Method for preparing silicon microwire by photovoltaic cutting silicon powder

Abstract

The application provides a preparation method of silicon microwire, the length of the silicon microwire is 100-500 mu m; the diameter of the silicon microwire is 0.5-2 mu m; and the silicon microwire is obtained after preparation of photovoltaic cutting silicon powder. The application uses photovoltaic cutting silicon powder as raw material to prepare uniformly dispersed linear micrometer silicon. The size of the photovoltaic silicon powder is reduced by sanding, and the silicon powder can be uniformly distributed in graphite; under high temperature conditions, the small-size silicon is distributed in large-particle graphite, and grows upward into silicon microwire through the gap between the graphites under high temperature conditions. The application uses photovoltaic cutting silicon powder to prepare silicon microwire, realizes recycling and utilization of resources, and solves the problem that about 40% of the total mass of silicon ingot, i.e. high-purity silicon, is discarded in the cutting process in the process of manufacturing crystalline silicon wafer for solar cells.

Description

Technical Field

[0001] This invention belongs to the field of silicon microwire material preparation technology, and relates to a method for preparing microwires by photovoltaic cutting silicon powder. Background Technology

[0002] In recent years, the photovoltaic industry has developed rapidly, and the demand for high-purity crystalline silicon wafers, as the fundamental material for solar cells, has surged. However, approximately 40% of the crystalline silicon wafers are lost as submicron-sized powder during diamond wire cutting. These powder particles are too small to be processed using conventional methods, placing significant pressure on environmental protection.

[0003] The silicon microwires fabricated in this way are expected to become important components in future integrated circuits, sensors, optoelectronics, and lithium batteries. With diameters on the micrometer scale and lengths exceeding the micrometer scale, these silicon microwires possess unique mechanical, optical, and electrical properties.

[0004] Therefore, finding a more suitable method for preparing silicon microwires, overcoming the aforementioned problems in existing silicon microwire production processes, and being more conducive to industrialization has become one of the urgent problems to be solved by many leading researchers in the industry. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a silicon microwire and a method for preparing the same, particularly a method for preparing microwires from photovoltaic silicon powder. The preparation method provided by the present invention can produce uniformly dispersed silicon microwire materials, and can also recycle and utilize silicon powder wasted in the photovoltaic industry, reducing the difficulty of environmental treatment and the risks to the environment. This aligns with current green and environmentally friendly technological concepts. Furthermore, the preparation method is simple, environmentally friendly, and easily scalable for large-scale production and application.

[0006] This invention provides a method for fabricating silicon microwires, wherein the length of the silicon microwires is 100–500 μm;

[0007] The diameter of the silicon microwire is 0.5–2 μm;

[0008] The silicon microwires are obtained from silicon powder through the following steps:

[0009] Step 1: The raw material photovoltaic cutting silicon powder and phenolic resin are added to a solvent and mixed to obtain a silicon powder solution;

[0010] The photovoltaic cutting silicon powder is silicon powder generated during the cutting process of silicon ingots in the process of manufacturing crystalline silicon wafers for solar cells; the mass ratio of photovoltaic cutting silicon powder to phenolic resin is 100:3-7.

[0011] The solvents include water, ethanol, isopropanol, etc.

[0012] The solid content of the silicon powder solution is 5% to 20%.

[0013] Step 2: Dissolve the silicon powder obtained in Step 1 in a solution that has been reduced in size by wet sand milling, add graphite and stir at a speed of 1000-1500 r / min to obtain a mixture.

[0014] The grinding time is 2 to 6 hours;

[0015] The graphite content in the mixture is 50% to 70% by mass;

[0016] The mass ratio of graphite to silicon powder is (50-70):(1.7-10).

[0017] Step 3: After drying the mixture obtained in Step 2, heat-treat it in an atmosphere furnace or tube furnace. After the temperature drops to room temperature, sieve it. The upper sample is silicon microwire.

[0018] The drying methods include freeze drying and / or spray drying;

[0019] The temperature of the high-temperature heat treatment is 1300–1450°C;

[0020] The heating rate of the high-temperature heat treatment is 5-10℃ / min;

[0021] The heat treatment holding time is 1 to 2 hours.

[0022] The equipment for the high-temperature heat treatment includes an atmosphere furnace and / or a tube furnace;

[0023] The sieve mesh size is 400 mesh.

[0024] The silicon microwire has a single-wire growth structure and / or a branching growth structure on the microwire.

