Composite powder, method for preparing the same, and use thereof

Abstract

The application discloses a composite powder and a preparation method and application thereof, and relates to the technical field of materials. The composite powder provided by the application comprises modified carbon black and modified array carbon nanotubes, wherein the surface of the modified carbon black is negatively charged, the surface of the modified array carbon nanotubes is positively charged, and the negative charge is used for mutual attraction with the positive charge. The modified carbon black with the negative charge in the composite powder of the application and the modified array carbon nanotubes with the positive charge are mutually attracted, the dispersion performance of the array carbon nanotubes and the carbon black in the composite powder can be improved, the conductive performance of the composite powder is improved, meanwhile, the use amount of the modified carbon black can be reduced, in addition, the process is simple and convenient to operate, and is beneficial to industrial production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of materials, and particularly relates to a composite powder and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries have a wide application prospect in the fields of portable electronic devices and electric vehicles due to the advantages of high working voltage, large specific capacity, stable discharge, small volume, light weight, no memory effect, high safety, long service life and environmental friendliness. Conductive agents are often used in positive and negative electrode sheets in lithium ion batteries, which can improve the activity of the electrode sheet material and thus improve the performance of lithium ion batteries.

[0003] Currently, common conductive agents for lithium ion batteries include conductive carbon black, carbon nanotubes and graphene. The advantages of conductive carbon black are that it can be added to the electrode sheet material in the form of powder, the process is simple and easy to operate, and the disadvantages are that the conductive performance of conductive carbon black is poor, and the addition amount is high (generally the addition amount needs to reach 5-10%, because a low addition amount will result in low capacity of lithium ion batteries); and the advantages of carbon nanotubes are good conductivity and low addition amount, which can improve the capacity and rate performance of lithium ion batteries, and the disadvantages are that carbon nanotubes need to be added to the electrode sheet material in the form of slurry, and the process is complex.

[0004] Therefore, it is necessary to provide a conductive agent with good conductivity, low addition amount and simple process. SUMMARY

[0005] The present application aims to overcome the above-mentioned deficiencies of the prior art, and provides a composite powder and a preparation method and application thereof, so as to solve the problems of poor conductive performance and high addition amount of existing conductive carbon black as a conductive agent, and the problems of the need to make a slurry and complex process of carbon nanotubes as a conductive agent.

[0006] In order to achieve the above-mentioned application purposes, the first aspect of the present application provides a composite powder, comprising:

[0007] The modified carbon black is obtained by the following steps: mixing carbon black with acid liquid and treating to obtain acidized carbon black, adding the acidized carbon black into an aqueous solution of anionic surfactant and treating to obtain anionic surfactant modified carbon black, and dispersing the anionic surfactant modified carbon black in a first salt solution and treating to obtain modified carbon black with negative charges on the surface;

[0008] The modified array carbon nanotubes are obtained by the following steps: mixing and treating array carbon nanotubes with acid liquor to obtain acidified array carbon nanotubes, adding the acidified array carbon nanotubes into an aqueous solution of amino-containing coupling agent and treating to obtain amino-containing coupling agent modified carbon nanotubes, and dispersing the amino-containing coupling agent modified carbon nanotubes in a second salt solution and treating to obtain modified array carbon nanotubes with positive charges on the surface.

[0009] The negative charges in the modified carbon black are used to attract the positive charges in the modified array carbon nanotubes.

[0010] Further, the mixing and treating of carbon black with acid liquor to obtain acidified carbon black comprises:

[0011] The conductive carbon black with a particle size range of 100-20000 nm is selected;

[0012] The conductive carbon black is placed in an acid liquor with a molar concentration range of 0.7-1.2 mol / L, pretreated at 70-100°C for 1-3h, filtered and washed until the filtrate is neutral, and then dried at 110-130°C for 19-24h to obtain the acidified carbon black.

[0013] Further, the adding of the acidified carbon black into an aqueous solution of anionic surfactant and treating to obtain anionic surfactant modified carbon black, and dispersing the anionic surfactant modified carbon black in a first salt solution and treating to obtain modified carbon black with negative charges on the surface comprises:

[0014] The acidified carbon black is placed in an aqueous solution of anionic surfactant with a concentration range of 0.003-0.008 g / mL, ultrasonically treated at a frequency of 10-30 Hz for 0.2-0.7h, and stirred at a stirring speed range of 100-300 r / min for 1-4h, and then the solution is placed in a water bath at 20-40°C for 2-6h, filtered and washed, and then dispersed in a salt solution with a concentration of 0.0005-0.003 M, ultrasonically treated at a frequency of 10-30 Hz for 0.1-2h to obtain the modified carbon black with negative charges on the surface.

[0015] Further, the mixing and treating of array carbon nanotubes with acid liquor to obtain acidified array carbon nanotubes comprises:

[0016] The array carbon nanotubes with an aspect ratio range of 5000-15000 and a Raman spectrum intensity ratio range of 0.8-1.3 are selected;

[0017] The array carbon nanotubes are treated in acid liquor, and then filtered, washed and dried to obtain the acidified array carbon nanotubes.

[0018] Further, the acidized array carbon nanotubes are added into an aqueous solution of amino-containing coupling agent and treated to obtain amino-containing coupling agent modified carbon nanotubes, and the amino-containing coupling agent modified carbon nanotubes are dispersed in a second salt solution and treated to obtain the modified array carbon nanotubes with positive charges on the surface.

[0019] The acidized carbon nanotubes are added into an aqueous solution of amino-containing coupling agent, ultrasonically treated at a frequency of 20-100 Hz for 0.5-24 h, and stirred at a stirring speed of 200-4000 r / min for 2-24 h, the solution with acidized array carbon nanotubes and amino-containing coupling agent is placed in a water bath at 35-70℃ and left to stand for 4-24 h, and then dried after multiple centrifugations in sequence to obtain the amino-containing coupling agent modified carbon nanotubes.

[0020] The amino-containing coupling agent modified carbon nanotubes are dispersed in a salt solution with a molar mass of 0.001-2 M, ultrasonically treated at a frequency of 20-100 Hz for 0.5-2 h to obtain the modified array carbon nanotubes with positive charges on the surface.

[0021] Further, the mass ratio of the modified carbon black to the modified array carbon nanotubes ranges from 90-98:2-10.

[0022] Further, the oil absorption of the composite powder ranges from 120-220 mg / 100 g.

[0023] and / or,

[0024] The resistivity of the composite powder ranges from 80-140 mΩ·cm.

[0025] and / or,

[0026] The specific surface area of the composite powder ranges from 50-150 m 2 / g.

[0027] In a second aspect of the present application, a lithium ion battery is provided, comprising the composite powder described above.

[0028] In a third aspect of the present application, a preparation method of the composite powder described above is provided, comprising the following steps:

[0029] The modified carbon black and the modified array carbon nanotubes are mixed and subjected to a pulverization treatment to obtain the composite powder.

[0030] Further, the mixture of the modified carbon black and the modified array carbon nanotubes is subjected to a pulverization treatment by using an air flow pulverization device.

