Deep eutectic solvent and method for recovering metal elements in retired lithium battery

Abstract

The invention provides a deep eutectic solvent and a method for recovering metal elements in a decommissioned lithium battery. The deep eutectic solvent is obtained by mixing a hydrogen bond donor and a hydrogen bond acceptor and reacting; the temperature in the reaction process is 70-100 DEG C, and the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1: (2-10); wherein. The hydrogen bond donor comprises at least one of imidazole, 1, 2, 4-triazole and 1-ethyl-3-methylimidazole, and the hydrogen bond receptor comprises at least one of propylene glycol, glycerol, n-butyl alcohol and triethylene glycol. The deep eutectic solvent has high safety, and when the deep eutectic solvent is used for recycling the positive electrode material of the decommissioned lithium battery, the leaching rate of the lithium element and the recycling rate of the cobalt element or the manganese element can be effectively increased, and the deep eutectic solvent has high recycling purity.

Description

Technical Field

[0001] The present invention relates to the technical field of battery recycling, in particular to a deep eutectic solvent and a method for recovering metal elements in retired lithium batteries. Background Art

[0002] Lithium-ion batteries, due to their high energy density, high safety, long service life, and environmental friendliness, are widely used in fields such as electric vehicles, aerospace, and portable electronic devices. However, the retirement cycle of lithium-ion batteries is approximately 4-8 years. With the large-scale use of lithium-ion batteries and the approaching retirement deadline, they will inevitably bring about huge environmental and economic crises. Therefore, how to effectively recover the metal elements in waste lithium-ion batteries has become imminent. Existing methods for extracting metal elements mainly include solvent extraction, which utilizes the special extraction properties of organic phases against metal elements to achieve the purpose of extracting metal elements.

[0003] Chinese patent application CN114645144A discloses a method for extracting lithium using a deep eutectic solvent. This method uses a β-diketone compound with an electron-withdrawing substituent as a hydrogen bond donor, and a compound containing P=O and / or N=O groups with electron-donating properties and capable of forming hydrogen bonds as a hydrogen bond acceptor. A lithium-containing solution is used as the aqueous extraction phase. The aqueous extraction phase is mixed with the deep eutectic solvent to extract a residual extract and a lithium-loaded deep eutectic solvent. The lithium-loaded deep eutectic solvent is then mixed with hydrochloric acid as a stripping agent for stripping, resulting in a lithium-rich solution and an empty deep eutectic solvent. However, this method can only recover lithium and cannot recover other metal elements in the cathode material, limiting its scope of application. Furthermore, the hydrochloric acid stripping agent used in the recovery process is corrosive, placing high demands on equipment and increasing recovery costs.

[0004] Chinese patent application CN113830842A discloses a method for recovering waste nickel-cobalt-manganese lithium-ion battery cathode materials. The method uses a deep eutectic solvent made by mixing choline chloride with p-toluenesulfonic acid, dodecylbenzenesulfonic acid, methanesulfonic acid, and aminosulfonic acid. The cathode material of the ternary nickel-cobalt-manganese lithium-ion battery is added to the deep eutectic solvent for reaction. After the reaction, the reaction filtrate is filtered to obtain a reaction filtrate. An alkaline solution is added to the reaction filtrate to recover the nickel-cobalt-manganese precursor. While metal ions can be recovered from waste lithium-ion battery cathode materials, the high viscosity of these choline chloride-based deep eutectic solvents hinders mass transfer of dissolved substances during leaching and separation, resulting in a low metal ion leaching rate. Furthermore, the strong acidity of the hydrogen bond donors p-toluenesulfonic acid (PKa = -1.3), dodecylbenzenesulfonic acid (PKa = 0.7), methanesulfonic acid (PKa = -0.6), and aminosulfonic acid (PKa = 1.2) also poses a risk of equipment corrosion, increasing production costs.

[0005] Therefore, how to maximize the recovery of metal elements in retired lithium battery positive electrode materials while ensuring equipment safety is an urgent problem to be solved. Summary of the Invention

[0006] In response to the above-mentioned defects, the present invention provides a deep eutectic solvent, which has high safety. The deep eutectic solvent is used to recover retired lithium battery positive electrode materials, which can effectively improve the lithium element leaching rate and the cobalt element or manganese element recovery rate, and has a high recovery purity.

