Method for selectively extracting lithium in positive electrode material of waste lithium battery through microwave-assisted DES

Abstract

The invention belongs to the technical field of waste lithium ion battery recycling, and particularly relates to a method for selectively extracting lithium in a waste lithium battery positive electrode material through microwave-assisted DES. The method comprises the following steps: carrying out ball milling and screening on the waste lithium ion battery positive electrode material to obtain pretreated positive electrode powder; mixing choline chloride and ethylene glycol, heating, stirring and uniformly dissolving to obtain a deep eutectic solvent; and adding the obtained positive electrode powder into a deep eutectic solvent, carrying out microwave heating to 200-230 DEG C, stirring and leaching, filtering the leached mixed solution, taking the filtrate, adding alkali liquor to adjust the pH value to 10-12, filtering to remove the precipitate, heating and concentrating the filtrate, then adding a Na2CO3 solution, precipitating, filtering, taking the solid phase, washing and drying to obtain the lithium carbonate. The method disclosed by the invention can be used for efficiently and selectively leaching and recycling lithium in the positive electrode material of the waste lithium battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of recycling of waste lithium-ion batteries, and particularly relates to a method for selectively extracting lithium from the cathode material of waste lithium batteries by microwave-assisted DES. Background Art

[0002] Lithium-ion batteries (LIBs), as an efficient energy storage device, have been widely used in fields such as electric vehicles, energy storage systems, and portable electronic devices, and their manufacturing and sales have also increased significantly. However, this has also caused many problems. On the one hand, the supply of key elements such as cobalt (Co), nickel (Ni), and lithium (Li) in the LIBs cathode faces huge challenges. These elements have limited reserves in the earth's crust, and the supply stability is difficult to guarantee. On the other hand, lithium-ion batteries will gradually age and their performance will decline during use, and eventually become waste batteries. These waste batteries contain a large amount of valuable metals such as lithium, cobalt, and nickel. If not effectively recycled, it will not only cause waste of resources, but also cause great pressure on the environment.

[0003] At present, the main methods for recycling the cathode material of lithium-ion batteries include pyrometallurgy, hydrometallurgy, and biohydrometallurgy, etc. Pyrometallurgy requires high-temperature smelting, which has high energy consumption and produces a large amount of harmful gases; although hydrometallurgy has the advantages of high recovery rate, traditional hydrometallurgy leaching agents are usually strong acids, strong bases, strong reducing agents or corrosive substances, etc. These leaching agents are not only harmful to human health and the environment, corrosive to equipment, but also have problems such as poor selectivity, long reaction time, and high neutralization cost during the leaching process, which greatly increases the overall operating cost of recycling; although biohydrometallurgy is environmentally friendly, its reaction rate is slow and the efficiency is low. Therefore, it is of great practical significance to develop an efficient, environmentally friendly, and low-cost method for recycling the cathode material of lithium-ion batteries.

[0004] Deep eutectic solvents (DES), as a green leaching agent, have received attention in recent years. It is composed of a hydrogen bond donor and an acceptor, and can extract metals from LIBs cathode materials without using additional reducing agents. At present, most battery recycling work mainly focuses on the extraction of transition metals (such as Co and Ni), while the recycling of lithium is often ignored due to its cumbersome process and high energy consumption. For example, the invention patent CN 118486938 A discloses a method for recycling the cathode of waste ternary batteries based on a reusable leaching agent, using a eutectic solvent DES with the ability to regulate the mixed crystal precipitation coefficient for recycling the cathode material of waste lithium-ion batteries, and using a specific oxalic acid as the hydrogen bond donor, which can achieve efficient recycling of nickel, cobalt, and manganese. However, compared with traditional leaching agents, DES has problems such as slow leaching kinetics, the need for high temperature, and low solid-liquid ratio (Rm / V), which limits its commercial feasibility. In addition, long-term heating will also cause some DES to decompose and produce toxic by-products, affecting its reusability and overall environmental friendliness.

