Method for efficiently leaching valuable metal from waste lithium battery positive electrode material based on deep eutectic solvent

Abstract

The invention discloses a method for efficiently leaching valuable metals from a waste lithium battery positive electrode material based on a deep eutectic solvent, and belongs to the technical field of waste lithium battery recovery. The method comprises the following steps: leaching the positive electrode material separated from the waste lithium battery by adopting a deep eutectic solvent (EDSs, including ethylene glycol and tetracarboxylphenyl porphyrin compounds), filtering and separating, taking a leaching solution as a lithium-containing ethylene glycol solution, taking a solid as a nickel-cobalt-manganese porphyrin complex, and taking the nickel-cobalt-manganese porphyrin complex as a cathode material. According to the method, leaching of valuable metals such as nickel, cobalt, manganese and lithium in the positive electrode material and separation of nickel, cobalt, manganese and lithium can be efficiently achieved through one-step leaching, no harmful chemical reagent is used in the leaching process, the treatment cost of industrial wastewater is not increased, the EDSs solvent can be recycled, the environmental pressure is relieved, and the cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to a method for recycling anode materials of waste lithium batteries, and in particular to a method for efficiently leaching valuable metals from anode materials of waste lithium batteries based on a deep eutectic solvent, belonging to the technical field of recycling waste lithium batteries. Background Art

[0002] At present, LiCoO2 and NCM batteries occupy more than half of the LIBs market share. The resulting waste battery positive electrode active materials contain a large amount of valuable metals such as lithium, nickel, cobalt, and manganese, which is also the focus of current research on waste LIBs recycling. Compared with direct regeneration and pyrometallurgical recycling processes, wet recycling processes have lower energy consumption and higher recycling efficiency, but the leaching system is difficult to recycle and there is a large amount of wastewater discharge. Therefore, the use of green solvents to achieve efficient recycling of positive electrode active materials has become a research hotspot in this field. In order to reduce global greenhouse gas emissions, the rapid increase in electric vehicles is imperative. The explosive growth is generating a large number of waste lithium batteries, which contain a large number of valuable metals, such as lithium, nickel, cobalt, and manganese, and have high recycling value. Extracting nickel, cobalt, and manganese from waste lithium batteries can not only alleviate the shortage of resources, but also save costs, develop a circular economy and a conservation economy, and reduce damage to the natural ecological environment, thereby improving the new quality productivity of waste energy materials.

[0003] Deep eutectic solvents (DESs) are considered to be a new type of ionic liquid analogs. They are composed of two or three components through hydrogen bonding interactions. They are considered to be green solvents due to their low volatility, low cost, biodegradability and low toxicity. They have broad application prospects. Deep eutectic solvents show great potential in recovering valuable elements in waste lithium-ion batteries and can be produced on a large scale. At present, the main way to achieve high-valent cathode active materials such as LiCoO2, LiNi 1 / 2 Co 1 / 2 Efficient leaching of valuable elements such as O2 and NCM. The DESs leaching system in the prior art has a high leaching rate for metals in the positive electrode material, but due to its high viscosity, it is not conducive to the leaching and solid-liquid separation process. For example, the existing choline chloride: organic acid system has a high viscosity (>100cp), which hinders the mass transfer of dissolved substances during the leaching / separation process. The subsequent metal separation and recovery process is cumbersome and complicated, and it is difficult to obtain a pure product. For example, Chinese patents CN113930618A, CN115522057A, etc., disclose the use of DESs to leach battery positive electrode materials and obtain a higher leaching rate. However, the viscosity of DESs composed of choline chloride: oxalic acid or choline chloride: urea is very large, resulting in the leaching process being mainly controlled by the diffusion process, and the soluble coordination component Cl present in large quantities in the system -, resulting in the dissolved cobalt being mainly in the form of [CoCl4] 2- The leaching efficiency is reduced because of its high viscosity, which affects its filtration performance. In addition, the lithium and nickel, cobalt and manganese in the leaching system need to be further separated, and the operation process is complicated. Summary of the invention

[0004] In view of the technical problems existing in the prior art for recovering valuable metals from waste lithium batteries, the purpose of the present invention is to propose a method for efficiently leaching valuable metals from positive electrode materials of waste lithium batteries based on deep eutectic solvents. This method can efficiently leach valuable metals such as nickel, cobalt and manganese from waste lithium batteries while achieving the separation of lithium from nickel, cobalt and manganese. The deep eutectic solvent is easy to obtain and can be easily recovered and recycled during use, thereby truly achieving the goal of green leaching of non-ferrous metals.

