Method for synergistically separating positive and negative materials in waste lithium battery by composite pretreatment and flotation

Abstract

The application discloses a method for separating positive and negative electrode materials in waste lithium batteries by composite pretreatment and flotation, and belongs to the technical field of recycling waste lithium batteries. The method comprises the following steps: discharging, disassembling, crushing and screening the scrapped lithium batteries to obtain positive and negative electrode material mixture powder; performing composite pretreatment on the positive and negative electrode material mixture powder, wherein the composite pretreatment comprises the following steps: firstly, using an organic solvent A to perform first soaking treatment on the positive and negative electrode material mixture powder; then, performing first roasting treatment on the material after the first soaking; secondly, using an organic solvent B to perform second soaking treatment on the material after the first roasting; and finally, performing second roasting treatment on the material after the second soaking; and performing flotation on the material after the composite pretreatment to obtain separated positive and negative electrode materials. The method can not only improve the separation efficiency of the positive and negative electrode materials, but also significantly improve the recovery rate and grade.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource recycling, and in particular relates to a method for efficiently separating positive and negative electrode materials in waste lithium batteries by synergistically combining composite pretreatment and flotation. Background Art

[0002] Lithium batteries, as highly efficient energy storage devices, have become an indispensable part of modern society. Their applications are vast, ranging from mobile phones to electric vehicles. Their superior performance meets the demands of a wide range of portable electronic devices. Their popularity stems primarily from their high energy density, long lifespan, and low self-discharge rate. These advantages have enabled lithium batteries to dominate the market and become a standard feature of modern electronic products.

[0003] However, the widespread use of lithium-ion batteries has also led to a significant consumption of scarce and finite resources, especially metals such as lithium, cobalt, and nickel. The mining of these resources not only puts pressure on the environment, but as demand increases, resource sustainability becomes a serious issue. Battery recycling is a promising method for resource utilization. The recycling process includes battery collection, decomposition, material recovery, and remanufacturing. Among these, it is important to effectively separate and recover valuable materials such as lithium, cobalt, and nickel from batteries.

[0004] However, the problems faced by lithium battery recycling should not be underestimated. For example, the negative electrode material is used as a fuel or reducing agent, and its own recycling value is often ignored. This practice not only wastes precious resources, but also reduces the economic benefits of the entire recycling process. Some researchers have proposed a technical solution of flotation separation of positive and negative electrodes after pretreatment and then recycling them separately. This solution can not only increase the recycling value of negative electrode materials, but also reduce the cost. However, there are also some problems and challenges. For example, the pretreatment step may produce environmental pollution problems such as waste gas and wastewater, and the flotation efficiency is limited by the presence of organic binders. These binders will reduce the surface wettability contrast of the electrode material and affect the flotation efficiency. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a method for efficiently separating positive and negative electrode materials in waste lithium batteries by combining composite pretreatment and flotation.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A method for efficiently separating positive and negative electrode materials in waste lithium batteries by combining composite pretreatment and flotation, comprising the following steps:

[0008] (1) Discharging, disassembling, crushing and screening the scrapped lithium batteries to obtain a mixture of positive and negative electrode materials;

[0009] (2) performing a composite pretreatment on the positive and negative electrode material mixture powder, wherein the composite pretreatment includes first soaking the positive and negative electrode material mixture powder in an organic solvent A, then performing a first roasting treatment on the material after the first soaking; then soaking the material after the first roasting treatment in an organic solvent B for a second time, and finally performing a second roasting treatment on the material after the second soaking;

[0010] (3) flotation of the material after the composite pretreatment in step (2);

[0011] (4) The tailings and concentrate obtained by flotation in step (3) are washed, filtered, and dried to obtain separated positive and negative electrode materials. The tailings serve as the positive electrode and the concentrate serves as the negative electrode.

[0012] By synergistically treating waste lithium battery materials through step-by-step solvent immersion and multi-stage atmosphere roasting, the binder, electrolyte, solvent and other organic substances coated on the surface of the positive electrode material can be removed, its hydrophilicity can be restored, and the difference in surface properties of the positive and negative electrode materials can be expanded, thereby ensuring that the positive and negative electrode materials can be separated by flotation.

