Waste oil-mediated preparation method of global low-defect pseudographite domain-rich hard carbon material and method and high-rate sodium storage

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a waste oil mediated preparation method of a whole-domain low-defect pseudographite domain-rich hard carbon material and a method and high-rate sodium ion energy storage. The preparation method comprises the following steps: uniformly mixing and stirring dried biomass and waste grease, putting the mixture into a tubular furnace, heating under protective gas, carrying out high-temperature carbonization, washing with a diluted hydrochloric acid solution and deionized water in sequence, and drying to obtain the waste oil mediated whole-domain low-defect pseudo-graphite domain high-rate hard carbon negative electrode material. According to the waste oil mediated global low-defect and pseudo-graphite domain-enriched high-rate hard carbon negative electrode material obtained by the invention, the structural stability of the material in an ion intercalation / deintercalation process is enhanced, the cycle life of an electrode is effectively prolonged, the high-rate performance of the material can be considered while the platform capacity is ensured, and the service life of the material is prolonged. And it is ensured that the electrode can still maintain high capacity output and good cycling stability under the large-current charging and discharging condition.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a method for preparing all-region low-defect, pseudo-graphite domain-rich hard carbon materials mediated by waste oil, and a method and high-rate sodium ion energy storage. Background Art

[0002] With the acceleration of the industrialization process and the booming development of the electric vehicle industry, the innovation of energy storage technology is regarded as the key breakthrough to solve the contradiction between environmental constraints and energy demand, and the social demand for high-performance energy storage devices is increasing day by day. The rate performance, as an important index for evaluating the discharge / charge speed of electrode materials at a given current density, is closely related to the improvement of power density and energy density. In order to achieve a breakthrough improvement in the rate performance of batteries, the current research focus is on developing high-performance electrode materials with fast charge transport kinetics characteristics.

[0003] For the anode materials of sodium-ion batteries, biomass-based hard carbon materials have become one of the most promising anode materials due to their unique structure and electrochemical properties. Traditional biomass carbonization processes directly utilize their natural components, which have the following defects: 1) The degree of disorder in the stacking of carbon layers is relatively high, and the proportion of sp³ hybridized carbon is too large, resulting in deteriorated electron conduction performance; 2) The pore structure distribution is uneven, and the proportion of closed pores is insufficient, restricting the effective insertion / extraction kinetics of sodium ions. Therefore, the rate performance of hard carbon is significantly insufficient, especially at low potentials, where the diffusion kinetics of sodium ions is slow. To solve the problem of insufficient rate performance of hard carbon materials, researchers usually adopt the method of coating the outer layer with soft carbon to improve its rate performance. However, this method has some defects: on the one hand, the soft carbon layer may slip or fall off during the cycling process of the electrode material, resulting in a decrease in the structural stability of the electrode material, thereby affecting the cycle life of the battery. In addition, considering that the soft carbon coating layer usually uses organic substances such as asphalt as raw materials, and such organic substances need to be combined with hard carbon under specific conditions to form a coating layer, this undoubtedly increases the difficulty of the coating process. Some researchers have also begun to explore other methods. Recently, the literature "Spatially Confined Carbonization-Induced Reorganization of Microcrystals and Nanopores in Carbon Framework for Enhanced Sodium Plateau Storage." Adv. Energy Mater.In 2025, 2405294, the authors introduced coal tar into activated carbon to promote the formation of pseudo-graphite with a large interlayer spacing, thereby optimizing the rate performance. However, this treatment method requires the use of specific solvents to ensure the uniform dispersion and effective penetration of coal tar, which to a certain extent limits its application scope. If this method is directly applied to biomass precursors, it may change the original chemical composition and physical structure of the biomass due to the introduction of solvents, thereby having unforeseen effects on the performance of the final product, and the toxicity of some solvents themselves will cause harm to the human body and the environment. In addition, chemical vapor deposition (CVD) has also been adopted as a method to form a pseudo-graphite structure to optimize the rate performance of hard carbon materials, but there are problems such as non-uniformity and instability of the pseudo-graphite structure, high cost, and environmental pollution, which to a certain extent limit the feasibility of its large-scale application. While achieving high rate performance, balancing the low-pressure platform capacity and the first Coulomb efficiency is the key to improving the overall electrochemical performance of hard carbon. Considering resource recycling, some waste oils are used as carbon sources to prepare hard carbon materials. Patent (CN116553513A) proposed a method for generating sheet-like hard carbon using oils that are easy to form soft carbon as carbon sources, aiming to improve the high rate performance of the materials. However, directly carbonizing the oils to generate sheet-like hard carbon will result in a relatively large specific surface area of the material, thereby causing a low first Coulomb efficiency. At the same time, the problem of low carbon yield also limits the possibility of its large-scale application to a certain extent.