[0005] Patent for invention CN 114645144 A discloses a method for extracting lithium using a deep eutectic solvent, which uses a β-diketone compound with an electron-withdrawing substituent as a hydrogen bond donor and a compound with a donating property and capable of forming a hydrogen bond group containing P=O and / or N=O as a hydrogen bond acceptor. The obtained deep eutectic solvent is used for the extraction and recovery of lithium ions in a lithium-containing solution. However, for the solid waste lithium-ion battery cathode material with complex components and containing multiple metal ions, the effect of selectively extracting lithium by this deep eutectic solvent is limited. Summary of the Invention

[0006] Aiming at the above-mentioned disadvantages and deficiencies existing in the prior art, the purpose of the present invention is to provide a method for selectively extracting lithium from waste lithium battery cathode materials by microwave-assisted DES. To solve the problems of low lithium recovery efficiency, high energy consumption, and environmental unfriendliness in the prior art in the lithium-ion battery cathode lithium recovery, realize the sustainable recycling of lithium resources, and promote the circular development of the lithium-ion battery industry.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for selectively extracting lithium from waste lithium battery cathode materials by microwave-assisted DES, comprising the following steps:

[0009] (1) Pretreatment: Ball-mill and screen the waste lithium-ion battery cathode material to obtain a pretreated cathode powder.

[0010] (2) Prepare the leaching agent: Mix choline chloride (ChCl) and ethylene glycol (EG), heat and stir to dissolve evenly to obtain a deep eutectic solvent (DES).

[0011] (3) Microwave-assisted leaching process: Add the cathode powder obtained in step (1) to the DES in step (2), fully mix, and then heat by microwave to 200-230 °C and stir for leaching to obtain a leaching mixture.

[0012] (4) Separation and recovery of lithium: Filter the leaching mixture in step (3), take the filtrate, add an alkali solution to adjust the pH value to 10-12, filter to remove the precipitate, heat and concentrate the filtrate, then add a Na2CO3 solution for precipitation, filter, take the solid phase, wash and dry to obtain lithium carbonate.

[0013] Furthermore, the waste lithium-ion battery cathode material in step (1) includes waste nickel cobalt aluminum ternary lithium battery cathode material (such as NCA), waste nickel cobalt manganese ternary lithium battery cathode material (such as NMC111, NMC811, etc.), and waste lithium cobalt oxide battery cathode material (LCO).

[0014] Further, the ball milling speed in step (1) is 500 - 700 rpm, and the ball milling time is 3 - 5 h; the particle size of the screening is 120 - 180 mesh. Through ball milling and screening, the contact area between the cathode material and the leaching agent can be increased, and the leaching rate can be improved.

[0015] Further, the molar ratio of choline chloride to ethylene glycol mixed in step (2) is 3:2.

[0016] Further, the heating temperature in step (2) is 30 - 60 °C.

[0017] Further, the solid-liquid ratio of the cathode powder added to the DES in step (3) is 5 - 30 g / L.

[0018] Further, the stirring leaching time in step (3) is 30 s - 30 min.

[0019] Further, the lye used in step (4) is 1M NaOH solution.

[0020] Further, the heating and concentration in step (4) means heating and concentrating to 1 / 3 - 2 / 3 of the original volume at 100 - 140 °C.

[0021] Further, the temperature control for precipitation by adding Na2CO3 solution in step (4) is 60 - 80 °C.

[0022] The principle of the present invention is as follows: A specific deep eutectic solvent (DES) is used in combination with microwave heating to extract valuable metals from the cathode material. In this process, microwave directly acts on the reaction medium through its characteristics of rapid heating and selective heating, prompting lithium ions to quickly leach from the cathode material into the DES, while reducing the dissolution of other impurities and improving the leaching selectivity.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) High efficiency and rapidity: Under the microwave-assisted effect, the leaching speed of lithium is extremely fast. The lithium leaching rate can reach 50% within 30 seconds. Compared with the traditional heating method, the reaction speed is increased by hundreds of times, greatly shortening the recovery time and improving the production efficiency.

[0025] (2) High selectivity: This method has a high selectivity for lithium and can effectively reduce the leaching of transition metals such as cobalt and nickel. For example, at the reaction time of 3 min, the lithium leaching rate is 67.9%, while the cobalt leaching rate is only 5.8%, and the nickel leaching rate is 2.7%. This is beneficial to the subsequent separation and purification of lithium, improving the recovery purity of valuable metals while reducing the recovery cost.

