Biomass-based carbon@iron oxide composite material and preparation method and application thereof
Biomass-based carbon@iron oxide composite materials were prepared by hydrothermal treatment of biomass powder and iron salt solution, which solved the problems of capacity decay and high production cost of lithium-ion battery anode materials and realized the preparation of efficient and environmentally friendly anode materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU UNIV OF SCI & TECH
- Filing Date
- 2023-01-05
- Publication Date
- 2026-08-04
AI Technical Summary
Existing lithium-ion battery anode materials, such as metal oxides, suffer from rapid capacity decay, and existing carbon-based composite materials have complex production processes, high costs, and severe environmental pollution.
Biomass-based carbon@iron oxide composite material was prepared by mixing biomass powder with iron salt solution and then subjecting the mixture to hydrothermal treatment to generate biomass carbon sheets, on which iron oxide nanoparticles were loaded.
The preparation process is simple and low-cost, with no secondary pollution. The material has high capacity and excellent cycle performance, making it suitable as a negative electrode material for lithium-ion batteries.
Smart Images
Figure CN116314652B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of new energy materials and preparation technology, specifically relating to a lithium-ion battery anode material and its preparation method and application, particularly to a biomass-based carbon@iron oxide composite material and its preparation method and application. Background Technology
[0002] With the rapid development of electric vehicles, energy storage power stations, and renewable energy worldwide, higher demands are being placed on energy storage devices, making energy storage technology crucial. Among various rechargeable batteries, lithium-ion batteries are considered the most important energy storage and conversion technology, possessing outstanding advantages of high energy and high power density, and are also considered one of the most efficient energy storage methods currently available. Therefore, further improving their energy density and cycle performance is both a current research challenge and a hot topic.
[0003] Metal oxides, as anode materials for lithium-ion batteries, possess high specific capacity. However, most metal oxides suffer from rapid capacity decay when used as electrodes in lithium-ion batteries, which limits their development and practical application. Carbon materials, on the other hand, possess unique and excellent properties, including good stability and conductivity, making them suitable as carriers for metal oxides. By buffering the volume change stress during the charge-discharge process of lithium-ion batteries, they enhance the cycle performance of the metal oxides. Furthermore, biomass, an abundant agricultural waste, with high contents of hemicellulose, lignin, and cellulose, makes it a suitable carbon source for carbon electrodes in high-performance energy storage systems. In recent years, many scientists have been dedicated to the preparation and potential applications of novel biomass-based carbon nanomaterials. The method of using composite anode materials combining high-performance, inexpensive carbon materials with iron oxides for high-performance anodes in lithium-ion batteries is of great significance for addressing the current energy crisis and environmental pollution problems. Chinese patent CN108975306A discloses a method for preparing iron oxide-doped biomass porous carbon materials. This method involves immersing decolorized *Ulva prolifera* in a ferric nitrate solution, followed by calcination under an inert gas atmosphere to obtain the iron oxide-doped biomass porous carbon material. This method uses a decolorizing agent, and the iron oxide particles obtained by combining immersion and calcination are relatively large and difficult to control. Chinese patent CN106732358A discloses a method for preparing iron oxide-loaded biomass carbonized microspheres. This method first adds an iron salt solution to a hot surfactant solution; after cooling, crushed coconut shells are added, stirred thoroughly, and dried; then, the mixture is added to a zinc acetate solution for hydrothermal reaction. After cooling, the product is washed and dried again to obtain iron oxide-loaded biomass carbonized microspheres. This method requires surfactants and zinc acetate. The addition of zinc acetate can easily introduce zinc-containing impurities into the final product, resulting in low material purity and high cost. Chinese patent CN108933251A discloses a biomass carbon / iron oxide composite material and its preparation method. The method involves preparing biomass carbon using KOH as an activator at high temperature, followed by loading the prepared iron oxide particles onto the biomass carbon via a hydrothermal method. However, this method first involves carbonizing the biomass at high temperatures (800–950°C), which is energy-intensive and uses a strong alkaline activator, making it environmentally unfriendly. Therefore, although existing carbon-based composite materials possess porous structures and disordered properties, most current reports indicate that their production processes are complex and costly, and they are accompanied by environmental pollution, making them unattractive. Summary of the Invention
[0004] The purpose of this invention is to overcome the problems and deficiencies of the prior art and to provide a biomass-based carbon@iron oxide composite material, its preparation method and application.
