Preparation method of artificial graphite

Abstract

The invention discloses a preparation method of artificial graphite, which comprises the following steps: uniformly mixing boric acid, water and anthracite, dipping, drying, uniformly mixing with a binder and nickel-plated carbon nanotubes, granulating, carbonizing, graphitizing, crushing and shaping to obtain the artificial graphite. The method is low in cost, low in energy consumption and high in graphitization degree, and the lithium ion battery prepared from the artificial graphite has good cycle performance.

Description

Technical Field

[0001] The invention relates to the technical field of artificial graphite, and in particular to a method for preparing artificial graphite. Background Art

[0002] Graphite materials have incomparable superior properties such as high temperature resistance, corrosion resistance, self-lubrication, thermal shock resistance, thermal and electrical conductivity, etc., which are unmatched by other materials. They have been widely used in aviation, aerospace, nuclear industry, military industry and many civilian industrial fields. Coal-based graphitized carbon is an ideal negative electrode material, which can replace natural graphite for negative electrode materials of lithium-ion batteries.

[0003] Anthracite is a macromolecular structure composed of aromatic rings, and graphene layers connected by aliphatic or ether groups form large units, with a certain ordered structure; anthracite is one of the commonly used carbon raw materials for preparing graphite materials. However, the graphitization of anthracite requires a relatively high temperature. The graphitization degree of anthracite treated at 2600°C is only about 80%, and its lithium storage performance is poor, with a discharge capacity of only 250mAh·g -1 In order to improve the graphitization degree and electrochemical performance of anthracite, it is necessary to graphitize it at a high temperature above 2800℃, but this process greatly increases the cost and energy consumption. Its high price and cumbersome production process hinder its large-scale production and commercial application. In addition, the cycle performance of artificial graphite made from existing anthracite is low and still needs to be improved. Summary of the invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a method for preparing artificial graphite. The present invention has low cost, low energy consumption, and high degree of graphitization. The lithium ion battery prepared from the obtained artificial graphite has good cycle performance.

[0005] The invention provides a method for preparing artificial graphite, comprising the following steps: mixing boric acid, water and anthracite for impregnation treatment, drying, mixing with a binder and nickel-plated carbon nanotubes for granulation, carbonizing, graphitizing, crushing and shaping to obtain artificial graphite.

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

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

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

[0009] Preferably, the anthracite is pretreated, and the pretreatment steps include: keeping the temperature at 400-500° C. for 30-40 minutes, and then keeping the temperature at 900-1000° C. for 60-90 minutes in an inert gas atmosphere.

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

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

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

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

[0014] The above-mentioned binder can be asphalt, phenolic resin, etc.; the above-mentioned nickel-plated carbon nanotubes can be purchased from the market.

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

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

[0017] Preferably, the graphitization temperature is 1400-1800° C., and the time is 2-3 hours.

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

[0019] The inert gas mentioned above may be argon or the like.

[0020] The present invention selects anthracite with suitable volatile matter, pre-treats it first so that the volatile matter can be fully released from the anthracite and a plurality of small holes can be formed, and then impregnates boric acid, which can promote the boric acid to enter the interior of the anthracite, promote the boric acid to be evenly dispersed in the anthracite, and avoid the problem of uneven graphitization caused by uneven distribution of boric acid on the surface and inside of the anthracite; selects anthracite with suitable particle size, which can further promote the uniform distribution of boric acid; and then mixes and granulates with a binder and nickel-plated carbon nanotubes, and through the mutual cooperation of boric acid and nickel-plated carbon nanotubes, the graphitization temperature can be greatly reduced while maintaining a high degree of graphitization, and a three-dimensional conductive network is formed to improve the conductivity and slightly increase the interlayer spacing of graphite, improve the microscopic morphology of artificial graphite, and greatly improve the cycle performance and discharge capacity of artificial graphite. The present invention has low cost, low energy consumption, and good cycle performance of the obtained artificial graphite. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1a is anthracite, 1b is comparative example 1, and 1c is embodiment 1.

[0022] Figure 22a is anthracite, 2b is example 1, and 2c is example 1. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is described in detail below through specific embodiments.

[0024] Example 1

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

[0026] Anthracite with a volatile content of 10 wt%, an ash content of less than 3.6 wt%, a moisture content of less than 2 wt%, and a particle size of less than 200 meshes was pretreated, and the pretreatment steps included: keeping the temperature at 500° C. for 30 minutes and then keeping the temperature at 1000° C. for 60 minutes in an argon atmosphere;

[0027] Take 30g of the pretreated anthracite in a 500ml beaker, add a boric acid aqueous solution (containing 3g of boric acid and 150ml of distilled water), stir and mix for 24h, soak at room temperature for 3 days, and then dry in a 100℃ forced air dryer;

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

[0029] Example 2

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

[0031] Taking anthracite with a volatile content of 8wt%, an ash content of less than 3.6wt%, a moisture content of less than 2wt%, and a particle size of less than 200 mesh, the pretreatment is performed, and the pretreatment steps include: keeping the temperature at 400°C for 40 minutes and then keeping the temperature at 900°C for 90 minutes in an argon atmosphere;

[0032] Take 15g of the pretreated anthracite in a 500ml beaker, add a boric acid aqueous solution (containing 3g of boric acid and 120ml of distilled water), stir and mix for 24h, soak at room temperature for 3.5 days, and then dry in a 100℃ forced air dryer;

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

[0034] Example 3

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

[0036] Taking anthracite with a volatile matter content of 9wt%, an ash content of less than 3.6wt%, a moisture content of less than 2wt%, and a particle size of less than 200 mesh, the pretreatment is performed, and the pretreatment steps include: keeping the temperature at 450°C for 35 minutes and then keeping the temperature at 950°C for 80 minutes in an argon atmosphere;

[0037] Take 45g of the pretreated anthracite in a 500ml beaker, add a boric acid aqueous solution (containing 3g of boric acid and 180ml of 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°C for 9h in an argon atmosphere, then heat to 1800°C at a rate of 6°C / min and graphitize for 2h, crush and shape to obtain artificial graphite.

