Method for recycling and utilizing waste lithium battery electrolyte

Abstract

The application discloses a method for recycling and utilizing waste lithium battery electrolyte resources, and comprises the following steps: freezing and cutting the waste lithium battery, and then putting the waste lithium battery into an organic solvent for leaching; performing solid-liquid separation to obtain first filtrate and first filter residue; performing distillation on the first filtrate to obtain mother liquor and organic distillate; adding a complexing solvent into the mother liquor for reaction, and then performing filtration to obtain second filtrate and second filter residue; heating the second filter residue to obtain lithium hexafluorophosphate solid; adding an amine compound into the second filtrate, and then performing filtration to obtain third filter residue; and heating the third filter residue to obtain lithium bisfluorosulfonylimide solid. The method realizes extraction and recovery of lithium hexafluorophosphate and carbonate solvents in the electrolyte, and can extract pure lithium bisfluorosulfonylimide from lithium hexafluorophosphate crystallization mother liquor.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology, and specifically relates to a method for recycling and utilizing waste lithium battery electrolyte. Background Technology

[0002] With the rapid development of the new energy electric vehicle industry, the installed capacity of power lithium-ion batteries has increased year by year. Simultaneously, a wave of lithium-ion battery obsolescence has followed. Obsolete lithium-ion batteries need to be recycled for resource utilization. Currently, the recycling of waste lithium-ion batteries mainly focuses on electrode materials and current collectors, with very little research on electrolyte recycling. Electrolytes generally consist of lithium salts, organic solvents, and additives. The lithium salt is primarily lithium hexafluorophosphate (LiPF6), the organic solvent is mainly carbonate solvents, and the additive content is relatively low. Because lithium hexafluorophosphate is toxic and easily decomposes, untreated electrolyte reacts with the external environment, generating a large amount of pollutants, which seriously affects human and environmental safety.

[0003] Industrially, the treatment of waste lithium-ion battery electrolyte involves heating and evaporating followed by calcination and pyrolysis. The pyrolysis of organic solvents requires high-temperature calcination, consuming heat. Furthermore, the electrolyte contains valuable solvents such as ethylene carbonate and propylene carbonate, as well as additives like lithium bis(fluorosulfonyl)imide. Direct pyrolysis followed by incineration hinders resource recycling and increases carbon emissions from industrial production. Therefore, efficiently recovering lithium salts, organic solvents, and additives from waste electrolytes while reducing harmful emissions is a critical challenge for the lithium-ion battery industry.

[0004] Researchers have disclosed a method for recycling electrolyte from waste lithium-ion batteries. After discharging the battery, the casing is opened, and the battery cell is removed from a glove box and placed in liquid nitrogen for freezing. The electrolyte ice-like particles in the liquid nitrogen are collected and distilled. After the electrolyte solvent is distilled off, water is added to the mother liquor, and the mixture is heated to decompose lithium hexafluorophosphate into HF and PF5, which are then absorbed by an alkaline solution. This method avoids the decomposition of lithium hexafluorophosphate into toxic substances in the air by treating the battery cell at low temperatures. However, the introduction of water during distillation causes lithium hexafluorophosphate to decompose, generating various impurities, affecting the purity of the recovered electrolyte solvent and increasing the cost of exhaust gas treatment. Furthermore, the high-value lithium hexafluorophosphate is also decomposed and absorbed, reducing the economics of the recycling process. In addition, the recycling of lithium difluorosulfonylimide (LiN(SO2F)2) and its decomposition product HN(SO2F)2 is rarely mentioned. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for recycling and utilizing waste lithium battery electrolyte, realizing the extraction and recovery of LiPF6 and carbonate solvents in the electrolyte, and preparing pure lithium bisfluorosulfonylimide from the LiPF6 crystallization mother liquor, achieving the goal of full recycling and zero emissions of all components of waste power batteries.

