Flaky catalyst and preparation method thereof, carbon nanotube array assembly and preparation method thereof, conductive agent, electrode sheet, and battery

Abstract

The application provides a flaky catalyst and a preparation method thereof, a carbon nanotube array assembly and a preparation method thereof, a conductive agent, a pole piece, and a battery. The flaky catalyst comprises a carrier, at least part of the surface of the carrier is provided with metal particles formed by a Q element, and the surface of the carrier comprises a central region and an edge region in sequence. The loading amount of the Q element in the central region is greater than that in the edge region. Thus, in the process of preparing the carbon nanotube array assembly, the metal particles formed in the central region of the flaky catalyst have a large particle size and a low surface density, can catalyze the growth of multi-walled carbon nanotubes, the metal particles in the edge region have a small particle size and a high surface density, can catalyze the growth of few / single-walled carbon nanotubes, and the multi-walled carbon nanotubes can guide the efficient growth of the few / single-walled carbon nanotubes, thereby obtaining the carbon nanotube array assembly.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular, to a sheet-shaped catalyst and a preparation method thereof, a carbon nanotube array assembly and a preparation method thereof, a conductive agent, a pole piece, and a battery. BACKGROUND

[0002] Carbon nanotubes, as a new type of material, have wide application prospects in the fields of composite material reinforcement, electrochemical energy storage, electronic devices, etc. and have attracted much attention. Among them, few-walled and single-walled carbon nanotubes have small diameters and high aspect ratios, and have super-strong mechanical properties, excellent electrical conductivity, excellent thermal properties, stable chemical properties, etc., which fully exhibit excellent characteristics in the field of electrochemical energy storage, etc. Moreover, as the length of few-walled / single-walled carbon nanotubes increases, they can build an excellent long-range conductive network in the negative electrode material of lithium ion batteries, and exhibit more excellent electrical properties. In particular, when few-walled / single-walled carbon nanotubes grow in an array form, they have the advantages of high yield, consistent length, and easy dispersion. However, the length of few-walled / single-walled carbon nanotube arrays prepared in batches is difficult to break through, which greatly limits their practical application.

[0003] Multi-walled carbon nanotubes can grow in the form of long arrays due to their hard texture, and the length can reach hundreds of microns. In contrast, few-walled / single-walled carbon nanotubes are relatively soft in texture, and their growth process is easily hindered by surrounding catalyst sheets, so their length is often difficult to match multi-walled carbon nanotubes.

[0004] In the process of preparing few-walled / single-walled carbon nanotubes, dispersing and laying the catalyst on the container can provide sufficient space for the growth of few-walled / single-walled carbon nanotubes, but the yield of few-walled / single-walled carbon nanotubes is limited by the amount of catalyst input. How to improve the growth length of few-walled / single-walled carbon nanotubes while ensuring the yield is a difficult problem to solve. SUMMARY

[0005] The present application aims to at least solve one of the technical problems in the related art to some extent.

[0006] The first aspect of the present application provides a sheet-shaped catalyst, the sheet-shaped catalyst comprising a carrier, at least part of the surface of the carrier having metal particles formed by a Q element, the carrier comprising an oxide containing a M element, the Q element comprising at least one of Fe, Co, Ni, Cu, Mo and W, the M element comprising at least one of Mg, Zn, Ca, Mn, Cr, Al and Ru; the surface of the carrier comprising a center region and an edge region from the center of the carrier to the edge of the carrier, the loading amount of the Q element in the center region being greater than the loading amount of the Q element in the edge region. Thus, in the process of preparing carbon nanotube array assembly, the loading amount of the Q element in the center region is greater, which can form Q metal particles with less quantity and larger average particle size, catalyzing the growth of multi-walled carbon nanotubes, and the loading amount of the Q element in the edge region is smaller, which can form Q metal particles with more quantity and smaller average particle size, catalyzing the growth of few / single-walled carbon nanotubes, and the multi-walled carbon nanotubes can play a role of pillar support, guiding the efficient growth of few / single-walled carbon nanotubes, and thus obtaining carbon nanotube array assembly with a length of up to hundreds of microns.

[0007] According to some embodiments of the present application, the surface density of the metal particles in the center region is less than the surface density of the metal particles in the edge region, the surface density of the metal particles in the center region being 10 12 / m 2 -10 15 / m 2 , and the surface density of the metal particles in the edge region being 10 14 / m 2 -10 16 / m 2 . Thus, carbon nanotubes with different wall numbers are catalytically grown to obtain carbon nanotube array assembly.

[0008] According to some embodiments of the present application, the average particle size of the metal particles in the center region is greater than the average particle size of the metal particles in the edge region, the average particle size of the metal particles in the center region being 7nm-50nm, and the average particle size of the metal particles in the edge region being 1nm-10nm.

[0009] The second aspect of the present application provides a method for preparing the flaky catalyst provided in the first aspect of the present application, the method comprising: mixing a salt solution containing M elements, a precipitant, and a salt solution containing Q elements to form a mixed solution, and obtaining a precursor by co-precipitation, wherein the co-precipitation comprises a first stage and a second stage performed in sequence, the first stage is 0h-6h from the start of the co-precipitation, and the mass of the Q elements added in the first stage is greater than the mass of the Q elements added in the second stage; and calcining and reducing the precursor to obtain the flaky catalyst. Thus, the method is simple in process, and in the process of reducing the precursor, the Q elements in the central region are more likely to gather and grow than the Q elements in the edge region, so that a flaky catalyst with fewer metal particles in the central region, larger average particle size, more metal particles in the edge region, and smaller average particle size can be obtained, and then used to prepare a carbon nanotube array assembly, so as to construct a conductive network with excellent performance in the pole piece.

[0010] According to some embodiments of the present application, the molar ratio of Q elements to M elements in the salt solution containing Q elements added in the first stage is (0.05-0.5):1. Thus, the content of the Q elements added in the first stage is relatively high, which can gradually nucleate and grow in the central region of the carrier to form crystals with relatively high Q element loading.

[0011] According to some embodiments of the present application, the molar ratio of Q elements to M elements in the salt solution containing Q elements added in the second stage is (0.005-0.05):1. Thus, the content of the Q elements added in the second stage is relatively low, which can form crystals with relatively low Q element loading in the edge region of the carrier.

[0012] According to some embodiments of the present application, the pH of the mixed solution in the co-precipitation process is 6-11.

[0013] According to some embodiments of the present application, at least one of the following conditions is met: the atmosphere of the calcination is inert gas or air; the temperature of the calcination is 400℃-900℃; and the heating rate of the calcination is 1℃ / min-20℃ / min.