[0007] The present invention provides a method for recovering metal elements in retired lithium batteries. By this method, a higher lithium element leaching rate and a cobalt element or manganese element recovery rate can be achieved, and a higher recovery purity can be achieved.

[0008] The present invention provides a deep eutectic solvent, which is obtained by a mixed reaction of a hydrogen bond donor and a hydrogen bond acceptor;

[0009] The temperature during the reaction is 70-100° C., and the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(2-10);

[0010] The hydrogen bond donor includes at least one of imidazole, 1,2,4-triazole, and 1-ethyl-3-methylimidazole, and the hydrogen bond acceptor includes at least one of propylene glycol, glycerol, n-butanol, and triethylene glycol.

[0011] Furthermore, the temperature during the reaction is 75-85°C.

[0012] Furthermore, the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(2-4).

[0013] Furthermore, the hydrogen bond donor is imidazole, and the hydrogen bond acceptor is propylene glycol;

[0014] The molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:3.

[0015] The present invention provides a method for recovering metal elements in retired lithium batteries, using any of the deep eutectic solvents described above to recover the metal elements in retired lithium batteries.

[0016] Further, the following steps are included:

[0017] The lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered is mixed with the deep eutectic solvent, and reacted at 80-150° C. for 8-12 hours to obtain a lithium-rich leachate and a cobalt-containing chelate or a manganese-containing chelate.

[0018] Furthermore, the cobalt-containing chelate is annealed at 400-600° C. to obtain cobalt trioxide, or the manganese-containing chelate is annealed at 400-600° C. to obtain manganese trimanganese tetraoxide.

[0019] Further, the lithium-rich leachate is treated, comprising the following steps: heating the lithium-rich leachate to 90-110° C., adjusting the pH value of the lithium-rich leachate to 8-10 with potassium hydroxide, and + )=1.2:1 molar ratio, sodium carbonate solution is added to obtain lithium carbonate precipitate.

[0020] Furthermore, the solid-to-liquid ratio of the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered to the deep eutectic solvent is 1:(20-100).

[0021] Furthermore, the solid-to-liquid ratio of the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered to the deep eutectic solvent is 1:(60-100).

[0022] The deep eutectic solvent of the present invention is obtained by reacting a specific hydrogen bond donor and a hydrogen bond acceptor at 70-100° C., and controlling the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor to be 1:(2-10). Therefore, when the deep eutectic solvent is finally obtained and the metal elements in the positive electrode material of waste lithium batteries are recovered, a high lithium element leaching rate and a cobalt element or manganese element recovery rate can be achieved, thereby realizing efficient recovery of lithium and cobalt or manganese elements and achieving a high recovery purity. In addition, no corrosive solvent is used in the recovery process, thereby ensuring the safety of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the process for recovering metal elements from retired lithium batteries in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0025] The first aspect of the present invention provides a deep eutectic solvent, which is obtained by a mixed reaction of a hydrogen bond donor and a hydrogen bond acceptor;

[0026] The temperature during the reaction is 70-100° C., and the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(2-10);

[0027] The hydrogen bond donor includes at least one of imidazole, 1,2,4-triazole, and 1-ethyl-3-methylimidazole, and the hydrogen bond acceptor includes at least one of propylene glycol, glycerol, n-butanol, and triethylene glycol.

[0028] It is understood that when the hydrogen bond donor or hydrogen bond acceptor includes two or more compounds, the present invention does not specifically limit the ratio between the compounds, and it is only necessary that the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor satisfies 1:(2-10).

[0029] The present invention does not specifically limit the sources of the hydrogen bond acceptors and hydrogen bond donors, and commercially available products or products prepared by conventional preparation methods well known to those skilled in the art may be used.

