An ion exchanger, its preparation method and application

Abstract

The present invention relates to an ion exchanger and a preparation method thereof. The raw materials for preparing the ion exchanger include a carrier, a functional group modifier, and a solvent; based on 1 mL of the volume of the functional group modifier, the mass of the carrier is 0.06 - 0.25 g; the volume ratio of the functional group modifier to the solvent is 1:(0.6 - 1.5); in the ion exchanger, the functional group modifier is fixed on the carrier. The ion exchanger of the present invention does not introduce new metal ion contamination, can achieve lower metal ion residues in the solution, reduce surface recombination, and thus improve the conversion efficiency of the battery chip. The ion exchanger can also be reused by desorption means to reduce costs.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an ion exchanger, a preparation method thereof, and an application thereof. Background Art

[0002] Solar energy is a clean and renewable energy source, and solar cells based on the photovoltaic effect have broad application prospects. The cleaning process plays an important role in the production of high-efficiency batteries and low-cost solar cells. Among them, post-acid cleaning often uses a mixed acid of hydrofluoric acid (HF) + hydrochloric acid (HCl). HCl in post-acid cleaning forms a complex with metal ions in the solution, reducing the residual metal ions on the silicon wafer surface, and then reducing the recombination of silicon wafer traps (RSH), thereby achieving an increase in conversion efficiency. Reducing the content of solution metal ions is a current trend in the photovoltaic industry.

[0003] CN107154449A discloses a process method for reducing the leakage of polycrystalline battery wafers. A step of tank cleaning is added to the existing process. After the silicon wafer is subjected to tank cleaning, the metal ions and organic contaminants on the silicon wafer surface are further cleaned, the leakage inside the silicon wafer is reduced, the yield is increased, and the conversion efficiency of the battery wafer is further improved. The cleaning solution in the disclosed tank cleaning includes hydrofluoric acid and hydrochloric acid.

[0004] CN107469796A discloses a method for preparing a core-shell magnetic composite resin microsphere adsorbent by modifying phenolic resin with lignin under acidic conditions. The disclosed method includes the following steps: First, prepare magnetic iron tetroxide particles and lignin phenolic resin, mix the iron tetroxide and lignin phenol evenly according to a certain ratio, add a certain amount of reverse solvent and surfactant, and stir well. Then add p-toluenesulfonic acid solution, and carry out acid curing at a certain temperature and stirring speed to form magnetic microspheres. The disclosed method uses a weak organic acid as an acid curing agent, creatively adopts an acid method for low-temperature curing, and prepares composite microspheres with uniform size by the reverse phase suspension method. The microspheres have the adsorption characteristics of magnetism and lignin, can be used as adsorbents to adsorb colored substances and heavy metal ions in wastewater, and can quickly separate water and microspheres by using an external magnet, providing a convenient and rapid separation method for wastewater treatment.

[0005] However, most of the EL-grade HCl currently used in photovoltaics comes from the chlor-alkali process, and its own metal ion concentration is high. Using EL-grade hydrochloric acid in post-acid cleaning will reintroduce metal ion pollution, resulting in an increase in silicon wafer trap recombination, thereby affecting the efficiency of battery wafers.

[0006] Therefore, it is particularly important to develop new products to replace the role of HCl in the cleaning process. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an ion exchanger, a preparation method and an application thereof. The ion exchanger will not introduce new metal ion pollution, can achieve lower metal ion residues in the solution, reduce surface recombination, and thus improve the conversion efficiency of battery wafers.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides an ion exchanger. The preparation raw materials of the ion exchanger include a carrier, a functional group modifier and a solvent;

[0010] Based on 1 mL of the volume of the functional group modifier, the mass of the carrier is 0.06 - 0.25 g, such as 0.08 g, 0.10 g, 0.15 g, 0.16 g, 0.18 g, 0.20 g, 0.22 g, 0.24 g, etc.;

[0011] The volume ratio of the functional group modifier to the solvent is 1:(0.6 - 1.5), where 0.6 - 1.5 can be 0.8, 1, 1.2, 1.4, etc.;

[0012] In the ion exchanger, the functional group modifier is fixed on the carrier.

