Carbon black, method for producing carbon black, electrode composition, electrode, and secondary battery

Abstract

To provide carbon black that has an extremely small iron content and can be suitably used as a conductive material for secondary batteries.SOLUTION: The present invention provides carbon black with an oil absorption amount of 150 mL / 100 g or more and 400 mL / 100 g or less, and an iron content of 500 ppb or less as measured by a high frequency inductively-coupled plasma mass spectrometry.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to carbon black and a method for producing the same, as well as an electrode composition, an electrode, and a secondary battery containing the carbon black. [Background technology]

[0002] Carbon black has been used as a conductive material and the like, and the development of carbon black having various characteristic values ​​has been investigated (for example, Patent Document 1).

[0003] Furthermore, Patent Document 2 describes a method for producing high-purity furnace black by a specific production method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-035598 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-105355 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the demand for secondary batteries has increased due to the increased demand for portable electronic devices, and there is a demand for innovations to reduce the defective rate of materials constituting secondary batteries.

[0006] Carbon black is an example of a material used as a conductive material for secondary batteries. However, the carbon black produced by the method described in Patent Document 2, although highly pure, does not have excellent properties as a conductive material for secondary batteries.

[0007] Therefore, an object of the present invention is to provide carbon black that has an extremely low iron content and is suitable for use as a conductive material for secondary batteries. Another object of the present invention is to provide a method for producing the carbon black. Still another object of the present invention is to provide an electrode composition, an electrode, and a secondary battery that contain the carbon black. [Means for solving the problem]

[0008] One aspect of the present invention relates to carbon black having an oil absorption of 150 mL / 100 g or more and 400 mL / 100 g or less, and an iron content of 500 ppb or less as measured by high-frequency inductively coupled plasma mass spectrometry.

[0009] In one embodiment, the iron content may be 150 ppb or less.

[0010] The carbon black according to one embodiment has a BET specific surface area of ​​35 m 2 / g or more 400m 2 / g or less.

[0011] The carbon black according to one embodiment has a BET specific surface area of ​​130 m 2 / g or more 400m 2 / g or less, the oil absorption may be 200 mL / 100 g or more and 400 mL / 100 g or less, and the BET specific surface area may be S(m 2 When the oil absorption is A (mL / 100g), the ratio S / A may be 0.3 to 2.5.

[0012] In one embodiment, the ratio S / A may be 0.4 to 2.5.

[0013] In one embodiment, the ratio S / A may be 0.5 to 1.5.

[0014] The carbon black according to one embodiment may be acetylene black.

[0015] Another aspect of the present invention relates to a method for producing carbon black, including: a synthesis step of treating a raw material gas containing hydrocarbons in a cylindrical cracking furnace to obtain carbon black; and a purification step of removing magnetic foreign matter from the carbon black using a magnet to obtain the carbon black of the present invention.

[0016] In one aspect, the purification step may be a step of bringing the carbon black obtained in the synthesis step into contact with the magnet or placing the carbon black in the vicinity of the magnet to remove the magnetic foreign matter from the carbon black.

[0017] In one embodiment, the maximum surface magnetic flux density of the magnet may be 1000 mT or more.

[0018] Yet another aspect of the present invention relates to a composition for an electrode, comprising the carbon black according to the present invention and an active material capable of absorbing and desorbing lithium ions.

[0019] Yet another aspect of the present invention relates to an electrode comprising the above-mentioned electrode composition.

[0020] Yet another aspect of the present invention relates to a secondary battery including the above electrode. [Effects of the Invention]

[0021] The present invention provides carbon black having an extremely low iron content and suitable for use as a conductive material for secondary batteries. The present invention also provides a method for producing the carbon black. The present invention further provides an electrode composition, an electrode, and a secondary battery each containing the carbon black. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of a cylindrical cracking furnace. DETAILED DESCRIPTION OF THE INVENTION

[0023] Preferred embodiments of the present invention will now be described in detail.

[0024] (carbon black) The carbon black of this embodiment has an oil absorption of 150 mL / 100 g or more and 400 mL / 100 g or less, and an iron content of 500 ppb or less.