[0030] The deep eutectic solvent (DES) of the present invention is obtained by reacting a hydrogen bond donor including at least one of imidazole, 1,2,4-triazole, and 1-ethyl-3-methylimidazole and a hydrogen bond acceptor including at least one of propylene glycol, glycerol, n-butanol, and triethylene glycol at 70 to 100°C, and controlling the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor to be 1: (2 to 10), so that the deep eutectic solvent finally obtained can achieve a high lithium element leaching rate and cobalt element or manganese element recovery rate when recovering metal elements in waste lithium battery positive electrode materials, realize efficient recovery of lithium and cobalt or manganese elements, and ensure high recovery purity. Based on this phenomenon, the inventor analyzed the deep eutectic solvent and believed that it may be that: a specific hydrogen bond donor and hydrogen bond acceptor react at the aforementioned temperature and molar ratio to generate a complex, which can remove the Li in the positive electrode material layer structure. + Replaced into the solvent, and the Co in the layered structure of the cathode material 3+ or Mn 3.5+ Reduction to Co 2+ or Mn 2+ , and the complex can be combined with Co 2+ or Mn 2+ Coordination bonds are formed to generate cobalt-containing chelates or manganese-containing chelates, which are precipitated from the solvent, thereby achieving effective separation of lithium and cobalt or manganese, achieving a high lithium leaching rate and cobalt or manganese recovery rate, and ensuring a high recovery purity; at the same time, no corrosive solvents are used in the recovery process, which has a high safety for the equipment.

[0031] In one embodiment, the temperature during the reaction is 75-85° C. When the reaction temperature is within this range, the hydrogen bond donor and the hydrogen bond acceptor can react more fully, so that the generated complex can better interact with the positive electrode material, thereby further improving the separation effect, achieving a higher lithium leaching rate and cobalt or manganese recovery rate, and improving the recovery purity.

[0032] In one embodiment, the molar ratio of hydrogen bond donor to hydrogen bond acceptor is 1:(2-4). Within this range, the hydrogen bond donor and hydrogen bond acceptor can better cooperate to further promote the complex and Co 2+ or Mn 2+ Chelation between 2 + or Mn 2+ The leaching rate of lithium elements and the recovery rate of cobalt elements or manganese elements can be further improved.

[0033] In one specific embodiment, the hydrogen bond donor is imidazole, the hydrogen bond acceptor is propylene glycol, and the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:3. When the hydrogen bond donor is imidazole and the hydrogen bond acceptor is propylene glycol, and the molar ratio between the two is 1:3, the synergistic effect between the hydrogen bond donor and the hydrogen bond acceptor can be further enhanced, thereby achieving a higher lithium leaching rate and a higher cobalt or manganese recovery rate during the recovery of metal elements in the positive electrode material, further improving the recovery effect.

[0034] A second aspect of the present invention provides a method for preparing a deep eutectic solvent, comprising the following steps:

[0035] At 70-100° C., a hydrogen bond donor and a hydrogen bond acceptor are mixed and reacted in a molar ratio of 1:(2-10) until the solution becomes colorless and transparent, thereby obtaining a deep eutectic solvent;

[0036] The hydrogen bond donor includes at least one of imidazole, 1,2,4-triazole, and 1-ethyl-3-methylimidazole, and the hydrogen bond acceptor includes at least one of propylene glycol, glycerol, n-butanol, and triethylene glycol.

[0037] Furthermore, stirring is performed during the reaction process, preferably at a stirring speed of 300 to 500 r / min. Within this range, the reaction can be more complete and the recovery effect can be further improved.

[0038] The present invention does not impose any specific limitation on the reaction time. For example, the reaction time is 40 to 60 minutes.

[0039] The deep eutectic solvent prepared by this preparation method can achieve a high lithium element leaching rate and cobalt element or manganese element recovery rate in the recovery of metal elements in waste lithium battery positive electrode materials, and has a high recovery purity; at the same time, there is no corrosive solvent in the recovery process, which has high safety for equipment.

[0040] The third aspect of the present invention provides a method for recovering metal elements from retired lithium batteries, using the deep eutectic solvent of the first aspect to recover the metal elements from retired lithium batteries. Since the deep eutectic solvent is obtained by reacting a hydrogen bond donor including at least one of imidazole, 1,2,4-triazole, and 1-ethyl-3-methylimidazole and a hydrogen bond acceptor including at least one of propylene glycol, glycerol, n-butanol, and triethylene glycol at 70 to 100°C, and the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(2 to 10), the deep eutectic solvent can be used to recover metal elements from retired lithium batteries, thereby achieving a high lithium leaching rate and a cobalt or manganese recovery rate, with a high recovery purity, and mild reaction conditions during the recovery process, thereby providing high safety.

