Method for recycling lithium salt in electrolyte and application

Abstract

The invention discloses a method for recycling a lithium salt in an electrolyte and application, and the method comprises the following steps: mixing the electrolyte of a waste battery with a carbonic ester solvent and an epoxy ether additive, and carrying out a reaction to generate a gelatinous substance; and taking out the gelatinous substance, dissolving the gelatinous substance in an ether solvent, drying and evaporating to obtain the sulfimide lithium salt. According to the method, the sulfonimide lithium salt is effectively recycled, the recycling process is simple, operation is easy, the recycling rate is high, and the recycling rate of the sulfonimide lithium salt reaches 80% or above. In addition, the purity of the recycled lithium sulfonimide salt is greater than 98%, and the chemical analysis purity is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of recycling waste batteries, and in particular to a method and use of recycling lithium salts in electrolyte. Background Art

[0002] With the rapid development of industries such as electric vehicles and energy storage systems, the demand for lithium-ion batteries is increasing, and with it comes the problem of handling a large number of waste lithium-ion batteries. The main components of lithium-ion batteries include positive electrode materials, negative electrode materials, electrolytes, and diaphragms. The electrolyte contains a large amount of organic solvents and lithium salts. If these substances are directly discharged into the environment, they will cause serious pollution to the environment. And there are lithium salts with high recycling value in the electrolyte. With the current market's pursuit of battery fast charging and high temperature stability and other performance, the use of sulfonyl imide lithium salts is increasing. And the price of sulfonyl imide lithium salts is relatively expensive. Therefore, how to effectively recycle sulfonyl imide lithium salts in waste lithium-ion batteries has become an important topic in the field of battery recycling.

[0003] The existing methods for recycling sulfonyl imide lithium salts mainly include obtaining electrolyte by freezing with liquid nitrogen or other freezing methods, collecting the frozen electrolyte, melting it to form a liquid, and then distilling it to obtain recyclable components. Alternatively, the electrolyte gas is collected by high-temperature gasification to achieve the processing and recycling of lithium salts.

[0004] The above recovery method has the following disadvantages: 1) The above method has complicated steps, low recovery rate, and it is difficult to completely extract the lithium salt of the electrolyte by freezing the electrolyte. 2) If gasified, PF5 is toxic, and if leaked, it will cause great safety hazards. 3) The lithium salt is extracted using a solution with strong binding ability with lithium ions. Since this type of solvent has strong binding ability with lithium salts, it is difficult to remove the solvent later, and this highly polar solvent is very toxic. Most importantly, the above recovery method cannot recover the sulfonyl imide lithium salt in the electrolyte. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the present application is to propose a method and use for recovering lithium salts in electrolytes. The present application effectively realizes the recovery of sulfonyl imide lithium salts, and the recovery process is simple, easy to operate, and has a high recovery rate. The recovery rate of sulfonyl imide lithium salts reaches more than 80%. In addition, the purity of the recovered sulfonyl imide lithium salt is greater than 98%, reaching the chemical analysis purity.

[0006] In one aspect of the present application, the present application proposes a method for recovering lithium salt in an electrolyte. According to an embodiment of the present application, the method comprises:

[0007] The electrolyte of the waste battery is mixed with a carbonate solvent and an epoxy ether additive to react and generate a colloid substance;

[0008] The colloid substance is taken out, dissolved in an ether solvent, dried and evaporated to obtain sulfonyl imide lithium salt.

[0009] According to the method for recovering lithium salt in electrolyte of the embodiment of the present application, the electrolyte of the waste battery is mixed with carbonate solvent and epoxy ether additive, and the acidity of the waste battery electrolyte is used to catalyze the ring opening of the epoxy ether additive, and polymerize with the sulfonyl imide lithium salt in the electrolyte to form a colloidal substance. The high viscosity of the polymer product can be used to extract the sulfonyl imide lithium salt in the electrolyte of the waste battery more thoroughly, and convert it from a volatile liquid state into a colloidal substance, greatly improving the recovery rate of the sulfonyl imide lithium salt. The present application effectively realizes the recovery of the sulfonyl imide lithium salt, and the recovery process is simple, easy to operate, and has a high recovery rate. The loss of the sulfonyl imide lithium salt recovered by the method of the present application only exists in the cleaning stage, and the recovery rate of the sulfonyl imide lithium salt reaches more than 80%. In addition, the purity of the recovered sulfonyl imide lithium salt is greater than 98%, reaching the chemical analysis purity.