[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 performance and high platform 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 the present invention is to provide a method for preparing a hard carbon material with low defects throughout the domain, rich pseudo-graphite domains mediated by waste oil, and high rate sodium storage.

[0006] In order to achieve the above technical objectives, the technical solution of the present invention is as follows: A method for preparing a hard carbon negative electrode material with low defects throughout the domain, pseudo-graphite domains, and high rate mediated by waste oil, comprising the following steps: (1) Wash the biomass with distilled water and then place it in a blast drying oven for drying treatment; (2) Take the dried biomass and uniformly mix and stir it with waste oil, and obtain a mixed material after standing; (3) Place the mixed material obtained in step (2) in a tube furnace, heat it up under the condition of an inert protective gas, and perform high-temperature carbonization to obtain a carbonized material; (4) Wash the carbonized material obtained in step (3) successively with dilute hydrochloric acid solution and deionized water until the solution is neutral, and then dry it to obtain a waste oil-mediated high-rate hard carbon anode material with low defects and rich pseudo-graphite domains throughout the material; wherein, the oil rapidly penetrates and diffuses into the interior of the biomass, modifying the biomass throughout the interior and exterior; the long-chain fatty acid molecules in the oil guide the orderly arrangement and stacking of carbon layers through π-π stacking interactions.

[0007] Preferably, the biomass in step (1) can be plants such as soybeans, poplar wood, straw, soybean dregs, leaves, pine wood, etc., and further preferably soybean dregs.

[0008] Preferably, the waste oil in step (2) is at least one of waste oils such as soybean oil, coconut oil, olive oil, peanut oil, pine nut oil, etc., and further preferably soybean oil because soybean oil contains rich unsaturated fatty acids.

[0009] Preferably, the mass ratio of the oil to the biomass in step (2) is 1-5:10 to ensure the structure-directing effect of the long-chain fatty acid molecules in the oil.

[0010] Preferably, the stirring time in step (2) is 0.5-2 h, and the standing time is 1-4 h.

[0011] Preferably, the high-temperature carbonization temperature in step (3) is between 1200-1600 °C to ensure the full carbonization and decomposition of the biomass components. Too high a high-temperature carbonization temperature will result in additional energy consumption and excessive growth and stacking of carbon layers, while too low a high-temperature carbonization temperature may cause the long-chain fatty acid molecules in the oil to be unable to guide the orderly arrangement and stacking of carbon layers through π-π stacking interactions. This incomplete guidance of the carbon layer structure may damage the reversible specific capacity and rate performance of the hard carbon material, thereby affecting the overall electrochemical performance of the material.

[0012] Preferably, the heating rate of high-temperature carbonization in step (3) is 0.5-10 °C / min, and the high-temperature carbonization time is 1-6 h.

[0013] Preferably, the protective gas for high-temperature carbonization in step (3) is one of hydrogen, argon, nitrogen, hydrogen-argon, hydrogen-nitrogen, and further preferably argon.

[0014] Preferably, the hydrochloric acid concentration in step (4) is 1-2 mol / L hydrochloric acid, and the pickling time is 12 h to ensure the full removal of impurities in the high-temperature carbonized material.

