Method for regulating and controlling graphitization degree based on boride catalyst

Abstract

The invention discloses a method for regulating and controlling the graphitization degree based on a boride catalyst. The method comprises the following steps: S1, providing a coke precursor; s2, needle coke is soaked in a mixed solution of a ferroboron compound and boron oxide for 1-5 min, a boron catalytic coke precursor is obtained after drying, and the mixed solution of boron oxide and iron boride is prepared according to the mol ratio of B element being (0.8-1): 1; and S3, carrying out graphitization treatment on the boron catalytic coke precursor. Compared with pure boron, the ferroboron compound and the boron oxide are better in compounding effect and better in compounding when being used as catalysts, and the iron boride is higher in temperature and better in catalytic effect when being combined with boron after being melted.

Description

Technical Field

[0001] The invention relates to the technical field of graphite materials, and in particular to a method for regulating graphitization degree based on a boride catalyst. Background Art

[0002] Carbon materials have the advantages of high lithium storage capacity, abundant raw materials, low electrode potential, low cost, non-toxicity and stability, and have been rapidly developed.

[0003] The carbon negative electrode materials of lithium-ion batteries are mainly natural graphite and artificial graphite. The gram capacity of artificial graphite is closely related to the degree of graphitization, which is positively correlated. Therefore, increasing the degree of graphitization can increase the gram capacity of artificial graphite, thereby increasing the energy density of lithium-ion batteries.

[0004] There are two main methods for improving the graphitization degree of artificial graphite: 1. Using easy-to-graphitize, low-sulfur needle coke as the raw material for producing artificial graphite negative electrode at the raw material end, so as to achieve the purpose of increasing the graphitization degree and gram capacity of artificial graphite; 2. Increasing the power delivery per ton of artificial graphite during the graphitization process, increasing the temperature and graphitization time of the graphitization process, so as to achieve the purpose of increasing the graphitization degree and gram capacity of artificial graphite; 3. There is currently related research that boron (B) can be used as a graphitization catalyst to promote the graphitization of carbon materials.

[0005] In patent CN202311025950.5, it is studied that the introduction of a boron catalyst on a carbonized fiber body and then graphitization heat treatment can obtain a carbon fiber with a higher modulus at a low graphitization heat treatment temperature, while reducing the graphitization heat treatment time. Boric acid and / or boron carbide powder are selected as the boride, and the carbonized fiber body is placed in a boride solution for soaking and drying in sequence, so that the boride is coated on the surface of the carbonized fiber body, and then graphitization heat treatment is performed. However, in this way, boric acid and / or boron carbide powder is mainly because it has good high temperature resistance, can be stably present during high temperature graphitization heat treatment, and helps to form a stable interface layer at high temperature, which is very important for improving the degree of graphitization and interface performance of carbon fiber.

[0006] Current research has found that the introduction of iron in the preparation of negative electrode materials plays a catalytic role in the graphitization process, which can improve the order and capacity of graphite; the introduction of boron can increase the flexibility of the graphite lattice, distort the lattice and further increase the capacity of graphite. At the same time, a boron atom lacking an electron entering the graphite lattice can change the electronic state inside the graphite, which is beneficial to the embedding of lithium ions, thereby improving the charging performance of graphite. Summary of the invention

[0007] The main purpose of the present invention is to provide a method for regulating the degree of graphitization based on a boride catalyst to solve the above technical problems.

[0008] To achieve the above object, the present invention provides a method for regulating graphitization degree based on a boride catalyst, comprising the steps of:

[0009] S1, providing coke precursors;

[0010] S2, immersing the needle coke in a mixed solution of boron oxide and iron boride for 1-5 minutes, and obtaining a boron-catalyzed coke precursor after drying, wherein the mixed solution of boron oxide and iron boride is prepared at a molar ratio of B element of 0.8-1:1;

[0011] S3, graphitizing the boron-catalyzed coke precursor.

[0012] Furthermore, the coke precursor is needle coke.

[0013] Furthermore, the graphitization treatment in step S3 is performed at 2300-2600° C. for about 1-1.5 hours under an inert atmosphere.

[0014] Furthermore, the graphitization treatment in step S3 is performed at 2500° C. for about 1.2 h under an inert atmosphere.

[0015] Furthermore, the ratio of boron oxide to iron boride in the mixed solution is 1:1 based on the molar ratio of the B element.

[0016] Furthermore, the solid-liquid ratio of the mixed solution is 7-8%.

[0017] Furthermore, the solid-liquid ratio of the mixed solution is 7.5%.

[0018] The present invention also provides a graphite negative electrode material, which is prepared by any of the preparation methods described above.

[0019] The present invention also provides a negative electrode current collector for a lithium ion battery, the negative electrode current collector comprising: a conductive substrate and a negative electrode slurry layer coated on one or both sides of the conductive substrate, the negative electrode slurry layer being prepared by any of the preparation methods described above.

[0020] The present invention further provides a lithium ion battery, comprising a positive electrode, an electrolyte and a negative electrode, characterized in that the negative electrode comprises the lithium ion battery negative electrode collector as described above.