[0013] In the above-mentioned method for the efficient separation of positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation, preferably, in step (2), the first calcination treatment adopts a two-stage continuous atmosphere calcination, first heating to 120-150°C, keeping warm for 1-1.5 hours, then heating to 550-650°C, keeping warm for 2-2.5 hours, and the first calcination treatment is carried out in an argon atmosphere;

[0014] The second calcination treatment is carried out in an argon atmosphere at a temperature of 200-250° C. for 1 to 1.5 hours.

[0015] In the above-mentioned method for the efficient separation of positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation, preferably, in step (2), the organic solvent A is one or more of NMP (N-methylpyrrolidone), DMF (N,N-dimethylformamide), DMI (1,3-dimethyl-2-imidazolidinone), and DMC (dimethyl carbonate);

[0016] The organic solvent B is one or more of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and Cyrene™ (dihydro-levulinone).

[0017] The above-mentioned method for the efficient separation of positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation, preferably, in step (2), the liquid-solid mass ratio of the first soaking treatment is 10-15:1, and ultrasound-assisted soaking is used during the soaking process, the ultrasound power is 80-100 W, and the ultrasound time is 20-25 min;

[0018] The liquid-to-solid mass ratio of the second soaking treatment is 10-15:1, and mechanical stirring is used to assist soaking during the soaking process. The stirring speed is 400-450 rpm, the soaking temperature is 70-90°C, and the soaking time is 40-45 min.

[0019] The soaking step enhanced by ultrasound and temperature can improve the processing efficiency and reduce energy consumption and time costs.

[0020] According to the principle of like dissolves like, organic solvent A can be used to dissolve the electrolyte, solvent and other organic substances in the mixed material, remove some organic substances on the surface of the positive electrode material, and change its surface properties. Ultrasonic assistance can shorten the soaking time to improve efficiency. However, after filtering and removing the organic solvent A, it will form an organic coating on the surface of the positive electrode material, which is difficult to remove by water washing alone. This technical problem can be solved by introducing a two-stage continuous atmosphere roasting process. The first stage of low-temperature roasting can preheat the material and remove the residue of organic solvent A at the same time. The second stage of high-temperature roasting can remove other organic substances including binders.

[0021] Based on the principle of like dissolves like, soaking in organic solvent B can dissolve the binder and other organic matter in the mixed material, remove the remaining organic matter, and restore its surface properties to complete hydrophilicity; similarly, after filtering out organic solvent B, it will form an organic coating on the surface of the positive electrode material. By introducing a low-temperature roasting process, the residue of organic solvent B can be removed.

[0022] It is particularly important to note that organic solvent B can be recycled multiple times. In practice, it can be recycled more than 50 times. Organic solvent B can be recycled multiple times and is non-toxic and harmless, greatly reducing processing costs and environmental impact.

[0023] In the above-mentioned method for synergistically separating positive and negative electrode materials in waste lithium batteries by composite pretreatment and flotation, preferably, in step (3), the flotation process specifically includes mixing the composite pretreated material with water and placing it in a flotation tank of a flotation machine, and starting a stirring program; during the stirring process, first adjusting the pH to 9-11, stirring for 2-3 minutes, then adding a collector, stirring for another 2-3 minutes, then adding a foaming agent, and finally stirring for 1-2 minutes, scraping out the foam tailings, and continuing for 3-6 minutes until foam is no longer generated and the bottom concentrate is retained in the flotation tank.

[0024] In the above-mentioned method for efficiently separating positive and negative electrode materials in waste lithium batteries by synergistically combining composite pretreatment and flotation, preferably, the flotation machine is an XFG type hanging tank flotation machine; the fixed speed in the stirring process is 1600-1800 rpm; and during the stirring process, sodium hydroxide or sodium carbonate is used to adjust the pH value.

