Preparation method of lithium ion battery conductive agent multi-walled carbon nanotube

Abstract

The invention relates to the technical field of preparation of multi-walled carbon nanotubes, in particular to a preparation method of a lithium ion battery conductive agent multi-walled carbon nanotube. The method specifically comprises the following steps: adding a catalyst and an organic carbon source into an organic acid solution, reacting for a period of time under a certain condition, supplementing an inorganic acid solution, continuously stirring and reacting, standing until a mixed solution is layered, filtering an upper-layer suspension to obtain a solid, repeatedly washing the solid with water until no acid radical ions are detected, and drying to obtain the multi-walled carbon nanotube. The preparation process of the method can be carried out at a lower temperature, so that energy is saved and cost is reduced; the structure of the carbon nanotube can be regulated and controlled by adjusting the composition of the catalyst and reaction conditions; the catalyst prepared by the method can effectively improve the yield of the multi-walled carbon nanotubes and the purity of the multi-walled carbon nanotubes.

Description

Technical Field

[0001] The invention relates to the technical field of multi-walled carbon nanotube preparation, in particular to a method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries. Background Art

[0002] Carbon nanotubes are another allotrope of carbon discovered after C60. They have a small radial size. The outer diameter of the tube is generally a few nanometers to tens of nanometers, and the inner diameter of the tube is even smaller, some are only about 1nm; and their length is generally in the micron level. The length-to-diameter ratio is very large, up to 103-106. Therefore, carbon nanotubes are considered to be a typical one-dimensional nanomaterial. Since they were discovered by humans, carbon nanotubes have been hailed as the material of the future and are one of the frontiers of international science in recent years.

[0003] A high-performance multi-walled carbon nanotube and a preparation method thereof (patent application number: CN202310336226.8) prepares a carbon source material, mixes graphene and silicon carbide particles, puts them into a furnace tube, and performs a carbonization reaction in a hydrogen atmosphere to obtain graphene-rich silicon carbide particles; prepares multi-walled carbon nanotubes, mixes the prepared carbon source material with auxiliary materials, puts them into a chemical vapor deposition reactor, and reacts in a high temperature and high pressure atmosphere to synthesize multi-walled carbon nanotubes; post-treats the multi-walled carbon nanotubes, oxidizes the prepared multi-walled carbon nanotubes, and reacts in a high temperature and oxygen atmosphere to obtain oxidized multi-walled carbon nanotubes; then reduces the oxidized multi-walled carbon nanotubes, and reacts in a high temperature and hydrogen atmosphere to obtain high-performance multi-walled carbon nanotubes.

[0004] A method for preparing multi-walled carbon nanotubes (patent application number: CN200910077054.7) uses an ionic liquid solution of polysaccharide as a carbon source, dehydrates the carbon source with concentrated sulfuric acid in the presence of a catalyst, and then carbonizes the solid obtained by dehydration carbonization under the condition of isolating oxygen to obtain multi-walled carbon nanotubes; wherein the polysaccharide is a polymer formed by polymerization of more than 10 monosaccharides, and the catalyst is selected from the following metal salts: palladium salts, iron salts, cobalt salts and nickel salts. The present invention mainly utilizes the dissolving characteristics of ionic liquids for polysaccharides, and uses a variety of polysaccharides (preferably natural polysaccharides) as raw materials to prepare bamboo-shaped multi-walled carbon nanotubes by carbonization at a relatively low temperature (below 900°C).

[0005] However, the applicant believes that the above disclosed technology has the following problems on one hand: high synthesis cost, large fluctuation in the quality of multi-walled carbon nanotubes between batches, and uneven distribution of nanotube diameters; on the other hand, defects will be formed on the surface of the multi-walled carbon nanotubes during the preparation process, which affects their electrical properties and is not conducive to their use in lithium-ion battery conductivity.

[0006] Based on this, the present invention proposes a method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries. Summary of the invention

[0007] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries, and prepares multi-walled carbon nanotubes with excellent electrical properties, which can be used for conductivity in lithium ion batteries.

[0008] Another object of the present invention is to provide multi-walled carbon nanotubes as a conductive agent for lithium ion batteries obtained by the above preparation method.

[0009] Another object of the present invention is to provide a catalyst and a preparation method thereof, wherein the catalyst can be used to catalyze the preparation of multi-walled carbon nanotubes.

