A flotation recycling method for waste lithium-ion batteries with zero fluorine and carbon emissions

Abstract

This invention discloses a flotation recycling method for waste lithium-ion batteries that produces no fluorine and no carbon emissions. The method includes: subjecting a mixture of positive and negative electrodes from waste lithium-ion batteries to low-temperature treatment, causing the surface binder to deform and exposing the surface of the positive electrode material particles; performing at least one of the following steps: adjusting the treated material to obtain a flotation slurry; sequentially adding an organic hydrophilic inhibitor, a collector, and a frother to the flotation slurry for flotation to obtain sediment; adjusting the sediment, adding the collector and frother, and performing flotation again to obtain ternary lithium concentrate. This invention utilizes low-temperature treatment to shrink and deform the organic film on the surface of the positive electrode material particles, exposing the particles and amplifying the hydrophilicity / hydrophobicity difference between the positive electrode material and graphite. The organic hydrophilic inhibitor binds to the hydrophilic surface of the positive electrode material particles, inhibiting the floating of the positive electrode material, thereby enhancing the flotation separation effect.

Description

Technical Field

[0001] This invention relates to the field of waste lithium-ion battery recycling technology, specifically to a flotation recycling method for waste lithium-ion batteries that are fluorine-free and carbon-free. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, long cycle life, fast charge and discharge speed, no memory effect, low self-discharge rate, and high safety, making them widely used in electronic devices, new energy vehicles, and energy storage. With the booming development of the electric vehicle industry in recent years, the demand for power batteries has exploded, and simultaneously, the number of used lithium-ion batteries is also increasing daily. These used lithium-ion batteries contain various valuable metals, such as cobalt, lithium, and nickel. If they are not effectively recycled, they will not only waste resources but also cause serious environmental pollution.

[0003] Currently, the main methods for recycling waste lithium-ion batteries include pyrometallurgy, hydrometallurgy, and mechanical-physical methods. Among these, flotation, as an effective physical separation method, shows promise for application in the recycling of waste lithium-ion batteries. Before flotation, heat treatment is generally required to remove the PVDF (polyvinylidene fluoride) binder from the electrode material surface, which helps improve flotation separation efficiency. However, conventional heat treatment temperatures are high, resulting in high energy consumption, and the decomposition of PVDF produces fluorine-containing compounds, polluting the environment. Summary of the Invention

[0004] This invention provides a flotation recycling method for waste lithium-ion batteries that is fluorine-free and carbon-free, in order to solve the problems of high energy consumption, environmental pollution from fluorine emissions, and low grade of cathode materials in the existing technology of recycling cathode materials and graphite from waste lithium-ion batteries by flotation.

[0005] To achieve the above objectives, the present invention provides a flotation recycling method for waste lithium-ion batteries that is fluorine-free and carbon-free, comprising the following steps:

[0006] S1. The mixture of positive and negative electrodes of waste lithium-ion batteries is subjected to low-temperature treatment, which deforms the surface binder and exposes the surface of the positive electrode material particles, with the exposed area ratio being 10-20%.

[0007] S2. Adjust the material processed in step S1 to obtain flotation slurry (adjust the slurry according to the conventional flotation concentration, the same below);

[0008] S3. Add organic hydrophilic inhibitor, collector and frother to the flotation pulp in sequence, then scrape the foam to scrape out the graphite product and obtain sediment.

[0009] S4. The sediment obtained in step S3 is slurry-adjusted, and a collector and frother are added. The sediment is then floated again to obtain ternary lithium concentrate.

[0010] This invention utilizes the characteristic of PVDF organic film shrinking and deforming before decomposition. By heat-treating the electrode material at a temperature below the thermal decomposition temperature of PVDF, compared to conventional heat treatment, it not only saves energy but also eliminates the emission of fluorine compounds. The low-temperature treatment causes the PVDF organic film on the surface of the cathode material particles to shrink and deform, breaking down its molecular structure, thus enabling the cathode material particles (ternary lithium cathode material, chemical formula LiNi) to undergo heat treatment. x Co y Mn 1-x-y O2) surface hydrophilic sites exposed (e.g. Figure 2 As shown in the figure, this widens the hydrophilicity difference between the cathode material and graphite. Furthermore, an organic hydrophilic inhibitor is used to bind to the hydrophilic sites on the surface of the cathode material particles to inhibit the flotation of the cathode material, thereby enhancing the flotation separation effect between the two.

[0011] Preferably, in step S1, the particle size of the mixture is less than 0.075 mm. Specifically, dry sieving is used to obtain the undersize material.