[0014] According to some embodiments of the present application, the reduction process comprises: pretreating the calcined precursor by a pretreatment gas, and the pretreatment satisfies at least one of the following conditions: the pretreatment gas comprises at least one of hydrogen, carbon monoxide, and methane; the temperature of the pretreatment is 400-900℃; and the time of the pretreatment is 1min-60min. Thus, metal nanoparticles are formed on the surface of the carrier by the reduction process.

[0015] The third aspect of the present application provides a method for preparing a carbon nanotube array assembly, the method comprising: mixing the flaky catalyst provided by the first aspect of the present application or the flaky catalyst prepared by the method provided by the second aspect of the present application with a carbon source gas to react, the temperature of the reaction being 500-900 DEG C, to obtain an array assembly containing multi-walled carbon nanotubes, few-walled carbon nanotubes and single-walled carbon nanotubes. Thus, the efficient catalytic growth of multi-walled carbon nanotubes guiding the array of few / single-walled carbon nanotubes is realized, the growth length of the few / single-walled carbon nanotubes is improved, and the obtained carbon nanotube array assembly has significant orientation and the length can reach hundreds of microns, and the carbon nanotubes with different diameters work together to construct a conductive network with excellent performance on the electrode sheet.

[0016] The fourth aspect of the present application provides a carbon nanotube array assembly, which is prepared by the method provided by the third aspect of the present application, and satisfies at least one of the following conditions: the length of the carbon nanotube array assembly is 20-200 microns; the diameter of the carbon nanotube array is 0.3-8 microns; and the specific surface area of the carbon nanotube array is 300-900 m 2 2 / g. Thus, when the carbon nanotube array assembly is used as a conductive agent on the negative electrode sheet, it can be used as a support skeleton to limit the volume expansion of the silicon-based negative electrode, the single / few-walled carbon nanotubes have good flexibility to wrap and wind the silicon-based material to reduce the contact resistance, and the long carbon nanotubes with different wall numbers form a conductive network, which can improve the conductivity and stability of the negative active material of the ion battery.

[0017] The fifth aspect of the present application provides a conductive agent, which comprises the carbon nanotube array assembly provided by the fourth aspect of the present application.

[0018] The sixth aspect of the present application provides an electrode sheet, which comprises the conductive agent provided by the fifth aspect of the present application.

[0019] The seventh aspect of the present application provides a battery, which comprises the electrode sheet provided by the sixth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0020] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the description of the embodiments, taken in conjunction with the following drawings in which:

[0021] Figure 1 A transmission electron microscope photo showing the distribution of metal particles of the catalyst prepared in an embodiment of the present application after pretreatment is shown.

[0022] Figure 2 A flowchart showing the method for preparing the flaky catalyst in an embodiment of the present application is shown.

[0023] Figure 3 ​is a typical transmission electron microscope image of multi-walled carbon nanotubes grown inside the catalyst sheet layer prepared in Example 1.

[0024] Figure 4 is a typical transmission electron microscope image of few / single carbon nanotubes grown on the periphery of the catalyst sheet layer prepared in Example 1.

[0025] Figure 5 is a typical low-magnification scanning electron microscope image of long array carbon nanotubes prepared in Example 3.

[0026] Reference signs:

[0027] 1 support; 11 central region; 12 edge region; 21 multi-walled carbon nanotube; 22 few-walled carbon nanotube; 23 single-walled carbon nanotube. DETAILED DESCRIPTION

[0028] The examples of the present application are described in detail below. The examples described below are exemplary only and are not to be construed as limiting the present application. Unless otherwise indicated, technical or conditions in the examples are in accordance with those described in the literature or in accordance with the product manual. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained commercially.

[0029] There are currently several methods for increasing the length of few / single-walled carbon nanotubes. One is to disperse the catalyst on a secondary support, such as a stainless steel mesh, a silicon wafer, a quartz plate, etc., thereby providing sufficient space and a relatively stable growth environment for the growth of array carbon nanotubes, but this method has limited dispersed catalyst, resulting in limited production of few / single-walled carbon nanotubes. Another is to increase the surface density of metal particles on the catalyst sheet layer, so that few / single-walled carbon nanotubes spontaneously self-assemble into a double helix structure, thereby having greater support and to some extent improving the growth stability, but this method is only realized in a small-scale horizontal tube furnace, and is difficult to be widely applied in large-scale and different types of reactors, and cannot be mass-produced.

[0030] The first aspect of the present application provides a sheet-shaped catalyst, the sheet-shaped catalyst comprising a support, at least part of the surface of the support having metal particles formed of a Q element, the support comprising an oxide containing an M element, the Q element comprising at least one of Fe, Co, Ni, Cu, Mo, W, the M element comprising at least one of Mg, Zn, Ca, Mn, Cr, Al, Ru; the surface of the support comprising a central region and an edge region in order from the center of the support to the edge of the support, the loading amount of the Q element in the central region being greater than the loading amount of the Q element in the edge region.

[0031] In the present application, the radius of the catalyst sheet layer is r, the central region of the carrier surface refers to the range of 0-0.6r of the catalyst sheet layer radius; the edge region refers to the range of 0.3r-r of the catalyst sheet layer radius.

[0032] For example, the central region can be the range of 0-0.3r of the catalyst sheet layer radius, and the edge region can be the range of 0.3r-r of the catalyst sheet layer radius. When the central region is 0-0.6r of the catalyst sheet layer, the edge region can be the range of 0.6r-r of the catalyst sheet layer.

[0033] It should be noted that the metal particles in the edge region can be distributed only near the central region, or the metal particles are distributed throughout the edge region.

[0034] Specifically, the sizes of the central region and the edge region can be designed according to the carbon nanotube array assembly to be prepared, for example, when preparing a carbon nanotube array assembly with a high content of multi-walled carbon nanotubes and a low content of few / single-walled carbon nanotubes, the central region with a high Q element loading can be made larger, and the edge region with a low Q element loading can be made smaller; when preparing a carbon nanotube array assembly with a low content of multi-walled carbon nanotubes and a high content of few / single-walled carbon nanotubes, the central region with a high Q element loading can be made smaller, and the edge region with a low Q element loading can be made larger.

[0035] For example, referring to Figure 1 , the central region 11 and the edge region 12 of the sheet-shaped catalyst carrier 1 are shown in the figure.

[0036] In the present application, the surface density and the average particle size of the metal particles in the central region and the edge region can be observed and compared by scanning electron microscopy. When calculating the surface density, the surface density of the region where the metal particles exist is referred to.

