Process for extracting waste lithium ion battery by using deep eutectic solvent

Abstract

The invention relates to a process for extracting a waste lithium ion battery by using a deep eutectic solvent. The process mainly comprises five stages of discharge treatment, DESs solvent preparation, metal leaching, solution purification and lithium recovery. After a 4-6% 4, 6-dihydroxypyrimidine-2-sodium sulfide solution is adopted for safe discharge, efficient leaching of the positive electrode material is achieved through a DESs solvent compounded by ethylene glycol and 5-chlorovanillic acid under the action of ozone oxidation and 5-thio-D-glucose reduction. And the regeneration cycle of the DESs solvent and the recovery of lithium are realized through step-by-step distillation. According to the process, a DESs system is constructed by adopting biocompatible organic weak acid, and an ozone redox regulation and control technology is combined, so that the problem of environmental pollution of a traditional strong acid leaching process is avoided. The solvent is recycled in the whole process, leaching residues can be recycled after being washed, the method has the advantages of being environmentally friendly, high in metal selectivity, closed in technological process and the like, and a sustainable solution is provided for lithium battery recycling.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste lithium battery recycling, and in particular relates to a process for extracting waste lithium-ion batteries using a deep eutectic solvent. Background Art

[0002] LiFePO4, a positive electrode material for lithium batteries 4 Because of its advantages such as high discharge capacity, relatively stable discharge platform, good cycle stability, thermal stability and low price, it is widely used in mobile phones, electric vehicles and other fields. In recent years, the production of lithium iron phosphate batteries has gradually increased, resulting in a gradual increase in the scrap volume of lithium iron phosphate batteries. Therefore, it is necessary to efficiently recycle and harmlessly treat waste lithium-ion batteries. At present, there are many studies on the recycling of waste lithium-ion batteries at home and abroad, but they mainly focus on the recovery of valuable metals from positive electrode powders using hydrometallurgical methods. In order to obtain the most valuable electrode active material powder in waste lithium-ion batteries for subsequent valuable metal extraction experiments, waste lithium-ion batteries need to be pretreated: discharge, crushing and disassembly, and thermal desorption of black powder. There is still some voltage remaining in waste lithium-ion batteries. When disposed of in large quantities, the mutual extrusion and contact between battery cells causes rapid discharge and heat generation, which is easy to cause fire and potential risk of explosion. Therefore, in order to ensure safe recycling, discharge operation is usually the first step in the recycling process of waste lithium-ion batteries. However, most of the current research on pre-treatment discharge of waste lithium-ion batteries focuses on improving discharge efficiency, ignoring the impact of pollutants generated during the discharge process on the environment. In addition, waste lithium-ion batteries placed in salt solutions will cause short circuits between the positive and negative electrodes and gradually release the residual pressure of the battery. Therefore, using a suitable salt solution to discharge lithium batteries to improve the above problems is the research focus of the present invention.

[0003] As an emerging green solvent, DESs are room temperature liquids formed by non-toxic or low-toxic hydrogen bond donors and amino bond acceptors, with excellent properties such as low saturated vapor pressure, wide liquid phase range and biodegradability. Studies have found that the proton activity, reducing ability, coordination ability and viscosity of DESs have an important influence on the solubility of metal oxides, especially acid-based DESs have a strong promoting effect on the leaching of metal oxides, and have gradually attracted people's attention in the research of green recovery of various metal resources.

[0004] One of the research directions of the present invention is how to improve the dissolution performance of positive electrode active materials by optimizing the properties of DESs themselves, such as proton activity, reducing ability, coordination ability and viscosity, and achieve efficient and mild leaching of high-valent positive electrode active materials. Summary of the invention

[0005] The object of the present invention is to provide a process for extracting waste lithium-ion batteries using a deep eutectic solvent.

[0006] In order to solve the above technical problems, the specific process of the present invention is as follows:

[0007] A process for extracting waste lithium-ion batteries with deep eutectic solvents, including discharge, DESs solvent preparation, waste battery leaching, leachate purification, and lithium recovery: wherein the discharge treatment is: using a salt solution with a mass fraction of 4-6% as a discharge medium, the discharge time is 6-10 hours, and the solid-liquid ratio is 1:10;

[0008] Wherein, the salt solution is 4,6-dihydroxypyrimidine-2-sodium sulfide solution.

