Fine crushing and surface modification integrated method for high-purity silicon powder

Abstract

The invention relates to the technical field of material science and powder engineering, in particular to a fine crushing and surface modification integrated method for high-purity silicon powder. Comprising the following steps: placing a raw material silicon block in an inert gas protection environment, and performing particle size control crushing through a multi-stage impact type crushing device; synchronously injecting a surface modifier atomized flow into the crushing cavity; directional adsorption is generated between the crushed particles and the modifier under the auxiliary action of an electromagnetic field; carrying out in-situ curing on the silicon powder subjected to composite treatment by adopting a gradient temperature control program; product collection and waste gas treatment are synchronously completed through the gas-solid separation device; and carrying out etching modification on the surface of the silicon powder through a plasma processing device. The continuous preparation method provided by the invention integrates efficient crushing, precise particle size control, low oxidation risk, high coating rate modification and surface characteristic regulation and control, and becomes a key technical breakthrough direction for improving the performance of the high-purity silicon powder and expanding the application field of the high-purity silicon powder.

Description

Technical Field

[0001] The present invention relates to the technical fields of material science and powder engineering, and particularly to an integrated method for fine grinding and surface modification of high-purity silicon powder. Background Art

[0002] As a core basic material in high-tech fields such as photovoltaic, semiconductor, and lithium battery, the purity, particle size distribution, and surface characteristics of silicon powder directly affect the performance of end products. The traditional preparation of high-purity silicon powder usually adopts a step-by-step process of mechanical grinding combined with wet chemical modification, which has problems such as complex process flow, high energy consumption, and easy introduction of impurities. For example, the surface oxidation of silicon powder (especially nano-scale silicon powder) caused by local high temperature during mechanical grinding will significantly increase the surface hydroxyl content and reduce the thermal stability and electrochemical performance of the material. And subsequent wet modification requires additional addition of solvents and dispersants, which not only increases production costs but also causes secondary pollution due to solvent residues.

[0003] In recent years, although the dry modification technology has solved the environmental protection problems of the wet process to a certain extent, the existing methods still have defects such as uneven dispersion of modifiers and weak binding force with the particle surface. At the same time, a single silane coupling agent is often used for surface treatment in the existing technology, which is difficult to simultaneously meet the dual requirements of hydrophobicity and interfacial compatibility of silicon powder in different application scenarios. Summary of the Invention

[0004] The present invention provides a continuous preparation method that integrates efficient grinding, precise particle size control, low oxidation risk, high coating rate modification, and adjustable surface characteristics, which becomes a key technical breakthrough direction for improving the performance of high-purity silicon powder and expanding its application fields.

[0005] The technical solution adopted by the present invention is as follows: an integrated method for fine grinding and surface modification of high-purity silicon powder, comprising the following steps:

[0006] Step 1: Place the raw silicon block in an inert gas protection environment and perform particle size control grinding through a multi-stage impact grinding device. During the grinding process, a circulating cooling system is used to maintain the temperature at -20°C to 10°C;

[0007] Step 2: Synchronously inject an atomized stream of surface modifier into the grinding cavity. The surface modifier is a bifunctional silane coupling agent containing amino and epoxy groups, and the injection flow rate is 0.5%-3% of the mass of the ground material;

[0008] Step 3: Through the auxiliary action of an electromagnetic field, make the ground particles and the modifier have directional adsorption. The field strength is controlled at 0.5-2T, and the action time is 5-30 minutes;

[0009] Step 4: In-situ curing of the silicon powder after composite treatment is carried out using a gradient temperature control program, including a first stage at 50 - 80 °C for 10 min and a second stage at 100 - 120 °C for 5 min;

[0010] Step 5: Synchronously complete product collection and waste gas treatment through a gas-solid separation device;

[0011] Step 6: Etch and modify the surface of the silicon powder through a plasma treatment device, with a treatment power of 200 - 500 W and a treatment time of 1 - 5 min.

[0012] As a further improvement of the present invention, the inert gas is a mixed gas composed of argon and nitrogen in a volume ratio of 3:1 - 5:1, and the oxygen content is controlled below 10 ppm.

[0013] As a further improvement of the present invention, the total flow rate of the mixed gas is controlled at 8 - 15 L / min, and dynamic ratio is achieved through a gas mass flowmeter, with a ratio error ≤ ±2%.