[0013] The ion exchanger formed by fixing the functional group modifier of the present invention on the carrier in a specific proportion is more stable. When treating battery wafers, it will not introduce new metal ion pollution, can achieve lower metal ion residues in the solution, reduce surface recombination, and thus improve the conversion efficiency of battery wafers.

[0014] Preferably, the preparation raw materials of the ion exchanger include, by proportion: carrier: functional group modifier: solvent = (2 - 5) g:(20 - 30) mL:(20 - 30) mL, where 2 - 5 g can be 2.5 g, 3 g, 3.5 g, 4 g, 4.5 g, etc., 20 - 30 mL can be 22 mL, 24 mL, 26 mL, 28 mL, etc. The volumes of the functional group modifier and the solvent can be equal or unequal.

[0015] Preferably, the carrier includes any one or at least two combinations of cross-linked lignin phenol aldehyde, activated carbon or cellulose. Typical but non-limiting combinations include: the combination of cross-linked lignin phenol aldehyde and activated carbon, the combination of activated carbon and cellulose, the combination of cross-linked lignin phenol aldehyde, activated carbon and cellulose, etc. Further preferably, it is cross-linked lignin phenol aldehyde.

[0016] The carrier of the present invention is further preferably cross-linked lignin phenol aldehyde. The reasons are as follows: firstly, the lignin carrier is an organic mixture without metal ion residues and will not introduce new ion pollution; secondly, lignin widely exists in rice straw and straw, and the raw materials are extensive.

[0017] Preferably, the functional group modifier includes ethylenediaminetetraacetic acid and / or sulfonic acid.

[0018] Preferably, the solvent includes hydrochloric acid.

[0019] Preferably, the concentration of the hydrochloric acid is 3 - 8 mol / L, such as 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, etc.

[0020] Preferably, the raw materials for preparing the crosslinked lignin phenolic aldehyde include lignin phenol, sulfuric acid, and paraformaldehyde.

[0021] Preferably, the mass concentration of the sulfuric acid is 70% - 75%, such as 71%, 72%, 73%, 74%, etc.

[0022] Preferably, based on 1 mL of the volume of the sulfuric acid, the mass of the lignin phenol is 0.05 - 0.2 g, such as 0.06 g, 0.08 g, 0.10 g, 0.12 g, 0.14 g, 0.16 g, 0.18 g, etc.

[0023] Preferably, based on 1 mL of the volume of the sulfuric acid, the mass of the paraformaldehyde is 0.065 - 0.21 g, such as 0.07 g, 0.08 g, 0.10 g, 0.12 g, 0.14 g, 0.16 g, 0.18 g, 0.20 g, etc.

[0024] Preferably, the raw materials for preparing the lignin phenol include rice straw, phenol, and sulfuric acid.

[0025] Preferably, the mass concentration of the sulfuric acid is 70% - 75%, such as 71%, 72%, 73%, 74%, etc.

[0026] Preferably, based on 1 mL of the volume of the phenol, the mass of the rice straw is 0.05 - 0.2 g, such as 0.06 g, 0.08 g, 0.10 g, 0.12 g, 0.14 g, 0.16 g, 0.18 g, etc.

[0027] Preferably, the volume ratio of the phenol to the sulfuric acid is 1:(1 - 4), where 1 - 4 can be 1.5, 2, 2.5, 3, 3.5, etc.

[0028] In a second aspect, the present invention provides a method for preparing the ion exchanger according to the first aspect, and the preparation method includes the following steps:

[0029] Mix the carrier, the functional group modifier, and the solvent, and heat for reaction to obtain the ion exchanger.

[0030] Preferably, the mixing time is 10 - 20 min, such as 12 min, 14 min, 16 min, 18 min, etc.

[0031] Preferably, the temperature of the heating reaction is 60 - 100 °C, such as 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, etc.

[0032] Preferably, the time of the heating reaction is 15 - 25 min, such as 16 min, 18 min, 20 min, 22 min, 24 min, etc.

[0033] Preferably, after the heating reaction, operations such as filtration, washing, and drying are also included.

[0034] As a preferred technical solution, the preparation method includes the following steps:

[0035] Mix the carrier, functional group modifier, and solvent for 10 - 20 min, carry out a heating reaction at 60 - 100 °C for 15 - 25 min, and then successively carry out filtration, washing, and drying to obtain the ion exchanger.

