A heteroatom-doped pitch-based hard carbon composite material and a preparation method thereof

Abstract

The application belongs to the technical field of lithium ion battery materials, and particularly relates to a kind of heteroatom doped pitch-based hard carbon composite material and a preparation method thereof, the preparation raw materials of the heteroatom doped pitch-based hard carbon composite material include the following components by weight fraction: 90-100 parts of pitch, 1-10 parts of crosslinking agent, 1-5 parts of heteroatomic compound, 1000-2000 parts of organic solvent, 1-10 parts of coupling agent, 5-20 parts of organic metal compound. The application uses lithium-containing heteroatomic compound to reduce the irreversible capacity loss inside the material, and at the same time, by matching pitch, crosslinking agent, coupling agent and the like, the electronic conductivity, tap density, first efficiency and other properties of the pitch-based hard carbon can be improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a heteroatom-doped pitch-based hard carbon composite material and its preparation method. Background Technology

[0002] Hard carbon refers to carbon that is difficult to graphitize. It consists of small carbon layers and has a highly disordered, isotropic, stable structure with a large interlayer spacing, allowing lithium ions to diffuse rapidly. In addition, hard carbon has good compatibility with electrolytes, a high Li+ diffusion coefficient, and a wide lithium intercalation potential range, which is conducive to the rapid intercalation of Li+ and prevents the precipitation of dendritic lithium, making it suitable for high-current charge and discharge. However, due to the disordered layer structure of hard carbon, its poor electronic conductivity affects its rate performance. To improve the electronic conductivity of hard carbon materials, it is generally necessary to dop with non-metallic compounds such as nitrogen and boron or metallic compounds such as silver and copper, or to select raw materials with high electronic conductivity to reduce electronic impedance. Coal-based pitch is a porous carbon material with low graphitization degree, characterized by short-range order and long-range disorder, and a disordered layer structure. Its material sources are wide and the process is controllable. However, due to the existence of short-range ordered structure, there are fewer pores formed between its materials, resulting in a lower specific capacity. Consequently, the electronic conductivity, tap density, and first-pass efficiency of pitch-based hard carbon still need to be improved. Based on the above problems, this invention proposes a heteroatom-doped pitch-based hard carbon composite material and its preparation method to improve the above problems. Summary of the Invention

[0003] The purpose of this invention is to provide a heteroatom-doped pitch-based hard carbon composite material. By utilizing lithium-containing heteroatom compounds, the irreversible capacity loss inside the material can be reduced. At the same time, by combining pitch, crosslinking agents, coupling agents, etc., the electronic conductivity, tap density, first-pass efficiency, and other properties of pitch-based hard carbon can be improved.

[0004] The specific technical solution adopted by this invention is as follows:

[0005] A heteroatom-doped pitch-based hard carbon composite material, wherein the raw materials for preparing the heteroatom-doped pitch-based hard carbon composite material include the following components by weight: 90-100 parts pitch, 1-10 parts crosslinking agent, 1-5 parts heteroatom compound, 1000-2000 parts organic solvent, 1-10 parts coupling agent, and 5-20 parts organometallic compound.

[0006] In a preferred embodiment, the crosslinking agent is m-hydroxybenzaldehyde, the heteroatom compound is lithium tetraborate, the organic solvent is dichloromethane, the coupling agent is bis-[3-(triethoxysilyl)propyl]-disulfide, and the organometallic compound is nickel acetylacetonate.

[0007] In a preferred embodiment, the following components are included (by weight): 95 parts bitumen, 8 parts m-hydroxybenzaldehyde, 5 parts lithium tetraborate, 1700 parts dichloromethane, 7 parts bis-[3-(triethoxysilyl)propyl]-disulfide, and 18 parts nickel acetylacetonate.

