A bean dregs-based hard carbon negative electrode material, a preparation method therefor, and an application thereof

Abstract

This invention discloses a soybean residue-based hard carbon anode material, its preparation method, and its application, belonging to the technical field of sodium-ion battery anode materials. The preparation method provided by this invention includes the following steps: crushing dried soybean residue that meets specific material requirements; then carbonizing the crushed soybean residue and cooling it to room temperature to obtain the anode material; wherein the soybean residue meeting the specific material requirements has a protein content of 15-25%, a carbohydrate content of 55-70%, a fat content of 3-6%, and the remainder being minerals containing calcium, phosphorus, and iron. This invention uses soybean residue as a raw material, which is inexpensive and widely available. The preparation method is simple. By carbonizing soybean residue that meets specific protein, carbohydrate, and fat content requirements, a hard carbon anode material with good electrochemical performance can be obtained, realizing the high-value utilization of waste and showing good application prospects.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery anode material technology, and in particular to a soybean residue-based hard carbon anode material, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The negative electrode material in sodium-ion batteries generally has a low reduction potential, playing a crucial role in loading and releasing sodium ions: it undergoes a reduction reaction during charging and an oxidation reaction during discharging. The efficiency of the negative electrode material directly affects the overall kinetic performance of the battery, such as rate performance and power density. Commonly used carbon-based materials mainly include two categories: graphitic carbon and non-graphitic carbon. Among them, non-graphitic hard carbon is a commonly used negative electrode material for sodium-ion batteries.

[0004] Hard carbon anode precursor materials are complex and diverse, including biomass, resin-based materials, and pitch. Different precursors result in hard carbon materials with varying electrochemical performance because the precursor composition affects the carbonization process, thus influencing the final electrochemical performance of the hard carbon material. Therefore, how to prepare hard carbon anode materials with good electrochemical performance at low cost is an urgent problem to be solved. Summary of the Invention

[0005] In view of this, the present invention provides a soybean residue-based hard carbon anode material, its preparation method and application. The preparation method of the present invention uses low-cost soybean residue waste as raw material, and can prepare a hard carbon anode material with good electrochemical performance. The raw material source is wide and realizes the high-value utilization of waste, which has good application prospects.

[0006] In a first aspect, the present invention provides a method for preparing a soybean residue-based hard carbon anode material, comprising the following steps:

[0007] The dried soybean residue that meets the specific material range is crushed; then the crushed soybean residue is carbonized and cooled to room temperature to obtain the final product.

[0008] The soybean residue that meets the specific material range has a protein content of 15-25%, a carbohydrate content of 55-70%, a fat content of 3-6%, and the remainder consists of minerals containing calcium, phosphorus, and iron.

[0009] Preferably, the drying temperature is 15–60°C.

[0010] Preferably, the particle size of the crushed soybean residue is 0.1 to 100 μm.

[0011] Preferably, the carbonization heating rate is 2-10℃ / min, the carbonization temperature is 1100-1500℃, and the carbonization time is 6-10h.

[0012] Furthermore, the carbonization heating rate is 3-7°C / min, the carbonization temperature is 1300-1500°C, and the carbonization time is 6-8 hours.

[0013] Preferably, after the drying step, the process further includes a step of determining the material content of the soybean residue raw material. Soybean residue that meets the specific material content range after the material content determination is subjected to a subsequent crushing step; soybean residue that does not meet the specific material content range after the material content determination is subjected to pretreatment.

[0014] Furthermore, the pretreatment includes using one or more of proteases, cellulases, or lipases to reduce the content of one or more of the protein, carbohydrates, or fats in the soybean residue raw material to meet specific material ranges.

[0015] Preferably, after the carbonization and cooling to room temperature steps, the product is further subjected to a crushing and sieving step.

[0016] Furthermore, the particle size of the sieved material is 2–40 μm.

[0017] Secondly, the present invention provides a soybean residue-based hard carbon anode material prepared by the above preparation method.

