Bimetal-nitrogen site anchored silicon-carbon composite material and preparation method thereof

Abstract

The invention provides a bimetal-nitrogen site anchored silicon-carbon composite material and a preparation method thereof. The preparation method comprises the following steps: mixing a first metal catalyst, a second metal catalyst and a liquid carbon source to obtain a secondary solution; preparing aerosol particles mixed with silicon source gas from the secondary solution and a silicon source gas medium; under the protective atmosphere, aerosol particles mixed with silicon source gas are sequentially fed into a first vapor deposition area and a second vapor deposition area through carrier gas for a deposition reaction, and the silicon-carbon composite material is obtained after the reaction is finished; and treating the silicon-carbon composite material in nitrogen-containing low-temperature plasma to obtain the bimetal-nitrogen site anchored silicon-carbon composite material. The silicon-carbon composite material is a nitrogen-doped silicon-carbon composite material and is composed of silicon nanowires and carbon microtubes. The method is shorter in flow, simpler in operation process, lower in energy consumption, more environment-friendly and suitable for large-scale preparation, and has a great application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of micro / nano materials, and more specifically, to a bimetallic-nitrogen site-anchored silicon-carbon composite material and a preparation method thereof. Background Art

[0002] Silicon-carbon composites can provide a continuous conductive network for silicon active materials, promote charge transfer, and enhance the multiple properties of silicon negative electrodes. In addition, the stable structure and good mechanical properties of carbon materials during charging and discharging can relieve the mechanical stress generated during silicon-lithium alloying / dealloying, thereby enhancing the stability of electrode materials during cycling.

[0003] However, the rational combination and compounding of nano- and micron-materials, as well as the short-process, low-cost, large-scale preparation of silicon-carbon materials with excellent volumetric energy density and good cycle stability have always been issues that need to be urgently addressed today. Summary of the invention

[0004] In view of the deficiencies in the prior art, one of the purposes of the present invention is to solve one or more problems in the prior art. For example, one of the purposes of the present invention is to provide a method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material with a simple operation process, a short process flow, and low raw material cost, so as to solve the technical problems of the existing multi-step process of preparing silicon-carbon composite materials using magnesium thermal reduction of silicon and CVD deposition of carbon, which is complicated in process flow, high in energy consumption, and environmentally unfriendly.

[0005] In order to achieve the above-mentioned purpose, one aspect of the present invention provides a method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material, which may include the following steps: mixing a first metal catalyst, a second metal catalyst and a liquid carbon source to obtain a secondary solution; preparing the secondary solution and a silicon source gas medium into aerosol particles mixed with a silicon source gas; under a protective atmosphere, using a carrier gas to sequentially deliver the aerosol particles mixed with the silicon source gas into a first vapor deposition zone and a second vapor deposition zone for a deposition reaction, and obtaining a silicon-carbon composite material after the reaction is completed; treating the silicon-carbon composite material in a nitrogen-containing low-temperature plasma to obtain a bimetallic-nitrogen site-anchored silicon-carbon composite material.

[0006] Further, the temperature of the first vapor deposition zone may be 600°C to 700°C; and the temperature of the second vapor deposition zone may be 1100°C to 1200°C.

[0007] Furthermore, the first metal catalyst can be ferrocene, nickelocene or cobaltocene, the second metal catalyst can be chloroauric acid or gold chloride, the liquid carbon source can be anhydrous ethanol, acetonitrile, methane, toluene, acetylene or ethylene, the concentration of the first metal catalyst in the liquid carbon source is 1000ppm to 5000ppm, and the concentration of the second metal catalyst in the liquid carbon source is 100ppm to 500ppm.

[0008] Furthermore, the bimetallic-nitrogen site-anchored silicon-carbon composite material may be composed of silicon nanowires and carbon microtubes, the diameter of the silicon nanowires may be 200 nm to 500 nm, and the diameter of the carbon microtubes may be 1 μm to 1.5 μm.

[0009] Furthermore, the silicon source gas may be silane, silicon tetrafluoride, trichlorosilane or silicon tetrachloride, the carrier gas may be a mixed gas of an inert gas and hydrogen, and the carrier gas flow rate may be 300 ml / min to 500 ml / min.

[0010] Furthermore, the temperature of the nitrogen-containing low-temperature plasma treatment can be 200°C to 500°C, and the treatment time can be 10min to 30min; the nitrogen-containing low-temperature plasma atmosphere can be a mixed gas of ammonia and nitrogen, wherein the volume of ammonia in the mixed gas can be 10%-30%.

[0011] Furthermore, an aerosol generator can be used to prepare aerosol particles mixed with a silicon source gas, which can include adding a secondary solution into the aerosol generator, introducing a silicon source gas into an air inlet at the front end of the aerosol generator, obtaining aerosol particles mixed with a silicon source gas at an air outlet at the rear end, and using an airflow meter to control the flow rate of the aerosol particles at the air outlet, wherein the excitation pressure of the aerosol generator can be 0.1 kpa to 0.8 kpa, and the airflow meter flow rate can be 10 mL / min to 100 mL / min.

