A bimetal-nitrogen site-anchored silicon-carbon composite material and a preparation method thereof

Abstract

The application 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 the secondary solution into aerosol particles mixed with a silicon source gas; under a protective atmosphere, using a carrier gas to sequentially send 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; and treating the silicon-carbon composite material in a 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, which is composed of silicon nanowires and carbon micrometer tubes. The process of the application is shorter, the operation process is simpler, the energy consumption is lower, the environment is more friendly, the application is suitable for large-scale preparation, and the application has great application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro / nano materials, and more particularly to a bimetal-nitrogen site anchored silicon-carbon composite material and a preparation method thereof. BACKGROUND

[0002] The silicon-carbon composite material can provide a continuous conductive network for the silicon active material, promote charge transfer, and enhance the multiple performance of the silicon negative electrode. In addition, the stable structure and good mechanical properties of the carbon material in the charging and discharging process can alleviate the mechanical stress generated in the silicon lithium alloying / de-alloying process, thereby enhancing the stability of the electrode material in the cycle process.

[0003] However, reasonable matching and compounding of nano and micro materials, as well as short process, low cost, and large-scale preparation of silicon-carbon materials with excellent volume energy density and good cycle stability are urgent problems to be solved at present. SUMMARY

[0004] In view of the deficiencies in the prior art, one of the purposes of the present application is to solve one or more problems existing in the prior art. For example, one of the purposes of the present application is to provide a bimetal-nitrogen site anchored silicon-carbon composite material preparation method which has a simple operation process, a short process, and low raw material cost, and solves the technical problems of complex process, high energy consumption, and environmental unfriendliness existing in the multi-step process of preparing silicon-carbon composite material by magnesium thermal reduction of silicon and CVD deposition of carbon.

[0005] To achieve the above-mentioned purposes, one aspect of the present application provides a bimetal-nitrogen site anchored silicon-carbon composite material preparation method, which can 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 into aerosol particles mixed with a silicon source gas medium; under a protective atmosphere, using a carrier gas to sequentially send the aerosol particles mixed with the silicon source gas into a first vapor deposition zone and a second vapor deposition zone for deposition reaction, and obtaining a silicon-carbon composite material after the reaction; and treating the silicon-carbon composite material in a nitrogen-containing low-temperature plasma to obtain a bimetal-nitrogen site anchored silicon-carbon composite material.

[0006] Further, the temperature of the first vapor deposition zone can be 600-700 DEG C, and the temperature of the second vapor deposition zone can be 1100-1200 DEG C.

[0007] Further, 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 1000-5000 ppm, and the concentration of the second metal catalyst in the liquid carbon source is 100-500 ppm.

[0008] Further, the bimetal-nitrogen site anchored silicon-carbon composite material can be composed of silicon nanowires and carbon microtubes, the diameter of the silicon nanowires can be 200 nm-500 nm, and the diameter of the carbon microtubes can be 1 μm-1.5 μm.

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

[0010] Further, the temperature of the nitrogen-containing low-temperature plasma treatment can be 200℃-500℃, and the treatment time can be 10 min-30 min; 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] Further, the aerosol particles mixed with the silicon source gas can be prepared by using an aerosol generator, which can include adding the secondary solution into the aerosol generator, introducing the silicon source gas into the front gas inlet of the aerosol generator, obtaining the aerosol particles mixed with the silicon source gas at the rear gas outlet, and controlling the flow rate of the aerosol particles at the gas outlet by using a gas flow meter, wherein the excitation pressure of the aerosol generator can be 0.1 kPa-0.8 kPa, and the flow rate of the gas flow meter can be 10 mL / min-100 mL / min.

[0012] Another aspect of the present application provides a bimetal-nitrogen site anchored silicon-carbon composite material, which is a nitrogen-doped silicon-carbon composite material, can be composed of silicon nanowires and carbon microtubes, the diameter of the silicon nanowires can be 200 nm-500 nm, and the diameter of the carbon microtubes can be 1 μm-1.5 μm, 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 bimetal-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] Still another aspect of the present application provides a battery negative electrode, which can include the above-mentioned bimetal-nitrogen site anchored silicon-carbon composite material.

