A selective flocculation flotation separation method for positive and negative electrode materials of lithium iron phosphate batteries

Abstract

This invention relates to a selective flocculation flotation separation method for positive and negative electrode materials of lithium iron phosphate batteries, belonging to the field of waste lithium battery recycling technology. The method includes: discharging and disassembling a lithium iron phosphate battery to obtain copper foil containing negative electrode material and aluminum foil containing positive electrode material; mixing the positive electrode aluminum foil and negative electrode copper foil in a specific ratio, coarsely crushing, performing a first wet sieve, fine crushing, a second wet sieve, and then filtering and drying to obtain a mixed positive and negative electrode powder of the lithium battery; mixing the mixed positive and negative electrode powder with water to obtain a flotation slurry of a certain concentration; stirring and adjusting the flotation slurry to obtain a first slurry; adding polyvinylpyrrolidone to the first slurry and stirring to obtain a second slurry; adding polyacrylic acid to the second slurry and stirring to obtain a third slurry; adding a collector to the third slurry, stirring, adding a foaming agent, stirring, aerating and skimming, and recovering the foam product (negative electrode material) and the product in the tank (positive electrode material).

Description

Technical Field

[0001] This invention relates to the field of waste lithium battery recycling technology, and in particular to a selective flocculation flotation separation method for positive and negative electrode materials of lithium iron phosphate batteries. Background Technology

[0002] Lithium-ion batteries are widely used in mobile electronic devices, new energy vehicles, and energy storage due to their superior performance, including safety, high energy density, and long lifespan. With the rapid growth of the national economy, the consumption of lithium batteries continues to increase. However, the lifespan of a typical lithium battery is only 3-5 years. As these batteries exceed their lifespan or are replaced with new electronic devices, the amount of discarded lithium batteries increases accordingly. The recycling of discarded lithium batteries is a significant technological challenge and an urgent problem that needs to be solved. Discarded lithium batteries contain large amounts of toxic chemicals and heavy metals. If these toxic chemicals are absorbed into the soil or leak into water and into the surrounding environment, they can potentially have harmful effects on the local ecosystem and, in severe cases, even pose serious threats to human health. From both an environmental protection and resource recycling perspective, the economic and environmental benefits of properly recycling discarded lithium batteries are undeniable.

[0003] Currently, recycling technologies for spent lithium batteries are mainly divided into three categories: hydrometallurgy, pyrometallurgy, and direct recycling. Compared to hydrometallurgy and pyrometallurgy, direct recycling is the most sustainable method with the lowest energy demand and the least emissions and pollution. The metal oxides in spent lithium batteries are mostly hydrophilic, while the negative electrode material (graphite) is naturally hydrophobic. In principle, the difference in wettability between the two can be used to achieve flotation separation. Before flotation, the separated electrode material needs to undergo certain pretreatment to remove the polyvinylidene fluoride (PVDF) coating from the electrode powder surface, thereby releasing a fresh surface with different wettability.

[0004] The release of electrode materials can be achieved through mechanical processing, chemical dissolution, and thermal treatment. Most chemical solvents developed to date are not environmentally friendly; while thermal treatment can control the recovery rate and grade of both positive and negative electrode materials at a high level, it easily generates harmful gases that pollute the environment. Inert gases must be continuously introduced during thermal treatment to isolate oxygen, and subsequent mechanical processing is still required to remove the electrode powder from the electrode sheet, resulting in high energy consumption and cost. Compared to chemical dissolution and thermal treatment, mechanical processing is cheaper, cleaner, and more environmentally friendly. Furthermore, this method has minimal impact on the properties of the electrode materials, which is beneficial for subsequent repair and regeneration. To remove PVDF-released electrode materials as much as possible, the particle size of the active material after mechanical processing is very fine. However, excessively fine positive electrode material particles are easily carried into the foam product (mainly negative electrode graphite) during flotation. In addition, the spontaneous hydrophobic flocculation of negative electrode graphite particles can encapsulate the positive electrode material within its flocs. These two factors combined lead to low separation accuracy of the positive and negative electrode materials during flotation; multiple separation processes are required to ensure the content and recovery rate of the positive and negative electrode materials. Currently, there is still a lack of an efficient, simple and convenient, low-cost, and environmentally friendly method for the flotation recycling of waste lithium batteries. Summary of the Invention

