Method for flotation separation of positive and negative electrode materials of waste lithium battery

Abstract

The invention provides a method for flotation separation of positive and negative electrode materials of waste lithium batteries. The method comprises the following steps: mixing pretreated positive and negative electrode powder and an H2O2 alkaline solution, and carrying out oxidation treatment to obtain mixed slurry; and the mixed slurry and a positive electrode collecting agent are mixed, then flotation treatment is conducted, and flotation foam and flotation tailings are obtained. The positive and negative electrode powder is treated by the H2O2 alkaline solution, the intrinsic hydrophilicity of the positive electrode material can be recovered by selectively dissociating a binder-metal interface and hydroxylating the surface of the positive electrode material, and meanwhile, OH <-> in the solution is adsorbed on the surface of the graphite negative electrode material, so that the dispersity of the graphite negative electrode material in water can be improved, the agglomeration condition is reduced, and the service life of the graphite negative electrode material is prolonged. And finally, the positive electrode recovery rate and the graphite purity are remarkably improved. Compared with a traditional flotation technology, the technological method has the advantages that the dosage of reagents is greatly reduced, and the flotation effect of positive and negative electrode materials is guaranteed while the dosage of the flotation reagents is reduced.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium battery recycling technology, specifically relating to a method for flotation separation of positive and negative electrode materials from waste lithium batteries. Background Technology

[0002] With the rapid growth of the national economy, the market demand and consumption of lithium batteries are increasing exponentially. However, the lifespan of a typical lithium battery is only 3-5 years. As these batteries exceed their lifespan or are replaced with electronic devices, the amount of discarded lithium batteries increases accordingly. The recycling of used lithium batteries is a significant technological challenge and an urgent problem that needs to be solved. It not only faces major technical challenges such as "difficult battery dismantling, low material sorting accuracy, and insufficient recovery rate of valuable metals," but also directly relates to the "closed-loop sustainable development" of the new energy industry and resource security.

[0003] In the recycling process of spent lithium batteries, the battery black powder obtained after discharge, mechanical dismantling, and crushing contains approximately 15-25% valuable metals such as lithium, cobalt, and nickel, and 40-60% graphite anode material. Effective separation of the positive and negative electrode materials is crucial for achieving efficient extraction of the metal components and recycling of the anode graphite.

[0004] Current mainstream technologies rely on flotation, utilizing the difference in hydrophilicity between positive electrode materials (such as LiCoO2, NCM, and other metal oxides) and the natural hydrophobicity of negative electrode graphite to achieve separation. However, organic binders such as polyvinylidene fluoride (PVDF), widely used in electrode manufacturing, form micron-sized films coating the surface of positive electrode particles after crushing. This hydrophobic polymer film masks the hydrophilic properties of the positive electrode material, and some graphite particles experience a decrease in hydrophobicity due to PVDF adsorption, leading to convergence of surface properties between the positive and negative electrodes. To compensate for the difference in surface properties, pretreatment of battery black powder through chemical dissolution, heat treatment, and grinding can be performed to improve the flotation separation rate. Grinding can remove some PVDF from the material surface using mechanical action, exposing the fresh surfaces of the positive and negative electrode powders, but it also damages the layered structure of the negative electrode graphite material to some extent, affecting subsequent recycling and reuse. Heat treatment typically involves calcining the battery black powder in an oxygen-free atmosphere at 400-700℃. Although the treatment effect is good, this method is energy-intensive and produces harmful gases, which is not conducive to large-scale industrial production. Chemical dissolution remains the primary method, but it relies on organic solvents such as N-methylpyrrolidone (NMP) and triethyl phosphate (TEP), which are highly toxic and have high recycling costs.

