Method for preparing porous negative electrode silicon-carbon material from one-dimensional silicon-carbon compound

Abstract

The invention discloses a method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon compound, and relates to the technical field of electrode materials.The method comprises the steps that firstly, nanometer silicon is deposited on the surface of CNT through a chemical vapor deposition method, and an S / CNT compound is formed; then mixing the compound and a surfactant in water, adding an ethanol mixed solution containing resin, performing ultrasonic stirring, and drying to obtain an S / CNT / C precursor; sintering the precursor in an argon atmosphere to obtain an S / CNT / C material; and mixing the material with a biomass material, carrying out vacuum drying, sintering in an argon atmosphere, and carrying out jet milling to finally obtain the porous negative electrode silicon-carbon material. According to the method for preparing the porous negative electrode silicon-carbon material from the one-dimensional silicon-carbon compound, nano silicon is deposited on the surface of a carbon nanotube CNT, so that volume expansion is effectively relieved; through double-layer carbon coating and a porous structure, electrolyte permeation and the contact area between electrolyte and silicon carbon are promoted, and the rate capability of the negative electrode material is improved.

Description

Technical Field

[0001] The present invention relates to the technology of electrode materials, and particularly to a method for preparing a porous anode silicon-carbon material from a one-dimensional silicon-carbon composite. Background Art

[0002] Silicon, as a material with a high theoretical specific capacity (about 4200 mAh / g), is considered to be one of the most promising anode materials for next-generation lithium-ion batteries. When silicon reacts with lithium, it can form a stable Li-Si alloy, thereby providing a higher lithium storage capacity. However, during the lithiation and delithiation processes, silicon undergoes a large volume expansion and contraction, and this volume change can lead to the pulverization of silicon particles and the destruction of the electrode structure, thus accelerating the attenuation of battery performance.

[0003] To solve this problem, researchers have found that silicon-carbon composite materials are considered an effective solution due to their excellent electrical conductivity, chemical stability, and good mechanical properties. By combining silicon nanoparticles with carbon materials, silicon-carbon composite materials can not only buffer the volume change of silicon during charge and discharge processes but also improve the electrical conductivity and structural stability of the electrode.

[0004] In the Chinese invention patent with the publication number CN117996047A, a method for preparing a biomass hard carbon composite silicon-carbon anode material is disclosed. In this method for preparing the biomass hard carbon composite silicon-carbon anode material, biomass raw materials are pre-carbonized, pulverized, and calcined to obtain biomass carbon materials; nano-silicon slurries are prepared; the biomass carbon materials, nano-silicon slurries, and asphalt are respectively put into a dispersion tank in a certain proportion, and after stirring with ethanol as a solvent, spray granulation is carried out to obtain reaction product III; asphalt is added to reaction product III for solid-phase mixing and primary granulation to obtain reaction product V; asphalt is added to reaction product V for solid-phase mixing and secondary granulation to obtain reaction product VII, and then reaction product VII is sieved to obtain the final product.

[0005] In the existing composite silicon-carbon anode materials, the size of the used silicon particles is too large (D50 = 100 - 120 nm), and the materials are extremely easy to break during the charge and discharge processes of the battery. Moreover, due to the very poor electrical conductivity of silicon, the lithium ion mobility is low. At high rates, lithium cannot penetrate deep into the silicon particles, resulting in rapid attenuation of battery performance, reduction of cycle life, and safety problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing a porous anode silicon-carbon material from a one-dimensional silicon-carbon composite to solve the above deficiencies in the prior art.

[0007] To achieve the above purpose, the present invention provides the following technical solution: A method for preparing a porous anode silicon-carbon material from a one-dimensional silicon-carbon composite, comprising:

[0008] S1. First, using carbon nanotubes CNT as the substrate, nano-silicon is deposited on the surface of the carbon nanotubes by chemical vapor deposition to prepare a one-dimensional silicon-carbon Si / CNT composite;

[0009] S2. Then, the one-dimensional silicon-carbon Si / CNT composite and a surfactant are added to water. After stirring evenly, an ethanol mixed solution dissolved with a resin material is added. After ultrasonic stirring evenly at room temperature, it is dried to obtain a Si / CNT / C precursor material;

[0010] S3. The Si / CNT / C precursor material is placed in a tube furnace and sintered under an argon atmosphere to obtain a Si / CNT / C material;

[0011] S4. The Si / CNT / C material is added to an organic solvent containing a biomass material. After stirring evenly, it is vacuum dried to obtain solid particles;

[0012] S5. Finally, the solid particles are transferred to a tube furnace and secondarily sintered under an argon atmosphere. After the secondary sintering product is ground by a jet mill, a porous anode silicon-carbon material is obtained.

