Composite carbon negative electrode material, negative electrode and preparation method and application thereof

Abstract

The invention relates to the technical field of battery negative electrode materials, in particular to a composite carbon negative electrode material, a negative electrode and a preparation method and application thereof. The preparation method comprises the following steps: mixing mesophase pitch nano-powder slurry with hard carbon precursor powder, and coating the surface of a hard carbon precursor with the mesophase pitch nano-powder slurry to obtain mixed slurry B; and heating the dried powder of the mixed slurry B to a temperature T DEG C ([t-(5-10)] < = T < = [t + (5-100)]), then carrying out pre-oxidation treatment at a temperature of 280-320 DEG C, and then carrying out high-temperature carbonization at 1200-1400 DEG C to prepare the composite carbon negative electrode material with the hard carbon core coated with the soft carbon. The prepared soft and hard carbon composite carbon negative electrode material for the negative electrode of the sodium ion battery has the advantages of high capacity, high first efficiency and good cycle performance.

Description

Technical Field

[0001] This invention relates to the field of battery anode material technology, and in particular to a composite carbon anode material, anode, preparation method and application thereof. Background Technology

[0002] With the rapid development of renewable energy and electric vehicles, lithium-ion batteries face challenges from lithium resource scarcity and rising costs. Sodium-ion batteries, due to the abundance, wide distribution, and low cost of sodium resources, have become a research hotspot in the energy storage field. However, the ionic radius of sodium ions is significantly larger than that of lithium ions, resulting in slow insertion / extraction kinetics and low capacity in traditional graphite anodes, which fails to meet practical needs. Therefore, developing high-performance sodium-ion battery anode materials has become a key technological breakthrough.

[0003] Hard carbon materials, due to their disordered microcrystalline structure and large interlayer spacing, can achieve high sodium storage capacity through mechanisms such as adsorption, intercalation, and pore filling, making them a mainstream candidate material for sodium-ion battery anodes. However, their disordered structure may lead to problems such as low initial coulombic efficiency and poor long-term cycling stability. Researchers have proposed a strategy of combining soft and hard carbon to achieve complementary advantages: hard carbon provides high-capacity sodium storage sites, while soft carbon constructs a continuous conductive network and suppresses structural collapse during cycling. For example, a core-shell structure (hard carbon as the core and soft carbon as the shell) can balance high capacity and interfacial stability, improving cycle life through synergistic effects. Nevertheless, the large-scale preparation process of composite materials and the screening of low-cost precursors remain key challenges in current research.

[0004] Patent CN202410780528.9 describes a soft-hard carbon composite negative electrode active material for sodium-ion batteries, its preparation method, and its application. The raw materials for preparing the composite negative electrode active material include asphaltene, carbonized reed straw, a pore-forming agent, and a sodium supplement. By using carbonized reed straw as the hard carbon, encapsulated within asphaltene soft carbon, a core-shell structure is formed. With the presence of the pore-forming agent and sodium supplement, the negative electrode active material has a high specific surface area and numerous active sites, resulting in batteries with advantages such as high specific capacity and low first-cycle loss. However, the preparation process requires the use of toluene as a solvent and a freeze-drying process to obtain the core-shell powder. After carbonization, it is thoroughly ground and sieved to obtain the soft-hard carbon composite negative electrode active material for sodium-ion batteries. The process of obtaining the core-shell structure is complex, and the final grinding is also required, making large-scale production difficult. Summary of the Invention

[0005] The main objective of this invention is to provide a composite carbon anode material, an anode, a preparation method thereof, and its application, in order to solve the aforementioned technical problems.

[0006] To achieve the above objectives, the present invention provides a method for preparing a composite carbon anode material, comprising the following steps: S11: Provides mesophase pitch nanopowder slurry A; S12 provides hard carbon precursor powder of organic matrix after low-temperature carbonization treatment; S2: Mix mesophase pitch nanopowder slurry A with hard carbon precursor powder at a mass ratio of 1.2-2.5:1.0, and coat the surface of hard carbon precursor with mesophase pitch nanopowder slurry A to obtain mixed slurry B. S3, after drying the mixed slurry B, powder C is obtained; S4, and powder C is heated to temperature T℃, kept at that temperature for 0.5-2h under a protective atmosphere, and then cooled to obtain powder D; wherein, the softening temperature of the mesophase pitch is t℃, [t-(5~10)]≤T≤[t+(5~100)]; S5: Disperse and deagglomerate powder D to obtain powder E; S6: Powder E is pre-oxidized at a temperature of 280-320℃ in air atmosphere for a final temperature holding time of 0.5-3h to obtain powder F; S7: Powder F is carbonized at high temperature of 1200-1400℃ to obtain a composite carbon anode material with soft carbon coating hard carbon core.