[0006] According to one aspect of the present invention, a method for recycling and utilizing waste lithium battery electrolyte is provided, comprising the following steps:

[0007] S1: After freezing and breaking the waste lithium batteries, they are leached in an organic solvent and the solid and liquid are separated to obtain the first filtrate and the first filter residue.

[0008] S2: The first filtrate is treated with a lithium-containing deacidifying agent and then distilled to obtain a mother liquor and an organic fraction. A complexing solvent is added to the mother liquor for complexation, followed by cooling and crystallization. Solid-liquid separation is then performed to obtain a second filtrate and a second filter residue.

[0009] S3: The second filter residue is heated and dissociated under reduced pressure to obtain solid lithium hexafluorophosphate;

[0010] S4: Add at least one of an amine compound or a hydrochloride salt of the amine compound to the second filtrate, filter to obtain a third filter residue, and heat the third filter residue to obtain lithium difluorosulfonylimide solid.

[0011] In some embodiments of the present invention, in step S1, the freezing temperature is -210°C to 4°C, the time is 4h to 36h, and the freezing is carried out under a dry inert atmosphere.

[0012] In some preferred embodiments of the present invention, in step S1, the inert gas is at least one of nitrogen, helium, or argon.

[0013] In some preferred embodiments of the present invention, in step S1, the freezing temperature can be set to -117°C (ethanol refrigeration), -78°C (CO2 refrigeration), or -20°C (conventional refrigeration temperature).

[0014] In some embodiments of the present invention, in step S1, the organic solvent is at least one selected from diethyl ether, acetonitrile, tetrahydrofuran, acetone and methanol.

[0015] In some preferred embodiments of the present invention, in step S1, the organic solvent is diethyl ether.

[0016] In some embodiments of the present invention, in step S1, the leaching time is 2h to 20h.

[0017] In some embodiments of the present invention, in step S2, the lithium-containing acid remover is at least one of lithium carbonate or lithium oxide.

[0018] In some embodiments of the present invention, the amount of the deacidifying agent added is 0.5 wt% to 2 wt% of the first filtrate.

[0019] In some preferred embodiments of the present invention, after the first filtrate is treated with a lithium-containing acid-removing agent, a dehydrating agent is also used to remove water from the first filtrate. The dehydrating agent is a lithium-ion molecular sieve, etc. Molecular sieve or At least one of the molecular sieves.

[0020] In some preferred embodiments of the present invention, the dehydrating agent is a lithium-ion molecular sieve. Using a lithium-ion molecular sieve for dehydration can reduce the adsorption of lithium hexafluorophosphate in the molecular sieve and its reaction with water, thus avoiding the loss of lithium hexafluorophosphate recovery.

[0021] In some embodiments of the present invention, in step S2, the distillation process is as follows: first, a first distillation is performed to remove the organic solvent, and then a second distillation is performed to remove the carbonate solvent.

[0022] In some preferred embodiments of the present invention, in step S2, the primary distillation is atmospheric distillation at a temperature of 40°C to 50°C. The primary distillation removes low-boiling-point leaching solvents, such as diethyl ether, tetrahydrofuran, acetone, methanol, or mixtures thereof, at a relatively low temperature, without damaging the electrolyte composition.

[0023] In some preferred embodiments of the present invention, in step S2, the secondary distillation is vacuum distillation, with a pressure of 10–90 kPa and a temperature of 80°C–100°C. The secondary distillation is used to remove the carbonate solvent. Vacuum distillation reduces the distillation temperature and prevents external moisture from entering the system, thus reducing the decomposition of lithium hexafluorophosphate.

[0024] In some embodiments of the present invention, in step S2, the complexing solvent is at least one of acetonitrile, an N-heterocyclic compound, or an O-heterocyclic compound.

[0025] In some preferred embodiments of the present invention, in step S2, the complexing solvent is at least one of acetonitrile, pyridine, or tetrahydrofuran.