[0005] This invention utilizes the hydrothermal process of mixing biomass powder with an iron salt solution to produce biomass carbon sheets through the catalytic effect of iron ions. Then, more iron salt is added to the biomass carbon sheets, and under hydrothermal conditions, iron oxide nanoparticles are generated and loaded onto the carbon sheets, thereby obtaining a biomass-based carbon@iron oxide composite material.
[0006] The composite material of this invention has a simple preparation process, low production cost, good adsorption performance, high thermal and acid stability, and no secondary pollution, enabling the high-value utilization of biomass resources. The prepared material, when applied as a negative electrode material for lithium-ion batteries, exhibits high capacity and excellent cycle performance.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0008] A biomass-based carbon@iron oxide composite material is prepared from biomass, iron salts, and ultrapure water through hydrothermal and calcination treatment. The biomass-based carbon@iron oxide composite material has a sheet-like structure, wherein iron oxide particles are anchored to a carbon matrix. The diameter of the iron oxide particles is 16–28 nm, and the BET specific surface area is 35.67–103.81 m². 2 g -1 .
[0009] To achieve the above objectives, another technical solution adopted by the present invention is as follows:
[0010] A method for preparing a biomass-based carbon@iron oxide composite material includes the following steps:
[0011] (1) After cleaning the biomass with ultrapure water, drying it in an oven, and grinding it into powder, mix the biomass powder, iron salt and ultrapure water in a mass-volume ratio of 1:(0.2~0.6):(50~100)g / mL and stir for 0.5~1.5h. Then transfer it to an autoclave and hydrothermally heat it at 150~200℃ for 5~12h. After cooling it to room temperature naturally, centrifuge, wash and dry it to obtain product A.
[0012] (2) According to the mass-volume ratio, the obtained product A, iron salt and ultrapure water are mixed in the order of 1:(0.5~2):(50~100)g / mL and stirred for 0.5~1.5h. Then, the mixture is transferred to an autoclave and hydrothermally heated at 150~200℃ for 5~12h. After cooling naturally to room temperature, the mixture is centrifuged, washed and freeze-dried to obtain product B.
[0013] (3) Spread the product B obtained in step 2 in a ceramic boat, place it in a tube furnace under an inert atmosphere, heat it at a rate of 0.5 to 2 °C / min at 500 to 600 °C for 1 to 3 hours, and then let it cool naturally to room temperature to obtain a biomass-based carbon@iron oxide composite material.
[0014] Further preferably, the biomass is one or more of the following in any mass ratio: peanut shells, sugarcane bagasse, coconut shells, corn leaves, reeds, etc.
[0015] Further preferably, the iron salt is one or more of ferric chloride, ferric nitrate, and ferric sulfate in any mass ratio.
[0016] Further preferably, the freeze-drying temperature range in step 2 is -40 to -80°C.
[0017] Further preferably, the inert atmosphere mentioned in step 3 is nitrogen, argon, or a nitrogen-argon mixture in any proportion.
[0018] To achieve the above objectives, the third technical solution adopted by the present invention is as follows:
[0019] A specific method for applying a biomass-based carbon@iron oxide composite material as a negative electrode material in lithium-ion batteries includes the following steps:
[0020] (a) Biomass-based carbon@iron oxide composite material, polyvinylidene fluoride and Ketjen black are mixed evenly in a mass ratio of (7-8):(1-2):1 to obtain a solid mixture;
[0021] (b) The solid mixture obtained in step (a) is mixed with N-methylpyrrolidone at a mass ratio of (10-20):(80-90), and stirred evenly to obtain a slurry;
[0022] (c) The slurry obtained in step (b) is coated onto copper foil, and after drying and rolling, a lithium-ion battery electrode sheet with a thickness of 10 to 25 μm is obtained.
[0023] (d) The lithium-ion battery electrode sheet obtained in step (c) is used as the negative electrode sheet, the lithium sheet is used as the positive electrode sheet, a microporous polypropylene membrane is used as the separator, and 1 mol / L LiPF6 and solvent are used as the electrolyte. The CR2032 button lithium-ion battery is assembled in a glove box filled with argon gas.
[0024] The advantages and beneficial effects of this invention are as follows:
[0025] (1) No surfactants or other transition metal salts are used in the preparation process, and no high-temperature treatment is required for biomass carbon. A composite anode material based on biomass-based carbon@iron oxide has been successfully prepared and used as a lithium-ion battery anode. This not only reduces the production cost of hard carbon materials, but also provides ideas for the industrialization of biomass-based carbon anode materials.