[0010] The purpose of the present invention is achieved through the following technical solutions: A method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries comprises the following steps: S1: Add 100-500 parts of an organic acid solution and 2-5 parts of a catalyst in a reaction kettle by mass, start stirring to mix the catalyst and the acid solution evenly, then add 10-45 parts of an organic carbon source, continue stirring for 10-30 minutes, and react to obtain a mixture; S2: Add 500-1200 parts of inorganic acid solution in step S1, stir for 10-20 minutes and then stand until the mixed solution is separated into layers, filter the upper suspension to obtain a solid that is repeatedly washed with deionized water until no acid radical ions are detected, and dry in a vacuum oven to obtain a multi-walled carbon nanotube conductive agent for lithium ion batteries.

[0011] As a further supplement to the above technical solution, the organic acid in step S1 is selected from at least one of formic acid, acetic acid, oxalic acid, propionic acid, n-butyric acid, and n-valeric acid, and the concentration of the organic acid solution is 15-45wt%.

[0012] As a further supplement to the above technical solution, the organic carbon source in step S1 is selected from at least one of glucose, sucrose, fructose and maltose.

[0013] As a further supplement to the above technical solution, the inorganic acid in step S2 is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and the concentration of the inorganic acid solution is 5-15wt%.

[0014] As a further supplement to the above technical solution, in step S2, the vacuum degree of the vacuum oven is 50-100 Pa and the temperature is 45-70°C.

[0015] As a further supplement to the above technical solution, the catalyst preparation method is: A1: 21-42 parts of 5,5-divinyl-2,2-bipyridine, 8-16 parts of vanadyl sulfate, and 1-3 parts of Co(NO3)2 are weighed in a reaction kettle, and then added to 1000-1600 parts of DMF, and reacted at 40-50°C for 30-60 minutes; A2: Add 300-400 parts of mercapto X molecular sieve, 0.05-0.5 parts of 1,1'-divinylferrocene, 8-16 parts of lithium acrylate, and 5-8 parts of sodium tert-butoxide into the reaction kettle, and react at 40-50°C for 30-60 minutes; A3: After the reaction is completed, filter, dry, and then calcine in air for 3-6 hours to obtain a catalyst.

[0016] As a further supplement to the above technical solution, the preparation method of the thiol X molecular sieve is: By weight, 4-7 parts of (3-mercaptopropyl)trimethoxysilane, 100-120 parts of X molecular sieve, and 1000-1500 parts of deionized water are added into a reaction kettle, nitrogen is introduced, and then stirred at room temperature for 100-150 minutes, centrifuged, and vacuum dried to obtain the mercapto X molecular sieve.

[0017] As a further supplement to the above technical solution, the calcination temperature is 400-500°C.

[0018] The reaction mechanism is: 5,5-divinyl-2,2-bipyridine reacts with vanadyl sulfate and Co(NO3)2 to generate a 5,5-divinyl-2,2-bipyridine / vanadium / Co precursor; a thiol-olefin addition reaction occurs between the thiol X molecular sieve, 1,1'-divinylferrocene, lithium acrylate, and the 5,5-divinyl-2,2-bipyridine / vanadium / Co precursor to uniformly bind vanadium / Co / iron / lithium to the surface of the X molecular sieve through chemical bonds, and then the vanadium / Co / iron / lithium oxide-loaded X molecular sieve is generated through oxygen-added calcination.

[0019] The beneficial effects achieved by the present invention using the above technical solution are as follows: 1. Improve catalytic efficiency: X molecular sieve loaded with vanadium / Co / iron / lithium oxide can enhance the activity of the catalyst, thereby improving the efficiency of carbon nanotube generation.

[0020] 2. Lower temperature: The use of supported catalysts allows the synthesis of carbon nanotubes at lower temperatures, which helps reduce energy consumption and costs.

[0021] 3. Controllable structure: By adjusting the composition of the catalyst and the reaction conditions, the diameter, length and structure of the generated carbon nanotubes can be controlled.

