Carbon black, slurry, coating liquid for forming positive electrode, positive electrode composition, positive electrode, and battery

Abstract

To provide carbon black capable of forming a positive electrode having good conductivity even with a low addition amount.SOLUTION: Wherein a pore volume of pores having a pore diameter of 2 to 10 nm is 0.15cm3 / g or more and 1.1cm3 / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to carbon black, a slurry, a coating liquid for forming a positive electrode, a positive electrode composition, a positive electrode, and a battery. [Background technology]

[0002] In response to growing environmental and energy issues, there has been active development of technologies aimed at realizing a low-carbon society that reduces dependence on fossil fuels. Such technological development is wide-ranging, and includes the development of low-pollution vehicles such as hybrid electric vehicles and electric vehicles, natural energy generation and storage systems such as solar and wind power generation, and next-generation power transmission networks that supply electricity efficiently and reduce transmission losses.

[0003] Batteries are one of the key devices required for these technologies, and they are required to have high energy density to miniaturize the systems. They also need high output characteristics to enable stable power supply regardless of the ambient temperature. Furthermore, they also need good cycle characteristics to withstand long-term use. Therefore, conventional lead-acid batteries, nickel-cadmium batteries, and nickel-metal hydride batteries are rapidly being replaced by lithium-ion secondary batteries, which have higher energy density, output characteristics, and cycle characteristics.

[0004] Conventionally, the positive electrode of a lithium-ion secondary battery is manufactured by coating a current collector with a positive electrode paste containing a positive electrode active material, a conductive material, and a binding material (also called a binder). Lithium-containing composite oxides such as lithium cobalt oxide and lithium manganese oxide have been used as the positive electrode active material. Furthermore, because the positive electrode active material has poor conductivity, a conductive material such as carbon black has been added to the positive electrode paste to impart conductivity (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-227481 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been a demand for further improvements in the performance of lithium-ion secondary batteries.

[0007] Increasing the content of active material in the positive electrode of a lithium-ion secondary battery can be considered as a way to improve the battery capacity, but increasing the content of active material reduces the content of conductive material, which can make it difficult to ensure sufficient conductivity.

[0008] The present disclosure aims to provide a carbon black capable of forming a positive electrode having good conductivity even at a low addition amount. The present disclosure also aims to provide a slurry, a coating liquid for forming a positive electrode, and a positive electrode composition containing the carbon black, which are useful for forming a lithium-ion secondary battery. The present disclosure also aims to provide a positive electrode and a battery containing the carbon black. [Means for solving the problem]

[0009] The present disclosure relates to, for example, the following [1] to

[11] . [1] The pore volume of pores with a diameter of 2 to 10 nm is 0.15 cm 3 / g or more 1.10cm 3 / g or less of carbon black. [2] BET specific surface area is 290m 2 / g or more 1300m 2 / g or less. [3] Average primary particle diameter D p The carbon black according to [1] or [2], wherein the average particle size is 12 nm or more and 27 nm or less. [4] Structure length D aggThe carbon black according to any one of [1] to [3], wherein the average particle diameter is 180 nm or more. [5] A slurry comprising the carbon black according to any one of [1] to [4] and a liquid medium. [6] A coating liquid for forming a positive electrode, comprising the carbon black according to any one of [1] to [4], an active material, a binder, and a liquid medium. [7] The coating liquid for forming a positive electrode according to [6], wherein the carbon black content is less than 1 mass % based on the total amount of solids. [8] A positive electrode composition comprising the carbon black according to any one of [1] to [4], an active material, and a binder. [9] The positive electrode composition according to [8], wherein the carbon black content is less than 1% by mass.

[10] a current collector; and a composite layer disposed on the current collector; The positive electrode, wherein the mixture layer contains the positive electrode composition according to [8] or [9].

[11] A battery comprising the positive electrode according to

[10] . [Effects of the Invention]

[0010] The present disclosure provides carbon black capable of forming a positive electrode having good conductivity even in a small amount. The present disclosure also provides a slurry, a coating liquid for forming a positive electrode, and a positive electrode composition containing the carbon black, which are useful for forming a lithium-ion secondary battery. The present disclosure also provides a positive electrode and a battery containing the carbon black. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present disclosure will be described in detail below.

[0012] (carbon black) The carbon black of this embodiment has a pore volume of pores having a pore diameter of 2 to 10 nm of 0.15 cm3 / g or more 1.10cm 3 / g or less.

[0013] The carbon black of this embodiment has a larger pore volume than ordinary carbon black, sufficient voids inside the particles, is lightweight, and has a large number of particles per unit weight. Therefore, even when the carbon black of this embodiment is added in a small amount (for example, when the content in the positive electrode composition is less than 1% by mass), it can efficiently form a conductive path in the positive electrode composition, thereby forming a positive electrode with good conductivity.

[0014] The pore volume is 0.15 cm 3 / g or more, and 0.16 cm 3 / g or more, 0.17cm 3 / g or more, 0.18cm 3 / g or more, 0.19cm 3 / g or more, or 0.2cm 3 / g or more. When the pore volume is large, the carbon black becomes lighter, the number of particles per unit weight increases, and the above-mentioned effects are more pronounced.

[0015] The pore volume is 1.10 cm 3 / g or less, and 1.05 cm 3 / g or less, 1.00cm 3 / g or less, or 0.95cm 3 / g or less. If the pore volume is too large, the dispersant will enter the pores, causing a decrease in dispersibility. By adjusting the pore volume appropriately, both weight reduction and good dispersibility of the carbon black can be achieved.