[0037] Therefore, in the process of preparing the carbon nanotube array assembly, the central region has a high Q element loading, which can form a small number of Q metal particles with a large average particle size, catalyze the growth of multi-walled carbon nanotubes, the edge region has a low Q element loading, which can form a large number of Q metal particles with a small average particle size, catalyze the growth of few / single-walled carbon nanotubes, the multi-walled carbon nanotubes can play a role in pillar supporting, guide the efficient growth of few / single-walled carbon nanotubes, and thus obtain a carbon nanotube array assembly with a length of up to hundreds of microns.

[0038] As an example, the carrier can be prepared from a sheet-shaped magnesium hydroxide, a layered double metal hydroxide.

[0039] According to some embodiments of the present application, the surface density of the metal particles in the central region is less than the surface density of the metal particles in the edge region, and the surface density of the metal particles in the central region is 10 12Individuals / m 2 -10 15 Individuals / m 2 The areal density of the metal particles in the edge region is 10 14 Individuals / m 2 -10 16 Individuals / m 2 Thus, carbon nanotube arrays assemblages with different wall numbers are catalytically grown.

[0040] For example, the areal density of the metal particles in the center region can be 10 12 Individuals / m 2 , 10 13 Individuals / m 2 , 10 14 Individuals / m 2 , 10 15 Individuals / m 2 , or a range consisting of any of the aforementioned values.

[0041] For example, the areal density of the metal particles in the edge region can be 10 14 Individuals / m 2 , 10 15 Individuals / m 2 , 10 16 Individuals / m 2 , or a range consisting of any of the aforementioned values.

[0042] According to some embodiments of the present application, the average particle size of the metal particles in the center region is greater than the average particle size of the metal particles in the edge region, the average particle size of the metal particles in the center region is 7nm-50nm, and the average particle size of the metal particles in the edge region is 1nm-10nm.

[0043] For example, the average particle size of the metal particles in the center region can be 7nm, 20nm, 30nm, 40nm, 50nm, or a range consisting of any of the aforementioned values.

[0044] For example, the average particle size of the metal particles in the edge region can be 1nm, 3nm, 4nm, 5nm, 6nm, 7nm, 10nm, or a range consisting of any of the aforementioned values.

[0045] Thus, the central region of the catalyst has fewer metal particles and larger average particle size, and the edge region has more metal particles and smaller average particle size. In the process of preparing carbon nanotubes, the metal particles in the central region can catalyze the growth of multi-walled carbon nanotubes in an array structure, and play a role of pillar support to expand the sheet-shaped catalyst around, so that the macroscopic volume of the catalyst bed is greatly expanded. The metal particles in the edge region can catalyze the growth of few / single-walled carbon nanotubes, and the few / single-walled carbon nanotubes climb on the multi-walled carbon nanotubes and grow in an array structure, which is beneficial to improve the growth length of the few / single-walled carbon nanotubes. The obtained carbon nanotube array assembly has significant orientation, and the length can reach hundreds of microns. Different diameter carbon nanotubes work together to construct a conductive network with excellent performance on the pole piece.

[0046] The second aspect of the present application provides a method for preparing the sheet-shaped catalyst provided in the first aspect of the present application, which comprises: mixing a salt solution containing M elements, a precipitant, and a salt solution containing Q elements to form a mixed solution, and obtaining a precursor by co-precipitation, wherein the co-precipitation comprises a first stage and a second stage performed in sequence, the first stage is 0h-6h from the beginning of the co-precipitation, and the mass of Q elements added in the first stage is greater than the mass of Q elements added in the second stage. The precursor is calcined and reduced to obtain the sheet-shaped catalyst. That is, in the first stage from the beginning of the co-precipitation, a high content of active metal Q is added, and in the subsequent stage of the co-precipitation, a low content of active metal Q is added, so as to obtain a sheet-shaped catalyst with relatively fewer metal particles and larger average particle size in the central region, and relatively more metal particles and smaller average particle size in the edge region. The sheet-shaped catalyst is further used to prepare a carbon nanotube array assembly, so as to construct a conductive network with excellent performance in the pole piece.

[0047] The method provided in the present application is described in detail below, and reference is made to Figure 2 , which comprises:

[0048] S10: mixing a salt solution containing M elements, a precipitant, and a salt solution containing Q elements to form a mixed solution, and obtaining a precursor by co-precipitation

[0049] According to some embodiments of the present application, a salt solution containing M elements, a precipitant, and a salt solution containing Q elements are mixed to form a mixed solution, and a precursor is obtained by co-precipitation, wherein the co-precipitation comprises a first stage and a second stage performed in sequence, the first stage is 0h-6h from the beginning of the co-precipitation, and the mass of Q elements added in the first stage is greater than the mass of Q elements added in the second stage.

[0050] According to some embodiments of the present application, the mixing method of the M-containing salt solution, the Q-containing salt solution and the precipitant is not particularly limited, which can be that the M-containing salt solution and the Q-containing salt solution are first mixed with half volume of the precipitant solution to form a mixed solution, which is then added into the reactor, and the Q-containing salt solution is mixed with the other half volume of the precipitant solution and added into the reactor in the second stage of the co-precipitation.

[0051] According to some embodiments of the present application, the adding method of the precipitant solution is not particularly limited, which can be that the M-containing salt solution and the Q-containing salt solution are first mixed with half volume of the precipitant solution to form a mixed solution, which is then added into the reactor, and the Q-containing salt solution is mixed with the other half volume of the precipitant solution and added into the reactor in the second stage of the co-precipitation.

[0052] According to some embodiments of the present application, the M-containing salt solution comprises at least one of M-containing sulfate, M-containing nitrate, M-containing chloride and M-containing acetate.

[0053] According to some embodiments of the present application, the precipitant comprises at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonium bicarbonate, urea and ammonia.

[0054] According to some embodiments of the present application, the Q-containing salt solution comprises at least one of Q-containing sulfate, Q-containing nitrate, Q-containing chloride and Q-containing acetate.

[0055] According to some embodiments of the present application, the first stage is 0h-6h from the start of the co-precipitation, for example, 0.5h, 1h, 2h, 3h, 4h, 5h or the like, or a range formed by any of the above values. For example, the high-content active metal is added in the first stage of the co-precipitation in 0-3h from the start of the reaction, and then the low-content active metal is added in the second stage of the co-precipitation in 3h from the start of the reaction.