[0031] Compared with the prior art, the present application has the following technical effects:

[0032] The composite powder provided by the embodiment of the application and the preparation method and application thereof, the composite powder is composed of modified carbon black with negative charge and modified array carbon nanotube with positive charge, the positive and negative charges attract each other, which can improve the dispersion performance of the array carbon nanotube and the carbon black in the composite powder, and improve the conductive performance of the composite powder, at the same time, the modified array carbon nanotube can reduce the amount of the modified carbon black while improving the conductive performance of the composite powder, in addition, when the composite powder is used as a conductive agent, it can be directly added into the system in the form of powder, which is very easy to disperse into various systems, that is, the mixed powder of the carbon black and the carbon nanotube is directly obtained, the process is simple and easy to operate, and is conducive to industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the drawings needed to be used in the description of the specific embodiments or prior art will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0034] Figure 1 is a preparation process flow chart of carbon black with negative charge on the surface provided by the embodiment of the present application;

[0035] Figure 2 is a preparation process flow chart of array carbon nanotube with positive charge on the surface provided by the embodiment of the present application;

[0036] Figure 3 is a preparation process flow chart of a composite powder provided by the embodiment of the present application;

[0037] Figure 4 is a structural schematic diagram of a jet mill provided by the embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects of the present application more clearly understood, the following will further describe the present application with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0039] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein, A and B can be singular or plural. The character " / " generally represents that the associated objects before and after it are in an "or" relationship.

[0040] In this application, "at least one" means one or more, "multiple" means two or more. "At least one of the following" or the like means any combination of the items, including a single item or any combination of multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c or a-b-c, where a, b and c can be single or multiple.

[0041] It should be understood that in various embodiments of the present application, the size of the sequence number of each process does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0042] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0043] The weight of the related components mentioned in the specification of the embodiments of the present application can not only refer to the specific content of each component, but also represent the weight ratio relationship between each component, therefore, as long as the content of the related components in the specification of the embodiments of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass in the specification of the embodiments of the present application can be μg, mg, g, kg and other well-known mass units.

[0044] The terms "first", "second" and the like are only used for description purposes and are used to distinguish the objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX can also be called the second XX, and similarly, the second XX can also be called the first XX. Therefore, the features limited by "first", "second" and the like can explicitly or implicitly include one or more of the features.

[0045] In a first aspect, the embodiments of the present application provide a preparation method of a composite powder with high dispersity and high conductivity.

[0046] As shown in Figure 1 The embodiments of the present application provide a preparation method of modified carbon black, comprising the following steps:

[0047] S11. Selecting conductive carbon black.

[0048] In applications, the conductive carbon black can be N326, etc.

[0049] The resistivity of the conductive carbon black can range from 0.2 to 50 Ω·cm. For example, the resistivity of the conductive carbon black can be 0.2 Ω·cm, 1 Ω·cm, 10 Ω·cm, 20 Ω·cm, 30 Ω·cm, or 50 Ω·cm, etc.

[0050] The powder particle size of the conductive carbon black can range from 100 to 20,000 nm.

[0051] S12. The conductive carbon black is placed in an acid solution and treated at a pretreatment temperature for a period of time. After filtration and washing until the filtrate is neutral, the conductive carbon black is dried to obtain acid-purified carbon black.

[0052] In applications, the acid solution can include one or more combinations of hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (H3PO4), etc. Preferably, the acid solution is one or more combinations of concentrated HCl, concentrated H2SO4, and concentrated H3PO4, etc. The concentrated HCl refers to a hydrochloric acid solution with a mass fraction of HCl exceeding 20%, the concentrated H2SO4 refers to a sulfuric acid solution with a mass fraction of H2SO4 greater than or equal to 70%, and the concentrated H3PO4 generally refers to a nitric acid solution with a concentration of H3PO4 exceeding 8 mol / L.

[0053] The molar concentration of the acid solution can range from 0.7 to 1.2 mol / L. For example, the molar concentration of the acid solution can be 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, or 1.2 mol / L, etc.

[0054] The pretreatment temperature can range from 70 to 100°C, and the pretreatment time can range from 1 to 3 h. For example, the pretreatment temperature can be 70°C, 80°C, 85°C, 90°C, 95°C, or 100°C, etc., and the pretreatment time can be 1 h, 1.5 h, 2 h, 2.5 h, 2.8 h, or 3 h, etc.

[0055] The drying temperature can range from 110 to 130°C, and the drying time can range from 19 to 24 h. For example, the drying temperature can be 110°C, 115°C, 120°C, 123°C, 128°C, or 130°C, etc., and the drying time can be 19 h, 20 h, 21 h, 22 h, 23 h, or 24 h, etc.

[0056] Thus, the metal impurities, ash and the like in the conductive carbon black can be removed by the acid liquid treatment, and the surface functional groups and defects of the conductive carbon black are increased, so as to improve the dispersibility of the conductive carbon black. At the same time, the acid liquid treatment can increase the active sites on the surface of the conductive carbon black, so that the anionic surfactant in the subsequent step is more easily adsorbed on the surface of the conductive carbon black purified by the acid liquid treatment, and the conductive carbon black purified by the acid liquid treatment is more easily reacted with the anionic surfactant.

[0057] S13. The acid liquid purified carbon black is added into the anionic surfactant aqueous solution, and is ultrasonically treated and stirred at a certain speed for a period of time. Then, the solution is placed in a water bath at a certain temperature and is left for a period of time to obtain an anionic surfactant non-covalent bond modified carbon black aqueous solution. The anionic surfactant non-covalent bond modified carbon black aqueous solution is sequentially filtered, washed and dried to obtain an anionic surfactant non-covalent bond modified carbon black.

[0058] In applications, the above-mentioned anionic surfactant can include a combination of one or more of poly(sodium-p-styrenesulfonate) (PSS), sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and the like.

[0059] The concentration of the anionic surfactant can be in the range of 0.003-0.008 g / mL. For example, the concentration of the anionic surfactant can be 0.003 g / mL, 0.004 g / mL, 0.005 g / mL, 0.006 g / mL, 0.007 g / mL or 0.008 g / mL, etc.

[0060] The mass-to-volume ratio of the acid liquid purified carbon black to the anionic surfactant aqueous solution can be in the range of 1 g:8 mL-1 g:13 mL. For example, the mass-to-volume ratio of the acid liquid purified carbon black to the anionic surfactant aqueous solution can be 1 g:8 mL, 1 g:9 mL, 1 g:10 mL, 1 g:11 mL, 1 g:12 mL or 1 g:13 mL, etc. Preferably, the mass-to-volume ratio of the acid liquid purified carbon black to the anionic surfactant aqueous solution is 1:10. In this case, the surface treatment effect of the acid liquid purified carbon black is better.

[0061] The ultrasonic treatment can be performed by an ultrasonic device, wherein the ultrasonic frequency range can be 10-30 Hz, and the ultrasonic treatment time range can be 0.2-0.7 h, and exemplarily, the ultrasonic frequency can be 10 Hz, 15 Hz, 20 Hz, 25 Hz, 28 Hz or 30 Hz, and the ultrasonic treatment time can be 0.2 h, 0.3 h, 0.4 h, 0.5 h, 0.6 h or 0.7 h.

[0062] The solution can be stirred by magnetic stirring or electric stirring, wherein the stirring time range can be 1-4 h, and the stirring speed range can be 100-300 r / min, and exemplarily, the stirring time can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h or 4 h, and the stirring speed can be 100 r / min, 150 r / min, 200 r / min, 250 r / min, 280 r / min or 300 r / min.

[0063] The water bath can be performed by a water bath device, wherein the water bath temperature range can be 20-40℃, and the standing time range in the water bath can be 2-6 h, and exemplarily, the water bath temperature can be 20℃, 25℃, 30℃, 33℃, 38℃ or 40℃, and the standing time in the water bath can be 2 h, 3 h, 4 h, 4.5 h, 5 h or 6 h.

[0064] Thus, in the reaction of the anionic surfactant with the acid-purified carbon black, the anionic surfactant can be adsorbed on the surface of the acid-purified carbon black particles, so that the acid-purified carbon black has a negative charge on the surface, and the dispersibility of the carbon black is improved.