[0016] The pore volume is a value measured by the following method. <Measurement of pore volume> The pore volume is measured using a specific surface area / pore distribution measuring device (BELSORP MINI X manufactured by MicroTracBEL) with nitrogen gas as the adsorbate at a measurement temperature of 77.35 K by the BJH method in the analysis range of 2 to 10 nm.

[0017] The BET specific surface area of ​​carbon black is, for example, 290 m 2 / g or more, and from the viewpoint of easily obtaining better conductivity, 292m 2 / g or more, 294m 2 / g or more, or 300m 2 The BET specific surface area of ​​the carbon black may be, for example, 1300 m / g or more. 2 / g or less, and from the viewpoint of being easily dispersed more uniformly around the active material, 2 / g or less, 1260m 2 / g or less, or 1250m 2 / g or less.

[0018] The BET specific surface area of ​​carbon black is measured using nitrogen as an adsorbate according to a method in accordance with JIS Z8830.

[0019] Average primary particle diameter of carbon black D p The average primary particle diameter D of the carbon black may be, for example, 12 nm or more, and from the viewpoint of increasing the number of electrical contacts with the active material and the current collector and easily achieving a better conductivity-imparting effect, it may be 13 nm or more, 14 nm or more, or 15 nm or more. p The particle size may be, for example, 27 nm or less, and from the viewpoint that the interparticle interaction between carbon black particles is reduced and better dispersibility is more easily obtained, it may be 26 nm or less or 25 nm or less.

[0020] Average primary particle diameter of carbon black D p is calculated from an SEM image acquired using the pretreatment method described in ASTM D3849-14a by the method specified in ASTM D3849-14a.

[0021] Carbon black structure length D agg may be, for example, 180 nm or more, 230 nm or more, 250 nm or more, or 280 nm or more. aggThe particle diameter may be, for example, 360 nm or less, and from the viewpoint of reducing the interparticle interaction between carbon black particles and making it easier to obtain better dispersibility, the particle diameter may be 350 nm or less, 340 nm or less, or 330 nm or less.

[0022] The carbon black structure is defined as the structure (agglomerates) of carbon black primary particles that are fused at contact points and cannot be easily separated by shear. The carbon black structure length D agg indicates the average particle size of the structure.

[0023] Carbon black structure length D agg is calculated from an SEM image acquired using the pretreatment method described in ASTM D3849-14a by the Feret diameter calculation method specified in ISO 9276-6.

[0024] The carbon black of this embodiment is, for example, 500 m 2 / g or more 1500m 2 / g or less BET specific surface area, and an average primary particle diameter D of 16 nm to 25 nm p , structure length (average aggregate diameter) D of 180 nm or more agg Such carbon black may have a large specific surface area and an average primary particle diameter D p is small, and the structure length D agg Because the carbon black has a long length, it can easily penetrate between particles of the active material and easily become entangled with the particles of the active material to form a suitable conductive path. Therefore, the above-mentioned effects are more pronounced with such carbon black.

[0025] The carbon black may be, for example, acetylene black, furnace black, channel black, etc., and from the viewpoint of obtaining the above-mentioned effects more significantly, acetylene black may be used.

[0026] Carbon black may be produced, for example, by the following method.

[0027] (Method of manufacturing carbon black) The method for producing carbon black according to the present embodiment may include, for example, a first step of reacting a raw material gas in a reactor to obtain a precursor, and a second step of activating the precursor obtained in the first step to obtain carbon black.

[0028] In the first step, carbon black is formed by a thermal decomposition reaction and / or a combustion reaction of a raw material gas. In the second step, the carbon black (precursor) obtained in the first step is activated to make it porous, thereby forming the carbon black of this embodiment. By appropriately adjusting the conditions for the activation treatment, the pore volume can be adjusted to a predetermined range.

[0029] The first step may be carried out, for example, by supplying a raw material gas from a nozzle installed at the top of a vertical reactor and collecting carbon nanotubes with a bag filter directly connected to the bottom of the reactor.

[0030] In the first step, the raw material gas may be, for example, acetylene gas.

[0031] In the first step, an oxygen-containing gas may be supplied to the reactor, and the oxygen-containing gas may be air, oxygen gas, or the like.

[0032] In the first step, water vapor may be supplied into the reactor. In particular, when acetylene gas is used as the raw material gas, supplying water vapor tends to cause incomplete combustion of the acetylene gas, resulting in a higher specific surface area. Furthermore, if the amount of water vapor supplied is too large, the formation of a structure due to fusion of carbon black particles may be inhibited. However, by adjusting the amount of water vapor supplied, the structure length D described above can be reduced. agg In other words, increasing the amount of water vapor tends to increase the BET specific surface area of ​​carbon black, and decreasing the amount of water vapor tends to decrease the structure length D agg tends to be larger.

[0033] The ratio (volume ratio) of the amount of water vapor supplied to the amount of raw material gas supplied may be, for example, 0 to 95 parts by volume, preferably 0.1 to 90 parts by volume, more preferably 3 to 90 parts by volume, and even more preferably 10 to 90 parts by volume, per 100 parts by volume of the carbon source (e.g., acetylene) in the raw material gas. When the content of water vapor gas is within the above range, the BET specific surface area of ​​the carbon black tends to be larger.

