Method for recycling and resource utilization of waste electrolyte and electrolyte

Abstract

The invention relates to a waste electrolyte recovery and resource utilization method and an electrolyte, and belongs to the technical field of electrolyte recovery, and the method comprises the following steps: step 1, carrying out cooling crystallization and extraction treatment on the waste electrolyte to realize separation of a lithium salt and a solvent; 2, washing and drying the separated lithium salt to obtain regenerated lithium salt; step 3, extracting the separated solvent to obtain a mixed ester solvent, placing the mixed ester solvent in a transparent sealing device of a carbon substrate template containing metal clusters, carrying out illumination catalytic decomposition on the mixed ester solvent by using a solar simulator according to specific light intensity and illumination time, and then carrying out separation and purification to obtain an alcohol solvent; step 4, carrying out synthesis reaction by taking an alcohol solvent as a raw material to prepare a carbonic ester solvent; and 5, mixing the regenerated lithium salt with the synthesized carbonic ester solvent according to a certain ratio, and compounding to obtain the reusable lithium ion battery electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolyte recovery, and in particular to a method for recycling and resourcefully utilizing waste electrolyte and an electrolyte. Background Art

[0002] Lithium-ion batteries are core components of modern electrochemical energy storage. Their large-scale application, coupled with the advent of a wave of retirement, is creating a huge demand for the disposal of used batteries. Electrolyte, as a core component of the battery, contains easily hydrolyzed organic solvents and high-concentration lithium salts. Improper handling will lead to the release of toxic fluorine-containing compounds, causing serious fluorine pollution and threatening the ecological environment and human health. It is particularly noteworthy that the lithium salts and solvents in the electrolyte themselves have considerable resource value. Through efficient recycling, not only can environmental risks be avoided, but also the closed-loop utilization of scarce resources can be achieved. However, the current recycling system is overly focused on the extraction of electrode metals and pays insufficient attention to the electrolyte components that account for 15-30% of the battery mass. This has resulted in a dilemma where resource waste and pollution risks coexist. Establishing targeted electrolyte recycling and resource utilization technology has become a key link in the full life cycle management of lithium batteries.

[0003] Existing electrolyte recovery technologies generally face efficiency bottlenecks and environmental challenges. Traditional high-temperature calcination, while simple, releases highly toxic gases like HF. Organic solvent extraction, while capable of partial recovery, suffers from high solvent consumption and low product purity, making its 20-35% recovery rate insufficient for industrialization. Supercritical CO2 extraction, while advantageous for preserving molecular structure, requires stringent operating conditions, resulting in significantly increased equipment investment and a cost-effectiveness imbalance for large-scale application. Further challenging issues arise from significant batch variability in electrolyte composition, with hundreds of formulation variations between manufacturers. Furthermore, residual extraction residues exceeding 40% due to adsorption on electrodes and diaphragms make precise component separation difficult with existing processes like vacuum distillation. Even more challenging, alternative methods like alkaline absorption, while simple to operate, generate secondary pollution, including fluoride-containing wastewater with F- concentrations reaching 500-800 mg / L, contradicting the concept of green recycling. This complex conflict between technical cost-effectiveness, environmental friendliness, and recovery efficiency urgently requires breakthrough innovations in new processes.