[0065] S14. The anionic surfactant non-covalently modified carbon black is dispersed in a salt solution, and ultrasonic treatment is performed for a period of time to obtain carbon black with a negative charge on the surface.

[0066] In applications, the salt in the above-mentioned salt solution can be sodium chloride (NaCl) or the like.

[0067] The molar mass of the salt solution can be in the range of 0.0005-0.003 M, and exemplarily, the molar mass of the salt solution can be 0.0005 M, 0.001 M, 0.0015 M, 0.002 M, 0.0025 M or 0.003 M.

[0068] The dispersing concentration of the anionic surfactant non-covalent modification carbon black in the salt solution can range from 0.001 mg / mL to 0.03 mg / mL. For example, the dispersing concentration of the anionic surfactant non-covalent modification carbon black in the salt solution can be 0.001 mg / mL, 0.01 mg / mL, 0.015 mg / mL, 0.02 mg / mL, 0.025 mg / mL, or 0.03 mg / mL, etc.

[0069] The ultrasonic frequency can range from 10 Hz to 30 Hz, and the ultrasonic treatment time can range from 0.1 h to 2 h. For example, the ultrasonic frequency can be 10 Hz, 15 Hz, 20 Hz, 25 Hz, 28 Hz, or 30 Hz, etc., and the ultrasonic treatment time can be 0.1 h, 0.5 h, 1 h, 1.3 h, 1.7 h, or 2 h, etc.

[0070] Thus, the salt solution can further improve the dispersing performance of the anionic surfactant non-covalent modification carbon black and form a stable dispersion system.

[0071] A specific preparation method of the carbon black with a negative surface charge (i.e., modified carbon black) is given below, which includes the following steps:

[0072] (1). Selection and pretreatment of carbon black:

[0073] Select conductive carbon black with a powder particle size of 100-20,000 nm, and pretreat it in an acid solution with a molar concentration of 0.7-1.2 mol / L at 70-100°C for 1-3 h, filter and wash until the filtrate is neutral, and then dry it at 110-130°C for 19-24 h to obtain acid-purified carbon black.

[0074] (2). Surface treatment of carbon black:

[0075] Add the acid-purified carbon black to an anionic surfactant aqueous solution with a concentration of 0.003-0.008 g / mL (the mass-to-volume ratio of the acid-purified carbon black to the anionic surfactant aqueous solution is 1:8-1:13), use an ultrasonic device to perform ultrasonic treatment at a frequency of 10-30 Hz for 0.2-0.7 h, use room-temperature magnetic stirring or electric stirring to stir the solution at a stirring speed of 100-300 r / min for 1-4 h, and then place the solution in a water bath at 20-40°C for 2-6 h of static standing to obtain an anionic surfactant non-covalent modification carbon black aqueous solution, filter and wash to obtain an anionic surfactant non-covalent modification carbon black.

[0076] (3). Preparation of modified carbon black:

[0077] The anionic surfactant non-covalently modified carbon black is dispersed in a 0.0005-0.003M salt solution (the dispersion concentration of the carbon black in the salt solution is 0.001-0.03mg / mL), and is subjected to ultrasonic treatment for 0.1-2h by using an ultrasonic device at 10-30Hz to obtain carbon black with negative charges on the surface.

[0078] Next, as shown in Figure 2 The application provides a preparation method of modified array carbon nanotubes, which comprises the following steps:

[0079] S21. Select array carbon nanotubes and perform acidification treatment on the array carbon nanotubes to obtain acid-purified array carbon nanotubes.

[0080] In applications, the aspect ratio of the array carbon nanotubes can range from 5000 to 15000. The array carbon nanotubes have a higher aspect ratio, which makes it easier to form a conductive path and thus improves the conductivity of the composite powder.

[0081] The Raman spectrum intensity ratio of the array carbon nanotubes can range from 0.8 to 1.3.

[0082] The acid solution can include one or more combinations of hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (H3PO4). Preferably, the acid solution is one or more combinations of concentrated HCl, concentrated H2SO4, and concentrated H3PO4.

[0083] Thus, the array carbon nanotubes can be modified by the acid solution treatment, and some specific functional groups can be introduced on the surface of the carbon nanotubes, which can chemically react with the amino-containing silane coupling agent in subsequent steps.

[0084] S22. The acid-purified array carbon nanotubes are added to an amino-containing coupling agent aqueous solution, ultrasonic treatment is performed, the solution is stirred at a certain speed for a period of time, the solution is placed in a water bath at a certain temperature for a period of time, a uniformly dispersed array carbon nanotube aqueous solution is obtained, and after multiple centrifugations, drying treatment is performed to obtain array carbon nanotubes modified by the amino-containing coupling agent.

[0085] In applications, the amino-containing coupling agent can include an amino-containing silane coupling agent, such as aminopropyltriethoxysilane (APTES) and γ-aminopropyltriethoxysilane (KH-550).

[0086] Thus, the array carbon nanotubes can be modified by the amino-containing coupling agent, which can improve the dispersion uniformity of the modified array carbon nanotubes.

[0087] The mass-volume ratio of the acid-purified array carbon nanotubes to the aqueous solution of the amino-containing coupling agent can range from 1 g:10 mL to 1 g:150 mL. For example, the mass-volume ratio of the acid-purified array carbon nanotubes to the aqueous solution of the amino-containing coupling agent can be 1 g:10 mL, 1 g:50 mL, 1 g:80 mL, 1 g:100 mL, 1 g:120 mL, or 1 g:150 mL, etc.

[0088] The concentration of the amino-containing coupling agent in the coupling agent solution can range from 0.01 wt% to 10 wt%. For example, the concentration of the amino-containing coupling agent in the coupling agent solution can be 0.01 wt%, 0.1 wt%, 1 wt%, 3 wt%, 6 wt%, or 10 wt%, etc.

[0089] The ultrasonic treatment can be performed using an ultrasonic device, wherein the ultrasonic frequency can range from 20 Hz to 100 Hz, and the ultrasonic treatment time can range from 0.5 h to 24 h. For example, the ultrasonic frequency can be 20 Hz, 40 Hz, 60 Hz, 70 Hz, 80 Hz, or 100 Hz, etc., and the ultrasonic treatment time can be 0.5 h, 1 h, 10 h, 15 h, 20 h, or 24 h, etc.

[0090] The solution can be stirred using magnetic stirring or electric stirring, etc., wherein the stirring speed can range from 200 r / min to 4000 r / min, and the stirring time can range from 2 h to 24 h. For example, the stirring speed can be 200 r / min, 700 r / min, 1000 r / min, 2000 r / min, 3000 r / min, or 4000 r / min, etc., and the stirring time can be 2 h, 7 h, 12 h, 18 h, 20 h, or 24 h, etc.

[0091] The water bath can be performed using a water bath instrument, wherein the water bath temperature can range from 35 °C to 70 °C, and the standing time in the water bath can range from 4 h to 24 h. For example, the water bath temperature can be 35 °C, 40 °C, 50 °C, 60 °C, 65 °C, or 70 °C, etc., and the standing time in the water bath can be 4 h, 7 h, 10 h, 15 h, 20 h, or 24 h, etc.

[0092] In the reaction of the amino-containing coupling agent with the acid-purified carbon nanotubes, the amino group in the coupling agent can react with the functional groups on the surface of the acid-purified carbon nanotubes to form a chemical bond, which can improve the dispersion performance of the carbon nanotubes, enhance the compatibility of the carbon nanotubes, and introduce hydrophilic groups on the surface of the carbon nanotubes, thereby improving the performance of the array carbon nanotubes modified by the amino-containing coupling agent.