[0018] Thirdly, the present invention provides a sodium-ion battery negative electrode sheet, which is prepared from raw materials including a negative electrode material, conductive additives, binders and solvents; the negative electrode material is the above-mentioned soybean residue-based hard carbon negative electrode material.

[0019] Fourthly, the present invention provides a sodium-ion battery comprising a positive electrode, a negative electrode, a separator, an organic electrolyte, and a counter electrode; wherein the negative electrode is the aforementioned sodium-ion battery negative electrode sheet.

[0020] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0021] The present invention provides a method for preparing soybean residue-based hard carbon anode material using soybean residue as raw material. Soybean residue, as a waste product in the soybean industry chain, is inexpensive and widely available. The preparation method is simple. By carbonizing soybean residue that meets specific protein, carbohydrate, and fat content requirements, a hard carbon anode material with good electrochemical performance can be obtained. Sodium-ion secondary batteries using this hard carbon anode material as the anode active material have high sodium storage capacity and high initial coulombic efficiency, good safety performance, and good application prospects. Attached Figure Description

[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0023] Figure 1 This is a cycle performance diagram of the battery assembled with soybean residue-based hard carbon material according to Example 6 of the present invention at a current density of 1A / g.

[0024] Figure 2 This is a graph showing the cycle performance of the battery assembled with soybean residue-based hard carbon material (Comparative Example 1) at a current density of 1 A / g.

[0025] Figure 3 This is a cycle performance diagram of a commercially available hard carbon battery assembled in a specific embodiment of the present invention at a current density of 1 A / g. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] This invention provides a method for preparing a soybean residue-based hard carbon anode material, comprising the following steps:

[0028] The dried soybean residue that meets the specific material range is crushed; then the crushed soybean residue is carbonized and cooled to room temperature to obtain the final product.

[0029] The soybean residue that meets the specific material range has a protein content of 15-25%, a carbohydrate content of 55-70%, a fat content of 3-6%, and the remainder consists of minerals containing calcium, phosphorus, and iron.

[0030] This invention uses soybean residue as a raw material. Soybean residue, a waste product in the soybean industry chain, is mainly composed of cellulose and polysaccharide polymers. During the production of soybean residue, an acid / alkali treatment process is used to separate soybean oil and soybean protein, which not only removes impurities from the residue but also further reduces the protein and fat content. Furthermore, soybean residue naturally contains minerals such as calcium, phosphorus, and iron. Appropriate amounts of these inorganic elements help inhibit the formation of graphite domains, which is beneficial for the formation of hard carbon closed-loop structures. This invention discovers that when the protein, carbohydrate, and fat content of soybean residue meets specific ranges, hard carbon anode materials with excellent electrochemical performance can be obtained.

[0031] In this invention, the drying temperature is 15–60°C. The soybean residue can be dried naturally or by oven drying, which facilitates subsequent crushing and prevents the soybean residue particles from sticking together. In this invention, the particle size of the crushed soybean residue is 0.1–100 μm, more preferably 10–50 μm. The crushed soybean residue particles have a large specific surface area, which is beneficial for the subsequent carbonization process. This invention does not impose special limitations on the crushing method; for example, a crusher, nanomill, or ball mill can be used.

[0032] In this invention, the heating rate for carbonization is 2–10 °C / min, more preferably 3–7 °C / min; the carbonization temperature is 1100–1500 °C, more preferably 1300–1500 °C; and the carbonization time is 6–10 h, more preferably 6–8 h. During the carbonization process, impurities and volatiles in the soybean residue gradually evaporate, while the carbon black in the soybean residue gradually transforms into hard carbon.

[0033] In this invention, the drying step is followed by a step of determining the substance content of the soybean residue raw material. Determining the substance content after drying avoids the influence of moisture. Soybean residue whose substance content meets the specific range after determination is then subjected to subsequent drying and crushing steps; soybean residue whose substance content does not meet the specific range after determination is then pretreated. The substance content determination method in this invention is near-infrared spectroscopy.