[0056] According to some embodiments of the present application, the molar ratio of the Q element to the M element in the Q-containing salt solution added in the first stage is (0.05-0.5):1, for example, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1 or the like, or a range formed by any of the above values.

[0057] According to some embodiments of the present application, the molar ratio of Q element to M element in the second stage added Q element containing salt solution is (0.005-0.05):1, for example, it can be 0.005:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, or it can be a range composed of any of the above values.

[0058] Thus, a high content of active metal Q is added at the beginning of the co-precipitation, and a low content of active metal Q is added in the subsequent stage of the co-precipitation, so as to obtain a sheet-shaped catalyst with relatively less metal nanoparticles in the central region, large average particle size, relatively more metal nanoparticles in the edge region, and small average particle size. In the process of preparing carbon nanotubes, the metal particles in the central region can catalyze the growth of multi-walled carbon nanotubes in an array structure, playing a role of pillar support, and the metal particles in the edge region can catalyze the growth of few / single-walled carbon nanotubes, which climb on the multi-walled carbon nanotubes and also grow in an array structure, which is conducive to improving the growth length of the few / single-walled carbon nanotubes. The obtained carbon nanotube array assembly has significant orientation, and the length can reach hundreds of microns. Different diameter carbon nanotubes work together to construct a conductive network with excellent performance on the electrode sheet.

[0059] According to some embodiments of the present application, the pH of the mixed solution in the co-precipitation process is 6-11, for example, it can be 6, 7, 8, 9, 10, 11, or it can be a range composed of any of the above values.

[0060] According to some embodiments of the present application, after co-precipitation, a step of standing and aging is further included, and then the product is filtered, washed to neutral, dried, and ground and broken to obtain a sheet-shaped catalyst.

[0061] S20: calcining the precursor

[0062] According to some embodiments of the present application, the atmosphere of the calcination can be inert gas or air.

[0063] According to some embodiments of the present application, the heating rate of the calcination can be 1℃ / min-20℃ / min, for example, it can be 1℃ / min, 5℃ / min, 10℃ / min, 15℃ / min, 20℃ / min, or it can be a range composed of any of the above values.

[0064] According to some embodiments of the present application, the temperature of the calcination can be 400℃-900℃, for example, it can be 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, or it can be a range composed of any of the above values.

[0065] S30: reducing the calcined precursor

[0066] According to some embodiments of the present application, the calcined precursor is placed in a reactor, and a pretreatment gas is introduced to reduce the precursor.

[0067] According to some embodiments of the present application, the pretreatment gas comprises at least one of hydrogen, carbon monoxide, and methane.

[0068] According to some embodiments of the present application, the temperature of the pretreatment is 400-900°C, for example, can be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, or can be a range consisting of any of the above values.

[0069] According to some embodiments of the present application, the time of the pretreatment is 1-60 minutes, for example, can be 1 minute, 10 minutes, 30 minutes, 45 minutes, 60 minutes, or can be a range consisting of any of the above values.

[0070] Thus, Q metal nanoparticles are formed on the surface of the carrier through the reduction process.

[0071] The third aspect of the present application provides a method for preparing a carbon nanotube array assembly, which comprises mixing the flaky catalyst provided by the first aspect of the present application or the catalyst prepared by the method provided by the second aspect of the present application with a carbon source gas to react, the temperature of the reaction is 500-900°C, to obtain an array assembly containing multi-walled carbon nanotubes, few-walled carbon nanotubes, and single-walled carbon nanotubes. Thus, in the process of preparing carbon nanotubes, the metal particles in the central region of the flaky catalyst, which have few metal nanoparticles and large average particle size, can catalyze the growth of multi-walled carbon nanotubes in an array structure, playing a role of pillar supporting, and the metal particles in the edge region, which have many metal nanoparticles and small average particle size, can catalyze the growth of few / single-walled carbon nanotubes, which climb on the multi-walled carbon nanotubes and also grow in an array structure, which is conducive to improving the growth length of the few / single-walled carbon nanotubes, and the obtained carbon nanotube array assembly has significant orientation, the length can reach hundreds of microns, and carbon nanotubes with different diameters work together to construct a conductive network with excellent performance on the electrode plate.

[0072] According to some embodiments of the present application, the flaky catalyst is placed in a reactor, a mixed gas of a carbon source gas, hydrogen, and a carrier gas is introduced into the reactor, the temperature of the reaction is 500-900°C, and the volume ratio of hydrogen, the carbon source gas, and the carrier gas in the mixed gas is (0-10):1:(0.1-10).

[0073] As an example, the temperature of the reaction can be 500°C, 600°C, 700°C, 800°C, 900°C, or can be a range consisting of any of the above values.

[0074] According to some embodiments of the present application, the reactor comprises at least one of a fixed bed, a fluidized bed, a moving bed, a rotating drum.

[0075] According to some embodiments of the present application, the carbon source gas comprises at least one of methane, methanol, ethylene, ethane, ethanol, propylene, propane, carbon monoxide, natural gas, liquefied petroleum gas, cyclohexane, n-hexane, benzene or toluene.

[0076] According to some embodiments of the present application, the volume space velocity of the mixed gas is 10 min -1 -10 7 min -1 .

[0077] The fourth aspect of the present application provides a carbon nanotube array assembly, which is prepared by the method provided in the third aspect of the present application.

[0078] According to some embodiments of the present application, the length of the carbon nanotube array assembly is 20 μm-200 μm. For example, it can be 20 μm, 50 μm, 80 μm, 110 μm, 140 μm, 170 μm, 200 μm, etc., or a range consisting of any of the above values.

[0079] According to some embodiments of the present application, the diameter of the carbon nanotube array is 0.3 μm-8 μm. For example, it can be 0.3 μm, 1 μm, 3 μm, 5 μm, 7 μm, 8 μm, etc., or a range consisting of any of the above values.

[0080] According to some embodiments of the present application, the specific surface area of the carbon nanotube array is 300 m 2 / g-900 m 2 / g. For example, it can be 300 m 2 / g, 400 m 2 / g, 500 m 2 / g, 600 m 2 / g, 700 m 2 / g, 800 m 2 / g, 900 m 2 / g, etc., or a range consisting of any of the above values.

[0081] Therefore, when the carbon nanotube array assembly is used as a conductive agent on the negative electrode tab, it can limit the volume expansion of the silicon-based negative electrode as a support framework, the single / multi-walled carbon nanotube has good flexibility to wrap and wind the silicon-based material to reduce the contact resistance, and the long carbon nanotube with different wall numbers forms a conductive network, which can improve the conductivity and stability of the negative active material of the ion battery.

