Method for recovering aluminum, iron and lithium from waste lithium iron phosphate battery

Abstract

The invention relates to a method for recycling aluminum, iron and lithium from waste lithium iron phosphate batteries. The method comprises the following steps: firstly, separating a positive electrode material of a waste battery cell, removing a binder through high-temperature treatment, adding the positive electrode material into a NaOH solution and a viscous liquid cosolvent, finally stirring and dissolving, neutralizing and adjusting the pH value through sulfuric acid, and precipitating and recovering aluminum; then sulfuric acid is matched with hydrogen peroxide, residual filter residues are stirred and dissolved, the pH value is adjusted in multiple steps, iron and lithium are precipitated respectively, and Fe (OH) 3 and Li2CO3 precipitates are obtained in sequence; the viscous liquid cosolvent disclosed by the invention is prepared from 1-aminoethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imine salt and boric acid powder; the recovery rate of aluminum, lithium and iron is high, the recovery cost is low, and the economic value is high.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recovery and reuse, and in particular to a method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries. Background Art

[0002] With the rapid development of the new energy industry, lithium-ion secondary batteries are widely used in electric vehicles, consumer electronics, and other fields. However, the large amount of waste lithium-ion secondary batteries has led to problems such as resource waste and environmental pollution. The cathode materials of waste lithium-ion secondary batteries contain various valuable metal elements such as aluminum, lithium, and iron. Effectively recycling these metal elements would not only alleviate resource shortages but also reduce environmental impact.

[0003] Currently, recycling methods for spent lithium-ion secondary battery cathode materials have several drawbacks. Some methods have low recovery efficiency and fail to fully extract metal elements; some are complex and energy-intensive, leading to increased production costs; and some methods are prone to metal element loss or impurities during the recycling process, affecting the quality of the recycled product. Therefore, there is an urgent need to develop an efficient, environmentally friendly, and economical method for recovering metal elements from spent lithium-ion secondary battery cathode materials. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries, the operating steps of which are as follows:

[0005] S1 Cell processing and cathode material acquisition: After removing the outer packaging of the waste lithium-ion secondary battery, take out the cell and separate the cathode material;

[0006] S2 Positive electrode sheet crushing and binder removal: The positive electrode sheet is crushed into small fragments, and then the crushed fragments are subjected to high temperature treatment to decompose and remove the binder at high temperature;

[0007] S3 aluminum recycling:

[0008] Aluminum foil dissolution: Place 14-22 parts of the positive electrode material after removing the binder into 120-200 parts of a 5-10% NaOH solution, add 1-5 parts of a viscous liquid co-solvent, and stir and dissolve at room temperature for 20-30 minutes to fully dissolve the aluminum to form NaAlO2;

[0009] Neutralization precipitation: Filter the dissolved solution to remove insoluble matter, add 10-20% sulfuric acid solution to the filtrate for neutralization, adjust the solution pH to 9, and precipitate aluminum in the form of Al(OH)3;

[0010] Filtration and collection: Filter the precipitated solution to obtain Al(OH)3 precipitate;

[0011] S4 lithium and iron element recovery:

[0012] Dissolution of filter residue: Place 12-18 parts of filter residue after removing the aluminum foil into 60-100 parts of sulfuric acid solution with a mass concentration of 10-20%, and add 50-80 parts of hydrogen peroxide with a mass concentration of 20-30%. Stir and dissolve at 50-60°C for 90-120 minutes. During this process, lithium iron phosphate reacts with sulfuric acid and hydrogen peroxide, and enters the solution in the form of Fe2(SO4)3 and Li2SO4, achieving separation from impurities such as carbon black and carbon coated on the surface of lithium iron phosphate;

[0013] Filtration and separation: Filter the dissolved solution to separate the filtrate containing Fe2(SO4)3 and Li2SO4 and the impurity residue;

[0014] Iron precipitation: add 5-10% NaOH solution and 5-10% ammonia solution to the filtrate to adjust the pH value to 7-8, so that the iron is precipitated as Fe(OH)3, and the Fe(OH)3 precipitate is separated by filtration;

[0015] Lithium element precipitation: Add 80-100 parts of saturated Na2CO3 solution to the residual liquid after separating the Fe(OH)3 precipitate, react at 80-90℃ for 90-120 minutes to precipitate lithium as Li2CO3, and collect the Li2CO3 precipitate by filtration.

