Carbon materials

Abstract

The present invention provides a carbon material that exhibits excellent conductivity and superior rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics when manufacturing electrodes for electrochemical elements. [Solution] The carbon material according to the present invention is a carbon material consisting of a linked structure in which hollow particles having a carbonaceous outer shell are connected, characterized in that the circularity (complexity) of the shape index in image analysis is 0.5 or less, the proportion of "Branched" in the morphological classification is 10% or more, and the bulk density is 0.5 g / cc or less.

Description

[Technical Field]

[0001] The present invention relates to a carbon material and a method for producing the same, a dispersion liquid obtained by dispersing the carbon material, a battery additive containing the carbon material, an electrode composition, an electrode slurry, an electrode, and a lithium-ion secondary battery. [Background technology]

[0002] Since its inception, lithium-ion rechargeable batteries have seen a wide range of applications in everyday life, including smartphones and electric vehicles (EVs). As a result, the manufacturing of lithium-ion rechargeable batteries faces ongoing competition in terms of cost, as well as continuous demands for higher performance in the market. For EVs, which emit less carbon dioxide (CO2), to replace gasoline-powered vehicles in order to protect the global environment, the lithium-ion rechargeable batteries they use must have high performance characteristics such as rapid discharge characteristics, long lifespan, high capacity, and charge / discharge characteristics.

[0003] Carbon materials are widely used in lithium-ion secondary batteries, where such high performance is required. For example, Patent Document 1 (Japanese Patent Application Publication No. 2004-22177) discloses that in a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, flake graphite or carbon black can be used as a conductive material to improve discharge characteristics. However, even with the use of such carbon materials, the rapid discharge characteristics and capacity characteristics are not sufficient.

[0004] Patent Document 2 (Japanese Patent Publication No. 2019-91587) describes a carbon material with a partially graphite structure treated with expanded graphite, with a BET specific surface area of ​​80-155 m². 2 It has been disclosed that carbon materials exhibit characteristics such as a pore volume of 1.6-2.1 mL / g and a DBP absorption (oil absorption) of 210-220 mL / 100g, and that when mixed with the positive electrode, they exhibit excellent electrolyte retention and cycle characteristics. However, such carbon materials do not have sufficient electrolyte retention, and their conductivity, rapid discharge characteristics, and charge / discharge characteristics are not sufficient.

[0005] Patent Document 3 (WO2017 / 119428) discloses a lithium-ion secondary battery with excellent charge-discharge cycle characteristics using carbon black with a DBP absorption rate (oil absorption rate) of 240 mL / 100 g or more, and a maximum value of 348 mL / 100 g in the examples. However, it has poor rapid discharge characteristics, and its capacity characteristics and charge-discharge characteristics are not sufficient.

[0006] Patent Document 4 (Japanese Patent Publication No. 2020-100556) states that the BET specific surface area is 80 to 250 m². 2 It has been disclosed that graphene powder with a carbon-to-oxygen ratio (O / C) of 0.09-0.3, as measured by X-ray photoelectron spectroscopy, is suitable for lithium-ion secondary batteries due to its high dispersibility and ionic conductivity. However, such carbon materials lack sufficient electronic and ionic conductivity, resulting in inferior rapid discharge characteristics and capacity characteristics.

[0007] Patent document 5 (Japanese Patent Publication No. 2017-183292) discloses a non-aqueous secondary battery positive electrode consisting of multiple active material particles and multiple graphene and binders with oxygen concentrations of 2 to 20 atomic percent, which exhibits excellent electronic conductivity with a small amount of conductive additive. However, its conductivity is still insufficient, and it is inferior in terms of rapid discharge characteristics and capacity characteristics.

[0008] Patent Document 6 (JP 2023-501558) discloses that if porous reduced graphene oxide containing mesopores and macropores of about 2 to 500 nm in size is used as the carbon material for a sulfur-carbon composite, the amount of sulfur supported can be increased by the pores, improving mass transfer capacity and electrolyte leakage, making it suitable for lithium-sulfur batteries.

[0009] Patent Document 7 (Japanese Patent Application Laid-Open No. 2021-84819) 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 mold composed of nanoparticles of an alkaline earth metal oxide, and a separation and removal step of dissolving the mold with an acid不含氟 and separating the mold from the precursor. Specifically, quartz sand is mixed as a spacer, nanoparticles of magnesium oxide are used as a mold, and a CVD reaction is carried out at 900°C for 2 hours to form a carbon material containing graphene with a stacking number of 1.9 layers, I D / I G = 1.47 to 1.77, a BET specific surface area of 1765 m 2 / g, an average pore diameter of 9.9 nm, and a total pore volume of 4.23 cm 3 / g, and a carbon material containing graphene with a stacking number of 2.5 layers, a BET specific surface area of 648 m 2 / g, an average pore diameter of 11.8 nm, and a total pore volume of 1.91 cm 3 / g are produced. However, these carbon materials have not been considered as lithium-ion secondary batteries.

[0010] ​​​​​​​​​​​​ However, the maximum BET specific surface area of ​​the carbon material actually produced in the examples is 85.9 m². 2 The value is / g, indicating that the raw material gas is explosively produced in the microwave plasma during a residence time of 0.001 seconds to approximately 2.0 seconds, resulting in almost no pore formation. Therefore, lithium-ion secondary batteries using the carbon material produced here have poor conductivity and are not adequate in terms of rapid discharge characteristics, capacity characteristics, or charge / discharge characteristics. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 2004-22177 [Patent Document 2] Japanese Patent Publication No. 2019-91587 [Patent Document 3] WO2017 / 119428 publication [Patent Document 4] Japanese Patent Publication No. 2020-100556 [Patent Document 5] Japanese Patent Publication No. 2017-183292 [Patent Document 6] Special Publication No. 2023-501558 [Patent Document 7] Japanese Patent Publication No. 2021-84819 [Patent Document 8] WO2020 / 080520 publication [Patent Document 9] Japanese Patent Publication No. 2022-191280 [Overview of the project] [Problems that the invention aims to solve]

[0014] The present invention has been made in view of the above circumstances, and provides a carbon material that can improve the conductivity of carbon materials and highly enhance the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries, a method for producing the same, a dispersion liquid obtained by dispersing the carbon material, a battery additive having the carbon material, an electrode composition, an electrode slurry, an electrode, and a lithium-ion secondary battery. [Means for solving the problem]

[0015] In view of the above problems, the inventors have conducted diligent research and have found that a carbon material having a linked structure in which hollow particles with a carbonaceous outer shell are connected, exhibiting complexity in shape index and morphological classification in image analysis, and having a low bulk density and spread, exhibits excellent electronic and ionic conductivity, enhances conductivity, and significantly improves the rapid discharge characteristics at 2C maintenance rate, battery capacity characteristics and Coulomb ratio (charge / discharge characteristics) in charge / discharge tests when used in lithium-ion secondary batteries.

[0016] The inventors have discovered that a carbon material consisting of a linked structure of hollow particles having a carbonaceous outer shell can have its conductivity enhanced and further improve the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries when the linked structure has a complex shape in which the linked structure has a wide portion with a width exceeding three times the outer diameter of the hollow particle and a narrow portion with a width of three times or less the outer diameter of the hollow particle.

[0017] The inventors have discovered that a carbon material with excellent conductivity, capable of improving the rapid discharge characteristics, battery capacity characteristics, and charge-discharge characteristics of lithium-ion secondary batteries, can be easily manufactured by using aggregates of specific inorganic materials as a template.

[0018] Based on these findings, the inventors have completed the present invention.

[0019] Thus, the present invention provides a carbon material comprising a linked structure in which hollow particles having a carbonaceous outer shell are connected, wherein the circularity (complexity) of the shape index in image analysis is 0.5 or less, the proportion of "Branched" in the morphological classification is 10% or more, and the bulk density is 0.5 g / cc or less.

[0020] In the carbon material of the present invention, it is preferable that the linked structure has a linear portion in which five or more hollow particles are connected in series along the longitudinal direction, and that the intermediate portion between the first end hollow particle located at one end of the linear portion and the second end hollow particle located at the other end has a wide portion with a width exceeding three times the outer diameter of the hollow particle and a narrow portion with a width of three times or less the outer diameter of the hollow particle.

[0021] In the carbon material of the present invention, it is preferable that the shape factor in image analysis is ML2 / A ≤ PM2 / A.

[0022] In the carbon material of the present invention, the intensity ratio of the G band to the 2D band in Raman spectroscopy is I G / I 2D If the intensity ratio between the D band and the G band is 0.1 or higher, then I D / I G It is preferable that the value is 0.3 or higher.

[0023] In the carbon material of the present invention, it is preferable that the average interplanar spacing d002 determined from the 002 diffraction lines measured by X-ray diffraction (XRD) is 3 to 5 Å, the crystallite size Lc(002) in the c-axis direction is 10 nm or less, and the crystallite size Lc(002) in the a-axis direction is in the range of 0.01 to 10 nm.

[0024] In the carbon material of the present invention, it is preferable that the total pore volume is 0.5 cc / g or more, and that the proportion of pore volume 10 nm or larger within the total pore volume is 20% or more.

[0025] In the carbon material of the present invention, it is preferable that the mode pore diameter is 10 nm or more and 60 nm or less.

[0026] In the carbon material of the present invention, it is preferable that the ash content is 0.5% by weight or less.

[0027] In the carbon material of the present invention, it is preferable that the oil absorption capacity is 250 mL / 100 g or more.

[0028] In the carbon material of the present invention, it is preferable that the particle size D90, where 90% of the particles in the particle size distribution curve are located, is 300 μm or less.

[0029] According to the book, a method for manufacturing a carbon material is provided, in which a carbonaceous layer is formed on the surface of the mold material and the mold material is removed, characterized in that the mold material is an aggregate in which primary particles of 1 to 100 nm are linked together in a chain-like manner with multiple branching structures.

[0030] In the method for producing a carbon material of the present invention, it is preferable that the carbon material is the carbon material described above.

[0031] The present invention also provides a battery additive having the above-mentioned carbon material.

[0032] The present invention also provides a dispersion liquid for dispersing the above-mentioned carbon material in a dispersion medium.

[0033] The present invention also provides an electrode composition having the above-mentioned carbon material, active material, and binder.

[0034] According to the present invention, an electrode slurry is provided in which the above-mentioned electrode composition is dispersed in a solvent.

[0035] According to the present invention, an electrode having the above-mentioned carbon material is provided.

[0036] The present invention further provides a lithium-ion secondary battery having the above-mentioned carbon material. [Effects of the Invention]

[0037] The present invention provides a carbon material that has excellent conductivity and can greatly enhance properties such as rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics when used in a lithium-ion secondary battery, a method for producing the same, a dispersion liquid obtained by dispersing the carbon material, a battery additive having the carbon material, an electrode composition, an electrode slurry, an electrode, and a lithium-ion secondary battery. [Brief explanation of the drawing]

[0038] [Figure 1] This is a schematic diagram illustrating the function of a carbon material relating to one embodiment of the present invention. [Figure 2] This is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention, measured at an accelerating voltage of 80 kV. [Figure 3] This is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention, measured at an accelerating voltage of 100 kV. [Figure 4] This is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention, measured at an accelerating voltage of 100 kV. [Figure 5] This figure shows an example of a Raman spectrum measured for a carbon material according to one embodiment of the present invention. [Figure 6] This figure shows discharge curves with different discharge current values ​​using a test battery of Example 1 according to one embodiment of the present invention. [Figure 7] This figure shows the relationship between the amount of carbon material blended, the 2C maintenance rate, and the discharge capacity of the test battery according to the example. The left vertical axis represents the 2C maintenance rate, the right vertical axis represents the discharge capacity, and the horizontal axis represents the amount of carbon material blended. In Figure 7, ● represents the 2C maintenance rate and △ represents the discharge capacity. [Modes for carrying out the invention]

[0039] Embodiments of the present invention will be described in detail below.

[0040] <Carbon materials> The carbon material of the present invention is a carbon material consisting of a linked structure in which hollow particles having a carbonaceous outer shell are connected, characterized in that the circularity (complexity) of the shape index in image analysis is 0.5 or less, the proportion of "Branched" in the morphological classification is 10% or more, and the bulk density is 0.5 g / cc or less.

[0041] (Structure of carbon materials) The structure of the carbon material of the present invention consists of a linked structure in which hollow particles having a carbonaceous outer shell are connected, wherein the linked structure has a linear portion in which five or more of the hollow particles are connected in series along the longitudinal direction, and preferably has a wide portion with a width exceeding three times the outer diameter of the hollow particle and a narrow portion with a width of three times or less the outer diameter of the hollow particle in the intermediate portion between the first end hollow particle located at one end of the linear portion and the second end hollow particle located at the other end.

[0042] The carbon material according to this embodiment has a linked structure 2, as shown in Figure 1. The linked structure 2 has a linear section 6 in which five or more hollow particles 4 are connected in series along the longitudinal direction. Each hollow particle 4 has a carbonaceous outer shell 4a with a hollow internal space 4b, and it is preferable that the internal spaces 4b of adjacent hollow particles 4 along the longitudinal direction are in communication with each other, but they do not necessarily have to be in communication. The linear section 6 has one or more wide sections with a width exceeding three times the outer diameter of the hollow particle 4 and one or more narrow sections 6a with a width of three times or less the outer diameter of the hollow particle 4 in the intermediate section between the first end hollow particle 41 located at one end and the second end hollow particle 42 located at the other end.

[0043] The wide section, although not shown in Figure 1, is clearly visible in Figures 2 and 3, in a connected structure where five or more hollow particles are connected longitudinally, is the portion where more than three hollow particles extend in the width direction. The number of hollow particles in the wide section is not particularly limited as long as it exceeds three; it just needs to be a number that distinguishes it from the narrow section of the linear chain described below. Furthermore, Figures 3 and 4 show that the connected structure has multiple wide sections.

[0044] The narrow portion 6a is the part in which one to three hollow particles 4 are connected along the longitudinal direction of the linear portion 6. The narrow portion 6a only needs to have a width of three times or less the outer diameter of the hollow particles 4, preferably two times or less, or as shown in Figure 1, a width of about one time or less may be acceptable.

[0045] In this embodiment, the linear portion 6 has the base ends of multiple branched structures 61, which constitute a separate path from the linear portion 6, connected to an intermediate portion between the first end hollow particle 41 located at one end and the second end hollow particle 42 located at the other end.

[0046] In this embodiment, the tip of each branch structure 61 has a third end hollow particle 43 that is different from the first end hollow particle 41 and the second end hollow particle 43. The longitudinal length of each branch structure 61 is the length of two or more hollow particles 4 connected in series along the longitudinal direction, with the third end hollow particle 43 located at its tip.

[0047] As shown by the dashed line in Figure 1, the branched structure 61 may be composed of hollow particles 4 that are connected in a ring shape to form macropores 8.

[0048] Furthermore, the carbonaceous outer shell 6a is preferably composed of carbonaceous material having a six-membered carbon ring structure, and more preferably, carbonaceous material having a graphene structure in which the six-membered carbon ring structures are linked in a network structure. As shown in Figure 2, graphene is a sheet-like material of sp2-bonded carbon, in which the six-membered carbon ring structures are linked to form a honeycomb-like hexagonal lattice structure. In addition, the carbonaceous material having a graphene structure in which the six-membered carbon ring structures are linked in a network structure is indicated by the intensity ratio of the G band to the 2D band in the Raman spectroscopy measurement described later. G / I 2D This can also be confirmed by checking if the value is 0.2 or higher.

[0049] Carbon materials typically consist of structures that exhibit elastic deformability and structures that exhibit plastic deformability. While plastic deformability exhibits high strength against stress, once deformed, it cannot be restored to its original state even after unloading.

[0050] It was found that the carbon material of this embodiment has the property of returning to its original shape without deforming under weak stress, that is, it has a large elastic deformation work rate. In the case of the carbon material of this embodiment, the portion consisting of graphene, which makes up the majority, exhibits elastic deformability, while the defective parts of the graphene structure other than graphene and the amorphous carbon parts exhibit plastic deformability, resulting in good properties against stress deformation. On the other hand, when the number of carbonaceous (graphene) layers is excessively exceeded (such as graphite), elastic deformability is maintained within a certain stress range, but when a predetermined threshold is exceeded, plastic deformation occurs rapidly, and the particle shape and linkage shape tend to be destroyed.

[0051] The size (e.g., inner diameter) of the internal space 4b of the hollow particle 4 surrounded by the carbonaceous shell portion 4a is not particularly limited, but is preferably within the range of 0.1 to 100 nm, or 1 to 80 nm, or 5 to 50 nm. The length of the linear portion 6, which consists of multiple hollow particles 4 having the above-mentioned internal space 4b, is preferably a length such that five or more hollow particles 4 are linked together along the longitudinal direction, and is not particularly limited, but is preferably within the range of 1 nm or more, preferably 10 nm or more, or 0.01 to 100 μm, 0.05 to 80 μm, or 0.1 to 50 μm. The outer diameter of each hollow particle 4 is not particularly limited, but is preferably within the range of 0.5 to 150 nm, or 1 to 100 nm, 2 to 90 nm, 4 to 65 nm, 8 to 50 nm, or 10 to 35 nm.

[0052] When the carbon material according to this embodiment is used, for example, as part of an electrode material for a secondary battery such as a lithium-ion secondary battery, it is possible to improve rapid discharge characteristics while maintaining good characteristics such as charge capacity, discharge capacity, and charge / discharge characteristics. The reason for this is thought to be as follows: As shown in Figure 1, the linear portion 6 of the hollow particle 4 flexibly entangles with, for example, the active material 10 of the battery material, forming a conductive path. Furthermore, the curved shape of the chain portion 6, the hollow portion (internal space) of the hollow particle 4, and the ring-shaped portion of the formed macropores contribute to increasing the electrolyte's liquid retention capacity, thereby improving rapid discharge characteristics and maintaining good characteristics such as charge capacity, discharge capacity, and charge / discharge characteristics.

[0053] The applications of this carbon material are not particularly limited, but it can be preferably used, for example, as part of the electrode material for secondary batteries such as lithium-ion batteries, such as a conductive material. Furthermore, this carbon material can be incorporated into conductive materials, dispersions, electrode compositions, electrode slurries, etc., and these can be preferably used as part of the material constituting electrodes for batteries or electrodes for other electronic components.

[0054] In the connected structure 2 of this embodiment, as shown in Figure 1, the base end of a branched linear portion 61, which constitutes a separate path from the linear portion 6, is connected to an intermediate portion of the linear portion 6. By having the branched linear portion 61 in addition to the linear portion 6 in the connected structure 2 of carbon material, the rapid discharge characteristics are further improved for reasons such as an increase in the portion that forms a conductive path and an increase in the portion that increases the electrolyte's liquid retention capacity, and thus the characteristics such as charge capacity, discharge capacity and charge / discharge characteristics are also improved.

[0055] Furthermore, a branched linear portion 61, which constitutes a separate path from the linear portion 6, may be connected between the first end hollow particle 41 and the second end hollow particle 42. By configuring it in this way, for example, the portion that forms the conductive path increases, and the portion that increases the electrolyte's liquid retention capacity also increases, which further improves the rapid discharge characteristics, and improves characteristics such as charge capacity, discharge capacity, and charge / discharge characteristics.