[0039] Comparative Example 1

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

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

[0042] The artificial graphite and anthracite of Example 1 and Comparative Example 1 were tested, and the results were as follows: Figure 1-2 shown.

[0043] Figure 1 1a is anthracite, 1b is comparative example 1, and 1c is embodiment 1.

[0044] Depend on Figure 1 It can be seen that in anthracite, the (002) diffraction peak representing graphite sheets and the (100) diffraction peak of the aromatic structure are relatively broad, indicating that a certain graphite microcrystalline structure exists 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 of the present invention effectively improves the crystal structure of coal-based graphitized carbon and reduces the graphitization temperature.

[0045] Figure 22a is anthracite, 2b is example 1, and 2c is example 1.

[0046] Depend on Figure 2 It can be seen that: anthracite has a certain ordered structure, the carbon sheets are stacked in layers, and certain wrinkles appear; the artificial graphite of Example 1 shows a highly ordered large-size flake structure; the microstructure of the artificial graphite of Comparative Example 1 presents a relatively smooth surface; This shows that the method of the present invention can promote the growth of microcrystals into carbon sheets and promote their arrangement, thereby promoting the graphitization of anthracite.

[0047] Comparative Example 2

[0048] The other steps are the same as those in Example 1 except that the impregnation with the boric acid aqueous solution is not performed.

[0049] Comparative Example 3

[0050] No nickel-plated carbon nanotubes were added, and the rest was the same as in Example 1.

[0051] Comparative Example 4

[0052] The nickel-plated carbon nanotubes were replaced with nickel, and the rest was the same as in Example 1.

[0053] Comparative Example 5

[0054] The nickel-plated carbon nanotubes were replaced with carbon nanotubes, and the rest was the same as in Example 1.

[0055] Take the artificial graphite obtained in Examples 1-3 and Comparative Examples 1-5 as active materials, add them to N-methyl-2-pyrrolidone according to the weight ratio of active material: carbon black: polyvinylidene fluoride (PVDF) of 8:1:1, use a mortar to fully grind for 40 minutes, then stir for 24 hours, use a 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 hours to obtain a negative electrode; assemble a lithium-ion battery in a Mikaelona Super (1220 / 750) glove box, use a lithium metal sheet as the positive electrode, a polypropylene microporous membrane (Celgard 2400) as a diaphragm, and the electrolyte is a 1M LiPF6 solution (the solvent is an equal volume of ethylene carbonate and dimethyl carbonate). The electrochemical performance of the assembled battery was tested on the Newwell CT-4800-5V10mA-164 battery test system, and the charge and discharge voltage range was 0.01-3V. The test results are shown in Table 1.

[0056] Table 1 Test results

[0057]

[0058] It can be seen from Table 1 that the artificial graphite prepared by the method of the present invention has a high degree of graphitization, and the prepared lithium ion battery has good cycle performance.

[0059] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing artificial graphite, characterized in that: The method comprises the following steps: mixing boric acid, water and anthracite for impregnation treatment, drying, mixing with a binder and nickel-plated carbon nanotubes for granulation, carbonizing, graphitizing, crushing and shaping to obtain artificial graphite.

2. The method for preparing artificial graphite according to claim 1, characterized in that: The volatile matter content of the anthracite is 8-10 wt %; preferably, the particle size of the anthracite is less than 200 meshes.

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

4. The method for preparing artificial graphite according to any one of claims 1 to 3, characterized in that: The anthracite is pretreated, and the pretreatment steps include: keeping the temperature at 400-500° C. for 30-40 minutes, and then keeping the temperature at 900-1000° C. for 60-90 minutes in an inert gas atmosphere.

5. The method for preparing artificial graphite according to any one of claims 1 to 4, characterized in that: The weight ratio of boric acid to anthracite is 1:5-15.

6. The method for preparing artificial graphite according to any one of claims 1 to 5, characterized in that: The dosage ratio of boric acid to water is 1g:40-60ml.

7. The method for preparing artificial graphite according to any one of claims 1 to 6, characterized in that: Soak at room temperature for 2.5-3.5 days.

8. The method for preparing artificial graphite according to any one of claims 1 to 7, 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 any one of claims 1 to 8, characterized in that: Both carbonization and graphitization are carried out in an inert gas atmosphere.

10. The method for preparing artificial graphite according to any one of claims 1 to 9, characterized in that: The carbonization temperature is 900-1000°C and the time is 8-10h; preferably, the graphitization temperature is 1400-1800°C and the time is 2-3h; preferably, the temperature is increased to 1400-1800°C at a rate of 4-6°C / min.

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