A self-supporting Si@ZnO / C nanofilm material and a preparation method and application thereof

Abstract

The application discloses a kind of self-supporting Si@ZnO / C nanometer membrane materials and its preparation method and application, belong to lithium ion battery electrode material field.The preparation method includes the following steps: S1.silicon powder and 2,5-dihydroxy terephthalic acid are dissolved in N,N-dimethylformamide, to obtain A liquid;Zinc nitrate is dissolved in ethanol solution, to obtain B liquid;In the state of stirring, deprotonation reagent is added to A liquid, then B liquid is added dropwise, after ultrasonic homogenization, it is extracted and filtered, after drying, Si / MOF-74 precursor is obtained;S2.polyacrylonitrile is dissolved in solvent, then sodium dodecyl sulfate and the Si / MOF-74 precursor obtained in step S1 are added, after stirring, precursor solution is obtained, then precursor solution is electrospun to obtain precursor film;S3.the precursor film obtained in step S2 is pre-cured, then calcined under protective gas atmosphere, after natural cooling, it is obtained.The self-supporting Si@ZnO / C nanometer membrane material prepared by the application shows excellent cycle stability when used as lithium ion battery electrode material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery electrode materials technology, specifically to a self-supporting Si@ZnO / C nanofilm material, its preparation method, and its applications. Background Technology

[0002] Compared to traditional anode material graphite (theoretical lithium storage capacity is 372 mAh·g), -1 For silicon anodes, more Li can be inserted and extracted, giving them a significant capacity advantage (4200 mAh / g). -1 Silicon, with its low discharge potential, high specific capacity, abundant reserves, and environmental friendliness, is one of the most promising next-generation high-energy-density lithium-ion battery anode materials. However, silicon anode materials suffer from extremely poor cycle life, leading to rapid capacity decline after cycling, and their inherent low porosity limits their commercial application. To address their failure mechanism, the main modification method for silicon anode materials is the construction of various Si / C composite materials, including core-shell structures, yolk-shell structures, porous structures, and embedded structures. Numerous studies have shown that core-shell structures, which completely encapsulate silicon particles, can effectively improve cycle life. During cycling, the carbon material acting as the shell layer has a triple effect: mitigating the volume expansion effect of silicon, maintaining the integrity of the SEI layer, and improving conductivity, thereby greatly improving cycle performance.

[0003] In recent years, electrospinning has attracted widespread attention for its effective preparation of self-supporting nanomaterials. As a technique for preparing nanofibers, electrospinning stands out among numerous methods due to its high efficiency and controllability. Compared to traditional electrode materials, the self-supporting electrode materials prepared by this method do not require copper as a current collector, thus significantly reducing the overall battery mass and substantially increasing the overall energy density. Furthermore, for silicon materials, the absence of rigid copper as a current collector allows Si to expand in all directions rather than being confined to one, helping to mitigate the volume expansion effect and improve cycle performance. For example, Chinese patent CN113471399A discloses a method for preparing a high-conductivity Si / C nanofilm. This method includes the following steps: First, a carbon source and a silicon source are dissolved in a solvent at a mass ratio of 8:1 and stirred to obtain a pre-solution; second, the pre-solution is electrospun to obtain a pre-product; third, the pre-product is sequentially dried, cured, and calcined to obtain a Si / C nanofilm; finally, the Si / C nanofilm is vacuum-deposited to form a conductive layer, thus obtaining a high-conductivity Si / C nanofilm. When used as a lithium-ion battery anode material, the high-conductivity Si / C nanofilm prepared by this invention not only exhibits excellent conductivity but also improves the cycle stability and rate performance of lithium-ion batteries. However, the self-supporting Si / C nanofilm prepared by this method still has some problems: ① The rate performance is still relatively poor because the porosity of carbon materials is much lower than that of copper, resulting in low overall material porosity and poor rate performance. ② The poor compatibility between nano-silicon and polymers makes it difficult to obtain a perfect core-shell structure, leading to poor cycle performance. Ideally, electrospinning would completely encapsulate silicon particles within carbon nanofibers, forming a perfect core-shell structure that increases porosity and suppresses the volume expansion effect of silicon. However, in practice, issues such as excessively large silicon particles, poor dispersibility in solution, and shrinkage during carbon fiber carbonization can easily lead to silicon particles being exposed on the carbon fiber surface, resulting in poor cycling performance. Some researchers have employed coaxial electrospinning to achieve complete silicon particle encapsulation; Si / C fibers prepared in this way exhibit good cycling stability. However, this method leads to a decrease in silicon content, ultimately resulting in a reduction in the overall material's specific capacity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, one objective of this invention is to provide a method for preparing self-supporting Si@ZnO / C nanofilm materials. By perfectly encapsulating silicon particles within a MOF-74 framework, and with the MOF-74 framework forming a hollow structure during calcination, the volume expansion effect of the nano-silicon material is mitigated, thus solving the volume expansion problem of nano-silicon during lithium insertion / extraction.

