Lithium ion-conducting material and method for purifying the same

Abstract

This disclosure relates to lithium-ion conductive materials and methods for purifying the same, and provides a lithium-ion conductive material comprising lithium sulfonylimide represented by the following general formula (I): where X and Y may be the same or different, and each is independently C. m F 2m+1 (m≥0). A method for purifying the aforementioned lithium-ion conductive material is also provided. The method disclosed herein provides high-purity lithium sulfonylimide lithium-ion conductive material.

Description

Technical Field

[0001] This disclosure relates to the field of electrolytes for secondary batteries, specifically to lithium-ion conductive materials and their purification methods. Background Technology

[0002] In the current fields of electronic materials and electrochemistry, lithium sulfonylimide (LiFSI), especially lithium bisfluorosulfonylimide, is an important lithium-ion conducting material widely used in lithium-ion batteries, electrolytes, and other high-energy-density energy storage devices. Existing technologies typically employ direct synthesis and simple solvent evaporation methods to obtain lithium bisfluorosulfonylimide. However, these methods have several drawbacks.

[0003] First, the solvents used in existing processes, such as carbonates, carboxylic esters, and ethers, have relatively strong interactions with lithium ions in lithium salts, forming solvation products that result in weak crystallization of the target product, low crystallization efficiency, and difficulty in further improving purity. Sodium and potassium ions have weak interactions with carbonates, carboxylic esters, and ethers, but lithium ions, with their small radius and strong polarization ability, have relatively strong interactions with these substances, making direct recrystallization difficult or resulting in low yields, and leaving residual solvents that are not easily removed. Therefore, it is necessary to find a better solvent that interacts weaker with lithium ions and stronger with bis(fluorosulfonyl)imide anions.

[0004] Secondly, the direct synthesis process of existing technologies easily introduces impurities and moisture, resulting in low product purity. In particular, when the obtained lithium bis(fluorosulfonyl)imide contains a certain amount of water, the water cannot be selectively retained in the mother liquor during recrystallization in solvents such as carbonates, carboxylic esters, and ethers. Instead, it is evenly distributed in the mother liquor and LiFSI, making it impossible to effectively remove the water from the LiFSI.

[0005] Furthermore, existing solvents are difficult to effectively separate high-purity lithium sulfonylimide using evaporation methods, especially when the crude material contains impurities with similar structures, which increases the difficulty of separation and purification.

[0006] These drawbacks limit the application of lithium sulfonylimide in high-performance lithium-ion conductive materials.

[0007] Therefore, there is an urgent need in this field to develop a method to improve the purity of lithium sulfonylimide. Summary of the Invention

[0008] The purpose of this application is to provide a novel high-purity lithium sulfonylimide lithium-ion conductive material and its purification method, which solves the problems of low purity, high moisture content, high production cost and excessive waste in the preparation of lithium sulfonylimide products in the prior art.

[0009] On the one hand, this disclosure provides a lithium-ion conductive material comprising lithium sulfonylimide represented by the following general formula (I):

[0010]

[0011] In the formula, X and Y can be the same or different, and each is independently represented by C. m F 2m+1 (m≥0);

[0012] The lithium-ion conductive material is prepared from good solvent molecules represented by the following general formulas (II) and / or (III):

[0013]

[0014] In the formula, R 1 For F, Cl, CF3, C n H 2n+1 C n H 2n+1-x F x One or any combination thereof; R 2 and R 3 Whether they are the same or different, and each is independently CF3, C n H 2n+1 Or C n H 2n+1-x F x ;R 4 C k H 2k-q F q Or (CH2) k-1 O has a ring-based structure, where n≥0, k≥3, 0≤q≤2k;

[0015] The lithium-ion conductive material contains greater than 0 and less than 95% by weight of the above-mentioned good solvent molecules.

[0016] In a preferred embodiment, the proportion of the good solvent molecules is 10ppm-5000ppm, 5000ppm-50%, or 50%-95%.

