Lithium difluorosulfonylimide and methods for purifying lithium difluorosulfonylimide

Abstract

This application relates to lithium bis(fluorosulfonyl)imide and a method for purifying lithium bis(fluorosulfonyl)imide. The method includes: providing a mixture containing lithium bis(fluorosulfonyl)imide; adding an organic ammonium salt to the mixture and reacting it to obtain an intermediate mixture; and reacting the intermediate mixture with lithium ions under alkaline conditions to obtain lithium bis(fluorosulfonyl)imide. The method described in this application can improve the purity of lithium bis(fluorosulfonyl)imide.

Description

Technical Field

[0001] This application relates to the field of chemical production technology, and in particular to lithium bisfluorosulfonylimide and methods for purifying lithium bisfluorosulfonylimide. Background Technology

[0002] Rechargeable batteries possess advantages such as small size, high energy density, high safety, low self-discharge, and long lifespan, and are widely used in various fields including energy storage, communications, electric vehicles, and aerospace. Lithium-ion batteries, among rechargeable batteries, exhibit particularly superior performance and are extensively studied in the battery field to further improve their performance.

[0003] Lithium bisfluorosulfonylimide is a major component of the electrolyte in lithium-ion batteries. The purity of lithium bisfluorosulfonylimide has a significant impact on the electrolyte. Higher purity results in better performance of the lithium-ion battery, while lower purity results in poorer performance. Therefore, improving the purity of lithium bisfluorosulfonylimide is an urgent problem to be solved. Summary of the Invention

[0004] This application provides lithium bis(fluorosulfonyl)imide and a method for purifying lithium bis(fluorosulfonyl)imide, the method being able to improve the purity of lithium bis(fluorosulfonyl)imide.

[0005] In a first aspect, this application proposes a method for purifying lithium bisfluorosulfonylimide, the method comprising: providing a mixture containing lithium bisfluorosulfonylimide; adding an organic ammonium salt to the mixture and reacting it to obtain an intermediate mixture; and reacting the intermediate mixture with lithium ions under alkaline conditions to obtain lithium bisfluorosulfonylimide.

[0006] Therefore, this application preconverts lithium bisfluorosulfonylimide in the mixture into an intermediate mixture, partially removes impurities in the mixture during this process, and then reconverts the intermediate mixture into lithium bisfluorosulfonylimide, thereby improving the purity of the final obtained lithium bisfluorosulfonylimide.

[0007] In some embodiments, the method further includes purifying the intermediate mixture.

[0008] Therefore, after generating the intermediate mixture, the intermediate mixture will inevitably contain impurities. The intermediate mixture is purified to remove the impurities, thereby improving the purity of the intermediate mixture. Then, the purified intermediate mixture is converted into lithium bisfluorosulfonylimide, thereby further improving the purity of lithium bisfluorosulfonylimide.

[0009] In some embodiments, the step of purifying the intermediate mixture includes contacting the intermediate mixture with a decolorizing agent to adsorb and remove colored impurities from the intermediate mixture.

[0010] Therefore, the decolorizing agent of this application can adsorb colored impurities, thereby achieving the purpose of decolorization.

[0011] In some embodiments, the step of purifying the intermediate mixture includes contacting the intermediate mixture with a cleaning agent to remove metal ions from the intermediate mixture.

[0012] Therefore, this application uses a cleaning agent to clean the intermediate mixture in order to wash out free metal ions such as sodium ions, potassium ions, calcium ions, iron ions, lead ions, chromium ions, and zinc ions from the intermediate mixture, thereby achieving the purpose of removing metal ions and improving the purity of lithium bis(fluorosulfonyl)imide.

[0013] In some embodiments, the decolorizing agent includes one or more of activated carbon particles, activated carbon fibers, zeolite, and diatomaceous earth.

[0014] Therefore, the decolorizing agent of this application can adsorb colored impurities, thereby achieving the purpose of improving the purity of the intermediate mixture.

[0015] In some embodiments, the cleaning agent includes one or more of water, sodium salt, potassium salt, and lithium salt; optionally, the sodium salt includes one or more of sodium chloride, sodium sulfate, and sodium carbonate; the potassium salt includes one or more of potassium chloride, potassium sulfate, and potassium sulfate; and the lithium salt includes one or more of lithium chloride, lithium sulfate, and lithium carbonate.

[0016] Therefore, the cleaning agent of this application has the ability to be miscible with metal ions, and can wash away metal ions, thereby achieving the purpose of improving the purity of the intermediate mixture.

