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 made of carbonaceous material having a carbon 6-membered ring structure, has an oil absorption capacity of 500 mL / 100 g or more, a mesopore volume of 0.5 cc / g or more, the proportion of the pore volume of 10 to 50 nm in the mesopore volume is 20% or more, and the ratio of the particle size D90, where 90% of the particles are located, to the particle size D10, where 10% of the particles are located (D90 / D10) is 10 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 not containing fluorine to separate the mold and the precursor. Specifically, quartz sand is mixed as a spacer, nanoparticles of magnesium oxide are used as a mold, and by a CVD reaction at 900°C for 2 hours, 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 by a CVD reaction at 950°C for 2 hours, 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 studied as lithium-ion secondary batteries.

[0010] Patent Document 8 (WO2020 / 080520) discloses a capacitor excellent in increasing the capacity and voltage, which uses a graphene porous carbon material having a specific surface area of 1940 m 2 / g, an average pore diameter of 7 nm, and an edge site amount of 0.10 mmol / g measured by temperature-programmed desorption mass spectrometry (TPD-MS) method, in which a carbonaceous layer is formed on the surface of alumina particles having an average particle diameter of 7 nm by the CVD method, then the alumina particles are removed with hydrofluoric acid, and then heat-treated at 1800°C.

[0011] Patent Document 9 (Japanese Patent Application Laid-Open No. 2022-191280) discloses that a carbon material containing a plurality of carbon nanoparticles containing graphene, having a median diameter of 0.1 to 50 μm, a BET specific surface area of 50 to 2,000 m 2 / g, a conductivity of 500 to 20,000 S / m when compressed at 12,000 psi, and containing pores with a size of 0.1 to 10 nm and pores with a size of 10 to 100 nm is used in a lithium-ion secondary battery.

[0012] 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 greatly 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 conducted diligent research and found that a carbon material having a specific six-membered carbon ring structure, which increases oil absorption, increases mesopore volume, increases the proportion of 10-50 nm pore volume within the mesopore volume, and reduces the ratio of particle size D90 to particle size D10 (D90 / D10) to weaken aggregation, exhibits excellent conductivity and can significantly improve the 2C maintenance rate (rapid discharge characteristics), battery capacity characteristics such as charge capacity and discharge capacity, and charge / discharge characteristics (Coulomb rate) of lithium-ion secondary batteries.

[0016] The inventors have discovered that carbon materials with high oil absorption capacity have a broad structure that can absorb a large amount of oil, and can form efficient electron conduction paths. The inventors have also discovered that carbon materials with high oil absorption capacity can hold a large amount of electrolyte, thereby significantly improving ionic conductivity. The inventors have found that carbon materials with high oil absorption capacity and both electron and ionic conductivity can enhance conductivity and significantly improve the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0017] The inventors have found that the above-mentioned carbon material with high oil absorption capacity increases the mesopore volume and the proportion of 10-50 nm pores within the mesopore volume, thereby enabling rapid movement of lithium ions and further improving the rapid discharge characteristics and charge-discharge characteristics of lithium-ion secondary batteries.

[0018] The inventors have found that by reducing the ratio (D90 / D10) between the particle size D90, where 90% of the particles are located, and the particle size D10, where 10% of the particles are located, in the particle size distribution curve of a carbon material, the dispersibility with the dispersion is improved, and the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries can be enhanced without variation.

[0019] The present inventors have identified the stacking index, known as I, which is measured by Raman spectroscopy. G / I 2D Ya I D / I G Alternatively, by identifying the average interplanar spacing d002 and the index Lc(002) of the number of crystalline carbonaceous layers obtained from the 002 diffraction lines measured by XRD analysis, it becomes possible to maintain the shape of large mesopores and macropores, increase the oil absorption capacity of the carbon material, enable rapid movement of lithium ions, and further improve the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries.

[0020] The inventors have discovered that a carbon material capable of increasing conductivity and improving the rapid discharge characteristics of lithium-ion secondary batteries can be easily manufactured by using aggregates of specific inorganic compounds as a template.

[0021] Based on these findings, the inventors have completed the present invention.

[0022] Thus, the present invention provides a carbon material having a carbonaceous material with a six-membered carbon ring structure, having an oil absorption capacity of 500 mL / 100 g or more, a mesopore volume of 0.5 cc / g or more, a proportion of the pore volume of 10 to 50 nm within the mesopore volume of 20% or more, and a ratio (D90 / D10) of the particle size distribution curve between the particle size D90, where 90% of the particles are located, and the particle size D10, where 10% of the particles are located, of 10% or less.

[0023] In the carbon material of the present invention, it is preferable that the hollow particles having a carbonaceous outer shell are linked together in a connected structure having multiple branched structures.

[0024] 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 0.1 or higher.

[0025] 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 and the crystallite size Lc(002) in the c-axis direction is 10 nm or less.

[0026] In the carbon material of the present invention, it is preferable that the particle size D90 is 300 μm or less.

[0027] In the carbon material of the present invention, it is preferable that the particle size D10 is 150 μm or less.

[0028] In the carbon material of the present invention, it is preferable that the mode pore size M is 10 nm or more and 60 nm or less.

[0029] In the carbon material of the present invention, it is preferable that the ratio of D90 to the mode pore diameter M (D90 / M) is 50 or less, calculated as (1 × 1000) × (D90 / M).

[0030] In the carbon material of the present invention, it is preferable that the macropore volume is 0.1 cc / g or more.

[0031] In the carbon material of the present invention, the number density is preferably in the range of 1E+16 to 1E+19 particles / g.

[0032] The present invention also provides a method for producing a carbon material, which involves using an aggregate of an inorganic compound as a mold material, wherein the ratio (D90 / D10) of the particle size D90, where 90% of the particles are located in the particle size distribution curve, to the particle size D10, where 10% of the particles are located, is 4 or less, forming a carbonaceous layer on the surface of the mold material, and then removing the mold material.

[0033] 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.

[0034] The present invention also provides a battery additive having the above-mentioned carbon material.

[0035] The present invention also provides a dispersion liquid obtained by dispersing the above-mentioned carbon material in a dispersion medium.

[0036] The present invention also provides an electrode composition having the above-mentioned carbon material, active material, and binder.

