Preparation method of fast-charging coated asphalt for negative electrode

Abstract

The preparation method comprises the following steps: preheating ethylene tar, mixing with a cross-linking agent, uniformly stirring, introducing air, heating to 260-280 DEG C for the first time, carrying out constant-temperature thermal polycondensation for the first time, introducing nitrogen to replace air, heating to 400-420 DEG C for the second time, and carrying out constant-temperature thermal polycondensation for the second time, the high-softening-point asphalt is obtained. The time period of the production process is greatly shortened, the process steps are reduced, the number of equipment and energy consumption are reduced, the production cost of the final product is reduced, and the competitiveness is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coating of negative electrode materials of lithium batteries, and in particular to a method for preparing asphalt for negative electrode fast charging coating. Background Art

[0002] With the rapid development of new energy vehicles, energy storage market and fast-moving consumer electronics, the demand for lithium-ion products has shown explosive growth. In 2022, domestic lithium battery shipments reached 650 GWh, and it is expected to reach 1.8 TWh in 2025. Driven by the combined efforts of power batteries, energy storage batteries and consumer batteries, the market demand for coated asphalt materials used in the modification of negative electrode materials for lithium-ion batteries has increased significantly, and will continue to grow until at least 2030. At present, natural graphite, as a negative electrode material for lithium-ion batteries, will continue to consume active lithium during the battery cycle due to structural defects and more surface side reactions, resulting in a certain degree of decline in battery cycle life performance, fast charge rate performance, energy density performance and first effect. As the mainstream graphite product in China, artificial graphite, especially when the demand for fast charging continues to increase, it is increasingly necessary to carry out coating treatment to reduce the specific surface area and improve the wettability of the electrolyte. As a must-have for negative electrode modification and upgrading, coating materials coat the surface of graphite with a layer of amorphous carbon, which not only retains the high capacity and low voltage of graphite, but also has good compatibility with the electrolyte, which can significantly improve its rate performance and cycle performance.

[0003] According to statistics, the amount of coated asphalt accounts for about 10% of negative electrode materials. In 2022, China shipped 1.2 million tons of negative electrode materials, and the amount of coated asphalt was about 130,000 tons. According to the new energy vehicle development plan, by 2025, China's new energy vehicle sales will reach 14.35 million units, accounting for about 50%. In 2020, China's new energy vehicle sales were 1.367 million units, accounting for only 10.9%, which has great growth prospects. It is estimated that in 2025, the total demand for negative electrode materials in my country will be 2.5 million tons, and the demand for coating asphalt will be nearly 300,000 tons, with a market size of more than 5 billion yuan, of which China's demand accounts for more than 80% of the global demand.

[0004] At present, the raw materials for the preparation of coated asphalt at home and abroad are divided into coal tar asphalt and petroleum asphalt. The preparation methods mainly involve separation technology and modification technology. The separation technology is mainly vacuum flash evaporation and short-range molecular distillation. The modification technology is mainly air oxidation, thermal polymerization and catalytic cross-linking. In the actual production process, the separation technology can be used alone according to the characteristics of the raw materials and production needs, or the modification technology can be used in combination with the separation technology.

[0005] Among them, the air oxidation method is to first add the raw materials into the reactor and heat them to the reaction temperature. During the heating process, the raw materials are continuously stirred and a certain amount of air is introduced as an oxidant. The reaction is carried out at a constant temperature for a period of time. After the reaction is completed, the coated asphalt product is obtained. The principle is that the asphalt molecules undergo an oxidative cross-linking reaction under the oxidation of air to form larger spatial configuration macromolecules, which can improve the product performance and yield of the coated asphalt. This method is simple to operate and has many applications, but the reaction time is long and it can only be operated intermittently.