[0026] In some preferred embodiments of the present invention, in step S2, the volume ratio of the complexing solvent to the first mother liquor is 1:(8-10). The complexing solvent needs to be used in a certain amount to complex lithium hexafluorophosphate; too little solvent will result in incomplete precipitation of lithium hexafluorophosphate.

[0027] In some embodiments of the present invention, in step S2, the crystallization temperature is 10°C to 20°C and the time is 2h to 6h.

[0028] In some embodiments of the present invention, in step S3, the heating dissociation temperature is 20°C to 60°C, and the time is 6 hours to 10 hours. Excessively high dissociation temperatures and excessively long dissociation times can lead to the decomposition and loss of lithium hexafluorophosphate.

[0029] In some embodiments of the present invention, in step S3, the pressure under reduced pressure is 0–30 kPa. Under reduced pressure, the complex solvent generated by the pyrolysis of the lithium hexafluorophosphate complex is removed in the form of vapor.

[0030] In some embodiments of the present invention, in step S4, the amine compound is at least one selected from triethylamine, tripropylamine, tributylamine, diisopropylethylamine, N,N-dimethylcyclohexylamine, and tetramethylethylenediamine.

[0031] In some preferred embodiments of the present invention, in step S4, the amount of the amine compound or the hydrochloride salt of the amine compound added is 2% to 4% of the volume of the second filtrate.

[0032] In some embodiments of the present invention, after adding an amine compound or the hydrochloride salt of the amine compound to the second filtrate in step S4, the method further includes the following step: stirring at a temperature of 40–80°C for 5–10 hours.

[0033] In some embodiments of the present invention, in step S4, the heating temperature is 80°C to 100°C and the heating time is 4 to 6 hours.

[0034] In some embodiments of the present invention, in step S4, the heating is carried out under reduced pressure, wherein the pressure is 0–90 kPa. Under reduced pressure, the amine compounds produced by solid pyrolysis are removed in the form of vapor.

[0035] In some preferred embodiments of the present invention, step S4 further includes a purification operation of the lithium difluorosulfonylimide solid: dissolving the lithium difluorosulfonylimide solid in acetone, then adding dichloromethane dropwise to the solution to precipitate LiN(SO2F)2, thereby obtaining a lithium difluorosulfonylimide solid with higher purity through solid-liquid separation. Further purification of lithium difluorosulfonylimide can be achieved by completely dissolving the lithium difluorosulfonylimide solid in a good solvent and then adding a poor solvent to precipitate the solid.

[0036] In some preferred embodiments of the present invention, in step S4, the filtration further yields a third filtrate. A mixture of CO2 and HCl is introduced into the third filtrate to obtain crude Li2CO3 precipitate. The third filtrate contains various alkyl lithium carbonates ROCOO-Li, which are formed by the decomposition of solvent carbonates and lithium hexafluorophosphate during battery cycling. The specific reaction formulas are shown in equations (a)-(d) below. The purpose of introducing HCl is to accelerate the separation of carbonate ions and lithium ions (carbonates coordinate with lithium ions, and the introduction of HCl generates carbonic acid, releasing lithium ions), which is beneficial for CO2 gas to precipitate lithium ions to form lithium carbonate.

[0037] In some more preferred embodiments of the present invention, the volume ratio of the mixed gas is CO2:HCl = 1:(0.05-0.25).

[0038]

[0039] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved:

[0040] 1. Freezing spent lithium-ion batteries at low temperatures causes the electrolyte between the positive and negative electrodes to solidify, expanding its volume to increase the gap between the electrodes and the separator. This improves the efficiency of leaching the electrolyte using a solvent after the batteries are broken down. Preferably, the freezing environment is filled with a dry, inert gas to prevent moisture condensation, which could introduce a large amount of water during electrolyte recovery and cause the decomposition of lithium hexafluorophosphate (LiPF6).

