A bio-based sodium-ion electrode hard carbon negative electrode material and a preparation method thereof

Abstract

This invention relates to the field of batteries, specifically to a bio-based sodium-ion electrode hard carbon anode material and its preparation method. The preparation method includes the following steps: Step 1, preparing niobium hafnium silicide powder; Step 2, preparing alkali-treated powder, then mixing the alkali-treated powder, composite microspheres, and reduced graphene oxide, followed by ball milling to obtain a bio-based mixture; Step 4, placing the bio-based mixture in a crucible, placing the crucible in a graphite furnace, and performing heat preservation sintering to obtain the anode material. This invention uses bamboo powder as a bio-based hard carbon precursor material, blending it with composite microspheres and reduced graphene oxide, followed by sintering to prepare a hard carbon anode material. The anode material prepared by this invention not only exhibits high initial discharge specific capacity but also high coulombic efficiency and excellent recyclability.

Description

Technical Field

[0001] This invention relates to the field of batteries, specifically to a bio-based sodium-ion electrode hard carbon anode material and its preparation method. Background Technology

[0002] Sodium-ion batteries possess advantages such as abundant resources, low cost, and environmental friendliness, and are considered one of the most likely ideal power sources to replace lithium-ion batteries for large-scale energy storage applications. The performance of sodium-ion batteries is primarily determined by the sodium-storage anode and cathode materials, with the anode material being a crucial component. Among the sodium-storage anode materials currently under research, carbon-based anodes not only exhibit a low sodium intercalation plateau, high capacity, and good cycle stability, but also possess advantages such as abundant resources and simple preparation, making them the most promising sodium-storage anode materials for current applications.

[0003] Currently, research on bio-based materials as precursors for hard carbon materials in sodium-ion batteries is very active. Bio-based hard carbon materials are hard carbon materials prepared using bio-based precursors through processes such as pyrolysis and carbonization. These materials have attracted widespread attention due to their wide availability of raw materials, low cost, environmental friendliness, unique microstructure, and excellent electrochemical performance. However, bio-based hard carbon materials typically have low initial discharge capacity (ICE) and poor cycle reversibility, which greatly limits their practical application in sodium-ion batteries. Therefore, there is a need to develop a bio-based hard carbon material with high initial efficiency, high coulombic efficiency, and good cycle reusability. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a bio-based sodium ion electrode hard carbon anode material and its preparation method.

[0005] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a bio-based sodium ion electrode hard carbon anode material, comprising the following steps: Step 1, Prepare niobium hafnium silicide powder: Silicon powder, niobium powder and hafnium powder are weighed and mixed. After being ball-milled, they are placed in a graphite furnace and heated to obtain niobium hafnium silicide powder. Step 2, Preparation of composite microspheres: Niobium hafnium silicide powder, nickel acetate, sodium selenite and deionized water were mixed, heated and stirred to obtain a precursor mixture; an aqueous solution of ascorbic acid was added dropwise to the precursor mixture, and then processed in a reaction vessel to obtain composite microspheres; Step 3, Preparation of bio-based mixture: Bamboo powder was weighed and soaked in sodium hydroxide solution. After soaking, it was washed with water and dried to obtain alkali-treated powder. Then, the alkali-treated powder, composite microspheres and reduced graphene oxide were mixed and ball-milled to obtain a bio-based mixture. Step 4, Prepare the negative electrode material: The bio-based mixture is placed in a crucible, which is then placed in a graphite furnace for heat preservation and sintering to obtain the negative electrode material.

[0006] Preferably, in step 1, the purity of silicon powder, niobium powder and hafnium powder is greater than 99% and the particle size is 50-60μm; the mass ratio of hafnium powder, niobium powder and silicon powder is 0.9-1.3:0.46-0.62:0.56-0.74.

[0007] Preferably, in step 1, the ball milling speed is 250-450 r / min, the ball milling time is 3-8 h, and the ball-to-material ratio is 1-5:1.