[0034] In this invention, pretreatment includes using one or more of proteases, cellulases, or lipases to reduce the content of one or more of the following in soybean residue raw materials to meet specific material ranges: protein, carbohydrates, or fat. This invention does not impose specific limitations on the use of proteases, cellulases, or lipases. For example, soybean residue is dispersed in water and treated with proteases, cellulases, or lipases at a mass ratio of soybean residue to enzyme powder of 1000:(0.8–1.2) and a solid-liquid ratio of 1:(2–4). After thorough mixing, the mixture is placed in an air-bath shaker at 40–60°C for 5–30 hours, then inactivated with hot water at 95–100°C, washed, and dried to obtain the final product. Specific treatment parameters are determined based on the difference between the initial range and the target range, and can be determined by those skilled in the art using conventional methods.

[0035] Following the carbonization and cooling to room temperature steps, this invention further includes a step of pulverizing and sieving the obtained product. The sieved particle size is 2–40 μm, more preferably 2–20 μm. Particles with excessively small particle sizes have a large specific surface area, which increases the amount of binder used in electrode preparation. Particles that are too large can lead to structural inhomogeneity in the prepared electrode coating, affecting the structural stability of the electrode and ultimately impacting the cycle stability of the battery.

[0036] The present invention also provides a soybean residue-based hard carbon anode material prepared by the above preparation method.

[0037] The present invention also provides a sodium-ion battery negative electrode sheet, which is prepared from raw materials including a negative electrode material, conductive additives, binders and solvents; the negative electrode material is the soybean residue-based hard carbon negative electrode material described above.

[0038] In this invention, the conductive additive is selected from one or more of Super-P, carbon black, or Ketjen black.

[0039] In this invention, the adhesive is selected from one or more of polyvinylidene fluoride, polyacrylic acid, sodium carboxymethyl cellulose, or sodium alginate.

[0040] In this invention, the mass ratio of the negative electrode material, conductive additive, and binder is (80-95):(3-10):(2-10). In some embodiments, the mass ratio of the negative electrode material, conductive additive, and binder is 95:3:2.

[0041] In this invention, the solvent is selected from N-methylpyrrolidone or deionized water. There are no special limitations on the amount of solvent used; any amount of solvent well-known to those skilled in the art can be used.

[0042] In this invention, the sodium-ion battery negative electrode sheet is prepared by the following method: negative electrode material, conductive additives, binders, and solvents are mixed, and then subjected to slurry preparation, coating, and drying to obtain the sodium-ion battery negative electrode sheet. This invention does not impose special restrictions on the current collector used in the coating process; it can be selected from copper foil, aluminum foil, or other commonly used current collectors.

[0043] The present invention does not impose any particular limitation on the method of smearing and drying; any method well known to those skilled in the art can be used. In some embodiments, the drying temperature is 70–100°C.

[0044] The present invention also provides a sodium-ion battery, comprising a positive electrode, a negative electrode, a separator, an organic electrolyte, and a counter electrode; wherein the negative electrode is the sodium-ion battery negative electrode sheet described above.

[0045] In this invention, the solvent of the organic electrolyte includes one or more of ethylene carbonate (EC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), diethylene glycol dimethyl ether (diglyme), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether. The solute of the organic electrolyte includes one or more of sodium hexafluorophosphate (NaPF6), sodium perchlorate, or sodium trifluoromethanesulfonate.

[0046] In this invention, the diaphragm is made of glass fiber.

[0047] In this invention, the counter electrode is a sodium metal counter electrode.

[0048] The present invention does not impose any special limitations on the preparation method of the sodium-ion battery; any sodium-ion battery preparation method well known to those skilled in the art can be used.

[0049] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0050] Example 1

[0051] This embodiment provides a method for preparing soybean residue-based hard carbon anode material, including the following steps:

[0052] (1) After drying the soybean residue raw material at 40℃ for 8 hours, the content of the soybean residue was determined by near-infrared spectroscopy. The carbohydrate content was found to be 65%, the protein content was 15%, the fat content was 5%, and the remainder was minerals such as calcium, phosphorus and iron.