[0056] Furthermore, the branched linear portions may be composed of hollow particles 4 linked in a ring shape to form macropores 8. This configuration also improves rapid discharge characteristics, charging capacity, discharging capacity, and charge / discharge characteristics, for example, by increasing the portion that forms conductive paths and increasing the portion that increases the electrolyte's liquid retention capacity.

[0057] The tip of the branched linear portion 61 may have a third-end hollow particle 43 that is different from the first-end hollow particle 41 and the second-end hollow particle 42. With this configuration, for example, the portion that forms the conductive path increases, and the portion that increases the electrolyte's liquid retention capacity also increases, further improving the rapid discharge characteristics, as well as characteristics such as charge capacity, discharge capacity, and charge / discharge characteristics.

[0058] The carbon material of the present invention has been shown to have a complex structure in the image analysis described later. This configuration increases the number of areas that form conductive paths and the number of areas that increase the electrolyte's liquid retention capacity, resulting in further improvements in rapid discharge characteristics, as well as improvements in charging capacity, discharge capacity, and charge / discharge characteristics. Furthermore, the carbon material of the present invention has been shown to have a broad structure with low bulk density, number density, and apparent density, as described later. This configuration increases the number of areas that form conductive paths and the number of areas that increase the electrolyte's liquid retention capacity, resulting in further improvements in rapid discharge characteristics, as well as improvements in charging capacity, discharge capacity, and charge / discharge characteristics.

[0059] (Bulk density) The carbon material of the present invention has the above structure, a bulk density of 0.5 g / cc or less, and is characterized by its ability to identify the circularity (complexity) in the image analysis and the proportion of "Branched" in the morphological classification.

[0060] The bulk density of the carbon material of the present invention is 0.5 g / cc or less, and preferably in the following order: 0.4 g / cc or less, 0.3 g / cc or less, 0.2 g / cc or less, 0.15 g / cc or less, 0.12 g / cc or less, 0.1 g / cc or less, 0.08 g / cc or less, 0.06 g / cc or less, 0.05 g / cc or less, and 0.04 g / cc or less. When the bulk density of the carbon material is within this range, it is possible to create a sufficient spread of carbon material that can form a conductive bath, thereby increasing the conductivity of the carbon material and making it easier for the electrolyte to penetrate the carbon material, which can contribute to the rapid discharge characteristics, charge-discharge characteristics, and battery capacity characteristics of lithium-ion secondary batteries. Bulk density is the mass per unit volume exhibited by carbon material filled in a container of a certain volume under certain conditions. Bulk density can be measured according to JIS K6219-2.

[0061] (Image analysis) The carbon material of the present invention has a complex shape, and image analysis is performed to derive an index of this complexity. Indices that show the complexity of the aggregate structure of carbon material include shape index and morphological classification methods, which can be measured by the methods described later. In particular, the present invention is characterized by a circularity (complexity) of 0.5 or less in the shape index, and a proportion of "Branched" in the morphological classification of 10% or more.

[0062] -Shape index- The circularity, which indicates the complexity of the carbon material's shape index in the present invention, is a numerical value expressed in comparison to a circle whose circumference is equal to its perimeter, and is 0.5 or less, or preferably 0.45 or less, 0.4 or less, and 0.38 or less, in that order. There is no particular lower limit to the circularity (complexity) of the carbon material, but it is usually 0.1 or more, preferably 0.12 or more, more preferably 1.5 or more, even more preferably 0.2 or more, and most preferably 0.25 or more. When the circularity of the carbon material is within this range, the electronic conductivity and ionic conductivity are highly balanced and preferable. Note that a smaller value for circularity indicates that the carbon material has a more complex shape.

[0063] The ML2 / A (shape factor) in the shape index of the carbon material of the present invention is not particularly limited, but is an index indicating a circular state, and is usually in the range of 1 to 5, preferably 1.5 to 4, more preferably 2 to 3.5, even more preferably 2.2 to 3.3, and most preferably 2.4 to 3. The PM2 / A (shape factor) in the shape index of the carbon material of the present invention is not particularly limited, but is an index indicating a spherical shape with an uneven circumferential surface, and is usually in the range of 1 to 10, preferably 2 to 7, more preferably 2.5 to 6.5, even more preferably 3 to 6, and most preferably 3.4 to 5.6.

[0064] The relationship between ML2 / A (shape factor) and PM2 / A (shape factor) in the carbon material of the present invention is not particularly limited, but it is preferable that ML2 / A ≤ PM2 / A. When both shape factors of the carbon material have this relationship, the electronic conductivity and ionic conductivity of the carbon material can be greatly enhanced, and the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries can be greatly improved, making it preferable.

[0065] -Morphological classification- Morphological classification of carbon materials in imaging diagnostics is divided into four types: "Spheroidal" and "Ellipsoidal," which indicate simple structures, and "Linear" and "Branched," which indicate complex structures.

[0066] In the classification of carbon materials of the present invention, the proportion of "Linear" is not particularly limited, but is usually 10% or more, preferably 15% or more, more preferably 20% or more, even more preferably 25% or more, and most preferably 30% or more. The upper limit is not particularly limited, but is usually 80% or less, preferably 70% or less, more preferably 60% or less, even more preferably 55% or less, and most preferably 50% or less. When the proportion of Linear (spherical) carbon materials is within this range, they exhibit excellent electronic conductivity and ionic conductivity, and are suitable for use in lithium-ion secondary battery materials because they can greatly improve rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics.

[0067] In the morphological classification of the carbon material of the present invention, the proportion of "Spheroidal" is not particularly limited, but is usually in the range of 50% or less, preferably 30% or less, more preferably 10% or less, even more preferably 5% or less, and most preferably 2% or less. When the proportion of Spheroidal carbon material is within this range, it is preferable to have highly enhanced electronic conductivity and ionic conductivity.

[0068] In the morphological classification of the carbon material of the present invention, the proportion of "Ellipsoidal" is not particularly limited, but is usually 10% or more, preferably 13% or more, more preferably 16% or more, even more preferably 18% or more, and most preferably 20% or more. The upper limit is not particularly limited, but is usually 80% or less, preferably 70% or less, more preferably 60% or less, even more preferably 55% or less, and most preferably 50% or less. When the proportion of Ellipsoidal in the carbon material is within this range, the electronic conductivity and ionic conductivity are greatly enhanced, and the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries can be greatly improved, making it preferable.

[0069] In the classification of carbon materials of the present invention, the proportion of "Branched" is 10% or more, and is preferably 12% or more, 14% or more, 16% or more, and 18% or more, in that order. There is no particular upper limit to the "Branched" proportion of the carbon material, but it is usually in the range of 80% or less, preferably 60% or less, more preferably 50% or less, even more preferably 40% or less, and most preferably 35% or less. When the proportion of Branched carbon material is within this range, it is preferable because it greatly enhances the electronic conductivity and ionic conductivity, and greatly improves the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0070] In the shape classification of carbon materials of the present invention, the total proportion of Spheroidal and Ellipsoidal shapes, which represent simple shapes, is not particularly limited, but is usually 80% or less, preferably 70% or less, more preferably 60% or less, even more preferably 55% or less, and most preferably 50% or less. The lower limit is not particularly limited, but is usually in the range of 5% or more, preferably 10% or more, more preferably 15% or more, even more preferably 17% or more, and most preferably 20% or more.

[0071] In the shape classification of the carbon material of the present invention, the total ratio of Linear and Branched shapes, which represent complex shapes, is not particularly limited, but is usually 20% or more, preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, and most preferably 55% or more. The upper limit is not particularly limited, but is usually 100% or less, preferably 95% or less, more preferably 90% or less, even more preferably 85% or less, and most preferably 80% or less. When the total ratio of Linear and Branched shapes of the carbon material is within this range, it is preferable because it can greatly improve the electronic conductivity and ionic conductivity, and significantly improve the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0072] In the shape classification of carbon materials of the present invention, the total ratio of Linear, Ellipsoidal, and Branched shapes is not particularly limited, but it is preferable when it is usually 50% or more, preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and most preferably 95% or more, because it can greatly improve the electronic conductivity and ionic conductivity, and greatly improve the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0073] The carbon material of the present invention is suitable because, in the morphological classification of image analysis, when the proportion of spheroidal is usually 10% or less, preferably 5% or less, more preferably 2% or less, the proportion of linear is usually 10-80%, preferably 20-60%, more preferably 28-50%, the proportion of ellipsoidal is usually 10-80%, preferably 15-60%, more preferably 20-50%, and the proportion of branched is usually 10-80%, preferably 20-60%, more preferably 18-40%, the material forms an aggregate in which linear, elliptic, and branched structures are balanced, and the electronic conductivity and ionic conductivity are greatly enhanced.

[0074] (Structural analysis) In this invention, the state of the carbon material can be analyzed by Raman spectroscopy. An example of a Raman spectrum measured for the carbon material of this invention is shown in Figure 5. Among the Raman spectra, the wavenumber 1593 cm⁻¹ is shown. -1 The peak in the surrounding region is called the G band, and this band represents the sp2 bond (aromatic ring C=C stretching motion) in carbon materials. This is the Raman spectrum at wavenumber 1356 cm⁻¹. -1 The peak present in this vicinity is called the D band, which represents sp3 bonding (CH stretching motion) in carbon materials. This band increases when sp2 bonds in the six-membered carbon ring structure of the carbonaceous layer are broken and replaced with sp3 bonds. This occurs in the Raman spectrum at wavenumber 2680 cm⁻¹. -1 The peaks in the surrounding region are called 2D bands, and they are bands that show second-order phonon scattering (CH stretching motion), and they represent the number of layers of carbon material.

[0075] Intensity ratio of the G-band to the 2D-band of a carbon material I G / I 2D This 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 the same paper, intensity ratio I G / I 2D It is assumed that when the value is 0.2, there is one graphene layer.

[0076] The intensity ratio of the G band and 2D band of the carbon material of the present invention G / I 2D There are no particular limitations, but it is usually 0.1 or higher, preferably 0.2 or higher, more preferably 0.5 or higher, or preferably in the order of 0.7 or higher, 0.8 or higher, 0.9 or higher, 1.0 or higher, 1.1 or higher, 1.2 or higher, 1.3 or higher, and 1.4 or higher. G / I 2D The upper limit of is not particularly limited, but is usually 10 or less, preferably 5.0 or less, or preferably in the order of 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, 2.5 or less, and 2.2 or less. G / I 2D When the value of is within this range, the strength properties and elastic deformability that maintain the hollow structure of the carbon material are balanced, and the desired rapid discharge characteristics, capacity characteristics, and durability of the lithium-ion secondary battery are greatly improved, making it suitable. G / I 2D However, if the lower limit is exceeded excessively, the formation of graphene material may be insufficient, leading to decreased electronic conductivity and reduced discharge capacity. Conversely, if the upper limit is exceeded excessively, the number of graphene layers may increase, resulting in reduced flexibility, decreased electrode density, and reduced packing capacity.

[0077] The intensity ratio of the D-band to the G-band of the carbon material of the present invention D / I GThere are no particular limitations, but it is usually 0.01 or higher, preferably 0.05 or higher, more preferably 0.1 or higher, or preferably in the order of 0.3 or higher, 0.4 or higher, 0.8 or higher, 0.9 or higher, 1 or higher, 1.1 or higher, 1.2 or higher, and 1.4 or higher. D / I G The upper limit is not particularly limited, but is usually 10 or less, preferably 5 or less, more preferably 3 or less, even more preferably 2.5 or less, and most preferably 2 or less. D / I G If this range is deviated excessively, the optimal crystal structure cannot be obtained, which is undesirable. D / I G If the size is excessively small, it is undesirable because a large pore diameter cannot be maintained.

[0078] I of the present invention, a carbon material D / I G The I of carbon material is typically in the range of 0.1 to 10, preferably 0.5 to 8, more preferably 1 to 5, even more preferably 1.2 to 4, and most preferably 1.5 to 3. D / I G When this range is maintained, the sp2 and sp3 orbitals of the carbonaceous carbon material are in an optimal state, achieving a high degree of balance between electron conduction paths and ion conduction paths, thereby greatly improving the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0079] The average interplanar spacing d002, determined from the 002 diffraction line measured by X-ray diffraction (XRD) of the carbon material of the present invention, is in the range of 3 to 5 Å, preferably 3.3 to 4.5 Å, more preferably 3.3 to 4 Å, even more preferably 3.3 to 3.9 Å, and most preferably 3.3 to 3.8 Å.

[0080] The size of the crystallites Lc(002) in the c-axis direction of the

[0002] plane, as measured by X-ray diffraction (XRD) of the carbon material of the present invention, is not particularly limited, but is usually 10 nm or less, preferably 7 nm or less, more preferably 5 nm or less, or preferably 4 nm or less, 3 nm or less, 2 nm or less, 1.7 nm or less, 1.5 nm or less, 1.4 nm or less, 1.3 nm or less, and 1.25 nm or less, in that order. The lower limit of Lc(002) of the carbon material is not particularly limited, but is usually 0.1 nm or more, preferably 0.3 nm or more, more preferably 0.5 nm or more, even more preferably 0.7 nm or more, particularly preferably 0.8 nm or more, and most preferably 1 nm or more. It is preferable that the Lc(002) representing the crystallinity of the carbon material is within this range while forming mesopores and macropores. If the Lc(002) of the carbon material deviates excessively from this range, an optimal crystal structure cannot be obtained, which is undesirable.

[0081] The size of the crystallites La(10) in the a-axis direction of the

[10] plane, as measured by X-ray diffraction (XRD) of the carbon material of the present invention, is not particularly limited, but is usually in the range of 0.01 to 10 nm, preferably 0.05 to 8 nm, more preferably 0.5 to 6 nm, even more preferably 1 to 5 nm, and most preferably 1.5 to 4 nm.

[0082] (Number of layers) In the present invention, the number of carbonaceous layers surrounding the pores is important in order to maintain a pore shape that can achieve the above-mentioned ionic conductivity and electronic conductivity. The number of carbonaceous layers in the present invention is not particularly limited, but is usually 1 or more, preferably 1.2 or more, more preferably 1.5 or more, even more preferably 2 or more, and most preferably 2.2 or more. The upper limit is usually 15 or less, preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and most preferably 5 or less. When the number of carbonaceous layers is within this range, the strength properties and elastic deformation of the carbonaceous layer are excellent, the hollow structure of the granular shape and the macropore shape formed by the linkage of granular shapes can be maintained, and the lithium-ion secondary battery characteristics can be greatly enhanced. The number of carbonaceous layers in the carbon material is calculated specifically as described in the examples below. After laminating the carbon layers on the mold particles, the weight of the carbon layers is calculated using thermogravimetric analysis (TG). The weight of the carbon layers per unit area of ​​the mold is then calculated from this weight of the carbon layers and the specific surface area of ​​the mold particles, and this is used as the weight of the carbon layers per unit area of ​​single-layer graphene (7.61 × 10⁻¹⁰). -4 g / m 2 This value is calculated by dividing by ).

[0083] (Pore characteristics measured by nitrogen adsorption / desorption) The specific surface area of ​​the carbon material of the present invention is not particularly limited, but is typically 10 m², calculated as the BET specific surface area from nitrogen adsorption as specified in JIS Z8830. 2 / g or more, preferably 50m 2 / g or more, more preferably 75m 2 It is 1 / g or more, or 100m 2 / g or more, 150m 2 / g or more, 200m 2 / g or more, 250m 2 / g or more, 300m 2 / g or more, 500m 2 / g or more, 600m 2 / g or more, 700m 2 / g or more, 800m 2 The preference is for values ​​of / g or higher. There is no particular upper limit to the specific surface area of ​​the carbon material, but it is usually 2500m². 2 Less than or equal to / g, preferably 2300m 2 / g or less, more preferably 2000m 2 It is less than / g, or 1900m 2 / g or less, 1800m 2 / g or less, 1700m 2 / g or less, 1600m 2 / g or less, 1500m 2 / g or less, 1400m 2 / g or less, 1300m 2 / g or less, 1200m 2 The order of preference is from / g to less. When the specific surface area of ​​the carbon material is within this range, the electronic conductivity and ionic conductivity can be greatly enhanced, making it preferable.

[0084] The total pore volume of the carbon material of the present invention is not particularly limited, but is measured by nitrogen adsorption / desorption and is usually 0.1 cc / g or more, preferably 0.5 cc / g or more, more preferably 1 cc / g or more, even more preferably 1.5 cc / g or more, and most preferably 2 cc / g or more, or preferably 2.5 cc / g or more, 2.6 cc / g or more, 2.8 cc / g or more, 3.0 cc / g or more, 3.2 cc / g or more, 3.4 cc / g or more, and 3.5 cc / g or more, in that order of preference. The upper limit of the total pore volume of the carbon material is not particularly limited, but is usually in the range of 20 cc / g or less, preferably 15 cc / g or less, more preferably 10 cc / g or less, even more preferably 8 cc / g or less, and most preferably 7 cc / g or less. If the total pore volume of the carbon material is excessively low, the amount of electrolyte held in the carbon material will be small, which is undesirable. Furthermore, if the total pore volume of a carbon material becomes excessively large, the skeletal strength of the pore structure may weaken, making it impossible to maintain the pore shape. In the carbon material of the present invention, the pore shape has appropriate strength when the total pore volume is as described above, contributing to the stability of the carbon material linkage structure.

[0085] The proportion of pore volume of 10 nm or larger in the carbon material of the present invention is not particularly limited, but is usually 10% or more, preferably 20% or more, and more preferably 30% or more, as a percentage of the total pore volume, or preferably in the order of 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, and 70% or more. When the proportion of pore volume of 10 nm or larger in the carbon material is within this range, the electronic conductivity and ionic conductivity are well balanced and preferable. If the proportion of pore volume of 10 nm or larger in the carbon material is excessively small, the movement of lithium ions is restricted, resulting in poor rapid discharge characteristics and charge / discharge characteristics.

[0086] The proportion of pore volume less than 10 nm in the carbon material of the present invention is not particularly limited, but is usually 90% or less, preferably 80% or less, and more preferably 70% or less, as a percentage of the total pore volume, or in order of preference 60% or less, 55% or less, 50% or less, 45% or less, 40%, 35% or less, and 30% or less.

[0087] The micropore volume of the carbon material of the present invention is not particularly limited, but is typically 2.5 cc / g or less, preferably 2 cc / g or less, more preferably 1.5 cc / g or less, even more preferably 1 cc / g or less, and most preferably 0.5 cc / g or less, for pores with a diameter of less than 2 nm. The lower limit of the micropore volume of the carbon material is not particularly limited, but is typically 0.001 cc / g or more, preferably 0.005 cc / g or more, more preferably 0.01 cc / g or more, even more preferably 0.05 cc / g or more, and most preferably 0.1 cc / g or more. If the micropore volume of the carbon material is excessively high, the ionic conductivity will be poor and undesirable. When the micropore volume of the carbon material is within this range, the electronic conductivity and ionic conductivity are highly balanced and preferable. If the micropore volume of the carbon material is excessively high, the ionic conductivity will be poor.