[0017] In another preferred embodiment, the lithium-ion conductive material further comprises 1-20% by weight of one or more of carbonates, carboxylic esters, and ethers, based on the weight of the lithium-ion conductive material; and other impurity ions, including but not limited to sodium ions and potassium ions.

[0018] In another preferred embodiment, R 1 It is F.

[0019] In another preferred embodiment, R 4This includes TFSPY, TFSPD, and TFSMP, represented by the following general formulas:

[0020]

[0021] In another preferred embodiment, the lithium-ion conductive material is a solid or a liquid.

[0022] On the other hand, this disclosure provides a method for purifying the above-mentioned lithium-ion conductive material, the method comprising the following steps:

[0023] (1) Obtain crude lithium-ion conductive material containing sulfonylimide salt represented by general formula (I);

[0024] (2) The crude lithium-ion conductive material obtained in step (1) is mixed evenly with a good solvent represented by general formula (II) and / or (III) to form a treatment solution;

[0025] (3) Recrystallize the treated solution obtained in step (2) to obtain recrystallized mother liquor and / or crystals; and

[0026] (4) Remove impurities from the mother liquor and / or crystals obtained in step (3) to obtain the lithium-ion conductive material.

[0027] In a preferred embodiment, in step (3), the recrystallization is performed in the following manner:

[0028] Adding a sulfonylimide salt as a poor solvent to the treatment solution for recrystallization, preferably, the poor solvent includes, but is not limited to, one or any combination of the following solvents: C 1-20 Aromatic hydrocarbons, halogenated C 1-20 Aromatics, C 1-20 Alkanes, chloroform, toluene, dichloromethane, and dichloroethane.

[0029] In another preferred embodiment, in step (3), the recrystallization is carried out using a high and low temperature method, wherein the high and low temperature range is -40°C to 150°C, preferably room temperature to 80°C.

[0030] In another preferred embodiment, in step (4), the impurity removal process includes at least one of the following: filtration, washing, drying, distillation, extraction, separation and / or cyclic repeating of the above operations.

[0031] In another preferred embodiment, the good solvent is further added to the crystal obtained in step (3), and the bad solvent is evaporated.

[0032] In another preferred embodiment, the method further includes filtering and centrifuging to remove impurities that are not soluble in good solvents.

[0033] In another preferred embodiment, the impurity removal process includes filtration and / or drying, wherein impurities soluble in a good solvent are retained in the mother liquor of the treatment solution to obtain a further treatment solution; and insoluble substances are removed from the further treatment solution to separate the sulfonamide salt and obtain the lithium-ion conductive material.

[0034] In another preferred embodiment, before performing step (3), the processed liquid obtained in step (2) is dehydrated, wherein the dehydration is performed by molecular sieve dehydration, solvent concentration dehydration or sacrificial heating dehydration.

[0035] In another preferred embodiment, if the treatment liquid obtained in step (2) is not dehydrated before step (3), the crystals are separated from the mother liquor, and the mother liquor is heated to a temperature greater than 80°C to 100°C to cause the lithium sulfonylimide in the mother liquor to react and decompose with water to form an insoluble substance, and then filtered to remove the insoluble substance.

[0036] In another preferred embodiment, in step (2), one or more of carbonates, carboxylic esters and ethers, weighing 1-20% by weight of the lithium-ion-conducting material, are mixed uniformly with a good solvent.

[0037] In another preferred embodiment, the insoluble substance includes: lithium chloride, lithium fluoride, lithium sulfate, lithium fluorosulfate, hydrogen fluoride, and fluorosulfonic acid.

[0038] Beneficial effects:

[0039] This application provides a method for improving the purity of lithium sulfonylimide and a high-purity lithium sulfonylimide conductive ion material prepared by the method, which solves the problems of low purity, high moisture content, high production cost and excessive waste in the preparation of lithium sulfonylimide products in the prior art.

[0040] The crystalline solid obtained through crystallization in this application is easy to package and transport.