[0017] In some embodiments, the organic ammonium salt includes the hydrogen fluoride salt of a tertiary amine and / or the hydrogen fluoride salt of a quaternary amine. The fluoride ions in the organic ammonium salt readily combine with the lithium ions in lithium bis(fluorosulfonyl)imide to form a lithium fluoride precipitate, thereby promoting the reaction; and the lithium fluoride precipitate may carry some impurities, thereby achieving the purpose of impurity removal.

[0018] In some embodiments, the hydrogen fluoride salt of the tertiary amine includes one or more of trimethylamine hydrogen fluoride, triethylamine hydrogen fluoride, tripropylamine hydrogen fluoride, diisopropylethylamine hydrogen fluoride, and tributylamine hydrogen fluoride; optionally, the hydrogen fluoride salt of the tertiary amine includes triethylamine hydrogen fluoride. The above-mentioned organic ammonium salts are readily available and react relatively thoroughly with lithium bis(fluorosulfonyl)imide.

[0019] In some embodiments, the quaternary ammonium hydrogen fluoride salt includes one or more of tetramethylamine hydrogen fluoride, tetraethylamine hydrogen fluoride, tetrapropylamine hydrogen fluoride, and tetrabutylamine hydrogen fluoride. The raw materials for these organoammonium salts are readily available and react relatively completely with lithium bis(fluorosulfonyl)imide.

[0020] In some embodiments, the molar ratio of the mixture to the organic ammonium salt is 1:(1 to 10).

[0021] Therefore, when the molar ratio of the mixture and the organic ammonium salt in this application meets the above range, the organic ammonium salt can fully react with the lithium difluorosulfonylimide in the mixture, thereby replacing the lithium ions in the lithium difluorosulfonylimide to a large extent with organic amine cations, and thus converting the lithium difluorosulfonylimide to the intermediate mixture to the greatest extent, thereby improving the final yield of lithium difluorosulfonylimide.

[0022] In some embodiments, the molar ratio of the intermediate mixture to lithium ions is 1:(1 to 10).

[0023] Therefore, the molar ratio of the intermediate mixture and lithium ions in this application is within the above range, which can ensure that the organic amine cations in the intermediate mixture are fully replaced by lithium ions, thereby converting the intermediate mixture to a large extent into bis(fluorosulfonyl)imide and improving the yield of bis(fluorosulfonyl)imide.

[0024] Secondly, this application proposes a lithium bisfluorosulfonylimide, which is prepared by the method of any embodiment of the first aspect of this application. Attached Figure Description

[0025] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0026] Figure 1 This is a schematic diagram of the process for purifying lithium bis(fluorosulfonyl)imide provided in some embodiments of this application;

[0027] Figure 2 This is a schematic diagram of the process for purifying lithium bis(fluorosulfonyl)imide provided in some other embodiments of this application;

[0028] Figure 3 This is a schematic diagram of the process for purifying lithium bis(fluorosulfonyl)imide according to some embodiments of this application;

[0029] Figure 4 This is a schematic diagram of the process for purifying lithium bisfluorosulfonylimide provided in some embodiments of this application. Detailed Implementation

[0030] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of lithium bisfluorosulfonylimide and methods for purifying lithium bisfluorosulfonylimide. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0031] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0033] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0034] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0036] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0037] The fluoride ions in lithium bis(fluorosulfonyl)imide (LiFSI) exhibit strong electron-withdrawing properties, which weakens the coordination between cations and anions. This results in highly mobile lithium ions with excellent conductivity, thermal stability, and electrochemical stability, and it virtually does not generate corrosive gases such as hydrofluoric acid. Given these superior properties, lithium bis(fluorosulfonyl)imide, as a lithium salt in lithium-ion battery electrolytes, can improve the rate performance, cycle life, and safety of lithium-ion batteries.

[0038] There are several methods for producing lithium bis(fluorosulfonyl)imide. For example, sulfonamides can be reacted with sulfonyl chloride and chlorosulfonic acid to obtain bis(fluorosulfonyl)imide, followed by fluorination and lithiation to finally obtain LiFSI. Alternatively, sulfonyl chloride or sulfuryl fluoride can be reacted with ammonia to obtain bis(fluoro)sulfonylimide or its basic salt, followed by fluorination and lithiation to obtain the product LiFSI. Another method involves reacting fluorosulfonic acid with urea to obtain bis(fluorosulfonyl)imide, followed by lithiation with a lithizing agent to obtain lithium bis(fluorosulfonyl)imide. Impurities are inevitably generated during the production of lithium bis(fluorosulfonyl)imide, resulting in a purity that cannot reach 100%.

