A ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, its preparation method and application

Abstract

This invention discloses a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, its preparation method, and its application, belonging to the field of sodium-ion battery technology. This invention constructs a ZnTe / SnTe heterostructure and a hierarchical porous carbon framework in situ through electrospinning of ZnSn bimetallic MOFs combined with carbonization and tellurization processes. Dynamic pore formation buffers volume expansion, and Te vacancies and the heterostructure interface synergistically promote Na+ absorption. + Diffusion and charge transfer yielded sodium-ion battery anode materials that combine high specific capacity, excellent rate performance, and long cycle life.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and particularly relates to a ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material, its preparation method and application. Background Technology

[0002] The global energy structure is rapidly transitioning towards a clean and low-carbon direction, the electric vehicle industry is booming, and the demand for large-scale energy storage continues to rise, placing more stringent requirements on electrochemical energy storage devices in terms of energy density, cycle life, cost, and safety. Lithium-ion batteries, due to their excellent overall performance, have long held a dominant position in portable electronic devices, power batteries, and small-to-medium-sized energy storage. However, the low abundance and highly concentrated geographical distribution of lithium resources, coupled with increasingly prominent supply-demand imbalances and frequent price fluctuations, pose significant resource bottlenecks and economic challenges for large-scale grid-scale energy storage applications. Sodium, belonging to the same Group 1 lithium family and possessing similar physicochemical properties, along with abundant and inexpensive sodium resources, makes sodium-ion batteries an important complementary technology to lithium-ion batteries in large-scale energy storage. However, sodium ions have a larger radius than lithium ions, and their insertion / extraction in electrode materials often involves severe lattice strain and complex interfacial side reactions, making it difficult to simultaneously achieve high energy density and power density, thus limiting their practical application. Therefore, designing and developing novel anode materials that combine high specific capacity with rapid sodium storage kinetics is a key breakthrough for improving the overall performance of sodium-ion batteries.

[0003] Tin-tellurium compounds (SnTe) and zinc-tellurium compounds (ZnTe), as well as their composites, undergo a multi-electron transfer reaction involving conversion and alloying during sodium storage, exhibiting high theoretical specific capacity and considered as promising anode materials for sodium-ion batteries. Among these, the ZnTe / SnTe@porous carbon fiber composite is a heterogeneous composite material prepared by electrospinning ZnSn bimetallic MOFs combined with carbonization and tellurization. It possesses advantages such as strong synergistic effects at the heterogeneous interface, well-developed hierarchical pore structure, excellent conductivity, and good controllability in the preparation process. Furthermore, due to the tellurization process, this composite material readily forms abundant Te vacancies. These Te vacancies not only lower the migration barrier of Na+ in the SnTe lattice, accelerating sodium ion diffusion and providing more active sites for sodium storage, but also act as charge transfer bridges to improve carrier migration efficiency, overcoming the problem of sluggish reaction kinetics in electrode materials. Furthermore, the carbon fiber skeleton in the composite material can construct a stable one-dimensional conductive network, while the hierarchical channels generated by in-situ dissolution during cycling can serve as rapid ion transport channels, achieving efficient ion and electron conduction. However, due to insufficient atomic-level bonding strength between the ZnTe and SnTe heterojunction interfaces, and the tendency for interface decoupling to occur during charge-discharge cycles, a large interfacial charge transfer barrier is generated, and problems such as volume expansion and structural collapse exist, resulting in poor battery cycle performance and stability. Summary of the Invention

[0004] To address the problems of structural pulverization, active particle agglomeration, and slow interfacial charge transfer caused by drastic volume expansion in existing SnTe-based composite materials during sodium storage, this invention proposes a ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material, its preparation method, and its applications. The ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material obtained by this invention exhibits high specific capacity, excellent fast-charge rate performance, and long cycle life as a negative electrode material. This invention constructs a ZnTe / SnTe heterojunction and hierarchical porous carbon framework in situ through electrospinning of ZnSn bimetallic MOFs combined with carbonization and tellurization processes. Dynamic pore formation buffers volume expansion, and Te vacancies and the heterojunction interface synergistically promote Na+ storage. + Diffusion and charge transfer techniques were employed to obtain sodium-ion battery anode materials that combine high specific capacity, excellent rate performance, and long cycle life.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material, comprising the following steps: S1: Dissolve soluble zinc salt and soluble tin salt in water to obtain zinc salt solution and tin salt solution respectively. Mix the two solutions and stir to react. Collect the product by centrifugation, wash and dry to obtain ZnSn bimetallic MOFs. S2: Dissolve the ZnSn bimetallic MOFs and polyacrylonitrile in N,N-dimethylformamide, stir until uniform, and obtain a spinning solution. Perform electrospinning to synthesize PAN / ZnSn-MOFs nanofiber materials. S3: After the PAN / ZnSn-MOFs nanofiber material is pre-oxidized and cured, it is carbonized under an inert atmosphere to obtain a precursor; the precursor is mixed with tellurium powder and subjected to tellurization treatment to obtain the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material (which is a ZnTe / SnTe@hierarchical porous carbon fiber composite anode material).

