Composite negative electrode material for sodium ion battery and preparation method of composite negative electrode material
By coating activated carbon with pitch and boron-doped TiO2 nanofibers using a fluidized bed method, a core-shell structured composite anode material is formed, which solves the problem of low initial coulombic efficiency of sodium-ion battery anode materials and improves the electrochemical performance and cycle stability of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-03-13
AI Technical Summary
Existing sodium-ion battery anode materials have low initial coulombic efficiency, and hard carbon has low initial efficiency and low compaction, resulting in poor performance of sodium-ion batteries.
Composite anode materials were prepared by fluidized bed method. A two-step oxidation process was used to coat the activated carbon surface with pitch and boron-doped TiO2 nanofibers to form a core-shell structure, which optimized the structure and porosity of the hard carbon layer and enhanced the interfacial bonding force.
It improves the initial coulombic efficiency and reversible capacity of sodium-ion batteries, and enhances the battery's cycle performance and energy density.
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Figure CN121662788A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of sodium-ion battery anode materials, specifically relating to a composite anode material for sodium-ion batteries and its preparation method. Background Technology
[0002] With the rapid development of renewable energy technologies, the requirements for energy storage products are becoming increasingly demanding in terms of economy and safety. The widespread use of lithium-ion batteries has exacerbated the scarcity of lithium resources, which will severely limit the future development of the energy storage sector. Compared to lithium-ion batteries, sodium-ion batteries have advantages such as abundant reserves, wide distribution, and lower cost, and are expected to become the mainstream in the future energy storage field.
[0003] In the field of sodium-ion battery anode materials, the graphite structure, which is originally suitable for lithium-ion battery anodes, is difficult to apply to sodium-ion battery anodes because the atomic radius of sodium is much larger than that of lithium. Hard carbon is currently the most widely chosen anode material for sodium-ion batteries due to its advantages such as good conductivity, high sodium storage capacity, small volume deformation after sodium intercalation, environmental friendliness, and low redox potential. However, the low initial efficiency and low compaction of hard carbon also limit its application. Sodium-ion batteries made of hard carbon have poor performance, so further adjustments are needed.
[0004] Activated carbon has attracted much attention due to its high specific surface area, low cost, tunable pore structure, and good electrical conductivity, electrochemical stability, and thermal stability. However, activated carbon contains a large number of micropores and mesopores, with a specific surface area ranging from 500 to 2000 m². 2 / g, directly using it as a negative electrode material for sodium-ion batteries often results in poor performance, with problems such as low initial coulombic efficiency and large irreversible capacity during discharge. Summary of the Invention
[0005] This invention provides a composite anode material for sodium-ion batteries and its preparation method, which can solve the problem of low initial coulombic efficiency caused by sodium-ion battery anode materials in the prior art.
[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing a composite negative electrode material for sodium-ion batteries includes the following steps: Step 1: Crush activated carbon and asphalt separately. Dissolve the crushed asphalt in toluene to form a solution. Add boron-doped TiO2 nanofibers and stir to form a mixture. Step 2: The pulverized activated carbon is placed in a fluidized bed, and the mixed solution is sprayed into the fluidized bed through atomization. The temperature of the fluidized bed is adjusted to carry out a primary oxidation treatment to obtain a primary precursor material. Step 3: Place the primary precursor material in a fluidized bed, prepare an asphalt toluene solution, atomize the solution and spray it into the fluidized bed, adjust the fluidized bed temperature to carry out secondary oxidation treatment, and obtain the secondary precursor material. Step 4: The secondary precursor material is carbonized at high temperature in an inert atmosphere, and after cooling, the composite anode material is obtained.
[0007] Activated carbon and asphalt were pulverized separately. The pulverized activated carbon was placed in a fluidized bed, while the pulverized asphalt and boron-doped TiO2 nanofibers were added to toluene to form a mixture. This mixture was atomized and sprayed into the fluidized bed. The toluene solvent was rapidly evaporated by hot gas within the fluidized bed, while the asphalt and boron-doped TiO2 nanofibers were deposited on the surface of the activated carbon particles to obtain a primary precursor material. During the primary oxidation process, the asphalt oxidized and initially cross-linked and solidified on the surface of the activated carbon. Simultaneously, the nanofibers existed interlaced within the cross-linked structure, forming a stable intermediate layer. A secondary oxidation deposition was then performed on the surface after atomization with the asphalt-toluene solution. After high-temperature calcination, the hard carbon obtained after asphalt carbonization had a larger interlayer spacing and increased closed pores, which was more conducive to sodium storage. This significantly reduced the specific surface area of the material, decreased the active sites on the material surface in contact with the electrolyte, hindered some irreversible sodium adsorption, suppressed electrolyte decomposition, reduced side reactions, and improved the initial coulombic efficiency and reversible capacity.
