High-power artificial graphite as well as preparation method and application thereof

Abstract

The invention discloses high-power artificial graphite as well as a preparation method and application thereof, and belongs to the technical field of new energy. The invention discloses a preparation method of high-power artificial graphite, which comprises the following steps: S1, mixing a carbon-based raw material, phenolic resin and a pore-forming agent in an organic solvent, and graphitizing; the carbon-based raw material comprises at least one of petroleum coke powder, needle coke powder and pitch coke powder; the pore-forming agent comprises at least one of alkali metal nitrates; s2, dipping a product obtained in the step S1 in a solution containing graphene quantum dots, and drying; 3, adopting a CVD (chemical vapor deposition) method to generate graphene on the product obtained in the step S2 in situ; and S4, coating the surface of the product obtained in the step S3 with a carbon layer. According to the preparation method provided by the invention, the high-power use stability of the artificial graphite can be effectively improved. The invention also provides the high-power artificial graphite prepared by the preparation method and application of the high-power artificial graphite.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to high-power artificial graphite and a preparation method and application thereof. Background Art

[0002] Lithium-ion secondary batteries have now become the mainstream chemical power source and are widely used in most mobile terminal devices and new energy vehicles. They have the advantages of high operating voltage, high specific energy and long cycle life. In recent years, with the rapid development of power tools, drones, model airplanes and new energy vehicles, especially with the mass application of lithium-ion batteries in HEV hybrid vehicles and 12V / 48V vehicle start-stop systems, the power requirements for lithium-ion secondary batteries are getting higher and higher. The power is related to factors such as the rate of the electrode material and the voltage of the battery. Therefore, the electrode materials in actual production even need to meet the 30-40C rate charge and discharge requirements, but the current commercial negative electrode materials are difficult to meet this high-power charge and discharge requirements.

[0003] In order to solve the above problems, many explorations have been made in traditional technologies, such as coating and doping the mature graphite negative electrode materials, etc. However, the obtained graphite negative electrode materials still cannot meet the requirements of high power. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing high-power artificial graphite, which can effectively improve the high-power use stability of artificial graphite.

[0005] The invention also provides high-power artificial graphite prepared by the preparation method.

[0006] The invention also provides application of the high-power artificial graphite.

[0007] According to an embodiment of the first aspect of the present invention, a method for preparing high-power artificial graphite is provided, the preparation method comprising the following steps: S1. The carbon-based raw material, phenolic resin and pore-forming agent are mixed in an organic solvent and graphitized; The carbon-based raw material includes at least one of petroleum coke powder, needle coke powder and pitch coke powder; The pore former includes at least one of alkali metal nitrates; S2. The product obtained in step S1 is immersed in a solution containing graphene quantum dots and then dried; S3. In situ generation of graphene on the product obtained in step S2 by CVD method; S4. Coating a carbon layer on the surface of the product obtained in step S3.

[0008] The method for preparing high-power artificial graphite according to the embodiment of the present invention has at least the following beneficial effects: In step S1, the phenolic resin actually acts as a binder for the carbon-based raw material, which can fully fill the defects of the raw material. When the specific carbon-based raw material and the phenolic resin are combined, an artificial graphite with good uniformity, complete particles and good crystallinity can be obtained. The artificial graphite in this state has higher rate performance and thermal conductivity, laying the foundation for high power.

[0009] In step S1, the pore-forming agent will volatilize or generate gas during the graphitization process, thereby generating pores in the product obtained in step S1; at the same time, the pyrolysis product of the pore-forming agent includes oxidizing gas, so it will also oxidize the artificial graphite to a certain extent. Generally, the oxidation process will be accompanied by the process of increasing the interlayer spacing of the artificial graphite. That is, the presence of the pore-forming agent will increase the interlayer spacing of the high-power artificial graphite to a certain extent, broaden the channel for lithium ion deintercalation, and increase the rate performance of the high-power artificial graphite.

[0010] In step S1, the combination of raw materials is prepared so that the product after graphitization treatment has a multi-level porous structure of micropores (<2nm), mesopores (2~50nm) and macropores (50~500nm), which on the one hand shortens the diffusion path of lithium ions (mainly due to the role of mesopores), and on the other hand provides space for alleviating volume expansion for rapid charging and discharging (mainly due to the role of macropores).

