A method for improving the flotation separation efficiency of positive and negative electrode materials of waste lithium batteries

Abstract

The present invention discloses a method for improving the flotation separation efficiency of the positive and negative electrode materials of waste lithium iron phosphate batteries, comprising the following steps: mixing the positive and negative electrode materials of waste lithium iron phosphate batteries with water, stirring and slurrying, adding a collector and stirring again, placing the slurry after stirring and slurrying in a flotation machine, adding a pH regulator to adjust the pH of the slurry, adding a dispersant, adding a foaming agent and flotation separation to obtain positive lithium iron phosphate powder and negative graphite powder. The present invention performs strong stirring and slurrying to treat the positive and negative electrode mixed slurry, so that the positive and negative electrode materials are fully dispersed, and the foam entrainment of excessive fine-grained positive electrode materials in the subsequent flotation process is avoided; the added collector diesel is subjected to ultrasonic emulsification treatment, so that the diesel is more evenly dispersed, the material flotation separation efficiency is improved, and conditions are created for further purification or regeneration and repair of subsequent electrode materials, and the recovered positive lithium iron phosphate powder and negative graphite powder have high recovery rate and grade.

Description

Technical Field

[0001] The invention belongs to the technical field of waste battery recycling, and in particular relates to a method for improving the flotation separation efficiency of positive and negative electrode materials of waste lithium batteries. Background Art

[0002] Lithium-ion batteries are widely used in new energy vehicles, energy storage and other technical fields due to their high energy density, high operating voltage, high cycle performance, long life, low self-discharge and environmental friendliness. With the rapid growth of economic level and the enhancement of people's environmental awareness, the power battery industry has developed rapidly. The rapid growth of power battery installed capacity will inevitably lead to the scrapping of a large number of power batteries, which will also bring double pressure to environmental governance and resource supply.

[0003] Lithium-ion batteries mainly include lithium iron phosphate batteries and ternary batteries. Lithium iron phosphate batteries are widely used because they do not contain relatively rare metals such as cobalt, nickel, and manganese, and the raw materials used to make lithium iron phosphate batteries are relatively cheap and have wide resource reserves, and have good stability in high temperature and heat environments. Lithium iron phosphate batteries are generally composed of positive electrode current collectors (aluminum foil plus positive electrode active material (lithium iron phosphate (LiFePO4)), negative electrode current collectors (copper foil plus negative electrode active material (carbon powder)), electrolytes, diaphragms and other materials. At present, with the continuous enhancement of people's environmental awareness and the continuous increase in the price of metallic lithium, the recycling of lithium batteries has attracted more and more attention.

[0004] At present, before recycling waste power batteries, they need to be disassembled, discharged, pyrolyzed, crushed, screened, re-selected, color sorted and other pre-treatments in order to obtain valuable components such as copper foil, aluminum foil and positive and negative electrode mixtures. At present, most of the research work focuses on the recovery of valuable metals in positive electrode materials, while ignoring the recovery of negative electrode materials graphite. The recovery of graphite can not only improve resource utilization, but also avoid environmental pollution. Since graphite has good natural hydrophobicity, it can be separated and enriched by flotation. However, due to the fine particle size of positive and negative electrode mixtures and the problem of easy foam entrainment of fine graphite, the separation efficiency of positive and negative electrode materials is often low. Therefore, it is of great significance to develop an economical and efficient method for flotation separation of positive and negative electrode materials. Summary of the invention

[0005] In view of the defect of low flotation separation efficiency of positive and negative electrode materials in waste lithium batteries, the purpose of the present invention is to provide a method for improving the flotation separation efficiency of positive and negative electrode materials in waste lithium batteries. The method has simple process, convenient operation, low production cost, clean and high efficiency.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: providing a method for improving the flotation separation efficiency of positive and negative electrode materials in waste lithium batteries, the method comprising the following steps:

[0007] (1) Mixing the positive and negative electrode materials of waste lithium batteries with water, and stirring to obtain a mixed slurry;

[0008] (2) adding a collector to the mixed slurry obtained in step (1) and stirring to prepare the slurry;

[0009] (3) placing the slurry after stirring and slurrying in step (2) in a flotation machine, adding a pH adjuster to adjust the pH of the slurry, adding a dispersant, adding a frother, and performing flotation separation to obtain lithium-containing positive electrode powder and negative electrode graphite powder.

