Preparation of hard carbon material with low defect and rich pseudo-graphite domain mediated by waste oil and method and high rate sodium storage

Abstract

The application belongs to the technical field of batteries, and particularly relates to a method for preparing a full-domain low-defect pseudo-graphite domain hard carbon material mediated by waste oil and a high-rate sodium ion energy storage device. The application is characterized in that: after drying, biomass is uniformly mixed with waste oil, stirred, placed in a tube furnace, heated under a protective gas, high-temperature carbonized, sequentially washed with a dilute hydrochloric acid solution and deionized water, and dried to obtain a full-domain low-defect pseudo-graphite domain high-rate hard carbon negative electrode material mediated by waste oil. The full-domain low-defect pseudo-graphite domain high-rate hard carbon negative electrode material mediated by waste oil obtained by the application enhances the structural stability of the material in the ion intercalation / deintercalation process, effectively prolongs the cycle life of the electrode, can guarantee the high-rate performance of the material while ensuring the platform capacity, and ensures that the electrode can still maintain a high capacity output and good cycle stability under a large-current charging and discharging condition.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to waste oil-mediated preparation of hard carbon materials with low defects across the entire domain and rich pseudo-graphite domains, as well as high-rate sodium-ion energy storage. Background Technology

[0002] With the acceleration of industrialization and the booming development of the electric vehicle industry, innovation in energy storage technology is seen as a key breakthrough in resolving the contradiction between environmental constraints and energy demand, leading to a growing demand for high-performance energy storage devices. Rate performance, as an important indicator for evaluating the discharge / charge speed of electrode materials at a given current density, is closely related to improvements in power density and energy density. To achieve a breakthrough in battery rate performance, current research focuses on developing high-performance electrode materials with rapid transport dynamics.

[0003] For sodium-ion battery anode materials, biomass-based hard carbon materials have become one of the most promising anode materials due to their unique structure and electrochemical performance. Traditional biomass carbonization processes directly utilize natural components, resulting in the following drawbacks: 1) High disorder in carbon layer stacking, with an excessive proportion of sp³ hybrid carbon, leading to deterioration in electronic conductivity; 2) Uneven pore structure distribution and insufficient closed-pore ratio, limiting the effective insertion / extraction kinetics of sodium ions. Therefore, hard carbon exhibits significantly insufficient rate performance, especially at low potentials where sodium ion diffusion kinetics are slow. To address the insufficient rate performance of hard carbon materials, researchers typically employ an outer layer of soft carbon to improve their rate performance. However, this method has some drawbacks: Firstly, the soft carbon layer may slip or detach during electrode cycling, leading to a decrease in the structural stability of the electrode material and consequently affecting the battery's cycle life. Secondly, since soft carbon coatings typically use organic materials such as asphalt as raw materials, and these organic materials require specific conditions to combine with hard carbon to form a coating layer, this undoubtedly increases the difficulty of the coating process. Some researchers have also begun to explore other methods, as exemplified by the recent paper "Spatially Confined Carbonization-Induced Reorganization of Microcrystals and Nanopores in CarbonFramework for Enhanced Sodium Plateau Storage". Adv. Energy Mater.The authors of "2025,2405294" optimized rate performance by introducing coal tar into activated carbon to promote the formation of pseudographite with large interlayer spacing. However, this method requires the use of specific solvents to ensure uniform dispersion and effective penetration of the coal tar, which limits its application range to some extent. Directly applying this method to biomass precursors may alter the original chemical composition and physical structure of the biomass due to the introduction of solvents, thus having unpredictable effects on the performance of the final product. Furthermore, the toxicity of some solvents can harm human health and the environment. In addition, chemical vapor deposition (CVD) has also been used as a method to form pseudographite structures to optimize the rate performance of hard carbon materials, but it suffers from inhomogeneity and unevenness in the pseudographite structure. Issues such as instability, high cost, and environmental pollution limit the feasibility of large-scale application. Achieving high-rate performance while maintaining low-voltage plateau capacity and initial coulombic efficiency is key to improving the overall electrochemical performance of hard carbon materials. Based on resource recycling considerations, some waste oils are used as carbon sources to prepare hard carbon materials. Patent (CN116553513A) proposes a method for generating sheet-like hard carbon using oils that easily form soft carbon as a carbon source, aiming to improve the high-rate performance of the material. However, directly carbonizing oils to generate sheet-like hard carbon results in a large specific surface area, leading to a lower initial coulombic efficiency. Simultaneously, the low carbon yield also limits its potential for large-scale application.

