A method for preparing silicon-based composite material by gas atomization

Abstract

The present invention discloses a method for preparing a silicon-based composite material by gas atomization. The method comprises the following steps: preparing porous nano-silicon and pressing it into a block structure, transferring it to a deposition chamber, and using a gas atomization method to respectively introduce a metal solution and a catalyst solution to deposit them on the surface of the porous nano-silicon at a certain temperature and pressure, then introducing gas under an inert atmosphere for deposition, carbonization, washing, and drying to obtain a metal and carbon nanotube-doped amorphous carbon-coated silicon-based composite material. The composite material utilizes the atomization method to uniformly dope the metal in the coating layer to reduce impedance, and utilizes the catalyst on the surface as a matrix to grow carbon nanotubes and the network structure formed thereby to improve the electronic conductivity of the material. At the same time, compared with traditional liquid / solid phase coating technology, the gas atomization method has strong uniformity, high efficiency, and controllable process, and the type of material and formula can be adjusted according to demand, with strong flexibility, which can significantly help improve the preparation efficiency of the material and reduce costs.

Description

Technical Field

[0001] The present invention relates to the field of lithium ion battery material preparation, and in particular to a method for preparing a silicon-based composite material using a gaseous atomization method. Background Art

[0002] Currently, silicon-carbon materials are mainly prepared using solid-phase and gas-phase methods. Amorphous carbon is deposited on the surface of nano-silicon or silicon monoxide in the core to obtain a silicon-carbon composite material. At the same time, different metal elements or compounds are doped on the surface according to different requirements to improve the impedance of the interface and enhance the cycle and storage performance. However, the use of solid-phase or gas-phase doping has poor uniformity, low efficiency, low density, and strong selectivity for materials, resulting in limited improvement. The gas atomization method is a technology that atomizes metal elements or compounds and evenly deposits them on the surface or inside the material. It has the advantages of being fast, efficient, and uniform, but it is not used in the field of negative electrode material preparation. Summary of the Invention

[0003] The purpose of the present invention is to address the above-mentioned defects in the prior art and to provide a method for preparing silicon-based composite materials by gas atomization. The present invention deposits metal compounds and their catalysts on the surface of nano-silicon through gas atomization and prepares silicon-based composite materials by vapor deposition, thereby improving the power performance and consistency of silicon-carbon materials.

[0004] The present invention mentions a gas atomization method for preparing silicon-based composite materials, and its technical solution is: a shell composed of a silicon-based material core and a metal and carbon nanotube-doped amorphous carbon coated on the surface of the core. Calculated based on the mass ratio of the composite material being 100%, the mass proportion of the shell is 1-10%.

[0005] The shell is composed of 1-5% metal, 1-5% carbon nanotubes, and the rest is amorphous carbon. The method for preparing the silicon-based composite material by gas atomization mentioned in the present invention includes the following steps:

[0006] (1) Using hydrofluoric acid vapor to etch the surface of the nano-silicon aluminum alloy to obtain porous nano-silicon; then, the porous nano-silicon and the binder are mixed and evenly pressed to obtain a porous nano-silicon composite; the mass ratio of the porous nano-silicon to the binder is 80-95:5-20;

[0007] (2) Afterwards, the porous nano-silicon composite is transferred to a deposition chamber by gas atomization. At a temperature of 100-200°C and a pressure of 1-3 MPa, a metal solution and a catalyst solution are introduced and vaporized for deposition. The deposition time is 10-60 min to obtain a metal-doped porous nano-silicon composite.

[0008] (3) Afterwards, the metal-doped porous nano-silicon composite is transferred to a tubular furnace. First, the air in the tube is exhausted under an inert atmosphere, and then a carbon source gas is introduced and carbonized at a temperature of 800-1200°C for 1-6 hours. The metal and its carbon nanotube-doped amorphous carbon-coated silicon-based composite material is obtained by washing and drying.

[0009] Preferably, the organic metal in the metal solution in the above step (2) is one of triisobutylaluminum, octadecyl aluminum oxide, and dihydroxyaminoaluminum acetate, and the flux is one of carbon tetrachloride, cyclohexane, and N-methylpyrrolidone;

[0010] Preferably, the catalyst solution is one of ferric nitrate, nickel nitrate and cobalt nitrate.

