A low-copper, aluminum, fluorine-free black powder and its preparation method

Abstract

This invention discloses a low-copper, aluminum, and fluorine-free black powder and its preparation method. Waste batteries are crushed and sieved to obtain a first black powder and a first sieve residue. The first sieve residue is pyrolyzed, and sieved again to obtain a second black powder and a second sieve residue. The second sieve residue is color-sorted to obtain copper foil and aluminum-containing electrodes. The aluminum-containing electrodes are reacted in an iron salt solution, and sieved again to obtain aluminum foil and a slurry. The slurry undergoes solid-liquid separation to obtain a third black powder. The first, second, and third black powders are calcined in air containing water vapor to obtain the low-copper, aluminum, and fluorine-free black powder. This invention employs a combined process of low-temperature pyrolysis, color sorting separation, salt washing desorption, and pyrometallurgical defluorination to recover high-value copper foil, aluminum foil, and black powder.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery recycling technology, specifically relating to a low-copper, aluminum, and fluorine-free black powder and its preparation method. Background Technology

[0002] Lithium-ion batteries possess advantages such as high voltage, small size, high energy density, low self-discharge, and high safety, and are widely used in various fields including consumer electronics, power batteries, and industrial energy storage. In recent years, with the rapid growth in the production and use of lithium-ion batteries, the number of waste lithium-ion batteries has also increased dramatically. Currently, the recycling and reuse of lithium-ion batteries is receiving increasing attention.

[0003] Waste battery black powder is a black powder containing metals such as nickel, cobalt, manganese, copper, aluminum and lithium, as well as carbon powder, obtained from waste lithium-ion batteries through processes such as dismantling, crushing, screening, pyrolysis and sorting.

[0004] Typically, valuable metals in black powder are recovered using a wet leaching process. Specifically, nickel, cobalt, manganese, and lithium are leached in a sulfuric acid system with a reducing agent; the leachate is then subjected to impurity removal, extraction, and back-extraction processes to obtain nickel sulfate, manganese sulfate, and cobalt sulfate solutions, respectively; finally, the final extract is evaporated and concentrated, and lithium carbonate is precipitated using a supersaturated sodium carbonate solution.

[0005] However, the pyrolysis pretreatment process used in the preparation of black powder is widely used in existing industrial production, but it also has some significant problems, such as: ① The conventional pyrolysis temperature is above 500℃. Due to the complexity of the materials, the electrolyte and separator may burn at this temperature, which can easily cause violent local reactions in the pyrolysis furnace, leading to temperature runaway. The aluminum metal in the battery will undergo aluminothermic reaction at temperatures above 600℃, resulting in a rapid temperature rise and burning through the pyrolysis furnace, posing a significant safety risk; ② At this temperature, a large amount of copper and aluminum metal in the battery is oxidized, resulting in a high impurity content in the battery powder. Furthermore, during subsequent acid leaching, the oxides dissolve, producing a large amount of copper and aluminum slag. The leaching and iron and aluminum removal processes consume a large amount of acid and alkali, resulting in low product added value and putting significant pressure on subsequent purification and refining. Although anaerobic pyrolysis using inert gas can improve the oxidation of copper and aluminum, current equipment is difficult to completely seal, and some copper and aluminum are still oxidized; ③ During the pyrolysis process, the binder PVDF and lithium hexafluorophosphate in the electrolyte decompose and remain, resulting in a high fluoride content in the black powder. After wet treatment, it enters the wastewater, causing the wastewater discharge to fail to meet standards. The calcium fluoride slag produced after calcium solidification is also a hazardous waste and requires specialized treatment by qualified treatment plants. In addition, lithium fluoride is a precipitate, and some fluoride enters the lithium extraction solution, resulting in a decrease in the subsequent lithium extraction rate, a decrease in the purity of lithium carbonate, and an increase in the fluoride impurity content.

[0006] Therefore, in order to avoid causing many problems for downstream manufacturers of wet-processed black powder, it is urgent to improve the front-end process in order to obtain black powder with low copper, aluminum and fluorine content. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a low-copper, aluminum, and fluorine-free black powder and its preparation method, which can recover the copper and aluminum foil therein through low-temperature pyrolysis and perform defluorination treatment to prepare a low-copper, aluminum, and fluorine-free black powder.

