A method for recycling and separating waste photovoltaic modules based on low-temperature recovery of waste lithium ion battery electrolyte

Abstract

The application discloses a method for recycling and separating waste photovoltaic modules based on waste lithium ion battery electrolyte at low temperature, and relates to the technical field of photovoltaic module recycling, and comprises the following steps: removing the aluminum frame and the junction box of the waste photovoltaic module, and cutting the laminated piece into unit pieces; placing the unit pieces in a reaction container, adding waste lithium ion battery electrolyte to immerse the unit pieces, applying microwave irradiation, softening and losing adhesion of the EVA adhesive film, realizing separation of the glass plate, the fluorine-containing back plate, the crystalline silicon cell piece and the solder strip; respectively taking out the separated glass plate, the fluorine-containing back plate, the crystalline silicon cell piece and the solder strip; the application introduces a microwave selective heating mechanism into an electrolyte swelling system, so that microwave energy is directly coupled to a reaction interface, selective destruction of an EVA crosslinked network can be realized at a temperature far lower than that of traditional pyrolysis, and thus high-temperature damage and release of harmful gases can be fundamentally avoided.

Description

Technical Field

[0001] This invention relates to the field of waste photovoltaic module recycling technology, specifically to a method for the low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte. Background Technology

[0002] With the global energy structure shifting towards cleaner energy, the photovoltaic industry has experienced explosive growth. Crystalline silicon photovoltaic modules, as the mainstream product, are constructed from multi-layered materials and typically have a service life of 20-25 years. According to the International Renewable Energy Agency (IRENA), the world will see a peak in photovoltaic module retirements starting in 2030, with a cumulative retirement volume reaching tens of millions of tons. How to efficiently and environmentally recover these modules has become a key bottleneck for the sustainable development of the photovoltaic industry.

[0003] Current mainstream recycling technologies for waste photovoltaic modules are divided into physical methods, pyrolysis methods, and organic solvent methods, all of which have significant drawbacks: 1. Physical crushing and sorting: This method achieves material separation through physical means, but photovoltaic modules are dense composite materials, and mechanical force is insufficient to break the adhesive strength of the EVA film, making it impossible to obtain intact glass and silicon wafers. Fine powder is difficult to separate, and there is a lot of EVA residue, resulting in low purity and value of recycled materials. 2. High-temperature pyrolysis: This method separates EVA by cracking it at temperatures above 400℃. Although interlayer separation can be achieved, silicon wafers are prone to breakage due to thermal stress, requiring downgrading for reuse and significantly reducing their value. Incomplete EVA cracking can easily form a coke layer on the silicon wafer surface, increasing the difficulty of cleaning. Fluorine-containing backsheets decompose at high temperatures, releasing highly toxic and corrosive hydrogen fluoride (HF), which corrodes equipment and requires expensive exhaust gas treatment, significantly increasing operating costs and environmental risks. 3. Organic Solvent Swelling Method: This method utilizes organic solvents to swell and dissolve EVA for separation. Commonly used solvents include dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), dimethylformamide (DMF), and dimethyl carbonate (DMC). However, high-purity solvents are expensive, and under traditional conditions, the solvent penetration rate is low and the reaction is slow, with single-batch processing times reaching several hours to tens of hours, making it difficult to meet the needs of industrial production. Furthermore, solvent recycling is easily contaminated, regeneration is difficult, and improper treatment of organic waste liquid can seriously harm the ecological environment. In addition to the above drawbacks, existing technologies all suffer from poor heating uniformity: traditional heat conduction heating for large-area components creates temperature gradients and heating blind zones, resulting in inconsistent EVA treatment levels in different areas of the same component, affecting the stability and consistency of batch processing.

[0004] At the same time, the development of the new energy vehicle industry has also brought about an explosive growth in retired power lithium-ion batteries. The waste electrolyte generated from the dismantling of lithium batteries is a hazardous waste, and its compliant disposal is costly and poses a great environmental risk. Currently, there is a lack of large-scale high-value utilization methods. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for the low-temperature recycling and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte. The method introduces a microwave selective heating mechanism into the electrolyte swelling system, allowing microwave energy to be directly coupled to the reaction interface. This enables the selective destruction of the EVA crosslinking network at a temperature far lower than that of traditional pyrolysis, thereby fundamentally avoiding high-temperature damage and the release of harmful gases.

