Carbon material and method for producing same, conductive asistant, dispersion, electrode composition, electrode slurry, electrode, and lithium ion secondary battery

Abstract

Provided is a carbon material that exhibits excellent conductivity and exhibits excellent charge / discharge characteristics, battery capacitance characteristics, and rapid discharge characteristics when an electrochemical element electrode is produced therefrom.　A carbon material according to the present invention is formed from a carbonaceous outer shell having a graphene structure, and has pores. In the carbon material, the BET specific surface area is in a range of 100-2500 m2 / g. The total pore volume measured by nitrogen adsorption / desorption measurement is at least 0.30 cc / g. With respect to the total pore volume, the volume percentage of pores each having a pore diameter of 10 nm or more is at least 30% and the volume percentage of macropores which are pores each having a pore diameter of more than 50 nm is at least 5%. The mode pore diameter is in a meso pore region, which is 2-50 nm. <sp / >

Description

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

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

[0002] Since their birth, lithium-ion secondary batteries have been widely used in a wide range of everyday applications, including smartphones and electric vehicles (EVs). As a result, the manufacturing of lithium-ion secondary batteries has been subject to cost competition and ongoing market demand for higher performance. In order to protect the global environment, carbon dioxide (CO ２ ) For low-emission EVs to replace gasoline-powered vehicles, the lithium-ion secondary batteries they use will need to have improved performance, including rapid discharge characteristics, longer life, higher capacity, and charge / discharge characteristics.

[0003] Carbon materials are widely used in lithium-ion secondary batteries, which require such high performance. For example, Patent Document 1 (JP 2004-22177 A) discloses a nonaqueous electrolyte secondary battery including a positive electrode containing a positive electrode mixture, a negative electrode, and a nonaqueous electrolyte, in which the positive electrode mixture contains a positive electrode active material and 1 part by weight to 10 parts by weight of a conductive agent per 100 parts by weight of the positive electrode active material, and the conductive agent contains flake graphite or carbon black, and the weight ratio of the flake graphite to the sum of the weights of the flake graphite and the carbon black is less than 15% by weight. However, even when such a carbon material is used as the conductive agent, there is a problem in that the rapid discharge characteristics and capacity characteristics are insufficient.

[0004] Patent Document 2 (JP 2019-091587 A) describes a carbon material having a graphene stack structure with a BET specific surface area of ​​10 m ２ / g or more 200m ２The carbon material for an electricity storage device has a pore volume of 0.3 nm or more and 1.0 nm or less in a pore distribution of the carbon material measured in accordance with the HK method of 0.2 mL / g or more, and a DBP absorption (oil absorption) of 150 mL / 100 g or more. However, such a carbon material has problems such as insufficient electrolyte retention, electrical conductivity, rapid discharge characteristics, charge / discharge characteristics, etc.

[0005] Patent Document 3 (WO 2017 / 119428) discloses a carbonaceous material for secondary battery negative electrodes, which contains a carbonaceous material having an average interlayer spacing d002 of the (002) plane of 0.340 nm or more as determined by X-ray diffraction using CuKα radiation as a radiation source, and carbon black having a DBP absorption (oil absorption) of 240 mL / 100 g or more. However, this carbonaceous material has poor rapid discharge characteristics and insufficient capacity characteristics and charge / discharge characteristics.

[0006] Patent Document 4 (JP 2020-100556 A) describes a method for producing a granular material having a specific surface area of ​​80 m2 measured by the BET measurement method. ２ / g or more 250m ２ / g or less and an oxygen to carbon element ratio (O / C) measured by X-ray photoelectron spectroscopy of 0.09 to 0.30. However, such a carbon material has insufficient electronic conductivity and ionic conductivity, and is inferior in rapid discharge properties and capacity characteristics.

[0007] Patent Document 5 (JP 2017-183292 A) discloses a positive electrode for a non-aqueous secondary battery having an active material layer on a current collector, the active material layer having a plurality of active material particles and a plurality of graphenes, the active material particles having a layered rock salt structure, one of the graphenes being in surface contact with the plurality of active material particles and another of the graphenes, and the graphene having an oxygen concentration of 2 atomic % or more and 20 atomic % or less. However, this positive electrode for a non-aqueous secondary battery still has problems such as insufficient conductivity and poor rapid discharge characteristics and capacity characteristics.

[0008] Patent Document 6 (Japanese Patent Publication No. 2023-501558) discloses porous reduced graphene oxide containing mesopores and macropores having a size of 2 nm to 500 nm.

[0009] Patent Document 7 (JP 2021-84819 A) discloses a method for producing a porous carbon material, which includes a coating step of forming a precursor containing graphene on the surface of a template made of alkaline earth metal oxide nanoparticles, and a separation and removal step of dissolving the template in a fluorine-free acid to separate the template and the precursor. However, the rapid discharge characteristics, capacity characteristics, and charge and discharge characteristics of the carbon material obtained by this production method, particularly when used in a lithium-ion secondary battery, have not been studied.

[0010] Patent Document 8 (WO 2020 / 080520) discloses a capacitor comprising at least a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a positive electrode active material and the negative electrode includes a negative electrode active material, the positive electrode active material and the negative electrode active material include a graphene porous carbon sheet, the graphene porous carbon sheet includes a graphene porous carbon material and carbon nanotubes, the graphene porous carbon material is a porous carbon material made of graphene, the positive electrode side current collector and the negative electrode side current collector are made of aluminum material, the aluminum material is coated with an amorphous carbon coating, and the amorphous carbon coating has a thickness of 60 nm or more and 300 nm or less.

[0011] Patent Document 9 (JP 2022-191280 A) describes a first substrate, Li ｘ S ｙa cathode disposed on a first substrate, the cathode comprising a cathode mixture comprising silicon particles and a second substrate; an anode disposed on a second substrate, the anode mixture comprising silicon particles and a second granular carbon; and an electrolyte disposed between the cathode and the anode, the electrolyte comprising a solvent and a lithium salt; wherein the first granular carbon or the second granular carbon comprises carbon aggregates comprising a plurality of carbon nanoparticles, each carbon nanoparticle comprising graphene, the graphene in the plurality of carbon nanoparticles comprising at most 15 layers; a ratio of carbon to elements other than hydrogen in the carbon aggregate is greater than 99%; a median diameter of the carbon aggregates comprising the carbon nanoparticles is 0.1 μm to 50 μm; and a surface area of ​​the carbon aggregates is 10 to 300 m as measured by a BET method using nitrogen as an adsorbate. ２ / g, and the carbon aggregates have an electrical conductivity of 500 S / m to 20,000 S / m when compressed. However, the carbon aggregates used in such lithium ion batteries have almost no pores because they are explosively produced in microwave plasma during a residence time of the raw material gas of 0.001 seconds to approximately 2.0 seconds.

[0012] In particular, the carbon materials described in Patent Documents 1 to 9 have room for further improvement in terms of increasing electrical conductivity and improving rapid discharge characteristics, capacity characteristics, and charge / discharge characteristics when used in lithium ion secondary batteries.

[0013] Japanese Patent Application Laid-Open No. 2004-22177 Japanese Patent Application Laid-Open No. 2019-091587 International Publication No. 2017 / 119428 Japanese Patent Application Laid-Open No. 2020-100556 Japanese Patent Application Laid-Open No. 2017-183292 Special Publication No. 2023-501558 Japanese Patent Application Laid-Open No. 2021-84819 International Publication No. 2020 / 080520 Japanese Patent Application Laid-Open No. 2022-191280

[0014] The present invention has been made in view of the above circumstances, and provides a carbon material that has excellent electrical conductivity and is capable of improving 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 conductive additive, a dispersion, an electrode composition, an electrode slurry, an electrode, and a lithium ion secondary battery.

[0015] In light of the above-mentioned problems, the present inventors conducted extensive research and found that a carbon material formed by a carbonaceous outer shell having a graphene structure and having pores has a large BET specific surface area and a large total pore volume, and in which the volume fraction of pores having a pore diameter of 10 nm or more and the volume fraction of macropores having a pore diameter of 50 nm or more account for a predetermined value or more of the total pore volume, and the carbon material has a peak top diameter (mode pore diameter) in the mesopore region of 2 nm to 50 nm or less, has excellent electrical conductivity as a carbon material, and when used in a lithium ion secondary battery, has excellent rapid discharge characteristics at a 2C retention rate, battery capacity characteristics in a charge-discharge test, and Coulomb rate (charge-discharge characteristics). In other words, the inventors found that by increasing the electronic conductivity of the carbon material and providing a structure capable of retaining a large amount of electrolyte, high ionic conductivity can be imparted, thereby significantly improving the rapid discharge characteristics, battery capacity characteristics, and charge-discharge characteristics of the lithium ion secondary battery.

[0016] The inventors have also found that specifying the number of particles per unit mass and the apparent density of the carbon material creates an efficient path for electron conductivity, and also allows a large amount of electrolyte to be retained, highly enhancing ionic conductivity, thereby further improving the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of the lithium ion secondary battery.The inventors have also found that specifying the ash content of the carbon material allows further improving the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics of the lithium ion secondary battery.

[0017] The inventors have further discovered that a carbon material that has excellent conductivity and stability and can significantly improve the rapid discharge properties, battery capacity characteristics, and charge / discharge characteristics of a lithium ion secondary battery can be easily produced by using an aggregate of a fumed compound as a template.

[0018] The present inventors have completed the present invention based on these findings.

[0019] (1) A carbon material formed by a carbonaceous outer shell having a graphene structure and having pores, the carbon material having a BET specific surface area of ​​100 m ２ / g or more 2500m ２ / g or less, a total pore volume measured by nitrogen adsorption / desorption measurement is 0.30 cc / g or more, a volume ratio of pores having a pore diameter of 10 nm or more to the total pore volume is 30% or more, a volume ratio of macropores having a pore diameter of more than 50 nm is 5% or more, and a mode pore diameter is in the mesopore region of 2 nm or more and 50 nm or less.

[0020] (2) Intensity of the 2D band in Raman spectroscopy (I ２Ｄ ) versus G band intensity (I Ｇ ) intensity ratio (I Ｇ / I ２Ｄ ) is in the range of 1.0 or more and 10 or less.

[0021] (3) The number of particles per unit mass of the carbon material is 1.0 × 10 １６ pieces / g or more 1.0×10 １９ The carbon material according to (1) or (2) above, wherein the number of carbon atoms is in the range of 0.01 to 0.01 / g or less.

[0022] (4) The carbon material according to any one of (1) to (3) above, having an apparent density expressed as 1 / (the total pore volume+1 / true density) of 1.00 g / cc or less.

[0023] (5) The carbon material according to any one of (1) to (4) above, wherein the ash content in the carbon material is 5000 ppm or less.

[0024] (6) The carbon material according to any one of (1) to (5) above, which is used in a lithium ion secondary battery.

[0025] (7) A method for producing a carbon material according to any one of (1) to (6) above, comprising: a carbonaceous layer forming step of forming a carbonaceous layer on the surface of a template made of an aggregate of a fumed compound; and a template removing step of removing the template.

[0026] (8) A conductive additive for a battery electrode, comprising the carbon material according to any one of (1) to (6) above.

[0027] (9) A dispersion liquid comprising the carbon material according to any one of (1) to (6) above and a dispersion medium in which the carbon material is dispersed.

[0028] (10) A composition for an electrode, comprising the carbon material according to any one of (1) to (6) above, an active material, and a binder.

[0029] (11) A slurry for an electrode, comprising the electrode composition according to (10) above and a solvent in which the electrode composition is dispersed.

[0030] (12) An electrode comprising the carbon material according to any one of (1) to (6) above.

[0031] (13) A lithium ion secondary battery containing the carbon material according to any one of (1) to (6) above.

[0032] According to the present invention, it is possible to provide a carbon material that has excellent conductivity and is capable of improving rapid discharge properties, battery capacity characteristics, and charge / discharge characteristics when used in a lithium ion secondary battery, a method for producing the same, a conductive additive, a dispersion, an electrode composition, an electrode slurry, an electrode, and a lithium ion secondary battery.

[0033] 6 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. FIG. 6 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. FIG. 6 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. FIG. 6 shows an example of a Raman spectrum measured for a carbon material according to one embodiment of the present invention. FIG. 6 is a diagram showing discharge curves with different discharge current values ​​using a test battery of Example 1 according to one embodiment of the present invention. FIG. 6 shows the relationship between the amount of carbon material blended and the 2C retention rate and discharge capacity for test batteries according to the examples. The left vertical axis represents the 2C retention rate, the right vertical axis represents the discharge capacity, and the horizontal axis represents the amount of carbon material blended. In FIG. 6, ● represents the 2C retention rate, and △ represents the discharge capacity.

[0034] Hereinafter, embodiments of the present invention will be described in detail.

[0035] <Carbon Material> The carbon material of the present invention is a carbon material formed by a carbonaceous outer shell having a graphene structure and having pores, and has a BET specific surface area of ​​10 m ２ / g or more 2500m ２ / g or less, the total pore volume is 0.30 cc / g or more, the volume ratio of pores having a pore diameter of 10 nm or more to the total pore volume is 30% or more, the volume ratio of macropores having a pore diameter of more than 50 nm is 5% or more, and the mode pore diameter is in the mesopore region of 2 nm or more and 50 nm or less.

