Method for recycling electrolyte of lithium-ion battery

Abstract

The present invention relates to the technical field of battery recycling and reuse, and more specifically, to a method for recycling and treating the electrolyte of a lithium-ion battery, comprising: cooling a fully discharged lithium-ion battery to below the freezing point of the electrolyte, then disassembling and crushing the battery to obtain a crushed solid containing the electrolyte; placing the crushed solid in a supercritical CO2 extraction apparatus under the protection of an inert gas, wherein an entrainer is added to the supercritical CO2 extraction apparatus; extracting the product; collecting the extracted product through a cryogenic device, using a lithiated molecular sieve to adsorb water from the extracted product, using a weakly basic anion exchange resin to adsorb HF from the extracted product, and using a lithiated molecular sieve to adsorb organic acids and alcohols from the extracted product. The lithiated molecular sieve, the weakly basic anion exchange resin, and the lithiated molecular sieve adsorb water, HF, organic acids, and alcohols from the extracted product, thereby obtaining a directly reusable electrolyte recovery product.

Description

Technical Field

[0001] The present invention relates to the technical field of battery recycling and reuse, and in particular to a method for recycling and processing electrolyte of lithium-ion batteries. Background Art

[0002] The cumulative growth of used lithium batteries is exponentially increasing, exponentially amplifying the potential health, environmental, and safety risks they pose. Recycling used lithium batteries can alleviate the environmental pollution and safety issues associated with their accumulation. In particular, the electrolytes in used lithium batteries contain toxic and hazardous substances, which are prone to side reactions in the natural environment, causing secondary pollution. Recycling used lithium battery electrolytes can effectively mitigate this secondary pollution problem.

[0003] The electrolyte recovery method of lithium batteries provided by related technologies mainly adopts organic solvent extraction process and supercritical CO2 extraction process. The organic solvent extraction process mainly introduces a solvent with similar solubility properties to the electrolyte, soaks the crushed battery, transfers the electrolyte into the solvent, and then separates the solvent from the electrolyte. The shortcomings of this method are high solvent cost, complex extraction product separation process, high energy consumption, and solvent residue in the extraction product. Compared with the organic solvent extraction process, the introduction of supercritical CO2 to extract the battery electrolyte can avoid problems such as solvent residue. However, the polarity of supercritical CO2 is weak, and the mutual solubility effect between supercritical CO2 and the electrolyte needs to be improved. The electrolyte recovery technology is difficult, and it is difficult to obtain electrolyte recovery products that can be directly reused. Summary of the Invention

[0004] The object of the present invention is to provide a method for recycling the electrolyte of a lithium ion battery, which can obtain a directly reusable electrolyte recovery product.

[0005] The present invention is achieved in that:

[0006] The present invention provides a method for recycling and treating the electrolyte of a lithium-ion battery, comprising:

[0007] S1: Cooling the fully discharged waste lithium-ion batteries to below the freezing point of the electrolyte, then disassembling and crushing them to obtain a crushed solid containing the electrolyte;

[0008] S2: placing the crushed solid in a supercritical CO2 extraction apparatus under the protection of an inert gas, and adding an entrainer into the supercritical CO2 extraction apparatus;

[0009] S3: extraction;

[0010] S4: The extracted product is collected by a low temperature device and used Type lithiated molecular sieve absorbs water from the extraction product, weakly basic anion exchange resin absorbs HF from the extraction product, and The organic acids and alcohols in the extracted products were adsorbed by the lithiated molecular sieve.

[0011] In an alternative embodiment, LiCl ethanol solution was used to treat the lithiated molecular sieve Type molecular sieve lithiation treatment; and / or,

[0012] LiCl ethanol solution was used to treat the lithiated molecular sieve It is prepared by lithiation treatment of type molecular sieve.

[0013] In an optional embodiment, the concentration of the LiCl ethanol solution is 1.8-2.2 mol / L; and the number of lithiation treatments is 5-10 times.