[0014] As a further improvement of the present invention, the multi-stage impact crushing device includes three-stage crushing units. The first stage crushes to 200 - 500 μm, the second stage crushes to 50 - 100 μm, and the third stage ultra-finely crushes to 0.1 - 10 μm. An on-line particle size monitoring and feedback system is provided between each stage of crushing cavities.

[0015] As a further improvement of the present invention, the on-line particle size monitoring and feedback system uses dual-mode detection of a laser diffraction sensor and an acoustic wave scattering sensor, with a data sampling frequency ≥ 100 Hz and a particle size regulation response time ≤ 0.5 seconds.

[0016] As a further improvement of the present invention, the surface modifier includes a composite system of KH-550 silane coupling agent and titanate coupling agent with a mass ratio of 1:0.2 - 0.5, and the atomization particle size is controlled at 5 - 20 μm.

[0017] As a further improvement of the present invention, the composite system is respectively vacuum dried at 50 - 60 °C for 2 - 4 hours before mixing, and mixed by ultrasonic dispersion, with an ultrasonic frequency of 20 - 40 kHz and a power of 200 - 500 W.

[0018] As a further improvement of the present invention, the electromagnetic field is a pulsed alternating magnetic field, with a frequency of 1 - 10 kHz and a pulse interval time of 0.1 - 1 ms.

[0019] As a further improvement of the present invention, the gradient temperature control program includes a rapid heating section (10 - 15 °C / min) and a slow cooling section (2 - 5 °C / min), and the vacuum degree is maintained at 10 - 100 Pa during the cooling process.

[0020] The high-purity silicon powder prepared according to the above method has a D50 particle size ≤ 1 μm, a specific surface area ≥ 15 m 2 / g, a surface hydroxyl content ≤ 0.5 wt%, and a tapped density ≥ 1.2 g / cm 3 .

[0021] Advantages of the present invention: (1) Through the cooperation of a three-stage impact crushing device and an on-line particle size monitoring and feedback system, the present invention realizes precise particle size control from millimeter level to sub-micron level (D50 ≤ 1 μm). With the cooperation of inert gas protection and a circulating cooling system at -20°C to 10°C, the local temperature rise and surface oxidation of silicon powder during the crushing process are effectively inhibited, reducing the surface hydroxyl content of the final product to less than 0.5 wt%. Compared with the traditional wet process, this dry integrated process avoids solvent pollution, and at the same time, the tapped density is increased to more than 1.2 g / cm 3 above, significantly improving the powder fluidity and filling performance. (2) The present invention uses a pulsed alternating magnetic field (1 - 10 kHz) to drive the directional migration of the modifier, combined with a compound system of KH-550 silane coupling agent and titanate coupling agent (atomization particle size 5 - 20 μm). Through the chemical anchoring effect of amino / epoxy bifunctional groups on the surface of silicon powder, a monolayer dense coating of the modifier on the particle surface is achieved. With the cooperation of a gradient temperature control program (stepwise curing in the stage of 80°C → 120°C) and a vacuum slow cooling process, the crosslinking degree of the modifier is increased by more than 40%, and the specific surface area is stabilized at more than 15 m 2 / g, while endowing the silicon powder with controllable hydrophobicity and interfacial compatibility. Detailed implementation manners

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to embodiments. It should be understood that the embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0023] The present invention provides an integrated method for fine crushing and surface modification of high-purity silicon powder, including the following steps:

[0024] Step 1: Place the raw silicon block in an inert gas protection environment, and perform particle size-controlled crushing through a multi-stage impact crushing device. During the crushing process, a circulating cooling system is used to maintain the temperature at -20°C to 10°C;

[0025] Step 2: Synchronously inject an atomized stream of surface modifier into the crushing cavity. The surface modifier is a bifunctional silane coupling agent containing amino and epoxy groups, and the injection flow rate is 0.5% - 3% of the mass of the crushed material;

[0026] Step 3: Through the auxiliary action of the electromagnetic field, the crushed particles and the modifier are subjected to directional adsorption, with the field strength controlled at 0.5 - 2 T and the action time being 5 - 30 minutes;

[0027] Step 4: The silicon powder after composite treatment is subjected to in-situ curing using a gradient temperature control program, including a first stage of 50 - 80 °C / 10 min and a second stage of 100 - 120 °C / 5 min;

[0028] Step 5: The product collection and waste gas treatment are synchronously completed through a gas-solid separation device;

[0029] Step 6: The surface of the silicon powder is etched and modified through a plasma treatment device, with the treatment power being 200 - 500 W and the treatment time being 1 - 5 min.

