WO2022057114A1 - 掺杂多壁碳纳米管及其制备方法和电极材料 - Google Patents

掺杂多壁碳纳米管及其制备方法和电极材料 Download PDF

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WO2022057114A1
WO2022057114A1 PCT/CN2020/135789 CN2020135789W WO2022057114A1 WO 2022057114 A1 WO2022057114 A1 WO 2022057114A1 CN 2020135789 W CN2020135789 W CN 2020135789W WO 2022057114 A1 WO2022057114 A1 WO 2022057114A1
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carbon nanotubes
walled carbon
doped
catalyst
doped multi
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PCT/CN2020/135789
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English (en)
French (fr)
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万远鑫
黄少真
孔令涌
任望保
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曲靖市飞墨科技有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • C01B32/162—Preparation characterised by catalysts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/06—Multi-walled nanotubes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/22—Electronic properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of multi-walled carbon nanotubes, in particular to a doped multi-walled carbon nanotube and an electrode material.
  • Carbon nanotubes are an allotrope of carbon, which can be regarded as seamless tubes with a diameter of nanometers, which are formed by rolling one or more layers of graphene sheets according to a certain helix angle. According to the number of graphene sheets, carbon nanotubes can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes. Multilayer graphene sheets are rolled up. Carbon nanotubes, as one-dimensional nanomaterials, have good electrical conduction paths in the axial direction. As shown in Fig. 1, the dashed arrows indicate the axial conduction channels of multi-walled carbon nanotubes, and electrons can migrate along the axial conduction channels.
  • the present application provides a doped multi-walled carbon nanotube
  • the doped multi-walled carbon nanotube has a radial conductive channel, which can promote the transmission of electrons along the radial direction of the multi-walled carbon nanotube, thereby making the doped multi-walled carbon nanotube more Wall carbon nanotubes have good electrical conductivity, and their application in electrode materials can improve the electrical conductivity of electrode materials.
  • a first aspect of the present application provides a doped multi-walled carbon nanotube
  • the doped multi-walled carbon nanotube includes a multi-walled carbon nanotube and dopant atoms doped in the multi-walled carbon nanotube;
  • the The doped multi-walled carbon nanotubes have radial conductive channels, and the radial conductive channels are formed by covalent bonding of the doping atoms and adjacent tube walls of the multi-walled carbon nanotubes.
  • the doped multi-walled carbon nanotubes provided in the first aspect of the present application have radial conductive channels, which promotes the radial transport of electrons in the multi-walled carbon nanotubes, so that the doped multi-walled carbon nanotubes have good electrical conductivity and good
  • the electronic conductivity of the multi-walled carbon nanotubes has been expanded.
  • a second aspect of the present application provides a method for preparing doped multi-walled carbon nanotubes, comprising the following steps:
  • the crude doped multi-walled carbon nanotubes are acid-washed, and dried to obtain the doped multi-walled carbon nanotubes described in the first aspect of the present application.
  • a third aspect of the present application also provides a method for preparing doped multi-walled carbon nanotubes, comprising the following steps:
  • the active component source includes a soluble transition metal salt
  • the catalyst precursor is calcined, steam is introduced into the calcination process, and a catalyst is obtained after cooling, the catalyst comprises the layered carrier, the active component supported on the layered carrier, and the doping source , the active component includes transition metal active particles;
  • the catalyst is placed in a reactor, a carbon source is introduced into an inert atmosphere, an array of doped multi-walled carbon nanotubes is formed on the layered support by chemical vapor deposition, and then the catalyst is removed, The doped multi-walled carbon nanotubes as described in the first aspect of the present application are obtained.
  • a fourth aspect of the present application also provides a method for preparing doped multi-walled carbon nanotubes, comprising the following steps:
  • the active component source includes a soluble transition metal salt
  • the catalyst precursor is calcined in an inert atmosphere to obtain a carbon coating material;
  • the carbon coating material includes a catalyst and a carbon coating layer that coats the catalyst, and the catalyst includes the layered carrier and transition metal active particles and the doping source supported on the layered carrier;
  • the catalyst is placed in a reactor, a second carbon source is introduced into an inert atmosphere, and an array of doped multi-walled carbon nanotubes is formed on the layered support by chemical vapor deposition; A catalyst is used to obtain the doped multi-walled carbon nanotubes as described in the first aspect of the present application.
  • the preparation method of doped multi-walled carbon nanotubes provided by the second aspect, the third aspect or the fourth aspect of the present application prepares the doped multi-walled carbon nanotubes with radial conductive channels by chemical vapor deposition method, and the process is simple, The operation controllability is strong and the yield of the prepared doped multi-walled carbon nanotubes is high.
  • a fifth aspect of the present application provides an electrode material, the electrode material includes an electrode active material, a binder and a conductive agent, and the conductive agent includes the doped multi-walled carbon nanotubes provided in the first aspect of the present application.
  • the doped multi-walled carbon nanotubes in this application have good electrical conductivity and can be added to the electrode material as a conductive agent, and can reduce the amount of the conductive agent in the electrode material, thereby increasing the content of the electrode active material in the electrode material. Electrode materials have higher energy density.
  • the electrode material provided in the fifth aspect of the present application has good electrical conductivity, and when applied in a battery, the energy density of the battery can be improved, and the performance of the battery can be improved.
  • 1 is a schematic structural diagram of an undoped multi-walled carbon nanotube
  • Example 3 is a transmission electron microscope image of the doped multi-walled carbon nanotubes prepared in Example 1 of the application;
  • the embodiments of the present application provide a doped multi-wall carbon nanotube, including the multi-wall carbon nanotube and doping atoms doped in the multi-wall carbon nanotube.
  • the doped multi-walled carbon nanotubes have radial conductive channels, and the radial conductive channels are formed by covalent bonding between doping atoms and adjacent tube walls of the multi-walled carbon nanotubes.
  • the dashed arrows represent the axial conduction channels of multi-walled carbon nanotubes, and electrons can migrate along the axial conduction channels;
  • the solid arrows represent the radial conduction channels of multi-walled carbon nanotubes, and electrons can be guided along the radial direction. electrical channel for migration.
  • the walls of the doped multi-wall carbon nanotubes only contain carbon atoms, and the doping atoms are located between the walls of the multi-wall carbon nanotubes.
  • the doping atoms form CXC covalent bonds with the carbon atoms of the adjacent walls in the multi-walled carbon nanotubes, wherein X is a dopant atom.
  • the CXC covalent bonds between different tube walls connect multiple tube walls to form a radial conductive channel, which can promote the radial transport of electrons in the multi-wall carbon nanotubes, thereby improving the performance of the multi-wall carbon nanotubes.
  • Conductivity
  • the doped multi-walled carbon nanotubes are linear as a whole, and a bent portion is partially formed, and the bent portion has corrugated folds.
  • the bent part is due to the formation of covalent bonds by the doping atoms on the walls of the multi-walled carbon nanotubes, which destroys the interlayer force of the multi-walled carbon nanotubes, resulting in the interlayer spacing between the walls of the doped multi-walled carbon nanotubes.
  • the different sizes also make the doped multi-walled carbon nanotubes wrinkled and twisted.
  • the above-mentioned interlayer spacing changes, wrinkles and torsional deformations are all defects of multi-walled carbon nanotubes after doping atoms are incorporated.
  • the defect ratio of the doped multi-walled carbon nanotube is 30%-80%.
  • the defect content of the doped multi-walled carbon nanotubes is related to the type and content of the doping atoms.
  • the dopant atoms include one or more of boron atoms, nitrogen atoms, phosphorus atoms, sulfur atoms and silicon atoms.
  • the dopant atoms can bond with carbon atoms on adjacent tube walls to form one of CBC, CNC, CPC, CSC, and C-Si-C.
  • One or more covalent bonds are formed, thereby effectively constructing electron transfer channels between the tube walls of the multi-walled carbon nanotubes, and promoting the radial transport of electrons in the multi-walled carbon nanotubes.
  • doping atoms in the multi-walled carbon nanotubes can also cause the conductivity type of the multi-walled carbon nanotubes to change.
  • the doping atoms are boron atoms, and the multi-walled carbon nanotubes are doped to form p-type conductivity, and conduct electricity with holes.
  • the doping atoms are nitrogen atoms
  • the multi-walled carbon nanotubes are doped to form n-type conductivity, and conduct electricity with majority carriers.
  • different doping atoms can be selected according to actual requirements to adjust the electrical conductivity of the doped multi-walled carbon nanotubes.
  • the mass percentage content of dopant atoms is 0.01%-10%. Further, the mass percentage content of doping atoms is 1%-10%, specifically, but not limited to, 0.01%, 0.05%, 0.1%, 0.5%, 1.5%, 3%, 5% or 10%. Controlling the content of dopant atoms can adjust the number of radial conductive channels, ensure the electron transport rate of the doped multi-wall carbon nanotubes in the axial and radial directions, and improve the conductivity of the doped multi-wall carbon nanotubes. In some embodiments of the present application, the dopant atoms are boron atoms, and the mass percentage of the boron atoms is 5%.
  • the number of layers of the doped multi-walled carbon nanotubes ranges from 3 layers to 10 layers. Generally, when the number of layers of multi-walled carbon nanotubes is greater than or equal to 3, it is usually difficult for electrons to transfer between graphene sheets. However, doping atoms into multi-walled carbon nanotubes can effectively promote electrons in multi-walled carbon nanotubes.
  • the radial migration of carbon nanotubes improves the conductivity of multi-walled carbon nanotubes; when the number of layers of multi-walled carbon nanotubes is less than or equal to 10, the doping atoms can be fully doped into the wall of each layer of multi-walled carbon nanotubes , which is conducive to the formation of shorter electron transport channels in the radial direction of the multi-walled carbon nanotubes and promotes electron transport.
  • the number of layers of the doped multi-walled carbon nanotubes may specifically be, but not limited to, 3 layers, 4 layers, 5 layers, 7 layers, 9 layers or 10 layers. In some embodiments, the number of layers of the doped multi-walled carbon nanotubes is 5-9 layers.
  • the wall thickness of the doped multi-walled carbon nanotubes is 2-3 nm.
  • the diameter of the doped multi-walled carbon nanotubes may be 3 nm-100 nm, and the length of the doped multi-walled carbon nanotubes may be 1 ⁇ m-100 ⁇ m. In some embodiments of the present application, the diameter of the doped multi-walled carbon nanotubes may be 3 nm-10 nm, preferably 3-8 nm. More preferably, it is 3-7.5 nm. At this time, the diameter of the doped multi-walled carbon nanotubes is very small, the aspect ratio is extremely high, and the performance is excellent (eg, the defect density is lower, and the electrical conductivity is better).
  • the length of the doped multi-walled carbon nanotubes may be 10 ⁇ m-100 ⁇ m. Further, the length of the doped multi-walled carbon nanotubes may be 30 ⁇ m-100 ⁇ m, 40 ⁇ m-90 ⁇ m, 30 ⁇ m-60 ⁇ m or 35 ⁇ m-55 ⁇ m.
  • the aspect ratio of the doped multi-walled carbon nanotube is 10-33333.
  • the aspect ratio of the doped multi-walled carbon nanotubes may be 125-33333, 300-33333, 300-20000. Preferably it is 3750-33333, More preferably, it is 4286-33333.
  • the specific surface area of the doped multi-walled carbon nanotubes is ⁇ 250 m 2 /g.
  • Doped multi-walled carbon nanotubes with larger specific surface area can better exert their electrical conductivity when used in battery electrode materials, supercapacitor electrode materials and other fields, and can also have better liquid absorption in batteries. It is beneficial to fully infiltrate the electrode material.
  • the interlayer spacing of the doped multi-walled carbon nanotube at the position where the covalent bond is formed is greater than the interlayer spacing at the position where the covalent bond is not formed.
  • the resistivity of the doped multi-walled carbon nanotubes is 20 m ⁇ cm-75 m ⁇ cm.
  • the resistivity of the doped multi-walled carbon nanotubes can be specifically, but not limited to, 20m ⁇ cm, 30m ⁇ cm, 35m ⁇ cm, 40m ⁇ cm, 45m ⁇ cm, 50m ⁇ cm, 55m ⁇ cm, 60m ⁇ cm, 65m ⁇ cm cm or 75m ⁇ cm.
  • the doped multi-walled carbon nanotubes in the present application have small resistivity values and good electrical conductivity.
  • the doped multi-walled carbon nanotubes can be used in battery electrode materials and supercapacitor electrode materials, but not limited thereto.
  • doping atoms are incorporated between the walls of the multi-walled carbon nanotube, so that the doping atom forms a covalent bond with the adjacent wall of the multi-walled carbon nanotube,
  • the covalent bond can extend the conjugated structure inside the multi-walled carbon nanotube to the outside of the multi-walled carbon nanotube, so that the multi-walled carbon nanotube has a radial conductive channel, and the radial conductive channel enriches electrons in the multi-walled carbon nanotube It promotes the radial transport of electrons in the multi-walled carbon nanotubes, makes the doped multi-walled carbon nanotubes have good electrical conductivity and good electron conductivity, and expands the application of multi-walled carbon nanotubes.
  • the present application also provides a method for preparing the above-mentioned doped multi-walled carbon nanotubes, comprising the following steps:
  • S02 pickling the crude doped multi-walled carbon nanotubes, and drying to obtain doped multi-walled carbon nanotubes;
  • the doped multi-walled carbon nanotubes include multi-walled carbon nanotubes and doped multi-walled carbon nanotubes Doping atoms in nanotubes;
  • the doped multi-walled carbon nanotubes have radial conductive channels that are shared by the doping atoms with adjacent walls of the multi-walled carbon nanotubes. Valence bonds are formed.
  • the doping source and the catalyst are mixed in advance, so that the doping source is attached to the surface of the catalyst.
  • the dopant source in the dopant precursor can decompose to generate dopant atoms, and the dopant atoms can be melted in the catalyst.
  • the carbon source will decompose under the action of the catalyst to form carbon atoms, and the carbon atoms can also be decomposed in the catalyst.
  • the dopant atoms and carbon atoms are saturated in the catalyst, they will precipitate out of the catalyst to form doped multi-wall carbon nanotubes.
  • the doping sites of the dopant atoms are outside the tube wall of the multi-wall carbon nanotube, that is, in the middle of the adjacent tube walls in the multi-wall carbon nanotube.
  • the doping precursor in step S01, includes a doping source and a catalyst, wherein the doping source is attached to the surface of the catalyst.
  • the catalyst includes one or more of iron catalyst, cobalt catalyst and nickel catalyst. Further, the catalyst is a metal matrix composite material. In some embodiments of the present application, the catalyst includes one or more of Fe-W/MgO, Co-Mo/Al 2 O 3 , Ni-Mo/Al 2 O 3 , and Fe-Mo/Al 2 O 3 .
  • the above catalyst can promote carbon atoms to form multi-walled carbon nanotubes, and the catalyst can be easily removed after the reaction is completed, which is beneficial to improve the purity of the doped multi-walled carbon nanotubes.
