Method for efficiently separating positive and negative electrode materials in waste lithium battery through cooperation of composite pretreatment and flotation

Abstract

The invention discloses a method for efficiently separating positive and negative electrode materials in a waste lithium battery through cooperation of composite pretreatment and flotation. The method comprises the following steps: discharging, disassembling, crushing and screening the scrapped lithium battery to obtain positive and negative electrode material mixture powder; carrying out composite pretreatment on the positive and negative electrode material mixture powder, namely carrying out first soaking treatment on the positive and negative electrode material mixture powder by adopting an organic solvent A, and then carrying out first roasting treatment on the material subjected to the first soaking treatment; performing second soaking treatment on the material subjected to the first roasting treatment by adopting an organic solvent B, and finally performing second roasting treatment on the material subjected to the second soaking treatment; and carrying out flotation on the material subjected to composite pretreatment to obtain separated positive and negative electrode materials. The method provided by the invention not only can improve the separation efficiency of positive and negative electrode materials, but also can 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 a highly efficient energy storage device, have become an indispensable part of modern society. They are widely used in a wide range of applications, from mobile phones to electric vehicles. Lithium batteries meet the needs of various portable electronic devices with their excellent performance. Lithium batteries are popular mainly because of their high energy density, long life and low self-discharge rate. These advantages have made lithium batteries dominate the market and become a standard feature of modern electronic products.

[0003] However, the widespread use of lithium batteries has also brought about a large consumption of rare and limited 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, the sustainability of resources has also become a serious issue. Battery recycling is a very promising method for resource utilization. The recycling process includes battery collection, decomposition, material recovery and remanufacturing. Among them, it is important to effectively separate and recover valuable materials in batteries, such as lithium, cobalt and nickel.

[0004] However, the problems faced by lithium battery recycling should not be underestimated. For example, the use of negative electrode materials as fuel or reducing agents often ignores their own recycling value. 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 to separate the positive and negative electrodes by flotation after pretreatment and then recycle them separately. This can not only increase the recovery 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: A method for efficiently separating positive and negative electrode materials in waste lithium batteries by composite pretreatment and flotation, comprising the following steps: (1) Discharging, disassembling, crushing and screening the scrapped lithium batteries to obtain a mixture of positive and negative electrode materials; (2) performing a composite pretreatment on the positive and negative electrode material mixture powder, wherein the composite pretreatment includes firstly soaking the positive and negative electrode material mixture powder in an organic solvent A, and 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; (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 respectively to obtain separated positive and negative electrode materials. The tailings are the positive electrode and the concentrate is the negative electrode.

[0007] Through the coordinated treatment of 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.

[0008] The above-mentioned method for the synergistic and efficient separation of positive and negative electrode materials in waste lithium batteries by composite pretreatment and flotation, preferably, in step (2), the first calcination treatment adopts a two-stage continuous atmosphere calcination, firstly 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, and the first calcination treatment is carried out in an argon atmosphere; The second calcination treatment is carried out in an argon atmosphere at a temperature of 200-250° C. for 1 to 1.5 hours.

[0009] 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); The organic solvent B is one or more of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinic acid ketone).

[0010] The above-mentioned method for the synergistic and efficient separation of positive and negative electrode materials in waste lithium batteries by composite pretreatment and flotation, preferably, 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.

[0011] The soaking step enhanced by ultrasound and temperature can improve the processing efficiency and reduce energy consumption and time costs.

[0012] According to the principle of like dissolves like, organic matter such as electrolyte and solvent in the mixed material can be dissolved by soaking in organic solvent A, and some organic matter on the surface of the positive electrode material can be removed, so that its surface properties can be changed. Ultrasonic assistance can be used to 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, in which a low-temperature roasting stage can preheat the material and remove the residue of organic solvent A at the same time, and a two-stage high-temperature roasting stage can remove other organic substances including binders.

[0013] According to the principle of like dissolves like, the organic matter such as the binder in the mixed material can be dissolved by soaking in organic solvent B, and the remaining organic matter can be removed, so that the surface properties can be completely restored to hydrophilicity; similarly, after filtering and removing 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.

[0014] It is particularly important to point out that the organic solvent B can be recycled for multiple times. In practice, it can be recycled for more than 50 times. The organic solvent B can be recycled for multiple times and is non-toxic and harmless, which greatly reduces the processing cost and environmental impact.