[0005] The objective of this invention is achieved through the following technical solutions.

[0006] A method for preparing a self-supporting Si@ZnO / C nanofilm material includes the following steps:

[0007] S1. Dissolve silicon powder and 2,5-dihydroxyterephthalic acid in N,N-dimethylformamide to obtain solution A; dissolve zinc nitrate in ethanol solution to obtain solution B; add deprotonating agent to solution A while stirring, then add solution B dropwise to solution A, sonicate to homogenize, filter, and dry to obtain Si / MOF-74 precursor;

[0008] S2. Dissolve polyacrylonitrile in a solvent, then add surfactant and Si / MOF-74 precursor obtained in step S1, stir to obtain precursor solution, and then electrospin the precursor solution to obtain precursor film.

[0009] S3. After pre-curing the precursor film obtained in step S2, it is calcined in a protective gas atmosphere and then naturally cooled to obtain the self-supporting Si@ZnO / C nanofilm material.

[0010] The preparation method of this invention involves adding silicon powder during the preparation of the MOF-74 framework to obtain a Si / MOF-74 precursor. The MOF-74 framework completely encapsulates the silicon particles, forming a coating structure. The compatibility between silicon and polyacrylonitrile after being encapsulated by MOF-74 is greatly improved, which is beneficial for silicon to be integrated into carbon fibers and significantly optimizes the microstructure of the material. At the same time, the Si / MOF-74 precursor decomposes during calcination to generate pores. The resulting hollow structure helps to buffer the volume expansion of silicon and forms a Si@ZnO composite after annealing. Although ZnO does not have lithium storage capacity, it can play a role in mitigating the volume expansion effect and stabilizing the material structure during charge and discharge. Therefore, the self-supporting Si@ZnO / C nanofilm material obtained by the preparation method of this invention has excellent cycle stability as a negative electrode material for lithium-ion batteries.

[0011] Preferably, in step S1, the mass ratio of the silicon powder, 2,5-dihydroxyterephthalic acid and zinc nitrate is (2-3):1:(1.5-6).

[0012] Preferably, in step S1, the particle size of the silicon powder is 30-50 nm.

[0013] Preferably, in step S2, the mass ratio of the polyacrylonitrile to the Si / MOF-74 precursor is (2-8):1.

[0014] Preferably, the mass ratio of the Si / MOF-74 precursor to the surfactant is (5-10):1.

[0015] Preferably, the surfactant is sodium dodecyl sulfate or sodium dodecylbenzene sulfonate.

[0016] Preferably, in step S3, the pre-curing temperature is 180–380°C and the time is 1–3 hours.

[0017] Preferably, in step S3, the calcination temperature is 600–1000°C and the time is 1–3 hours.

[0018] Preferably, in step S1, the deprotonating agent includes at least one of triethylamine, sodium formate, and sodium acetate.

[0019] Preferably, in step S2, the electrospinning parameters are: high voltage 16-18kV, low voltage -2.3kV, and jetting speed 1-5mL / h.

[0020] Another object of the present invention is to provide a self-supporting Si@ZnO / C nanofilm material prepared by the preparation method described above.

