Preparation method of hard carbon material based on bran derivatives, and product and application thereof

Abstract

The present application relates to a kind of preparation method of hard carbon material based on bran derivative and its product and application, belong to the technical field of hard carbon material preparation.The present application is mainly with bran biomass as raw material, first oil is removed by alkali washing, drying, low-temperature pretreatment in inert environment, then acid washing treatment is carried out after once ball milling, alkali washing, carbonization treatment in inert environment at high temperature, finally after secondary ball milling, hard carbon material is obtained.The preparation method of the present application uses bran biomass as the precursor of hard carbon negative material, not only the raw material source is extensive, cost is lower, and preparation method is green, environment-friendly, simple process, suitable for mass production.In addition, the hard carbon material based on bran derivative prepared in the present application has excellent electrochemical performance, and is a potential sodium ion battery negative material.

Description

Technical Field

[0001] This invention belongs to the field of hard carbon material preparation technology, and relates to a method for preparing hard carbon materials based on meal derivatives, as well as their products and applications. Background Technology

[0002] Currently, sodium-ion batteries, which are low-cost and highly safe, have shown great potential for development in the field of large-scale energy storage. However, graphite, which is widely used as the anode material in lithium-ion batteries, is not suitable as the anode material for sodium-ion batteries. Therefore, selecting a suitable anode material is of great importance to the development of sodium-ion batteries.

[0003] Among numerous anode materials, hard carbon has attracted widespread attention due to its excellent electrochemical performance, simple preparation methods, and wide availability of raw materials. The porosity and pore size uniformity of hard carbon determine its electrochemical properties, which in turn largely depend on the properties of the precursor itself. Hard carbon precursors mainly include biomass, synthetic polymers, or fossil fuels, such as coconut shells, starch, phenolic resins, and asphalt. Although diverse, they all possess some drawbacks that have consistently hindered the development of the hard carbon anode industry. For example, coconut shells rely on imports; starch and phenolic resins have high processing costs; and asphalt requires exhaust gas treatment. In short, the cost of current hard carbon precursors, carbon yield after carbonization, and economic viability still require further optimization. Therefore, the key to the large-scale industrialization of hard carbon is finding low-cost precursor materials suitable for mass production.

[0004] Oilseed meals (such as rapeseed meal, peanut meal, sesame meal, and soybean meal) are the residues left after oil extraction. They are mainly used as a raw material for livestock and poultry feed, and can also be used to make pastries, health foods, cosmetics, and antibiotic raw materials. They are a very rich source of biomass raw materials. Expanding their applications can demonstrate the higher added value of these materials.

[0005] Therefore, it is necessary to study the preparation methods and products of hard carbon materials derived from meal. Summary of the Invention

[0006] In view of this, one objective of the present invention is to provide a method for preparing a hard carbon material based on meal residues; a second objective of the present invention is to provide a hard carbon material based on meal residues; and a third objective of the present invention is to provide an application of a hard carbon material based on meal residues as an electrode material in a sodium-ion battery.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] 1. A method for preparing a hard carbon material derived from soybean meal, the method comprising the following steps:

[0009] (1) After the oil removal treatment of the meal biomass by alkaline washing, it is dried at 50-120℃ and then pretreated at low temperature at 300-550℃ in an inert environment to obtain hard carbon precursor.

[0010] (2) The hard carbon precursor is ball-milled again to obtain ball-milled hard carbon precursor. After acid washing, the acid-washed hard carbon precursor is obtained. Then, after alkaline washing to remove impurities, the alkaline-washed hard carbon precursor is obtained. High-temperature carbonization is carried out at 850-1600℃ in an inert environment. After a second ball milling treatment, the hard carbon material based on meal derivative is obtained.

[0011] Preferably, in step (1), the oilseed meal biomass includes one or more of the following: sunflower kernels, rapeseed, camellia seed, tea seed, peanut, sesame, olive, soybean, tung oil fruit, gardenia fruit, hemp seed, flax seed, castor seed, and residue after pressing corn germ for oil.

[0012] Preferably, in step (1), the specific method for the first alkaline washing and oil removal is as follows: the meal biomass is added to the alkaline washing solution I to form a mixed solution I, stirred to mix it thoroughly, and filtered to obtain the meal biomass that has been alkaline washed and oil removed;

[0013] The alkaline washing solution I is any one or more of the following: saturated sodium carbonate aqueous solution, saturated lithium carbonate aqueous solution, saturated sodium hydroxide aqueous solution, or saturated potassium hydroxide aqueous solution.

[0014] The concentration of meal biomass in the mixed solution I is 3-100 mg / ml, and the stirring time is 2-15 h.

[0015] Preferably, in step (1), the heating rate of the low-temperature pretreatment is 0.5 to 10 °C / min, the treatment time is 2 to 12 h, and the temperature range is 300 to 550 °C.