[0036] In the synthesis process of the present invention, more modification sites are introduced during the phenolation process, so it has a larger saturated adsorption capacity; the formed ion exchanger can be desorbed by thiourea, and the resin after reaching saturation adsorption can be reused; it has stronger acid resistance and hydrolysis resistance.

[0037] Exemplarily, the preparation method of the crosslinked lignin phenol formaldehyde includes the following steps:

[0038] Mix lignin phenol with sulfuric acid and paraformaldehyde in sequence, carry out a heating reaction, then mix with a neutralizing agent, filter, wash, and dry to obtain the crosslinked lignin phenol formaldehyde.

[0039] Preferably, the raw materials for the preparation of the crosslinked lignin phenol formaldehyde include, by proportion: lignin phenol : sulfuric acid : paraformaldehyde = (5 - 10) g : (50 - 100) mL : (6.5 - 10.5) g, where 5 - 10 g can be 6 g, 7 g, 8 g, 9 g, etc., 50 - 100 mL can be 60 mL, 70 mL, 80 mL, 90 mL, etc., and 6.5 - 10.5 g can be 7 g, 8 g, 9 g, 10 g, etc.

[0040] Preferably, the temperature of the heating reaction is 80 - 120 °C, such as 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, etc.

[0041] Preferably, the time of the heating reaction is 12 - 36 h, such as 14 h, 16 h, 20 h, 25 h, 30 h, 35 h, etc.

[0042] Preferably, after the heating reaction, it is cooled.

[0043] Preferably, the neutralizing agent includes a sodium bicarbonate solution. The sodium bicarbonate solution is slowly added until no bubbles are generated in the system.

[0044] Preferably, the washing sequentially includes hot water washing, hydrochloric acid washing, and cold water washing. The washing is carried out until the pH value of the system is neutral.

[0045] Exemplarily, the preparation method of the lignophenol includes the following steps:

[0046] First, straw and phenol are mixed, then sulfuric acid is slowly added to the mixed system. After mixing is completed, it is immediately and rapidly stirred until the viscosity of the system remains stable. Then it is cooled and allowed to stand for layer separation. The upper organic phase is selected for washing to obtain the lignophenol.

[0047] Preferably, the raw materials for the preparation of the lignophenol include, by proportion: straw: phenol: sulfuric acid = (5 - 10) g : (50 - 100) mL : (100 - 200) mL, where 5 - 10 g can be 6 g, 7 g, 8 g, 9 g, etc., 50 - 100 mL can be 60 mL, 70 mL, 80 mL, 90 mL, etc., and 100 - 200 mL can be 110 mL, 120 mL, 130 mL, 140 mL, 150 mL, 160 mL, 170 mL, 180 mL, 190 mL, etc.

[0048] Preferably, the temperature for mixing the straw and phenol is 50 - 70 °C, such as 55 °C, 60 °C, 65 °C, etc.

[0049] Preferably, the temperature for adding the sulfuric acid is 20 - 30 °C, such as 22 °C, 24 °C, 26 °C, 28 °C, etc.

[0050] Preferably, after cooling, it is stirred for 0.5 - 2 h, such as 0.6 h, 0.8 h, 1.0 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, etc.

[0051] Preferably, the washing specifically includes: taking the upper organic phase and dropwise adding ether thereto while stirring under ice bath conditions. After stirring, it is allowed to stand for layer separation. The lower layer product is added to acetone, and after stirring and filtration, the impurities insoluble in acetone are removed. The obtained solution is vacuum dried and concentrated and then allowed to stand for layer separation. The upper organic phase is the lignophenol.

[0052] In a third aspect, the present invention provides a method for cleaning metal ions in a battery. The cleaning method includes the following steps:

[0053] Mix the ion exchanger described in the first aspect with hydrofluoric acid to form a cleaning solution, and then place the silicon wafer of the battery to be cleaned in the cleaning solution to complete the cleaning.