  • the doping source includes, but is not limited to, one or more of magnesium borate, sodium borate, boron nitride, aluminum nitride, aluminum sulfate, and magnesium sulfate.
  • the above-mentioned doping source can be effectively combined with the catalyst to form a doping precursor, thereby facilitating doping atoms into the walls of the multi-walled carbon nanotubes and improving the yield of the doped multi-walled carbon nanotubes.
  • the doping precursor is obtained by mixing the doping source and the catalyst according to the mole ratio of doping atoms in the doping source and metal atoms in the catalyst being 1:(5-100).
  • the equipment for preparing the doping precursor can be any one of a ball mill, a sand mill, a mixer or a fusion coater.
  • the equipment for preparing the doping precursor is a fusion coating machine, and the preparation process of the doping precursor is specifically: adding the raw materials into the fusion coating machine respectively, and under the action of blade shearing force, doping The interface between the source and the catalyst is fused, and the doping source is attached to the surface of the catalyst to form a doping precursor.
  • the doping atoms can be fully incorporated into each tube wall of the multi-walled carbon nanotubes.
  • the carbon source may be one or more of C 1 -C 4 alkanes (such as methane, ethane, propane, butane), alkenes (such as ethylene, propylene, butene), and alkynes .
  • the carrier gas includes one or more of nitrogen, argon, helium, and hydrogen.
  • the chemical vapor deposition process is specifically as follows: adding a doping precursor, a carbon source and a carrier gas into the reactor, and heating up to 600°C-1500°C at a heating rate of 1°C/min-10°C/min , kept for 0.5h-4h and then cooled to room temperature naturally.
  • the temperature of chemical vapor deposition is 700°C-1200°C
  • the holding time is 0.5h-1.5h.
  • the inert gas may be one or more of nitrogen, helium, argon and hydrogen.
  • the reactor may be any one of a box furnace, a tube furnace or a fluidized bed.
  • step S02 the process of pickling the crude doped multi-walled carbon nanotubes is specifically as follows: adding the crude doped multi-walled carbon nanotubes into an acid solution, and at a temperature of 40°C-100°C Infiltrated for 2h-30h, washed with water until neutral, and dried to obtain doped multi-walled carbon nanotubes.
  • the acid solution may be one or more of a nitric acid solution, a hydrochloric acid solution, and a sulfuric acid solution.
  • the mass fraction of the acid solution is 2wt%-15wt%, specifically, but not limited to, 2wt%, 5wt%, 10wt%, 13wt% or 15wt%.
  • the temperature of pickling is 50°C-80°C, and the time of pickling is 12h-24h.
  • the chemical vapor deposition method is used to prepare the doped multi-wall carbon nanotubes with radial conductive channels, the process is simple, the operation controllability is strong, and the prepared doped multi-wall carbon nanotubes have a high yield.
  • the present application also provides the second preparation method of the above-mentioned doped multi-walled carbon nanotubes, comprising the following steps:
  • the catalyst placing the catalyst in a reactor, feeding a carbon source in an inert atmosphere, forming an array of doped multi-walled carbon nanotubes on the layered carrier by chemical vapor deposition, and then removing the A layered carrier to obtain the doped multi-walled carbon nanotubes;
  • the doped multi-walled carbon nanotubes include multi-walled carbon nanotubes and doped atoms doped in the multi-walled carbon nanotubes;
  • the heteromulti-walled carbon nanotube has a radial conductive channel, and the radial conductive channel is formed by covalent bonding of the dopant atoms and the adjacent tube wall of the multi-walled carbon nanotube.
  • the interlayer spacing of the layered carrier is expanded by using an intercalating agent, which effectively increases the amount of active components carried by the layered carrier, and the intercalating agent can also inhibit the
  • the agglomeration of the active component source is conducive to the formation of small particle size active components, which in turn promotes the formation of arrayed carbon nanotubes with higher aspect ratios; the use of water vapor for catalyst preactivation has better safety and reduces production Cost; the doping source is introduced during the preparation of the catalyst precursor, so that the doping source can be effectively combined with the catalyst formed by the calcination of the catalyst precursor, thereby facilitating the incorporation of doping atoms into the tube wall of the multi-walled carbon nanotube. between.
  • the array-type doped multi-walled carbon nanotubes prepared by the method have high aspect ratio, good uniformity of tube diameter and excellent electrical conductivity; the preparation method is simple in process, strong in operation controllability, and can be applied to large-scale industrial production
  • the doping source may include, but is not limited to, one or more of magnesium borate, sodium borate, boron nitride, aluminum nitride, aluminum sulfate, and magnesium sulfate.
  • the molar ratio of the dopant atoms in the dopant source and the transition metal atoms in the active component source is 1:(5-100) to use the dopant source and the active component source.
  • the layered carrier has a large specific surface area and a high loading capacity for the active component source, and the carrier used in this application has a good adsorption capacity, which is conducive to the attachment of the intercalating agent and the active component source to the carrier. surface.
  • the layered carrier can be subsequently used as a carrier of a catalyst for carbon nanotube growth, providing a plane for the growth of carbon nanotubes, so that the carbon nanotubes are grown vertically to form a carbon nanotube array.
  • the layered supports include layered alumina, layered magnesia, pseudo-boehmite, layered silica, vermiculite, expanded graphite, mica, hydrotalcite (LDH), montmorillonite, kaolin and One or more of the supporting stones, but not limited thereto.
  • the lateral dimension of the layered carrier is 0.02 mm-2 mm.
  • the lateral dimension here refers to the length or width, etc. of the layered carrier.
  • the lateral dimension of the layered carrier may be, but not limited to, 0.03 mm, 0.05 mm, 0.1 mm, 0.15 mm, 0.3 mm, 0.5 mm, 1 mm, 1.5 mm or 2 mm. Controlling the lateral dimension of the layered carrier can ensure that the layered carrier, the intercalant, the active component source, and the dopant source can be fully mixed.
  • the active component refers to a component with catalytic activity.
  • the active component source in this application can form the active component after calcination, and the active component can catalyze the carbon source and the doping source to form doping Carbon nanotubes;
  • the active component source includes a soluble transition metal salt, so that the resulting active component includes transition metal active particles.
  • the transition metal salt may specifically be a salt of at least one of iron, cobalt, nickel, manganese, titanium, molybdenum, tungsten, ruthenium and palladium, and may specifically be a nitrate of these transition metal elements, One or more of chloride salts, sulfate salts, and soluble organic salts.
  • the active component source includes one or more of soluble titanium salts, manganese salts, iron salts, cobalt salts, nickel salts, ruthenium salts and palladium salts, and accordingly, the active components are titanium, At least one of manganese, iron, cobalt, nickel, ruthenium and palladium.
  • the active component source includes titanium sulfate, titanium nitrate, manganese sulfate, manganese nitrate, manganese chloride, iron acetate, iron sulfate, iron nitrate, cobalt sulfate, cobalt acetate, cobalt nitrate, nickel sulfate, nitric acid
  • nickel, ruthenium nitrate and palladium nitrate but not limited thereto.
  • the active component source includes one or more of titanium nitrate, manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, ruthenium nitrate and palladium nitrate.
  • nitrate will decompose at high temperature, thereby forming a local high partial pressure in the gas phase around the active component, which is favorable for carbon atoms in the active component from the adsorbed crystal face to the carbon nanometer.
  • the crystal planes of the tube growth are diffused, thereby forming arrayed carbon nanotubes with uniform tube diameter and high aspect ratio.
  • an auxiliary source in the process of uniformly mixing the layered carrier, the intercalating agent, the active component source, the doping source and the solvent, an auxiliary source is also added.
  • the auxiliary source can form an auxiliary, which not only plays a role in synergistic catalysis, but also promotes the dispersion of the active components and reduces the particle size of the active components, making the carbon nanotubes in the The region grown in the active component becomes smaller, thereby forming arrayed carbon nanotubes with smaller tube diameters.
  • the auxiliary source includes one or more of a molybdenum-containing soluble salt, a lanthanum-containing soluble salt, and a tungsten-containing soluble salt.
  • the adjuvant source includes one or more of sodium molybdate, ammonium molybdate, lanthanum nitrate or tungsten nitrate.
  • the mass ratio of the active component source to the auxiliary agent source is 1:(0.002-1). In some embodiments of the present application, the mass ratio of the active component source to the adjuvant source is 1:(0.01-0.5).
  • the mass ratio of the active ingredient source to the auxiliary agent source can be specifically, but not limited to, 1:0.002, 1:0.01, 1:0.02, 1:0.05, 1:0.1, 1:0.4, 1:0.5, 1:0.7 or 1 :1.
  • adding an intercalating agent can effectively expand the interlayer spacing of the carrier, thereby improving the loading capacity of the layered carrier for the active component source, and at the same time, the intercalating agent can encapsulate the active component source, avoiding the active component source during the calcination process. Aggregate to form large-diameter particles, thereby improving the dispersion uniformity of the active components in the layered carrier, which is beneficial to the formation of an array of doped carbon nanotubes with uniform diameter and high aspect ratio.
  • the intercalating agent can be inserted into the carrier sheet layer by means of adsorption.
  • an intercalating agent with an opposite charge to the layered carrier when the interlayers of the layered carrier are charged, an intercalating agent with an opposite charge to the layered carrier can be selected, so that the intercalating agent can be inserted into the carrier sheet layer through electrostatic action.
  • an anionic intercalating agent when the layered carrier is expanded graphite, an anionic intercalating agent can be selected to be mixed with the expanded graphite, thereby enhancing the effect of the intercalating agent in expanding the interlayer spacing of the expanded graphite.
  • the intercalating agent may be inserted into the sheets of the layered support by ion exchange.
  • the intercalating agent When the intercalating agent is loaded on the layered carrier, it can improve the wettability of the surface of the layered carrier, so that the solvent can fully infiltrate the layered carrier, which is conducive to the entry of the active component source into the interlayer of the layered carrier, and the improvement of the layered carrier. Loading capacity of the active ingredient source.
  • the intercalating agent is an organic intercalating agent.
  • the organic intercalating agent has a large spatial structure, which can well expand the interlayer spacing of the layered support; and it can be oxidized to carbon dioxide or other gaseous compounds during the calcination process, and will not remain in the catalyst and affect the activity of the catalyst. ;
  • the acidity and alkalinity of the organic intercalating agent are weaker, which has little effect on the activity of the catalyst.
  • the intercalating agent may include one or more of an anionic intercalating agent, a cationic intercalating agent, and an organic amine intercalating agent.
  • the anionic intercalating agent includes one or more of organic sulfonates and organic sulfates.
  • the organic sulfonate includes one or more of sodium dodecylbenzenesulfonate, sodium isethionate, and sodium styrenesulfonate; the organic sulfate salt includes dodecyl Sodium sulfate.
  • the cationic intercalating agent includes one or more of alkyl quaternary ammonium salts and quaternary ammonium salts containing benzene rings.
  • the alkyl quaternary ammonium salt includes one or more of dodecyltrimethylammonium bromide, cetyltrimethylammonium bromide and octadecyltrimethylammonium bromide.
  • the organic amine-based intercalating agent includes one or more of aliphatic amine-based organic amines, amide-based organic amines, and aromatic amine-based organic amines.
  • the aliphatic amine intercalating agents include ethanolamine, diethanolamine, triethanolamine, 3-propanolamine, isopropanolamine, N,N-dimethylethanolamine and N,N-diethylethanolamine
  • the amide intercalating agents include one or more of acetamide, propionamide, acrylamide, polyacrylic acid amine and dimethylformamide
  • aromatic amine intercalating agents include aniline, dimethicone One or more of aniline, etc.
  • the above-mentioned intercalating agent has good affinity to the carrier in the application, and can be effectively combined with the carrier, wherein, selecting an intercalating agent with a larger molecular weight and a longer chain length is more conducive to expanding the interlayer spacing of the layered carrier.
  • the carbon number of the intercalating agent is 6-40. In other embodiments of the present application, the carbon number of the intercalating agent is 12-40.
  • the intercalating agent When the number of carbon atoms is in the range of 6-40, the intercalating agent has a good affinity with the layered carrier, which can more effectively expand the interlayer spacing of the layered carrier and facilitate the entry of active substances into the interlayer of the layered carrier; and the intercalating agent It is easy to dissolve and can better disperse the active ingredient source.
  • the mass ratio of the intercalating agent to the layered carrier is 1:1-50. In some embodiments of the present application, the mass ratio of the intercalant to the layered carrier is 1:1-20. Further, the mass ratio of the intercalant to the layered carrier is 1:1-10.
  • the mass ratio of the intercalating agent to the layered carrier can be specifically, but not limited to, 1:1, 1:3, 1:5, 1:10, 1:15, 1:20, 1:30, 1:40 or 1:1: 50. Controlling the mass ratio of the intercalating agent to the layered carrier can ensure that the intercalating agent can expand the interlayer spacing of the layered carrier and does not affect the adsorption of the active component source by the layered carrier.
  • the mass ratio of the active component source, the intercalating agent and the layered carrier is (5-50):(1-10):(10-50). In some embodiments of the present application, the mass ratio of the active ingredient source, the intercalating agent and the layered carrier is (10-30):(2-7):(20-30). Controlling the mass ratio of each component is beneficial to the formation of a catalyst with more active components and uniform dispersion of the active components. In some embodiments, the mass ratio of the active ingredient source to the layered carrier is (0.1-5):1, eg, (0.33-1.5):1.
  • the solvent in step S100 may include one or more of water, methanol, ethanol and propanol, but is not limited thereto.
  • the above solvent can infiltrate the carrier, which is favorable for the layered carrier to fully adsorb the intercalating agent and the active component source, and enhances the uniformity of the active component source on the layered carrier.
  • the mass ratio of the solvent to the layered carrier is (1-10):(0.1-1).
  • the mass ratio of the solvent to the layered carrier is (3-7):(0.1-1). Controlling the mass ratio of the layered carrier to the solvent can ensure that the solvent fully wets the layered carrier, thereby promoting the effective attachment of the intercalating agent and the active component source on the layered carrier.
  • the manner of uniformly mixing the layered carrier, the intercalating agent, the active component source, the doping source and the solvent may be stirring and mixing.
  • the mixing process further includes sonication. Sonication is beneficial to facilitate the entry of the intercalant into the carrier sheet.
  • the mixing temperature is 15°C-50°C. At a higher mixing temperature, the molecular motion in the solution is accelerated, and the intercalation agent can better expand the interlayer spacing of the layered carrier.
  • the layered carrier, the intercalating agent, the active component source, the doping source and the solvent are directly mixed, and the mixing time is 1h-15h.
  • the layered carrier, the intercalating agent and the solvent are first mixed to form the first solution, and the mixing time is 0.5h-15h, and then the active component source, the doping source, the auxiliary agent source and the solvent are formed.
  • the second solution is added to the first solution, and the mixing time of the first solution and the second solution is 1h-5h.
  • the step-by-step mixing method can improve the loading capacity of the layered carrier for the active component source and the doping source, so that the active component source and the doping source are uniformly dispersed in the layered carrier.