[0041] 2. Only perform the cutting and shredding operation on the waste lithium batteries to reduce the thermal decomposition of lithium hexafluorophosphate (LiPF6) during the battery crushing process, control the types of impurities in the solvent, and reduce the difficulty of electrolyte separation and purification.

[0042] 3. Using lithium-containing acid removers such as lithium carbonate or lithium oxide for the acid removal operation of the leaching solution can reduce the amount of hydrofluoric acid in the solution, while also reducing the amount of impurity metal ions introduced by other acid removers, simplifying the recovery process, and improving the recovery purity of the solvent and lithium hexafluorophosphate. Furthermore, since the leaching solution contains a small amount of water, the hydrolysis of lithium hexafluorophosphate on the surface of lithium carbonate and lithium oxide during the acid removal process can adsorb the generated lithium fluoride. The lithium fluoride can then re-lithilate with HN(SO₂F)₂ generated from the hydrolysis of lithium carbonate and lithium oxide to form LiN(SO₂F)₂, reducing the generation of free lithium in the solution.

[0043] 4. Use a complexing solvent to complex lithium hexafluorophosphate in the mother liquor after evaporation. The resulting lithium hexafluorophosphate complex, such as lithium hexafluorophosphate pyridine complex, has low solubility in the solvent. The complexing product can be crystallized at low temperature to form a precipitate. After solid-liquid separation, solvent pyrolysis separation is carried out at a low temperature to achieve high purification of lithium hexafluorophosphate.

[0044] 5. Adding amine compounds to the mother liquor of lithium hexafluorophosphate complex crystallization, tertiary amines (or tertiary amine hydrochloride compounds HCl·NEt3) react with LiN(SO2F)2 to form a solid plastic crystal, LiN(SO2F)2NEt3, which precipitates from the solution. After solid-liquid separation, various organic solutions of alkyl lithium carbonate ROCOO-Li and the solid precipitate LiN(SO2F)2NEt3 are obtained. The solid precipitate LiN(SO2F)2NEt3 is then pyrolyzed under vacuum to obtain pure solid LiN(SO2F)2. LiN(SO2F)2 is currently mainly used as an additive in lithium battery electrolytes. However, due to its excellent conductivity, thermal stability, and electrochemical stability, lithium difluorosulfonylimide can also be used as a novel electrolyte lithium salt. Attached Figure Description

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0046] Figure 1 This is a schematic diagram of the process flow of Embodiment 1 of the present invention;

[0047] Figure 2 The image shows the hydrogen nuclear magnetic resonance spectrum of the lithium hexafluorophosphate pyridine complex prepared in Example 1 of this invention. Detailed Implementation

[0048] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0049] Example 1

[0050] A method for recycling and utilizing waste lithium battery electrolyte, such as Figure 1 As shown, it includes the following steps:

[0051] (1) Freeze the waste lithium-ion batteries at a low temperature of -20℃, and keep the freezing environment filled with dry N2 inert gas;

[0052] (2) After freezing the battery for 8 hours, perform a cutting operation to cut the waste lithium battery into multiple segments;

[0053] (3) The battery shredded material from step (2) is put into the ether solvent for 8 hours of leaching, and then stirred, vibrated and screened to obtain the shredded battery material and the powder-containing solution. The solution is then subjected to solid-liquid separation to obtain the leaching solution and battery powder.

[0054] (4) Use lithium carbonate to remove acid from the leaching solution. The amount of lithium carbonate added is 0.5 wt% of the leaching solution.

[0055] (5) The leaching solution that has undergone acid removal in step (4) is dehydrated by lithium molecular sieve;

[0056] (6) The leaching solution after deacidification and dehydration is distilled once at 50°C for 3 hours to distill off the ether leaching solvent with a lower boiling point.

[0057] (7) Based on step (6), increase the temperature to 80℃ and 50kPa and perform vacuum double distillation for 4 hours to distill off carbonate solvents with higher boiling points.