[0010] Preferably, the mass concentration of the mixed slurry described in step (1) is 10% to 50%.

[0011] Preferably, the stirring and slurrying time in step (1) and step (2) is 5 to 30 minutes, the stirrer for stirring and slurrying is an electric mechanical stirrer or a magnetic stirrer, and the stirring speed is 1500 to 10000 r / min. Strong stirring and slurrying is performed on the positive and negative electrode mixed slurry to fully disperse the positive and negative electrode materials, thereby avoiding foam entrainment of excessive fine positive electrode materials in the subsequent flotation process.

[0012] Preferably, the collector in step (2) is emulsified diesel obtained by ultrasonic emulsification of diesel and water, and the amount of the collector per ton of mixed slurry is 80g to 200g; the ultrasonic emulsification time is 3 to 30min, the ultrasonic power of the ultrasonic emulsification is 300 to 600w, and the frequency of the ultrasonic power is 20 to 80kHz. The diesel with the added collector is ultrasonically emulsified, which can make the diesel more evenly dispersed, improve the efficiency and effect of material flotation separation, and at the same time improve the dispersibility of the collector, improve the flotation separation efficiency of the positive and negative electrode materials, and create conditions for further purification or regeneration and repair of subsequent electrode materials.

[0013] Preferably, the water-to-oil ratio of the emulsified diesel in step (2) is 1:1 to 1:3.

[0014] Preferably, the dispersant in step (3) is one or a combination of water glass, sodium hexametaphosphate, sodium tripolyphosphate or sodium pyrophosphate, and the amount of the dispersant used in each ton of the slurry after stirring and slurrying is 10 to 1000 g.

[0015] Preferably, in step (3), the pH of the slurry is adjusted to 8-10, and the pH adjuster in step (3) is one or a combination of sodium carbonate, sodium hydroxide, hydrochloric acid or sulfuric acid.

[0016] Preferably, the foaming agent in step (3) is one or a combination of eucalyptus oil, 2# oil, camphor oil or MIBC, and the amount of the foaming agent used in each ton of the slurry after stirring and slurrying is 10 to 50 g.

[0017] Preferably, the flotation machine described in step (3) is an XFD single-tank flotation machine.

[0018] Preferably, in the flotation separation operation of step (3), the speed of the flotation machine is 1500-2500 r / min, and the aeration volume is 0.2-0.8 m 3 / min.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The dosing sequence adopted by the present invention is collector-pH regulator-dispersant-foaming agent. The dosing sequence adopted in the flotation separation in the prior art is pH regulator-dispersant-collector-foaming agent. The present invention first adds the collector for pre-adsorption of the collector to prevent the adsorption of the dispersant on the graphite surface, thereby avoiding the inhibitory effect of the dispersant on the graphite and improving the flotation recovery rate of the graphite.

[0021] 2. The present invention carries out strong stirring and slurry adjustment to process the positive and negative electrode mixed slurry, and the stirring speed is 1500-10000r / min, so that the positive and negative electrode materials are fully dispersed, and the foam entrainment of excessive fine-grained positive electrode materials in the subsequent flotation process is avoided; the added collector diesel is subjected to ultrasonic emulsification treatment, which can make the diesel dispersed more evenly and improve the efficiency and effect of material flotation separation. At the same time, it can improve the dispersibility of the collector and the flotation separation efficiency of the positive and negative electrode materials, creating conditions for the subsequent further purification or regeneration and repair of the electrode materials.

[0022] 3. The method provided by the present invention has high separation of positive and negative electrode materials, and the recovered positive electrode lithium iron phosphate powder and negative electrode graphite powder have high recovery rate and grade. The recovery rate and grade of the positive electrode lithium iron phosphate powder are as high as 98.21% and 97.59, respectively, and the recovery rate and grade of the negative electrode graphite powder are as high as 99.86% and 98.89%, respectively.