[0012] Another aspect of the present invention provides a bimetallic-nitrogen site-anchored silicon-carbon composite material, which is a nitrogen-doped silicon-carbon composite material and can be composed of silicon nanowires and carbon microtubes. The diameter of the silicon nanowires can be 200nm to 500nm, and the diameter of the carbon microtubes can be 1μm to 1.5μm. The surface of the silicon nanowires and the surface of the carbon microtubes have first metal nanoparticles and second metal nanoparticles. The first metal and the second metal form bimetallic-nitrogen sites with nitrogen to anchor the silicon nanowires and the carbon microtubes, wherein the first metal is iron, nickel or cobalt, and the second metal is gold.

[0013] Another aspect of the present invention provides a battery negative electrode, which may include the bimetallic-nitrogen site-anchored silicon-carbon composite material described above.

[0014] Another aspect of the present invention provides a lithium battery, which may include the battery negative electrode described above.

[0015] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0016] (1) The present invention sets gas phase deposition areas with different temperatures according to the different deposition temperatures required for silicon and carbon, and uses floating catalyst chemical vapor deposition (FCCVD) to achieve one-step preparation of silicon-carbon composite materials. Compared with the industrial preparation method of first using magnesium thermal reduction to prepare silicon and then using chemical vapor deposition (CVD) to deposit carbon on the silicon surface, the process of the present invention is shorter, the operation process is simpler, and the energy consumption is lower, the environment is more friendly, and it is suitable for large-scale preparation, and has great application prospects.

[0017] (2) The method of the present invention is to treat with low-temperature nitrogen-containing plasma so that the residual second metal catalyst active atoms grow in situ at the end points of the silicon nanowires, and the second metal nanoparticles and the residual first metal catalyst active atoms grow in situ on the surface of the carbon microtubes to form stable first metal and second metal nanoparticles. These first metal and second metal nanoparticles with active sites form bimetallic-nitrogen active sites (bimetallic-N) with the doped nitrogen. x Active sites), which is beneficial to promote the self-assembly of silicon nanowires and carbon microtubes, making the structure of the silicon-carbon composite material prepared by FCCVD more stable.

[0018] (3) The silicon-carbon composite material prepared by the present invention is composed of silicon nanowires and carbon microtubes. Compared with nanostructured carbon tubes, carbon microtubes can inhibit the volume expansion of silicon nanowires in electrode materials. In addition, since the structural stability of carbon nanotubes is weak, they are easily deformed or damaged under mechanical loads, while the carbon microtubes of the present invention have larger sizes and higher mechanical strength, and are more stable in response to external pressure and stress. For example, when the battery falls and collides, the electrode material inside the battery is less likely to be damaged and collapsed, thereby avoiding safety hazards, and thus has greater development prospects.

[0019] (5) The full battery using the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared by the present invention as the negative electrode and assembled with the commercial NCM811 positive electrode has excellent cycle performance. The full battery has a cycle performance of 0.5C (1C = 160mAg -1 ) can still obtain about 153.9 mAh g after 300 charge / discharge cycles. -1 The reversible capacity of 573.43Wh kg was achieved with a capacity retention rate of 81.9%. -1 High energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects and features of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0021] Figure 1 This is the XRD pattern of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in Example 1 of the present invention.

[0022] Figure 2 This is the XRD pattern of the product prepared after replacing the silane in Example 1 with argon.

[0023] Figure 3 These are digital photos and SEM images of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in Example 1 of the present invention.

[0024] Figure 4 This is a TEM image of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in Example 1 of the present invention.

[0025] Figure 5 High-angle annular dark-field TEM image and EDS image of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in Example 1 of the present invention.

[0026] Figure 6 This is a full battery cycle performance diagram of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in Example 1 as the negative electrode and assembled with a commercial NCM811 positive electrode. DETAILED DESCRIPTION

[0027] Hereinafter, the bimetallic-nitrogen site-anchored silicon-carbon composite material and the preparation method thereof according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0028] In one aspect, the present invention provides a method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material. In some embodiments, the preparation method may include the following steps:

[0029] S100, mixing a first metal catalyst, a second metal catalyst and a liquid carbon source to obtain a secondary solution.

[0030] S200, preparing aerosol particles mixed with silicon source gas by mixing the secondary solution with the silicon source gas medium.

[0031] S300, under a protective atmosphere, using a carrier gas to sequentially deliver aerosol particles mixed with a silicon source gas into a first vapor deposition zone and a second vapor deposition zone for a deposition reaction, and after the reaction is completed, a silicon-carbon composite material is obtained.

[0032] S400, treating the silicon-carbon composite material in nitrogen-containing low-temperature plasma to obtain a bimetallic-nitrogen site-anchored silicon-carbon composite material.