[0011] Preferably, the binder in the above step (1) is one of asphalt, styrene-butadiene rubber, and polyacrylic acid.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] 1) This utility model uses a gas atomization method to deposit metal solution and catalyst solution on the surface of nano-silicon. Compared with traditional solid-phase coating doping, it has the advantages of good uniformity, high efficiency, and controllable process. In addition, the density of the deposited material is high, thereby increasing the tap density of the material and reducing the impedance.

[0014] 2) By doping the material with organic metal compounds, the carbonized metal reduces the impedance of the material on the one hand, and the amorphous carbon formed after the carbonization of the organic metal compound interacts with the metal compound to isolate the core nano-silicon from direct contact with the electrolyte, thereby improving storage and cycle performance; at the same time, the catalyst deposited by gas atomization is doped inside, so that the amorphous carbon generated by high-temperature carbonization as a catalyst has the advantages of good isotropy and stable structure, thereby improving circulation and reducing expansion. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a SEM image of the silicon-based composite material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0016] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0017] Example 1: A gas atomization method for preparing a silicon-based composite material mentioned in the present invention includes the following steps:

[0018] (1) Nano-silicon aluminum (silicon content 90%) was transferred into a flask and hydrofluoric acid vapor was introduced to etch the surface of the nano-silicon aluminum alloy, followed by washing with deionized water to obtain porous nano-silicon; 90 g of porous nano-silicon and 10 g of asphalt were then mixed and evenly pressed to obtain a porous nano-silicon composite;

[0019] (2) Then, the porous nano-silicon composite was transferred to a deposition chamber by gas atomization method. At a temperature of 150°C and a pressure of 2 MPa, a 5% mass concentration of triisobutylaluminum tetrachloride solution and a 5% ferric nitrate tetrachloride catalyst solution were introduced, and vaporized for deposition for 30 minutes to obtain a metal-doped porous nano-silicon composite.

[0020] (3) The metal-doped porous nano-silicon composite was then transferred to a tubular furnace. The air in the tube was first exhausted under an argon atmosphere, and then methane carbon source gas was introduced and carbonized at a temperature of 900°C for 3 hours. The composite was washed and dried to obtain a metal and carbon nanotube-doped amorphous carbon-coated silicon-based composite material.

[0021] Example 2, a gas atomization method for preparing a silicon-based composite material mentioned in the present invention, wherein the preparation method comprises the following steps:

[0022] (1) Nano-silicon aluminum (silicon content 90%) was transferred into a flask and hydrofluoric acid vapor was introduced to etch the surface of the nano-silicon aluminum alloy, followed by washing with deionized water to obtain porous nano-silicon; then 80 g of porous nano-silicon and 20 g of styrene-butadiene rubber were mixed and evenly pressed to obtain a porous nano-silicon composite;

[0023] (2) Then, the porous nano-silicon composite was transferred to a deposition chamber by gas atomization method. At a temperature of 100°C and a pressure of 3 MPa, a 5% octadecyl alumina cyclohexane solution and a 5% cobalt nitrate catalyst solution were introduced and vaporized for deposition. The deposition time was 10 min, and a metal-doped porous nano-silicon composite was obtained.

[0024] (3) The metal-doped porous nano-silicon composite is then transferred to a tubular furnace. Argon gas is first passed through the tube to expel the air, and then acetylene carbon source gas is passed through the tube to carbonize at a temperature of 1200°C for 1 hour. The composite is then washed and dried to obtain a metal and carbon nanotube-doped amorphous carbon-coated silicon-based composite material.

[0025] Example 3, a gas atomization method for preparing a silicon-based composite material mentioned in the present invention, wherein the preparation method comprises the following steps:

[0026] (1) Nano-silicon aluminum (silicon content 90%) was transferred into a flask and hydrofluoric acid vapor was introduced to etch the surface of the nano-silicon aluminum alloy, followed by washing with deionized water to obtain porous nano-silicon; then 95g of porous nano-silicon and 5g of polyacrylic acid were mixed and evenly pressed to obtain a porous nano-silicon composite;

[0027] (2) Then, the porous nano-silicon composite was transferred to a deposition chamber by gas atomization method. At a temperature of 200°C and a pressure of 1 MPa, a 5% mass concentration of dihydroxyaminoacetic acid aluminum N-methylpyrrolidone solution and a 5% nickel nitrate catalyst solution were introduced and vaporized for deposition. The deposition time was 60 min to obtain a metal-doped porous nano-silicon composite.

[0028] (3) The metal-doped porous nano-silicon composite is then transferred to a tubular furnace. Argon gas is first passed through the tube to expel the air inside the tube, and then methane carbon source gas is passed through the tube to carbonize at a temperature of 1200°C for 1 hour. The metal-doped porous nano-silicon composite is then washed and dried to obtain a metal and carbon nanotube-doped amorphous carbon-coated silicon-based composite material.