[0030] In the present invention, the inert gas is a mixed gas composed of argon and nitrogen in a volume ratio of 3:1 - 5:1, with the oxygen content controlled below 10 ppm, the total flow rate of the mixed gas controlled at 8 - 15 L / min, and the dynamic ratio is achieved through a gas mass flowmeter, with the ratio error ≤ ±2%.

[0031] The multi-stage impact crushing device in the present invention includes three-stage crushing units. The first stage crushes to 200 - 500 μm, the second stage crushes to 50 - 100 μm, and the third stage ultra-finely crushes to 0.1 - 10 μm. An on-line particle size monitoring and feedback system is provided between each stage of the crushing cavity. The on-line particle size monitoring and feedback system uses dual-mode detection of a laser diffraction sensor and an acoustic wave scattering sensor, with the data sampling frequency ≥ 100 Hz and the particle size regulation response time ≤ 0.5 seconds.

[0032] The surface modifier in the present invention includes a composite system of KH-550 silane coupling agent and titanate coupling agent with a mass ratio of 1:0.2 - 0.5. The atomization particle size is controlled at 5 - 20 μm. The composite system is vacuum dried at 50 - 60 °C for 2 - 4 hours respectively before mixing, and is mixed in an ultrasonic dispersion manner, with the ultrasonic frequency being 20 - 40 kHz and the power being 200 - 500 W.

[0033] In the present invention, the electromagnetic field is a pulsed alternating magnetic field, with a frequency of 1 - 10 kHz and a pulse interval time of 0.1 - 1 ms.

[0034] The gradient temperature control program in the present invention includes a rapid heating section (10 - 15 °C / min) and a slow cooling section (2 - 5 °C / min). The vacuum degree is maintained at 10 - 100 Pa during the cooling process.

[0035] The high-purity silicon powder prepared according to the above method has a D50 particle size ≤ 1 μm, a specific surface area ≥ 15 m 2 / g, a surface hydroxyl content ≤ 0.5 wt%, and a tapped density ≥ 1.2 g / cm 3 .

[0036] Example 1:

[0037] Polycrystalline silicon blocks with a purity of ≥99.99% are crushed into 10-mm particles and loaded into a multi-stage impact crushing system protected by an argon-nitrogen mixed gas (volume ratio 4:1, oxygen content <5 ppm).

[0038] Step 1: The temperature of the first-stage crushing cavity is set at -10°C, the impact frequency is 2000 rpm, and the silicon blocks are crushed to 350 ± 50 μm; the temperature of the second-stage cavity is -5°C, and turbo shear crushing is used to crush to 80 ± 20 μm; the temperature of the third-stage cavity is 0°C, and supersonic airflow crushing is used to crush to D50 = 0.8 μm (specific surface area 18.2 m 2 / g).

[0039] Step 2: In the third-stage crushing cavity, a KH-550 and titanate coupling agent composite modifier (mass ratio 1:0.3) is atomized and sprayed synchronously. The atomization pressure is 0.3 MPa, the droplet size is 10 ± 5 μm, and the injection flow rate is 1.5% of the mass of the silicon powder.

[0040] Step 3: A pulsed alternating magnetic field (field strength 1.2 T, frequency 5 kHz, pulse interval 0.5 ms) is applied for 15 minutes to enable the directional adsorption of the modifier.

[0041] Step 4: Gradient curing procedure: Heat up to 70°C at 12°C / min and hold for 10 min, then heat up to 115°C at 8°C / min and hold for 5 min, and then slowly cool to room temperature at 3°C / min under a vacuum of 50 Pa.

[0042] Step 5: The product is collected by a cyclone separator (separation efficiency >99%), and the waste gas is treated by a molecular sieve adsorption tower.

[0043] Step 6: Plasma treatment is carried out in an argon atmosphere (power 350 W, treatment time 3 min), and the plate spacing is 20 mm.

[0044] Product performance: D50 = 0.78 μm, specific surface area 19.5 m 2 / g, surface hydroxyl content 0.38 wt%, tapped density 1.28 g / cm 3 . XPS analysis shows that the proportion of Si-O-Si bonding reaches 89.2%, and the modifier coating rate is 97.4%.

[0045] Example 2:

[0046] In view of the requirements for the anode material of lithium batteries, the process parameters are adjusted:

[0047] Step 1: In the third-stage crushing, liquid nitrogen-assisted cooling (-25°C) is used to obtain nano-silicon powder with D50 = 0.3 μm (specific surface area 35.6 m2 / g).