[0016] The high temperature treatment temperature of S2 is 300-350°C and the time is 40-60 minutes.

[0017] The volume ratio of the NaOH solution to the ammonia water in the S4 iron element precipitation is 2-3:1.

[0018] The preparation method of the viscous liquid cosolvent is:

[0019] H1: Dissolve 43-86 parts of 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in deionized water to prepare a solution with a mass concentration of 20-30%. Heat to 40-60°C and stir until completely dissolved.

[0020] H2: Slowly add 6-12 parts of boric acid powder and continue stirring at 60-70°C for 2-6 hours. During this time, add 5-10% NaOH solution to adjust the pH to 8-9;

[0021] H3: After the reaction is completed, water is removed by distillation under reduced pressure to obtain a viscous liquid co-solvent containing an ionic liquid structure.

[0022] Reaction mechanism

[0023] In lithium battery recycling, the anions and cations of ionic liquids interact electrostatically and coordinate with metal ions such as lithium, aluminum, and iron. + Form a stable ion pair to reduce the crystallization free energy of Li2CO3; the imidazole ring structure of the cation can react with Al³ + 、Fe³ + Weak coordination occurs, promoting its dissolution and dispersion in the solution. At the same time, ionic liquids have good solubility for binder decomposition products and carbon impurities, accelerating material separation.

[0024] Technical Effects

[0025] The present invention provides a method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries. Compared with the prior art, the present invention has the following significant effects:

[0026] 1. Enhance the synergy between impurity dispersion and metal dissolution: effectively improve the carbon impurity dispersion efficiency and metal ion leaching rate, and significantly improve the stability of the dissolution system.

[0027] 2. Reduce solution viscosity and filtration resistance: effectively inhibit the formation of colloidal substances during the dissolution process, reduce solution viscosity and shorten filtration time.

[0028] 3. Efficient recycling: The present invention can efficiently recover metal elements such as aluminum, lithium, and iron from the positive electrode materials of waste lithium-ion secondary batteries, thereby improving the recycling rate of resources.

[0029] 4. Good environmental protection: It reduces the pollution of waste lithium-ion secondary batteries to the environment, and at the same time realizes the recycling of resources, which meets the requirements of sustainable development. DETAILED DESCRIPTION

[0030] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention object, the following is a detailed description in conjunction with examples and comparative examples:

[0031] Recovery rate test of aluminum, lithium and iron: determined by inductively coupled plasma atomic emission spectrometry.

[0032] Example 1

[0033] A method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries, the operating steps of which are as follows:

[0034] S1 Cell processing and cathode material acquisition: After removing the outer packaging of the waste lithium-ion secondary battery, take out the cell and separate the cathode material;

[0035] S2 Positive electrode sheet crushing and binder removal: The positive electrode sheet is crushed into small fragments, and then the crushed fragments are subjected to high temperature treatment to decompose and remove the binder at high temperature;

[0036] S3 aluminum recycling:

[0037] Dissolution of aluminum foil: Place 14g of the positive electrode material after removing the binder into 120g of a 5% NaOH solution, add 1g of a viscous liquid co-solvent, and stir and dissolve at room temperature for 20min to fully dissolve the aluminum to form NaAlO2;

[0038] Neutralization precipitation: Filter the dissolved solution to remove insoluble matter, add 10% sulfuric acid solution to the filtrate for neutralization, adjust the solution pH to 9, and precipitate aluminum in the form of Al(OH)3;

[0039] Filtration and collection: Filter the precipitated solution to obtain Al(OH)3 precipitate;

[0040] S4 lithium and iron element recovery:

[0041] Dissolution of filter residue: 12g of filter residue after removing the aluminum foil is placed in 60g of 10% sulfuric acid solution, and 50g of 20% hydrogen peroxide is added. Stir and dissolve at 50°C for 90min. During this process, lithium iron phosphate reacts with sulfuric acid and hydrogen peroxide, and enters the solution in the form of Fe2(SO4)3 and Li2SO4, achieving separation from impurities such as carbon black and carbon coated on the surface of lithium iron phosphate;

