Carbon material, auxiliary electrically conductive agent, dispersion liquid, composition for electrode, slurry for electrode, electrode, lithium ion battery, and method for producing carbon material

Abstract

Provided are: a carbon material that can improve charging and discharging characteristics so as to enable rapid charging and discharging; an auxiliary electrically conductive agent; a dispersion liquid; a composition for an electrode; a slurry for an electrode; an electrode; and a lithium-ion battery. A carbon material 2 is configured such that hollow particles 4 having a carbonaceous outer shell 4a are linked. The carbon material 2 has: a linear chain portion 6 constituted from a plurality of hollow particles 4 linked in series; and a branched chain portion 7 which is connected to at least one mid-way hollow particle 44 positioned at a mid-way portion between a first end hollow particle 41 that constitutes one end of the linear chain portion 6 and a second end hollow particle 42 that constitutes the other end of the linear chain portion, and which branches from the linear chain portion 6. At least one portion selected from among a portion between the first end hollow particle 41 and the mid-way hollow particle 44, a portion between mutually adjacent mid-way hollow particles 44 and a portion between the mid-way hollow particle 44 and the second end hollow particle 42 is connected to one or more hollow particles 44.

Description

Carbon material, conductive aid, dispersion, electrode composition, electrode slurry, electrode, lithium ion battery, and method for producing carbon material

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

[0002] Carbon materials are widely used in fields such as lithium ion secondary batteries. For example, Patent Document 1 (JP 2004-22177 A) discloses that flake graphite or carbon black is used as a conductive additive in a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte, thereby improving high-rate discharge characteristics. However, even when such carbon materials are used, rapid discharge characteristics and capacity characteristics are insufficient.

[0003] Patent Document 2 (JP 2019-091587 A) discloses a carbon material with a partial graphite structure obtained by treating expanded graphite. This carbon material has a BET specific surface area of ​​10 to 200 m ２ / g, pore volume of 0.2 mL / g or more, and DBP absorption (oil absorption) of 150 mL / 100 g or more. In the examples, the BET specific surface area is 80 to 155 m ２ The carbon material exhibits a pore volume of 1.6 to 2.1 mL / g, a DBP absorption (oil absorption) of 210 to 220 mL / 100 g. It has been disclosed that mixing this carbon material into a positive electrode results in excellent electrolyte retention and cycle characteristics. However, this carbon material is insufficient in terms of electrical conductivity, rapid discharge performance, charge / discharge characteristics, etc.

[0004] Patent Document 3 (WO2017 / 119428) discloses a battery using carbon black with a DBP absorption (oil absorption) of 240 mL / 100 g or more, with the maximum value in the examples being 348 mL / 100 g. This battery has excellent charge / discharge cycle characteristics, but poor rapid discharge performance and insufficient capacity characteristics and charge / discharge characteristics.

[0005] Patent Document 4 (JP 2020-100556 A) describes a method for producing a sintered body having a BET specific surface area of ​​80 to 250 m ２ / g and an oxygen to carbon element ratio (O / C) of 0.09 to 0.3 as measured by X-ray photoelectron spectroscopy has high dispersibility and ionic conductivity, and is suitable for lithium ion secondary batteries. However, such carbon materials have insufficient electronic and ionic conductivity, and are inferior in rapid discharge performance, capacity characteristics, stability, etc.

[0006] Patent Document 5 (JP 2017-183292 A) discloses that a non-aqueous secondary battery positive electrode composed of multiple active material particles, multiple graphenes with an oxygen concentration of 2 to 20 atomic %, and a binder has excellent electronic conductivity with a small amount of conductive additive. However, the conductivity is insufficient, and the rapid discharge characteristics, life characteristics, capacity characteristics, etc. are poor.

[0007] Patent Document 6 (JP 2021-84819 A) discloses a method for producing a porous carbon material, which includes a coating step of forming a precursor containing graphene on the surface of a template made of nanoparticles of alkaline earth metal oxide, and a separation and removal step of dissolving the template with a fluorine-free acid to separate the template from the precursor.

[0008] Specifically, magnesium oxide nanoparticles mixed with quartz sand as spacers were used as a template, and a CVD reaction was carried out at 900°C for 2 hours. The number of layers was 1.9, the ID / IG ratio was 1.47 to 1.77, and the BET specific surface area was 1,765 m. ２ / g, average pore diameter 9.9 nm, total pore volume 4.23 cm ３ 1 / g of graphene was produced. In addition, a carbon material containing 2.5 layers and a BET specific surface area of ​​648 m was produced by a CVD reaction at 950°C for 2 hours. ２ / g, average pore diameter 11.8 nm, total pore volume 1.91 cm ３ / g of graphene-containing carbon materials have been produced. However, it has not been investigated whether these carbon materials are effective for use in lithium-ion secondary batteries.

[0009] Patent Document 7 (JP 2022-191280 A) describes a method for producing a carbon nanoparticle containing graphene, the carbon nanoparticle having a median diameter of 0.1 to 50 μm and a BET specific surface area of ​​50 to 2,000 m２ It is disclosed that a carbon material having a conductivity of 500 to 20,000 S / m at 12,000 psi compression, pores of 0.1 to 10 nm size and pores of 10 to 100 nm size is used in a lithium ion secondary battery.

[0010] However, the maximum BET specific surface area of ​​the carbon material actually produced in the examples is 85.9 m ２ / g, which indicates that almost no pores are formed because the pores are explosively formed during the residence time of the raw material gas in microwave plasma of 0.001 to approximately 2.0 seconds. Therefore, lithium ion secondary batteries using the carbon material produced here have poor conductivity and are insufficient in terms of rapid discharge, capacity characteristics, and charge / discharge characteristics.

[0011] JP 2004-22177 A JP 2019-091587 A WO2017 / 119428 A JP 2020-100556 A JP 2017-183292 A JP 2021-84819 A JP 2022-191280 A

[0012] A first object of the present invention is to provide a carbon material, a conductive additive, a dispersion, an electrode composition, an electrode slurry, an electrode, and a lithium-ion battery that can improve charge-discharge characteristics (particularly, 2C retention rate) that enable rapid charge-discharge. A second object of the present invention is to provide a production method that can efficiently produce a carbon material that is suitable for use in producing electrodes for secondary batteries such as lithium-ion batteries that have excellent charge-discharge characteristics (particularly, 2C retention rate) that enable rapid charge-discharge.

[0013] The present inventors have conducted extensive research into carbon materials that can improve charge-discharge characteristics (particularly 2C retention rate) that enable rapid charge-discharge, and as a result have found that a carbon material having a chain structure of specific hollow particles can improve charge-discharge characteristics and also has good characteristics such as charge capacity and discharge capacity, which led to the completion of the present invention.

[0014] That is, a carbon material according to one aspect of the present invention is a carbon material in which hollow particles having a carbonaceous outer shell are linked together, and the carbon material has a series chain portion formed by a plurality of the hollow particles being linked in series, and a branched chain portion formed by hollow particles branching off from the series chain portion and linked to central hollow particles that are located in at least one or more intermediate portions between a first end hollow particle that is the hollow particle that forms one end of the series chain portion and a second end hollow particle that is the hollow particle that forms the other end of the series chain portion, wherein at least one of the portions between the first end hollow particle and the central hollow particle, the portion between adjacent central hollow particles, and the portion between the central hollow particle and the second end hollow particle in the longitudinal direction of the series chain portion is a portion in which one or more of the hollow particles are linked together.

[0015] When this carbon material is used as a part of an electrode material for a secondary battery such as a lithium-ion battery, it can improve charge / discharge characteristics and maintain good characteristics such as charge capacity and discharge capacity. The reason for this is thought to be, for example, as follows: The series chain portions of the hollow particles flexibly entangle with, for example, the active material of the battery material, forming a conductive path, and the curved shape of the chain portions and the hollow portions (internal spaces) of the hollow particles contribute to increasing the electrolyte retention, improving rapid charge / discharge characteristics and maintaining good characteristics such as charge capacity and discharge capacity.

[0016] This carbon material can be preferably used as a part of an electrode material for a secondary battery such as a lithium ion battery, for example, as a conductive additive, etc. Furthermore, this carbon material can be contained in a conductive additive, dispersion, electrode composition, electrode slurry, etc., and can be preferably used as a part of a material constituting a battery electrode or an electrode for other electronic components.

[0017] In this carbon material, branched chains branch from the series chains. The presence of branched chains in addition to series chains in the carbon material increases the number of portions that form conductive paths and increase the amount of oil absorption, thereby improving the electrolyte retention and further improving rapid charge / discharge characteristics, as well as properties such as charge capacity and discharge capacity.

[0018] The number of hollow particles connected in series that constitute the series chain portion may be five or more. Furthermore, the branched chain portion may be configured by hollow particles connected in a ring shape to form macropores. This configuration also further improves rapid charge / discharge characteristics and properties such as charge capacity and discharge capacity, for example, by increasing the number of portions that form conductive paths and increase the number of portions that enhance the electrolyte retention.

[0019] The tip of the branched chain portion has a third end hollow particle different from the first end hollow particle and the second end hollow particle. This configuration also increases the number of areas that form conductive paths and increase the number of areas that improve the electrolyte retention, thereby further improving rapid charge / discharge characteristics and characteristics such as charge capacity and discharge capacity.

[0020] The outer diameter of the hollow particles is, for example, within the range of 0.5 to 150 nm.

[0021] In the carbon material, the internal spaces of adjacent hollow particles are preferably interconnected, but some may not be interconnected. The carbonaceous outer shell is preferably made of a carbonaceous material having a six-membered carbon ring structure. In addition, in this carbon material, the intensity ratio I of the G band to the 2D band in Raman spectroscopy is Ｇ / I ２Ｄ is preferably in the range of 0.1 to 10, more preferably in the range of 1 to 5, and the oil absorption measured in accordance with JIS K5101-13-1 is preferably 100 mL / 100 g or more.

[0022] Intensity ratio of D band to G band in Raman spectroscopy of carbon materials I Ｄ / I Ｇis in the range of 0.1 to 10.

[0023] The modal pore size of the carbon material is preferably in the range of 1 to 500 nm.

[0024] The total pore volume of the carbon material is preferably in the range of 0.1 to 20 cc / g.

[0025] The proportion of the macropore volume in the total pore volume is preferably 5% or more.

[0026] The BET specific surface area of ​​the carbon material is preferably 100 to 2700 m ２ / g range.

[0027] In the carbon material, the size Lc(002) of the single crystal in the c-axis direction of the (002) plane measured by X-ray diffraction (XRD) is preferably within the range of 0.1 to 5 nm.

[0028] In the carbon material, the lattice spacing d002 of the (002) plane measured by X-ray diffraction (XRD) is preferably within the range of 3 to 5 angstroms.

[0029] The carbon material preferably has a median diameter D50 in particle size distribution measurement of 1 to 150 μm.

[0030] The carbon material preferably has a (D90 / D10) ratio of 100 or less in particle size distribution measurement.

[0031] The conductive additive for a battery electrode according to one aspect of the present invention includes any one of the carbon materials described above.

[0032] A dispersant according to one aspect of the present invention includes any of the carbon materials described above and a dispersion medium in which the carbon material is dispersed.

[0033] An electrode composition according to one aspect of the present invention includes any of the carbon materials described above, an active material, and a binder.

[0034] An electrode slurry according to one aspect of the present invention includes the electrode composition described above and a solvent in which the electrode composition is dispersed.

[0035] An electrode according to one embodiment of the present invention includes the carbon material described above.

[0036] A lithium secondary battery according to one aspect of the present invention includes any of the carbon materials described above.

[0037] A method for producing a carbon material according to one aspect of the present invention includes the steps of: preparing a template having a series-chain template portion in which a plurality of template particles are linked in series; forming a carbonaceous outer shell on the surface of the template; and removing the template from the inside of the carbonaceous outer shell, wherein the template has a series-chain template portion in which a plurality of the template particles are linked in series; and branched-chain template portions made up of template particles that are linked to intermediate template particles that are located at at least one intermediate portion between a first end template particle that is the template particle constituting one end of the series-chain template portion and a second end template particle that is the template particle constituting the other end of the series-chain template portion, and that branch off from the series-chain template portion, The serially linked mold portion is a portion where one or more of the mold particles are connected, at least one of the portions between the first end mold particle and the intermediate mold particle, the portion between adjacent intermediate mold particles, and the portion between the intermediate mold particle and the second end mold particle.

[0038] According to this method for producing a carbon material, it is possible to easily produce electrodes for secondary batteries such as lithium ion batteries that have excellent charge / discharge characteristics (particularly 2C retention rate) that enable rapid charge / discharge.

[0039] FIG. 1 is a schematic structural diagram of a carbon material according to an embodiment of the present invention. FIG. 2A is a transmission electron microscope (TEM) image of a carbon material according to one embodiment of the present invention. FIG. 2B is a transmission electron microscope (TEM) image of a carbon material according to another embodiment of the present invention. FIG. 2C is a transmission electron microscope (TEM) image of a carbon material according to yet another embodiment of the present invention. FIG. 2D is a transmission electron microscope (TEM) image of a carbon material according to yet another embodiment of the present invention. FIG. 2E is a transmission electron microscope (TEM) image of a carbon material according to yet another embodiment of the present invention. FIG. 2F is a transmission electron microscope (TEM) image of a carbon material according to yet another embodiment of the present invention. FIG. 2G is a transmission electron microscope (TEM) image of a carbon material according to a reference example of the present invention. FIG. 2H is a transmission electron microscope (TEM) image of a carbon material according to yet another reference example of the present invention. A schematic cross-sectional view showing an example of the cross-sectional structure of a lithium-ion battery according to one embodiment of the present invention. FIG. 4 is a graph showing an example of a Raman spectrum measured for a carbon material according to an embodiment of the present invention. FIG. 5 is a graph showing discharge curves of test batteries according to examples of the present invention, with different discharge current values. Fig. 6 is a graph showing the relationship between the blend amount of carbon material and the 2C retention rate and discharge capacity for the test battery according to the embodiment of the present invention. Fig. 7 is a diagram illustrating an ultra-high sensitivity vacuum TPD device used for thermal desorption analysis.

[0040] A carbon material according to one embodiment of the present invention will be described below.

[0041] (Structure of Carbon Material) A schematic structural diagram of a carbon material according to this embodiment, which is an example of the present invention, is shown in Figure 1. As shown in Figure 1, the carbon material according to this embodiment is a carbon material 2 in which hollow particles 4 having carbonaceous outer shells 4a are linked together. Note that the hollow particle 4' portion represented by the two-dot chain line is a virtual component part, and the carbon material 2 according to this embodiment is a structure composed only of hollow particles 4, excluding the hollow particle 4' portion.

[0042] The carbon material 2 according to this embodiment has a series chain portion 6 formed by a series connection of a plurality of hollow particles 4. The carbon material 2 also has a branched chain portion 7 formed by hollow particles 4 branching off from the series chain portion 6 and connected to at least one intermediate hollow particle 44, which is a hollow particle 4 located in at least one intermediate portion between a first end hollow particle 41, which is a hollow particle 4 forming one end of the series chain portion 6, and a second end hollow particle 42, which is a hollow particle 4 forming the other end of the series chain portion 6.

[0043] Here, the series chain portion 6 refers to a portion formed by hollow particles 4 connected in series between the first end hollow particle 41 and the second end hollow particle 42, with any two (hollow particles 4A and 4G in the example of FIG. 1 ) of hollow particles 4A to 4I, which are hollow particles 4 located at the ends of the carbon material 2, defined as a first end hollow particle 41 and a second end hollow particle 42. In the example of FIG. 1 , the series chain portion 6 is formed by hollow particles 4 connected in series along the dashed dotted line.

[0044] Furthermore, the intermediate hollow particles 44 are hollow particles 4 located in at least one or more intermediate portions between a first end hollow particle 41, which is a hollow particle 4 constituting one end of an arbitrarily determined series chain portion 6, and a second end hollow particle 42, which is a hollow particle 4 constituting the other end, and are hollow particles 4 that are connected to hollow particles 4 branching off from the series chain portion 6 (in FIG. 1, the intermediate hollow particles 44 are indicated by dotted imaginary lines). In this example, the four hollow particles 4 designated by the reference numerals 44a to 44d correspond to the intermediate hollow particles 44.

[0045] The branched chain portion 7 refers to a portion connected to a central hollow particle 44 and composed of hollow particles 4 branching off from the serial chain portion 6. In the example of Fig. 1 , the following chains correspond to the branched chain portion 7: a chain connected to central hollow particle 44a and ending at hollow particle 4B; a chain connected to central hollow particle 44b and ending at hollow particle 4I; a chain connected to central hollow particle 44c and further branching into three chains and ending at hollow particles 4C, 4D, and 4E; and two chains connected to central hollow particle 44d and ending at hollow particles 4F and 4H. Hereinafter, the terminal hollow particles (4B to 4F, 4H, and 4I) in the branched chain portion 7 are referred to as third end hollow particles 43.

[0046] In determining the series chain portion, any two of hollow particles 4A-4I other than the combination of hollow particles 4A and 4G may be designated as the first end hollow particle and the second end hollow particle. In the present invention, it is sufficient that a branched chain portion is formed by connecting hollow particles 4 4 in series between an arbitrarily selected first end hollow particle and a selected second end hollow particle, and the hollow particles 4 are connected to an intermediate hollow particle located midway along the series chain portion, and branching off from the series chain portion. For example, if hollow particle 4D is designated the first end hollow particle and hollow particle 4F is designated the second end hollow particle, then the series chain portion is formed by the hollow particles 4 connected in series between hollow particle 4D and hollow particle 4F, and each chain branching off from any of the hollow particles 4 constituting the series chain portion and ending at hollow particles 4A-4C, 4E, and 4G-4I corresponds to a branched chain portion.

[0047] In short, as long as a material contains a series-linked chain portion and has three or more hollow particles located at its ends, any two of the particles can be defined as first end hollow particles and second end hollow particles, and the remaining particles can be defined as third end hollow particles 43. Therefore, it can be said that a necessary and sufficient condition for a material to be a carbon material according to this embodiment is that it contains a series-linked chain portion, has three or more hollow particles located at its ends, and has hollow particles (connected hollow particle portion 6a) other than the hollow particles located at its ends and the hollow particles in its branched portions (middle hollow particles 44).

[0048] However, in order to easily determine the overall structure of the carbon material, it is preferable to define the longest chain as the serial chain portion. Furthermore, from the viewpoint of confirming and understanding the function of macropores 8 (described below) consisting of curved chains in the carbon material, it is more preferable to define the chain of hollow particles whose ends are as far apart in linear distance as possible as the serial chain portion, so that the curved chains can be regarded as branched chain portions. In the carbon material of 1, it is particularly preferable to define the chain of hollow particles whose ends are furthest apart in linear distance as the serial chain portion. In this case, the measurement points at both ends of the chain are the furthest apart points on the hollow particles at both ends. These can be determined by actual measurements from a micrograph.

