Method for preparing core-shell coated conductive material from medium-low temperature coal tar and application thereof

Abstract

The application belongs to the technical field of conductive material preparation, and relates to a method for preparing core-shell coated conductive material from medium and low temperature coal tar and application, which comprises the following steps: S1, cutting phenol oil, dephenolized oil and pitch from the medium and low temperature coal tar; S2, gradient extraction of the dephenolized oil, compounding, adding a viscosity reducer, phenol oil and a crosslinking agent, and then performing an oxidation crosslinking reaction to obtain a coating agent; S3, performing hydrogenation refining and thermal polymerization reaction on the pitch to obtain a spherical core; and S4, performing carbonization coating on the coating agent and the spherical core to obtain the core-shell coated conductive material. The core-shell coated conductive material is prepared from the medium and low temperature coal tar, which is beneficial to enhancing the stability of the material; the core-shell coated conductive material has high specific capacitance and coulomb efficiency, good electrochemical performance and low process preparation cost.

Description

Technical Field

[0001] This invention belongs to the field of conductive material preparation technology, and relates to a method and application for preparing core-shell coated conductive materials from medium- and low-temperature coal tar. Background Technology

[0002] In recent years, with increasing interest in electric and hybrid vehicles, the global demand for lithium-ion batteries has been growing year by year. Highly crystalline graphite carbon is often used as a negative electrode material for lithium-ion batteries due to its high capacity, excellent cycle performance, and high coulombic efficiency. However, the diffusion coefficient of lithium ions between graphite layers is relatively small, severely limiting the improvement of high-rate charge-discharge performance of lithium-ion batteries. Furthermore, highly graphitized graphite materials have poor compatibility with electrolytes, thus requiring further improvements to enhance the rate performance and electrolyte compatibility of graphite-based negative electrode materials.

[0003] Modification methods can be broadly categorized into three types: surface oxidation or reduction treatment, doping, and coating. For industrial production, coating modification is the primary method. Core-shell structured carbon materials possess bilayer or multilayer structures, with the core and shell achieving a coating effect through chemical bonds or other interactions. This combines the advantages of both the core and shell, allowing for the preparation of novel materials with properties distinct from or even superior to those of the core or shell itself. The properties of the material can be controlled by adjusting the types of core and shell materials, or by controlling the preparation process and thus the thickness of the core and shell layers, thereby optimizing the overall material performance.

[0004] Chinese patent application CN201410205734.3 discloses a method for preparing a coated electrode material, an electrode material prepared according to the method, and a lithium-ion battery containing the electrode material. This method uses a silicon compound containing alkoxy groups as a coating agent, with the negative electrode material as the electrode material. The electrode material and the coating agent are contacted with a vaporized substance, and a heating reaction is performed to form the coated electrode material. This method uses a gas-phase method to coat existing electrode materials and stabilize the electrode material structure. However, this method directly coats the negative electrode material with silicon compounds, and silicon is prone to pulverization in actual electrode use, reducing the utilization rate of the active components of the conductive material and thus affecting the electrochemical performance of the material. Shen Wanci of Tsinghua University prepared a phenolic resin-coated spherical graphite composite material using spray granulation, and then obtained a pyrolytic carbon-coated spherical graphite composite material through carbonization. Compared with spherical graphite, this composite graphite material showed a significantly improved initial coulombic efficiency, significantly extended cycle performance, and significantly improved compatibility of the electrode material with the electrolyte. However, its stability and electrochemical performance remained poor. Summary of the Invention

[0005] To address the technical problems of poor stability, poor electrochemical performance, and high processing costs of existing conductive materials, this invention provides a method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar and its application.

[0006] This invention uses medium- and low-temperature coal tar as raw material to prepare a coating agent and a core, which are then carbonized to form a core-shell coated conductive material. This process enhances the stability of the material. The core-shell coated conductive material has a high specific capacitance and coulombic efficiency, and its electrochemical performance is improved. The process has low preparation cost.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar includes the following steps:

[0009] S1, Fraction Cutting

[0010] Take two portions of medium-low temperature coal tar. Use atmospheric and vacuum distillation to cut the phenolic oil from the first portion into the 180℃~220℃ fraction. The remaining fraction is recorded as dephenolized oil.

