Electrolyte leaching solvent as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of new energy battery recovery, and discloses an electrolyte leaching solvent as well as a preparation method and application thereof. The electrolyte leaching solvent comprises a first component, a second component, a third component, a fourth component and a solubilizing solvent; the first component is selected from esters; the second component is selected from nitriles; the third component is a compound as shown in a formula I, and R1-R6 in the formula I are the same or different fluorine substituent, methoxyl, ethoxyl, fluorine-substituted methoxyl, fluorine-substituted ethoxyl or phenoxyl. And the fourth component is at least one of perfluoro hexanone, perfluoro heptanone, perfluoro octanone and perfluoro nonanone. The electrolyte leaching solvent has the good lithium salt leaching rate, through cooperative use of the third component, the fourth component and the hydrotropy solvent, flame retardance of the volatile solvent is synergistically achieved, the leaching solvent has the property of high flash point or even no flash point, and the safety of the leaching solvent in the large-batch use process is greatly guaranteed.

Description

Technical Field

[0001] This invention belongs to the field of new energy battery recycling technology, specifically relating to an electrolyte leaching solvent, its preparation method, and its application. Background Technology

[0002] As the market for new energy batteries expands, the scale of retired batteries is also growing rapidly. Currently, research on the recycling and utilization of retired batteries focuses primarily on high-value-added cathode and anode materials, with relatively little research on electrolyte recycling. However, electrolyte is a crucial component of batteries, accounting for approximately 15% of their mass. Even after charge-discharge cycles during use, about 70% of the electrolyte remains in the battery cells after retirement. If this residual electrolyte is not recycled, the LiPF6 in it will decompose into highly toxic products such as PF5, HF, and POF3 upon contact with air during disassembly, harming human health and the environment. Furthermore, the main organic solvents in the electrolyte, including carbonates and carboxylic esters, also contribute to organic pollution. In the process of recycling retired batteries, if the residual electrolyte cannot be recycled and treated simply and effectively, it will not only increase the risk of wastewater and waste pollution during the recycling process but also waste non-renewable resources such as lithium and fluorine. Therefore, completing the recycling and utilization of residual electrolyte in retired batteries, and achieving full-component recycling of new energy batteries, is an important link in realizing the closed loop of the new energy materials industry.

[0003] Currently, in the mainstream industrial processes of battery recycling, whether it's hydrometallurgical recycling or high-temperature pyrometallurgical recycling, the treatment of residual electrolyte in battery cells often involves using high temperatures to promote the evaporation and decomposition of the electrolyte, followed by harmless fluorination treatment as waste gas at the end. There are also a few patent reports on electrolyte treatment and recycling technologies from retired batteries. However, these generally involve simple organic solvent leaching or supercritical carbon dioxide extraction. To improve leaching efficiency, pretreatment such as crushing the battery materials is required. This crushing pretreatment damages the cell structure, hindering the fine disassembly of the positive and negative electrode materials. High impurity content in the positive and negative electrode powder makes subsequent impurity removal difficult, and a large amount of protective gas is needed to prevent fires or explosions during the recycling process, resulting in high costs. Supercritical carbon dioxide extraction technology relies on high-voltage equipment, requiring significant investment, incurring high operating costs, and operating under harsh conditions, making it unsuitable for large-scale application in the electrolyte recycling field. Furthermore, currently available leaching solvents generally use flammable and explosive solvents, posing significant safety hazards during large-scale use. Alternatively, liquefied gases with low boiling points can be used, requiring high pressure to maintain their liquid state and thus demanding high levels of equipment airtightness and pressure resistance during operation.

[0004] In summary, currently reported electrolyte leaching solvents and processes generally suffer from drawbacks such as requiring the pulverization and destruction of the battery cell during the leaching process, using flammable and explosive solvents, employing specialized pressure-resistant equipment, and incurring high operating costs. These limitations pose significant constraints for large-scale industrial processing. Therefore, developing a method that can safely and efficiently leach electrolyte from battery cells at ambient temperature and pressure without damaging the cell structure, and then recycle it to ensure no electrolyte residue remains in the cell structure, is crucial for advancing the industrialization of electrolyte recycling and refined cell dismantling in new energy batteries. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide an electrolyte leaching solvent.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned electrolyte leaching solvent.

