A method for recovering positive electrode active material from waste lithium iron phosphate batteries

Abstract

The invention discloses a method for recovering positive active materials from waste lithium iron phosphate batteries, the steps comprising: (1) preparing an ethanol solution of aniline, keeping the solution constant temperature at 60±2°C in a water bath, adding 1,3-propane sultone to the solution, continuing to keep the temperature and stir after the addition is completed, removing ethanol, washing with ethyl acetate, standing for liquid separation, removing the ethyl acetate phase, and mixing the residue with hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-formic acid, and [BSO3HPy]HSO4 to form a leachate; (2) the battery soaks the positive electrode powder in the leachate to obtain a Li-containing leachate and a filter residue; (3) removing impurities, precipitating lithium, and obtaining a lithium-containing active material. The method of the invention can efficiently extract lithium from the positive electrode material of waste lithium iron phosphate batteries, and the leaching rate of Li can reach more than 95%, and the process method is simple and easy to promote industrialization.

Description

Technical Field

[0001] The invention relates to the technical field of waste battery recycling, and in particular to a method for recycling positive electrode active materials from waste lithium iron phosphate batteries. Background Art

[0002] Lithium iron phosphate battery cathode has developed rapidly due to its advantages such as long life, low cost and non-toxicity, especially in the electric vehicle market. The increase in demand for electric vehicles has greatly stimulated the production of lithium-ion batteries, resulting in a significant increase in the number of waste lithium-ion batteries. The recycling of waste lithium iron phosphate batteries has recently attracted attention because it can recover the high content of active elements in them and eliminate the potential negative impact of their disposal on the environment. At present, lithium battery recycling is to recycle the lithium, nickel, cobalt and other metals in the failed cathode powder in the form of oxides or salts through a series of physical and chemical treatments after the battery is crushed. Since lithium iron phosphate does not contain cobalt and nickel, and iron does not have a separate recycling value, its main recycling object is lithium salt, and the remaining iron and phosphorus are recovered together in the form of iron phosphate, the precursor of lithium iron phosphate. The current mainstream recycling methods are pyrometallurgy, hydrometallurgy and pyrometallurgy combined with hydrometallurgy. At present, the recycling and treatment methods for waste lithium-ion batteries in industry are mainly wet methods. Ionic liquids are increasingly used as a new type of green leaching agent. . Ionic liquids, also known as room temperature ionic liquids, are salts composed of organic cations and inorganic or organic anions. They are liquid at room temperature and have good physical and chemical stability, are not easy to volatilize, have good selective solubility, adjustable polarity, high thermal stability, etc. Using ionic liquids as leaching agents can not only achieve effective treatment of waste lithium-ion batteries, but also the leachate can be recycled and reused, which is in line with efficient and green carbon emission policies. Summary of the invention

[0003] The present invention provides a method for recovering positive electrode active materials from waste lithium iron phosphate batteries, the steps comprising:

[0004] (1) preparing an aniline ethanol solution, keeping the aniline ethanol solution in a water bath at a constant temperature of 60±2° C., stirring the aniline ethanol solution, adding 1,3-propane sultone to the solution under stirring, and continuing to keep the solution at 60±2° C. and stirring for more than 20 hours after the addition is completed, then distilling under reduced pressure to remove ethanol, washing with ethyl acetate, standing to separate the liquids, removing the ethyl acetate phase, and mixing the residue with hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 to form a leachate;

[0005] (2) discharging the waste lithium iron phosphate battery to consume the remaining power, and then disassembling it to obtain a conductive foil and positive electrode powder and negative electrode powder; soaking the positive electrode powder in the leachate to form a mixed solution, and keeping the mixed solution in a water bath at a constant temperature of 70±2° C. for more than 5 hours, condensing and refluxing the mixed solution and magnetically stirring the mixed solution during the insulation process, and separating the solid and liquid after the insulation is completed to obtain a Li-containing leachate and a filter residue;

[0006] (3) adding sodium hydroxide solution to the Li-containing leachate, stirring the solution for more than 1 hour after the addition is completed, filtering to remove the precipitate, and keeping the filtrate constant temperature at 50±5° C. in a water bath, and then adding sodium carbonate to the filtrate, stirring the solution at a constant temperature of 50±5° C. for more than 2 hours after the addition is completed, and then separating the solid and liquid, washing the solid phase with deionized water, and drying to obtain a lithium-containing active material.

