Carbon material, production method for carbon material, dispersion liquid, composition for electrodes, slurry for electrodes, electrode, positive electrode, negative electrode, lithium ion battery, carbon material precursor, and production method for carbon material precursor

Abstract

The present invention provides: a carbon material which has a graphene crystal structure, and in which graphene layers are controlled to be in a prescribed stacked state and the oil absorption value is high; a production method for the carbon material; a dispersion liquid which contains the carbon material; a composition for electrodes; a slurry for electrodes; an electrode; a positive electrode; a negative electrode; a lithium ion battery; a carbon material precursor which is a precursor of the carbon material; and a production method for the carbon material precursor.　The carbon material includes a connection structure that has an extension shape in which a plurality of hollow particulate parts are connected in the form of a string of beads, each of the hollow particulate parts having a surrounding wall that defines the internal space, has a plurality of pores formed therein, and has a graphene crystal structure. The intensity ratio (IG / I2D) of the intensity (IG) of the G band to the intensity (I2D) of the 2D band in the Raman spectrum obtained by Raman spectrometry is 0.40 to 5.00 inclusive, and the oil absorption value as measured in accordance with JIS K 5101-13-1:2004 is 400 mL / 100 g or more.

Description

Carbon material and method for producing the same, dispersion, electrode composition, electrode slurry, electrode, positive electrode, negative electrode, lithium ion battery, and carbon material precursor and method for producing the same

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

[0002] Various carbon materials have been studied for a long time. For example, carbon black is used in a wide range of fields.

[0003] Carbon nanotubes, a type of nanocarbon, have high mechanical strength and electrical conductivity. However, they tend to aggregate or entangle, so they must be dispersed. Furthermore, it is not easy to improve the uniformity of the physical properties and shape of carbon nanotubes.

[0004] Graphene, a nanocarbon that differs from carbon nanotubes, has high mechanical strength and electrical conductivity, as well as flexibility, making it promising for applications in a variety of fields.

[0005] For example, Patent Document 1 discloses a graphene-based composite having a stacked graphene structure and a BET specific surface area of ​​80 to 155 m ２ / g, a pore volume of pores with diameters of 0.3 nm or more and 1.0 nm or less in the pore distribution of 1.6 to 2.1 mL / g, and a DBP absorption of 210 to 220 mL / 100 g. The carbon material in Patent Document 1 has a graphene laminate structure, a high DBP absorption, and excellent electrolyte retention. Therefore, when the carbon material is applied to a positive electrode, the cycle characteristics of the battery can be improved. Thus, Patent Document 1 considers a technology in which a carbon material having a graphene laminate structure is applied to a battery.

[0006] Meanwhile, products in various fields, including batteries, are rapidly improving in performance and functionality. As products become more multifunctional, the performance levels required of the components that make up the products are also rapidly increasing. For example, in the field of batteries, the liquid retention properties of the carbon material disclosed in Patent Document 1 are insufficient, and even if the carbon material disclosed in Patent Document 1 is applied to batteries, the battery characteristics, such as rapid discharge ability and charge / discharge characteristics, are insufficient. Therefore, there is a demand for carbon materials that can achieve the required product levels even when applied to products that are becoming increasingly multifunctional.

[0007] Furthermore, Non-Patent Document 1 describes electrolyte movement in cylindrical lithium-ion batteries. During charging, when lithium ions are inserted into a negative electrode material such as graphite, the negative electrode material particles expand. When lithium ions are deintercalated during the next discharge, the negative electrode material particles contract, causing changes in the voids within the electrode. In response to these changes in voids, the electrolyte present in the voids within the electrode moves, being pushed out or re-impregnated. This non-uniformity in the amount and location of the electrolyte within the electrode is thought to be one of the causes of charge-discharge cycle deterioration.

[0008] In lithium-ion batteries such as those described in Non-Patent Document 1, the materials for the positive and negative electrodes and the basic reactions are common, but there are various approaches to battery manufacturing depending on business environment factors such as the use of the battery, the availability of existing facilities, consideration of manufacturing costs, and collaboration with other companies, and the reality is that batteries, electrodes, electrolytes, etc. have been devised.

[0009] Japanese Patent Application Laid-Open No. 2019-091587

[0010] C. P. Aiken, et. al. , Journal of The Electrochemical Society, 2023, 170, 040529

[0011] An object of the present invention is to provide a carbon material that has a graphene crystal structure, in which graphene layers are controlled to a predetermined stacking state, and has a high oil absorption capacity, a method for producing the same, a dispersion containing the carbon material, a composition for an electrode, a slurry for an electrode, an electrode, a positive electrode, a negative electrode, and a lithium-ion battery, as well as a carbon material precursor that is a precursor of the carbon material, and a method for producing the same.

[0012] In order to achieve the above object, the gist of the present invention is as follows: [1] A method for producing a graphene-based nanoparticle having a structure in which a plurality of hollow particulate portions are connected in a beaded shape, the hollow particulate portions having an inner space partitioned and formed with a plurality of pores and a surrounding wall having a graphene crystal structure, the structure having an elongated shape, and the G band intensity (I Ｇ ) 2D band intensity (I ２Ｄ ) to the intensity ratio (I Ｇ / I ２Ｄ [2] The carbon material has an oil absorption of 400 mL / 100 g or more as measured in accordance with JIS K5101-13-1:2004, and an intensity of the D band (I Ｄ ) G band intensity (I Ｇ ) to the intensity ratio (I Ｄ / I Ｇ ) is 0.1 or more and 10.0 or less. [3] The carbon material according to the above [1] or [2], wherein the mode pore diameter is 1 nm or more and 500 nm or less. [4] The carbon material according to any one of the above [1] to [3], wherein the total pore volume is 0.10 cc / g or more and 20.00 cc / g or less. [5] The carbon material according to any one of the above [1] to [4], wherein the proportion of the macropore volume in the total pore volume is 5% or more. [6] The carbon material according to any one of the above [1] to [5], wherein the apparent density is 2.00 g / cc or less. [7] The carbon material according to any one of the above [1] to [5], wherein the BET specific surface area is 100 m ２ / g or more 2700m ２ / g or less. [8] The carbon material according to any one of [1] to [7] above, wherein the crystallite size Lc(002) in the c-axis direction measured by X-ray diffraction is 0.10 nm or more and 20.00 nm or less. [9] The carbon material according to any one of [1] to [8] above, wherein the interplanar spacing d002 of the (002) plane measured by X-ray diffraction is 3.0 Å or more and 5.0 Å or less.

[10] The carbon material according to any one of [1] to [9] above, wherein the D50 obtained from a volume-based particle size distribution curve measured by laser diffraction scattering is 1 μm or more and 100 μm or less.

[11] The carbon material according to any one of [1] to

[10] above, wherein the ratio of D90 to D10 (D90 / D10) obtained from a volume-based particle size distribution curve measured by laser diffraction scattering is 100 or less.

[12] The carbon material according to any one of the above [1] to

[11] , wherein the ratio (D90 / M) of D90 obtained from a volume-based particle size distribution curve measured by a laser diffraction scattering method to the mode pore diameter M is 50 or less, divided by 1000.

[13] The carbon material according to any one of the above [1] to

[12] , wherein the interconnected structure is a graphene meso-sponge.

[14] The carbon material according to any one of the above [1] to

[13] , wherein the carbon material is for a secondary battery.

[15] A dispersion obtained by dispersing the carbon material according to any one of the above [1] to

[14] in a dispersion medium.

[16] A composition for an electrode, comprising the carbon material according to any one of the above [1] to

[14] , an active material, and a binder.

[17] A slurry for an electrode, comprising the composition for an electrode according to the above

[16] in a dispersion medium.

[18] An electrode comprising the carbon material according to any one of the above [1] to

[14] .

[19] The electrode according to

[18] above, containing the carbon material in an amount of 0.1 wt % or more and 6.0 wt % or less.

[20] A positive electrode containing the carbon material according to any one of [1] to

[14] above.

[21] A negative electrode containing the carbon material according to any one of [1] to

[14] above.

[22] The negative electrode according to

[21] above, which is for a lithium ion battery and further contains graphite.

[23] The negative electrode according to

[21] above, which is for a lithium ion battery and further contains silicon.

[24] A lithium ion battery comprising the positive electrode according to

[20] above, the negative electrode according to

[21] above, and a liquid electrolyte.

[25] A lithium ion battery comprising the positive electrode according to

[20] above, the negative electrode according to

[21] above, and a semi-solid electrolyte.

[26] A lithium ion battery wherein at least one of the positive electrode and the negative electrode in the lithium ion battery according to

[24] or

[25] above is a dry electrode.

[27] A lithium ion battery comprising a clay-type positive electrode containing the carbon material according to any one of [1] to

[14] above, and a clay-type negative electrode containing the carbon material according to any one of [1] to

[14] above.

[28] A lithium ion battery comprising the carbon material according to any one of [1] to

[14] above.

[29] A method for producing a carbon material according to any one of [1] to

[14] above, comprising a removal step of obtaining a carbon material by removing a template material from a carbon material precursor in which the template material is an aggregate of a plurality of primary particles linked together in a beaded shape, the surface of which is coated with a carbonaceous layer.

[30] The method for producing a carbon material according to

[29] above, further comprising a heating step of heating the carbon material at 1000°C or more and 3000°C or less after the removing step.

[31] The method for producing a carbon material according to

[29] or

[30] above, wherein the template material is a smoky compound.

[32] A carbon material precursor comprising a template material composed of an aggregate of a plurality of primary particles agglomerated and linked together in a beaded shape, and a carbonaceous layer covering the surface of the template material and having a plurality of pores.

[33] The method for producing a carbon material precursor according to

[32] above, further comprising a coating step of coating the surface of the template material, which is an aggregate of a plurality of primary particles agglomerated and linked together in a beaded shape, with a carbonaceous layer to obtain a carbon material precursor.

[34] The method for producing a carbon material precursor according to

[33] above, wherein the template material is a smoky compound.

[0013] The present invention can provide a carbon material having a graphene crystal structure, in which graphene layers are controlled to a predetermined stacking state, and having a high oil absorption, a method for producing the same, a dispersion containing the carbon material, a composition for an electrode, a slurry for an electrode, an electrode, a positive electrode, a negative electrode, and a lithium-ion battery, as well as a carbon material precursor that is a precursor of the carbon material, and a method for producing the same.

[0014] FIG. 1 is a cross-sectional view showing an example of a lithium-ion battery according to an embodiment. FIG. 2 is an enlarged TEM image of carbon material A of Example 1 observed using a transmission electron microscope (TEM) at an accelerating voltage of 80 kV. FIG. 3 is a TEM image of carbon material A of Example 1 observed using a TEM at an accelerating voltage of 100 kV. FIG. 4 is an enlarged TEM image of the carbon material of Example 1 observed using a TEM at an accelerating voltage of 100 kV. FIG. 5 is a graph showing discharge curves of different discharge current values ​​using the test battery of Example 1. FIG. 6 is a Raman spectrum of carbon material B of Example 2. FIG. 7 is a graph showing the relationship between oil absorption and 2C retention rate for the test batteries of Examples 1 and 9 and Comparative Example 1. FIG. 8 is a graph showing the relationship between the blend amount of carbon material and 2C retention rate and discharge capacity for the test batteries of Examples 1 and 10 to 16. FIG. 9 is a schematic diagram illustrating the ultra-high sensitivity vacuum TPD apparatus used for thermal desorption gas analysis.

[0015] The embodiments will be described in detail below.

[0016] As a result of extensive research, the present inventors have discovered a method for producing a quartz crystal particle having an elongated structure in which a plurality of hollow particulate portions each having a surrounding wall with a predetermined structure are connected in a rosary-like manner, and wherein the Raman spectrum has an intensity ratio (I Ｇ / I ２Ｄ The present inventors have found that, by controlling the crystal structure of the carbon material and the oil absorption within a predetermined range, the carbon material can have a graphene crystal structure, the graphene layers can be controlled to a predetermined stacking state, and the carbon material can have a high oil absorption, and have completed the present invention based on this finding.

[0017] (Carbon Material) First, the carbon material of the embodiment will be described.

[0018] The carbon material of the embodiment has a connected structure having an elongated shape in which a plurality of hollow particulate portions, which partition and form an internal space, and in which a plurality of pores are formed and which have surrounding walls having a graphene crystal structure, are connected in a rosary-like manner, and the G band intensity (I Ｇ ) 2D band intensity (I ２Ｄ ) to the intensity ratio (I Ｇ / I２Ｄ ) is 0.40 or more and 5.00 or less, and the oil absorption measured in accordance with JIS K5101-13-1:2004 is 400 mL / 100 g or more.

[0019] The carbon material of the embodiment includes a connected structure having an elongated shape. The connected structure having an elongated shape is formed by connecting a plurality of hollow particulate portions in a rosary shape. The hollow particulate portions have a surrounding wall, and the interior of the hollow particulate portions is hollow. The surrounding wall defines an internal space of the hollow particulate portion in the connected structure. The surrounding wall has a plurality of pores formed therein and has a graphene crystal structure.

[0020] The carbon material has a hollow structure. The internal spaces of the interconnected structures, including the internal spaces of the hollow particulate portions, are interconnected. Such a carbon material is porous, having micropores, mesopores, and macropores.

[0021] The surrounding wall of the carbon material is preferably composed of graphene or multi-layer graphene, or a mixture of graphene and multi-layer graphene may be present. Graphene is a sheet-like substance of SP2-bonded carbon, in which six-membered carbon ring structures are connected to form a honeycomb-like hexagonal lattice structure. Thus, the surrounding wall has a six-membered carbon ring structure. The connecting structure is preferably graphene meso-sponge (GMS).

[0022] Carbon materials consist of structures that have elastic deformation and structures that have plastic deformation. A structure that has plastic deformation will deform and become distorted when an external force less than a certain value is applied, but if an external force exceeding the elastic limit is applied, the material will not return to its original shape even after the external force is removed, resulting in permanent deformation. The degree of elastic deformation and plastic deformation of carbon materials can be measured using a very small load-unload test.

[0023] Carbon materials have the property of returning to their original shape without plastic deformation under weak external forces, such as those in extremely small load / unload tests, i.e., they have a large elastic deformation work capacity. In carbon materials, the graphene portion, which accounts for the majority of the carbon material, exhibits elastic deformability, while structural portions other than graphene, such as defects in the graphene structure and amorphous carbon portions, exhibit plastic deformability. Therefore, carbon materials are thought to exhibit favorable properties against deformation under external forces. Furthermore, when the number of graphene layers is excessively large, the material maintains elastic deformability under external forces below a predetermined value, but tends to undergo sudden plastic deformation under external forces exceeding the elastic limit, resulting in the destruction of hollow particulate portions and the like.

[0024] Furthermore, the carbon material preferably has a branched portion where the connecting structure branches, more preferably has multiple branched portions. Furthermore, the carbon material preferably has a ring-shaped portion where the connecting structure has multiple ring-shaped portions. The connecting structure having an extended shape may have only a branched portion, may have only a ring-shaped portion, or may have both a branched portion and a ring-shaped portion. For example, one end and the other end of the connecting structure may be connected to form a ring-shaped portion. Furthermore, the tips of the branches that branch out and extend may be connected to form a ring-shaped portion. Furthermore, a link-shaped portion may be formed in a portion of the connecting structure other than the end portion.

[0025] The size of the multiple pores provided in the connected structure is preferably 0.1 nm or more and 100.0 nm or less, more preferably 1.0 nm or more and 80.0 nm or less, and even more preferably 5.0 nm or more and 50.0 nm or less. The length of the connected structure is preferably 0.01 μm or more and 100.00 μm or less, more preferably 0.05 μm or more and 80.00 μm or less, and even more preferably 0.10 μm or more and 50.00 μm or less. The average particle diameter (average outer diameter) of the hollow particulate portion in the connected structure is preferably 0.05 μm or more and 50.00 μm or less, more preferably 0.05 μm or more and 6.00 μm or less, even more preferably 0.10 μm or more and 10.00 μm or less, particularly preferably 0.10 μm or more and 5.00 μm or less, and most preferably 0.50 μm or more and 5.00 μm or less.

[0026] A constriction may be provided at the connecting portion (joint portion) between the hollow particulate portions. For example, when two hollow particulate portions are connected, the shape is like a peanut shell or a dumbbell. A plurality of such hollow particulate portions are connected to form a connected structure. The connected structure is a complex structure that does not have a fixed shape.

[0027] As described above, carbon materials are interconnected structures (structures) in which multiple hollow particulate portions are connected in a beaded pattern. The term "structure" is used to describe the complex structure of carbon black, and refers to an aggregate structure in which multiple primary particles of carbon black are connected with multiple branching points. In other words, carbon materials can be likened to highly conductive primary particles of carbon black, each of which has a hollow interior, an outer shell (the surrounding wall constituting the hollow particulate portion of the carbon material) made of multiple carbon atoms with a graphene crystal structure, and the internal spaces of the carbon black aggregates are interconnected. Therefore, carbon materials have high conductivity and can stably secure electrolytes. Carbon materials can significantly improve the battery characteristics of lithium secondary batteries, such as rapid discharge, battery capacity, and charge / discharge characteristics.

[0028] When many hollow particulate portions are connected and the surface area of ​​the connected structure increases, the electronic conductivity of the carbon material increases. Furthermore, when the overall complexity of the connected structure increases, voids surrounded by the outer surface of the surrounding wall of the connected structure are also formed in addition to the internal space of the connected structure. When a carbon material having such a connected structure is contained in a battery electrode, electrolyte enters these spaces and voids. In other words, the larger the volume of the internal space of the connected structure or the volume of the voids surrounded by the surrounding wall, the greater the amount of electrolyte retained by the carbon material. The volume of the internal space of the connected structure in a carbon material and the volume of the voids surrounded by the surrounding wall can be compared with the volume of a conventionally used conductive additive using the oil absorption capacity described below as an indicator.

[0029] The positive electrode material for lithium-ion batteries is a lithium-containing transition metal oxide powder with a particle size distribution and low electronic conductivity. In conventional technology, an electronic conduction path is established by pressurizing a mixture of a binder resin and a conductive additive made of a carbon material that aids in electronic conduction for the battery reaction onto a current collector. All materials except the binder resin are powder particles, and the electrolyte exists in the spaces between the particles. Therefore, it was difficult with conventional technology to actively position the electrolyte, or in other words, lithium ions, near the positive electrode material.

[0030] Furthermore, complex-shaped carbon black has been widely used as a conductive additive in the past. By using the carbon material of the present embodiment instead of the conventional conductive additive, the hollow particulate portions of the interconnected structure have internal spaces, allowing the electrolyte to be retained in the internal spaces of the hollow particulate portions. The carbon material has larger internal spaces than the carbon black conventionally used as a conductive additive. Therefore, the carbon material simultaneously assists in the supply of electrons and ions necessary for the battery reaction, making it possible to realize a rapid battery reaction.

[0031] The state of the fine crystal structure of the carbon material can be analyzed by Raman spectroscopy. In the Raman spectrum obtained by Raman spectroscopy of the carbon material, －１ The peak present around 1356 cm is called the G band and indicates the sp2 bond (C=C stretching motion of the aromatic ring) of the carbon material. －１ The peak present around 2680 cm is called the D band and indicates the sp3 bond (C-H stretching motion) of the carbon material. When the sp2 bond is broken and the sp3 bond is formed, the D band increases. In addition, in the above Raman spectrum, the peak at the wave number of 2680 cm －１ The peak near this point is called the 2D band and indicates second-order phonon scattering (C-H stretching motion). The 2D band also indicates the number of surrounding walls, i.e., the number of stacked graphene layers.