[0037] The present invention also provides an electrode slurry obtained by dispersing the above electrode composition in a solvent.

[0038] The present invention also provides an electrode having the above-mentioned carbon material.

[0039] According to the present invention, a lithium-ion secondary battery having the above-mentioned carbon material is further provided. [Effects of the Invention]

[0040] The present invention provides a carbon material with excellent conductivity that can greatly enhance the 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]

[0041] [Figure 1] 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 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 100 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 figure shows an example of a Raman spectrum measured for a carbon material according to one embodiment of the present invention. [Figure 5] 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 6] 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 6, ● represents the 2C maintenance rate and △ represents the discharge capacity. [Modes for carrying out the invention]

[0042] Embodiments of the present invention will be described in detail below.

[0043] <Carbon materials> The carbon material of the present invention is characterized by comprising a carbonaceous material having a carbon 6-membered ring structure, having an oil absorption capacity of 500 mL / 100 g or more, a mesopore volume of 0.5 cc / g or more, a proportion of the pore volume of 10 to 50 nm within the mesopore volume of 20% or more, and a ratio (D90 / D10) of the particle size distribution curve between the particle size D90, where 90% of the particles are located, and the particle size D10, where 10% of the particles are located, of 10 or less.

[0044] (Structure of carbon materials) The carbon material of the present invention consists of a carbonaceous material having a six-membered carbon ring structure, preferably a carbonaceous material having a graphene structure in which the six-membered carbon ring structures are linked in a network structure. Figure 1 shows a TEM image observed using a transmission electron microscope (TEM: JEM-ARM300F, manufactured by JEOL Ltd.) at an acceleration voltage of 80 kV. Graphene is a sheet-like material of SP2-bonded carbon, and as shown in Figure 1, the six-membered carbon ring structures are linked together to form a honeycomb-like hexagonal lattice structure. Furthermore, when the carbon material of the present invention consists of a carbonaceous material having a graphene structure, the intensity ratio of the G band to the 2D band in the Raman spectroscopy measurement described later is IG / I 2D This can also be confirmed by checking if the value is 0.2 or higher.

[0045] One embodiment of the carbon material of the present invention has a complex structure. Figure 2 shows a TEM image of an example of the carbon material according to this embodiment, observed using a transmission electron microscope (TEM; H-7650 model, Hitachi High-Technologies Corporation) at an acceleration voltage of 100 kV. The carbon material of this embodiment is a linked structure in which hollow particles having a carbonaceous outer shell are connected in a plurality of branched structures. Preferably, it can be seen that there is a series chain portion in which five or more of the hollow particles are connected in series along the longitudinal direction, and in the intermediate portion between the first end hollow particle located at one end of the series chain portion and the second end hollow particle located at the other end, there is one or more wide portions with a width exceeding three times the outer diameter of the hollow particle and one or more narrow portions with a width of three times or less the outer diameter of the hollow particle. The degree of particle transmission in Figure 2 also shows that the inside of the particle shape is hollow. Furthermore, in the carbon material of this embodiment, some of the branched ends of the linearly extending linked structure form a ring shape, and the ring shape may or may not have hollow particles having a carbonaceous outer shell connected to it.

[0046] One embodiment of the carbon material of the present invention has an aggregate structure composed of carbon materials having the complex structure described above. Figure 3 shows a TEM image of an example of the carbon material according to this embodiment, observed using a transmission electron microscope (TEM: JEM-2100Plus model, manufactured by JEOL Ltd.) at an acceleration voltage of 100 kV.

[0047] As in the embodiments described above, the carbon material of the present invention forms a connected structure in which hollow particles having a carbonaceous outer shell containing a highly electronically conductive graphene structure are linked together in a plurality of branched structures. The interior of the hollow particles enclosed in the carbonaceous outer shell consists of mesopores, preferably 10 to 50 nm in size, and the ring-shaped structures formed by the linked branched structures and the inter-branch voids of aggregates consist of macropores of 50 nm or larger. The carbon material of the present invention, configured in this way, has a structure with a large specific surface area, a large total pore volume, large 10 to 50 nm mesopores, large macropores, and a large oil absorption capacity, which allows it to hold a large amount of electrolyte and enables the free movement of lithium ions. In other words, the carbon material of the present invention possesses both electronic and ionic conductivity, and when used as a conductive material in lithium-ion secondary batteries, it enhances conductivity and improves rapid discharge characteristics in a step-by-step manner.

[0048] (Oil absorption, mesopore volume, 10~50nm pore volume, D90 / D10) The carbon material of the present invention has the above structure and is characterized by having an oil absorption capacity of 500 mL / 100 g or more, a mesopore volume of 0.5 cc / g or more, a ratio of pore volume of 10 to 50 nm in the mesopore volume of 20% or more, and a D90 / D10 of 10 or less.

[0049] The oil absorption capacity of the carbon material of the present invention is 500 mL / 100g or more, preferably 600 mL / 100g or more, more preferably 700 mL / 100g or more, or preferably 800 mL / 100g or more, 900 mL / 100g or more, 1000 mL / 100g or more, 1050 mL / 100g or more, and 1100 mL / 100g or more, in that order. Furthermore, there is no particular upper limit to the oil absorption capacity of the carbon material, but 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.

[0050] Because the carbon material of the present invention possesses high oil absorption properties, when used in electrochemical elements such as lithium-ion secondary batteries, it can retain a large amount of electrolyte and exhibit excellent ionic conductivity. This high oil absorption property allows for a large amount of electrolyte to be retained not only in the space inside the hollow particles of the linked structure, but also in the periphery of the branched structure, the parts surrounded by the complex linked outer shell, the large ring-shaped parts formed, and the gaps in the parts surrounded by the linked aggregate structure, enabling a stable supply of lithium ions. Furthermore, because the carbon material of the present invention has a structure that can absorb a large amount of oil, it forms efficient conductive paths (electron conductivity), enhances the conductivity of the carbon material itself, and greatly improves the rapid discharge characteristics of lithium-ion secondary batteries. If the amount of oil absorbed by the carbon material is excessively small, the amount of electrolyte that can be retained will be small, causing a delay in ion supply during rapid reactions and reducing the discharge capacity. 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 it may be difficult to control the amount of electrolyte that can be retained.