[0041] In a specific embodiment, the method comprises the following steps:

[0042] The lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered is mixed with a deep eutectic solvent, and reacted at 80-150° C. for 8-12 hours to obtain a lithium-rich leachate and a cobalt-containing chelate or a manganese-containing chelate.

[0043] Furthermore, after the reaction is completed, solid-liquid separation is performed to obtain lithium-rich leaching solution and solid phase, and the solid phase is washed and dried to obtain the cobalt-containing chelate or manganese-containing chelate.

[0044] Furthermore, in order to avoid the loss of hydrogen bond acceptors in the deep eutectic solvent at the reaction temperature, a condensation reflux device can be connected to the reaction.

[0045] The present invention does not specifically limit the method of solid-liquid separation. For example, separation can be performed by filtration or centrifugation.

[0046] The present invention does not specifically limit the washing method. It only needs to clean the lithium-rich leaching solution. For example, the solid phase is washed with deionized water and anhydrous ethanol respectively for 1 to 3 times.

[0047] The present invention does not impose any specific restrictions on the drying temperature and time. For example, the drying temperature is 70 to 100° C., and the drying time is 12 to 24 hours.

[0048] The present invention does not specifically limit the preparation method of the lithium cobalt oxide positive electrode material to be recycled. For example, it can be prepared by the following steps:

[0049] A lithium cobalt oxide battery or a lithium manganese oxide battery is placed in a sodium chloride solution until it is fully discharged, and a cathode sheet is obtained by disassembling the battery. The cathode sheet is cut and placed in a sodium hydroxide solution with a pH value greater than 13. After the aluminum foil is completely dissolved, a solid phase is obtained by solid-liquid separation. After the solid phase is washed, the solid phase is sintered at 400-600°C to remove the binder, thereby obtaining a lithium cobalt oxide positive electrode material to be recycled or a lithium manganese oxide positive electrode material to be recycled.

[0050] The present invention does not impose any specific limitation on the concentration of the sodium chloride solution. For example, the concentration of the sodium chloride solution is 0.1 to 1 M, and it is sufficient to fully discharge the lithium cobalt oxide battery.

[0051] The present invention does not impose any specific restrictions on the concentration of the sodium hydroxide solution. For example, the concentration of the sodium hydroxide solution is 0.5 to 2 M, and the pH value of the solution only needs to be greater than 13.

[0052] The limitation of the solid-liquid separation method in the present invention is consistent with the above and will not be repeated here.

[0053] The present invention does not specifically limit the washing method. For example, distilled water can be used for washing 1 to 3 times to clean the residual NaOH solution in the solid phase.

[0054] By recycling the metal elements in the positive electrode material through the above method, a higher lithium element leaching rate and cobalt element or manganese element recovery rate can be achieved, thereby improving the recovery effect.

[0055] In one embodiment, a cobalt-containing chelate is annealed at 400-600°C to obtain cobalt trioxide, or a manganese-containing chelate is annealed at 400-600°C to obtain manganese trioxide. The cobalt trioxide or manganese trioxide thus prepared can be used as a cobalt source or manganese source to prepare a new lithium cobalt oxide positive electrode material.

[0056] The present invention does not impose any specific limitation on the annealing time. For example, the annealing time is 3 to 5 hours.

[0057] In a specific embodiment, the lithium-rich leachate is treated, comprising the following steps: heating the lithium-rich leachate to 90-110° C., adjusting the pH value of the lithium-rich leachate to 8-10 with potassium hydroxide, and + )=1.2:1 molar ratio, sodium carbonate solution is added to obtain lithium carbonate precipitate. The pH of the lithium-rich leachate is adjusted with potassium hydroxide to neutralize unreacted hydrogen bond donors in the lithium-rich leachate, thereby maximizing the precipitation of lithium. Further treatment of the lithium-rich leachate by this method can recover the lithium as lithium carbonate.

[0058] It can be understood that the lithium concentration in the lithium-rich leachate can be obtained through ICP testing, and then the mass of lithium can be obtained according to the volume of the lithium-rich leachate, and then the molar amount of lithium can be obtained.