[0034] In the first step, a hydrocarbon gas other than the raw material gas may be further supplied to the reactor. Examples of the hydrocarbon gas include methane, ethane, propane, ethylene, propylene, butadiene, benzene, toluene, xylene, gasoline, kerosene, light oil, and heavy oil. The addition of such a hydrocarbon gas can change the reaction temperature and thereby increase or decrease the specific surface area of ​​the carbon black.

[0035] The activation treatment in the second step may be, for example, a dry method using an oxidizing gas such as air or ozone or water vapor, or a wet method using an aqueous solution containing an oxidizing agent.

[0036] The dry method may be, for example, a method in which carbon black is brought into contact with an oxidizing gas or water vapor in a high-temperature environment (for example, 500°C or higher when an oxidizing gas is used, or 750°C or higher when water vapor is used).

[0037] The dry method may be carried out, for example, by placing carbon black (precursor) inside a horizontal furnace maintained at a high temperature and introducing an oxidizing gas or water vapor into the horizontal furnace.

[0038] In the dry method, the pore volume can be adjusted to a predetermined range by appropriately adjusting the temperature conditions, treatment time, and the amount of gas (oxidizing gas or water vapor) introduced.

[0039] The wet method can be carried out by, for example, adding carbon black (precursor) to an aqueous solution containing an oxidizing agent, treating it at 50 to 120° C. for 5 to 30 hours, and then washing and drying it. Examples of the oxidizing agent that can be used include inorganic acids such as hydrogen peroxide, hydrogen chloride, sulfuric acid, and nitric acid, and salts such as aqueous sodium hypochlorite and aqueous potassium dichromate solutions.

[0040] In the wet method, the pore volume can be adjusted to a predetermined range by appropriately adjusting the temperature conditions, treatment time, and oxidizing agent concentration.

[0041] When the activation treatment conditions are made stricter, the pore volume of the carbon black increases, the BET specific surface area increases, and the average primary particle diameter D p becomes smaller, and the structure length D agg tends to be shorter.

[0042] In this embodiment, the BET specific surface area and average primary particle diameter D p , and structure length D agg may be adjusted by controlling the shape of the reactor in the first step, the temperature distribution inside the reactor, etc., or by supplying water vapor into the reactor, or by adjusting the activation treatment conditions in the second step.

[0043] (slurry) The slurry of this embodiment contains the carbon black of the above embodiment and a liquid medium. The slurry of this embodiment may further contain a dispersant.

[0044] The slurry of this embodiment can be suitably used as a raw material for forming a coating liquid for forming a positive electrode by mixing it with an active material and a binder.

[0045] The carbon black content in the slurry is not particularly limited and may be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 7% by mass or more. A high carbon black content makes it easier to prepare a coating liquid for forming a positive electrode with a high solids concentration. Furthermore, the carbon black content in the slurry may be, for example, 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less. A low carbon black content makes it easier to prepare a coating liquid for forming a positive electrode with a low viscosity.

[0046] The liquid medium may be any liquid medium capable of dispersing carbon black. Examples of liquid media include water, N-methyl-2-pyrrolidone, cyclohexane, methyl ethyl ketone, and methyl isobutyl ketone. Among these, N-methyl-2-pyrrolidone is preferred from the viewpoint of easy dispersibility of carbon black. In this specification, N-methyl-2-pyrrolidone may be abbreviated as "NMP."

[0047] The dispersant may be any component that has the function of assisting the dispersion of carbon black in a liquid medium. The dispersant may also be referred to as a dispersant for dispersing carbon black in a liquid medium, a dispersant for carbon black, or the like.

[0048] Examples of the dispersant include polymeric dispersants and low molecular weight dispersants, and from the viewpoint of long-term dispersion stability of carbon black, polymeric dispersants are preferred.

[0049] The polymer dispersant may be any polymer that functions as a dispersant. Examples of polymer dispersants include vinyl polymers having polar groups, carboxymethyl cellulose, and salts thereof. Such polymer dispersants are preferred because they have high affinity with both carbon black and the liquid medium and have excellent functionality as a dispersant.

[0050] Examples of polar groups include hydroxyl groups, acetyl groups, amino groups, amide groups, acetal groups, oxycarbonyl groups, and nitrile groups. The vinyl polymer preferably has at least one polar group selected from the group consisting of hydroxyl groups, acetyl groups, amino groups, and oxycarbonyl groups, and more preferably has a hydroxyl group. The hydroxyl group is preferred from the viewpoints of excellent voltage resistance and resistance to decomposition even after repeated charge and discharge.

[0051] Examples of vinyl polymers having a polar group include polyvinyl alcohol, polyvinyl acetal (e.g., polyvinyl butyral, polyvinyl formal, etc.), polyvinyl pyrrolidone, polyvinyl amine, polyvinyl acetate, polyacrylonitrile, etc. Among these, polyvinyl alcohol and polyvinyl pyrrolidone are preferred from the viewpoints of high solubility in NMP and high adsorption to carbon black, and polyvinyl alcohol is more preferred from the viewpoints of excellent voltage resistance and having hydroxy groups that are not easily decomposed even after repeated charge and discharge.

[0052] The content of the dispersant in the slurry may be, for example, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, or 7 parts by mass or more, relative to 100 parts by mass of carbon black. A high content of the dispersant tends to make it easier for the carbon black to be dispersed more uniformly, and to obtain better battery characteristics. The content of the dispersant in the slurry may be, for example, 30 parts by mass or less, 25 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less, relative to 100 parts by mass of carbon black. A low content of the dispersant tends to reduce the insulating component in the positive electrode composition, making it easier to obtain better conductivity.

