Carbon material

Abstract

The present invention provides a carbon material, such as graphene and a graphene mesosponge, in which an internal space is formed inside the carbon material and in which pores are formed in the carbon material to increase the specific surface area, in order to improve electron conductivity or ion conductivity and suppress a reduction in mechanical strength. A carbon material 1 according to the present invention comprises a plurality of hollow particle-like sections 21 that are each formed by a surrounding wall 22 which defines an internal space 23 and which comprises a carbonaceous material including a graphene structure, said carbon material 1 comprising one or more connection structures 2 having an extending shape in which the plurality of hollow particle-like sections 21 are connected in the form of a string of beads, wherein pores are formed in the connection structures 2.

Description

Carbon material

[0001] The present invention relates to a carbon material.

[0002] Carbon bonds three-dimensionally to form a diamond structure and becomes an insulator. Also, when carbon bonds two-dimensionally to form a hexagonal network structure, it becomes conductive because there are electrons that do not participate in the bonding. Furthermore, carbon is chemically and electrochemically stable and is widely used industrially. Moreover, it is known that actual carbon takes various structures depending on the raw material and manufacturing method. In fact, various carbon structures include crystalline structures such as fullerenes, carbon nanotubes, graphene, and graphene meso sponges, and may also have a particulate or fibrous shape.

[0003] In particular, carbon materials are excellent in thermal conductivity, electron conductivity, and mechanical strength, and are being studied for applications in various fields such as electronics and energy materials. Among them, porous carbon materials such as graphene and graphene meso sponges can improve conductivity such as electron conductivity and ion conductivity by increasing the number of conductive paths due to their large specific surface area. Also, carbon materials have a space and pores inside surrounded by a connected structure body, so that an electrolyte solution in which lithium ions are dissolved can penetrate and be retained, and they are excellent in ion conductivity during the reaction. Therefore, in recent years, active research has been conducted as electrodes and peripheral materials for energy device applications such as batteries and capacitors. However, there is still a problem that the specific surface area and pore size are not sufficient for improving electron conductivity and ion conductivity. Also, it is required to improve electron conductivity and ion conductivity by increasing the specific surface area including pores by connecting the internal space surrounded by the connected structure body to the external space. In addition, it is required to improve electron conductivity and ion conductivity by increasing the specific surface area including pores by using not only particulate carbon materials but also sheets, tubes, etc. having the same graphene structure.

[0004] For example, Patent Document 1 discloses a plurality of carbon nanoparticles containing graphene, having a median diameter of 0.1 to 50 μm and a BET specific surface area of 50 to 2,00〖0m〗２ It has been disclosed that carbon materials with a conductivity of 500 to 20,000 S / m at a compression of 12,000 psi, and containing pores of 0.1 to 10 nm and pores of 10 to 100 nm are used in lithium-ion secondary batteries. Furthermore, Patent Document 2 discloses a carbon material in which, in the X-ray diffraction spectrum, no peak originating from the (002) plane of carbon is observed, or the full width at half maximum of the peak originating from the (002) plane of carbon is 5° or more, and the full width at half maximum of the peak originating from the (10) plane of carbon is 3.2° or less. Furthermore, Patent Document 3 discloses a method for producing a carbon material, which includes a coating step of forming a precursor containing graphene on the surface of a mold made of alkaline earth metal oxide nanoparticles, and a separation and removal step of dissolving the mold with a fluorine-free acid to separate the mold and the precursor.

[0005] However, Patent Document 1 states that the maximum BET specific surface area of ​​the carbon material actually manufactured in the example is 85.9 m². ２ The carbon material is produced explosively using microwave plasma with a residence time of 0.001 to 2.0 seconds for the raw material gas, resulting in virtually no pores being formed. Therefore, lithium-ion secondary batteries using the carbon material produced here are known to have poor electronic conductivity and insufficient rapid discharge, capacity, and charge / discharge characteristics. Patent document 2 states that a shell-like structure formed from approximately 5 to 7 layers of carbon network surfaces was confirmed from measurements of the carbon material using a transmission electron microscope (TEM). However, it does not describe that the shell structures communicate to form spaces, making it clear that the individual carbon materials are separated. Patent document 3 discloses that the pores of the carbon material have pore walls formed by graphene, and that adjacent pores may communicate, and multiple pores may communicate. However, it does not describe that the internal spaces formed by graphene in the carbon material are interconnected. Therefore, even with a large specific surface area, there is a problem of low electronic and ionic conductivity.

[0006] Japanese Patent Publication No. 2022-191280, Japanese Patent Publication No. 6460448, Japanese Patent Publication No. 2021-084891

[0007] Therefore, the present invention has been made in view of these circumstances, and aims to provide a carbon material that improves electronic and ionic conductivity and has a low composite layer resistance when applied to an electrode, by providing a connected structure having a specific structure in which the internal space is partitioned, for example, like a communicating space, and in which pores of a specific size are mainly formed. Furthermore, the present invention aims to provide a carbon material in which the specific surface area is further increased to improve electronic and ionic conductivity, even in a connected structure having an internal space. Furthermore, the present invention aims to provide a carbon material that increases mechanical strength and improves electronic and ionic conductivity by arranging fibrous carbon material in addition to particulate carbon material.

[0008] To solve the above problems, the inventors conducted diligent research and developed a connected structure having an extended shape in which hollow particulate portions are linked together in a bead-like fashion as a surrounding wall made of carbonaceous material containing graphene. The present invention was completed by providing a carbon material comprising one or multiple connected connected structures, in which pores are formed in the connected structure. The features of the present invention are listed below.

[0009] (1) A carbon material comprising one or more connected structures having an extended shape in which a plurality of hollow particulate portions, formed by surrounding walls made of carbonaceous material including a graphene structure, are linked together in a bead-like manner, and pores are formed in the connected structures. (2) The carbon material according to (1) above, wherein the pores are divided into micropores of less than 2 nm, mesopores of 2 nm to 50 nm, and macropores of more than 50 nm, and the mesopores are further divided into first mesopores of 2 nm to 10 nm and second mesopores of more than 10 nm to 50 nm, the percentage of the volume of the second mesopores (second mesopore volume) to the total volume (total mesopore volume) formed by the mesopores in the range of 2 nm to 50 nm is 50% or more. (3) The carbon material is the volume percentage V of the total volume formed by the mesopores (total mesopore volume) M2, which is the sum of the total volume of the micropores (total micropore volume) M1 and the total mesopore volume M2. Ｍ２is the carbon material according to (2) above, with a content of 82.0% or more. (4) The carbon material divides the pores into first pores in the range of 10 nm or less and second pores in the range of more than 10 nm, and when the total pore volume of the pores is divided into the volume of the first pores (first pore volume) and the volume of the second pores (second pore volume), the percentage of the second pore volume in the total pore volume is 50% or more, which is the carbon material according to (1) above. (5) The carbon material is composed of the plurality of connected structures, and a part of the hollow particle portions constituting the plurality of connected structures is connected to form a communication space in which the internal spaces of the plurality of connected structures communicate with each other, which is the carbon material according to (1) above. (6) The carbon material has an opening formed in one or more of the plurality of hollow particle portions constituting the connected structure, through which the internal space communicates with the external space, which is the carbon material according to (1) above. (7) The carbon material further includes a fibrous portion, and the connected structure and the fibrous portion are formed by being mixed and integrated or being close to each other, which is the carbon material according to (1) above. (8) The carbon material is formed of a carbonaceous layer in the range of 1 or more and 6 or less layers for the surrounding wall, which is the carbon material according to (1) above. (9) The carbon material is such that in Raman spectroscopic measurement, the intensity ratio (I ２Ｄ / I Ｇ ), of the intensity of the G band (I Ｇ ) with respect to the intensity of the 2D band (I ２Ｄ ) is in the range of 1.00 or more and 5.0 or less, which is the carbon material according to (1) above. (10) The carbon material is such that the average primary particle diameter forming the connected structure is in the range of 20 nm or more and 200 nm or less, which is the carbon material according to (1) above. (11) The carbon material is such that the average pore diameter of the pores formed in the connected structure is in the range of 8 nm or more and 100 nm or less, which is the carbon material according to (1) above. (12) The carbon material is such that the total pore volume of the pores is in the range of 2.5 cc / g or more and 20.0 cc / g or less, which is the carbon material according to (1) above. (13) The carbon material is such that the BET specific surface area is in the range of 100 m ２ / g or more and 2700 m ２ / g or less, which is the carbon material according to (1) above.

[0010] According to the present invention, by providing a connecting structure having a specific structure in which the internal space is partitioned, for example, like a communicating space, and in which pores of a specific size are mainly formed, it is possible to provide a carbon material that improves electronic conductivity and ionic conductivity and has a low composite layer resistance when applied to an electrode.

[0011] Figure 1 shows graphene formed by a six-membered ring that constitutes the carbon material of the present invention. Figure 2 shows an example of a Raman spectrum measured for the carbon material of the present invention. Figure 3 shows four classifications of the carbon material's existence forms: branched, linear, spherical, and elliptical. Figure 4 shows the branched form among the four types of existence forms of the linked structure constituting the carbon material of the present invention. Figure 5 shows the linear form among the four types of existence forms of the linked structure constituting the carbon material of the present invention. Figure 6 is a photograph showing an example of an SEM image of the carbon material of the present invention observed with a scanning electron microscope (SEM). Figure 7 is a photograph showing an example of an SEM image of the carbon material of the present invention observed with a scanning electron microscope (SEM). Figure 8 is a schematic diagram illustrating the ultra-high sensitivity vacuum temperature-controlled desorption mass spectrometer used for temperature-controlled desorption mass spectrometry of the carbon material of the present invention. Figure 9 is a photograph showing an example of a TEM image of the carbon material of the present invention observed with a transmission electron microscope (TEM).

[0012] The carbon material according to the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the embodiments and examples described below. Various design modifications within the scope of the present invention are included in the present invention.

[0013] The carbon material according to the present invention comprises hollow particles having a surrounding wall made of carbonaceous material containing graphene that partitions an internal space, wherein the hollow particles form a linked structure having an extended shape in which they are linked together in a bead-like manner, and the carbon material is composed of one linked structure or a plurality of linked linked structures, and pores are formed in the linked structure. Figure 1 shows graphene formed by a six-membered ring that forms the carbon material of the present invention.

[0014] (Carbon Material) The carbon material of the present invention can improve conductivity by possessing the electronic conductivity of graphene 11 and the ability to retain chemical substances and possess ionic conductivity due to its large pore volume, and can also improve ion supply by retaining and appropriately supplying ions due to its large pore volume. Furthermore, due to these properties, it can exhibit a function that assists the battery reaction in lithium-ion secondary batteries. In addition, one embodiment of the carbon material of the present invention is a connected structure in which hollow granular parts covered with a surrounding wall made of carbonaceous material containing graphene 11 are connected, and by having a communication space inside surrounded by the hollow granular parts and the connected structure, it can contribute to good electronic conductivity and ion supply.

[0015] The carbon material of the present invention is a sheet-like material of sp2-bonded carbon, in which the carbon has a six-membered ring structure, and further possesses a graphene structure in which the six-membered ring structures are linked in a network structure. Perfect graphene 11 consists only of six-membered rings, and everything outside of the six-membered rings becomes a lattice defect. The presence of a graphene structure in which the carbon six-membered ring structure is linked in a network structure can also be confirmed by Raman spectroscopy.

[0016] (Graphene crystal structure) The carbon material has a surrounding wall with a graphene crystal structure. Such a crystal structure is, for example, the intensity ratio of the G band to the 2D band in Raman spectroscopy measurements I Ｇ / I ２Ｄ This can also be confirmed by checking if the value becomes 0.2 or higher.

