Method for separating positive and negative plates of waste lithium battery and regenerating positive active material

Abstract

The invention provides a method for separating positive and negative pole pieces of a waste lithium battery and regenerating a positive pole active material, which comprises the following steps: carrying out hot drying, winnowing and AI color sorting treatment on crushed waste lithium battery pieces to respectively obtain the positive and negative pole pieces, treating the positive and negative pole pieces by a granulator, and sieving by screens with different mesh numbers to obtain the positive pole active material. Positive electrode powder, aluminum powder, negative electrode powder and copper powder are obtained respectively; the method ingeniously avoids the traditional positive and negative electrode wet separation process, reduces the use of strong acid and oxidant, fundamentally changes the defects of the existing recovery process, reduces the labor cost, and improves the production efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery material recycling, and particularly relates to a method for separating positive and negative electrode sheets of waste lithium batteries and regenerating positive electrode active materials. BACKGROUND

[0002] With the rapid development of electric vehicles and energy storage technology, lithium ion batteries are increasingly widely used. However, the performance of lithium batteries will decrease significantly after a long time of charge and discharge cycles, and eventually become scrap. In addition, waste lithium batteries contain a large amount of heavy metals, electrolytes and organic solvents and other harmful substances. If discarded at will, it will cause serious pollution to soil, water and ecosystems, and threaten human health.

[0003] The mainstream recycling process in the industry at present is electric crushing -> pyrolysis -> screening, that is, first, the waste lithium batteries are crushed with electricity to destroy the internal structure of the batteries, then the organic matter and other impurities are removed by pyrolysis, and finally the crushed products are separated by means such as screening to obtain black powder mixed with positive and negative electrodes. However, the black powder obtained by this method usually needs to be further treated by a wet lithium extraction process. This process requires a large amount of acid and oxidizing agent. On the one hand, the use of acid and oxidizing agent may cause many safety hazards, such as the strong corrosiveness of acid which may cause harm to equipment and operating personnel, and the instability of oxidizing agent which may cause dangerous accidents such as explosion. On the other hand, the purchase and use of these chemical reagents are costly, and a large amount of wastewater and waste gas is generated during the treatment process. The purification and discharge treatment of wastewater and waste gas further increases the cost, resulting in a complex recycling process and high cost, which limits the large-scale development of the waste lithium battery recycling industry.

[0004] Related research has found that in addition to valuable metals such as lithium, cobalt and nickel, the positive electrode active material in waste lithium batteries will gradually become inactive and become iron phosphate as the battery is used. These iron phosphates can be repaired by lithium supplementation and used for the production of lithium batteries again, which not only reduces the dependence on primary minerals, but also creates considerable economic value. Therefore, the recycling of waste lithium batteries is urgent.

[0005] In existing repair and lithium supplementation technologies, the method of liquid-phase lithium supplementation combined with high-temperature calcination repair is more common. However, this lithium supplementation repair method has the following problems:

[0006] (1) The liquid-phase reaction temperature is high, and high-pressure reaction equipment is required;

[0007] (2) The liquid-phase reaction time is long, and the cost of lithium supplementation and the regeneration performance are not balanced;

[0008] (3) When thiourea and other substances interact with iron in iron phosphate, although the iron ions can be accurately positioned, the lithium source cannot be one-to-one corresponding to the iron phosphate, and the lithium supplementation efficiency is not high enough.

[0009] Against this industry backdrop, there is an urgent need to develop a method that can effectively separate positive and negative electrode powders after battery cell crushing, providing strong technical support for the sustainable development of the waste lithium battery recycling industry. Summary of the Invention

[0010] To address the technical problems existing in the background art, this invention proposes a method for separating and regenerating positive electrode active materials from waste lithium battery positive and negative electrode sheets, comprising the following steps:

[0011] S1. The crushed waste lithium battery sheet material is subjected to heat drying treatment.

[0012] S2. The waste lithium battery sheet material after heat drying is separated into positive and negative electrode sheets by air separation and color separation.

[0013] S3. After the positive and negative electrode sheets are granulated, they are sieved to obtain positive electrode powder, negative electrode powder, aluminum powder and copper powder.

[0014] Preferably, in step S1, the heat drying temperature is 150-200℃.

[0015] Preferably, in step S1, the atmosphere for the thermal drying process is an inert gas;

[0016] More preferably, the oxygen content of the atmosphere in the drying process is <3%.

[0017] Preferably, in step S2, the wind separation is a two-stage wind separation;

[0018] More preferably, the wind speed is 5-8 m / s;

[0019] More preferably, the wind tilt angle is 20-30°.