[0014] In an alternative embodiment, the entrainer comprises cyclic carbonates.

[0015] In an alternative embodiment, the entrainer further comprises N,N-dimethylformamide.

[0016] In an optional embodiment, the mass ratio of cyclic carbonates to N,N-dimethylformamide is 3-4:1.

[0017] In an alternative embodiment, the extraction includes static extraction and dynamic extraction.

[0018] In an alternative embodiment, at the start of dynamic extraction, the entrainer addition rate is 8-10% of the CO2 rate.

[0019] In an optional embodiment, the static extraction time is 18-22 minutes, and the dynamic extraction time is 35-55 minutes.

[0020] In an optional embodiment, the extraction pressure is 21-35 MPa and the temperature is 40-55°C.

[0021] The present invention has the following beneficial effects:

[0022] The embodiment of the present invention provides a method for recycling the electrolyte of a lithium ion battery, after supercritical CO2 extraction, using Type lithiated molecular sieve absorbs water from the extraction product, weakly basic anion exchange resin absorbs HF from the extraction product, and Type lithiated molecular sieve adsorbs organic acids and alcohols in the extraction product; thus, by Type lithiated molecular sieve, weakly basic anion exchange resin, and The lithiated molecular sieve adsorbs water, HF, organic acid and alcohol in the extraction product to obtain an electrolyte recovery product that can be directly reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 The graph is a relationship between the extraction efficiency of the electrolyte with and without the addition of the cyclic carbonate entrainer in the present invention;

[0025] Figure 2 The graph is a relationship between different mass ratios of the cyclic carbonate and N,N-dimethylformamide mixed entrainer and the electrolyte extraction efficiency in the present invention;

[0026] Figure 3 The figure is a relationship curve diagram of different types of entrainers and entrainer dosages and electrolyte extraction efficiency in the present invention. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0028] The present invention provides a method for recycling the electrolyte of a lithium ion battery, which can be used to recycle the electrolyte of waste lithium ion batteries, comprising:

[0029] S1: Cooling the fully discharged waste lithium-ion batteries to below the freezing point of the electrolyte, then disassembling and crushing them to obtain a crushed solid containing the electrolyte;

[0030] S2: placing the crushed solid in a supercritical CO2 extraction apparatus under the protection of an inert gas, and adding an entrainer into the supercritical CO2 extraction apparatus;

[0031] S3: extraction;

[0032] S4: The extracted product is collected by a low temperature device and used The lithium molecular sieve is used to absorb the water in the extraction product, and the weakly basic anion exchange resin (weakly basic anion exchange membrane) is used to absorb the HF in the extraction product. The organic acids and alcohols in the extracted products were adsorbed by the lithiated molecular sieve.

[0033] pass Type lithiated molecular sieve, weakly basic anion exchange resin, and The lithiated molecular sieve adsorbs water, HF, organic acid and alcohol in the extraction product to obtain an electrolyte recovery product that can be directly reused.

[0034] Because used lithium-ion batteries with residual power have undergone multiple cycles, the probability of internal defects increases. In this state, if they encounter mechanical collisions or special conditions or environments such as temperature, humidity, and poor contact, they may instantly discharge and generate a large amount of current, causing spontaneous combustion or explosion. In order to minimize the occurrence of these hazards and accidents, in step S1, the used lithium-ion batteries need to be fully discharged before starting subsequent processes. For example, the used lithium-ion batteries can be placed in a 0.8 mol / L MnSO4 electrolyte at a temperature of 80°C and a pH of 2.78 for 8 hours. When the residual voltage drops to 0.54V, the lithium battery discharge reaches its optimal state, meeting green and efficient discharge conditions. For lithium-ion battery packs used in electric vehicles, due to the large residual capacity, it is more appropriate to use a charger and discharger to collect the residual power. After the residual voltage is detected to be within a safe range, the subsequent disassembly or crushing process can be started.