[0008] In a preferred embodiment, the following components are included (by weight): 100 parts bitumen, 5 parts m-hydroxybenzaldehyde, 4 parts lithium tetraborate, 1500 parts dichloromethane, 9 parts bis-[3-(triethoxysilyl)propyl]-disulfide, and 14 parts nickel acetylacetonate.

[0009] In a preferred embodiment, the following components are included (by weight): 92 parts bitumen, 4 parts m-hydroxybenzaldehyde, 2 parts lithium tetraborate, 1300 parts dichloromethane, 4 parts bis-[3-(triethoxysilyl)propyl]-disulfide, and 10 parts nickel acetylacetonate.

[0010] In a preferred embodiment, the following components are included (by weight): 100 parts bitumen, 1 part m-hydroxybenzaldehyde, 1 part lithium tetraborate, 1000 parts dichloromethane, 1 part bis-[3-(triethoxysilyl)propyl]-disulfide, and 5 parts nickel acetylacetonate.

[0011] A method for preparing heteroatom-doped pitch-based hard carbon composite material includes the following steps:

[0012] S1: Add asphalt, m-hydroxybenzaldehyde and lithium tetraborate to a pulverizing device for pulverization and mixing to obtain mixture A;

[0013] S2: Add mixture A to the reactor, introduce oxidant, heat mixture A to melt it into a liquid state for 30-300 minutes to obtain heteroatom-doped oxidized asphalt;

[0014] S3: The heteroatom-doped oxidized pitch was added to dichloromethane, along with bis-[3-(triethoxysilyl)propyl]-disulfide and nickel acetylacetonate, and spray-dried to obtain mixture B;

[0015] S4: Add the mixture B to a tube furnace and heat it for carbonization to obtain mixture C. The heating temperature is 1200-1500℃ and the carbonization time is 1-6H. Cool it to room temperature in an argon environment, pulverize it, and then use a vapor deposition method at a temperature of 700-1000℃ with acetylene gas introduced for a deposition time of 30-300min to obtain heteroatom-doped pitch-based hard carbon composite material.

[0016] In a preferred embodiment, in step S1, before adding asphalt, m-hydroxybenzaldehyde, and lithium tetraborate to the pulverizing equipment for pulverization and mixing, the asphalt is first pulverized to obtain powdered asphalt, wherein the particle diameter of the powdered asphalt is in the range of 1-3 mm.

[0017] In a preferred embodiment, in step S2, the oxidant is sulfur dioxide, and the flow rate of the sulfur dioxide is 100-300 ml / min.

[0018] The technical effects achieved by this invention are as follows:

[0019] This invention achieves heteroatom doping by uniformly mixing asphalt, crosslinking agent, and heteroatom compound. The heteroatoms enhance the electronic conductivity of the material, and the crosslinking agent forms a porous structure, thereby improving the lithium and sodium storage performance of the material. Furthermore, oxidation causes the dehydration reaction between the hydroxyl and carboxyl groups on the surface of the asphalt material to form pores, thus improving the specific capacity of the material.

[0020] This invention utilizes a coupling agent to form a chemical bond connection between organometallic compounds and oxidized asphalt, and to create a porous structure between the materials to improve lithium and sodium storage performance. At the same time, it utilizes the metal compounds formed after the carbonization of organometallic compounds to improve the electronic conductivity of the materials.

[0021] This invention utilizes heteroatoms that are lithium-containing compounds, which can reduce irreversible capacity loss within the material and, together with the amorphous carbon deposited on the outer shell, coat the defects to further reduce the material's irreversible capacity, thereby improving the material's initial efficiency. Attached Figure Description

[0022] Figure 1 This is a SEM image of the heteroatom-doped pitch-based hard carbon composite material in Example 4 of this invention;

[0023] Figure 2 These are schematic diagrams illustrating the physicochemical properties of atomically doped pitch-based hard carbon composite materials and their performance in preparing coin cells in Examples 1 to 4 of the present invention.