[0004] Electrolyte recovery is difficult to separate and purify due to its complex composition and the similar melting and boiling points of some components. Currently, most existing technologies focus on extracting metallic lithium from the electrolyte. However, these methods often leave a large amount of residual mixed organic solution, making it difficult to utilize in industrial applications. These solutions are generally treated as hazardous waste, increasing processing costs and wasting resources. Existing electrolyte separation technologies have difficulty in overcoming the problem of component mutual extraction. A typical example is Chinese patent CN201110427431.2, which uses high vacuum reduced pressure distillation to separate organic solvents and lithium hexafluorophosphate. However, experimental data show that under a vacuum of -0.095 MPa, the DMC / EMC binary system can only achieve a solvent removal rate of 63-68%, and the residual solvent causes the lithium salt purity to be less than 95%. Although the concentrated liquid regeneration method proposed in Chinese patent CN201810012129.2 can recover lithium hexafluorophosphate, it does not remove PF6- decomposition products such as LiF and HF, resulting in a 18.7% decrease in the conductivity of the regenerated electrolyte. Chinese patent CN201910746383.X achieves fluorine fixation through lime milk precipitation, but the generated CaF2 / Ca3(PO4)2 composite slag phase has a mixed crystal form, and its β-CaF2 accounts for less than or equal to 72%, making it difficult to meet the standards for fluorine chemical raw materials. Chinese patent CN202210601906.3 proposes a method for efficiently separating and recovering organic solvents and lithium from waste electrolytes. However, the organic solvent cannot be reused. Therefore, comprehensive recovery of the active components of lithium-ion battery electrolytes, while also removing as much as possible impurities that affect their performance, is crucial for resourceful electrolyte recycling. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for recycling and resource utilization of waste electrolyte and an electrolyte to solve the problems raised in the background technology.

[0006] In order to achieve the above-mentioned purpose of the invention, the present invention provides a method for recycling and resource utilization of waste electrolyte, wherein the electrolyte is electrolyte recovered from waste lithium-ion batteries and / or failed electrolyte in the electrolyte production process. The method for recycling and resource utilization of waste electrolyte and the electrolyte include the following steps:

[0007] Step 1: Cooling, crystallizing and extracting the waste electrolyte to separate the lithium salt from the solvent;

[0008] Step 2: Rinse and dry the separated lithium salt to obtain regenerated lithium salt;

[0009] Step 3: extracting the separated solvent to obtain a mixed ester solvent, placing the mixed ester solvent in a transparent sealed device on a carbon substrate template containing metal clusters, and photocatalytically decomposing the mixed ester solvent using a solar simulator at a specific light intensity and illumination time, followed by separation and purification to obtain an alcohol solvent;

[0010] Step 4: using an alcohol solvent as a raw material to carry out a synthesis reaction to prepare a carbonate solvent;

[0011] Step 5: Mix the regenerated lithium salt and the synthesized carbonate solvent in a certain proportion to obtain a reusable lithium-ion battery electrolyte.

[0012] Furthermore, in step 3, the carbon material in the carbon-based template containing metal clusters is one or more of graphite, graphite oxide, graphene, graphene oxide, hard carbon, and soft carbon materials, the metal clusters are metals with catalytically active transitions, and the area of the carbon-based template containing metal clusters satisfies a linear relationship with the volume of the waste electrolyte.

[0013] Furthermore, in step 3, the solar simulator sets the light intensity to satisfy a linear relationship with the volume of the electrolyte. Taking one sunlight intensity as a unit, the light intensity required for 1 mL of the waste electrolyte is 0.5-2 sunlight intensities.

[0014] Furthermore, in step 3, the illumination time and the volume of the waste electrolyte satisfy a linear relationship, and the illumination time required for 1 mL of the waste electrolyte is not less than 10 minutes and not more than 60 minutes.

[0015] Furthermore, the mixed ester solvent decomposition reaction satisfies the following equation:

[0016] EC(C3H4O3)→CO2+HOCH2CH2OH

[0017] DMC(C3H6O3)→CO2+2CH3OH

[0018] DEC(C5H 10 O3)→CO2+2C2H5OH

[0019] EMC(C4H8O3)→CO2+C2H5OH+CH3OH.

[0020] Furthermore, the synthesis reaction formula described in step 4 satisfies the following equation:

[0021] (NH2)2O+HOCH2CH2OH→EC(C3H4O3)

[0022] 2CH3OH+ClCOOCH3→DMC(C3H6O3)

[0023] EC(C3H4O3)+CH3OH→DMC(C3H6O3).