[0014] Still another aspect of the present application provides a lithium battery, which can include the above-mentioned battery negative electrode.

[0015] Compared with the prior art, the present application has the following beneficial effects:

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

[0017] (2) The method of the present application is treated by low-temperature nitrogen-containing plasma, so that the residual second metal catalyst active atoms grow in situ at the end of the silicon nanowire, and the second metal nanoparticles and the residual first metal catalyst active atoms grow in situ on the surface of the carbon microporous tube. The first metal and the second metal nanoparticles with active sites form a bimetallic-nitrogen active site (bimetallic-N x active site) with doped nitrogen, which is beneficial to promote the self-assembly of silicon nanowires and carbon microporous tubes, and makes the structure of the silicon-carbon composite material prepared by FCCVD more stable.

[0018] (3) The silicon-carbon composite material prepared by the present application is composed of silicon nanowires and carbon microporous tubes. Compared with nanometer-structured carbon tubes, carbon microporous tubes can inhibit the volume expansion of silicon nanowires in electrode materials. Moreover, due to the weak structural stability of carbon nanotubes, they are easy to deform or damage under mechanical load. The carbon microporous tubes of the present application have larger size and higher mechanical strength, and are more stable in response to external pressure and stress. For example, in the case of battery drop and collision, the internal electrode material of the battery is less likely to be damaged and collapsed, thereby avoiding safety hazards, and thus has greater development prospect.

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

[0020] The above and other objects and features of the present application will become more apparent from the following description made with reference to the accompanying drawings, in which:

[0021] Figure 1 XRD pattern of the bimetallic-nitrogen site anchored silicon-carbon composite material prepared for Example 1 of the present application.

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

[0023] Figure 3 Digital photograph and SEM image of the bimetal-nitrogen site-anchored silicon-carbon composite material prepared in Example 1 of the present application.

[0024] Figure 4 TEM image of the bimetal-nitrogen site-anchored silicon-carbon composite material prepared in Example 1 of the present application.

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

[0026] Figure 6 Cycle performance chart of the full cell assembled by using the bimetal-nitrogen site-anchored silicon-carbon composite material prepared in Example 1 as the negative electrode and a commercial NCM811 positive electrode. DETAILED DESCRIPTION

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

[0028] In one aspect, the present application provides a preparation method of a bimetal-nitrogen site-anchored silicon-carbon composite material. In some embodiments, the preparation method can 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 the secondary solution into aerosol particles mixed with a silicon source gas.

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

[0032] S400, treating the silicon-carbon composite material in a nitrogen-containing low-temperature plasma to obtain a bimetal-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 the liquid carbon source at room temperature with magnetic stirring to obtain a secondary solution. 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, ethyne, or ethylene. In certain embodiments, the concentration of the first metal catalyst in the liquid carbon source can be 1000 ppm to 5000 ppm. For example, the concentration of the first metal catalyst in the liquid carbon source can be 1200 ppm to 4500 ppm, 1500 ppm to 4000 ppm, 1800 ppm to 3600 ppm, 2200 ppm to 3300 ppm, 2500 ppm to 3000 ppm, or a combination of ranges above. In certain embodiments, the concentration of the second metal catalyst in the liquid carbon source can be 100 ppm to 500 ppm. 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 ranges above.

[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 a conventional aerosol generator. The secondary solution can be introduced into the aerosol generator, and a silicon source gas can be introduced into the front end of the aerosol generator, and the aerosol particles mixed with the silicon source gas can be obtained from the back end of the aerosol generator. The silicon source gas for activating the aerosol generator can be silane, silicon tetrafluoride, trichlorosilane, or silicon tetrachloride. The activation pressure can be 0.1 kPa to 0.8 kPa. For example, the activation pressure can be 0.2 kPa to 0.7 kPa, 0.3 kPa to 0.6 kPa, 0.4 kPa to 0.5 kPa, or a combination of ranges above. The flow rate of the aerosol particles from the back end of the aerosol generator can be controlled using a flow meter. For example, the flow meter can be set to a flow rate of 10 mL / min to 100 mL / min. For another example, the flow meter can be set to a flow rate of 20 mL / min to 90 mL / min, 30 mL / min to 85 mL / min, 45 mL / min to 70 mL / min, 52 mL / min to 65 mL / min, or a combination of ranges above.