[0015] In the above-mentioned method for the synergistic and efficient separation of positive and negative electrode materials in waste lithium batteries by composite pretreatment and flotation, preferably, in step (3), the flotation process specifically comprises mixing the composite pretreated material with water and placing it in a flotation tank of a flotation machine, and starting a stirring procedure; during the stirring process, first adjusting the pH value to 9-11, stirring for 2-3 minutes, then adding a collector, stirring for another 2-3 minutes, then adding a frother, and finally stirring for 1-2 minutes, scraping out the foam tailings, and continuing for 3-6 minutes until the foam is no longer generated and the bottom concentrate is retained in the flotation tank.

[0016] In the above-mentioned method for efficiently separating positive and negative electrode materials in waste lithium batteries by combined 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; during the stirring process, sodium hydroxide or sodium carbonate is used to adjust the pH value.

[0017] In the above-mentioned method for synergistically separating positive and negative electrode materials in 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.

[0018] In the above-mentioned method for efficiently separating positive and negative electrode materials in waste lithium batteries by combining composite pretreatment and flotation, preferably, in step (1), the positive and negative electrode material mixture powder is a material under a 200-mesh sieve.

[0019] In the above-mentioned method of combining composite pretreatment with flotation to efficiently separate positive and negative electrode materials from waste lithium batteries, preferably, in step (4), the suction filtration uses a water filter membrane with a pore size of 0.45 μm.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention can effectively remove organic matter such as electrolyte, solvent, binder, etc. on the surface of positive electrode materials through composite pretreatment of step-by-step solvent immersion and multi-stage atmosphere roasting, so that the surface property of the positive electrode materials is completely converted into hydrophilicity, thereby expanding the surface property difference between the positive and negative electrode materials; and 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, which provides a fundamental guarantee for the subsequent separation of the positive and negative electrode materials and contributes to the economic value and environmental sustainability of the entire recovery process of the positive and negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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

[0022] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional 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.

[0024] 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.

[0025] The scrapped ternary lithium batteries treated 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 Co0.2 Mn 0.3 O2, the negative electrode material is graphite.

[0026] Embodiment 1: A method for the composite pretreatment and flotation synergistically and efficiently separating positive and negative electrode materials in waste lithium batteries of the present invention, the process flow chart of which is as follows Figure 1 As shown, the following steps are included: (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; (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 for 1 h, then raised to 550 °C and kept for 2 h. The roasting was carried out in an argon atmosphere. (3) using a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinic acid ketone) in a mass ratio of 3:3:4 to soak the material calcined in step (2) at a temperature-enhanced soaking temperature, the mass ratio of the mixed solvent to the material is 10:1, the soaking temperature is 70°C, the soaking time is 40 min, and the soaking process is assisted by mechanical stirring at a speed of 400 rpm; filtering the soaked material and sending it into a tubular furnace for atmosphere roasting at a roasting temperature of 200°C for 1 hour in an argon atmosphere; (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, 1 mol / L sodium hydroxide solution was first used to adjust the pH to 9, and after stirring for 2 minutes, a collector kerosene (200 g / t) was added, and after stirring for 2 minutes, a foaming agent 2-octanol (100 g / t) was added, and finally, stirring was performed for 1 minute to scrape out the foam tailings, and the scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank; (5) The tailings and concentrate were washed three times with pure water respectively, and after filtration, they were placed in an oven at 80°C 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.

[0027] Embodiment 2: A method for the composite pretreatment and flotation synergistically and efficiently separating positive and negative electrode materials in waste lithium batteries of the present invention, the process flow chart of which is as follows Figure 1 As shown, the following steps are included: (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, 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; (2) Use DMF (N,N-dimethylformamide) to ultrasonically soak the material, with a liquid-to-solid mass ratio of 10:1, an ultrasonic time of 20 min, and a power of 80 W; filter the soaked material and send it into a tube furnace for continuous atmosphere roasting, first heating to 120 ° C, keeping it warm for 1 h, then heating to 550 ° C, keeping it warm for 2 h, and roasting is carried out in an argon atmosphere; (3) using a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinic acid ketone) in a mass ratio of 3:3:4 to soak the material calcined in step (2) at a temperature-enhanced soaking temperature, the mass ratio of the mixed solvent to the material is 10:1, the soaking temperature is 70°C, the soaking time is 40 min, and the soaking process is assisted by mechanical stirring at a speed of 400 rpm; filtering the soaked material and sending it into a tubular furnace for atmosphere roasting at a roasting temperature of 200°C for 1 hour in an argon atmosphere; (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, 1 mol / L sodium hydroxide solution was first used to adjust the pH to 9, and after stirring for 2 minutes, a collector kerosene (200 g / t) was added, and after stirring for another 2 minutes, a foaming agent 2-octanol (100 g / t) was added, and finally stirring for 1 minute to scrape out the foam tailings, and the scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank; (5) The tailings and concentrate were washed three times with pure water respectively, and after filtration, they were placed in an oven at 80°C 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.