[0004] Therefore, there is an urgent need for a green and low-cost coating agent that can both coat hard carbon and optimize its structure. This coating agent should enable hard carbon materials to have both high rate capability and high plateau capacity without changing the original components of the biomass precursor, while ensuring the uniformity of its internal structure, thereby achieving efficient sodium storage performance. Summary of the Invention

[0005] The purpose of this invention is to provide a waste oil-mediated preparation method for hard carbon materials with low defects across the entire domain and rich pseudographite domains, as well as a high-rate sodium storage method.

[0006] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material includes the following steps:

[0008] (1) Wash the biomass with distilled water and then dry it in a forced-air drying oven;

[0009] (2) Take the dried biomass and waste oil, mix them evenly, and let them stand to obtain the mixture;

[0010] (3) The mixture obtained in step (2) is placed in a tube furnace and heated under inert protective gas conditions to carry out high-temperature carbonization to obtain carbonized material;

[0011] (4) The carbonized material obtained in step (3) is washed with dilute hydrochloric acid solution and deionized water in sequence until the solution is neutral, and then dried to obtain a waste oil-mediated, low-defect, pseudo-graphite domain-rich, high-rate hard carbon anode material with low defects throughout the entire domain; wherein, the oil rapidly penetrates and diffuses into the material interior in the biomass, modifying the biomass throughout the entire domain; the long-chain fatty acid molecules in the oil guide the carbon layers to arrange and stack in an orderly manner through π-π stacking.

[0012] Preferably, the biomass in step (1) can be plants such as soybeans, poplar wood, straw, soybean residue, leaves, and pine wood, and more preferably soybean residue.

[0013] Preferably, the waste oil in step (2) is at least one of the following: soybean oil, coconut oil, olive oil, peanut oil, pine nut oil, etc., and more preferably soybean oil, because soybean oil contains abundant unsaturated fatty acids.

[0014] Preferably, in step (2), the mass ratio of oil to biomass is 1-5:10 to ensure the structural guiding effect of long-chain fatty acid molecules in the oil.

[0015] Preferably, the stirring time in step (2) is 0.5-2 h and the standing time is 1-4 h.

[0016] Preferably, the high-temperature carbonization temperature in step (3) is between 1200-1600 °C to ensure sufficient carbonization and decomposition of the biomass components. Excessively high high-temperature carbonization temperatures will lead to additional energy consumption and excessive growth and stacking of carbon layers, while excessively low high-temperature carbonization temperatures may prevent long-chain fatty acid molecules in the oil from guiding the orderly arrangement and stacking of carbon layers through π-π stacking interactions. This incomplete guidance of the carbon layer structure may impair the reversible specific capacity and rate performance of hard carbon materials, thereby affecting the overall electrochemical performance of the material.

[0017] Preferably, in step (3), the high-temperature carbonization heating rate is 0.5-10 ℃ / min, and the high-temperature carbonization time is 1-6 h.

[0018] Preferably, the high-temperature carbonization protective gas in step (3) is one of hydrogen, argon, nitrogen, hydrogen-argon, or hydrogen-nitrogen, and more preferably argon.

[0019] Preferably, in step (4), the hydrochloric acid concentration is 1-2 mol / L and the pickling time is 12 h to ensure the full removal of impurities from the high-temperature carbonized material.

[0020] Preferably, the water washing process involves repeated filtration and washing with deionized water, with the number of washes being 3 to 10 times, to ensure the removal of hydrochloric acid.

[0021] Waste oil, also known as waste cooking oil, usually refers to oil that is no longer suitable for consumption, expired, or used, generated during food business, processing, and consumption activities.

[0022] It is important to note that the high-temperature carbonization temperature affects the development of the carbon layer and the formation of closed pores, ultimately impacting the material's performance. Furthermore, the high-temperature carbonization process should not be too long; excessive processing time can cause the carbon layer to grow beyond its limits, resulting in overgrowth, bending, and stacking, which in turn affects the specific capacity or rate performance of the hard carbon material.

[0023] The present invention also provides a waste oil-mediated, globally low-defect, pseudo-graphite domain-rich hard carbon anode material, which is obtained through the above-described preparation process.

[0024] This invention also provides the above-mentioned waste oil-mediated, globally low-defect, pseudo-graphite domain-rich hard carbon anode material for use as anode material in sodium-ion batteries.

