Method for preparing silver-coated silicon composite material by adopting recycled silicon powder and application of silver-coated silicon composite material

Abstract

The invention provides application of a silver-coated silicon composite material in silicon powder recovery. According to the invention, the prepared silver-coated silicon composite material is applied to the specific mode of silicon powder recovery, so that the use amount of silver in the conductive silver paste can be remarkably reduced, the material cost is controlled, and high-value recovery of resources of photovoltaic modules is realized; and the silver-coated silicon particles are stable in structure, good in dispersity and high in adaptability, and the oxidation resistance of the silver-coated silicon particles is superior to that of a silver-coated copper material. The invention also provides a method for preparing the silver-coated silicon composite material by using the recovered silicon powder, the silicon powder recovered from the decommissioned solar cell module is used as a core material, and a compact silver layer is coated outside the core material to form a silver-coated silicon structure, so that the silver-coated silicon composite material has the characteristics of good conductivity, cost advantage and resource recycling, can effectively replace the existing silver powder or silver-coated copper material, and has a good application prospect. The silver paste can be used for solar cell paste and can also be applied to multiple high-added-value fields such as lithium ion battery negative electrode materials and conductive composite materials, and the use boundary of traditional silver powder products is broken through.

Description

Technical Field

[0001] This invention belongs to the field of silicon powder recycling technology, and relates to the application of silver-coated silicon composite material in silicon powder recycling, a method for preparing silver-coated silicon composite material using recycled silicon powder and its application. Background Technology

[0002] In the manufacturing process of solar cells, conductive silver paste is a key component of the front electrode material, and its performance directly affects the cell's conductivity and conversion efficiency. Currently, the conductive pastes widely used in industry mainly employ silver powder or silver-coated copper powder as conductive fillers. Silver powder has excellent conductivity and chemical stability, but its high price leads to a high overall cost. To reduce the amount of silver used, silver-coated copper (Ag@Cu) structure powder has been used as an alternative in recent years. It uses copper powder as the core and is coated with a silver layer to improve oxidation resistance and stability. However, copper itself is easily oxidized, the integrity of the coating layer is required to a high degree, and the overall process is complex, posing certain challenges to cost control and paste performance. Currently, the waste silicon powder generated in the solar cell slicing and preparation processes is mainly recycled for low value, failing to fully realize high-value-added utilization and causing resource waste. Existing conductive paste fillers still have shortcomings in balancing electrical performance, cost control, and environmental recycling, making it difficult to meet the needs of high-efficiency, green, and low-cost photovoltaic module manufacturing.

[0003] Therefore, how to obtain a more reasonable processing technology, improve the above-mentioned shortcomings in the existing waste silicon powder recycling process, and efficiently utilize this by-product resource has become one of the technical problems that urgently need to be solved in green manufacturing and sustainable development. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide the application of silver-coated silicon composite material in silicon powder recycling, a method for preparing silver-coated silicon composite material using recycled silicon powder, and its application. The present invention uses silicon powder recovered from retired solar cell modules as the core material, and coats it with a dense silver layer to form a silver-coated silicon structure. This structure possesses good conductivity, cost advantages, and resource recycling characteristics, and can effectively replace existing silver powder or silver-coated copper materials. Moreover, the preparation process is simple, the conditions are mild, the controllability is good, and the stability is strong, making it more suitable for industrial promotion and application.

[0005] This invention provides the application of silver-coated silicon composite material in silicon powder recycling.

[0006] Preferably, the silver-coated silicon composite material is specifically silver-coated silicon particles;

[0007] The silver-coated silicon composite material has a core-shell structure, with a silicon particle core and a silver layer as the shell.

[0008] The particle size of the silver-coated silicon composite material is 2–40 μm;

[0009] The thickness of the silver layer is 50–500 nm;

[0010] The resistivity of the silver layer is 4.1 × 10⁻⁶. -8 Ω·m~7.2×10 -8 Ω·m.

[0011] Preferably, the silicon powder includes crystalline silicon particle powder recovered from decommissioned solar cell modules, waste silicon powder generated in solar cell wafer slicing, and waste silicon powder generated during the solar cell manufacturing process;

[0012] In the silver-coated silicon composite material, the mass content of the silver layer is 10% to 55%;

[0013] The specific application involves preparing silver-coated silicon composite material from the recycled silicon powder for reuse.

[0014] The silver-coated silicon composite material is specifically a silver / silicon composite conductive material used in conductive pastes.

