Preparation Method and Application of an Asphalt-Based Hard Carbon Composite Material

Abstract

An embodiment of the present invention discloses an asphalt-based hard carbon composite material. Using asphalt as a raw material, it is mixed and heated with a crosslinking agent and a heteroatom compound containing nitrogen and / or phosphorus, and acidic gas and alkaline gas are sequentially introduced for reaction. After carbonization, sodium metaaluminate and amorphous carbon are deposited on the material surface by magnetron sputtering and chemical vapor deposition methods. Relying on sodium metaaluminate to improve the sodium ion transport rate of the material and amorphous carbon to improve its electronic conductivity, and leveraging the synergistic effect between the two on the outer layer, the first efficiency and rate performance of the material are enhanced. By adding a crosslinking agent to the asphalt for reaction, a hard carbon with a porous turbostratic structure is formed to enhance the sodium storage function of the material; by introducing acidic gas and alkaline gas, active sites are generated, and the surface defects of the material are also reduced. During the charge and discharge process, sodium ions can be adsorbed at the active sites of the material, enhancing the reversible capacity of the material and the first efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage materials, relates to a negative electrode material for a battery, and in particular to a preparation method and application of an asphalt-based hard carbon composite material. Background Art

[0002] As a porous carbon material with short-range order, long-range disorder, and a turbostratic structure and low graphitization degree, the asphalt-based hard carbon used in sodium-ion batteries has defects such as low specific capacity (≤300 mAh / g) and low first efficiency (90 - 92%). Its main preparation method is the solid-phase method. The prior art realizes pore formation inside the hard carbon material through solid-phase mixing methods such as doping and sintering to improve the specific capacity of the material. However, the uneven distribution of pores will result in poor consistency of the material and low first efficiency. Although the first efficiency of the material can be improved by coating amorphous carbon on the surface of the material by liquid phase or solid phase, it will reduce its specific capacity and also affect its consistency. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, in order to improve the first efficiency and deposition efficiency of the hard carbon material, the present invention uses asphalt as the matrix, reacts with a cross-linking agent, and then reacts with an acidic gas and a basic gas in sequence to form porous hard carbon and reduce its surface defects, generate active sites, and then deposit sodium metaaluminate and amorphous carbon on the surface of the hard carbon to improve the first efficiency and fast charging performance of the material.

[0004] The technical object of the present invention is achieved through the following technical solutions:

[0005] The technical object of the first aspect of the present invention is to provide a preparation method of an asphalt-based hard carbon composite material, including:

[0006] Mix asphalt, a cross-linking agent, and a heteroatom compound containing nitrogen and / or phosphorus, heat and melt them, sequentially introduce an acidic gas and a basic gas to react, and carbonize to obtain a hard carbon precursor material;

[0007] Deposit sodium metaaluminate on the surface of the hard carbon precursor material by magnetron sputtering;

[0008] Introduce a carbon source gas, deposit amorphous carbon on the surface of the material by chemical vapor deposition to obtain the asphalt-based hard carbon composite material.

[0009] Further, the weight ratio of the asphalt, the cross-linking agent, and the heteroatom compound containing nitrogen and / or phosphorus is 100:10 - 30:1 - 5. The asphalt is first crushed before use.

[0010] Further, the crosslinking agent is selected from at least one of 5-chloro-2-methylbenzothiazole, 2-amino-5-nitrothiazole, 2-methylbenzothiazole, 2-fluorobenzothiazole, 2-aminobenzothiazole, 2-amino-5-ethyl-thiazole, 2-amino-4-methylbenzothiazole, and 2-mercaptobenzothiazole.

[0011] Further, the temperature of the heat melting is 200 - 300 °C, the temperature of the carbonization is 1000 - 1500 °C, and the time is 1 - 6 h.

[0012] Further, the acidic gas is selected from at least one of hydrogen sulfide, sulfur dioxide, sulfur trioxide, and nitrogen dioxide, the flow rate is 10 - 100 mL / min, and the introduction time is 30 - 300 min; the basic gas is selected from at least one of ammonia, phosphine, methylamine, dimethylamine, and trimethylamine, the flow rate is 10 - 100 mL / min, and the time is 30 - 300 min.

