Silicon-based anode material, preparation method and use thereof

Abstract

The present invention discloses a silicon-based anode material, a preparation method thereof and uses thereof. The silicon-based anode material includes: a silicon matrix material; a first coating layer and a second coating layer sequentially formed on the surface of the silicon matrix material; wherein, the first coating layer is composed of MOFs, the central metal atom in the MOFs is a transition metal, and the organic ligand is an organic carboxylic acid; the second coating layer is composed of HNTs. By forming an HNTs@MOFs composite coating layer on the surface of the silicon matrix material, the present invention enables the silicon-based anode material to have a stable structure, small volume expansion during charge and discharge, good electrical conductivity, and excellent cycle stability and rate performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and particularly relates to a silicon-based anode material coated with HNTs@MOFs composites, a preparation method thereof, and uses thereof. Background Art

[0002] Currently, commercially available lithium-ion batteries mainly use graphite as the anode material. The theoretical specific capacity of graphite is 372 mAh / g, and high-end graphite materials on the market have reached 360 - 365 mAh / g. Therefore, the room for improving the energy density of corresponding lithium-ion batteries is quite limited. Due to the high theoretical specific capacity of silicon (4200 mAh / g at high temperature and 3580 mAh / g at room temperature), low de-lithiation potential (<0.5 V), and advantages such as environmental friendliness, rich reserves, and low cost, silicon-based anode materials are considered the first choice for the next-generation high-capacity lithium-ion battery anode materials.

[0003] Although there are still some key problems for silicon-based anode materials to achieve large-scale applications at present: ① pulverization of materials and damage to electrodes: during charge and discharge processes, silicon and lithium will undergo an alloying reaction, and the volume of silicon will expand by 100% - 300%. This continuous shrinkage and expansion will cause cracks in the silicon anode material until it pulverizes, damaging the contact between the electrode material and the current collector, causing the active material to detach from the electrode sheet, and leading to a rapid decay of the battery capacity; ② unstable SEI film: the SEI film on the surface of the silicon anode will rupture with the change of the silicon volume, and the newly exposed silicon on the surface will continue to form a new SEI film during the charge and discharge process; the continuously growing SEI film will continuously consume lithium from the positive electrode and the electrolyte, ultimately resulting in an increase in the internal resistance of the battery and a rapid decay of the capacity; ③ conductivity: the conductivity of silicon is poor, which is not conducive to the effective release of battery capacity at high rates and is also one of the factors restricting its further application.

[0004] In view of the above defects, current research on the modification of silicon-based anode materials mainly focuses on how to solve the volume effect, maintain the stability of the SEI film, and improve the first Coulomb efficiency. Coating, as a relatively common modification method, is widely used. On the one hand, it improves the conductivity of the material, and at the same time, it also avoids the direct contact between the silicon matrix material and the electrolyte, improving the cycling performance of the material. However, the current coating modification has a very limited improvement in the performance of silicon-based anode materials and is still insufficient to meet the requirements of its large-scale application. Summary of the Invention

[0005] In view of this, it is necessary for the present invention to provide a silicon-based anode material. By forming an HNTs@MOFs composite coating layer on the surface of the silicon matrix material, the structure of the silicon-based anode material is stable, with small volume expansion during charge and discharge processes, good conductivity, and excellent cycling stability and rate performance.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a silicon-based anode material, comprising:

[0008] A silicon matrix material;

[0009] A first coating layer and a second coating layer formed sequentially on the surface of the silicon matrix material;

[0010] Wherein, the first coating layer is composed of MOFs, the central metal atom in the MOFs is a transition metal, and the organic ligand is an organic carboxylic acid; the second coating layer is composed of HNTs.

[0011] In a further aspect, the silicon matrix material is silicon suboxide or nanosilicon;

[0012] Preferably, based on the mass of the silicon-based anode material, the mass percentage content of the first coating layer is 0.5-5%, and the mass percentage content of the second coating layer is 0.5-5%.

[0013] In a further aspect, the HNTs in the second coating layer are modified by a polymer;

[0014] Preferably, the polymer is selected from one of polyacetylene, polyphosphazene, polyacrylonitrile, polysiloxane, polylactic acid, chitosan, polyimide, polyaniline, polyether copolyamide, polydopamine, polypyrrole, polythiophene, polyvinyl alcohol, polyvinyl butyral, polyvinylidene fluoride, poly(phenylene vinylene).