[0017] Here, Figure 2 shows an example of a Raman spectrum measured for the carbon material of the present invention. An example of a Raman spectrum measured for the carbon material is shown. The Raman spectrum shows a wavenumber of 1593 cm⁻¹. －１ The peak in the surrounding region is called the G band, and this band represents the sp2 bond (aromatic ring C=C stretching motion) in carbon materials. This is the Raman spectrum at wavenumber 1356 cm⁻¹. －１ The peak present in the vicinity is called the D band, which represents sp3 bonding (C-H stretching motion) in carbon materials. This band increases when sp2 bonds in the six-membered carbon ring structure of the carbonaceous layer are broken and replaced with sp3 bonds. This occurs at wavenumber 2680 cm⁻¹ in the Raman spectrum. －１The peaks in the surrounding region are called 2D bands, and they are bands that exhibit second-order phonon scattering (C-H stretching motion), and they represent the number of layers of carbon material.

[0018] Intensity ratio of the G-band to the 2D-band of a carbon material I Ｇ / I ２Ｄ This is said to reflect the stacking state of graphene 11 (D. Graf et al., NANO LETTERS, 7, 238-242, 2007). Therefore, I Ｇ / I ２Ｄ This is sometimes called the "layering index." The paper states that when the (G / 2D) intensity ratio is 0.2, graphene 11 forms one layer.

[0019] The intensity ratio of the G band to the 2D band in carbon materials (I Ｇ / I ２Ｄ The I of the carbon material is preferably in the range of 1.00 to 5.0, and may also be in the range of 1.10 to 4.50, 1.20 to 4.00, 1.30 to 3.57, 1.40 to 3.00, or 1.43 to 2.08. Ｇ / I ２Ｄ When the value of is within this range, the mechanical strength properties and elastic deformability are highly balanced by maintaining the hollow structure (internal space) of the carbon material, and desired properties such as rapid discharge, capacity characteristics and durability can be greatly improved when used as a conductive material in lithium-ion secondary batteries, for example. The carbon material of the present invention has an internal space, and the surrounding wall deforms in response to external pressure, and it has deformability through elastic deformation. In particular, the strength ratio (I) of the carbon material Ｇ / I ２Ｄ The fact that the ratio is in the range of 1.00 to 5.00 allows for a balance between mechanical strength and elastic deformability, unlike a simply rigid graphite structure. Furthermore, the carbon material of this application has pores and openings, which in particular allows it to absorb energy when subjected to pressure, and then exhibits elastic deformability that returns it to its original state when the compressive pressure is released.

[0020] Furthermore, the strength of the G band in the carbon material of this embodiment (I ＧThe intensity ratio of the D-band intensity to (I Ｄ / I Ｇ The I of the carbon material 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, even more preferably in the range of 1.2 to 2.5, and particularly preferably in the range of 1.57 to 2.00. Ｄ / I Ｇ When this range is reached, the sp2 and sp3 orbitals of the carbon material are in an optimal state, the electron conduction path and ion conduction path are highly balanced, and for example, the rapid discharge performance, capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries can be further enhanced. Ｄ / I Ｇ This is sometimes referred to as the "amorphous index" below.

[0021] The carbon material may be either graphene mesoponge (GMS) or carbon mesoponge (CMS), or both. Here, graphene mesoponge is a porous carbon material having the crystalline structure of graphene, or a porous carbon material. Carbon mesoponge is a porous carbon material similar to GMS, except that the surrounding walls constituting the sponge do not have, or have very little of, the crystalline structure of graphene.

[0022] (Number of carbonaceous layers) The carbon material of the present invention has both elastic and plastic deformability properties because it contains carbonaceous material including graphene. The carbon material of the present invention has been found to have the property of returning to its original state without permanent deformation under weak stress, that is, the property of having a large amount of work done in elastic deformation. In the carbon material of the present invention, the portion consisting of one or more layers of graphene exhibits elastic deformability, while the defective portions of graphene and amorphous carbon portions exhibit plastic deformability. On the other hand, if the carbonaceous material containing graphene has an excessive number of carbonaceous layers (such as graphite), it will maintain elastic deformation within a certain stress range, but when a predetermined threshold is exceeded, it will suddenly undergo plastic deformation, and the particle shape and linkage shape may be destroyed.

[0023] Therefore, in order to maintain high elastic deformability, the number of carbonaceous layers containing graphene in the carbon material of the present invention is one or more, preferably two or more. Furthermore, in order to maintain mechanical strength within the range where plastic deformation does not occur, the number of carbonaceous layers containing graphene is six or less, preferably five or less. When the number of carbonaceous layers containing graphene is within this range, the carbon material of the present invention exhibits excellent mechanical strength properties and elastic deformation, and can maintain the surrounding wall of hollow particles. The number of carbonaceous layers containing graphene that form the surrounding wall introduced to the surface of the mold material can be appropriately selected by the CVD reaction time, but the flow rate of the carrier gas can be adjusted to form a thin layer of carbonaceous material containing graphene. Furthermore, the amount of organic compound contained in the carrier gas can be adjusted to form a thick film of carbonaceous material containing graphene.

[0024] (Method for measuring the number of carbonaceous layers containing graphene) The number of carbonaceous layers containing graphene in the carbon material of the present invention is determined by first forming graphene on mold particles, then calculating the weight of the carbonaceous layers using thermogravimetric analysis (TG) or the like, calculating the weight of the carbonaceous layers per mold area from the weight of the carbonaceous layers containing graphene and the BET specific surface area of ​​the mold particles, and using this as the weight of carbon per unit area of ​​single-layer graphene (7.61 × 10⁻¹⁰). －４ g / m ２ This value is calculated by dividing by ( ).

[0025] (Hollow Particulate Section) The carbon material of the present invention comprises a hollow particulate section in which an enclosing wall made of carbonaceous material containing graphene partitions the internal space. The enclosing wall made of carbonaceous material containing graphene, which is composed of carbon, partitions the interior and forms an internal space by forming a shell structure. The formation of a space inside the carbon material of the present invention can be observed by transmission electron microscopy. Here, the inner diameter of the particles in the internal space of the hollow particulate section surrounded by the enclosing wall made of carbonaceous material containing graphene has a lower limit of at least 2 nm, 5 nm, and 20 nm, with 40 nm or more being the most preferred. The upper limit is 300 nm or less, 150 nm or less, more preferably 100 nm or less, and further, within the range of 50 nm or less. The inner diameter of the particles in the internal space of this hollow particulate section can be determined using the mode pore diameter. Furthermore, the outer diameter (primary particle diameter) of the primary particles forming the hollow particulate portion of the carbon material of the present invention can be determined by adding twice the value obtained by multiplying the average number of layers n by the interplanar spacing of the (002) plane to the mode pore diameter. Alternatively, the primary particle diameter may be determined by TEM image analysis or the like. The average primary particle diameter is in the range of 20 nm to 200 nm. If the average primary particle diameter is less than 20 nm, for example, the specific surface area becomes small, and the electronic conductivity and ion density decrease. If the average primary particle diameter exceeds 200 nm, the mechanical strength decreases, and cracking and breakage may occur. As a lower limit for the average primary particle diameter of the carbon material of the present invention, it is preferable to be at least 5 nm, 10 nm, or 20 nm. As an upper limit, it is 200 nm or less, 150 nm or less, more preferably 100 nm or less, and further, within the range of 50 nm or less. Note that the inner diameter of the hollow particulate portion in the carbon material of the present invention can be considered to be the same as the mode pore diameter obtained from nitrogen adsorption measurement. Furthermore, the primary particle size can be determined by methods such as TEM image analysis.

[0026] (Internal Space) Furthermore, the carbon material of the present invention has an internal space in the hollow particulate portion, which increases the specific surface area. In addition, the hollow particulate portion has an increased surface area, which increases the number of conductive paths through which electrons flow, thereby improving electronic conductivity. Furthermore, the large internal space allows for the retention and appropriate supply of ions, thereby improving ion supply. For example, when incorporated into the electrodes of a battery, electrolyte can enter these internal spaces and voids, increasing the volume of the internal space formed by the surrounding walls of the hollow particulate portion, and thus increasing the amount of electrolyte that can be retained. As a result, for example, it is possible to enhance the electronic conductivity of the carbon material and impart high ionic conductivity with a structure that can retain a large amount of electrolyte, thereby greatly improving the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0027] The carbon material of the present invention was observed for its shape using a transmission electron microscope (TEM: H-7650, manufactured by Hitachi High-Technologies Corporation). The observation of the carbon material using a transmission electron microscope (TEM) was performed, for example, at an acceleration voltage of 100 to 1000 kV. It was confirmed that the carbon material of the present invention has a structure in which hollow particulate portions having an internal space surrounded by a carbonaceous enclosing wall are connected.

[0028] The carbon material of the present invention, when used as part of an electrode material for secondary batteries such as lithium-ion batteries, can improve charge-discharge characteristics while maintaining good characteristics such as charge capacity and discharge capacity. For example, when it has a linear form in which hollow particulate portions are linked in series, it is thought that it can flexibly entwine with the active material of the battery material, forming a conductive path, and that the curved shape of the linked portion and the internal space of the hollow particulate portion contribute to increased supply of electrolyte containing ions, thereby improving rapid charge-discharge characteristics and maintaining good characteristics such as charge capacity and discharge capacity.

[0029] (Connected Structure) The carbon material of the present invention forms a connected structure having an extended shape in which hollow particulate parts are connected in a bead-like manner. Bead-like means a state in which many spheres are connected as if threaded through holes in spheres. In order to connect in a bead-like manner, the connected structure has an appearance in which multiple hollow particulate parts are connected and aggregated in a continuous manner. Furthermore, extended means existing in a direction that extends. Therefore, the extended shape refers to a shape in which hollow particulate parts exist connected in a bead-like manner. There may be a constricted portion at the joint portion of adjacent hollow particulate parts. For example, when two hollow particulate parts are joined together, they take on a peanut shell-like shape or a dumbbell-like shape. Multiple such hollow particulate interiors are combined and further connected to form a connected structure.

[0030] (Communication Space) Each hollow particulate portion 21 has a surrounding wall 22 made of carbonaceous material including graphene, which has a hollow internal space 23, as shown in Figures 4 and 5 described later. The internal spaces 23 of adjacent hollow particulate portions 21 along a straight line communicate with each other to form a communication space 25. This communication space 25 does not form a single space with all the hollow particulate portions 21 that make up the connecting structure 2. The presence of a surrounding wall 22 at the connection point between hollow particulate portions 21 does not prevent the internal spaces 23 from including parts that do not communicate. However, it is sufficient that at least a part of the connecting structure 2, for example, at least two hollow particulate portions 21, communicate to form a communication space 25. It is preferable that the communication space 25 in the connecting structure 2 connects all the hollow particulate portions 21. The length of the connecting space 25, which consists of multiple connected hollow particulate portions 21 having an internal space 23, is preferably such that five or more hollow particulate portions 21 are connected along the longitudinal direction. For example, it may be 1 nm or more, preferably 10 nm or more, or within the range of 0.01 μm to 100 μm, 0.05 μm to 80 μm, or 0.1 μm to 50 μm. This increases the number of paths for electron flow, thereby improving the conductivity in terms of electronic and ionic conductivity.

[0031] In this way, by applying both the front and back surfaces of the carbonaceous material containing graphene that forms the surrounding wall 22 of the communication space 25, the specific surface area is increased. Furthermore, the pores formed in the surrounding wall 22 also increase the specific surface area on the surface, and the back surface of the pores within the communication space 25 also increases the specific surface area within the space, allowing them to be used as electron conduction paths. In addition, by applying both the front and back surfaces of the carbonaceous material containing graphene in the hollow particulate portion 21 and the pores, a large surface area is obtained, making it easy to retain and supply ions and improving ion supply performance.