[0039] The inventors discovered that, in order to improve the purity of lithium bisfluorosulfonylimide, recrystallization purification is usually performed. However, due to the continuous accumulation of impurities in the recrystallization mother liquor, recrystallization mother liquor is inevitably generated. As a result, the purity of lithium bisfluorosulfonylimide can be partially improved, but cannot be further improved. The purified lithium bisfluorosulfonylimide may still not meet the production requirements.

[0040] To address the aforementioned problems, the inventors proposed a method for purifying lithium bis(fluorosulfonyl)imide, such as... Figure 1 As shown, the method includes: step S100, providing a mixture containing lithium bis(fluorosulfonyl)imide; step S200, adding an organic ammonium salt to the mixture and reacting it to obtain an intermediate mixture; step S300, reacting the intermediate mixture with lithium ions under alkaline conditions to obtain lithium bis(fluorosulfonyl)imide. The method of this application can further improve the purity of lithium bis(fluorosulfonyl)imide. The method of this application is applicable not only to recrystallized lithium bis(fluorosulfonyl)imide but also to wastewater containing lithium bis(fluorosulfonyl)imide.

[0041] Step S100: Provide a mixture containing lithium bis(fluorosulfonyl)imide.

[0042] The mixture containing lithium bis(fluorosulfonyl)imide can be a recrystallization mother liquor with high purity, such as 90% or 85%, or wastewater containing lithium bis(fluorosulfonyl)imide with lower purity, such as 2% or 5%. In this document, the mixture inevitably contains impurities in addition to lithium bis(fluorosulfonyl)imide. Exemplarily, impurities can include metal ions, anions, and colored impurities such as pigments. Metal ions can include, for example, sodium ions, potassium ions, calcium ions, iron ions, lead ions, chromium ions, zinc ions, etc. Anions can include, for example, chloride ions, etc. Purity refers to the ratio of the mass of lithium bis(fluorosulfonyl)imide to the total mass of the mixture.

[0043] Step S200: An organic ammonium salt is added to the mixture, and the intermediate mixture is obtained by reaction.

[0044] Organic ammonium salts can react with lithium bis(fluorosulfonyl)imide in the mixture. The lithium ions in lithium bis(fluorosulfonyl)imide are easily replaced by organic ammonium cations to generate an intermediate mixture. The intermediate mixture is then further purified to improve its purity.

[0045] In some embodiments, the organic ammonium salt includes the hydrogen fluoride salt of a tertiary amine and / or the hydrogen fluoride salt of a quaternary amine. When the hydrogen fluoride salt of the organic amine reacts with lithium bis(fluorosulfonyl)imide, the fluoride ions in the organic ammonium salt readily combine with the lithium ions in the lithium bis(fluorosulfonyl)imide to form a lithium fluoride precipitate, thereby promoting the reaction; and the lithium fluoride precipitate may carry some impurities, thus achieving the purpose of impurity removal. Furthermore, the lithium ions in the lithium fluoride precipitate can be recycled.

[0046] For example, the hydrogen fluoride salt of a tertiary amine may include one or more of trimethylamine trihydrofluoride, triethylamine trihydrofluoride (TEAHF), tripropylamine trihydrofluoride, diisopropylethylamine trihydrofluoride, and tributylamine trihydrogen fluoride. Optionally, the hydrogen fluoride salt of a tertiary amine may include triethylamine hydrogen fluoride. The hydrogen fluoride salts of tertiary amines are readily available and react relatively completely with lithium difluorosulfonylimide.

[0047] Taking triethylamine hydrogen fluoride (TEAHF) as an example, the reaction process with lithium difluorosulfonylimide is illustrated:

[0048]

[0049] For example, the quaternary ammonium hydrogen fluoride salt may include one or more of tetramethylamine hydrogen fluoride, tetraethylamine hydrogen fluoride, tetrapropylamine hydrogen fluoride, and tetrabutylamine hydrogen fluoride. The reaction between the quaternary ammonium hydrogen fluoride salt and lithium bis(fluorosulfonyl)imide is more complete.

[0050] In some embodiments, the molar ratio of the mixture to the organic ammonium salt can be 1:(1 to 10).

