Carbon material

Abstract

The present invention provides a carbon material comprising connection structures that form internal spaces inside the carbon material, with the internal spaces communicating with each other to form a communication space, wherein the existence form of the outer shape of the connection structure is controlled. A carbon material 1 according to the present invention comprises one or more connection structures 2 having an extension shape in which a plurality of hollow particle-like parts 21 are connected in a bead shape, wherein the hollow particle-like parts 21 partition and form internal spaces 23 and are defined by surrounding walls 22 composed of a carbonaceous material including a graphene structure. Pores are formed in the connection structures 2. When the existence form of the connection structures 2 is classified into four types: branched, linear, spherical, and elliptical, the proportion of the branched form to the total of the connection structures 2 classified into these four types is 10.0 to 50.0%.

Description

Carbon materials

[0001] This invention relates to carbon materials.

[0002] Carbon can bond three-dimensionally to form a diamond structure, making it an insulator. It can also bond two-dimensionally to form a hexagonal network structure, becoming conductive due to the presence of electrons that do not participate in bonding. Furthermore, carbon is chemically and electrochemically stable and widely used industrially. In addition, it is known that actual carbon can take on various structures depending on the raw materials and manufacturing methods. In fact, carbon in various structures can exist as crystalline structures such as fullerenes, carbon nanotubes, graphene, and graphene mesosponges, as well as in particulate and fibrous forms.

[0003] Carbon materials possess excellent thermal conductivity, electrical conductivity, and mechanical strength, and are being studied for applications in various fields, including electronics and energy materials. Among these, porous carbon materials such as graphene and graphene mesosponges, due to their large specific surface area, can improve electrical conductivity, including electronic and ionic conductivity, by increasing the number of conductive pathways. Furthermore, carbon materials have pores and spaces within their granular structure and surrounding interconnected structures, allowing for the penetration and retention of electrolytes containing dissolved lithium ions, resulting in excellent ion supply during reactions. Therefore, in recent years, active research has been conducted on carbon materials as electrodes and peripheral materials for energy devices such as batteries and capacitors.

[0004] For example, Patent Document 1 describes a plurality of carbon nanoparticles containing graphene, with a median diameter of 0.1 to 50 μm and a BET specific surface area of ​​50 to 2,000 m². ２It 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 size 0.1 to 10 nm and pores of size 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 conductivity and insufficient characteristics in terms of 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. Furthermore, 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 if the BET specific surface area is large, 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 conductivity or ionic conductivity and has a low composite layer resistance when applied to an electrode, by providing a connecting structure in which the internal space is partitioned, for example, such as a communicating space, and in which pores are formed and have a specific structure.

[0008] To solve the above problems, the present inventors conducted diligent research and succeeded in developing a carbon material that improves conductivity or ion supply and reduces the composite layer resistance when applied to an electrode, provided that the carbon material comprises one or more connected structures having an extended shape in which a plurality of hollow particulate parts formed by a surrounding wall made of carbonaceous material containing graphene are linked together in a bead-like manner, pores are formed in the connected structures, and furthermore, when the existence form of the carbon material is classified into four types of forms: branched form, linear form, spherical form, and elliptical form, the proportion of the branched form in the total of the four types of forms of the connected structure is 10.0% or more and 50.0% or less. Furthermore, the inventors have diligently studied and succeeded in developing a carbon material that has improved conductivity or ion supply and low composite layer resistance when applied to an electrode, comprising one or more connected structures having an extended shape in which a plurality of hollow particulate parts formed by a surrounding wall made of carbonaceous material including a graphene structure are linked together in a bead-like manner, pores are formed in the connected structures, and the shape coefficient SF is within a predetermined range, thereby completing the present invention.