[0011] In step S2 to step S3, graphene quantum dots act as seeds to guide the internal growth of graphene in the product obtained in step S1, such as vertical growth between layers, or modification of mesopores and macropores; compared with surface coating, the distribution of graphene in the present invention is more uniform, which significantly improves the electronic conductivity of the obtained artificial graphite; the newly generated graphene also forms an interlayer support for the high-power artificial graphite, further improving the operating stability of the obtained high-power artificial graphite.

[0012] Due to the oxidation in step S1, the edge of the artificial graphite obtained in step S3 is highly active and easily corroded by the electrolyte. Therefore, the coating in step S4 can significantly overcome this shortcoming and improve the structural stability of the obtained high-power artificial graphite during use.

[0013] According to some embodiments of the present invention, in step S1, the D50 particle size of the carbon-based raw material is 5-12 μm; for example, it can be about 6 μm, 7 μm, 8 μm, 9 μm, 10 μm or about 11 μm.

[0014] According to some embodiments of the present invention, in step S1, the ash content of the carbon-based raw material is ≤10wt%; for example, it may be about 8wt% or about 5wt%.

[0015] According to some embodiments of the present invention, in step S1, the carbon-based raw material includes needle coke powder.

[0016] According to some embodiments of the present invention, in step S1, the mass ratio of the carbon-based raw material to the phenolic resin is 10:1-2. For example, it can be about 10:1.2, 10:1.5 or about 10:1.8.

[0017] Combining the parameters of the carbon-based raw material and the phenolic resin, as well as the ratio of the two, can significantly improve the wettability between the carbon-based raw material and the phenolic resin, promote the phenolic resin to coat the surface of the carbon-based raw material, and repair obvious defects, so that the particle size and performance consistency of the resulting product are better. Furthermore, during use, the particles are stacked more closely, significantly improving the electronic and ionic conductivity of the negative electrode including the high-power artificial graphite.

[0018] According to some embodiments of the present invention, in step S1, the mass volume ratio of the carbon-based raw material to the organic solvent is 1 g: 0.5-1.5 mL, for example, about 1 g: 0.8 mL, 1 g: 1.0 mL or about 1 g: 1.2 mL.

[0019] According to some embodiments of the present invention, in step S1, the pore-forming agent includes lithium nitrate. In addition to the general function of the pore-forming agent, when lithium nitrate is used, a certain amount of lithium may remain in the obtained high-power artificial graphite, and the lithium acts as a lithium supplement to a certain extent, thereby improving the initial efficiency and capacity.

[0020] According to some embodiments of the present invention, in step S1, the amount of the pore-forming agent used is the saturated concentration capacity of the pore-forming agent in the organic solvent.

[0021] According to some embodiments of the present invention, in step S1, the mixing comprises the following steps: S1a. The organic solvent and the pore-forming agent are mixed to prepare a saturated solution; S1b. The phenolic resin is dispersed in the saturated solution; S1c. kneading the carbon-based raw material and the mixture obtained in step S1b.

[0022] According to some embodiments of the present invention, in step S1b, the dispersion temperature is 45-55°C; for example, it can be about 50°C. The time required for dispersion is not strictly limited. In actual production, the time can be flexibly adjusted according to the test volume, with the aim of obtaining a more uniform dispersion. Within the above temperature range, the time required for dispersion can be significantly shortened without damaging the overall performance of the phenolic resin.

[0023] According to some embodiments of the present invention, in step S1c, the kneading temperature is 45-55° C., for example, specifically about 50° C. Within this temperature range, the wettability between the carbon-based raw material and the phenolic resin can be improved.

[0024] According to some embodiments of the present invention, in step S1c, the kneading time is 4 to 6 hours; for example, it may be about 4.5 hours, 5 hours or about 5.5 hours.

[0025] According to some embodiments of the present invention, in step S1, the graphitization treatment is performed in a protective atmosphere. Specifically, the protective atmosphere includes at least one of nitrogen, helium or argon.