[0082] The fifth aspect of the present application provides a conductive agent comprising the carbon nanotube array assembly provided in the fourth aspect of the present application.

[0083] The carbon nanotube array assembly provided in the present application comprises multi-walled, few-walled and single-walled long array carbon nanotubes. When the carbon nanotube assembly is used as a conductive agent on a negative electrode tab, it can serve as a support framework to limit the volume expansion of a silicon-based negative electrode. The single / few-walled carbon nanotubes have good flexibility to wrap and wind the silicon-based material to reduce the contact resistance. The long carbon nanotubes with different wall numbers form a conductive network, which can improve the conductivity and stability of the negative active material of an ionic battery.

[0084] In the present application, the multi-walled carbon nanotubes refer to carbon nanotubes with 5-20 tube walls, and the few-walled carbon nanotubes refer to carbon nanotubes with 2-4 tube walls.

[0085] The sixth aspect of the present application provides an electrode tab comprising the conductive agent provided in the fifth aspect of the present application.

[0086] The seventh aspect of the present application provides a battery comprising the electrode tab provided in the sixth aspect of the present application.

[0087] Embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in the art or according to the product instructions are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be obtained by purchase.

[0088] Example 1

[0089] The carbon nanotube array was prepared by using MgAl layered double hydroxide loaded with Fe in a fixed bed:

[0090] (1) 0.2 mol of magnesium sulfate, 0.05 mol of aluminum sulfate and 0.1 mol of iron sulfate were dissolved in water, stirred uniformly to form solution A;

[0091] 1.5 mol of sodium bicarbonate was dissolved in water, stirred uniformly to form solution B;

[0092] 0.2 mol of magnesium sulfate, 0.05 mol of aluminum sulfate and 0.01 mol of iron sulfate were dissolved in water, stirred uniformly to form solution C.

[0093] (2) Solution A is added dropwise into solution B, the temperature is set to 80 °C, the stirring speed is 300 rpm, and the reaction is carried out for 2 h. Then solution C is added dropwise into the mixed solution of A and B, the end point pH is 8-10, and the reaction is carried out under the same conditions for 6 h, and the product is aged for 12 h. After the reaction is completed, the product is filtered, washed to neutral, and dried in a blast drying oven at 80 °C, and then ground and broken to obtain a flaky catalyst. The transmission electron microscope (TEM) image of the catalyst is shown in FIG. 2. Figure 1 .

[0094] The steps for synthesizing carbon nanotube arrays using the flaky catalyst are as follows:

[0095] (1) 0.5 g of the flaky catalyst is placed in a fixed bed reactor, nitrogen gas is introduced at 0.5 L / min, the temperature is raised to 650 °C, and hydrogen gas is introduced at 0.2 L / min for 10 min for pretreatment;

[0096] (2) At 650 °C, ethylene gas is introduced at 0.5 L / min for 30 min to prepare carbon nanotube arrays. After the reaction is completed, the temperature is lowered to room temperature under the protection of inert gas, and the black fluffy product is collected.

[0097] After the catalyst is reduced, the Fe particle size in the center region of the flaky layer is large (20 nm-50 nm), the surface density is 3×10 14 m -2 , the loading amount of Fe element is 27wt%, the Fe particle size in the edge region is small (2 nm-7 nm), the surface density is 1×10 15 m -2 , and the loading amount of Fe element is 3.5wt%. The carbon nanotubes grown in the center region of the flaky catalyst are multi-walled carbon nanotubes, and the carbon nanotubes in the edge region are few / single-walled carbon nanotubes, both of which grow in long array structures. The length of the carbon nanotube array assembly is 50 μm-100 μm, the diameter is 1.2 μm, the specific surface area is 569 m 2 / g, and the reference Figure 3 It can be seen that the prepared carbon nanotube array assembly contains, the reference Figure 4 It can be seen that the prepared carbon nanotube array assembly contains few / single-walled carbon nanotubes.

[0098] The carbon nanotube array assembly is subjected to liquid phase impurity removal and dispersed in water to obtain a carbon nanotube slurry containing multi-walled carbon nanotubes and few / single-walled carbon nanotubes. The carbon nanotube slurry is mixed with a silicon-carbon negative electrode material, a binder carboxymethyl cellulose (CMC) and a butadiene-styrene rubber (SBR) to obtain an electrode slurry, and the mass ratio of the silicon-carbon negative electrode material: carbon nanotube array assembly: CMC: SBR in the electrode slurry is 93:0.5:1:2. The electrode slurry is coated on an insulating polyethylene terephthalate (PET film) and dried to form an active material layer with a thickness of 30 μm. The electrode sheet resistivity is 1.33 Ω·cm, which is low, indicating that the carbon nanotube array assembly can improve the conductivity of the electrode sheet.

[0099] Example 2

[0100] The carbon nanotube array is prepared in a fixed bed using MgAl layered double hydroxide loaded with FeCo:

[0101] (1) 0.2 mol of magnesium sulfate, 0.05 mol of aluminum nitrate and 0.05 mol of iron nitrate are dissolved in water, stirred uniformly to form solution A;

[0102] 1.46 mol of sodium bicarbonate is dissolved in water, stirred uniformly to form solution B;

[0103] 0.2 mol of magnesium sulfate, 0.05 mol of aluminum nitrate and 0.01 mol of cobalt nitrate are dissolved in water, stirred uniformly to form solution C.

[0104] (2) Solution A and half the volume of solution B are simultaneously added dropwise, the dropwise addition speed is set to 5 mL / min, the pH is controlled to be always kept at 8-10, the temperature is 80 °C, the stirring speed is 300 rpm, and the reaction is carried out for 2 h. Then solution C and the remaining half volume of solution B are simultaneously added dropwise into the above mixed solution, and the stirring reaction is carried out under the same conditions for 6 h, and the standing aging is carried out for 12 h. After the reaction is completed, the product is filtered, washed to neutral, and the solid is dried in a blast drying oven at 80 °C, ground and broken to obtain a flaky catalyst.

[0105] The steps for synthesizing the carbon nanotube array using the flaky catalyst are as follows:

[0106] (1) 0.5 g of the flaky catalyst is placed in a fixed bed reactor, 0.5 L / min of nitrogen is introduced, the temperature is raised to 750 °C, and 0.2 L / min of hydrogen is continuously introduced for pretreatment for 10 min;

[0107] (2) Carbon nanotube arrays were prepared by flowing 0.5 L / min ethylene at 750 °C for 60 min. After the reaction, the black fluffy product was collected under inert gas protection and cooled to room temperature.

