Waste coke regenerated graphite, preparation method and application thereof, and lithium ion battery

Abstract

The application belongs to the field of battery material regeneration, and particularly relates to waste coke regenerated graphite, a preparation method and application thereof, and a lithium ion battery. The preparation method comprises the following steps: mixing graphitized coke waste and an aqueous polymer solution, and then performing pressure treatment to obtain a composite material F1; then performing fusion treatment on the composite material F1, waste green coke tail powder and a targeted metal halide to obtain a core-shell composite coke; and then performing a first-stage modification heat treatment on the core-shell composite coke, and then performing a second-stage targeted heat treatment to obtain the waste coke regenerated graphite. The weight ratio of the graphitized coke waste, the waste green coke tail powder and the targeted metal halide is 1:0.1-0.8:0.001-0.15. The temperature of the first-stage modification heat treatment is 600-1200 DEG C. The temperature of the second-stage targeted heat treatment is 1800-2500 DEG C. The method can realize the joint consumption of waste graphitized coke and waste green coke, and can obtain a graphite material with high capacity and fast charging performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery anode materials, specifically relating to the field of waste coke recycled graphite technology. Background Technology

[0002] With the rapid development of the new energy vehicle industry and the electrochemical energy storage market, the demand for lithium-ion batteries has exploded. However, artificial graphite anodes, as their core material, are facing a dual challenge in terms of resource supply and environmental sustainability. On the one hand, the demand for high-quality petroleum coke required for production continues to rise, but its output has decreased due to upgrades in refining processes, leading to increasing supply pressure. On the other hand, a large amount of carbonaceous solid waste generated during production has not yet been efficiently and effectively utilized, resulting not only in the waste of high-quality coke resources but also in environmental risks. Specifically, this manifests in two major resource loss stages: First, approximately 30% of the waste coke tailings with a particle size of 0.1~5μm are generated during the raw material crushing process. Due to their excessively fine particles, large specific surface area, low tap density, and poor morphology, they are difficult to reuse in the production of artificial graphite anodes and are usually only treated as fuel or low-value raw materials for aluminum electrolysis anodes. Second, in the graphitization process of anodes, the performance of calcined petroleum coke, used as insulation and resistance materials, deteriorates after repeated use, forming graphitized coke waste. Approximately 400 kg of graphitized coke is discharged for every ton of anode produced. This type of graphitized coke has a low carbon content, generally 96-99%, and a large specific surface area after crushing. It has poor homogenization and processing performance, making it difficult to use directly as a high-rate anode material. Currently, it is mainly used as a carbon raiser in the steel industry and other low-value-added applications.

[0003] To further improve the resource value of waste coke, existing technologies have also provided some methods for recycling waste coke into graphite. For example, Chinese patent document CN119176553A discloses a method for preparing artificial graphite using waste coke powder. The method uses micro powder, a by-product generated during the coke grinding stage, as raw material and asphalt-like substances as binders. The asphalt-like substances are subjected to aerobic baking, during which some of the asphalt-like substances are oxidized. These substances are then mixed with waste coke powder and granulated. During the subsequent carbonization process, these oxidized substances form special pores on the graphite surface. These special porous carbon coating layers give the artificial graphite good porosity and solve the problem of low tap density after granulation of waste coke powder.

[0004] While existing technologies involve some methods for the resource-based preparation of graphite from waste coke, they rarely involve methods for the resource-based preparation of graphite from waste graphitized coke, and even less so methods for the efficient resource-based preparation of graphite from waste graphitized coke and other coke wastes. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the first objective of this invention is to provide a method for preparing recycled graphite from waste coke, which aims to synergistically process waste coke tail powder and graphitized coke waste, increase its added value, and improve the performance of the prepared material, such as its rate of return.

[0006] The second objective of this invention is to provide recycled graphite from waste coke prepared by the aforementioned method.

[0007] A third objective of this invention is to provide applications of the recycled graphite from waste coke prepared by the aforementioned method, and to produce lithium-ion batteries from it.

