Method for recovering graphite from waste lithium ion battery powder

Abstract

The invention discloses a method for recovering graphite in waste lithium ion battery powder, and relates to the technical field of lithium ion battery recovery. The method comprises the following steps: S1, discharging and crushing the waste lithium ion battery to obtain mixed powder; s2, the mixed powder and an ethanol solution are mixed and stirred to obtain ore pulp; s3, the ore pulp subjected to ultrasonic treatment is transferred into a flotation tank, after a collecting agent is added and stirred, an inhibitor is added and stirred, a foaming agent is added and stirred, and air is introduced to generate foam; s4, scraping the foam until the foam is clarified to obtain a foam layer containing graphite and flotation tailing slurry containing a positive electrode material; s5, filtering and drying the foam layer to obtain graphite concentrate; and S6, the graphite concentrate is subjected to acid pickling treatment, and then high-grade graphite is obtained. According to the method, coating layers attached to the surfaces of positive and negative electrode material particles are effectively broken, repeated flotation, concentration and roughing are not needed, graphite with the purity larger than 80% can be obtained only through one-time flotation, and the purity of the graphite can be further improved after acid pickling treatment.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery recycling technology, and in particular to a method for recycling graphite from waste lithium-ion battery powder. Background Technology

[0002] With the widespread use of lithium-ion batteries in electronic devices, electric vehicles, and other fields, the number of used lithium-ion batteries has increased dramatically. Used lithium-ion batteries contain a large amount of valuable metals, such as lithium, cobalt, and nickel, as well as some harmful substances, such as organic solvents and heavy metals in the electrolyte. If not effectively recycled, this will not only waste resources but also cause serious environmental pollution.

[0003] Currently, methods for recycling waste lithium-ion battery black powder include pyrometallurgy, hydrometallurgy, and physical methods. Among these, flotation separation technology in physical methods has received widespread attention due to its significant advantages such as high efficiency, environmental friendliness, and low cost. However, in the preparation process of lithium-ion battery cathode materials, their surfaces are usually coated with a layer of amorphous carbon. Simultaneously, both the cathode material and graphite surfaces have a PVDF (polyvinylidene fluoride) coating. This surface coating leads to homogenization of the surface properties of the cathode material and graphite, significantly increasing the difficulty of flotation separation in large-scale industrial production environments.

[0004] CN118676463A discloses a method for flotation separation of positive and negative electrode materials from waste lithium-ion batteries. This method utilizes amino acids as inhibitors for the separation of positive and negative electrode materials. The recovery rate and grade of the separated positive electrode lithium cobalt oxide are 98.03% and 97.23%, respectively; the recovery rate and grade of the negative electrode graphite powder are 98.89% and 98.26%, respectively. Although the obtained graphite powder has a high grade, this method is complex, requires a large dosage of reagents, and necessitates repeated flotation, cleaning, and roughing processes to achieve the aforementioned recovery rates and grades. It also results in high energy consumption and a large amount of reagent usage.

[0005] CN114256527A describes a method for removing impurities from a mixed material of waste lithium-ion batteries and separating the positive and negative electrodes. In this method, waste lithium-ion batteries are mechanically crushed and classified to obtain a mixed material containing positive electrode material, negative electrode material, binder, electrolyte and metal impurities. The mixed material is then subjected to magnetic separation, roasting, alkaline leaching to remove aluminum, ammonia leaching to remove copper and flotation to obtain concentrate and tailings. However, this method is cumbersome and energy-intensive.

[0006] Overall, existing flotation separation methods generally suffer from problems such as low separation efficiency, low product purity, and high reagent consumption when processing waste lithium-ion battery positive and negative electrode materials, and urgently need further optimization and improvement. Summary of the Invention

[0007] The purpose of this invention is to provide a method for recycling graphite from waste lithium-ion battery powder, which solves the problems of low separation efficiency, low product purity and high reagent consumption in the prior art.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for recycling graphite from waste lithium-ion battery powder, characterized by comprising the following steps: Step S1: After being discharged and crushed, the waste lithium-ion batteries are mixed with positive electrode material, negative electrode material, electrolyte and metal impurities to obtain mixed powder. Step S2: Mix the powder with the ethanol solution and stir to obtain a slurry; Step S3: Transfer the ultrasonically treated slurry to the flotation cell, add water to adjust the slurry concentration to 20-25%, add collector and stir for 3-5 minutes, add inhibitor and stir for 3-5 minutes, add frother and stir for 3-5 minutes, and aerate to generate foam. Step S4: Scrape the foam until it becomes clear to obtain a foam layer containing graphite and a flotation tailings slurry containing positive electrode material; Step S5: After filtering and drying the foam layer, high-grade graphite concentrate is obtained, and after filtering and drying the tailings slurry, cathode material is obtained. Step S6: The high-grade concentrate obtained by flotation is acid washed to remove metal impurities and obtain a high-purity graphite product.