[0016] Preferably, the gas in the inert environment is any one or more of argon, nitrogen, a mixture of argon and hydrogen, and a mixture of nitrogen and hydrogen, wherein the volume ratio of argon to hydrogen in the mixture of argon and hydrogen is 90:10 to 99:1, and the volume ratio of nitrogen to hydrogen in the mixture of nitrogen and hydrogen is 90:10 to 99:1.

[0017] Preferably, in step (2), the pickling process specifically involves: adding the ball-milled hard carbon precursor to the pickling solution to form a mixed solution II, then stirring to ensure thorough mixing, and filtering to obtain the pickled hard carbon precursor;

[0018] The pickling solution is any one or more of the following: acetic acid aqueous solution, sulfuric acid aqueous solution, hydrochloric acid or nitric acid aqueous solution with a concentration of 3-20 wt.%.

[0019] The concentration of the ball-milled hard carbon precursor in the mixed solution II is 3–100 mg / ml, and the stirring time in the acid washing treatment is 3–20 h.

[0020] Preferably, in step (2), the secondary alkaline washing method is as follows: the acid-washed hard carbon precursor is added to the alkaline washing solution II to form a mixed solution III, stirred to mix it thoroughly, and filtered to obtain the alkaline-washed hard carbon precursor.

[0021] The alkaline washing solution II is any one or more of the following: an aqueous solution of sodium carbonate, an aqueous solution of lithium carbonate, an aqueous solution of sodium hydroxide, or an aqueous solution of potassium hydroxide with a concentration of 5-20 wt.%. The concentration of the acid-washed hard carbon precursor in the mixed solution III is 3-100 mg / ml. The stirring time during the alkaline washing and impurity removal process is 3-20 h.

[0022] Preferably, in step (2), the heating rate of the high-temperature carbonization is 0.5 to 10 °C / min, the processing time is 2 to 12 h, and the carbonization temperature range is 850 to 1600 °C.

[0023] The ball mills used in the primary and secondary ball milling processes are planetary or horizontal. The rotation speed of the primary and secondary ball mills is 200-600 rpm, and the milling time is 2-20 h. The ball-to-material ratio in the primary ball mill is 5:1-20:1, and the ball-to-material ratio in the secondary ball mill is 30:1-150:1.

[0024] 2. Hard carbon material based on meal derivatives prepared according to the above preparation method.

[0025] 3. The application of the above-mentioned hard carbon materials derived from soybean meal as electrode materials in sodium-ion batteries.

[0026] The beneficial effects of this invention are as follows: This invention discloses a method for preparing hard carbon materials based on soybean meal derivatives. The method primarily uses soybean meal biomass as raw material, first undergoing alkaline washing to remove oil, drying, and low-temperature pretreatment under an inert environment. Then, after a single ball milling, it undergoes acid washing, alkaline washing to remove impurities, and high-temperature carbonization under an inert environment. Finally, it undergoes a second ball milling to obtain the hard carbon material. This method uses soybean meal biomass as a precursor for synthesizing hard carbon anode materials, which not only provides widely available and low-cost raw materials but also employs a green and environmentally friendly preparation method with simple processes, making it suitable for mass production. Furthermore, the hard carbon material based on soybean meal derivatives prepared by this invention exhibits excellent electrochemical performance and is a potential anode material for sodium-ion batteries.

[0027] Other advantages, objectives, and features of the invention will be set forth in the following description, and in some respects will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0029] Figure 1 The image shows the XRD pattern of the hard carbon material prepared in Example 1.

[0030] Figure 2 A scanning electron microscope image of the hard carbon material prepared in Example 1;

[0031] Figure 3 The rate charge-discharge curves of a coin cell assembled using the hard carbon material prepared in Example 1 as the electrode material are shown.

[0032] Figure 4 The circuit performance diagram shows the coin cell assembled using the hard carbon material prepared in Example 1 as the electrode material.

[0033] Figure 5 The image shows the XRD pattern of the hard carbon material prepared in Example 2.

[0034] Figure 6 Scanning electron microscope image of the hard carbon material prepared in Example 2;

[0035] Figure 7 The rate charge-discharge curves of a coin cell assembled using the hard carbon material prepared in Example 2 as the electrode material are shown.

[0036] Figure 8 The image shows the XRD pattern of the hard carbon material prepared in Example 3.

[0037] Figure 9 The rate charge-discharge curves of a coin cell assembled using the hard carbon material prepared in Example 3 as the electrode material are shown.

[0038] Figure 10 The image shows the XRD pattern of the hard carbon material prepared in Example 4.

[0039] Figure 11 The rate charge-discharge curves of a coin cell assembled using the hard carbon material prepared in Example 4 as the electrode material are shown.

[0040] Figure 12 The image shows the XRD pattern of the hard carbon material prepared in Example 5.

