Method for modifying and granulating natural graphite spherical tailings
By using transition metal selenide intercalation and carbon fiber composite technology, the problem of utilizing graphite spherical tailings in lithium-ion batteries has been solved, achieving efficient granulation and improved electrochemical performance, making it suitable for lithium-ion battery anode materials.
Patent Information
- Application Number
- CN202511721905.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-21
- Publication Date
- 2026-01-20
AI Technical Summary
Existing technologies cannot effectively utilize the spherical graphite tailings generated during lithium-ion battery production. Furthermore, the expansion of the graphite interlayer spacing after the intercalation of transition metal selenides leads to a decrease in loose packing density, making it difficult to use directly as a negative electrode for lithium-ion batteries. In addition, the small size of the graphite spherical tailings results in uneven granulation.
Modified granulation products are prepared by using transition metal selenide intercalated natural graphite spherical tailings, combined with carbon fiber composites and pitch coating, and through processes such as calcination and ball milling, thereby improving the interlayer spacing and density of graphite and achieving uniform granulation.
This improved the initial coulombic efficiency and cycle stability of lithium-ion battery anode materials, and enabled the efficient utilization and improved electrochemical performance of natural graphite spherical tailings.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of negative electrode materials of lithium ion batteries, and particularly relates to a method for modifying and granulating spherical tailings of natural graphite. BACKGROUND
[0002] The negative electrode is an important component of a lithium ion battery, and most of the negative electrode materials of lithium ion batteries are graphite. At present, the graphite mainly used in commercialized lithium ion batteries is spherical graphite, and the preparation technology thereof is relatively mature. However, about 40% of tailings are generated in the granulation process of the spherical graphite. Although the spherical tailings have high purity and good graphitization degree, they cannot be continuously used in the traditional granulation process due to the small and irregular size, thereby causing great waste of resources. Compared with graphite, transition metal selenides have a high theoretical specific capacity (usually greater than 410 mAh / g), and the selenide material has high electrical conductivity and good cycle performance when applied to the negative electrode of a lithium ion battery. However, due to the cost problem, the transition metal selenide alone is difficult to be directly used in commercial lithium ion batteries.
[0003] Studies have shown that the transition metal selenide can intercalate the graphite to further improve the lithium storage performance of the graphite (ACSAppl. Electron. Mater. 2023, 5, 6964 6973). The intercalation of the graphite increases the interlayer spacing of the graphite, improves the ion insertion kinetics, and can be used not only in lithium ion batteries but also in sodium ion batteries. Although the graphite intercalation technology can improve the lithium storage behavior of the material, from the technical application aspect, the graphite intercalated with the transition metal selenide alone is difficult to be directly used in the negative electrode of a lithium ion battery. The reason is that the intercalation is a process of expanding the interlayer spacing of the graphite, which is easy to cause further decrease of the bulk density of the graphite, especially for the spherical tailings of flaky graphite, which has a low bulk density. Moreover, the traditional granulation behavior is mainly suitable for large-sized flaky graphite, and the spherical tailings of graphite are small in size, and most of the sizes are concentrated at about 5 μm. How to uniformly granulate the spherical tailings of graphite is a current research hotspot and difficulty. SUMMARY
[0004] In order to overcome the above-mentioned defects of the prior art, the purpose of the present application is to provide a method for modifying and granulating spherical tailings of natural graphite, which solves the technical problems that the intercalated graphite is difficult to be directly used in the negative electrode of a lithium ion battery and the spherical tailings of graphite are difficult to be uniformly granulated.
[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions: The present application provides a method for modifying and granulating spherical tailings of natural graphite, which comprises the following steps: mixing the spherical tailings of natural graphite with a metal salt and then performing first calcination to obtain product A; The product A is mixed with selenium powder under an inert atmosphere for a second calcination to obtain product B; The product B is modified by a cationic surfactant solution to obtain product C; The product C is mixed with modified carbon fibers, and then pressed into a block material, and the block material is calcined for a third time to obtain product D; The product D is ball milled to obtain product E; The product E is mixed with pitch and calcined at high temperature to obtain a modified granulation product.
[0006] In an embodiment, the spherical tailings of natural graphite are graphite after granulation of natural flake graphite, and the size is 5-10 μm.
[0007] In an embodiment, the metal salt is a mixture of nickel salt and cobalt salt, and the nickel salt accounts for 20-80% of the total mass of the metal salt; the nickel salt is any one of nickel chloride, nickel sulfate and nickel nitrate, and the cobalt salt is any one of cobalt chloride, cobalt sulfate and cobalt nitrate.
