Method of manufacturing artificial graphite material

Abstract

The present invention provides a method for manufacturing artificial graphite, comprising the steps of: preparing a crushed artificial graphite product; classifying the crushed artificial graphite product to obtain a third fine powder and a third sieve product; and disintegrating the third sieve product to produce a product together with the third fine powder, wherein the step of disintegrating the third sieve product to produce a product together with the third fine powder utilizes an air classifier mill (ACM disintegration) method. (Here, the first classification refers to a grade where the amount of sieve material remaining on the sieve surface during classification is 20% by weight or more, the second classification refers to a grade where the amount of sieve material is more than 5% by weight and less than 20% by weight, and the third classification refers to a grade where the amount of sieve material is 5% by weight or less.)

Description

Technology Field

[0001] This relates to a method for manufacturing artificial graphite. Background Technology

[0002] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly rising. Among secondary batteries, lithium-ion batteries, which exhibit high energy density and operating potential, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0003] Furthermore, as interest in environmental issues grows, there is increasing interest in electric vehicles and hybrid electric vehicles that can replace fossil fuel-using vehicles, such as gasoline and diesel vehicles, which are one of the major causes of air pollution; consequently, research is actively underway to use lithium-ion batteries as a power source for the aforementioned electric vehicles and hybrid electric vehicles.

[0004] A lithium secondary battery generally consists of a positive electrode containing a positive active material, a negative electrode containing a negative active material, a separator, and an electrolyte, and charging and discharging are performed through the intercalation and decalation of lithium ions. Since the lithium secondary battery possesses the advantages of high energy density, high electromotive force, and the ability to exhibit high capacity, it is being applied in various fields.

[0005] Materials such as metallic lithium negative electrode active materials, carbon-based negative electrode active materials, or silicon oxide (SiOx) are used as the above negative electrode active materials. The carbon-based negative electrode active materials exhibit excellent capacity retention characteristics and efficiency. Since carbon-based negative electrode active materials used as negative electrodes in lithium secondary batteries have a potential close to that of lithium metal, changes in the crystal structure are small during the insertion and extraction processes of ionic lithium. Furthermore, the carbon-based negative electrode active materials enable continuous and repetitive oxidation and reduction reactions at the electrode, allowing the lithium secondary battery to exhibit high capacity and excellent lifespan.

[0006] Various types of materials are used as the carbon-based negative electrode active materials, such as crystalline carbon-based materials like natural graphite and artificial graphite, or amorphous carbon-based materials like hard carbon and soft carbon. Among the carbon-based negative electrode active materials, graphite-based negative electrode active materials are the most widely used because they have excellent reversibility and can improve the lifespan characteristics of lithium secondary batteries. Since the discharge voltage of the graphite-based negative electrode active material is low at -0.2 V compared to lithium, a battery using the graphite-based active material can exhibit a high discharge voltage of 3.6 V, which has an excellent advantage in terms of energy density of lithium secondary batteries.

[0007] The artificial graphite, which is a crystalline carbon-based material, has a more stable crystal structure than the natural graphite because it is formed by applying high thermal energy of 2,700°C or higher. Since the change in the crystal structure is small even during repeated charging and discharging of lithium ions, the artificial graphite has the advantage of having a lifespan that is 2 to 3 times longer than that of the natural graphite. The soft carbon and hard carbon, which are amorphous carbon-based materials with unstable crystal structures, have the characteristic of allowing lithium ions to advance more smoothly and can increase the charging and discharging speeds, so they can be used in electrodes that require high-speed charging. Therefore, it is common practice to mix the carbon-based materials in a certain ratio, taking into account the lifespan and output characteristics of the lithium secondary battery to be used.

[0008] Among the graphite-based materials that serve as the above-mentioned cathode active material, artificial graphite can be manufactured through the carbonization and graphitization of various carbon raw materials such as coke. Although a certain level of sphericity and secondary particle formation can be achieved through aggregation and disintegration processes during the graphitization reaction, artificial graphite that does not satisfy product commercialization standards is produced due to the clumping or enlargement of some particles.