[0008] According to one aspect of the present invention, a low-copper, aluminum, and fluorine-free black powder is provided, wherein the low-copper, aluminum, and fluorine-free black powder has a water content ≤1.0wt%, a total nickel, cobalt, and manganese metal content ≥30.0wt%, a lithium content ≥3.3wt%, a copper content ≤0.8wt%, an aluminum content ≤1.0wt%, and a fluorine content ≤0.1wt%.

[0009] In some embodiments of the present invention, the particle size of the low-copper, aluminum, fluorine-free black powder is ≤0.25mm.

[0010] This invention also provides a method for preparing the aforementioned low-copper, aluminum, fluorine-free black powder, comprising the following steps:

[0011] S1: Waste lithium-ion batteries are discharged, disassembled, crushed and screened for the first time to obtain the first black powder and the first sieve oversize.

[0012] S2: The first sieve oversize is pyrolyzed at 300-400℃ under an inert atmosphere. After pyrolysis, the material is sieved a second time to obtain the second black powder and the second sieve oversize. The second sieve oversize is then separated by color sorting to obtain copper foil and aluminum-containing electrode sheets.

[0013] S3: The aluminum-containing electrode is placed in a ferric salt solution for reaction. The resulting reaction material is screened for the third time to obtain aluminum foil and slurry. The slurry is subjected to solid-liquid separation, and the resulting solid is dried to obtain the third black powder.

[0014] S4: The first black powder, the second black powder, and the third black powder are baked by blowing air at 500-1000℃, and the water vapor volume content in the air is 10%-40%, to obtain the low copper aluminum fluorine-free black powder.

[0015] In some embodiments of the present invention, in step S1, the particle size of the crushed material obtained after crushing is ≤5cm.

[0016] In some embodiments of the present invention, in step S1, the waste lithium-ion battery is at least one of ternary lithium-ion battery, lithium cobalt oxide battery, lithium manganese oxide battery or lithium nickel oxide battery.

[0017] In some embodiments of the present invention, the mesh size of the screens for the first screening, the second screening, and the third screening is independently 0.2-0.3 mm.

[0018] In some embodiments of the present invention, in step S2, the pyrolysis is carried out in a pyrolysis furnace, and the filling rate of the first sieve oversize in the pyrolysis furnace is 5%-15%.

[0019] In some embodiments of the present invention, the pyrolysis time in step S2 is 3-5 hours.

[0020] In some embodiments of the present invention, in step S3, the solid-liquid ratio of the aluminum-containing electrode to the ferric salt solution is 0.5-2.0 g / mL, and the concentration of iron ions in the ferric salt solution is 0.1-0.5 mol / L.

[0021] In some embodiments of the present invention, in step S3, the reaction temperature is 40-90°C. Further, the reaction time is 0.5-1.0 h.

[0022] In some embodiments of the present invention, in step S3, the ferric salt solution is at least one of ferric sulfate solution, ferric nitrate solution, or ferric chloride solution.

[0023] In some embodiments of the present invention, in step S3, the drying temperature is 100-120°C and the drying time is 1-2 hours.

[0024] In some embodiments of the present invention, in step S4, the air flow rate is 8-15 Nm. 3 / min.

[0025] In some embodiments of the present invention, the calcination time in step S4 is 0.5-1.0 h.

[0026] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved:

[0027] 1. In this invention, in response to the problems of safety hazards, large-scale oxidation of copper and aluminum, and residual fluorine in black powder that are easily generated by waste lithium-ion batteries at high pyrolysis temperatures, a combined process of low-temperature pyrolysis, color sorting separation, salt washing desorption, and pyrolysis defluorination is adopted to recover high-value copper foil, aluminum foil, and black powder.