[0053] The slurry of the present embodiment may further contain components other than the carbon black, the liquid medium, and the dispersant, such as carbon nanotubes, graphite, graphene, a binder, a dispersion stabilizer, and a defoaming agent.

[0054] The content of other components may be, for example, 50 parts by mass or less, 45 parts by mass or less, 40 parts by mass or less, or 35 parts by mass or less, relative to 100 parts by mass of carbon black, or may be 0% by mass.

[0055] The slurry of this embodiment can be produced by mixing carbon black with a liquid medium (and further with a dispersant, if necessary).

[0056] The mixing method is not limited, and may be carried out by a known method (for example, stirring and mixing using a bead mill, ball mill, sand mill, twin-screw kneader, planetary mixer, disper mixer, etc.). These methods and devices may also be used in appropriate combination.

[0057] (Coating liquid for positive electrode formation) The coating liquid for forming a positive electrode of this embodiment contains the carbon black of the above embodiment, a liquid medium, an active material, and a binder. The coating liquid for forming a positive electrode of this embodiment may further contain a dispersant.

[0058] The positive electrode-forming coating liquid of this embodiment can be applied to a current collector and dried to form a composite layer on the current collector. The current collector and the composite layer disposed on the current collector can be suitably used as a positive electrode, particularly as a positive electrode for a lithium-ion secondary battery.

[0059] In the coating liquid for forming a positive electrode of this embodiment, examples of the liquid medium and dispersant are the same as those mentioned above.

[0060] The active material (positive electrode active material) is not particularly limited as long as it is a material that can reversibly store and release cations. 4 The lithium-containing composite oxide containing manganese may have a resistivity of Ω·cm or more, or may be a lithium-containing polyanion compound. Examples of the lithium-containing composite oxide containing manganese include LiMnO2, LiMnO3, LiMn2O3, and Li 1+x Mn 2-x Lithium manganese oxide such as O4 (where x = 0 to 0.33); LiMnx Ni y Co z O2 (x+y+z=1, 0≦y<1, 0≦z<1, 0≦x<1), Li 1+x Mn 2-x-y M y O4 (where x = 0 to 0.33, y = 0 to 1.0, 2-xy>0), LiMn 2-x M x Examples of the lithium-containing polyanion compounds include polyanion compounds such as LiFePO4, LiMnPO4, and Li2MPO4F (where M is at least one metal selected from Co, Ni, Fe, Cr, and Zn). In each composition formula, M is at least one metal selected from the group consisting of Fe, Co, Ni, Al, Cu, Mg, Cr, Zn, and Ta.

[0061] Average particle diameter of the active material (D 50 ) may be, for example, 3 μm or more, and from the viewpoint of obtaining the above-mentioned effect of carbon black more significantly, it may be 5 μm or more, 10 μm or more, or 20 μm or more. 50 ) may be, for example, 45 μm or less, and from the viewpoint of more significantly obtaining the above-mentioned effects of carbon black, it may be 40 μm or less, 35 μm or less, or 30 μm or less.

[0062] Average particle diameter of the active material (D 50 ) is measured by laser light scattering.

[0063] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene copolymer, (meth)acrylic acid ester copolymer, etc. The polymer structure of the binder may be, for example, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, etc. As the binder, polyvinylidene fluoride is preferred from the viewpoint of excellent voltage resistance.

[0064] The carbon black content in the positive electrode-forming coating liquid may be, for example, 0.01% by mass or more, based on the total amount of solids, and from the viewpoint of obtaining higher conductivity, may be 0.05% by mass or more, 0.1% by mass or more, 0.3% by mass or more, or 0.5% by mass or more. The carbon black content in the positive electrode-forming coating liquid may be, for example, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, based on the total amount of solids, and from the viewpoint of achieving sufficiently high conductivity with a small amount added, may be less than 1% by mass, 0.9% by mass or less, or 0.8% by mass or less.

[0065] The content of the active material in the coating liquid for forming a positive electrode may be, for example, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, or 98% by mass or more, based on the total amount of solids. In this embodiment, since the above-mentioned carbon black is used, sufficiently high conductivity is achieved even when the amount of carbon black added is reduced and the content of the active material is increased. The content of the active material in the coating liquid for forming a positive electrode may be, for example, 99.9% by mass or more, based on the total amount of solids, or 99.7% by mass or less, 99.5% by mass or less, 99.3% by mass or less, or 99% by mass or less.

[0066] The content of the binder in the coating liquid for forming a positive electrode may be, for example, 0.1% by mass or more based on the total amount of solids, and from the viewpoint of further improving the binding property of the composite layer and further improving battery performance, it may be 0.2% by mass or more, 0.3% by mass or more, 0.4% by mass or more, or 0.5% by mass or more. Furthermore, the content of the binder in the coating liquid for forming a positive electrode may be, for example, 10% by mass or less based on the total amount of solids, and from the viewpoint of easily obtaining higher conductivity, it may be 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1.5% by mass or less.

[0067] When the positive electrode-forming coating liquid contains a dispersant, the content of the dispersant in the positive electrode-forming coating liquid may be, for example, 1 part by mass or more, or may be 3 parts by mass or more, 5 parts by mass or more, or 7 parts by mass or more, relative to 100 parts by mass of carbon black. Furthermore, the content of the dispersant in the positive electrode-forming coating liquid may be, for example, 30 parts by mass or less, or may be 25 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less, relative to 100 parts by mass of carbon black.