[0108] After reduction of the catalyst, the Fe particle size in the center of the sheet was large (10-30 nm), the surface density was 2 x 10 14 / m 2 , the loading of Fe element was 16 wt%, the Co particle size in the edge region was small (2-4 nm), the surface density was 5 x 10 15 / m 2 , and the loading of Co element was 3.7 wt%. The carbon nanotubes grown in the center of the sheet were multi-walled carbon nanotubes, and the carbon nanotubes grown in the edge region were few / single-walled carbon nanotubes. Both were grown in long array structures, the length of the carbon nanotube array assembly was 50-200 μm, the diameter was 1.2 μm, and the specific surface area was 661 m 2 / g.

[0109] The method for preparing the electrode sheet was the same as in Example 1. The resistivity of the electrode sheet was 1.06 Ω·cm, which was low, indicating that the carbon nanotube array assembly could improve the conductivity of the electrode sheet.

[0110] Example 3

[0111] Carbon nanotube arrays were prepared using MgAl layered double hydroxide supported NiCo in a fixed bed:

[0112] (1) 0.1 mol of magnesium nitrate, 0.05 mol of aluminum nitrate, and 0.08 mol of nickel nitrate were dissolved in water, stirred uniformly, and a solution A was formed;

[0113] 3 mol of urea was dissolved in water, stirred uniformly, and a solution B was formed;

[0114] 0.1 mol of magnesium sulfate, 0.05 mol of aluminum nitrate, and 0.01 mol of cobalt nitrate were dissolved in water, stirred uniformly, and a solution C was formed.

[0115] (2) Solution A and solution B were directly mixed in one pot, the temperature was set to 95 °C, and the stirring speed was 200 rpm. The reaction was carried out for 1 h. Then solution C was added dropwise to the mixed solution of A and B, the final pH was 7-11, and the reaction was carried out under the same conditions for 10 h, and the product was aged for 12 h. After the reaction was completed, the product was filtered, washed to neutral, and dried at 80 °C in a blast drying oven. The solid was ground and broken to obtain a sheet-shaped catalyst.

[0116] The steps for synthesizing carbon nanotube arrays using the sheet-shaped catalyst were as follows:

[0117] (1) 0.5 g of the flaky catalyst was placed in a fixed bed reactor, 0.5 L / min of nitrogen was introduced, and the temperature was raised to 700 °C, and 0.2 L / min of methane was continuously introduced for 10 min for pretreatment;

[0118] (2) 0.5 L / min of propylene was introduced at 700 °C for 45 min to prepare carbon nanotube arrays. After the reaction, the black fluffy product was collected under inert gas protection and cooled to room temperature.

[0119] After reduction of the catalyst, the Ni particle size in the center region of the flaky layer was large (10 nm-35 nm), the surface density was 3.5×10 14 / m 2 , the loading of Ni element was 48wt%, the Co particle size in the edge region was small (2 nm-4 nm), the surface density was 5.5×10 15 / m 2 , and the loading of Co element was 6.2wt%. The carbon nanotubes grown in the center region of the flaky layer were multi-walled, and those in the edge region were few / single-walled, both of which were grown in long array structures. The length of the carbon nanotube array assembly was 20 μm-100 μm, the diameter was 1.6 μm, the specific surface area was 605 m 2 / g, and the structure of the carbon nanotube array assembly was shown in Figure 5 .

[0120] The method for preparing the electrode sheet was the same as in Example 1. The resistivity of the electrode sheet was 1.17 Ω·cm, which was low, indicating that the carbon nanotube array assembly could improve the conductivity of the electrode sheet.

[0121] Example 4

[0122] A flaky magnesium hydroxide was used to load Cu to prepare carbon nanotube arrays in a fluidized bed:

[0123] (1) 0.2 mol of magnesium nitrate was dissolved in water to form solution A;

[0124] 0.65 mol of sodium hydroxide was dissolved in water and stirred uniformly to form solution B;

[0125] 0.1 mol of copper nitrate was dissolved in water and stirred uniformly to form solution C;

[0126] 0.01 mol of copper nitrate was dissolved in water and stirred uniformly to form solution D.

[0127] (2) Mix half volume of solution A with solution C, and add solution B drop by drop, set the temperature to 100 °C, the stirring speed to 150 rpm, and react for 0.5 h. Then mix the remaining volume of solution A with solution D, and add solution B drop by drop, the final pH being 8-11, and stir to react for 3 h under the same conditions, and stand for aging for 12 h. After the reaction is completed, filter the product, wash until neutral, take the solid to dry in a blast drying oven at 80 °C, grind and crush to obtain a flaky catalyst.

[0128] The steps for synthesizing carbon nanotube arrays using the flaky catalyst are as follows:

[0129] (1) Put 0.5 g of the flaky catalyst into a fixed bed reactor, pass in 0.5 L / min of nitrogen, and heat to 800 °C, and continue to pass in 0.2 L / min of carbon monoxide for 10 min of pretreatment;

[0130] (2) Pass in 0.5 L / min of natural gas at 800 °C for 120 min to prepare carbon nanotube arrays. After the reaction is completed, lower to room temperature under the protection of inert gas, and collect the black fluffy product.

[0131] After the catalyst is reduced, the Cu particle size in the center region of the flake is large (10 nm-40 nm), the surface density is 3×10 14 / m 2 , the loading of Cu element is 39 wt%, the Cu particle size in the edge region is small (2 nm-7 nm), the surface density is 4×10 15 / m 2 , and the loading of Cu element is 4.8 wt%. The carbon nanotubes grown in the center region of the flake are multi-walled, and those in the edge region are few / single-walled, both of which grow in long array structures, the length of the carbon nanotube array assembly is 20 μm-100 μm, the diameter is 0.8 μm, and the specific surface area is 573 m 2 / g.

[0132] The method for preparing the electrode sheet is the same as in Example 1. The resistivity of the electrode sheet is 1.25 Ω·cm, which is low, indicating that the carbon nanotube array assembly can improve the conductivity of the electrode sheet.

[0133] Example 5

[0134] Preparation of carbon nanotube arrays using flaky magnesium hydroxide loaded with FeNi in a fluidized bed:

[0135] (1) Dissolve 0.2 mol of magnesium nitrate in water to form solution A;

[0136] Dissolve 0.9 mol of ammonia in water, stir until uniform, and form solution B;

[0137] Dissolve 0.1 mol of ferric nitrate in water, stir to form solution C;

[0138] Dissolve 0.02 mol of nickel nitrate in water, stir to form solution D.