[0048] Step 2: Adjust the modifier ratio to KH-550: titanate = 1:0.5, and increase the injection flow rate to 2.8%.

[0049] Step 3: Treat with a high-frequency pulsed magnetic field (field strength 1.8 T, frequency 10 kHz) for 25 minutes.

[0050] Step 4: Optimize the curing program to a two-stage process of 60 °C → 110 °C with a heating rate of 15 °C / min.

[0051] Step 6: Increase the plasma treatment power to 450 W and extend the time to 5 min.

[0052] Product performance: D50 = 0.28 μm, specific surface area 34.2 m 2 / g, surface hydroxyl content 0.18 wt%, and the initial Coulomb efficiency is increased to 92.3% (compared with 86.5% of the untreated sample). TEM shows that a dense organic-inorganic composite layer of 3-5 nm is formed on the surface.

[0053] Example 3:

[0054] For photovoltaic encapsulation film applications, optimize the hydrophobic performance:

[0055] Step 2: Use a composite modifier of KH-550: γ-(2,3-epoxypropoxy)propyltrimethoxysilane = 1:0.4.

[0056] Step 3: Shorten the magnetic field treatment time to 8 minutes and adjust the field strength to 0.8 T to reduce particle agglomeration.

[0057] Step 4: Adjust the curing program to the 80 °C → 120 °C stage and introduce nitrogen purge during the cooling stage.

[0058] Step 6: Replace the plasma treatment with a CF4 / O2 mixed gas (volume ratio 9:1) and treat at 250 W for 2 min.

[0059] Product performance: The contact angle reaches 152° (the original powder is 32°), and the water and oxygen permeability is reduced to 3.1×10-3 g / (m 2 ·day). Thermogravimetric analysis shows that the thermal decomposition temperature of the modifier is increased to 285 °C (the conventionally treated product is 230 °C), and the char residue rate after calcination at 800 °C is only 0.07%.

[0060] Comparative experiment:

[0061] Traditional wet modification control group: Disperse the pulverized silicon powder in Example 1 in absolute ethanol, add an equal amount of modifier, ultrasonically treat for 1 hour, and then dry.

[0062] The results show that the surface hydroxyl content is 0.82 wt%, and the tapped density is 1.05 g / cm 3 , and obvious hard agglomeration phenomenon is observed by SEM.

[0063]

[0063] Summary:

[0064] The data and performance indexes of Examples 1 - 3 and the comparative experiment are shown in the following table.

[0065]

[0066]

[0065]

[0066] As can be seen from the above table, the performance of this application is as follows: (1) The method of the present invention significantly reduces the particle size of silicon powder (D50 ≤ 1 μm). Among them, in Example 2, nano - scale pulverization (D50 = 0.28 μm) is achieved through liquid nitrogen - assisted cooling, which is more than 3 times higher than that of the traditional wet process (D50 = 1.2 μm); the specific surface area is generally higher than that of the traditional process (≥15 m 2 / g vs. 12.8 m 2 / g), especially in Example 2, it reaches 34.2 m 2 / g, which is more suitable for the high - activity anode material of lithium batteries.

[0067]

[0067] (2) Surface characteristics and purity: The surface hydroxyl content is lower than 0.5 wt% (1.05 wt% for the traditional process), indicating that inert gas protection and cryogenic pulverization effectively inhibit oxidation. Through plasma etching and composite modifier optimization in Example 3, the contact angle is increased to 152°, and the water - oxygen permeability is reduced by 64%, which is suitable for the high - hydrophobic requirements of photovoltaic encapsulation films.

[0068]

[0068] (3) Physical properties: The tapped density ≥ 1.2 g / cm 3 (only 0.95 g / cm 3 for the traditional process), and the powder fluidity and filling performance are significantly improved. The initial Coulomb efficiency (92.3% in Example 2) is higher than that of the control group (86.5%), confirming the enhancing effect of the modifier's directional adsorption and cross - linking process on the electrochemical performance.

[0069]

[0069] (4) Thermal stability: The thermal decomposition temperature of the modified silicon powder in Example 3 is increased to 285 °C, which is 55 °C higher than that of the traditional process, indicating that gradient temperature control and plasma treatment can effectively improve the heat resistance of the material.