  • the layered carrier is mixed with the solvent to form a first solution, and the mixing time is 0.5h-3h; after mixing, an intercalating agent is added to the first solution to form a second solution.
  • the mixing time is 1h-15h; then the third solution formed by the active component source, the doping source, the auxiliary source and the solvent is added to the second solution, and the mixing time of the second solution and the third solution is 1h-5h.
  • Pre-mixing the layered carrier with the solvent can make the solvent fully infiltrate the layered carrier, which is beneficial for the intercalation agent to enter the layered carrier sheet, thereby expanding the interlayer spacing of the layered carrier.
  • the catalyst precursor is obtained by stirring and filtering the mixed solution to remove the filtrate, and drying the filter residue.
  • the method of drying the filter residue may be drying in an oven or natural drying.
  • the calcination process can be specifically as follows: calcining the catalyst precursor at a temperature of 300°C-800°C, and after keeping the temperature for 1h-8h, a certain amount of water vapor is introduced, and the temperature is kept at 300°C-550°C for 0.5h- After 4 h, the catalyst was cooled to room temperature to obtain the catalyst.
  • the calcination temperature of the catalyst precursor will affect the structure of the catalyst, and further, the catalyst structure will affect the activity of the catalyst.
  • the calcination temperature may be, but not limited to, 300°C, 400°C, 500°C, 550°C, 600°C, 700°C or 800°C.
  • the calcination temperature is 300°C-550°C.
  • the solvent and intercalating agent in the catalyst precursor can be completely removed, and in the process of decomposing and gasifying the intercalating agent and evaporation of the solvent, the interlayer spacing of the layered carrier will be further expanded, which is beneficial to reduce the doping
  • the steric hindrance of the growth of heteromulti-walled carbon nanotubes in the interlayer promotes the formation of doped carbon nanotube arrays with high aspect ratios.
  • the equipment for calcining the catalyst precursor includes any one of a microwave high temperature furnace, a high temperature carbonization furnace, an intermediate frequency induction high temperature furnace and a muffle furnace.
  • the introduction of water vapor during the calcination process can reduce the active component source and the auxiliary agent source to metal particles to realize the activation of the catalyst.
  • the activation process does not require the introduction of flammable and explosive reducing gas, which is beneficial to safety. production and reduced production costs.
  • some intercalating agents will form carbon deposits on the surface of the catalyst due to incomplete combustion, resulting in a decrease in the activity of the catalyst, and the introduction of water vapor can effectively inhibit the decomposition products of the intercalating agent in the activity.
  • the inflow rate of water vapor is 50mL/min-200mL/min.
  • the introduction amount of water vapor can be, but not limited to, 50 mL/min, 60 mL/min, 80 mL/min, 100 mL/min, 110 mL/min, 130 mL/min, 170 mL/min, 190 mL/min or 200 mL/min.
  • Controlling the flow of water vapor can ensure that the catalyst is fully activated, and will not affect the decomposition of the intercalating agent, ensure that the intercalating agent is fully burned, and inhibit the formation of carbon deposits.
  • the time for preactivation by introducing water vapor is 0.5h-4h.
  • the time for the pre-activation by passing in water vapor can be specifically, but not limited to, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h and 4h.
  • step S300 the process of chemical vapor deposition can be specifically as follows: placing the catalyst in the reactor, feeding an inert gas and raising the temperature to a reaction temperature of 600°C-900°C, and then feeding a carbon source gas to carry out the deposition reaction, and the reaction time is 10min -100min, after the reaction is completed, inert gas is introduced and the temperature is lowered to room temperature to obtain an array of doped multi-walled carbon nanotubes on a layered carrier.
  • a second doping source may also be introduced during the chemical vapor deposition process in step S300, so as to also introduce doping atoms on the surface of the multi-walled carbon nanotube.
  • the material of the second doping source can be the same as the doping source in the above step S100, or different (for example, gaseous or liquid, etc., can be delivered to the reactor with an inert gas as a carrier).
  • the temperature of the chemical vapor deposition may be 650°C-780°C, and the reaction time may be 20min-90min.
  • the temperature of chemical vapor deposition can be specifically, but not limited to, 600°C, 650°C, 700°C, 750°C, 780°C, 800°C or 900°C. Controlling the temperature of chemical vapor deposition can ensure that the catalyst has good activity and is not easy to be deactivated, so that the rate of dehydrogenation of carbon source gas to form carbon atoms is moderate; and at this temperature, the diffusion resistance of carbon atoms in the active components is small, and there are It is beneficial to the formation of doped multi-walled carbon nanotubes. Among them, the inert gas, carbon source gas, reactor, etc. are as described above, and will not be repeated here.
  • step S300 the method for removing the catalyst (including the layered carrier and the active component) is pickling, and the specific process may be as follows: adding the crude doped multi-walled carbon nanotube array obtained by chemical vapor deposition into the acid solution, It is soaked for 2h-30h at a temperature of 40°C-100°C, washed with water until neutral, and dried to obtain doped multi-walled carbon nanotubes.
  • the specific acid solution, pickling time, and pickling temperature can be as described in the above step S02, and details are not repeated here.
  • the second method for preparing doped multi-walled carbon nanotubes has the advantages of simplified process, wide source of raw materials, strong operation controllability, small diameter and high aspect ratio of the prepared doped multi-walled carbon nanotubes. , the size and length are uniform, the product is regular, the consistency is good, and the electrical conductivity is good.
  • the preparation method has low cost and is suitable for large-scale industrial preparation.
  • the present application also provides a third preparation method of doped multi-walled carbon nanotubes, comprising the following steps:
  • S1 Disperse the active component source, the doping source, the layered carrier and the first carbon source in a solvent, and obtain a catalyst precursor after drying;
  • the active component source includes a soluble transition metal salt;
  • the active component source in the third preparation method of the doped multi-walled carbon nanotubes, by calcining the catalyst precursor containing the active component source, the doping source, the layered carrier and the first carbon source, the active component source can be During the calcination process, it is decomposed and reduced to active components by the reducing gases (such as H 2 , CO) obtained by the pyrolysis of the first carbon source, and supported on the layered carrier (specifically, it can be distributed on the surface of the layered carrier and its layers). time), the active component and the doping source are then coated with the amorphous carbon obtained by the pyrolysis of the first carbon source to obtain a carbon coating material, and then the carbon coating layer is removed to obtain a bare catalyst for growing carbon nanotubes .
  • the reducing gases such as H 2 , CO
  • the introduction of the dopant source during the preparation of the catalyst precursor can enable the dopant source to be effectively combined with the catalyst formed by the calcination of the catalyst precursor, thereby facilitating the incorporation of dopant atoms into the tube of the multi-walled carbon nanotube.
  • the existence of the carbon coating layer in the carbon coating material can effectively limit the particle size growth of the catalyst particles, so that the particle size of the obtained catalyst particles is small, for example, ⁇ 8 nm.
  • the catalyst was used for chemical vapor deposition to generate an array of doped multi-walled carbon nanotubes with smaller diameters.
  • the active component source and the material of the layered carrier in step S1 are as described in step S100 above.
  • the active component source may be a salt of at least one transition metal element selected from iron, nickel, cobalt, manganese, molybdenum, and tungsten. These transition metal salts have high carbon solubility and can form certain carbides, and carbon atoms have a high diffusion rate in these transition metals, which is conducive to nucleation and growth into carbon nanotubes.
  • the first carbon source can undergo complex reaction with metal ions to form a stable complex, which can effectively improve the impregnation efficiency of the metal active material and the layered carrier, and at the same time can avoid the agglomeration of the metal active material particles during the reaction process;
  • it is used for carbon coating to inhibit the crystal growth of the catalyst during the calcination process, and to control the particle size of the active component, so that the particle size of the active component in the catalyst is smaller, and then guide the synthesis of small particles through it. diameter carbon nanotubes.
  • the first carbon source is selected from at least one of citric acid, malic acid, tartaric acid, oxalic acid, salicylic acid, succinic acid, glycine, EDTA, sucrose, and glucose.
  • step S1 in order to improve the dispersibility of the active component source, the doping source, the layered carrier and the first carbon source in the solvent, the active component source and the doping source are first dissolved in the solvent. , after a saturated solution is formed, the layered carrier is added under stirring conditions to form a uniformly dispersed suspension, and finally the first carbon source is added under stirring conditions to form a uniformly dispersed suspension.
  • the mass ratio of the active component source and the layered carrier is controlled at (0.1-10): 1, and the mass of the first carbon source accounts for 10% of the total mass of the active component source and the layered carrier- 500%.
  • the addition amount of the first carbon source is too small, the coating will be uneven, the particles of the formed active component will be uneven, and large particles will be generated, so that the diameter of the obtained doped carbon nanotube array is larger; If the amount of carbon source added is too high, on the one hand, the cost is too high, resulting in waste, on the other hand, when the carbon coating layer is removed, it is easy to cause unclean removal, so that the catalyst is easily deactivated, and the yield of doped carbon nanotubes is not high. high.
  • the molar ratio of the dopant atoms in the dopant source and the transition metal atoms in the active component source is 1:(5-100) to use the dopant source and the active component source.
  • the drying method in step S1 is freeze-drying, which can prevent the metal active material particles from agglomerating, so that the diameter of the obtained carbon nanotubes is smaller.
  • suction filtration is performed before the catalyst precursor is dried to remove excess active component sources, reduce the active component sources that cannot be supported on the surface of the layered carrier, and help obtain high-purity doping Array of carbon nanotubes.
  • the calcination process is performed in an inert atmosphere to prevent the carbon material from burning under high temperature conditions to generate carbon dioxide gas.
  • the inert atmosphere is at least one of nitrogen, argon, and helium.
  • the calcination treatment is calcination at 300°C-700°C for 1 h-10 h.
  • typical and non-limiting calcination treatment temperatures are 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C; typical non-limiting calcination treatment times are 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h.
  • the way to remove the carbon coating material in S3 is calcination, and calcination can decompose the amorphous carbon into carbon dioxide gas. Calcination should be carried out in a non-inert and non-reducing atmosphere. In some specific embodiments, the calcination is carried out at 500°C-700°C for 1 h-10 h in at least one atmosphere of air, oxygen, and carbon dioxide. Among them, when calcined in a carbon dioxide atmosphere, the carbon dioxide can react with the amorphous carbon to form carbon monoxide, so as to achieve the purpose of removing the carbon coating layer. By controlling the temperature and calcination time of the calcination treatment, the carbon coating layer can be fully removed, and the catalytic activity of the obtained catalyst can be improved.
  • typical and non-limiting calcination treatment temperatures are 500°C, 550°C, 600°C, 650°C, 700°C; typical non-limiting calcination treatment times are 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h.
  • the second carbon source is mainly used to provide carbon for the chemical vapor deposition reaction to grow carbon nanotubes, and the specific selection of the second carbon source will also have a significant impact on the length of the resulting array carbon nanotubes.
  • the second carbon source is selected from at least one of methane, ethane, propane, ethylene, propylene, absolute ethanol, and carbon monoxide, but is not limited thereto.
  • transition metal salt when the transition metal salt is nickel nitrate, nickel chloride and/or a soluble organic salt of nickel, at least one of methane, ethane and propane is used as the second carbon source; when the transition metal salt is In the case of iron or cobalt nitrate, chloride and/or soluble organic salt, ethylene and propylene are used as the second carbon source.
  • a reducing gas is also introduced during the chemical vapor deposition reaction in step S4 to reduce the oxides of the active components in the catalyst, so that they are in a metal element state, and the oxidized carbon reduction of nanotubes.
  • the reducing gas is hydrogen, which has the advantages of strong reducibility, readily available raw materials and relatively low cost.
  • a second doping source may be introduced during the chemical vapor deposition reaction, so as to also introduce doping atoms on the surface of the multi-walled carbon nanotube to further improve the electrical conductivity.
  • the chemical vapor deposition reaction is at 600°C-1000°C for 30min-120min.
  • the temperature of the chemical vapor deposition reaction is set to 600°C-750°C; when alkane is used as the carbon source, the temperature of the chemical vapor deposition reaction is set to 800°C- 1000°C; when alkane is used as carbon source or active component source is nickel nitrate, nickel chloride and/or nickel soluble organic salt, due to the relatively poor activity of metallic nickel as active component, the rate of carbon nanotube formation It is relatively low, so the time of chemical vapor deposition reaction is set to 60min-120min.
  • typical and non-limiting chemical vapor deposition reaction temperatures are 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C; typical and non-limiting chemical vapor deposition
  • the deposition reaction time was 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min.
  • the method of removing the catalyst includes, but is not limited to, acid washing, graphitization, and the like.
  • the acid washing method is to add the crude product after chemical vapor deposition reaction into the acid solution to fully infiltrate, and stir the reaction at 60 °C-100 °C for 1h-20h, and then filter, wash and dry to obtain the purified doped carbon nanometers. Tube.
  • the graphitization method is to heat the crude product after chemical vapor deposition reaction at 1500°C-3000°C for 0.5h-10h in an environment with a vacuum degree lower than 20Pa to obtain purified doped carbon nanotubes.
  • the present application also provides an electrode material, the electrode material includes an electrode active material, a binder and a conductive agent, and the conductive agent includes the doped multi-walled carbon nanotubes provided in the first aspect of the present application.
  • the electrode active material can include nano silicon, silicon dioxide, silicon carbon alloy, silicon tin alloy, tin alloy, lithium titanate, lithium cobaltate, lithium nickelate, lithium manganate, lithium ferrosilicate, lithium manganese phosphate , one or more of lithium iron manganese phosphate and lithium iron phosphate.
  • the binder can include carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, sodium alginate, chitosan and styrene-butadiene rubber one or more of.
  • the conductive agent may only include the doped multi-walled carbon nanotubes of the present application.
  • the conductive agent may also include other conductive agent materials, for example, the conductive agent is one of the doped multi-walled carbon nanotubes and graphite, carbon black, graphene, carbon fiber and acetylene black in the present application or multiple formed compositions.
  • the mass percentage content of the electrode active material in the electrode material is 85.0%-97.0%
  • the mass percentage content of the doped multi-walled carbon nanotubes is 0.1%-3.0%
  • the mass percentage content of the binder is 2.0%-12.0%.
  • the preparation process of the electrode material is as follows: mixing lithium iron phosphate, doped multi-walled carbon nanotubes and polyvinylidene fluoride to obtain electrode slurry, and coating, drying, rolling, Die cutting and other steps are used to prepare electrode materials.
  • the volume resistivity of the lithium iron phosphate electrode material containing 2% by mass of doped multi-walled carbon nanotubes is 0.7 ⁇ cm-2 ⁇ cm.
  • the preparation process of the electrode material is as follows: mixing nano-silicon, doped multi-walled carbon nanotubes and sodium carboxymethyl cellulose to obtain electrode slurry, and coating, drying and rolling the electrode slurry. Pressing, die-cutting, and other steps are used to prepare electrode materials.