[0053] (2) The soybean residue is crushed by a crusher into soybean residue with a particle size of 10-30μm;

[0054] (3) The crushed soybean residue was heated to 1100℃ in a tube furnace under Ar atmosphere at a heating rate of 5℃ / min for 6h, and then cooled to room temperature with the furnace.

[0055] (4) The product cooled to room temperature is crushed and sieved to obtain hard carbon products with a particle size of 2 to 40 μm.

[0056] Example 2

[0057] This embodiment provides a method for preparing soybean residue-based hard carbon anode material, including the following steps:

[0058] (1) After drying the soybean residue raw material at 40℃ for 8 hours, the content of the soybean residue was determined by near-infrared spectroscopy. The carbohydrate content was found to be 50%, the protein content was 25%, the fat content was 6%, and the remainder was minerals such as calcium, phosphorus and iron.

[0059] (2) The soybean residue is crushed by a crusher into soybean residue with a particle size of 10-30μm;

[0060] (3) The crushed soybean residue was heated to 1300℃ in a tube furnace under Ar atmosphere at a heating rate of 5℃ / min for 8h, and then cooled to room temperature with the furnace.

[0061] (4) The product cooled to room temperature is crushed and sieved to obtain hard carbon products with a particle size of 2 to 40 μm.

[0062] Example 3

[0063] This embodiment provides a method for preparing soybean residue-based hard carbon anode material, including the following steps:

[0064] (1) After drying the soybean residue raw material at 40℃ for 8 hours, the content of the soybean residue was determined by near-infrared spectroscopy. The carbohydrate content was found to be 70%, the protein content was 20%, the fat content was 3%, and the remainder was minerals such as calcium, phosphorus and iron.

[0065] (2) The soybean residue is crushed by a crusher into soybean residue with a particle size of 10-30μm;

[0066] (3) The crushed soybean residue was heated to 1500℃ in a tube furnace under Ar atmosphere at a heating rate of 5℃ / min for 8h, and then cooled to room temperature with the furnace.

[0067] (4) The product cooled to room temperature is crushed and sieved to obtain hard carbon products with a particle size of 2 to 40 μm. Then, products with different particle sizes are mixed to obtain the final product.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing a soybean residue-based hard carbon anode material, including the following steps:

[0070] (1) After drying the soybean residue raw material at 40℃ for 8 hours, the content of the soybean residue was determined by near-infrared spectroscopy. The carbohydrate content was found to be 48%, the protein content was 33%, the fat content was 4%, and the remainder was minerals such as calcium, phosphorus and iron.

[0071] (2) The soybean residue is crushed by a crusher into soybean residue with a particle size of 10-30μm;

[0072] (3) The crushed soybean residue was heated to 1100℃ in a tube furnace under Ar atmosphere at a heating rate of 5℃ / min for 6h, and then cooled to room temperature with the furnace.

[0073] (4) The product cooled to room temperature is crushed and sieved to obtain hard carbon products with a particle size of 2 to 40 μm.

[0074] Comparative Example 2

[0075] This comparative example provides a method for preparing a soybean residue-based hard carbon anode material, including the following steps:

[0076] (1) After drying the soybean residue raw material at 40℃ for 8 hours, the content of the soybean residue was determined by near-infrared spectroscopy. The carbohydrate content was found to be 50%, the protein content was 18%, the fat content was 15%, and the remainder was minerals such as calcium, phosphorus and iron.

[0077] (2) The soybean residue is crushed by a crusher into soybean residue with a particle size of 10-30μm;

[0078] (3) The crushed soybean residue was heated to 1100℃ in a tube furnace under Ar atmosphere at a heating rate of 5℃ / min for 6h, and then cooled to room temperature with the furnace.