[0015] Preferably, the water washing process is to repeatedly filter and wash with deionized water, and the number of washing times is 3-10 times to ensure the removal of hydrochloric acid.

[0016] Waste grease, also known as discarded grease, generally refers to grease that is no longer suitable for consumption, expired or used in food management, processing, consumption and other activities.

[0017] It should be noted that the temperature of high-temperature carbonization will affect the development of the carbon layer and the formation of closed pores, which will ultimately affect the performance of the material; and the high-temperature carbonization treatment time should not be too long. If the treatment time is too long, the carbon layer growth will break through the limit, resulting in excessive growth, bending and stacking, which will affect the specific capacity or rate performance of the hard carbon material.

[0018] The present invention also provides a waste oil-mediated global low-defect, pseudographite domain-rich hard carbon negative electrode material, which is obtained through the above-mentioned preparation process.

[0019] The present invention also provides the above waste oil-mediated global low-defect, pseudographite domain-rich hard carbon negative electrode material for use as a negative electrode material for sodium ion batteries.

[0020] The global low-defect, rich pseudographite domain structure is formed by global interference of the strong penetration of waste oil, which provides more embedding sites for sodium ions and significantly increases the specific capacity of the material. The long-chain fatty acid molecules in the waste oil guide the orderly arrangement and stacking of the carbon layers through the π-π stacking effect, while building a conductive network inside the material and forming a uniform coating on the outside, which enhances the structural stability of the material during the ion embedding / ejection process and effectively extends the cycle life of the electrode. In addition, the bending characteristics of the pseudographite microcrystals form a rich closed-pore structure inside the material. These closed pores provide efficient channels for the rapid transmission of ions during the sodium ion embedding process, thereby ensuring the platform capacity while taking into account the high rate performance of the material, ensuring that the electrode can still maintain a high capacity output and good cycle stability under high current charge and discharge conditions.

[0021] Compared with the prior art, the technical effects of the present invention are as follows: The present invention uses biomass as raw material, introduces low-cost and environmentally friendly waste oil as a structure-directing agent, obtains high-temperature carbonization products through temperature control under an inert atmosphere, and prepares hard carbon negative electrode materials rich in long-range pseudographite structures. Cheap and renewable waste vegetable oil exhibits a strong penetration effect in bio-based materials, which not only globally interferes with the growth process of biomass hard carbon, but also more effectively promotes the rapid and uniform growth of pseudographite in the entire domain. At the same time, by reducing hard carbon defects and constructing an efficient conductive network, the electronic transmission performance of the material is significantly improved. In addition, the curved structure of a large number of graphite domains constructs a closed-cell morphology. This unique microstructural design not only ensures the high specific capacity of the material, but also takes into account its high rate performance, thereby achieving high-performance sodium ion storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 HRTEM image of Example 1 of the present invention; Figure 2 HRTEM image of Comparative Example 1 of the present invention; Figure 3 First charge-discharge curves of the hard carbon negative electrode materials prepared in Example 1 and Comparative Example 1 of the present invention for sodium-ion batteries at a current density of 20 mA / g; Figure 4 Rate performance of the hard carbon negative electrode materials prepared in Example 1 and Comparative Example 1 of the present invention for sodium-ion batteries; Figure 5 XRD patterns of Example 1 and Comparative Example 1 of the present invention; Figure 6 Raman patterns of Example 1 and Comparative Example 1 of the present invention. Detailed implementation manners

[0023] The present invention will be further described below in conjunction with 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 to the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solutions of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the protection scope of the present invention.

[0024] Example 1 Preparation method of a waste oil-mediated all-region low-defect and pseudo-graphite domain high-rate hard carbon negative electrode material (1) Weigh 8 g of soybean dregs, wash them with an appropriate amount of distilled water, and place them in a blast drying oven at a drying temperature of 80 °C for 12 h to remove impurities and moisture, obtaining a dried material; (2) Take the dried material and mix it with 0.8 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material; (3) Place the mixed material obtained in step (2) in a tubular furnace, and under argon conditions, heat it to 1400 °C at a heating rate of 5 °C / min, with a holding time of 2 h. After cooling to room temperature, take it out to obtain a carbonized material; (4) Wash the carbonized material obtained in step (3) in 1 mol / L hydrochloric acid solution and distilled water for 6 h, and place it in a blast drying oven at 60 °C for 12 h to obtain a waste oil-mediated all-region low-defect and pseudo-graphite domain-rich hard carbon material.

