Conductive composite material and preparation method and application thereof

Abstract

The invention belongs to the field of materials, and particularly relates to a conductive composite material and a preparation method and application thereof. The conductive composite material comprises a carbon nanotube and carbon black, and the carbon black is coated on the surface of the carbon nanotube. The mass of the carbon black is 1-65% of the total mass of the conductive composite material. According to the conductive composite material disclosed by the invention, the surface of the carbon nano tube is coated with a layer of carbon black particles with good conductivity, so that the carbon nano tube can be inhibited from being reagglomerated in a slurry preparation process, and non-conductive components such as a polymeric dispersant are not required to be introduced during slurry preparation; and meanwhile, a two-dimensional conductive network in which carbon nano tubes are distributed in a linear manner and carbon black is distributed in a dot manner is formed in the conductive composite material, so that the conductive performance is excellent.

Description

Technical Field

[0001] This invention belongs to the field of materials, specifically relating to a conductive composite material, its preparation method, and its application. Background Technology

[0002] Carbon nanotubes (CNTs), as typical one-dimensional carbon materials, possess excellent electrical conductivity, a high aspect ratio, and a mesoporous structure that facilitates lithium-ion shuttle passage. Even with relatively low addition amounts, they can form an effective, highly conductive network between battery active materials, making them a promising alternative to traditional particulate conductive agents in the design and manufacturing of high-end lithium-ion batteries. However, CNTs exhibit a nanoparticle effect and entanglement between CNT bundles, leading to difficulty in dispersion and the formation of numerous aggregates, hindering uniform distribution of CNTs in the positive and negative electrode slurries. Currently, CNT agglomerates can be broken up using physical methods such as stirring, shearing, and ultrasound. Simultaneously, small-molecule surfactants and large-molecule polymer dispersants are used to prepare various stable and dispersed slurries, which are ultimately used in lithium-ion battery production. However, the prepared slurries have low solids content, requiring large amounts of solvent, resulting in high raw material and transportation costs. Furthermore, specific processes and equipment are needed to handle the evaporated solvent after electrode baking, further increasing manufacturing costs. Currently, there are no commercially available dispersible carbon nanotube powders. Summary of the Invention

[0003] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a conductive composite material.

[0004] The second objective of this invention is to provide a method for preparing a conductive composite material.

[0005] The third objective of this invention is to provide an electrode paste.

[0006] The fourth objective of this invention is to provide an electrode.

[0007] The fifth objective of this invention is to provide a battery.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides a conductive composite material comprising carbon nanotubes and carbon black, wherein the carbon black is coated on the surface of the carbon nanotubes.

[0009] In some embodiments of the present invention, the mass of the carbon black is 1 to 65% of the total mass of the conductive composite material; in some embodiments of the present invention, the mass of the carbon black is any value or a range formed by any two of the following: 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% of the total mass of the conductive composite material.

[0010] In some embodiments of the present invention, the conductive composite material is in powder form.

[0011] In some embodiments of the present invention, the carbon nanotubes include at least one of single-walled carbon nanotubes (the number of walls in a single carbon nanotube is 1), oligo-walled carbon nanotubes (the number of walls in a single carbon nanotube is 1 to 4), and multi-walled carbon nanotubes (the number of walls in a single carbon nanotube is ≥ 5).

[0012] In this process, carbon black is grown in situ on the surface of carbon nanotubes and coats the carbon nanotubes. The resulting conductive composite material can inhibit the agglomeration of carbon nanotubes during the preparation of a slurry. It can be dispersed by simple mechanical stirring, and the dispersed slurry can contain a high concentration of carbon nanotubes.

[0013] The second aspect of the present invention provides a method for preparing the conductive composite material described in the first aspect of the present invention, comprising the following steps: S1: Disperse carbon nanotubes in a supercritical fluid, then depressurize; S2: The carbon source gas is subjected to a thermal decomposition reaction on the surface of the carbon nanotubes to generate carbon black, thereby obtaining the conductive composite material.

[0014] The preparation method in this invention disperses the prepared carbon nanotubes using supercritical fluid technology, and grows carbon black in situ on the surface of the carbon nanotubes using pyrolysis, resulting in a tight bond between the carbon black and the carbon nanotubes.

[0015] In some embodiments of the present invention, the carbon nanotubes are prepared by fluidized bed vapor deposition.