[0009] Since yield issues during the manufacturing of such synthetic graphite ultimately weaken product competitiveness, it is necessary to improve yield while maintaining product-grade performance. The problem to be solved

[0010] The present invention aims to provide a method for manufacturing artificial graphite that maintains the performance of product-grade artificial graphite while improving the yield. means of solving the problem

[0011] In one embodiment of the present invention, the process efficiency is improved after obtaining artificial graphite by preparing an artificial graphite raw material and passing it through steps such as carbonization, grinding, heat treatment, granulation, graphitization, and coating as needed.

[0012] Finally, once the artificial graphite product is obtained, it is crushed and classified to separate it into product-grade artificial graphite and sieved material remaining after classification. At this stage, since the sieved material is also crystalline artificial graphite, there is a need to commercialize it.

[0013] The first thing to consider is reusing it in the grinding and classification process. As will be discussed later, however, this method causes problems with classification efficiency and ultimately has a negative impact on the yield.

[0014] Accordingly, the inventors propose a method to ultimately improve the yield through various post-processing of the aforementioned finished products.

[0015] First, in the present invention, classification is defined as follows.

[0016] The first classification is a grade in which the amount of sieve material remaining on the upper surface of the sieve during classification is 20% by weight or more, the second classification is a grade in which the amount of sieve material is more than 5% by weight and less than 20% by weight, and the third classification is a grade in which the amount of sieve material is 5% by weight or less.

[0017] The first classification above may use a mesh with a diameter of 100 to 800 mm, the second classification may use a mesh with a diameter of 900 to 1,300 mm, and the third classification may use a mesh with a diameter of 1,400 to 1,800 mm.

[0018] The size of the particles according to the first classification above is 100 to 500 μm, and the size of the particles according to the second and third classifications may be independently greater than 0 and less than or equal to 500 μm.

[0019] Table 1 below summarizes the types of classification used in the present invention by major factors.

[0020] division Mesh diameter Body product separation structure Giant size Particle size of the passed product Body weight (weight%) 1st Classification (Lab Classification) 200 mm Open the closed structural cover to directly separate the mesh-type products. 100~500 μm Similarity (no difference since it is a product after passing through the mesh) 20 weight% or more 2nd Class (PP Class) 1,000 mm The hole through which the body product exits is sucked into that hole during existence-classification vibration. 0~500 μm (form containing some fine particles) 5~20 wt% 3rd Class (Mass Production Class) 1,500 mm 0~500 μm (the proportion of fine particles in the class is slightly higher than in the second class) 5 weight% or less

[0021] 1st classSmall equipment is primarily used. It has a diameter of approximately 200 mm and a closed structure on all sides, allowing it to remain directly on the upper surface of the mesh of the sieve product. It is advantageous for verifying the rejection ratio. 2nd Class: Pilot-scale equipment is mainly used. It has a diameter of approximately 1,000 mm and a hole for removing sieve products, so during the classification process using vibration and ultrasound, the sieve products do not remain on the mesh but pass through this hole.

[0022] Third Class: It is primarily applied to mass production equipment. It is basically the same as the second classification equipment but on a larger scale. It is characterized by a large sieve volume because the mesh size differs and the yield of the classified product is a critical factor.

[0024] Furthermore, when this classification is performed, classified products and sieve products remain once again. At this time, while some powder of the classified product level remains in the sieve products, coarse particles are also present.

[0025] To commercialize these large particles, crushing is required.

[0026] In this invention, the following two methods are proposed for dissolving the above steps.

[0027] Air Classifier Mill (ACM): Particle crushing is performed by an impactor, and the particles are drawn into a classifier via an incoming airflow. As the particles pass through the classifier driven by the airflow, the particle size is controlled through the adjustment of the classifier. This enables a high-intensity raw material crushing effect and offers excellent final yield.