[0008] Waste coke powder has excessively fine particles, a large specific surface area, low tap density, and poor morphology, making graphitization difficult and costly, and thus unsuitable for reuse in the production of artificial graphite anodes. Furthermore, graphitized coke waste has low purity, numerous micropores, and a large specific surface area after pulverization, making it difficult to use directly as a high-performance anode material. Moreover, the combined treatment of waste coke and graphitized coke waste, compared to the treatment of waste coke alone, requires addressing the challenge of adapting their physicochemical properties for joint processing. To address this technical problem, this invention provides the following technical solution:

[0009] The method for preparing recycled graphite from waste coke involves mixing graphitized coke waste with an aqueous polymer solution and then pressurizing it (also known as pressure holding treatment in this invention) to obtain composite material F1. Composite material F1 is then fused with waste coke tail powder and targeted metal halide to obtain core-shell composite coke. The core-shell composite coke is then subjected to a first stage of modification heat treatment, followed by a second stage of targeted heat treatment to obtain recycled graphite from waste coke.

[0010] The weight ratio of the graphitized coke waste, waste coke tail powder, and targeted metal halide is 1:0.1~0.8:0.001~0.15;

[0011] The temperature for the first stage of modification heat treatment is 600~1200℃;

[0012] The temperature for the second stage of targeted heat treatment is 1800~2500℃.

[0013] The graphitized coke waste is at least one of the following: graphitized insulation material, graphitized resistive material, and graphitized dust collection powder discharged during the negative electrode graphitization process.

[0014] Preferably, the graphitized coke has a particle size of ≤25mm, a resistivity of ≤100Ω·m, and an ash content of ≤5%.

[0015] Preferably, the graphitized coke waste has a particle size of 8-15 μm and a specific surface area of ​​4-7 m². 2 / g.

[0016] The aqueous polymer in the aqueous polymer solution includes at least one of sodium carboxymethyl cellulose, sodium carboxymethyl starch, starch, hydroxypropyl cellulose, polyacrylic acid, sodium polyacrylate, acrylic acid-acrylamide copolymer, and polyvinyl alcohol.

[0017] Preferably, the aqueous polymer comprises polyvinyl alcohol and sodium carboxymethyl cellulose in a weight ratio of 1 to 3:1. Studies have shown that the preferred polymer, combined with the process described in this invention, can further synergistically enhance the joint disposal effect of waste graphitized coke and waste green coke, and improve the electrochemical performance of recycled materials.

[0018] Preferably, the concentration of the aqueous polymer in the aqueous polymer solution is 1% to 5%;

[0019] Preferably, the weight ratio of graphitized coke waste to water-soluble polymer in the aqueous polymer solution is 1:0.01~0.05; more preferably, it can be 1:0.01~0.03.

[0020] The pressure for pressurization is 2~15MPa.

[0021] Preferably, the pressure holding time during the pressurization process is 5 to 30 minutes.

[0022] Preferably, the pressurization process includes a first pressurization process and a second pressurization process, wherein the pressure of the first pressurization process is 5-6 MPa, and the pressure of the second pressurization process is 8-12 MPa. Studies have shown that the preferred two-stage gradient pressurization process can be combined synergistically with the process of the present invention to further enhance the capacity and fast-charging performance of the recycled graphite material.

[0023] Preferably, the time for the first stage of pressurization is 2.5 to 15 minutes, and more preferably 5 to 10 minutes; the time for the second stage of pressurization is 2.5 to 15 minutes, and more preferably 5 to 10 minutes.

[0024] The waste coke tailings are tailings produced by crushing petroleum coke raw coke; the particle size is 0.1~5μm, the volatile matter is 8~20%, and the true density is 1.3~1.5g / cm³. 3 The sulfur content is 0.5%~6%;

[0025] Preferably, the waste coke powder has a particle size of 1-3 μm, a volatile matter content of 12-20%, and a true density of 1.3-1.4 g / cm³. 3 The sulfur content is 0.5%~3%.