[0026] (3) Energy conservation and environmental protection: Microwave radiation acts directly on molecules with high energy utilization efficiency. Compared with traditional oil bath heating, the energy consumption is significantly reduced. For example, when achieving 50% lithium leaching, oil bath heating takes more than 2 hours with an energy consumption of 2.595 kWh, while microwave only takes 30 seconds with an energy consumption of 0.00292 kWh, effectively reducing energy consumption and carbon emissions, meeting environmental protection requirements. At the same time, using the green and environmentally friendly DES as the leaching agent reduces environmental pollution.

[0027] (4) Improving commercial feasibility: The recovery method of the present invention is simple to operate and has relatively low equipment requirements, which can effectively reduce the recovery cost and has good economic and social benefits. Under microwave radiation, the solid-liquid ratio (Rm / V) of the deep eutectic solvent can be increased. Even when Rm / V is increased to 30 g / L, the lithium leaching rate can still remain at a certain level (such as 68.7%), making this recovery method more competitive in commercial applications.

[0028] (5) Solvent reusable: The microwave-assisted reaction time is short, effectively avoiding the decomposition of the deep eutectic solvent due to long-term high-temperature heating. After multiple cycle experiments, the deep eutectic solvent can still maintain a high lithium leaching rate after multiple uses, reducing production costs and improving resource utilization. Specific embodiments

[0029] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

[0030] Example 1

[0031] (1) Pretreatment: The spent NCA (LiNi 0.8 Co 0.15 Al 0.05 O2) cathode material was ball milled at a ball mill speed of 600 rpm for 4 hours and screened through a 160-mesh sieve to obtain the pretreated cathode powder.

[0032] (2) Preparation of leaching agent: Choline chloride (ChCl) and ethylene glycol (EG) were mixed at a molar ratio of 3:2 and heated and stirred in a 50 °C water bath for 10 minutes until dissolved evenly to form a clear and transparent deep eutectic solvent (DES).

[0033] (3) Microwave-assisted leaching process: 50 mg of the cathode powder obtained in step (1) was added to 5 mL of the DES in step (2), stirred evenly and then transferred to a sealed microwave reactor. The microwave temperature was set at 220 °C and the reaction time was 3 minutes. After the reaction, it was observed that the color of the leaching mixture changed to light brown.

[0034] (4) Separation and recovery of lithium: Cool the leaching mixture obtained in step (3) to room temperature, and then filter it with filter paper to obtain the leaching solution and the leaching residue. Slowly add 1M NaOH solution dropwise to the leaching solution while stirring until the pH value of the solution reaches 11. At this time, a small amount of precipitate is formed, and the precipitate is removed by filtration again. Transfer the filtrate to an evaporating dish and heat-concentrate it on a hot plate at 120 °C to reduce the solution volume by about 50%. Then place the evaporating dish in a water bath at 70 °C, add 3 mL of saturated Na2CO3 solution, and stir for 15 min. Finally, filter while it is hot, wash the white precipitate with boiling water several times, and then dry it in an oven at 80 °C for 12 h to obtain the recovered lithium carbonate compound.

[0035] In this example, the leaching rate of Li was detected to be 67.9% (500 μL of the leaching solution was diluted to 10 mL with a 2% (volume fraction) HNO3 solution to prepare an ICP analysis solution, and then the Li leaching rate was detected by ICP-OES). The purity of the recovered lithium carbonate compound reached over 98%, which was at a relatively high level.

[0036] Example 2

[0037] (1) Pretreatment: Ball-mill the waste NMC111 (LiNi 0.33 Co 0.33 Mn 0.33 O2) cathode material with a ball-milling speed of 500 rpm for 5 h, and screen it through a 120-mesh sieve to obtain the pretreated cathode powder.

[0038] (2) Preparation of leaching agent: Mix choline chloride (ChCl) and ethylene glycol (EG) in a molar ratio of 3:2, heat and stir in a water bath at 50 °C for 10 min until dissolved uniformly to form a clear and transparent deep eutectic solvent (DES).

[0039] (3) Microwave-assisted leaching process: Add 50 mg of the cathode powder obtained in step (1) to 5 mL of the DES obtained in step (2), stir evenly and transfer it to a sealed microwave reactor, set the microwave temperature to 220 °C, and the reaction time to 20 min. After the reaction, it was observed that the color of the leaching mixture changed to light brown.