[0025] (5) Use the waste oil-mediated all-region low-defect and pseudo-graphite domain-rich hard carbon material prepared above as the active substance of the battery negative electrode material for the preparation of sodium-ion batteries.

[0026] Weigh 80 mg of hard carbon material, 10 mg of acetylene black, and 10 mg of PVDF according to the mass ratio of 80% : 10% : 10%. Add an appropriate amount of deionized water and stir for 20 min until a homogeneous slurry is obtained. Use a 100-μm doctor blade to evenly coat it on a copper (Cu) foil, and place it in a forced-air drying oven to dry for 12 h. Cut the Cu foil with the active material into circular electrode sheets for standby.

[0027] The assembly of the coin cell is carried out in a glove box filled with an Ar atmosphere. Use the prepared electrode sheet as the negative electrode, 1.0 M NaPF6 in DME = 100 Vol% of commercial electrolyte as the electrolyte, and a Na metal sheet as the counter electrode to assemble a 2032 coin cell.

[0028] Figure 1 This is the TEM image of the waste oil-mediated pseudo-graphite domain hard carbon negative electrode material prepared in Example 1 of the present invention. It can be seen from the figure that a long-range curved pseudo-graphite microcrystalline structure can be clearly observed on the surface, which has high conductivity. At the same time, the curved pseudo-graphite domains are cross-linked with each other to form a closed-pore structure, which is beneficial to sodium storage in the low-potential plateau region.

[0029] Comparative Example 1 The present invention provides a preparation method of a biomass-based hard carbon negative electrode material for a sodium-ion battery in a comparative example, and its steps include: (1) Weigh 8 g of soybean dregs, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 °C, and the drying time is 12 h to remove impurities and moisture to obtain a dried material. (2) Take the dried material and place it in a tubular furnace. Under argon conditions, heat it at a heating rate of 5 °C / min to 1400 °C, keep it warm for 2 h, and take it out after cooling to room temperature to obtain a carbonized material. (3) Wash the carbonized material obtained in step (2) with 1 mol / L hydrochloric acid solution and distilled water. The washing time is 6 h, and place it in a forced-air drying oven to dry at 60 °C for 12 h to obtain a purified carbonized material.

[0030] (4) Use the purified carbonized material prepared above as the active substance of the battery negative electrode material for the preparation of a sodium-ion battery. The specific method is the same as that in Example 1. The first-cycle charge specific capacity of the assembled half-cell is 266.33 mAh / g at a current density of 20 mA / g.

[0031] Figure 2 This is the TEM image of the hard carbon negative electrode material without waste oil mediation prepared in Comparative Example 1. It can be seen from the figure that the pseudo-graphite structure on the surface is not fully developed, the internal conductive network is not completely constructed, and the closed-pore content is less, which is not conducive to high-rate sodium storage.

[0032] Figure 3 This is the first-cycle charge-discharge curve of Example 1 and Comparative Example 1 of the present invention; as shown in the figure, at a current density of 20 mA / g, the first-cycle charge specific capacity is 330.41 mAh / g. Among them, the plateau capacity contributes 257.88 mAh g -1 , accounting for 60.84%. While the first-cycle charge specific capacity of Comparative Example 1 is 266.33, and the plateau capacity contributes 206.4 mAh g -1 , accounting for 52.89%. The high proportion of plateau capacity in Example 1 can be attributed to the long-range pseudo-graphite domains and the closed pore structure formed by bending.

