laser was used for the measurement, and the filter was set to D1 and the hole was set to 100 μm. The measurement range was 300 to 3500 cm －１ From the measured Raman spectrum, (I Ｇ / I ２Ｄ ), (I Ｄ / I Ｇ The intensity ratios of the above were calculated and are shown in Table 1.

[0198] (Preparation of Polymer Composite Material) The carbon material A obtained above was used to prepare a dispersion (slurry) containing it, and a polymer composite material was prepared using the dispersion. The carbon material A (0.5 mass %) was mixed with a ternary NCM (LiNi) having an average particle size of 8 μm. ０．５ Co ０．２ Mn ０．３ O ２ 97.5% by mass of PVDF (Kelong Co., Ltd., a positive electrode active material) powder and 2% by mass of PVDF (Kureha Co., Ltd.) were added to the solvent N-methylpyrrolidone (NMP) and mixed. The resulting mixture was placed in a planetary mixer and kneaded at 2000 rpm while adding NMP in several portions until a uniform and moderate viscosity was achieved, producing a slurry. The slurry was applied to a 100 μm thick PET film at a constant speed using a micrometer-equipped doctor blade coating device. The film was then dried in a vacuum dryer set at 110 °C to obtain a raw sheet. The raw sheet was then punched using a φ20 mm punch-type punching machine, pressed at 45 kN using a cylinder-type jig, and vacuum-dried at 120 °C to obtain a composite sample.

[0199] (Measurement of electrical resistance of composite material) The composite material samples obtained above were measured for composite layer resistivity at room temperature using a low resistivity meter (Loresta-FX MCP-T380, manufactured by Nitto Seiko Analytech Co., Ltd.) The results are shown in Table 1.

[0200] Example 2: Fumed silicon dioxide (SiO ２ / AEROSIL (registered trademark) R972, particle size 25 nm, BET specific surface area 111 m ２ Carbon material B was prepared in the same manner as in Example 1, except that a carbon nanotube (CuO 3 0.15 / g, carbon content 0.6-1.2%, manufactured by Nippon Aerosil Co., Ltd.) was used and the CVD reaction time was 120 minutes. It was confirmed by electron microscopy that the template material was an aggregate of multiple primary particles linked together in a beaded pattern with multiple branched structures. Figure 4 shows the Raman spectrum of carbon material B.

[0201] Examples 3 to 6 Carbon materials C to F were prepared in the same manner as in Example 1, except that the CVD reaction time was changed to 75 minutes (Example 3), 60 minutes (Example 4), 40 minutes (Example 5), and 130 minutes (Example 6), respectively. For some of the carbon materials, polymer composites were prepared in the same manner as in Example 1, and the composite layer resistivity was measured.

[0202] Example 7 Carbon material A was prepared in the same manner as in Example 1, except that heat treatment was not performed. ０ Carbon material A was prepared and subjected to the same measurements as in Example 1. ０ A polymer composite material was prepared in the same manner as in Example 1 using the above, and the resistivity of the composite layer was measured.

[0203] Comparative Example 1 The oil absorption and other properties were measured and a polymer composite material was produced in the same manner as in Example 1, except that commercially available carbon black (DENKA BLACK Li-100, manufactured by Denka Co., Ltd.) was used as the carbon material.

[0204] Comparative Example 2: Alumina (Al ２ O ３ / PURALOX SBa200, particle size 7nm, BET specific surface area 202m ２ Carbon material G was obtained and a polymer composite was produced in the same manner as in Example 1, except that a carbon material (carbon dioxide, SiO2, SiO2 / g, manufactured by SASOL) was used and the CVD reaction time was set to 120 minutes. As will be described later, in carbon material G, the total pore volume, particularly the macropore volume, was larger than that of carbon materials A to F and A. ０ In other words, in carbon material G, the voids formed by the extension of the continuous structure are few, that is, the connected structure having an extended shape is smaller than those in carbon materials A to F and A. ０ Although the same operation as in Example 1 according to the manufacturing method of the present invention was carried out, it is believed that the carbonaceous layer-coated template material defined in the present invention was not sufficiently formed. For this reason, this example was selected as a comparative example.