[0041] Figure 13 The rate charge-discharge curves of a coin cell assembled using the hard carbon material prepared in Example 5 as the electrode material are shown.

[0042] Figure 14 The XRD pattern of the hard carbon material prepared in Comparative Example 1;

[0043] Figure 15 The image shows a scanning electron microscope image of the hard carbon material prepared in Comparative Example 1.

[0044] Figure 16 The rate charge-discharge curves of a coin cell assembled using the hard carbon material prepared in Comparative Example 1 as the electrode material are shown.

[0045] Figure 17 The rate charge-discharge curves of the coin cell assembled using the hard carbon material prepared in Comparative Example 2 as the electrode material are shown. Detailed Implementation

[0046] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0047] Example 1

[0048] A method for preparing hard carbon materials derived from soybean meal, the specific preparation method is as follows:

[0049] (1) Soybean meal is added to a saturated sodium carbonate aqueous solution to form a mixed solution (the concentration of soybean meal in the mixed solution is 20 mg / ml). The mixture is stirred to ensure thorough mixing and then subjected to alkaline washing and degreasing treatment for 5 hours to remove surface oil stains. After the alkaline washing and degreasing treatment is completed, the mixture is filtered, washed, and dried at 80°C. Then, under the protection of argon atmosphere, the dried material is placed in a tube furnace and heated to 350°C at a rate of 5°C / min. The temperature is maintained for 5 hours for low-temperature pretreatment. The material is then cooled to room temperature to obtain a hard carbon precursor.

[0050] (2) The above-mentioned hard carbon precursor was ball-milled once in a planetary ball mill at a speed of 400 rpm and a ball-to-material ratio of 15:1 for 15 hours to obtain the ball-milled hard carbon precursor. It was then added to a 10 wt.% nitric acid aqueous solution to form a mixed solution (the concentration of the ball-milled hard carbon precursor in the mixed solution was 30 mg / ml) and stirred to ensure thorough mixing, i.e., acid washing treatment for 5 hours. After the acid washing treatment was completed, the precursor was filtered out, washed and dried to obtain the acid-washed hard carbon precursor.

[0051] (3) The above-mentioned acid-washed hard carbon precursor was added to a 15 wt.% sodium hydroxide aqueous solution to form a mixed solution (the concentration of acid-washed hard carbon precursor in the mixed solution was 30 mg / ml). After stirring to make it fully mixed, it was subjected to alkaline washing and impurity removal treatment for 5 hours. After filtration, washing and drying, the alkaline-washed hard carbon precursor was obtained.

[0052] (4) Under the protection of argon atmosphere, the above-mentioned hard carbon precursor that has been cleaned by alkali is placed in a tube furnace and heated to 1400°C at a heating rate of 5°C / min. After holding at the temperature for 3 hours for high-temperature carbonization treatment, it is cooled to room temperature.

[0053] (5) Finally, the material that has undergone high-temperature carbonization is subjected to secondary ball milling in a planetary ball mill with a rotation speed of 500 rpm and a ball-to-material ratio of 80:1. After ball milling for 6 hours, hard carbon material based on meal is obtained.

[0054] Figure 1 The image shows the XRD pattern of the hard carbon material prepared in Example 1. Figure 1 As can be seen from the data, the diffraction peaks of the hard carbon material prepared in Example 1 are relatively broad, indicating that it is an amorphous carbon material, which is consistent with the XRD pattern of hard carbon materials.

[0055] Figure 2 Scanning electron microscope image of the hard carbon material prepared in Example 1. Figure 2 As can be seen, the particle size of the hard carbon material prepared in Example 1 is 0.5–3 μm.

[0056] The hard carbon material prepared in Example 1 was used as the electrode material and assembled into a coin cell (where the sodium metal sheet was the counter electrode and the 1 mol / L PC / FEC (95:5) solution was the electrolyte). Figure 3 The rate charge-discharge curves of the coin cell using the hard carbon material prepared in Example 1 are shown. Figure 3 As can be seen, the reversible specific capacity of the material is as high as 310.6 mAh / g at a current density of 0.1C, and the specific capacity can still reach 240.5 mAh / g at a current density of 2C, indicating that the battery using the hard carbon material prepared in Example 1 as the electrode material has good rate performance. Figure 4This is a cycle performance graph of a coin cell using the hard carbon material prepared in Example 1 as the electrode material. From... Figure 4 As can be seen, after 50 cycles at a current density of 0.2C, the capacity still reaches 277.3 mAh / g, with a capacity retention rate of 97.5%, indicating that the battery using the hard carbon material prepared in Example 1 as the electrode material has good cycle performance.