  • the electrode material provided by the present application has good conductivity due to the use of the doped multi-walled carbon nanotubes of the present application, and the abundant conductive channels of the doped multi-walled carbon nanotubes enable electrons to conduct multidirectional conduction in the electrode material.
  • the application of the electrode material in the battery can improve the conductivity of the battery and enhance the performance of the battery.
  • a preparation method of doped multi-walled carbon nanotubes comprising the following steps:
  • the Fe-W/MgO catalyst containing 1% mass fraction of boron nitride is added to the quartz boat, and the mixed gas of propane and nitrogen is fed into the tube furnace, wherein the gas partial pressure ratio of propane and nitrogen is 3:2.
  • the reaction was carried out at 1200 °C for 1 h to obtain crude boron-nitrogen doped multi-walled carbon nanotubes.
  • the preparation method of the electrode test sample includes the following steps:
  • the electrode slurry is obtained by mixing lithium iron phosphate, boron-nitrogen-doped multi-walled carbon nanotubes and polyvinylidene fluoride, wherein the mass percentage of lithium iron phosphate is 94.0%, and the boron-nitrogen-doped multi-walled carbon nanotubes The mass percentage of 1.5%, the mass percentage of polyvinylidene fluoride is 4.5%.
  • the electrode slurry was coated on the insulating layer and dried to prepare an electrode test sample.
  • a preparation method of doped multi-walled carbon nanotubes comprising the following steps:
  • the preparation method of the electrode test sample includes the following steps:
  • the electrode slurry is obtained by mixing lithium iron phosphate, nitrogen-doped multi-walled carbon nanotubes and sodium carboxymethyl cellulose, wherein the mass percentage of lithium iron phosphate is 96.0%, and the nitrogen-doped multi-walled carbon nanotubes are The mass percentage of carboxymethyl cellulose is 1.3%, and the mass percentage of sodium carboxymethyl cellulose is 2.7%.
  • the electrode slurry was coated on the insulating layer and dried to prepare an electrode test sample.
  • a preparation method of doped multi-walled carbon nanotubes comprising the following steps:
  • the Ni-Mo/Al 2 O 3 catalyst containing 20% mass fraction of aluminum sulfate was added to the quartz boat, and the mixed gas of methane and hydrogen was passed into the tube furnace, wherein the gas partial pressure of methane and hydrogen was The ratio is 1:1.
  • the reaction was carried out at 850 °C for 1 h to obtain crude sulfur-doped multi-walled carbon nanotubes.
  • the preparation method of the electrode test sample includes the following steps:
  • the electrode slurry is obtained by mixing lithium iron phosphate and sulfur-doped multi-walled carbon nanotubes with polyacrylonitrile, wherein the mass percentage of lithium iron phosphate is 94.0%, and the mass of sulfur-doped multi-walled carbon nanotubes is 100%. The fractional content is 2.0%, and the mass percentage of polyacrylonitrile is 4.0%.
  • the electrode slurry was coated on the insulating layer and dried to prepare an electrode test sample.
  • the preparation method of the electrode test sample includes the following steps:
  • the electrode slurry is obtained by mixing lithium iron phosphate, undoped multi-walled carbon nanotubes and polyvinylidene fluoride, wherein the mass percentage of lithium iron phosphate is 94.5%, and the mass of undoped multi-walled carbon nanotubes is 94.5%.
  • the percentage content is 2.0%, and the mass percentage content of polyvinylidene fluoride is 3.5%.
  • the electrode slurry was coated on the insulating layer and dried to prepare an electrode test sample.
  • the present invention also provides effect examples
  • FIG. 3 is a transmission electron microscope image of the boron-nitrogen-doped multi-walled carbon nanotubes prepared in Example 1 of the application
  • FIG. 4 is a transmission electron microscope view of the nitrogen-doped multi-walled carbon nanotubes prepared in Example 2 of the application.
  • Electron microscope image, FIG. 5 is a transmission electron microscope image of the multi-walled carbon nanotubes prepared in Comparative Example 1 of the application.
  • the doped multi-walled carbon nanotubes are linear as a whole, with local bends, which have corrugated folds, and the interlayer spacing between the tube walls is different. It can be seen from Figure 5 that the undoped multi-wall carbon nanotubes have flat walls, uniform interlayer spacing between the tube walls, and basically no defects, which are completely different from the morphology of the doped multi-wall carbon nanotubes.
  • Example 1-3 The electrode test samples in Examples 1-3 and Comparative Example 1 were subjected to volume resistivity test, wherein the volume resistivity was represented by ⁇ 2 . Please refer to Table 1 for the results.
  • Example 1 50.3 1.1
  • Example 2 52.3 1.0
  • Example 3 56.5 1.3 Comparative Example 1 80.5 5.6
  • the electrical conductivity of the doped multi-walled carbon nanotubes in the present application is significantly improved after atomic doping, and the doped multi-walled carbon nanotubes in the present application are added to the electrode material as a conductive agent, It can improve the conductivity of the electrode material and enhance the performance of the battery.
  • a preparation method of doped carbon nanotubes comprising the following steps:
  • the catalyst precursor was calcined in a muffle furnace at 550°C for 2h, pre-activated with steam at 550°C for 30min, and cooled to room temperature to obtain a catalyst; the catalyst includes hydrotalcite and magnesium borate and magnesium borate supported on hydrotalcite. Metallic cobalt particles.
  • step (3) Mix the product obtained in step (3) with 5% nitric acid solution at 80°C for 12h to remove the catalyst, filter, wash and dry to obtain boron-doped multi-walled carbon nanotubes.
  • the measured diameter of the boron-doped multi-walled carbon nanotubes in Example 4 is 5-8 nm, the length is 40-80 ⁇ m, the aspect ratio is 5000:1-16000:1, and the resistivity is 0.02 ⁇ cm.
  • the boron-doped multi-walled carbon nanotubes of Example 4 were prepared into electrode test samples in the manner described in Example 1, and the volume resistivity of the electrode test samples was measured to be 0.5 ⁇ cm.
  • a preparation method of doped carbon nanotubes comprising the following steps:
  • the catalyst precursor was calcined in a muffle furnace at 500°C for 3 hours, pre-activated with steam at 500°C for 60 minutes, and cooled to room temperature to obtain a catalyst; the catalyst includes expanded graphite and metal nickel particles supported on the expanded graphite , tungsten particles and aluminum sulfate.