[0042] Filtration and separation: Filter the dissolved solution to separate the filtrate containing Fe2(SO4)3 and Li2SO4 and the impurity residue;

[0043] Iron precipitation: add 5% NaOH solution and 5% ammonia water to the filtrate to adjust the pH value to 7, so that the iron is precipitated as Fe(OH)3, and the Fe(OH)3 precipitate is separated by filtration;

[0044] Lithium element precipitation: add 80g of saturated Na2CO3 solution to the residual liquid after separating the Fe(OH)3 precipitate, react at 80℃ for 90min, so that lithium is precipitated as Li2CO3, and collect the Li2CO3 precipitate by filtration.

[0045] The high temperature treatment temperature of S2 is 300° C. and the time is 40 minutes.

[0046] The volume ratio of the NaOH solution to the ammonia water in the S4 iron element precipitation is 2:1.

[0047] The preparation method of the viscous liquid cosolvent is:

[0048] H1: Dissolve 43g of 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in deionized water to prepare a 20% solution by mass, heat to 40°C and stir until completely dissolved;

[0049] H2: Slowly add 6 g of boric acid powder and continue stirring at 60 °C for 2 hours. During this time, add 5% NaOH solution to adjust the pH to 8.

[0050] H3: After the reaction is completed, water is removed by distillation under reduced pressure to obtain a viscous liquid co-solvent containing an ionic liquid structure.

[0051] Example 2

[0052] A method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries, the operating steps of which are as follows:

[0053] S1 Cell processing and cathode material acquisition: After removing the outer packaging of the waste lithium-ion secondary battery, take out the cell and separate the cathode material;

[0054] S2 Positive electrode sheet crushing and binder removal: The positive electrode sheet is crushed into small fragments, and then the crushed fragments are subjected to high temperature treatment to decompose and remove the binder at high temperature;

[0055] S3 aluminum recycling:

[0056] Dissolution of aluminum foil: Place 16g of the positive electrode material after removing the binder into 140g of a 6% NaOH solution, add 2g of a viscous liquid co-solvent, and stir and dissolve at room temperature for 25min to fully dissolve the aluminum to form NaAlO2;

[0057] Neutralization precipitation: Filter the dissolved solution to remove insoluble matter, add 15% sulfuric acid solution to the filtrate for neutralization, adjust the solution pH to 9, and precipitate aluminum in the form of Al(OH)3;

[0058] Filtration and collection: Filter the precipitated solution to obtain Al(OH)3 precipitate;

[0059] S4 lithium and iron element recovery:

[0060] Dissolution of filter residue: 14g of filter residue after removing the aluminum foil is placed in 70g of 15% sulfuric acid solution, and 60g of 25% hydrogen peroxide is added. Stir and dissolve at 55°C for 100min. During this process, lithium iron phosphate reacts with sulfuric acid and hydrogen peroxide, and enters the solution in the form of Fe2(SO4)3 and Li2SO4, achieving separation from impurities such as carbon black and carbon coated on the surface of lithium iron phosphate;

[0061] Filtration and separation: Filter the dissolved solution to separate the filtrate containing Fe2(SO4)3 and Li2SO4 and the impurity residue;

[0062] Iron precipitation: add 6% NaOH solution and 6% ammonia water to the filtrate to adjust the pH value to 7, so that the iron is precipitated as Fe(OH)3, and the Fe(OH)3 precipitate is separated by filtration;

[0063] Lithium element precipitation: add 85g of saturated Na2CO3 solution to the residual liquid after separating the Fe(OH)3 precipitate, react at 85℃ for 100min, so that lithium is precipitated as Li2CO3, and filter and collect the Li2CO3 precipitate.

[0064] The high temperature treatment temperature of S2 is 310° C. and the time is 45 minutes.

[0065] The volume ratio of the NaOH solution to the ammonia water in the S4 iron element precipitation is 2:1.

[0066] The preparation method of the viscous liquid cosolvent is:

[0067] H1: Dissolve 55g of 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in deionized water to prepare a 25% solution by mass, heat to 45°C and stir until completely dissolved;

[0068] H2: Slowly add 8 g of boric acid powder and continue stirring at 65 °C for 3 hours. During this time, add 6% NaOH solution to adjust the pH to 8.