[0013] Further, the specific process of the magnetron sputtering method is as follows: Transfer the hard carbon precursor material into the magnetron sputtering cavity as the substrate, use sodium metaaluminate as the target, adjust the vacuum degree in the cavity to (1 - 10)×10 -3 Pa, then introduce argon gas, keep the pressure in the cavity at 1 - 10 Pa, then adjust the target current to 100 - 500 mA, the voltage to 1000 - 2000 V, and the sputtering time to 10 - 120 min.

[0014] Further, the temperature of the chemical vapor deposition method is 700 - 1000 °C, and the time is 1 - 6 h.

[0015] Further, the carbon source gas is selected from at least one of methane, acetylene, and ethylene, and the flow rate is 10 - 100 mL / min.

[0016] The technical object of the second aspect of the present invention is to provide the pitch-based hard carbon composite material prepared by the above preparation method. The material prepared by the present invention has sodium metaaluminate and amorphous carbon coated on the outer layer of the hard carbon, improving the sodium ion transport rate and the electron conductivity of the material.

[0017] The technical object of the third aspect of the present invention is to provide the application of the above pitch-based hard carbon composite material as a negative electrode material for a sodium ion battery or a lithium ion battery.

[0018] Implementing the technical solution of the present invention has the following beneficial effects:

[0019] (1) The composite material of the present invention coats a sodium metaaluminate layer and an amorphous carbon layer on the surface of hard carbon by magnetron sputtering and chemical vapor deposition. Relying on sodium metaaluminate to improve the sodium ion transport rate of the material and amorphous carbon to improve its electronic conductivity, and exerting the synergistic effect between the two outer layers, the first efficiency and rate performance of the material are improved;

[0020] (2) The present invention uses asphalt as the hard carbon matrix material. By adding a crosslinking agent, the asphalt is carbonized to form a hard carbon with a porous turbostratic structure, and the porous structure improves the sodium storage function of the material; at the same time, acidic gas and alkaline gas are introduced to generate active sites, and sodium ions can be adsorbed at the active sites of the material during charge and discharge; through the reaction process of acidic gas and alkaline gas, the surface defects of the material are also reduced, the reversible capacity of the material is improved, and the first efficiency is improved.

[0021] (3) The present invention uses magnetron sputtering to deposit sodium metaaluminate, which has the advantages of high deposition efficiency, strong bonding force between the core and the shell, and high density, improving the structural stability of the material and the cycle performance. Description of the Drawings

[0022] Figure 1 SEM image of the asphalt-based hard carbon composite material prepared in Example 1. Detailed Embodiments

[0023] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] Example 1

[0025] Step S1: Take 100 g of asphalt and crush it to a particle size D50 of 20 μm, then mix it evenly with 20 g of 5-chloro-2-methylbenzothiazole crosslinking agent and 3 g of phosphoric acid, heat it to 250 °C and melt it into a liquid state, then introduce acidic gas hydrogen sulfide (flow rate 50 mL / min) for 90 min, then change to introduce alkaline gas ammonia (flow rate 50 mL / min) for 90 min, and finally heat it to 1250 °C for high-temperature carbonization for 3 h to obtain a hard carbon precursor material;

[0026] Step S2: By magnetron sputtering, transfer the hard carbon precursor material into the magnetron sputtering cavity as the substrate, use sodium metaaluminate as the target, and adjust the vacuum degree in the cavity to 5×10 -3After Pa, argon gas is introduced, and the pressure in the cavity is maintained at 5 Pa. Then, the target current is adjusted to 300 mA, the voltage is 1500 V, and the sputtering time is 60 min to obtain an intermediate product.

[0027] Step S3: Then, the intermediate product is transferred to a tubular furnace. First, argon gas is introduced to exhaust the air in the tube. Then, methane gas is introduced, and deposition is carried out at a flow rate of 50 mL / min and a temperature of 800 °C for 3 h to deposit amorphous carbon on the material surface, obtaining an asphalt-based hard carbon composite material.