[0011] The second sample was prepared by atmospheric and vacuum distillation to separate phenolic oil from the 180℃ to 220℃ fraction and asphalt from the 350℃ to 550℃ fraction.

[0012] S2, preparation of coating agent

[0013] The phenol-free oil from step S1 was separated into component a and component b by gradient extraction, and then component a and component b were mixed in a mass ratio of (1-3):1 to obtain a compound material.

[0014] A viscosity reducer is added to the compound; then, under an inert gas atmosphere, a crosslinking agent and an oxidizing agent are added, and a coating agent is obtained through an oxidative crosslinking reaction; the oxidizing agent is phenolic oil from the 180℃~220℃ distillation fraction in step S1; the amount of viscosity reducer added is 1%~5% of the mass of the compound; the amount of oxidizing agent added is 5%~10% of the mass of the compound; the amount of crosslinking agent added is 7%~14% of the mass of the compound.

[0015] S3, Core Making

[0016] Take the 350℃~550℃ fraction of asphalt cut in step S1, and obtain the sphere core through hydrorefining, thermal polymerization reaction and separation;

[0017] S4, Covering

[0018] The coating agent obtained in step S2 is ground into powder and dissolved in tetrahydrofuran. The amount of coating agent added is 5wt% to 15wt%. Then, the spherical cores obtained in step S3 are added. After stirring, sonicating, filtering, drying and carbonizing, a core-shell coated conductive material is obtained.

[0019] Further specifying, the specific steps of the gradient extraction process in step S2 are as follows:

[0020] S2.1. Mix the dephenolized oil from step S1 with toluene at a mass ratio of 1:(1.5~2.5), stir at 60℃~90℃ for 50min~80min, let stand for 2h~4h, take the upper light phase to obtain component a, and the lower layer is the remaining component.

[0021] S2.2. Mix the remaining components with quinoline at a mass ratio of 1:(1.5~2.5), stir at 60℃~90℃ for 50min~80min, let stand for 2h~4h, and take the upper light phase to obtain component b.

[0022] Further specifying, in step S2, the viscosity reducer is one or more of carboxymethyl cellulose, 2-acrylamido-2-methylpropanesulfonic acid, sodium dodecylbenzenesulfonate, and sodium N and N-dimethyl-dithiocarbonylpropanesulfonate; the crosslinking agent is one or more of polydopamine, polyvinylidene fluoride, hydroxyl-terminated polybutadiene, polytetrafluoroethylene, and stearic acid.

[0023] Further specifying, in step S2, the process conditions for the oxidative crosslinking reaction are:

[0024] The first stage involves heating to 260℃~290℃ and holding at that temperature for 2h~4h, with a heating rate of 2℃ / min~4℃ / min. The second stage involves further heating to 300℃~360℃ and holding at that temperature for 2h~5h, with a heating rate of 0.5℃ / min~2℃ / min.

[0025] Further specified, the yield of the coating agent is ≥65.5%, and the properties of the coating agent are: softening point of 244℃~287℃, coking value of ≥67.54%, toluene insoluble content of 50%~75%, and quinoline insoluble content of 0.02%~0.13%.

[0026] Further specifying, in step S3, the conditions for hydrorefining are: catalyst NiMo / Al2O3-SiO2; under H2 atmosphere, pressure 6MPa~12MPa, time 0.5h~2.5h, temperature 330℃~390℃; the mass ratio of asphalt to catalyst in the 350℃~550℃ distillation section is (20~40):1.

[0027] The moderate heat polymerization process is as follows: in the first stage, the temperature is raised to 300℃~340℃ and held for 1h~2h, with a heating rate of 2℃ / min~4℃ / min; in the second stage, the temperature is raised to 420℃~450℃ and held for 4h~7h, with a heating rate of 0.5℃ / min~2℃ / min.

[0028] Further specifying, in step S3, the yield of spherical cores is ≥35%, and the particle size is 5μm~15μm.

[0029] Further specifying, in step S4, the carbonization process is as follows: the temperature is increased to 800℃ to 1000℃ at a rate of 0.5℃ / min to 3℃ / min, and then held at a constant temperature for 0.5h to 2h.

[0030] The core-shell coated conductive material prepared by the method described above for preparing core-shell coated conductive materials from medium- and low-temperature coal tar has the following properties: initial coulombic efficiency of 90% to 93% and capacity retention of 85% to 96%.