[0010] In addition, the method for recovering lithium salt in the electrolyte according to the above embodiment of the present application may also have the following additional technical features:

[0011] In some embodiments of the present application, the mixing of the electrolyte of the waste battery with the carbonate solvent and the epoxy ether additive comprises: immersing the battery cell of the waste battery in a mixture of the carbonate solvent and the epoxy ether additive.

[0012] In some embodiments of the present application, the battery cells of the waste battery are immersed in a mixture of the carbonate solvent and the epoxy ether additive for 1 hour to 2.5 hours; and / or, before immersing the battery cells of the waste battery in the mixture of the carbonate solvent and the epoxy ether additive, it also includes: discharging the waste battery to a lower limit voltage.

[0013] In some embodiments of the present application, the pH value range of the electrolyte of the waste battery is 1≤pH<7; and / or the volume ratio of the carbonate solvent to the epoxy ether additive is (1:10) to (10:1).

[0014] In some embodiments of the present application, the carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate and propylene carbonate; and / or, the epoxy ether additive includes at least one of a ternary epoxy ether additive, a pentacyclic epoxy ether additive and a heptatic epoxy ether additive.

[0015] In some embodiments of the present application, the ternary epoxy ether additive includes at least one of ethylene oxide, propylene oxide, and 1,4-butylene oxide; and / or the pentacyclic epoxy ether additive includes at least one of tetrahydrofuran, 1,3-dioxolane, epichlorohydrin, and cyclopentane.

[0016] In some embodiments of the present application, before dissolving the colloid substance in the ether solvent, the process further includes: washing the colloid substance with a solvent.

[0017] In some embodiments of the present application, the colloidal substance is immersed in the ether solvent for 1 h to 2.5 h so that the colloidal substance is dissolved in the ether solvent; and / or the ether solvent includes at least one of isopropyl ether and ethylene glycol butyl ether.

[0018] In some embodiments of the present application, the sulfonyl imide lithium salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

[0019] In the second aspect of the present application, the present application proposes a method for recovering lithium salt in electrolyte according to the above embodiment for use in recycling waste lithium-ion batteries, thereby effectively realizing the recycling and reuse of sulfonyl imide lithium salt and saving costs.

[0020] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0022] Figure 1 Schematic diagram of the process of recovering lithium salt in electrolyte according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0024] In one aspect of the present application, the present application proposes a method for recovering lithium salt in an electrolyte, see the attached Figure 1According to an embodiment of the present application, the method comprises: mixing the electrolyte of the waste battery with a carbonate solvent and an epoxy ether additive, reacting to generate a colloidal substance; taking out the colloidal substance, dissolving the colloidal substance in an ether solvent, drying and evaporating, and obtaining a sulfonyl imide lithium salt. The following is a detailed description of the beneficial effects that can be achieved by the method for recovering lithium salts in electrolytes proposed in the present application:

[0025] The present application mixes the electrolyte of waste batteries with carbonate solvents and epoxy ether additives, utilizes the acidity of the waste battery electrolyte itself, catalyzes the ring opening of the epoxy ether additive, and polymerizes with the sulfonyl imide lithium salt in the electrolyte to form a colloidal substance. The high viscosity of the polymer product can be used to more thoroughly extract the sulfonyl imide lithium salt in the waste battery electrolyte, and convert it from a volatile liquid state into a colloidal substance, greatly improving the recovery rate of the sulfonyl imide lithium salt. The present application effectively realizes the recovery of the sulfonyl imide lithium salt, and the recovery process is simple, easy to operate, and has a high recovery rate. The loss of the sulfonyl imide lithium salt recovered by the method of the present application only occurs in the cleaning stage, and the recovery rate of the sulfonyl imide lithium salt reaches more than 80%. In addition, the purity of the recovered sulfonyl imide lithium salt is greater than 98%, reaching the chemical analysis purity.

[0026] The method for recovering lithium salt in the electrolyte proposed in this application is described in detail below:

[0027] Specifically, refer to the attached Figure 1 The above method for recovering lithium salt in electrolyte comprises the following steps:

[0028] S100: mixing the electrolyte of the waste battery with a carbonate solvent and an epoxy ether additive to react and generate a colloid substance;

[0029] In this step, the electrolyte of the waste battery is mixed with a carbonate solvent and an epoxy ether additive, and the acidity of the waste battery electrolyte is used to catalyze the ring opening of the epoxy ether additive, and polymerize with the sulfonyl imide lithium salt in the electrolyte to form a white or milky white colloidal substance. Among them, the carbonate solvent is used as a solvent to fully dissolve the sulfonyl imide lithium salt in the electrolyte of the waste battery, and the mixed solution formed by the carbonate solvent and the epoxy ether additive can effectively soak the battery core of the waste battery.

