Graphitization production process for the negative electrode material of a lithium battery

Abstract

The present invention relates to the technical field of anode materials, and specifically, to a graphitization production process for lithium battery anode materials. The process includes the following steps: After washing carbon materials with water and grinding them into granular form, pitch is added for mixed coating to produce coated materials; the coated materials are put into a stirring container, and a forming agent and deionized water are added. After stirring evenly, magnetic removal treatment is carried out to produce a mixed slurry; the mixed slurry is heated for dehydration to produce a material slurry, and the material slurry is placed in a crucible and preheated under a nitrogen atmosphere; the crucible is transported into a graphitization furnace for heating graphitization to produce anode materials, and the anode materials are taken out after cooling. In the present invention, through the three-dimensional highly cross-linked network structure of resin pyrolytic carbon and the cooperation of carbon black to form a conductive network, the discharge effect of the anode material can be ensured, and after the anode material is graphitized, the disordered carbon structure therein is also transformed into a crystalline structure similar to graphite, with a smaller interlayer spacing, thereby ensuring the discharge effect of the anode material.

Description

Technical Field

[0001] The present invention relates to the technical field of anode materials, and specifically, to a graphitization production process for a lithium battery anode material. Background Art

[0002] To ensure the discharge performance of a lithium-ion battery, it is necessary to make the insertion / oxidation reduction potential of lithium ions in the anode matrix as low as possible, close to the potential of metallic lithium, so that the input voltage of the battery is high, and during the insertion / extraction process, the main structure of the anode does not change or changes very little.

[0003] For example, CN103384007B involves a carbon nanotube / graphene composite anode material and its preparation method and a lithium battery, including steps of placing graphene powder and a catalyst for carbon source cracking in a microwave reaction chamber, evacuating the microwave reaction chamber and introducing a protective gas, and using microwave chemical vapor deposition to grow carbon nanotubes on a graphene matrix to prepare the carbon nanotube / graphene composite anode material. The anode of this lithium battery contains the carbon nanotube / graphene composite anode material. This preparation method uses microwave chemical vapor deposition for in-situ preparation of the carbon nanotube / graphene composite material, does not require a pre-synthesis process to reduce production costs, uses microwave heating, is efficient, has low energy consumption, and has a short production cycle. The lithium battery is beneficial to the insertion and extraction of lithium due to the above carbon nanotube / graphene composite anode material, reduces the irreversible capacity of the first charge and discharge, and has good safety and high power for the lithium battery. However, in this preparation method, only by containing the carbon nanotube / graphene composite anode material is it convenient for the insertion / extraction of lithium ions to reduce the irreversible capacity of the first charge and discharge, and the internal structure of its anode has not been correspondingly improved, resulting in a lower discharge efficiency.

[0004] In order to enable the lithium battery anode material to have a better discharge effect, a graphitization process for the lithium battery anode material is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a graphitization production process for a lithium battery anode material to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides a graphitization production process for a lithium battery anode material, including the following steps:

[0007] S1. Wash the carbon material and grind it into granular form, then add pitch for mixing and coating to produce a coated material;

[0008] S2. Put the coated material into a stirring container, add a forming agent and deionized water, stir evenly, and then perform a demagnetization treatment to produce a mixed slurry;

[0009] S3. Heat and dehydrate the mixed pulp to produce a material pulp, and place the material pulp in a crucible for preheating under a nitrogen atmosphere;

[0010] S4. Transfer the crucible to a graphitization furnace for heating and graphitization to produce a negative electrode material, and take out the negative electrode material after cooling.

[0011] As a further improvement of this technical solution, in S1, the carbon material is resin pyrolytic carbon prepared from phenolic resin as a precursor.

[0012] As a further improvement of this technical solution, in S1, the coating method is chemical vapor deposition.

[0013] As a further improvement of this technical solution, in S2, the forming agent includes polyacrylic acid and carbon black, and the weight ratio of polyacrylic acid to carbon black is 9:1.

[0014] As a further improvement of this technical solution, in S2, the stirring speed is 40 - 60 rpm.