[0051] The mesopore volume of the carbon material of the present invention is 0.5 cc / g or more, preferably 0.75 cc / g or more, more preferably 1 cc / g or more, or preferably in the order of 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. There is no particular upper limit to the carbon material, 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. If the mesopore volume of the carbon material is excessively small, the amount of electrolyte held in the carbon material will be small, which is undesirable. In the carbon material of the present invention, when the mesopore volume is as described above, the pore shape has appropriate strength and contributes to the stability of the carbon material itself.

[0052] In the carbon material of the present invention, the proportion of pore volume in the 10-50 nm mesopore region is 20% or more, preferably 30% or more, more preferably 40% or more, or, in order of preference, 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 in the 10-50 nm mesopore region of the carbon material is within this range, the oil absorption capacity is greatly increased, and the interconnected structure of the hollow particles has appropriate strength and maintains its shape.

[0053] The ratio of particle size D90 to particle size D10 of the carbon material of the present invention is 10 or less in terms of the D90 / D10 value, or preferably in the order of 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, and 4.5 or less. There is no particular limit to the lower limit of D90 / D10 of the carbon material, but it is usually in the range of 1 or more, preferably 1.5 or more, more preferably 2 or more, even more preferably 2.5 or more, and most preferably 3 or more. If the D90 / D10 of the carbon material is excessively large, the cohesiveness will be strong and the dispersibility will be poor, which is undesirable because the conductivity and high-performance characteristics of the lithium-ion secondary battery cannot be sufficiently obtained.

[0054] (Pore characteristics measured by nitrogen adsorption / desorption) The specific surface area of ​​the carbon material of the present invention is not particularly limited, but the BET specific surface area calculated from nitrogen adsorption as specified in JIS Z8830 is typically 10 to 2500 m². 2 / g, preferably 100-2000m 2 / g, more preferably 300-1800m 2 / g, more preferably 500-1500m 2 / g, most preferably 800-1200m 2 The range is / g. When the specific surface area of ​​the carbon material of the present invention is within this range, it is preferable to have highly enhanced electronic and ionic conductivity.

[0055] 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 typically 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. The upper limit is 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. Also, if the total pore volume of the carbon material is excessively high, the skeletal strength of the pore structure may weaken, and the pore shape may not be maintained. In the carbon material of the present invention, when the total pore volume is as described above, the pore shape has appropriate strength and contributes to the stability of the connected structure.

[0056] The micropore volume of the carbon material of the present invention is not particularly limited, but is usually 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. The lower limit of the micropore volume of the carbon material 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.

[0057] The macropore volume of the carbon material of the present invention is not particularly limited, but is usually 0.01 cc / g or more, 0.05 cc / g or more, more preferably 0.1 cc / g or more, or preferably in the order of 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 usually 5 cc / g or less, preferably 4.5 cc / g or less, more preferably 4 cc / g or less, even more preferably 3.5 cc / g or less, and most preferably 3 cc / g or less. If the macropore volume of the carbon material is excessively small, it is undesirable because it results in 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.

[0058] 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.

[0059] 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, particularly preferably 35 nm or less, and most preferably 30 nm or less. When the mode pore diameter of the carbon material is within this range, high ionic conductivity and electronic conductivity can be achieved. Furthermore, when the mode pore diameter of the carbon material is within this range, the pore shape has appropriate strength, contributing to the stability of the carbon material itself.

[0060] (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 ).

[0061] (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 4. Among the Raman spectra, 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.

[0062] 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.

[0063] 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.

[0064] The intensity ratio of the D-band to the G-band of the carbon material of the present invention D / I G There are no particular limitations, but it is usually 0.1 or higher, preferably 0.5 or higher, more preferably 1 or higher, or preferably in the order of 1.1 or higher, 1.15 or higher, 1.2 or higher, 1.25 or higher, 1.3 or higher, 1.35 or higher, and 1.4 or higher. D / I GThe upper limit is not particularly limited, but is usually 10 or less, preferably 8 or less, more preferably 5 or less, even more preferably 4 or less, especially preferably 3 or less, and most preferably 2.5 or less. D / I G When this range is maintained, the sp2 and sp3 orbitals of the carbonaceous carbon material are in an optimal state, and the electron conduction paths and ion conduction paths are highly balanced, thereby greatly improving the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of lithium-ion secondary batteries. D / I G If the value is excessively small, an optimal crystal structure cannot be obtained, which is undesirable.

[0065] 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.

[0066] 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.

[0067] (particle characteristics) In one embodiment, the carbon material of the present invention is preferably a linked structure in which hollow particles having the carbonaceous outer shell described above are connected in a plurality of branched structures.

[0068] The size of a single hollow particle is not particularly limited, but is usually in the range of 0.1 to 100 nm, preferably 1 to 80 nm, more preferably 5 to 50 nm, even more preferably 10 to 45 nm, and most preferably 15 to 40 nm. The longitudinal length of a linked structure, which consists of multiple single hollow particles, is not particularly limited, but is usually in the range of 0.01 to 100 μm, preferably 0.05 to 80 μm, more preferably 0.1 to 50 μm, even more preferably 0.5 to 45 μm, and most preferably 1 to 40 μm. The average particle size of the linked structure is not particularly limited, but is usually in the range of 0.01 to 50 μm, preferably 0.05 to 10 μm, and more preferably 0.1 to 5 μm.

[0069] 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 carbon material.

[0070] 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, is not particularly limited, but is usually 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less, particularly preferably 60 μm or less, and most preferably 50 μm or less. The lower limit of the median diameter D50 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 2 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 will be poor, and the rapid discharge characteristics will be poor when used in lithium-ion secondary batteries.

[0071] 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.

[0072] 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 250 μm or less, preferably 200 μm or less, more preferably 150 μm or less, or preferably 100 μm or less, preferably 80 μm or less, 75 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 5 μm or more, more 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 highly enhanced, which is preferable. If the particle size D90 of the carbon material is excessively large, the dispersion stability will be poor, and when used in a lithium-ion secondary battery, the rapid discharge characteristics, battery capacity characteristics and charge / discharge characteristics will be poor.

[0073] The ratio of D90 to mode pore size M of the carbon material of the present invention (D90 / M) 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, 8 or less, 6 or less, 5 or less, and 4 or less. If the (D90 / M) ratio of the carbon material is excessively large, it will have strong cohesiveness and poor dispersibility, as well as poor electrolyte retention, and the conductivity and high-performance characteristics of the lithium-ion secondary battery cannot be sufficiently obtained, which is undesirable.