[0031] The application of core-shell coated conductive materials in lithium battery anode materials, as described above.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. This invention uses medium- and low-temperature coal tar as raw material, which is fractionated to obtain fractions and asphalt at different temperature ranges. The fractions at different temperature ranges are then blended and subjected to oxidative cross-linking reactions to obtain a coating agent. The asphalt is hydrorefined and thermally polycondensed to obtain spherical cores, which are then carbonized. The spherical cores are then coated with the coating agent to form a core-shell coated conductive material. The coating agent and spherical cores are prepared separately, and then carbonized to form the core-shell coated conductive material. The coating agent has a high yield, a high softening point, and a low quinoline insoluble content. The spherical core shape facilitates the uniformity of the coating agent coating, which can better enhance the stability of the material. The resulting core-shell coated material has high specific capacitance and coulombic efficiency, improving the electrochemical performance of the conductive material, and the process preparation cost is low.

[0034] 2. This invention reduces the content of quinoline-insoluble matter in the raw materials through gradient extraction, thereby preparing a coating agent with a lower quinoline-insoluble matter content. By adding a viscosity reducer, the viscosity of the system is reduced, the compatibility between components is improved, and the rapid conversion of β resin to quinoline-insoluble matter caused by deposition on the container wall is effectively prevented, thus achieving the highest possible coating agent yield. At the same time, the oxidant used is phenolic oil from the 180-220℃ fraction cut from medium-low temperature coal tar atmospheric and vacuum distillation, which effectively avoids incompatibility and mismatch of reactivity between raw materials from different sources.

[0035] 3. By adding a crosslinking agent, this invention promotes the crosslinking of light components in asphalt into macromolecules, increasing the coking value of the coating agent. This facilitates the carbonization of the coating agent during coating treatment, forming more amorphous carbon and improving its electrochemical performance as a negative electrode material. Furthermore, during the reaction, it enables the formation of bridging bonds between molecules with fewer aromatic rings, resulting in higher molecular weight polycyclic aromatic hydrocarbon molecules. This allows oxygen-containing functional groups to be located on the side chains of the polycyclic aromatic hydrocarbons, effectively improving the removal of oxygen-containing functional groups during induced polycondensation and increasing the yield of the coating agent product.

[0036] 4. This invention enables the aromatic components in the raw materials to be fully converted into quinoline-soluble toluene-insoluble substances (β resin) and some macromolecular toluene-soluble substances (γ resin) through an oxidative crosslinking reaction, thereby significantly increasing the softening point of the coating agent.

[0037] 5. The oxidative crosslinking reaction of the present invention, through multi-stage gentle heating, can suppress excessive polycondensation reaction and inhibit the formation of quinoline insolubles, thereby improving product quality.

[0038] 6. This invention uses medium- and low-temperature coal tar as raw material to prepare conductive materials. The raw material is readily available, making full use of secondary coal resources, causing no pollution to the environment, and achieving the goals of cost reduction, efficiency improvement, energy conservation, and environmental protection. It provides a new approach for the preparation of core-shell coated conductive materials. Attached Figure Description

[0039] Figure 1 The preparation process flow diagram provided by the present invention. Detailed Implementation

[0040] The technical solutions protected by the present invention will now be described in detail with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0041] See Figure 1 This invention provides a method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar, comprising the following steps:

[0042] S1, Fraction Cutting

[0043] Take two portions of medium-low temperature coal tar. Use atmospheric and vacuum distillation to cut the phenolic oil from the first portion into the 180℃~220℃ fraction. The remaining fraction is recorded as dephenolized oil.

[0044] The second sample was prepared by atmospheric and vacuum distillation, yielding phenolic oil in the 180℃–220℃ range and asphalt in the 350℃–550℃ range.

[0045] S2, preparation of coating agent

[0046] The phenol-free oil from step S1 is used to separate component a and component b sequentially by gradient extraction, and component a and component b are mixed in a mass ratio of (1-3):1 to obtain a compound material.

[0047] A viscosity reducer is added to the compound; then, under an inert gas atmosphere, a crosslinking agent and an oxidizing agent are added, and a coating agent is obtained through an oxidative crosslinking reaction.

[0048] In this invention, the oxidant is phenolic oil from the 180℃~220℃ distillation fraction in step S1; the amount of viscosity reducer added is 1%~5% of the mass of the compound; the amount of oxidant added is 5%~10% of the mass of the compound; and the amount of crosslinking agent added is 7%~14% of the mass of the compound.