[0015] As a further improvement of this technical solution, in S3, the preheating temperature is 80 - 180 °C.

[0016] As a further improvement of this technical solution, in S3, the water content of the material pulp is 0.05 - 0.20%.

[0017] As a further improvement of this technical solution, in S4, the graphitization temperature is 2450 - 2850 °C.

[0018] As a further improvement of this technical solution, in S4, the graphitization time is 8 - 15 h.

[0019] In the present invention, using resin pyrolytic carbon prepared from phenolic acid resin as a precursor as the carbon source of the negative electrode material can utilize the three-dimensional highly cross-linked network structure of resin pyrolytic carbon, and utilize the high chemical bond energy between carbon atoms in the benzene ring to provide the cohesion between molecular chains and strengthen the structural stability. In addition, by depositing an amorphous asphalt layer on the surface to form a shell structure, it can reduce the impact of lithium ion insertion / extraction on the structure, reduce the pulverization amplitude of the structure, and ensure the discharge effect of the negative electrode material after forming a conductive network in combination with carbon black. After graphitization, the disordered carbon structure in the negative electrode material is also transformed into a crystalline structure similar to graphite, and the layer spacing becomes smaller, thereby ensuring the discharge effect of the negative electrode material.

[0020] Compared with the prior art, the beneficial effects of the present invention:

[0021] In the graphitization production process of the lithium battery anode material, through the three-dimensional highly cross-linked network structure of resin pyrolytic carbon, and by utilizing the high chemical bond energy between carbon atoms in the benzene ring, the cohesion between molecular chains is provided, the stability of the structure is strengthened, the influence of lithium ion insertion / extraction on the structure can be reduced, the pulverization degree of the structure can be reduced, and after being combined with carbon black to form a conductive network, the discharge effect of the anode material can be ensured. After the anode material is graphitized, the disordered carbon structure inside it is also transformed into a crystalline structure similar to graphite, and the interlayer spacing becomes smaller, thereby ensuring the discharge effect of the anode material. Brief Description of the Drawings

[0022] Figure 1 This is a flowchart of the present invention. Detailed Embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0024] Please refer to Figure 1 As shown, the object of the present invention is to provide a graphitization production process for a lithium battery anode material, including the following steps:

[0025] S1. After washing the carbonaceous material with water and grinding it into granular form, pitch is added for mixing and coating to produce a coated material. Among them, the carbonaceous material is resin pyrolytic carbon prepared from phenolic resin as a precursor. Phenolic resin belongs to thermosetting resin, and the cured structure shows the characteristics of three-dimensional network high cross-linking. In the benzene ring structure that accounts for a large proportion in the main structure, the chemical bond energy between carbon atoms is high, and the cohesion between molecular chains is relatively large. After phenolic resin pyrolysis, it has the characteristics of high residual carbon rate and strong carbon-forming ability, thereby improving the cyclic discharge efficiency of the anode material. The coating method is chemical vapor deposition method, that is, by heating, plasma excitation or light radiation and other means, the gaseous or vapor-state chemical substances form solid deposits through chemical reactions on the gas-solid interface. By depositing an amorphous pitch layer on the surface of the carbonaceous material to form a shell structure, the volume expansion or structural damage of the active center of the anode material can be restricted and buffered, achieving the effect of maintaining the stability of the electrode material;

[0026] S2. Put the coating material into the stirring container, add the forming agent and deionized water, stir evenly at a speed of 40 - 60 rpm, and then perform demagnetization treatment to produce a mixed slurry. Among them, the forming agent includes polyacrylic acid and carbon black. The weight ratio of polyacrylic acid to carbon black is 9:1. Polyacrylic acid is used as an aqueous binder and realizes the polymerization and forming of materials through the adsorption of electrolyte charges. Carbon black particles have a large specific surface area and can form a conductive network in the negative electrode material. Through stirring, it can ensure the full contact between the coating material and the forming agent, thereby producing a uniformly mixed material slurry;