[0007] Preferably, in step S11, mesophase asphalt with a mesophase content of 100% is pulverized to a Dv50 of 3μm using an air jet mill, and mixed with water and sodium dodecyl sulfate in a mass ratio of 1:45-55:4-6. The mixture is then placed in a sand mill and milled at 2000rpm for 15-30min, and the mixture is circulated for more than 5 milling cycles to obtain nano-mesophase asphalt powder slurry A.

[0008] Preferably, the organic matrix is ​​selected from at least one of the following materials: wood-based or bamboo-based.

[0009] Preferably, in step S12, the organic matrix is ​​subjected to low-temperature treatment at 450-650℃ and then powdered to obtain hard carbon precursor powder with a diameter of 5-10μm.

[0010] Preferably, in step S3, slurry B is dried at 90-120℃ for 4-6 hours to obtain dried powder C; in step S4, powder C is heated to temperature T℃ at 3-6℃ / min under a nitrogen atmosphere, and then kept at that temperature for 0.5-2 hours to melt the mesophase asphalt, and then cooled to room temperature in the furnace to obtain powder D.

[0011] Preferably, in step S6, the temperature is increased to 280-320℃ at a rate of 1-3℃ / min, the final temperature holding time in air atmosphere is 0.5-3h, the air flow rate per unit mass sample is 8-12L / (min·kg), and powder E is obtained after cooling.

[0012] Preferably, in step S7, nitrogen is used as a protective gas, the temperature is increased to 1200-1400℃ at 1-3℃ / min, held at that temperature for 0.5-2h, cooled to room temperature, and then sieved to obtain the composite carbon anode material.

[0013] The present invention also provides a negative electrode material, including a composite carbon negative electrode material prepared by the preparation method described above.

[0014] The present invention also provides a negative electrode, which is prepared using the negative electrode material described above.

[0015] The present invention also provides an application of the composite carbon anode material prepared according to the above preparation method as an anode material for sodium-ion batteries.

[0016] The composite carbon anode material of this invention can form a stable soft and hard carbon core-shell structure material by nano-sizing, melting and oxidizing the mesophase pitch. The prepared material has high capacity, high initial efficiency and good cycle stability. The preparation method does not produce harmful waste liquids such as waste acid, is environmentally friendly, and the production process is simple and easy to scale up. Attached Figure Description

[0017] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the preparation process of the composite carbon anode material in this invention.

[0018] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The following is in conjunction with the appendix Figure 1 The present invention provides a clear and complete description of the technical problems solved by the embodiments, the technical solutions adopted, and the technical effects achieved. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other equivalent or obvious variations of embodiments obtained by those skilled in the art without creative effort fall within the protection scope of this invention. The embodiments of this invention can be embodied in various different ways as defined and covered by the claims.

[0020] It should be noted that many specific details are given in the following description for ease of understanding. However, it is obvious that the present invention may be implemented without these specific details.

[0021] It should be noted that, in the absence of explicit limitations or conflicts, the various embodiments and their technical features in this invention can be combined with each other to form a technical solution.

[0022] Example 1-1: S11. Mesophase pitch with a softening point of 320℃ and a mesophase content of 100% is pulverized to a Dv50 of 3μm using an air jet mill. Then, the mesophase pitch powder, water, and SDS (sodium dodecyl sulfate) are mixed in a mass ratio of 1:50:5 and placed in a sand mill. The mixture is then milled at 2000rpm for 20min and circulated 10 times to obtain mesophase pitch nanopowder slurry A containing nano-sized mesophase pitch powder. S12, the wood matrix (pine) is subjected to low-temperature carbonization treatment at 450℃, and after pulverization, a hard carbon precursor powder of wood matrix with Dv50 of 6.7μm is obtained. S2, mix the above-mentioned mesophase asphalt nanopowder slurry A with hard carbon precursor powder at a mass ratio of 1.5:1.0; the mixing method is mechanical stirring, the stirring speed is 500 rpm, and the stirring time is 20 min, to obtain slurry B; S3, the slurry B is dried at 100°C for 5 hours to obtain dried powder C; S4. Powder C is placed in a box-type atmosphere furnace, nitrogen is introduced as a protective gas, the temperature is raised to 370℃ at 5℃ / min, and then held for 1h to melt the mesophase asphalt. The furnace is then cooled to room temperature to obtain powder D. S5: Disperse and deagglomerate powder D to obtain powder E; S6, the above powder D is heated to 280°C in a box-type atmosphere furnace at 2°C / min and held for 3 hours in a continuous air atmosphere with a flow rate of 10L / (min·kg). After cooling to room temperature, the material is taken out to obtain powder F. S7. Powder F is placed in a high-temperature carbonization furnace, nitrogen is introduced as a protective gas, the temperature is raised to 1350℃ at 2℃ / min, and held for 1 hour. After cooling to room temperature, the material is taken out and screened through a 325-mesh sieve to obtain a soft and hard carbon composite carbon anode material with a core-shell structure.