[0068] The solids concentration of the coating liquid for forming a positive electrode is not particularly limited, and may be any solids concentration that allows for the formation of a composite layer, i.e., the viscosity that allows for coating on a current collector. The solids concentration of the coating liquid for forming a positive electrode may be, for example, 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more. The solids concentration of the coating liquid for forming a positive electrode may be, for example, 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less.

[0069] The solid content of the coating liquid for forming a positive electrode may be, for example, the remainder after removing the liquid medium from the coating liquid for forming a positive electrode, and includes carbon black, an active material, and a binder.

[0070] The coating liquid for forming a positive electrode of this embodiment may be prepared by, for example, mixing the slurry of the above embodiment, a binder-containing solution, and an active material, or by mixing the slurry of the above embodiment with the binder-containing solution and then further mixing the active material. Furthermore, the viscosity may be adjusted by adding a liquid medium after mixing the active material.

[0071] The binder-containing solution may contain a binder and a solvent, and examples of the solvent include the same liquid medium as in the slurry of the above embodiment.

[0072] The solids concentration of the binder-containing solution is not particularly limited and may be, for example, 0.3% by mass or more, and from the viewpoint of further improving the binding strength of the positive electrode plate and further improving the cycle characteristics, it may be 0.5% by mass or more, 1.0% by mass or more, or 1.5% by mass or more. The binder content may be, for example, 5.0% by mass or less based on the total mass of the solids in the positive electrode composition, and from the viewpoint of further reducing the resistance of the positive electrode plate and further improving the discharge rate characteristics, it may be 4.5% by mass or less, 4.0% by mass or less, or 3.5% by mass or less.

[0073] (Positive electrode composition) The positive electrode composition of this embodiment contains the carbon black of the above embodiment, an active material, and a binder. The positive electrode composition of this embodiment may further contain a dispersant.

[0074] The positive electrode composition of the present embodiment may be a composition constituting a composite layer disposed on a current collector. A positive electrode including a composite layer made of the positive electrode composition of the present embodiment can be suitably used as a positive electrode for a lithium-ion secondary battery.

[0075] In the positive electrode composition of this embodiment, examples of the active material, binder, and dispersant are the same as those described above.

[0076] The carbon black content in the positive electrode composition may be, for example, 0.01% by mass or more, and from the viewpoint of obtaining higher conductivity, may be 0.05% by mass or more, 0.1% by mass or more, 0.3% by mass or more, or 0.5% by mass or more. The carbon black content in the positive electrode composition may be, for example, 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less, and from the viewpoint of achieving sufficiently high conductivity with a small amount added, may be less than 1% by mass, 0.9% by mass or less, or 0.8% by mass or less.

[0077] The content of the active material in the positive electrode composition may be, for example, 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, or 98% by mass or more. In this embodiment, since the above-mentioned carbon black is used, even if the amount of carbon black added is reduced and the content of the active material is increased, sufficiently high conductivity is achieved. The content of the active material in the positive electrode composition may be, for example, 99.9% by mass or more, or 99.7% by mass or less, 99.5% by mass or less, 99.3% by mass or less, or 99% by mass or less.

[0078] The content of the binder in the positive electrode composition may be, for example, 0.1% by mass or more, and from the viewpoint of further improving the binding property of the composite layer and further improving battery performance, may be 0.2% by mass or more, 0.3% by mass or more, 0.4% by mass or more, or 0.5% by mass or more. The content of the binder in the positive electrode composition may be, for example, 10% by mass or less, and from the viewpoint of easily obtaining higher conductivity, may be 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1.5% by mass or less.

[0079] When the positive electrode composition contains a dispersant, the content of the dispersant in the positive electrode composition may be, for example, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, or 7 parts by mass or more relative to 100 parts by mass of carbon black. Furthermore, the content of the dispersant in the positive electrode composition may be, for example, 30 parts by mass or less, 25 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less relative to 100 parts by mass of carbon black.

[0080] (positive electrode) The positive electrode of this embodiment includes a current collector and a mixture layer. The mixture layer includes the carbon black of the above embodiment.

[0081] The composite layer may include the positive electrode composition of the above embodiment, or may be made of the positive electrode composition of the above embodiment. Furthermore, the composite layer may be formed by applying and drying the positive electrode-forming coating liquid of the above embodiment, or may include the solid content of the positive electrode-forming coating liquid of the above embodiment.

[0082] The positive electrode of this embodiment may be manufactured, for example, by forming a composite layer on a current collector using a positive electrode-forming coating liquid. The composite layer can be formed, for example, by applying the positive electrode-forming coating liquid to a current collector, drying it, and, if necessary, pressing, cutting, or the like.

[0083] The current collector is not particularly limited, and known current collectors can be used without any particular limitation. For example, metal foils (metals such as gold, silver, copper, platinum, aluminum, iron, nickel, chromium, manganese, lead, tungsten, and titanium, and alloys containing any one of these as the main component) are used as current collectors. Among these, it is preferable to use aluminum for the positive electrode and copper for the negative electrode. Current collectors are generally provided in the form of foils, but are not limited thereto, and perforated foil and mesh-shaped current collectors can also be used.

[0084] The method for applying the coating liquid for forming a positive electrode onto the current collector is not particularly limited, and may be, for example, a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method, or an electrostatic coating method.

[0085] The amount of the coating liquid for forming a positive electrode to be applied is not particularly limited, and may be adjusted appropriately so that the thickness of the composite layer falls within a desired range.