[0007] Another object of the present invention is to provide the application of the above-mentioned electrolyte leaching solvent in the leaching and recycling of electrolytes from decommissioned lithium-ion batteries.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] An electrolyte leaching solvent comprises a first component, a second component, a third component, a fourth component, and a co-solvent; the first component is selected from esters; the second component is selected from nitriles; the third component is a compound represented by Formula I; and the fourth component is at least one selected from perfluorohexanone (perfluorohexaketone), perfluoroheptanone (perfluoroheptanone), perfluorooctanone (perfluorooctanone), and perfluorononanone (perfluorononaketone).

[0010] R1 to R6 can be the same or different fluorine substituents, methoxy groups, ethoxy groups, fluorine-substituted methoxy groups, fluorine-substituted ethoxy groups, or phenoxy groups.

[0011] Furthermore, the third component is selected from one or more mixtures of ethoxypentafluorocyclotriphosphazene, hexafluorocyclotriphosphazene, pentafluoro(phenoxy)cyclotriphosphazene, trifluoroethoxypentafluorocyclotriphosphazene, hexamethoxycyclotriphosphazene, hexaethoxycyclotriphosphazene, and trimethoxycyclotriphosphazene. These raw materials are widely available and have low costs.

[0012] The third component used in this invention primarily achieves flame retardancy of the leaching solvent by capturing active free radicals such as H·, O·, and HO· that sustain combustion during the process, thereby terminating the chain reaction and ensuring the safety of the leaching solvent during use. Because the leaching solvent is designed for easier removal from the battery cell after leaching, and considering subsequent battery cell drying, all solvents used are low-boiling-point, volatile solvents. Relying solely on the third component cannot achieve vapor flame retardancy on the liquid-gas surface of the leaching solvent. By further using a fourth component, which has a lower boiling point, a non-flammable vapor protective layer can be formed on the liquid surface of the leaching solvent, thus preventing combustion and explosion problems caused by the volatilization of flammable solvents on the surface of the leaching solvent during use.

[0013] Further, the first component is selected from one or more mixtures of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl formate, methyl acetate, ethyl formate, ethyl acetate, methyl propionate, ethyl propionate, propyl acetate, propyl propionate, butyl propionate, propyl butyrate, butyl butyrate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethyl monofluoroacetate, ethyl trifluoroacetate, butyl trifluoroacetate, trifluoroethyl n-butyrate, methyl trifluoroethyl carbonate, and dimethyl sulfite. The first component used in this invention has high solubility for lithium hexafluorophosphate and mainly functions to dissolve residual lithium hexafluorophosphate in the battery cell in the overall leaching solvent, effectively leaching out solid lithium hexafluorophosphate remaining inside the battery cell and in the pores of the electrode material.

[0014] Furthermore, the second component is selected from one or more mixtures of acetonitrile, propionitrile, butyronitrile, fluoroacetonitrile, and chloroacetonitrile. The second component used in this invention has a high dielectric constant (e.g., a dielectric constant higher than 20), which helps to increase the dielectric constant of the leaching solvent. Because the electrolyte remaining in retired lithium-ion batteries has a high water content, and the water content during solvent leaching of the electrolyte is much higher than that of the electrolyte, lithium hexafluorophosphate is prone to decomposition in an environment with high water content. Introducing a solvent with a high dielectric constant can effectively increase the dielectric constant of Li... + The proportion of solvated structures ensures that lithium hexafluorophosphate exists in the leaching solvent as solvated molecules, avoiding the reaction between lithium hexafluorophosphate molecules and water molecules.

[0015] Furthermore, the co-solvent is selected from one or more of anhydrous ethanol, propanol, acetone, butanone, and isopropanol. Because the fourth component used in this invention is almost immiscible with the first and second components (carbonates, carboxylic esters, etc.) that dissolve lithium hexafluorophosphate, the co-solvent greatly increases the solubility of the fourth component in the first and second components, ensuring that the fourth component is uniformly dispersed in the leaching solvent, thereby exerting its excellent flame-retardant effect and enabling the leaching solvent to reach a non-flammable level.