[0005] To address the aforementioned shortcomings, the industry has made relevant improvements. Patent CN116651910A discloses a selective flocculation flotation separation method for positive and negative electrode materials of lithium iron phosphate batteries. This method requires slurrying the mixed positive and negative electrode powders of lithium batteries, using polyvinylpyrrolidone and polyacrylic acid instead of the aforementioned organic solvents for slurry preparation, and then adding a trapping agent and a foaming agent for flotation separation to obtain foamed products (negative electrode materials) and products in the tank (positive electrode materials). This technology requires multiple slurry preparations, resulting in high time costs, and the use of reagents such as polyvinylpyrrolidone does not consider the small difference in surface wettability between PVDF-coated negative electrode materials and lithium iron phosphate positive electrode materials. Patent CN118676463A discloses a flotation separation method for positive and negative electrode materials of waste lithium batteries. This method targets the binder coating the surface of the positive electrode material, using hydrophilic amino acids as flotation inhibitors. Utilizing the strong adsorption between amino acids and PVDF, the surface of the positive electrode material changes from hydrophobic to hydrophilic, thereby achieving flotation separation of the positive and negative electrode materials. It uses amino acids as inhibitors, without taking into account the problem that graphite is prone to agglomeration in aqueous solutions due to its hydrophobic surface.

[0006] Therefore, developing a simple, efficient, low-cost separation method that can simultaneously guarantee the flotation effect of positive and negative electrode materials is an urgent technical problem to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for flotation separation of positive and negative electrode materials from spent lithium-ion batteries. This invention treats the positive and negative electrode powders with an alkaline H₂O₂ solution, selectively dissociating the binder-metal interface, hydroxylating the surface of the positive electrode material, restoring its intrinsic hydrophilicity, and simultaneously reducing the OH groups in the solution. - Adsorption onto the surface of graphite anode materials improves their dispersibility in water, reduces agglomeration, and ultimately significantly improves both cathode recovery rate and graphite purity. Compared to traditional flotation techniques, this process greatly reduces reagent usage while maintaining the flotation effect of both cathode and anode materials, providing a new approach to overcoming the challenges of flotation separation.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for flotation separation of positive and negative electrode materials from waste lithium batteries, the method comprising the following steps:

[0010] The pretreated positive and negative electrode powders are mixed with an alkaline H2O2 solution and subjected to oxidation treatment to obtain a mixed slurry.

[0011] The mixed slurry is mixed with the positive electrode collector and then subjected to flotation treatment to obtain flotation foam and flotation tailings.

[0012] This invention treats the positive and negative electrode powders with an alkaline H2O2 solution. This selectively dissociates the binder-metal interface, hydroxylates the surface of the positive electrode material, and restores the intrinsic hydrophilicity of the positive electrode material. Simultaneously, the OH groups in the solution... - Adsorption onto the surface of graphite anode materials improves their dispersibility in water, reduces agglomeration, and ultimately significantly improves both cathode recovery rate and graphite purity. Compared to traditional flotation techniques, this process greatly reduces reagent usage while maintaining the flotation effect of both cathode and anode materials, providing a new approach to overcoming the challenges of flotation separation.

[0013] It should be noted that this invention does not limit the source of the waste lithium batteries; for example, waste smartphones, waste tablets, waste small household appliances, or waste power batteries, etc. This invention also does not limit the type of waste lithium batteries; for example, waste lithium cobalt oxide batteries or waste lithium iron phosphate batteries, etc.

[0014] Preferably, the preprocessing step includes:

[0015] Waste lithium batteries are discharged and then crushed to obtain a mixed material containing positive and negative electrode materials, separators, and other substances.

[0016] The mixed materials are screened, and then the screened positive and negative electrode materials are pulverized to obtain positive and negative electrode powders.

[0017] Preferably, the mesh size of the positive and negative electrode powders is less than 200 mesh, for example, it can be 180 mesh, 150 mesh, 130 mesh or 100 mesh, etc.

[0018] Preferably, the mass fraction of H2O2 in the alkaline H2O2 solution is 0.3-0.7%, for example, it can be 0.3%, 0.4%, 0.5%, 0.6% or 0.7%, etc.

[0019] In this invention, the mass fraction of H2O2 in the alkaline H2O2 solution is limited to 0.3-0.7%, which helps to improve the effective utilization rate of H2O2.

[0020] Preferably, the pH value of the H2O2 alkaline solution is 9.8-10.2, for example, it can be 9.8, 9.9, 10, 10.1 or 10.2.

[0021] In this invention, the pH value of the alkaline H2O2 solution is limited to 9.8-10.2, which serves to provide an environment for the effective decomposition of H2O2.