[0027] S3. Heat and dehydrate the mixed slurry to produce a material slurry, and place the material slurry in a crucible and preheat it under a nitrogen atmosphere. Among them, the preheating temperature is 80 - 180 °C. By preheating the material slurry, the excess water in the material slurry can be removed, and heating under a nitrogen atmosphere can avoid the introduction of impurities. The water content of the material slurry is 0.05 - 0.20%. When the water content is too low or too high, it will affect the stability of the structure inside the negative electrode material;

[0028] S4. Transfer the crucible to a graphitization furnace and heat it for graphitization at 2450 - 2850 °C for 8 - 15 h to produce a negative electrode material, and then cool it to take out the negative electrode material. Through graphitization, the carbon structure in the negative electrode material can be changed from disordered to ordered, and the solidification of the negative electrode material can be realized. In addition, it can improve the electrical conductivity of the negative electrode material. Long - term high - temperature heating is beneficial to the complete graphitization of the negative electrode material, thereby being beneficial to improving the performance of the negative electrode material.

[0029] In the present invention, using resin pyrolytic carbon prepared from phenolic resin as the carbon source of the negative electrode material, through the three - dimensional highly cross - linked network structure of resin pyrolytic carbon, and utilizing the high chemical bond energy between carbon atoms in the benzene ring, it can provide the cohesion between molecular chains and strengthen the structural stability. In addition, by depositing an amorphous asphalt layer on the surface to form a shell structure, it can reduce the impact of lithium ion insertion / extraction on the structure, reduce the pulverization amplitude of the structure, and ensure the discharge effect of the negative electrode material after forming a conductive network in cooperation with carbon black. After the negative electrode material is graphitized, the disordered carbon structure inside it is also transformed into a crystalline structure similar to graphite, and the interlayer spacing becomes smaller, thereby ensuring the discharge effect of the negative electrode material.

[0030] According to the differences in process parameters during production, the following specific examples are used to further illustrate the graphitization production process of a lithium - battery negative electrode material provided by the present invention.

[0031] Example 1

[0032] S1. After washing the carbon material with water and grinding it into granular form, pitch is added for mixed coating to produce coated material. Among them, the carbon material is resin pyrolytic carbon prepared from phenolic resin as the precursor, and the coating method is chemical vapor deposition;

[0033] S2. The coated material is put into a stirring container, and a forming agent and deionized water are added. After stirring evenly at a speed of 40 rpm and then undergoing demagnetization treatment, a mixed slurry is produced. Among them, the forming agent includes polyacrylic acid and carbon black, and the weight ratio of polyacrylic acid to carbon black is 9:1;

[0034] S3. The mixed slurry is heated to dehydrate to produce a material slurry, and the material slurry is placed in a crucible and preheated under a nitrogen atmosphere. Among them, the preheating temperature is 80 °C, and the water content of the material slurry is 0.05%;

[0035] S4. The crucible is transferred to a graphitization furnace and heated for graphitization at 2450 °C for 8 h to produce a negative electrode material, and the negative electrode material is taken out after cooling.

[0036] Example 2

[0037] S1. After washing the carbon material with water and grinding it into granular form, pitch is added for mixed coating to produce coated material. Among them, the carbon material is resin pyrolytic carbon prepared from phenolic resin as the precursor, and the coating method is chemical vapor deposition;

[0038] S2. The coated material is put into a stirring container, and a forming agent and deionized water are added. After stirring evenly at a speed of 50 rpm and then undergoing demagnetization treatment, a mixed slurry is produced. Among them, the forming agent includes polyacrylic acid and carbon black, and the weight ratio of polyacrylic acid to carbon black is 9:1;

[0039] S3. The mixed slurry is heated to dehydrate to produce a material slurry, and the material slurry is placed in a crucible and preheated under a nitrogen atmosphere. Among them, the preheating temperature is 140 °C, and the water content of the material slurry is 0.12%;

[0040] S4. The crucible is transferred to a graphitization furnace and heated for graphitization at 2700 °C for 10 h to produce a negative electrode material, and the negative electrode material is taken out after cooling.