[0033] In some embodiments, for step S100, the first metal catalyst and the second metal catalyst can be mixed with a liquid carbon source at room temperature, and a secondary solution is obtained by magnetic stirring. In certain embodiments, the first metal catalyst can be ferrocene, nickelocene or cobaltocene. The second metal catalyst can be chloroauric acid or gold chloride. The liquid carbon source can be anhydrous ethanol, acetonitrile, methane, toluene, acetylene or ethylene. In certain embodiments, the concentration of the first metal catalyst in the liquid carbon source can be 1000ppm to 5000ppm. For example, the concentration of the first metal catalyst in the liquid carbon source can be 1200ppm to 4500ppm, 1500ppm to 4000ppm, 1800ppm to 3600ppm, 2200ppm to 3300ppm, 2500ppm to 3000ppm or a combination of the above ranges. In certain embodiments, the concentration of the second metal catalyst in the liquid carbon source can be 100ppm to 500ppm. For example, the concentration of the second metal catalyst in the liquid carbon source can be 120 ppm to 460 ppm, 145 ppm to 425 ppm, 200 ppm to 380 ppm, 240 ppm to 300 ppm, or a combination of the above ranges.

[0034] In some embodiments, the aerosol particles mixed with the silicon source gas can be prepared using an aerosol generator. The aerosol generator can be an existing conventional aerosol generator. The secondary solution is added to the aerosol generator, the silicon source gas is introduced into the front air inlet of the aerosol generator, and the aerosol particles mixed with the silicon source gas are obtained at the rear air outlet. The silicon source gas that excites the aerosol generator can be silane, silicon tetrafluoride, trichlorosilane or silicon tetrachloride. The excitation pressure can be 0.1kpa~0.8kpa, for example, the excitation pressure can be 0.2kpa~0.7kpa, 0.3kpa~0.6kpa, 0.4kpa~0.5kpa or a combination of the above ranges. The airflow meter can be used to control the air outlet aerosol particle flow rate at the rear air outlet of the aerosol generator. For example, the airflow meter flow rate can be set to 10mL / min~100mL / min. For another example, the air flow meter flow rate can be set to 20mL / min to 90mL / min, 30mL / min to 85mL / min, 45mL / min to 70mL / min, 52mL / min to 65mL / min, or a combination of the above ranges.

[0035] In some embodiments, for step S300, the present invention can achieve heating of the two gas deposition reaction zones to different temperatures by using a segmented heating tube furnace, and then the aerosol particles mixed with the silicon source gas prepared in step S200 are transported by a carrier gas composed of an inert gas and a reducing gas to the two high-temperature areas of the tube furnace for constant temperature reaction. In the first gas deposition zone, the silicon source gas decomposes at high temperature, and the silicon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and a metal catalyst. The silicon atoms are connected and gradually diffused and deposited, and then grow into silicon nanowires. In the second gas deposition zone, the liquid carbon source decomposes at high temperature, and the carbon atoms gradually dissolve and reach saturation under the catalytic action of high temperature and another metal catalyst. The carbon atoms are connected and gradually diffused and deposited, and then grow into carbon microtubes, and finally the silicon-carbon composite material is collected on the tail collector. In some embodiments, the deposition reaction needs to be carried out under a protective atmosphere. For example, deposition can be carried out under the protection of argon. Specifically, when the first metal catalyst is ferrocene and the second metal catalyst is chloroauric acid, in the first vapor deposition zone, the metal catalyst mainly involved in the growth of silicon nanowires is the gold catalyst (HAuCl4→Au+2Cl2+HCl), and the iron catalyst may indirectly participate in the growth of silicon nanowires through synergistic effects. In the second vapor deposition zone, the metal catalyst mainly involved in the growth of carbon microtubes is the iron catalyst (C 14 H 14 Fe→Fe+C 14 H 12 ), the gold catalyst may indirectly participate in the growth of carbon microtubes through a synergistic effect.

[0036] In some embodiments, the temperature of the first vapor deposition zone may be 600°C to 700°C; the temperature of the second vapor deposition zone may be 1100°C to 1200°C. For example, the temperature of the first vapor deposition zone may be 620°C to 680°C; the temperature of the second vapor deposition zone may be 1120°C to 1180°C. For another example, the temperature of the first vapor deposition zone may be 630°C to 650°C; the temperature of the second vapor deposition zone may be 1130°C to 1150°C. In certain embodiments, the temperature may be raised to the temperature set in the first vapor deposition zone and the second vapor deposition zone at a heating rate of 2°C / min to 5°C / min.

[0037] In some embodiments, the carrier gas can be a mixture of an inert gas and hydrogen. For example, the carrier gas can be a mixture of argon and hydrogen. The hydrogen can account for 4% to 6% of the volume of the mixed gas. For example, the hydrogen can account for 5% of the volume of the mixed gas. In certain embodiments, the flow rate of the carrier gas can be set to 300 ml / min to 500 ml / min. For example, the flow rate of the carrier gas can be set to 400 ml / min.

[0038] In some embodiments, the temperature for treating the silicon-carbon composite material in the nitrogen-containing low-temperature plasma can be 200°C to 500°C, and the treatment time can be 10min to 30min. For example, the treatment temperature can be 240°C to 420°C, and the treatment time can be 15min to 25min. For another example, the treatment temperature can be 300°C to 380°C, and the treatment time can be 18min to 22min. In certain embodiments, the nitrogen-containing low-temperature plasma atmosphere can be a mixed gas of ammonia and nitrogen, wherein the volume of ammonia in the mixed gas can be 10%-30%. For example, the volume of ammonia in the mixed gas can be 20%. The mixed gas flow rate can be 10sccm to 30sccm (standard cubic centimeters per minute), for example, the mixed gas flow rate can be 20sccm.