[0049] 1, the linear distance L1 of the chain between hollow particle 4A and hollow particle 4G is longer than the linear distance L2 of the chain between hollow particle 4C and hollow particle 4I, which have a larger number of hollow particles 4 in the chain (i.e., a longer extension length) (L1>L2), and is the longest in carbon material 2. Therefore, in the example of FIG. 1, hollow particle 4A is defined as a first end hollow particle 41, and hollow particle 4G is defined as a second end hollow particle 42, thereby determining the serial chain portion 6.

[0050] In the carbon material 2 according to this embodiment, the number of hollow particles 4 connected in series to form a series chain portion 6 is preferably 5 or more, and more preferably 9 or more. A relatively long chain of series chain portions 6 effectively exhibits the special functions of the carbon material according to this embodiment, which will be described later. However, if the chain of series chain portions 6 is too long, handling becomes difficult. Therefore, the number of hollow particles 4 connected in series to form a series chain portion 6 is preferably approximately 500 or less, and more preferably approximately 200 or less.

[0051] In the carbon material 2 of this embodiment, in the longitudinal direction of the serial chain portion 6, at least one of the portions between the first end hollow particle 41 and the middle hollow particle 44, the portion between adjacent middle hollow particles 44, and the portion between the middle hollow particle 44 and the second end hollow particle 42 is a portion where one or more hollow particles 4 are connected.

[0052] 1 , one hollow particle 4 is connected in the portion between the first end hollow particle 41 and the central hollow particle 44a. Furthermore, two hollow particles 4 are connected in the portion between adjacent central hollow particles 44b and 44c, and two hollow particles 4 are connected in the portion between adjacent central hollow particles 44c and 44d, respectively. Furthermore, two hollow particles 4 are connected in the portion between the central hollow particle 44d and the second end hollow particle 42. Note that no hollow particles 4 exist between adjacent central hollow particles 44a and 44b.

[0053] 1, a hypothetical constituent portion of hollow particle 4' represented by the two-dot chain line may be connected to hollow particle 4H and hollow particle 4I of carbon material 2 according to this embodiment to form a branched chain portion 7 in which hollow particles 4 are linked in a ring shape to form macropores 8. Actual macropores 8 may have a configuration, for example, as shown in FIG. 2A of Example 1 described later.

[0054] In the carbon materials of the embodiment and modified examples shown in Fig. 1 , the serial chain portions 6 and branched chain portions 7 have the shape of individual hollow particles 4 strung together like beads, but they may also have the shape of a bundle of two or more hollow particles. In this case, the entire thick portion of the bundle of hollow particles becomes the serial chain portion or branched chain portion. In such a case where hollow particles branch from a serial chain portion having a thick portion of the bundle of hollow particles to branched chain portions, the outermost hollow particles in the bundle of serial chain portions, which are directly connected by the branched chain portions, are considered to be the "middle hollow particle."

[0055] However, when an actual carbon material is observed under a microscope, etc., it may not be possible to clearly distinguish the boundary between the series chain portion and the branched chain portion. Even in such cases, if there is a series chain portion 6 in which hollow particles 44 are chained from a first end hollow particle 41 to a second end hollow particle 42, and there is also a branched chain portion 7 that branches from the series chain portion 6 to a third end hollow particle 43, then there is certainly a hollow particle that can be considered a middle hollow particle at the branching point, and therefore there is no point in specifically identifying the middle hollow particle.

[0056] Specific examples of serial chain portions and branched chain portions in which hollow particles are connected together and have thick bundles will be described in the examples below using the micrographs in FIGS. 2A to 2F.

[0057] The carbonaceous shell 4a is preferably made of a carbonaceous material having a six-membered carbon ring structure, and more preferably a carbonaceous material having a graphene structure in which the six-membered carbon ring structures are connected in a network structure. Graphene is a sheet-like substance of SP2 bonded carbon, in which the six-membered carbon ring structures are connected to form a honeycomb-like hexagonal lattice structure. Furthermore, the carbonaceous material having a graphene structure in which the six-membered carbon ring structures are connected in a network structure can be identified by the intensity ratio I of the G band to the 2D band in Raman spectroscopy measurement described later. Ｇ / I ２Ｄ This can also be confirmed by the fact that is 0.2 or more.

[0058] Carbon materials usually consist of a structure that has elastic deformation and a structure that has plastic deformation. Such a structure that has plastic deformation exhibits high strength against stress, but once it is deformed, it cannot recover even after unloading. The degree of elastic deformation and plastic deformation of carbon materials can be measured by an ultra-small load-unload test.

[0059] It was found that the carbon material of this embodiment has the property of returning to its original shape without deformation under weak stress, as in an extremely small load / unload test, i.e., the property of a large elastic deformation work. It is believed that the carbon material of this embodiment has good properties against stress deformation, with the graphene portion, which accounts for the majority of the carbon material, exhibiting elastic deformability, and the defective portions of the graphene structure other than graphene and the amorphous carbon portion exhibiting plastic deformability. On the other hand, when the number of carbonaceous (graphene) layers is excessively large (such as graphite), elastic deformability is maintained within a certain stress range, but when a certain stress threshold is exceeded, plastic deformation occurs suddenly, and the particle shape and the interconnected shape tend to be destroyed.

[0060] The size of the internal space 4b of the hollow particle 4 surrounded by the carbonaceous outer shell 4a (i.e., the inner diameter D ０(=modal pore diameter, described later) is preferably within the range of 0.1 to 100 nm, 1 to 80 nm, or 5 to 50 nm. The extension length of the serial chain portion 6, in which a plurality of hollow particles 4 having the hollow internal space 4b are connected (for example, the length indicated by the dashed line in FIG. 1 ), is preferably a length sufficient for five or more hollow particles 4 to be connected in the longitudinal direction, and is, for example, 1 nm or more, preferably 10 nm or more, or within the range of 0.01 to 100 μm, 0.05 to 80 μm, or 0.1 to 50 μm. The outer diameter D of each hollow particle 4 １ (the value obtained by adding twice the value obtained by multiplying the number of layers of the outer shell by the layer (plane) spacing, which will be described later) is preferably within the range of 0.5 to 150 nm, or also preferably within the range of 1 to 100 nm, 2 to 90 nm, 4 to 65 nm, 8 to 50 nm, or 10 to 35 nm.

[0061] When the carbon material according to this embodiment is used as a part of an electrode material for a secondary battery such as a lithium-ion battery, the charge / discharge characteristics can be improved, and characteristics such as charge capacity and discharge capacity can be maintained at a good level. The reason for this is thought to be, for example, as follows: As shown in FIG. 1 , the series chain portions 6 of the hollow particles 4 flexibly entangle with, for example, the active material 10 of the battery material, forming a conductive path. The curved shape of the chain portions 6 and the hollow portions (internal spaces) of the hollow particles 4 contribute to increasing the electrolyte retention, improving rapid charge / discharge characteristics and maintaining good characteristics such as charge capacity and discharge capacity.

[0062] This carbon material can be preferably used as a part of an electrode material for a secondary battery such as a lithium ion battery, for example, as a conductive additive, etc. Furthermore, this carbon material can be contained in a conductive additive, dispersion, electrode composition, electrode slurry, etc., and can be preferably used as a part of a material constituting a battery electrode or an electrode for other electronic components.

[0063] 1 , in the carbon material 2 of this embodiment, branched chains 7 branch off from the series chains 6. The presence of branched chains 7 in addition to the series chains 6 in the carbon material 2 increases the number of portions that form conductive paths and increase the portions that enhance the electrolyte retention, thereby further improving the rapid charge / discharge characteristics and properties such as the charge capacity and discharge capacity.

[0064] Furthermore, at least one of the branched chain portions may have a configuration in which hollow particles 4 are connected in a ring shape to form macropores 8, as shown by the two-dot chain line in Fig. 1 as a modified example. This configuration also increases the number of portions that form conductive paths and increase the portions that enhance the electrolyte retention, thereby further improving the rapid charge / discharge characteristics and properties such as charge capacity and discharge capacity.

[0065] The tip of the branched chain portion 7 has a third end hollow particle 43 similar to the first end hollow particle 41 and the second end hollow particle 42. This configuration also increases the areas that form conductive paths and the areas that increase the electrolyte retention, thereby further improving the rapid charge / discharge characteristics and improving properties such as charge capacity and discharge capacity.

[0066] The total pore volume of the carbon material, as measured by nitrogen adsorption / desorption analysis, is preferably 0.1 cc / g or more, or 1 cc / g or more, 1.5 cc / g or more, 2 cc / g or more, or 2.95 cc / g or more. The upper limit is preferably 20 cc / g or less, or 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 is excessively large, the skeletal strength of the pore structure weakens, making it difficult to maintain the particle shape of the hollow particles 4. If the total pore volume is excessively small, the amount of electrolyte retained within the particle shape of the hollow particles 4 tends to decrease. When the total pore volume is within the above range, the particle shape of the hollow particles 4 has appropriate strength, contributing to the stability of the particle shape and maintaining the shape. This makes it possible to maintain a good balance between electronic conductivity and the supply of ions held within the pores.

[0067] The micropore volume of the carbon material is the volume of pores having a pore diameter of less than 2 nm, and 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. The lower limit is preferably 0.01 cc / g or more, or 0.05 cc / g or more, 0.1 cc / g or more, 0.2 cc / g or more, or 0.3 cc / g or more. If the micropore volume of the carbon material is too small, the ionic conductivity will be poor, and conversely, if it is too large, the strength characteristics of the carbonaceous material will tend to be poor.

[0068] The proportion of the micropore volume of the carbon material, expressed as the proportion of the volume of pores having a diameter of less than 2 nm relative to the total pore volume, is preferably 20% or less, or preferably 15% or less, 12% or less, 10% or less, or 9% or less. The lower limit is preferably 5% or more. If the proportion of the micropore volume of the carbon material is too small, the ionic conductivity tends to be poor, and conversely, if it is too large, the strength characteristics of the carbonaceous material tend to be poor.

[0069] The mesopore volume of the carbon material is the volume of pores with a pore diameter of 2 to 50 nm, and is preferably 0.1 cc / g or more, or 0.5 cc / g or more, 1 cc / g or more, 1.5 cc / g or more, or 2 cc / g or more. The upper limit is preferably 15 cc / g or less, or 10 cc / g or less, 5 cc / g or less, 4 cc / g or less, or 3.5 cc / g or less. When the mesopore volume of the carbon material is in this range, ionic conductivity and strength characteristics are well balanced.

[0070] The mesopore volume ratio of the carbon material, expressed as the ratio of the volume of pores having a pore diameter in the range of 2 to 50 nm to the total pore volume, is preferably 10% or more, or 20% or more, 30% or more, 40% or more, or 50% or more. The upper limit is preferably 90% or less, or 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 particles 4 has appropriate strength, which contributes to the stability of the particle shape of the hollow particles and allows the shape to be maintained. This allows a good balance to be maintained between electronic conductivity and the supply of ions held within the pores.

[0071] The pore volume of the carbon material having a pore diameter of 2 nm or more and less than 10 nm is preferably 0.05 cc / g or more, or 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 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 having a pore diameter of 2 nm or more and less than 10 nm is within these ranges, ionic conductivity and strength characteristics are highly balanced, which is preferable.

[0072] The proportion of the volume of pores having a pore diameter of 2 nm or more and less than 10 nm in the total pore volume of the carbon material is preferably 0.1% or more, or 1% or more, 3% or more, 5% or more, or 10% or more. The upper limit is preferably 50% or less, or 40% or less, 30% or less, 26% or less, or 20% or less. When the volume of pores having a pore diameter of 2 nm or more and less than 10 nm in the total pore volume of the carbon material is within these ranges, ionic conductivity and strength characteristics are well balanced.

[0073] The pore volume of the carbon material having a pore diameter of 10 to 50 nm is preferably 0.05 cc / g or more, or preferably any of 0.1 cc / g or more, 0.5 cc / g or more, 1 cc / g or more, 1.35 cc / g or more, 1.50 cc / g or more, and 2 cc / g or more. The upper limit is preferably any of the following ranges: 15 cc / g or less, 10 cc / g or less, 5 cc / g or less, 4 cc / g or less, and 3 cc / g or less. When the pore volume of the carbon material having a pore diameter of 10 to 50 nm is within this range, the particle shape of the hollow particles has appropriate strength, contributing to the stability of the particle shape and maintaining the shape. This allows a good balance to be maintained between electronic conductivity and the supply of ions held within the pores.

[0074] The proportion of pore volume having a pore diameter of 10 to 50 nm in the total pore volume of the carbon material is preferably 10% or more, or 15% or more, 20% or more, 25% or more, or 30% or more. The upper limit is preferably 80% or less, or 70% or less, 60% or less, 55% or less, or 50% or less. When the volume of pores having a pore diameter of less than 10 to 50 nm in the total pore volume of the carbon material is in this range, it is preferable in that ionic conductivity and strength characteristics are well balanced.

[0075] The macropore volume of the carbon material is the volume of pores with a pore diameter exceeding 50 nm, and is preferably 0.01 cc / g or more, or 0.05 cc / g or more, 0.1 cc / g or more, 0.48 cc / g or more, or 1 cc / g or more. The upper limit is preferably 15 cc / g or less, or preferably 10 cc / g or less, 5 cc / g or less, 3 cc / g or less, or 2.57 cc / g or less. When the macropore volume of the carbon material is within this range, the particle shape of the hollow particles has appropriate strength, which contributes to the stability of the particle shape and maintains the shape. This allows a good balance to be maintained between electronic conductivity and the supply of ions held in the pores.

[0076] The proportion of the macropore volume of the carbon material, expressed as the proportion of the volume of pores having a pore diameter of more than 50 nm in the total pore volume, is preferably 5% or more, or 10% or more, 15% or more, 20% or more, or 25% or more. The upper limit is preferably 80% or less, or 70% or less, 60% or less, 50% or less, or 45% or less. If the proportion of the macropore volume of the carbon material is too small, the ionic conductivity tends to be poor, and conversely, if it is too large, the strength characteristics of the carbonaceous material tend to be poor.

[0077] The proportion of the volume of pores of 10 nm or larger in the carbon material, expressed as the proportion of the volume of pores having a pore diameter of 10 nm or larger in the total pore volume, is preferably 50% or larger, or 55% or larger, 60% or larger, 65% or larger, or 70% or larger. The upper limit is preferably 95% or smaller, or any of the ranges of 92% or smaller, 90% or smaller, 88% or smaller, or 85% or smaller. If the proportion of the volume of pores of 10 nm or larger in the carbon material is too small, the ionic conductivity tends to be poor, and conversely, if it is too large, the strength characteristics of the carbonaceous material tend to be poor.

[0078] The mode pore diameter (M) in the pore distribution of the carbon material is the peak top value in the pore distribution curve, and is preferably in the range of 1 to 500 nm, or 5 to 100 nm, 10 to 50 nm, 15 to 40 nm, or 15 to 30 nm. When the peak top pore diameter of the pore distribution of the carbon material is in this range, the oil absorption can be improved and high ionic conductivity and electronic conductivity can be achieved, which is preferable.

[0079] The average pore diameter of the carbon material is preferably in the range of 1 to 500 nm, or 5 to 100 nm, 10 to 75 nm, 15 to 50 nm, or 20 to 40 nm. When the average pore diameter of the carbon material is in this range, the oil absorption can be improved and high ionic conductivity and electronic conductivity can be achieved.

[0080] The particle size distribution curve of the carbon material was measured after immersion of the unground material in a solvent for 9 minutes, and shows the difference in cohesive strength of the linked structures.

[0081] The median diameter D50 of the carbon material may be 1 to 150 μm, or may be any of the ranges of 5 to 150 μm, 10 to 80 μm, 15 to 60 μm, 20 to 50 μm, 25 to 45 μm, and 30 to 40 μm. When the median diameter D50 of the carbon material is within these ranges, the electronic conductivity and ionic conductivity are highly enhanced. Note that the median diameter D50 of the carbon material is not the median diameter D50 of the hollow particles 4, but is, for example, the diameter of a volume-equivalent sphere of the carbon material 2 shown in FIG. 1 .

[0082] The particle diameter D10 at which 10% of the carbon material 2 exists in the particle size distribution curve of the carbon material is preferably any of the ranges of 0.1 to 100 μm, 0.5 to 50 μm, 1 to 50 μm, 5 to 30 μm, and 10 to 15 μm.

[0083] The particle diameter D90 at which 90% of the carbon material 2 exists in the particle size distribution curve of the carbon material is preferably 5 to 250 μm, and also preferably any of 10 to 150 μm, 20 to 100 μm, 30 to 70 μm, 45 to 65 μm, 45 to 55 μm, and 40 to 60 μm. When the D90 of the carbon material is in this range, the conductivity is highly enhanced.

[0084] The ratio of D90 to D10 of the carbon material, in terms of the (D90 / D10) ratio, is preferably in the range of 100 or less, or 50 or less, 10 or less, or 5 or less. If the (D90 / D10) ratio of the carbon material is excessively large, the carbon material tends to aggregate, making dispersion difficult.

[0085] The ratio of D90 to the mode pore diameter M (D90 / M), which is the value obtained by dividing the D90 value (nm) by the mode pore diameter M (nm) and multiplying the result by 1000, is preferably 50 or less, or preferably 20 or less, 10 or less, 6 or less, or 4 or less. If the (D90 / M) ratio of the carbon material is excessively large, the carbon material tends to have strong agglomeration properties and poor dispersibility.

[0086] One of the indicators that indicate the structural complexity of carbon materials is the shape index and aggregate shape classification measured by image analysis, which will be described later.

[0087] The bulk density of the carbon material of this embodiment is preferably 0.01 to 1000 g / L, or any of the ranges of 0.05 to 500 g / L, 0.1 to 100 g / L, 0.5 to 50 g / L, and 1 to 25 g / L. A bulk density of the carbon material within these ranges is advantageous because it has high conductivity and facilitates permeation of the electrolyte into the carbon material. Note that bulk density refers to the mass per unit volume of a carbon material filled into a container of a certain volume under certain conditions. Bulk density can be measured, for example, according to JIS K6219-2.

[0088] The number density of the carbon material of this embodiment is a value calculated by the method described below, and is preferably 5×10 １４ ~1 x 10 ２０ pieces / g, or 1 x 10 １６ ~1 x 10 １９ pieces / g, 5×10 １６ ~5 x 10 １８ pieces / g, 1×10 １７ ~1 x 10 １８ pieces / g, 3×10 １７ ~7 x 10 １７ It is also preferable that the number density of the carbon material is in any of the ranges of particles / g. When the number density of the carbon material is in this range, the oil absorption becomes optimal, which is preferable. The number density P (particles / g) is calculated based on the volume V (m ３ ) and carbon density ρ (g / m ３ ) can be calculated using the following formula: P = 1 / (V × ρ) Here, the true density of graphite, 2.2 g / cc, can be used as the carbon density. V (m ３ ) can be calculated from the following formula: V = π × (D １ -D ０ ) ３ / 6 where D ０ is the inner diameter of the primary particle, and D １ is the outer diameter of the primary particle. ０ The above-mentioned mode pore diameter can be used. １ is D ０ The average number of layers n is multiplied by the interplanar spacing of the (002) plane, and the resulting value is doubled and added to the mode diameter. １ may be determined by TEM image analysis or the like. In addition, in the case of a solid carbon material, D０ For example, the known DENKA BLACK Li-100 has a particle outer diameter (D １ ) with an average particle size of 35 nm, D ０ = 0.