[0008] Using pitch as the hard carbon raw material on the surface of activated carbon, the oxidative cross-linking of pitch forms a chemical bond on the activated carbon surface. However, the effectiveness of this interfacial bonding decreases after high-temperature treatment, and the hard carbon structure is at risk of detachment after long-term battery charge-discharge cycles. By optimizing the structure of the hard carbon layer, pitch and boron-doped TiO2 nanofibers are used as an intermediate layer. Boron-doped TiO2 nanofibers have a high sodium storage capacity. After being mixed and deposited with pitch, the fibers can buffer the volume changes during sodium ion insertion / extraction and act as "steel bars," achieving a physical bond between the activated carbon and the pitch hard carbon layer. This ensures that the interfacial bonding force is maintained even after the chemical bonding weakens. However, directly using pitch fiber mixture as the outer layer would disrupt the integrity of the hard carbon layer due to gaps around the fibers. Using pitch fiber mixture as the intermediate layer can improve the closed-pore structure formed by the outer hard carbon layer and achieve a stable connection between the activated carbon and the pure pitch hard carbon layer, making the pitch-based hard carbon structure more stable and improving the cycle performance of the sodium-ion battery.
[0009] Furthermore, the activated carbon is one of wood-based activated carbon, coal-based activated carbon, coconut shell activated carbon, and fruit shell activated carbon.
[0010] Furthermore, the asphalt is one of petroleum asphalt, coal tar pitch, or natural asphalt.
[0011] Furthermore, the D50 of the pulverized asphalt is 3-4 μm; The D50 of the pulverized activated carbon is 5-6 μm; The boron-doped TiO2 nanofibers have a diameter of 50-70 nm and a length of 200-300 nm.
[0012] Furthermore, in step one, the concentration of the solution is 20-50 g / L; The mass ratio of boron-doped TiO2 nanofibers to asphalt is 0.05-0.2:1.
[0013] Furthermore, the preparation steps of the boron-doped TiO2 nanofibers are as follows: S1. Add tetrabutyl titanate and acetic acid to ethanol and stir to obtain sol A. Let stand for 1-2 hours to fully hydrolyze. S2. Add tributyl borate, polyvinylpyrrolidone and dimethylformamide to ethanol and stir until homogeneous to obtain sol B; S3. Stir and mix sol A and sol B to obtain spinning solution. Obtain nanofibers from the spinning solution through electrospinning process. S4. The nanofibers were calcined at high temperature in air and then ball-milled to obtain boron-doped TiO2 nanofibers.
[0014] Tetrabutyl titanate is hydrolyzed in ethanol, and the hydroxyl groups undergo a condensation reaction to form Ti-O-Ti bonds. Acetic acid is added to keep the system in a transparent sol state. Meanwhile, tributyl borate is used as a boron source and is mixed in polyvinylpyrrolidone (PVP), dimethylformamide (DMF), and ethanol to form sol B. Sol A and sol B are stirred and mixed to uniformly integrate the TiO2 precursor, boron source, and polymer template to form a homogeneous spinning solution. After high-temperature calcination, both the polymer and solvent are removed, resulting in boron doping.
[0015] Furthermore, the concentration of the tetrabutyl titanate in ethanol is 0.3-0.5 g / mL.
[0016] Furthermore, the acetic acid is added to ethanol to adjust the pH of the system to 3-4.
[0017] Further, the mass ratio of tributyl borate, polyvinylpyrrolidone, and dimethylformamide is 0.1-0.2:0.2-0.3:1; The total mass of the tributyl borate, polyvinylpyrrolidone, and dimethylformamide is 20-30% of that of ethanol.
[0018] Furthermore, the mass ratio of sol A to sol B is 1:1-1.2.
[0019] Furthermore, the parameters of the electrospinning process are: voltage of 50-60kV and feed rate of 2-3mL / h.
[0020] Furthermore, the high-temperature calcination temperature is 500-600℃, and the duration is 2-3 hours.