[0028] 2. First, the battery is crushed through coarse crushing, and some of the black powder that falls off during the crushing process is screened out. Then, it undergoes low-temperature pyrolysis, with the temperature controlled below 400℃ throughout the process. Pyrolysis is carried out under anaerobic conditions to avoid the combustion of electrolyte and separator in the crushed material, prevent the occurrence of aluminothermic reaction that could lead to temperature runaway, protect the pyrolysis furnace, reduce the degree of copper and aluminum oxidation, and simultaneously cause carbonization of the binder. Some of the black powder that falls off during the pyrolysis process is screened out again. Due to the low-temperature reaction, the positive electrode powder is not completely desorbed, while the negative electrode binder decomposes at slightly higher temperatures and is relatively easy to fall off. Therefore, a color sorting method is used to select out the copper foil, and the aluminum-containing electrode sheets enter the salt washing process. During the salt washing process, the aluminum is corroded using the principle of the reaction between ferric ions and metallic aluminum, thereby achieving the removal of black powder. The reaction equation is:

[0029] Al + 3Fe 3+ →Al 3+ +3Fe 2+

[0030] 3. The obtained black powder is subjected to high-temperature defluorination. On the one hand, the binder attached to it is completely carbonized and decomposed at high temperature, and the fluorine is dissociated in gaseous form. On the other hand, during the decomposition of the binder, fluorine will also combine with metal elements to form fluorides, which can be removed by displacement with high-temperature steam. The reaction equation is as follows:

[0031] 2LiF + H₂O → Li₂O + 2HF

[0032] MeF2+H2O→MeO+2HF(Me=Ni,Co,Mn) Attached Figure Description

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0034] Figure 1 This is a schematic diagram of the process flow of Embodiment 1 of the present invention. Detailed Implementation

[0035] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for reducing the copper, aluminum, and fluorine content in battery black powder, the specific process is as follows:

[0038] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0039] Step 2: The crushed material is screened for the first time through a sieve with a sieve aperture of 0.25mm to obtain the undersize material as the first black powder and the oversize material as the first sieve.

[0040] Step 3: Add the material from the first sieve into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 5%, continuously introduce nitrogen gas, and raise the temperature to 300℃ for 5 hours;

[0041] Step 4: The pyrolyzed material is sieved a second time through a sieve with a sieve aperture of 0.25 mm to obtain the undersize material as the second black powder and the oversize material.

[0042] Step 5: The material on the second sieve is separated by a color sorter to obtain copper foil and aluminum-containing electrode sheets;

[0043] Step 6: Add the aluminum-containing electrode to a ferric sulfate solution with an iron ion concentration of 0.1 mol / L at a solid-liquid ratio of 0.5 g / mL, and react at 90°C for 0.5 h.

[0044] Step 7: The reacted mixture is sieved a third time through a sieve with a pore size of 0.25 mm to obtain aluminum foil and slurry;

[0045] Step 8: The obtained slurry is filtered by pressure and dried at 100℃ for 2 hours to obtain the third black powder;

[0046] Step 9: Place the obtained first, second, and third black powders in a fluidized bed roasting furnace, and blow air in at 500°C for 1.0 h. The water vapor volume content of the air is 40%, and the air flow rate is 15 Nm³. 3 / min;

[0047] Step 10: After dust collection at the outlet of the fluidized bed roasting furnace, black powder with low copper, aluminum and fluorine content is obtained.

[0048] Monitoring of the pyrolysis furnace: No obvious sparks were observed inside the furnace.

[0049] Example 2

[0050] A method for reducing the copper, aluminum, and fluorine content in battery black powder, the specific process is as follows:

[0051] Step 1: After being discharged and dismantled, the waste lithium cobalt oxide batteries are crushed into crushed material with a particle size of less than 5cm.

[0052] Step 2: The crushed material is screened for the first time through a sieve with a sieve aperture of 0.25mm to obtain the undersize material as the first black powder and the oversize material as the first sieve.

[0053] Step 3: Add the material from the first sieve into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 10%, continuously introduce nitrogen gas, and raise the temperature to 350℃ for 4 hours;

[0054] Step 4: The pyrolyzed material is sieved a second time through a sieve with a sieve aperture of 0.25 mm to obtain the undersize material as the second black powder and the oversize material.