[0032] G band intensity (I Ｇ ) 2D band intensity (I ２Ｄ ) to the intensity ratio (I Ｇ / I２Ｄ ) is said to be an index that indicates the stacking state of graphene layers (D. Graf, et al., NANO LETTERS, 7, 238-242 (2007)). Ｇ / I ２Ｄ ) is 0.2, the graphene layer is described as being one layer.

[0033] The intensity of the G band (I Ｇ ) 2D band intensity (I ２Ｄ ) to the intensity ratio (I Ｇ / I ２Ｄ ) is 0.40 or more, preferably 1.00 or more, more preferably 1.10 or more, even more preferably 1.20 or more, and particularly preferably 1.43 or more. Ｇ / I ２Ｄ ) is 5.00 or less, and is more preferably 4.50 or less, 4.00 or less, 3.57 or less, 3.00 or less, 2.50 or less, and 2.08 or less in that order.

[0034] The intensity ratio (I Ｇ / I ２Ｄ When the strength ratio (I) of the carbon material is within the above range, the strength characteristics and elastic deformability that maintain the hollow structure of the carbon material are well balanced. Furthermore, when the carbon material is used as a conductive additive in a lithium ion battery, the battery characteristics such as the rapid discharge characteristics, capacity characteristics, and durability of the lithium ion battery can be improved. In addition, when the strength ratio (I) of the carbon material is within the above range, the strength ratio (I) of the carbon material is well balanced. Ｇ / I ２Ｄ When the intensity ratio (I ) of the carbon material is less than 0.40, the generation of the graphene crystal structure is insufficient. As a result, the electron conductivity decreases, and the discharge capacity decreases. Ｇ / I ２Ｄ If the ratio (R) exceeds 5.00, the number of stacked graphene layers increases excessively, resulting in poor flexibility of the carbon material, which in turn reduces the electrode density and the battery packing capacity.

[0035] The oil absorption of the carbon material, measured in accordance with JIS K5101-13-1:2004 (Pigment Testing Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method), is 400 mL / 100 g or more, preferably 600 mL / 100 g or more, more preferably 800 mL / 100 g or more, even more preferably 1000 mL / 100 g or more, and particularly preferably 1400 mL / 100 g or more. When the oil absorption of the carbon material is within the above range, battery characteristics such as 2C retention rate can be improved. In addition, the upper limit of the oil absorption of the carbon material is not particularly limited, but is preferably, for example, 5000 mL / 100 g or less, 4000 mL / 100 g or less, 3500 mL / 100 g or less, 3000 mL / 100 g or less, and 2500 mL / 100 g or less, in that order.

[0036] Carbon materials can retain electrolyte in the internal space of the connecting structure and in the voids surrounded by the outer surface of the surrounding wall of the connecting structure, and therefore can retain a large amount of electrolyte. Therefore, the oil absorption of carbon materials is significantly higher than that of carbon black, which is commonly used as a conductive additive in lithium-ion batteries. This allows for a stable supply of lithium ions, contributing to improvements in battery characteristics such as the rapid charging capability, charge / discharge characteristics, and battery capacity of lithium-ion batteries. On the other hand, if the oil absorption of a carbon material is less than 400 mL / 100 g, the electrolyte retention capacity is low, resulting in a delay in the supply of ions during a rapid reaction and a decrease in discharge capacity. Furthermore, if the oil absorption of a carbon material is excessively high, it may be difficult to maintain the structure of the carbon material, making it difficult to control the amount of electrolyte retention.

[0037] In addition, the intensity of the D band (I Ｄ ) G band intensity (I Ｇ ) to the intensity ratio (I Ｄ / I Ｇ ) is preferably 0.1 or more and 10.0 or less, more preferably 0.5 or more and 5.0 or less, even more preferably 1.0 or more and 3.0 or less, particularly preferably 1.2 or more and 2.5 or less, and most preferably 1.4 or more and 2.0 or less. Ｄ / I ＧWhen the carbon material has a molecular weight of 1.0 or 2.0, the carbon material has a molecular weight of 1.0 or 2.0, and the molecular weight of the carbon material is 1.0 or 2.0. When the carbon material has a molecular weight of 1.0 or 2.0, the carbon material has a molecular weight of 1.0 or 2.0, and the molecular weight of the carbon material is 1.0 or 2.0.

[0038] The interplanar spacing d002 of the (002) plane of the carbon material measured by X-ray diffraction (XRD) is preferably 3.0 Å or more and 5.0 Å or less, more preferably 3.3 Å or more and 4.5 Å or less, even more preferably 3.3 Å or more and 4.0 Å or less, particularly preferably 3.3 Å or more and 3.9 Å or less, and most preferably 3.3 Å or more and 3.8 Å or less.

[0039] In addition, the size Lc (002) of the crystallite in the c-axis direction measured by X-ray diffraction of the carbon material is preferably 0.10 nm or more, more preferably 0.30 nm or more, 0.50 nm or more, 1.00 nm or more, and 1.10 nm or more. In addition, the upper limit of the size Lc (002) of the crystallite in the c-axis direction is preferably 20.00 nm or less, more preferably 5.00 nm or less, 3.00 nm or less, 2.50 nm or less, 2.00 nm or less, 1.90 nm or less, 1.50 nm or less, 1.25 nm or less, and 1.21 nm or less. When the Lc (002), which indicates the degree of crystallinity of the carbon material, is within the above range, the linked structure tends to have mesopores or macropores.

[0040] The lower limit of the crystallite size La(10) of the (10) plane in the a-axis direction measured by X-ray diffraction of the carbon material is preferably 0.1 nm or more, more preferably 0.5 nm or more, 1.0 nm or more, 1.5 nm or more, and 1.8 nm or more. The upper limit of La(10) is preferably 10.0 nm or less, more preferably 5.0 nm or less, 4.5 nm or less, 4.0 nm or less, and 3.8 nm or less.

[0041] The BET specific surface area of ​​the carbon material is the specific surface area calculated from nitrogen adsorption as specified in JIS Z8830, and is preferably 100 m ２ / g or more 2700m ２ / g or less, and ２ / g or more 2500m ２ / g or less, 500m ２ / g or more 2000m ２ / g or less, 600m ２ / g or more 1800m ２ / g or less, 800m ２ / g or more 1200m ２ When the BET specific surface area of ​​the carbon material is within the above range, the electrical conductivity and oil absorption of the carbon material are further improved.

[0042] The total pore volume of the carbon material, as measured by nitrogen adsorption / desorption analysis, is preferably 0.10 cc / g or more, more preferably 1.00 cc / g or more, 1.50 cc / g or more, 2.00 cc / g or more, and 2.95 cc / g or more in this order. 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, 10.00 cc / g or less, 8.00 cc / g or less, 7.00 cc / g or less, 6.10 cc / g or less, and 5.70 cc / g or less in this order.

[0043] When the total pore volume of the carbon material is 20.00 cc / g or less, the strength of the connected structure is improved and the shape of the hollow particulate portions can be well maintained. When the total pore volume of the carbon material is 0.10 cc / g or more, the amount of electrolyte held in the hollow particulate portions tends to increase. Thus, when the total pore volume of the carbon material is within the above range, the hollow particulate portions have good strength, which contributes to the stability of the hollow particulate portions and allows the shape of the hollow particulate portions to be well maintained. Therefore, the carbon material can maintain a good balance between electronic conductivity and the ability to supply ions held in the pores.

[0044] Furthermore, the micropore volume of the carbon material is the volume of pores having a pore diameter of less than 2 nm, and is preferably 5.00 cc / g or less, with 2.00 cc / g or less, 1.00 cc / g or less, 0.50 cc / g or less, and 0.40 cc / g or less being more preferred in this order. The lower limit of the micropore volume of the carbon material is preferably 0.01 cc / g or more, with 0.05 cc / g or more, 0.10 cc / g or more, 0.20 cc / g or more, and 0.30 cc / g or more being more preferred in this order. When the micropore volume of the carbon material is 5.00 cc / g or less, the ionic conductivity is further improved, and when the micropore volume of the carbon material is 0.01 cc / g or more, the strength properties of the carbon material are further improved.

[0045] The ratio of the micropore volume to the total pore volume in the carbon material is preferably 20% or less, with 15% or less, 12% or less, 10% or less, and 9% or less being more preferred in that order. The lower limit of the micropore volume ratio of the carbon material is preferably 5% or more. If the micropore volume ratio is too small, the ionic conductivity tends to be poor, and conversely, if it is too large, the strength characteristics of the carbonaceous material tend to be poor.

[0046] The mesopore volume of the carbon material is the volume of pores having a pore diameter of 2 nm to 50 nm, and is preferably 0.1 cc / g or more, with 0.5 cc / g or more, 1.0 cc / g or more, 1.5 cc / g or more, and 2.0 cc / g or more being more preferred in this order. The upper limit of the mesopore volume of the carbon material is preferably 15.0 cc / g or less, with 10.0 cc / g or less, 5.0 cc / g or less, 4.0 cc / g or less, and 3.5 cc / g or less being more preferred in this order. When the mesopore volume of the carbon material is within the above range, the ionic conductivity and strength characteristics of the carbon material are more highly balanced.

[0047] Furthermore, the proportion of mesopore volume to the total pore volume of the carbon material is preferably 10% or more, with 20% or more, 30% or more, 40% or more, and 50% or more being more preferred in this order. The upper limit of the mesopore volume proportion of the carbon material is preferably 90% or less, with 85% or less, 80% or less, 75% or less, and 70% or less being more preferred in this order. When the mesopore volume of the carbon material is within the above range, the hollow particulate portions have good strength, which contributes to the stability of the hollow particulate portions and maintains the shape of the hollow particulate portions well. Therefore, the carbon material can maintain a good balance between electronic conductivity and the supply of ions held in the pores.

[0048] Furthermore, the macropore volume of the carbon material, which is the volume of pores with a pore diameter of more than 50 nm, is preferably 0.01 cc / g or more, with 0.05 cc / g or more, 0.10 cc / g or more, 0.48 cc / g or more, and 1.00 cc / g or more being more preferred in this order. The upper limit of the macropore volume of the carbon material is preferably 15.00 cc / g or less, with 10.00 cc / g or less, 5.00 cc / g or less, 3.00 cc / g or less, and 2.57 cc / g or less being more preferred in this order. When the macropore volume of the carbon material is within the above range, the hollow particulate portions have good strength, which contributes to the stability of the hollow particulate portions and maintains the shape of the hollow particulate portions well. Therefore, the carbon material can maintain a good balance between electronic conductivity and the supply of ions held in the pores.

[0049] Furthermore, the proportion of the macropore volume to the total pore volume of the carbon material is preferably 5% or more, with 10% or more, 15% or more, 20% or more, and 25% or more being more preferred in this order. The upper limit of the macropore volume proportion of the carbon material is preferably 80% or less, with 70% or less, 60% or less, 50% or less, and 45% or less being more preferred in this order. When the macropore volume proportion of the carbon material is 5% or more, the ionic conductivity of the carbon material is further improved, and when the macropore volume proportion of the carbon material is 80% or less, the strength characteristics of the carbon material are further improved.

[0050] The mode pore diameter (M) in the pore distribution of the carbon material is the peak top value in the pore distribution curve, and is preferably 1 nm or more and 500 nm or less, more preferably 5 nm or more and 100 nm or less, 10 nm or more and 50 nm or less, 15 nm or more and 40 nm or less, and 15 nm or more and 30 nm or less. When the mode pore diameter of the carbon material is within the above range, the oil absorption capacity is further improved and high ionic conductivity and electronic conductivity can be achieved.

[0051] The average pore diameter of the carbon material is preferably 1 nm or more and 500 nm or less, more preferably 5 nm or more and 100 nm or less, 10 nm or more and 75 nm or less, 15 nm or more and 50 nm or less, and 20 nm or more and 40 nm or less. When the average pore diameter of the carbon material is within the above range, the oil absorption capacity is further improved and high ionic conductivity and electronic conductivity can be achieved.

[0052] Furthermore, the volume-based particle size distribution curve of the carbon material measured by the laser diffraction scattering method was obtained by immersing the unpulverized carbon material in a solvent for 9 minutes and then measuring, and this curve revealed the difference in the cohesive strength of the linked structures.

[0053] D50, obtained from a volume-based particle size distribution curve measured by a laser diffraction scattering method, is the particle size at which 50% of particles have a particle size of D50 or less, and is preferably 1 μm or more and 100 μm or less, with 5 μm or more and 90 μm or less, 10 μm or more and 80 μm or less, 15 μm or more and 60 μm or less, 20 μm or more and 50 μm or less, 25 μm or more and 45 μm or less, and 30 μm or more and 40 μm or less being more preferred in this order. When the D50 of the carbon material is within the above range, the electronic conductivity and ionic conductivity of the carbon material are further improved.

[0054] Furthermore, D10 obtained from the particle size distribution curve is the particle size at which the proportion of particles having a particle size of D10 or less is 10%, and is preferably 0.1 μm or more and 100.0 μm or less, more preferably 0.5 μm or more and 50.0 μm or less, 1.0 μm or more and 50.0 μm or less, 5.0 μm or more and 30.0 μm or less, and 10.0 μm or more and 15.0 μm or less, in that order.

[0055] Furthermore, D90 obtained from the particle size distribution curve is the particle size at which 90% of particles have a particle size of D90 or less, and is preferably 5 μm or more and 250 μm or less, more preferably 10 μm or more and 150 μm or less, 20 μm or more and 100 μm or less, 30 μm or more and 70 μm or less, 40 μm or more and 60 μm or less, 45 μm or more and 65 μm or less, and 45 μm or more and 55 μm or less, in that order. When the D90 of the carbon material is within the above range, the conductivity of the carbon material is further improved.

[0056] Furthermore, the ratio of D90 to D10 (D90 / D10) of the carbon material obtained from the particle size distribution curve is preferably 100 or less, and more preferably 50 or less, 10 or less, and then 5 or less. When the ratio (D90 / D10) of the carbon material is 100 or less, the dispersibility of the carbon material is further improved, and the conductivity of the lithium ion battery is further improved.

[0057] Furthermore, the ratio (D90 / M) of the D90 of the carbon material obtained from the particle size distribution curve to the mode pore diameter M of the carbon material, divided by 1000, (D90 / M×1000) is preferably 50 or less, and more preferably 20 or less, 10 or less, 6 or less, and 4 or less, in that order. When (D90 / M×1000) is 50 or less, the dispersibility of the carbon material is further improved, and the conductivity of the lithium ion battery is further improved.

[0058] Furthermore, carbon materials contained in electrodes of lithium-ion batteries preferably have high electrical conductivity. Because electron migration in carbon occurs through the transfer of π electrons, forming an ideal conductive path within an electrode using a carbon material requires a network-like arrangement of single-layer graphene in which carbon atoms are bonded in the planar direction. Furthermore, when a conductive material such as a carbon material is filled into a non-conductive material such as a positive electrode material, if the filling rate of the conductive material is low, electrical conductivity is not achieved. When the conductive material reaches a certain filling rate, paths of the conductive material are formed within the compound, causing a rapid increase in electronic conductivity, which then remains constant. The lower the filling rate threshold at which electronic conductivity rises sharply, the more suitable the carbon material is as a conductive material. Therefore, it is believed that the connection of multiple hollow particulate portions having surrounding walls of a graphene structure extending in the planar direction allows the carbon material to exhibit high electrical conductivity by achieving a high balance between in-plane electrical conductivity and path-formed electrical conductivity.

[0059] The electrical conductivity of carbon materials can be measured by measuring the electrical conductivity of powder using lateral constrained uniaxial compression as described below. Dry carbon material is filled into a cylindrical container consisting of an insulating cylinder and a negative electrode. A positive electrode is inserted into the insulating cylindrical container filled with the carbon material, and the container is placed on a force gauge stand with the carbon material sandwiched between the negative and positive electrodes. A spring-type force gauge attached to the force gauge stand is lowered to apply force to the carbon material inside the cylindrical container, compressing it. While measuring the compressive force and the height of the carbon material with a length measuring device, the resistance value of the carbon material is measured with a digital multimeter connected to the positive and negative electrodes. The electrical conductivity of the carbon material powder during compression is calculated from the obtained resistance value, the packed cross-sectional area of ​​the carbon material, and the packed height.

[0060] The electrical conductivity of the carbon material is preferably 1 S / cm or more and 100 S / cm or less, measured at a pressure of 10 MPa, with the order of preference being 5 S / cm or more and 70 S / cm or less, 10 S / cm or more and 50 S / cm or less, and 20 S / cm or more and 30 S / cm or less. The electrical conductivity of the carbon material is calculated as the reciprocal of the electrical resistivity. The electrical resistivity of the carbon material can be measured according to JIS K1469.

[0061] The apparent density of the carbon material is preferably 2.00 g / cc or less, with 1.50 g / cc or less, 1.00 g / cc or less, 0.50 g / cc or less, and 0.30 g / cc or less being more preferred in this order. The lower limit of the apparent density of the carbon material is preferably 0.05 g / cc or more, 0.10 g / cc or more, and 0.15 g / cc or more in this order. When the apparent density of the carbon material is within the above range, the hollow structure in the carbon material is maintained, and the carbon material is suitably used as a material for constituting a battery.

[0062] The apparent density of a carbon material can be calculated from the total pore volume and true density using the following formula (1): The total pore volume (cc / g) is the value calculated using P / P0 = 0.99, and the true density is the value of graphite, 2.2 g / cc.

[0063] Apparent density (g / cc)=1 / (total pore volume+(1 / true density)) Equation (1)

[0064] The bulk density of the carbon material is preferably 0.01 g / L or more and 1000.00 g / L or less, with 0.10 g / L or more and 100.00 g / L or less, 0.50 g / L or more and 50.00 g / L or less, and 1.00 g / L or more and 25.00 g / L or less being more preferred in this order. When the bulk density of the carbon material is within the above range, the conductivity of the carbon material is further increased and the electrolyte solution easily penetrates the carbon material. Note that bulk density is the mass per unit volume of a carbon material filled in a container of a certain volume under certain conditions. Bulk density can be measured according to JIS K6219-2.

[0065] The number density of the carbon material is a value calculated by the method described below, and is preferably 5×10 １４ pieces / g or more 1×10 ２０ particles / g or less, and １６ pieces / g or more 1×10 １９ pieces / g or less, 5×10 １６ pieces / g or more 5×10 １８ pieces / g or less, 1×10 １７ pieces / g or more 1×10 １８ pieces / g or less, 3×10 １７ pieces / g or more 7×10 １７When the number density of the carbon material is within the above range, the oil absorption of the carbon material is further improved.

[0066] The number density P (particles / g) of a carbon material is expressed as the volume V (m ３ ) and carbon density ρ (g / m ３ ), it can be calculated from the following formula (2). Here, the carbon density ρ is the true density of graphite, 2.2 g / cc. ３ ) can be calculated from the following formula (3).

[0067] Number density P = 1 / (V × ρ) Equation (2)

[0068] Volume V = π × (D １ -D ０ ) ３ / 6 Formula (3)

[0069] Here, D ０ is the inner diameter of the primary particle, and D １ is the outer diameter of the primary particle. ０ The above-mentioned mode pore diameter can be used. １ is D ０ The modal pore diameter can be calculated by multiplying the average number of layers n by the interplanar spacing d002 of the (002) plane and adding the doubled value to the modal pore diameter. １ may be determined by TEM image analysis or the like. Although it is not a carbon material of the embodiment, for example, the known DENKA BLACK Li-100 has a particle outer diameter (D １ ) with an average particle size of 35 nm, D ０ = 0, and the calculation can be performed.