[0025] The globally low-defect, pseudo-graphite-domain-rich structure, formed by the strong permeation of waste oil, provides more insertion sites for sodium ions, significantly increasing the material's specific capacity. Long-chain fatty acid molecules in the waste oil guide the orderly arrangement and stacking of carbon layers through π-π stacking interactions, simultaneously constructing a conductive network within the material and forming a uniform coating on the outside. This enhances the structural stability of the material during ion insertion / extraction, effectively extending the electrode's cycle life. Furthermore, the bending characteristics of the pseudo-graphite microcrystals create a rich closed-pore structure within the material. These pores provide efficient channels for rapid ion transport during sodium ion insertion, thus ensuring both plateau capacity and high rate performance. This guarantees that the electrode maintains high capacity output and good cycle stability even under high-current charge-discharge conditions.

[0026] Compared with the prior art, the technical effects of the present invention are as follows:

[0027] This invention uses biomass as raw material and introduces inexpensive and environmentally friendly waste oil as a structure-directing agent. Through temperature control under an inert atmosphere, high-temperature carbonization products are obtained, resulting in a hard carbon anode material rich in long-range pseudo-graphite structures. Inexpensive and renewable waste vegetable oil exhibits a strong permeation effect in bio-based materials. This effect not only globally interferes with the growth process of biomass hard carbon but also effectively promotes the rapid and uniform growth of pseudo-graphite across the entire range. Simultaneously, by reducing hard carbon defects and constructing a highly efficient conductive network, the electron transport performance of the material is significantly improved. Furthermore, the curved structure of numerous graphite domains constructs a closed-pore morphology. This unique microstructure design ensures both high specific capacity and high rate performance, thereby achieving high-performance sodium ion storage. Attached Figure Description

[0028] Figure 1 This is an HRTEM image of Embodiment 1 of the present invention;

[0029] Figure 2 This is the HRTEM image of Comparative Example 1 of the present invention;

[0030] Figure 3 The hard carbon anode materials prepared in Example 1 and Comparative Example 1 of this invention are shown as the first charge-discharge curves of sodium-ion batteries at a current density of 20 mA / g.

[0031] Figure 4 The hard carbon anode materials prepared in Example 1 and Comparative Example 1 of this invention are used for the rate performance of sodium-ion batteries;

[0032] Figure 5 These are the XRD patterns of Embodiment 1 and Comparative Example 1 of the present invention;

[0033] Figure 6 The above are Raman diagrams of Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0035] Example 1

[0036] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0037] (1) Weigh 8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0038] (2) Take the dried material and mix it with 0.8 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0039] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1400 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0040] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0041] (5) The waste oil prepared above is used as the active material for preparing sodium-ion batteries to prepare hard carbon materials with low defects and rich pseudo-graphite domains throughout the entire domain as the negative electrode material.

[0042] Weigh 80 mg of hard carbon material, 10 mg of acetylene black, and 10 mg of PVDF according to a mass ratio of 80% : 10% : 10%. Add an appropriate amount of deionized water and stir for 20 min until a uniform slurry is formed. Use a 100 μm scraper to evenly coat the slurry onto a copper (Cu) foil. Place the slurry in a forced-air drying oven and dry for 12 h. Cut the Cu foil with active material into circular electrode sheets for later use.

[0043] The coin cell assembly was carried out in a glove box filled with Ar atmosphere. The prepared electrode sheet was used as the negative electrode, the commercial electrolyte 1.0 M NaPF6in DME=100 Vol% was used as the electrolyte, and the Na metal sheet was used as the counter electrode to assemble a 2032 coin cell.

[0044] Figure 1 This is a TEM image of the waste oil-mediated pseudo-graphite domain hard carbon anode material prepared in Example 1 of the present invention. As can be seen from the figure, a long-range curved pseudo-graphite microcrystalline structure with high conductivity can be clearly seen on the surface. At the same time, the curved pseudo-graphite domains cross-link to form a closed-pore structure, which is beneficial for sodium storage in the low potential plateau region.

[0045] Comparative Example 1

[0046] This invention provides a comparative example of a method for preparing a biomass-based hard carbon anode material for sodium-ion batteries, the steps of which include:

[0047] (1) Weigh 8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0048] (2) Take the dried material and place it in a tube furnace. Under argon conditions, heat it to 1400℃ at a heating rate of 5℃ / min and hold it for 2 hours. After cooling to room temperature, take it out to obtain carbonized material.

[0049] (3) The carbonized material obtained in step (2) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain the purified carbonized material.