[0024] Another aspect of the present invention discloses an electrolyte prepared by the above method, wherein the lithium salt concentration in the electrolyte is 0.8-1.2M.

[0025] Furthermore, the moisture content and acidity of the electrolyte do not exceed 50 ppm.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention achieves the coordinated and efficient recovery of lithium salts, solvents and fluorine impurities in the electrolyte by coupling multi-stage physical separation and photocatalytic directional conversion technology.

[0028] In response to the problems of low solvent removal rate, residual impurities in the regenerated electrolyte and inability to reuse the solvent in the existing technology, the present invention innovatively proposes a solvent photolysis-resynthesis pathway based on a metal cluster catalytic system: a solar simulator is used to drive the decomposition of mixed ester solvents into alcohol intermediates, which are then regenerated into carbonate solvents with a purity greater than 99.2% through controlled synthesis, and the comprehensive solvent recovery rate is increased to more than 85%. At the same time, by adopting cooling crystallization and gradient extraction technology, the purity of lithium salt recovery exceeds 99.5%, and secondary pollution is effectively avoided through the directional conversion of fluorine impurities. Compared with traditional processes, the acidity and moisture content of the composite electrolyte of the present invention meet industrial standards, and energy consumption is reduced by more than 40%, realizing the closed-loop resource utilization of all components of the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A flow chart for recycling and reusing waste electrolyte from lithium-ion batteries provided for the implementation of the present invention.

[0030] Figure 2 This is the GC-MS retention time diagram of Example 1 of the present invention.

[0031] Figure 3 This is the mass spectrum of Example 1 of the present invention obtained by GC-MS at a retention time of 8.382 min. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments 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 accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the invention, not all of them. The embodiments of the present invention are described below in conjunction with the accompanying drawings.

[0033] On one hand, the present invention provides a method for recycling and resource utilization of waste electrolyte, wherein the electrolyte is electrolyte recovered from waste lithium-ion batteries and / or spent electrolyte in the electrolyte production process, and is characterized in that the method for recycling and resource utilization of waste electrolyte and the electrolyte include the following steps:

[0034] Step 1: Cooling, crystallizing and extracting the waste electrolyte to separate the lithium salt from the solvent;

[0035] Step 2: Rinse and dry the separated lithium salt to obtain regenerated lithium salt;

[0036] Step 3: extracting the separated solvent to obtain a mixed ester solvent, placing the mixed ester solvent in a transparent sealed device on a carbon substrate template containing metal clusters, and photocatalytically decomposing the mixed ester solvent using a solar simulator at a specific light intensity and illumination time, followed by separation and purification to obtain an alcohol solvent;

[0037] Step 4: using an alcohol solvent as a raw material to carry out a synthesis reaction to prepare a carbonate solvent;

[0038] Step 5: Mix the regenerated lithium salt and the synthesized carbonate solvent in a certain proportion to obtain a reusable lithium-ion battery electrolyte.

[0039] In some embodiments, the carbon material in the carbon-based template containing metal clusters in step 3 is one or more of graphite, graphite oxide, graphene, graphene oxide, hard carbon, and soft carbon materials, the metal clusters are metals with catalytically active transitions, and the area of the carbon-based template containing metal clusters satisfies a linear relationship with the volume of the waste electrolyte.

[0040] In some embodiments, the solar simulator in step 3 sets the light intensity to satisfy a linear relationship with the volume of the electrolyte. Taking one sunlight intensity as a unit, the light intensity required for 1 mL of the spent electrolyte is 0.5-2 sunlight intensities.

[0041] In some embodiments, the illumination time in step 3 satisfies a linear relationship with the volume of the waste electrolyte, and the illumination time required for 1 mL of the waste electrolyte is not less than 10 min and not more than 60 min.