[0033] Figure 4 This is the rate performance of Example 1 and Comparative Example 1 of the present invention; as can be seen from the figure, at a current density of 1 A g -1 , the reversible specific capacity is 268.78 mAh g -1 , at a current density of 2 A g -1 , the reversible specific capacity is 245.62 mAh g -1 , and the excellent rate performance can be attributed to fewer surface defects and long-range pseudo-graphite structure, making it have high conductivity. While in Comparative Example 1 at a current density of 2 A g -1 , the reversible specific capacity is 149.5 mAh g -1 , which can be attributed to the structural instability during the ion insertion / extraction process and the imperfect internal conductive network in Comparative Example 1.

[0034] Figure 5 This is the XRD pattern of Example 1 and Comparative Example 1 of the present invention; as can be seen from the figure, it can be clearly seen that the (002) peak of Example 1 shows a sharper peak shape than that of Comparative Example 1, indicating that the orderliness of its carbon layer has been significantly enhanced. In addition, this peak shifts to a higher angle, highlighting the reduction of the carbon layer spacing; and the degree of disorder in Example 1 is significantly reduced compared to Comparative Example 1, while the pseudo-graphite region shows an obvious increasing trend, which is consistent with the pseudo-graphite structure observed in the TEM image.

[0035] Figure 6 This is the Raman pattern of Example 1 and Comparative Example 1 of the present invention; as can be seen from the figure, it can be clearly seen that the orderliness of Example 1 is improved and the defects are fewer compared to Comparative Example 1, which can be attributed to the long-range pseudo-graphite structure with bent stacking in Example 1, which is consistent with the pseudo-graphite structure observed in the TEM image.

[0036] Example 2 A preparation method of a waste oil-mediated all-region low-defect, high-rate pseudo-graphite domain hard carbon anode material (1) Weigh 8 g of soybean dregs, wash them with an appropriate amount of distilled water, and place them in a blast drying oven at a drying temperature of 80 °C for 12 h to remove impurities and moisture, obtaining a dried material. (2) Take the dried material and mix it with 0.5 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3) Place the mixed material obtained in step (2) into a tubular furnace, heat it to 1400 °C at a heating rate of 5 °C / min under argon conditions, hold for 2 h, cool to room temperature, and then take it out to obtain a carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and place it in a blast drying oven at 60 °C for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects throughout the region and rich pseudo-graphite domains.

[0037] (5) Use the waste oil-mediated preparation of a hard carbon material with low defects throughout the region and rich pseudo-graphite domains obtained above as the active substance of the battery anode material for the preparation of a sodium ion battery. The specific method is the same as that in Example 1.

[0038] Example 3 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1) Weigh 8 g of soybean dregs, wash them with an appropriate amount of distilled water, and place them in a blast drying oven at a drying temperature of 80 °C for 12 h to remove impurities and moisture, obtaining a dried material. (2) Take the dried material and mix it with 1.6 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3) Place the mixed material obtained in step (2) into a tubular furnace, heat it to 1400 °C at a heating rate of 5 °C / min under argon conditions, hold for 2 h, cool to room temperature, and then take it out to obtain a carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and place it in a blast drying oven at 60 °C for 12 h to obtain a waste oil-mediated preparation of a hard carbon material with low defects throughout the region and rich pseudo-graphite domains.

[0039] (5) Use the waste oil-mediated preparation of a hard carbon material with low defects throughout the region and rich pseudo-graphite domains obtained above as the active substance of the battery anode material for the preparation of a sodium ion battery. The specific method is the same as that in Example 1.

[0040] Example 4 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1) Weigh 8 g of soybean dregs, wash them with an appropriate amount of distilled water, and place them in a forced-air drying oven. The drying temperature is 80 °C, and the drying time is 12 h to remove impurities and moisture, obtaining a dried material. (2) Take the dried material and mix it with 2.4 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3) Place the mixed material obtained in step (2) into a tubular furnace, heat it to 1400 °C at a heating rate of 5 °C / min under argon conditions, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain a carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven to dry at 60 °C for 12 h to obtain a hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation.