[0006] The ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material prepared by the method of the present invention has a heterojunction core layer formed by the synergistic effect of ZnTe and SnTe and a nitrogen-doped porous carbon fiber conductive coating layer covering the surface of the heterojunction core layer.

[0007] In the ZnTe / SnTe@hierarchical porous carbon fiber composite anode material of this invention, the nitrogen-doped porous carbon fiber skeleton not only possesses excellent mechanical stability and good flexibility, which can buffer the volume expansion of the material during sodium storage and maintain the integrity of the overall structure, but its well-developed hierarchical channel structure also has high carrier migration efficiency and a short sodium ion diffusion path, effectively improving the rate performance of the material. The ZnTe / SnTe heterojunction not only synergistically improves the internal conductivity of the material, but the built-in electric field formed at the heterojunction interface can stabilize the material structure, promote rapid electron / ion transport, and accelerate Na+ diffusion. + Reaction kinetics: The formation of Te vacancies can further enhance heterogeneous interface bonding, forming stable charge transport channels, accelerating charge transfer efficiency, and simultaneously reducing Na... + The migration barrier within the crystal lattice provides additional sodium-storing active sites. The outer porous carbon fiber skeleton layer obtained by carbonization can improve the structural stability of the composite material, suppress structural collapse and active material shedding during charge and discharge, and significantly improve the cycle stability of the material. Furthermore, nitrogen doping in the carbon fibers further increases the active sites and conductivity of the composite material, enabling the adsorption of Na. + Accelerate Na + Reaction kinetics were studied to improve the cycling performance and sodium storage capacity of the composite material.

[0008] Further, in step S1, the molar ratio of the soluble zinc salt to the soluble tin salt is (1~2):(1~2).

[0009] For example, the soluble zinc salt is zinc sulfate heptahydrate; the soluble tin salt is potassium stannate trihydrate.

[0010] Further, in step S2, the mass ratio of the ZnSn bimetallic MOFs to polyacrylonitrile is (1~5):(1~4).

[0011] Further, in step S2, the electrospinning conditions are: voltage 12~18 kV, distance between the receiving electrode and the needle tip 12~18 cm, and feed rate 0.1~0.3 mL·min. -1 The ambient humidity is 30%~50%.

[0012] Furthermore, in step S3, the pre-oxidation temperature is 150~280 ℃, the holding time is 1~3 h, and the heating rate is 1~5 ℃·min. -1 .

[0013] Further, in step S3, the mass ratio of the precursor to tellurium powder is 1:(1~3), preferably 1:2.

[0014] Furthermore, in step S3, the carbonization treatment temperature is 500~600 ℃, the holding time is 2~6 h, and the heating rate is 2~5 ℃·min. -1 .

[0015] Furthermore, in step S3, the temperature of the tellurization treatment is 500~600 ℃, and the holding time is 2~6 h.

[0016] The present invention also provides a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material prepared according to the above method.

[0017] This invention maximizes the synergistic effect of ZnTe and SnTe and the structural advantages of nitrogen-doped hierarchical porous carbon fiber skeleton, synthesizing a sodium-ion battery anode material with high specific capacity, excellent rate performance and long cycle performance.

