Method for preparing carbon electrode material of lithium battery from balsa wood biomass

Abstract

Provided is a method for preparing a carbon electrode material of a lithium battery from balsa wood biomass, which method belongs to the technical field of electrode materials of lithium ion batteries. The preparation method comprises the following steps: S1, selecting balsa wood and three kinds of residues thereof as a biomass carbon source; S2, performing a pre-carbonization treatment on the crushed balsa wood; S3, uniformly mixing a pre-carbonization product and a pore-forming agent, grinding same, and then performing high-temperature carbonization under two stages of temperature control; S4, performing acid pickling and water washing on a product of the two-stage high-temperature carbonization until the product is neutral, and thereby obtaining a porous carbon material having a hierarchical pore structure with micropores and mesopores; and S5, stirring and dispersing the porous carbon material, a conductive agent and a binder in a solvent, so as to form a negative-electrode slurry, then coating a negative-electrode current collector with the slurry, and performing drying and cutting to obtain a carbon negative electrode of a lithium ion battery. The preparation method involves a simple process and low costs, and is suitable for industrial batch production; a porous carbon material prepared thereby has an ultra-high specific surface area, rich micropores, a low ash content and few impurities; and the preparation method is of great significance and value for the development of a carbon negative electrode material of lithium ion batteries.

Description

A method for preparing a carbon electrode material for a lithium battery made of balsa wood biomass Technical Field

[0001] The present invention belongs to the technical field of ion battery electrode materials, and particularly relates to a method for preparing a balsa wood biomass carbon electrode material for a lithium battery. Background Art

[0002] Existing porous carbon materials have advantages such as large specific surface area, well-developed micro- and nanoporous structures, stable physical and chemical properties, acid and alkali resistance, high temperature resistance, low cost, easy availability, and renewability. They are widely used in fields such as adsorption, catalytic reactions, and electrochemistry. Porous carbon materials with a unique microporous-mesoporous multi-level pore structure are gaining increasing attention as negative electrode materials for lithium-ion batteries. This is because the abundant micropores in these porous carbon materials have excellent lithium storage properties, while the relatively large mesopores can serve as channels for the rapid insertion and deinsertion of lithium ions. Therefore, they may be a relatively ideal lithium storage negative electrode material.

[0003] my country is particularly rich in forest resources, with over 1 billion tons of forest waste alone generated annually. Compared to coal-based porous carbon, the production of wood-based porous carbon from forest products and their waste offers advantages such as a wide range of raw material sources, low carbon emissions, and low cost. The development of this industry aligns well with China's "dual carbon" strategy, promoting green carbon-to-carbon conversion and possessing significant value for energy and environmental sustainability.

[0004] Woody biomass is a rich raw material for preparing porous carbon materials. Balsa is the fastest-growing and lightest tree in nature. Compared to other trees, balsa has a high specific surface area and a well-developed micro- and nanopore structure, making it an ideal raw material for preparing porous carbon materials. This invention uses balsa and its "three residues" as carbon sources, leveraging their naturally rich pore structure. Through further pore creation and activation using pore-forming agents and activators, high-quality, high-value-added wood-based porous carbon materials can be produced.

[0005] Existing porous carbon electrode materials have a small number of micropores, a small specific surface area, a high ash content, many impurities, low purity, and a low lithium storage capacity.

[0006] Therefore, a method for preparing a balsa wood biomass lithium battery carbon electrode material is needed to solve the problems of porous carbon electrode materials in the prior art, such as a small number of micropores, a small specific surface area, a high ash content, many impurities, low purity, and a low lithium storage capacity. Summary of the Invention

[0007] One of the purposes of the present invention is to provide a method for preparing a balsa wood biomass carbon electrode material for lithium batteries, wherein the prepared porous material has a large specific surface area, low ash content, stable properties, and high added value. A second purpose of the present invention is to provide a balsa wood biomass carbon electrode material for lithium batteries, wherein the carbon electrode material has abundant micropores and a unique micropore-mesoporous multi-level pore structure. The size of the micropores matches the spatial dimensions of the lithium ion storage, and the lithium storage capacity is high, while the mesopores can serve as transmission channels for the rapid embedding and de-embedding of lithium ions, and the rapid charge and discharge performance is excellent, and thus it may be a relatively ideal negative electrode material for lithium ion batteries.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] S1. Balsa wood and its residues are selected as biomass carbon sources, which are cleaned to remove surface impurities, dried, and crushed to prepare the carbon source raw materials for porous carbon negative electrode materials;