[0021] The method for regulating the degree of graphitization based on a boride catalyst of the present invention comprises the steps of: S1, providing a coke precursor; S2, soaking needle coke in a mixed solution of a boron iron compound and boron oxide for 1-5 minutes, and obtaining a boron-catalyzed coke precursor after drying, wherein the mixed solution of boron oxide and ferric boride is configured with a molar ratio of B element of 0.8-1:1; S3, graphitizing the boron-catalyzed coke precursor. Compared with pure boron, the composite effect of the boron iron compound and boron oxide as catalysts of the present invention is better, and the composite is better, and the catalytic effect of ferric boride combined with boron after melting at a sufficiently high temperature is better. DETAILED DESCRIPTION

[0022] The following will be combined with this embodiment to clearly and completely describe the technical solution in this embodiment. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0025] Coke precursor: commercially available needle coke.

[0026] Mixed solution of boron oxide and iron boride: the solid-liquid ratio of the mixed solution is 2%, 5%, 7.5%, 10% and 15% in five groups, and the ratio of boron oxide to iron boride is 1:1 based on the mol ratio of the B element.

[0027] The following table provides 5 groups of mixed solutions of boron oxide and iron boride with different concentrations and a blank group without B.

[0028] During the graphitization process, the higher the heat treatment temperature, the higher the degree of graphitization of the product, the more orderly the arrangement of the graphite layer, and the improved lithium storage capacity, that is, the higher the initial capacity. However, too high an ordered arrangement increases the probability of solvated lithium ions being embedded in the negative electrode graphite microcrystalline layers during the first charge, thereby hindering the smooth insertion of subsequent lithium ions and affecting the uniformity and consistency of the SEI film. On the contrary, after 2600°C-2800°C, as the graphitization temperature increases, the first effect and cycle capacity retention rate decrease. This embodiment selects a graphitization temperature of 2500°C and an annealing time of 1h.

[0029] First, the needle coke was immersed in 5 mixed solutions of boron oxide and iron boride with different concentrations and 1 group of pure water at room temperature for 120 seconds. After the immersion, it was taken out and dried at 120℃ in a vacuum environment. The product was graphitized at 2500℃ in an inert atmosphere for about 70 minutes and annealed for 1 hour to obtain graphite products with different graphitization degrees after being immersed in mixed solutions of boron oxide and iron boride with different concentrations. The graphitization degree results are as follows:

[0030]

[0031] It can be seen from the table above that the graphitization immersion effect is best at a 7.5% immersion concentration. Under the condition of graphitization temperature of 2500℃, the graphitization degree of the product without boron oxide and iron boride catalyst is about 80%. After adding the catalyst, the graphitization degree rises to 95% at the highest, and then the graphitization degree decreases with the increase of the addition amount. It can be considered that the increase in the graphitization degree in the early stage is because the solid solution of B solid solution in graphite has an upper limit. During the heat treatment process, boron diffuses and dissolves in the graphite structure. Part of the boron exceeding the solid solution limit exists in the graphite interlayer in the form of interstitial solid solution, and part exists in the composite material in the form of boron carbide. The boron in the interstitial reacts with carbon to form boron carbide, so there are both elemental boron and boron carbide in the graphite interlayer. Due to the presence of interstitial boron and boron carbide, the distance between graphite layers becomes larger, causing the graphitization degree to decrease. When the temperature is high enough, the catalytic effect of iron boride combined with boron after melting is better.

[0032] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for regulating graphitization degree based on a boride catalyst, characterized in that: Includes steps: S1, providing coke precursors; S2, immersing the needle coke in a mixed solution of boron oxide and iron boride for 1-5 minutes, and obtaining a boron-catalyzed coke precursor after drying, wherein the mixed solution of boron oxide and iron boride is prepared at a molar ratio of B element of 0.8-1:1; S3, graphitizing the boron-catalyzed coke precursor.

2. The method according to claim 1, characterized in that The coke precursor is needle coke.

3. The method according to claim 1, characterized in that The graphitization treatment in step S3 is performed at 2300-2600° C. for about 1-1.5 hours under an inert atmosphere.

4. The method according to claim 3, characterized in that The graphitization treatment in step S3 is performed at 2500° C. for about 1.2 h under an inert atmosphere.

5. The method according to claim 1, characterized in that The ratio of boron oxide to iron boride in the mixed solution is 1:1 based on the molar ratio of the B element.

6. The method according to claim 1, characterized in that The solid-to-liquid ratio of the mixed solution is 7-8%.

7. The method according to claim 6, characterized in that The solid-to-liquid ratio of the mixed solution is 7.5%.

8. A graphite negative electrode material, characterized in that: The method is prepared according to any one of claims 1 to 6.

9. A negative electrode current collector for a lithium ion battery, characterized in that: The negative electrode current collector comprises: a conductive substrate and a negative electrode slurry layer coated on one side or both sides of the conductive substrate, wherein the negative electrode slurry layer is prepared by the preparation method according to any one of claims 1 to 7.

10. A lithium ion battery comprising a positive electrode, an electrolyte and a negative electrode, characterized in that: The negative electrode comprises the negative electrode current collector of the lithium ion battery as claimed in claim 9.

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