A method for recycling cathode materials from retired lithium iron phosphate batteries

Abstract

This invention relates to the field of lithium battery material recycling technology, specifically to a method for recycling and utilizing cathode materials from retired lithium iron phosphate batteries. The recycled retired lithium iron phosphate battery cathode materials are crushed, and the fragments are soaked in a solvent with stirring. After filtration, the filter residue is repeatedly washed with deionized water and dried to obtain coarse powder of the recycled cathode material. The coarse powder is subjected to ICP testing, and lithium, iron, phosphorus, grinding aids, and anhydrous ethanol are added for wet ball milling. After ball milling, the powder is dried to obtain a precursor. The precursor is then sintered under a nitrogen atmosphere to obtain the lithium iron phosphate cathode material. This method for recycling retired lithium iron phosphate battery cathode materials is simple, environmentally friendly, and economically efficient. The recycled cathode material meets the requirements for use in the battery industry.

Description

Technical Field

[0001] This invention relates to the field of lithium battery material recycling technology, and in particular to a method for recycling and utilizing cathode materials from retired lithium iron phosphate batteries. Background Technology

[0002] While the new energy vehicle industry is experiencing rapid growth, the number of retired power batteries is also increasing year by year, becoming a pressing problem for the industry. Without a viable business model, this will undoubtedly pose a significant threat to the development of the electric vehicle industry. Data shows that in 2020, my country's cumulative retired power batteries amounted to approximately 200,000 tons, and the cumulative amount is projected to reach approximately 780,000 tons by 2025. If we calculate based on the current installed capacity of 50kWh to 70kWh power batteries in electric vehicles, then assuming the retirement of 600,000 electric vehicles, the corresponding retired power battery capacity would reach 30GWh. This is an unavoidable issue for the new energy vehicle industry.

[0003] A method for recycling cathode materials, the obtained cathode materials, and their uses (Patent Publication No.: CN111799522B) describes a method comprising the following steps: sintering the cathode material to be recycled under an oxidizing atmosphere to obtain the cathode material; the gas in the oxidizing atmosphere includes CO2. This invention addresses the problems in existing technologies where the recycled cathode materials have significantly high carbon content and low effective active material content, resulting in lower energy density. This invention uses an oxidizing atmosphere containing CO2 as the basic oxidant to remove excess carbon components from the recycled cathode material. The resulting cathode material has a low carbon content, good cycle stability and rate performance, with a carbon content ≤2.86wt% and a 200-cycle capacity retention rate ≥99.0%.

[0004] A method for wet recycling and reuse of waste lithium iron phosphate cathode materials (patent publication number: CN116281916A) includes separating waste lithium iron phosphate batteries to obtain lithium-containing cathode material powder; soaking the lithium-containing cathode material powder in an organic solvent; pressing the lithium cathode material powder and binder into blocks and calcining them to obtain a mixture; subjecting the mixture and a reducing agent to high-temperature vacuum reduction, vacuum distillation, and vacuum condensation in sequence to obtain metallic lithium and residue; dissolving the residue in an inorganic acid solution and adding a precipitant, then drying the precipitate; heating the dried precipitate and cooling it to room temperature to obtain battery-grade lithium iron phosphate.

[0005] Currently, the recycling of lithium iron phosphate cathode materials mainly relies on wet recycling. However, this method is quite complex and requires the use of large amounts of acid and alkali reagents, which can easily cause secondary pollution.

[0006] Based on this, the present invention proposes a method for recycling and utilizing the cathode material of retired lithium iron phosphate batteries. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, this invention provides a method for recycling and utilizing the cathode material of retired lithium iron phosphate batteries, which improves the utilization rate of metal raw materials, reduces the loss of valuable metals, and is economical, environmentally friendly and efficient.

[0008] In another aspect, the present invention provides a lithium iron phosphate battery cathode material prepared by the above method.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for recycling cathode materials from retired lithium iron phosphate batteries, characterized by comprising the following steps:

[0011] Step 1: Crush 100-450 parts of the recycled retired lithium iron phosphate battery cathode material, add 1500-6000 parts of solvent to the fragmented material and stir and soak for 60-120 minutes. After filtration, wash and dry the filter residue with deionized water to obtain coarse powder of recycled cathode material.