[0039] In some embodiments, the silicon-carbon composite material prepared by step S300 is treated with nitrogen-containing plasma at low temperature. At low temperature, the residual first metal and second metal nanoparticles are decomposed into single atoms and coordinated with nitrogen, and finally form bimetallic-nitrogen (bimetallic-Nx) active sites. Specifically, by low-temperature nitrogen-containing plasma treatment, the residual second metal catalyst active atoms can be grown in situ at the end of the silicon nanowire, and the second metal nanoparticles and the residual first metal catalyst active atoms can grow stable first metal and second metal nanoparticles on the surface of the carbon microtube in situ. These first metal and second metal nanoparticles with active sites (bimetallic-Nx active sites) are conducive to promoting the self-assembly of silicon nanowires and carbon microtubes, and synergistically stabilizing the silicon-carbon composite material. In some embodiments, the time for treating the silicon-carbon composite material in nitrogen-containing low-temperature plasma can be 10min to 30min. For example, the low-temperature plasma treatment time can be 12min to 25min, 18min to 22min or a combination of the above ranges. By treating in nitrogen-containing low-temperature plasma, the nitrogen element in the atmosphere can be doped in the silicon-carbon composite material to obtain a nitrogen-doped silicon-carbon composite material.

[0040] In some embodiments, the bimetallic-nitrogen site-anchored silicon-carbon composite material may be a nitrogen-doped silicon-carbon composite material. The silicon-carbon composite material may be composed of silicon nanowires and carbon microtubes, wherein the diameter of the silicon nanowires may be 200nm to 500nm, and the diameter of the carbon microtubes may be 1μm to 1.5μm. The silicon-carbon composite material of the present invention comprises microstructured carbon microtubes, which can inhibit the volume expansion of silicon nanowires in electrode materials compared to nanostructured carbon tubes, and the microstructured carbon microtubes have larger sizes and higher mechanical strength, and are more stable in response to external pressure and stress. In certain embodiments, the diameter of the silicon nanowire may be 220nm to 480nm, 248nm to 445nm, 295nm to 400nm, 315nm to 345nm, or a combination of the above ranges. The diameter of the carbon microtube may be 1.1μm to 1.4μm, 1.2μm to 1.3μm, or a combination of the above ranges.

[0041] Specifically, the mechanism of preparing the bimetallic-nitrogen site-anchored silicon-carbon composite material of the present invention is as follows:

[0042] (I) Interaction between solvent and solute. As a carbon source solution, it has polarity and can generate hydrogen bonds and van der Waals forces with the polar part of the ferrocene molecule (taking ferrocene catalyst as an example). These interactions help the dissolution of ferrocene. The mechanism of dissolution of chloroauric acid (HAuCl4) (taking chloroauric acid catalyst as an example) in alcohol includes ion dissociation, hydrogen bonding and electrostatic solvation. HAuCl4 will dissociate into H + and AuCl4 - , H + Forms hydrogen bonds with -OH of ethanol, AuCl4 - The electrostatic interaction causes solvation with the polar part of ethanol, and finally the chloroauric acid is dissolved in the alcohol. Furthermore, the ferrocene catalyst, the chloroauric acid catalyst and the anhydrous ethanol are mixed to form a secondary solution.

[0043] (ii) Deposition is performed using the FCCVD method.

[0044] (1) Catalyst pyrolysis: In the high temperature deposition zone, ferrocene (C 14 H 14 Fe) will first decompose into iron and organic matter. This process can be expressed as: 14 H 14 Fe→Fe+C 14 H 12 After ferrocene decomposes, the iron nanoparticles act as a catalyst to promote subsequent reactions.

[0045] Similarly, chloroauric acid will also decompose at high temperatures: HAuCl4→Au+2Cl2+HCl, and then gold nanoparticles will act as catalysts to promote subsequent reactions.

[0046] (2) Decomposition of carbon source: Ethanol (C2H5OH) as a carbon source will decompose at high temperature. This process can be expressed as:

[0047] C2H5OH→CH4+CO+H2; CO+CO→C+CO2;

[0048] CH4→C+2H2.

[0049] In these reactions, the CH and CO bonds of ethanol are broken, releasing carbon atoms.

[0050] Similarly, when silane is introduced into the reaction chamber and contacts the catalyst at high temperature, it decomposes to form silicon atoms and hydrogen. The chemical reaction is as follows:

[0051] SiH4→Si+2H2.

[0052] The decomposed silicon atoms diffuse in the gas phase and react with the liquid metal catalyst.

[0053] (iii) Deposition and diffusion of carbon atoms.

[0054] The generated carbon atoms diffuse on the catalyst surface. When the catalyst particles adsorb enough carbon atoms, a supersaturated state is formed. At this time, the catalyst particles will promote the aggregation and recombination of carbon atoms to form a tubular structure.