[0020] Preferably, in step S2, the color sorting is performed using an AI color sorter;

[0021] More preferably, the AI ​​color sorter uses a combination of visible and invisible light sources, integrates multi-path compensation and true 4K ultra-high-definition sensor technology, and employs a distributed AI sorting engine.

[0022] Preferably, in step S3, the granulation is performed using a dry roller press granulator;

[0023] Preferably, the roller pressing pressure of the dry roller press granulator is 120-250 MPa.

[0024] In this invention, the crushing and thermal drying process can completely evaporate the electrolyte in the waste battery. The dried waste battery sheet can retain the positive and negative electrode sheets through air separation. Then, the positive and negative electrode sheets are efficiently separated by using the color characteristics of the visible light identification material and the different absorption and reflectivity of the positive and negative electrode sheets to specific wavelengths of invisible light. The final positive and negative electrode sheets have a purity of up to 99.9%.

[0025] Preferably, the method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets in this invention further includes step S4: subjecting positive electrode powder to a self-polymerization reaction with dopamine, then adding an alkaline lithium source and carbon disulfide to a chelation reaction, and calcining the resulting solid to obtain the regenerated positive electrode active material.

[0026] In this invention, the dopamine achieves a tight bond with the cathode powder through metal coordination bonding. Then, an alkaline lithium source and carbon disulfide are added, so that the carbon disulfide, lithium ions, and amino groups in polydopamine generate lithium dithiocarbamate with strong adsorption and chelation properties under alkaline conditions. The lithium dithiocarbamate carrying lithium ions preferentially interacts with positively charged metal ions other than lithium ions in the cathode powder, and in-situ lithium replenishment and regeneration of the cathode active material is achieved in the subsequent calcination process.

[0027] Preferably, in step S4, the mass ratio of the positive electrode powder: dopamine: carbon disulfide is 1:0.2-1:1-8.5.

[0028] More preferably, in step S4, the alkaline lithium source is lithium hydroxide.

[0029] Preferably, in step S4, the calcination temperature is 700-900℃ and the calcination time is 6-10h.

[0030] The beneficial effects of this invention are as follows: This invention separates the positive and negative electrode sheets using an AI color sorter in the front-end process, and then obtains positive and negative electrode powders separately using a granulator. This avoids the wet separation process caused by mixing positive and negative electrodes. It not only eliminates the complex subsequent wet separation process of mixed positive and negative electrode powders, but also significantly reduces the amount of hazardous chemicals such as acids and oxidants used, and significantly reduces the overall recycling cost. This improves the economic efficiency and safety of waste lithium battery recycling, and provides strong technical support for the sustainable development of the waste lithium battery recycling industry. It has important practical significance and broad application prospects. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets in Examples 1-3. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0034] The technical solution of the present invention will now be described more clearly and completely with reference to specific embodiments and comparative examples.

[0035] Example 1

[0036] This embodiment proposes a method for separating and regenerating the positive electrode active material from waste lithium battery positive and negative electrode sheets. The specific steps are as follows:

[0037] S1. Under a nitrogen atmosphere (oxygen content <3%), waste lithium batteries (waste lithium iron phosphate) are fed into the crusher via a feeding belt. The lithium batteries are crushed into flakes of 3±2cm. The flakes are then conveyed to a low-temperature volatilization furnace via a conveying screw. Under a nitrogen atmosphere (oxygen content <3%), the electrolyte is completely evaporated at 200℃.

[0038] S2. The sheet material undergoes a two-stage air separation process using a grading wheel and an induced draft fan. The induced draft fan blows the sheet material upwards at a 30° angle with a wind speed of 6 m / s, causing it to fall in a parabolic trajectory from the air separation chamber into the collection area below. Due to the weight differences among the components of the sheet material, the aluminum shell, diaphragm, and positive and negative electrode sheets fall at different positions in the collection area. This process separates the aluminum shell and diaphragm, leaving the positive and negative electrode sheets. These sheets are then processed by an AI color sorter, which uses a combination of visible and invisible light sources. The visible light is used to identify the color characteristics of the material. Furthermore, the different absorption and reflectivity of the positive and negative electrode sheets for specific wavelengths of invisible light are utilized. This process incorporates multi-path compensation and true 4K ultra-high-definition sensor technology, and employs a distributed AI sorting engine. After processing by the AI ​​color sorter, the purity of the positive and negative electrode sheets can reach 99.9%.