[0028] D10 (μm) D50 (μm) D90 (μm) BET (㎡ / g) Tap density (g / cc) (vertical) Tap density (g / cc) (horizontal) Body weight (weight%) Air Classifier Mill (ACM) 10~12 13~17 23~26 0.5~2.5 1.00~1.10 0.95~1.05 Less than 2 Simple airflow disintegration 10~13 15~19 28~32 0.5~1.5 1.06~1.20 1.00~1.10 10~20

[0029] In one embodiment of the present invention, a method for manufacturing artificial graphite is provided, comprising the steps of: preparing a crushed artificial graphite product; classifying the crushed artificial graphite product to obtain a third fine powder and a third sieve product; and crushing the third sieve product to produce a product together with the third fine powder; wherein the step of crushing the third sieve product to produce a product together with the third fine powder utilizes an air classifier mill (ACM) method.

[0030] As described above, in order to reuse the sieve product after the mass production classification level of artificial graphite, the entire sieve product can be crushed. At this time, the Dmax of the obtained artificial graphite can be 55 μm or less, and the D50 can be 17 μm or less. This method can maintain a high level of yield.

[0031] Alternatively, the step of classifying the artificial graphite crushed product to a third degree to obtain a third fine powder and a third sieve product; and the step of crushing the third sieve product to produce a product together with the third fine powder; may be the step of classifying the artificial graphite crushed product to a third degree to obtain a third fine powder and a third sieve product; the step of classifying the third sieve product to a first degree to obtain a first fine powder and a first sieve product; and the step of crushing the first sieve product to produce a product together with the third fine powder and the first fine powder.

[0032] Specifically, instead of crushing the entire product obtained after mass production classification, a method may be used to further finely classify it (lab scale level) and crush only the coarse particles. In this case, the Dmax of the obtained artificial graphite may be 53 μm or less, and a yield of 99.x% or more may also be achieved.

[0033] As mentioned above, if only the excess is selectively pulverized rather than the entire product, the resulting product can be more finely differentiated. In other words, it can be observed that the Dmax value decreases.

[0034] The step of classifying the above-mentioned artificial graphite crushed product to obtain a third fine powder and a third sieve product; and the step of crushing the third sieve product to produce a product together with the third fine powder; may be the step of classifying the above-mentioned artificial graphite crushed product to obtain a third fine powder and a third sieve product; the step of classifying the above-mentioned third sieve product to obtain a second fine powder and a second sieve product; the step of classifying the above-mentioned second sieve product to obtain a first fine powder and a first sieve product; and the step of crushing the above-mentioned first sieve product to produce a product together with the third fine powder, the second fine powder, and the first fine powder.

[0035] This is a method in which the sieve product obtained after mass production classification is first classified to the PP level, and the sieve product resulting from the PP classification is then classified again to the lab-scale level to grind the resulting coarse particles. As a method designed to significantly improve the final yield, it can be beneficial for yield improvement when a large number of product-grade particles are present in the initial powder.

[0036] At this time, in the above-mentioned air-flow classifier mill (ACM milling) method, the amount of debris can be minimized by controlling the RPM of the classifier and the Hz of the blower. The basis for controlling these factors will be explained based on the experimental examples described later.

[0038] In another embodiment of the present invention, a method for manufacturing artificial graphite is provided, comprising the steps of: preparing a crushed artificial graphite product; classifying the crushed artificial graphite product to obtain a third fine powder and a third sieve product; and crushing the third sieve product to produce a product together with the third fine powder; wherein the step of crushing the third sieve product to produce a product together with the third fine powder utilizes a simple airflow crushing method.

[0039] As described above, in order to reuse the sieve product after the mass production classification level of artificial graphite, the entire sieve product can be crushed. At this time, the vertical tap density of the obtained artificial graphite may be 1.00 g / cc or higher. In addition, the D50 of the obtained artificial graphite may be 18 μm or lower.

[0040] The final yield of the obtained synthetic graphite can achieve more than 98%.