[0009] The DESs solvent is prepared as follows: ethylene glycol and 60-80% organic weak acid by mass are mixed in a ratio of 8-10:1, heated and stirred in a water bath at 60°C, and the mixture is stirred at a speed of 200-300 rpm for 30 minutes to obtain a clear and transparent DESs solvent, which is then sealed and stored in a desiccator at room temperature for later use.

[0010] Wherein, the organic weak acid is 5-chlorovanillic acid solution.

[0011] A process for extracting waste lithium-ion batteries using a deep eutectic solvent is carried out in the following steps:

[0012] Leaching of waste batteries: Put the raw materials of the positive electrode materials of the waste batteries separated after discharge into DESs solvent with a solid-liquid ratio of 50g / L. After heating to 60°C in a water bath, pass the ozone atmosphere into the slurry through a glass tube with an ozone flow rate of 16L / min and continuous magnetic stirring at 30rpm. The leaching time is 6-8h. Every two hours, add 2-5% of the reducing agent to the solvent. After the reaction is completed, filter to obtain the leachate and leach residue. The leach residue is repeatedly washed with deionized water and anhydrous ethanol for 3 times, and dried in an oven at 90°C for 12h, ground into powder and set aside.

[0013] Purification of leachate: Place the leachate in a flask of a distillation device and put it into a heat-collecting magnetic stirrer. Use dimethyl silicone oil for oil bath heating. After heating to 150°C, stir magnetically for 0.5h at a speed of 100-200rpm. Cool the slurry with a light yellow precipitate to room temperature and obtain a pure lithium-containing solution and yellow precipitate by suction filtration. The obtained yellow precipitate is washed 3 times with anhydrous ethanol, then dried in an oven at 90°C for 12h, and fully ground into powder for use;

[0014] Lithium recovery process: Place the lithium-containing solution in a distillation device, place the flask in a heat-collecting magnetic stirrer, use an oil bath to heat to 220°C, use a micro diaphragm vacuum pump to extract the evaporated ethylene glycol vapor, and condense the vapor through the condenser of the distillation device to obtain ethylene glycol; after distillation for 1 hour, obtain the distilled regenerated ethylene glycol and residue; take out the residue and calcine it at 600°C for 1 hour, and then grind it into powder.

[0015] The reducing agent is a 5-thio-D-glucose solution with a mass fraction of 20-30%.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention includes optimizing the discharge treatment of waste batteries, and realizing efficient leaching of positive electrode materials through the DESs solvent compounded with ethylene glycol and 5-chlorovanillic acid under the synergistic effect of ozone oxidation and 5-thio-D-glucose reduction. The DESs system is constructed using organic weak acid, combined with ozone redox regulation technology, to avoid the environmental pollution problem of traditional strong acid leaching process, and realize efficient green recovery and utilization of valuable metals in waste lithium batteries.

[0018] Sodium sulfide in 2.4,6-dihydroxypyrimidine-2-sodium sulfide solution is a highly conductive salt that can provide sufficient conductive ions. During the battery discharge process, the conductive ions can migrate between the two poles of the battery to maintain the flow of current. Compared with some traditional salt solutions, 4,6-dihydroxypyrimidine-2-sodium sulfide solution provides high conductivity while not producing corrosive byproducts like chlorides, thereby improving discharge efficiency while avoiding corrosion to the battery casing.

[0019] 3. During the discharge process, many salt solutions may produce a lot of sediment. These sediments not only increase the internal impedance of the battery, but may also affect the long-term cycle performance of the battery. However, the amount of sediment generated by the sodium 4,6-dihydroxypyrimidine-2-sulfide solution during the discharge process is small, and the main component is sulfur. This byproduct is usually stable and is not likely to have an adverse effect on battery performance. The reduction of sediment helps the battery maintain a lower internal resistance and prolongs the cycle life of the battery.