[0018] The present invention also provides an application of the above-mentioned ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material in the preparation of sodium-ion batteries, wherein the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material is used as a negative electrode material.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: 1. Nitrogen-doped hierarchical porous carbon fiber skeletons not only have excellent mechanical stability and good flexibility, which can buffer the volume expansion during sodium storage and maintain structural integrity, but also have high carrier migration efficiency and short sodium ion diffusion path due to their well-developed hierarchical channel structure, thus improving electrochemical performance. 2. The ZnTe / SnTe heterojunction not only synergistically improves the internal conductivity of the material, but the built-in electric field formed at the heterojunction interface can also stabilize the material structure, promote rapid electron / ion transport, and accelerate Na+ transport. + Reaction kinetics; 3. The formation of Te vacancies can further enhance heterogeneous interface bonding, forming stable charge transport channels, while reducing Na... + The migration barrier in the crystal lattice provides additional sodium storage active sites, enhancing the conductivity of the material; 4. Nitrogen doping in the carbon fiber skeleton further increases the active sites and conductivity of the material, enabling the adsorption of Na. + Accelerate Na + Reaction kinetics were studied to improve the cycling performance and sodium storage capacity of the composite material. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The image shown is a field emission scanning electron microscope image of the product obtained in Example 1 of this invention. Figure 2 The image shows the X-ray diffraction (XRD) pattern of the product obtained in Example 1 of this invention. Figure 3 This is a field emission scanning electron microscope image of the product obtained in Example 4 of the present invention; Figure 4 The X-ray diffraction pattern of the product obtained in Example 4 of this invention; Figure 5 This is a field emission scanning electron microscope image of the product obtained in Example 5 of the present invention; Figure 6 The X-ray diffraction pattern of the product obtained in Example 5 of this invention; Figure 7 After assembling batteries from the products obtained in Examples 1, 4, and 5 of this invention, the battery temperature was 50 mA·g. -1 After activation at a current density of 10 cycles, at 1.0 A·g -1 Cyclic performance at current density; Figure 8 The product obtained in Comparative Example 1 of this invention was used to assemble a battery at 50 mA·g. -1 After activation at a current density of 10 cycles, at 1.0 A·g -1 Cyclic performance at current density; Figure 9 The product obtained in Comparative Example 2 of this invention was used to assemble a battery at 50 mA·g. -1After activation at a current density of 10 cycles, at 1.0 A·g -1 Cyclic performance at current density; Figure 10 The product obtained in Example 1 of this invention was assembled into a battery at 0.1 A·g -1 0.2A·g -1 0.5A·g -1 1.0A·g -1 2.0A·g -1 Cyclic performance diagrams at different current densities; Figure 11 After assembling batteries from the products obtained in Examples 2 and 3 of this invention, the performance at 50 mA·g -1 After activation at a current density of 10 cycles, at 1.0 A·g -1 Cyclic performance at current density; Figure 12 This is a high-resolution transmission electron microscope image of the product obtained in Example 1 of the present invention. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] Embodiments of the present invention provide a method for preparing ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material, comprising the following steps: S1: Dissolve soluble zinc salt and soluble tin salt in water to obtain zinc salt solution and tin salt solution respectively. Mix the two solutions and stir to react. Collect the product by centrifugation, wash and dry to obtain ZnSn bimetallic MOFs. S2: Dissolve ZnSn bimetallic MOFs and polyacrylonitrile in N,N-dimethylformamide, stir until uniform to obtain a spinning solution, and perform electrospinning to synthesize PAN / ZnSn-MOFs nanofiber materials. S3: After pre-oxidation and curing, PAN / ZnSn-MOF nanofibers are carbonized in an inert atmosphere to obtain a precursor; the precursor is mixed with tellurium powder and then subjected to tellurization to obtain ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material.

[0027] In a preferred embodiment of the present invention, in step S1, the molar ratio of the soluble zinc salt to the soluble tin salt is (1~2):(1~2). For example, the molar ratio of the soluble zinc salt to the soluble tin salt is 1:1, 1:2, or 2:1.

[0028] For example, the soluble zinc salt is zinc sulfate heptahydrate; the soluble tin salt is potassium stannate trihydrate.

[0029] In a preferred embodiment of the present invention, in step S1, washing is performed by washing with deionized water 3 to 5 times; drying is performed by forced air drying or vacuum drying at a temperature of 60 to 80 ℃ for 12 to 24 h.

[0030] In the following embodiments of the present invention, in step S1, the stirring reaction is carried out at room temperature.

[0031] In a preferred embodiment of the present invention, in step S2, the mass ratio of ZnSn bimetallic MOFs to polyacrylonitrile (PAN) is (1~5):(1~4). For example, the mass ratio of ZnSn bimetallic MOFs to PAN is 1:1, 5:4, or 5:3.

[0032] In a preferred embodiment of the present invention, in step S2, the electrospinning conditions are: voltage 12~18 kV, distance between the receiving electrode and the needle tip 12~18 cm, and feed rate 0.1~0.3 mL·min. -1 The ambient humidity is 30%~50%.

