Preparation method of phosphorus modified hard carbon material and application thereof
By introducing tetraethylphosphine hydroxide during the synthesis of phenolic resin and employing low-temperature crosslinking and multi-stage calcination processes, the prepared phosphorus-modified hard carbon material solves the problems of low specific capacity and low initial efficiency of hard carbon anode materials, achieving high specific capacity and good cycle performance, and is suitable for sodium-ion battery anode materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YANTAI ADVANCED MATERIALS & GREEN MFG SHANDONG PROVINCIAL LAB
- Filing Date
- 2023-11-28
- Publication Date
- 2026-07-03
AI Technical Summary
Existing hard carbon anode materials have low specific capacity and initial efficiency, and insufficient cycle performance, making it difficult to meet the high-performance requirements of sodium-ion batteries.
Phosphorus-modified hard carbon materials were prepared by introducing tetraethylphosphine hydroxide during the synthesis of phenolic resin. Low-temperature crosslinking and multi-stage calcination processes were used to form a spatial network structure and uniform doping, thereby improving the interlayer spacing and specific surface area.
The prepared phosphorus-modified hard carbon material has a specific capacity of over 350 mAh/g, an initial efficiency of over 90%, and can still maintain over 90% of its specific capacity after 1000 cycles, demonstrating excellent electrochemical performance.
Abstract
Description
Technical Field
[0001] This application relates to a method for preparing phosphorus-modified hard carbon materials and their applications. Background Technology
[0002] Sodium-ion batteries have advantages such as abundant reserves, low cost of large-scale production, and high safety, and have broad application prospects in fields such as two-wheeled vehicles and energy storage systems.
[0003] Compared to lithium ions, sodium ions have a larger radius, therefore traditional graphite anode materials for lithium batteries (interlayer spacing of 0.334 nm) cannot be directly used in sodium-ion batteries. Compared to graphite, hard carbon possesses short-range ordered, isotropic structural characteristics and a larger interlayer spacing, allowing for the free insertion and extraction of sodium ions between layers. Furthermore, hard carbon materials also exhibit better cycle performance and rate capability, as well as lower cost. Therefore, hard carbon anode materials are considered highly promising anode materials for the commercialization of sodium-ion batteries.
[0004] Currently, the specific capacity of hard carbon anode materials is generally around 300 mAh / g, and the initial efficiency is around 85%. Therefore, how to develop hard carbon anode materials for sodium-ion batteries with high specific capacity, high initial efficiency, and excellent cycle performance is a technical problem that urgently needs to be solved. Summary of the Invention
[0005] To address the aforementioned problems, this application proposes a method for preparing phosphorus-modified hard carbon materials, comprising the following steps:
[0006] Starch was added to the carbon source mixture to obtain a composite carbon source precursor;
[0007] Tetraethylphosphine hydroxide was introduced into the above precursor and then cured.
[0008] The intermediate product can be obtained by cross-linking the precursor at low temperature.
[0009] The intermediate product was ball-milled and sieved to obtain primary particles;
[0010] Phosphorus-modified hard carbon material is obtained by high-temperature carbonization of primary particles. Introducing starch into the synthesis process of phenolic resin, followed by low-temperature cross-linking treatment, promotes the hydroxyl reaction of starch molecules, thereby cross-linking multiple starch molecules to form a three-dimensional network structure. This avoids the expansion and foaming phenomenon of starch during calcination, improves carbon yield, and results in a smaller specific surface area of the hard carbon material, ranging from 3-5 m². 2 / g.
[0011] Preferably, the carbon source is a phenolic resin.
[0012] Preferably, the starch is ball-milled to obtain starch with a particle size of less than 100 μm, which is then dispersed into a carbon source.