[0012] Step 2: Perform ICP testing on the coarse powder, add lithium source, iron source, phosphorus source, grinding aid and anhydrous ethanol, and perform wet ball milling for 8-12 hours. After ball milling, dry to obtain the precursor.

[0013] Step 3: The precursor is sintered in a nitrogen atmosphere for 2-5 hours to obtain lithium iron phosphate cathode material.

[0014] Optionally, the solvent in step one is selected from at least one of N-methylpyrrolidone, acetone, ethylene glycol, N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

[0015] Optionally, in step two, after adding phosphorus, lithium, and iron sources, the molar ratio of P:Li:Fe in the material is 1:1-1.12:0.92-1.

[0016] Optionally, in step two, the phosphorus source is selected from at least one of phosphoric acid, iron phosphate, lithium phosphate, and lithium dihydrogen phosphate.

[0017] Optionally, in step two, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, and lithium nitrate.

[0018] Optionally, the iron source in step two is selected from at least one of ferric phosphate, ferrous sulfate, and ferrous oxalate.

[0019] Optionally, in step two, the mass ratio of material, milling beads, and ethanol in the ball mill is 1:1.5-2:0.8-1.2.

[0020] Optionally, in step two, the grinding aid accounts for 1-5% of the material mass percentage during ball milling.

[0021] Optionally, the preparation method of the grinding aid in step two ball milling is as follows:

[0022] By weight, add 2-5 parts of lithium mercaptosuccinate, 15-30 parts of mercaptoacetic acid monoethanolamine, and 20-40 parts of ethylene glycol diglycidyl ether to a stirred tank, continuously stir mechanically and purge with N2 for protection, heat to 90-100℃, add 3-6 parts of 1,8-bis(dimethylaminonaphthalene), and react for 60-120 minutes to obtain the grinding aid.

[0023] Optionally, the sintering temperature in step three is 650-900℃.

[0024] The beneficial effects achieved by the present invention using the above technical solution are as follows:

[0025] This method involves the reaction of lithium mercaptosuccinate and monoethanolamine mercaptoacetate with ethylene glycol diglycidyl ether via a mercapto-epoxy addition reaction. The mercapto functional group loses its chloride ion under the action of 1,8-bis(dimethylaminonaphthalene), forming a thiol anion and the conjugate acid of the oxidizing agent. The thiol anion has strong nucleophilicity, and after the epoxy functional group opens the ring, it forms an alkoxide anion intermediate. It can also abstract hydrogen ions from the potential hydrogen source in the reaction system to form a grinding aid.

[0026] Lithium disuccinate complexes can enhance the interaction forces between particles, promoting particle fragmentation and mixing. Ethanolamine can reduce the surface tension between particles, aiding in particle dispersion and lubrication during the grinding process, reducing inter-particle friction, and improving ball milling efficiency. Ethylene glycol may act as a humidifier during ball milling, keeping the particle surface moist, which helps with grinding and mixing. The functions of grinding aids can include enhancing the interaction forces between particles, reducing surface tension, providing lubrication, and humidifying, thereby promoting particle grinding and mixing and improving ball milling efficiency.

[0027] This method for recycling cathode materials from retired lithium iron phosphate batteries is simple, environmentally friendly, and economically efficient. The specific capacity of the recycled cathode material is above 153 mAh / g, and the initial efficiency is above 96.3%, which meets the requirements of the battery industry. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

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

[0030] Example Test Method:

[0031] The cathode materials prepared in the examples and comparative examples were assembled into button batteries CR2032 and charged and discharged under conditions of 4.0-2.5V and 0.1C.

[0032] Example 1

[0033] A method for recycling cathode materials from retired lithium iron phosphate batteries, characterized by comprising the following steps:

[0034] Step 1: Crush 100g of recycled retired lithium iron phosphate battery cathode material, add 1500g of solvent to the fragments and stir and soak for 60 minutes. After filtration, wash and dry the filter residue repeatedly with deionized water to obtain coarse powder of recycled cathode material.