[0051] When the molar ratio of the mixture to the organic ammonium salt meets the above-mentioned range, the organic ammonium salt can fully react with lithium difluorosulfonylimide in the mixture, thereby largely replacing the lithium ions in the lithium difluorosulfonylimide with organic amine cations, and thus largely converting the lithium difluorosulfonylimide into the intermediate mixture, thereby improving the yield and purity of the final lithium difluorosulfonylimide. For example, the molar ratio of the mixture to the organic ammonium salt can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10; or the molar ratio can be any range of any two of the above values.

[0052] In step S300, the intermediate mixture is reacted with lithium ions under alkaline conditions to obtain lithium bis(fluorosulfonyl)imide.

[0053] Under alkaline conditions, the intermediate mixture and lithium ions can undergo a lithium exchange reaction, replacing the cations in the intermediate mixture with lithium ions to generate lithium bisfluorosulfonylimide. For example, lithium hydroxide can be added to the system to create alkaline conditions, thereby preventing the further introduction of other metal ions.

[0054] Taking triethylamine hydrogen fluoride as an example of an organic amine salt, the reaction process in step S300 is as follows:

[0055]

[0056] In some embodiments, the molar ratio of the intermediate mixture to lithium ions is 1:(1.0 to 10.0).

[0057] When the molar ratio of the intermediate mixture to lithium ions is within the above-mentioned range, it ensures that the organic amine cations in the intermediate mixture are fully replaced by lithium ions, thereby enabling the intermediate mixture to be largely converted into bis(fluorosulfonyl)imide and improving the yield of bis(fluorosulfonyl)imide. For example, the molar ratio of the intermediate mixture to lithium ions can be 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:3.0, 1:4.0, 1:5.0, 1:6.0, 1:7.0, 1:8.0, 1:9.0, or 1:10.0; or the molar ratio can be any range consisting of any two of the above values.

[0058] In this embodiment, lithium bisfluorosulfonylimide in the mixture is pre-converted into an intermediate mixture, during which impurities in the mixture are partially removed, and then the intermediate mixture is converted back into lithium bisfluorosulfonylimide, thereby improving the purity of the final obtained lithium bisfluorosulfonylimide.

[0059] like Figure 2 As shown, in some embodiments, after step S200, the following may also be included:

[0060] Step S400: Purify the intermediate mixture.

[0061] After the intermediate mixture is generated, it inevitably contains impurities, mostly metal ions, anions, and colored impurities carried by the mixture containing lithium bisfluorosulfonylimide. Purifying the intermediate mixture removes these impurities, thereby increasing its purity. Then, the purified intermediate mixture is converted into lithium bisfluorosulfonylimide, further increasing the purity of the final product, lithium bisfluorosulfonylimide. This application embodiment achieves the goal of increasing the purity of lithium bisfluorosulfonylimide by converting lithium bisfluorosulfonylimide into an intermediate mixture and removing impurities from the entire system through purification.

[0062] like Figure 3 As shown, as some examples, step S400 may include:

[0063] Step S410: Contact the intermediate mixture with a decolorizing agent to adsorb and remove colored impurities from the intermediate mixture.

[0064] The decolorizing agent has a decolorizing function. For example, the decolorizing agent may include one or more of activated carbon particles, activated carbon fibers, zeolite, and diatomaceous earth. Optionally, the decolorizing agent may have a porous framework structure, which can adsorb colored impurities into the pores of the porous framework structure, thereby achieving the purpose of decolorization; and the decolorizing agent basically does not react with the system. The above-mentioned decolorizing agents can be used individually or in combination.

[0065] In this embodiment, colored impurities in the intermediate mixture are removed by a decolorizing agent, thereby removing some impurities from the entire system and improving the purity of the final lithium bis(fluorosulfonyl)imide.

[0066] like Figure 4 As shown, as some other examples, step S400 may also include:

[0067] Step S420: Contact the intermediate mixture with a cleaning agent to remove metal ions from the intermediate mixture.

[0068] Metal ions can include sodium ions, potassium ions, calcium ions, iron ions, lead ions, chromium ions, and zinc ions. Sodium, potassium, and lithium are in the same group, making them difficult to remove from the lithium system through chemical reactions. In this step, lithium ions are pre-precipitated, meaning they exist primarily as lithium fluoride precipitates. However, sodium and potassium ions may still exist as cations in the intermediate mixture. Therefore, this application uses a cleaning agent to wash the intermediate mixture, eluting free sodium, potassium, calcium, iron, lead, chromium, and zinc ions from the system, thereby removing metal ions and improving the purity of lithium bis(fluorosulfonyl)imide. Furthermore, the eluted metal ions can be recycled; this step also removes anions to some extent, further removing impurities from the system.