[0008] In an embodiment, the mass ratio of the natural graphite spherical tailings to the metal salt is 100:(5-20); the mass ratio of the product A to the selenium powder is 1:(0.5-2); and the use amount ratio of the product C to the modified carbon fibers is 100:(5-15).
[0009] In an embodiment, the cationic surfactant in the cationic surfactant solution is one of octadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride and succinic monoester quaternary ammonium salt; and the mass fraction of the cationic surfactant in the cationic surfactant solution is 5-20 wt%.
[0010] In an embodiment, the use amount ratio of the product B to the cationic surfactant solution is 1 g:(2-10) mL, and the treatment time of the modification treatment is 2-8 h.
[0011] In an embodiment, the modified carbon fibers are obtained by modifying carbon fibers by an acid solution; the acid solution is one or more of sulfuric acid solution, hydrochloric acid solution and nitric acid solution; the mass fraction of the acid solution is 5-20 wt%; the use amount ratio of the carbon fibers to the acid solution is 1 g:(2-10) mL, and the treatment time of the modification is 2-8 h.
[0012] In an embodiment, the mass ratio of the grinding balls to the product D in the ball milling process is (30-50):1, and the mass ratio of the product E to the pitch powder is 100:(5-15).
[0013] In an embodiment, the pressing pressure is 10-50 Mpa; the diameter of the modified carbon fiber is 1-5 μm, and the length is 20-50 μm; the softening point of the pitch is 80-280 ℃; the ball milling time is 0.5-2 h, and the ball milling is carried out under air condition.
[0014] In an embodiment, the first calcination is carried out under argon, nitrogen or argon-hydrogen mixed gas, at a temperature of 500-800 ℃ for 1-3 h; the second calcination is carried out under argon, nitrogen or argon-hydrogen mixed gas, at a temperature of 300-600 ℃ for 30 min-3 h; the third calcination is carried out under argon, nitrogen or argon-hydrogen mixed gas, at a temperature of 500-800 ℃ for 3-10 h; and the high-temperature calcination is carried out under argon, nitrogen or argon-hydrogen mixed gas, at a temperature of 800-1200 ℃ for 3-10 h.
[0015] Compared with the prior art, the present application has the following advantages: The present application provides a method for modifying and granulating natural graphite spherical tailings. First, transition metal selenide is used to intercalate the natural graphite spherical tailings, which not only expands the interlayer spacing of the graphite and optimizes the ion deintercalation reaction kinetics, but also realizes the micro-expansion of the graphite based on the intercalation behavior of the transition metal selenide. At present, pre-expansion of the graphite is generally used to improve the pressing behavior of the bulk material and increase the densification degree. Therefore, this advantage makes the bulk material have a higher density during the later compounding process with carbon fibers. Meanwhile, considering that the bulk material with high density is prone to uneven pulverization during the ball milling process and the powder classification is difficult, the present application introduces carbon fibers with a larger size during the compounding process. The carbon fibers initially wrap and separate the graphite tailings by electrostatic force, and then the fibers in the bulk material undergo radial splitting and longitudinal peeling during the later ball milling process. The graphite particles are separated and pulverized at the fibers, thereby maximizing the control of the particle size distribution of the powder. The collected powder has a high particle size concentration, and the waste powder is reduced during the ball milling process. By controlling the number of carbon fibers, the granulation of graphite spherical tailings of different sizes can be realized. On this basis, the present application further coats the granulated agglomerates with pitch, thereby ensuring the acquisition of a carbon shell with a suit of armor and improving the structural stability of the graphite tailing granulation product. Compared with other common granulation methods such as spray granulation, the present application can realize the uniform granulation of the graphite spherical tailings by simply regulating the optimization method (intercalation of transition metal selenide) of the graphite spherical tailings, the material design during the powder pressing process and the ball milling process, thereby simplifying the preparation process and cost. BRIEF DESCRIPTION OF DRAWINGS
[0016] Figure 1In the figure, a and b are the first charge-discharge curves and cycle performance comparison diagrams of the negative electrode materials prepared in Example 1 and Comparative Example 1 of the present application, respectively. Figure 2 In the figure, a and b are the SEM images of the negative electrode materials prepared in Example 2 and Comparative Example 2 of the present application, respectively, c is the electrochemical curve diagram of the negative electrode materials prepared in Example 2 and Comparative Example 2 of the present application, and d is the cycle performance diagram of the negative electrode materials prepared in Example 2 and Comparative Example 2 of the present application. DETAILED DESCRIPTION
[0017] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used herein have their usual meanings to those skilled in the art of the present application, and in the event of conflict, the definitions in the specification shall prevail.