[0055] Growth mechanism of carbon microtubes: The growth of CWTs on the catalyst surface can be carried out in two modes:

[0056] (1) Base growth mode: Carbon atoms are deposited from the bottom of the catalyst particles to form the bottom of the nanotubes.

[0057] (2) Tip growth mode: Carbon atoms grow from the top of the microtube, and the catalyst particles are inside the microtube.

[0058] Similarly, the deposition and diffusion of silicon atoms: silicon atoms dissolve in the catalyst metal droplets. As the reaction proceeds, more silicon atoms are continuously transferred from the gas phase (silane decomposition) to the droplets, and are absorbed and supersaturated by the droplets, and silicon is deposited at the solid-liquid interface. When the supersaturation state is reached, silicon begins to precipitate from the droplets. Starting from the bottom of the catalyst droplet, silicon atoms are deposited downward in the form of crystals (nanowires continue to extend downward) to form silicon nanowires. The metal droplet is always at the top of the nanowire, guiding the growth direction.

[0059] As the reaction continues, more silicon atoms are continuously transferred from the gas phase (silane decomposition) to the droplets and are absorbed and supersaturated by the droplets, and silicon is deposited at the solid-liquid interface.

[0060] (IV) Cooperative stabilization mechanism of bimetallic-nitrogen sites:

[0061] Low-temperature nitrogen-containing plasma treatment allows the residual Au catalyst active atoms to grow in situ at the ends of silicon nanowires, and Au nanoparticles and residual Fe catalyst active atoms to grow stable Au and Fe nanoparticles on the surface of carbon microtubes in situ. These Au and Fe nanoparticles with active sites (bimetallic-nitrogen active sites) are beneficial to promoting the self-assembly of silicon nanowires and carbon microtubes, making the structure of the silicon-carbon composite material prepared by FCCVD more stable.

[0062] Another aspect of the present invention provides a bimetallic-nitrogen site-anchored silicon-carbon composite material. In some embodiments, the bimetallic-nitrogen site-anchored silicon-carbon composite material is a nitrogen-doped silicon-carbon composite material, which can be composed of silicon nanowires and carbon microtubes, the silicon nanowire diameter can be 200nm to 500nm, the carbon microtube diameter can be 1μm to 1.5μm, the silicon nanowire surface and the carbon microtube surface have a first metal nanoparticle and a second metal nanoparticle, the first metal and the second metal form a bimetallic-nitrogen site with nitrogen to anchor the silicon nanowire and the carbon microtube, wherein the first metal is iron, nickel or cobalt, and the second metal is gold.

[0063] Another aspect of the present invention provides a battery negative electrode, which may include the bimetallic-nitrogen site-anchored silicon-carbon composite material described above.

[0064] Another aspect of the present invention provides a lithium battery, which may include the battery negative electrode described above. The full battery assembled with the negative electrode and the commercial NCM811 positive electrode has excellent lithium storage capacity and cycle stability.

[0065] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

[0066] Example 1

[0067] A method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material, the specific steps of which are as follows:

[0068] Step 1: At room temperature, weigh 0.5 g of ferrocene and 0.01 g of chloroauric acid and dissolve them in 100 mL of ethanol solution. Stir magnetically at 450 r / min for 1 h until ferrocene and chloroauric acid are completely dissolved to obtain a secondary solution.

[0069] Step 2, adding the obtained secondary solution to the aerosol generator, introducing silane gas into the front air inlet of the aerosol generator, using air pressure to excite the generator, the air pressure is 0.5kpa, and ferrocene, chloroauric acid, and ethanol aerosol particles mixed with silane gas are obtained at the rear air outlet, and the flow rate of the aerosol particles at the air outlet is controlled by an air flow meter, and the flow rate is 50mL / min.

[0070] Step 3, the two-stage heating tube furnace heats the two gas deposition reaction zones to 650°C (first gas deposition zone) and 1150°C (second gas deposition zone) respectively under argon atmosphere, and then introduces hydrogen (5% hydrogen) in argon to transport the aerosol particles mixed with the silicon source gas in step 2 to the two high-temperature areas of the tube furnace for constant temperature reaction, with a flow rate of 300ml / min. In the first gas deposition zone, the silane gas decomposes at high temperature, and the silicon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and gold nanoparticles, and the silicon atoms connect and gradually diffuse and deposit, and then grow into silicon nanowires; in the second gas deposition zone, ethanol decomposes at high temperature, and the carbon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and iron nanoparticles, and the carbon atoms connect and gradually diffuse and deposit, and then grow into carbon microtubes; finally, the silicon-carbon composite material is collected on the tail collector.

[0071] Step 4: Treat the silicon-carbon composite material prepared in step 3 with nitrogen-containing plasma at 250°C for 20 minutes. The nitrogen-containing plasma is a mixture of NH3 and N2 (20% ammonia) with a flow rate of 15 sccm (standard cubic centimeters per minute). At low temperature, the two remaining metal nanoparticles are decomposed into single atoms and coordinated with nitrogen to form Au-N x 、Fe-N x Active sites are obtained to obtain a bimetallic-nitrogen site-anchored silicon-carbon composite material.