  • step (3) The product obtained in step (3) is soaked in 10% nitric acid solution at 80° C. for 24 hours to remove the catalyst, and after suction filtration, washing and drying, boron-doped multi-walled carbon nanotubes are obtained.
  • the diameter of the boron-doped multi-walled carbon nanotubes in Example 5 was measured to be 3-6 nm, the length was 40-80 ⁇ m, the aspect ratio was 6666:1-26666:1, and the resistivity was 0.021 ⁇ cm.
  • the boron-doped multi-walled carbon nanotubes of Example 5 were prepared into electrode test samples in the manner described in Example 3, and the volume resistivity of the electrode test samples was measured to be 0.4 ⁇ cm.
  • a preparation method of array-type doped carbon nanotubes comprising the following steps:
  • the catalyst precursor was calcined in a muffle furnace at 600° C. for 2 hours, pre-activated with steam at 550° C. for 90 minutes, and cooled to room temperature to obtain a catalyst.
  • step (3) The product obtained in step (3) is soaked in a 10% nitric acid solution at 80° C. for 24 hours to remove the catalyst, and after suction filtration, washing and drying, nitrogen-doped multi-walled carbon nanotubes are obtained.
  • the diameter of the boron-doped multi-walled carbon nanotubes in Example 6 was measured to be 7-10 nm, the length was 30-50 ⁇ m, the aspect ratio was 3000:1-7142:1, and the resistivity was 0.022 ⁇ cm.
  • the preparation of electrode test samples includes: mixing lithium iron phosphate, nitrogen-doped multi-walled carbon nanotubes in Example 6, and sodium methyl cellulose to obtain electrode slurry, wherein the mass percentage of lithium iron phosphate is 96.0 %, the mass percentage of nitrogen-doped multi-walled carbon nanotubes is 1.3%, and the mass percentage of sodium carboxymethyl cellulose is 2.7%.
  • the electrode slurry was coated on the insulating layer and dried to prepare an electrode test sample. The volume resistivity of the electrode test sample was measured to be 0.6 ⁇ cm.
  • a preparation method of doped carbon nanotubes comprising the following steps:
  • the diameter of the sulfur-doped multi-walled carbon nanotubes in Example 7 is 5-8 nm, the length is 30-50 ⁇ m, the specific surface area is 272 m 2 /g, and the resistivity is 0.035 ⁇ cm.
  • the sulfur-doped multi-walled carbon nanotubes in Example 7 were prepared into electrode test samples in the manner described in Example 1, and the volume resistivity of the electrode test samples was measured to be 0.7 ⁇ cm.
  • a preparation method of doped carbon nanotubes comprising the following steps:
  • boron and nitrogen co-doped carbon nanotube arrays were obtained by deposition on the stone; after the deposition was completed, the obtained product was soaked in a 5% nitric acid solution at 80 °C for 12 h, filtered, washed and dried to obtain boron and nitrogen doped carbon nanotube arrays. Walled carbon nanotubes.
  • the diameter of the multi-walled carbon nanotubes co-doped with boron and nitrogen in Example 8 is 7-8 nm, the length is 30-50 ⁇ m, the specific surface area is 258 m 2 /g, and the resistivity is 0.038 ⁇ cm.
  • the boron-nitrogen co-doped multi-walled carbon nanotubes in Example 5 were prepared into electrode test samples in the manner described in Example 1, and the volume resistivity of the electrode test samples was measured to be 0.8 ⁇ cm.

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Abstract

一种掺杂多壁碳纳米管，包括多壁碳纳米管和掺杂在多壁碳纳米管中的掺杂原子；该掺杂多壁碳纳米管具有径向导电通道，径向导电通道是由掺杂原子与多壁碳纳米管的相邻管壁通过共价键合形成。该掺杂多壁碳纳米管具有良好的导电性，将其应用在电极材料中能够提高电极材料的导电性。还提供了掺杂多壁碳纳米管的制备方法。该制备方法工艺简单，操作便捷，所得的掺杂多壁碳纳米管良品率高。

Description

掺杂多壁碳纳米管及其制备方法和电极材料
本申请要求于2020年09月18日提交至中国专利局、申请号为202010990044.9、发明名称为“掺杂多壁碳纳米管和电极材料”的中国专利申请的优先权，上述在先申请的内容以引入的方式并入本文本中。
技术领域
本申请涉及多壁碳纳米管技术领域，具体涉及一种掺杂多壁碳纳米管和电极材料。
背景技术
碳纳米管是碳的一种同素异形体，其可看作是由一层或多层石墨烯片按照一定螺旋角卷曲而成的、直径为纳米级的无缝管。根据石墨烯片层数可将碳纳米管分为单壁碳纳米管和多壁碳纳米管，单壁碳纳米管是由一层石墨烯片卷曲而成，而多壁碳纳米管则是由多层石墨烯片卷曲而成。碳纳米管作为一维纳米材料，其轴向具有良好的导电通路。如图1所示，虚线箭头表示多壁碳纳米管的轴向导电通道，电子可沿轴向导电通道进行迁移。然而由于碳纳米管的管壁是由石墨烯片卷曲形成，电子难以在石墨烯片层之间传输，因此多壁碳纳米管沿径向的导电性差，从而限制了其作为导电剂在电极中的应用。为进一步提高多壁碳纳米管的导电性能，有必要提高其径向导电性能。
申请内容
鉴于此，本申请提供了一种掺杂多壁碳纳米管，该掺杂多壁碳纳米管具有径向导电通道，能够促进电子沿多壁碳纳米管的径向传输，进而使掺杂多壁碳纳米管具有良好的导电性，将其应用在电极材料中能够提高电极材料的导电性。
本申请第一方面提供了一种掺杂多壁碳纳米管，所述掺杂多壁碳纳米管包括多壁碳纳米管和掺杂在所述多壁碳纳米管中的掺杂原子；所述掺杂多壁碳纳米管具有径向导电通道，所述径向导电通道由所述掺杂原子与所述多壁碳纳米管的相邻管壁通过共价键合形成。
本申请第一方面提供的掺杂多壁碳纳米管具有径向导电通道，促进了电子在多壁碳纳米管的径向传输，使掺杂多壁碳纳米管具有良好的导电性以及较好的电子传导能力，从而拓展了多壁碳纳米管的应用。
本申请第二方面提供了一种掺杂多壁碳纳米管的制备方法，包括以下步骤：
将掺杂前体、碳源和载气加入反应器，通过化学气相沉积得到掺杂多壁碳纳米管粗品；
将所述掺杂多壁碳纳米管粗品进行酸洗，干燥后得到如本申请第一方面所述的掺杂多壁碳纳米管。
本申请第三方面也提供了一种掺杂多壁碳纳米管的制备方法，包括以下步骤：
将层状载体、插层剂、活性组分源、掺杂源和溶剂混合均匀，干燥后得到催化剂前驱体；所述活性组分源包括可溶性的过渡金属盐；
将所述催化剂前驱体进行煅烧，在煅烧过程中通入水蒸气，冷却后得到催化剂，所述催化剂包括所述层状载体和负载在所述层状载体上的活性组分及所述掺杂源，所述活性组 分包括过渡金属活性颗粒；
将所述催化剂置于反应器中，在惰性气氛中通入碳源，通过化学气相沉积的方式在所述层状载体上形成掺杂多壁碳纳米管的阵列，之后再去除所述催化剂，得到如本申请第一方面所述的掺杂多壁碳纳米管。
本申请第四方面也提供了一种掺杂多壁碳纳米管的制备方法，包括以下步骤：
将活性组分源、掺杂源、层状载体和第一碳源分散于溶剂中，经干燥处理得到催化剂前驱体；所述活性组分源包括可溶性的过渡金属盐；
将所述催化剂前驱体在惰性气氛中进行煅烧处理，得到碳包覆材料；所述碳包覆材料包括催化剂和包覆所述催化剂的碳包覆层，所述催化剂包括所述层状载体及负载在所述层状载体上的过渡金属活性颗粒及所述掺杂源；
去除所述碳包覆层，得到裸露的所述催化剂；
将所述催化剂置于反应器中，在惰性气氛中通入第二碳源，通过化学气相沉积的方式在所述层状载体上形成掺杂多壁碳纳米管的阵列；之后再去除所述催化剂，得到如本申请第一方面所述的掺杂多壁碳纳米管。
本申请第二方面、第三方面或第四方面提供的掺杂多壁碳纳米管的制备方法，通过化学气相沉积法制备出具有径向导电通道的掺杂多壁碳纳米管，工艺简单、操作可控性强并且制备出的掺杂多壁碳纳米管的良品率高。
本申请第五方面提供了一种电极材料，该电极材料包括电极活性材料、粘合剂和导电剂，导电剂包括本申请第一方面提供的掺杂多壁碳纳米管。
本申请中的掺杂多壁碳纳米管具有良好的导电性，可作为导电剂添加到电极材料中，并且能够减少电极材料中导电剂的用量，从而提高电极材料中电极活性材料的含量，使电极材料具有更高的能量密度。本申请第五方面提供的电极材料具有较好的导电性，应用在电池中能够提高电池的能量密度，提升电池的性能。
附图说明
图1为未掺杂的多壁碳纳米管的结构示意图；
图2为本申请的掺杂多壁碳纳米管的结构示意图；
图3为本申请实施例1所制得的掺杂多壁碳纳米管的透射电镜图；
图4为本申请实施例2所制得的掺杂多壁碳纳米管的透射电镜图；
图5为本申请对比例1所制得的多壁碳纳米管的透射电镜图。
具体实施方式
以下所述是本申请的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本申请的保护范围。
本申请实施例提供了一种掺杂多壁碳纳米管，包括多壁碳纳米管和掺杂在多壁碳纳米管中的掺杂原子。掺杂多壁碳纳米管具有径向导电通道，径向导电通道是由掺杂原子与多壁碳纳米管的相邻管壁通过共价键合形成。请参见图2，其中虚线箭头表示多壁碳纳米管 的轴向导电通道，电子可沿轴向导电通道进行迁移；实线箭头表示多壁碳纳米管的径向导电通道，电子可沿径向导电通道进行迁移。
本申请实施方式中，掺杂多壁碳纳米管的管壁只含有碳原子，掺杂原子位于多壁碳纳米管的管壁之间。本申请实施方式中，通过在多壁碳纳米管的管壁之间掺入掺杂原子，使掺杂原子与多壁碳纳米管中的相邻管壁的碳原子形成C-X-C共价键，其中X为掺杂原子。不同管壁之间的C-X-C共价键将多个管壁连接形成径向导电通道，该径向导电通道可以促进电子在多壁碳纳米管的径向传输，进而提高了多壁碳纳米管的导电性。
本申请实施方式中，掺杂多壁碳纳米管整体为直线型，局部形成弯折部，弯折部具有波纹状的褶皱。弯折部是由于掺杂原子在多壁碳纳米管的管壁形成共价键，破坏了多壁碳纳米管的层间作用力，导致掺杂多壁碳纳米管管壁之间的层间距大小不一，从而也使得掺杂多壁碳纳米管出现褶皱和扭转变形。上述层间距变化、褶皱和扭转变形均为掺入掺杂原子后多壁碳纳米管出现的缺陷。本申请实施方式中，掺杂多壁碳纳米管的缺陷占比为30％-80％。通过控制掺杂多壁碳纳米管的缺陷含量，不仅能够保证径向导电通道数量充足，而且不影响电子沿掺杂多壁碳纳米管轴向的传输速率，从而使多壁碳纳米管在轴向和径向都具有良好的电子传输速率。
本申请中，掺杂多壁碳纳米管的缺陷含量与掺杂原子的种类和含量有关。本申请实施方式中，掺杂原子包括硼原子、氮原子、磷原子、硫原子和硅原子中的一种或多种。通过在多壁碳纳米管的管壁之间掺入掺杂原子，掺杂原子能够与相邻管壁上的碳原子键合形成C-B-C、C-N-C、C-P-C、C-S-C和C-Si-C中的一种或多种共价键，从而在多壁碳纳米管的管壁之间有效构建电子迁移通道，促进电子在多壁碳纳米管的径向传输。本申请实施方式中，在多壁碳纳米管中掺杂原子还能够引起多壁碳纳米管的导电类型发生变化。本申请一些实施方式中，掺杂原子为硼原子，掺杂多壁碳纳米管形成p型导电，以空穴进行导电。本申请另一些实施方式中，掺杂原子为氮原子，掺杂多壁碳纳米管形成n型导电，以多数载流子进行导电。本申请中的掺杂多壁碳纳米管可根据实际需求选择不同的掺杂原子来调节掺杂多壁碳纳米管的导电性能。