[0041] The liquid obtained through distillation in this application is convenient for subsequent use and does not require further dissolution, as lithium-conducting solvents require a relatively harsh environment. The pre-prepared solution does not need further preparation. Direct purification using this good solvent yields a high-purity liquid product (due to the removal of undesirable solvents through distillation), avoiding the need for repeated solvent addition and removal processes when using the solid. Detailed Implementation

[0042] The "range" disclosed herein 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 expected. 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.

[0043] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions. Similarly, unless otherwise specified, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0044] In this application, unless otherwise specified, the terms "comprising" and "including" as used herein are open-ended or closed-ended. For example, "comprising" and "including" may mean that other components not listed may also be included, or that only the listed components may be included.

[0045] In this description, unless otherwise stated, the term "or" is inclusive. 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).

[0046] It should be understood that in the description of this disclosure, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0047] To address the shortcomings of existing technologies in preparing lithium sulfonylimide products, such as low purity, high moisture content, high production costs, and excessive waste, this application overcomes the defects of existing technologies by mixing crude materials containing fluorosulfonylimide salts with a good solvent that has a weaker interaction with lithium ions but a stronger interaction with bisfluorosulfonylimide anions, and then adding a poor solvent to remove impurities, ultimately obtaining high-purity lithium-ion conductive materials.

[0048] In a first aspect of this disclosure, a lithium-ion conductive material is provided, comprising lithium sulfonylimide represented by the following general formula (I):

[0049]

[0050] In the formula, X and Y can be the same or different, and each is independently represented by C. m F 2m+1 (m≥0);

[0051] The lithium-ion conductive material is prepared from good solvent molecules represented by the following general formulas (II) and / or (III):

[0052]

[0053] In the formula, R 1 For F, Cl, CF3, C n H 2n+1 C n H 2n+1-x F x One or any combination thereof; R 2 and R 3 Whether they are the same or different, and each is independently CF3, C n H 2n+1 Or C n H 2n+1-x F x ;R 4 C k H 2k-q F q Or (CH2) k-1 O has a ring-based structure, where n≥0, k≥3, 0≤q≤2k;

[0054] The lithium-ion conductive material contains greater than 0 and less than 95% by weight of the above-mentioned good solvent molecules.

[0055] In this application, the good solvent molecules represented by general formulas (II) and (III) have a -SO2- group, which has similar miscibility to the -SO2-N-SO2- group of lithium sulfonylimide represented by general formula (I), and their interaction with lithium ions is relatively weak. In contrast, carbonates, carboxylic esters, ethers, etc., used in existing processes have relatively strong interactions with lithium ions, forming solvations and exhibiting weak recrystallization. The good solvent molecules represented by general formulas (II) and (III) primarily interact with the anion -SO2-N-SO2-, Li + The interference from lithium ions is minimal, making recrystallization easier. Furthermore, sodium and potassium ions exhibit weak interactions with carbonates, carboxylic esters, and ethers. However, due to the small radius and strong polarization ability of lithium ions, their interactions with carbonates, carboxylic esters, and ethers are relatively strong, making direct recrystallization difficult or resulting in low yields, and residual solvents are not easily removed. In contrast, the good solvent molecules represented by general formulas (II) and (III) interact even weaker with lithium ions and more strongly with the anions -SO2-N-SO2-.

[0056] Furthermore, removing impurities and water from lithium sulfonamide is very difficult, especially water removal. When it contains a certain amount of water, during recrystallization using carbonates, carboxylic esters, ethers, etc., the water cannot be selectively retained in the mother liquor and will be evenly distributed in the mother liquor and lithium sulfonamide, thus failing to remove the water. However, when using good solvents represented by general formulas (II) and (III) (such as N,N-dimethylsulfonamide (FSA)) as the main solvent, water can be selectively retained in the mother liquor, and the water content in the crystal is drastically reduced, achieving a highly efficient and extreme water removal effect.

