A method for producing artificial graphite

Abstract

The application discloses a preparation method of artificial graphite, which comprises the following steps: uniformly mixing boric acid, water and anthracite, and then performing impregnation treatment; after drying, uniformly mixing the mixture with a binder and nickel-plated carbon nanotubes, and then performing granulation; carbonizing, graphitizing, crushing, and shaping to obtain artificial graphite. The application has the advantages of low cost, low energy consumption, high graphitization degree, and the lithium ion battery prepared from the obtained artificial graphite has good cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of artificial graphite, in particular to a preparation method of artificial graphite. BACKGROUND

[0002] Graphite material has superior performance such as high temperature resistance, corrosion resistance, self-lubrication, thermal shock resistance, thermal conductivity and electrical conductivity, which cannot be compared with other materials, and has been widely used in aviation, aerospace, nuclear industry, military industry and many civil industrial fields. Coal-based graphitized carbon is an ideal negative material, which can replace natural graphite for lithium ion battery negative material.

[0003] Anthracite is a macromolecular structure composed of aromatic rings, and is composed of large units of graphene layers connected by aliphatic or ether groups, and has a certain ordered structure; anthracite is one of the common carbon raw materials for preparing graphite materials. However, the graphitization of anthracite requires a high temperature, and the graphitization degree of anthracite treated at 2600℃ is only about 80%, and its lithium storage performance is poor, and the discharge capacity is only 250mAh·g -1 In order to improve the graphitization degree and electrochemical performance of anthracite, graphitization needs to be carried out at a high temperature of more than 2800℃, but this process greatly increases the cost and energy consumption, and the high price and complicated production process hinder its large-scale production and commercial application. And the cycle performance of the artificial graphite prepared from the existing anthracite is low, and still needs to be improved. SUMMARY

[0004] Based on the technical problems existing in the background art, the present application provides a preparation method of artificial graphite, which has low cost, low energy consumption, high graphitization degree, and the lithium ion battery prepared from the obtained artificial graphite has good cycle performance.

[0005] The present application provides a preparation method of artificial graphite, which comprises the following steps: uniformly mixing boric acid, water and anthracite for impregnation treatment, drying, uniformly mixing with a binder and nickel-plated carbon nanotubes for granulation, carbonization, graphitization, crushing, shaping, and obtaining artificial graphite.

[0006] Preferably, the volatile content of the anthracite is 8-10wt%.

[0007] Preferably, the particle size of the anthracite is <200 mesh.

[0008] Preferably, the ash content of the anthracite is <3.6wt%, and the moisture content is <2wt%.

[0009] Preferably, the anthracite is pretreated, and the pretreatment step comprises: keeping at 400-500℃ for 30-40min in an inert gas atmosphere, and then keeping at 900-1000℃ for 60-90min.

[0010] Preferably, the weight ratio of boric acid to anthracite is 1:5-15.

[0011] Preferably, the ratio of the amount of boric acid to water is 1g:40-60ml.

[0012] Preferably, the impregnation is carried out at room temperature for 2.5-3.5 days.

[0013] Preferably, the weight ratio of anthracite, binder and nickel-plated carbon nanotube is 85-90:10-15:2-3.

[0014] The binder can be pitch, phenolic resin, etc.; the nickel-plated carbon nanotube can be purchased from the market.

[0015] Preferably, both carbonization and graphitization are carried out in an inert gas atmosphere.

[0016] Preferably, the carbonization temperature is 900-1000℃, and the time is 8-10h.

[0017] Preferably, the graphitization temperature is 1400-1800℃, and the time is 2-3h.

[0018] Preferably, the temperature is raised to 1400-1800℃ at a rate of 4-6℃ / min.

[0019] The inert gas can be argon, etc.

[0020] The anthracite with suitable volatile matter is selected, and the anthracite is pretreated to make the volatile matter fully released from the anthracite and form multiple small pores, then the anthracite is impregnated with boric acid, which can promote the boric acid to enter the interior of the anthracite and promote the uniform distribution of the boric acid in the anthracite, avoiding the problem of uneven graphitization caused by uneven distribution of the boric acid on the surface and in the interior of the anthracite; the anthracite with a suitable particle size is selected, which can further promote the uniform distribution of the boric acid; then the anthracite is mixed with a binder and nickel-plated carbon nanotube and granulated, through the mutual cooperation of the boric acid and the nickel-plated carbon nanotube, the graphitization temperature can be greatly reduced while maintaining a high graphitization degree, and a three-dimensional conductive network is formed to improve the conductivity and slightly increase the interlayer spacing of the graphite, improve the microstructure of the artificial graphite, and greatly improve the cycle performance and discharge capacity of the artificial graphite. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The XRD curves of anthracite, artificial graphite of Example 1 and artificial graphite of Comparative Example 1, wherein 1a is anthracite, 1b is Comparative Example 1, and 1c is Example 1.