[0041] (5) Use the hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation as the active substance of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0042] Example 5 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1) Weigh 8 g of soybean dregs, wash them with an appropriate amount of distilled water, and place them in a forced-air drying oven. The drying temperature is 80 °C, and the drying time is 12 h to remove impurities and moisture, obtaining a dried material. (2) Take the dried material and mix it with 3.2 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3) Place the mixed material obtained in step (2) into a tubular furnace, heat it to 1400 °C at a heating rate of 5 °C / min under argon conditions, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain a carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven to dry at 60 °C for 12 h to obtain a hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation.

[0043] (5) Use the hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation as the active substance of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0044] Example 6 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1)Weigh 8 g of soybean dregs, wash them with an appropriate amount of distilled water, and place them in a forced-air drying oven. The drying temperature is 80 °C and the drying time is 12 h to remove impurities and moisture, obtaining a dried material. (2)Take the dried material and mix it with 4 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3)Place the mixed material obtained in step (2) into a tube furnace, heat it to 1400 °C at a heating rate of 5 °C / min under argon conditions, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain a carbonized material. (4)Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation.

[0045] (5)Use the hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation as the active substance of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0046] Example 7 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1)Weigh 8 g of soybean dregs, wash them with an appropriate amount of distilled water, and place them in a forced-air drying oven. The drying temperature is 80 °C and the drying time is 12 h to remove impurities and moisture, obtaining a dried material. (2)Take the dried material and mix it with 0.8 g of oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3)Place the mixed material obtained in step (2) into a tube furnace, heat it to 1200 °C at a heating rate of 5 °C / min under argon conditions, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain a carbonized material. (4)Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation.

[0047] (5)Use the hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation as the active substance of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0048] Example 8 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1) Weigh 0.8 g of soybean dregs, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 °C, and the drying time is 12 h to remove impurities and moisture, obtaining a dried material. (2) Take the dried material and mix it with 4 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3) Place the mixed material obtained in step (2) into a tubular furnace, heat it to 1600 °C at a heating rate of 5 °C / min under argon conditions, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain a carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation.

[0049] (5) Use the hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation as the active substance of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0050] Example 9 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1) Weigh 0.8 g of soybean dregs, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 °C, and the drying time is 12 h to remove impurities and moisture, obtaining a dried material. (2) Take the dried material and mix it with 0.8 g of peanut oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3) Place the mixed material obtained in step (2) into a tubular furnace, heat it to 1600 °C at a heating rate of 5 °C / min under argon conditions, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain a carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation.

[0051] (5) Use the hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared by waste oil mediation as the active substance of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0052] Example 10 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1) Weigh 8 g of poplar wood, wash it with an appropriate amount of distilled water, and then place it in a forced-air drying oven. The drying temperature is 80 °C, and the drying time is 12 h to remove impurities and moisture, obtaining the dried material. (2) Take the dried material and mix it with 0.8 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain the mixed material. (3) Place the mixed material obtained in step (2) into a tube furnace, under argon atmosphere, heat it at a heating rate of 5 °C / min to 1600 °C, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain the carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a waste oil-mediated hard carbon material with low defects throughout the region and rich pseudo-graphite domains.

[0053] (5) Use the waste oil-mediated hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared above as the active substance of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0054] Example 11 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (1) Weigh 8 g of straw, wash it with an appropriate amount of distilled water, and then place it in a forced-air drying oven. The drying temperature is 80 °C, and the drying time is 12 h to remove impurities and moisture, obtaining the dried material. (2) Take the dried material and mix it with 0.8 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain the mixed material. (3) Place the mixed material obtained in step (2) into a tube furnace, under argon atmosphere, heat it at a heating rate of 5 °C / min to 1600 °C, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain the carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a waste oil-mediated hard carbon material with low defects throughout the region and rich pseudo-graphite domains.