[0024] Figure 3 These are schematic diagrams illustrating the rate performance of soft-pack batteries prepared from atomically doped pitch-based hard carbon composite materials in Examples 1 to 4 of this invention.

[0025] Figure 4 This is a schematic diagram of the charge-discharge cycle performance of soft-pack batteries prepared from atomically doped pitch-based hard carbon composite materials in Examples 1 to 4 of the present invention.

[0026] Figure 5 This is a flowchart illustrating the preparation process of the heteroatom-doped pitch-based hard carbon composite material of the present invention. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in a preferred embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments.

[0030] Example

[0031] Example 1

[0032] A heteroatom-doped pitch-based hard carbon composite material comprises the following components: 95g pitch, 8g m-hydroxybenzaldehyde, 5g lithium tetraborate, 1700g dichloromethane, 7g bis-[3-(triethoxysilyl)propyl]-disulfide, and 18g nickel acetylacetone.

[0033] Furthermore, the crosslinking agent can be any of the following substances: p-dimethylaminobenzaldehyde, m-hydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, 4-hydroxy-3-methoxy-benzaldehyde; the heteroatom compound can be any of the following substances: lithium borate, lithium tetraborate, lithium phosphate, lithium metaphosphate; the organic solvent can be any of the following substances: toluene, xylene, dichloromethane, or ethyl acetate; the coupling agent can be any of the following substances: bis-[γ-(triethoxysilyl)propyl]tetrasulfide, bis-[3 ... The organometallic compound can be any one of the following: copper acetylacetonate, nickel acetylacetonate, cobalt acetylacetonate, and iron acetylacetonate. Specifically, in this embodiment, the crosslinking agent is preferably m-hydroxybenzaldehyde, the heteroatom compound is preferably lithium tetraborate, the organic solvent is preferably dichloromethane, the coupling agent is preferably bis-[3-(triethoxysilyl)propyl]-disulfide, and the organometallic compound is preferably nickel acetylacetonate.

[0034] A method for preparing heteroatom-doped pitch-based hard carbon composite material comprises the following process: Pitch is pulverized using a pulverizing device to obtain powdered pitch with a particle size of 1 mm. 95 g of powdered pitch, 8 g of m-hydroxybenzaldehyde, and 5 g of lithium tetraborate are added to a ball mill and ball-milled until homogeneous, yielding mixture A1. Mixture A1 is placed in a reaction vessel and heated to 200°C to melt it into a liquid state. An oxidant is then introduced to carry out the reaction, and the heating time is 300 min, yielding heteroatom-doped oxidized pitch. The heteroatom-doped oxidized pitch is then uniformly dispersed in 17... 00g of dichloromethane was used to uniformly disperse 7g of bis-[3-(triethoxysilyl)propyl]-disulfide and 18g of nickel acetylacetonate in dichloromethane. The mixture was spray-dried to obtain mixture B1. Mixture B1 was added to a tube furnace and heated and carbonized for 6 hours at a temperature of 1200℃ to obtain mixture C1. Mixture C1 was cooled to room temperature in an argon atmosphere, pulverized, and then deposited by vapor deposition at 700℃ with acetylene gas introduced for 300 minutes to obtain heteroatom-doped pitch-based hard carbon composite material.

[0035] Here, the oxidant can be any one of the following substances: oxygen, sulfur dioxide, and nitrogen dioxide; specifically, in this embodiment, the oxidant is preferably sulfur dioxide.

[0036] Example 2

[0037] A heteroatom-doped pitch-based hard carbon composite material comprises the following components: 100g pitch, 5g m-hydroxybenzaldehyde, 4g lithium tetraborate, 1500g dichloromethane, 9g bis-[3-(triethoxysilyl)propyl]-disulfide, and 14g nickel acetylacetone.