[0069] H3: After the reaction is completed, water is removed by distillation under reduced pressure to obtain a viscous liquid co-solvent containing an ionic liquid structure.

[0070] Example 3

[0071] A method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries, the operating steps of which are as follows:

[0072] S1 Cell processing and cathode material acquisition: After removing the outer packaging of the waste lithium-ion secondary battery, take out the cell and separate the cathode material;

[0073] S2 Positive electrode sheet crushing and binder removal: The positive electrode sheet is crushed into small fragments, and then the crushed fragments are subjected to high temperature treatment to decompose and remove the binder at high temperature;

[0074] S3 aluminum recycling:

[0075] Aluminum foil dissolution: 20g of the positive electrode material after removing the binder is placed in 180g of 8% NaOH solution, 4g of viscous liquid co-solvent is added, and stirred and dissolved at room temperature for 25min to fully dissolve the aluminum to form NaAlO2;

[0076] Neutralization precipitation: Filter the dissolved solution to remove insoluble matter, add 15% sulfuric acid solution to the filtrate for neutralization, adjust the solution pH to 9, and precipitate aluminum in the form of Al(OH)3;

[0077] Filtration and collection: Filter the precipitated solution to obtain Al(OH)3 precipitate;

[0078] S4 lithium and iron element recovery:

[0079] Dissolution of filter residue: 16g of filter residue after removing the aluminum foil is placed in 90g of 15% sulfuric acid solution, and 70g of 25% hydrogen peroxide is added. Stir and dissolve at 55°C for 110min. During this process, lithium iron phosphate reacts with sulfuric acid and hydrogen peroxide, entering the solution in the form of Fe2(SO4)3 and Li2SO4, achieving separation from impurities such as carbon black and carbon coated on the surface of lithium iron phosphate;

[0080] Filtration and separation: Filter the dissolved solution to separate the filtrate containing Fe2(SO4)3 and Li2SO4 and the impurity residue;

[0081] Iron precipitation: add 8% NaOH solution and 8% ammonia water to the filtrate to adjust the pH value to 8, so that the iron is precipitated as Fe(OH)3, and the Fe(OH)3 precipitate is separated by filtration;

[0082] Lithium element precipitation: Add 95g of saturated Na2CO3 solution to the residual liquid after separating the Fe(OH)3 precipitate, react at 85℃ for 110min, so that lithium is precipitated as Li2CO3, and filter and collect the Li2CO3 precipitate.

[0083] The high temperature treatment temperature of S2 is 340° C. and the time is 55 minutes.

[0084] The volume ratio of the NaOH solution to the ammonia water in the S4 iron element precipitation is 3:1.

[0085] The preparation method of the viscous liquid cosolvent is:

[0086] H1: Dissolve 80g of 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in deionized water to prepare a 25% solution, heat to 55°C and stir until completely dissolved;

[0087] H2: Slowly add 10 g of boric acid powder and continue stirring at 65 °C for 5 hours. During this time, add 8% NaOH solution dropwise to adjust the pH to 9.

[0088] H3: After the reaction is completed, water is removed by distillation under reduced pressure to obtain a viscous liquid co-solvent containing an ionic liquid structure.

[0089] Example 4

[0090] A method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries, the operating steps of which are as follows:

[0091] S1 Cell processing and cathode material acquisition: After removing the outer packaging of the waste lithium-ion secondary battery, take out the cell and separate the cathode material;

[0092] S2 Positive electrode sheet crushing and binder removal: The positive electrode sheet is crushed into small fragments, and then the crushed fragments are subjected to high temperature treatment to decompose and remove the binder at high temperature;

[0093] S3 aluminum recycling:

[0094] Dissolution of aluminum foil: Place 22g of the cathode material after removing the binder into 200g of a 10% NaOH solution, add 5g of a viscous liquid co-solvent, and stir and dissolve at room temperature for 30min to fully dissolve the aluminum to generate NaAlO2;