[0022] 4. High purity: The loaded catalyst can effectively focus the reaction on the formation of carbon nanotubes, avoiding the formation of other by-products, thereby obtaining high-purity carbon nanotubes. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the embodiments. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0025] Embodiment 1, a method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries, comprising the following steps: S1: Add 100 g of organic acid solution and 2 g of catalyst into a reactor, start stirring to mix the catalyst and acid solution evenly, then add 10 g of organic carbon source, continue stirring for 10 minutes, and react to obtain a mixture; S2: Add 500g of inorganic acid solution to step S1, stir for 10 minutes and then let the mixed solution stand until the mixed solution separates into layers, filter the upper suspension to obtain a solid that is repeatedly washed with deionized water until no acid radical ions are detected, and dry in a vacuum oven to obtain a multi-walled carbon nanotube conductive agent for lithium ion batteries.

[0026] In step S1, the organic acid is selected from formic acid, and the concentration of the organic acid solution is 15 wt %.

[0027] In step S1, the organic carbon source is selected from glucose.

[0028] In step S2, the inorganic acid is selected from hydrochloric acid, and the concentration of the inorganic acid solution is 5wt%.

[0029] In step S2, the vacuum degree of the vacuum oven is 50 Pa and the temperature is 45°C.

[0030] The catalyst preparation method: A1: 21 g of 5,5-divinyl-2,2-bipyridine, 8 g of vanadyl sulfate, and 1 g of Co(NO3)2 were weighed into a reaction kettle, then added into 1000 g of DMF and reacted at 40°C for 30 minutes; A2: 300 g of mercapto X molecular sieve, 0.1 g of 1,1'-divinylferrocene, 8 g of lithium acrylate, and 5 g of sodium tert-butoxide were added to the reaction kettle and reacted at 40° C. for 30 minutes; A3: After the reaction is completed, filter, dry, and then calcine in air for 3 hours to obtain a catalyst.

[0031] The preparation method of the thiol X molecular sieve is: 4 g (3-mercaptopropyl)trimethoxysilane, 100 g X molecular sieve, and 1000 g deionized water were added to a reaction kettle, nitrogen was introduced, and then stirred at room temperature for 100 min, centrifuged, and vacuum dried to obtain the mercapto X molecular sieve.

[0032] The calcination temperature is 400°C.

[0033] Embodiment 2, a method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries, comprising the following steps: S1: Add 220 g of organic acid solution and 3 g of catalyst into a reactor, start stirring to mix the catalyst and acid solution evenly, then add 25 g of organic carbon source, continue stirring for 15 minutes, and react to obtain a mixture; S2: Add 700g of inorganic acid solution to step S1, stir for 15 minutes and then let the mixed solution stand until the mixed solution separates into layers, filter the upper suspension to obtain a solid which is repeatedly washed with deionized water until no acid radical ions are detected, and dry in a vacuum oven to obtain a multi-walled carbon nanotube conductive agent for lithium ion batteries.

[0034] In step S1, the organic acid is selected from acetic acid, and the concentration of the organic acid solution is 25 wt %.

[0035] In step S1, the organic carbon source is selected from sucrose.

[0036] In step S2, the inorganic acid is selected from sulfuric acid, and the concentration of the inorganic acid solution is 8 wt %.

[0037] In step S2, the vacuum degree of the vacuum oven is 70 Pa and the temperature is 50° C.

[0038] The catalyst preparation method: A1: 28 g of 5,5-divinyl-2,2-bipyridine, 12 g of vanadyl sulfate, and 1 g of Co(NO3)2 were weighed into a reaction kettle, and then added into 1200 g of DMF, and reacted at 40°C for 40 minutes; A2: 320 g of mercapto X molecular sieve, 0.25 g of 1,1'-divinylferrocene, 12 g of lithium acrylate, and 6 g of sodium tert-butoxide were added to the reaction kettle and reacted at 40° C. for 40 minutes; A3: After the reaction is completed, filter, dry, and then calcine in air for 4 hours to obtain a catalyst.

[0039] The preparation method of the thiol X molecular sieve is: 5 g of (3-mercaptopropyl)trimethoxysilane, 105 g of X molecular sieve, and 1150 g of deionized water were added to a reaction kettle, and nitrogen was introduced. The mixture was then stirred at room temperature for 120 min, centrifuged, and vacuum dried to obtain the mercapto X molecular sieve.

[0040] The calcination temperature is 400°C.