[0009] A further technical solution is that the particle size of the mixed powder in step S1 is 150~325 mesh; preferably, the particle size of the mixed powder is 200~300 mesh.

[0010] A further technical solution is that the concentration of the ethanol solution in step S2 is 20-60%, and the amount added is 30-50 g / L; preferably, the concentration of the ethanol solution is 30-50%.

[0011] A further technical solution is that the ultrasonic treatment in step S3 is performed at 1000W for 15-60 minutes; preferably, the ultrasonic treatment time is 25-45 minutes.

[0012] A further technical solution is to simultaneously stir during ultrasonic treatment in step S3, with a stirring rate between 200 and 1000 r / min; preferably, the stirring rate is 300 to 600 r / min.

[0013] A further technical solution is that the collector is at least one of kerosene, diesel oil, or n-dodecane; preferably, the collector is n-dodecane, and the addition amount is 400g~1000g / t.

[0014] A further technical solution is that the inhibitor is sodium carboxymethyl cellulose (CMC) or Na2SO3; preferably, the inhibitor is Na2SO3, 200~600g / t.

[0015] A further technical solution is that the foaming agent is at least one of methyl isobutyl methanol (MIBC), 2-octanol, or terpineol; preferably, the foaming agent is methyl isobutyl methanol (MIBC), and the addition amount is 50~200g / t.

[0016] In a further technical solution, step S6 involves acid washing by adding graphite concentrate to a leaching agent, stirring and allowing it to stand, then filtering, separating, and drying to obtain the graphite product. The leaching agent used is at least one of hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, sodium sulfate, and ammonium sulfate.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1) In this invention, the mixed powder is mixed with ethanol to form a slurry, and ultrasonic treatment is performed before flotation. At the same time, the appropriate order and amount of reagent addition can effectively destroy the coating layer structure formed on the graphite surface, which is conducive to increasing the contact area between graphite particles and flotation reagents. There is no need to repeatedly perform flotation, cleaning and roughing. With one flotation separation, the yield of graphite in large-scale recycling of waste lithium-ion batteries can be improved. The graphite obtained by this method without purification and impurity removal treatment can reach a purity of over 80%. After one acid washing to remove impurities, a graphite product with a purity of over 90% can be obtained, and the graphite recovery rate can reach 89.15%.

[0018] 2) This invention can separate positive and negative electrode materials without damaging the structure of the positive and negative electrode materials, and can realize the comprehensive utilization of positive and negative electrode materials, which greatly improves resource utilization and economic benefits. Compared with hydrometallurgy and pyrometallurgy, the process is simple and reduces pollution and energy consumption. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but this does not limit the present invention in any way. Any modifications or improvements made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0021] Unless otherwise specified, all materials and instruments used in the following embodiments were obtained through commercial channels; and all detection methods used are existing methods unless otherwise specified.

[0022] Example 1: Recycling graphite anodes from spent lithium-ion batteries This method is as follows Figure 1 The process, as shown, includes the following steps: Ultrasonic pretreatment: 20g of a mixed powder containing positive electrode material, negative electrode material, electrolyte and metal impurities was obtained after discharge and crushing treatment. The particle size was 150 mesh. The mixed powder was added to 500ml of 50% ethanol solution and ultrasonically treated for 30min at an ultrasonic power of 1000W. Stirring was carried out simultaneously during ultrasonic treatment at a stirring rate of 800 r / min.

[0023] Foam flotation: The treated slurry is transferred to a flotation cell, and the slurry concentration is adjusted to 20%. First, kerosene collector is added at a dosage of 600 g / t, and stirred for 3 min; then 300 g / t inhibitor sodium carboxymethyl cellulose is added, and stirred for 3 min; finally, 100 g / t frother octanol is added, and aeration is carried out to generate foam; the foam is scraped until clear, resulting in a foam layer containing graphite and a flotation tailings slurry containing cathode material; after filtering and drying the foam layer, 8.5 g of graphite concentrate is obtained, and after filtering and drying the tailings slurry, cathode material is obtained.

[0024] Acid washing treatment: The graphite concentrate obtained by flotation was added to 350ml of 25% sodium persulfate solution for leaching for 90min, filtered and dried to obtain 7.65g of graphite product.

[0025] After testing, the recovery rate of negative electrode graphite was 85%, and the purity was 93.5%, while the recovery rate of positive electrode material was 83.5%, and the purity was 88%.