[0055] (5) Use the waste oil-mediated hard carbon material with low defects throughout the region and rich pseudo-graphite domains prepared above as the active substance of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0056] Example 12 A preparation method of a waste oil-mediated hard carbon anode material with low defects throughout the region and high-rate pseudo-graphite domains (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 at a drying temperature of 80 °C for 12 h to remove impurities and moisture, obtaining a dried material. (2) Take the dried material and mix it with 0.8 g of soybean oil, stir for 2 h, and let it stand for 2 h to obtain a mixed material. (3) Place the mixed material obtained in step (2) into a tubular furnace, and under argon atmosphere, heat it at a heating rate of 5 °C / min to 1600 °C, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain a carbonized material. (4) Wash the carbonized material obtained in step (3) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a hard carbon material with low defects and rich pseudo-graphite domains prepared by waste oil mediation.

[0057] (5) Use the hard carbon material with low defects and rich pseudo-graphite domains prepared by waste oil mediation as the active material of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1.

[0058] Comparative Example 2 The comparative example of the present invention provides a preparation method of a biomass-based hard carbon anode material for sodium-ion batteries, and its steps include: (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 at a drying temperature of 80 °C for 12 h to remove impurities and moisture, obtaining a dried material. (2) Place the dried material into a tubular furnace, and under argon atmosphere, heat it at a heating rate of 5 °C / min to 1400 °C, keep it at this temperature for 2 h, cool it to room temperature, and then take it out to obtain a carbonized material. (3) Wash the carbonized material obtained in step (2) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a purified carbonized material.

[0059] (4) Use the purified carbonized material obtained above as the active material of the battery anode material for the preparation of sodium-ion batteries. The specific method is the same as that in Example 1. The first-cycle charge specific capacity of the assembled half-cell is 300.03 mAh / g at a current density of 20 mA / g.

[0060] Comparative Example 3 The comparative example of the present invention provides a preparation method of a biomass-based hard carbon anode material for sodium-ion batteries, and its steps include: (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 °C, and the drying time is 12 h to remove impurities and moisture, obtaining a dried material. (2) Place the dried material in a tubular furnace, heat it to 1400 °C at a heating rate of 5 °C / min under argon atmosphere, hold for 2 h, cool to room temperature, and then take it out to obtain a carbonized material. (3) Wash the carbonized material obtained in step (2) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a purified carbonized material.

[0061] (4) Use the purified carbonized material prepared above as the active material of the battery anode material for the preparation of a sodium-ion battery. The specific method is the same as that in Example 1. The first-cycle charge specific capacity of the assembled half-cell is 298.47 mAh / g at a current density of 20 mA / g.

[0062] Comparative Example 4 The present invention provides a preparation method of a biomass-based hard carbon anode material for a sodium-ion battery in a comparative example. The steps include: (1) Weigh 8 g of walnut shell, wash it with an appropriate amount of distilled water, and place it in a forced-air drying oven. The drying temperature is 80 °C, and the drying time is 12 h to remove impurities and moisture, obtaining a dried material. (2) Place the dried material in a tubular furnace, heat it to 1400 °C at a heating rate of 5 °C / min under argon atmosphere, hold for 2 h, cool to room temperature, and then take it out to obtain a carbonized material. (3) Wash the carbonized material obtained in step (2) with 1 mol / L hydrochloric acid solution and distilled water for 6 h, and then place it in a forced-air drying oven at 60 °C for 12 h to obtain a purified carbonized material.

[0063] (4) Use the purified carbonized material prepared above as the active material of the battery anode material for the preparation of a sodium-ion battery. The specific method is the same as that in Example 1. The first-cycle charge specific capacity of the assembled half-cell is 309.26 mAh / g at a current density of 20 mA / g.

[0064] The relevant performance parameters of the half-cells assembled in each example and comparative example are shown in Table 1.

