A method and product for preparing lithium salt materials from spent lithium batteries

Abstract

This application pertains to the field of lithium-ion battery recycling, specifically disclosing a method and product for preparing lithium salt materials from spent lithium batteries. The method includes the following steps: S1. Extracting active lithium from the negative electrode of spent lithium batteries using an aromatic compound solution to obtain an aromatic-active lithium composite solution; wherein the aromatic compound is C6-C6. 30 The process involves: S1. A benzene ring aromatic hydrocarbon or a heterocyclic aromatic hydrocarbon containing at least one benzene ring, wherein the concentration of the aromatic hydrocarbon solution is 0.2 M to 4 M; S2. Mixing the aromatic hydrocarbon-active lithium composite solution with a lithium salt precursor and subjecting it to a redox reaction to obtain the lithium salt material; wherein the molar mass of the active component in the lithium salt precursor is 1 to 1.3 times that of the active lithium in the aromatic hydrocarbon-active lithium composite. This application recovers lithium resources from retired lithium batteries and directly synthesizes various lithium salts through chemical reactions, which has the advantages of simple process, low energy consumption, and low environmental pollution.

Description

Technical Field

[0001] This application pertains to the field of lithium-ion battery recycling, and more specifically, relates to a method for preparing lithium salt materials using waste lithium batteries. Background Technology

[0002] Lithium-ion batteries, as the core energy storage devices in modern portable electronic devices, electric vehicles, and energy storage systems, are widely used in various fields due to their advantages such as high energy density, long cycle life, and low self-discharge rate. However, the limited service life of lithium-ion batteries has led to the recycling problem of a large number of retired batteries. How to effectively handle these retired batteries is a significant challenge to achieving the sustainable development of lithium resources.

[0003] Electrolytes are a core component of lithium-ion batteries, and lithium salts (LiPF6, LiFSI, LiTFSI, LiDFOB, LiOTf, etc.) have significant advantages in improving battery conductivity, stability, and safety, playing a crucial role in the normal operation of batteries. However, the scarcity of lithium resources and the high cost of mining limit the large-scale application and development of lithium salts. Waste lithium-ion batteries contain a large amount of lithium resources. How to extract pure lithium metal or lithium-containing compounds through efficient recycling technologies and reuse them to prepare key lithium salts such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is a key challenge. This would not only help reduce the production cost of lithium salts and decrease dependence on new lithium resources, but also significantly reduce the environmental pollution caused by waste batteries, promoting the sustainable development of the lithium-ion battery industry.

[0004] Patent document CN113061726A discloses a safe and efficient method for recycling lithium, which involves leaching lithium from spent lithium batteries using an organic solution containing aromatic hydrocarbons, and then using the leached lithium for pre-lithiation of the negative electrode in lithium-ion batteries. However, this method can only be used for lithium replenishment and cannot be used for lithium battery production, thus limiting its application scope.

[0005] Patent document CN 115232033 A discloses a method for preparing lithium bis(trifluoromethanesulfonyl)imide, characterized by obtaining a high-purity aqueous solution of bis(trifluoromethanesulfonyl)imide through chlorination, amination, acidification, and distillation of sodium trifluoromethanesulfonate, followed by neutralization reaction with an alkaline lithium source to obtain lithium bis(trifluoromethanesulfonyl)imide. Patent document CN 112142628 A discloses a method for preparing lithium bis(trifluoromethanesulfonyl)imide, characterized by neutralizing trifluoromethanesulfonamide with an alkali metal lithium salt to obtain trifluoromethanesulfonamide lithium salt. These patented technologies all require the use of expensive alkali metal lithium salts as lithium raw materials, resulting in high production costs. Furthermore, the synthesis process involves pH control, multi-step temperature control, long preparation time, and complex synthesis steps, ultimately leading to limited yield and purity of the obtained lithium salt product. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to reduce the cost of lithium salt synthesis and simplify the synthesis process by directly synthesizing multifunctional lithium salt materials from recycled lithium batteries, thereby achieving more efficient and high-value applications. This application aims to develop a simple and efficient method for recycling lithium resources from retired batteries.