本申请实施方式中，掺杂原子的质量百分含量为0.01％-10％。进一步地，掺杂原子的质量百分含量为1％-10％，具体可以但不限于为0.01％、0.05％、0.1％、0.5％、1.5％、3％、5％或10％。控制掺杂原子的含量能够调节径向导电通道的数量，保证掺杂多壁碳纳米管在轴向和径向的电子传输速率，提高掺杂多壁碳纳米管的导电性。本申请一些实施方式中，掺杂原子为硼原子，硼原子的质量百分含量为5％。
本申请实施方式中，掺杂多壁碳纳米管的层数为3层-10层。一般地，多壁碳纳米管的层数大于或等于3时，电子通常难以在石墨烯片层之间传输，而将掺杂原子掺入多壁碳纳米管，则能有效促进电子在多壁碳纳米管的径向迁移，提高多壁碳纳米管的导电性；多壁碳纳米管的层数小于或等于10时，掺杂原子能够充分掺杂到多壁碳纳米管的每层管壁，有利于在多壁碳纳米管的径向方向形成较短的电子传输通道，促进电子传输。其中，掺杂多壁碳纳米管的层数具体可以但不限于为3层、4层、5层、7层、9层或10层。在一些实施方式中，掺杂多壁碳纳米管的层数为5-9层。可选地，掺杂多壁碳纳米管的管壁厚度为2-3nm。
本申请实施方式中，掺杂多壁碳纳米管的直径可以为3nm-100nm，掺杂多壁碳纳米管的长度可以为1μm-100μm。本申请一些实施方式中，掺杂多壁碳纳米管的直径可以为3nm-10nm，优选为3-8nm。更优选为3-7.5nm。此时，该掺杂多壁碳纳米管的管径很小，长径比极高，性能会较优异(如缺陷密度较低、导电性能更好)。
在一些实施方式中，掺杂多壁碳纳米管的长度可以为10μm-100μm。进一步地，掺杂多壁碳纳米管的长度可以为30μm-100μm、40μm-90μm、30μm-60μm或35μm-55μm。
本申请实施方式中，掺杂多壁碳纳米管的长径比为10-33333。在一些实施方式中，该掺杂多壁碳纳米管的长径比可以为125-33333、300-33333、300-20000。优选为3750-33333，进一步优选为4286-33333。
本申请实施方式中，所述掺杂多壁碳纳米管的比表面积≥250m 2/g。较大比表面积的掺杂多壁碳纳米管在用于电池电极材料、超级电容器电极材料等领域时，可以更好地发挥其导电性能，在其用于电池中还可以具有较好的吸液性，有利于电极材料得到充分浸润。
本申请实施方式中，所述掺杂多壁碳纳米管在形成所述共价键合的位置处的层间距大于未形成所述共价键合的位置处的层间距。将掺杂原子掺入到多壁碳纳米管的管壁之间时，由于形成共价键，多壁碳纳米管的管壁之间的层间作用力发生变化，导致管壁在共价键合的位置处的层间距会变大，使得多壁碳纳米管呈现出扭曲的结构，进一步地，扭曲的结构能够使多壁碳纳米管接收电子的空穴增多，从而提高多壁碳纳米管的导电性。
本申请实施方式中，掺杂多壁碳纳米管的电阻率为20mΩ·cm-75mΩ·cm。掺杂多壁碳纳米管的电阻率具体可以但不限于为20mΩ·cm、30mΩ·cm、35mΩ·cm、40mΩ·cm、45mΩ·cm、50mΩ·cm、55mΩ·cm、60mΩ·cm、65mΩ·cm或75mΩ·cm。本申请中的掺杂多壁碳纳米管的电阻率数值较小，具有良好的导电性。
本申请实施方式中，掺杂多壁碳纳米管可应用在电池电极材料和超级电容器电极材料中，但不限于此。
本申请提供的掺杂多壁碳纳米管通过在多壁碳纳米管的管壁之间掺入掺杂原子，使掺杂原子与多壁碳纳米管中的相邻管壁形成共价键，该共价键能够将多壁碳纳米管内部的共轭结构延伸至多壁碳纳米管外部，使得多壁碳纳米管具有径向导电通道，该径向导电通道丰富了电子在多壁碳纳米管的迁移路径，促进了电子在多壁碳纳米管的径向传输，使掺杂多壁碳纳米管具有良好的导电性以及较好的电子传导能力，拓展了多壁碳纳米管的应用。
本申请还提供了上述掺杂多壁碳纳米管的一种制备方法，包括以下步骤：
S01：将掺杂前体、碳源和载气加入反应器，通过化学气相沉积的方式得到掺杂多壁碳纳米管粗品；
S02：将掺杂多壁碳纳米管粗品进行酸洗，干燥后得到掺杂多壁碳纳米管；所述掺杂多壁碳纳米管包括多壁碳纳米管和掺杂在所述多壁碳纳米管中的掺杂原子；所述掺杂多壁碳纳米管具有径向导电通道，所述径向导电通道由所述掺杂原子与所述多壁碳纳米管的相邻管壁通过共价键合形成。
本申请中，通过将掺杂源与催化剂预先进行混合处理，使掺杂源附着到催化剂表面。在气相沉积过程中，掺杂前体中的掺杂源能够分解产生掺杂原子，掺杂原子可以熔解在催化剂中，同时碳源在催化剂作用下会分解形成碳原子，碳原子也能够在催化剂中熔解；当 掺杂原子和碳原子在催化剂中饱和时，二者会从催化剂中析出，进而形成掺杂多壁碳纳米管。由于掺杂原子与碳原子在催化剂中的熔解度不同，因此掺杂原子的掺杂位点在多壁碳纳米管管壁之外，即多壁碳纳米管中相邻管壁中间。
本申请实施方式中，步骤S01中，掺杂前体包括掺杂源和催化剂，其中，掺杂源附着在催化剂表面。催化剂包括铁催化剂、钴催化剂和镍催化剂中的一种或多种。进一步地，催化剂为金属基复合材料。本申请一些实施方式中，催化剂包括Fe-W/MgO、Co-Mo/Al 2O 3、Ni-Mo/Al 2O 3、Fe-Mo/Al 2O 3中的一种或多种。采用上述催化剂能够促进碳原子形成多壁碳纳米管，并且在反应结束后该催化剂易被除去，有利于提高掺杂多壁碳纳米管的纯度。
本申请实施方式中，掺杂源包括硼酸镁、硼酸钠、氮化硼、氮化铝、硫酸铝、硫酸镁中的一种或多种，但不限于此。上述掺杂源能够与催化剂有效结合形成掺杂前体，从而有利于将掺杂原子掺入到多壁碳纳米管的管壁之间，提升掺杂多壁碳纳米管的良品率。
本申请实施方式中，掺杂前体由掺杂源与催化剂按照掺杂源中掺杂原子和催化剂中金属原子的摩尔数比为1：(5-100)进行混合得到。制备掺杂前体的设备可以是球磨机、砂磨机、混料机或融合包覆机中的任意一种。本申请一些实施方式中，制备掺杂前体的设备为融合包覆机，掺杂前体的制备过程具体为：将原料分别加入融合包覆机，在刀片剪切力的作用下，掺杂源与催化剂界面发生融合，掺杂源附着在催化剂表面形成掺杂前体。通过将催化剂与掺杂源制备为掺杂前体，在化学气相沉积法制备掺杂多壁碳纳米管时，能够使掺杂原子充分掺入到多壁碳纳米管的每层管壁中。本申请实施方式中，碳源可以是C 1-C 4的烷烃(如甲烷、乙烷、丙烷、丁烷)、烯烃(如乙烯、丙烯、丁烯)、炔烃中的一种或多种。本申请实施方式中，载气包括氮气、氩气、氦气、氢气中的一种或多种。
本申请一些实施方式中，化学气相沉积的过程具体为：将掺杂前体、碳源和载气加入反应器，以1℃/min-10℃/min的升温速率升温至600℃-1500℃，保温0.5h-4h后自然冷却至室温。本申请一些实施方式中，化学气相沉积的温度为700℃-1200℃，保温时间为0.5h-1.5h。本申请实施方式中，惰性气体可以是氮气、氦气、氩气和氢气中的一种或者多种。本申请实施方式中，反应器可以是箱式炉、管式炉或流化床中的任意一种。
本申请实施方式中，步骤S02中，将掺杂多壁碳纳米管粗品进行酸洗的过程具体为：将掺杂多壁碳纳米管粗品加入到酸溶液中，在40℃-100℃的温度下浸润2h-30h，再将其水洗至中性，干燥后得到掺杂多壁碳纳米管。本申请实施方式中，酸溶液可以为硝酸溶液、盐酸溶液、硫酸溶液中的一种或多种。本申请实施方式中，酸溶液的质量分数为2wt％-15wt％，具体可以但不限于为2wt％、5wt％、10wt％、13wt％或15wt％。本申请一些实施方式中，酸洗的温度为50℃-80℃，酸洗的时间为12h-24h。
本申请采用化学气相沉积法制备出具有径向导电通道的掺杂多壁碳纳米管，工艺简单、操作可控性强、制备出的掺杂多壁碳纳米管的良品率高。
本申请还提供了上述掺杂多壁碳纳米管的第二种制备方法，包括以下步骤：
S100：将层状载体、插层剂、活性组分源、掺杂源和溶剂混合均匀，干燥后得到催化剂前驱体；其中，所述活性组分源包括可溶性的过渡金属盐；
S200：将所述催化剂前驱体进行煅烧，在煅烧过程中通入水蒸气，冷却后得到催化剂，所述催化剂包括所述层状载体和负载在所述层状载体上的活性组分及所述掺杂源，所述活 性组分包括过渡金属活性颗粒；
S300：将所述催化剂置于反应器中，在惰性气氛中通入碳源，通过化学气相沉积的方式在所述层状载体上形成掺杂多壁碳纳米管的阵列，之后再去除所述层状载体，得到所述掺杂多壁碳纳米管；所述掺杂多壁碳纳米管包括多壁碳纳米管和掺杂在所述多壁碳纳米管中的掺杂原子；所述掺杂多壁碳纳米管具有径向导电通道，所述径向导电通道由所述掺杂原子与所述多壁碳纳米管的相邻管壁通过共价键合形成。
该掺杂多壁碳纳米管的第二种制备方法中，通过采用插层剂使层状载体的层间距扩大，有效地增加了层状载体负载活性组分的量，插层剂还能够抑制活性组分源团聚，有利于形成小粒径的活性组分，进而促进形成具有较高长径比的阵列碳纳米管；使用水蒸气进行催化剂的预活化具有较好的安全性并降低了生产成本；在制备催化剂前驱体时就引入掺杂源，可以使掺杂源能够与催化剂前驱体煅烧形成的催化剂实现有效结合，从而有利于将掺杂原子掺入到多壁碳纳米管的管壁之间。采用本方法制备出的阵列型掺杂多壁碳纳米管具有较高的长径比、良好的管径均一性和优良的导电性；该制备方法工艺精简，操作可控性强，可应用于大规模的工业化生产。
步骤S100中，掺杂源可以包括硼酸镁、硼酸钠、氮化硼、氮化铝、硫酸铝、硫酸镁中的一种或多种，但不限于此。可选地，掺杂源中掺杂原子和活性组分源中过渡金属原子的摩尔数比为1：(5-100)来取用掺杂源和活性组分源。
本申请中，层状载体具有大的比表面积，对活性组分源具有较高的负载能力，并且本申请使用的载体具有良好的吸附能力，有利于插层剂和活性组分源附着在载体表面。此外，层状载体可以后续作为碳纳米管生长用催化剂的载体，为碳纳米管的生长提供一个平面，使碳纳米管垂直生长形成碳纳米管阵列。其中，层状载体包括层状氧化铝、层状氧化镁、拟薄水铝石、层状二氧化硅、蛭石、膨胀石墨、云母石、水滑石(LDH)、蒙脱石、高岭土和累托石中的一种或多种，但不限于此。本申请实施方式中，层状载体的横向尺寸为0.02mm-2mm。这里的横向尺寸是指层状载体的长度或宽度等。具体地，层状载体的横向尺寸可以但不限于为0.03mm、0.05mm、0.1mm、0.15mm、0.3mm、0.5mm、1mm、1.5mm或2mm。控制层状载体的横向尺寸能够保证层状载体、插层剂、活性组分源、掺杂源可充分混合。
本申请中，活性组分指的是具有催化活性的组分，本申请中的活性组分源在煅烧后能够形成所述活性组分，活性组分能够催化碳源和掺杂源形成掺杂碳纳米管；本申请中，活性组分源包括可溶性的过渡金属盐，这样所得活性组分包括过渡金属活性颗粒。本申请实施方式中，所述过渡金属盐具体可以为铁、钴、镍、锰、钛、钼、钨、钌和钯中的至少一种的盐，具体可以是这些过渡金属元素的硝酸盐、氯化盐、硫酸盐、可溶性有机盐中的一种或多种。在一些实施方式中，活性组分源包括可溶性的钛盐、锰盐、铁盐、钴盐、镍盐、钌盐和钯盐中的一种或多种，相应地，活性组分为钛、锰、铁、钴、镍、钌和钯中的至少一种。
本申请一些实施方式中，活性组分源包括硫酸钛、硝酸钛、硫酸锰、硝酸锰、氯化锰、乙酸铁、硫酸铁、硝酸铁、硫酸钴、乙酸钴、硝酸钴、硫酸镍、硝酸镍、硝酸钌和硝酸钯中的一种或多种，但不限于此。进一步地，活性组分源包括硝酸钛、硝酸锰、硝酸铁、硝 酸钴、硝酸镍、硝酸钌和硝酸钯中的一种或多种。在煅烧过程中，硝酸根在高温下会发生分解，从而在活性组分周围形成局部较高的气相分压，该气相分压有利于碳原子在活性组分中由被吸附的晶面向碳纳米管生长的晶面扩散，从而形成管径均匀且长径比较高的阵列碳纳米管。
本申请一些实施方式中，将层状载体、插层剂、活性组分源、掺杂源和溶剂混合均匀的过程中，还加入了助剂源。在催化剂前驱体的煅烧过程中，助剂源能够形成助剂，助剂不仅起到协同催化的作用，还能够促进活性组分的分散，减小活性组分的颗粒大小，使得碳纳米管在活性组分中生长的区域变小，从而形成管径较小的阵列碳纳米管。本申请实施方式中，助剂源包括含钼的可溶性盐、含镧的可溶性盐和含钨的可溶性盐中的一种或多种。本申请一些实施方式中，助剂源包括钼酸钠、钼酸铵、硝酸镧或硝酸钨中的一种或多种。本申请实施方式中，活性组分源与助剂源的质量比为1:(0.002-1)。本申请一些实施方式中，活性组分源与助剂源的质量比为1:(0.01-0.5)。活性组分源与助剂源的质量比具体可以但不限于为1:0.002、1:0.01、1:0.02、1:0.05、1:0.1、1:0.4、1:0.5、1:0.7或1:1。
本申请中，添加插层剂能够有效扩大载体的层间距，进而提升层状载体对活性组分源的负载能力，同时插层剂能够包裹活性组分源，避免活性组分源在煅烧过程中聚集形成大粒径的颗粒，从而提高活性组分在层状载体中的分散均匀性，有利于形成管径均一、长径比较高的掺杂碳纳米管的阵列。本申请实施方式中，插层剂可通过吸附的方式插入载体片层。本申请另一些实施方式中，当层状载体的层间带有电荷时，可选用与层状载体带有相反电荷的插层剂，以便插层剂可通过静电作用插入载体片层。具体地，当层状载体为膨胀石墨时，可选用阴离子型插层剂与膨胀石墨混合，从而提升插层剂扩大膨胀石墨的层间距的效果。本申请另一些实施方式中，插层剂可通过离子交换插入层状载体的片层。当插层剂负载在层状载体上时，能够改善层状载体表面的润湿性，使溶剂充分浸润层状载体，有利于活性组分源进入层状载体的层间，提升层状载体对活性组分源的负载能力。
本申请中，插层剂为有机插层剂。有机插层剂具有较大的空间结构，能很好地扩大层状载体的层间距；且其在煅烧过程中能够被氧化为二氧化碳或其它气态化合物，不会残留在催化剂中，影响催化剂的活性；除此之外，有机插层剂的酸碱性较弱，对催化剂的活性影响较小。本申请实施方式中，插层剂可以包括阴离子型插层剂、阳离子型插层剂和有机胺类插层剂中的一种或多种。
本申请实施方式中，阴离子型插层剂包括有机磺酸盐和有机硫酸酯盐中的一种或多种。本申请实施一些方式中，有机磺酸盐包括十二烷基苯磺酸钠、羟乙基磺酸钠和苯乙烯磺酸钠中的一种或多种；有机硫酸酯盐包括十二烷基硫酸钠。本申请实施方式中，阳离子型插层剂包括烷基季铵盐和含有苯环的季铵盐中的一种或多种。其中，烷基季铵盐包括十二烷基三甲基溴化铵、十六烷基三甲基溴化铵和十八烷基三甲基溴化铵中的一种或多种。本申请实施方式中，有机胺类插层剂包括脂肪胺类有机胺、酰胺类有机胺和芳香胺类有机胺中的一种或多种。本申请实施一些方式中，脂肪胺类插层剂包括乙醇胺、二乙醇胺、三乙醇胺、3-丙醇胺、异丙醇胺、N,N-二甲基乙醇胺和N,N-二乙基乙醇胺中的一种或多种；酰胺类插层剂包括乙酰胺、丙酰胺、丙烯酰胺、聚丙烯酸胺和二甲基甲酰胺中的一种或多种；芳香胺类插层剂包括苯胺、二苯胺等中的一种或多种。上述插层剂对本申请中的载体具有 较好的亲和力，能够与载体有效地结合，其中，选择分子量较大、链长较长的插层剂，更有利于扩大层状载体的层间距。本申请一些实施方式中，插层剂的碳原子数为6-40。本申请另一些实施方式中，插层剂的碳原子数为12-40。碳原子数在6-40的范围时，插层剂与层状载体有较好的亲和力，能更有效扩大层状载体的层间距，便于活性物质进入层状载体的层间；并且插层剂易于溶解，能够较好地分散活性组分源。