[0006] The technical solution of the present invention is as follows: In a first aspect of the present invention, a method for low-temperature recycling and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte is provided, comprising the following steps: S1. Remove the aluminum frame and junction box of the discarded photovoltaic module and cut the laminate into unit pieces; S2. Place the unit sheet in a reaction vessel, add waste lithium-ion battery electrolyte to immerse the unit sheet, apply microwave irradiation to soften and de-adhere the EVA film, thereby achieving the separation of the glass plate, fluorine-containing backsheet, crystalline silicon battery cell and solder ribbon; wherein, the waste lithium-ion battery electrolyte is the waste electrolyte obtained from the dismantling of retired lithium-ion batteries, containing carbonate solvents and lithium hexafluorophosphate electrolyte; S3. Remove the separated glass plate, fluorine-containing backplate, crystalline silicon solar cell and solder strip respectively.

[0007] In some embodiments of the present invention, the temperature of the microwave irradiation treatment is 70-90°C, the power of the microwave irradiation is 200-800W, the microwave frequency is 2.45 GHz or 915 MHz, and the treatment time is 10-30 minutes.

[0008] In some embodiments of the present invention, the mass ratio of the waste electrolyte to the unit cell is 0.5-3:1.

[0009] In some embodiments of the present invention, the microwave irradiation treatment is carried out in an inert atmosphere, wherein the inert atmosphere is nitrogen or argon.

[0010] In some embodiments of the present invention, the carbonate solvent in the waste lithium-ion battery electrolyte includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0011] In some embodiments of the present invention, the size of the unit piece is from 5cm×5cm to 20cm×20cm.

[0012] In some embodiments of the present invention, the microwave irradiation is carried out in three stages, with the microwave irradiation time and power increasing sequentially in each stage.

[0013] In some embodiments of the present invention, the microwave irradiation time in the first stage is 2 minutes and the power is 200-400W; the microwave irradiation time in the second stage is 3-8 minutes and the power is 400-600W; and the microwave irradiation time in the third stage is 8-12 minutes and the power is 600-800W.

[0014] In some embodiments of the present invention, the waste electrolyte obtained in step S3 is regenerated by vacuum distillation or membrane separation and recycled back to step S2 for use.

[0015] In some embodiments of the present invention, the selective heating of microwave irradiation acts only on the polar components in the electrolyte; the bulk heating penetrates the entire unit sheet, so that the interlayer electrolyte is heated synchronously and uniformly; the bulk heating penetrates the entire unit sheet, so that the interlayer electrolyte is heated synchronously and uniformly, and the molecular-level reinforcement enables polar molecules to accelerate their penetration into the EVA molecular chains under the drive of the alternating electric field.

[0016] One or more technical solutions of the present invention have the following beneficial effects: (1) The method provided by this invention only requires three major steps: pretreatment, microwave-assisted swelling, and direct recovery of components. A single microwave process can simultaneously complete the softening and de-adhesion of EVA and the separation of multiple layers. Compared with the traditional multi-step combined process, the process is greatly shortened and the difficulty of industrialization is low. At the same time, microwave bulk heating greatly improves the processing efficiency: there is no traditional heating temperature gradient and heating blind zone, and the batch processing consistency is good; microwave molecular-level enhanced mass transfer shortens the traditional swelling time of several hours to 10-30 minutes, which is suitable for continuous large-scale industrial production.