[0010] S2, pre-carbonizing the crushed balsa wood, drying to remove moisture, and naturally cooling to room temperature to obtain a pre-carbonized product;

[0011] S3, mixing the pre-carbonized product and the pore-forming agent uniformly and grinding, then transferring the material to a high-temperature tube furnace, carbonizing at a high temperature under a two-stage temperature-controlled N2 or Ar gas atmosphere, and grinding after natural cooling;

[0012] S4, acid-washing and water-washing the two-stage high-temperature carbonization product until neutral, removing impurities in the material, filtering and drying, to obtain a porous carbon material with a microporous and mesoporous multi-level pore structure;

[0013] S5. The porous carbon material, the conductive agent, and the binder are stirred and dispersed in a solvent to form a negative electrode slurry, and then the slurry is coated on the negative electrode current collector, and dried and cut into pieces to obtain a lithium-ion battery carbon negative electrode.

[0014] Preferably, in S1, the three residues are sawdust, bark and wood shavings.

[0015] Preferably, in S2, the pre-carbonization temperature is 150-200°C, the heating rate is 5-10°C / min, and the pre-carbonization time is 4-10h.

[0016] Preferably, in S3, the pore-forming agent used is two or more of KOH, KHCO3, Li2CO3, and CaCO3, and the weight ratio of the pre-carbonized product to the pore-forming agent is 1:0.1-0.3.

[0017] Preferably, in S3, the first stage carbonization temperature is 500-700°C, and the carbonization time is 6-10 hours; the second stage carbonization temperature is 800-1000°C, and the carbonization time is 1-4 hours.

[0018] Preferably, in S4, the acid used in the pickling process is one or both of HCl and H3PO4.

[0019] Preferably, in S5, the conductive agent and the binder are acetylene black and polyvinylidene fluoride, respectively, wherein the porous carbon material, acetylene black and polyvinylidene fluoride are uniformly mixed in a weight ratio of 1:0.05-0.1:0.05-0.1.

[0020] Preferably, in S5, the specific surface area of ​​the prepared porous carbon material is greater than 1800 m 2 / g, the pore size is mainly distributed between 0.1 and 6 nm, and the volume of micropores of 0.5-1 nm accounts for more than 50%.

[0021] Preferably, the prepared lithium-ion battery carbon negative electrode has a lithium storage capacity of ≥400 mAh / g, a charge and discharge rate of 0.1-3C, and a cycle life of more than 2000 times.

[0022] The present invention also provides a balsa wood biomass lithium battery carbon electrode material, which is prepared by adopting the preparation method of the balsa wood biomass lithium battery carbon electrode material.

[0023] Compared with the prior art, the method for preparing a carbon electrode material for a lithium battery made of balsa wood biomass provided by the present invention has at least the following beneficial effects:

[0024] In terms of screening biomass carbon sources, using balsa wood as a carbon source, which has natural advantages such as high specific surface area and developed microporous structure, is conducive to the preparation of high-quality, high-value-added porous carbon materials; in terms of carbonization process innovation, the use of a two-stage temperature-controlled high-temperature carbonization strategy combined with a variety of pore-forming agents is conducive to obtaining porous carbon materials with richer micro- and nano-multi-level pore structures. Furthermore, the preparation method provided by the present invention is simple in process and low in price, suitable for industrial mass production. The porous carbon material prepared by this method has ultra-high specific surface area, rich micropores, low ash content, few impurities, high purity, and extremely high lithium storage capacity, which is of great significance and value to the development of new carbon negative electrode materials for lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a BET test result of a porous carbon material prepared in Example 1 of the present invention, wherein: (a) pore size distribution diagram; (b) isothermal adsorption curve;

[0026] FIG2 is a charge-discharge cycle curve of the negative electrode material prepared in Example 1 of the present invention: charge-discharge current density of 100 mA / g (left graph); charge-discharge current density of 1000 mA / g (right graph);

[0027] FIG3 is a charge-discharge cycle curve of the negative electrode material prepared in Example 2 of the present invention: charge-discharge current density of 100 mA / g (left graph); charge-discharge current density of 500 mA / g (right graph);

[0028] FIG4 is a graph showing the rate performance of the negative electrode material prepared in Example 3 of the present invention: (a) rate cycle curve, (b) charge and discharge curve;

