Resin-based hard carbon material, method for preparing the same, and use thereof

Abstract

The application discloses a resin-based hard carbon material and a preparation method and application thereof, and belongs to the technical field of sodium batteries. In order to solve the problem of producing the hard carbon material by using the existing process, the application provides the resin-based hard carbon material, which is prepared by mixing resin prepolymers, a crosslinking agent and a foaming agent in proportion, crosslinking and foaming at 130-250 DEG C first, then pre-carbonizing at 300-650 DEG C, further high-temperature carbonizing at 1000-1600 DEG C, and finally crushing, removing magnetism and grading. In the application, the foaming agent is introduced in the crosslinking and solidification, and the foaming and crosslinking and solidification are simultaneously performed in the heating and solidification process, so that the resin material prepolymers with continuous porous structures are formed, the gas produced in the carbonization process can be uniformly and sufficiently decomposed, and therefore the high-quality and uniform hard carbon product is obtained, and the first efficiency and capacity of the obtained hard carbon are obviously improved. Meanwhile, the crushing is performed after the carbonization, the process steps are simplified, and the operation difficulty and cost are reduced.

Description

Technical Field

[0001] This invention belongs to the field of sodium battery technology, specifically relating to a resin-based hard carbon material, its preparation method, and its application. Background Technology

[0002] Due to the high and volatile price of lithium salts, and the uneven distribution of lithium resources, primarily concentrated in South America, hard carbon is one of the few sodium-ion battery anode materials currently in mass production. It boasts advantages such as high capacity and a low voltage plateau. Depending on the type of raw material, hard carbon can be categorized into biomass-based hard carbon, pitch-based hard carbon, and resin-based hard carbon. Among these, resin-based hard carbon offers advantages such as high carbon yield, good consistency, and excellent electrochemical performance.

[0003] Resin-based hard carbon typically requires thermosetting polymers, and there are two main preparation routes depending on the cured state. First, the cured resin is in block form. To ensure smooth diffusion of the gas produced by resin decomposition during subsequent carbonization processes, thus guaranteeing uniform carbonization and product homogeneity, the resin needs to be broken up after further curing. CN202211247384.8 discloses a hard carbon material that provides phenolic resin and obtains resin pyrolysis carbon through carbonization pyrolysis. The resin pyrolysis carbon is then mixed with hexamethylenetetramine to obtain a blend, which is then pyrolyzed and coated to obtain the hard carbon material. However, the cured crosslinked resin has high strength, making it difficult to break up, resulting in significant equipment wear, easy introduction of impurities, and a long processing time. CN202310482383.X discloses a hard carbon anode material, the preparation method of which includes: step 1, pulverizing phenolic resin foam material; step 2, high-temperature carbonization under an inert atmosphere; step 3, CO2-CO mixed gas pore adjustment: after high-temperature carbonization, a CO2-CO mixed gas is introduced into the furnace lining to adjust the pores of the hard carbon precursor; step 4, carbon deposition: the pore-adjusted hard carbon precursor is placed in the converter furnace lining, and a pore-blocking agent is introduced under nitrogen protection while maintaining the furnace temperature at 300-400℃ for adsorption; then, the pore-blocking agent adsorbed on the carbon material is decomposed at 800-950℃, thereby depositing pyrolytic carbon on the hard carbon material. This method essentially involves first solidifying and crushing, then carbonizing, which also suffers from problems such as high crushing difficulty. Furthermore, the pore structure of its phenolic foam material is a closed-cell structure, which is discontinuous and cannot provide a pathway for gas diffusion.