[0035] In some embodiments, for step S300, the present application can be performed by using a segmented heating tube furnace to heat two segments of vapor deposition reaction zone to different temperatures, and then performing constant temperature reaction on the aerosol particles of the silicon source gas mixture prepared in step S200 by the carrier gas composed of inert and reducing gas to the two high temperature regions of the tube furnace. In the first vapor deposition zone, the silicon source gas is decomposed at high temperature, silicon atoms are gradually dissolved and saturated under high temperature and the catalysis of the metal catalyst, silicon atoms are connected and gradually diffuse and deposit, and then grow into silicon nanowires. In the second vapor deposition zone, the liquid carbon source is decomposed at high temperature, carbon atoms are gradually dissolved and saturated under high temperature and the catalysis of another metal catalyst, carbon atoms are connected and gradually diffuse and deposit, and then grow into carbon micropipes, and finally collect the silicon-carbon composite material on the tail collector. In some embodiments, the deposition reaction needs to be performed in a protective atmosphere. For example, the deposition can be performed 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 gold catalyst (HAuCl4→Au+2Cl2+HCl), and the iron catalyst may 14 H 14 Fe→Fe+C 14 H 12 ) indirectly participate in the growth of carbon micropipes through synergistic effect.

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

[0037] In some embodiments, the carrier gas can be a mixed gas of inert gas and hydrogen. For example, the carrier gas can be a mixed gas of argon and hydrogen. The hydrogen can account for 4-6% of the volume of the mixed gas. For example, the hydrogen can account for 5% of the volume of the mixed gas. In some embodiments, the flow rate of the carrier gas can be set to 300-500 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 10 min to 30 min. For example, the treatment temperature can be 240 °C to 420 °C, and the treatment time can be 15 min to 25 min. For another example, the treatment temperature can be 300 °C to 380 °C, and the treatment time can be 18 min to 22 min. In certain embodiments, the nitrogen-containing low-temperature plasma atmosphere can be a mixed gas of ammonia and nitrogen, in which the volume of ammonia in the mixed gas can be 10% to 30%. For example, the volume of ammonia in the mixed gas can be 20%. The flow rate of the mixed gas can be 10 seem (standard cubic centimeters per minute) to 30 seem, for example, the flow rate of the mixed gas can be 20 seem.

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

[0040] In some embodiments, the bimetal-nitrogen site-anchored silicon-carbon composite material can be a nitrogen-doped silicon-carbon composite material. The silicon-carbon composite material can be composed of silicon nanowires and carbon microtubes, where the silicon nanowires can have a diameter of 200 nm to 500 nm and the carbon microtubes can have a diameter of 1 μm to 1.5 μm. The silicon-carbon composite material of the present application includes microstructured carbon microtubes, which can suppress the volume expansion of the silicon nanowires in the electrode material compared to nanoscale carbon tubes, and the microstructured carbon microtubes have a larger size and higher mechanical strength, and are more stable in response to external pressure and stress. In some embodiments, the silicon nanowires can have a diameter of 220 nm to 480 nm, 248 nm to 445 nm, 295 nm to 400 nm, 315 nm to 345 nm, or a combination of the above ranges. The carbon microtubes can have a diameter of 1.1 μm to 1.4 μm, 1.2 μm to 1.3 μm, or a combination of the above ranges.

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

[0042] (I) Interaction between solvent and solute. As a carbon source solution has polarity, it can form hydrogen bonds and van der Waals forces with the polar part of the ferrocene molecule (for example, ferrocene catalyst), which helps the dissolution of ferrocene. The mechanism of dissolving chloroauric acid (HAuCl4) (for example, chloroauric acid catalyst) in alcohol includes ion dissociation, hydrogen bonding and electrostatic solvation. HAuCl4 will dissociate into H + and AuCl4 - in ethanol, H + forms hydrogen bonds with the -OH of ethanol, and AuCl4 - is solvated with the polar part of ethanol through electrostatic interaction, finally making chloroauric acid dissolve in alcohol. Further, the mixture of ferrocene catalyst, chloroauric acid catalyst and anhydrous ethanol can form a secondary solution.

