Recycling method of lithium iron phosphate pole piece waste

Abstract

The invention belongs to the technical field of material recycling, and particularly relates to a recycling method of lithium iron phosphate pole piece waste. The invention provides a recycling method of lithium iron phosphate positive pole piece waste, which comprises the steps of high-temperature treatment, crushing, screening, mixing with a surfactant aqueous solution, adding of aluminum removal liquid, reaction, solid-liquid separation, cleaning, drying, calcination and the like. According to the method, the aluminum foil is separated by adding the PVDF binder into the aluminum foil, so that the binder PVDF is decomposed to lose the binding force, and then the steps of nonionic surfactant treatment, organic acid soaking and the like are sequentially performed, so that direct contact between lithium iron phosphate particles and acid liquor can be reduced, lithium ions are prevented from being separated, the specific capacity of the material is not lost, and the overall recovery of the lithium iron phosphate is realized. And the recycled lithium iron phosphate material is directly used for preparing the lithium ion battery, so that the battery performance is good, and the application value of the lithium iron phosphate material can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of material recycling, and in particular relates to a method for recycling waste lithium iron phosphate pole pieces. Background Art

[0002] During the production process of lithium iron phosphate batteries, such as coating, rolling, slicing, and winding, a large amount of positive electrode scraps will be generated due to quality defects, foil breakage, and winding failure. The lithium iron phosphate material in the electrode scrap is only adhered to the aluminum foil together with the binder PVDF and conductive carbon black through the slurry coating process. It has not undergone chemical changes. The lithium iron phosphate itself has not undergone phase changes and there is no lithium loss. Recycling is relatively simple and does not require complex processing procedures.

[0003] Recycling of lithium iron phosphate cathode scraps typically involves mechanical crushing followed by separation of the lithium iron phosphate and the aluminum foil. However, during long-term production practice and experimentation, the inventors discovered that the resulting lithium iron phosphate powder often contained a high aluminum content, affecting the quality of the regenerated lithium iron phosphate. Therefore, improvements to the recycling method for lithium iron phosphate electrodes are needed.

[0004] Chinese patent publication number CN117401664A discloses a wet-dry regeneration method for lithium iron phosphate scraps. The method involves soaking the scraps in a temperature A to separate the active material from the aluminum foil. The aluminum foil material is stirred at a linear velocity A and filtered through a filter with a pore size A to obtain material A that passes through the filter. The material A is stirred at a linear velocity B and filtered through a filter with a pore size B to obtain material B that passes through the filter. Material B is dried in air to obtain the lithium iron phosphate active material. The lithium iron phosphate active material is crushed. The lithium iron phosphate active material is calcined in a carbon dioxide atmosphere to obtain regenerated lithium iron phosphate powder. The lithium iron phosphate powder is crushed to obtain the finished lithium iron phosphate product. The advantages of this method are that the scraps are not subjected to high-temperature treatment, the aluminum foil is tough, and it is not subjected to strong mechanical crushing, resulting in less aluminum metal impurities that are mixed into the positive electrode powder. However, the disadvantage of this method is that the sheet aluminum foil easily entrains the muddy positive electrode material during the soaking and stirring mode, preventing sufficient separation and making industrial application difficult.

[0005] Chinese patent publication number CN119797299A discloses a method for removing aluminum from lithium iron phosphate black powder, comprising the following steps: Step S1: discharging the lithium iron phosphate batteries to be recycled, followed by mechanical crushing and screening to remove the lithium iron phosphate black powder; Step S2: adding the lithium iron phosphate black powder to a first-stage leaching tank for leaching to obtain a first-stage leachate and a first-stage leach residue; Step S3: performing a second-stage leaching using acid leaching, followed by separation to obtain a second-stage leach residue and a second-stage leachate; Step S4: heating and precipitating the phosphorus, iron, and lithium leachate to obtain hydrated iron phosphate solid and a lithium-containing leachate; and Step S5: precipitating the lithium-containing leachate to obtain lithium carbonate solid. While this method removes aluminum, it destroys the structure of the lithium iron phosphate, resulting in iron phosphate rather than lithium iron phosphate, meaning that material regeneration is not achieved.

