Separation and recovery method of waste aluminum back surface field battery piece

Abstract

The invention relates to a method for separating and recycling a waste aluminum back surface field battery piece, which comprises the following steps of: soaking the waste aluminum back surface field battery piece in a hydrochloric acid solution and a nitric acid solution in sequence, and separating and recycling metal on the waste aluminum back surface field battery piece; soaking the waste aluminum back surface field battery piece subjected to metal separation and recovery in a hydrofluoric acid solution to obtain a battery piece subjected to preliminary silicon nitride removal; and soaking the battery piece of which the silicon nitride is preliminarily removed in a sodium hydroxide solution, and removing residual silicon nitride and phosphorus elementary substance to obtain a purified silicon wafer. According to the separation and recovery method provided by the invention, the purified silicon wafer can be obtained, and the separation and recovery effect on the waste silicon battery piece is greatly improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic waste recycling technology, and in particular to a method for separating and recycling waste aluminum back-field solar cells. Background Technology

[0002] Against the backdrop of global dual-carbon goals, the energy sector will play a crucial role. Among them, the photovoltaic industry is a key battleground for achieving carbon neutrality in the energy sector. Early-installed photovoltaic modules, after completing their 25-year service life, still possess significant economic value due to the high economic value of their main materials (such as aluminum frames, glass, and solar cells), allowing for resource recycling to achieve a green closed loop. Aluminum back surface field (Al-BSF) solar cells are one of the earliest industrialized crystalline silicon cell structures. Many of these products have reached their end-of-life, necessitating the development of a separation and recycling process that enables a resource-based green closed loop. However, current separation and recycling methods are not ideal, often resulting in impurities remaining on the recovered silicon wafers. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for separating and recycling waste aluminum back surface area solar cells, which can improve the purity of silicon wafers obtained from the separation and recycling of waste aluminum back surface area solar cells.

[0004] This application provides a method for separating and recycling waste aluminum back-side battery cells, comprising the following steps:

[0005] Waste aluminum back-side surface-coupled battery cells are sequentially immersed in hydrochloric acid solution and nitric acid solution to separate and recover the metals on the waste aluminum back-side surface-coupled battery cells;

[0006] The waste aluminum back-side battery cells after metal separation and recovery are immersed in hydrofluoric acid solution to obtain battery cells with preliminary removal of silicon nitride.

[0007] The preliminarily silicon nitride-removed battery cell is immersed in a sodium hydroxide solution to remove residual silicon nitride and elemental phosphorus, resulting in a purified silicon wafer.

[0008] In some embodiments, the metal includes aluminum and silver, and the step of separating and recovering the metal from the waste aluminum back-side surface-mount solar cells by sequentially immersing them in hydrochloric acid solution and nitric acid solution includes:

[0009] Waste aluminum back-side battery cells are immersed in hydrochloric acid solution to obtain aluminum chloride solution and battery cells after aluminum separation.

[0010] The aluminum-separated battery cells are immersed in a nitric acid solution to obtain a silver nitrate solution and silver-separated battery cells.

[0011] In some embodiments, the following steps are also included:

[0012] The aluminum chloride solution is evaporated to obtain solid aluminum oxide, which is then recovered.

[0013] In some embodiments, the following steps are also included:

[0014] Sodium chloride solution was added to the silver nitrate solution to precipitate silver chloride solid, which was then recovered.

[0015] In some embodiments, after immersing the preliminarily silicon nitride-removed battery cell in a sodium hydroxide solution to remove residual silicon nitride and elemental phosphorus, a sodium silicate solution is obtained. The treatment steps for the sodium silicate solution include:

[0016] Carbon dioxide gas is first introduced into the sodium silicate solution to produce a colloidal precipitate, and then calcium chloride solution is added for further precipitation.

[0017] Add flocculant to the obtained precipitate to flocculate.

[0018] In some embodiments, after the step of adding a flocculant to the resulting precipitate for flocculation, a sodium chloride solution is also obtained, which is used to react with the silver nitrate solution to obtain solid silver chloride.