[0018] Theories or mechanisms described and disclosed herein, whether correct or not, should not be considered limiting the scope of the present application, that is, the present application can be practiced without regard to any particular theory or mechanism.
[0019] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, amounts, contents and concentrations, are for the sake of brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have encompassed and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).
[0020] In this document, unless otherwise specified, "comprise", "include", "contain", "have", or similar words encompass the meaning of "consist of" and "consist essentially of", for example, "A comprises a" encompasses the meaning of "A comprises a and other" and "A comprises only a".
[0021] In this document, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as the combinations of the technical features do not conflict, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope of the present specification.
[0022] The purpose of the present application is to provide a method for modifying and granulating natural graphite spherical tailings, directly using natural graphite spherical tailings as the basic structural unit, using transition metal selenide intercalation technology to control the interlayer spacing of graphite (make it slightly expand) and improve the electrochemical performance of graphite, and in view of the problems of low bulk density and many electrochemical side reactions of the intercalation compound, the present application carries out liquid phase granulation and pressing treatment on it in the later stage, improves the uniformity and density of the bulk material, ensures the high bulk density of the negative electrode material, and this property can continue to use pitch to improve the structural stability of the classified powder after ball milling and classification in the later stage, at the same time, pitch coating can also reduce the end face exposure of the graphite spherical tailings, reduce the cycle attenuation rate, and ensure the improvement and stability of the electrochemical performance of the battery.
[0023] The present application provides a method for modifying and granulating natural graphite spherical tailings, comprising the following steps: S1: mixing natural graphite spherical tailings with metal salt and then calcining to obtain product A; S2: mixing product A with selenium powder under inert atmosphere and then calcining to obtain product B; S3: modifying product B with a cationic surfactant to obtain product C; S4: mixing product C with modified carbon fiber first, then pressing into a bulk material under a certain pressure, and calcining the bulk material at high temperature to obtain product D; S5: putting product D into a ball mill to obtain product E; S6: mixing product E with pitch, high-temperature calcining to obtain the final modified and granulated product.
[0024] The above method not only can modify the natural graphite spherical tailings with metal selenide intercalation, but also can achieve good granulation effect, and the modified and granulated product obtained is finally used as the negative electrode of lithium ion battery, which has high first coulomb efficiency, good cycle stability and rate performance, and realizes efficient utilization of natural graphite spherical tailings.
[0025] In the specific implementation process, in S1, the natural graphite spherical tailings are graphite after granulation of natural flake graphite, and the size is about 5-10 μm. The metal salt is a mixture of nickel salt and cobalt salt, and the nickel salt accounts for 20-80% of the total mass of the mixed metal salt. The nickel salt is any one of nickel chloride, nickel sulfate and nickel nitrate, and the cobalt salt is any one of cobalt chloride, cobalt sulfate and cobalt nitrate.
[0026] In the specific implementation process, in S1, the amount ratio of natural graphite spherical tailings to metal salt is 100g: (5-20) g. The calcination atmosphere is argon, nitrogen or argon-hydrogen mixed gas, the calcination temperature is 500-800℃, and the calcination time is 1-3h.
[0027] In the implementation process, in S2, the mass ratio of product A to selenium powder is 1:(0.5-2), the calcination atmosphere is argon, nitrogen or argon-hydrogen mixed gas, the calcination temperature is 300-600℃, and the calcination time is 30 min-3 h.
[0028] In the implementation process, in S3, the cationic surfactant is one of octadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride and quaternary ammonium salt of succinic acid monoester; the solvent in the cationic surfactant solution is water; the mass fraction of the cationic surfactant in the cationic surfactant solution is 5-20 wt%; the dosage ratio of product B to the cationic surfactant solution is 1 g:(2-10) mL, and the treatment time is 2-8 h.
[0029] In the implementation process, in S4, the modification of the carbon fiber is carried out in an acid solution, the acid solution is one or more of sulfuric acid solution, hydrochloric acid solution and nitric acid solution, the mass fraction of the acid solution is 5-20 wt%; the dosage ratio of the carbon fiber to the acid solution is 1 g:(2-10) mL, and the treatment time is 2-8 h.