[0074] (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.

[0075] (Apparent density) The apparent density of the carbon material of the present invention is calculated from 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 not particularly limited, but is usually 2 g / cc or less, preferably 1.5 g / cc or less, more preferably 1.2 g / cc or less, or preferably 1 g / cc or less, 0.8 g / cc or less, 0.6 g / cc or less, 0.5 g / cc or less, 0.4 g / cc or less, 0.3 g / cc or less, and 0.26 g / cc or less, in that order. If the apparent density of the carbon material is excessively high, the conductivity and electrolyte retention of the carbon material will decrease. It is presumed that when the apparent density of the carbon material is reduced, the carbon material will have a more spread-out structure, making it easier for the electrolyte to penetrate. The lower limit of the apparent density of the carbon material is not particularly limited, but is usually 0.01 g / cc or more, preferably 0.02 g / cc or more, more preferably 0.05 g / cc or more, even more preferably 0.1 g / cc or more, and most preferably 0.15 g / cc or more. If the apparent density of a carbon material is excessively low, it may become difficult to maintain the structure of the carbon material itself, or to maintain pore sizes of 10 nm or larger, such as mesopores and macropores.

[0076] 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 conductivity and electrolyte retention are optimized and therefore preferable.

[0077] (Imparting conductivity) The carbon material of the present invention possesses electron transfer properties due to its graphene structure, lithium ion conductivity that allows it to absorb a large amount of oil and hold a large volume of electrolyte, and excellent stability in the electrolyte, thus enabling it to assist in battery reactions in lithium-ion secondary batteries. Furthermore, one embodiment of the carbon material of the present invention is a linked structure in which hollow granular objects covered with an outer shell made of carbonaceous material containing graphene are connected. Because there is space inside the granular objects and inside the area surrounded by the linked structure, the electrolyte containing dissolved lithium ions can penetrate and be held, resulting in excellent ion supply during reactions. For this reason, the carbon material of the present invention can suitably assist in secondary battery reactions.

[0078] 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.

[0079] The carbon material of this embodiment has a space inside its carbonaceous outer shell, allowing it to hold an electrolyte. 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, making it a material that enables rapid battery reactions.

[0080] <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, it can be easily produced by using an aggregate of an inorganic compound as a mold material in which the ratio (D90 / D10) of the particle size D90, in which 90% of the particles in the particle size distribution curve are located, to the particle size D10, in which 10% of the particles are located, is 4 or less, forming a carbonaceous layer on the surface of the mold material, and then removing the mold material.

[0081] (Mold material) There are no particular limitations on the inorganic compounds used as mold materials, but examples 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.

[0082] There are no particular limitations on nonmetallic compounds, but examples include ceramic compounds. Examples of ceramics include glass, cement, and fine ceramics.

[0083] 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.

[0084] Examples of metal compound mold materials 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, with calcium compounds, magnesium compounds, and aluminum compounds being preferred. Examples of calcium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, with carbonates and oxides being preferred, and oxides being more preferred. Examples of magnesium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, with carbonates and oxides being preferred, and oxides being more preferred. Examples of aluminum compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, with carbonates and oxides being preferred, and oxides being more preferred.

[0085] Furthermore, atomized compounds can be suitably used as mold materials because they form large aggregate structures. Examples of atomized compounds include compounds obtained by flame hydrolysis, which is one of the dry manufacturing methods for inorganic compounds.

[0086] A typical example of an atomized 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, average particle size of 7-40 nm and specific surface area of ​​50-380 m² can be achieved. 2 Particles of silicon dioxide are obtained at a density of / g.

[0087] Other examples of atomized compounds produced by flame hydrolysis include atomized alumina, atomized titania, and atomized zirconia. Other examples of atomized metal compounds include chlorides of Na, Ba, or Sr, sulfates of K, Na, Sr, or Mg, nitrates of Na or K, phosphates of Na or K, carbonates of Na, K, Ca, or Mg, and metal oxides of Na, K, Ca, or Ba. The shape of the mold material is preferably in an atomized form.

[0088] (Properties of the mold material) The inorganic compound used as a mold is characterized by having a ratio (D90 / D10) of 4 or less between the particle size D90, where 90% of the particles are located, and the particle size D10, where 10% of the particles are located.

[0089] The ratio of particle size D90 to particle size D10 (D90 / D10) of the inorganic compound used is 4 or less, or preferably 3.9 or less, 3.8 or less, 3.7 or less, 3.6 or less, 3.5 or less, and 3.4 or less, in that order. There is no particular limit to the lower limit of D90 / D10 of the inorganic compound, but it is usually 0.001 or more, preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, particularly preferably 0.5 or more, and most preferably 1 or more. When the D90 / D10 of the inorganic compound is within this range, the electronic conductivity and ionic conductivity of the resulting carbon material are well balanced and preferable.

[0090] The primary particle size of the inorganic compound used is not particularly limited, but is usually 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 template 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 inorganic compound 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 uniform carbon coating.

[0091] There are no particular limitations on the specific surface area of ​​the inorganic compound used, but it is typically expressed as the BET specific surface area, which is 500 m². 2 Less than or equal to / g, preferably 400m 2 / g or less, more preferably 300m 2 It is less than / g, or 200m 2 / g or less, 150m 2 / g or less, 140m 2 / g or less, 130m 2 / g or less, 120m 2 / g or less, 110m 2 / g or less, 100m 2 / g or less, 90m 2 / g or less, 80m 2 The order of preference is from less than / g. Furthermore, there are no particular limitations on the lower limit of the specific surface area of ​​the inorganic compound used, but it is usually 1 m². 2 / g or more, preferably 10m 2 / g or more, more preferably 20m 2 / g or more, more preferably 40m 2 / g or more, most preferably 50m 2 It is 1 / g or more. When the BET specific surface area of ​​the mold material is within this range, the pore volume of 10 nm or larger in the manufactured carbon material can be significantly increased and maintained.