[0021] Another object of the present invention is to provide the application of the self-supporting Si@ZnO / C nanofilm material prepared by the above preparation method in the preparation of lithium-ion battery anode materials.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. This invention utilizes the MOF-74 framework to perfectly encapsulate silicon particles, improving the compatibility of silicon particles in the material and forming a structure in which carbon nanofibers perfectly encapsulate silicon particles. Simultaneously, during the calcination process, the Si / MOF-74 precursor undergoes thermal decomposition to generate pores, and the resulting hollow structure helps to buffer the volume expansion of silicon. The resulting self-supporting Si@ZnO / C nanofilm material, as an anode material for lithium-ion batteries, exhibits excellent rate performance and cycle stability. After 200 cycles, the material's discharge specific capacity is 1037.1 mAh / g.

[0024] 2. When the self-supporting Si@ZnO / C nanofilm material prepared by this invention is used as the negative electrode material of lithium-ion batteries, it can completely eliminate the need for inactive materials such as rigid current collectors, binders, and conductive agents, thereby greatly improving the overall energy density of the battery. Attached Figure Description

[0025] Figure 1 Scanning electron microscope image of the self-supporting Si@ZnO / C nanofilm material prepared in Example 1;

[0026] Figure 2 Scanning electron microscope image of the Si / C nanofilm material prepared in Comparative Example 1;

[0027] Figure 3Cyclic performance of the self-supporting Si@ZnO / C nanofilm material prepared in Example 1 and the Si / C nanofilm material prepared in Comparative Example 1 at a current density of 0.1 A / g;

[0028] Figure 4 Rate performance diagrams of the self-supporting Si@ZnO / C nanofilm material prepared in Example 1 and the Si / C nanofilm material prepared in Comparative Example 1 at different current densities. Detailed Implementation

[0029] The applicant will now provide a detailed description of the method of the present invention with reference to specific embodiments, in order to enable those skilled in the art to clearly understand the present invention. However, the following embodiments should not be construed in any way as limiting the scope of protection claimed in the present invention.

[0030] In the following examples and comparative examples, the particle size of the silicon powder was 30-50 nm; the weight-average molecular weight of the polyacrylonitrile was 150,000; and the purity of the polyacrylonitrile, N,N-dimethylformamide, sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate was not lower than that of chemically pure.

[0031] Example 1

[0032] This embodiment provides a method for preparing a self-supporting Si@ZnO / C nanofilm material, including the following steps:

[0033] S1. Dissolve 0.4g of silicon powder and 0.198g of 2,5-dihydroxyterephthalic acid in 20mL of N,N-dimethylformamide to obtain solution A; dissolve 0.594g of zinc nitrate hexahydrate in 40mL of 50% (v / v) ethanol aqueous solution to obtain solution B; add 0.7g of triethylamine to solution A under stirring, and then use a peristaltic pump to add solution B dropwise to solution A at a uniform rate over 30min. After sonication for 10min, filter with ethanol and deionized water, and freeze-dry to obtain the Si / MOF-74 precursor;

[0034] S2. Dissolve 1.5g of polyacrylonitrile in 12mL of N,N-dimethylformamide, then add 60mg of sodium dodecyl sulfate and 0.4g of the Si / MOF-74 precursor obtained in step S1. Sonicate for 30min and stir at room temperature for 12h until completely mixed to obtain a precursor solution. Then pour the precursor solution into a syringe and push it to the needle for later use. The parameters of the electrospinning machine are set as follows: high voltage 16kV, low voltage -2.3kV, syringe push speed 1.2mL / h, and the closest distance between the needle tip and the roller surface 18cm. After electrospinning, a precursor film is obtained.

[0035] S3. Place the precursor film obtained in step S2 in a muffle furnace, heat it to 280°C at a heating rate of 2°C / min, hold it at that temperature for 2 hours for pre-curing treatment, and then let it cool naturally to room temperature. Place it in a tube furnace, heat it to 800°C at a heating rate of 2°C / min, and then calcine it under nitrogen protection for 2 hours. Finally, let it cool naturally to room temperature to obtain the self-supporting Si@ZnO / C nanofilm material.