[0007] To achieve the above objectives, a method for preparing lithium salt materials using spent lithium batteries includes the following steps:

[0008] S1. Using an aromatic compound solution, active lithium is extracted from the negative electrode of a spent lithium battery to obtain an aromatic-active lithium complex solution; wherein the aromatic compound is C6-C6. 30 The aromatic hydrocarbon is a benzene ring aromatic hydrocarbon or a heterocyclic aromatic hydrocarbon containing at least one benzene ring, wherein the concentration of the aromatic hydrocarbon compound solution is 0.2 M to 4 M;

[0009] S2. A solution of the aromatic hydrocarbon-active lithium complex is thoroughly mixed with a lithium salt precursor, and a redox reaction is carried out to obtain the lithium salt material; the molar mass of active lithium in the aromatic hydrocarbon-active lithium complex is 1 to 1.3 times that of the effective component in the lithium salt precursor, and the lithium salt precursor is an electrolyte lithium salt precursor or a functional lithium salt precursor; the electrolyte lithium salt precursor is one or more of bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, trifluoromethanesulfonic acid, difluorophosphoric acid, difluorooxalateboronic acid, dioxalateboronic acid, trifluoromethanesulfonamide, bis(trifluoromethanesulfinyl)imide, trifluoromethanesulfonyl chloride, trifluoromethanesulfinyl chloride, tetrafluoroboronic acid, phosphorus pentafluoride, or hexafluorophosphoric acid; the functional lithium salt precursor is one or more of oxalic acid, squaric acid, acetic acid, hydrochloric acid, sulfuric acid, nitric acid, hydrogen halide, formic acid, benzoic acid, 3,4-dihydroxybenzonitrile, or ammonia.

[0010] Preferably, in step S1, the aromatic compound has 10-20 carbon atoms.

[0011] As a further preferred embodiment, in step S1, the aromatic compound is one or more of biphenyl, naphthalene, phenanthrene, anthracene, tetraphenylene, pyrene, perylene, pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, or phenothiazine.

[0012] As a further preferred embodiment, in step S1, the solvent for the aromatic compound solution is an ether-based organic solvent.

[0013] As a further preferred embodiment, in step S1, the ether organic solvent is one or more of ethylene glycol dimethyl ether, tetrahydrofuran, or 2-methyltetrahydrofuran.

[0014] Preferably, in step S1, the mass ratio of the aromatic compound solution to the lithium battery negative electrode is (1~5):1.

[0015] Preferably, in step S1, the extraction time is 0.2h to 10h, and the extraction temperature is 0℃ to 80℃.

[0016] Preferably, in step S2, the concentrations of hydrochloric acid, sulfuric acid, and nitric acid are less than 10 wt%.

[0017] Preferably, in step S2, the molar mass of active lithium in the aromatic hydrocarbon-active lithium complex is 1 to 1.05 times that of the effective component in the lithium salt precursor.

[0018] Preferably, the reaction time in step S2 is 1 hour to 6 hours.

[0019] Preferably, after step S2, the process further includes the extraction, cleaning, and impurity removal of the lithium salt material.

[0020] As a further preferred embodiment, the extraction is performed by first removing the solvent by vacuum distillation, then removing the remaining aromatic compounds by washing with deionized water, and then removing the deionized water by vacuum distillation once more.

[0021] As a further preferred embodiment, the cleaning process involves dispersing the lithium salt material in a weakly polar organic solvent with a polarity less than 6 and then stirring and cleaning it. As an even more preferred embodiment, the weakly polar organic solvent has a polarity less than 4. As an even more preferred embodiment, the weakly polar organic solvent is one or more of dichloromethane, n-hexane, cyclohexane, or toluene.

[0022] As a further preferred embodiment, the impurity removal is performed by removing impurities from the lithium salt material using a linear carbonate organic solvent; as an even more preferred embodiment, the linear carbonate organic solvent is one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, etc.