[0205] Comparative Example 3: Magnesia (MgO / Kyowamag MF150, particle size 30 nm, BET specific surface area 129 m) was used as the raw material for the mold. ２Carbon material H was obtained by the same procedure as in Example 1, except that a carbon nanotube (C10 / g, manufactured by Kyowa Chemical Industry Co., Ltd.) was used, the CVD reaction time was set to 120 minutes, and the template removal operation was performed as follows. As will be described later, carbon material H also has a small total pore volume, particularly a small macropore volume, and the connected structure having an extended shape is formed in a manner similar to that of carbon materials A to F and A. ０ was not formed as in

[0206] (MgO template removal) 1-1.4 g of the laminate after the CVD reaction, approximately 100 g of hydrochloric acid (Fujifilm Wako Pure Chemical Industries, 5 mol / L), and a stir bar were added to a Teflon (registered trademark) beaker and stirred at room temperature for 5 hours. After that, the sample was filtered using a membrane filter (0.1 μm), washed five times with pure water, and then suction filtered. Care was taken to prevent the deposits from drying on the filter paper. Next, the deposits were placed in a glass beaker containing approximately 100 mL of acetone. The beaker was covered with aluminum foil and held in a vacuum dryer at 0.06 MPa for 2 minutes. After that, the pressure was returned to normal and the mixture was heated in a thermostatic chamber at 60°C for 10 minutes to perform acetone replacement. The supernatant liquid in the beaker was removed with a pipette, and the same acetone replacement procedure was repeated. The mixture was then dried under reduced pressure at 150°C for 6 hours to obtain carbon material H from which the template had been removed.

[0207]

[0208] As shown in Table 1, in Examples 1 to 7, the oil absorption was in the range of 703 to 2297 mL / 100 g, and carbon materials with an oil absorption of 550 mL / 100 g or more were obtained. The oil absorption of commercially available carbon black is about 300 mL / 100 g, even for acetylene black (Comparative Example 1), which is considered to be high among carbon materials. An oil absorption of 550 mL / 100 g or more is not achievable with ordinary carbon materials. The internal space of the carbon material of the present invention has a larger total pore volume (see Table 1) than the fine voids inside acetylene black, so carbon materials A to F and A ０ It is believed that the oil was absorbed more.

[0209] On the other hand, in Comparative Examples 2 and 3, the total pore volume was smaller than that in the Examples, suggesting that the carbonaceous layer-coated template material was not sufficiently formed during the carbon material preparation process. The oil absorption was also less than 550 mL / 100 g. Carbon materials with oil absorptions exceeding 700 mL / 100 g and even 2000 mL / 100 g, as in Examples 1 to 7, are clearly novel carbon materials.

[0210] In addition, carbon material A in Example 7 ０ I Ｄ / I Ｇ The graphene content was 1.72, indicating that the carbon material contained a relatively large amount of sp3 carbon. This indicates that even a carbon material that does not necessarily have a high degree of graphene conversion can exhibit a high oil absorption.

[0211] The polymer composite material containing the carbon material A etc. exhibited significantly lower composite layer resistivity than the composite material containing acetylene black etc. It was shown that the carbon material of the present invention having an oil absorption of 550 mL / 100 g or more can form a polymer composite material with excellent electrical conductivity.

[0212] Experiment 2: Confirmation of the basic physical properties of carbon materials (comparison of oil absorption amounts using different measurement methods)

[0213] <Comparative Examples 4 to 6> Three types of carbon black, the oil absorption of which is specified in JIS K6217-4 in their catalogs, were measured by a method in accordance with JIS K5101-13-1, and the results are shown together with the catalog values ​​based on the former JIS in Table 2. There was no significant difference in the oil absorption between the two measurement methods.

[0214]

[0215] Experiment 3: Analysis of carbon materials by nitrogen adsorption / desorption measurements (comparing specific surface area, pore volume, etc. with other carbon materials)

[0216] (Nitrogen adsorption / desorption measurement) Carbon materials A to F and carbon material A prepared in Examples 1 to 7 ０ The carbon black (DENKA BLACK Li-100: manufactured by Denka Co., Ltd.) used in Comparative Example 1 and the carbon materials G and H prepared in Comparative Examples 2 and 3 were subjected to nitrogen adsorption / desorption measurements by the method described above.