[0025] Such carbon black contains very little iron-based foreign matter, significantly reducing the occurrence of defects due to iron-based foreign matter. Furthermore, because the carbon black has sufficient oil absorption, when used as an electrode conductive material for a lithium secondary battery, for example, it easily retains electrolyte and efficiently supplies lithium ions to the active material. Furthermore, the carbon black has good dispersibility, allowing it to be uniformly dispersed, for example, among active materials. Therefore, the carbon black can realize a secondary battery with few defects and excellent battery performance.

[0026] The iron content of the carbon black is preferably 300 ppb or less, more preferably 150 ppb or less, even more preferably 100 ppb or less, and even more preferably less than 100 ppb.

[0027] In this embodiment, the iron content of carbon black is a value measured by inductively coupled plasma mass spectrometry. Specifically, the measurement by inductively coupled plasma mass spectrometry is carried out as follows.

[0028] <Measurement by inductively coupled plasma mass spectrometry> Approximately 1 g of carbon black sample was weighed into a quartz beaker and heated in an air atmosphere in an electric furnace at 800°C for 3 hours. Next, 10 mL of mixed acid (hydrochloric acid + nitric acid = 7:3) and 10 mL or more of ultrapure water were added to the residue, and the mixture was heated and dissolved on a hot plate at 200°C for 1 hour. After cooling, the solution was diluted to 25 mL with ultrapure water and analyzed using a high-frequency inductively coupled plasma mass spectrometer (Agilent 8800, manufactured by Agilent).

[0029] The carbon black of the present embodiment may be a carbon material having aggregates (primary agglomerates) in which primary particles having a diameter of several tens of nanometers are fused together in a beaded shape, and further having agglomerates (secondary agglomerates) in which the aggregates are physically entangled with each other.

[0030] The BET specific surface area of ​​carbon black is, for example, 35 m 2 / g or more, preferably 50m 2 / g or more, more preferably 100m 2 / g or more, more preferably 130m 2 / g or more, more preferably 150m 2 / g or more, more preferably 170m 2 / g or more. This increases the number of contact points between the active material and the current collector when used as an electrode conductive material for a lithium ion secondary battery, which tends to provide a better conductivity. In addition, the BET specific surface area of ​​the carbon black is, for example, 400 m 2 / g or less, and preferably 350m 2 / g or less. This suppresses interactions between primary particles and entanglement between aggregates, improving dispersibility and achieving, for example, more uniform dispersion among active materials. That is, the BET specific surface area of ​​carbon black is, for example, 35 to 400 m 2 / g, 35-350m 2 / g, 50-400m 2 / g, 50-350m 2 / g, 100-400m 2 / g, 100-350m 2 / g, 130-400m 2 / g, 130-350m 2 / g, 150-400m 2 / g, 150-350m 2 / g, 170-400m 2 / g or 170-350m 2 / g.

[0031] The BET specific surface area of ​​carbon black is measured by the single-point nitrogen adsorption method, Method B, described in JIS K 6217-2.

[0032] The oil absorption of carbon black is 150 mL / 100 g or more, preferably 180 mL / 100 g or more, more preferably 220 mL / 100 g or more, and even more preferably 260 mL / 100 g or more. 2 / g or more. This allows the carbon black to retain the electrolyte more easily, making it easier to supply lithium ions to the active material, and thus making it easier to obtain better battery performance, for example, when used as an electrode conductive material for a lithium-ion secondary battery. Furthermore, the oil absorption of the carbon black is 400 mL / 100 g or less, preferably 370 mL / 100 g or less, and more preferably 350 mL / 100 g or less. This reduces the entanglement of the agglomerates, improving dispersibility and achieving, for example, more uniform dispersion among the active material. That is, the oil absorption of the carbon black may be, for example, 150 to 400 mL / 100 g, 150 to 370 mL / 100 g, 150 to 350 mL / 100 g, 180 to 400 mL / 100 g, 180 to 370 mL / 100 g, 180 to 350 mL / 100 g, 220 to 400 mL / 100 g, 220 to 370 mL / 100 g, 220 to 350 mL / 100 g, 260 to 400 mL / 100 g, 260 to 370 mL / 100 g, or 260 to 350 mL / 100 g.