[0006] Chinese patent publication number CN119391972A discloses a method for removing aluminum and copper from ferrophosphorus slag. The ferrophosphorus slag raw material is ball-milled and screened; activation dispersion is performed: the milled and screened raw material is mixed with an activation and dispersing agent and activation dispersion is performed; aluminum and copper are removed: an acid leaching agent is mixed with the activated and dispersed material, acid leaching is performed, and solid-liquid separation is performed to obtain a ferrophosphorus slag low in aluminum and copper. The activation and dispersing agent contains a surfactant, and the acid leaching agent contains an organic acid and an oxidant. The inventors followed this patented method and removed aluminum impurities from lithium iron phosphate by immersing the material in an organic acid solution containing a surfactant. The results showed that the acid solution removed some lithium from the lithium iron phosphate, resulting in a lower specific capacity of the lithium iron phosphate after aluminum removal. Summary of the Invention

[0007] To address the challenges of the prior art, the present invention proposes a method for recycling waste lithium iron phosphate (LiFePO4) electrodes. This method involves subjecting the waste LiFePO4 cathode electrodes to high-temperature embrittlement in an inert atmosphere, decomposing the PVDF binder and losing its adhesive strength, thereby separating the aluminum foil. The process then sequentially involves treatment with a nonionic surfactant and soaking the material in an organic acid. This method reduces direct contact between the LiFePO4 particles and the acid solution, preventing lithium ion release and ensuring the material's specific capacity is not lost, thereby enabling the overall recovery of the LiFePO4. The recovered LiFePO4 material can be directly used to prepare lithium-ion batteries, resulting in excellent battery performance and enhanced application value.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for recycling lithium iron phosphate electrode waste comprises the following steps:

[0010] S1: The lithium iron phosphate electrode waste is subjected to high temperature treatment under a protective atmosphere to make it embrittled, and then crushed and sieved to remove the aluminum foil to obtain powder A;

[0011] S2: mixing the powder A from step S1 with a surfactant aqueous solution, stirring evenly to obtain slurry B;

[0012] S3: mixing slurry B with aluminum removal liquid, reacting, solid-liquid separation, washing, drying, and calcining the solid to obtain regenerated lithium iron phosphate.

[0013] Furthermore, in step S1, the high-temperature treatment temperature is 350-500°C, and the treatment time is 1-2h. The high-temperature treatment method adopted in this application can decompose the binder PVDF in the lithium iron phosphate electrode waste to lose its adhesive force, which is beneficial to the separation of lithium iron phosphate and aluminum foil. At the same time, the decomposition produces hydrogen fluoride and fluorocarbon compound gases, which are absorbed by alkaline solution for harmless treatment.

[0014] Furthermore, in step S2, the mixing ratio (mass ratio) of powder A to surfactant aqueous solution is 1:(1-2).

[0015] Furthermore, in step S2, the concentration of the surfactant in the surfactant aqueous solution is 1 to 5 wt%.

[0016] Furthermore, in step S2, the surfactant is preferably a non-ionic surfactant, and the non-ionic surfactant is preferably polyethylene glycol (PEG), which can be wrapped on the surface of lithium iron phosphate particles to reduce direct contact with acid, thereby preventing lithium ions from escaping.

[0017] Furthermore, the molecular weight of polyethylene glycol is preferably 400-600. PEG with a molecular weight that is too small has a poor encapsulation effect and cannot prevent lithium ion escape. PEG with a molecular weight that is too large will reduce the dissolution rate of aluminum impurities, resulting in insufficient aluminum removal. If a nonionic surfactant is not used, a small amount of lithium ions will be dissolved even under weakly acidic conditions, thereby reducing the specific capacity of the material. Polyethylene glycol also has a certain steric effect, preventing lithium iron phosphate from agglomerating and clogging the filter.

[0018] Furthermore, in step S3, the aluminum removal liquid is an organic acid aqueous solution containing an anionic surfactant.

[0019] Furthermore, in step S3, the weight ratio of slurry B to aluminum removal liquid is 10:(2-10).

[0020] Furthermore, in step S3, the organic acid should be a weaker acid, as a stronger acid will cause lithium ions to be released. In the present application, the organic acid is preferably at least one of acetic acid, formic acid, benzoic acid, and citric acid.

[0021] Furthermore, in step S3, the concentration of the organic acid in the organic acid aqueous solution is 5-20 wt%.

[0022] Furthermore, in step S3, the anionic surfactant is selected from at least one of sodium lauryl sulfate and sodium polyoxyethylene fatty alcohol ether sulfate, and its negatively charged anions can be adsorbed on the aluminum surface, destroying the dense aluminum oxide film, making hydrogen ions more easily accessible to metallic aluminum, and accelerating the dissolution of aluminum impurities.