[0072] The XRD pattern of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in this embodiment is shown in FIG. Figure 1 As shown. Since carbon is amorphous, Figure 1 The XRD pattern of the product is not shown. Therefore, the inventor replaced the silane in step 2 of this embodiment with argon gas for FCCVD. The XRD pattern of the collected product is as follows: Figure 2 As shown, the XRD pattern shows that the product is an amorphous carbon material. Figure 1 and Figure 2 It shows that the present invention prepares a silicon-carbon composite material.

[0073] The digital photo and SEM image of the bimetallic-nitrogen site anchored silicon-carbon composite material prepared in this example are as follows: Figure 3 As shown, from Figure 3It can be seen that the prepared bimetallic-nitrogen site-anchored silicon-carbon composite material is mainly composed of silicon nanowires and carbon microwires / tubes, the diameter of the silicon nanowires is 350nm, and the diameter of the carbon microwires / tubes is 1.25μm.

[0074] The TEM image of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in this example is as follows: Figure 4 As shown. Figure 4 As can be seen from Figures (a) and (b), the material with a diameter of micrometer scale in the prepared silicon-carbon composite material is an amorphous tubular structure material; Figure 4 As can be seen from Figures (c) and (d), the nanometer-scale material in the prepared silicon-carbon composite material is a crystalline linear structure material. Figure 1 XRD patterns and Figure 2 The digital photos and SEM images prove that the prepared bimetallic-nitrogen site-anchored silicon-carbon composite material is composed of silicon nanowires and carbon microtubes.

[0075] High-angle annular dark-field TEM image of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in this example ( Figure 5 a) and EDS images ( Figure 5 a l , a2), where a l Figure 1 shows the N element distribution diagram, and Figure 2 shows the C element distribution diagram. The EDS images show that Au-N was successfully generated on the surface of carbon microtubes. x 、Fe-N x active site, where x represents the number of nitrogen atoms.

[0076] The bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in this example was used as the negative electrode and assembled with the commercial NCM811 positive electrode to form a full battery such as Figure 6 As shown. Figure 6 It can be seen that the full battery is at 0.5C (1C = 160mAg -1 ) can still obtain about 153.9 mAh g after 300 charge / discharge cycles. -1 The reversible capacity of 573.43Wh kg was achieved with a capacity retention rate of 81.9%. -1 High energy density.

[0077] Example 2

[0078] A method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material, the specific steps of which are as follows:

[0079] Step 1: At room temperature, weigh 0.2 g of ferrocene and 0.02 g of chloroauric acid and dissolve them in 100 mL of ethanol solution. Stir magnetically at 350 r / min for 1.5 h until ferrocene and chloroauric acid are completely dissolved to obtain a secondary solution.

[0080] Step 2, adding the obtained secondary solution into the aerosol generator, introducing silane gas into the front air inlet of the aerosol generator, using air pressure to excite the generator, the air pressure is 0.3kpa, and ferrocene, chloroauric acid, and ethanol aerosol particles mixed with silane gas are obtained at the rear air outlet, and the flow rate of the aerosol particles at the air outlet is controlled by an air flow meter, and the flow rate is 80mL / min.

[0081] Step 3, the two-stage heating tube furnace heats the two gas deposition reaction zones to 620°C (first gas deposition zone) and 1100°C (first gas deposition zone) respectively under argon atmosphere, and then introduces hydrogen (5% hydrogen) in argon to transport the aerosol particles mixed with the silicon source gas in step 2 to the two high-temperature areas of the tube furnace for constant temperature reaction, with a flow rate of 400ml / min. In the first gas deposition zone, the silane gas decomposes at high temperature, and the silicon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and gold nanoparticles, and the silicon atoms connect and gradually diffuse and deposit, and then grow into silicon nanowires; in the second gas deposition zone, ethanol decomposes at high temperature, and the carbon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and iron nanoparticles, and the carbon atoms connect and gradually diffuse and deposit, and then grow into carbon microtubes; finally, the silicon / carbon composite material is collected on the tail collector.

[0082] Step 4: Treat the silicon-carbon composite material prepared in step 3 with nitrogen-containing plasma at 200°C for 25 minutes. The nitrogen-containing plasma is a mixture of NH3 and N2 (10% ammonia) with a flow rate of 20 sccm (standard cubic centimeters per minute). At low temperature, the two remaining metal nanoparticles are decomposed into single atoms and coordinated with nitrogen to form Au-N x 、Fe-N x Active sites are obtained to obtain a bimetallic-nitrogen site-anchored silicon-carbon composite material.

[0083] Example 3

[0084] A method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material, the specific steps of which are as follows:

[0085] Step 1: At room temperature, weigh 0.4 g of ferrocene and 0.03 g of chloroauric acid and dissolve them in 100 mL of ethanol solution. Stir magnetically at a speed of 550 r / min for 0.5 h until ferrocene and chloroauric acid are completely dissolved to obtain a secondary solution.