[0030] According to some specific embodiments of the present application, the above-mentioned mixing of the electrolyte of the waste battery with the carbonate solvent and the epoxy ether additive includes the following steps: immersing the battery core of the waste battery in the mixed solution of the carbonate solvent and the epoxy ether additive, thereby ensuring that the lithium sulfonimide salt in the electrolyte of the waste battery and the epoxy ether additive are fully polymerized, and the high viscosity of the polymerized product can be used to more thoroughly extract the lithium sulfonimide salt in the electrolyte of the waste battery, further improving the recovery rate of the lithium sulfonimide salt. However, the method of taking the electrolyte by freezing, adding the mixed solution of the carbonate solvent and the epoxy ether additive after the electrolyte is melted, cannot completely remove the lithium sulfonimide salt in the electrolyte, and more lithium sulfonimide salt remains in the battery, resulting in a relatively low recovery rate.

[0031] Specifically, the battery can be opened mechanically, and a mixture of carbonate solvent and epoxy ether additive can be added into the battery shell, so that the battery core of the used battery is immersed in the mixture of carbonate solvent and epoxy ether additive. Alternatively, the battery core can be taken out and immersed in a mixture of dimethyl carbonate and epoxy ether additive.

[0032] According to some further specific embodiments of the present application, the battery cells of the used batteries are immersed in a mixture of a carbonate solvent and an epoxy ether additive for 1 h to 2.5 h, for example, 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h, etc., thereby ensuring that the epoxy ether additive is ring-opened and fully polymerized with the lithium sulfonimide salt in the electrolyte to form a colloidal substance.

[0033] According to some specific embodiments of the present application, before immersing the battery cell of the waste battery in the mixed solution of the carbonate solvent and the epoxy ether additive, the method further includes: discharging the waste battery to a lower limit voltage. Different types of batteries have different lower limit voltages, for example, the lower limit voltage of the LFP battery is 2.0V, and the lower limit voltage of the NCM battery is 2.5V.

[0034] According to some other specific embodiments of the present application, the pH value of the electrolyte of the waste battery is in the range of 1≤pH<7. The acidity of the electrolyte itself can effectively catalyze the ring opening of epoxy ether additives and polymerize with the lithium sulfonimide salt in the electrolyte to form a colloidal substance. The fluorine-containing lithium salt (such as lithium hexafluorophosphate) or fluorine-containing additives in the electrolyte of the waste battery will react with the water vapor in the air to generate hydrofluoric acid, making the electrolyte of the waste battery acidic. The pH value of the electrolyte of the waste battery is not particularly limited. Different types of waste batteries, battery preparation processes and different degrees of battery waste will lead to different pH values ​​of the electrolyte.

[0035] According to some specific embodiments of the present application, the volume ratio of the carbonate solvent to the epoxy ether additive is (1:10) to (10:1), for example, it can be 1:10, 1:8, 1:5, 1:2, 1:1, 2:1, 5:1, 7:1, 10:1, etc., thereby ensuring that the epoxy ether additive and the sulfonyl imide lithium salt in the electrolyte are fully polymerized to form a colloidal substance, and at the same time ensuring that the carbonate solvent fully dissolves the sulfonyl imide lithium salt in the electrolyte of the waste battery. Preferably, it is (1:5) to (5:1).

[0036] In the embodiments of the present application, the specific types of the above-mentioned carbonate solvents are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred embodiments, the carbonate solvents include at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate and propylene carbonate.

[0037] In the embodiments of the present application, the specific types of the above-mentioned epoxy ether additives are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred embodiments, the epoxy ether additives include at least one of a ternary epoxy ether additive, a pentacyclic epoxy ether additive, and a heptatic epoxy ether additive.

[0038] Specifically, the specific types of ternary epoxy ether additives are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred embodiments, ternary epoxy ether additives include at least one of ethylene oxide, propylene oxide, and 1,4-butylene oxide. Similarly, the specific types of pentacyclic epoxy ether additives are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred embodiments, pentacyclic epoxy ether additives include at least one of tetrahydrofuran, 1,3-dioxolane, epichlorohydrin, and cyclopentane.

[0039] S200: taking out the colloid substance, dissolving the colloid substance in an ether solvent, drying and evaporating the colloid substance to obtain sulfonyl imide lithium salt.