[0025] In the above-mentioned method for synergistically and efficiently separating positive and negative electrode materials from waste lithium batteries by composite pretreatment and flotation, preferably, the collector is kerosene in an amount of 200-300 g / t; the foaming agent is octanol in an amount of 100-150 g / t.

[0026] In the above-mentioned method for efficiently separating positive and negative electrode materials from waste lithium batteries by combining composite pretreatment and flotation, preferably, in step (1), the positive and negative electrode material mixture powder is a material that falls under a 200-mesh sieve.

[0027] In the above-mentioned method for synergistically separating positive and negative electrode materials from waste lithium batteries by composite pretreatment and flotation, preferably, in step (4), the filtration uses a water-based filter membrane with a pore size of 0.45 μm.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention can effectively remove organic matter such as electrolyte, solvent, binder, etc. on the surface of the positive electrode material through step-by-step solvent immersion and multi-stage atmosphere roasting composite pretreatment, so that the surface property of the positive electrode material is completely converted into hydrophilicity, thereby expanding the surface property difference between the positive and negative electrode materials; then, through subsequent flotation treatment, during the flotation process, by accurately controlling the pH value and adding an appropriate amount of collector and frother, not only the separation efficiency of the positive and negative electrode materials can be improved, but also the recovery rate and grade can be significantly improved, providing a fundamental guarantee for the subsequent separation of the positive and negative electrode materials, and contributing to the economic value and environmental sustainability of the entire recovery process of the positive and negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a process flow chart of the present invention for the coordinated and efficient separation of positive and negative electrode materials in waste lithium batteries by composite pretreatment and flotation. DETAILED DESCRIPTION

[0031] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0034] The scrapped ternary lithium batteries processed in the following examples and comparative examples are from the same batch of nickel-cobalt-manganese ternary lithium batteries, whose positive electrode materials are LiNi 0.5 Co 0.2 Mn 0.3 O2, the negative electrode material is graphite.

[0035] Example 1:

[0036] A method for the efficient separation of positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation is shown in the process flow chart. Figure 1 As shown, the following steps are included:

[0037] (1) After discharging, disassembling and crushing the scrapped ternary lithium battery (waste ternary battery), a mixture of positive and negative electrode materials is obtained, which is graded and continuously sieved, and 20 g of powder under a 200-mesh sieve is taken as the material;

[0038] (2) The material was ultrasonically soaked in NMP (N-methylpyrrolidone) with a liquid-to-solid mass ratio of 10:1, an ultrasonic time of 20 min, and a power of 80 W. The soaked material was filtered and sent into a tube furnace for continuous atmosphere roasting. The temperature was first raised to 120 °C and kept at this temperature for 1 h, then raised to 550 °C and kept at this temperature for 2 h. The roasting was carried out in an argon atmosphere.

[0039] (3) The material calcined in step (2) was subjected to temperature-enhanced soaking using a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinone) in a mass ratio of 3:3:4. The mass ratio of the mixed solvent to the material was 10:1, the soaking temperature was 70°C, the soaking time was 40 min, and the soaking process was assisted by mechanical stirring at a speed of 400 rpm. The soaked material was filtered and sent into a tube furnace for atmosphere roasting at a roasting temperature of 200°C for 1 hour in an argon atmosphere.

[0040] (4) The calcined material in step (3) was mixed with water and placed in the flotation tank of an XFG type hanging tank flotation machine, and the stirring program was started at a speed of 1600 rpm. During the stirring process, the pH was first adjusted to 9 using a 1 mol / L sodium hydroxide solution. After stirring for 2 minutes, a collector, kerosene (200 g / t), was added. After stirring for 2 minutes, a foaming agent, octanol (100 g / t), was added. Finally, stirring was performed for 1 minute to scrape out the foam tailings. The scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank.

[0041] (5) The tailings and concentrate were washed three times with pure water, filtered, and placed in an 80°C oven for 12 hours to obtain separated positive and negative electrode materials. The tailings were used as the positive electrode and the concentrate was used as the negative electrode. The overall product of the system was calculated, and the results are listed in Table 1.