[0054] When the ion exchanger described in the present invention is used for removing metal ions in battery wafers, compared with the combination of hydrochloric acid and hydrofluoric acid in the prior art, it will not introduce new metal ion pollution, and can achieve lower metal ion residues in the solution, reduce surface recombination, and thus improve the conversion efficiency of the battery wafers.

[0055] Preferably, based on 1 mL of the volume of hydrofluoric acid, the mass of the ion exchanger is 0.001 - 0.003 g, such as 0.0015 g.

[0056] Preferably, before the ion exchanger is mixed with hydrofluoric acid, the ion exchanger is first placed in a mesh cloth.

[0057] Preferably, after the silicon wafer of the battery to be cleaned is placed in the cleaning solution, the ion exchanger is taken out for desorption after 40 - 100 min (such as 50 min, 60 min, 70 min, 80 min, 90 min, etc.), and finally the desorbed ion exchanger is re-put into the cleaning solution;

[0058] The above operation is performed at least once.

[0059] The ion exchanger described in the present invention can be reused by desorption means, reducing costs.

[0060] Preferably, the desorbing agent for desorption includes thiourea and / or urea.

[0061] As a preferred technical solution, the cleaning method includes the following steps:

[0062] Place the ion exchanger described in the first aspect in a mesh cloth, then mix it with hydrofluoric acid to form a cleaning solution, then place the silicon wafer of the battery to be cleaned in the cleaning solution, take out the ion exchanger for desorption after 40 - 100 min, and finally re-put the desorbed ion exchanger into the cleaning solution for continuous cleaning. The desorption process of the ion exchanger is performed at least once to complete the cleaning.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] (1) The ion exchanger described in the present invention will not introduce new metal ion pollution, and can achieve lower metal ion residues in the solution, reduce surface recombination, and thus improve the conversion efficiency of the battery wafers.

[0065] (2) The ion exchanger described in the present invention can be reused by desorption means, reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 is the schematic diagram when the ion exchanger described in the present invention removes metal ions;

[0067] Among them, 1 - hydrofluoric acid-containing solution; 2 - ion exchanger; 3 - metal ion; 4 - ion adsorption site. Specific implementation mode

[0068] For the convenience of understanding the present invention, the following examples are listed for the present invention. Those skilled in the art should understand that the said examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0069] Example 1

[0070] This example provides a proton exchanger. The raw materials for preparing the ion exchanger include a carrier (crosslinked lignin phenol, 3 g), a functional group modifier (ethylenediaminetetraacetic acid, 25 mL), and a solvent (25 mL of 5 mol / L hydrochloric acid).

[0071] The preparation method of the proton exchanger includes the following steps:

[0072] (1) Preparation of lignin phenol: Take the treated rice straw powder in a 500 mL beaker, add phenol, stir vigorously at 60 °C for 5 min, then cool to 30 °C, and slowly add 72 wt.% sulfuric acid under stirring. After mixing, immediately stir vigorously until the viscosity of the reactant remains stable. Then stir for 1 h at 30 °C. Let the reaction mixture stand for layer separation. Take the upper organic phase and dropwise add 300 mL of ether drop by drop under stirring in an ice bath. After stirring for 1 h, let it stand for layer separation. Take the lower product and add it to 150 mL of acetone. After stirring and filtering, remove the impurities insoluble in acetone. Vacuum dry and concentrate the obtained solution, and then let it stand for layer separation. The upper black organic phase is lignin phenol, where rice straw:phenol:sulfuric acid = 8 g:75 mL:75 mL;

[0073] (2) Preparation of crosslinked lignin phenol formaldehyde: Take lignin phenol and 72 wt.% sulfuric acid and add them to a 300 mL flask and stir for several minutes. Add 6.5 g of paraformaldehyde, heat in an oil bath to 100 °C and react for 24 h, then cool to room temperature. Slowly add 5 wt.% sodium bicarbonate solution under stirring until no more bubbles are generated in the solution. After filtration, wash with hot water first, then wash with 1 g·L -1 hydrochloric acid, and finally wash with cold water until the pH value is neutral. Put the filtered product into a constant temperature drying oven and dry at 90 °C for 48 h to obtain crosslinked lignin phenol formaldehyde, where lignin phenol:sulfuric acid:paraformaldehyde = 8 g:75 mL:8 g;