[0028] Example 2

[0029] Step S1: 100 g of asphalt is crushed to a particle size D50 of 20 μm, and then mixed evenly with 10 g of 2-amino-5-nitrothiazole crosslinking agent and 1 g of melamine and heated to 200 °C to melt into a liquid state. Then, acidic gas sulfur dioxide (flow rate 10 mL / min) is introduced for 300 min. Then, alkaline gas phosphine (flow rate 10 mL / min) is introduced for 300 min. Finally, it is heated to 1000 °C for high-temperature carbonization for 6 h to obtain a hard carbon precursor material.

[0030] Step S2: By magnetron sputtering method, the hard carbon precursor material is transferred to the magnetron sputtering cavity as a substrate, and sodium metaaluminate is used as the target. The vacuum degree in the cavity is adjusted to 1×10 -3 Pa, then argon gas is introduced, and the pressure in the cavity is maintained at 1 Pa. Then, the target current is adjusted to 100 mA, the voltage is 1000 V, and the sputtering time is 10 min to obtain an intermediate product.

[0031] Step S3: Then, the intermediate product is transferred to a tubular furnace. First, argon gas is introduced to exhaust the air in the tube. Then, ethylene gas is introduced, and deposition is carried out at a flow rate of 10 mL / min and a temperature of 700 °C for 6 h to deposit amorphous carbon on the material surface, obtaining an asphalt-based hard carbon composite material.

[0032] Example 3

[0033] Step S1: 100 g of asphalt is crushed to a particle size D50 of 20 μm, and then mixed evenly with 30 g of 2-methylbenzothiazole and 5 g of tetramethylurea and heated to 300 °C to melt into a liquid state. Then, acidic gas sulfur trioxide (flow rate 100 mL / min) is introduced for 30 min. Then, alkaline gas methylamine (flow rate 100 mL / min) is introduced for 30 min. Finally, it is heated to 1500 °C for high-temperature carbonization for 1 h to obtain a hard carbon precursor material.

[0034] Step S2: By magnetron sputtering method, the hard carbon precursor material is transferred to the magnetron sputtering cavity as a substrate, and sodium metaaluminate is used as the target. The vacuum degree in the cavity is adjusted to 10×10-3 At a pressure of 10 Pa, argon gas was introduced, and the pressure inside the cavity was maintained at 10 Pa. Then, the target current was adjusted to 500 mA, the voltage to 2000 V, and the sputtering time to 300 min to obtain an intermediate product.

[0035] Step S3: Then, the intermediate product was transferred to a tube furnace. First, argon gas was introduced to expel the air inside the tube, and then acetylene gas was introduced. Deposition was carried out at a flow rate of 100 mL / min and a temperature of 1000 °C for 1 h to deposit amorphous carbon on the material surface, obtaining an asphalt-based hard carbon composite material.

[0036] Comparative Example 1

[0037] Differing from Example 1, hydrogen sulfide acidic gas and ammonia basic gas were not introduced. Specifically:

[0038] Step S1: 100 g of asphalt was crushed to a particle size D50 of 20 μm, and then mixed evenly with 20 g of 5-chloro-2-methylbenzothiazole crosslinking agent and 3 g of phosphoric acid, and heated to 250 °C to melt into a liquid state. The reaction was carried out for 3 h, and finally the temperature was raised to 1250 °C for high-temperature carbonization for 3 h to obtain a hard carbon precursor material.

[0039] Step S2: By means of magnetron sputtering, the hard carbon precursor material was transferred to the magnetron sputtering cavity as a substrate, and sodium metaaluminate was used as the target material. The vacuum degree inside the cavity was adjusted to 5×10 -3 Pa, then argon gas was introduced, and the pressure inside the cavity was maintained at 5 Pa. Then, the target current was adjusted to 300 mA, the voltage to 1500 V, and the sputtering time was 60 min to obtain an intermediate product.

[0040] Step S3: Then, the intermediate product was transferred to a tube furnace. First, argon gas was introduced to expel the air inside the tube, and then methane gas was introduced. Deposition was carried out at a flow rate of 50 mL / min and a temperature of 800 °C for 3 h to deposit amorphous carbon on the material surface, obtaining a hard carbon composite material.