[0015] This invention provides a method for preparing silver-coated silicon composite materials using recycled silicon powder, comprising the following steps:

[0016] 1) The recycled silicon powder is washed to obtain silicon powder particles;

[0017] The cleaning process includes one or more steps of organic solvent pre-washing, acid washing, RCA cleaning and water washing;

[0018] 2) Place the silicon powder particles obtained in the above steps into a vibrating glass container, and then place it into a magnetron sputtering device equipped with a silver target, so that the silicon powder particles are in a vibrating state. Under the condition of filling with inert gas as the working gas, magnetron sputtering is performed to deposit a silver layer, and a silver-coated silicon composite material is obtained.

[0019] Preferably, the recycled silicon powder includes crystalline silicon particle powder recovered from decommissioned solar cell modules, waste silicon powder generated from solar cell wafers, and waste silicon powder generated during the solar cell manufacturing process;

[0020] The cleaning process consists of organic solvent pre-washing, acid washing, RCA cleaning, and water washing.

[0021] Preferably, the organic solvent prewash includes ethanol cleaning and / or acetone cleaning;

[0022] The pickling includes hydrofluoric acid pickling;

[0023] The mass concentration of the hydrofluoric acid is 5% to 10%.

[0024] The pickling time is 0.5 to 3 minutes.

[0025] Preferably, the RCA cleaning includes SC-1 chemical cleaning and SC-2 chemical cleaning;

[0026] The water washing specifically refers to washing with water until neutral;

[0027] The washing process also includes a drying step.

[0028] Preferably, the vibration frequency of the vibration state is 20 to 100 Hz;

[0029] The amplitude of the vibrating silicon powder particles is 0.5–5 mm.

[0030] The working gas is specifically a low-pressure working gas;

[0031] The working gas pressure is 0.5 to 1.0 Pa.

[0032] Preferably, the process further includes a vacuuming step before filling with inert gas;

[0033] The vacuum pressure during the evacuation process is 3.2 x 10⁻⁶. -4 Pa ~ 7.0 x 10 -4 Pa;

[0034] The sputtering power of the magnetron sputtering is 100-600W;

[0035] The deposition time for magnetron sputtering is 30–180 min.

[0036] The present invention also provides the application of silver-coated silicon composite material in any of the above-described technical solutions, or the application of silver-coated silicon composite material prepared by any of the above-described technical solutions in sintered solar cell paste systems, conductive fillers, and conductive pastes.

[0037] This invention provides the application of silver-coated silicon composite materials in silicon powder recycling. Compared with existing technologies, this invention argues that the high cost of conductive silver paste raw materials and the expensive price of traditional silver powder, which constitutes a large proportion of the cost in conductive pastes, limits further cost reduction and efficiency improvement in solar cell products. While silver-coated copper powder has a complex process and poor stability, although it can partially replace silver powder, the copper core is easily oxidized, requiring a complete and uniform silver coating, making process control difficult. Furthermore, it still faces risks of conductivity degradation and interface reactions in long-term use. Simultaneously, resource utilization is low; currently, the waste silicon powder generated during solar cell slicing and manufacturing processes is mainly recycled for low-value purposes, failing to achieve full high-value utilization and resulting in resource waste. In addition, existing conductive paste fillers are insufficient in balancing electrical performance, cost control, and environmental recycling, making it difficult to meet the demands of high-efficiency, green, and low-cost photovoltaic module manufacturing. Therefore, there is an urgent need to develop new conductive fillers that balance cost and performance.

[0038] Based on this, the present invention creatively applies the preparation of silver-coated silicon composite materials to a specific method of silicon powder recycling. The recycled silicon powder is used to prepare silver-coated silicon composite materials for reuse, thus broadening the technical field of silicon powder recycling and improving the recycling rate of resources. The application provided by this invention can significantly reduce the amount of silver used in conductive silver paste, control material costs, and achieve high-value resource recovery for photovoltaic modules. Furthermore, silver-coated silicon particles have a stable structure, good dispersibility, strong adaptability, and superior oxidation resistance compared to silver-coated copper materials. Simultaneously, the process is highly controllable and easy to industrialize.

[0039] This invention also provides a method for preparing silver-coated silicon composite materials using recycled silicon powder. This is a novel method for preparing silver-coated silicon composite conductive particles for conductive silver paste in solar cells. Using recycled silicon powder from retired solar cell modules as the core material, a dense silver layer is coated onto it to form a silver-coated silicon structure. This structure possesses good conductivity, cost advantages, and resource recycling characteristics, effectively replacing existing silver powder or silver-coated copper materials. Furthermore, the preparation process is simple, the conditions are mild, the controllability is good, and the stability is strong, making it more suitable for industrial promotion and application.