[0074] (3) Preparation of ion exchanger: Take crosslinked lignin phenolic chloride in a 500 mL beaker, add 200 mL of sodium carbonate and sodium chloride solutions with a concentration of 2 wt.% each for washing, stir for 3 h and then filter, wash with distilled water, dry at 75 °C for 24 h. Take the treated crosslinked lignin phenolic and the functional group modifier and stir in a 100 mL flask with hydrochloric acid solution with a concentration of 5 mol·L -1 for 15 min, then gradually heat to 80 °C and react for 20 h. After filtration and washing with distilled water, dry at 75 °C for 24 h, and grind into particles with a size of 0.147 mm to obtain the ion exchanger. Among them, the treated crosslinked lignin phenolic: functional group modifier: hydrochloric acid = 3 g: 25 mL: 25 mL.

[0075] Example 2

[0076] This example provides a proton exchanger. The raw materials for preparing the ion exchanger include a carrier (5 g of crosslinked lignin phenolic), a functional group modifier (ethylenediaminetetraacetic acid, 20 mL), and a solvent (30 mL of 8 mol / L hydrochloric acid).

[0077] The preparation method of the proton exchanger includes the following steps:

[0078] (1) Preparation of lignin phenol: Take the treated rice straw powder in a 500 mL beaker, add phenol, stir vigorously at 60 °C for 5 min and then cool to 30 °C. Slowly add 72 wt.% sulfuric acid under stirring. After mixing, immediately stir vigorously until the viscosity of the reactant remains stable, and then stir for another 1 h at 30 °C. Let the reaction mixture stand for stratification, take the upper organic phase, and dropwise add 300 mL of ether drop by drop while stirring in an ice bath. After stirring for 1 h, let it stand for stratification, take the lower product and add it to 150 mL of acetone. After stirring and filtering, remove the impurities insoluble in acetone. Vacuum dry and concentrate the obtained solution and let it stand for stratification. The upper black organic phase is lignin phenol, where rice straw: phenol: sulfuric acid = 5 g: 50 mL: 200 mL;

[0079] (2) Preparation of crosslinked lignin phenolic: Take lignin phenol and 72 wt.% sulfuric acid and add them to a 300 mL flask and stir for a few minutes. Add 6.5 g of paraformaldehyde, heat in an oil bath to 100 °C and react for 24 h, then cool to room temperature. Slowly add 5 wt.% sodium bicarbonate solution under stirring until no more bubbles are generated in the solution. After filtration, first wash with hot water, then wash with 1 g·L -1 hydrochloric acid solution, and finally wash with cold water until the pH value is neutral. Put the filtered product into a constant temperature drying oven and dry at 90 °C for 48 h to obtain crosslinked lignin phenolic, where lignin phenol: sulfuric acid: paraformaldehyde = 5 g: 50 mL: 10.5 g;

[0080] (3) Preparation of ion exchanger: Take crosslinked lignin phenolic chloride in a 500 mL beaker, add 200 mL of sodium carbonate and sodium chloride solutions with a concentration of 2 wt.% each for washing, stir for 3 h and then filter, wash with distilled water, dry at 75 °C for 24 h. Take the treated crosslinked lignin phenolic and the functional group modifier in a 100 mL flask with hydrochloric acid solution at a concentration of 8 mol·L -1 and stir for 15 min, then gradually heat to 80 °C and react for 20 h. After filtration and washing with distilled water, dry at 75 °C for 24 h, and grind into particles with a size of 0.147 mm to obtain the ion exchanger, where the treated crosslinked lignin phenolic: functional group modifier: hydrochloric acid = 5 g: 20 mL: 30 mL.

[0081] Example 3

[0082] This example provides a proton exchanger, and the raw materials for preparing the ion exchanger include a carrier (2 g of crosslinked lignin phenolic), a functional group modifier (ethylenediaminetetraacetic acid, 30 mL), and a solvent (20 mL of 3 mol / L hydrochloric acid).