[0093] S23. The amino-containing coupling agent modified arrayed carbon nanotubes are dispersed in a salt solution, and ultrasonic treatment is performed for a period of time to obtain arrayed carbon nanotubes with positive charges on the surface.

[0094] In the application, the salt in the salt solution can be one or a combination of NaCl, potassium chloride (KCl), calcium chloride (CaCl2), etc.

[0095] The molar mass of the salt solution can range from 0.001 to 2M. For example, the molar mass of the salt solution can be 0.001M, 0.01M, 0.1M, 1M, 1.5M, or 2M, etc.

[0096] The dispersion concentration of the amino-containing coupling agent modified arrayed carbon nanotubes in the salt solution can range from 0.01 to 10mg / mL. For example, the dispersion concentration of the amino-containing coupling agent modified arrayed carbon nanotubes in the salt solution can be 0.01mg / mL, 0.1mg / mL, 1mg / mL, 3mg / mL, 6mg / mL, or 10mg / mL, etc.

[0097] The ultrasonic treatment can be performed using an ultrasonic device, wherein the ultrasonic frequency can range from 20 to 100Hz, and the ultrasonic treatment time can range from 0.5 to 2h. For example, the ultrasonic frequency can be 20Hz, 30Hz, 50Hz, 70Hz, 80Hz, or 100Hz, etc., and the ultrasonic treatment time can be 0.5h, 0.7h, 0.8h, 1.0h, 1.5h, or 2h, etc.

[0098] Thus, the salt solution can further improve the dispersion performance of the amino-containing coupling agent modified arrayed carbon nanotubes and form a stable dispersion system.

[0099] A specific preparation method of arrayed carbon nanotubes with positive charges on the surface (i.e., modified arrayed carbon nanotubes) is given below, which comprises the following steps:

[0100] (1). Carbon nanotube surface treatment:

[0101] The acid-purified arrayed carbon nanotubes are added to an amino-containing coupling agent aqueous solution (the mass / volume ratio of the acid-purified arrayed carbon nanotubes to the amino-containing coupling agent aqueous solution is 1:10-1:150, and the concentration of the amino-containing coupling agent is 0.01-10wt%), and ultrasonic treatment is performed using an ultrasonic device at 20-100Hz for 0.5-24h. Subsequently, magnetic stirring or electric stirring is performed at a stirring speed of 200-4000r / min for 2-24h, and the solution is placed in a water bath at 35-70℃ for 4-24h of static standing. A uniformly dispersed arrayed carbon nanotube aqueous solution is obtained, which is dried after multiple centrifugations to obtain amino-containing coupling agent modified arrayed carbon nanotubes.

[0102] (2). Preparation of modified array carbon nanotubes:

[0103] The amino-containing coupling agent modified array carbon nanotubes are dispersed in a 0.001-2M salt solution (the dispersion concentration of the amino-containing coupling agent modified array carbon nanotubes in the salt solution is 0.01-10 mg / mL), and then ultrasonic treatment is performed on the dispersion by using an ultrasonic device at 20-100 Hz for 0.5-2 h to obtain array carbon nanotubes with positive charges on the surface.

[0104] It should be noted that the preparation sequence of the modified carbon black and the modified array carbon nanotubes is not specifically limited, and the modified carbon black can be prepared first, and then the modified array carbon nanotubes are prepared; or the modified array carbon nanotubes can be prepared first, and then the modified carbon black is prepared; or the modified carbon black and the modified array carbon nanotubes can be prepared at the same time.

[0105] Finally, as shown in Figure 3 , the embodiment of the present application provides a preparation method of a composite powder, which comprises the following steps:

[0106] S1. The carbon black with negative charges on the surface and the array carbon nanotubes with positive charges on the surface are mixed and subjected to a crushing treatment to obtain a composite powder.

[0107] Figure 4 A structural schematic diagram of an air flow crushing device is shown. As shown in Figure 4 , the air flow crushing device comprises a mixing mechanism 1, a gas crusher 2, a first cyclone separator 3 and a second cyclone separator 4 which are sequentially connected through pipelines, the mixing mechanism 1 comprises a frame body 5, a tank body 6 is rotatably arranged on the frame body 5, an inlet is arranged at the upper end of the tank body 6 for inputting a mixture of the carbon black with negative charges on the surface and the array carbon nanotubes with positive charges on the surface and a medium, a plurality of stirring mechanisms are arranged in the tank body 6, a first collection tank 7 for collecting the medium is arranged at the outlet of the first cyclone separator 3, and a second collection tank 8 for collecting the mixture of the carbon black with negative charges on the surface and the array carbon nanotubes with positive charges on the surface after crushing is arranged at the outlet of the second cyclone separator 4.

[0108] In operation, the carbon black with negative charges on the surface and the array carbon nanotubes with positive charges on the surface and the medium are sent into the tank body 6 of the mixing mechanism 1 through the inlet, the raw materials after being fully mixed under the action of the mixing mechanism 1 enter the gas crusher 2 to be crushed, the medium is collected by the first cyclone separator 3 after crushing, and the carbon nanotubes after crushing are collected by the second cyclone separator 4.

[0109] The medium can be chromium oxide (Cr2O3), and the gas crusher 2 can be crushed by 2-6 times supersonic gas flow.

[0110] ​In applications, the prepared composite powder has a maximum particle size Dmax less than or equal to 50 nm. Exemplarily, the maximum particle size of the composite powder can be 20 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm, etc.

[0111] The preparation method of the composite powder provided in the embodiments of the present application has the following advantages. On the one hand, the array carbon nanotubes with high aspect ratio are selected and used to modify the carbon black, so that the conductive path is more easily formed, the conductive performance of the composite powder is effectively improved, the amount of carbon black is reduced, and the dispersibility of the array carbon nanotubes is good. On the other hand, the surface of the carbon black is negatively charged, and the surface of the carbon nanotubes is positively charged, so that the positive and negative charges attract each other, thereby improving the dispersibility of the carbon nanotubes and the carbon black in the composite powder and the conductive performance of the composite powder. When the composite powder is used as a conductive agent, it can be directly added to the system in the form of powder and is very easy to disperse in various systems, that is, the mixed powder of the carbon black and the carbon nanotubes is directly obtained. The process is simple and easy to operate, and is conducive to industrial production.

[0112] In the second aspect, based on the preparation process of the composite powder, the embodiments of the present application provide a composite powder, which comprises modified carbon black and modified array carbon nanotubes. The surface of the modified carbon black is negatively charged, the surface of the modified array carbon nanotubes is positively charged, and the negative charge and the positive charge are bonded.

[0113] In applications, the mass ratio of the modified carbon black to the modified array carbon nanotubes can be 90-98:2-10. Preferably, the mass ratio of the modified carbon black to the modified array carbon nanotubes is 95:5. In this way, a small amount of array carbon nanotubes can significantly improve the conductive performance of the carbon black and significantly reduce the amount of carbon black.

[0114] The oil absorption of the composite powder can be 120-220 mg / 100 g. Exemplarily, the oil absorption of the composite powder can be 120 mg / 100 g, 140 mg / 100 g, 160 mg / 100 g, 180 mg / 100 g, 200 mg / 100 g or 220 mg / 100 g, etc. In this way, the wettability is good, so that the composite powder can be better dispersed in other systems and the dispersibility of the composite powder is improved.

[0115] The resistivity of the composite powder can be 80-140 mΩ·cm. Exemplarily, the resistivity of the composite powder can be 80 mΩ·cm, 90 mΩ·cm, 100 mΩ·cm, 110 mΩ·cm, 120 mΩ·cm or 140 mΩ·cm, etc. In this way, the conductive performance of the composite powder is good.