[0016] In some embodiments of the present invention, the carbon nanotubes are prepared by a method comprising the following steps: Carbon nanotubes are prepared by reacting a carbon-containing gas under a protective atmosphere with the catalysis of a catalyst. In some embodiments of the present invention, the carbon nanotubes are prepared by a method comprising the following steps: introducing a mixture of carbon-containing gas and protective gas into a fluidized bed containing a catalyst, and reacting to generate carbon nanotubes.

[0017] In some embodiments of the present invention, the carbon-containing gas includes at least one of methane, ethylene, and propylene.

[0018] In some embodiments of the present invention, the flow rate of the carbon-containing gas is 80~120 L / min.

[0019] In some embodiments of the present invention, the protective atmosphere is formed by introducing a protective gas at a flow rate of 200-400 L / min.

[0020] In some embodiments of the present invention, the protective gas includes at least one of nitrogen, argon, and helium.

[0021] This invention does not impose special requirements on the type of catalyst; any catalyst commonly used in the field for preparing carbon nanotubes can be used. The amount and type of catalyst can be adjusted reasonably according to production needs. In some embodiments of this invention, the catalyst uses at least one of Fe, Co, Ni, Mo, and Mn as the active component and an oxide of at least one of Al, Mg, Si, and La as the support; in some embodiments of this invention, the catalyst is an FeCoNiAlMg catalyst.

[0022] In some embodiments of the present invention, the reaction temperature for preparing carbon nanotubes is 500~800℃.

[0023] In some embodiments of the present invention, the reaction time for preparing carbon nanotubes is 30-60 min.

[0024] In some embodiments of the present invention, the preparation of carbon nanotubes is carried out in a fluidized bed.

[0025] In some embodiments of the present invention, step S1 is: introducing supercritical fluid into a fluidized bed and stirring to disperse carbon nanotubes in the supercritical fluid. During this process, the fluidized bed is kept at a certain pressure and temperature so that the supercritical fluid is kept in a supercritical fluid state.

[0026] In some embodiments of the present invention, the pressure of the supercritical fluid is 1 to 100 MPa; in some embodiments of the present invention, the pressure of the supercritical fluid is any value or a range formed by any two of the following: 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, 50 MPa, 60 MPa, 70 MPa, 80 MPa, 90 MPa, 100 MPa.

[0027] In some embodiments of the present invention, the temperature of the supercritical fluid is 40~2000℃; in some embodiments of the present invention, the temperature of the supercritical fluid is any value or a range formed by any two of the following: 40℃, 50℃, 100℃, 200℃, 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃, 1700℃, 1800℃, 1900℃, and 2000℃.

[0028] In some embodiments of the present invention, the step of dispersing carbon nanotubes in a supercritical fluid is as follows: a supercritical fluid with a pressure of 1 to 100 MPa is introduced into a fluidized bed, and then stirred at 50 to 2000 °C for 1 to 5 hours to fully disperse the carbon nanotubes in the supercritical fluid.

[0029] In some embodiments of the present invention, the supercritical fluid is selected from at least one of nitrogen and carbon dioxide.

[0030] In some embodiments of the present invention, the pressure relief is to reduce the pressure from 1 to 100 MPa to 0.1 to 0.11 MPa within 0.1 to 10 seconds.

[0031] In some embodiments of the present invention, the pressure relief time is any value of 0.1s, 0.5s, 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s or a range formed by any two of them.

[0032] In some embodiments of the present invention, the temperature of the thermal decomposition reaction is not lower than 800°C; in some embodiments of the present invention, the temperature of the thermal decomposition reaction is 800°C to 1500°C; in some embodiments of the present invention, the temperature of the thermal decomposition reaction is any value of 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, or a range formed by any two of these values.

[0033] In some embodiments of the present invention, the carbon source gas is selected from at least one of methane and unsaturated hydrocarbons.

[0034] In some embodiments of the present invention, the unsaturated hydrocarbon includes at least one of ethylene and propylene.

[0035] In some embodiments of the present invention, the preparation method is carried out in a fluidized bed. A fluidized bed can test high temperature and pressure as well as material transport, and the material can enter a material hopper via pipelines; in some embodiments of the present invention, the carbon source gas is located within the material hopper of the fluidized bed.

