Preparation method and application of high-rate hard carbon negative electrode material

Abstract

The present application belongs to the technical field of biomass hard carbon, and particularly relates to a preparation method and application of a high-rate hard carbon negative electrode material. The preparation steps are as follows: biomass raw materials are pre-carbonized under a protective atmosphere to obtain a pre-carbonized product; the pre-carbonized product is added into a p-nitrophenol solution, stirred uniformly, poured into a reaction kettle containing a polytetrafluoroethylene carbonization bottle, and subjected to a hydrothermal reaction in a blast drying oven to obtain pretreated material, which is then crushed to obtain crushed material; the crushed material is subjected to high-temperature heat treatment under an inert atmosphere to obtain heat-treated material; the heat-treated material is mixed with liquid pitch, fused in a high-speed fusion machine to obtain fused material; and the fused material is subjected to surface modification under an inert atmosphere to obtain a high-rate hard carbon negative electrode material after cooling. The finished material can be applied in sodium ion batteries. The present application introduces nitrogen atoms, optimizes defects, improves the sodium ion transmission rate, and improves the rate performance.

Description

Technical Field

[0001] This invention belongs to the field of biomass hard carbon technology, specifically relating to a method for preparing and applying a high-rate hard carbon anode material. Background Technology

[0002] Currently, the sodium-ion battery industry chain is accelerating its development, with multiple cell manufacturers announcing new products and progress on GWh-level production lines, ushering in a historic development opportunity for sodium-ion batteries. However, the rate performance of current hard carbon materials in the industry remains poor in low-temperature and high-current charge-discharge conditions. The core issues lie in the slow ion transport rate and insufficient electron conduction, severely limiting the fast-charging and high-power capabilities of sodium batteries, becoming one of the key bottlenecks restricting their large-scale application. Therefore, developing a high-rate hard carbon anode material from a commercial perspective to meet the needs of consumer and energy storage batteries is a crucial technological support for sodium-ion batteries to seize market growth opportunities. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying high-rate hard carbon anode materials, thereby solving the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows: A method for preparing a high-rate hard carbon anode material includes the following steps: Biomass raw materials are pre-carbonized under a protective atmosphere to obtain pre-carbonized products; Then, the pre-carbonized product is added to the p-nitrophenol solution, stirred evenly, poured into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, and subjected to hydrothermal reaction in a forced-air drying oven to obtain the pretreated material, which is then pulverized to obtain the pulverized material. The pulverized material is subjected to high-temperature heat treatment under an inert atmosphere to obtain heat-treated material; Heat-treated material is mixed with liquid phase asphalt and then fused in a high-speed fusion machine to obtain fused material; The fused material was surface modified under an inert atmosphere and then cooled to obtain a high-rate hard carbon anode material.

[0005] Furthermore, the preparation method of biomass raw materials includes the following steps: selecting cedar wood as raw material, cutting it into regular wood blocks using a wood cutting machine to obtain biomass raw materials.

[0006] Preferably, the fir trees are harvested at an age of 15-30 years.

[0007] Furthermore, the pre-carbonization temperature is 400–800℃, the holding time is 1–10h, the pre-carbonization heating rate is 0.2–10℃ / min, and the protective atmosphere for pre-carbonization includes at least one of nitrogen, helium, and argon.

[0008] It should be noted that by adopting the above technical solution, pre-carbonization, through slow heating and heat preservation, improves the carbon yield and initial structural uniformity of biomass, providing a stable framework for subsequent modification.

[0009] Furthermore, the mass concentration of the p-nitrophenol solution is 0.5–16 g / L; the mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:0.5–5; the temperature of the forced-air drying oven is 150–300 °C, and the heating time is 5–18 h.

[0010] It should be noted that by using the above technical solution, p-nitrophenol is used for hydrothermal reaction to introduce nitrogen-containing functional groups, which functionalize the active groups on the surface of the pre-carbonized material, thereby improving the stability of the material structure and enhancing the sodium affinity and interfacial activity of the carbon surface.

[0011] Furthermore, airflow milling is used for pulverization, and the particle size D50 is controlled between 2 and 10 μm.