[0086] The composite layer may be formed by removing at least a portion of the liquid medium from a coating film of the positive electrode-forming coating liquid formed on the current collector. The method for removing the liquid medium is not particularly limited, and examples thereof include methods for vaporizing and removing at least a portion of the liquid medium by heating and / or reducing pressure, such as leaving to dry, using a blower dryer, a hot air dryer, an infrared heater, and a far-infrared heater.

[0087] In manufacturing the positive electrode of this embodiment, a pressurizing step may be performed in which the composite layer and the current collector are pressed in the stacking direction. The pressurizing step can improve the adhesion between the composite layer and the current collector.

[0088] The pressing method in the pressing step is not particularly limited, and may be, for example, a roll press, a mold press, a calendar press, or the like.

[0089] The thickness of the composite layer in the positive electrode is not particularly limited and may be, for example, 50 μm or more, and from the viewpoint of increasing the capacity of the battery, it is preferably 55 μm or more, more preferably 60 μm or more, and may be 65 μm or more or 70 μm or more. Also, the thickness of the composite layer in the positive electrode may be, for example, 150 μm or less, and from the viewpoint of further improving the discharge rate characteristics, it is preferably 140 μm or less, more preferably 130 μm or less, and may be 120 μm or less or 110 μm or less.

[0090] The positive electrode of this embodiment can be suitably used as a positive electrode for a battery, particularly a secondary battery (lithium ion secondary battery).

[0091] (battery) The battery of this embodiment includes the positive electrode of the above embodiment. The battery of this embodiment may be a secondary battery or a lithium ion secondary battery.

[0092] In the battery of this embodiment, the configuration other than the positive electrode may be the same as that of a known battery.

[0093] The uses of the battery of the present embodiment are not particularly limited, and the battery can be used in a wide range of fields, for example, portable AV devices such as digital cameras, video cameras, portable audio players, and portable LCD televisions, portable information terminals such as notebook personal computers, smartphones, and mobile PCs, as well as portable game devices, power tools, electric bicycles, hybrid vehicles, electric vehicles, and power storage systems.

[0094] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. [Example]

[0095] Hereinafter, the present disclosure will be described in more detail by way of examples, but the present disclosure is not limited to these examples.

[0096] <Example 1> (1) Production of Carbon Black A-1 (Preparation of Precursor) Acetylene as a raw material was supplied at 12 Nm 3 / h, toluene at 32 kg / h, and oxygen at 20 Nm 3 / h from a nozzle installed upstream of a carbon black reactor (reactor length 6 m, reactor diameter 0.65 m) to produce carbon black, which was collected by a bag filter installed downstream of the reactor. Then, it was passed through a dry cyclone device and a magnet for iron removal and recovered in a tank. Note that acetylene, toluene, and oxygen were heated to 115 °C and then supplied to the reactor to obtain carbon black (precursor). The obtained carbon black (precursor) had a BET specific surface area of 301 m 2 / g, an average primary particle diameter D p of 19 nm, and a crystallite size (Lc) of 16 Å.

[0097] (Activation Treatment) The obtained carbon black (precursor) was subjected to an activation treatment in a kiln under a nitrogen atmosphere at a temperature of 800 °C, a steam amount of 3 mL / min, and for 1 h to obtain carbon black A-1.

[0098] (Evaluation) For the obtained carbon black A-1, the BET specific surface area, pore volume, average primary particle diameter D p , and structure length D agg were measured by the following methods. The results are shown in Table 1. (Measurement of BET Specific Surface Area) The BET specific surface area was measured using "Macsorb1201" (manufactured by MOUNTECH) in accordance with JISK6217-2. (Measurement of Pore Volume) The pore volume was measured by a specific surface area / pore distribution measuring device (BELSORP MINI X manufactured by MicroTracBEL) using nitrogen gas as an adsorbate at a measurement temperature of 77.35 K by the BJH method in the analysis range of 2 to 10 nm. <Average primary particle diameter D p Measurement of Average primary particle diameter D p was calculated from SEM images acquired using the pretreatment method described in ASTM D3849-14a using the method specified in ASTM D3849-14a. <Structure length D agg Measurement of Structure length D agg was calculated from SEM images obtained using the pretreatment method described in ASTM D3849-14a using the Feret diameter calculation method specified in ISO 9276-6.

[0099] (2) Preparation of carbon black slurry Carbon black A-1, N-methyl-2-pyrrolidone (NMP) as a dispersion medium, and polyvinyl alcohol (Poval B05, manufactured by Denka Co., Ltd.) as a dispersant were prepared. 1.0% by mass of polyvinyl alcohol and 11.0% by mass of carbon black A-1 were added to 89.0% by mass of NMP and stirred for 120 minutes using a planetary mixer (Hivis Dispermix 3D-5, manufactured by Primix Corporation) to obtain a slurry. The resulting slurry was then placed in a bead mill (Mugen Flow MGF2-ZA, manufactured by Ashizawa Finetech Co., Ltd.) equipped with zirconia beads (0.5 mm diameter) and dispersed. After dispersion, the zirconia beads were removed by filtration to obtain a slurry of carbon black A-1 (Slurry (A-1)).

[0100] (3) Preparation and evaluation of battery (A-1-1) (Preparation of coating liquid for forming positive electrode) Average particle diameter D of the active material 50A lithium nickel manganese cobalt oxide having a particle size of 10 μm (manufactured by Beijing Dangsheng Co., Ltd., "ME6E"), a slurry (A-1) as a conductive material, an NMP solution of polyvinylidene fluoride as a binder, and NMP as a dispersion medium were prepared, and added to a container so that the solid content had the composition shown in Table 2. The mixture was mixed until uniform using a planetary centrifugal mixer (manufactured by Thinky Corporation, Awatori Rentaro ARV-310), to obtain a coating liquid for forming a positive electrode.