[0035] In some embodiments, the disassembly of waste lithium-ion batteries is performed in a liquid nitrogen environment at -200°C, which can serve as a safety protection.

[0036] The inventors have found that due to limitations of process conditions and equipment requirements, after the solubility of supercritical CO2 fluid reaches a certain upper limit, it is difficult to further increase the extraction effect by simply changing the process conditions; therefore, the present invention improves the extraction effect and efficiency by adding a specific entrainer.

[0037] In some embodiments, the entrainer includes a cyclic carbonate, such as ethylene carbonate, propylene carbonate, or butylene carbonate. Cyclic carbonates are commonly used organic solvents in electrolytes and are highly polar, eliminating the need for residual solvents. Furthermore, cyclic carbonate entrainers improve the extraction efficiency of LiPF6 without accelerating its decomposition.

[0038] Furthermore, the entrainer also includes N,N-dimethylformamide, that is, in other embodiments, the entrainer is a mixture of cyclic carbonates and N,N-dimethylformamide, and the mass ratio of cyclic carbonates to N,N-dimethylformamide is 3-4:1, for example: 3:1, 4:1, etc.

[0039] N,N-dimethylformamide is also a commonly used organic solvent in electrolytes. It is a highly polar solvent and does not require residual problems. That is, the entrainers of the present invention are all reagents that are easily separated from the extract. If the entrainer remains, an additional treatment process for separating the entrainer is required after the use of the entrainer and after the extraction. If the entrainer remains in the extract and is not removed or is difficult to remove, then the supercritical fluid extraction loses its clean and environmentally friendly advantages.

[0040] The inventors determined through gas chromatography analysis that neither cyclic carbonates nor N,N-dimethylformamide, two entraining agents, destroyed the chemical properties of the electrolyte. Thus, the electrolyte recovery method of the present invention does not decompose the organic solvent components of the electrolyte or generate new substances, and can extract the components in the electrolyte relatively completely.

[0041] A mixed entrainer of cyclic carbonates and N,N-dimethylformamide is used, wherein the N,N-dimethylformamide entrainer is used to synergistically enhance the extraction efficiency. The extraction efficiency is optimal when the mass ratio of the two is 3-4:1.

[0042] The inventors discovered that CO₂ has relatively weak polarity, allowing for high extraction efficiency of less polar lipophilic substances in lithium-ion battery electrolytes in pure supercritical CO₂. However, the extraction efficiency of more polar compounds or electrolyte lithium salts is less than ideal. While the extraction efficiency of polar components can be improved by adjusting the pressure and temperature of the supercritical CO₂ during the extraction process, practical application is constrained by various factors. Therefore, a mixed entrainer of cyclic carbonates and N,N-dimethylformamide was employed to reduce the dissolution pressure of polar solutes, effectively increasing their solubility and significantly improving the extraction efficiency of polar substances.

[0043] On the other hand, the present invention utilizes N,N-dimethylformamide entrainer, which has a greater polarity than cyclic carbonate entrainers and a lower viscosity than cyclic carbonate entrainers, which is more conducive to the diffusion of the two entrainers in the electrolyte adsorbent, increases the contact between the two entrainers and the electrolyte, and also increases the dissolution of the electrolyte.

[0044] It can be seen that when a compound N,N-dimethylformamide entrainer is added to cyclic carbonates, the synergistic use of the two entrainers enhances the extraction efficiency under the combined effect of multiple factors, and the extraction effect is much greater than that of using a single entrainer.

[0045] In some embodiments, in step S3, supercritical CO2 and an entrainer are co-extracted at a pressure of 21-35 MPa, for example, 21 MPa, 25 MPa, 27 MPa, 30 MPa, 35 MPa, etc., and a temperature of 40-55°C, for example, 40°C, 45°C, 50°C, 55°C, etc. to separate the electrolyte from the electrolyte and obtain an extraction product.