[0025] This invention provides silicon microwires with a length of 100–500 μm and a diameter of 0.5–2 μm. The silicon microwires are prepared from photovoltaic-cut silicon powder. Compared with existing technologies, this invention uses photovoltaic-cut silicon powder as raw material to prepare uniformly dispersed linear micron-sized silicon, particularly silicon microwires. This invention reduces the size of the silicon powder through milling, and then achieves uniform distribution in graphite through liquid-phase stirring. Then, under high-temperature conditions, due to the small silicon particles distributed within large graphite particles, they grow upwards through the gaps between graphite particles to form silicon microwires. This invention enables the preparation of silicon microwires using photovoltaic-cut silicon powder, achieving resource recycling and utilization, thereby solving the problem that approximately 40% of the total mass of high-purity silicon in the silicon ingot is discarded during the cutting process in the manufacture of crystalline silicon wafers for solar cells.

[0026] The preparation method provided by this invention can produce uniformly dispersed silicon microwires and effectively recycle and utilize silicon powder wasted in the photovoltaic industry, reducing the difficulty of environmental treatment and the risks to the environment, thus aligning with current green and environmentally friendly technological concepts. This invention does not use toxic or harmful solvents, is pollution-free, easily achieves closed-loop processing, and has no restrictions on the type of graphite used. After the finished product is produced, the silicon microwires can be separated from the graphite using a simple process. Furthermore, the preparation method is simple, easy to implement, highly operable, stable, and environmentally friendly, making it easier to promote and apply in industrial production, laying a solid foundation for expanding the applications of linear micron silicon. Attached Figure Description

[0027] Figure 1 A simplified process flow diagram illustrating the fabrication process of silicon microwires provided by this invention;

[0028] Figure 2 This is a scanning electron microscope (SEM) image of the silicon microwires prepared in Example 1 of this invention.

[0029] Figure 3 The first charge-discharge curve of the lithium-ion battery made from the sample obtained in this invention. Detailed Implementation

[0030] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0031] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0032] There are no particular restrictions on the purity of any raw materials used in this invention. It is preferable to use analytical grade or conventionally pure materials prepared from silicon microwires.

[0033] All raw materials of this invention are conventional in the field, and each brand name and abbreviation is clear and distinct in its relevant application. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand name, abbreviation and corresponding application.

[0034] In all processes of this invention, the abbreviations are conventional abbreviations in the field. Each abbreviation is clear and unambiguous in its relevant application area, and those skilled in the art can understand its conventional process steps based on the abbreviation.

[0035] This invention aims to complete and refine the overall technical solution, better ensure the structure and composition of silicon microwires, and further improve the stability, efficiency, and environmental friendliness of the preparation process. The method for preparing silicon microwires from photovoltaic-cut silicon powder may specifically include the following steps:

[0036] 1) After grinding silicon powder and phenolic resin, they are mixed with graphite to obtain a mixed solution, which is then dried to obtain a mixed powder;

[0037] 2) Under a protective atmosphere, the mixed powder obtained in the above steps is subjected to high-temperature heat treatment to obtain silicon microwires.

[0038] In this invention, the mass ratio of phenolic resin to silicon powder is 3-7:100; the mass ratio of graphite to silicon powder is preferably (50-70):(1.7-10), more preferably (55-65):(1.7-10), even more preferably (50-70):(3-8), and even more preferably (50-70):(5-6).

[0039] In this invention, the mixing step is preferably:

[0040] (1) First, the raw material silicon powder, phenolic resin and solvent are mixed to obtain silicon powder solution;

[0041] The solvent preferably includes water, ethanol, or isopropanol;

[0042] The raw material silicon powder preferably includes photovoltaic cutting silicon powder;

[0043] The silicon powder preferably includes silicon powder generated during the cutting process of silicon ingots in the process of manufacturing crystalline silicon wafers for solar cells.

[0044] The mass ratio of phenolic resin to silicon powder is 3-7:100, and the solid content of the silicon powder solution is preferably 5%-20%, more preferably 8%-17%, and even more preferably 11%-14%.

[0045] (2) After the silicon powder solution obtained in the above steps is milled, graphite is added and stirred at a speed of 1000-1500 r / min to obtain a mixed solution. After drying, a mixed powder is obtained.

[0046] The equipment for sand milling preferably includes a sand mill;

[0047] The preferred grinding time is 2 to 6 hours, more preferably 2.5 to 5.5 hours, more preferably 3 to 5 hours, and even more preferably 3.5 to 4.5 hours;

[0048] The graphite content in the mixture is preferably 50% to 70%, more preferably 54% to 66%, and even more preferably 58% to 62%.