[0041] Alternatively, the step of classifying the artificial graphite crushed product to a third degree to obtain a third fine powder and a third sieve product; and the step of crushing the third sieve product to produce a product together with the third fine powder; may be the step of classifying the artificial graphite crushed product to a third degree to obtain a third fine powder and a third sieve product; the step of classifying the third sieve product to a first degree to obtain a first fine powder and a first sieve product; and the step of crushing the first sieve product to produce a product together with the third fine powder and the first fine powder.

[0042] Specifically, instead of crushing the entire product obtained after mass production classification, a method may be used to further finely classify it (lab scale level) and crush only the excess material.

[0043] The step of classifying the above-mentioned artificial graphite crushed product to obtain a third fine powder and a third sieve product; and the step of crushing the third sieve product to produce a product together with the third fine powder; may be the step of classifying the above-mentioned artificial graphite crushed product to obtain a third fine powder and a third sieve product; the step of classifying the above-mentioned third sieve product to obtain a second fine powder and a second sieve product; the step of classifying the above-mentioned second sieve product to obtain a first fine powder and a first sieve product; and the step of crushing the above-mentioned first sieve product to produce a product together with the third fine powder, the second fine powder, and the first fine powder.

[0044] This is a method in which the sieve product obtained after mass production classification is first classified to the PP level, and the sieve product resulting from the PP classification is then classified again to the lab-scale level to grind the resulting coarse particles. As a method designed to significantly improve the final yield, it can be beneficial for yield improvement when a large number of product-grade particles are present in the initial powder. Effects of the invention

[0045] A method for manufacturing artificial graphite can be provided that maintains the performance of product-grade artificial graphite while improving the yield. Brief explanation of the drawing

[0046] Figure 1 is a flowchart of a method for disassembling an entire product. Figure 2 is a flowchart of a method for dissolving only the waste through the first classification of sieve products. FIG. 3 is a flowchart showing that the product is first subjected to a second classification, and the resulting waste is processed again using the first classification method. Figure 4 is an SEM image showing the shape of the granules when the ACM disintegration conditions were different. Figures 5 to 7 show the results of evaluating particle size and amount of waste when ACM disintegration conditions are controlled in detail. Figure 8 shows the results of the electrochemical characteristics evaluation of the cell using the product and the disintegrated product. Specific details for implementing the invention

[0047] Hereinafter, embodiments / examples of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0049] Examples

[0050] Manufacture of artificial graphite

[0051] Coal-based coke was coarsely ground using a fin mill and then finely ground using a grinder to produce coke fine particles. Subsequently, pitch was ground using a jet mill to obtain ground pitch. The coke fine particles and ground pitch were mixed, fed into a granulator, and heated to 700°C under a nitrogen atmosphere to obtain granules. Next, the granules were disintegrated. .

[0052] The fragmented granular material was subjected to preliminary carbonization at a temperature of 1,200 ℃, and subsequently, a graphitization step was performed at 3,000 ℃.

[0053] Subsequently, the artificial graphite obtained after the coating process was classified to obtain the product and the waste material discharged during classification. The classification performed at this stage refers to mass production classification, which is the third classification level.

[0055] Experimental Example 1: Reprocessing of Body Products

[0056] The obtained sieve product was fed back into the classifier for reprocessing when classifying the artificial graphite obtained in the above example. At this time, the yield of artificial graphite was checked depending on whether reprocessing was performed.

[0057] When reprocessing, the objective of reusing the artificial graphite residue can be achieved, but problems such as mesh clogging occur during classification due to the residue, and the yield of artificial graphite is reduced to 92%.

[0058] If reprocessing is not performed, the artificial graphite cannot be reused, but the manufacturing yield of artificial graphite was achieved at 93%.

[0060] Experimental Example 2: Disintegration of Sieve Products - Air Classification Disintegration (Air Classifier Mill, ACM Disintegration)

[0061] An attempt was made to commercialize the product that was difficult to reuse, as identified in Experimental Example 1, through additional disintegration.