[0017] (2) The method of the present invention has low and mild processing conditions, is energy-saving and ensures the integrity of materials: the entire process is at a low temperature of 70-90℃, which is far lower than the high temperature of 400℃ or above in traditional pyrolysis, and the heating energy consumption is significantly reduced; there is no thermal stress, the integrity rate of silicon wafers can reach 95-99%, and the glass and backplate are free from breakage and deformation, and the recycled materials retain their original high added value. Since the temperature is lower than the thermal decomposition temperature of the fluorine-containing backplate, the fluorine element is stably sealed in the solid backplate, and there is no release of hydrogen fluoride or organic toxic fumes; the fluorine component of the electrolyte is in a closed loop and does not leak out, so there is no need to set up defluorination and tail gas purification equipment, which greatly reduces the investment and maintenance costs of the production line, and the process is environmentally friendly and safe.

[0018] (3) This invention abandons the high-cost external purchase of pure solvents such as DMF, THF, and DMC, and uses waste electrolyte from the dismantling of scrapped lithium batteries as the core reagent; it disposes of hazardous waste from the new energy industry, reduces the purchase cost of organic solvents, and forms a closed-loop treatment model for solid waste; the electrolyte has two irreplaceable functions: the carbonate solvent permeates and swells EVA, and lithium hexafluorophosphate provides strong microwave loss. The two functions are naturally coupled, and no additional microwave absorption agent is needed.

[0019] (4) The method of the present invention only causes physical softening and loss of adhesion of EVA, and the chemical structure, composition and performance of all materials remain unchanged; the whole silicon wafer can be directly remanufactured into battery cells, and the glass, backsheet and solder ribbon can be directly recycled for the corresponding industrial chain without degradation or low-value products. At the same time, the separated products have high purity and do not require secondary purification. The separation interface of glass, backsheet and silicon wafer is clear and there is no cross-contamination. There is no coke or colloidal residue on the surface, and no additional cleaning and purification process is required, which reduces post-processing costs.

[0020] (5) The electrolyte of the present invention is recyclable and has low long-term operating costs. The electrolyte can be reused after being regenerated by vacuum distillation / membrane separation. The reagent consumption is extremely low. Compared with the traditional chemical method that consumes organic solvents once, the waste liquid treatment cost is greatly reduced. It simultaneously solves the problem of disposal of retired lithium battery electrolyte and the pain point of photovoltaic module recycling, reduces the cost of hazardous waste disposal and chemical solvent procurement, and significantly improves the utilization rate of solid waste resources. It has both industrial economic benefits and ecological environmental protection benefits. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the changes during the low-temperature separation and recycling process of waste photovoltaic modules according to the present invention. Detailed Implementation

[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Terminology Explanation: Waste photovoltaic modules: Solar photovoltaic laminated components that have reached the end of their service life of 20-25 years and whose performance has degraded and are no longer usable. They are composed of photovoltaic glass, EVA film, crystalline silicon cells, solder strips, and fluorine-containing backsheets, and are equipped with aluminum frames and junction boxes.

[0025] EVA film: a cross-linked film of ethylene-vinyl acetate copolymer, a core encapsulation adhesive material for photovoltaic modules, which tightly bonds glass, solar cells and backsheet after curing at room temperature.

[0026] Waste lithium-ion battery electrolyte: Waste liquid recovered after dismantling retired lithium batteries, mainly containing carbonate solvents (DMC / EMC / EC, etc.) and lithium hexafluorophosphate, which has both polar swelling capacity and microwave absorption characteristics.

[0027] Microwave coupling treatment: This process utilizes an alternating microwave electric field to selectively heat polar molecules and ions in the electrolyte, relying on molecular oscillation to enhance solvent penetration and achieve a synergistic process of low-temperature swelling and stripping.

[0028] Selective heating: Microwaves only heat the polar components of electrolytes that have a dipole moment, while non-polar materials such as photovoltaic glass and crystalline silicon hardly absorb microwave energy.

[0029] Bulk heating: Microwaves penetrate the entire component, and the interlayer electrolyte is heated synchronously and uniformly, without the temperature gradient and heating blind zone of traditional heat conduction.

[0030] Inert atmosphere: Protective gases such as nitrogen and argon that do not react with electrolyte or EVA are used to suppress solvent evaporation and oxidation side reactions during microwave processing.