[0036] The carbon material of the present invention is formed by a carbonaceous outer shell having a graphene structure, and has excellent electronic conductivity. FIG. 1 shows a TEM image observed using a transmission electron microscope (TEM, model number: JEM-ARM300F, manufactured by JEOL Ltd.) at an acceleration voltage of 80 kV. Graphene is a sheet-like substance of sp2-bonded carbon, and as shown in FIG. 1, six-membered carbon ring structures are connected in a planar manner to form a honeycomb-like hexagonal lattice structure. Furthermore, the carbon material of the present invention has a graphene structure, and the strength of the 2D band (I ２Ｄ ) versus G band intensity (I Ｇ) intensity ratio (I Ｇ / I ２Ｄ ) is 0.4 or more.

[0037] 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, model number: H-7650, manufactured by Hitachi High-Technologies Corporation) at an accelerating voltage of 100 kV and a magnification of 15,000 times. The degree of particle transmission in Figure 2 also reveals that the interior 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 ring shapes, and the ring shapes may or may not be connected to hollow particles having a carbonaceous outer shell.

[0038] One embodiment of the carbon material of the present invention has an aggregate structure in which carbon materials having the above-described complex structure are aggregated. Fig. 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 accelerating voltage of 100 kV and a magnification of 40,000 times.

[0039] As described above, the carbon material of the present invention is formed by a carbonaceous outer shell containing a highly electronically conductive graphene structure and has pores. Here, each pore enclosed by the carbonaceous outer shell is a mesopore, preferably a mesopore with a pore diameter of 10 nm or more. Furthermore, the ring-shaped structures formed by the chains of branched connected structures or the interbranch voids of the aggregates form macropores with a pore diameter of 50 nm or more. This allows for a large BET specific surface area, a large total pore volume, and a high volumetric ratio of pores with a pore diameter of 10 nm or more and macropores with a pore diameter of 50 nm or more. As a result, it is possible to impart ionic conductivity that allows for the retention of a large amount of electrolyte and the migration of lithium ions. That is, the carbon material of the present invention has both electronic and ionic conductivity, and when used as a conductive additive in lithium-ion secondary batteries, it significantly increases conductivity and improves rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics.

[0040] (BET specific surface area, pore volume, mode pore diameter) The BET specific surface area of ​​the carbon material of the present invention is the BET specific surface area calculated from nitrogen adsorption as specified in JIS Z8830, and is ２ / g or more 2500m ２ / g or less, preferably 100m ２ / g or more 2000m ２ / g or less, more preferably 300m ２ / g or more 1800m ２ / g or less, more preferably 500m ２ / g or more 1500m ２ / g or less, particularly preferably 800m ２ / g or more 1200m ２ When the BET specific surface area of ​​the carbon material of the present invention is in this range, it is preferable in that the electronic conductivity and the ionic conductivity can be highly increased.

[0041] The total pore volume of the carbon material of the present invention, as measured by nitrogen adsorption / desorption analysis, is 0.30 cc / g or more, preferably 0.50 cc / g or more, more preferably 1.00 cc / g or more, even more preferably 1.50 cc / g or more, and particularly preferably 2.00 cc / g or more. On the other hand, the upper limit of the total pore volume of the carbon material is preferably 20.00 cc / g or less, more preferably 15.00 cc / g or less, even more preferably 10.00 cc / g or less, even more preferably 8.00 cc / g or less, and particularly preferably 7.00 cc / g or less. If the total pore volume of the carbon material is too small, the amount of electrolyte retained in the carbon material will be reduced, which is undesirable. On the other hand, if the total pore volume of the carbon material is too large, the skeleton strength of the pore structure will be weakened and the pore shape will not be able to be maintained, which is undesirable. In the carbon material of the present invention, when the total pore volume is within the above range, the pore shape will have appropriate strength, contributing to the stability of the connected structure.

[0042] The present invention is characterized in that the carbon material has a mode pore diameter (M), which is the most frequent value of pore diameters, in the mesopore region of 2 nm to 50 nm in a pore distribution curve. Specifically, the mode pore diameter (M) of the carbon material of the present invention is in the range of 2 nm to 50 nm, preferably 5 nm to 45 nm, more preferably 10 nm to 40 nm, even more preferably 12 nm to 30 nm, and particularly preferably 15 nm to 25 nm. When the mode pore diameter (M) of the pore distribution of the carbon material is in this range, high ionic conductivity and electronic conductivity can be achieved, which is preferable.

[0043] In the carbon material of the present invention, the volume ratio of mesopores, which are pores having a pore diameter in the range of 2 nm to 50 nm, to the total pore volume is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, even more preferably 45% or more, and particularly preferably 50% or more. On the other hand, the upper limit of the volume ratio of mesopores to the total pore volume is preferably 90% or less, more preferably 85% or less, even more preferably 80% or less, even more preferably 75% or less, and particularly preferably 70% or less. When the mesopore volume of the carbon material is within this range, the interconnected structure of the hollow particles has appropriate strength, which contributes to the stability of the hollow particles and allows them to maintain their shape.

[0044] In the carbon material of the present invention, the volume fraction of pores having a pore diameter of 10 nm or more is 30% or more, preferably 40% or more, more preferably 50% or more, even more preferably 60% or more, and particularly preferably 70% or more. This allows for a high level of balance between electronic conductivity and ionic conductivity. On the other hand, the upper limit of the volume fraction of pores having a pore diameter of 10 nm or more relative to the total pore volume is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.

[0045] In the carbon material of the present invention, the volume fraction of macropores, which are pores with a pore diameter exceeding 50 nm, relative to the total pore volume is 5% or more, preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, and particularly preferably 25% or more. On the other hand, the upper limit of the volume fraction of macropores relative to the total pore volume is preferably 80% or less, more preferably 70% or less, even more preferably 60% or less, even more preferably 50% or less, and particularly preferably 45% or less. An excessively small volume fraction of macropores (the volume fraction of pores with a diameter exceeding 50 nm) in the carbon material results in poor ionic conductivity, while an excessively large volume fraction results in poor strength characteristics of the carbonaceous material, so neither is preferable. In this specification, "micropores" refers to pores with a pore diameter of less than 2 nm. In this specification, "mesopores" refers to pores with a pore diameter in the range of 2 nm to 50 nm. In this specification, "macropores" refers to pores with a pore diameter exceeding 50 nm.

[0046] 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, for example, 1 or more, preferably 1.2 or more, more preferably 1.5 or more, even more preferably 2 or more, and particularly preferably 2.2 or more, with an upper limit of, for example, 15 or less, preferably 10 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 5 or less. When the number of carbonaceous layers is within this range, the strength characteristics and elastic deformation of the carbonaceous material are excellent, the hollow structure of the particles and the macropore shape formed by the interconnection of the particles can be maintained, and the lithium-ion secondary battery characteristics can be highly improved. The number of carbonaceous layers of the carbon material is specifically calculated as described in the Examples below. After laminating the carbon layers on the template particles, the weight of the carbon layers is calculated using thermogravimetric analysis (TG). The weight of the carbon layers per unit area of ​​the template is calculated from the weight of the carbon layers and the BET specific surface area of ​​the template particles, and this is then used as the weight of the carbon layers per unit area of ​​single-layer graphene (7.61 × 10 －４ g / m ２ ) is the value calculated by dividing

[0047] (Structural Analysis) In the present invention, the state of the carbon material can be analyzed by Raman spectroscopy. An example of the Raman spectrum measured for the carbon material of the present invention is shown in FIG. 4. In the Raman spectrum, the wave number 1593 cm －１ The peak in the region around 1356 cm in the Raman spectrum is called the G band, which indicates the sp2 bond (C=C stretching motion of the aromatic ring) of the carbon material. －１ The peak present around the wavenumber 2680 cm in the Raman spectrum is called the D band, which indicates the sp3 bond (C-H stretching motion) of the carbon material, and increases when the sp2 bond in the carbon six-membered ring structure of the carbonaceous layer is broken to form an sp3 bond. －１ The peak present in the region nearby is called the 2D band, which is a band indicating secondary phonon scattering (C—H stretching motion) and is a band indicating the number of layers of the carbon material.

[0048] The intensity of the 2D band of the carbon material (I ２Ｄ ) versus G band intensity (I Ｇ ) intensity ratio (I Ｇ / I ２Ｄ ) is said to be an index that indicates the stacking state of graphene layers (D. Graf, et al., NANO LETTERS, 7, 238-242; (2007)). In the same paper, the intensity ratio I Ｇ / I ２Ｄ It is said that when is 0.2, the graphene layer becomes one layer.

[0049] The carbon material of the present invention has a 2D band intensity (I ２Ｄ ) versus G band intensity (I Ｇ ) intensity ratio (I Ｇ / I ２Ｄ ) is, for example, preferably 1.0 or more, more preferably 1.2 or more, and particularly preferably 1.4 or more, and the upper limit is, for example, preferably 10 or less, 5.0 or less, 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 ２ＤWhen the value of the intensity ratio I of the carbon material is in this range, the strength characteristics and elastic deformability that maintain the hollow structure of the carbon material are balanced, and the desired characteristics of the lithium ion secondary battery, such as rapid discharge characteristics, capacity characteristics, and durability, are highly improved. Ｇ / I ２Ｄ However, if the value deviates too much from the lower limit, graphene generation will be insufficient, resulting in a decrease in electronic conductivity and a decrease in discharge capacity. If the value deviates too much from the upper limit, the number of graphene layers will increase, resulting in poor flexibility, a decrease in electrode density and a decrease in filling capacity, both of which are undesirable.

[0050] (Particle Shape Characteristics) In one embodiment, the carbon material of the present invention preferably has a connected structure in which the hollow particles having the above-described carbonaceous outer shell are linked together with a plurality of branched structures.

[0051] The particle size distribution curve of the carbon material of the present invention was measured after immersing the unground material in a solvent for 9 minutes, and shows the difference in cohesive strength of the linked structure.

[0052] The median diameter D50 of the carbon material of the present invention, at which half of the particles are present in the particle size distribution curve, is, for example, in the range of 0.5 μm to 150 μm, preferably 1 μm to 100 μm, more preferably 10 μm to 80 μm, even more preferably 15 μm to 60 μm, and particularly preferably 20 μm to 50 μm. When the median diameter D50 of the carbon material is in this range, it is preferable because the electronic conductivity and ionic conductivity are highly enhanced.

[0053] The particle diameter D10 at which 10% of the particles exist in the particle size distribution curve of the carbon material of the present invention is, for example, in the range of 0.1 μm or more and 100 μm or less, preferably in the range of 0.5 μm or more and 50 μm or less, more preferably in the range of 1 μm or more and 50 μm or less, even more preferably in the range of 5 μm or more and 30 μm or less, and particularly preferably in the range of 10 μm or more and 15 μm or less.

[0054] The particle diameter D90 at which 90% of the particles exist in the particle size distribution curve of the carbon material of the present invention is, for example, in the range of 5 μm to 250 μm, preferably in the range of 10 μm to 150 μm, more preferably in the range of 20 μm to 100 μm, even more preferably in the range of 30 μm to 70 μm, and particularly preferably in the range of 40 μm to 60 μm. When the D90 of the carbon material is in this range, it is preferable because the conductivity can be highly increased.

[0055] The ratio of D90 to D10 of the carbon material of the present invention, expressed as the value of D90 / D10, is, for example, 100 or less, preferably 50 or less, more preferably 25 or less, even more preferably 10 or less, and particularly preferably 5 or less, with the lower limit being, for example, 1 or more, preferably 1.5 or more, more preferably 2 or more, even more preferably 2.5 or more, and particularly preferably 3 or more. If the D90 / D10 of the carbon material is excessively large, the carbon material will have strong agglomeration properties and poor dispersibility, which makes it difficult to obtain sufficient conductivity and high-performance properties for the lithium-ion secondary battery, and is therefore undesirable.

[0056] The ratio (D90 / M) of D90 to the mode pore diameter (M) of the carbon material of the present invention is calculated by dividing the D90 value [μm] by the mode pore diameter (M) [nm] and multiplying the result by 1000, and is, for example, 50 or less, preferably 20 or less, more preferably 10 or less, even more preferably 6 or less, and particularly preferably 4 or less. If the (D90 / M) ratio of the carbon material is excessively large, the carbon material will have strong agglomeration properties and poor dispersibility, which is undesirable as it will not be able to sufficiently obtain the conductivity and high performance properties of the lithium ion secondary battery.

[0057] (General Properties) The carbon content of the carbon material of the present invention is, for example, 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 particularly preferably 99% by weight or more. If the carbon content of the carbon material is too low, the electronic conductivity will be poor, which is undesirable.