[0026] (2) In a biomass-based carbon@iron oxide composite material of the present invention, the iron oxide nanoparticles are 16-28 nm in size and are uniformly distributed in the carbon material.
[0027] (3) The composite material prepared by hydrothermal synthesis and calcination in this invention provides the electrode with a larger contact area between the material and the electrolyte, resulting in a more suitable diffusion path for the transport of active materials in the lithium-ion battery and a lower electron transfer resistance. This not only improves the conductivity of the material but also effectively alleviates the volume expansion of the material, thereby improving the cycle performance and rate performance of the battery, meeting the needs of more high-capacity electronic devices, and expanding the application range of lithium-ion batteries. The biomass-based carbon@iron oxide composite material of this invention, as a negative electrode material for lithium-ion batteries, exhibits significantly better cycle performance than Chinese patent CN108933251A (see...). Figure 6 ). Attached Figure Description
[0028] Figure 1 The image shows the XRD pattern of the peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of this invention.
[0029] Figure 2 This is a scanning electron microscope image of the peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of the present invention.
[0030] Figure 3 This is a transmission electron microscope (TEM) image of the peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of this invention.
[0031] Figure 4 This is the Raman spectrum of the peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of this invention.
[0032] Figure 5 This is a nitrogen adsorption-desorption isotherm curve of the peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of the present invention.
[0033] Figure 6 The peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of this invention is used as a negative electrode material for lithium-ion batteries at 200 mA g. -1 The constant current charge-discharge curve of the second cycle below.
[0034] Figure 7 The peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of this invention is used as a negative electrode material for lithium-ion batteries at 200 mAg. -1 The following is a graph showing the cyclic performance. Detailed Implementation
[0035] To enable those skilled in the art to more fully understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0036] Example 1
[0037] 1. A method for preparing a biomass-based carbon@iron oxide composite material, specifically including the following steps:
[0038] (1) The peanut shells were cleaned with ultrapure water, dried in an oven, and ground into powder. 1g of peanut shell powder and 0.4g of ferric nitrate were added to 70mL of ultrapure water and stirred for 1h. Then the mixture was transferred to a 100mL autoclave and hydrothermally heated at 200℃ for 12h. After cooling to room temperature, the mixture was centrifuged, washed, and dried to obtain product A.
[0039] (2) Add 1g of iron salt and 80mL of ultrapure water to product A and stir for 0.5h. Then transfer it to a 100mL autoclave, hydrothermally heat it at 200℃ for 12h and then cool it to room temperature naturally. Centrifuge, wash and freeze dry to obtain product B.
[0040] (3) The product B obtained in step 2 is spread in a ceramic boat and placed in a tube furnace under an inert atmosphere. The temperature is increased at 2℃ / min and maintained at 500℃ for 3h. After natural cooling to room temperature, peanut shell-based porous carbon@iron oxide composite material is obtained.
[0041] 2. The application of a biomass-based carbon@iron oxide composite material in CR2032 coin cell lithium-ion batteries, the specific method including the following steps:
[0042] (a) Peanut shell-based porous carbon@iron oxide composite material, polyvinylidene fluoride, and Ketjen black were mixed evenly in a mass ratio of 8:1:1 to obtain a solid mixture;
[0043] (b) The solid mixture obtained in step (a) is mixed with N-methylpyrrolidone at a mass ratio of 20:80 and stirred evenly to obtain a slurry;
[0044] (c) The slurry obtained in step (b) is coated onto copper foil, and after drying and rolling, a lithium-ion battery electrode sheet with a thickness of 10 to 25 μm is obtained.
[0045] (d) The lithium-ion battery electrode sheet obtained in step (c) is used as the negative electrode sheet, the lithium sheet is used as the positive electrode sheet, a microporous polypropylene membrane is used as the separator, and 1 mol / L LiPF6 and solvent are used as the electrolyte. The CR2032 button lithium-ion battery is assembled in a glove box filled with argon gas.
[0046] 3. Performance testing of CR2032 button lithium-ion batteries: The lithium-ion batteries assembled in step (d) above were subjected to a voltage range of 0.01-3V and a test at 100mA g. -1 The first three cycles of charge-discharge activation were performed using a current density of 200 mAg. After activation, the voltage range was 0.01-3V. -1 The current density was used for charge-discharge cycle testing.
[0047] Test results: XRD pattern of Example 1 (e.g.) Figure 1 As shown in the figure, the peanut shell-based porous carbon@iron oxide composite material exhibits typical diffraction peaks, which correspond to the crystal planes of iron oxide, further confirming the successful preparation of the material.