[0092] There are no particular limitations on the amount of oil absorbed by the inorganic compound used, but it is usually 10 mL / 100g or more, preferably 50 mL / 100g or more, more preferably 100 mL / 100g or more, even more preferably 130 mL / 100g or more, and most preferably 150 mL / 100g or more. There are no particular limitations on the upper limit of the amount of oil absorbed by the inorganic compound, 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 amount of oil absorbed by the inorganic compound is within this range, it is preferable to increase the pore volume of 10 nm or more and the amount of oil absorbed by the resulting carbon material.

[0093] The total pore volume of the inorganic compound used is not particularly limited, but is usually 500 cc / g or less, preferably 400 cc / g, more preferably 300 cc / g or less, or preferably 250 cc / g or less, 200 cc / g or less, 150 cc / g or less, 130 cc / g or less, 120 cc / g or less, 110 cc / g or less, 100 cc / g or less, 90 cc / g or less, and 80 cc / g or less, in that order. The lower limit of the total pore volume of the inorganic compound is not particularly limited, but is usually 1 cc / g or more, preferably 5 cc / g or more, more preferably 10 cc / g or more, even more preferably 30 cc / g or more, and most preferably 50 cc / g or more. When the total pore volume of the inorganic compound is within this range, it is preferable because the amount of carbon material supplied can be greatly increased. If the total pore volume of the inorganic compound is excessively large, it becomes difficult to maintain pores of 10 nm or larger in the manufactured carbon material.

[0094] There are no particular limitations on the structure of the aggregates of the compounds used, but it is preferable that they be complex and long-extending, and capable of realizing higher-order structures. For example, an aggregate structure in which primary particles have multiple branched structures and are linked together in a bead-like manner is preferred.

[0095] The structure length of the inorganic compound aggregates 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.

[0096] There are no particular limitations on the particle size D10 of the inorganic compound used, where 10% of the particles are located in the particle size distribution curve. However, it 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 inorganic compound, but it 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 inorganic compound is within this range, the conductivity of the resulting carbon material can be greatly enhanced, which is preferable. When the particle size D10 of the inorganic compound is excessively small, the oil absorption and pore volume of 10 nm or more of the resulting carbon material may not be sufficient.

[0097] The median diameter D50 of the inorganic compound used as a template material is not particularly limited, but it is the value at which half of the particles are present in the particle size distribution curve measured after immersion in a 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, 15 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 an inorganic compound with a large median diameter D50 as a template material, a carbon material with a large oil absorption capacity can be manufactured. The larger the median diameter D50 of the inorganic compound, the stronger the cohesive force, and when used as a template material, the gaps formed between inorganic compound aggregates and the ring shape formed by the inorganic compound aggregates become the pores of 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 inorganic compound 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.

[0098] There are no particular limitations on the particle size D90 of the inorganic compound used, where 90% of the particles are located in the particle size distribution curve. However, it 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 or larger, in that order. There are no particular limitations on the upper limit of the D90 of the inorganic compound, but it 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 inorganic compound is within this range, the electronic conductivity and ionic conductivity of the carbon material produced are highly enhanced, which is preferable. When the particle size D90 of the inorganic compound is excessively small, the oil absorption and pore volume of 10 nm or more of the resulting carbon material may not be sufficient.

[0099] The bulk density of the inorganic compound 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. When the bulk density of the inorganic compound is in this range, it is preferable because it can increase the conductivity of the carbon material produced and significantly increase the pore volume of 10 nm or more.

[0100] The carbon content of the inorganic compound used is not particularly limited, but is usually 0.001% by weight or more, preferably 0.01% by weight or more, more preferably 0.05% by weight or more, even more preferably 0.1% by weight or more, and most preferably 0.5% or more. The upper limit is usually 5% or less, preferably 4% or less, more preferably 3% or less, even more preferably 2.5% or less, and most preferably 2% or less. When the carbon content of the inorganic compound is within this range, it is preferable because it facilitates the formation of a carbonaceous layer on the mold surface.

[0101] There are no particular limitations on the surface of the inorganic compound used, but a surface treatment is preferred, and for example, a compound having a hydrocarbon that serves as a carbon source is 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.

[0102] Examples of inorganic compounds having hydrocarbons on their surface include inorganic compounds treated with a hydrocarbon-containing surface treatment agent, preferably inorganic compounds surface-treated with a hydrocarbon-containing silane coupling agent, and more preferably silica compounds surface-treated with a hydrocarbon-containing silane coupling agent. 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. The amount of silane coupling agent is appropriately selected depending on the intended use, but is adjusted so that the carbon content in the inorganic compound is usually 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 inorganic compound is within this range, carbon deposition on the mold surface can be easily facilitated, making it preferable.

[0103] The moisture content of the mold material used in the present invention is not particularly limited, but is usually in the range of 5% by weight or less, preferably 3% by weight or less, more preferably 1.5% by weight or less, even more preferably 1% by weight or less, and most preferably 0.5% by weight or less.

[0104] These mold materials can be used individually or in combination of two or more types.

[0105] (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.

[0106] 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.

[0107] -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.

[0108] 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.

[0109] 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.

[0110] -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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] Since carbonization of the carbon layer can also proceed by CVD reactions, no other special carbonization treatment is necessary, but it may be performed.

[0118] (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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] (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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] Thus, the carbon material of the present invention can be easily manufactured.

[0128] <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.

[0129] (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.

[0130] 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.

[0131] (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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] (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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] (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.

[0144] 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.).

[0145] <Electrode compositions, electrode slurries, and electrodes> Next, the electrode composition, electrode slurry, and electrode according to the present invention will be described.

[0146] The electrode having the carbon material of the present invention, preferably an electrode for lithium-ion secondary batteries, is suitable because it has excellent fast discharge properties, capacity characteristics, and charge / discharge characteristics. To manufacture such an electrode, it is useful to use the electrode composition and electrode slurry having the carbon material of the present invention.

[0147] (Composition for electrode) The electrode composition of the present invention comprises the carbon material, active material, and binder of the present invention.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] (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.

[0153] 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.

[0154] 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.

[0155] (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.

[0156] As a method for applying the electrode slurry onto the current collector, a 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 method for drying, a known method can be used without particular limitation, and examples include drying with warm air, hot air, low-humidity air, vacuum drying, and drying methods 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 mold press, a roll press, or the like. By the pressure treatment, the positive electrode composite layer can be well adhered to the current collector.

[0157] <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 collector 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.