[0050] (4) The purified carbonized material prepared above was used as the active material of the negative electrode material for the preparation of sodium-ion batteries, and the specific method was the same as in Example 1. The assembled half-cell had a first-cycle charging specific capacity of 266.33 mAh / g at a current density of 20 mA / g.

[0051] Figure 2 The image shows a TEM image of the hard carbon anode material prepared in Comparative Example 1 without waste oil mediation. As can be seen from the image, the surface pseudographite structure is not fully developed, the internal conductive network is incomplete, and the closed-pore content is low, which is not conducive to high-rate sodium storage.

[0052] Figure 3 The figure shows the first charge-discharge curves for Example 1 and Comparative Example 1 of this invention; as shown, at a current density of 20 mA / g, the first charge specific capacity is 330.41 mAh / g. The plateau capacity contribution is 257.88 mAh / g. -1 This accounts for 60.84%. In contrast, Comparative Example 1 had a first-cycle charging capacity of 266.33, with the platform contributing 206.4 mAh g. -1 The platform capacity percentage in Example 1 is 52.89%. The high platform capacity percentage in Example 1 can be attributed to long-range pseudographite domains and the closed-cell structure formed by bending.

[0053] Figure 4 The figure shows the rate performance of Example 1 and Comparative Example 1 of the present invention; as can be seen from the figure, at 1 A g -1 At the current density, the reversible specific capacity is 268.78 mAh g. -1 , in 2 Ag -1 At the current density, the reversible specific capacity is 245.62 mAh g. -1 The excellent rate capability can be attributed to fewer surface defects and a long-range pseudo-graphite structure, which gives it high electrical conductivity. In Comparative Example 1, at 2 A g... -1 At the current density, the reversible specific capacity is 149.5 mAh g.-1 This can be attributed to the structural instability and imperfect internal conductive network during the ion insertion / extraction process in Comparative Example 1.

[0054] Figure 5 The figures show the XRD patterns of Example 1 and Comparative Example 1 of the present invention. As can be seen from the figures, the (002) peak of Example 1 is significantly sharper than that of Comparative Example 1, indicating that the orderliness of its carbon layers has been significantly enhanced. In addition, the peak shifts to a higher angle, which highlights the reduction in the carbon layer spacing. Furthermore, the disorder level of Example 1 is significantly reduced compared to Comparative Example 1, while the pseudo-graphite region shows a significant increasing trend, which is consistent with the pseudo-graphite structure observed in the TEM image.

[0055] Figure 6 The figures show Raman spectroscopy of Embodiment 1 and Comparative Example 1 of the present invention. As can be seen from the figures, it is obvious that Embodiment 1 has a higher degree of order and fewer defects than Comparative Example 1. This can be attributed to the long-range pseudo-graphite structure with bent stacking in Embodiment 1, which is consistent with the pseudo-graphite structure observed in the TEM image.

[0056] Example 2

[0057] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0058] (1) Weigh 8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0059] (2) Take the dried material and mix it with 0.5 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0060] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1400 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0061] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0062] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0063] Example 3

[0064] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0065] (1) Weigh 8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0066] (2) Take the dried material and mix it with 1.6 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0067] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1400 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0068] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0069] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0070] Example 4

[0071] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0072] (1) Weigh 8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0073] (2) Take the dried material and mix it with 2.4 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0074] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1400 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0075] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0076] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0077] Example 5

[0078] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0079] (1) Weigh 8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0080] (2) Take the dried material and mix it with 3.2 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0081] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1400 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0082] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0083] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0084] Example 6

[0085] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0086] (1) Weigh 8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0087] (2) Take the dried material and mix it with 4 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0088] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1400 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0089] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0090] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0091] Example 7

[0092] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0093] (1) Weigh 8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0094] (2) Take 0.8 g of dried material and oil, mix and stir for 2 h, let stand for 2 h to obtain the mixture;

[0095] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1200 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0096] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0097] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0098] Example 8

[0099] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0100] (1) Weigh 0.8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0101] (2) Take the dried material and mix it with 4 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0102] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1600 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0103] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0104] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0105] Example 9

[0106] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0107] (1) Weigh 0.8 g of soybean residue, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0108] (2) Take the dried material and mix it with 0.8 g of peanut oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0109] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1600 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0110] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0111] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0112] Example 10

[0113] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0114] (1) Weigh 8 g of poplar wood, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0115] (2) Take the dried material and mix it with 0.8 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0116] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1600 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0117] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0118] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0119] Example 11

[0120] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0121] (1) Weigh 8 g of straw, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0122] (2) Take the dried material and mix it with 0.8 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0123] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1600 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0124] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0125] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0126] Example 12

[0127] A method for preparing a waste oil-mediated, globally low-defect, pseudographite domain high-rate hard carbon anode material

[0128] (1) Weigh 8 g of walnut shells, wash them with an appropriate amount of distilled water, and place them in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0129] (2) Take the dried material and mix it with 0.8 g of soybean oil for 2 hours, let it stand for 2 hours to obtain the mixture;

[0130] (3) The mixture obtained in step (2) is placed in a tube furnace and heated to 1600 ℃ at a heating rate of 5 ℃ / min under argon conditions. The temperature is held for 2 h and then cooled to room temperature to obtain carbonized material.