[0043] (II) Deposition using the FCCVD method.

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

[0045] Similarly, chloroauric acid also decomposes at high temperature: HAuCl4→ Au + 2Cl2+ HCl, and subsequently gold nanoparticles act as catalysts to promote the subsequent reactions.

[0046] (2) Decomposition of carbon source: Ethanol (C2H5OH) as carbon source decomposes at high temperature. This process can be represented as:

[0047] C2H5OH→ CH4+ CO + H2; CO + CO→ C + CO2;

[0048] CH4→ C + 2H2.

[0049] In these reactions, the C-H and C-O 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, silane decomposes to form silicon atoms and hydrogen gas. 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] (Three) Deposition and diffusion of carbon atoms.

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

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

[0056] (1) Base growth: Carbon atoms are deposited from the bottom of the catalyst particles, forming the bottom of the nanotube.

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

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

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

[0060] (Four) Bimetallic-nitrogen site synergistic stabilization mechanism:

[0061] Low-temperature nitrogen-containing plasma treatment enables in-situ growth of residual Au catalyst active atoms at the end of silicon nanowires, and in-situ growth of stable Au, Fe nanoparticles on the surface of carbon microtubules from residual Fe catalyst active atoms, and these active site-containing Au, Fe nanoparticles (bimetallic-nitrogen active sites) are conducive to promoting the self-assembly of silicon nanowires and carbon microtubules, making the structure of the silicon-carbon composite material prepared by FCCVD more stable.

[0062] Another aspect of the present application 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 microtubules, the diameter of the silicon nanowires can be 200-500 nm, the diameter of the carbon microtubules can be 1-1.5 μm, the surface of the silicon nanowires and the surface of the carbon microtubules 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 microtubules, wherein the first metal is iron, nickel or cobalt, and the second metal is gold.

[0063] Still another aspect of the present application provides a battery negative electrode, which can include the above-mentioned bimetallic-nitrogen site-anchored silicon-carbon composite material.

[0064] Still another aspect of the present application provides a lithium battery, which can include the above-mentioned battery negative electrode. The full battery assembled by the negative electrode and a commercial NCM811 positive electrode has excellent lithium storage capacity and cycle stability.

[0065] In order to better understand the present application, the content of the present application will be further illustrated below in conjunction with specific examples, but the content of the present application is not limited only to the following examples.

[0066] Example 1

[0067] A bimetallic-nitrogen site-anchored silicon-carbon composite material preparation method, the specific steps 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, magnetically stir at a speed of 450 r / min for 1 h, and after the ferrocene and chloroauric acid are completely dissolved, a secondary solution is obtained.

[0069] Step 2: Add the obtained secondary solution to the aerosol generator. Silane gas is introduced into the inlet of the aerosol generator. The generator is activated by gas pressure at 0.5 kPa. Ferrocene, chloroauric acid and ethanol aerosol particles mixed with silane gas are obtained at the outlet. The flow rate of the aerosol particles at the outlet is controlled by a gas flow meter at 50 mL / min.

[0070] Step 3: In a two-segment heated tube furnace, the two vapor deposition reaction zones are heated to 650℃ (first vapor deposition zone) and 1150℃ (second vapor deposition zone) respectively under an argon atmosphere. Then, argon-infused hydrogen (5% hydrogen) gas is introduced to transport the aerosol particles mixed with the silicon source gas from Step 2 to the two high-temperature zones of the tube furnace for isothermal reaction, at a flow rate of 300 ml / min. In the first vapor deposition zone, silane gas decomposes at high temperature, and silicon atoms gradually dissolve and reach saturation under the catalytic effect of high temperature and gold nanoparticles. The silicon atoms connect and gradually diffuse to deposit, subsequently growing into silicon nanowires. In the second vapor deposition zone, ethanol decomposes at high temperature, and carbon atoms gradually dissolve and reach saturation under the catalytic effect of high temperature and iron nanoparticles. The carbon atoms connect and gradually diffuse to deposit, subsequently growing into carbon microtubes. Finally, the silicon-carbon composite material is collected in the tail collector.