[0012] Specifically, in step S1, the low-temperature treatment is one or more of low-temperature roasting, low-temperature pyrolysis, low-temperature radiation, or low-temperature contact.

[0013] Preferably, the low-temperature treatment temperature is 300-350°C and the time is 0.5-1h.

[0014] Preferably, in steps S2 and S4, the mixing speed is 1600-1800 r / min and the time is 3-5 min.

[0015] Specifically, in step S3, the organic hydrophilic inhibitor is one or more of carboxymethyl cellulose, soluble starch, and dextrin; the collector is one or more of dodecane, kerosene, and emulsified kerosene; and the foaming agent is one or more of methyl isobutyl methanol, sec-octanol, and No. 2 oil.

[0016] Preferably, in step S3, relative to 1 ton of dry mixed material, the amount of the inhibitor added is 100-250g, the amount of the collector added is 150-250g, and the amount of the foaming agent added is 150-250g.

[0017] Further, the inhibitor is added to the flotation slurry and stirred for 2-3 minutes, then the collector is added, stirred again for 2-3 minutes, then the frother is added, and stirred for 1-2 minutes.

[0018] Preferably, in step S4, the amount of the collector added is 100-150g relative to 1 ton of dried mixed material, and the amount of the foaming agent added is 100-150g.

[0019] Through the above technical solution, the present invention achieves the following beneficial effects:

[0020] 1. This invention utilizes the characteristic of PVDF organic film shrinking and deforming before decomposition. The electrode material is heat-treated at a temperature lower than the thermal decomposition temperature of PVDF. Compared with conventional heat treatment, this not only saves energy but also eliminates the emission of fluorine-containing compounds. The low-temperature treatment causes the PVDF organic film on the surface of the cathode material particles to shrink and deform, exposing the hydrophilic sites on the particle surface. This amplifies the hydrophilic-hydrophobic difference between the cathode material and graphite. Furthermore, an organic hydrophilic inhibitor is used to bind to the hydrophilic sites on the cathode material particle surface, inhibiting the flotation of the cathode material and thus enhancing the flotation separation effect.

[0021] 2. The process of this invention is simple, easy to operate, clean and efficient, and has low energy consumption. It does not require expensive equipment and complex processes, thus reducing recycling costs.

[0022] 3. This invention calcines the electrode material at a temperature lower than that at which PVDF is thermally decomposed. The entire recycling process is free of fluorine and carbon emissions, making it environmentally friendly.

[0023] 4. In the flotation process, the present invention uses inhibitors to effectively suppress the floating of ternary lithium particles in the positive electrode, thereby improving the flotation separation efficiency of positive and negative electrode materials.

[0024] 5. The method provided by this invention has a high separation rate of positive and negative electrode materials, and the grade and recovery rate of the recovered ternary lithium positive electrode powder are high, which creates conditions for further purification or regeneration and repair of subsequent electrode materials.

[0025] 6. The fluorine-free and carbon-free flotation recycling method for waste lithium-ion batteries provided by this invention has significant environmental, economic and social benefits and broad application prospects. Attached Figure Description

[0026] Figure 1 This is a flow chart of the flotation separation process for positive and negative electrode materials of waste ternary lithium batteries in Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic diagram illustrating how the low-temperature treatment of the present invention causes changes on the surface of the electrode material. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0029] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0031] In the following embodiments, the mixed black powder of positive and negative electrodes of waste ternary lithium batteries comes from a new energy technology company in Shanghai. Its main components are ternary lithium powder and graphite powder, as well as impurities such as separators.

[0032] Example 1

[0033] The flotation separation method for positive and negative electrode materials of waste batteries in this embodiment is used to process waste ternary lithium batteries. The process flow is as follows: Figure 1 As shown, it includes the following steps:

[0034] (1) 500g of waste ternary lithium battery positive and negative electrode mixture was screened using a 0.075mm sieve. The material on the sieve was other impurities, and the material below the sieve was the positive and negative electrode mixture.

[0035] (2) Place the sieved material into a ceramic boat and place it in a muffle furnace. Heat the material to 300°C in an air atmosphere and keep it at that temperature for 1 hour. After cooling, the roasted material is obtained.

[0036] (3) Weigh 35g of roasted material and place it in an XFD single-cell flotation machine. Add water to 140ml, stir and adjust the slurry for 3min. The flotation machine speed is 1600r / min. Add 100g / t of carboxymethyl cellulose and adjust the slurry for 2min. Add 200g / t of dodecane and adjust the slurry for 2min. Add 200g / t of methyl isobutyl methanol and adjust the slurry for 1min before proceeding with the flotation operation. The flotation time is 3min, and the aeration rate is 0.2m. 3 The froth product obtained is graphite, and the sediment product is ternary lithium middlings. The graphite and ternary lithium middlings are filtered and dried separately. To obtain a sufficient amount of ternary lithium middlings, this step is repeated 3 times. The ternary lithium middlings are collected and then subjected to subsequent two-stage flotation.