[0009] The features of the present invention are listed below. (1) A carbon material comprising one or more connected structures having an extended shape in which a plurality of hollow particulate parts formed by surrounding walls made of carbonaceous material containing graphene partitions an internal space and are linked together in a bead-like manner, wherein pores are formed in the connected structures, and when the existence form of the connected structures is classified into four types of forms: branched form, linear form, spherical form and elliptical form, the proportion of the branched form in the total of the four types of forms of the connected structures is 10.0% or more and 50.0% or less. (2) A carbon material comprising one or more connected structures having an extended shape in which a plurality of hollow particulate parts formed by surrounding walls made of carbonaceous material containing graphene partitions an internal space and are linked together in a bead-like manner, wherein pores are formed in the connected structures, and the shape coefficient SF, represented by formula (1), is in the range of 0.4 or more and 3.0 or less. Here, SF = (PM2 / A) - (ML2 / A): Equation (1), and furthermore, the shape factor PM2 / A = (L ２ π) / (4A): Equation (2), the shape factor is ML2 / A = P ２ / (4・π・A): Equation (3), where L is the maximum length of the carbon material, P is the perimeter of the carbon material, and A is the projected area of ​​the carbon material. (3) The carbon material is the carbon material described in (2) above, wherein the relationship between ML2 / A and PM2 / A is ML2 / A ≤ PM2 / A. (4) The carbon material is the carbon material described in (1) or (2) above, wherein the average primary particle diameter forming the hollow particulate portion is in the range of 20 nm to 200 nm. (5) The carbon material has a number density of 5 × 10 １４ ~1 x 10 １８The carbon material according to the above (1) or (2) within the range of g / g. (6) The carbon material divides the pores into micropores less than 2 nm, mesopores of 2 nm or more and 50 nm or less, and macropores more than 50 nm, and when the mesopores are further divided into the first mesopores of 2 nm or more and 10 nm or less and the second mesopores of more than 10 nm and 50 nm or less, the percentage of the volume of the second mesopores (second mesopore volume) in the total volume formed by the mesopores within the range of 2 nm or more and 50 nm or less (total mesopore volume) M2 is 50.0% or more, the carbon material according to the above (1) or (2). (7) The carbon material is the volume percentage V of the total volume of the micropores (total micropore volume) M1 and the total mesopore volume M2 of the mesopores in the total volume (M1 + M2) obtained by adding the total volume formed by the mesopores (total mesopore volume) M2 Ｍ２ is 82.0% or more, the carbon material according to the above (6). (8) The carbon material divides the pores into the first pores within the range of 10 nm or less and the second pores within 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 volume of the second pores in the total pore volume is 50% or more, the carbon material according to the above (1) or (2). (9) The carbon material is composed of the plurality of connected structures, and a communication space in which the internal spaces of the plurality of connected structures communicate with each other is formed by connecting a part of the hollow particle-like parts constituting the plurality of connected structures, the carbon material according to the above (1) or (2). (10) The carbon material is the carbon material according to the above (1) or (2), in which the surrounding wall is formed of one or more and six or less carbonaceous layers containing graphene. (11) The carbon material is the intensity ratio (I ２Ｄ ) of the intensity of the G band (I Ｇ ) to the intensity of the 2D band in Raman spectroscopic measurement (I Ｇ / I ２Ｄ(1) or (2) above, wherein the carbon material has a BET specific surface area of ​​1.00 or more and 5.0 or less. (12) The carbon material is the ２ / g or more 2700m ２ A carbon material as described in (1) or (2) above, which is in the range of / g or less.

[0010] According to the present invention, by providing a connecting structure in which the internal space is partitioned, for example, as a communicating space, and which has a branched shape and a predetermined proportion of the whole, it is possible to provide a carbon material that has improved conductivity or ion supply properties and a low composite layer resistance when applied to an electrode. Furthermore, according to the present invention, by providing a connecting structure in which the internal space is partitioned, for example, as a communicating space, and which has a shape coefficient SF within a predetermined range, it is possible to provide a carbon material that has improved conductivity or ion supply properties and 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 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 7 shows an example of a TEM image obtained by observing the carbon material of the present invention 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 a plurality of hollow particulate portions formed by surrounding walls made of carbonaceous material containing graphene, which partition the internal space, and these plurality of hollow particulate portions form a connected structure having an extended shape in which they are linked in a bead-like manner, and the carbon material is composed of one connected structure or a plurality of connected connected structures, and pores are formed in the connected 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 1 of the present invention can improve conductivity by possessing the electronic conductivity of graphene 11 and having a large pore volume that allows it to retain chemical substances and possess ionic conductivity, 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 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 ２ＤThis can also be confirmed by checking if the value is 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. －１ The 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 ２ＤWhen the value 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.

[0020] Furthermore, the strength of the G band in the carbon material of this embodiment (I Ｇ The 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 10.00, more preferably in the range of 0.5 to 5.00, even more preferably in the range of 1 to 3.00, even more preferably in the range of 1.2 to 2.50, 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 of the present invention may be either or both graphene mesoponge (GMS) and carbon mesoponge (CMS). 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 due to having a carbonaceous layer containing 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 by elastic deformation. In the carbon material of the present invention, the portion consisting of a single or multiple graphene structure exhibits elastic deformability, while the defective portions of graphene and amorphous carbon portions exhibit plastic deformability. On the other hand, if the carbonaceous layer containing graphene excessively exceeds the number of carbonaceous layers (such as graphite), it will maintain elastic deformability within a certain stress range, but if 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, and 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 then 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 primary 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 preferably within the range of 50 nm or less. The inner diameter of the primary 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, for example, in the range of 20 nm to 200 nm. If the average primary particle diameter is less than 20 nm, the specific surface area decreases, and the electronic conductivity and ionic conductivity 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 have 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. Alternatively, the primary particle diameter can be determined by TEM image analysis or the like.