[0042] Example 2:

[0043] A method for the efficient separation of positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation is shown in the process flow chart. Figure 1 As shown, the following steps are included:

[0044] (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, a mixture of positive and negative electrode materials is obtained, which is then graded and continuously sieved, and 20 g of powder under a 200-mesh sieve is taken as the material;

[0045] (2) The material was ultrasonically soaked in DMF (N,N-dimethylformamide) with a liquid-to-solid mass ratio of 10:1, an ultrasonic time of 20 min, and a power of 80 W. The soaked material was filtered and sent into a tube furnace for continuous atmosphere roasting. The temperature was first raised to 120 °C and kept at this temperature for 1 h, then raised to 550 °C and kept at this temperature for 2 h. The roasting was carried out in an argon atmosphere.

[0046] (3) The material calcined in step (2) was subjected to temperature-enhanced soaking using a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinone) in a mass ratio of 3:3:4. The mass ratio of the mixed solvent to the material was 10:1, the soaking temperature was 70°C, the soaking time was 40 min, and the soaking process was assisted by mechanical stirring at a speed of 400 rpm. The soaked material was filtered and sent into a tube furnace for atmosphere roasting at a roasting temperature of 200°C for 1 hour in an argon atmosphere.

[0047] (4) The calcined material in step (3) was mixed with water and placed in the flotation tank of an XFG type hanging tank flotation machine, and the stirring program was started at a speed of 1600 rpm. During the stirring process, the pH was first adjusted to 9 using a 1 mol / L sodium hydroxide solution. After stirring for 2 minutes, a collector, kerosene (200 g / t), was added. After stirring for another 2 minutes, a foaming agent, octanol (100 g / t), was added. Finally, stirring was continued for 1 minute to scrape out the foam tailings. The scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank.

[0048] (5) The tailings and concentrate were washed three times with pure water, filtered, and placed in an 80°C oven for 12 hours to obtain separated positive and negative electrode materials. The tailings were used as the positive electrode and the concentrate was used as the negative electrode. The overall product of the system was calculated, and the results are listed in Table 1.

[0049] Example 3:

[0050] A method for the efficient separation of positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation is shown in the process flow chart. Figure 1As shown, the following steps are included:

[0051] (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, a mixture of positive and negative electrode materials is obtained, which is then graded and continuously sieved, and 20 g of powder under a 200-mesh sieve is taken as the material;

[0052] (2) The material was ultrasonically soaked in DMI (1,3-dimethyl-2-imidazolidinone) with a liquid-to-solid mass ratio of 15:1, an ultrasonic time of 25 min, and a power of 100 W. The soaked material was filtered and sent into a tube furnace for continuous atmosphere roasting. The temperature was first raised to 150 ° C and kept warm for 1.5 h, then raised to 650 ° C and kept warm for 2.5 h. The roasting was carried out in an argon atmosphere.

[0053] (3) The material after calcination in step (2) was soaked in a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinone) in a mass ratio of 2:4:4. The mass ratio of the mixed solvent to the material was 15:1. The soaking temperature was 90°C and the soaking time was 45 min. The soaking process was assisted by mechanical stirring at a speed of 450 rpm. The soaked material was filtered and sent into a tube furnace for atmosphere roasting at a roasting temperature of 250°C for 1.5 h in an argon atmosphere.

[0054] (4) The calcined material in step (3) was mixed with water and placed in the flotation tank of an XFG type hanging tank flotation machine, and the stirring program was started at a speed of 1800 rpm. During the stirring process, the pH was first adjusted to 11 using a 2 mol / L sodium carbonate solution. After stirring for 3 minutes, a collector kerosene (300 g / t) was added. After stirring for another 3 minutes, a foaming agent octanol (150 g / t) was added. Finally, stirring was continued for 2 minutes to scrape out the foam tailings. The scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank.

[0055] (5) The tailings and concentrate were washed three times with pure water, filtered, and placed in an 80°C oven for 12 hours to obtain separated positive and negative electrode materials, with the tailings as the positive electrode and the concentrate as the negative electrode. The overall product of the system was calculated, and the results are listed in Table 1.

