A high-power artificial graphite and its preparation method and application

Abstract

The present invention discloses a high-power artificial graphite and its preparation method and application, belonging to the field of new energy technology. The present invention discloses a preparation method of high-power artificial graphite, which comprises the following steps: S1. mixing a carbon-based raw material, a phenolic resin and a pore-forming agent in an organic solvent and graphitizing the mixture; 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. immersing the product obtained in step S1 in a solution containing graphene quantum dots and then drying the mixture; 3. in-situ generating graphene on the product obtained in step S2 by CVD; S4. coating the surface of the product obtained in step S3 with a carbon layer. The preparation method provided by the present invention can effectively improve the high-power use stability of artificial graphite. The present invention also provides high-power artificial graphite obtained by the above preparation method and its application.

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 become the mainstream chemical power source, widely used in most mobile devices and new energy vehicles. They offer advantages such as high operating voltage, high specific energy, and long cycle life. In recent years, with the rapid development of power tools, drones, model aircraft, and new energy vehicles, and particularly with the mass adoption of lithium-ion batteries in HEVs and 12V / 48V in-vehicle start-stop systems, the power requirements for lithium-ion secondary batteries have become increasingly demanding. Power is related to factors such as the rate capability of the electrode material and the battery voltage. Therefore, in actual production, electrode materials must even meet 30-40C rate charge and discharge requirements. However, currently commercialized negative electrode materials struggle to meet these high-power charge and discharge requirements.

[0003] To solve the above problems, many explorations have been made in conventional technologies, such as coating and doping the now mature graphite negative electrode materials. 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 present invention also provides high-power artificial graphite prepared by the above preparation method.

[0006] The present invention also provides applications 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:

[0008] S1. The carbon-based raw material, phenolic resin and pore-forming agent are mixed in an organic solvent and graphitized;

[0009] The carbon-based raw material comprises at least one of petroleum coke powder, needle coke powder and pitch coke powder;

[0010] The pore-forming agent includes at least one of alkali metal nitrates;

[0011] S2. The product obtained in step S1 is immersed in a solution containing graphene quantum dots and then dried;

[0012] S3. In situ generation of graphene on the product obtained in step S2 by CVD;

[0013] S4. Coating a carbon layer on the surface of the product obtained in step S3.

[0014] The method for preparing high-power artificial graphite according to the embodiment of the present invention has at least the following beneficial effects:

[0015] In step S1, the phenolic resin effectively acts as a binder for the carbon-based raw material, fully filling any imperfections in the raw material. When the specific carbon-based raw material and phenolic resin are combined, a uniform, fully crystallized artificial graphite is obtained. This artificial graphite exhibits enhanced rate performance and thermal conductivity, laying the foundation for high power.

[0016] During the graphitization process in step S1, the pore-forming agent volatilizes or generates gases, thereby creating pores in the product obtained in step S1. Furthermore, the pyrolysis products of the pore-forming agent include oxidizing gases, which can also oxidize the artificial graphite to some extent. This oxidation process is typically accompanied by an increase in the interlayer spacing of the artificial graphite. In other words, the presence of the pore-forming agent increases the interlayer spacing of the high-power artificial graphite, broadens the channels for lithium ion insertion and extraction, and improves the rate performance of the high-power artificial graphite.

[0017] In step S1, a 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). On the one hand, it shortens the diffusion path of lithium ions (mainly due to the role of mesopores), and on the other hand, it provides space to alleviate volume expansion for rapid charging and discharging (mainly due to the role of macropores).

[0018] In steps S2 to S3, graphene quantum dots act as seeds to guide the internal growth of graphene in the product obtained in step S1, for example, 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, significantly improving the electronic conductivity of the obtained artificial graphite; the newly generated graphene also forms interlayer support for the high-power artificial graphite, further improving the operational stability of the obtained high-power artificial graphite.

[0019] Due to the oxidation in step S1, the edges of the artificial graphite obtained in step S3 are 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.