[0023] Examples 1-2: The difference between this embodiment and Embodiment 1-1 is in step S4: powder C is placed in a box-type atmosphere furnace, nitrogen is introduced as a protective gas, the temperature is raised to 325°C at 5°C / min, and then held for 1 hour to melt the mesophase asphalt. The furnace is then cooled to room temperature to obtain powder D. The remaining steps and parameters are the same as in Embodiment 1-1.

[0024] Examples 1-3: The difference between this embodiment and Embodiment 1-1 is in step S4: powder C is placed in a box-type atmosphere furnace, nitrogen is introduced as a protective gas, the temperature is raised to 315°C at 5°C / min, and then held for 1 hour to perform micro-melting treatment on the mesophase asphalt. Subsequently, the furnace is cooled to room temperature to obtain powder D. The remaining steps and parameters are consistent with those of Embodiment 1-1.

[0025] Examples 1-4: The difference between this embodiment and Embodiment 1-1 is in step S4: powder C is placed in a box-type atmosphere furnace, nitrogen is introduced as a protective gas, the temperature is raised to 310°C at 5°C / min, and then held for 1 hour to perform micro-melting treatment on the mesophase asphalt. Subsequently, the furnace is cooled to room temperature to obtain powder D; the remaining steps and parameters are consistent with those of Embodiment 1-1.

[0026] Example 2: The difference between this embodiment and embodiment 1-1 is that in step S11, the sand mill is used to cycle 30 times, while the remaining steps and parameters are the same as in embodiment 1.

[0027] Example 3: The difference between this embodiment and Embodiment 1-1 is that in step S12, bamboo matrix is ​​used as the organic matrix material, and hard carbon precursor powder is obtained by low-temperature carbonization treatment. The remaining steps and parameters are consistent with those of Embodiment 1-1. The bamboo matrix is ​​subjected to low-temperature carbonization treatment at 450℃, and after pulverization, hard carbon precursor powder of wood matrix with Dv50 of 6.7μm is obtained.

[0028] Example 4-1: The difference between this embodiment and Embodiment 1-1 is that in step S6, powder E is heated to 310°C at a rate of 2°C / min in a box-type atmosphere furnace and held at that temperature for 0.5h. The remaining steps and parameters are consistent with those of Embodiment 1-1.

[0029] Example 4-2: The difference between this embodiment and Embodiment 1-1 is that in step S6, powder E is heated to 320°C in a box-type atmosphere furnace at a rate of 2°C / min and held at that temperature for 0.5h. The remaining steps and parameters are consistent with those of Embodiment 1-1.

[0030] Example 5: The difference between this embodiment and Embodiment 1-1 is that in step S7, the final temperature of high-temperature carbonization is 1250°C, while the remaining steps and parameters are consistent with those of Embodiment 1-1.

[0031] Example 6: The difference between this embodiment and Embodiment 1-1 is that in step S12, wood hard carbon powder with a Dv50 of 6.7μm that has undergone low-temperature carbonization treatment at 650℃ is used. The remaining steps and parameters are consistent with those of Embodiment 1-1.

[0032] Example 7 (Highest ratio of mesophase pitch nanopowder slurry A to hard carbon precursor powder): The difference between this embodiment and Embodiment 1-1 is that in step S2, the mass ratio of slurry A to wood hard carbon powder is 2.5:1.0, while the remaining steps and parameters are consistent with Embodiment 1-1.

[0033] Comparative Example 1 (without sanding): The difference between this comparative example and Example 1-1 is that in step S11, after mixing the mesophase pitch powder, water, and SDS (sodium dodecyl sulfate) in a mass ratio of 1:50:5, sand milling was not performed. The remaining steps and parameters are consistent with those of Example 1.