[0026] (Internal Space) Furthermore, the carbon material of the present invention has an internal space in the hollow particulate portion, which increases its specific surface area. In addition, the increased surface area of ​​the hollow particulate portion increases the number of conductive paths through which electrons flow, thereby improving 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 can improve charge-discharge characteristics when used as part of an electrode material for secondary batteries such as lithium-ion batteries, while also maintaining good characteristics such as charge capacity and discharge capacity. For example, when it has a linear form in which hollow particulate parts 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 parts and the internal space of the hollow particulate parts contribute to increasing the 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 exhibits an external shape 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 connected, 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 a length 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 conductivity such as electronic conductivity 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 supplyability.

[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, conductivity can be improved. Moreover, the carbon material of the present invention can improve ion supply by retaining and supplying ions through the large volume of pores. The carbon material of the present invention connects the internal and external spaces 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, by having pores in the surrounding wall made of carbonaceous material containing graphene, forms a larger specific surface area, increasing the number of conductive paths, lowering electrical resistance, and improving 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 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, high ionic and electronic conductivity can be achieved, making it suitable for improving 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 ionic conductivity and electronic conductivity.

[0036] The total pore volume V of the carbon material of the present invention is preferably 2.5 cc / g or more, more preferably 2.75 cc / g or more, and more preferably 3.0 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, conductivity and ion supply properties can be well balanced. 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 conductivity and ion supply, 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 the graphene structure 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 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 of more than 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 ion supply capacity 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 conductivity and ion supply capacity 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 conductivity and strength characteristics 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, conductivity and mechanical strength are highly balanced.

[0045] Furthermore, in the carbon material of the present invention, the total volume M2 formed by mesopores in the range of 2 nm to 50 nm relative to the total pore volume V is a volume percentage of the total volume (M1 + M2) obtained by adding the total volume of micropores less than 2 nm (total micropore volume) M1 and the total mesopore volume M2. Ｍ２ The ratio (= 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. The upper limit is preferably 95.0% or less. Furthermore, it is preferable that the micropore ratio M1 is 18.0% or less. This is because fewer micropores result in greater mechanical strength and improved ion supply. Also, if there are many pores larger than 50 nm, the mechanical strength of the hollow particulate portion may decrease. In this respect, by having mesopores in the range of 2 nm to 50 nm occupy a predetermined range of mesopore volume ratios, the decrease in the mechanical strength of the hollow particulate portion can be suppressed.

[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 and 50 nm (second mesopore volume), it is preferable that the ratio of the second mesopore volume to the total mesopore volume is in the range of 50.0% or more. Even if many first mesopores in the range of 2 nm to less than 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 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 setting the percentage of second mesopores in the range of 2 nm to 50 nm to 50% of the total mesopores M2 to 50 nm to 50% or more, the decrease in the mechanical strength of the hollow particulate material can be suppressed.

[0047] Furthermore, when the carbon material of the present invention divides the pores formed in the linked structure 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), it is preferable that the ratio (percentage) of the second pore volume to the total pore volume is in the range of 50.0% or more. In the carbon material of the present invention, the ratio of the second pore volume is 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 92% or less, 90% or less, 89% or less, or 88% or less. If the ratio of the second pore volume more than 10 nm in the carbon material 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 imaging diagnostics, the forms of existence of the carbon material of the present invention are classified into four types: "Sphereoidal (spherical)", "Ellipsoidal (elliptical)", "Linear (linear)", and "Branched (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 Formation) Figure 4 is a schematic diagram showing a branched form, one of the four forms of existence of the connected structure constituting the carbon material. In the carbon material 1 of the present invention, the branched base ends of the second hollow particulate portion 212, which constitutes a different path, are connected to the first hollow particulate portion 211, which 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, the branched portion that constitutes a path different from at least one of the first hollow particulate portion 211 and the second hollow particulate portion may also be connected. With this configuration, for example, the portion that forms the conductive path is increased, and the portion that increases the supply capacity of the electrolyte containing ions is also increased, so the rapid charge and discharge characteristics are further improved, and characteristics such as charge capacity and discharge capacity are also improved. Furthermore, the branched form 32 may be composed of a connected structure that is connected in a ring shape. By configuring it in this way, for example, the number of conductive paths can be increased, and the supply capacity of the electrolyte can also be improved.

[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, 10.0% 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. The branched forms 32 can improve mechanical strength by arranging linearly and forming a structure in which the hollow particulate portions 21 at the branched ends come into contact with other connecting structures 2.