[0023] Another objective of this application is to provide a method for recovering lithium resources from spent lithium batteries using the above-described method, for use in preparing high-purity electrolyte lithium salts.

[0024] Overall, compared with the prior art, the technical solution conceived in this application realizes a method for recycling and reusing active lithium from retired lithium-ion batteries, and mainly possesses the following technical advantages:

[0025] 1. This application directly recovers lithium resources from retired lithium batteries, with a simple process, low energy consumption and minimal environmental pollution; by using different organic lithium salt precursors, various different lithium salts can be synthesized through chemical reactions;

[0026] 2. Compared with the prior art, this application extracts active lithium from the negative electrode of waste lithium battery in one step. Since the lithium-containing solution recovered by one step has high purity and reactivity, it can be used to directly synthesize lithium salt materials. It has been verified that the purity of the synthesized lithium salt materials exceeds 99.5%, which can effectively realize the efficient recycling of lithium resources.

[0027] 3. This application can be operated entirely at room temperature, without the need for other auxiliary processes, and the reaction conditions are mild;

[0028] 4. This application avoids using alkali metal inorganic lithium salts or metallic lithium as lithium sources, which are costly and have complex preparation processes. It recovers lithium resources from retired lithium batteries and directly synthesizes a variety of different lithium salts through chemical reactions. It has the advantages of high utilization rate of waste resources, simple process, high economic benefits and environmental friendliness. Attached Figure Description

[0029] Figure 1 LiTFSI NMR synthesized in Example 1 of this application 19 F-spectrum;

[0030] Figure 2 The LiTFSI XRD pattern synthesized in Example 1 of this application;

[0031] Figure 3 Charge-discharge curves of the electrolyte prepared for battery testing in Example 2 of this application;

[0032] Figure 4 Cycling curves of the electrolyte prepared for battery testing in Example 2 of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0034] Furthermore, throughout this specification, references to "an embodiment"; "an embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. Therefore, the appearance of the phrase "in one embodiment;" throughout this specification, and similar language, may, but not necessarily, refer to the same embodiment.

[0035] This application provides a method for preparing lithium salt materials using waste lithium batteries, which can be used to prepare high-purity lithium salts. The method includes the following steps:

[0036] S1. The retired lithium battery (capacity decayed to below 80%) is pretreated by constant current / constant voltage charging to embed lithium into the negative electrode material; then the pretreated retired lithium battery is disassembled and the negative electrode is separated in an inert environment;

[0037] Under conditions of 0℃ to 80℃, the lithium battery negative electrode is thoroughly immersed in an aromatic compound solution of 1 to 5 times its mass for 0.2 h to 10 h. The lithium battery negative electrode is then separated to obtain a solution of a reactive aromatic-active lithium complex. The concentration of the aromatic compound solution is 0.2 M to 4 M, and the aromatic compound is C6-C. 30 (C is preferred) 10 -C 20 The aromatic hydrocarbon is a benzene ring aromatic hydrocarbon or a heterocyclic aromatic hydrocarbon containing at least one benzene ring. The number of carbon atoms in the aromatic hydrocarbon compound is 10-20, such as biphenyl, naphthalene, phenanthrene, anthracene, tetraphenyl, pyrene, perylene, pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, or phenothiazine, etc.; the solvent of the aromatic hydrocarbon compound solution is an ether organic solvent, such as ethylene glycol dimethyl ether, tetrahydrofuran, or 2-methyltetrahydrofuran, etc.

[0038] S2. Under conditions of 0℃~40℃, the solution of the aromatic hydrocarbon-active lithium complex is thoroughly mixed with the lithium salt precursor. Since the active lithium in the aromatic hydrocarbon-active lithium complex has strong reducing properties, and hydrogen protons have high electron affinity, they preferentially donate electrons to hydrogen ions to generate hydrogen gas. Thus, the lithium salt precursor and the active lithium in the aromatic hydrocarbon-active lithium complex undergo a coordination reaction to generate crude lithium salt. During the reaction, stirring, ultrasound, or other conditions can be used to increase the rate of complete reaction. The molar mass of active lithium should be slightly excess compared to the organolithium salt precursor. The molar mass of active lithium can be determined first through elemental analysis, and then the mass of the organolithium salt precursor to be added can be determined. The molar mass of active lithium in the aromatic hydrocarbon-active lithium complex is 1~1.3 times that of the effective component in the lithium salt precursor; considering reagent conservation, it can be set to 1~1.05 times.