[0059] In a specific embodiment, the solid-liquid ratio of the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered to the deep eutectic solvent is 1: (20-100). The solid-liquid ratio in the present invention refers to the ratio of the mass of the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered to the volume of the deep eutectic solvent, wherein the mass unit is g and the volume unit is mL. Within this range, the deep eutectic solvent can better interact with the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide to be recovered, so that the reaction proceeds more fully, thereby further improving the leaching rate of lithium element and the recovery rate of cobalt element or manganese element.

[0060] In a specific embodiment, the solid-liquid ratio of the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered to the deep eutectic solvent is 1: (60-100). Within this range, the degree of reaction between the deep eutectic solvent and the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide to be recovered can be further improved, and more lithium and cobalt or manganese elements in the positive electrode material can be extracted, thereby achieving a higher recovery effect.

[0061] The deep eutectic solvent of the present invention is described in detail below through specific examples.

[0062] Example 1

[0063] 1) Preparation of the lithium cobalt oxide positive electrode material to be processed: Place the retired lithium cobalt oxide battery in a 500 mL beaker, add 0.2 M NaCl solution, and discharge until no bubbles are generated and the discharge is completed; in a glove box, use a screwdriver to remove the battery casing, then cut off the metal sheet connecting the battery, separate the positive and negative electrodes of the battery, collect the cathode sheet, and cut the cathode sheet into small pieces of 2 cm × 2 cm; move the cut cathode sheet to a beaker, add 1 M NaOH solution (pH = 14.9), and stir. When no bubbles escape, stop stirring; filter the reaction system with a vacuum pump to leave the solid phase; place the filter cake in an 80 ° C oven to dry to obtain the lithium cobalt oxide positive electrode material to be recycled, wherein the molar ratio of lithium element to cobalt element in the lithium cobalt oxide positive electrode material to be recycled is 0.795:1, wherein the mass content of lithium is 5.71%, and the mass content of cobalt is 61.11%;

[0064] (2) Synthesis of a deep eutectic solvent: imidazole and propylene glycol were mixed in a molar ratio of 1:3, the temperature was raised to 80°C, and stirring was started at a stirring speed of 400 r / min. After reacting at 80°C for 30 minutes, heating and stirring were stopped to obtain a deep eutectic solvent;

[0065] (3) Recovering metal elements from retired lithium batteries: Weigh 0.3 g of the lithium cobalt oxide cathode material to be recovered and place it in a 50 mL crystallizer, weigh 30 mL of deep eutectic solvent and add it to the crystallizer; raise the temperature to 100 ° C and start stirring at a stirring speed of 200 r / min. After reacting at 100 ° C for 12 hours, stop heating and stirring, perform solid-liquid separation, and obtain lithium-rich leachate and cobalt-containing chelate;

[0066] (4) The cobalt-containing chelate was washed twice with deionized water and anhydrous ethanol respectively, dried at 80°C for 14 hours, placed in a muffle furnace, and annealed at 500°C for 4 hours to obtain cobalt tetroxide. Figure 1 FIG. 1 is a schematic diagram of a process for recovering metal elements from retired lithium batteries in this embodiment.

[0067] Example 2

[0068] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (2), the hydrogen bond acceptor is adjusted to glycerol.

[0069] Example 3

[0070] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (2), the hydrogen bond acceptor is adjusted to n-butanol.

[0071] Example 4

[0072] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (2), the hydrogen bond acceptor is adjusted to triethylene glycol.

[0073] Example 5

[0074] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (2), the hydrogen bond donor is adjusted to 1,2,4-triazole and the hydrogen bond acceptor is adjusted to propylene glycol.

[0075] Example 6

[0076] The preparation method of the deep eutectic solvent in this example is basically the same as that in Example 5, except that in step (2), the hydrogen bond acceptor is adjusted to glycerol.

[0077] Example 7

[0078] The preparation method of the deep eutectic solvent in this example is basically the same as that in Example 5, except that in step (2), the hydrogen bond acceptor is adjusted to n-butanol.

[0079] Example 8

[0080] The preparation method of the deep eutectic solvent in this example is basically the same as that in Example 5, except that in step (2), the hydrogen bond acceptor is adjusted to triethylene glycol.

[0081] Example 9

[0082] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (2), the hydrogen bond donor is adjusted to 1-ethyl-3-methylimidazole and the hydrogen bond acceptor is adjusted to propylene glycol.