[0028] Embodiment 3: A method for the composite pretreatment and flotation synergistically and efficiently separating positive and negative electrode materials in waste lithium batteries of the present invention, the process flow chart of which is as follows Figure 1 As shown, the following steps are included: (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, 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; (2) Use DMI (1,3-dimethyl-2-imidazolidinone) to ultrasonically soak the material, 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 is filtered and 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 is carried out in an argon atmosphere; (3) using a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinic acid ketone) in a mass ratio of 2:4:4 to soak the material calcined in step (2) at a temperature-enhanced soaking temperature, the mass ratio of the mixed solvent to the material is 15:1, the soaking temperature is 90°C, the soaking time is 45 min, and the soaking process is assisted by mechanical stirring at a speed of 450 rpm; filtering the soaked material and sending it into a tubular furnace for atmosphere roasting at a roasting temperature of 250°C for 1.5 hours in an argon atmosphere; (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, 2 mol / L sodium carbonate solution was first used to adjust the pH to 11, and after stirring for 3 minutes, a collector kerosene (300 g / t) was added, and after stirring for another 3 minutes, a foaming agent 2-octanol (150 g / t) was added, and finally stirring for 2 minutes to scrape out the foam tailings, and the scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank; (5) The tailings and concentrate were washed three times with pure water respectively, and after filtration, they were placed in an oven at 80°C 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.

[0029] Embodiment 4: A method for the composite pretreatment and flotation synergistically and efficiently separating positive and negative electrode materials in waste lithium batteries of the present invention, the process flow chart of which is as follows Figure 1 As shown, the following steps are included: (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, 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; (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; filter the soaked material and send it into a tube furnace for continuous atmosphere roasting, first heating to 150°C, keeping it warm for 1.5 hours, then heating to 650°C, keeping it warm for 2.5 hours, and roasting is carried out in an argon atmosphere; (3) Using a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levulinic acid ketone) in a mass ratio of 2:4:4, the material after calcination in step (2) was soaked in a temperature-enhanced manner, 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 tubular furnace for atmosphere roasting at a roasting temperature of 250°C for 1.5 hours in an argon atmosphere; (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, 2 mol / L sodium carbonate solution was first used to adjust the pH to 11, and after stirring for 3 minutes, a collector kerosene (300 g / t) was added, and after stirring for another 3 minutes, a foaming agent 2-octanol (150 g / t) was added, and finally stirring for 2 minutes to scrape out the foam tailings, and the scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank; (5) The tailings and concentrate were washed three times with pure water respectively, and after filtration, they were placed in an oven at 80°C 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.

[0030] Comparative Example 1: The method for separating positive and negative electrode materials in waste lithium batteries in this comparative example comprises the following steps: (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, 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; (2) Use NMP (N-methylpyrrolidone) to ultrasonically soak the material, with a liquid-to-solid mass ratio of 20:1, an ultrasonic time of 10 min, and a power of 60 W; filter the soaked material and send it into a tube furnace for continuous atmosphere roasting, first heating to 200 ° C, keeping it warm for 1 h, then heating to 800 ° C, keeping it warm for 2 h, and roasting is carried out in an argon atmosphere; (3) Using a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levorotatory glucosone) in a mass ratio of 4:3, the material after calcination in step (2) was soaked in a temperature-enhanced manner, 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 tubular furnace for atmosphere roasting at a roasting temperature of 150°C for 1 hour in an argon atmosphere; (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 12 using a 1 mol / L sodium hydroxide solution, and then kerosene (500 g / t) as a collector was added after stirring for 2 minutes. After stirring for another 2 minutes, octanol (20 g / t) as a foaming agent was added. Finally, stirring was performed for 1 minute to scrape out the foam tailings, and the scraping was continued for 6 minutes. The bottom concentrate was retained in the flotation tank; (5) The tailings and concentrate were washed three times with pure water respectively, and after filtration, they were placed in an oven at 80°C 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.