[0029] FIG5 is a charge-discharge cycle curve diagram of the negative electrode material prepared in Example 4 of the present invention (500 mA / g). DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] Example 1:

[0032] S1. Balsa wood is selected as a biomass carbon source, and is washed with deionized water to remove impurities on the surface, and then dried and crushed to prepare a carbon source raw material for a porous carbon negative electrode material;

[0033] S2. Pre-carbonizing the crushed carbon source raw material in an air atmosphere at a pre-carbonization temperature of 180° C., a heating rate of 5° C. / min, and a pre-carbonization time of 6 h, followed by natural cooling to room temperature to obtain a pre-carbonized product;

[0034] S3. The pre-carbonized product was uniformly mixed with four pore-forming agents, namely KOH, KHCO3, Li2CO3, and CaCO3, and ground. The weight ratio of the pre-carbonized product to the pore-forming agent was 1:0.3. High-temperature carbonization was then performed under an Ar atmosphere. The first stage carbonization temperature was 550°C for 7 hours, and the second stage carbonization temperature was 900°C for 2 hours. The product was then naturally cooled to room temperature to obtain a high-temperature carbonized product.

[0035] S4, washing the two-stage high-temperature carbonization product with hydrochloric acid and water until neutral to remove impurities in the material, filtering and drying to obtain a porous carbon material;

[0036] S5. The porous carbon material is uniformly mixed with acetylene black and polyvinylidene fluoride in a weight ratio of 1:0.1:0.1, water is added and stirred to obtain a lithium-ion battery carbon negative electrode slurry, and then the slurry is coated on the negative electrode collector, and the mixture is dried and cut into pieces to obtain a lithium-ion battery carbon negative electrode.

[0037] Example 2:

[0038] S1. Select the three residues of balsa wood (sawdust, bark and shavings, etc.) as biomass carbon source, wash them with deionized water to remove impurities on the surface, and dry and crush them to prepare the carbon source raw material of porous carbon negative electrode material;

[0039] S2. Pre-carbonizing the crushed carbon source raw material in an air atmosphere at a pre-carbonization temperature of 180° C., a heating rate of 5° C. / min, and a pre-carbonization time of 6 h, followed by natural cooling to room temperature to obtain a pre-carbonized product;

[0040] S3. The pre-carbonized product is uniformly mixed with KOH, KHCO3, Li2CO3 and CaCO3 pore-forming agents and ground. The weight ratio of the pre-carbonized product to the pore-forming agent is 1:0.2. Then, high-temperature carbonization is carried out under an Ar gas atmosphere. The first stage carbonization temperature is 650°C and the carbonization time is 7 hours. The second stage carbonization temperature is 800°C and the carbonization time is 2 hours. The product is naturally cooled to room temperature to obtain a high-temperature carbonized product.

[0041] S4, washing the two-stage high-temperature carbonization product with hydrochloric acid and water until neutral to remove impurities in the material, filtering and drying to obtain a porous carbon material;

[0042] S5. The porous carbon material is uniformly mixed with acetylene black and polyvinylidene fluoride in a weight ratio of 1:0.1:0.1, water is added and stirred to obtain a lithium-ion battery carbon negative electrode slurry, and then the slurry is coated on the negative electrode collector, and the mixture is dried and cut into pieces to obtain a lithium-ion battery carbon negative electrode.

[0043] Example 3:

[0044] S1. Select the three residues of balsa wood (sawdust, bark and shavings) as biomass carbon source, wash them with deionized water to remove impurities on the surface, and dry and crush them to prepare the carbon source raw material of porous carbon negative electrode material;

[0045] S2. Pre-carbonizing the crushed carbon source raw material in an air atmosphere at a pre-carbonization temperature of 180° C., a heating rate of 5° C. / min, and a pre-carbonization time of 6 h, followed by natural cooling to room temperature to obtain a pre-carbonized product;

[0046] S3. The pre-carbonized product was uniformly mixed with three pore-forming agents, KOH, KHCO3, and CaCO3, and ground. The weight ratio of the pre-carbonized product to the pore-forming agent was 1:0.3. Then, high-temperature carbonization was performed under an Ar gas atmosphere. The first stage carbonization temperature was 550°C and the carbonization time was 7 hours. The second stage carbonization temperature was 900°C and the carbonization time was 2 hours. The product was naturally cooled to room temperature to obtain a high-temperature carbonized product.

