Method for preparing silicon-carbon negative electrode based on retired photovoltaic panel and impregnated asphalt tailings

Abstract

The invention belongs to the technical field of preparation of silicon-carbon negative electrodes, and particularly relates to a method for preparing a silicon-carbon negative electrode based on a decommissioned photovoltaic panel and impregnated asphalt tailings, and the method comprises the following steps: S1, carrying out mechanical disassembly on the decommissioned photovoltaic panel, and separating an aluminum frame, a junction box and a battery piece in the decommissioned photovoltaic panel, carrying out simple crushing treatment on the battery piece to obtain a primary treatment silicon material; s2, the obtained primarily-treated silicon material is placed in a muffle furnace protected by argon flow to be subjected to heat treatment, EVA glue in the primarily-treated silicon material is converted into EVA carbon black through the high-temperature thermal decomposition process, and the EVA carbon black is purged to a collecting device. According to the method, the EVA glue is efficiently converted into the carbon black in the retired photovoltaic panel treatment process, nanocrystallization treatment of silicon is achieved, and the service life of the photovoltaic panel is prolonged; nano silicon and EVA carbon black are uniformly and tightly combined by utilizing a negative pressure deposition technology, the use of strong acid and strong alkali is completely avoided, the environmental friendliness is ensured, no waste gas is discharged in the whole process flow, and the green sustainability of the production process is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing silicon-carbon anodes, and particularly to a method for preparing silicon-carbon anodes based on retired photovoltaic panels and impregnated asphalt tailings. Background Art

[0002] Regarding the reuse of retired photovoltaic panels, extensive research has been carried out in the industry. Among them, silicon, as a negative electrode material for lithium-ion batteries, has become a strong candidate for the next-generation high-energy negative electrode material with its mass specific capacity as high as 4200 mAh g^-1. Converting the silicon material in photovoltaic panels into high-performance silicon-based negative electrode materials, especially through nanosizing treatment to improve their performance, has become a high-value-added technical path. However, the current mainstream acid-base etching and high-energy ball milling methods both have limitations: acid-base etching involves the use of strong acids (bases), causing pressure on the environment; while high-energy ball milling faces technical difficulties in controlling the shape, size, and surface oxidation of nanosilicon. In addition, the plastic styrene-butadiene rubber (EVA) glue in photovoltaic panels has not been fully emphasized during the recycling process, and there is a lack of effective recycling methods.

[0003] On the other hand, when silicon serves as a lithium storage host, it faces problems such as poor conductivity, severe volume expansion, and side reactions with the electrolyte. To solve these problems, introducing carbon materials to form silicon-carbon composite materials has become a common strategy, and asphalt is widely used for the coating of commercial anodes due to its low cost and excellent conductivity of the derived carbon.

[0004] In summary, developing a green and efficient method to simultaneously recycle the silicon material and EVA glue in photovoltaic panels, combine them with recycled asphalt, and achieve green circular utilization throughout the process is of great significance for promoting the sustainable development of the photovoltaic industry, alleviating resource pressure, and environmental protection, and is a technical problem that urgently needs to be solved in the future. Summary of the Invention

[0005] The present invention provides a method for preparing silicon-carbon anodes based on retired photovoltaic panels and impregnated asphalt tailings, aiming to develop a green and efficient method to simultaneously recycle the silicon material and EVA glue in photovoltaic panels, combine them with recycled asphalt, and achieve green circular utilization throughout the process, which is of great significance for promoting the sustainable development of the photovoltaic industry, alleviating resource pressure, and environmental protection.