[0040] This invention uses recycled silicon powder from solar cell modules as the core material and achieves silver-coated silicon core-shell structure particles through surface cleaning, sputtering, and other means to replace the silver powder or silver-coated copper powder in existing conductive pastes. It has the following advantages: (1) Green conversion of raw material sources: This invention is the first to use silicon powder from retired solar cell modules after high purification treatment for conductive functional materials, which effectively promotes the recycling and reuse of resources in the photovoltaic industry chain. (2) Innovative material structure: Unlike traditional silver powder or silver-coated copper particles, this invention constructs a silver-coated silicon structure, adopting a non-metallic core and silver shell composite form, which significantly reduces the proportion of silver used while maintaining conductivity. (3) Innovative combination of pretreatment and physical coating process: This invention organically combines the stringent wet chemical cleaning with the advanced dry physical coating process. First, it adopts a multi-stage cleaning process of "organic solvent + HF + RCA" to provide an ideal clean particle surface for subsequent high-quality coating. More importantly, this invention innovatively proposes a powder coating scheme of "bottom vibration + magnetron sputtering". By using a specially designed glass container and an external vibration module, the silicon powder particles are controlled and continuously moved in a high vacuum environment during the sputtering process, thereby solving the technical problem that traditional PVD technology is difficult to uniformly coat micron-sized powders with 360° no dead angles, and ensuring the uniformity and density of the silver layer. (4) Cross-border expansion of application scope: In addition to being used in solar cell pastes, the high-purity silicon powder and its silver-coated products in this invention can also be applied to multiple high-value-added fields such as lithium-ion battery anode materials and conductive composite materials, breaking through the application boundaries of traditional silver powder products. Detailed Implementation

[0041] 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.

[0042] 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.

[0043] There are no particular restrictions on the purity of any of the raw materials used in this invention. However, it is preferred to use analytical grade or conventional purity used in the preparation of conductive silver paste for solar cells.

[0044] This invention provides the application of silver-coated silicon composite material in silicon powder recycling.

[0045] In this invention, the silver-coated silicon composite material is preferably silver-coated silicon particles.

[0046] In this invention, the silver-coated silicon composite material preferably has a core-shell structure, wherein the core is preferably a silicon particle and the shell is preferably a silver layer.

[0047] In this invention, the particle size of the silver-coated silicon composite material is preferably 2-40 μm, more preferably 5-35 μm, more preferably 10-30 μm, and even more preferably 15-25 μm.

[0048] In this invention, the thickness of the silver layer is preferably 50-500 nm, more preferably 150-400 nm, and even more preferably 250-300 nm.

[0049] In this invention, the resistivity of the silver layer is preferably 4.1 × 10⁻⁶. -8 Ω·m~7.2×10 -8 Ω·m, more preferably 4.6 × 10 -8 Ω·m~6.7×10 -8 Ω·m, more preferably 5.1 × 10 -8 Ω·m~6.2×10 -8 Ω·m.

[0050] In this invention, the silicon powder preferably includes crystalline silicon particle powder recovered from retired solar cell modules, waste silicon powder generated in solar cell wafer slicing, and waste silicon powder generated during the solar cell manufacturing process.

[0051] In this invention, the mass content of the silver layer in the silver-coated silicon composite material is preferably 10% to 55%, more preferably 15% to 50%, more preferably 20% to 45%, more preferably 25% to 40%, and even more preferably 30% to 35%.

[0052] In this invention, the preferred application is to prepare a silver-coated silicon composite material from the recycled silicon powder for reuse. Specifically, the application is the use of the silver-coated silicon composite material in a specific silicon powder recycling method.

[0053] In this invention, the silver-coated silicon composite material is preferably a silver / silicon composite conductive material used in conductive pastes.

[0054] This invention provides a method for preparing silver-coated silicon composite materials using recycled silicon powder, comprising the following steps:

[0055] 1) The recycled silicon powder is washed to obtain silicon powder particles;

[0056] The cleaning process includes one or more steps of organic solvent pre-washing, acid washing, RCA cleaning and water washing;

[0057] 2) Place the silicon powder particles obtained in the above steps into a vibrating glass container, and then place it into a magnetron sputtering device equipped with a silver target, so that the silicon powder particles are in a vibrating state. Under the condition of filling with inert gas as the working gas, magnetron sputtering is performed to deposit a silver layer, and a silver-coated silicon composite material is obtained.

[0058] This invention first involves washing the recycled silicon powder to obtain silicon powder particles.