[0070] The carbon content of the carbon material can be determined by temperature programmed desorption mass spectrometry (TPD-MS) measurement shown in FIG. 8, which will be described later, and is preferably 95.0% or more, more preferably 97.0% or more, 98.0% or more, 99.0% or more, and 99.3% or more in that order.

[0071] The oxygen content of the carbon material was measured by thermal desorption mass spectrometry. ２ O release, CO release and CO ２The oxygen content of the carbon material is preferably 5.0% or less, calculated from the amount of released oxygen, and more preferably 3.0% or less, 2.0% or less, 1.0% or less, and 0.6% or less, in that order. When the oxygen content of the carbon material is within the above range, the stability of the lithium ion battery is further improved, which can further contribute to improving the performance of the lithium ion battery.

[0072] To improve the performance and extend the life of lithium-ion batteries, highly efficient battery reactions are required without any loss of efficiency due to side reactions, and the carbon materials in the electrodes must have electrochemical stability, i.e., oxidation resistance and corrosion resistance. Side reactions such as electrochemical oxidation are believed to originate from oxygen-containing functional groups and edge faces of carbon materials. To improve the oxidation resistance of carbon materials, it is effective to reduce the number of oxygen-containing functional groups and edge faces, which have low oxidation resistance.

[0073] Thermal desorption mass spectrometry, which measures the oxygen content of carbon materials, is a method for measuring the amount of H released from carbon materials. ２ Amount, H ２ Amount of O, amount of CO and CO ２ The amount of oxygen-containing gases measured is derived from oxygen-containing functional groups such as hydroxyl groups (including phenol groups), carbonyl groups (including quinones), ethers, acid anhydrides, carboxyl groups, and lactones at the edge terminals of the carbon material. Therefore, a high amount of oxygen-containing functional groups in a carbon material means a high amount of oxygen-containing functional groups and edges present in the structure of the carbon material. The amount of oxygen-containing functional groups and edges in a carbon material can be adjusted by the CVD conditions and heat treatment temperature, which will be described later.

[0074] The ratio of oxygen content to carbon content (O / C) of the carbon material is preferably 1.00 or less, and more preferably 0.50 or less, 0.10 or less, 0.05 or less, and 0.01 or less in that order. When the ratio (O / C) of the carbon material is within the above range, it can further contribute to extending the life and improving the performance of the lithium ion battery.

[0075] The gas amount of the carbon material measured by thermal desorption mass spectrometry is preferably 5000 μmol / g or less, and more preferably 3000 μmol / g or less, 1000 μmol / g or less, 750 μmol / g or less, and 500 μmol / g or less, in that order. When the gas amount of the carbon material is within the above range, it can further contribute to extending the life and improving the performance of the lithium ion battery.

[0076] The edge amount of the carbon material is a value calculated from the gas amount measured by thermal desorption mass spectrometry, and is preferably 500 m ２ / g or less, and ２ / g or less, 100m ２ / g or less, 50m ２ / g or less, 30m ２ / g or less is more preferable. The edge amount of the carbon material is 750 μmol / g or less, and 500 μmol / g or less is more preferable, in this order. When the edge amount of the carbon material is within the above range, durability is further improved, which can further contribute to the stability and high performance of the lithium ion battery.

[0077] The ash content of the carbon material is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, 4,000 ppm or less, 3,500 ppm or less, and 3,000 ppm or less, in that order. When the ash content of the carbon material is within the above range, the stability of the electrolyte is further improved, and the durability and performance of the lithium ion battery can be further improved.

[0078] The pH of the carbon material is preferably 5.0 or more and 10.0 or less, more preferably 5.5 or more and 9.5 or less, 6.0 or more and 9.0 or less, 6.5 or more and 8.5 or less, and 7.0 or more and 8.0 or less. When the pH of the carbon material is within the above range, the stability is further improved.

[0079] The combustion temperature of the carbon material is preferably 300° C. or higher, and more preferably 400° C. or higher, 450° C. or higher, 500° C. or higher, 550° C. or higher, and 600° C. or higher in that order. The combustion temperature test of the carbon material is carried out as a simple test of corrosion resistance, and when the combustion temperature of the carbon material is 300° C. or higher, the electrochemical stability in the electrode is good.

[0080] Furthermore, carbon materials have excellent electron transport properties due to the inclusion of graphene. Therefore, when incorporated into an electrode of a lithium-ion battery, the carbon material can function to assist the battery reaction in the lithium-ion battery. Furthermore, the carbon material has a connected structure in which a plurality of hollow particulate portions, each having a surrounding wall with a plurality of pores, are connected in a beaded pattern. The connected structure has internal spaces within the hollow particulate portions, allowing for the penetration and retention of an electrolyte solution containing dissolved lithium ions, resulting in excellent ion supply during the reaction. Therefore, the carbon material is suitable as a material for secondary batteries because it can favorably assist the secondary battery reaction.

[0081] Such a carbon material has a graphene crystal structure, the graphene layers are controlled to a predetermined stacking state, and has a high oil absorption capacity, and therefore is suitable for use in dispersions, electrode compositions, electrode slurries, electrodes, and lithium-ion batteries. Furthermore, due to its physical properties, the carbon material of the present invention can be used in new technologies in addition to conventional electrolyte systems and electrode systems.

[0082] Furthermore, carbon materials can be effectively utilized in any electrochemical device, in addition to lithium-ion batteries, by exhibiting their functionality. Specifically, carbon materials have functions such as a function as an intra-electrode conduction 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 third material (such as a catalyst) and a reaction material by utilizing the durability of the graphene crystal structure when the reaction material is in an oxidized or reduced state.

[0083] Suitable usable devices include non-aqueous electrolyte batteries such as lithium ion batteries, sodium ion batteries, potassium ion batteries, magnesium ion batteries, calcium ion batteries, aluminum ion batteries, lithium-sulfur batteries, and lithium-air batteries; inorganic solid electrolyte batteries such as sulfide-based solid electrolytes and oxide-based solid electrolytes; polymer solid electrolyte batteries such as polyethylene oxide-based batteries; and semi-solid batteries typified by polymer gel electrolyte batteries containing an electrolyte such as PVDF.

[0084] 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 above embodiment can be suitably applied to any of the above active materials and can effectively increase conductivity. In addition, carbon materials are also suitable as materials for lithium-sulfur batteries such as those described in WO2018 / 225619, JP2023-501679A, JP2019-517116A, and JP2022-191280A.

[0085] Carbon materials can also be suitably used in organic electrolyte capacitors, aqueous electrolyte capacitors, and aqueous electrolyte batteries. In fuel cells, carbon materials can be used in PEFCs, SOFCs, DMPCs, etc., and can be used particularly to provide conductivity to electrodes and as supports for redox catalysts.

[0086] Furthermore, carbon materials can be suitably applied to batteries using gel polymer electrolytes or semi-solid electrolytes made of gel polymers or the like, which are produced by gelling a polymer with an organic solvent and containing Li salt as an electrolyte, dry electrode batteries that can shorten the battery manufacturing process, and clay electrode batteries that can realize thick electrodes.

[0087] Gel electrolyte batteries, which are semi-solid electrolyte batteries, have traditionally been mainly batteries in which the battery element is housed in a cylindrical or rectangular metal case, but gel electrolyte batteries using aluminum laminate film as the exterior material have been considered to reduce weight and thickness.Gel electrolyte batteries use polymers such as PVDF to swell the electrolyte solution and suppress vapor pressure, which makes it possible to prevent swelling of gel electrolyte batteries even with weak exterior materials.

[0088] In the case of clay (clay-like) electrode batteries, the production of electrodes in battery manufacturing generally requires several types of large-scale dedicated equipment, which can result in high capital investment in coating and drying equipment, as well as high costs for recovering the solvent from the electrode slurry. Furthermore, increasing battery capacity requires thick electrodes that increase the density of the electrode capacity. Clay-type electrodes are well-suited to achieving these goals. Instead of using the solvent (NMP) for the electrode slurry, an electrolyte solution is used, and the resulting mixed electrode composition is clay-like. This can be directly applied to a current collector and then used to assemble the battery, achieving both low manufacturing costs and high capacity.

[0089] For dry electrodes, in order to improve the efficiency of the electrode production process as described above, instead of using a liquid slurry as in the past, a powder of a dry positive electrode composition is prepared in advance by mixing an active material, a conductive agent, and a binder, and this is directly pressed to form a thin layer on a current collector, which is then pressed with a roll press or the like to form an electrode.

[0090] Carbon materials can also be used in applications other than electrochemical devices. Other suitable applications include electronic device applications such as graphene-based sensors, electromagnetic interference suppression materials, antenna modules, heat dissipation substrates, heat exchangers, separation membranes, reverse osmosis membranes, transparent electrode materials, structural material applications utilizing mechanical flexibility, conductive inks, pastes, and the like. Furthermore, as there is a demand for lighter vehicle bodies, which directly contributes to reducing carbon dioxide emissions and energy conservation, carbon materials are also suitable for use in applications that lead to weight reduction by utilizing the hollow shape of connecting structures, such as reinforcing agents for various rubbers, including tires, paints, coloring pigments, conductive fillers for various polymers, and additives for magnetic recording media.

[0091] (Method for Producing Carbon Material) Next, a method for producing a carbon material according to an embodiment will be described.

[0092] The method for producing a carbon material according to the embodiment includes a removal step of obtaining a carbon material by removing a template material from a carbon material precursor, the template material being an aggregate of a plurality of primary particles linked together in a beaded shape, the surface of which is coated with a carbonaceous layer.

[0093] As described above, the method for producing a carbon material according to the embodiment includes a removal step, and can produce the carbon material according to the embodiment.

[0094] In the removal step, the template material in the carbon material precursor, which has a carbonaceous layer covering the surface of the template material, is removed, thereby obtaining a carbon material.

[0095] The carbonaceous layer covers the entire surface of the template material. The template material removed in the removal step is an aggregate of multiple primary particles that are linked together like beads. The primary particles that make up the aggregate are preferably nano primary particles having a size on the order of nanometers. The aggregate has an elongated shape.

[0096] Furthermore, the template material preferably has a branched portion where the aggregate is branched. When the template material has a branched portion, the resulting carbon material also has a branched portion. Furthermore, the template material preferably has an aggregate having one or more ring-shaped portions. When the template material has a ring-shaped portion, the resulting carbon material also has a ring-shaped portion. For example, one end and the other end of the aggregate may be connected to form a ring-shaped portion, or the tips of branches extending from the branched portion may be connected to form a ring-shaped portion, or a link-shaped portion may be formed in a portion of the aggregate other than the end portion.

[0097] The particle size of the primary particles constituting the template material is 1 nm or more and 150 nm or less, preferably 5 nm or more and 100 nm or less, more preferably 10 nm or more and 60 nm or less, even more preferably 15 nm or more and 50 nm or less, and particularly preferably 20 nm or more and 40 nm or less. When the particle size of the primary particles is within the above range, the oil absorption capacity and mesopore volume of the resulting carbon material can be further increased. Furthermore, the template material is easy to handle. Furthermore, the permeability of the raw material gas, which serves as the carbon source for the carbonaceous layer formed on the surface of the template material, is improved, making it easier to uniformly coat the surface of the template material with the carbonaceous layer.

[0098] The BET specific surface area of ​​the mold material is preferably 1 m ２ / g or more 1000m ２ / g or less, more preferably 10m ２ / g or more 500m ２ / g or less, more preferably 20m２ / g or more 200m ２ / g or less, particularly preferably 40m ２ / g or more 160m ２ / g or less, most preferably 50m ２ / g or more 120m ２ When the BET specific surface area of ​​the template material is within the above range, the oil absorption capacity and mesopore volume of the resulting carbon material can be further increased.

[0099] The specific surface area of ​​the resulting carbon material depends on the specific surface area of ​​the template material. The smaller the particle diameter, the greater the ratio of particle volume to surface area. Therefore, the smaller the particle diameter, the greater the surface area per volume, i.e., the surface area per unit mass. Therefore, by using aggregates of nanoparticles with small primary particle diameters, carbon materials with a high specific surface area can be obtained.

[0100] The average particle size of the primary particles constituting the template material is preferably 1 nm to 100 nm, with 2 nm to 50 nm, 4 nm to 50 nm, and 3 nm to 30 nm being more preferred. The length of the aggregates is preferably 0.01 μm to 100.00 μm, more preferably 0.05 μm to 10.00 μm, and even more preferably 0.10 μm to 5.00 μm. The average particle size of the aggregates is preferably 0.05 μm to 10.00 μm, more preferably 0.10 μm to 5.00 μm.

[0101] The bulk density of the template material is preferably 0.1 g / L to 500.0 g / L, more preferably 0.5 g / L to 250.0 g / L, even more preferably 1.0 g / L to 200.0 g / L, particularly preferably 10.0 g / L to 100.0 g / L, and most preferably 30.0 g / L to 70.0 g / L. When the bulk density of the template material is within the above range, the electrical conductivity of the resulting carbon material can be further increased, and the oil absorption and mesopore volume can be further increased.

[0102] Furthermore, the template material is preferably basic or acidic. Suitable basic template materials include magnesium oxide and calcium carbonate. Suitable acidic template materials include aluminum oxide and silanol-containing silica compounds. The acidic pH, as measured in 4% water, is 7.0 or less, preferably 6.5 or less, more preferably 6.0 or less, even more preferably 5.5 or less, and particularly preferably 5.0 or less. The acidic pH is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 3.0 or more, particularly preferably 3.5 or more, and most preferably 4.0 or more.

[0103] The carbon content of the mold material is preferably 0.0001 wt% or more, more preferably 0.0100 wt% or more, even more preferably 0.0500 wt% or more, particularly preferably 0.100 wt% or more, and most preferably 0.500 wt% or more. The upper limit of the carbon content of the mold material is preferably 5.0000 wt% or less, more preferably 4.0000 wt% or less, even more preferably 3.0000 wt% or less, particularly preferably 2.5000 wt% or less, and most preferably 2.0000 wt% or less. When the carbon content of the mold material is within the above range, it is easy to form a carbonaceous layer on the mold surface.

[0104] The template material is preferably a compound that has catalytic activity for the carbon deposition reaction, and such compounds are preferably non-metallic compounds, metalloid (semi-metallic) compounds, or metallic compounds, more preferably metalloid compounds or metallic compounds.

[0105] The non-metallic compound is preferably a ceramic compound (non-metallic inorganic solid material), and the ceramic is preferably glass, cement, or fine ceramics.

[0106] The metalloid compounds are preferably boron compounds, silicon compounds, germanium compounds, and antimony compounds, more preferably silicon compounds.The silicon compounds are preferably silicon monoxide, silicon dioxide, silicon nitride, silicon carbide, and silicon, more preferably silicon dioxide.

[0107] The metal compounds are preferably monovalent metal compounds or polyvalent metal compounds, more preferably polyvalent metal compounds. Suitable monovalent metal compounds include chlorides, sulfates, nitrates, phosphates, and carbonates of alkali metals such as sodium and potassium. Suitable polyvalent metal compounds include alkaline earth metal compounds such as calcium and magnesium, and trivalent metal compounds such as aluminum, more preferably calcium compounds, magnesium compounds, and aluminum compounds. Preferred calcium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, more preferably carbonates and oxides, and even more preferably oxides. Preferred magnesium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, more preferably carbonates and oxides, and even more preferably oxides. Preferred aluminum compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, more preferably carbonates and oxides, and even more preferably oxides.

[0108] In addition, the fumed compound can be suitably used as a template material because it forms an aggregate in which a plurality of primary nanoparticles have a plurality of branched structures and are strung together like beads. As the fumed compound, a compound obtained by flame hydrolysis, which is one of the dry production methods for inorganic materials, is preferred.

[0109] As the fumed compound, fumed silicon dioxide is suitable. Fumed silicon dioxide produced by flame hydrolysis does not undergo a liquid phase process during production, and therefore agglomeration is gentle. For this reason, fumed silicon dioxide has excellent dispersibility in the liquid phase or compound (solid phase). Fumed silicon dioxide is produced by high-temperature gas phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame, accompanied by hydrochloric acid as a by-product. By changing 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 particle size of 7 nm to 40 nm and a specific surface area of ​​50 m ２ / g or more 380m ２ / g or less of silicon dioxide particles are obtained.

[0110] As the fumed compound produced by the flame hydrolysis method, in addition to fumed silicon dioxide, fumed alumina, fumed titania, and fumed wet zirconia are preferred. Other fumed metal compounds are preferred, such as chlorides of Na, Ba, or Sr, sulfates of K, Na, Sr, or Mg, nitrates of Na or K, phosphates of Na or K, carbonates of Na, K, Ca, or Mg, and metal oxides of Na, K, Ca, or Ba. The mold material is preferably in the form of a fumed form.

[0111] Precipitated silica can also be used as the template material. Precipitated silica can be obtained by reacting a sodium silicate solution with an acid in the liquid phase, followed by precipitation, filtration, washing, drying, and pulverization. By adjusting the reaction conditions, it is possible to obtain silica with an average particle size of 7 nm to 140 nm and a specific surface area of ​​about 20. ２ / g or more 400m ２ / g or less of silicon dioxide particles are obtained.

[0112] The water content of the mold material is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less.

[0113] When using CVD as a means for forming a carbonaceous layer on the surface of a mold material, the amount of carbon deposited on the surface of the mold material is affected by CVD reaction conditions such as the source gas type, source gas concentration, flow rate, reaction temperature, and reaction time, as well as the surface of the mold material, and is particularly affected by the surface of the mold material. Template materials with surfaces suitable for carbon deposition by CVD are compounds containing oxygen atoms (oxygen-containing compounds). In the CVD reaction, carbon from the source gas is replaced by oxygen atoms from the oxygen-containing compound, which then become the starting point for carbon deposition. Preferred oxygen-containing compounds are metal oxides and metal carbonates, and more preferably acidic or basic compounds. Preferred basic oxygen-containing compounds are magnesium oxide and calcium carbonate.

[0114] Furthermore, a template material suitable for forming a carbonaceous layer by a CVD method preferably has a surface that contains a hydrocarbon serving as a carbon source. The hydrocarbon is a compound that can be used as a source gas, and is preferably a compound having a methyl group or a carbon-carbon unsaturated bond. A suitable template material is an inorganic compound that has a hydrocarbon on its surface.

[0115] In addition, as the inorganic compound having hydrocarbon on its surface, preferably, the inorganic material that is surface-treated with silane coupling agent, more preferably, the silica compound that is surface-treated with silane coupling agent.As the silane coupling agent, the one that is usually used as a surface pretreatment agent can be used without any limitation, and preferably, methoxy type silane coupling agent, ethoxy type silane coupling agent, vinyl type silane coupling agent, dialkoxy type silane coupling agent, trialkoxy type silane coupling agent, more preferably, the trialkoxy type silane coupling agent that has many methyl groups per molecule, and more preferably, trimethoxysilane compound.