[0046] Furthermore, the extraction includes static extraction and dynamic extraction; optionally, the time of static extraction is 18-22 minutes, for example: 18 minutes, 20 minutes, 22 minutes, etc., and the time of dynamic extraction is 35-55 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, etc.

[0047] Combining static extraction and dynamic extraction methods, first using static extraction and then using dynamic extraction after the solute is fully dissolved, can reduce the residual solute in the sample matrix and improve the extraction efficiency.

[0048] Optionally, an entrainer is added to the supercritical CO2 extraction apparatus in advance at the start of extraction. The amount of entrainer can be adjusted to a ratio corresponding to the solvent in the extraction kettle, such as 10% of the kettle solvent. When dynamic extraction begins, the amount of entrainer in the supercritical CO2 extraction apparatus is maintained at 8-10%, i.e., the entrainer addition rate is 8-10% of the CO2 flow rate, for example, 8%, 9%, 10%, etc.

[0049] In some embodiments, LiCl ethanol solution was used to treat the lithiated molecular sieve Prepared by lithiation treatment of type molecular sieve; LiCl ethanol solution was used to treat the lithiated molecular sieve It is prepared by lithiation treatment of type molecular sieve.

[0050] Furthermore, the concentration of the LiCl ethanol solution is 1.8-2.2 mol / L, for example, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, etc.; the number of lithiation treatments is 5-10 times, for example, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times.

[0051] It should be noted that Type molecular sieve and The molecular sieve is soaked in LiCl ethanol solution for about 36 hours, vacuum dried, and repeated 5-10 times to obtain Type lithiated molecular sieves and Type lithiated molecular sieve.

[0052] The present invention is described in further detail below with reference to the examples.

[0053] Example 1

[0054] S1: Fully discharge the waste lithium-ion battery, then cool the waste lithium-ion battery to below the freezing point of the electrolyte, and then dismantle and crush the waste lithium-ion battery to obtain a crushed solid containing the electrolyte.

[0055] S2: Adding cyclic carbonate entrainer to a supercritical CO2 extraction apparatus. Place the pulverized solid from step S1 in a supercritical CO2 extraction apparatus under the protection of an inert gas.

[0056] S3: performing a co-extraction with supercritical CO2 and an entrainer at a pressure of 21 MPa and a temperature of 40°C to separate the electrolyte in the electrolyte and obtain an extraction product. The extraction time is 20 minutes for static extraction and 55 minutes for dynamic extraction.

[0057] When the dynamic extraction starts, the amount of the cyclic carbonate entrainer in the supercritical CO2 extraction instrument is maintained at 8%, and the addition flow rate of the cyclic carbonate entrainer is 8% of the CO2 flow rate.

[0058] S4: The extraction product in step S3 is collected by a cryogenic device and used Type lithiated molecular sieve absorbs water from the extraction product, weakly basic anion exchange resin absorbs HF from the extraction product, and The organic acid and alcohol in the extraction product are adsorbed by the lithiated molecular sieve to obtain a reusable electrolyte recovery product.

[0059] Example 2

[0060] S1: Fully discharge the waste lithium-ion battery, then cool the waste lithium-ion battery to below the freezing point of the electrolyte, and then dismantle and crush the waste lithium-ion battery to obtain a crushed solid containing the electrolyte.

[0061] S2: Add a mixed entrainer of cyclic carbonates and N,N-dimethylformamide to a supercritical CO2 extraction apparatus, wherein the mass ratio of cyclic carbonates to N,N-dimethylformamide is 4:1. Under the protection of an inert gas, place the pulverized solid from step S1 in the supercritical CO2 extraction apparatus.

[0062] S3: performing a co-extraction with supercritical CO2 and an entrainer at a pressure of 21 MPa and a temperature of 40°C to separate the electrolyte in the electrolyte and obtain an extraction product. The extraction time is 20 minutes for static extraction and 55 minutes for dynamic extraction.