[0008] Preferably, in step 1, the temperature of the graphite furnace is 860-1280℃, and the processing time is 3-5 hours.

[0009] Preferably, in step 2, the mass ratio of niobium hafnium silicide powder, nickel acetate, sodium selenite, and deionized water is 1:0.12-0.24:0.17-0.34:20-30.

[0010] Preferably, in step 2, the temperature for heating and stirring is 60-80℃, and the reaction time is 1-5h.

[0011] Preferably, in step 2, the aqueous solution of ascorbic acid is obtained by mixing ascorbic acid and deionized water in a mass ratio of 0.2-0.6:10.

[0012] Preferably, in step 2, the mass ratio of the aqueous solution of ascorbic acid to the precursor mixture is 0.2-0.7:1.

[0013] Preferably, in step 2, the ascorbic acid aqueous solution is added at a rate of 50-80 drops / minute, the reaction temperature in the reactor is 120-170℃, and the reaction time is 4-10 hours.

[0014] Preferably, in step 3, the bamboo powder is first dried in an oven until the moisture content is less than 10%; the particle size of the bamboo powder is 100-200μm.

[0015] Preferably, in step 3, the sodium hydroxide solution has a mass fraction of 10%-30%, and the soaking time is 1-3 hours.

[0016] Preferably, in step 3, the purity of the reduced graphene oxide is ≥99%, the single-layer sheet diameter is 0.5-10μm, and the carbon-oxygen ratio is 9.89.

[0017] Preferably, in step 3, the mass ratio of alkali-treated powder, composite microspheres, and reduced graphene oxide is 1:0.06-0.16:0.01-0.1.

[0018] Preferably, in step 3, the ball milling speed is 250-450 r / min, the ball milling time is 3-10 h, and the ball-to-material ratio is 2-8:1.

[0019] Preferably, in step 4, the heating process in the graphite furnace is as follows: under nitrogen protection, the temperature is first raised to 450-550℃, held for 1-3 hours, and then raised to 850-1150℃ and held for 1-3 hours.

[0020] Secondly, the present invention provides a bio-based sodium ion electrode hard carbon anode material, which is prepared by the above-described preparation method.

[0021] The beneficial effects of this invention are as follows: 1. This invention uses bamboo powder as a bio-based hard carbon precursor material, which is then blended and sintered with composite microspheres and reduced graphene oxide to prepare a hard carbon anode material. The anode material prepared by this invention not only exhibits high initial discharge specific capacity and high coulombic efficiency, but also demonstrates excellent recyclability.

[0022] 2. This invention uses composite microspheres and reduced graphene oxide together as reinforcing agents for hard carbon anode materials. The composite microspheres use niobium hafnium silicide powder as the matrix material, with a layer of nickel selenide generated in situ on its surface, thus forming a composite coated microsphere structure. These composite microspheres and reduced graphene oxide are then co-doped into bamboo powder for carbonization, ultimately preparing a hard carbon anode material. Compared to conventional hard carbon anode materials, this material exhibits significantly higher initial efficiency, sodium storage capacity, and cycle life.

[0023] 3. In this invention, the bamboo powder is soaked in an alkaline solution before carbonization, which enhances the activity of the bamboo charcoal, making it easier to combine with the composite microspheres and graphene. After ball milling, the resulting product is also more tightly and uniformly bonded.

[0024] 4. The matrix used in the composite microspheres is niobium hafnium silicide, which is obtained by sintering niobium and hafnium mixed with silicon in a suitable ratio. Testing revealed that, compared to composite microspheres obtained with niobium silicide or hafnium silicide alone, the composite microspheres prepared in this invention improve the electrode's initial efficiency, capacity, and cycle life, especially demonstrating superior performance in cycle life. Attached Figure Description

[0025] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0026] Figure 1 This is a SEM schematic diagram of the bio-based sodium ion electrode hard carbon anode material prepared in Example 1 of the present invention. Detailed Implementation

[0027] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0028] The present invention will be further described below with reference to the following embodiments. Example