[0038] Furthermore, the crosslinking agent can be any of the following substances: p-dimethylaminobenzaldehyde, m-hydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, 4-hydroxy-3-methoxy-benzaldehyde; the heteroatom compound can be any of the following substances: lithium borate, lithium tetraborate, lithium phosphate, lithium metaphosphate; the organic solvent can be any of the following substances: toluene, xylene, dichloromethane, or ethyl acetate; the coupling agent can be any of the following substances: bis-[γ-(triethoxysilyl)propyl]tetrasulfide, bis-[3 ... The organometallic compound can be any one of the following: copper acetylacetonate, nickel acetylacetonate, cobalt acetylacetonate, and iron acetylacetonate. Specifically, in this embodiment, the crosslinking agent is preferably m-hydroxybenzaldehyde, the heteroatom compound is preferably lithium tetraborate, the organic solvent is preferably dichloromethane, the coupling agent is preferably bis-[3-(triethoxysilyl)propyl]-disulfide, and the organometallic compound is preferably nickel acetylacetonate.

[0039] A method for preparing heteroatom-doped pitch-based hard carbon composite material comprises the following process: Pitch is pulverized using a pulverizing device to obtain powdered pitch with a particle size of 1 mm. 100 g of powdered pitch, 5 g of m-hydroxybenzaldehyde, and 4 g of lithium tetraborate are added to a ball mill and ball-milled until homogeneous, yielding mixture A2. Mixture A2 is placed in a reaction vessel and heated to 200°C to melt it into a liquid state. An oxidant is then introduced to carry out the reaction, and the heating time is 300 min, yielding heteroatom-doped oxidized pitch. The heteroatom-doped oxidized pitch is then uniformly dispersed in 1… In 500g of dichloromethane, 9g of bis-[3-(triethoxysilyl)propyl]-disulfide and 14g of nickel acetylacetonate were uniformly dispersed in dichloromethane and spray-dried to obtain mixture B2. Mixture B2 was added to a tube furnace and heated and carbonized for 6 hours at a temperature of 1200℃ to obtain mixture C2. Mixture C2 was cooled to room temperature in an argon atmosphere, pulverized, and then deposited by vapor deposition at 700℃ with acetylene gas introduced for 300 minutes to obtain heteroatom-doped pitch-based hard carbon composite material.

[0040] Here, the oxidant can be any one of the following substances: oxygen, sulfur dioxide, and nitrogen dioxide; specifically, in this embodiment, the oxidant is preferably sulfur dioxide.

[0041] Example 3

[0042] A heteroatom-doped pitch-based hard carbon composite material comprises the following components: 92g pitch, 4g m-hydroxybenzaldehyde, 2g lithium tetraborate, 1300g dichloromethane, 4g bis-[3-(triethoxysilyl)propyl]-disulfide, and 10g nickel acetylacetonate.

[0043] Furthermore, the crosslinking agent can be any of the following substances: p-dimethylaminobenzaldehyde, m-hydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, 4-hydroxy-3-methoxy-benzaldehyde; the heteroatom compound can be any of the following substances: lithium borate, lithium tetraborate, lithium phosphate, lithium metaphosphate; the organic solvent can be any of the following substances: toluene, xylene, dichloromethane, or ethyl acetate; the coupling agent can be any of the following substances: bis-[γ-(triethoxysilyl)propyl]tetrasulfide, bis-[3 ... The organometallic compound can be any one of the following: copper acetylacetonate, nickel acetylacetonate, cobalt acetylacetonate, and iron acetylacetonate. Specifically, in this embodiment, the crosslinking agent is preferably m-hydroxybenzaldehyde, the heteroatom compound is preferably lithium tetraborate, the organic solvent is preferably dichloromethane, the coupling agent is preferably bis-[3-(triethoxysilyl)propyl]-disulfide, and the organometallic compound is preferably nickel acetylacetonate.