[0033] The oil absorption of carbon black is a value measured using DBP (dibutyl phthalate) as the oil according to the method described in JIS K6221, Method B, and converted into a value equivalent to JIS K6217-4:2008 using the following formula (a). DBP absorption amount = (A-10.974) / 0.7833 …(a) [In the formula, A represents the value of DBP absorption measured by the method described in JIS K6221, Method B.]

[0034] The BET specific surface area of ​​carbon black is S(m 2When the S / A ratio is A (mL / 100g) and the oil absorption is A (mL / 100g), the ratio S / A may be, for example, 0.2 or more, preferably 0.3 or more, more preferably 0.4 or more, and even more preferably 0.5 or more. The ratio S / A is, for example, 3.0 or less, preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.3 or less. This provides a more suitable balance between the number, size, and dispersibility of aggregates as an electrode conductive material for lithium-ion secondary batteries, making it easier to supply lithium ions to the active material while forming sufficient contact points between the active material and the current collector, and making it easier to obtain better battery performance. That is, the ratio S / A may be, for example, 0.2 to 3.0, 0.2 to 2.0, 0.2 to 1.5, 0.2 to 1.3, 0.3 to 3.0, 0.3 to 2.0, 0.3 to 1.5, 0.3 to 1.3, 0.4 to 3.0, 0.4 to 2.0, 0.4 to 1.5, 0.4 to 1.3, 0.5 to 3.0, 0.5 to 2.0, 0.5 to 1.5, or 0.5 to 1.3.

[0035] In a preferred embodiment, the carbon black has a BET specific surface area of ​​130 to 400 m 2 The carbon black may have a viscosity of 1000 MPa / g, an oil absorption of 200 to 400 mL / 100 g, and an S / A ratio of 0.3 to 2.5 (preferably 0.4 to 2.5, more preferably 0.5 to 2.5, and even more preferably 0.5 to 1.5). Such carbon black has excellent electron conductivity, ion conductivity, and dispersibility, and is therefore particularly suitable for use as a conductive material. Such carbon black may be produced, for example, by a method involving injection of oxygen gas, which will be described later.

[0036] In addition, within the ranges of the BET specific surface area and oil absorption capacity of this embodiment, the larger the ratio S / A, the more difficult it tends to be to remove magnetic foreign matter. By intentionally keeping the ratio S / A within the above range and reducing the iron content, the carbon black of this embodiment achieves both the excellent effect as a conductive material described above and the reduction of problems caused by magnetic foreign matter.

[0037] The carbon black in this embodiment is preferably acetylene black.

[0038] The carbon black of the present embodiment can be produced by the following method.

[0039] (Method of manufacturing carbon black) The method for producing carbon black according to the present embodiment includes a synthesis step of treating a hydrocarbon-containing raw material gas in a cylindrical cracking furnace to obtain carbon black, and a purification step of removing magnetic foreign matter from the carbon black obtained in the synthesis step using a magnet to obtain carbon black having an oil absorption of 150 mL / 100 g or more and 400 mL / 100 g or less and an iron content of 500 ppb or less.

[0040] In the synthesis step, the raw material gas is treated in a cylindrical cracking furnace. The cylindrical cracking furnace may include, for example, a thermal cracking section for carrying out a thermal cracking reaction of hydrocarbons and an aging section for reforming the thermal cracking reaction product.

[0041] The cylindrical cracking furnace may further include a supply port for supplying a raw material gas to the thermal cracking section, and a recovery port for recovering the carbon black produced from the aging section.

[0042] From the viewpoint of making the carbon black more homogenous and more efficiently removing magnetic foreign matter in the purification step described below, the cylindrical cracking furnace preferably has a ratio (D1 / D2) of the diameter D1 of the thermal separation section to the diameter D2 of the aging section of 1.2 to 2.2, and a ratio (L1 / L2) of the length L1 of the thermal cracking section to the length L2 of the aging section of 0.4 to 1.0. This allows the raw material gas supplied to the thermal cracking section to remain, thereby more reliably completing the thermal cracking reaction and forming a carbon aerosol through the development of aggregates.

[0043] The ratio (D1 / D2) is preferably 1.3 to 1.8, and the ratio (L1 / L2) is preferably 0.6 to 0.8. That is, the ratio (D1 / D2) may be, for example, 1.2 to 2.2, 1.3 to 2.2, 1.2 to 1.8, or 1.3 to 1.8, and the ratio (L1 / L2) may be, for example, 0.4 to 1.0, 0.6 to 1.0, 0.4 to 0.8, or 0.6 to 0.8.