[0004] Secondly, the cured resin is in powder form, which allows for direct carbonization. However, sol-gel or hydrothermal methods are typically required to obtain the cured resin powder. CN201611136195.8 discloses a novel method for preparing hard carbon, comprising: performing a polycondensation reaction on phenolic and aldehyde monomers and obtaining a phenolic resin precursor using a co-precipitation method; subjecting the phenolic resin precursor to a hydrothermal reaction to obtain phenolic resin; centrifuging and washing the phenolic resin; freeze-drying the phenolic resin to obtain phenolic resin powder; sintering the phenolic resin powder to obtain hard carbon with a uniform spherical structure; and performing chemical vapor deposition on the spherical hard carbon at 800℃ to obtain hard carbon with a uniform surface. However, this method suffers from drawbacks such as difficult separation, low yield, and high cost, making it unsuitable for large-scale production.

[0005] Therefore, there is a need to develop an efficient method for producing resin-based hard carbon. Summary of the Invention

[0006] To address the problems in the production of hard carbon materials using existing processes, this invention introduces a foaming agent into the crosslinking and curing process. During the heating and curing process, foaming occurs simultaneously, forming a resin material prepolymer with a continuous porous structure. This continuous porous structure ensures that the decomposition and gas generation during carbonization can proceed uniformly and fully, thereby obtaining a high-quality hard carbon product with good uniformity.

[0007] This invention provides a method for preparing a resin-based hard carbon material, comprising the following steps:

[0008] A. Mix the resin prepolymer, crosslinking agent, and foaming agent in a certain proportion to obtain a mixture;

[0009] B. Inert gas is introduced, and the mixture is cross-linked and foamed at 130-250°C to form a cured resin with a continuous porous structure.

[0010] C. After cross-linking and foaming, the temperature is raised to 300-650℃ for pre-carbonization;

[0011] D. After pre-carbonization, continue to raise the temperature to 1000-1600℃ for high-temperature carbonization to obtain carbonized products;

[0012] E. The carbonization products are crushed, demagnetized, and graded to obtain resin-based hard carbon materials.

[0013] In the preparation method of the above-mentioned resin-based hard carbon material, in step A, the resin prepolymer is selected from phenolic resin prepolymer, epoxy resin prepolymer or unsaturated polyester resin prepolymer.

[0014] In the preparation method of the above-mentioned resin-based hard carbon material, in step A, when the resin prepolymer is a phenolic resin prepolymer, the crosslinking agent is at least one of formaldehyde, hexamethylenetetramine, or NL-type curing agent; when the resin prepolymer is an epoxy resin prepolymer, the crosslinking agent is at least one of ethylenediamine, m-phenylenediamine, phenylenediamine, polyamide, maleic anhydride, or phthalic anhydride; when the resin prepolymer is an unsaturated polyester resin prepolymer, the crosslinking agent is at least one of benzoyl peroxide, tert-butyl peroxide, dimeryl diisopropanol, dimeryl propanol, maleic anhydride, or phthalic anhydride.

[0015] In the preparation method of the above-mentioned resin-based hard carbon material, in step A, the amount of crosslinking agent is 4 to 14 wt% of the resin prepolymer.

[0016] In the preparation method of the above-mentioned resin-based hard carbon material, in step A, the foaming agent is at least one of sodium bicarbonate, ammonium bicarbonate, dinitrosopeptimethylenetetramine, 4,4'-oxobis(benzenesulfonylhydrazine), p-toluenesulfonylhydrazine, benzenesulfonylhydrazine, 3,3'-disulfonylhydrazine diphenyl sulfone, azobisisobutyronitrile, and azodicarbonamide.

[0017] In the preparation method of the above-mentioned resin-based hard carbon material, in step A, the amount of foaming agent is 4 to 12 wt% of the resin prepolymer.

[0018] In the preparation method of the above-mentioned resin-based hard carbon material, step B involves crosslinking and foaming at 130–250°C for 0.5–1.5 hours.

[0019] In the preparation method of the above-mentioned resin-based hard carbon material, step C involves pre-carbonization at 300–650°C for 1–3 hours.

[0020] In the preparation method of the above-mentioned resin-based hard carbon material, step D involves high-temperature carbonization at 1000–1600°C for 1–3 hours.

