Method for low-toxicity purification of waste lithium ion battery positive electrode material

Abstract

The invention relates to the technical field of resource regeneration and cyclic utilization, and particularly discloses a low-toxicity purification method of a waste lithium ion battery positive electrode material. The method comprises the following steps: 1) disassembling a positive plate from the waste battery; (2) carrying out ozone-assisted differential heat treatment on the positive plate, and realizing the aging of a binder and the mechanical expansion and contraction of each component by utilizing the strong oxidizing property of ozone and different thermal stress of each component of the positive plate, so that the positive plate and a current collector are smoothly stripped; and 3) winnowing each component of the anode after sheet stripping to obtain various battery-grade purified materials. The method is favorable for realizing waste-free purification of the lithium ion battery positive electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of resource recycling and utilization, and more specifically, it relates to a method for low-toxic purification of the positive electrode material of waste lithium-ion batteries. Background Technique

[0002] Lithium-ion batteries have become the most promising new energy storage technology at present due to their core advantages of high energy density, high power, and long life. The continuously increasing demand and production of lithium-ion batteries have also been accompanied by the generation of a large number of retired waste lithium-ion batteries. Therefore, the recycling and reuse of waste lithium-ion batteries is a topic of great significance, which can not only solve the shortage of resources but also further prevent environmental pollution and damage. The positive electrode material in lithium-ion batteries accounts for nearly 1 / 3 of the cost and is also the primary step in the recycling of waste lithium-ion batteries. The positive electrode sheet of a lithium-ion battery is made by uniformly mixing the positive electrode material (90%), organic binder (3% - 4%), and conductive agent (6% - 7%) and then coating it on an aluminum foil current collector.

[0003] In the prior art, the common methods for separating the positive electrode material are the dissolution method and the pyrolysis method. The dissolution method uses the difference in the solubility of each component of the positive electrode sheet in organic solvents or acid-base solutions to achieve separation. For example, a strongly polar organic solvent, N-methylpyrrolidone, is selected to soak and remove the organic binder, thereby separating the positive electrode material from the aluminum foil. The pyrolysis method uses the difference in the decomposition temperature or melting temperature of each component of the positive electrode sheet to achieve separation. However, at present, the dissolution method and the pyrolysis method have high costs, and toxic substances are used or generated during the operation process, and a supporting collection and purification device is required. These disadvantages have affected the rapid development of this field. Therefore, developing a low-toxic purification method for lithium-ion battery positive electrode materials is of great significance for the development of this field. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for low-toxic purification of the positive electrode material of waste lithium-ion batteries, which can recycle the positive electrode material of waste lithium batteries safely, with low toxicity, fully and effectively, and at low cost.

[0005] To achieve the above object, the present invention provides the following technical solutions: A method for low-toxic purification of the positive electrode material of waste lithium-ion batteries, comprising the following preparation steps: S1. Discharge the waste lithium-ion battery and then disassemble it to obtain the positive electrode sheet of the waste lithium battery; S2. Treat the positive electrode sheet with an ozone generator. After the reaction is completed, keep it in an oven at 50 - 200 °C for constant temperature heating for 0.1 - 24 h. Freeze the obtained positive electrode sheet in a low-temperature environment, and repeat the differential heat treatment step until the positive electrode material and the aluminum foil are completely separated; S3. Screen the cathode material to obtain a cathode mixture. Then, perform air separation on the screened cathode mixture. Subsequently, ball-mill and mix it evenly with a lithium salt, and then calcine and screen it under an inert gas to obtain a purified cathode material of waste lithium-ion batteries.

[0006] Preferably, during the ozone treatment in step S2, the concentration is 25 - 180 mg / L and the time is 1 - 10 min.

[0007] Preferably, the low-temperature environment in step S2 is provided by low-temperature or ultra-low-temperature liquefied gases.

[0008] Preferably, the low-temperature liquefied gas is dry ice, and the ultra-low-temperature liquefied gas is one or more of liquefied air, nitrogen, or liquid helium. The freezing time is 0.1 - 120 min.

[0009] Preferably, in step S3, the screening treatment is carried out using a vibrating screen, and the time is 0.1 - 24 h.

[0010] Preferably, in step S3, the ball-milling speed is 100 - 500 rpm, and the ball-milling time is 0.5 - 12 h.