[0065] Table 1 Relevant performance parameter table of the assembled half-cell

[0066] From the above examples and comparative examples, it can be seen that after adding 0.8 g of oil to the soybean dregs in Example 1 and performing high-temperature carbonization, the reversible specific capacity of the material can reach 330.41 mAh / g. In contrast, in Comparative Example 1, the biomass did not add oil. After the same high-temperature carbonization treatment, there are many surface defects in the material, the graphite layer is not fully developed, the pseudo-graphite structure is less, and it fails to cross-link and form an effective closed pore structure, which greatly affects its rate performance and reversible specific capacity. Further, in Example 6, when the addition amount of oil exceeds the optimal range, the long-chain fatty acids in the oil will excessively guide the growth, bending, and stacking of the carbon layer, thereby hindering the formation of closed pores. In this case, its rate performance is poor, and the reversible specific capacity is also reduced to 276.94 mAh / g.

[0067] Compared with the control group, a large number of small interlayer-spacing graphite domains uniformly exist inside and at the edges of the experimental group samples, and the graphite domains are relatively long. The carbon layer undergoes topological bending to form a rich closed pore structure; the oil-mediated hard carbon in the experimental group has more excellent high-rate performance in sodium storage compared with the hard carbon in the control group.

[0068] Verified by Examples 1, 7, and 8, keeping the temperature at 1400 °C for 2 h is the optimal condition for preparing a hard carbon material with a globally low-defect and pseudo-graphite domain-rich structure mediated by waste oil. Too high a temperature will cause excessive development, stacking, and bending of the graphite domains, while too low a temperature will lead to insufficient development of the graphite domains.

[0069] Verified by Examples 1 and 9, soybean dregs and soybean oil have the best matching degree. Compared with peanut oil, soybean oil is more likely to globally regulate the microcrystalline structure of graphite domains for soybean dregs.

[0070] Thus, it can be seen that the addition amount of oil has a significant impact on the microstructure and electrochemical performance of the biomass soybean dregs-based derived hard carbon anode material. With the increase in the addition amount of oil, a large number of small interlayer-spacing graphite domains uniformly exist inside and at the edges of the material's microstructure, the graphite domains are relatively long, and the carbon layer undergoes topological bending to form a rich closed pore structure. The optimization of this microstructure directly promotes the improvement of the material's electrochemical performance.

[0071] In summary, the preparation method proposed in the present invention relies on the mutual cooperation of the component ratios and each process step. It is precisely due to the global interference achieved by the strong penetration of this waste oil that endows the biomass-based hard carbon material with excellent electrochemical characteristics. If any one of the conditions deviates from the range specified in the present invention, it may cause a reduction in the performance of the hard carbon material.

[0072] The basic principles, main features and advantages of the present invention have been described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, various changes and improvements will occur to the present invention, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a waste oil-mediated global low-defect, pseudographite-rich high-rate hard carbon negative electrode material, characterized in that: The preparation method comprises the following steps: (1) Wash the biomass with distilled water and dry it in a forced air drying oven; (2) uniformly mixing the dried biomass and waste oil and grease, and leaving them to stand to obtain a mixture; (3) placing the mixed material obtained in step (2) in a tubular furnace, heating it under inert protective gas conditions, and performing high-temperature carbonization to obtain a carbonized material; (4) The carbonized material obtained in step (3) is washed with a dilute hydrochloric acid solution and deionized water in turn until the solution is neutral, and then dried to obtain a waste oil-mediated global low-defect, pseudographite domain high-rate hard carbon negative electrode material.

2. The preparation method according to claim 1, characterized in that: In the step (1), the biomass may be soybean, poplar, straw, bean dregs, leaves, pine and other plants, preferably bean dregs.

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, pine nut oil and the like, preferably soybean oil.

4. The preparation method according to claim 1, characterized in that: In the step (2), the mass ratio of oil to biomass is 1-5:

10.

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

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

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

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

9. A waste oil-mediated global low-defect, pseudographite-domain-rich, high-rate hard carbon negative electrode material obtained by the preparation method as described in claims 1-8.

10. Use of the waste oil-mediated global low-defect, pseudographite domain-rich high-rate hard carbon negative electrode material as claimed in claim 9 in sodium ion battery negative electrode materials.

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