[0029] A method for preparing a bio-based sodium ion electrode hard carbon anode material includes the following steps: Step 1, Prepare niobium hafnium silicide powder: Silicon powder, niobium powder, and hafnium powder with a purity greater than 99% and a particle size of 50-60 μm were weighed and mixed. The mass ratio of hafnium powder, niobium powder, and silicon powder was 1.1:0.54:0.65. The mixture was placed in a ball mill for ball milling at a speed of 350 r / min for 5 h with a ball-to-material ratio of 3:1. After ball milling, the product was placed in a graphite furnace and heated to 1120℃ for 4 h. After cooling to room temperature in the furnace, the product was passed through a 400-mesh sieve to obtain niobium hafnium silicide powder. Step 2, Preparation of composite microspheres: Niobium hafnium silicide powder, nickel acetate, sodium selenite, and deionized water were mixed in a mass ratio of 1:0.18:0.25:25. The mixture was heated to 70°C and stirred for 3 hours to obtain a precursor mixture. Ascorbic acid and deionized water were mixed in a mass ratio of 0.4:10 to obtain an aqueous solution of ascorbic acid. The aqueous solution of ascorbic acid was added dropwise to the precursor mixture in a mass ratio of 0.5:1 at a dropping rate of 50-60 drops / minute. After the addition was complete, the mixture was poured into a reaction vessel and heated to 150°C for 6 hours to obtain composite microspheres. Step 3, Preparation of bio-based mixture: Weigh out bamboo powder (Jiangxi Ruimei Bamboo and Wood Technology Co., Ltd.) with a moisture content of less than 10% and a particle size of 100-200μm, and then soak it in a 20% sodium hydroxide solution at a solid-liquid ratio of 1:10 for 2 hours. After soaking, wash it with water until neutral, and then dry it in an oven to obtain alkali-treated powder. Then, reduced graphene oxide (purity ≥99%, single-layer sheet diameter 0.5-10μm, carbon-oxygen ratio 9.89) was taken, and alkali-treated powder, composite microspheres and reduced graphene oxide were mixed at a mass ratio of 1:0.11:0.08, and ball milled in a ball mill at a speed of 350 r / min for 6 h with a ball-to-material ratio of 5:1 to obtain a bio-based mixture. Step 4, Prepare the negative electrode material: The bio-based mixture is placed in a crucible, which is then placed in a graphite furnace. Nitrogen gas is introduced as a protective gas. The temperature is first raised to 500°C and held for 2 hours. Then, the temperature is raised to 1050°C and held for 2 hours. After cooling to room temperature with the furnace, the negative electrode material is obtained. Example

[0030] A method for preparing a bio-based sodium ion electrode hard carbon anode material includes the following steps: Step 1, Prepare niobium hafnium silicide powder: Weigh out silicon powder, niobium powder and hafnium powder with a purity greater than 99% and a particle size of 50-60μm, mix them, and the mass ratio of hafnium powder, niobium powder and silicon powder is 0.9:0.62:0.56. Place them in a ball mill for ball milling at a speed of 250 r / min for 3 h and a ball-to-material ratio of 1:1. After ball milling, place the product in a graphite furnace and heat it to 860℃ for 3 h. After cooling to room temperature with the furnace, pass it through a 200-mesh sieve to obtain niobium hafnium silicide powder. Step 2, Preparation of composite microspheres: Niobium hafnium silicide powder, nickel acetate, sodium selenite, and deionized water were mixed in a mass ratio of 1:0.12:0.17:20. The mixture was heated to 60°C and stirred for 1 hour to obtain a precursor mixture. Ascorbic acid and deionized water were mixed in a mass ratio of 0.2:10 to obtain an aqueous solution of ascorbic acid. The aqueous solution of ascorbic acid was added dropwise to the precursor mixture in a mass ratio of 0.2:1 at a dropping rate of 50 drops / minute. After the addition was complete, the mixture was poured into a reaction vessel and heated to 120°C for 4 hours to obtain composite microspheres. Step 3, Preparation of bio-based mixture: Weigh out bamboo powder with a moisture content of less than 10% and a particle size of 100-200μm, then soak it in a 10% sodium hydroxide solution for 1 hour. After soaking, wash it with water until it is neutral, and then dry it in an oven to obtain alkali-treated powder. Then, the alkali-treated powder, composite microspheres, and reduced graphene oxide were mixed at a mass ratio of 1:0.06:0.01 and ball-milled in a ball mill at a speed of 250 r / min for 3 h with a ball-to-material ratio of 2:1 to obtain a bio-based mixture. Step 4, Prepare the negative electrode material: The bio-based mixture is placed in a crucible, which is then placed in a graphite furnace. Nitrogen gas is introduced as a protective gas. The temperature is first raised to 450°C and held for 3 hours. Then, the temperature is raised to 850°C and held for 3 hours. After cooling to room temperature with the furnace, the negative electrode material is obtained. Example