[0049] In step S2 of this invention, the specific steps of the gradient extraction process are as follows:

[0050] S2.1. Mix the dephenolized oil from step S1 with toluene at a mass ratio of 1:(1.5~2.5), stir at 60℃~90℃ for 50min~80min, let stand for 2h~4h, take the upper light phase to obtain component a, and the lower layer is the remaining component.

[0051] S2.2. Mix the remaining components with quinoline at a mass ratio of 1:(1.5~2.5), stir at 60℃~90℃ for 50min~80min, let stand for 2h~4h, and take the upper light phase to obtain component b.

[0052] In step S2 of this invention, the viscosity reducer is one or more of carboxymethyl cellulose, 2-acrylamido-2-methylpropanesulfonic acid, sodium dodecylbenzenesulfonate, and sodium N and N-dimethyl-dithiocarbonylpropanesulfonate; the crosslinking agent is one or more of polydopamine, polyvinylidene fluoride, hydroxyl-terminated polybutadiene, polytetrafluoroethylene, and stearic acid.

[0053] In step S2 of this invention, the process conditions for the oxidative crosslinking reaction are:

[0054] The first stage involves heating to 260℃~290℃ and holding at that temperature for 2h~4h, with a heating rate of 2℃ / min~4℃ / min. The second stage involves further heating to 300℃~360℃ and holding at that temperature for 2h~5h, with a heating rate of 0.5℃ / min~2℃ / min.

[0055] In step S2 of this invention, the yield of the coating agent is ≥65.5%, and the properties of the coating agent are: softening point of 244℃~287℃, coking value of ≥67.54%, toluene insoluble content of 50%~75%, and quinoline insoluble content of 0.02%~0.13%.

[0056] S3, Core Making

[0057] The 350℃~550℃ fraction of asphalt cut in step S1 is taken and obtained by hydrogenation refining, moderate thermal polymerization reaction and separation to obtain the sphere core.

[0058] In step S3 of this invention, the conditions for hydrorefining are: catalyst NiMo / Al2O3-SiO2; under H2 atmosphere, pressure 6MPa~12MPa, time 0.5~2.5h, temperature 330℃~390℃, and the mass ratio of asphalt to catalyst in the 350℃~550℃ distillation section is (20~40):1.

[0059] The thermal polymerization process of this invention is as follows: in the first stage, the temperature is raised to 300℃~340℃ and held for 1h~2h, with a heating rate of 2℃ / min~4℃ / min; in the second stage, the temperature is raised to 420℃~450℃ and held for 4h~7h, with a heating rate of 0.5℃ / min~2℃ / min.

[0060] In step S3 of this invention, the yield of spherical cores is ≥35%, and the particle size is 5μm~15μm.

[0061] S4, Covering

[0062] The coating agent obtained in step S2 is ground into powder, dissolved in tetrahydrofuran, and the spherical core obtained in step S3 is added. After stirring, sonicating, filtering, drying and carbonizing, a core-shell coated conductive material is obtained.

[0063] In step S4 of this invention, the carbonization process is as follows: the temperature is increased to 800℃ to 1000℃ at a rate of 0.5℃ / min to 3℃ / min, and then kept at a constant temperature for 0.5h to 2h.

[0064] The core-shell coated conductive material prepared by the above method of the present invention has the following properties: initial coulombic efficiency of 90% to 93% and capacity retention of about 85% to 96%.

[0065] The core-shell coated conductive material prepared by this invention has high performance and can be used in lithium battery anode materials.

[0066] The preparation method of the present invention is illustrated below with several examples, and the performance of the core-shell coated conductive material is verified by experiments.

[0067] It should be noted that, unless otherwise specified, the reagents and medicines used in the following examples and experiments are all conventional commercially available products.

[0068] It should be noted that, unless otherwise specified, the operations used in the following embodiments and experiments are all conventional operations in the art.

[0069] Example 1

[0070] This embodiment provides a method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar, including the following steps:

[0071] S1, Fraction Cutting

[0072] 1 kg of medium-low temperature coal tar was subjected to vacuum distillation to obtain phenolic oil in the 180℃~220℃ fraction. The remaining part was retained and referred to as dephenolized oil. Another 1 kg of medium-low temperature coal tar was subjected to vacuum distillation to obtain phenolic oil in the 180~220℃ fraction and pitch in the 350~550℃ fraction.