[0083] Example 10

[0084] The preparation method of the deep eutectic solvent in this example is basically the same as that in Example 9, except that in step (2), the hydrogen bond acceptor is adjusted to glycerol.

[0085] Example 11

[0086] The preparation method of the deep eutectic solvent in this example is basically the same as that in Example 9, except that in step (2), the hydrogen bond acceptor is adjusted to n-butanol.

[0087] Example 12

[0088] The preparation method of the deep eutectic solvent in this example is basically the same as that in Example 9, except that in step (2), the hydrogen bond acceptor is adjusted to triethylene glycol.

[0089] Example 13

[0090] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (2), the molar ratio of imidazole to propylene glycol is adjusted to 1:6, the reaction temperature is adjusted to 70°C, and the reaction time is adjusted to 60 min;

[0091] In step (3), the volume of the deep eutectic solvent is adjusted to 18 mL, the solid-liquid ratio of the recovered lithium cobalt oxide cathode material to the deep eutectic solvent becomes 1:60, the reaction temperature is adjusted to 80° C., and the reaction time is adjusted to 10 h;

[0092] In step (4), the annealing temperature is adjusted to 400°C.

[0093] Example 14

[0094] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (2), the molar ratio of imidazole to propylene glycol is adjusted to 1:10, the reaction temperature is adjusted to 100°C, and the reaction time is adjusted to 40 min;

[0095] In step (3), the volume of the deep eutectic solvent is adjusted to 6 mL, the solid-liquid ratio of the lithium cobalt oxide cathode material to be recovered and the deep eutectic solvent becomes 1:20, the reaction temperature is adjusted to 150° C., and the reaction time is adjusted to 8 h;

[0096] In step (4), the annealing temperature is adjusted to 600°C.

[0097] Example 15

[0098] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that, in step (1), the retired lithium cobalt oxide battery is replaced with a retired lithium manganese oxide battery, and the molar ratio of lithium element to manganese element in the finally obtained lithium manganese oxide positive electrode material to be recovered is 0.693:2, wherein the mass content of lithium is 2.69%, and the mass content of manganese is 61.49%.

[0099] Example 16

[0100] The preparation method of the deep eutectic solvent in this example is basically the same as that in Example 1, except that in step (2), the reaction temperature is adjusted to 90°C.

[0101] Example 17

[0102] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (2), the molar ratio of imidazole to propylene glycol is adjusted to 1:8.

[0103] Example 18

[0104] The preparation method of the deep eutectic solvent in this example is basically the same as that in Example 1, except that in step (3), the reaction temperature is adjusted to 75° C. and the reaction time is adjusted to 16 h.

[0105] Example 19

[0106] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (3), the volume of the deep eutectic solvent is adjusted to 3 mL, and the solid-liquid ratio of the lithium cobalt oxide positive electrode material to be recovered and the deep eutectic solvent becomes 1:10.

[0107] Example 20

[0108] The preparation method of the deep eutectic solvent in this embodiment is basically the same as that in Example 1, except that in step (3), the volume of the deep eutectic solvent is adjusted to 12 mL, and the solid-liquid ratio of the lithium manganese oxide positive electrode material to be recovered and the deep eutectic solvent becomes 1:40.

[0109] Comparative Example 1

[0110] (1) Choline chloride and p-toluenesulfonic acid were mixed in a flask at a molar ratio of 3:1 and stirred at 60°C for 2 h until the solid was gradually dissolved to form a colorless, transparent, viscous deep eutectic solvent;

[0111] (2) Weigh 0.3 g of the lithium cobalt oxide positive electrode material to be treated in Example 1 and 15 mL of the deep eutectic solvent in step (1) at a solid-liquid ratio of 1:50, and react in an oil bath at 90° C. for 1 h;

[0112] (3) The reaction system after the reaction is filtered to obtain a reaction filtrate, and the lithium-rich solution is diluted 5 times with distilled water and then subjected to an ICP test to obtain the leaching rates of lithium and cobalt.