[0057] Example 2

[0058] A method for preparing hard carbon materials derived from soybean meal, the specific preparation method is as follows:

[0059] (1) Add peanut meal to a saturated sodium carbonate aqueous solution to form a mixed solution (the concentration of peanut meal in the mixed solution is 10 mg / ml), stir to mix it thoroughly, and then perform alkaline washing and degreasing treatment for 5 hours to remove the oil stains on the surface. After the alkaline washing and degreasing treatment is completed, filter, wash and dry at 80°C; then place the above-dried material in a tube furnace under argon atmosphere protection, heat it to 400°C at a rate of 5°C / min, hold it at 5 hours for low temperature pretreatment, and cool it to room temperature to obtain hard carbon precursor.

[0060] (2) The above-mentioned hard carbon precursor was ball-milled once in a planetary ball mill with a rotation speed of 400 rpm and a ball-to-material ratio of 20:1. After ball milling for 15 hours, the ball-milled hard carbon precursor was obtained. It was then added to a 20 wt.% hydrochloric acid solution to form a mixed solution (the concentration of the ball-milled hard carbon precursor in the mixed solution was 20 mg / ml) and stirred to ensure thorough mixing. This was followed by acid washing for 5 hours. After the acid washing was completed, the precursor was filtered out, washed, and dried to obtain the acid-washed hard carbon precursor.

[0061] (3) The above-mentioned acid-washed hard carbon precursor was added to a 15 wt.% sodium hydroxide aqueous solution to form a mixed solution (the concentration of acid-washed hard carbon precursor in the mixed solution was 30 mg / ml). After stirring to make it fully mixed, it was subjected to alkaline washing and impurity removal treatment for 5 hours. After filtration, washing and drying, the alkaline-washed hard carbon precursor was obtained.

[0062] (4) Under the protection of argon atmosphere, the hard carbon precursor that has been cleaned by alkali is placed in a tube furnace and heated to 1200°C at a heating rate of 5°C / min. After holding at the temperature for 3 hours for high-temperature carbonization treatment, it is cooled to room temperature.

[0063] (5) Finally, the material that has undergone high-temperature carbonization is subjected to secondary ball milling in a planetary ball mill with a rotation speed of 500 rpm and a ball-to-material ratio of 30:1. After ball milling for 1 hour, hard carbon material based on meal is obtained.

[0064] Figure 5The image shows the XRD pattern of the hard carbon material prepared in Example 2. Figure 5 As can be seen from the data, the diffraction peaks of the hard carbon material prepared in Example 2 are relatively broad, indicating that it is an amorphous carbon material, which is consistent with the XRD pattern of hard carbon materials.

[0065] Figure 6 This is a scanning electron microscope image of the hard carbon material prepared in Example 2. Figure 6 As can be seen, the particle size of the hard carbon material prepared in Example 1 is 2-8 μm.

[0066] The hard carbon material prepared in Example 2 was used as the electrode material and assembled into a coin cell (where the sodium metal sheet was the counter electrode and the 1 mol / L PC / FEC (95:5) solution was the electrolyte). Figure 7 The rate charge-discharge curves of a coin cell using the hard carbon material prepared in Example 2 as the electrode material are shown. Figure 7 As can be seen, the reversible specific capacity of the material is as high as 267.4 mAh / g at a current density of 0.1C, and the specific capacity can still reach 198.0 mAh / g at a current density of 2C, indicating that the battery using the hard carbon material prepared in Example 2 as the electrode material has good rate performance.

[0067] Example 3

[0068] A method for preparing hard carbon materials derived from soybean meal, the specific preparation method is as follows:

[0069] (1) Sesame meal is added to a saturated sodium carbonate aqueous solution to form a mixed solution (the concentration of sesame meal in the mixed solution is 5 mg / ml). The mixture is stirred to ensure thorough mixing and then subjected to alkaline washing and degreasing treatment for 8 hours to remove surface oil stains. After the alkaline washing and degreasing treatment is completed, the mixture is filtered, washed, and dried at 80°C. Then, under the protection of argon atmosphere, the dried material is placed in a tube furnace and heated to 400°C at a rate of 5°C / min. The temperature is maintained for 5 hours for low-temperature pretreatment. The material is then cooled to room temperature to obtain a hard carbon precursor.

[0070] (2) The above-mentioned hard carbon precursor was ball-milled once in a planetary ball mill with a rotation speed of 400 rpm and a ball-to-material ratio of 20:1. After ball milling for 15 hours, the ball-milled hard carbon precursor was obtained. It was then added to a 20 wt.% hydrochloric acid solution to form a mixed solution (the concentration of the ball-milled hard carbon precursor in the mixed solution was 20 mg / ml) and stirred to ensure thorough mixing. This was followed by acid washing for 5 hours. After the acid washing was completed, the precursor was filtered out, washed, and dried to obtain the acid-washed hard carbon precursor.