[0055] Step 5: The material on the second sieve is separated by a color sorter to obtain copper foil and aluminum-containing electrode sheets;

[0056] Step 6: Add the aluminum-containing electrode to a ferric nitrate solution with an iron ion concentration of 0.3 mol / L at a solid-liquid ratio of 1.0 g / mL, and react at 60 °C for 1.0 h.

[0057] Step 7: The reacted mixture is sieved a third time through a sieve with a pore size of 0.25 mm to obtain aluminum foil and slurry;

[0058] Step 8: The obtained slurry is filtered by pressure and dried at 110℃ for 1.5h to obtain the third black powder;

[0059] Step 9: Place the obtained first, second, and third black powders in a fluidized bed roasting furnace, and blow air in at 800°C for 1.0 h. The water vapor volume content of the air is 20%, and the air flow rate is 12 Nm³. 3 / min;

[0060] Step 10: After dust collection at the outlet of the fluidized bed roasting furnace, black powder with low copper, aluminum and fluorine content is obtained.

[0061] Monitoring of the pyrolysis furnace: No obvious sparks were observed inside the furnace.

[0062] Example 3

[0063] A method for reducing the copper, aluminum, and fluorine content in battery black powder, the specific process is as follows:

[0064] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0065] Step 2: The crushed material is screened for the first time through a sieve with a sieve aperture of 0.25mm to obtain the undersize material as the first black powder and the oversize material as the first sieve.

[0066] Step 3: Add the material from the first sieve into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 15%, continuously introduce nitrogen gas, and raise the temperature to 400℃ for 3 hours;

[0067] Step 4: The pyrolyzed material is sieved a second time through a sieve with a sieve aperture of 0.25 mm to obtain the undersize material as the second black powder and the oversize material.

[0068] Step 5: The material on the second sieve is separated by a color sorter to obtain copper foil and aluminum-containing electrode sheets;

[0069] Step 6: Add the aluminum-containing electrode to a ferric chloride solution with an iron ion concentration of 0.5 mol / L at a solid-liquid ratio of 2.0 g / mL, and react at 40 °C for 1.0 h.

[0070] Step 7: The reacted mixture is sieved a third time through a sieve with a pore size of 0.25 mm to obtain aluminum foil and slurry;

[0071] Step 8: The obtained slurry is filtered by pressure and dried at 120℃ for 1 hour to obtain the third black powder;

[0072] Step 9: Place the obtained first, second, and third black powders in a fluidized bed roasting furnace, and blow air in at 1000℃ for 0.5 hours. The water vapor volume content of the air is 10%, and the air flow rate is 8 Nm³. 3 / min;

[0073] Step 10: After dust collection at the outlet of the fluidized bed roasting furnace, black powder with low copper, aluminum and fluorine content is obtained.

[0074] Monitoring of the pyrolysis furnace: No obvious sparks were observed inside the furnace.

[0075] Comparative Example 1

[0076] A method for preparing black powder, differing from Example 1, involves directly subjecting the crushed material to low-temperature pyrolysis and sieving. The specific process is as follows:

[0077] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0078] Step 2: Add the crushed material into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 5%, continuously introduce nitrogen gas, and raise the temperature to 300℃ for 5 hours;

[0079] Step 3: The pyrolyzed material is sieved through a sieve with a pore size of 0.25 mm to obtain black powder as the undersize and copper-aluminum foil as the oversize.

[0080] Step 4: Color sort to separate copper and aluminum foil, obtaining copper foil and aluminum foil.

[0081] Monitoring of the pyrolysis furnace: No obvious sparks were observed inside the furnace.

[0082] Comparative Example 2

[0083] A method for preparing black powder, differing from Example 2, involves directly subjecting the crushed material to low-temperature pyrolysis and sieving. The specific process is as follows:

[0084] Step 1: After being discharged and dismantled, the waste lithium cobalt oxide batteries are crushed into crushed material with a particle size of less than 5cm.

[0085] Step 2: Add the crushed material into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 10%, continuously introduce nitrogen gas, and raise the temperature to 350℃ for 4 hours;

[0086] Step 3: The pyrolyzed material is sieved through a sieve with a pore size of 0.25 mm to obtain black powder as the undersize and copper-aluminum foil as the oversize.