[0113] Comparative Example 2

[0114] The method for recovering metal elements in retired lithium batteries in this comparative example includes the following steps: mixing 5 mol / L formic acid and a hydrogen peroxide solution with a volume fraction of 8 vol% in a crystallizer at a volume ratio of 3:1, adding the lithium cobalt oxide positive electrode material to be recovered in Example 1, raising the temperature to 80°C, and continuously stirring during this process at a stirring speed of 300 r / min, reacting at 80°C for 120 minutes, and immediately filtering by vacuum filtration to obtain a solid phase, washing the solid phase multiple times to make the pH value of the washing liquid close to 7.0, combining all the washing liquids with the filtrate to obtain a leachate, and diluting the lithium-rich solution 5 times with distilled water, and then performing an ICP test to obtain the leaching rate of lithium and cobalt;

[0115] The above leachate was subjected to precipitation reaction at room temperature, and the lithium-rich leachate obtained after precipitation and separation of cobalt was evaporated and concentrated until the concentration of lithium in the leachate reached a concentration of more than 20000 mg / L, and then the lithium was concentrated according to the ratio of n(Na2CO3): n(Li + )=1.2:1 molar ratio of sodium carbonate, precipitation reaction was carried out at 95 ° C for 1 hour, and then the precipitated product Li2CO3 was obtained by filtration.

[0116] Comparative Example 3

[0117] The method for recovering metal elements from retired lithium batteries in this comparative example is basically the same as that in Example 1, except that in step (2), the reaction temperature is adjusted to 60°C.

[0118] Comparative Example 4

[0119] The method for recovering metal elements from retired lithium batteries in this comparative example is basically the same as that in Example 1, except that in step (2), the molar ratio of imidazole to propylene glycol is adjusted to 1:1.

[0120] Comparative Example 5

[0121] The method for recovering metal elements from retired lithium batteries in this comparative example is basically the same as that in Example 1, except that, in step (2), sodium imidazole is used instead of imidazole, and ethylene glycol is used instead of propylene glycol.

[0122] Test example

[0123] 1. The concentrations of lithium and cobalt or manganese in the lithium-rich leachates prepared in the above embodiments and comparative examples were measured by inductively coupled plasma mass spectrometry (ICP), and the lithium leaching rate and the cobalt or manganese leaching rate were calculated by formula 1.

[0124]

[0125] In formula 1, η is the leaching rate of metal elements, C m is the concentration of metal elements in the lithium-rich leachate, in g / L; V f is the volume of lithium-rich leachate, in L; M c W is the mass of the lithium cobalt oxide positive electrode material to be recycled or the lithium manganese oxide positive electrode material to be recycled, in g; m It is the mass percentage of the metal element in the lithium cobalt oxide positive electrode material to be recycled or the lithium manganese oxide positive electrode material to be recycled, in wt%.

[0126] The calculation results are shown in Table 1.

[0127] 2. The recovery rates of cobalt and manganese in the above examples and comparative examples were measured, and the recovery rates of cobalt or manganese were calculated by formula 2.

[0128]

[0129] In formula 2, γ is the recovery rate of cobalt or manganese, M d is the mass of cobalt trioxide or manganese trioxide, in g; W n is the mass percentage of cobalt in cobalt oxide or manganese in manganese oxide, in wt%; M c is the mass of the lithium cobalt oxide positive electrode material to be recycled or the mass of the lithium manganese oxide positive electrode material to be recycled, in g; W m It is the mass percentage of the cobalt element in the lithium cobalt oxide positive electrode material to be recovered or the mass percentage of the manganese element in the lithium manganate positive electrode material to be recovered, in wt%.

[0130] The calculation results are shown in Table 1.

[0131] 3. The cobalt trioxide or manganese trioxide prepared in the above embodiments and comparative examples also contains unreacted lithium cobaltate or lithium manganate (the molar ratio of lithium element to cobalt element is 0.795:1, and the molar ratio of lithium element to manganese element is 0.693:2). The prepared cobalt trioxide or manganese trioxide is subjected to ICP testing to obtain the mass of lithium element therein (equivalent to the mass of lithium element in unreacted lithium cobaltate or lithium manganate). The mass of cobalt element in lithium cobaltate or the mass of manganese element in lithium manganate, as well as the mass of unreacted lithium cobaltate or lithium manganate, can be calculated based on the mass of lithium element, thereby obtaining the mass of pure cobalt trioxide or pure manganese trioxide. The purity of cobalt trioxide / manganese trioxide is calculated by formula 3, and the recovery rate of cobalt is calculated by formula 4.