[0005] Based on the above analysis, the embodiments of the present invention aim to provide a selective flocculation flotation separation method for positive and negative electrode materials of lithium iron phosphate batteries, which at least solves one of the following technical problems: 1. In the process of peeling off electrode materials using existing mechanical processing methods, the electrode material particles are very fine. During the flotation process, the spontaneous hydrophobic flocculation of the negative electrode graphite material encapsulates the positive electrode material within its flocs, causing the positive electrode material to enter the foam product, resulting in a decrease in the recovery rate of LiFePO4 in the positive electrode material and a decrease in the graphite content in the negative electrode material; 2. In the process of peeling off electrode materials using existing mechanical processing methods, the electrode material particles are very fine. During the flotation process, the positive electrode material is easily carried into the foam product by the water flow, resulting in a decrease in the recovery rate of LiFePO4 in the positive electrode material and a decrease in the graphite content in the negative electrode material; 3. Existing methods that use mechanical processing to coat the surface of the electrode powder with polyvinylidene fluoride (PVDF) before flotation require multiple separations to ensure the content and recovery rate of the positive and negative electrode materials.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides a method for selective flocculation and flotation separation of positive and negative electrode materials in lithium iron phosphate batteries, comprising the following steps:

[0008] Step 1: Discharge the lithium iron phosphate battery, and disassemble the discharged lithium battery to obtain copper foil containing negative electrode material and aluminum foil containing positive electrode material.

[0009] Step 2: Mix the positive electrode aluminum foil and the negative electrode copper foil in a certain ratio, and then coarsely crush them, perform a first wet sieve, fine crush them, perform a second wet sieve, filter and dry them to obtain the mixed electrode powder of positive and negative electrodes for lithium batteries.

[0010] Step 3: Mix the positive and negative electrode powders of lithium battery with water to obtain a flotation slurry of a certain concentration. Stir and adjust the flotation slurry to obtain the first slurry.

[0011] Step 4: Add polyvinylpyrrolidone to the first slurry and continue stirring to adjust the slurry, thus obtaining the second slurry;

[0012] Step 5: Add polyacrylic acid to the second slurry, stir and adjust the slurry to obtain the third slurry;

[0013] Step 6: Add the collector to the third slurry, stir, add the foaming agent, stir again, aerate and scrape the foam, and recover the foam product (negative electrode material) and the product in the tank (positive electrode material).

[0014] Furthermore, in step 2, the ratio of the number of positive electrode aluminum foil sheets to the number of negative electrode copper foil sheets is 1:1, the coarse crushing time is 10-30s, and the fine crushing time is 10-20min.

[0015] Furthermore, in step 2, the mesh size of the first wet sieve is 0.8-1.2 mm, and the mesh size of the second wet sieve is 0.074-0.078 mm.

[0016] Furthermore, in step 3, the mass concentration of the first slurry is 4-10%.

[0017] Furthermore, in step 3, the stirring speed is 1400-1800 rpm and the stirring time is 3-4 min.

[0018] Furthermore, in step 4, the amount of polyvinylpyrrolidone used is 20-40 g / t.

[0019] Furthermore, in step 4, the stirring speed is 1400-1800 rpm and the stirring time is 2-3 min.

[0020] Furthermore, in step 5, the amount of polyacrylic acid used is 200-300 g / t.

[0021] Furthermore, in step 5, the stirring speed is 1400-1800 rpm and the stirring time is 2-3 min.

