Preparation method of low-cost artificial graphite negative electrode material, product and application thereof

Abstract

This invention discloses a method for preparing low-cost artificial graphite anode materials, as well as their products and applications. The preparation method includes: (1) pretreating graphitized waste to obtain raw materials; (2) mixing a solid carbon source with a poor solvent to obtain a suspension; (3) heating the suspension to T1, then uniformly spraying it onto the surface of the raw materials, followed by carbonization and post-treatment to obtain low-cost artificial graphite anode materials. The preparation method disclosed in this invention directly uses graphitized resistive material, crucible fragments, and connector powder as raw materials. The artificial graphite anode materials prepared have high tap density and small specific surface area. The lithium-ion batteries assembled with these materials have high initial charge capacity and high initial charge efficiency. This not only realizes the resource utilization of graphitized waste but also reduces the amount of organic solvent used in the production process, effectively reducing the production cost of artificial graphite.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion batteries, and in particular to a method for preparing a low-cost artificial graphite anode material, its product, and its application in lithium-ion batteries. Background Technology

[0002] Graphitization waste refers to high-graphitization resistivity material in the core of the Atchison graphitization furnace, crucible fragments, and electrode connector powder. Resistivity material is an auxiliary material used in the graphitization of artificial graphite in the Atchison graphitization furnace, typically used in quantities 3-4 times that of artificial graphite. After graphitization, its resistance decreases significantly, rendering it unusable as a graphitization auxiliary material. Previously, it was disposed of as a carbonizer or sold at a low price. Crucible fragments are containers used to hold artificial graphite during the graphitization process; they are consumables and were previously sold at a low price. Electrode connector powder consists of electrode processing chips from the Atchison graphitization furnace; previously, it was mixed with artificial graphite tailings and sold at a low price.

[0003] The common practice in the industry to utilize the graphitized waste is to first coarsely crush it, then pulverize it to the micron level, and finally shape it. This conventional approach typically produces graphitized waste with a large specific surface area and low tap density. The large specific surface area and numerous surface active sites result in poor processing performance and low initial charge efficiency; the low tap density also leads to low energy density.

[0004] A common method used in the industry to address the large specific surface area and low tap density of graphite materials is to use asphalt as a coating material. This coating method is categorized into solid-phase coating and liquid-phase coating, depending on the application method. While solid-phase coating is convenient, simple, and easy to operate, the uneven distribution of the coating layer results in poor specific surface area reduction. Liquid-phase coating, although producing a more uniform coating layer, requires a large amount of auxiliary materials (organic solvents), making the process complex and costly. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention discloses a low-cost method for preparing artificial graphite anode materials. The method directly uses graphitized resistive material, crucible fragments, and connector powder as raw materials. The resulting artificial graphite anode material exhibits high tap density and small specific surface area. Lithium-ion batteries assembled with this material have high initial charge capacity and high initial charge efficiency. This method not only achieves resource utilization of graphitized waste but also reduces the amount of organic solvents used in the production process, effectively lowering the production cost of artificial graphite.

[0006] The specific technical solution is as follows:

[0007] A method for preparing a low-cost artificial graphite anode material includes the following steps:

[0008] (1) Pre-treat the graphitized waste to obtain raw materials;

[0009] (2) The solid carbon source is mixed with a poor solvent to obtain a suspension;

[0010] (3) The suspension is heated to T1, then sprayed evenly on the surface of the raw material, and then carbonized and post-treated to obtain the low-cost artificial graphite anode material.

[0011] The T1 is greater than or equal to the softening point temperature of the solid carbon source.

[0012] This invention discloses a low-cost method for preparing artificial graphite anode materials. Using graphitized waste as raw material, the method involves coating the graphitized waste with a solid-phase carbon source wetted by a poor solvent. This coating method differs from existing solid-phase and liquid-phase coating methods. Specifically, the poor solvent of the solid-phase carbon source serves as the dispersed phase, utilizing its strong dispersing effect to allow the solid-phase carbon source to fully penetrate the micropores of the graphitized waste, blocking the pores and uniformly coating the surface of the graphitized waste. This significantly reduces its specific surface area and effectively increases its tap density. Lithium-ion batteries assembled from the artificial graphite anode material prepared by this method exhibit high initial charge capacity and efficiency, comparable to lithium-ion batteries assembled from anode materials prepared directly from conventional artificial graphite. Therefore, this invention not only achieves resource utilization of graphitized waste but also significantly reduces the amount of organic solvent used in the production process, effectively lowering the production cost of artificial graphite.