[0013] Preferably, the precursor is obtained according to the following method:
[0014] Phenol and deionized water are mixed to obtain a mixed solution at 65-70℃;
[0015] Add starch and tetraethylphosphine hydroxide to the mixed solution, stir continuously, and heat at 65-70℃ for no less than 3 hours;
[0016] A starch mixture is added to a formaldehyde solution, controlling the molar ratio of phenol to formaldehyde at 1:(1.5-2), and subjected to a first heating and reflux reaction. Then, ammonia water is added, with the amount of ammonia water being 5-10% of the phenol mass, and subjected to a second heating and reflux reaction. Finally, a curing reaction is carried out to obtain a hard carbon precursor. This application achieves uniform phosphorus distribution in the carbon precursor by introducing an organophosphorus source during the synthesis of phenolic resin. Through a multi-stage calcination method, effective bonding and uniform doping of phosphorus with the hard carbon material can be achieved, resulting in a larger interlayer spacing in the prepared hard carbon material. 002 Above 0.40nm.
[0017] Preferably, the mass ratio of starch, deionized water, phenol and tetraethylphosphine hydroxide is (0.5-2):(3-5):1:(0.1-0.2).
[0018] Preferably, the temperature of the first heating and reflow is 65-70℃ and the time is 10-20 min; the temperature of the second heating and reflow is 65-70℃ and the time is 1.5-2 h; and the temperature of the curing reaction is 150-180℃ and the time is 0.5-2 h.
[0019] Preferably, the low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 80-100℃ for 20-30 minutes; then the temperature is raised to 150-250℃ and maintained for 2-10 hours, thus completing the low-temperature crosslinking treatment.
[0020] Preferably, the intermediate product is ball-milled to obtain primary particles with a particle size of less than 100 μm.
[0021] Preferably, the primary particles are carbonized at high temperature in the following manner:
[0022] The primary particles were treated in a CH4 atmosphere of 60-120 L / h at 500-700℃ for 1-5 h to finally obtain phosphorus-modified hard carbon materials.
[0023] On the other hand, this application also discloses the application of phosphorus-modified hard carbon materials in sodium-ion battery anode materials. The phosphorus-modified hard carbon anode material prepared in this application has a specific capacity of over 350 mAh / g, an initial efficiency of over 90%, and can maintain over 90% of its specific capacity after 1000 cycles, making it a sodium-ion battery anode material with excellent electrochemical performance.
[0024] This application can bring the following beneficial effects:
[0025] 1. This application introduces starch into the synthesis process of phenolic resin. After low-temperature cross-linking treatment, it can promote the hydroxyl reaction of starch molecules, thereby cross-linking multiple starch molecules to form a three-dimensional network structure. This avoids the expansion and foaming phenomenon of starch during calcination, improves carbon yield, and at the same time makes the specific surface area of the hard carbon material smaller, with a specific surface area of 3-5m². 2 / g.
[0026] 2. This application achieves uniform phosphorus distribution in the carbon precursor by introducing an organophosphorus source during the synthesis of phenolic resin. Through multi-stage calcination, effective bonding and uniform doping of phosphorus with hard carbon materials can be achieved, resulting in a larger interlayer spacing in the prepared hard carbon material. 002 Above 0.40nm.
[0027] 3. The phosphorus-modified hard carbon anode material prepared in this application has a specific capacity of over 350 mAh / g, an initial efficiency of over 90%, and can still maintain over 90% of its specific capacity after 1000 cycles. It is a sodium-ion battery anode material with excellent electrochemical performance. Detailed Implementation
[0028] To clearly illustrate the technical features of this solution, the following detailed description of specific implementation methods will be provided.
[0029] This application discloses a method for preparing phosphorus-modified hard carbon material, comprising the following steps:
[0030] S1 adds starch to a carbon source mixture to obtain a composite carbon source precursor, introduces tetraethylphosphine hydroxide into the precursor, and then cures it; the carbon source is phenolic resin.
[0031] S11 involves ball milling starch to obtain starch particles smaller than 100 μm, which are then dispersed into a carbon source.
[0032] S12 involves mixing phenol and deionized water to obtain a mixed solution at 65-70℃;
[0033] Add starch and tetraethylphosphine hydroxide to the mixed solution, stir continuously, and heat at 65-70℃ for no less than 3 hours;
[0034] S13 involves adding a starch mixture to a formaldehyde solution, controlling the molar ratio of phenol to formaldehyde at 1:(1.5-2), and performing a first reflux reaction. Then, ammonia water is added, with the amount of ammonia water being 5-10% of the phenol mass, and a second reflux reaction is performed. Finally, a curing reaction is carried out to obtain a hard carbon precursor. The mass ratio of starch, deionized water, phenol, and tetraethylphosphine hydroxide is (0.5-2):(3-5):1:(0.1-0.2). The first reflux reaction is performed at 65-70℃ for 10-20 min; the second reflux reaction is performed at 65-70℃ for 1.5-2 h; and the curing reaction is performed at 150-180℃ for 0.5-2 h.