[0026] According to some embodiments of the present invention, in step S1, the temperature of the graphitization treatment is 1200-2800°C.

[0027] According to some embodiments of the present invention, in step S1, the graphitization treatment includes a first constant temperature platform, a second constant temperature platform and a third constant temperature platform performed in sequence. The temperature of the first constant temperature platform is 1200-1800° C., for example, it may be about 1400° C., 1500° C. or about 1600° C. This stage is pre-graphitization, and its main purpose is carbonization, that is, burning away the main impurities and initially obtaining a pore structure.

[0028] The duration of the first constant temperature platform is 0.5-1.5 hours; for example, it can be specifically about 1 hour.

[0029] The temperature of the second constant temperature platform is 2000-2500°C; for example, it may be about 2200°C, 2300°C or about 2400°C.

[0030] The duration of the second constant temperature platform is 0.5-1.5 hours; for example, it can be specifically about 1 hour.

[0031] The temperature of the third constant temperature platform is 2500-2800° C. For example, by specifically combining the temperatures of the second constant temperature platform and the third constant temperature platform, graphitization is fully achieved, the effect of graphitization is significantly improved, and the crystal phase purity of the obtained product is high.

[0032] The duration of the third constant temperature platform is 0.5-1.5 hours; for example, it can be specifically about 1 hour.

[0033] According to some embodiments of the present invention, step S1 further includes crushing and grading after the graphitization treatment. Thus, the D50 particle size of the obtained graphitization product is 8-15 μm; for example, it can be about 10 μm or about 12 μm. Since the subsequent graphene exists in the interlayer and pore structure, and the carbon layer coating is very thin, the particle size is basically equivalent to the particle size of the high-power artificial graphite.

[0034] According to some embodiments of the present invention, in step S2, the concentration of the graphene quantum dot solution is 1-5wt%, for example, about 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt% or about 4.5wt%.

[0035] According to some embodiments of the present invention, in step S2, the mass volume ratio of the product obtained in step S1 to the graphene quantum dot solution is 1 g: 5-15 mL, for example, about 1 g: 8 mL, 1 g: 10 mL or about 1 g: 12 mL.

[0036] According to some embodiments of the present invention, in step S2, the duration of the immersion is 10 to 60 minutes, for example, about 15 minutes, 20 minutes, 25 minutes, 30 minutes, 40 minutes or about 50 minutes.

[0037] According to some embodiments of the present invention, in step S2, the drying method includes freeze drying. Compared with other types of drying, freeze drying can retain the structure of the product to the greatest extent and avoid structural collapse.

[0038] According to some embodiments of the present invention, in step S3, the carrier gas of the CVD method is a mixture of argon and hydrogen.

[0039] According to some embodiments of the present invention, in step S3, the volume ratio of hydrogen to argon in the carrier gas is 5:90-100; for example, it may be about 5:95.

[0040] According to some embodiments of the present invention, in step S3, the graphene precursor includes at least one of methane, ethane, ethylene and acetylene.

[0041] According to some embodiments of the present invention, in step S3, the in-situ generation time of the graphene is 3 to 10 minutes, for example, about 5 minutes or about 8 minutes.

[0042] According to some embodiments of the present invention, in step S3, in the CVD method, the volume ratio of the graphene precursor to the carrier gas is 0.5-1.5:100, for example, about 0.8:100, 1.0:100 or about 1.2:100.

[0043] According to some embodiments of the present invention, in step S3, the temperature of the CVD method is 950-1150° C. For example, it may be about 1000° C.

[0044] According to some embodiments of the present invention, in step S3, the total flow rate of the carrier gas and the graphene precursor is 500-1000 sccm, for example, about 600 sccm, 800 sccm or about 900 sccm.

[0045] According to some embodiments of the present invention, in step S4, the specific operation of coating the carbon layer is: mixing the product obtained in step S3, the raw materials for preparing the carbon layer and the initiator in water for reaction and then heat treating.