[0088] The mesopore volume of the carbon material of the present invention is not particularly limited, but for pores with a diameter of 2 to 50 nm, it is usually 0.01 cc / g or more, preferably 0.05 cc / g or more, more preferably 0.1 cc / g or more, or preferably 0.5 cc / g or more, 0.75 cc / g or more, 1 cc / g or more, 1.2 cc / g or more, 1.4 cc / g or more, 1.5 cc / g or more, 1.6 cc / g or more, 1.8 cc / g or more, and 2 cc / g or more, in that order. The upper limit of the carbon material is not particularly limited, but it is usually 5 cc / g or less, preferably 4.8 cc / g or less, more preferably 4.5 cc / g or less, even more preferably 4 cc / g or less, and most preferably 3.5 cc / g or less. When the mesopore volume of the carbon material is within this range, the linkage structure of the hollow particles has appropriate strength, contributing to the stability of the hollow particles, maintaining their shape, and highly enhancing both electronic and ionic conductivity. If the mesopore volume of the carbon material is excessively small, it will have poor ionic conductivity, resulting in inferior rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0089] The macropore volume of the carbon material of the present invention is not particularly limited, but is typically 0.001 cc / g or more, preferably 0.005 cc / g or more, more preferably 0.01 cc / g or more, for pores with a diameter of 50 nm or more, and is preferred in the order of 0.05 cc / g or more, 0.1 cc / g or more, 0.15 cc / g or more, 0.2 cc / g or more, 0.3 cc / g or more, 0.4 cc / g or more, 0.5 cc / g or more, 0.6 cc / g or more, 0.8 cc / g or more, and 1 cc / g or more. The upper limit of the macropore volume of the carbon material is not particularly limited, but is typically 10 cc / g or less, preferably 5 cc / g or less, more preferably 4.5 cc / g or less, even more preferably 4 cc / g or less, particularly preferably 3.5 cc / g or less, and most preferably 3 cc / g or less. When the macropore volume of the carbon material is within this range, it is possible to greatly enhance both electronic and ionic conductivity, significantly improving conductivity, rapid discharge characteristics of lithium-ion secondary batteries, battery capacity characteristics, and charge / discharge characteristics. If the macropore volume of the carbon material is excessively small, it will have poor electrolyte retention and poor lithium ion mobility. If the macropore volume of the carbon material is excessively large, it may not be possible to maintain the pore structure of the carbon material.

[0090] The mode pore diameter of the carbon material of the present invention is not particularly limited, but is the peak top pore diameter in the pore distribution curve and is usually 1 nm or more, preferably 2 nm or more, more preferably 5 nm or more, or preferably 10 nm or more, 12 nm or more, 13 nm or more, 14 nm or more, and 15 nm or more in that order. The upper limit of the mode pore diameter of the carbon material is not particularly limited, but is usually 100 nm or less, preferably 60 nm or less, more preferably 50 nm or less, even more preferably 40 nm or less, and most preferably 30 nm or less. When the mode pore diameter of the carbon material is within this range, it is suitable for achieving high ionic conductivity and electronic conductivity. Furthermore, when the mode pore diameter of the carbon material is within this range, the pore shape has appropriate strength, which contributes to the stability of the carbon material itself.

[0091] The average pore size of the carbon material of the present invention is not particularly limited, but is usually in the range of 1 to 100 nm, preferably 5 to 75 nm, more preferably 8 to 50 nm, even more preferably 12 to 40 nm, and most preferably 15 to 35 nm. When the average pore size of the carbon material of the present invention is within this range, high ionic conductivity and electronic conductivity can be achieved.

[0092] (particle characteristics) The particle size distribution curve of the carbon material of this invention was measured after immersing the unground material in a solvent for 9 minutes, and it shows the difference in cohesive force of the linked structures. In this invention, the dispersion is preferable when the cohesive force of the carbon material is low, as it exhibits excellent dispersibility in the dispersion.

[0093] The particle size D10 of the carbon material of the present invention, in which 10% of the particles are located, is not particularly limited, but is usually 150 μm or less, preferably 100 μm or less, more preferably 80 μm or less, or preferably 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, and 15 μm or less in that order. The lower limit of the particle size D10 of the carbon material is not particularly limited, but is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 1.5 μm or more, particularly preferably 2 μm or more, and most preferably 2.5 μm or more. When the particle size D10 of the carbon material is within this range, the electronic conductivity and ionic conductivity are greatly enhanced, which is preferable. If the particle size D10 of the carbon material is excessively large, the dispersion stability is poor, and when used in lithium-ion secondary batteries, the rapid discharge characteristics, battery capacity characteristics, charge / discharge characteristics, etc. are poor.

[0094] There are no particular limitations on the median diameter D50 of the carbon material of the present invention, where half of the particles are located in the particle size distribution curve. However, it is usually 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less, or preferably 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, and 50 μm or less, in that order. There are no particular limitations on the lower limit of the median diameter D50 of the carbon material. However, it is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 2 μm or more, particularly preferably 3 μm or more, and most preferably 5 μm or more. When the median diameter D50 of the carbon material is within this range, the electronic conductivity and ionic conductivity are greatly enhanced, which is preferable. If the median diameter D50 of the carbon material is excessively large, the dispersion stability is poor, and when used in lithium-ion secondary batteries, the rapid discharge characteristics, battery capacity characteristics, charge-discharge characteristics, etc. are inferior.

[0095] The particle size D90 of the carbon material of the present invention, where 90% of the particles are located, is not particularly limited, but is usually 300 μm or less, preferably 250 μm or less, more preferably 200 μm or less, or preferably 150 μm or less, 100 μm or less, 80 μm or less, 70 μm or less, 65 μm or less, 60 μm or less, and 55 μm or less, in that order. The lower limit of the particle size D90 of the carbon material is not particularly limited, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, even more preferably 7 μm or more, and most preferably 10 μm or more. When the particle size D90 of the carbon material is within this range, the electronic conductivity and ionic conductivity are greatly enhanced, which is preferable. If the particle size D90 of the carbon material is excessively large, the stability of the dispersion will be poor, and when used in a lithium-ion secondary battery, the rapid discharge characteristics, battery capacity characteristics, charge-discharge characteristics, etc. will be inferior.

[0096] The ratio of particle size D90 to particle size D10 (D90 / D10) in the particle size distribution curve of the carbon material of the present invention is not particularly limited, but is usually 100 or less, preferably 50 or less, more preferably 25 or less, or preferably 20 or less, 15 or less, 10 or less, 8 or less, 7 or less, 6 or less, and 5 or less in that order. The lower limit of D90 / D10 of the carbon material is not particularly limited, but is usually in the range of 0.1 or more, preferably 1 or more, more preferably 1.5 or more, even more preferably 2 or more, particularly preferably 2.5 or more, and most preferably 3 or more. When the D90 / D10 of the carbon material is within this range, the electronic conductivity and ionic conductivity of the resulting carbon material are highly balanced and preferable. If the D90 / D10 of the carbon material is excessively large, the cohesiveness is strong and the dispersibility is poor, which is undesirable because the conductivity and various performances cannot be improved when used in lithium-ion secondary batteries.

[0097] The ratio of particle size D90 to mode pore size (M) (D90 / M) of the carbon material of the present invention is not particularly limited, but is a value calculated by (1 / 1000) × (D90 / M), and is usually 50 or less, preferably 40 or less, more preferably 30 or less, or preferably in the order of 20 or less, 15 or less, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, and 5 or less. If the D90 / M of the carbon material is excessively large, the carbon material will have strong cohesiveness and poor dispersibility, and the electrolyte retention will also be insufficient, which is undesirable as it will not improve the conductivity and various performances of the lithium-ion secondary battery.

[0098] (General characteristics) The carbon content of the carbon material of the present invention is not particularly limited, but is usually 95% by weight or more, preferably 96% by weight or more, more preferably 97% by weight or more, even more preferably 98% by weight or more, and most preferably 99% by weight or more. If the carbon content of the carbon material is too low, the electronic conductivity will be poor and undesirable.

[0099] The conductivity of the carbon material of the present invention is not particularly limited, but is typically in the range of 1 to 100 S / cm, preferably 5 to 70 S / cm, more preferably 10 to 50 S / cm, even more preferably 15 to 40 S / cm, and most preferably 20 to 30 S / cm, when pressurized at 10 MPa. The conductivity of the carbon material can be determined by the reciprocal of its electrical resistivity. For example, the electrical resistivity of the carbon material can be measured according to JIS K1469.

[0100] The oil absorption capacity of the carbon material of the present invention is the oil absorption capacity of refined linseed oil measured in accordance with JIS K5101-13-1 (Pigment Test Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method). There are no particular limitations, but it is usually 100 mL / 100 g or more, preferably 200 mL / 100 g or more, more preferably 250 mL / 100 g or more, or preferably 300 mL / 100 g or more, 400 mL / 100 g or more, 500 mL / 100 g or more, 600 mL / 100 g or more, 700 mL / 100 g or more, 800 mL / 100 g or more, 900 mL / 100 g, 1000 mL / 100 g or more, 1050 mL / 100 g or more, and 1100 mL / 100 g or more. Furthermore, while there is no particular upper limit to the amount of oil absorbed by the carbon material, it is usually 5000 mL / 100g or less, preferably 4000 mL / 100g or less, more preferably 3500 mL / 100g or less, even more preferably 3000 mL / 100g or less, and most preferably 2500 mL / 100g or less. If the amount of oil absorbed by the carbon material is excessively small, the amount of electrolyte held will be small, causing a delay in ion supply during rapid reactions and reducing the discharge capacity, which is undesirable. Conversely, if the amount of oil absorbed by the carbon material is excessively large, it may be difficult to maintain the structure of the carbon material and control the amount of electrolyte held.

[0101] The number density of the carbon material of the present invention is not particularly limited, but is a value calculated by the method described later, and is usually in the range of 5E+14 to 1E+20 particles / g, preferably 1E+16 to 1E+19 particles / g, more preferably 5E+16 to 5E+18 particles / g, even more preferably 1E+17 to 1E+18 particles / g, and most preferably 3E+17 to 7E+17 particles / g. When the number density of the carbon material is in this range, the spread of the carbon material and the retention of the electrolyte are optimized.

[0102] The apparent density of carbon materials can be calculated using the following formula. Apparent density (g / cc) = 1 / (Total pore volume + (1 / True density)) [Note that the total pore volume (cc / g) is calculated using the formula P / P0 = 0.99, and the true density is calculated using the graphite value of 2.2 g / cc.] The apparent density of the carbon material of the present invention, calculated from the above formula, is usually 2 g / cc or less, preferably 1.5 g / cc or less, more preferably 1.3 g / cc or less, or preferably in the order of 1 g / cc or less, 0.7 g / cc or less, 0.5 g / cc or less, 0.4 g / cc or less, 0.3 g / cc or less, 0.28 g / cc or less, and 0.26 g / cc or less. If the apparent density of the carbon material is excessively high, the expansion of the carbon material's linkage structure will be reduced, leading to decreased conductivity and electrolyte retention.

[0103] The pH of the carbon material of the present invention is not particularly limited, but is usually in the range of 5 to 10, preferably 5.5 to 9.5, more preferably 6 to 9, even more preferably 6.5 to 8.5, and most preferably 7 to 8. The stability of the electrolyte is good when the pH of the carbon material is in the neutral range.

[0104] The combustion temperature of the carbon material of the present invention is not particularly limited, but is usually 500°C or higher, preferably 560°C or higher, more preferably 580°C or higher, and even more preferably 590°C or higher. Particularly preferably it is 600°C or higher, and most preferably 610°C or higher. The combustion temperature test of the carbon material is performed as a simple test of the stability within the battery, and if the combustion temperature is excessively low, the life characteristics and stability of each characteristic of the lithium-ion secondary battery will be inferior.

[0105] The ash content of the carbon material of the present invention is not particularly limited, but is usually 1% by weight or less, preferably 0.7% by weight or less, more preferably 0.5% by weight or less, even more preferably 0.4% by weight or less, particularly preferably 0.35% by weight or less, and most preferably 0.3% by weight or less. When the ash content of the carbon material is within this range, the stability of the electrolyte is excellent, and it is suitable for improving the durability and performance of lithium-ion secondary batteries.

[0106] (Imparting conductivity) The carbon material of the present invention has an electron transfer mechanism with a graphene structure, and due to its large pore volume, it retains electrolyte and possesses ionic conductivity for lithium ions, as well as excellent stability in the electrolyte. Therefore, when incorporated into the electrodes of a lithium-ion secondary battery, it can exert a function that assists the battery reaction in the lithium-ion secondary battery. Furthermore, one embodiment of the carbon material of the present invention is a linked structure in which hollow particles covered with an outer shell made of carbonaceous material containing graphene are linked together. Because there is space inside the hollow particles and inside the area surrounded by the linked structure of hollow particles, an electrolyte containing dissolved lithium ions can penetrate and be retained, resulting in excellent ion supply during the reaction. For this reason, the carbon material of the present invention can suitably assist the secondary battery reaction.

[0107] The positive electrode material of a lithium-ion secondary battery is a lithium-containing transition metal oxide with low electronic conductivity and a particle size distribution in powder form. In conventional methods, an electron conduction path is established by mixing a conductive material made of carbon, which assists electron conduction for the battery reaction, with a binder resin and then pressing and fixing it to a current collector. The materials other than the binder resin are powder particles, and the electrolyte exists in the spaces between the particles. For this reason, it has been difficult with conventional techniques to actively place the electrolyte, or in other words lithium ions, near the positive electrode material.

[0108] The carbon material of this embodiment has a space inside its carbonaceous outer shell and a ring-shaped space formed by a connected structure of hollow particles, allowing it to hold an electrolyte in that space. Compared to carbon black, which has been conventionally used as a conductive material, the carbon material of this embodiment has a larger internal space. Therefore, the carbon material of this embodiment can simultaneously assist in the supply of electrons and ions necessary for battery reactions, and can be said to be a material that enables rapid battery reactions.

[0109] <Method for manufacturing carbon materials> Next, a method for producing carbon materials according to the present invention will be described. The method for producing carbon materials according to the present invention is not particularly limited, but for example, in a method for producing carbon materials in which a carbonaceous layer is formed on the surface of a mold material and then the mold material is removed, the material can be easily produced by using an aggregate in which primary particles of 1 to 100 nm are linked together in a chain-like manner with multiple branching structures as the mold material.

[0110] (Mold material) There are no particular limitations on the material used as the mold material, as long as it can be removed later, but inorganic materials are usually used. Examples of inorganic materials that can be used include nonmetallic compounds, metalloid compounds, and metallic compounds, with metalloid compounds and metallic compounds being preferred, and metalloid compounds being particularly preferred. Examples of inorganic compounds include inorganic hydrogen compounds, inorganic oxides, inorganic oxoacids, inorganic hydroxides, inorganic halides, inorganic sulfates, inorganic nitrates, inorganic carbonates, and inorganic metal complexes (inorganic coordination compounds), with inorganic oxides and inorganic carbonates being preferred, and inorganic oxides being more preferred.

[0111] There are no particular limitations on nonmetallic compounds, but examples include ceramic compounds. Examples of ceramics include glass, cement, and fine ceramics.

[0112] There are no particular limitations on the metalloid (semimetallic) compound, but examples include compounds of boron, silicon, germanium, and antimony, with silicon compounds being preferred. Examples of silicon compounds include silicon monoxide, silicon dioxide, silicon nitride, silicon carbide, and silicone, with silicon dioxide compounds being preferred.

[0113] Examples of metal compounds include monovalent metal compounds and polyvalent metal compounds, but polyvalent metal compounds are 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 alkaline earth metal compounds such as calcium and magnesium, and trivalent metal compounds such as aluminum, but calcium compounds, magnesium compounds, and aluminum compounds are preferred. Examples of calcium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, but carbonates and oxides are preferred, and oxides are more preferred. Examples of magnesium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, but carbonates and oxides are preferred, and oxides are more preferred. Examples of aluminum compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, but carbonates and oxides are preferred, and oxides are more preferred.

[0114] As a mold material, atomized inorganic compounds can be suitably used because they form large aggregate structures. Examples of atomized inorganic compounds include compounds obtained by flame hydrolysis, which is one of the dry manufacturing methods for inorganic materials.

[0115] A typical example of an atomized inorganic compound is atomized silicon dioxide. Atomized silicon dioxide produced by flame hydrolysis does not undergo a liquid-phase process, resulting in slow aggregation. Therefore, atomized silicon dioxide exhibits excellent dispersibility in both liquid and solid phases. Atomized silicon dioxide is produced by high-temperature gas-phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame, producing hydrochloric acid as a by-product. By varying production conditions such as flame temperature, oxygen and hydrogen supply ratio, raw material supply amount, and residence time, the average particle size can be 7-40 nm and the specific surface area 50-380 m². 2 Particles of silicon dioxide are obtained at a density of / g.

[0116] Other examples of atomized inorganic compounds produced by flame hydrolysis include atomized alumina, atomized titania, and atomized zirconia. Other examples of atomized metallic compounds include chlorides of Na, Ba, or Sr, sulfates of K, Na, Sr, or Mg, nitrates of Na or K, phosphates of Na or K, carbonates of Na, K, Ca, or Mg, and metal oxides of Na, K, Ca, or Ba. The shape of the mold material is preferably in an atomized form.

[0117] (Primary particle size) The present invention is characterized by using a primary particle size in the range of 1 to 150 nm as the mold material.

[0118] The primary particle size of the mold material used is in the range of 1 to 150 nm, preferably 5 to 100 nm, more preferably 10 to 80 nm, even more preferably 13 to 70 nm, particularly preferably 15 to 60 nm, and most preferably 20 to 50 nm. When the primary particle size of the mold material is in this range, the pore volume of 10 nm or more in the manufactured carbon material can be significantly increased, which is advantageous. Furthermore, when the primary particle size of the mold material is in this range, it is easy to handle, and the permeability of the raw material gas that serves as the carbon source for the carbonaceous layer is good, making it easy to achieve a uniform carbon coating.

[0119] (Other characteristics) The carbon content of the mold material used is not particularly limited, but is usually 0.001% by weight or more, preferably 0.01% by weight or more, or preferably in the order of 0.05% by weight or more, 0.1% by weight or more, 0.2% by weight or more, 0.3% by weight or more, 0.4% by weight or more, and 0.5% by weight or more. The upper limit of the carbon content of the mold material is not particularly limited, but is usually 5% by weight or less, preferably 4.5% by weight or less, more preferably 4% by weight or less, or preferably in the order of 3.5% by weight or less, 3% by weight or less, 2.5% by weight or less, and 2% by weight or less. When the carbon content of the inorganic material is within this range, it is preferable because it facilitates the formation of a carbonaceous layer on the mold surface.