[0062] At this time, the disintegration of the product was carried out through the following methods.

[0063] First, as shown in Fig. 1, a method of disintegrating the entire product was performed.

[0064] Alternatively, as shown in Fig. 2, a method was performed to crush only the portion of the product that was separated through the first classification.

[0065] Alternatively, as shown in FIG. 3, the product is first subjected to a second classification. The excess material obtained through this process is then processed again by the first classification method. Through this, the excess material finally obtained can be broken down.

[0066] At this stage, the final coarse particles were crushed using an air classifier mill (ACM). In both methods, after crushing, all particles except the final coarse particles were mixed and used as a product.

[0067] Table 3 below shows the evaluation results of powders reused as products by crushing the sieves according to each of the aforementioned methods.

[0068] division Physical properties Electrochemical evaluation Particle size (um) T / D (g / cc) BET (m 2 / g) efficiency (%) volume (mAh / g) D10 D50 D90 Dmax Comparison group According to the example, the product after third classification following the manufacture of artificial graphite 10.8 16.3 24.6 51.7 1.05 1.0 93.3 349.6 After the third classification, the finished product 11.7 18.8 51.6 209.3 - - - The third grade of products after the first grade 12.2 18.3 32.8 88.0 0.99 1.5 1 All ACM shredded products after 3rd classification 10.9 17.1 31.9 88.0 1.03 1.2 92.7 350.0 Final product properties (93.2 : 6.8) 10.8 16.2 24.5 51.2 1.05 1.0 93.2 349.4 2 Third-grade sieve products separated after first grade ACM crushed products 10.3 16.8 31.7 88.0 0.98 1.8 92.2 348.0 Final product properties (97.6 : 2.4) 10.8 16.3 24.8 52.6 1.05 1.0 93.3 349.6

[0069] - Particle size analysis evaluation method: 0.04g of the sample was mixed with distilled water and Triton X100, dispersed in an ultrasonic disperser for 1 minute, and then the particle size was measured using a Microtac particle size analyzer. - Tap density evaluation method: 15g of the sample was placed in a 25ml cylinder and tapped 3,000 times at 250 rpm using a Bettersize tap density meter to measure the tap density.

[0070] - BET evaluation method: 2g of the sample was placed in a cylinder, pretreated at 300℃ under vacuum for 1 hour, cooled at room temperature for 30 minutes, and then measured using a Tristar instrument.

[0071] - Battery characteristic evaluation method

[0072] (Cell manufacturing): A negative electrode active material slurry was prepared by mixing 95.6 wt% of the negative electrode active material prepared above, 3.4 wt% of a binder containing carboxymethyl cellulose and styrene butadiene rubber, and 1.0 wt% of Super P conductive material in a distilled water solvent.

[0073] The above cathode active material slurry was applied to a copper (Cu) current collector, dried at 80°C for 10 minutes, and then compressed in a roll press. Subsequently, the cathode was prepared by vacuum drying in a vacuum oven at 100°C for 12 hours. After vacuum drying, the electrode density of the cathode was set to 1.55 g / cc.

[0074] Lithium metal (Li-metal) was used as the counter electrode, and a solution of 1 mole of LiPF6 was dissolved in a mixed solvent with a volume ratio of ethylene carbonate (EC) to dimethyl carbonate (DMC) of 2:8 as the electrolyte.

[0075] Using each of the above components, a 2032 coin cell type half coin cell was manufactured according to a conventional manufacturing method, and its efficiency and capacity were evaluated through a charge / discharger.

[0076] (Capacity [mAh / g]): The 3rd discharge capacity when charging and discharging in 0.1CC / CV, 0.1CC mode at a C-rate of 0.1C after a 30-hour rest time following cell manufacturing.

[0077] (Efficiency[%]): Discharge capacity / charge capacity of the first cycle when charging and discharging are performed in 0.1CC / CV, 0.1CC mode at a C-rate of 0.1C after a 30-hour rest time following cell manufacturing.