[0022] Figure 2SEM images of anthracite, artificial graphite of Example 1, and artificial graphite of Comparative Example 1, wherein 2a is anthracite, 2b is Example 1, and 2c is Comparative Example 1. DETAILED DESCRIPTION

[0023] Hereinafter, the technical solutions of the present application will be described in detail through specific examples.

[0024] Example 1

[0025] A method for preparing artificial graphite, comprising the following steps:

[0026] Take 30 g of anthracite with a volatile content of 10 wt%, an ash content of <3.6 wt%, a moisture content of <2 wt%, and a particle size of <200 mesh, and perform pretreatment, the pretreatment steps comprising: holding at 500°C for 30 min in an argon atmosphere, and then holding at 1000°C for 60 min;

[0027] Put the above-mentioned 30 g of pretreated anthracite into a 500 ml beaker, add a boric acid aqueous solution (containing 3 g of boric acid and 150 ml of distilled water), stir and mix for 24 h, immerse at room temperature for 3 days, and then dry in a blast drying machine at 100°C;

[0028] Add 3.3 g of pitch and 1 g of nickel-plated carbon nanotubes, mix and granulate, transfer to a high-temperature graphitization furnace, carbonize at 1000°C for 8 h in an argon atmosphere, then heat to 1600°C at a rate of 5°C / min, graphitize for 2 h, crush, and shape to obtain artificial graphite.

[0029] Example 2

[0030] A method for preparing artificial graphite, comprising the following steps:

[0031] Take 15 g of anthracite with a volatile content of 8 wt%, an ash content of <3.6 wt%, a moisture content of <2 wt%, and a particle size of <200 mesh, and perform pretreatment, the pretreatment steps comprising: holding at 400°C for 40 min in an argon atmosphere, and then holding at 900°C for 90 min;

[0032] Put the above-mentioned 15 g of pretreated anthracite into a 500 ml beaker, add a boric acid aqueous solution (containing 3 g of boric acid and 120 ml of distilled water), stir and mix for 24 h, immerse at room temperature for 3.5 days, and then dry in a blast drying machine at 100°C;

[0033] Add 2.6 g of pitch and 0.35 g of nickel-plated carbon nanotubes, mix and granulate, transfer to a high-temperature graphitization furnace, carbonize at 900°C for 8 h in an argon atmosphere, then heat to 1400°C at a rate of 4°C / min, graphitize for 3 h, crush, and shape to obtain artificial graphite.

[0034] Example 3

[0035] A method for preparing artificial graphite includes the following steps:

[0036] Anthracite with a volatile matter content of 9 wt%, an ash content of <3.6 wt%, a moisture content of <2 wt%, and a particle size of <200 mesh was pretreated. The pretreatment steps included: holding at 450℃ for 35 min in an argon atmosphere, and then holding at 950℃ for 80 min.

[0037] Take 45g of the pretreated anthracite into a 500ml beaker, add boric acid aqueous solution (containing 3g boric acid and 180ml distilled water), stir and mix for 24h, soak at room temperature for 2.5 days, and then dry in a 100℃ forced-air dryer.

[0038] Add 5g of asphalt and 1.25g of nickel-plated carbon nanotubes, mix and granulate, transfer to a high-temperature graphitization furnace, carbonize at 1000℃ for 9h in an argon atmosphere, then graphitize at 1800℃ for 2h at a rate of 6℃ / min, crush and shape to obtain artificial graphite.

[0039] Comparative Example 1

[0040] Direct graphitization of anthracite includes the following steps:

[0041] The pretreated anthracite from Example 1 was placed in a high-temperature graphitization furnace and graphitized at 1600°C for 2 hours in an argon atmosphere at a rate of 5°C / min. The graphitized coal was then crushed and shaped to obtain artificial graphite.

[0042] The artificial graphite and anthracite from Example 1 and Comparative Example 1 were tested, and the results are as follows: Figures 1-2 As shown.

[0043] Figure 1 XRD curves of anthracite, artificial graphite of Example 1, and artificial graphite of Comparative Example 1 are shown, where 1a is anthracite, 1b is Comparative Example 1, and 1c is Example 1.