[0023] Furthermore, in step S3, the concentration of the anionic surfactant in the organic acid aqueous solution is 0.2-0.5 wt%.

[0024] Furthermore, in step S3, the reaction is carried out at room temperature (25±5° C.) until no bubbles are generated, generally for 1-3 hours.

[0025] Furthermore, in step S3, the calcination is to solidify the structure of the lithium iron phosphate material, enhance stability, and increase the service life of the material.

[0026] Furthermore, in step S3, calcination is generally carried out at 600-800° C. for 2-6 hours under a protective atmosphere.

[0027] Furthermore, in order to further increase the specific capacity of the material, a small amount of lithium source, such as lithium oxalate, lithium acetate or lithium carbonate, may be added before calcination in step S3 to make the molar excess of lithium to phosphate ion 0.1-0.5%.

[0028] Furthermore, in the method for recycling waste lithium iron phosphate pole pieces, the protective atmosphere refers to a protective atmosphere formed by nitrogen, argon, etc.

[0029] Furthermore, based on a general inventive concept, the present invention also provides a lithium iron phosphate product prepared by the above method, specifically in the form of gray-black powder.

[0030] Furthermore, based on a general inventive concept, the present invention also provides the use of the prepared lithium iron phosphate product in the preparation of lithium-ion batteries.

[0031] Compared with the prior art, the advantages of the present invention are:

[0032] The present invention embrittles the lithium iron phosphate positive electrode sheet waste at high temperature under an inert atmosphere, causing the binder PVDF to decompose and lose its adhesive force, which is beneficial for the separation of lithium iron phosphate and aluminum foil during subsequent crushing and screening. Then, steps such as non-ionic surfactant treatment and organic acid soaking are carried out in sequence, which can reduce the direct contact between the lithium iron phosphate particles and the acid solution, avoid the escape of lithium ions, and ensure that the specific capacity of the material is not lost. The anionic surfactant added together with the organic acid can accelerate the dissolution of aluminum impurities (including Al and Al2O3) and improve the generation efficiency. The entire recycling and regeneration process of the present invention is simple and efficient, and is suitable for industrial application. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described in detail below with reference to specific embodiments. However, it should be clear to those skilled in the art that the embodiments described below are only some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0034] The experimental methods in the following examples without specifying specific conditions were generally carried out under conventional conditions or conditions recommended by the manufacturers, and the raw materials and reagents used were conventional commercially available products unless otherwise specified.

[0035] The lithium iron phosphate positive electrode scraps (lithium iron phosphate electrode scraps) used in the examples were from a domestic lithium battery factory. The current collector of the electrode was aluminum foil, and the theoretical content of lithium iron phosphate was 94.7 wt%.

[0036] In the following examples and comparative examples, room temperature or normal temperature refers to 25±5°C.

[0037] Example 1

[0038] A method for recycling lithium iron phosphate electrode waste, the specific steps are as follows:

[0039] S1: 3000 g of lithium iron phosphate electrode waste was treated at 350°C for 2 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2867 g of powder A;

[0040] S2: Powder A from step S1 was mixed with 2900 g of a 3 wt% aqueous solution of PEG-400 (polyethylene glycol with an average molecular weight of 400) and stirred to obtain slurry B (5767 g);

[0041] S3: Slurry B from step S2 was mixed with 2150 g of an aqueous solution containing 0.4 wt% SDS (sodium dodecyl sulfate) and 12 wt% acetic acid, reacted at room temperature for 2 h, solid-liquid separation was performed, the solid was washed and dried, and calcined at 700 ° C for 2.5 h under nitrogen atmosphere to obtain 2815 g of regenerated lithium iron phosphate.

[0042] Example 2

[0043] A method for recycling lithium iron phosphate electrode waste, the specific steps are as follows:

[0044] S1: 3000 g of lithium iron phosphate electrode waste was treated at 400°C for 1.5 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2880 g of powder A;

[0045] S2: Powder A from step S1 was mixed with 5000 g of a 2 wt% aqueous solution of PEG-600 (polyethylene glycol with an average molecular weight of 600), and stirred to obtain slurry B (7880 g);

[0046] S3: Slurry B from step S2 was mixed with 1960 g of an aqueous solution containing 0.5 wt% SDS (sodium dodecyl sulfate) and 20 wt% acetic acid, reacted at room temperature for 1 h, solid-liquid separation was performed, the solid was washed and dried, and calcined at 750°C for 2 h under nitrogen atmosphere to obtain 2810 g of regenerated lithium iron phosphate.