[0048] Taking the peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 as an example, electron microscopy was performed, and the scanning results are as follows: Figure 2 As shown, from Figure 2 As can be seen from the data, the prepared peanut shell-based porous carbon@iron oxide composite material has a sheet-like structure.
[0049] Figure 3 This is a transmission electron microscope (TEM) image of the peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of this invention. It can be seen that iron oxide nanoparticles with a size of approximately 20 nm are uniformly dispersed in the carbon matrix, indicating good dispersion in the iron oxide composite material.
[0050] Figure 4 This is the Raman spectrum of the peanut shell-based porous carbon@iron oxide composite material prepared in Example 1 of this invention. It can be seen that at ~1350 and ~1600 cm⁻¹... -1 There are two broad characteristic peaks at this point, corresponding to sp... 2 D-band and G-band delocalization of π bonds. D / I G A value of approximately 0.15 indicates that the material contains a large number of defects, which can provide more active sites for the reaction and shorten the Li... + The transmission path is improved to enhance material properties.
[0051] Figure 5The nitrogen adsorption-desorption isotherms of the material are shown. It can be seen that the isotherms are typical type IV isotherms, with a hysteresis loop where P / P0 is in the range of approximately 0.45–1.0, indicating the presence of mesoporous structures and slit-like pores in the material. The specific surface area of the material is 92.66 m². 2 g -1 This highly porous structure can shorten the electron migration path and increase the Li... + Storing active sites, thereby improving the lithium storage of materials.
[0052] Figure 6 200mAg -1 The constant current charge-discharge curves for the second cycle are shown in the figure. It can be seen from the graph that the charge-discharge capacity for the second cycle is approximately 719.86 / 854.32 mAh g. -1 The Coulomb efficiency is approximately 84.26%.
[0053] Figure 7 Peanut shell-based porous carbon@iron oxide composite material as a negative electrode material for lithium-ion batteries at 200 mA g -1 The following is a graph showing the cycle performance. After 100 cycles, the charge / discharge capacity is 711.7 / 716.71 mAh g. -1 It has excellent cycle performance.
[0054] Example 2
[0055] 1. A method for preparing a biomass-based carbon@iron oxide composite material, specifically including the following steps:
[0056] (1) The peanut shells were cleaned with ultrapure water, dried in an oven, and ground into powder. 1g of peanut shell powder and 0.2g of ferric nitrate were added to 70mL of ultrapure water and stirred for 1h. Then the mixture was transferred to a 100mL autoclave and hydrothermally heated at 150℃ for 12h. After cooling to room temperature, the mixture was centrifuged, washed, and dried to obtain product A.
[0057] (2) Add 1.5g of ferric nitrate and 80mL of ultrapure water to product A and stir for 0.5h. Then transfer it to a 100mL autoclave, hydrothermally heat it at 180℃ for 12h and then cool it to room temperature naturally. Centrifuge, wash and freeze dry to obtain product B.
[0058] (3) The product B obtained in step 2 is spread in a ceramic boat and placed in a tube furnace under an inert atmosphere. The temperature is increased at 2℃ / min and maintained at 550℃ for 3h. After natural cooling to room temperature, peanut shell-based porous carbon@iron oxide composite material is obtained.
[0059] 2. The application of a biomass-based carbon@iron oxide composite material in CR2032 coin cell lithium-ion battery, the specific method and steps are the same as in Example 1.
[0060] 3. The performance testing method for the CR2032 coin cell lithium-ion battery is the same as in Example 1. The lithium battery performance results are shown in Table 1.
[0061] Example 3
[0062] 1. A method for preparing a biomass-based carbon@iron oxide composite material, specifically including the following steps:
[0063] (1) The peanut shells were cleaned with ultrapure water, dried in an oven, and ground into powder. 1g of peanut shell powder and 0.6g of ferric chloride were added to 70mL of ultrapure water and stirred for 1h. Then the mixture was transferred to a 100mL autoclave and hydrothermally heated at 180℃ for 12h. After cooling to room temperature, the mixture was centrifuged, washed, and dried to obtain product A.
[0064] (2) Add 1g of ferric chloride and 80mL of ultrapure water to product A and stir for 0.5h. Then transfer it to a 100mL autoclave, hydrothermally heat it at 200℃ for 12h and then cool it to room temperature naturally. Centrifuge, wash and freeze dry to obtain product B.