[0005] In order to achieve the above technical objectives, the present invention provides a method for efficiently leaching valuable metals from positive electrode materials of waste lithium batteries based on deep eutectic solvents. The method is to separate positive electrode materials from waste lithium batteries. The positive electrode materials are leached with deep eutectic solvents and then filtered and separated. The leachate is an ethylene glycol solution containing lithium, and the solid is a porphyrin complex containing nickel, cobalt and manganese. The deep eutectic solvent includes ethylene glycol and tetracarboxyphenylporphyrin compounds.

[0006] The method for efficiently leaching valuable metals from waste lithium battery positive electrode materials based on deep eutectic solvent provided by the present invention lies in the use of a deep eutectic solvent mainly composed of ethylene glycol and tetracarboxyphenylporphyrin compounds as a leaching agent, wherein ethylene glycol can be used as a solvent medium and a reducing agent to promote the reduction leaching of valuable metal elements such as nickel, cobalt, manganese and lithium, while the tetracarboxyphenylporphyrin derivatives provide hydrogen protons and strong coordination ability, which is beneficial to promote the dissolution of nickel, cobalt and manganese ions. At the same time, ethylene glycol and the tetracarboxyphenylporphyrin derivatives are combined through hydrogen bonds to form a deep eutectic solvent, and ethylene glycol strengthens the coordination ability of the tetracarboxyphenylporphyrin derivatives, thereby achieving efficient leaching of valuable metals such as nickel, cobalt, manganese and lithium. More importantly, the deep eutectic solvent formed by ethylene glycol and tetracarboxyphenylporphyrin compounds has the characteristic of low viscosity. During the leaching process, it not only has high mass transfer efficiency, but also good subsequent solid-liquid separation effect. After leaching of the positive electrode material, the nickel, cobalt, and manganese ions in the leachate can form coordination complexes with tetracarboxyphenylporphyrin derivatives. The coordination complexes have low solubility in ethylene glycol and exist in solid form, while lithium ions are retained in the ethylene glycol solution. The separation of lithium and nickel, cobalt, and manganese can be achieved by simple filtration, which has obvious technical advantages over the existing DESs leaching system.

[0007] As a preferred solution, the deep eutectic solvent is composed of ethylene glycol and tetracarboxyphenylporphyrin compounds in a molar ratio of 5:1 to 15:1. Tetracarboxyphenylporphyrin compounds include tetracarboxyphenylporphyrin, or tetracarboxyphenylporphyrin derivatives. Tetracarboxyphenylporphyrin derivatives can be understood as a parent tetracarboxyphenylporphyrin, and the parent structure also contains other common small molecule substituents, such as methyl, methoxy, etc. on the benzene ring. The ratio of ethylene glycol to tetracarboxyphenylporphyrin compounds is mainly obtained based on the optimization of the coordination ability and viscosity of DESs. Too low a proportion of ethylene glycol will cause the viscosity of the system to be too high, and too low a proportion of tetracarboxyphenylporphyrin compounds will cause leaching and decreased coordination ability. Therefore, the ratio of the two needs to be controlled within an appropriate range.

[0008] As a preferred solution, the solid-liquid ratio of the cathode material to the deep eutectic solvent is 1 g:10-30 mL. In the presence of a sufficient amount of deep eutectic solvent, the valuable metals in the cathode material can be efficiently processed.

[0009] As a preferred solution, the leaching conditions are: temperature of 50-80°C and time of 2-5 hours. Under the preferred leaching conditions, a higher metal leaching rate can be obtained, while strengthening the coordination reaction between nickel, cobalt, manganese ions and tetracarboxylphenylporphyrin compounds.

[0010] As a preferred solution, the process of separating positive electrode materials from waste lithium batteries is: discharging the waste lithium batteries, disassembling the positive electrode sheets, and then soaking, drying, pyrolyzing and ball milling the positive electrode sheets to obtain positive electrode materials.

[0011] As a preferred solution, the pyrolysis condition is: heat treatment at 400-500° C. for 1-3 hours in an oxygen-containing atmosphere. The oxygen-containing atmosphere is a pure oxygen atmosphere, a mixed atmosphere of oxygen and air, or an air atmosphere. The pyrolysis of the organic binder can be promoted in an oxygen-containing atmosphere.