[0019] In some embodiments, the hydrochloric acid solution contains 10% to 30% hydrochloric acid by mass.

[0020] In some embodiments, the nitric acid solution contains 20% to 30% by mass of nitric acid.

[0021] In some embodiments, the hydrofluoric acid solution contains 5% to 30% hydrofluoric acid by mass.

[0022] In some embodiments, the sodium hydroxide solution contains 5% to 20% sodium hydroxide by mass.

[0023] This application provides a method for separating and recycling waste aluminum back-side surface-emitting diode (BSSN) solar cells. First, the waste BSSN solar cells are immersed in hydrochloric acid and nitric acid solutions to separate and recover high-value metals. Then, the metal-separated waste BSSN solar cells are sequentially immersed in hydrofluoric acid and sodium hydroxide solutions to deeply remove silicon nitride from the antireflective coating layer and simultaneously remove elemental phosphorus from the phosphorus diffusion layer to obtain purified silicon wafers. This method can significantly improve the separation and recycling efficiency of waste aluminum back-side surface-emitting diode (BSSN) solar cells. Attached Figure Description

[0024] Figure 1This is a schematic diagram of the structure of waste aluminum back surface field solar cells in some embodiments.

[0025] Figure 2 This is a process flow diagram for separating and recycling waste aluminum back surface area solar cells in some embodiments.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1: Silicon wafer; 2: Back antireflection coating; 3: Aluminum back field; 4: Back electrode; 5: Phosphorus diffusion layer; 6: Front antireflection coating; 7: Front electrode. Detailed Implementation

[0028] To facilitate understanding of this application, a more comprehensive description of the application will be provided below with reference to embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0029] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] In this application, terms such as "preferred," "better," "more suitable," and "ideal" are used only to describe implementation methods or embodiments with better effects, and should be understood not to limit the scope of protection of this application.

[0032] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0033] In this application, the terms "optionally," "optionally," and "optional" refer to options that are optional, meaning they are selected from either "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent.

[0034] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0035] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0036] like Figure 1 As shown, the structure of a waste aluminum back-side surface-mount solar cell includes:

[0037] Silicon wafer 1, silicon wafer 1 has a back side and a front side disposed opposite to each other;

[0038] On the back side of silicon wafer 1, a back antireflection film layer 2, an aluminum back field 3 and a back electrode 4 are sequentially disposed in a direction that gradually moves away from silicon wafer 1.

[0039] On the front side of silicon wafer 1, a phosphorus diffusion layer 5, a front antireflection film layer 6, and a front electrode 7 are sequentially disposed in a direction that gradually moves away from silicon wafer 1.

[0040] Among them, the silicon wafer 1 is made of monocrystalline silicon or polycrystalline silicon, the back antireflection film layer 2 and the front antireflection film layer 6 are made of silicon nitride, the aluminum back field 3 is made of aluminum, the back electrode 4 and the front electrode 7 are made of silver, and the phosphorus diffusion layer 5 is made of elemental phosphorus.

[0041] Understandably, aluminum, silver, and silicon wafers in waste aluminum back-side solar cells are solid waste resources with recycling value, making it essential to find a process that can efficiently recycle these resources.

[0042] like Figure 2 As shown, this application provides a method for separating and recycling waste aluminum back-side battery cells, including the following steps S1 to S3.

[0043] Step S1: Immerse the waste aluminum back surface area solar cells in hydrochloric acid solution and nitric acid solution in sequence to separate and recover the metals on the waste aluminum back surface area solar cells.

[0044] Step S2: Immerse the waste aluminum back surface solar cells after metal separation and recycling in a hydrofluoric acid solution to obtain solar cells with preliminary removal of silicon nitride.

[0045] Step S3: Immerse the preliminarily silicon nitride-free solar cell in sodium hydroxide solution to remove residual silicon nitride and elemental phosphorus, and obtain purified silicon wafer.