[0021] In the preparation method of the above-mentioned resin-based hard carbon material, steps B to D are all carried out under the introduction of an inert gas, and the flow rate of the inert gas is 40 to 200 ml / min.

[0022] In the above-mentioned method for preparing resin-based hard carbon materials, in step E, the D of the obtained resin-based hard carbon material... 50 It is 4 to 15 micrometers in size.

[0023] The present invention also provides a resin-based hard carbon material, which is prepared by the above method.

[0024] The present invention also provides the application of the above-mentioned resin-based hard carbon material in sodium-ion batteries.

[0025] The beneficial effects of this invention are:

[0026] Before carbonization, this invention introduces a crosslinking agent and a foaming agent to simultaneously foam and crosslink, forming a resin with a continuous porous structure. This ensures that the gases generated during carbonization can diffuse smoothly, resulting in high-performance products with good uniformity in large-scale production. The initial efficiency and capacity of the hard carbon are significantly improved. At the same time, the resin with a continuous porous structure is more conducive to crushing after carbonization, simplifying the process steps and reducing the difficulty of crushing. This invention can complete the entire heating process in one heating device, simplifying the preparation process and reducing the difficulty and cost of operation. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation process of the resin-based hard carbon of the present invention.

[0028] Figure 2 This is a SEM image of the resin-based hard carbon of this invention.

[0029] Figure 3 The XRD pattern of the resin-based hard carbon of this invention is shown.

[0030] Figure 4 This is the first charge-discharge curve of the resin-based hard carbon of this invention. Detailed Implementation

[0031] Specifically, a method for preparing a resin-based hard carbon material includes the following steps:

[0032] A. Mix the resin prepolymer, crosslinking agent, and foaming agent in a certain proportion to obtain a mixture;

[0033] B. Inert gas is introduced, and the mixture is cross-linked and foamed at 130-250°C to form a cured resin with a continuous porous structure.

[0034] C. After cross-linking and foaming, the temperature is raised to 300-650℃ for pre-carbonization;

[0035] D. After pre-carbonization, continue to raise the temperature to 1000-1600℃ for high-temperature carbonization to obtain carbonized products;

[0036] E. The carbonization products are crushed, demagnetized, and graded to obtain resin-based hard carbon materials.

[0037] Before carbonization, this invention mixes a resin prepolymer with a crosslinking agent and a foaming agent to achieve simultaneous foaming and crosslinking curing, forming a resin with a continuous porous structure. This ensures that the gases generated during carbonization can diffuse smoothly, thereby obtaining a high-performance product with good uniformity in large-scale production. In step A, the resin prepolymer is selected from phenolic resin prepolymers, epoxy resin prepolymers, or unsaturated polyester resin prepolymers.

[0038] Studies have found that different types of resin prepolymers require different types of curing agents to form a continuous porous structure. Therefore, in step A of this invention, when the resin prepolymer is a phenolic resin prepolymer, the crosslinking agent is at least one of formaldehyde, hexamethylenetetramine, or an NL-type curing agent; when the resin prepolymer is an epoxy resin prepolymer, the crosslinking agent is at least one of ethylenediamine, m-phenylenediamine, phenylenediamine, polyamide, maleic anhydride, or phthalic anhydride; when the resin prepolymer is an unsaturated polyester resin prepolymer, the crosslinking agent is at least one of benzoyl peroxide, tert-butyl peroxide, dimeryl diisopropanol, dimeryl propanol, maleic anhydride, or phthalic anhydride.