[0012] As a preferred solution, the ball milling conditions are: using water and / or ethanol as the medium, the ball milling speed is 50-100r / min, the ball material diameter is 3-10mm, the ball material ratio is 5:1-10:1, and the ball milling time is 1-2h. Ball milling in water or ethanol medium can promote the stripping of active substances. Under the preferred ball milling conditions, on the one hand, complete stripping can be ensured, and on the other hand, the recovery efficiency of the positive electrode material can be improved. If the diameter of the ball milling beads is too large, the aluminum foil will also be ground, the impurities in the recycled material will increase, and the subsequent processing will be more cumbersome.

[0013] The process of discharging the waste lithium battery of the present invention is to immerse the waste lithium battery in a 5% NaCl solution for discharge.

[0014] In the present invention, the process of soaking the positive electrode sheet adopts an organic solvent, such as ethanol, acetone and N,N'-dimethylformamide, etc., and the soaking time is 2 to 10 minutes.

[0015] The cathode material of the waste lithium battery of the present invention comprises at least one metal component of manganese, cobalt and nickel, such as LiMn2O4, LiCoO2, LiNi 1 / 2 Co 1 / 2 O2 and NCM, etc.

[0016] The lithium-containing ethylene glycol solution of the present invention is recycled by vacuum distillation and the like to recover ethylene glycol for reuse.

[0017] The nickel, cobalt, manganese and other ions coordinated with the tetracarboxyphenylporphyrin compound of the present invention can be recovered by elution.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0019] 1) The present invention uses a special deep eutectic solvent to leach nickel, cobalt and manganese from waste ternary lithium batteries, avoids the use of harmful chemical reagents, does not cause secondary pollution, and does not increase the cost of industrial wastewater treatment.

[0020] 2) The deep eutectic solvent of the present invention is composed of ethylene glycol and a tetracarboxyphenylporphyrin derivative, which can realize the efficient leaching of valuable metals such as Co, Ni, Mn, and Li in the ternary positive electrode material, as well as the separation and recovery of nickel, cobalt, manganese and lithium, thereby improving the utilization value of waste lithium batteries, avoiding the pollution of the environment caused by waste lithium batteries, and turning waste into treasure.

[0021] 3) The deep eutectic solvent of the present invention is easy to obtain and can be recycled, truly achieving the goal of green and efficient leaching of non-ferrous metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Tetracarboxyphenylporphyrin 1 H NMR spectra.

[0023] Figure 2 This is the XRD pattern of the positive electrode active material LiMn2O4.

[0024] Figure 3 This is the XRD pattern of the positive electrode active material NCM811.

[0025] Figure 4 FTIR spectra of regenerated ethylene glycol and pure ethylene glycol. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the claims of the present invention is not limited to the specific embodiments.

[0027] In the following specific embodiments:

[0028] The preparation method of tetracarboxyphenylporphyrin is divided into the following three steps: 1. Accurately weigh 3.00g of p-carboxybenzaldehyde and add it to a 250mL three-necked flask, and add 80mL of propionic acid, stir for 20min, and heat to 140°C; 2. Add 1.4mL of freshly distilled pyrrole (dissolved in 10mL of propionic acid solution in advance) to the flask dropwise within 30min, reflux at 140°C for 1h, and after the reaction is complete, add the reaction product to 100mL of ice formaldehyde solution; The solid was dissolved in 150 mL of hot water, anhydrous sodium carbonate was added to adjust the pH to 12, the product was filtered with a Buchner funnel, the pH was adjusted to 4-5 with 8% dilute hydrochloric acid, repeated 3 times, and the pH was finally adjusted to 6, extracted with 25 mL of n-butanol, allowed to stand for stratification, the n-butanol layer was collected, and distilled under reduced pressure to obtain solid tetracarboxyphenylporphyrin.

[0029] Tetracarboxyphenylporphyrin 1 H NMR characterization data are as follows: 1 H NMR (400M, DMSO-D6) δ13.36(s,4H), δ8.6~8.8(m,8H), δ8.2~8.4(m,16H), δ2.96(s,2H).

[0030] The specific steps for efficiently leaching nickel, cobalt and manganese from waste ternary lithium batteries are as follows:

[0031] (1) The waste battery is first immersed in a 5% NaCl solution for discharge, and then disassembled by an existing method to obtain a positive electrode sheet, and the positive electrode sheet is immersed in an organic solvent, dried, and heat-treated at 400-500° C. in an oxygen atmosphere for 1-3 hours; the immersion solvent includes at least one of ethanol, acetone and N,N-dimethylformamide, and the immersion time is about 2-10 minutes; the oxygen atmosphere includes a pure oxygen atmosphere, a mixed atmosphere of oxygen and air, or an air atmosphere.