[0056] Example 4:

[0057] A method for the efficient separation of positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation is shown in the process flow chart. Figure 1 As shown, the following steps are included:

[0058] (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, a mixture of positive and negative electrode materials is obtained, which is then graded and continuously sieved, and 20 g of powder under a 200-mesh sieve is taken as the material;

[0059] (2) Use DMC (dimethyl carbonate) to ultrasonically soak the material with a liquid-solid mass ratio of 15:1, an ultrasonic time of 25 minutes, and a power of 100W; the soaked material is filtered and sent into a tube furnace for continuous atmosphere roasting, first heating to 150°C, keeping warm for 1.5 hours, then heating to 650°C, keeping warm for 2.5 hours, and roasting is carried out in an argon atmosphere;

[0060] (3) The material after calcination in step (2) was soaked in a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinic ketone) in a mass ratio of 2:4:4. The mass ratio of the mixed solvent to the material was 15:1. The soaking temperature was 90°C and the soaking time was 45 min. The soaking process was assisted by mechanical stirring at a speed of 450 rpm. The soaked material was filtered and sent into a tubular furnace for atmosphere roasting at a temperature of 250°C for 1.5 h in an argon atmosphere.

[0061] (4) The calcined material from step (3) was mixed with water and placed in the flotation cell of an XFG type hanging trough flotation machine, and the stirring program was started at a speed of 1800 rpm. During the stirring process, the pH was first adjusted to 11 using a 2 mol / L sodium carbonate solution. After stirring for 3 minutes, a collector, kerosene (300 g / t), was added. After stirring for another 3 minutes, a foaming agent, octanol (150 g / t), was added. Finally, stirring was performed for 2 minutes to scrape out the foam tailings. The scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation cell.

[0062] (5) The tailings and concentrate were washed three times with pure water, filtered, and placed in an 80°C oven for 12 hours to obtain separated positive and negative electrode materials, with the tailings as the positive electrode and the concentrate as the negative electrode. The overall product of the system was calculated, and the results are listed in Table 1.

[0063] Comparative Example 1:

[0064] The method for separating positive and negative electrode materials in waste lithium batteries in this comparative example comprises the following steps:

[0065] (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, a mixture of positive and negative electrode materials is obtained, which is then graded and continuously sieved, and 20 g of powder under a 200-mesh sieve is taken as the material;

[0066] (2) The material was ultrasonically soaked in NMP (N-methylpyrrolidone) with a liquid-to-solid mass ratio of 20:1, an ultrasonic time of 10 min, and a power of 60 W. The soaked material was filtered and sent into a tube furnace for continuous atmosphere roasting. The temperature was first raised to 200 °C and kept at this temperature for 1 h, then raised to 800 °C and kept at this temperature for 2 h. The roasting was carried out in an argon atmosphere.

[0067] (3) The material after calcination in step (2) was soaked in a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinic acid ketone) in a mass ratio of 4:3. The mass ratio of the mixed solvent to the material was 20:1, the soaking temperature was 25°C, the soaking time was 20 min, and the soaking process was assisted by mechanical stirring at a speed of 400 rpm. The soaked material was filtered and sent into a tube furnace for atmosphere roasting at a roasting temperature of 150°C for 1 hour in an argon atmosphere.

[0068] (4) The calcined material in step (3) was mixed with water and placed in the flotation cell of an XFG type hanging trough flotation machine, and the stirring program was started at a speed of 1600 rpm. During the stirring process, the pH was first adjusted to 12 using a 1 mol / L sodium hydroxide solution. After stirring for 2 minutes, a collector kerosene (500 g / t) was added. After stirring for another 2 minutes, a foaming agent octanol (20 g / t) was added. Finally, stirring was continued for 1 minute to scrape out the foam tailings. The scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation cell.

[0069] (5) The tailings and concentrate were washed three times with pure water, filtered, and placed in an 80°C oven for 12 hours to obtain separated positive and negative electrode materials. The tailings were used as the positive electrode and the concentrate was used as the negative electrode. The overall product of the system was calculated, and the results are listed in Table 1.