[0217] From the obtained adsorption / desorption isotherms, the BET specific surface area, mode pore diameter, total pore volume (relative pressure 0.99), micropore volume (relative pressure up to 0.1), mesopore volume (relative pressure 0.1 to 0.96), and macropore volume (relative pressure 0.96 to 0.99) were determined. The average pore diameter d was calculated from the BET specific surface area S and total pore volume V, assuming cylindrical pores, by d = 4V / S. The results are shown in Table 3. In Comparative Example 1, since there was no peak in the pore distribution, the column for "mode pore diameter" was entered as "-".

[0218] Comparative Examples 7 and 8 In addition to the above, nitrogen adsorption and desorption measurements were also carried out on the following carbon materials. The results are shown in Table 3. Note that, like Comparative Example 1, Comparative Example 7 also had no peak in the pore size distribution, and therefore the column for "mode pore size" was marked with "-".

[0219] Comparative Example 7: Graphite (KS6, manufactured by Imerys) Comparative Example 8: Activated carbon (YP-5, manufactured by Kuraray)

[0220] Furthermore, for each carbon material, the proportions of the micropore volume, mesopore volume, and macropore volume in the total pore volume were calculated and shown in Table 4.

[0221]

[0222]

[0223] From Table 3, carbon materials A to F of the present invention and carbon material A ０ has a large BET specific surface area (817-1145 m ２ / g) and a large total pore volume (2.95 cc / g or more) (Examples 1 to 7). On the other hand, for Comparative Examples 1, 7 and 8 shown in Table 4, the specific surface area was 800 m ２ / g or more was only the activated carbon of Comparative Example 8, but the total pore volume of the activated carbon of Comparative Example 8 was small, at 1.00 cc / g or less.

[0224] From Table 4, carbon materials A to F and A of the present invention ０It can be seen that carbon material No. 1 has a large modal pore diameter, a large specific surface area, a large total pore volume, and a large macropore volume, and is therefore a carbon material with unparalleled porosity. On the other hand, in carbon materials G and H, the proportion of the macropore volume to the total pore volume was low at less than 5%, and it is presumed that the connected structures having an extended shape were not sufficiently formed.

[0225] Experiment 4: Structural analysis of the carbonaceous layer in the carbon material (analysis of the carbonaceous layer of the carbon materials produced in the Examples and Reference Examples by X-ray analysis)

[0226] (XRD Measurement) X-ray diffraction (XRD) measurement was performed on the carbon material using an X-ray diffractometer (Miniflex 600, manufactured by Rigaku Corporation). A Si non-reflective plate was used as the sample stage, and the measurement sample was placed on the circular part. Measurement was performed under the following measurement conditions. The values ​​of d002 and Lc(002) are shown in Table 5 together with the Raman spectrum data.

[0227] X-ray source: CuKa Tube voltage: 40 kV Tube current: 15 mA Measurement angle: 5 to 90 deg Scan speed: 2 deg / min Scan axis: 2θ / θ

[0228]

[0229] The D band in the Raman spectrum is a band that indicates the sp3 bond (C-H stretching motion) of the carbon material, and increases when the sp2 bond in the carbon six-membered ring structure of the carbonaceous layer is broken to form an sp3 bond. ０ The carbonaceous layer is a layer in which crystalline and amorphous materials are mixed, which is thought to be the cause of the formation of large spaces.

[0230] Experiment 5: Determining the number of carbonaceous layers in carbon materials (examination of the relationship between the number of carbonaceous layers, pore size, and oil absorption capacity)

[0231] (Number of Carbonaceous Layers) The number of carbonaceous layers was calculated from the carbon weight reduction rate for Examples 1 to 7 and Comparative Examples 2 and 3, and the results are shown in Table 6 together with the manufacturing conditions.