[0006] The present invention provides the following technical solutions:

[0007] A method for preparing silicon-carbon anodes based on retired photovoltaic panels and impregnated asphalt tailings, comprising the following steps:

[0008] S1: Mechanically disassemble the retired photovoltaic panels, separate the aluminum frames, junction boxes, and battery cells therein, and then simply crush the battery cells to obtain primary treated silicon material;

[0009] S2: placing the obtained primary treated silicon material in a muffle furnace protected by argon gas flow for heat treatment, converting the EVA glue in the primary treated silicon material into EVA carbon black through a high temperature thermal decomposition process and blowing it into a collection device, and then mechanically peeling off the surface glass of the silicon wafer, and obtaining the secondary treated silicon material through cleaning, separation and drying;

[0010] S3: placing the secondary treated silicon material and EVA carbon black in the high temperature evaporation zone and the low temperature deposition zone of the physical vapor deposition furnace respectively, and evaporating the silicon in the secondary treated silicon material and transferring it to the surface of the EVA carbon black for condensation deposition by setting different evaporation and deposition temperatures, pressures and airflows to form a primary silicon-carbon composite material;

[0011] S4: Mechanically mix the primary silicon-carbon composite material with the impregnated asphalt tailings to form a block coating material, and then obtain the secondary silicon-carbon composite material through carbonization treatment.

[0012] In a possible embodiment, in step S2, the heat treatment temperature is 300-500°C, the treatment time is 1-4h, and the purge gas flow rate is 1-5L / min; in the cleaning, separation and drying treatments, the cleaning method is mechanical stirring, the cleaning agent is deionized water, and the cleaning time is 0.2-1h; the separation method is natural sedimentation separation, the sedimentation time is 0.5-1.5h, and the number of cleaning times is 3-5 times; the drying temperature is 60-100°C, and the drying time is 8-12h.

[0013] In a possible implementation, in step S3, the evaporation temperature is 1400-2500° C., the deposition temperature is 800-1100° C., the pressure in the furnace is 10-50 Pa, the air flow is 20-100 mL / min, and the deposition time is 1-4 h.

[0014] In one possible embodiment, the asphalt tailings impregnated in step S4 are high-temperature asphalt, the mixing ratio of the primary silicon-carbon composite material and asphalt is 3:1-5:1, the stirring time is 1-2h, the stirring temperature is 150-250°C, the carbonization temperature is 700-1000°C, and the treatment time is 1-3h.

[0015] It is to be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the invention.

[0016] In the present invention, the EVA glue in the process of treating retired photovoltaic panels is innovatively and efficiently utilized to convert into carbon black, which is used as the carbon base material of the silicon-carbon anode. By only adopting physical vapor deposition technology, not only the nanometerization treatment of silicon is realized, but also the negative pressure deposition technology is skillfully used to make the nanosilicon and EVA carbon black achieve uniform and tight combination. This process completely avoids the use of strong acids and alkalis, ensures environmental friendliness, and there is no waste gas emission in the whole technological process, significantly improving the green sustainability of the production process.

[0017] In the present invention, through the physical evaporation process, the Ag and Al elements in the photovoltaic panel are effectively evaporated and deposited on the surface of the EVA carbon black, forming a metal transition layer, enhancing the bonding strength between the silicon and the carbon black substrate, and significantly improving the electrical conductivity of the material. At the same time, this process also improves the comprehensive utilization rate of the metal components in the photovoltaic panel, realizing the maximum recovery and reuse of resources.

[0018] In the present invention, the physical vapor deposition technology used can form nanosilicon structures with a size of about 10 nm from bottom to top. Such nanoscale silicon particles significantly increase the active surface area of the battery, thus effectively improving the capacity, cycle stability and rate performance of the battery, providing strong support for the high performance of lithium-ion batteries.