[0013] Further, the diameter of the carbon nanotubes CNT described in S1 is 1 - 10 nm, and the length is 10 - 60 μm; the carbon nanotubes CNT described in S1 are at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, and few-walled carbon nanotubes; the deposition temperature of the chemical vapor deposition method is 400 - 600 °C.

[0014] Further, the D50 particle size of the nano-silicon described in S1 is 7 - 20 nm, and the mass ratio of Si to carbon nanotubes CNT in the one-dimensional silicon-carbon Si / CNT composite described in S1 is 4 - 10:1.

[0015] Further, the surfactant described in S2 is a cationic surfactant, and the cationic surfactant is at least one of alkyl quaternary ammonium salts, alkyl pyridinium chlorides, amine salts, alkyl imidazolines, amino amides, and quaternized polysaccharides.

[0016] Further, the mass ratio of the one-dimensional silicon-carbon Si / CNT composite, surfactant, and resin material described in S2 is 1 - 2:0.5 - 3:1 - 3.

[0017] Further, the resin material described in S2 is at least one of phenolic resins, epoxy resins, polyfurfuryl alcohol, phenol, formaldehyde, resorcinol, and phloroglucinol.

[0018] Further, the sintering temperature described in S3 is 600 - 900 °C, and the heating rate is 5 °C / min; the pressure inside the tube furnace described in S3 is 0.1 - 1 atmosphere.

[0019] Further, the biomass material in S4 is at least one of rice straw, corn straw, wheat straw, corn, soybean, sugarcane, coconut shell, litchi shell, shrimp shell, crab shell, and fish oil.

[0020] Further, the organic solvent in S4 is at least one of ethanol, methanol, isopropanol, acetic acid, acetone, DMSO, and NMP.

[0021] Further, the temperature of the secondary sintering in S5 is 600 - 900 °C, and the heating rate is 5 °C / min; the pressure in the tubular furnace in S5 is 0.1 - 1 atmospheric pressure; the silicon-carbon particle size D50 of the porous anode silicon-carbon material in S5 is 7 - 11 μm; the mass ratio of silicon to carbon in the porous anode silicon-carbon material in S5 is 1 - 1.5:2.

[0022] Compared with the prior art, the method for preparing a porous anode silicon-carbon material from a one-dimensional silicon-carbon composite provided by the present invention deposits nano-silicon on the surface of carbon nanotubes CNT by chemical vapor deposition. The carbon nanotubes CNT provide a fast lithium-ion transport channel. Due to the small size of the nano-silicon, it effectively alleviates the volume expansion caused by lithium intercalation and also facilitates the easier and more uniform intercalation of lithium into silicon to form a lithium-silicon alloy.

[0023] Double-layer carbon coating is adopted. The inner layer of carbon is used to isolate the electrolyte from contacting with silicon, and the outer layer uses biomass raw materials. Because biomass has a porous property, there is no need to add a pore-forming agent. The porous structure is conducive to promoting the penetration of the electrolyte, increasing the contact area between the electrolyte and silicon-carbon, and also helps to alleviate volume expansion. This overall structure is also conducive to improving the rate performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic flow chart of the method for preparing a porous anode silicon-carbon material provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the following will further introduce the present invention in detail with reference to the drawings.