[0032] (Pores) The carbon material of the present invention has pores. The pores are formed in the internal space of the hollow particulate portion of the carbon material of the present invention and have a carbonaceous material containing graphene similar to the surrounding wall. The surrounding wall can be formed by creating a carbonaceous material containing graphene on the surface of metal oxides such as silica oxide, alumina, titania, and calcium carbonate using a dry method such as CVD. Pores are formed on the surface of silica, alumina, etc. At this time, the pores are formed so that the silica, etc. having these pores can be used as a mold.

[0033] Furthermore, the pores are formed from carbonaceous material containing graphene. The internal space of the hollow particulate portion also becomes part of the pores, increasing the specific surface area. By increasing the specific surface area of ​​the carbon material composed of graphene through these pores, the electronic and ionic conductivity can be improved. Moreover, the carbon material of the present invention can improve ionic conductivity by retaining and supplying ions through the large volume of pores. The carbon material of the present invention has a connection between the internal and external space of the hollow particulate portion. This allows the mold particles to be dissolved and discharged to the outside. As described above, the carbon material of the present invention has pores in the surrounding wall made of carbonaceous material containing graphene, which forms a larger specific surface area, increases the number of conductive paths, lowers electrical resistance, and improves conductivity.

[0034] The pores in the carbon material of the present invention form spaces within which the pore volume corresponds to that of the template particles. The International Union of Pure and Applied Chemistry (IUPAC) defines pores with a diameter of less than 2 nm as micropores, pores with a diameter of 2 nm to 50 nm as mesopores, and pores with a diameter greater than 50 nm as macropores. Furthermore, the average pore diameter (4V / SA) calculated from the BET specific surface area (SA) and total pore volume (V) of the carbon material of the present invention is preferably in the range of 8.0 nm to 100 nm, preferably 10 nm to 90 nm, more preferably 12 nm to 80 nm, even more preferably 15 nm to 70 nm, and most preferably 20 nm to 55 nm. When the average pore diameter of the carbon material of the present invention is within this range, it is suitable for achieving high electronic and ionic conductivity and improving electrical conductivity. Moreover, by setting the pores within this range, a decrease in the mechanical strength of the carbon material of the present invention can be suppressed.

[0035] The mode pore diameter (M) in the pore distribution of the carbon material of the present invention is the peak top value in the pore distribution curve, and is preferably in the range of 1 nm to 500 nm, or 5 nm to 100 nm, 10 nm to 50 nm, 15 nm to 40 nm, or 15 nm to 30 nm. When the peak top pore diameter of the pore distribution of the carbon material of the present invention is within this range, it is preferable to achieve high electronic conductivity and ionic conductivity.

[0036] The total pore volume V of the carbon material of the present invention is 2.5 cc / g or more, preferably 2.75 cc / g or more, and more preferably 3.00 cc / g or more. The upper limit of the total pore volume V is preferably 20 cc / g or less, or preferably 15 cc / g or less, 10 cc / g or less, 8 cc / g or less, 7 cc / g or less, 6.1 cc / g or less, or 5.7 cc / g or less. If the total pore volume of the carbon material of the present invention is excessively large, the mechanical strength of the pore structure weakens, making it difficult to maintain the particle shape of the hollow particulate portion. If the total pore volume is excessively small, the amount of electrolyte containing ions held within the particle shape of the hollow particulate portion tends to decrease. When the total pore volume is within the above range, the particle shape of the hollow particulate portion has appropriate strength, contributing to particle shape stability and maintaining the shape. As a result, a good balance between electronic conductivity and ionic conductivity can be maintained. Furthermore, when the total pore volume V is between 2.5 cc / g and 20.0 cc / g, the micropore volume is simultaneously kept within the range of 0.50 cc / g or less. A small micropore volume allows for a good balance between electronic and ionic conductivity, while the particle shape of the hollow particulate portion has appropriate strength, contributing to particle shape stability.

[0037] The micropore volume of the carbon material of the present invention is preferably 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, with a pore diameter of less than 2 nm (total micropore volume) M1. The lower limit is preferably 0.01 cc / g or more, or within the range of 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 will be poor, and conversely, if it is excessively small, the strength characteristics of the carbonaceous layer containing graphene tend to be poor.

[0038] The proportion of the micropore volume (total micropore volume) M1 of the carbon material of the present invention is the proportion of pores with a size of less than 2 nm in the total pore volume V, preferably 20% or less, or preferably 15% or less, 12% or less, 10% or less, or 9% or less. The lower limit is preferably 2% or more. If the proportion of the micropore volume of the carbon material of the present invention is excessively large, the electronic conductivity tends to be poor, and conversely, if it is excessively small, the strength characteristics of the surrounding wall tend to be poor.

[0039] The mesopore volume of the carbon material of the present invention is the total volume formed by mesopores with a pore diameter of 2 nm to 50 nm (total mesopore volume), and is preferably 0.1 cc / g or more, or preferably 0.5 cc / g or more, 1 cc / g or more, 1.5 cc / g or more, or 2 cc / g or more. The upper limit is preferably 15 cc / g or less, or preferably within the range of 10 cc / g or less, 5 cc / g or less, 4 cc / g or less, or 3.5 cc / g or less. When the total mesopore volume of the carbon material of the present invention is within this range, the conductivity and strength characteristics are highly balanced.

[0040] The macropore volume of the carbon material of the present invention is the pore volume of pores with a pore diameter exceeding 50 nm, preferably 0.01 cc / g or more, or preferably 0.05 cc / g or more, 0.1 cc / g or more, 0.48 cc / g or more, or 1 cc / g or more. The upper limit is preferably 15 cc / g or less, or preferably within the range of 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 grain shape has appropriate strength, contributes to the stability of the grain shape, and maintains its shape. As a result, a good balance can be maintained between electronic conductivity and ionic conductivity retained within the pores.

[0041] The macropore volume ratio of the carbon material of the present invention is the ratio of the pore volume with a pore diameter greater than 50 nm to the total pore volume, and is preferably 5% or more, or preferably 10% or more, 15% or more, 20% or more, or 25% or more. The upper limit is preferably 80% or less, or preferably within the range of 70% or less, 60% or less, 50% or less, or 45% or less. If the macropore volume ratio of the carbon material is excessively small, the ionic conductivity tends to be poor, and conversely, if it is excessively large, the carbonaceous strength properties tend to be poor.

[0042] The ratio of mesopore volume in the carbon material of the present invention is the ratio of the mesopore volume (total mesopore volume) with a pore diameter in the range of 2 nm to 50 nm to the total pore volume, preferably 10% or more, or preferably 20% or more, 30% or more, 40% or more, or 50% or more. The upper limit is preferably 90% or less, or preferably 85% or less, 80% or less, 75% or less, or 70% or less. When the mesopore volume of the carbon material is within this range, the particle shape of the hollow particulate portion has appropriate strength, contributes to the stability of the particle shape of the hollow particulate portion, and maintains its shape. As a result, a good balance can be maintained between electronic conductivity and ionic conductivity retained within the pores.

[0043] The pore diameter of the mesopores in the carbon material of the present invention is 2 nm to 10 nm, and the mesopore volume (first mesopore volume) is preferably 0.05 cc / g or more, or preferably 0.01 cc / g or more, 0.05 cc / g or more, 0.1 cc / g or more, or 0.5 cc / g or more. The upper limit is preferably 10 cc / g or less, or preferably within the range of 5 cc / g or less, 2 cc / g or less, 1.5 cc / g or less, or 1 cc / g or less. When the pore volume of the carbon material of the present invention is 2 nm to 10 nm, it is preferable that the electronic conductivity and mechanical strength are well balanced.

[0044] The ratio of the volume of pores with a diameter of 2 nm to 10 nm within mesopores (first mesopore volume ratio) to the total pore volume of the carbon material of the present invention is preferably 5.8% or more, or preferably 6.8% or more, 7.8% or more, 9.8% or more, or 14.8% or more. The upper limit is preferably 50% or less, or preferably within the range of 40% or less, 30% or less, 26% or less, or 20% or less. When the ratio of the volume of pores with a diameter of 2 nm to 10 nm within mesopores (first mesopore volume ratio) to the total pore volume of the carbon material of the present invention is within these ranges, the electronic conductivity and mechanical strength are highly balanced.

[0045] Furthermore, in the carbon material of the present invention, the volume percentage V is the total volume (M1 + M2) obtained by adding the total volume (M1 + M2) of the total volume (M1) of micropores smaller than 2 nm (M1) and the total volume (M2) of mesopores (M2) that are in the range of 2 nm to 50 nm relative to the total pore volume V. Ｍ２ (=100 × (M2 / (M1+M2)) is preferably in the range of 82.0% or more. The carbon material of the present invention forms many mesopores. Even if many micropores are formed, they are rarely formed deeply within the internal space of the hollow particulate portion, and the pore diameter becomes small, making it difficult to increase the micropore volume. There is no particular upper limit, but 95.0% or less is preferred. Furthermore, it is preferable that the total micropore volume M1 is 18.0% or less. This is because fewer micropores result in greater mechanical strength and improved ionic conductivity. Also, if there are many pores larger than 50 nm, the mechanical strength of the hollow particulate portion may decrease. In this respect, mesopores in the range of 2 nm to 50 nm are preferably in a predetermined volume percentage V Ｍ２ This makes it possible to suppress the decrease in mechanical strength of the hollow particulate portion.

[0046] Furthermore, when the carbon material of the present invention is divided into the volume of first mesopores in the range of 2 nm to 10 nm (first mesopore volume) and the volume of second mesopores in the range of more than 10 nm to 50 nm (second mesopore volume), it is preferable that the percentage of the second mesopore volume to the total mesopore volume is 50% or more. Even if many first mesopores in the range of 2 nm to 10 nm are formed, they are rarely formed deeply within the internal space of the hollow particulate material, resulting in a small mesopore volume ratio N1 and an inability to increase the total mesopore volume. Also, if there are many second mesopores in the range of more than 10 nm to 50 nm, the area ratio occupied by pores on the surface of the hollow particulate material increases, and the mechanical strength decreases. In this respect, by having the second mesopores in the range of 2 nm to 50 nm occupy 50% or more of the material, the decrease in the mechanical strength of the hollow particulate material can be suppressed.

[0047] Furthermore, when the carbon material of the present invention is divided into the volume of first pores in the range of 10 nm or less (first pore volume) and the volume of second pores in the range of more than 10 nm (second pore volume), the percentage of the second pore volume to the total pore volume is preferably 50% or more, more preferably 75% or more, or 77% or more, 80% or more, 83% or more, or 85% or more. The upper limit is preferably 95% or less, or preferably in the range of 92% or less, 90% or less, 89% or less, or 88% or less. If the proportion of the pore volume of carbon material more than 10 nm is excessively small, the ionic conductivity tends to be poor, and conversely, if it is excessively large, the carbonaceous strength characteristics tend to be poor.

[0048] (Forms of Existence) Figure 3 is a diagram showing the forms of the carbon material of the present invention, classified into four types of forms of existence: branched, linear, spherical, and elliptical. As shown in Figure 3, the forms of existence of the linked structure in the carbon material of the present invention are complex. In diagnostic imaging, the forms of existence of the carbon material of the present invention are classified into four types: "Sphereoidal," "Ellipsoidal," "Linear," and "Branched." The carbon material of the present invention is a linked structure having a branched form in which hollow particulate parts are linked together in a bead-like manner, and mainly has linear and branched forms of existence, but may also have other forms of existence. The classification of forms and the measurement of shape coefficients can be measured by image analysis of TEM images.