[0022] Preferably, the alkaline H2O2 solution includes a pH adjuster and a stabilizer.

[0023] The purpose of introducing a stabilizer into the alkaline H2O2 solution in this invention is to inhibit the rapid decomposition of H2O2 in an alkaline environment, maintain its effective concentration and reactivity to the maximum extent, thereby ensuring the stability, controllability and safety of the process.

[0024] Preferably, the stabilizer includes inorganic stabilizers and / or organic stabilizers.

[0025] In this invention, an inorganic stabilizer is used to form an adsorption layer on the surface of H2O2 molecules, hindering the absorption of OH-. - The combination with H2O2 simultaneously inhibits the formation of perhydroxyl anions (hydroxyl anions are key intermediate products in the decomposition reaction of H2O2). Using organic stabilizers allows them to form chemical bonds with H2O2, reducing its reactivity and stabilizing H2O2 under specific alkaline conditions.

[0026] Preferably, the inorganic stabilizer includes sodium phosphate and / or sodium silicate.

[0027] Preferably, the organic stabilizer includes urea and / or aminourea.

[0028] Preferably, in the alkaline H2O2 solution, the mass ratio of stabilizer to H2O2 is (0.1-0.5):1, for example, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1 or 0.5:1, etc.

[0029] In this invention, a specific mass ratio of stabilizer and H2O2 is used in synergy to effectively suppress the ineffective decomposition of H2O2, thereby retaining sufficient H2O2 to interact with the positive and negative electrode powders, achieving surface hydroxylation of the positive electrode material, and ensuring that the oxidation process is controllable, uniform, and efficient. After uniform and controllable oxidation treatment, the hydrophilicity of the positive electrode material is significantly enhanced, while the negative electrode material still maintains good hydrophobicity, thereby greatly improving the flotation separation efficiency of the positive and negative electrode materials, and significantly improving the recovery rate and purity of the negative electrode material, as well as the recovery rate and grade of the positive electrode material.

[0030] Preferably, the solid-liquid ratio of the positive and negative electrode powders and the H2O2 alkaline solution is 1g:(2-10)mL, for example, it can be 1g:2mL, 1g:4mL, 1g:6mL, 1g:8mL or 1g:10mL, etc.

[0031] In this invention, a suitable solid-liquid ratio of positive and negative electrode powders to H2O2 alkaline solution is defined, which is beneficial to the full hydroxylation of positive electrode powders.

[0032] Preferably, the oxidation treatment temperature is 20-60℃, for example, it can be 20℃, 30℃, 40℃, 50℃ or 60℃.

[0033] Preferably, the oxidation treatment time is 20-40 minutes, for example, it can be 20 minutes, 30 minutes or 40 minutes.

[0034] In this invention, an appropriate oxidation treatment time can not only hydroxylate the surface of the positive electrode material and improve its hydrophilicity, but also ensure that the graphite negative electrode material is not easily oxidized due to its hydrophobicity, so an appropriate oxidation treatment time is not enough to destroy its structure.

[0035] Preferably, the oxidation process is accompanied by stirring.

[0036] Preferably, the stirring speed is 1500-2000 rpm, for example, it can be 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm or 2000 rpm.

[0037] Preferably, the positive electrode collector comprises sodium oleate.

[0038] Preferably, the amount of the positive electrode collector is 3-10% of the mass of the positive and negative electrode powders, for example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0039] Preferably, the mixing of the slurry and the positive electrode collector is accompanied by stirring.

[0040] Preferably, the stirring time is 2-5 minutes, for example, 2 minutes, 3 minutes, 4 minutes or 5 minutes.

[0041] Preferably, the flotation treatment method includes microbubble flotation.

[0042] Preferably, in the microbubble flotation method, the diameter of the microbubbles is 50-100 μm, for example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, etc.

[0043] In this invention, a suitable microbubble diameter is advantageous for sufficient flotation.

[0044] Preferably, the method includes the following steps:

[0045] (1) Discharge the waste lithium battery and then break it into small pieces of 5-20mm (e.g., 5mm, 10mm, 15mm or 20mm) to obtain a mixed material containing positive and negative electrode materials, separator and other substances.