[0036] In some embodiments of the present invention, the step of generating carbon black by thermal decomposition of the carbon source gas on the surface of the carbon nanotubes specifically involves: introducing the depressurized mixture (a mixture of nitrogen and carbon nanotubes) into a material silo through a pipeline; contacting the carbon source gas in the material silo; and conducting thermal decomposition of the carbon source gas on the surface of the carbon nanotubes to generate carbon black in situ, which then coats the surface of the carbon nanotubes. During the depressurization process, the carbon nanotubes are fully dispersed, and simultaneously, the carbon source gas undergoes thermal decomposition upon contact with the carbon nanotubes, generating carbon black particles on the surface of the carbon nanotubes. As the carbon black particles aggregate and form a grape-like morphology, a two-dimensional conductive network is ultimately formed, consisting of carbon nanotube "lines" and carbon black "dots".

[0037] In some embodiments of the present invention, the carbon source gas needs to be preheated to 600-700°C before contacting the carbon nanotubes.

[0038] A third aspect of the present invention provides an electrode paste comprising the conductive composite material described in the first aspect of the present invention.

[0039] In some embodiments of the present invention, the electrode slurry further includes a positive electrode active material, conductive carbon black, and a binder.

[0040] In some embodiments of the present invention, the mass ratio of the positive electrode active material to the conductive composite material is (90~200):1.

[0041] In some embodiments of the present invention, the mass ratio of the conductive carbon black to the conductive composite material is (0~5):1.

[0042] In some embodiments of the present invention, the mass ratio of the adhesive to the conductive composite material is (1~10):1.

[0043] In some embodiments of the present invention, the adhesive is selected from at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium alginate, and polyimide.

[0044] In some embodiments of the present invention, the positive electrode active material includes at least one of lithium nickel cobalt manganese, lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium iron phosphate.

[0045] The electrode slurry of this invention can effectively disperse conductive composite materials under simple stirring conditions. Its structure is a two-dimensional conductive network of "dots and lines", which has excellent conductivity. Its preparation method is simple, does not require the introduction of polymeric dispersants, and eliminates the process difficulties of impurity removal and purification.

[0046] A fourth aspect of the present invention provides an electrode comprising the conductive composite material described in the second aspect of the present invention.

[0047] A fifth aspect of the present invention provides a battery comprising the conductive composite material described in the first aspect of the present invention, or the electrode described in the fourth aspect of the present invention.

[0048] The beneficial effects of this invention are as follows: The conductive composite material of this invention, by coating the surface of carbon nanotubes with a layer of carbon black particles with good conductivity, can suppress the re-agglomeration of carbon nanotubes during the slurry preparation process, and eliminates the need to introduce non-conductive components such as polymeric dispersants during slurry preparation. Simultaneously, this conductive composite material forms a two-dimensional conductive network with carbon nanotubes distributed as "lines" and carbon black particles distributed as "dots," resulting in excellent conductivity. Furthermore, the conductive composite material of this invention exhibits excellent dispersibility; it can be dispersed in the slurry through simple mechanical stirring, solving the problem of difficult dispersion of carbon nanomaterials and significantly reducing the application cost of carbon nanotubes.

[0049] The electrode slurry of this invention, by adding conductive composite material, can suppress the re-agglomeration of carbon nanotubes during the slurry preparation process, and has low viscosity and high stability. Specifically, the viscosity is 5000~6000 Pa·s, and the viscosity after standing for 24 hours is 8000~9000 Pa·s. Compared with carbon nanotubes without carbon black coating, the stability is significantly improved.

[0050] The electrodes in this invention utilize the conductive composite material described in this invention, resulting in superior conductivity and a significantly reduced two-probe film resistance, down to <0.2Ω. Attached Figure Description

[0051] Figure 1 This is a SEM image of the conductive composite material in Example 2.

[0052] Figure 2 This is a SEM image of the multi-walled carbon nanotubes in Comparative Example 1. Detailed Implementation

[0053] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0054] Example 1 This example provides a method for preparing a conductive composite material, which includes the following steps: Step 1: Set the fluidized bed temperature to 600℃, evacuate the vacuum, introduce nitrogen gas at a flow rate of 300L / min and add 10g of FeCoNiAlMg catalyst; introduce ethylene (flow rate of 100L / min), react for 40min and then stop introducing ethylene to obtain multi-walled carbon nanotubes.

[0055] Step 2: Evacuate the fluidized bed to remove exhaust gas, then inject N2 at a pressure of 5 MPa, maintain the temperature at 50℃, and stir for 2 hours to fully disperse the multi-walled carbon nanotubes in the supercritical fluid formed by N2.