[0027] COMPARATIVE EXAMPLE

[0028] Comparative Example 1: Provide a method for preparing a negative electrode material:

[0029] (1) After uniformly mixing single-walled carbon nanotubes CNT and purchased micron silicon, put them into a sanding device. The rotation speed of the sanding device is 100 r / min - 1000 r / min, and the sanding time is 0.5 h - 18 h. Sand the mixed material, where the particle size D50 of Si after sanding is 100 - 120 nm, and finally obtain a one-dimensional silicon-carbon Si / CNT composite;

[0030] (2) Add 1.5 g of Si / CNT composite and 0.2 g of cetyltrimethylammonium bromide (CTAB) to 50 ml of deionized water, stir evenly, then add a mixed solution of 0.5 g of resorcinol, 0.8 g of paraformaldehyde, 0.6 g of phenolic resin and 25 ml of ethanol. After ultrasonic stirring evenly, place the mixed solution at 80 °C for drying and curing to obtain a Si / CNT / C precursor;

[0031] (3) Put the Si / CNT / C precursor into a tube furnace, heat it to 800 °C at a rate of 5 °C / min, and keep it warm for 2 h under an argon atmosphere to obtain a Si / CNT / C material;

[0032] (4) Take 2 g of Si / CNT / C material and add it to 20 ml of a DMSO solution containing 2 g of coconut shell. After stirring evenly, carry out vacuum drying to obtain solid particles.

[0033] (5) Put the solid particles into a tube furnace, heat it to 800 °C at a rate of 5 °C / min and keep it warm for 2 h to obtain a negative electrode material.

[0034] Comparative Example 2: Provide a method for preparing a negative electrode material:

[0035] (1) Place 0.3 g of single-walled carbon nanotubes CNT in a fluidized bed, heat it to 500 °C at a rate of 5 °C / min, and introduce 95% argon and 5% SiH4 gas at a rate of 200 ml / min. After 120 min, change to argon and cool down to room temperature to obtain 1.5 g of a one-dimensional silicon-carbon Si / CNT composite;

[0036] (2) Add the Si / CNT composite and 0.2 g of cetyltrimethylammonium bromide (CTAB) to 50 ml of deionized water, stir evenly, then add a mixed solution of 0.5 g of resorcinol, 0.8 g of paraformaldehyde, 0.6 g of phenolic resin and 25 ml of ethanol. After ultrasonic stirring evenly, place the mixed solution at 80 °C for drying and curing to obtain a Si / CNT / C precursor;

[0037] (3) Put the Si / CNT / C precursor into a tube furnace, heat it to 800 °C at a rate of 5 °C / min, and keep it warm for 2 h under an argon atmosphere to obtain a Si / CNT / C material, which is the negative electrode material.

[0038] Comparative Example 3: A method for preparing a negative electrode material is provided:

[0039] (1) Place 0.3 g of single-walled carbon nanotubes CNT in a fluidized bed, heat it to 500 °C at a rate of 5 °C / min, and introduce a gas mixture of 95% argon and 5% SiH4 at a rate of 200 ml / min. After 120 min, change to argon and cool to room temperature to obtain 1.5 g of one-dimensional silicon-carbon Si / CNT composite;

[0040] (2) Take 1.5 g of the one-dimensional silicon-carbon Si / CNT composite and add it to 20 ml of a DMSO solution containing 2 g of coconut shell. After stirring evenly, perform vacuum drying, and then place it in a tube furnace. Heat it to 800 °C at a rate of 5 °C / min and hold for 2 h to obtain the negative electrode material.

[0041] Comparative Example 4: A method for preparing a negative electrode material is provided:

[0042] (1) Place 0.3 g of single-walled carbon nanotubes CNT in a fluidized bed, heat it to 500 °C at a rate of 5 °C / min, and introduce a gas mixture of 95% argon and 5% SiH4 at a rate of 200 ml / min. After 120 min, change to argon and cool to room temperature to obtain 1.5 g of one-dimensional silicon-carbon Si / CNT composite;

[0043] (2) Add the Si / CNT composite and 0.2 g of cetyltrimethylammonium bromide (CTAB) to 50 ml of deionized water, stir evenly, then add a mixture of 0.5 g of resorcinol, 0.8 g of paraformaldehyde, 0.6 g of phenolic resin, and 25 ml of ethanol. After ultrasonic stirring evenly, place the mixture at 80 °C for drying and curing to obtain the Si / CNT / C precursor;

[0044] (3) Place the Si / CNT / C precursor in a tube furnace, heat it to 800 °C at a rate of 5 °C / min, and hold for 2 h under an argon atmosphere to obtain the Si / CNT / C material;

[0045] (4) Take 2 g of the Si / CNT / C material and add it to 20 ml of a DMSO solution containing asphalt. After stirring evenly, perform vacuum drying. After vacuum drying, place it in a tube furnace and heat it to 800 °C at a rate of 5 °C / min under an argon atmosphere and hold for 2 h to obtain the negative electrode material.