[0039] The lithium salt precursor is an electrolyte lithium salt precursor or a functional lithium salt precursor; the electrolyte lithium salt precursor is one or more of the following: bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, trifluoromethanesulfonic acid, difluorophosphoric acid, difluorooxalate boric acid, dioxalate boric acid, trifluoromethanesulfonamide, bis(trifluoromethanesulfinyl)imide, trifluoromethanesulfonyl chloride, trifluoromethanesulfinyl chloride, tetrafluoroboric acid, phosphorus pentafluoride, or hexafluorophosphoric acid; the functional lithium salt precursor is oxalic acid, squaric acid, acetic acid, hydrochloric acid, sulfuric acid, nitric acid, hydrogen halide, formic acid, benzoic acid, or 3,4-dihydroxy... The lithium salt precursor is one or more of benzonitrile or ammonia. When the lithium salt precursor is an electrolyte lithium salt precursor, the active ingredient refers to the precursor itself. When the lithium salt precursor is a functional lithium salt precursor, the active ingredient refers to the component that can react with active lithium, such as sulfuric acid, nitric acid, oxalic acid, and squaric acid. The active ingredient refers to the amount of hydrogen ions after complete ionization. The active ingredient of 3,4-dihydroxybenzonitrile refers to the amount of hydroxyl groups. When the lithium salt precursor is hydrochloric acid, sulfuric acid, or nitric acid, its concentration should be less than 10 wt% to avoid an overly vigorous reaction.

[0040] The method of mixing the aromatic hydrocarbon-active lithium complex solution with the lithium salt precursor depends on the state of the lithium salt precursor. For example, when the lithium salt precursor is solid or liquid, the aromatic hydrocarbon-active lithium complex solution can be added to the lithium salt precursor, while when the lithium salt precursor is gas, the lithium salt precursor can be passed into the aromatic hydrocarbon-active lithium complex solution to react.

[0041] S3. The crude lithium salt is extracted, washed, impurity removed, and purified to obtain high-purity lithium salt, the specific process of which is as follows:

[0042] S31. The solvent is removed by vacuum distillation to obtain a solid mixture of lithium salt, the remaining aromatic compounds from the reaction, and other impurities; the solid mixture is thoroughly mixed with deionized water so that the lithium salt dissolves in the deionized water, while the remaining aromatic compounds from the reaction cannot dissolve in the water; after filtration and separation, a lithium salt solution is obtained; the water in the lithium salt solution is removed again by vacuum distillation to obtain solid lithium salt.

[0043] S32. The lithium salt solid is stirred and washed in a weakly polar organic solvent to further remove organic impurities from the lithium salt solid; the polarity of the weakly polar organic solvent is generally less than 6, and preferably less than 4, for example, dichloromethane, n-hexane, cyclohexane or toluene can be used.

[0044] S33. The lithium salt solid is purified and refined using linear carbonate organic solvents (such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, etc.). Inorganic salts and other insoluble substances are removed by filtration, and high-purity lithium salt materials are finally obtained through vacuum distillation and vacuum drying. The applications of the prepared lithium salt materials vary depending on the lithium salt precursor; lithium salt materials prepared from electrolyte lithium salt precursors are mainly used as electrolytes in lithium batteries; lithium salt materials prepared from functional lithium salt precursors have a wider range of applications.

[0045] The following are examples.