[0029] Comparative Example:

[0030] Take 90g of the porous nano-silicon composite in step (1) of Example 1, then add 100ml of a xylene solution with a mass concentration of 5% dihydroxyaminoacetic acid aluminum and 100ml of a 5% ferric nitrate catalyst solution to disperse evenly, filter, and vacuum dry. Then, transfer the metal-doped porous nano-silicon composite to a tubular furnace, first pass argon gas to expel the air in the tube, then pass methane carbon source gas at a temperature of 1200℃ for 1h, wash, and dry to obtain a metal and its carbon nanotube-doped amorphous carbon-coated silicon-based composite material.

[0031] (1) Morphology test

[0032] The silicon-based composite material in Example 1 was subjected to SEM testing, and the test results are as follows: Figure 1 As shown. Figure 1 It can be seen that the material has a granular structure, and a small amount of carbon nanotubes are coated on the surface between the material particles. The particle size is between 5-15μm.

[0033] (2) Button battery test

[0034] The silicon-based composite materials in Examples 1-3 and the comparative example were used as negative electrode materials for lithium-ion batteries and assembled into button batteries, which were respectively designated as A1, A2, A3, and B1.

[0035] The specific preparation method involves adding a binder, a conductive agent, and a solvent to a lithium-ion battery anode material, stirring to form a slurry, coating the mixture on copper foil, and drying and rolling to produce a negative electrode sheet. The binder used was LA132, the conductive agent was SP, and the solvent was NMP. The ratio of the anode material, SP, PVDF, and NMP was 95g:1g:4g:220mL. The electrolyte consisted of LiPF6 and a 1:1 volume ratio of EC and DEC. The metal lithium sheet served as the counter electrode, and the separator was a polypropylene (PP) film. The button cell was assembled in a hydrogen-filled glove box. Electrochemical performance was measured on a Wuhan Landian CT2001A battery tester over a charge and discharge voltage range of 0.005V to 2.0V and a charge and discharge rate of 0.1C.

[0036] The test results are shown in Table 1.

[0037] Table 1

[0038]

[0039] As can be seen from the data in Table 1, the specific capacity and initial efficiency of the silicon-based composite material prepared in the examples of the present invention are significantly better than those of the comparative examples. This may be due to the following: by doping the nano-silicon with metal to reduce impedance and the carbon nanotubes to reduce impedance, thereby improving initial efficiency, while the amorphous carbon and metal coating in the shell reduce the probability of direct contact between the nano-silicon and the electrolyte, reducing the occurrence of side reactions and improving initial efficiency; at the same time, the metal itself has a high specific capacity, which slightly improves the specific capacity of the material.

[0040] (3) Soft pack battery test:

[0041] Anode sheets were prepared using the silicon-based composite materials from Examples 1-3 and the comparative example doped with 90% artificial graphite as the negative electrode material. NCM532 was used as the positive electrode material. LiPF6 was used as the electrolyte, and a mixture of EC and DEC in a 1:1 volume ratio was used as the solvent. Celgard 2400 membrane was used as the separator. 5Ah soft-pack batteries, labeled C1, C2, C3, and D1, were fabricated. The negative electrode sheets were tested for their liquid absorption and retention capacity, electrode resilience, and cycling performance.

[0042] a. Liquid absorption capacity test

[0043] Using a 1mL burette, draw up VmL of electrolyte and drip one drop onto the electrode surface. The time is measured until the electrolyte is completely absorbed. The time t is recorded and the electrode absorption rate (V / t) is calculated. The test results are shown in Table 2.

[0044] b. Liquid retention rate test

[0045] The theoretical liquid absorption of the electrode, m1, was calculated based on the electrode parameters. The electrode was weighed as m2. The electrode was then placed in the electrolyte and soaked for 24 hours. The electrode was weighed as m3. The liquid absorption of the electrode was calculated as m3-m2, and the liquid retention rate was calculated according to the following formula: (m3-m2)*100% / m1. The test results are shown in Table 2.

[0046] Table 2

[0047]

[0048] As can be seen in Table 2, the liquid absorption and retention capacities of the silicon-based composite materials obtained in Examples 1-3 were significantly higher than those of the comparative example. These experimental results demonstrate that the silicon-based composite materials of the present invention possess high liquid absorption and retention capacities. This may be due to the larger specific surface area of the composite materials in the examples, which enhances their liquid absorption and retention capacities.