[0049] The extended shape was classified according to the following criteria. The shape index, which is an indicator of the extended shape in linked structures of carbon materials, was obtained by statistically analyzing various parameters obtained from image analysis of transmission electron microscope (TEM) images of monodisperse materials. The specific analysis method is as follows (K. Ono et al., Influence of furnace temperature and residence time on configurations of carbon black, Chemical Engineering Journal, 200-202, 2012, 541-548). A small amount of carbon material sample was placed in a test tube, ethanol was added, and it was dispersed for several minutes using an ultrasonic homogenizer. The dispersed sample was fixed to a coated grid for transmission electron microscopy and imaged using a transmission electron microscope (Reference: ASTM D3849-22). Using an image analysis system (image processing, particle analysis, and length measurement software, MultiImageTool, System Infrontia Co., Ltd.), the maximum length L, minimum width W, projected area A, perimeter P, and envelope area A were determined from the projected image of the connected structure. Ｃ The following measurements were taken. From the obtained measurements, the anisotropy X (X = L / W), circularity:complexity Y (Y = (1 / 4π) × (P) were calculated using the following formula. ２ / A)), Envelopment rate Z(Z=A ＣThe formula (A) is calculated to determine the shape index and classify the form. Here, L represents the maximum length, W represents the diagonal width, P represents the perimeter, A represents the projected area, and Ac represents the envelope area.

[0050] Furthermore, the extended morphology of each carbon material was classified based on the following conditions using data on anisotropy X, complexity Y, and envelope coefficient Z: Linear: 1.7 < X Spheroidal: X ≤ 1.7 and Y ≤ 1.2 Ellipsoidal: X ≤ 1.7, 1.2 < Y and Z ≤ 1.3 Branched: X ≤ 1.7, 1.2 < Y and 1.3 < Z

[0051] (Branched Form) Figure 4 is a schematic diagram showing the branched form, one of the four forms of existence of the connected structure constituting the carbon material of the present invention. As shown in Figure 4, when the carbon material 1 of the present invention has hollow particulate parts 21 that branch out and connect, extending in a bead-like manner while branching out like the leaves of a growing tree, it takes on a branched form 2 (32) (hereinafter referred to only as "32"). In the carbon material 1 of the present invention, the branched base end of a second hollow particulate part 212 that constitutes a different path is connected to a first hollow particulate part 211 that is linearly connected in a bead-like manner. By having the branched form 32 in the connected structure 2 of the carbon material 1 of the present invention, the specific surface area can be increased, and the portion that forms the conductive path can be increased. In addition, the supply capacity of the electrolyte containing ions can be increased by holding it in the internal space. Furthermore, branched parts that constitute a different path from at least one of the first hollow particulate part 211 and the second hollow particulate part may be connected. This configuration also increases the number of parts that form conductive paths and the number of parts that increase the supply capacity of the electrolyte containing ions, thereby further improving rapid charge and discharge characteristics, as well as characteristics such as charge capacity and discharge capacity. The branched form 32 may also be composed of a ring-shaped connected structure. This configuration also increases the number of conductive paths and increases the supply capacity of the electrolyte.

[0052] In the classification of carbon materials of the present invention, the proportion of branched forms 32 in the total is, as a lower limit, 9.1% or more, preferably 12% or more, more preferably 14% or more, even more preferably 16% or more, and most preferably 18% or more, and as an upper limit, 50.0% or less, preferably 45.0% or less, more preferably 40.0% or less, even more preferably 37.0% or less, and most preferably 35.0% or less. When the proportion of branched carbon materials is within this range, conductivity can be improved. In particular, the branched forms 32 can improve mechanical strength by arranging linearly and forming a structure in which the intermediate particulate portion at the end of the branch comes into contact with other connecting structures.

[0053] (Linear form) Figure 5 is a schematic diagram showing the linear form, one of the four forms of existence of the linked structure constituting the carbon material of the present invention. As shown in Figure 5, when a plurality of hollow particulate portions 21 of the carbon material 1 of the present invention are linked together in a bead-like manner in a long, straight direction, it takes on the linear form 2 (31). Also, when the linked structure 2 takes on a long linked structure, one end and the other end may be connected to form a ring shape. Alternatively, the tips of branches that extend in multiple directions may be connected to form a ring shape. In the linear form 31 (hereinafter referred to only as "31") of the carbon material 1 of the present invention, as shown in Figure 5, the hollow particulate portions 21 are surrounded by carbonaceous material containing graphene as shown in Figure 1, forming an internal space 23. The linked structure 2 has pores. The internal spaces 23 are also linked together to form a communication space 25. The linear form 31 does not mean a single link, and hollow particulate portions 21 may extend in the lateral direction. The linear form 31 in the carbon material 1 of the present invention has one or more narrow sections with a width of three times or less the inner diameter of the hollow particulate portion 21, located between the first end 41 of the connecting structure 2, where the linearly connected portion is located at one end, and the second end 42 of the connecting structure 2, where the linearly connected portion is located at the other end. The tip of the linear form 31 of the carbon material 1 of the present invention has a third end 43 of the connecting structure 2, which is different from the first end 41 and the second end 42 of the connecting structure 2. The longitudinal length of each linear form 31 is the length of two or more hollow particulate portions 21 connected in series along the longitudinal direction, with the third end 43 of the connecting structure 2 located at its tip. The narrow section may have a width of three times or less the outer diameter of the hollow particulate portion 21, preferably two times or less, or even one time or less. Furthermore, the narrow portion refers to a portion that is narrower than the portion that has a width of three times or more the outer diameter of the hollow particulate portion 21 formed in the middle of the longitudinal direction of the linear form 31.

[0054] In the morphological classification of the carbon material of the present invention, the proportion of linear morphology 31 in the total is, as a lower limit, 17.0% or more, preferably 20.0% or more, more preferably 22.0% or more, even more preferably 25.0% or more, and most preferably 30.0% or more, and as an upper limit, 45.0% or less, more preferably 42.0% or less, even more preferably 40.0% or less, and most preferably 35.0% or less. When the proportion of Linear (linear) in the carbon material of the present invention is within this range, the conductivity can be improved.

[0055] In the morphological classification of the carbon material of the present invention, the proportion of "Spheroidal" is, for example, 50% or less, preferably 30% or less, more preferably 10% or less, even more preferably 5% or less, and most preferably 2% or less. When the proportion of Spheroidal (spherical) carbon material is within this range, the conductivity can be improved.

[0056] In the morphological classification of the carbon material of the present invention, the proportion of "Ellipsoidal" material is, as a lower limit, for example, 10% or more, preferably 13% or more, more preferably 16% or more, even more preferably 18% or more, and most preferably 20% or more, and as an upper limit, for example, 80% or less, preferably 70% or less, more preferably 60% or less, even more preferably 55% or less, and most preferably 50% or less. When the proportion of Ellipsoidal material in the carbon material is within this range, the conductivity can be improved.

[0057] The total ratio of spherical and ellipsoidal forms in the carbon material of the present invention is, as an upper limit, 80% or less, preferably 70% or less, more preferably 60% or less, even more preferably 55% or less, and most preferably 50% or less, and as a lower limit, 5% or more, preferably 10% or more, more preferably 15% or more, even more preferably 17% or more, and most preferably 20% or more.

[0058] The total ratio of linear and branched carbon materials in the carbon material of the present invention is, as a lower limit, 20% or more, preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, and most preferably 55% or more, and as an upper limit, for example, 100% or less, preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, and most preferably 80% or less. When the total ratio of linear and branched carbon materials is within this range, it is preferable because it can greatly improve the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries by increasing conductivity such as electronic conductivity and ionic conductivity, and by improving ion retention and supply. In particular, due to the linear structure, the carbon materials are aligned linearly by the kneading pressure in a vehicle such as resin, and by the influence of an electric field in a solution, etc., which greatly enhances the penetration effect and improves conductivity. In particular, the branched form can improve mechanical strength by forming a network with other carbon materials through the linear arrangement and branching. Furthermore, the proportion of branched forms in the carbon material of the present invention (the sum of the proportions of branched and linear forms) is in the range of 22.0% to 70.0%. In particular, being within this range allows for a balance between the effect of increased conductivity due to the large penetration effect achieved by arranging linearly and the effect of improving mechanical strength by forming a network.

[0059] (Shape Factor SF) Furthermore, the carbon material of the present invention has a shape factor SF, expressed by formula (1), which is in the range of 0.4 to 3.0. Here, SF = (PM2 / A) - (ML2 / A): formula (1) Furthermore, the shape factor PM2 / A = P ２ / (4・π・A): Equation (2) The shape factor is ML2 / A = (L ２Equation (3) is given by π) / (4A), where L is the maximum length, P is the perimeter, and A is the projected area. The shape factor SF is preferably 0.0 or greater, or preferably 0.4 or greater, or 1.0 or greater as a lower limit, and preferably 3.0 or less, or 2.6 or less as an upper limit. When the carbon material of the present invention satisfies the relationship between the shape factor ML2 / A and the shape factor PL2 / A, the specific surface area per unit weight increases, which is preferable as it balances the effect of increasing electronic conductivity with the effect of forming a network and improving mechanical strength.

[0060] Furthermore, the shape factor ML2 / A calculated by the image analysis method of the carbon material of the present invention is in the range of 1.0 to 5.0, with a lower limit of 1.0 or more, preferably 2.0 or more, more preferably 2.25 or more, and even more preferably 2.40 or more, and an upper limit of 5.0 or less, preferably 3.5 or less, and even more preferably 3.10 or less. The shape factor ML2 / A indicates the degree of circularity, with a value closer to 1 indicating a perfect circle, and a larger value indicating a shape that is further from a circle and more irregular. It represents a comparison with a circle whose circumference is equal to its perimeter. Therefore, by making the carbon material of the present invention have a shape with a shape factor ML2 / A in the range of 1.0 to 5.0, the specific surface area per unit weight can be increased and conductivity can be improved.

[0061] Furthermore, the shape factor PM2 / A calculated by the image analysis method for the carbon material of the present invention is in the range of 1.0 to 10.0, with a lower limit of 1.0 or more, preferably 1.5 or more, more preferably 2.0 or more, even more preferably 2.2 or more, and most preferably 2.4 or more, and an upper limit of 10.0 or less, preferably 8.0 or less, more preferably 7.5 or less, and even more preferably 7.0 or less. The shape factor PM2 / A is a coefficient that indicates the degree of unevenness of a circle or surface, and is compared with a sphere whose diameter is equal to its maximum length. A smaller value indicates less unevenness and a smoother surface, while a larger value indicates the presence of larger uneven areas. Therefore, by making the carbon material of the present invention have a shape in which the shape factor PM2 / A is in the range of 1.0 to 10.0, the specific surface area per unit weight can be increased and the conductivity can be improved.

[0062] Furthermore, if the PM2 / A value is 1, the ML2 / A value is 1, and the SF value is 0, it indicates that the material is a perfect circle without any irregularities and is a perfect sphere. This allows for maximizing the specific surface area. The relationship between ML2 / A and PM2 / A is ML2 / A ≤ PM2 / A. This enhances the conductivity of the carbon material of the present invention and significantly improves the rapid discharge performance, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries that utilize an electrolyte containing ions.

[0063] Furthermore, the carbon material of the present invention has openings exceeding 1 nm in the surrounding wall of the hollow particulate portion, allowing communication from the internal space to the external space which is outside the connected structure. Figure 6 is a photograph showing an example of an SEM image obtained by observing the carbon material of the present invention with a scanning electron microscope (SEM). By providing openings, a connected space is formed inside the hollow particulate portion, and by further communication between the internal space and the external space, the movement of electrons, ions, or substances throughout the connected structure becomes easier and can be increased. In particular, the carbon material of the present invention has a very large specific surface area due to having many pores in the internal space from the surrounding wall, so the internal space can be effectively utilized. The openings have shapes such as circles and ellipses. The shape of the openings is formed by the uniform contraction of the surrounding wall during the heat treatment process, resulting in a circular shape, or by uneven contraction in a specific direction. The openings have a diameter exceeding 1 nm. Here, the diameter is derived by considering the area of ​​the opening as the area equivalent to the diameter of a circle. When the aperture is 1 nm or less, the mechanical strength of the connecting structure increases, making it less prone to breakage. However, the amount of electrons, ions, etc. that can move decreases. Conversely, when the aperture exceeds 100 nm, the mechanical strength of the connecting structure decreases. However, as the aperture increases, the amount of electrons, ions, etc. that can move increases, and the limitations on the size of substances moving in the internal space decrease, allowing many substances to move easily. Therefore, by providing an aperture in the hollow particulate portion of the connecting structure, the internal space and the external space are connected, making it easier for electrons, ions, and other substances to move through the pore-containing internal space, and thus increasing conductivity.