[0044] In the thermal decomposition section, the supplied raw material gas preferably resides at a temperature of 1900°C or higher for 30 to 150 seconds. A residence time of 30 seconds or longer ensures the completion of the thermal decomposition reaction and the development of a chain structure to form a carbon aerosol. Furthermore, a residence time of 150 seconds or shorter suppresses the aggregation of the carbon aerosol, making it easier to obtain carbon black from which magnetic impurities can be more easily removed in the high-purity step described below.

[0045] In the aging section, the pyrolysis reaction product supplied from the pyrolysis section preferably resides at a temperature of 1700°C or higher for 20 to 90 seconds. A residence time of 20 seconds or longer modifies the carbon aerosol and strengthens the aggregates, making it easier to obtain higher quality carbon black. Furthermore, a residence time of 90 seconds or shorter suppresses the aggregation of the carbon aerosol, making it easier to obtain carbon black from which magnetic impurities can be more easily removed in the high-purity step described below.

[0046] The residence speeds in the pyrolysis section and the aging section can be appropriately adjusted by adjusting the linear velocity of the gas flowing through them. The residence time in the aging section is preferably shorter than the residence time in the pyrolysis section. That is, the linear velocity of the gas in the aging section is preferably higher than the linear velocity of the gas in the pyrolysis section.

[0047] Fig. 1 is a schematic cross-sectional view showing one embodiment of a cylindrical cracking furnace. The cylindrical cracking furnace 10 shown in Fig. 1 includes a thermal cracking section 1 and a maturation section 2. The cylindrical cracking furnace further includes a nozzle (supply port) 3 for supplying a raw material gas to the thermal cracking section 1.

[0048] In this embodiment, the source gas preferably contains acetylene as a first carbon source. The content of the carbon source (e.g., acetylene) in the source gas is, for example, 10% by volume or more, preferably 20% by volume or more, more preferably 30% by volume or more, and may be 100% by volume. The content of each component in the source gas is expressed as a volume ratio based on the volume at 150°C and 1 atmosphere.

[0049] The feed gas may further contain one or more other carbon sources in addition to the first carbon source (e.g., acetylene). Examples of other carbon sources include saturated hydrocarbons such as methane, ethane, and propane; unsaturated hydrocarbons such as ethylene, propylene, and butadiene; and aromatic hydrocarbons such as benzene, toluene, and xylene. By combining these carbon sources, the reaction temperature can be changed to increase or decrease the specific surface area of ​​the carbon black. The carbon source is preferably selected from the group consisting of unsaturated hydrocarbons such as acetylene, ethylene, and propylene, and aromatic hydrocarbons such as benzene and toluene. Petroleum fractions such as gasoline, kerosene, light oil, and heavy oil may also be used as the carbon source.

[0050] When the raw material gas contains acetylene and another carbon source, the ratio of the other carbon source to acetylene (volume of the other carbon source / volume of the acetylene) may be, for example, 0.01 or more. The ratio of the other carbon source to acetylene (volume of the other carbon source / volume of the acetylene) may be, for example, 99 or less, preferably 50 or less, more preferably 30, or may be 10 or less, or 2 or less. That is, the ratio (volume ratio) of the other hydrocarbon to acetylene may be, for example, 0.01 to 99, 0.01 to 50, 0.01 to 30, 0.01 to 10, or 0.01 to 2.

[0051] The raw material gas may further contain water vapor, oxygen, hydrogen, carbon dioxide, etc. These gases are preferably high-purity gases with a purity of 99.9% by volume or higher. The use of such high-purity gases tends to facilitate the production of carbon black with a low content of magnetic impurities and a stable BET specific surface area and oil absorption.