[0035] S2 cross-links the precursor at low temperature to obtain the intermediate product;
[0036] The low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 80-100℃ for 20-30 minutes; then the temperature is raised to 150-250℃ and maintained for 2-10 hours, thus completing the low-temperature crosslinking treatment.
[0037] S3 ball mills and sieves the intermediate product to obtain primary particles;
[0038] The intermediate product was ball-milled to obtain primary particles with a particle size of less than 100 μm.
[0039] S4 is a phosphorus-modified hard carbon material obtained by high-temperature carbonization of primary particles.
[0040] The primary particles were treated in a CH4 atmosphere of 60-120 L / h at 500-700℃ for 1-5 h to finally obtain phosphorus-modified hard carbon materials.
[0041] Application of phosphorus-modified hard carbon materials in sodium-ion battery anode materials. The phosphorus-modified hard carbon anode material prepared in this application has a specific surface area of 3-5 m². 2 / g,d 002 Above 0.40 nm, this material was used as the negative electrode active material, mixed uniformly with conductive carbon black and binder in a mass ratio of 92:4:4, coated into an electrode film, and dried in a vacuum drying oven at 120℃ for 12 hours. After rolling and punching, a sodium-ion battery negative electrode sheet was obtained. Using a metallic sodium sheet as the counter electrode and 1 mol / L NaPF6 (EC:DEC = 1:1) as the electrolyte, the obtained sodium-ion battery negative electrode sheet was assembled into a button cell in a glove box, and its electrochemical performance was tested. The specific capacity was above 350 mAh / g, the initial efficiency was above 90%, and the specific capacity could still be maintained above 90% after 1000 cycles, making it a sodium-ion battery negative electrode material with excellent electrochemical performance.
[0042] To characterize the material properties of this application, the following comparative examples and embodiments are provided.
[0043] Example 1:
[0044] S101 involves adding starch to a carbon source mixture to obtain a composite carbon source precursor, introducing tetraethylphosphine hydroxide into the precursor, and then curing it; the carbon source is phenolic resin.
[0045] S111 ball mills starch to obtain starch with a particle size of less than 100 μm, which is then dispersed into a carbon source.
[0046] S112 mixes phenol and deionized water to obtain a mixed solution at 65°C;
[0047] Starch and tetraethylphosphine hydroxide were added to the mixed solution, and the mixture was stirred continuously. The temperature was 65°C and the time was 4 hours.
[0048] S113 involves adding a starch mixture to a formaldehyde solution, controlling the molar ratio of phenol to formaldehyde at 1:1.5, and performing a first reflux reaction. Then, ammonia water is added, at an amount equal to 5% of the phenol mass, and a second reflux reaction is performed. Finally, a curing reaction is carried out to obtain a hard carbon precursor. The mass ratio of starch, deionized water, phenol, and tetraethylphosphine hydroxide is 0.5:3:1:0.1. The first reflux reaction is performed at 65°C for 20 minutes; the second reflux reaction is performed at 65°C for 2 hours; and the curing reaction is performed at 150°C for 2 hours.
[0049] S102 involves low-temperature cross-linking of the precursor to obtain the intermediate product;
[0050] The low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 80°C for 30 minutes; then the temperature is raised to 150°C and maintained for 10 hours, thus completing the low-temperature crosslinking treatment.
[0051] S103 ball mills and sieves the intermediate product to obtain primary particles;
[0052] The intermediate product was ball-milled to obtain primary particles with a particle size of less than 100 μm.
[0053] S104 is used to carbonize the primary particles at high temperature to obtain material No. 1.
[0054] The primary particles were treated at 700℃ for 1 hour in a CH4 atmosphere with a flow rate of 60 L / h to obtain material No. 1.