[0030] In the implementation process, in S4, the dosage ratio of product C to the modified carbon fiber is 100:(5-15); the diameter of the carbon fiber is 1-5 μm, the length is 20-50 μm, the block pressing pressure is 10-50 MPa, the block calcination temperature is 500-800℃, the calcination atmosphere is argon, nitrogen or argon-hydrogen mixed gas, and the calcination time is 3-10 h.
[0031] In the implementation process, in S5, the ball milling time is 0.5-2 h, the mass ratio of the milling ball to product D is (30-50):1 during the ball milling, the ball milling is carried out in air, and product E is obtained.
[0032] In the implementation process, in S6, the mass ratio of product E to the asphalt powder is 100:(5-15); the softening point of the asphalt is 80-280℃; the calcination atmosphere is argon, nitrogen or argon-hydrogen mixed gas, the calcination temperature is 800-1200℃, and the calcination time is 3-10 h.
[0033] In the implementation process, the final negative electrode product E is mainly used for lithium ion battery negative electrode.
[0034] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. Furthermore, it should be understood that those skilled in the art can make various modifications or amendments to the application after reading the content of the application, and these equivalent forms also fall within the scope defined by the appended claims of the application.
[0035] The following examples use apparatus and equipment that are conventional in the art. The experimental methods in the following examples, unless otherwise specified, are generally carried out according to conventional conditions, or according to the conditions recommended by the manufacturer. The following examples use various raw materials, unless otherwise specified, all of which are conventional commercially available products, and the specifications thereof are conventional in the art. In the specification of the present application and in the following examples, unless otherwise specified, "%" means "percent by weight", "parts" means "parts by weight", and the ratio means "ratio by weight".
[0036] Example 1 The present example provides a method for modifying and granulating spherical tailings of natural graphite, comprising the following steps: 100 g of spherical tailings of natural graphite was mixed with 5 g of metal salt, wherein the proportion of nickel salt in the total metal salt was 20%. Then, product A was obtained by adding under argon at 500°C for 3h; Product A was mixed with selenium powder at a ratio of 1:0.5, calcined at 300°C for 3h under argon to obtain product B; 100 g of product B was dispersed in 200 mL of 5 wt% octadecyltrimethylammonium chloride aqueous solution for 2h to obtain a positively charged graphite tailings modified product C; Product C was mixed with modified carbon fiber at a ratio of 100:5, wherein the carbon fiber had a diameter of 1 μm and a length of 20 μm, the carbon fiber used was pretreated in a 5 wt% sulfuric acid solution at a ratio of 1 g:2 mL for 2h, the mixture was prepared into a block material D under a pressure of 10 MPa, and then calcined at 800°C for 10h under argon to obtain product D; Product D was ball milled, wherein the mass ratio of grinding balls to product D was 30:1, and the ball milling time was 2h to obtain product E; 100 g of product E was mixed with pitch powder at a mass ratio of 100:5, the pitch used had a softening point of 80°C, and then calcined at 800°C for 10h under argon to obtain the final negative electrode material.
[0037] The negative electrode material prepared in Example 1 was coated on a copper foil to prepare a negative electrode, and a PP separator, 1 mol / L LiPF6 (solvent: a mixture of ethylene carbonate and dimethyl carbonate at a volume ratio of 1:1) as an electrolyte, and lithium sheet were assembled into a button cell for electrochemical performance test, and the initial specific capacity was 854.8 mAh g -1 at 0.1 A g -1 , and the specific capacity could still be maintained at 658.7 mAh g -1 after 300 cycles.
[0038] Example 2 The present example provides a method for modifying and granulating spherical tailings of natural graphite, comprising the following steps: Mix 100 g of natural graphite spherical tailings with 20 g of metal salts uniformly, wherein the proportion of nickel salt accounts for 80% of the total metal salt. Then add it under argon gas, calcine at 800 ℃ for 1 h to obtain product A; Mix product A with selenium powder in a ratio of 1:2, calcine at 800 ℃ for 1 h under argon-hydrogen mixed gas to obtain product B; Disperse 100 g of product B in 1000 mL of 20 wt% cetyltrimethylammonium chloride aqueous solution for 8 h to obtain a positively charged graphite tailings modified product C; Mix product C with modified carbon fibers in a ratio of 100:15, wherein the carbon fibers have a diameter of 5 μm and a length of 50 μm, the carbon fibers used are pretreated in 15 wt% hydrochloric acid solution at a ratio of 1 g:10 mL for 8 h, the mixture is prepared into a block material D under a pressure of 50 MPa, and then calcined at 500 ℃ for 10 h under argon-hydrogen mixed gas to obtain product D; Ball mill product D, wherein the mass ratio of grinding balls to product D is 50:1, and the ball milling time is 0.5 h to obtain product E; Mix 100 g of product E with pitch powder in a mass ratio of 100:15, wherein the softening point of the pitch used is 280 ℃, and then calcine at 1200 ℃ for 3 h under argon gas to obtain the final negative electrode material.