[0046] Comparative Example 5: A method for preparing a negative electrode material is provided:

[0047] (1) Mix the purchased nano-silicon (size D50 = 10 - 15 nm) with phenolic resin, stir evenly by ultrasonic, then place the mixture at 80 °C for drying and curing. Put the cured mixture into a tube furnace, heat it to 800 °C at a rate of 5 °C / min, and keep it for 2 h under an argon atmosphere to obtain an intermediate material;

[0048] (2) Take 2 g of the intermediate material and add it to 20 ml of a DMSO solution containing 2 g of coconut shell. Stir evenly and then conduct vacuum drying. Then put it into a tube furnace, heat it to 800 °C at a rate of 5 °C / min and keep it for 2 h to obtain the anode material.

[0049] Example 1:

[0050] Please refer to Figure 1 , a method for preparing a porous anode silicon-carbon material from a one-dimensional silicon-carbon composite, comprising:

[0051] S1. First, using carbon nanotubes CNT as a substrate, deposit nano-silicon on the surface of the carbon nanotubes by chemical vapor deposition to prepare a one-dimensional silicon-carbon Si / CNT composite; the diameter of the carbon nanotubes CNT is 1 - 10 nm, and the length is 10 - 60 μm; the carbon nanotubes CNT are at least one of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes; the deposition temperature of the chemical vapor deposition method is 400 - 600 °C; the D50 particle size of the nano-silicon is 7 - 20 nm, and the mass ratio of Si to carbon nanotubes CNT in the one-dimensional silicon-carbon Si / CNT composite is 4 - 10:1.

[0052] The specific implementation is as follows: Place 0.3 g of single-walled carbon nanotubes CNT in a fluidized bed, heat it to 500 °C at a rate of 5 °C / min, and introduce 95% argon and 5% SiH4 gas at a rate of 200 ml / min. After 120 min, change to argon and cool to room temperature to deposit nano-silicon on the surface of the carbon nanotubes CNT to obtain 1.5 g of one-dimensional silicon-carbon Si / CNT composite. Among them, the diameter of the carbon nanotubes CNT is 1 - 10 nm, and the length is 10 - 60 μm; the D50 particle size of the nano-silicon deposited on the surface of the carbon nanotubes CNT is 7 - 20 nm; the mass ratio of Si to carbon nanotubes CNT in the one-dimensional silicon-carbon Si / CNT composite is 4 - 10:1.

[0053] S2. Then, add the one-dimensional silicon carbide Si / CNT composite and a surfactant into water. After stirring evenly, add the ethanol mixed solution dissolved with the resin material. After ultrasonic stirring evenly at room temperature, dry to obtain the Si / CNT / C precursor material; the surfactant is a cationic surfactant, and the cationic surfactant is at least one of alkyl quaternary ammonium salts, alkyl pyridine chlorides, amine salts, alkyl imidazolines, amino amides, and quaternized polysaccharides; the mass ratio of the one-dimensional silicon carbide Si / CNT composite, the surfactant, and the resin material is 1-2:0.5-3:1-3; the resin material is at least one of phenolic resin, epoxy resin, polyfurfuryl alcohol, phenol, formaldehyde, resorcinol, and phloroglucinol.

[0054] Specifically, add the Si / CNT composite and 0.2 g of cetyltrimethylammonium bromide (CTAB) into 50 ml of deionized water. After stirring evenly, add the mixed solution of 0.5 g of resorcinol, 0.8 g of paraformaldehyde, 0.6 g of phenolic resin, and 25 ml of ethanol. After ultrasonic stirring evenly at room temperature, place the mixed solution at 80 °C for drying and curing to obtain the Si / CNT / C precursor.