[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 seen in Figure 5, when the carbon material 1 of the present invention has multiple hollow particulate parts 21 connected 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 parts 21 have carbonaceous material containing graphene 11 as shown in Figure 1 as a surrounding wall 22 that forms an internal space 23. The surrounding wall 22 has pores on its surface. The internal space 23 is also connected to form a communication space 25. The linear form 31 does not necessarily mean a single connection, and hollow particulate portions 21 may extend laterally. In the carbon material 1 of the present invention, the linear form 31 has one or more narrow sections with a width of three times or less the inner diameter of the hollow particulate portion 21 in the intermediate portion 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. In the carbon material 1 of the present invention, the tip of the linear form 31 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, and the third end 43 of the connecting structure 2 is located at its tip. The narrow section 26 only needs to 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 the linear morphology 31 to 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, 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. Due to the linear structure, the conductivity can be increased by the penetration effect, which is greatly enhanced by the kneading pressure in the resin or by the influence of an electric field in the solution, causing the elements to align linearly.

[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 improving ion retention and supply. In particular, by making the carbon materials linear or branched, conductivity can be increased by increasing the penetration effect as they align linearly due to the kneading pressure in the resin or the influence of an electric field in the solution. Furthermore, the branched morphology, in particular, can improve mechanical strength by arranging linearly and forming a structure in which the hollow particulate portions at the branched ends come into contact with other connecting structures. In addition, the proportion of branched morphology in the carbon material of the present invention / (the sum of the proportion of branched morphology and linear morphology) 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 from the linear arrangement and the effect of improving mechanical strength by forming a structure in which the branched ends come into contact with other branched connecting structures.

[0059] The carbon material of the present invention enhances the conductivity of the carbon material and significantly improves the rapid discharge performance, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries using ion-containing electrolytes. This is achieved by, in the image analysis of the aggregates of carbon material assemblies, setting the circularity, which represents the complexity of the aggregates, below a specific value, and by making PM2 / A, which indicates the degree of unevenness of the circumferential surface, larger than ML2 / A, which indicates the circular state of the shape factor, and further defining the relationship between ML2 / A and PM2 / A in the shape factor SF. The shape factor of the present invention is described in detail below.

[0060] (Shape Factor SF) 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), and furthermore, the shape factor PM2 / A = P ２ / (4・π・A): Equation (2) The shape factor is ML2 / A = (L ２ Equation (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 0.4 or more, preferably 1.0 or more. The upper limit of SF is 3.0 or less, preferably 2.6 or less. The present invention is suitable when the shape factor SF is in the range of 0.4 to 3.0, as it increases the specific surface area per unit weight, balancing the effect of improving conductivity with the effect of forming a structure that comes into contact with other carbon materials and improving mechanical strength.

[0061] 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 further departure from a circle and an irregular shape. It represents a comparison with a circle whose circumference is equal to its perimeter. Therefore, by setting the shape factor ML2 / A of the carbon material of the present invention to the range of 1.0 to 5.0, preferably 2.4 to 3.5, the specific surface area per unit weight can be increased, and conductivity can be improved.

[0062] Furthermore, the shape factor PM2 / A calculated by the image analysis method for the carbon material of the present invention is preferably in the range of 1.0 to 10.0, more preferably 1.5 to 2.0 to 2.5, and most preferably 2.7 or higher. The upper limit is preferably 10.0 or less, 8.0 or less, 7.5 or less, and most preferably 6.0. 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 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.

[0063] 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. Preferably, 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 greatly improves the rapid discharge performance, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries using an electrolyte containing ions.

[0064] (Number Density) The number density of the carbon material of the present invention is preferably 5 × 10 １４ ~1 x 10 １８ It is preferable that the amount is pieces / g, and more preferably 1 × 10 １５ ~6 x 10 １７ pieces / g, 1.5×10 １５ ~5 x 10 １７ pieces / g, 1.8×10 １５ ~4 x 10 １７ pieces / g, 1.0×10 １７ ~3.5 x 10 １７ It is also preferable that the number density of the carbon material is within the range of pieces / g. When the number density of the carbon material is within this range, the amount of oil absorbed is optimal and therefore preferable.

[0065] The number density Np (particles / g) of carbon material can be calculated using the following formula (4): Number density Np (particles / g) = SA / (π・D １ ２ +π・D ２ ２ ): Equation (4) Here, SA is the BET specific surface area (m ２ / g) to, D １ D is the outer diameter of the primary particle. ２ Here, D represents the inner diameter of the primary particle (for hollow particles, it is "0" for solid particles). ２ D is the inner diameter of the primary particle. １ D is the outer diameter of the primary particle. ２ The aforementioned mode pore size can be used. D １ This 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. Also, D １ This can be determined by TEM image analysis, etc.