[0040] In this step, the battery can be disassembled to take out the colloid substance, which is then dissolved in an ether solvent and then vacuum dried. The epoxy ether additive evaporates along with the ether solvent to obtain a solid lithium sulfonyl imide salt.

[0041] According to some specific embodiments of the present application, before dissolving the colloid substance in the ether solvent, the process further includes: washing the colloid substance with a solvent. For example, the colloid substance may be washed several times with a solvent such as chloroform or dichloromethane to wash away the organic solvent and other related impurities attached to the surface of the colloid substance.

[0042] According to some further specific embodiments of the present application, the colloidal substance is immersed in an ether solvent for 1 h to 2.5 h, for example, 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h, etc., thereby ensuring that the colloidal substance is fully dissolved in the ether solvent.

[0043] In the embodiments of the present application, the specific types of the above-mentioned ether solvents are not particularly limited, and those skilled in the art can select them according to actual needs. As some preferred embodiments, the ether solvent includes at least one of isopropyl ether and ethylene glycol butyl ether.

[0044] The method for recovering lithium salts in electrolyte of the present application can effectively recover lithium sulfonyl imide salts in the electrolyte of waste batteries, such as lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), etc.

[0045] In the embodiments of the present application, in the above steps, the specific temperature of vacuum drying is not particularly limited, as long as the purpose of evaporating the ether solvent and the epoxy ether additive can be achieved. As some preferred embodiments, the temperature can be heated to 250°C to 360°C for vacuum drying, and the white solid remaining after drying and evaporation is the lithium sulfonimide salt.

[0046] In the second aspect of the present application, the present application proposes a method for recovering lithium salt in electrolyte according to the above embodiment for use in recycling waste lithium-ion batteries, thereby effectively realizing the recycling and reuse of sulfonyl imide lithium salt and saving costs.

[0047] The embodiments of the present application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, unless otherwise explicitly stated, all reagents used in the following embodiments are commercially available or can be synthesized according to this article or known methods, and the reaction conditions not listed are also easily available to those skilled in the art.

[0048] Example 1

[0049] This embodiment provides a method for recovering lithium salt in an electrolyte, comprising:

[0050] Step 1: Discharge the waste lithium-ion battery (lithium iron phosphate battery) to a lower voltage limit of 2.0 V. The pH value of the electrolyte of the waste lithium-ion battery is about 4.8.

[0051] Step 2: Mix dimethyl carbonate and 1,3-dioxolane in a volume ratio of 1:1 to form a mixed solution, mechanically open the battery opening, and add the mixed solution into the battery shell so that the battery cell is immersed in the mixed solution for 2 hours. In this process, the acidic conditions of the battery itself are used to catalyze the ring opening of 1,3-dioxolane, and polymerize with the lithium sulfonimide salt in the electrolyte to form a white colloidal substance.

[0052] Step 3: Remove the battery casing and take out the white gelatinous substance.

[0053] Step 4: The obtained white colloid was washed with dichloromethane (CH2Cl2) three times, each washing time was 10 minutes, and then soaked with isopropyl ether for 2 hours. The white colloid was completely dissolved in isopropyl ether, heated to 330°C for vacuum drying, and 1,3-dioxolane was evaporated together with the solvent to obtain sulfonimide lithium salt LiFSI.

[0054] Example 2

[0055] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0056] Step 1: The pH value of the electrolyte of the waste lithium-ion battery is about 3.9.

[0057] Example 3

[0058] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0059] Step 1: The pH value of the electrolyte of the waste lithium-ion battery is about 5.8.

[0060] Example 4

[0061] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0062] Step 2: The volume ratio of dimethyl carbonate to 1,3-dioxolane is 1:4.

[0063] Example 5

[0064] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0065] Step 2: The volume ratio of dimethyl carbonate to 1,3-dioxolane is 4:1.

[0066] Example 6

[0067] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0068] Step 2: The volume ratio of dimethyl carbonate to 1,3-dioxolane is 1:8.

[0069] Example 7

[0070] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0071] Step 2: The volume ratio of dimethyl carbonate to 1,3-dioxolane is 8:1.

[0072] Example 8

[0073] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0074] Step 2: Replace 1,3-dioxolane with 1,4-butylene oxide.

[0075] Example 9

[0076] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0077] Step 2: Replace 1,3-dioxolane with tetrahydrofuran.

[0078] Example 10

[0079] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0080] Step 2: Replace dimethyl carbonate with ethyl methyl carbonate.