[0071] (3) The above-mentioned acid-washed hard carbon precursor was added to a 15 wt.% sodium hydroxide aqueous solution to form a mixed solution (the concentration of acid-washed hard carbon precursor in the mixed solution was 30 mg / ml). After stirring to make it fully mixed, it was subjected to alkaline washing and impurity removal treatment for 5 hours. After filtration, washing and drying, the alkaline-washed hard carbon precursor was obtained.

[0072] (4) Under the protection of argon atmosphere, the above-mentioned hard carbon precursor that has been cleaned by alkali is placed in a tube furnace and heated to 1300°C at a heating rate of 5°C / min. After holding at the temperature for 5 hours for high-temperature carbonization treatment, it is cooled to room temperature.

[0073] (5) Finally, the material that has undergone high-temperature carbonization is subjected to secondary ball milling in a planetary ball mill with a rotation speed of 500 rpm and a ball-to-material ratio of 40:1. After ball milling for 3 hours, hard carbon material based on meal is obtained.

[0074] Figure 8 The image shows the XRD pattern of the hard carbon material prepared in Example 3. Figure 8 As can be seen from the data, the diffraction peaks of the hard carbon material prepared in Example 3 are relatively broad, indicating that it is an amorphous carbon material, which is consistent with the XRD pattern of hard carbon materials.

[0075] The hard carbon material prepared in Example 3 was used as the electrode material and assembled into a coin cell (where the sodium metal sheet was the counter electrode and the 1 mol / L PC / FEC (95:5) solution was the electrolyte). Figure 9 The rate charge-discharge curves of a coin cell using the hard carbon material prepared in Example 3 as the electrode material are shown. Figure 9 As can be seen, the reversible specific capacity of the material is as high as 286.8 mAh / g at a current density of 0.1C, and the specific capacity can still reach 239.5 mAh / g at a current density of 2C, indicating that the battery using the hard carbon material prepared in Example 3 as the electrode material has good rate performance.

[0076] Example 4

[0077] A method for preparing hard carbon materials derived from soybean meal, the specific preparation method is as follows:

[0078] (1) Add rapeseed meal to a 20 wt.% sodium carbonate aqueous solution to form a mixed solution (where the concentration of rapeseed meal in the mixed solution is 50 mg / ml), stir to mix thoroughly, and then perform alkaline washing and degreasing treatment for 8 hours to remove surface oil stains. After the alkaline washing and degreasing treatment, filter, wash, and dry at 80°C. Then, under the protection of argon atmosphere, place the above-dried material in a tube furnace, heat it to 450°C at a rate of 5°C / min, hold it at 5 hours for low-temperature pretreatment, and cool it to room temperature to obtain hard carbon precursor.

[0079] (2) The above-mentioned hard carbon precursor was subjected to a single grinding process in a planetary ball mill at a speed of 400 rpm and a ball-to-material ratio of 15:1 for 20 h to obtain the ball-milled hard carbon precursor. It was then added to a 20 wt.% hydrochloric acid solution to form a mixed solution (the concentration of the ball-milled hard carbon precursor in the mixed solution was 50 mg / ml) and stirred to ensure thorough mixing, i.e., acid washing treatment for 5 h. After the acid washing treatment was completed, the precursor was filtered out, washed and dried to obtain the acid-washed hard carbon precursor.

[0080] (3) The above-mentioned acid-washed hard carbon precursor was added to a 15 wt.% sodium hydroxide aqueous solution to form a mixed solution (the concentration of acid-washed hard carbon precursor in the mixed solution was 50 mg / ml). After stirring to make it fully mixed, it was subjected to alkaline washing and impurity removal treatment for 5 hours. After filtration, washing and drying, the alkaline-washed hard carbon precursor was obtained.

[0081] (4) Under the protection of argon atmosphere, the above-mentioned hard carbon precursor that has been cleaned by alkali is placed in a tube furnace and heated to 1600°C at a heating rate of 5°C / min. After holding at the temperature for 3 hours for high-temperature carbonization treatment, it is cooled to room temperature.

[0082] (5) Finally, the material that has undergone high-temperature carbonization is subjected to secondary ball milling in a planetary ball mill with a rotation speed of 500 rpm and a ball-to-material ratio of 50:1. After ball milling for 12 hours, hard carbon material based on meal is obtained.

[0083] Figure 10 The image shows the XRD pattern of the hard carbon material prepared in Example 4. Figure 10 As can be seen from the data, the diffraction peaks of the hard carbon material prepared in Example 4 are relatively broad, indicating that it is an amorphous carbon material, which is consistent with the XRD pattern of hard carbon materials.

[0084] The hard carbon material prepared in Example 4 was used as the electrode material and assembled into a coin cell (where the sodium metal sheet was the counter electrode and the 1 mol / L PC / FEC (95:5) solution was the electrolyte). Figure 11 The rate charge-discharge curves of a coin cell using the hard carbon material prepared in Example 4 as the electrode material are shown. Figure 11 As can be seen, the reversible specific capacity of the material is 244.8 mAh / g at a current density of 0.1C and 174.5 mAh / g at a current density of 2C, indicating that the battery using the hard carbon material prepared in Example 4 as the electrode material has good rate performance.