[0015] In a further aspect, the modification method of the HNTs is: providing a solution in which the polymer is dissolved; adding HNTs to the solution, stirring, heating and refluxing to complete the polymer modification of the HNTs.

[0016] In a further aspect, in the MOFs, the transition metal is selected from one of Co 2+ 、Zn 2+ 、Cu 2+ 、Ni 2+ 、Pd 2+ 、Pt 2+ 、Ru 2+ ; and the organic carboxylic acid is selected from one of pyridine dicarboxylic acid, terephthalic acid, imidazole, triazole, oxalic acid, succinic acid, mesitylenic acid.

[0017] In a further aspect, the preparation method of the MOFs is: dropping a structure-directing agent into methanol containing an organic carboxylic acid, and then mixing it with methanol containing a soluble transition metal salt, stirring, separating, washing and drying the obtained mixture to prepare a transition metal organic framework compound MOFs.

[0018] The present invention further provides a method for preparing the silicon-based negative electrode material as described above, comprising the following steps:

[0019] S1. Providing transition metal organic framework compounds MOFs;

[0020] S2, fully mixing MOFs with silicon matrix materials, and calcining in an inert atmosphere to form a MOFs-coated silicon-based negative electrode material;

[0021] S3, adding the MOFs-coated silicon-based negative electrode material and HNTs into an organic solvent and mixing them evenly, after electrospinning, calcining in an inert atmosphere to obtain the HNTs@MOFs composite-coated silicon-based negative electrode material;

[0022] Preferably, in step S2, the calcination parameters are: temperature 600-900°C, heating rate 3-10°C / min, time 2-5h;

[0023] Preferably, in step S3, the step of uniform mixing is specifically stirring in a 60-100°C oil bath for 12-24h; and / or the step of electrospinning is specifically spinning at a propulsion speed of 1-2mL / h, the voltage is set to 14-20kV, and the spinning distance is adjusted to 10-16cm; and / or the parameters of calcination are temperature 600-900°C, heating rate 3-10°C / min, and time 2-5h.

[0024] The present invention further provides the use of the silicon-based negative electrode material as described above or the silicon-based negative electrode material prepared by the preparation method as described above in a lithium-ion battery.

[0025] The present invention further provides a negative electrode sheet, which contains the silicon-based negative electrode material as described above or the silicon-based negative electrode material prepared by the preparation method as described above.

[0026] The present invention further provides a lithium ion battery comprising the negative electrode sheet as described above.

[0027] The present invention has the following beneficial effects:

[0028] The present invention firstly coats the surface of a silicon substrate with a MOFs material, wherein the MOFs material is a coordination polymer self-assembled from an organic carboxylic acid and a transition metal ion, has a large specific surface area and a regular pore structure of adjustable size, has good thermal stability, can effectively alleviate the volume expansion problem of Si and SiO in the process of lithium insertion and extraction, and improves the cycle stability of the silicon-based negative electrode material; and because of the large specific surface area and large interlayer spacing, it is easy for lithium ions to be inserted and extracted, and at the same time, the doping of nitrogen elements and the carbon structure can improve the conductivity of the silicon-based negative electrode material.

[0029] In the present invention, on the basis of the MOF coating, HNTs are further coated. HNTs have high anisotropic ionic conductivity, high mechanical strength, good thermal stability, and a unique nanotubular structure, which can cooperate with the MOF coating layer to improve the cycle stability and rate performance of the silicon-based anode material. Description of the Drawings

[0030] Figure 1 It is the rate and cycle performance curves of the button cells prepared from the silicon-based anode materials in Example 1 and Comparative Example 1 of the present invention. Detailed Embodiments

[0031] The embodiments of the present invention will be described in detail below. The following described embodiments are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0033] The first aspect of the present invention discloses a silicon-based anode material, which includes a silicon matrix material, and a first coating layer and a second coating layer formed in sequence on the surface of the silicon matrix material; wherein, the first coating layer is composed of MOFs, the central metal atom in the MOFs is a transition metal, and the organic ligand is an organic carboxylic acid; the second coating layer is composed of HNTs.