[0046] The mixed materials are screened, and then the screened positive and negative electrode materials are pulverized to obtain positive and negative electrode powders with a mesh size of <200 mesh.

[0047] (2) Preparation of an alkaline H2O2 solution:

[0048] Hydrogen peroxide, a pH adjuster, and a stabilizer are mixed to prepare an alkaline H2O2 solution with a pH of 9.8-10.2; wherein the pH adjuster includes sodium hydroxide; the stabilizer includes inorganic and / or organic stabilizers, the inorganic stabilizer includes sodium phosphate and / or sodium silicate, and the organic stabilizer includes urea and / or aminourea; the mass fraction of H2O2 in the alkaline H2O2 solution is 0.3-0.7%; and the mass ratio of stabilizer to H2O2 in the alkaline H2O2 solution is (0.1-0.5):1.

[0049] (3) The positive and negative electrode powders are mixed with H2O2 alkaline solution and oxidized at a temperature of 20-60℃ for 20-40 minutes to hydroxylate the surface of the positive electrode material to obtain a mixed slurry; wherein the oxidation process is accompanied by stirring at a speed of 1500-2000 rpm.

[0050] (4) Add the positive electrode collector to the mixed slurry and stir. After stirring for 2-5 minutes, turn on the gas flow meter and apply gas at a flow rate of 0.03-0.05 m³ / min. 3 / h (for example, it could be 0.03m) 3 / h, 0.04m 3 / h or 0.05m 3 A flow rate of gas (e.g., / h) is introduced to form microbubbles with a diameter of 50-100μm for microbubble flotation. The bubbles are scraped for 2-5 minutes (e.g., 2 minutes, 3 minutes, 4 minutes, or 5 minutes) to obtain flotation foam and flotation tailings. The flotation foam is a graphite negative electrode material, and the flotation tailings are a positive electrode material. The positive electrode collector includes sodium oleate, and the amount of the positive electrode collector is 3-10% of the mass of the positive and negative electrode powders.

[0051] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] This invention treats the positive and negative electrode powders with an alkaline H2O2 solution. This selectively dissociates the binder-metal interface, hydroxylates the surface of the positive electrode material, and restores the intrinsic hydrophilicity of the positive electrode material. Simultaneously, the OH groups in the solution... -Adsorption onto the surface of graphite anode materials improves their dispersibility in water, reduces agglomeration, and ultimately significantly improves both cathode recovery rate and graphite purity. Compared to traditional flotation techniques, this process greatly reduces reagent usage while maintaining the flotation effect of both cathode and anode materials, providing a new approach to overcoming the challenges of flotation separation. Attached Figure Description

[0054] Figure 1 This is a process flow diagram provided in Embodiment 1 of the present invention. Detailed Implementation

[0055] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0056] Example 1

[0057] This embodiment provides a method for flotation separation of positive and negative electrode materials from waste lithium batteries, and its process flow diagram is as follows: Figure 1 As shown, the method includes the following steps:

[0058] (1) Pretreatment: Discharge the waste lithium cobalt oxide batteries, and then crush the waste lithium cobalt oxide batteries into small pieces of 5-20mm to obtain a mixed material containing positive and negative electrode materials, separators and other substances.

[0059] The mixed materials are screened to remove other substances such as the separator, and then the screened positive and negative electrode materials are pulverized to obtain positive and negative electrode powders with a mesh size of <200 mesh.

[0060] (2) Preparation of an alkaline H2O2 solution:

[0061] Hydrogen peroxide, a pH adjuster, and a stabilizer are mixed to prepare an alkaline H2O2 solution with a pH of 10.013; wherein the pH adjuster includes sodium hydroxide; the stabilizer is sodium phosphate; the mass fraction of H2O2 in the alkaline H2O2 solution is 0.5%; and the mass ratio of stabilizer to H2O2 in the alkaline H2O2 solution is 0.3:1.