[0081] Embodiment 11

[0082] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0083] Step 2: The battery cell is immersed in the mixed solution for 1 hour.

[0084] Example 12

[0085] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0086] Step 4: Soak the white colloidal substance in isopropyl ether for 1 hour.

[0087] Example 13

[0088] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0089] Step 4: Replace isopropyl ether with ethylene glycol butyl ether.

[0090] Embodiment 14

[0091] The preparation method of this embodiment is basically the same as that of embodiment 1, except that:

[0092] Step 2: Take the electrolyte from the waste lithium-ion battery by freezing, and after the electrolyte melts, add the mixture of dimethyl carbonate and 1,3-dioxolane and soak for 2 hours. In this process, the acidic conditions of the battery itself are used to catalyze the ring opening of 1,3-dioxolane, and polymerize with the lithium sulfonimide salt in the electrolyte to form a white colloidal substance.

[0093] Step 3: Take out the white gelatinous substance.

[0094] The purity of the lithium sulfonyl imide salts recovered in Examples 1 to 14 was tested, and the results are shown in Table 1. The recovery rates of the lithium sulfonyl imide salts recovered in Examples 1 to 14 were calculated, and the results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] As can be seen from Table 1, Examples 1 to 14 all effectively achieve the recovery of sulfonyl imide lithium salt, and the recovery process is simple, easy to operate, and the recovery rate is high. In addition, the purity of the sulfonyl imide lithium salt recovered in Examples 1 to 14 is greater than 98%, reaching the chemical analysis purity.

[0099] As can be seen from Table 1, compared with Example 14, the recovery rates of Examples 1 to 13 have been significantly improved, which shows that Examples 1 to 13 can more thoroughly extract the lithium sulfonimide salt in the electrolyte of the waste battery, further improving the recovery rate of the lithium sulfonimide salt. However, Example 14 uses a freezing method to extract the electrolyte, which cannot completely remove the lithium sulfonimide salt in the electrolyte, and more lithium sulfonimide salt remains in the battery, resulting in a relatively low recovery rate.

[0100] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0101] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for recovering lithium salt in an electrolyte, characterized in that: include: The electrolyte of the waste battery is mixed with a carbonate solvent and an epoxy ether additive to react and generate a colloid substance; The colloid substance is taken out, dissolved in an ether solvent, dried and evaporated to obtain sulfonyl imide lithium salt.

2. The method according to claim 1, characterized in that The method of mixing the electrolyte of the waste battery with the carbonate solvent and the epoxy ether additive comprises: The cells of the waste batteries are immersed in a mixed solution of the carbonate solvent and the epoxy ether additive.

3. The method according to claim 2, characterized in that Soaking the cell of the waste battery in a mixed solution of the carbonate solvent and the epoxy ether additive for 1 hour to 2.5 hours; And / or, before immersing the battery core of the waste battery in the mixed solution of the carbonate solvent and the epoxy ether additive, the method further comprises: The waste battery is discharged to a lower voltage limit.

4. The method according to claim 1, characterized in that: The pH value range of the electrolyte of the waste battery is 1≤pH<7; And / or, the volume ratio of the carbonate solvent to the epoxy ether additive is (1:10) to (10:1).

5. The method according to claim 1, characterized in that The carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate and propylene carbonate; And / or, the epoxy ether additive includes at least one of a ternary epoxy ether additive, a pentaary epoxy ether additive and a heptaary epoxy ether additive.

6. The method according to claim 5, characterized in that The ternary epoxy ether additive includes at least one of ethylene oxide, propylene oxide and 1,4-butylene oxide; And / or, the five-membered epoxy ether additive includes at least one of tetrahydrofuran, 1,3-dioxolane, epichlorohydrin, and cyclopentane.

7. The method according to any one of claims 1 to 6, characterized in that: Before dissolving the colloidal substance in the ether solvent, the method further comprises: The colloid substance is washed with a solvent.

8. The method according to any one of claims 1 to 6, characterized in that: Soaking the colloid substance in the ether solvent for 1 hour to 2.5 hours so that the colloid substance is dissolved in the ether solvent; And / or, the ether solvent includes at least one of isopropyl ether and ethylene glycol butyl ether.

9. The method according to any one of claims 1 to 6, characterized in that: The sulfonyl imide lithium salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

10. Use of the method for recovering lithium salt in electrolyte according to any one of claims 1 to 9 in recovering waste lithium-ion batteries.

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