[0020] 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.

[0021] According to some embodiments of the present invention, in step S1, the ash content of the carbon-based raw material is ≤10 wt%; for example, it may be about 8 wt% or about 5 wt%.

[0022] According to some embodiments of the present invention, in step S1, the carbon-based raw material includes needle coke powder.

[0023] 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, about 10:1.2, 10:1.5, or about 10:1.8.

[0024] By combining the parameters of the carbon-based raw material and the phenolic resin, as well as the ratio of the two, the wettability between the carbon-based raw material and the phenolic resin can be significantly improved, which can 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 tightly, which significantly improves the electronic and ionic conductivity of the negative electrode including the high-power artificial graphite.

[0025] 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.

[0026] 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 high-power artificial graphite produced. This lithium acts as a lithium supplement to a certain extent, improving the initial efficiency and capacity.

[0027] 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.

[0028] According to some embodiments of the present invention, in step S1, the mixing includes the following steps:

[0029] S1a. The organic solvent and the pore-forming agent are mixed to prepare a saturated solution;

[0030] S1b dispersing the phenolic resin in the saturated solution;

[0031] S1c. kneading the carbon-based raw material and the mixture obtained in step S1b.

[0032] According to some embodiments of the present invention, in step S1b, the dispersion temperature is 45-55°C; for example, it can be approximately 50°C. The dispersion time is not strictly limited; in actual production, the time can be flexibly adjusted based on the test volume to obtain a more uniform dispersion. Within this temperature range, the dispersion time can be significantly shortened without compromising the overall performance of the phenolic resin.

[0033] According to some embodiments of the present invention, in step S1c, the kneading temperature is 45-55° C., for example, about 50° C. Within this temperature range, the wettability between the carbon-based raw material and the phenolic resin can be improved.

[0034] According to some embodiments of the present invention, in step S1c, the mixing time is 4 to 6 hours; for example, it can be about 4.5 hours, 5 hours or about 5.5 hours.

[0035] 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.

[0036] According to some embodiments of the present invention, in step S1, the temperature of the graphitization treatment is 1200-2800°C.

[0037] According to some embodiments of the present invention, in step S1, the graphitization treatment includes sequentially performing a first constant temperature platform, a second constant temperature platform, and a third constant temperature platform.

[0038] The temperature of the first constant temperature platform is 1200-1800° C., for example, about 1400° C., 1500° C., or about 1600° C. This stage is pre-graphitization, and its main purpose is carbonization, that is, burning away major impurities and initially obtaining a pore structure.

[0039] The duration of the first constant temperature platform is 0.5-1.5 hours; for example, it can be about 1 hour.

[0040] The temperature of the second constant temperature platform is 2000-2500°C; for example, it can be about 2200°C, 2300°C or about 2400°C.

[0041] The duration of the second constant temperature platform is 0.5-1.5 hours; for example, it can be about 1 hour.

[0042] 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 graphitization effect is significantly improved, and the purity of the crystalline phase in the obtained product is high.

[0043] The duration of the third constant temperature platform is 0.5-1.5 hours; for example, it can be about 1 hour.

[0044] According to some embodiments of the present invention, step S1 further includes crushing and grading after the graphitization process. The resulting graphitized product thus has a D50 particle size of 8 to 15 μm; for example, it can be approximately 10 μm or 12 μm. Because the subsequent graphene exists between layers and within the pore structure, and the carbon coating is very thin, this particle size is substantially comparable to that of the high-power artificial graphite.

[0045] According to some embodiments of the present invention, in step S2, the concentration of the graphene quantum dot solution is 1-5 wt %, for example, about 1.5 wt %, 2.0 wt %, 2.5 wt %, 3.0 wt %, 3.5 wt %, 4.0 wt %, or about 4.5 wt %.

[0046] According to some embodiments of the present invention, in step S2, the mass-to-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.