[0066] Furthermore, by specifying the shape factor and then the number density of the carbon material of the present invention, an efficient conductive path for electronic conductivity can be created, and by holding and supplying a large amount of electrolyte, ionic conductivity can also be greatly enhanced at the same time. As a result, lithium-ion secondary batteries to which the carbon material of the present invention is applied can further improve rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics. Therefore, the outer diameter D of the primary particles １ and the inner diameter D of the primary particle ２ It can be seen that the smaller the difference between the dove and the number of particles, the higher the number density can be. In particular, hollow particles can have a higher number density than solid particles.

[0067] (Graphene Mesosponge) The carbon material in this embodiment may be a graphene mesosponge (GMS). A graphene mesosponge is a porous carbon material having a graphene crystal structure, or a porous carbon material. Due to its large specific surface area, it tends to exhibit high oil absorption. In particular, GMS having the above-described linked structure tends to exhibit extremely high oil absorption. The average number of graphene layers N is, for example, 0.9 to 5.0, and preferably 1.0 to 2.0. The fewer layers of the graphene crystal structure there are, the larger the specific surface area of ​​the porous carbon material. GMS also has a particularly large elastic deformation work rate and tends to recover without plastic deformation under weak stress.

[0068] (Carbon Mesosponge) The carbon material of this embodiment may also be a carbon mesosponge (CMS). CMS is a porous carbon material similar to GMS, except that the surrounding walls constituting the sponge do not have or have very little graphene crystal structure. Therefore, it does not necessarily exhibit the same level of conductivity as GMS, but it can exhibit high oil absorption similar to GMS.

[0069] (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.

[0070] By using the ultra-high-sensitivity vacuum temperature-controlled desorption mass spectrometer (hereinafter sometimes simply referred to as "temperature-controlled desorption mass spectrometer") 300 (developed at Tohoku University, see T. Ishii et al., CARBON 80, 2014, 135-145), temperature-controlled desorption mass spectrometry (TPD-MS) can accurately qualitatively and quantitatively analyze oxygen-containing functional groups and hydrogen-terminated edge sites. 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 by the mass spectrometer 300, thereby accurately qualitatively and quantitatively analyzing oxygen-containing functional groups and hydrogen-terminated edge sites. Figure 6 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 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.

[0071] 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 ２ The 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.

[0072] The present invention's temperature-controlled desorption mass spectrometer 300, which measures the desorbed gas from a carbon material during temperature increase, uses H2O2 to measure the gas released from the carbon material. ２ Amount, H ２ O amount, CO amount and CO ２Although 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.

[0073] Furthermore, the amount of gas measured by the thermal 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 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] 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 ２ The 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.

[0075] 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.

[0076] 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 temperature-controlled 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%))

[0077] 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 preferably 0.50 or less, 0.10 or less, 0.05 or less, or 0.01 or less. 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.

[0078] (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 1500m 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, it is possible to easily supply ions, thereby improving ion supplyability. 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.

[0079] (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.

[0080] 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.

[0081] (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.

[0082] (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.

[0083] (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.

[0084] (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 in the range of, for example, 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.

[0085] (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.

[0086] (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.

[0087] (Electrodes) The carbon material of the present invention is used, for example, as an electrode in a lithium-ion secondary battery. This electrode may be either a negative electrode or a positive electrode, and can be obtained, for example, by coating the above electrode slurry onto a current collector and then drying it. The current collector can be any type that is normally used for positive or negative electrodes.

[0088] (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.

[0089] (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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] The carbon material of the present invention can be used for applications other than electrochemical devices. For example, it is suitable for use in electronic device systems 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 leads to the reduction of carbon dioxide emissions and energy conservation, it can be used in applications that contribute to weight reduction by taking advantage of its hollow shape, such as reinforcing agents for various types of rubber including tires, paints, coloring pigments, conductive fillers for various polymers, and additives for magnetic recording media. Because the carbon material of the present invention exhibits high oil absorption, it is also suitable as a filler for polymers, including the rubber reinforcing materials mentioned above.

[0094] (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.

[0095] 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.

[0096] 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. A heat treatment temperature within this range is preferable because it allows for the acquisition of a carbon material with 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.

[0097] This adjusts the structural defects in the carbonaceous material, including the graphene structure that makes up 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 intrusion pores created in the surrounding wall formed from the carbonaceous material. By changing reaction conditions such as heat treatment temperature and heat treatment time, the degree of these structural defects can be adjusted; that is, the size of the communication space inside the hollow particulate portion and the size of the intrusion pores that allow the electrolyte to penetrate into the particles can be adjusted.

[0098] 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.

[0099] During the heating process, structural defects in the graphene and non-graphene components that make up the carbonaceous layer may be adjusted. These structural defects include spaces created within the aggregate structure due to the dissolution of the template material and penetration pores created in the outer shell formed from the carbonaceous layer. By changing reaction conditions such as heat treatment temperature and heat treatment 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 penetration pores that allow oil or electrolyte to penetrate into the particles can be adjusted.