[0020] 4. A solvent composed of low-viscosity ethylene glycol and 5-chlorovanillic acid is used in conjunction with an ozone atmosphere to construct a selective leaching system. The system has low viscosity and excellent mass transfer and filtration performance. As a solvent, ethylene glycol can interact with the carboxyl and phenolic hydroxyl groups of 5-chlorovanillic acid through hydrogen bonds, enhance the proton transfer efficiency, and improve its coordination ability. Through this synergistic effect, ethylene glycol and 5-chlorovanillic acid can more effectively bind and coordinate metal ions, thereby improving the efficiency of dissolving metals. 5-chlorovanillic acid has stronger reducing and selective coordination abilities, and 5-chlorovanillic acid is an organic weak acid, which is more friendly to the equipment environment. 5-chlorovanillic acid has strong proton activity and strong coordination synergy with Cl ions, which can significantly improve its solubility. Selecting organic weak acids with strong coordination ability to synthesize DESs will make the leaching and recovery process of active materials more green and efficient. Accelerate the efficient leaching of lithium iron phosphate.

[0021] The chlorine atom in 5-chlorovanillic acid is located at the 5th position of the benzene ring. Compared with ordinary vanillic acid, the chlorine atom can adjust the electron density of other parts of its molecule through electronic effects. The presence of chlorine atoms enhances its ability as a reducing agent, and can effectively participate in redox reactions, thereby improving its ability to dissolve metals. As an organic acid, 5-chlorovanillic acid contains strong proton activity. It has a good proton donor effect and can form hydrogen bonds or directly coordinate with metal ions. This enables 5-chlorovanillic acid to effectively coordinate with metal ions and promote the dissolution of metals. Its weak acidic properties prevent it from excessively corroding equipment in an acidic environment and are more environmentally friendly.

[0022] 6. The deep crystal eutectic solvent has a significant improvement in the leaching rate. As a similar hydrogen bonding type solvent, a reducing agent is introduced into the deep crystal eutectic system to enhance the reducing property of the original solvent. 2 O 2 As a reducing agent to improve the diffusion capacity of high-valent metals, it does not perform well in the present invention, not only inhibiting the leaching of metals, but even causing incompatibility. The system itself has low viscosity and good solubility, so it is possible to consider introducing a more effective reducing agent;

[0023] 7. Therefore, the present invention introduces a green reducing agent 5-thio-D-glucose. 5-thio-D-glucose is a natural sugar derivative in which oxygen is replaced by sulfur. Its structure is similar to glucose, and its reducing property is stronger than glucose. It has high biodegradability, is safe to use, and its products are environmentally friendly, meeting the requirements of green chemistry. 5-thio-D-glucose as a reducing agent can effectively improve the leaching rate, especially for the leaching of Co. It helps to increase the dissolution rate of metals by reducing metal ions, and helps the leaching of Li by promoting the formation of an acidic environment. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the examples. Waste lithium batteries are used as LIBs positive electrode materials, and the following tests are carried out.

[0025] Example 1

[0026] A 5% mass fraction of 4,6-dihydroxypyrimidine-2-sodium sulfide solution was used as the discharge medium, the discharge time was 8 hours, the solid-liquid ratio was 1:10, and the battery cell was mechanically separated to obtain the positive electrode, the negative electrode and the separator; the positive electrode sheet was cut into small pieces of 1x1 cm, and immersed in a 15% NMP solution and stirred at 100°C and 240W for 1 hour to accelerate the separation of the positive electrode material and dissolve the PVDF binder; the separated positive electrode material was calcined in a muffle furnace at 700°C for 2 hours, and then ground and used as a raw material for acid hydrolysis;

[0027] Example 2

[0028] A 6% mass fraction of 4,6-dihydroxypyrimidine-2-sodium sulfide solution was used as the discharge medium, the discharge time was 6 hours, the solid-liquid ratio was 1:10, and the battery cell was mechanically separated to obtain the positive electrode, the negative electrode and the separator; the positive electrode sheet was cut into small pieces of 1x1 cm, and immersed in a 15% NMP solution and stirred at 100°C and 240W for 1 hour to accelerate the separation of the positive electrode material and dissolve the PVDF binder; the separated positive electrode material was calcined in a muffle furnace at 700°C for 2 hours, and then ground and used as a raw material for acid hydrolysis;