[0055] The specific surface area of No. 1 prepared in this application is 3.1 m². 2 / g,d 002The nanometer diameter is 0.41 nm. Using this material as the negative electrode active material, it is mixed uniformly with conductive carbon black and binder in a mass ratio of 92:4:4, coated into an electrode film, and dried in a vacuum drying oven at 120℃ for 12 hours. After rolling and punching, a sodium-ion battery negative electrode sheet is obtained. Using a metallic sodium sheet as the counter electrode and 1 mol / L NaPF6 (EC:DEC = 1:1) as the electrolyte, the obtained sodium-ion battery negative electrode sheet is assembled into a button cell in a glove box, and its electrochemical performance is tested. The specific capacity is 358 mAh / g, the initial efficiency is 96.7%, and the cycle efficiency is 95.8% after 1000 cycles.
[0056] Example 2:
[0057] S201 involves adding starch to a carbon source mixture to obtain a composite carbon source precursor, introducing tetraethylphosphine hydroxide into the precursor, and then curing it; the carbon source is phenolic resin.
[0058] S211 ball mills starch to obtain starch with a particle size of less than 100 μm, which is then dispersed into a carbon source.
[0059] S212 mixes phenol and deionized water to obtain a mixed solution at 70°C;
[0060] Starch and tetraethylphosphine hydroxide were added to the mixed solution, and the mixture was stirred continuously. The temperature was 70°C and the time was 3 hours.
[0061] S213 involves adding a starch mixture to a formaldehyde solution, controlling the molar ratio of phenol to formaldehyde at 1:2, and performing a first reflux reaction. Then, ammonia water is added, with the amount of ammonia water being 10% of the mass of phenol, and a second reflux reaction is performed. Finally, a curing reaction is carried out to obtain a hard carbon precursor. The mass ratio of starch, deionized water, phenol, and tetraethylphosphine hydroxide is 2:5:1:0.2. The first reflux reaction is performed at 70°C for 10 minutes; the second reflux reaction is performed at 70°C for 1.5 hours; and the curing reaction is performed at 180°C for 0.5 hours.
[0062] S202 cross-links the precursor at low temperature to obtain the intermediate product;
[0063] The low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 100°C for 20 minutes; then the temperature is raised to 250°C and maintained for 2 hours, thus completing the low-temperature crosslinking treatment.
[0064] S203 ball mills and sieves the intermediate product to obtain primary particles;
[0065] The intermediate product was ball-milled to obtain primary particles with a particle size of less than 100 μm.
[0066] S204 is used to carbonize the primary particles at high temperature to obtain material No. 2.
[0067] The primary particles were treated at 500℃ for 5 hours in a CH4 atmosphere at a flow rate of 120 L / h to obtain material No. 2.
[0068] The specific surface area of material No. 2 prepared in this application is 4.8 m². 2 / g,d 002 The nanometer diameter is 0.42 nm. Using this material as the negative electrode active material, it is mixed uniformly with conductive carbon black and binder in a mass ratio of 92:4:4, coated into an electrode film, and dried in a vacuum drying oven at 120℃ for 12 hours. After rolling and punching, a sodium-ion battery negative electrode sheet is obtained. Using a metallic sodium sheet as the counter electrode and 1 mol / L NaPF6 (EC:DEC = 1:1) as the electrolyte, the obtained sodium-ion battery negative electrode sheet is assembled into a button cell in a glove box, and its electrochemical performance is tested. The specific capacity is 371 mAh / g, the initial efficiency is 95.4%, and the cycle efficiency after 1000 cycles is 94.2%.
[0069] Example 3:
[0070] S301 involves adding starch to a carbon source mixture to obtain a composite carbon source precursor, introducing tetraethylphosphine hydroxide into the precursor, and then curing it; the carbon source is phenolic resin.
[0071] S311 ball mills starch to obtain starch with a particle size of less than 100 μm, which is then dispersed into a carbon source.
[0072] S312 mixes phenol and deionized water to obtain a mixed solution at 68°C;
[0073] Starch and tetraethylphosphine hydroxide were added to the mixed solution, and the mixture was stirred continuously. The temperature was 68°C and the time was 3 hours.