[0089] (Characteristic Values ​​of Carbon Material) The state of the carbonaceous microcrystalline structure of a carbon material can be analyzed by Raman spectroscopy. An example of a Raman spectrum measured on a carbon material is shown in FIG. 4. In the Raman spectrum, the wave number 1593 cm －１ The peak in the region around 1356 cm in the Raman spectrum is called the G band, which indicates the sp2 bond (C=C stretching motion of the aromatic ring) of the carbon material. －１ The peak present around the wavenumber 2680 cm in the Raman spectrum is called the D band, which indicates the sp3 bond (C-H stretching motion) of the carbon material, and increases when the sp2 bond in the carbon six-membered ring structure of the carbonaceous layer is broken to form an sp3 bond. －１ The peak present in the region nearby is called the 2D band, which is a band indicating secondary phonon scattering (C—H stretching motion) and is a band indicating the number of layers of the carbon material.

[0090] Intensity ratio I between the G band and the 2D band of carbon materials Ｇ / I ２Ｄ is said to be an index that indicates the stacking state of graphene layers (D. Graf, et al., NANO LETTERS, 7, 238-242; (2007)). In this paper, it is stated that when the (G / 2D) intensity ratio is 0.2, the graphene layer becomes one layer.

[0091] Intensity ratio I between the G band and the 2D band of carbon materials Ｇ / I ２Ｄ is preferably 0.1 or more, more preferably 0.5 or more, or any one of 1.0 or more, 1.1 or more, 1.2 or more, 1.3 or more, and 1.4 or more. The upper limit is also preferably any one of 10.0 or less, 7.0 or less, 5.0 or less, 4.5 or less, 4.0 or less, 3.57 or less, 3.0 or less, 2.5 or less, and 2.08 or less. Ｇ / I ２ＤWhen the value of is within such a range, the strength characteristics and elastic deformability that maintain the hollow structure of the carbon material are well balanced, and when used as a conductive additive for a lithium ion secondary battery, desired characteristics such as rapid discharge characteristics, capacity characteristics, and durability are highly improved, which is preferable.

[0092] Intensity ratio of D band to G band of carbon material I Ｄ / I Ｇ is preferably 0.1 to 10, more preferably 0.5 to 5, or any one of 1 to 3, 1.2 to 2.5, and 1.4 to 2. Ｄ / I Ｇ However, when the carbon content is within this range, the sp2 orbitals and sp3 orbitals of the carbonaceous carbon material are in an optimal state, and the electron conduction path and the ion conduction path are highly balanced, which is thought to highly improve the rapid discharge characteristics, capacity characteristics, and charge / discharge characteristics of the lithium ion secondary battery.

[0093] The oil absorption of the carbon material is the oil absorption of refined linseed oil measured in accordance with JIS K5101-13-1 (Pigment Testing Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method), and is 100 mL / 100 g or more, preferably 400 mL / 100 g or more, or 500 mL / 100 g or more, 600 mL / 100 g or more, 800 mL / 100 g or more, 900 mL / 100 g or more, 1,000 mL / 100 g or more, or even 1,400 mL / 100 g or more. The upper limit of the oil absorption is not particularly limited, but may be preferably 5,000 mL / 100 g or less, or 4,000 mL / 100 g or less, 3,500 mL / 100 g or less, 3,000 mL / 100 g or less, or 2,500 mL / 100 g or less. When the content is in this range, it becomes possible to further improve the charge-discharge characteristics (particularly the 2C retention rate).

[0094] The oil absorption capacity of carbon materials is significantly higher than that of carbon black, which is commonly used as a conductive additive in lithium-ion secondary batteries. This is thought to be due to the increased capacity of the electrolyte within the hollow particles, as well as the increased capacity of the electrolyte within the interconnected shells and the gaps formed within the interconnected aggregate structures (series chains and branched chains). This allows for a stable supply of lithium ions, contributing to the rapid charging, charge / discharge characteristics, and battery capacity of lithium-ion batteries. If the oil absorption capacity of a carbon material is too low, the electrolyte capacity will be low, resulting in a delay in the supply of ions during rapid reactions and a decrease in discharge capacity. Conversely, if the oil absorption capacity is too high, it will be difficult to maintain the structure of the carbon material, making it difficult to control the amount of electrolyte held.

[0095] The interplanar spacing d002 of the

[002] plane of the carbon material measured by X-ray diffraction (XRD) is also preferably in the range of 3 to 5 angstroms, preferably 3.3 to 4.5 angstroms, more preferably 3.3 to 4 angstroms, alternatively 3.3 to 3.9 angstroms, or 3.3 to 3.8 angstroms.

[0096] The size of the crystallite Lc(002) in the c-axis direction of the

[002] plane measured by X-ray diffraction (XRD) of the carbon material of this embodiment is preferably 0.1 nm or more, or preferably any one of 0.3 nm or more, 0.5 nm or more, 1.0 nm or more, and 1.1 nm or more. Furthermore, the upper limit of the size of the crystallite Lc(002) in the c-axis direction of the

[002] plane is preferably 20 nm or less, or preferably any one of 5 nm or less, 3 nm or less, 2.5 nm or less, 2.0 nm or less, 1.9 nm or less, 1.5 nm or less, 1.25 nm or less, and 1.21 nm or less. When Lc(002), which represents the degree of crystallinity of the carbon material, is within this range, large mesopores and macropores tend to be easily formed.

[0097] The BET specific surface area of ​​the carbon material of this embodiment is a specific surface area calculated from nitrogen adsorption as specified in JIS Z8830, and is preferably 100 to 2,700 m ２ / g, or 300 to 2,500 m ２ / g, 500-2,000m２ / g, 600-1,800m ２ / g, 800-1,200m ２ When the BET specific surface area of ​​the carbon material is in this range, the oil absorption amount, which leads to electrical conductivity and electrolyte retention, is highly increased.

[0098] The theoretical specific surface area of ​​single-layer graphene is 2,627 m ２ / g, and it can be said that the closer the specific surface area is to this value, the more ideal the carbon conductive substance is. The carbon material of the present embodiment has both electronic conductivity and ionic conductivity as a graphene layer that can maintain a pore or void structure, and highly improves the rapid discharge property, capacity characteristics, and charge / discharge characteristics of lithium ion secondary batteries.

[0099] Carbon materials contained in electrodes of lithium-ion batteries preferably have high electrical conductivity. Because electron migration in carbon occurs through the transfer of π electrons, forming an ideal conductive path within an electrode using a carbon material requires a network-like arrangement of single-layer graphene, in which carbon atoms are bonded in the planar direction. Furthermore, when filling a non-conductive material such as a positive electrode material with a conductive material such as a carbon material, a low filling rate of the conductive material makes it difficult for conductivity to be achieved. At a certain filling rate, paths of the conductive material are formed within the compound, causing a rapid increase in electronic conductivity, which then stabilizes. The lower the threshold filling rate at which electronic conductivity rises, the more suitable the material is for a conductive material. Therefore, the carbon material of this embodiment is preferably made of a carbonaceous material having a graphene structure that extends in the planar direction. Furthermore, the carbonaceous material forms a series-chain structure in which granular hollow particles 4, which form the hollow outer shell, are connected longitudinally, resulting in a high balance between in-plane electrical conductivity and path-formed electrical conductivity, resulting in high electrical conductivity.

[0100] The electrical conductivity of carbon materials can be evaluated by measuring the electrical conductivity of powder using lateral constrained uniaxial compression as described below. A dried sample is filled into a cylindrical container consisting of an insulating cylinder and a negative electrode. A positive electrode is inserted into the insulating cylindrical container filled with the sample, and the container is placed on a force gauge stand with the sample sandwiched between the negative and positive electrodes. A spring-loaded force gauge attached to the force gauge stand is lowered to apply force to the sample inside the cylindrical container, compressing it. While measuring the compressive force and sample height with a length measuring instrument, the resistance of the sample is measured with a digital multimeter connected to the positive and negative electrodes. The conductivity of the powder during compression is calculated from the obtained resistance value, the packed cross-sectional area of ​​the sample, and the packed height.

[0101] The electrical conductivity of the carbon material of this embodiment, measured at a pressure of 10 MPa, is preferably in the range of 1 to 100 S / cm, or 5 to 70 S / cm, 10 to 50 S / cm, or 20 to 30 S / cm. The electrical conductivity of a carbon material is calculated as the reciprocal of its electrical resistivity. The electrical resistivity of a carbon material can be measured, for example, according to JIS K1469.

[0102] The carbon content of the carbon material of this embodiment can be determined by temperature programmed desorption mass spectrometry (TPD-MS) measurement using the configuration shown in Figure 7, and is preferably 95% or more, or 97% or more, 98% or more, 99% or more, or 99.3% or more. The thermal desorption mass spectrometry apparatus 50 includes a radioactive thermometer 41, a quartz reactor including a sample holder 42 and a high-frequency induction coil 43, and a detection unit connected to the quartz reactor. The detection unit includes, for example, a gas reservoir, a turbomolecular pump TMP, a rotary pump RP, a cold cathode Pirani gauge P1, and a capacitance gauge P2.

[0103] The oxygen content of the carbon material of this embodiment is measured by temperature-programmed desorption mass spectrometry (TPD-MS). ２ O, CO and CO ２The oxygen content of the carbon material of the present embodiment is preferably 5% or less, or 3% or less, 2% or less, 1% or less, or 0.6% or less, as a value calculated from the amount of released oxygen. When the oxygen content of the carbon material of the present embodiment is within these ranges, the stability of the lithium ion secondary battery is further improved, which can contribute to higher performance.

[0104] To improve the performance and extend the life of lithium-ion batteries, a highly efficient battery reaction without a decrease in efficiency due to side reactions is required, and the carbon materials in the electrodes are required to have electrochemical stability, i.e., oxidation resistance and corrosion resistance. Electrochemical side reactions such as oxidation are believed to be initiated from oxygen-containing functional groups and edge faces of carbon materials. To improve the oxidation resistance of carbon materials, it is effective to reduce the number of oxygen-containing functional groups and edge faces with low oxidation resistance.

[0105] The TPD-MS measurement method for measuring the oxygen content of the carbon material of this embodiment is based on the H released from the carbon material. ２ , H ２ O, CO and CO ２ The amount of oxygen-containing gases measured is derived from oxygen-containing functional groups such as hydroxyl groups (including phenolic groups), carbonyl groups (including quinones), ethers, acid anhydrides, carboxyl groups, and lactones at the edge terminals of the carbon material. Therefore, a high amount of oxygen-containing functional groups in a carbon material means that there are a large number of oxygen-containing functional groups and edges present in the carbon material structure, which results in poor durability and is a barrier to improving the lifespan and performance of lithium-ion secondary batteries. The amount of oxygen-containing functional groups and edges in a carbon material can be adjusted by the CVD conditions and heat treatment temperature.

[0106] The ratio of the oxygen content to the carbon content of the carbon material of this embodiment, expressed as an O / C ratio, is preferably 1 or less, or also preferably 0.5 or less, 0.1 or less, 0.05 or less, or 0.01 or less. When the O / C ratio of the carbon material is within these ranges, it can contribute to extending the life and improving the performance of lithium ion secondary batteries.

[0107] The amount of gas generated by the carbon material of this embodiment as measured by TPD-MS is preferably 5,000 μmol / g or less, or may be any of 3,000 μmol / g or less, 1,000 μmol / g or less, 750 μmol / g or less, and 500 μmol / g or less. When the amount of gas generated by the carbon material is within these ranges, it can contribute to extending the life and improving the performance of lithium-ion secondary batteries.

[0108] The edge amount of the carbon material of this embodiment is a value calculated from the gas amount measured by TPD-MS measurement, and is preferably 500 m ２ / g or less, or 300m ２ / g or less, 100m ２ / g or less, 50m ２ / g or less, 30m ２ / g or less is also preferable. Alternatively, the edge amount of the carbon material of this embodiment is also preferably either 750 μmol / g or less or 500 μmol / g or less. When the edge amount of the carbon material is within these ranges, the durability is excellent and can contribute to the stability and high performance of the lithium ion secondary battery.

[0109] The ash content of the carbon material of this embodiment is preferably 10,000 ppm or less, or also preferably 5,000 ppm or less, 4,000 ppm or less, 3,500 ppm or less, or 3,000 ppm or less. When the ash content of the carbon material is in this range, the stability of the electrolyte is excellent, and the durability and performance of the lithium ion secondary battery can be improved.

[0110] The pH of the carbon material of the present embodiment is not particularly limited, but is preferably in the range of 5 to 10, or any of 5.5 to 9.5, 6 to 9, 6.5 to 8.5, and 7 to 8. When the pH of the carbon material is in these ranges, the stability is increased and this is preferable.

[0111] The combustion temperature of the carbon material of this embodiment is not particularly limited, but is preferably 300° C. or higher, or any of 400° C. or higher, 450° C. or higher, 500° C. or higher, and 550° C. or higher. The combustion temperature test of the carbon material is carried out as a simple test of corrosion resistance, and an excessively low combustion temperature tends to deteriorate the electrochemical stability in the electrode.

[0112] The carbon material of this embodiment contains graphene and therefore has excellent electron transport properties. Therefore, when the carbon material of this embodiment is contained in an electrode of a lithium ion battery, it can exhibit a function of supporting the battery reaction in the lithium ion battery. Furthermore, the carbon material of this embodiment has a connected structure in which hollow granular objects surrounded by a carbonaceous shell containing graphene are connected. Therefore, an electrolyte solution containing dissolved lithium ions penetrates and is retained in both the interior of the granular objects and the interior enclosed by the connected structure, resulting in excellent ion supply during the reaction. Therefore, the carbon material of this embodiment can favorably support the secondary battery reaction.

[0113] <Method for Producing Carbon Material> Next, a method for producing a carbon material according to this embodiment will be described. The carbon material according to this embodiment can be easily produced by, for example, using a method for producing a carbon material in which a carbonaceous layer is formed on the surface of a template and then the template is removed. That is, the method for producing a carbon material according to this embodiment can include the steps of: preparing a template having a series-linked template portion in which a plurality of template particles are connected in series (hereinafter referred to as the "template preparation step"); forming a carbonaceous outer shell on the surface of the template (hereinafter referred to as the "carbonaceous outer shell formation step"); and removing the template from the inside of the carbonaceous outer shell (hereinafter referred to as the "template removal step").

[0114] (Mold Preparation Step) The mold used in this embodiment is not particularly limited as long as it can realize a complex, elongated, and highly structured carbon material having interconnected internal spaces, such as the carbon material 2 having the structure shown in FIG. 1 .

[0115] The template used in this embodiment has a series-chain template portion in which a plurality of the template particles are connected in series, and a branched-chain template portion made up of template particles that are connected to intermediate template particles, which are template particles located at at least one or more intermediate portions between a first end template particle, which is a template particle that constitutes one end of the series-chain template portion, and a second end template particle, which is a template particle that constitutes the other end of the series-chain template portion, and that branch off from the series-chain template portion.

[0116] Furthermore, in the mold used in this embodiment, the serially linked mold portion is a portion in which one or more mold particles are connected to one another, at least in one of the portions between the first end mold particle and the intermediate mold particle, the portion between adjacent intermediate mold particles, and the portion between the intermediate mold particle and the second end mold particle.

[0117] The mold used in this embodiment may be a material that originally has the above structure, or may be manufactured by controlling the shape so as to have the above structure.

[0118] The diameter of the primary particles (template particles) of the template material (hereinafter referred to as "template material") used in this embodiment is preferably 1 to 150 nm, or preferably in the ranges of 5 to 100 nm, 10 to 60 nm, 15 to 50 nm, or 20 to 40 nm. When the diameter of the primary particles of the template material is within these ranges, the oil absorption capacity of the produced carbon material can be significantly increased. Furthermore, when the primary particle diameter of the template material is within these ranges, handling is easy and the permeability of the raw material gas that serves as the carbon source for the carbonaceous layer is good, facilitating uniform carbon coating.

[0119] The BET specific surface area of ​​the mold material used in this embodiment is preferably 1 to 1000 m ２ / g, or 10 to 500 m ２ / g, 20-200m ２ / g, 40-160m ２ / g, 50-120m ２ When the BET specific surface area of ​​the template material is within these ranges, the oil absorption capacity of the produced carbon material can be significantly increased.

[0120] The specific surface area of ​​the produced carbon material depends on the specific surface area of ​​the template. The smaller the particle diameter, the greater the ratio of particle volume to surface area (particle surface area / particle volume). Therefore, the smaller the particle diameter, the greater the surface area per volume, i.e., the surface area per unit mass. Therefore, carbon materials with a high specific surface area can be obtained by using nanoparticles with a small primary particle diameter as the template material.

[0121] The bulk density of the template material used in this embodiment is preferably in the range of 0.1 to 500 g / L, or alternatively, 0.5 to 250 g / L, 1 to 200 g / L, 10 to 100 g / L, or 30 to 70 g / L. When the bulk density of the template material is in this range, the electrical conductivity of the produced carbon material can be increased and the oil absorption can be significantly increased.

[0122] The template material used in this embodiment is preferably basic or acidic. Examples of suitable basic compounds include magnesium oxide and calcium carbonate. Examples of suitable acidic compounds include aluminum oxide and silanol-containing silica compounds. The acidic pH, measured in 4% water, is preferably 7 or less, or 6.5 or less, 6 or less, 5.5 or less, or 5 or less, and the lower limit is preferably 1 or more, or 2 or more, 3 or more, 3.5 or more, or 4 or more.

[0123] The carbon content of the mold material used in this embodiment is preferably 0.0001% by weight or more, or 0.01% by weight or more, 0.05% by weight or more, 0.1% by weight or more, or 0.5% by weight or more. The upper limit is preferably 5% or less, or 4%, 3%, 2.5%, or 2% or less. When the carbon content of the mold material is within these ranges, it is preferable because it facilitates the formation of a carbonaceous layer on the mold surface.

[0124] The template material used in this embodiment is preferably a compound that has catalytic activity for the carbon deposition reaction. Examples of the template material include non-metallic compounds, metalloid compounds, and metal compounds, and metalloid compounds and metal compounds are preferred.

[0125] The non-metallic compound is not particularly limited, but examples thereof include ceramic compounds (non-metallic inorganic solid materials), etc. Examples of ceramics include glass, cement, fine ceramics, etc.

[0126] The metalloid (semimetal) compound is not particularly limited, but examples thereof include compounds of boron, silicon, germanium, antimony, etc., and is preferably a silicon compound. Examples of the silicon compound include silicon monoxide, silicon dioxide, silicon nitride, silicon carbide, and silicone, and is preferably silicon dioxide.