[0056] Step 3: Inject 22g of acetylene gas into the receiving hopper and preheat it to 650℃. Open the valve between the fluidized bed and the hopper, then rapidly depressurize. The carbon nanotubes dispersed in the supercritical fluid enter the receiving hopper with the gas flow. Instantaneous rapid depressurization (i.e., reducing the pressure from 5MPa to atmospheric pressure within 0.1s) vaporizes the supercritical fluid N2, causing the multi-walled carbon nanotubes to expand rapidly, disperse uniformly, and generate more pores. When the multi-walled carbon nanotubes come into contact with the acetylene gas, the acetylene gas temperature is increased to ≥800℃. The acetylene gas thermally decomposes into carbon black on the surface of the multi-walled carbon nanotubes, yielding the conductive composite material in this example.

[0057] This example also provides a method for preparing a positive electrode sheet, including the following steps: The positive electrode active material is lithium nickel cobalt manganese (LiNi). 0.5 Co 0.2 Mn 0.3 O2, carbon black, conductive composite material, and PVDF binder are mixed evenly in a mass ratio of 97.5:0.5:0.5:1.5. N-methylpyrrolidone (NMP) is then added and the mixture is stirred evenly in a vacuum mixer to obtain a positive electrode active material slurry.

[0058] The above-mentioned positive electrode active material slurry is uniformly coated on the upper and lower surfaces of the aluminum foil (12μm thick) current collector, and after drying, cold pressing and slitting, the positive electrode sheet is obtained.

[0059] Example 2 The only difference between the preparation method of the conductive composite material in this example and that in Example 1 is that the mass of acetylene gas injected into the receiving hopper in step 3 is 440g.

[0060] The surface morphology of the conductive composite material prepared in this example was examined using scanning electron microscopy, as shown in the following figures. Figure 1 As shown. By Figure 1 It can be seen that the surface of carbon nanotubes is coated with a large amount of carbon black.

[0061] The difference between the preparation method of the positive electrode in this example and that in Example 1 is that the positive electrode active material in this example is lithium nickel cobalt manganese (LiNi). 0.5 Co 0.2 Mn0.3 The mass ratio of O2, carbon black, conductive composite material, and PVDF adhesive is 97.5:0:1:1.5.

[0062] Comparative Example 1 This example provides a method for preparing multi-walled carbon nanotubes and a method for preparing a positive electrode containing the multi-walled carbon nanotubes. The method for preparing multi-walled carbon nanotubes includes the following steps: Step 1: Set the fluidized bed temperature to 600℃, evacuate the vacuum, introduce nitrogen gas at a flow rate of 300mL / min and add 10g of FeCoNiAlMg catalyst; introduce ethylene (flow rate of 100mL / min), react for 40min and then stop introducing ethylene to obtain multi-walled carbon nanotubes.

[0063] Step 2: Evacuate the fluidized bed to remove exhaust gas, then inject N2 at a pressure of 5 MPa, maintain the temperature at 50℃, and stir for 2 hours to fully disperse the multi-walled carbon nanotubes in the supercritical fluid formed by N2.

[0064] Step 3: Open the valve between the fluidized bed and the silo, then rapidly depressurize. The carbon nanotubes dispersed in the supercritical fluid enter the silo with the airflow. The instantaneous rapid depressurization vaporizes the supercritical fluid N2, causing the carbon nanotubes to expand rapidly, disperse uniformly, and generate more pores, thus producing the multi-walled carbon nanotubes in this example. The SEM image of the obtained multi-walled carbon nanotubes is shown below. Figure 2 As shown, by Figure 2 It can be seen that the surface of multi-walled carbon nanotubes is not covered with carbon black.

[0065] The preparation method of the positive electrode sheet in this example is as follows: The positive electrode active material is lithium nickel cobalt manganese (LiNi). 0.5 Co 0.2 Mn 0.3 O2, carbon black, multi-walled carbon nanotubes prepared in this example, and PVDF binder are mixed evenly in a mass ratio of 97.5:0.5:0.5:1.5. N-methylpyrrolidone (NMP) is added, and the mixture is stirred evenly in a vacuum mixer to obtain a positive electrode active material slurry.

[0066] The above-mentioned positive electrode active material slurry is uniformly coated on the upper and lower surfaces of the aluminum foil (12μm thick) current collector, and after drying, cold pressing and slitting, the positive electrode sheet is obtained.

[0067] Performance testing: The initial viscosity and viscosity after standing for 24 hours of the positive electrode active material slurry prepared in Examples 1-2 and Comparative Example 1 were tested at 25°C. The viscosity test method was as follows: 1. The viscosity was tested using a Brookfield DV2T rotational viscometer. Before the test, the rotor was cleaned, 350 g of the positive electrode active material slurry was placed in a 400 mL beaker, and the sample bottle was placed in a constant temperature water bath at 25±0.1°C. The measurement was performed after the temperature was constant. 2. After the temperature was constant, the measurement was performed using a 64# rotor at 60 rpm for 19 seconds. 3. The value was read after the value was displayed. The specific viscosity test data are shown in Table 1 below.