[0029] Example 3

[0030] A 4% mass fraction of 4,6-dihydroxypyrimidine-2-sodium sulfide solution was used as the discharge medium, the discharge time was 10 hours, the solid-liquid ratio was 1:10, and the battery cell was mechanically separated to obtain the positive electrode, the negative electrode and the separator; the positive electrode sheet was cut into small pieces of 1x1 cm, and immersed in a 15% NMP solution and stirred at 100°C and 240W for 1 hour to accelerate the separation of the positive electrode material and dissolve the PVDF binder; the separated positive electrode material was calcined in a muffle furnace at 700°C for 2 hours, and then ground as a raw material for acid hydrolysis;

[0031] Comparative Example 1

[0032] The difference between this comparative example and Example 1 is that the 4,6-dihydroxypyrimidine-2-sodium sulfide solution in this comparative example is a sodium chloride solution, and the rest is the same as Example 1.

[0033] Comparative Example 2

[0034] The difference between this comparative example and Example 1 is that the mass fraction of 4,6-dihydroxypyrimidine-2-sodium sulfide solution is different, specifically: using 10% mass fraction of 4,6-dihydroxypyrimidine-2-sodium sulfide solution as the discharge medium, the discharge time is 8h, the solid-liquid ratio is 1:10, and the battery cell is mechanically separated to obtain the positive electrode, the negative electrode and the separator; the positive electrode sheet is cut into small pieces of 1x1cm, and immersed in 15% NMP solution and ultrasonically stirred at 100℃ and 240w for 1h to accelerate the separation of the positive electrode material and dissolve the PVDF binder; the separated positive electrode material is calcined in a muffle furnace at 700℃ for 2h, and then ground as a raw material for acid hydrolysis.

[0035] Comparative Example 3

[0036] The difference between this comparative example and Example 1 is that the mass fraction of 4,6-dihydroxypyrimidine-2-sodium sulfide solution is different, specifically: using 2% mass fraction of 4,6-dihydroxypyrimidine-2-sodium sulfide solution as the discharge medium, the discharge time is 8h, the solid-liquid ratio is 1:10, and the battery cell is mechanically separated to obtain the positive electrode, the negative electrode and the separator; the positive electrode plate is cut into small pieces of 1x1cm, and immersed in 15% NMP solution and ultrasonically stirred at 100℃ and 240w for 1h to accelerate the separation of the positive electrode material and dissolve the PVDF binder; the separated positive electrode material is calcined in a muffle furnace at 700℃ for 2h, and then ground as a raw material for acid hydrolysis.

[0037] Test 1: Detection of sediment after discharge treatment

[0038] The precipitate remaining in the solution after discharge is washed and dried, and then precipitated with a mixed solution of hydrochloric acid and nitric acid (HCl and HNO 3 , volume ratio of 3:1) was fully dissolved, and the elemental composition was determined by ICP-OES. The results are shown in Table 1.

[0039] Table 1

[0040]

[0041] The following implementation modes are all carried out on the basis of Example 1.

[0042] Example 4

[0043] Preparation of DESs solvent: Mix ethylene glycol and 70% by mass 5-chlorovanillic acid solution in a ratio of 9:1, heat and stir in a water bath at 60°C, and stir the mixture at 250 rpm for 30 min to obtain a clear and transparent DESs solvent. Seal it and store it in a desiccator at room temperature for later use.

[0044] Leaching of waste batteries: the raw materials of the positive electrode materials of the waste batteries separated after discharge are placed in a DESs solvent with a solid-liquid ratio of 50 g / L. After being heated to 60°C in a water bath, an ozone atmosphere is introduced into the slurry using a glass tube. The ozone flow rate is 16 L / min, and the magnetic stirring is continued at 30 rpm. The leaching time is 7 hours. Every two hours, 3.5% of a 25% mass fraction of 5-thio-D-glucose solution is added to the solvent. After the reaction is completed, the leaching solution and leaching residue are obtained by suction filtration. The leaching residue is repeatedly washed with deionized water and anhydrous ethanol for 3 times, and dried in an oven at 90°C for 12 hours, and ground into powder for later use.