[0158] (Positive electrode active material) The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, it may include a lithium composite metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium.

[0159] 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-based oxides (e.g., LiCo 1-d Mn d O2 (where 0 < d < 1), LiMn 2-e Co e O4 (where 0 < e < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (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), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (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 the atomic fractions of the respective 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.

[0160] Among these, from the viewpoint of being able to enhance 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.

[0161] As the positive electrode active material, as a highly stable one, there may 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.

[0162] 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.

[0163] Specific examples of the olivine-type lithium-containing phosphate compound include LiFePO4, LiCoPO4, LiMnPO4, Li 0.90 Ti 0.05 Nb 0.05 Fe 0.30 Co0.30Mn 0.30 PO4 and the like. Among these, LiFePO4 (lithium iron phosphate) is particularly preferable because the iron compound used as a raw material is easily available and inexpensive.

[0164] 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.

[0165] 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 diameter and distribution, specific surface area, density, and the like.

[0166] 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.

[0167] These positive electrode active materials can be used individually or in combination of two or more types.

[0168] (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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] (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.

[0173] 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.

[0174] These binders can be used individually or in combination of two or more types. The amount used is appropriately selected according to the purpose of use, and is typically 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. When the amount of binder used is within this range, the adhesive strength between the electrode active materials and between the electrode active materials and the conductive material can be improved, and consequently the bonding strength with the electrode current collector can be improved, which is preferable.

[0175] (Positive electrode: slurry) The electrode formation slurry used is prepared by mixing the above-mentioned positive electrode active material, conductive material, binder, and other compounding agents as needed, in a dispersion medium. Other compounding agents are selected appropriately according to the intended use, and those commonly used in lithium-ion secondary batteries can be used within their normal range of application.

[0176] There are no particular limitations on the dispersion medium used, but for example, in order to sufficiently uniformly distribute the binder and form a coating film of a predetermined size in the slurry, a medium that dissolves only the binder and does not dissolve other materials is preferably used. Specifically, for example, organic solvents such as dimethylformamide, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, or water may be used, and one of these solvents alone or a mixture of two or more solvents may be used.

[0177] When polyvinylidene fluoride (PVDF) is used as the binder, dimethylformamide or N-methyl-2-pyrrolidone (NMP) is preferred as the dispersion medium, with NMP being particularly preferred.

[0178] The solid content concentration of the electrode-forming slurry, excluding the dispersion medium, can be appropriately selected depending on the method of applying the slurry to the electrode, and is typically in the range of 10 to 90% by weight, preferably 20 to 80% by weight, more preferably 40 to 80% by weight, even more preferably 40 to 70% by weight, and most preferably 50 to 65% by weight.

[0179] The viscosity of the electrode-forming slurry is not particularly limited, but at a temperature 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, even more preferably 10,000 to 35,000 cP, and most preferably 10,000 to 30,000 cP. When the viscosity of the electrode-forming slurry is within this range, the solid components excluding the dispersion medium are uniformly dispersed, and when the electrode-forming slurry is applied to the electrode current collector, it is applied with a uniform thickness, which is preferable.

[0180] (Current collector and positive electrode) The positive electrode can be manufactured by applying the electrode molding slurry described above onto a current collector and drying it. There are no particular limitations on the current collector as long as it is one of the commonly used materials, such as aluminum foil, nickel foil, titanium foil, and stainless steel foil, with rolled aluminum foil being particularly preferred.

[0181] For applying the electrode-forming slurry to the current collector, commonly used printing techniques can be employed. For small coating thicknesses, gravure printing is suitable, while for larger thicknesses, doctor blade printing or die printing are preferable. The coating is then heat-dried; any drying method is acceptable, and the method that achieves the desired bonding strength with the binder is preferred.

[0182] Then, when forming the positive electrode to the predetermined dimensions, industrially available cutting blades and the like, and methods thereof, are preferably used. Furthermore, in order to achieve the predetermined density, industrially available pressurizing devices and the like, and methods thereof, are preferably used as needed.

[0183] <Negative electrode> Next, the negative electrode will be described. The negative electrode is obtained by coating a slurry in which a negative electrode active material, a conductive material, a binder, and a dispersion medium are mixed on a current collecting metal foil such as rolled copper foil, heating and drying to remove the solvent, and then forming it into a predetermined size and density.

[0184] (Negative electrode: active material) As the negative electrode active material, those that can bind and stabilize lithium ions flowing from an external circuit with electrons and have a large number of stabilization sites inside are preferable. 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.

[0185] 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 dedoping 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.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] (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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] (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.

[0196] 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.

[0197] These binders can be used individually or in combination of two or more types. The amount used is appropriately selected according to the purpose of use, and is typically 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, even more preferably 0.2 to 2 parts by weight, and most preferably 0.5 to 1.5 parts by weight per 100 parts by weight of positive electrode active material. When the amount of binder used is within this range, the adhesive strength between the electrode active materials and between the electrode active materials and the conductive material can be improved, and consequently the bonding strength with the electrode current collector can be improved, which is preferable.

[0198] These binders can be used individually or in combination of two or more types. The proportion of each binder in the electrode-forming slurry is typically 0.5 to 3 parts by weight, preferably 0.8 to 2.5 parts by weight, and more preferably 1 to 2.2 parts by weight, per 100 parts by weight of solids excluding the dispersion medium. When the binder content in the electrode-forming slurry is within this range, it is preferable because it can improve the adhesion between electrode active materials and between electrode active materials and conductive materials, and consequently improve the bonding force with the electrode current collector.

[0199] (Negative electrode: dispersion medium) The dispersion medium used is not particularly limited as long as it is a solvent commonly used in the art. 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 mixture of two or more solvents may be used. The dispersion medium is used to dissolve or disperse the electrode active material, conductive material, and binder, taking into consideration the coating thickness of the electrode forming slurry and the manufacturing yield.

[0200] (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.

[0201] (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.

[0202] 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.

[0203] 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.

[0204] <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.

[0205] (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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] (electrolyte) Typically, a non-aqueous electrolyte solution, in which an electrolyte is dissolved in an organic solvent, is used as the electrolyte.

[0210] -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.

[0211] 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.

[0212] 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.

[0213] -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.