[0032] (2) ball milling the heat-treated positive electrode sheet in water and / or ethanol as a stripping agent, with a ball diameter of 3 to 10 mm, a ball-to-material ratio of 5:1 to 10:1, a ball milling time of 1 to 2 h, and a ball milling speed of 50 to 100 r / min, to obtain the positive electrode active material in the discarded LIBs for use;

[0033] (3) placing the positive electrode active material in step (2) in a deep eutectic solvent for immersion, the leaching temperature is 50 to 80° C., the leaching time is 2 to 5 hours, and the solid-liquid ratio is 1:10 to 1:30 g / mL, wherein the deep eutectic solvent is a mixture of ethylene glycol and tetracarboxyphenylporphyrin, and the molar ratio of ethylene glycol to tetracarboxyphenylporphyrin is 5 to 15:1, washing and filtering, and obtaining a leaching liquid of ethylene glycol solution containing lithium, and a solid of nickel-cobalt-manganese porphyrin complex.

[0034] (4) Recovery of lithium: The lithium-containing ethylene glycol solution obtained in step (3) is separated and recovered from the ethylene glycol in the leachate by vacuum distillation, thereby simultaneously achieving regeneration of ethylene glycol and enrichment and recovery of lithium, and detecting the lithium content in the regenerated ethylene glycol; characterizing the FTIR spectrum of the regenerated ethylene glycol and comparing it with that of pure ethylene glycol.

[0035] (5) Quantitative analysis: The contents of nickel, cobalt and manganese in the leaching solution and the complex obtained in step (3) are determined by plasma emission spectrometry, and finally the leaching rate is calculated.

[0036] The method for obtaining the positive electrode active material in the following specific embodiments is:

[0037] (1) The used battery is first immersed in a 5% NaCl solution for discharge, and then disassembled by an existing method to obtain a positive electrode sheet, which is then immersed in an organic solvent, dried, and heat treated at 450° C. in an air atmosphere for 2 h; the immersion solvent is N,N-dimethylformamide, and the immersion time is about 8 minutes.

[0038] (2) The heat-treated positive electrode sheet was ball-milled in ethanol as a stripping agent, with a ball diameter of 5 mm, a ball-to-material ratio of 8:1, a ball-milling time of 1.5 h, and a ball-milling speed of 80 r / min, to obtain the positive electrode active material in the discarded LIBs for use.

[0039] Example 1

[0040] (1) Weigh 2.0 g of LiMn2O4 positive electrode material and soak it in a deep eutectic solvent, wherein the deep eutectic solvent is a mixture of ethylene glycol and tetracarboxyphenylporphyrin, wherein the molar ratio of ethylene glycol to tetracarboxyphenylporphyrin is 10:1, the leaching temperature is 50°C, the leaching time is 2 h, and the solid-liquid ratio is 1:10 g / mL. Wash and filter to obtain a leaching solution containing lithium in ethylene glycol solution and a solid containing manganese in porphyrin complex.

[0041] (2) Recovery of lithium: The lithium-containing ethylene glycol solution obtained above is used to separate and recover the ethylene glycol in the leachate by vacuum distillation, thereby achieving the regeneration of ethylene glycol and the enrichment and recovery of lithium. It was found through testing that the regenerated ethylene glycol does not contain lithium, indicating that the lithium recovery efficiency is close to 100%; the FTIR spectrum shows that the regenerated ethylene glycol is almost the same as the pure reagent and can be used to synthesize new DESs.

[0042] (3) The obtained leaching solution and complex were measured for the content of metallic manganese by inductively coupled plasma emission spectrometer, and then the leaching rate was calculated. The leaching rate of metallic manganese reached 98.0%.

[0043] Example 2

[0044] (1) Weigh 2.0 g of the positive electrode active material NCM811 and soak it in a deep eutectic solvent, wherein the deep eutectic solvent is a mixture of ethylene glycol and tetracarboxyphenylporphyrin, wherein the molar ratio of ethylene glycol to tetracarboxyphenylporphyrin is 10:1, the leaching temperature is 50°C, the leaching time is 3 h, the solid-liquid ratio is 1:10 g / mL, and the mixture is washed and filtered to obtain a leaching solution of lithium-containing ethylene glycol solution and a solid of nickel-cobalt-manganese porphyrin complex.