[0074] S313 involves adding a starch mixture to a formaldehyde solution, controlling the molar ratio of phenol to formaldehyde at 1:1.8, and performing a first reflux reaction. Then, ammonia water is added, at an amount equal to 8% of the phenol mass, and a second reflux reaction is performed. Finally, a curing reaction is carried out to obtain a hard carbon precursor. The mass ratio of starch, deionized water, phenol, and tetraethylphosphine hydroxide is 1.2:4:1:0.15. The first reflux reaction is performed at 68°C for 15 minutes; the second reflux reaction is performed at 68°C for 1.8 hours; and the curing reaction is performed at 160°C for 1.2 hours.
[0075] S302 performs low-temperature cross-linking treatment on the precursor to obtain the intermediate product;
[0076] The low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 90°C for 25 minutes; then the temperature is raised to 200°C and maintained for 6 hours, thus completing the low-temperature crosslinking treatment.
[0077] S303 ball mills and sieves the intermediate product to obtain primary particles;
[0078] The intermediate product was ball-milled to obtain primary particles with a particle size of less than 100 μm.
[0079] S304 obtains material No. 3 by high-temperature carbonization of primary particles.
[0080] The primary particles were treated at 600℃ for 3 hours in a CH4 atmosphere with a flow rate of 90 L / h to obtain material No. 3.
[0081] The specific surface area of material No. 3 prepared in this application is 5.0 m². 2 / g,d 002 The nanometer diameter is 0.41 nm. Using this material as the negative electrode active material, it is mixed uniformly with conductive carbon black and binder in a mass ratio of 92:4:4, coated into an electrode film, and dried in a vacuum drying oven at 120℃ for 12 hours. After rolling and punching, a sodium-ion battery negative electrode sheet is obtained. Using a metallic sodium sheet as the counter electrode and 1 mol / L NaPF6 (EC:DEC = 1:1) as the electrolyte, the obtained sodium-ion battery negative electrode sheet is assembled into a button cell in a glove box, and its electrochemical performance is tested. The specific capacity is 387 mAh / g, the initial efficiency is 96.1%, and the efficiency after 1000 cycles is 96.0%.
[0082] The following are examples of comparisons:
[0083] Comparative Example 1:
[0084] S401 involves adding starch to a carbon source mixture to obtain a composite carbon source precursor, introducing tetraethylphosphine hydroxide into the precursor, and then curing it; the carbon source is phenolic resin.
[0085] S411 ball mills starch to obtain starch with a particle size of less than 100 μm, which is then dispersed into a carbon source.
[0086] S412 mixes phenol and deionized water to obtain a mixed solution at 68°C;
[0087] Starch and tetraethylphosphine hydroxide were added to the mixed solution, and the mixture was stirred continuously. The temperature was 68°C and the time was 3 hours.
[0088] S413 involves adding a starch mixture to a formaldehyde solution, controlling the molar ratio of phenol to formaldehyde at 1:1.8, and performing a first reflux reaction. Then, ammonia water is added, at an amount equal to 8% of the phenol mass, and a second reflux reaction is performed. Finally, a curing reaction is carried out to obtain a hard carbon precursor. The mass ratio of starch, deionized water, phenol, and tetraethylphosphine hydroxide is 1.2:4:1:0.15. The first reflux reaction is performed at 68°C for 15 minutes; the second reflux reaction is performed at 68°C for 1.8 hours; and the curing reaction is performed at 160°C for 1.2 hours.
[0089] S402 cross-links the precursor at low temperature to obtain the intermediate product;
[0090] The low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 90°C for 25 minutes; then the temperature is raised to 200°C and maintained for 6 hours, thus completing the low-temperature crosslinking treatment.
[0091] S403 ball mills and sieves the intermediate product to obtain material No. 4;
[0092] The intermediate product was ball-milled to obtain material No. 4 with a particle size of less than 100 μm.
[0093] The specific surface area of material No. 4 prepared in this application is 24.5 m². 2 / g,d 002 The nanometer diameter is 0.36 nm. Using this material as the negative electrode active material, it is mixed uniformly with conductive carbon black and binder in a mass ratio of 92:4:4, coated into an electrode film, and dried in a vacuum drying oven at 120℃ for 12 hours. After rolling and punching, a sodium-ion battery negative electrode sheet is obtained. Using a metallic sodium sheet as the counter electrode and 1 mol / L NaPF6 (EC:DEC = 1:1) as the electrolyte, the obtained sodium-ion battery negative electrode sheet is assembled into a button cell in a glove box, and its electrochemical performance is tested. The specific capacity is 286 mAh / g, the initial efficiency is 80.7%, and the cycle efficiency is 59.2% after 1000 cycles.