[0039] S3. The positive electrode sheet is granulated using a dry roller press granulator (roller pressure of 150MPa) and then passed through a 200-mesh sieve to obtain positive electrode powder and aluminum powder. The negative electrode sheet is granulated using a dry roller press granulator (roller pressure of 170MPa) and then passed through a 300-mesh sieve to obtain negative electrode powder and copper powder. The positive electrode powder is alternately washed with deionized water and anhydrous ethanol and dried to obtain regenerated positive electrode active material, namely lithium iron phosphate. The recovery rate of lithium iron phosphate is 89.5%.

[0040] Example 2

[0041] This embodiment proposes a method for separating and regenerating the positive electrode active material from waste lithium battery positive and negative electrode sheets. The specific steps are as follows:

[0042] S1. Under a nitrogen atmosphere (oxygen content <3%), waste lithium batteries (waste lithium iron phosphate) are fed into the crusher via a feeding belt. The lithium batteries are crushed into flakes of 3±2cm. The flakes are then conveyed to a low-temperature volatilization furnace via a conveying screw. Under a nitrogen atmosphere (oxygen content <3%), the electrolyte is completely evaporated at 180℃.

[0043] S2. The sheet material undergoes a two-stage air separation process using a grading wheel and an induced draft fan. The induced draft fan blows the sheet material upwards at a 25° angle with a wind speed of 5 m / s, causing it to fall in a parabolic trajectory from the air separation chamber into the collection area below. Due to the weight differences among the components of the sheet material, the aluminum shell, diaphragm, and positive and negative electrode sheets fall at different positions in the collection area. This process separates the aluminum shell and diaphragm, leaving the positive and negative electrode sheets. The positive and negative electrode sheets are then processed by an AI color sorter, which uses a combination of visible and invisible light sources. The visible light is used to identify the color characteristics of the material. Furthermore, the different absorption and reflectivity of the positive and negative electrode sheets for specific wavelengths of invisible light are utilized. This process incorporates multi-path compensation and true 4K ultra-high-definition sensor technology, and employs a distributed AI sorting engine. After processing by the AI ​​color sorter, the purity of the positive and negative electrode sheets can reach 99.9%.

[0044] S3. The positive electrode sheet is granulated using a dry roller press granulator (roller pressure of 120MPa) and then passed through a 250-mesh sieve to obtain positive electrode powder and aluminum powder. The negative electrode sheet is granulated using a dry roller press granulator (roller pressure of 190MPa) and then passed through a 325-mesh sieve to obtain negative electrode powder and copper powder. The positive electrode powder is alternately washed with deionized water and anhydrous ethanol and then dried to obtain regenerated positive electrode active material, namely lithium iron phosphate. The recovery rate of lithium iron phosphate is 91.2%.

[0045] Example 3

[0046] This embodiment proposes a method for separating and regenerating the positive electrode active material from waste lithium battery positive and negative electrode sheets. The specific steps are as follows:

[0047] S1. Under a nitrogen atmosphere (oxygen content < 3%), waste lithium batteries (waste lithium iron phosphate) are fed into the crusher via a feeding belt. The lithium batteries are crushed into flakes of 3±2cm. The flakes are then conveyed to a low-temperature volatilization furnace via a conveying screw. Under a nitrogen atmosphere (oxygen content < 3%), the electrolyte is completely evaporated at 160℃.

[0048] S2. The sheet material undergoes a two-stage air separation process using a grading wheel and an induced draft fan. The induced draft fan blows the sheet material upwards at a 20° angle with an air force of 8 m / s, causing it to fall in a parabolic trajectory from the air separation chamber into the collection area below. Due to the weight differences among the components of the sheet material, the aluminum shell, diaphragm, and positive and negative electrode sheets fall at different positions in the collection area. This process separates the aluminum shell and diaphragm, leaving the positive and negative electrode sheets. These sheets are then processed by an AI color sorter, which uses a combination of visible and invisible light sources. The visible light is used to identify the color characteristics of the material. Furthermore, the different absorption and reflectivity of the positive and negative electrode sheets for specific wavelengths of invisible light are utilized. This process incorporates multi-path compensation and true 4K ultra-high-definition sensor technology, and employs a distributed AI sorting engine. After processing by the AI ​​color sorter, the purity of the positive and negative electrode sheets can reach 99.9%.

[0049] S3. The positive electrode sheet is granulated using a dry roller press granulator (roller pressure of 160MPa) and then passed through a 200-mesh sieve to obtain positive electrode powder and aluminum powder. The negative electrode sheet is granulated using a dry roller press granulator (roller pressure of 200MPa) and then passed through a 400-mesh sieve to obtain negative electrode powder and copper powder. The positive electrode powder is alternately washed with deionized water and anhydrous ethanol and then dried to obtain regenerated positive electrode active material, namely lithium iron phosphate. The recovery rate of lithium iron phosphate is 90.1%.