[0046] This application provides a method for separating and recycling waste aluminum back-side surface-mount solar cells. First, the waste aluminum back-side surface-mount solar cells are immersed in hydrochloric acid and nitric acid solutions to separate and recover high-value metals. Then, the metal-recovered waste aluminum back-side surface-mount solar cells are sequentially immersed in hydrofluoric acid and sodium hydroxide solutions to deeply remove silicon nitride from the antireflective coating layer. Simultaneously, elemental phosphorus is removed from the phosphorus diffusion layer to obtain purified silicon wafers. This method can significantly improve the purity of silicon wafers separated and recovered from waste aluminum back-side surface-mount solar cells.

[0047] Specifically:

[0048] Step S1: Immerse the waste aluminum back surface area solar cells in hydrochloric acid solution and nitric acid solution in sequence to separate and recover the metals on the waste aluminum back surface area solar cells.

[0049] In some embodiments, the metals include aluminum and silver. Step S1 involves immersing the waste aluminum back surface area solar cells in hydrochloric acid solution and nitric acid solution in sequence to separate and recover the metals from the waste aluminum back surface area solar cells. The steps include the following steps S11 and S12.

[0050] Step S11: Immerse the waste aluminum back surface cell in hydrochloric acid solution to obtain aluminum chloride solution and the cell after aluminum separation.

[0051] Step S12: Immerse the aluminum-separated battery cells in nitric acid solution to obtain silver nitrate solution and silver-separated battery cells.

[0052] Understandably, the aluminum comes from the aluminum back surface of the solar cell, while the silver comes from the back electrode and the front electrode.

[0053] Furthermore, step S11 also includes the following step S111.

[0054] Step S111: Evaporate the aluminum chloride solution to obtain solid aluminum oxide and recover it.

[0055] The reaction equation is as follows:

[0056]

[0057] Understandably, the process may also include steps for recovering and treating gases such as H2 and HCl generated during step S11.

[0058] Furthermore, step S12 also includes the following step S112.

[0059] Step S112: Add sodium chloride solution to silver nitrate solution to precipitate silver chloride solid and recover it.

[0060] The reaction equation is as follows:

[0061]

[0062] Preferably, the hydrochloric acid solution contains 10% to 30% hydrochloric acid by mass. Understandably, the mass percentage of hydrochloric acid may be, for example, but not limited to, 10%, 20%, 30%, etc.

[0063] Preferably, the ratio of the mass of the waste aluminum back surface area solar cell to the volume of the hydrochloric acid solution is 250g:1L to 750g:1L.

[0064] Preferably, the soaking time of the waste aluminum back surface area solar cells in hydrochloric acid solution is 10 min to 30 min. Understandably, the soaking time can be, for example, but is not limited to, 10 min, 20 min, 30 min, etc.

[0065] Preferably, the mass percentage of nitric acid in the nitric acid solution is 20% to 30%. Understandably, the mass percentage of nitric acid may be, for example, but not limited to, 20%, 25%, 30%, etc.

[0066] Preferably, the ratio of the mass of the battery cell after aluminum separation to the volume of the nitric acid solution is 400g:1L to 800g:1L.

[0067] Preferably, the soaking time of the battery cells after aluminum separation in nitric acid solution is 10 min to 30 min. Understandably, the soaking time can be, for example, but is not limited to, 10 min, 20 min, 30 min, etc.

[0068] Preferably, the sodium chloride solution contains 1% to 5% by mass. Understandably, the mass percentage of sodium chloride can be, for example, but not limited to, 1%, 2%, 3%, 4%, 5%, etc.

[0069] Preferably, the volume ratio of silver nitrate solution to sodium chloride solution is 1L:2L to 1L:3L.

[0070] Preferably, the precipitation time for adding sodium chloride solution to silver nitrate solution is 4 to 5 hours. Understandably, the precipitation time can be, but is not limited to, 4 hours, 4.5 hours, 5 hours, etc.

[0071] Understandably, the process may also include steps for recovering and treating gases such as NO2 generated during step S12.