[0039] In this invention, to ensure simultaneous foaming and crosslinking, a thermally decomposable foaming agent is required, and the thermal decomposition temperature should be less than or equal to the crosslinking temperature (130–250°C). Through testing, commonly used thermally decomposable foaming agents that meet this condition include: sodium bicarbonate, ammonium bicarbonate, dinitrosopeptimethylenetetramine, 4,4'-oxobis(benzenesulfonylhydrazine), p-toluenesulfonylhydrazine, benzenesulfonylhydrazine, 3,3'-disulfonylhydrazine diphenyl sulfone, azobisisobutyronitrile, and azodicarbonamide. Therefore, in step A, the foaming agent is at least one of sodium bicarbonate, ammonium bicarbonate, dinitrosopeptimethylenetetramine, 4,4'-oxobis(benzenesulfonylhydrazine), p-toluenesulfonylhydrazine, benzenesulfonylhydrazine, 3,3'-disulfonylhydrazine diphenyl sulfone, azobisisobutyronitrile, and azodicarbonamide.

[0040] In step A of this invention, the amount of the crosslinking agent is 4 to 14 wt% of the resin prepolymer.

[0041] Experiments showed that when the amount of foaming agent was less than 4 wt%, it was difficult to obtain a continuous porous structure; while when the amount of foaming agent was greater than 12 wt%, it led to over-foaming, severe volume expansion, and the product easily adhered to the furnace wall, causing excessive carbonization of some products and equipment contamination. Therefore, this invention controls the amount of foaming agent to be 4-12 wt% of the resin prepolymer.

[0042] The production of hard carbon requires the use of cross-linked polymers; otherwise, only soft carbon products can be obtained. Therefore, in step B of this invention, cross-linking and foaming are carried out first at 130–250°C for 0.5–1.5 hours to form a resin with a continuous porous structure. If the temperature is directly raised to a higher pre-carbonization temperature, the product yield and performance will decrease.

[0043] In step C of this invention, pre-carbonization is carried out by holding at 300-650°C for 1-3 hours.

[0044] In step D of this invention, high-temperature carbonization is carried out by holding the temperature at 1000-1600℃ for 1-3 hours.

[0045] In steps B to D of this invention, the inert gas can be common nitrogen, argon, etc., and the flow rate of the inert gas is controlled to be 40-200 ml / min. Using a flowing atmosphere serves two purposes: first, it prevents oxygen from entering and ensures that the reaction always takes place under an inert atmosphere; second, it allows the gases produced by the reaction to be discharged in a timely manner, which is more conducive to the formation of a continuous porous structure.

[0046] In step E of this invention, the carbonization product is crushed, demagnetized, and graded to obtain resin-based hard carbon material; gold impurities are removed by demagnetization to ensure purity for later use as battery material, and the D of the obtained resin-based hard carbon material is controlled. 50 It is 4 to 15 micrometers in size.

[0047] The present invention also provides a resin-based hard carbon material, which is prepared by the above method.

[0048] The present invention also provides the application of the above-mentioned resin-based hard carbon material in sodium-ion batteries.

[0049] The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described herein.

[0050] Example 1

[0051] Step 1: Mix 100g of phenolic resin prepolymer, 8g of azodicarbonamide and 10g of NL type curing agent thoroughly.

[0052] Step 2: Transfer the mixture to a tube furnace, purge with nitrogen gas at a flow rate of 100 ml / min, heat to 200°C, and hold for 1 hour to perform crosslinking and foaming.

[0053] Step 3: Raise the temperature to 600℃ and hold for 1.5 hours for pre-carbonization.

[0054] Step 4: Raise the temperature to 1200℃ and hold for 2 hours for high-temperature carbonization.

[0055] Step 5: Mechanically crush the carbonized products, demagnetize and classify the powder particles to make the D50 of the hard carbon powder within 4-15 micrometers.

[0056] Example 2

[0057] Step 1: Mix 100g of phenolic resin prepolymer, 8g of azodicarbonamide and 10g of NL type curing agent thoroughly.

[0058] Step 2: Transfer the mixture to a tube furnace, purge with nitrogen gas at a flow rate of 100 ml / min, heat to 200°C, and hold for 1 hour to perform crosslinking and foaming.

[0059] Step 3: Raise the temperature to 600℃ and hold for 1.5 hours for pre-carbonization.