[0070] Comparative Example 2:

[0071] The method for separating positive and negative electrode materials in waste lithium batteries in this comparative example specifically comprises the following steps:

[0072] (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, a mixture of positive and negative electrode materials is obtained, which is then graded and continuously sieved, and 20 g of powder under a 200-mesh sieve is taken as the material;

[0073] (2) The material was soaked in a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinone) in a mass ratio of 2:4:4. The mass ratio of the mixed solvent to the material was 15:1, the soaking temperature was 90°C, the soaking time was 45 min, and the soaking process was assisted by mechanical stirring at a speed of 450 rpm. The soaked material was filtered and sent into a tube furnace for continuous atmosphere roasting. The temperature was first raised to 150°C and kept at this temperature for 1.5 h, then raised to 650°C and kept at this temperature for 2.5 h. The roasting was carried out in an argon atmosphere.

[0074] (3) Using DMC (dimethyl carbonate) to ultrasonically soak the material after calcination in step (2), the liquid-solid mass ratio is 15:1, the ultrasonic time is 25 minutes, and the power is 100W; the material after ultrasonic soaking is filtered and sent into a tube furnace for atmosphere roasting at a roasting temperature of 250°C, and kept warm for 1.5 hours in an argon atmosphere;

[0075] (4) The calcined material from step (3) was mixed with water and placed in the flotation cell of an XFG type hanging trough flotation machine, and the stirring program was started at a speed of 1800 rpm. During the stirring process, the pH was first adjusted to 11 using a 2 mol / L sodium carbonate solution. After stirring for 3 minutes, a collector, kerosene (300 g / t), was added. After stirring for another 3 minutes, a foaming agent, octanol (150 g / t), was added. Finally, stirring was performed for 2 minutes to scrape out the foam tailings. The scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation cell.

[0076] (5) The tailings and concentrate were washed three times with pure water, filtered, and placed in an 80°C oven for 12 hours to obtain separated positive and negative electrode materials. The tailings were used as the positive electrode and the concentrate was used as the negative electrode. The overall product of the system was calculated, and the results are listed in Table 1.

[0077] Comparative Example 3:

[0078] The method for separating positive and negative electrode materials in waste lithium batteries in this comparative example specifically comprises the following steps:

[0079] (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, a mixture of positive and negative electrode materials is obtained, which is then graded and continuously sieved, and 20 g of powder under a 200-mesh sieve is taken as the material;

[0080] (2) The material was sent into a tube furnace for continuous atmosphere roasting, first heated to 150 ° C, kept warm for 1.5 hours, then heated to 650 ° C, kept warm for 2.5 hours, and roasting was carried out in an argon atmosphere; the roasted material was ultrasonically soaked in DMC (dimethyl carbonate), with a liquid-to-solid mass ratio of 15:1, an ultrasonic time of 25 minutes, and a power of 100W;

[0081] (3) The material after ultrasonic soaking in step (2) was sent to a tube furnace for atmosphere roasting at a roasting temperature of 250°C for 1.5 hours in an argon atmosphere; the roasted material was subjected to temperature-enhanced soaking in a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinone) in a mass ratio of 2:4:4, the mass ratio of the mixed solvent to the material was 15:1, the soaking temperature was 90°C, the soaking time was 45 minutes, and the soaking process was assisted by mechanical stirring at a rotation speed of 450 rpm;

[0082] (4) The material after temperature-enhanced soaking in step (3) was mixed with water and placed in the flotation tank of the XFG hanging tank flotation machine, and the stirring program was started at a speed of 1800 rpm. During the stirring process, 2 mol / L sodium carbonate solution was first used to adjust the pH to 11, and after stirring for 3 minutes, kerosene (300 g / t) as a collector was added, and after stirring for another 3 minutes, octanol (150 g / t) as a foaming agent was added. Finally, stirring was carried out for 2 minutes to scrape out the foam tailings, and the scraping was continued for 6 minutes. The bottom concentrate was retained in the flotation tank;

[0083] (5) The tailings and concentrate were washed three times with pure water, filtered, and placed in an 80°C oven for 12 hours to obtain separated positive and negative electrode materials. The tailings were used as the positive electrode and the concentrate was used as the negative electrode. The overall product of the system was calculated, and the results are listed in Table 1.