[0116] The specific surface area of the composite powder can be 50-150 m 2 / g, for example, the resistivity of the composite powder can be 50 m 2 / g, 70 m 2 / g, 90 m 2 / g, 120 m 2 / g, 140 m 2 / g, or 150 m 2 / g, etc. Thus, the specific surface area of the composite powder is small, and the dispersion performance is better.

[0117] It should be noted that the modified carbon black, modified array carbon nanotubes, etc. in the embodiments of the present application can refer to the above embodiments, which will not be repeated here.

[0118] The embodiments of the present application provide a composite powder, which is composed of modified carbon black with negative charge and modified array carbon nanotubes with positive charge. The positive and negative charges attract each other, which can improve the dispersion performance of the array carbon nanotubes and carbon black in the composite powder, and improve the conductive performance of the composite powder. At the same time, the modified array carbon nanotubes can reduce the amount of modified carbon black while improving the conductive performance of the composite powder. In addition, when the composite powder is used as a conductive agent, it can be directly added to the system in the form of powder, which is very easy to disperse in various systems and simple to implement.

[0119] The preparation method and application of the composite powder provided by the embodiments of the present application and the comparative examples are illustrated by a plurality of specific embodiments.

[0120] First, the composite powder and the preparation method thereof according to the present application are described.

[0121] Embodiment 1

[0122] 1. Preparation of carbon black with negative charge on the surface:

[0123] (1). Selection and pretreatment of carbon black:

[0124] N326 with a powder particle size of 100-20000 nm and a resistivity of 0.2 Ω·cm is selected. The N326 is placed in HCl with a molar concentration of 0.7 mol / L, and is pretreated at 70℃ for 1 h. After filtration and washing until the filtrate is neutral, the N326 is dried at 110℃ for 19 h to obtain N326 purified by concentrated HCl.

[0125] (2). Surface treatment of carbon black:

[0126] The concentrated HCl purified N326 was added to the PSS aqueous solution with a concentration of 0.003 g / mL (the mass-volume ratio of the concentrated HCl purified N326 to the PSS aqueous solution was 1 g:8 mL), ultrasonic treatment was performed for 0.2 h at a frequency of 10 Hz using an ultrasonic device, the solution was stirred at a stirring speed of 100 r / min using room temperature magnetic stirring, and the solution was left to stand in a water bath at 20°C for 2 h, to obtain a PSS non-covalently modified N326 aqueous solution, which was filtered and washed to obtain the PSS non-covalently modified N326.

[0127] (3) Preparation of modified carbon black:

[0128] The PSS non-covalently modified N326 was dispersed in a 0.0005 M NaCl solution (the dispersion concentration of the N326 in the NaCl solution was 0.001 mg / mL), ultrasonic treatment was performed for 0.1 h at a frequency of 10 Hz using an ultrasonic device, to obtain N326 with a negative charge on the surface.

[0129] 2. Preparation of carbon nanotubes with a positive charge on the surface:

[0130] (1) Array carbon nanotubes with a length-diameter ratio of 5000-15000 and a Raman ID / IG of 0.8-1.3 were selected, and the array carbon nanotubes were subjected to acidification treatment using HCl, to obtain concentrated HCl purified array carbon nanotubes.

[0131] (2) Carbon nanotube surface treatment:

[0132] The concentrated HCl purified array carbon nanotubes were added to an APTES aqueous solution (the mass-volume ratio of the concentrated HCl purified array carbon nanotubes to the APTES aqueous solution was 1 g:10 mL, and the concentration of the APTES aqueous solution was 0.01 wt%), ultrasonic treatment was performed for 0.5 h at a frequency of 20 Hz using an ultrasonic device, followed by magnetic stirring at a stirring speed of 200 r / min for 2 h, and the solution was left to stand in a water bath at 35°C for 4 h, to obtain a uniformly dispersed array carbon nanotube aqueous solution, which was then dried after multiple centrifugations, to obtain APTES modified array carbon nanotubes.

[0133] (3) Preparation of modified array carbon nanotubes:

[0134] The APTES modified array carbon nanotubes were dispersed in a 0.001 M NaCl solution (the dispersion concentration of the APTES modified array carbon nanotubes in the NaCl solution was 0.01 mg / mL), and ultrasonic treatment was performed for 0.5 h at a frequency of 20 Hz using an ultrasonic device, to obtain array carbon nanotubes with a positive charge on the surface.

[0135] 3. Preparation of composite powder:

[0136] The above treated surface with negative charge carbon black and surface with positive charge carbon nanotube array are mixed, together with Cr2O3, sent into the tank of the mixing mechanism through the feeding port of the gas flow pulverizing equipment, the raw materials mixed by the mixing mechanism enter the gas pulverizer, the gas pulverizer uses 2 times supersonic speed airflow for pulverizing, the first cyclone separator collects the Cr2O3 after pulverizing, and the second cyclone separator collects the composite powder after pulverizing.

[0137] Example 2

[0138] 1. Preparation of surface with negative charge carbon black:

[0139] (1). Selection and pretreatment of carbon black:

[0140] Select N326 with powder particle size of 100-20000 nm and resistivity of 1 Ω·cm, put the N326 into H2SO4 with concentration of 0.8 mol / L, pretreat at 80℃ for 1.5 h, filter and wash until the filtrate is neutral, then dry at 115℃ for 20 h, to obtain N326 treated by concentrated H2SO4.

[0141] (2). Surface treatment of carbon black:

[0142] Add N326 treated by concentrated H2SO4 into PSS aqueous solution with concentration of 0.004 g / mL (mass-volume ratio of N326 treated by concentrated H2SO4 and PSS aqueous solution is 1 g:9 mL), use the ultrasonic device to treat at 15 Hz for 0.3 h, use the electric mixer to stir the solution at 150 r / min for 1.5 h, then place the solution in a water bath at 25℃ for 3 h, to obtain PSS non-covalent modified N326 aqueous solution, filter and wash to obtain PSS non-covalent modified N326.

[0143] (3). Preparation of modified carbon black:

[0144] Disperse PSS non-covalent modified N326 in 0.001 M NaCl solution (dispersion concentration of N326 in NaCl solution is 0.01 mg / mL), use the ultrasonic device to treat at 15 Hz for 0.5 h, to obtain N326 with negative charge on the surface.

[0145] 2. Preparation of surface with positive charge carbon nanotube:

[0146] (1). Select array carbon nanotube with aspect ratio of 5000-15000 and Raman ID / IG of 0.8-1.3, and use concentrated H2SO4 to acidize the array carbon nanotube, to obtain array carbon nanotube treated by concentrated H2SO4.

[0147] (2). Carbon nanotube surface treatment:

[0148] The array carbon nanotubes treated by concentrated H2SO4 were added into the APTES aqueous solution (the mass-volume ratio of the array carbon nanotubes treated by concentrated H2SO4 to the APTES aqueous solution was 1 g:50 mL, and the concentration of the APTES aqueous solution was 0.1 wt%), and were treated by an ultrasonic device at a frequency of 40 Hz for 1 h, followed by electric stirring at a stirring speed of 700 r / min for 7 h, and the solution was placed in a water bath at 40℃ for 7 h. Then, the array carbon nanotubes were uniformly dispersed in the solution, and were dried after multiple centrifugations to obtain the APTES-modified array carbon nanotubes.

[0149] (3). Preparation of modified array carbon nanotubes:

[0150] The APTES-modified array carbon nanotubes were dispersed in a KCl solution with a molar mass of 0.01 M (the dispersion concentration of the APTES-modified array carbon nanotubes in the KCl solution was 0.1 mg / mL), and were treated by an ultrasonic device at a frequency of 30 Hz for 0.7 h to obtain the array carbon nanotubes with positive charges on the surface.