[0214] 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] The content ratio of cyclic carbonates in the electrolyte is preferably 1 to 70% by weight, more preferably 3 to 30% by weight, and still more preferably 4 to 50% by weight. A plurality of cyclic carbonates can be mixed and used. The content ratio of linear carbonates in the electrolyte is preferably 40 to 70% by weight, and still more preferably 43 to 68% by weight. A plurality of linear carbonates can be mixed and used.

[0220] As the organic solvent used in the electrolyte, fluorine-containing carbonates can also be preferably used. Specifically, cyclic carbonates having one fluorine atom, linear carbonates having one fluorine atom, cyclic carbonates having two or more fluorine atoms, linear carbonates having two or more fluorine atoms, etc. can be mentioned. From the viewpoint of improving battery characteristics, fluorine-containing cyclic carbonates having two or more fluorine atoms are preferred.

[0221] Specific examples of the 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, 4,4-difluoro-1,3-dioxolan-2-one, etc.

[0222] These fluorine-containing carbonates can be used alone or in combination of two or more. The ratio of the fluorine-containing carbonate in the electrolyte is not particularly limited, but is usually 0.001 to 10% by weight, preferably 0.01 to 5% by weight, more preferably 0.1 to 2% by weight, still more preferably 0.2 to 1% by weight or more, and most preferably 0.25 to 0.5% by weight. If the content of the fluorine-containing carbonate is excessively low, the effect of the addition is difficult to appear. On the contrary, if it is excessively high, the internal pressure of the battery may increase during high-temperature storage.

[0223] As the organic solvent used in the electrolyte, cyclic carbonates having an unsaturated bond or aromatic compounds having 7 to 18 carbon atoms may also be mixed in the electrolyte.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] (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.

[0228] <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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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]

[0234] 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.

[0235] Various physical properties were evaluated according to the following method.

[0236] <Oil absorption measurement> The oil absorption of the carbon material was determined in accordance with "JIS K5101-13-1 Pigment Test Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method".

[0237] <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

[0238] <Nitrogen adsorption / desorption measurement> (Specific surface area, pore volume, mode pore diameter) The nitrogen adsorption and desorption measurements of carbon materials were carried out using an automatic specific surface area / pore size distribution measuring device (BELSORP MINI, manufactured by MicrotracBEL Corp.). 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 isotherm obtained by nitrogen adsorption and desorption measurements. The applicable range of the BET method was set as P / P0 = 0.05 - 0.3. Based on the adsorption and desorption isotherm, the total pore volume was measured by converting the nitrogen adsorption amount at a relative pressure P / P0 = 0.99 at -196 °C into the volume of liquid nitrogen density. The pore size distribution was determined by the BJH method. The average pore diameter d was determined by assuming cylindrical pores and using d = 4V / S from the BET specific surface area S and the total pore volume V. In addition, the mode diameter of the pore size distribution was determined.

[0239] Note that the applicable range of each measured pore volume was as follows. Total pore volume: P / P0 = 0.99 Micropore volume: P / P0 =~0.1 Mesopore volume: P / P0 = 0.1 - 0.96 2 - 10 nm mesopore volume: P / P0 = 0.1 - 0.79 10 - 50 nm mesopore volume: P / P0 = 0.79 - 0.96 Macropore (pores 50 nm or more) volume: P / P0 = 0.96 - 0.99

[0240] <Structural analysis> As one of the indicators showing the complexity of the structure of carbon materials, there are shape indices and aggregate shape judgment methods. The shape index is obtained by statistically analyzing various parameters obtained by image analysis from the transmission electron microscope images of monodispersed materials.

[0241] (Transmission electron microscope observation) The shape of the carbon material was observed using a transmission electron microscope (JEM-2100Plus type, manufactured by JEOL Ltd.). The observation of the carbon material using a transmission electron microscope (TEM) was carried out at an acceleration voltage of 80 - 100 kV.

[0242] (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.

[0243] (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

[0244] <Particle characteristics> (Particle size distribution measurement) Using a laser diffraction particle size distribution analyzer (MT3300EXII, manufactured by Microtrac-Bell Co., Ltd.), particle size distribution measurements were performed to investigate the aggregation state of primary particles in carbon material. The measurement samples used were carbon material that had been immersed in ethanol for 9 minutes without being ground. Median diameters D50, D10, D90, D90 / D10, and D90 / M were determined in the particle size distribution curves.

[0245] <General characteristics> (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.

[0246] (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.

[0247] Various performance evaluations were conducted according to the following methods.

[0248] <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. ◎:5S / cm or more 〇:4S / cm or more but less than 5S / cm △:3S / cm or more but less than 4S / cm ×: Less than 3S / cm

[0249] <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.

[0250] (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

[0251] 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

[0252] 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

[0253] 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%

[0254] <Examples 1-2> (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. 2Approximately 1 g of (manufactured by Nippon Aerosil Co., Ltd., with a total pore volume of 0.138 cc / g, oil absorption of 199 mL / 100 g, D10: 27.6 μm, D50: 49.4 μm, D90: 93.7 μm, D90 / D10: 3.39, carbon content of 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. Subsequently, the carbonaceous-template laminate was extracted by cooling it to room temperature while flowing argon gas 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.

[0255] -Mold removal- Next, the template was removed from the resulting laminate by the following procedure to obtain carbon material A. (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.

[0256] -Heat treatment- The carbon material A 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 that, it was cooled to room temperature, and the calcined carbon material was removed to obtain heat-treated carbon material B.

[0257] Using the carbon materials A and B obtained above, oil absorption properties, 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.

[0258] (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.

[0259] (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.

[0260] <Example 3> Except for a CVD reaction time of 40 minutes, carbon material C was heat-treated in the same manner as in Example 1 to obtain a 2032-size coin-type battery. The obtained carbon material C and test battery were used for material property measurements, conductivity evaluation, and battery evaluation, and the results are shown in Table 1.

[0261] <Example 4> Except for a CVD reaction time of 60 minutes, carbon material D was heat-treated in the same manner as in Example 1 to obtain a 2032-size coin-type battery, 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.

[0262] <Example 5> Except for a CVD reaction time of 80 minutes, carbon material E was heat-treated in the same manner as in Example 1 to obtain a 2032-size coin-type battery, 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.

[0263] <Example 6> A carbon material F was obtained by heat treatment in the same manner as in Example 1, except that the CVD reaction time was set to 130 minutes, 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.