[0100] 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 for carbon deposition reactions. Examples of mold materials include metal compounds, metalloid compounds, and nonmetal compounds, and preferably ceramic particles and / or carbonate particles.

[0101] Examples of ceramic particles include glass, cement, fine ceramics, and more specifically, particles such as silica (silicon dioxide), alumina, and magnesia (magnesium oxide).

[0102] 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.

[0103] 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.

[0104] 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.

[0105] By the manufacturing method described above, the carbon materials of the present invention, such as CMS and GMS, can be easily manufactured.

[0106] 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.

[0107] <Example 1> (Manufacturing of carbon material 1) (CVD process) As a raw material for the mold material, atomized silicon dioxide (SiO ２ AEROSIL® NX90G; particle size 38 nm, BET specific surface area 71 m² ２Approximately 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.

[0108] (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.

[0109] (1) The carbonaceous layer-coated mold material was taken into a 100-ml PFA beaker, and ultrapure water was added to the extent that the entire carbonaceous layer-coated mold material was wetted. (2) After adding 46% hydrofluoric acid, it was stirred with a stirrer for 2 hours. (3) After stopping the stirring, it was allowed to stand until the sample settled. (4) A PTFE membrane filter (47 mmφ, pore size 0.1 μm) was used to perform suction filtration from the supernatant. (5) The sample on the filter paper was washed with about 39 mL of ultrapure water and suction-filtered. This operation was repeated 3 times. (6) The sample on the filter paper was collected into the original PFA beaker. (7) The operations in (2) to (6) above were repeated again. (8) About 40 mL of ultrapure water was added, and it was stirred with a stirrer for 1 hour. (9) After stopping the stirring, it was allowed to stand until the sample settled. (10) The supernatant was discarded, 5% caustic soda was added, and it was stirred for 12 hours while heating to 80 °C. (11) After stopping the stirring, it was allowed to stand until the sample settled. (12) A PTFE membrane filter (47 mmφ, pore size 0.1 μm) was used to perform suction filtration from the supernatant. (13) The sample on the filter paper was washed with ultrapure water and suction-filtered. This operation was repeated until the filtrate became neutral. (14) The sample on the filter paper was collected into a petri dish and dried in a dryer at 110 °C for 8 hours.

[0110] (Heat Treatment) The obtained carbon material precursor was put into a rectangular high-temperature heating furnace (manufactured by Izumi Techno Co., Ltd.), and after reducing the pressure to the order of 10 －１ Pa, it was heated to 1800 °C at a heating rate of 15 °C / min under the flow of argon gas (10 mL / min) and held at that temperature for 1 hour for firing. Then, it was cooled to room temperature to obtain a carbon material.

[0111] <Example 2>A carbon material was obtained by operating in the same manner as in Example 1 except that the CVD reaction time was 60 minutes.

[0112] <Example 3>A carbon material was obtained by operating in the same manner as in Example 1 except that the CVD reaction time was 75 minutes.

[0113] <Example 4> A carbon material was obtained by operating in the same manner as in Example 1 except that the CVD reaction time was 130 minutes.

[0114] <Example 5> A carbon material was obtained by the same procedure as in Example 1, except that no heat treatment was performed.

[0115] (Manufacturing of carbon materials 2) <Example 6> (CVD process) Synthetic calcium carbonate (Shirataka O; average particle size 40 nm, BET specific surface area 51 m²) was used as the mold. ２ Approximately 8 g of (composed of 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 (a transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). While flowing argon gas at a rate of 320 mL / min and acetylene gas at a rate of 80 mL / min (raw material gas concentration of 20%), 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.

[0116] (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.

[0117] (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 setting it to the Pa order), it was heated to 1600 °C at a heating rate of 15 °C / min under the flow of argon gas (10 mL / min) and held at that temperature for 1 hour for firing. Then, it was cooled to room temperature, and the carbon material after firing was taken out, and 0.57 g of the carbon material containing heat-treated graphene was obtained. The obtained carbon material had a high carbon deposition rate of 7.1% with respect to the mold used.

[0118] <Example 7> As a mold, synthetic calcium carbonate (trade name: Viscoexcel-30; average particle diameter 80 nm, BET specific surface area 29 m ２ / g, most probable pore diameter 19 nm, linseed oil absorption amount 24 mL / 100 g, bulk density 0.40 g / mL, pH 9.5, manufactured by Shiraishi Kogyo Co., Ltd.) was used, and it was produced in the same manner as in Example 6.