[0079] (4) The product cooled to room temperature is crushed and sieved to obtain hard carbon products with a particle size of 2 to 40 μm.

[0080] Comparative Example 3

[0081] This comparative example provides a method for preparing a soybean residue-based hard carbon anode material, including the following steps:

[0082] (1) After drying the soybean residue raw material at 40℃ for 8 hours, the content of the soybean residue was determined by near-infrared spectroscopy. The carbohydrate content was found to be 75%, the protein content was 10%, the fat content was 2%, and the remainder was minerals such as calcium, phosphorus and iron.

[0083] (2) The soybean residue is crushed by a crusher into soybean residue with a particle size of 10-30μm;

[0084] (3) The crushed soybean residue was heated to 1100℃ in a tube furnace under Ar atmosphere at a heating rate of 5℃ / min for 6h, and then cooled to room temperature with the furnace.

[0085] (4) The product cooled to room temperature is crushed and sieved to obtain hard carbon products with a particle size of 2 to 40 μm.

[0086] Example 4

[0087] The soybean residue raw material in this embodiment is the same as that in Comparative Example 1, and the crushing, carbonization, and post-processing procedures are the same. However, in this embodiment, the soybean residue raw material in Comparative Example 1 is pretreated with protease. The specific steps are as follows:

[0088] Soybean residue was dispersed in water and treated with protease at a mass ratio of 1000:1 and a solid-liquid ratio of 1:3. After being mixed evenly, the mixture was placed in an air bath shaker and kept at 50°C for 10 hours. Then, it was inactivated with hot water at 100°C, washed, filtered, and dried at 40°C for 10 hours to obtain the pretreated soybean residue.

[0089] Near-infrared spectroscopy analysis revealed that the pretreated soybean residue contained 63% carbohydrates, 16% protein, 6% fat, and the remainder consisted of minerals such as calcium, phosphorus, and iron.

[0090] Example 5

[0091] The soybean residue raw material in this embodiment is the same as that in Comparative Example 2, and the crushing, carbonization, and post-processing processes are the same. However, in this embodiment, the soybean residue raw material in Comparative Example 2 is pretreated with lipase. The specific steps are as follows:

[0092] Soybean residue was dispersed in water and treated with lipase at a mass ratio of 1000:1 and a solid-liquid ratio of 1:3. After being mixed evenly, the mixture was placed in an air bath shaker and kept at 50°C for 15 hours. Then, it was inactivated with hot water at 100°C, washed, filtered, and dried at 40°C for 10 hours to obtain the pretreated soybean residue.

[0093] Near-infrared spectroscopy analysis revealed that the pretreated soybean residue contained 55% carbohydrates, 24% protein, 3% fat, and the remainder consisted of minerals such as calcium, phosphorus, and iron.

[0094] Example 6

[0095] The soybean residue raw material in this embodiment is the same as that in Comparative Example 3, and the crushing, carbonization, and post-processing processes are the same. However, in this embodiment, the soybean residue raw material in Comparative Example 3 is pretreated with cellulase. The specific steps are as follows:

[0096] Soybean residue was dispersed in water and treated with cellulase at a mass ratio of 1000:1 and a solid-liquid ratio of 1:3. After being mixed evenly, the residue was placed in an air bath shaker and kept at 50°C for 24 hours. Then, it was inactivated with hot water at 100°C, washed, filtered, and dried at 40°C for 10 hours to obtain the pretreated soybean residue.

[0097] Near-infrared spectroscopy analysis revealed that the pretreated soybean residue contained 60% carbohydrates, 21% protein, 6% fat, and the remainder consisted of minerals such as calcium, phosphorus, and iron.