[0042] In some embodiments, the mixed ester solvolysis reaction satisfies the following equation:

[0043] EC(C3H4O3)→CO2+HOCH2CH2OH

[0044] DMC(C3H6O3)→CO2+2CH3OH

[0045] DEC(C5H 10O3)→CO2+2C2H5OH

[0046] EMC(C4H8O3)→CO2+C2H5OH+CH3OH.

[0047] In some embodiments, the synthesis reaction in step 4 satisfies the following equation:

[0048] (NH2)2O+HOCH2CH2OH→EC(C3H4O3)

[0049] 2CH3OH+ClCOOCH3→DMC(C3H6O3)

[0050] EC(C3H4O3)+CH3OH→DMC(C3H6O3).

[0051] Another aspect of the present invention discloses an electrolyte prepared by the above method, wherein the lithium salt concentration in the electrolyte is 0.8-1.2M.

[0052] In some embodiments, the electrolyte has a moisture content and an acidity content not exceeding 50 ppm.

[0053] The present invention achieves the coordinated and efficient recovery of lithium salts, solvents and fluorine impurities in the electrolyte by coupling multi-stage physical separation and photocatalytic directional conversion technology.

[0054] In response to the problems of low solvent removal rate, residual impurities in the regenerated electrolyte and inability to reuse the solvent in the existing technology, the present invention innovatively proposes a solvent photolysis-resynthesis pathway based on a metal cluster catalytic system: a solar simulator is used to drive the decomposition of mixed ester solvents into alcohol intermediates, which are then regenerated into carbonate solvents with a purity greater than 99.2% through controlled synthesis, and the comprehensive solvent recovery rate is increased to more than 85%. At the same time, by adopting cooling crystallization and gradient extraction technology, the purity of lithium salt recovery exceeds 99.5%, and secondary pollution is effectively avoided through the directional conversion of fluorine impurities. Compared with traditional processes, the acidity and moisture content of the composite electrolyte of the present invention meet industrial standards, and energy consumption is reduced by more than 40%, realizing the closed-loop resource utilization of all components of the electrolyte.

[0055] Example 1

[0056] A method for recycling and resource utilization of waste electrolyte, first prepare the following equipment:

[0057] 1L of spent lithium-ion battery electrolyte, containing 1.2M LiPF6, a solvent composition of EC / DMC / EMC = 3:4:3, and containing trace amounts of LiF and HF impurities;

[0058] Cooling crystallization device with a temperature control accuracy of ±1°C and a centrifuge with a rotation speed of ≥5000 rpm;

[0059] Graphene oxide composite template containing Ni clusters, size 20 cm × 20 cm, Ni loading 5 wt%;

[0060] Solar simulator, light intensity adjustable range 0.5~2s;

[0061] Gas chromatograph (GC), inductively coupled plasma optical emission spectrometer (ICP-OES).

[0062] refer to Figure 1-Figure 3 A method for recycling and utilizing waste electrolyte comprises the following steps:

[0063] Step 1: Separation of lithium salt and solvent

[0064] 100 mL of waste electrolyte was placed in a -15°C environment and cooled for crystallization for 12 hours. Centrifugation was performed to obtain crude LiPF6 crystals containing about 8% residual solvent. The crude crystals were washed three times with 50 mL of 0°C ultra-dry DMC and dried to obtain regenerated LiPF6 powder. The purity of the regenerated LiPF6 powder was 99.6%, and the Li content was 19.4% as determined by ICP-OES. About 92 mL of the remaining mixed solvent was extracted and layered with acetonitrile. The volume ratio of the remaining mixed solvent to the acetonitrile extraction was 1:1, and an ester mixed solvent was separated. The EC / DMC / EMC of the ester mixed solvent was 2.8:3.9:3.3, and the purity was 98.7% as determined by GC.