[0031] A method for preparing a bio-based sodium ion electrode hard carbon anode material includes the following steps: Step 1, Prepare niobium hafnium silicide powder: Silicon powder, niobium powder, and hafnium powder with a purity greater than 99% and a particle size of 50-60 μm were weighed and mixed. The mass ratio of hafnium powder, niobium powder, and silicon powder was 1.3:0.46:0.74. The mixture was placed in a ball mill for ball milling at a speed of 450 r / min for 8 h. The ball-to-material ratio was 5:1. After ball milling, the product was placed in a graphite furnace and heated to 1280℃ for 5 h. After cooling to room temperature with the furnace, the product was passed through a 500-mesh sieve to obtain niobium hafnium silicide powder. Step 2, Preparation of composite microspheres: Niobium hafnium silicide powder, nickel acetate, sodium selenite, and deionized water were mixed in a mass ratio of 1:0.24:0.34:30. The mixture was heated to 80°C and stirred for 5 hours to obtain a precursor mixture. Ascorbic acid and deionized water were mixed in a mass ratio of 0.6:10 to obtain an aqueous solution of ascorbic acid. The aqueous solution of ascorbic acid was added dropwise to the precursor mixture in a mass ratio of 0.7:1 at a dropping rate of 80 drops / minute. After the addition was complete, the mixture was poured into a reaction vessel and heated to 170°C for 10 hours to obtain composite microspheres. Step 3, Preparation of bio-based mixture: Weigh out bamboo powder with a moisture content of less than 10% and a particle size of 100-200μm, then soak it in a 30% sodium hydroxide solution for 3 hours. After soaking, wash it with water until it is neutral, and then dry it in an oven to obtain alkali-treated powder. Then, the alkali-treated powder, composite microspheres, and reduced graphene oxide were mixed at a mass ratio of 1:0.16:0.1 and ball-milled in a ball mill at a speed of 450 r / min for 10 h with a ball-to-material ratio of 8:1 to obtain a bio-based mixture. Step 4, Prepare the negative electrode material: The bio-based mixture is placed in a crucible, which is then placed in a graphite furnace. Nitrogen gas is introduced as a protective gas. The temperature is first raised to 550°C and held for 1 hour. Then, the temperature is raised to 1150°C and held for 1 hour. After cooling to room temperature with the furnace, the negative electrode material is obtained.

[0032] Comparative Example 1 A bio-based sodium-ion electrode hard carbon anode material differs from the preparation method in Example 1 in that it does not incorporate composite microspheres; instead, it is prepared directly using bamboo powder and reduced graphene oxide as raw materials. Specifically: Step 1, Preparation of bio-based mixture Take bamboo powder with a moisture content of less than 10% and a particle size of 100-200μm, then soak it in a 20% sodium hydroxide solution for 2 hours. After soaking, wash it with water until neutral, and then dry it in an oven to obtain alkali-treated powder. Then, reduce graphene oxide was taken, and the alkali-treated powder and reduced graphene oxide were mixed at a mass ratio of 1:0.08. The mixture was then placed in a ball mill for ball milling at a speed of 350 r / min for 6 h. The ball-to-material ratio was 5:1 to obtain a bio-based mixture. Step 2, Preparation of negative electrode material: The bio-based mixture is placed in a crucible, which is then placed in a graphite furnace. Nitrogen gas is introduced as a protective gas. The temperature is first raised to 500°C and held for 2 hours. Then, the temperature is raised to 1050°C and held for 2 hours. After cooling to room temperature with the furnace, the negative electrode material is obtained.