[0031] Reduced pressure distillation / membrane separation: Electrolyte regeneration and recycling process, removes impurities entrained after swelling, restores the swelling and microwave absorption properties of the electrolyte, and can be reused.

[0032] In a typical embodiment of the present invention, a method for low-temperature recycling and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte is proposed, comprising the following steps: S1. Remove the aluminum frame and junction box of the discarded photovoltaic module and cut the laminate into unit pieces; S2. Place the unit sheet in a reaction vessel, add waste lithium-ion battery electrolyte to immerse the unit sheet, apply microwave irradiation to soften and de-adhere the EVA film, thereby achieving the separation of the glass plate, fluorine-containing backsheet, crystalline silicon battery cell and solder ribbon; wherein, the waste lithium-ion battery electrolyte is the waste electrolyte obtained from the dismantling of retired lithium-ion batteries, containing carbonate solvents and lithium hexafluorophosphate electrolyte; S3. Remove the separated glass plate, fluorine-containing backplate, crystalline silicon solar cell and solder strip respectively.

[0033] The above method utilizes the dual functions of waste electrolyte to achieve low-temperature recycling and separation of photovoltaic modules. Among them, carbonate solvent penetrates and swells the EVA crosslinking network, weakening the interfacial adhesion strength; lithium hexafluorophosphate electrolyte has strong ion loss and efficiently absorbs microwave energy in the microwave field, serving as a dedicated microwave absorbing medium. Microwave irradiation plays a triple role: (1) Selective heating: Only the polar components of the electrolyte are heated, while the glass and silicon wafers hardly absorb heat, avoiding thermal stress cracking from the source; (2) Bulk phase whole-domain heating: Microwaves penetrate the entire module, and the interlayer electrolyte is heated synchronously, with no heating blind spots, resulting in uniform swelling of large-area materials; (3) Molecular-level dynamic enhancement: The high-frequency alternating electric field of microwaves drives the polar molecules to oscillate at high speed, greatly increasing the solvent penetration rate. At the same time, the micro-vaporization of interlayer solvent generates micro-pressure pulses, assisting in EVA peeling and shortening the swelling time from several hours to 10-30 minutes.

[0034] The following provides a detailed explanation of each step, such as... Figure 1 As shown: S1. Remove the aluminum frame and junction box from the discarded photovoltaic module, and cut the laminate into unit pieces; wherein the size of the unit piece is from 5cm×5cm to 20cm×20cm. The method for removing the aluminum frame and junction box is a conventional method in the field and is not particularly limited.

[0035] S2. Place the unit sheet in a reaction vessel, add waste lithium-ion battery electrolyte to immerse the unit sheet, apply microwave irradiation to soften and de-adhere the EVA film, thereby achieving the separation of the glass plate, fluorine-containing backsheet, crystalline silicon battery cell and solder ribbon.

[0036] The waste lithium-ion battery electrolyte is obtained from the dismantling of retired lithium-ion batteries and contains carbonate solvents and lithium hexafluorophosphate electrolyte. The carbonate solvents include one or more of ethylene carbonate (EC), dimethyl carbonate (EMC), and ethyl methyl carbonate (DMC). The carbonate solvents permeate and swell the EVA crosslinking network, weakening the interfacial adhesion strength. The lithium hexafluorophosphate electrolyte has strong ion loss and efficiently absorbs microwave energy in a microwave field, serving as a dedicated microwave absorbing medium.

[0037] The mass ratio of waste electrolyte to cell wafers should be 0.5-3:1. When the mass ratio is <0.5:1 (too little electrolyte), the cell wafers cannot be fully wetted, resulting in insufficient swelling and separation failure; furthermore, uneven microwave heating may cause localized hot spots that damage the cells. When the mass ratio is >3:1 (too much electrolyte), a large amount of electrolyte will absorb excessive microwave energy, reducing the effective power applied to the interface and prolonging the processing time; it also increases reagent waste and the load on subsequent vacuum distillation / membrane separation.