[0127] Examples of metal compound template materials include monovalent metal compounds and polyvalent metal compounds, with polyvalent metal compounds being preferred. Examples of monovalent metal compounds include chlorides, sulfates, nitrates, phosphates, and carbonates of alkali metals such as sodium and potassium. Examples of polyvalent metal compounds include alkali metal compounds such as calcium and magnesium, and trivalent metal compounds such as aluminum, with calcium compounds, magnesium compounds, and aluminum compounds being preferred. Examples of calcium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, with carbonates and oxides being preferred, and oxides being more preferred. Examples of magnesium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, with carbonates and oxides being preferred, and oxides being more preferred. Examples of aluminum compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, with carbonates and oxides being preferred, and oxides being more preferred.

[0128] Smoked compounds can also be suitably used as template materials. Examples of smoked compounds include compounds obtained by flame hydrolysis, which is one of the dry manufacturing methods for inorganic materials. A typical example of a smoked compound is fumed silicon dioxide (commonly referred to as fumed silica or fumed silica). Since fumed silicon dioxide produced by flame hydrolysis does not undergo a liquid-phase process during its production, it aggregates slowly. Therefore, fumed silicon dioxide has excellent dispersibility in liquid phases and compounds (solid phases). Fumed silicon dioxide is produced by high-temperature gas-phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame, accompanied by hydrochloric acid as a by-product. By changing the production conditions, such as the flame temperature, oxygen and hydrogen supply ratios, raw material supply amounts, and residence time, it is possible to obtain particles with an average particle size of 7 to 40 nm and a specific surface area of ​​50 to 380 m. ２ / g of silicon dioxide particles are obtained.

[0129] Other examples of fumed compounds produced by flame hydrolysis include fumed alumina, fumed titania, fumed wet zirconia, etc. Other fumed metal compounds include chlorides of Na, Ba, or Sr, sulfates of K, Na, Sr, or Mg, nitrates of Na or K, phosphates of Na or K, carbonates of Na, K, Ca, or Mg, and metal oxides of Na, K, Ca, or Ba.

[0130] Precipitated silica can also be used as a template material. Precipitated silica is obtained by reacting a sodium silicate solution with an acid in the liquid phase, followed by precipitation, filtration, washing, drying, and pulverization. By adjusting the reaction conditions, precipitates with an average particle size of about 7 to 140 nm and a specific surface area of ​​about 20 to 400 m can be obtained. ２ / g of silicon dioxide particles are obtained.

[0131] The water content of the mold material used in this embodiment is in the range of 5% or less, preferably 3% or less, more preferably 1.5% or less, even more preferably 1% or less, and most preferably 0.5% or less.

[0132] (Carbonaceous Shell Forming Process) In this embodiment, a method for forming a carbonaceous shell (hereinafter sometimes referred to as a "carbonaceous layer") on the surface of the mold can be exemplified by the CVD method. When the CVD method is used, the amount of carbon deposited on the surface of the mold is affected by CVD reaction conditions such as the source gas species, source gas concentration, flow rate, reaction temperature, and reaction time, but is also greatly affected by the surface condition of the mold. Examples of compounds having a suitable surface for carbon deposition by the CVD method include compounds containing oxygen atoms, where carbon in the source gas is replaced by oxygen atoms during the CVD reaction, and this becomes the starting point for carbonaceous deposition. Examples of oxygen-containing compounds include metal oxides and metal carbonates. Among oxygen-containing compounds, acidic or basic compounds are particularly suitable. Examples of basic oxygen-containing compounds include magnesium oxide and calcium carbonate.

[0133] Furthermore, surfaces suitable for forming carbonaceous layers using CVD methods include those having hydrocarbons as carbon sources. Hydrocarbons are compounds that can be used as source gases, as described below, such as compounds having methyl groups or carbon-carbon unsaturated bonds. Suitable template materials are inorganic compounds having hydrocarbons on their surfaces.

[0134] Suitable examples of inorganic compounds having hydrocarbons on their surfaces include inorganic materials surface-treated with a silane coupling agent, with silica compounds surface-treated with a silane coupling agent being particularly preferred. Silane coupling agents may be used without particular limitation, including those commonly used as surface treatment agents, such as methoxy-type silane coupling agents, ethoxy-type silane coupling agents, vinyl-type silane coupling agents, dialkoxy-type silane coupling agents, and trialkoxy-type silane coupling agents. Among these, trialkoxy-type silane coupling agents with a high number of methyl groups per molecule are preferred, with trimethoxysilane compounds being particularly preferred. The amount of silane coupling agent is selected appropriately depending on the intended use, but is expressed as the amount of hydrocarbons in the inorganic material and is in the range of 0.01 to 10 wt%, preferably 0.02 to 8 wt%, more preferably 0.05 to 5 wt%, even more preferably 0.1 to 3 wt%, and most preferably 0.5 to 1.5 wt%. When the amount of silane coupling agent (hydrocarbon amount) in the inorganic compound is within this range, the carbon mass on the surface of the mold can be easily adjusted, which is advantageous.

[0135] These template materials can be used either alone or in combination of two or more.

[0136] The manufacturing method according to this embodiment makes it possible to easily manufacture electrodes for secondary batteries such as lithium ion batteries that have excellent charge / discharge characteristics (particularly 2C retention rate) that enable rapid charge / discharge.

[0137] In this embodiment, the carbonaceous layer can be formed on the surface of the template by contacting the template with an organic substance that serves as a carbon source and subjecting the template to a carbonization heat treatment. The contact with the carbon source and the carbonization heat treatment can be performed simultaneously or separately. The contact between the template and the carbon source is performed at a temperature ranging from room temperature to 1000°C.

[0138] Methods for contacting a carbon source with a template are roughly divided into liquid-phase contact methods and gas-phase contact methods, with the gas-phase contact method being preferred. The liquid-phase contact method is, for example, a method in which the template is immersed in an organic liquid. The gas-phase contact method is, for example, a method in which an organic vapor is introduced at high temperature and brought into contact with the template, and is the so-called CVD method.

[0139] Liquid-Phase Contact Method In the liquid-phase contact method, organic compounds having functional groups reactive with functional groups present on the template surface, specifically hydroxyl groups, are preferably used, particularly benzene-based hydrocarbon compounds having functional groups reactive with hydroxyl groups. Among these, benzene-based aromatic hydrocarbon compounds having hydroxyl and / or carboxyl groups are preferred, with phenol, hydronaphthalene, and dihydronaphthalene being more preferred. This is because the use of an organic compound having functional groups reactive with functional groups present on the template surface results in the formation of strong bonds, such as ester bonds, between the template material and the organic compound, which facilitates in-situ carbonization without volatilization during the carbonization heat treatment.

[0140] In the liquid-phase contact method, an organic compound serving as a carbon source is dissolved in a solvent and then impregnated into the template material at room temperature for contact. To strongly bond the organic material to the template material, the temperature is maintained at 250 to 600°C for a certain period of time. This causes a dehydration condensation reaction, such as an esterification reaction, between the hydroxyl groups on the template material surface and the organic material, resulting in ester bonds and other bonds, making it easier to obtain a carbonaceous layer with a graphene sheet structure. The temperature is then lowered, and excess organic material that has not reacted with the template material can be washed away with a solvent or the like.

[0141] Heat treatment is performed to carbonize the organic compound that serves as the carbon source and is brought into contact with the template material. This heat treatment causes a dehydrogenation reaction or the like in the organic material, such as hydrocarbon, and converts it into carbon with a graphene sheet structure or the like. The heat treatment temperature is 600°C or higher, preferably 600 to 1,500°C, more preferably 750 to 1,500°C, and particularly preferably 800 to 1,000°C. Note that heat treatment at 1,500°C or higher is acceptable as long as the template material does not collapse or melt.

[0142] - Vapor Phase Contact Method - In the vapor phase contact method, an organic compound serving as a carbon source is brought into contact with a mold material, and in order to strongly bond the carbon source and the mold material, the CVD (Chemical Vapor Deposition) method is preferably carried out at a temperature range in which a dehydrogenation reaction can proceed, specifically, 400 to 1,000°C.

[0143] The organic compound used as the carbon source in the gas-phase contact method may be appropriately selected depending on the intended use. For example, hydrocarbons such as saturated hydrocarbons, unsaturated hydrocarbons having double and / or triple bonds, alicyclic hydrocarbons, and aromatic hydrocarbons are preferably used. Saturated hydrocarbons may be either linear or branched, and examples thereof include methane, ethane, and propane. Unsaturated hydrocarbons may be either linear or branched, and examples thereof include ethylene, propylene, isoprene, and acetylene. Alicyclic hydrocarbons include cyclopropane and cyclohexane. Aromatic hydrocarbons include benzene and toluene. Among these hydrocarbons, it is desirable to use methane, ethane, acetylene, ethylene, propylene, and benzene, and methane, propylene, and benzene are preferred from the viewpoint of precipitating highly crystalline carbon. Methane is particularly preferred from the viewpoint of its high thermal decomposition temperature and the ability to obtain highly crystalline carbon.

[0144] As the organic compound used in the gas phase contact method, alcohols such as methanol, ethanol, propanol, butanol, etc., and nitrogen-containing compounds such as acetonitrile, acrylonitrile, etc. can also be used.

[0145] The reaction temperature in the CVD reaction is appropriately selected depending on the decomposition temperature of the organic compound used as the carbon source, and is in the range of 400 to 1,000°C, preferably 600 to 950°C, and more preferably 800 to 900°C.

[0146] In the method for producing a carbon material according to this embodiment, the number of carbonaceous layers is appropriately selected depending on the intended use, but is preferably 1 layer or more, or 1.2 layers or more, 1.5 layers or more, 2 layers or more, or 2.2 layers or more, and the upper limit is preferably 15 layers or less, or 10 layers or less, 8 layers or less, 6 layers or less, or 5 layers or less. When the number of carbonaceous layers is within this range, the strength characteristics and elastic deformation of the carbonaceous are excellent, the hollow structure can be easily maintained, and the lithium-ion secondary battery characteristics can be highly improved. Note that the number of carbonaceous layers of the carbon material is specifically calculated as described in the examples below. After the carbonaceous layers are laminated on the template particles, the weight of the carbonaceous layers is calculated using thermogravimetric analysis (TG). The weight of the carbonaceous layers per template area is calculated from the weight of the carbonaceous layers and the surface area of ​​the template particles, and this is then used as the weight of the carbonaceous layers per area of ​​the single-layer graphene (7.61 × 10 －４ g / m ２ ) is the value calculated by dividing

[0147] The reaction time in the CVD reaction (CVD treatment time at a predetermined heating temperature) is appropriately selected depending on the type of template material, the type of organic compound used as the carbon source, or the number of carbonaceous layers to be deposited, but is in the range of 0.1 to 10 hours, preferably 0.5 to 5 hours, and more preferably 1 to 3 hours. Furthermore, the analytical methods disclosed herein can be used to analyze the product, and the time required for sufficient carbon deposition can be appropriately set based on the results.

[0148] The CVD reaction can be carried out under an inert gas atmosphere, if necessary. Examples of inert gases include nitrogen, helium, neon, and argon, with argon being preferred. In the CVD method, carbon can be easily adsorbed or deposited on the template material in the gas phase by heating a gaseous organic compound together with a carrier gas while flowing the compound in contact with the template material. The type, flow rate, flow rate, and heating temperature of the carrier gas can be adjusted appropriately depending on the type of organic compound used. Examples of the carrier gas include the inert gases listed above, but they may also be mixtures with oxygen gas or hydrogen gas. Preferably, argon is used as the carrier gas.

[0149] The number of carbonaceous layers introduced onto the template material can be appropriately selected depending on the CVD reaction time, but to form thin graphene layers, the flow rate of the carrier gas is preferably adjusted to 0.05 to 5 m / min, more preferably 0.1 to 1 m / min, even more preferably 0.2 to 0.8 m / min, and most preferably 0.32 to 0.64 m / min. To form an optimal number of graphene layers, the amount of organic compound introduced is also adjusted to preferably 1 to 70 vol%, more preferably 5 to 50 vol%, even more preferably 10 to 40 vol%, and most preferably 15 to 35 vol%, based on the total amount of the carrier gas and organic compound.

[0150] Since the carbonization of the carbonaceous layer can also proceed by a CVD reaction, no other special carbonization treatment is necessary, but may be performed.

[0151] (Template Removal Step) In the production method of this embodiment, the template can be removed after the carbonaceous layer is formed by any method that removes the template and leaves the formed carbonaceous layer. For example, a dissolution method using an acid or alkali can be used, and a dissolution method using an acid is preferred.

[0152] The acid used in this embodiment is appropriately selected depending on the type of template material, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, and hydrofluoric acid, with hydrochloric acid and hydrofluoric acid being preferred. The concentration of the acid used to dissolve and remove the template is appropriately adjusted to a range that allows for dissolution and removal of the template. The amount of acid used may be, for example, 30 times or more the stoichiometric ratio relative to the template material, or 50 times or more the stoichiometric ratio, as long as it allows for dissolution and removal of the template material.

[0153] The temperature for dissolving and removing the template material is in the range of 5 to 100°C, preferably 10 to 50°C, and more preferably 20 to 30°C. The step of dissolving and removing the template material may be carried out while adding stirring, vibration, and other operations. The time required for the removal step is appropriately selected within a range that allows the template to be dissolved and removed.

[0154] After the template is removed, the carbon material can be recovered by, for example, filtration and then washed with pure water. The washing conditions may be appropriately selected, but the washing can be completed by confirming that the pH of the washing solution is neutral.

[0155] The carbon material after the removal of the template material after washing can be dried by vacuum heat drying, etc. The conditions for vacuum heat drying can be, for example, a vacuum heat drying temperature of 100 to 200°C and a vacuum heat drying time of 1 to 10 hours.

[0156] (Heat Treatment Step) In the method for producing a carbon material according to the present embodiment, the carbon material (separated carbonaceous layer) after removal of the template material can be heat-treated as needed. By heat-treating the carbonaceous layer from which the template material has been removed, the crystallinity of the carbon is enhanced and stabilized, making it possible to produce a carbon material with higher levels of electrical conductivity, corrosion resistance, and / or a large specific surface area.

[0157] The conditions for the heat treatment step are not particularly limited as long as they enhance the crystallinity of carbon. The holding temperature in the heat treatment step is in the range of 1,000 to 3,000°C, preferably 1,300 to 2,500°C, more preferably 1,500 to 2,000°C, even more preferably 1,600 to 1,900°C, and most preferably 1,750 to 1,850°C. A heat treatment temperature within this range is suitable because it can provide a carbon material with higher levels of electrical conductivity, corrosion resistance, and / or a large specific surface area. The heat treatment time in the heat treatment step (holding time at a predetermined heat treatment temperature) is in the range of 0.1 to 10 hours, preferably 0.2 to 5 hours, and more preferably 0.5 to 5 hours. The atmospheric pressure in the heat treatment step is not particularly limited, but is preferably atmospheric pressure or reduced pressure.

[0158] Furthermore, by carrying out a heat treatment step, functional groups (mainly oxygen-containing functional groups) bonded to carbon and carbon chains that do not form six-membered rings are detached at temperatures exceeding 1,000°C, forming dangling bonds. When the dangling bonds that are formed bond with other nearby carbons, the surface of the carbon material becomes a state in which functional groups are less likely to bond. By carrying out a heat treatment at 1,500°C or higher, preferably 1,600°C or higher, the carbon material of this embodiment can exhibit favorable functions such as electron conductivity and maintaining internal space.

[0159] These heat treatments adjust structural defects in the graphene and non-graphene components that make up the carbonaceous material. These structural defects include voids created within the aggregate structure due to dissolution of the template material and infiltration pores created in the outer shell formed from the carbonaceous material. By changing reaction conditions such as the heat treatment temperature and time, the extent of these structural defects can be adjusted, i.e., the size of the voids present within the carbonaceous material and the size of the infiltration pores that allow the electrolyte to penetrate into the particles can be adjusted.

[0160] Thus, the carbon material of this embodiment can be easily produced.

[0161] <Dispersion> Next, the dispersion according to this embodiment will be described. The dispersion according to this embodiment is obtained by dispersing the carbon material in a dispersion medium.

[0162] (Dispersion Medium) The dispersion medium used in this embodiment is not particularly limited and is selected depending on the intended use. For example, in order to maintain a good dispersion state of the powder in the solvent, an organic or inorganic dispersant (e.g., a monomolecular or plastic resin material) can be suitably used. When used in the production of a lithium ion secondary battery, a polar solvent is suitably used. From the viewpoint of affinity with the binder polymer, N,N-dimethylformamide, N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and water are preferred, and N-methylpyrrolidone (NMP) is particularly preferred. N-methylpyrrolidone (NMP) is suitable for dispersing carbon materials including graphene.

[0163] The ratio of the carbon material of this embodiment to the dispersion medium is selected appropriately depending on the intended use, and the ratio of the carbon material of this embodiment to 100 parts by weight of the dispersion medium is in the range of 0.01 to 50 parts by weight, preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, even more preferably 0.15 to 4.5 parts by weight, and most preferably 0.2 to 4 parts by weight. If the ratio of the carbon material is too low, it becomes difficult to form a conductive path in the lithium ion secondary battery, and conversely, if the content is too high, the fluidity of the carbon material dispersion is likely to be impaired.

[0164] (Dispersant) In this embodiment, since carbon materials with a high specific surface area tend to aggregate due to van der Waals interactions, a dispersant can be used to improve dispersibility. The dispersant may be attached to the carbon material in advance or may be added directly to the dispersion medium. The dispersant is appropriately selected depending on the intended use, but typically, one having an acidic group or a basic group can be used. In addition, one that is adsorbed to the surface of solid particles to disperse the solid particles by steric repulsion or electrostatic repulsion, or that reduces the interfacial tension between the solid particles and the solvent can be used.

[0165] A dispersant having an acidic group exhibits the effect of enhancing the dispersibility of the carbon material by having at least a portion of the dispersant adhere to the surface of the carbon material. The acidic group of the dispersant is preferably a phenolic hydroxy group. Examples of compounds having a phenolic hydroxy group include phenol, nitrophenol, cresol, catechol, and compounds having a structure in which a portion of these groups is substituted.

[0166] Among these, compounds having a catechol group are preferred as dispersants because they have adhesive properties to carbon materials and dispersibility in dispersion media. Examples of compounds having a catechol group include catechol, dopamine hydrochloride, 3-(3,4-dihydroxyphenyl)-L-alanine, 4-(1-hydroxy-2-aminoethyl)catechol, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol, and 4-tert-butylpyrocatechol.

[0167] As a compound having a basic group, a compound having an amino group is preferred because of its good dispersibility. In particular, a compound having an aromatic ring and an amino group is preferred. Examples of such compounds include benzylamine and phenylethylamine. As a dispersant, a compound having a basic group and a catechol group is also preferred, such as dopamine hydrochloride.