[0031] Comparative Example 2: The method for separating positive and negative electrode materials in waste lithium batteries in this comparative example specifically comprises the following steps: (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, 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; (2) The material 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 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 continuous atmosphere roasting. The temperature was first raised to 150°C and kept for 1.5 hours, then raised to 650°C and kept for 2.5 hours. The roasting was carried out in an argon atmosphere. (3) using DMC (dimethyl carbonate) to ultrasonically immerse the material after calcination in step (2), with a liquid-solid mass ratio of 15:1, an ultrasonic time of 25 min, and a power of 100 W; filtering the material after ultrasonic immersion and sending it into a tube furnace for atmosphere calcination at a calcination temperature of 250°C for 1.5 h in an argon atmosphere; (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, 2 mol / L sodium carbonate solution was first used to adjust the pH to 11, and after stirring for 3 minutes, a collector kerosene (300 g / t) was added, and after stirring for another 3 minutes, a foaming agent 2-octanol (150 g / t) was added, and finally stirring for 2 minutes to scrape out the foam tailings, and the scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank; (5) The tailings and concentrate were washed three times with pure water respectively, and after filtration, they were placed in an oven at 80°C 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.

[0032] Comparative Example 3: The method for separating positive and negative electrode materials in waste lithium batteries in this comparative example specifically comprises the following steps: (1) After the scrapped ternary lithium battery is discharged, disassembled and crushed, 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; (2) The material was 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 hours, and then raised to 650°C and kept at this temperature for 2.5 hours. The 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 100 W. (3) The material after ultrasonic soaking in step (2) is sent into a tube furnace for atmosphere roasting at a roasting temperature of 250°C for 1.5 hours in an argon atmosphere; a mixed solvent of GVL (γ-valerolactone), DMAC (N,N-dimethylacetamide), and CyreneTM (dihydro-levorotatory glucosone) in a mass ratio of 2:4:4 is used to soak the roasted material in a temperature-enhanced manner, the mass ratio of the mixed solvent to the material is 15:1, the soaking temperature is 90°C, the soaking time is 45 minutes, and the soaking process is assisted by mechanical stirring at a rotation speed of 450 rpm; (4) The material after temperature-enhanced soaking 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, 2 mol / L sodium carbonate solution was first used to adjust the pH to 11, and after stirring for 3 minutes, a collector kerosene (300 g / t) was added, and after stirring for another 3 minutes, a foaming agent 2-octanol (150 g / t) was added, and finally stirring for 2 minutes to scrape out the foam tailings, and the scraping was continued for 6 minutes, and the bottom concentrate was retained in the flotation tank; (5) The tailings and concentrate were washed three times with pure water respectively, and after filtration, they were placed in an oven at 80°C 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.

[0033] Table 1 Product recovery and grade of Examples 1-4 and Comparative Example 1

[0034] 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 in waste lithium batteries by 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) performing a composite pretreatment on the positive and negative electrode material mixture powder, wherein the composite pretreatment includes firstly soaking the positive and negative electrode material mixture powder in an organic solvent A, and 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; (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 as claimed in claim 1, characterized in that: In step (2), the first calcination treatment adopts a two-stage continuous atmosphere calcination, firstly 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, and the first calcination treatment is carried out in an argon atmosphere; The second calcination treatment is carried out in an argon atmosphere at a temperature of 200-250° C. for 1-1.5 h.

3. The method for efficiently separating positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation as claimed in claim 1, characterized in that: In step (2), 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-levulinic ketone.

4. The method for efficiently separating positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation as claimed in 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.

5. The method for separating positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation synergistically and efficiently as claimed in claim 1, characterized in that: In step (3), the flotation process specifically includes mixing the composite pre-treated 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 and then adding the collector, stirring for another 2-3 minutes and then adding the frother, and finally stirring for 1-2 minutes, scraping out the foam tailings, and retaining the bottom concentrate in the flotation tank.

6. The method for separating positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation synergistically and efficiently as claimed in claim 5, characterized in that: The flotation machine is an XFG type hanging tank flotation machine; the fixed rotation speed in the stirring process is 1600-1800rpm; during the stirring process, sodium hydroxide or sodium carbonate is used to adjust the pH value.

7. The method for separating positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation synergistically and efficiently as claimed in claim 5, 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.

8. The method for separating positive and negative electrode materials in waste lithium batteries by combined pretreatment and flotation synergistically and efficiently as claimed in claim 5, characterized in that: In step (1), the positive and negative electrode material mixture powder is a 200-mesh sieve.

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