[0052] The content of the water vapor gas may be, for example, 0 to 80 parts by volume, preferably 0.1 to 70 parts by volume, more preferably 1 to 60 parts by volume, and even more preferably 3 to 55 parts by volume, relative to 100 parts by volume of the carbon source (e.g., acetylene) in the raw material gas. When the content of the water vapor gas is within the above range, the BET specific surface area of ​​the carbon black tends to be larger. That is, the content of the water vapor gas may be, for example, 0 to 80 parts by volume, 0 to 70 parts by volume, 0 to 60 parts by volume, 0 to 55 parts by volume, 0.1 to 80 parts by volume, 0.1 to 70 parts by volume, 0.1 to 60 parts by volume, 0.1 to 55 parts by volume, 1 to 80 parts by volume, 1 to 70 parts by volume, 1 to 60 parts by volume, 1 to 55 parts by volume, 3 to 80 parts by volume, 3 to 70 parts by volume, 3 to 60 parts by volume, or 3 to 55 parts by volume, relative to 100 parts by volume of the carbon source (e.g., acetylene) in the raw material gas.

[0053] In the synthesis process, it is preferable to supply oxygen gas to the pyrolysis section together with the raw material gas, and it is more preferable to supply oxygen gas to the pyrolysis section by spraying it from around the supply port through which the raw material gas is supplied to the pyrolysis section.

[0054] The cylindrical cracking furnace preferably has an oxygen gas injection port near the raw material gas supply port, and more preferably has a plurality of injection ports provided at equal intervals so as to surround the supply port. The number of injection ports is preferably 3 or more, more preferably 3 to 8.

[0055] The cylindrical cracking furnace may also be equipped with a nozzle having a multi-tube structure (e.g., a double-tube structure, a triple-tube structure, etc.) having a raw material gas supply port and an injection port for injecting oxygen gas from the periphery thereof. In the case of a double-tube structure, for example, the raw material gas may be injected from a gap on the inner tube side, and the oxygen gas may be injected from a gap on the outer tube side. In the case of a triple-tube structure consisting of an inner tube, a middle tube, and an outer tube, for example, the oxygen gas may be injected from a gap formed by the outer wall of the middle tube and the inner wall of the outer tube, and the raw material gas may be injected from the remaining gap.

[0056] The amount of oxygen gas injected is not particularly limited as long as the production yield of carbon black is not taken into consideration. Carbon black can be produced even if more oxygen gas than necessary is injected. From the viewpoint of obtaining carbon black having the above-mentioned suitable oil absorption, the amount of oxygen gas injected may be, for example, 0 to 200 parts by volume per 100 parts by volume of the carbon source (e.g., acetylene) in the raw material gas, and is preferably 0.1 to 190 parts by volume, more preferably 0.5 to 180 parts by volume, and even more preferably 1 to 160 parts by volume. That is, the injection amount of oxygen gas may be, for example, 0 to 200 parts by volume, 0 to 190 parts by volume, 0 to 180 parts by volume, 0 to 160 parts by volume, 0.1 to 200 parts by volume, 0.1 to 190 parts by volume, 0.1 to 180 parts by volume, 0.1 to 160 parts by volume, 0.5 to 200 parts by volume, 0.5 to 190 parts by volume, 0.5 to 180 parts by volume, 0.5 to 160 parts by volume, 1 to 200 parts by volume, 1 to 190 parts by volume, 1 to 180 parts by volume, or 1 to 160 parts by volume, relative to 100 parts by volume of the carbon source (e.g., acetylene) in the raw material gas.

[0057] In the synthesis step, the BET specific surface area and oil absorption capacity of the resulting carbon black can be increased or decreased by adjusting, for example, the addition rate of hydrocarbons other than acetylene, the amount of oxygen gas injected, etc.

[0058] The iron content in the carbon black obtained in the synthesis process may be, for example, greater than 500 ppb, 600 ppb or more, 700 ppb or more, or 800 ppb or more.

[0059] The purification step is a step of removing magnetic foreign matter from the carbon black obtained in the synthesis step using a magnet.

[0060] The purification step may be, for example, a step of removing magnetic foreign matter from the carbon black obtained in the synthesis step by bringing the carbon black into contact with a magnet or placing it near a magnet (e.g., passing it near a magnet).

[0061] There is no particular limitation on the magnet to be used, and for example, a magnet bar with a neodymium magnet packed inside a stainless steel 304 cylinder may be used.