[0012] Furthermore, the conditions for high-temperature heat treatment include: a heating rate of 0.2–10 °C / min, a heat treatment temperature of 1000–1600 °C, a holding time of 1–15 h, and the heat treatment being carried out in a box-type resistance furnace.

[0013] Furthermore, the liquid phase asphalt includes at least one of petroleum-based asphalt and coal-based asphalt; the mass ratio of heat-treated material to liquid phase asphalt is 100:1~10; the heating temperature of the high-speed fusion machine is 100~300℃; the working speed of the high-speed fusion machine is 100-1000 rpm, and the fusion time is 10~90 minutes.

[0014] Furthermore, the surface modification conditions include: a heating rate of 0.2–10 °C / min, a high-temperature holding temperature of 800–1300 °C, a holding time of 1–12 h, and the modification is carried out in a high-temperature furnace with an inert atmosphere; the inert atmosphere includes at least one of nitrogen, helium, and argon.

[0015] It should be noted that, using the above technical solution, asphalt coating forms a semi-graphitized layer, which, after surface modification treatment, generates a stable, continuous, low-resistance conductive layer, enhancing structural integrity and electron migration efficiency.

[0016] The present invention also provides the application of the high-rate hard carbon anode material prepared by the aforementioned method in sodium-ion batteries.

[0017] Specifically, CMC (sodium carboxymethyl cellulose), Super P (conductive carbon black), high-rate hard carbon anode material, and SBR (styrene-butadiene rubber) are mixed to form a slurry. This slurry is then uniformly coated onto the surface of copper foil using a coater. After drying, the slurry is sliced ​​and fabricated in an Ar atmosphere glove box. The high-rate hard carbon anode material is used as the positive electrode, a sodium metal sheet is used as the counter electrode, and glass fiber is used as the separator. Combined with an electrolyte, a CR2032 coin cell is manufactured.

[0018] Specifically, the negative electrode of the full cell is made of hard carbon material: CMC:SP:SBR = 92%: 2%: 3%: 3% by mass, and the positive electrode is made of NFPP system, to produce a pouch cell.

[0019] The beneficial effects of this invention are: Following the commercialization of sodium-ion batteries in recent years, cell manufacturers have increasingly stringent requirements for low-temperature and rate performance. This patent addresses this issue by introducing nitrogen atoms to optimize defects, improve sodium-ion transport rate, and enhance rate performance. The invention uses cedar wood as raw material, pre-carbonizing it at 400–800℃ with precise temperature control to increase the carbon yield of biomass. After pyrolysis, p-nitrophenol is used to functionalize the active groups on the surface of the pre-carbonized material, improving the stability of the material structure and effectively ensuring its thermal stability during high-temperature carbonization. This allows for more complete decomposition of small-molecule gases and promotes positive rearrangement of the carbon structure. High-temperature heat treatment optimizes the degree of defects and order in the material to a suitable ratio, increasing the sodium-ion transport rate. Liquid-phase coating followed by surface modification creates a protective layer on the material surface, optimizing ion transport, charge transfer, and structural stability at the interface, improving ion and electron conduction, and enhancing rate performance, enabling the battery to be used in fast-charging and fast-discharging applications.

[0020] Specifically, in the Raman spectrum of Example 1, I D / I G =1.18 indicates that the prepared material is in a balance between order and defects, taking into account both ion channels and structural stability, which is beneficial for the release of high-rate performance.

[0021] After hydrothermal functionalization and high-temperature rearrangement, a graphite-randomized carbon composite structure is formed, which widens the interlayer spacing, forms more sodium-intercalated active sites, and improves electron mobility.

[0022] After secondary pyrolysis of liquid-phase asphalt, a carbon-rich and graphite-like conductive coating is formed, which effectively buffers the volume effect and stabilizes the electrode structure.