[0072] Step S2: Immerse the waste aluminum back surface solar cells after metal separation and recycling in a hydrofluoric acid solution to obtain solar cells with preliminary removal of silicon nitride.

[0073] The reaction equation is as follows:

[0074]

[0075] Preferably, the hydrofluoric acid solution contains 5% to 30% by mass. Understandably, the mass percentage of hydrofluoric acid may be, for example, but not limited to, 5%, 10%, 15%, 20%, 25%, 30%, etc.

[0076] Preferably, the ratio of the mass of the waste aluminum back-side battery cells after metal separation and recovery to the volume of the hydrofluoric acid solution is 40g:1L to 160g:1L.

[0077] Preferably, the immersion time of the waste aluminum back-side battery cells after metal separation and recovery in hydrofluoric acid solution is 10 min to 25 min. Understandably, the immersion time can be, for example, but is not limited to, 10 min, 15 min, 20 min, 25 min, etc.

[0078] In some embodiments, after immersing the waste aluminum back-side battery cells after separating and recycling the metals in a hydrofluoric acid solution, step S2 further includes the following step S21.

[0079] Step S21: Treat the silicon tetrafluoride gas and ammonia gas generated from the reaction of silicon nitride and hydrofluoric acid as exhaust gases. Exhaust gas treatment prevents the silicon tetrafluoride gas and ammonia gas from being directly released into the atmosphere, which is more environmentally friendly.

[0080] Step S3: Immerse the preliminarily silicon nitride-free solar cell in sodium hydroxide solution to remove residual silicon nitride and elemental phosphorus, and obtain purified silicon wafer.

[0081] The reaction equation between silicon nitride and sodium hydroxide is as follows:

[0082]

[0083] Furthermore, the phosphorus elemental doping in the phosphorus diffusion layer is distributed on the front side of the silicon wafer. During the process of immersing the solar cell in a sodium hydroxide solution, the sodium hydroxide reacts with the surface of the silicon wafer, causing the phosphorus elemental doping in the silicon wafer to fall off with the corrosion reaction, thereby removing the phosphorus in the phosphorus diffusion layer.

[0084] Preferably, the sodium hydroxide solution contains 5% to 20% sodium hydroxide by mass. Understandably, the mass percentage of sodium hydroxide may be, for example, but not limited to, 5%, 10%, 15%, 20%, etc.

[0085] Preferably, the ratio of the mass of the battery cell after initial removal of silicon nitride to the volume of the sodium hydroxide solution is 80g:1L to 320g:1L.

[0086] Preferably, the soaking time of the battery cell after initial removal of silicon nitride in sodium hydroxide solution is 5 min to 20 min. Understandably, the soaking time may be, for example, but is not limited to, 5 min, 10 min, 15 min, 20 min, etc.

[0087] Understandably, the process may also include steps for recovering and treating the NH3 generated during step S3.

[0088] In some embodiments, step S3 involves immersing the preliminarily silicon nitride-removed battery cell in a sodium hydroxide solution to remove residual silicon nitride and elemental phosphorus, thereby obtaining a sodium silicate solution. The treatment steps for the sodium silicate solution include step S31.

[0089] Step S31: First, carbon dioxide gas is introduced into the sodium silicate solution to produce a colloidal precipitate. Then, calcium chloride solution is added to produce a large amount of precipitate. Finally, flocculant is added to flocculate the precipitate.

[0090] Furthermore, after adding flocculant in step S31 for flocculation, a sodium chloride solution is obtained. The sodium chloride solution can be used to react with the silver nitrate solution in step S12 to obtain solid silver chloride.

[0091] The reaction equation is as follows:

[0092]

[0093] Understandably, before the sodium chloride obtained in step S31 is used to react with the silver nitrate solution in step S12, the mass percentage of the sodium chloride obtained in step S31 needs to be adjusted to be the same as the mass percentage of the sodium chloride in step S12 before it can be used to react with the silver nitrate solution.