[0086] Step 2, adding the obtained secondary solution to the aerosol generator, introducing silane gas into the front air inlet of the aerosol generator, using air pressure to excite the generator, the air pressure is 0.1kPa, and ferrocene, chloroauric acid, and ethanol aerosol particles mixed with silane gas are obtained at the rear air outlet, and the flow rate of the aerosol particles at the air outlet is controlled by an air flow meter, and the flow rate is 60mL / min.

[0087] Step 3, the two-stage heating tube furnace heats the two gas deposition reaction zones to 640°C (first gas deposition zone) and 1180°C (second gas deposition zone) respectively under argon atmosphere, and then introduces hydrogen (5% hydrogen) in argon to transport the aerosol particles mixed with the silicon source gas in step 1 to the two high-temperature areas of the tube furnace for constant temperature reaction, with a flow rate of 450ml / min. In the first gas deposition zone, the silane gas decomposes at high temperature, and the silicon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and gold nanoparticles, and the silicon atoms connect and gradually diffuse and deposit, and then grow into silicon nanowires; in the second gas deposition zone, ethanol decomposes at high temperature, and the carbon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and iron nanoparticles, and the carbon atoms connect and gradually diffuse and deposit, and then grow into carbon microtubes; finally, the silicon / carbon composite material is collected on the tail collector.

[0088] Step 4: Treat the silicon-carbon composite material prepared in step 3 with nitrogen-containing plasma at 320°C for 15 minutes. The nitrogen-containing plasma is a mixture of NH3 and N2 (10% ammonia) with a flow rate of 20 sccm (standard cubic centimeters per minute). At low temperature, the two remaining metal nanoparticles are decomposed into single atoms and coordinated with nitrogen to form Au-N x 、Fe-N x Active sites are obtained to obtain a bimetallic-nitrogen site-anchored silicon-carbon composite material.

[0089] Example 4

[0090] A method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material, the specific steps of which are as follows:

[0091] Step 1: At room temperature, weigh 0.1 g of ferrocene and 0.05 g of chloroauric acid and dissolve them in 100 mL of ethanol solution. Stir magnetically at a speed of 520 r / min for 1.5 h until ferrocene and chloroauric acid are completely dissolved to obtain a secondary solution.

[0092] Step 2, adding the obtained secondary solution to the aerosol generator, introducing silane gas into the front air inlet of the aerosol generator, using air pressure to excite the generator, the air pressure is 0.8kPa, and ferrocene, chloroauric acid, and ethanol aerosol particles mixed with silane gas are obtained at the rear air outlet, and the flow rate of the aerosol particles at the air outlet is controlled by an air flow meter, and the flow rate is 100mL / min.

[0093] Step 3, the two-stage heating tube furnace heats the two gas deposition reaction zones to 700°C (first gas deposition zone) and 1150°C (second gas deposition zone) respectively under argon atmosphere, and then introduces hydrogen (5% hydrogen) in argon to transport the aerosol particles mixed with the silicon source gas in step 2 to the two high-temperature areas of the tube furnace for constant temperature reaction, with a flow rate of 500ml / min. In the first gas deposition zone, the silane gas decomposes at high temperature, and the silicon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and gold nanoparticles, and the silicon atoms connect and gradually diffuse and deposit, and then grow into silicon nanowires; in the second gas deposition zone, ethanol decomposes at high temperature, and the carbon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and iron nanoparticles, and the carbon atoms connect and gradually diffuse and deposit, and then grow into carbon microtubes; finally, the silicon / carbon composite material is collected on the tail collector.

[0094] Step 4: Treat the silicon-carbon composite material prepared in step 3 with nitrogen-containing plasma at 400°C for 15 minutes. The nitrogen-containing plasma is a mixture of NH3 and N2 (25% ammonia) with a flow rate of 20 sccm (standard cubic centimeters per minute). At low temperature, the two remaining metal nanoparticles are decomposed into single atoms and coordinated with nitrogen to form Au-N x 、Fe-N x Active sites are obtained to obtain a bimetallic-nitrogen site-anchored silicon-carbon composite material.

[0095] Example 5

[0096] A method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material, the specific steps of which are as follows:

[0097] Step 1: At room temperature, weigh 0.5 g of cobaltocene and 0.05 g of chloroauric acid and dissolve them in 100 mL of ethanol solution, stir magnetically at a speed of 600 r / min for 2 h, and wait until the cobaltocene and chloroauric acid are completely dissolved to obtain a secondary solution.

[0098] Step 2, adding the obtained secondary solution to the aerosol generator, introducing silane gas into the front air inlet of the aerosol generator, using air pressure to excite the generator, the air pressure is 0.8kPa, and obtaining cobaltocene, chloroauric acid, and ethanol aerosol particles mixed with silane gas at the rear air outlet, and using an airflow meter to control the flow rate of the aerosol particles at the air outlet, the flow rate is 100mL / min.