[0047] Example 3

[0048] A method for recycling lithium iron phosphate electrode waste, the specific steps are as follows:

[0049] S1: 3000 g of lithium iron phosphate electrode waste was treated at 500°C for 1 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2858 g of powder A;

[0050] S2: Powder A from step S1 was mixed with 3800 g of a 5 wt% aqueous solution of PEG-500 (polyethylene glycol with an average molecular weight of 500), and stirred to obtain slurry B (6658 g);

[0051] S3: Slurry B from step S2 was mixed with 2800 g of an aqueous solution containing 0.2 wt% SDS (sodium dodecyl sulfate) and 6 wt% acetic acid, reacted at room temperature for 3 h, solid-liquid separation was performed, the solid was washed and dried, and calcined at 600 ° C for 3 h under nitrogen atmosphere to obtain 2812 g of regenerated lithium iron phosphate.

[0052] Example 4

[0053] A method for recycling lithium iron phosphate electrode waste, the specific steps are as follows:

[0054] S1: 3000 g of lithium iron phosphate electrode waste was treated at 450°C for 1 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2865 g of powder A;

[0055] S2: Powder A from step S1 was mixed with 3000 g of a 4 wt% aqueous solution of PEG-500 (polyethylene glycol with an average molecular weight of 500), and stirred to obtain slurry B (5865 g);

[0056] S3: Slurry B from step S2 was mixed with 1860 g of an aqueous solution containing 0.3 wt% AES (sodium fatty alcohol polyoxyethylene ether sulfate) and 10 wt% formic acid, reacted at room temperature for 3 h, and the solid-liquid was separated. The solid was washed and dried, and calcined at 600°C for 3 h under nitrogen atmosphere to obtain 2798 g of regenerated lithium iron phosphate.

[0057] Example 5

[0058] A method for recycling lithium iron phosphate electrode waste, the specific steps are as follows:

[0059] S1: 3000 g of lithium iron phosphate electrode waste was treated at 450°C for 1 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2870 g of powder A;

[0060] S2: Powder A from step S1 was mixed with 3000 g of a 4 wt% aqueous solution of PEG-500 (polyethylene glycol with an average molecular weight of 500), and stirred to obtain slurry B (5870 g).

[0061] S3: Slurry B from step S2 was mixed with 3900 g of an aqueous solution containing 0.3 wt% SDS and 15 wt% benzoic acid, reacted at room temperature for 3 h, solid-liquid separation was performed, the solid was washed and dried, and calcined at 600°C for 3 h under nitrogen atmosphere to obtain 2796 g of regenerated lithium iron phosphate.

[0062] Example 6

[0063] A method for recycling lithium iron phosphate electrode waste, the specific steps are as follows:

[0064] S1: 3000 g of lithium iron phosphate electrode waste was treated at 350°C for 2 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2854 g of powder A;

[0065] S2: Powder A from step S1 was mixed with 2900 g of a 3 wt% aqueous solution of PEG-400 (polyethylene glycol with an average molecular weight of 400), and stirred to obtain slurry B (5754 g);

[0066] S3: Slurry B from step S2 was mixed with 1050 g of an aqueous solution containing 0.4 wt% SDS and 12 wt% acetic acid, and the mixture was reacted at room temperature for 2 h. The solid-liquid separation was performed, the solid was washed with water and dried, 81 g of lithium acetate was added, and the mixture was calcined at 700°C for 2.5 h under nitrogen atmosphere to obtain 2816 g of regenerated lithium iron phosphate.

[0067] Comparative Example 1

[0068] A method for recycling lithium iron phosphate electrode waste is basically the same as Example 1, but does not use a non-ionic surfactant. The specific steps are as follows:

[0069] S1: 3000 g of lithium iron phosphate electrode waste was treated at 350°C for 2 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2864 g of powder A;

[0070] S2: Powder A from step S1 was mixed with 2900 g of pure water and stirred to obtain slurry B (5764 g);

[0071] S3: Slurry B from step S2 was mixed with 2150 g of an aqueous solution containing 0.4 wt% SDS and 12 wt% acetic acid, reacted at room temperature for 2 h, solid-liquid separation was performed, the solid was washed and dried, and calcined at 700°C for 2.5 h under nitrogen atmosphere to obtain 2773 g of regenerated lithium iron phosphate.