[0264] <Reference example 1> Alumina (Al2O3 / RURALOX SBa200; particle size 7nm, BET specific surface area 205m²) is used as the template. 2 A carbon material G was obtained by heat treatment in the same manner as in Example 1, except that a carbon material (manufactured by SASOL) with a total pore volume of 434 cc / g, oil absorption of 94 mL / 100 g, D10: 2.3 μm, D50: 5.2 μm, D90: 9.2 μm, D90 / D10: 4.05, carbon content <0.1%, manufactured by SASOL) was used, and a 2032 size coin cell 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, and the results are shown in Table 1.

[0265] <Reference example 2> As a template, we used magnesia (MgO / Kyowa Mag MF150; particle size 30 nm, BET specific surface area 132 m²). 2Using carbon material H (manufactured by Kyowa Chemical Industry Co., Ltd.), with a total pore volume of 0.240 cc / g, oil absorption of 198 mL / 100 g, D10: 0.6 μm, D50: 1.9 μm, D90: 3.5 μm, D90 / D10: 5.44, carbon content <0.1%, manufactured by Kyowa Chemical Industry Co., Ltd.), a carbon material H was obtained by heat treatment in the same manner as in Example 1, except that the mold removal operation was performed as described below. Subsequently, a 2032 size coin-type battery was fabricated. Using the obtained carbon material H and test battery, material properties were measured, conductivity was evaluated, and battery evaluation was performed, and the results are shown in Table 1.

[0266] (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.

[0267] <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.

[0268] [Table 1]

[0269] 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 their characteristics in battery performance, such as rapid discharge characteristics (2C maintenance rate), battery capacity characteristics such as charge capacity and discharge capacity, and charge / discharge characteristics (Coulomb rate), are also greatly improved.

[0270] <Example 7> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 2, except that the amount of carbon material B was changed to 0.1% by weight and the amount of positive electrode material NCM was changed to 96.9%.

[0271] <Example 8> In the preparation of the positive electrode, the test battery was manufactured under the same conditions as in Example 2, except that the amount of carbon material B was changed to 0.3% by weight and the amount of positive electrode material NCM was changed to 96.7%.

[0272] <Example 9> In the preparation of the positive electrode, a test battery was manufactured under the same conditions as in Example 2, except that the amount of carbon material B was changed to 1% by weight and the amount of positive electrode material NCM was changed to 96%.

[0273] <Example 10> In the preparation of the positive electrode, the test battery was manufactured under the same conditions as in Example 2, except that the amount of carbon material B was changed to 2% by weight and the amount of positive electrode material NCM was changed to 95%.

[0274] <Example 11> In the preparation of the positive electrode, the test battery was manufactured under the same conditions as in Example 2, except that the amount of carbon material B was changed to 3% by weight and the amount of positive electrode material NCM was changed to 94%.

[0275] <Example 12> In the preparation of the positive electrode, the test battery was manufactured under the same conditions as in Example 2, except that the amount of carbon material B was changed to 4% by weight and the amount of positive electrode material NCM was changed to 93%.

[0276] <Example 13> In the preparation of the positive electrode, the test battery was manufactured under the same conditions as in Example 2, except that the amount of carbon material B was changed to 6% by weight and the amount of positive electrode material NCM was changed to 91%.

[0277] 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 6. Figure 6 shows the relationship between the amount of carbon material, the 2C maintenance rate, and the charge and discharge capacity.

[0278] [Table 2]

[0279] Table 2 and Figure 6 confirm that the high-rate characteristics of the test batteries remained good within the range of carbon material blending amounts for Example 2, 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.

[0280] <Example 14> A negative electrode test battery was manufactured by incorporating carbon material B from Example 2 into the negative electrode. A negative electrode slurry was prepared by stirring and mixing 97% artificial graphite, 1% carbon material B from Example 2, 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.

[0281] 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.

[0282] <Comparative Example 2> In Example 2, instead of carbon material B, commercially available carbon black (DENKA BLACK Li-100; manufactured by Denka Co., Ltd.) was used as the conductive material, and the amount of this conductive material added to the negative electrode was set to 1%, but otherwise, a negative electrode test battery was manufactured in the same manner as in Example 14. When the obtained negative electrode battery was evaluated, the maintenance ratio at 2C discharge was 0.16.

[0283] 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 highly conductive carbonaceous material backbone containing graphene with a six-membered carbon ring structure, compared to the conductive material used in the comparative example, and has space within the particles to hold the electrolyte. The discharge reaction is the reaction in which lithium ions that have been desorbed 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 example can achieve this "simultaneity".

[0284] 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 carbonaceous material having a six-membered carbon ring structure, having an oil absorption capacity of 500 mL / 100 g or more, a mesopore volume of 0.5 cc / g or more, a proportion of the pore volume of 10 to 50 nm within the mesopore volume of 20% or more, and a ratio (D90 / D10) of the particle size of particle diameter D90, where 90% of the particles are located, to the particle size of particle diameter D10, where 10% of the particles are located, of 10% or less in the particle size distribution curve.

2. The carbon material according to claim 1, wherein the hollow particles having the carbonaceous outer shell are linked together in a connected structure having a plurality of branched structures.

3. 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 0.1 or greater.

4. 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 and the crystallite size Lc(002) in the c-axis direction is 10 nm or less.

5. The carbon material according to claim 1, wherein the particle size D90 is 300 μm or less.

6. The carbon material according to claim 1, wherein the particle size D10 is 150 μm or less.

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

8. The carbon material according to claim 1, wherein the ratio of D90 to the mode pore diameter M (D90 / M) is 50 or less, calculated by (1 × 1000) × (D90 / M).

9. The carbon material according to claim 1, wherein the macropore volume is 0.1 cc / g or more.

10. The carbon material according to claim 1, wherein the number density is in the range of 1E+16 to 1E+19 particles / g.

11. A method for producing a carbon material, comprising using an aggregate of an inorganic compound as a mold material, wherein the ratio (D90 / D10) of the particle size D90, where 90% of the particles are located in the particle size distribution curve, to the particle size D10, where 10% of the particles are located, is 4 or less, forming a carbonaceous layer on the surface of the mold material, and then removing the mold material.

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 obtained by 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 obtained by 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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