[0069] The cleaning agent does not react significantly with the intermediate mixture, but it is miscible with metal ions. For example, the cleaning agent may include one or more of water, sodium salts, potassium salts, and lithium salts. For instance, sodium salts may include one or more of sodium chloride, sodium sulfate, and sodium carbonate; potassium salts may include one or more of potassium chloride, potassium sulfate, and potassium sulfate; and lithium salts may include one or more of lithium chloride, lithium sulfate, and lithium carbonate.

[0070] Steps S410 and S420 can be executed individually, for example, only the operation of step S410 can be executed, or only the operation of step S420 can be executed; of course, both steps can also be executed. When both steps are executed, there is no order of execution. For example, step S410 can be executed first, followed by step S420; or step S420 can be executed first, followed by step S410.

[0071] Optionally, to further improve the purity of the final obtained lithium bis(fluorosulfonyl)imide, it can be repeatedly cleaned with a cleaning agent, or different cleaning agents can be used for cleaning separately.

[0072] This application also provides a lithium bisfluorosulfonylimide, which can be prepared from the above embodiments. This lithium bisfluorosulfonylimide has high purity, meeting production requirements. The lithium bisfluorosulfonylimide obtained in the embodiments of this application can be used in electrolytes, and further in lithium-ion batteries, thereby improving the electrochemical performance of lithium-ion batteries.

[0073] Example

[0074] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0075] Example 1

[0076] The mixture is the mother liquor from recrystallization after multiple recrystallizations.

[0077] Example 1-1

[0078] S110 provides a mixture containing lithium bis(fluorosulfonyl)imide.

[0079] The mixture has a mass of 100g and, based on the total mass of the mixture, contains 1528.3ppm sodium ions, 9.67ppm calcium ions, 7.63ppm iron ions, 2.22ppm chromium ions, 2.02ppm zinc ions, 6.42ppm potassium ions, 75.15ppm chloride ions, 55.3% LiFSI, and 29.6% triethylamine difluorosulfonamide; its color is brownish-black.

[0080] S120, an organic ammonium salt is added to the mixture, and the intermediate mixture is obtained by reaction.

[0081] The molar ratio of the mixture to the organic amine salt is 1:1.3. The organic amine salt is an aqueous solution of triethylamine hydrogen fluoride. Based on the mass of the aqueous solution of triethylamine hydrogen fluoride, the triethylamine hydrogen fluoride contains 6.39% fluoride ions, 18.87% triethylamine, and 25.26% triethylamine hydrogen fluoride as the main component.

[0082] During the reaction, a white solid was produced and separated into layers, with the lower layer being a brown liquid intermediate mixture. The white solid was filtered and dried to yield 6.8 g of lithium fluoride, with a lithium ion recovery rate of 88.9%. The intermediate mixture had a mass of 108 g, a water content of 9%, and an anion (main component FSI) recovery rate of 95.3%.

[0083] S411, the intermediate mixture is contacted with activated carbon particles to adsorb and remove colored impurities in the intermediate mixture.

[0084] 108g of brown liquid was decolorized by stirring with 5g of powdered activated carbon at 50℃ for 3 hours, resulting in a color of 130, which meets the internal control color index.

[0085] S421, the intermediate mixture is contacted with deionized water to remove metal ions from the intermediate mixture.

[0086] The following ions were recovered: sodium ions (0.73 ppm), calcium ions (0.78 ppm), iron ions (0.42 ppm), chromium ions (0.02 ppm), zinc ions (0.23 ppm), potassium ions (0.82 ppm), and chloride ions (1.33 ppm), meeting the internal control parameters for intermediates. A final yield of 95.3 g of qualified difluorosulfonylimide triethylamine salt was obtained, with a total recovery rate of 85.5%. The total recovery rate refers to the overall recovery rate after three steps, including reaction, dehydration, and washing.

[0087] S300, under alkaline conditions, reacts an intermediate mixture with lithium ions to obtain lithium bisfluorosulfonylimide.

[0088] The triethylamine bis(fluorosulfonyl)imide salt obtained in step S421 was subjected to alkali exchange with lithium hydroxide following the lithium addition process, wherein the molar ratio of triethylamine bis(fluorosulfonyl)imide salt to lithium hydroxide was 1:1.1. After dehydration, recrystallization in dichloromethane, filtration, drying, and dissolution, a dimethyl carbonate solution of LiFSI was finally obtained (water content 20.3 ppm; density 1.2233 g / cm³). 3 HF: 2.4ppm, color 32.3; chloride ion 1.71ppm; calcium ion 0.34ppm; sodium ion 13.57ppm; iron ion 0.26ppm; potassium ion 1.43ppm; LiFSI: 30.25%, all of which meet the finished product specifications.