[0084] Table 1 Product recovery and grade of Examples 1-4 and Comparative Example 1

[0085]

[0086] The above experimental results show that the present invention has obvious advantages over traditional processes, and is particularly outstanding in improving recycling efficiency, optimizing product quality and saving energy. At the same time, it has broad development prospects for the economic value and environmental sustainability of the recycling process.

Claims

1. A method for efficiently separating positive and negative electrode materials from waste lithium batteries by combining composite pretreatment and flotation, characterized in that: The following steps are involved: (1) Discharging, disassembling, crushing and screening the scrapped lithium batteries to obtain a mixture of positive and negative electrode materials; (2) The positive and negative electrode material mixture powder is subjected to composite pretreatment, the composite pretreatment comprising first soaking the positive and negative electrode material mixture powder with an organic solvent A, and then subjecting the material after the first soaking to a first roasting treatment; then soaking the material after the first roasting treatment with an organic solvent B for a second time, and finally subjecting the material after the second soaking to a second roasting treatment; wherein the first roasting treatment adopts a two-stage continuous atmosphere roasting, first heating to 120-150°C, keeping warm for 1-1.5 h, then heating to 550-650°C, keeping warm for 2-2.5 h, the first roasting treatment is carried out in an argon atmosphere; the second roasting treatment is carried out in an argon atmosphere, the temperature of the second roasting treatment is 200-250°C, and keeping warm for 1-1.5 h; the organic solvent A is one or more of N-methylpyrrolidone, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, and dimethyl carbonate; the organic solvent B is one or more of γ-valerolactone, N,N-dimethylacetamide, and dihydro-levulinone; (3) flotation of the material after the composite pretreatment in step (2); (4) The tailings and concentrate obtained by flotation in step (3) are washed, filtered, and dried to obtain separated positive and negative electrode materials.

2. The method for efficiently separating positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation according to claim 1, characterized in that: In step (2), the liquid-to-solid mass ratio of the first immersion treatment is 10-15:1, and ultrasound-assisted immersion is used during the immersion process, the ultrasound power is 80-100 W, and the ultrasound time is 20-25 min; The liquid-to-solid mass ratio of the second soaking treatment is 10-15:1, and mechanical stirring is used to assist soaking during the soaking process. The stirring speed is 400-450 rpm, the soaking temperature is 70-90° C., and the soaking time is 40-45 min.

3. The method for efficiently separating positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation according to claim 1, characterized in that: In step (3), the flotation process specifically includes mixing the composite pretreated material with water and placing it in the flotation tank of the flotation machine, and starting the stirring process; during the stirring process, first adjusting the pH value to 9-11, stirring for 2-3 minutes, adding the collector, stirring for another 2-3 minutes, adding the frother, and finally stirring for 1-2 minutes, scraping out the foam tailings, and retaining the bottom concentrate in the flotation tank.

4. The method for efficiently separating positive and negative electrode materials from waste lithium batteries by combined pretreatment and flotation according to claim 3, characterized in that: The flotation machine is an XFG hanging trough flotation machine; the fixed rotation speed in the stirring process is 1600-1800 rpm; during the stirring process, sodium hydroxide or sodium carbonate is used to adjust the pH value.

5. The method for efficiently separating positive and negative electrode materials from waste lithium batteries by combined pretreatment and flotation according to claim 3, characterized in that: The collector is kerosene, and the dosage is 200-300 g / t; the foaming agent is octanol, and the dosage is 100-150 g / t.

6. The method for efficiently separating positive and negative electrode materials from waste lithium batteries by combined pretreatment and flotation as claimed in claim 3, characterized in that: In step (1), the positive and negative electrode material mixture powder is a 200-mesh sieve.

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