[0119] <Example 8> As a mold, synthetic calcium carbonate (trade name: NEOLIGHT VT, BET specific surface area 40 m ２ / g, oil absorption amount 65 mL / 100 g, bulk density 0.25 g / mL, pH 9.5, manufactured by Takehara Chemical Industry Co., Ltd.) was used, and it was produced in the same manner as in Example 6.

[0120] <Comparative Example 1> As a carbon material, as a mold material, aluminum oxide (Al ２ O ３ / PURALOX SBa200; particle diameter 7 nm, BET specific surface area 202 m ２ / g, manufactured by SASOL) was used, and the carbon material was produced in the same manner as in Example 1.

[0121] <Comparative Example 2> As a carbon material, as a mold material, magnesium oxide (MgO / Chowa Mag MF-150; particle diameter 30 nm, BET specific surface area 129 m ２Carbon materials were produced in the same manner as in Example 1, except that a solution (MgO / g, manufactured by Kyowa Chemical Industry Co., Ltd.) was used and the mold MgO removal procedure described below was performed. (MgO mold removal) 1 to 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. Then, the sample was filtered using 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. This 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, the acetone was replaced by heating in a 60°C constant temperature bath for 10 minutes. The supernatant liquid in the beaker was removed using a pipette, and the same acetone substitution procedure was repeated. The material was then dried under reduced pressure at 150°C for 6 hours to obtain the carbon material containing graphene after mold removal.

[0122] Next, we evaluated the following items.

[0123] (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 ( ).

[0124] (Morphological Classification) Figure 7 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 primary 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 primary structure, an area equivalent diameter of 70 pixels to 500 nm was used. ２ Objects smaller than a certain size were excluded from the analysis. The parameters of the primary structures used in the analysis were the same values ​​used for calculating the shape index.

[0125] (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 automatic 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. The applicable range of the BET method was set to P / P0 = 0.05 to 0.3. 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 of 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), 2 to 10 nm mesopore volume (P / P0 = 0.1 to 0.79), and 10 to 50 nm mesopore volume (P / P0 = 0.79 to 0.96).

[0126] (Average primary particle diameter) The inner diameter of the hollow portion of the primary particles in the carbon material of the present invention can be determined using the mode pore diameter obtained by the nitrogen adsorption / desorption measurement described above. 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 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. In addition, the number density (particles / g) was calculated from the measured specific surface area, the inner diameter of the primary particles, and the outer diameter of the primary particles.

[0127] (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.

[0128] (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 mass spectrometer 300 to qualitatively and quantitatively analyze oxygen-containing functional groups and hydrogen-terminated edge sites.

[0129] (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 (Rolester FX MCP-T380, manufactured by Nitto Seikou Analytech Co., Ltd.).

[0130] Examples 1 to 8 and Comparative Examples 1 to 2 are as shown in Table 1 below: carbonaceous layer number, average primary particle diameter of hollow particulate portion, BET specific surface area (m²). ２ The number of particles per g, average pore size (nm), mode pore size (nm), and number density (particles / g) were measured.

[0131] (Measurement results)

[0132] (Evaluation Results) Examples 1 to 8 were found to have a number of layers in the range of 1 to 6 layers, 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. In addition, Examples 1 to 8 have a number density of 5 × 10 １４ ~1 x 10 １８ It can be seen that it is within the range of pieces / gram.

[0133] 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.

[0134] (Measurement results)

[0135] (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.

[0136] From the measured values ​​of micropore volume (P / P0 = ~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.

[0137]

[0138] 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.

[0139] Furthermore, the volume of mesopores between 2 nm and 10 nm (first mesopore volume) and its ratio to the total pore volume (first mesopore volume ratio), the volume of mesopores between 10 nm and 50 nm (second mesopore volume) and its ratio to the total pore volume (second mesopore volume ratio), and the ratio of the second mesopore volume to the total volume formed by the mesopores (total mesopore volume) were determined. These results are shown in Table 4 below.

[0140]

[0141] As is clear from Table 4, in Examples 1 to 8, the percentage of the second mesopore volume was large, in the range of 65.0% to 95%, and was 50% or more.

[0142] Furthermore, the percentage of pore volume smaller than 10 nm relative to the total pore volume (percentage of the first pore volume) and the percentage of pore volume larger than 10 nm relative to the total pore volume (percentage of the second pore volume) were determined. The results are shown in Table 5.

[0143]

[0144] Examples 1 to 8 show that the percentage of the second pore volume to the total pore volume is 77.5% or more and within the range of 82.0% or more.

[0145] Furthermore, Raman spectroscopy is performed using the measured Raman spectrum (I Ｇ / I ２Ｄ ), (I Ｄ / I Ｇ The intensity ratios of ) and other factors were calculated and are shown in Table 6.