[0011] Preferably, in step S3, the inert gas is a mixed gas of nitrogen and hydrogen, the volume ratio of nitrogen is 85 - 99%, and the ratio of hydrogen is 1 - 15%.

[0012] Preferably, in step S3, the calcination temperature is 150 - 800 °C, and the time is 0.1 - 8 h.

[0013] Preferably, in step S3, the mesh number for screening is 50 - 400 meshes.

[0014] In summary, the present invention has the following beneficial effects: The present invention utilizes the mechanism of organic matter aging and the different thermal stresses of each component of the cathode plate at the same temperature to perform ozone-assisted differential heat treatment on the cathode plate, achieving the efficient detachment of the cathode material from the cathode plate. After air separation of the cathode mixture obtained by ball-milling and vibrating screening, purification is achieved, and the active cathode (such as ternary cathodes like LiNi x Co y Mn z O2, etc., LiCoO2, lithium iron phosphate, etc.) is repaired and regenerated under the protection of an inert gas. The advantage of the present invention is that compared with the traditional hydrometallurgical recycling method, the whole process of the present invention reduces the use of toxic reagents and the emission of toxic substances, realizing an efficient and low-toxic recycling process flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative work, other drawings can be obtained based on these drawings.

[0016] Figure 1 It is a comparison diagram of the peeling effect between the positive electrode material and the aluminum foil current collector under different numbers of ozone-assisted differential heat treatment times in Example 1 (a. differential heat treatment 1 time, b. differential heat treatment 2 times, c. differential heat treatment 3 times, d. differential heat treatment 4 times); Figure 2 It is the charge-discharge performance curve of the purified waste lithium-ion battery positive electrode material under the conditions of Example 1. Specific Embodiments

[0017] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present invention.

[0018] In the following embodiments, the experimental methods are conventional methods unless otherwise specified, and the test materials used are obtained from conventional biochemical reagent stores unless otherwise specified. In the following quantitative tests, three repeated experiments are set, and the data are the average value or the average value ± standard deviation of the three repeated experiments.

[0019] Example 1

[0020] A method for low-toxic purification of waste lithium-ion battery positive electrode materials includes the following steps: S1. After discharging the waste lithium-ion battery, disassemble it to obtain the waste lithium battery positive electrode sheet; S2. Place the waste lithium iron phosphate battery positive electrode sheet in an environment with an ozone concentration of 85 mg / L for 10 min, then heat it at a constant temperature of 200 °C in a ceramic box for 10 min, place the treated positive electrode sheet in dry ice for freezing for 10 min, and repeat the differential heat treatment step 4 times.

[0021] S3. Collect the completely detached cathode material, put it into a vibrating screen for 30 minutes of treatment, perform air separation on the screened cathode mixture, with an air volume of 0.5 m³ / min and a wind speed of 1100 Pa, and then calcine it with lithium salt in an atmosphere of nitrogen and hydrogen with a volume ratio of 95:5 at 500 °C for 2 hours. Put the calcined and cooled material into a ball mill and ball mill it at a speed of 400 rpm for 10 hours, and sieve it with a 300-mesh sieve to finally obtain the repaired cathode material of waste lithium-ion batteries.

[0022] Example 2

[0023] A method for low-toxic purification of the cathode material of waste lithium-ion batteries, comprising the following steps: S1. Discharge the waste lithium-ion battery and then disassemble it to obtain the cathode plate of the waste lithium battery; S2. Place the cathode plate of the waste lithium iron phosphate battery in an environment with an ozone concentration of 100 mg / L for 1 minute of treatment, then heat it at a constant temperature of 90 °C in a ceramic box for 10 minutes, place the treated cathode plate in liquid nitrogen for 5 minutes of freezing, and repeat the differential heat treatment step 6 times.

[0024] S3. Collect the completely detached cathode material, put it into a vibrating screen for 20 minutes of treatment, perform air separation on the screened cathode mixture, with an air volume of 3 m³ / min and a wind speed of 1300 Pa, and then calcine it with lithium salt in an atmosphere of nitrogen and hydrogen with a volume ratio of 90:10 at 650 °C for 4 hours. Put the calcined and cooled material into a ball mill and ball mill it at a speed of 300 rpm for 4 hours, and sieve it with a 200-mesh sieve to finally obtain the repaired cathode material of waste lithium-ion batteries.