[0049] c. Electrode rebound rate test

[0050] First, the average electrode thickness was measured using a thickness gauge, D1. The electrode was then dried in a vacuum drying oven at 80°C for 48 hours. The electrode thickness was then measured as D2, and the rebound rate was calculated using the following formula: (D2 - D1) * 100% / D1. The test results are shown in Table 3.

[0051] d. Electrode resistivity test

[0052] The resistivity of the electrode was tested using a resistivity tester, and the test results are shown in Table 3.

[0053] Table 3

[0054]

[0055] The data in Table 3 show that the rebound rate and resistivity of the negative electrode sheets using the silicon-based composite materials obtained in Examples 1-3 are significantly lower than those of the comparative example. This indicates that the negative electrode sheets produced using the silicon-based composite materials of the present invention exhibit lower rebound rate and resistivity. This may be due to the expansion of the outer metal coating and its amorphous carbon-bound core material during charge-discharge and roller pressing, which reduces the rebound of the electrode sheet.

[0056] e. Cyclic performance test

[0057] The battery's cycling performance was tested at a charge / discharge rate of 1C / 1C, a voltage range of 2.8V-4.2V, and a temperature of 25±3°C. The test results are shown in Table 4.

[0058] F. Fast charging performance

[0059] Perform constant current + constant voltage charging at a rate of 3C, with a cut-off voltage of 4.2V, and calculate the constant current ratio = constant current capacity / (constant current capacity + constant voltage capacity).

[0060] Table 4

[0061]

[0062] As can be seen from Table 4, the cycle performance and fast charging performance (constant current ratio) of the battery made of the silicon-based composite material of the present invention are significantly better than those of the comparative example. The reason may be that the electrode made of the silicon-based composite material of the present invention has a lower expansion rate, and the structure of the electrode is more stable during the charge and discharge process, thereby improving its cycle performance; in addition, the impedance is reduced by doping metal, thereby improving the constant current ratio of the battery.

[0063] The above descriptions are merely some preferred embodiments of the present invention. Anyone skilled in the art may be able to modify the above-described technical solutions or convert them into equivalent technical solutions. Therefore, any corresponding simple modifications or equivalent transformations based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a silicon-based composite material by gas atomization, characterized by: The silicon-based composite material prepared by gas atomization method consists of a silicon-based material core and a shell composed of metal and carbon nanotube-doped amorphous carbon coated on the surface of the core. Based on the composite material mass ratio of 100%, the mass ratio of the shell is 1-10%; The shell is composed of 1-5% metal, 1-5% carbon nanotubes, and the rest is amorphous carbon; The method for preparing silicon-based composite materials by gas atomization comprises the following steps: (1) Using hydrofluoric acid vapor to etch the surface of the nano-silicon aluminum alloy to obtain porous nano-silicon; then, the porous nano-silicon and the binder are mixed and evenly pressed to obtain a porous nano-silicon composite; the mass ratio of the porous nano-silicon to the binder is 80-95:5-20; (2) Afterwards, the porous nano-silicon composite is transferred to a deposition chamber by gas atomization. At a temperature of 100-200°C and a pressure of 1-3 MPa, a metal solution and a catalyst solution are introduced and vaporized for deposition. The deposition time is 10-60 min to obtain a metal-doped porous nano-silicon composite. (3) Afterwards, the metal-doped porous nano-silicon composite is transferred to a tubular furnace. First, the air in the tube is exhausted under an inert atmosphere, and then a carbon source gas is introduced and carbonized at a temperature of 800-1200°C for 1-6 hours. The metal and its carbon nanotube-doped amorphous carbon-coated silicon-based composite material is obtained by washing and drying.

2. The method for preparing a silicon-based composite material by gas atomization according to claim 1, characterized in that: In the step (2), the organic metal in the metal solution is one of triisobutylaluminum, octadecyl aluminum oxide, and dihydroxyaminoaluminum acetate, and the flux is one of carbon tetrachloride, cyclohexane, and N-methylpyrrolidone.

3. The method for preparing a silicon-based composite material by gas atomization according to claim 1, characterized in that: The catalyst solution is one of ferric nitrate, nickel nitrate and cobalt nitrate.

4. The method for preparing a silicon-based composite material by gas atomization according to claim 1, characterized in that: The binder in step (1) is one of asphalt, styrene-butadiene rubber and polyacrylic acid.

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