[0022] Furthermore, in step 6, the amount of the collector is 200-400 g / t, and the amount of the foaming agent is 100-200 g / t.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. This invention removes the polyvinylidene fluoride (PVDF) coating from the surface of the electrode powder through a two-stage crushing and wet screening mechanical treatment method. Then, before adding polyacrylic acid (PAA) to flocculate the positive electrode material, polyvinylpyrrolidone (PVP) is added to modify the surface of the negative electrode graphite material. PVP adsorbs on the graphite surface, making the graphite more dispersed. This not only hinders the spontaneous hydrophobic flocculation of graphite, but also inhibits the flocculation effect of the subsequently added polyacrylic acid (PAA) on the negative electrode material. In the flotation process, PVP is added first, followed by PAA. PAA only flocculates the positive electrode material of lithium iron phosphate batteries, thereby reducing the entrainment of excessive fine-particle positive electrode material. Therefore, only one roughing process is needed to ensure the content and recovery rate of LiFePO4 in the positive electrode material (in-cell product) and the negative electrode material (foam product).

[0025] 2. The method of this invention can obtain the mixed electrode material for flotation separation using only two stages of crushing and wet screening. Compared with mixed electrode material obtained by flotation separation through heat treatment, it has less pollution and lower cost. This invention uses waste lithium batteries to directly prepare mixed electrode powder for flotation, without the need to adjust the pulp pH. Flotation can be carried out at the natural pH value, and the experimental process is simple. Through flotation, not only can a high content of positive electrode material be obtained, but also a high content of negative electrode graphite material can be obtained, which is beneficial for the recycling of positive and negative electrode materials and can make full use of waste lithium batteries.

[0026] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0028] Figure 1 This is a flowchart of the selective flocculation and flotation separation method for positive and negative electrode materials of lithium iron phosphate batteries according to the present invention.

[0029] Figure 2 The particle size distribution diagrams of the cathode material flocs obtained in Example 1 and the comparative example of the present invention are shown.

[0030] Figure 3The particle size distribution diagrams of the anode material flocs obtained in Example 1 and the comparative example of the present invention are shown. Detailed Implementation

[0031] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0032] This invention provides a method for selective flocculation and flotation separation of positive and negative electrode materials in lithium iron phosphate batteries, comprising the following steps:

[0033] Step 1: Discharge the lithium iron phosphate battery, and disassemble the discharged lithium battery to obtain copper foil containing negative electrode material and aluminum foil containing positive electrode material.

[0034] Step 2: Mix the positive electrode aluminum foil and the negative electrode copper foil in a certain ratio, and then coarsely crush them, perform a first wet sieve, fine crush them, perform a second wet sieve, filter and dry them to obtain the mixed electrode powder of positive and negative electrodes for lithium batteries.

[0035] Step 3: Mix the positive and negative electrode powders of lithium battery with water to obtain a flotation slurry of a certain concentration. Stir and adjust the flotation slurry to obtain the first slurry.

[0036] Step 4: Add polyvinylpyrrolidone to the first slurry and continue stirring to adjust the slurry, thus obtaining the second slurry;

[0037] Step 5: Add polyacrylic acid to the second slurry, stir and adjust the slurry to obtain the third slurry;

[0038] Step 6: Add the collector to the third slurry, stir, add the foaming agent, stir again, aerate and scrape the foam, and recover the foam product (negative electrode material) and the product in the tank (positive electrode material).