[0085] Example 5

[0086] A method for preparing hard carbon materials derived from soybean meal, the specific preparation method is as follows:

[0087] (1) Olive meal is added to a 10 wt.% sodium carbonate aqueous solution to form a mixed solution (the concentration of olive meal in the mixed solution is 30 mg / ml). The mixture is stirred to ensure thorough mixing and then subjected to alkaline washing and degreasing treatment for 5 hours to remove surface oil stains. After the alkaline washing and degreasing treatment, the mixture is filtered, washed, and dried at 80°C. Then, under the protection of argon atmosphere, the dried material is placed in a tube furnace and heated to 350°C at a rate of 5°C / min. The temperature is held for 5 hours for low-temperature pretreatment. The material is then cooled to room temperature to obtain a hard carbon precursor.

[0088] (2) The above-mentioned hard carbon precursor was ball-milled once in a planetary ball mill at a speed of 450 rpm and a ball-to-material ratio of 15:1 for 15 hours to obtain the ball-milled hard carbon precursor. It was then added to a 15 wt.% nitric acid aqueous solution to form a mixed solution (the concentration of the ball-milled hard carbon precursor in the mixed solution was 30 mg / ml) and stirred to ensure thorough mixing, i.e., acid washing treatment for 5 hours. After the acid washing treatment was completed, the precursor was filtered out, washed and dried to obtain the acid-washed hard carbon precursor.

[0089] (3) The above-mentioned acid-washed hard carbon precursor was added to a 10 wt.% sodium hydroxide aqueous solution to form a mixed solution (the concentration of acid-washed hard carbon precursor in the mixed solution was 30 mg / ml). After stirring to make it fully mixed, it was subjected to alkaline washing and impurity removal treatment for 5 hours. After filtration, washing and drying, the alkaline-washed hard carbon precursor was obtained.

[0090] (4) Under the protection of argon atmosphere, the above-mentioned hard carbon precursor that has been cleaned by alkali is placed in a tube furnace and heated to 1600°C at a heating rate of 5°C / min. After holding at the temperature for 3 hours for high-temperature carbonization treatment, it is cooled to room temperature.

[0091] (5) Finally, the material that has undergone high-temperature carbonization is subjected to secondary ball milling in a planetary ball mill with a rotation speed of 500 rpm and a ball-to-material ratio of 50:1. After ball milling for 18 hours, hard carbon material based on meal is obtained.

[0092] Figure 12 The image shows the XRD pattern of the hard carbon material prepared in Example 5. Figure 12 As can be seen from the data, the diffraction peaks of the hard carbon material prepared in Example 5 are relatively broad, indicating that it is an amorphous carbon material, which is consistent with the XRD pattern of hard carbon materials.

[0093] The hard carbon material prepared in Example 5 was used as the electrode material and assembled into a coin cell (where the sodium metal sheet was the counter electrode and the 1 mol / L PC / FEC (95:5) solution was the electrolyte). Figure 13 The rate charge-discharge curves of a coin cell using the hard carbon material prepared in Example 5 as the electrode material are shown. Figure 13As can be seen, the reversible specific capacity of the material is as high as 290.6 mAh / g at a current density of 0.1C, and the specific capacity can still reach 154.2 mAh / g at a current density of 2C, indicating that the battery using the hard carbon material prepared in Example 5 as the electrode material has good rate performance.

[0094] Comparative Example 1

[0095] A hard carbon material without secondary ball milling was prepared. The preparation steps were the same as in Example 1, except that there was no secondary ball milling (no ball milling treatment in step (5) of Example 1).

[0096] Figure 14 The image shows the XRD pattern of the hard carbon material prepared in Comparative Example 1. Figure 14 As can be seen, the diffraction peaks of the hard carbon material prepared in Comparative Example 1 are also relatively broad, indicating that it is an amorphous carbon material, which is consistent with the XRD pattern of hard carbon materials. However, its angle is larger than that of Example 1, indicating that its interlayer spacing is smaller. Figure 15 This is a scanning electron microscope image of the hard carbon material prepared in Comparative Example 1. From... Figure 15 As can be seen, the particle size of the hard carbon material prepared in Comparative Example 1 is 5–15 μm, which is much larger than that in Example 1. Since the smaller interlayer spacing and larger particle size are not conducive to the effective and rapid storage of sodium ions, it indicates that the hard carbon material prepared in Example 1 is more suitable as a negative electrode material for sodium-ion batteries compared to Comparative Example 1.