[0016] Furthermore, the mass percentage composition of each component in the electrolyte leaching solvent (based on a total leaching solvent content of 100%) is as follows:

[0017] The first component is 5%–40%, the second component is 5%–40%, the third component is 5%–20%, the fourth component is 10%–60%, and the co-solvent is 5%–40%.

[0018] More preferably, the mass ratio of the first component to (the third component + the fourth component) is 1:(0.5 to 10).

[0019] The preparation method of the above-mentioned electrolyte leaching solvent includes the following preparation steps:

[0020] Add the first component, the second component, the third component, the fourth component and the co-solvent to the reaction vessel, seal and stir until the mixed solution becomes uniform and transparent, thus obtaining the electrolyte leaching solvent.

[0021] Furthermore, the stirring refers to continuous stirring for 1 to 5 hours at a rotation speed of 500 to 2000 ppm.

[0022] The application of the above-mentioned electrolyte leaching solvent in the leaching and recycling of electrolytes from decommissioned lithium-ion batteries.

[0023] Because the leaching solvent of this invention has the characteristics of high leaching efficiency and non-flammability, the application process and equipment requirements in actual production are relatively simple, as detailed below:

[0024] (1) Immerse the retired lithium battery in sodium chloride solution for discharge treatment, so that its voltage drops to below 1.5V, and blow dry the surface moisture of the battery casing after discharge.

[0025] (2) Cut off the metal casing of the battery after the treatment in step (1) to expose the battery cell or remove the battery cell and immerse it in the electrolyte leaching solvent prepared above. After standing and soaking, remove the battery cell and then blow dry it to obtain a battery cell structure without electrolyte residue.

[0026] Furthermore, the time for static soaking treatment in step (2) is 2 to 10 days.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) The electrolyte leaching solvent of the present invention achieves flame retardancy through the combined use of a third component, a fourth component, and a co-solvent. The third component primarily terminates the chain reaction by capturing active free radicals such as H·, O·, and HO· that sustain combustion during the combustion process. The fourth component forms a non-flammable vapor protective layer on the liquid surface of the leaching solvent, achieving vapor flame retardancy on the liquid-gas surface of the leaching solvent. Simultaneously, the co-solvent significantly increases the solubility of the fourth component in the first and second components, ensuring uniform dispersion of the fourth component in the leaching solvent and thus maximizing its flame retardant effect. Through the synergistic effect of these three components, flame retardancy of the volatile solvent is achieved, giving the leaching solvent a high flash point or even no flash point, greatly ensuring the safety of the leaching solvent during large-scale use.

[0029] (2) The electrolyte leaching solvent of the present invention increases the solubility ratio of LiPF6 after dissolution by introducing a second component with a high dielectric constant, which effectively prevents the decomposition of LiPF6 due to high ambient moisture during the leaching process.

[0030] (3) The electrolyte leaching solvent of the present invention is selected as a low-boiling-point solvent, which can ensure the rapid drying of the battery cell after soaking in the leaching solvent, and is also conducive to dissolving the electrolyte in the leaching solvent. It can be used to quickly separate the leaching solvent from the high-boiling-point solvent in the electrolyte by distillation, so that the leaching solvent can be easily recycled; and LiPF6 can be recovered by distillation below the decomposition temperature of LiPF6.

[0031] (4) The application process of the electrolyte leaching solvent of the present invention in the leaching and recycling of electrolyte of retired lithium-ion batteries is simple. It only requires immersing the battery cell in the leaching solvent for static soaking treatment. There is no need for additional power, manpower, gas, etc., and the overall production cost is low.

[0032] (5) By controlling the content range of the first component and (the third component + the fourth component) to be 1:(0.5~10), the leaching solvent of the present invention can simultaneously achieve good lithium salt leaching rate and flame retardant effect. Attached Figure Description

[0033] Figure 1 This is a graph showing the IC detection results of the leaching recovery solution in Example 1;

[0034] Figure 2 This is a graph showing the IC detection results of the leaching recovery solution in Example 2;

[0035] Figure 3The graph shows the IC detection results of the leaching recovery solution in Comparative Example 1;

[0036] Figure 4 The graph shows the IC detection results of the leaching recovery solution in Comparative Example 2;

[0037] Figure 5 This is a photograph showing the layered structure of the leaching recovery solution in Comparative Example 5. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0039] The performance testing methods in the following examples are as follows:

[0040] a. Flash point test of leaching solvent: The flash point test shall be performed in accordance with GB / T 261-2008 Determination of flash point, Binski-Martin closed cup method.