[0034] Comparative Example 2 (without bitumen melting stage): The difference between this comparative example and Example 1-1 is that this comparative example does not include the process of melting asphalt in step S4, while the remaining steps and parameters are consistent with those of Example 1-1.

[0035] Comparative Example 3 (without asphalt pre-oxidation stage): The difference between this comparative example and Example 1-1 is that this comparative example does not include the pre-oxidation treatment process in step S6, while the remaining steps and parameters are consistent with those of Example 1-1.

[0036] The samples obtained in the examples and comparative examples were tested using the following methods, and the data are listed in Table 1: (1) Nano-mesophase pitch particle size D v 50: Tested using Malvern Zetasizer (DLS); (2) Particle size D of composite carbon anode material v 50: Tested using a Baxter laser particle size analyzer; (3) Specific surface area: The specific surface area (BET) of the sample shall be determined in accordance with the provisions of GB / T 19587; (4) XRD pattern: The sample was scanned by XRD pattern. The X-ray diffractometer used a copper target with a wavelength of 0.154056 nm and a scanning speed of about 4 ° / min. The spectral information was obtained by analysis software such as HighScore Plus and Jade to obtain the interlayer spacing d corresponding to the (002) peak. 002 ; (5) Electrochemical performance testing of sodium-ion battery system: According to the composite carbon anode material:CMC:SBR:SP=95:1.5:2.5:1.0, after slurry preparation, coating, drying, and rolling, a coin cell was prepared, and the counter electrode was a sodium metal sheet. The first delithiation capacity and first coulombic efficiency performance of carbon material were tested. The coin cell was discharged at 0.1C to 0.05 V, discharged at a constant voltage of 0.05V to 0.01C, and left to stand for 10 min; then charged at 0.1C to 2.0 V and left to stand for 10 min to obtain the reversible specific capacity and the first coulombic efficiency; the cycle was repeated for 300 cycles to obtain the capacity retention rate after 300 cycles. Rate performance testing was conducted by discharging at 1 C to 0.01 V, then discharging at a constant voltage of 0.01 V to 0.01 C, and allowing it to stand for 10 min; charging at 1 C to 2.0 V, allowing it to stand for 10 min; discharging at 3 C to 0.01 V, then discharging at a constant voltage of 0.01 V to 0.01 C, and finally charging at 3 C to 2.0 V. The sodium intercalation capacity under 1 C and 3 C conditions was obtained, and the 3 C / 1 C ratio was obtained. This ratio represents the rate performance of the material. (6) Micro-area analysis of carbon materials was performed using a laser Raman spectrometer coupled with a laser wavelength of 532 nm. The obtained Raman spectra were analyzed, and R=I D / I G I D I represents the peak intensity value of peak D. G The peak intensity of peak G is given, and the Raman shift of peak D is at 1350 cm⁻¹. -1 Nearby, the Raman shift of peak G is at 1580 cm⁻¹. -1 The sample was scanned nearby, and the scanning results consisted of 100 single-point Raman spectra. The average value of the R value was obtained by statistical calculation.

[0037] Table 1 The data from the composite carbon anode material samples obtained in Examples 1-7 show that the D of the samples... v The micrometer diameter (μm) of the 50 series ranges from 6.5 to 9.6 μm, and the specific surface area ranges from 1.14 to 2.87 m². 2 / g, average interlayer spacing d 002The range is 0.3629-0.3815, the R value range is 0.74-1.06, the first reversible capacity range is 287.1-311.8 mAh / g, and the first coulombic efficiency range is 87.5-91.4%.

[0038] As can be seen from Examples 1-1 and 1-2, by raising the temperature to above the softening point of the mesophase asphalt, the mesophase asphalt melts, causing the asphalt to bind tightly with the hard carbon precursor (hard carbon) to form a core-shell structure. This helps to reduce the specific surface area, reduce sodium ion loss during the cycle, and improve the cycle performance.

[0039] In Examples 1-3 and 1-4, the temperature was raised to about 5-10°C below the softening point of the mesophase asphalt. The mesophase asphalt micro-melted to form nanospheres, which were tightly bonded to the hard carbon precursor. The nano-mesophase asphalt powder was wrapped on the surface of the hard carbon precursor due to micro-melting, forming a discontinuous asphalt layer.