[0033] In a preferred embodiment of the present invention, in step S3, the pre-oxidation temperature is 150~280 °C, the holding time is 1~3 h, and the heating rate is 1~5 °C·min. -1 .

[0034] In a preferred embodiment of the present invention, in step S3, the mass ratio of the precursor to tellurium powder is 1:(1~3), preferably 1:2.

[0035] In a preferred embodiment of the present invention, in step S3, the carbonization temperature is 500~600 ℃, the holding time is 2~6 h, and the heating rate is 2~5 ℃·min. -1 .

[0036] In a preferred embodiment of the present invention, in step S3, the temperature of the tellurization treatment is 500~600 ℃, and the holding time is 2~6 h.

[0037] For example, in step S3, the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.

[0038] Embodiments of the present invention also provide a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material prepared according to the above method.

[0039] Embodiments of the present invention also provide an application of the above-mentioned ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material in the preparation of sodium-ion batteries, wherein the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material is used as a negative electrode material.

[0040] In this invention, carbon nanofiber materials prepared in each embodiment and comparative example are used as active materials and assembled into coin cells according to the following method: A negative electrode slurry is prepared by mixing the active material, conductive agent Super P conductive carbon black, binder SBR (styrene-butadiene rubber), and binder CMC (sodium carboxymethyl cellulose) in a mass ratio of 80:10:5:5. The solid content of the slurry is adjusted to 50% using deionized water. The adjusted slurry is coated onto copper foil using an automatic coating machine, dried in a vacuum drying oven at 80°C, then rolled by a roller press, punched by a slicing machine, and finally assembled into coin cells (2032) in a glove box. The electrolyte is a 1 mol / L NaClO4 solution, wherein the solvent is EC (ethylene carbonate):PC (propylene carbonate) = 1:1, with an additional 5 wt.% FEC (fluoroethylene carbonate). The separator is a glass fiber separator, and a sodium metal sheet is used as the counter electrode. Each button cell was tested for charge and discharge on a Newway tester in the voltage range of 0.01~3.0V: 10 charge and discharge cycles at 0.05A, followed by a charge and discharge test at 1A. The initial discharge capacity and first charge and discharge efficiency at 0.05A, as well as the cycle stability at 1A, were tested.

[0041] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0042] All raw materials used in the embodiments of the present invention were obtained through commercial purchase.

[0043] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0044] The technical solution of the present invention will be further illustrated by the following embodiments.

[0045] Example 1 A method for preparing a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, comprising the following steps: S1. Dissolve 5 mmol of zinc sulfate heptahydrate and 5 mmol of potassium stannate trihydrate in 100 mL and 15 mL of deionized water, respectively, to obtain zinc sulfate heptahydrate solution and potassium stannate trihydrate solution; add potassium stannate trihydrate solution dropwise to zinc sulfate heptahydrate solution, stir at 600 r / min for 6 h, after the reaction is completed, wash 4 times with deionized water by centrifugation, and then dry in a vacuum oven at 80 ℃ for 12 h to obtain ZnSn bimetallic MOFs; S2. ZnSn bimetallic MOFs and polyacrylonitrile (PAN) were dissolved in 3 mL of N,N-dimethylformamide at a mass ratio of 1:1. The mixture was stirred until homogeneous to obtain a spinning solution, which was then subjected to electrospinning. The electrospinning conditions were: voltage 15 kV, distance between the receiving electrode and the needle tip 15 cm, and feed rate 0.10 mL / min. -1 PAN / ZnSn-MOF nanofiber materials were obtained under an ambient humidity of 40%. S3. The PAN / ZnSn-MOFs nanofiber material was heated to 200 ℃ for 2 h in air at a heating rate of 2 ℃ / min, and then heated to 550 ℃ for 2 h in argon at a heating rate of 2 ℃ / min to obtain a precursor. The precursor was then mixed with tellurium powder at a mass ratio of 1:2 and heated to 550 ℃ for 2 h in argon at a heating rate of 2 ℃ / min to obtain a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material.

[0046] Field emission scanning electron microscope (FESEM) images of the ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material obtained in this embodiment are shown below. Figure 1 As shown, the composite material exhibits a nanofiber structure with a uniform fiber diameter distribution.

[0047] The X-ray diffraction pattern of the ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material (ZnTe / SnTe@C-0.5) obtained in this embodiment is as follows: Figure 2As shown, all diffraction peaks in Example 1 match well with the PDF cards of ZnTe and SnTe, proving the successful synthesis of the material in Example 1.