[0139] (2) Half volume of solution A and solution C are added dropwise into solution B at the same time, the temperature is set to 105 °C, the stirring speed is 200 rpm, and the reaction is carried out for 2 h. Then the remaining volume of solution A and solution D are added dropwise into solution B at the same time, the final pH is 7-10, and the reaction is carried out under the same conditions for 4 h, and aged for 24 h. After the reaction is completed, the product is filtered, washed to neutral, and dried in a blast drying oven at 80 °C, ground and broken, to obtain a flaky catalyst.

[0140] The steps for synthesizing carbon nanotube arrays using the flaky catalyst are as follows:

[0141] (1) Take 0.5 g of flaky catalyst and place it in a fixed bed reactor, introduce 0.5 L / min of nitrogen, and heat to 800 °C, then continue to introduce 0.2 L / min of hydrogen for 10 min of pretreatment;

[0142] (2) Introduce 0.5 L / min of methane at 850 °C for 120 min to prepare carbon nanotube arrays. After the reaction is completed, cool to room temperature under inert gas protection, and collect the black fluffy product.

[0143] After reduction of the catalyst, the Fe particle size in the center region of the flaky layer is large (10 nm-40 nm), the surface density is 3×10 14 / m 2 , the loading of Fe element is 34wt%, the Ni particle size in the edge region is small (2 nm-7 nm), the surface density is 5×10 15 / m 2 , and the loading of Ni element is 7.9wt%. The carbon nanotubes grown in the center region of the flaky layer are multi-walled, and those in the edge region are few / single-walled, both of which grow in long array structures, the length of the carbon nanotube array assembly is 20 μm-50 μm, the diameter is 1.0 μm, and the specific surface area is 592 m 2 / g.

[0144] The method for preparing the electrode sheet is the same as in Example 1. The resistivity of the electrode sheet is 1.27 Ω·cm, which is relatively low, indicating that the carbon nanotube array assembly can improve the conductivity of the electrode sheet.

[0145] Comparative Example 1

[0146] On the basis of Example 1, only the content of the active metal introduced in the initial stage and the amount of the precipitant used are changed, and the specific steps are as follows:

[0147] Preparation of carbon nanotube arrays in a fixed bed using MgAl layered double hydroxide supported Fe:

[0148] (1) Dissolve 0.2 mol of magnesium sulfate, 0.05 mol of aluminum sulfate and 0.01 mol of iron sulfate in water, stir uniformly to form solution A; dissolve 1.218 mol of sodium bicarbonate in water, stir uniformly to form solution B; dissolve 0.2 mol of magnesium sulfate, 0.05 mol of aluminum sulfate and 0.01 mol of iron sulfate in water, stir uniformly to form solution C.

[0149] (2) Add solution A dropwise to solution B, set the temperature to 80 °C and the stirring speed to 300 rpm, and react for 2 h. Then add solution C dropwise to the mixed solution of A and B, stir under the same conditions for 6 h, and stand for aging for 12 h. After the reaction is completed, filter the product, wash to neutral, take the solid to dry in a blast drying oven at 80 °C, grind and break, and obtain a flaky catalyst.

[0150] The steps for synthesizing carbon nanotubes using the flaky catalyst are the same as in Example 1. After reduction of the catalyst, the Fe particles distributed on the flaky layer have uniform particle sizes (2 nm-4 nm) and uniform surface densities (3×10 15 / m 2 ). The grown carbon nanotubes are all single-walled and double-walled, grow in a reticular interwoven structure, and fail to form an array structure, with a length of 2 μm-4 μm and a specific surface area of 907 m 2 / g.

[0151] It is shown that introducing the same low content of active metal in the initial stage and the subsequent stage of the growth of the carrier precipitate causes the active metal nanoparticles to be uniformly distributed in the form of small particle sizes, the carbon nanotubes to grow in the form of small diameters, non-array and non-assembly, and it is difficult to obtain long carbon nanotubes.

[0152] The preparation method of the electrode sheet is the same as in Example 1. The resistivity of the electrode sheet is tested by a four-probe resistivity meter to be 2.31 Ω·cm. This resistivity indicates that when the carbon nanotubes grow in the form of small diameters, non-array and non-assembly, the effect of improving the conductivity of the silicon-carbon negative electrode is low.

[0153] Comparative Example 2

[0154] On the basis of Example 2, only the content of the active metal introduced in the subsequent stage and the amount of the precipitant are changed, and the specific steps are as follows:

[0155] Preparation of carbon nanotube arrays in a fixed bed using MgAl layered double hydroxide supported FeCo:

[0156] (1) Dissolve 0.2 mol of magnesium sulfate, 0.05 mol of aluminum nitrate and 0.05 mol of iron nitrate in water, stir uniformly to form solution A; dissolve 1.55 mol of sodium bicarbonate in water, stir uniformly to form solution B; dissolve 0.2 mol of magnesium sulfate, 0.05 mol of aluminum nitrate and 0.05 mol of cobalt nitrate in water, stir uniformly to form solution C.

[0157] (2) Add solution A dropwise into solution B, set the temperature to 80 °C and the stirring speed to 300 rpm, and react for 2 h. Then add solution C dropwise into the mixed solution of A and B, stir under the same conditions for 6 h, and stand for aging for 12 h. After the reaction is completed, filter the product, wash to neutral, take the solid to dry in a blast drying oven at 80 °C, grind and crush to obtain a flaky catalyst.

[0158] The steps for synthesizing carbon nanotubes using the flaky catalyst are the same as in Example 2. After reduction of the catalyst, the Fe and Co particles distributed on the flaky layer are respectively located in the central region and the edge region, and the particle size is uniform (10 nm-20 nm) and the surface density is uniform (6×10 14 / m 2 ). The grown carbon nanotubes are all multi-walled, grown in a long array structure, the length is 100 μm-200 μm, the diameter is 1.2 μm, and the specific surface area is 328 m 2 / g.

[0159] It is illustrated that introducing the same high content of active metal in the initial stage and the subsequent stage of the growth of the carrier precipitation, the obtained active metal nanoparticles are uniformly distributed in the form of large particle size, the carbon nanotubes are grown in the form of large diameter, array and non-assembly, and long carbon nanotubes are easily obtained.

[0160] The preparation method of the electrode sheet is the same as in Example 1. The resistivity of the electrode sheet is 1.75 Ω·cm tested by a four-probe resistivity meter. The resistivity indicates that when the carbon nanotubes are grown in the form of large diameter, array and non-assembly, the effect of improving the conductivity of the silicon-carbon negative electrode is limited.