[0094] Comparative Example 2:
[0095] S501 involves adding starch to a carbon source mixture to obtain a composite carbon source precursor, followed by curing treatment; the carbon source is phenolic resin.
[0096] S511 ball mills starch to obtain starch with a particle size of less than 100 μm, which is then dispersed into a carbon source.
[0097] S512 mixes phenol and deionized water to obtain a mixed solution at 68°C;
[0098] Add starch to the mixed solution, stir continuously, and heat at 68°C for 3 hours;
[0099] S513 involves adding a starch mixture to a formaldehyde solution, controlling the molar ratio of phenol to formaldehyde at 1:1.8, and performing a first reflux reaction. Then, ammonia water is added, at an amount equal to 8% of the phenol mass, and a second reflux reaction is performed. Finally, a curing reaction is carried out to obtain a hard carbon precursor. The mass ratio of starch, deionized water, and phenol is 1.2:4:1. The first reflux reaction is performed at 68°C for 15 minutes; the second reflux reaction is performed at 68°C for 1.8 hours; and the curing reaction is performed at 160°C for 1.2 hours.
[0100] S502 performs low-temperature cross-linking treatment on the precursor to obtain the intermediate product;
[0101] The low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 90°C for 25 minutes; then the temperature is raised to 200°C and maintained for 6 hours, thus completing the low-temperature crosslinking treatment.
[0102] S503 ball mills and sieves the intermediate product to obtain primary particles.
[0103] The intermediate product was ball-milled to obtain primary particles with a particle size of less than 100 μm.
[0104] S504 obtains material No. 5 by high-temperature carbonization of primary particles.
[0105] The primary particles were treated at 600℃ for 3 hours in a CH4 atmosphere with a flow rate of 90 L / h to obtain material No. 5.
[0106] The specific surface area of material No. 5 prepared in this application is 15.3 m². 2 / g,d 002 The nanometer diameter is 0.37 nm. Using this material as the negative electrode active material, it is mixed uniformly with conductive carbon black and binder in a mass ratio of 92:4:4, coated into an electrode film, and dried in a vacuum drying oven at 120℃ for 12 hours. After rolling and punching, a sodium-ion battery negative electrode sheet is obtained. Using a metallic sodium sheet as the counter electrode and 1 mol / L NaPF6 (EC:DEC = 1:1) as the electrolyte, the obtained sodium-ion battery negative electrode sheet is assembled into a button cell in a glove box, and its electrochemical performance is tested. The specific capacity is 218 mAh / g, the initial efficiency is 82.2%, and the cycle efficiency is 65.8% after 1000 cycles.
[0107] Comparative Example 3:
[0108] S601 involves adding starch to a carbon source mixture to obtain a composite carbon source precursor, introducing tetraethylphosphine hydroxide into the precursor, and then curing it; the carbon source is phenolic resin.
[0109] S611 ball mills starch to obtain starch with a particle size of less than 100 μm, which is then dispersed into a carbon source.
[0110] S612 mixes phenol and deionized water to obtain a mixed solution at 68°C;
[0111] Starch and tetraethylphosphine hydroxide were added to the mixed solution, and the mixture was stirred continuously. The temperature was 68°C and the time was 3 hours.
[0112] S613 involves adding a starch mixture to a formaldehyde solution, controlling the molar ratio of phenol to formaldehyde at 1:1.8, and performing a first reflux reaction. Then, ammonia water is added, at an amount equal to 8% of the phenol mass, and a second reflux reaction is performed. Finally, a curing reaction is carried out to obtain a hard carbon precursor. The mass ratio of starch, deionized water, phenol, and tetraethylphosphine hydroxide is 1.2:4:1:0.15. The first reflux reaction is performed at 68°C for 15 minutes; the second reflux reaction is performed at 68°C for 1.8 hours; and the curing reaction is performed at 160°C for 1.2 hours.