[0059] In this invention, the cleaning process includes one or more steps of organic solvent pre-washing, acid washing, RCA cleaning, and water washing, and may include multiple steps of organic solvent pre-washing, acid washing, RCA cleaning, and water washing.

[0060] In this invention, the recycled silicon powder preferably includes crystalline silicon particle powder recovered from retired solar cell modules, waste silicon powder generated in solar cell wafer slicing, and waste silicon powder generated during the solar cell manufacturing process.

[0061] In this invention, the cleaning process is preferably carried out in sequence as follows: pre-washing with organic solvent, acid washing, RCA cleaning, and water washing.

[0062] In this invention, the organic solvent prewash preferably includes ethanol cleaning and / or acetone cleaning, more preferably ethanol cleaning or acetone cleaning.

[0063] In this invention, the pickling preferably includes hydrofluoric acid pickling.

[0064] In this invention, the mass concentration of the hydrofluoric acid is preferably 5% to 10%, more preferably 6% to 9%, and even more preferably 7% to 8%.

[0065] In this invention, the pickling time is preferably 0.5 to 3 min, more preferably 1.0 to 2.5 min, and even more preferably 1.5 to 2.0 min.

[0066] In this invention, the RCA cleaning preferably includes SC-1 chemical cleaning and SC-2 chemical cleaning.

[0067] In this invention, the water washing is preferably performed until the water is neutral.

[0068] In this invention, the washing process preferably includes a drying step.

[0069] Finally, the silicon powder particles obtained in the above steps are placed in a vibrating glass container and then placed in a magnetron sputtering device equipped with a silver target, so that the silicon powder particles are in a vibrating state. Under the condition of filling with inert gas as the working gas, a silver layer is deposited by magnetron sputtering to obtain a silver-coated silicon composite material.

[0070] In this invention, the vibration frequency of the vibration state is preferably 20-100Hz, more preferably 35-85Hz, and even more preferably 50-70Hz.

[0071] In this invention, the amplitude of the silicon powder particles in the vibrating state is preferably 0.5-5 mm, more preferably 1.5-4 mm, and even more preferably 2.5-3 mm.

[0072] In this invention, the working gas is preferably a low-pressure working gas.

[0073] In this invention, the working gas pressure is preferably 0.5 to 1.0 Pa, more preferably 0.6 to 0.9 Pa, and even more preferably 0.7 to 0.8 Pa.

[0074] In this invention, the process of filling with inert gas preferably includes a vacuuming step.

[0075] In this invention, the vacuum pressure for evacuation is preferably 3.2 x 10⁻⁶. -4 Pa ~ 7.0 x 10 -4 Pa, more preferably 3.5 x 10 Pa. -4 Pa ~ 6.5 x 10 -4 Pa, more preferably 4.0 x 10 Pa. -4 Pa ~ 6.0 x 10 -4 Pa, more preferably 4.5 x 10 Pa. -4 Pa ~ 5.5 x 10 -4 Pa.

[0076] In this invention, the sputtering power of the magnetron sputtering is preferably 100-600W, more preferably 200-500W, and even more preferably 300-400W.

[0077] In this invention, the deposition time of the magnetron sputtering is preferably 30-180 min, more preferably 50-160 min, more preferably 70-140 min, and even more preferably 90-120 min.

[0078] This invention provides the application of silver-coated silicon composite materials or silver-coated silicon composite materials prepared by the method described in any of the above technical solutions in sintered solar cell paste systems, conductive fillers, and conductive pastes.

[0079] In this invention, the conductive paste can be a conductive paste and / or conductive filler used in lithium-ion battery anode materials, conductive composite materials, etc.

[0080] This invention aims to complete and refine the overall technical solution, better ensure the structure and parameters of the silver-coated silicon composite material prepared from recycled silicon powder, and further improve the comprehensive performance of the silver-coated silicon composite material. The application of the aforementioned silver-coated silicon composite material in silicon powder recycling, and a method for preparing silver-coated silicon composite materials using recycled silicon powder and its specific applications, may include the following:

[0081] The present invention proposes a method for preparing novel silver-coated silicon composite conductive particles for conductive silver paste in solar cells, comprising the following steps:

[0082] 1. Acquisition and cleaning treatment of recycled silicon powder

[0083] The silicon powder used in this invention comes from retired solar cell modules. First, the modules are mechanically crushed and sorted to obtain crystalline silicon particles. The recovered silicon powder then undergoes a multi-step cleaning process to remove organic residues, metallic impurities, and oxide layers to the greatest extent possible, improving surface cleanliness and the adhesion of the subsequent silver layer.