[0026] Example 2: Recycling graphite anodes from waste lithium-ion batteries Ultrasonic pretreatment: 20g of pretreated and crushed waste lithium-ion battery positive and negative electrode material particles with a particle size of 325 mesh were added to 500ml of 60% ethanol solution and ultrasonically treated for 45 minutes at an ultrasonic power of 1000W. Stirring was carried out simultaneously during ultrasonic treatment at a stirring rate of 200 r / min.

[0027] Foam flotation: The treated slurry is transferred to a flotation cell, and the slurry concentration is adjusted to 25%. First, kerosene collector is added at a dosage of 500 g / t, and stirred for 3 min; then 500 g / t inhibitor Na2SO4 is added, and stirred for 3 min; finally, 150 g / t frother MIBC is added, and aeration is carried out to generate foam; the foam is skimmed until clear, resulting in a foam layer containing graphite and a flotation tailings slurry containing cathode material; after filtering and drying the foam layer, 8.35 g of graphite concentrate is obtained, and after filtering and drying the tailings slurry, cathode material is obtained.

[0028] Acid washing treatment: The graphite concentrate obtained by flotation was added to 350ml of 25% ammonium sulfate solution for leaching for 90min. After filtration and drying, 7.88g of graphite product was obtained.

[0029] After testing, the recovery rate of negative electrode graphite was 87.5% and the purity was 94.9%, while the recovery rate of positive electrode material was 81.3% and the purity was 87.6%.

[0030] Example 3: Recycling graphite anodes from spent lithium-ion batteries Ultrasonic pretreatment: 20g of pretreated and crushed waste lithium-ion battery positive and negative electrode material particles with a particle size of 150 mesh were added to 500ml of 60% ethanol solution and ultrasonically treated for 60 minutes at an ultrasonic power of 1000W. Stirring was carried out simultaneously during ultrasonic treatment at a stirring rate of 600 r / min.

[0031] Foam flotation: The treated slurry is transferred to a flotation cell, and the slurry concentration is adjusted to 25%. First, 700 g / t of collector n-dodecane is added and stirred for 3 min; then 500 g / t of inhibitor Na2SO3 is added and stirred for 3 min; finally, 150 g / t of frother MIBC is added, and aeration is carried out to generate foam; the foam is scraped until clear, and a foam layer containing graphite and a flotation tailings slurry containing cathode material are obtained; after filtering and drying the foam layer, 8.77 g of graphite concentrate is obtained, and after filtering and drying the tailings slurry, cathode material is obtained.

[0032] Acid washing treatment: The graphite concentrate obtained by flotation was added to 350ml of 25% oxalic acid solution for leaching for 90min. After filtration and drying, 8.01g of graphite product was obtained.

[0033] After testing, the recovery rate of negative electrode graphite was 89.15% and the purity was 93.4%, while the recovery rate of positive electrode material was 81.5% and the purity was 89.8%.

[0034] Example 4 The difference from Example 1 is as follows: the ultrasonically treated slurry was transferred to a flotation cell, a collector was added and stirred for 5 minutes, followed by an inhibitor and stirring for 5 minutes, then a frother and stirring for 5 minutes. Aeration was then performed to generate foam. The amounts of collector, inhibitor, and frother were the same as in Example 1, and the concentration of the ethanol solution was 20%. Ultrasonic treatment lasted 60 minutes, with simultaneous stirring at a rate of 300 r / min. The collector was diesel oil; the inhibitor was sodium carboxymethyl cellulose; and the frother was terpineol. During the acid leaching process, 350 ml of 25% sulfuric acid was used as the leaching agent. The obtained graphite product was 7.71 g. Product testing showed that the purity of the obtained graphite was 93.2%, and the recovery rate was 85.7%.

[0035] Example 5 The difference from Example 1 is as follows: the ultrasonically treated slurry was transferred to a flotation cell, a collector was added and stirred for 4 minutes, followed by an inhibitor and stirring for 4 minutes, then a frother and stirring for 4 minutes. Aeration was then performed to generate foam. The amounts of collector, inhibitor, and frother were the same as in Example 1, and the concentration of the ethanol solution was 30%. Ultrasonic treatment was performed for 15 minutes, with simultaneous stirring at a speed of 1000 r / min. The collector was n-dodecane; the inhibitor was Na2SO3; and the frother was a mixture of 2-octanol and terpineol at a volume ratio of 1:1. The leaching agent used in the acid washing process was 350 ml of 25% hydrochloric acid. The obtained graphite product was 7.78 g. Testing of the product showed that the purity of the obtained graphite was 92.8%, and the recovery rate was 86.6%.