[0007] Furthermore, in the step (1), the concentration of aniline in the ethanol solution of aniline is 0.5 mol / L, and the solvent is ethanol; the molar ratio of the added amount of 1,3-propane sultone to the aniline in the ethanol solution of aniline is aniline:1,3-propane sultone=1:2.

[0008] Furthermore, in the step (1), the mass ratio of the residue and hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 is residue: hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: pyridine-3-carboxylic acid: [BSO3HPy]HSO4 = 1-3:100:2-4:0.4-0.6:0.5-0.8:2-3; the mass percentage of the solute in the hydrogen peroxide is 3%.

[0009] Furthermore, in the step (2), the positive electrode powder is immersed in the leaching solution at a solid-liquid mass ratio of positive electrode powder: leaching solution = 1:15.

[0010] Furthermore, in the step (3), the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:2-4; the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4.

[0011] The beneficial effects of the present invention are as follows: the method of the present invention can efficiently extract lithium from the positive electrode material of waste lithium iron phosphate batteries, the leaching rate of Li can reach more than 95%, and the process method is simple and easy to promote industrialization. DETAILED DESCRIPTION

[0012] The present invention will be further described below in conjunction with the embodiments.

[0013] Example 1

[0014] A method for recovering positive electrode active materials from waste lithium iron phosphate batteries, comprising the following steps:

[0015] (1) preparing an aniline ethanol solution, wherein the aniline concentration in the aniline ethanol solution is 0.5 mol / L and the solvent is ethanol; the aniline ethanol solution is kept at a constant temperature of 60±2° C. in a water bath, then the aniline ethanol solution is stirred, and 1,3-propane sultone is added to the solution under stirring, wherein the molar ratio of the added 1,3-propane sultone to the aniline in the aniline ethanol solution is aniline:1,3-propane sultone=1:2; after the addition is completed, the solution is kept at 60±2° C. and stirred for 20 hours, then the ethanol is removed by distillation under reduced pressure, and the solution is washed with ethyl acetate, The mixture was allowed to stand for separation, and the ethyl acetate phase was removed. The residue was mixed with hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 to form a leachate; the residue and hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 were mixed in a mass ratio of residue: hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: pyridine-3-carboxylic acid: [BSO3HPy]HSO4 = 1:100:2:0.4:0.5:2; the mass percentage of the solute in the hydrogen peroxide was 3%;

[0016] (2) The waste lithium iron phosphate battery is discharged to consume the remaining power, and then disassembled to obtain a conductive foil and positive electrode powder and negative electrode powder; the positive electrode powder is immersed in the leachate to form a mixed solution, and the solid-liquid mass ratio of the positive electrode powder immersed in the leachate is positive electrode powder: leachate = 1:15; the mixed solution is kept constant at 70±2°C in a water bath for 5 hours, condensed and refluxed during the insulation process, and the mixed solution is magnetically stirred. After the insulation is completed, the solid and liquid are separated to obtain a Li-containing leachate and a filter residue; the mass of lithium in the Li leachate and the filter residue is tested respectively, and the lithium leaching rate is calculated. The results are shown in Table 1, wherein the leaching rate L = (M1) / (M1+M2)×100%, wherein M1 is the mass of lithium in the Li leachate, and M2 is the mass of lithium in the filter residue;

[0017] (3) adding sodium hydroxide solution to the Li-containing leachate, wherein the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:2; after the addition is completed, the solution is stirred for 1 hour, the precipitate is filtered to remove the precipitate, the filtrate is kept at a constant temperature of 50±5°C in a water bath, and then sodium carbonate is added to the filtrate, and the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4; after the addition is completed, the solution is stirred at a constant temperature of 50±5°C for 2 hours, and then the solid-liquid separation is performed, the solid phase is washed with deionized water, and dried to obtain a lithium-containing active material.

[0018] Example 2

[0019] A method for recovering positive electrode active materials from waste lithium iron phosphate batteries, comprising the following steps:

[0020] (1) preparing an aniline ethanol solution, wherein the aniline concentration in the aniline ethanol solution is 0.5 mol / L and the solvent is ethanol; the aniline ethanol solution is kept at a constant temperature of 60±2° C. in a water bath, then the aniline ethanol solution is stirred, and 1,3-propane sultone is added to the solution under stirring, wherein the molar ratio of the added 1,3-propane sultone to the aniline in the aniline ethanol solution is aniline:1,3-propane sultone=1:2; after the addition is completed, the solution is kept at 60±2° C. and stirred for 20 hours, then the ethanol is removed by distillation under reduced pressure, and the solution is washed with ethyl acetate, The mixture was allowed to stand for separation, and the ethyl acetate phase was removed. The residue was mixed with hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 to form a leachate; the residue and hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 were mixed in a mass ratio of residue: hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: pyridine-3-carboxylic acid: [BSO3HPy]HSO4 = 2:100:3:0.5:0.6:2; the mass percentage of the solute in the hydrogen peroxide was 3%;