[0062] (3) The H2O2 alkaline solution is placed in a 1L flotation cell, and then 300g of the positive and negative electrode powders are added and mixed. The mixture is then subjected to an oxidation treatment at 30°C for 30min to hydroxylate the surface of the positive electrode material, thereby obtaining a mixed slurry. The solid-liquid ratio of the positive and negative electrode powders to the H2O2 alkaline solution is 1g:3mL. The oxidation treatment is accompanied by stirring at a speed of 1600rpm.

[0063] (4) Add 10g of sodium oleate to the mixed slurry and stir. After stirring for 3 minutes, turn on the gas flow meter and apply gas at a flow rate of 0.04m³ / min. 3 Air is introduced at a flow rate of / h to form microbubbles with a diameter of 75μm for microbubble flotation. The bubbles are scraped for 3 minutes to obtain flotation foam (graphite anode material) and flotation tailings (lithium cobalt oxide cathode material); wherein the amount of sodium oleate used is 3.33% of the mass of the cathode and anode powder.

[0064] (5) The solution containing the flotation tailings is filtered, and then the resulting filter residue is washed and dried to obtain lithium cobalt oxide product.

[0065] Example 2

[0066] This embodiment provides a method for flotation separation of positive and negative electrode materials from waste lithium batteries, the method comprising the following steps:

[0067] (1) Discharge the waste lithium iron phosphate batteries, and then crush the waste lithium iron phosphate batteries into small pieces of 5-20mm to obtain a mixed material containing positive and negative electrode materials, separator and other substances.

[0068] The mixed materials are screened to remove other substances such as the separator, and then the screened positive and negative electrode materials are pulverized to obtain positive and negative electrode powders with a mesh size of <200 mesh.

[0069] (2) Preparation of an alkaline H2O2 solution:

[0070] Hydrogen peroxide, a pH adjuster, and a stabilizer are mixed to prepare an alkaline H2O2 solution with a pH value of 9.947; wherein the pH adjuster includes sodium hydroxide; the stabilizer is sodium silicate; the mass fraction of H2O2 in the alkaline H2O2 solution is 0.4%; and the mass ratio of stabilizer to H2O2 in the alkaline H2O2 solution is 0.1:1.

[0071] (3) The H2O2 alkaline solution is placed in a 1.5L flotation cell, and then 200g of the positive and negative electrode powders are added and mixed. The mixture is then subjected to an oxidation treatment at 30°C for 30min to hydroxylate the surface of the positive electrode material, thereby obtaining a mixed slurry. The solid-liquid ratio of the positive and negative electrode powders to the H2O2 alkaline solution is 1g:5mL. The oxidation treatment is accompanied by stirring at a speed of 1900rpm.

[0072] (4) Add 6g of sodium oleate to the mixed slurry and stir. After stirring for 3 minutes, turn on the gas flow meter and apply gas at a flow rate of 0.03m³ / min. 3Air is introduced at a flow rate of / h to form microbubbles with a diameter of 50μm for microbubble flotation. The bubbles are scraped for 5 minutes to obtain flotation foam (graphite anode material) and flotation tailings (lithium cobalt oxide cathode material); wherein the amount of sodium oleate used is 3% of the mass of the cathode and anode powder.

[0073] (5) The solution containing the flotation tailings is filtered, and then the resulting filter residue is washed and dried to obtain lithium cobalt oxide product.

[0074] Example 3

[0075] This embodiment provides a method for flotation separation of positive and negative electrode materials from waste lithium batteries, the method comprising the following steps:

[0076] (1) Discharge the waste lithium iron phosphate batteries, and then crush the waste lithium iron phosphate batteries into small pieces of 5-20mm to obtain a mixed material containing positive and negative electrode materials, separator and other substances.

[0077] The mixed materials are screened to remove other substances such as the separator, and then the screened positive and negative electrode materials are pulverized to obtain positive and negative electrode powders with a mesh size of <200 mesh.

[0078] (2) Preparation of an alkaline H2O2 solution:

[0079] Hydrogen peroxide, a pH adjuster, and a stabilizer are mixed to prepare an alkaline H2O2 solution with a pH of 10.02; wherein the pH adjuster includes sodium hydroxide; the stabilizer is urea; the mass fraction of H2O2 in the alkaline H2O2 solution is 0.6%; and the mass ratio of stabilizer to H2O2 in the alkaline H2O2 solution is 0.5:1.