[0038] The microwave irradiation treatment temperature is 70-90℃, and the system temperature is controlled at 70~90℃ throughout the process, which is far lower than the pyrolysis temperature of EVA (>400℃) and the decomposition temperature of PVF / PVDF backsheet (>300℃). EVA only undergoes physical softening and loss of adhesion, without chemical cracking. Fluorine is stably fixed in the solid backsheet, and there is no release of toxic HF gas.

[0039] The power density of microwave irradiation is 200-800W, the microwave frequency is 2.45 GHz or 915 MHz, and the processing time is 10-30 minutes.

[0040] The microwave irradiation is carried out in three stages, with the irradiation time and power increasing sequentially in each stage. Specifically, the first stage has a microwave irradiation time of 2 minutes and a power of 200-400W; the second stage has a microwave irradiation time of 3-8 minutes and a power of 400-600W; and the third stage has a microwave irradiation time of 8-12 minutes and a power of 600-800W.

[0041] Segmented microwave irradiation can achieve the following effects: (1) By using segmented microwave irradiation, "thermal bursts" can be avoided, and the low temperature window can be accurately locked. The electrolyte (especially containing LiPF6) has a strong microwave absorption capacity. If high power (such as 600-800W) is used at the beginning, the system will heat up violently in a very short time, which can easily break through the target window of 70-90℃, leading to solvent boiling and increased risk of backsheet decomposition. Using low power to start (200-400W) and using a slow rise of 2 minutes, the heat can be fully conducted between the layers to achieve a smooth transition to the target temperature and prevent local overheating from the source. (2) Segmented microwave irradiation can match the physicochemical process of "wetting-swelling-peeling": EVA softening and de-adhesion is a gradual process. The first stage (low power): the main purpose is preheating and wetting, so that the electrolyte can fully wet and penetrate into the surface of EVA. The second stage (medium power): drives polar molecules to accelerate penetration, realizes EVA bulk swelling, and weakens the overall cross-linking network. The third stage (high power): The pressure pulse generated by the interlayer micro vaporization is used to complete the final embrittlement and physical peeling of the interface. (3) Segmented microwave irradiation can ensure the uniform treatment of large-area components. The photovoltaic module is large in size (up to 20cm×20cm). Gradient heating can ensure that the heat energy is uniformly transferred from the edge to the center and from the surface to the bottom layer (maximizing the advantages of bulk heating), avoiding the phenomenon of "over-peeling at the edge and no reaction at the center" caused by excessive energy input at the same time, and improving the consistency of batch processing. (4) Segmented microwave irradiation can reduce energy consumption and reagent volatilization. It only runs at full power in the peeling stage (third stage) where the most energy is needed, instead of high power throughout the process. With the help of an inert atmosphere, it can effectively reduce the vaporization loss of electrolyte and reduce the burden of subsequent condensation and recovery.

[0042] Furthermore, the microwave frequencies of 2.45 GHz and 915 MHz are internationally recognized dedicated bands for Industrial, Scientific, and Medical (ISM) applications. Using these frequencies avoids interference with critical operations such as radar and communications. Polar molecules (such as carbonate solvents) and ions (such as lithium hexafluorophosphate) in electrolytes can efficiently absorb microwave energy and convert it into heat at these frequencies. Non-polar materials such as glass and silicon wafers absorb almost no energy, enabling precise selective heating and preventing thermal damage at the source. The appropriate frequency can be chosen flexibly based on the processing scale. 2.45 GHz equipment is more widely available and suitable for small to medium scales; 915 MHz has stronger penetration and more uniform heating, making it more suitable for processing thicker or larger modules. The wavelengths of these two frequencies (approximately 12 cm for 2.45 GHz and approximately 33 cm for 915 MHz) are well-matched to the size of photovoltaic modules, enabling bulk heating, effectively avoiding localized overheating, and ensuring consistency in batch processing.

[0043] The microwave irradiation treatment is carried out under an inert atmosphere, which is nitrogen or argon gas, and does not react with the electrolyte or EVA. This atmosphere is used to suppress solvent evaporation and oxidation side reactions during the microwave treatment process.