[0035] Step 2: The coarse powder was subjected to ICP testing. Lithium source, iron source, phosphorus source, grinding aid, and anhydrous ethanol were added, and the powder was wet ball-milled for 8 hours. After ball milling, the powder was dried to obtain the precursor.

[0036] Step 3: The precursor is sintered in a nitrogen atmosphere for 2 hours to obtain lithium iron phosphate cathode material.

[0037] The solvent in step one is selected from N-methylpyrrolidone.

[0038] In step two, after adding phosphorus, lithium, and iron sources, the molar ratio of P:Li:Fe in the material is 1:1:0.92.

[0039] In step two, the phosphorus source is selected from phosphoric acid.

[0040] In step two, the lithium source is selected from lithium carbonate.

[0041] In step two, the iron source is selected from iron phosphate.

[0042] In step two, the mass ratio of the material, grinding beads, and ethanol in the ball mill is 1:1.5:0.8.

[0043] In step two, the grinding aid accounts for 1% of the material mass during ball milling.

[0044] The preparation method of the grinding aid in step two ball milling is as follows:

[0045] Add 2g of dilithium mercaptosuccinate, 15g of monoethanolamine mercaptoacetic acid, and 20g of ethylene glycol diglycidyl ether to a stirred tank. Stir continuously with N2 protection. Heat to 90°C, then add 3g of 1,8-bis(dimethylaminonaphthalene). React for 60 minutes to obtain a grinding aid.

[0046] The sintering temperature in step three is 650℃.

[0047] According to the test analysis, the discharge capacity of the button battery assembled with the positive electrode material in this case is 153.2 mAh / g, and the first efficiency is 96.3%.

[0048] Example 2

[0049] A method for recycling cathode materials from retired lithium iron phosphate batteries, characterized by comprising the following steps:

[0050] Step 1: Crush 250g of recycled retired lithium iron phosphate battery cathode material, add 3000g of solvent to the fragments and stir and soak for 90 minutes. After filtration, wash and dry the filter residue repeatedly with deionized water to obtain coarse powder of recycled cathode material.

[0051] Step 2: The coarse powder is subjected to ICP testing, and lithium source, iron source, phosphorus source, grinding aid and anhydrous ethanol are added for wet ball milling for 10 hours. After ball milling, it is dried to obtain the precursor.

[0052] Step 3: The precursor is sintered in a nitrogen atmosphere for 3 hours to obtain lithium iron phosphate cathode material.

[0053] The solvent in step one is acetone.

[0054] In step two, after adding phosphorus, lithium, and iron sources, the molar ratio of P:Li:Fe in the material is 1:1.06:0.94.

[0055] In step two, the phosphorus source is selected from lithium phosphate.

[0056] In step two, the lithium source is selected from lithium carbonate.

[0057] In step two, the iron source is selected from ferrous sulfate.

[0058] In step two, the mass ratio of the material, grinding beads, and ethanol in the ball mill is 1:1.6:0.9.

[0059] In step two, the grinding aid accounts for 2.5% of the material mass percentage during ball milling.

[0060] The preparation method of the grinding aid in step two ball milling is as follows:

[0061] Add 3g of lithium mercaptosuccinate, 20g of mercaptoacetic acid monoethanolamine, and 30g of ethylene glycol diglycidyl ether to a stirred tank. Stir continuously with N2 protection. Heat to 95°C, then add 4g of 1,8-bis(dimethylaminonaphthalene). React for 80 minutes to obtain a grinding aid.

[0062] The sintering temperature in step three is 750℃.

[0063] According to the test analysis, the discharge capacity of the button battery assembled with the positive electrode material in this case is 155.0 mAh / g, and the initial efficiency is 96.7%.

[0064] Example 3

[0065] A method for recycling cathode materials from retired lithium iron phosphate batteries, characterized by comprising the following steps:

[0066] Step 1: Crush 380g of recycled retired lithium iron phosphate battery cathode material, add 4500g of solvent to the fragments and stir and soak for 100 minutes. After filtration, wash and dry the filter residue repeatedly with deionized water to obtain coarse powder of recycled cathode material.