[0072] Comparative Example 2

[0073] A method for recycling lithium iron phosphate electrode waste is basically the same as Example 1, but does not use anionic surfactants. The specific steps are as follows:

[0074] S1: 3000 g of lithium iron phosphate electrode waste was treated at 350°C for 2 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2865 g of powder A;

[0075] S2: Powder A from step S1 was mixed with 2900 g of a 3 wt% PEG-400 aqueous solution and stirred to obtain slurry B (5765 g);

[0076] S3: Slurry B from step S2 was mixed with 2150 g of an aqueous solution containing only 12 wt% acetic acid, reacted at room temperature for 2 h, solid-liquid separation was performed, the solid was washed and dried, and calcined at 700°C for 2.5 h under nitrogen atmosphere to obtain 2815 g of regenerated lithium iron phosphate.

[0077] Comparative Example 3

[0078] A method for recycling lithium iron phosphate electrode waste is basically the same as Example 1, but a non-ionic surfactant is used together with the aluminum removal liquid. The specific steps are as follows:

[0079] S1: 3000 g of lithium iron phosphate electrode waste was treated at 350°C for 2 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2864 g of powder A;

[0080] S2: Powder A from step S1 was mixed with 5050 g of an aqueous solution containing 3 wt% PEG-400, 0.4 wt% SDS, and 12 wt% acetic acid, and the mixture was reacted at room temperature for 2 h. The solid-liquid separation was performed, the solid was washed with water, dried, and calcined at 700°C for 2.5 h under nitrogen atmosphere to obtain 2780 g of regenerated lithium iron phosphate.

[0081] Comparative Example 4

[0082] A method for recycling lithium iron phosphate electrode waste is basically the same as Example 1, except that the nonionic surfactant is replaced by a cationic surfactant. The specific steps are as follows:

[0083] S1: 3000 g of lithium iron phosphate electrode waste was treated at 350°C for 2 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2864 g of powder A;

[0084] S2: Powder A from step S1 was mixed with 2900 g of a 3 wt% DTAC (dodecyltrimethylammonium chloride) aqueous solution and stirred to obtain slurry B (5764 g);

[0085] S3: Slurry B from step S2 was mixed with 2150 g of an aqueous solution containing 0.4 wt% SDS and 12 wt% acetic acid, reacted at room temperature for 2 h, solid-liquid separation was performed, the solid was washed and dried, and calcined at 700°C for 2.5 h under nitrogen atmosphere to obtain 2776 g of regenerated lithium iron phosphate.

[0086] Comparative Example 5

[0087] A method for recycling lithium iron phosphate electrode waste is basically the same as Example 1, except that the nonionic surfactant PEG-400 is replaced by PEG-200. The specific steps are as follows:

[0088] S1: 3000 g of lithium iron phosphate electrode waste was treated at 350°C for 2 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2866 g of powder A;

[0089] S2: Powder A from step S1 was mixed with 2900 g of a 3 wt% PEG-200 aqueous solution and stirred to obtain slurry B (5766 g);

[0090] S3: Slurry B from step S2 was mixed with 2150 g of an aqueous solution containing 0.4 wt% SDS and 12 wt% acetic acid, reacted at room temperature for 2 h, solid-liquid separation was performed, the solid was washed and dried, and calcined at 700°C for 2.5 h under nitrogen atmosphere to obtain 2800 g of regenerated lithium iron phosphate.

[0091] Comparative Example 6

[0092] A method for recycling lithium iron phosphate electrode waste is basically the same as Example 1, except that the nonionic surfactant PEG-400 is replaced by PEG-800. The specific steps are as follows:

[0093] S1: 3000 g of lithium iron phosphate electrode waste was treated at 350°C for 2 h under nitrogen atmosphere, then mechanically crushed and sieved (through a 50-100 mesh sieve) to remove the aluminum foil to obtain 2866 g of powder A;

[0094] S2: Powder A from step S1 was mixed with 2900 g of a 3 wt% PEG-800 aqueous solution and stirred to obtain slurry B (5766 g);

[0095] S3: Slurry B from step S2 was mixed with 2150 g of an aqueous solution containing 0.4 wt% SDS and 12 wt% acetic acid, reacted at room temperature for 2 h, and the solid-liquid was separated. The solid was washed and dried, and calcined at 700°C for 2.5 h under nitrogen atmosphere to obtain 2818 g of regenerated lithium iron phosphate.