[0044] A method for preparing heteroatom-doped pitch-based hard carbon composite material comprises the following process: Pitch is pulverized using a pulverizing device to obtain powdered pitch with a particle size of 1 mm. 92 g of powdered pitch, 4 g of m-hydroxybenzaldehyde, and 2 g of lithium tetraborate are added to a ball mill and ball-milled until homogeneous, yielding mixture A3. Mixture A3 is placed in a reaction vessel and heated to 200°C to melt it into a liquid state. An oxidant is then introduced to carry out the reaction, and the heating time is 300 min, yielding heteroatom-doped oxidized pitch. The heteroatom-doped oxidized pitch is then uniformly dispersed in 13... 00g of dichloromethane was used to uniformly disperse 4g of bis-[3-(triethoxysilyl)propyl]-disulfide and 10g of nickel acetylacetonate in dichloromethane. The mixture was spray-dried to obtain mixture B3. Mixture B3 was added to a tube furnace and heated and carbonized for 6 hours at a temperature of 1200℃ to obtain mixture C3. Mixture C3 was cooled to room temperature in an argon atmosphere, pulverized, and then deposited by vapor deposition at 700℃ with acetylene gas introduced for 300 minutes to obtain heteroatom-doped pitch-based hard carbon composite material.

[0045] Here, the oxidant can be any one of the following substances: oxygen, sulfur dioxide, and nitrogen dioxide; specifically, in this embodiment, the oxidant is preferably sulfur dioxide.

[0046] Example 4

[0047] A heteroatom-doped pitch-based hard carbon composite material comprises the following components: 100g pitch, 1g m-hydroxybenzaldehyde, 1g lithium tetraborate, 1000g dichloromethane, 1g bis-[3-(triethoxysilyl)propyl]-disulfide, and 5g nickel acetylacetone.

[0048] Furthermore, the crosslinking agent can be any of the following substances: p-dimethylaminobenzaldehyde, m-hydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, 4-hydroxy-3-methoxy-benzaldehyde; the heteroatom compound can be any of the following substances: lithium borate, lithium tetraborate, lithium phosphate, lithium metaphosphate; the organic solvent can be any of the following substances: toluene, xylene, dichloromethane, or ethyl acetate; the coupling agent can be any of the following substances: bis-[γ-(triethoxysilyl)propyl]tetrasulfide, bis-[3 ... The organometallic compound can be any one of the following: copper acetylacetonate, nickel acetylacetonate, cobalt acetylacetonate, and iron acetylacetonate. Specifically, in this embodiment, the crosslinking agent is preferably m-hydroxybenzaldehyde, the heteroatom compound is preferably lithium tetraborate, the organic solvent is preferably dichloromethane, the coupling agent is preferably bis-[3-(triethoxysilyl)propyl]-disulfide, and the organometallic compound is preferably nickel acetylacetonate.

[0049] A method for preparing heteroatom-doped pitch-based hard carbon composite material comprises the following process: Pitch is pulverized using a pulverizing device to obtain powdered pitch with a particle size of 1 mm. 100 g of powdered pitch, 1 g of m-hydroxybenzaldehyde, and 1 g of lithium tetraborate are added to a ball mill and ball-milled until homogeneous, yielding mixture A4. Mixture A4 is placed in a reaction vessel and heated to 200°C to melt it into a liquid state. An oxidant is then introduced to carry out the reaction, and the heating time is 300 min, yielding heteroatom-doped oxidized pitch. The heteroatom-doped oxidized pitch is then uniformly dispersed in 1… In 000g of dichloromethane, 1g of bis-[3-(triethoxysilyl)propyl]-disulfide and 5g of nickel acetylacetonate were uniformly dispersed in dichloromethane and spray-dried to obtain mixture B4. Mixture B4 was added to a tube furnace and heated and carbonized for 6 hours at a temperature of 1200℃ to obtain mixture C4. Mixture C4 was cooled to room temperature in an argon atmosphere, pulverized, and then deposited by vapor deposition at 700℃ with acetylene gas introduced for 300 minutes to obtain heteroatom-doped pitch-based hard carbon composite material.