[0101] (Preparation of positive electrode) The prepared positive electrode-forming coating liquid was applied to one side of a 15 μm-thick aluminum foil (manufactured by UACJ Corporation) using an applicator, and then placed in a dryer and pre-dried at 105 ° C for one hour to completely remove the NMP solvent. Next, the aluminum foil was pressed with a roll press at a linear pressure of 200 kg / cm to form a composite layer on the aluminum foil. The amount of the positive electrode-forming coating liquid applied was such that the total thickness of the aluminum foil and the composite layer was 80 μm. Next, to completely remove residual moisture, the resulting product was vacuum-dried at 170 ° C for 3 hours to obtain a positive electrode.

[0102] (Preparation of negative electrode) Pure water (Kanto Chemical Co., Ltd.) was used as the solvent, artificial graphite (Hitachi Chemical Co., Ltd., "MAG-D") was used as the negative electrode active material, styrene butadiene rubber (Zeon Corporation, "BM-400B" hereafter referred to as SBR) was used as the binder, and carboxymethyl cellulose (Daicel Corporation, "D2200" hereafter referred to as CMC) was used as the dispersant. Next, CMC was weighed out to 1% by mass solids and artificial graphite was weighed out to 97% by mass solids and mixed. Pure water was added to this mixture and mixed until uniform using a planetary mixer (Thinky Corporation, Awatori Rentaro ARV-310). Furthermore, SBR was weighed out to 2% by mass solids and added to the above mixture. The mixture was mixed until uniform using a planetary mixer (Thinky Corporation, Awatori Rentaro ARV-310) to obtain a negative electrode slurry. Next, the negative electrode slurry was applied to a 10 μm thick copper foil (manufactured by UACJ Corporation) using an applicator and pre-dried in a dryer at 60 ° C for one hour. Next, the coating was pressed with a roll press at a linear pressure of 50 kg / cm to prepare a coating containing the copper foil with a thickness of 60 μm. To completely remove residual moisture, the coating was vacuum dried at 120 ° C for 3 hours to obtain a negative electrode.

[0103] (Battery construction) In a dry room controlled to a dew point of -50°C or less, the positive electrode was cut to 40 x 40 mm and the negative electrode to 44 x 44 mm. An aluminum tab was then welded to the positive electrode and a nickel tab to the negative electrode. The composite-coated surfaces of the positive and negative electrodes were aligned in the center, and a 45 x 45 mm polyolefin microporous membrane was placed between the positive and negative electrodes. Next, a sheet-like exterior was cut and processed to a 70 x 140 mm square and folded in half at the center of the long side. The exterior was then positioned so that the aluminum tab for the positive electrode and the nickel tab for the negative electrode were exposed to the outside of the exterior, and the positive electrode-polyolefin microporous membrane-negative electrode laminate was sandwiched between the folded exterior. Next, using a heat sealer, two sides of the exterior, including the side where the aluminum tab for the positive electrode and the nickel tab for the negative electrode were exposed, were heat-sealed, and then 2 g of electrolyte (Kishida Chemical, ethylene carbonate / diethyl carbonate = 1 / 2 (volume ratio) + 1 M LiPF6 solution, hereinafter referred to as electrolyte) was poured into the other side that was not heat-sealed, and allowed to fully soak into the positive electrode, negative electrode, and polyolefin microporous membrane. After that, the remaining side of the exterior was heat-sealed using a vacuum heat sealer while reducing the internal pressure to obtain a battery. The resulting battery was evaluated using the following methods.

[0104] (Battery evaluation) The fabricated battery was charged at 25°C to 4.3 V at a constant current and voltage of 0.2 C, and then discharged to 3.0 V at a constant current of 0.2 C. Next, after five charge / discharge cycles under the same conditions, the battery was charged to a charge depth of 50%. Impedance measurements were then performed at a frequency range of 10 MHz to 0.001 Hz and an oscillating voltage of 5 mV to evaluate the internal resistance. The results are shown in Table 2.

[0105] (4) Preparation and evaluation of battery (A-1-2) A battery was fabricated and evaluated in the same manner as in (3) above, except that the solid content of the coating solution for forming the positive electrode was changed to 0.75% by mass of carbon black, 98.25% by mass of active material, and 1% by mass of binder. The results are shown in Table 2.

[0106] (5) Preparation and evaluation of battery (A-1-3) A battery was fabricated and evaluated in the same manner as in (3) above, except that the solid content of the coating solution for forming the positive electrode was changed to 0.5% by mass of carbon black, 98.5% by mass of active material, and 1% by mass of binder. The results are shown in Table 2.

[0107] [Table 1]

[0108] [Table 2]

[0109] <Example 2> (1) Preparation of Carbon Black A-2 Carbon black A-2 was produced in the same manner as in Example 1, except that the activation treatment conditions for the carbon black were changed to a temperature of 900°C, a steam amount of 36 ml / min, and a treatment time of 4 hours. The BET specific surface area, pore volume, and average primary particle diameter D of the obtained carbon black A-2 were measured in the same manner as in Example 1. p , and structure length D agg The results are shown in Table 3.

[0110] (2) Preparation and evaluation of slurry and battery Except for using carbon black A-2 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 4.