[0067] Step 2: The coarse powder is subjected to ICP testing, and lithium source, iron source, phosphorus source, grinding aid and anhydrous ethanol are added for wet ball milling for 10 hours. After ball milling, it is dried to obtain the precursor.

[0068] Step 3: The precursor is sintered in a nitrogen atmosphere for 4 hours to obtain lithium iron phosphate cathode material.

[0069] The solvent in step one is selected from dimethyl sulfoxide.

[0070] In step two, after adding phosphorus, lithium, and iron sources, the molar ratio of P:Li:Fe in the material is 1:1.12:0.97.

[0071] In step two, the phosphorus source is selected from iron phosphate.

[0072] In step two, the lithium source is selected from lithium nitrate.

[0073] In step two, the iron source is selected from iron phosphate.

[0074] In step two, the mass ratio of the material, grinding beads, and ethanol in the ball mill is 1:1.8:1.

[0075] In step two, the grinding aid accounts for 3.8% of the material mass during ball milling.

[0076] The preparation method of the grinding aid in step two ball milling is as follows:

[0077] Add 4g of dilithium mercaptosuccinate, 25g of monoethanolamine mercaptoacetic acid, and 30g of ethylene glycol diglycidyl ether to a stirred tank. Stir continuously with N2 protection. Heat to 95°C, then add 5g of 1,8-bis(dimethylaminonaphthalene). React for 100 minutes to obtain a grinding aid.

[0078] The sintering temperature in step three is 800℃.

[0079] According to the test analysis, the discharge capacity of the button battery assembled with the positive electrode material in this case is 156.4 mAh / g, and the initial efficiency is 97.1%.

[0080] Example 4

[0081] A method for recycling cathode materials from retired lithium iron phosphate batteries, characterized by comprising the following steps:

[0082] Step 1: Crush 450g of recycled retired lithium iron phosphate battery cathode material, add 6000g of solvent to the fragments and stir and soak for 120 minutes. After filtration, wash and dry the filter residue repeatedly with deionized water to obtain coarse powder of recycled cathode material.

[0083] Step 2: The coarse powder was subjected to ICP testing. Lithium source, iron source, phosphorus source, grinding aid, and anhydrous ethanol were added and wet ball milled for 12 hours. After ball milling, the powder was dried to obtain the precursor.

[0084] Step 3: The precursor is sintered in a nitrogen atmosphere for 5 hours to obtain lithium iron phosphate cathode material.

[0085] The solvent in step one is selected from tetrahydrofuran.

[0086] In step two, after adding phosphorus, lithium, and iron sources, the molar ratio of P:Li:Fe in the material is 1:1.12:1.

[0087] In step two, the phosphorus source is selected from lithium dihydrogen phosphate.

[0088] In step two, the lithium source is selected from lithium nitrate.

[0089] The iron source in step two is selected from ferrous oxalate.

[0090] In step two, the mass ratio of the material, grinding beads, and ethanol in the ball mill is 1:2:1.2.

[0091] In step two, the grinding aid accounts for 5% of the material mass percentage during ball milling.

[0092] The preparation method of the grinding aid in step two ball milling is as follows:

[0093] Add 5g of dilithium mercaptosuccinate, 30g of monoethanolamine mercaptoacetic acid, and 40g of ethylene glycol diglycidyl ether to a stirred tank. Stir continuously with N2 protection. Heat to 100℃, add 6g of 1,8-bis(dimethylaminonaphthalene), and react for 120 minutes to obtain a grinding aid.

[0094] The sintering temperature in step three is 900℃.

[0095] According to testing and analysis, the discharge capacity of the button battery assembled with the positive electrode material in this case is 158.2 mAh / g, and the initial efficiency is 97.3%.

[0096] Comparative Example 1

[0097] In this example, no grinding aid is added in step two, and the rest of the operation is consistent with that in Example 1.