[0041] b. Self-extinguishing time test of leaching solvent: Immerse a glass cotton ball with a diameter of 0.3 cm in the leaching solvent, remove it, and use filter paper to remove the leaching solvent from the surface to ensure that each glass cotton ball absorbs the same mass of leaching solvent. Record the mass as m (in grams), ignite it with a lighter, and record the burning time T (in seconds). The self-extinguishing time t = T / m. The average value of three measurements for each sample is taken.

[0042] c. LiPF6 leaching efficiency test in leaching solvent: After immersing the battery cell in the leaching solvent for a certain period of time, samples were taken and analyzed by ion chromatography (ion chromatograph, 930 Compact IC flex). The content of LiPF6 in the IC data results is X (ppm). The leached mass of LiPF6 is calculated as n = X * M / 1000000 (where M refers to the mass of the leached recovery liquid, in g), and the leaching rate of LiPF6 (in %) is 100n / Y (where Y refers to the residual mass of LiPF6 in the battery cell, in g).

[0043] Example 1

[0044] The electrolyte leaching solvent formulation in this embodiment is as follows: dimethyl carbonate (24%), anhydrous ethanol (16%), acetonitrile (16%), perfluorohexanone (36%), and ethoxypentafluorocyclotriphosphazene (8%). The composition and content of this formulation are shown in Table 1.

[0045] The preparation method of the electrolyte leaching solvent is as follows: add the first component (dimethyl carbonate), the second component (acetonitrile), the third component (ethoxypentafluorocyclotriphosphazene), the fourth component (perfluorohexanone), and the co-solvent (anhydrous ethanol) weighed according to the above mass percentages into the reaction vessel, seal and stir to avoid excessive volatilization of low-boiling-point solvents, and continue stirring for 2 hours at a speed of 1000 ppm to ensure that the solution does not separate into layers and is uniform and transparent before it can be used for subsequent leaching.

[0046] The application process of the electrolyte leaching solvent in the leaching and recycling of electrolyte from decommissioned lithium-ion batteries, as described in this embodiment, is as follows:

[0047] (1) Using an MSK-530 cylindrical battery disassembly machine in a glove box, the retired 32650 cylindrical lithium batteries were immersed in a sodium chloride solution for discharge treatment, reducing their voltage to below 1.5V. After discharge, the surface moisture of the battery casing was dried by blowing air. (The application of the leaching solvent designed in this invention is not limited to 32650 cylindrical batteries. It is applicable to batteries with other cell structures such as pouch batteries, cylindrical batteries, and square batteries. This example uses the 32650 cylindrical battery as an illustration. The 32650 cylindrical batteries used in this example are retired batteries from the same batch disassembled from the same module, ensuring the consistency of the residual electrolyte in the cells. The amount of residual LiPF6 in the cells is 2.1g / cell.)

[0048] (2) Cutting steps (1) After processing, remove the stainless steel outer shell of the battery, take out the complete battery cell structure, and quickly immerse the battery cell in 120ml of electrolyte leaching solvent. In order to avoid the evaporation of the leaching solvent, seal the container after placing the battery cell and let it sit for 5 days. Then take out the battery cell and dry it. Then conduct flash point test, self-extinguishing time test and LiPF6 leaching rate test on the leaching solvent.

[0049] The flash point test, self-extinguishing time test, and LiPF6 leaching rate test results of the electrolyte leaching solvent obtained in this embodiment are shown in Table 2. As can be seen from Table 2, the self-extinguishing time of the electrolyte leaching solvent obtained in this embodiment is 0 s, and its LiPF6 leaching rate after 5 days of wetting for electrolyte recovery from retired lithium-ion batteries is 95.9%.

[0050] The IC (ion chromatography) detection results of the leaching recovery solution in this embodiment are as follows: Figure 1 As shown.

[0051] Example 2

[0052] The electrolyte leaching solvent formulation in this embodiment is as follows: dimethyl carbonate (21%), anhydrous ethanol (16%), acetonitrile (16%), perfluorohexanone (33%), and ethoxypentafluorocyclotriphosphazene (14%). The composition and content of this formulation are shown in Table 1.