[0084] Organic solvent pre-wash: First, use anhydrous ethanol for preliminary cleaning to remove surface polar contaminants and organic impurities; then use acetone to further remove oily components and resin residues;

[0085] HF pickling: Silicon powder is treated with a 5% to 10% hydrofluoric acid solution for a short time to remove the natural oxide layer and glass impurities on the silicon surface and improve surface reactivity.

[0086] RCA cleaning: Chemical cleaning is performed according to the standard RCA method (SC-1: NH4OH / H2O2 / H2O and SC-2: HCl / H2O2 / H2O) to further remove residual metal ions, fine particles and organic matter;

[0087] After cleaning, rinse with deionized water until neutral, and dry in a vacuum oven at 40°C for later use.

[0088] 2. Powder loading and vacuum environment preparation

[0089] The high-purity silicon powder, after being cleaned and dried as described above, is placed into a specially designed glass container. An adjustable frequency vibration module is connected to the bottom of this container. The entire glass container containing the silicon powder is placed in the vacuum chamber of a magnetron sputtering equipment, and a high-purity silver (Ag) target is installed.

[0090] Then, the vacuum pump unit is started to evacuate the air in the vacuum chamber to a high vacuum state (e.g., 4x10⁻¹). 4 To remove gaseous impurities that might interfere with the coating process, a pressure of 0.5–1.0 Pa is applied. Then, high-purity argon (Ar) is introduced as the working gas and maintained at a specific low pressure (e.g., 0.5–1.0 Pa).

[0091] 3. Magnetron sputtering deposition of silver layer

[0092] Before sputtering begins, a vibration module at the bottom of the glass container is activated, causing the silicon powder particles inside the container to continuously and controllably jump and tumble. Subsequently, a negative high voltage is applied to the silver target, and under the influence of a magnetic field, the argon gas in the vacuum chamber is ionized, generating plasma through glow discharge. Positively charged argon ions are accelerated and bombard the surface of the silver target under the high-voltage electric field, sputtering silver atoms from the target. The sputtered high-energy silver atoms move in a near-linear manner and are eventually uniformly deposited on the entire surface of the continuously moving silicon powder particles driven by the vibration module, forming a complete and dense silver coating layer through atomic stacking.

[0093] By precisely controlling process parameters such as sputtering power, working gas pressure, deposition time, and the frequency and amplitude of the vibration module, precise control over the thickness, density, and crystal structure of the silver layer can be achieved.

[0094] 4. Cooling and finished product collection

[0095] After the sputtering deposition process is complete, turn off the high-voltage power supply and vibration module, and stop the argon gas supply. Once the vacuum chamber and substrate have cooled sufficiently, release the vacuum. Open the vacuum chamber and remove the coated silver-coated silicon composite powder from the glass container to obtain the finished product. This is a physical dry process and requires no cleaning.

[0096] 5. Product Characteristics

[0097] The silver-coated silicon particles prepared by this invention have the following characteristics:

[0098] The particle size range is 2–40 μm;

[0099] The thickness of the silver layer is controllable, ranging from 50 to 500 nm;

[0100] The surface silver layer is dense and uniform, with strong oxidation resistance; the resistivity of the silver layer is 4.1 × 10⁻⁶.-8 Ω·m~7.2×10 -8 Ω·m.

[0101] It is compatible with sintering-type solar cell paste systems and exhibits excellent adhesion and conductivity during the cell sintering process.

[0102] The present invention provides the application of silver-coated silicon composite material in silicon powder recycling, a method for preparing silver-coated silicon composite material using recycled silicon powder, and its application. Specifically, the present invention applies the preparation of silver-coated silicon composite material to a specific method of silicon powder recycling, using recycled silicon powder to prepare silver-coated silicon composite material for reuse, thus broadening the technical field of silicon powder recycling and improving the recycling rate of resources. The application provided by the present invention can significantly reduce the amount of silver used in conductive silver paste, control material costs, and achieve high-value resource recycling of photovoltaic modules; moreover, silver-coated silicon particles have a stable structure, good dispersibility, strong adaptability, and superior oxidation resistance compared to silver-coated copper materials. Furthermore, the process is highly controllable and easy to industrialize.

[0103] This invention also provides a method for preparing silver-coated silicon composite materials using recycled silicon powder. This is a novel method for preparing silver-coated silicon composite conductive particles for conductive silver paste in solar cells. Using recycled silicon powder from retired solar cell modules as the core material, a dense silver layer is coated onto it to form a silver-coated silicon structure. This structure possesses good conductivity, cost advantages, and resource recycling characteristics, effectively replacing existing silver powder or silver-coated copper materials. Furthermore, the preparation process is simple, the conditions are mild, the controllability is good, and the stability is strong, making it more suitable for industrial promotion and application.