[0021] Furthermore, in step two, the mass ratio of activated carbon to asphalt in the mixture is 3-5:1.
[0022] Furthermore, in step two, the oxidation temperature of the primary oxidation treatment is 120~280℃, and the time is 2~6h.
[0023] Furthermore, in step three, the concentration of the asphalt toluene solution is 20-50 g / L; The mass ratio of the primary precursor material to the asphalt in the solution is 4-20:1.
[0024] Furthermore, in step three, the oxidation temperature of the secondary oxidation treatment is 120~280℃, and the time is 4-8h.
[0025] Furthermore, the inert atmosphere is at least one of nitrogen, helium, and argon.
[0026] Furthermore, the high-temperature carbonization temperature is 1200-1500℃, and the time is 2-5 hours.
[0027] The present invention also provides a composite negative electrode material for sodium-ion batteries, which is prepared by the preparation method described above.
[0028] The beneficial effects of this invention are: (1) This invention constructs a boron-doped Ti core with activated carbon as the core through a two-step fluidized bed coating and oxidative carbonization process. The nanofibers feature a core-shell structure with a pitch-carbon hybrid structure as the middle layer and a pitch-based hard carbon structure as the outer layer. This structure combines the high porosity of activated carbon, the high capacity of hard carbon, and boron-doped Ti. The sodium storage active sites provided by nanofibers comprehensively enhance electrochemical performance.
[0029] (2) The microporous structure of activated carbon itself is conducive to sodium storage. The pore structure can be controlled by coating the surface of activated carbon. In this invention, hard carbon is formed by coating with asphalt and then oxidizing and crosslinking. This transforms a large number of open pores into closed pores, which hinders some irreversible sodium adsorption, inhibits the decomposition of electrolyte, reduces the occurrence of side reactions, and is more conducive to sodium ion storage. In addition, the asphalt-based hard carbon structure of the outer layer also has a certain sodium storage effect, which improves the initial coulombic efficiency and reversible capacity.
[0030] (3) This invention uses a fluidized bed as an oxidation device to atomize asphalt and coat it onto the surface of activated carbon. This allows the asphalt to be uniformly coated and oxidized, resulting in a deeper degree of oxidation, a more complete cross-linked structure, an increased yield of fully oxidized hard carbon, lower costs, and a larger interlayer spacing and increased closed pores in the hard carbon obtained after carbonization, which is more conducive to sodium storage.
[0031] (4) This invention uses boron-doped Ti The nanofibers, with their pitch-carbon hybrid structure as the intermediate layer, enhance the physical bonding of the fibers in addition to the chemical bonding formed by the oxidative cross-linking of pitch. This not only suppresses the volume expansion of the carbon material but also ensures the stable bonding of the pitch-based hard carbon on the activated carbon surface, thus improving cycle stability. The composite anode material prepared in this invention, when used in sodium-ion batteries, can achieve sodium-ion batteries with high energy density and good cycle performance. Attached Figure Description
[0032] The invention will now be further described with reference to the accompanying drawings.
[0033] Figure 1 This is a schematic diagram of the first charge and discharge of Embodiment 1 of the present invention. Detailed Implementation
[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0035] Example 1
[0036] Preparation of boron-doped TiO2 nanofibers: S1. Weigh out tetrabutyl titanate at a concentration of 0.4 g / mL and add it to ethanol. Add acetic acid to adjust the pH of the system to 3.6. After stirring continuously for 20 min, obtain sol A. Let it stand for 1.2 h and then fully hydrolyze it.
[0037] S2. Weigh out tributyl borate, polyvinylpyrrolidone and dimethylformamide in a mass ratio of 0.15:0.3:1 and add them to ethanol. The total mass of tributyl borate, polyvinylpyrrolidone and dimethylformamide is 26% of the ethanol. After stirring continuously for 10 minutes, mix evenly to obtain sol B.
[0038] S3. Mix sol A and sol B at a mass ratio of 1:1.1 to obtain a spinning solution. Add the spinning solution to the electrospinning syringe. The power supply voltage for electrospinning is 60kV. Control the propulsion speed of the spinning solution to 2.5mL / L using a micro-injection pump. Obtain nanofibers by electrospinning.
[0039] S4. The obtained nanofibers are calcined at high temperature in air atmosphere. The calcination temperature is set at 580℃ and the calcination is continued for 2.6h. The calcined fibers are then ball-milled to obtain boron-doped TiO2 nanofibers with a diameter of 50-70nm and a length of 200-300nm.