[0039] Example 2 -1 The first specific capacity of the battery at 0.1 A g -1 was 960.2 mAh g -1 , and the specific capacity after 300 cycles was 744.3 mAh g .
[0040] Example 3 The present embodiment provides a method for modifying and granulating natural graphite spherical tailings, comprising the following steps: Mix 100 g of natural graphite spherical tailings with 15 g of metal salts uniformly, wherein the proportion of nickel salt accounts for 50% of the total metal salt. Then add it under argon gas, calcine at 700 ℃ for 2 h to obtain product A; Mix product A with selenium powder in a ratio of 1:1, calcine at 500 ℃ for 2 h under nitrogen gas to obtain product B; Disperse 100 g of product B in 500 mL of 20 wt% quaternary ammonium salt of succinic acid monoester aqueous solution for 5 h to obtain a positively charged graphite tailings modified product C; Mix product C with modified carbon fibers in a ratio of 100:10, wherein the carbon fibers have a diameter of 3 μm and a length of 40 μm, the carbon fibers used are pretreated in 20 wt% nitric acid solution at a ratio of 1 g:5 mL for 6 h, the mixture is prepared into a block material D under a pressure of 40 MPa, and then calcined at 700 ℃ for 7 h under nitrogen gas to obtain product D; The product D is ball milled, with a mass ratio of grinding ball to product D of 40:1, for 1 h, to obtain product E; 100 g of product E is mixed with pitch powder at a mass ratio of 100:10, with a pitch softening point of 200℃, and then calcined at 1000℃ for 5 h under argon to obtain the final negative electrode material.
[0041] The obtained material can be stably cycled for more than 300 cycles after being assembled into a lithium ion battery.
[0042] Comparative Example 1 The material preparation method of Comparative Example 1 is similar to that of Example 1, except that the natural graphite spherical tailings and carbon fibers are directly used without any modification treatment, i.e. 100 g of natural graphite spherical tailings is directly mixed with carbon fibers at a ratio of 100:5, pressed, ball milled with a mass ratio of grinding ball to product D of 30:1 for 2 h, the carbon fibers have a diameter of 1 μm and a length of 20 μm, then mixed with pitch having a softening point of 80℃, and the material is calcined at 800℃ for 10 h under argon to obtain the final negative electrode material.
[0043] Comparative Example 2 The material preparation method of Comparative Example 2 is similar to that of Example 2, except that no carbon fibers are used and no pressing step is needed, i.e. 100 g of natural graphite spherical tailings is mixed with 20 g of metal salt, with the proportion of nickel salt in the total metal salt being 80%. Then product A is obtained by adding and calcining at 800℃ for 1 h under argon; product B is obtained by mixing product A with selenium powder at a ratio of 1:2 and calcining at 800℃ for 1 h under argon and hydrogen; and the final negative electrode material is obtained by mixing product B with pitch powder at a ratio of 100:15, with a pitch softening point of 280℃, and calcining at 1200℃ for 3 h under argon.
[0044] Figure 1 The first charge-discharge curves (a) and the cycle performance (b) of the negative electrode materials prepared in Example 1 and Comparative Example 1 are shown in the following figures. Figure 1 a) and the cycle performance (b) of the negative electrode materials prepared in Example 1 and Comparative Example 1 are shown in the following figures. Figure 1 b) It can be seen from the figures that the negative electrode material obtained by modifying the tailings with transition metal selenide has a higher specific lithium storage capacity, and has a relatively stable voltage platform during the entire discharge process. It can also be seen from the cycle performance curve of the electrode that the discharge performance is stable during the cycle process of up to 300 times. Therefore, the modification of graphite with transition metal selenide can improve the specific capacity of the material and has a good application prospect.