[0021] (2) The waste lithium iron phosphate battery is discharged to consume the remaining power, and then disassembled to obtain a conductive foil and positive electrode powder and negative electrode powder; the positive electrode powder is immersed in the leachate to form a mixed solution, and the solid-liquid mass ratio of the positive electrode powder immersed in the leachate is positive electrode powder: leachate = 1:15; the mixed solution is kept constant at 70±2°C in a water bath for 5 hours, condensed and refluxed during the insulation process, and the mixed solution is magnetically stirred. After the insulation is completed, the solid and liquid are separated to obtain a Li-containing leachate and a filter residue; the mass of lithium in the Li leachate and the filter residue is tested respectively, and the lithium leaching rate is calculated. The results are shown in Table 1, wherein the leaching rate L = (M1) / (M1+M2)×100%, wherein M1 is the mass of lithium in the Li leachate, and M2 is the mass of lithium in the filter residue;

[0022] (3) adding sodium hydroxide solution to the Li-containing leachate, wherein the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:3; after the addition is completed, the solution is stirred for 1 hour, the precipitate is filtered to remove the precipitate, the filtrate is kept at a constant temperature of 50±5°C in a water bath, and then sodium carbonate is added to the filtrate, and the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4; after the addition is completed, the solution is stirred at a constant temperature of 50±5°C for 2 hours, and then the solid-liquid separation is performed, the solid phase is washed with deionized water, and dried to obtain a lithium-containing active material.

[0023] Example 3

[0024] A method for recovering positive electrode active materials from waste lithium iron phosphate batteries, comprising the following steps:

[0025] (1) preparing an aniline ethanol solution, wherein the aniline concentration in the aniline ethanol solution is 0.5 mol / L and the solvent is ethanol; the aniline ethanol solution is kept at a constant temperature of 60±2° C. in a water bath, then the aniline ethanol solution is stirred, and 1,3-propane sultone is added to the solution under stirring, wherein the molar ratio of the added 1,3-propane sultone to the aniline in the aniline ethanol solution is aniline:1,3-propane sultone=1:2; after the addition is completed, the solution is kept at 60±2° C. and stirred for 20 hours, then the ethanol is removed by distillation under reduced pressure, and the solution is washed with ethyl acetate, The mixture was allowed to stand for separation, and the ethyl acetate phase was removed. The residue was mixed with hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 to form a leachate; the residue and hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 were mixed in a mass ratio of residue: hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: pyridine-3-carboxylic acid: [BSO3HPy]HSO4 = 2:100:3:0.5:0.7:3; the mass percentage of the solute in the hydrogen peroxide was 3%;

[0026] (2) The waste lithium iron phosphate battery is discharged to consume the remaining power, and then disassembled to obtain a conductive foil and positive electrode powder and negative electrode powder; the positive electrode powder is immersed in the leachate to form a mixed solution, and the solid-liquid mass ratio of the positive electrode powder immersed in the leachate is positive electrode powder: leachate = 1:15; the mixed solution is kept constant at 70±2°C in a water bath for 5 hours, condensed and refluxed during the insulation process, and the mixed solution is magnetically stirred. After the insulation is completed, the solid and liquid are separated to obtain a Li-containing leachate and a filter residue; the mass of lithium in the Li leachate and the filter residue is tested respectively, and the lithium leaching rate is calculated. The results are shown in Table 1, wherein the leaching rate L = (M1) / (M1+M2)×100%, wherein M1 is the mass of lithium in the Li leachate, and M2 is the mass of lithium in the filter residue;

[0027] (3) adding sodium hydroxide solution to the Li-containing leachate, wherein the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:3; after the addition is completed, the solution is stirred for 1 hour, the precipitate is filtered to remove the precipitate, the filtrate is kept at a constant temperature of 50±5°C in a water bath, and then sodium carbonate is added to the filtrate, and the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4; after the addition is completed, the solution is stirred at a constant temperature of 50±5°C for 2 hours, and then the solid-liquid separation is performed, the solid phase is washed with deionized water, and dried to obtain a lithium-containing active material.