[0046] According to some embodiments of the present invention, in step S4, the raw material for preparing the carbon layer includes a dopant; the dopant includes at least one of a nitrogen precursor and a phosphorus precursor. Thus, nitrogen doping or phosphorus doping can be performed in the shell layer; thereby, the adhesion strength between the shell layer and the core can be improved, and the conductivity of the shell layer can also be improved.

[0047] In actual production, the raw material for preparing the carbon layer may be only the dopant.

[0048] According to some embodiments of the present invention, the raw material for preparing the carbon layer includes at least one of pyrrole and aniline. In these embodiments, pyrrole and aniline also serve as dopants.

[0049] According to some embodiments of the invention, the initiator comprises ammonium persulfate.

[0050] According to some embodiments of the present invention, the mass ratio of the raw material for preparing the carbon layer to the initiator is 1:0.5-1; for example, it can be specifically about 1:0.8.

[0051] According to some embodiments of the present invention, in step S4, the mass ratio of the raw material for preparing the carbon layer to the product obtained in step S3 is 1:10-25. For example, it can be about 1:15 or about 1:20.

[0052] According to some embodiments of the present invention, the mass volume ratio of the product obtained in step S3 to water is 1 g: 5-15 mL, for example, about 1 g: 10 mL.

[0053] According to some embodiments of the present invention, the temperature for the mixed reaction of the product obtained in step S3 and the raw materials for preparing the carbon layer is 30-50° C.; for example, it may be specifically about 40° C.

[0054] According to some embodiments of the present invention, the time length for the mixed reaction of the product obtained in step S3 and the raw materials for preparing the carbon layer is 10 to 60 minutes; for example, it can be about 20 minutes, 30 minutes or about 40 minutes.

[0055] According to some embodiments of the present invention, in step S4, the heat treatment temperature when preparing the carbon layer is 500-1000°C; for example, it can be about 600°C, 700°C, 800°C or about 900°C.

[0056] According to some embodiments of the present invention, in step S4, the heat treatment time for preparing the carbon layer is 1 to 3 hours; for example, it can be about 1.5 hours, 2 hours or about 2.5 hours.

[0057] According to some embodiments of the present invention, in step S4, the heat treatment of preparing the carbon layer is performed in a protective atmosphere, wherein the protective atmosphere includes at least one of nitrogen and argon.

[0058] According to an embodiment of the second aspect of the present invention, there is provided a high-power artificial graphite prepared by the preparation method provided by the embodiment of the first aspect of the present invention, wherein the high-power artificial graphite has a core-shell structure; wherein: The core includes porous graphite and graphene grown inside and on the surface of the porous graphite; The shell is a carbon layer.

[0059] Since the high-power artificial graphite adopts all the technical solutions of the preparation method of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0060] According to some embodiments of the present invention, the shell is doped with N or P.

[0061] According to some embodiments of the present invention, the core has micropores, mesopores and macropores, wherein the volume percentage of the mesopores in the total pore volume is ≥50%, for example, about 60% or about 70%.

[0062] According to some embodiments of the present invention, the interlayer spacing of the high-power artificial graphite is greater than 0.345 nm, for example, about 0.35 nm, 0.36 nm, 0.37 nm or about 0.38 nm.

[0063] According to some embodiments of the present invention, the D50 particle size of the high-power artificial graphite is 8-15 μm.

[0064] According to an embodiment of the third aspect of the present invention, a lithium ion battery is provided, wherein the raw materials for preparing the lithium ion battery include the high-power artificial graphite provided by the second aspect of the present invention.

[0065] Since the lithium-ion battery adopts all the technical solutions of the high-power artificial graphite of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment.

[0066] According to some embodiments of the present invention, the lithium-ion battery includes at least one of a button battery, a soft-pack battery, a square-shell battery, and a cylindrical battery.

[0067] According to some embodiments of the present invention, the lithium-ion battery includes at least one of a symmetrical battery, a half-cell, and a full battery.

[0068] It should be noted that in the full battery, the high-power artificial graphite is used as the negative electrode active material, while the positive electrode active material, separator, electrolyte and other materials can be selected from commercial materials according to actual conditions, and the present invention does not make strict limitations.