[0046] Example 1

[0047] I. Pretreatment of retired lithium batteries and lithium resource recycling

[0048] S1. The retired lithium iron phosphate batteries, whose capacity has decayed to below 80%, are charged with a low-current constant current to 4.3V. Charging is stopped once the voltage stabilizes. The pre-treated batteries are disassembled in an environment with controlled relative humidity to separate the lithium-intercalated negative electrode material, which is then transferred to an inert atmosphere for later use.

[0049] S2. Prepare a lithium extraction solution using polycyclic aromatic hydrocarbon reagents. Weigh 404.5 g of pyrene reagent and 2000 mL of ethylene glycol dimethyl ether solvent (DME) into a reaction vessel. Stir at room temperature (RT) until the pyrene reagent is completely dissolved to form a transparent solution, thus obtaining an aromatic compound solution for lithium extraction.

[0050] S3. The lithium-intercalated anode material is cut and crushed, then immersed in an aromatic compound solution for lithium extraction. The solution is stirred at room temperature for 2-8 hours to leach out the lithium from the anode material. The lithium reacts fully with the pyrene reagent and is extracted. The solution is then allowed to settle and filtered to obtain a recovered lithium-containing solution for later use.

[0051] The reaction equation is as follows:

[0052]

[0053] II. Recycling of lithium-containing solutions into direct high-purity lithium salts

[0054] S4. The lithium content in the lithium-containing solution was tested by elemental analysis. The lithium-containing solution was gradually added to the bis(trifluoromethanesulfonyl)imide powder at a molar ratio of lithium to lithium salt precursor of 1.05:1. The mixture was stirred for 4 hours to obtain a mixed solution. During this process, the bis(trifluoromethanesulfonyl)imide precursor generated lithium bis(trifluoromethanesulfonyl)imide through a spontaneous redox reaction at room temperature.

[0055] The reaction equation is as follows:

[0056]

[0057] S5. The solvent in the above solution is removed by vacuum distillation to obtain a solid mixture of organic compounds such as lithium bis(trifluoromethanesulfonylimide) and pyrene.

[0058] S6. Dissolve the solid mixture in deionized water and stir for 1 hour. Since highly polar water readily dissolves lithium bis(trifluoromethanesulfonyl)imide, while having extremely low solubility for low-polarity polycyclic aromatic hydrocarbons such as pyrene, the lithium salt in the solid mixture can be extracted efficiently. Filter to separate an aqueous solution containing lithium bis(trifluoromethanesulfonyl)imide and water-insoluble organic solids such as pyrene. Then, remove the water from the lithium salt-containing solution by vacuum distillation to obtain the crude lithium bis(trifluoromethanesulfonyl)imide solid.

[0059] The crude lithium bis(trifluoromethanesulfonyl)imide solid was dissolved in weakly polar dichloromethane and stirred and washed repeatedly to remove pyrene and other organic impurities from the crude lithium salt. The washed lithium bis(trifluoromethanesulfonyl)imide was then obtained by filtration and separation.

[0060] Then, lithium salt is dissolved in dimethyl carbonate for impurity removal and purification. Inorganic salts and other insoluble substances are removed by filtration. Finally, high-purity lithium bis(trifluoromethanesulfonyl)imide is obtained by vacuum distillation and vacuum drying.

[0061] NMR of the high-purity LiTFSI sample synthesized in Example 1 of this application 19 F-plots and XRD plots, as follows Figure 1 and Figure 2 As shown in the results, the synthesized LiTFSI contains no other impurity peaks, indicating that a high-purity LiTFSI sample has been prepared. The purity of the synthesized LiTFSI was tested and found to be above 99.5%.

[0062] Example 2

[0063] Repeat Example 1 using the same steps, except that the solvent used for cleaning in step S6 is n-hexane.

[0064] Example 3

[0065] Repeat Example 1 using the same steps, except that the solvent used for cleaning in step S6 is cyclohexane.

[0066] Example 4

[0067] The same steps as described in Example 1 were repeated, except that the solvent used for impurity removal and purification in step S6 was diethyl carbonate.