[0026] The targeted metal halide is at least one of the chlorides and bromides of iron, nickel, and magnesium;

[0027] The weight ratio of the graphitized coke waste, waste raw coke tail powder, and targeted metal halide is 1:0.15~0.5:0.001~0.05. This preferred ratio can further improve the combined synergistic utilization effect of waste graphitized coke and waste raw coke, and can also improve the fast-charging performance of the regenerated graphite.

[0028] In this invention, after fusion, the material can be further subjected to briquetting as needed to obtain the core-shell composite coke.

[0029] In this invention, the fusion and sphere pressing can be achieved using conventional methods.

[0030] Before undergoing the first stage of modification heat treatment, the core-shell composite coke can be dried as needed. The drying temperature can be, for example, 100~300℃.

[0031] The temperature for the first stage of modification heat treatment is 750~1150℃; the temperature for the second stage of targeted heat treatment is 2100~2450℃.

[0032] Preferably, the holding time at the temperature of the first stage of modification heat treatment is 1 to 5 hours; the holding time at the temperature of the second stage of targeted heat treatment is 1 to 5 hours.

[0033] Preferably, the atmosphere for the first stage of modification heat treatment and the second stage of targeted heat treatment is an inert atmosphere, which is at least one inert gas such as nitrogen, argon, or helium.

[0034] The present invention also provides a recycled graphite from waste coke prepared by the aforementioned preparation method.

[0035] The preparation method described in this invention can endow the prepared material with special physicochemical properties. In addition to realizing the high-value utilization of waste coke that is difficult to process in the prior art, the material obtained by the preparation method can also obtain graphite material with excellent capacity and fast charging performance.

[0036] The present invention also provides an application of the recycled graphite obtained by the preparation method described above, which is used as a negative electrode active material for the preparation of lithium-ion batteries.

[0037] The present invention also provides a lithium-ion battery comprising recycled graphite from waste coke prepared by the aforementioned method.

[0038] Beneficial effects

[0039] This invention provides a resource-based treatment approach for graphitized coke waste and raw coke tailings. Based on the physicochemical characteristics of graphitized coke waste and raw coke tailings, it further combines the pre-pressurization of the graphitized coke waste and water-soluble polymers with the joint control of the core-shell structure of the raw coke and metal halides, further enhanced by a two-stage roasting process. This achieves synergy, optimizes the interfacial structure between particles, and constructs a lithium-ion compatible storage structure and conduction network. The method of this invention not only improves the tap density and compaction density of the raw coke tailings and optimizes the particle morphology, but also significantly reduces the specific surface area and purity of the graphitized coke waste, thereby improving its rate performance. Based on a component structure matching and functional complementarity strategy, this invention achieves synergistic efficiency in the production of two types of carbonaceous solid waste from artificial graphite, laying the foundation for their high-value utilization in high-performance anode materials. Attached Figure Description

[0040] Figure 1 Image of the core-shell precursor obtained in Example 1;

[0041] Figure 2 This is a SEM image of the recycled graphite obtained in Example 1.

[0042] Figure 3 This is a charge-discharge data graph of the recycled graphite obtained in Example 1. Detailed Implementation

[0043] The graphitized coke waste described in this invention can be at least one of the following: graphitized insulation material discharged during the negative electrode graphitization process, graphitized resistive material, and graphitized dust collection powder. As an optional embodiment, the graphitized coke waste has a particle size ≤25mm, resistivity ≤100Ω·m, and ash content ≤5%; for example, 8~15μm, and a specific surface area of ​​4~7m². 2 / g.

[0044] The waste coke tailings are tailings produced by crushing any type of petroleum coke raw coke. As an optional configuration, its particle size is 0.1~5μm, volatile matter is 8~20%, and true density is 1.3~1.5g / cm³. 3 The sulfur content is 0.5%~6%.