[0120] The specific surface area of the template particles used is a value represented by the BET specific surface area, and there is no particular limitation, but it is usually 500 m 2 / g or less, preferably 400 m 2 / g or less, more preferably 300 m 2 / g or less, or 200 m 2 / g or less, 180 m 2 / g or less, 170 m 2 / g or less, 160 m 2 / g or less, 150 m 2 / g or less, 140 m 2 / g or less, 130 m 2 / g or less, 125 m 2 / g or less, 120 m 2 / g or less, 115 m 2 / g or less in this order is preferable. Also, the lower limit value of the specific surface area of the template particles used is not particularly limited, but it is usually 0.1 m 2 / g or more, preferably 0.1 m 2 / g or more, more preferably 1 m 2 / g or more, or 5 m 2 / g or more, 10 m 2 / g or more, 20 m 2 / g or more, 30 m 2 / g or more, 40 m 2 / g or more, 50 m 2 / g or more, 60 m 2 / g or more in this order is preferable. When the BET specific surface area of the template particles is within this range, the pore volume of 10 nm or more of the produced carbon material can be significantly increased and maintained. If the BET specific surface area of the template particles is excessively large, there is a problem that it is difficult to form large pores and macropores of 10 nm or more in the produced carbon material.

[0121] There are no particular limitations on the amount of oil absorbed by the mold particles used, but it is usually 10 mL / 100g or more, preferably 50 mL / 100g or more, more preferably 100 mL / 100g or more, or preferably 110 mL / 100g or more, 120 mL / 100g or more, 130 mL / 100g or more, 140 mL / 100g or more, 150 mL / 100g or more, 160 mL / 100g or more, and 170 mL / 100g or more, in that order. There are no particular limitations on the upper limit of the amount of oil absorbed by the mold particles, but it is usually 500 mL / 100g or less, preferably 450 mL / 100g or less, more preferably 400 mL / 100g or less, even more preferably 350 mL / 100g or less, and most preferably 300 mL / 100g or less. When the oil absorption amount of the mold particles is within this range, it is preferable to increase the pore volume of 10 nm or more and the oil absorption amount of the resulting carbon material.

[0122] The total pore volume of the mold particles used is not particularly limited, but is usually 1 cc / g or less, preferably 0.8 cc / g or less, more preferably 0.6 cc / g or less, or preferably 0.5 cc / g or less, 0.4 cc / g or less, 0.35 cc / g or less, 0.3 cc / g or less, 0.25 cc / g or less, 0.23 cc / g or less, and 0.22 cc / g or less, in that order. The lower limit of the total pore volume of the mold particles is not particularly limited, but is usually 0.001 cc / g or more, preferably 0.005 cc / g or more, more preferably 0.01 cc / g or more, even more preferably 0.05 cc / g or more, and most preferably 0.1 cc / g or more. When the total pore volume of the mold particles is within this range, it is preferable because the oil absorption capacity of the resulting carbon material can be greatly increased. If the total pore volume of the mold particles is excessively large, it becomes difficult to maintain pores of 10 nm or larger in the manufactured carbon material.

[0123] (aggregate) There are no particular limitations on the structure of the aggregates of the mold particles used, but examples include those in which primary particles extend in a complex and long manner to realize a higher-order structure. It is preferable to have an aggregate structure in which primary particles have multiple branching structures and are linked together in a bead-like manner. It is even more preferable to have a linear portion in which five or more mold particles are connected in series along the longitudinal direction, and it is particularly preferable to have a linear portion in which five or more mold particles are connected in series along the longitudinal direction and a multiple branching structure.

[0124] The structure length of the mold material (aggregate) used is not particularly limited, but is usually in the range of 0.01 to 100 μm, preferably 0.05 to 10 μm, and more preferably 0.1 to 5 μm. The average particle size of the structure is not particularly limited, but is usually in the range of 0.05 to 10 μm, preferably 0.1 to 5 μm.

[0125] The median diameter D50 of the mold material used is not particularly limited, but is the value at which half of the particles are present in the particle size distribution curve measured after immersion in the solvent for 9 minutes, and is usually 0.5 μm or more, preferably 1 μm or more, more preferably 5 μm or more, or preferably in the order of 10 μm or more, 12 μm or more, 15 μm or more, 18 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, and 45 μm or more. In the present invention, by using a mold material with a large median diameter D50, carbon materials with large pore sizes and oil absorption can be manufactured. A larger median diameter D50 indicates stronger cohesive force, and by using a mold material with a large median diameter D50, the gaps between aggregates and the ring shapes formed by the aggregates become large pores in the manufactured carbon material, and in particular, the pore volume of 10 nm or more and the macropore volume of the carbon material can be significantly increased. There are no particular limitations on the upper limit of the median diameter D50 of the mold material used, but it is usually 200 μm or less, preferably 100 μm or less, more preferably 80 μm or less, and most preferably 60 μm or less.

[0126] There are no particular limitations on the particle size D10 of the mold material used, where 10% of the particles are located in the particle size distribution curve. However, it is a value measured after immersion in a solvent for 9 minutes, and is usually 0.1 μm or larger, preferably 0.5 μm or larger, more preferably 1 μm or larger, or preferably 2 μm or larger, 5 μm or larger, 10 μm or larger, 13 μm or larger, 15 μm or larger, and 20 μm or larger, in that order. There are no particular limitations on the upper limit of the particle size D10 of the mold material, but is usually 100 μm or smaller, preferably 75 μm or smaller, more preferably 50 μm or smaller, even more preferably 40 μm or smaller, and most preferably 30 μm or smaller. When the particle size D10 of the mold material is within this range, the conductivity of the carbon material can be greatly enhanced, which is preferable. When the particle size D10 of the mold material is excessively small, the oil absorption amount and pore volume of 10 nm or more of the resulting carbon material may not be sufficient.

[0127] There are no particular limitations on the particle size D90 of the mold material used, where 90% of the particles are located in the particle size distribution curve. However, it is a value measured after immersion in a solvent for 9 minutes, and is usually 1 μm or larger, preferably 5 μm or larger, more preferably 10 μm or larger, or preferably 20 μm or larger, 30 μm or larger, 40 μm or larger, 50 μm or larger, 60 μm or larger, and 80 μm in that order. There are no particular limitations on the upper limit of the particle size D90 of the mold material, but is usually 300 μm or smaller, preferably 250 μm or smaller, more preferably 200 μm or smaller, even more preferably 150 μm or smaller, and most preferably 130 μm or smaller. When the particle size D90 of the mold material is within this range, the electronic conductivity and ionic conductivity of the manufactured carbon material are highly enhanced, which is preferable. When the particle size D90 of the mold material is excessively small, the oil absorption and pore volume of 10 nm or more of the resulting carbon material may be insufficient.

[0128] The bulk density of the mold material used is not particularly limited, but is usually in the range of 0.1 to 500 g / L, preferably 0.5 to 250 g / L, more preferably 1 to 200 g / L, even more preferably 10 to 100 g / L, and most preferably 30 to 70 g / L. A bulk density of the mold material within this range is preferable because it enhances the conductivity of the manufactured carbon material and significantly increases the pore volume of 10 nm or larger.

[0129] (Surface treatment) There are no particular limitations on the mold material used, but surface-treated materials are preferred. For example, materials surface-treated with a compound having a hydrocarbon that serves as a carbon source are preferred. The hydrocarbon is a compound similar to the raw material gas described later, such as a compound having a methyl group or a carbon-carbon unsaturated bond.

[0130] There are no particular limitations on the surface treatment agent having such hydrocarbons, but examples include hydrocarbon-containing silane coupling agents. Examples of hydrocarbon-containing silane coupling agents include 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 large number of methyl groups per molecule are preferred, and trimethoxysilane compounds are particularly preferred.

[0131] The amount of silane coupling agent used is appropriately selected depending on the intended use, but it is adjusted so that the carbon content in the mold material is typically in the range of 0.1 to 10% by weight, preferably 0.2 to 8% by weight, more preferably 0.3 to 5% by weight, even more preferably 0.4 to 3% by weight, and most preferably 0.5 to 1.5% by weight. When the amount of silane coupling agent (carbon content) in the mold material is within this range, carbon deposition on the mold surface is facilitated, which is preferable.

[0132] The moisture content of the mold material used in the present invention is not particularly limited, but is usually 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.

[0133] These mold materials can be used individually or in combination of two or more types.

[0134] (Carbon layer formation and carbonization process) In this invention, the formation of a carbonaceous layer on the surface of the mold material can be achieved by contacting the mold material with an organic substance that serves as a carbon source and performing a carbonization heat treatment. Contact with the carbon source and the carbonization heat treatment can be performed simultaneously or separately. Contact between the mold material and the carbon source is usually carried out in a temperature range of room temperature to 1000°C.

[0135] Methods for bringing a carbon source into contact with a mold material can be broadly classified into liquid-phase contact methods and gas-phase contact methods, with gas-phase contact methods being preferred. Liquid-phase contact methods include, for example, immersing the mold material in a liquid of organic matter. Gas-phase contact methods involve, for example, introducing an organic gas at high temperatures and bringing it into contact with the mold material; this is the so-called CVD (Chemical Vapor Deposition) method.

[0136] -Liquid phase contact method- In the liquid-phase contact method, organic compounds having functional groups on the mold surface, specifically functional groups that can react with hydroxyl groups, are preferably used, and benzene-based hydrocarbon compounds having functional groups that can react with hydroxyl groups are particularly preferred. Among these, benzene-based aromatic hydrocarbon compounds having hydroxyl groups and / or carboxyl groups are preferred, with phenol, hydronaphthalene, and dihydronaphthalene being more preferred. This is because using organic compounds having functional groups that can react with functional groups on the mold surface creates strong bonds, such as ester bonds, between the mold material and the organic compound, making it easier for the organic compound to carbonize in situ during the carbonization heat treatment without volatilizing.

[0137] In the liquid-phase contact method, an organic compound, used as a carbon source, is dissolved in a solvent and impregnated into the mold material at room temperature, thereby bringing them into contact. To strongly bond the organic material and the mold material, the temperature is maintained in the range of 250-600°C for a certain period of time. This causes the hydroxyl groups on the surface of the mold material and the organic material to undergo dehydration condensation reactions such as esterification, fixing them through bonds such as ester bonds, making it easier to obtain a carbon layer with a graphene sheet structure. After that, the temperature is lowered, and any excess organic material that did not react with the mold material can be washed and removed with a solvent or the like.

[0138] The organic compound used as a carbon source, which is in contact with the mold material, is subjected to heat treatment to carbonize it. This heat treatment causes dehydrogenation reactions in organic substances such as hydrocarbons, transforming them into carbon such as graphene sheet structures. The heat treatment temperature is usually 600°C or higher, preferably 600 to 1500°C, more preferably 750 to 1500°C, and particularly preferably 800 to 1000°C. However, the heat treatment may be performed at 1500°C or higher, as long as the mold material does not collapse or melt.

[0139] -Vapor-phase contact method- In the vapor-phase contact method, an organic compound as a carbon source is brought into contact with the mold material, and in order to strongly bond the carbon source and the mold material, it is preferable to carry out the CVD method in a temperature range in which the dehydrogenation reaction can proceed, specifically 400 to 1000°C.

[0140] As an organic compound used as a carbon source in the gas-phase contact method, it may be appropriately selected according to the intended use, but hydrocarbons such as saturated hydrocarbons, unsaturated hydrocarbons having double and / or triple bonds, alicyclic hydrocarbons, and aromatic hydrocarbons are preferably used. Saturated hydrocarbons may be either straight-chain or branched-chain, and examples include methane, ethane, and propane. Unsaturated hydrocarbons may be either straight-chain or branched-chain, and examples include ethylene, propylene, isoprene, and acetylene. Examples of alicyclic hydrocarbons include cyclopropane and cyclohexane. Examples of aromatic hydrocarbons include benzene and toluene. Among these hydrocarbons, it is desirable to use methane, ethane, acetylene, ethylene, propylene, and benzene, and from the viewpoint of precipitating highly crystalline carbon, methane, propylene, and benzene are preferred. In particular, methane is preferably used from the viewpoint of obtaining highly crystalline carbon at a high thermal decomposition temperature.

[0141] Organic compounds that can be used in the gas-phase contact process include alcohols such as methanol, ethanol, propanol, and butanol, as well as nitrogen-containing compounds such as acetonitrile and acrylonitrile.

[0142] The reaction temperature in the CVD reaction is appropriately selected according to the decomposition temperature of the organic compound used as the carbon source, but is usually in the range of 400 to 1000°C, preferably 600 to 950°C, and preferably 800 to 900°C.

[0143] The reaction time in a 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 carbon layers deposited, but is usually in the range of 0.1 to 10 hours, preferably 0.5 to 5 hours, and more preferably 1 to 3 hours. Furthermore, the product can be analyzed by applying the analytical methods disclosed herein, and the time required for sufficient carbon deposition can be appropriately set based on the results.

[0144] CVD reactions 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 usually be easily adsorbed or deposited on the mold material in the gas phase by heating while passing a gaseous organic compound in contact with the mold material together with a carrier gas. The type of carrier gas, flow rate, flow rate, and heating temperature can be appropriately adjusted depending on the type of organic compound used. Examples of carrier gases include the inert gases mentioned above, but a mixture with oxygen gas or hydrogen gas may also be used. Argon is preferably used as the carrier gas.

[0145] The carrier gas flow rate is not particularly limited, but is usually adjusted to 0.05 to 5 m / min, preferably 0.1 to 1 m / min, more preferably 0.2 to 0.8 m / min, and most preferably 0.32 to 0.64 m / min. In order to form the optimal number of graphene layers, the amount of organic compound introduced is usually adjusted to 1 to 70 volume%, preferably 5 to 50 volume%, more preferably 10 to 40 volume%, and most preferably 15 to 35 volume%, relative to the total amount of carrier gas and organic compound.

[0146] Since carbonization of the carbon layer can also proceed by CVD reactions, no other special carbonization treatment is necessary, but it may be performed.

[0147] (Mold removal process) In the manufacturing method of the present invention, any method that removes the mold after the formation of the carbonaceous layer is acceptable, as long as the mold is removed and the formed carbonaceous layer remains. Examples include dissolution with acid or alkali, and dissolution with acid is preferred.

[0148] The acid used in this invention is appropriately selected depending on the type of mold material, but examples include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, and hydrofluoric acid, with hydrochloric acid and hydrofluoric acid being preferred. The acid concentration used for dissolving and removing the mold is appropriately adjusted within a range that allows for the dissolution and removal of the mold. The amount of acid used is not particularly limited as long as it is within a range that allows for the dissolution and removal of the mold material, but for example, it may be 30 times or more the stoichiometric ratio or 50 times or more the stoichiometric ratio relative to the mold material.

[0149] The temperature for dissolving and removing the mold material is not particularly limited, but is usually in the range of 5 to 100°C, preferably 10 to 50°C, and more preferably 20 to 30°C. The dissolving and removal process of the mold material may be carried out with stirring, vibration, and other operations. The time required for the removal process is appropriately selected within a range in which the mold can be dissolved and removed.

[0150] The carbon material after mold removal can be recovered, for example, by filtration, and then washed with pure water. Washing conditions can be selected as appropriate, but the process can be terminated after confirming that the pH of the washing solution is neutral.

[0151] The carbon material, after cleaning and removal of the mold material, can be dried by vacuum heating and drying. The conditions for vacuum heating and drying are not particularly limited, but for example, the vacuum heating and drying temperature can be 100 to 200°C and the vacuum heating and drying time can be 1 to 10 hours.

[0152] (Heat treatment process) In the method for producing carbon materials of the present invention, the carbon material (separated carbonaceous layer) after the removal of the mold material can be heat-treated as needed. By heat-treating the carbonaceous layer from which the mold 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 conductivity, corrosion resistance, and / or high specific surface area.

[0153] The conditions for the heat treatment process are not particularly limited as long as they enhance the crystallinity of the carbon. The holding temperature during the heat treatment process is usually in the range of 1000 to 3000°C, preferably 1300 to 2500°C, more preferably 1400 to 2000°C, even more preferably 1500 to 1900°C, and most preferably 1600 to 1850°C. A heat treatment temperature within this range is preferable because it allows for the acquisition of carbon materials with higher levels of conductivity, corrosion resistance, and / or high specific surface area. The heat treatment time (holding time at a predetermined heat treatment temperature) is usually 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 during the heat treatment process is not particularly limited, but it is preferably carried out under atmospheric pressure or reduced pressure.

[0154] Furthermore, through the heat treatment process, functional groups that bond to carbon (mainly oxygen-containing functional groups) and carbon chains that do not form six-membered rings detach above 1000°C, forming unbonded bonds. When these unbonded bonds bond to other nearby carbon atoms, the surface of the carbon material becomes less receptive to the bonding of functional groups. By heat-treating at 1500°C or higher, preferably 1600°C or higher, the carbon material of the present invention can exhibit desirable functions such as electronic conductivity and the maintenance of internal spaces.

[0155] These heat treatments adjust structural defects in the graphene and non-graphene components that make up the carbonaceous material. These structural defects include spaces created within the aggregate structure due to the dissolution of the template material and intrusion pores created in the outer shell formed from the carbonaceous material. By changing reaction conditions such as heat treatment temperature and time, the degree of these structural defects can be adjusted. In other words, the size of the spaces within the carbon material and the size of the intrusion pores that allow the electrolyte to penetrate into the particles can be adjusted.

[0156] Thus, the carbon material of the present invention can be easily manufactured.

[0157] <Dispersion> Next, the dispersion according to the present invention will be described. The dispersion according to the present invention is obtained by dispersing the above-mentioned carbon material in a dispersion medium.

[0158] (dispersion medium) There are no particular limitations on the dispersion medium used in the present invention, and it can be selected according to the purpose of use. For example, organic or inorganic dispersants can be suitably used to maintain good dispersion of the powder in the solvent. When used in the manufacture of lithium-ion secondary batteries, polar solvents are suitably used, and from the viewpoint of affinity with the binder polymer, N,N-dimethylformamide, N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and water are preferred, and it is more preferable to include N-methylpyrrolidone (NMP). NMP is suitable for dispersing carbon materials including graphene.

[0159] The proportion of the carbon material of the present invention to the above dispersion medium is appropriately selected depending on the intended use, but the proportion of the carbon material of the present invention to 100 parts by weight of the dispersion medium is usually 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 proportion of carbon material is too low, it is difficult to form conductive paths in the lithium-ion secondary battery, and conversely, if the content is too high, the fluidity of the carbon material dispersion is impaired, and both are undesirable.

[0160] (Dispersant) In this invention, carbon materials having a high specific surface area tend to aggregate due to van der Waals interactions; therefore, a dispersant can be used to improve dispersibility as needed. The dispersant may be attached to the carbon material in advance or added directly to the dispersion medium. The dispersant is appropriately selected according to the intended use, but typically, dispersants having acidic or basic groups can be used. In addition, dispersants that are adsorbed onto the surface of solid particles and disperse the solid particles by steric hindrance and electrostatic repulsion, thereby reducing the interfacial tension between the solid particles and the solvent, can also be used.

[0161] Dispersants having acidic groups exert the effect of improving the dispersibility of carbon materials by having at least a portion of them adhering to the surface of the carbon material. A phenolic hydroxyl group is preferred as the acidic group of the dispersant. Examples of compounds having phenolic hydroxyl groups include phenol, nitrophenol, cresol, catechol, and compounds having structures in which parts of these are substituted.

[0162] Among these, compounds having a catechol group are preferred as dispersants because they have good adhesion to carbon materials and good 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.