[0068] The two-probe film resistance of the positive electrode sheets prepared in Examples 1-2 and Comparative Example 1 was tested. The test method for the two-probe film resistance was as follows: the positive active material slurry was uniformly coated on the upper and lower surfaces of the aluminum foil (12 μm thick) current collector, and the positive electrode sheet was obtained after drying, cold pressing and cutting. The two-probe film resistance of the positive electrode sheet was tested using a BSR2300 two-probe tester. The specific test results are shown in Table 1 below.

[0069] Table 1. Viscosity and two-probe film resistance test results

[0070] As shown in Table 1, in Comparative Example 1, the multi-walled carbon nanotubes were not coated with carbon black, leading to agglomeration of the carbon nanotubes. This resulted in poor stability of the positive electrode active material slurry. Furthermore, the agglomeration of carbon nanotubes reduced the electron transport channels, resulting in higher film resistance. In contrast, Examples 1 and 2, which used carbon black to coat the multi-walled carbon nanotubes, effectively suppressed the re-agglomeration of carbon nanotubes in the positive electrode active material slurry, improving the conductivity of the resulting positive electrode and significantly reducing the two-probe film resistance.

[0071] The specific surface area of ​​the conductive composite materials prepared in Examples 1 and 2 and the multi-walled carbon nanotubes prepared in Comparative Example 1 were tested respectively. The specific test results are shown in Table 2 below. Then, the conductive composite materials prepared in Examples 1 and 2 and the multi-walled carbon nanotubes prepared in Comparative Example 1 were mixed with polyvinylpyrrolidone (PVP) at a mass ratio of 4:1 to prepare conductive agent slurry. The particle size of the conductive agent slurry was measured. The specific test results are shown in Table 2 below.

[0072] Table 2. Specific surface area of ​​powder and particle size of slurry in each embodiment and comparative example.

[0073] As shown in Table 2, compared with the multi-walled carbon nanotubes prepared in Comparative Example 1, the conductive composite materials prepared in Examples 1-2 of this invention have a larger specific surface area and a smaller particle size in the slurry obtained after dispersion in the solution, exhibiting better dispersion effect. Because the conductive composite materials prepared in Examples 1-2 of this invention are a two-dimensional conductive network with carbon nanotubes distributed as "lines" and carbon black as "dots," maintaining the original high aspect ratio of the carbon nanotube material and relatively uniform carbon black distribution, the prepared conductive composite material powder has a larger specific surface area, and the dispersed conductive slurry has a smaller particle size and higher stability.

[0074] The conductive composite materials prepared in Examples 1 and 2 and the multi-walled carbon nanotubes prepared in Comparative Example 1 were respectively used to fabricate pouch batteries. The specific steps are as follows: Step a: Mix LiNi in a mass ratio of 97.5:0.5:0.5:1.5 0.5 Co 0.2 Mn 0.3 O2, carbon black, the conductive composite material prepared in the above examples or the multi-walled carbon nanotubes prepared in the comparative examples, and PVDF binder are dispersed in N-methyl-2-pyrrolidone to obtain a positive electrode slurry. Then, the positive electrode slurry is uniformly coated on both sides of an aluminum foil. After drying, calendering, and vacuum drying, aluminum leads are welded on using an ultrasonic welder to obtain a positive electrode sheet with a thickness of 180 μm. Step b: Graphite, conductive agent (i.e., Super P), carboxymethyl cellulose, and styrene-butadiene rubber are mixed in a mass ratio of 96.5:1.3:1.4:1.7 and dispersed in deionized water to obtain a negative electrode slurry. Then, the negative electrode slurry is coated on both sides of a copper foil. Then, after drying, calendering, and vacuum drying, nickel leads are welded on using an ultrasonic welder to obtain a negative electrode sheet with a thickness of 90 μm. Step c: The prepared positive electrode, negative electrode, and ion-exchange separator (PP / PE / PP three-layer composite separator) are stacked to prepare a bare cell. Then, the bare cell is installed in an aluminum-plastic film casing and encapsulated to prepare a lithium-ion soft-pack battery. After high-temperature baking, the battery is injected with electrolyte, and after encapsulation, settling, formation, shaping, and capacity testing, the battery assembly is completed. The battery capacity is tested (denoted as: capacity). 初始 ) and internal resistance (denoted as: internal resistance) 初始 The prepared battery was placed at 60°C for 7 days, and then the remaining capacity of the battery was tested (denoted as: remaining capacity). 高温后 ) and internal resistance (denoted as: internal resistance) 高温后 Then, after one charge-discharge cycle, the battery capacity is tested (recorded as: recovery capacity). 高温后 Then calculate the battery's capacity retention rate, capacity recovery rate, and internal resistance change rate, where the capacity retention rate = (capacity) / (capacity / internal resistance change rate). 初始 - Remaining capacity 高温后 ) / capacity 初始 ×100%; Capacity recovery rate == (capacity ×100%) 初始-Restore capacity 高温后 ) / capacity 初始 ×100%; Rate of change of internal resistance = (Internal resistance) 高温后 -Internal resistance 初始 ) / Internal resistance 初始 ×100%; the specific test results are shown in Table 3 below.