[0060] Step 4: Raise the temperature to 1400℃ and hold for 2 hours for high-temperature carbonization.

[0061] Step 5: Mechanically crush the carbonized products, demagnetize and classify the powder particles to make the D50 of the hard carbon powder within 4-15 micrometers.

[0062] Example 3

[0063] Step 1: Mix 100g of phenolic resin prepolymer, 8g of azodicarbonamide and 10g of NL type curing agent thoroughly.

[0064] Step 2: Transfer the mixture to a tube furnace, purge with nitrogen gas at a flow rate of 100 ml / min, heat to 200°C, and hold for 1 hour to perform crosslinking and foaming.

[0065] Step 3: Raise the temperature to 600℃ and hold for 1.5 hours for pre-carbonization.

[0066] Step 4: Raise the temperature to 1600℃ and hold for 2 hours for high-temperature carbonization.

[0067] Step 5: Mechanically crush the carbonization products, demagnetize and classify the powder particles, and reduce the D of the hard carbon powder. 50 Within 4-15 micrometers.

[0068] Example 4

[0069] Step 1: Mix 100g of epoxy resin prepolymer, 8g of benzenesulfonyl hydrazine and 10g of ethylenediamine thoroughly.

[0070] Step 2: Transfer the mixture to a tube furnace, purge with nitrogen gas at a flow rate of 100 ml / min, heat to 180°C, and hold for 1 hour to perform crosslinking and foaming.

[0071] Step 3: Raise the temperature to 600℃ and hold for 1.5 hours for pre-carbonization.

[0072] Step 4: Raise the temperature to 1400℃ and hold for 2 hours for high-temperature carbonization.

[0073] Step 5: Mechanically crush the carbonization products, demagnetize and classify the powder particles, and reduce the D of the hard carbon powder. 50 Within 4-15 micrometers.

[0074] Example 5

[0075] Step 1: Mix 100g of epoxy resin prepolymer, 10g of benzenesulfonyl hydrazine and 6g of ethylenediamine thoroughly.

[0076] Step 2: Transfer the mixture to a tube furnace, purge with nitrogen gas at a flow rate of 100 ml / min, heat to 180°C, and hold for 1 hour to perform crosslinking and foaming.

[0077] Step 3: Raise the temperature to 400℃ and hold for 1.5 hours for pre-carbonization.

[0078] Step 4: Raise the temperature to 1400℃ and hold for 2 hours for high-temperature carbonization.

[0079] Step 5: Mechanically crush the carbonization products, demagnetize and classify the powder particles, and reduce the D of the hard carbon powder. 50 Within 4-15 micrometers.

[0080] Example 6

[0081] Step 1: Mix 100g of epoxy resin prepolymer, 10g of benzenesulfonyl hydrazine and 6g of ethylenediamine thoroughly.

[0082] Step 2: Transfer the mixture to a tube furnace, purge with nitrogen gas at a flow rate of 100 ml / min, heat to 180°C, and hold for 1 hour to perform crosslinking and foaming.

[0083] Step 3: Raise the temperature to 500℃ and hold for 1.5 hours for pre-carbonization.

[0084] Step 4: Raise the temperature to 1400℃ and hold for 2 hours for high-temperature carbonization.

[0085] Step 5: Mechanically crush the carbonization products, demagnetize and classify the powder particles, and reduce the D of the hard carbon powder. 50 Within 4-15 micrometers.

[0086] Comparative Example 1

[0087] The preparation process is basically the same as in Example 1, except that the foaming agent azodicarbonamide is not added in step 1.

[0088] Comparative Example 2

[0089] The preparation process is basically the same as in Example 4, except that the foaming agent benzyl sulfonyl hydrazine is not added in step 1.