[0116] The amount of silane coupling agent is selected appropriately depending on the intended use, but is expressed as the amount of hydrocarbon in the inorganic material, and is preferably 0.01% by weight to 10.00% by weight, more preferably 0.02% by weight to 8.00% by weight, even more preferably 0.05% by weight to 5.00% by weight, particularly preferably 0.10% by weight to 3.00% by weight, and most preferably 0.50% by weight to 1.50% by weight. When the amount of silane coupling agent (hydrocarbon amount) in the inorganic material is within the above range, the amount of carbonaceous layer formed on the surface of the template material can be easily adjusted.

[0117] The template material may be used alone or in combination of two or more.

[0118] In the removal step, the method for removing the template material may be any method that removes the template material and leaves the carbonaceous layer, and is preferably a dissolution method using an acid or alkali, more preferably a dissolution method using an acid.

[0119] The acid used to dissolve and remove the template material is selected appropriately depending on the type of template material, but is preferably hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, or hydrofluoric acid, and more preferably hydrochloric acid or hydrofluoric acid. The concentration of the acid used to dissolve and remove the template material is appropriately adjusted to a range that allows for dissolution and removal of the template material. The amount of acid used is not particularly limited as long as it is within a range that allows for dissolution and removal of the template material, but is, for example, 30 times or more the stoichiometric ratio or 50 times or more the stoichiometric ratio relative to the template material.

[0120] The temperature for dissolving and removing the template material is preferably 5° C. or higher and 100° C. or lower, more preferably 10° C. or higher and 50° C. or lower, and even more preferably 20° C. or higher and 30° C. or lower. The removal step may be performed while stirring, vibrating, or other operations are added. The time required for the removal step is appropriately selected within a range that allows the template material to be removed.

[0121] The carbonaceous layer after removing the template material can be recovered, for example, by filtration, and then washed with pure water. The washing conditions can be selected appropriately, and the washing is completed after confirming that the pH of the washing solution used for the carbonaceous layer is neutral.

[0122] The carbonaceous layer after washing can be dried by vacuum heat drying, etc. The conditions for vacuum heat drying are not particularly limited, but it is preferable that the vacuum heat drying temperature is 100° C. or higher and 200° C. or lower, and the vacuum heat drying time is 1 hour or higher and 10 hours or lower.

[0123] Preferably, the method for producing a carbon material further comprises a heating step of heating the carbon material at 1000° C. or higher and 3000° C. or lower after the removing step.

[0124] In the heating step performed after the removing step, the carbon material obtained in the removing step is heated at a heating temperature of 1000°C or higher and 3000°C or lower, preferably 1300°C or higher and 2500°C or lower, more preferably 1500°C or higher and 2000°C or lower, even more preferably 1600°C or higher and 1900°C or lower, and particularly preferably 1750°C or higher and 1850°C or lower.

[0125] The heating time (retention time at a predetermined heating temperature) in the heating step is preferably 0.1 to 10.0 hours, more preferably 0.2 to 5.0 hours, and even more preferably 0.5 to 5.0 hours. The atmospheric pressure in the heating step is preferably atmospheric pressure or reduced pressure.

[0126] Furthermore, by carrying out a heating step, functional groups (mainly oxygen-containing functional groups) bonded to the carbon constituting the carbon material and carbon chains that do not form six-membered rings are detached from the carbon material at temperatures above 1000°C, forming dangling bonds. When the formed dangling bonds bond with other nearby carbon, 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 preferably 1500°C or higher, more preferably 1600°C or higher, the carbon material can have functions such as further improved electronic conductivity and maintenance of internal space.

[0127] Furthermore, by performing the heating step, structural defects in the graphene and other portions constituting the surrounding wall of the carbon material can be adjusted. These structural defects include spaces formed in the interconnected structure of the carbon material due to elution of the template material and infiltration holes formed in the surrounding wall of the carbon material. By adjusting the heating step conditions, such as the heating temperature and heating time, the extent of these structural defects can be controlled; that is, the size of the spaces present inside the carbon material and the size of the infiltration holes that allow the electrolyte to penetrate into the carbon material can be adjusted.

[0128] (Carbon Material Precursor) Next, a carbon material precursor according to an embodiment will be described.

[0129] The carbon material precursor of the embodiment includes a template material composed of an aggregate of a plurality of primary particles that are aggregated and linked together like beads, and a carbonaceous layer that covers the surface of the template material and has a plurality of pores.

[0130] The carbon material precursor of the embodiment includes a template material and a carbonaceous layer covering the surface of the template material. The carbon material precursor is the carbon material precursor used in the removal step in the method for producing a carbon material of the embodiment.

[0131] The template material of the carbon material precursor is an aggregate in which a plurality of primary particles are aggregated and linked together like beads, and preferably has the same configuration as the template material constituting the carbon material precursor used in the method for producing a carbon material of the above embodiment.

[0132] The carbonaceous layer formed on the surface of the template material has a plurality of pores, preferably covers the entire surface of the template material, and preferably has a graphene crystal structure.

[0133] (Method for Producing Carbon Material Precursor) Next, a method for producing a carbon material precursor according to an embodiment will be described.

[0134] The method for producing a carbon material precursor according to the embodiment includes a coating step of obtaining a carbon material precursor by coating the surface of a template material, which is an aggregate of a plurality of primary particles that are linked together like beads, with a carbonaceous layer.

[0135] As described above, the method for producing a carbon material precursor according to the embodiment includes a coating step, and can produce the carbon material precursor according to the embodiment.

[0136] In the coating step, the surface of the template material is coated with a carbonaceous layer to obtain a carbon material precursor. The template material is an aggregate of multiple primary particles that are linked together in a beaded pattern, and preferably has the same structure as the template material that constitutes the carbon material precursor of the above embodiment.

[0137] A carbonaceous 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 then subjecting the mold material to a carbonization heat treatment. The contact with the carbon source and the carbonization heat treatment can be performed simultaneously or separately. The contact between the mold material and the carbon source is preferably performed at a temperature of from room temperature (25°C) to 1000°C.

[0138] The number of carbonaceous layers is appropriately selected depending on the intended use, and is preferably 1.0 layer or more, more preferably 1.2 layers or more, even more preferably 1.5 layers or more, particularly preferably 2.0 layers or more, and most preferably 2.2 layers or more. The upper limit of the number of carbonaceous layers is preferably 15.0 layers or less, more preferably 10.0 layers or less, even more preferably 8.0 layers or less, particularly preferably 6.0 layers or less, and most preferably 5.0 layers or less. When the number of carbonaceous layers is within the above range, the strength characteristics and elastic deformation of the carbon material obtained by heating the carbonaceous layer are excellent, and the hollow structure of the hollow particulate portions in the carbon material can be well maintained, thereby highly improving the performance of lithium-ion batteries. The number of carbonaceous layers is determined by forming a carbonaceous layer on the surface of a template material, calculating the weight of the carbonaceous layer using thermogravimetric analysis (TG), calculating the weight of the carbonaceous layer per area of ​​the template material from the weight of the carbonaceous layer and the surface area of ​​the template material, and then multiplying this value by the weight per area of ​​single-layer graphene (7.61 × 10 －４ g / m ２ ) is the value calculated by dividing

[0139] Methods for contacting a carbon source with a template material are roughly divided into liquid-phase contacting and gas-phase contacting, with the gas-phase contacting being preferred. The liquid-phase contacting method is, for example, a method in which the template material is immersed in an organic liquid. The gas-phase contacting method is, for example, a method in which an organic vapor is introduced at high temperature and brought into contact with the template material, which is a so-called CVD method.

[0140] In the liquid-phase contact method, organic compounds having functional groups reactive with functional groups present on the surface of the template material, specifically hydroxyl groups, are preferred, particularly benzene-based hydrocarbon compounds having functional groups reactive with hydroxyl groups. Among these, benzene-based aromatic hydrocarbon compounds having at least one of hydroxyl and carboxyl groups are preferred, with phenol, hydronaphthalene, and dihydronaphthalene being more preferred. When using an organic compound having functional groups reactive with functional groups present on the surface of the template material, strong bonds such as ester bonds are formed between the template material and the organic compound, allowing the organic compound to be easily carbonized in situ without volatilizing during the carbonization heat treatment.

[0141] In the liquid-phase contact method, an organic compound serving as a carbon source is dissolved in a solvent and the template material is immersed in the solution at room temperature, thereby bringing the template material into contact with the organic substance serving as the carbon source. To strongly bond the template material and the organic substance, the mixture is maintained at a temperature ranging from 250°C to 600°C for a certain period of time. This causes a dehydration condensation reaction, such as an esterification reaction, between the hydroxyl groups on the template material surface and the organic substance, resulting in bonding via bonds such as ester bonds, making it easier to obtain a carbonaceous layer with a graphene structure. The temperature is then lowered, and excess organic substance that has not reacted with the template material is washed away with a solvent or the like.

[0142] Thereafter, a heat treatment is performed to carbonize the organic compound as a carbon source that has been brought into contact with the template material. This heat treatment causes a dehydrogenation reaction or the like in the organic material, such as hydrocarbon, and further promotes the formation of a graphene structure in the carbonaceous layer. The heat treatment temperature is preferably 600°C or higher and 1500°C or lower, more preferably 750°C or higher and 1500°C or lower, and even more preferably 800°C or higher and 1000°C or lower. Note that the heat treatment may be performed at 1500°C or higher as long as the template material does not collapse or melt.

[0143] In the gas-phase contact method, an organic compound serving as a carbon source is brought into contact with a template material, and in order to strongly bond the carbon source and the template material, the CVD (Chemical Vapor Deposition) method is preferably carried out in a temperature range in which a dehydrogenation reaction can proceed, specifically, 400°C or higher and 1000°C or lower.

[0144] The organic compound used as a carbon source in the gas-phase contact method may be appropriately selected depending on the purpose of use, and hydrocarbons such as saturated hydrocarbons, unsaturated hydrocarbons having at least one of a double bond and a triple bond, alicyclic hydrocarbons, and aromatic hydrocarbons are preferably used. The saturated hydrocarbons may be either linear or branched, and methane, ethane, and propane are preferred. The unsaturated hydrocarbons may be either linear or branched, and ethylene, propylene, isoprene, and acetylene are preferred. The alicyclic hydrocarbons are cyclopropane and cyclohexane are preferred. The aromatic hydrocarbons are benzene and toluene are preferred. Among these hydrocarbons, methane, ethane, acetylene, ethylene, propylene, and benzene are preferred, and methane, propylene, and benzene are preferred from the viewpoint of precipitating highly crystalline carbon. Methane is particularly preferred from the viewpoint of its high thermal decomposition temperature and the ability to obtain highly crystalline carbon.

[0145] In addition to the above-mentioned substances, suitable organic compounds used in the gas phase contact method include alcohols such as methanol, ethanol, propanol, and butanol, and nitrogen-containing compounds such as acetonitrile and acrylonitrile.

[0146] The reaction temperature in the CVD reaction is appropriately selected depending on the type of template material, the decomposition temperature of the organic compound used as the carbon source, and the like, but is preferably 400°C or higher and 1000°C or lower, more preferably 600°C or higher and 950°C or lower, and even more preferably 800°C or higher and 900°C or lower.

[0147] The reaction time in the CVD reaction (CVD treatment time at a predetermined heating temperature) is appropriately selected depending on the type of template material and organic compound used as the carbon source, and the number of carbonaceous layers to be deposited, but is preferably 0.1 to 10.0 hours, more preferably 0.5 to 5.0 hours, and even more preferably 1.0 to 3.0 hours. Furthermore, the analytical methods disclosed herein can be used to analyze the product, and the time required for sufficient carbon deposition can be appropriately set based on the results.

[0148] Furthermore, the CVD reaction may be carried out under an inert gas atmosphere, if necessary. The inert gas is preferably nitrogen, helium, neon, or argon, more preferably argon. 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 gaseous organic compound in contact with the template material. The type, flow rate, and heating temperature of the carrier gas can be appropriately adjusted 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.

[0149] The number of carbonaceous layers formed on the template material can be appropriately selected depending on the CVD reaction time. To form a carbonaceous layer with a small number of layers, the flow rate of the carrier gas is preferably 0.05 m / min to 5.00 m / min, more preferably 0.10 m / min to 1.00 m / min, even more preferably 0.20 m / min to 0.80 m / min, and particularly preferably 0.32 m / min to 0.64 m / min. The amount of the organic compound introduced is preferably 1 vol% to 70 vol%, more preferably 5 vol% to 50 vol%, even more preferably 10 vol% to 40 vol%, and particularly preferably 15 vol% to 35 vol%, based on the total amount of the carrier gas and the organic compound.

[0150] Since the carbonization of the carbonaceous layer can also proceed by a CVD reaction, other carbonization treatments are not necessary, but may be performed.

[0151] (Dispersion) Next, the dispersion will be described.

[0152] The dispersion liquid is prepared by dispersing the above carbon material in a dispersion medium.

[0153] The dispersion medium is appropriately selected depending on the intended use of the dispersion liquid. For example, in order to maintain a good dispersion state of the carbon material in the solvent, an organic or inorganic dispersant (e.g., a monomolecular or plastic resin material) is suitable. When the dispersion liquid is used for manufacturing a lithium ion battery, a polar solvent is suitable. 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 is more preferred. N-methylpyrrolidone is suitable for dispersing the carbon material.

[0154] The ratio of the carbon material to the dispersion medium is appropriately selected depending on the purpose of use of the dispersion, but the ratio of the carbon material to 100 parts by weight of the dispersion medium is preferably 0.01 parts by weight or more and 50.00 parts by weight or less, more preferably 0.05 parts by weight or more and 10.00 parts by weight or less, even more preferably 0.10 parts by weight or more and 5.00 parts by weight or less, particularly preferably 0.15 parts by weight or more and 4.50 parts by weight or less, and most preferably 0.20 parts by weight or more and 4.00 parts by weight or less. When the ratio of the carbon material is 0.01 parts by weight or more, conductive paths are easily formed in the lithium ion battery, and when the ratio of the carbon material is 50.00 parts by weight or less, the fluidity of the dispersion is good.

[0155] Furthermore, since carbon materials with a high specific surface area tend to aggregate due to van der Waals interactions, the dispersion may further contain a dispersant to improve dispersibility. The dispersant may be attached to the carbon material in advance or may be added directly to the dispersion medium. The dispersant is appropriately selected depending on the intended use of the dispersion, and dispersants having acidic or basic groups can be used. Dispersants that are adsorbed onto the surface of the carbon material and disperse the carbon material by steric repulsion or electrostatic repulsion, or dispersants that reduce the interfacial tension between the carbon material and the solvent can be used.

[0156] A dispersant having an acidic group exhibits the effect of enhancing the dispersibility of the carbon material by having at least a portion of the dispersant adhere to the surface of the carbon material. The acidic group of the dispersant is preferably a phenolic hydroxy group. As a dispersant having a phenolic hydroxy group, phenol, nitrophenol, cresol, catechol, and compounds having a structure in which a portion of these groups is substituted are preferred.

[0157] Among these, compounds having a catechol group are preferred as dispersants because they have adhesive properties to carbon materials and dispersibility in dispersion media. Preferred dispersants having a catechol group include catechol, dopamine hydrochloride, 3-(3,4-dihydroxyphenyl)-L-alanine, 4-(1-hydroxy-2-aminoethyl)catechol, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol, and 4-tert-butylpyrocatechol.

[0158] As the dispersant having a basic group, a compound having an amino group is preferred because of its good dispersibility, and a compound having an aromatic ring and an amino group is more preferred.As such a compound, benzylamine and phenylethylamine are preferred.As the dispersant having a basic group other than the above, a compound having a basic group and a catechol group is also preferred, and dopamine hydrochloride is preferred.

[0159] In addition, surfactants having acidic or basic groups are also suitable as dispersants. Cationic surfactants, anionic surfactants, and nonionic surfactants can all be used as surfactants, but cationic surfactants and anionic surfactants themselves may be involved in electrochemical reactions. Therefore, when using a dispersion as a battery material, non-ionized nonionic surfactants are preferred.

[0160] Furthermore, as the dispersant for the polymer compound, one that can also be used as a binder for batteries can be used, and preferred examples thereof include polyvinylidene fluoride, vinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride modified with maleic acid, polyvinylpyrrolidone, polyvinyl alcohol, polymethyl vinyl ether, polyacrylonitrile, nitrile rubber, acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, poly(meth)acrylic acid and its esters, polyvinyl acetal, polyvinyl butyral, and cellulose ether.

[0161] These dispersants can be used alone or in combination of two or more, and the amount of dispersant contained in the dispersion may be appropriately selected depending on the purpose of use of the dispersion.

[0162] Furthermore, the dispersion may further contain, as necessary, other carbon materials in addition to the carbon materials of the above-described embodiments, such as at least one selected from the group consisting of carbon black, graphite, activated carbon, carbon nanotubes, carbon nanofibers, carbon fibers, and fullerenes.

[0163] Suitable carbon blacks include acetylene black, ketjen black, and furnace black, with acetylene black and ketjen black being preferred from the viewpoint of electrical conductivity. Graphite, also known as graphite or graphite, is a material made up of multiple layers of graphene. Suitable carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes (including cup-stacked multi-walled carbon nanotubes). Suitable carbon fibers include mesophase pitch-based carbon fibers, isotropic pitch-based carbon fibers, vapor-grown carbon fibers (VGCF), and milled carbon fibers obtained by calcining and then crushing polymer fibers.

[0164] The other carbon materials can be used alone or in combination of two or more. The amount of the other carbon materials used can be appropriately selected depending on the intended use of the dispersion, and can be selected, for example, within the same range as the carbon material. The ratio of the carbon material of the embodiment to the other carbon materials used can be selected depending on the intended use of the dispersion, and is preferably 10:90 to 90:10, 20:80 to 80:20, or 40:60 to 60:40 by weight ratio, in this order.

[0165] The solids concentration of the dispersion is appropriately selected depending on the intended use of the dispersion, and is preferably 0.01% by mass or more and 50.00% by mass or less, more preferably 0.05% by mass or more and 30.00% by mass or less, even more preferably 0.10% by mass or more and 20.00% by mass or less, particularly preferably 0.50% by mass or more and 10.00% by mass or less, and most preferably 1.00% by mass or more and 5.00% by mass or less. When the solids concentration of the dispersion is 50.00% by mass or less, stacking of the carbon material in the dispersion is less likely to occur, and a good dispersion state can be maintained. When the solids concentration of the dispersion is 0.01% by mass or more, when the dispersion is used to produce an electrode slurry, a decrease in the viscosity of the electrode paste can be suppressed, thereby improving coatability.

[0166] The solid content of the dispersion refers to the material remaining after the dispersion medium is dried and removed from the dispersion. The solid content of the dispersion can be calculated by measuring the weight of the dispersion after the dispersion medium is dried and removed from the dispersion, and dividing the measured value by the weight of the dispersion itself. Specifically, after weighing out about 1 g of the dispersion, the dispersion is applied to a glass substrate of known weight, and the glass substrate is heated on a hot plate adjusted to 120 ° C. for 1.5 hours to volatilize the dispersion medium, and the weight of the remaining material is measured.

[0167] The viscosity of the dispersion is appropriately selected depending on the purpose of use of the dispersion, and is determined by the solid content concentration of 3 mass %, the temperature of 23°C, and the shear rate of 1 s －１The viscosity of the dispersion under the conditions is preferably 20,000 cP or less, more preferably 15,000 cP or less, and even more preferably 10,000 cP or less. The lower limit of the viscosity of the dispersion is preferably 100 cP or more, more preferably 500 cP or more, even more preferably 1,000 cP or more, particularly preferably 2,000 cP or more, and most preferably 4,000 cP or more. ... more. －１ The viscosity of the dispersion liquid under the above conditions is preferably 30 cP or less. The viscosity of the dispersion liquid may be adjusted to a predetermined value by adding a surface treatment agent or the like.