[0045] (2) Recovery of lithium: The lithium-containing ethylene glycol solution obtained above is used to separate and recover ethylene glycol in the leachate by vacuum distillation, thereby achieving the regeneration of ethylene glycol and the enrichment and recovery of lithium. It was found through testing that the regenerated ethylene glycol does not contain lithium, indicating that the lithium recovery efficiency is close to 100%; the regenerated ethylene glycol is almost the same as the pure reagent through FTIR spectroscopy, and can be used to synthesize new DESs.

[0046] (3) The contents of nickel, cobalt and manganese in the complexes were determined by inductively coupled plasma emission spectrometry, and then the leaching rates were calculated. The leaching rates of nickel, cobalt and manganese were 98.7%, 98.4% and 98.0%, respectively.

[0047] Example 3

[0048] (1) Weigh 2.0 g of the positive electrode active material NCM811 and soak it in a deep eutectic solvent, wherein the deep eutectic solvent is a mixture of ethylene glycol and tetracarboxyphenylporphyrin, wherein the molar ratio of ethylene glycol to tetracarboxyphenylporphyrin is 15:1, the leaching temperature is 50°C, the leaching time is 3 h, the solid-liquid ratio is 1:10 g / mL, and the mixture is washed and filtered to obtain a leaching solution of lithium-containing ethylene glycol solution and a solid of nickel-cobalt-manganese porphyrin complex.

[0049] (2) Recovery of lithium: The lithium-containing ethylene glycol solution obtained above is used to separate and recover ethylene glycol in the leachate by vacuum distillation, thereby achieving the regeneration of ethylene glycol and the enrichment and recovery of lithium. It was found through testing that the regenerated ethylene glycol does not contain lithium, indicating that the lithium recovery efficiency is close to 100%; the regenerated ethylene glycol is almost the same as the pure reagent through FTIR spectroscopy, and can be used to synthesize new DESs.

[0050] (3) The contents of metallic nickel, cobalt and manganese in the complex were determined by inductively coupled plasma emission spectrometry, and then the leaching rates were calculated. The leaching rates of metallic nickel, cobalt and manganese reached 99.0%, 98.6% and 98.1%, respectively.

Claims

1. A method for efficiently leaching valuable metals from waste lithium battery positive electrode materials based on deep eutectic solvents, characterized in that: A positive electrode material is separated from waste lithium batteries, wherein the positive electrode material is leached with a deep eutectic solvent and then filtered and separated, wherein the leached liquid is an ethylene glycol solution containing lithium, and the solid is a porphyrin complex containing nickel, cobalt and manganese; The deep eutectic solvent includes ethylene glycol and tetracarboxyphenylporphyrin compounds.

2. The method for efficiently leaching valuable metals from waste lithium battery positive electrode materials based on deep eutectic solvent according to claim 1, characterized in that: The deep eutectic solvent is composed of ethylene glycol and tetracarboxylphenylporphyrin compounds in a molar ratio of 5:1 to 15:

1.

3. The method for efficiently leaching valuable metals from waste lithium battery positive electrode materials based on deep eutectic solvent according to claim 1, characterized in that: The solid-to-liquid ratio of the positive electrode material to the deep eutectic solvent is 1 g:10 to 30 mL.

4. A method for efficiently leaching valuable metals from waste lithium battery positive electrode materials based on a deep eutectic solvent according to any one of claims 1 to 3, characterized in that: The leaching conditions are: temperature of 50-80°C, The time is 2 to 5 hours.

5. A method for efficiently leaching valuable metals from waste lithium battery positive electrode materials based on a deep eutectic solvent according to any one of claims 1 to 3, characterized in that: The process of separating positive electrode materials from waste lithium batteries is as follows: discharging the waste lithium batteries, disassembling the positive electrode sheets, and then soaking, drying, pyrolyzing and ball milling the positive electrode sheets to obtain positive electrode materials.

6. The method for efficiently leaching valuable metals from waste lithium battery positive electrode materials based on deep eutectic solvent according to claim 5, characterized in that: The pyrolysis conditions are: heat treatment at 400-500° C. for 1-3 hours in an oxygen-containing atmosphere.

7. The method for efficiently leaching valuable metals from waste lithium battery positive electrode materials based on deep eutectic solvent according to claim 5, characterized in that: The ball milling conditions are: using water and / or ethanol as the medium, The ball mill speed is 50-100 r / min, the ball material diameter is 3-10 mm, the ball material ratio is 5:1-10:1, and the ball milling time is 1-2 h.

Images