[0050] Here, the oxidant can be any one of the following substances: oxygen, sulfur dioxide, and nitrogen dioxide; specifically, in this embodiment, the oxidant is preferably sulfur dioxide.

[0051] Test methods

[0052] (a) SEM testing

[0053] SEM testing was performed according to JY / T 0584-2020 "General Rules for Analytical Methods of Scanning Electron Microscopy", using the following steps:

[0054] Step 1: Take 10g of sample from each of Examples 1, 2, 3 and 4, and record them as sample A1, sample A2, sample A3 and sample A4 respectively;

[0055] Step 2: Take sample A1, fix sample A1 on the sample stage with electrical tape, perform SEM test, and record the best image;

[0056] Step 3: Repeat the same steps as in Step 2 until samples A2, A3, and A4 have been tested.

[0057] (II) Physicochemical properties and button cell battery testing

[0058] The physicochemical properties and coin cell tests were conducted according to GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries," using the following steps:

[0059] Step 1: Using the heteroatom-doped pitch-based hard carbon composite materials obtained in Examples 1, 2, 3 and 4, coin cells were fabricated and labeled as Sample B1, Sample B2, Sample B3 and Sample B4, respectively.

[0060] Step 2: Take sample B1 for battery testing and record the test results;

[0061] Step 3: Repeat the same steps as in Step 2 until samples B2, B3, and B4 have been tested.

[0062] Furthermore, the tests include particle size, tap density, specific surface area, heteroatom content, and capacity retention. The specific steps for these tests are all in accordance with the test procedures in GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries", and will not be elaborated further here.

[0063] It should be noted that in the process of preparing the coin cell, binder, conductive agent and solvent are added to the negative electrode material, stirred to form a slurry, coated on copper foil, dried and rolled to obtain the negative electrode sheet. The electrolyte is LiPF6 / EC+DEC, the separator is polyethylene (PE), and the counter electrode is a lithium metal sheet. The simulated battery assembly is carried out in an argon-filled glove box. The specific assembly process is an existing mature technology, which will not be elaborated further here.

[0064] Specifically, in this preparation example, the negative electrode material is the heteroatom-doped pitch-based hard carbon composite material obtained in the examples, the binder is LA132 binder, the conductive agent is conductive agent SP, and the solvent is double-distilled water, with the following ratio: negative electrode material: conductive agent SP: LA132 binder: double-distilled water = 95g: 1g: 4g: 220mL;

[0065] Here, the concentration of the electrolyte is 1.3 mol / L, and the volume ratio of LiPF6 to EC+DEC is 1:1.

[0066] (III) Testing of Soft Pack Batteries

[0067] According to GB 31241-2014 "Safety Requirements for Lithium-ion Batteries and Battery Packs for Portable Electronic Products", the following steps are used to test soft-pack batteries:

[0068] Step 1: Using the heteroatom-doped pitch-based hard carbon composite materials obtained in Examples 1, 2, 3 and 4, multiple soft-pack batteries were fabricated and labeled as Sample C1, Sample C2, Sample C3 and Sample C4, respectively.

[0069] Step 2: Take multiple samples C1 for rate performance testing. The charge and discharge voltage range is 2.8 to 4.2V, and the test temperature is 25±3.0℃. Charge at 1.0C, 2.0C, 3.0C, and 5.0C respectively, and discharge at 1.0C. Test the constant current ratio and temperature of multiple samples C1 under different charging modes, and record the test results.

[0070] Step 3: Take multiple C1 samples for cycle performance testing. At a 2C / 2C charge / discharge rate and a voltage range of 2.8-4.2V, perform 100, 300, and 500 charge / discharge cycles sequentially to test the capacity retention rate and record the test results.

[0071] Step 4: Repeat the steps 2 and 3 until all samples C2, C3, and C4 have been tested.