[0028] Example 4

[0029] A method for recovering positive electrode active materials from waste lithium iron phosphate batteries, comprising the following steps:

[0030] (1) preparing an aniline ethanol solution, wherein the aniline concentration in the aniline ethanol solution is 0.5 mol / L and the solvent is ethanol; the aniline ethanol solution is kept at a constant temperature of 60±2° C. in a water bath, then the aniline ethanol solution is stirred, and 1,3-propane sultone is added to the solution under stirring, wherein the molar ratio of the added 1,3-propane sultone to the aniline in the aniline ethanol solution is aniline:1,3-propane sultone=1:2; after the addition is completed, the solution is kept at 60±2° C. and stirred for 20 hours, then the ethanol is removed by distillation under reduced pressure, and the solution is washed with ethyl acetate, The mixture was allowed to stand for separation, and the ethyl acetate phase was removed. The residue was mixed with hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 to form a leachate; the mass ratio of the residue to hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 was residue: hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: pyridine-3-carboxylic acid: [BSO3HPy]HSO4 = 3:100:4:0.6:0.8:3; the mass percentage of the solute in the hydrogen peroxide was 3%;

[0031] (2) The waste lithium iron phosphate battery is discharged to consume the remaining power, and then disassembled to obtain a conductive foil and positive electrode powder and negative electrode powder; the positive electrode powder is immersed in the leachate to form a mixed solution, and the solid-liquid mass ratio of the positive electrode powder immersed in the leachate is positive electrode powder: leachate = 1:15; the mixed solution is kept constant at 70±2°C in a water bath for 5 hours, condensed and refluxed during the insulation process, and the mixed solution is magnetically stirred. After the insulation is completed, the solid and liquid are separated to obtain a Li-containing leachate and a filter residue; the mass of lithium in the Li leachate and the filter residue is tested respectively, and the lithium leaching rate is calculated. The results are shown in Table 1, wherein the leaching rate L = (M1) / (M1+M2)×100%, wherein M1 is the mass of lithium in the Li leachate, and M2 is the mass of lithium in the filter residue;

[0032] (3) adding sodium hydroxide solution to the Li-containing leachate, wherein the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:4; after the addition is completed, the solution is stirred for 1 hour, the precipitate is filtered to remove the precipitate, the filtrate is kept at a constant temperature of 50±5°C in a water bath, and then sodium carbonate is added to the filtrate, and the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4; after the addition is completed, the solution is stirred at a constant temperature of 50±5°C for 2 hours, and then the solid-liquid separation is performed, the solid phase is washed with deionized water, and dried to obtain a lithium-containing active material.

[0033] Comparative Example 1

[0034] A comparative method for recovering positive electrode active materials from waste lithium iron phosphate batteries comprises the following steps:

[0035] (1) mixing hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 to form a leachate; the mass ratio of hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, and [BSO3HPy]HSO4 is hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: pyridine-3-carboxylic acid: [BSO3HPy]HSO4 = 100:3:0.5:0.7:3; the mass percentage of the solute in the hydrogen peroxide is 3%;

[0036] (2) The waste lithium iron phosphate battery is discharged to consume the remaining power, and then disassembled to obtain a conductive foil and positive electrode powder and negative electrode powder; the positive electrode powder is immersed in the leachate to form a mixed solution, and the solid-liquid mass ratio of the positive electrode powder immersed in the leachate is positive electrode powder: leachate = 1:15; the mixed solution is kept constant at 70±2°C in a water bath for 5 hours, condensed and refluxed during the insulation process, and the mixed solution is magnetically stirred. After the insulation is completed, the solid and liquid are separated to obtain a Li-containing leachate and a filter residue; the mass of lithium in the Li leachate and the filter residue is tested respectively, and the lithium leaching rate is calculated. The results are shown in Table 1, wherein the leaching rate L = (M1) / (M1+M2)×100%, wherein M1 is the mass of lithium in the Li leachate, and M2 is the mass of lithium in the filter residue;

[0037] (3) adding sodium hydroxide solution to the Li-containing leachate, wherein the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:3; after the addition is completed, the solution is stirred for 1 hour, the precipitate is filtered to remove the precipitate, the filtrate is kept at a constant temperature of 50±5°C in a water bath, and then sodium carbonate is added to the filtrate, and the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4; after the addition is completed, the solution is stirred at a constant temperature of 50±5°C for 2 hours, and then the solid-liquid separation is performed, the solid phase is washed with deionized water, and dried to obtain a lithium-containing active material.