本申请实施方式中，插层剂与层状载体的质量比为1:1-50。本申请一些实施方式中，插层剂与层状载体的质量比为1:1-20。进一步地，插层剂与层状载体的质量比为1:1-10。插层剂与层状载体的质量比具体可以但不限于为1:1、1:3、1:5、1:10、1:15、1:20、1:30、1:40或1:50。控制插层剂与层状载体的质量比可以保证插层剂能够扩大层状载体的层间距并且不影响层状载体对活性组分源的吸附。本申请实施方式中，活性组分源、插层剂和层状载体的质量比为(5-50):(1-10):(10-50)。在本申请一些实施方式中，活性组分源、插层剂和层状载体的质量比为(10-30):(2-7):(20-30)。控制各个组分的质量比有利于形成具有较多活性组分且活性组分均匀分散的催化剂。在一些实施方式中，活性组分源和层状载体的质量比为(0.1-5):1，例如为(0.33-1.5):1。
步骤S100中的溶剂可以包括水、甲醇、乙醇和丙醇中的一种或多种，但不限于此。上述溶剂能够浸润载体，有利于层状载体充分吸附插层剂和活性组分源，并且增强活性组分源在层状载体上的均一性。本申请实施方式中，溶剂与层状载体的质量比为(1-10)：(0.1-1)。本申请一些实施方式中，溶剂与层状载体的质量比为(3-7)：(0.1-1)。控制层状载体与溶剂的质量比能够保证溶剂充分浸润层状载体，从而促进插层剂和活性组分源有效附着在层状载体上。
本申请实施方式中，将层状载体、插层剂、活性组分源、掺杂源和溶剂混合均匀的方式可以是搅拌混合。本申请一些实施方式中，混合过程还包括超声处理。超声处理有利于促进插层剂进入载体片层。本申请实施方式中，混合的温度为15℃-50℃。在较高的混合的温度下，溶液中的分子运动加快，插层剂能够更好的扩大层状载体的层间距。
本申请一些实施方式中，层状载体、插层剂、活性组分源、掺杂源和溶剂是直接混合的，混合时间为1h-15h。本申请另一些实施方式中，先将层状载体、插层剂与溶剂混合形成第一溶液，混合时间为0.5h-15h，再将活性组分源、掺杂源、助剂源和溶剂形成的第二溶液加入到第一溶液中，第一溶液与第二溶液的混合时间为1h-5h。采用分步混合的方式能够提升层状载体对活性组分源和掺杂源的负载能力，使活性组分源和掺杂源均匀分散在层状载体中。本申请另一些实施方式中，先将层状载体与溶剂混合形成第一溶液，混合时间为0.5h-3h；混合后再向第一溶液中加入插层剂形成第二溶液，第二溶液的混合时间为1h-15h；再将活性组分源、掺杂源、助剂源和溶剂形成的第三溶液加入到第二溶液中，第二溶液与第三溶液的混合时间为1h-5h。将层状载体与溶剂预先混合能够使溶剂充分浸润层状载体，有利于插层剂的进入层状载体片层，从而扩大层状载体的层间距。本申请实施方式中，将混合液搅拌过滤除去滤液、将滤渣烘干后得到催化剂前驱体。本申请实施方式中，将滤渣干燥的方式可以是在烘箱中干燥，也可以是自然干燥。
步骤S200中，煅烧的过程可以具体为：将催化剂前驱体在300℃-800℃温度下煅烧，保温1h-8h后，通入一定量的水蒸气，在300℃-550℃下保温0.5h-4h后冷却至室温得到催 化剂。本申请中，催化剂前驱体的煅烧温度会影响催化剂的结构，进一步地，催化剂结构会影响催化剂的活性。本申请实施方式中，煅烧温度可以但不限于为300℃、400℃、500℃、550℃、600℃、700℃或800℃。本申请一些实施方式中，煅烧温度为300℃-550℃。在上述煅烧温度条件下能够完全除去催化剂前驱体中的溶剂和插层剂，并且在插层剂分解气化和溶剂蒸发的过程中，层状载体的层间距会进一步扩大，有利于减小掺杂多壁碳纳米管在层间生长的空间位阻，促进形成长径比较高的掺杂碳纳米管阵列。本申请实施方式中，催化剂前驱体煅烧的设备包括微波高温炉、高温炭化炉、中频感应高温炉和马弗炉中的任意一种。
本申请中，在煅烧过程中通入水蒸气能够将活性组分源与助剂源还原为金属粒子，实现催化剂的活化，该活化过程不需要通入易燃易爆的还原性气体，有利于安全生产并降低了生产成本。除此之外，在煅烧过程中，会有部分插层剂因燃烧不完全而形成积碳覆盖在催化剂表面，导致催化剂活性降低，而通入水蒸气则能够有效抑制插层剂的分解产物在活性组分表面形成积碳，并且水蒸气能够溶解部分插层剂反应的产物从而达到除杂的效果，进而保证催化剂具有丰富的活性位点。本申请实施方式中，水蒸气的通入量为50mL/min-200mL/min。水蒸气的通入量可以但不限于为50mL/min、60mL/min、80mL/min、100mL/min、110mL/min、130mL/min、170mL/min、190mL/min或200mL/min。控制水蒸气的通入量能够保证催化剂充分活化，并且不会影响插层剂的分解，保证插层剂充分燃烧，抑制积碳的形成。本申请实施方式中，通入水蒸气预活化的时间为0.5h-4h。通入水蒸气预活化的时间具体可以但不限于为0.5h、1h、1.5h、2h、2.5h、3h和4h。
步骤S300中，化学气相沉积的过程可以具体为：将催化剂置于反应器中，通入惰性气体并升温至反应温度600℃-900℃，再通入碳源气体进行沉积反应，反应时间为10min-100min，反应结束后通入惰性气体并降温至室温，在层状载体上得到掺杂多壁碳纳米管的阵列。本申请一些实施方式中，可以在步骤S300的化学气相沉积过程中还引入第二掺杂源，以在多壁碳纳米管的表面也引入掺杂原子。该第二掺杂源的材质可以上述步骤S100的掺杂源相同，或者不同(例如是气态或液态等，可以以惰性气体作为载体输送到反应器中)。
本申请一些实施方式中，化学气相沉积的温度可以为650℃-780℃，反应时间可以为20min-90min。化学气相沉积的温度具体可以但不限于为600℃、650℃、700℃、750℃、780℃、800℃或900℃。控制化学气相沉积的温度，能保证催化剂的活性较好，不易失活，使碳源气体脱氢形成碳原子的速率适中；并且在该温度下碳原子在活性组分中扩散阻力较小，有利于掺杂多壁碳纳米管的形成。其中，惰性气体、碳源气体、反应器等如上所述，这里不再赘述。
步骤S300中，去除所述催化剂(包括层状载体和活性组分)的方法为酸洗，具体过程可以为：将化学气相沉积得到的掺杂多壁碳纳米管阵列粗品加入到酸溶液中，在40℃-100℃的温度下浸润2h-30h，再将其水洗至中性，干燥后得到掺杂多壁碳纳米管。具体的酸溶液、酸洗时间、酸洗温度可以如上述步骤S02中所述，这里不再赘述。
本申请提供的掺杂多壁碳纳米管的第二种制备方法，工艺精简、原料来源广泛，操作可控性强、制备出的掺杂多壁碳纳米管的管径小，长径比较高，尺寸、长度均一，产品规 整，一致性好，导电性良好，该制备方法成本低，适于大批量工业化制备。
本申请还提供了掺杂多壁碳纳米管的第三种制备方法，包括以下步骤：
S1：将活性组分源、掺杂源、层状载体和第一碳源分散于溶剂中，经干燥处理得到催化剂前驱体；所述活性组分源包括可溶性的过渡金属盐；
S2：将所述催化剂前驱体在惰性气氛中进行煅烧处理，得到碳包覆材料；所述碳包覆材料包括催化剂和包覆所述催化剂的碳包覆层，所述催化剂包括所述层状载体及负载在所述层状载体上的活性组分及所述掺杂源，所述活性组分包括过渡金属活性颗粒；
S3：去除所述碳包覆层，得到裸露的所述催化剂；
S4：将上述催化剂置于反应器中，在惰性气氛中通入第二碳源，通过化学气相沉积的方式在所述层状载体上形成掺杂多壁碳纳米管的阵列，之后再去除所述催化剂，得到所述掺杂多壁碳纳米管；所述掺杂多壁碳纳米管包括多壁碳纳米管和掺杂在所述多壁碳纳米管中的掺杂原子；所述掺杂多壁碳纳米管具有径向导电通道，所述径向导电通道由所述掺杂原子与所述多壁碳纳米管的相邻管壁通过共价键合形成。
该掺杂多壁碳纳米管的第三种制备方法中，通过将含活性组分源、掺杂源、层状载体和第一碳源的催化剂前驱体进行煅烧处理，活性组分源可在煅烧过程中分解并被第一碳源高温分解所得的还原性气体(如H 2、CO)还原为活性组分，并负载在层状载体上(具体可以分布在层状载体的表面及其层间)，该活性组分及掺杂源再被第一碳源高温分解所得的无定型碳包覆，得到碳包覆材料，然后去除碳包覆层可得到用于生长碳纳米管的裸露催化剂。其中，在制备催化剂前驱体时就引入掺杂源，可以使掺杂源后续能够与催化剂前驱体煅烧形成的催化剂实现有效结合，从而有利于将掺杂原子掺入到多壁碳纳米管的管壁之间；碳包覆材料中碳包覆层的存在，可以有效限制催化剂颗粒的粒径生长，使所得催化剂颗粒的粒径较小，例如≤8nm。最后将该催化剂用于化学气相沉积法生成得到管径较小的掺杂多壁碳纳米管的阵列。
步骤S1中的活性组分源、层状载体的材质如上述步骤S100中所述。在一些实施方式中，活性组分源可以为铁、镍、钴、锰、钼、钨中的至少一种过渡金属元素的盐。这些过渡金属盐具有较高的碳溶解能力，可形成一定的碳化物，且碳原子在这些过渡金属中具有较高的扩散速率，有利于成核并生长为碳纳米管。
第一碳源，一方面可以与金属离子发生络合反应，形成稳定的络合物，有效提高金属活性物质与层状载体的浸渍效率，同时可以避免在反应过程中金属活性物质颗粒发生团聚；另一方面则用于碳包覆，以抑制催化剂在煅烧过程中的晶体长大，控制活性组分的粒径，使得催化剂中活性组分的颗粒粒径较小，进而通过其引导合成出小管径碳纳米管。在一些实施方式中，第一碳源选自柠檬酸、苹果酸、酒石酸、草酸、水杨酸、琥珀酸、甘氨酸、乙二胺四乙酸、蔗糖、葡萄糖中的至少一种。
步骤S1中，在一些实施方式中，为了提升活性组分源、掺杂源、层状载体和第一碳源在溶剂中的分散性，先将活性组分源和掺杂源溶于溶剂中，形成饱和溶液后，再在搅拌条件下加入层状载体，形成均匀分散的悬浊液，最后在搅拌条件下加入第一碳源，形成均匀分散的悬浊液。在一些实施例中，将活性组分源和层状载体的质量比控制在(0.1-10):1，且第一碳源的质量占活性组分源和层状载体总质量的10％-500％。第一碳源的添加量过少， 会导致包覆不均匀，导致形成的活性组分的颗粒不均匀，且会有大颗粒产生，使所得掺杂碳纳米管阵列的管径较大；第一碳源的添加量过多，一方面成本过高，造成浪费，另一方面去除碳包覆层时容易导致去除不干净，使所述催化剂容易失活，掺杂碳纳米管的产率不高。可选地，掺杂源中掺杂原子和活性组分源中过渡金属原子的摩尔数比为1：(5-100)来取用掺杂源和活性组分源。
在一些实施例中，步骤S1中干燥处理的方法为冷冻干燥，可防止金属活性物质颗粒发生团聚，使得到的碳纳米管管径更小。在一些实施例中，对催化剂前驱体进行干燥处理之前先进行抽滤，以去除多余的活性组分源，减少无法负载在层状载体表面的活性组分源，有利于获得高纯度的掺杂碳纳米管阵列。
在一些实施例中，S2中，煅烧处理在惰性气氛中进行，以避免高温条件下碳材料发生燃烧生成二氧化碳气体。具体地，惰性气氛为氮气、氩气、氦气中的至少一种。在一些实施例中，煅烧处理是在300℃-700℃下煅烧1h-10h。通过控制煅烧处理的温度，可以避免温度过高导致活性组分的颗粒过大，进而使生成的碳纳米管管径不致过大。具体地，典型而非限制性的煅烧处理温度为300℃、350℃、400℃、450℃、500℃、550℃、600℃、650℃、700℃；典型而非限制性的煅烧处理时间为1h、2h、3h、4h、5h、6h、7h、8h、9h、10h。
S3中去除碳包覆材料的方式为煅烧，煅烧可使无定形碳分解为二氧化碳气体。煅烧应在非惰性气氛且非还原性气氛中进行。在一些具体实施例中，煅烧在空气、氧气、二氧化碳的至少一种气氛中，在500℃-700℃下煅烧1h-10h。其中，当在二氧化碳气氛中煅烧时，二氧化碳可以无定形碳发生反应形成一氧化碳，从而达到去除碳包覆层的目的。通过控制煅烧处理的温度和煅烧时间，可以充分去除碳包覆层，提升所得催化剂的催化活性。具体地，典型而非限制性的煅烧处理温度为500℃、550℃、600℃、650℃、700℃；典型而非限制性的煅烧处理时间为1h、2h、3h、4h、5h、6h、7h、8h、9h、10h。
步骤S4中，第二碳源主要用于为化学气相沉积反应生长碳纳米管提供碳，同时第二碳源的具体选择也会对所得阵列型碳纳米管的长度产生显著影响。在一些实施例中，第二碳源选自甲烷、乙烷、丙烷、乙烯、丙烯、无水乙醇、一氧化碳中的至少一种，但不限于此。在一些具体实施例中，当过渡金属盐为硝酸镍、氯化镍和/或镍的可溶性有机盐时，以甲烷、乙烷、丙烷中的至少一种作为第二碳源；当过渡金属盐为铁或钴的硝酸盐、氯化盐和/或可溶性有机盐时，以乙烯、丙烯作为第二碳源。
在一些实施例中，在步骤S4中进行化学气相沉积反应时还通入了还原性气体，用于还原催化剂中的活性组分的氧化物，使其呈金属单质态，同时将被氧化的碳纳米管进行还原。具体地，还原性气体为氢气，具有还原性强、原料易得、成本相对较低的优点。与上述步骤S300中类似，在一些实施例中，进行化学气相沉积反应时还可以引入第二掺杂源，以在多壁碳纳米管的表面也引入掺杂原子，进一步提升导电性能。
在一些实施例中，化学气相沉积反应是在600℃-1000℃下反应30min-120min。在一些具体实施例中，当采用烯烃作为碳源时，将化学气相沉积反应的温度设置为600℃-750℃；当采用烷烃作为碳源时，将化学气相沉积反应的温度设置为800℃-1000℃；当采用烷烃作为碳源或活性组分源为硝酸镍、氯化镍和/或镍的可溶性有机盐时，由于金属镍作为活性组分的活性相对较差，生成碳纳米管的速率相对较低，因此将化学气相沉积反应的时间设置 为60min-120min。当采用烯烃作为碳源或过渡金属盐为铁或钴的硝酸盐、氯化盐和/或可溶性有机盐时，由于金属铁、金属钴作为活性物质的活性相对较高，生成碳纳米管的速率也较高，因此所需反应时间相对较短，将化学气相沉积反应的时间设置为30min-90min。具体地，典型而非限制性的化学气相沉积反应温度为600℃、650℃、700℃、750℃、800℃、850℃、900℃、950℃、1000℃；典型而非限制性的化学气相沉积反应时间为30min、40min、50min、60min、70min、80min、90min、100min、110min、120min。
化学气相沉积反应后，所得掺杂碳纳米管阵列是垂直生长在层状载体表面的，需要去除所述催化剂(即层状载体和活性组分)，以最终获得高纯度的掺杂碳纳米管。在一些实施例中，去除催化剂的方法包括但不限于酸洗法、石墨化法等。其中，酸洗法是将化学气相沉积反应后的产物粗品加入到酸性溶液中充分浸润，并在60℃-100℃下搅拌反应1h-20h，再经过滤洗涤干燥得到纯化后的掺杂碳纳米管。石墨化法是将化学气相沉积反应后的产物粗品在真空度低于20Pa的环境下1500℃-3000℃保温0.5h-10h，得到纯化后的掺杂碳纳米管。
本申请还提供了一种电极材料，该电极材料包括电极活性材料、粘合剂和导电剂，导电剂包括本申请第一方面提供的掺杂多壁碳纳米管。
其中，电极活性材料可以包括纳米硅、二氧化硅、硅碳合金、硅锡合金、锡合金、钛酸锂、钴酸锂、镍酸锂、锰酸锂、硅酸亚铁锂、磷酸锰锂、磷酸铁锰锂和磷酸铁锂中的一种或多种。其中，粘合剂可以包括羧甲基纤维素、羟丙基甲基纤维素、甲基纤维素、聚偏氟乙烯、聚丙烯腈、聚乙烯醇、海藻酸钠、壳聚糖和丁苯橡胶中的一种或多种。本申请一些实施方式中，导电剂可以仅包括本申请的掺杂多壁碳纳米管。本申请另一些实施方式中，导电剂还可以包括其他导电剂材料，例如导电剂为本申请中的掺杂多壁碳纳米管与石墨、炭黑、石墨烯、碳纤维和乙炔黑中的一种或多种形成的组合物。可选地，电极活性材料在电极材料中的质量百分含量为85.0％-97.0％，掺杂多壁碳纳米管的质量百分含量为0.1％-3.0％，粘合剂的质量百分含量为2.0％-12.0％。
本申请一些实施方式中，电极材料的制备过程为：将磷酸铁锂、掺杂多壁碳纳米管与聚偏氟乙烯混合得到电极浆料，将电极浆料经涂布、干燥、辊压、模切等步骤制备为电极材料。本申请一些实施方式中，含有质量分数2％掺杂多壁碳纳米管的磷酸铁锂电极材料的体积电阻率为0.7Ω·cm-2Ω·cm。本申请另一些实施方式中，电极材料的制备过程为：将纳米硅、掺杂多壁碳纳米管与羧甲基纤维素钠混合得到电极浆料，将电极浆料经涂布、干燥、辊压、模切、等步骤制备为电极材料。
本申请提供的电极材料由于使用了本申请的掺杂多壁碳纳米管而具有较好的导电性，掺杂多壁碳纳米管的丰富导电通道使得电子在电极材料中能够进行多向传导。将该电极材料应用在电池中能够提高电池的导电性，增强电池的性能。