[0095] Neutralization precipitation: The dissolved solution is filtered to remove insoluble matter, and a 20% sulfuric acid solution is added to the filtrate for neutralization. The pH value of the solution is adjusted to 9, and aluminum is precipitated in the form of Al(OH)3;

[0096] Filtration and collection: Filter the precipitated solution to obtain Al(OH)3 precipitate;

[0097] S4 lithium and iron element recovery:

[0098] Dissolution of filter residue: 18g of filter residue after removing the aluminum foil is placed in 100g of 20% sulfuric acid solution, and 80g of 30% hydrogen peroxide is added. Stir and dissolve at 60°C for 120min. During this process, lithium iron phosphate reacts with sulfuric acid and hydrogen peroxide, and enters the solution in the form of Fe2(SO4)3 and Li2SO4, achieving separation from impurities such as carbon black and carbon coated on the surface of lithium iron phosphate;

[0099] Filtration and separation: Filter the dissolved solution to separate the filtrate containing Fe2(SO4)3 and Li2SO4 and the impurity residue;

[0100] Iron precipitation: add 10% NaOH solution and 10% ammonia solution to the filtrate to adjust the pH value to 8, so that the iron is precipitated as Fe(OH)3, and the Fe(OH)3 precipitate is separated by filtration;

[0101] Lithium element precipitation: Add 100g of saturated Na2CO3 solution to the residual liquid after separating the Fe(OH)3 precipitate, react at 90℃ for 120min to precipitate lithium as Li2CO3, and collect the Li2CO3 precipitate by filtration.

[0102] The high temperature treatment temperature of S2 is 350° C. and the time is 60 minutes.

[0103] The volume ratio of the NaOH solution to the ammonia water in the S4 iron element precipitation is 3:1.

[0104] The preparation method of the viscous liquid cosolvent is:

[0105] H1: Dissolve 86g of 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in deionized water to prepare a 30% solution by mass, heat to 60°C and stir until completely dissolved;

[0106] H2: Slowly add 12 g of boric acid powder and continue stirring at 70 °C for 6 h. During this time, add 10% NaOH solution dropwise to adjust the pH to 9.

[0107] H3: After the reaction is completed, water is removed by distillation under reduced pressure to obtain a viscous liquid co-solvent containing an ionic liquid structure.

[0108] Comparative Example 1

[0109] A method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries, the operating steps of which are as follows:

[0110] S1 Cell processing and cathode material acquisition: After removing the outer packaging of the waste lithium-ion secondary battery, take out the cell and separate the cathode material;

[0111] S2 Positive electrode sheet crushing and binder removal: The positive electrode sheet is crushed into small fragments, and then the crushed fragments are subjected to high temperature treatment to decompose and remove the binder at high temperature;

[0112] S3 aluminum recycling:

[0113] Dissolution of aluminum foil: Place 14g of the positive electrode material after removing the binder into 120g of a 5% NaOH solution and stir and dissolve it at room temperature for 20min to fully dissolve the aluminum to form NaAlO2.

[0114] Neutralization precipitation: Filter the dissolved solution to remove insoluble matter, add 10% sulfuric acid solution to the filtrate for neutralization, adjust the solution pH to 9, and precipitate aluminum in the form of Al(OH)3;

[0115] Filtration and collection: Filter the precipitated solution to obtain Al(OH)3 precipitate;

[0116] S4 lithium and iron element recovery:

[0117] Dissolution of filter residue: 12g of filter residue after removing the aluminum foil is placed in 60g of 10% sulfuric acid solution, and 50g of 20% hydrogen peroxide is added. Stir and dissolve at 50°C for 90min. During this process, lithium iron phosphate reacts with sulfuric acid and hydrogen peroxide, and enters the solution in the form of Fe2(SO4)3 and Li2SO4, achieving separation from impurities such as carbon black and carbon coated on the surface of lithium iron phosphate;

[0118] Filtration and separation: Filter the dissolved solution to separate the filtrate containing Fe2(SO4)3 and Li2SO4 and the impurity residue;

[0119] Iron precipitation: add 5% NaOH solution and 5% ammonia water to the filtrate to adjust the pH value to 7, so that the iron is precipitated as Fe(OH)3, and the Fe(OH)3 precipitate is separated by filtration;

[0120] Lithium element precipitation: add 80g of saturated Na2CO3 solution to the residual liquid after separating the Fe(OH)3 precipitate, react at 80℃ for 90min, so that lithium is precipitated as Li2CO3, and collect the Li2CO3 precipitate by filtration.