[0006] Due to factors such as the high content of light components in ethylene tar, light components will polymerize at higher temperatures, making it difficult to obtain asphalt raw materials with higher softening points. In view of the characteristics of the ethylene tar air oxidation method, relevant practitioners have made improvements. Therefore, some researchers have used the oxidative crosslinking-thermal polycondensation method for modification. This process is mainly divided into two steps: oxidative crosslinking and high-temperature thermal polycondensation. Other researchers have also found through research on the preparation of high-purity mesophase asphalt that when using ethylene tar and boron trifluoride ether complex to catalyze the polymerization of mesophase asphalt, adding 30% (w) of refined naphthalene can reduce the pressure, thereby changing the polarization structure of the mesophase asphalt, and obtaining a streamlined polarization structure of 100% of the mesophase asphalt, thereby obtaining a high thermal conductivity asphalt-based carbon fiber with a thermal conductivity of 730W / (m·K). The above-mentioned related processes have long production cycles, complex process control, high equipment energy consumption, high production costs of the final products, and limited competitiveness. Summary of the invention

[0007] The object of the present invention is to provide a method for preparing asphalt for negative electrode fast charging coating to solve one or more of the above-mentioned prior art problems.

[0008] The present invention provides a method for preparing asphalt for negative electrode fast charging coating, comprising the following steps: preheating ethylene tar and mixing it with a cross-linking agent, stirring evenly and introducing air, heating it to 260-280° for the first time and performing a first constant temperature thermal polycondensation, introducing nitrogen to replace the air, heating it to 400-420° for the second time and performing a second constant temperature thermal polycondensation to obtain the high softening point asphalt.

[0009] In some embodiments, the C / H mass ratio of the ethylene tar is 1.1, the N element content is 0.03%, the S element content is 0.04%, and the ash content is 0.06%.

[0010] In some embodiments, the cross-linking agent is selected from maleic anhydride, diammonium hydrogen phosphate, polyoxygen atom compounds, alkylbenzene sulfonic acids, unsaturated fatty acids, petroleum cyclopentane acid compounds or unsaturated olefins, alkyne organic matter and a combination of the above solvents. Preferably, the cross-linking agent is maleic anhydride or diammonium hydrogen phosphate.

[0011] In some embodiments, the softening point of the high softening point asphalt is above 235 °C. Preferably, the softening point of the high softening point asphalt is above 255 °C.

[0012] In some embodiments, the mass ratio of the ethylene tar to the cross-linking agent is 3%-7%.

[0013] In some embodiments, the preheating temperature of the ethylene tar is 150°, and the preheating time is 30 minutes.

[0014] In some embodiments, the air has a gas velocity of 1 L / min.

[0015] In some embodiments, the first heating rate is 6° C. / min, and the time of the first isothermal thermal polycondensation is 3-7 h.

[0016] In some embodiments, the nitrogen gas has a gas rate of 0.9 L / min.

[0017] In some embodiments, the second heating rate is 6° C. / min, and the time of the second isostatic heat polycondensation is 3-7 h.

[0018] Beneficial effects of the present invention: The present invention proposes a process for preparing high softening point asphalt for graphite coating in one step and one pot using ethylene tar, which greatly shortens the production process cycle, reduces the process steps, reduces the number of equipment and energy consumption, reduces the production cost of the final product, and greatly improves competitiveness. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the examples. The following examples are only used to more clearly illustrate the performance of the present invention, and are not limited to the following examples.

[0020] 240 g of ethylene tar (C / H mass ratio of 1.1, N element content of 0.03%, S element content of 0.04%, ash content of 0.06%) was preheated at 150 °C for 30 min, and then 10 g of maleic anhydride, a crosslinking agent, was added, stirred evenly, and air was introduced at a gas rate of 1 L / min. The temperature was raised to 270 °C at a rate of 6 °C / min and heat-condensed at a constant temperature for 5 h. Subsequently, the introduced air was replaced with N2 at a gas rate of 0.9 L / min, and the temperature was further raised to 410 °C at a rate of 6 °C / min and heat-condensed at a constant temperature for 3 h. 103.5 g of ethylene tar-based asphalt was prepared with a yield of 43.12%, a softening point of 287 °C, a TI content of 76%, a QI content of 2.1%, a carbon residue rate of 71% at 850 °C, and an aromaticity of 0.85.

[0021] The difference between Example 2 and Example 1 is that the mass ratio of ethylene tar to cross-linking agent is 7%.

[0022] The difference between Example 3 and Example 1 is that the mass ratio of ethylene tar to cross-linking agent is 3%.

[0023] The difference between Example 4 and Example 1 is that the carbon-to-hydrogen ratio of ethylene tar is greater than 1.1.