[0053] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1. The flash point, self-quenching time, and LiPF6 leaching rate results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 s, and its LiPF6 leaching rate after 5 days of soaking in the electrolyte for recovery from retired lithium-ion batteries is 95.1%.

[0054] The IC (ion chromatography) detection results of the leaching recovery solution in this embodiment are as follows: Figure 2 As shown.

[0055] Example 3

[0056] The electrolyte leaching solvent formulation in this embodiment is as follows: ethyl trifluoroacetate (30%), anhydrous ethanol (20%), propionitrile (35%), perfluorohexanone (10%), and pentafluoro(phenoxy)cyclotriphosphazene (5%). The composition and content of this formulation are shown in Table 1.

[0057] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1. The flash point, self-quenching time, and LiPF6 leaching rate results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 s, and its LiPF6 leaching rate after 5 days of soaking in the electrolyte for recovery from retired lithium-ion batteries is 98.2%.

[0058] Example 4

[0059] The electrolyte leaching solvent formulation in this embodiment is as follows: methyltrifluoroethyl carbonate (25%), anhydrous ethanol (25%), propionitrile (25%), perfluorohexanone (20%), and pentafluoro(phenoxy)cyclotriphosphazene (5%). The composition and content of this formulation are shown in Table 1.

[0060] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1. The flash point, self-quenching time, and LiPF6 leaching rate results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 s, and its LiPF6 leaching rate after 5 days of soaking in the electrolyte from retired lithium-ion batteries is 97.1%.

[0061] Example 5

[0062] The electrolyte leaching solvent formulation in this embodiment is as follows: propyl acetate (25%), acetone (25%), fluoroacetonitrile (25%), perfluorohexanone (20%), and hexafluorocyclotriphosphazene (5%). The composition and content of this formulation are shown in Table 1.

[0063] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1. The flash point, self-quenching time, and LiPF6 leaching rate results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 seconds, and its LiPF6 leaching rate after 5 days of soaking in the electrolyte for recovery from retired lithium-ion batteries is 97.6%.

[0064] Example 6

[0065] The electrolyte leaching solvent formulation in this embodiment is as follows: trifluoroethyl butyrate (40%), propanol (10%), chloroacetonitrile (5%), perfluoroheptanone (30%), and trifluoroethoxypentafluorocyclotriphosphazene (15%). The composition and content of this formulation are shown in Table 1.

[0066] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1, with a leaching and resting time of 2 days. The flash point test, self-quenching time test, and LiPF6 leaching rate test results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from the results in Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 seconds, and its LiPF6 leaching rate after 2 days of leaching and recovery of retired lithium-ion battery electrolyte is 96.4%.

[0067] Example 7

[0068] The electrolyte leaching solvent formulation in this embodiment is as follows: dimethyl sulfite (5%), butanone (15%), propionitrile (40%), perfluorooctanone (20%), and hexaethoxycyclotriphosphazene (20%). The composition and content of this formulation are shown in Table 1.

[0069] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1, with a leaching and resting time of 10 days. The flash point test, self-quenching time test, and LiPF6 leaching rate test results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from the results in Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 seconds, and its LiPF6 leaching rate after 10 days of leaching and recovery of retired lithium-ion battery electrolyte is 94.7%.

[0070] Example 8

[0071] The electrolyte leaching solvent formulation in this embodiment is as follows: methyl ethyl carbonate (20%), isopropanol (10%), butyronitrile (5%), perfluorohexanone (60%), and trimethoxytrifluorocyclotriphosphazene (5%). The composition and content of this formulation are shown in Table 1.

[0072] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1, with a leaching and resting time of 7 days. The flash point test, self-quenching time test, and LiPF6 leaching rate test results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from the results in Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 seconds, and its LiPF6 leaching rate after 7 days of leaching and recovery of retired lithium-ion battery electrolyte is 95.0%.

[0073] Example 9

[0074] The electrolyte leaching solvent formulation in this embodiment is as follows: propyl acetate (40%), isopropanol (5%), acetonitrile (25%), perfluorohexanone (10%), and ethoxypentafluorocyclotriphosphazene (20%). The composition and content of this formulation are shown in Table 1.