[0161] Comparative Example 3

[0162] On the basis of Example 3, only the content of the introduced active metal in the initial and subsequent stages is exchanged, and the specific steps are as follows:

[0163] Using MgAl layered double hydroxide to load NiCo to prepare carbon nanotube arrays in a fixed bed:

[0164] (1) Dissolve 0.1 mol magnesium nitrate, 0.05 mol aluminum nitrate and 0.01 mol nickel nitrate in water and stir until homogeneous to form solution A; dissolve 3 mol urea in water and stir until homogeneous to form solution B; dissolve 0.1 mol magnesium sulfate, 0.05 mol aluminum nitrate and 0.08 mol cobalt nitrate in water and stir until homogeneous to form solution C.

[0165] (2) Solution A and solution B were directly mixed in one pot, the temperature was set at 95 °C, the stirring speed was 200 rpm, and the reaction was carried out for 1 h. Then solution C was added dropwise to the mixture of A and B, and the reaction was stirred for 10 h under the same conditions. After standing and aging for 12 h, the product was filtered after the reaction was completed, washed until neutral, and the solid was dried in a forced-air drying oven at 80 °C. The solid was then ground and crushed to obtain a flake catalyst.

[0166] The steps for synthesizing carbon nanotubes using this sheet-like catalyst are the same as in Example 3. After catalyst reduction, the Ni particles in the central region of the sheet have a smaller particle size (2nm-3nm) and an areal density of 4×10⁻⁶. 15 pcs / m 2 The Co particles in the edge region have a larger particle size (10nm-20nm) and an areal density of 4×10⁻⁶. 14 pcs / m 2 The grown carbon nanotubes have a central region with few or no single walls, growing in a network-like interwoven structure with a length of 1 μm-3 μm; the peripheral region has multiple walls, growing in a long array structure with a length of 100 μm-200 μm, and a specific surface area of ​​406 m². 2 / g.

[0167] This indicates that introducing low and high concentrations of active metals in the initial and subsequent stages of carrier precipitation growth, respectively, resulted in active metal nanoparticles distributed with small diameters in the central region and large diameters in the peripheral region. The carbon nanotubes in the central region grew with small diameters and a non-array structure, making it difficult for them to grow long; conversely, the carbon nanotubes in the peripheral region grew with large diameters and an array structure, making it easier to obtain long carbon nanotubes. The multi-walled carbon nanotubes in the peripheral region failed to provide pillar support for the few / single-walled carbon nanotubes in the central region, thus failing to guide them to form a long array.

[0168] The electrode sheet was prepared using the same method as in Example 1. The resistivity of the electrode sheet was measured to be 1.70 Ω·cm using a four-probe resistivity meter. This resistivity indicates that when carbon nanotubes are grown in the form of large-diameter arrays and small-diameter non-array assemblies, the effect on improving the conductivity of the silicon-carbon anode is limited.

[0169] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A sheet-like catalyst, characterized in that, The carrier includes a support having metal particles formed from element Q on at least a portion of its surface, the support comprising an oxide containing element M, wherein element Q comprises at least one of Fe, Co, Ni, Cu, Mo, and W, and element M comprises at least one of Mg, Zn, Ca, Mn, Cr, Al, and Ru. The surface of the carrier includes a central region and an edge region from the center of the carrier to the edge of the carrier. The load of the Q element in the central region is greater than the load of the Q element in the edge region; The areal density of the metal particles in the central region is less than that in the edge regions, and the areal density of the metal particles in the central region is 10. 12 pcs / m 2 -10 14 pcs / m 2 The areal density of the metal particles in the edge region is 10. 15 pcs / m 2 -10 16 pcs / m 2 ; The average particle size of the metal particles in the central region is greater than that in the edge region. The average particle size of the metal particles in the central region is 10nm-50nm, and the average particle size of the metal particles in the edge region is 1nm-5nm.

2. A method for preparing the sheet-like catalyst according to claim 1, characterized in that, include: A salt solution containing element M, a precipitant, and a salt solution containing element Q are mixed to form a mixture. A precursor is obtained through coprecipitation. The coprecipitation includes a first stage and a second stage performed sequentially. The first stage lasts for 0.5-6 hours from the start of the coprecipitation. The mass of element Q added in the first stage is greater than the mass of element Q added in the second stage. The molar ratio of element Q to element M in the salt solution containing element Q added in the first stage is (0.05-0.5):1, and the molar ratio of element Q to element M in the salt solution containing element Q added in the second stage is (0.005-0.05):

1. The precipitant is added either only in the first stage or in both the first and second stages. The precursor is calcined and reduced to obtain the sheet-like catalyst.

3. The method according to claim 2, characterized in that, The pH of the mixture during the co-precipitation process is 6-11.

4. The method according to claim 2, characterized in that, At least one of the following conditions must be met: (1) The calcination atmosphere is an inert gas or air; (2) The calcination temperature is 400℃-900℃; (3) The heating rate of the calcination is 1℃ / min-20℃ / min.

5. The method according to claim 2, characterized in that, The reduction process includes: pretreating the calcined precursor with a pretreatment gas, wherein the pretreatment satisfies at least one of the following conditions: (1) The pretreatment gas includes at least one of hydrogen, carbon monoxide, and methane; (2) The pretreatment temperature is 400℃-900℃; (3) The pretreatment time is 1 min to 60 min.

6. A method for preparing a carbon nanotube array assembly, characterized in that, include: The sheet catalyst of claim 1 or the sheet catalyst prepared by the method of any one of claims 2-5 is mixed with a carbon source gas and reacted at a temperature of 500℃-900℃ to obtain an array assembly containing multi-walled carbon nanotubes, few-walled carbon nanotubes and single-walled carbon nanotubes.

7. A carbon nanotube array assembly, characterized in that, The carbon nanotube array assembly is prepared by the method of claim 6, and the assembly satisfies at least one of the following conditions: (1) The length of the carbon nanotube array assembly is 20μm-200μm; (2) The diameter of the carbon nanotube array is 0.3 μm-8 μm; (3) The specific surface area of ​​the carbon nanotube array is 300 m². 2 / g-900m 2 / g.

8. A conductive agent, characterized in that, Includes the carbon nanotube array assembly as described in claim 7.

9. An electrode sheet, characterized in that, Includes the conductive agent as described in claim 8.

10. A battery, characterized in that, Includes the electrode sheet as described in claim 9.

Images