[0050] Example 4

[0051] This embodiment proposes a method for separating and regenerating the positive electrode active material from waste lithium battery positive and negative electrode sheets. The specific steps are as follows:

[0052] S1. Under a nitrogen atmosphere (oxygen content <3%), waste lithium batteries (waste lithium iron phosphate) are fed into the crusher via a feeding belt. The lithium batteries are crushed into flakes of 3±2cm. The flakes are then conveyed to a low-temperature volatilization furnace via a conveying screw. Under a nitrogen atmosphere (oxygen content <3%), the electrolyte is completely evaporated at 200℃.

[0053] S2. The sheet material undergoes a two-stage air separation process using a grading wheel and an induced draft fan. The induced draft fan blows the sheet material upwards at a 30° angle with a wind speed of 6 m / s, causing it to fall in a parabolic trajectory from the air separation chamber into the collection area below. Due to the weight differences among the components of the sheet material, the aluminum shell, diaphragm, and positive and negative electrode sheets fall at different positions in the collection area. This process separates the aluminum shell and diaphragm, leaving the positive and negative electrode sheets. These sheets are then processed by an AI color sorter, which uses a combination of visible and invisible light sources. The visible light is used to identify the color characteristics of the material. Furthermore, the different absorption and reflectivity of the positive and negative electrode sheets for specific wavelengths of invisible light are utilized. This process incorporates multi-path compensation and true 4K ultra-high-definition sensor technology, and employs a distributed AI sorting engine. After processing by the AI ​​color sorter, the purity of the positive and negative electrode sheets can reach 99.9%.

[0054] S3. The positive electrode sheet is granulated by a dry roller press granulator (roller pressure of 150MPa) and then passed through a 200-mesh sieve to obtain positive electrode powder and aluminum powder. The negative electrode sheet is granulated by a dry roller press granulator (roller pressure of 170MPa) and then passed through a 300-mesh sieve to obtain negative electrode powder and copper powder.

[0055] S4. The positive electrode powder was uniformly dispersed in deionized water at room temperature to form a 0.8 g / L positive electrode powder mixed solution. Then, a PBS buffer solution with a dopamine concentration of 0.4 g / L (pH = 7.2) was added. After sonication for 40 min, the mixture was stirred continuously at 600 rpm for 3 h and then filtered to obtain polydopamine-coated positive electrode powder. The polydopamine-coated positive electrode powder was added to a 1 mol / L LiOH aqueous solution. Then, carbon disulfide was slowly added dropwise at a mass ratio of positive electrode powder to carbon disulfide of 0.5:1. After the addition was completed, the mixture was stirred continuously at 200 rpm for 2 h and then filtered. Since lithium dithiocarbamate carrying lithium ions preferentially interacts with iron ions in the positive electrode powder, the resulting filter residue was calcined at 700℃ for 8 h, and the iron phosphate in the positive electrode powder was replenished in situ. After washing with deionized water and anhydrous ethanol alternately and drying, the regenerated positive electrode active material, namely lithium iron phosphate, was obtained. The recovery rate of lithium iron phosphate was 97.6%.

[0056] Comparative Example 1

[0057] This comparative example presents a method for separating and regenerating positive electrode active materials from waste lithium battery positive and negative electrode sheets. The specific steps are the same as in Example 4, except that carbon disulfide is not added in step S4.

[0058] Comparative Example 2

[0059] This comparative example presents a method for separating and regenerating positive electrode active materials from waste lithium battery positive and negative electrode sheets. The specific steps are the same as in Example 4, except that dopamine and carbon disulfide are not added in step S4.

[0060] Comparative Example 3

[0061] This comparative example proposes a method for separating and regenerating positive electrode active materials from waste lithium battery positive and negative electrode sheets. The specific steps are the same as in Example 4, except that "LiOH" is replaced with "LiCl" in step S4.

[0062] Comparative Example 4

[0063] This comparative example proposes a method for separating and regenerating positive electrode active materials from waste lithium battery positive and negative electrode sheets. The specific steps are the same as in Example 4, except that in step S4, "dopamine" is replaced with "polyethylene glycol".