[0041] Embodiment 3, a method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries, comprising the following steps: S1: Add 380 g of organic acid solution and 4 g of catalyst into a reactor, start stirring to mix the catalyst and acid solution evenly, then add 35 g of organic carbon source, continue stirring for 20 minutes, and react to obtain a mixture; S2: Add 1000g of inorganic acid solution to step S1, stir for 15 minutes and then let the mixed solution stand until the mixed solution separates into layers, filter the upper suspension to obtain a solid which is repeatedly washed with deionized water until no acid radical ions are detected, and dry in a vacuum oven to obtain a multi-walled carbon nanotube conductive agent for lithium ion batteries.

[0042] In step S1, the organic acid is selected from oxalic acid, and the concentration of the organic acid solution is 35 wt %.

[0043] In step S1, the organic carbon source is selected from fructose.

[0044] In step S2, the inorganic acid is selected from nitric acid, and the concentration of the inorganic acid solution is 12 wt %.

[0045] In step S2, the vacuum degree of the vacuum oven is 85 Pa and the temperature is 60°C.

[0046] The catalyst preparation method: A1: 35 g of 5,5-divinyl-2,2-bipyridine, 14 g of vanadyl sulfate, and 2 g of Co(NO3)2 were weighed into a reaction kettle, and then added into 1400 g of DMF, and reacted at 45°C for 50 minutes; A2: 350 g of mercapto X molecular sieve, 0.4 g of 1,1'-divinylferrocene, 14 g of lithium acrylate, and 7 g of sodium tert-butoxide were added to the reaction kettle and reacted at 45° C. for 50 minutes; A3: After the reaction is completed, filter, dry, and then calcine in air for 5 hours to obtain a catalyst.

[0047] The preparation method of the thiol X molecular sieve is: 6 g of (3-mercaptopropyl)trimethoxysilane, 115 g of X molecular sieve, and 1400 g of deionized water were added to a reaction kettle, nitrogen was introduced, and then stirred at room temperature for 140 min, centrifuged, and vacuum dried to obtain the mercapto X molecular sieve.

[0048] The calcination temperature is 450°C.

[0049] Embodiment 4, a method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries, comprising the following steps: S1: Add 500 g of organic acid solution and 5 g of catalyst into a reactor, start stirring to mix the catalyst and acid solution evenly, then add 45 g of organic carbon source, continue stirring for 30 minutes, and react to obtain a mixture; S2: Add 1200g of inorganic acid solution to step S1, stir for 20 minutes and then let the mixed solution stand until it separates into layers. Filter the upper suspension to obtain a solid that is repeatedly washed with deionized water until no acid radical ions are detected. Dry it in a vacuum oven to obtain a multi-walled carbon nanotube conductive agent for lithium ion batteries.

[0050] In step S1, the organic acid is selected from n-butyric acid, and the concentration of the organic acid solution is 45 wt %.

[0051] In step S1, the organic carbon source is selected from maltose.

[0052] In step S2, the inorganic acid is selected from phosphoric acid, and the concentration of the inorganic acid solution is 15 wt %.

[0053] In step S2, the vacuum degree of the vacuum oven is 100 Pa and the temperature is 70°C.

[0054] The catalyst preparation method: A1: 42 g of 5,5-divinyl-2,2-bipyridine, 16 g of vanadyl sulfate, and 3 g of Co(NO3)2 were weighed into a reaction kettle, then added into 1600 g of DMF and reacted at 50°C for 60 minutes; A2: 400 g of mercapto X molecular sieve, 0.5 g of 1,1'-divinylferrocene, 16 g of lithium acrylate, and 8 g of sodium tert-butoxide were added to the reactor and reacted at 50° C. for 60 minutes; A3: After the reaction is completed, filter, dry, and then calcine in air for 6 hours to obtain a catalyst.

[0055] The preparation method of the thiol X molecular sieve is: 7 g of (3-mercaptopropyl)trimethoxysilane, 120 g of X molecular sieve, and 1500 g of deionized water were added to a reaction kettle, nitrogen was introduced, and then stirred at room temperature for 150 min, centrifuged, and vacuum dried to obtain the mercapto X molecular sieve.

[0056] The calcination temperature is 500°C.

[0057] Comparative Example 1 In this example, no vanadyl sulfate is added, and the rest of the technical scheme is the same as in Example 1.

[0058] Comparative Example 2 In this example, Co(NO3)2 is not added, and the rest of the technical scheme is the same as that of Example 1.

[0059] Comparative Example 3 In this example, 1,1'-divinylferrocene was not added, and the other technical schemes were the same as those in Example 1.