[0089] Examples 1-2

[0090] Unlike Example 1-1, the molar ratio of the mixture and the organic amine salt in step S120 is 1:1.1.

[0091] In step S120, the resulting off-white solid was filtered and dried to obtain 6.7 g of lithium fluoride, with a lithium ion recovery rate of 87.6%. The intermediate mixture had a mass of 108 g, a moisture content of 10.2%, and an anion recovery rate of 94.5%.

[0092] In step S300, a dimethyl carbonate solution of LiFSI is obtained (water content 17.5 ppm; density 1.2236 g / cm³). 3 HF: 15.1ppm, color 15; chloride ion: 0.7387ppm; calcium ion: 1.969ppm; sodium ion: 65.829ppm; iron ion: 0.522ppm; potassium ion: 2.113ppm; LiFSI: 30.88%, all of which meet the finished product specifications.

[0093] Examples 1-3

[0094] Unlike Example 1-1, the molar ratio of the mixture and the organic amine salt in step S120 is 1:1.5.

[0095] In step S120, the resulting off-white solid was filtered and dried to obtain 6.82 g of lithium fluoride, with a lithium ion recovery rate of 89.0%. The intermediate mixture had a mass of 109 g, a moisture content of 11.1%, and an anion recovery rate of 95.3%.

[0096] In step S300, a dimethyl carbonate solution of LiFSI is obtained (water content 13.3 ppm; density 1.2232 g / cm³). 3 HF: 19.0ppm, color 11; chloride ion 0.6323ppm; calcium ion 1.190ppm; sodium ion 51.161ppm; iron ion 0.374ppm; potassium ion 1.349ppm; LiFSI: 30.87%, all of which meet the finished product specifications.

[0097] Examples 1-4

[0098] Unlike Example 1-1, the molar ratio of the mixture and the organic amine salt in step S120 is 1:1.0.

[0099] In step S120, the resulting off-white solid was filtered and dried to obtain 6.3 g of lithium fluoride, with a lithium ion recovery rate of 81.2%. The intermediate mixture had a mass of 99 g, a moisture content of 9.5%, and an anion recovery rate of 86.6%.

[0100] In step S300, a dimethyl carbonate solution of LiFSI is obtained (water content 12.9 ppm; density 1.2250 g / cm³). 3 HF: 7.9ppm, color 15; chloride ion: 0.7211ppm; calcium ion: 1.105ppm; sodium ion: 56.476ppm; iron ion: 0.599ppm; potassium ion: 3.279ppm; LiFSI: 30.87%, all of which meet the finished product specifications.

[0101] Examples 1-5

[0102] Unlike Example 1-1, the molar ratio of the mixture and the organic amine salt in step S120 is 1:5.

[0103] In step S120, the resulting off-white solid was filtered and dried to obtain 7.1 g of lithium fluoride, with a lithium ion recovery rate of 91.5%. The intermediate mixture had a mass of 109 g, a moisture content of 10.1%, and an anion recovery rate of 95.3%.

[0104] In step S300, a dimethyl carbonate solution of LiFSI was obtained (water content 17.9 ppm; density 1.2235 g / cm³). 3HF: 22.9ppm, color 11; chloride ion 0.7774ppm; calcium ion 1.781ppm; sodium ion 67.169ppm; iron ion 0.841ppm; potassium ion 2.397ppm; LiFSI: 30.79%, all of which meet the finished product specifications.

[0105] Examples 1-6

[0106] Unlike Example 1-1, the molar ratio of the mixture and the organic amine salt in step S120 is 1:10.

[0107] In step S120, the resulting off-white solid was filtered and dried to obtain 7.0 g of lithium fluoride, with a lithium ion recovery rate of 90.2%. The intermediate mixture had a mass of 108 g, a moisture content of 8.9%, and an anion recovery rate of 94.5%.

[0108] In step S300, a dimethyl carbonate solution of LiFSI was obtained (water content 9.6 ppm; density 1.2241 g / cm³). 3 HF: 30.9ppm, color 13; chloride ion 0.7428ppm; calcium ion 1.952ppm; sodium ion 58.922ppm; iron ion 0.438ppm; potassium ion 1.420ppm; LiFSI: 30.77%, all of which meet the finished product specifications.