[0064] Electrochemical performance testing

[0065] Battery assembly:

[0066] The regenerated positive electrode active materials from Examples 1-4 and Comparative Examples 1-2 were mixed with acetylene black box PVDF at a mass ratio of 75:15:10 to form a uniform slurry, which was then uniformly coated onto an aluminum foil substrate as the positive electrode of the battery. Lithium foil was used as the negative electrode, and a polypropylene porous membrane was used as the separator. The electrolyte was 1 mol LiPF6 dissolved in 1 L of a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 1:1). The positive electrode, negative electrode, electrolyte, and separator were assembled into a battery in an argon-protected glove box.

[0067] Discharge specific capacity and cycle performance at different rates:

[0068] First, the assembled battery is charged to 4.2V with constant current, and then discharged to 2.0V at a 1C rate. The discharged capacity is the discharge capacity at the 1C rate. This process is repeated multiple times at this rate until the capacity retention rate is less than 80%. The number of cycles is calculated. After the discharge is completed, a 3C rate test is performed. The test results are shown in Table 1.

[0069] Table 1. Electrochemical performance test results of each embodiment and comparative example.

[0070]

[0071]

[0072] As shown in Table 1, compared with Examples 1-4, although lithium sources were added in Comparative Examples 1-4, the lithium replenishment effect was generally average.

[0073] In Comparative Example 1, although dopamine can accumulate on the surface of cathode powder particles due to its strong adhesion, it cannot accurately match the lithium source with the iron phosphate in the cathode powder, resulting in limited lithium replenishment effect.

[0074] In Comparative Example 2, due to the lack of dopamine and carbon disulfide, the amount of lithium ions adhering to the surface of the cathode powder was small and not very targeted, and the lithium replenishment effect was generally poor during the subsequent calcination process.

[0075] In Comparative Example 3, because the alkaline lithium source was replaced with a neutral lithium salt, carbon disulfide reacted with dopamine to form thiourea in a non-alkaline environment, instead of lithium dithiocarbamate.

[0076] In Comparative Example 4, since dopamine was replaced with polyethylene glycol, although polyethylene glycol has similar adhesive properties to dopamine, it lacks amino groups and cannot form a strong adsorption chelate with the subsequently added carbon disulfide to form lithium dithiocarbamate. Therefore, neither Comparative Example 3 nor Comparative Example 4 can achieve a good lithium replenishment effect.

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets, characterized in that, Includes the following steps: S1. The crushed waste lithium battery sheet material is subjected to heat drying treatment. S2. The waste lithium battery sheet material after heat drying is separated into positive and negative electrode sheets by air separation and color separation. S3. The positive and negative electrode sheets are then granulated and sieved to obtain positive electrode powder, negative electrode powder, aluminum powder and copper powder.

2. The method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets according to claim 1, characterized in that, In step S1, the heat drying temperature is 150-200℃.

3. The method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets according to claim 1 or 2, characterized in that, In step S1, the atmosphere for the thermal drying process is an inert gas; Preferably, the oxygen content of the atmosphere in the heat drying process is <3%.

4. The method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets according to any one of claims 1-3, characterized in that, In step S2, the wind separation is a two-stage wind separation; Preferably, the wind speed is 5-8 m / s; Preferably, the wind tilt angle is 20-30°.

5. The method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets according to any one of claims 1-4, characterized in that, In step S2, the color sorting is performed using an AI color sorter; Preferably, the AI ​​color sorter uses a combination of visible and invisible light sources, integrates multi-path compensation and true 4K ultra-high-definition sensor technology, and employs a distributed AI sorting engine.

6. The method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets according to any one of claims 1-5, characterized in that, In step S3, the granulation is performed using a dry roller press granulator; Preferably, the roller pressing pressure of the dry roller press granulator is 120-250 MPa.

7. The method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets according to any one of claims 1-6, characterized in that, It also includes step S4, which involves reacting the positive electrode powder with dopamine via a self-polymerization reaction, then adding carbon disulfide and an alkaline lithium source for a chelation reaction, and finally calcining the resulting solid to obtain a regenerated positive electrode active material.

8. The method for separating and regenerating the positive electrode active material from waste lithium battery positive and negative electrode sheets according to claim 7, characterized in that, In step S4, the mass ratio of the positive electrode powder, dopamine, and carbon disulfide is 1:0.2-1:1-8.

5.

9. The method for separating and regenerating the positive electrode active material from waste lithium battery positive and negative electrode sheets according to claim 7 or 8, characterized in that, In step S4, the alkaline lithium source is lithium hydroxide.

10. The method for separating and regenerating positive electrode active material from waste lithium battery positive and negative electrode sheets according to any one of claims 7-9, characterized in that, In step S4, the calcination temperature is 700-900℃ and the calcination time is 6-10h.

Images