[0097] The hard carbon material prepared in Comparative Example 1 was used as the electrode material and assembled into a coin cell (where the sodium metal sheet was the counter electrode and the 1 mol / L PC / FEC (95:5) solution was the electrolyte). Figure 16 The image shows the rate charge-discharge curves of a coin cell using the hard carbon material prepared in Comparative Example 1 as the electrode material. From... Figure 16 As can be seen, the reversible specific capacity of the material is only 229.6 mAh / g at a current density of 0.1C, and 150.2 mAh / g at a current density of 2C. This further demonstrates that the secondary ball milling process used in Example 1 is positive and effective in improving the electrochemical performance of the hard carbon material.

[0098] Comparative Example 2

[0099] Starch was heated to 350°C in a tube furnace under argon atmosphere at a heating rate of 5°C / min, held at that temperature for 5 hours for low-temperature pretreatment, and then cooled to room temperature to obtain hard carbon precursor.

[0100] The aforementioned precursor was ball-milled once in a planetary ball mill at a speed of 400 rpm and a ball-to-material ratio of 15:1.

[0101] Under an argon atmosphere, the material obtained from the ball mill was heated to 1400°C in a tube furnace at a heating rate of 5°C / min, held at that temperature for 3 hours for high-temperature carbonization, and then cooled to room temperature to obtain hard carbon material.

[0102] The hard carbon material prepared in Comparative Example 2 was used as the electrode material and assembled into a coin cell (where the sodium metal sheet was the counter electrode and the 1 mol / L PC / FEC (95:5) solution was the electrolyte). Figure 17 The image shows the rate charge-discharge curves of a coin cell using the hard carbon material prepared in Comparative Example 2 as the electrode material. From... Figure 17 As can be seen, the reversible specific capacity of the hard carbon material prepared in Comparative Example 2 is only 227.7 mAh / g at a current density of 0.1C, while at a current density of 2C, the specific capacity can only reach 119.4 mAh / g. This indicates that the electrochemical performance of the hard carbon material prepared in Comparative Example 2 is inferior to that of the examples and Comparative Example 1, further demonstrating the unique advantages of the hard carbon precursor described in this invention.

[0103] The initial coulombic efficiency and capacity retention after 100 cycles of the hard carbon materials obtained in each embodiment and comparative example are shown in Table 1 below. This indicates that the hard carbon materials based on meal derivatives prepared in this invention have good electrochemical performance (initial coulombic efficiency is above 77%, and capacity retention after 100 cycles is above 87%).

[0104] Table 1 Electrochemical performance of batteries using different hard carbon materials as electrode materials

[0105]

[0106]

[0107] The raw materials and conditions used in the preparation methods of the above embodiments can be varied (e.g., replacing one or more of the following biomass after pressing sunflower seeds, rapeseed, camellia seeds, tea seeds, peanuts, sesame seeds, olives, soybeans, tung oil fruit, gardenia fruit, hemp seeds, flax seeds, castor seeds, and corn germ for oil extraction; replacing the alkaline washing solution used in alkaline washing degreasing with any one or more of the following saturated aqueous solutions of sodium carbonate, lithium carbonate, sodium hydroxide, or potassium hydroxide; adding biomass to make its concentration 3-100 mg / L). ml; the time limit for alkaline washing and degreasing is 2–15 h; the heating rate limit for low-temperature pretreatment is 0.5–10 °C / min, and the treatment time limit is 2–12 h, of which the temperature range for low-temperature pretreatment is 300–550 °C; the gas in the inert environment is argon, nitrogen, a mixture of argon and hydrogen (the volume ratio of argon to hydrogen in the mixture of argon and hydrogen is 90:10–99:1), or a mixture of nitrogen and hydrogen (the volume ratio of nitrogen to hydrogen in the mixture of nitrogen and hydrogen is 90:1). The acid washing solution used in the pickling process is replaced by any one or more of the following: acetic acid aqueous solution, sulfuric acid aqueous solution, hydrochloric acid or nitric acid aqueous solution with a concentration of 3-20 wt.%, and the concentration of meal biomass is increased to 3-100 mg / ml; the pickling time is 3-20 h; the heating rate of high-temperature carbonization is limited to 0.5-10℃ / min, and the treatment time is limited to 2-12 h, wherein the temperature range of high-temperature carbonization is limited to 850℃. At 1600℃; the ball mill used for ball milling is a planetary or horizontal type, with the ball milling speed limited to 200-600 rpm and the ball milling time limited to 2-20 h. The ball-to-material ratio for the first ball milling is limited to 5:1-20:1, and the ball-to-material ratio for the second ball milling is limited to 30:1-150:1. Hard carbon materials derived from soybean meal can still be prepared as in the examples. Relevant tests have proven that they have excellent electrochemical performance and have good application prospects as a negative electrode material for sodium-ion batteries.