[0080] (3) The H2O2 alkaline solution is placed in a 1.5L flotation cell, and then 500g of the positive and negative electrode powders are added and mixed. The mixture is then subjected to an oxidation treatment at 25°C for 30min to hydroxylate the surface of the positive electrode material, thereby obtaining a mixed slurry. The solid-liquid ratio of the positive and negative electrode powders to the H2O2 alkaline solution is 1g:3mL. The oxidation treatment is accompanied by stirring at a speed of 1900rpm.

[0081] (4) Add 50g of sodium oleate to the mixed slurry and stir. After stirring for 3 minutes, turn on the gas flow meter and apply gas at a flow rate of 0.05m. 3 Air is introduced at a flow rate of / h to form microbubbles with a diameter of 100μm for microbubble flotation. The bubbles are scraped for 2 minutes to obtain flotation foam (graphite anode material) and flotation tailings (lithium cobalt oxide cathode material); wherein the amount of sodium oleate used is 10% of the mass of the cathode and anode powder.

[0082] (5) The solution containing the flotation tailings is filtered, and then the resulting filter residue is washed and dried to obtain lithium cobalt oxide product.

[0083] Example 4

[0084] The difference between this embodiment and embodiment 1 is that the mass fraction of H2O2 in the alkaline H2O2 solution in step (2) is 0.1%.

[0085] The remaining methods and parameters are consistent with those in Example 1.

[0086] Example 5

[0087] The difference between this embodiment and Embodiment 1 is that the mass fraction of H2O2 in the alkaline H2O2 solution is 0.9%.

[0088] The remaining methods and parameters are consistent with those in Example 1.

[0089] Example 6

[0090] The difference between this embodiment and embodiment 1 is that the pH value of the H2O2 alkaline solution in step (2) is 9.5.

[0091] The remaining methods and parameters are consistent with those in Example 1.

[0092] Example 7

[0093] The difference between this embodiment and embodiment 1 is that the pH value of the H2O2 alkaline solution in step (2) is 10.5.

[0094] The remaining methods and parameters are consistent with those in Example 1.

[0095] Example 8

[0096] The difference between this embodiment and embodiment 1 is that no stabilizer is added during the preparation of the H2O2 alkaline solution in step (2).

[0097] The remaining methods and parameters are consistent with those in Example 1.

[0098] Example 9

[0099] The difference between this embodiment and embodiment 1 is that the mass ratio of the stabilizer to H2O2 in step (2) is 0.6:1.

[0100] The remaining methods and parameters are consistent with those in Example 1.

[0101] Example 10

[0102] The difference between this embodiment and embodiment 1 is that the solid-liquid ratio of the positive and negative electrode powder and the H2O2 alkaline solution in step (3) is 1g:12mL.

[0103] The remaining methods and parameters are consistent with those in Example 1.

[0104] Example 11

[0105] The difference between this embodiment and embodiment 1 is that the solid-liquid ratio of the positive and negative electrode powder and the H2O2 alkaline solution in step (3) is 1g:1mL.

[0106] The remaining methods and parameters are consistent with those in Example 1.

[0107] Example 12

[0108] The difference between this embodiment and embodiment 1 is that the oxidation treatment time in step (3) is 10 min.

[0109] The remaining methods and parameters are consistent with those in Example 1.

[0110] Example 13

[0111] The difference between this embodiment and embodiment 1 is that the oxidation treatment time in step (3) is 60 min.

[0112] The remaining methods and parameters are consistent with those in Example 1.

[0113] Comparative Example 1

[0114] The difference between this comparative example and Example 1 is that the H2O2 alkaline solution in step (2) is replaced with pure sodium hydroxide solution with a pH of 10.01.

[0115] The remaining methods and parameters are consistent with those in Example 1.

[0116] Comparative Example 2

[0117] The difference between this comparative example and Example 1 is that the alkaline H2O2 solution in step (2) is replaced with an H2O2 solution with a pH of 4.5.

[0118] The remaining methods and parameters are consistent with those in Example 1.