[0168] As the dispersant, a surfactant having an acidic group or a basic group can also be suitably used. As such a surfactant, any of cationic surfactants, anionic surfactants, nonionic surfactants, etc. can be used, but since anions and cations themselves may be involved in electrochemical reactions, non-ionized nonionic surfactants are suitable for use as a battery material.

[0169] Examples of the dispersant for the polymer compound that can be used include those that can also be used as binders for batteries, such as polyvinylidene fluoride, vinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride modified with maleic acid, polyvinylpyrrolidone, polyvinyl alcohol, polymethyl vinyl ether, polyacrylonitrile, nitrile rubber, acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, poly(meth)acrylic acid and its esters, polyvinyl acetal, polyvinyl butyral, and cellulose ether.

[0170] These dispersants can be used either alone or in combination of two or more. When added to a dispersion, the amount added may be appropriately selected depending on the purpose of use.

[0171] (Other Carbon Materials) The dispersion liquid of the present embodiment may contain, as necessary, other carbon materials in addition to the carbon material of the present embodiment. The other carbon materials are not particularly limited, and examples thereof include at least one carbon material selected from the group consisting of carbon black, graphite, activated carbon, carbon nanotubes, carbon nanofibers, carbon fibers, and fullerenes.

[0172] Examples of carbon black include acetylene black, ketjen black, and furnace black, with acetylene black and ketjen black being preferred from the viewpoint of electrical conductivity. Graphite, also known as graphite or graphite, is used, which is made up of multiple layers of graphene. Examples of carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes (multi-walled carbon nanotubes include cup-stacked types). Examples of carbon fibers include mesophase pitch-based carbon fibers, isotropic pitch-based carbon fibers, and vapor-grown carbon fibers (VGCF). Milled carbon fibers obtained by calcining and then crushing polymer fibers can be used.

[0173] These other carbon materials can be used alone or in combination of two or more. The amount of the other carbon materials used can be selected depending on the intended use, and can be selected, for example, within the same range as that of the carbon material of the present embodiment. The ratio of the carbon material of the present embodiment to the other carbon materials used can be selected depending on the intended use, and can be, for example, in the range of 10:90 to 90:10, 20:80 to 80:20, or 40:60 to 60:40 by weight ratio of [carbon material of the present embodiment]:[other carbon material].

[0174] The solids concentration of the dispersion of this embodiment is appropriately selected depending on the intended use, but is in the range of 0.01 to 50 mass%, preferably 0.05 to 30 mass%, more preferably 0.1 to 20 mass%, even more preferably 0.5 to 10 mass%, and most preferably 1 to 5 mass%. If the solids concentration of the carbon material dispersion of this embodiment is excessively high, stacking of the carbon material in the dispersion is likely to occur, making it difficult to maintain a good dispersion state. Conversely, if the solids concentration is excessively low, when the carbon material dispersion is used to produce an electrode slurry, the viscosity of the electrode paste decreases, tending to deteriorate the coatability.

[0175] Here, the solid content of the carbon material dispersion refers to the matter remaining after the dispersion medium has been dried and removed from the carbon material dispersion. The solid content percentage of the carbon material dispersion can be calculated by measuring the weight of the carbon material dispersion after the dispersion medium has been dried and removed from it, and dividing the measured value by the weight of the carbon material dispersion itself. Specifically, about 1 g of the carbon material dispersion is weighed out, and then attached to a glass substrate of known weight, and heated on a hot plate adjusted to a temperature of 120°C for 1.5 hours to volatilize the dispersion medium, and then the weight of the remaining carbon material is measured.

[0176] The viscosity of the dispersion of this embodiment is appropriately selected depending on the intended use. In the case of a dispersion adjusted to a solid content concentration of 3 mass %, the viscosity is －１ The viscosity under the conditions is 20,000 cP or less, preferably 15,000 cP or less, and more preferably 10,000 cP or less. The lower limit is 100 cP or more, preferably 500 cP or more, more preferably 1,000 cP or more, even more preferably 2,000 cP or more, and most preferably 4,000 cP or more. The viscosity of the carbon material dispersion of this embodiment is measured at a temperature of 23°C, a shear rate of 1 s, and a solid content of 2% by mass. －１ It is preferable that the viscosity under the above conditions is 30 cP or less. In the carbon material dispersion liquid of this embodiment, the viscosity can be adjusted to a preferred value by adding the surface treatment agent or the like.

[0177] (Method for Producing Dispersion Liquid) The method for producing the dispersion liquid of this embodiment is not particularly limited, and can be carried out, for example, by mixing the carbon material of this embodiment and, if necessary, a dispersant or other carbon materials in a dispersion medium.

[0178] Since the carbon material of this embodiment has a relatively large BET specific surface area, in order to disperse it well in a dispersion liquid, it is effective to apply high shear force using a mixer with strong stirring power while the carbon material and dispersion medium are present. Examples of mixing devices that can apply high shear force include a planetary mixer, "FILMICS" (registered trademark) (Primix Corporation), a planetary ball mill, and a three-roll mill. In order to eliminate stacking of carbon material particles, a strong stirring step may be performed using a high-shear mixer at a shear rate of 5,000 to 50,000 per second. Preferred high shear mixers are those employing a thin film rotation system, a rotor / stator system, or a media mill system, and examples thereof include "Filmix" (registered trademark) 30-30 type (Primix Corporation), "Clearmix" (registered trademark) CLM-0.8S (M Technique Co., Ltd.), "Labostar" (registered trademark) Mini LMZ015 (Ashizawa Finetech Co., Ltd.), and "Super Shear Mixer" (registered trademark) SDRT0.35-0.75 (Satake Chemical Machinery Co., Ltd.).

[0179] <Electrode Composition, Electrode Slurry, and Electrode> Next, the electrode composition, electrode slurry, and electrode according to the present embodiment will be described. An electrode containing the carbon material according to the present embodiment, preferably an electrode for a lithium ion secondary battery, is suitable because of its excellent high-rate discharge properties, capacity characteristics, and charge / discharge characteristics. To produce such an electrode, it is useful to use an electrode composition or electrode slurry containing the carbon material according to the present embodiment.

[0180] (Electrode Composition) The electrode composition of this embodiment contains the carbon material of this embodiment, an active material, and a binder.

[0181] The active material used in this embodiment is not particularly limited, and examples thereof include the active material used in the positive electrode described below, the active material used in the negative electrode described below, etc. The ratio of the active material to the carbon material of this embodiment used is appropriately selected depending on the intended use, and is in the range of 0.005 to 20 parts by weight, preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, even more preferably 0.1 to 2 parts by weight, and most preferably 0.5 to 1 part by weight, of the carbon material of this embodiment relative to 100 parts by weight of the active material.

[0182] The binder used in this embodiment is not particularly limited, and examples thereof include the binders used in the positive electrode and the negative electrode described below. The amount of binder used is appropriately selected depending on the intended use, and is in the range of 0.05 to 10 parts by weight, preferably 0.1 to 8 parts by weight, more preferably 0.5 to 6 parts by weight, even more preferably 1 to 5 parts by weight, and most preferably 2 to 4 parts by weight, relative to 100 parts by weight of the active material.

[0183] In addition to the carbon material, active material, and binder of the present embodiment, other compounding agents may be added to the electrode composition of the present embodiment as needed. There are no particular limitations on the other compounding agents, so long as they are typically used in electrode compositions for lithium-ion secondary batteries. The amount of the other compounding agents used is 20 parts by weight or less, preferably 15 parts by weight or less, more preferably 10 parts by weight or less, even more preferably 5 parts by weight or less, and most preferably 2 parts by weight or less, per 100 parts by weight of the active material.

[0184] The method for mixing the electrode composition of this embodiment is not particularly limited, but examples thereof include a dry mixing method and a wet mixing method using a dispersion medium.

[0185] (Slurry for Electrodes) The slurry for two electrodes of this embodiment is prepared by mixing the electrode composition described above using a dispersion medium by a wet mixing method. The dispersion medium used may be any dispersion medium capable of dissolving or dispersing the binder, and examples thereof include the dispersion medium used in the positive electrode described below, the dispersion medium used in the negative electrode described below, and the dispersion medium used in the carbon material-containing dispersion liquid of this embodiment described above. The amount of dispersion medium used may be an appropriate amount, and is adjusted so that the viscosity of the electrode slurry in the next step can be applied to a current collector.

[0186] The method for producing the electrode slurry of this embodiment is not particularly limited, and examples thereof include a method in which the carbon material of this embodiment, the binder, and the dispersion medium are mixed together, and then the active material is mixed in. The mixing of the carbon material, the binder, and the dispersion medium of this embodiment includes a method in which the binder is mixed into the carbon material-containing dispersion liquid, and a method in which the carbon material-containing dispersion liquid is mixed with a binder liquid in which the binder is dissolved or dispersed in the dispersion medium.

[0187] The mixing method is not particularly limited, and a known mixer or kneader can be used. Known mixers include an automatic mortar, a homogenizer, a planetary mixer, a homodisper, and a planetary mixer, among which a planetary mixer is particularly preferred.

[0188] (Electrode) The electrode of this embodiment may be either a negative electrode or a positive electrode, and can be obtained by applying the electrode slurry to a current collector and then drying it. The current collector may be either one used for a positive electrode or a negative electrode, as described below.

[0189] The method for applying the electrode slurry to the current collector is not particularly limited, and known methods can be used. Specifically, the electrode slurry can be applied manually or using an automatic coater, such as a Baker applicator, a micrometer-equipped film applicator, a bar coater, or a doctor blade. The drying method is not particularly limited, and known methods can be used, such as drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. After the drying step, the electrode mixture layer may be subjected to a pressure treatment using a mold press or a roll press. The pressure treatment allows the positive electrode mixture layer to adhere well to the current collector.

[0190] <Positive Electrode> The positive electrode will now be described. A positive electrode is generally obtained by applying a slurry containing a positive electrode active material, a conductive additive that enhances electronic conductivity, a binder, and a solvent to a current collecting metal foil such as rolled aluminum foil to form a coating film, which is then heated and dried to remove the solvent, and then formed into a predetermined size and density. The carbon material of this embodiment can be useful as a conductive additive.

[0191] (Positive Electrode Active Material) The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum.

[0192] Specific examples of the positive electrode active material include lithium-manganese oxides (e.g., LiMnO ２ , LiMn ２ O ４ etc.), lithium-cobalt oxides (e.g., LiCoO ２ etc.), lithium-nickel oxides (e.g., LiNiO ２ etc.), lithium-nickel-manganese oxides (e.g., LiNi １－ａ Mn ａ O ２ (where 0<a<1), LiMn ２－ｂ Ni ｂ O ４(where 0<b<2), lithium-nickel-cobalt oxides (e.g., LiNi １－ｃ Co ｃ O ２ (where 0<c<1), lithium-manganese-cobalt oxides (e.g., LiCo １－ｄ Mn ｄ O ２ (where 0<d<1), LiMn ２－ｅ Co ｅ O ４ (where 0<e<2), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni) ｆ Co ｇ Mn ｈ ) O ２ (where 0<f<1, 0<g<1, 0<h<1, f+g+h=1) or Li(Ni ｊ Co ｋ Mn ｍ ) O ４ (where 0<j<2, 0<k<2, 0<m<2, j+k+m=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni ｐ Co ｑ Mn ｒ M Ｓ ) O ２ (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p, q, r, and s are each atomic fractions of independent elements, with 0<p<1, 0<q<1, 0<r<1, 0<s<1, and p+q+r+s=1), and the like, and compounds of any one or more of these may be included.

[0193] Among these, LiCoO is preferred because it can improve the capacity characteristics and stability of the battery. ２ , LiMnO ２ , LiNiO ２ , lithium nickel manganese cobalt oxide (e.g., Li(Ni ０．６ Mn ０．２ Co ０．２ ) O ２ , Li(Ni ０．５ Mn ０．３ Co ０．２ ) O ２, or Li(Ni ０．８ Mn ０．１ Co ０．１ ) O ２ ), or lithium nickel cobalt aluminum oxide (e.g., LiNi ０．８ Co ０．１５ Al ０．０５ O ２ etc.) are preferred.

[0194] As a highly stable positive electrode active material, a lithium atom-containing oxide (olivine-type lithium-containing phosphate compound) represented by the following general formula (1) and having an olivine-type crystal structure can be given. Li １－ｘ M ｘ (A.O. ４ ) (1) (In formula (1), M is an ion of at least one metal selected from the group consisting of Mg, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Ge, and Sn, A is at least one selected from the group consisting of Si, S, P, and V, and x is a number satisfying the relationship 0<x<1.) The value of x in general formula (1) is selected depending on the valences of M and A so that the valence of the entire general formula (1) is 0.

[0195] Specific examples of olivine-type lithium-containing phosphate compounds include LiFePO ４ , LiCoPO ４ , LiMnPO ４ , Li ０．９０ Ti ０．０５ Nb ０．０５ Fe ０．３０ Co ０．３０ Mn ０．３０ P.O. ４ Among these, LiFePO is particularly preferred. ４ (Lithium iron phosphate) is preferred because the iron compound that serves as the raw material is readily available and inexpensive.

[0196] As the positive electrode active material, organic compounds such as polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds, and N-fluoropyridinium salts can also be used.

[0197] The physical properties of the positive electrode active material are determined by the requirements of the battery design and manufacturing process, which are based on constraints such as the type of use of the lithium-ion battery. In manufacturing the positive electrode material, the process is designed to achieve the desired physical properties. Physical properties include powder particle size and distribution, specific surface area, density, etc.

[0198] As an example, the powder particle size is appropriately selected in consideration of other constituent requirements of the lithium ion battery, but from the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, an average particle size of 1 to 30 μm is preferable, and an average particle size of 1 to 10 μm is more preferable.

[0199] These positive electrode active materials can be used either alone or in combination of two or more.

[0200] (Positive electrode: conductive additive) Since the positive electrode active material generally has low electronic conductivity, it is preferable to add a conductive additive that enhances electronic conductivity to the positive electrode, and the carbon material of this embodiment is preferably used. The amount of the carbon material of this embodiment used is appropriately selected depending on the intended use, but is in the range of 0.01 to 4 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight, even more preferably 0.2 to 1.5 parts by weight, and most preferably 0.5 to 1.5 parts by weight, per 100 parts by weight of the positive electrode active material.

[0201] In this embodiment, other conductive substances can be combined as the conductive additive in addition to the carbon material of this embodiment. Examples of other conductive substances include graphite; carbon-based substances such as carbon black, carbon nanotubes, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0202] These other conductive substances can be used alone or in combination of two or more. The amount of the other conductive substances used is selected appropriately depending on the intended use, and is selected appropriately within the range of use of the carbon material of this embodiment. The ratio of the carbon material of this embodiment to the other conductive substances used is selected appropriately depending on the intended use, and is in the range of 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40, in terms of weight ratio, [carbon material of this embodiment]:[other conductive substances].

[0203] Furthermore, among the above, the carbon material of this embodiment can achieve even greater effectiveness when combined with conventionally used conductive additives. For example, carbon blacks such as acetylene black are composed of linked structural particles with diameters of several tens of nanometers. On the other hand, carbon does not have high crystallinity, has a short structural length, and is prone to collapse, making it difficult to transmit electrons over long distances. By combining this with the carbon material of this embodiment, it is possible to realize a system that maintains electronic conductivity and also has ion supply ability, even when the three-dimensional structure is maintained or when the three-dimensional structure is crushed and flattened like flake graphite.

[0204] (Positive Electrode: Binder) The binder used is a component that aids in bonding between the positive electrode active material, conductive additive, and electrode current collector, and is usually an organic polymer. Examples include fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene, CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide, polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol, halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride, conductive polymers such as polyaniline, alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene, unsaturated polymers such as polybutadiene and polyisoprene, polymers having rings such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone, and acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, methyl polyacrylate, ethyl polyacrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide. Modified products or derivatives of the above organic polymers may also be used.

[0205] Among these binders, fluorine-based resins are preferred, with PVDF being particularly preferred. The weight-average molecular weight of these binders may be appropriately selected depending on the intended use, and may be, for example, 10,000 to 8,000,000, 10,000 to 3,000,000, 50,000 to 5,000,000, 80,000 to 3,000,000, or 100,000 to 1,000,000. If the weight-average molecular weight of the binder is too small, the strength of the coating film decreases, while if it is too large, the viscosity increases, making it difficult to form an electrode.

[0206] These binders can be used alone or in combination of two or more, and the amount used is appropriately selected depending on the intended use, and is in the range of 0.01 to 4 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight, even more preferably 0.2 to 1.5 parts by weight, and most preferably 0.5 to 1.5 parts by weight, relative to 100 parts by weight of the positive electrode active material. When the amount of binder used is in this range, the adhesive strength between the electrode active materials and between the electrode active material and the conductive material can be improved, and therefore the bonding strength with the electrode current collector can be improved, which is preferable.

[0207] (Positive electrode: slurry) The electrode-forming slurry used is prepared by blending the positive electrode active material, the conductive additive, the binder, and other compounding agents as required, and mixing them in a dispersion medium. The other compounding agents are appropriately selected depending on the intended use, and those typically used in lithium-ion secondary batteries can be used within their normal range of use.

[0208] The dispersion medium to be used is not particularly limited, but for example, a medium that dissolves only the binder and does not dissolve other materials is preferably used in order to distribute the binder sufficiently uniformly and form a coating film of the slurry to a predetermined size. Specifically, for example, organic solvents such as dimethylformamide, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, or water may be used, and one of these may be used alone, or a mixture of two or more of them may be used.

[0209] When polyvinylidene fluoride (PVDF) is used as the binder, dimethylformamide or N-methyl-2-pyrrolidone (NMP) is preferred as the dispersion medium, with NMP being particularly preferred.

[0210] The solids concentration of the electrode-forming slurry, excluding the dispersion medium, may be appropriately selected depending on the method for applying the slurry to the electrode, and is in the range of 10 to 90% by weight, preferably 20 to 80% by weight, more preferably 40 to 80% by weight, even more preferably 40 to 70% by weight, and most preferably 50 to 65% by weight.

[0211] The viscosity of the electrode-forming slurry is in the range of 1,000 to 50,000 cP, preferably 2,000 to 40,000 cP, more preferably 5,000 to 35,000 cP, even more preferably 10,000 to 35,000 cP, and most preferably 10,000 to 30,000 cP at a temperature of 24 to 26° C. When the viscosity of the electrode-forming slurry is in this range, the solids excluding the dispersion medium are uniformly dispersed, and the electrode-forming slurry can be suitably applied to an electrode current collector with a uniform thickness.

[0212] (Current Collector and Positive Electrode) The positive electrode can be produced by applying the electrode forming slurry to a current collector and drying it. The current collector is not particularly limited as long as it is a commonly used one, and examples thereof include aluminum foil, nickel foil, titanium foil, and stainless steel foil, with rolled aluminum foil being particularly preferred.

[0213] The electrode-forming slurry can be applied to the current collector by a commonly used printing technique. When the thickness of the coating film is small, gravure printing or the like is preferably used, and when the thickness is large, doctor blade printing, die printing or other printing techniques are preferably used.