[0068] Example 5

[0069] The same steps as described in Example 1 were repeated, except that the solvent used for impurity removal and purification in step S6 was ethyl methyl carbonate.

[0070] Example 6

[0071] Example 1 was repeated using the same steps, except that the lithium salt precursor in step S5 was bis(fluorosulfonyl)imide, and lithium bis(fluorosulfonyl)imide (LIFSI) was prepared in step S6.

[0072] Example 7

[0073] Example 1 was repeated with the same steps, except that the lithium salt precursor in step S5 was bis(fluorosulfonyl)imide and the solvent used for cleaning in step S6 was n-hexane, to prepare lithium bis(fluorosulfonyl)imide (LIFSI).

[0074] Example 8

[0075] Example 1 was repeated with the same steps, except that the lithium salt precursor in step S5 was bis(fluorosulfonyl)imide and the solvent used for cleaning in step S6 was cyclohexane, in order to prepare lithium bis(fluorosulfonyl)imide (LIFSI).

[0076] Example 9

[0077] Example 1 was repeated using the same steps, except that the lithium salt precursor in step S5 was bis(fluorosulfonyl)imide, and the solvent used for impurity removal and purification in step S6 was diethyl carbonate, to prepare lithium bis(fluorosulfonyl)imide (LIFSI).

[0078] Example 10

[0079] The same steps as described in Example 1 were repeated, except that the lithium salt precursor in step S5 was trifluoromethanesulfonic acid, and lithium trifluoromethanesulfonate (LiOTf) was prepared in step S6.

[0080] Example 11

[0081] The same steps as described in Example 1 were repeated, except that the lithium salt precursor in step S5 was trifluoromethanesulfonic acid and the solvent used for cleaning in step S6 was n-hexane, in order to prepare lithium trifluoromethanesulfonate (LiOTf).

[0082] Example 12

[0083] Example 1 was repeated with the same steps, except that the lithium salt precursor in step S5 was trifluoromethanesulfonic acid and the solvent used for cleaning in step S6 was cyclohexane, in order to prepare lithium trifluoromethanesulfonate (LiOTf).

[0084] Example 13

[0085] Example 1 was repeated with the same steps, except that the lithium salt precursor in step S5 was trifluoromethanesulfonic acid and the solvent used for impurity removal and purification in step S6 was diethyl carbonate, in order to prepare lithium trifluoromethanesulfonate (LiOTf).

[0086] Example 14

[0087] The same steps as described in Example 1 were repeated, except that the lithium salt precursor in step S5 was difluorophosphoric acid, and lithium difluorophosphate (LFP) was prepared in step S6.

[0088] Example 15

[0089] Example 1 was repeated using the same steps, except that the lithium salt precursor in step S5 was difluorophosphoric acid and the solvent used for cleaning in step S6 was n-hexane, in order to prepare lithium difluorophosphate (LFP).

[0090] Example 16

[0091] Example 1 was repeated with the same steps, except that the lithium salt precursor in step S5 was difluorooxalate boric acid, and lithium difluorooxalate borate (LiDFOB) was prepared in step S6.

[0092] Example 17

[0093] Example 1 was repeated with the same steps, except that the lithium salt precursor in step S5 was difluorooxalate boric acid, and the solvent used for cleaning in step S6 was n-hexane, to prepare lithium difluorooxalate boric acid (LiDFOB).

[0094] Example 18

[0095] Example 1 was repeated using the same steps, except that the lithium salt precursor in step S5 was bis(oxalate-boronic acid), and lithium bis(oxalate-boronic acid) (LiBOB) was prepared in step S6.

[0096] Example 19

[0097] Example 1 was repeated using the same steps, except that the lithium salt precursor in step S5 was dioxaloric acid borate, and the solvent used for cleaning in step S6 was n-hexane, to prepare lithium dioxaloric acid borate (LiBOB).