[0055] When ultrasonically stirring to prepare the Si / CNT / C precursor, the ultrasonic power can be but is not limited to 30 W, 40 W, 50 W, 60 W, 70 W, 80 W, 90 W, 100 W, and the stirring speed can be but is not limited to 300 rpm, 400 rpm, 500 rpm, 600 rpm, 800 rpm, 1000 rpm, 1500 rpm, 2000 rpm, 3000 rpm.

[0056] S3. Place the Si / CNT / C precursor material in a tube furnace and sinter it under an argon atmosphere to obtain the Si / CNT / C material; the sintering temperature is 600-900 °C, and the heating rate is 5 °C / min; the pressure in the tube furnace is 0.1-1 atmosphere.

[0057] Specifically, put the Si / CNT / C precursor into the tube furnace, and the pressure in the tube furnace is 0.1-1 atmosphere; heat it to 800 °C at a rate of 5 °C / min and sinter it for 2 h under an argon atmosphere to obtain the Si / CNT / C material.

[0058] S4. Add the Si / CNT / C material into the organic solvent containing the biomass material, stir evenly, and then perform vacuum drying to obtain solid particles; the biomass material is at least one of rice straw, corn straw, wheat straw, corn, soybean, sugarcane, coconut shell, litchi shell, shrimp shell, crab shell, and fish oil; the organic solvent is at least one of ethanol, methanol, isopropanol, acetic acid, acetone, DMSO, and NMP.

[0059] Specific implementation method: Take 2 g of Si / CNT / C material and add it to 20 ml of DMSO solution containing 2 g of coconut shell. After stirring evenly, perform vacuum drying to obtain solid particles.

[0060] S5. Finally, transfer the solid particles to a tube furnace and perform secondary sintering under an argon atmosphere. After the secondary sintering product is ground by a jet mill, a porous negative electrode silicon-carbon material is obtained; the temperature of the secondary sintering is 600-900 °C, and the heating rate is 5 °C / min; the pressure in the tube furnace is 0.1-1 atmospheric pressure; the silicon-carbon particle size D50 of the porous negative electrode silicon-carbon material is 7-11 μm; the mass ratio of silicon to carbon in the porous negative electrode silicon-carbon material is 1-1.5:2.

[0061] Specific implementation method: Put the solid particles into a tube furnace. The pressure in the tube furnace is 0.1-1 atmospheric pressure. Heat up to 800 °C at a rate of 5 °C / min and hold for 2 h to obtain a porous negative electrode silicon-carbon material. The silicon-carbon particle size D50 of the porous negative electrode silicon-carbon material is 7-11 μm; the mass ratio of silicon to carbon in the porous negative electrode silicon-carbon material is 1-1.5:2.

[0062] Electrochemical performance test:

[0063] Based on the porous negative electrode silicon-carbon material provided in this example and the negative electrode materials provided in Comparative Example 1-Comparative Example 5, button cells are respectively made, and the button cells are subjected to electrochemical performance tests.

[0064] The steps for preparing a button cell based on the porous negative electrode silicon-carbon material provided in this example include: stirring and mixing the porous negative electrode silicon-carbon material, binder LA133, conductive carbon black and deionized water to obtain a negative electrode slurry; wherein, the mass ratio of the porous negative electrode silicon-carbon material, conductive carbon black, binder LA132, SBR and deionized water is 3:0.03148:0.04722:0.21:5.5; coat the negative electrode slurry on a copper foil, and after drying and rolling, a negative electrode sheet is made; the electrolyte is a solution with LiPF6 and 10% FEC as electrolytes, with a concentration of 1 mol / L, wherein the solvent uses a mixed solution of ethylene carbonate and diethyl carbonate with a volume ratio of 1:1; a lithium metal sheet is used as the counter electrode, and a polypropylene membrane is used as the separator to obtain a button cell.

[0065] The steps for preparing button cells based on the negative electrode materials provided in Comparative Example 1-Comparative Example 5 are the same as above.