[0045] Purification of leachate: Place the leachate in a flask of a distillation device and put it into a heat-collecting magnetic stirrer. Use dimethyl silicone oil for oil bath heating. After heating to 150°C, stir magnetically for 0.5h at a speed of 150rpm. Cool the slurry with a light yellow precipitate to room temperature and obtain a pure lithium-containing solution and yellow precipitate by suction filtration. The obtained yellow precipitate is washed 3 times with anhydrous ethanol, then dried in an oven at 90°C for 12h, and fully ground into powder for use;

[0046] Lithium recovery process: Place the lithium-containing solution in a distillation device, place the flask in a heat-collecting magnetic stirrer, use an oil bath to heat to 220°C, use a micro diaphragm vacuum pump to extract the evaporated ethylene glycol vapor, and condense the vapor through the condenser of the distillation device to obtain ethylene glycol; after distillation for 1 hour, obtain the distilled regenerated ethylene glycol and residue; take out the residue and calcine it at 600°C for 1 hour, and then grind it into powder.

[0047] Example 5

[0048] Preparation of DESs solvent: Mix ethylene glycol and 60% 5-chlorovanillic acid solution in a ratio of 10:1, heat and stir in a water bath at 60°C, and stir the mixture at 200 rpm for 30 min to obtain a clear and transparent DESs solvent. Seal it and store it in a desiccator at room temperature for later use.

[0049] Leaching of waste batteries: the raw materials of the positive electrode materials of the waste batteries separated after discharge are placed in a DESs solvent with a solid-liquid ratio of 50 g / L. After being heated to 60°C in a water bath, an ozone atmosphere is introduced into the slurry using a glass tube. The ozone flow rate is 16 L / min, and the magnetic stirring is continued at 30 rpm. The leaching time is 8 hours. Every two hours, 5% of a 20% mass fraction of 5-thio-D-glucose solution is added to the solvent. After the reaction is completed, the leaching solution and leaching residue are obtained by suction filtration. The leaching residue is repeatedly washed with deionized water and anhydrous ethanol for 3 times, and dried in an oven at 90°C for 12 hours. It is ground into powder for later use.

[0050] Purification of leachate: Place the leachate in a flask of a distillation device and put it into a heat-collecting magnetic stirrer. Use dimethyl silicone oil for oil bath heating. After heating to 150°C, stir magnetically for 0.5h at a speed of 200rpm. Cool the slurry with a light yellow precipitate to room temperature and obtain a pure lithium-containing solution and yellow precipitate by suction filtration. The obtained yellow precipitate is washed 3 times with anhydrous ethanol, then dried in an oven at 90°C for 12h, and fully ground into powder for use;

[0051] Lithium recovery process: Place the lithium-containing solution in a distillation device, place the flask in a heat-collecting magnetic stirrer, use an oil bath to heat to 220°C, use a micro diaphragm vacuum pump to extract the evaporated ethylene glycol vapor, and condense the vapor through the condenser of the distillation device to obtain ethylene glycol; after distillation for 1 hour, obtain the distilled regenerated ethylene glycol and residue; take out the residue and calcine it at 600°C for 1 hour, and then grind it into powder.

[0052] Example 6

[0053] Preparation of DESs solvent: Mix ethylene glycol and 80% 5-chlorovanillic acid solution in a ratio of 8:1, heat and stir in a water bath at 60°C, and stir the mixture at 300 rpm for 30 min to obtain a clear and transparent DESs solvent. Seal it and store it in a desiccator at room temperature for later use.

[0054] Leaching of waste batteries: the raw materials of the positive electrode materials of the waste batteries separated after discharge are placed in a DESs solvent with a solid-liquid ratio of 50 g / L. After being heated to 60°C in a water bath, an ozone atmosphere is introduced into the slurry using a glass tube. The ozone flow rate is 16 L / min, and the magnetic stirring is continued at 30 rpm. The leaching time is 6 hours. Every two hours, 2% of a 30% mass fraction of 5-thio-D-glucose solution is added to the solvent. After the reaction is completed, the leaching solution and leaching residue are obtained by suction filtration. The leaching residue is repeatedly washed with deionized water and anhydrous ethanol for 3 times, and dried in an oven at 90°C for 12 hours. It is ground into powder for later use.