[0079] As shown in Table 3 above, when the entire sieve product was ACM-shredded after the third classification, the final product yield was 99.9%, consisting of classified product (93.0%), shredded product (6.9%), and scrap (0.1%). The yield was calculated using the following method.

[0080] order Ratio by process Total ratio process transference number Classified goods Contains Classified goods Seashell Contains 1 3rd Class (Mass Production Class) 100.0% 93.0% 7.0% 93.0% 0.0% 0.0% 2 After the third classification, the entire product is ACM crushed. 100.0% 99.0% 1.0% 0.0% 6.9% 0.1% Final total 93.0% 6.9% 0.1%

[0081] In addition, in the case of only the discarded portion among the sieve products being crushed (the discarded ACM crushed product from the 3rd classification after the 1st classification), the final product yield was found to be 99.6%, consisting of classified product (97.2%), crushed sieve product (2.4%), and discarded portion (0.4%). At this time, the yield was calculated as follows.

[0082] order Ratio by process Total ratio process transference number Classified goods Contains Classified goods Seashell * Contains 1 3rd Class (Mass Production Class) 100.0% 93.0% 7.0% 93.0% 0.0% 0.0% 2 The third grade of products after the first grade 100.0% 60.0% 40.0% 4.2% 0.0% 0.0% 3 Third-grade sieve products are separated and crushed in ACM after the first grade. 100.0% 84.0% 16.0% 0.0% 2.4% 0.4% Final total 97.2% 2.4% 0.4%

[0083] That is, it was confirmed that the excess material after the third classification (mass production classification) following the manufacture of artificial graphite can be reused through ACM disintegration, with a final yield of 99.x% or higher in all cases where only the excess material is disintegrated and the entire product is disintegrated.

[0084] Table 4 below shows the experimental results of controlling the conditions of the Air Classifier Mill (ACM). Specifically, when manufacturing the entire ACM-disassembled product after the third classification above, the ACM disassembled conditions were adjusted as shown in Table 4 below.

[0085] ACM conditions Physical properties Electrochemical evaluation Final yield Labger portion (%) Classifier (RPM) Grinding (RPM) Feeder (Hz) Blower (Hz) Particle size (μm) perpendicular (g / cc) horizontality (g / cc) BET (m 2 / g) efficiency (%) volume (mAh / g) (%) ~5μm D10 D50 D90 Dmax Dmin Span 4k 1k 30 30 0.0 10.9 17.1 31.9 88.0 6.0 1.2 1.03 1.02 0.8 92.7 350.0 99.3 10 2k 1k 30 30 0.0 11.6 17.5 31.7 88.0 7.1 1.1 1.06 1.00 1.1 - 98.3 24 2k 1k 30 75 0.0 11.1 16.7 29.8 88.0 7.1 1.1 1.06 1.03 1.1 98.4 23 4k 3k 30 30 0.0 10.8 16.2 26.6 62.2 6.0 1.0 1.06 1.01 1.3 92.3 347.5 99.5 7 4k 5k 30 30 0.0 10.6 15.9 25.4 52.3 6.0 0.9 1.04 1.01 1.3 92.2 347.4 99.8 3

[0086] At this time, it was confirmed that when the RPM of the classifier was controlled to a level of 4,000 and the Hz of the blower was controlled to a level of 30, the amount of waste in the subsequent stage was minimized.

[0087] Figure 4 is an SEM image showing the shape of the particles when the ACM disintegration conditions were varied. As can be seen in Figure 4, the shape of the sieve particles is observed to consist of agglomerated graphite and pitch, and it can be confirmed that the particle size is large, at the level of ~300 μm.

[0088] When the ACM crushing strength is controlled to be weak during the crushing of the sieve product, it can be seen that the graphite and pitch are clumped together in the same form as the sieve product, but the size of the sieve product is reduced to the level of 100 to 200 μm.