[0023] 4. The method provided by the present invention has simple process, convenient operation, clean and efficient, low production cost and easy industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 This is a process flow chart for flotation separation of positive and negative electrode materials of waste lithium iron phosphate batteries. DETAILED DESCRIPTION

[0026] 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.

[0027] 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.

[0028] 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.

[0029] Embodiment 1:

[0030] The method for flotation separation of positive and negative electrode materials of waste batteries in this embodiment is used to treat waste lithium iron phosphate batteries. The process flow is as follows: Figure 1 As shown, the following steps are included:

[0031] (1) 500 g of the positive and negative electrode mixture of waste lithium iron phosphate battery was placed in a beaker and mixed with water to a volume of 1000 mL to obtain a mixed slurry, and then an electric mechanical stirrer was used to stir and adjust the slurry, wherein the stirring speed was 3000 r / min and the stirring time was 20 min;

[0032] (2) Diesel was emulsified at a water-oil ratio of 1:1, and the ultrasonic power, frequency, and time were 400w, 20kH, and 5min, respectively. After the treatment, 100g / t of emulsified diesel was added as a collector to the mixed slurry and stirred for slurry preparation;

[0033] (3) The stirred slurry was placed in a 1.5L XFD single-tank flotation machine, sodium hydroxide was added to adjust the slurry pH to 10 and the slurry was adjusted for 3 minutes, 100g / t of sodium hexametaphosphate was added and the slurry was adjusted for 3 minutes, 30g / t of eucalyptus oil was added and the slurry was adjusted for 1 minute and flotation was performed. The flotation time was 5 minutes, the flotation machine speed was 2000r / min, and the aeration volume was 0.4m 3 / min, the concentrate product obtained is graphite, the negative electrode material, and the tailings product is lithium iron phosphate, the positive electrode material.

[0034] After testing, the final results are as follows: positive electrode lithium iron phosphate powder with a recovery rate and grade of 98.31% and 97.86% respectively, and negative electrode graphite powder with a recovery rate and grade of 99.81% and 98.86% respectively.

[0035] Embodiment 2:

[0036] The method for flotation separation of positive and negative electrode materials of waste batteries in this embodiment is used to treat waste lithium iron phosphate batteries. The process flow is as follows: Figure 1 As shown, the following steps are included:

[0037] (1) 500 g of the positive and negative electrode mixture of waste lithium iron phosphate battery was placed in a beaker and mixed with water to a volume of 1000 mL to obtain a mixed slurry, and then an electric mechanical stirrer was used to stir and adjust the slurry, wherein the stirring speed was 4000 r / min and the stirring time was 18 min;

[0038] (2) Diesel was emulsified at a water-to-oil ratio of 1:1.25, and the ultrasonic power, frequency, and time were 350w, 30kH, and 6min, respectively. After the treatment, 90g / t of emulsified diesel was added as a collector to the mixed slurry and stirred for slurry preparation;

[0039] (3) The stirred slurry was placed in a 1.5LXFD single-tank flotation machine, sodium hydroxide was added to adjust the slurry pH to 10 and the slurry was mixed for 3 minutes, 100 g / t of water glass was added and the slurry was mixed for 3 minutes, 25 g / t of camphor oil was added and the slurry was mixed for 1 minute and flotation was performed. The flotation time was 5 minutes, the flotation machine speed was 2000 r / min, and the aeration volume was 0.4 m 3 / min, the concentrate product obtained is graphite, the negative electrode material, and the tailings product is lithium iron phosphate, the positive electrode material.

[0040] After testing, the final results are as follows: positive electrode lithium iron phosphate powder with a recovery rate and grade of 98.21% and 97.59% respectively, and negative electrode graphite powder with a recovery rate and grade of 99.86% and 98.89% respectively.