[0013] In step (1):

[0014] The graphitized waste material is selected from one or more of graphitized resistive material, graphitized electrode connector powder, and graphitized crucible fragments.

[0015] The pretreatment includes coarse crushing, pulverizing and shaping processes;

[0016] The particle size of the raw material is: D min >5μm, D 10 >8μm, D 50 =18±3μm, D 90 <38μm, D max <70μm.

[0017] Preferably, the graphitized waste is selected from graphitized resistive material. Experiments have shown that the preparation method disclosed in this invention is applicable to graphitized resistive material, graphitized electrode connector powder, and graphitized crucible fragments, and can realize the resource utilization of the above-mentioned graphitized waste. However, lithium-ion batteries assembled from artificial graphite anode materials prepared using graphitized resistive material as raw material have higher initial coulombic efficiency.

[0018] In step (2):

[0019] The solid carbon source is selected from one or more of asphalt, phenolic resin, and sucrose; preferably, it is asphalt, which is inexpensive and widely available.

[0020] The undesirable solvent is selected from one or more of dimethyl sulfoxide (DMSO), methylpyrrolidone (NMP), dimethylformamide (DMF), and ethylene glycol; preferably, the undesirable solvent is selected from one or more of DMSO, DMF, and ethylene glycol.

[0021] Experiments have shown that the artificial graphite anode material obtained by coating with the above-mentioned preferred unsuitable solvent has a lower specific surface area and a higher tap density.

[0022] Preferably, the solid content of the suspension is 25-50 wt%; more preferably, the solid content of the suspension is 30-40 wt%; and even more preferably, it is 40 wt%. Experiments have shown that the artificial graphite anode material obtained by coating with the suspension having the continuously optimized solid content has a lower specific surface area, a higher tap density, and results in a higher initial efficiency for the assembled lithium-ion battery.

[0023] In step (3):

[0024] To ensure that the solid carbon source is uniformly coated on the surface of the raw material, preferably, the raw material is preheated to temperature T2 before the suspension is uniformly sprayed onto the surface of the raw material.

[0025] The temperature difference between T2 and T1 is 0–30℃, and T 2≥ T1.

[0026] Preferably, the mass ratio of the solid carbon source in the suspension to the raw material is 5-15:85-95; more preferably, the mass ratio is 5-8:92-95; and even more preferably, it is 5:95. Experiments have shown that the artificial graphite anode material obtained after coating with the above-mentioned further preferred mass ratio has a lower specific surface area, higher tap density, and results in a higher initial efficiency for the assembled lithium-ion battery.

[0027] In step (3):

[0028] The carbonization process is carried out under an inert atmosphere. First, the temperature is raised from room temperature to 400-550°C and held for 1-8 hours. Then, the temperature is raised to 1000-1200°C and held for another 1-8 hours.

[0029] The post-processing includes demagnetization and sieving.

[0030] The present invention also discloses a low-cost artificial graphite anode material prepared according to the above method and its application in the preparation of lithium-ion batteries.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention discloses a low-cost method for preparing artificial graphite anode materials. The method uses graphitized waste as raw material and coats the graphitized waste with a solid carbon source that is wetted by a poor solvent. This coating method not only solves the problem of uneven distribution of the coating layer formed by solid-phase coating, but also solves the problem that liquid-phase coating requires a large amount of organic solvent to achieve. Attached Figure Description

[0033] Figure 1 Scanning electron microscope image of the low-cost artificial graphite anode material prepared in Example 1;

[0034] Figure 2 Scanning electron microscope (SEM) image of the liquid-phase coated resistive material prepared for Comparative Example 3. Detailed Implementation

[0035] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to embodiments and accompanying drawings. However, it should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] In this invention, D min D 10 D 50 D 90 D max The dispersion of particle size distribution was measured using a laser particle size analyzer MS3000; the tap density was measured using a tap tester BT-301; and the specific surface area was measured using a CANTA comparator Novatouch Lx2.

[0037] Example 1

[0038] (1) The high graphitization resistive material (graphitization greater than 90%) is coarsely crushed and pulverized to obtain pretreated resistive material. 95g of the pretreated resistive material (Dmin = 5.8μm, D) is then processed. 10 =8.3μm, D 50 It is 18.1 μm, D 90 =34.6μm, D max =56.8μm, specific surface area is 5.2m² 2 / g) is placed into a 500mL beaker and preheated in an oven to 190℃.

[0039] (2) 5g of asphalt (softening point of 180℃) was mixed with 7.5g of dimethyl sulfoxide (DMSO), a poor solvent, to obtain a suspension with a solid content of 40wt%; the suspension was placed on a heating plate and heated to 190℃.