[0069] According to an embodiment of the fourth aspect of the present invention, there is provided an application of the lithium-ion battery provided by the embodiment of the third aspect of the present invention in electric vehicles, drones and model aircraft.

[0070] Since the application adopts all the technical solutions of the lithium-ion battery of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment.

[0071] If there is no special explanation, the actual meaning of “about” in the present invention is that the error is allowed to be within the range of ±2%, for example, about 100 is actually 100±2%×100.

[0072] Unless otherwise specified, “between” in the present invention includes the number itself, for example, “between 2 and 3” includes the endpoint values ​​2 and 3.

[0073] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0074] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0075] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0076] Example 1 In this example, a high-power artificial graphite was prepared. The specific steps are as follows: S1. Prepare a saturated solution of lithium nitrate in ethanol using 6 mL of ethanol; Disperse 0.6 g of phenolic resin (model PF-6815, purchased from Shandong Shengquan Chemical Co., Ltd.) in the saturated solution at about 50° C. to obtain a mixed dispersion; At about 50°C, 5 g of carbon-based raw material needle coke powder (D50 particle size is about 6.5 μm; ash content ≤ 8 wt%) and the above mixed dispersion are kneaded for 5 hours; during this process, ethanol is basically volatilized; Under a nitrogen atmosphere, the kneaded product was treated at 1500° C. for 1 h, graphitized at 2400° C. for 1 h, and finally graphitized at 2800° C. for 1 h.

[0077] After the treatment, the product was crushed to obtain a graphitized product with a D50 particle size of about 11 μm.

[0078] S2. Under nitrogen protection, the product obtained in step S1 was impregnated in a solution containing graphene quantum dots and then freeze-dried; the impregnation time was 20 min; Graphene quantum dots were prepared according to the method in Example 1 of CN 112938950 B, with a mass concentration of about 1.6%.

[0079] The mass volume ratio of the product obtained in step S1 to the solution is 1 g:10 mL.

[0080] S3. In situ generation of graphene on the product obtained in step S2 by CVD method; wherein: The temperature of the CVD method is 1000°C, the carrier gas is a mixed gas of argon and hydrogen in a ratio of 95:5, and the carbon source is methane; the volume ratio of methane to carrier gas is 1:100; during the CVD process, the total gas flow rate is 800sccm; and the constant temperature of 1000°C is maintained for 8 minutes.

[0081] S4. Coating the surface of the product obtained in step S3 with a carbon layer. The specific operation is: The product obtained in step S3 is dispersed in water at a ratio of 1 g:10 mL; pyrrole and ammonium persulfate are added to the obtained dispersion; after mixing at 40° C. for 30 min, the filter is filtered and the filter cake is dried; the mass ratio of pyrrole to the product obtained in step S3 is 1:15; the mass ratio of pyrrole to ammonium persulfate is 1:0.7.

[0082] Under nitrogen protection, the dried filter cake was heat treated at 800°C for 1.5 h.

[0083] Example 2 This example provides a method for preparing high-power artificial graphite, which is different from Example 1 in that: In step S1, the amount of ethanol used is 3 mL; correspondingly, the amount of the pore-forming agent used is reduced by half.

[0084] Example 3 This example provides a method for preparing high-power artificial graphite, which is different from Example 1 in that: In step S3, the duration of the CVD method is 3 minutes.

[0085] Comparative Example 1 This example provides a method for preparing artificial graphite, which is different from Example 1 in that: In step S1, no pore-forming agent is added.

[0086] Comparative Example 2 This example provides a method for preparing artificial graphite, which is different from Example 1 in that: Steps S2~S3 are not included.

[0087] Comparative Example 3 This example provides a method for preparing artificial graphite, which is different from Example 1 in that: In step S1, the phenolic resin is replaced with an equal amount of medium-temperature asphalt.

[0088] Comparative Example 4 This example provides a method for preparing artificial graphite, which is different from Example 1 in that: Step S2 is not included.