下面将分为多个实施例对本申请的实施方式做进一步的说明。
实施例1
一种掺杂多壁碳纳米管的制备方法，包括以下步骤：
(1)将含有1％质量分数氮化硼的Fe-W/MgO催化剂加入到石英舟中，向管式炉中通入丙烷和氮气的混合气体，其中，丙烷和氮气的气体分压力比为3:2。在1200℃下反应1h，得 到硼氮掺杂的多壁碳纳米管粗品。
(2)将硼氮掺杂的多壁碳纳米管粗品与5％的硝酸溶液在80℃混合12h，抽滤、洗涤、干燥后得到硼氮掺杂的多壁碳纳米管。
电极测试样品的制备方法包括以下步骤：
将磷酸铁锂、硼氮掺杂的多壁碳纳米管与聚偏氟乙烯混合得到电极浆料，其中，磷酸铁锂的质量百分含量为94.0％，硼氮掺杂的多壁碳纳米管的质量百分含量为1.5％，聚偏氟乙烯的质量百分含量为4.5％。将电极浆料涂布在绝缘层上经干燥后制备为电极测试样品。
实施例2
一种掺杂多壁碳纳米管的制备方法，包括以下步骤：
(1)将含有10％质量分数氮化铝的Co-Mo/Al 2O 3催化剂加入到石英舟中，向管式炉中通入丙烯和氦气的混合气体，其中，丙烯和氦气的气体分压力比为2:1。在750℃下反应0.5h，得到氮掺杂的多壁碳纳米管粗品。
(2)将氮掺杂的多壁碳纳米管粗品与10％的盐酸溶液在80℃混合24h，抽滤、洗涤、干燥后得到氮掺杂的多壁碳纳米管。
电极测试样品的制备方法包括以下步骤：
将磷酸铁锂、氮掺杂的多壁碳纳米管与羧甲基纤维素钠混合得到电极浆料，其中，磷酸铁锂的质量百分含量为96.0％，氮掺杂的多壁碳纳米管的质量百分含量为1.3％，羧甲基纤维素钠的质量百分含量为2.7％。将电极浆料涂布在绝缘层上经干燥后制备为电极测试样品。
实施例3
一种掺杂多壁碳纳米管的制备方法，包括以下步骤：
(1)将含有质量分数20％硫酸铝的Ni-Mo/Al 2O 3催化剂加入到石英舟中，向管式炉中通入甲烷和氢气的混合气体，其中，甲烷和氢气的气体分压力比为1:1。在850℃下反应1h，得到硫掺杂的多壁碳纳米管粗品。
(2)将硫掺杂的多壁碳纳米管粗品与10％的硝酸溶液在80℃混合24h，抽滤、洗涤、干燥后得到硫掺杂的多壁碳纳米管。
电极测试样品的制备方法包括以下步骤：
将磷酸铁锂、硫掺杂的多壁碳纳米管与聚丙烯腈混合得到电极浆料，其中，磷酸铁锂的质量百分含量为94.0％，硫掺杂的多壁碳纳米管的质量百分含量为2.0％，聚丙烯腈的质量百分含量为4.0％。将电极浆料涂布在绝缘层上经干燥后制备为电极测试样品。
对比例1
(1)将不含掺杂源的Co-Mo/Al 2O 3催化剂加入到石英舟中，向管式炉中通入丙烯和氦气的混合气体，其中，丙烯和氦气的气体分压力比为2:1。在750℃下反应0.5h，得到未掺杂的多壁碳纳米管粗品。
(2)将未掺杂的多壁碳纳米管粗品与10％的盐酸溶液在80℃混合24h，抽滤、洗涤、干燥后得到未掺杂的多壁碳纳米管。
电极测试样品的制备方法包括以下步骤：
将磷酸铁锂、未掺杂的多壁碳纳米管与聚偏氟乙烯混合得到电极浆料，其中，磷酸铁锂的质量百分含量为94.5％，未掺杂的多壁碳纳米管的质量百分含量为2.0％，聚偏氟乙烯的 质量百分含量为3.5％。将电极浆料涂布在绝缘层上经干燥后制备为电极测试样品。
为验证本申请制得的掺杂多壁碳纳米管的形貌和性能，本发明还提供了效果实施例
(1)形貌表征
将实施例1和2中的掺杂多壁碳纳米管和对比例1中的未掺杂的多壁碳纳米管采用透射电镜进行形貌表征。其中，图3为本申请实施例1制得的硼氮掺杂的多壁碳纳米管的透射电镜图，图4为本申请实施例2制得的氮掺杂的多壁碳纳米管的透射电镜图，图5为本申请对比例1制得的多壁碳纳米管的透射电镜图。
通过图3和图4可以看出掺杂多壁碳纳米管整体呈现为直线型，局部存在弯折部，弯折部具有波纹状的褶皱，并且管壁之间的层间距大小不一。通过图5可以看出，未掺杂的多壁碳纳米管管壁平整，管壁之间的层间距大小均一，基本没有缺陷，与掺杂多壁碳纳米管的形貌完全不同。
(2)导电性能
将实施例1-3中的掺杂多壁碳纳米管和对比例1中的未掺杂的多壁碳纳米管进行粉体电阻率测试，其中粉体电阻率用ρ 1表示，结果请参见表1。
将实施例1-3和对比例1中的电极测试样品进行体积电阻率测试，其中体积电阻率用ρ 2表示，结果请参见表1。
表1 实施例1-3和对比例1的测试结果
  ρ 1(mΩ·cm) ρ 2(Ω·cm)
实施例1 50.3 1.1
实施例2 52.3 1.0
实施例3 56.5 1.3
对比例1 80.5 5.6
从表1中可以看出，本申请中的掺杂多壁碳纳米管经过原子掺杂后导电性能显著提升，将本申请中的掺杂多壁碳纳米管作为导电剂添加到电极材料中，能够提升电极材料的导电性，增强电池的性能。
实施例4
一种掺杂碳纳米管的制备方法，包括以下步骤：
(1)在150mL水中加入30g水滑石，搅拌0.5h后，再加入20g十二烷基苯磺酸钠，在25℃下搅拌12h形成均匀悬浮液；将48g六水合硝酸钴、8g六水合硝酸镧和5g硼酸镁加入悬浮液中，搅拌过滤得到滤渣，将滤渣在100℃下烘干得催化剂前驱体。
(2)将催化剂前驱体在马弗炉中550℃煅烧2h，在550℃下通入水蒸气预活化30min，冷却至室温后得到催化剂；该催化剂包括水滑石和负载在水滑石上的硼酸镁和金属钴颗粒。
(3)将0.3g催化剂加入到石英舟中，再移至固定床反应器中，在氮气保护气的氛围下以10℃/min升温至750℃，停止通入氮气，改为通入乙烯，在750℃下反应30min，形成硼掺杂的多壁碳纳米管阵列。
(4)将步骤(3)得到的产品与5％的硝酸溶液在80℃混合12h以去除上述催化剂，抽 滤、洗涤、干燥后得到硼掺杂的多壁碳纳米管。
测得实施例4中硼掺杂的多壁碳纳米管的管径为5-8nm，长度为40-80μm，长径比为5000:1～16000:1，其电阻率为0.02Ω·cm。按实施例1记载的方式将实施例4硼掺杂的多壁碳纳米管制备成电极测试样品，测得该电极测试样品的体积电阻率为0.5Ω·cm。
实施例5
一种掺杂碳纳米管的制备方法，包括以下步骤：
(1)在200mL水和乙醇的混合溶液(V 水：V 乙醇＝1:1)中加入30g膨胀石墨和25g十六烷基三甲基溴化铵，在40℃下搅拌12h形成均匀悬浮液；将50g硝酸镍、6g硝酸钨和8g硫酸铝加入悬浮液中，搅拌过滤得到滤渣，将滤渣在100℃下烘干得催化剂前驱体。
(2)将催化剂前驱体在马弗炉中500℃煅烧3h，在500℃下通入水蒸气预活化60min，冷却至室温后得到催化剂；该催化剂包括膨胀石墨和负载在膨胀石墨上的金属镍颗粒、钨颗粒及硫酸铝。
(3)将0.5g的催化剂加入到石英舟中，再移至固定床反应器中，在氮气保护气的氛围下以15℃/min升温至650℃，停止通入氮气改为通入甲烷，在650℃下反应30min，形成硫掺杂的多壁碳纳米管阵列。
(4)将步骤(3)得到的产品在10％的硝酸溶液中于80℃下浸润24h以去除上述催化剂，抽滤、洗涤、干燥后得到硼掺杂的多壁碳纳米管。
测得实施例5中硼掺杂的多壁碳纳米管的管径为3-6nm，长度为40-80μm，长径比为6666:1～26666:1，其电阻率为0.021Ω·cm。按实施例3记载的方式将实施例5硼掺杂的多壁碳纳米管制备成电极测试样品，测得该电极测试样品的体积电阻率为0.4Ω·cm。
实施例6
一种阵列型掺杂碳纳米管的制备方法，包括以下步骤：
(1)在200mL水中加入20g云母石、1g的氮化铝和10g二乙醇胺，在50℃下搅拌5h形成均匀悬浮液；将40g硝酸铁和3g钼酸铵加入悬浮液中，搅拌过滤得到滤渣，将滤渣在100℃下烘干得催化剂前驱体。
(2)将催化剂前驱体在马弗炉中600℃煅烧2h，在550℃下通入水蒸气预活化90min，冷却至室温后得到催化剂。
(3)将0.5g催化剂加入到石英舟中，再移至固定床反应器中，在氮气保护气的氛围下以15℃/min升温至700℃，停止通入氮气改为通入乙烷，在700℃下反应30min，形成氮掺杂的多壁碳纳米管阵列。
(4)将步骤(3)得到的产品在10％的硝酸溶液中于80℃下浸润24h以去除上述催化剂，抽滤、洗涤、干燥后得到氮掺杂的多壁碳纳米管。
测得实施6中硼掺杂的多壁碳纳米管的管径为7-10nm，长度为30-50μm，长径比为3000:1～7142:1，其电阻率为0.022Ω·cm。
电极测试样品的制备，包括：将磷酸铁锂、实施例6中氮掺杂的多壁碳纳米管与甲基纤维素钠混合得到电极浆料，其中，磷酸铁锂的质量百分含量为96.0％，氮掺杂的多壁碳纳米管的质量百分含量为1.3％，羧甲基纤维素钠的质量百分含量为2.7％。将电极浆料涂布在绝缘层上经干燥后制备为电极测试样品。测得该电极测试样品的体积电阻率为0.6Ω·cm。
实施例7
一种掺杂碳纳米管的制备方法，包括以下步骤：
将500g六水合硝酸铁、45g的硫酸铝、55g柠檬酸溶解在1000mL去离子水中，加入50g层状氧化铝形成悬浊液，常温下搅拌24h后，使用冷冻干燥机进行干燥，得到催化剂前驱体。将得到的前驱体在300℃氮气气氛下煅烧10h后，将温度升高至500℃空气中煅烧10h，得到催化剂178g。降至室温后，取所得催化剂0.3g放置于石英舟，通氮气至700℃，通入丙烯后在700℃下反应60min，在层状氧化铝上沉积得到硫掺杂的碳纳米管阵列；在沉积完成后，将所得产品置于5％的硝酸溶液于80℃下浸润12h以洗去催化剂，抽滤、洗涤、干燥后得到硫掺杂的多壁碳纳米管。
测得实施例7中硫掺杂的多壁碳纳米管的管径在5-8nm，长度为30-50μm，比表面积为272m 2/g，其电阻率为0.035Ω·cm。按实施例1记载的方式将实施例7中硫掺杂的多壁碳纳米管制备成电极测试样品，测得该电极测试样品的体积电阻率为0.7Ω·cm。
实施例8
一种掺杂碳纳米管的制备方法，包括以下步骤：
将50g六水合硝酸镍、100g葡萄糖溶解在500mL去离子水中，加入50g蛭石和和10g氮化铝形成悬浊液。常温下搅拌48h后，使用冷冻干燥机进行干燥，得到催化剂前驱体。将得到的前驱体在700℃氩气气氛下煅烧1h后，保持700℃并通入二氧化碳气体继续煅烧3h，得到催化剂65g。降至室温后，将所得催化剂0.3g放置于石英舟，通氩气至900℃，之后通入体积比为1:20的甲烷和氨气，在900℃下进行化学气相沉积反应120min，在蛭石上沉积得到硼氮共掺杂的碳纳米管阵列；在沉积完成后，将所得产品置于5％的硝酸溶液于80℃下浸润12h，抽滤、洗涤、干燥后得到硼氮掺杂的多壁碳纳米管。
测得实施例8中硼氮共掺杂的多壁碳纳米管的管径在7-8nm，长度为30-50μm，比表面积为258m 2/g，其电阻率为0.038Ω·cm。按实施例1记载的方式将实施例5中硼氮共掺杂的多壁碳纳米管制备成电极测试样品，测得该电极测试样品的体积电阻率为0.8Ω·cm。
以上实施例仅表达了本申请的几种示例性实施方式，其描述较为具体和详细，但并不能因此而理解为对本申请专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准。

Claims (15)

  1. 一种掺杂多壁碳纳米管，其特征在于，所述掺杂多壁碳纳米管包括多壁碳纳米管和掺杂在所述多壁碳纳米管中的掺杂原子；所述掺杂多壁碳纳米管具有径向导电通道，所述径向导电通道由所述掺杂原子与所述多壁碳纳米管的相邻管壁通过共价键合形成。
  2. 如权利要求1所述的掺杂多壁碳纳米管，其特征在于，所述掺杂原子与所述多壁碳纳米管的相邻管壁上的碳原子形成C-X-C共价键合，所述X为所述掺杂原子。
  3. 如权利要求1或2所述的掺杂多壁碳纳米管，其特征在于，所述掺杂原子包括硼原子、氮原子、磷原子、硫原子和硅原子中的一种或多种。
  4. 如权利要求1-3任一项所述的掺杂多壁碳纳米管，其特征在于，所述掺杂原子的质量百分含量为0.01％-10％。
  5. 如权利要求1-4任一项所述的掺杂多壁碳纳米管，其特征在于，所述掺杂多壁碳纳米管的层数为3层-10层。
  6. 如权利要求1-5任一项所述的掺杂多壁碳纳米管，其特征在于，所述掺杂多壁碳纳米管在形成所述共价键合的位置处的层间距大于未形成所述共价键合的位置处的层间距。
  7. 如权利要求1-6任一项所述的掺杂多壁碳纳米管，其特征在于，所述掺杂多壁碳纳米管的电阻率为20mΩ·cm-75mΩ·cm。
  8. 如权利要求1-7任一项所述的掺杂多壁碳纳米管，其特征在于，所述掺杂多壁碳纳米管的管径为3nm-100nm，长度为1μm-100μm。
  9. 一种掺杂多壁碳纳米管的制备方法，其特征在于，包括：
    将掺杂前体、碳源和载气加入反应器，通过化学气相沉积的方式得到掺杂多壁碳纳米管粗品；
    将所述掺杂多壁碳纳米管粗品进行酸洗，干燥后得到掺杂多壁碳纳米管；所述掺杂多壁碳纳米管包括多壁碳纳米管和掺杂在所述多壁碳纳米管中的掺杂原子；所述掺杂多壁碳纳米管具有径向导电通道，所述径向导电通道由所述掺杂原子与所述多壁碳纳米管的相邻管壁通过共价键合形成。
  10. 如权利要求9所述的掺杂多壁碳纳米管的制备方法，其特征在于，所述掺杂前体包括催化剂和掺杂源，所述掺杂源附着在所述催化剂表面；所述催化剂包括铁催化剂、钴催化剂和镍催化剂中的一种或多种；所述掺杂源包括硼酸镁、硼酸钠、氮化硼、氮化铝、硫酸铝、硫酸镁中的一种或多种；所述载气包括氮气、氩气、氦气、氢气中的一种或多种。
  11. 一种掺杂多壁碳纳米管的制备方法，其特征在于，包括：
    将层状载体、插层剂、活性组分源、掺杂源和溶剂混合均匀，干燥后得到催化剂前驱体；所述活性组分源包括可溶性的过渡金属盐；
    将所述催化剂前驱体进行煅烧，在煅烧过程中通入水蒸气，冷却后得到催化剂，所述催化剂包括所述层状载体和负载在所述层状载体上的活性组分及所述掺杂源，所述活性组分包括过渡金属活性颗粒；
    将所述催化剂置于反应器中，在惰性气氛中通入碳源，通过化学气相沉积的方式在所述层状载体上形成掺杂多壁碳纳米管的阵列，之后再去除所述催化剂，得到所述掺杂多壁 碳纳米管；所述掺杂多壁碳纳米管包括多壁碳纳米管和掺杂在所述多壁碳纳米管中的掺杂原子；所述掺杂多壁碳纳米管具有径向导电通道，所述径向导电通道由所述掺杂原子与所述多壁碳纳米管的相邻管壁通过共价键合形成。
  12. 如权利要求11所述的掺杂多壁碳纳米管的制备方法，其特征在于，所述过渡金属盐包括铁、钴、镍、锰、钛、钼、钨、钌和钯中的至少一种的盐；所述层状载体包括层状氧化铝、层状氧化镁、拟薄水铝石、层状二氧化硅、蛭石、膨胀石墨、云母石、水滑石、蒙脱石、高岭土和累托石中的一种或多种。
  13. 一种掺杂多壁碳纳米管的制备方法，其特征在于，包括：
    将活性组分源、掺杂源、层状载体和第一碳源分散于溶剂中，经干燥处理得到催化剂前驱体；所述活性组分源包括可溶性的过渡金属盐；
    将所述催化剂前驱体在惰性气氛中进行煅烧处理，得到碳包覆材料；所述碳包覆材料包括催化剂和包覆所述催化剂的碳包覆层，所述催化剂包括所述层状载体和负载在所述层状载体上的活性组分及所述掺杂源，所述活性组分包括过渡金属活性颗粒；
    去除所述碳包覆层，得到裸露的所述催化剂；
    将所述催化剂置于反应器中，在惰性气氛中通入第二碳源，通过化学气相沉积的方式在所述层状载体上形成掺杂多壁碳纳米管的阵列；之后再去除所述催化剂，得到掺杂多壁碳纳米管；所述掺杂多壁碳纳米管包括多壁碳纳米管和掺杂在所述多壁碳纳米管中的掺杂原子；所述掺杂多壁碳纳米管具有径向导电通道，所述径向导电通道由所述掺杂原子与所述多壁碳纳米管的相邻管壁通过共价键合形成。
  14. 如权利要求13所述的掺杂多壁碳纳米管的制备方法，其特征在于，所述催化剂的粒径＜8nm。
  15. 一种电极材料，其特征在于，包括电极活性材料、粘合剂和导电剂，所述导电剂包括如权利要求1-8任一项所述的掺杂多壁碳纳米管。
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