[0109] Examples 1-7

[0110] Unlike Example 1-1, the molar ratio of difluorosulfonylimide triethylamine salt to lithium hydroxide in step S300 is 1:1.2.

[0111] In step S300, a dimethyl carbonate solution of LiFSI was obtained (water content 14.3 ppm; density 1.2215 g / cm³). 3 HF: 8.2ppm, color 20; chloride ion 1.018ppm; calcium ion 0.461ppm; sodium ion 63.687ppm; iron ion 0.229ppm; potassium ion 3.308ppm; LiFSI: 30.62%, all of which meet the finished product specifications.

[0112] Examples 1-8

[0113] Unlike Example 1-1, the molar ratio of difluorosulfonylimide triethylamine salt to lithium hydroxide in step S300 is 1:1.8.

[0114] In step S300, a dimethyl carbonate solution of LiFSI is obtained (water content 13.2 ppm; density 1.2240 g / cm³). 3HF: 12.3ppm, color 19, chloride ion 0.8029ppm; calcium ion 0.542ppm; sodium ion 69.551ppm; iron ion 0.287ppm; potassium ion 1.23ppm; LiFSI: 30.87%, all of which meet the finished product specifications.

[0115] Examples 1-9

[0116] Unlike Example 1-1, in step S300, the molar ratio of difluorosulfonylimide triethylamine salt to lithium hydroxide is 1:1.0.

[0117] In step S300, a dimethyl carbonate solution of LiFSI is obtained (water content 13.0 ppm; density 1.2237 g / cm³). 3 HF: 26.4ppm, color 19; chloride ion 0.7964ppm; calcium ion 0.970ppm; sodium ion 68.161ppm; iron ion 0.256ppm; potassium ion 4.062ppm; LiFSI: 30.86%, all of which meet the finished product specifications.

[0118] Examples 1-10

[0119] Unlike Example 1-1, in step S300, the molar ratio of difluorosulfonylimide triethylamine salt to lithium hydroxide is 1:5.

[0120] In step S300, a dimethyl carbonate solution of LiFSI is obtained (water content 13.2 ppm; density 1.2236 g / cm³). 3 HF: 8.6m, color 31; chloride ion 1.4972ppm; calcium ion 0.91ppm; sodium ion 52.94ppm; iron ion 0.373ppm; potassium ion 1.782ppm; LiFSI: 30.72%, all of which meet the finished product specifications.

[0121] Examples 1-11

[0122] Unlike Example 1-1, in step S300, the molar ratio of difluorosulfonylimide triethylamine salt to lithium hydroxide is 1:10.

[0123] In step S300, a dimethyl carbonate solution of LiFSI was obtained (water content 9.8 ppm; density 1.2230 g / cm³). 3 HF: 11.1ppm, color 15; chloride ion 0.9278ppm; calcium ion 0.883ppm; sodium ion 47.284ppm; iron ion 0.225ppm; potassium ion 1.607ppm; LiFSI: 30.90%, all of which meet the finished product specifications.

[0124] Example 2

[0125] S210 provides a mixture containing lithium bis(fluorosulfonyl)imide.

[0126] The mixture is derived from 100g of washing waste liquid (such as washing filter residue, filter cartridges, etc.). Based on the total mass of the mixture, the main components are lithium difluorosulfonamide 24.02%, sodium ions 1523.22ppm, calcium ions 314.76ppm, iron ions 3.48ppm, lead ions 4.73ppm, and lithium ions 8414.81ppm; its color is yellow.

[0127] S220, an organic ammonium salt is added to the mixture, and the intermediate mixture is obtained by reaction.

[0128] The molar ratio of the mixture to the organic amine salt is 1:1.3. The organic amine salt is an aqueous solution of triethylamine hydrogen fluoride. Based on the mass of the aqueous solution of triethylamine hydrogen fluoride, the triethylamine hydrogen fluoride contains 6.39% fluoride ions, 18.87% triethylamine, and 0.58% triethylamine hydrogen fluoride.

[0129] During the reaction, a white solid was produced and separated into layers, with the lower layer being a brown liquid intermediate mixture. The white solid was filtered and dried to yield 2.51 g of lithium fluoride, with a lithium ion recovery rate of 86.85%. The intermediate mixture had a mass of 38.5 g, a water content of 8.9%, and an anion recovery rate of 96.7%.

[0130] S422, the intermediate mixture is contacted with deionized water to remove metal ions from the intermediate mixture.