[0058] (8) Add anhydrous pyridine complexing solvent to the mother liquor of the second distillation to complex lithium hexafluorophosphate. The volume ratio of pyridine complexing solvent to mother liquor is 1:10. After lowering the solution temperature to 20°C, the lithium hexafluorophosphate complex is crystallized and precipitated for 6 hours.

[0059] (9) Solid-liquid separation was performed to obtain lithium hexafluorophosphate pyridine complex solid and lithium hexafluorophosphate crystallization mother liquor. A portion of the lithium hexafluorophosphate pyridine complex solid was subjected to 1H NMR spectroscopy analysis. The lithium hexafluorophosphate pyridine complex was dissociated by incubation at 60℃ and 30kPa for 10h to obtain lithium hexafluorophosphate solid;

[0060] (10) Add 2% triethylamine to the mother liquor of lithium hexafluorophosphate crystallization, stir at 40°C for 10 h, filter and separate to obtain an organic solution containing various alkyl lithium carbonate ROCOO-Li and a solid precipitate of LiN(SO2F)2NEt3.

[0061] (11) The solid precipitate of LiN(SO2F)2NEt3 was pyrolyzed at 10 kPa and heated to 80 °C for 6 h to obtain pure LiN(SO2F)2 solid;

[0062] (12) A mixed gas with a volume ratio of CO2:HCl = 1:0.05 was passed into an organic solution containing various types of alkyl lithium carbonate ROCOO-Li to obtain crude Li2CO3 precipitate.

[0063] The 1H NMR spectrum of lithium hexafluorophosphate pyridine complex is as follows: Figure 2As shown, the intensity ratio of the three strong peaks around 8.00 ppm, 8.50 ppm, and 8.70 ppm is 2:1:2, corresponding to the five H atoms and four types in lithium pyridine hexafluorophosphate, which corresponds to the number of peaks in the figure. The peak at 4.60 ppm is the proton chemical shift characteristic peak of the deuterated solvent D2O, which confirms that the product is lithium pyridine hexafluorophosphate.

[0064] Example 2

[0065] A method for recycling and utilizing waste lithium battery electrolyte includes the following steps:

[0066] (1) Freeze the waste lithium-ion batteries at a low temperature of -78°C, and keep the freezing environment filled with dry N2 inert gas;

[0067] (2) After freezing the battery for 4 hours, perform a cutting operation to cut the waste lithium battery into multiple segments;

[0068] (3) The battery shredded material from step (2) is put into acetone solvent for 8 hours of leaching, and then stirred, vibrated and screened to obtain shredded battery material and a solution containing powder. The solution is then subjected to solid-liquid separation to obtain leaching solution and battery powder.

[0069] (4) Use lithium carbonate to remove acid from the leaching solution. The amount of lithium carbonate added is 1 wt% of the leaching solution.

[0070] (5) The leaching solution that has undergone acid removal in step (4) is dehydrated by lithium molecular sieve;

[0071] (6) The leaching solution after deacidification and dehydration was distilled once at 40°C for 4 hours to distill off the acetone leaching solvent with a lower boiling point.

[0072] (7) Based on step (6), increase the temperature to 100℃ and 10kPa and perform vacuum double distillation for 3 hours to distill off carbonate solvents with higher boiling points.

[0073] (8) Add anhydrous tetrahydrofuran complexing solvent to the mother liquor of the second distillation to complex lithium hexafluorophosphate. The volume ratio of tetrahydrofuran complexing solvent to mother liquor is 1:8. After lowering the solution temperature to 10°C, the lithium hexafluorophosphate complex is crystallized and precipitated for 4 hours.

[0074] (9) Solid-liquid separation was performed to obtain lithium hexafluorophosphate tetrahydrofuran complex solid and lithium hexafluorophosphate crystallization mother liquor. The lithium hexafluorophosphate furan complex was dissociated by keeping it at 40℃ and 10kPa for 8h to obtain lithium hexafluorophosphate solid.