[0083] The preparation method of the proton exchanger includes the following steps:

[0084] (1) Preparation of lignin phenol: Take the treated rice straw powder in a 500 mL beaker, add phenol, stir vigorously at 60 °C for 5 min and then cool to 30 °C. Slowly add 72 wt.% sulfuric acid with stirring. After mixing, immediately stir vigorously until the viscosity of the reactant remains stable, and then stir for another 1 h at 30 °C. Let the reaction mixture stand and separate layers. Take the upper organic phase and slowly add 300 mL of ether drop by drop with stirring in an ice bath. After stirring for 1 h, let it stand and separate layers. Take the lower product and add it to 150 mL of acetone. After stirring and filtering, remove the impurities insoluble in acetone. Vacuum dry and concentrate the obtained solution and let it stand and separate layers. The upper black organic phase is lignin phenol, where rice straw: phenol: sulfuric acid = 10 g: 100 mL: 100 mL;

[0085] (2) Preparation of crosslinked lignin phenolic: Take lignin phenol and 72 wt.% sulfuric acid and add them to a 300 mL flask and stir for a few minutes. Add 6.5 g of paraformaldehyde, heat in an oil bath to 100 °C and react for 24 h, then cool to room temperature. Slowly add 5 wt.% sodium bicarbonate solution with stirring until no more bubbles are produced in the solution. After filtration, first wash with hot water, then wash with 1 g·L -1 hydrochloric acid solution, and finally wash with cold water until the pH value is neutral. Put the filtered product into a constant temperature drying oven and dry at 90 °C for 48 h to obtain crosslinked lignin phenolic, where lignin phenol: sulfuric acid: paraformaldehyde = 10 g: 100 mL: 6.5 g;

[0086] (3) Preparation of ion exchanger: Take crosslinked lignin phenolic chloride in a 500 mL beaker, add 200 mL of sodium carbonate and sodium chloride solutions with a concentration of 2 wt.% each for washing, stir for 3 h and then filter, wash with distilled water, dry at 75 °C for 24 h. Take the treated crosslinked lignin phenolic and the functional group modifier and stir in a 100 mL flask with hydrochloric acid solution with a concentration of 3 mol·L -1 for 15 min, then gradually heat to 80 °C and react for 20 h. After filtration and washing with distilled water, dry at 75 °C for 24 h, and grind into particles with a size of 0.147 mm to obtain the ion exchanger, where the treated crosslinked lignin phenolic: functional group modifier: hydrochloric acid = 2 g: 30 mL: 20 mL.

[0087] Example 4

[0088] The difference between the proton exchanger in this example and that in Example 1 is that the carrier is activated carbon.

[0089] The preparation method of the proton exchanger includes the following steps:

[0090] Stir activated carbon and the functional group modifier in a 100 mL flask with hydrochloric acid solution with a concentration of 5 mol·L -1 for 15 min, then gradually heat to 80 °C and react for 20 h. After filtration and washing with distilled water, dry at 75 °C for 24 h, and grind into particles with a size of 0.147 mm to obtain the ion exchanger.

[0091] Example 5

[0092] The difference between this example and Example 4 is that the carrier is replaced with cellulose of equal mass to the crosslinked lignin phenolic substitute, and the rest are the same as in Example 1.

[0093] Comparative Example 1

[0094] The difference between this comparative example and Example 1 is that the preparation raw material of the ion exchanger does not include a carrier, and the ion exchanger is directly obtained by mixing ethylenediaminetetraacetic acid.

[0095] Comparative Examples 2 - 3

[0096] The differences between Comparative Examples 2 - 3 and Example 1 are that the masses of the crosslinked lignin phenolic are 1 g (Comparative Example 2) and 8 g (Comparative Example 3) respectively, and the rest are the same as in Example 1.

[0097] Comparative Examples 4 - 5

[0098] The differences between Comparative Examples 4 - 5 and Example 1 are that the volumes of hydrochloric acid are 10 mL (Comparative Example 4) and 40 mL (Comparative Example 5) respectively, and the rest are the same as in Example 1.

[0099] Application Example 1

[0100] This application example provides a method for cleaning metal ions in a battery. The cleaning method includes the following steps:

[0101] Place the ion exchanger described in Example 1 in a 500-mesh screen cloth, then mix it with hydrofluoric acid to form a cleaning solution. Then place the silicon wafer of the battery to be cleaned in the cleaning solution, take out the ion exchanger for desorption after 40 minutes, and finally place the desorbed ion exchanger back into the cleaning solution to continue cleaning. The desorption process of the ion exchanger is carried out twice to complete the cleaning.