[0113] S602 performs low-temperature cross-linking treatment on the precursor to obtain the intermediate product;
[0114] The low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 90°C for 25 minutes; then the temperature is raised to 200°C and maintained for 6 hours, thus completing the low-temperature crosslinking treatment and obtaining primary particles.
[0115] S603 obtains material No. 6 by high-temperature carbonization of primary particles.
[0116] The primary particles were treated at 600℃ for 3 hours in a CH4 atmosphere with a flow rate of 90 L / h to obtain material No. 6.
[0117] The specific surface area of material No. 6 prepared in this application is 28.5 m². 2 / g,d 002The nanometer diameter is 0.38 nm. Using this material as the negative electrode active material, it is mixed uniformly with conductive carbon black and binder in a mass ratio of 92:4:4, coated into an electrode film, and dried in a vacuum drying oven at 120℃ for 12 hours. After rolling and punching, a sodium-ion battery negative electrode sheet is obtained. Using a metallic sodium sheet as the counter electrode and 1 mol / L NaPF6 (EC:DEC = 1:1) as the electrolyte, the obtained sodium-ion battery negative electrode sheet is assembled into a button cell in a glove box, and its electrochemical performance is tested. The specific capacity is 147 mAh / g, the initial efficiency is 73.8%, and the cycle efficiency is 48.9% after 1000 cycles.
[0118] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.
Claims
1. A method for preparing a phosphorus-modified hard carbon material, characterized in that: Includes the following steps: Starch was added to the carbon source mixture to obtain a composite carbon source precursor; Tetraethylphosphine hydroxide was introduced into the above precursor and then cured. The intermediate product can be obtained by cross-linking the precursor at low temperature. The intermediate product was ball-milled and sieved to obtain primary particles; Phosphorus-modified hard carbon material is obtained by high-temperature carbonization of primary particles. The starch, carbon source mixture, and tetraethylphosphine hydroxide were mixed as follows: Phenol and deionized water are mixed to obtain a mixed solution at 65-70℃; Add starch and tetraethylphosphine hydroxide to the mixed solution, stir continuously, and heat at 65-70℃ for no less than 3 hours; The starch mixture is added to the formaldehyde solution, and the molar ratio of phenol to formaldehyde is controlled at 1:(1.5-2). The mixture is then subjected to a first heating and reflux reaction. Ammonia water is then added, with the amount of ammonia water being 5-10% of the mass of phenol. The mixture is then subjected to a second heating and reflux reaction. Finally, the mixture is cured.
2. The method for preparing a phosphorus-modified hard carbon material according to claim 1, characterized in that: The starch was ball-milled to obtain starch with a particle size of less than 100 μm, which was then dispersed into a carbon source.
3. The method for preparing a phosphorus-modified hard carbon material according to claim 1, characterized in that: The mass ratio of starch, deionized water, phenol and tetraethylphosphine hydroxide is (0.5-2): (3-5): 1: (0.1-0.2).
4. The method for preparing a phosphorus-modified hard carbon material according to claim 1, characterized in that: The first reflow temperature is 65-70℃ for 10-20 min; the second reflow temperature is 65-70℃ for 1.5-2 h; the curing reaction temperature is 150-180℃ for 0.5-2 h.
5. The method for preparing a phosphorus-modified hard carbon material according to claim 1, characterized in that: The low-temperature crosslinking treatment is obtained as follows: the precursor is placed in a carbonization furnace, oxygen is isolated, and it is first heated to 80-100℃ for 20-30 minutes; then the temperature is raised to 150-250℃ and maintained for 2-10 hours, thus completing the low-temperature crosslinking treatment.
6. The method for preparing a phosphorus-modified hard carbon material according to claim 1, characterized in that: The intermediate product was ball-milled to obtain primary particles with a particle size of less than 100 μm.
7. The method for preparing a phosphorus-modified hard carbon material according to claim 6, characterized in that: The primary particles are carbonized at high temperature in the following manner: The primary particles were treated in a CH4 atmosphere of 60-120 L / h at 500-700℃ for 1-5 h to finally obtain phosphorus-modified hard carbon materials.
8. The application of the phosphorus-modified hard carbon material according to any one of claims 1-7 in the anode material of sodium-ion batteries.