[0066] Electrochemical cycling performance test: In an argon glove box, assemble the above button cells on a Neware CT-4008Tn type battery tester for electrochemical cycling performance testing. The charge-discharge voltage range is 0.01 V-2.0 V, and the charge-discharge rate is 1 C.

[0067] The negative electrode plate is subjected to a swelling test: The thickness D1 of the negative electrode plate of the button cell after rolling is measured. Then, the button cell is fully charged, and then the button cell is disassembled, and the thickness D2 of the negative electrode plate under full charge is measured. Then, the swelling rate of the electrode plate is calculated, and the calculation formula is as follows:

[0068]

[0069] Capacity retention rate test: The above-mentioned button cells are cycled 3 times at 0.1C, 0.3C, 0.5C, 1C, 2C, and 3C respectively (the average specific capacity Q1 is recorded), and then cycled 3 times at a rate of 0.1C (the average specific capacity Q2 is recorded), and the capacity retention rate is calculated. The calculation formula is as follows:

[0070]

[0071] The test results of the electrochemical performance test are as follows in the table:

[0072]

[0073] Nanoscale silicon is deposited on the surface of carbon nanotubes CNT. The carbon nanotubes CNT provide a fast transmission channel for lithium ions. Due to the small size of nanoscale silicon, the volume expansion caused by lithium intercalation is effectively alleviated, and it is also beneficial for lithium to be more easily and uniformly intercalated into silicon to form a lithium-silicon alloy.

[0074] Double-layer carbon coating is adopted. The inner layer of carbon is used to isolate the electrolyte from contacting with silicon, and the outer layer uses biomass raw materials. Because biomass has porous characteristics, there is no need to add a pore-forming agent. The porous structure is beneficial to promoting the penetration of the electrolyte, increasing the contact area between the electrolyte and silicon-carbon, and also helps to alleviate volume expansion. This overall structure is also beneficial to improving the rate performance of the material.

[0075] By controlling the dispersibility of CNT in the resin, the uniform distribution of silicon particles is achieved. After the resin is carbonized, amorphous carbon cross-linked with carbon nanotubes can be formed, which can uniformly coat the surface of Si / CNT, and is beneficial to improving the structural stability and conductivity of the material.

[0076] Example 2:

[0077] Based on Example 1, this example provides a technical solution: A method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite, including the following steps:

[0078] (1) Place 0.3 g of single-walled CNT in a fluidized bed, heat it to 450 °C at a rate of 5 °C / min, and introduce a gas mixture of 95% argon and 5% SiH4 at a rate of 200 ml / min. After 120 min, change to argon and cool down to room temperature to obtain 1.5 g of Si / CNT composite;

[0079] (2) Add the Si / CNT composite and 0.2 g of cetyltrimethylammonium bromide (CTAB) to 50 ml of deionized water, stir evenly, then add 2 g of epoxy resin and a 25-ml ethanol mixture. After ultrasonic stirring evenly, place the mixture at 80 °C for drying and curing to obtain the Si / CNT / C precursor;

[0080] (3) Put the Si / CNT / C precursor into a tube furnace, heat it to 800 °C at a rate of 5 °C / min, keep it at this temperature for 2 h under an argon atmosphere to obtain the Si / CNT / C material.

[0081] Take 2 g of the Si / CNT / C material and add it to 20 ml of an acetone solution containing 2 g of lignin. After stirring evenly, dry it under vacuum, then put it into a tube furnace, heat it to 800 °C at a rate of 5 °C / min and keep it at this temperature for 2 h to obtain the porous anode silicon-carbon material.

[0082] Electrochemical performance test: The test steps are the same as in Example 1, and the test results are as follows in the table:

[0083]

[0084] Example 3:

[0085] Based on Example 1, this example provides a technical solution: A method for preparing a porous anode silicon-carbon material from a one-dimensional silicon-carbon composite, which includes the following steps:

[0086] (1) Place 0.3 g of few-walled CNTs in a fluidized bed, heat it to 500 °C at a rate of 5 °C / min, use a vacuum pump to keep the pressure in the tube at 100 - 200 MPa, and introduce a gas mixture of 95% argon and 5% SiH4 at a rate of 250 ml / min. After 150 min, change to argon and cool it to room temperature to obtain 1.5 g of the Si / CNT composite;