[0049] The drying method preferably includes freeze drying and / or spray drying, more preferably freeze drying.

[0050] (3) Finally, under a protective atmosphere, the mixed powder obtained in the above steps is subjected to high-temperature heat treatment. After the temperature drops to room temperature, it is sieved. The upper sample is silicon microwire.

[0051] The protective atmosphere preferably includes high-purity argon;

[0052] The preferred temperature for the high-temperature heat treatment is 1300–1450°C, more preferably 1330–1420°C, and even more preferably 1360–1390°C;

[0053] The heating rate of the high-temperature heat treatment is preferably 5-10℃ / min, more preferably 6-9℃ / min, and even more preferably 7-8℃ / min;

[0054] The holding time for the high-temperature heat treatment is preferably 1 to 2 hours, more preferably 1.2 to 1.8 hours, and even more preferably 1.4 to 1.6 hours;

[0055] The equipment for the high-temperature heat treatment preferably includes a high-temperature heating device with a refractory lining, preferably including an atmosphere furnace and / or a tube furnace, more preferably an atmosphere furnace or a tube furnace;

[0056] The sieve mesh size is 400 mesh.

[0057] See Figure 1 , Figure 1 A simplified process flow diagram illustrating the silicon microwire fabrication process provided by this invention.

[0058] The present invention provides silicon microwires and a method for preparing microwires from photovoltaic-cut silicon powder. The present invention uses silicon powder as raw material to prepare uniformly dispersed silicon microwires. The silicon powder is reduced in size through milling, and then uniformly distributed in graphite through liquid-phase stirring. Because the small silicon particles are distributed within large graphite particles, they grow upwards through the gaps between graphite particles under high temperature conditions to form silicon microwires. Furthermore, the present invention can utilize photovoltaic-cut silicon powder to prepare silicon microwires, achieving the recycling and utilization of waste resources, thereby solving the problem that approximately 40% of the total mass of high-purity silicon in silicon ingots is discarded during the cutting process in the manufacture of crystalline silicon wafers for solar cells.

[0059] The preparation method provided by this invention can produce uniformly dispersed silicon microwire materials and effectively recycle and utilize silicon powder wasted in the photovoltaic industry, reducing the difficulty of environmental treatment and the risks to the environment, which aligns with current green and environmentally friendly technological concepts. This invention does not use toxic or harmful solvents, is pollution-free, easily achieves closed-loop processing, and has no restrictions on the type of graphite used. The finished product can be easily separated from the graphite, and the graphite can be used in subsequent production. Furthermore, the preparation method is simple, easy to implement, highly operable, stable, and environmentally friendly, making it easier to promote and apply in industrial production, laying a solid foundation for expanding the applications of linear micron silicon.

[0060] To further illustrate the present invention, the following describes in detail a silicon microwire and its preparation method provided by the present invention with reference to embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. They are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0061] Example 1

[0062] 1. Take 75g of photovoltaic cutting silicon powder, mechanically crush it, add 1000mL of water and stir to disperse it, then add 3.75g of phenolic resin and mix evenly;

[0063] 2. Place it in a sand mill for sanding for 4 hours;

[0064] 3. Take out the solution and add 1200g of graphite, stirring and dispersing at 1000r / min;

[0065] 4. Perform freeze-drying to obtain a silicon powder-graphite mixed powder;

[0066] 5. Place the powder in a high-temperature furnace, purge with argon gas, set the temperature to 1440℃, set the heating rate to 5℃ / min, and hold for 2 hours.

[0067] 6. Cool, sieve, and obtain the final product, silicon microwires.

[0068] Figure 2 This is a scanning electron microscope (SEM) image of the silicon microwires prepared in Example 1 of the present invention.

[0069] The silicon microwires prepared in this embodiment were mixed with graphite, binder (CMC), conductive agent (SP), and SBR in a mass ratio of 0.8:7.2:0.5:1:0.5 to form a negative electrode slurry, which was then used to prepare the working electrode. After being assembled into a button cell, the electrode was left to stand for more than 10 hours and then charged and discharged at an ambient temperature of 25°C. At a current of 0.1C, the specific capacity was 574.21 mAh / g, the initial efficiency was 91.11%, and the capacity retention rate was 82.6% after 300 cycles.

[0070] Figure 3 The first charge-discharge curve of the lithium-ion battery made from the sample obtained in this invention.