[0040] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm. Dissolve the pulverized asphalt in toluene to form a solution with a concentration of 30g / L. Add boron-doped TiO2 nanofibers to the solution. The mass ratio of boron-doped TiO2 nanofibers to asphalt is 0.14:1. Stir and mix to form a mixture.
[0041] Step 2: Place the pulverized activated carbon in a fluidized bed. The mixture is sprayed into the fluidized bed through atomization. The mass ratio of activated carbon to asphalt in the mixture is 4:1. Adjust the fluidized bed temperature to 180℃ for a primary oxidation treatment, which lasts for 5 hours. Then, cool the mixture to room temperature to obtain the primary precursor material.
[0042] Step 3: Place the primary precursor material in a fluidized bed. Dissolve the asphalt in toluene to prepare a solution with a concentration of 30 g / L. Atomize the solution and spray it into the fluidized bed. At this time, the mass ratio of the primary precursor material to the asphalt in the solution is 10:1. Adjust the fluidized bed temperature to 180℃ for secondary oxidation treatment for 5 hours. Cool the temperature to room temperature to obtain the secondary precursor material.
[0043] Step 4: The secondary precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0044] Example 2
[0045] The only difference from Example 1 is that the oxidation treatment temperature is increased to 250°C.
[0046] The steps for preparing boron-doped TiO2 nanofibers are the same as in Example 1.
[0047] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm. Dissolve the pulverized asphalt in toluene to form a solution with a concentration of 30g / L. Add boron-doped TiO2 nanofibers to the solution. The mass ratio of boron-doped TiO2 nanofibers to asphalt is 0.14:1. Stir and mix to form a mixture.
[0048] Step 2: Place the pulverized activated carbon in a fluidized bed. The mixture is sprayed into the fluidized bed through atomization. The mass ratio of activated carbon to asphalt in the mixture is 4:1. Adjust the fluidized bed temperature to 250℃ for a primary oxidation treatment for 5 hours. Then, cool the temperature to room temperature to obtain the primary precursor material.
[0049] Step 3: Place the primary precursor material in a fluidized bed. Dissolve the asphalt in toluene to prepare a solution with a concentration of 30 g / L. Atomize the solution and spray it into the fluidized bed. At this time, the mass ratio of the primary precursor material to the asphalt in the solution is 10:1. Adjust the fluidized bed temperature to 250℃ for secondary oxidation treatment for 5 hours. Cool the temperature to room temperature to obtain the secondary precursor material.
[0050] Step 4: The secondary precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0051] Example 3
[0052] The only difference from Example 1 is that the oxidation treatment temperature is increased to 130°C.
[0053] The steps for preparing boron-doped TiO2 nanofibers are the same as in Example 1.
[0054] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm. Dissolve the pulverized asphalt in toluene to form a solution with a concentration of 30g / L. Add boron-doped TiO2 nanofibers to the solution. The mass ratio of boron-doped TiO2 nanofibers to asphalt is 0.14:1. Stir and mix to form a mixture.
[0055] Step 2: Place the pulverized activated carbon in a fluidized bed. The mixture is sprayed into the fluidized bed through atomization. The mass ratio of activated carbon to asphalt in the mixture is 4:1. Adjust the fluidized bed temperature to 130℃ for a primary oxidation treatment for 5 hours. Then, cool the temperature to room temperature to obtain the primary precursor material.
[0056] Step 3: Place the primary precursor material in a fluidized bed. Dissolve the asphalt in toluene to prepare a solution with a concentration of 30 g / L. Atomize the solution and spray it into the fluidized bed. At this time, the mass ratio of the primary precursor material to the asphalt in the solution is 10:1. Adjust the fluidized bed temperature to 130℃ for secondary oxidation treatment for 5 hours. Cool the temperature to room temperature to obtain the secondary precursor material.
[0057] Step 4: The secondary precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0058] Example 4
[0059] The only difference from Example 1 is that, in preparing the composite negative electrode material for sodium-ion batteries, the mass ratio of boron-doped TiO2 nanofibers to pitch in step one is adjusted to 0.05:1.
[0060] The steps for preparing boron-doped TiO2 nanofibers are the same as in Example 1.