[0214] Thereafter, the coating film is dried by heating. Any drying method can be used, and a method that can achieve the desired binding strength by the binder is preferably used.

[0215] Thereafter, when forming the cathode into a predetermined size, an industrially available cutting blade and the like and the method thereof are preferably used. In addition, to achieve a predetermined density, an industrially available pressing device and the like and the method thereof are preferably used as needed.

[0216] The negative electrode can be obtained by coating a current-collecting metal foil such as rolled copper foil with a slurry containing a negative electrode active material, a conductive additive, a binder, and a dispersion medium, drying the coated foil by heating to remove the solvent, and then forming the coated foil into a desired size and density.

[0217] (Negative Electrode: Active Material) The negative electrode active material is preferably one that can bond and stabilize Li ions with electrons flowing from an external circuit and has numerous stabilization sites within it. For example, materials of organic origin, whether high or low crystallinity, can be used, and graphite, coke, amorphous carbon, hard carbon, polymer carbon, etc. are suitable. In this case, the principle is that Li ions are sandwiched between graphene layers, etc., and bond with electrons to stabilize them. Another stabilization mechanism is the electrochemical formation of intermetallic compounds, and silicon, tin, zinc, bismuth, antimony, cadmium, lead, germanium, etc. are suitable. In addition, other materials that exhibit low electrochemical reaction potentials and control the negative electrode side of lithium-ion batteries can also be used. Suitable examples include compounds of metals with oxygen, sulfur, halogens, nitrogen, phosphorus, etc.

[0218] Specific examples of the negative electrode active material include compounds capable of reversible intercalation and deintercalation of lithium, such as carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO. ｘ (0<x=2), SnO ２ Examples include metal oxides that can be doped and dedoped with lithium, such as vanadium oxide and lithium vanadium oxide; or composites containing the above metallic compounds and carbonaceous materials, such as Si—C composites or Sn—C composites.

[0219] The negative electrode active material may also be a metallic lithium thin film. The carbonaceous material may be either low-crystalline carbon or high-crystalline carbon. Typical examples of low-crystalline carbon include softened carbon and hardened carbon. Typical examples of high-crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microspheres, mesophase pitch, and high-temperature-calcined carbon such as petroleum- and coal-based coke.

[0220] The physical properties of anode materials are determined by the requirements of the device (e.g., storage battery) design and manufacturing process, which are based on constraints such as the use of lithium-ion batteries. The manufacturing process is designed to achieve the desired physical properties. Physical properties include powder particle size and distribution, specific surface area, and density.

[0221] As an example, the powder particle size is appropriately selected in consideration of other constituent requirements of the lithium ion battery, but from the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, an average particle size of 1 to 70 μm is preferable, and 3 to 30 μm is more preferable.

[0222] These negative electrode active materials can be used alone or in combination of two or more. The ratio of the negative electrode active material in the electrode-forming slurry is in the range of 95.5 to 99 parts by weight, preferably 96 to 98.7 parts by weight, and more preferably 97 to 98 parts by weight, per 100 parts by weight of the solid content excluding the dispersion medium. When the content of the negative electrode active material is in this range, the battery capacity, conductivity, and adhesiveness are well balanced, which is preferable.

[0223] (Conductive Aid) The carbon material of this embodiment may be used as a carbonaceous material for the negative electrode active material, but it can also be suitably used as a conductive aid for the negative electrode active material. For example, while the negative electrode active materials generally have high electronic conductivity, some materials have smooth surfaces and insufficient particle-to-particle contact. In such cases, the carbon material of this embodiment can be used as a conductive aid to enhance electronic conductivity. Furthermore, flake graphite and artificial graphite used as negative electrode active materials have high electronic conductivity but low ion storage capacity and poor ionic conductivity. By combining these properties with the carbon material of this embodiment, a favorable battery reaction assist system can be constructed that combines electronic conductivity with ionic conductivity. Furthermore, even when the three-dimensional structure of the negative electrode active material is crushed and flattened like flake graphite, the addition of the carbon material of this embodiment is advantageous because it can add ionic conductivity while maintaining electronic conductivity.

[0224] The ratio of the carbon material of this embodiment in the electrode-forming slurry is in the range of 0.8 to 3 parts by weight, preferably 1 to 2.5 parts by weight, and more preferably 1 to 2.2 parts by weight, per 100 parts by weight of the solid content excluding the dispersion medium. When the content of the carbon material of this embodiment is in this range, the high-speed chargeability, life characteristics, capacity characteristics, and charge / discharge characteristics of the lithium-ion secondary battery can be suitably improved.

[0225] In this embodiment, the carbon material of this embodiment can be used in combination with other carbon materials. The other carbon materials are not particularly limited as long as they are conventional materials used as electrode materials, and examples thereof include acetylene black, ketjen black, lamp black, furnace black, carbon black, graphite, carbon fiber, graphite fiber, nanofiber, nanotube, coke, hard carbon, and amorphous carbon.

[0226] These other carbon materials can be used alone or in combination of two or more, and the amount used is selected depending on the purpose of use and can be used in the same range as the carbon material of the present embodiment. The weight ratio of the carbon material of the present embodiment to the other carbon materials is 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0227] Further benefits can be achieved by combining these conventional materials with the carbon material of this embodiment. For example, highly linear carbon nanotubes have high electronic conductivity but low ion storage capacity. Therefore, by combining them with the carbon material of this embodiment, it is possible to construct an excellent battery reaction assistance system that combines electronic conductivity with ionic conductivity. Furthermore, carbon blacks such as acetylene black are composed of linked structural particles with diameters of several tens of nanometers. On the other hand, carbon crystallinity is not very high, the structural length is short, and it is prone to collapse, making long-distance electron transport difficult. Despite these properties, by combining them with the carbon material of this embodiment, it is possible to realize a system that maintains a three-dimensional structure and also has ion supply capacity.

[0228] (Negative electrode: binder) The binder used is a component that aids in bonding between the electrode active material, conductive assistant, and electrode current collector, and examples thereof include fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide, polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol, halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride, conductive polymers such as polyaniline, alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene, unsaturated polymers such as polybutadiene and polyisoprene, polymers having rings such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone, acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, methyl polyacrylate, ethyl polyacrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide, carboxymethyl cellulose, and styrene butadiene rubber. Modified products or derivatives of the above organic polymers may also be used.

[0229] Among these binders, carboxymethyl cellulose, styrene butadiene rubber, etc. are preferred. The weight-average molecular weight of these binders may be appropriately selected depending on the intended use, and may be, for example, in the range of 10,000 to 8,000,000, 10,000 to 3,000,000, 50,000 to 5,000,000, 80,000 to 3,000,000, or 100,000 to 1,000,000. If the weight-average molecular weight of the binder is too small, the strength of the coating film decreases, while if it is too large, the viscosity increases, tending to make it difficult to form an electrode.

[0230] These binders can be used alone or in combination of two or more, and the amount used is appropriately selected depending on the intended use, and is in the range of 0.01 to 4 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight, even more preferably 0.2 to 1.5 parts by weight, and most preferably 0.5 to 1.5 parts by weight, relative to 100 parts by weight of the positive electrode active material. When the amount of binder used is in this range, the adhesive strength between the electrode active materials and between the electrode active material and the conductive material can be improved, and therefore the bonding strength with the electrode current collector can be improved, which is preferable.

[0231] These binders can be used alone or in combination of two or more, and their proportion in the electrode-forming slurry is in the range of 0.8 to 3 parts by weight, preferably 1 to 2.5 parts by weight, and more preferably 1 to 2.2 parts by weight, per 100 parts by weight of the solid content excluding the dispersion medium. When the binder content in the electrode-forming slurry is in this range, the adhesive strength between electrode active materials and between the electrode active material and the conductive assistant can be improved, and thus the bonding strength with the electrode current collector can be improved, which is preferable.

[0232] (Negative electrode: Dispersion medium) The dispersion medium used is not particularly limited as long as it is a solvent commonly used in the technical field, and for example, organic solvents such as N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, or water may be used, and one or more of these may be used alone or in combination. The dispersion medium is used to dissolve or disperse the electrode active material, conductive material, and binder, taking into consideration the coating thickness of the electrode-forming slurry and the production yield.

[0233] (Negative electrode: slurry) The amount of the dispersion medium used is adjusted, for example, so that the concentration of the solids including the electrode active material, the conductive material, and the binder is in the range of 10 to 90 wt %, preferably 20 to 80 wt %, more preferably 30 to 75 wt %, preferably 40 to 70 wt %, more preferably 50 to 65 wt %.

[0234] (Current Collector and Negative Electrode) The current collector for the negative electrode is not particularly limited, but may be, for example, a material that does not have electrochemical reactivity to the potential generated by the negative electrode. Specific examples include copper foil, nickel foil, titanium foil, and stainless steel foil, and electrolytic copper foil and rolled copper foil are preferred.

[0235] The electrode-forming slurry can be applied to the current collector by a commonly used printing technique. When the thickness is small, gravure printing or the like is preferably used, and when the thickness is large, doctor blade printing, die printing or the like is preferably used.

[0236] Thereafter, the coating film is dried by heating. Any drying method can be used, and a method that can achieve the desired binding strength by the binder is preferably used.

[0237] Thereafter, when forming the negative electrode into a predetermined size, an industrially available cutting blade and the like and the method thereof are preferably used. In addition, to achieve a predetermined density, an industrially available pressing device and the like and the method thereof are preferably used as needed.

[0238] <Lithium-ion Secondary Battery> Next, a lithium-ion secondary battery according to the present embodiment will be described. The lithium-ion secondary battery according to the present embodiment is characterized by including the carbon material according to the present embodiment. Specifically, the lithium-ion secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and at least one of the positive electrode and the negative electrode uses the electrode (positive electrode and / or negative electrode) according to the present embodiment. Meanwhile, the lithium-ion secondary battery may optionally further include a battery container that houses the electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container. Meanwhile, the positive electrode and the negative electrode are the same as those described above, and therefore detailed description thereof will be omitted.

[0239] (Separator) The separator used separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator that is typically used as a separator in a lithium ion secondary battery can be used without any particular limitation. In particular, a separator that has low resistance to the movement of ions in the electrolyte and excellent electrolyte solution impregnation ability is preferred.

[0240] Specifically, porous polymer films may be used, such as porous polymer films made of polyolefins such as polyethylene, polypropylene, polybutene, polyvinyl chloride, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminate structures of two or more layers thereof. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material may also be used, and may be used in a single-layer or multi-layer structure.

[0241] Polyethylene and polypropylene are particularly suitable materials for the porous polymer film. Polyethylene has a relatively low melting temperature, and when the battery temperature rises for some reason (e.g., an unsafe condition such as a short circuit), the pores in the film are blocked by thermal melting, preventing the movement of driving ions, thereby stopping the reaction and ensuring safety. Polypropylene is also suitable as a material that can be stretched to become porous without the use of plasticizers.

[0242] Alternatively, a polymer compound can be applied to both sides of the separator. Examples of such polymer compounds include ether-based polymer compounds such as polyvinyl formal, polyethylene oxide, and crosslinked polyethylene oxide-containing compounds, ester-based polymer compounds such as polymethacrylate, acrylate-based polymer compounds, and fluorine-based polymer compounds such as polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer. Among these, it is particularly desirable to use a fluorine-based polymer compound such as polyvinylidene fluoride, from the viewpoint of preventing swelling during high-temperature storage.

[0243] (Electrolyte) As the electrolyte, a non-aqueous electrolyte in which an electrolyte is dissolved in an organic solvent is usually used.

[0244] -Electrolyte- As the electrolyte, for example, a lithium salt is used. As the lithium salt, for example, LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ )NLi, LiN(CF ３ SO２ ) (C ４ F ９ SO ２ ), LiC(CF ３ SO ２ ) ３ , LiPF ４ (CF ３ ) ２ , LiPF ４ (C ２ F ５ ) ２ , LiPF ４ (CF ３ SO ２ ) ２ , LiPF ４ (C ２ F ５ SO ２ ) ２ , LiBF ２ (CF ３ ) ２ , LiBF ２ (C ２ F ５ ) ２ , LiBF ２ (CF ３ SO ２ ) ２ , LiBF ２ (C ２ F ５ SO ２ ) ２ , Li cyclic 1,2-perfluoroethane disulfonylimide, Li cyclic 1,3-perfluoropropane disulfonylimide, etc. Among these, LiPF is preferred because it is easily soluble in solvents and exhibits a high degree of dissociation. ６ , LiBF ４ , LiClO ４ , C.F. ３ SO ３ Li, LiN(CF ３ SO ２ ) ２ , LiN(C ２ F ５ SO ２ ) ２ and the like are preferred, and LiPF ６ and LiBF ４ is particularly preferred.

[0245] The electrolyte may be a gel electrolyte containing a polymer compound that swells in an organic solvent to serve as a support for the nonaqueous electrolyte. The inclusion of a polymer compound that swells in an organic solvent is advantageous because it can provide high ionic conductivity, excellent charge / discharge efficiency, and prevent leakage from the battery. The content of such a polymer compound is preferably in the range of 0.1 to 10 wt % of the electrolyte.

[0246] These electrolytes can be used alone or in combination of two or more. The concentration of the electrolyte in the electrolytic solution is not particularly limited and can be appropriately adjusted, but is in the range of 5 to 15 wt %, preferably 2 to 13 wt %, and more preferably 5 to 10 wt %.

[0247] - Organic Solvent - As the organic solvent used in the electrolytic solution, any solvent that can dissolve the electrolyte is suitably used, such as cyclic carbonates, chain carbonates, esters such as γ-butyrolactone and methyl formate, ethers such as 1,2-dimethoxyethane and tetrahydrofuran, sulfur-containing compounds such as sulfolane and dimethyl sulfoxide, etc. These organic solvents can be used alone or in combination of two or more.

[0248] Among these, cyclic carbonates and chain carbonates are preferred because they have a high dielectric constant and suitable viscosity and solvating ability that affect the migration of Li ions. Note that solvating ability is the force that dissociates dissolved ions, and if it is too strong, it will inhibit the migration of ions, so there is an optimum value.

[0249] Examples of cyclic carbonates include alkylene carbonates having an alkylene group having 2 to 4 carbon atoms, such as ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are preferred from the viewpoint of improving battery characteristics, and ethylene carbonate is particularly preferred.

[0250] As the chain carbonates, for example, dialkyl carbonates are preferred, and the number of carbon atoms in the constituent alkyl groups is preferably 1 to 5, particularly preferably 1 to 4. Specific examples include dialkyl carbonates such as symmetric chain alkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; and asymmetric chain alkyl carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. Of these, dimethyl carbonate and diethyl carbonate are preferred from the viewpoints of viscosity and boiling point, and diethyl carbonate is particularly preferred.

[0251] Furthermore, practical lithium ion batteries are used under a wide range of environmental conditions, and the physical properties of the non-aqueous solvent, such as the melting point and boiling point, must fall within certain ranges. Therefore, it is preferable to use a mixture of cyclic carbonates and chain carbonates.

[0252] The combination of cyclic carbonates and chain carbonates is not particularly limited, but for example, a combination of ethylene carbonate and a chain carbonate is preferable. Specifically, combinations such as ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, and ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferable because they have a good balance between cycle characteristics and high-power discharge characteristics.

[0253] The mixing ratio of the cyclic carbonates to the chain carbonates is appropriately selected depending on the desired practical properties, and is, for example, in the range of a weight ratio of [cyclic carbonates]:[chain carbonates] of 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0254] The content of the cyclic carbonate in the electrolyte may be 1 to 70% by weight, 1 to 35% by weight, 3 to 30% by weight, or 4 to 50% by weight. A mixture of multiple cyclic carbonates can be used.

[0255] The content of the chain carbonate in the electrolyte is preferably 40 to 70% by weight, more preferably 43 to 68% by weight. A mixture of a plurality of chain carbonates can be used.

[0256] As the organic solvent used in the electrolyte, a fluorine-containing carbonate can also be suitably used. Specifically, cyclic carbonates having one fluorine atom, chain carbonates having one fluorine atom, cyclic carbonates having two or more fluorine atoms, chain carbonates having two or more fluorine atoms, etc. can be mentioned, and from the viewpoint of improving battery characteristics, fluorine-containing cyclic carbonates having two or more fluorine atoms are preferred.

[0257] Specific examples of fluorine-containing cyclic carbonates having two or more fluorine atoms include cis-4,5-difluoro-1,3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, and 4,4-difluoro-1,3-dioxolan-2-one.

[0258] These fluorine-containing carbonates can be used alone or in combination of two or more. The proportion of the fluorine-containing carbonate in the electrolyte is 0.001 to 10 wt %, preferably 0.01 to 5 wt %, more preferably 0.1 to 2 wt %, even more preferably 0.2 to 1 wt %, and most preferably 0.25 to 0.5 wt %. If the content of the fluorine-containing carbonate is too low, the effect of adding it is difficult to be exerted, whereas if it is too high, the internal pressure of the battery may increase during high-temperature storage.

[0259] As the organic solvent used in the electrolyte, a cyclic carbonate having an unsaturated bond or an aromatic compound having 7 to 18 carbon atoms may be mixed in the electrolyte.

[0260] As the cyclic carbonate having an unsaturated bond, for example, vinylene carbonate, vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate, 4,5-divinylethylene carbonate, etc. are preferred from the viewpoint of improving cycle characteristics, and among these, vinylene carbonate and vinylethylene carbonate are particularly preferred.

[0261] As the aromatic compound having 7 to 18 carbon atoms, for example, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferred because they suppress side reactions with the negative electrode and positive electrode, thereby suppressing a significant decrease in discharge characteristics after high-temperature storage.

[0262] These cyclic carbonates having unsaturated bonds and aromatic compounds having 7 to 18 carbon atoms can be used either alone or in combination of two or more. The proportion of each in the electrolytic solution is in the range of 0.001 to 5 wt %, preferably 0.1 to 4 wt %, more preferably 0.3 to 3 wt %, even more preferably 0.4 to 2.5 wt %, and most preferably 0.5 to 2 wt %.

[0263] 3 shows an example of the cross-sectional structure of a coin-type lithium-ion battery 200 according to one embodiment of the present invention. This lithium-ion battery 200 has a disk-shaped positive electrode 212 housed in a metal exterior part 211 and a disk-shaped negative electrode 214 housed in a metal exterior part 113, which are stacked with a separator 215 interposed therebetween. A metal spring 218 and a spacer 219 are disposed between the exterior part 213 and the negative electrode 214. The interiors of the exterior parts 211 and 213 are filled with a liquid electrolyte, and the peripheral portions of the exterior parts 211 and 213 are sealed by being crimped via a seal gasket 217.

[0264] (Method for Manufacturing Lithium-Ion Secondary Battery) The lithium-ion secondary battery according to this embodiment can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the resulting assembly as necessary according to the battery shape, placing it in a battery container, injecting an electrolyte into the battery container, and sealing it. To prevent internal pressure rise, overcharge / discharge, and the like within the secondary battery, a fuse, an overcurrent prevention element such as a PTC element, expanded metal, lead plates, and the like may be provided as necessary. The shape of the secondary battery may be any type, such as a coin type, button type, sheet type, cylindrical type, prismatic type, or flat type.