[0232] Specifically, TGA measurement was performed to determine the number of layers. Using a STA-2500 (NETZSCH), the sample was heated to 900°C at a temperature increase rate of 5°C / min under a flow of argon gas (80 mL / min) and oxygen (20 mL / min), and then cooled at a temperature decrease rate of 20°C / min, followed by TG measurement. Blank measurements performed using empty pans under the same temperature profile conditions were subtracted. Alumina pans were used. The number of carbonaceous layers was calculated from the carbon weight reduction rate (%) determined by TG measurement as follows. The weight of the carbonaceous layer was calculated from the carbon weight reduction rate, and the weight of the carbonaceous layer per area was calculated from the weight of this carbonaceous layer and the surface area of ​​the template material. Next, the weight of the carbonaceous layer per area of ​​the template material was multiplied by the weight of the carbonaceous layer per area of ​​single-layer graphene (7.61 × 10 －４ g / m ２ ) to calculate the number of carbonaceous layers.

[0233]

[0234] From Table 6, carbon materials A to F and A of the present invention ０ It was confirmed that carbon materials with different properties can be obtained by controlling the number of carbonaceous layers so that it falls within a predetermined range. It was also found that the oil absorption of the carbon material tends to increase rapidly as the number of carbonaceous layers increases, and that the two are correlated (Examples 1 to 7, Comparative Examples 2 to 3).

[0235] As shown in Tables 4 and 6, carbon materials A to F and A each having 1.9 to 4.5 carbonaceous layers. ０ had a large volume of macropores of 50 nm or more and showed a high oil absorption.

[0236] Experiment 6: Analyzing the particle structure of carbon materials (particle size distribution measurement and TEM image analysis)

[0237] (Particle size distribution measurement) Particle size distribution was measured using a laser diffraction particle size distribution analyzer (MT3300EXII, manufactured by Microtrac Bell Co., Ltd.) to examine the aggregation state of the carbon material. The measurement sample was an unpulverized carbon material that had been immersed in ethanol for 9 minutes. D50, D10, D90, D90 / D10, and D90 / M in the particle size distribution curve were determined, and the results are shown in Table 7.

[0238]

[0239] Table 7 shows that the D50 values ​​of carbon materials A to F of the present invention are in the range of 26.0 to 45.0 μm. This indicates that the measurement samples were unground and simply immersed in a solvent, and the cohesive strength was not particularly high. Furthermore, although only (D90 / M) is shown in Table 7, the values ​​(D10 / M, D50 / M, D90 / M) obtained by dividing the cumulative particle size measured in the particle size distribution by the mode pore diameter (M) in the pore distribution measurement are all much smaller, indicating weak cohesive strength (comparison of Examples 1 to 6 with Comparative Examples 1 to 3 and 8).

[0240] Experiment 7: Measurement of desorbed gas and combustion temperature of carbon material (to estimate the stability of carbon material when used in batteries)

[0241] (Thermal Desorption Gas Analysis) Using an ultra-sensitive vacuum TPD instrument (developed at Tohoku University, see T. Ishii et al., CARBON 80, 2014, pp. 135-145) with the configuration shown in FIG. 5 , oxygen-containing functional groups and hydrogen-terminated edge sites were accurately qualitatively and quantitatively analyzed. More specifically, 1 to 3 mg of each carbon material was placed on a graphite sample stage, heated in vacuum to 1800°C at a heating rate of 10°C / min, and the gases released during heating were analyzed by mass spectrometry to accurately qualitatively and quantitatively analyze the oxygen-containing functional groups and hydrogen-terminated edge sites. The instrument 50 included a quartz reactor equipped with a radioactive thermometer 41, a sample holder 42, and a high-frequency induction coil 43, as well as a detection unit connected to the quartz reactor. The detection unit included a gas reservoir, a turbomolecular pump (TMP), a rotary pump (RP), a cold cathode Pirani gauge (P1), and a capacitance gauge (P2).

[0242] (Combustion Temperature Measurement) The combustion temperature of the carbon material was determined as the temperature at which the weight of the carbon material became 90% of the initial weight in a combustion oxidation test performed using a thermogravimetric analyzer under air flow at a temperature increase rate of 5°C / min. A combustion temperature of 550°C or higher was determined to be good.