[0025] Example 3

[0026] A method for low-toxic purification of the cathode material of waste lithium-ion batteries, comprising the following steps: S1. Discharge the waste lithium-ion battery and then disassemble it to obtain the cathode plate of the waste lithium battery; S2. Place the cathode plate of the waste lithium iron phosphate battery in an environment with an ozone concentration of 130 mg / L for 3 minutes of treatment, then heat it at a constant temperature of 120 °C in a ceramic box for 5 minutes, place the treated cathode plate in liquid nitrogen for 6 minutes of freezing, and repeat the differential heat treatment step 4 times.

[0027] S3. Collect the completely detached cathode material, put it into a vibratory sieve for 60 minutes of treatment, perform air separation on the sieved cathode mixture, with an air volume of 1.5 m³ / min and a wind speed of 1500 Pa, and then calcine it with lithium salt in an atmosphere of nitrogen and hydrogen with a volume ratio of 90:10 at 550 °C for 5 hours. Put the calcined and cooled material into a ball mill and mill it at a rotation speed of 450 rpm for 5 hours, and then sieve it with a 50-mesh sieve to finally obtain the repaired waste lithium-ion battery cathode material.

[0028] Example 4

[0029] A method for low-toxic purification of waste lithium-ion battery cathode materials includes the following steps: S1. Discharge the waste lithium-ion battery and then disassemble it to obtain the waste lithium battery cathode sheet; S2. Place the waste lithium iron phosphate battery cathode sheet in an environment with an ozone concentration of 150 mg / L for 1 minute of treatment, then heat it at a constant temperature of 140 °C in a ceramic box for 1 minute, place the treated cathode sheet in dry ice for freezing for 5 minutes, and repeat the differential heat treatment step 2 times.

[0030] S3. Collect the completely detached cathode material, put it into a vibratory sieve for 15 minutes of treatment, perform air separation on the sieved cathode mixture, with an air volume of 1.35 m³ / min and a wind speed of 1350 Pa, and then calcine it with lithium salt in an atmosphere of nitrogen and hydrogen with a volume ratio of 99:1 at 700 °C for 6 hours. Put the calcined and cooled material into a ball mill and mill it at a rotation speed of 270 rpm for 8 hours, and then sieve it with a 200-mesh sieve to finally obtain the repaired waste lithium-ion battery cathode material.

[0031] Comparative Example 1

[0032] A method for low-toxic purification of waste lithium-ion battery cathode materials includes the following steps: S1. Discharge the waste lithium-ion battery and then disassemble it to obtain the waste lithium battery cathode sheet; S2. Place the waste lithium iron phosphate battery cathode sheet in a muffle furnace, heat it at a heating rate of 5 °C / min to 300 °C, and keep it at this temperature for 2 hours. Take out the pyrolyzed cathode sheet, naturally cool it to room temperature, and then use a jaw crusher to perform mechanical crushing at a rotation speed of 1000 rpm for 15 minutes; S3. Screen the crushed cathode material with a 100-mesh sieve for 20 minutes, and then perform air separation at an air volume of 2 m³ / min and a wind speed of 1200 Pa to obtain the repaired waste lithium-ion battery cathode material.

[0033] Comparative Example 2

[0034] A method for low-toxicity purification of the cathode material of waste lithium-ion batteries, comprising the following steps: S1. Discharge the waste lithium-ion batteries and then disassemble them to obtain the cathode plates of waste lithium batteries; S2. Place the cathode plates of waste lithium iron phosphate batteries in an environment with an ozone concentration of 150 mg / L for 1 min, then heat them at a constant temperature of 140 °C in a ceramic box for 1 min, cool the heated cathode plates at room temperature for 5 h, and repeat the differential heat treatment step 4 times; S3. Collect the completely detached cathode materials, put them into a rotary vibrating sieve for 15 min, perform air separation on the screened cathode mixture at a air volume of 1.35 m³ / min and a wind speed of 1350 Pa, then calcine them at 700 °C for 6 h in an atmosphere of nitrogen and hydrogen with a volume ratio of 99:1, put the calcined and cooled materials into a ball mill, ball mill them at a rotation speed of 270 rpm for 8 h, and sieve them with a 200-mesh sieve to finally obtain the repaired cathode materials of waste lithium-ion batteries.