[0034] By forming a composite coating layer of HNTs and MOFs on the surface of the silicon matrix material, while stabilizing the structure of the silicon-based anode material, the volume expansion of the silicon-based anode material during charge and discharge is small, the conductivity is good, and the cycle stability and rate performance of the silicon-based anode material are synergistically improved.

[0035] The "silicon matrix material" in the present invention refers to a conventional silicon-containing anode material in the art. For example, it includes at least one of elemental silicon (such as nano-silicon particles, metallic silicon), silicon oxide materials (SiOx, where 0 < x < 2, such as silicon monoxide), silicon carbide materials (such as SiC), and silicon alloys (Si-Y, where Y can be an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element or a combination thereof, and does not include Si). The specific type can be selected according to the performance requirements of the silicon-based anode material, etc. In some specific embodiments of the present invention, the silicon matrix material is selected from silicon monoxide or nano-silicon.

[0036] "MOFs" in the present invention refers to metal-organic framework compounds, that is, coordination polymers self-assembled from organic carboxylic acids and transition metal ions. Among them, the transition metal ions can be selected from Co 2+ 、Zn 2+ 、Cu 2+ 、Ni 2+ 、Pd 2+ 、Pt 2+ 、Ru 2+ ; and the organic carboxylic acid is selected from one of pyridine dicarboxylic acid, terephthalic acid, imidazole, triazole, oxalic acid, succinic acid, and mesitylenic acid. In some specific embodiments of the present invention, specific volumetric examples of MOFs include but are not limited to MOF-5 metal-organic framework (C 24 H 12 O 13 Zn), MOF-74 metal-organic framework (C 14 H 16 N2O8Zn2), MOF-808 metal-organic framework (C 24 H 12 O 32 Zr6), etc. It can be understood that there is no particular limitation on the specific preparation method of MOFs, and conventional solvent methods, liquid-phase diffusion methods, etc. in the art can be used. In some specific embodiments of the present invention, the specific preparation method of MOFs is: dropping a structure-directing agent (such as triethylamine) into methanol containing an organic carboxylic acid, and then mixing it with methanol containing a soluble transition metal salt, stirring, separating, washing, and drying the obtained mixture to prepare the metal-organic framework compound MOFs.

[0037] "HNTs" in the present invention refers to halloysite nanotubes, whose chemical composition is Al2[Si2O5](OH)4·nH2O (n = 0 or n = 2), which has a typical silicate structure and has the advantages of rich reserves, large aspect ratio and specific surface area, environmental friendliness, good mechanical properties, and biocompatibility. Preferably, in some specific embodiments of the present invention, the HNTs in the second coating layer are polymer-modified to further improve conductivity. The specific polymer can be selected from one of polyacetylene, polyphosphazene, polyacrylonitrile, polysiloxane, polylactic acid, chitosan, polyimide, polyaniline, polyether copolyamide, polydopamine, polypyrrole, polythiophene, polyvinyl alcohol, polyvinyl butyral, polyvinylidene fluoride, and poly(phenylene vinylene). Among them, the specific modification method is: providing a solution (such as ethanol) in which the polymer is dissolved; adding HNTs to the solution, stirring, heating, and refluxing to complete the polymer modification of HNTs.

[0038] A further solution is to adjust the content of each coating layer according to actual material performance requirements. In some specific embodiments of the present invention, based on the mass of the silicon-based negative electrode material, the mass percentage of the first coating layer is 0.5-5%, and the mass percentage of the second coating layer is 0.5-5%.

[0039] The second aspect of the present invention discloses a method for preparing the silicon-based negative electrode material as described in the first aspect of the present invention, the main steps of which are as follows:

[0040] S1. Providing transition metal organic framework compounds MOFs: they can be prepared by the preparation method described in the first aspect of the present invention, or directly obtained from the market.

[0041] S2. Fully mix the MOFs and the silicon matrix material, and calcine them in an inert atmosphere to form a MOFs-coated silicon-based negative electrode material; preferably, the calcination parameters are: temperature 600-900° C., heating rate 3-10° C. / min, and time 2-5 h.