[0039] When recovering lithium iron phosphate batteries by flotation, the dissociated electrode materials need to undergo pretreatment before flotation to remove the polyvinylidene fluoride (PVDF) coating on the electrode powder surface, thereby releasing a fresh surface with different wettability. The release of electrode materials can be achieved through mechanical processing, chemical dissolution, and thermal treatment. Most chemical solvents developed to date are not environmentally friendly. While thermal treatment can control the recovery rate and grade of both positive and negative electrode materials at a high level, it easily generates harmful gases that pollute the environment and produces hydrophobic pyrolysis carbon residues on the surface of the positive electrode material, which need to be removed by ultrasound. Furthermore, the thermal treatment process requires continuous introduction of inert gas to isolate oxygen, and subsequent mechanical processing is still needed to remove the electrode powder from the electrode sheet, resulting in high energy consumption and cost. Compared to chemical dissolution and thermal treatment, mechanical processing is cheaper, cleaner, and more environmentally friendly. Existing methods involve mechanically coating electrode powder with polyvinylidene fluoride (PVDF) followed by flotation. After two or more flotations, the positive electrode material content can reach over 95%, but the recovery rate is generally only around 50%; the negative electrode material content can reach over 80%, with a recovery rate of over 70%. Compared to existing technologies, the method of this invention is a single-stage separation, requiring only one coarse separation step. After this coarse separation, the LiFePO4 content is over 69%, with a recovery rate of over 79%, and the graphite negative electrode content reaches over 83%, with a recovery rate of over 73%. The method of this invention, with only one coarse separation, achieves a higher overall content and recovery rate of positive and negative electrode materials for lithium iron phosphate batteries than existing methods that rely on mechanically coating electrode powder with PVDF followed by flotation to recover the positive and negative electrode materials of lithium batteries.

[0040] Specifically, in step 2, the positive electrode aluminum foil and the negative electrode copper foil are mixed in a 1:1 ratio and added to a crusher for coarse crushing for 10-30 seconds. The mixture is then subjected to a first wet sieve through a 0.8-1.2 mm sieve to separate aluminum and copper foil particles larger than 0.8-1.2 mm, which are then removed. The undersized portion is returned to the crusher for fine crushing for 10-20 minutes, followed by a second wet sieve through a 0.072-0.078 mm sieve. The sieve is used to filter and dry the undersize portion, collecting the positive and negative electrode powder with a particle size of less than 0.072-0.078 mm, thus obtaining the lithium battery positive and negative electrode powder. It should be noted that the electrode powder itself is already very fine; the two wet sieving processes, breaking it down to less than 0.072-0.078 mm, are to break the polyvinylidene fluoride (PVDF) coating on the particle surface, releasing the electrode material and exposing fresh surfaces with different hydrophilic and hydrophobic properties, which is beneficial for subsequent interaction with reagents. Preferably, the mesh size of the first wet sieving is 1.0-1.2 mm, and the mesh size of the second wet sieving is 0.074-0.078 mm.

[0041] Specifically, in step 3, the positive and negative electrode powders of the lithium battery are mixed with water to obtain a flotation slurry of a certain concentration. The flotation slurry is added to the flotation cell, and the flotation machine is started to stir and adjust the slurry to obtain the first slurry. The mass concentration of the flotation slurry is 4-10%, the stirring speed is 1400-1800 rpm, and the stirring time is 3-4 min.

[0042] Specifically, in step 4, polyvinylpyrrolidone (PVP) is added to the first slurry obtained after stirring and preparing the slurry in step 3, at a dosage of 20-40 g / t, with a stirring speed of 1400-1800 rpm and a stirring time of 2-3 min, to obtain the second slurry.

[0043] In step 5, polyacrylic acid (PAA) is added to the second slurry obtained in step 4 at a dosage of 200-300 g / t, the stirring speed is 1400-1800 rpm, and the stirring time is 2-3 min to obtain the third slurry.