[0064] The carbon material of the present invention has fibrous portions arranged on the surface of a connected structure. The fibrous portions may be cylindrical or cup-stack type tubular shapes with a hollow interior, and have a diameter of 1 nm to 100 nm. Figure 7 is a photograph showing an example of an SEM image obtained by observing the carbon material of the present invention with a scanning electron microscope (SEM). The fibrous portions are firmly arranged with the hollow particulate portions of the connected structure by covalent bonds or van der Waals force interactions. In particular, through a heat treatment process, the fibrous portions have a structure in which they are integrated with or in close proximity to the hollow particulate portions of the connected structure while in close proximity or in contact with them. The fibrous portions have high electrical conductivity and high tensile strength in the cylindrical direction. Whether the fibrous portions are mixed and integrated on the surface of the connected structure, dispersed and in close proximity on the surface of the connected structure, or exist in a network on the hollow particulate portions of the connected structure, they can contribute to high electrical conductivity to the connected structure even without communicating with the internal space of the connected structure. Furthermore, when fibrous carbon is tubular, electrons, ions, and other substances move easily within the tubular portion, and the diameter of the tubular portion allows for selective movement of substances. Therefore, by providing fibrous portions, high conductivity and ease of substance movement can be further enhanced in the carbon material of the connecting structure. In addition, the fibrous portions have high tensile strength in the cylindrical direction, and the side tube portions have high elastic modulus, contributing to the tensile strength and elastic modulus of the carbon material. The fibrous portions, like the hollow particulate portions, are generated in the CVD process in the presence of specific metal ions. The generation of fibrous portions can be controlled by the type of raw material, temperature, time, or mold material used in the CVD process.

[0065] (Analysis of carbon materials: Temperature-controlled desorption mass spectrometry (TPD-MS)) To improve the performance and lifespan of lithium-ion secondary batteries, high-efficiency battery reactions that do not show a decrease in efficiency due to side reactions are required, and the carbon materials in the electrodes need to have electrochemical stability, i.e., oxidation resistance and corrosion resistance. Side reactions such as oxidation that occur electrochemically are said to originate from oxygen-containing functional groups and edge surfaces of carbon materials. Edge surfaces are the ends of the graphene structure that makes up the carbon material, and are often terminated with hydrogen or oxygen functional groups. To improve the oxidation resistance of carbon materials, it is effective to reduce oxygen-containing functional groups and reduce the number of edge surfaces with low oxidation resistance.

[0066] By using the ultra-high-sensitivity vacuum temperature-controlled desorption mass spectrometer 300 (developed at Tohoku University, see T. Ishii et al., CARBON 80, 2014, 135-145), oxygen-containing functional groups and hydrogen-terminated edge sites can be accurately qualitatively and quantitatively analyzed by temperature-controlled desorption mass spectrometry (TPD-MS). More specifically, 1 to 3 mg of each carbon material is placed on a graphite sample stage, vacuum-heated to 1800°C at a heating rate of 10°C / min, and the gas released during heating is analyzed using the ultra-high-sensitivity vacuum temperature-controlled desorption mass spectrometer 300, thereby accurately qualitatively and quantitatively analyzing oxygen-containing functional groups and hydrogen-terminated edge sites. Figure 8 is a schematic diagram illustrating the ultra-high-sensitivity vacuum temperature-controlled desorption mass spectrometer used for temperature-controlled desorption mass spectrometry of carbon materials in the present invention. The ultra-high-sensitivity vacuum temperature-controlled desorption mass spectrometer 300 includes a quartz reactor 310 equipped with a radioactive thermometer 311, a sample holder 312, and a high-frequency induction coil 313, as well as a detection unit 320 connected to the quartz reactor 310. The detection unit 320 includes, for example, a gas reservoir 327, a turbomolecular pump 324, a rotary pump 325, a cold cathode Pirani gauge 321, and a capacitance gauge 322.

[0067] The oxygen content of the carbon material of the present invention is determined by H2, which is obtained by temperature-controlled desorption mass spectrometry. ２ O emissions, CO emissions, and CO ２The value calculated from the amount released is preferably 5.0% by mass or less, and is preferably in the order of 3.0% by mass or less, 2.0% by mass or less, 1.0% by mass or less, and 0.6% by mass or less. When the oxygen content of the carbon material of the present invention is within the above range, the stability of the lithium-ion secondary battery is further improved, and it can further contribute to the high performance of the lithium-ion secondary battery.

[0068] The ultra-high-sensitivity vacuum temperature-controlled desorption mass spectrometer 300 of the present invention measures the desorbed gases released from carbon materials during temperature increase. ２ Amount, H ２ O amount, CO amount and CO ２ Although the quantities are measured, these released gases originate 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 ends of carbon materials. Therefore, a high amount of oxygen functional groups in a carbon material means a high amount of oxygen-containing functional groups and edge groups present in the structure of the carbon material. The amount of oxygen-containing functional groups and edge groups in a carbon material can be adjusted by the CVD conditions and heat treatment temperature described later.

[0069] Furthermore, the amount of gas measured by the ultra-high-sensitivity vacuum temperature-controlled desorption mass spectrometer 300 of the present invention is preferably 5000 μmol / g or less, and is preferably in the order of 3000 μmol / g or less, 1000 μmol / g or less, 750 μmol / g or less, and 500 μmol / g or less. When the above amount of gas in the carbon material is within the above range, it can further contribute to extending the lifespan and improving the performance of lithium-ion secondary batteries.

[0070] Furthermore, the edge area of ​​the carbon material of the present invention is a value calculated from the amount of gas measured by the temperature-controlled desorption mass spectrometer 300, and is preferably 500 m². ２ It is less than / g and 300m ２ / g or less, 100m ２ / g or less, 50m ２ / g or less, 30m ２The order of preference is from 0 / g to 0. Furthermore, the edge content of the carbon material is 10,000 μmol / g or less, and the order of preference is from 6,000 μmol / g, 2,000 μmol / g, 1,000 μmol / g, and 600 μmol / g or less. When the edge content of the carbon material is within the above range, durability is further improved, which can further contribute to the stability and high performance of lithium-ion secondary batteries.

[0071] Furthermore, the ash content of the carbon material of the present invention is preferably 10,000 ppm or less, and is preferably in the order of 5,000 ppm or less, 4,000 ppm or less, 3,500 ppm or less, and 3,000 ppm or less. When the ash content of the carbon material is within the above range, the stability of the electrolyte containing ions is further improved, and the durability and performance of the lithium-ion secondary battery can be further enhanced.

[0072] Furthermore, the carbon content of the carbon material of the present invention is preferably 95.0% by mass or more, and is preferably 97.0% by mass or more, 98.0% by mass or more, 99.0% by mass or more, and 99.3% by mass or more, in that order. The carbon content is determined by the following formula. The amount of generated gas is the gas (H) measured by the ultra-high sensitivity vacuum temperature rise desorption mass spectrometer 300. ２ H ２ O, CO and CO ２ This is the total amount of carbon in the carbon material. Carbon content (mass%) = 100 - (Ash content (mass%) + Amount of generated gas (mass%))

[0073] Furthermore, the ratio of oxygen content to carbon content (O / C) of the carbon material of the present invention is preferably 1.00 or less, and is preferably 0.50 or less, 0.10 or less, 0.05 or less, and 0.01 or less, in that order. When the above ratio (O / C) of the carbon material is within the above range, it can further contribute to extending the lifespan and improving the performance of lithium-ion secondary batteries.

[0074] (BET specific surface area) The carbon material of the present invention has a BET specific surface area SA which is the specific surface area calculated from nitrogen adsorption as specified in JIS Z8830, preferably 100 m². ２ / g or more 2700m ２ / g or less, or 300m ２ / g or more 2500m ２ / g or less, 350m ２ / g or more 2000m ２ / g or less, 400m ２ / g or more 1200m ２ It is also preferable that the BET specific surface area of ​​the carbon material of the present invention be within this range, as this increases the number of conductive pathways for electronic conductivity and improves conductivity. Furthermore, ionic conductivity can be improved by easily supplying ions. The theoretical value of the specific surface area of ​​single-layer graphene is 2627 m². ２ Since it is calculated as / g, it can be said that the closer the specific surface area is to this value, the more ideal the carbon conductive material becomes. However, the carbon material of the present invention can utilize a wide surface area by applying both the front and back surfaces of the graphene-containing carbonaceous material, which can maintain a pore and void structure.

[0075] (Conductivity) The carbon material of the present invention preferably has high electronic conductivity. Since electron transfer in carbon occurs through the movement of π electrons, in order to form an ideal conductive path within an electrode using a carbon material, it is necessary to arrange single-layer graphene, in which carbon atoms are bonded in the planar direction, in a mesh-like structure. Furthermore, when a conductive material such as a carbon material is filled into a non-conductive material such as a positive electrode material, conductivity will not be exhibited if the filling rate of the conductive material is low. Once a certain level of filling rate is reached, conductive paths of the conductive material are formed within the compound, causing a rapid increase in electronic conductivity, which then settles to a constant value. The lower the threshold of the filling ratio at which this rapid increase in electronic conductivity occurs, the more suitable the material is as a conductive material. Therefore, the carbon material of the present invention consists of carbonaceous material having a graphene structure that extends in the planar direction, and is thought to exhibit high electronic conductivity because it is a linked structure in which granular shapes with a hollow outer shell of carbonaceous material are connected, resulting in a high balance between in-plane electronic conductivity and electronic conductivity due to the formation of conductive paths.

[0076] The electrical conductivity of the carbon material of the present invention is typically in the range of 1 to 100 S / cm, preferably 5 to 70 S / cm, more preferably 10 to 50 S / cm, even more preferably 15 to 40 S / cm, and most preferably 20 to 30 S / cm, when pressurized at 10 MPa. The electrical conductivity of the carbon material can be determined by the reciprocal of its electrical resistivity. For example, the electrical resistivity of the carbon material can be measured according to JIS K1469.

[0077] (Electrical resistivity of composite layer) The carbon material of the present invention can be used in composite materials or asphalt mixtures that have excellent high conductivity when blended into polymer composite materials, and high hardness and high tensile strength when the carbon material is applied as a filler. For this reason, it is suitable for use in conductive composite materials, especially for secondary batteries. Furthermore, the carbon material of the present invention can be incorporated into synthetic resins by melt-kneading and forming it into a plate to create conductive members. In addition, it can be incorporated not only in resins but also dispersed in solutions.

[0078] The carbon material of the present invention can be applied to dispersions of the carbon material, electrode compositions containing the carbon material, and electrode slurries. These embodiments will be outlined below.

[0079] (Dispersion) In the dispersion obtained by dispersing the carbon material of the present invention in a dispersion medium, a polar solvent is preferred as the dispersion medium, especially when the dispersion is used in the manufacture of lithium-ion secondary batteries. From the viewpoint of affinity with the binder polymer, N,N-dimethylformamide, N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and water are preferred, and it is more preferable to include N-methylpyrrolidone (NMP). Furthermore, for carbon materials containing graphene, N-methylpyrrolidone (NMP) is suitable as the dispersion medium.