[0065] Step 2: Photocatalytic decomposition of solvent

[0066] A mixed ester solvent was added to a transparent reactor containing a Ni / GO template with an area of 400 cm2, satisfying the requirement that 1 mL of solvent corresponds to a 4 cm2 template. The light intensity of the solar simulator was set to 0.5 sun, and the illumination time was 30 min. After illumination, the mixed liquid was separated by distillation to obtain alcohol products: 12 mL of ethylene glycol (HOCH2CH2OH), 28 mL of methanol (CH3OH), and 16 mL of ethanol (C2H5OH). The purity of the alcohols was detected by gas chromatography (GC) and the decomposition efficiency was calculated.

[0067] Step 3: Carbonate Solvent Resynthesis

[0068] Methanol was used as the raw material and reacted with methyl chloroformate (ClCOOCH3) under alkaline conditions with a molar ratio of 2:1. The reaction was stirred at 60°C for 4 hours to synthesize DMC with a yield of 92% and a purity of 99.3%. Ethylene glycol was catalyzed and condensed with urea (NH2CONH2) at 180°C for 6 hours to produce EC with a yield of 88% and a purity of 99.1%.

[0069] Step 4: Electrolyte preparation

[0070] 1.2M regenerated LiPF6 powder was mixed with synthesized DMC and EC in a volume ratio of DMC to EC of 4:3 to obtain a composite electrolyte.

[0071] Example 2

[0072] In the process of recycling and reusing waste electrolyte resources, the experimental conditions for the photocatalytic decomposition of the solvent in step 2 of Example 1 were changed from 0.5 sun to 1.0 sun, while the other conditions remained unchanged.

[0073] Example 3

[0074] In the process of recycling and reusing waste electrolyte resources, the experimental conditions for the photocatalytic decomposition of the solvent in step 2 of Example 1 were changed from 0.5 sun to 1.5 sun, while the other conditions remained unchanged.

[0075] Example 4

[0076] In the process of recycling and reusing waste electrolyte resources, the experimental conditions for the photocatalytic decomposition of the solvent in step 2 of Example 1 were changed from 0.5 sun to 2 sun, while the other conditions remained unchanged.

[0077] Example 5

[0078] In the process of recycling and reusing waste electrolyte resources, the experimental conditions for the photocatalytic decomposition of the solvent in step 2 of Example 2 were changed from 30 min to 20 min, while the other conditions remained unchanged.

[0079] Example 6

[0080] In the process of recycling and reusing waste electrolyte resources, the experimental conditions for the photocatalytic decomposition of the solvent in step 2 of Example 3 were changed from 30 min to 15 min, and the other conditions remained unchanged.

[0081] Example 7

[0082] In the process of recycling and reusing waste electrolyte resources, the experimental conditions for the photocatalytic decomposition of the solvent in step 2 of Example 4 were changed from 30 min to 10 min, and the other conditions remained unchanged.

[0083] The test results of moisture and acidity of the composite electrolyte are shown in Table 1 below.

[0084] Table 1

[0085]

[0086] According to Table 1, comparing Examples 1-4, it can be seen that the higher the light intensity, the higher the photolysis efficiency. Comparing Examples 2 and 5, and Examples 3 and 6, it can be seen that at 1 sun and 1.5 sun light intensities, the longer the light exposure time, the higher the photolysis efficiency. Comparing Examples 4 and 7, it can be seen that at a light intensity of 2 suns, a light exposure time of 10 minutes is sufficient. Therefore, increasing the light intensity can effectively save decomposition time. For practical applications, the corresponding light exposure time can be adjusted for different seasons and regions. This method is highly economical, environmentally friendly, and energy-saving.

[0087] The moisture and acidity test results of the composite electrolyte are shown in Table 2 below.

[0088] Table 2

[0089] Example electrolyte water Electrolyte acidity Example 1 30ppm 55ppm Example 2 27ppm 44ppm Example 3 32ppm 41ppm Example 4 22ppm 37ppm Example 5 39ppm 36ppm Example 6 33ppm 38ppm Example 7 36ppm 39ppm

[0090] The test results of moisture and acidity of the composite electrolyte showed that Example 4 had the lowest moisture and acidity, indicating that greater light intensity and longer light exposure time have a significant effect on reducing moisture and acidity.