[0061] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm. Dissolve the pulverized asphalt in toluene to form a solution with a concentration of 30g / L. Add boron-doped TiO2 nanofibers to the solution, with a mass ratio of boron-doped TiO2 nanofibers to asphalt of 0.05:1. Stir and mix to form a mixture.
[0062] Step 2: Place the pulverized activated carbon in a fluidized bed. The mixture is sprayed into the fluidized bed through atomization. The mass ratio of activated carbon to asphalt in the mixture is 4:1. Adjust the fluidized bed temperature to 180℃ for a primary oxidation treatment, which lasts for 5 hours. Then, cool the mixture to room temperature to obtain the primary precursor material.
[0063] Step 3: Place the primary precursor material in a fluidized bed. Dissolve the asphalt in toluene to prepare a solution with a concentration of 30 g / L. Atomize the solution and spray it into the fluidized bed. At this time, the mass ratio of the primary precursor material to the asphalt in the solution is 10:1. Adjust the fluidized bed temperature to 180℃ for secondary oxidation treatment for 5 hours. Cool the temperature to room temperature to obtain the secondary precursor material.
[0064] Step 4: The secondary precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0065] Example 5
[0066] The only difference from Example 1 is that, in preparing the composite negative electrode material for sodium-ion batteries, the mass ratio of boron-doped TiO2 nanofibers to asphalt in step one is adjusted to 0.2:1.
[0067] The steps for preparing boron-doped TiO2 nanofibers are the same as in Example 1.
[0068] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm. Dissolve the pulverized asphalt in toluene to form a solution with a concentration of 30g / L. Add boron-doped TiO2 nanofibers to the solution, with a mass ratio of boron-doped TiO2 nanofibers to asphalt of 0.2:1. Stir and mix to form a mixture.
[0069] Step 2: Place the pulverized activated carbon in a fluidized bed. The mixture is sprayed into the fluidized bed through atomization. The mass ratio of activated carbon to asphalt in the mixture is 4:1. Adjust the fluidized bed temperature to 180℃ for a primary oxidation treatment, which lasts for 5 hours. Then, cool the mixture to room temperature to obtain the primary precursor material.
[0070] Step 3: Place the primary precursor material in a fluidized bed. Dissolve the asphalt in toluene to prepare a solution with a concentration of 30 g / L. Atomize the solution and spray it into the fluidized bed. At this time, the mass ratio of the primary precursor material to the asphalt in the solution is 10:1. Adjust the fluidized bed temperature to 180℃ for secondary oxidation treatment for 5 hours. Cool the temperature to room temperature to obtain the secondary precursor material.
[0071] Step 4: The secondary precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0072] Example 6
[0073] The only difference from Example 1 is that, in preparing the composite negative electrode material for sodium-ion batteries, the mass ratio of the primary precursor material to the asphalt in the solution in step three is adjusted to 5:1.
[0074] The steps for preparing boron-doped TiO2 nanofibers are the same as in Example 1.
[0075] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm. Dissolve the pulverized asphalt in toluene to form a solution with a concentration of 30g / L. Add boron-doped TiO2 nanofibers to the solution. The mass ratio of boron-doped TiO2 nanofibers to asphalt is 0.14:1. Stir and mix to form a mixture.
[0076] Step 2: Place the pulverized activated carbon in a fluidized bed. The mixture is sprayed into the fluidized bed through atomization. The mass ratio of activated carbon to asphalt in the mixture is 4:1. Adjust the fluidized bed temperature to 180℃ for a primary oxidation treatment, which lasts for 5 hours. Then, cool the mixture to room temperature to obtain the primary precursor material.
[0077] Step 3: Place the primary precursor material in a fluidized bed. Dissolve the asphalt in toluene to prepare a solution with a concentration of 30 g / L. Atomize the solution and spray it into the fluidized bed. At this time, the mass ratio of the primary precursor material to the asphalt in the solution is 5:1. Adjust the fluidized bed temperature to 180℃ for secondary oxidation treatment for 5 hours. Cool the temperature to room temperature to obtain the secondary precursor material.
[0078] Step 4: The secondary precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0079] Example 7
[0080] The only difference from Example 1 is that, in preparing the composite negative electrode material for sodium-ion batteries, the mass ratio of the primary precursor material to the asphalt in the solution in step three is adjusted to 15:1.
[0081] The steps for preparing boron-doped TiO2 nanofibers are the same as in Example 1.