[0044] S3. Remove the separated glass plate, fluorine-containing backplate, crystalline silicon solar cell, and solder ribbon respectively. The waste electrolyte obtained in step S3 is regenerated by vacuum distillation or membrane separation and recycled back to step S2. After separation, the electrolyte is regenerated by vacuum distillation / membrane separation to remove impurities and reused in the swelling process, realizing a closed-loop electrolyte cycle and significantly reducing reagent consumption.

[0045] The core of this method lies in utilizing waste lithium-ion battery electrolyte as both an absorbing medium and a swelling agent, combined with controllable microwave technology, to achieve rapid, low-temperature interlayer separation of photovoltaic modules. Its essence is a precise match between "controllable microwaves" and "electrolyte absorption," rather than a simple superposition of the two. The three main characteristics of microwaves are clearly reflected in the process: selective heating ensures energy is coupled only to the carbonate solvent and lithium salt in the electrolyte, achieving precise temperature rise at the reaction interface, while the glass plate and crystalline silicon wafer absorb almost no microwave energy, thus preventing thermal damage to the cells at the source; bulk heating ensures uniform heating of the electrolyte across the module layers, eliminating temperature gradients under traditional heat conduction methods and ensuring consistent swelling progress across large-area modules; and molecular-level reinforcement accelerates the penetration of polar molecules into the EVA molecular chains under the drive of an alternating electric field, reducing the time required for traditional swelling (several hours or even longer) to minutes. Simultaneously, the vaporization of solvent micro-regions at the interface generates pressure pulses, assisting in the peeling of the EVA adhesive layer and further improving separation efficiency.

[0046] In terms of process control, this method employs a controllable microwave heating strategy. By adjusting the power, time, and electrolyte dosage, the system temperature is stabilized within a low-temperature range of 70-90℃. This ensures the swelling rate while remaining well below the EVA pyrolysis temperature (>400℃) and the solvent boiling point. Programmed power control further suppresses temperature overshoot. Without control, continuous irradiation at a fixed power can easily cause the system to exceed its boiling point, leading to solvent loss and reaction instability. From a coupling effect perspective, without microwaves, the electrolyte swelling reaction kinetics are slow, require a long time, and have limited swelling depth, making large-scale application difficult. With the introduction of microwaves, the strong absorption characteristics of the electrolyte are fully activated. The three characteristics work synergistically—selective heating to avoid damage, bulk heating to ensure uniformity, and molecular-level enhancement to increase the rate—significantly improving processing efficiency, reducing energy consumption, and protecting the integrity of the solar cells. This coupling mechanism fundamentally solves the dual problems of high-temperature pyrolysis damaging solar cells and the high reagent consumption and cost of pure solvent methods in existing technologies.

[0047] Example 1 S1. Remove the aluminum frame and junction box of the discarded photovoltaic module, and cut the laminate into unit pieces; wherein the size of the unit piece is 5cm×5cm.

[0048] S2. Place the unit sheet in a reaction vessel, add waste lithium-ion battery electrolyte to immerse the unit sheet, apply microwave irradiation to soften and de-adhere the EVA film, thereby achieving the separation of the glass plate, fluorine-containing backsheet, crystalline silicon battery cell and solder ribbon.

[0049] The mass ratio of waste electrolyte to unit wafer was 0.5:1, the microwave irradiation treatment temperature was 70℃, the microwave frequency was 2.45 GHz, and the treatment time was 10 minutes.

[0050] The microwave irradiation is carried out in three stages, with the irradiation time and power increasing sequentially in each stage. Specifically, the first stage has a microwave irradiation time of 2 minutes and a power of 200W; the second stage has a microwave irradiation time of 3 minutes and a power of 200W; and the third stage has a microwave irradiation time of 8 minutes and a power of 600W.

[0051] The microwave irradiation treatment is carried out in an inert atmosphere, which is nitrogen.

[0052] S3. Remove the separated glass plate, fluorine-containing backplate, crystalline silicon solar cell and solder strip respectively.