[0036] Figure 1 The image shows a SEM image of the self-supporting Si@ZnO / C nanofilm material prepared in this embodiment. As can be seen from the image, there are bulges on the carbon nanofibers, and the particles are well encapsulated inside the carbon nanofibers.

[0037] Example 2

[0038] This embodiment provides a method for preparing a self-supporting Si@ZnO / C nanofilm material, including the following steps:

[0039] S1. Dissolve 0.6g of silicon powder and 0.198g of 2,5-dihydroxyterephthalic acid in 25mL of N,N-dimethylformamide to obtain solution A; dissolve 1.188g of zinc nitrate hexahydrate in 40mL of 50% (v / v) ethanol aqueous solution to obtain solution B; add 0.5g of sodium formate to solution A under stirring, and then use a peristaltic pump to add solution B dropwise to solution A at a uniform rate over 60min. After sonication for 10min, filter with ethanol and deionized water, and freeze-dry to obtain the Si / MOF-74 precursor;

[0040] S2. Dissolve 1.5g of polyacrylonitrile in 12mL of N,N-dimethylformamide, then add 30mg of sodium dodecyl sulfate and 0.2g of the Si / MOF-74 precursor obtained in step S1. Sonicate for 30min and stir at room temperature for 12h until completely mixed to obtain a precursor solution. Then pour the precursor solution into a syringe and push it to the needle tip for later use. The parameters of the electrospinning machine are set as follows: high voltage 16kV, low voltage -2.3kV, syringe push speed 1.2mL / h, and the closest distance between the needle tip and the roller surface is 18cm. After electrospinning, a precursor film is obtained.

[0041] S3. Place the precursor film obtained in step S2 in a muffle furnace, heat it to 180°C at a heating rate of 2°C / min, hold it at that temperature for 3 hours for pre-curing treatment, and then let it cool naturally to room temperature. Then place it in a tube furnace, heat it to 1000°C at a heating rate of 5°C / min, and calcine it under nitrogen protection for 1 hour. Then let it cool naturally to room temperature to obtain the self-supporting Si@ZnO / C nanofilm material.

[0042] Example 3

[0043] This embodiment provides a method for preparing a self-supporting Si@ZnO / C nanofilm material, including the following steps:

[0044] S1. Dissolve 0.4g of silicon powder and 0.198g of 2,5-dihydroxyterephthalic acid in 20mL of N,N-dimethylformamide to obtain solution A; dissolve 0.287g of zinc nitrate hexahydrate in 40mL of 50% (v / v) ethanol aqueous solution to obtain solution B; add 0.7g of sodium acetate to solution A while stirring, and then use a peristaltic pump to add solution B dropwise to solution A at a uniform rate over 30min. After sonication for 10min, filter with ethanol and deionized water, and freeze-dry to obtain the Si / MOF-74 precursor.

[0045] S2. Dissolve 1.5g of polyacrylonitrile in 12mL of N,N-dimethylformamide, then add 60mg of sodium dodecyl sulfate and 0.6g of the Si / MOF-74 precursor obtained in step S1. Sonicate for 30min and stir at room temperature for 12h until completely mixed to obtain a precursor solution. Then pour the precursor solution into a syringe and push it to the needle for later use. The parameters of the electrospinning machine are set as follows: high voltage 16kV, low voltage -2.3kV, syringe advance speed 1.2mL / h, and the closest distance between the needle tip and the roller surface 18cm. After electrospinning, a precursor film is obtained.

[0046] S3. The precursor film obtained in step S2 is placed in a muffle furnace and heated to 380°C at a heating rate of 3°C / min and held for 1 hour for pre-curing treatment. After naturally cooling to room temperature, it is placed in a tube furnace and heated to 600°C at a heating rate of 2°C / min and calcined under nitrogen protection for 3 hours. Then it is naturally cooled to room temperature to obtain the self-supporting Si@ZnO / C nanofilm material.

[0047] Example 4

[0048] This embodiment is basically the same as Embodiment 1, except that sodium dodecyl sulfate in step S2 is replaced with sodium dodecylbenzenesulfonate.