[0075] (10) Add 3% triethylamine to the mother liquor of lithium hexafluorophosphate crystallization, stir at 60°C for 8 hours, filter and separate to obtain an organic solution containing various alkyl lithium carbonate ROCOO-Li and a solid precipitate of LiN(SO2F)2NEt3.

[0076] (11) The solid precipitate of LiN(SO2F)2NEt3 was pyrolyzed at 50 kPa and heated to 90 °C for 5 h to obtain pure solid LiN(SO2F)2.

[0077] (12) A mixed gas with a volume ratio of CO2:HCl = 1:0.15 was introduced into an organic solution containing various types of alkyl lithium carbonate ROCOO-Li to obtain crude Li2CO3 precipitate.

[0078] Example 3

[0079] A method for recycling and utilizing waste lithium battery electrolyte includes the following steps:

[0080] (1) Freeze the waste lithium-ion batteries at a low temperature of -37°C, and keep the freezing environment filled with dry N2 inert gas;

[0081] (2) After freezing the battery for 4 hours, perform a cutting operation to cut the waste lithium battery into multiple segments;

[0082] (3) The battery shredded material from step (2) is put into the ether solvent for 8 hours of leaching, and then stirred, vibrated and screened to obtain the shredded battery material and the powder-containing solution. The solution is then subjected to solid-liquid separation to obtain the leaching solution and battery powder.

[0083] (4) Use lithium carbonate to deacidify the leaching solution, with the amount of lithium carbonate added being 2 wt% of the leaching solution;

[0084] (5) The leaching solution that has undergone acid removal in step (4) is dehydrated by lithium molecular sieve;

[0085] (6) The leaching solution after deacidification and dehydration is distilled once at 40°C for 5 hours to distill off the ether leaching solvent with a lower boiling point.

[0086] (7) Based on step (6), increase the temperature to 90℃ and 30kPa and perform vacuum double distillation for 2 hours to distill off carbonate solvents with higher boiling points;

[0087] (8) Add anhydrous acetonitrile complexing solvent to the mother liquor of the second distillation to complex lithium hexafluorophosphate. The volume ratio of acetonitrile complexing solvent to mother liquor is 1:8. After lowering the solution temperature to 0℃, the lithium hexafluorophosphate complex is crystallized and precipitated for 4h.

[0088] (9) Solid-liquid separation was performed to obtain lithium hexafluorophosphate pyridine complex solid and lithium hexafluorophosphate crystallization mother liquor. The lithium hexafluorophosphate pyridine complex was dissociated by keeping it at 60℃ and 20kPa for 8h to obtain lithium hexafluorophosphate solid.

[0089] (10) Add 4% triethylamine to the mother liquor of lithium hexafluorophosphate crystallization, stir at 80°C for 5 h, filter and separate to obtain an organic solution containing various alkyl lithium carbonate ROCOO-Li and a solid precipitate of LiN(SO2F)2NEt3.

[0090] (11) The solid precipitate of LiN(SO2F)2NEt3 was pyrolyzed at 90 kPa and heated to 100 °C for 4 h to obtain pure solid LiN(SO2F)2.

[0091] (12) A mixed gas with a volume ratio of CO2:HCl = 1:0.25 was passed into an organic solution containing various types of alkyl lithium carbonate ROCOO-Li to obtain crude Li2CO3 precipitate.

[0092] Test case

[0093] 1. The composition ratio of the main impurities in the lithium hexafluorophosphate obtained in Examples 1-3 was detected respectively, and the detection results are shown in Table 1.