[0243] The desorbed gas and combustion temperature of the carbon material were investigated, and the results are shown in Table 8.

[0244]

[0245] From the results shown in Table 8, it was confirmed that the carbon materials A to F of the present invention have sufficiently low oxygen contents, O / C ratios, total gas amounts, and edge amounts determined by TPD-MS measurement. It was also confirmed that the carbon materials of the present invention have sufficiently high combustion temperatures.

[0246] (Apparent Density) The apparent density of each carbon material was calculated using the total pore volume and true density according to the following formula (8).

[0247] Apparent density (g / cc)=1 / (total pore volume+(1 / true density)) Equation (8)

[0248] The total pore volume (cc / g) was calculated at a relative pressure of 0.99, and the true density was calculated using the graphite value of 2.2 g / cc. The results are shown in Table 9.

[0249]

[0250] From the results shown in Table 9, it was confirmed that the carbon material of the present invention has a lower apparent density than the comparative examples, and that the apparent density is preferably 2.000 g / cc or less, more preferably 1.500 g / cc or less, 1.000 g / cc or less, 0.500 g / cc or less, and 0.300 g / cc or less, and is more preferably 0.050 g / cc or more, 0.100 g / cc or more, and 0.150 g / cc or more, in that order.

[0251] Experiment 8: Fabrication of Lithium-ion Batteries Lithium-ion secondary batteries containing various carbon materials were fabricated using the composite samples fabricated as in Example 1 as positive electrodes (electrodes). The polymer composites used to fabricate the composite samples in Example 1 and elsewhere can be used as battery compositions or (positive electrode) electrode composites, and the slurries can be used as electrode slurries.

[0252] (Fabrication of Lithium-ion Battery) The above-mentioned positive electrode and metallic Li punched to a diameter of 16 mm in a glove box under an argon gas atmosphere were used, and a 25 μm-thick separator (a microporous polypropylene film) was sandwiched between the positive electrode mixture layer and metallic Li, and a 1M LiPF ６A solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC)) was added as an electrolyte, and the battery was sealed by crimping to prepare a 2032 size coin-type test battery. The battery was then washed with ethanol and subjected to the battery evaluation described below.

[0253] The battery performance was evaluated using the prepared test battery according to the following procedure, and the 2C retention rate, charge capacity, discharge capacity, and coulomb rate were determined.

[0254] (Positive electrode evaluation method) At room temperature (25 ° C.), a constant current of 1.25 mA (equivalent to 0.2 C) was applied per test battery from the open circuit voltage to 4.2 V (constant current charging), and after reaching 4.2 V, constant voltage charging was performed. Charging was continued until the current reached 0.31 mA (0.05 C). Then, the battery was discharged at a constant current of 1.25 mA to 3.0 V. The charge capacity, discharge capacity, and average voltage at this time were determined, and the coulomb rate ((discharge capacity ÷ charge capacity) × 100) (%) was calculated. Next, using the same test battery, a constant current of 1.25 mA (equivalent to 0.2 C) was applied from the open circuit voltage to 4.2 V (constant current charging), and after reaching 4.2 V, constant voltage charging was performed. Charging was continued until the current reached 0.31 mA (0.05 C). Then, the battery was discharged at a high rate of 12.5 mA (equivalent to 2 C) to 3.0 V. The 2C retention rate ((2C capacity ÷ 0.2C capacity) × 100) (%) of each test battery was calculated from the discharge capacity of the test battery obtained. The results are shown in Table 10 together with the data on oil absorption, etc.

[0255]

[0256] The 2C retention rate of battery performance is an evaluation item that measures the possibility of high-speed discharge of the battery. ０ The 2C retention rate of the battery was significantly higher than those of Comparative Examples 1 to 3. It was also revealed that the 2C retention rate of battery performance correlates to some extent with the oil absorption rate of the carbon material, and that the 2C retention rate increases when a carbon material having an oil absorption of 550 mL / 100 g or more, particularly 700 mL / 100 g or more, is used. It was also revealed that the 2C retention rate correlates to some extent with the total pore volume of the carbon material.