[0038] Comparative Example 2

[0039] A comparative method for recovering positive electrode active materials from waste lithium iron phosphate batteries comprises the following steps:

[0040] (1) preparing an aniline ethanol solution, wherein the concentration of aniline in the aniline ethanol solution is 0.5 mol / L and the solvent is ethanol; the aniline ethanol solution is kept at a constant temperature of 60±2° C. in a water bath, then the aniline ethanol solution is stirred, and 1,3-propane sultone is added to the solution under stirring, wherein the molar ratio of the 1,3-propane sultone added to the aniline in the aniline ethanol solution is aniline:1,3-propane sultone=1:2; after the addition is completed, the solution is kept at 60±2° C. and stirred for 20 hours, and then evaporated under reduced pressure. The ethanol is removed by distillation, and the mixture is washed with ethyl acetate. The mixture is allowed to stand for separation, and the ethyl acetate phase is removed. The residue is mixed with hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, and [BSO3HPy]HSO4 to form a leachate. The residue and hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, and [BSO3HPy]HSO4 are mixed in a mass ratio of residue: hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: [BSO3HPy]HSO4 = 2:100:3:0.5:3. The mass percentage of the solute in the hydrogen peroxide is 3%.

[0041] (2) The waste lithium iron phosphate battery is discharged to consume the remaining power, and then disassembled to obtain a conductive foil and positive electrode powder and negative electrode powder; the positive electrode powder is immersed in the leachate to form a mixed solution, and the solid-liquid mass ratio of the positive electrode powder immersed in the leachate is positive electrode powder: leachate = 1:15; the mixed solution is kept constant at 70±2°C in a water bath for 5 hours, condensed and refluxed during the insulation process, and the mixed solution is magnetically stirred. After the insulation is completed, the solid and liquid are separated to obtain a Li-containing leachate and a filter residue; the mass of lithium in the Li leachate and the filter residue is tested respectively, and the lithium leaching rate is calculated. The results are shown in Table 1, wherein the leaching rate L = (M1) / (M1+M2)×100%, wherein M1 is the mass of lithium in the Li leachate, and M2 is the mass of lithium in the filter residue;

[0042] (3) adding sodium hydroxide solution to the Li-containing leachate, wherein the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:3; after the addition is completed, the solution is stirred for 1 hour, the precipitate is filtered to remove the precipitate, the filtrate is kept at a constant temperature of 50±5°C in a water bath, and then sodium carbonate is added to the filtrate, and the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4; after the addition is completed, the solution is stirred at a constant temperature of 50±5°C for 2 hours, and then the solid-liquid separation is performed, the solid phase is washed with deionized water, and dried to obtain a lithium-containing active material.

[0043] Comparative Example 3

[0044] A comparative method for recovering positive electrode active materials from waste lithium iron phosphate batteries comprises the following steps:

[0045] (1) mixing hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, and [BSO3HPy]HSO4 to form a leachate; the mass ratio of hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, and [BSO3HPy]HSO4 is hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: [BSO3HPy]HSO4 = 100:3:0.5:3; the mass percentage of the solute in the hydrogen peroxide is 3%;

[0046] (2) The waste lithium iron phosphate battery is discharged to consume the remaining power, and then disassembled to obtain a conductive foil and positive electrode powder and negative electrode powder; the positive electrode powder is immersed in the leachate to form a mixed solution, and the solid-liquid mass ratio of the positive electrode powder immersed in the leachate is positive electrode powder: leachate = 1:15; the mixed solution is kept constant at 70±2°C in a water bath for 5 hours, condensed and refluxed during the insulation process, and the mixed solution is magnetically stirred. After the insulation is completed, the solid and liquid are separated to obtain a Li-containing leachate and a filter residue; the mass of lithium in the Li leachate and the filter residue is tested respectively, and the lithium leaching rate is calculated. The results are shown in Table 1, wherein the leaching rate L = (M1) / (M1+M2)×100%, wherein M1 is the mass of lithium in the Li leachate, and M2 is the mass of lithium in the filter residue;

[0047] (3) adding sodium hydroxide solution to the Li-containing leachate, wherein the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:3; after the addition is completed, the solution is stirred for 1 hour, the precipitate is filtered to remove the precipitate, the filtrate is kept at a constant temperature of 50±5°C in a water bath, and then sodium carbonate is added to the filtrate, and the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4; after the addition is completed, the solution is stirred at a constant temperature of 50±5°C for 2 hours, and then the solid-liquid separation is performed, the solid phase is washed with deionized water, and dried to obtain a lithium-containing active material.