[0045] Example 1

[0046] Step 1:

[0047] Graphitized coke waste and aqueous polymer solution were stirred, mixed, and pressurized at 5 MPa for 10 min to obtain material F1 (composite material F1); in the aqueous polymer solution, the aqueous polymer is sodium carboxymethyl cellulose with a concentration of 1%, and the weight ratio of graphitized coke waste to aqueous polymer is 1:0.01.

[0048] The material F1 is then fused with waste coke tail powder and targeted metal halide and briquetteed to obtain briquette material F2 (core-shell composite coke); wherein, the targeted metal halide is ferric chloride; the weight ratio of graphitized coke waste, waste coke tail powder and targeted metal halide in material F1 is 1:0.2:0.003.

[0049] Step 2:

[0050] The briquette F2 was preheated to T1 (100℃) in air at a heating rate of V1 (3℃ / min) for drying treatment. Nitrogen gas was introduced and heated to T2 (800℃) at a heating rate of V2 (5℃ / min) for 3 hours for modification treatment. Then, nitrogen gas was introduced and heated to T3 (2400℃) at a heating rate of V3 (30℃ / min) for targeted high-temperature heat treatment for 2 hours to prepare the graphite anode active material.

[0051] Example 2

[0052] Compared to Example 1, the only difference is that the conditions in step 1 are changed, and the experimental groups are as follows:

[0053] Group A: The water-soluble polymer in the water-soluble polymer solution is polyvinyl alcohol; the weight ratio of graphitized coke waste to water-based polymer is 1:0.03; the holding time is 15 min.

[0054] Group B: The water-soluble polymer in the water-soluble polymer solution is a mixture of polyvinyl alcohol and sodium carboxymethyl cellulose in a ratio of 2:1; the solute concentration and total amount of the water-soluble polymer solution are the same as in Example 1;

[0055] Group C: Change the pressurization method, specifically, first maintain pressure at 5 MPa for 5 minutes, and then maintain pressure at 10 MPa for 5 minutes;

[0056] Group D: The holding pressure is 10 MPa, and the holding time is 10 min.

[0057] Group E: The weight ratio of graphitized coke waste, waste coke tail powder, and targeted metal halide (ferric chloride) in material F1 is 1:0.5:0.003;

[0058] Group F: The weight ratio of graphitized coke waste, waste coke tail powder, and targeted metal halide (magnesium chloride) in material F1 is 1:0.4:0.005;

[0059] Group G: The weight ratio of graphitized coke waste, waste coke tail powder, and targeted metal halide (ferric fluoride) in material F1 is 1:0.3:0.001.

[0060] All other operations and parameters are the same as in Example 1.

[0061] Example 3

[0062] Compared with Example 1, the only difference is that the conditions of step 2 are changed. Specifically, the briquette F2 is preheated to T1 (80°C) under Ar atmosphere at a heating rate of V1 (5°C / min) for drying, then heated to T2 (1100°C) at a heating rate of V2 (8°C / min) for modification treatment for 2 hours, and then heated to T3 (2200°C) at a heating rate of V3 (10°C / min) for high-temperature heat treatment for 5 hours to prepare the graphite anode active material.

[0063] All other operations and parameters are the same as in Example 1.

[0064] Example 4

[0065] Compared with Example 1, the only difference is that the weight ratio of graphitized coke waste to targeted metal halide in material F1 is 1:0.15, and all other operations and parameters are the same as in Example 1.

[0066] Comparative Example 1

[0067] Compared with Example 1, the only difference is that in step 1, the graphitized coke waste and the water-soluble polymer solution are treated under normal pressure, while other operations and parameters are the same as in Example 1.

[0068] Comparative Example 2

[0069] Compared to Example 1, the only difference is that in step 1, the graphitized coke and water-soluble polymer solution were not mixed beforehand. Instead, the graphitized coke waste, waste coke tail powder, water-based polymer solution, and targeted metal halide were pressurized together (pressurization conditions were the same as in Example 1) and then evaporated to obtain composite coke. The composite coke was then subjected to subsequent processing, with other operations and parameters the same as in Example 1. This case did not pre-construct a core-shell composite coke with graphitized coke as the core and waste coke as the shell.