[0132] Purity (%) = mass of pure cobalt oxide or manganese oxide / (mass of pure cobalt oxide or manganese oxide + mass of unreacted lithium cobaltate or lithium manganate) × 100% (Equation 3);

[0133] Recovery rate (%) = (mass of cobalt element in pure cobalt trioxide or mass of manganese element in pure manganese trioxide / mass of cobalt element in the lithium cobaltate positive electrode material to be recovered or mass of manganese element in the lithium manganate positive electrode material to be recovered) × 100% Formula 4.

[0134] The test and calculation results are shown in Table 2.

[0135] Table 1

[0136]

[0137]

[0138] Table 2

[0139]

[0140]

[0141] From Table 1 and Table 2, we can see that:

[0142] In the lithium-rich leachates of Examples 1 to 20, the lithium leaching rate is high and the cobalt or manganese leaching rate is low. The lithium leaching rate can reach up to 98.2%, and the corresponding cobalt leaching rate is as low as 1.2%. The lithium content in the cobalt tetraoxide or manganese tetraoxide separated from Examples 1 to 20 is low, and a high recovery rate can be achieved, with a maximum recovery rate of 96.52% and a corresponding purity of 98.52%. However, Comparative Examples 1 and 2 cannot achieve efficient separation of lithium and cobalt or manganese, and the separation and recovery effects in Comparative Examples 3 to 5 are also significantly lower than those in Examples 1 to 20. It can be seen that the deep eutectic solvent of the present invention can effectively improve the lithium leaching rate and the cobalt or manganese recovery rate while ensuring the safety of the equipment, and can achieve a high recovery purity.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A deep eutectic solvent, characterized in that The deep eutectic solvent is obtained by a mixed reaction of a hydrogen bond donor and a hydrogen bond acceptor; The temperature during the reaction is 70-100° C., and the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(2-10); The hydrogen bond donor includes at least one of imidazole, 1,2,4-triazole, and 1-ethyl-3-methylimidazole, and the hydrogen bond acceptor includes at least one of propylene glycol, glycerol, n-butanol, and triethylene glycol.

2. The deep eutectic solvent according to claim 1, characterized in that The temperature during the reaction is 75-85°C.

3. The deep eutectic solvent according to claim 1 or 2, characterized in that The molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:(2-4).

4. The deep eutectic solvent according to any one of claims 1 to 3, characterized in that The hydrogen bond donor is imidazole, and the hydrogen bond acceptor is propylene glycol; The molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:

3.

5. A method for recovering metal elements from retired lithium batteries, characterized in that: The deep eutectic solvent according to any one of claims 1 to 4 is used to recover metal elements in retired lithium batteries.

6. The method for recovering metal elements from retired lithium batteries according to claim 5, characterized in that: The following steps are involved: The lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered is mixed with the deep eutectic solvent, and reacted at 80-150° C. for 8-12 hours to obtain a lithium-rich leachate and a cobalt-containing chelate or a manganese-containing chelate.

7. The method for recovering metal elements from retired lithium batteries according to claim 6, characterized in that: The cobalt-containing chelate is annealed at 400-600° C. to obtain tricobalt tetraoxide, or the manganese-containing chelate is annealed at 400-600° C. to obtain trimanganese tetraoxide.

8. The method for recovering metal elements from retired lithium batteries according to claim 6 or 7, characterized in that: The lithium-rich leachate is treated, comprising the following steps: heating the lithium-rich leachate to 90-110° C., adjusting the pH value of the lithium-rich leachate to 8-10 with potassium hydroxide, and + )=1.2:1 molar ratio, sodium carbonate solution is added to obtain lithium carbonate precipitate.

9. The method for recovering metal elements from retired lithium batteries according to any one of claims 6 to 8, characterized in that: The solid-to-liquid ratio of the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered to the deep eutectic solvent is 1: (20-100).

10. The method for recovering metal elements from retired lithium batteries according to any one of claims 6 to 9, characterized in that: The solid-to-liquid ratio of the lithium cobalt oxide positive electrode material to be recovered or the lithium manganese oxide positive electrode material to be recovered to the deep eutectic solvent is 1: (60-100).

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