[0040] Subsequently, by oxidizing the mesophase pitch, a cross-linking structure is introduced. During the subsequent high-temperature carbonization process, the mesophase pitch will not foam. After high-temperature carbonization, it is completely coated on the surface of the hard carbon precursor or hard carbon particles, ultimately forming a core-shell structure soft-hard carbon composite carbon anode material with a hard carbon core and a soft carbon shell.

[0041] Among them, the asphalt must be 100% mesophase asphalt. If the mesophase content is low, it will easily lead to insufficient soft carbon content in the shell layer, thus affecting the electrochemical performance. If the size of the nano-asphalt is too large, it will easily lead to uneven soft carbon coating. If the size of the nano-asphalt is too small, it will place too demanding requirements on the sand milling equipment and increase production costs. In addition, it is not conducive to the formation of soft carbon film.

[0042] Before being coated with nano-mesophase bitumen slurry, hard carbon precursor powder needs to undergo low-temperature carbonization treatment, with the organic matrix carbonization temperature being 450-650℃. If the first carbonization temperature of the hard carbon precursor powder is too high (high-temperature carbonization treatment), the soft carbon coating layer formed after coating the mesophase bitumen will have weak bonding strength with the hard carbon particles, thus affecting cycle life. This phenomenon is due to the significant shrinkage that occurs when bitumen undergoes high-temperature carbonization, while the hard carbon particles have already undergone high carbonization, leading to a mismatch in shrinkage between the two carbon precursors during high-temperature carbonization. Conversely, if the first carbonization temperature of the hard carbon precursor is too low (low-temperature carbonization treatment), the total content of non-carbon elements retained in the hard carbon precursor will be too high. During subsequent simultaneous high-temperature carbonization of the mesophase bitumen and the hard carbon precursor, the hard carbon precursor will release excessive gas due to heating, affecting the interfacial bonding between the soft carbon coating layer and the hard carbon particles, resulting in adverse effects.

[0043] The high-temperature carbonization temperature is 1250-1350℃. If the temperature is too high, the capacity will decrease significantly, causing the sodium-ion battery to exhibit low capacity. If the temperature is too low, the initial coulombic efficiency will be too low, thus affecting the overall energy density and cycle life of the sodium-ion battery.

[0044] In sodium-ion battery applications, core-shell carbon materials offer several advantages. The soft carbon shell, being easily graphitized, forms a continuous conductive network, reducing the overall electrode resistance. The hard carbon core serves as the main sodium storage component. The soft carbon shell directly contacts the current collector or conductive agent through surface coating, reducing interfacial electron transport losses. The chemically inert surface of the soft carbon facilitates the formation of a stable SEI film, minimizing capacity decay during cycling. Simultaneously, the core-shell structure buffers the sodium storage volume changes of the hard carbon through the mechanical flexibility of the soft carbon shell, forming a stable support structure and thus improving structural stability. Consequently, the cycle retention rate of the battery after 300 cycles is ≥87.5%.

[0045] By sand milling mesophase pitch using a sand mill, nano-sized mesophase pitch nano-slurry is obtained. The slurry is then mixed with a pre-carbonized hard carbon precursor. The hydrophobic chains of SDS are adsorbed onto the surface of the pre-carbonized hard carbon precursor or hard carbon particles. SDS is also adsorbed onto the surface of the nano-sized mesophase pitch. The hydrophilic sulfate ions face the aqueous phase, preventing particle aggregation through charge repulsion. SDS molecules achieve a dynamic equilibrium on the pitch and hard carbon surfaces. During the dispersion process, the particle surface is continuously covered with an active agent layer. Combined with physical dispersion methods such as mechanical stirring, the nano-sized mesophase pitch particles are dispersed on the hard carbon surface.

[0046] Data from Examples 1 and 5 show that the soft carbon d 002 As the carbonization temperature increases, the interlayer spacing decreases, the sp² carbon ratio increases, and a more ordered graphite-like microcrystalline structure is formed. High temperature causes the mesopores and some micropores of soft carbon to close, resulting in a decrease in specific surface area. The reduction in interlayer spacing is not conducive to sodium ion insertion and reduces capacity, but it is beneficial to improve the first efficiency.

[0047] As can be seen from the data of Examples 1 and 7, as the proportion of nano-asphalt slurry increases, the nano-asphalt particles attached to the core surface become more abundant. After melting, the nano-asphalt completely coats the surface of the hard carbon precursor (or hard carbon), resulting in a lower specific surface area of ​​the carbon material. The soft carbon shell formed has more support when sodium ions are inserted and extracted, which is beneficial to cycle stability.