[0019] In the present invention, the impregnated asphalt tailings are used as the coating agent, not only realizing the efficient recycling of the graphite impregnated asphalt tailings, but also using the highly conductive carbon layer formed after the high-temperature carbonization of the tailings to further enhance the electrical conductivity of the material. In addition, this carbon layer can effectively isolate the direct contact between the silicon and the electrolyte, reduce the occurrence of side reactions, and relieve the volume change of the silicon material during charge and discharge, thus significantly improving the safety and cycle life of the battery. Description of the Drawings

[0020] Figure 1 It is the process flow chart of a method for preparing a silicon-carbon anode based on retired photovoltaic panels and impregnated asphalt tailings provided by an embodiment of the present invention;

[0021] Figure 2 It is the SEM image of the EVA carbon black of Example 1 of a method for preparing a silicon-carbon anode based on retired photovoltaic panels and impregnated asphalt tailings provided by an embodiment of the present invention;

[0022] Figure 3 It is the TEM images of the (a-c) EVA carbon black / Si sample and the (d) EVA carbon black / Si / asphalt carbon sample of Example 1 of a method for preparing a silicon-carbon anode based on retired photovoltaic panels and impregnated asphalt tailings provided by an embodiment of the present invention;

[0023] Figure 4The charge and discharge performance of the EVA carbon black / Si / asphalt carbon samples at a current density of 0.1 A / g in Examples 1-3 of a method for preparing a silicon-carbon negative electrode based on retired photovoltaic panels and impregnated asphalt tailings provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0025] In Example 1, the retired photovoltaic panel is first mechanically disassembled, and the aluminum frame, junction box and battery cell therein are separated, and then the battery cell is simply crushed to obtain a primary processed silicon material; then the primary processed silicon material is placed in a muffle furnace protected by an argon gas flow (gas flow rate is 1 L / min) for heat treatment at 300° C. for 4 h, and the EVA glue in the primary processed silicon material is converted into carbon black through a high-temperature thermal decomposition process and purged to a collection device, and then the surface glass of the silicon wafer is mechanically peeled off, and the silicon wafer is mechanically stirred and cleaned with deionized water for 0.2 h and precipitated and separated for 5 times, and then dried at 60° C. for 12 h to obtain a secondary processed silicon material. material; then the secondary treated silicon material and EVA carbon black are placed in the high temperature evaporation zone and low temperature deposition zone of the physical vapor deposition furnace respectively, and the silicon in the secondary treated silicon material is evaporated and transferred to the surface of the EVA carbon black for condensation deposition by setting the evaporation temperature to 1400°C and the deposition temperature to 800°C, the pressure in the furnace to 50pa, the air flow to 100mL / min and the deposition time to 4h, so as to form a primary silicon-carbon composite material; finally, the primary silicon-carbon composite material and the impregnated asphalt tailings are mechanically mixed at a mixing ratio of 5:1 for 1h to form a block coating material, and the stirring temperature is 250°C; and then the secondary silicon-carbon composite material is obtained by carbonization treatment at 700°C for 3h.

[0026] like Figure 2 As shown in the figure, through the physical evaporation process, the Ag and Al elements in the photovoltaic panel are effectively evaporated and deposited on the surface of EVA carbon black, forming a metal transition layer, which enhances the bonding strength between silicon and the carbon black substrate and significantly improves the conductive properties of the material. At the same time, this process also improves the comprehensive utilization rate of metal components in photovoltaic panels and realizes the maximum recycling and reuse of resources.

[0027] like Figure 3As shown, the physical vapor deposition technology used can form a nano-silicon structure with a size of about 10nm from bottom to top. This nano-scale silicon particle significantly increases the active surface area of ​​the battery, thereby effectively improving the battery capacity, cycle stability and rate performance, and provides strong support for the high performance of lithium-ion batteries. The impregnated asphalt tailings are used as coating agents, which not only realizes the efficient recycling of graphite impregnated asphalt tailings, but also utilizes the highly conductive carbon layer formed after the tailings are carbonized by high-temperature asphalt to further enhance the conductivity of the material. In addition, the carbon layer can effectively isolate the direct contact between silicon and the electrolyte, reduce the occurrence of side reactions, and alleviate the volume change of silicon material during charging and discharging, thereby significantly improving the safety and cycle life of the battery.