[0151] 3. Preparation of composite powder:

[0152] The above-mentioned carbon black with negative charges on the surface and the array carbon nanotubes with positive charges on the surface were mixed, and were sent into the tank of the mixing mechanism through the feeding port of the airflow crushing equipment together with Cr2O3. The raw materials were fully mixed under the action of the mixing mechanism, and were sent into the gas crusher. The gas crusher was used to crush the raw materials by using 3 times supersonic airflow. The first cyclone separator was used to collect the Cr2O3, and the second cyclone separator was used to collect the composite powder after crushing.

[0153] Example 3

[0154] 1. Preparation of carbon black with negative charges on the surface:

[0155] (1). Selection and pretreatment of carbon black:

[0156] N326 with a powder particle size of 100-20,000 nm and a resistivity of 10 Ω·cm was selected, and was pretreated in H3PO4 with a molar concentration of 0.9 mol / L at 85℃ for 2 h. After filtration and washing until the filtrate was neutral, the N326 was dried at 120℃ for 21 h to obtain N326 treated by concentrated H3PO4.

[0157] (2). Carbon black surface treatment:

[0158] The N326 purified by concentrated H3PO4 was added into the SDS aqueous solution with a concentration of 0.005 g / mL (the mass-volume ratio of the N326 purified by concentrated H3PO4 to the SDS aqueous solution was 1 g:10 mL), and was treated by an ultrasonic device at a frequency of 20 Hz for 0.4 h. The solution was stirred at a stirring speed of 200 r / min for 2 h by a magnetic stirrer at room temperature, and was then placed in a water bath at 30 °C for 4 h. An N326 aqueous solution non-covalently modified by SDS was obtained, and was filtered and washed to obtain the N326 non-covalently modified by SDS.

[0159] (3) Preparation of modified carbon black:

[0160] The N326 non-covalently modified by SDS was dispersed in a NaCl solution with a concentration of 0.0015 M (the dispersion concentration of the N326 in the NaCl solution was 0.015 mg / mL), and was treated by an ultrasonic device at a frequency of 20 Hz for 1 h to obtain the N326 with a negative charge on the surface.

[0161] 2. Preparation of carbon nanotubes with a positive charge on the surface:

[0162] (1) Array carbon nanotubes with a length-diameter ratio of 5000-15000 and a Raman ID / IG of 0.8-1.3 were selected, and were acidized by concentrated H3PO4 to obtain array carbon nanotubes purified by concentrated H3PO4.

[0163] (2) Surface treatment of carbon nanotubes:

[0164] The array carbon nanotubes purified by concentrated H3PO4 were added into an APTES aqueous solution (the mass-volume ratio of the array carbon nanotubes purified by concentrated H3PO4 to the APTES aqueous solution was 1 g:80 mL, and the concentration of the APTES aqueous solution was 1 wt.%), and were treated by an ultrasonic device at a frequency of 60 Hz for 10 h, followed by magnetic stirring at a stirring speed of 1000 r / min for 12 h. The solution was placed in a water bath at 50 °C for 10 h to obtain an array carbon nanotube aqueous solution uniformly dispersed, which was then dried after multiple centrifugations to obtain array carbon nanotubes modified by APTES.

[0165] (3) Preparation of modified array carbon nanotubes:

[0166] The array carbon nanotubes modified by APTES were dispersed in a CaCl2 solution with a molar mass of 0.1 M (the dispersion concentration of the array carbon nanotubes modified by APTES in the CaCl2 solution was 1 mg / mL), and were treated by an ultrasonic device at a frequency of 50 Hz for 0.8 h to obtain array carbon nanotubes with a positive charge on the surface.

[0167] 3. Preparation of composite powder:

[0168] The above treated surface with negative charge carbon black and surface with positive charge carbon nanotube array mixed, together with Cr2O3 through the feeding port of gas flow pulverizing equipment into the tank of mixing mechanism, under the action of mixing mechanism, the raw materials fully mixed into the gas pulverizer, the gas pulverizer uses 4 times supersonic speed airflow for pulverizing, after pulverizing, the first cyclone separator collects Cr2O3, the second cyclone separator collects the composite powder after pulverizing.

[0169] Example 4

[0170] 1. Preparation of surface with negative charge carbon black:

[0171] (1). Selection and pretreatment of carbon black:

[0172] Select N326 with powder particle size of 100-20000nm and resistivity of 20Ω·cm, put N326 in HCl with concentration of 1.0mol / L, pretreat at 90℃ for 2.5h, filter and wash until the filtrate is neutral, then dry at 123℃ for 22h, to obtain N326 treated by concentrated HCl purification.

[0173] (2). Surface treatment of carbon black:

[0174] Add N326 treated by concentrated HCl purification into SDBS aqueous solution with concentration of 0.006g / mL (mass volume ratio of N326 treated by concentrated HCl purification and SDBS aqueous solution is 1g:11mL), use ultrasonic device to treat at frequency of 25Hz for 0.5h, use room temperature electric stirring to stir the solution at stirring speed of 250r / min for 2.5h, then place the solution in water bath at 33℃ for 4.5h, to obtain SDBS non-covalent modified N326 aqueous solution, filter and wash to obtain SDBS non-covalent modified N326.

[0175] (3). Preparation of modified carbon black:

[0176] Disperse SDBS non-covalent modified N326 in NaCl solution with concentration of 0.002M (dispersion concentration of N326 in NaCl solution is 0.02mg / mL), use ultrasonic device to treat at frequency of 25Hz for 1.3h, to obtain N326 with negative charge on the surface.

[0177] 2. Preparation of surface with positive charge carbon nanotube:

[0178] (1). Selecting array carbon nanotubes with aspect ratio of 5000-15000 and Raman ID / IG of 0.8-1.3, and acidizing the array carbon nanotubes with concentrated HCl to obtain array carbon nanotubes purified by concentrated HCl.

[0179] (2). Carbon nanotube surface treatment:

[0180] The array carbon nanotubes purified by concentrated HCl are added into a KH-550 aqueous solution (the mass-volume ratio of the array carbon nanotubes purified by concentrated HCl to the KH-550 aqueous solution is 1 g:100 mL, and the concentration of the KH-550 aqueous solution is 3 wt%), and ultrasonic treatment is performed for 15 h at a frequency of 70 Hz using an ultrasonic device, followed by electric stirring at a stirring speed of 2000 r / min at room temperature for 18 h, and the solution is placed in a water bath at 60°C for 15 h to obtain a uniformly dispersed array carbon nanotube aqueous solution, which is then dried after multiple centrifugations to obtain array carbon nanotubes modified by KH-550.

[0181] (3). Preparation of modified array carbon nanotubes:

[0182] The array carbon nanotubes modified by KH-550 are dispersed in a NaCl solution with a molar mass of 1M (the dispersion concentration of the array carbon nanotubes modified by KH-550 in the NaCl solution is 3 mg / mL), and ultrasonic treatment is then performed for 1.0 h at a frequency of 70 Hz using an ultrasonic device to obtain array carbon nanotubes with positive charges on the surface.

[0183] 3. Preparation of composite powder:

[0184] The above carbon black with negative charges on the surface and array carbon nanotubes with positive charges on the surface that have been treated are mixed, and together with Cr2O3, are fed into the tank body of a mixing mechanism through the feeding port of an airflow crushing device, and the raw materials that are fully mixed under the action of the mixing mechanism enter a gas crusher, which uses 5 times supersonic airflow for crushing. After crushing, the first cyclone separator collects Cr2O3, and the second cyclone separator collects the composite powder after crushing.