[0048] Example 2 A method for preparing a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, comprising the following steps: S1. Dissolve 2.5 mmol zinc sulfate heptahydrate and 5 mmol potassium stannate trihydrate in 100 mL and 15 mL of deionized water, respectively, to obtain zinc sulfate heptahydrate solution and potassium stannate trihydrate solution; add potassium stannate trihydrate solution dropwise to zinc sulfate heptahydrate solution, stir at 600 r / min for 8 h, after the reaction is completed, wash three times with deionized water by centrifugation, and then dry in a vacuum oven at 60 ℃ for 24 h to obtain ZnSn bimetallic MOFs; S2. ZnSn bimetallic MOFs and PAN were dissolved in 3 mL of N,N-dimethylformamide at a mass ratio of 1:1. The solution was stirred until homogeneous to obtain a spinning solution, which was then subjected to electrospinning. The electrospinning conditions were: voltage 12 kV, distance between the receiving electrode and the needle tip 18 cm, and feed rate 0.30 mL / min. -1 PAN / ZnSn-MOF nanofiber materials were obtained under an ambient humidity of 30%. S3. The PAN / ZnSn-MOFs nanofiber material was heated to 150 ℃ for 3 h in air at a heating rate of 1 ℃ / min, and then heated to 500 ℃ for 6 h in argon at a heating rate of 3 ℃ / min to obtain a precursor. The precursor was then mixed with tellurium powder at a mass ratio of 1:2 and heated to 500 ℃ for 6 h in argon at a heating rate of 3 ℃ / min to obtain a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material.

[0049] Example 3 A method for preparing a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, comprising the following steps: S1. Dissolve 5 mmol of zinc sulfate heptahydrate and 2.5 mmol of potassium stannate trihydrate in 100 mL and 15 mL of deionized water, respectively, to obtain zinc sulfate heptahydrate solution and potassium stannate trihydrate solution; add potassium stannate trihydrate solution dropwise to zinc sulfate heptahydrate solution, stir at 600 r / min for 4 h, after the reaction is completed, wash three times with deionized water by centrifugation, and then dry in a vacuum oven at 70 ℃ for 15 h to obtain ZnSn bimetallic MOFs; S2. ZnSn bimetallic MOFs and PAN were dissolved in 3 mL of N,N-dimethylformamide at a mass ratio of 1:1. The solution was stirred until homogeneous to obtain a spinning solution, which was then subjected to electrospinning. The electrospinning conditions were: voltage 18 kV, distance between the receiving electrode and the needle tip 12 cm, and feed rate 0.20 mL / min. -1 PAN / ZnSn-MOF nanofiber materials were obtained under an ambient humidity of 50%. S3. The PAN / ZnSn-MOFs nanofiber material was heated to 280 ℃ for 1 h in air at a heating rate of 5 ℃ / min, and then heated to 600 ℃ for 3 h in nitrogen at a heating rate of 5 ℃ / min to obtain a precursor. The precursor was then mixed with tellurium powder at a mass ratio of 1:1 and heated to 600 ℃ for 3 h in nitrogen at a heating rate of 5 ℃ / min to obtain a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material.

[0050] Example 4 A method for preparing a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, comprising the following steps: S1. Dissolve 5 mmol of zinc sulfate heptahydrate and 5 mmol of potassium stannate trihydrate in 100 mL and 15 mL of deionized water, respectively, to obtain zinc sulfate heptahydrate solution and potassium stannate trihydrate solution; add potassium stannate trihydrate solution dropwise to zinc sulfate heptahydrate solution, stir at 600 r / min for 6 h, after the reaction is completed, wash with deionized water by centrifugation, and then dry in a vacuum oven at 80 ℃ for 12 h to obtain ZnSn bimetallic MOFs; S2. ZnSn bimetallic MOFs and PAN were dissolved in 3 mL of N,N-dimethylformamide at a mass ratio of 5:4. The mixture was stirred until homogeneous to obtain a spinning solution, which was then subjected to electrospinning. The electrospinning conditions were: voltage 15 kV, distance between the receiving electrode and the needle tip 15 cm, and feed rate 0.20 mL / min. -1 PAN / ZnSn-MOF nanofiber materials were obtained under an ambient humidity of 40%. S3. The PAN / ZnSn-MOFs nanofiber material was heated to 200 ℃ for 2 h in air at a heating rate of 2 ℃ / min, and then heated to 550 ℃ for 2 h in argon at a heating rate of 2 ℃ / min to obtain a precursor. The precursor was then mixed with tellurium powder at a mass ratio of 1:2 and heated to 550 ℃ for 2 h in argon at a heating rate of 2 ℃ / min to obtain a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material.