[0094] Understandably, during the flocculation process of adding flocculant in step S31, the detached elemental phosphorus is also removed by flocculation, which is beneficial to further improve the purity of silicon wafers.

[0095] In some embodiments of this application, a method of first soaking in hydrogen fluoride and then soaking in sodium hydroxide can deeply remove silicon nitride and elemental phosphorus from waste aluminum back-side surface-mount solar cells, resulting in purer silicon wafers. Furthermore, the acid-base waste liquid, such as sodium silicate, obtained after the sodium hydroxide soaking reaction is treated by flocculation, which can greatly reduce the pollution and harm to the environment. Simultaneously, the sodium chloride produced from the waste liquid treatment can be reused to react with silver nitrate solution to recover silver from the waste aluminum back-side surface-mount solar cells, achieving waste liquid recycling, reducing resource waste, and realizing a green closed loop.

[0096] Preferably, the calcium chloride solution contains 5% to 30% by mass. Understandably, the mass percentage of calcium chloride can be, for example, but not limited to, 5%, 10%, 15%, 20%, 25%, or 30%.

[0097] Preferably, the volume ratio of sodium silicate solution to calcium chloride solution is 1L:2L to 1L:3L.

[0098] Preferably, the flocculant is an inorganic polymeric flocculant. Optionally, the inorganic polymeric flocculant may include, but is not limited to, polyaluminum chloride (PAC), polyaluminum sulfate (PAS), polyferric chloride (PFC), and polyferric sulfate (PFS).

[0099] Preferably, the flocculation time is 1h to 6h. Understandably, the flocculation time can be, for example, but not limited to, 1h, 2h, 3h, 4h, 5h, 6h, etc.

[0100] This application employs an acid solution to separate and recover metals from waste silicon solar cells, followed by a two-step method to deeply remove silicon nitride from the antireflection layer and elemental phosphorus from the phosphorus diffusion layer, thereby obtaining purified silicon wafers. Furthermore, in some embodiments of this application, the waste liquid and waste gas generated in each step are further treated to reduce their environmental pollution and to obtain solid materials such as alumina and silver chloride with high reuse value. At the same time, the sodium chloride solution obtained after waste liquid treatment can be used as a recycled salt solution, which can be used as an additive for extracting silver chloride solid from silver nitrate solution in step S21. This effectively reduces the cost of chemical reagents and fully realizes the high-value reuse of resources.

[0101] The following are specific examples.

[0102] Example 1

[0103] Step 1: Immerse 100g of waste aluminum back surface solar cells in 0.4L of 10% hydrochloric acid solution at room temperature for 30 minutes to obtain aluminum chloride solution and solar cells after aluminum separation. Evaporate and purify the aluminum chloride solution to obtain solid aluminum oxide.

[0104] Step 2: Immerse 94.5g of the aluminum-separated battery cell in 0.2L of 20% nitric acid solution at room temperature for 30min to obtain silver nitrate solution and the silver-separated battery cell. Add 0.4L of 1% sodium chloride solution to the silver nitrate solution to precipitate the silver. After standing for 4.5h, centrifuge and filter to collect the filter residue to obtain solid silver chloride and recover it.

[0105] Step 3: Immerse 92.7g of the silver-separated solar cell in 2.3L of 5% hydrofluoric acid solution at room temperature for 25 minutes to obtain a solar cell with preliminary silicon nitride removal. Collect and treat the volatile gases such as silicon tetrafluoride and ammonia generated by the reaction of silicon nitride and hydrofluoric acid.

[0106] Step 4: Immerse 87.7g of the preliminarily de-siliconized solar cell in 1L of 5% sodium hydroxide solution at room temperature for 20 minutes. This allows the residual silicon nitride on the surface of the solar cell to react fully with the alkaline solution, thereby removing the residual silicon nitride and also removing elemental phosphorus from the phosphorus diffusion layer to obtain purified silicon wafers and sodium silicate solution.