[0070] Comparative Example 3

[0071] Compared to Example 1, the only difference is that the core-shell composite coke structure construction in step 1 is not performed. Instead, the graphitized coke waste, waste coke tail powder, water-based polymer, and targeted metal halide are physically mixed and then directly processed in step 2. Other operations and parameters are the same as in Example 1. This case does not pre-construct a core-shell composite coke with graphitized coke as the core and waste coke as the shell.

[0072] Comparative Example 4

[0073] Compared with Example 1, the only difference is that the waste coke tail powder and aqueous polymer solution are pre-pressurized and then mixed with graphitized coke waste and targeted metal halide, and then the composite coke is processed in step 2. Other operations and parameters are the same as in Example 1.

[0074] This case constructs a core-shell composite coke with waste coke as the core and graphitized coke as the shell, but does not construct the core-shell composite coke with graphitized coke as the core and waste coke as the shell required by this invention.

[0075] Comparative Example 5

[0076] Compared with Example 1, the only difference is that a single waste graphitized coke is used for treatment, that is, the waste raw coke in step 1 is replaced by the graphitized coke in an equal amount. All other operations and parameters are the same as in Example 1.

[0077] Comparative Example 6

[0078] Compared with Example 1, the only difference is that a single waste coke is used for treatment, that is, the waste coke is used to replace the graphitized coke in step 1 in an equal amount. All other operations and parameters are the same as in Example 1.

[0079] Comparative Example 7

[0080] Compared with Example 1, the only difference is that the graphitized coke waste is replaced by an equal weight of calcined coke, while the other operations and parameters are the same as in Example 1.

[0081] Comparative Example 8

[0082] Compared with Example 1, the only difference is that the aqueous polymer solution is replaced with an N-methylpyrrolidone organic solution of polyvinylidene fluoride, while the polymer solute concentration and dosage, and other operations and parameters are the same as in Example 1.

[0083] Comparative Example 9

[0084] Compared with Example 1, the only difference is that no targeted metal halide is added; all other operations and parameters are the same as in Example 1.

[0085] The physicochemical properties of the waste coke modified graphite in Examples 1-4 and Comparative Examples 1-9 were tested respectively, and the test results are shown in Table 1.

[0086] The working electrode was prepared according to the mass ratio of active material (recycled material in each case): conductive agent (Super P): sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) = 95:1.5:1.5:2. A lithium metal sheet was used as the counter electrode, a ceramic separator was selected, and the electrolyte was LB-5315C organic electrolyte produced by Guotai Huarong. 2016-type button batteries were assembled in an argon-filled glove box. The electrochemical performance of the assembled batteries was tested using a Blue Battery Testing System (CT3001A). The initial charge-discharge curve test was conducted at a rate of 0.1 C, with a voltage range of 0.001~1.5 V. Rate charge-discharge tests were conducted at rates of 0.1 C, 0.2 C, 0.5 C, 1 C, and 2 C, with a voltage range of 0.001~1.5 V.

[0087] The test results are shown in Table 1:

[0088]

[0089] As demonstrated in Examples 1 and Comparative Examples 1-9, the innovative method of pre-pressurizing graphitized coke waste and aqueous polymer solution, followed by mixing with waste raw coke and targeted metal halides, enables the construction of a core-shell composite coke with waste graphitized coke as the core and waste raw coke as the shell, exhibiting excellent interfacial interaction between the core and shell structures. Furthermore, the innovative two-stage calcination process of the core-shell composite coke optimizes the interfacial structure between waste coke of different materials, constructs and optimizes the physicochemical structure for lithium insertion and extraction, and constructs and optimizes the electron conduction network. This invention demonstrates that the preparation method can achieve the joint disposal and treatment of the two types of waste coke, and also enables the high-value resource recovery of graphite materials with high capacity and fast-charging performance.

[0090] Furthermore, as demonstrated in Examples 1 and 2, the use of a water-soluble polymer composed of polyvinyl alcohol and sodium carboxymethyl cellulose, and / or a gradient pressurization process, can further improve the combined disposal effect of waste graphitized coke and waste green coke, and help to further enhance the fast-charging performance of the recycled composite material.