[0075] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1, with a leaching and resting time of 5 days. The flash point test, self-quenching time test, and LiPF6 leaching rate test results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from the results in Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 seconds, and its LiPF6 leaching rate after 5 days of leaching and recovery of retired lithium-ion battery electrolyte is 97.9%.

[0076] Example 10

[0077] The electrolyte leaching solvent formulation in this embodiment is as follows: diethylene glycol dimethyl ether (20%), anhydrous ethanol (40%), propionitrile (15%), perfluorononanone (20%), and hexamethoxycyclotriphosphazene (5%). The composition and content of this formulation are shown in Table 1.

[0078] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1, with a leaching and resting time of 5 days. The flash point test, self-quenching time test, and LiPF6 leaching rate test results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from the results in Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 seconds, and its LiPF6 leaching rate after 5 days of leaching and recovery of retired lithium-ion battery electrolyte is 96.2%.

[0079] Example 11

[0080] The electrolyte leaching solvent formulation in this embodiment is as follows: dimethyl sulfite (5%), isopropanol (20%), propionitrile (25%), perfluorononanone (30%), and hexaethoxycyclotriphosphazene (20%). The composition and content of this formulation are shown in Table 1.

[0081] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1, with a leaching and resting time of 5 days. The flash point test, self-quenching time test, and LiPF6 leaching rate test results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from the results in Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 seconds, and its LiPF6 leaching rate after 5 days of leaching and recovery of retired lithium-ion battery electrolyte is 90.4%.

[0082] Example 12

[0083] The electrolyte leaching solvent formulation in this embodiment is as follows: dimethyl sulfite (5%), isopropanol (20%), propionitrile (15%), perfluorononanone (35%), and hexaethoxycyclotriphosphazene (25%). The composition and content of this formulation are shown in Table 1.

[0084] The electrolyte leaching solvent of this embodiment was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1, with a leaching and resting time of 5 days. The flash point, self-quenching time, and LiPF6 leaching rate results of the obtained electrolyte leaching solvent are shown in Table 2. In this embodiment, the mass ratio of the first component to (third component + fourth component) in the solvent formulation is 1:12. As can be seen from the results in Table 2, the self-quenching time of the electrolyte leaching solvent obtained in this embodiment is 0 seconds, and its LiPF6 leaching rate after 5 days of leaching and recovery of retired lithium-ion battery electrolyte is 88.7%.

[0085] Comparative Example 1

[0086] The formulation of the electrolyte leaching solvent in this comparative example is: dimethyl carbonate solvent (100%). Its composition and content are shown in Table 1.

[0087] The electrolyte from retired lithium-ion batteries was leached and recovered using the electrolyte leaching solvent of this comparative example, following the method in Example 1. Results showed that LiPF6 decomposed after 5 days of leaching recovery. The IC (ion chromatography) results of the recovered leaching solution are as follows: Figure 3 As shown, only 905 ppm of LiPF6 remained in the leaching recovery solution, approximately 0.11 g. Furthermore, strong LiPO2F2 and LiF peaks were observed in the test results, and a white precipitate of LiF was observed in the leaching recovery solution after leaching and settling. The flash point and self-extinguishing time test results of the obtained electrolyte leaching solvent are shown in Table 2. The results in Table 2 indicate that the leaching solvent of the electrolyte obtained in this comparative example is flammable.

[0088] In this comparative example, without the addition of the second, third, and fourth components, the lithium salt was easily decomposed in the leaching recovery solution with a high moisture content, and the resulting electrolyte leaching solvent was flammable.

[0089] Comparative Example 2

[0090] The formulation of the electrolyte leaching solvent in this comparative example is: dimethyl carbonate (60%) and acetonitrile (40%). The composition and content of this formulation are shown in Table 1.

[0091] The electrolyte leaching solvent of this comparative example was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method in Example 1. The flash point, self-extinguishing time, and LiPF6 leaching rate results of the obtained electrolyte leaching solvent are shown in Table 2. As can be seen from Table 2, the electrolyte leaching solvent obtained in this comparative example is flammable, and its LiPF6 leaching rate after 5 days of soaking in the electrolyte from retired lithium-ion batteries was 99.5%. The IC (ion chromatography) detection results of the leached recovery solution are as follows: Figure 4 As shown, no large amounts of LiPO2F2 and LiF were found in the detection results.