[0047] S4, washing the two-stage high-temperature carbonization product with hydrochloric acid and water until neutral to remove impurities in the material, filtering and drying to obtain a porous carbon material;

[0048] S5. The porous carbon material is uniformly mixed with acetylene black and polyvinylidene fluoride in a weight ratio of 1:0.1:0.1, water is added and stirred to obtain a lithium-ion battery carbon negative electrode slurry, and then the slurry is coated on the negative electrode collector, and the mixture is dried and cut into pieces to obtain a lithium-ion battery carbon negative electrode.

[0049] Example 4:

[0050] S1. Select the three residues of balsa wood (sawdust, bark and shavings) as biomass carbon source, wash them with deionized water to remove impurities on the surface, and dry and crush them to prepare the carbon source raw material of porous carbon negative electrode material;

[0051] S2. Pre-carbonizing the crushed carbon source raw material in an air atmosphere at a pre-carbonization temperature of 180° C., a heating rate of 5° C. / min, and a pre-carbonization time of 6 h, followed by natural cooling to room temperature to obtain a pre-carbonized product;

[0052] S3. The pre-carbonized product was uniformly mixed with three pore-forming agents, KOH, KHCO3, and CaCO3, and ground. The weight ratio of the pre-carbonized product to the pore-forming agent was 1:0.3. Then, high-temperature carbonization was performed under an Ar gas atmosphere. The first stage carbonization temperature was 550°C and the carbonization time was 7 hours. The second stage carbonization temperature was 900°C and the carbonization time was 2 hours. The product was naturally cooled to room temperature to obtain a high-temperature carbonized product.

[0053] S4, washing the two-stage high-temperature carbonization product with hydrochloric acid and water until neutral to remove impurities in the material, filtering and drying to obtain a porous carbon material;

[0054] S5. The porous carbon material is uniformly mixed with acetylene black and polyvinylidene fluoride in a weight ratio of 1:0.1:0.1, water is added and stirred to obtain a lithium-ion battery carbon negative electrode slurry, and then the slurry is coated on the negative electrode collector, and the mixture is dried and cut into pieces to obtain a lithium-ion battery carbon negative electrode.

[0055] In summary, this embodiment provides a lithium-ion battery half-cell. The prepared electrode sheets are compacted using a sheet press, a glass fiber disc with a diameter of 19 mm is used as the separator, and a 1 mol / L LiPF6 / EC / DMC / EMC electrolyte is used. A lithium sheet is used as the counter electrode, and a CR2032 button cell is assembled in a glove box with a high-purity argon atmosphere. The battery is left to stand for 5 hours and then charge and discharge tests are performed on a blue dot test platform using current densities of 100 mA / g and 500 mA / g.

[0056] Figure 1 (a) and (b) are the pore size distribution and isothermal adsorption curve of the porous carbon material prepared in Example 1 of the present invention. According to the BET test results, the specific surface area of ​​the prepared porous carbon material is as high as 2240m 2 / g or more; the porous carbon material is primarily composed of micropores smaller than 1 nanometer, which account for over 60% of the total pore volume. It also contains micropores of 1-2 nanometers, as well as mesopores of 2-3 nanometers and 4-6 nanometers, creating a porous carbon material with a multi-level micro- and mesoporous structure. The high micropore volume can accommodate more lithium ions, and the mesopores serve as diffusion channels for the rapid insertion and deinsertion of lithium ions.

[0057] Figure 2 shows the charge-discharge cycle curves of the negative electrode material prepared in Example 1 at current densities of 100 and 1000 mA / g, respectively. At a current density of 100 mA / g, the charge capacity reaches 600 mAh / g, and the capacity remains stable for 700 cycles with almost no capacity degradation. Even at a high current density of 1000 mA / g, the specific capacity remains as high as over 400 mAh / g, and the capacity retention rate remains above 90% after 2500 cycles, demonstrating excellent fast-charging potential and high cycling stability.

[0058] Figure 3 shows the charge-discharge cycle curves of the negative electrode material prepared in Example 2 at current densities of 100 and 500 mA / g, respectively. At a current density of 100 mA / g, the initial charge capacity reaches over 780 mAh / g, and after more than 200 cycles, the specific capacity can still be maintained at around 590 mAh / g. At a higher current density of 500 mA / g, the initial charge capacity reaches over 510 mAh / g, and after more than 1000 cycles, the specific capacity can still be maintained at around 500 mAh / g.