[0058] The oil absorption of the carbon material of the present invention is the oil absorption of refined linseed oil measured in accordance with, for example, JIS K5101-13-1 (Testing methods for pigments - Part 13: Oil absorption - Section 1: Refined linseed oil method), and is, for example, 100 mL / 100 g or more, preferably 300 mL / 100 g, more preferably 500 mL / 100 g or more, even more preferably 800 mL / 100 g or more, and particularly preferably 1000 mL / 100 g or more, with the upper limit being, for example, 5000 mL / 100 g or less, preferably 4000 mL / 100 g or less, more preferably 3500 mL / 100 g or less, even more preferably 3000 mL / 100 g or less, and particularly preferably 2500 mL / 100 g or less.

[0059] The oil absorption of the carbon material of the present invention is significantly higher than that of carbon black, which is commonly used as a conductive additive in lithium-ion secondary batteries, and not only can the amount of electrolyte that can be held in the internal space of the hollow particles of the connected structure, but also the amount of electrolyte that can be held in the gaps formed in the parts surrounded by the connecting outer shells and the parts surrounded by the connecting aggregate structures is large, making it possible to stably supply lithium ions and contributing to the rapid discharge characteristics, charge / discharge characteristics, battery capacity characteristics, etc. of lithium-ion secondary batteries. If the oil absorption of the carbon material is too low, the amount of electrolyte that can be held is small, causing a delay in the supply of ions during a rapid reaction and reducing the discharge capacity. Conversely, if the oil absorption is too high, it becomes difficult to maintain the structure of the carbon material and makes it difficult to control the amount of electrolyte that can be held, both of which are undesirable.

[0060] The electrical conductivity of the carbon material of the present invention, as a value at a pressure of 10 MPa, is, for example, in the range of 1 S / cm to 100 S / cm, preferably 5 S / cm to 70 S / cm, more preferably 10 S / cm to 50 S / cm, even more preferably 15 S / cm to 40 S / cm, and particularly preferably 20 S / cm to 30 S / cm. The electrical conductivity of a carbon material is calculated as the reciprocal of its electrical resistivity. The electrical resistivity of a carbon material can be measured, for example, according to JIS K1469.

[0061] The number per unit mass of the carbon material of the present invention (number density of the carbon material) is a value calculated by the method described below, and is, for example, 1.0 × 10 １６ pieces / g or more 1.0×10１９ particles / g or less, preferably 5.0 × 10 １６ pieces / g or more 5.0×10 １８ particles / g or less, more preferably 1.0 × 10 １７ pieces / g or more 3.0×10 １８ 10 pieces / g or less, particularly preferably 2.0 × 10 １７ pieces / g or more 2.0×10 １８ When the number of particles per unit mass of the carbon material is in this range, the retention of the electrolyte becomes optimal, which is preferable.

[0062] The carbon material of the present invention has an apparent density, expressed as 1 / (total pore volume + 1 / true density), calculated using the total pore volume value described below, of, for example, 1.00 g / cc or less, preferably 0.80 g / cc or less, more preferably 0.50 g / cc or less, even more preferably 0.34 g / cc or less, and particularly preferably 0.30 g / cc or less, with the lower limit being, for example, 0.01 g / cc or more, preferably 0.02 g / cc or more, more preferably 0.05 g / cc or more, even more preferably 0.10 g / cc or more, and particularly preferably 0.15 g / cc or more. When the apparent density of the carbon material is within this range, the conductivity and electrolyte retention of the carbon material are highly enhanced, which is suitable.

[0063] The ash content of the carbon material of the present invention is, for example, 10,000 ppm or less, preferably 5,000 ppm or less, more preferably 4,000 ppm or less, even more preferably 3,500 ppm or less, still more preferably 3,000 ppm or less, and particularly preferably 2,100 ppm or less. When the ash content of the carbon material is in this range, the stability of the electrolyte is excellent and the durability and performance of the lithium ion secondary battery can be improved, which is suitable.

[0064] (Uses of Carbon Material) The carbon material can be preferably used as a part of an electrode material for a battery such as a lithium ion secondary battery, for example, as a conductive assistant, etc. Furthermore, the carbon material can be contained in a conductive assistant, a dispersion, an electrode composition, an electrode slurry, etc., and can be preferably used as a part of a material constituting an electrode for a battery or an electrode for other electronic components.

[0065] The carbon material of the present invention has the electron transport properties of the graphene structure, a large pore volume that allows it to retain an electrolyte, provides ionic conductivity for lithium ions, and exhibits excellent stability in the electrolyte. Therefore, when incorporated into an electrode of a lithium-ion secondary battery, the carbon material can exhibit a function of supporting the battery reaction in the lithium-ion secondary battery. Furthermore, one embodiment of the carbon material of the present invention has a connected structure in which hollow granular objects surrounded by a carbonaceous outer shell containing graphene are connected to one another. The presence of spaces within the granular objects and within the space surrounded by the connected structure allows for the penetration and retention of an electrolyte containing dissolved lithium ions, resulting in excellent ion supply during the reaction. Therefore, the carbon material of the present invention can favorably support the secondary battery reaction.

[0066] The positive electrode material for lithium-ion secondary batteries is a lithium-containing transition metal oxide with low electronic conductivity, in the form of a powder with a particle size distribution. Conventionally, an electron conduction path is established by mixing a binder resin with a conductive additive made of a carbon material that aids in the electron conduction of the battery reaction, and then pressurizing and fixing the mixture to a current collector. All materials other than the binder resin are powder particles, and the electrolyte exists in the spaces between the particles. For this reason, it was difficult with conventional technology to actively position the electrolyte, or in other words, lithium ions, near the positive electrode material.

[0067] In contrast, in this embodiment, the above-described carbon material is used instead of the conventionally used conductive additive. The carbon material of this embodiment has a space inside the carbonaceous outer shell, and can therefore hold an electrolyte in that space. The carbon material of this embodiment has a larger space inside than carbon black, which has conventionally been used as a conductive additive. Therefore, the carbon material of this embodiment can be said to be a material that simultaneously assists in the supply of electrons and ions necessary for the battery reaction and enables a rapid battery reaction.

[0068] <Method for Producing Carbon Material> Next, a method for producing a carbon material according to the present invention will be described. The carbon material according to the present invention can be easily produced by, for example, forming a carbonaceous layer on the surface of a template made of an aggregate of a fumed compound, and then removing the template.

[0069] (Template Material) Examples of fumed compounds used as template materials include compounds obtained by flame hydrolysis, which is a dry manufacturing method for inorganic materials. These compounds are suitable for use because they form complex, elongated aggregate structures of primary particles.

[0070] A typical example of a fumed compound is fumed silicon dioxide (fumed silica). Fumed silicon dioxide produced by flame hydrolysis does not undergo a liquid phase process during production, so aggregation is gentle. For this reason, fumed silicon dioxide has excellent dispersibility in liquid phases and compounds (solid phases). Fumed silicon dioxide is produced by high-temperature gas phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame. By changing production conditions such as the flame temperature, oxygen and hydrogen supply ratio, raw material supply amount, and residence time, it is possible to produce fumed silicon dioxide with an average primary particle size of 7 nm to 40 nm and a BET specific surface area of ​​50 m. ２ / g~380m ２ / g of silicon dioxide particles are obtained.

[0071] The structure of the fumed compound used in the template of the present invention is preferably a particulate structure. The average primary particle size of the fumed compound used in the template of the present invention is, for example, 1 nm to 150 nm, preferably 5 nm to 100 nm, more preferably 10 nm to 60 nm, even more preferably 15 nm to 50 nm, and particularly preferably 20 nm to 40 nm. When the average primary particle size of the template material is within this range, the pore volume of pores of 10 nm or more in the produced carbon material can be significantly increased, which is preferable. Furthermore, when the average primary particle size of the fumed compound is within this range, handling is easy and the permeability of the raw material gas that serves as the carbon source for the carbonaceous layer is improved, facilitating uniform carbon coating.

[0072] The BET specific surface area of ​​the fumed compound used in the mold of the present invention is, for example, 1 m ２ / g to 1000m ２ / g, preferably 10m ２ / g~500m ２ / g, more preferably 20m ２ / g to 200m ２ / g, more preferably 40m ２ / g~160m ２ / g, particularly preferably 50m ２ / g~105m ２ When the BET specific surface area of ​​the template material is in this range, the volume of pores of 10 nm or more in size can be significantly increased in the produced carbon material, which is preferable.

[0073] The BET specific surface area of ​​the produced carbon material depends on the BET specific surface area of ​​the template. The smaller the average primary particle diameter, the larger the ratio of the volume to the surface area of ​​the particles that serve as the template. Therefore, the smaller the average primary particle diameter of the particles, the larger the surface area per volume, i.e., the surface area per unit mass. Therefore, by using particles of a fumed compound with a small average primary particle diameter, a carbon material with a large BET specific surface area can be obtained.

[0074] The structure of the agglomerate of the fumed compound used as a template in the present invention is preferably complex and elongated, and capable of realizing a higher-order structure. For example, an agglomerate structure in which the primary particle diameter has a plurality of branched structures and is linked together like beads is preferred.

[0075] The carbon content of the fumed compound used as a template in the present invention is, for example, 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 particularly preferably 0.5% by weight or more, with the upper limit being, for example, 5% by weight or less, preferably 4% by weight or less, more preferably 3% by weight or less, even more preferably 2.5% by weight or less, and particularly preferably 2% by weight or less. When the carbon content of the fumed compound is in this range, it is preferable because it facilitates the formation of a carbonaceous layer on the surface of the template.

[0076] These template materials can be used either alone or in combination of two or more.

[0077] (Carbonous Layer Forming Process) In the present invention, the carbonous layer can be formed on the surface of the mold material by contacting the mold material with an organic substance that serves as a carbon source and subjecting it to a carbonization heat treatment. The contact with the carbon source and the carbonization heat treatment can be performed simultaneously or separately. The mold material is contacted with the carbon source at a temperature ranging from room temperature to 1000°C, for example. The carbonization heat treatment is performed at a temperature at which the organic substance that serves as the carbon source thermally decomposes, for example, at a temperature ranging from 400°C to 1000°C.

[0078] The method for contacting the carbon source with the template material is preferably a gas-phase contacting method, which is a method in which an organic gas is introduced at high temperature and brought into contact with the template material, such as the so-called CVD (chemical vapor deposition) method.

[0079] In the CVD method, an organic compound as a carbon source is brought into contact with a mold material, and the carbon source is carbonized to bond strongly to the mold material. In this case, the CVD method is preferably carried out in a temperature range in which a dehydrogenation reaction can proceed, specifically, 400°C to 1000°C.

[0080] The organic compound used as a carbon source in the gas-phase contact method may be appropriately selected depending on the intended use. Suitable examples include hydrocarbons such as saturated hydrocarbons, unsaturated hydrocarbons having double and / or triple bonds, alicyclic hydrocarbons, and aromatic hydrocarbons. Saturated hydrocarbons may be either linear or branched, and examples include methane, ethane, and propane. Unsaturated hydrocarbons may be either linear or branched, and examples include ethylene, propylene, isoprene, and acetylene. Alicyclic hydrocarbons include cyclopropane and cyclohexane. Aromatic hydrocarbons include benzene and toluene. Among these hydrocarbons, it is desirable to use methane, ethane, acetylene, ethylene, propylene, and benzene, and methane, propylene, and benzene are preferred from the viewpoint of precipitating highly crystalline carbon. Methane is particularly preferred because it has a high thermal decomposition temperature and can produce highly crystalline carbon.

[0081] As the organic compound used in the gas phase contact method, alcohols such as methanol, ethanol, propanol, and butanol, and nitrogen-containing compounds such as acetonitrile and acrylonitrile can also be used.

[0082] The reaction temperature in the CVD reaction is appropriately selected depending on the decomposition temperature of the organic compound as the carbon source, and is, for example, in the range of 400°C to 1000°C, preferably 600°C to 950°C, and more preferably 800°C to 900°C.

[0083] The reaction time in the CVD reaction (CVD treatment time at a predetermined heating temperature) is appropriately selected depending on the type of template material, the type of organic compound used as the carbon source, or the number of carbon layers to be deposited, but is, for example, in the range of 0.1 to 10 hours, preferably 0.5 to 5 hours, and more preferably 1 to 3 hours. Furthermore, the analysis method disclosed herein can be applied to analyze the product, and the time required for sufficient carbon deposition can be appropriately set based on the results.

[0084] The CVD reaction can be carried out under an inert gas atmosphere, if necessary. Examples of inert gases include nitrogen, helium, neon, and argon, with argon being preferred. In the CVD method, carbon can be easily adsorbed or deposited on the template material in the gas phase by heating a gaseous organic compound together with a carrier gas while flowing the compound in contact with the template material. The type, flow rate, flow rate, and heating temperature of the carrier gas can be adjusted appropriately depending on the type of organic compound used. Examples of the carrier gas include the inert gases listed above, but they may also be mixtures with oxygen gas or hydrogen gas. Preferably, argon is used as the carrier gas.

[0085] The ratio of the amount of the organic compound introduced to the total amount of the carrier gas and the organic compound is adjusted to a range of preferably 1 vol % to 70 vol %, more preferably 5 vol % to 50 vol %, still more preferably 10 vol % to 40 vol %, and particularly preferably 15 vol % to 35 vol %, from the viewpoint of forming an optimum number of graphene layers.