[0119] Performance testing

[0120] The positive electrode products obtained in the above embodiments and comparative examples were subjected to recovery rate and grade tests; the flotation foam was dried to obtain negative electrode graphite powder, and then the negative electrode graphite powder was subjected to recovery rate and grade tests.

[0121] The recovery rate is tested using the following method: (mass of the target component in the positive electrode product (mass of graphite in the negative electrode graphite powder) / mass of the corresponding component in the waste lithium battery (mass of the corresponding graphite in the waste lithium battery)) × 100%. The grade is tested using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0122] The test results are shown in Table 1.

[0123] Table 1

[0124]

[0125] analyze:

[0126] As shown in Examples 1-3, the present invention treats the positive and negative electrode powders with an alkaline H2O2 solution. This selectively dissociates the binder-metal interface, hydroxylates the surface of the positive electrode material, and restores the intrinsic hydrophilicity of the positive electrode material. Simultaneously, the OH groups in the solution... - Adsorption onto the surface of graphite anode material improves its dispersibility in water, reduces agglomeration, and ultimately achieves a cathode recovery rate of over 98% and a graphite purity of over 96%. Compared to traditional flotation techniques, this process significantly reduces reagent usage while maintaining the flotation effect of both anode and cathode materials, providing a new approach to overcoming the challenges of flotation separation.

[0127] As can be seen from the comparison between Example 1 and Examples 4-5, if the mass fraction of H2O2 in the alkaline H2O2 solution in step (2) is too small, it is not conducive to the hydroxylation of the metal surface and it is difficult to completely float and separate; if the mass fraction of H2O2 in the alkaline H2O2 solution in step (2) is too large, it is not conducive to cost control and it is not conducive to H2O2 fully exerting its effect.

[0128] As can be seen from the comparison between Example 1 and Examples 6-7, if the pH value of the H2O2 alkaline solution in step (2) is too low, it will not be conducive to the effective adsorption of the hydroxyl groups generated by H2O2 on the surface of the metal material; if the pH value of the H2O2 alkaline solution in step (2) is too high, it will not be conducive to the effective utilization of H2O2.

[0129] As can be seen from the comparison between Example 1 and Examples 8-9, if no stabilizer is added during the preparation of the alkaline H2O2 solution in step (2), the H2O2 will decompose too quickly and cannot effectively improve the surface properties of the metal powder; if the mass ratio of the stabilizer to H2O2 in step (2) is too large, it will be detrimental to the flotation recovery of graphite.

[0130] A comparison of Example 1 and Examples 10-11 shows that if the solid-liquid ratio of the positive and negative electrode powder and the H2O2 alkaline solution in step (3) is too small, it will be detrimental to cost control and H2O2 will not be able to fully exert its effect; if the solid-liquid ratio of the positive and negative electrode powder and the H2O2 alkaline solution in step (3) is too large, it will be detrimental to the recovery of metal elements.

[0131] As can be seen from the comparison between Example 1 and Examples 12-13, if the oxidation treatment time in step (3) is too short, the reaction will be incomplete and the recovery rate of positive and negative electrode materials will be low; if the oxidation treatment time in step (3) is too long, the long-term oxidation treatment will damage the edge of the graphite material, and fine graphite powder will enter the lower part of the flotation cell, reducing the recovery quality of the positive electrode material.

[0132] As can be seen from the comparison between Example 1 and Comparative Example 1, if the H2O2 alkaline solution is replaced with pure sodium hydroxide solution, the separation effect of the positive and negative electrode materials will be poor.

[0133] As can be seen from the comparison between Example 1 and Comparative Example 2, if the alkaline H2O2 solution is replaced with an H2O2 solution with a pH of 4.5, the H2O2 decomposes too quickly and has a low utilization rate, ultimately resulting in poor separation effect of the positive and negative electrode materials.

[0134] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for flotation separation of positive and negative electrode materials from waste lithium batteries, characterized in that, The method includes the following steps: The pretreated positive and negative electrode powders were mixed with an alkaline H2O2 solution and subjected to oxidation treatment to obtain a mixed slurry. The mixed slurry is mixed with the positive electrode collector and then subjected to flotation treatment to obtain flotation foam and flotation tailings.