[0059] Figure 4 shows the negative electrode material prepared in Example 3, and Figure 3 shows the rate cycle curve and the corresponding charge and discharge curve of the negative electrode material prepared in Example 2. The specific capacities at current densities of 50, 100, 500, 1000, 2000, and 5000 mA / g are approximately 670 mAh / g, 560 mAh / g, 450 mAh / g, 320 mAh / g, 280 mAh / g, and 200 mAh / g, respectively. As the current density returns to 50 mA / g, the specific capacity approaches the initial specific capacity, showing excellent rate performance.

[0060] Figure 5 is a charge-discharge cycle curve of the negative electrode material prepared in Example 4. At a current density of 500 mA / g, the specific capacity of the negative electrode is as high as 400 mAh / g, which is significantly higher than the various commercial carbon-based negative electrode materials currently available. After 400 cycles, it still has a high specific capacity of 380 mAh / g, a capacity retention rate of more than 95%, and a coulombic efficiency of 100%, demonstrating excellent capacity and cycle stability.

[0061] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a carbon electrode material for a balsa wood biomass lithium battery, characterized in that: The following steps are involved: S1. Select balsa wood and its residues as biomass carbon sources, wash them to remove impurities on the surface, and dry and crush them as carbon source raw materials for preparing porous carbon negative electrode materials; S2, pre-carbonizing the crushed balsa wood, drying to remove moisture, and naturally cooling to room temperature to obtain a pre-carbonized product; S3, mixing the pre-carbonized product and the pore-forming agent uniformly and grinding, then transferring the material to a high-temperature tube furnace, carbonizing at high temperature under a two-stage temperature control in an atmosphere of N2 or Ar gas, and grinding after natural cooling; S4, washing the two-stage high-temperature carbonization product with acid and water until it is neutral, removing impurities in the material, filtering and drying, and obtaining a porous carbon material with a microporous and mesoporous multi-level pore structure; S5. The porous carbon material, the conductive agent and the binder are stirred and dispersed in a solvent to form a negative electrode slurry, and then the slurry is coated on the negative electrode current collector, and dried and cut into pieces to obtain a carbon negative electrode for a lithium-ion battery.

2. The method for preparing a balsa wood biomass lithium battery carbon electrode material according to claim 1, characterized in that: In S1, the three wastes are sawdust, bark and wood shavings.

3. The method for preparing a balsa wood biomass lithium battery carbon electrode material according to claim 1, characterized in that: In S2, the pre-carbonization temperature is 150-200°C, the heating rate is 5-10°C / min, and the pre-carbonization time is 4-10h.

4. The method for preparing a balsa wood biomass lithium battery carbon electrode material according to claim 1, characterized in that: In S3, the pore-forming agents used are two or more of KOH, KHCO3, Li2CO3, and CaCO3, and the weight ratio of the pre-carbonized product to the pore-forming agent is 1:0.1-0.

3.

5. The method for preparing a balsa wood biomass lithium battery carbon electrode material according to claim 1, characterized in that: In S3, the first stage carbonization temperature is 500-700°C, and the carbonization time is 6-10h; the second stage carbonization temperature is 800-1000°C, and the carbonization time is 1-4h.

6. The method for preparing a balsa wood biomass lithium battery carbon electrode material according to claim 1, characterized in that: In S4, the acid used in the pickling process is one or both of HCl and H3PO4.

7. The method for preparing a balsa wood biomass lithium battery carbon electrode material according to claim 1, characterized in that: In S5, the conductive agent and the binder are acetylene black and polyvinylidene fluoride, respectively, wherein the porous carbon material, acetylene black and polyvinylidene fluoride are uniformly mixed in a weight ratio of 1:0.05-0.1:0.05-0.

1.

8. The method for preparing a balsa wood biomass lithium battery carbon electrode material according to claim 1, characterized in that: In S5, the specific surface area of ​​the prepared porous carbon material is greater than 1800 m 2 / g, the pore size is mainly distributed between 0.1 and 6 nm, and the volume of micropores of 0.5-1 nm accounts for more than 50%.

9. The method for preparing a balsa wood biomass lithium battery carbon electrode material according to claim 1, characterized in that: The prepared lithium-ion battery carbon negative electrode has a lithium storage capacity of ≥400mAh / g, a charge and discharge rate of 0.1-3C, and a cycle life of more than 2000 times.

10. A balsa wood biomass lithium battery carbon electrode material, characterized in that: The carbon electrode material is prepared by the method for preparing the carbon electrode material of balsa wood biomass lithium battery according to claims 1 to 9.

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