[0041] Comparative Example 2

[0042] Differing from Example 1, hydrogen sulfide acidic gas was not introduced. Specifically:

[0043] Step S1: 100 g of asphalt was crushed to a particle size D50 of 20 μm, and then mixed evenly with 20 g of 5-chloro-2-methylbenzothiazole crosslinking agent and 3 g of phosphoric acid, and heated to 250 °C to melt into a liquid state. The reaction was carried out for 90 min, and then basic gas ammonia (flow rate of 50 mL / min) was introduced for 90 min. Finally, the temperature was raised to 1250 °C for high-temperature carbonization for 3 h to obtain a hard carbon precursor material.

[0044] Step S2: By magnetron sputtering method, transfer the hard carbon precursor material into the magnetron sputtering cavity as the substrate, use sodium metaaluminate as the target, adjust the vacuum degree in the cavity to 5×10 -3 Pa, then introduce argon gas, keep the pressure in the cavity at 5 Pa, then adjust the target current to 300 mA, voltage to 1500 V, and the sputtering time is 60 min to obtain an intermediate product;

[0045] Step S3: Then transfer the intermediate product into a tube furnace, first introduce argon gas to discharge the air in the tube, then introduce methane gas, deposit amorphous carbon on the material surface at a flow rate of 50 mL / min and a temperature of 800 °C for 3 h to obtain a hard carbon composite material.

[0046] Comparative Example 3

[0047] Different from Example 1, do not introduce ammonia alkaline gas. Specifically:

[0048] Step S1: Take 100 g of pitch and crush it to a particle size D50 of 20 μm, then mix it evenly with 20 g of 5-chloro-2-methylbenzothiazole crosslinking agent and 3 g of phosphoric acid, heat it to 250 °C and melt it into a liquid state, then introduce acidic gas hydrogen sulfide (flow rate 50 mL / min), the introduction time is 90 min, then stop ventilation, keep the temperature for reaction for 90 min, and finally raise the temperature to 1250 °C for high-temperature carbonization for 3 h to obtain a hard carbon precursor material;

[0049] Step S2: By magnetron sputtering method, transfer the hard carbon precursor material into the magnetron sputtering cavity as the substrate, use sodium metaaluminate as the target, adjust the vacuum degree in the cavity to 5×10 -3 Pa, then introduce argon gas, keep the pressure in the cavity at 5 Pa, then adjust the target current to 300 mA, voltage to 1500 V, and the sputtering time is 60 min to obtain an intermediate product;

[0050] Step S3: Then transfer the intermediate product into a tube furnace, first introduce argon gas to discharge the air in the tube, then introduce methane gas, deposit amorphous carbon on the material surface at a flow rate of 50 mL / min and a temperature of 800 °C for 3 h to obtain a hard carbon composite material.

[0051] Comparative Example 4

[0052] Compared with Example 1, do not perform the operation of Step S2, and the others are the same as Example 1. Specifically:

[0053] Step S1: Take 100 g of asphalt and crush it to a particle size D50 of 20 μm. Then mix it evenly with 20 g of 5-chloro-2-methylbenzothiazole crosslinking agent and 3 g of phosphoric acid, and heat it to 250 °C to melt it into a liquid state. Then introduce acidic gas hydrogen sulfide (flow rate 50 mL / min) for 90 min. After that, change to introduce basic gas ammonia (flow rate 50 mL / min) for 90 min. Finally, raise the temperature to 1250 °C for high-temperature carbonization for 3 h to obtain a hard carbon precursor material;

[0054] Step S2: Then transfer the hard carbon precursor material to a tube furnace. First, introduce argon to exhaust the air in the tube. Then introduce methane gas, deposit for 3 h at a flow rate of 50 mL / min and a temperature of 800 °C to deposit amorphous carbon on the material surface to obtain a hard carbon composite material.