[0257] 50 Apparatus 41 Radioactive thermometer 42 Sample holder 43 High frequency induction coil TMP Turbo molecular pump RP Rotary pump P1 Cold cathode Pirani gauge P2 Capacitance gauge

Claims

1. A carbon material having an oil absorption amount of 550 mL / 100 g or more as measured in accordance with JIS K5101-13-1:2004.

2. The carbon material according to claim 1, comprising one or more connected structures having an extended shape in which a plurality of hollow particulate portions formed of a carbonaceous material including a graphene structure and partitioning an internal space are connected in a bead-like manner, and pores are formed in the connected structure.

3. In Raman spectroscopic measurement, the intensity ratio (I ２Ｄ / I Ｇ ), of the intensity (I Ｇ ) of the G band to the intensity (I ２Ｄ ) of the 2D band is in the range of 0.4 to 5.

0. The carbon material according to claim 1.

4. The carbon material according to claim 1, wherein the modal pore diameter ranges from 1 to 100 nm.

5. The carbon material according to claim 1, wherein the total pore volume ranges from 0.1 to 20 cc / g.

6. The carbon material according to claim 5, wherein the ratio of the macropore volume to the total pore volume is 5% or more.

7. The carbon material according to claim 1, having an apparent density of 2 g / cc or less.

8. The carbon material according to claim 1, wherein the BET specific surface area is in the range of 100 to 2700 m ２ / g.

9. The carbon material according to claim 1, wherein the size Lc(002) of crystallites in the c-axis direction, measured by X-ray diffraction (XRD), ranges from 0.1 to 5 nm.

10. The carbon material according to claim 1, wherein the interplanar spacing d002 of the (002) plane, measured by X-ray diffraction (XRD), is 3 to 5 Å.

11. The carbon material according to claim 1, having a median diameter D50 in the particle size distribution measurement by the laser diffraction / scattering method of 1 to 100 μm.

12. The carbon material according to claim 1, wherein the ratio (D90 / D10 ratio) of D90 to D10 in the particle size distribution measurement by the laser diffraction / scattering method is 100 or less.

13. The carbon material according to claim 1, wherein the ratio (D90 / M ratio) of D90 to the modal pore diameter M in the particle size distribution measurement by the laser diffraction / scattering method is 50000 or less.

14. The carbon material according to claim 1, wherein the carbon material is a graphene mesoporous sponge.

15. The carbon material according to claim 1, which is for a secondary battery.

16. In a method for producing a carbon material according to any one of claims 1 to 15, a removing step of removing the mold material from a carbonaceous layer-coated mold material composed of a mold material that is an aggregate in which a plurality of primary particles are aggregated and connected in a bead-like manner and a carbonaceous layer formed so as to coat the surface of the mold material to form a carbon material precursor. A method for producing a carbon material.

17. In the method for producing a carbon material according to any one of claims 1 to 15, a carbonaceous layer-coated mold material composed of a mold material in which a plurality of primary particles are aggregated in a bead-like manner and connected in a series, and a carbonaceous layer formed so as to cover the surface of the mold material, a removal step of forming a carbon material precursor by eluting and removing the mold material by acid treatment; By heat-treating the carbon material precursor, a plurality of hollow particle-shaped portions formed of a carbonaceous material including a graphene structure and partitioning an internal space are connected in a bead-like manner, and one or more connection structures having an extending shape are provided. A heating step of obtaining a carbon material in which pores are formed in the connection structure. A method for producing a carbon material, comprising:

18. The method for producing a carbon material according to claim 17, wherein the mold material is composed of one or more particles selected from the group consisting of ceramic particles and carbonate particles.

19. A dispersion obtained by dispersing the carbon material according to any one of claims 1 to 15 in a dispersion medium.

20. An electrode composition comprising the carbon material according to any one of claims 1 to 15, an active material, and a binder.

21. An electrode slurry obtained by dispersing the electrode composition according to claim 20 in a solvent.

22. An electrode comprising the carbon material according to any one of claims 1 to 15.

23. A lithium ion secondary battery comprising the carbon material according to any one of claims 1 to 15.

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