[0044] It should be noted that in step 3, the lithium battery positive and negative electrode powder slurry is treated by strong stirring and slurry preparation. The stirring speed is 1400-1800 r / min and the stirring time is 3-4 min, so that the positive and negative electrode materials are fully dispersed. In step 4, polyvinylpyrrolidone (PVP) is added to the slurry after stirring and conditioning in step 3. PVP acts as a dispersant to modify the surface of the negative electrode graphite material. PVP adsorbs onto the surface of the negative electrode graphite material, making it more dispersed. This not only hinders the spontaneous hydrophobic flocculation of the negative electrode graphite material but also suppresses the flocculation effect of the subsequently added polyacrylic acid (PAA, flocculant) on the negative electrode graphite material, thus improving the flocculation selectivity of PAA. By adding PVP first and then adding PAA in step 5, PAA only flocculates the positive electrode material of the lithium iron phosphate battery, thereby reducing the entrainment loss of fine positive electrode material, improving the flotation separation efficiency of the positive and negative electrode materials, and creating conditions for further purification or regeneration repair of the electrode materials.

[0045] Specifically, in step 6, the collector is kerosene, with a dosage of 200-400 g / t and a stirring time of 2-3 min; the foaming agent is methyl isobutyl methanol (MIBC), with a dosage of 100-200 g / t and a stirring time of 2-3 min; the aeration rate is 0.02-0.08 m³ / t. 3 / h, the foaming time is 3-4min; the foam product is the negative electrode material (graphite), and the product in the tank is the positive electrode material (LiFePO4).

[0046] Example 1

[0047] Step 1: Discharge the lithium iron phosphate battery, and disassemble the discharged lithium battery to obtain copper foil containing negative electrode material and aluminum foil containing positive electrode material.

[0048] Step 2: Mix the positive electrode aluminum foil and the negative electrode copper foil at a ratio of 1:1, add them to the crusher for coarse crushing for 15 seconds, and then perform a first wet sieve through a 1.0 mm sieve to separate aluminum foil and copper foil particles with a pore size greater than 1.0 mm and remove them; return the sieved portion to the crusher for fine crushing for 10 minutes, and then perform a second wet sieve through a 0.074 mm sieve. Filter and dry the sieved portion to collect the positive and negative electrode material mixture with a particle size of less than 0.074 mm, thus obtaining lithium battery positive and negative electrode mixed electrode powder;

[0049] Step 3: Mix the positive and negative electrode powders of lithium battery with water to obtain a flotation slurry with a mass concentration of 4%. Add the flotation slurry to the flotation cell, start the flotation machine, and stir for 3 minutes at a stirring speed of 1800 rpm. The flotation machine used is a 100 mL XFGC type laboratory aerated hanging tank flotation machine to obtain the first slurry.

[0050] Step 4: Add 25g / t of polyvinylpyrrolidone (PVP) to the first slurry and stir at 1800rpm for 2min to obtain the second slurry;

[0051] Step 5: Add 250g / t of polyacrylic acid (PAA) to the second slurry and stir at 1800rpm for 2min to obtain the third slurry;

[0052] Step 6: Add 300g / t of collector kerosene to the third slurry and stir at 1800rpm for 2 minutes; then add MIBC foaming agent and stir at 1800rpm for 2 minutes, followed by aeration and foam removal, with an aeration rate of 0.04m³. 3 / h, the foaming time is 3min, to obtain foam product (negative electrode material) and product in tank (positive electrode material).

[0053] Example 2

[0054] In this embodiment, 20 g / t of polyvinylpyrrolidone (PVP) was added to the slurry after stirring and conditioning in step 3, and the other steps and process parameters were the same as in Example 1.

[0055] Example 3

[0056] In this embodiment, 30 g / t of polyvinylpyrrolidone (PVP) was added to the slurry after stirring and conditioning in step 3, and the other steps and process parameters were the same as in Example 1.

[0057] Example 4

[0058] In this embodiment, the slurry concentration is adjusted to 10% in step 3, and the other steps and process parameters are the same as in embodiment 1.

[0059] Example 5

[0060] In this embodiment, the stirring rate is adjusted to 1400 rpm in step 3, and the other steps and process parameters are the same as in embodiment 1.