[0055] Comparative Example 5

[0056] Compared with Example 1, the operation of Step S3 is not carried out, and the others are the same as in Example 1. Specifically:

[0057] Step S1: Take 100 g of asphalt and crush it to a particle size D50 of 20 μm. Then mix it evenly with 20 g of 5-chloro-2-methylbenzothiazole crosslinking agent and 3 g of phosphoric acid, and heat it to 250 °C to melt it into a liquid state. Then introduce acidic gas hydrogen sulfide (flow rate 50 mL / min) for 90 min. After that, change to introduce basic gas ammonia (flow rate 50 mL / min) for 90 min. Finally, raise the temperature to 1250 °C for high-temperature carbonization for 3 h to obtain a hard carbon precursor material;

[0058] Step S2: By magnetron sputtering method, transfer the hard carbon precursor material to the magnetron sputtering cavity as the substrate, use sodium metaaluminate as the target, adjust the vacuum degree in the cavity to 5×10 -3 Pa, then introduce argon to keep the pressure in the cavity at 5 Pa. Then adjust the target current to 300 mA and the voltage to 1500 V, and the sputtering time is 60 min to obtain a hard carbon composite material.

[0059] Performance testing of the materials prepared in the above examples and comparative examples:

[0060] (1) SEM testing

[0061] Perform SEM testing on the asphalt-based hard carbon composite material prepared in Example 1, and the test results are as Figure 1 shown. It can be seen from Figure 1 that the composite material presents a granular structure, with a uniform size distribution, and the particle size D50 is between 5 μm - 10 μm.

[0062] (2) Physical and chemical properties

[0063] The interlayer spacing (D002), specific surface area, tapped density, particle size D50, and powder conductivity of the hard carbon composites prepared in Examples 1-3 and Comparative Examples 1-5 were measured. The test methods were carried out according to the methods of the national standard GBT-24533-2019 "Graphite Anode Materials for Lithium-Ion Batteries", and the XRD was used to test its interlayer spacing. The test results are shown in Table 1.

[0064] Table 1.

[0065]

[0066] (3) Coin cell test

[0067] The hard carbon composites in Examples 1-3 and Comparative Examples 1-5 were assembled into coin cells as the anode materials for sodium-ion batteries. The specific preparation method of the anode material was as follows: The hard carbon composite: CMC: SBR: SP: H 2 O was mixed at a mass ratio of 94:2.5:1.5:2:150 to prepare the anode sheet; the sodium sheet was used as the counter electrode; NaPF 6 (The solvent was EC: DEC: PC: polypropylene glycol polyoxypropylene ether = 1:2:1:0.05, and the concentration was 1.3 mol / L) was used as the electrolyte; the separator was a composite membrane of polyethylene PE, polypropylene PP, and polyethylene-propylene PEP. The coin cell assembly was carried out in a glove box filled with argon. The electrochemical performance was tested on a Wuhan Blue Electric CT2001A battery tester. The charge-discharge voltage range was 0.00V to 2.0V, and the charge-discharge rate was 0.1C. The first discharge capacity and the first efficiency of the coin cell were tested, and the rate performance (1C / 0.1C) was also tested. The test results are shown in Table 2. The test methods were determined according to the GBT-24533-2019 "Graphite Anode Materials for Lithium-Ion Batteries" standard. The test results are shown in Table 2.

[0068] Table 2.

[0069]

[0070] As can be seen from Table 1 and Table 2, the tapped density and powder conductivity of the hard carbon composites prepared in Examples 1-3 are greater than those of the materials prepared in Comparative Examples 1-5, and the first discharge capacity and the first efficiency are also better than those of the comparative examples. The reason is that sodium hypochlorite is deposited on its surface by magnetron sputtering to improve the first efficiency and its density of the material, and to improve the tapped density and powder conductivity of the material; by introducing acidic gas or alkaline gas, the defects of the material are reduced, the active sites of the material are increased, the irreversible capacity of the material is reduced, and the specific capacity and the first efficiency of the material are improved.