[0070]

[0070] In summary, the integrated method for fine pulverization and surface modification of high-purity silicon powder according to the present invention not only achieves significant improvements in particle size control and surface modification effect compared with the traditional wet modification process, but also has obvious advantages in production efficiency and environmental protection performance. By precisely regulating various parameters in the pulverization and modification processes, the present invention has successfully realized the continuous preparation of silicon powder from raw materials to high-performance products, providing a better material basis for the application of silicon powder in fields such as photovoltaics, semiconductors, and lithium batteries. In addition, this method also has good scalability and flexibility, and can customize silicon powder products with specific properties by adjusting process parameters according to the requirements of different application fields, so as to meet the diverse market demands.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An integrated method for fine grinding and surface modification of high-purity silicon powder, characterized in that, It includes the following steps: Step 1: Place the raw material silicon blocks in an inert gas protection environment, and perform particle size controlled crushing through a multi-stage impact crushing device. During the crushing process, a circulating cooling system is used to maintain the temperature at -20°C to 10°C; Step 2: Synchronously inject an atomized stream of surface modifier inside the crushing cavity. The surface modifier is a bifunctional silane coupling agent containing amino and epoxy groups, and the injection flow rate is 0.5%-3% of the mass of the crushed material; Step 3: Through the auxiliary action of an electromagnetic field, the crushed particles and the modifier generate directional adsorption. The field strength is controlled at 0.5-2T, and the action time is 5-30 minutes; Step 4: Adopt a gradient temperature control program to perform in-situ curing on the silicon powder after composite treatment, including the first stage at 50-80°C / 10min and the second stage at 100-120°C / 5min; Step 5: Synchronously complete the product collection and waste gas treatment through a gas-solid separation device; Step 6: Etch and modify the surface of the silicon powder through a plasma treatment device. The treatment power is 200-500W, and the treatment time is 1-5min.

2. The integrated method for fine pulverization and surface modification of high-purity silicon powder according to claim 1, characterized in that, The inert gas is a mixed gas composed of argon and nitrogen in a volume ratio of 3:1-5:1, and the oxygen content is controlled below 10ppm.

3. The integrated method for fine pulverization and surface modification of high-purity silicon powder according to claim 2, characterized in that, The total flow rate of the mixed gas is controlled at 8-15L / min, and dynamic ratio is achieved through a gas mass flowmeter, with the ratio error ≤ ±2%.

4. The integrated method for fine grinding and surface modification of high-purity silicon powder according to claim 1, characterized in that, The multi-stage impact crushing device includes three-stage crushing units. The first stage crushes to 200-500μm, the second stage crushes to 50-100μm, and the third stage ultra-finely crushes to 0.1-10μm. An on-line particle size monitoring and feedback system is provided between each stage of crushing cavities.

5. The integrated method for fine grinding and surface modification of high-purity silicon powder according to claim 4, characterized in that, The on-line particle size monitoring and feedback system adopts dual-mode detection of a laser diffraction sensor and an acoustic wave scattering sensor. The data sampling frequency ≥ 100Hz, and the particle size regulation response time ≤ 0.5 seconds.

6. The integrated method for fine pulverization and surface modification of high-purity silicon powder according to claim 1, characterized in that, The surface modifier includes a composite system of KH-550 silane coupling agent and titanate coupling agent with a mass ratio of 1:0.2-0.5, and the atomized particle size is controlled at 5-20μm.

7. An integrated method for fine grinding and surface modification of high-purity silicon powder according to claim 6, characterized in that, The composite system is respectively vacuum dried at 50-60°C for 2-4 hours before mixing, and mixed in an ultrasonic dispersion manner. The ultrasonic frequency is 20-40kHz, and the power is 200-500W.

8. An integrated method for fine pulverization and surface modification of high-purity silicon powder according to claim 1, characterized in that, The electromagnetic field is a pulsed alternating magnetic field with a frequency of 1-10kHz, and the pulse interval time is 0.1-1ms.

9. The integrated method for fine grinding and surface modification of high-purity silicon powder according to claim 1, wherein The gradient temperature control program includes a rapid heating section (10-15°C / min) and a slow cooling section (2-5°C / min). The vacuum degree is maintained at 10-100Pa during the cooling process.

10. High-purity silicon powder prepared by the method according to any one of claims 1-9, characterized in that: The D50 particle size is ≤ 1 μm, the specific surface area is ≥ 15 m 2 / g, the surface hydroxyl content is ≤ 0.5 wt%, and the tapped density is ≥ 1.2 g / cm 3 .

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