[0062] The maximum surface magnetic flux density of the magnet is not particularly limited, but may be, for example, 700 mT or more, preferably 1000 mT or more, and more preferably 1200 mT or more. This allows fine magnetic foreign matter attached to the carbon black to be more strongly adsorbed, making it easier to obtain carbon black with a lower iron content. The upper limit of the maximum surface magnetic flux density of the magnet is not particularly limited, and may be, for example, 1400 mT or less. That is, the maximum surface magnetic flux density of the magnet may be, for example, 700 to 1400 mT, 1000 to 1400 mT, or 1200 to 1400 mT.

[0063] The purification step may be a step of removing magnetic foreign matter from the carbon black so that the iron content is 500 ppb or less (preferably 300 ppb or less, more preferably 100 ppb or less, and even more preferably 95 ppb or less). There is no particular lower limit for the iron content, but the iron content in the carbon black may be, for example, 1 ppb or more, and from the viewpoints of cost and productivity, it may be 10 ppb or more, 30 ppb or more, or 50 ppb or more. That is, the iron content in the carbon black may be, for example, 1 to 500 ppb, 1 to 300 ppb, 1 to 100 ppb, 1 to 95 ppb, 10 to 500 ppb, 10 to 300 ppb, 10 to 100 ppb, 10 to 95 ppb, 30 to 500 ppb, 30 to 300 ppb, 30 to 100 ppb, 30 to 95 ppb, 50 to 500 ppb, 50 to 300 ppb, 50 to 100 ppb, or 50 to 95 ppb.

[0064] (Application) The carbon black of this embodiment has a significantly low content of iron-based foreign matter and is therefore suitable for use as a conductive material for secondary batteries, a semiconductive layer for power cables, etc. Furthermore, the carbon black of this embodiment has an oil absorption amount within the above range and is therefore particularly suitable for use as a conductive material for secondary batteries.

[0065] The carbon black of this embodiment can be suitably used, for example, as an electrode composition containing carbon black and an active material capable of absorbing and releasing lithium ions. As the active material in the electrode composition, any known active material can be used without any particular limitation.

[0066] Examples of active materials include: Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), layered lithium manganese oxide (LiMnO2), and LiMn, a composite oxide containing multiple transition metals. x Ni y Co z Layered compounds such as O2 (x+y+z=1, 0≦y<1, 0≦z<1, 0≦x<1); Li 1+x Mn 2-x O4 (x is 0 to 0.33), Li 1+x Mn 2-x-y M y O4 (M represents at least one metal selected from the group consisting of Ni, Co, Cr, Cu, Fe, Al, and Mg, x represents 0 to 0.33, and y represents 0 to 1.0, with the proviso that 2-xy>0), LiMnO3, LiMn2O3, LiMnO2, LiMn 2-x M x manganese-based compounds such as O2 (M represents at least one metal selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and x represents 0.01 to 0.1), Li2Mn3MO8 (M represents at least one metal selected from Co, Ni, Fe, Cr, and Zn); Copper-lithium oxide (Li2CuO2); Iron-lithium oxide (LiFe3O4); Olivine compounds such as LiFePO4, LiMnPO4, LiMnFePO4, and Li2MPO4F (M represents at least one metal selected from the group consisting of Co, Ni, Fe, Cr, and Zn); Vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; Disulfide compounds; Silicate compounds such as Li2MSiO4 (M represents at least one metal selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta); Examples include Li2MO3·LiMO2 (M represents at least one metal selected from the group consisting of Mn, Co, Ni, Fe, Cr, and Zn), Fe2(MoO4)3, Li2S, and S.

[0067] The secondary battery of this embodiment includes an electrode containing the above-described electrode composition. In the secondary battery of this embodiment, the positive electrode and / or negative electrode may contain the above-described electrode composition, and it is preferable that the positive electrode contains the above-described electrode composition.

[0068] In the secondary battery of this embodiment, the electrode that does not contain the electrode composition and the configuration other than the electrode are not particularly limited, and electrodes and configurations in known secondary batteries can be used without particular limitations.

[0069] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. [Example]

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0071] Example 1 The feedstock gas mixture, consisting of 86% acetylene gas and 14% other carbon source (toluene gas), was sprayed from a nozzle installed at the top of a cylindrical cracking furnace at a velocity of 6.5 m / s. Carbon black was produced by the thermal decomposition and / or combustion reaction of the acetylene gas. The carbon black was collected in an intermediate tank through a bag filter directly connected to the bottom of the furnace. (Synthesis process) The collected carbon black was passed through a transfer pipe equipped with an iron collection magnet (a 20 mm diameter, 300 mm long stainless steel 304 tube containing a neodymium magnet, with a maximum surface magnetic flux density of 1000 mT) and collected in a product tank (purification process), yielding carbon black (CB1). The resulting CB1 was used to prepare conductive electrode compositions and battery electrodes as described below, and various evaluations were performed. The evaluation results are shown in Table 1.