[0086] (Template Removal Step) The template can be removed after the carbonaceous layer is formed by any method that removes the template and leaves the formed carbonaceous layer. For example, a dissolution method using an acid or alkali can be mentioned, and a dissolution method using an acid is preferred.

[0087] The acid used in the present invention is appropriately selected depending on the type of template material, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, and hydrofluoric acid, with hydrochloric acid and hydrofluoric acid being preferred. The concentration of the acid used to dissolve and remove the template is appropriately adjusted to a range that allows for dissolution and removal of the template. The amount of acid used is not particularly limited as long as it allows for dissolution and removal of the template material, and may be, for example, 30 times or more the stoichiometric ratio or 50 times or more the stoichiometric ratio relative to the template material.

[0088] After the template is removed, the carbon material can be recovered by, for example, filtration and then washed with pure water. Washing conditions may be selected as appropriate, and the washing can be completed by confirming that the pH of the washing solution is neutral.

[0089] The carbon material after the removal of the template material after washing can be dried by heating, for example, at a drying temperature of 100°C to 200°C for a drying time of 1 hour to 10 hours.

[0090] (Heat Treatment Step) In the method for producing a carbon material of the present invention, the carbon material (separated carbonaceous layer) after removal of the template material can be heat-treated as needed. By heat-treating the carbonaceous layer from which the template material has been removed, the crystallinity of the carbon is enhanced and stabilized, making it possible to produce a carbon material with higher levels of electrical conductivity, corrosion resistance, and / or a large BET specific surface area.

[0091] The conditions for the heat treatment step are not particularly limited as long as they enhance the crystallinity of carbon. The holding temperature in the heat treatment step is, for example, 1000°C to 3000°C, preferably 1300°C to 2500°C, more preferably 1500°C to 2000°C, even more preferably 1600°C to 1900°C, and particularly preferably 1750°C to 1850°C. A heat treatment temperature within this range is advantageous because it can provide a carbon material with higher levels of electrical conductivity, corrosion resistance, and / or a large BET specific surface area. The heat treatment time (holding time at a predetermined heat treatment temperature) in the heat treatment step is, for example, 0.1 hours to 10 hours, preferably 0.2 hours to 5 hours, and more preferably 0.5 hours to 5 hours. The atmosphere in the heat treatment step can be, for example, an inert gas such as argon gas. The atmospheric pressure in the heat treatment step can be, for example, atmospheric pressure or reduced pressure.

[0092] Furthermore, by carrying out a heat treatment step, functional groups (mainly oxygen-containing functional groups) bonded to carbon and carbon chains that do not form six-membered rings are detached at temperatures exceeding 1000°C, forming dangling bonds. When the formed dangling bonds bond with other nearby carbons, the surface of the carbon material becomes a state in which functional groups are less likely to bond. By carrying out a heat treatment at 1500°C or higher, preferably 1600°C or higher, the carbon material of the present invention can exhibit favorable functions such as electron conductivity and maintaining internal space.

[0093] These heat treatments adjust the structural defects of the graphene and non-graphene components that make up the carbonaceous material. These structural defects include voids created within the aggregate structure due to dissolution of the template material and infiltration holes created in the outer shell formed from the carbonaceous material. The extent of these structural defects can be adjusted by changing reaction conditions such as the heat treatment temperature and time. In other words, the size of the voids present inside the carbonaceous material and the size of the infiltration holes that allow the electrolyte to penetrate into the particles can be adjusted.

[0094] Thus, the carbon material of the present invention can be easily produced.

[0095] <Dispersion> Next, the dispersion according to the present invention will be described. The dispersion according to the present invention is obtained by dispersing the carbon material described above in a dispersion medium. The dispersion may contain a dispersant that improves the dispersibility of the carbon material, as necessary.

[0096] The dispersion medium used in the present invention is selected depending on the intended use. For example, an organic or inorganic dispersant can be suitably used to maintain a good dispersion state of the powder in the solvent. When used in the production of a lithium ion secondary battery, a polar solvent is suitably used. From the viewpoint of affinity with the binder polymer, N,N-dimethylformamide, N-methylpyrrolidone (NMP), N,N-dimethylacetamide, and water are preferred, and N-methylpyrrolidone (NMP) is particularly preferred. NMP is suitable for dispersing carbon materials including graphene.

[0097] <Electrode Composition, Electrode Slurry, and Electrode> Next, the electrode composition, electrode slurry, and electrode according to the present invention will be described.

[0098] An electrode containing the carbon material of the present invention, preferably an electrode for a lithium ion secondary battery, is suitable in that it has excellent high-rate discharge properties, capacity characteristics, and charge / discharge characteristics. To produce such an electrode, it is useful to use an electrode composition or electrode slurry containing the carbon material of the present invention.

[0099] (Electrode Composition) The electrode composition of the present invention comprises the carbon material of the present invention, an active material, and a binder.

[0100] Examples of the active material used in the present invention include the active material used in the positive electrode described below, the active material used in the negative electrode described below, etc. The ratio of the active material to the carbon material of the present invention used is appropriately selected depending on the intended use, and is, for example, 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 particularly 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.

[0101] Examples of the binder used in the present invention include binders used in positive electrodes and negative electrodes, which will be described later. The amount of binder used is appropriately selected depending on the intended use, and is, for example, 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 particularly preferably 2 to 4 parts by weight, relative to 100 parts by weight of the active material.

[0102] 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. As the other compounding agents, those typically used in electrode compositions for lithium ion secondary batteries are used, and the amount used is, for example, 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 particularly preferably 2 parts by weight or less, per 100 parts by weight of the active material.

[0103] Examples of the method for mixing the electrode composition of the present invention include a dry mixing method and a wet mixing method using a dispersion medium.

[0104] (Slurry for Electrodes) The slurry for two electrodes of the present invention is prepared by mixing the electrode composition described above using a dispersion medium by a wet mixing method. The dispersion medium used may be any dispersion medium capable of dissolving or dispersing the binder, and examples thereof include the dispersion medium used in the positive electrode described below, the dispersion medium used in the negative electrode described below, and the dispersion medium used in the carbon material-containing dispersion liquid of the present invention described above. The amount of the dispersion medium used may be an appropriate amount, and is adjusted so that the viscosity of the electrode slurry in the next step can be applied to a current collector.

[0105] Examples of the method for producing an electrode slurry of the present invention include a method of mixing the carbon material of the present invention, a binder, and a dispersion medium, and then mixing an active material. The mixing of the carbon material of the present invention, a binder, and a dispersion medium includes a method of mixing the binder into the carbon material-containing dispersion liquid, and a method of mixing the carbon material-containing dispersion liquid with a binder liquid in which the binder is dissolved or dispersed in the dispersion medium.

[0106] As a mixing method, a known mixer or kneader can be used. Known mixers include an automatic mortar, a homogenizer, a planetary mixer, a homodisper, and a planetary mixer, among which a planetary mixer is particularly preferred.

[0107] 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 the applied current collector. The current collector may be either a current collector used for a positive electrode or a current collector used for a negative electrode, which will be described later.

[0108] The method for applying the electrode slurry to the current collector is not particularly limited, and known methods can be used. Specifically, the slurry can be applied manually or using an automatic coater, such as a Baker applicator, a micrometer-equipped film applicator, a bar coater, or a doctor blade. The drying method is not particularly limited, and known methods can be used, such as drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. After the drying step, the electrode mixture layer may be subjected to a pressure treatment using a mold press or a roll press. The pressure treatment allows the positive electrode mixture layer to adhere well to the current collector.

[0109] <Positive Electrode> The positive electrode will now be described. A positive electrode is generally obtained by coating a slurry containing a positive electrode active material, a conductive additive for enhancing electronic conductivity, a binder, and a solvent on a current collecting metal foil such as rolled aluminum foil to form a coating film, which is then heated and dried to remove the solvent, and then formed into a desired size and density. The carbon material of the present invention can be useful as a conductive additive.

[0110] (Positive Electrode Active Material) The positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel, or aluminum.

[0111] Specific examples of the positive electrode active material include lithium-manganese oxides (e.g., LiMnO ２ , LiMn ２ O４ etc.), lithium-cobalt oxides (e.g., LiCoO ２ etc.), lithium-nickel oxides (e.g., LiNiO ２ etc.), lithium-nickel-manganese oxides (e.g., LiNi １－ａ Mn ａ O ２ (where 0<a<1), LiMn ２－ｂ Ni ｂ O ４ (where 0<b<2), lithium-nickel-cobalt oxides (e.g., LiNi １－ｃ Co ｃ O ２ (where 0<c<1), lithium-manganese-cobalt oxides (e.g., LiCo １－ｄ Mn ｄ O ２ (where 0<d<1), LiMn ２－ｅ Co ｅ O ４ (where 0<e<2), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni ｆ Co ｇ Mn ｈ ) O ２ (where 0<f<1, 0<g<1, 0<h<1, f+g+h=1) or Li(Ni ｊ Co ｋ Mn ｍ ) O ４ (where 0<j<2, 0<k<2, 0<m<2, j+k+m=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni ｐ Co ｑ Mn ｒ M Ｓ ) O ２ (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p, q, r and s are each atomic fractions of independent elements, with 0<p<1, 0<q<1, 0<r<1, 0<s<1, and p+q+r+s=1), and the battery may contain one or more compounds thereof. Among these, LiCoO is preferred because it can improve the capacity characteristics and stability of the battery. ２, LiMnO ２ , LiNiO ２ , lithium nickel manganese cobalt oxide (e.g., Li(Ni ０．６ Mn ０．２ Co ０．２ ) O ２ , Li(Ni ０．５ Mn ０．３ Co ０．２ ) O ２ , or Li(Ni ０．８ Mn ０．１ Co ０．１ ) O ２ ), or lithium nickel cobalt aluminum oxide (e.g., LiNi ０．８ Co ０．１５ Al ０．０５ O ２ etc.) are preferred.

[0112] As a highly stable positive electrode active material, a lithium atom-containing oxide (olivine-type lithium-containing phosphate compound) represented by the following general formula (1) and having an olivine-type crystal structure can also be mentioned.

[0113] Li １－ｘ M ｘ (A.O. ４ ) (1) (In formula (1), M is an ion of at least one metal selected from the group consisting of Mg, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Ge, and Sn, A is at least one selected from the group consisting of Si, S, P, and V, and x is a number satisfying the relationship 0<x<1.) The value of x in general formula (1) is selected depending on the valences of M and A so that the valence of the entire general formula (1) is 0.

[0114] Specific examples of olivine-type lithium-containing phosphate compounds include LiFePO ４ , LiCoPO ４ , LiMnPO ４ , Li ０．９０ Ti ０．０５ Nb ０．０５ Fe ０．３０ Co0.3 ０ Mn ０．３０ P.O. ４Among these, LiFePO is particularly preferred. ４ (Lithium iron phosphate) is preferred because the iron compound that serves as the raw material is readily available and inexpensive.

[0115] As the positive electrode active material, organic compounds such as polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds, and N-fluoropyridinium salts can also be used.

[0116] The physical properties of the positive electrode active material are determined by the requirements of the battery design and manufacturing process, which are caused by constraints such as the usage of lithium-ion batteries. In the manufacturing of the positive electrode material, the process is designed to realize the physical properties. The physical properties include the powder particle size and distribution, BET specific surface area, density, etc.

[0117] As an example, the powder particle size is appropriately selected in consideration of the balance with other constituent requirements of the lithium ion battery. From the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, for example, the powder particle size is preferably 1 μm to 30 μm on average, and more preferably 1 μm to 10 μm.

[0118] These positive electrode active materials can be used either alone or in combination of two or more.

[0119] (Positive electrode: conductive additive) Since the positive electrode active material generally has low electronic conductivity, it is preferable to have a conductive additive that enhances electronic conductivity coexist in the positive electrode, and the carbon material of the present invention is suitably used. The amount of the carbon material of the present invention used is appropriately selected depending on the intended use, but is, for example, 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 particularly preferably 0.5 to 1.5 parts by weight, relative to 100 parts by weight of the positive electrode active material.

[0120] In the present invention, other conductive substances can be combined as the conductive auxiliary in addition to the carbon material of the present invention. Examples of other conductive substances include carbon-based substances 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.

[0121] These other conductive substances can be used alone or in combination of two or more. The amount of the other conductive substances used is appropriately selected depending on the intended use, and is selected appropriately within the above-mentioned range of use of the carbon material of the present invention. The ratio of the carbon material of the present invention to the other conductive substances used is appropriately selected depending on the intended use, and is, for example, in the range of 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40, in terms of the weight ratio of [carbon material of the present invention]:[other conductive substances].

[0122] Furthermore, among the above, the carbon material of the present invention can achieve even greater efficacy when combined with conventionally used conductive additives. For example, carbon blacks such as acetylene black are composed of linked structural particles with diameters of several tens of nanometers. However, carbon does not have high crystallinity, has a short structural length, and is prone to collapse, making it difficult to transmit electrons over long distances. By combining it with the carbon material of the present invention, it is possible to realize a system that maintains electronic conductivity and also has ion supply ability, even when the three-dimensional structure is maintained or when the three-dimensional structure is crushed and flattened like flake graphite.