[0163] As a compound having a basic group, a compound having an amino group is preferred due to its good dispersibility. In particular, a compound having both an aromatic ring and an amino group is preferred. Examples of such compounds include benzylamine and phenylethylamine. As a dispersant, it is also preferable to have both a basic group and a catechol group, such as dopamine hydrochloride.

[0164] Furthermore, surfactants having acidic or basic groups are also suitably used. Cationic surfactants, anionic surfactants, and nonionic surfactants can all be used as such surfactants. However, since anions and cationic surfactants can themselves participate in electrochemical reactions, nonionic surfactants that are not ionized are preferred when used as battery materials.

[0165] Examples of dispersants for polymer compounds that can also be used as battery binders include polyvinylidene fluoride, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride maleic acid modified product, 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.

[0166] These dispersants can be used individually or in combination of two or more, and the amount added to a dispersion should be appropriately selected according to the intended use.

[0167] (Other carbon materials) The dispersion of the present invention may optionally contain other carbon materials besides the carbon material of the present invention. While there are no particular limitations on the other carbon materials, examples 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.

[0168] Examples of carbon black include acetylene black, Ketjen black, and furnace black, with acetylene black and Ketjen black being preferred from the viewpoint of conductivity. Graphite, also known as graphite or slate, is used, consisting 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 carbon fibers, isotropic pitch carbon fibers, vapor-grown carbon fibers (VGCF), and milled carbon fibers obtained by crushing polymer fibers after firing.

[0169] These other carbon materials can be used individually or in combination of two or more. The amount of other carbon materials used can be selected according to the intended use, for example, within the same range as the carbon materials of the present invention described above. The ratio of the carbon materials of the present invention to the other carbon materials can be selected according to the intended use, for example, the weight ratio of [carbon materials of the present invention]:[other carbon materials] is usually in the range of 10:90 to 90:10, preferably 20:80 to 80:20, and more preferably 40:60 to 60:40.

[0170] The solid content concentration of the dispersion of the present invention is appropriately selected depending on the intended use, but is usually in the range of 0.01 to 50% by weight, preferably 0.05 to 30% by weight, more preferably 0.1 to 20% by weight, even more preferably 0.5 to 10% by weight, and most preferably 1 to 5% by weight. If the solid content concentration of the carbon material dispersion of the present invention is excessively high, carbon material stacking is likely to occur in the dispersion, making it difficult to maintain a good dispersion state. Conversely, if it is excessively low, when the carbon material dispersion is used to manufacture an electrode slurry, the viscosity of the electrode slurry decreases, which tends to worsen the coating properties. Both are undesirable. Here, the solid content of the carbon material dispersion refers to the material remaining after the dispersion medium has been dried and removed from the carbon material dispersion. The solid content concentration of the carbon material dispersion can be calculated by measuring the weight after the dispersion medium has been dried and removed from the carbon material dispersion, and dividing the measured value by the weight of the carbon material dispersion itself. Specifically, approximately 1 g of carbon material dispersion is weighed, applied to a glass substrate of known weight, and heated on a hot plate heated to 120°C for 1.5 hours to volatilize the dispersion medium. The weight of the remaining carbon material is then measured.

[0171] The viscosity of the dispersion of the present invention can be appropriately selected depending on the intended use, but in a dispersion with a solid content concentration of 3% by mass, the viscosity is as follows: temperature 23°C, shear rate 1s -1 The viscosity under these conditions is typically 20,000 cP or less, preferably 15,000 cP or less, and more preferably 10,000 cP or less. The lower limit is typically 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. Furthermore, the viscosity of the carbon material dispersion of the present invention is measured in a liquid-liquid solution with a solid content concentration adjusted to 2% by mass, at a temperature of 23°C and a shear rate of 1 s. -1 It is preferable that the viscosity under these conditions is 30 cP or less. In the carbon material dispersion of the present invention, the viscosity can be adjusted to a preferred level by adding the surface treatment agent, etc.

[0172] (Method for producing dispersion) The method for producing the dispersion of the present invention is not particularly limited, and can be carried out by mixing the carbon material of the present invention, and optionally a dispersant or other carbon material, in a dispersion medium.

[0173] Since the carbon material of the present invention has a relatively large BET specific surface area, to disperse it well in a dispersion, it is effective to apply a high shear force using a mixer with strong stirring power while the carbon material and dispersion medium are present. Examples of mixing devices capable of applying a high shear force include planetary mixers, "Filmix" (registered trademark) (Primix Corporation), rotational and revolutionary mixers, planetary ball mills, and three-roll mills. To eliminate stacking of carbon materials, a strong stirring process may be performed using a high-shear mixer at a shear rate of 5,000 to 50,000 per second. For high shear mixers, thin-film swirling type, rotor / stator type, and media mill type are preferred. Examples include "Filmix" (registered trademark) 30-30 type (Primix Co., Ltd.), "Clearmix" (registered trademark) CLM-0.8S (M-Technic Co., Ltd.), "Labostar" (registered trademark) Mini LMZ015 (Ashizawa Finetech Co., Ltd.), and "Super Shear Mixer" (registered trademark) SDRT0.35-0.75 (Satake Chemical Machinery Industry Co., Ltd.).

[0174] <Electrode compositions, electrode slurries, and electrodes> Next, the electrode composition, electrode slurry, and electrode according to the present invention will be described.

[0175] The electrodes containing the carbon material of the present invention, preferably electrodes for lithium-ion secondary batteries, are suitable because they have excellent fast discharge properties, capacity characteristics, and charge-discharge characteristics. To manufacture such electrodes, it is useful to use electrode compositions and electrode slurries containing the carbon material of the present invention.

[0176] (Composition for electrode) The electrode composition of the present invention comprises the carbon material, active material, and binder of the present invention.

[0177] There are no particular limitations on the active material used in the present invention. Examples include the active material used in the positive electrode and the active material used in the negative electrode, which will be described later. The ratio of the active material to the carbon material of the present invention is appropriately selected according to the purpose of use, and is typically 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, in terms of the ratio of the carbon material of the present invention to 100 parts by weight of the active material.

[0178] There are no particular limitations on the binder used in the present invention, and examples include binders used in the positive electrode and binders used in the negative electrode, as described later. The amount of binder used is appropriately selected according to the purpose of use, and is usually in the range of 0.05 to 10 parts by 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 per 100 parts by weight of active material.

[0179] In addition to the carbon material, active material, and binder of the present invention, other compounding agents may be added to the electrode composition of the present invention as needed. The other compounding agents are not particularly limited as long as they are commonly used in electrode compositions for lithium-ion secondary batteries, and the amount used is usually 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.

[0180] There are no particular limitations on the mixing method for the electrode composition of the present invention, but examples include a dry mixing method and a wet mixing method using a dispersion medium.

[0181] (Electrode slurry) The two-electrode slurry of the present invention is obtained by mixing the above-mentioned electrode composition using a wet mixing method with a dispersion medium. Any dispersion medium capable of dissolving or dispersing the binder can be used, such as the dispersion medium used for the positive electrode described later, the dispersion medium used for the negative electrode described later, and the dispersion medium used for the carbon material-containing dispersion liquid of the present invention described above. The amount of dispersion medium used can be an appropriate amount, adjusted so that the electrode slurry for the next step can be applied to the current collector.

[0182] The method for producing the electrode slurry of the present invention is not particularly limited, and examples include a method in which the carbon material of the present invention, a binder, and a dispersion medium are mixed, and then an active material is mixed. In the mixing of the carbon material, binder, and dispersion medium of the present invention, there are methods such as mixing the binder into a dispersion liquid containing the carbon material, and mixing the dispersion liquid containing the carbon material with a binder liquid obtained by dissolving or dispersing the binder in the dispersion medium.

[0183] There are no particular limitations on the mixing method, and any known mixer or kneader can be used. Known mixers include automatic mortars, homogenizers, planetary mixers, homodispersers, and revolving mixers, with planetary mixers being particularly preferred.

[0184] (electrode) The electrode of the present invention 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 the positive electrode or one used for the negative electrode, as described later.

[0185] As a method for applying the electrode slurry onto the current collector, any known method can be used without particular limitation. Specifically, it can be applied using a manual or automatic coater such as a baker coater, a film coater with a micrometer, a bar coater, a doctor blade, etc. As a drying method, any known method can be used without particular limitation, and examples thereof include drying by warm air, hot air, low humidity air, vacuum drying, and drying by irradiation with infrared rays, electron beams, etc. After the drying process, a pressure treatment may be applied to the electrode composite layer using a die press, a roll press, or the like. By the pressure treatment, the positive electrode composite layer can be well adhered to the current collector.

[0186] <Positive electrode> The positive electrode will be described. Generally, the positive electrode is obtained by applying a slurry in which a positive electrode active material, a conductive material for assisting electron conductivity, a binder, and a solvent are mixed onto a current collecting metal foil such as rolled aluminum foil to form a coating film, heating and drying to remove the solvent, and then forming it into a predetermined size and density. The carbon material of the present invention can be usefully used as a conductive material.

[0187] (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 one or more metals such as cobalt, manganese, nickel, or aluminum and lithium.

[0188] Specific examples of the positive electrode active material include lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi 1-a Mn a O2 (where 0 < a < 1), LiMn 2-b Ni b O4 (where 0 < b < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-c Co cO2 (where 0 < c < 1), lithium-manganese-cobalt oxide (e.g., LiCo 1-d Mn d O2 (where 0 < d < 1), LiMn 2-e Co e O4 (where 0 < e < 2), lithium-nickel-manganese-cobalt oxide (e.g., Li(Ni f Co g Mn h )O2 (where 0 < f < 1, 0 < g < 1, 0 < h < 1, f + g + h = 1) or Li(Ni j Co k Mn m )O4 (where 0 < j < 2, 0 < k < 2, 0 < m < 2, j + k + m = 2), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p Co q Mn r M S )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p, q, r, and s are atomic fractions of independent elements, 0 < p < 1, 0 < q < 1, 0 < r < 1, 0 < s < 1, and p + q + r + s = 1), etc.), and any one or two or more of these compounds may be included.

[0189] Among these, from the viewpoint of being able to improve the capacity characteristics and stability of the battery, LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., LiNi 0.8 Co 0.15 Al 0.05 O2, etc.) are preferred.

[0190] As the positive electrode active material, as a highly stable one, there can be mentioned 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.

[0191] Li 1-x M x (AO4)·····(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.) Note that the value of x in the general formula (1) is selected so that the valence of the entire general formula (1) becomes 0 in accordance with the valences of M and A.

[0192] Specific examples of the olivine-type lithium-containing phosphate compound include LiFePO4, LiCoPO4, LiMnPO4, Li 0.90 Ti 0.05 Nb 0.05 Fe and the like. Among these, LiFePO4 (lithium iron phosphate) is particularly preferable because the iron compound as a raw material is easily available and inexpensive. 0.30 Co0.30Mn 0.30 PO4 and the like. Among these, LiFePO4 (lithium iron phosphate) is particularly preferable because the iron compound as a raw material is easily available and inexpensive.

[0193] As the positive electrode active material, organic compounds such as polyaniline, polypyrrole, polyacene, disulfide-based compounds, polysulfide-based compounds, and N-fluoropyridinium salts can also be used.

[0194] The physical properties of the positive electrode active material are determined from the required items in the battery design and manufacturing process due to constraints such as the usage form of the lithium-ion battery. In the production of the positive electrode material, process design and the like are carried out so as to realize its physical properties. Examples of the physical property values include powder particle size and distribution, specific surface area, density, and the like.

[0195] 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 value of 1 to 30 μm is generally preferred, and 1 to 10 μm is even more preferred.

[0196] These positive electrode active materials can be used individually or in combination of two or more types.

[0197] (Positive electrode: conductive material) Since the above-mentioned positive electrode active material generally has low electronic conductivity, it is preferable to include a conductive material to assist electronic conductivity within the positive electrode, and the carbon material of the present invention is suitably used for this purpose. The amount of the carbon material of the present invention used is appropriately selected depending on the purpose of use, but is usually 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 positive electrode active material.

[0198] In the present invention, in addition to the carbon material of the present invention described above, other conductive materials can be combined as conductive materials. Examples of other conductive materials include carbon-based materials such as graphite, 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.

[0199] These other conductive materials can be used individually or in combination of two or more. The amount of other conductive materials used is appropriately selected according to the intended use and within the range of use of the carbon material of the present invention described above. The ratio of the carbon material of the present invention to the other conductive materials is appropriately selected according to the intended use and is typically in the range of 10:90 to 90:10 by weight ratio of [carbon material of the present invention] to [other conductive materials], preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0200] Furthermore, among the above, the carbon material of the present invention can be made even more effective when combined with conventionally used conductive materials. For example, carbon blacks such as acetylene black are composed of linked structural particles with a diameter of several tens of nanometers. On the other hand, carbon does not have high crystallinity, its structural length is short, and it is easily broken down, making it poor at long-distance electron transport. By combining it with the carbon material of the present invention, it is possible to realize a system that maintains electron conductivity and ion supply ability, whether the three-dimensional structure is maintained or the three-dimensional structure is flattened into a flaky graphite-like state.

[0201] (Positive electrode: Binder) The binder used is a component that helps bond the positive electrode active material, conductive material, and electrode current collector, and is usually an organic polymer. Examples include fluororesins such as polyvinyl fluoride, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene; nitrile 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; ring-containing polymers such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone; and acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl polyacrylate, polyethyl polyacrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide. Modified or derivative products of the above organic polymers may also be used.

[0202] Among these binders, fluororesins are preferred, and PVDF is particularly preferred. The weight-average molecular weight of these binders can be appropriately selected depending on the intended use, for example, in the range of 10,000 to 8,000,000, preferably 50,000 to 5,000,000, more preferably 80,000 to 3,000,000, and even more preferably 100,000 to 1,000,000. If the weight-average molecular weight of the binder is excessively small, the strength of the coating film will decrease, and if it is excessively large, the viscosity will increase, making electrode formation difficult, both of which are undesirable.

[0203] These binders can be used individually or in combination of two or more, and the amount used can be appropriately selected according to the purpose of use. Usually, it 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, still more preferably 0.2 to 1.5 parts by weight, and most preferably 0.5 to 1.5 parts by weight with respect to 100 parts by weight of the positive electrode active material. When the amount of the binder used is within this range, the adhesive force between the electrode active materials and between the electrode active material and the conductive material can be improved, and thus the bonding force with the electrode current collector can be improved, which is suitable.

[0204] (Positive electrode: Slurry) The electrode-forming slurry used is a mixture obtained by blending the above positive electrode active material, conductive material, binder, and other compounding agents as required and mixing them in a dispersion medium. Other compounding agents can be appropriately selected according to the purpose of use, and those usually used in lithium-ion secondary batteries can be used within the normal range of use.

[0205] The dispersion medium used is not particularly limited. For example, in order to sufficiently and uniformly distribute the binder and form a coating film of the slurry with a predetermined size, a medium that dissolves only the binder and does not dissolve other materials can be preferably used. Specifically, for example, organic solvents such as dimethylformamide, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, or water can be used, and one of these alone or a mixed solvent of two or more can be used.

[0206] When polyvinylidene fluoride (PVDF) is used as the binder, dimethylformamide or N-methyl-2-pyrrolidone (NMP) is preferable as the dispersion medium, and NMP is particularly preferable.

[0207] The solid content concentration excluding the dispersion medium of the slurry for electrode formation may be appropriately selected according to the coating method of the slurry onto the electrode, and is usually in the range of 10 to 90% by weight, preferably 20 to 80% by weight, more preferably 40 to 80% by weight, still more preferably 40 to 70% by weight, and most preferably 50 to 65% by weight.

[0208] The viscosity of the slurry for electrode formation is not particularly limited, but under the temperature condition of 24 to 26 °C, it is usually 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, still more preferably 10,000 to 35,000 cP, and most preferably 10,000 to 30,000 cP. When the viscosity of the slurry for electrode formation is within this range, while the solid content excluding the dispersion medium is uniformly dispersed, it is suitable for coating the electrode current collector with the slurry for electrode formation in a uniform thickness.

[0209] (Current collector and positive electrode) The positive electrode can be manufactured by coating the above slurry for electrode forming on a current collector and drying it. The current collector is not particularly limited as long as it is commonly used, and examples include aluminum foil, nickel foil, titanium foil, stainless steel foil, etc., and rolled aluminum foil is particularly preferred.

[0210] As a method for coating the slurry for electrode formation on the current collector, generally used printing techniques can be utilized. When the thickness dimension of the coating film is small, gravure printing etc. are used, and when it is large, printing methods such as doctor blade printing and die printing are preferably used. Thereafter, the coating film is dried by heating, and any drying method can be used, and a method capable of achieving the binding strength by the desired binder is preferably used.

[0211] And then, when the positive electrode is formed into a predetermined dimension, industrially available cutting blades etc. and their methods are preferably used. Also, in order to achieve a predetermined density, industrially available pressing devices etc. and methods are preferably used as necessary.

[0212] <Negative electrode>e Next, the negative electrode will be described. The negative electrode is obtained by coating, for example, a slurry in which a negative electrode active material, a conductive material, a binder, and a dispersion medium are mixed onto a current collector metal foil such as rolled copper foil, heating and drying to remove the solvent, and then forming it into a predetermined size and density.

[0213] (Negative electrode: active material) As the negative electrode active material, those that can bind and stabilize lithium ions and electrons flowing from the external circuit and have a large number of stabilization sites inside are preferred. For example, those originating from organic substances, whether highly crystalline or lowly crystalline, can all be used, and graphite, coke, amorphous carbon, hard carbon, polymer carbon, etc. can be preferably used. In this case, in principle, lithium ions are sandwiched between graphene layers or the like and combined with electrons to be stabilized. In addition, as another stabilization mechanism, a method of electrochemically forming an intermetallic compound can also be used, and silicon, tin, zinc, bismuth, antimony, cadmium, lead, germanium, etc. can be preferably used. In addition, other materials showing a low electrochemical reaction potential that control the negative electrode side of the lithium ion battery can also be used. Preferably, compounds of metals and oxygen, sulfur, halogen, nitrogen, phosphorus, etc. are exemplified.

[0214] 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, or Al alloys; metal oxides capable of doping and undoping lithium, such as SiOx (0 < x = 2), SnO2, vanadium oxides, and lithium vanadium oxides; and composites containing the metallic compound and the carbonaceous material, such as Si-C composites or Sn-C composites.

[0215] As the negative electrode active material, a metallic lithium thin film may also be used. Furthermore, the carbonaceous material may be either low-crystalline carbon or high-crystalline carbon. Typical low-crystalline carbons include softened carbon and hardened carbon, while high-crystalline carbons include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, quiche graphite, pyrolysis carbon, mesophase pitch carbon fibers, mesocarbon microspheres, mesophase pitch, and high-temperature calcined carbon such as petroleum and coal-based coke.

[0216] The physical properties of the negative electrode material are determined by requirements in the device design and manufacturing process (e.g., storage batteries) due to constraints such as the usage patterns of lithium-ion batteries. In material manufacturing, process design and other measures are implemented to achieve these physical properties. Examples of physical properties include powder particle size and distribution, specific surface area, and density.

[0217] 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 value of 1 to 70 μm is usually preferred, and 3 to 30 μm is more preferred.