[0146]

[0147] As shown in Table 6, Examples 1 to 8 have an intensity ratio (I Ｇ / I ２Ｄ ) is in the range of 1.0 to 5.0, and the intensity ratio (I Ｄ / I Ｇ It can be seen that the value is in the range of 1.57 to 10.

[0148] 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.

[0149]

[0150] 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.

[0151] Furthermore, regarding the shape and form of the carbon material, the proportion of each form is shown in Table 8.

[0152]

[0153] 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.

[0154] Furthermore, the shape factors of the carbon material of the present invention are shown in Table 9.

[0155]

[0156] As shown in Table 9, it can be seen that in all of Examples 1-4 and 6-8, the shape factor ML2 / A is between 1.0 and 5.0, the shape factor PM2 / A is between 1.0 and 10.0, and the shape factor SF is between 0.4 and 3.0.

[0157] Furthermore, the results of the composite layer resistance, which represents the electrical properties of the carbon material, are shown in Table 10.

[0158]

[0159] As shown in Table 10, 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 values. Here, for example, a comprehensive assessment of the results in Tables 8 and 10 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. Furthermore, a comprehensive assessment of the results in Tables 9 and 10 revealed that in all examples where the shape factor SF was in the range of 0.4 to 3.0, the asphalt layer resistance was low, at 128 (Ω・cm) or less. In contrast, in Comparative Examples 1 and 2, the shape factor SF was in the range of less than 0.4, which is outside the appropriate range for the present invention, resulting in significantly higher asphalt layer resistance values.

[0160] 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

1. A carbon material comprising one or more connected structures having an extended shape in which a plurality of hollow particulate parts, each formed by a surrounding wall made of carbonaceous material containing graphene and partitioning an internal space, are linked together in a bead-like manner, wherein pores are formed in the connected structures, and when the forms of existence of the connected structures are classified into four types: branched form, linear form, spherical form, and elliptical form, the proportion of the branched form in the total of the four types of forms of the connected structures is 10.0% or more and 50.0% or less.

2. A carbon material comprising one or more connected structures having an extended shape in which a plurality of hollow particulate parts, formed by surrounding walls made of carbonaceous material containing graphene, are connected in a bead-like manner, with pores formed in the connected structures, and the shape factor SF, represented by formula (1), is in the range of 0.4 to 3.

0. Here, SF = (PM2 / A) - (ML2 / A): formula (1), and further, the shape factor PM2 / A = (L ２ π) / (4A): Equation (2), the shape factor is ML2 / A = P ２ Equation (3) is given by / (4・π・A), where L is the maximum length of the carbon material, P is the perimeter of the carbon material, and A is the projected area of ​​the carbon material.

3. The carbon material according to claim 2, wherein the relationship between ML2 / A and PM2 / A is ML2 / A ≤ PM2 / A.

4. The carbon material according to claim 1 or 2, wherein the average primary particle diameter forming the hollow particulate portion is in the range of 20 nm to 200 nm.

5. The carbon material has a number density of 5 × 10 １４ ~1 x 10 １８ A carbon material according to claim 1 or 2, having a range of pieces / g.

6. The carbon material according to claim 1 or 2, wherein the carbon material is further 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 50 nm, and the percentage of the volume of the second mesopores (volume of the second mesopores) to the total volume (total volume of mesopores) M2 formed by the mesopores in the range of 2 nm and 50 nm is 50.0% or more.

7. 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 (M1) of the micropores (M1) and the total volume (M2) of the mesopores, where M2 is the total volume of the mesopores formed by the mesopores. Ｍ２ The carbon material according to claim 6, wherein the carbon content is 82.0% or more.

8. The carbon material according to claim 1 or 2, wherein the carbon material is 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.

9. The carbon material according to claim 1 or 2, wherein the carbon material is composed of a plurality of interconnected structures, and a portion of the hollow particulate portion constituting the plurality of interconnected structures is connected to form a communicating space in which the internal spaces of the plurality of interconnected structures are in communication.

10. The carbon material according to claim 1 or 2, wherein the surrounding wall is formed of one to six carbonaceous layers containing graphene.

11. The carbon material has an intensity ratio (I ２Ｄ / I Ｇ ) of the intensity of the G band (I Ｇ ) to the intensity of the 2D band (I ２Ｄ ) in Raman spectroscopic measurement within a range of 1.00 or more and 5.0 or less. The carbon material according to claim 1 or 2.

12. The carbon material according to claim 1 or 2, wherein the average pore diameter of the pores formed in the connecting structure is in the range of 8 nm to 100 nm.

13. The carbon material according to claim 1 or 2, 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.

14. The carbon material has a BET specific surface area of ​​100 m². ２ / g or more 2700m ２ A carbon material according to claim 1 or 2, wherein the carbon material is in the range of / g or less.

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