[0040] (4) Separation and recovery of lithium: Cool the leaching mixture obtained in step (3) to room temperature, then filter it with filter paper to obtain the leachate and the leaching residue. Slowly add 1M NaOH solution dropwise to the leachate while stirring until the pH value of the solution reaches 10. At this time, a small amount of precipitate is formed, and filter again to remove the precipitate. Transfer the filtrate to an evaporating dish and heat and concentrate it on a hot plate at 120 °C to reduce the solution volume by about 50%. Then place the evaporating dish in a water bath at 70 °C, add 3 mL of saturated Na2CO3 solution, and stir for 15 min. Finally, filter while it is hot, wash the white precipitate with boiling water several times, and then dry it in an oven at 80 °C for 12 h to obtain the recovered lithium carbonate compound.

[0041] In this example, the leaching rate of Li was detected to be 90.4%, and the purity of the recovered lithium carbonate compound reached over 98%, which is a relatively high level.

[0042] Example 3

[0043] (1) Pretreatment: Ball-mill the waste LCO (LiCoO2) cathode material at a ball-milling speed of 700 rpm for 3 h, and screen it through a 180-mesh sieve to obtain the pretreated cathode powder.

[0044] (2) Preparation of leaching agent: Mix choline chloride (ChCl) and ethylene glycol (EG) at a molar ratio of 3:2, heat and stir in a water bath at 50 °C for 10 min until dissolved evenly to form a clear and transparent deep eutectic solvent (DES).

[0045] (3) Microwave-assisted leaching process: Add 50 mg of the cathode powder obtained in step (1) to 5 mL of the DES obtained in step (2), stir evenly and transfer it to a sealed microwave reactor. Set the microwave temperature to 220 °C and the reaction time to 15 min. After the reaction, it was observed that the color of the leaching mixture changed to light brown.

[0046] (4) Separation and recovery of lithium: Cool the leaching mixture obtained in step (3) to room temperature, then filter it with filter paper to obtain the leachate and the leaching residue. Slowly add 1M NaOH solution dropwise to the leachate while stirring until the pH value of the solution reaches 12. At this time, a small amount of precipitate is formed, and filter again to remove the precipitate. Transfer the filtrate to an evaporating dish and heat and concentrate it on a hot plate at 120 °C to reduce the solution volume by about 50%. Then place the evaporating dish in a water bath at 70 °C, add 3 mL of saturated Na2CO3 solution, and stir for 15 min. Finally, filter while it is hot, wash the white precipitate with boiling water several times, and then dry it in an oven at 80 °C for 12 h to obtain the recovered lithium carbonate compound.

[0047] In this example, the leaching rate of Li was detected to be 95.2%, and the purity of the recovered lithium carbonate compound reached over 98%, which is a relatively high level.

[0048] Example 4

[0049] (1) Pretreatment: The spent NCA (LiNi 0.8 Co 0.15 Al 0.05 O2) cathode material was ball-milled at a rotation speed of 600 rpm for 4 h and then screened through a 160-mesh sieve to obtain the pretreated cathode powder. Two samples of 50 mg each were taken out for experiments in the microwave group and the oil bath group respectively.

[0050] (2) Preparation of leaching agent: Choline chloride (ChCl) and ethylene glycol (EG) were mixed at a molar ratio of 3:2 and heated and stirred in a water bath at 50 °C for 10 min until dissolved uniformly to form a clear and transparent deep eutectic solvent (DES).

[0051] (3) Leaching in the microwave group: 50 mg of the cathode powder obtained in step (1) was added to 5 mL of the DES in step (2), stirred evenly and then transferred to a sealed microwave reactor. The microwave temperature was set at 220 °C to start the reaction. Samples were taken at 30 s, 1 min, 3 min, 10 min, 15 min, and 30 min respectively, and the mixture was filtered. 500 μL of the filtered solution was diluted to 10 mL with a HNO3 solution with a volume fraction of 2% to prepare an ICP analysis solution, and then the Li leaching rate was detected by ICP-OES.