[0218] These negative electrode active materials can be used individually or in combination of two or more. There are no particular limitations on the proportion of negative electrode active material in the electrode forming slurry, but it is usually in the range of 95.5 to 99.5 parts by weight, preferably 96 to 99 parts by weight, and more preferably 97 to 98 parts by weight, per 100 parts by weight of solid content excluding the dispersion medium. When the negative electrode active material content is within this range, a high balance of battery capacity, conductivity, and adhesion is achieved, which is preferable.

[0219] (Negative electrode: conductive material) The carbon material of the present invention may be used as a carbonaceous material for the negative electrode active material, but it can be suitably used as a conductive material for the negative electrode active material. For example, although the negative electrode active material generally has high electronic conductivity, some materials have a smooth surface, and when contact between particles is insufficient, the carbon material of the present invention can be used as a conductive material to support electronic conductivity. Furthermore, while flake-shaped graphite and artificial graphite used as negative electrode active materials have high electronic conductivity, they have low ion storage capacity and poor ionic conductivity. By combining these with the carbon material of the present invention, it is possible to construct a good battery reaction support system that adds ionic conductivity to electronic conductivity. Moreover, even when the three-dimensional structure of the negative electrode active material is crushed and flattened like flake-shaped graphite, adding the carbon material of the present invention is suitable because it can add ionic conductivity while maintaining electronic conductivity.

[0220] The proportion of the carbon material of the present invention in the electrode forming slurry is typically 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 solid content excluding the dispersion medium. When the content of the carbon material of the present invention is within this range, the high-speed discharge characteristics, life characteristics, capacity characteristics, and charge-discharge characteristics of the lithium-ion secondary battery can be greatly enhanced, making it preferable.

[0221] In the present invention, the carbon material of the present invention can be used in combination with other carbon materials. Other carbon materials are not particularly limited as long as they are conventional materials used as electrode materials. Examples include acetylene black, Ketjen black, lamp black, furnace black, carbon black, graphite, carbon fiber, graphite fiber, nanofiber, nanotube, coke, hard carbon, amorphous carbon, and the like.

[0222] These other carbon materials can be used individually or in combination of two or more, and the amount used is selected according to the purpose of use, and can usually be used within the same range as the carbon material of the present invention described above. The ratio of the carbon material of the present invention to the other carbon materials is usually in the range of 10:90 to 90:10 by weight ratio of [carbon material of the present invention]:[other carbon materials], preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0223] By combining these conventional materials with the carbon materials of the present invention, further benefits can be obtained. For example, highly linear carbon nanotubes have high electronic conductivity but low ion storage capacity. Therefore, by combining them with the carbon materials of the present invention, it is possible to construct a good battery reaction support system that adds ionic conductivity to electronic conductivity. Also, carbon blacks such as acetylene black are composed of linked structural particles with a diameter of several tens of nanometers. On the other hand, carbon does not have high crystallinity, its structural length is short, and it is easily broken down, making it poor at long-distance electron transport. Despite these properties, by combining them with the carbon materials of the present invention, it is possible to realize a system that maintains its three-dimensional structure while also possessing ion supply capabilities.

[0224] (Negative electrode: Binder) The binder used is a component that helps to bond the electrode active material, conductive material, and electrode current collector. Examples include fluororesins such as polyvinyl fluoride, polyvinylidene fluoride, 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 polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; ring-containing polymers such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone; acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl polyacrylate, polyethyl polyacrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide; carboxymethylcellulose; and styrene-butadiene rubber. Modified or derivative products of the above organic polymers may also be used.

[0225] Among these binders, carboxymethylcellulose and styrene-butadiene rubber are preferred. The weight-average molecular weight of these binders can be appropriately selected depending on the intended use, for example, in the range of 10,000 to 8,000,000, preferably 50,000 to 5,000,000, more preferably 80,000 to 3,000,000, and even more preferably 100,000 to 1,000,000. If the weight-average molecular weight of the binder is too small, the strength of the coating film will decrease, and if it is too large, the viscosity will increase, making electrode formation difficult, which is undesirable.

[0226] These binders can be used individually or in combination of two or more kinds. The usage amount is appropriately selected according to the purpose of use. With respect to 100 parts by weight of the positive electrode active material, it is usually in the range of 0.01 to 4 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2.5 parts by weight, still more preferably 0.2 to 2 parts by weight, and most preferably 0.5 to 1.5 parts by weight. When the usage amount of the binder is within this range, the adhesive force between the electrode active materials and between the electrode active material and the conductive material can be improved, and thus the binding force with the electrode current collector can be improved, which is suitable.

[0227] These binders can be used individually or in combination of two or more kinds. The ratio in the slurry for electrode formation is usually in the range of 0.5 to 3 parts by weight, preferably 0.8 to 2.5 parts by weight, more preferably 1 to 2.2 parts by weight with respect to 100 parts by weight of the solid content excluding the dispersion medium. When the content of the binder in the slurry for electrode formation is within this range, the adhesive force between the between the electrode active materials and between the electrode active material and the conductive material can be improved, and thus the binding force with the electrode current collector can be improved, which is suitable.

[0228] (Negative electrode: dispersion medium) The dispersion medium used is not particularly limited as long as it is a solvent generally used in the technical field. 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 of these alone or a mixed solvent of two or more may be used. The dispersion medium is used to dissolve or disperse the electrode active material, conductive material, and binder in consideration of the coating thickness of the slurry for electrode formation and the production yield.

[0229] (Negative electrode: slurry) There are no particular limitations on the amount of dispersion medium used, but for example, the concentration of solids including the electrode active material, conductive material, and binder is usually adjusted to be in the range of 10 to 90% by weight, preferably 20 to 80% by weight, more preferably 30 to 75% by weight, even more preferably 40 to 70% by weight, and most preferably 50 to 65% by weight.

[0230] (Current collector and negative electrode) There are no particular limitations on the current collector for the negative electrode, but for example, a material that does not exhibit electrochemical reactivity to the potential generated by the negative electrode is used. Specifically, examples include copper foil, nickel foil, titanium foil, and stainless steel foil, with electrolytic copper foil and rolled copper foil being preferred.

[0231] For applying the electrode-forming slurry onto the current collector, commonly used printing techniques can be employed. For small thicknesses, gravure printing is preferable, while for larger thicknesses, doctor blade printing or die printing are more suitable.

[0232] Subsequently, the coating film is heat-dried. Any drying method is available, and a method that achieves the desired bonding strength with the binder is preferably used. Then, when forming the negative electrode to the predetermined dimensions, industrially available cutting blades and methods are preferably used. Furthermore, to achieve the predetermined density, industrially available pressurizing devices and methods are preferably used as needed.

[0233] <Lithium-ion rechargeable battery> Next, the lithium-ion secondary battery according to the present invention will be described. The lithium-ion secondary battery of the present invention is characterized by containing the carbon material of the present invention. Specifically, it includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode uses the electrode (positive electrode and / or negative electrode) of the present invention described above. On the other hand, the lithium-ion secondary battery may further selectively include a battery container that houses the electrode assembly consisting of the positive electrode, negative electrode and separator, and a sealing member that seals the battery container. On the other hand, the positive electrode and the negative electrode are the same as described above, so a detailed explanation will be omitted.

[0234] (Separator) The separator used separates the negative and positive electrodes and provides a pathway for lithium ions to move. Any separator commonly used as a separation membrane in lithium-ion secondary batteries can be used without particular limitations, but one that has low resistance to electrolyte ion movement while having excellent electrolyte impregnation ability is particularly preferred.

[0235] Specifically, porous polymer films are used, for example, porous polymer films made from polyolefins such as polyethylene, polypropylene, polybutene, polyvinyl chloride, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separation membranes containing ceramic components or polymeric substances may be used, and may be used selectively in single-layer or multi-layer structures.

[0236] Polyethylene and polypropylene are particularly suitable materials for porous polymer films. Polyethylene has a relatively low melting point, and when the battery temperature rises for any reason (for example, due to an unsafe condition such as a short circuit), the pores in the film become blocked by thermal melting, inhibiting the movement of driving ions, thereby stopping the reaction and ensuring safety. Polypropylene is also suitable as a material that can be stretched and made porous without the use of plasticizers.

[0237] Furthermore, polymer compounds can be applied to both sides of the separator before use. Examples of such polymer compounds include ether-based polymer compounds such as polyvinyl formal, polyethylene oxide, and crosslinked polyethylene oxide; ester-based polymer compounds such as polymethacrylate; acrylate-based polymer compounds; and fluorine-based polymer compounds such as polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene copolymer. Among these, it is particularly desirable to use fluorine-based polymer compounds such as polyvinylidene fluoride from the viewpoint of preventing swelling during high-temperature storage.

[0238] (electrolyte) Typically, a non-aqueous electrolyte solution, in which an electrolyte is dissolved in an organic solvent, is used as the electrolyte.

[0239] -Electrolytes- For example, lithium salts are used as electrolytes. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, (C2F5SO2)NLi, LiN(CF3SO2)(C4F9SO2), LiC(CF3SO2)3, LiPF4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2, Licyclic 1,2-perfluoroethanedisulfonylimide, and cyclic 1,3-perfluoropropanedisulfonylimide. Among these, LiPF6, LiBF4, LiClO4, CF3SO3Li, LiN(CF3SO2)2, and LiN(C2F5SO2)2 are preferred because they are easily soluble in the solvent and exhibit a high degree of dissociation, with LiPF6 and LiBF4 being particularly preferred.

[0240] As the electrolyte, a gel-like electrolyte may be used that contains a polymer compound that swells in an organic solvent to form a retainer that holds the non-aqueous electrolyte. Including a polymer compound that swells in an organic solvent allows for high ionic conductivity, excellent charge-discharge efficiency, and prevention of battery leakage, making it preferable. The content of such polymer compound is preferably in the range of 0.1 to 10% by weight of the electrolyte.

[0241] These electrolytes can be used individually or in combination of two or more. The concentration of the electrolyte in the electrolyte solution is not particularly limited and can be adjusted as appropriate, usually in the range of 5 to 15% by weight, preferably 2 to 13% by weight, and more preferably 5 to 10% by weight.

[0242] -Organic solvents- The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the electrolyte, but solvents such as cyclic carbonates; linear carbonates; esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolanes and dimethyl sulfoxide are preferably used. These organic solvents can be used individually or in combination of two or more.

[0243] Among these, cyclic carbonates and linear carbonates are preferred because they have high dielectric constants and suitable viscosity and solvation capacity that affect lithium ion movement. Solvation capacity is the ability to dissociate dissolved ions; if it is too strong, it inhibits ion movement, so there is an optimal value.

[0244] Examples of cyclic carbonates include alkylene carbonates having alkylene groups with 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.

[0245] As for the chain-like carbonates, dialkyl carbonates are preferred, and the number of carbon atoms in each constituent alkyl group is preferably 1 to 5, and particularly preferably 1 to 4. Specifically, examples include symmetric chain-like alkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; and dialkyl carbonates such as asymmetric chain-like alkyl carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. Among these, dimethyl carbonate and diethyl carbonate are preferred from the viewpoint of viscosity and boiling point, and diethyl carbonate is particularly preferred.

[0246] Furthermore, practical lithium-ion batteries operate under a wide range of environmental conditions, and in particular, the physical properties of non-aqueous solvents, such as their melting and boiling points, must be kept within a certain range. Therefore, it is preferable to use a mixture of cyclic carbonates and linear carbonates. There are no particular limitations on the combination of cyclic carbonates and linear carbonates, but for example, a combination of ethylene carbonate and a linear carbonate is preferred. 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 preferred because they offer a good balance between cycle characteristics and high-power discharge characteristics.

[0247] The mixing ratio of cyclic carbonates and linear carbonates is appropriately selected according to the desired practical properties. For example, the weight ratio of [cyclic carbonates]:[linear carbonates] is usually 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.

[0248] The content of cyclic carbonates in the electrolyte is preferably 1 to 70% by weight, more preferably 3 to 30% by weight, and even more preferably 4 to 50% by weight. Multiple cyclic carbonates can be used in mixture form. The content of linear carbonates in the electrolyte is preferably 40 to 70% by weight, and even more preferably 43 to 68% by weight. Multiple linear carbonates can be used in mixture form.

[0249] As the organic solvent used in the electrolyte, fluorine-containing carbonates can also be suitably used. Specifically, examples include cyclic carbonates having one fluorine atom, chain carbonates having one fluorine atom, cyclic carbonates having two or more fluorine atoms, and chain carbonates having two or more fluorine atoms. From the viewpoint of improving battery characteristics, fluorine-containing cyclic carbonates having two or more fluorine atoms are preferred.

[0250] Specific examples of fluorine-containing cyclic carbonates having two or more fluorine atoms include, for example, 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.

[0251] These fluorine-containing carbonates can be used individually or in combination of two or more. While there are no particular limitations on the proportion of fluorine-containing carbonates in the electrolyte, it is typically in the range of 0.001 to 10% by weight, preferably 0.01 to 5% by weight, more preferably 0.1 to 2% by weight, even more preferably 0.2 to 1% or more by weight, and most preferably 0.25 to 0.5% by weight. If the fluorine-containing carbonate content is excessively low, the effect of the addition may not be readily apparent; conversely, if it is excessively high, the internal pressure of the battery may increase during high-temperature storage.

[0252] As the organic solvent used in the electrolyte, cyclic carbonates having unsaturated bonds or aromatic compounds with 7 to 18 carbon atoms may also be mixed into the electrolyte.

[0253] As cyclic carbonates having unsaturated bonds, vinylene carbonate, vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate, and 4,5-divinylethylene carbonate are preferred from the viewpoint of improving cycle characteristics, and among these, vinylene carbonate and vinylethylene carbonate are particularly preferred.

[0254] Aromatic compounds having 7 to 18 carbon atoms are suitable because they suppress the significant decrease in discharge characteristics after high-temperature storage by suppressing side reactions with the negative and positive electrodes. Examples of suitable aromatic compounds include biphenyl, alkylbiphenyl, terphenyl, terphenyl, and their partially hydrogenated forms, as well as cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran.

[0255] These cyclic carbonates having unsaturated bonds and aromatic compounds with 7 to 18 carbon atoms can be used individually or in combination of two or more, and the proportion of each in the electrolyte is usually in the range of 0.001 to 5% by weight, preferably 0.1 to 4% by weight, more preferably 0.3 to 3% by weight, even more preferably 0.4 to 2.5% by weight, and most preferably 0.5 to 2% by weight.

[0256] (Manufacturing method for lithium-ion secondary batteries) A lithium-ion secondary battery according to the present invention can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator in between, winding or folding them as needed according to the battery shape, placing them in a battery container, injecting an electrolyte into the battery container, and sealing it. To prevent pressure rise inside the secondary battery, overcharge and discharge, etc., an overcurrent prevention element such as a fuse or PTC element, expanded metal, lead plates, etc. may be provided as needed. The shape of the secondary battery may be any of the following: coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc.

[0257] <Application> The carbon material of the present invention can exhibit its functionality and be effectively utilized in any electrochemical device other than the lithium-ion secondary battery described above. Specifically, it has functions such as acting as an internal conductive path in electrodes when electron transfer is involved in device reactions, providing reinforcement when electrodes undergo physical deformation, and preventing direct contact between a third material (such as a catalyst) and the reaction material by utilizing the durability of graphene when the reaction material is in an oxidized or reduced state.

[0258] Examples of usable devices include non-aqueous electrolyte batteries such as lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, calcium-ion batteries, aluminum-ion batteries, lithium-sulfur batteries, and lithium-air batteries; inorganic solid electrolyte batteries such as sulfide-based solid electrolytes and oxide-based solid electrolytes; polymer solid electrolyte batteries such as polyethylene oxide-based batteries; and semi-solid batteries such as polymer gel electrolyte batteries in which electrolyte is impregnated into PVDF.

[0259] These devices utilize readily graphitizable carbon, non-graphitizable carbon, graphite, lithium alloy materials such as silicon and tin, and other metallic materials such as lithium as negative electrode active materials. Similarly, lithium-containing metal oxides, particularly lithium-containing transition metal oxides with layered, spinel, or olivine structures, lithium-free metal oxides, organic positive electrode materials, charge-transfer complex positive electrode materials, sulfur, and fluoride-based materials are used as positive electrode active materials. The carbon material of the present invention is capable of effectively enhancing conductivity for any of these active materials. Furthermore, the carbon material of the present invention is also suitable as a material for lithium-sulfur batteries, as described in publications such as WO2018 / 225619, JP 2023-501679, JP 2019-517116, and JP 2022-191280.

[0260] The carbon material of the present invention can also be suitably used in organic electrolyte capacitors, aqueous electrolyte capacitors, and aqueous solution batteries. In fuel cells, it can be used in PEFCs, SOFCs, DMPCs, etc., and in particular, it can be used not only to impart conductivity to electrodes but also as a support for oxidation-reduction catalysts.

[0261] The carbon material of the present invention can be used for applications other than electrochemical devices. Other suitable applications include, for example, electronic device systems other than the above-mentioned devices such as graphene-based sensors, electromagnetic interference suppression materials, antenna modules, heat dissipation substrates, heat exchange devices, separation membranes, reverse osmosis membranes, transparent electrode materials, structural materials that take advantage of mechanical flexibility, and conductive inks and pastes.

[0262] Furthermore, in response to the growing demand for vehicle weight reduction, which directly contributes to reducing carbon dioxide emissions and conserving energy, this material is suitable for applications that leverage its hollow shape and other properties to achieve weight reduction, such as reinforcing agents for various types of rubber including tires, paints, coloring pigments, conductive fillers for various polymers, and additives for magnetic recording media. [Examples]

[0263] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%", "ppm", and "parts" used to express quantities refer to weight unless otherwise specified.

[0264] Various physical properties were evaluated according to the following method.

[0265] <Basic characteristics> (Number of carbonaceous layers) The number of carbonaceous layers in the carbon material was calculated from the amount of carbon deposited during manufacturing in the examples and reference examples. Specifically, it was determined by thermogravimetric analysis (TGA) measurement. Using STA-2500 (NETZSCH), the material was heated to 900°C at a heating rate of 5°C / min under the flow of argon gas (80 mL / min) and oxygen (20 mL / min), then cooled at a cooling rate of 20°C / min, and TG measurement was performed. Blank measurement results were subtracted using empty pans under the same temperature profile conditions. A Pt pan was used for the sample obtained using MgO (Reference Example 2), and an alumina pan was used for the others. From the carbon weight loss rate (%) obtained by TG measurement, the average number of carbon layers was calculated as follows. From the carbon weight loss rate, the weight of the carbon layer per unit mass of the mold (W) g Calculate (g-carbon / g-template) and determine the weight W of this carbon layer. g and the specific surface area SA of the template particles temp (g / m 2 ) Weight W of the carbon layer per unit area of ​​the mold a (g / m 2 Next, calculate W. a The weight of the carbon layer per unit area of ​​single-layer graphene is W graphene (7.61 × 10 -4 g / m 2 The average number of layers was calculated by dividing by ). Average number of layers = W a / W graphene

[0266] <Nitrogen adsorption / desorption measurement> (Specific surface area, pore volume, mode pore diameter) Nitrogen adsorption and desorption measurements of carbon materials were performed using an automated specific surface area / pore size distribution analyzer (BELSORP MINI, manufactured by Microtrac-Bel Co., Ltd.). Before measurement, the samples were dried under reduced pressure at 150°C for 6 hours using BEL pre. The BET specific surface area was determined using the BET method from the adsorption isotherms obtained from the nitrogen adsorption and desorption measurements. The applicable range of the BET method was set to P / P0 = 0.05 to 0.3. Based on the adsorption and desorption isotherms, the total pore volume was measured by converting the amount of nitrogen adsorbed at a relative pressure of P / P0 = 0.99 at -196°C to the volume of liquid nitrogen density. The pore size distribution was determined by the BJH method. The average pore size d was determined assuming cylindrical pores, using the BET specific surface area S and total pore volume V as d = 4V / S. In addition, the mode diameter of the mesopore region of the pore size distribution was determined.