[0047] According to some embodiments of the present invention, in step S2, the immersion time is 10 to 60 minutes, for example, about 15 minutes, 20 minutes, 25 minutes, 30 minutes, 40 minutes, or about 50 minutes.

[0048] 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 preserve the structure of the product to the greatest extent and avoid structural collapse.

[0049] 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.

[0050] 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 can be about 5:95.

[0051] According to some embodiments of the present invention, in step S3, the graphene precursor includes at least one of methane, ethane, ethylene and acetylene.

[0052] According to some embodiments of the present invention, in step S3, the in-situ generation of graphene takes 3 to 10 minutes, for example, about 5 minutes or about 8 minutes.

[0053] 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.

[0054] According to some embodiments of the present invention, in step S3, the temperature of the CVD method is 950-1150°C, for example, about 1000°C.

[0055] 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.

[0056] 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, and then heat-treating the mixture.

[0057] According to some embodiments of the present invention, in step S4, the raw materials for preparing the carbon layer include a dopant; the dopant includes at least one of a nitrogen precursor and a phosphorus precursor. This allows nitrogen doping or phosphorus doping in the shell layer, thereby improving the adhesion between the shell layer and the core and also improving the electrical conductivity of the shell layer.

[0058] In actual production, the raw material for preparing the carbon layer may be only the dopant.

[0059] 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.

[0060] According to some embodiments of the present invention, the initiator comprises ammonium persulfate.

[0061] 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 about 1:0.8.

[0062] 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.

[0063] 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.

[0064] 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 about 40° C.

[0065] According to some embodiments of the present invention, the time for the mixing 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.

[0066] 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.

[0067] 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.

[0068] According to some embodiments of the present invention, in step S4, the heat treatment during preparation of the carbon layer is performed in a protective atmosphere comprising at least one of nitrogen and argon.

[0069] 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 in the embodiment of the first aspect of the present invention, wherein the high-power artificial graphite has a core-shell structure; wherein

[0070] The core includes porous graphite and graphene grown inside and on the surface of the porous graphite;

[0071] The shell is a carbon layer.

[0072] 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.

[0073] According to some embodiments of the present invention, the shell is doped with N or P.

[0074] According to some embodiments of the present invention, the core has microporous, mesoporous, and macroporous structures, wherein the volume percentage of the mesopores in the total pore volume is ≥50%, for example, about 60% or about 70%.

[0075] 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.

[0076] According to some embodiments of the present invention, the D50 particle size of the high-power artificial graphite is 8-15 μm.

[0077] 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.

[0078] Since the lithium-ion battery adopts all the technical solutions of the high-power artificial graphite of the above embodiment, it has at least all the beneficial effects brought about by the technical solutions of the above embodiment.

[0079] 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.

[0080] According to some embodiments of the present invention, the lithium-ion battery comprises at least one of a symmetrical cell, a half cell, and a full cell.

[0081] It should be noted that in the full battery, the high-power artificial graphite is used as the negative electrode active material, while other materials such as the positive electrode active material, separator, electrolyte, etc. can be selected from commercial materials according to actual conditions, and the present invention does not impose strict limitations.

[0082] According to an embodiment of the fourth aspect of the present invention, there is provided an application of the lithium-ion battery provided by an embodiment of the third aspect of the present invention in electric vehicles, drones and model aircraft.

[0083] 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.

[0084] Unless otherwise specified, the term “about” in the present invention means that the error is allowed to be within the range of ±2%. For example, about 100 is actually 100±2%×100.

[0085] 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.

[0086] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. DETAILED DESCRIPTION

[0087] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described 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.

[0088] In the description of the present invention, reference to terms such as "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 exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0089] Example 1

[0090] In this example, a high-power artificial graphite was prepared. The specific steps are as follows:

[0091] S1. Prepare a saturated solution of lithium nitrate in ethanol using 6 mL of ethanol.