[0024] The difference between Example 5 and Example 1 is that the carbon-to-hydrogen ratio of ethylene tar is less than 1.1.

[0025] The difference between Example 6 and Example 1 is that the first heating is carried out at a heating rate of 6°C / min to 290°C and the first constant temperature heat shrinkage is carried out for 7h.

[0026] The difference between Example 7 and Example 1 is that the first heating is carried out at a heating rate of 6°C / min to 290°C and the first constant temperature heat shrinkage is carried out for 3 hours.

[0027] The difference between Example 8 and Example 1 is that the second heating is carried out at a heating rate of 6°C / min to 450°C and the second constant temperature heat shrinking is carried out for 7h.

[0028] The difference between Example 9 and Example 1 is that the second heating is carried out at a heating rate of 6° C. / min to 450° C. and the second constant temperature heat shrinkage is carried out for 3 hours.

[0029] The difference between Comparative Example 1 and Example 1 is that no crosslinking agent is added.

[0030] The difference between Comparative Example 2 and Example 1 is that no air is introduced.

[0031] The performance data of Examples 1-9 and Comparative Examples 1-2 are as follows: From the above results, it can be seen that through the above process improvements, ethylene tar can be used to prepare highly softened asphalt above 255°C, and the process time is reduced from 14h to 8h, the corresponding multi-stage reaction tank equipment is also reduced accordingly, and energy consumption is also reduced at the same time.

[0032] The innovative process of this patent comprehensively considers the multi-step thermal polycondensation reaction process of high-soft asphalt. On the basis of air thermal polycondensation, a cross-linking agent is added to accelerate the rapid thermal polycondensation reaction of organic free radicals under low temperature conditions, thereby rapidly and orderly polymerizing small molecules to obtain highly polymerized asphalt materials. At the same time, it is necessary to reasonably control the experimental parameters to prevent excessive polymerization and coking, and control the proportion of corresponding toluene insolubles (TI) and quinoline insolubles (QI).

[0033] Therefore, the present invention proposes a process for preparing high softening point asphalt for graphite coating in one step and one pot using ethylene tar. The production process time cycle is greatly shortened, the process steps are reduced, the number of equipment and energy consumption are reduced, the production cost of the final product is reduced, and the competitiveness is greatly improved.

[0034] The above description is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the creative concept of the present invention, and these should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing asphalt for negative electrode fast charging coating, characterized in that: The following steps are involved: The ethylene tar is preheated and mixed with the crosslinking agent, stirred evenly and introduced with air, heated to 260-280° for the first time and subjected to a first constant temperature heat polycondensation, nitrogen is introduced to replace the air, heated to 400-420° for the second time and subjected to a second constant temperature heat polycondensation to obtain the high softening point asphalt.

2. The method according to claim 1, characterized in that The C / H mass ratio of the ethylene tar is 1.1, the N element content is 0.03%, the S element content is 0.04%, and the ash content is 0.06%.

3. The method according to claim 1, characterized in that The crosslinking agent is selected from maleic anhydride, diammonium hydrogen phosphate, polyoxygen atom compounds, alkylbenzene sulfonic acids, unsaturated fatty acids, petroleum cyclopentane acid compounds or unsaturated olefins, alkyne organic matter and a combination of the above solvents. Preferably, the crosslinking agent is maleic anhydride or diammonium hydrogen phosphate.

4. The method according to claim 1, characterized in that: The softening point of the high softening point asphalt is above 235 °C. Preferably, the softening point of the high softening point asphalt is above 255 °C.

5. The method according to claim 1, characterized in that The mass ratio of the ethylene tar to the cross-linking agent is 3%-7%.

6. The method according to claim 1, characterized in that The preheating temperature of the ethylene tar is 150°, and the preheating time is 30 minutes.

7. The method according to claim 1, characterized in that The air velocity is 1 L / min.

8. The method according to claim 1, characterized in that The first heating rate is 6°C / min, and the time of the first constant temperature thermal polycondensation is 3-7h.

9. The method according to claim 1, characterized in that: The gas velocity of the nitrogen gas was 0.9 L / min.

10. The method according to claim 1, characterized in that The second heating rate is 6°C / min, and the time of the second constant temperature thermal polycondensation is 3-7h.

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