[0049] Comparative Example 1

[0050] This comparative example provides a method for preparing a self-supporting Si / C nanofilm material, including the following steps:

[0051] S1. Dissolve 1.5g of polyacrylonitrile in 12mL of N,N-dimethylformamide, then add 0.4g of silica powder and 60mg of sodium dodecyl sulfate. Sonicate for 30min and stir at room temperature for 12h until completely mixed to obtain a precursor solution. Pour the precursor solution into a syringe and push it to the needle tip for later use. Set the parameters of the electrospinning machine as follows: high voltage 16kV, low voltage -2.3kV, syringe push speed 1.2mL / h, and the closest distance between the needle tip and the roller surface 18cm. Obtain the precursor film after electrospinning.

[0052] S2. Place the precursor film obtained in step S1 in a muffle furnace, heat it to 280°C at a heating rate of 2°C / min, hold it at that temperature for 2 hours for pre-curing treatment, and then let it cool naturally to room temperature. Place it in a tube furnace, heat it to 800°C at a heating rate of 2°C / min, and then calcine it under nitrogen protection for 2 hours. Finally, let it cool naturally to room temperature to obtain the self-supporting Si / C nanofilm material.

[0053] Figure 2 The image shows a scanning electron microscope image of the Si / C nanofilm material prepared for Comparative Example 1. As can be seen from the image, a large number of silicon particles are attached to the fiber surface and have not been successfully spun into the fiber.

[0054] Comparative Example 2

[0055] This comparative example provides a method for preparing a self-supporting Si@ZnO / C nanofilm material, including the following steps:

[0056] S1. Dissolve 0.4g of silicon powder and 1.234g of 2-methylimidazole in 20mL of N,N-dimethylformamide to obtain solution A; dissolve 0.594g of zinc nitrate hexahydrate in 40mL of 50% (v / v) ethanol aqueous solution to obtain solution B; add solution B dropwise to solution A at a uniform rate under stirring for 30min; after aging at room temperature for 24h, filter with ethanol and deionized water, and freeze-dry to obtain Si / ZIF-8 precursor;

[0057] S2. Dissolve 1.5g of polyacrylonitrile in 12mL of N,N-dimethylformamide, then add 60mg of sodium dodecyl sulfate and 0.4g of the Si / ZIF-8 precursor obtained in step S1. Sonicate for 30min and stir at room temperature for 12h until completely mixed to obtain a precursor solution. Then pour the precursor solution into a syringe and push it to the needle tip for later use. The parameters of the electrospinning machine are set as follows: high voltage 16kV, low voltage -2.3kV, syringe push speed 1.2mL / h, and the closest distance between the needle tip and the roller surface 18cm. After electrospinning, a precursor film is obtained.

[0058] S3. Place the precursor film obtained in step S2 in a muffle furnace, heat it to 280°C at a heating rate of 2°C / min, hold it at that temperature for 2 hours for pre-curing treatment, and then let it cool naturally to room temperature. Place it in a tube furnace, heat it to 800°C at a heating rate of 2°C / min, and then calcine it under nitrogen protection for 2 hours. Finally, let it cool naturally to room temperature to obtain the self-supporting Si@ZnO / C nanofilm material.

[0059] Comparative Example 3

[0060] This comparative example provides a method for preparing a self-supporting Si@ZnO / C nanofilm material, including the following steps:

[0061] S1. Dissolve 0.198 g of 2,5-dihydroxyterephthalic acid in 20 mL of N,N-dimethylformamide to obtain solution A; dissolve 0.594 g of zinc nitrate hexahydrate in 40 mL of 50% (v / v) ethanol aqueous solution to obtain solution B; add 0.7 g of triethylamine to solution A while stirring, and then use a peristaltic pump to add solution B dropwise to solution A at a uniform rate over 30 min. After sonication for 10 min, filter with ethanol and deionized water, and freeze-dry to obtain the MOF-74 precursor.