[0028] The silicon-carbon composite material obtained in this embodiment is mixed with acetylene black and polyacrylic acid in a mass ratio of 80:10:10, and an appropriate amount of deionized water is added as a solvent to prepare a slurry and coated on a copper foil, and then vacuum dried and cut into pole pieces. A battery is composed of a metal lithium counter electrode, a polypropylene (PP) diaphragm, a 1 mol / L LiPF6 (the solvent is EC+DMC+FEC with a volume ratio of 1:1:1, and an additional FEC accounting for 5% of the total weight) electrolyte and the prepared silicon-carbon electrode for battery testing. The test voltage window is 0.01-2V, the charge and discharge current density is 0.1A / g, the test temperature is 25°C, and the test results are as follows: Figure 4 shown.

[0029] Example 2, firstly, the retired photovoltaic panel is mechanically disassembled, the aluminum frame, junction box and battery cell therein are separated, and then the battery cell is simply crushed to obtain a primary processed silicon material; secondly, the primary processed silicon material is placed in a muffle furnace protected by an argon gas flow (gas flow rate is 3L / min) and heat treated at 400°C for 2h, and the EVA glue in the primary processed silicon material is converted into carbon black through a high temperature thermal decomposition process and purged to a collection device, and then the surface glass of the silicon wafer is mechanically peeled off, and the silicon wafer is mechanically stirred and cleaned with deionized water for 0.6h and precipitated and separated for 4 times, and then dried at 80°C for 10h to obtain a secondary processed silicon material ; Then, the secondary treated silicon material and EVA carbon black are placed in the high temperature evaporation zone and low temperature deposition zone of the physical vapor deposition furnace respectively. By setting the evaporation temperature to 1900°C and the deposition temperature to 950°C, the pressure in the furnace to 30pa, the air flow to 60mL / min and the deposition time to 2h, the silicon in the secondary treated silicon material is evaporated and transferred to the surface of the EVA carbon black for condensation and deposition to form a primary silicon-carbon composite material; finally, the primary silicon-carbon composite material and the impregnated asphalt tailings are mechanically mixed at a mixing ratio of 4:1 for 1.5h to form a block coating material, and the stirring temperature is 200°C; and then the secondary silicon-carbon composite material is obtained by carbonization treatment at 850°C for 2h.

[0030] The silicon-carbon composite material obtained in this example is mixed with acetylene black and polyacrylic acid in a mass ratio of 80:10:10, and an appropriate amount of deionized water is added as a solvent to prepare a slurry, which is then coated on a copper foil and cut into electrode sheets through vacuum drying. Using metallic lithium as the counter electrode, a polypropylene (PP) separator, and a 1mol / L LiPF6 electrolyte (the solvent is EC + DMC + FEC with a volume ratio of 1:1:1, and an additional 5% of FEC by total weight is added), a battery is assembled with the fabricated silicon-carbon electrode for battery testing. The test voltage window is 0.01 - 2V, the charge-discharge current density is 0.1A / g, the test temperature is 25°C, and the test results are as Figure 4 shown.

[0031] Example 3: First, the retired photovoltaic panel is mechanically disassembled to separate the aluminum frame, junction box, and solar cells. Then, the solar cells are simply crushed to obtain primary treated silicon material. Next, the obtained primary treated silicon material is placed in a muffle furnace protected by an argon gas flow (gas flow rate is 5L / min) and heat-treated at 500°C for 1h. Through the high-temperature thermal decomposition process, the EVA glue in the primary treated silicon material is converted into carbon black and purged into a collection device. Then, the glass on the surface of the silicon wafer is mechanically peeled off, mechanically stirred and washed with deionized water for 1h and separated by precipitation 3 times. Subsequently, it is dried at 100°C for 8h to obtain secondary treated silicon material. Secondly, the secondary treated silicon material and EVA carbon black are respectively placed in the high-temperature evaporation zone and low-temperature deposition zone of a physical vapor deposition furnace. By setting the evaporation temperature at 2500°C, the deposition temperature at 1100°C, the furnace pressure at 50 Pa, the gas flow rate at 20 mL / min, and the deposition time at 1h, the silicon in the secondary treated silicon material is evaporated and transferred to the surface of the EVA carbon black for condensation and deposition to form a primary silicon-carbon composite material. Finally, the primary silicon-carbon composite material and the impregnated asphalt tailings are mechanically mixed at a mixing ratio of 3:1 for 2h to form a massive coating material, and the stirring temperature is 150°C. Then, it is carbonized at 1000°C for 1h to obtain a secondary silicon-carbon composite material.