[0092] 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;

[0093] 5 g of carbon-based raw material needle coke powder (D50 particle size of about 6.5 μm; ash content ≤ 8 wt%) was mixed with the above-mentioned mixed dispersion at about 50°C for 5 hours; during this process, the ethanol was largely volatilized;

[0094] Under a nitrogen atmosphere, the obtained kneaded product was graphitized at 1500° C. for 1 h, at 2400° C. for 1 h, and finally at 2800° C. for 1 h.

[0095] After the treatment, the product was crushed to obtain a graphitized product with a D50 particle size of about 11 μm.

[0096] S2. Under nitrogen protection, the product obtained in step S1 was impregnated in a solution containing graphene quantum dots and then freeze-dried; the immersion time was 20 min;

[0097] Graphene quantum dots were prepared according to the method in Example 1 of CN 112938950 B, with a mass concentration of about 1.6%.

[0098] The mass volume ratio of the product obtained in step S1 to the solution is 1 g:10 mL.

[0099] S3. In situ generation of graphene on the product obtained in step S2 by CVD; wherein:

[0100] The temperature of the CVD method is 1000°C, the carrier gas is a mixture 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 800 seem; and the constant temperature of 1000°C is maintained for 8 minutes.

[0101] S4. Coating the surface of the product obtained in step S3 with a carbon layer. The specific steps are:

[0102] The product obtained in step S3 was dispersed in water at a ratio of 1 g:10 mL; pyrrole and ammonium persulfate were added to the resulting dispersion; after mixing at 40° C. for 30 minutes, the mixture was filtered and the filter cake was dried; the mass ratio of pyrrole to the product obtained in step S3 was 1:15; and the mass ratio of pyrrole to ammonium persulfate was 1:0.7.

[0103] Under nitrogen protection, the dried filter cake was heat treated at 800°C for 1.5 h.

[0104] Example 2

[0105] This example provides a method for preparing high-power artificial graphite, which differs from Example 1 in that:

[0106] In step S1, the amount of ethanol used is 3 mL; correspondingly, the amount of the pore-forming agent used is reduced by half.

[0107] Example 3

[0108] This example provides a method for preparing high-power artificial graphite, which differs from Example 1 in that:

[0109] In step S3 , the duration of the CVD process is 3 minutes.

[0110] Comparative Example 1

[0111] This example provides a method for preparing artificial graphite, which differs from Example 1 in that:

[0112] In step S1 , no pore-forming agent is added.

[0113] Comparative Example 2

[0114] This example provides a method for preparing artificial graphite, which differs from Example 1 in that:

[0115] Steps S2~S3 are not included.

[0116] Comparative Example 3

[0117] This example provides a method for preparing artificial graphite, which differs from Example 1 in that:

[0118] In step S1, the phenolic resin is replaced with an equal amount of medium-temperature asphalt.

[0119] Comparative Example 4

[0120] This example provides a method for preparing artificial graphite, which differs from Example 1 in that:

[0121] Step S2 is not included.

[0122] Application Examples

[0123] In a first aspect of this example, a 2025 button cell is provided, wherein the button cell half-cell is prepared as follows:

[0124] 95.5% of the artificial graphite obtained in the embodiment and comparative example, 1.5% carbon black, 1.5% styrene-butadiene rubber (SBR), and 1.5% sodium carboxymethyl cellulose (CMC) were stirred in water to prepare a negative electrode slurry. The slurry was then coated on a battery-grade copper foil and dried in a vacuum oven at 110°C for 4 hours. The sheets were then rolled to prepare nitrogen-doped carbon-coated graphite negative electrode sheets. The surface density of the artificial graphite negative electrode sheet was 10 mg / cm 2 , compacted density is 1.65g / cm 3 ;

[0125] The counter electrode is a metal lithium sheet, the separator is polyethylene, and 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) to prepare a button half-cell.

[0126] The second aspect of this example provides a soft pack battery, wherein the preparation method of the soft pack battery is as follows:

[0127] Negative electrode separator and electrolyte: same as button battery.