[0091] The technical solutions of the present invention have been described above in conjunction with specific embodiments. However, it should be noted that the above descriptions are merely for the purpose of explaining the solutions of the present invention and are not to be construed in any way as limiting the scope of protection of the invention. Based on the explanations herein, those skilled in the art can conceive of other specific embodiments of the present invention or equivalent replacements without inventive effort, and these will fall within the scope of protection of the present invention.

Claims

1. A method for recycling and resource utilization of waste electrolyte, wherein the electrolyte is electrolyte recovered from waste lithium-ion batteries and / or spent electrolyte in the electrolyte production process, characterized in that: The method for recycling and resource utilization of waste electrolyte and the electrolyte include the following steps: Step 1: Cooling, crystallizing and extracting the waste electrolyte to separate the lithium salt from the solvent; Step 2: Rinse and dry the separated lithium salt to obtain regenerated lithium salt; Step 3: extracting the separated solvent to obtain a mixed ester solvent, placing the mixed ester solvent in a transparent sealed device on a carbon substrate template containing metal clusters, and photocatalytically decomposing the mixed ester solvent using a solar simulator at a specific light intensity and illumination time, followed by separation and purification to obtain an alcohol solvent; Step 4: using an alcohol solvent as a raw material to carry out a synthesis reaction to prepare a carbonate solvent; Step 5: Mix the regenerated lithium salt and the synthesized carbonate solvent in a certain proportion to obtain a reusable lithium-ion battery electrolyte.

2. The method for recycling and resource utilization of waste electrolyte according to claim 1, characterized in that: In step 3, the carbon material in the carbon-based template containing metal clusters is one or more of graphite, graphite oxide, graphene, graphene oxide, hard carbon, and soft carbon materials, the metal clusters are metals with catalytically active transitions, and the area of the carbon-based template containing metal clusters satisfies a linear relationship with the volume of the waste electrolyte.

3. The method for recycling and resource utilization of waste electrolyte according to claim 1, characterized in that: In step 3, the solar simulator sets the light intensity to satisfy a linear relationship with the volume of the electrolyte. Taking one sunlight intensity as a unit, the light intensity required for 1 mL of the waste electrolyte is 0.5-2 sunlight intensities.

4. The method for recycling and resource utilization of waste electrolyte according to claim 1, characterized in that: In step 3, the illumination time satisfies a linear relationship with the volume of the waste electrolyte, and the illumination time required for 1 mL of the waste electrolyte is not less than 10 minutes and not more than 60 minutes.

5. The method for recycling and resource utilization of waste electrolyte according to claim 1, characterized in that: The mixed ester solvolysis reaction satisfies the following equation: EC(C3H4O3)→CO2+HOCH2CH2OH DMC(C3H6O3)→CO2+2CH3OH <h2 style=";text-align:left;direction:ltr">DEC(C5H<h2 style=";text-align:left;direction:ltr"> 10 <h2 style=";text-align:left;direction:ltr"> O3)→CO2+2C2H5OH EMC(C4H8O3)→CO2+C2H5OH+CH3OH.

6. The method for recycling and resource utilization of waste electrolyte according to claim 1, characterized in that: The synthesis reaction formula described in step 4 satisfies the following equation: (NH2)2O+HOCH2CH2OH→EC(C3H4O3) 2CH3OH+ClCOOCH3→DMC(C3H6O3) EC(C3H4O3)+CH3OH→DMC(C3H6O3).

7. An electrolyte prepared by the method according to any one of claims 1 to 6, characterized in that: The lithium salt concentration in the electrolyte is 0.8-1.2M.

8. The electrolyte according to claim 7, characterized in that The moisture and acidity of the electrolyte do not exceed 50 ppm.

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