[0104] This invention uses recycled silicon powder from solar cell modules as the core material and achieves silver-coated silicon core-shell structure particles through surface cleaning, sputtering, and other means to replace the silver powder or silver-coated copper powder in existing conductive pastes. It has the following advantages: (1) Green conversion of raw material sources: This invention is the first to use silicon powder from retired solar cell modules after high purification treatment for conductive functional materials, which effectively promotes the recycling and reuse of resources in the photovoltaic industry chain. (2) Innovative material structure: Unlike traditional silver powder or silver-coated copper particles, this invention constructs a silver-coated silicon structure, adopting a non-metallic core and silver shell composite form, which significantly reduces the proportion of silver used while maintaining conductivity. (3) Innovative combination of pretreatment and physical coating process: This invention organically combines the stringent wet chemical cleaning with the advanced dry physical coating process. First, it adopts a multi-stage cleaning process of "organic solvent + HF + RCA" to provide an ideal clean particle surface for subsequent high-quality coating. More importantly, this invention innovatively proposes a powder coating scheme of "bottom vibration + magnetron sputtering". By using a specially designed glass container and an external vibration module, the silicon powder particles are controlled and continuously moved in a high vacuum environment during the sputtering process, thereby solving the technical problem that traditional PVD technology is difficult to uniformly coat micron-sized powders with 360° no dead angles, and ensuring the uniformity and density of the silver layer. (4) Cross-border expansion of application scope: In addition to being used in solar cell pastes, the high-purity silicon powder and its silver-coated products in this invention can also be applied to multiple high-value-added fields such as lithium-ion battery anode materials and conductive composite materials, breaking through the application boundaries of traditional silver powder products.

[0105] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, describes the application of the silver-coated silicon composite material provided by the present invention in silicon powder recycling, a method for preparing silver-coated silicon composite material using recycled silicon powder, and its application. 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 operating procedures. 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.

[0106] Example 1

[0107] (1) Material pretreatment

[0108] Raw material preparation: Weigh 1000mg of recycled silicon powder from solar cells with an average particle size of 15μm, and perform the following cleaning steps in sequence:

[0109] Organic matter cleaning: Place the above-mentioned silicon powder in a beaker containing anhydrous ethanol and treat it in an ultrasonic cleaner at 40 kHz for 30 minutes; after filtration, ultrasonically clean it with acetone under the same conditions for 30 minutes to completely remove organic residues.

[0110] Oxide etching: Immerse the cleaned silicon powder in an 8% (w / w) aqueous solution of hydrofluoric acid (HF) and gently stir with a magnetic stirrer for 2.0 minutes at room temperature. This step aims to completely remove the natural oxide layer on the surface of the silicon powder.

[0111] RCA Standard Cleaning: SC-1 Cleaning: Quickly transfer the HF-treated silicon powder to SC-1 cleaning solution (NH4OH:H2O2:H2O volume ratio 1:1:4) and heat in a 75°C water bath for 15 minutes. Deionized Water Rinsing: Rinse the silicon powder repeatedly with ultrapure deionized water until the pH of the washing solution is neutral. SC-2 Cleaning: After vacuum drying, transfer the rinsed silicon powder to SC-2 cleaning solution (HCl:H2O2:H2O volume ratio 1:1:8) and heat in a 75°C water bath for 15 minutes.

[0112] Final washing and drying: The silicon powder is thoroughly rinsed with ultrapure deionized water until neutral, and then placed in a vacuum oven and dried at 40°C for 4 hours to obtain ultra-clean, highly active silicon powder to be coated.

[0113] Magnetron sputtering coating

[0114] Loading: The processed silicon powder is loaded into a vibrating glass container and placed on the sample stage of the magnetron sputtering equipment. Simultaneously, a 1cm × 1cm silicon wafer is fixed nearby as a companion sample. The equipment is pre-loaded with a 99.99% pure silver target.

[0115] Sputtering process: Base vacuum: Start the vacuum pump unit to evacuate the cavity to a vacuum level of 4.0 × 10⁻⁶. -4 Pa. Working gas: High-purity argon (Ar) is introduced to stabilize the working gas pressure in the cavity at 0.8 Pa.

[0116] Dynamic deposition process: The vibration module was activated, with a vibration frequency of 50Hz and an amplitude of 2mm, causing the silicon powder particles to continuously tumble. While the powder was in continuous motion, the sputtering power supply was activated and set to 300W. To obtain a thicker coating, the deposition time was extended to 110 minutes.