[0032] The silicon-carbon composite material obtained in this example is mixed with acetylene black and polyacrylic acid in a mass ratio of 80:10:10, and an appropriate amount of deionized water is added as a solvent to prepare a slurry, which is then coated on a copper foil and cut into electrode sheets through vacuum drying. Using metallic lithium as the counter electrode, a polypropylene (PP) separator, and a 1mol / L LiPF6 electrolyte (the solvent is EC + DMC + FEC with a volume ratio of 1:1:1, and an additional 5% of FEC by total weight is added), a battery is assembled with the fabricated silicon-carbon electrode for battery testing. The test voltage window is 0.01 - 2V, the charge-discharge current density is 0.1A / g, the test temperature is 25°C, and the test results are as Figure 4 shown.

[0033] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention; without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing a silicon-carbon negative electrode based on retired photovoltaic panels and impregnated asphalt tailings, characterized in that: The following steps are involved: S1: Mechanically dismantle the retired photovoltaic panels, separate the aluminum frame, junction box and solar cells, and then simply crush the solar cells to obtain primary processed silicon materials; S2: placing the obtained primary treated silicon material in a muffle furnace protected by argon gas flow for heat treatment, converting the EVA glue in the primary treated silicon material into EVA carbon black through a high temperature thermal decomposition process and blowing it into a collection device, and then mechanically peeling off the surface glass of the silicon wafer, and obtaining the secondary treated silicon material through cleaning, separation and drying; S3: placing the secondary treated silicon material and EVA carbon black in the high temperature evaporation zone and the low temperature deposition zone of the physical vapor deposition furnace respectively, and evaporating the silicon in the secondary treated silicon material and transferring it to the surface of the EVA carbon black for condensation deposition by setting different evaporation and deposition temperatures, pressures and airflows to form a primary silicon-carbon composite material; S4: Mechanically mix the primary silicon-carbon composite material with the impregnated asphalt tailings to form a block coating material, and then obtain the secondary silicon-carbon composite material through carbonization treatment.

2. The method for preparing a silicon-carbon negative electrode based on retired photovoltaic panels and impregnated asphalt tailings according to claim 1, characterized in that: In the step S2, the heat treatment temperature is 300-500°C, the treatment time is 1-4h, and the purge air flow rate is 1-5L / min; in the cleaning, separation and drying treatments, the cleaning method is mechanical stirring, the cleaning agent is deionized water, and the cleaning time is 0.2-1h; the separation method is natural sedimentation separation, the sedimentation time is 0.5-1.5h, and the number of cleaning times is 3-5 times; the drying temperature is 60-100°C, and the drying time is 8-12h.

3. The method for preparing a silicon-carbon negative electrode based on retired photovoltaic panels and impregnated asphalt tailings according to claim 2 is characterized in that: In the step S3, the evaporation temperature is 1400-2500° C., the deposition temperature is 800-1100° C., the pressure in the furnace is 10-50 Pa, the air flow is 20-100 mL / min, and the deposition time is 1-4 h.

4. The method for preparing a silicon-carbon negative electrode based on retired photovoltaic panels and impregnated asphalt tailings according to claim 3 is characterized in that: In the step S4, the asphalt tailings impregnated are high-temperature asphalt, the mixing ratio of the primary silicon-carbon composite material and asphalt is 3:1-5:1, the stirring time is 1-2 hours, the stirring temperature is 150-250°C, the carbonization temperature is 700-1000°C, and the processing time is 1-3 hours.

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