[0071] Step 4: The silicon-carbon composite material prepared in Step 3 was treated with nitrogen-containing plasma at 250℃ for 20 min. The nitrogen-containing plasma was a mixture of NH3 and N2 gas (20% ammonia) at a flow rate of 15 sccm (standard cubic centimeters per minute). At this low temperature, the remaining two metal nanoparticles were decomposed into single atoms and coordinated with nitrogen, ultimately forming Au-N. x Fe-N x Active sites were identified, resulting in 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 the figure below. Figure 1 As shown. Because carbon is amorphous, in Figure 1 Since the XRD pattern was not shown, the inventors replaced the silane in step 2 of this embodiment with argon for FCCVD, and the XRD pattern of the collected product is shown below. Figure 2 As shown, the XRD pattern indicates that the product is an amorphous carbon material. Combined with... Figure 1 and Figure 2 This indicates that the present invention has successfully prepared a silicon-carbon composite material.

[0073] Digital photographs and SEM images of the bimetallic-nitrogen site-anchored silicon-carbon composite material prepared in this embodiment are shown below. Figure 3 As shown, from Figure 3It can be seen that the prepared bimetal-nitrogen site anchored silicon-carbon composite material is mainly composed of silicon nanowires and carbon microwires / tubes, the diameter of the silicon nanowires is 350 nm, and the diameter of the carbon microwires / tubes is 1.25 μm.

[0074] The TEM image of the bimetal-nitrogen site anchored silicon-carbon composite material prepared in this example is shown in Figure 4 Figure 4 It can be seen from the (a) and (b) images of Figure 4 that the material with a micron-scale diameter in the prepared silicon-carbon composite material is an amorphous tubular structure material; it can be seen from the (c) and (d) images of Figure 1 that the material with a nanometer-scale diameter in the prepared silicon-carbon composite material is a crystalline linear structure material. In combination with the XRD image of Figure 2 and the digital photograph and SEM image, it can be proved that the prepared bimetal-nitrogen site anchored silicon-carbon composite material is composed of silicon nanowires and carbon microwires / tubes.

[0075] The high-angle annular dark field TEM image Figure 5 (a) and the EDS image Figure 5 (a l , a2) of the bimetal-nitrogen site anchored silicon-carbon composite material prepared in this example are shown, wherein the a l graph is an N element distribution graph, and the a2 graph is a C element distribution graph. It can be proved from the EDS image that the Au-N x , Fe-N x active sites are successfully generated on the surface of the carbon microwires, wherein x represents the number of nitrogen atoms.

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

[0077] Example 2

[0078] A bimetal-nitrogen site anchored silicon-carbon composite material preparation method, the specific steps are as follows:

[0079] ​Step 1, at room temperature, 0.2g of ferrocene and 0.02g of chloroauric acid were weighed and dissolved in 100mL of ethanol solution, and stirred at a speed of 350r / min for 1.5h. After the ferrocene and chloroauric acid were completely dissolved, a secondary solution was obtained.

[0080] Step 2, the obtained secondary solution was added to the aerosol generator, and silane gas was introduced into the gas inlet at the front end of the aerosol generator. The generator was activated by gas pressure, and the gas pressure was 0.3kpa. The silane gas mixed with the aerosol particles of ferrocene, chloroauric acid and ethanol was obtained at the gas outlet at the rear end. The flow rate of the aerosol particles at the gas outlet was controlled by the airflow meter, and the flow rate was 80mL / min.

[0081] Step 3, the two-section heating tube furnace was used to heat the two-section vapor deposition reaction zone to 620℃ (first vapor deposition zone) and 1100℃ (second vapor deposition zone) respectively under argon atmosphere. Then, the argon-hydrogen (5% hydrogen) gas was used to transport the aerosol particles mixed with the silicon source gas in step 2 to the two-section high-temperature region of the tube furnace for constant temperature reaction, and the flow rate was 400ml / min. In the first vapor deposition zone, the silane gas was decomposed at high temperature, and the silicon atoms were gradually dissolved and saturated under the catalytic action of gold nanoparticles at high temperature. The silicon atoms were connected and gradually deposited and diffused, and then grew into silicon nanowires. In the second vapor deposition zone, the ethanol was decomposed at high temperature, and the carbon atoms were gradually dissolved and saturated under the catalytic action of iron nanoparticles at high temperature. The carbon atoms were connected and gradually deposited and diffused, and then grew into carbon microporous tubes. Finally, the silicon / carbon composite material was collected in the tail collector.