[0023] More specifically, Chinese fir biomass provides abundant pore structure and carbon source, and has natural channel structure that is conducive to mass transfer, and pre-carbonization forms a multi-level pore structure; Introducing N / O functional groups into p-nitrophenol can increase active sites and sodium affinity, and stabilize the carbon skeleton during high-temperature rearrangement. P-nitrophenol modification promotes the full release of small molecule gases during high-temperature pyrolysis, avoids structural collapse, and allows carbon microcrystals to be reconstructed along favorable directions. Liquid-phase asphalt can form a surface conductive layer, reduce contact impedance, suppress interfacial side reactions, and synergistically construct a conductive network with the particle surface. The conductive layer formed by coating not only improves electron migration efficiency, but also acts as a buffer layer for the SEI film, suppressing sodium ion side reactions on the surface and improving cycle stability. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a charge-discharge curve of Embodiment 1 of the present invention at a current density of 0.1C. Figure 2 This is a SEM image of the biomass hard carbon anode material of Example 1 of the present invention; Figure 3 This is a graph showing the 10C cycle specific capacity and 500-cycle retention rate of biomass hard carbon as the negative electrode material of sodium-ion batteries in Example 1 of the present invention. Figure 4 This is the Raman spectrum of biomass hard carbon from Example 1 of the present invention. Detailed Implementation

[0025] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0026] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0027] Unless otherwise specified, the equipment and materials used in the embodiments can be readily obtained from commercial companies.

[0028] It should be noted that, In the examples and comparative examples, the biomass raw material was Chinese fir, and the trees were harvested at an age of 15-30 years.

[0029] The parameters of the liquid phase asphalt used are: softening point of 185℃, rotational viscosity of about 300 mPa·s at 190℃, and carbonization residue of not less than 75% at 950℃ under nitrogen atmosphere.

[0030] Example 1 A method for preparing a high-rate hard carbon anode material comprises the following steps: Step 1: Cut the cedar wood into regular blocks using a wood cutter to obtain biomass raw materials; Step 2: Place the raw material into an electric resistance furnace and heat it to 560°C at a heating rate of 1°C / min under a nitrogen atmosphere. Hold the temperature for 3 hours to obtain the pre-carbonized product. Step 3: Add the pre-carbonized product obtained in step (2) to a 3 g / L p-nitrophenol solution. The mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:1.3. Stir evenly, pour into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, heat at 235°C in a forced-air drying oven for 10 h, and cool naturally to obtain the pretreated material. Step 4: Crush the pretreated material using an air jet mill, controlling the particle size D50 to around 3µm, to obtain the crushed material; Step 5: Place the pulverized material into a box-type resistance furnace, heat it to 1300℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, hold it at high temperature for 6 hours, and then cool it to obtain the heat-treated material. Step 6: Mix the heat-treated material and liquid phase asphalt at a mass ratio of 100:5, heat at 190°C and 480 rpm in a high-speed fusion machine for 35 minutes to obtain the fused material; Step 7: Place the fused material obtained in step (6) into a high-temperature atmosphere furnace, and then heat it to 950°C at a heating rate of 2°C / min under a nitrogen atmosphere. Hold it at high temperature for 5 hours. After taking it out of the furnace, a high-ratio hard carbon anode material is obtained.

[0031] Example 2 A method for preparing a high-rate hard carbon anode material comprises the following steps: Step 1: Cut the cedar wood into regular blocks using a wood cutter to obtain biomass raw materials; Step 2: Place the raw material into an electric resistance furnace and heat it to 560°C at a heating rate of 1°C / min under a nitrogen atmosphere. Hold the temperature for 3 hours to obtain the pre-carbonized product. Step 3: Add the pre-carbonized product obtained in step (2) to a 1 g / L p-nitrophenol solution. The mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:1.3. Stir evenly, pour into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, heat at 235°C in a forced-air drying oven for 10 h, and cool naturally to obtain the pretreated material. Step 4: Crush the pretreated material using an air jet mill, controlling the particle size D50 to around 3µm, to obtain the crushed material; Step 5: Place the pulverized material into a box-type resistance furnace, heat it to 1300℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, hold it at high temperature for 6 hours, and then cool it to obtain the heat-treated material. Step 6: Mix the heat-treated material and liquid phase asphalt at a mass ratio of 100:5, heat at 190°C and 480 rpm in a high-speed fusion machine for 35 minutes to obtain the fused material; Step 7: Place the fused material obtained in step (6) into a high-temperature atmosphere furnace, and then heat it to 950°C at a heating rate of 2°C / min under a nitrogen atmosphere. Hold it at high temperature for 5 hours. After taking it out of the furnace, a high-ratio hard carbon anode material is obtained.