[0089] Application Examples The first aspect of this example provides a 2025 button cell, wherein the preparation method of the button half cell is as follows: 95.5% of the artificial graphite obtained in the embodiment and the comparative example, 1.5% of carbon black, 1.5% of styrene-butadiene rubber (SBR) and 1.5% of sodium carboxymethyl cellulose (CMC) were stirred in water to prepare a negative electrode slurry, and then the slurry was coated on a battery-grade copper foil and dried in a vacuum oven at 110°C for 4 hours, and the nitrogen-doped carbon-coated graphite negative electrode sheet was prepared by rolling the sheet. The surface density of the artificial graphite negative electrode sheet is 10 mg / cm 2 , compacted density is 1.65g / cm 3 ; The counter electrode is a metal lithium sheet, the separator is polyethylene, the electrolyte includes 1M LiPF6 and a solvent (the solvent includes ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), and the volume ratio is 1:1:1), and a button half-cell is prepared.

[0090] The second aspect of this example provides a soft pack battery, wherein the preparation method of the soft pack battery is as follows: Negative electrode separator and electrolyte: same as button cell.

[0091] Positive electrode: Add lithium nickel cobalt manganese oxide (NCM111) with a D50 of 2μm to 4μm, conductive carbon black and PVDF in a proper amount of N-methylpyrrolidone (NMP) solvent at a mass percentage of 94%, 3%, and 3%, respectively, and stir to obtain a positive electrode slurry with a solid content of 76%. The positive electrode sheet is obtained through coating, rolling and die-cutting processes.

[0092] Test Case In the first aspect of this example, the physical and chemical properties of the artificial graphite obtained in the embodiment and the comparative example were tested, specifically: Interlayer spacing: The test method is XRD test to calculate the lattice spacing; Porosity: The test method is BET, and the pore volume occupancy of the mesopores is calculated; Particle size: laser particle size analyzer, record D50 result (keep one decimal place); The test results of the above two aspects are shown in Table 1: From the results, the high-power artificial graphite provided by the present invention has two main reasons for the improvement of the interlayer spacing. One is the synergistic effect between the carbon-based raw materials and the phenolic resin; the other is the oxidation provided by the pore-forming agent. Specifically, the phenolic resin is replaced with asphalt in Comparative Example 3, and the pore-forming agent is not included in Comparative Example 1. In these two examples, the interlayer spacing of the obtained artificial graphite is significantly reduced, and the path of lithium ion deintercalation is narrowed. It can be expected that its rate performance will be significantly reduced. Comparing Example 1 and Example 2, similar interlayer spacing change trends can also be obtained. In addition, comparing the results of Example 1, Example 3 and Comparative Example 2, it can be seen that in the process of preparing graphene by CVD, the growth of graphene has a certain orientation, which may affect the measurement of the interlayer spacing of artificial graphite. Specifically, the higher the amount of graphene, the lower the interlayer spacing has a certain tendency to decrease. In Comparative Example 4, step S2 is omitted, i.e., the seeds for graphene growth are lacking. In step S3, the growth of graphene increases randomness and tends to coat the surface rather than modify the macropores and mesopores. Therefore, judging from the test results, the interlayer spacing is improved to a certain extent.

[0093] Since step S1 is the same in the embodiment and the comparative example, and the subsequent graphene deposition and carbon layer preparation have little effect on the particle size, the particle sizes of the artificial graphites obtained in the embodiment and the comparative example are comparable.

[0094] The porosity is mainly related to the amount of pore-forming agent used, and the pore structure formed by the pore-forming agent is more of a mesoporous structure, thus forming the result trend of Examples 1, 2 and Comparative Example 1, that is, the amount of mesopores decreases, and the amount of macropores and micropores increases relatively. In addition, graphene has a certain pore-filling effect, filling more macropores and a small amount of mesopores, thus forming the result trend of Examples 1, Example 3 and Comparative Example 2, that is, the amount of macropores increases relatively, while the actual content of micropores and mesopores is not much different, and their relative values ​​decrease. As described above, in Comparative Example 4, it is equivalent to forming a uniform and dense coating, and the overall pore structure decreases; the distribution regularity of the pore structure disappears.

[0095] The second aspect of this example tests the first reversible capacity and first efficiency of the button cell obtained in the application example; specifically: the 1C current is set to 370mA / g; the test voltage is 0.005V~2.0V; and the test rate is 0.5C charge and discharge.