[0062] S2. Dissolve 0.4g of silicon powder and 1.5g of polyacrylonitrile in 12mL of N,N-dimethylformamide, then add 60mg of sodium dodecyl sulfate and 0.4g of the MOF-74 precursor obtained in step S1. Sonicate for 30min and stir at room temperature for 12h until completely mixed to obtain a precursor solution. Then pour the precursor solution into a syringe and push it to the needle for later use. The parameters of the electrospinning machine are set as follows: high voltage 16kV, low voltage -2.3kV, syringe advance speed 1.2mL / h, and the closest distance between the needle tip and the roller surface 18cm. After electrospinning, a precursor film is obtained.

[0063] S3. Place the precursor film obtained in step S2 in a muffle furnace, heat it to 280°C at a heating rate of 2°C / min, hold it at that temperature for 2 hours for pre-curing treatment, and then let it cool naturally to room temperature. Place it in a tube furnace, heat it to 800°C at a heating rate of 2°C / min, and then calcine it under nitrogen protection for 2 hours. Finally, let it cool naturally to room temperature to obtain the self-supporting Si@ZnO / C nanofilm material.

[0064] Comparative Example 4

[0065] This embodiment is basically the same as Embodiment 1, except that sodium dodecyl sulfate is not added in step S2.

[0066] Application examples

[0067] The nanofilm materials prepared in Examples 1-4 and Comparative Examples 1-4 were assembled into lithium-ion coin cells for electrochemical performance testing. The specific methods are as follows: The nanofilms prepared in the examples and comparative examples were dried under vacuum at 80°C, then cut into electrode sheets. In a glove box, the positive electrode shell, electrode sheets, separator, lithium sheet, nickel foam, and negative electrode shell were stacked sequentially, and an appropriate electrolyte was added before encapsulation. The battery shell used was CR2016 type, the separator was Celgard2400, and the electrolyte was a mixed electrolyte of ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1M LiPF6 (the volume ratio of EC to DEC in the mixed electrolyte was 1:1). Cyclic performance testing was then conducted using a Landian CT2001A battery testing system (manufactured by Wuhan Landian Electronics Co., Ltd.).

[0068] Figure 3 The graphs show the cycling performance of the self-supported Si@ZnO / C nanofilm material prepared in Example 1 and the Si / C nanofilm material prepared in Comparative Example 1 at a current density of 0.1 A / g. Figure 3 As can be seen, the self-supporting Si@ZnO / C nanofilm material of Example 1 exhibits a specific capacity of 1710.9 mAh / g during the first discharge, and retains 1037.1 mAh / g after 200 cycles at a current density of 0.1 A / g, demonstrating excellent cycle stability. In contrast, the Si / C nanofilm material of Comparative Example 1 only shows a specific capacity of 491.2 mAh / g after 200 cycles at a current density of 0.1 A / g.

[0069] Figure 4 The figure shows the rate performance of the self-supported Si@ZnO / C nanofilm material prepared in Example 1 and the Si / C nanofilm material prepared in Comparative Example 1 at different current densities. As can be seen from the figure, the self-supported Si@ZnO / C nanofilm material of Example 1 exhibits the best rate performance at 0.1 A·g⁻¹. -1 The current density can reach 1735.4 mAh·g -1 The specific capacity, at 2A·g -1 Even under high current, it still has 768.3 mAh·g -1 The above specific capacity, and the lack of capacity loss when returning to a low current, demonstrates that the composite material of the present invention has excellent rate performance. The Si / C nanofilm material of Comparative Example 1 at 0.1 A·g -1 The current density can reach 1612.9 mAh·g -1 Specific capacity, but at 2A·g -1 Under high current, it only has 370.4 mAh·g -1 The specific capacity was high, but when the current returned to a low level, the specific capacity was only 641.6 mAh·g. -1 The capacity loss is significant.

[0070] The specific capacity of the self-supporting Si@ZnO / C nanofilm materials prepared in Examples 1-4 and Comparative Examples 1-4 after 200 cycles at a current density of 0.1 A / g is shown in Table 1.