[0032] Example 3 A method for preparing a high-rate hard carbon anode material comprises the following steps: Step 1: Cut the cedar wood into regular blocks using a wood cutter to obtain biomass raw materials; Step 2: Place the raw material into an electric resistance furnace and heat it to 560°C at a heating rate of 1°C / min under a nitrogen atmosphere. Hold the temperature for 3 hours to obtain the pre-carbonized product. Step 3: Add the pre-carbonized product obtained in step (2) to a 6 g / L p-nitrophenol solution. The mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:1.3. Stir evenly, pour into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, heat at 235°C in a forced-air drying oven for 10 h, and cool naturally to obtain the pretreated material. Step 4: Crush the pretreated material using an air jet mill, controlling the particle size D50 to around 3µm, to obtain the crushed material; Step 5: Place the pulverized material into a box-type resistance furnace, heat it to 1300℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, hold it at high temperature for 6 hours, and then cool it to obtain the heat-treated material. Step 6: Mix the heat-treated material and liquid phase asphalt at a mass ratio of 100:5, heat at 190°C and 480 rpm in a high-speed fusion machine for 35 minutes to obtain the fused material; Step 7: Place the fused material obtained in step (6) into a high-temperature atmosphere furnace, and then heat it to 950°C at a heating rate of 2°C / min under a nitrogen atmosphere. Hold it at high temperature for 5 hours. After taking it out of the furnace, a high-ratio hard carbon anode material is obtained.

[0033] Example 4 A method for preparing a high-rate hard carbon anode material comprises the following steps: Step 1: Cut the cedar wood into regular blocks using a wood cutter to obtain biomass raw materials; Step 2: Place the raw material into an electric resistance furnace and heat it to 560°C at a heating rate of 1°C / min under a nitrogen atmosphere. Hold the temperature for 3 hours to obtain the pre-carbonized product. Step 3: Add the pre-carbonized product obtained in step (2) to a 3 g / L p-nitrophenol solution. The mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:1.3. Stir evenly, pour into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, heat at 235°C in a forced-air drying oven for 10 h, and cool naturally to obtain the pretreated material. Step 4: Crush the pretreated material using an air jet mill, controlling the particle size D50 to around 3µm, to obtain the crushed material; Step 5: Place the pulverized material into a box-type resistance furnace, heat it to 1300℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, hold it at high temperature for 6 hours, and then cool it to obtain the heat-treated material. Step 6: Mix the heat-treated material and liquid phase asphalt at a mass ratio of 100:2, heat in a high-speed fusion machine at 190°C and 480 rpm for 35 minutes to obtain the fused material; Step 7: Place the fused material obtained in step (6) into a high-temperature atmosphere furnace, and then heat it to 950°C at a heating rate of 2°C / min under a nitrogen atmosphere. Hold it at high temperature for 5 hours. After taking it out of the furnace, a high-ratio hard carbon anode material is obtained.

[0034] Example 5 A method for preparing a high-rate hard carbon anode material comprises the following steps: Step 1: Cut the cedar wood into regular blocks using a wood cutter to obtain biomass raw materials; Step 2: Place the raw material into an electric resistance furnace and heat it to 560°C at a heating rate of 1°C / min under a nitrogen atmosphere. Hold the temperature for 3 hours to obtain the pre-carbonized product. Step 3: Add the pre-carbonized product obtained in step (2) to a 10 g / L p-nitrophenol solution. The mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:1.3. Stir evenly, pour into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, heat at 235°C in a forced-air drying oven for 10 h, and cool naturally to obtain the pretreated material. Step 4: Crush the pretreated material using an air jet mill, controlling the particle size D50 to around 3µm, to obtain the crushed material; Step 5: Place the pulverized material into a box-type resistance furnace, heat it to 1300℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, hold it at high temperature for 6 hours, and then cool it to obtain the heat-treated material. Step 6: Mix the heat-treated material and liquid phase asphalt at a mass ratio of 100:5, heat at 190°C and 480 rpm in a high-speed fusion machine for 35 minutes to obtain the fused material; Step 7: Place the fused material obtained in step (6) into a high-temperature atmosphere furnace, and then heat it to 950°C at a heating rate of 2°C / min under a nitrogen atmosphere. Hold it at high temperature for 5 hours. After taking it out of the furnace, a high-ratio hard carbon anode material is obtained.