[0096] The third aspect of this example tests the rate performance and long cycle performance of the soft-pack battery obtained in the application example; specifically, the test voltage range is 2.5~4.2V; the test conditions for the rate performance are that the charging rate is 1C, and the discharge gram-to-gram capacity at 1C, 2C, 5C, and 10C discharge rates are tested; the charging rate of the cycle test is 1C, and the discharge rate is 5C; the capacity retention rate after 100 weeks and 800 weeks is tested.

[0097] The test results of the second and third aspects of this example are shown in Table 2: Comparing the results of the examples and comparative examples, it can be seen that if the amount of pore-forming agent added is small, the mesopore content formed is small, the channels for lithium ion deintercalation are small, and the corresponding rate performance and first efficiency of the obtained artificial graphite are reduced; the corresponding pore structure is reduced, and the volume change of artificial graphite during charging and discharging is difficult to alleviate, which will also lead to a decrease in the high-rate long cycle results. If the content of graphene decreases, on the one hand, the deintercalation channel of lithium ions will be smoother, which may improve the rate performance, but on the other hand, due to the decrease in electronic conductivity, the rate performance will decrease, and the lack of support between the layers will reduce the high-rate cycle performance; however, from the results, the latter has a greater role weight. In comparative example 4, since graphene is more coated, there is a lack of interlayer support, and the uniformity of conductivity deteriorates. Although the coating can alleviate the erosion of the electrolyte on the artificial graphite material, the overall performance is still significantly reduced. The decrease in the results in comparative example 3 shows that in the preparation method provided by the present invention, a significant synergistic effect occurs between the preparation raw materials, which has a significant positive effect on the establishment of multi-level pore structure and spatial structure.

[0098] In summary, the preparation method of high-power artificial graphite provided by the present invention has excellent capacity, first efficiency, rate and cycle of the obtained high-power artificial graphite due to the limitation of the preparation raw materials and preparation conditions. Therefore, the obtained high-rate artificial graphite is expected to be widely used in fast-discharging electronic products such as electric vehicles, drones and model airplanes.

[0099] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing high-power artificial graphite, characterized in that: The preparation method comprises the following steps: S1. The carbon-based raw material, phenolic resin and pore-forming agent are mixed in an organic solvent and graphitized; The carbon-based raw material includes at least one of petroleum coke powder, needle coke powder and pitch coke powder; The pore former includes at least one of alkali metal nitrates; S2. The product obtained in step S1 is immersed in a solution containing graphene quantum dots and then dried; S3. In situ generation of graphene on the product obtained in step S2 by CVD method; S4. Coating a carbon layer on the surface of the product obtained in step S3.

2. The preparation method according to claim 1, characterized in that: In step S1, the mass ratio of the carbon-based raw material to the phenolic resin is 10:1-2.

3. The preparation method according to claim 1, characterized in that: In step S1, the mass volume ratio of the carbon-based raw material and the organic solvent is 1 g: 0.5-1.5 mL.

4. The preparation method according to claim 1, characterized in that: In step S3, the in-situ generation time of the graphene is 3 to 10 minutes.

5. The preparation method according to claim 1, characterized in that: In step S4, the raw material for preparing the carbon layer includes a dopant; the dopant includes at least one of a nitrogen precursor and a phosphorus precursor.

6. A high-power artificial graphite prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The high-power artificial graphite has a core-shell structure; wherein, The core includes porous graphite and graphene grown inside and on the surface of the porous graphite; The shell is a carbon layer.

7. The high-power artificial graphite according to claim 6, characterized in that: The shell is doped with N or P.

8. The high-power artificial graphite according to claim 6, characterized in that: The core has micropores, mesopores and macropores; wherein the volume percentage of the mesopores in all pore volumes is ≥50%.

9. A lithium ion battery, characterized in that: The raw material for preparing the lithium-ion battery includes the high-power artificial graphite as described in any one of claims 6 to 8.

10. Use of the lithium-ion battery as claimed in claim 9 in electric vehicles, unmanned aerial vehicles and model aircraft.

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