[0071] Table 1 Electrochemical performance of lithium-ion batteries

[0072] <![CDATA[Initial discharge specific capacity (mAh·g -1 )]]> <![CDATA[Specific capacity after 200 cycles (mAh·g -1 )]]> Example 1 1710.9 1037.1 Example 2 1423.2 890.2 Example 3 2012.3 862.6 Example 4 1670.9 720.2 Comparative Example 1 1611.3 491.2 Comparative Example 2 1632.5 381.5 Comparative Example 3 1682.3 523.2 Comparative Example 4 1645.5 619.4

[0073] As can be seen from the data in Table 1, the self-supporting Si@ZnO / C nanofilm material prepared in this invention, when used as an electrode material for lithium-ion batteries, exhibits high specific capacity retention and excellent cycle stability after 200 cycles at a current density of 0.1 A / g. Compared with Example 1, Comparative Example 1 did not use MOF-74 to encapsulate the silicon particles. The carbon nanofibers could not completely encapsulate the silicon particles, causing them to adhere to the carbon fiber surface. This resulted in a significant decrease in specific capacity and a markedly worse cycle stability after 200 cycles. Comparative Example 2 used a ZIF-8 framework instead of the MOF-74 framework, and the battery's cycle stability also significantly deteriorated. This may be because the ZIF-8 structure is not conducive to the encapsulation of silicon particles; only the MOF-74 framework specified in this invention can perfectly encapsulate the silicon particles. In Comparative Example 3, silicon powder was added after the MOF-74 precursor was prepared. The coating effect of MOF-74 on the silicon particles deteriorated, and the cycle stability of the battery also significantly worsened. This is because simply mixing silicon particles with MOF-74 particles cannot form a coating structure, preventing the silicon particles from integrating well into the carbon fibers. In Comparative Example 4, sodium dodecyl sulfate was not added in step S2, resulting in poor material compatibility and significantly reduced cycle stability of the battery.

[0074] 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 self-supporting Si@ZnO / C nanofilm material, characterized in that, Includes the following steps: S1. Dissolve silicon powder and 2,5-dihydroxyterephthalic acid in N,N-dimethylformamide to obtain solution A; dissolve zinc nitrate in ethanol solution to obtain solution B; add deprotonating agent to solution A while stirring, then add solution B dropwise to solution A, sonicate to homogenize, filter, and dry to obtain Si / MOF-74 precursor; S2. Dissolve polyacrylonitrile in a solvent, then add surfactant and Si / MOF-74 precursor obtained in step S1, stir to obtain precursor solution, and then electrospin the precursor solution to obtain precursor film. S3. After pre-curing the precursor film obtained in step S2, it is calcined in a protective gas atmosphere and then naturally cooled to obtain the self-supporting Si@ZnO / C nanofilm material.

2. The method for preparing a self-supporting Si@ZnO / C nanofilm material according to claim 1, characterized in that, In step S1, the mass ratio of the silicon powder, 2,5-dihydroxyterephthalic acid and zinc nitrate is (2-3):1:(1.5-6).

3. The method for preparing a self-supporting Si@ZnO / C nanofilm material according to claim 1, characterized in that, In step S2, the mass ratio of the polyacrylonitrile to the Si / MOF-74 precursor is (2-8):

1.

4. The method for preparing a self-supporting Si@ZnO / C nanofilm material according to claim 1, characterized in that, The mass ratio of the Si / MOF-74 precursor to the surfactant is (5-10):

1.

5. The method for preparing a self-supporting Si@ZnO / C nanofilm material according to claim 1, characterized in that, In step S3, the pre-curing temperature is 180–380℃ and the time is 1–3 hours.

6. The method for preparing a self-supporting Si@ZnO / C nanofilm material according to claim 1, characterized in that, In step S3, the calcination temperature is 600–1000℃ and the time is 1–3 hours.

7. The method for preparing a self-supporting Si@ZnO / C nanofilm material according to claim 1, characterized in that, In step S1, the deprotonating agent includes at least one of triethylamine, sodium formate, and sodium acetate.

8. The method for preparing a self-supporting Si@ZnO / C nanofilm material according to claim 1, characterized in that, In step S2, the electrospinning parameters are: high voltage 16-18kV, low voltage -2.3kV, and jetting speed 1-5mL / h.

9. The self-supporting Si@ZnO / C nanofilm material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the self-supporting Si@ZnO / C nanofilm material according to claim 9 in the preparation of lithium-ion battery anode materials.

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