[0042] S3. Add the MOFs-coated silicon-based negative electrode material and HNTs to an organic solvent and mix them evenly. After electrospinning, calcinate in an inert atmosphere to obtain the HNTs@MOFs composite-coated silicon-based negative electrode material; preferably, the step of mixing evenly is specifically stirring in a 60-100°C oil bath for 12-24h; and / or the step of electrospinning is specifically spinning at a propulsion speed of 1-2mL / h, the voltage is set to 14-20kV, and the spinning distance is adjusted to 10-16cm; and / or the calcination parameters are temperature 600-900°C, heating rate 3-10°C / min, and time 2-5h.

[0043] It is understood that the specific processing parameters in steps S2 and S3 can be adjusted accordingly according to the needs of those skilled in the art, so there is no particular limitation. The "inert atmosphere" described in the above steps refers to one of a rare gas (such as helium, argon, etc.) or nitrogen, which will not be elaborated here.

[0044] The third aspect of the present invention provides the use of the silicon-based negative electrode material described in the first aspect of the present invention or the silicon-based negative electrode material prepared by the preparation method described in the second aspect of the present invention in a lithium-ion battery, which can significantly improve the cycle stability and rate performance of the battery.

[0045] In a typical embodiment of the present invention, a negative electrode sheet is provided, which contains the silicon-based negative electrode material as described in the first aspect of the present invention or the silicon-based negative electrode material prepared by the preparation method as described in the second aspect of the present invention. The preparation and composition of the negative electrode sheet can be carried out according to those skilled in the art, and will not be described in detail here.

[0046] In another typical embodiment of the present invention, a lithium ion battery is provided, which includes the negative electrode sheet as described above. It is understandable that the lithium ion battery also includes a positive electrode sheet, a separator and an electrolyte, etc. These can be selected by those skilled in the art according to actual needs, and the specific assembly of the battery can adopt conventional methods in the art, so it will not be described in detail here.

[0047] The present invention is described below by means of specific examples. It should be noted that the following specific examples are only for illustrative purposes and do not limit the scope of the present invention in any way. In addition, unless otherwise specified, methods without specific conditions or steps are conventional methods, and the reagents and materials used can be obtained from commercial channels.

[0048] Example 1

[0049] The HNTs@MOFs composite-coated silicon-based negative electrode material in this embodiment is prepared by the following method:

[0050] (1) 291 g (1.0 mmol) of cobalt nitrate hexahydrate was dissolved in 25 L of methanol to form a pink solution I; 328 g of 2-methylimidazole was dissolved in 25 L of methanol to form a solution II; 20 mL of triethylamine was added dropwise to solution II, and after sufficient stirring to dissolve, solution II was introduced into cobalt nitrate solution I; the obtained mixture was stirred at room temperature for 24 hours, the purple solid was collected by centrifugation, washed three times with methanol, and dried in air at 70°C for 6 hours to obtain a transition metal organic framework compound (ZIF-67).

[0051] (2) 25 g of metal organic framework compound ZIF-67 and 475 g of silicon-based negative electrode material SiO x The mixture was evenly mixed by ball milling, and then placed in a tubular furnace for high-temperature calcination in nitrogen. The calcination temperature was 800°C, the heating rate was 5°C / min, and the calcination time was 3h to obtain a 5% MOFs-coated silicon-based negative electrode material.

[0052] (3) Dissolve 50 mL of polypyrrole in 1000 mL of ethanol solution, add 50 g of HNTs sample, heat and reflux for 24 h under stirring at 400 rpm, centrifuge, wash the solid product with fresh ethanol solvent three times, and finally dry the obtained solid in an oven at 105°C to obtain a polypyrrole-modified HNTs sample.

[0053] (4) Weigh 20 g of polypyrrole-modified HNTs powder and add it to 380 g of the organic solvent dimethylformamide (DMF). Stir and dissolve it at room temperature for 8 h to obtain a solution with a mass fraction of 5%. Add 380 g of the MOFs-coated silicon-based anode material to the above solution, stir and disperse it for 5 h to obtain a uniformly dispersed mixed spinning solution. Add the mixed spinning solution to a syringe, extrude the spinning solution at a flow rate of 1.2 mL / h, and perform electrospinning under a high-voltage electric field of 15 kV. The receiving distance is 15 cm, the ambient temperature is 25 °C, and the air humidity is 40%. The electrospun fine fibers are solidified by air and collected on the surface of aluminum foil, and then dried at 60 °C and a vacuum degree of 50 mbar for 12 h under low-temperature vacuum to remove the solvent. The spun material is calcined at a high temperature under nitrogen. The calcination temperature is 700 °C, the heating rate is 5 °C / min, and the calcination time is 4 h to obtain a 5% HNTs@5% MOFs composite-modified silicon-based anode material (SiO x @MOFs@HNTs).