[0048] As can be seen from the data of Example 1 and Comparative Example 1, when micron-sized asphalt is used for coating, the micron-sized asphalt particles cannot completely cover the surface of the hard carbon precursor (or hard carbon) due to the particle size, resulting in an increased specific surface area. Therefore, the probability of particle adhesion increases during subsequent carbonization, which leads to an increase in the particle size of the carbon material and a decrease in the coating effect. During the sodium ion insertion and extraction process, more sodium ions are consumed, resulting in a decrease in the initial coulombic efficiency and cycle retention rate.

[0049] Data from Example 1 and Comparative Example 2 show that without direct carbonization after melting and oxidation, the specific surface area of ​​the carbon material increases, the thickness of the soft carbon structure increases, and the core surface is not coated with soft carbon, resulting in a reduced coating effect and decreased initial coulombic efficiency and cycle retention rate.

[0050] Data from Example 1 and Comparative Example 3 show that mesophase pitch without an oxidation step and without stabilization treatment during subsequent high-temperature carbonization results in foaming. Consequently, the specific surface area of ​​the carbon material increases, surface defects increase, and the initial coulombic efficiency and cycle retention rate are poor.

[0051] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite carbon anode material, characterized in that, Including the following steps: S11: Provides mesophase pitch nanopowder slurry A; S12 provides hard carbon precursor powder of organic matrix after low-temperature carbonization treatment; S2: Mix mesophase pitch nanopowder slurry A with hard carbon precursor powder at a mass ratio of 1.2-2.5:1.0, and coat the surface of hard carbon precursor with mesophase pitch nanopowder slurry A to obtain mixed slurry B. S3, after drying the mixed slurry B, powder C is obtained; S4, and powder C is heated to temperature T℃, kept at that temperature for 0.5-2h under a protective atmosphere, and then cooled to obtain powder D; wherein, the softening temperature of the mesophase pitch is t℃, [t-(5~10)]≤T≤[t+(5~100)]; S5: Disperse and deagglomerate powder D to obtain powder E; S6: Powder E is pre-oxidized at a temperature of 280-320℃ in air for a final temperature holding time of 0.5-3h to obtain powder F; S7: Powder F is carbonized at high temperature of 1200-1400℃ to obtain a composite carbon anode material with soft carbon coating hard carbon core.

2. The method for preparing the composite carbon anode material according to claim 1, characterized in that, In step S11, mesophase asphalt with a mesophase content of 100% is pulverized to a Dv50 of 3μm using an air jet mill. The mixture is then mixed with water and sodium dodecyl sulfate in a mass ratio of 1:45-55:4-6. The mixture is then placed in a sand mill and milled at 2000rpm for 15-30min, with the mixture being milled more than 5 times to obtain nano-mesophase asphalt powder slurry A.

3. The method for preparing the composite carbon anode material according to claim 1, characterized in that, The organic matrix is ​​selected from at least one of the following materials: wood-based or bamboo-based.

4. The method for preparing the composite carbon anode material according to claim 3, characterized in that, In step S12, the organic matrix is ​​subjected to low-temperature treatment at 450-650℃ and then powdered to obtain hard carbon precursor powder with a diameter of 5-10μm.

5. The method for preparing the composite carbon anode material according to claim 1, characterized in that, In step S3, slurry B is dried at 90-120℃ for 4-6 hours to obtain dried powder C; in step S4, powder C is heated to temperature T℃ at 3-6℃ / min under nitrogen atmosphere, and then kept at that temperature for 0.5-2 hours to melt the mesophase asphalt, and then cooled to room temperature in the furnace to obtain powder D.

6. The method for preparing the composite carbon anode material according to claim 1, characterized in that, In step S6, the temperature is increased to 280-320℃ at a rate of 1-3℃ / min, and the final temperature holding time in air atmosphere is 0.5-3h. The air flow rate per unit mass sample is 8-12L / (min·kg). After cooling, powder F is obtained.

7. The method for preparing the composite carbon anode material according to claim 1, characterized in that, In step S7, nitrogen is used as a protective gas, the temperature is increased to 1200-1400℃ at 1-3℃ / min, held at that temperature for 0.5-2h, cooled to room temperature, and then sieved to obtain the composite carbon anode material.

8. A negative electrode material, characterized in that, Including composite carbon anode materials prepared by any one of claims 1-7.

9. A negative electrode, characterized in that, Prepared using the negative electrode material as described in claim 8.

10. The application of a composite carbon anode material prepared by any one of claims 1-7 as an anode in a sodium-ion battery.

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