[0168] Next, a method for producing the dispersion will be described.

[0169] The method for producing the dispersion is not particularly limited, and for example, the above carbon material and, if necessary, a dispersant and other carbon materials are mixed in a dispersion medium.

[0170] Since the above carbon materials have a relatively large BET specific surface area, in order to disperse them well in a dispersion liquid, it is effective to apply high shear force using a mixer with strong stirring power while the carbon material and dispersion medium are present. Suitable mixing devices that can apply high shear force include a planetary mixer, FILMICS (registered trademark) (Primix Corporation), a planetary ball mill, and a three-roll mill. Furthermore, in order to eliminate stacking of carbon materials, a strong stirring step may be performed using a high-shear mixer to stir the materials at a shear rate of 5,000 to 50,000 per second. The high shear mixer is preferably a thin film rotation type, rotor / stator type, or media mill type, and suitable examples include FILMICS (registered trademark) 30-30 type (Primix Corporation), CLEARMIX (registered trademark) CLM-0.8S (M Technique Co., Ltd.), LABOSTAR (registered trademark) Mini LMZ015 (Ashizawa Finetech Co., Ltd.), and SUPER SHEAR MIXER (registered trademark) SDRT0.35-0.75 (Satake Chemical Machinery Co., Ltd.).

[0171] (Electrode Composition) Next, the electrode composition will be described.

[0172] The electrode composition contains the above-mentioned carbon material, an active material, and a binder.

[0173] The active material contained in the electrode composition is preferably the active material used in the positive electrode, which will be described later, or the active material used in the negative electrode, which will be described later. The ratio of the active material to the carbon material is appropriately selected depending on the intended use of the electrode composition, and the ratio of the carbon material to 100 parts by weight of the active material is preferably 0.005 parts by weight or more and 20,000 parts by weight or less, more preferably 0.010 parts by weight or more and 10,000 parts by weight or less, even more preferably 0.050 parts by weight or more and 5,000 parts by weight or less, particularly preferably 0.100 parts by weight or more and 2,000 parts by weight or less, and most preferably 0.500 parts by weight or more and 1,000 parts by weight or less.

[0174] The binder contained in the electrode composition is preferably a binder used in a positive electrode or a binder used in a negative electrode. The amount of binder used is appropriately selected depending on the intended use of the electrode composition, and is preferably 0.05 parts by weight or more and 10.00 parts by weight or less, more preferably 0.10 parts by weight or more and 8.00 parts by weight or less, even more preferably 0.50 parts by weight or more and 6.00 parts by weight or less, particularly preferably 1.00 parts by weight or more and 5.00 parts by weight or less, and most preferably 2.00 parts by weight or more and 4.00 parts by weight or less, relative to 100 parts by weight of the active material.

[0175] In addition, the electrode composition may further contain other compounding agents as needed in addition to the above-mentioned carbon material, active material, and binder. The other compounding agents are not particularly limited as long as they are used in electrode compositions for lithium-ion batteries. The amount of the other compounding agents used is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, even more preferably 10 parts by weight or less, particularly preferably 5 parts by weight or less, and most preferably 2 parts by weight or less, per 100 parts by weight of the active material.

[0176] Next, a method for producing the electrode composition will be described.

[0177] The method for producing the electrode composition is not particularly limited, and for example, the above-mentioned carbon material, active material, binder, and, if necessary, other compounding agents are mixed. Suitable mixing methods include dry mixing and wet mixing using a dispersion medium.

[0178] (Slurry for Electrodes) Next, the slurry for electrodes will be described.

[0179] The electrode slurry is prepared by dispersing the electrode composition in a dispersion medium. The electrode slurry may also contain an electrolytic solution.

[0180] The dispersion medium may be any medium capable of dissolving or dispersing the binder, and is preferably the dispersion medium used in the positive electrode described below, the dispersion medium used in the negative electrode described below, or the dispersion medium used in the dispersion liquid of the above-described embodiment. The amount of the dispersion medium used may be adjusted so that the electrode slurry has a viscosity that allows it to be applied onto the current collector.

[0181] In the case where the electrode slurry is a clay-type electrode containing an electrolytic solution, the electrode slurry is preferably in the form of a clay with the above-mentioned electrode composition and electrolytic solution kneaded in. In this case, the electrode slurry does not need to contain a binder.

[0182] Next, a method for producing the electrode slurry will be described.

[0183] The method for producing the electrode slurry is not particularly limited, and for example, the electrode composition may be mixed in a dispersion medium, or the carbon material, binder, and dispersion medium may be mixed together and then the active material may be mixed in. The mixing of the carbon material, binder, and dispersion medium may include a method of mixing the dispersion liquid with the binder, or a method of mixing the dispersion liquid with a binder liquid in which the binder is dissolved or dispersed in the dispersion medium.

[0184] The mixing method is not particularly limited, and a known mixer or kneader can be used. As known mixers, an automatic mortar, a homogenizer, a planetary mixer, a homodisper, or a planetary mixer is preferred, and a planetary mixer is more preferred.

[0185] (Electrodes) Next, the electrodes will be described.

[0186] The electrode contains the carbon material. The electrode containing the carbon material may be either a negative electrode or a positive electrode, or both a negative electrode and a positive electrode. It can be obtained by applying the electrode slurry to a current collector to form a coating film, and then drying the coating film. The electrode containing the carbon material has excellent high-rate discharge properties, capacity characteristics, and charge / discharge characteristics, and is therefore suitable for use as an electrode, positive electrode, or negative electrode for a lithium-ion battery. From the viewpoint of exhibiting good battery characteristics, the electrode preferably contains 0.1 wt % to 6.0 wt % of the carbon material. The current collector is preferably a current collector used in a positive electrode, as described below, or a current collector used in a negative electrode, as described below.

[0187] The method for applying the electrode slurry to the current collector is not particularly limited, and known methods can be used. Among these, it is preferable to apply the electrode slurry using a manual or automatic coater, such as a baker-type 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. Among these, drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams is preferred. After drying, 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.

[0188] The positive electrode is obtained by applying a slurry containing a positive electrode active material, a conductive additive for enhancing electronic conductivity, a binder, and a dispersion medium to a current collector metal foil such as rolled aluminum foil to form a coating film, and then heating and drying the coating film to remove the solvent in the coating film, followed by forming the film into a desired size and density. The carbon material can be useful as a conductive additive. The slurry may also contain an electrolyte.

[0189] The positive electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, and specifically may include a lithium composite metal oxide containing lithium and at least one metal selected from the group consisting of cobalt, manganese, nickel, and aluminum.

[0190] Among these, the positive electrode active material is preferably a lithium-manganese oxide (preferably LiMnO ２ , LiMn ２ O ４ ), lithium-cobalt oxide (preferably LiCoO ２ ), lithium-nickel oxide (preferably LiNiO ２ ), lithium-nickel-manganese oxide (preferably LiNi １－ａ Mn ａ O ２ (0<a<1), LiMn ２－ｂ Ni ｂ O ４ (0<b<2)), lithium-nickel-cobalt oxide (preferably LiNi １－ｃ Co ｃ O ２ (0<c<1)), lithium-manganese-cobalt oxide (preferably LiCo １－ｄ Mn ｄ O ２ (0<d<1), LiMn ２－ｅ Co ｅ O ４ (0<e<2)), lithium-nickel-manganese-cobalt oxide (preferably Li(Ni ｆ Mn ｇ Co ｈ ) O ２ (0<f<1, 0<g<1, 0<h<1, f+g+h=1), Li(Ni ｊ Mn ｋ Co ｍ ) O ４ (0<j<2, 0<k<2, 0<m<2, j+k+m=2)), lithium-nickel-cobalt-transition metal (M) oxide (preferably Li(Ni ｐ Co ｑ Mn ｒ M Ｓ ) O ２ (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, 0≦p<1, 0≦q<1, 0≦r<1, 0≦s<1, p+q+r+s=1) is preferred, and compounds of any one or more of these may be included.

[0191] Among these, from the viewpoint of improving the capacity characteristics and stability of the battery, LiCoO ２ , LiMnO ２ , LiNiO ２ , lithium-nickel-manganese-cobalt oxide (preferably Li(Ni ０．６ Mn ０．２ Co ０．２ ) O ２ , Li(Ni ０．５ Mn ０．３ Co ０．２ ) O ２ , Li(Ni ０．８ Mn ０．１ Co ０．１ ) O ２ )), lithium-nickel-cobalt-aluminum oxide (preferably LiNi ０．８ Co ０．１５ Al ０．０５ O ２ ) is preferred.

[0192] Furthermore, as a highly stable positive electrode active material, a lithium atom-containing oxide (preferably an olivine-type lithium-containing phosphate compound) represented by the following formula (4) and having an olivine-type crystal structure is suitable.

[0193] LiM ｘ A １－ｘ O ４ Formula (4)

[0194] In the above formula (4), M is at least one metal element 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 element selected from the group consisting of Si, S, P, and V, and x is greater than 0 and less than 1. The value of x in formula (4) is selected depending on the valences of M and A so that the valence of the entire formula (4) is 0.

[0195] As the positive electrode active material, organic compounds such as polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds, and N-fluoropyridinium salts are suitable.

[0196] The physical properties of positive electrode active materials are determined by the requirements of the battery design and manufacturing process, which are based on constraints such as the type of use of lithium-ion batteries. In manufacturing positive electrode active materials, processes are designed to achieve the desired physical properties. Physical properties include powder particle size and distribution, specific surface area, and density.

[0197] As an example, the powder particle size is appropriately selected in consideration of other constituent requirements of the lithium ion battery, but from the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, the average particle size is preferably 1 μm or more and 30 μm or less, and more preferably 1 μm or more and 10 μm or less.

[0198] These positive electrode active materials can be used alone or in combination of two or more.

[0199] 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 above embodiment is suitable as the conductive additive for the positive electrode. When the conductive additive is the carbon material, the amount of the conductive additive (carbon material) used is appropriately selected depending on the intended use of the electrode, but is preferably 0.01 parts by weight or more and 4.00 parts by weight or less, more preferably 0.05 parts by weight or more and 3.00 parts by weight or less, even more preferably 0.10 parts by weight or more and 2.00 parts by weight or less, particularly preferably 0.20 parts by weight or more and 1.50 parts by weight or less, and most preferably 0.50 parts by weight or more and 1.50 parts by weight or less, relative to 100 parts by weight of the positive electrode active material.

[0200] The conductive additive can be a combination of the above carbon material and other conductive substances. Suitable 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 powder, 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.

[0201] The 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 of the electrode, and is selected appropriately within the same range of use as the carbon material. The ratio of the carbon material to the other conductive substances used is appropriately selected depending on the intended use of the electrode, and is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, even more preferably 30:70 to 70:30, and particularly preferably 40:60 to 60:40 by weight.

[0202] Furthermore, the above carbon materials can be combined with conventionally used conductive additives to achieve even greater effectiveness. For example, carbon blacks such as acetylene black are composed of linked particles with diameters of several tens of nanometers. However, the carbon crystallinity is not very high, the structure is short, and they are prone to collapse, making them difficult to transmit electrons over long distances. By combining carbon blacks with the above carbon materials, it is possible to realize a system that maintains electronic conductivity and also has ion supply capabilities, even when the three-dimensional structure is maintained or when the three-dimensional structure is crushed and flattened like flake graphite.

[0203] The positive electrode binder is a component that helps bond between the positive electrode active material, conductive additive, and current collector, and is usually an organic polymer. Suitable binders include fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride (PVDF), and polytetrafluoroethylene, CN group-containing polymers such as polyacrylonitrile and polyvinylidene cyanide, polyvinyl alcohol-based polymers such as polyvinyl acetate and polyvinyl alcohol, halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride, conductive polymers such as polyaniline, alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene, unsaturated polymers such as polybutadiene and polyisoprene, ring-containing polymers 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. The binder may also be a modified product or derivative of the above organic polymer.

[0204] Among these, the binder is preferably a fluorine-based resin, and particularly preferably polyvinylidene fluoride (PVDF). The weight-average molecular weight of the binder may be appropriately selected depending on the intended use of the electrode, and is preferably 10,000 to 8,000,000, more preferably 10,000 to 5,000,000, 50,000 to 3,000,000, 80,000 to 3,000,000, and 100,000 to 1,000,000. When the weight-average molecular weight of the binder is 10,000 or more, the strength of the coating film is improved, and when the weight-average molecular weight of the binder is 8,000,000 or less, the viscosity is reduced, making it easier to form the electrode.

[0205] The binders can be used alone or in combination of two or more. The amount of binder used is appropriately selected depending on the purpose of the electrode, and is preferably 0.01 to 4.00 parts by weight, more preferably 0.05 to 3.00 parts by weight, even more preferably 0.10 to 2.00 parts by weight, particularly preferably 0.20 to 1.50 parts by weight, and most preferably 0.50 to 1.50 parts by weight, relative to 100 parts by weight of the positive electrode active material. When the amount of binder used is within the above range, the adhesive strength between the positive electrode active materials and between the positive electrode active material and the conductive additive can be improved, and thus the bonding strength between these materials and the current collector can be improved.

[0206] The positive electrode forming slurry is a mixture of the above-mentioned positive electrode active material, conductive additive, and binder in a dispersion medium. The positive electrode forming slurry may also contain an electrolyte. This is called a clay-type electrode, and when the positive electrode forming slurry contains an electrolyte, the positive electrode forming slurry is preferably in the form of clay in which the above-mentioned positive electrode active material, conductive additive, and electrolyte are kneaded. In this case, the positive electrode forming slurry does not need to contain a binder.

[0207] The positive electrode-forming slurry may also contain other additives as needed. The additives are appropriately selected depending on the intended use of the electrode, and additives used in lithium-ion batteries can be used in amounts within the normal range of use.

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

[0209] When polyvinylidene fluoride is used as the binder, the dispersion medium is preferably dimethylformamide or N-methyl-2-pyrrolidone (NMP), and more preferably NMP.

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

[0211] The viscosity of the positive electrode-forming slurry is preferably 1,000 cP to 50,000 cP, more preferably 2,000 cP to 40,000 cP, even more preferably 5,000 cP to 35,000 cP, particularly preferably 10,000 cP to 35,000 cP, and most preferably 10,000 cP to 30,000 cP, under a temperature condition of 24° C. to 26° C. When the viscosity of the positive electrode-forming slurry is within the above range, the positive electrode-forming slurry can be applied to a uniform thickness while the solid content excluding the dispersion medium is uniformly dispersed.

[0212] The positive electrode can be produced by applying the positive electrode-forming slurry to a current collector and drying it as needed. The positive electrode current collector is not particularly limited as long as it is a commonly used one, but aluminum foil, nickel foil, titanium foil, and stainless steel foil are preferred, and rolled aluminum foil is more preferred.

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

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

[0215] After drying, the cathode is formed to a predetermined size, preferably using an industrially available cutting blade, and if necessary, preferably using an industrially available pressure device to achieve a predetermined density.

[0216] The negative electrode is obtained by applying a slurry containing a negative electrode active material, a conductive additive, a binder, and a dispersion medium to a current collector metal foil such as rolled copper foil to form a coating film, heating and drying the coating film to remove the solvent in the coating film, and then forming the coating film into a predetermined size and density. The slurry may contain an electrolyte solution.

[0217] As the negative electrode active material, one that can bond and stabilize Li ions with electrons flowing from an external circuit and has numerous stabilization sites within it is preferred. Materials of organic origin, whether high or low crystallinity, can be used, with graphite, coke, amorphous carbon, hard carbon, and polymer carbon being preferred. In this case, the principle is that Li ions are sandwiched between graphene layers and bond with electrons to stabilize them. Another stabilization mechanism is the electrochemical formation of intermetallic compounds, with silicon, tin, zinc, bismuth, antimony, cadmium, lead, and germanium being preferred. In addition, other materials that exhibit low electrochemical reaction potentials and serve as the negative electrode of lithium-ion batteries can also be used. Preferred examples include compounds of metals with oxygen, sulfur, halogens, nitrogen, phosphorus, and the like.

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

[0219] A metal lithium thin film is suitable as the negative electrode active material. The carbonaceous material may be either low-crystalline carbon or high-crystalline carbon. Low-crystalline carbon is preferably softened carbon or hardened carbon, while high-crystalline carbon is preferably amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microspheres, mesophase pitch, and high-temperature calcined carbon such as petroleum and coal-based coke.

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

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

[0222] These negative electrode active materials can be used alone or in combination of two or more. The proportion of the negative electrode active material in the negative electrode slurry is not particularly limited, but is preferably 95.5 parts by weight or more and 99.0 parts by weight or less, more preferably 96.0 parts by weight or more and 98.7 parts by weight or less, and even more preferably 97.0 parts by weight or more and 98.0 parts by weight or less, relative to 100 parts by weight of the solid content of the negative electrode slurry excluding the dispersion medium. When the proportion of the negative electrode active material is within the above range, the battery capacity, conductivity, and adhesiveness are well balanced.

[0223] The carbon material of the above embodiment may be used as a negative electrode active material and can be suitably used as a negative electrode conductive additive. For example, although the above negative electrode active materials generally have high electronic conductivity, some materials have smooth surfaces and insufficient particle-to-particle contact. In such cases, the above carbon material can be used as a conductive additive 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 a substance having such properties with the above carbon material, 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 application of the above carbon material can increase ionic conductivity while maintaining electronic conductivity.

[0224] When the conductive additive is the carbon material, the proportion of the conductive additive (carbon material) in the negative electrode slurry is preferably 0.8 parts by weight or more and 3.0 parts by weight or less, more preferably 1.0 parts by weight or more and 2.5 parts by weight or less, and even more preferably 1.0 parts by weight or more and 2.2 parts by weight or less, relative to 100 parts by weight of the solid content excluding the dispersion medium. When the content of the conductive additive is within the above range, the high-speed chargeability, life characteristics, capacity characteristics, and charge / discharge characteristics of the lithium ion battery can be further improved.

[0225] The conductive additive may be a combination of the above carbon materials with other carbon materials. The other carbon materials are not particularly limited as long as they are conventional materials used as electrode materials, and suitable examples include acetylene black, ketjen black, lamp black, furnace black, carbon black, graphite, carbon fiber, graphite fiber, nanofiber, nanotube, coke, hard carbon, and amorphous carbon.

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

[0227] Further benefits can be achieved by combining these conventional conductive additives with the carbon material of the above embodiment. For example, highly linear carbon nanotubes have high electronic conductivity but low ion storage capacity. Therefore, by combining them with the above carbon materials, it is possible to construct an excellent battery reaction assist system that combines electronic conductivity with ionic conductivity. Furthermore, while carbon blacks such as acetylene black are composed of linked particles with diameters of several tens of nanometers, they have low carbon crystallinity, a short structural length, and are prone to collapse, making them difficult to transport electrons over long distances. By combining carbon blacks with these properties with the above carbon materials, it is possible to realize a system that maintains its three-dimensional structure while also having ion supply capabilities.