[0041] Embodiment 3:

[0042] The method for flotation separation of positive and negative electrode materials of waste batteries in this embodiment is used to treat waste lithium iron phosphate batteries. The process flow is as follows: Figure 1 As shown, the following steps are included:

[0043] (1) 500 g of the positive and negative electrode mixture of waste lithium iron phosphate battery was placed in a beaker and mixed with water to a volume of 1000 mL to obtain a mixed slurry, and then an electric mechanical stirrer was used to stir and adjust the slurry, wherein the stirring speed was 4500 r / min and the stirring time was 16 min;

[0044] (2) Diesel was emulsified at a water-to-oil ratio of 1:1.5, and the ultrasonic power, frequency, and time were 400w, 40kH, and 8min, respectively. After the treatment, 80g / t of emulsified diesel was added as a collector to the mixed slurry and stirred for slurry preparation;

[0045] (3) The stirred slurry was placed in a 1.5LXFD single-tank flotation machine, sodium hydroxide was added to adjust the slurry pH to 10 and the slurry was adjusted for 3 minutes, 120 g / t of sodium pyrophosphate was added and the slurry was adjusted for 3 minutes, 25 g / t of 2# oil was added and the slurry was adjusted for 1 minute and flotation was performed. The flotation time was 5 minutes, the flotation machine speed was 2000 r / min, and the aeration volume was 0.4 m 3 / min, the concentrate product obtained is graphite, the negative electrode material, and the tailings product is lithium iron phosphate, the positive electrode material.

[0046] After testing, the final results are as follows: positive electrode lithium iron phosphate powder with a recovery rate and grade of 98.32% and 97.56% respectively, and negative electrode graphite powder with a recovery rate and grade of 99.81% and 98.76% respectively.

Claims

1. A method for improving the flotation separation efficiency of positive and negative electrode materials of waste lithium batteries, characterized in that: The following steps are involved: (1) Mixing the positive and negative electrode materials of waste lithium batteries with water, and stirring to obtain a mixed slurry, with a stirring speed of 3000 to 10000 r / min; (2) adding a collector to the mixed slurry obtained in step (1) and stirring the mixture to prepare the slurry; the collector is emulsified diesel obtained by ultrasonic emulsification of diesel and water, and the amount of the collector per ton of mixed slurry is 80g to 200g; the ultrasonic emulsification time is 3 to 30min, the ultrasonic power of the ultrasonic emulsification is 300 to 600w, and the frequency of the ultrasonic power is 20 to 80kHz; (3) placing the slurry after stirring and slurrying in step (2) in a flotation machine, adding a pH adjuster to adjust the pH of the slurry, adding a dispersant, adding a frother, and performing flotation separation to obtain lithium-containing positive electrode powder and negative electrode graphite powder.

2. The method according to claim 1, characterized in that: The mass concentration of the mixed slurry described in step (1) is 10% to 50%.

3. The method according to claim 1, characterized in that The stirring and slurrying time in step (1) and step (2) is 5 to 30 minutes, and the stirrer for stirring and slurrying is an electric mechanical stirrer or a magnetic stirrer.

4. The method according to claim 1, characterized in that: The water-to-oil ratio of the emulsified diesel in step (2) is 1:1 to 1:

3.

5. The method according to claim 1, characterized in that The dispersant in step (3) is one or a combination of water glass, sodium hexametaphosphate, sodium tripolyphosphate or sodium pyrophosphate, and the amount of the dispersant used in each ton of the slurry after stirring and slurrying is 10 to 1000 g.

6. The method according to claim 1, characterized in that In step (3), the pH of the slurry is adjusted to 8-10, and the pH adjuster in step (3) is one or a combination of sodium carbonate, sodium hydroxide, hydrochloric acid or sulfuric acid.

7. The method according to claim 1, characterized in that The foaming agent in step (3) is one or a combination of eucalyptus oil, 2# oil, camphor oil or MIBC, and the amount of the foaming agent used in each ton of the slurry after stirring and slurrying is 10 to 50 g.

8. The method according to claim 1, characterized in that The flotation machine described in step (3) is an XFD type single-tank flotation machine.

9. The method according to any one of claims 1 to 8, characterized in that In the flotation separation operation of step (3), the flotation machine speed is 1500-2500 r / min, and the aeration volume is 0.2-0.8m 3 / min.

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