[0053] Example 2 S1. Remove the aluminum frame and junction box of the discarded photovoltaic module, and cut the laminate into unit pieces; wherein the size of the unit piece is 15cm×15cm.

[0054] S2. Place the unit sheet in a reaction vessel, add waste lithium-ion battery electrolyte to immerse the unit sheet, apply microwave irradiation to soften and de-adhere the EVA film, thereby achieving the separation of the glass plate, fluorine-containing backsheet, crystalline silicon battery cell and solder ribbon.

[0055] The mass ratio of waste electrolyte to unit cell is 2:1. The microwave irradiation treatment was carried out at a temperature of 80℃, a microwave frequency of 915 MHz, and a treatment time of 20 minutes.

[0056] The microwave irradiation is carried out in three stages, with the irradiation time and power increasing sequentially in each stage. Specifically, the first stage has a microwave irradiation time of 2 minutes and a power of 300W; the second stage has a microwave irradiation time of 5 minutes and a power of 500W; and the third stage has a microwave irradiation time of 10 minutes and a power of 700W.

[0057] The microwave irradiation treatment is carried out in an inert atmosphere, which is argon.

[0058] S3. Remove the separated glass plate, fluorine-containing backplate, crystalline silicon solar cell and solder strip respectively.

[0059] Example 3 S1. Remove the aluminum frame and junction box of the discarded photovoltaic module, and cut the laminate into unit pieces; wherein the size of the unit piece is 15cm×15cm.

[0060] S2. Place the unit sheet in a reaction vessel, add waste lithium-ion battery electrolyte to immerse the unit sheet, apply microwave irradiation to soften and de-adhere the EVA film, thereby achieving the separation of the glass plate, fluorine-containing backsheet, crystalline silicon battery cell and solder ribbon.

[0061] The mass ratio of waste electrolyte to unit cell is 3:1. The microwave irradiation treatment was carried out at a temperature of 90℃, a microwave frequency of 915 MHz, and a treatment time of 30 minutes.

[0062] The microwave irradiation is carried out in three stages, with the irradiation time and power increasing sequentially in each stage. Specifically, the first stage has a microwave irradiation time of 2 minutes and a power of 400W; the second stage has a microwave irradiation time of 8 minutes and a power of 600W; and the third stage has a microwave irradiation time of 12 minutes and a power of 800W.

[0063] The microwave irradiation treatment is carried out in an inert atmosphere, which is argon.

[0064] S3. Remove the separated glass plate, fluorine-containing backplate, crystalline silicon solar cell and solder strip respectively.

[0065] Comparative Example 1 The difference from Example 1 is that DMF organic solvent is used.

[0066] Comparative Example 2 The difference from Example 1 is that microwave irradiation is not used; instead, conventional heating methods, such as electric heating, are employed.

[0067] Comparative Example 3 The difference from Example 2 is that the microwave irradiation process is not carried out in stages, and the entire process uses 400W microwave irradiation.

[0068] Comparative Example 4 The difference from Example 2 is that the microwave irradiation temperature is 50°C.

[0069] Comparative Example 5 The difference from Example 3 is that the microwave irradiation temperature is 200°C.

[0070] Comparative Example 6 The difference from Example 3 is that the electrolyte is a pure carbonate solution and does not contain LiPF6.

[0071] The process properties of the components separated in Examples 1-3 and Comparative Examples 1-6 were analyzed, as shown in Table 1.

[0072] Table 1. Process properties of each component separated in the examples and comparative examples.