[0072] Example 2 Carbon black (CB2) was obtained in the same manner as in Example 1, except that the raw material gas mixture ratio was changed to 100% by volume of acetylene gas. The obtained CB2 was used to prepare a conductive composition for electrodes and a battery electrode, and various evaluations were performed. The evaluation results are shown in Table 1.

[0073] Example 3 Carbon black (CB3) was obtained in the same manner as in Example 1, except that the mixture ratio of the raw material gases was changed to 71% by volume of acetylene gas, 15% by volume of oxygen gas, 12% by volume of water vapor, and 2% by volume of another carbon source (toluene gas). A conductive composition for electrodes and a battery electrode were prepared using the obtained CB3, and various evaluations were carried out. The evaluation results are shown in Table 1.

[0074] Example 4 Carbon black (CB4) was obtained in the same manner as in Example 1, except that the raw material gas mixture ratio was changed to 69% by volume of acetylene gas, 8% by volume of oxygen gas, 13% by volume of water vapor, and 10% by volume of another carbon source (toluene gas). Using the obtained CB4, a conductive composition for electrodes and a battery electrode were produced, and various evaluations were carried out. The evaluation results are shown in Table 1.

[0075] Example 5 Carbon black (CB5) was obtained in the same manner as in Example 1, except that the raw material gas mixture ratio was changed to 67% by volume of acetylene gas, 3% by volume of oxygen gas, 15% by volume of water vapor, and 15% by volume of another carbon source (benzene gas). Using the obtained CB5, a conductive composition for electrodes and a battery electrode were produced, and each evaluation was carried out. The evaluation results are shown in Table 1.

[0076] Example 6 Carbon black (CB6) was obtained in the same manner as in Example 1, except that the mixture ratio of the raw material gases was changed to 51% by volume of acetylene gas, 27% by volume of oxygen gas, 20% by volume of water vapor, and 2% by volume of another carbon source (toluene gas). A conductive composition for electrodes and a battery electrode were prepared using the obtained CB6, and various evaluations were carried out. The evaluation results are shown in Table 1.

[0077] (Comparative Example 1) Carbon black (CB7) was obtained in the same manner as in Example 1, except that the mixture ratio of the raw material gases was changed to 71% by volume of acetylene gas, 15% by volume of oxygen gas, 12% by volume of water vapor, and 2% by volume of another carbon source (toluene gas), and samples were collected from the intermediate tank without undergoing the high-purification process. The obtained CB7 was used to prepare a conductive composition for electrodes and a battery electrode, and various evaluations were performed. The evaluation results are shown in Table 1.

[0078] (Comparative Example 2) Carbon black (CB8) was obtained in the same manner as in Example 1, except that the mixture ratio of the raw material gases was changed to 67% by volume of acetylene gas, 3% by volume of oxygen gas, 15% by volume of water vapor, and 15% by volume of another carbon source (benzene gas), and samples were collected from the intermediate tank without undergoing the high-purification process. The obtained CB8 was used to prepare a conductive composition for electrodes and a battery electrode, and various evaluations were performed. The evaluation results are shown in Table 1.

[0079] (Comparative Example 3) As the carbon black of Comparative Example 3, SUPER P Li (manufactured by IMERYS Graphite & Carbon Co., Ltd., trade name: SUPER P Li) was prepared.

[0080] Comparative Example 4 As the carbon black of Comparative Example 4, ECP (manufactured by Lion Specialty Chemicals, trade name: Carbon ECP) ​​was prepared.

[0081] <Evaluation method> (Measurement of iron content) Approximately 1 g of carbon black sample was weighed into a quartz beaker and heated in an air atmosphere in an electric furnace at 800°C for 3 hours. Next, 10 mL of mixed acid (hydrochloric acid + nitric acid = 7:3) and 10 mL or more of ultrapure water were added to the residue, and the mixture was heated and dissolved on a hot plate at 200°C for 1 hour. After cooling, the solution was diluted to 25 mL with ultrapure water, and the iron content was measured using a high-frequency inductively coupled plasma mass spectrometer (Agilent 8800, manufactured by Agilent).