[0121] The high temperature treatment temperature of S2 is 300° C. and the time is 40 minutes.

[0122] The volume ratio of the NaOH solution to the ammonia water in the S4 iron element precipitation is 2:1.

[0123] Aluminum recovery rate / % Lithium recovery rate / % Iron recovery rate / % Example 1 90.3 90.9 98.4 Example 2 90.6 91.2 98.7 Example 3 91.1 91.8 99.3 Example 4 91.3 92.1 99.5 Comparative Example 1 60.8 63.4 76.7

[0124] Through the data analysis of the above embodiments and comparative examples, the aluminum, lithium and iron recovery rates of the present invention are high, the recovery cost is low and the economic value is high.

[0125] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries, the operating steps of which are: S1 Cell processing and cathode material acquisition: After removing the outer packaging of the waste lithium-ion secondary battery, take out the cell and separate the cathode material; S2 Positive electrode sheet crushing and binder removal: The positive electrode sheet is crushed into small fragments, and then the crushed fragments are subjected to high temperature treatment to decompose and remove the binder at high temperature; S3 aluminum recycling: Aluminum foil dissolution: Place 14-22 parts of the positive electrode material after removing the binder into 120-200 parts of a 5-10% NaOH solution, add 1-5 parts of a viscous liquid co-solvent, and stir and dissolve at room temperature for 20-30 minutes to fully dissolve the aluminum to form NaAlO2; Neutralization precipitation: Filter the dissolved solution to remove insoluble matter, add 10-20% sulfuric acid solution to the filtrate for neutralization, adjust the solution pH to 9, and precipitate aluminum in the form of Al(OH)3; Filtration and collection: Filter the precipitated solution to obtain Al(OH)3 precipitate; S4 lithium and iron element recovery: Dissolution of filter residue: Place 12-18 parts of filter residue after removing the aluminum foil into 60-100 parts of sulfuric acid solution with a mass concentration of 10-20%, and add 50-80 parts of hydrogen peroxide with a mass concentration of 20-30%. Stir and dissolve at 50-60°C for 90-120 minutes. During this process, lithium iron phosphate reacts with sulfuric acid and hydrogen peroxide, and enters the solution in the form of Fe2(SO4)3 and Li2SO4, achieving separation from impurities such as carbon black and carbon coated on the surface of lithium iron phosphate; Filtration and separation: Filter the dissolved solution to separate the filtrate containing Fe2(SO4)3 and Li2SO4 and the impurity residue; Iron precipitation: add 5-10% NaOH solution and 5-10% ammonia solution to the filtrate to adjust the pH value to 7-8, so that the iron is precipitated as Fe(OH)3, and the Fe(OH)3 precipitate is separated by filtration; Lithium element precipitation: Add 80-100 parts of saturated Na2CO3 solution to the residual liquid after separating the Fe(OH)3 precipitate, react at 80-90℃ for 90-120 minutes to precipitate lithium as Li2CO3, and collect the Li2CO3 precipitate by filtration.

2. The method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries according to claim 1, wherein: The high temperature treatment temperature of S2 is 300-350°C and the time is 40-60 minutes.

3. The method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries according to claim 1, wherein: The volume ratio of the NaOH solution to the ammonia water in the S4 iron element precipitation is 2-3:

1.

4. The method for recovering aluminum, iron and lithium from waste lithium iron phosphate batteries according to claim 1, wherein: The preparation method of the viscous liquid cosolvent is: H1: Dissolve 43-86 parts of 1-aminoethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt in deionized water to prepare a solution with a mass concentration of 20-30%. Heat to 40-60°C and stir until completely dissolved. H2: Slowly add 6-12 parts of boric acid powder and continue stirring at 60-70°C for 2-6 hours. During this time, add 5-10% NaOH solution to adjust the pH to 8-9; H3: After the reaction is completed, water is removed by distillation under reduced pressure to obtain a viscous liquid co-solvent containing an ionic liquid structure.