[0060] Evaluation of the embodiment: method: Yield of multi-walled carbon nanotubes: Yield = (total weight after reaction - weight of catalyst used) / weight of catalyst used Multi-walled carbon nanotubes packing density: Packing density (kg / m 3 ) = carbon nanotube weight (kg) / carbon nanotube volume (m 3 ) Purity test of multi-walled carbon nanotubes: refer to GB / T 24490-2009 Purity test method of multi-walled carbon nanotubes result: Yield % <![CDATA[Bulk density kg / m 3 > purity% Example 1 67 34 98.5 Example 2 74 40 99.3 Example 3 72 37 98.9 Example 4 77 44 99.5 Comparative Example 1 53 35 96.5 Comparative Example 2 48 31 97.1 Comparative Example 3 57 33 96.6 From the comparison results of the above embodiments and comparative examples, it can be seen that the catalyst prepared by the present method effectively improves the yield and purity of multi-walled carbon nanotubes. This is mainly because the X molecular sieve can enhance the activity of the catalyst and thus improve the generation efficiency of carbon nanotubes, and the supported catalyst can effectively focus the reaction on the generation of carbon nanotubes, avoiding the generation of other by-products.

[0061] The present invention has been described above through specific implementation methods and examples, but these descriptions are only illustrative and should not be understood as limiting the scope of protection of the present invention. Without departing from the spirit and scope of protection of the present invention, those skilled in the art may make various improvements, modifications or equivalent substitutions to the technical solutions and implementation methods of the present invention, all of which should fall within the scope of protection of the present invention.

Claims

1. A method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries, characterized in that: The following steps are involved: S1: Add 100-500 parts of an organic acid solution and 2-5 parts of a catalyst in a reaction kettle by mass, start stirring to mix the catalyst and the acid solution evenly, then add 10-45 parts of an organic carbon source, continue stirring for 10-30 minutes, and react to obtain a mixture; S2: Add 500-1200 parts of inorganic acid solution in step S1, stir for 10-20 minutes and then stand until the mixed solution is separated into layers, filter the upper suspension to obtain a solid that is repeatedly washed with deionized water until no acid radical ions are detected, and dry in a vacuum oven to obtain a multi-walled carbon nanotube conductive agent for lithium ion batteries.

2. The method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries according to claim 1, characterized in that: In step S1, the organic acid is selected from at least one of formic acid, acetic acid, oxalic acid, propionic acid, n-butyric acid, and n-valeric acid, and the concentration of the organic acid solution is 15-45wt%.

3. The method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries according to claim 1, characterized in that: The catalyst preparation method in step S1: A1: In a reaction kettle, weigh 21-42 parts of 5,5-divinyl-2,2-bipyridine, 8-16 parts of vanadyl sulfate, and 1-3 parts of Co(NO3)2, then add 1000-1600 parts of DMF and react at 40-50°C for 30-60 minutes. A2: Add 300-400 parts of mercapto X molecular sieve, 0.05-0.5 parts of 1,1'-divinylferrocene, 8-16 parts of lithium acrylate, and 5-8 parts of sodium tert-butoxide into the reaction kettle, and react at 40-50°C for 30-60 minutes; A3: After the reaction is completed, filter, dry, and then calcine in air for 3-6 hours to obtain a catalyst.

4. The method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries according to claim 3, characterized in that: The preparation method of the thiol X molecular sieve is: By weight, 4-7 parts of (3-mercaptopropyl)trimethoxysilane, 100-120 parts of X molecular sieve, and 1000-1500 parts of deionized water are added into a reaction kettle, nitrogen is introduced, and then stirred at room temperature for 100-150 minutes, centrifuged, and vacuum dried to obtain the mercapto X molecular sieve.

5. The method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries according to claim 3, characterized in that: The calcination temperature is 400-500°C.

6. The method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries according to claim 1, characterized in that: In step S1, the organic carbon source is selected from at least one of glucose, sucrose, fructose and maltose.

7. The method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries according to claim 1, characterized in that: In step S2, the inorganic acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and the concentration of the inorganic acid solution is 5-15wt%.

8. The method for preparing multi-walled carbon nanotubes as a conductive agent for lithium ion batteries according to claim 1, characterized in that: In step S2, the vacuum degree of the vacuum oven is 50-100 Pa and the temperature is 45-70°C.