[0073] S2, Ingredients

[0074] 100g of dephenolized oil was mixed with toluene at a mass ratio of 1:2 and placed in a constant temperature water bath at 80℃. The mixture was stirred for 60 min and allowed to stand for 3 h. The upper light phase a was collected. The remaining lower component was collected and extracted with quinoline under the same conditions as above. The upper light phase b was collected. The obtained upper light phases a and b were subjected to rotary evaporation to evaporate the solvent and obtain the corresponding components a and b.

[0075] Components a and b are mixed in a mass ratio of 1:1 to obtain a compound raw material. The compound raw material is prepared by uniformly mixing the components with a viscosity reducer content of 1%, an oxidant content of 5%, and a crosslinking agent content of 7%.

[0076] S3, Coating Agent

[0077] The compounded raw materials were placed in a reaction vessel. Under a nitrogen atmosphere, a crosslinking agent and an oxidizing agent were added. The oxidizing agent was phenolic oil from the 180℃~220℃ fraction in step S1, and the amount of oxidizing agent added was 5% of the mass of the compounded materials. The viscosity reducer was selected as carboxymethyl cellulose, and the amount of viscosity reducer added was 1% of the mass of the compounded materials. The crosslinking agent was polydopamine, and the amount of crosslinking agent added was 7% of the mass of the compounded materials. The oxidative crosslinking reaction was carried out under the following conditions: the first stage was heated to 260℃ and held at that temperature for 2 hours at a heating rate of 2℃ / min; the second stage was heated to 310℃ and held at that temperature for 2 hours at a heating rate of 0.5℃ / min to obtain the coating agent.

[0078] S4, Ball-making Core

[0079] Place 150g of the 350℃~550℃ fraction of asphalt in a magnetically driven high-pressure reactor. Add a catalyst at an oil-to-catalyst ratio of 30:1. The oil refers to the 350℃~550℃ fraction of asphalt, and the catalyst is NiMo / Al2O3-SiO2. 2。 After N2 replacement, H2 is added to 8 MPa and the reaction is carried out at 350℃ for 1.5 h. After the reaction is completed, the hydrogenation product is separated from the catalyst to obtain the purified raw material.

[0080] The refined raw materials were placed in a magnetically driven reactor for thermal polymerization. The thermal polymerization process was as follows: the first stage was heated to 320℃ and held at that temperature for 1 hour at a heating rate of 4℃ / min; the second stage was heated to 430℃ and held at that temperature for 6 hours at a heating rate of 0.5℃ / min. After the reaction was completed, the thermally polymerized product was taken out.

[0081] The thermally polymerized product was subjected to Soxhlet extraction with pyridine. The insoluble extract was washed with anhydrous ethanol and then dried in an oven at 150°C for 12 hours to obtain the spherical core.

[0082] S5, Covering

[0083] The coating agent from step S3 was ground into powder and dissolved in tetrahydrofuran at a doping concentration of 6%. The cores obtained in step S4 were added, and a uniformly dispersed mixture of coating agent and cores was obtained by stirring and sonication. After removing the organic solvent under reduced pressure using a rotary evaporator, the sample was dried at 120°C and then heated to 800°C in a tube furnace at a heating rate of 0.5°C / min under a nitrogen atmosphere and held at that temperature for 0.5 h to obtain a core-shell coated conductive material.

[0084] Examples 2 to 6

[0085] The preparation methods provided in Examples 2 to 6 are the same as those in Example 1, except that the amount of raw materials and process parameters are different, as shown in Table 1.

[0086] Table 1. Process parameters for Examples 2 to 6

[0087]

[0088]

[0089] Comparative Example 1

[0090] The difference between this comparative example and Example 1 is that the dephenolized oil was used directly for the oxidative crosslinking reaction, without gradient extraction of the ingredients.

[0091] Comparative Example 2

[0092] The difference between this comparative example and Example 2 is that all components a and b obtained from gradient extraction are directly mixed to obtain a mixture. The mass ratio of this mixture is not in the range of (1~3):1. Then the mixture continues to undergo subsequent reactions.

[0093] Comparative Example 3

[0094] The difference between this comparative example and Example 3 is that it uses a single-stage heated oxidative crosslinking reaction.