[0089] In addition, when the crushing strength is strongly controlled during the ACM crushing of the sieve product, many fragmented shapes and spherical shapes on the surface are observed, and it can be seen that the size of the fragments has decreased to the level of ~100 μm.

[0090] Figures 5 to 7 show the results of evaluating particle size and coarseness when ACM disintegration conditions are controlled in detail. As can be seen from this, when the Classifier condition is increased, D10 and D50 decrease, and the coarseness content and size decrease. In addition, when the Blower is increased, D50 and D90 decrease, but the change in coarseness content and size is not significant. When the Grinding is increased, the decrease in particle size is distinct, and consequently, the coarseness amount decreases. However, it can be seen that the coarseness size does not change significantly. From this, it can be seen that control of the classifier and grinding is required during the ACM disintegration stage.

[0091] Table 7 and Figure 8 below are the results of the electrochemical characteristic evaluation by manufacturing a cell using the product after the third classification and the entire ACM disintegrated product after the third classification of Table 3 mentioned above.

[0092] Under the same conditions, it was confirmed that the voltage of the ACM disintegration product relative to the product dropped at a relatively fast rate with 3C charging, but it can be seen that commercialization is possible at a level that does not show a significant difference from the product.

[0093] SOC Average voltage value SOC Average voltage value % V % V product 10 -0.06565 ACM dismantle 10 -0.04134 20 -0.11815 20 -0.11173 30 -0.15445 30 -0.15682 40 -0.1785 40 -0.17689 50 -0.18207 50 -0.18303 60 -0.1859 60 -0.2048 70 -0.19555 70 -0.21936

[0095] The present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art will understand that the invention can be implemented in other specific forms without changing the technical concept or essential features of the invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

Claims

Claim 1 A method for manufacturing artificial graphite comprising: a step of preparing a crushed artificial graphite product; a step of classifying the crushed artificial graphite product to a third degree to obtain a third fine powder and a third sieve product; a step of classifying the third sieve product to a first degree to obtain a first fine powder and a first sieve product; and a step of disintegrating the first sieve product to form a product together with the third fine powder and the first fine powder, wherein the disintegration method utilizes an air classifier mill (ACM disintegration) method. (Here, the first degree refers to a grade in which the amount of sieve material remaining on the sieve surface during classification is 20 weight% or more, the second degree refers to a grade in which the amount of sieve material is greater than 5 weight% and less than 20 weight%, and the third degree refers to a grade in which the amount of sieve material is 5 weight% or less.) Claim 2 delete Claim 3 A method for manufacturing artificial graphite according to claim 1, wherein the D50 of the obtained artificial graphite is 17 μm or less. Claim 4 delete Claim 5 A method for manufacturing artificial graphite according to claim 1, wherein the Dmax of the obtained artificial graphite is 53 μm or less. Claim 6 A method for manufacturing artificial graphite according to claim 1, further comprising, prior to the step of first classifying the third sieve product to obtain a first fine powder and a first sieve product, a step of secondarily classifying the third sieve product to obtain a second fine powder and a second sieve product, wherein the first classification is performed on the second sieve product to obtain a first fine powder and a first sieve product, and the step of producing the product is to crush the first sieve product to produce the product together with the third fine powder, the second fine powder, and the first fine powder, and the crushing method is an air classifier mill (ACM crushing) method. Claim 7 A method for manufacturing artificial graphite according to claim 1, wherein in the above-mentioned air classifier mill (ACM milling) method, the amount of waste is minimized by controlling the RPM of the classifier and the Hz of the blower. Claim 8 A method for manufacturing artificial graphite according to claim 1, wherein the first classification uses a mesh with a diameter of 100 to 800 mm, the second classification uses a mesh with a diameter of 900 to 1,300 mm, and the third classification uses a mesh with a diameter of 1,400 to 1,800 mm. Claim 9 A method for manufacturing artificial graphite according to claim 1, wherein the size of the particles according to the first classification is 100 to 500 μm, and the sizes of the particles according to the second and third classifications are independently greater than 0 and less than or equal to 500 μm.

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