[0098] The soybean residue-based hard carbon anode materials from Examples 1-6 and Comparative Examples 1-3, along with commercially available hard carbon products, were mixed uniformly with conductive carbon black and sodium carboxymethyl cellulose at a mass ratio of 95:3:2, and then dispersed in an aqueous solution to form a uniform slurry. The slurry was then coated onto copper foil and vacuum dried at 90°C to obtain a hard carbon anode sheet. The hard carbon anode sheet was paired with a sodium metal anode, and a CR2032 coin cell was assembled in an inert atmosphere. The electrochemical performance of the hard carbon electrode was tested. The organic electrolyte was 1M NaPF6, EC / DEC (volume ratio 1:1) + 5% FEC. The coin cell structure included a positive electrode shell (stainless steel), a negative electrode shell (stainless steel), a gasket (stainless steel), a hard carbon electrode sheet, a sodium metal sheet, an organic electrolyte, and a separator (glass fiber). The voltage range was 0.01–1.5V.

[0099] The electrochemical test results are shown in Table 1 (test current density is 30 mA / g).

[0100] Table 1. Electrochemical performance data of batteries assembled using examples, comparative examples, and commercially available hard carbon anode materials.

[0101]

[0102] As can be seen from Table 1, the batteries assembled from the various soybean residue-based hard carbon materials provided in the embodiments of the present invention exhibit good electrochemical performance, reaching a level comparable to commercially available hard carbon materials. Comparative Examples 1-3 show that excessively high cellulose, protein, or fat content leads to a decrease in electrochemical performance, while soybean residue-based hard carbon materials treated with cellulase, protease, or lipase exhibit good electrochemical performance.

[0103] The battery assembled from the soybean residue-based hard carbon material in Example 6 retained 97.5% of its charge capacity after 100 cycles at a current density of 1 A / g. Figure 1 As shown; the battery assembled from soybean residue-based hard carbon material in Comparative Example 1 retained 89.7% of its charge capacity after 100 cycles at a current density of 1 A / g. Figure 2 As shown, the commercially available sample retained 93.2% of its charging capacity after 100 cycles at a current density of 1 A / g. Figure 3 As shown.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a soybean residue-based hard carbon anode material, characterized in that, Includes the following steps: The dried soybean residue that meets the specific material range is crushed; then the crushed soybean residue is carbonized and cooled to room temperature to obtain the final product. The drying step is followed by a step of determining the substance content of the soybean residue raw material. Soybean residue that meets the specific substance content range after the substance content determination is subjected to the subsequent crushing step; soybean residue that does not meet the specific substance content range after the substance content determination is subjected to pretreatment. The pretreatment includes using one or more of protease, cellulase or lipase to reduce the content of one or more of protein, carbohydrate or fat in soybean residue raw material to meet a specific range. The soybean residue that meets the specific material range has a protein content of 15-25%, a carbohydrate content of 55-70%, a fat content of 3-6%, and the remainder consists of minerals containing calcium, phosphorus, and iron. Alternatively, the soybean residue that meets the specific material range has a protein content of 25%, a carbohydrate content of 50%, a fat content of 6%, and the remainder consists of minerals containing calcium, phosphorus, and iron.

2. The preparation method according to claim 1, characterized in that, The drying temperature is 15~60℃; the particle size of the crushed soybean residue is 0.1~100μm.

3. The preparation method according to claim 1, characterized in that, The carbonization heating rate is 2~10℃ / min, the carbonization temperature is 1100~1500℃, and the carbonization time is 6~10h.

4. The preparation method according to claim 1, characterized in that, After the carbonization and cooling to room temperature steps, the product is further subjected to crushing and sieving.

5. The preparation method according to claim 4, characterized in that, The particle size of the sieved material is 2~40μm.

6. The soybean residue-based hard carbon anode material prepared by the preparation method according to any one of claims 1 to 5.

7. A sodium-ion battery negative electrode sheet, prepared from raw materials including a negative electrode material, conductive additives, binders, and solvents, characterized in that, The negative electrode material is the soybean residue-based hard carbon negative electrode material as described in claim 6.

8. A sodium-ion battery, comprising a positive electrode, a negative electrode, a separator, an organic electrolyte, and a counter electrode, characterized in that, The negative electrode is the sodium-ion battery negative electrode sheet according to claim 7.

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