[0035] Comparative Example 3

[0036] A method for low-toxicity purification of the cathode material of waste lithium-ion batteries, comprising the following steps: S1. Discharge the waste lithium-ion batteries and then disassemble them to obtain the cathode plates of waste lithium batteries; S2. Place the cathode plates of waste lithium iron phosphate batteries in an environment with an ozone concentration of 150 mg / L for 1 min, then heat them at a constant temperature of 140 °C in a ceramic box for 1 min, place the treated cathode plates in dry ice for freezing for 5 min, and repeat the differential heat treatment step 2 times.

[0037] S3. Perform air separation on the screened cathode mixture at a air volume of 1.35 m³ / min and a wind speed of 1350 Pa to obtain the repaired cathode materials of waste lithium-ion batteries.

[0038] Performance test

[0039] According to the GB / T 31486-2015 standard, make the purified cathode materials of Examples 1-4 and Comparative Examples 1-3 into batteries, conduct charge-discharge cycle tests, and measure their initial charge-discharge capacities (mAh / g), Coulomb efficiencies (%) and cycle stabilities (capacity retention rate % after 100 cycles).

[0040] Test item Example 1 Example 2 Example 3 Example 4 Comparative example 1 Comparative example 2 Comparative example 3 Discharge capacity 160 155 150 160 140 130 145 Coulombic efficiency 92 91 90 92 85 80 88 Stability 85 83 80 85 74 70 78 Through the detailed testing and analysis of Examples 1-4 and Comparative Examples 1-3, the low-toxic purification method for the cathode material of waste lithium-ion batteries of the present invention shows significant advantages in terms of material purity, electrochemical performance, and environmental friendliness. The first discharge capacity of the materials in Examples 1-4 is above 150 mAh / g, the Coulomb efficiency is above 90%, and the cycle stability is above 80%. In contrast, the material purity and electrochemical performance of Comparative Examples 1-3 are relatively low. In addition, the method of the present invention reduces the use and emission of toxic reagents and meets the environmental protection requirements. Therefore, the present invention provides an efficient, low-toxic, and environmentally friendly purification solution for the cathode material of waste lithium-ion batteries, with good application prospects and market potential.

[0041] The above content is merely an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should fall within the protection scope of the present invention.

Claims

1. A method for low-toxicity purification of the positive electrode material of waste lithium-ion batteries, characterized in that, It includes the following steps: S1. Discharge the waste lithium-ion battery and then disassemble it to obtain the waste lithium battery positive electrode sheet; S2. Use an ozone generator to treat the positive electrode sheet. After the reaction is completed, keep it in an oven at 50-200 °C for constant temperature heating for 0.1-24 h. Freeze the obtained positive electrode sheet in a low-temperature environment and repeat the differential heat treatment step until the positive electrode material and the aluminum foil are completely separated; S3. Screen the positive electrode material to obtain a positive electrode mixture. Then, perform air separation on the screened positive electrode mixture. Subsequently, mix it evenly with lithium salt by ball milling and then calcine and screen it under an inert gas to obtain the purified waste lithium-ion battery positive electrode material.

2. The method according to claim 1, wherein In step S2, the concentration of ozone treatment is 25-180 mg / L and the time is 1-10 min.

3. The method according to claim 1, characterized in that, The low-temperature environment in step S2 is provided by low-temperature or ultra-low-temperature liquefied gas.

4. The method according to claim 2, wherein The low-temperature liquefied gas is dry ice, and the ultra-low-temperature liquefied gas is one or more of liquefied air, nitrogen, or liquid helium. The freezing time is 0.1-120 min.

5. The method according to claim 1, wherein In step S3, the screening treatment is carried out using a vibrating screen, and the time is 0.1-24 h.

6. The method according to claim 1, characterized in that In step S3, the ball milling speed is 100-500 rpm and the ball milling time is 0.5-12 h.

7. The method according to claim 1, wherein In step S3, the inert gas is a mixed gas of nitrogen and hydrogen, the volume ratio of nitrogen is 85-99%, and the ratio of hydrogen is 1-15%.

8. The method according to claim 1, characterized in that, In step S3, the calcination temperature is 150-800 °C and the time is 0.1-8 h.

9. The method according to claim 1, wherein In step S3, the mesh number of screening is 50-400 meshes.

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