[0228] The binder for the negative electrode is a component that aids in bonding between the negative electrode active material, the conductive additive, and the current collector, and is typically an organic polymer. Suitable binders 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 polyvinyl chloride and polyvinylidene chloride, conductive polymers such as polyaniline, alkane-based polymers such as polyethylene, polypropylene, and poly-1,1-dimethylethylene, unsaturated polymers such as polybutadiene and polyisoprene, ring-containing polymers such as polystyrene, polymethylstyrene, polyvinylpyridine, and poly-N-vinylpyrrolidone, acrylic polymers such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, methyl polyacrylate, ethyl polyacrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide, carboxymethyl cellulose, and styrene butadiene rubber. The binder may also be a modified product or derivative of the above organic polymer.

[0229] Among these, carboxymethyl cellulose and styrene butadiene rubber are preferred as the binder. The weight-average molecular weight of the binder may be appropriately selected depending on the intended use of the electrode, and is preferably 10,000 to 8,000,000, more preferably 10,000 to 5,000,000, 50,000 to 5,000,000, 80,000 to 3,000,000, and 100,000 to 1,000,000. When the weight-average molecular weight of the binder is 10,000 or more, the strength of the coating film is improved, and when the weight-average molecular weight of the binder is 8,000,000 or less, the viscosity is reduced, making it easier to form the electrode.

[0230] The amount of binder used is preferably 0.01 to 4.00 parts by weight, more preferably 0.05 to 3.00 parts by weight, even more preferably 0.10 to 2.00 parts by weight, particularly preferably 0.20 to 1.50 parts by weight, and most preferably 0.50 to 1.50 parts by weight, relative to 100 parts by weight of the negative electrode active material. When the amount of binder used is within the above range, the adhesive strength between the negative electrode active materials and between the negative electrode active material and the conductive additive can be improved, and thus the bonding strength between these materials and the current collector can be improved.

[0231] The proportion of the binder in the negative electrode-forming slurry is preferably 0.8 parts by weight or more and 3.0 parts by weight or less, more preferably 1.0 parts by weight or more and 2.5 parts by weight or less, and even more preferably 1.0 parts by weight or more and 2.2 parts by weight or less, relative to 100 parts by weight of the solid content excluding the dispersion medium. When the binder content in the negative electrode-forming slurry is within the above range, the adhesive strength between the negative electrode active materials and between the negative electrode active material and the conductive additive can be improved, and therefore the bonding strength between these materials and the current collector can be improved.

[0232] The negative electrode-forming slurry is a mixture of the above-mentioned negative electrode active material, conductive additive, and binder in a dispersion medium. The negative electrode-forming slurry may also contain an electrolyte. This is called a clay-type electrode, and when the negative electrode-forming slurry contains an electrolyte, the negative electrode-forming slurry is preferably in the form of a clay mixture containing the above-mentioned negative electrode active material, conductive additive, and electrolyte. In this case, the negative electrode-forming slurry does not necessarily contain a binder.

[0233] The dispersion medium for the slurry is not particularly limited as long as it is a solvent commonly used in the technical field, and organic solvents such as N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, and water are suitable, and one of these can be used alone or two or more can be used in combination. The dispersion medium is used to dissolve or disperse the negative electrode active material, conductive additive, and binder, taking into consideration the coating thickness of the negative electrode-forming slurry and the production yield.

[0234] The amount of the dispersion medium used is not particularly limited, but is adjusted so that the concentration of the solids in the negative electrode-forming slurry, including the negative electrode active material, the conductive additive, and the binder, is preferably 10% by weight or more and 90% by weight or less, more preferably 20% by weight or more and 80% by weight or less, even more preferably 30% by weight or more and 75% by weight or less, particularly preferably 40% by weight or more and 70% by weight or less, and most preferably 50% by weight or more and 65% by weight or less.

[0235] The current collector for the negative electrode is not particularly limited, but may be, for example, a material that does not have electrochemical reactivity to the potential generated by the negative electrode. Suitable current collectors include copper foil, nickel foil, titanium foil, and stainless steel foil, and electrolytic copper foil and rolled copper foil are more preferred.

[0236] The negative electrode-forming slurry can be applied to the current collector by a commonly used printing technique. When the thickness of the coating film is small, gravure printing is suitable, and when the thickness of the coating film is large, printing techniques such as doctor blade printing and die printing are suitable.

[0237] Thereafter, the coating film is dried by heating as necessary. Any drying method can be used, and a method that can achieve the desired binding strength by the binder is preferred.

[0238] After drying, the negative electrode is formed to a predetermined size, preferably using an industrially available cutting blade, and if necessary, preferably using an industrially available pressure device to achieve a predetermined density.

[0239] In addition, instead of using a liquid electrode slurry using a volatile solvent (N-methylpyrrolidone, water, etc.) as in the past, a dry electrode is formed by spreading a mixed dry composition of an active material, a conductive agent, and a binder on a current collector in advance and then pressurizing and molding it using a roll press or the like.

[0240] Advantages include the elimination of environmental pollution caused by volatile solvents during drying, the elimination of electrical energy used for drying, and the elimination of capital investments related to these.

[0241] Specifically, the dry electrode is manufactured by the following method.

[0242] The mixed dry composition preferably uses a microsphere emulsion of fluororesin as a binder, and the micro- to nano-scale fibril fibers generated during the mixing process favorably hold the active material and conductive agent. A thin layer is formed by spraying or atomizing precursor powder obtained by pulverizing and classifying the bulk mixed dry composition onto an aluminum current collector, which is thinly coated with an anchor layer made of a mixture of carbon and resin as needed. The resulting layer is then placed in a hot roll press or similar and pressed to obtain a thin-film electrode.

[0243] The precursor powder has a particle size of several tens of microns, and unlike conventional liquid slurries, it does not undergo migration that occurs when the solvent evaporates, making it suitable for producing thick electrodes.

[0244] In addition to the positive electrode, dry electrodes can also be produced for the negative electrode. Using a conventional separator, batteries can be produced in cylindrical, square, or pouch shapes, and liquid or semi-solid electrolytes (gel electrolytes) can be used as the electrolyte.

[0245] (Lithium-ion battery) Next, the lithium-ion battery will be described.

[0246] The lithium-ion battery includes the carbon material described above. Specifically, the lithium-ion battery has a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte, where at least one of the positive and negative electrodes, preferably both, is the electrode (positive electrode, negative electrode) described in the above embodiment. The electrolyte is preferably a liquid electrolyte or a semi-solid electrolyte because the carbon material can retain the electrolyte solution therein. In this case, at least one of the positive and negative electrodes is preferably a dry electrode. The lithium-ion battery also preferably includes a clay-type positive electrode containing the carbon material described above and a clay-type negative electrode containing the carbon material described above. The lithium-ion battery may further include a battery container that houses an electrode assembly consisting of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container. Note that the positive and negative electrodes of the lithium-ion battery are substantially the same as the positive and negative electrodes described above, and therefore detailed description thereof will be omitted.

[0247] The separator of a lithium ion battery separates the negative electrode and the positive electrode and provides a path for the movement of lithium ions. There are no particular limitations on the separator as long as it is one that is normally used as a separator in a lithium ion battery, and it is preferable that the separator has low resistance to the movement of ions of the electrolyte and excellent electrolyte solution impregnation ability.

[0248] Specific examples of separators include porous polymer films, and 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 of these films are preferred. Furthermore, typical porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, are preferred. Furthermore, to ensure heat resistance or mechanical strength, coated separation membranes containing ceramic components or polymeric materials are preferred. Separators may be used in either a single-layer or multi-layer structure.

[0249] Polyethylene and polypropylene are 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 because it can be stretched to become porous without the use of plasticizers.

[0250] Alternatively, a polymer compound can be applied to both sides of the separator. The polymer compound provided on the surface of the separator may be gelled with an electrolytic solution. Suitable 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, fluorine-based polymer compounds are preferred, and polyvinylidene fluoride is more preferred, from the viewpoints of preventing swelling and gelling during high-temperature storage.

[0251] As the electrolyte for lithium ion batteries, a non-aqueous electrolyte solution in which an electrolyte is dissolved in an organic solvent is usually used.

[0252] Lithium salts are suitable as electrolytes for lithium ion batteries. Examples of lithium salts include 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 ) ２ , LiN(C ２ F ５ SO ２ ) ２ , LiN(CF ３ 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 Among these, LiPF is preferred because it is easily soluble in a solvent 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 is preferred, and LiPF ６ , LiBF ４ is more preferred.

[0253] The electrolyte is preferably a gel electrolyte containing a polymer compound that swells in an organic solvent to serve as a support for the nonaqueous electrolyte. By containing a polymer compound that swells in an organic solvent, high ionic conductivity can be achieved, excellent charge / discharge efficiency can be achieved, and battery leakage can be prevented. The content of this polymer compound is preferably 0.1 wt % to 10.0 wt % of the electrolyte. The polymer compound is preferably polyvinylidene fluoride.

[0254] The electrolytes may be used alone or in combination of two or more. The concentration of the electrolyte in the electrolytic solution is preferably 5% by weight or more and 15% by weight or less, more preferably 2% by weight or more and 13% by weight or less, and even more preferably 5% by weight or more and 10% by weight or less.

[0255] The organic solvent for the electrolytic solution is not particularly limited as long as it can dissolve the electrolyte, but preferred are 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.

[0256] Among these, cyclic carbonates and chain carbonates are preferred because they have a high dielectric constant and suitable viscosity and solvating ability that affect the migration of Li ions. Note that solvating ability is the force that dissociates dissolved ions, and if it is too strong, it will inhibit the migration of ions, so there is an optimal value.

[0257] Suitable cyclic carbonates are alkylene carbonates having an alkylene group with 2 to 4 carbon atoms, such as ethylene carbonate, propylene carbonate, and butylene carbonate. Among these, ethylene carbonate and propylene carbonate are preferred from the viewpoint of improving battery characteristics, and ethylene carbonate is more preferred.

[0258] As the chain carbonate, dialkyl carbonate is preferred. The number of carbon atoms in the constituent alkyl group is preferably 1 to 5, more preferably 1 to 4. Specifically, 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 are preferred. Among these, from the viewpoints of viscosity and boiling point, dimethyl carbonate and diethyl carbonate are preferred, and diethyl carbonate is more preferred.

[0259] Furthermore, practical lithium ion batteries are used under a wide range of environmental conditions, and the physical properties of the non-aqueous solvent, such as the melting point and boiling point, must fall within certain ranges. Therefore, it is preferable to use a mixture of cyclic carbonates and chain carbonates.

[0260] As a combination of a cyclic carbonate and a chain carbonate, a combination of ethylene carbonate and a chain carbonate is preferable. Specifically, the combinations of ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, and ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferable because they have a good balance between cycle characteristics and high-power discharge characteristics.

[0261] The mixing ratio of the cyclic carbonates to the chain carbonates is appropriately selected depending on the desired practical properties, and is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, even more preferably 30:70 to 70:30, and particularly preferably 40:60 to 60:40, in terms of the weight ratio of [cyclic carbonates]:[chain carbonates].

[0262] The content of cyclic carbonates in the electrolyte is preferably 1% by weight or more and 70% by weight or less, more preferably 1% by weight or more and 35% by weight or less, 3% by weight or more and 30% by weight or less, and 4% by weight or more and 50% by weight or less. A mixture of multiple cyclic carbonates can be used. The content of chain carbonates in the electrolyte is preferably 40% by weight or more and 70% by weight or less, more preferably 43% by weight or more and 68% by weight or less. A mixture of multiple chain carbonates can be used.

[0263] The organic solvent is preferably a fluorine-containing carbonate. Specifically, a cyclic carbonate having one fluorine atom, a chain carbonate having one fluorine atom, a cyclic carbonate having two or more fluorine atoms, or a chain carbonate having two or more fluorine atoms is preferred, and from the viewpoint of improving battery characteristics, a fluorine-containing cyclic carbonate having two or more fluorine atoms is more preferred.

[0264] As the fluorine-containing cyclic carbonate having two or more fluorine atoms, cis-4,5-difluoro-1,3-dioxolane-2-one, trans-4,5-difluoro-1,3-dioxolane-2-one, and 4,4-difluoro-1,3-dioxolane-2-one are preferred.

[0265] The above-mentioned fluorine-containing carbonates can be used alone or in combination of two or more. The proportion of the fluorine-containing carbonate in the electrolyte is preferably 0.001 wt% to 10.000 wt%, more preferably 0.010 wt% to 5.000 wt%, even more preferably 0.100 wt% to 2.000 wt%, particularly preferably 0.200 wt% to 1.000 wt%, and most preferably 0.250 wt% to 0.500 wt%. When the content of the fluorine-containing carbonate is 0.001 wt% or more, the effect of the fluorine-containing carbonate is well exhibited, and when the content of the fluorine-containing carbonate is 10.000 wt% or less, an increase in the internal pressure of the battery during high-temperature storage can be suppressed.

[0266] Furthermore, as the organic solvent, a cyclic carbonate having an unsaturated bond or an aromatic compound having 7 to 18 carbon atoms may be mixed in the electrolyte.

[0267] As the cyclic carbonate having an unsaturated bond, vinylene carbonate, vinylethylene carbonate, 4-methyl-4-vinylethylene carbonate, and 4,5-divinylethylene carbonate are preferred from the viewpoint of improving cycle characteristics, with vinylene carbonate and vinylethylene carbonate being more preferred.

[0268] As the aromatic compound having 7 to 18 carbon atoms, from the viewpoint of suppressing a significant decrease in discharge characteristics after high-temperature storage by suppressing side reactions with the negative electrode and the positive electrode, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferred.

[0269] These cyclic carbonates having unsaturated bonds and aromatic compounds having 7 to 18 carbon atoms can be used alone or in combination of two or more. The proportion of each in the electrolyte is preferably 0.001% by weight to 5.000% by weight, more preferably 0.100% by weight to 4.000% by weight, even more preferably 0.300% by weight to 3.000% by weight, particularly preferably 0.400% by weight to 2.500% by weight, and most preferably 0.500% by weight to 2.000% by weight. When the proportion is 0.001% by weight or more, safety during overcharge can be further improved. When the proportion is 5.000% by weight or less, battery properties such as high-temperature storage characteristics can be further improved.

[0270] FIG. 1 is a cross-sectional view showing an example of a lithium ion battery according to an embodiment, specifically, a cross-sectional view showing an example of the cross-sectional structure of a coin-type lithium ion battery. As shown in FIG. 1 , the lithium ion battery 200 has a disk-shaped positive electrode 212 housed in a metal exterior part 211 and a disk-shaped negative electrode 214 housed in a metal exterior part 213, with the positive electrode 212 and the negative electrode 214 stacked with a separator 215 interposed therebetween. A metal spring 218 and a spacer 219 are disposed between the exterior part 213 and the negative electrode 214. The interiors of the exterior parts 211 and 213 are filled with a liquid electrolyte. The peripheral portions of the exterior parts 211 and 213 are sealed by crimping with a seal gasket 217 interposed therebetween.

[0271] For example, a lithium ion battery can be produced by stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the stack as necessary according to the battery shape, placing the stack in a battery container, injecting an electrolyte into the battery container, and sealing the container. To prevent internal pressure buildup and overcharging / discharging of the lithium ion battery, a fuse, an overcurrent protection element such as a PTC element, an expanded metal, a lead plate, or the like may be provided as necessary. The shape of the lithium ion battery may be, for example, a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, a flat type, or the like.

[0272] Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept and scope of the claims of the present disclosure, and can be modified in various ways within the scope of the present disclosure.

[0273] Next, examples and comparative examples will be described, but the present invention is not limited to these examples. In the following, "%", "ppm" and "parts" that represent amounts are based on weight unless otherwise specified.

[0274] Experiment 1: Preparation of carbon material, dispersion, electrode composition, battery slurry, electrode, and lithium-ion battery

[0275] Example 1 (Production of Carbon Material) - CVD Reaction: Formation of Carbonaceous Layer on Template Material - Fumed silica (SiO ２ / AEROSIL (registered trademark) NX90G, particle size 38 nm, BET specific surface area 71 m ２ Approximately 1 g of 10 ...

[0276] -Removal of Template Material- Next, the template material was removed from the obtained carbon material precursor by the following procedure, thereby obtaining a carbon material.

[0277] (1) The carbon material precursor was placed in a 100 ml PFA beaker, and ultrapure water was added to wet the entire carbon material precursor. (2) 46% hydrofluoric acid was added, followed by stirring 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 mm diameter, 0.1 μm pore size), the supernatant was filtered by suction. (5) The sample on the filter paper was washed with approximately 39 mL of ultrapure water and then filtered by suction. This procedure was repeated three times. (6) The sample on the filter paper was returned to the original PFA beaker. (7) The above procedures (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 stopping the stirring, the sample was left to settle until it had settled. (10) The supernatant was discarded, and 5% caustic soda was added. The mixture was stirred for 12 hours while being heated to 80°C. (11) After stopping the stirring, the mixture was left to stand until the sample settled. (12) A PTFE membrane filter (47 mmφ, pore size 0.1 μm) was used to suction-filter the supernatant. (13) The sample on the filter paper was washed with ultrapure water and suction-filtered. This procedure was repeated until the filtrate became neutral. (14) The sample on the filter paper was collected in a petri dish and dried in a dryer at 110°C for 8 hours.

[0278] - Heat Treatment - The carbonaceous layer 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 adjusting the pressure to the order of Pa, the mixture was heated to 1800°C at a temperature increase rate of 15°C / min under an argon gas flow (10 mL / min) and maintained at that temperature for 1 hour for firing. Thereafter, the mixture was cooled to room temperature to obtain carbon material A.

[0279] (Method for measuring oil absorption of carbon material) The oil absorption of the obtained carbon material A was measured in accordance with "JIS K5101-13-1 Pigment testing methods - Part 13: Oil absorption - Section 1: Refined linseed oil method." The results are shown in Table 1.

[0280] (Transmission Electron Microscope Observation) The shape of the obtained carbon material A was observed. FIG. 2 is an enlarged TEM image of the carbon material A of Example 1 observed using a transmission electron microscope (TEM: JEM-ARM300F, manufactured by JEOL Ltd.) at an acceleration voltage of 80 kV. FIG. 3 is a TEM image of the carbon material A of Example 1 observed using a transmission electron microscope (TEM: H-7650, manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 100 kV. As shown in FIGS. 2 and 3 , it was confirmed that the surrounding wall of the carbon material A had a graphene structure consisting of a six-membered carbon ring structure. It was also confirmed that the carbon material A of Example 1 had a connected structure in which a plurality of hollow particulate portions were connected together, each of which was composed of a surrounding wall having a plurality of pores.

[0281] (Nitrogen Adsorption / Desorption Measurement) Nitrogen adsorption / desorption measurements were performed on the obtained carbon material A using an automatic specific surface area / pore size distribution analyzer (BELSORP MINI, manufactured by Microtrac-BEL Corporation). Prior to the measurement, the measurement sample was dried under reduced pressure at 150°C for 6 hours using a BEL pre. The BET specific surface area was determined from the obtained adsorption isotherm using the BET method. The applicable range of the BET method was P / P0 = 0.05 to 0.3. Furthermore, based on the obtained adsorption / desorption isotherm, the total pore volume was measured by converting the amount of nitrogen adsorbed at -196°C and a relative pressure P / P0 = 0.99 into a volume at the density of liquid nitrogen. The results are shown in Table 1. The pore size distribution was determined using the BJH method.

[0282] (Raman Spectroscopic Measurement) Raman spectroscopy was performed on the obtained carbon material A using a micro-Raman device (LabRAM HR-800, manufactured by Horiba, Ltd.). A 532 nm laser was used for the measurement, and the filter was set to D1 and the hole was set to 100 μm. The measurement range was 300 to 3500 cm －１ From the measured Raman spectrum, (I Ｇ / I ２Ｄ ), (I Ｄ / I Ｇ The intensity ratios of the above were calculated and are shown in Table 1.