[0045] Figure 2The SEM images of the negative electrode materials prepared for Example 2 and Comparative Example 2 (a is the comparative example, and b is the example) of the present application can be seen that after the carbon fiber assisted pressing step, the obtained negative electrode material presents a relatively good granulation state, while the negative electrode material obtained in Comparative Example 2 is relatively loose and does not achieve the purpose of granulation. From the electrochemical curve (Figure 2), it can be seen that the first coulombic efficiency of the granulated negative electrode material is high (90.6%), and the cycle stability is good (Figure 3). Figure 2 The first coulombic efficiency of the material without granulation is low (60.9%), and the reason is that the specific surface area of the material without granulation is large, and the material side reaction such as SEI film growth is serious, which confirms the feasibility of the introduction of carbon fiber and the auxiliary pressing step to improve the overall electrochemical performance of the material. Figure 2 d), while the material without granulation has a low first coulombic efficiency (60.9%), and the reason is that the specific surface area of the material without granulation is large, and the material side reaction such as SEI film growth is serious, which confirms the feasibility of the introduction of carbon fiber and the auxiliary pressing step to improve the overall electrochemical performance of the material.
[0046] The above content only illustrates the technical idea of the present application and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical solution falls within the protection scope of the claims of the present application.
Claims
1. A method for modifying and granulating spherical tailings of natural graphite, characterized by, The method comprises the following steps: mixing the natural graphite spherical tailings with metal salt and performing first calcination to obtain product A; mixing product A with selenium powder and performing second calcination under inert atmosphere to obtain product B; performing modification treatment on product B with cationic surfactant solution to obtain product C; mixing product C with modified carbon fiber and then pressing into block material, and performing third calcination on the block material to obtain product D; performing ball milling on product D to obtain product E; mixing product E with pitch and performing high-temperature calcination to obtain modified granulation product.
2. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The natural graphite spherical tailings are graphite after granulation of natural flake graphite, and the size is 5-10 μm.
3. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The metal salt is a mixture of nickel salt and cobalt salt, and the nickel salt accounts for 20-80% of the total mass of the metal salt; the nickel salt is any one of nickel chloride, nickel sulfate and nickel nitrate, and the cobalt salt is any one of cobalt chloride, cobalt sulfate and cobalt nitrate.
4. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The mass ratio of the natural graphite spherical tailings to the metal salt is 100:(5-20); the mass ratio of product A to selenium powder is 1:(0.5-2); and the dosage ratio of product C to modified carbon fiber is 100:(5-15).
5. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The cationic surfactant in the cationic surfactant solution is one of octadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride and succinic monoester quaternary ammonium salt; and the mass fraction of the cationic surfactant in the cationic surfactant solution is 5-20 wt%.
6. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The dosage ratio of product B to the cationic surfactant solution is 1 g:(2-10) mL, and the treatment time of the modification treatment is 2-8 h.
7. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The modified carbon fiber is obtained by modifying carbon fiber with an acid solution; the acid solution is one or more of sulfuric acid solution, hydrochloric acid solution and nitric acid solution; the mass fraction of the acid solution is 5-20 wt%; the dosage ratio of the carbon fiber to the acid solution is 1 g:(2-10) mL, and the treatment time of the modification is 2-8 h.
8. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The mass ratio of the grinding ball to product D in the ball milling process is (30-50):1, and the mass ratio of product E to pitch powder is 100:(5-15).
9. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The pressure of the pressing is 10-50 Mpa; the diameter of the modified carbon fiber is 1-5 μm, and the length is 20-50 μm; the softening point of the pitch is 80-280℃; the ball milling time is 0.5-2 h, and the ball milling is performed under air condition.
10. The method of modifying and pelletizing natural graphite spherical tailings according to claim 1, characterized in that, The calcination atmosphere of the first calcination is argon, nitrogen or argon-hydrogen mixed gas, the calcination temperature is 500-800℃, and the calcination time is 1-3 h; the calcination atmosphere of the second calcination is argon, nitrogen or argon-hydrogen mixed gas, the calcination temperature is 300-600℃, and the calcination time is 30 min-3 h; the calcination atmosphere of the third calcination is argon, nitrogen or argon-hydrogen mixed gas, the calcination temperature is 500-800℃, and the calcination time is 3-10 h; and the calcination atmosphere of the high-temperature calcination is argon, nitrogen or argon-hydrogen mixed gas, the calcination temperature is 800-1200℃, and the calcination time is 3-10 h.