[0040] (3) Take out the raw material obtained by preheating in the oven in step (1), and spray the suspension heated to 190°C in step (2) evenly on the surface of the raw material (the mass ratio of raw material to asphalt in the suspension is 95:5). Stir while spraying, control the stirring speed to 150 rpm, and spray for 5 min to obtain the coated resistive material.

[0041] (4) The coated resistive material prepared in step (3) is placed in a box-type atmosphere resistance furnace and carbonized at high temperature under nitrogen atmosphere protection. The carbonization curve is as follows: the temperature is raised from room temperature to 480℃ and held for 1 hour, then raised to 1150℃ and held for 1 hour. The heating rate is 6℃ / min.

[0042] (5) After demagnetizing the carbonized graphitized resistive material, it is passed through a 200-mesh sieve to obtain a low-cost artificial graphite anode material.

[0043] Figure 1 The scanning electron microscope image of the low-cost artificial graphite anode material prepared in this embodiment shows that the material surface is smooth and flat without burrs.

[0044] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0045] Example 2

[0046] The preparation process is basically the same as in Example 1, except that DMSO in step (2) is replaced with an equal mass of NMP.

[0047] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0048] Example 3

[0049] The preparation process is basically the same as in Example 1, except that DMSO in step (2) is replaced with an equal mass of ethylene glycol.

[0050] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0051] Example 4

[0052] The preparation process is basically the same as in Example 1, except that the DMSO in step (2) is replaced with an equal mass of DMF.

[0053] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0054] Example 5

[0055] The preparation process is basically the same as in Example 1, except that the mass of DMSO added in step (2) is replaced with 5g, and a suspension with a solid content of 50wt% is obtained.

[0056] The D50, tap density, specific surface area, initial charge capacity, and coulombic efficiency of the low-cost artificial graphite anode material prepared in this embodiment are listed in Table 2 below.

[0057] Example 6

[0058] The preparation process is basically the same as in Example 1, except that the mass of DMSO added in step (2) is replaced with 11.6g, and a suspension with a solid content of 30wt% is obtained.

[0059] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0060] Example 7

[0061] The preparation process is basically the same as in Example 1, except that the mass of DMSO added in step (2) is replaced with 15.0g, and a suspension with a solid content of 25wt% is obtained.

[0062] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0063] Example 8

[0064] The preparation process is basically the same as in Example 1, except that: the mass of the pretreated resistive material added in step (1) is replaced with 90g; in step (2), 10g of asphalt is mixed with 15.0g of DMSO to obtain a suspension with a solid content of 40wt%; but at this time, the mass ratio of the raw material (pretreated resistive material) to the asphalt in the suspension is 90:10.

[0065] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0066] Example 9

[0067] The preparation process is basically the same as in Example 1, except that the mass of the pretreated resistive material added in step (1) is replaced with 85g; in step (2), 15g of asphalt is mixed with 22.5g of DMSO to obtain a suspension with a solid content of 40wt%; but at this time, the mass ratio of the raw material (pretreated resistive material) to the asphalt in the suspension is 85:15.

[0068] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0069] Example 10

[0070] The preparation process is basically the same as that in Example 1, except that the high graphitization resistive material in step (1) is replaced with high graphitization electrode connector powder.

[0071] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0072] Example 11

[0073] The preparation process is basically the same as that in Example 1, except that the high graphitization resistive material in step (1) is replaced with high graphitization crucible fragments.

[0074] The low-cost artificial graphite anode material prepared in this embodiment has a D... 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0075] Comparative Example 1

[0076] (1) The high graphitization resistive material (graphitization greater than 90%) is coarsely crushed and pulverized to obtain the pretreated resistive material;

[0077] (2) Take 95g of pretreated resistive material and 5g of asphalt and mix them evenly with a stirrer at a speed of 150rpm for 20min. Place the mixed sample in a box-type atmosphere resistance furnace and carbonize it at high temperature under nitrogen atmosphere protection. The heating curve is as follows: heat up from room temperature to 480℃, hold for 1h, then heat up to 1150℃ and hold for 1h. The heating rate is 6℃ / min. After demagnetizing the carbonized graphitized waste, pass it through a 200-mesh sieve to obtain solid-phase coated resistive material.

[0078] The solid-phase coated resistive material D prepared in this comparative example 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0079] Comparative Example 2

[0080] The preparation process is basically the same as that of Comparative Example 1, except that in step (2), 85g of pretreated resistive material is mixed with 15g of asphalt.