[0073] As shown in Table 1, Examples 1-3, using waste lithium-ion battery electrolyte in combination with staged microwave irradiation, and treated at a low temperature of 70-90℃, showed that the chemical composition of the recovered glass plate, fluorine-containing backplate, crystalline silicon solar cell, and solder ribbon remained unchanged, the crystal structure was intact and without distortion, and the physical morphology was intact and without breakage, with a silicon wafer integrity rate of 95%-99%. In contrast, Comparative Example 1, using DMF organic solvent instead of waste electrolyte, suffered from low microwave absorption efficiency and poor swelling uniformity due to the lack of strong ion loss from lithium salt, resulting in a silicon wafer integrity rate of only 78%. Comparative Example 2, using conventional electric heating instead of microwave irradiation, experienced uneven heating and localized problems due to the temperature gradient and heating blind zone in heat conduction. Oxidation resulted in a silicon wafer integrity rate of only 72%; Comparative Example 3 used constant power 400W microwave irradiation without phased heating, and the high initial energy input caused thermal shock, leading to localized microcracks in the silicon wafer, resulting in an integrity rate of 82%; Comparative Example 4 controlled the temperature at 50℃, which was below the effective softening temperature of EVA, resulting in insufficient swelling and separation failure; Comparative Example 5 raised the temperature to 200℃, and the thermal decomposition of EVA produced coke contamination on the silicon wafer surface, and thermal stress caused severe fragmentation, resulting in an integrity rate that plummeted to 35%; Comparative Example 6 used pure carbonate solvent without LiPF6, and the lack of microwave absorbing medium resulted in extremely low microwave heating efficiency and insufficient softening of EVA, with a silicon wafer integrity rate of only 52% after forced peeling. The above comparisons fully demonstrate that the present invention, through the synergistic combination of waste electrolyte (which has both swelling and microwave absorption functions) and phased controllable microwave irradiation, can achieve selective softening and deadhesion of EVA under low-temperature conditions. The resulting components are of excellent quality, and the silicon wafer integrity rate is significantly better than that of the comparative examples, verifying the significant progress and industrial applicability of the technical solution of the present invention.

[0074] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte, characterized in that, Includes the following steps: S1. Remove the aluminum frame and junction box of the discarded photovoltaic module and cut the laminate into unit pieces; S2. Place the unit sheet in a reaction vessel, add waste lithium-ion battery electrolyte to immerse the unit sheet, apply microwave irradiation to soften and de-adhere the EVA film, thereby achieving the separation of the glass plate, fluorine-containing backsheet, crystalline silicon battery cell and solder ribbon; wherein, the waste lithium-ion battery electrolyte is the waste electrolyte obtained from the dismantling of retired lithium-ion batteries, containing carbonate solvents and lithium hexafluorophosphate electrolyte; S3. Remove the separated glass plate, fluorine-containing backplate, crystalline silicon solar cell and solder strip respectively.

2. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 1, characterized in that, The microwave irradiation treatment is carried out at a temperature of 70-90℃, with a power of 200-800W, a microwave frequency of 2.45 GHz or 915 MHz, and a treatment time of 10-30 minutes.

3. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 1, characterized in that, The mass ratio of the waste electrolyte to the unit cell is 0.5-3:

1.

4. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 1, characterized in that, The microwave irradiation treatment is carried out in an inert atmosphere, which is either nitrogen or argon.

5. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 1, characterized in that, The carbonate solvents in the waste lithium-ion battery electrolyte include one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

6. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 1, characterized in that, The size of the unit piece ranges from 5cm×5cm to 20cm×20cm.

7. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 1, characterized in that, The microwave irradiation is carried out in three stages, with the irradiation time and power increasing sequentially in each stage.

8. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 7, characterized in that, The first stage of microwave irradiation lasts for 2 minutes with a power of 200-400W; the second stage lasts for 3-8 minutes with a power of 400-600W; and the third stage lasts for 8-12 minutes with a power of 600-800W.

9. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 1, characterized in that, The waste electrolyte obtained in step S3 is regenerated by vacuum distillation or membrane separation and recycled back to step S2 for use.

10. The method for low-temperature recovery and separation of waste photovoltaic modules based on waste lithium-ion battery electrolyte as described in claim 1, characterized in that, The selective heating of the microwave irradiation acts only on the polar components in the electrolyte; the bulk heating penetrates the entire unit sheet, so that the electrolyte between the layers is heated synchronously and uniformly; the molecular-level reinforcement enables polar molecules to penetrate into the EVA molecular chains more quickly under the drive of the alternating electric field.

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