[0123] (Positive electrode: binder) The binder used is a component that aids in bonding between the positive electrode active material, conductive additive, and electrode current collector, and for example, an organic polymer is used. Examples include fluorine-based resins 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, polymers having rings such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone, and acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, methyl polyacrylate, ethyl polyacrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide. Modified products or derivatives of the above organic polymers may also be used.

[0124] Among these binders, fluorine-based resins are preferred, and PVDF is particularly preferred.

[0125] These binders can be used alone or in combination of two or more, and the amount used is appropriately selected depending on the intended use, and is, for example, 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 particularly preferably 0.5 to 1.5 parts by weight, relative to 100 parts by weight of the positive electrode active material. When the amount of binder used is within this range, the adhesive strength between the electrode active materials and between the electrode active material and the conductive additive can be improved, and thus the bonding strength with the electrode current collector can be improved, which is preferable.

[0126] (Positive electrode: slurry) The electrode-forming slurry used is prepared by blending the positive electrode active material, the conductive additive, the binder, and other compounding agents as required, and mixing them in a dispersion medium. The other compounding agents are appropriately selected depending on the intended use, and those typically used in lithium-ion secondary batteries can be used within their normal range of use.

[0127] The dispersion medium used is preferably one that dissolves only the binder but not other materials, for example, in order to distribute the binder sufficiently uniformly and form a coating film of the slurry to a predetermined size. Specifically, for example, organic solvents such as dimethylformamide, N-methyl-2-pyrrolidine (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, or water may be used, and one of these may be used alone, or a mixture of two or more of them may be used.

[0128] 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.

[0129] (Current Collector and Positive Electrode) The positive electrode can be produced by applying the electrode forming slurry to a current collector and drying it. Examples of the current collector include aluminum foil, nickel foil, titanium foil, and stainless steel foil, and rolled aluminum foil is particularly preferred.

[0130] Commonly used printing techniques can be used to apply the electrode-forming slurry to the current collector. When the thickness of the coating film is small, gravure printing or the like is preferably used, and when the thickness is large, printing techniques such as doctor blade printing or die printing are preferably used. The coating film is then dried by heating. Any drying method can be used, and the method that can achieve the desired binding strength by the binder is preferably used.

[0131] Thereafter, when forming the cathode into a predetermined size, an industrially available cutting blade and the like and the method thereof are preferably used. In addition, to achieve a predetermined density, an industrially available pressing device and the like and the method thereof are preferably used as needed.

[0132] The negative electrode can be obtained by coating a current collecting metal foil such as rolled copper foil with a slurry containing a negative electrode active material, a conductive additive, a binder, and a dispersion medium, drying the coated foil by heating to remove the solvent, and then forming the coated foil into a desired size and density.

[0133] (Negative Electrode: Active Material) The negative electrode active material is preferably one that can bond and stabilize lithium ions with electrons flowing from an external circuit and has numerous stabilization sites within it. For example, materials of organic origin, whether high or low crystallinity, can be used. Suitable examples include graphite, coke, amorphous carbon, hard carbon, and polymer carbon. The principle is that lithium ions are sandwiched between graphene layers and bond with electrons to stabilize them. Another stabilization mechanism is the electrochemical formation of intermetallic compounds, and suitable materials include silicon, tin, zinc, bismuth, antimony, cadmium, lead, and germanium. In addition, other materials that exhibit low electrochemical reaction potentials and serve as the negative electrode of lithium-ion batteries can also be used. Suitable examples include compounds of metals with oxygen, sulfur, halogens, nitrogen, phosphorus, and the like.

[0134] Specific examples of the negative electrode active material include compounds capable of reversible intercalation and deintercalation of lithium, such as carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO. ｘ (0<x≦2), SnO ２ Examples of the metallic compounds include metal oxides that can be doped and dedoped with lithium, such as vanadium oxide and lithium vanadium oxide; and composites containing the metallic compounds and carbonaceous materials, such as Si—C composites or Sn—C composites.

[0135] The negative electrode active material may also be a metallic lithium thin film. The carbonaceous material may be either low-crystalline carbon or high-crystalline carbon. Typical examples of low-crystalline carbon include softened carbon and hardened carbon. Typical examples of high-crystalline carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microspheres, mesophase pitch, and high-temperature-calcined carbon such as petroleum- and coal-based coke.

[0136] The physical properties of anode materials are determined by the requirements of device (e.g., storage battery) design and manufacturing process, which are based on constraints such as the usage of lithium-ion batteries. The manufacturing process is designed to achieve the desired physical properties. Physical properties include powder particle size and distribution, BET specific surface area, and density.

[0137] As an example, the powder particle size is appropriately selected in consideration of other constituent requirements of the lithium ion battery. From the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, for example, the powder particle size is preferably 1 μm to 70 μm on average, and more preferably 3 μm to 30 μm.

[0138] These negative electrode active materials can be used alone or in combination of two or more. The ratio of the negative electrode active material in the electrode-forming slurry is, for example, 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 the solid content excluding the dispersion medium. When the content of the negative electrode active material is in this range, it is preferable in that the battery capacity, conductivity, and adhesiveness are well balanced.

[0139] (Conductive Aid) The carbon material of the present invention may be used as a carbonaceous material for the negative electrode active material, but can also be suitably used as a conductive aid for the negative electrode active material. For example, although the negative electrode active material generally has high electronic conductivity, some materials have smooth surfaces and insufficient particle-to-particle contact. In such cases, the carbon material of the present invention can be used as a conductive aid to enhance electronic conductivity. Furthermore, flake graphite and artificial graphite used as negative electrode active materials have high electronic conductivity but low ion storage capacity and poor ionic conductivity. By combining these properties with the carbon material of the present invention, a good battery reaction assist system can be constructed that combines electronic conductivity with ionic conductivity. Furthermore, even when the three-dimensional structure of the negative electrode active material is crushed and flattened like flake graphite, the addition of the carbon material of the present invention is advantageous because it can maintain electronic conductivity while adding ionic conductivity.

[0140] The ratio of the carbon material of the present invention in the electrode-forming slurry is, for example, 0.8 to 3 parts by weight, preferably 1 to 2.5 parts by weight, and more preferably 1 to 2.2 parts by weight, per 100 parts by weight of the solid content excluding the dispersion medium. When the content of the carbon material of the present invention is in this range, it is preferable in that the high-rate discharge characteristics, life characteristics, capacity characteristics, and charge / discharge characteristics of the lithium ion secondary battery can be highly improved.

[0141] In the present invention, the carbon material of the present invention can be used in combination with other carbon materials, such as acetylene black, ketjen black, lamp black, furnace black, carbon black, graphite, carbon fiber, graphite fiber, nanofiber, nanotube, coke, hard carbon, and amorphous carbon.

[0142] These other carbon materials can be used either alone or in combination of two or more, and the amount used is selected depending on the purpose of use and can be used in the same range as the carbon material of the present invention. The weight ratio of the carbon material of the present invention to the other carbon materials is, for example, 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.

[0143] By combining these conventional materials with the carbon material of the present invention, further benefits can be achieved. For example, highly linear carbon nanotubes have high electronic conductivity but low ion storage capacity. Therefore, by combining them with the carbon material of the present invention, it is possible to construct an excellent battery reaction support system that combines electronic conductivity with ionic conductivity. Furthermore, carbon blacks such as acetylene black are composed of linked structural particles with diameters of several tens of nanometers. On the other hand, carbon crystallinity is not very high, the structural length is short, and it is prone to collapse, making long-distance electron transport difficult. Despite these properties, by combining them with the carbon material of the present invention, it is possible to realize a system that maintains a three-dimensional structure and also has ion supply capacity.

[0144] (Negative electrode: binder) The binder used is a component that aids in bonding between the electrode active material, conductive assistant, and electrode current collector, and examples thereof include fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, 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 polyvinylidene chloride and polyvinylidene chloride, conductive polymers such as polyaniline, alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene, unsaturated polymers such as polybutadiene and polyisoprene, polymers having rings such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone, acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide, carboxymethyl cellulose, and styrene butadiene rubber. Modified products or derivatives of the above organic polymers may also be used.

[0145] Among these binders, carboxymethyl cellulose and styrene butadiene rubber are preferred.

[0146] These binders can be used alone or in combination of two or more, and the amount used is appropriately selected depending on the intended use, and is, for example, 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, and even more preferably 0.2 to 2 parts by weight, relative to 100 parts by weight of the 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 material and the conductive additive can be improved, and thus the bonding strength with the electrode current collector can be improved, which is preferable.

[0147] These binders can be used alone or in combination of two or more, and their proportion in the electrode-forming slurry is, for example, 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, relative to 100 parts by weight of the solid content excluding the dispersion medium. When the binder content in the electrode-forming slurry is within this range, the adhesive strength between electrode active materials and between the electrode active material and the conductive assistant can be improved, and thus the bonding strength with the electrode current collector can be improved, which is preferable.

[0148] (Negative electrode: dispersion medium) The dispersion medium used may be a solvent commonly used in the technical field, and may be, for example, an organic solvent such as N-methyl-2-pyrrolidine (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, or acetone, or water, or one or more of these may be used alone or in combination. The dispersion medium is used to dissolve or disperse the electrode active material, conductive additive, and binder, taking into consideration the coating thickness of the electrode-forming slurry and the production yield.

[0149] (Negative electrode: slurry) The amount of the dispersion medium used is adjusted so that the concentration of the solids including the electrode active material, the conductive additive, and the binder is, for example, in the range of 10 wt % to 90 wt %, preferably 20 wt % to 80 wt %, more preferably 30 wt % to 75 wt %, even more preferably 40 wt % to 70 wt %, and particularly preferably 50 wt % to 65 wt %.

[0150] (Current Collector and Negative Electrode) As the current collector of the negative electrode, for example, a material that does not have electrochemical reactivity with the potential generated by the negative electrode is used. Specific examples include copper foil, nickel foil, titanium foil, and stainless steel foil, and electrolytic copper foil and rolled copper foil are preferred.

[0151] The electrode-forming slurry can be applied to the current collector by a commonly used printing technique. When the thickness is small, gravure printing or the like is preferably used, and when the thickness is large, doctor blade printing, die printing or the like is preferably used.

[0152] The coating is then dried by heating. Any drying method can be used, and a method that can achieve the desired binding strength of the binder is preferably used. Then, when forming the negative electrode into a predetermined size, an industrially available cutting blade and method are preferably used. Furthermore, to achieve a predetermined density, an industrially available pressure device and method are preferably used as needed.

[0153] <Lithium-ion secondary battery> Next, a lithium-ion secondary battery according to the present invention will be described. The lithium-ion secondary battery according to the present invention is characterized by including the carbon material according to the present invention. Specifically, the lithium-ion secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and at least one of the positive electrode and the negative electrode uses the electrode (positive electrode and / or negative electrode) according to the present invention. Meanwhile, the lithium-ion secondary battery may optionally further include a battery container that houses the electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container. Meanwhile, the positive electrode and the negative electrode are the same as those described above, and therefore detailed description thereof will be omitted.

[0154] (Separator) The separator used separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator that is typically used as a separator in a lithium ion secondary battery can be used without any particular limitation. In particular, a separator that has low resistance to the movement of ions in the electrolyte and excellent electrolyte solution impregnation ability is preferred.

[0155] Specifically, porous polymer films may be used, such as porous polymer films made of polyolefins such as polyethylene, polypropylene, polybutene, polyvinyl chloride, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminate structures of two or more layers thereof. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. To ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material may also be used, and may be used in a single-layer or multi-layer structure.

[0156] Polyethylene and polypropylene are particularly suitable materials for the porous polymer film. Polyethylene has a relatively low melting temperature, and when the battery temperature rises for some reason (e.g., an unsafe condition such as a short circuit), the pores in the film are blocked by thermal melting, preventing the movement of driving ions, thereby stopping the reaction and ensuring safety. Polypropylene is also suitable as a material that can be stretched to become porous without the use of plasticizers.

[0157] Alternatively, a polymer compound can be applied to both sides of the separator. Examples of such polymer compounds include ether-based polymer compounds such as polyvinyl formal, polyethylene oxide, and crosslinked polyethylene oxide-containing compounds, ester-based polymer compounds such as polymethacrylate, acrylate-based polymer compounds, and fluorine-based polymer compounds such as polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer. Among these, it is particularly desirable to use a fluorine-based polymer compound such as polyvinylidene fluoride, from the viewpoint of preventing swelling during high-temperature storage.

[0158] (Electrolyte) As the electrolyte, for example, a non-aqueous electrolyte in which an electrolyte is dissolved in an organic solvent is used.