[0090] Electrochemical performance testing:

[0091] All samples underwent electrochemical performance testing using half-cell methods. Hard carbon, Super-P, sodium carboxymethyl cellulose, and styrene-butadiene rubber were homogenized for 30 minutes at ratios of 92%, 3%, 1.5%, and 3.5% respectively to obtain a uniform electrode slurry. This slurry was then coated with aluminum foil as the current collector to a thickness of 100 micrometers. Finally, it was vacuum dried at 80°C for 12 hours to obtain the electrode sheet. A sodium sheet was used as the counter electrode, 1M sodium hexafluorophosphate (solvents being ethylene carbonate and diethyl carbonate) as the electrolyte, and a glass fiber membrane as the separator to assemble a coin cell.

[0092] Table 1 Electrochemical performance test results

[0093]

[0094]

[0095] As can be seen from the test data in Table 1, after the introduction of the foaming agent, the initial efficiency and capacity of the hard carbon obtained are significantly improved due to the full diffusion of the decomposition gas, which has great commercial value.

Claims

1. A method for preparing resin-based hard carbon materials, characterized in that: Includes the following steps: A. Mix the resin prepolymer, crosslinking agent, and foaming agent in a certain proportion to obtain a mixture; B. Inert gas is introduced, and the mixture is cross-linked and foamed at 130~250℃ to form a cured resin with a continuous porous structure. C. After cross-linking and foaming, the temperature is raised to 300~650℃ for pre-carbonization; D. After pre-carbonization, continue to raise the temperature to 1000~1600℃ for high-temperature carbonization to obtain carbonized products; E. The carbonization products are crushed, demagnetized and graded to obtain resin-based hard carbon materials. In step A, the resin prepolymer is selected from phenolic resin prepolymer, epoxy resin prepolymer, or unsaturated polyester resin prepolymer; In step A, when the resin prepolymer is a phenolic resin prepolymer, the crosslinking agent is at least one of formaldehyde, hexamethylenetetramine, or NL-type curing agent; when the resin prepolymer is an epoxy resin prepolymer, the crosslinking agent is at least one of ethylenediamine, m-phenylenediamine, phenylenediamine, polyamide, maleic anhydride, or phthalic anhydride; when the resin prepolymer is an unsaturated polyester resin prepolymer, the crosslinking agent is at least one of benzoyl peroxide, dimeryl diisopropanol, dimeryl propanol, maleic anhydride, or phthalic anhydride. In step A, the amount of crosslinking agent used is 4-14 wt% of the resin prepolymer; In step A, the foaming agent is at least one of sodium bicarbonate, ammonium bicarbonate, dinitrosopeptimide, 4,4'-oxobis(benzenesulfonylhydrazine), p-toluenesulfonylhydrazine, benzenesulfonylhydrazine, 3,3'-disulfonylhydrazine diphenyl sulfone, azobisisobutyronitrile, and azodicarbonamide. In step A, the amount of foaming agent used is 4 to 12 wt% of the resin prepolymer.

2. The method for preparing resin-based hard carbon material according to claim 1, characterized in that: In step B, cross-linking and foaming are carried out by holding the temperature at 130~250℃ for 0.5~1.5 hours.

3. The method for preparing resin-based hard carbon material according to claim 1, characterized in that: In step C, pre-carbonization is carried out by holding the temperature at 300~650℃ for 1~3 hours.

4. The method for preparing resin-based hard carbon material according to claim 1, characterized in that: In step D, high-temperature carbonization is carried out by holding the temperature at 1000~1600℃ for 1~3 hours.

5. The method for preparing resin-based hard carbon material according to claim 1, characterized in that: Steps B through D are all carried out under the influence of an inert gas, with a flow rate of 40 to 200 ml / min.

6. The method for preparing the resin-based hard carbon material according to any one of claims 1 to 5, characterized in that: In step E, the D of the obtained resin-based hard carbon material 50 It is 4~15 micrometers in size.

7. The resin-based hard carbon material prepared by the method according to any one of claims 1 to 6.

8. The application of the resin-based hard carbon material of claim 7 in sodium-ion batteries.

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