[0102] Application Examples 2 - 5

[0103] The differences between Application Examples 2 - 5 and Application Example 1 are that the ion exchangers are the ion exchangers described in Examples 2 - 5 respectively.

[0104] Application Comparative Example 1

[0105] This application comparative example provides a method for cleaning metal ions in a battery. The cleaning method includes the following steps:

[0106] Mix the ion exchanger described in Comparative Example 1 with hydrofluoric acid to form a cleaning solution. Then place the silicon wafer of the battery to be cleaned in the cleaning solution to complete the cleaning.

[0107] Application Comparative Examples 2 - 5

[0108] The differences between Application Comparative Examples 2 - 5 and Application Example 1 are that the ion exchangers are the ion exchangers described in Comparative Examples 2 - 5 respectively.

[0109] Application Comparative Example 6

[0110] This application comparative example provides a method for cleaning metal ions in a battery. The cleaning method includes the following steps:

[0111] Mix hydrochloric acid and hydrofluoric acid with a volume ratio of 1:1 to form a cleaning solution. Then place the silicon wafer of the battery to be cleaned in the cleaning solution to complete the cleaning.

[0112] Performance Test

[0113] Perform the following tests on the silicon wafers cleaned by the methods described in Application Examples 1 - 5 and Application Comparative Examples 1 - 6:

[0114] First, the silicon wafers used in Application Examples 1 - 5 and Application Comparative Examples 1 - 6 are the same.

[0115] (1) Metal ion concentration of the silicon wafer after cleaning: Use ICP to measure the metal ion concentration in the solution. The present invention mainly monitors the iron ion concentration;

[0116] (2) The conversion efficiency of the cell after the cleaned silicon wafers are assembled back into the cell: Halm is used to test the conversion efficiency of the cell.

[0117] The test results are summarized in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] From the analysis of the data in Table 1, it can be seen that in each embodiment, when the carrier selects cross-linked lignin phenolic acid, the ion exchanger of the present invention can be used to remove metal ions in the battery cell. After removal, the concentration of metal ions is below 50 ppb, and the conversion efficiency of the battery cell is above 23.25%. When the ion exchanger treats the battery cell, no new metal ion pollution is introduced, and lower metal ion residues can be achieved in the solution, reducing surface recombination, thereby improving the conversion efficiency of the battery cell.

[0122] The principle diagram of the ion exchanger of the present invention when removing metal ions is as follows Figure 1 As shown, the ion exchanger 2 is placed in a solution 1 containing hydrofluoric acid, and the metal ions 3 on the silicon wafer in the battery cell are distributed in the solution. The metal ions combine with the negative ions on the ion adsorption sites 4 to complete the adsorption, that is, remove the metal ions. After the adsorption is saturated, the ion exchanger is taken out, desorbed, and then reused until the metal ions are completely removed.

[0123] Analysis of application comparison example 1 and application example 1 shows that the performance of application comparison example 1 is not as good as that of application example 1. The reason is that: when the exchange agent is directly mixed into the comparison example 1, an ion exchange reaction can occur, so the ion concentration in the solution will decrease. However, due to the lack of carrier fixation, the adsorbed metal ions will still adhere to the surface of the silicon wafer, increasing the silicon wafer recombination rate, which is not conducive to its conversion efficiency. This proves that the ion exchanger formed by fixing the functional group modifier on the carrier through reaction is more conducive to the removal of metal ions on the silicon wafer in the battery cell.

[0124] Analysis of application examples 2-5 and application example 1 shows that the performance of application examples 2-5 is not as good as that of application example 1, which proves that the ion exchanger formed under a certain ratio of each raw material has better performance. Specifically, the volume of the functional group modifier is 1 mL, the mass of the carrier is 0.06-0.25 g; the volume ratio of the functional group modifier to the solvent is 1:(0.6-1.5). The reason is that the amount of modification sites carried by the carrier is fixed, so the amount that reacts with the functional group modifier is also certain. It is a very important process to explore the optimal reaction conditions by reacting different raw material ratios and combining the residual amount of metal ions after adsorption.