[0081] The solid-phase coated resistive material D prepared in this comparative example 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0082] Comparative Example 3

[0083] Dissolve 5g of asphalt in 7.5g of tetrahydrofuran and stir at high speed for 0.5h to ensure more complete dissolution. Then add 95g of pretreated resistive material (the pretreatment process is exactly the same as in Example 1) and mix for 1h. Dry the sample afterward. Place the mixed sample in an inert gas environment for high-temperature carbonization. The heating curve is as follows: heat from room temperature to 480℃, hold for 1h, then heat to 1150℃, hold for 1h, with a heating rate of 6℃ / min. After demagnetizing the carbonized graphitized waste, pass it through a 200-mesh sieve to obtain the liquid-coated resistive material.

[0084] The D of the liquid-phase coated resistive material prepared in this comparative example 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0085] Figure 2 The image shows a scanning electron microscope image of the liquid-phase coated resistive material prepared in this comparative example. Due to the low amount of tetrahydrofuran added, the asphalt concentration was too high, resulting in a large amount of adhesion after drying.

[0086] Comparative Example 4

[0087] The preparation process is basically the same as that of Comparative Example 3, except that 5g of asphalt is dissolved in 15g of tetrahydrofuran and stirred at high speed until completely dissolved.

[0088] The liquid-phase coated resistive material D prepared in this comparative example 50 The tap density, specific surface area, initial charge capacity, and coulombic efficiency are listed in Table 2 below.

[0089] Performance testing

[0090] Using the products prepared in each embodiment and each comparative example as negative electrode materials, half-cells were assembled and tested according to the following method:

[0091] Weigh the negative electrode material, PVDF, and conductive carbon black SP according to a mass ratio of 91.6:6.6:1.8, stir evenly to prepare a negative electrode slurry, and apply the negative electrode slurry to the rough surface of copper foil using a coater. Place the coated electrode sheet in a forced-air drying oven at 100℃ and dry for 2 hours, then press it to form the negative electrode. The compaction density is calculated as: compaction density = areal density / (thickness of the rolled electrode sheet - thickness of the current collector). After rolling, the electrode sheet is placed in a vacuum drying oven at 90℃ and -0.09Mpa for 2 hours. Then, CR-2430 coin cells are assembled in a glove box filled with high-purity argon gas. After assembly, the cells are hung in a Blue Electric test cabinet for testing. The general charging and discharging conditions for the test are shown in Table 1.

[0092] Table 1

[0093]

[0094] The first-charge efficiency and first-charge capacity of the button batteries assembled in each embodiment and each comparative example under the above test conditions are listed in Table 2 below.

[0095] Table 2

[0096]

Claims

1. A method for preparing a low-cost artificial graphite negative electrode material, characterized by, Includes the following steps: (1) Pre-treat the graphitized waste to obtain raw materials; The graphitized waste material is selected from one or more of graphitized resistive material, graphitized electrode connector powder, and graphitized crucible fragments. (2) The solid carbon source is mixed with a poor solvent to obtain a suspension; The undesirable solvent is selected from one or more of dimethylformamide, ethylene glycol, and dimethyl sulfoxide; The solid content of the suspension is 30-40 wt%; (3) The suspension is heated to T1 and then sprayed evenly on the surface of the raw material, followed by carbonization and post-treatment to obtain the low-cost artificial graphite anode material; The T1 is greater than or equal to the softening point temperature of the solid carbon source; The raw material is preheated to temperature T2, and then the suspension is evenly sprayed onto the surface of the raw material. The temperature difference between T2 and T1 is 0~30℃, and T2≥T1. The mass ratio of the solid carbon source in the suspension to the raw material is 5~8:92~95.

2. The method for preparing low-cost artificial graphite anode material according to claim 1, characterized in that, In step (1): The pretreatment includes coarse crushing, pulverizing and shaping processes; Particle size of the raw material: D min > 5 μm, D 10 > 8 μm, D 50 = 18 ± 3 μm, D 90 < 38 μm, D max < 70 μm.

3. The method for preparing low-cost artificial graphite anode material according to claim 1, characterized in that, In step (2): The solid carbon source is selected from one or more of asphalt, phenolic resin, and sucrose.

4. The method for preparing low-cost artificial graphite anode material according to claim 1, characterized in that, In step (3): The carbonization process is carried out in an inert atmosphere. The temperature is first raised from room temperature to 400-550°C and held for 1-8 hours. Then the temperature is raised to 1000-1200°C and held for another 1-8 hours.

5. A low-cost artificial graphite anode material prepared by the method according to any one of claims 1 to 4.

6. The application of a low-cost artificial graphite anode material according to claim 5 in the preparation of lithium-ion batteries.

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