[0265] <Applications> The carbon material of this embodiment can exhibit its functionality and be effectively used in any electrochemical device other than the lithium-ion secondary battery. Specifically, it has functions such as a function as an internal conductive path in an electrode when electrons are exchanged in a device reaction, a reinforcing function when an electrode or the like is physically deformed, and a function of preventing direct contact between a reaction material and a third material (such as a catalyst) by taking advantage of the durability of the graphene when the reaction material is in an oxidized or reduced state.

[0266] Usable devices 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 typified by polymer gel electrolyte batteries in which an electrolyte is impregnated in PVDF or the like.

[0267] In these devices, as the negative electrode active material, graphitizable carbon, non-graphitizable carbon, graphite, lithium alloy-based materials such as silicon and tin, and other metal-based materials such as lithium are used, and as the positive electrode active material, lithium-containing metal oxides, particularly lithium-containing transition metal oxides having a layered structure, spinel structure, or olivine structure, lithium-free metal oxides, organic positive electrode materials, charge transfer complex positive electrode materials, sulfur, fluoride-based materials, etc. are used, but the carbon material of this embodiment can effectively increase the conductivity of any active material. In addition, the carbon material of this embodiment is also suitable as a material for lithium-sulfur batteries and the like described in WO2018 / 225619, JP2023-501679A, JP2019-517116A, JP2022-191280A, etc.

[0268] The carbon material of this embodiment can also be suitably used in organic electrolyte capacitors, aqueous electrolyte capacitors, and aqueous electrolyte batteries. It can be used in fuel cells such as PEFC, SOFC, and DMPC, and in particular can be used as a support for redox catalysts in addition to providing electrical conductivity to electrodes.

[0269] The carbon material of this embodiment can also be used for applications other than electrochemical devices, such as electronic device applications such as graphene-based sensors, electromagnetic interference suppression materials, antenna modules, heat dissipation substrates, heat exchangers, separation membranes, reverse osmosis membranes, transparent electrode materials, structural material applications that utilize mechanical flexibility, conductive inks, pastes, and the like.

[0270] The following examples will be described in detail, but the present invention is not limited to these examples. In the following description, "%", "ppm" and "parts" are by weight unless otherwise specified.

[0271] Example 1 (Production of Carbon Material) - CVD Reaction: Carbonaceous Layer Formation - Fumed silica (SiO ２ / AEROSIL (registered trademark) NX90G; average primary particle diameter 38 nm (calculated value), BET specific surface area 71 m ２Approximately 1 g of 1000 sachets (1000 sachets / g, carbon content 0.5-1.5%, manufactured by Nippon Aerosil Co., Ltd.) was placed in a quartz boat and placed in the center of a quartz reaction tube of a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). While flowing argon gas at a flow rate of 400 mL / min inside the reaction tube, the reaction tube was heated to 900 ° C at a temperature increase rate of 10 ° C / min and held for 30 minutes. While maintaining the temperature at 900 ° C, argon gas was flowed at a flow rate of 320 mL / min, and methane gas was flowed at a flow rate of 80 mL / min (raw material gas concentration 20%), and the temperature was held for 90 minutes. Thereafter, while flowing argon gas at a flow rate of 400 mL / min, the mixture was cooled to room temperature, and the carbonaceous (outer shell)-template (mold) laminate was removed.

[0272] - Template Removal - Next, the template was removed from the resulting laminate by the following procedure to obtain a carbon material. (1) The carbonaceous-template laminate was placed in a 100 ml PFA beaker, and ultrapure water was added to the sample until the entire sample was wet. (2) 46% hydrofluoric acid was added, and the mixture was stirred with a stirrer for 2 hours. (3) After stopping the stirring, the sample was left to settle. (4) The supernatant was suction-filtered using a PTFE membrane filter (47 mm diameter, 0.1 μm pore size). (5) The sample on the filter paper was washed with approximately 39 mL of ultrapure water and suction-filtered. This procedure was repeated three times. (6) The sample on the filter paper was returned to the original PFA beaker. (7) Steps (2) to (6) were repeated again. (8) Approximately 40 mL of ultrapure water was added, and the mixture was stirred with a stirrer for 1 hour. (9) After stirring was stopped, the sample was left to stand until it settled. (10) The supernatant was discarded, and 5% caustic soda was added, followed by stirring for 12 hours while heating to 80°C. (11) After stirring was stopped, the sample was left to stand until it settled. (12) Using a PTFE membrane filter (47 mmφ, pore size 0.1 μm), the supernatant was suction filtered. (13) The sample on the filter paper was washed with ultrapure water and suction filtered. This procedure was repeated until the filtrate became neutral. (14) The sample on the filter paper was collected in a petri dish and dried in a dryer at 110°C for 8 hours.

[0273] - Heat Treatment - The carbon material obtained above was placed in a square high-temperature heating furnace (manufactured by Izumi Tech Co., Ltd.) and heated under reduced pressure (10 －１After adjusting the pressure to the order of Pa, the mixture was heated to 1800°C at a temperature increase rate of 15°C / min under an argon gas flow (10 mL / min) and then calcined by maintaining the temperature for 1 hour. Thereafter, the mixture was cooled to room temperature, and the calcined carbon material was taken out to obtain a heat-treated graphene-containing carbon material A (a representative photograph of which is shown in FIG. 2A ).

[0274] (Method for measuring oil absorption of carbon material) The oil absorption of the obtained carbon material was measured in accordance with "JIS K5101-13-1 Pigment testing methods - Part 13: Oil absorption - Section 1: Refined linseed oil method." The results are shown in Table 1.

[0275] (Transmission Electron Microscope Observation) The shape of the obtained carbon material was observed using a transmission electron microscope (TEM: H-7650 model, manufactured by Hitachi High-Technologies Corporation). Observation of the carbon material using a transmission electron microscope (TEM) was performed at an acceleration voltage of 100 kV. FIG. 2A is a transmission electron microscope (TEM) image of a representative structure of the carbon material of Example 1. From the TEM image in FIG. 2A, it was confirmed that the carbonaceous layer of the carbon material of Example 1 had a graphene structure consisting of a six-membered carbon ring structure. It was also confirmed that the carbon material of the example had a structure in which granular hollow particles 4, each having an internal space 4b surrounded by a carbonaceous outer shell 4a, were connected together. Note that in FIG. 2A, reference numerals are omitted from the individual hollow particles 4 (the same applies to FIGS. 2B to 2F hereinafter).

[0276] 2A , carbon material 2 of Example 1 has three or more hollow particles located at the ends, and also has hollow particles other than the hollow particles located at the ends and the hollow particles located in the branched portions. Therefore, it can be seen that carbon material 2 of Example 1 is a carbon material according to this embodiment. In carbon material 2 of Example 1, some regions of the serial chain portions 6 and the branched chain portions 7 have a shape in which two or more hollow particles are connected together, with thick portions formed as bundles.

[0277] As shown in the TEM image of Figure 2A, the combination of hollow particles located at the ends of the chain with the greatest linear distance between both ends of the chain was designated as the first end hollow particle 41 and the second end hollow particle 42, thereby determining the serial chain portion 6. A branched chain portion 7 is also present, which is connected to a middle hollow particle 44 (the arrow indicates the approximate location of the hollow particle) and branches off to a third end hollow particle 43 from the serial chain portion 6. Furthermore, the sample contains hollow particles (connected hollow particle portion 6a) other than the hollow particle located at the end and the hollow particle at the branched portion (middle hollow particle 44). In part of the branched chain portion 7, hollow particles 4 are connected in a ring shape to form macropores 8.

[0278] (Nitrogen Adsorption / Desorption Measurement) Nitrogen adsorption / desorption measurements were performed on the obtained carbon material using an automatic specific surface area / pore size distribution analyzer (BELSORP MINI, manufactured by Microtrac BEL Co., Ltd.). Prior to the measurement, the sample was dried under reduced pressure at 150°C for 6 hours using a BEL pre. From the obtained adsorption isotherm, the BET specific surface area was determined using the BET method. The applicable range of the BET method was P / P0 = 0.05 to 0.3. Furthermore, based on the obtained adsorption / desorption isotherm, the total pore volume was measured by converting the amount of nitrogen adsorbed at -196°C and a relative pressure P / P0 = 0.99 into a volume at the density of liquid nitrogen. The results are shown in Table 1. The pore size distribution was determined using the BJH method.

[0279] (Raman Spectroscopic Measurement) The obtained carbon material was subjected to Raman spectroscopic measurement using a micro-Raman device (LabRAM HR-800, manufactured by Horiba, Ltd.). The measurement was performed using a 532 nm laser, with the filter set to D1 and the hole set to 100 μm. The measurement range was 300 to 3,500 cm －１ From the measured Raman spectrum, (I Ｇ / I ２Ｄ ), (I Ｄ / I Ｇ The intensity ratios of the above were calculated and are shown in Table 1.

[0280] (Preparation of Positive Electrode) A ternary positive electrode material NCM (LiNi) with an average particle size of 8 μm was prepared. ０．５ Co ０．２ Mn ０．３ O ２96.5% of the active material (Kelong Co., Ltd.), 0.5% of the carbon material A obtained above as a conductive additive, and 3 wt. % of PVDF (Kureha Co., Ltd.) were mixed with N-methylpyrrolidone (NMP) as a solvent. The conductive additive was either used as is, or a dispersion of carbon material A dispersed in NMP solvent was used. The mixture of the active material, conductive additive, and PVDF was placed in a planetary mixer and kneaded at 2000 rpm while adding NMP in several portions until a uniform and appropriate viscosity was achieved, producing a positive electrode agent slurry. This was applied to 15 μm thick aluminum foil at a constant speed using a doctor blade applicator with a micrometer. The mixture was then dried in a vacuum dryer set at 110 °C to obtain a positive electrode blank. The positive electrode blank was then punched using a φ15 mm punch-type punching machine, pressed at 45 kN using a cylinder-type jig, and vacuum-dried at 120 °C to obtain a positive electrode for battery assembly.

[0281] (Fabrication of Lithium-Ion Secondary Battery) The positive electrode fabricated as described above and metallic Li punched to a diameter of 16 mm in a glove box under an argon gas atmosphere were used, and a 25 μm thick separator (a microporous polypropylene film) was sandwiched between the positive electrode mixture layer and metallic Li, and a 1M LiPF ６ A solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC)) was added as an electrolyte, and the battery was sealed by crimping to prepare a 2032 size coin-type test battery. The battery was then washed with ethanol and subjected to the battery evaluation described below.

[0282] The battery performance was evaluated using the prepared test battery according to the following procedure, and the 2C retention rate, charge capacity, discharge capacity, and coulomb rate were determined.

[0283] (Positive Electrode Evaluation Method) Each test battery was energized to 4.2 V at a constant current of 1.25 mA (equivalent to 0.2 C). After reaching 4.2 V, it was charged at a constant voltage and continued until it reached 0.31 mA (0.05 C). It was then discharged to 3 V at a constant current of 1.25 mA. The charge capacity, discharge capacity, and average voltage at this time were determined, and the coulombic rate (discharge capacity ÷ charge capacity) was calculated. Next, using the same test battery, it was energized to 4.2 V at a constant current of 1.25 mA (equivalent to 0.2 C). After reaching 4.2 V, it was charged at a constant voltage and continued until it reached 0.31 mA (0.05 C). It was then discharged to 3 V at a high rate of 12.5 mA (equivalent to 2 C). The 2 C retention rate (2 C capacity ÷ 0.2 C capacity) of each test battery was calculated from the discharge capacity of the resulting test battery. The results are shown in Table 1.

[0284] FIG. 5 shows discharge curves for different discharge current values ​​using the test battery of Example 1.

[0285] Example 2: Fumed silica (SiO ２ / AEROSIL (registered trademark) R972; average primary particle diameter 25 nm (calculated value), BET specific surface area 111 m ２ A graphene-containing carbon material B was obtained in the same manner as in Example 1, except that a graphene-containing carbon material (carbon material B) containing 2032 mm diameter coin-type batteries was fabricated using a graphene-containing carbon material B (carbon material B) containing 2032 mm diameter coin-type batteries ... coin-type batteries (carbon material B) containing 2032 mm diameter coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin-type coin

[0286] As can be seen from the TEM image in Figure 2B, carbon material 2 of Example 2 has three or more hollow particles located at the ends, and also has hollow particles other than the hollow particles located at the ends and the hollow particles located in the branched portions. Therefore, it can be seen that carbon material 2 of Example 2 is a carbon material according to this embodiment. In carbon material 2 of Example 2, most of the regions of the serial chain portions 6 and the branched chain portions 7 have a shape in which two or more hollow particles are connected together, with thick portions forming bundles.

[0287] As shown in the TEM image of Figure 2B, the combination of hollow particles located at the ends of the chain with the greatest linear distance between both ends was defined as a first end hollow particle 41 and a second end hollow particle 42, thereby determining a serial chain portion 6. A branched chain portion 7 is also present, which is connected to a middle hollow particle 44 (the arrow indicates the approximate location of the middle hollow particle 44) and branches off to a third end hollow particle 43 from the serial chain portion 6. Furthermore, the sample contains hollow particles (connected hollow particle portion 6a) other than the hollow particle located at the end and the hollow particle in the branched portion (middle hollow particle 44).

[0288] Example 3 A graphene-containing carbon material C was obtained in the same manner as in Example 1, except that the CVD reaction time was set to 75 minutes. A 2032-size coin-type battery was fabricated and subjected to the same tests as in Example 1. The results are shown in Table 1. FIG. 2C is a transmission electron microscope (TEM) image of a typical structure of the carbon material according to Example 3.

[0289] 2C , carbon material 2 of Example 3 has three or more hollow particles located at the ends, and also has hollow particles other than the hollow particles located at the ends and the hollow particles located in the branched portions. Therefore, it is clear that carbon material 2 of Example 3 is a carbon material according to this embodiment. In carbon material 2 of Example 3, most of the regions of the serial chain portions 6 and the branched chain portions 7 have a shape in which two or more hollow particles are connected together, with thick portions forming bundles.

[0290] As shown in the TEM image of Figure 2C, the combination of hollow particles located at the ends of the chain with the greatest linear distance between both ends was designated as the first end hollow particle 41 and the second end hollow particle 42, thereby determining the serial chain portion 6. A branched chain portion 7 is also formed, which is connected to a middle hollow particle 44 (the arrow indicates the approximate location of the hollow particle) and branches off to a third end hollow particle 43 from the serial chain portion 6. Furthermore, the sample contains hollow particles (connected hollow particle portion 6a) other than the hollow particle located at the end and the hollow particle at the branched portion (middle hollow particle 44). In part of the branched chain portion 7, hollow particles 4 are connected in a ring shape to form macropores 8.

[0291] Example 4 A graphene-containing carbon material D was obtained in the same manner as in Example 1, except that the CVD reaction time was set to 60 minutes, and a coin-type battery with a size of 2032 was fabricated and subjected to the same tests as in Example 1. The results are shown in Table 1. FIG. 2D is a transmission electron microscope (TEM) image of a typical structure of the carbon material according to Example 4.

[0292] 2D , carbon material 2 of Example 4 has three or more hollow particles located at the ends, and also has hollow particles other than the hollow particles located at the ends and the hollow particles located in the branched portions. Therefore, it is clear that carbon material 2 of Example 4 is a carbon material according to this embodiment. In carbon material 2 of Example 4, some regions of the serial chain portions 6 and the branched chain portions 7 have a shape in which two or more hollow particles are connected together, with thick portions formed as bundles.

[0293] As shown in the TEM image of Figure 2D, the combination of hollow particles located at the ends of the chain with the greatest linear distance between both ends was designated as the first end hollow particle 41 and the second end hollow particle 42, thereby determining the serial chain portion 6. A branched chain portion 7 is also present, which is connected to a middle hollow particle 44 (the arrow indicates the approximate location of the hollow particle) and branches off to a third end hollow particle 43 from the serial chain portion 6. Furthermore, the sample contains hollow particles (connected hollow particle portion 6a) other than the hollow particle located at the end and the hollow particle at the branched portion (middle hollow particle 44). In part of the branched chain portion 7, hollow particles 4 are connected in a ring shape to form two macropores 8.

[0294] Example 5 A graphene-containing carbon material E was obtained in the same manner as in Example 1, except that the CVD reaction time was set to 40 minutes, and a 2032 size coin-type battery was fabricated and subjected to the same tests as in Example 1. The results are shown in Table 1. FIG. 2E is a transmission electron microscope (TEM) image of a typical structure of the carbon material according to Example 5.

[0295] 2E , carbon material 2 of Example 5 has three or more hollow particles located at the ends, and also has hollow particles other than the hollow particles located at the ends and the hollow particles located in the branched portions. Therefore, it is clear that carbon material 2 of Example 5 is a carbon material according to this embodiment. In carbon material 2 of Example 5, many regions of the serial chain portions 6 and branched chain portions 7 have a shape in which two or more hollow particles are connected together, with thick portions forming bundles.

[0296] As shown in the TEM image of Figure 2E, the combination of hollow particles located at the ends of the chain with the greatest linear distance between both ends of the chain was designated as the first end hollow particle 41 and the second end hollow particle 42, thereby determining the serial chain portion 6. A branched chain portion 7 is also present, which is connected to a middle hollow particle 44 (the arrow indicates the approximate location of the middle hollow particle 44) and branches off to a third end hollow particle 43 from the serial chain portion 6. Furthermore, the sample contains hollow particles (connected hollow particle portion 6a) other than the hollow particle located at the end and the hollow particle at the branched portion (middle hollow particle 44). In part of the branched chain portion 7, hollow particles 4 are connected in a ring shape to form two macropores 8.

[0297] Example 6 A graphene-containing carbon material G was obtained in the same manner as in Example 1, except that the CVD reaction time was set to 130 minutes. A 2032-size coin-type battery was fabricated and subjected to the same tests as in Example 1. The results are shown in Table 1. FIG. 2F is a transmission electron microscope (TEM) image of a typical structure of the carbon material according to Example 6.

[0298] 2F , carbon material 2 of Example 6 has three or more hollow particles located at the ends, and also has hollow particles other than the hollow particles located at the ends and the hollow particles located in the branched portions. Therefore, it is clear that carbon material 2 of Example 6 is a carbon material according to this embodiment. In carbon material 2 of Example 6, some regions of the serial chain portions 6 and the branched chain portions 7 have a shape in which two or more hollow particles are connected together, with thick portions formed as bundles.

[0299] As shown in the TEM image of Figure 2F, the combination of hollow particles located at the ends of the chain with the greatest linear distance between both ends was defined as a first end hollow particle 41 and a second end hollow particle 42, thereby determining a serial chain portion 6. A branched chain portion 7 is also present, which is connected to a middle hollow particle 44 (the arrow indicates the approximate location of the particle) and branches off to a third end hollow particle 43 from the serial chain portion 6. Furthermore, the sample contains hollow particles (connected hollow particle portion 6a) other than the hollow particle located at the end and the hollow particle in the branched portion (middle hollow particle 44).