[0063] When the dynamic extraction starts, the amount of the two entrainer mixture in the supercritical CO2 extraction instrument is maintained at 8%, and the addition flow rate of the two entrainer mixture is 8% of the CO2 flow rate.

[0064] S4: The extraction product in step S3 is collected by a cryogenic device and used Type lithiated molecular sieve absorbs water from the extraction product, weakly basic anion exchange resin absorbs HF from the extraction product, and The organic acid and alcohol in the extraction product are adsorbed by the lithiated molecular sieve to obtain a reusable electrolyte recovery product.

[0065] Example 3

[0066] S1: Fully discharge the waste lithium-ion battery, then cool the waste lithium-ion battery to below the freezing point of the electrolyte, and then dismantle and crush the waste lithium-ion battery to obtain a crushed solid containing the electrolyte.

[0067] S2: Add a mixed entrainer of cyclic carbonates and N,N-dimethylformamide to a supercritical CO2 extraction apparatus, wherein the mass ratio of cyclic carbonates to N,N-dimethylformamide is 4:1. Under the protection of an inert gas, place the pulverized solid from step S1 in the supercritical CO2 extraction apparatus.

[0068] S3: performing a co-extraction with supercritical CO2 and an entrainer at a pressure of 35 MPa and a temperature of 55° C. to separate the electrolyte in the electrolyte and obtain an extraction product. The extraction time is 20 minutes for static extraction and 35 minutes for dynamic extraction.

[0069] When the dynamic extraction starts, the amount of the two entrainer mixture in the supercritical CO2 extraction instrument is maintained at 8%, and the addition flow rate of the two entrainer mixture is 8% of the CO2 flow rate.

[0070] S4: The extraction product in step S3 is collected by a cryogenic device and used Type lithiated molecular sieve absorbs water from the extraction product, weakly basic anion exchange resin absorbs HF from the extraction product, and The organic acid and alcohol in the extraction product are adsorbed by the lithiated molecular sieve to obtain a reusable electrolyte recovery product.

[0071] Comparative Example 1

[0072] Compared with Example 1, in Comparative Example 1, no entrainer was added in step S2, and the rest of the process was the same as in Example 1.

[0073] Comparative Example 2

[0074] Comparative Example 2 Compared with Example 2, in step S2, the mass ratio of cyclic carbonates to N,N-dimethylformamide is 1:1, and the rest of the process is referred to Example 2.

[0075] Comparative Example 3

[0076] Comparative Example 3 Compared with Example 2, at the beginning of dynamic extraction, the addition flow rate of the two entrainer mixture is 4% of the CO2 flow rate, and the rest of the process is based on Example 2.

[0077] Comparative Example 4

[0078] Comparative Example 4 Compared with Example 2, at the beginning of dynamic extraction, the addition flow rate of the two entrainer mixture is 6% of the CO2 flow rate, and the rest of the process is based on Example 2.

[0079] Comparative Example 5

[0080] Compared with Example 2, in Comparative Example 5, acetone is used as the entrainer in step S2, and the rest of the process is the same as that of Example 2.

[0081] Comparative Example 6

[0082] Comparative Example 6 Compared with Example 2, in step S4, the Type molecular sieve and The extraction product in step S3 is adsorbed by a molecular sieve, and the rest of the process is referred to Example 2.

[0083] 1. Based on the comparative experiment of Example 1 and Comparative Example 1, under the optimized process conditions (pressure of 21 MPa, temperature of 40°C, extraction time of static extraction for 20 min and dynamic extraction for 55 min), the extraction conditions of entrainer addition of 0-8%, the relationship curve between the extraction efficiency of electrolyte without entrainer and cyclic carbonate entrainer is as follows: Figure 1 shown.