[0082] (BET specific surface area measurement) The BET specific surface area of ​​carbon black was measured by the BET single-point method in accordance with JIS K 6217-2 B method, using nitrogen as the adsorption gas under the condition of a relative pressure p / p0 = 0.30 ± 0.04.

[0083] (Oil absorption measurement) The oil absorption of carbon black is a value measured using DBP (dibutyl phthalate) as the oil according to the method described in JIS K6221, Method B, and converted into a value equivalent to JIS K6217-4:2008 using the following formula (a). DBP absorption amount = (A-10.974) / 0.7833 …(a) [In the formula, A represents the value of DBP absorption measured by the method described in JIS K6221, Method B.]

[0084] (Preparation of dispersion of electrode composition) The solvent was N-methyl-2-pyrrolidone (manufactured by Kanto Chemical Co., Ltd., hereafter referred to as NMP), and the active material was LiNi 0.5 Mn 0.3 Co 0.2O2 (manufactured by Umicore, trade name: TX10), polyvinylidene fluoride (manufactured by Arkema, trade name: HSV900, hereinafter referred to as PVdF) as a binder, carbon black from the examples or comparative examples as a conductive material, and polyvinyl alcohol (manufactured by Denka, trade name: B05, hereinafter referred to as polyvinyl alcohol) as a dispersant were prepared. 0.5 Mn 0.3 Co 0.2 O2 was weighed out and mixed to a solid content of 98 mass %, PVdF to a solid content of 2 mass %, carbon black to a solid content of 1 mass %, and polyvinyl alcohol to a solid content of 0.1 mass %, and NMP was added to this mixture so that the solid content was 68 mass %. The mixture was mixed until homogeneous using a planetary centrifugal mixer (Thinky Corporation, Awatori Rentaro ARV-310), to obtain a dispersion of an electrode composition (positive electrode composition).

[0085] (Preparation of positive electrode) The prepared electrode composition dispersion was applied to a 15 μm thick aluminum foil (manufactured by UACJ Corporation) using an applicator, and then pre-dried in a dryer at 105 ° C for one hour. The film was then pressed with a roll press at a linear pressure of 200 kg / cm, resulting in a film containing the 15 μm thick aluminum foil with a thickness of 80 μm. To remove volatile components, the film was vacuum dried at 170 ° C for three hours to obtain a positive electrode.

[0086] (Electrode evaluation) The prepared positive electrode was cut into a disk shape with a diameter of 14 mm, and the front and back were sandwiched between flat electrodes made of SUS304. Using an electrochemical measurement system (Solatron, Function Generator 1260 and Potentiogalvanostat 1287), AC impedance was measured at an amplitude voltage of 10 mV and a frequency range of 0.1 Hz to 1 MHz, and the intersection with the X-axis of the Cole-Cole plot was taken as the resistance value.

[0087] The evaluation results of the Examples and Comparative Examples are shown in Table 1. In Table 1, the mixing ratio of "hydrocarbon gas" means the mixing ratio of other carbon sources.

[0088] [Table 1] [Explanation of symbols]

[0089] 1...thermal cracking section, 2...aging section, 3...nozzle, 10...cylindrical cracking furnace.

Claims

1. a synthesis step of treating a hydrocarbon-containing raw material gas in a cylindrical cracking furnace to obtain carbon black; a purification step of removing magnetic foreign matter from the carbon black using a magnet to obtain carbon black having an oil absorption of 150 mL / 100 g or more and 400 mL / 100 g or less and an iron content of 500 ppb or less as measured by high-frequency inductively coupled plasma mass spectrometry; A method for producing carbon black, comprising:

2. 2. The production method according to claim 1, wherein the purification step is a step of bringing the carbon black obtained in the synthesis step into contact with the magnet or arranging the carbon black in the vicinity of the magnet to remove the magnetic foreign matter from the carbon black.

3. The manufacturing method according to claim 1 or 2, wherein the maximum surface magnetic flux density of the magnet is 1000 mT or more.

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