[0048] As shown in Table 1, the method of the present invention can efficiently extract lithium from the positive electrode material of waste lithium iron phosphate battery, and the leaching rate of Li can reach more than 95%, and the process method is simple and easy to promote industrialization. Comparative Example 3 and Comparative Examples 1 to 3 show that adding the prepared residue and pyridine-3-carboxylic acid to the leaching solution is conducive to improving the leaching efficiency, which may be mainly due to the fact that the residue and pyridine-3-carboxylic acid improve the ion exchange efficiency in the process of leaching Li by the ionic liquid [BSO3HPy]HSO4, promote phase transfer, and thus improve the leaching rate of lithium.

[0049] Table 1

[0050] Experimental Group Li leaching rate Example 1 95.2％ Example 2 96.3％ Example 3 96.9％ Example 4 96.2％ Comparative Example 1 83.1％ Comparative Example 2 86.7％ Comparative Example 3 81.5％

[0051] The technical solution provided by the present invention is introduced in detail above. For those skilled in the art, according to the concept of the embodiments of the present invention, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for recovering positive electrode active materials from waste lithium iron phosphate batteries, characterized in that the steps include: (1) preparing an aniline ethanol solution, wherein the aniline concentration in the aniline ethanol solution is 0.5 mol / L and the solvent is ethanol; the aniline ethanol solution is kept at a constant temperature of 60±2° C. in a water bath, then the aniline ethanol solution is stirred, and 1,3-propane sultone is added to the solution under stirring, wherein the molar ratio of the 1,3-propane sultone added to the aniline in the aniline ethanol solution is aniline:1,3-propane sultone=1:2; after the addition is completed, the solution is kept at 60±2° C. and stirred for more than 20 hours, then the ethanol is removed by distillation under reduced pressure, washed with ethyl acetate, allowed to stand for separation, and removed The ethyl acetate phase, the residue and hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, [BSO3HPy]HSO4 are mixed to form a leachate; the residue and hydrogen peroxide, phosphoric acid, dodecyltrimethylammonium bromide, pyridine-3-carboxylic acid, [BSO3HPy]HSO4 are mixed in a mass ratio of residue: hydrogen peroxide: phosphoric acid: dodecyltrimethylammonium bromide: pyridine-3-carboxylic acid: [BSO3HPy]HSO4 = 1-3:100:2-4:0.4-0.6:0.5-0.8:2-3; the mass percentage of the solute in the hydrogen peroxide is 3%; (2) discharging the waste lithium iron phosphate battery to consume the remaining power, and then disassembling it to obtain a conductive foil, a positive electrode powder, and a negative electrode powder; soaking the positive electrode powder in the leachate to form a mixed solution, and keeping the mixed solution in a water bath at a constant temperature of 70±2° C. for more than 5 hours, condensing and refluxing the mixed solution during the insulation process and magnetically stirring the mixed solution, and separating the solid and liquid after the insulation is completed to obtain a Li-containing leachate and a filter residue; (3) Adding sodium hydroxide solution to the Li-containing leachate, stirring the solution for more than 1 hour after the addition is completed, filtering to remove the precipitate, and keeping the filtrate constant temperature at 50±5° C. in a water bath, and then adding sodium carbonate to the filtrate, stirring the solution at a constant temperature of 50±5° C. for more than 2 hours after the addition is completed, and then separating the solid and liquid, washing the solid phase with deionized water, and drying to obtain a lithium-containing active material.

2. The method for recovering positive electrode active materials from waste lithium iron phosphate batteries according to claim 1, characterized in that: In the step (2), the positive electrode powder is immersed in the leaching solution at a solid-liquid mass ratio of positive electrode powder: leaching solution = 1:

15.

3. The method for recovering positive electrode active materials from waste lithium iron phosphate batteries according to claim 1, characterized in that: In the step (3), the mass percentage of the solute in the sodium hydroxide is 10%, and the solvent is water; the volume ratio of the sodium hydroxide solution added to the Li-containing leachate is Li-containing leachate: sodium hydroxide solution = 10:2-4; the liquid-solid mass ratio of sodium carbonate added to the filtrate is filtrate: sodium carbonate = 10:1.4.