[0080] (Electrode Composition) The present invention provides an electrode composition comprising a carbon material, an active material, and a binder. The materials used in the electrode composition are described in detail below.

[0081] (Active Material) As the active material used in the electrode composition using the carbon material of the present invention, for example, an active material used in a normal positive or negative electrode can be used. The ratio of the active material to the carbon material is appropriately selected according to the purpose of use, and is in the range of 0.005 to 20 parts by mass of carbon material per 100 parts by mass of active material, 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.

[0082] (Binder) As the binder used in the electrode composition using the carbon material of the present invention, for example, a binder that is normally used in positive or negative electrodes can be used. The amount of binder used is appropriately selected according to the purpose of use, and is usually 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 per 100 parts by mass of active material.

[0083] (Other Compounding Agents) In addition to the carbon material, active material, and binder, other compounding agents may be added to the electrode composition using the carbon material of the present invention as desired. The other compounding agents can be any agents that are commonly used in electrode compositions for batteries, 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, per 100 parts by mass of the active material.

[0084] (Electrode Slurry) This electrode slurry is obtained by dispersing the electrode composition using the carbon material of the present invention in a solvent. Any solvent capable of dissolving or dispersing the binder can be used, such as solvents commonly used in positive or negative electrodes, or dispersion media used in the carbon material dispersion liquid described above. The amount of solvent used can be an appropriate amount, adjusted so that the electrode slurry for the next step has a viscosity that allows it to be applied to the current collector.

[0085] (Electrodes) The carbon material of the present invention is used, for example, in electrodes used in lithium-ion secondary batteries. These electrodes may be either negative or positive electrodes, and can be obtained, for example, by coating the above electrode slurry onto a current collector and then drying it. Any current collector used for conventional positive or negative electrodes may be used. The carbon material of the present invention is elastically deformable, and when the electrode slurry is coated and dried, and then pressurized, the voids within the particles are partially and temporarily almost completely crushed, resulting in a non-porous state (transient deformation state). However, depending on the magnitude of the pressure and residual stress, the crushed particles may return to their original state. In this case, the density of the electrode is measured and calculated in the restored equilibrium state. Furthermore, if the carbon material in the electrode remains crushed, and the electrode is assembled as a battery, and then the electrolyte is finally injected, the electrolyte will enter the pores that are not crushed. However, even in the crushed state, the electrolyte may enter through the remaining crushed external openings (SEM image) due to capillary action, and the material may return to an uncrushed state (permanent deformation state). Figure 9 is a photograph showing an example of a TEM image obtained by observing the carbon material of the present invention with a transmission electron microscope (TEM). While other carbon materials may also recover due to residual stress, in the carbon material of the present invention, the electrolyte permeates into the pores after recovery, allowing for the rapid supply of lithium ions necessary for the electrode reaction, and enabling the suitable realization of an electrode with a highly balanced electronic conductivity and ionic conductivity. The permanent deformation state is determined by the electrode mixing ratio of the carbon material in the electrode composition comprising the carbon material of the present invention, an active material, and a binder. The ratio of active material to carbon material is appropriately selected according to the purpose of use, and is 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, as the ratio of carbon material to 100 parts by mass of active material.

[0086] (Lithium-ion secondary battery) This lithium-ion secondary battery comprises an electrode composition using the carbon material of the present invention. Specifically, it comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode uses the above-mentioned electrodes (positive electrode and / or negative electrode). An electrode without the above-mentioned carbon material may be used for either the positive electrode or the negative electrode. Furthermore, any separator and electrolyte that are commonly used in lithium-ion secondary batteries can be used. The lithium-ion secondary battery of this embodiment may also optionally further include a battery container for housing the electrode assembly consisting of the positive electrode, negative electrode and separator, and a sealing member for sealing the battery container.

[0087] (Other Applications) The carbon material of the present invention can exhibit its functionality and be effectively utilized in any electrochemical device other than the lithium-ion secondary battery described above. Specifically, it can function as an electrical conduction path within an electrode when electron transfer is involved in a device reaction, and as a reinforcing function when electrodes or the like undergo physical deformation. Depending on the embodiment of the carbon material, it is also possible to take advantage of the durability of the graphene structure to prevent a third material (such as a catalyst) from directly contacting the reaction material when the reaction material is in an oxidized or reduced state.

[0088] Other usable devices besides lithium-ion secondary batteries include, for example, non-aqueous 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, such as polymer gel electrolyte batteries in which electrolyte is impregnated into PVDF, etc.

[0089] These devices use readily graphitizable carbon, non-graphitizable carbon, graphite, lithium alloy materials such as silicon and tin, and other metallic materials such as lithium as negative electrode active materials. Similarly, lithium-containing metal oxides, particularly lithium-containing transition metal oxides having layered, spinel, or olivine structures, lithium-free metal oxides, organic positive electrode materials, charge-transfer complex positive electrode materials, sulfur, and fluoride-based materials are used as positive electrode active materials. The carbon material of the present invention can effectively enhance the conductivity of any of these active materials. Furthermore, the carbon material of the present invention is also suitable as a material for lithium-sulfur batteries, as described in publications such as WO2018 / 225619, JP 2023-501679, JP 2019-517116, and JP 2022-191280.

[0090] The carbon material of the present invention can also be suitably used in organic electrolyte capacitors, aqueous electrolyte capacitors, and aqueous solution batteries. In fuel cells, it can be used in PEFCs, SOFCs, DMPCs, etc., and in particular, it can be used not only to impart conductivity to electrodes but also as a support for oxidation-reduction catalysts.

[0091] The carbon material of the present invention can be used for applications other than electrochemical devices. For example, it is suitable for electronic device applications such as graphene-based sensors, electromagnetic interference suppression materials, antenna modules, heat dissipation substrates, heat exchange devices, separation membranes, reverse osmosis membranes, transparent electrode materials, structural materials that take advantage of mechanical flexibility, and conductive inks and pastes. Furthermore, in response to the demand for vehicle weight reduction, which directly contributes to reducing carbon dioxide emissions and saving energy, it can be used as a reinforcing agent for various types of rubber, including tires, as well as in paints, coloring pigments, conductive fillers for various polymers, and additives for magnetic recording media, taking advantage of its hollow shape to contribute to weight reduction. 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 materials mentioned above. The carbon material of the present invention has an internal space, which deforms when subjected to compressive load to absorb compressive pressure, and then restores to its original shape when the pressure is released, making it suitable for impact-resistant structural materials that can withstand repeated deformation. In addition, its hollow structure provides high tensile strength per unit mass, making it suitable for weight reduction of structural materials.

[0092] (Method for Manufacturing Carbon Materials) The method for manufacturing the carbon materials of the present invention will now be described. The carbon materials of the present invention can be manufactured by template chemical vapor deposition (CVD). This method involves passing an organic gas through a ceramic that functions as a template, which has CVD activity and is heated in an inert gas atmosphere, and forming a carbonaceous film by condensing carbon atoms of organic substances in the gas.

[0093] First, ceramic particles are placed in a reaction vessel. Next, the reaction vessel is heated and a carbon-containing raw material gas is introduced into the vessel. Subsequently, the carbon-containing raw material gas is thermally decomposed by CVD, and the resulting product is deposited on the surface of the ceramic particles, covering the surface of the ceramic particles with a carbonaceous layer precursor. The temperature of the thermal decomposition of the raw material gas can be determined based on the material of the mold and the type of raw material gas, and is preferably between 400°C and 900°C. In order to create space inside the resulting carbonaceous layer precursor, the ceramic particles coated with the carbonaceous film are treated with a reagent capable of dissolving ceramics (for example, an acidic solution such as hydrofluoric acid). This treatment dissolves and removes the ceramic portion of the ceramic particles coated with the carbonaceous film. After dissolution, the inside of the carbonaceous layer precursor is washed with water or the like to ensure that no residue remains in the space. As the ceramic particles are dissolved and removed, space is formed inside the carbonaceous precursor.

[0094] Next, the carbonaceous precursor is heat-treated at a temperature of 3000°C or lower. The conditions for the heating process are not particularly limited as long as they enhance the crystallinity of the carbon. For example, the holding temperature may be set to a range of 1000 to 3000°C, preferably 1300 to 2500°C, more preferably 1400 to 2000°C, even more preferably 1500 to 1900°C, and particularly preferably 1600 to 1800°C. If the heat treatment temperature is within this range, it is preferable to obtain a carbon material that has higher levels of conductivity, corrosion resistance, and / or high specific surface area. The heat treatment time (holding time at the 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 during the heat treatment process can be, for example, atmospheric pressure or reduced pressure.

[0095] This adjusts the structural defects in the carbonaceous material, including the graphene structure that constitutes the carbonaceous precursor particles, as well as in the parts other than that portion. These structural defects include internal spaces created within the linked structure due to the dissolution of the template ceramic particles, and openings created in the surrounding walls formed from the carbonaceous material. By changing reaction conditions such as heat treatment temperature and time, the degree of these structural defects can be adjusted; that is, the size of the communication spaces within the hollow particulate portion and the size of the openings that allow the electrolyte to penetrate into the particles can be adjusted. In addition, due to the uneven distribution of metal ions and impurities on the surface of the template material, they may act as catalysts, resulting in the formation of cylindrical fibrous portions.

[0096] Furthermore, during the heating process, functional groups that bond to carbon (mainly oxygen-containing functional groups) and carbon chains that do not form six-membered rings detach when the temperature exceeds 1000°C, potentially forming unbonded bonds. When these unbonded bonds bond to other nearby carbon atoms, the surface of the carbon material becomes less receptive to the bonding of functional groups. Therefore, by heat-treating the carbon material at, for example, 1500°C or higher, preferably 1600°C or higher, it is possible to make the carbon material more electrically conductive and more likely to maintain its internal space.

[0097] During the heating process, structural defects in the graphene and non-graphene components of the carbonaceous layer may be adjusted. These structural defects include spaces created within the aggregate structure due to the dissolution of the mold material and openings created in the surrounding wall formed from the carbonaceous layer. By changing reaction conditions such as heat treatment temperature and time, the degree of these structural defects can be adjusted; that is, the size of the spaces within the carbon material and the size of the openings that allow oil or electrolyte to penetrate into the particles can be adjusted. Furthermore, by controlling the type and size of the mold material, the heating temperature in the heat treatment process, and the acid treatment during mold removal, the diameter and length of the fibrous portion can be adjusted, thereby obtaining excellent conductivity or elastic deformability.

[0098] The mold material used in this embodiment only needs to have an aggregate structure in which primary particles have multiple branched structures linked together in a bead-like manner, and preferably it is a compound that has catalytic activity in carbon deposition reactions. Examples of mold materials include metal compounds, metalloid compounds, and nonmetal compounds, and preferably ceramic particles and / or carbonate particles.

[0099] Examples of ceramic particles include glass, cement, fine ceramics, and more specifically, particles such as silica (silicon dioxide), alumina, and magnesia (magnesium oxide).

[0100] Alumina has acidic sites on its surface and acts as a solid acid. When the acidic sites of the solid acid come into contact with hydrocarbons, the acidic sites act as catalysts for the hydrocarbon reforming reaction. In addition, contact between the acidic sites and hydrocarbons causes a carbon precipitation reaction, and carbon can precipitate on the surface of the solid acid. This function is called solid acid catalytic function, and by utilizing it, it becomes possible to decompose the raw material gas, polymerize the carbon radicals that are the decomposition products, and precipitate the carbonaceous layer even at temperatures below the decomposition temperature of the raw material gas that will become the source of the carbonaceous layer.

[0101] In addition to the above, inorganic carbonates can be used as the mold material for producing the carbon material of the present invention. Examples of inorganic carbonates include ammonium carbonate, sodium carbonate, potassium carbonate, calcium carbonate, barium carbonate, magnesium carbonate, and iron carbonate, with sodium carbonate, potassium carbonate, and calcium carbonate being preferred, and particularly preferred being particles of calcium carbonate, but the material is not limited to these. These mold materials can be used individually or in combination of two or more.