[0082] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm. Dissolve the pulverized asphalt in toluene to form a solution with a concentration of 30g / L. Add boron-doped TiO2 nanofibers to the solution. The mass ratio of boron-doped TiO2 nanofibers to asphalt is 0.14:1. Stir and mix to form a mixture.
[0083] Step 2: Place the pulverized activated carbon in a fluidized bed. The mixture is sprayed into the fluidized bed through atomization. The mass ratio of activated carbon to asphalt in the mixture is 4:1. Adjust the fluidized bed temperature to 180℃ for a primary oxidation treatment, which lasts for 5 hours. Then, cool the mixture to room temperature to obtain the primary precursor material.
[0084] Step 3: Place the primary precursor material in a fluidized bed. Dissolve the asphalt in toluene to prepare a solution with a concentration of 30 g / L. Atomize the solution and spray it into the fluidized bed. At this time, the mass ratio of the primary precursor material to the asphalt in the solution is 15:1. Adjust the fluidized bed temperature to 180℃ for secondary oxidation treatment for 5 hours. Cool the temperature to room temperature to obtain the secondary precursor material.
[0085] Step 4: The secondary precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0086] Comparative Example 1
[0087] The difference from Example 1 is that in this comparative example, pulverized asphalt and pulverized activated carbon are directly oxidized in a fluidized bed.
[0088] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm.
[0089] Step 2: Place the pulverized activated carbon and pulverized asphalt simultaneously in a fluidized bed with a mass ratio of 3:1. Adjust the fluidized bed temperature to 180℃ for oxidation treatment for 5 hours, then cool to room temperature to obtain the precursor material.
[0090] Step 3: The precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0091] Comparative Example 2
[0092] The difference from Example 1 is that in this comparative example, pulverized asphalt and pulverized activated carbon are directly oxidized in a tube furnace.
[0093] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm.
[0094] Step 2: Place the pulverized activated carbon and pulverized asphalt simultaneously in a tube furnace with a mass ratio of 3:1. Adjust the temperature of the tube furnace to 180℃ for oxidation treatment for 5 hours, and then cool to room temperature to obtain the precursor material.
[0095] Step 3: The precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0096] Comparative Example 3
[0097] The difference from Example 1 is that boron-doped TiO2 nanofibers are not added in this comparative example.
[0098] Preparation of composite anode materials for sodium-ion batteries: Step 1: Use a mechanical pulverizer to pulverize activated carbon to a D50 of 5μm and asphalt to a D50 of 3μm. Dissolve the pulverized asphalt in toluene to form a solution with a concentration of 30g / L.
[0099] Step 2: Place the pulverized activated carbon in a fluidized bed. The solution obtained in Step 1 is sprayed into the fluidized bed through atomization. The mass ratio of activated carbon to asphalt in the solution is 4:1. Adjust the fluidized bed temperature to 180℃ for a single oxidation treatment, which lasts for 5 hours. Then, cool the solution to room temperature to obtain the primary precursor material.
[0100] Step 3: Place the primary precursor material in a fluidized bed. Dissolve the asphalt in toluene to prepare a solution with a concentration of 30 g / L. Atomize the solution and spray it into the fluidized bed. At this time, the mass ratio of the primary precursor material to the asphalt in the solution is 10:1. Adjust the fluidized bed temperature to 180℃ for secondary oxidation treatment for 5 hours. Cool the temperature to room temperature to obtain the secondary precursor material.
[0101] Step 4: The secondary precursor material is heated to 1400℃ under a nitrogen atmosphere at a heating rate of 5℃ / min and held for 2 hours for high-temperature carbonization treatment. After cooling, the composite anode material is obtained.
[0102] The composite anode materials prepared in Examples 1-7 and Comparative Examples 1-3 were subjected to performance tests under the following conditions: The negative electrode material consists of a composite negative electrode material: Super P:PVDF in a mass ratio of 8:1:1, using NMP as a solvent. After mixing, the mixture is coated onto aluminum foil, dried, and rolled to obtain the negative electrode sheet. The electrolyte is a mixed solvent of EC and DEC in a volume ratio of 1:1, with sodium hexafluorophosphate as the solute at a concentration of 1M. The separator is a glass fiber membrane, and the positive electrode is a sodium sheet. A CR2032 coin cell is fabricated and subjected to charge-discharge testing. The current density is 20 mA·g. -1 The voltage range is 3 to 0.002 V, and the electrochemical performance test results are shown in Table 1.