[0082] Step 4, the silicon / carbon composite material prepared in step 3 was treated with nitrogen-containing plasma at 200℃ for 25min. The nitrogen-containing plasma was a mixture of NH3 and N2 (10% ammonia), and the flow rate was 20sccm (standard cubic centimeter per minute). The residual two metal nanoparticles were decomposed into single atoms at low temperature and coordinated with nitrogen, and finally formed Au-N x , Fe-N x active sites, obtaining a bimetallic-nitrogen site-anchored silicon / carbon composite material.

[0083] Example 3

[0084] A bimetallic-nitrogen site-anchored silicon / carbon composite material preparation method, the specific steps are as follows:

[0085] Step 1, at room temperature, 0.2g of ferrocene and 0.02g of chloroauric acid were weighed and dissolved in 100mL of ethanol solution, and stirred at a speed of 350r / min for 1.5h. After the ferrocene and chloroauric acid were completely dissolved, a secondary solution was obtained.

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

[0087] Step 3, the two-section heating tube furnace is used to heat the two-section vapor deposition reaction zones to 640 DEG C (the first vapor deposition zone) and 1180 DEG C (the second vapor deposition zone) respectively under an argon atmosphere, then argon-hydrogen (5% hydrogen) gas is introduced to transport the aerosol particles mixed with the silicon source gas in step 1 to the two-section high-temperature zones of the tube furnace for constant-temperature reaction, and the flow rate is 450 ml / min. In the first vapor deposition zone, silane gas is decomposed at high temperature, silicon atoms are gradually dissolved and gradually saturated under the catalysis of gold nanoparticles at high temperature, silicon atoms are connected and gradually diffuse and deposit, and then grow into silicon nanowires; in the second vapor deposition zone, ethanol is decomposed at high temperature, carbon atoms are gradually dissolved and gradually saturated under the catalysis of iron nanoparticles at high temperature, carbon atoms are connected and gradually diffuse and deposit, and then grow into carbon microporous tubes; and finally, the silicon / carbon composite material is collected on the tail collector.

[0088] Step 4, the silicon / carbon composite material prepared in step 3 is treated by using nitrogen-containing plasma at 320 DEG C for 15 min, the nitrogen-containing plasma is a mixed gas of NH3 and N2 (10% ammonia), and the flow rate is 20 sccm (standard cubic centimeter per minute). The residual two metal nanoparticles are decomposed into single atoms at low temperature and coordinated with nitrogen, and finally form Au-N x , Fe-N x active sites, to obtain a bimetallic-nitrogen site-anchored silicon / carbon composite material.

[0089] Example 4

[0090] A bimetallic-nitrogen site-anchored silicon / carbon composite material preparation method, the specific steps are as follows:

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

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

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

[0094] Step 4, the silicon / carbon composite material prepared in step 3 was treated with nitrogen-containing plasma at 400℃ for 15 min, the nitrogen-containing plasma was a mixed gas of NH3 and N2 (25% ammonia), the flow rate was 20 sccm (standard cubic centimeter per minute). At low temperature, the residual two metal nanoparticles are decomposed into single atoms and coordinated with nitrogen, finally forming Au-N x , Fe-N x active sites, obtaining a bimetallic-nitrogen site-anchored silicon / carbon composite material.

[0095] Example 5

[0096] A bimetallic-nitrogen site-anchored silicon / carbon composite material preparation method, the specific steps are as follows:

[0097] Step 1, at room temperature, 0.5g of cobaltocene and 0.05g of chloroauric acid were weighed and dissolved in 100mL of ethanol solution, and the solution was magnetically stirred at a speed of 600r / min for 2h. After the cobaltocene and chloroauric acid were completely dissolved, a secondary solution was obtained.