[0098] Verification example: electrolyte preparation and electrochemical performance testing

[0099] The high-purity lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) obtained in Examples 1-19 was used to prepare a conventional carbonate electrolyte (specifically, LiTFSI was dissolved in an EC / EMC solution with a volume ratio of 3:7 to obtain a 1 mol / L LiTFSI solution), and the properties of LiTFSI were evaluated by measuring the electrochemical performance of the electrolyte through conductivity testing.

[0100] Table 1 shows the high-purity lithium salts synthesized in Examples 1-19 by adjusting parameters such as the type of lithium salt precursor, the type of cleaning solvent, and the type of impurity removal and purification solvent. The yield of lithium salts obtained in different examples was also tested.

[0101] Table 1. Experimental parameters and yields of synthesized low-crystallinity lithium sulfide in Examples 1-19

[0102]

[0103] The high-purity LiTFSI electrolyte synthesized in Example 2 of this application was used in a lithium iron phosphate coin cell, and its charge-discharge curves and cycle performance are as follows: Figure 3 and Figure 4 As shown in the figure, the synthesized LiTFSI electrolyte can function normally, and after 100 cycles at 0.5C, the capacity retention rate is 98% of the initial specific capacity. Other examples also exhibit similar charge-discharge curves and cycling performance. These results indicate that the synthesized lithium salt electrolyte possesses excellent electrochemical performance.

[0104] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing lithium salt materials using spent lithium batteries, characterized in that: Includes the following steps: S1. Using an aromatic compound solution with a concentration of 0.2 M to 4 M, active lithium is extracted from the negative electrode of a spent lithium battery to obtain an aromatic-active lithium complex solution; wherein the aromatic compound is C6-C6. 30 Benzene ring aromatic hydrocarbons or heterocyclic aromatic hydrocarbons containing at least one benzene ring; S2. The solution of the aromatic hydrocarbon-active lithium complex is thoroughly mixed with the lithium salt precursor, and a redox reaction is carried out to obtain the lithium salt material; the molar mass of active lithium in the aromatic hydrocarbon-active lithium complex is 1 to 1.3 times that of the effective component in the lithium salt precursor, and the lithium salt precursor is one or more of the following: bis(fluorosulfonyl)imide, bis(trifluoromethanesulfonyl)imide, trifluoromethanesulfonic acid, difluorophosphoric acid, difluorooxalateboronic acid, dioxalateboronic acid, trifluoromethanesulfonamide, bis(trifluoromethanesulfinyl)imide, trifluoromethanesulfonyl chloride, trifluoromethanesulfinyl chloride, tetrafluoroboronic acid, phosphorus pentafluoride, hexafluorophosphoric acid, oxalic acid, squaric acid, acetic acid, hydrochloric acid, sulfuric acid, nitric acid, hydrogen halide, formic acid, benzoic acid, 3,4-dihydroxybenzonitrile, or ammonia.

2. The method as described in claim 1, characterized in that: In step S1, the aromatic compound is one or more of biphenyl, naphthalene, phenanthrene, anthracene, tetraphenyl, pyrene, perylene, pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, or phenothiazine.

3. The method as described in claim 2, characterized in that: In step S1, the solvent for the aromatic compound solution is an ether-based organic solvent.

4. The method as described in claim 1, characterized in that: In step S1, the mass ratio of the aromatic compound solution to the lithium battery negative electrode is (1~5):

1.

5. The method as described in claim 1, characterized in that: In step S2, the concentrations of hydrochloric acid, sulfuric acid, and nitric acid are less than 10 wt%.

6. The method as described in claim 1, characterized in that: In step S2, the molar mass of active lithium in the aromatic hydrocarbon-active lithium complex is 1 to 1.05 times that of the effective component in the lithium salt precursor.

7. The method as described in claim 1, characterized in that: After step S2, the process also includes the extraction, cleaning, and impurity removal of the lithium salt material.

8. The method as described in claim 7, characterized in that: The cleaning process uses an organic solvent with a polarity of less than 6.

9. The method as described in claim 7, characterized in that: The impurity removal process uses a linear carbonate solvent, which is one or more of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

10. A lithium salt material prepared by the method according to any one of claims 1-9.

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