[0052] (4) Leaching in the oil bath group: 50 mg of the cathode powder obtained in step (1) was added to 5 mL of the DES in step (2), stirred evenly in a sealed bottle, and then placed in an oil bath pot. The temperature was set at 220 °C, and continuous stirring was carried out under the heating state. Samples were taken at 30 min, 1 h, 3 h, 6 h, 12 h, and 24 h respectively, and the mixture was filtered. 500 μL of the filtered solution was diluted to 10 mL with a HNO3 solution with a volume fraction of 2% to prepare an ICP analysis solution, and then the Li leaching rate was detected by ICP-OES.

[0053] After detection, the Li leaching rates in the microwave group at 30 s, 1 min, 3 min, 10 min, 15 min, and 30 min were 49.6%, 56.1%, 67.9%, 84.8%, 87.7%, and 96.8% respectively; while no Li leaching was detected in the oil bath group at 30 min, and its leaching rates at 1 h, 2 h, 3 h, 6 h, 12 h, and 24 h were 2.1%, 43.5%, 76.2%, 82.1%, 87.0%, and 91.7% respectively. Even after 24 h of leaching reaction using oil bath heating, the Li leaching rate was lower than that of the microwave group at 30 min, and the leaching rate could reach more than 90%.

[0054] From the above results, it can be seen that the microwave-assisted leaching method adopted in the present invention can increase the Li leaching rate by hundreds of times. The efficiency within 30 seconds can exceed that of oil bath heating for 2 hours, which is significantly better than the traditional method.

[0055] Example 5

[0056] (1) Pretreatment: The spent NCA (LiNi 0.8 Co 0.15 Al 0.05 O2) cathode material was ball-milled at a rotation speed of 600 rpm for 4 hours and screened through a 160-mesh sieve to obtain the pretreated cathode powder.

[0057] (2) Preparation of leaching agent: Choline chloride (ChCl) and ethylene glycol (EG) were mixed at a molar ratio of 3:2 and heated and stirred in a 50°C water bath for 10 minutes until dissolved uniformly to form a clear and transparent deep eutectic solvent (DES).

[0058] (3) Microwave-assisted leaching process: 50 mg of the cathode powder obtained in step (1) was added to 5 mL of the DES in step (2). After stirring evenly, it was transferred to a sealed microwave reactor. The microwave temperature was set at 220°C and the reaction was started. Samples were taken at 30 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 15 minutes, and 30 minutes respectively, and the mixture was filtered. 500 μL of the filtered solution was diluted to 10 mL with a 2% (v / v) HNO3 solution to prepare the ICP analysis solution, and then the leaching rates of Li, Co, and Ni were detected by ICP-OES respectively.

[0059] (4) Comparison of leaching rates: The leaching rates measured in step (3) were summarized, analyzed, and the specific results are shown in Table 1 below.

[0060] Table 1. Comparison results of Li, Co, and Ni leaching rates at different reaction times

[0061]

[0062] From the results in Table 1, it can be seen that microwave-assisted leaching has significant selectivity for Li. At 3 minutes, the Li leaching rate (67.9%) is 11.7 times that of Co (5.8%) and 25.1 times that of Ni (2.7%). As the time prolongs, the Li leaching rate continues to increase, while the leaching rates of Co and Ni increase slowly, verifying the high selectivity advantage of the present invention.

[0063] Example 6

[0064] (1) Pretreatment: The spent NCA (LiNi 0.8 Co 0.15 Al 0.05(O2) The cathode material is ball-milled at a rotation speed of 600 rpm for 4 h and then screened through a 160-mesh sieve to obtain the pretreated cathode powder.

[0065] (2) Prepare the leaching agent: Mix choline chloride (ChCl) and ethylene glycol (EG) at a molar ratio of 3:2, heat and stir in a 50 °C water bath for 10 min until dissolved uniformly to form a clear and transparent deep eutectic solvent (DES).

[0066] (3) Set up experimental groups with different solid-liquid ratios: Take 50 mg, 100 mg, and 150 mg of the cathode powder obtained in step (1) respectively, add them to 5 mL of the DES in step (2), stir evenly and then transfer to a sealed microwave reactor. Set the microwave temperature to 220 °C and react for 10 minutes. After the reaction, filter the mixture. Dilute 500 μL of the filtered solution to 10 mL with a 2% (volume fraction) HNO3 solution to prepare the ICP analysis solution, and then detect the leaching rates of Li, Co, and Ni in the three groups of experiments by ICP-OES respectively.