[0159] -Electrolyte- As the electrolyte, for example, a lithium salt is used. As the lithium salt, for example, LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ )NLi, LiN(CF３ SO ２ ) (C ４ F ９ SO ２ ), LiC(CF ３ SO ２ ) ３ , LiPF ４ (CF ３ ) ２ , LiPF ４ (C ２ F ５ ) ２ , LiPF ４ (CF ３ SO ２ ) ２ , LiPF ４ (C ２ F ５ SO ２ ) ２ , LiBF ２ (CF ３ ) ２ , LiBF ２ (C ２ F ５ ) ２ , LiBF ２ (CF ３ SO ２ ) ２ , LiBF ２ (C ２ F ５ SO ２ ) ２ , Li cyclic 1,2-perfluoroethane disulfonylimide, Li cyclic 1,3-perfluoropropane disulfonylimide, etc. Among these, LiPF is preferred because it is easily soluble in solvents and exhibits a high degree of dissociation. ６ , LiBF ４ , LiClO ４ , C.F. ３ SO ３ Li, LiN(CF ３ SO ２ ) ２ , LiN(C ２ F ５ SO ２ ) ２ and the like are preferred, and LiPF ６ and LiBF ４ is particularly preferred.

[0160] The electrolyte may be a gel electrolyte containing a polymer compound that swells in an organic solvent to serve as a support for the nonaqueous electrolyte. The inclusion of a polymer compound that swells in an organic solvent is advantageous because it can provide high ionic conductivity, excellent charge / discharge efficiency, and prevent leakage from the battery. The content of such a polymer compound is preferably in the range of 0.1% by weight to 10% by weight of the electrolyte.

[0161] These electrolytes can be used alone or in combination of two or more. The concentration of the electrolyte in the electrolytic solution is, for example, in the range of 5 to 15% by weight, preferably 2 to 13% by weight, and more preferably 5 to 10% by weight.

[0162] The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the electrolyte, but suitable solvents include, for example, cyclic carbonates, chain carbonates, esters such as γ-butyrolactone and methyl formate, ethers such as 1,2-dimethoxyethane and tetrahydrofuran, and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. These organic solvents can be used alone or in combination of two or more.

[0163] Among these, cyclic carbonates and chain carbonates are preferred because they have a high dielectric constant and suitable viscosity and solvating ability that affect the migration of lithium ions. Note that solvating ability is the force that dissociates dissolved ions, and if it is too strong, it will inhibit the migration of ions, so there is an optimum value.

[0164] Examples of cyclic carbonates include alkylene carbonates having an alkylene group having 2 to 4 carbon atoms, such as ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are preferred from the viewpoint of improving battery characteristics, and ethylene carbonate is particularly preferred.

[0165] As the chain carbonates, for example, dialkyl carbonates are preferred, and the number of carbon atoms in the constituent alkyl groups is preferably 1 to 5, particularly preferably 1 to 4. Specific examples include dialkyl carbonates such as symmetric chain alkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; and asymmetric chain alkyl carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. Of these, dimethyl carbonate and diethyl carbonate are preferred from the viewpoints of viscosity and boiling point, and diethyl carbonate is particularly preferred.

[0166] Furthermore, practical lithium-ion batteries are used under a wide range of environmental conditions, and physical properties such as the melting point and boiling point of the non-aqueous solvent must fall within certain ranges. Therefore, it is preferable to use a mixture of cyclic carbonates and chain carbonates. A suitable combination of cyclic carbonates and chain carbonates is, for example, ethylene carbonate and chain carbonate. Specifically, 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, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, and the like are suitable because they offer a good balance between cycle characteristics and high-power discharge characteristics.

[0167] The mixing ratio of the cyclic carbonates to the chain carbonates is appropriately selected depending on the desired practical properties, and is, for example, in the range of 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40, in terms of the weight ratio of [cyclic carbonates]:[chain carbonates].

[0168] As the organic solvent used in the electrolyte, a fluorine-containing carbonate can also be suitably used. Specifically, cyclic carbonates having one fluorine atom, chain carbonates having one fluorine atom, cyclic carbonates having two or more fluorine atoms, chain carbonates having two or more fluorine atoms, etc. can be mentioned, and from the viewpoint of improving battery characteristics, fluorine-containing cyclic carbonates having two or more fluorine atoms are preferred.

[0169] Specific examples of fluorine-containing cyclic carbonates having two or more fluorine atoms include cis-4,5-difluoro-1,3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, and 4,4-difluoro-1,3-dioxolan-2-one.

[0170] These fluorine-containing carbonates can be used alone or in combination of two or more.

[0171] (Method for Manufacturing Lithium-Ion Secondary Battery) The 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 interposed therebetween, rolling or folding the resulting assembly as necessary according to the battery shape, placing it in a battery container, injecting an electrolyte into the battery container, and sealing it. To prevent internal pressure rise, overcharge / discharge, and the like in the secondary battery, a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, or the like may be provided as necessary. The shape of the secondary battery may be any of a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, a flat type, and the like.

[0172] <Uses> The carbon material of the present invention can exhibit its functionality and be effectively used in any electrochemical device other than the lithium-ion secondary battery. Specifically, it has functions such as a function as an intra-electrode conductive path when electrons are exchanged in a device reaction, a reinforcing function when an electrode or the like is physically deformed, and a function of preventing direct contact between a reaction material and a third material (such as a catalyst) by taking advantage of the durability of the graphene when the reaction material is in an oxidized or reduced state.

[0173] Usable devices include, for example, nonaqueous electrolyte batteries such as lithium ion batteries, sodium ion batteries, potassium ion batteries, magnesium ion batteries, calcium ion batteries, aluminum ion batteries, lithium-sulfur batteries, and lithium-air batteries; inorganic solid electrolyte batteries such as sulfide-based solid electrolytes and oxide-based solid electrolytes; polymer solid electrolyte batteries such as polyethylene oxide-based batteries; and semi-solid batteries typified by polymer gel electrolyte batteries in which an electrolyte is impregnated in PVDF or the like.

[0174] In these devices, as the negative electrode active material, graphitizable carbon, non-graphitizable carbon, graphite, lithium alloy-based materials such as silicon and tin, and other metal-based materials such as lithium are used, and as the positive electrode active material, lithium-containing metal oxides, particularly lithium-containing transition metal oxides having a layered structure, spinel structure, or olivine structure, lithium-free metal oxides, organic positive electrode materials, charge transfer complex positive electrode materials, sulfur, fluoride-based materials, etc. are used, but the carbon material of the present invention can effectively increase the conductivity of any active material. In addition, the carbon material of the present invention is also suitable as a material for lithium-sulfur batteries and the like described in WO2018 / 225619, JP2023-501679A, JP2019-517116A, JP2022-191280A, etc.

[0175] The carbon material of the present invention can also be suitably used in organic electrolyte capacitors, aqueous electrolyte capacitors, and aqueous electrolyte batteries. It can be used in fuel cells such as PEFC, SOFC, and DMPC, and in particular can be used as a support for redox catalysts in addition to providing electrical conductivity to electrodes.

[0176] The carbon material of the present invention can also be used in applications other than electrochemical devices. Examples of other applications include electronic device applications other than the above-mentioned devices, such as graphene-based sensors, electromagnetic interference suppression materials, antenna modules, heat dissipation substrates, heat exchangers, separation membranes, reverse osmosis membranes, transparent electrode materials, structural material applications utilizing mechanical flexibility, conductive inks, pastes, and the like. Furthermore, as the need for lighter vehicle bodies, which directly contributes to reducing carbon dioxide emissions and energy conservation, is growing, the carbon material of the present invention can also be used in applications that utilize hollow shapes and other factors to reduce weight, such as reinforcing agents for various rubbers, including tires, paints, coloring pigments, conductive fillers for various polymers, and additives for magnetic recording media.

[0177] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, the units "%", "ppm" and "parts" that represent amounts are by weight unless otherwise specified.

[0178] Various physical properties were evaluated according to the following methods.

[0179] <Basic Properties> (Number of Carbonaceous Layers) The number of carbonaceous layers of the carbon material was calculated from the amount of carbon deposited during production in the Examples and Comparative Examples. Specifically, it was determined by thermogravimetric analysis (TGA) measurements. Using a STA-2500 (manufactured by NETZSCH), the sample was heated to 900°C at a temperature increase rate of 5°C / min under a flow of argon gas (80 mL / min) and oxygen (20 mL / min), and then cooled at a temperature decrease rate of 20°C / min, followed by TG measurements. Blank measurements performed using empty pans under the same temperature profile conditions were subtracted. A Pt pan was used for the sample obtained using MgO (Comparative Example 2), and an alumina pan was used for the other samples. The average number of carbon layers was calculated from the carbon weight reduction rate (%) determined by TG measurements as follows. The weight of the carbon layer per unit mass of the mold, W ｇ (g-carbon / g-template) was calculated, and the weight W of this carbon layer was ｇ and the BET specific surface area SA of the template particles ｔｅｍｐ (g / m ２) The weight W of the carbon layer per unit area of ​​the mold ａ (g / m ２ ) was calculated. ａ is the weight of the carbon layer per unit area of ​​the single-layer graphene, W ｇｒａｐｈｅｎｅ (7.61 x 10 －４ g / m ２ ) to calculate the average number of layers. Average number of layers = W ａ / W ｇｒａｐｈｅｎｅ

[0180] (Purity Measurement) The carbon content of the carbon material was calculated by subtracting the ash content (described later) and the amount of thermal desorption gas, which were converted into percentages, based on the following formula: Carbon content = 100 - 100 × (ash content + total amount of gas calculated from thermal desorption gas) / amount of carbon material

[0181] <Nitrogen Adsorption / Desorption Measurement> (BET Specific Surface Area, Pore Volume, Mode Pore Diameter) Nitrogen adsorption / desorption measurements of carbon materials were performed using an automatic specific surface area / pore distribution analyzer (BELSORP MINI, manufactured by Microtrac-BEL Co., Ltd.). Prior to measurement, the samples were dried under reduced pressure at 150°C for 6 hours using a BEL pre. The BET specific surface area was determined using the adsorption isotherm obtained from the nitrogen adsorption / desorption measurement. The applicable range of the BET method was P / P0 = 0.05 to 0.3. Based on the adsorption / desorption isotherm, the total pore volume was measured by converting the amount of nitrogen adsorbed at -196°C and a relative pressure P / P0 = 0.99 into a volume at the density of liquid nitrogen. The pore size distribution was determined using the BJH method. The mode pore size of the pore size distribution was also determined.

[0182] The applicable ranges for each measured pore volume were as follows: Total pore volume: P / P0 = 0.99 Volume of micropores (pores with a pore diameter of less than 2 nm): P / P0 = up to 0.1 Volume of mesopores (pores with a pore diameter in the range of 2 nm to 50 nm): P / P0 = 0.1 to 0.96 Volume of pores with a pore diameter of 10 nm or more: P / P0 = 0.79 to 0.99 Volume of macropores (pores with a pore diameter of more than 50 nm): P / P0 = 0.96 to 0.99

[0183] <Structural analysis> Shape index and aggregate shape evaluation method are indicators of the structural complexity of carbon materials. Shape index is obtained by statistically analyzing various parameters obtained by image analysis of transmission electron microscope images of monodispersed materials.

[0184] (Transmission Electron Microscope Observation) The shape of the carbon material was observed using a transmission electron microscope (JEM-2100Plus, manufactured by JEOL Ltd.) Observation of the carbon material using a transmission electron microscope (TEM) was carried out at an acceleration voltage of 80 kV to 100 kV.

[0185] (Raman Spectroscopic Measurement) The Raman spectrum of the carbon material was measured using a micro-Raman spectrometer (LabRAM HR-800, manufactured by Horiba, Ltd.). The measurement was performed using a 532 nm laser, with the filter set to D1 and the hole set to 100 μm. The measurement range was 300 cm －１ ~3500cm －１ From the measured Raman spectrum, the intensity of the 2D band (I ２Ｄ ) versus G band intensity (I Ｇ ) intensity ratio (I Ｇ / I ２Ｄ ) and the intensity ratio was calculated.

[0186] <Particle Characteristics> (Particle Size Distribution Measurement) Particle size distribution was measured using a laser diffraction particle size distribution analyzer (MT3300EXII-SDC, manufactured by Microtrac-Bell Corporation) to examine the aggregation state of primary particles of the carbon material. The measurement sample was an unpulverized carbon material that had been immersed in ethanol for 9 minutes. The median diameters D50, D10, D90, D90 / D10, and D90 / M in the particle size distribution curve were determined.

[0187] <General Properties> (Oil Absorption Measurement) The oil absorption of the carbon material was measured in accordance with "JIS K5101-13-1 Pigment Testing Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method".

[0188] (Number density) The number density (number per unit mass) P of a carbon material is calculated by dividing the volume V (m ３ ) and carbon density ρ (g / m ３) can be calculated using the following formula: P = 1 / (V × ρ) Here, the true density of graphite, 2.2 g / cc, can be used as the carbon density ρ. V (m ３ ) can be calculated from the following formula: V = n × (D １ -D ０ ) ３ / 6 where D ０ is the inner diameter of the primary particle, and D １ is the outer diameter of the primary particle. ０ The above-mentioned mode pore diameter (M) can be used. １ is D ０ The average number of layers n is multiplied by the average interplanar spacing determined from the 002 diffraction line, and the doubled value is added to the mode diameter. １ may be determined by TEM image analysis, etc. In addition, in the case of a solid carbon material, D ０ For example, the known DENKA BLACK Li-100 has a particle outer diameter (D １ ) with an average primary particle diameter of 35 nm, D ０ = 0.