[0054] Example 2

[0055] The HNTs@MOFs composite-coated silicon-based anode material in this example is prepared by the following method:

[0056] (1) Prepare the metal-organic framework compound (ZIF-67) by the same implementation method as in Example 1.

[0057] (2) Ball-mill 30 g of the metal-organic framework compound ZIF-67 and 720 g of the silicon-based anode material SiO x mix them evenly, place them in a tubular furnace, and perform high-temperature calcination in nitrogen. The calcination temperature is 800 °C, the heating rate is 5 °C / min, and the calcination time is 3 h to obtain a 4% MOFs-coated silicon-based anode material.

[0058] (3) Prepare the polypyrrole-modified HNTs sample by the same implementation method as in Example 1.

[0059] (4) Weigh 20 g of polypyrrole-modified HNTs powder and add it to 380 g of the organic solvent N,N-dimethylformamide (DMF). Stir and dissolve it at room temperature for 8 h to obtain a solution with a mass fraction of 5%. Add 480 g of the MOFs-coated silicon-based anode material to the above solution, stir and disperse it for 5 h to obtain a uniformly dispersed mixed spinning solution. Add the mixed spinning solution to a syringe, extrude the spinning solution at a flow rate of 1.2 mL / h, and perform electrospinning under a high-voltage electric field of 15 kV. The receiving distance is 15 cm, the ambient temperature is 25 °C, and the air humidity is 40%. The electrospun fine fibers are solidified by air and collected on the surface of the aluminum foil. Then, perform low-temperature vacuum drying at 60 °C and a vacuum degree of 50 mbar for 12 h to remove the solvent. The spun material is subjected to high-temperature calcination under nitrogen. The calcination temperature is 700 °C, the heating rate is 5 °C / min, and the calcination time is 4 h to obtain a 4% HNTs@4% MOFs composite-modified silicon-based anode material (SiO x @MOFs@HNTs).

[0060] Example 3

[0061] The silicon-based anode material coated with HNTs@MOFs composite in this example is prepared by the following method:

[0062] (1) Dissolve 291 g (1.0 mmol) of cobalt(II) nitrate hexahydrate in 25 L of methanol to form a pink solution I; dissolve 328 g of 2-methylimidazole in 25 L of methanol to form solution II; add 20 mL of triethylamine dropwise to solution II. After fully stirring and dissolving, introduce solution II into cobalt(II) nitrate solution I; stir the obtained mixture at room temperature for 24 h, centrifuge to collect the purple solid, wash it three times with methanol, and dry it at 70 °C in air for 6 h to obtain the metal-organic framework compound (ZIF-67).

[0063] (2) Mix 25 g of the metal-organic framework compound ZIF-67 and 475 g of the silicon-based anode material SiO x uniformly by ball milling, place it in a tube furnace, and perform high-temperature calcination in nitrogen. The calcination temperature is 800 °C, the heating rate is 5 °C / min, and the calcination time is 3 h to obtain a 5% MOFs-coated silicon-based anode material.

[0064] (3) Weigh 20 g of HNTs powder and add it to 380 g of the organic solvent dimethylformamide (DMF). Stir and dissolve it at room temperature for 8 h to obtain a solution with a mass fraction of 5%. Add 380 g of the silicon-based anode material coated with MOFs to the above solution, stir and disperse for 5 h to obtain a uniformly dispersed mixed spinning solution. Add the mixed spinning solution to a syringe, extrude the spinning solution at a flow rate of 1.2 mL / h, and perform electrospinning under a high-voltage electric field of 15 kV. The receiving distance is 15 cm, the ambient temperature is 25 °C, and the air humidity is 40%. The electrospun fine fibers are solidified by air and collected on the surface of aluminum foil, and then dried at 60 °C and a vacuum degree of 50 mbar for 12 h to remove the solvent. The spun material is calcined at high temperature under nitrogen. The calcination temperature is 700 °C, the heating rate is 5 °C / min, and the calcination time is 4 h, thus obtaining a silicon-based anode material (SiO x @MOFs@HNTs) modified by 5% HNTs@5% MOFs.