[0092] The comparison results between this comparative example and Comparative Example 1 show that the addition of acetonitrile, a solvent with a high dielectric constant, can suppress the decomposition of LiPF6 in solvents with high water content.

[0093] In this comparative example, without the addition of the third and fourth components and the co-solvent, the solvent leaching solvent of the resulting electrolyte is flammable.

[0094] Comparative Example 3

[0095] The electrolyte leaching solvent formulation in this embodiment is as follows: dimethyl carbonate (24%), anhydrous ethanol (16%), acetonitrile (16%), and perfluorohexanone (44%). The composition and content of this formulation are shown in Table 1.

[0096] The electrolyte leaching solvent of this comparative example was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1. The flash point test, self-quenching time test, and LiPF6 leaching rate test results of the obtained electrolyte leaching solvent are shown in Table 2.

[0097] As can be seen from the results in Table 2, the leaching solvent of the electrolyte obtained in this comparative example is flammable, and the leaching rate of LiPF6 after 5 days of wetting in the electrolyte of retired lithium-ion batteries is 94.6%.

[0098] This comparative example cannot achieve effective flame retardancy without the addition of the third component.

[0099] Comparative Example 4

[0100] The electrolyte leaching solvent formulation in this embodiment is as follows: dimethyl carbonate (24%), anhydrous ethanol (16%), acetonitrile (16%), and ethoxypentafluorocyclotriphosphazene (44%). The composition and content of this formulation are shown in Table 1.

[0101] The electrolyte leaching solvent of this comparative example was used to leach and recover the electrolyte from retired lithium-ion batteries according to the method of Example 1. The flash point test, self-quenching time test, and LiPF6 leaching rate test results of the obtained electrolyte leaching solvent are shown in Table 2.

[0102] As can be seen from the results in Table 2, the leaching solvent of the electrolyte obtained in this comparative example is flammable, and the leaching rate of LiPF6 after 5 days of wetting in the electrolyte of retired lithium-ion batteries is 92.5%.

[0103] This comparative example cannot achieve effective flame retardancy without the addition of the fourth component.

[0104] Comparative Example 5

[0105] The electrolyte leaching solvent formulation in this embodiment is as follows: dimethyl carbonate (34%), acetonitrile (22%), perfluorohexanone (36%), and ethoxypentafluorocyclotriphosphazene (8%). The composition and content of this formulation are shown in Table 1.

[0106] The electrolyte from retired lithium-ion batteries was leached and recovered using the electrolyte leaching solvent of this comparative example, following the method in Example 1. The results showed that the leached and recovered solution exhibited obvious stratification, as illustrated in the photographs below. Figure 5 As shown in Table 2, the flash point and self-extinguishing time results of the obtained electrolyte leaching solvent are presented. Figure 5 It can be seen that the leaching solvent of this formulation exhibits obvious stratification. This is because perfluorohexanone is insoluble in dimethyl carbonate and acetonitrile, and has a high density; therefore, the lower layer of the solution is perfluorohexanone. Since perfluorohexanone is located in the lower layer, it cannot form a non-flammable protective layer at the gas-liquid interface. Therefore, the flash point and self-extinguishing properties of the mixed solvent are not significantly improved, with test results of 8℃ and 116 s / g.

[0107] In this comparative example, no co-solvent was added, and the fourth component had poor solubility in the electrolyte leaching solvent, thus failing to achieve effective flame retardancy.

[0108] Table 1. Composition and content of electrolyte leaching solvent in each embodiment and comparative example

[0109]

[0110]

[0111] Table 2. Electrolyte leaching solvent test results

[0112]

[0113]

[0114] The comparison between Examples 1-12 and Comparative Examples 1-5 in Table 2 shows that when the leaching solvent includes the first component, the second component, the third component, the fourth component, and the co-solvent, it can simultaneously achieve a good LiPF6 leaching rate and flame retardant effect.