[0033] Comparative Example 2 A bio-based sodium-ion electrode hard carbon anode material differs from the preparation method of Example 1 in that the composite microspheres are niobium silicide and nickel selenide, while the rest is the same as in Example 1. Specifically: Step 1, Preparation of niobium silicide powder: Weigh out silicon powder and niobium powder with a purity greater than 99% and a particle size of 50-60μm, mix them, and the mass ratio of niobium powder to silicon powder is 1.64:0.65. Place them in a ball mill for ball milling at a speed of 350r / min for 5h and a ball-to-material ratio of 3:1. After ball milling, place the product in a graphite furnace and heat it to 1120℃ for 4h. After cooling to room temperature with the furnace, pass it through a 200-mesh sieve to obtain niobium silicide powder. Step 2, Preparation of composite microspheres: Niobium silicide powder, nickel acetate, sodium selenite, and deionized water were mixed in a mass ratio of 1:0.18:0.25:25. The mixture was heated to 70°C and stirred for 3 hours to obtain a precursor mixture. Ascorbic acid and deionized water were mixed in a mass ratio of 0.4:10 to obtain an aqueous solution of ascorbic acid. The aqueous solution of ascorbic acid was added dropwise to the precursor mixture in a mass ratio of 0.5:1 at a dropping rate of 50-60 drops / minute. After the addition was complete, the mixture was poured into a reaction vessel and heated to 150°C for 6 hours to obtain composite microspheres. Step 3: Prepare the bio-based mixture, the same as in Example 1; Step 4: Prepare the negative electrode material, the same as in Example 1.

[0034] Comparative Example 3 A bio-based sodium ion electrode hard carbon anode material differs from the preparation method of Example 1 in that the composite microspheres are hafnium silicide and nickel selenide, while the rest is the same as in Example 1. Specifically: Step 1, Prepare hafnium silicide powder: Weigh out silicon powder and hafnium powder with a purity greater than 99% and a particle size of 50-60μm, mix them, and the mass ratio of hafnium powder to silicon powder is 1.64:0.65. Place them in a ball mill for ball milling at a speed of 350r / min for 5h and a ball-to-material ratio of 3:1. After ball milling, place the product in a graphite furnace and heat it to 1120℃ for 4h. After cooling to room temperature with the furnace, pass it through a 200-mesh sieve to obtain hafnium silicide powder. Step 2, Preparation of composite microspheres: Hafnium silicide powder, nickel acetate, sodium selenite, and deionized water were mixed in a mass ratio of 1:0.18:0.25:25. The mixture was heated to 70°C and stirred for 3 hours to obtain a precursor mixture. Ascorbic acid and deionized water were mixed in a mass ratio of 0.4:10 to obtain an aqueous solution of ascorbic acid. The aqueous solution of ascorbic acid was added dropwise to the precursor mixture in a mass ratio of 0.5:1 at a dropping rate of 50-60 drops / minute. After the addition was complete, the mixture was poured into a reaction vessel and heated to 150°C for 6 hours to obtain composite microspheres. Step 3: Prepare the bio-based mixture, the same as in Example 1; Step 4: Prepare the negative electrode material, the same as in Example 1.

[0035] Experimental testing The performance of the hard carbon anode materials prepared in Examples 1 and Comparative Examples 1-3 was tested according to standard GB / T 43114-2023. The button cell preparation included: the anode materials prepared in Examples 1 and Comparative Examples 1-3; a polyethylene-polypropylene (PE-PP) composite membrane with a thickness of 80 μm; a 1 mol / L NaPF6 solution as the electrolyte; a CR2032 battery casing; sodium metal sheets as the counter electrode and reference electrode; and a charge / discharge rate of 0.1C and a voltage range of 0.005-1.5V used for the initial discharge specific capacity, initial coulombic efficiency, and cycle life tests. The test results are shown in Table 1.