[0107] Excess carbon dioxide gas is first introduced into the sodium silicate solution obtained after the reaction. Once a colloidal precipitate (silicic acid) forms, 2 L of a 5% (w / w) calcium chloride solution is added, resulting in a large amount of precipitate (calcium carbonate). Then, an appropriate amount of polyaluminum chloride (PAC) flocculant is added for flocculation. After standing for 3 hours, the mixture is centrifuged and filtered to obtain the flocculated precipitate and sodium chloride solution. The sodium chloride solution is adjusted to 1% (w / w) and can then be reused in step 2 to react with silver nitrate solution.

[0108] Example 2

[0109] Similar to Example 1, except that the type of reagent, mass percentage, or soaking time used are different.

[0110] Step 1: Immerse 150g of waste aluminum back surface solar cells in 0.6L of 20% hydrochloric acid solution at room temperature for 20 minutes to obtain aluminum chloride solution and solar cells after aluminum separation. Evaporate and purify the aluminum chloride solution to obtain solid aluminum oxide.

[0111] Step 2: Immerse 139.1g of the aluminum-separated battery cell in 0.3L of 25% nitric acid solution at room temperature for 20min to obtain silver nitrate solution and the silver-separated battery cell. Add 0.6L of 3% sodium chloride solution to the silver nitrate solution to precipitate the silver. After standing for 4.5h, centrifuge and filter to collect the filter residue to obtain solid silver chloride and recover it.

[0112] Step 3: Immerse 135.5g of the silver-separated battery cell in 3.3L of 10% hydrofluoric acid solution at room temperature for 20 minutes to obtain a battery cell with preliminary silicon nitride removal. Collect and treat the volatile gases such as silicon tetrafluoride and ammonia generated by the reaction of silicon nitride and hydrofluoric acid.

[0113] Step 4: Immerse 125.5g of the preliminarily desiliconized solar cell in 1.5L of 12% sodium hydroxide solution at room temperature for 15 minutes. This allows the residual silicon nitride on the surface of the solar cell to react fully with the alkaline solution, thereby removing the residual silicon nitride and also removing elemental phosphorus from the phosphorus diffusion layer to obtain purified silicon wafers and sodium silicate solution.

[0114] Excess carbon dioxide gas is first introduced into the sodium silicate solution obtained after the reaction. Once a colloidal precipitate (silicic acid) forms, 3 L of a 15% calcium chloride solution is added, resulting in a large amount of precipitate (calcium carbonate). Then, an appropriate amount of polyaluminum sulfate (PAS) is added for flocculation. After standing for 3 hours, the mixture is centrifuged and filtered to obtain the flocculated precipitate and sodium chloride solution. The sodium chloride solution is adjusted to 3% by mass and can then be reused in step 2 to react with the silver nitrate solution.

[0115] Comparative Example 1

[0116] It is largely the same as Example 2, except that step 4 is omitted and the soaking time in step 3 is extended.

[0117] Step 1: Immerse 150g of waste aluminum back surface solar cells in 0.6L of 20% hydrochloric acid solution at room temperature for 20 minutes to obtain aluminum chloride solution and solar cells after aluminum separation. Evaporate and purify the aluminum chloride solution to obtain solid aluminum oxide.

[0118] Step 2: Immerse 139.1g of the aluminum-separated battery cell in 0.3L of 25% nitric acid solution at room temperature for 20min to obtain silver nitrate solution and the silver-separated battery cell. Add 0.6L of 3% sodium chloride solution to the silver nitrate solution to precipitate the silver. After standing for 4.5h, centrifuge and filter to collect the filter residue to obtain solid silver chloride.

[0119] Step 3: Immerse 135.5g of the silver-separated battery cell in 3.3L of 10% hydrofluoric acid solution at room temperature for 40 minutes to obtain a battery cell with silicon nitride removed. Collect and treat the volatile gases such as silicon tetrafluoride and ammonia generated by the reaction of silicon nitride and hydrofluoric acid.