[0084] Depend on Figure 1 As can be seen, there is a significant difference in extraction efficiency between the electrolyte without entrainer and the electrolyte with cyclic carbonate entrainer. The electrolyte extraction efficiency of the electrolyte without entrainer (i.e., the entrainer addition amount is 0%) is only 66.05%. Within the range of 0-8% of the cyclic carbonate entrainer dosage, the electrolyte extraction efficiency increases with the increase in the amount of entrainer. When the entrainer dosage reaches 8% (Example 1), the electrolyte extraction efficiency of the electrolyte with the addition of cyclic carbonate entrainer is 88.87%.

[0085] 2. Based on the comparative experiment of Example 2 and Comparative Example 2, under the optimized process conditions (pressure of 21 MPa, temperature of 40°C, extraction time of static extraction for 20 min, then dynamic extraction for 55 min, entrainer dosage of 8%), the relationship curve between the different mass ratios of the mixed entrainer and the electrolyte extraction efficiency is shown in the figure: Figure 2 shown.

[0086] Depend on Figure 2As can be seen, as the mass ratio of cyclic carbonate to N,N-dimethylformamide decreases, the electrolyte extraction efficiency increases accordingly. When the mass ratio of cyclic carbonate to N,N-dimethylformamide reaches 4:1 (Example 2), the electrolyte extraction efficiency is 96.24%. Therefore, the optimal ratio of 4:1 is selected.

[0087] 3. Based on comparative experiments conducted on Example 2 and Comparative Examples 3, 4 and 5, under the optimized process conditions (pressure of 21 MPa, temperature of 40°C, extraction time of static extraction for 20 min, then dynamic extraction for 55 min, mass ratio of cyclic carbonate to N,N-dimethylformamide of 4:1), the relationship curves of different types of entrainers and entrainer dosages with electrolyte extraction efficiency are shown in FIG. Figure 3 shown.

[0088] Depend on Figure 3 As can be seen, the extraction efficiency of the electrolyte increases with the increase in the amount of the mixed entrainer of cyclic carbonate and N,N-dimethylformamide, reaching 96.24% at 8% (Example 2). The growth rate of the electrolyte extraction efficiency then tends to slow down, so 8% is selected as the optimal entrainer amount.

[0089] Moreover, the electrolyte extraction efficiency of the mixed entrainer of cyclic carbonates and N,N-dimethylformamide of the present invention is much higher than that of using acetone.

[0090] 4. It can be seen from the above examples that the difference between Example 1 and Example 2 is that the entrainer in Example 1 only includes cyclic carbonates, while the entrainer in Example 2 is a mixture of cyclic carbonates and N,N-dimethylformamide; Figure 1 and Figure 3 It can be seen that the electrolyte extraction efficiency of Example 1 is 88.87%, and the electrolyte extraction efficiency of Example 2 is 96.24%. This shows that the cyclic carbonates and N,N-dimethylformamide work together to significantly improve the electrolyte extraction effect.

[0091] 5. In the electrolyte recovered by supercritical CO2, the decomposition of fluorine-containing lithium salts will lead to a high HF content. HF removal is also an important step in achieving electrolyte reuse. Since the influence of moisture in the supercritical CO2 extraction process cannot be completely eliminated (for example: moisture in the CO2, extraction kettle and extraction equipment pipelines), a certain amount of moisture will be introduced into the electrolyte during the extraction process. Although the hydrolysis process of the electrolyte lithium salt will consume a certain amount of water, the moisture content will still be too high.

[0092] Example 1 uses Type lithiated molecular sieve, The invention relates to a method for removing moisture and HF from the recovered electrolyte of waste lithium-ion batteries by using a lithiated molecular sieve and a weakly alkaline anion exchange resin; the water content can be reduced to below 20 ppm and the HF content to below 50 ppm. The electrolyte recovered in Example 1 was supplemented with components according to the formula of a commercial electrolyte to synthesize a recycled electrolyte. The physical and chemical properties of the recycled electrolyte were characterized. The results showed that the recycled electrolyte met the relevant index requirements for HF content, moisture content, ionic conductivity, lithium ion transference number, and electrochemical window.