[0117] Sampling: After sputtering, turn off the power and vibration module, and after the cavity cools down, break the vacuum to collect the powder sample (silver-coated silicon composite particles) and the accompanying sample.

[0118] The performance of the silver-coated silicon composite particles prepared in Example 1 of the present invention was tested.

[0119] Sheet resistance of the thin film on the particle surface: The average sheet resistance was measured at multiple points on the surface of the silver thin film sample using a four-probe tester and found to be 0.21 Ω / sq.

[0120] Thin film thickness on particle surface: A step was lightly scratched on the film surface with a tool. Multiple measurements were taken across the step using a profilometer, and the average value was recorded. The film thickness was found to be 280 nm.

[0121] Resistivity ≈ Shear resistance * Thickness = 5.8 × 10⁻⁶ -8 Ω·m

[0122] Silver accounts for approximately 34% of the total mass.

[0123] Example 2

[0124] (1) Material pretreatment

[0125] All steps are consistent with Example 1.

[0126] (2) Magnetron sputtering coating

[0127] Loading: Consistent with Example 1

[0128] Sputtering process: Base vacuum: Start the vacuum pump unit to evacuate the cavity to a vacuum level of 4.0 × 10⁻⁶. -4 Pa. Working gas: High-purity argon (Ar) is introduced to stabilize the working gas pressure in the cavity at 0.6 Pa.

[0129] Dynamic deposition process: The vibration module is activated, and the vibration frequency is set to 70Hz with an amplitude of 2mm to continuously tumble the silicon powder particles. While the powder is in continuous motion, the sputtering power supply is activated, and the power is set to 350W for a sputtering time of 85 minutes.

[0130] Sampling: Consistent with Example 1

[0131] (3) Test

[0132] Thin film thickness: The thickness of the silver film on the accompanying sample (complementary film) was measured using a profilometer, and the average thickness was found to be 270 nm.

[0133] Thin film sheet resistance: Measured using a four-probe tester, the average sheet resistance was found to be 0.22 Ω / sq.

[0134] Resistivity: Calculated using the formula (resistivity ≈ sheet resistance × thickness), the resistivity of the resulting silver film is approximately 5.9 × 10⁻⁶. -8 Ω·m.

[0135] Silver mass percentage: The silver mass percentage of the silver-coated silicon composite material prepared under these conditions is approximately 33%.

[0136] Example 3

[0137] (1) Material pretreatment

[0138] Raw material preparation: Weigh 1000mg of recycled silicon powder from solar cells with an average particle size of 8μm, and perform the following cleaning steps in sequence.

[0139] The remaining steps are the same as in Example 1.

[0140] (2) Magnetron sputtering coating

[0141] Loading: Consistent with Example 1

[0142] Sputtering process: consistent with Example 1

[0143] Dynamic deposition process: The vibration module is activated, with the vibration frequency set to 50Hz and the amplitude to 2mm, causing the silicon powder particles to continuously tumble. While the powder is in continuous motion, the sputtering power supply is activated, with the power set to 400W and the deposition time to 75 minutes.

[0144] Sampling: Consistent with Example 1

[0145] (3) Test

[0146] Thin film thickness: The thickness of the silver film on the accompanying sample (complementary film) was measured using a profilometer, and the average thickness was found to be 260 nm.

[0147] Thin film sheet resistance: Measured using a four-probe tester, the average sheet resistance was found to be 0.23 Ω / sq.

[0148] Resistivity: Calculated using the formula (resistivity ≈ sheet resistance × thickness), the resistivity of the resulting silver film is approximately 6.0 × 10⁻⁶. -8 Ω·m.

[0149] Silver mass percentage: The silver mass percentage of the silver-coated silicon composite material prepared under these conditions is approximately 48%.

[0150] Example 4

[0151] (1) Material pretreatment

[0152] Raw material preparation: Weigh 1000mg of recycled silicon powder from solar cells with an average particle size of 25μm, and perform the following cleaning steps in sequence.

[0153] The remaining steps are the same as in Example 1.

[0154] (2) Magnetron sputtering coating

[0155] Loading: Consistent with Example 1

[0156] Sputtering process: Base vacuum: Start the vacuum pump unit to evacuate the cavity to a vacuum level of 4.0 × 10⁻⁶. -4 Pa. Working gas: High-purity argon (Ar) is introduced to stabilize the working gas pressure in the cavity at 0.9 Pa.