[0087] (2) Add the Si / CNT composite and 0.15 g of PVP to 50 ml of deionized water, stir evenly, then add 0.5 g of resorcinol, 0.8 g of formaldehyde, 0.45 ml of ammonia and a 25-ml ethanol mixture. Stir in a water bath at 60 °C for 6 h, and wash the obtained product with pure water multiple times to obtain the Si / CNT / C precursor;

[0088] (3) Put the Si / CNT / C precursor into a tube furnace, heat it to 800 °C at a rate of 5 °C / min, keep it at this temperature for 2 h under an argon atmosphere to obtain the Si / CNT / C material.

[0089] Take 2 g of Si / CNT / C material and add it to 20 ml of a DMSO solution containing 2 g of corn straw. After stirring evenly, conduct vacuum drying, then place it in a tube furnace, heat it to 800 °C at a rate of 5 °C / min and hold for 2 h to obtain a porous anode silicon-carbon material.

[0090] Electrochemical performance test: The test steps are the same as in Example 1, and the test results are as follows in the table:

[0091]

[0092] Example 4:

[0093] Based on Example 1, this example provides a technical solution: A method for preparing a porous anode silicon-carbon material from a one-dimensional silicon-carbon composite, comprising the following steps:

[0094] (1) Place 0.3 g of single-walled CNT in a fluidized bed, heat it to 500 °C at a rate of 5 °C / min, and introduce 95% argon and 5% SiH4 gas at a rate of 200 ml / min. After 120 min, change to argon and cool to room temperature to obtain 1.5 g of Si / CNT composite;

[0095] (2) Add the Si / CNT composite, 0.2 g of cetyltrimethylammonium bromide (CTAB), and lithium hydroxide to 50 ml of deionized water, stir evenly, then add 0.5 g of resorcinol, 0.8 g of paraformaldehyde, 0.6 g of phenolic resin, and a 25 ml ethanol mixture. After ultrasonic stirring evenly, place the mixture at 80 °C for drying and curing to obtain a Si / CNT / C precursor;

[0096] (3) Place the Si / CNT / C precursor in a tube furnace, heat it to 800 °C at a rate of 5 °C / min, and hold for 2 h under an argon atmosphere to obtain Si / CNT / C material.

[0097] Take 2 g of Si / CNT / C material and add it to 20 ml of a DMSO solution containing 2 g of coconut shell. After stirring evenly, conduct vacuum drying, then place it in a tube furnace, heat it to 800 °C at a rate of 5 °C / min and hold for 2 h to obtain an anode silicon-carbon material.

[0098] Electrochemical performance test: The test steps are the same as in Example 1, and the test results are as follows in the table:

[0099]

[0100] Example 5:

[0101] Based on Example 1, this example provides a technical solution: A method for preparing a porous anode silicon-carbon material from a one-dimensional silicon-carbon composite, comprising the following steps:

[0102] S1. Place 0.3 g of single-walled carbon nanotubes CNT in a fluidized bed, heat it to 500 °C at a rate of 5 °C / min, introduce a gas mixture of 95% argon and 5% SiH4 at a rate of 200 ml / min. After 120 min, change to argon and cool it to room temperature to obtain 1.5 g of one-dimensional silicon-carbon Si / CNT composite;

[0103] S2. Add the Si / CNT composite and 0.2 g of cetyltrimethylammonium bromide (CTAB) to 50 ml of deionized water, stir evenly, then add a mixture of 0.5 g of resorcinol, 0.8 g of paraformaldehyde, 0.6 g of phenolic resin and 25 ml of ethanol. After ultrasonic stirring evenly, place the mixture at 80 °C for drying and curing to obtain the Si / CNT / C precursor;

[0104] S3. Put the Si / CNT / C precursor into a tube furnace, heat it to 800 °C at a rate of 5 °C / min, and keep it at this temperature for 2 h under an argon atmosphere to obtain the Si / CNT / C material;

[0105] S4. Take 2 g of the Si / CNT / C material and add it to 20 ml of a DMSO solution containing asphalt. After stirring evenly, carry out vacuum drying. After vacuum drying, put it into a tube furnace and heat it to 800 °C at a rate of 5 °C / min in a CO2 atmosphere and keep it at this temperature for 2 h to obtain the porous negative electrode silicon-carbon material.