[0103] Table 1
[0104] As can be seen from Table 1, Example 1 has better electrochemical performance than the comparative example, with the highest initial reversible specific capacity reaching 292 mAh / g, the highest initial coulombic efficiency reaching 88%, and the highest capacity retention rate after 100 cycles reaching 80%. When the composite anode material prepared in the present invention is applied to sodium-ion batteries, it can improve the initial coulombic efficiency and reversible capacity, and its cycle performance is significantly improved compared to the comparative example.
[0105] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0106] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a composite negative electrode material for sodium-ion batteries, characterized in that, Includes the following steps: Step 1: Crush activated carbon and asphalt separately. Dissolve the crushed asphalt in toluene to form a solution. Add boron-doped TiO2 nanofibers and stir to form a mixture. Step 2: The pulverized activated carbon is placed in a fluidized bed, and the mixed solution is sprayed into the fluidized bed through atomization. The temperature of the fluidized bed is adjusted to carry out a primary oxidation treatment to obtain a primary precursor material. Step 3: Place the primary precursor material in a fluidized bed, prepare an asphalt toluene solution, atomize the solution and spray it into the fluidized bed, adjust the fluidized bed temperature to carry out secondary oxidation treatment, and obtain the secondary precursor material. Step 4: The secondary precursor material is carbonized at high temperature in an inert atmosphere, and after cooling, the composite anode material is obtained.
2. The method for preparing a composite negative electrode material for sodium-ion batteries according to claim 1, characterized in that, The D50 of the pulverized asphalt is 3-4 μm; The D50 of the pulverized activated carbon is 5-6 μm; The boron-doped TiO2 nanofibers have a diameter of 50-70 nm and a length of 200-300 nm.
3. The method for preparing a composite negative electrode material for sodium-ion batteries according to claim 1, characterized in that, In step one, the concentration of the solution is 20-50 g / L; The mass ratio of boron-doped TiO2 nanofibers to asphalt is 0.05-0.2:
1.
4. The method for preparing a composite negative electrode material for sodium-ion batteries according to claim 1, characterized in that, The preparation steps of the boron-doped TiO2 nanofibers are as follows: S1. Add tetrabutyl titanate and acetic acid to ethanol and stir to obtain sol A, and let stand for 1-2 hours to hydrolyze; S2. Add tributyl borate, polyvinylpyrrolidone and dimethylformamide to ethanol and stir until homogeneous to obtain sol B; S3. Stir and mix sol A and sol B to obtain spinning solution. Obtain nanofibers from the spinning solution through electrospinning process. S4. The nanofibers were calcined at 500-600℃ in air for 2-3 hours and then ball-milled to obtain boron-doped TiO2 nanofibers.
5. The method for preparing a composite negative electrode material for sodium-ion batteries according to claim 4, characterized in that, In step S1, the concentration of tetrabutyl titanate in ethanol is 0.3-0.5 g / mL; The acetic acid was added to ethanol to adjust the pH of the system to 3-4.
6. The method for preparing a composite negative electrode material for sodium-ion batteries according to claim 4, characterized in that, The mass ratio of tributyl borate, polyvinylpyrrolidone, and dimethylformamide is 0.1-0.2:0.2-0.3:
1. The total mass of the tributyl borate, polyvinylpyrrolidone, and dimethylformamide is 20-30% of that of ethanol; the mass ratio of sol A to sol B is 1:1-1.
2.
7. The method for preparing a composite negative electrode material for sodium-ion batteries according to claim 1, characterized in that, In step two, the mass ratio of activated carbon to asphalt in the mixture is 3-5:1; The oxidation temperature of the first oxidation treatment is 120~280℃, and the time is 2~6h.
8. The method for preparing a composite negative electrode material for sodium-ion batteries according to claim 1, characterized in that, In step three, the concentration of the asphalt toluene solution is 20-50 g / L; the mass ratio of the primary precursor material to the asphalt in the solution is 4-20:
1. The secondary oxidation treatment is carried out at an oxidation temperature of 120~280℃ for 4-8 hours.
9. The method for preparing a composite negative electrode material for sodium-ion batteries according to claim 1, characterized in that, The high-temperature carbonization is carried out at a temperature of 1200-1500℃ for 2-5 hours.
10. A composite negative electrode material for sodium-ion batteries, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.