[0067] (4) Compare the leaching rates: Summarize, analyze the leaching rates measured in step (3), and the specific results are shown in Table 2 below.

[0068] Table 2. Comparison results of leaching rates at different solid-liquid ratios

[0069]

[0070] As can be seen from the results in Table 2, under microwave assistance, when the solid-liquid ratio (R m / V) is increased from 10 g / L to 30 g / L, the Li leaching rate only decreases by 16% (84.7% → 68.7%), while the Co and Ni leaching rates decrease synchronously, indicating that high selectivity is still maintained at a high solid-liquid ratio.

[0071] In traditional oil bath heating, increasing R m / V will significantly reduce the leaching rate. However, due to the uniform heating and non-thermal effect of microwave radiation, the Li leaching rate can still reach 68.7% at 30 g / L, verifying the high solid-liquid ratio adaptability of the present invention.

[0072] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for selectively extracting lithium from waste lithium battery positive electrode materials using microwave-assisted DES, characterized in that: The steps include: (1) Pretreatment: ball milling and sieving the waste lithium-ion battery positive electrode material to obtain pretreated positive electrode powder; (2) preparing an extracting agent: mixing choline chloride and ethylene glycol, heating and stirring to dissolve evenly, to obtain a deep eutectic solvent; (3) Microwave-assisted leaching process: adding the cathode powder obtained in step (1) to the deep eutectic solvent of step (2), fully mixing, heating by microwave to 200-230° C., stirring and leaching, to obtain a leaching mixture; (4) Separation and recovery of lithium: Filter the leached mixed solution of step (3), add alkali solution to the filtrate to adjust the pH value to 10-12, filter to remove the precipitate, heat and concentrate the filtrate, then add Na2CO3 solution to precipitate, filter and take the solid phase, wash and dry to obtain lithium carbonate.

2. The method for selectively extracting lithium from waste lithium battery positive electrode materials by microwave-assisted DES according to claim 1, characterized in that: The waste lithium-ion battery positive electrode material in step (1) includes waste nickel-cobalt-aluminum ternary lithium battery positive electrode material, waste nickel-cobalt-manganese ternary lithium battery positive electrode material, and waste cobalt oxide lithium battery positive electrode material.

3. The method for selectively extracting lithium from waste lithium battery positive electrode materials by microwave-assisted DES according to claim 1, characterized in that: In step (1), the ball milling speed is 500-700 rpm, and the ball milling time is 3-5 hours; the sieved particle size is 120-180 meshes.

4. The method of microwave-assisted DES selective extraction of lithium from waste lithium battery positive electrode materials according to claim 1, characterized in that: The molar ratio of choline chloride and ethylene glycol mixed in step (2) is 3:

2.

5. The method for selectively extracting lithium from waste lithium battery positive electrode materials by microwave-assisted DES according to claim 1, characterized in that: The heating temperature in step (2) is 30-60°C.

6. The method of microwave-assisted DES selective extraction of lithium from waste lithium battery positive electrode materials according to claim 1, characterized in that: The solid-to-liquid ratio of the positive electrode powder added to DES in step (3) is 5 to 30 g / L.

7. The method of microwave-assisted DES selective extraction of lithium from waste lithium battery positive electrode materials according to claim 1, characterized in that: The stirring and leaching time in step (3) is 30 seconds to 30 minutes.

8. The method of microwave-assisted DES selective extraction of lithium from waste lithium battery positive electrode materials according to claim 1, characterized in that: The alkali solution in step (4) is 1M NaOH solution.

9. The method of microwave-assisted DES selective extraction of lithium from waste lithium battery positive electrode materials according to claim 1, characterized in that: The heating concentration in step (4) refers to heating and concentrating at 100-140° C. to 1 / 3-2 / 3 of the original volume.

10. The method for selectively extracting lithium from waste lithium battery positive electrode materials by microwave-assisted DES according to claim 1, characterized in that: The temperature of adding Na2CO3 solution for precipitation in step (4) is controlled to be 60-80°C.

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