[0072] Furthermore, the specific operations in steps two and three shall be carried out in accordance with the test operations in GB 31241-2014 "Safety Requirements for Lithium-ion Batteries and Battery Packs for Portable Electronic Products", and will not be elaborated further here.

[0073] It should be noted that in the process of preparing the soft-pack battery, a heteroatom-doped pitch-based hard carbon composite material is used as the negative electrode, and the negative electrode sheet is prepared by slurry mixing and coating. A ternary material is used as the positive electrode, the electrolyte is LiPF6 / EC+DEC, and the separator is Celgard2400 membrane to prepare a 5Ah soft-pack battery. The specific preparation process of the soft-pack battery is a mature existing technology, and will not be elaborated further here.

[0074] Here, the ternary material is LiNi1 / 3Co1 / 3Mn1 / 3O2, the electrolyte concentration is 1.1 mol / L, and the volume ratio of LiPF6 to EC+DEC is 1:1.

[0075] Please see Figures 1 to 4 As shown, samples A4, B4, and C4, prepared from heteroatom-doped pitch-based hard carbon composite materials in Example 4, exhibited superior overall performance compared to other samples in the same tests. Specifically, in SEM testing, sample A4 displayed a near-spherical structure with uniform size distribution and a particle size range of 10-15 µm. In physicochemical properties and coin cell battery tests, sample B4 had a tap density of 0.82 g / cm³, a specific surface area of ​​6.5 m² / g, an initial discharge capacity of 309 mAh / g, and a capacity retention rate of 93.2%. In the soft-pack battery rate performance test, sample C4 achieved constant current ratios of 97.44%, 93.54%, 89.93%, and 85.24% at 1C, 2C, 3C, and 5C rates, respectively. In the soft-pack battery cycle performance test, sample C4 maintained capacity retention rates of 99.35%, 97.27%, and 95.19% after 100, 300, and 500 cycles, respectively.

[0076] The above tests and results demonstrate that lithium-containing heteroatom compounds can reduce irreversible capacity loss within the material and, together with the amorphous carbon deposited on the outer shell, reduce the irreversible capacity at defects, thereby improving the material's initial efficiency. Heteroatom doping is achieved by uniformly mixing asphalt, crosslinking agents, and heteroatom compounds. The heteroatoms enhance the material's electronic conductivity, and the crosslinking agent forms a porous structure, improving the material's lithium and sodium storage performance. Oxidation further enhances the specific capacity by causing dehydration reactions between the hydroxyl and carboxyl groups on the asphalt surface, leading to pore formation. Simultaneously, coupling agents connect organometallic compounds and oxidized asphalt through chemical bonds, creating porous structures that improve lithium and sodium storage performance. Furthermore, the metal compounds formed after the carbonization of organometallic compounds enhance the material's electronic conductivity. In summary, the heteroatom-doped asphalt-based hard carbon composite material obtained in Example 4 exhibits superior overall performance compared to the heteroatom-doped asphalt-based hard carbon composite materials in other examples.

[0077] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A heteroatom-doped pitch-based hard carbon composite material, characterized in that: The raw materials for preparing the heteroatom-doped pitch-based hard carbon composite material include the following components by weight: 90-100 parts pitch, 1-10 parts crosslinking agent, 1-5 parts heteroatom compound, 1000-2000 parts organic solvent, 1-10 parts coupling agent, and 5-20 parts organometallic compound. Wherein, the crosslinking agent is m-hydroxybenzaldehyde, the heteroatom compound is lithium tetraborate, the organic solvent is dichloromethane, the coupling agent is bis-[3-(triethoxysilyl)propyl]-disulfide, and the organometallic compound is nickel acetylacetonate; The preparation method of the heteroatom-doped pitch-based hard carbon composite material includes the following steps: S1: Add asphalt, m-hydroxybenzaldehyde and lithium tetraborate to a pulverizing device for pulverization and mixing to obtain mixture A; S2: Add mixture A to the reactor, introduce oxidant, heat mixture A to melt it into a liquid state for 30-300 minutes to obtain heteroatom-doped oxidized asphalt; S3: The heteroatom-doped oxidized pitch was added to dichloromethane, along with bis-[3-(triethoxysilyl)propyl]-disulfide and nickel acetylacetonate, and spray-dried to obtain mixture B; S4: Add the mixture B to a tube furnace and heat it for carbonization to obtain mixture C. The heating temperature is 1200-1500℃ and the carbonization time is 1-6h. Cool it to room temperature in an argon environment, pulverize it, and then use a vapor deposition method at a temperature of 700-1000℃ with acetylene gas introduced for a deposition time of 30-300min to obtain heteroatom-doped pitch-based hard carbon composite material.