[0189] (Apparent Density) The apparent density of the carbon material was calculated from the total pore volume and true density according to the following formula: Apparent density (g / cc) = 1 / (total pore volume + 1 / true density) The total pore volume (cc / g) was calculated using P / P0 = 0.99, and the true density was 2.2 g / cc, which is the value for graphite.

[0190] (Measurement of Ash Content) The carbon material was dried under reduced pressure at 150°C for 2 hours using a vacuum dryer, then cooled, placed in a porcelain crucible, and weighed (W ｓ Then, the sample was placed in a muffle furnace and burned at 900°C for 1 hour, after which the weight was measured (W ｉ ), crucible tare (W ｃ ) to obtain the ash content ((W ｉ -W ｃ ) / W ｓ × 100(%)) was calculated.

[0191] Various performance evaluations were carried out according to the following methods.

[0192] <Evaluation of Electrical Conductivity> The electrical conductivity of the carbon material was evaluated by measuring the electrical conductivity of the powder by lateral constrained uniaxial compression. A dried 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 container was placed on a force gauge stand with the sample sandwiched between the negative and positive electrodes. A spring-type force gauge attached to the force gauge stand was lowered to compress the sample in the cylindrical container by applying a pressure of 10 MPa. The height of the compressed sample 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 packed cross-sectional area of ​​the sample, and the compressed sample height. Evaluation was based on the following criteria: ◎: 18 S / cm or more; ◯: 15 S / cm or more but less than 18 S / cm; Δ: 12 S / cm or more but less than 15 S / cm; ×: less than 12 S / cm.

[0193] <Positive Electrode Evaluation> (High Rate Characteristics) At room temperature (25 ° C.), a constant current of 1.25 mA (equivalent to 0.2 C) was applied per test battery from the open circuit voltage to 4.2 V (constant current charging), and constant voltage charging was performed after reaching 4.2 V, and continued until the current reached 0.31 mA (0.05 C). Then, discharged to 3 V at a constant current of 1.25 mA (equivalent to 0.2 C). The charge capacity and discharge capacity at this time were determined, and the initial coulomb rate (discharge capacity ÷ charge capacity) was calculated. Next, using the same test battery, a constant current of 1.25 mA (equivalent to 0.2 C) was applied from the open circuit voltage to 4.2 V (constant current charging), and constant voltage charging was performed after reaching 4.2 V, and continued until the current reached 0.31 mA (0.05 C). Then, discharged to 3 V at a high rate of 12.5 mA (equivalent to 2 C). The 2C retention rate ((2C capacity / 0.2C capacity) x 100) (%) of each test battery was calculated from the discharge capacity of the obtained test battery. A higher value indicates better high-rate characteristics. The results are shown in Table 1. FIG. 5 shows discharge curves when the test battery of Example 1 was discharged at a discharge current value equivalent to 2C and a discharge current value equivalent to 0.2C.

[0194] The rapid discharge characteristics were evaluated based on the 2C retention rate determined according to the following criteria: ⊚: Over 70% ◯: Over 50% to 70% △: Over 30% to 50% ×: 30% or less

[0195] The charge capacity characteristics were evaluated based on the average charge capacity according to the following criteria: ⊚: 160 mAh / g or more; ◯: 150 mAh / g or more and less than 160 mAh / g; Δ: 140 mAh / g or more and less than 150 mAh / g; ×: Less than 140 mAh / g.

[0196] The discharge capacity characteristics were evaluated based on the average charge capacity according to the following criteria: ⊚: 140 mAh / g or more; ◯: 130 mAh / g or more and less than 140 mAh / g; Δ: 120 mAh / g or more and less than 130 mAh / g; ×: Less than 120 mAh / g.

[0197] The charge / 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%.

[0198] Example 1 (Production of Carbon Material) - CVD Reaction: Carbon Layer Formation - Fumed silica (SiO ２ , Model number: AEROSIL (registered trademark) NX90G, average primary particle diameter 38 nm, BET specific surface area 71 m ２ Approximately 1 g of carbon nanotubes (carbon nanotubes, 0.5% to 1.5%, manufactured by Nippon Aerosil Co., Ltd.) was placed in a quartz boat and placed in the center of a quartz reaction tube of a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). While flowing argon gas at a flow rate of 400 mL / min inside the reaction tube, the reaction tube was heated to 900 ° C at a temperature increase rate of 10 ° C / min and held for 30 minutes. While maintaining the temperature at 900 ° C, argon gas was flowed at a flow rate of 320 mL / min, while methane gas was flowed at a flow rate of 80 mL / min (raw material gas concentration 20%), and the temperature was held for 90 minutes to form a carbonaceous layer. Subsequently, while flowing argon gas at a flow rate of 400 mL / min, the mixture was cooled to room temperature, and the template on which the carbonaceous layer was formed was removed. At this time, it was confirmed by electron microscopy that the template was an aggregate of primary particles connected in a rosary shape with multiple branched structures.

[0199] - Template Removal - Next, the template with the carbonaceous layer formed was removed from the template by the following procedure to obtain a carbon material. (1) The template with the carbonaceous layer formed was placed in a 100 mL PFA beaker, and ultrapure water was added to the sample so that the entire sample was wet. (2) 46% hydrofluoric acid was added, and the mixture was stirred with a stirrer for 2 hours. (3) After stopping the stirring, the sample was left to settle until it had settled. (4) Using a PTFE membrane filter (47 mmφ, pore size 0.1 μm), the supernatant was suction-filtered. (5) The sample on the filter paper was washed with approximately 39 mL of ultrapure water and suction-filtered. This procedure was repeated three times. (6) The sample on the filter paper was returned to the original PFA beaker. (7) Steps (2) to (6) were repeated again. (8) Approximately 40 mL of ultrapure water was added, and the mixture was stirred with a stirrer for 1 hour. (9) After stirring was stopped, the sample was left to stand until it settled. (10) The supernatant was discarded, and 5% caustic soda was added, followed by stirring for 12 hours while heating to 80°C. (11) After stirring was stopped, the sample was left to stand until it settled. (12) Using a PTFE membrane filter (47 mmφ, pore size 0.1 μm), the supernatant was 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 (washing liquid) became neutral. (14) The sample on the filter paper was collected in a petri dish and dried in a dryer at 110°C for 8 hours.

[0200] - Heat Treatment - The carbon material obtained above was placed in a square high-temperature heating furnace (manufactured by Izumi Tech Co., Ltd.) and heated under reduced pressure (10 －１ After heating to a pressure of 1000 Pa (order of 10 Pa), the mixture was heated to 1800°C at a heating rate of 15°C / min in a flow of argon gas (10 mL / min) and maintained at that temperature for 1 hour for calcination. The mixture was then cooled to room temperature, and the calcined carbon material was removed to obtain a carbon material A containing heat-treated graphene. Using the obtained carbon material A, basic properties, nitrogen adsorption / desorption measurements, Raman spectroscopy measurements, XRD analysis, image analysis, particle size distribution measurements, TDP-MS measurements, general properties, and electrical conductivity evaluations were performed, and the results are shown in Table 1.

[0201] (Preparation of Positive Electrode) A ternary positive electrode material NCM (LiNi) having an average particle diameter of 8 μm was used as the positive electrode active material. ０．５ Co ０．２ Mn ０．３96.5% of the carbon material A (manufactured by Kelong Co., Ltd.) powder, 0.5% of the carbon material A obtained above as a conductive additive, and 3 wt. % of PVDF (manufactured by Kureha Corporation) as a binder were added to and mixed with N-methyl-pyrrolidone (NMP) as a solvent. The conductive additive was a dispersion of carbon material A dispersed in NMP solvent. The mixture of the active material, conductive additive, and PVDF was placed in a planetary mixer and kneaded until uniform while adding NMP in several portions at a rotation speed of 2000 rpm to prepare a positive electrode agent slurry. This was applied to 15 μm thick aluminum foil at a constant speed using a doctor blade applicator with a micrometer. It was then dried in a vacuum dryer set at 110 °C to obtain a positive electrode blank. The positive electrode blank was then punched using a φ15 mm punch-type punching machine, pressed at 45 kN using a cylinder-type jig, and vacuum-dried at 120 °C to obtain a positive electrode for battery assembly.

[0202] (Fabrication of Lithium-Ion Secondary Battery) The positive electrode fabricated as described above and metallic lithium punched to a diameter of 16 mm in a glove box under an argon gas atmosphere were used, and a 25 μm thick separator (a microporous polypropylene film) was sandwiched between the positive electrode mixture layer and the metallic lithium, and a 1M LiPF ６ A solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC)) was added as an electrolyte, and the battery was sealed by crimping to prepare a 2032 size coin-type test battery. The battery was then washed with ethanol and subjected to battery evaluation. The evaluation results are shown in Table 1.

[0203] Example 2 The same procedure as in Example 1 was carried out except that the CVD reaction time was set to 40 minutes to obtain a graphene-containing carbon material B, and a 2032 size coin-type battery was produced using this carbon material B. Using the obtained carbon material B and the test battery, material property measurement, conductivity evaluation, and battery evaluation were carried out, and the results are shown in Table 1.

[0204] Example 3 The same procedure as in Example 1 was performed except that the CVD reaction time was set to 60 minutes to obtain a graphene-containing carbon material C, and a 2032 size coin-type battery was produced using this carbon material C. Using the obtained carbon material C and the test battery, material property measurement, conductivity evaluation, and battery evaluation were performed, and the results are shown in Table 1.

[0205] Example 4 A graphene-containing carbon material D was obtained in the same manner as in Example 1, except that the CVD reaction time was set to 80 minutes, and a 2032 size coin-type battery was produced using this carbon material D. Using the obtained carbon material D and the test battery, material property measurement, conductivity evaluation, and battery evaluation were performed, and the results are shown in Table 1.

[0206] Example 5 A graphene-containing carbon material E was obtained in the same manner as in Example 1, except that the CVD reaction time was set to 130 minutes, and a 2032 size coin-type battery was produced using this carbon material E. Using the obtained carbon material E and the test battery, material property measurement, conductivity evaluation, and battery evaluation were performed, and the results are shown in Table 1.

[0207] Example 6: Fumed silica (SiO ２ , Model number: AEROSIL (registered trademark) R972, average primary particle diameter 25 nm, BET specific surface area 111 m ２ A graphene-containing carbon material F was obtained in the same manner as in Example 1, except that a graphene-containing carbon material (carbon dioxide, SiO2 ...

[0208] Comparative Example 1: Alumina (Al ２ O ３ Model number: RURALOX SBa200, average primary particle diameter 7 nm, BET specific surface area 202 m ２A graphene-containing carbon material G was obtained in the same manner as in Example 1, except that a graphene-containing carbon material (e.g., 1000 sachets / g, manufactured by SASOL) was used instead, and a 2032 size coin-type battery was fabricated using this carbon material G. Using the obtained carbon material G and the test battery, material property measurement, conductivity evaluation, and battery evaluation were performed, and the results are shown in Table 1.

[0209] Comparative Example 2: Magnesia (MgO, model number: Kyowamag MF150, average primary particle diameter 30 nm, BET specific surface area 129 m) was used as a template. ２ Carbon material H was obtained in the same manner as in Example 1, except that carbon material H (1000 MPa / g, manufactured by Kyowa Chemical Industry Co., Ltd.) was used and the template removal operation was performed as described below. A 2032 size coin-type battery was fabricated using this carbon material H. Using the obtained carbon material H and the test battery, material property measurements, conductivity evaluations, and battery evaluations were performed, and the results are shown in Table 1.

[0210] (Removal of MgO template) 1 g to 1.4 g of the carbonaceous template, approximately 100 g of hydrochloric acid (Fujifilm Wako Pure Chemical Industries, Ltd., 5 mol / L), and a stir bar were placed in a Teflon (registered trademark) beaker and stirred at room temperature for 5 hours. After that, the sample was filtered using a membrane filter (0.1 μm), washed five times with pure water, and then suction filtered. Care was taken to prevent the deposits from drying on the filter paper. Next, the deposits were placed in a glass beaker containing approximately 100 mL of acetone. The beaker was covered with aluminum foil and held in a vacuum dryer at 0.06 MPa for 2 minutes. After that, the pressure was returned to normal and the mixture was heated in a thermostatic chamber at 60°C for 10 minutes to perform acetone replacement. The supernatant liquid in the beaker was removed with a pipette, and the same acetone replacement procedure was repeated. The mixture was then dried under reduced pressure at 150°C for 6 hours to obtain a graphene-containing carbon material H after template removal.

[0211] Comparative Example 3 A 2032 size coin-type battery was fabricated in the same manner as in Example 1, except that commercially available carbon black (model number: Denka Black Li-100, manufactured by Denka Co., Ltd.) was used as the carbon material. Material property measurements, conductivity evaluations, and battery evaluations were carried out, and the results are shown in Table 1.