[0102] Examples of metal compound template materials other than carbonate particles include monovalent metal compounds and polyvalent metal compounds, but polyvalent metal compounds are 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, but calcium compounds, magnesium compounds, and aluminum compounds are preferred. Examples of calcium, magnesium, and aluminum compounds include chlorides, sulfates, nitrates, phosphates, and oxides, but oxides are preferred.

[0103] By the manufacturing method described above, the carbon materials of the present invention, such as CMS and GMS, can be easily manufactured.

[0104] The carbon material of the present invention will be described below with reference to examples. As shown below, Examples 1 to 8 and Comparative Examples 1 to 2 were manufactured, and their various physical properties were evaluated according to the following methods.

[0105] <Example 1> (Manufacturing of carbon material 1) (CVD process) As a raw material for the mold material, atomized silicon dioxide (SiO ２ AEROSIL® NX90G, BET specific surface area 50-80 m² ２ Approximately 1 g of (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 in a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). Argon gas was flowed into the reaction tube at a flow rate of 400 mL / min while the temperature was raised to 900°C at a heating rate of 10°C / min and held for 30 minutes. While maintaining 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 held for 90 minutes. After that, the material was cooled to room temperature while argon gas was flowed at a flow rate of 400 mL / min, the quartz boat was removed, and a carbonaceous layer coated mold material was obtained by coating the surface of the mold material with a carbonaceous layer. At this time, it was confirmed by electron microscopy that the mold material was an aggregate in which multiple primary particles were linked together in a bead-like manner with multiple branching structures.

[0106] (Mold removal) Next, the mold material was removed from the obtained carbonaceous layer-coated mold material by the following procedure to obtain a carbon material precursor.

[0107] (1) A 100 ml PFA beaker was filled with carbonaceous layer-coated mold material, and ultrapure water was added until the entire carbonaceous layer-coated mold material was wet. (2) After adding 46% hydrofluoric acid, the mixture was stirred with a stirrer for 2 hours. (3) After stopping the stirring, the mixture was allowed to stand until the sample settled. (4) Using a PTFE membrane filter (47 mmφ, pore size 0.1 μm), the supernatant was filtered by suction. (5) The sample on the filter paper was washed with approximately 39 mL of ultrapure water and filtered by suction. This operation was repeated three times. (6) The sample on the filter paper was collected in the original PFA beaker. (7) The operations in (2) to (6) above 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 stopping the stirring, the mixture was allowed to stand until the sample settled. (10) Discard the supernatant, add 5% caustic soda, and stir for 12 hours while heating to 80°C. (11) After stopping the stirring, allow the sample to stand until it settles. (12) Filter the supernatant using a PTFE membrane filter (47 mmφ, pore size 0.1 μm). (13) Wash the sample on the filter paper with ultrapure water and filter by suction. Repeat this operation until the filtrate is neutral. (14) Collect the sample on the filter paper in a petri dish and dry in a 110°C oven for 8 hours.

[0108] (Heat treatment) The carbon material precursor obtained above is placed in a rectangular high-temperature heating furnace (manufactured by Izumi Tech Co., Ltd.) and subjected to reduced pressure (10 －１ After heating to the Pa order, the material was heated to 1800°C under argon gas flow (10 mL / min) at a heating rate of 15°C / min, and held at that temperature for 1 hour for calcination. It was then cooled to room temperature to produce the carbon material.

[0109] <Example 2> A carbon material was produced in the same manner as in Example 1, except that the CVD reaction time was set to 60 minutes.

[0110] <Example 3> A carbon material was produced in the same manner as in Example 1, except that the CVD reaction time was set to 75 minutes.

[0111] <Example 4> A carbon material was produced in the same manner as in Example 1, except that the CVD reaction time was set to 130 minutes.

[0112] <Example 5> A carbon material was produced in the same manner as in Example 1, except that no heat treatment was performed.

[0113] <Example 6> (Manufacturing of carbon material 2) (CVD process) Synthetic calcium carbonate (Hakutsuka O; average particle size 40 nm, BET specific surface area 51 m²) was used as the mold material. ２ Approximately 8 g of (manufactured by Shiraishi Kogyo Co., Ltd., with a maximum probability void diameter of 35 nm, linseed oil absorption of 38 mL / 100 g, bulk density of 0.28 g / mL, pH 8.4) was spread on a quartz boat and placed in the center of a quartz reaction tube in a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). Argon gas was flowed at a flow rate of 320 mL / min and acetylene gas at 80 mL / min (raw material gas concentration 20%), and the apparatus was heated to 540°C at a heating rate of 10°C / min, and maintained at 540°C for 180 minutes. After that, it was cooled to room temperature and the mold carbonaceous laminate was removed.

[0114] (Mold Removal) Next, the mold was removed from the obtained mold carbonaceous laminate by the following procedure to obtain the carbon material. (1) Approximately 8 g of the mold carbonaceous laminate was placed in a 500 mL glass beaker, and approximately 40 mL of ultrapure water was added and stirred with a stirrer. (2) Approximately 40 mL of 8% (2.3 M) hydrochloric acid was added and stirred with a stirrer for 2 hours. (3) The stirred liquid was filtered by suction using a PTFE membrane filter (90 mmφ, pore size 1 μm). (4) The sample remaining in the beaker was rinsed with a small amount of ultrapure water and filtered by suction. (5) The sample on the filter was collected in the original glass beaker, and steps (2) to (4) were repeated. (6) Ultrapure water was added to the filter and allowed to stand for 5 minutes, then filtered by suction. (7) Step (6) was repeated until the filtrate was confirmed to be neutral using pH test paper. (8) The sample on the filter paper was collected in a beaker and dried overnight in a 200°C drying oven.

[0115] (Heat treatment) The obtained carbon material is placed in a rectangular high-temperature heating furnace (manufactured by Izumi Tech Co., Ltd.) and subjected to reduced pressure (10 －１After heating to the Pa order, the material was heated to 1600°C at a rate of 15°C / min under argon gas flow (10 mL / min) and held at that temperature for 1 hour for firing. After cooling to room temperature, the fired carbon material was removed, and 0.57 g of heat-treated graphene-containing carbon material was produced. The produced carbon material had a high carbon deposition rate of 7.1% relative to the mold used.

[0116] <Example 7> As a mold material, synthetic calcium carbonate (product name: Viscoexcel-30; average particle size 80 nm, BET specific surface area 29 m²) was used. ２ The product was manufactured in the same manner as in Example 6, except that it used (a linseed oil with a maximum probability void diameter of 19 nm, linseed oil absorption of 24 mL / 100 g, bulk density of 0.40 g / mL, pH 9.5, manufactured by Shiraishi Kogyo Co., Ltd.).

[0117] <Example 8> As a mold material, synthetic calcium carbonate (product name: NEOLIGHT VT, BET specific surface area 40 m²) was used. ２ The same procedure as in Example 6 was used, except that (a specific product was used: / g, oil absorption capacity 65 mL / 100g, bulk density 0.25 g / mL, pH 9.5, manufactured by Takehara Chemical Industry Co., Ltd.) was used.

[0118] <Comparative Example 1> As a carbon material, aluminum oxide (Al) is used as a mold material. ２ O ３ / PURALOX SBa200; Particle size 7 nm, BET specific surface area 202 m ２ A carbon material was produced in the same manner as in Example 1, except that a carbon dioxide ( / g, manufactured by SASOL) was used.

[0119] <Comparative Example 2> As a carbon material, magnesium oxide (MgO / Kyowa Mag MF-150; particle size 30 nm, BET specific surface area 129 m²) was used as a mold material. ２ A carbon material was produced in the same manner as in Example 1, except that a solution (manufactured by Kyowa Chemical Industry Co., Ltd.) was used and the mold MgO removal procedure described below was performed.

[0120] (Removal of MgO template) 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 stirring bar were added to a Teflon® beaker and stirred at room temperature for 5 hours. The sample was then filtered through a membrane filter (0.1 μm) and washed five times with pure water, followed by suction filtration. Care was taken to prevent the deposits on the filter paper from drying out. Next, the deposits were placed in a glass beaker containing approximately 100 mL of acetone. The beaker was covered with aluminum foil and held at a vacuum pressure of 0.06 MPa for 2 minutes in a vacuum dryer. After returning to atmospheric pressure, it was heated in a 60°C constant temperature bath 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 the graphene-containing carbon material after template removal.

[0121] Next, we evaluated the following items.

[0122] (Number of layers) The number of graphene structural layers in the carbon material of the present invention is determined by forming a graphene structure on mold particles, calculating the weight of the carbon layers using thermogravimetric analysis (TG), calculating the weight of the carbon layers per mold area from the weight of the graphene structural layers and the surface area of ​​the mold particles, and using this as the weight of carbon per unit area of ​​the single-layer graphene structure (7.61 × 10⁻¹⁰). －４ g / m ２ This value is calculated by dividing by ( ).

[0123] (Morphological Classification) Figure 9 shows a TEM image of the carbon material of the present invention observed with a transmission electron microscope (TEM). Various parameters were calculated for the shape index of the linked structure of the carbon material using values ​​obtained from image analysis of the TEM image of the carbon material. First, a sample for TEM observation was prepared in order to obtain an image to be used for image analysis. A small amount of the carbon material sample (about one level scoop with a Hi-Mine style spatula) was placed in a 20 cc vial, 10 mL of ethanol was added thereto, and the mixture was dispersed in an ultrasonic disperser for 10 minutes. One drop of the sample solution in which the carbon material was dispersed was placed onto a TEM coated grid using a Pasteur pipette, and the grid with the drop was placed in a vacuum dryer and dried until the solvent had completely evaporated. The TEM image of the carbon material was acquired using a transmission electron microscope (H-7650 model, Hitachi High-Technologies Corporation) at an acceleration voltage of 100 kV. The acquired TEM images were analyzed using an image analysis system (image processing, particle analysis, and length measurement software, MultiImageTool, manufactured by System Infrontia Co., Ltd.) to measure the morphological classification and shape coefficient of approximately 1000 carbon materials. The image analysis was performed at a resolution of 6 nm or less per pixel, and to reliably capture the morphological information of the connected structures, an area equivalent diameter of 70 pixels to 500 nm was used. ２ Objects smaller than the specified size were excluded from the analysis. The various parameters of the connected structures used in the analysis were the same values ​​used for morphological classification and the calculation of shape factors.

[0124] (Measurement Method for Specific Surface Area, Pore Diameter, and Pore Volume) Nitrogen adsorption and desorption measurements were performed on the carbon material of the present invention using an automated specific surface area / pore distribution analyzer (BELSORP MINI, manufactured by Microtrac-Bel Co., Ltd.). Before measurement, the sample was dried under reduced pressure at 150°C for 6 hours using BEL pre. From the obtained adsorption isotherms, the BET specific surface area was determined using the BET method. Furthermore, based on the obtained adsorption and desorption isotherms, the total pore volume was measured by converting the amount of nitrogen adsorbed at a relative pressure P / P0 = 0.99 at -196°C to the volume of liquid nitrogen density. The pore diameter distribution was determined by the BJH method. Nitrogen adsorption and desorption measurements were performed using the method described above to determine the BET specific surface area, average pore diameter, mode pore diameter, total pore volume (P / P0 = 0.99), micropore volume (P / P0 = ~0.1), mesopore volume (P / P0 = 0.1 to 0.96), and macropore volume (P / P0 = 0.96 to 0.99).