[0128] Positive Electrode: 94%, 3%, and 3% by mass of lithium nickel cobalt manganese oxide (NCM111) with a D50 of 2 to 4 μm, conductive carbon black, and PVDF were added to an appropriate amount of N-methylpyrrolidone (NMP) solvent and stirred to create a positive electrode slurry with a solid content of 76%. The positive electrode sheet was produced through coating, roll pressing, and die-cutting.

[0129] Test Case

[0130] In the first aspect of this example, the physical and chemical properties of the artificial graphite obtained in the examples and comparative examples were tested, specifically:

[0131] Interlayer spacing: The test method is XRD test to calculate the lattice spacing;

[0132] Porosity: The test method is BET, and the pore volume occupancy of the mesopores is calculated;

[0133] Particle size: Laser particle size analyzer, record D50 result (keep one decimal place);

[0134] The test results of the above two aspects are shown in Table 1:

[0135]

[0136] 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, in Comparative Example 3, the phenolic resin is replaced with asphalt, and Comparative Example 1 does not include a pore-forming agent. In these two cases, the interlayer spacing of the obtained artificial graphite decreases significantly, and the path of lithium ion deintercalation becomes narrower. It can be expected that its rate performance will decrease significantly. Comparing Example 1 and Example 2, a similar interlayer spacing variation trend can also be obtained. In addition, the results of Comparative Example 1, Example 3 and Comparative Example 2 show 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. In Comparative Example 4, step S2 is omitted, that is, the seeds for graphene growth are missing. In step S3, the growth of graphene increases randomness and tends to be more random, rather than modifying the macropores and mesopores. Therefore, judging from the test results, the interlayer spacing is improved to a certain extent.

[0137] 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.

[0138] 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, 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.

[0139] The second aspect of this example tests the first reversible capacity and first efficiency of the button battery 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.

[0140] 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 the discharge rates of 1C, 2C, 5C, and 10C is 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.

[0141] The test results of the second and third aspects of this example are shown in Table 2:

[0142]

[0143] 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 rate performance and first efficiency of the corresponding obtained artificial graphite decrease; the corresponding pore structure decreases, and the volume change during the charge and discharge process of the artificial graphite is difficult to alleviate, which also leads 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 cause the high-rate cycle performance to decrease; however, from the results, the role of the latter is more important. In comparative example 4, since graphene is more coated, the interlayer support is lacking, and the uniformity of conductivity deteriorates. Although the coating can alleviate the erosion of the electrolyte on the artificial graphite material, the overall performance still decreases significantly. 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.

[0144] In summary, the method for preparing high-power artificial graphite provided by the present invention, due to the limited raw materials and preparation conditions, produces high-power artificial graphite with excellent capacity, initial efficiency, rate, and cycle life. Therefore, the resulting high-rate artificial graphite is expected to be widely used in fast-discharging electronic products such as electric vehicles, drones, and model aircraft.

[0145] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a 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 comprises at least one of petroleum coke powder, needle coke powder and pitch coke powder; The pore-forming agent is lithium nitrate; The mass volume ratio of the carbon-based raw material and the organic solvent is 1g:0.5~1.5mL; The amount of the pore-forming agent is the saturated concentration capacity of the pore-forming agent in the organic solvent; 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; 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 S3, the in-situ generation time of the graphene is 3 to 10 minutes.

4. 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.

5. A high-power artificial graphite prepared by the preparation method according to any one of claims 1 to 4, 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.

6. The high-power artificial graphite according to claim 5, characterized in that: The shell is doped with N or P.

7. The high-power artificial graphite according to claim 5, characterized in that: The core has micropore, mesopore and macropore structures; wherein the volume percentage of the mesopores in the total pore volume is ≥50%.

8. 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 5 to 7.

9. Use of the lithium-ion battery according to claim 8 in electric vehicles, drones and model aircraft.

Images