Claims

1. A method for preparing recycled graphite from waste coke, characterized in that, Graphitized coke waste and aqueous polymer solution are mixed and pressurized to obtain composite material F1. Composite material F1 is then fused with waste coke tail powder and targeted metal halide to obtain core-shell composite coke. The core-shell composite coke is pre-treated with a first stage of modification heat treatment, followed by a second stage of targeted heat treatment to obtain waste coke recycled graphite. The graphitized coke waste mentioned above is at least one of the following: graphitized insulation material, graphitized resistance material, and graphitized dust collection powder discharged during the graphitization process of negative electrode. The aqueous polymer in the aqueous polymer solution includes at least one of sodium carboxymethyl cellulose, sodium carboxymethyl starch, starch, hydroxypropyl cellulose, polyacrylic acid, sodium polyacrylate, acrylic acid-acrylamide copolymer, and polyvinyl alcohol; The waste coke tailings are the tailings produced by crushing petroleum coke raw coke. The targeted metal halide is at least one of the chlorides and bromides of iron, nickel, and magnesium; The weight ratio of the graphitized coke waste, waste coke tail powder, and targeted metal halide is 1:0.1~0.8:0.001~0.15; The pressure for pressurization is 2~15MPa; The pressure holding time during the pressurization process is 5~30 minutes; The temperature for the first stage of modification heat treatment is 600~1200℃; The temperature for the second stage of targeted heat treatment is 1800~2500℃.

2. The method for preparing recycled graphite from waste coke as described in claim 1, characterized in that, The particle size of graphitized coke waste is ≤25mm, resistivity is ≤100Ω·m, and ash content is ≤5%; The particle size of graphitized coke waste is 8~15μm, and the specific surface area is 4~7m². 2 / g.

3. The method for preparing recycled graphite from waste coke as described in claim 1, characterized in that, The concentration of aqueous polymer in the aqueous polymer solution is 1% to 5%; The weight ratio of graphitized coke waste to aqueous polymer in the aqueous polymer solution is 1:0.01~0.

05.

4. The method for preparing recycled graphite from waste coke as described in claim 1, characterized in that, The pressurization process includes a first pressurization process and a second pressurization process. The pressure in the first pressurization process is 5-6 MPa, and the pressure in the second pressurization process is 8-12 MPa. The first stage of pressurization treatment lasts for 2.5 to 15 minutes; the second stage of pressurization treatment lasts for 2.5 to 15 minutes.

5. The method for preparing recycled graphite from waste coke as described in claim 1, characterized in that, The waste coke tail powder has a particle size of 0.1~5μm, a volatile matter content of 8~20%, and a true density of 1.3~1.5g / cm³. 3 The sulfur content is 0.5%~6%.

6. The method for preparing recycled graphite from waste coke as described in claim 1, characterized in that, The weight ratio of the graphitized coke waste, waste coke tail powder, and targeted metal halide is 1:0.15~0.5:0.001~0.

05.

7. The method for preparing recycled graphite from waste coke as described in claim 1, characterized in that, The temperature for the first stage of modification heat treatment is 750~1150℃; the temperature for the second stage of targeted heat treatment is 2100~2450℃. The holding time at the temperature of the first stage of modification heat treatment is 1~5h; the holding time at the temperature of the second stage of targeted heat treatment is 1~5h. The atmosphere for the first stage of modification heat treatment and the second stage of targeted heat treatment is an inert gas.

8. A recycled graphite from waste coke prepared by the preparation method according to any one of claims 1 to 7.

9. The application of recycled graphite from waste coke prepared by the method according to any one of claims 1 to 7, characterized in that, It is used as a negative electrode active material in the preparation of lithium-ion batteries.

10. A lithium-ion battery, characterized in that, It includes recycled graphite from waste coke prepared by the preparation method according to any one of claims 1 to 7.

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