[0041] Example 3

[0042] S1. After washing the carbon material with water and grinding it into granular form, pitch is added for mixed coating to produce coated material. Among them, the carbon material is resin pyrolytic carbon prepared from phenolic resin as the precursor, and the coating method is chemical vapor deposition;

[0043] S2. Put the coating material into a stirring container, add the forming agent and deionized water, stir evenly at a speed of 60 rpm, and then perform demagnetization treatment to produce a mixed slurry. Among them, the forming agent includes polyacrylic acid and carbon black, and the weight ratio of polyacrylic acid to carbon black is 9:1;

[0044] S3. Heat and dehydrate the mixed slurry to produce a material slurry, and place the material slurry in a crucible and preheat it under a nitrogen atmosphere. Among them, the preheating temperature is 180 °C, and the water content of the material slurry is 0.20%;

[0045] S4. Transfer the crucible to a graphitization furnace, heat and graphitize it at 2850 °C for 15 h to produce a negative electrode material, and then cool it to take out the negative electrode material.

[0046] Example 4

[0047] S1. Wash the carbon material with water, grind it into granular form, and then add pitch for mixing and coating to produce a coating material. Among them, the carbon material is resin pyrolytic carbon prepared from phenolic resin as a precursor, and the coating method is chemical vapor deposition;

[0048] S2. Put the coating material into a stirring container, add the forming agent and deionized water, stir evenly at a speed of 45 rpm, and then perform demagnetization treatment to produce a mixed slurry. Among them, the forming agent includes polyacrylic acid and carbon black, and the weight ratio of polyacrylic acid to carbon black is 9:1;

[0049] S3. Heat and dehydrate the mixed slurry to produce a material slurry, and place the material slurry in a crucible and preheat it under a nitrogen atmosphere. Among them, the preheating temperature is 150 °C, and the water content of the material slurry is 0.15%;

[0050] S4. Transfer the crucible to a graphitization furnace, heat and graphitize it at 2800 °C for 12 h to produce a negative electrode material, and then cool it to take out the negative electrode material.

[0051] Table 1 Comparison of process parameters in Examples 1-4

[0052] Example 1 Example 2 Example 3 Example 4 Stirring speed / (rpm) 40 50 60 45 Preheating temperature / °C 80 140 180 150 Water content / % 0.05 0.12 0.20 0.15 Graphitization temperature / °C 2450 2700 2850 2800 Graphitization time / h 8 10 15 12

[0053] Comparative Example 1

[0054] This comparative example adopts the production process of Example 1, sets the stirring speed to 30 rpm, and the rest remains unchanged. The specific steps are similar to those of Example 1, and will not be elaborated in this comparative example.

[0055] Comparative Example 2

[0056] This comparative example adopts the production process of Example 2, sets the stirring speed to 80 rpm, and the rest remains unchanged. The specific steps are similar to those of Example 2, and will not be elaborated in this comparative example.

[0057] Comparison of process parameters in Comparative Examples 1-2 in Table 2

[0058]

[0059]

[0060] Comparative Example 3

[0061] This comparative example adopts the production process of Example 3, sets the preheating temperature to 65 °C, and keeps the rest unchanged. The specific steps are similar to those of Example 3 and will not be elaborated here.

[0062] Comparative Example 4

[0063] This comparative example adopts the production process of Example 4, sets the preheating temperature to 200 °C, and keeps the rest unchanged. The specific steps are similar to those of Example 4 and will not be elaborated here.

[0064] Comparison of process parameters in Comparative Examples 3-4 in Table 3

[0065]

[0066] Comparative Example 5

[0067] This comparative example adopts the production process of Example 1, sets the water content of the material slurry to 0.25%, and keeps the rest unchanged. The specific steps are similar to those of Example 1 and will not be elaborated here.

[0068] Comparative Example 6

[0069] This comparative example adopts the production process of Example 2, sets the water content of the material slurry to 0.30%, and keeps the rest unchanged. The specific steps are similar to those of Example 2 and will not be elaborated here.

[0070] Comparison of process parameters in Comparative Examples 5-6 in Table 4

[0071]

[0072] Comparative Example 7

[0073] This comparative example adopts the production process of Example 3, sets the graphitization temperature to 2400 °C, and keeps the rest unchanged. The specific steps are similar to those of Example 3 and will not be elaborated here.