[0283] (Preparation of Positive Electrode) As the active material, a ternary positive electrode material NCM (LiNi) with an average particle diameter of 8 μm was used. ０．５ Co ０．２ Mn０．３ O ２ 96.5% of the active material (Kelong Co., Ltd.), 0.5 wt. % of the carbon material A obtained above as a conductive additive, and 3 wt. % of PVDF (Kureha Co., Ltd.) were added to and mixed with N-methylpyrrolidone (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 at 2000 rpm while adding NMP in several portions until a uniform and appropriate viscosity was achieved, producing a cathode material slurry. The cathode material slurry 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 cathode blank. The cathode 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 cathode electrode for battery assembly.

[0284] (Fabrication of Lithium-ion Battery) The positive electrode fabricated as described above and metallic Li punched to a diameter of 16 mm in a glove box under an argon gas atmosphere were used, and a 1M LiPF ６ A solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC)) was added as an electrolyte, and the battery was sealed by crimping to prepare a 2032 size coin-type test battery. The battery was then washed with ethanol and subjected to the battery evaluation described below.

[0285] The battery performance was evaluated using the prepared test battery according to the following procedure, and the 2C retention rate, charge capacity, discharge capacity, and coulomb rate were determined.

[0286] (Positive Electrode Evaluation Method) Each test battery was energized to 4.2 V at a constant current of 1.25 mA (equivalent to 0.2 C). After reaching 4.2 V, it was charged at a constant voltage and continued until it reached 0.31 mA (0.05 C). It was then discharged to 3 V at a constant current of 1.25 mA. The charge capacity, discharge capacity, and average voltage at this time were determined, and the coulombic rate (discharge capacity ÷ charge capacity) was calculated. Next, using the same test battery, it was energized to 4.2 V at a constant current of 1.25 mA (equivalent to 0.2 C). After reaching 4.2 V, it was charged at a constant voltage and continued until it reached 0.31 mA (0.05 C). It was then discharged to 3 V at a high rate of 12.5 mA (equivalent to 2 C). The 2 C retention rate (2 C capacity ÷ 0.2 C capacity) of each test battery was calculated from the discharge capacity of the resulting test battery. The results are shown in Table 1. FIG. 5 is a graph showing discharge curves of different discharge current values ​​using test batteries.

[0287] Example 2 Fumed silica (SiO ２ / AEROSIL (registered trademark) R972, particle size 25 nm, BET specific surface area 111 m ２ Carbon material B was obtained in the same manner as in Example 1, except that a carbon material having a molecular weight of 0.6 to 1.2% (carbon content: 0.6 to 1.2%, manufactured by Nippon Aerosil Co., Ltd.) was used and the CVD reaction time was 120 minutes. A 2032-size coin-type test battery was fabricated using this carbon material. It was confirmed by electron microscopy that the template material was an aggregate of multiple primary nanoparticles linked together in a beaded pattern with multiple branched structures. Figure 6 shows the Raman spectrum of carbon material B.

[0288] Example 3 Carbon material C was obtained in the same manner as in Example 1 except that the CVD reaction time was changed to 75 minutes, and a 2032 size coin-type test battery was fabricated.

[0289] Example 4 Carbon material D was obtained in the same manner as in Example 1 except that the CVD reaction time was changed to 60 minutes, and a 2032 size coin-type test battery was fabricated.

[0290] Example 5 Carbon material E was obtained in the same manner as in Example 1 except that the CVD reaction time was changed to 40 minutes, and a 2032 size coin-type test battery was fabricated.

[0291] Example 6 Carbon material F was obtained in the same manner as in Example 1 except that the CVD reaction time was changed to 130 minutes, and a 2032 size coin-type test battery was fabricated.

[0292] Example 7 Alumina (Al ２ O ３ / PURALOX SBa200, particle size 7nm, BET specific surface area 202m ２ A graphene-containing carbon material G was obtained in the same manner as in Example 1, except that a graphene-containing carbon material (carbon material G) was used (carbon material G, manufactured by SASOL). The graphene-containing carbon material G was used to prepare a 2032 size coin-type test battery.

[0293] Example 8 Magnesia (MgO / Kyowamag MF150, particle size 30 nm, BET specific surface area 129 m) was used as the raw material for the mold. ２ Carbon material H was obtained in the same manner as in Example 1, except that carbon material H was used (carbon material H = carbon black, manufactured by Kyowa Chemical Industry Co., Ltd. / g, manufactured by Kyowa Chemical Industry Co., Ltd.) and the template material was removed as follows, and a 2032 size coin-type test battery was fabricated.

[0294] (Removal of template material) 1-1.4 g of the carbon material precursor after the CVD reaction, approximately 100 g of hydrochloric acid (Fujifilm Wako Pure Chemical Industries, 5 mol / L), and a stir bar were added to a Teflon® beaker and stirred at room temperature for 5 hours. After stirring, 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. The deposits were then placed in a glass beaker containing approximately 100 mL of acetone. The beaker was covered with aluminum foil and placed in a vacuum dryer at 0.06 MPa for 2 minutes. The pressure was then 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 carbon material H.

[0295] Example 9 Carbon material I was obtained in the same manner as in Example 1, except that no heat treatment was carried out, and a 2032 size coin-type test battery was fabricated.

[0296] Comparative Example 1 A 2032 size coin-type test battery was fabricated in the same manner as in Example 1, except that commercially available carbon black (DENKA BLACK Li-100, manufactured by Denka Co., Ltd.) was used as the carbon material.

[0297]

[0298] 7 is a graph showing the relationship between the oil absorption and the 2C retention rate of the test batteries of Examples 1 and 9 and Comparative Example 1. The vertical axis represents the 2C retention rate, and the horizontal axis represents the oil absorption rate. Table 1 and FIG. 7 show that carbon materials A to I satisfying the specified configuration are highly excellent in the battery characteristics of the 2C retention rate (rapid chargeability), charge capacity, discharge capacity, and coulomb rate (comparison of Examples 1 to 9 and Comparative Example 1).

[0299] In particular, it can be seen that the test batteries using carbon materials A to F of Examples 1 to 6 all had significantly increased initial capacity (charged capacity) and coulombic capacity. It is not clear which characteristic of the carbon material is responsible for this difference in battery performance, but it is possible that the I measured by Raman spectroscopy described above, which is related to the shape of the pores, Ｇ / I ２Ｄ Ya I Ｄ / I Ｇ It is thought to be influenced by.

[0300] The oil absorption capacity of acetylene black (Comparative Example 1), a type of carbon black considered to be high among carbon materials, was shown to be approximately 300 mL / 100 g. In contrast, carbon materials A to I of Examples 1 to 9 exceeded 400 mL / 100 g, even exceeding 700 mL / 100 g, which is difficult to achieve with ordinary carbon materials, and some even exceeded 2000 mL / 100 g, demonstrating that they are novel carbon materials. It is believed that carbon materials A to I can absorb more oil because the internal space of the carbon material of the present invention is larger than the microscopic voids inside acetylene black.

[0301] The 2C retention rate of battery performance is an evaluation item for measuring the possibility of high-speed discharge of a battery, and it can be seen that the 2C retention rates of carbon materials A to I are large. It can also be seen that the 2C retention rate of battery performance is closely correlated with the oil absorption rate of the carbon material. It can be seen that the 2C retention rate increases when the oil absorption of the carbon material exceeds 400 mL / g and reaches around 1000 mL / g, and then peaks around 1600 to 1900 mL / g. The structure of the carbon material of the present invention with such a large oil absorption rate is characterized by a large total pore volume and the need for I to form large pores. Ｄ / I Ｇ is large enough (the D band is the sp3 orbital when the graphene crystal structure consisting of sp2 orbitals is disordered, and the larger it is, the more distortion of space occurs) and to maintain large holes, the stacking index I Ｇ / I ２Ｄ This seems to mean that a certain number of graphene layers is required.

[0302] Experiment 2: Confirmation of the basic physical properties of carbon materials (comparison of oil absorption amounts using different measurement methods)

[0303] Comparative Examples 2 to 4 Three types of carbon black, the oil absorption of which is specified in JIS K6217-4 in the catalog, were measured according to a method in accordance with JIS K5101-13-1, and the results are shown in Table 2. There was no significant difference in the oil absorption between the two measurement methods.

[0304]

[0305] Experiment 3: Confirmation of the basic performance of carbon materials (comparison of the performance of batteries with different amounts of carbon material added to the electrodes)

[0306] 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 changed to 0.3 wt % and the blending amount of positive electrode material NCM was changed to 96.7%.

[0307] 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 changed to 1.0 wt % and the blending amount of positive electrode material NCM was changed to 96.0%.

[0308] 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 changed to 2.0 wt % and the blending amount of positive electrode material NCM was changed to 95.0%.

[0309] 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 changed to 3.0 wt % and the blending amount of positive electrode material NCM was changed to 94.0%.

[0310] Example 14 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 changed to 4.0 wt % and the blending amount of positive electrode material NCM was changed to 93.0%.

[0311] Example 15 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 changed to 6.0 wt % and the blending amount of positive electrode material NCM was changed to 91.0%.

[0312] Example 16 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 changed to 0.1 wt % and the blending amount of positive electrode material NCM was changed to 96.9%.

[0313] For the test batteries of Examples 10 to 16, the 2C retention rate, charge capacity, discharge capacity, and coulomb rate were determined in the same manner as in Example 1. The results are shown in Table 3.

[0314]

[0315] Figure 8 is a graph showing the relationship between the amount of carbon material and the 2C retention rate and discharge capacity for the test batteries of Examples 1 and 10 to 16. 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. In Figure 8, the dots represent the 2C retention rate and the triangles represent the discharge capacity. Table 3 and Figure 8 confirm that the high-rate characteristics of the test batteries remained favorable within the range of the amount of carbon material in Examples 1 and 10 to 16. It was found that battery characteristics could be significantly improved in Examples where the amount of carbon material was within the range of 0.5 to 4.0 wt % or 1.0 to 4.0 wt %. While increasing the amount of carbon material increases the battery charge / discharge capacity, excessively increasing the amount of carbon material likely reduces the active material content, thereby reducing the charge / discharge capacity of the electrode.

[0316] Experiment 4: Analysis of carbon materials by nitrogen adsorption / desorption measurements (comparing specific surface area, pore volume, etc. with other carbon materials)

[0317] (Nitrogen Adsorption / Desorption Measurement) Nitrogen adsorption / desorption measurement was carried out for the carbon materials A to I used in Examples 1 to 9 and the carbon black (DENKA BLACK Li-100: manufactured by Denka Co., Ltd.) used in Comparative Example 1 by the method described above.

[0318] From the obtained adsorption / desorption isotherms, the BET specific surface area, mode pore diameter, total pore volume (P / P = 0.99), micropore volume (P / P = ∼0.1), mesopore volume (P / P = 0.1-0.96), 2-10 nm mesopore volume (P / P = 0.1-0.79), 10-50 nm mesopore volume (P / P = 0.79-0.96), and macropore volume (P / P = 0.96-0.99) were calculated. The average pore diameter d was calculated from the BET specific surface area S and total pore volume V, assuming cylindrical pores, using d = 4V / S. The results are shown in Table 4. Note that in Comparative Example 1, since there was no peak in the pore distribution, the "mode pore diameter" column was entered as "-".

[0319] Comparative Examples 5 and 6 In addition to the above, nitrogen adsorption and desorption measurements were also carried out on the following carbon materials. The results are shown in Table 4. Note that, like Comparative Example 1, Comparative Example 5 also had no peak in the pore size distribution, and therefore the column for "mode pore size" was marked with "-".

[0320] Comparative Example 5: Graphite (KS6, manufactured by Imerys) Comparative Example 6: Activated carbon (YP-5, manufactured by Kuraray)

[0321]

[0322] Furthermore, the ratios of the micropore volume, mesopore volume, and macropore volume to the total pore volume, as well as the ratios of the 2-10 nm mesopore volume and the 10-50 nm mesopore volume to the total pore volume were calculated and are shown in Table 5.

[0323]

[0324] From Table 4, the carbon materials A to I of the present invention have a large BET specific surface area (817 to 1747 m ２ It can be seen that the specific surface area of ​​the sintered body is 400 m / g and the total pore volume is large (1.98 cc / g or more) (Examples 1 to 9). ２ / g or more or 800m ２ / g or more is the activated carbon of Comparative Example 6, but the total pore volume of the activated carbon of Comparative Example 6 is small, at 1.00 cc / g or less. Comparative Examples 1, 5, and 6 did not have both a large specific surface area and a large total pore volume.

[0325] It is also clear that the carbon materials A to I of the present invention have significantly different mode pore diameters and macropore volumes. Compared to carbon materials G to H, carbon materials A to F and I have larger mode pore diameters (peak top pore diameters) (comparison of Examples 7 to 8 with Examples 1 to 6 and 9). That is, carbon materials A to F and I have larger pores than carbon materials G to H, which is thought to be the reason for the differences in oil absorption. It is also clear that carbon materials A to F and I have larger macropore volumes than other carbon materials. In particular, carbon materials G and H of Examples 7 to 8 have almost no macropore volume.

[0326] From Table 5, it can be seen that the ratio of the macropore volume to the total pore volume is 16 to 43% for carbon materials A to F and I, but only 2 to 3% for carbon materials G to H of Examples 7 and 8. The graphite of Comparative Example 5 has a large macropore volume ratio, but its specific surface area is 19 m ２ / g, which is small.

[0327] Furthermore, when the mesopore volume is divided into the 2-10 nm mesopore volume and the 10-50 nm mesopore volume, it is found that carbon materials A to F and I are biased toward the 10-50 nm mesopore volume.

[0328] Tables 4 and 5 show that carbon materials A to F and I have large modal pore diameters, and also large specific surface areas, total pore volumes, pore volumes of 10 to 50 nm, and macropore volumes, and are therefore carbon materials with unparalleled porosity.

[0329] Experiment 5: Structural analysis of the carbon layer in the carbon material (analysis of the carbon layer of the carbon material produced in the examples by X-ray analysis)

[0330] (XRD Measurement) X-ray diffraction (XRD) measurement was performed on the carbon material using an X-ray diffractometer (Miniflex 600, manufactured by Rigaku Corporation). A Si non-reflective plate was used as the sample stage, and the measurement sample was placed on the circular part. Measurement was performed under the following measurement conditions. The values ​​of d002, Lc(002), and La(10) are shown in Table 6.

[0331] X-ray source: CuKa Tube voltage: 40 kV Tube current: 15 mA Measurement angle: 5 to 90 deg Scan speed: 2 deg / min Scan axis: 2θ / θ

[0332]

[0333] The Lc(002) measured by XRD is referred to as the distance between the crystalline structure portions, and the larger the Lc(002), the higher the crystallinity. That is, the Lc(002) of carbon materials A to I is small. This indicates that the crystallinity of the carbonaceous layer of the carbon material of the present invention is not very high. Furthermore, the D band in the Raman spectrum is a band indicating the sp3 bond (C-H stretching motion) of the carbon material, and increases when the sp2 bond in the 6-membered carbon ring structure of the carbon layer is broken to form an sp3 bond. Therefore, the carbon layers of carbon materials A to I of the present invention are layers in which crystalline and amorphous portions are mixed, which is thought to be the cause of the formation of large spaces.

[0334] Experiment 6: Determining the number of carbon layers in carbon materials (examining the relationship between the number of carbon layers, pore size, and oil absorption)

[0335] (Number of Carbon Layers) The number of carbon layers was calculated from the carbon weight loss rate during the production of Examples 1 to 9. The results are shown in Table 7.

[0336] Specifically, TGA measurement was performed to determine the number of layers. Using a STA-2500 (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 measurement. Blank measurements performed using empty pans under the same temperature profile conditions were subtracted. Alumina pans were used. The number of carbon layers was calculated from the carbon weight reduction rate (%) determined by TG measurement as follows: The weight of the carbon layer was calculated from the carbon weight reduction rate, and the weight of the carbon layer per area was calculated from the weight of this carbon layer and the surface area of ​​the template material. Next, the weight of the carbon layer per area of ​​the template material was multiplied by the weight of the carbon layer per area of ​​single-layer graphene (7.61 × 10 －４ g / m ２ ) to calculate the number of carbon layers.

[0337]

[0338] Table 7 confirms that, for carbon materials A to I of the present invention, controlling the number of carbon layers to fall within a predetermined range makes it possible to obtain carbon materials with different properties. It was also found that as the number of carbon layers increases, the oil absorption of the carbon material increases sharply, demonstrating a correlation between the two (Examples 1 to 9).

[0339] In particular, as shown in Tables 5 and 7, carbon materials A to F and I, which had 1.9 to 4.5 carbon layers, had a large mesopore volume of 10 to 50 nm and a large macropore volume of 50 nm or more, and exhibited high oil absorption.

[0340] Experiment 7: Analyzing the particle structure of carbon materials (particle size distribution measurement and TEM image analysis)

[0341] (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 the carbon material. The measurement sample was an unpulverized carbon material that had been immersed in ethanol for 9 minutes. D50, D10, D90, D90 / D10, and D90 / M×1000 in the particle size distribution curve were determined, and the results are shown in Table 8.

[0342]

[0343] Table 8 shows that the D50 values ​​for carbon materials A to I are within the specified range. This indicates that the measurement samples were unground and simply immersed in a solvent, and the cohesive strength was not particularly high. Furthermore, for carbon materials A to F and I, although only (D90 / M x 1000) is shown in Table 8, the values ​​obtained by dividing the cumulative particle size measured in the particle size distribution by the mode pore diameter (M) in the pore distribution measurement and then dividing by 1000 ((D10 / M x 1000), (D50 / M x 1000), (D90 / M x 1000)) are all significantly smaller, indicating weak cohesive strength (comparison of Examples 1 to 6, 9 with Comparative Examples 1, 5, and 6).

[0344] Experiment 8: Measurement of desorbed gas and combustion temperature of carbon materials (to estimate the stability of carbon materials when used in batteries)

[0345] (Thermal Desorption Gas Analysis) Using an ultra-sensitive vacuum TPD instrument (developed at Tohoku University, see T. Ishii et al., CARBON 80, 2014, pp. 135-145) with the configuration shown in FIG. 9 , oxygen-containing functional groups and hydrogen-terminated edge sites were accurately qualitatively and quantitatively analyzed. More specifically, 1 to 3 mg of each carbon material was placed on a graphite sample stage, heated in vacuum to 1800°C at a heating rate of 10°C / min, and the gases released during heating were analyzed by mass spectrometry to accurately qualitatively and quantitatively analyze the oxygen-containing functional groups and hydrogen-terminated edge sites. The instrument 50 included a quartz reactor equipped with a radioactive thermometer 41, a sample holder 42, and a high-frequency induction coil 43, as well as a detection unit connected to the quartz reactor. The detection unit included a gas reservoir, a turbomolecular pump (TMP), a rotary pump (RP), a cold cathode Pirani gauge (P1), and a capacitance gauge (P2).

[0346] (Combustion Temperature Measurement) The combustion temperature of the carbon material was determined as the temperature at which the weight of the carbon material became 90% of the initial weight in a combustion oxidation test performed using a thermogravimetric analyzer under air flow at a temperature increase rate of 5°C / min. A combustion temperature of 550°C or higher was determined to be good.