[0036] Comparative Example 1 The difference from Example 1 is that the order of reagent addition is inhibitor-collector-frother. Testing of the obtained product showed that the purity of the obtained graphite was 58.4%, and the recovery rate was only 60%. This demonstrates that the optimal flotation effect is achieved when the collector is added first, then the inhibitor, and finally the frother.

[0037] Comparative Example 2 The difference from Example 1 is that the amount of reagent added is 200 g / t of collector, 100 g / t of inhibitor, and 20 g / t of frother. Testing of the obtained product showed that the purity of the obtained graphite was 48.2%, and the recovery rate was only 51%. This indicates that insufficient reagent addition results in poor flotation performance.

[0038] Comparative Example 3 The difference from Example 1 is that no ultrasonic treatment was performed. Testing of the resulting product showed that the purity of the obtained graphite was 56.2%, and the recovery rate was only 53.3%. This demonstrates that ultrasonic treatment before flotation can significantly improve the flotation effect.

[0039] Comparative Example 4 The difference from Example 1 is that the mixed powder used has a particle size of 500 mesh. Filtration of the foam layer after flotation was difficult, and testing of the obtained product showed that the purity of the obtained graphite was 50.6%, and the recovery rate was only 51.6%.

[0040] Comparative Example 5 The difference from Example 1 is that the mixed powder used has a particle size of 80 mesh. During the flotation process, foaming was difficult, and testing of the obtained product showed that the purity of the obtained graphite was 55.9%, and the recovery rate was only 44.8%.

[0041] It is evident that both excessively large and excessively small particle sizes in the mixed powder will lead to a decrease in graphite purity and recovery rate.

[0042] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering graphite from a spent lithium-ion battery powder, characterized by, The method comprises the following steps: Step S1: obtaining a mixed powder containing positive electrode material, negative electrode material, electrolyte and metal impurities after discharging and crushing treatment of the waste lithium ion battery; Step S2: mixing and stirring the mixed powder with an ethanol solution to obtain a slurry; Step S3: transferring the slurry treated by ultrasonic to a flotation tank, adjusting the concentration of the slurry to 20-25% by adding water, then adding a collector and stirring for 3-5 min, then adding an inhibitor and stirring for 3-5 min, then adding a foaming agent and stirring for 3-5 min, and generating foam by aeration; Step S4: scraping the foam to clarify to obtain a foam layer containing graphite and a flotation tailing slurry containing positive electrode material; Step S5: filtering and drying the foam layer to obtain high-grade graphite concentrate, and filtering and drying the tailing slurry to obtain positive electrode material; Step S6: performing acid washing treatment on the high-grade graphite concentrate obtained by flotation to remove metal impurities therein to obtain a high-purity graphite product.

2. The method of claim 1, wherein the method is characterized by, The particle size of the mixed powder in step S1 is 150-325 mesh. 3.The method of claim 1, wherein the graphite is recovered from the waste lithium-ion battery powder by the steps of, The concentration of the ethanol solution in step S2 is 20-60%, and the addition amount is 30-50 g / L. 4.The method of claim 1, wherein the method further comprises a step of separating the graphite from the other components of the waste lithium ion battery powder. The ultrasonic treatment in step S3 is performed under the condition of 1000 W for 15-60 min. 5.The method of claim 1, wherein the method further comprises a step of separating the graphite from the waste lithium ion battery powder. The stirring is performed synchronously during the ultrasonic treatment in step S3, and the stirring rate is 200-1000 r / min. 6.The method of claim 1, wherein the method is characterized by, The collector is at least one of kerosene, diesel oil or n-dodecane. 7.The method of claim 1, wherein the graphite is recovered from the waste lithium-ion battery powder. The inhibitor is sodium carboxymethyl cellulose or Na2SO3. 8.The method of claim 1, wherein the method further comprises a step of separating the graphite from the other components of the waste lithium ion battery powder. The foaming agent is at least one of methyl isobutyl carbinol, sec-octyl alcohol or terpineol. 9.The method of claim 1, wherein the method further comprises a step of separating the graphite from the waste lithium ion battery powder. The addition amount of the collector is 400-1000 g / t, the addition amount of the inhibitor is 200-600 g / t, and the addition amount of the foaming agent is 50-200 g / t. 10.The method of claim 1, wherein the method is characterized by, In step S6, the acid washing process is as follows: adding the graphite concentrate into a leaching agent, stirring and standing, then filtering, separating and drying to obtain the graphite product; wherein the leaching agent used is at least one of hydrochloric acid, nitric acid, sulfuric acid, oxalic acid, sodium sulfate and ammonium sulfate.

Images