[0131] The recovered sodium ions were 0.84 ppm, calcium ions 2.1 ppm, iron ions 30.27 ppm, lead ions 0.16 ppm, lithium ions 1.82 ppm, and chloride ions 2.15 ppm, etc. The color was 103, which met the internal control index of the intermediate. Finally, 35.1 g of qualified difluorosulfonylimide triethylamine salt was obtained, with a total recovery rate of 88.2%.

[0132] S300, under alkaline conditions, reacts an intermediate mixture with lithium ions to obtain lithium bisfluorosulfonylimide.

[0133] The triethylamine bis(fluorosulfonyl)imide salt obtained in step S422 was subjected to alkali exchange with lithium hydroxide according to the lithium addition process, wherein the molar ratio of triethylamine bis(fluorosulfonyl)imide salt to lithium hydroxide was 1:1.5. After dehydration, recrystallization in dichloromethane, filtration, drying, and dissolution, a dimethyl carbonate solution of LiFSI was finally obtained (water content 20.3 ppm; density 1.2233 g / cm³). 3HF: 2.4ppm, color 32.3; chloride ion 1.71ppm; calcium ion 0.34ppm; sodium ion 13.57ppm; iron ion 0.26ppm; potassium ion 1.43ppm; LiFSI: 30.25%, all of which meet the finished product specifications.

[0134] As can be seen from Examples 1 and 2, the purification method of this application has a wide range of applications, applicable not only to high-purity recrystallization mother liquor but also to low-purity wastewater. During the testing process, adjusting the molar ratio of the mixture to the organic ammonium salt can regulate the degree of purity improvement. For example, when the molar ratio of the mixture to the organic ammonium salt is 1:(1-10), the reaction between the mixture and the organic ammonium salt is more complete, and lithium difluorosulfonylimide in the mixture can be converted into lithium difluorosulfonylimide organic ammonium salt. When the molar ratio of the intermediate mixture to lithium ions is 1:(1-10), the intermediate mixture can be converted into lithium difluorosulfonylimide through the lithium loading reaction, thereby improving the purity of lithium difluorosulfonylimide.

[0135] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for purifying lithium difluorosulfonylimide, comprising: A mixture comprising lithium bis(fluorosulfonyl)imide is provided, the mixture comprising metal ions, the metal ions comprising sodium ions; An organic ammonium salt is added to the mixture, and an intermediate mixture is obtained by reaction. The intermediate mixture is purified and then contacted with a cleaning agent to remove metal ions from the intermediate mixture. The cleaning agent includes one or more of water, sodium salt, potassium salt, and lithium salt. Under alkaline conditions, the intermediate mixture is reacted with lithium ions to obtain lithium bis(fluorosulfonyl)imide.

2. The method according to claim 1, characterized in that, The step of purifying the intermediate mixture further includes: The intermediate mixture is contacted with a decolorizing agent to adsorb and remove colored impurities from the intermediate mixture.

3. The method according to claim 2, characterized in that, The decolorizing agent includes one or more of activated carbon particles, activated carbon fibers, zeolite, and diatomaceous earth.

4. The method according to claim 1, characterized in that, The sodium salt includes one or more of sodium chloride, sodium sulfate, and sodium carbonate; The potassium salt includes one or more of potassium chloride, potassium sulfate, and potassium sulfate; The lithium salt includes one or more of lithium chloride, lithium sulfate, and lithium carbonate.

5. The method according to claim 1, characterized in that, The organic ammonium salts include hydrogen fluoride salts of tertiary amines and / or hydrogen fluoride salts of quaternary amines.

6. The method according to claim 5, characterized in that, The hydrogen fluoride salts of the tertiary amines include one or more of trimethylamine hydrogen fluoride, triethylamine hydrogen fluoride, tripropylamine hydrogen fluoride, diisopropylethylamine hydrogen fluoride, and tributylamine hydrogen fluoride. The quaternary ammonium hydrogen fluoride salt includes one or more of tetramethylamine hydrogen fluoride, tetraethylamine hydrogen fluoride, tetrapropylamine hydrogen fluoride, and tetrabutylamine hydrogen fluoride.

7. The method according to claim 6, characterized in that, The tertiary amine's hydrogen fluoride salt includes triethylamine hydrogen fluoride salt.

8. The method according to claim 1, characterized in that, The molar ratio of the mixture to the organic ammonium salt is 1:(1~10).

9. The method according to claim 1, characterized in that, The molar ratio of the intermediate mixture to the lithium ions is 1:(1~10).

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