[0051] Field emission scanning electron microscope (FESEM) images of the ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material obtained in this embodiment are shown below. Figure 3 As shown, the material exhibits a nanofiber structure with a relatively uniform fiber diameter distribution, indicating successful material synthesis.

[0052] The X-ray diffraction pattern of the ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material (ZnTe / SnTe@C-0.4) obtained in this embodiment is as follows: Figure 4 As shown, all diffraction peaks in Example 5 match well with the PDF cards of ZnTe and SnTe, proving the successful synthesis of the materials in Example 5.

[0053] Example 5 A method for preparing a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, comprising the following steps: S1. Dissolve 5 mmol of zinc sulfate heptahydrate and 5 mmol of potassium stannate trihydrate in 100 mL and 15 mL of deionized water, respectively, to obtain zinc sulfate heptahydrate solution and potassium stannate trihydrate solution; add potassium stannate trihydrate solution dropwise to zinc sulfate heptahydrate solution, stir at 600 r / min for 6 h, after the reaction is completed, wash with deionized water by centrifugation, and then dry in a vacuum oven at 80 ℃ for 12 h to obtain ZnSn bimetallic MOFs; S2. ZnSn bimetallic MOFs and PAN were dissolved in 3 mL of N,N-dimethylformamide at a mass ratio of 5:3. The mixture was stirred until homogeneous to obtain a spinning solution, which was then subjected to electrospinning. The electrospinning conditions were: voltage 15 kV, distance between the receiving electrode and the needle tip 15 cm, and feed rate 0.10 mL / min. -1 PAN / ZnSn-MOF nanofiber materials were obtained under an ambient humidity of 40%. S3. The PAN / ZnSn-MOFs nanofiber material was heated to 200 ℃ for 2 h in air at a heating rate of 2 ℃ / min, and then heated to 550 ℃ for 2 h in argon at a heating rate of 2 ℃ / min to obtain a precursor. The precursor was then mixed with tellurium powder at a mass ratio of 1:2 and heated to 550 ℃ for 2 h in argon at a heating rate of 2 ℃ / min to obtain a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material.

[0054] Field emission scanning electron microscope (FESEM) images of the ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material obtained in this embodiment are shown below. Figure 5 As shown, the material exhibits a nanofiber structure with a relatively uniform fiber diameter distribution, indicating successful material synthesis.

[0055] The X-ray diffraction pattern of the ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material (ZnTe / SnTe@C-0.3) obtained in this embodiment is as follows: Figure 6 As shown, all diffraction peaks in Example 5 match well with the PDF cards of ZnTe and SnTe, proving the successful synthesis of the material in Example 6.

[0056] The products obtained in Examples 1, 4, and 5, after being assembled into batteries, showed performance at 50 mA·g -1 After activation at a current density of 10 cycles, at 1.0 A·g -1 Cyclic performance test graph at current density is shown below Figure 7 As shown, after 4000 charge-discharge cycles, the capacity of the material obtained in Example 1 remains at a high level and has a higher capacity than that of the material in Example 5, indicating that the negative electrode material prepared in Example 1 has a better cycle life.

[0057] Comparative Example 1 S1. Dissolve 5 mmol of zinc sulfate heptahydrate and 5 mmol of potassium stannate trihydrate in 100 mL and 15 mL of deionized water, respectively, to obtain zinc sulfate heptahydrate solution and potassium stannate trihydrate solution; add potassium stannate trihydrate solution dropwise to zinc sulfate heptahydrate solution, stir at 600 r / min for 6 h, after the reaction is completed, wash with deionized water by centrifugation, and then dry in a vacuum oven at 80 ℃ for 12 h to obtain ZnSn bimetallic MOFs; S2. ZnSn bimetallic MOFs were heated to 550 ℃ at a heating rate of 2 ℃ / min under an argon atmosphere and carbonized at a constant temperature for 2 h to obtain a precursor. The precursor was then mixed with tellurium powder at a mass ratio of 1:2 and heated to 550 ℃ at a heating rate of 2 ℃ / min under an argon atmosphere for tellurization treatment to obtain ZnTe / SnTe heterojunction composite material.