[0106] Electrochemical performance test: The test steps are the same as those in Example 1, and the test results are as follows in the table:

[0107]

[0108]

[0109] In summary, the present invention not only effectively reduces the irreversible capacity of the silicon-carbon composite negative electrode material, but also improves the first efficiency and cycle stability of the silicon-carbon composite negative electrode material; and, by means of CNT in the core, especially single-walled CNT, the rate performance of the material is improved.

[0110] Only some exemplary embodiments of the present invention are described by way of illustration above. Undoubtedly, for those of ordinary skill in the art, without departing from the spirit and scope of the present invention, the described embodiments can be modified in various different ways. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the protection scope of the claims of the present invention.

Claims

1. A method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite, characterized in that: include: S1. First, using carbon nanotubes (CNT) as a substrate, nano-silicon is deposited on the surface of the carbon nanotubes by chemical vapor deposition to prepare a one-dimensional silicon-carbon Si / CNT composite; S2, then adding the one-dimensional silicon-carbon Si / CNT composite and the surfactant into water, stirring evenly, adding the ethanol mixed solution containing the resin material, stirring evenly under ultrasonic conditions at room temperature, and drying to obtain the Si / CNT / C precursor material; S3, placing the Si / CNT / C precursor material in a tube furnace and sintering it under an argon atmosphere to obtain a Si / CNT / C material; S4, adding the Si / CNT / C material to an organic solvent containing a biomass material, stirring evenly and then vacuum drying to obtain solid particles; S5. Finally, the solid particles are transferred to a tubular furnace and secondary sintered in an argon or CO2 atmosphere. The secondary sintered product is subjected to air flow milling to obtain a porous negative electrode silicon-carbon material.

2. The method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: The carbon nanotubes CNT described in S1 have a diameter of 1 to 10 nm and a length of 10 to 60 μm; the carbon nanotubes CNT described in S1 are at least one of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes; the deposition temperature of the chemical vapor deposition method described in S1 is 400 to 600°C.

3. The method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: The D50 particle size of the nano-silicon in S1 is 7 to 20 nm, and the mass ratio of Si to carbon nanotubes CNT in the one-dimensional silicon-carbon Si / CNT composite in S1 is 4 to 10:

1.

4. The method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: S2 The surfactant is a cationic surfactant, and the cationic surfactant is at least one of alkyl quaternary ammonium salts, alkyl pyridinium chlorides, amine salts, alkyl imidazolines, aminoamides, and quaternized polysaccharides.

5. The method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: The mass ratio of the one-dimensional silicon-carbon Si / CNT composite, surfactant and resin material described in S2 is 1-2:0.5-3:1-3.

6. The method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: The resin material in S2 is at least one of phenolic resin, epoxy resin, polyfurfuryl alcohol, phenol, formaldehyde, resorcinol and phloroglucinol.

7. The method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: The sintering temperature in S3 is 600-900°C, and the heating rate is 5°C / min; the pressure in the tubular furnace in S3 is 0.1-1 atmosphere.

8. The method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: S4 The biomass material is at least one of rice straw, corn stalks, wheat stalks, corn, soybeans, sugar cane, coconut shells, lychee shells, shrimp shells, crab shells, and fish oil.

9. The method for preparing a porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: The organic solvent in S4 is at least one of ethanol, methanol, isopropanol, acetic acid, acetone, DMSO, and NMP.

10. The method for preparing porous negative electrode silicon-carbon material from a one-dimensional silicon-carbon composite according to claim 1, characterized in that: The temperature of the secondary sintering in S5 is 600-900°C, and the heating rate is 5°C / min; the pressure in the tubular furnace in S5 is 0.1-1 atmospheres; the silicon-carbon particle size D50 of the porous negative electrode silicon-carbon material in S5 is 7-11 μm; the mass ratio of silicon to carbon in the porous negative electrode silicon-carbon material in S5 is 1-1.5:2.

Images