[0055] Purification of leachate: Place the leachate in a flask of a distillation device and put it into a heat-collecting magnetic stirrer. Use dimethyl silicone oil for oil bath heating. After heating to 150°C, stir magnetically for 0.5h at a speed of 100rpm. Cool the slurry with a light yellow precipitate to room temperature and obtain a pure lithium-containing solution and yellow precipitate by suction filtration. The obtained yellow precipitate is washed 3 times with anhydrous ethanol, then dried in an oven at 90°C for 12h, and fully ground into powder for use;

[0056] Lithium recovery process: Place the lithium-containing solution in a distillation device, place the flask in a heat-collecting magnetic stirrer, use an oil bath to heat to 220°C, use a micro diaphragm vacuum pump to extract the evaporated ethylene glycol vapor, and condense the vapor through the condenser of the distillation device to obtain ethylene glycol; after distillation for 1 hour, obtain the distilled regenerated ethylene glycol and residue; take out the residue and calcine it at 600°C for 1 hour, and then grind it into powder.

[0057] Comparative Example 4

[0058] The difference between this comparative example and Example 4 is that the 5-chlorovanillic acid solution in this comparative example is oxalic acid; the rest is the same as Example 4.

[0059] Comparative Example 5

[0060] The difference between this comparative example and Example 4 is that the amount of 5-chlorovanillic acid solution added in this comparative example is different. The specific DESs solvent preparation is as follows: ethylene glycol and 70% 5-chlorovanillic acid solution by mass are mixed in a ratio of 9:2, heated and stirred in a water bath at 60°C, and the mixture is stirred at a speed of 250 rpm for 30 minutes to obtain a clear and transparent DESs solvent, which is sealed and placed in a desiccator for storage at room temperature for future use; the rest is the same as Example 4.

[0061] Comparative Example 6

[0062] The difference between this comparative example and Example 4 is that the amount of 5-chlorovanillic acid solution added in this comparative example is different. The specific DESs solvent preparation is as follows: ethylene glycol and 70% 5-chlorovanillic acid solution by mass are mixed in a ratio of 9:0.5, heated and stirred in a water bath at 60°C, and the mixture is stirred at a speed of 250 rpm for 30 minutes to obtain a clear and transparent DESs solvent, which is sealed and placed in a desiccator for storage at room temperature for future use; the rest is the same as Example 4.

[0063] Comparative Example 7

[0064] The difference between this comparative example and Example 4 is that the reducing agent 5-thio-D-glucose solution is not supplemented in this comparative example; the rest is the same as Example 4.

[0065] Comparative Example 8

[0066] The difference between this comparative example and Example 4 is that the 5-thio-D-glucose solution in this comparative example is H 2 O 2 ; The rest is the same as Example 4.

[0067] Comparative Example 9

[0068] The difference between this comparative example and Example 4 is that the amount of 5-thio-D-glucose solution added in this comparative example is different. Specifically, for leaching of waste batteries: the raw materials of the positive electrode materials of the waste batteries disassembled and separated after discharge are placed in a DESs solvent with a solid-liquid ratio of 50 g / L. After being heated to 60°C in a water bath, an ozone atmosphere is introduced into the slurry using a glass tube. The ozone flow rate is 16 L / min, and the magnetic stirring is continued at 30 rpm. The leaching time is 7 h. Every two hours, 8% of a 25% 5-thio-D-glucose solution by mass fraction is added to the solvent. After the reaction is completed, suction filtration is performed to obtain a leachate and a leach residue. The leach residue is repeatedly washed 3 times with deionized water and anhydrous ethanol, and dried in an oven at 90°C for 12 h, ground into powder and set aside. The rest is the same as in Example 4.