[0125] Analysis of Comparative Application Example 6 and Application Example 1 shows that the performance of Comparative Application Example 6 is inferior to that of Application Example 1, proving that when the ion exchanger described in the present invention is used to remove metal ions on silicon wafers in battery chips, it has more obvious advantages compared with the combined treatment of hydrochloric acid and hydrofluoric acid in the prior art.

[0126] Compared with Example 1, the performance of Application Examples 4-5 decreased, proving that the ion exchanger formed by selecting cross-linked lignin phenolic as the carrier has better performance.

[0127] The applicant declares that the present invention uses the above-mentioned examples to illustrate the detailed method of the present invention, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for cleaning metal ions in a battery, characterized in that, The cleaning method includes the following steps: Mix an ion exchanger with hydrofluoric acid to form a cleaning solution, and then place the silicon wafer of the battery to be cleaned in the cleaning solution to complete the cleaning; The preparation raw materials of the ion exchanger include a carrier, a functional group modifier, and a solvent; the carrier is crosslinked lignin phenolic; the functional group modifier is ethylenediaminetetraacetic acid; the solvent is hydrochloric acid; The concentration of the hydrochloric acid is 3 - 8 mol / L; Based on the volume of the functional group modifier being 1 mL, the mass of the carrier is 0.06 - 0.25 g; The volume ratio of the functional group modifier to the solvent is 1:(0.6 - 1.5); In the ion exchanger, the functional group modifier is fixed on the carrier; The preparation method of the ion exchanger includes the following steps: Mix the carrier, the functional group modifier, and the solvent for 10 - 20 min, heat and react at 60 - 100 °C for 15 - 25 min, and then perform filtration, washing, and drying in sequence to obtain the ion exchanger.

2. The cleaning method according to claim 1, characterized in that, The preparation raw materials of the crosslinked lignin phenolic include lignin phenol, sulfuric acid, and paraformaldehyde.

3. The cleaning method according to claim 2, characterized in that, The mass concentration of the sulfuric acid is 70% - 75%; 4. The cleaning method according to claim 2, characterized in that, Based on the volume of the sulfuric acid being 1 mL, the mass of the lignin phenol is 0.05 - 0.2 g; 5. The cleaning method according to claim 2, characterized in that, Based on the volume of the sulfuric acid being 1 mL, the mass of the paraformaldehyde is 0.065 - 0.21 g; 6. The cleaning method according to claim 2, characterized in that, The preparation raw materials of the lignin phenol include rice straw, phenol, and sulfuric acid.

7. The cleaning method according to claim 6, characterized in that, The mass concentration of the sulfuric acid is 70% - 75%; 8. The cleaning method according to claim 6, characterized in that, Based on the volume of the phenol being 1 mL, the mass of the rice straw is 0.05 - 0.2 g; 9. The cleaning method according to claim 6, characterized in that, The volume ratio of the phenol to the sulfuric acid is 1:(1 - 4); 10. The cleaning method according to claim 1, characterized in that, Based on the volume of the hydrofluoric acid being 1 mL, the mass of the ion exchanger is 0.001 - 0.003 g; 11. The cleaning method according to claim 1, characterized in that, Before mixing the ion exchanger with the hydrofluoric acid, first place the ion exchanger in a mesh cloth; 12. The cleaning method according to claim 1, characterized in that, After the silicon wafer of the battery to be cleaned is placed in the cleaning solution, take out the ion exchanger for desorption after 40 - 100 min, and finally re - place the desorbed ion exchanger into the cleaning solution; The desorption process of the ion exchanger is carried out at least once.

13. The cleaning method according to claim 12, characterized in that, The desorption agent for desorption includes thiourea and / or urea.

14. The cleaning method according to claim 1, characterized in that, The cleaning method includes the following steps: Place the ion exchanger in a mesh cloth, then mix it with hydrofluoric acid to form a cleaning solution, then place the silicon wafer of the battery to be cleaned in the cleaning solution, take out the ion exchanger for desorption after 40 - 100 min, and finally re - place the desorbed ion exchanger into the cleaning solution to continue cleaning. The desorption process of the ion exchanger is carried out at least once to complete the cleaning.

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