[0065] Comparative Example 1

[0066] The silicon-based anode material in this comparative example is the silicon-based anode material SiOx without any coating modification in Example 1.

[0067] Comparative Example 2

[0068] The silicon-based anode material coated with MOFs in this example is prepared by the following method:

[0069] (1) Dissolve 291 g (1.0 mmol) of cobalt nitrate hexahydrate in 25 L of methanol to form a pink solution I; dissolve 328 g of 2-methylimidazole in 25 L of methanol to form solution II; add 20 mL of triethylamine dropwise to solution II. After fully stirring and dissolving, introduce solution II into cobalt nitrate solution I; stir the obtained mixture at room temperature for 24 h, centrifuge to collect the purple solid, wash it three times with methanol, and dry it at 70 °C in air for 6 h to obtain the transition metal organic framework compound (ZIF-67).

[0070] (2) Mix 50 g of the metal organic framework compound ZIF-67 and 450 g of the silicon-based anode material SiO x by ball milling until evenly mixed, place it in a tube furnace and perform high-temperature calcination in nitrogen. The calcination temperature is 800 °C, the heating rate is 5 °C / min, and the calcination time is 3 h to obtain a silicon-based anode material coated with 10% MOFs.

[0071] Comparative Example 3

[0072] The silicon-based anode material coated with HNTs in this example is prepared by the following method:

[0073] (1) Dissolve 50 mL of polypyrrole in 1000 mL of ethanol solution, add 50 g of HNTs sample, heat and reflux for 24 h under stirring at 400 rpm, centrifuge and separate, wash the solid product 3 times with fresh ethanol solvent, and finally dry the obtained solid in an oven at 105 °C to obtain the polypyrrole-modified HNTs sample.

[0074] (2) Weigh 20 g of polypyrrole-modified HNTs powder and add it to 380 g of the organic solvent dimethylformamide (DMF). Stir and dissolve at room temperature for 8 h to obtain a solution with a mass fraction of 5%; add 180 g of the silicon-based anode material to the above solution, stir and disperse for 5 h to obtain a uniformly dispersed mixed spinning solution; add the mixed spinning solution to a syringe, extrude the spinning solution at a flow rate of 1.2 mL / h, and perform electrospinning under a high-voltage electric field of 15 kV. The receiving distance is 15 cm, the ambient temperature is 25 °C, and the air humidity is 40%. The electrospun fine fibers are solidified by air and collected on the surface of aluminum foil, and then dried at 60 °C and a vacuum degree of 50 mbar for 12 h to remove the solvent; the spun material is calcined at high temperature under nitrogen, the calcination temperature is 700 °C, the heating rate is 5 °C / min, and the calcination time is 4 h to obtain the silicon-based anode material coated with 10% HNTs.

[0075] Test Example

[0076] Perform relevant electrochemical performance tests on the silicon-based anode materials prepared in Examples 1-3 and Comparative Examples 1-3. The specific steps are as follows:

[0077] (1) Battery assembly: Assemble CR2016 button cells, where the negative electrode active materials are the silicon-based anode materials in Examples 1-3 and Comparative Examples 1-3 respectively. The weight ratio of the active material, conductive agent, and binder in the negative electrode sheet is 91:2:7. The separator is made of polyethylene (PE), the positive electrode is a lithium sheet, and the electrolyte is a special electrolyte for lithium-ion batteries. The battery assembly is carried out in a glove box (the water and oxygen content is less than 0.1 ppm).

[0078] (2) Battery test: Use an Arbin BT2000 test system to test the battery. First, activate the CR2016 button cell for two cycles at 0.05C (~0.05 mA / cm 2 ), and then cycle 5 times at 0.1C, 0.2C, 0.3C, 0.4C, and 0.5C currents respectively, and then cycle 50 times at 0.2C current to investigate the rate performance and cycle performance of the silicon-based anode material. The charge-discharge voltage range of the battery is 0.005V to 1.5V. The test results are shown in Table 1 and Figure 1 .