[0185] Example 5

[0186] 1. Preparation of carbon black with negative charges on the surface:

[0187] (1). Selection and pretreatment of carbon black:

[0188] N326 with particle size of 100-20000 nm and resistivity of 30 Ω·cm was pretreated in 1.1 mol / L H2SO4 at 95℃ for 2.8 h, filtered, washed until the filtrate was neutral, and then dried at 128℃ for 23 h to obtain N326 treated by concentrated H2SO4.

[0189] (2). Carbon black surface treatment:

[0190] N326 treated by concentrated H2SO4 was added into PSS aqueous solution with a concentration of 0.007 g / mL (the mass-volume ratio of N326 treated by concentrated H2SO4 to PSS aqueous solution was 1 g:12 mL), and was treated by an ultrasonic device at a frequency of 28 Hz for 0.6 h. The solution was stirred at a stirring speed of 280 r / min for 3 h, and then was placed in a water bath at 38℃ for 5 h to obtain PSS non-covalently modified N326 aqueous solution. After filtration and washing, PSS non-covalently modified N326 was obtained.

[0191] (3). Preparation of modified carbon black:

[0192] N326 with PSS non-covalently modified was dispersed in 0.0025 M NaCl solution (the dispersion concentration of N326 in NaCl solution was 0.025 mg / mL), and was treated by an ultrasonic device at a frequency of 28 Hz for 1.7 h to obtain N326 with negative charges on the surface.

[0193] 2. Preparation of carbon nanotubes with positive charges on the surface:

[0194] (1). Array carbon nanotubes with an aspect ratio of 5000-15000 and a Raman ID / IG of 0.8-1.3 were selected, and were acidized by H2SO4 to obtain H2SO4 treated array carbon nanotubes.

[0195] (2). Carbon nanotube surface treatment:

[0196] H2SO4 treated array carbon nanotubes were added into APTES aqueous solution (the mass-volume ratio of H2SO4 treated array carbon nanotubes to APTES aqueous solution was 1 g:120 mL, and the concentration of APTES aqueous solution was 6 wt%), and were treated by an ultrasonic device at a frequency of 80 Hz for 20 h. Subsequently, the solution was magnetically stirred at a stirring speed of 3000 r / min for 20 h, and was placed in a water bath at 65℃ for 20 h to obtain uniformly dispersed array carbon nanotube aqueous solution. After multiple centrifugations, APTES modified array carbon nanotubes were obtained after drying.

[0197] (3). Preparation of modified array carbon nanotubes:

[0198] The APTES modified array carbon nanotubes were dispersed in a KCl solution with a molar mass of 1.5 M (the dispersion concentration of the APTES modified array carbon nanotubes in the KCl solution was 6 mg / mL), and then were treated by an ultrasonic device at a frequency of 80 Hz for 1.5 h to obtain array carbon nanotubes with positive charges on the surface.

[0199] 3. Preparation of composite powder:

[0200] The above treated carbon black with negative charges on the surface and array carbon nanotubes with positive charges on the surface were mixed, and were sent into the tank of the mixing mechanism through the feeding port of the airflow crushing device together with Cr2O3. The raw materials mixed by the mixing mechanism were sent into the gas crusher, and were crushed by the airflow with a speed of 6 times the speed of sound. The first cyclone separator collected the Cr2O3, and the second cyclone separator collected the composite powder after crushing.

[0201] Example 6

[0202] 1. Preparation of carbon black with negative charges on the surface:

[0203] (1). Selection and pretreatment of carbon black:

[0204] N326 with a powder particle size of 100-20,000 nm and a resistivity of 50 Ω·cm was selected, and was pretreated in H3PO4 with a molar concentration of 1.2 mol / L at 100°C for 3 h. After filtration and washing until the filtrate was neutral, the N326 was dried at 130°C for 24 h to obtain N326 purified by concentrated H3PO4.

[0205] (2). Surface treatment of carbon black:

[0206] The N326 purified by concentrated H3PO4 was added into PSS aqueous solution with a concentration of 0.008 g / mL (the mass-volume ratio of the N326 purified by concentrated H3PO4 to the PSS aqueous solution was 1 g:13 mL). The solution was treated by an ultrasonic device at a frequency of 30 Hz for 0.7 h, and was stirred at a stirring speed of 300 r / min for 4 h. Then, the solution was placed in a water bath at 40°C for 6 h to obtain N326 modified by non-covalent bonds of PSS. After filtration and washing, the N326 modified by non-covalent bonds of PSS was obtained.

[0207] (3). Preparation of modified array carbon nanotubes:

[0208] The PSS non-covalently modified N326 is dispersed in 0.003M NaCl solution (the dispersion concentration of N326 in the NaCl solution is 0.03mg / mL), and is treated by an ultrasonic device at a frequency of 30Hz for 2h to obtain N326 with negative charges on the surface.

[0209] 2. Preparation of carbon nanotubes with positive charges on the surface:

[0210] (1). Array carbon nanotubes with a length-diameter ratio of 5000-15000 and a Raman ID / IG of 0.8-1.3 are selected, and the array carbon nanotubes are subjected to acidification treatment by concentrated H3PO4 to obtain array carbon nanotubes subjected to purification treatment by concentrated H3PO4.

[0211] (2). Carbon nanotube surface treatment:

[0212] The array carbon nanotubes subjected to purification treatment by concentrated H3PO4 are added into an APTES aqueous solution (the mass-volume ratio of the array carbon nanotubes subjected to purification treatment by concentrated H3PO4 to the APTES aqueous solution is 1g:150mL, and the concentration of the APTES aqueous solution is 10wt%), and are treated by an ultrasonic device at a frequency of 100Hz for 24h, followed by magnetic stirring or electric stirring at a stirring speed of 4000r / min for 24h, and the solution is placed in a water bath at 70°C for 24h to obtain an array carbon nanotube aqueous solution uniformly dispersed, which is then dried after multiple centrifugations to obtain APTES-modified array carbon nanotubes.

[0213] (3). Preparation of modified array carbon nanotubes:

[0214] The APTES-modified array carbon nanotubes are dispersed in a CaCl2 solution with a molar mass of 2M (the dispersion concentration of the APTES-modified array carbon nanotubes in the CaCl2 solution is 10mg / mL), and are treated by an ultrasonic device at a frequency of 100Hz for 2h to obtain array carbon nanotubes with positive charges on the surface.

[0215] 3. Preparation of composite powder:

[0216] The above treated carbon black with negative charges on the surface and array carbon nanotubes with positive charges on the surface are mixed, and are sent into a tank of a mixing mechanism through a feeding port of an airflow crushing device together with Cr2O3, and the raw materials mixed sufficiently by the mixing mechanism enter a gas crusher, the gas crusher is crushed by 2 times supersonic airflow, and the Cr2O3 is collected by a first cyclone separator after crushing, and the composite powder after crushing is collected by a second cyclone separator.

[0217] II. Comparative Example Single-walled carbon nanotube conductive slurry and preparation method thereof

[0218] Comparative Example 1

[0219] Compared with Example 1, unmodified carbon black is used, and the surface of the unmodified carbon black is not negatively charged.

[0220] Comparative Example 2

[0221] Compared with Example 1, unmodified carbon nanotubes are used, and the surface of the unmodified carbon nanotubes is not positively charged.

[0222] Comparative Example 3

[0223] Compared with Example 1, the preparation process of the composite powder does not use a jet milling process.