[0037] (4) Weigh 35g of ternary lithium middlings and place it in an XFD single-cell flotation machine. Add water to 140ml, stir and adjust the slurry for 3 minutes. The flotation machine speed is 1600r / min. Add 100g / t of dodecane and adjust the slurry for 3 minutes. Add 100g / t of methyl isobutyl methanol and adjust the slurry for 1 minute before proceeding with the flotation operation. The flotation time is 3 minutes, and the aeration rate is 0.2m³. 3The foam product obtained was graphite, and the sediment product was ternary lithium concentrate. The graphite and ternary lithium concentrate were filtered and dried separately, and the grade of the ternary lithium concentrate was determined.

[0038] After testing, the final yield was a ternary lithium cathode powder with a grade of 96.56% and a recovery rate of 95.84%.

[0039] Example 2

[0040] The flotation separation method for positive and negative electrode materials of waste batteries in this embodiment is used to process waste ternary lithium batteries, and includes the following steps:

[0041] (1) 500g of waste ternary lithium battery positive and negative electrode mixture was screened using a 0.075mm sieve. The material on the sieve was other impurities, and the material below the sieve was the positive and negative electrode mixture.

[0042] (2) The screened material is placed in a ceramic boat and placed in a tube furnace. The temperature is raised to 350°C in a nitrogen atmosphere and held for 0.5 hours. After cooling, the pyrolyzed material is obtained.

[0043] (3) Weigh 35g of the pyrolysis material and place it in an XFD single-cell flotation machine. Add water to 140ml and stir for 4min. The flotation machine speed is 1700r / min. Add 200g / t of soluble starch and stir for 3min. Add 150g / t of dodecane and stir for 3min. Add 150g / t of methyl isobutyl methanol and stir for 1min before proceeding with the flotation operation. The flotation time is 3min and the aeration rate is 0.2m. 3 The foam product obtained was graphite, and the sediment product was ternary lithium middlings. The graphite and ternary lithium middlings were filtered and dried separately, and the grade of the ternary lithium middlings was determined. This step was repeated 3 times, and the ternary lithium middlings were collected.

[0044] (4) Weigh 35g of ternary lithium middlings and place it in an XFD single-cell flotation machine. Add water to 140ml, stir and adjust the slurry for 3 minutes. The flotation machine speed is 1700r / min. Add 100g / t of dodecane and adjust the slurry for 3 minutes. Add 100g / t of sec-octanol and adjust the slurry for 1 minute before proceeding with the flotation operation. The flotation time is 3 minutes, and the aeration rate is 0.2m³. 3 The froth product obtained is graphite, and the sediment product is ternary lithium concentrate. The graphite and ternary lithium concentrate are filtered and dried separately. To obtain a sufficient amount of ternary lithium middlings, this step is repeated 3 times. The ternary lithium middlings are collected and then subjected to subsequent two-stage flotation.

[0045] After testing, the final yield was a ternary lithium cathode powder with a grade of 97.34% and a recovery rate of 96.72%.

[0046] Example 3

[0047] The flotation separation method for positive and negative electrode materials of waste batteries in this embodiment is used to process waste ternary lithium batteries, and includes the following steps:

[0048] (1) 500g of waste ternary lithium battery positive and negative electrode mixture was screened using a 0.075mm sieve. The material on the sieve was other impurities, and the material below the sieve was the positive and negative electrode mixture.

[0049] (2) Place the sieved material into a ceramic boat and place it in a muffle furnace. Heat the material to 350°C in an air atmosphere and keep it at that temperature for 1 hour. After cooling, the roasted material is obtained.

[0050] (3) Weigh 35g of roasted material and place it in an XFD single-cell flotation machine. Add water to 140ml and stir for 5 minutes. The flotation machine speed is 1800r / min. Add 250g / t of dextrin and stir for 3 minutes. Add 250g / t of kerosene and stir for 3 minutes. Add 250g / t of No. 2 oil and stir for 2 minutes before flotation. The flotation time is 3 minutes and the aeration rate is 0.2m³. 3 The foam product obtained was graphite, and the sediment product was ternary lithium middlings. The graphite and ternary lithium middlings were filtered and dried separately, and the grade of the ternary lithium middlings was determined. This step was repeated 3 times, and the ternary lithium middlings were collected.