[0065] (3) The product B obtained in step 2 is spread in a ceramic boat and placed in a tube furnace under an inert atmosphere. The temperature is increased at 2℃ / min and maintained at 600℃ for 3h. After natural cooling to room temperature, peanut shell-based porous carbon@iron oxide composite material is obtained.
[0066] 2. The application of a biomass-based carbon@iron oxide composite material in CR2032 coin cell lithium-ion battery, the specific method and steps are the same as in Example 1.
[0067] 3. The performance testing method for the CR2032 button lithium-ion battery is the same as in Example 1. The lithium battery performance results are shown in Table 1.
[0068] Example 4
[0069] 1. A method for preparing a biomass-based carbon@iron oxide composite material, specifically including the following steps:
[0070] (1) The peanut shells were cleaned with ultrapure water, dried in an oven, and ground into powder. 1g of peanut shell powder and 0.5g of ferric nitrate were added to 70mL of ultrapure water and stirred for 1h. Then the mixture was transferred to a 100mL autoclave and hydrothermally heated at 200℃ for 12h. After cooling to room temperature, the mixture was centrifuged, washed, and dried to obtain product A.
[0071] (2) Add 2g of ferric nitrate and 80mL of ultrapure water to product A and stir for 0.5h. Then transfer it to a 100mL autoclave, hydrothermally heat it at 200℃ for 12h and then cool it to room temperature naturally. Centrifuge, wash and freeze dry to obtain product B.
[0072] (3) The product B obtained in step 2 is spread in a ceramic boat and placed in a tube furnace under an inert atmosphere. The temperature is increased at 1.5℃ / min and maintained at 500℃ for 3 hours. After natural cooling to room temperature, peanut shell-based porous carbon@iron oxide composite material is obtained.
[0073] 2. The application of a biomass-based carbon@iron oxide composite material in CR2032 coin cell lithium-ion battery, the specific method and steps are the same as in Example 1.
[0074] 3. The performance testing method for the CR2032 button lithium-ion battery is the same as in Example 1. The lithium battery performance results are shown in Table 1.
[0075] Example 5
[0076] 1. A method for preparing a biomass-based carbon@iron oxide composite material, specifically including the following steps:
[0077] (1) The coconut shell was cleaned with ultrapure water, dried in an oven, and ground into powder. Then, 1g of peanut shell powder and 0.2g of ferric nitrate were added to 70mL of ultrapure water and stirred for 1h. Then, it was transferred to a 100mL autoclave and hydrothermally heated at 150℃ for 12h. After cooling to room temperature, it was centrifuged, washed, and dried to obtain product A.
[0078] (2) Add 1.5g of ferric nitrate and 80mL of ultrapure water to product A and stir for 0.5h. Then transfer it to a 100mL autoclave, hydrothermally heat it at 180℃ for 12h and then cool it to room temperature naturally. Centrifuge, wash and freeze dry to obtain product B.
[0079] (3) The product B obtained in step 2 is spread in a ceramic boat and placed in a tube furnace under an inert atmosphere. The temperature is increased at 2℃ / min and maintained at 550℃ for 3h. After natural cooling to room temperature, a coconut shell-based porous carbon@iron oxide composite material is obtained.
[0080] 2. The application of a biomass-based carbon@iron oxide composite material in CR2032 coin cell lithium-ion battery, the specific method and steps are the same as in Example 1.
[0081] 3. The performance testing method for the CR2032 button lithium-ion battery is the same as in Example 1. The lithium battery performance results are shown in Table 1.
[0082] Example 6
[0083] 1. A method for preparing a biomass-based carbon@iron oxide composite material, specifically including the following steps:
[0084] (1) The sugarcane bagasse was cleaned with ultrapure water, dried in an oven, and ground into powder. Then, 1g of peanut shell powder and 0.2g of ferric nitrate were added to 70mL of ultrapure water and stirred for 1h. Then, it was transferred to a 100mL autoclave and hydrothermally heated at 150℃ for 12h. After cooling to room temperature, it was centrifuged, washed, and dried to obtain product A.
[0085] (2) Add 1.5g of ferric nitrate and 80mL of ultrapure water to product A and stir for 0.5h. Then transfer it to a 100mL autoclave, hydrothermally heat it at 180℃ for 12h and then cool it to room temperature naturally. Centrifuge, wash and freeze dry to obtain product B.
[0086] (3) The product B obtained in step 2 is spread in a ceramic boat and placed in a tube furnace under an inert atmosphere. The temperature is increased at 2℃ / min and maintained at 600℃ for 3h. After natural cooling to room temperature, a bagasse-based porous carbon@iron oxide composite material is obtained.