[0115] As can be seen from Table 2 under different first component:(third component + fourth component) conditions, as the ratio of the third and fourth components increases, the flash point of the leaching solvent increases, but the leaching rate shows a decreasing trend. Examples 1-12 show that when the mass ratio of the first component:(third component + fourth component) is higher than 0.5, the electrolyte of this formulation exhibits better flame retardant effect in leaching the solvent. With the increase of the ratio of the third and fourth components, the flash point increases, and the self-extinguishing time can reach 0 s, but the leaching rate decreases as the proportion of the third and fourth components increases. Under the condition of a first component:(third component + fourth component) mass ratio of 1:(0.5-10) (as in Examples 1-11), the self-extinguishing time of the electrolyte leaching solvent is 0 s, and the leaching rate is greater than 90%.

[0116] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. An electrolyte leaching solvent, characterized in that, It includes a first component, a second component, a third component, a fourth component, and a co-solvent; The first component is selected from esters; the second component is selected from nitriles; the third component is a compound represented by Formula I; and the fourth component is at least one of perfluorohexanone, perfluoroheptanone, perfluorooctanone, and perfluorononanone. R1 to R6 can be the same or different fluorine substituents, methoxy groups, ethoxy groups, fluorine-substituted methoxy groups, fluorine-substituted ethoxy groups, or phenoxy groups.

2. The electrolyte leaching solvent according to claim 1, characterized in that, The third component is selected from one or more of ethoxypentafluorocyclotriphosphazene, hexafluorocyclotriphosphazene, pentafluoro(phenoxy)cyclotriphosphazene, trifluoroethoxypentafluorocyclotriphosphazene, hexamethoxycyclotriphosphazene, hexaethoxycyclotriphosphazene, and trimethoxycyclotriphosphazene.

3. The electrolyte leaching solvent according to claim 1, characterized in that, The first component is selected from one or more of the following: dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl formate, methyl acetate, ethyl formate, ethyl acetate, methyl propionate, ethyl propionate, propyl acetate, propyl propionate, butyl propionate, propyl butyrate, butyl butyrate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethyl monofluoroacetate, ethyl trifluoroacetate, butyl trifluoroacetate, trifluoroethyl butyrate, methyl trifluoroethyl carbonate, and dimethyl sulfite.

4. The electrolyte leaching solvent according to claim 1, characterized in that, The second component is selected from one or more of acetonitrile, propionitrile, butyronitrile, fluoroacetonitrile, and chloroacetonitrile.

5. The electrolyte leaching solvent according to claim 1, characterized in that, The co-solvent is selected from one or more of anhydrous ethanol, propanol, acetone, butanone, and isopropanol.

6. An electrolyte leaching solvent according to any one of claims 1 to 5, characterized in that, The mass percentage composition of each component in the electrolyte leaching solvent is as follows: The first component is 5%–40%, the second component is 5%–40%, the third component is 5%–20%, the fourth component is 10%–60%, and the co-solvent is 5%–40%.

7. The electrolyte leaching solvent according to claim 6, characterized in that, The mass ratio of the first component to (the third component + the fourth component) is 1:(0.5 to 10).

8. A method for preparing an electrolyte leaching solvent according to any one of claims 1 to 7, characterized in that, The preparation steps include the following: Add the first component, the second component, the third component, the fourth component and the co-solvent to the reaction vessel, seal and stir until the mixed solution becomes uniform and transparent, thus obtaining the electrolyte leaching solvent; The stirring refers to continuous stirring for 1 to 5 hours at a rotation speed of 500 to 2000 ppm.

9. The application of the electrolyte leaching solvent according to any one of claims 1 to 7 in the leaching and recycling of electrolyte from decommissioned lithium-ion batteries.

10. The application of the electrolyte leaching solvent according to claim 9 in the leaching and recycling of electrolytes from decommissioned lithium-ion batteries, characterized in that, The specific application steps are as follows: (1) Immerse the retired lithium battery in sodium chloride solution for discharge treatment, so that its voltage drops to below 1.5V, and blow dry the surface moisture of the battery casing after discharge. (2) Cut off the metal casing of the battery after the treatment in step (1) to expose the battery cell or remove the battery cell and immerse it in the electrolyte leaching solvent described in any one of claims 1 to 7. After standing and soaking for 2 to 10 days, remove the battery cell and then dry it with a blower to obtain a battery cell structure without electrolyte residue.

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