[0051] (4) Weigh 35g of ternary lithium middlings and place it in an XFD single-cell flotation machine. Add water to 140ml, stir and adjust the slurry for 3 minutes. The flotation machine speed is 1800r / min. Add 150g / t of dodecane and adjust the slurry for 3 minutes. Add 150g / t of methyl isobutyl methanol and adjust the slurry for 1 minute before proceeding with the flotation operation. The flotation time is 3 minutes, and the aeration rate is 0.2m³. 3 The foam product obtained was graphite, and the sediment product was ternary lithium concentrate. The graphite and ternary lithium concentrate were filtered and dried separately, and the grade of the ternary lithium concentrate was determined.

[0052] After testing, the final yield was a ternary lithium cathode powder with a grade of 98.76% and a recovery rate of 98.33%.

[0053] Comparative Example

[0054] The flotation separation method for the positive and negative electrode materials of waste batteries in this comparative example is a traditional processing method, including the following steps:

[0055] (1) 500g of waste ternary lithium battery positive and negative electrode mixture was screened using a 0.075mm sieve. The material on the sieve was other impurities, and the material below the sieve was the positive and negative electrode mixture.

[0056] (2) The screened material is placed in a ceramic boat and placed in a tube furnace. The temperature is raised to 550°C in a nitrogen atmosphere and held for 2 hours. After cooling, the pyrolyzed material is obtained.

[0057] (3) Weigh 35g of the pyrolysis material and place it in an XFD single-cell flotation machine. Add water to 140ml, stir and adjust the slurry for 3 minutes. The flotation machine speed is 1800r / min. Add 250g / t of dodecane and adjust the slurry for 3 minutes. Add 200g / t of methyl isobutyl methanol and adjust the slurry for 1 minute before proceeding with the flotation operation. The flotation time is 3 minutes, and the aeration rate is 0.2m³. 3 The foam product obtained was graphite, and the sediment product was ternary lithium concentrate. The graphite and ternary lithium concentrate were filtered and dried separately, and the grade of the ternary lithium concentrate was determined.

[0058] After testing, the final yield of ternary lithium cathode powder was 92.45% and 91.68% in grade and recovery rate, respectively.

[0059] The preferred embodiments of the present invention have been described in detail above with reference to the examples. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0060] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0061] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A flotation recycling method for waste lithium-ion batteries with no fluorine or carbon emissions, characterized in that, Includes the following steps: S1. The mixture of positive and negative electrodes from waste lithium-ion batteries is subjected to low-temperature treatment at a temperature of 300~350℃ for 0.5~1 h, which causes the surface binder to deform and exposes the surface of the positive electrode material particles. S2. Adjust the material processed in step S1 to obtain flotation slurry. S3. Perform the following steps at least once: add an organic hydrophilic inhibitor, a collector and a frother to the flotation slurry in sequence, then scrape the foam to remove the graphite product and obtain sediment. The organic hydrophilic inhibitor is one or more of carboxymethyl cellulose, soluble starch and dextrin. S4. The sediment obtained in step S3 is slurry-adjusted, and a collector and frother are added. The sediment is then floated again to obtain ternary lithium concentrate.

2. The method according to claim 1, characterized in that, In step S1, the particle size of the mixture is less than 0.075 mm.

3. The method according to claim 1, characterized in that, In step S1, the low-temperature treatment is one or more of the following: low-temperature calcination, low-temperature pyrolysis, low-temperature radiation, or low-temperature contact.

4. The method according to claim 1, characterized in that, In steps S2 and S4, the mixing speed is 1600~1800 r / min, and the time is 3~5 min.

5. The method according to claim 1, characterized in that, In step S3, the collector is one or more of dodecane, kerosene, and emulsified kerosene; the foaming agent is one or more of methyl isobutyl methanol, 2-octanol, and No. 2 oil.

6. The method according to claim 1, characterized in that, In step S3, relative to 1 ton of dry mixed material, the amount of the inhibitor added is 100-250 g, the amount of the collector added is 150-250 g, and the amount of the foaming agent added is 150-250 g.

7. The method according to claim 6, characterized in that, Add the inhibitor to the flotation slurry and stir for 2-3 minutes, then add the collector, stir again for 2-3 minutes, then add the frother and stir for 1-2 minutes.

8. The method according to claim 1, characterized in that, In step S4, the amount of the collector added is 100-150 g relative to 1 ton of dry mixed material, and the amount of the foaming agent added is 100-150 g.

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