[0224] A lithium ion battery using the composite powder of the present application is provided as follows:

[0225] 1. Preparation of the positive electrode sheet:

[0226] The positive electrode slurry was prepared according to the mass ratio of lithium iron phosphate (LFP), polyvinylidene fluoride (PVDF), and composite powder of 94:2:0.6, and then N-methyl pyrrolidone was added to adjust the solid content to 55wt%. After that, the mixture was put into a double-planetary mixer for vacuum high-speed homogenization, with the revolution speed adjusted to 2000RPM and the rotation speed adjusted to 800RPM. After homogenization for 20min, the mixture was coated on the positive current collector and dried at 80℃ to obtain the positive electrode sheet. The sheet resistance of the positive electrode sheet was tested under a pressure of 40KG, and the test results are shown in Table 1.

[0227] 2. Assembly and testing of the lithium ion battery

[0228] The above positive electrode sheet was cut into a positive electrode, and a lithium sheet was used as a negative electrode to prepare a CR2032 button cell, which was tested on a blue light test system.

[0229] The charge and discharge conditions were set as follows: charging to a cutoff voltage of 4.2V, discharging to a cutoff voltage of 2.5V, and then cycling at 0.1C, 0.5C, 1C, 3C, and 5C for 5 weeks each, to obtain the 0.1C discharge capacity and the 5C discharge capacity of the CR2032 button cell. The test results are shown in Table 1.

[0230] Table 1

[0231]

[0232] As can be seen from Table 1, compared with Comparative Example 1, the carbon black added in Comparative Example 1 is not modified, resulting in no negative charge on the surface, unable to attract the array carbon nanotubes with positive charge on the surface, difficult to form a conductive path, unable to reduce the amount of carbon black, poor dispersibility of the array carbon nanotubes, and decreased overall conductive performance of the composite powder. Thus, the tabletting resistance of the positive electrode sheet is high, the 0.1C and 5C discharge capacities of the battery are low, the service life of the lithium ion battery is short, and the effect is poor.

[0233] Compared with Comparative Example 2, the carbon nanotubes added in Comparative Example 2 are not modified, neither are array carbon nanotubes, and no positive charge on the surface, unable to attract the carbon black with negative charge on the surface, difficult to form a conductive path, unable to reduce the amount of carbon black, poor dispersibility of the array carbon nanotubes, and decreased overall conductive performance of the composite powder. Thus, the tabletting resistance of the positive electrode sheet is high, the 0.1C and 5C discharge capacities of the battery are low, the service life of the lithium ion battery is short, and the effect is poor.

[0234] Compared with Comparative Example 3, the composite powder in Comparative Example 3 is not subjected to the airflow crushing process, so that the amount of carbon black cannot be significantly reduced, the dispersibility of the array carbon nanotubes is not so good, and the overall conductive performance of the composite powder is slightly decreased. Thus, the tabletting resistance of the positive electrode sheet is high, the 0.1C and 5C discharge capacities of the lithium ion battery are low, the service life of the lithium ion battery is short, and the effect is poor.

[0235] Compared with Example 1, only the formula and part of the parameters in the process of the composite powder are slightly different in Examples 2-6, so that the amount of carbon black can be reduced as much as possible, the dispersibility of the array carbon nanotubes is good, and the overall conductive performance of the composite powder is significantly improved. Thus, the tabletting resistance of the positive electrode sheet is low, the 0.1C and 5C discharge capacities of the lithium ion battery are high, the service life of the lithium ion battery is long, and the effect is good.

[0236] Only the content related to the invention point is introduced here, and the rest can be obtained by referring to the related art, which will not be described in detail here.

[0237] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent of the present application. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for producing a composite powder, characterized by comprising the steps of: 2 ​ The modified carbon black is mixed with modified array carbon nanotubes and subjected to airflow crushing treatment to obtain the composite powder, the oil absorption of the composite powder ranges from 120 to 220 mg / 100 g; the resistivity of the composite powder ranges from 80 to 140 mΩ·cm; the specific surface area of the composite powder ranges from 50 to 150 m 2 / g. The modified carbon black is obtained by mixing and treating carbon black with acid solution to obtain acidified carbon black, adding the acidified carbon black into an aqueous solution of anionic surfactant and treating to obtain anionic surfactant modified carbon black, dispersing the anionic surfactant modified carbon black in a first salt solution and treating to obtain modified carbon black with negative surface charge; The modified array carbon nanotube is obtained by mixing and treating array carbon nanotube with acid solution to obtain acidified array carbon nanotube, adding the acidified array carbon nanotube into an aqueous solution of amino-containing coupling agent and treating to obtain array carbon nanotube modified by amino-containing coupling agent, dispersing the array carbon nanotube modified by amino-containing coupling agent in a second salt solution and treating to obtain modified array carbon nanotube with positive surface charge; Wherein, the negative charge in the modified carbon black is used to attract the positive charge in the modified array carbon nanotube.

2. The method for producing a composite powder according to claim 1, wherein The mixing and treating of carbon black with acid solution to obtain acidified carbon black comprises: Selecting conductive carbon black with particle size range of 100-20000 nm; Placing the conductive carbon black in acid solution with molar concentration range of 0.7-1.2 mol / L, pretreating at 70-100℃ for 1-3 h, filtering and washing until the filtrate is neutral, and then drying at 110-130℃ for 19-24 h to obtain the acidified carbon black.

3. The method for producing a composite powder according to claim 2, wherein The mixing and treating of carbon black with acid solution to obtain acidified carbon black comprises: Placing the acidified carbon black in an aqueous solution of anionic surfactant with concentration range of 0.003-0.008 g / mL, ultrasonic treating at 10-30 Hz for 0.2-0.7 h, and stirring the solution at stirring speed range of 100-300 r / min for 1-4 h, then placing the solution in a water bath at 20-40℃ and standing for 2-6 h, filtering and washing, and then dispersing in a salt solution with concentration of 0.0005-0.003 M, ultrasonic treating at 10-30 Hz for 0.1-2 h to obtain the modified carbon black with negative surface charge.

4. The method for preparing the composite powder according to claim 1, characterized in that, The mixing and treating of carbon black with acid solution to obtain acidified carbon black comprises: Selecting array carbon nanotube with aspect ratio range of 5000-15000 and Raman spectrum intensity ratio range of 0.8-1.3; Placing the array carbon nanotube in acid solution for treatment, and then filtering, washing and drying to obtain the acidified array carbon nanotube.

5. The method for producing a composite powder according to claim 4, wherein The mixing and treating of carbon black with acid solution to obtain acidified carbon black comprises: Placing the acidified array carbon nanotube in an aqueous solution of amino-containing coupling agent for treatment, and then dispersing the array carbon nanotube modified by amino-containing coupling agent in a second salt solution and treating to obtain modified array carbon nanotube with positive surface charge. The acidized array carbon nanotubes are added into an aqueous solution of amino-containing coupling agent, ultrasonic treatment is performed at a frequency of 20-100 Hz for 0.5-24 h, and stirring is performed at a stirring speed of 200-4000 r / min for 2-24 h, the solution of acidized array carbon nanotubes and amino-containing coupling agent is placed in a water bath at 35-70 ℃ and left to stand for 4-24 h, and then dried after multiple centrifugations in sequence, to obtain array carbon nanotubes modified by amino-containing coupling agent; The array carbon nanotubes modified by amino-containing coupling agent are dispersed in a salt solution with a molar mass in the range of 0.001-2 M, ultrasonic treatment is performed at a frequency of 20-100 Hz for 0.5-2 h, to obtain the modified array carbon nanotubes with positive charges on the surface.

6. The method of producing a composite powder according to any one of claims 1 to 5, characterized in that, The mass ratio of the modified carbon black to the modified array carbon nanotubes is in the range of 90-98 : 2-10.

7. A lithium-ion battery, characterized by The composite powder prepared by the preparation method of the composite powder according to any one of claims 1-6.

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