[0099] Step 3, the two-stage heating tube furnace heats the two gas deposition reaction zones to 650°C (first gas deposition zone) and 1200°C (second gas deposition zone) respectively under argon atmosphere, and then introduces hydrogen (5% hydrogen) in argon to transport the aerosol particles mixed with the silicon source gas in step 2 to the two high-temperature areas of the tube furnace for constant temperature reaction, with a flow rate of 300ml / min. In the first gas deposition zone, the silane gas decomposes at high temperature, and the silicon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and gold nanoparticles, and the silicon atoms connect and gradually diffuse and deposit, and then grow into silicon nanowires; in the second gas deposition zone, ethanol decomposes at high temperature, and the carbon atoms gradually dissolve and gradually reach saturation under the catalytic action of high temperature and cobalt nanoparticles, and the carbon atoms connect and gradually diffuse and deposit, and then grow into carbon microtubes; finally, the silicon / carbon composite material is collected on the tail collector.

[0100] Step 4: Treat the silicon / carbon composite material prepared in step 3 with nitrogen-containing plasma at 350°C for 15 minutes. The nitrogen-containing plasma is a mixture of NH3 and N2 (20% ammonia) with a flow rate of 10 sccm (standard cubic centimeters per minute). At low temperature, the two remaining metal nanoparticles are decomposed into single atoms and coordinated with nitrogen to form Au-N x 、Co-N x active sites to obtain a bimetallic-nitrogen site-anchored silicon-carbon composite material.

[0101] Although the present invention has been described above by combining with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims.

Claims

1. A method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material, characterized in that: The following steps are involved: mixing a first metal catalyst, a second metal catalyst and a liquid carbon source to obtain a secondary solution; The secondary solution and the silicon source gas medium are prepared into aerosol particles mixed with the silicon source gas; Under a protective atmosphere, aerosol particles mixed with a silicon source gas are sequentially sent into a first vapor deposition zone and a second vapor deposition zone by a carrier gas for deposition reaction, and a silicon-carbon composite material is obtained after the reaction is completed; The silicon-carbon composite material is treated in nitrogen-containing low-temperature plasma to obtain a bimetallic-nitrogen site-anchored silicon-carbon composite material.

2. The method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material according to claim 1, characterized in that: The temperature of the first vapor deposition zone is 600°C to 700°C; the temperature of the second vapor deposition zone is 1100°C to 1200°C.

3. The method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material according to claim 1 or 2, characterized in that: The first metal catalyst is ferrocene, nickelocene or cobaltocene, the second metal catalyst is chloroauric acid or gold chloride, the liquid carbon source is anhydrous ethanol, acetonitrile, methane, toluene, acetylene or ethylene, the concentration of the first metal catalyst in the liquid carbon source is 1000ppm to 5000ppm, and the concentration of the second metal catalyst in the liquid carbon source is 100ppm to 500ppm.

4. The method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material according to claim 1 or 2, characterized in that: The bimetallic-nitrogen site-anchored silicon-carbon composite material consists of silicon nanowires and carbon microtubes. The diameter of the silicon nanowires is 200nm to 500nm, and the diameter of the carbon microtubes is 1μm to 1.5μm.

5. The method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material according to claim 1 or 2, characterized in that: The silicon source gas is silane, silicon tetrafluoride, trichlorosilane or silicon tetrachloride, the carrier gas is a mixed gas of an inert gas and hydrogen, and the carrier gas flow rate is 300ml / min to 500ml / min.

6. The method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material according to claim 1 or 2, characterized in that: The temperature of the nitrogen-containing low-temperature plasma treatment is 200° C. to 500° C., and the treatment time is 10 min to 30 min. The nitrogen-containing low-temperature plasma atmosphere is a mixed gas of ammonia and nitrogen, wherein the volume of ammonia in the mixed gas is 10% to 30%.

7. The method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material according to claim 1 or 2, characterized in that: A silicon source gas-mixed aerosol particle is prepared by using an aerosol generator, comprising adding a secondary solution into the aerosol generator, introducing a silicon source gas into an air inlet at the front end of the aerosol generator, obtaining a silicon source gas-mixed aerosol particle at an air outlet at the rear end, and controlling the flow rate of the aerosol particle at the air outlet by using an air flow meter, wherein the excitation pressure of the aerosol generator is 0.1 kpa to 0.8 kpa, and the air flow meter flow rate is 10 mL / min to 100 mL / min.

8. A bimetallic-nitrogen site-anchored silicon-carbon composite material, characterized in that: The silicon-carbon composite material is a nitrogen-doped silicon-carbon composite material, which is composed of silicon nanowires and carbon microtubes. The diameter of the silicon nanowires is 200nm to 500nm, and the diameter of the carbon microtubes is 1μm to 1.5μm. The surface of the silicon nanowires and the surface of the carbon microtubes have first metal nanoparticles and second metal nanoparticles. The first metal and the second metal form bimetallic-nitrogen sites with nitrogen to anchor the silicon nanowires and the carbon microtubes, wherein the first metal is iron, nickel or cobalt, and the second metal is gold.

9. A negative electrode of a battery, characterized in that: It includes a silicon-carbon composite material prepared by the method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material as described in any one of claims 1 to 7, or a bimetallic-nitrogen site-anchored silicon-carbon composite material as described in claim 8.

10. A lithium battery, characterized in that: The negative electrode of the battery comprises the negative electrode of claim 9.

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