[0058] Figure 8 The product obtained in Comparative Example 1 of this invention was used to assemble a battery at 50 mA·g. -1 After activation at a current density of 10 cycles, at 1.0 A·g -1 The cycling performance graph at current density shows that, compared with Example 1, Comparative Example 1 has lower cycle life and capacity retention at higher current densities, and the battery capacity drops sharply to 42 mAh·g after activation. -1The significant difference compared to Example 1 indicates that electrospinning can suppress the volume expansion of Sn-based materials, ensuring their performance and cycle life. Comparative Example 1 omits the electrospinning step, relying solely on the carbon framework generated by the pyrolysis of MOFs. This derived carbon is mostly a short-range disordered accumulation of nanoparticles, lacking long-range continuous conductive pathways, leading to severe polarization of the electrode at high current densities and a significant reduction in rate performance. Furthermore, without the encapsulation of flexible carbon fibers, the heterojunction particles are directly exposed to the electrolyte during cycling, lacking macroscopic mechanical support to buffer the drastic volume expansion, making them highly susceptible to structural collapse and active material shedding.

[0059] Comparative Example 2 S1. Dissolve 5 mmol of zinc sulfate heptahydrate and 5 mmol of potassium stannate trihydrate in 100 mL and 15 mL of deionized water, respectively, to obtain zinc sulfate heptahydrate solution and potassium stannate trihydrate solution; add potassium stannate trihydrate solution dropwise to zinc sulfate heptahydrate solution, stir at 600 r / min for 6 h, after the reaction is completed, wash with deionized water by centrifugation, and then dry in a vacuum oven at 80 ℃ for 12 h to obtain ZnSn bimetallic MOFs; S2. ZnSn bimetallic MOFs were heated to 550 ℃ under argon atmosphere at a heating rate of 2 ℃ / min and carbonized at a constant temperature for 2 h. The mixture was then acid-etched with 0.5 M hydrochloric acid for 5 days to obtain SnO2 material. S3. Dissolve SnO2 material and PAN in 3 mL of N,N-dimethylformamide at a mass ratio of 1:1, stir until homogeneous, and perform electrospinning. The electrospinning conditions are: voltage 15 kV, distance between the receiving electrode and the needle tip 15 cm, and feed rate 0.10 mL·min. -1 PAN / SnO2 nanofiber material was obtained under an ambient humidity of 40%. S4. The PAN / SnO2 nanofiber material was heated to 200℃ for 2 h in air at a heating rate of 2 ℃ / min, and then heated to 550℃ for 2 h in argon atmosphere at a heating rate of 2 ℃ / min to obtain a precursor. The precursor was then heated to 550℃ for 2 h in argon atmosphere with a heating rate of 2 ℃ / min to obtain SnTe@hierarchical porous carbon fiber composite material.

[0060] Figure 9 The product obtained in Comparative Example 2 of this invention was used to assemble a battery at 50 mA·g. -1 After activation at a current density of 10 cycles, at 1.0 A·g -1 The cycling performance graph at current density shows that, compared with Example 1, Comparative Example 2 has lower cycle life and capacity retention at higher current densities, and the battery capacity drops to 122 mAh·g after activation.-1 Furthermore, the capacity continued to decrease in subsequent cycles, showing a significant difference compared to Example 1. This indicates that constructing a telluride-based bimetallic heterostructure is more effective than single-metal telluride in maintaining battery cycle life and improving electrochemical performance. Comparative Example 2, by removing the Zn component through acid etching and retaining only SnO2 for spinning and Te-ation, fundamentally weakens the material's two core functions: First, it completely loses the self-optimizing structural mechanism of in-situ dissolution of the Zn component during cycling, preventing the electrode from dynamically generating multi-level buffer channels during charge and discharge. The structural collapse caused by SnTe volume expansion cannot be effectively mitigated, leading to a sharp deterioration in long-cycle stability. Second, the removal of Zn hinders the in-situ construction of the ZnTe / SnTe heterostructure. The lack of a built-in electric field within the heterostructure weakens the charge transfer driving force, and the disappearance of the interface pinning effect leads to irreversible coarsening of SnTe particles during cycling, significantly reducing the reversibility of the conversion and alloying reactions.