[0095] Comparative Example 4

[0096] The difference between this comparative example and Example 4 is that no viscosity reducer was added.

[0097] Comparative Example 5

[0098] The difference between Comparative Example 5 and Example 5 is that no oxidant was added.

[0099] Comparative Example 6

[0100] The difference between Comparative Example 6 and Example 6 is that no crosslinking agent was added.

[0101] Experiment 1

[0102] The softening point (SP), toluene insoluble matter (TI), quinoline insoluble matter (QI), and coking value (CV) of the 12 groups of coating agents prepared in the above embodiments and comparative examples were tested according to the national standards for coking products in the metallurgical industry GB / T4507—1999, GB / T2292—1997, GB / T2293—1997, and GB / T2727—88, respectively. The results are shown in Table 2.

[0103] Table 2. Performance test results of coating agents in the examples and comparative examples.

[0104]

[0105] As shown in Table 2 above, in Examples 1 to 6, the yield of the coating agent was ≥65.5%, the softening point was 244℃ to 287℃, the coking value was ≥67.54%, the toluene insoluble content was 50% to 75%, and the quinoline insoluble content was 0.02% to 0.13%. Compared with the comparative examples, the coating agents prepared in Examples 1 to 6 showed a decrease in quinoline insoluble content, and a significant increase in yield, softening point, and toluene insoluble coking value. This indicates that through gradient extraction and component adjustment, under the combined action of oxidant, crosslinking agent, viscosity reducer, and two-stage heated oxidative crosslinking reaction, the prepared coating agent exhibits excellent performance, further improving the electrochemical performance of the final core-shell coated conductive material.

[0106] Experiment 2

[0107] Lithium-ion batteries were prepared using the core-shell coated conductive materials obtained in Examples 1-6 and Comparative Examples 1-6 as negative electrode materials, and the electrochemical performance of the batteries was measured.

[0108] The specific steps are as follows: Weigh the negative electrode material, acetylene black, and binder PVDF (polyvinylidene fluoride), and mix them in a mass ratio of 89:3:8. Then add an appropriate amount of N,N-dimethylpyrrolidone, and stir magnetically for 5 hours. Coat the resulting slurry onto a copper foil with a thickness of 9 μm, dry it at 80°C for 6 hours, and press it into shape under a pressure of 1.0 MPa. Cut an electrode sheet with a diameter of 12 mm as the working electrode of the battery. Use a lithium metal sheet as the counter electrode, and the electrolyte is 1 mol / L LiPF6 / EC+EMC+DMC (volume ratio: 1:1:1). The separator is an Asahi Kasei lithium battery separator from Japan. Assemble the coin cell in a glove box filled with high-purity argon gas.

[0109] The experimental battery was charged and discharged using a CT2001A LAND battery testing system. The cutoff voltage was 0.001V to 2.0V, and the current density was 37.2mA / g, equivalent to 0.1C. The electrochemical performance results are shown in Table 3.

[0110] Table 3. Battery test results prepared from negative electrode materials in the examples and comparative examples.

[0111]

[0112]

[0113] As shown in Table 3, the core-shell coated conductive material prepared in this invention has an initial coulombic efficiency of 90%–93% and a capacity retention of 85%–96% after 50 cycles. Compared with Comparative Examples 1–6, the core-shell coated conductive material prepared in this invention exhibits good stability and electrochemical performance, thereby improving the electrochemical performance of lithium batteries.

[0114] The viscosity reducer used in the above method is carboxymethyl cellulose, and the crosslinking agent is polydopamine. However, when the types of viscosity reducers and crosslinking agents are changed according to the material range defined by this invention, the prepared coating agent and core-shell coated conductive material also exhibit similar effects as shown in Tables 2 and 3. In the preparation of conductive materials by this invention, the obtained spherical core shape is beneficial to the uniformity of coating agent coverage, which can better enhance the stability of the material; the core-shell coated material has high specific capacitance and coulombic efficiency, improving the electrochemical performance of the negative electrode material; and the process has low preparation cost, high yield, and no environmental pollution, thus developing a new approach for preparing core-shell coated conductive materials.