[0098] According to testing and analysis, the discharge capacity of the button battery assembled with the positive electrode material in this case is 148.5 mAh / g, and the initial efficiency is 95.1%.

[0099] Comparative Example 2

[0100] In this example, lithium mercaptosuccinate is not added during the preparation of the grinding aid, and the rest of the operation is consistent with that in Example 1.

[0101] According to the test analysis, the discharge capacity of the button battery assembled with the positive electrode material in this case is 149.5 mAh / g, and the first efficiency is 95.2%.

[0102] Comparative Example 3

[0103] In this example, mercaptoacetic acid monoethanolamine is not added during the preparation of the grinding aid, and the rest of the operation is consistent with that in Example 1.

[0104] According to the test analysis, the discharge capacity of the button battery assembled with the positive electrode material in this case is 151.8 mAh / g, and the initial efficiency is 95.7%.

[0105] The present invention has been described above through specific embodiments and examples. However, these descriptions are merely illustrative and should not be construed as limiting the scope of protection of the present invention. Without departing from the spirit and scope of the present invention, those skilled in the art can make various improvements, modifications, or equivalent substitutions to the technical solutions and implementation methods of the present invention, and all such modifications and substitutions should fall within the scope of protection of the present invention.

Claims

1. A method for recycling and utilizing cathode materials from retired lithium iron phosphate batteries, characterized in that, Includes the following steps: Step 1: Crush 100-450 parts of the recycled retired lithium iron phosphate battery cathode material, add 1500-6000 parts of solvent to the fragmented material and stir and soak for 60-120 minutes. After filtration, wash and dry the filter residue with deionized water to obtain coarse powder of recycled cathode material. Step 2: Perform ICP testing on the coarse powder, add lithium source, iron source, phosphorus source, grinding aid and anhydrous ethanol, and perform wet ball milling for 8-12 hours. After ball milling, dry to obtain the precursor. Step 3: The precursor is sintered in a nitrogen atmosphere for 2-5 hours to obtain lithium iron phosphate cathode material; The preparation method of the grinding aid in step two ball milling is as follows: according to the weight parts, 2-5 parts of lithium mercaptosuccinate, 15-30 parts of mercaptoacetic acid monoethanolamine, and 20-40 parts of ethylene glycol diglycidyl ether are added to a stirred tank, continuously mechanically stirred and protected with N2, and after heating to 90-100℃, 3-6 parts of 1,8-bis(dimethylaminonaphthalene) are added, and the reaction is carried out for 60-120 minutes to obtain the grinding aid.

2. The method for recycling retired lithium iron phosphate battery cathode materials according to claim 1, characterized in that, The solvent in step one is selected from at least one of N-methylpyrrolidone, acetone, ethylene glycol, N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran.

3. The method for recycling retired lithium iron phosphate battery cathode materials according to claim 1, characterized in that, In step two, after adding phosphorus, lithium, and iron sources, the molar ratio of P:Li:Fe in the material is 1:1-1.12:0.92-1.

4. The method for recycling retired lithium iron phosphate battery cathode materials according to claim 1, characterized in that, In step two, the phosphorus source is selected from at least one of phosphoric acid, iron phosphate, lithium phosphate, and lithium dihydrogen phosphate.

5. A method for recycling retired lithium iron phosphate battery cathode materials according to claim 1, characterized in that, In step two, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, and lithium nitrate.

6. A method for recycling retired lithium iron phosphate battery cathode materials according to claim 1, characterized in that, In step two, the iron source is selected from at least one of ferric phosphate, ferrous sulfate, and ferrous oxalate.

7. A method for recycling retired lithium iron phosphate battery cathode materials according to claim 1, characterized in that, In step two, the mass ratio of material, grinding beads, and ethanol in the ball mill is 1:1.5-2:0.8-1.

2.

8. A method for recycling retired lithium iron phosphate battery cathode materials according to claim 1, characterized in that, In step two, the grinding aid accounts for 1-5% of the material mass during ball milling.

9. A method for recycling retired lithium iron phosphate battery cathode materials according to claim 1, characterized in that, The sintering temperature in step three is 650-900℃.