[0093] However, the excessively high HF content in the electrolyte of Comparative Example 6 may cause internal corrosion of the battery, increase the internal resistance of the battery, and cause problems such as attenuation of the battery specific capacity and coulombic efficiency.

[0094] In summary, the recovery and treatment method of the electrolyte of the lithium-ion battery of the present invention optimizes the parameters of the supercritical CO2 extraction process of the electrolyte, controls the polarity of CO2 at a specific pressure and system temperature to improve the electrolyte extraction efficiency, and controls the physical properties of CO2 such as density and polarity through pressure and temperature, making CO2 more selective for solutes. The present invention also combines static extraction with dynamic extraction. Static extraction is conducive to the full dissolution of the solute, and then dynamic extraction is performed to reduce the residual solute in the matrix, thereby improving the extraction efficiency. The entire extraction time is short to reduce the loss of volatile components and easily decomposable components, and a cyclic carbonate entrainer is added to improve the extraction efficiency of the components. It can take into account the extraction rules of most major components and ensure that each component in the extraction product achieves a high recovery efficiency.

[0095] Under the specific system temperature and pressure conditions of the present invention, the addition of a cyclic carbonate entrainer to supercritical CO2 increases the fluid density, leading to increased electrolyte solubility. Furthermore, under specific process parameters, the cyclic carbonate and N,N-dimethylformamide entrainer synergistically enhance the electrolyte extraction effect without decomposing the organic solvent components of the electrolyte or generating new substances, significantly improving the electrolyte extraction efficiency.

[0096] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for recycling the electrolyte of a lithium-ion battery, characterized in that: include: S1: Cooling the fully discharged waste lithium-ion batteries to below the freezing point of the electrolyte, then disassembling and crushing them to obtain a crushed solid containing the electrolyte; S2: placing the pulverized solid in a supercritical CO2 extraction apparatus under the protection of an inert gas, wherein an entrainer is added to the supercritical CO2 extraction apparatus; S3: extraction; S4: The extracted product is collected by a low temperature device and used Type lithiated molecular sieve adsorbs water in the extraction product, weakly basic anion exchange resin adsorbs HF in the extraction product, and Type lithiated molecular sieve adsorbs organic acids and alcohols in the extraction product; wherein, described LiCl ethanol solution was used to treat the lithiated molecular sieve Prepared by lithiation treatment of type molecular sieve; The entrainer includes a mixture of cyclic carbonates and N,N-dimethylformamide, and the mass ratio of the cyclic carbonates to the N,N-dimethylformamide is 3-4:

1.

2. The method for recycling the electrolyte of a lithium-ion battery according to claim 1, wherein: described LiCl ethanol solution was used to treat the lithiated molecular sieve It is prepared by lithiation treatment of type molecular sieve.

3. The method for recycling the electrolyte of a lithium ion battery according to claim 2, wherein: The concentration of the LiCl ethanol solution is 1.8-2.2 mol / L; the number of lithiation treatments is 5-10 times.

4. The method for recycling the electrolyte of a lithium-ion battery according to any one of claims 1 to 3, characterized in that: The extraction includes static extraction and dynamic extraction.

5. The method for recycling the electrolyte of a lithium-ion battery according to claim 4, wherein: At the beginning of the dynamic extraction, the entrainer addition flow rate is 8-10% of the CO2 flow rate.

6. The method for recycling the electrolyte of a lithium-ion battery according to claim 4, wherein: The static extraction time is 18-22 minutes, and the dynamic extraction time is 35-55 minutes.

7. The method for recycling the electrolyte of a lithium-ion battery according to claim 4, wherein: The extraction pressure is 21-35 MPa and the temperature is 40-55°C.

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