[0300] Reference Example 1: Alumina (Al ２ O ３ / PURALOX SBa200; Average particle diameter 7 nm, BET specific surface area 202 m ２ A graphene-containing carbon material G was obtained in the same manner as in Example 1, except that a graphene-containing carbon material (carbon material G) of 2032 mm in size was used instead of the graphene-containing carbon material G. A coin-type battery was fabricated using the graphene-containing carbon material G in the same manner as in Example 1, and the same tests as in Example 1 were carried out. The results are shown in Table 1. FIG. 2G is a transmission electron microscope (TEM) image of a typical structure of the carbon material according to Reference Example 1.

[0301] Reference Example 2: Magnesia (MgO / Kyowamag MF150; average particle size 30 nm, BET specific surface area 129 m) was used as a template. ２ Carbon material H was obtained in the same manner as in Example 1, except that carbon material H (carbon dioxide equivalent to 1000 ppm / g, manufactured by Kyowa Chemical Industry Co., Ltd.) was used and the template removal process was carried out as follows. A 2032 size coin-type battery was fabricated and subjected to the same tests as in Example 1. The results are shown in Table 1. FIG. 2H is a transmission electron microscope (TEM) image of a typical structure of the carbon material of Reference Example 2.

[0302] (Removal of MgO template) 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 stir bar were added to a Teflon (registered trademark) beaker and stirred at room temperature for 5 hours. After that, the sample was filtered using a membrane filter (0.1 μm), washed five times with pure water, and then suction filtered. Care was taken to prevent the deposits from drying on the filter paper. Next, the deposits were placed in a glass beaker containing approximately 100 mL of acetone. The beaker was covered with aluminum foil and held in a vacuum dryer at 0.06 MPa for 2 minutes. After that, the pressure was returned to normal and the mixture was heated in a thermostatic chamber at 60°C for 10 minutes to perform acetone replacement. The supernatant liquid in the beaker was removed with a pipette, and the same acetone replacement procedure was repeated. The mixture was then dried under reduced pressure at 150°C for 6 hours to obtain a graphene-containing carbon material H after template removal.

[0303] Comparative Example 1 A 2032 size coin-type battery was fabricated in the same manner as in Example 1, except that commercially available carbon black (DENKA BLACK Li-100, manufactured by Denka Co., Ltd.) was used as the carbon material, and the same tests were carried out. The results are shown in Table 1.

[0304]

[0305] Evaluation From Table 1, by comparing Examples 1 to 6 with Reference Examples 1 and 2 and Comparative Example 1, it can be seen that the carbon materials of the Examples (FIGS. 2A to 2F) satisfying the predetermined configuration are highly improved in all of the battery characteristics, namely, the 2C retention rate (difficulty in discharging), charge capacity, discharge capacity, and coulomb rate.

[0306] On the other hand, the carbon materials of Reference Examples 1 and 2, which were prepared using alumina or magnesia as a template, had an oil absorption of 400 mL / 100 g or more. Ｇ / I ２Ｄ The battery characteristics such as the 2C retention rate and the coulomb rate are lower than those of Examples 1 to 6.

[0307] The charge capacity of the battery performance was small in all of Reference Examples 1 and 2 and Comparative Example 1, and was particularly poor for the carbon material manufactured using an alumina mold (Reference Example 1). It can also be seen that the test battery using the carbon material (Reference Example 1) shown in Figure 2G also had a poor Coulombic rate. On the other hand, it can be seen that the test batteries using the carbon materials of Examples 1 to 6 (Figures 2A to 2F) all had significantly increased initial capacity (charge capacity) and Coulombic rate.

[0308] The oil absorption capacity of the carbon materials was shown for acetylene black (Comparative Example 1), which is considered to be high among carbon materials, but it was in the 300 mL / 100 g range. In contrast, the carbon materials of Examples 1 to 6 (Figs. 2A to 2F) exceeded 400 mL / 100 g, even exceeding 700 mL / 100 g, which is difficult to achieve with ordinary carbon materials, and some even exceeded 2000 mL / 100 g, demonstrating that they are novel carbon materials.

[0309] The high oil absorption of the carbon materials of Examples 1 to 6 (FIGS. 2A to 2F) is thought to be related to the fact that the carbon material 2 has serial chain portions 6 formed by serially connecting hollow particles 4, each having an internal space 4a surrounded by a carbonaceous outer shell 4a containing graphene, as shown in FIGS. 2A to 2F. Another reason is that the branched chain portion 7 is formed of hollow particles 4 branching off from the serial chain portion 6 and connected to at least one intermediate hollow particle 44 located between the first end hollow particle 41 (the hollow particle 4 forming one end of the serial chain portion 6) and the second end hollow particle 42 (the hollow particle 4 forming the other end of the serial chain portion 6), and at least one of the portions between the first end hollow particle 41 and the intermediate hollow particle 44, the portion between adjacent intermediate hollow particles 44, and the portion between the intermediate hollow particle 44 and the second end hollow particle 42 in the longitudinal direction of the serial chain portion 6 is a connected hollow particle portion 6a in which one or more hollow particles 4 are connected. This structure is thought to have the effect of absorbing more oil than Comparative Example 1 and Reference Examples 1 and 2.

[0310] The 2C retention rate of battery performance is an evaluation item that indicates the possibility of high-speed discharge of a battery, and it is found that the carbon materials of Examples 1 to 6 show a significant improvement effect. It is also found that the 2C retention rate of battery performance is closely correlated with the oil absorption rate of the carbon material. It is found that the 2C retention rate is significantly improved when the oil absorption of the carbon material exceeds 500 mL / g and reaches around 1,500 mL / g.

[0311] There are two methods for measuring oil absorption: "JIS K5101-13-1 Pigment testing methods - Part 13: Oil absorption - Section 1: Refined linseed oil method" which was adopted in this example, and "JIS K6217-4: Carbon black for rubber - Fundamental properties - Part 4: Determination of oil absorption" which measures dibutyl phthalate (DBP) absorption.

[0312] Comparative Examples 2 to 4 Three types of carbon black, the oil absorption (corresponding to oil absorption) specified in JIS K6217-4 of which is listed in the product catalog, were measured by a method in accordance with JIS K5101-13-1, and the results are shown in Table 2. There was no significant difference in the oil absorption between the two measurement methods.

[0313]

[0314] Example 10 A test battery was manufactured under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A (having the structure shown in FIG. 2A ) was changed to 0.3 wt % and the blending amount of the positive electrode material NCM was changed to 96.7%. The results are shown in Table 3.

[0315] Example 11 A test battery was manufactured under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was changed to 1 wt % and the blending amount of the positive electrode material NCM was changed to 96%. The results are shown in Table 3.

[0316] Example 12 A test battery was manufactured under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was changed to 2 wt % and the blending amount of the positive electrode material NCM was changed to 95%. The results are shown in Table 3.

[0317] Example 13 A test battery was manufactured under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was changed to 3 wt % and the blending amount of the positive electrode material NCM was changed to 94%. The results are shown in Table 3.

[0318] Example 14 A test battery was manufactured under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was changed to 4 wt % and the blending amount of the positive electrode material NCM was changed to 93%, and the same test was carried out. The results are shown in Table 3.

[0319] Example 15 A test battery was manufactured under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was changed to 6 wt % and the blending amount of the positive electrode material NCM was changed to 91%, and the same test was carried out. The results are shown in Table 3.

[0320]

[0321] Evaluation Figure 6 shows the relationship between the amount of carbon material blended and the 2C retention rate and charge / discharge capacity. The left vertical axis represents the 2C retention rate, the right vertical axis represents the discharge capacity, and the horizontal axis represents the amount of carbon material added. In Figure 6, the dots represent the 2C retention rate, and the triangles represent the discharge capacity. Figure 6 confirms that the high-rate characteristics of the test batteries remained favorable within the range of carbon material blended in Examples 1 and 10 to 15. It was found that battery characteristics could be significantly improved in each Example where the blending amount was within the range of 0.5 to 4 wt%, particularly 1 to 3 wt%. While increasing the blending amount of carbon material increases the battery charge / discharge capacity, excessively increasing the blending amount is thought to reduce the active material content and decrease the electrode charge / discharge capacity.

[0322] Analysis of the internal space 4b and macropores 8 of hollow particles 4 The carbon materials used in Examples 1 to 6 and Reference Examples 1 and 2 were subjected to nitrogen adsorption and desorption measurements using the method described above to determine the BET specific surface area, mode pore diameter (inner diameter of the internal space 4b), total pore volume (P / P0 = 0.99), micropore (pores smaller than the internal space 4b) volume (P / P0 = 0.1 to 0.96), mesopore (corresponding to the internal space 4b) volume (P / P0 = 0.1 to 0.96), and macropore volume (P / P0 = 0.96 to 0.99). The results are shown in Table 4.

[0323]

[0324] Furthermore, the proportions of the micropore volume, mesopore volume and macropore volume to the total pore volume were calculated and are shown in Table 5.

[0325]

[0326] As shown in Table 4, the carbon materials according to Reference Examples 1 and 2 have a total pore volume of 1.98 to 2.40 cc / g and an oil absorption of 400 m ２ / g, which is larger than commercially available carbon materials, but much smaller than the carbon materials of Examples 1 to 6 (comparison of Reference Examples 1-2 with Examples 1-6). Table 4 shows that the mode pore diameter and macropore volume of carbon materials A to F of Examples 1 to 6 are significantly different from those of carbon materials G to H of Reference Examples 1 and 2. Furthermore, the carbon materials of Examples 1 to 6 have macropore volumes exceeding 0.45 cc / g (and even exceeding 1 cc / g for the carbon materials of Examples 1-4 and 6), which is a significant difference from other carbon materials. In particular, the carbon materials of Reference Examples 1 and 2 have almost no macropore volume.

[0327] Table 5 shows that the ratio of macropore volume to total pore volume is 16 to 43% for the carbon materials of Examples 1 to 6, but only 2 to 3% for the carbon materials of Reference Examples 1 and 2. Tables 4 and 5 show that the carbon materials of Examples 1 to 6 are carbon materials with unparalleled porosity.

[0328] Structural analysis of carbonaceous matter in outer shell (XRD measurement) X-ray diffraction (XRD) measurement was performed on the carbon materials according to Examples 1 to 6 and Reference Examples 1 and 2 using an X-ray diffractometer (Miniflex 600, manufactured by Rigaku Corporation). A Si non-reflector plate was used as the sample stage, and the sample was placed on the circular portion. Measurement was performed under the following measurement conditions, and the values ​​of d002 and Lc(002) are shown in Table 6. X-ray source: CuKa, tube voltage: 40 kV, tube current: 15 mA, measurement angle: 5 to 90 deg, scan speed: 2 deg / min, scan axis: 2θ / θ

[0329]

[0330] Evaluation The Lc(002) measured by XRD is referred to as the distance between the crystalline structure portions, and the larger the Lc(002), the higher the crystallinity. The Lc(002) of the carbon materials of Examples 1 to 6 is smaller than the Lc(002) of the carbon materials of Reference Examples 1 and 2. This indicates that the crystallinity of the carbonaceous layer of the carbon materials of the Examples is not very high. Furthermore, the D band in the Raman spectrum is a band indicating the sp3 bond (C-H stretching motion) of the carbon material, and increases when the sp2 bond in the 6-membered carbon ring structure of the carbonaceous layer is broken to form an sp3 bond. Therefore, it can be seen that the carbonaceous layer of the carbon material of the Examples is a layer in which crystalline and amorphous phases coexist.

[0331] (Number of Carbonaceous Layers) The number of carbonaceous layers was calculated from the carbon weight loss rate during production in Examples 1 to 6 and Reference Examples 1 and 2. The results are shown in Table 7.

[0332] Specifically, TGA measurement was performed on each carbon material to determine the number of carbonaceous layers. Using a STA-2500 (NETZSCH), the material was heated to 900°C at a temperature increase rate of 5°C / min under a flow of argon gas (80 mL / min) and oxygen (20 mL / min), and then cooled at a temperature decrease rate of 20°C / min, followed by TG measurement. Blank measurements performed using empty pans under the same temperature profile conditions were subtracted. An alumina pan was used as the pan. The number of carbonaceous layers was calculated from the carbon weight reduction rate (%) determined by TG measurement as follows. The weight of the carbonaceous layer was calculated from the carbon weight reduction rate, and the weight of the carbonaceous layer per area was calculated from the weight of this carbonaceous layer and the surface area of ​​the template particle. Next, the weight of the carbonaceous layer per area of ​​the template particle was multiplied by the weight of the carbonaceous layer per area of ​​the single-layer graphene (7.61 × 10 －４ g / m ２ ) to calculate the number of carbonaceous layers.

[0333]

[0334] Evaluation Table 7 confirms that the number of carbonaceous layers is preferably 1 or more, or 1.7 or more, 1.9 or more, or 2.0 or more. It is also confirmed that the upper limit may be preferably 5.0 or less, or 4.5 or less.

[0335] Particle size distribution of the structure Particle size distribution was measured using a laser diffraction particle size distribution analyzer (MT3300EXII-SDC, manufactured by Microtrac Bell Co., Ltd.) to examine the aggregation state of the structure in the carbon material. The measurement sample was an unground carbon material that had been immersed in ethanol for 9 minutes. The median diameter (D50), D10, D90, D90 / D10, and D90 / M (mode pore size in the pore distribution curve) in the particle size distribution curve were determined, and the results are shown in Table 8.

[0336]

[0337] Table 8 shows that the D50 of the carbon materials of Examples 1 to 6 is within the specified range (26.0 to 45.0 μm). This indicates that the measurement samples were unpulverized and simply immersed in a solvent at rest, and the cohesive strength was not very strong. Furthermore, although only (D90 / M) is shown in Table 8, the values ​​(D10 / M, D50 / M, D90 / M) obtained by dividing the cumulative particle size measured by particle size distribution by the mode pore diameter (M) in pore distribution measurement are all much smaller values, indicating weak cohesive strength (comparison of Examples 1 to 6 with Reference Examples 1 and 2).

[0338] Measurement of desorbed gas and combustion temperature of carbon material The following tests were carried out to estimate the stability of carbon materials when used for battery applications.

[0339] (Thermal Desorption Gas Analysis) Using an ultra-high sensitivity vacuum TPD instrument (developed at Tohoku University, see T. Ishii et al., CARBON 80, 2014, pp. 135-145) with the configuration shown in Figure 7, oxygen-containing functional groups and hydrogen-terminated edge sites were accurately qualitatively and quantitatively analyzed. More specifically, 1 to 3 mg of each carbon material was placed on a graphite sample stage, and heated in vacuum to 1800°C at a heating rate of 10°C / min. The gas released during heating was analyzed by mass spectrometry, and the oxygen-containing functional groups and hydrogen-terminated edge sites were accurately qualitatively and quantitatively analyzed.

[0340] When carbon materials are heated to 1,800°C, the edge sites terminated with hydrogen and oxygen are converted into H ２ , CO, CO ２ , H ２O, and the total amount of edge sites in the carbon material can be estimated by measuring the amount of these gases released.

[0341] (Combustion Temperature Measurement) The combustion temperature of the carbon material was determined as the temperature at which the weight of the carbon material became 90% of the initial weight in a combustion oxidation test performed using a thermogravimetric analyzer under air flow at a temperature increase rate of 5°C / min. A combustion temperature of 550°C or higher was determined to be good.

[0342] The desorbed gas and combustion temperature of the carbon materials of the examples were investigated, and the results are shown in Table 9.

[0343]

[0344] Evaluation From the results shown in Table 9, it can be seen that the carbon materials of Examples 1 to 6 have the oxygen content, O / C, total gas amount (Total Gas), and edge amount (S) determined by TPD-MS measurement, as compared with Comparative Example 1. ｅｄｇｅ It was also confirmed that the carbon materials of Examples 1 to 6 had sufficiently high combustion temperatures.

[0345] 2... Carbon material 4, 4A to 4I... Hollow particle 4a... Carbonaceous outer shell 4b... Internal space 41... First end hollow particle 42... Second end hollow particle 43... Third end hollow particle 44, 44a to 44d... Intermediate hollow particle 6... Series chain portion 6a... Connected hollow particle portion 7... Branched chain portion 8... Macropore 10... Active material

Claims

1. A carbon material in which hollow particles having a carbonaceous outer shell are connected in series, comprising: a series connection portion in which a plurality of the hollow particles are connected in series; and at least one intermediate hollow particle located at an intermediate portion between a first end hollow particle, which is the hollow particle constituting one end of the series connection portion, and a second end hollow particle, which is the hollow particle constituting the other end of the series connection portion, and being connected to the intermediate hollow particle, and a branched chain portion formed by the hollow particles that are connected and extend from the series connection portion; and in the longitudinal direction of the series connection portion, at least one of a portion between the first end hollow particle and the intermediate hollow particle, a portion between adjacent intermediate hollow particles, and a portion between the intermediate hollow particle and the second end hollow particle is a portion where one or more of the hollow particles are connected.

2. The carbon material according to claim 1, wherein the number of the hollow particles connected in series to form the series connection portion is 5 or more.

3. The carbon material according to claim 1, wherein at least one of the branched chain portions is formed by the hollow particles connected in a ring shape so as to form macropores.

4. The carbon material according to claim 1, wherein the outer diameter of the hollow particle is in the range of 0.5 to 150 nm.

5. A conductive aid for an electrode of a battery having the carbon material according to claim 1 or 2.

6. A dispersion liquid having the carbon material according to claim 1 or 2 and a dispersion medium in which the carbon material is dispersed.

7. An electrode composition comprising the carbon material according to claim 1 or 2, an active material, and a binder.

8. An electrode slurry having the electrode composition according to claim 7 and a solvent in which the electrode composition is dispersed.

9. An electrode comprising the carbon material according to claim 1 or 2.

10. A lithium-ion secondary battery comprising the carbon material according to claim 1 or 2.

11. A step of preparing a mold having a series-connected mold part in which a plurality of mold particles are connected in series; a step of forming a carbonaceous outer shell on the surface of the mold; and a step of removing the mold from inside the carbonaceous outer shell. A method for producing a carbon material, wherein the mold has a series-connected mold part in which a plurality of the mold particles are connected in series, and from the first-end mold particle, which is the mold particle constituting one end of the series-connected mold part, to the second-end mold particle, which is the mold particle constituting the other end of the series-connected mold part. It is connected to the intermediate mold particle, which is the mold particle located in at least one intermediate portion therebetween, and is composed of the mold particles that are branched and continuous from the series-connected mold part. A branched chain mold part, and the series-connected mold part is at least one of a portion between the first-end mold particle and the intermediate mold particle, a portion between adjacent intermediate mold particles, and a portion between the intermediate mold particle and the second-end mold particle. A method for producing a carbon material, wherein the portion is a portion where one or more of the mold particles are connected.

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