[0131] (4) The carbonized material obtained in step (3) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects and rich pseudo-graphite domains.

[0132] (5) The waste oil prepared above was used as the active material for preparing sodium-ion batteries by preparing hard carbon material with low defects and rich pseudo-graphite domains in the whole domain as a battery negative electrode material. The specific method is the same as in Example 1.

[0133] Comparative Example 2

[0134] This invention provides a comparative example of a method for preparing a biomass-based hard carbon anode material for sodium-ion batteries, the steps of which include:

[0135] (1) Weigh 8 g of poplar wood, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0136] (2) Take the dried material and place it in a tube furnace. Under argon conditions, heat it to 1400℃ at a heating rate of 5℃ / min and hold it for 2 hours. After cooling to room temperature, take it out to obtain carbonized material.

[0137] (3) The carbonized material obtained in step (2) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain the purified carbonized material.

[0138] (4) The purified carbonized material prepared above was used as the active material of the negative electrode material for the preparation of sodium-ion batteries, and the specific method was the same as in Example 1. The assembled half-cell had a first-cycle charge specific capacity of 300.03 mAh / g at a current density of 20 mA / g.

[0139] Comparative Example 3

[0140] This invention provides a comparative example of a method for preparing a biomass-based hard carbon anode material for sodium-ion batteries, the steps of which include:

[0141] (1) Weigh 8 g of straw, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0142] (2) Take the dried material and place it in a tube furnace. Under argon conditions, heat it to 1400℃ at a heating rate of 5℃ / min and hold it for 2 hours. After cooling to room temperature, take it out to obtain carbonized material.

[0143] (3) The carbonized material obtained in step (2) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain the purified carbonized material.

[0144] (4) The purified carbonized material prepared above was used as the active material of the negative electrode material for the preparation of sodium-ion batteries, and the specific method was the same as in Example 1. The assembled half-cell had a first-cycle charging specific capacity of 298.47 mAh / g at a current density of 20 mA / g.

[0145] Comparative Example 4

[0146] This invention provides a comparative example of a method for preparing a biomass-based hard carbon anode material for sodium-ion batteries, the steps of which include:

[0147] (1) Weigh 8 g of walnut shells, wash them with an appropriate amount of distilled water, and place them in a forced-air drying oven. The drying temperature is 80 ℃ and the drying time is 12 h to remove impurities and moisture, and obtain dried material.

[0148] (2) Take the dried material and place it in a tube furnace. Under argon conditions, heat it to 1400℃ at a heating rate of 5℃ / min and hold it for 2 hours. After cooling to room temperature, take it out to obtain carbonized material.

[0149] (3) The carbonized material obtained in step (2) was washed in 1 mol / L hydrochloric acid solution and distilled water for 6 h. It was then dried in a forced-air drying oven at 60 ℃ for 12 h to obtain the purified carbonized material.

[0150] (4) The purified carbonized material prepared above was used as the active material of the negative electrode material for the preparation of sodium-ion batteries, and the specific method was the same as in Example 1. The assembled half-cell had a first-cycle charge specific capacity of 309.26 mAh / g at a current density of 20 mA / g.

[0151] The relevant performance parameters of the half-cells assembled in each embodiment and comparative example are shown in Table 1.

[0152] Table 1. Performance parameters of the assembled half-cell

[0153]

[0154] As can be seen from the above examples and comparative examples, in Example 1, after adding 0.8g of oil to the soybean residue and carbonizing it at high temperature, the reversible specific capacity of the material reached 330.41 mAh / g. In contrast, the biomass in Comparative Example 1, without the addition of oil, showed more surface defects, insufficient graphite layer development, fewer pseudo-graphite structures, and failed to cross-link to form an effective closed-pore structure. This significantly affected its rate performance and reversible specific capacity. Furthermore, in Example 6, when the amount of oil added exceeded the optimal range, the long-chain fatty acids in the oil excessively guided the growth, bending, and stacking of the carbon layer, thereby hindering the formation of closed pores. In this case, its rate performance was poor, and the reversible specific capacity decreased to 276.94 mAh / g.