[0044] Depend on Figure 1 It can be seen that in anthracite, the (002) diffraction peak representing graphite flakes and the (100) diffraction peak representing aromatic structure are relatively broad, indicating that there is a certain graphite microcrystalline structure in anthracite; in Comparative Example 1, the relative intensity of the diffraction peak of the (002) crystal plane is enhanced; in Example 1, the (002) and (100) peaks are higher and sharper than the (002) and (100) peaks of anthracite, indicating that the method described in this invention effectively improves the crystal structure of coal-based graphitized carbon and reduces the graphitization temperature.

[0045] Figure 2SEM images of anthracite, artificial graphite of Example 1, and artificial graphite of Comparative Example 1, wherein 2a is anthracite, 2b is Example 1, and 2c is Comparative Example 1.

[0046] By Figure 2 It can be seen that anthracite has a certain ordered structure, and carbon sheets are stacked in layers with a certain wrinkle; the artificial graphite of Example 1 shows a highly ordered large-size sheet structure; the microstructure of the artificial graphite of Comparative Example 1 presents a relatively smooth surface; it is shown that the method described in the application can promote the growth of microcrystals into carbon sheets and promote their arrangement, thereby promoting the graphitization of anthracite.

[0047] Comparative Example 2

[0048] Without immersion in aqueous boric acid solution, and the rest is the same as Example 1.

[0049] Comparative Example 3

[0050] Without nickel-plated carbon nanotubes, and the rest is the same as Example 1.

[0051] Comparative Example 4

[0052] Replace the nickel-plated carbon nanotubes with nickel, and the rest is the same as Example 1.

[0053] Comparative Example 5

[0054] Replace the nickel-plated carbon nanotubes with carbon nanotubes, and the rest is the same as Example 1.

[0055] Take the artificial graphite prepared in Examples 1-3 and Comparative Examples 1-5 as active materials, and add them to N-methyl-2-pyrrolidone according to a weight ratio of active material: carbon black: polyvinylidene fluoride (PVDF) of 8:1:1, and use a mortar to grind them thoroughly for 40 min, then stir them thoroughly for 24 h, and then use a film coating machine to evenly spread the slurry on a copper foil collector, and then dry it in a vacuum drying oven at 105°C for 10 h to obtain a negative electrode; assemble a lithium ion battery in a Mikrona Super (1220 / 750) glove box, use a lithium metal sheet as a positive electrode, a polypropylene microporous membrane (Celgard 2400) as a separator, and a 1M LiPF6 solution (its solvent is equal volume of ethylene carbonate and dimethyl carbonate) as an electrolyte. Perform electrochemical performance testing on the assembled battery on a Neware CT-4800-5V10mA-164 battery testing system, and the charge and discharge voltage range is 0.01-3V. The test results are shown in Table 1.

[0056] Table 1 Test Results

[0057]

[0058] As shown in Table 1, the artificial graphite prepared by the method has a high graphitization degree, and the lithium ion battery prepared has good cycle performance.

[0059] The above description is merely preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes to the technical scheme and the inventive concept of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for preparing artificial graphite, characterized in that, The process includes the following steps: mixing boric acid, water, and anthracite for impregnation, drying, mixing with binder and nickel-plated carbon nanotubes for granulation, carbonization, graphitization, crushing, and shaping to obtain artificial graphite. Anthracite undergoes pretreatment, which includes the following steps: holding at 400-500℃ for 30-40 minutes in an inert gas atmosphere, and then holding at 900-1000℃ for 60-90 minutes.

2. The method for preparing artificial graphite according to claim 1, characterized in that, Anthracite has a volatile matter content of 8-10 wt%.

3. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, Anthracite has a particle size of <200 mesh.

4. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, The ash content of anthracite is <3.6wt%, and the moisture content is <2wt%.

5. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, The weight ratio of boric acid to anthracite is 1:5-15.

6. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, The ratio of boric acid to water is 1g:40-60ml.

7. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, Immerse at room temperature for 2.5-3.5 days.

8. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, The weight ratio of anthracite, binder, and nickel-plated carbon nanotubes is 85-90:10-15:2-3.

9. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, Both carbonization and graphitization are carried out in an inert gas atmosphere.

10. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, The carbonization temperature is 900-1000℃, and the time is 8-10h.

11. The method for preparing artificial graphite according to claim 1 or 2, characterized in that, The graphitization temperature is 1400-1800℃, and the time is 2-3 hours.

12. The method for preparing artificial graphite according to claim 11, characterized in that, Heat to 1400-1800℃ at a rate of 4-6℃ / min.

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