[0087] Step 4: Color sort to separate copper and aluminum foil, obtaining copper foil and aluminum foil.

[0088] Monitoring of the pyrolysis furnace: No obvious sparks were observed inside the furnace.

[0089] Comparative Example 3

[0090] A method for preparing black powder, differing from Example 3, involves directly subjecting the crushed material to low-temperature pyrolysis and sieving. The specific process is as follows:

[0091] Step 1: After being discharged and disassembled, the waste ternary lithium-ion batteries are crushed into crushed material with a particle size of less than 5cm.

[0092] Step 2: Add the crushed material into the pyrolysis furnace, control the filling rate of the pyrolysis furnace to 15%, continuously introduce nitrogen gas, and raise the temperature to 400℃ for 3 hours.

[0093] Step 3: The pyrolyzed material is sieved through a sieve with a pore size of 0.25 mm to obtain black powder as the undersize and copper-aluminum foil as the oversize.

[0094] Step 4: Color sort to separate copper and aluminum foil, obtaining copper foil and aluminum foil.

[0095] Monitoring of the pyrolysis furnace: No obvious sparks were observed inside the furnace.

[0096] The black powder obtained in Examples 1-3 and Comparative Examples 1-3 was tested, and the results are shown in Table 1.

[0097] Table 1

[0098]

[0099] As shown in Table 1, the black powder in Comparative Examples 1-3 has a high fluorine content, indicating that there is a lot of fluoride residue. The pyrolysis temperature of Comparative Examples 1-3 is insufficient, making it difficult for the pyrolysis reaction to occur completely. The total nickel, cobalt and manganese content is low, indicating that the desorption rate of the cathode powder is low.

[0100] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for preparing low-copper, aluminum, fluorine-free black powder, characterized in that, Includes the following steps: S1: Waste lithium-ion batteries are discharged, disassembled, crushed and screened for the first time to obtain the first black powder and the first sieve oversize. S2: The first sieve oversize is pyrolyzed at 300-400℃ under an inert atmosphere. After pyrolysis, the material is sieved a second time to obtain the second black powder and the second sieve oversize. The second sieve oversize is then separated by color sorting to obtain copper foil and aluminum-containing electrode sheets. S3: The aluminum-containing electrode is placed in a ferric salt solution for reaction. The resulting reaction material is screened for the third time to obtain aluminum foil and slurry. The slurry is subjected to solid-liquid separation, and the resulting solid is dried to obtain the third black powder. S4: The first, second, and third black powders are calcined at 500-1000℃ by blowing air in, and the water vapor volume content in the air is 10%-40%, to obtain the low-copper, aluminum, fluorine-free black powder. The air flow rate is 8-15 Nm. 3 / min; The low-copper, aluminum, and fluorine-free black powder has a water content of ≤1.0wt%, a total nickel, cobalt, and manganese metal content of ≥30.0wt%, a lithium content of ≥3.3wt%, a copper content of ≤0.8wt%, an aluminum content of ≤1.0wt%, and a fluorine content of ≤0.1wt%.

2. The preparation method according to claim 1, characterized in that, In step S1, the particle size of the crushed material obtained after crushing is ≤5cm.

3. The preparation method according to claim 1, characterized in that, In step S1, the waste lithium-ion battery is at least one of ternary lithium-ion battery, lithium cobalt oxide battery, lithium manganese oxide battery, or lithium nickel oxide battery.

4. The preparation method according to claim 1, characterized in that, The screen apertures for the first, second, and third screenings are each 0.2-0.3 mm.

5. The preparation method according to claim 1, characterized in that, In step S2, the pyrolysis time is 3-5 hours.

6. The preparation method according to claim 1, characterized in that, In step S3, the solid-liquid ratio of the aluminum-containing electrode to the ferric salt solution is 0.5-2.0 g / mL, and the concentration of iron ions in the ferric salt solution is 0.1-0.5 mol / L.

7. The preparation method according to claim 1, characterized in that, In step S3, the reaction temperature is 40-90℃.

8. The preparation method according to claim 1, characterized in that, In step S3, the ferric salt solution is at least one of ferric sulfate solution, ferric nitrate solution, or ferric chloride solution.

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