[0111] [Table 3]

[0112] [Table 4]

[0113] Example 3 (1) Preparation of Carbon Black A-3 Carbon black A-3 was produced in the same manner as in Example 1, except that the activation treatment conditions for the carbon black were changed to a temperature of 800°C, a steam flow rate of 5 ml / min, and a treatment time of 3 hours. The BET specific surface area, pore volume, and average primary particle diameter D of the obtained carbon black A-3 were measured in the same manner as in Example 1. p , and structure length D agg The results are shown in Table 5.

[0114] (2) Preparation and evaluation of slurry and battery Except for using carbon black A-3 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 6.

[0115] [Table 5]

[0116] [Table 6]

[0117] Example 4 (1) Preparation of Carbon Black A-4 Carbon black A-2 was produced in the same manner as in Example 1, except that the activation treatment conditions for the carbon black were changed to a temperature of 1000°C, a steam amount of 2.5 ml / min, and a treatment time of 3 hours. The BET specific surface area, pore volume, and average primary particle diameter D of the obtained carbon black A-4 were measured in the same manner as in Example 1. p , and structure length D agg The results are shown in Table 7.

[0118] (2) Preparation and evaluation of slurry and battery Except for using carbon black A-4 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 8.

[0119] [Table 7]

[0120] [Table 8]

[0121] <Example 5> (1) Preparation of Carbon Black A-5 Carbon black A-5 was produced in the same manner as in Example 1, except that the activation treatment conditions for carbon black were changed to a temperature of 950°C, a steam amount of 36 ml / min, and a treatment time of 1 hour. The BET specific surface area, pore volume, and average primary particle diameter D of the obtained carbon black A-5 were measured in the same manner as in Example 1. p , and structure length D agg The results are shown in Table 9.

[0122] (2) Preparation and evaluation of slurry and battery Except for using carbon black A-5 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 10.

[0123] [Table 9]

[0124] [Table 10]

[0125] Example 6 (1) Preparation of Carbon Black A-6 Carbon black A-6 was produced in the same manner as in Example 1, except that the activation treatment conditions for the carbon black were changed to a temperature of 1000°C, a steam amount of 3.6 ml / min, and a treatment time of 4 hours. The BET specific surface area, pore volume, and average primary particle diameter D of the obtained carbon black A-6 were measured in the same manner as in Example 1.p , and structure length D agg The results are shown in Table 11.

[0126] (2) Preparation and evaluation of slurry and battery Except for using carbon black A-6 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 12.

[0127] [Table 11]

[0128] [Table 12]

[0129] <Comparative Example 1> (1) Preparation of carbon black B-1 Carbon black B-1 having the properties shown in Table 13 was prepared.

[0130] (2) Preparation and evaluation of slurry and battery Except for using carbon black B-1 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 14.

[0131] [Table 13]

[0132] [Table 14]

[0133] <Comparative Example 2> (1) Preparation of carbon black B-2 Carbon black B-2 having the properties shown in Table 15 was prepared.

[0134] (2) Preparation and evaluation of slurry and battery Except for using carbon black B-2 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 16.

[0135] [Table 15]

[0136] [Table 16]

[0137] <Comparative Example 3> (1) Preparation of carbon black B-3 Carbon black B-3 having the properties shown in Table 17 was prepared.

[0138] (2) Preparation and evaluation of slurry and battery Except for using carbon black B-3 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 18.

[0139] [Table 17]

[0140] [Table 18]

[0141] <Comparative Example 4> (1) Preparation of carbon black B-4 Carbon black B-4 having the properties shown in Table 19 was prepared.

[0142] (2) Preparation and evaluation of slurry and battery Except for using carbon black B-4 instead of carbon black A-1, slurry preparation and battery production and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 20.

[0143] [Table 19]

[0144] [Table 20]

[0145] As described above, in Comparative Examples 1 to 4, when the amount of carbon black added was less than 1% by mass, the conductivity was significantly reduced compared to when the amount of carbon black added was 1% by mass. On the other hand, in Examples 1 to 6, even in compositions with a low amount of carbon black added of less than 1% by mass, conductivity close to that when the amount of carbon black added was 1% by mass was obtained.

Claims

1. The pore volume of pores with a pore diameter of 2 to 10 nm is 0.15 cm ３ / g or more 1.10cm ３ / g or less.

2. BET specific surface area is 290m ２ / g or more 1300m ２ 2. The carbon black according to claim 1, wherein the molecular weight of the carbon black is 1 / g or less.

3. Average primary particle diameter D ｐ 2. The carbon black according to claim 1, wherein the average particle diameter is 12 nm or more and 27 nm or less.

4. Structure length D ａｇｇ 2. The carbon black according to claim 1, wherein the average particle diameter (nm) of the carbon black is 180 nm or greater.

5. A slurry comprising the carbon black according to any one of claims 1 to 4 and a liquid medium.

6. A coating liquid for forming a positive electrode, comprising the carbon black according to any one of claims 1 to 4, an active material, a binder, and a liquid medium.

7. The coating liquid for forming a positive electrode according to claim 6 , wherein the content of the carbon black is less than 1% by mass based on the total amount of solids.

8. A positive electrode composition comprising the carbon black according to any one of claims 1 to 4, an active material, and a binder.

9. 9. The positive electrode composition according to claim 8, wherein the carbon black content is less than 1% by mass.

10. a current collector; and a composite layer disposed on the current collector; The positive electrode, wherein the composite layer comprises the positive electrode composition of claim 8 .

11. A battery comprising the positive electrode of claim 10.

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