[0267] The applicable range for each pore volume measurement is as follows. Total pore volume: P / P0 = 0.99 Pore ​​volume less than 10 nm: P / P0 = ~0.79 Pore ​​volume above 10 nm: P / P0 = 0.79~0.99 Micropore volume: P / P0 = ~0.1 Mesopore volume: P / P0=0.1~0.96 Macropore volume (pores larger than 50 nm): P / P0 = 0.96~0.99

[0268] <Structural analysis> Shape indices and aggregate shape determination methods are indicators of the structural complexity of carbon materials. Shape indices are obtained by statistically analyzing various parameters obtained from image analysis of transmission electron microscope images of monodisperse materials.

[0269] (Transmission electron microscope observation) The shape of the carbon material was observed using a transmission electron microscope (JEM-2100Plus model, manufactured by JEOL Ltd.). The carbon material was observed using a transmission electron microscope (TEM) at an acceleration voltage of 80–100 kV.

[0270] (Raman spectroscopy measurement) Raman spectroscopy of carbon materials was performed using a micro-Raman spectrometer (LabRAM HR-800, Horiba, Ltd.). A 532 nm laser was used, with the filter set to D1 and the hole size to 100 μm. The measurement range was 300–3500 cm². -1 This was determined from the measured Raman spectrum. 2D / I G , I G / I 2D and I D / I G The intensity ratio was calculated.

[0271] (XRD measurement) X-ray diffraction (XRD) measurements were performed on carbon materials using an X-ray diffractometer (Miniflex600, manufactured by Rigaku Corporation). A Si non-reflective plate was used as the sample stage, and the sample was placed on the circular part. Measurements were taken under the following conditions, and the values ​​of d002 and Lc were determined. X-ray source:CuKa Tube voltage: 40kV Tube current: 15mA Measurement angle: 5~90deg Scan speed: 2deg / min Scan axis: 2θ / θ

[0272] <Image Analysis> (Shape index and morphological classification of aggregates) Regarding the shape index of the primary structure of carbon materials, various parameters were calculated using values ​​obtained from image analysis of TEM images of carbon materials.

[0273] First, to obtain images for image analysis, a sample for TEM observation was prepared. A small amount of carbon material sample (about one level scoop using a high-mine style spatula) was placed in a 20cc vial, 10mL of ethanol was added, and the mixture was dispersed in an ultrasonic disperser for 10 minutes. One drop of the dispersed carbon material sample solution was placed onto a TEM coated grid using a Pasteur pipette, and the grid was placed in a vacuum dryer and dried until the solvent had completely evaporated.

[0274] The prepared grid sample was set in a TEM and imaged so that multiple single primary structures were present within the same field of view. If the primary structures overlapped or aggregated during TEM observation, this was due to the dispersion being too concentrated. In such cases, ethanol was added to the dispersion to dilute it, and the dispersion was dispersed in an ultrasonic disperser for several minutes. The above procedure for preparing a TEM observation sample was then repeated. Figures 1 and 2 of ASTM D3849-22 were used as a guideline for determining whether the dispersion was appropriate.

[0275] The acquired TEM images were analyzed using an image analysis system (image processing, particle analysis, and length measurement software, MultiImageTool, manufactured by System Infrontia Co., Ltd.) to determine the maximum length L, minimum width W, projected area A, perimeter P, and envelope area A for approximately 1000 primary structures of carbon material. C The output was as follows. The image analysis was performed at a resolution of 6nm or less per pixel, and to reliably capture the morphological information of the primary structure, the area was set to 500nm. 2 Objects smaller than this were excluded from the analysis.

[0276] (shape index) Using values ​​obtained from image analysis, the circularity, ML2 / A, and PM2 / A of each primary structure were calculated and evaluated using the following formulas. Circularity = 4π × A / P 2 ML2 / A=L 2 ×π / (4×A) PM2 / A=P 2 / (4π×A)

[0277] The circularity is measured by comparing the circumference to a circle whose circumference is equal to its perimeter; a value closer to 1 indicates a more circular shape, while a value closer to 0 indicates a higher level of complexity. The shape factor ML2 / A is measured by comparing the diameter to a circle whose diameter is equal to its maximum length; a value closer to 1 indicates a more circular or square shape. The shape factor PM2 / A is measured by comparing the circumference to a circle whose circumference is equal to its perimeter; a value closer to 1 indicates a less irregular shape.

[0278] (morphological classification) Regarding the morphological classification of primary structures of carbon materials, we classified them into four morphologies by analyzing various parameters obtained from image analysis of TEM images of carbon materials. The specific analysis method is as follows.

[0279] The parameters of the primary structures used in the analysis were the same values ​​used for calculating the shape index. The anisotropy X, complexity Y, and envelope Z of each primary structure were calculated from the output values ​​of the image analysis device and the following formula. X = L / W Y = (1 / 4π) × (P 2 / A) Z=A C / A

[0280] Next, using the above X, Y, and Z, similar to the following literature which performed structural analysis of complex carbon black aggregates, we classified the primary structural forms of carbon materials into four types (Linear, Spheroidal, Ellipsoidal, Branched) and calculated the relative abundance of each form. K.Ono et al,Influence of furnace temperature and residence time on configurations of carbon black,Chemical Engineering Journal 200-202 (2012) 541-548 Linear: 1.7 <X Spheroidal: X ≤ 1.7 and Y ≤ 1.2 Ellipsoidal: X ≤ 1.7, 1.2 <YかつZ≦1.3 Branched: X ≤ 1.7, 1.2 <Yかつ1.3<Z

[0281] <Particle characteristics> (Particle size distribution measurement) The aggregation state of carbon materials was investigated by measuring the particle size distribution using a laser diffraction particle size distribution analyzer (MT3300EXII, manufactured by Microtrac-Bell Co., Ltd.). The measurement sample was prepared by immersing the unground carbon material in ethanol for 9 minutes. The median diameter D50, particle size D10, and particle size D90 were determined in the particle size distribution curve.

[0282] <General characteristics> (Oil absorption measurement) The oil absorption of the carbon material was measured in accordance with "JIS K5101-13-1 Pigment Test Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method".

[0283] (Bulk density) The bulk density of the carbon material was measured in accordance with JIS K6219-2.

[0284] (Number density) The number density P of a carbon material is given by the volume V (m³) per primary particle. 3 ) and carbon density ρ(g / m³) 3 ) can be calculated using the following formula. P = 1 / (V × ρ) Here, the carbon density ρ can be the true density of graphite, which is 2.2 g / cc. V(m 3 ) can be calculated from the following formula. V = n × (D1 - D0) 3 / 6 Here, D0 is the diameter of the hollow portion of the primary particle, and D1 is the outer diameter of the primary particle. D0 can be obtained using the mode pore diameter described above. D1 can be obtained by adding twice the value obtained by multiplying D0 by the average number of layers n and the average interplanar spacing obtained from the 002 diffraction line to the mode diameter. Alternatively, D1 may be obtained by TEM image analysis or other methods. Furthermore, for solid carbon materials, calculations can be performed with D0=0. For example, for the known DENKA BLACK Li-100, the particle outer diameter (D1) was calculated with an average primary particle diameter of 35 nm and D0=0.

[0285] (Apparent density) The apparent density of the carbon material was calculated using the total pore volume and true density from the following formula. Apparent density (g / cc) = 1 / (Total pore volume + (1 / True density)) The total pore volume (cc / g) was calculated using the formula P / P0 = 0.99, and the true density used was the graphite value of 2.2 g / cc.

[0286] (Measuring combustion temperature) In a combustion oxidation test conducted using a thermogravimetric analyzer under air circulation and a heating rate of 5°C / min, the combustion temperature was defined as the temperature at which the weight became 90% of the initial weight.

[0287] (ash content measurement) The carbon material was dried in a vacuum dryer under reduced pressure at 150°C for 2 hours, then cooled and weighed in a magnetic crucible (W). s Next, it was placed in a muffle furnace and weighed after burning at 900°C for 1 hour (W i ), crucible tare (W c Subtract the ash content ((W i -W c ) / W s The percentage :% was calculated.

[0288] Various performance evaluations were conducted according to the following methods.

[0289] <Evaluation of conductivity> The electrical conductivity of carbon materials was evaluated by measuring the electrical conductivity of the powder under uniaxial compression with lateral constraint. A dry sample was filled into a cylindrical container consisting of an insulating cylinder and a negative electrode. A positive electrode was inserted into the insulating cylindrical container filled with the sample, and the sample was placed on a force gauge stand, sandwiched between the negative and positive electrodes. A spring-type force gauge mounted on the force gauge stand was lowered, applying a pressure of 10 MPa to the sample in the cylindrical container and compressing it. The height of the sample after compression was measured, and the resistance value of the sample was measured using a digital multimeter connected to the positive and negative electrodes. The electrical conductivity of the powder during compression was calculated from the obtained resistance value, the filled cross-sectional area of ​​the sample, and the height of the compressed sample. The evaluation was performed according to the following criteria. ◎:18S / cm or more ○: 15S / cm or more and less than 18S / cm △: 12S / cm or more and less than 15S / cm ×: Less than 12S / cm

[0290] <Positive electrode evaluation> Each test battery was energized to 4.2V with a constant current of 1.25mA (equivalent to 0.2C), and after reaching 4.2V, it was charged at a constant voltage until it reached 0.31mA (0.05C). Then, it was discharged to 3V with a constant current of 1.25mA. The charge capacity, discharge capacity, and average voltage were calculated, and the Coulomb ratio (discharge capacity ÷ charge capacity) was determined. Next, using the same test battery, it was energized to 4.2V with a constant current of 1.25mA (equivalent to 0.2C), and after reaching 4.2V, it was charged at a constant voltage until it reached 0.31mA (0.05C). Then, it was discharged to 3V with a high-rate constant current of 12.5mA (equivalent to 2C). From the discharge capacity of the obtained test batteries, the 2C maintenance rate (2C capacity ÷ 0.2C capacity) for each test battery was calculated. The results are shown in Table 1.

[0291] (Battery characteristics) The rapid discharge characteristics were evaluated by assessing the calculated 2C maintenance rate according to the following criteria. ◎: Over 70% ○: Over 50% up to 70% △: Over 30% up to 50% ×: 30% or less

[0292] The charging capacity of the capacity characteristics was evaluated based on the average value according to the following criteria. ◎:160mAh / g or more ○: 150mAh / g or more and less than 160mAh / g △: 140mAh / g or more and less than 150mAh / g ×: Less than 140mAh / g

[0293] The discharge capacity of the capacity characteristics was evaluated based on the average value according to the following criteria. ◎:135mAh / g or more ○: 130mAh / g or more and less than 135mAh / g △: 125mAh / g or more and less than 130mAh / g ×: Less than 125mAh / g

[0294] The charge and discharge characteristics were evaluated based on the initial Coulomb rate according to the following criteria. ◎: 80% or more ○: 70% or more but less than 80% △: 60% or more but less than 70% ×: Less than 60%

[0295] <Example 1> (Manufacturing of carbon materials) -CVD reaction: carbon layer formation- Fumed silica (SiO2 / AEROSIL(registered trademark) NX90G; particle size 38 nm, BET specific surface area 71 m²) is used as a template for carbonaceous films. 2 Approximately 1 g of (manufactured by Nippon Aerosil Co., Ltd., total pore volume 0.138 cc / g, oil absorption 199 mL / 100 g, D10: 27.6 μm, D50: 49.4 μm, D90: 93.7 μm, carbon content 0.5-1.5%) was spread on a quartz boat and set in the center of a quartz reaction tube in a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). Argon gas was flowed into the reaction tube at a flow rate of 400 mL / min while heating to 900 °C at a heating rate of 10 °C / min and held for 30 minutes. While maintaining 900 °C, argon gas was flowed at a flow rate of 320 mL / min while methane gas was flowed at a flow rate of 80 mL / min (raw material gas concentration 20%) and held for 90 minutes. After that, the carbonaceous-template laminate was removed while cooling to room temperature while argon gas was flowed at a flow rate of 400 mL / min. At this time, electron microscopy confirmed that the template was an aggregate in which primary particles were linked together in a bead-like manner with multiple branching structures.

[0296] -Mold removal- Next, the template was removed from the resulting laminate by the following procedure to obtain the carbon material. (1) The carbonaceous template laminate was placed in a 100 mL PFA beaker, and ultrapure water was added until the entire sample was wet. (2) After adding 46% hydrofluoric acid, the mixture was stirred with a stirrer for 2 hours. (3) After stirring was stopped, the sample was left to stand until it settled. (4) Using a PTFE membrane filter (47 mmφ, pore size 0.1 μm), the supernatant was filtered by suction. (5) The sample on the filter paper was washed with approximately 39 mL of ultrapure water and filtered by suction. This procedure was repeated three times. (6) The sample on the filter paper was collected and returned to the original PFA beaker. (7) Repeated the operations in (2) to (6). (8) Add approximately 40 mL of ultrapure water and stir with a stirrer for 1 hour. (9) After stirring was stopped, the sample was allowed to stand until it settled. (10) Discard the supernatant, add 5% caustic soda, and stir for 12 hours while heating to 80°C. (11) After stirring was stopped, the sample was allowed to stand until it settled. (12) Using a PTFE membrane filter (47 mmφ, pore size 0.1 μm), the supernatant was filtered by suction. (13) The sample on the filter paper was washed with ultrapure water and filtered by suction. This procedure was repeated until the filtrate was neutral. (14) The sample on the filter paper was collected in a Petri dish and dried in a 110°C oven for 8 hours.

[0297] -Heat treatment- The carbon material obtained above was placed in a rectangular high-temperature heating furnace (manufactured by Izumi Tech Co., Ltd.) under reduced pressure (10 -1 After heating to the Pa order, the material was heated to 1800°C under argon gas flow (10 mL / min) at a heating rate of 15°C / min and held at that temperature for 1 hour for calcination. After cooling to room temperature, the calcined carbon material was removed to obtain carbon material A containing heat-treated graphene. Using the obtained carbon material A, basic properties, nitrogen adsorption / desorption measurements, Raman spectroscopy measurements, XRD analysis, image analysis, particle size distribution measurements, TDP-MS measurements, general properties, and conductivity evaluations were performed, and the results are shown in Table 1.

[0298] (Fabrication of positive electrode) The cathode active material is a ternary cathode material NCM (LiNi) with an average particle size of 8 μm. 0.5 Co 0.2 Mn 0.396.5% of the active material (manufactured by Kelong), 0.5% of the above-mentioned carbon material A as a conductive material, and 3% by weight of PVDF (manufactured by Kureha Corporation) were mixed with N-methyl-pyrrolidone (NMP) as a solvent. The conductive material used was a dispersion of carbon material A dispersed in NMP solvent. The mixture of the active material, conductive material, and PVDF was placed in a planetary mixer and kneaded at a rotation speed of 2000 rpm while adding NMP in several batches until homogeneous, to prepare a cathode slurry. This slurry was applied to 15 μm thick aluminum foil at a constant speed using a doctor blade coating device with a micrometer. Then, it was dried in a vacuum dryer set to 110°C to obtain a cathode base. Subsequently, the cathode base was punched out using a φ15 mm punch-type die-cutting machine, pressurized with 45 kN using a cylinder-type jig, and then vacuum dried at 120°C to obtain a cathode electrode for battery integration.

[0299] (Manufacturing of lithium-ion secondary batteries) Using the positive electrode prepared as described above and metallic lithium punched to a diameter of φ16 mm in a glove box under an argon gas atmosphere, a 25 μm thick separator (microporous film made of polypropylene) was placed between the positive electrode mixture layer and the metallic lithium. A 1 M LiPF6 solution (a 1:1 mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC)) was added as the electrolyte, and the battery was crimped and sealed to produce a 2032 size coin-type test battery. After that, it was washed with ethanol and subjected to battery evaluation. The evaluation results are shown in Table 1.

[0300] <Example 2> Except for a CVD reaction time of 40 minutes, the procedure was the same as in Example 1 to obtain graphene-containing carbon material B, and a 2032-size coin-type battery was fabricated. Material properties were measured, conductivity was evaluated, and the battery was evaluated using the obtained carbon material B and the test battery, and the results are shown in Table 1.

[0301] <Example 3> Except for a CVD reaction time of 60 minutes, the procedure was the same as in Example 1 to obtain graphene-containing carbon material C, and a 2032-size coin-type battery was fabricated. Material properties, conductivity evaluation, and battery evaluation were performed using the obtained carbon material C and the test battery, and the results are shown in Table 1.

[0302] <Example 4> Except for a CVD reaction time of 80 minutes, the procedure was the same as in Example 1 to obtain graphene-containing carbon material D, and a 2032-size coin-type battery was fabricated. Material properties were measured, conductivity was evaluated, and the battery was evaluated using the obtained carbon material D and the test battery, and the results are shown in Table 1.

[0303] <Example 5> Except for a CVD reaction time of 130 minutes, the procedure was the same as in Example 1 to obtain graphene-containing carbon material E, and a 2032-size coin-type battery was fabricated. Material properties were measured, conductivity was evaluated, and the battery was evaluated using the obtained carbon material E and the test battery, and the results are shown in Table 1.

[0304] <Example 6> As a template, fumed silica (SiO2 / AEROSIL® R972; particle size 21 nm, BET specific surface area 111 m²) is used. 2 A graphene-containing carbon material F was obtained by following the same procedure as in Example 1, except that the CVD reaction time was set to 120 minutes using (a CVD reaction time of 120 minutes with a total pore volume of 0.215 cc / g, oil absorption of 237 mL / 100 g, D10: 17.9 μm, D50: 46.4 μm, D90: 114 μm, carbon content of 0.6-1.2%, manufactured by Nippon Aerosil Co., Ltd.), and a 2032 size coin-type battery was fabricated. Material properties were measured, conductivity was evaluated, and the battery was evaluated using the obtained carbon material F and the test battery, and the results are shown in Table 1.

[0305] <Reference example 1> Alumina (Al2O3 / RURALOX SBa200; particle size 7nm, BET specific surface area 202m²) is used as the template. 2A graphene-containing carbon material G was obtained by the same procedure as in Example 1, except that graphene was used (with a total pore volume of 0.434 cc / g, oil absorption of 94 mL / 100 g, D10: 2.3 μm, D50: 5.2 μm, D90: 9.2 μm, manufactured by SASOL). A 2032-size coin-type battery was then fabricated. Material properties were measured, conductivity was evaluated, and the battery was evaluated using the obtained carbon material G and the test battery. The results are shown in Table 1.