[0098] Step 2, the obtained secondary solution was added to the aerosol generator, the front end of the aerosol generator was connected to the silane gas inlet, and the generator was started by using air pressure, the air pressure was 0.8kpa, and the silane gas mixed with the cobaltocene, chloroauric acid and ethanol aerosol particles were obtained at the rear outlet, the flow rate of the aerosol particles at the outlet was controlled by using the air flow meter, the flow rate was 100mL / min.

[0099] Step 3, two-stage heating tube furnace, two-stage vapor deposition reaction zone was heated to 650℃ (first vapor deposition zone), 1200℃ (second vapor deposition zone) under argon atmosphere, then the aerosol particles of the mixed gas source of step 2 were transported into the two-stage high-temperature area of the tube furnace for constant temperature reaction under argon-hydrogen (5% hydrogen) gas, the flow rate was 300ml / min. In the first vapor deposition zone, silane gas decomposed at high temperature, silicon atoms gradually dissolved under high temperature and the catalysis of gold nanoparticles, gradually reached saturation, silicon atoms connected and gradually diffused and deposited, then grew into silicon nanowires; in the second vapor deposition zone, ethanol decomposed at high temperature, carbon atoms gradually dissolved under high temperature and the catalysis of cobalt nanoparticles, gradually reached saturation, carbon atoms connected and gradually diffused and deposited, then grew into carbon microporous tubes; finally, the silicon / carbon composite material was collected on the tail collector.

[0100] Step 4, the silicon / carbon composite material prepared in step 3 was treated with nitrogen-containing plasma at 350℃ for 15min, the nitrogen-containing plasma was a mixed gas of NH3 and N2 (20% ammonia), the flow rate was 10sccm (standard cubic centimeter per minute). The residual two metal nanoparticles were decomposed into single atoms at low temperature and coordinated with nitrogen, finally forming Au-N x , Co-N x active sites, obtaining a bimetal-nitrogen site-anchored silicon / carbon composite material.

[0101] Although the present application has been described above with reference to exemplary embodiments, it is clear to those skilled in the art that various modifications and changes can be made to the exemplary embodiments of the present application without departing from the spirit and scope defined by the claims.

Claims

1. A method for preparing a bimetallic-nitrogen site-anchored silicon-carbon composite material, characterized in that, Includes the following steps: The first metal catalyst, the second metal catalyst, and the liquid carbon source are mixed to obtain a secondary solution; The secondary solution was mixed with a silicon source gas medium to prepare aerosol particles containing silicon source gas. Under a protective atmosphere, aerosol particles mixed with silicon source gas are sequentially fed into the first gas phase deposition zone and the second gas phase deposition zone using a carrier gas to carry out the deposition reaction. After the reaction is completed, silicon-carbon composite material is obtained. Silicon-carbon composite materials were treated in nitrogen-containing low-temperature plasma to obtain bimetallic-nitrogen site-anchored silicon-carbon composite materials.

2. The method for preparing 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 ℃~700 ℃; the temperature of the second vapor deposition zone is 1100 ℃~1200 ℃.

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

4. The method for preparing 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, with silicon nanowires having a diameter of 200 nm to 500 nm and carbon microtubes having a diameter of 1 μm to 1.5 μm.

5. The method for preparing 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, and the carrier gas is a mixture of inert gas and hydrogen, with a carrier gas flow rate of 300 ml / min to 500 ml / min.

6. The method for preparing 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 ℃~500 ℃, and the treatment time is 10 min~30 min. The atmosphere of the nitrogen-containing low-temperature plasma is a mixture of ammonia and nitrogen, wherein ammonia occupies 10%–30% of the volume of the mixture.

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

8. A bimetallic-nitrogen-site-anchored silicon-carbon composite material prepared by the method for preparing bimetallic-nitrogen-site-anchored silicon-carbon composite materials according to any one of claims 1 to 7, characterized in that, The silicon-carbon composite material is a nitrogen-doped silicon-carbon composite material composed of silicon nanowires and carbon microtubes. The diameter of the silicon nanowires is 200 nm to 500 nm, and the diameter of the carbon microtubes is 1 μm to 1.5 μm. The surfaces of the silicon nanowires and 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 carbon microtubes. The first metal is iron, nickel or cobalt, and the second metal is gold.

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

10. A lithium battery, characterized in that, Includes the battery negative electrode as described in claim 9.

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