[0074] Comparative Example 8

[0075] This comparative example adopts the production process of Example 4, sets the graphitization temperature to 2950 °C, and keeps the rest unchanged. The specific steps are similar to those of Example 4 and will not be elaborated here.

[0076] Comparison of process parameters in Comparative Examples 7-8 in Table 5

[0077]

[0078] Comparative Example 9

[0079] This comparative example adopts the production process of Example 1, sets the graphitization time to 5h, and keeps the rest unchanged. The specific steps are similar to those of Example 1 and will not be elaborated here.

[0080] Comparative Example 10

[0081] This comparative example adopts the production process of Example 2, sets the graphitization time to 15h, and keeps the rest unchanged. The specific steps are similar to those of Example 2 and will not be elaborated here.

[0082] Table 6 Comparison of process parameters in Comparative Examples 9 - 10

[0083]

[0084] Test Example

[0085] The negative electrode materials are produced respectively according to the graphitization production processes of a lithium - ion battery negative electrode material provided in Examples 1 - 4 and Comparative Examples 1 - 10. The initial discharge capacity and initial discharge efficiency of the negative electrode materials are tested according to GB / T 24533 - 2019 "Graphite - based Negative Electrode Materials for Lithium - Ion Batteries", and the data are filled in Table 7.

[0086] Table 7 Comparison of discharge effects of negative electrode materials produced in Examples and Comparative Examples

[0087] Initial discharge capacity / (mA·h) / g Initial discharge efficiency / % Example 1 370 94 Example 2 374 96 Example 3 369 93 Example 4 372 95 Comparative Example 1 364 89 Comparative Example 2 368 92 Comparative Example 3 364 89 Comparative Example 4 367 91 Comparative Example 5 362 88 Comparative Example 6 366 90 Comparative Example 7 362 88 Comparative Example 8 364 89 Comparative Example 9 365 90 Comparative Example 10 368 92

[0088] It can be seen from Table 7 that when comparing the graphitization production processes of a lithium - ion battery negative electrode material provided in Examples 1 - 4 with those provided in Comparative Examples 1 - 10, the initial discharge capacity and initial discharge efficiency of the negative electrode materials produced by the process of Examples are higher than those of the negative electrode materials produced by the process of Comparative Examples. Moreover, the initial discharge capacity of the negative electrode materials produced by the process of Examples is higher than 369 (mA·h) / g, and the initial discharge efficiency is higher than 93%. While the initial discharge capacity and initial discharge efficiency of the negative electrode materials produced by the process of Comparative Examples with different process parameters have both decreased. Therefore, the graphitization production process of a lithium - ion battery negative electrode material provided by the present invention can produce negative electrode materials with good discharge effects.

[0089] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and the descriptions in the specification are only preferred examples of the present invention, and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A graphitization production process for the anode material of a lithium battery, characterized in that, it comprises the following steps: S1. After washing the carbon material with water and grinding it into granular form, add pitch for mixing and coating to produce a coated material; S2. Put the coated material into a stirring container, add a forming agent and deionized water, stir evenly, and then perform a demagnetization treatment to produce a mixed slurry; S3. Heat the mixed slurry to dehydrate it to produce a material slurry, and place the material slurry in a crucible for preheating under a nitrogen atmosphere; S4. Transfer the crucible to a graphitization furnace for heating graphitization to produce the anode material, and take out the anode material after cooling; wherein, in the said S1, the carbon material is resin pyrolytic carbon prepared from phenolic resin as a precursor; in the said S2, the forming agent includes polyacrylic acid and carbon black, and the weight ratio of polyacrylic acid to carbon black is 9:1; in the said S2, the stirring speed is 40 - 60 rpm; in the said S3, the preheating temperature is 80 - 180 °C; in the said S3, the water content of the material slurry is 0.05 - 0.20%; in the said S4, the graphitization temperature is 2450 - 2850 °C; in the said S4, the graphitization time is 8 - 15 h.

2. The graphitization production process for the anode material of a lithium battery according to claim 1, characterized in that: in the said S1, the coating method is chemical vapor deposition.

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