[0036] As can be seen from Table 1, the hard carbon anode material prepared in Example 1 of the present invention has an initial discharge specific capacity of 415.3 mA·h / g, an initial coulombic efficiency of 88.2%, and a capacity retention rate of 90.1% after 200 cycles. This indicates that the hard carbon anode material prepared in Example 1 of the present invention exhibits excellent initial efficiency, capacity, and cycle life in sodium-ion battery applications.

[0037] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0038] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a biobased sodium-ion electrode hard carbon anode material, characterized in that, Includes the following steps: Step 1: Weigh out silicon powder, niobium powder and hafnium powder, mix them, first ball mill them, and then heat them in a graphite furnace to obtain niobium hafnium silicide powder; Step 2: Mix niobium hafnium silicide powder, nickel acetate, sodium selenite and deionized water, heat and stir to obtain precursor mixture; add ascorbic acid aqueous solution dropwise to precursor mixture, and then process in reaction vessel to obtain composite microspheres; Step 3: Weigh out bamboo powder and soak it in sodium hydroxide solution. After soaking, wash it with water and dry it to obtain alkali-treated powder. Then mix the alkali-treated powder, composite microspheres and reduced graphene oxide, and ball mill it to obtain a bio-based mixture. Step 4: Place the bio-based mixture in a crucible, place the crucible in a graphite furnace, and perform heat preservation and sintering treatment to obtain the negative electrode material; In step 1, the purity of silicon powder, niobium powder, and hafnium powder is greater than 99%, and the particle size is 50-60 μm; the mass ratio of hafnium powder, niobium powder, and silicon powder is 0.9-1.3:0.46-0.62:0.56-0.

74. In step 2, the mass ratio of niobium hafnium silicide powder, nickel acetate, sodium selenite, and deionized water is 1:0.12-0.24:0.17-0.34:20-30; the aqueous solution of ascorbic acid is obtained by mixing ascorbic acid and deionized water at a mass ratio of 0.2-0.6:

10. In step 3, the mass fraction of sodium hydroxide solution is 10%-30%, and the soaking time is 1-3 hours; in step 3, the mass ratio of alkali-treated powder, composite microspheres and reduced graphene oxide is 1:0.06-0.16:0.01-0.

1.

2. The method according to claim 1, wherein the method is characterized by, In step 1, the ball milling speed is 250-450 r / min, the ball milling time is 3-8 h, and the ball-to-material ratio is 1-5:1; the temperature of the graphite furnace is 860-1280℃, and the processing time is 3-5 h.

3. The method according to claim 1, wherein the method is characterized by, In step 2, the temperature for heating and stirring is 60-80℃, and the reaction time is 1-5h.

4. The method according to claim 1, wherein the method is characterized by, In step 2, the mass ratio of the aqueous solution of ascorbic acid to the precursor mixture is 0.2-0.7:1; the dropping rate of the aqueous solution of ascorbic acid is 50-80 drops / minute; the reaction temperature in the reactor is 120-170℃; and the reaction time is 4-10 hours.

5. The method for preparing a bio-based sodium ion electrode hard carbon anode material according to claim 1, characterized in that, In step 3, the ball milling speed is 250-450 r / min, the ball milling time is 3-10 h, and the ball-to-material ratio is 2-8:

1.

6. The method for preparing a bio-based sodium ion electrode hard carbon anode material according to claim 1, characterized in that, In step 4, the heating process in the graphite furnace is as follows: under nitrogen protection, the temperature is first raised to 450-550℃, held for 1-3 hours, and then raised to 850-1150℃ and held for 1-3 hours.

7. A bio-based sodium ion electrode hard carbon anode material prepared using the preparation method according to any one of claims 1-6.

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