2. The heteroatom-doped pitch-based hard carbon composite material according to claim 1, characterized in that: It includes the following components by weight: 95 parts bitumen, 8 parts m-hydroxybenzaldehyde, 5 parts lithium tetraborate, 1700 parts dichloromethane, 7 parts bis-[3-(triethoxysilyl)propyl]-disulfide, and 18 parts nickel acetylacetonate.

3. The heteroatom-doped pitch-based hard carbon composite material according to claim 1, characterized in that: It includes the following components by weight: 100 parts bitumen, 5 parts m-hydroxybenzaldehyde, 4 parts lithium tetraborate, 1500 parts dichloromethane, 9 parts bis-[3-(triethoxysilyl)propyl]-disulfide, and 14 parts nickel acetylacetonate.

4. The heteroatom-doped pitch-based hard carbon composite material according to claim 1, characterized in that: It includes the following components by weight: 92 parts bitumen, 4 parts m-hydroxybenzaldehyde, 2 parts lithium tetraborate, 1300 parts dichloromethane, 4 parts bis-[3-(triethoxysilyl)propyl]-disulfide, and 10 parts nickel acetylacetonate.

5. The heteroatom-doped pitch-based hard carbon composite material according to claim 1, characterized in that: It includes the following components by weight: 100 parts bitumen, 1 part m-hydroxybenzaldehyde, 1 part lithium tetraborate, 1000 parts dichloromethane, 1 part bis-[3-(triethoxysilyl)propyl]-disulfide, and 5 parts nickel acetylacetonate.

6. A method for preparing a heteroatom-doped pitch-based hard carbon composite material, characterized in that: Includes the following steps: S1: Add asphalt, m-hydroxybenzaldehyde and lithium tetraborate to a pulverizing device for pulverization and mixing to obtain mixture A; S2: Add mixture A to the reactor, introduce oxidant, heat mixture A to melt it into a liquid state for 30-300 minutes to obtain heteroatom-doped oxidized asphalt; S3: The heteroatom-doped oxidized pitch was added to dichloromethane, along with bis-[3-(triethoxysilyl)propyl]-disulfide and nickel acetylacetonate, and spray-dried to obtain mixture B; S4: Add the mixture B to a tube furnace and heat it for carbonization to obtain mixture C. The heating temperature is 1200-1500℃ and the carbonization time is 1-6h. Cool it to room temperature in an argon environment, pulverize it, and then use a vapor deposition method at a temperature of 700-1000℃ with acetylene gas introduced for a deposition time of 30-300min to obtain heteroatom-doped pitch-based hard carbon composite material.

7. The method for preparing a heteroatom-doped pitch-based hard carbon composite material according to claim 6, characterized in that: In step S1, before adding asphalt, m-hydroxybenzaldehyde, and lithium tetraborate to the pulverizing equipment for pulverization and mixing, the asphalt is first pulverized to obtain powdered asphalt, wherein the particle diameter of the powdered asphalt is in the range of 1-3 mm.

8. The method for preparing a heteroatom-doped pitch-based hard carbon composite material according to claim 6, characterized in that: In step S2, the oxidant is sulfur dioxide, and the flow rate of sulfur dioxide is 100-300 ml / min.

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