[0071] Example 2

[0072] 1. Take 85g of photovoltaic cutting silicon powder, mechanically crush it, add 1000mL of water and stir to disperse it, then add 5.1g of phenolic resin and mix evenly;

[0073] 2. Place it in a sand mill for sanding for 3.5 hours;

[0074] 3. Take out the solution and add 1300g of graphite, stirring and dispersing at a speed of 1200r / min;

[0075] 4. Spray drying is performed to obtain a silicon powder-graphite mixed powder;

[0076] 5. Place the powder in a high-temperature furnace, purge with argon gas, set the temperature to 1390℃, set the heating rate to 5℃ / min, and hold for 2 hours.

[0077] 6. Cool, sieve, and obtain the final product, silicon microwires.

[0078] Example 3

[0079] 1. Take 110g of photovoltaic cutting silicon powder, mechanically crush it, add 2000mL of water and stir to disperse it, then add 6.6g of phenolic resin and mix evenly;

[0080] 2. Transfer to a sand mill for sanding, which takes 4 hours;

[0081] 3. Take out the solution and add 2500g of graphite, then stir at 1000r / min to disperse;

[0082] 4. Perform freeze-drying to obtain a silicon powder-graphite mixed powder;

[0083] 5. Place the powder in a high-temperature furnace, purge with argon gas, set the temperature to 1410℃, set the heating rate to 5℃ / min, and hold for 2 hours.

[0084] 6. Cool to obtain the final product, silicon microwires.

[0085] The above provides a detailed description of a method for preparing micron-sized wires from photovoltaic-grade silicon powder. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of these embodiments are merely illustrative of the method and its core ideas, including the best mode, and are intended to enable any person skilled in the art to practice this invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing silicon microwires by cutting silicon powder for photovoltaic applications, characterized in that, The length of the silicon microwire is 100~500 μm; The diameter of the silicon microwire is 0.5~2μm; The silicon microwires are obtained by preparing photovoltaic-cut silicon powder, characterized by comprising the following steps: Step 1: The raw material photovoltaic cutting silicon powder and phenolic resin are added to a solvent and mixed to obtain a silicon powder solution; The mass ratio of the photovoltaic cutting silicon powder to the phenolic resin is 100:3~7; Step 2: The silicon powder solution obtained in Step 1 is subjected to wet sand milling to reduce its size. After adding graphite, it is stirred at a speed of 1000~1500 r / min to obtain a mixture. The mass ratio of graphite to silicon powder is (50~70):(1.7~10). Step 3: After drying the mixture obtained in Step 2, heat-treat it in an atmosphere furnace. After the temperature drops to room temperature, sieve it. The upper sample is silicon microwires. The heat treatment temperature is 1390~1440℃.

2. The method for preparing silicon microwires by cutting photovoltaic silicon powder according to claim 1, characterized in that, The silicon microwires are obtained by growing silicon powder on graphite.

3. The method for preparing silicon microwires by cutting silicon powder for photovoltaic applications according to claim 1, characterized in that, The silicon microwire has a single-wire growth structure and / or a branching growth structure on the microwire.

4. The method for preparing silicon microwires by cutting photovoltaic silicon powder according to claim 1, characterized in that, The photovoltaic cutting silicon powder is the silicon powder generated during the cutting process of silicon ingots in the process of manufacturing crystalline silicon wafers for solar cells.

5. The method for preparing silicon microwires by cutting photovoltaic silicon powder according to claim 1, characterized in that, The solvent includes water, ethanol, or isopropanol; The solid content of the silicon powder solution is 5% to 20%.

6. The method for preparing silicon microwires by cutting photovoltaic silicon powder according to claim 1, characterized in that, The grinding time is 2-6 hours; The graphite content in the mixture is 50% to 70% by mass.

7. The method for preparing silicon microwires by cutting photovoltaic silicon powder according to claim 1, characterized in that, The drying methods include freeze drying and / or spray drying.

8. The method for preparing silicon microwires by cutting silicon powder according to claim 1, characterized in that, The protective atmosphere of the atmosphere furnace is high-purity argon.

9. The method for preparing silicon microwires by cutting photovoltaic silicon powder according to claim 1, characterized in that, The heating rate of the heat treatment is 5~10℃ / min; The heat treatment holding time is 1~2 hours.

10. The method for preparing silicon microwires by cutting photovoltaic silicon powder according to claim 1, characterized in that, The sieving process uses a 400-mesh sieve.

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