[0069] Comparative Example 10

[0070] The difference between this comparative example and Example 4 is that the amount of 5-thio-D-glucose solution added in this comparative example is different. Specifically, the leaching of waste batteries: the raw materials of the positive electrode materials of the waste batteries disassembled and separated after discharge are placed in a DESs solvent with a solid-liquid ratio of 50 g / L. After heating to 60°C in a water bath, an ozone atmosphere is introduced into the slurry using a glass tube. The ozone flow rate is 16 L / min, and the magnetic stirring is continued at 30 rpm. The leaching time is 7 h. Every two hours, 1% of a 25% mass fraction of 5-thio-D-glucose solution is added to the solvent. After the reaction is completed, suction filtration is performed to obtain a leachate and a leach residue. The leach residue is repeatedly washed 3 times with deionized water and anhydrous ethanol, and dried in an oven at 90°C for 12 h, ground into powder and set aside. The rest is the same as Example 4.

[0071] Test 2: Leaching rate

[0072] The leachate after DESs solvent treatment was taken, the metal ion concentration was detected, and the leaching rate (ξ) was measured.

[0073] Leaching rate

[0074] c is the numerical value of the ion concentration in the leachate, in g / L; V is the numerical value of the volume of the leachate, in L; m is the numerical value of the mass of the raw material, in g; w is the numerical value of the content of each valuable metal in the raw material, in %, as shown in Table 2 below.

[0075] Table 2

[0076]

Claims

1. A process for extracting waste lithium-ion batteries with deep eutectic solvents, comprising discharge, DESs solvent preparation, waste battery leaching, leachate purification, and lithium recovery, characterized in that: The discharge treatment is as follows: using a salt solution with a mass fraction of 4-6% as the discharge medium, the discharge time is 6-10 hours, and the solid-liquid ratio is 1:10; The salt solution is 4,6-dihydroxypyrimidine-2-sodium sulfide solution.

2. The process for extracting waste lithium-ion batteries using a deep eutectic solvent as claimed in claim 1, characterized in that: The DESs solvent is prepared as follows: ethylene glycol and an organic weak acid with a mass fraction of 60-80% are mixed in a ratio of 8-10:1, heated and stirred in a water bath at 60°C, and the mixture is stirred at a speed of 200-300 rpm for 30 minutes to obtain a clear and transparent DESs solvent, which is then sealed and stored in a desiccator at room temperature for later use.

3. The process for extracting waste lithium-ion batteries using a deep eutectic solvent as claimed in claim 2, characterized in that: The organic weak acid is 5-chlorovanillic acid solution.

4. The process for extracting waste lithium-ion batteries using a deep eutectic solvent as claimed in claim 1, characterized in that: Proceed as follows: Leaching of waste batteries: Put the raw materials of the positive electrode materials of the waste batteries separated after discharge into DESs solvent with a solid-liquid ratio of 50g / L. After heating to 60°C in a water bath, pass the ozone atmosphere into the slurry through a glass tube with an ozone flow rate of 16L / min and continuous magnetic stirring at 30rpm. The leaching time is 6-8h. Every two hours, add 2-5% of the reducing agent to the solvent. After the reaction is completed, filter to obtain the leachate and leach residue. The leach residue is repeatedly washed with deionized water and anhydrous ethanol for 3 times, and dried in an oven at 90°C for 12h, ground into powder and set aside. Purification of leachate: Place the leachate in a flask of a distillation device and put it into a heat-collecting magnetic stirrer. Use dimethyl silicone oil for oil bath heating. After heating to 150°C, stir magnetically for 0.5h at a speed of 100-200rpm. Cool the slurry with a light yellow precipitate to room temperature and obtain a pure lithium-containing solution and yellow precipitate by suction filtration. The obtained yellow precipitate is washed 3 times with anhydrous ethanol, then dried in an oven at 90°C for 12h, and fully ground into powder for use; Lithium recovery process: Place the lithium-containing solution in a distillation device, place the flask in a heat-collecting magnetic stirrer, use an oil bath to heat to 220°C, use a micro diaphragm vacuum pump to extract the evaporated ethylene glycol vapor, and condense the vapor through the condenser of the distillation device to obtain ethylene glycol; after distillation for 1 hour, obtain the distilled regenerated ethylene glycol and residue; take out the residue and calcine it at 600°C for 1 hour, and then grind it into powder.

5. The process for extracting waste lithium-ion batteries using a deep eutectic solvent as claimed in claim 4, characterized in that: The reducing agent is a 5-thio-D-glucose solution with a mass fraction of 20-30%.

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