[0108] In summary, this invention discloses a method for preparing hard carbon materials derived from soybean meal. The method primarily uses soybean meal biomass as raw material, first undergoing alkaline washing to remove oil, drying, and low-temperature pretreatment under an inert environment. Then, after a single ball milling, it undergoes acid washing, alkaline washing to remove impurities, and high-temperature carbonization under an inert environment. Finally, a second ball milling is performed to obtain the hard carbon material. This method uses soybean meal biomass as a precursor for synthesizing hard carbon anode materials, which not only provides widely available and low-cost raw materials but also employs a green and environmentally friendly preparation method with simple processes, making it suitable for mass production. Furthermore, the hard carbon material derived from soybean meal prepared by this invention exhibits excellent electrochemical performance and is a potential anode material for sodium-ion batteries.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for the preparation of a bran-based derived hard carbon material for sodium-ion battery electrode materials, characterized by, The preparation method comprises the following steps: (1) drying the oil-removed biomass at 50-120°C after alkali washing, and then performing low-temperature pretreatment at 300-550°C in an inert environment to obtain a hard carbon precursor; (2) performing secondary ball milling on the hard carbon precursor to obtain a ball-milled hard carbon precursor, performing acid washing to obtain an acid-washed hard carbon precursor, and then performing alkali washing to remove impurities to obtain an alkali-washed hard carbon precursor, and performing high-temperature carbonization at 850-1600°C in an inert environment, and then performing secondary ball milling to obtain the hard carbon material derived from the biomass; The biomass comprises one or more of sunflower kernel, oil tea seed, tea seed, sesame, olive, tung nut, gardenia fruit, hemp seed, flaxseed, castor seed, and corn germ after oil extraction.

2. The production method according to claim 1, characterized by, In step (1), the specific method of the first alkali washing to remove oil is: adding the biomass into an alkali washing solution I to form a mixed solution I, stirring to fully mix, and filtering to obtain the biomass after alkali washing to remove oil. The alkali washing solution I is any one or several of a saturated sodium carbonate aqueous solution, a saturated lithium carbonate aqueous solution, a saturated sodium hydroxide aqueous solution, or a saturated potassium hydroxide aqueous solution. The concentration of the biomass in the mixed solution I is 3-100 mg / ml, and the stirring time is 2-15 h.

3. The preparation method according to claim 1, characterized in that, In step (1), the temperature rising rate of the low-temperature pretreatment is 0.5-10°C / min, the treatment time is 2-12 h, and the temperature range is 300-550°C.

4. The method of claim 1, wherein, The gas in the inert environment is any one or several of argon, nitrogen, a mixture of argon and hydrogen, or a mixture of nitrogen and hydrogen, wherein the volume ratio of argon to hydrogen in the mixture of argon and hydrogen is 90:10-99:1, and the volume ratio of nitrogen to hydrogen in the mixture of nitrogen and hydrogen is 90:10-99:

1.

5. The preparation method according to claim 1, characterized in that, In step (2), the acid washing treatment is specifically: adding the ball-milled hard carbon precursor into an acid washing solution to form a mixed solution II, stirring to fully mix, and filtering to obtain the acid-washed hard carbon precursor. The acid washing solution is any one or several of a 3-20 wt.% acetic acid aqueous solution, a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, or a nitric acid aqueous solution. The concentration of the ball-milled hard carbon precursor in the mixed solution II is 3-100 mg / ml, and the stirring time in the acid washing treatment is 3-20 h.

6. The preparation method according to claim 5, characterized in that, The acid washing solution is any one or several of a 10-20 wt.% acetic acid aqueous solution, a sulfuric acid aqueous solution, a hydrochloric acid aqueous solution, or a nitric acid aqueous solution.

7. The preparation method according to claim 1, characterized in that, In step (2), the method of the second alkali washing to remove impurities is: adding the acid-washed hard carbon precursor into an alkali washing solution II to form a mixed solution III, stirring to fully mix, and filtering to obtain the alkali-washed hard carbon precursor after removing impurities. The alkali cleaning solution II is any one or several of a 5-20 wt.% sodium carbonate aqueous solution, a lithium carbonate aqueous solution, a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution, the concentration of the hard carbon precursor in the mixed solution III after acid cleaning is 3-100 mg / ml, and the stirring time during the alkali cleaning impurity removal process is 3-20 h.

8. The method of claim 1, wherein, In step (2), the heating rate of the high-temperature carbonization is 0.5-10 ℃ / min, the treatment time is 2-12 h, and the carbonization temperature is 850-1600 ℃. The type of the ball mill used in the primary and secondary ball milling processes is planetary or horizontal, the rotation speed of the primary and secondary ball milling is 200-600 rpm, the ball milling time is 2-20 h, and the ball-to-material ratio of the primary ball milling is 5:1-20:

1.

9. The hard carbon material based on bran derivative prepared by the preparation method according to any one of claims 1-8.

10. The application of the hard carbon material based on bran derivative according to claim 9 as an electrode material in a sodium ion battery.

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