[0079] Table 1 Performance test results

[0080]

[0081] From the test results in Table 1 and Figure 1 it can be seen that the cycling and rate performance of the silicon-based anode material coated with HNTs@MOFs are better than those of other materials, and the electrochemical performance of the 5% HNTs@5% MOFs coating is the best. Coating the surface of the silicon matrix material with MOFs material has a large specific surface area and a regular pore structure with adjustable size, good thermal stability, and improves the rate performance and cycling stability of the silicon-based anode material. HNTs have high anisotropic ionic conductivity and a unique nanotubular structure. After being modified by polymers, HNTs can further improve the conductivity of the material and can cooperate with the MOFs coating layer to enhance the cycling stability and rate performance of the silicon-based anode material.

[0082] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0083] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent shall be subject to the appended claims.

Claims

1. A preparation method of a silicon-based anode material, characterized in that, The following steps are involved: S1. Providing a transition metal organic framework compound MOFs, wherein the central metal atom in the MOFs is a transition metal, and the organic ligand is 2-methylimidazole; S2, fully mixing MOFs and silicon matrix materials, calcining in an inert atmosphere to form a MOFs-coated silicon-based negative electrode material, wherein the calcination parameters are: temperature 600-900° C., heating rate 3-10° C. / min, time 2-5 h; S3, adding the MOFs-coated silicon-based negative electrode material and HNTs to an organic solvent and mixing them evenly, after electrospinning, calcining in an inert atmosphere, forming a first coating layer and a second coating layer on the surface of the silicon-based material in sequence, to obtain a HNTs@MOFs composite-coated silicon-based negative electrode material, wherein the mass percentage of the first coating layer is 0.5-5%, and the mass percentage of the second coating layer is 0.5-5% based on the mass of the silicon-based negative electrode material; In step S3, the step of uniform mixing is specifically stirring in an oil bath at 60-100°C for 12-24h; and / or the step of electrospinning is specifically spinning at a propulsion speed of 1-2mL / h, the voltage is set to 14-20kV, and the spinning distance is adjusted to 10-16cm; and / or the parameters of calcination are temperature 600-900°C, heating rate 3-10°C / min, and time 2-5h.

2. The preparation method according to claim 1, wherein Among the MOFs, the transition metal is selected from Co 2+ , Zn 2 + , Cu 2+ , Ni 2+ , Pd 2+ , Pt 2+ , Ru 2+ and is one of them.

3. The preparation method according to claim 1 or 2, characterized in that, The preparation method of the MOFs is: dropwise adding a structure directing agent into methanol containing an organic ligand, then mixing it with methanol containing a soluble transition metal salt, stirring, separating, washing and drying the obtained mixture to obtain a transition metal organic framework compound MOFs.

4. The preparation method according to claim 1, characterized in that, The silicon matrix material is silicon monoxide or nano silicon.

5. The preparation method according to claim 1, characterized in that, The HNTs in the second coating layer are polymer modified.

6. The preparation method according to claim 5, characterized in that, The polymer is selected from one of polyacetylene, polyphosphazene, polyacrylonitrile, polysiloxane, polylactic acid, chitosan, polyimide, polyaniline, polyether copolyamide, polydopamine, polypyrrole, polythiophene, polyvinyl alcohol, polyvinyl butyral, polyvinylidene fluoride and poly(p-phenylene vinylene).

7. The preparation method according to claim 5 or 6, characterized in that, The modification method of the HNTs is as follows: providing a solution in which the polymer is dissolved; adding HNTs to the solution, stirring, heating and refluxing for reaction, thereby completing the polymer modification of the HNTs.

8. Use of the silicon-based negative electrode material obtained by the method for preparing the silicon-based negative electrode material according to any one of claims 1 to 7 in a lithium-ion battery.

9. A negative electrode sheet, characterized in that, A silicon-based negative electrode material prepared by the method for preparing a silicon-based negative electrode material as described in any one of claims 1 to 7.

10. A lithium-ion battery, characterized in that, Contains the negative electrode sheet as claimed in claim 9.

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