[0115] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a core-shell coated conductive material using a medium-low temperature coal tar, characterized by, Includes the following steps: S1, Fraction Cutting Take two portions of medium-low temperature coal tar. Use atmospheric and vacuum distillation to cut the phenolic oil from the first portion into the 180℃~220℃ fraction. The remaining fraction is recorded as dephenolized oil. The second sample was prepared by atmospheric and vacuum distillation to separate phenolic oil from the 180℃~220℃ fraction and asphalt from the 350℃~550℃ fraction. S2, preparation of coating agent The phenol-free oil from step S1 was used to separate component a and component b sequentially using gradient extraction, and then component a and component b were mixed in a mass ratio of (1~3):1 to obtain a compound material. A viscosity reducer is added to the compound; then, under an inert gas atmosphere, a crosslinking agent and an oxidizing agent are added, and a coating agent is obtained through an oxidative crosslinking reaction; the oxidizing agent is phenolic oil from the 180℃~220℃ distillation fraction in step S1; the amount of viscosity reducer added is 1%~5% of the mass of the compound; the amount of oxidizing agent added is 5%~10% of the mass of the compound; and the amount of crosslinking agent added is 7%~14% of the mass of the compound. The specific steps of the gradient extraction method are as follows: S2.

1. Mix the phenol-free oil from step S1 with toluene at a mass ratio of 1:(1.5~2.5), stir at 60℃~90℃ for 50min~80min, let stand for 2h~4h, take the upper light phase to obtain component a, and the lower layer is the remaining component; S2.

2. Mix the remaining components with quinoline at a mass ratio of 1:(1.5~2.5), stir at 60℃~90℃ for 50min~80min, let stand for 2h~4h, and take the upper light phase to obtain component b; S3, Core Making Take the 350℃~550℃ fraction of asphalt cut in step S1, and obtain the sphere core through hydrorefining, thermal polymerization reaction and separation; S4, Covering The coating agent obtained in step S2 is ground into powder and dissolved in tetrahydrofuran. The amount of coating agent added is 5wt%~15wt%. Then, the spherical core obtained in step S3 is added. After stirring, sonicating, filtering, drying and carbonizing, a core-shell coated conductive material is obtained.

2. The method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar according to claim 1, characterized in that, In step S2, the viscosity reducer is sodium dodecylbenzenesulfonate; the crosslinking agent is polydopamine.

3. The method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar according to claim 1, characterized in that, In step S2, the process conditions for the oxidative crosslinking reaction are: The first stage involves heating to 260℃~290℃ and holding the temperature for 2h~4h, with a heating rate of 2℃ / min~4℃ / min; the second stage involves further heating to 300℃~360℃ and holding the temperature for 2h~5h, with a heating rate of 0.5℃ / min~2℃ / min.

4. The method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar according to claim 3, characterized in that, The yield of the coating agent is ≥65.5%, and the properties of the coating agent are: softening point of 244℃~287℃, coking value of ≥67.54%, toluene insoluble content of 50%~75%, and quinoline insoluble content of 0.02%~0.13%.

5. The method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar according to claim 1, characterized in that, In step S3, the conditions for hydrorefining are: catalyst NiMo / Al2O3-SiO2; under H2 atmosphere, pressure 6MPa~12MPa, time 0.5h~2.5h, temperature 330℃~390℃, and the mass ratio of asphalt to catalyst in the 350℃~550℃ distillation section is (20~40):

1. The thermal polymerization process is as follows: in the first stage, the temperature is raised to 300℃~340℃ and held for 1h~2h, with a heating rate of 2℃ / min~4℃ / min; in the second stage, the temperature is raised to 420℃~450℃ and held for 4h~7h, with a heating rate of 0.5℃ / min~2℃ / min.

6. The method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar according to claim 1, characterized in that, In step S3, the yield of spherical cores is ≥35%, and the particle size is 5μm~15μm.

7. The method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar according to claim 1, characterized in that, In step S4, the carbonization process is as follows: the temperature is increased to 800℃~1000℃ at a rate of 0.5℃ / min~3℃ / min, and then held at a constant temperature for 0.5h~2h.

8. The core-shell coated conductive material prepared by the method for preparing core-shell coated conductive materials from medium- and low-temperature coal tar as described in any one of claims 1-7, characterized in that, The properties of core-shell coated conductive materials are: initial coulombic efficiency of 90%~93% and capacity retention of 85%~96%.

9. The application of the core-shell coated conductive material as described in claim 8 in lithium battery anode materials.

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