[0094] Table 1. Proportion of major impurity components in lithium hexafluorophosphate

[0095] w(moisture) / % w(Ni) / % w(Co) / % w(Mn) / % w(Fe) / % w(Al) / % Example 1 0.002 0.0036 0.0017 0.0012 0.0010 0.0210 Example 2 0.006 0.0056 0.0024 0.0019 0.0015 0.0250 Example 3 0.012 0.0073 0.0031 0.0027 0.0026 0.0330

[0096] As shown in Table 1, the purity of lithium hexafluorophosphate obtained in Example 1 is approximately 99.9695%, the purity of lithium hexafluorophosphate obtained in Example 2 is approximately 99.9576%, and the purity of lithium hexafluorophosphate obtained in Example 3 is approximately 99.9393%, all of which achieved efficient recovery of lithium hexafluorophosphate.

[0097] 2. The purity of lithium difluorosulfonylimide obtained in Examples 1-3 and the proportion of its main impurities were tested respectively. The test results are shown in Table 2.

[0098] Table 2. Purity of lithium bis(fluorosulfonylimide) and percentage of its main impurities

[0099]

[0100] As shown in Table 2, the purity of lithium difluorosulfonylimide prepared in Examples 1-3 is higher than 96%, which effectively realizes the recovery of lithium difluorosulfonylimide.

[0101] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for recycling and utilizing resources of electrolyte of waste lithium battery, characterized in that, The method comprises the following steps: S1: freezing and cutting waste lithium batteries, and then immersing the waste lithium batteries in an organic solvent to obtain a first filtrate and a first residue through solid-liquid separation; S2: treating the first filtrate with a lithium-containing acid-removing agent, and then distilling to obtain a mother liquor and an organic fraction, adding a complexing solvent to the mother liquor to perform complexing, and then performing cooling crystallization and solid-liquid separation to obtain a second filtrate and a second residue; S3: heating and dissociating the second residue under reduced pressure to obtain lithium hexafluorophosphate solid; S4: adding at least one of an amine compound or a hydrochloride salt of the amine compound to the second filtrate, filtering to obtain a third residue, and then heating the third residue to obtain lithium bisfluorosulfonylimide solid. 2.The method for recycling and utilizing waste lithium battery electrolyte according to claim 1, characterized in that, In step S1, the freezing temperature is -210 DEG C to 4 DEG C, and the freezing time is 4 h to 36 h, and the freezing is performed in a dry inert atmosphere.

3. The method for recycling and utilizing resources of waste lithium battery electrolyte according to claim 1, characterized in that, In step S1, the organic solvent is at least one of diethyl ether, acetonitrile, tetrahydrofuran, acetone or methanol. 4.The method for recycling and utilizing waste lithium battery electrolyte according to claim 1, characterized in that, In step S2, the lithium-containing acid-removing agent is at least one of lithium carbonate or lithium oxide.

5. The method for recycling and utilizing resources of waste lithium battery electrolyte according to claim 1, characterized in that, In step S2, the distillation process is: first, one-time distillation is performed to distill out the organic solvent, and then two-time distillation is performed to distill out the carbonate solvent. 6.The method for recycling and utilizing waste lithium battery electrolyte according to claim 1, characterized in that, In step S2, the complexing solvent is at least one of acetonitrile, an N-heterocyclic compound or an O-heterocyclic compound.

7. The method for recycling and utilizing resources of waste lithium battery electrolyte according to claim 1, characterized in that, In step S2, the crystallization temperature is 10 DEG C to 20 DEG C, and the crystallization time is 2 h to 6 h. 8.The method of recycling and utilizing resources of waste lithium battery electrolyte according to claim 1, characterized in that, In step S3, the heating and dissociation temperature is 20 DEG C to 60 DEG C, and the heating and dissociation time is 6 h to 10 h. 9.The method of recycling and utilizing waste lithium battery electrolyte according to claim 1, characterized in that, In step S4, the amine compound is at least one of triethylamine, tripropylamine, tributylamine, diisopropyl ethylamine, N, N-dimethylcyclohexylamine or tetramethyl ethylenediamine. 10.The method of recycling and utilizing waste lithium battery electrolyte according to claim 1, characterized in that, In step S4, the heating temperature is 80 DEG C to 100 DEG C, and the heating time is 4 h to 6 h.

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