[0035] Comparative Example 1 Step 1: Cut the cedar wood into regular blocks using a wood cutter to obtain biomass raw materials; Step 2: Place the raw material into an electric resistance furnace and heat it to 560°C at a heating rate of 1°C / min under a nitrogen atmosphere. Hold the temperature for 3 hours to obtain the pre-carbonized product. Step 3: Add the pre-carbonized product obtained in step (2) to ultrapure water. The mass ratio of the pre-carbonized product to ultrapure water is 1:1.3. Stir evenly, pour into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, heat at 235°C in a forced-air drying oven for 10 hours, and cool naturally to obtain the pretreated material. Step 4: Crush the pretreated material using an air jet mill, controlling the particle size D50 to around 3µm, to obtain the crushed material; Step 5: Place the pulverized material into a box-type resistance furnace, heat it to 1300℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, hold it at high temperature for 6 hours, and then cool it to obtain the heat-treated material.

[0036] Step 6: Mix the heat-treated material and liquid phase asphalt at a mass ratio of 100:5, heat at 190°C and 480 rpm in a high-speed fusion machine for 35 minutes to obtain the fused material; Step 7: Place the fused material obtained in step (6) into a high-temperature atmosphere furnace, and then heat it to 950°C at a heating rate of 2°C / min under a nitrogen atmosphere. Hold it at high temperature for 5 hours. After taking it out of the furnace, a high-ratio hard carbon anode material is obtained.

[0037] Comparative Example 2 Step 1: Cut the cedar wood into regular blocks using a wood cutter to obtain biomass raw materials; Step 2: Place the raw material into an electric resistance furnace and heat it to 560°C at a heating rate of 1°C / min under a nitrogen atmosphere. Hold the temperature for 3 hours to obtain the pre-carbonized product. Step 3: Add the pre-carbonized product obtained in step (2) to a 3 g / L p-nitrophenol solution. The mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:1.3. Stir evenly, pour into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, heat at 235°C in a forced-air drying oven for 10 h, and cool naturally to obtain the pretreated material. Step 4: Crush the pretreated material using an air jet mill, controlling the particle size D50 to around 3µm, to obtain the crushed material; Step 5: Place the pulverized material into a box-type resistance furnace, heat it to 1300℃ at a heating rate of 2℃ / min under a nitrogen atmosphere, hold it at high temperature for 6 hours, and then cool it to obtain the heat-treated material. Step 6: Heat the heat-treated material to 190°C and 480 rpm in a high-speed melting machine for 35 minutes to obtain the fused material; Step 7: Place the fused material obtained in step (6) into a high-temperature atmosphere furnace, and then heat it to 950°C at a heating rate of 2°C / min under a nitrogen atmosphere. Hold it at high temperature for 5 hours. After taking it out of the furnace, a high-ratio hard carbon anode material is obtained.

[0038] Comparative Example 3 Step 1: Cut the cedar wood into regular blocks using a wood cutter to obtain biomass raw materials; Step 2: Place the raw material into an electric resistance furnace and heat it to 560°C at a heating rate of 1°C / min under a nitrogen atmosphere. Hold the temperature for 3 hours to obtain the pre-carbonized product. Step 3: Add the pre-carbonized product obtained in step (2) to a 3 g / L p-nitrophenol solution. The mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:1.3. Stir evenly, pour into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, heat at 235°C in a forced-air drying oven for 10 h, and cool naturally to obtain the pretreated material. Step 4: Crush the pretreated material using an air jet mill, controlling the particle size D50 to around 3µm, to obtain the crushed material; Step 5: Mix the pulverized material and liquid asphalt at a mass ratio of 100:5, heat to 190°C and 480 rpm in a high-speed fusion machine for 35 minutes to obtain the fused material; Step 6: Place the fused material obtained in step (5) into a high-temperature atmosphere furnace, and then heat it to 950°C at a heating rate of 2°C / min under a nitrogen atmosphere. Hold it at high temperature for 5 hours. After taking it out of the furnace, a high-ratio hard carbon anode material is obtained.