[0061] Example 6

[0062] In this embodiment, in step 5, 200 g / t of polyacrylic acid (PAA) is added to the second slurry, and the other steps and process parameters are the same as in Example 1.

[0063] Comparative Example 1

[0064] The source of the waste lithium iron phosphate batteries in this comparative example is the same as that in Example 1. PVP and PAA are not added during the flotation process. Collectors and frothers are added directly to the first slurry obtained after stirring and adjusting the slurry in step 3, following steps 1-3 of Example 1, and step 6 in Example 1 is executed.

[0065] Comparative Example 2

[0066] The source of the waste lithium iron phosphate batteries in this comparative example is the same as that in Example 1. PAA is not added during the flotation process. Collectors and frothers are directly added to the second slurry obtained in step 4 according to steps 1-4 of Example 1, and step 6 in Example 1 is executed.

[0067] Comparative Example 3

[0068] The source of the waste lithium iron phosphate batteries in this comparative example is the same as that in Example 1. PVP is not added during the flotation process. PAA, collector and frother are directly added to the first slurry after stirring and adjusting in step 3, following steps 1-3 of Example 1. Steps 5 and 6 of Example 1 are then performed.

[0069] Comparative Example 4

[0070] In this embodiment, 125 g / t of polyvinylpyrrolidone (PVP) was added to the first slurry obtained after stirring and adjusting the slurry in step 3. Other steps and process parameters were the same as in Example 1.

[0071] Table 1. Flotation process results of the examples and comparative examples.

[0072]

[0073]

[0074] As can be seen from the data in Table 1, the selective flocculation and flotation separation of positive and negative electrode materials of lithium iron phosphate batteries using the method of the present invention resulted in the following: the content of LiFePO4 in the positive electrode after flotation recovery was 68.77%-72.08%, with a recovery rate of 79.60%-83.59%; the content of graphite in the negative electrode was 83.84%-88.36%, with a recovery rate of 73.21%-79.60%.

[0075] In Comparative Example 1, no PVP and PAA were added during the flotation process. Compared with Example 1, the LiFePO4 recovery rate decreased significantly to only 71.41%. This is because: due to the strong natural hydrophobicity of graphite, it will form hydrophobic flocculation, which will cause the hydrophilic lithium iron phosphate cathode material that should have settled at the bottom of the tank to be wrapped in the hydrophobic negative electrode graphite material and enter the foam product. In addition, the particle size of the mixed positive and negative electrode powder of the lithium battery obtained by mechanical processing is too fine, which causes the lithium iron phosphate cathode material to be trapped in the water flow between the bubbles. The combination of these two reasons causes the cathode material that should have entered the bottom of the tank to enter the foam layer and be scraped out, thus reducing the recovery rate of the cathode material.

[0076] In Comparative Example 2, no PAA was added during the flotation process. Compared with Example 1, the LiFePO4 content decreased significantly. This is because the particle size of the mixed positive and negative electrode powder of the lithium battery obtained by mechanical processing is too fine, which causes the lithium iron phosphate positive electrode material to be trapped in the water flow between the bubbles. The positive electrode material that should have entered the bottom of the tank enters the foam layer and is scraped out, thereby reducing the recovery rate of LiFePO4 in the positive electrode material.

[0077] In Comparative Example 3, no PVP was added during the flotation process. Compared with Example 1, the LiFePO4 content, LiFePO4 recovery rate, graphite content, and graphite recovery rate all decreased significantly. This is because without PVP, PAA flocculation is not selective, resulting in both lithium iron phosphate cathode material and anode graphite material being flocculated, making it difficult to separate the two.

[0078] In Comparative Example 4, an excessive amount of PVP was added during the flotation process. Compared with Example 1, the LiFePO4 content, LiFePO4 recovery rate, and graphite recovery rate all decreased significantly. This is because the excessive PVP caused the graphite to be over-dispersed, and some of the graphite entered the product (cathode material) in the cell during the flotation process, thereby reducing the LiFePO4 content, LiFePO4 recovery rate, and graphite recovery rate.