[0120] The silicon wafers obtained after separation and recovery in Examples 1, 2, and Comparative Example 1 were subjected to elemental analysis by ICP-MS, and the purity of the silicon wafers (i.e., the mass percentage of silicon in the recovered silicon wafers) was calculated using the formula: Silicon wafer purity (%) = Mass of pure silicon / Total mass of recovered silicon wafers × 100%. The test results showed that the purity of the silicon wafers in Examples 1, 2, and Comparative Example 1 were 99.6%, 99.8%, and 94.1%, respectively. This demonstrates that the methods of Examples 1 and 2 can effectively remove other impurities, especially silicon nitride, from the silicon wafers, resulting in silicon wafers with higher purity. Comparative Example 1, because it did not use sodium hydroxide for further deep removal of silicon nitride, still contained a significant amount of impurities even after prolonged immersion in hydrogen fluoride.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for separating and recycling waste aluminum back-side battery cells, characterized in that, Includes the following steps: Waste aluminum back-side surface-mount solar cells are sequentially immersed in hydrochloric acid solution and nitric acid solution to separate and recover the metals from the waste aluminum back-side surface-mount solar cells; The waste aluminum back-side battery cells after metal separation and recovery are immersed in hydrofluoric acid solution to obtain battery cells with preliminary removal of silicon nitride. The preliminarily silicon nitride-removed battery cell is immersed in a sodium hydroxide solution to remove residual silicon nitride and elemental phosphorus, resulting in a purified silicon wafer.

2. The method for separating and recycling waste aluminum back-side battery cells according to claim 1, characterized in that, The metals include aluminum and silver. The steps of separating and recovering the metals from the waste aluminum back-side surface-mount solar cells by sequentially immersing them in hydrochloric acid solution and nitric acid solution include: Waste aluminum back-side battery cells are immersed in hydrochloric acid solution to obtain aluminum chloride solution and battery cells after aluminum separation. The aluminum-separated battery cells are immersed in a nitric acid solution to obtain a silver nitrate solution and silver-separated battery cells.

3. The method for separating and recycling waste aluminum back-side battery cells according to claim 2, characterized in that, It also includes the following steps: The aluminum chloride solution is evaporated to obtain solid aluminum oxide, which is then recovered.

4. The method for separating and recycling waste aluminum back-side battery cells according to claim 2, characterized in that, It also includes the following steps: Sodium chloride solution was added to the silver nitrate solution to precipitate silver chloride solid, which was then recovered.

5. The method for separating and recycling waste aluminum back-side battery cells according to claim 2, characterized in that, After immersing the preliminarily silicon nitride-removed battery cell in a sodium hydroxide solution to remove residual silicon nitride and elemental phosphorus, a sodium silicate solution is obtained. The treatment steps for the sodium silicate solution include: Carbon dioxide gas is introduced into the sodium silicate solution to produce a colloidal precipitate, and then calcium chloride solution is added for further precipitation. Add flocculant to the obtained precipitate to flocculate.

6. The method for separating and recycling waste aluminum back-side battery cells according to claim 5, characterized in that, After the step of adding a flocculant to the obtained precipitate for flocculation, a sodium chloride solution is also obtained, which is used to react with the silver nitrate solution to obtain solid silver chloride.

7. The method for separating and recycling waste aluminum back-side battery cells according to any one of claims 1 to 6, characterized in that, The hydrochloric acid solution contains 10% to 30% hydrochloric acid by mass.

8. The method for separating and recycling waste aluminum back-side battery cells according to any one of claims 1 to 6, characterized in that, The nitric acid solution contains 20% to 30% nitric acid by mass.

9. The method for separating and recycling waste aluminum back-side battery cells according to any one of claims 1 to 6, characterized in that, The hydrofluoric acid solution contains 5% to 30% hydrofluoric acid by mass.

10. The method for separating and recycling waste aluminum back-side battery cells according to any one of claims 1 to 6, characterized in that, The sodium hydroxide solution contains 5% to 20% sodium hydroxide by mass.

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