[0061] The product obtained in Example 1 of this invention, after being assembled into a battery, has a content of 0.1 A·g -1 0.2A·g -1 0.5A·g -1 1.0A·g -1 2.0A·g -1 Cyclic performance graphs at different current densities are shown below. Figure 10 As shown, the composite material obtained in Example 1 exhibits excellent reversible capacity and good capacity retention at different current densities. With current density increasing from 0.1 A·g... -1 Gradually increased to 2.0 A·g -1 The capacity decay is small, and when the current density returns to its initial value, the reversible capacity can quickly recover to near the initial level, indicating that the material possesses excellent rate performance, highly reversible electrochemical reactions, and a stable electrode structure. This is mainly attributed to the confinement protection of the one-dimensional hierarchical porous carbon fiber skeleton, the rapid charge transport at the ZnTe / SnTe heterostructure interface, and the Te vacancies' influence on Na. + The promoting effect of diffusion.

[0062] The products obtained in Examples 2 and 3 of this invention, after being assembled into batteries, exhibited a performance of 50 mA·g -1 After activation at a current density of 10 cycles, at 1.0 A·g -1 Cyclic performance at current density is shown in the figure. Figure 11 As shown, the cycling performance of Examples 2 and 3 is inferior to that of Example 1, indicating that Zn / Sn = 1:1 is the optimal ratio. At this ratio, the contents of ZnTe and SnTe phases are best matched, maximizing the heterostructure interface density. A Zn / Sn ratio that is too high or too low will disrupt the balance between the heterostructure interface and the cyclic porosity function, leading to decreased cycling stability.

[0063] Figure 12 This is a high-resolution transmission electron microscope image of the product obtained in Example 1 of the present invention. Figure 12 The image on the right shows two distinct lattice fringes, forming a clear heterostructure. Combined with XRD analysis, this indicates the formation of a ZnTe / SnTe heterostructure. Figure 12 The left-hand image shows that a nitrogen-doped hierarchical porous carbon fiber skeleton, obtained by carbonizing polyacrylonitrile, exists outside the heterojunction metal MOFs. That is, the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material prepared using the method of this invention has a heterojunction core layer formed by the synergistic effect of ZnTe and SnTe, and a nitrogen-doped porous carbon fiber conductive coating layer covering the surface of the heterojunction core layer.

[0064] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, characterized in that, Includes the following steps: S1: Dissolve soluble zinc salt and soluble tin salt in water to obtain zinc salt solution and tin salt solution respectively. Mix the two solutions and stir to react. Collect the product by centrifugation, wash and dry to obtain ZnSn bimetallic MOFs. S2: Dissolve the ZnSn bimetallic MOFs and polyacrylonitrile in N,N-dimethylformamide, stir until uniform, and obtain a spinning solution. Perform electrospinning to synthesize PAN / ZnSn-MOFs nanofiber materials. S3: After the PAN / ZnSn-MOFs nanofiber material is pre-oxidized and cured, it is carbonized under an inert atmosphere to obtain a precursor; the precursor is mixed with tellurium powder and subjected to tellurization treatment to obtain the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material.

2. The method for preparing the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material according to claim 1, characterized in that, In step S1, the molar ratio of the soluble zinc salt to the soluble tin salt is (1~2):(1~2).

3. The method for preparing the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material according to claim 1, characterized in that, In step S2, the mass ratio of the ZnSn bimetallic MOFs to polyacrylonitrile is (1~5):(1~4).

4. The method for preparing the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material according to claim 1, characterized in that, In step S2, the electrospinning conditions are: voltage 12-18 kV, distance between receiving electrode and needle 12-18 cm, pushing rate 0.1-0.3 mL·min -1 , and ambient humidity 30%-50%.

5. The method for preparing the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material according to claim 1, characterized in that, In step S3, the pre-oxidation temperature is 150-280℃, the holding time is 1-3h, and the heating rate is 1-5℃·min -1 .

6. The method for preparing the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material according to claim 1, characterized in that, In step S3, the mass ratio of the precursor to tellurium powder is 1:(1~3).

7. The method for preparing the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material according to claim 1, characterized in that, In step S3, the temperature of the carbonization treatment is 500-600 ℃, the holding time is 2-6 h, and the heating rate is 2-5 ℃·min -1 .

8. The method for preparing the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material according to claim 1, characterized in that, In step S3, the temperature of the tellurization treatment is 500~600 ℃, and the holding time is 2~6 h.

9. A ZnTe / SnTe heterostructure@hierarchical porous carbon fiber composite material, characterized in that, It is prepared according to any one of claims 1 to 8.

10. The application of the ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material as described in claim 9 in the preparation of sodium-ion batteries, characterized in that, The ZnTe / SnTe heterojunction@hierarchical porous carbon fiber composite material is used as the negative electrode material.

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