[0096] Performance Testing

[0097] The lithium iron phosphate products of the above examples and comparative examples were tested for aluminum content before and after aluminum removal using the ICP-MS method (referring to GB / T 20899.15-2023), that is, the aluminum content of powder A and regenerated lithium iron phosphate was tested, and the obtained regenerated lithium iron phosphate was used to prepare button batteries for testing specific capacity and cycle performance. The results are listed in Table 1.

[0098] Specifically, during the test, regenerated lithium iron phosphate was mixed with a binder (polyvinylidene fluoride (PVDF)) and a solvent (N-methylpyrrolidone (NMP)) to form a slurry. This slurry was then coated on aluminum foil, dried, rolled, and sliced ​​to form a positive electrode sheet. The lithium sheet served as the negative electrode and was assembled with a separator and electrolyte into a CR2032 button cell. The voltage ranged from 2.0 to 3.65V. The specific capacity was tested at 0.2C charge and discharge, and the cycle retention was tested at 0.5C charge and discharge for 100 cycles. Comparative Examples 1, 3, 4, and 5 had lower initial specific capacities, so their cycling performance was not tested.

[0099] Table 1 Lithium iron phosphate test results

[0100]

[0101] As can be seen from the data in Table 1, the aluminum content of the lithium iron phosphate after aluminum removal in Examples 1-6 has dropped to a very low level (<300ppm). Comparative Example 1 does not use a nonionic surfactant, Comparative Example 3 adds the nonionic surfactant later, Comparative Example 4 replaces the nonionic surfactant with a cationic surfactant, and Comparative Example 5 uses a nonionic surfactant with a smaller molecular weight. None of these can prevent lithium ion elution, resulting in a lower specific capacity of the regenerated lithium iron phosphate. Comparative Example 2 does not use anionic surfactants, which slows the dissolution of aluminum impurities. Aluminum removal is not complete within the same timeframe, resulting in a higher aluminum content in the regenerated lithium iron phosphate. Comparative Example 6 uses a nonionic surfactant with a larger molecular weight, which prevents lithium elution while suppressing aluminum removal efficiency, resulting in inadequate aluminum removal and a higher aluminum content in the regenerated lithium iron phosphate. In Example 6, a lithium source is added during calcination, which improves the specific capacity of the regenerated product.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for recycling lithium iron phosphate pole piece waste, characterized in that: The following steps are involved: S1: The lithium iron phosphate electrode waste is treated at high temperature under a protective atmosphere, and then crushed and sieved to remove the aluminum foil to obtain powder A; S2: mixing the powder A from step S1 with a surfactant aqueous solution, stirring evenly to obtain slurry B; S3: mixing slurry B with aluminum removal liquid, reacting, solid-liquid separation, washing, drying, and calcining the solid to obtain regenerated lithium iron phosphate.

2. The method according to claim 1, wherein In step S1, the high temperature treatment temperature is 350-500° C., and the treatment time is 1-2 hours.

3. The method according to claim 1, characterized in that In step S2, the mass ratio of powder A to surfactant aqueous solution is 1:(1-2); the concentration of surfactant in the surfactant aqueous solution is 1-5 wt%.

4. The method according to claim 3, characterized in that In step S2, the surfactant is a non-ionic surfactant, and the non-ionic surfactant is polyethylene glycol with an average molecular weight of 400-600.

5. The method according to claim 1, wherein In step S3, the aluminum removal liquid is an organic acid aqueous solution containing an anionic surfactant; and the weight ratio of slurry B to the aluminum removal liquid is 10:(2-10).

6. The method according to claim 5, characterized in that In step S3, the organic acid is at least one of acetic acid, formic acid, benzoic acid, and citric acid, and the concentration of the organic acid in the organic acid aqueous solution is 5-20 wt %; The anionic surfactant is at least one of sodium lauryl sulfate and sodium fatty alcohol polyoxyethylene ether sulfate, and the concentration of the anionic surfactant in the organic acid aqueous solution is 0.2-0.5wt%.

7. The method according to claim 1, characterized in that In step S3, the reaction is carried out at room temperature and the reaction time is 1-3 hours.

8. The method according to claim 1, characterized in that In step S3, the calcination is carried out at 600-800° C. for 2-6 hours.

9. A lithium iron phosphate product prepared by the method according to any one of claims 1 to 8.

10. Use of the lithium iron phosphate product according to claim 9 in the preparation of lithium ion batteries.

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