[0087] 2. The application of a biomass-based carbon@iron oxide composite material in CR2032 coin cell lithium-ion battery, the specific method and steps are the same as in Example 1.
[0088] 3. The performance testing method for the CR2032 button lithium-ion battery is the same as in Example 1. The lithium battery performance results are shown in Table 1.
[0089] The lithium battery performance results of Examples 1-6 are shown in Table 1.
[0090] Table 1 shows the lithium-ion batteries in Examples 1-6 at 200 mA g. -1 The capacity obtained in the 2nd and 100th cycles of charge-discharge testing under current.
[0091] Table 1
[0092]
[0093] As shown in Table 1, when the biomass-based carbon@iron oxide composite material of the present invention is used as the anode material in a lithium-ion battery, it achieves a performance of 200 mAg. -1 After 100 cycles, the charge / discharge capacity is 700mAh g. -1 The above exhibits excellent cycle performance, far exceeding that of currently commercialized graphite anode materials.
[0094] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a biomass-based carbon@iron oxide composite material, characterized in that, The biomass-based carbon@iron oxide composite material is prepared from biomass, iron salts, and ultrapure water through hydrothermal and calcination treatment. The biomass-based carbon@iron oxide composite material has a sheet-like structure, in which iron oxide particles are anchored to a carbon matrix. The diameter of the iron oxide particles is 16–28 nm, and the BET specific surface area is 35.67–103.81 m². 2 g -1 The biomass is one or more of peanut shells, sugarcane bagasse, coconut shells, corn leaves, and reeds in any mass ratio; the preparation method of the biomass-based carbon@iron oxide composite material includes the following steps: (1) After cleaning the biomass with ultrapure water, drying it in an oven, and grinding it into powder, mix the biomass powder, iron salt and ultrapure water in a mass-volume ratio of 1g:(0.2~0.6)g:(50~100)mL and stir for 0.5~1.5h. Then transfer it to an autoclave and hydrothermally heat it at 150~200℃ for 5~12h. After cooling it to room temperature naturally, centrifuge, wash and dry it to obtain product A. (2) According to the mass-volume ratio, the obtained product A, iron salt and ultrapure water are mixed in a ratio of 1g:(0.5~2)g:(50~100)mL and stirred for 0.5~1.5h. Then, the mixture is transferred to an autoclave and hydrothermally heated at 150~200℃ for 5~12h. After cooling naturally to room temperature, the mixture is centrifuged, washed and freeze-dried to obtain product B. (3) Spread the product B obtained in step (2) in a ceramic boat, place it in a tube furnace under an inert atmosphere, heat it at a rate of 0.5 to 2 °C / min at 500 to 600 °C for 1 to 3 hours, and then let it cool naturally to room temperature to obtain a biomass-based carbon@iron oxide composite material.
2. The method for preparing a biomass-based carbon@iron oxide composite material according to claim 1, characterized in that: The iron salt is one of ferric chloride, ferric nitrate, and ferric sulfate, or multiple salts in any mass ratio.
3. The method for preparing a biomass-based carbon@iron oxide composite material according to claim 1, characterized in that: The freeze-drying temperature range described in step (2) is -40 to -80°C.
4. The method for preparing a biomass-based carbon@iron oxide composite material according to claim 1, characterized in that: The inert atmosphere mentioned in step (3) is nitrogen, argon, or a nitrogen-argon mixture in any proportion.
5. The application of a biomass-based carbon@iron oxide composite material prepared by the preparation method of claim 1 as a negative electrode material in a lithium-ion battery.
6. The application according to claim 5, characterized in that, Specifically, the steps include the following: (a) Biomass-based carbon@iron oxide composite material, polyvinylidene fluoride and Ketjen black are mixed evenly in a mass ratio of (7-8):(1-2):1 to obtain a solid mixture; (b) The solid mixture obtained in step (a) is mixed with N-methylpyrrolidone at a mass ratio of (10-20):(80-90), and stirred evenly to obtain a slurry; (c) The slurry obtained in step (b) is coated onto copper foil, and after drying and rolling, a lithium-ion battery electrode sheet with a thickness of 10 to 25 μm is obtained. (d) The lithium-ion battery electrode sheet obtained in step (c) is used as the negative electrode sheet, the lithium sheet is used as the positive electrode sheet, a microporous polypropylene membrane is used as the separator, and 1 mol / L LiPF6 and solvent are used as the electrolyte. The CR2032 button lithium-ion battery is assembled in a glove box filled with argon gas.