[0075] Table 3 Performance test results after 7 days of storage at 60℃

[0076] As shown in Table 3, compared with Comparative Example 1, the soft-pack battery of the present invention can improve both the capacity retention rate and capacity recovery rate by introducing conductive composite materials, and significantly reduce the rate of change of internal resistance of the battery.

[0077] The soft-pack batteries prepared above were cycled for 200 cycles at room temperature and 45°C, respectively, with a charge and discharge rate of 1C. The capacity retention rate was then calculated, and the specific test results are shown in Table 4 below.

[0078] Table 4 Results of room temperature and high temperature cycling performance tests

[0079] As shown in Table 4, compared with Comparative Example 1, the soft-pack battery of the present invention can significantly improve the capacity retention rate of the battery after 200 cycles at 25°C and 45°C by introducing conductive composite materials.

[0080] In summary, the conductive composite material of this invention utilizes carbon black to coat multi-walled carbon nanotubes, solving the problem of difficult carbon nanotube dispersion. It can be transported directly as a powder during transportation, eliminating the need for slurry preparation and reducing transportation and storage costs. Furthermore, the conductive composite material can be dispersed using sand milling or ball milling processes, significantly reducing preparation and usage costs. The conductive composite material of this invention forms a two-dimensional conductive network with carbon nanotubes distributed as "lines" and carbon black distributed as "dots," maintaining the original high aspect ratio of the carbon nanotube material and ensuring relatively uniform carbon black distribution. The carbon black grows in situ on the surface of the carbon nanotubes, resulting in a stronger bond and facilitating electron conduction, effectively maintaining the good conductivity of the carbon nanomaterial.

[0081] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A conductive composite material, characterized in that: It includes carbon nanotubes and carbon black, with the carbon black coating the surface of the carbon nanotubes.

2. The conductive composite material according to claim 1, characterized in that: The mass of the carbon black is 1 to 65% of the total mass of the conductive composite material.

3. The method for preparing the conductive composite material according to any one of claims 1 to 2, characterized in that: Includes the following steps: S1: Disperse carbon nanotubes in a supercritical fluid, then depressurize; S2: The carbon source gas is subjected to a thermal decomposition reaction on the surface of the carbon nanotubes to generate carbon black, thereby obtaining the conductive composite material.

4. The method for preparing the conductive composite material according to claim 3, characterized in that: The carbon nanotubes were prepared by fluidized bed vapor deposition.

5. The method for preparing the conductive composite material according to claim 3, characterized in that: The supercritical fluid has at least one of the following characteristics: (a1) The pressure of the supercritical fluid is 1~100MPa; (a2) The temperature of the supercritical fluid is 40~2000℃; (a3) The supercritical fluid is selected from at least one of nitrogen and carbon dioxide.

6. The method for preparing the conductive composite material according to claim 3, characterized in that: The pressure relief is achieved by reducing the pressure from 1-100 MPa to 0.1-0.11 MPa within 0.1-10 seconds. And / or, the temperature of the thermal decomposition reaction is not lower than 800°C.

7. The method for preparing the conductive composite material according to claim 3, characterized in that: The carbon source gas is selected from at least one of methane and unsaturated hydrocarbons.

8. An electrode paste, characterized in that: Including the conductive composite material as described in claim 1 or 2.

9. An electrode, characterized in that: Including the conductive composite material as described in claim 1 or 2.

10. A battery, characterized in that: It includes the conductive composite material as described in claim 1 or 2, or the electrode as described in claim 9.

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