[0155] Compared to the control group, the experimental group samples have a large number of small-interlayer graphite domains uniformly present inside and at the edges, and the graphite domains are longer. The carbon layer undergoes topological bending, forming a rich closed-pore structure. The oil-mediated hard carbon in the experimental group has a superior high-rate performance in sodium storage compared to the hard carbon in the control group.

[0156] Verification through Examples 1, 7, and 8 shows that holding at 1400 ℃ for 2 h is the optimal condition for preparing a globally low-defect, pseudo-graphite domain-rich structure mediated by waste oil. Excessive temperature will lead to overdevelopment, stacking, and bending of graphite domains, while excessively low temperature will lead to insufficient development of graphite domains.

[0157] Through verification in Examples 1 and 9, soybean residue and soybean oil have the best compatibility. Compared with peanut oil, soybean oil is more effective at regulating the graphite domain microcrystalline structure of soybean residue.

[0158] It is evident that the amount of oil added has a significant impact on the microstructure and electrochemical performance of biomass soybean residue-derived hard carbon anode materials. With the increase of oil addition, the microstructure of the material exhibits a large number of small-interlayer-spacing graphite domains uniformly inside and at the edges. The graphite domains are relatively long, and the carbon layers undergo topological bending, forming a rich closed-pore structure. This optimization of the microstructure directly promotes the improvement of the material's electrochemical performance.

[0159] In summary, the preparation method proposed in this invention relies on the synergistic ratio of each component and the coordination of each process step. It is precisely this strong permeation effect of waste oil that achieves global interference, endowing biomass-based hard carbon materials with excellent electrochemical properties. If any condition deviates from the range specified in this invention, it may lead to a decrease in the performance of the hard carbon materials.

[0160] The basic principles, main features, and advantages of this invention have been described above. Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made without departing from the spirit and scope of the invention, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection claimed by this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a waste oil-mediated, globally low-defect, pseudo-graphite domain-rich, high-rate hard carbon anode material, characterized in that, The preparation method includes the following steps: (1) Wash the biomass with distilled water and then dry it in a forced-air drying oven; (2) Take the dried biomass and waste oil and mix them evenly. After standing, a mixture is obtained. The mass ratio of waste oil to biomass is 1-5:

10. (3) The mixture obtained in step (2) is placed in a tube furnace and heated under inert protective gas conditions to carry out high-temperature carbonization to obtain carbonized material; (4) The carbonized material obtained in step (3) is washed with dilute hydrochloric acid solution and deionized water in sequence until the solution is neutral, and then dried to obtain a waste oil-mediated, low-defect, pseudo-graphite domain high-rate hard carbon anode material.

2. The preparation method according to claim 1, characterized in that, In step (1), the biomass is any one of the following plants: soybean, poplar, straw, soybean residue, leaves, and pine.

3. The preparation method according to claim 1, characterized in that, The waste oil in step (2) is at least one of soybean oil, coconut oil, olive oil, peanut oil, and pine nut oil.

4. The preparation method according to claim 1, characterized in that, In step (2), the stirring time is 0.5-2 h and the standing time is 1-4 h.

5. The preparation method according to claim 1, characterized in that, The high-temperature carbonization temperature in step (3) is 1200-1600 ℃.

6. The preparation method according to claim 1, characterized in that, In step (3), the high-temperature carbonization heating rate is 0.5-10 ℃ / min, and the high-temperature carbonization time is 1-6 h; the high-temperature carbonization protective gas is any one of hydrogen, argon, nitrogen, hydrogen-argon, or hydrogen-nitrogen.

7. The preparation method according to claim 6, characterized in that, In step (3), the high-temperature carbonization protective gas is argon.

8. The preparation method according to claim 1, characterized in that, In step (4), the concentration of hydrochloric acid is 1-2 mol / L and the acid washing time is 12 h; the water washing process is to repeatedly filter and wash with deionized water, and the number of washing times is 3-10.

9. The waste oil-mediated, globally low-defect, pseudographite-domain-rich, high-rate hard carbon anode material obtained by the preparation method described in claims 1-8.

10. The application of the waste oil-mediated, globally low-defect, pseudographite-domain-rich, high-rate hard carbon anode material as described in claim 9 in sodium-ion battery anode materials.

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