[0125] (Average Primary Particle Diameter) The mode pore diameter obtained by the nitrogen adsorption / desorption measurement described above can be used as the inner diameter of the hollow portion of the primary particles in the carbon material of the present invention. Furthermore, the primary particle diameter, which is the outer diameter of the primary particles in the carbon material of the present invention, can be determined by adding twice the value obtained by multiplying the average number of layers n by the average interplanar spacing obtained from the 002 diffraction line to the mode pore diameter. The primary particle diameter may also be determined by image analysis of TEM images.

[0126] (Raman Spectroscopy) Raman spectroscopy was performed on the obtained carbon material using a micro-Raman spectrometer (LabRAM HR-800, manufactured by Horiba, Ltd.). A 532 nm laser was used for the measurement, with the filter set to D1 and the hole set to 100 μm. The measurement range was 300–3500 cm². －１ This was determined from the measured Raman spectrum (I Ｇ / I ２Ｄ ), (I Ｄ / I Ｇ The intensity ratios of ) and other factors were calculated.

[0127] (Temperature-Pressure Desorption Mass Spectrometry (TPD-MS)) Temperature-pressure desorption mass spectrometry (TPD-MS) using an ultra-high-sensitivity vacuum temperature-pressure desorption mass spectrometer (developed at Tohoku University; see T. Ishii et al., CARBON 80, 2014, 135-145) allows for accurate qualitative and quantitative analysis of oxygen-containing functional groups and hydrogen-terminated edge sites. Specifically, 1 to 3 mg of carbon material was placed on a graphite sample stage, vacuum-heated to 1800°C at a heating rate of 10°C / min, and the gas released during heating was analyzed using the ultra-high-sensitivity vacuum temperature-pressure desorption mass spectrometer 300 to qualitatively and quantitatively analyze oxygen-containing functional groups and hydrogen-terminated edge sites.

[0128] (Measurement of composite layer resistance) Using the carbon material of the present invention, dispersions containing it were prepared, and polymer composite materials were fabricated using these dispersions. The carbon material (0.5 mass%) was mixed with ternary NCM (LiNi) with an average particle size of 8 μm. ０．５ Co ０．２ Mn ０．３ O ２ 97.5% by mass of Kelong's positive electrode active material powder and 2% by mass of PVDF (Kureha Corporation) were added to the solvent N-methylpyrrolidone (NMP) and mixed. The resulting mixture was placed in a rotary mixer and kneaded at a rotation speed of 2000 rpm while adding NMP in several batches until a uniform and appropriate viscosity was achieved, thereby preparing a slurry. The slurry was applied to a 100 μm thick PET film at a constant speed using a doctor blade coating device with a micrometer. The film was then dried at 110°C to obtain a raw material. The raw material was then punched out using a φ20 mm punch-type die-cutting machine to obtain a composite material layer sample. The resistivity of the composite material layer obtained above was measured using a low resistivity meter (Lorestar-FX MCP-T380, manufactured by Nitto Seikou Analytech Co., Ltd.).

[0129] Examples 1 to 8 and Comparative Examples 1 to 2 are as shown in Table 1 below: number of carbonaceous layers, average primary particle diameter of hollow particulate portion, BET specific surface area (m²). ２ The following parameters were measured: cubic centimeters per g, average pore diameter (nm), mode pore diameter (nm), total pore volume (cc / g) (P / P0 = ~0.99), micropore volume (cc / g) (P / P0 = 0 to 0.1), mesopore volume (cc / g) (P / P0 = 0.1 to 0.96), and macropore volume (cc / g) (P / P0 = 0.96 to 0.99).

[0130] (Measurement results)

[0131] (Evaluation Results) Examples 1 to 8 were found to have a number of layers in the range of 1 to 6, and an average primary particle diameter in the range of 20 to 200 nm. In addition, Examples 1 to 8 had a BET specific surface area SA of 100 to 2700 m². ２ It can be seen that the values ​​are within the range of / g. Examples 1 to 8 show that the average pore diameter is in the range of 8 nm to 100 nm, and the mode pore diameter is in the range of 1 nm to 500 nm.

[0132] For Examples 1 to 8 and Comparative Examples 1 to 2, the total pore volume (cc / g) (P / P0 = ~0.99), micropore volume (cc / g) (P / P0 = 0 to 0.1), mesopore volume (cc / g) (P / P0 = 0.1 to 0.96), and macropore volume (cc / g) (P / P0 = 0.96 to 0.99) were measured, as shown in Table 2 below.

[0133] (Measurement results)

[0134] (Evaluation results) Examples 1 to 8 show that the total pore volume is in the range of 2.5 cc / g to 20.0 cc / g.

[0135] From the measured values ​​of micropore volume (P / P0 = 0 to 0.1) and mesopore volume (P / P0 = 0.1 to 0.96) shown in Table 2, the percentage V of the total volume (total mesopore volume) formed by mesopores in the range of 2 nm to 50 nm relative to the sum of the micropore volume M1 and the total mesopore volume M2 was measured. The results are shown in Table 3.

[0136]

[0137] Table 3 shows that Examples 1 to 8 represent the volume percentage V of the total volume (M1 + M2) of the total mesopore volume M2. Ｍ２ It can be seen that the percentage is 82.0% or higher.

[0138] Also, the mesopore volume (first mesopore volume) of 2 nm or more and 10 nm or less, the ratio thereof to the total pore volume (first mesopore volume ratio), the mesopore volume (second mesopore volume) of more than 10 nm and 50 nm or less, and the ratio thereof to the total pore volume (second mesopore volume ratio), and the ratio of the second mesopore volume to the total volume of mesopores (total mesopore volume) were determined. The results are shown in Table 4 below.

[0139]

[0140] As is clear from Table 4, in Examples 1 to 8, the ratio of the second mesopore volume was large, in the range of 65.0% or more and 95% or less, and was 50% or more.

[0141] Also, the percentage of the pore volume of 10 nm or less in the total pore volume (percentage of the first pore volume) and the percentage of the pore volume of more than 10 nm in the total pore volume (percentage of the second pore volume) were determined. The results are shown in Table 5.

[0142]

[0143] It can be seen that in Examples 1 to 8, the percentage of the second pore volume in the total pore volume is in the range of 77.5% or more and 82.0% or more. On the other hand, Comparative Examples 1 and 2 are 36.9% or less, indicating that they are outside the scope of the present invention.

[0144] Also, for Raman spectrum measurement, intensity ratios such as (I Ｇ / I ２Ｄ ), (I Ｄ / I Ｇ ) are calculated from the measured Raman spectrum and shown in Table 6.

[0145]

[0146] As shown in Table 6, in Examples 1 to 8, the intensity ratio (I Ｇ / I ２Ｄ ) is in the range of 1.0 to 5.0, and the intensity ratio (I Ｄ / I Ｇ ) is in the range of 1.57 to 10.

[0147] Furthermore, the amount of gas released from the carbon material when it was heated to 1800°C was measured using thermal desorption mass spectrometry (TPD-MS), and the results were analyzed by mass spectrometry. The results are shown in Table 7.

[0148]

[0149] As shown in Table 7, it can be seen that the total gas volume is small in Examples 1 to 8. Furthermore, it was confirmed that the oxygen content, O / C ratio, total gas volume, and edge area are sufficiently low.

[0150] Furthermore, regarding the morphological features of the carbon material, Table 8 shows the numerical proportion of each morphology present.

[0151]

[0152] As shown in Table 8, Examples 1-4 and 6-8 show that branched shapes account for 12.5% ​​or more, linear shapes account for 31.2% or more, and the combined proportion of branched and linear shapes is 51.3% or more.

[0153] Furthermore, the results for the composite layer resistance, which represents the electrical properties of the carbon material, are shown in Table 9.

[0154]

[0155] As shown in Table 9, Examples 1 to 8 have asphalt layer resistances in the range of 42 to 128 (Ω·cm), indicating low resistance values. In contrast, Comparative Examples 1 and 2, which are carbon materials manufactured using the same metal oxide mold material, have asphalt layer resistances in the range of 475 to 7051 (Ω·cm), indicating very high resistance. Here, for example, a comprehensive assessment of the results in Tables 8 and 9 reveals that all examples with a branched morphology ratio of 10.0% to 50.0% have low asphalt layer resistances of 128 (Ω·cm) or less, while Comparative Examples 1 and 2 have a branched morphology ratio of less than 10.0%, resulting in significantly higher asphalt layer resistances.

[0156] 1 Carbon material 11 Graphene 2 Connecting structure 21 Hollow particulate part 22 Enclosing wall 23 Internal space 25 Communicating space 31 Linear form 32 Branched form 41 First end of connecting structure 42 Second end of connecting structure 43 Third end of connecting structure 300 Ultra-high sensitivity vacuum temperature-precipitation desorption mass spectrometer 310 Quartz reactor 311 Radioactive thermometer 312 Sample holder 313 High-frequency induction coil 320 Detection unit 321 Cold cathode Pirani gauge 322 Capacitance gauge 323 Quadrupole mass spectrometer 324 Turbomolecular pump 325 Rotary pump 326 Valve 327 Gas reservoir 328 Resistance g Calibration gas w Cooling water

Claims

A carbon material comprising one or more connected structures having an extended shape in which multiple hollow particulate portions, formed by surrounding walls made of carbonaceous material including a graphene structure, are linked together in a bead-like fashion, and pores are formed in the connected structures. 　 When the carbon material is divided into micropores less than 2 nm, mesopores between 2 nm and 50 nm, and macropores greater than 50 nm, and the mesopores are further divided into first mesopores between 2 nm and 10 nm, and second mesopores greater than 10 nm and less than 50 nm, The carbon material according to claim 1, wherein the percentage of the volume of the second mesopore (second mesopore volume) relative to the total volume (total mesopore volume) M2 formed by the mesopores in the range of 2 nm to 50 nm is 50% or more. 　 The carbon material represents a volume percentage V of the total volume (M1 + M2) obtained by adding the total volume (M1 + M2) of the total volume (M2) of the total volume (M2) of the mesopores (total volume of mesopores) M2. Ｍ２ The carbon material according to claim 2, wherein the carbon content is 82.0% or more. 　 The carbon material according to claim 1, wherein the pores of the carbon material are divided into first pores in the range of 10 nm or less and second pores in the range of more than 10 nm, and when the total pore volume of the pores is divided into the volume of the first pores (first pore volume) and the volume of the second pores (second pore volume), the percentage of the second pore volume to the total pore volume is 50% or more. 　 The carbon material according to claim 1, wherein the carbon material is composed of the connecting structure, and a portion of the hollow particulate portion constituting the connecting structure is connected to form a communicating space in which the internal spaces of the connecting structure are interconnected. 　 The carbon material according to claim 1, wherein one or more of the plurality of hollow particulate parts constituting the connecting structure have openings formed in them, such that the internal space communicates with the external space. 　 The carbon material according to claim 1, wherein the carbon material further includes fibrous portions, and the connecting structure and the fibrous portions are mixed and integrated or formed in close proximity to each other. 　 The carbon material according to claim 1, wherein the surrounding wall is formed of carbonaceous layers in the range of one to six layers. 　 The carbon material is measured by the intensity of the 2D band (I) in Raman spectroscopy. ２Ｄ The intensity of the G band (I) Ｇ ) intensity ratio (I Ｇ / I ２Ｄ The carbon material according to claim 1, wherein the coefficient of 　 The carbon material according to claim 1, wherein the average primary particle diameter forming the hollow particulate portion is in the range of 20 nm to 200 nm. 　 The carbon material according to claim 1, wherein the average pore diameter of the pores formed in the connecting structure is in the range of 8 nm to 100 nm. 　 The carbon material according to claim 1, wherein the total pore volume of the pores is in the range of 2.5 cc / g or more and 20.0 cc / g or less. 　 The carbon material has a BET specific surface area of ​​100 m². ２ / g or more 2700m ２ The carbon material according to claim 1, wherein the carbon material is in the range of / g or less.

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