[0039] application: Another aspect of the present invention provides the application of the above-mentioned high-rate biomass hard carbon material in sodium-ion batteries.

[0040] Specifically, the biomass hard carbon anode materials prepared in Examples 1-5 and Comparative Examples 1-3 were used as anode materials for sodium-ion batteries, and battery performance was tested using the following methods: Weigh out 0.2g of CMC, 0.2g of Super P, 9.4g of hard carbon material, and 0.4g of SBR (40% solid content) according to a mass ratio of 2%:2%:94%:2%. Add an appropriate amount of deionized water and mechanically stir for 30 minutes until a uniform slurry is formed. Coat the slurry evenly onto the surface of copper foil using a coater. Dry the slurry in a 105℃ forced-air drying oven for 3 hours. Then, slice the coated electrode using a slicer. In an Ar atmosphere glove box, use the electrode with hard carbon material as the positive electrode, 1.0mol / L NaPF6 / EC:DMC (1:1) (V:V) commercial electrolyte, sodium metal sheet as the counter electrode, and glass fiber as the separator to fabricate a CR2032 coin cell. Then, use constant current charge-discharge mode to conduct charge-discharge tests at a current density of 0.1C.

[0041] The commercial electrolyte is prepared by adding NaPF6 to a volume ratio of EC:DMC = 1:1.

[0042] The negative electrode of the full cell is made of hard carbon material: CMC:SP:SBR = 92%:2%:3%:3% by mass, and the positive electrode is NFPP system. The soft pack battery is made and subjected to 1C constant current and constant voltage charging and 1C constant current discharging to test the cycle performance. The rate performance is tested by 1C / 5C / 10C current charge and discharge.

[0043] The battery performance of the eight biomass hard carbon anode materials prepared in Examples 1-5 and Comparative Examples 1-3 was tested, and the test results are shown in Table 1.

[0044] Table 1. Charge-discharge specific capacity, initial efficiency, and capacity retention at 1C / 5C / 10C current test rates for sodium-ion batteries.

[0045] Table 1 shows that the biomass hard carbon anode material obtained by the present invention has a high specific capacity and a high rate retention rate in 5C / 10C charge-discharge tests. The 5C and 10C rate charge-discharge retention rates of Example 1 are significantly better than those of other examples and Comparative Examples 1-3. This is mainly because after pre-carbonization, the materials in Examples 1-5 were functionalized with p-nitrophenol to modify the active groups on the surface of the pre-carbonized material, thereby improving the stability of the material structure. Examples 1 and 2-5 present different concentrations of p-nitrophenol solution for treatment. Example 1 has the highest charging capacity, and its appropriate p-nitrophenol solution concentration has the best effect on modifying the active groups on the pre-carbonized surface. Too low or too high a concentration will slightly reduce the rate performance, possibly due to insufficient modification or local blockage of the carbon structure. Compared with Comparative Example 1, Comparative Example 1 did not use p-nitrophenol solution for hydrothermal modification, and the performance of Comparative Example 1 decreased significantly, indicating that surface functionalization greatly improved the material structure stability and conductivity. Compared to Example 4, Example 1, with its different amounts of liquid-phase asphalt, exhibits superior performance. Example 1 (high asphalt ratio): provides more complete coating, forming a continuous and dense graphite-like carbon layer, which enhances the connectivity of electron conduction pathways; inhibits repeated rupture of the SEI film; and provides a larger electron-ion composite interface during fast charging. Example 4 (low asphalt ratio): results in thinner or locally discontinuous coating. While still providing protection, the conductive network is insufficiently constructed, limiting the electron / ion co-transport capability at high rates.