2. The method according to claim 1, characterized in that, The preprocessing steps include: Waste lithium batteries are discharged and then crushed to obtain a mixed material containing positive and negative electrode materials, separators and other substances. The mixed material is screened, and then the screened positive and negative electrode materials are pulverized to obtain positive and negative electrode powders; Preferably, the mesh size of the positive and negative electrode powders is <200 mesh.

3. The method according to claim 1 or 2, characterized in that, The mass fraction of H2O2 in the alkaline H2O2 solution is 0.3-0.7%.

4. The method according to any one of claims 1-3, characterized in that, The pH value of the alkaline H2O2 solution is 9.8-10.2; Preferably, the alkaline H2O2 solution includes a pH adjuster and a stabilizer; Preferably, the stabilizer includes inorganic stabilizers and / or organic stabilizers; Preferably, the inorganic stabilizer comprises sodium phosphate and / or sodium silicate; Preferably, the organic stabilizer comprises urea and / or aminourea; Preferably, in the alkaline H2O2 solution, the mass ratio of stabilizer to H2O2 is (0.1-0.5):

1.

5. The method according to any one of claims 1-4, characterized in that, The solid-liquid ratio of the positive and negative electrode powders and the H2O2 alkaline solution is 1g:(2-10)mL.

6. The method according to any one of claims 1-5, characterized in that, The oxidation treatment temperature is 20-60℃; Preferably, the oxidation treatment time is 20-40 minutes.

7. The method according to any one of claims 1-6, characterized in that, The oxidation process is accompanied by stirring; Preferably, the stirring speed is 1500-2000 rpm.

8. The method according to any one of claims 1-7, characterized in that, The positive electrode collector includes sodium oleate; Preferably, the amount of the positive electrode collector is 3-10% of the mass of the positive and negative electrode powders; Preferably, the mixing of the slurry and the positive electrode collector is accompanied by stirring; Preferably, the stirring time is 2-5 minutes.

9. The method according to any one of claims 1-8, characterized in that, The flotation process includes microbubble flotation. Preferably, in the microbubble flotation method, the diameter of the microbubbles is 50-100 μm.

10. The method according to any one of claims 1-9, characterized in that, The method includes the following steps: (1) Discharge the waste lithium battery and then crush the waste lithium battery into small pieces of 5-20mm to obtain a mixed material containing positive and negative electrode materials, separator and other substances; The mixed material is screened, and then the screened positive and negative electrode materials are pulverized to obtain positive and negative electrode powder with a mesh size of <200 mesh. (2) Preparation of an alkaline H2O2 solution: Hydrogen peroxide, a pH adjuster, and a stabilizer are mixed to prepare an alkaline H2O2 solution with a pH of 9.8-10.2; wherein the pH adjuster includes sodium hydroxide; the stabilizer includes inorganic and / or organic stabilizers, the inorganic stabilizer includes sodium phosphate and / or sodium silicate, and the organic stabilizer includes urea and / or aminourea; the mass fraction of H2O2 in the alkaline H2O2 solution is 0.3-0.7%; the mass ratio of stabilizer to H2O2 in the alkaline H2O2 solution is (0.1-0.5):1; (3) The positive and negative electrode powders are mixed with H2O2 alkaline solution and oxidized at a temperature of 20-60℃ for 20-40 minutes to hydroxylate the surface of the positive electrode material to obtain a mixed slurry; wherein the oxidation process is accompanied by stirring at a speed of 1500-2000 rpm. (4) Add the positive electrode collector to the mixed slurry and stir. After stirring for 2-5 minutes, turn on the gas flow meter and apply gas at a flow rate of 0.03-0.05 m³ / min. 3 A flow rate of / h is used to introduce gas to form microbubbles with a diameter of 50-100μm for microbubble flotation. The bubbles are scraped for 2-5 minutes to obtain flotation foam and flotation tailings. The flotation foam is a graphite negative electrode material and the flotation tailings is a positive electrode material. The positive electrode collector includes sodium oleate, and the amount of the positive electrode collector is 3-10% of the mass of the positive and negative electrode powders.

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