[0306] <Reference example 2> As a template, we used magnesia (MgO / Kyowa Mag MF150; particle size 30 nm, BET specific surface area 129 m²). 2 Using carbon material H (manufactured by Kyowa Chemical Industry Co., Ltd.), with a total pore volume of 0.240 cc / g, oil absorption capacity of 198 mL / 100 g, D10: 0.6 μm, D50: 1.9 μm, D90: 3.5 μm), and performing the mold removal procedure in the same manner as in Example 1, a 2032 size coin cell was then fabricated. Using the obtained carbon material H and the test cell, material properties were measured, conductivity was evaluated, and the results are shown in Table 1.

[0307] (Removal of MgO template) 1-1.4 g of the laminate after the CVD reaction, approximately 100 g of hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd., 5 mol / L), and a stirring bar were added to a Teflon® beaker and stirred at room temperature for 5 hours. The sample was then filtered through a membrane filter (0.1 μm) and washed five times with pure water, followed by suction filtration. Care was taken to prevent the deposits on the filter paper from drying out. Next, the deposits were placed in a glass beaker containing approximately 100 mL of acetone. This beaker was covered with aluminum foil and held at a vacuum pressure of 0.06 MPa for 2 minutes in a vacuum dryer. After returning to atmospheric pressure, it was heated in a 60°C constant temperature bath for 10 minutes to perform acetone replacement. The supernatant liquid in the beaker was pipetted, and the same acetone replacement procedure was repeated. Finally, the sample was dried under reduced pressure at 150°C for 6 hours to obtain carbon material H containing graphene after mold removal.

[0308] <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. Material properties were measured, conductivity was evaluated, and the battery was evaluated, and the results are shown in Table 1.

[0309] [Table 1]

[0310] Table 1 shows that by comparing Examples 1-6 with Reference Examples 1-2 or Comparative Example 1, it can be seen that carbon materials A-F of this embodiment, which satisfy the predetermined configuration, have high conductivity and all of the characteristics of the battery, including rapid discharge characteristics (2C maintenance rate), charge capacity, discharge capacity, and charge / discharge characteristics (Coulomb rate), are greatly improved.

[0311] Regarding conductivity, carbon materials A to F of the present invention are overwhelmingly superior to carbon materials G to H of the reference examples and carbon black of the comparative example. This is thought to be because carbon materials A to F of the present invention consist of carbonaceous material having a graphene structure with a highly electronically conductive carbon 6-membered ring structure, and moreover, have a structure in which pores of 10 nm or more and macropores of 50 nm or more are connected, allowing for the formation of efficient electron conduction paths. Furthermore, looking at density characteristics such as bulk density, number density, and apparent density, carbon materials A to F of the present invention are far smaller than carbon materials G to H of the reference examples, and it is thought that the extended structure of this carbon material contributes to the formation of effective conduction paths for electron conductivity.

[0312] Regarding rapid discharge characteristics, carbon materials A to F of the present invention are overwhelmingly superior to the carbon material of the reference example and the carbon black of the comparative example. This difference is due to differences in the structure and spatial arrangement of the carbon materials, which will be explained below.

[0313] The carbon materials A to F of the present invention and the carbon materials G to H of the reference example are structures in which hollow particles are linked together. However, the carbon black of the comparative example is an aggregate of particles that are clumps of carbon, so there is almost no space, which restricts the rapid movement of lithium ions and results in poor rapid discharge characteristics. This can also be seen from the fact that the total pore volume of the carbon black of the comparative example is small, at 0.26 cc / g.

[0314] Next, the difference between carbon materials A to F of the present invention and the carbon materials of the reference example lies in the difference in the space created by the structural shape. As mentioned above, the carbon materials of the present invention have a complex structure, being a linked structure having a linear structure in which five or more hollow particles having a carbonaceous outer shell are connected. Multiple wide and narrow sections are intermittently connected in the linear section, and there are bent sections and multiple branched structures, and some of the branched structures form large ring shapes, resulting in a complex shape. On the other hand, the carbon materials of the reference example are simple structures made up of hollow particles having a carbonaceous outer shell, as described in Japanese Patent Publication No. 2019-102711 and WO2020 / 080521. Unlike the carbon materials of the present invention, there is no space created by the complex linear structure with wide and narrow sections, space around the branched structure, ring-shaped space where large pores such as macropores are formed, or space in gaps created by overlapping linear sections. This difference in space results in a difference in the amount of electrolyte held, which is reflected in the difference in the effect of rapid discharge characteristics. Furthermore, the difference in this space indicates that the structure is widely spread out, with low density in terms of bulk density, number density, and apparent density.

[0315] In reality, this difference in space is reflected in the pore volume characteristics. Reference examples of carbon materials G to H have a total pore volume of 2.00 to 2.40 cc / g, but the proportion of pores larger than 10 nm is small at 13 to 37%, and the macropore volume larger than 50 nm is also small at 0.05 to 0.07 cc / g. Comparative example carbon black has a total pore volume of only 0.26 cc / g. In contrast, carbon materials A to F of the present invention have a total pore volume of 2.90 to 5.60 cc / g, of which pores larger than 10 nm account for a large proportion at 62 to 81%, and the macropore volume larger than 50 nm is 0.48 to 2.41 cc / g, overwhelmingly surpassing the other materials.

[0316] Furthermore, the differences in the structure and spatial arrangement of these carbon materials are reflected in their oil absorption. The oil absorption of carbon materials A to F in Examples 1 to 6 ranged from 703 to 2280 ml / 100g, while carbon materials G to H in Reference Examples 1 and 2, manufactured using alumina and magnesia as molds, absorbed 430 to 492 mL / 100g, and the carbon black in Comparative Example 1 absorbed 303 mL / 100g, overwhelmingly surpassing the other carbon materials. These results also correlate with the effect of rapid discharge characteristics.

[0317] Regarding battery capacity characteristics, it can be seen that carbon materials A to F of the present invention are overwhelmingly superior in both charge and discharge capacity. This is because carbon materials A to F of the present invention are characterized by possessing both electronic and ionic conductivity, and the difference in pore volume of 10 nm or more and macropore volume of 50 nm or more is thought to be the reason for the difference in effect. Furthermore, differences in bulk density and number density are also thought to have influenced these characteristics.

[0318] Regarding charge-discharge characteristics, all materials except carbon material G in Reference Example 1 showed good results. While this result alone does not allow us to pinpoint the extent of the poor rapid discharge characteristics of carbon material G, it suggests that, out of a total pore volume of 2.40 cc, the pore volume of pores larger than 10 nm was only 0.32 cc / g and the macropore volume was only 0.07 cc / g (totaling less than 0.5 cc / g), or that the specific surface area was 1747 m². 2 The large value of / g may have been a contributing factor.

[0319] Based on image analysis results, the structures of carbon materials A to F in this invention can be classified as "complex."

[0320] From the shape index results in the image analysis, it can be seen that the circularity of carbon materials A to F of the present invention is more complex (smaller circularity) than that of carbon materials G to H of the reference example, and is equivalent to that of carbon black, which is representative of complex structures. Furthermore, the shape factor ML2 / A is an index that indicates a circular state, and PM2 / A is an index that indicates a spherical shape with an uneven circumferential surface, but it can be seen that for carbon materials A to F of the present invention, the relationship PM2 / A > ML2 / A is observed between the two indices. Thus, as can be seen from the image analysis, carbon materials A to F of the present invention have a complex shape, and it is thought that this is what allows for a high balance between electronic conductivity and ionic conductivity.

[0321] Morphological classification results from image analysis reveal that carbon materials A-F of the present invention have a high proportion of linear and branched structures, indicating complexity. In particular, branched structures, which represent the most complex shape, account for approximately 30%. Furthermore, carbon materials A-F of the present invention have almost no spheroidal structures, and the remaining three classifications of linear, ellipsoidal, and branched structures are present in a well-balanced manner. As carbon materials A-F of the present invention are aggregates composed of these structures, they are thought to have excellent conductivity, significantly improving the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0322] Table 1 shows that the proportions of the four morphological classifications of carbon materials A to F of the present invention are very similar to those of carbon black in Comparative Example 1, which is a representative example of a complex shape. Carbon black exhibits good electronic conductivity due to its complex aggregate structure and is used in many applications as a conductive material, including lithium-ion secondary batteries. Carbon materials A to F of the present invention have similar complex structures, and because the inside of the complex linked structure is hollow, it can hold a large amount of electrolyte and enhance ionic conductivity, and it is thought that the rapid discharge characteristics and battery capacity characteristics have been significantly improved compared to carbon black in Comparative Example 1. Furthermore, since the complexity of carbon materials A to F of the present invention is a characteristic of the linked structure itself, rather than a characteristic of the aggregate like carbon black, it is thought that the electronic conductivity has been enhanced more stably and reliably.

[0323] The following describes other information that can be gleaned from Table 1.

[0324] I in Raman spectroscopy G / I 2D The ratio of carbon materials G to H is smaller than that of carbon materials A to F. G / I 2D This is also called the layering index, I G / I 2D A value of 0.2 is considered equivalent to one graphene layer, and the larger the value, the greater the number of layers. Therefore, it is inferred that the carbon materials G to H in the reference examples had a small number of carbonaceous graphene layers surrounding the pores, and were unable to maintain large pores such as pores of 10 nm or more or macropores of 50 nm or more.

[0325] Lc(002), measured by XRD using X-rays, is said to be the distance of the crystalline structure, and a larger value indicates higher crystallinity. The Lc(002) of carbon materials A to F of the present invention is smaller than that of carbon materials G to H of the reference example, indicating that the crystallinity of the carbonaceous layer of carbon materials A to F of the present invention is not very high. Furthermore, the Raman spectra of carbon materials A to F of the present invention are as follows: D / I GThe value is large, above 1.40. The D band in the Raman spectrum is a band that indicates sp3 bonding (CH stretching motion) in carbon materials, and it increases when sp2 bonds in the carbon 6-membered ring structure of the carbonaceous layer are broken and become sp3 bonds. Therefore, the carbonaceous layers of carbon materials A to F of the present invention are layers in which crystalline and amorphous materials coexist, which is thought to be the cause of the formation of large spaces.

[0326] The carbon materials A to F of the present invention exhibit small particle size D10, median diameter D50, or particle size D90 characteristics. Furthermore, the ratio of particle size D90 to particle size D10 (D90 / D10) and the ratio of particle size D90 to mode pore size M (D90 / M) are also small, improving dispersibility with dispersions and consistently enhancing the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of the manufactured lithium-ion secondary batteries. The dispersibility of the carbon materials is also influenced by the fact that the pH is in the neutral range.

[0327] Table 1 shows that the ash content of carbon materials A to F of the present invention is very small, ranging from 0.18 to 0.20% by weight. Furthermore, the pH of carbon materials A to F of the present invention is in the neutral range after washing until the washing solution becomes neutral. Because carbon materials A to F of the present invention have a low ash content and a neutral pH, they exhibit excellent electrolyte stability, improving the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0328] The combustion temperatures of carbon materials A to F of the present invention are very high, ranging from 610 to 636°C. The combustion temperature decreases as the amount of impurities increases. Carbon materials A to F of the present invention have high combustion temperatures, excellent electrolyte stability, and improve the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0329] <Example 7> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 1, except that the amount of carbon material A was changed to 0.1% by weight and the amount of positive electrode material NCM was changed to 96.9%.

[0330] <Example 8> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 1, except that the amount of carbon material A was changed to 0.3% by weight and the amount of positive electrode material NCM was changed to 96.7%.

[0331] <Example 9> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 1, except that the amount of carbon material A was changed to 1% by weight and the amount of positive electrode material NCM was changed to 96%.

[0332] <Example 10> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 1, except that the amount of carbon material A was changed to 2% by weight and the amount of positive electrode material NCM was changed to 95%.

[0333] <Example 11> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 1, except that the amount of carbon material A was changed to 3% by weight and the amount of positive electrode material NCM was changed to 94%.

[0334] <Example 12> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 1, except that the amount of carbon material A was changed to 4% by weight and the amount of positive electrode material NCM was changed to 93%.

[0335] <Example 13> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 1, except that the amount of carbon material A was changed to 6% by weight and the amount of positive electrode material NCM was changed to 91%.

[0336] Charge and discharge tests were performed on the test batteries of Examples 7 to 13. Each test battery was energized to 4.2V with a constant current of 1.25mA (equivalent to 0.2C). After reaching 4.2V, constant voltage charging was continued until the current reached 0.31mA (0.05C). Then, the battery was discharged to 3V with a constant current of 1.25mA. The charge and discharge capacities at this time were determined. The results are shown in Table 2 and Figure 7. Figure 7 shows the relationship between the amount of carbon material, the 2C maintenance rate, and the charge and discharge capacity.

[0337] [Table 2]

[0338] Table 2 and Figure 7 confirm that the high-rate characteristics of the test batteries remained good within the range of carbon material blending amounts for Example 1, Comparative Example 1, and Examples 7-13. While increasing the carbon material blending amount also increased the battery's charge / discharge capacity, excessive increases in the blending amount led to a decrease in the active material content and a reduction in the electrode's charge / discharge capacity.

[0339] <Example 14> A negative electrode test battery was manufactured by incorporating carbon material A from Example 1 into the negative electrode. A negative electrode slurry was prepared by stirring and mixing 97% artificial graphite, 1% carbon material A from Example 1, 1% carboxymethylcellulose, and 1% styrene-butadiene rubber (SBR) with distilled water as the solvent until homogeneous. The obtained slurry was coated onto a 20 μm thick copper foil, dried at 110°C, then punched out to a diameter of φ15 mm and pressurized with 30 kN to form the negative electrode. After vacuum drying the obtained negative electrode at 120°C, a 2032 size coin-type test battery with a metallic lithium counter electrode was fabricated in a glove box under an argon gas atmosphere using a 1 M LiPF6 solution (a 1:1 mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC)) as the electrolyte and a polypropylene separator.

[0340] Each test battery was energized to 0V with a constant current of 1.23mA (equivalent to 0.2C), and after reaching 0V, it was charged at a constant voltage until it reached 0.31mA (0.05C). Then, it was discharged to 1.5V with a constant current of 1.23mA. The discharge capacity at this time was determined. Next, using the same test battery, it was energized to 0V with a constant current of 1.23mA (equivalent to 0.2C), and after reaching 0V, it was charged at a constant voltage until it reached 0.31mA (0.05C). Then, it was discharged to 1.5V with a high-rate constant current of 12.3mA (equivalent to 2C). From the discharge capacity of the test battery obtained in the above evaluation test, the 2C maintenance rate (2C capacity ÷ 0.2C capacity) was calculated. As a result of evaluating the obtained negative electrode battery, the maintenance rate at 2C discharge was 0.47.

[0341] <Comparative Example 2> In Example 1, a negative electrode test battery was manufactured in the same manner as in Example 14, except that commercially available carbon black (DENKA BLACK Li-100; manufactured by Denka Co., Ltd.) was used as the conductive material instead of carbon material A, and the amount of this conductive material added to the negative electrode was set to 1%. When the obtained negative electrode battery was evaluated, the maintenance ratio at 2C discharge was 0.16.

[0342] As is clear from the above-described examples, the 2C maintenance rate (rapid discharge characteristics) of the battery using the carbon material of the present invention is higher than that of the battery in the comparative example. This is due to the high electronic and ionic conductivity of the carbon material of the present invention. In other words, the carbon material of the present invention has a backbone of highly conductive carbonaceous material containing graphene, and has space within the particles to hold electrolyte, compared to the conductive material used in the comparative example. The discharge reaction is the reaction in which lithium ions that have been released during charging return to the positive electrode material. When discharge begins, electrons flow from the external circuit to the positive electrode, and these electrons and lithium ions return to the crystal structure sites of the positive electrode in a bonded state, restoring the bonded state before charging. In other words, the bonding of lithium ions and electrons and the phase change of the crystal structure of the positive electrode occur simultaneously. The phase change can be observed from the change in voltage. The "simultaneity" of this phase change is important for the high maintenance rate of high-rate discharge, and it has been confirmed that the carbon material of this embodiment can achieve this "simultaneity".

[0343] The present invention is not limited to the embodiments and examples described above. Various design modifications within the scope of the present invention are included.

Claims

1. A carbon material comprising a linked structure in which hollow particles having a carbonaceous outer shell are connected, wherein the circularity (complexity) of the shape index in image analysis is 0.5 or less, the proportion of "Branched" in the morphological classification is 10% or more, and the bulk density is 0.5 g / cc or less.

2. The carbon material according to claim 1, wherein the connecting structure has a linear portion in which five or more hollow particles are connected in series along the longitudinal direction, and the intermediate portion between the first end hollow particle located at one end of the linear portion and the second end hollow particle located at the other end has a wide portion with a width exceeding three times the outer diameter of the hollow particle and a narrow portion with a width of three times or less the outer diameter of the hollow particle.

3. The carbon material according to claim 1, wherein the shape factor in image analysis is in the relationship ML2 / A ≤ PM2 / A.

4. Intensity ratio of G-band to 2D-band in Raman spectroscopy Ｇ / I ２Ｄ If the intensity ratio between the D band and the G band is 0.1 or higher, then I Ｄ / I Ｇ The carbon material according to claim 1, wherein the ratio is 0.3 or higher.

5. The carbon material according to claim 1, wherein the average interplanar spacing d002 determined from the 002 diffraction lines measured by X-ray diffraction (XRD) is 3 to 5 Å, the crystallite size Lc(002) in the c-axis direction is 10 nm or less, and the crystallite size Lc(002) in the a-axis direction is in the range of 0.01 to 10 nm.

6. The carbon material according to claim 1, wherein the total pore volume is 0.5 cc / g or more, and the proportion of pore volume of 10 nm or more in the total pore volume is 20% or more.

7. The carbon material according to claim 1, wherein the mode pore diameter is 10 nm or more and 60 nm or less.

8. The carbon material according to claim 1, wherein the ash content is 0.5% by weight or less.

9. The carbon material according to claim 1, wherein the oil absorption capacity is 250 mL / 100 g or more.

10. The carbon material according to claim 1, wherein the particle size D90, where 90% of the particles in the particle size distribution curve are located, is 300 μm or less.

11. A method for producing a carbon material, comprising forming a carbonaceous layer on the surface of a mold material and then removing the mold material, characterized in that the mold material is an aggregate in which primary particles of 1 to 100 nm in size are linked together in a chain-like manner with multiple branched structures.

12. The method for producing a carbon material according to claim 11, wherein the carbon material is the carbon material described in claim 1 or 2.

13. A battery additive having the carbon material according to claim 1 or 2.

14. A dispersion liquid for dispersing the carbon material according to claim 1 or 2 in a dispersion medium.

15. An electrode composition comprising a carbon material, an active material, and a binder as described in claim 1 or 2.

16. An electrode slurry comprising dispersing the electrode composition according to claim 15 in a solvent.

17. An electrode having the carbon material according to claim 1 or 2.

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

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