[0046] Compared to Comparative Example 2, Example 1 underwent liquid-phase coating via a fusion machine at the rear end. The hard carbon material of Example 1 exhibited higher initial efficiency. Figure 3 This is a graph showing the 10C cycle specific capacity and 500-cycle retention rate of the sodium-ion battery as the negative electrode material in Example 1. The sodium battery corresponding to Example 1 maintains a high capacity retention rate even after full high-current cycling. (Attached) Figure 4 The image shows the Raman spectrum of biomass hard carbon from Example 1, where I... D / I G =1.18, the degree of defect and the degree of ordering are adjusted to improve the rate performance.

[0047] Compared to Example 3, Example 3 did not undergo heat treatment and was directly mixed with asphalt; Example 1 showed significantly better performance at higher rates than Comparative Example 3, especially with a nearly 20% increase in capacity retention at a 10C rate. This indicates that the heat treatment step can improve the orderliness, conductivity, and structural stability of carbon materials, and optimize defect distribution and interface structure.

[0048] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-rate hard carbon anode material, characterized in that, Includes the following steps: Biomass raw materials are pre-carbonized under a protective atmosphere to obtain pre-carbonized products; Then, the pre-carbonized product is added to the p-nitrophenol solution, stirred evenly, poured into a reaction vessel containing a polytetrafluoroethylene carbonization bottle, and subjected to hydrothermal reaction in a forced-air drying oven to obtain the pretreated material, which is then pulverized to obtain the pulverized material. The pulverized material is subjected to high-temperature heat treatment under an inert atmosphere to obtain heat-treated material; Heat-treated material is mixed with liquid phase asphalt and then fused in a high-speed fusion machine to obtain fused material; The fused material was surface modified under an inert atmosphere and then cooled to obtain a high-rate hard carbon anode material.

2. The method for preparing a high-rate hard carbon anode material according to claim 1, characterized in that, The preparation method of biomass raw materials includes the following steps: selecting cedar wood as raw material, cutting it into regular wood blocks using a wood cutting machine to obtain biomass raw materials.

3. The method for preparing a high-rate hard carbon anode material according to claim 2, characterized in that, Chinese fir trees are typically felled when they are 15-30 years old.

4. The method for preparing a high-rate hard carbon anode material according to claim 1, characterized in that, The pre-carbonization temperature is 400–800℃, the holding time is 1–10h, the pre-carbonization heating rate is 0.2–10℃ / min, and the protective atmosphere for pre-carbonization includes at least one of nitrogen, helium, and argon.

5. The method for preparing a high-rate hard carbon anode material according to claim 1, characterized in that, The mass concentration of the p-nitrophenol solution is 0.5–16 g / L; the mass ratio of the pre-carbonized product to the p-nitrophenol solution is 1:0.5–5; the temperature of the forced-air drying oven is 150–300℃, and the heating time is 5–18 h.

6. The method for preparing a high-rate hard carbon anode material according to claim 1, characterized in that, The pulverization is carried out by air jet milling, and the particle size D50 is controlled between 2 and 10 μm.

7. The method for preparing a high-rate hard carbon anode material according to claim 1, characterized in that, The conditions for high-temperature heat treatment include: a heating rate of 0.2–10 °C / min, a heat treatment temperature of 1000–1600 °C, a holding time of 1–15 h, and the heat treatment being carried out in a box-type resistance furnace.

8. The method for preparing a high-rate hard carbon anode material according to claim 1, characterized in that, Liquid phase asphalt includes at least one of petroleum-based asphalt and coal-based asphalt; the mass ratio of heat-treated material to liquid phase asphalt is 100:1~10; the heating temperature of the high-speed fusion machine is 100~300℃; the working speed of the high-speed fusion machine is 100-1000 rpm, and the fusion time is 10~90 minutes.

9. The method for preparing a high-rate hard carbon anode material according to claim 1, characterized in that, The surface modification conditions include: a heating rate of 0.2–10 °C / min, a high-temperature holding temperature of 800–1300 °C, a holding time of 1–12 h, and the modification is carried out in a high-temperature furnace with an inert atmosphere; the inert atmosphere includes at least one of nitrogen, helium, and argon.

10. The high-rate hard carbon anode material prepared by the method according to any one of claims 1-9 is used in sodium-ion batteries.

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