[0071] (4) Soft-pack battery test:

[0072] The hard carbon composite materials in the examples and comparative examples were mixed into a slurry and coated to prepare negative electrode sheets. Using layered oxide (NaFe 1 / 3 Mn 1 / 3 Ni 1 / 3 O 2 ) as the positive electrode and NaPF 6 (the solvent is EC:DEC:PC:propylene glycol polyoxypropylene ether = 1:2:1:0.05, concentration 1.3 mol / L) as the electrolyte, a 5 Ah soft-pack battery was prepared.

[0073] The cycle performance was tested: charge and discharge current 1.0C / 1.0C, voltage range 1.0 - 4.0V, cycle number 500 times, and its DCR was tested.

[0074] The rate performance was tested: the initial cycle DCR of the soft-pack battery and the constant current ratio under the condition of 2C charging were tested.

[0075] The test results are shown in Table 3.

[0076] Table 3.

[0077]

[0078] As can be seen from Table 3, compared with the comparative examples, the cycle performance and fast charging performance of the batteries prepared from the hard carbon composite materials prepared in Examples 1 - 3 are significantly better than those of the comparative examples. The reason is that depositing sodium metaaluminate by magnetron sputtering method has the advantages of high deposition efficiency, strong binding force between the core and the shell, high density, etc., which improves the structural stability of the material and the cycle performance; at the same time, introducing alkaline or acidic gas can increase the active sites of the material, improve the powder conductivity of the material, reduce the DCR and increase the constant current ratio.

[0079] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of an asphalt-based hard carbon composite material, comprising: mixing asphalt, a crosslinking agent and a heteroatom compound containing nitrogen and / or phosphorus, heating and melting, sequentially introducing an acidic gas and a basic gas for reaction, and carbonizing to obtain a hard carbon precursor material; depositing sodium metaaluminate on the surface of the hard carbon precursor material by magnetron sputtering; introducing a carbon source gas, and depositing amorphous carbon on the surface of the material by chemical vapor deposition to obtain the asphalt-based hard carbon composite material.

2. The preparation method according to claim 1, characterized in that the weight ratio of the asphalt, the crosslinking agent and the heteroatom compound containing nitrogen and / or phosphorus is 100:10-30:1-5.

3. The preparation method according to claim 1, characterized in that the crosslinking agent is selected from at least one of 5-chloro-2-methylbenzothiazole, 2-amino-5-nitrothiazole, 2-methylbenzothiazole, 2-fluorobenzothiazole, 2-aminobenzothiazole, 2-amino-5-ethyl-thiazole, 2-amino-4-methylbenzothiazole and 2-mercaptobenzothiazole.

4. The preparation method according to claim 1, characterized in that the temperature of the heating and melting is 200-300 °C, the temperature of the carbonization is 1000-1500 °C, and the time is 1-6 h.

5. The preparation method according to claim 1, characterized in that the acidic gas is selected from at least one of hydrogen sulfide, sulfur dioxide, sulfur trioxide and nitrogen dioxide, the flow rate is 10-100 mL / min, and the introduction time is 30-300 min; the basic gas is selected from at least one of ammonia, phosphine, methylamine, dimethylamine and trimethylamine, the flow rate is 10-100 mL / min, and the time is 30-300 min.

6. The preparation method according to claim 1, characterized in that The specific process of the magnetron sputtering method is as follows: Transfer the hard carbon precursor material to the magnetron sputtering cavity as the substrate, use sodium metaaluminate as the target, adjust the vacuum degree in the cavity to (1-10)×10 -3 Pa, then introduce argon gas to keep the pressure in the cavity at 1-10 Pa, then adjust the target current to 100-500 mA, the voltage to 1000-2000 V, and the sputtering time to 10-120 min.

7. The preparation method according to claim 1, characterized in that the temperature of the chemical vapor deposition is 700-1000 °C, and the time is 1-6 h.

8. The preparation method according to claim 1, characterized in that the carbon source gas is selected from at least one of methane, acetylene and ethylene, and the flow rate is 10-100 mL / min.

9. An asphalt-based hard carbon composite material prepared by the preparation method according to any one of claims 1-8.

10. Application of the asphalt-based hard carbon composite material according to claim 9 as a negative electrode material for a sodium ion battery or a lithium ion battery.

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