[0347] The desorbed gas and combustion temperature of the carbon material were investigated, and the results are shown in Table 9.

[0348]

[0349] From the results shown in Table 9, it was confirmed that the carbon material of the present invention has a sufficiently low oxygen content, O / C, total gas amount, and edge amount as determined by TPD-MS measurement. It was also confirmed that the carbon material of the present invention has a sufficiently high combustion temperature.

[0350] (Apparent Density) The apparent density of each carbon material was calculated from the total pore volume and true density according to the following formula (5).

[0351] Apparent density (g / cc)=1 / (total pore volume+(1 / true density)) Equation (5)

[0352] The total pore volume (cc / g) was calculated using P / P0 = 0.99, and the true density was the graphite value of 2.2 g / cc. The results are shown in Table 10.

[0353]

[0354] From the results shown in Table 10, it was confirmed that the carbon material of the present invention has a lower apparent density than the comparative examples, and that the apparent density is preferably 2.000 g / cc or less, more preferably 1.500 g / cc or less, 1.000 g / cc or less, 0.500 g / cc or less, and 0.300 g / cc or less, and is more preferably 0.050 g / cc or more, 0.100 g / cc or more, and 0.150 g / cc or more, in that order.

[0355] Experiment 9: Study of anodes containing carbon materials

[0356] Example 17: A negative electrode test battery was manufactured using 0.5 wt% of the carbon material of Example 1 added to the negative electrode. 97 wt% of artificial graphite, 1 wt% of the carbon material of Example 1, 1 wt% of carboxymethyl cellulose, and 1 wt% of styrene butadiene rubber (SBR) were mixed and stirred uniformly using distilled water as a solvent to prepare a negative electrode paste. The resulting paste was applied to a 20 μm-thick copper foil, dried at 110°C, and then punched to a diameter of 15 mm and pressed at 30 kN to form a negative electrode.

[0357] The resulting negative electrode was dried in vacuum at 120°C, and then reconstituted in a glove box under an argon gas atmosphere with 1M LiPF ６ A 2032 size coin-type test battery with a metal Li counter electrode was fabricated using a solution (a 1:1 mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC)) as an electrolyte and a polypropylene separator.

[0358] 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) was calculated from the discharge capacity of the test battery determined in the above evaluation test.

[0359] The negative electrode battery thus obtained was evaluated, and the retention rate during 2C discharge was 0.47.

[0360] Comparative Example 7 A negative electrode test battery was produced in the same manner as in Example 17, except that acetylene black (trade name: Denka Black, manufactured by Denki Kagaku Kogyo Kogyo Co., Ltd.) was used as a conductive additive instead of the carbon material of Example 1, and the amount of this conductive additive added to the negative electrode was 1.0 wt %.

[0361] The negative electrode battery thus obtained was evaluated, and the retention rate during 2C discharge was 0.16.

[0362] As is clear from the above examples, the 2C retention rate of the battery using the carbon material of this embodiment is higher than that of the battery of the comparative example. This is due to the high electronic conductivity of the carbon material of this embodiment. Specifically, compared to the conductive additive used in the comparative example, the carbon material of this embodiment has a surrounding wall with a graphene crystal structure and has spaces within the hollow particulate portions that can hold 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 return to the crystalline structure sites of the positive electrode in a bonded form, restoring the bonded state before charging. In other words, the bonding of lithium ions and electrons and the phase change of the crystalline structure of the positive electrode occur simultaneously. The phase change can be observed from a change in voltage. The "simultaneity" of this phase change is important for high-rate discharge retention, and it was confirmed that the carbon material of this example can achieve this "simultaneity."

[0363] Experiment 10: Study of semi-solid electrolyte batteries

[0364] Example 18 A battery including the positive electrode and metallic Li negative electrode of Example 1 was fabricated using a gel electrolyte instead of an electrolytic solution (liquid electrolyte). The fabrication work was all carried out in a dry atmosphere with a dew point of −30° C. or lower.

[0365] The gel electrolyte layer was prepared as follows: First, modified PVDF (7% hexafluoropropylene copolymer) and an electrolyte solution (50 wt% ethylene carbonate, 50 wt% propylene carbonate, 1.0 mol / kg LiPF ６The sol electrolyte precursor was prepared by mixing PVDF, electrolyte solution, and DMC (dimethyl carbonate) and stirring at 50°C to dissolve the sol electrolyte precursor. The precursor composition was PVDF:electrolyte:DMC=1:6:12. The resulting precursor solution (sol electrolyte precursor) was uniformly applied to the surfaces of the positive and negative electrodes. The resulting solution was then dried at 85°C for 3 minutes to remove the DMC. In this way, a gel electrolyte layer was formed on the surfaces of the positive and negative electrodes.

[0366] Next, a 9 μm thick polyethylene separator cut to a size larger than the electrode system was sandwiched between the positive and negative electrodes, and the resulting assembly was incorporated into a battery case to prepare a 2032 size coin-type test battery. The battery was then washed with ethanol and left overnight at 60° C. The battery was then subjected to battery evaluation in the same manner as in Example 1.

[0367] As a result, the initial discharge capacity at 0.2 C was 145 mAh / g, the initial charge / discharge efficiency was 86.3%, and the capacity retention rate at 2 C discharge was 78%.

[0368] Comparative Example 8 A coin-type test battery was produced in the same manner as in Example 18, except that acetylene black was used as the conductive additive for the positive electrode, and the battery was evaluated in the same manner as in Example 18. As a result, the 0.2 C initial discharge capacity was 120 mAh / g, the initial charge / discharge efficiency was 82.2%, and the capacity retention rate at 2 C discharge was 15%.

[0369] Experiment 11: Study of dry electrodes

[0370] Example 19: While mixing 95% by weight of NCM523 and 1% by weight of carbon material A in a V-blender, a mixed emulsion of PTFE (solid content 2% by weight) and PVDF (solid content 2% by weight) was added dropwise in several portions, mixed for 3 hours, and then dried at 110°C for 3 hours. The dried product was then pulverized in a jet mill and then passed through an air classifier to obtain a cathode material powder with an average particle size of 30 μm. The cathode material powder was then uniformly spray-coated onto a cathode current collector foil prepared by thinly coating a paste of PVDF and carbon material A on aluminum foil, and the resulting mixture was continuously introduced into a hot roll press heated to 130 to 200°C to obtain a pressure-molded dry electrode.

[0371] Thereafter, a 2032 size coin-type test battery was fabricated and subjected to battery evaluation in the same manner as in Example 1. As a result, the 0.2 C initial discharge capacity was 140 mAh / g, the initial charge / discharge efficiency was 85.1%, and the capacity retention rate at 2 C discharge was 80%.

[0372] Comparative Example 9 A coin-type test battery was produced in the same manner as in Example 19, except that acetylene black was used as the conductive additive in the negative electrode, and the battery was evaluated in the same manner as in Example 19. As a result, the 0.2 C initial discharge capacity was 118 mAh / g, the initial charge / discharge efficiency was 83.0%, and the capacity retention rate at 2 C discharge was 22%.

[0373] Experiment 12: Study of semi-solid battery using clay-type electrodes

[0374] Example 20: Electrolyte: 1M LiPF ６ A solution (a mixed solvent of ethylene carbonate (EC): diethyl carbonate (DEC) in a volume ratio of 1:1) was prepared. NCM523 was added to 45 cm ３ , carbon material A is 8 cm ３ , electrolyte 47cm ３ was weighed into a small batch mixer container. The mixture was mixed at 100 rpm for 6 minutes at 8°C using a mixer equipped with a roller mill adapter to prepare a positive electrode material slurry. Measurement using a conductivity tester revealed a conductivity of 8.2 × 10 －３ S / cm was confirmed.

[0375] The cathode material slurry was applied at a constant rate using a discharge applicator onto 15 μm thick aluminum foil pre-cut into 2 cm squares to obtain a 200 μm thick clay-type cathode electrode. The clay-type cathode electrode and a 2 cm square piece of metallic lithium were then quickly placed face-to-face with a 2.5 cm square separator sandwiched between them. This was then sandwiched between aluminum laminate films, and the current collecting tabs previously attached to each electrode were removed and heat-sealed to produce a pouch-type test battery. All operations were performed in a dry atmosphere with a dew point of -30°C.

[0376] Thereafter, the pouch-type test battery was subjected to battery evaluation in the same manner as in Example 1. As a result, the 0.2 C initial discharge capacity was 143 mAh / g, the initial charge / discharge efficiency was 84.7%, and the capacity retention rate at 2 C discharge was 71%.

[0377] Comparative Example 10 A pouch-type test battery was produced in the same manner as in Example 20, except that acetylene black was used as the conductive additive for the negative electrode, and the battery was evaluated in the same manner as in Example 20. As a result, the 0.2 C initial discharge capacity was 120 mAh / g, the initial charge / discharge efficiency was 81.7%, and the capacity retention rate at 2 C discharge was 12%.

[0378] Experiment 13: Examination of graphite anode

[0379] Example 21: 97% by weight of artificial graphite, 1% by weight of carbon material A as a conductive additive, 1% by weight of carboxymethyl cellulose, and 1% by weight of styrene butadiene rubber (SBR) were mixed and stirred uniformly using distilled water as a solvent to prepare a negative electrode paste. The obtained paste was applied to a copper foil having a thickness of 20 μm and dried. This was punched out to a diameter of 15 mm and then pressed to obtain a negative electrode.

[0380] The resulting negative electrode and metallic Li punched to a diameter of 16 mm were used in a glove box under an argon gas atmosphere. A separator (a microporous polypropylene film) having a thickness of 25 μm was sandwiched between the negative electrode mixture layer and metallic Li, and a 1M LiPF ６ A solution (a mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC) in a volume ratio of 1:1) was added as an electrolyte, and the battery was sealed by crimping to prepare a 2032 size coin-type test battery. The battery was then washed with ethanol and subjected to the battery evaluation described below.

[0381] Each test battery was charged to 0 V at a constant current of 1.23 mA (equivalent to 0.2 C), and then charged at a constant voltage of 0.31 mA (0.05 C). The battery was then discharged to 1.5 V at a constant current of 1.23 mA. The battery was charged in the same manner, and then discharged at a constant current of 12.3 mA (equivalent to 2 C), and the voltage was measured after the initial discharge time of 1 second.

[0382] As a result, the voltage after the initial 1 second of discharge was 0.27 V. The DC resistance calculated by dividing the voltage by the current was 22 Ω.

[0383] Comparative Example 11 A coin-type test battery was produced in the same manner as in Example 21, except that acetylene black (trade name: Denka Black, manufactured by Denki Kagaku Kogyo Kogyo Co., Ltd.) was used as the conductive additive instead of carbon material A, and the battery was evaluated in the same manner as in Example 21. As a result, the voltage after the initial 1 second of discharge was 0.32 V. The DC resistance, calculated by dividing the voltage by the current, was 26 Ω.

[0384] Experiment 14: Study of silicon-based anode

[0385] Example 22: Si—C powder (manufactured by Zichen Co., Ltd., China, average particle size 10 μm, 2 m ２ / g) was used as the negative electrode active material, and carbon material A, which is a conductive additive, and a binder were blended with this. The blending ratio was Si-C powder:carbon material A:binder = 85:5:10, and water was further added to prepare a slurry. Next, the slurry was applied to a Cu current collector with a thickness of 20 μm, dried at 110°C, and then punched out to a diameter of 15 mm and pressed at 30 kN to obtain a negative electrode. After vacuum drying the negative electrode at 120°C, 1M LiPF was added to the electrolyte in a glove box with an argon gas atmosphere. ６ Using the solution (a mixed solvent of ethylene carbonate (EC):diethyl carbonate (DEC) in a volume ratio of 1:1) and a polypropylene separator, a 2032 size coin-type test battery with a metallic Li counter electrode was fabricated.

[0386] The test battery was charged to 0 V (vs Li / Li) at 0.2 A / g per negative electrode active material. ＋ ) and charged until the current reached 0.01 A / g. Then, at 0.5 A / g, the battery was charged to 2.0 V (vs. Li / Li ＋ ), and then discharge was completed. Next, the same charging and discharging cycle was repeated 10 times. The charge-discharge efficiency of the obtained test battery in the first cycle (1 ｓｔ CE), initial discharge capacity, charge-discharge efficiency at the 10th cycle (10 ｔｈ CE) was measured.

[0387] As a result, the charge-discharge efficiency in the first cycle was 87.0%, the first discharge capacity was 1780 mAh / g, and the charge-discharge efficiency in the tenth cycle was 89.2%.

[0388] Comparative Example 12 A coin-type test battery was fabricated and evaluated in the same manner as in Example 12, except that acetylene black was used instead of carbon material A and the compounding ratio of the negative electrode raw materials was Si—C powder:acetylene black:binder=80:10:10. As a result, the charge-discharge efficiency in the first cycle was 83.6%, the initial discharge capacity was 1630 mAh / g, and the charge-discharge efficiency at the 10th cycle was 86.3%.

[0389] As shown in Examples 18 to 22, the carbon material of the present invention can be suitably used in various electrolyte systems and electrode systems, in addition to conventional liquid electrolyte (electrolyte) batteries and the positive and negative electrodes of those batteries. In batteries using semi-solid electrolytes (gel electrolytes), the electrolyte is retained by swelling the polymer, and it is believed that the carbon material of the present invention also retains the electrolyte within itself, thereby achieving good characteristics. In positive and negative electrodes using the carbon material of the present invention, which has this electrolyte retention property, electrolyte movement (electrolyte motion) is suppressed, and when used in batteries, the battery reaction is stabilized and an excellent cycle life is obtained.

[0390] Furthermore, in dry electrode batteries, which can simplify the manufacturing process, and semi-solid lithium-ion batteries using clay electrodes, which can reduce the amount of current collecting foil by using thick electrodes and improve battery capacity, higher performance can be obtained than in the comparative examples, making it possible to ideally realize high-performance batteries.

[0391] 50 Apparatus 41 Radioactive thermometer 42 Sample holder 43 High frequency induction coil 200 Lithium ion battery 211 Exterior part 212 Positive electrode 213 Exterior part 214 Negative electrode 215 Separator 217 Seal gasket 218 Spring 219 Spacer P1 Cold cathode Pirani gauge P2 Capacitance gauge QMS Quadrupole mass spectrometer TMP Turbo molecular pump RP Rotary pump

Claims

1. A carbon material comprising a connecting structure having an extending shape in which a plurality of hollow particle-like portions having an inner space partitioned and formed with a plurality of pores and having an enveloping wall with a graphene crystal structure are connected in a bead-like manner, and the intensity ratio (I Ｇ / I ２Ｄ ) of the intensity (I Ｇ ) of the G band to the intensity (I ２Ｄ ) of the 2D band in the Raman spectrum obtained by Raman spectroscopic measurement is 0.40 or more and 5.00 or less, and the oil absorption amount measured in accordance with JIS K5101-13-1:2004 is 400 mL / 100 g or more.

2. The intensity ratio (I Ｄ / I Ｇ ) of the intensity (I Ｄ ) of the D band to the intensity (I Ｇ ) of the G band in the Raman spectrum is 0.1 or more and 10.0 or less. The carbon material according to claim 1.

3. The carbon material according to claim 1, wherein the mode pore diameter is 1 nm or more and 500 nm or less.

4. The carbon material according to claim 1, wherein the total pore volume is 0.10 cc / g or more and 20.00 cc / g or less.

5. The carbon material according to claim 1, wherein the ratio of the macropore volume to the total pore volume is 5% or more.

6. The carbon material according to claim 1, wherein the apparent density is 2.00 g / cc or less.

7. The BET specific surface area is 100 m ２ / g or more and 2700 m ２ / g or less. The carbon material according to claim 1.

8. The carbon material according to claim 1, wherein the crystallite size Lc(002) in the c-axis direction measured by the X-ray diffraction method is 0.10 nm or more and 20.00 nm or less.

9. The carbon material according to claim 1, wherein the interplanar spacing d002 of the (002) plane measured by the X-ray diffraction method is 3.0 Å or more and 5.0 Å or less.

10. The carbon material according to claim 1, wherein D50 obtained from the volume-based particle size distribution curve measured by the laser diffraction scattering method is 1 μm or more and 100 μm or less.

11. The carbon material according to claim 1, wherein the ratio (D90 / D10) of D90 to D10 obtained from the volume-based particle size distribution curve measured by the laser diffraction scattering method is 100 or less.

12. The carbon material according to claim 1, wherein the value obtained by dividing the ratio (D90 / M) of D90 to the mode pore diameter M obtained from the volume-based particle size distribution curve measured by the laser diffraction scattering method by 1000 is 50 or less.

13. The carbon material according to claim 1, wherein the connecting structure is a graphene mesosponge.

14. The carbon material according to claim 1, wherein the carbon material is for a secondary battery.

15. A dispersion liquid obtained by dispersing the carbon material according to any one of claims 1 to 14 in a dispersion medium.

16. An electrode composition containing the carbon material according to any one of claims 1 to 14, an active material, and a binder.

17. An electrode slurry obtained by dispersing the electrode composition according to claim 16 in a dispersion medium.

18. An electrode containing the carbon material according to any one of claims 1 to 14.

19. The electrode according to claim 18, containing 0.1 wt% or more and 6.0 wt% or less of the carbon material.

20. A positive electrode containing the carbon material according to claim 1.

21. A negative electrode containing the carbon material according to claim 1.

22. The negative electrode according to claim 21, which is a negative electrode for a lithium-ion battery and further contains graphite.

23. The negative electrode according to claim 21, which is a negative electrode for a lithium-ion battery and further contains silicon.

24. A lithium-ion battery comprising the positive electrode according to claim 20, the negative electrode according to claim 21, and a liquid electrolyte.

25. A lithium-ion battery comprising the positive electrode according to claim 20, the negative electrode according to claim 21, and a semi-solid electrolyte.

26. A lithium-ion battery according to claim 24, wherein at least one of the positive electrode and the negative electrode is a dry electrode.

27. A lithium-ion battery according to claim 25, wherein at least one of the positive electrode and the negative electrode is a dry electrode.

28. A lithium-ion battery comprising a clay-type positive electrode containing the carbon material according to any one of claims 1 to 14 and a clay-type negative electrode containing the carbon material according to any one of claims 1 to 14.

29. A lithium-ion battery containing the carbon material according to any one of claims 1 to 14.

30. A method for producing a carbon material according to any one of claims 1 to 14, the method having a removing step of removing the mold material of a carbon material precursor in which the surface of a mold material, which is an aggregate in which a plurality of primary particles are aggregated in a bead-like manner and connected in a series, is coated with a carbonaceous layer to obtain a carbon material.

31. The method for producing a carbon material according to claim 30, further having a heating step of heating the carbon material at 1000 °C or higher and 3000 °C or lower after the removing step.

32. The method for producing a carbon material according to claim 30, wherein the mold material is a fumed compound.

33. A carbon material precursor comprising a mold material composed of an aggregate in which a plurality of primary particles are aggregated in a bead-like manner and connected in a series, and a carbonaceous layer covering the surface of the mold material and having a plurality of pores.

34. A method for producing a carbon material precursor according to claim 33, the method having a coating step of coating the surface of a mold material, which is an aggregate in which a plurality of primary particles are aggregated in a bead-like manner and connected in a series, with a carbonaceous layer to obtain a carbon material precursor.

35. The method for producing a carbon material precursor according to claim 34, wherein the mold material is a fumed compound.

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