[0157] Dynamic deposition process: The vibration module is activated, with the vibration frequency set to 60Hz and the amplitude to 2mm, causing the silicon powder particles to continuously tumble. While the powder is in continuous motion, the sputtering power supply is activated, with the power set to 450W and the deposition time to 50 minutes.

[0158] Sampling: Consistent with Example 1

[0159] (3) Test

[0160] Thin film thickness: The thickness of the silver film on the accompanying sample (complementary film) was measured using a profilometer, and the average thickness was found to be 200 nm.

[0161] Thin film sheet resistance: Measured using a four-probe tester, the average sheet resistance was found to be 0.34 Ω / sq.

[0162] Resistivity: Calculated using the formula (resistivity ≈ sheet resistance × thickness), the resistivity of the resulting silver film is approximately 6.7 × 10⁻⁶. -8 Ω·m.

[0163] Silver mass percentage: The silver mass percentage in the silver-coated silicon composite material prepared under these conditions is approximately 18%.

[0164] The application of the silver-coated silicon composite material provided by this invention in silicon powder recycling, a method for preparing silver-coated silicon composite material using recycled silicon powder, and its application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention, including the best mode, and also 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 for those skilled in the art, several improvements and modifications can be made to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the textual description of the claims, or if they include equivalent structural elements that are not substantially different from the textual description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. Application of silver-coated silicon composite materials in silicon powder recycling.

2. The application according to claim 1, characterized in that, The silver-coated silicon composite material is specifically silver-coated silicon particles; The silver-coated silicon composite material has a core-shell structure, with a silicon particle core and a silver layer as the shell. The particle size of the silver-coated silicon composite material is 2–40 μm; The thickness of the silver layer is 50–500 nm; The resistivity of the silver layer is 4.1 × 10⁻⁶. -8 Ω·m~7.2×10 -8 Ω·m.

3. The application according to claim 1, characterized in that, The silicon powder includes crystalline silicon particle powder recovered from decommissioned solar cell modules, waste silicon powder generated from solar cell wafers, and waste silicon powder generated during the solar cell manufacturing process. In the silver-coated silicon composite material, the mass content of the silver layer is 10% to 55%; The specific application involves preparing silver-coated silicon composite material from the recycled silicon powder for reuse. The silver-coated silicon composite material is specifically a silver / silicon composite conductive material used in conductive pastes.

4. A method for preparing silver-coated silicon composite material using recycled silicon powder, characterized in that, Includes the following steps: 1) The recycled silicon powder is washed to obtain silicon powder particles; The cleaning process includes one or more steps of organic solvent pre-washing, acid washing, RCA cleaning and water washing; 2) Place the silicon powder particles obtained in the above steps into a vibrating glass container, and then place it into a magnetron sputtering device equipped with a silver target, so that the silicon powder particles are in a vibrating state. Under the condition of filling with inert gas as the working gas, magnetron sputtering is performed to deposit a silver layer, and a silver-coated silicon composite material is obtained.

5. The method according to claim 4, characterized in that, The recycled silicon powder includes crystalline silicon particle powder recovered from decommissioned solar cell modules, waste silicon powder generated from solar cell wafers, and waste silicon powder generated during the solar cell manufacturing process. The cleaning process consists of organic solvent pre-washing, acid washing, RCA cleaning, and water washing.

6. The method according to claim 5, characterized in that, The organic solvent prewash includes ethanol cleaning and / or acetone cleaning; The pickling includes hydrofluoric acid pickling; The mass concentration of the hydrofluoric acid is 5% to 10%. The pickling time is 0.5 to 3 minutes.

7. The method according to claim 5, characterized in that, The RCA cleaning includes SC-1 chemical cleaning and SC-2 chemical cleaning; The water washing specifically refers to washing with water until neutral; The washing process also includes a drying step.

8. The method according to claim 4, characterized in that, The vibration frequency of the vibration state is 20 to 100 Hz; The amplitude of the vibrating silicon powder particles is 0.5–5 mm. The working gas is specifically a low-pressure working gas; The working gas pressure is 0.5 to 1.0 Pa.

9. The method according to claim 4, characterized in that, The process of filling with inert gas also includes a vacuuming step. The vacuum pressure during the evacuation process is 3.2 x 10⁻⁶. -4 Pa ~ 7.0 x 10 -4 Pa; The sputtering power of the magnetron sputtering is 100-600W; The deposition time for magnetron sputtering is 30–180 min.

10. The application of the silver-coated silicon composite material in any one of claims 1 to 3, or the silver-coated silicon composite material prepared by the method of any one of claims 4 to 9, in sintered solar cell paste systems, conductive fillers, and conductive pastes.