[0079] Figure 2 The particle size distribution diagrams of the cathode material flocs obtained in Example 1 and the comparative example of the present invention are shown. Figure 3 This is a particle size distribution diagram of the anode material flocs obtained in Example 1 and the comparative example of the present invention. From... Figure 2As can be seen, after adding PAA, the particle size line of the cathode material flocs shifts to the right, indicating that PAA can flocculate the cathode material, making the cathode material particles larger. Even after adding PVP first and then PAA, PAA still has a flocculating effect on the cathode material; the addition of PVP does not affect the flocculation effect of PAA on the cathode material. Figure 3 As can be seen from the data, the volume percentage of fine particles in the negative electrode material increases after the addition of PVP, indicating that PVP has a dispersing effect on graphite. When PAA is added alone, the particle size line of the anode material flocs shifts to the right, indicating that the overall particle size of the anode material increases, and PAA has a flocculation effect on the anode. After adding PVP first and then PAA, the flocculation effect of PAA on the anode material is significantly suppressed, indicating that PVP will inhibit the flocculation effect of PAA on the anode material.

[0080] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for selective flocculation and flotation separation of positive and negative electrode materials of lithium iron phosphate batteries, characterized in that, Includes the following steps: Step 1: Discharge the lithium iron phosphate battery, and disassemble the discharged lithium battery to obtain copper foil containing negative electrode material and aluminum foil containing positive electrode material. Step 2: Mix the positive electrode aluminum foil and the negative electrode copper foil in a certain ratio, and then coarsely crush them, perform a first wet sieve, fine crush them, perform a second wet sieve, filter and dry them to obtain the mixed electrode powder of positive and negative electrodes for lithium batteries. Step 3: Mix the positive and negative electrode powders of lithium battery with water to obtain a flotation slurry of a certain concentration. Stir and adjust the flotation slurry to obtain the first slurry. Step 4: Add polyvinylpyrrolidone to the first slurry and continue stirring to adjust the slurry, thus obtaining the second slurry; Step 5: Add polyacrylic acid to the second slurry, stir and adjust the slurry to obtain the third slurry; Step 6: Add a collector to the third slurry, stir, add a foaming agent, stir again, aerate and scrape the foam, and recover the foam product and the product in the tank; the foam product is the negative electrode material, and the product in the tank is the positive electrode material.

2. The flotation separation method according to claim 1, characterized in that, In step 2, the ratio of the number of positive electrode aluminum foil sheets to the number of negative electrode copper foil sheets is 1:1, the coarse crushing time is 10-30s, and the fine crushing time is 10-20min.

3. The flotation separation method according to claim 2, characterized in that, In step 2, the mesh size of the first wet sieve is 0.8-1.2 mm, and the mesh size of the second wet sieve is 0.074-0.078 mm.

4. The flotation separation method according to claim 1, characterized in that, In step 3, the mass concentration of the first slurry is 4-10%.

5. The flotation separation method according to claim 4, characterized in that, In step 3, the stirring speed is 1400-1800 rpm and the stirring time is 3-4 min.

6. The flotation separation method according to claim 1, characterized in that, In step 4, the amount of polyvinylpyrrolidone used is 20-40 g / t.

7. The flotation separation method according to claim 6, characterized in that, In step 4, the stirring speed is 1400-1800 rpm and the stirring time is 2-3 min.

8. The flotation separation method according to claim 1, characterized in that, In step 5, the amount of polyacrylic acid used is 200-300 g / t.

9. The flotation separation method according to claim 8, characterized in that, In step 5, the stirring speed is 1400-1800 rpm and the stirring time is 2-3 min.

10. The flotation separation method according to claim 1, characterized in that, In step 6, the amount of the collector is 200-400 g / t, and the amount of the foaming agent is 100-200 g / t.

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