[0212]

[0213] From Table 1, it can be seen that the carbon materials A to F of the present invention are formed by a carbonaceous outer shell having a graphene structure, have pores, and have a BET specific surface area of ​​817 m ２ / g or more 1020m ２ / g or less, the total pore volume is in the range of 2.95 cc / g or more and 5.62 cc / g or less, the volume ratio of pores having a pore diameter of 10 nm or more to the total pore volume is in the range of 62% or more and 81% or less, and the volume ratio of macropores having a pore diameter of more than 50 nm is in the range of 16% or more and 43% or less, and the mode pore diameter is in the mesopore region of 15.8 nm or more and 2 nm or more and 50 nm or less. When this is the case, it can be seen that the electrical conductivity is excellent, and when used in a lithium ion secondary battery, all of the rapid discharge characteristics, battery capacity characteristics, and charge / discharge characteristics can be significantly improved (comparison between Examples 1 to 6 and Comparative Examples 1 to 3).

[0214] In terms of electrical conductivity, carbon materials A to F of the present invention are overwhelmingly superior to carbon materials G to H of Comparative Examples 1 and 2 and the carbon black of Comparative Example 3. This is thought to be because carbon materials A to F of the present invention are formed by a carbonaceous outer shell having a graphene structure with high electronic conductivity, and further have a structure in which large pores such as pores with a pore diameter of 10 nm or more and macropores (pores with a pore diameter of more than 50 nm) are connected together, which allows for the formation of efficient electron conduction paths (comparison between Examples 1 to 6 and Comparative Examples 1 and 2). Furthermore, this is thought to be because a conductive path effective for electron conductivity is formed, also judging from the apparent density value of the carbon material of the present invention.

[0215] With regard to rapid discharge characteristics, the carbon materials A to F of the present invention have significantly higher BET specific surface areas, total pore volumes, and mesopore volumes than the carbon black of Comparative Example 3, and it can be seen that not only is the electronic conductivity of the carbon material itself different, but ionic conductivity is also imparted, resulting in a significant improvement (comparison between Examples 1 to 6 and Comparative Example 3). On the other hand, the carbon materials G to H of Comparative Examples 1 and 2 have poor rapid discharge performance despite their large total pore volumes and mesopore volumes. This is presumably because the pores possessed by carbon materials G to H are mostly pores with a pore size of less than 10 nm, with few large pores of 10 nm or more, and even less than 2% to 3% of macropores with a pore size of more than 50 nm, resulting in no improvement in ionic conductivity (comparison between Examples 1 to 6 and Comparative Examples 1 and 2).

[0216] The difference between the carbon materials A to F of the present invention and the carbon materials G to H of Comparative Examples 1 and 2 is also the intensity of the 2D band (I ２Ｄ ) versus G band intensity (I Ｇ ) intensity ratio (I Ｇ / I ２Ｄ ) is smaller for carbon materials G to H than for carbon materials A to F. Ｇ / I ２Ｄ is also called the lamination index, and the intensity ratio I Ｇ / I ２Ｄ It is considered that a carbon material has one graphene layer when its pore diameter is 0.2, and the larger the value, the greater the number of layers. Therefore, it is believed that carbon materials G to H of Comparative Examples 1 and 2 were unable to maintain large pores such as macropores with a pore diameter of more than 50 nm because they had fewer carbonaceous graphene layers surrounding the pores than carbon materials A to F (comparison of Examples 1 to 6 with Comparative Examples 1 and 2).

[0217] Furthermore, it is clear that the greater the oil absorption of the carbon material, the better the rapid discharge characteristics. Carbon materials A to F of the present invention have overwhelmingly greater oil absorption values ​​than the carbon materials of Comparative Examples 1 to 3, and are therefore presumably able to retain a large amount of electrolyte, thereby enhancing ionic conductivity (comparison between Examples 1 to 6 and Comparative Examples 1 to 3).

[0218] Regarding battery capacity characteristics, it can be seen that carbon materials A to F of the present invention are overwhelmingly superior in both charge capacity and discharge capacity. This is thought to be because carbon materials A to F of the present invention have both electronic conductivity and ionic conductivity, and are different from carbon materials G to H of Comparative Examples 1 and 2, which have almost no pores with a pore size of 10 nm or more, particularly macropores with a pore size of more than 50 nm, and the carbon black of Comparative Example 3, which is solid and has no pores (comparison between Examples 1 to 6 and Comparative Examples 1 to 3). It is also thought that the difference in the number of particles per unit mass affected this characteristic.

[0219] It can be seen that the carbon materials A to F of the present invention exhibited better results in terms of charge-discharge characteristics than the carbon material G of Comparative Example 1 (comparison of Examples 1 to 6 with Comparative Example 1). Carbon material G exhibited a large total pore volume exceeding 2 cc / g, but most of the pore volume was less than 10 nm, and the volume ratio of pores with a pore diameter of 10 nm or more to the total pore volume was only 13%, which is thought to have affected the migration speed of lithium ions.

[0220] Table 1 also shows that in the method for producing a carbon material, when a carbon-containing inorganic compound is used as a template, a larger amount of carbon is deposited on the template surface, making it suitable for producing a carbon material (comparison of Comparative Examples 1 and 2 with Examples 1 to 6). Specifically, in a CVD reaction at 900°C for 120 minutes, the amount of carbon deposited on the template surface was 15.1% in Comparative Example 1 and 12.3% in Comparative Example 2, but in Example 4, a deposition amount equal to or greater than the above (15.6%) was achieved in 80 minutes at 900°C. Furthermore, although not shown in this specification, when silica with a carbon content below the detection limit was used as the template, the carbon deposition rate was slower under similar conditions.

[0221] Example 7 A test battery was produced under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was set to 0.1 wt % and the blending amount of positive electrode material NCM was set to 96.9%.

[0222] Example 8 A test battery was produced under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was set to 0.3 wt % and the blending amount of the positive electrode material NCM was set to 96.7%.

[0223] Example 9 A test battery was produced under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was set to 1 wt % and the blending amount of the positive electrode material NCM was set to 96%.

[0224] Example 10 A test battery was produced under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was set to 2 wt % and the blending amount of positive electrode material NCM was set to 95%.

[0225] Example 11 A test battery was produced under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was set to 3 wt % and the blending amount of positive electrode material NCM was set to 94%.

[0226] Example 12 A test battery was produced under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was set to 4 wt % and the blending amount of the positive electrode material NCM was set to 93%.

[0227] Example 13 A test battery was produced under the same conditions as in Example 1, except that in the preparation of the positive electrode, the blending amount of carbon material A was set to 6 wt % and the blending amount of positive electrode material NCM was set to 91%.

[0228] Charge-discharge tests were conducted on the test batteries of Example 1, Examples 7 to 13, and Comparative Example 3. At room temperature (25°C), each test battery was charged at a constant current of 1.25 mA (equivalent to 0.2 C) up to 4.2 V (constant current charging). After reaching 4.2 V, the battery was charged at a constant voltage of 0.31 mA (0.05 C). The battery was then discharged at a constant current of 1.25 mA (equivalent to 0.2 C) down to 3 V. The charge and discharge capacities were determined. The results are shown in Table 2 and FIG. 6. FIG. 6 shows the relationship between the amount of carbon material blended and the 2C retention and discharge capacity for the test batteries of Example 1 and Examples 7 to 13.

[0229]

[0230] 6, within the range of the carbon material blending amount in Example 1 and Examples 7 to 13, the 2C retention rate of the test batteries improved when the carbon material blending amount was between 0.1 wt% and 2.0 wt%, maintained a maximum value when the carbon material blending amount was between 2.0 wt% and 4.0 wt%, but decreased when the carbon material blending amount was excessively increased to 6.0 wt%. As the carbon material blending amount increased, the battery discharge capacity also increased, but if the blending amount was increased too much, the active material content decreased and the electrode discharge capacity decreased.

[0231] Example 14: A negative electrode test battery was manufactured by incorporating the carbon material A of Example 1 into the negative electrode. 97% artificial graphite, 1% carbon material A of Example 1, 1% carboxymethyl cellulose, and 1% styrene butadiene rubber (SBR) were mixed and stirred uniformly using distilled water as the solvent to prepare a negative electrode additive slurry. The resulting slurry was applied to a 20 μm thick copper foil and dried at 110°C. It was then punched out to a diameter of 15 mm and pressed at 30 kN to form a negative electrode. The resulting negative electrode was vacuum dried at 120°C and then placed in an argon gas glove box. A 2032-size coin-type test battery with a metal Li counter electrode was fabricated using a 1M LiPF6 solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC)) as the electrolyte and a polypropylene separator.

[0232] Each test battery was energized to 0 V at a constant current of 1.23 mA (equivalent to 0.2 C). After reaching 0 V, it was charged at a constant voltage and continued until it reached 0.31 mA (0.05 C). It was then discharged to 1.5 V at a constant current of 1.23 mA. The discharge capacity at this time was determined. Next, using the same test battery, it was energized to 0 V at a constant current of 1.23 mA (equivalent to 0.2 C). After reaching 0 V, it was charged at a constant voltage and continued until it reached 0.31 mA (0.05 C). It was then discharged to 1.5 V at a high rate of 12.3 mA (equivalent to 2 C). The 2C retention rate ((2C capacity / 0.2C capacity) × 100) was calculated from the discharge capacity of the test battery obtained in the above evaluation test. Evaluation of the resulting negative electrode battery revealed a 2C retention rate of 47%.

[0233] Comparative Example 4 A negative electrode test battery was produced in the same manner as in Example 14, except that commercially available carbon black (model number: Denka Black Li-100, manufactured by Denka Company Ltd.) was used as a conductive additive instead of carbon material A in Example 1, and the amount of this conductive additive added to the negative electrode was 1%. Evaluation of the resulting negative electrode battery revealed that the 2C retention rate was 16%.

[0234] As is clear from the above examples, the 2C retention rate (rapid discharge characteristics) of the battery using the carbon material of the present invention is higher than that of the battery of Comparative Example 4. This is due to the high electronic and ionic conductivity of the carbon material of the present invention. Specifically, compared to the conductive additive used in the battery of Comparative Example 4, the carbon material of the present invention has a highly conductive carbonaceous structure containing graphene as its skeleton and has spaces within the particles capable of retaining an electrolyte. The discharge reaction is a reaction in which lithium ions released during charging return to the positive electrode material. When discharge begins, electrons flow from the external circuit to the positive electrode, and the electrons and lithium ions bond with each other and return to the crystalline structure sites of the positive electrode, restoring the bonding state before charging. In other words, the bonding between lithium ions and electrons and the phase change in the crystalline 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 high high-rate discharge retention, and it was confirmed that the carbon material of this example can achieve this "simultaneity."

[0235] The present invention is not limited to the above-described embodiments and examples, and various design modifications within the scope of the present invention are included in the present invention.

Claims

1. A carbon material formed by a carbonaceous outer shell having a graphene structure and having pores, wherein the BET specific surface area is 100 m ２ / g or more and 2500 m ２ / g or less, the total pore volume measured by nitrogen adsorption / desorption measurement is 0.30 cc / g or more, the volume ratio of pores having a pore diameter of 10 nm or more in the total pore volume is 30% or more, and the volume ratio of macropores having a pore diameter exceeding 50 nm is 5% or more, and the carbon material is in the mesopore region where the mode pore diameter is 2 nm or more and 50 nm or less.

2. In the Raman spectroscopic measurement, the intensity ratio (I ２Ｄ / I Ｇ ) of the intensity (I Ｇ ) of the G band to the intensity (I ２Ｄ ) of the 2D band is in the range of 1.0 or more and 10 or less, and the carbon material according to claim 1.

3. The number per unit mass of the carbon material is in the range of 1.0×10 １６ pieces / g or more and 1.0×10 １９ pieces / g or less. The carbon material according to claim 1.

4. The carbon material according to claim 1, wherein the apparent density represented by 1 / (the total pore volume + 1 / true density) is 1.00 g / cc or less.

5. The carbon material according to claim 1, wherein the ash content in the carbon material is 5000 ppm or less.

6. The carbon material according to claim 1, which is used in a lithium-ion secondary battery.

7. A method for producing a carbon material according to any one of claims 1 to 6, comprising: a carbonaceous layer forming step of forming a carbonaceous layer on the surface of a mold composed of an aggregate of a fume-like compound; and a mold removing step of removing the mold.

8. A conductive auxiliary agent for an electrode for a battery, which has the carbon material according to any one of claims 1 to 6.

9. A dispersion liquid having the carbon material according to any one of claims 1 to 6 and a dispersion medium in which the carbon material is dispersed.

10. An electrode composition containing the carbon material according to any one of claims 1 to 6, an active material, and a binder.

11. An electrode slurry having the electrode composition according to claim 10 and a solvent in which the electrode composition is dispersed.

12. An electrode containing the carbon material according to any one of claims 1 to 6.

13. A lithium-ion secondary battery containing the carbon material according to any one of claims 1 to 6.

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