[0057] Preferably, the proportion of the good solvent molecules is 10ppm-5000ppm, 5000ppm-50%, or 50%-95%.

[0058] Preferably, the lithium-ion conductive material further comprises 1-20% by weight of other solvents such as carbonates, carboxylic esters, and ethers, based on the weight of the lithium-ion conductive material.

[0059] In this disclosure, the lithium-ion conductive material further includes other impurity ions, including but not limited to sodium ions and potassium ions.

[0060] Preferably, R 1 It is F.

[0061] Preferably, R 4 This includes TFSPY, TFSPD, and TFSMP, represented by the following general formulas:

[0062]

[0063] Preferably, the good solvent includes N,N-dimethylsulfonamide (FSA).

[0064] Preferably, the lithium-ion conductive material is a solid or a liquid.

[0065] In a second aspect of this disclosure, a method for purifying the above-mentioned lithium-ion conductive material is provided, the method comprising the following steps:

[0066] (1) Obtain crude lithium-ion conductive material containing sulfonylimide salt represented by general formula (I);

[0067] (2) The crude lithium-ion conductive material obtained in step (1) is mixed evenly with a good solvent represented by general formula (II) and / or (III) to form a treatment solution;

[0068] (3) Recrystallize the treated solution obtained in step (2) to obtain recrystallized mother liquor and / or crystals; and

[0069] (4) Remove impurities from the mother liquor and / or crystals obtained in step (3) to obtain the lithium-ion conductive material.

[0070] In this disclosure, in step (3), the recrystallization is performed in the following manner:

[0071] Adding a poor solvent for sulfonamide salts to the treatment solution for recrystallization (with or without prior dehydration), wherein the poor solvent is a solvent with weak solubility for sulfonamide salts, including: C 1-20 Aromatic hydrocarbons, halogenated C 1-20 Aromatics, C 1-20 Alkanes, chloroform, toluene, dichloromethane, and dichloroethane, etc.; or

[0072] The recrystallization is carried out using a high and low temperature method, wherein the high and low temperature range is -40℃ to 150℃, preferably room temperature to 80℃.

[0073] In this disclosure, the dehydration is carried out in the following ways: molecular sieve dehydration, solvent concentration dehydration, or sacrificial heating dehydration, etc.

[0074] In this disclosure, without dehydration, the crystals are separated from the mother liquor, and the mother liquor is heated to a temperature greater than 80°C to 100°C, causing the lithium sulfonamide in the mother liquor to react and decompose with water to form insoluble substances (such as lithium chloride, lithium fluoride, lithium sulfate, lithium fluorosulfate, hydrogen fluoride, and fluorosulfonic acid, etc.), and then filtered to remove the insoluble substances.

[0075] In this disclosure, in step (4), the impurity removal process includes at least one of the following: filtration, washing, drying, distillation, extraction, separation and / or cyclic repeating of the above operations.

[0076] Preferably, the good solvent is further added to the crystal obtained in step (3), and the bad solvent is evaporated.

[0077] Preferably, the method further includes filtering and centrifuging to remove impurities that are not soluble in good solvents.

[0078] Preferably, the impurity removal process includes filtration and / or drying, wherein impurities soluble in a good solvent are retained in the mother liquor of the treatment solution to obtain a further treatment solution; and insoluble substances are removed from the further treatment solution to separate the sulfonamide salt and obtain the lithium-ion conductive material.

[0079] Preferably, in step (2), 1-20% by weight of other solvents such as carbonates, carboxylic esters and ethers, based on the weight of the lithium-ion conductive material, are mixed uniformly with a good solvent. More preferably, the ratio of other solvents to good solvent is 2:8.

[0080] Preferably, step (2) is performed at a temperature below 25°C.

[0081] Preferably, step (2) is carried out under inert conditions, which are generated by using argon and / or nitrogen and / or other inert dry (i.e. anhydrous) gases, among others.

[0082] Preferably, step (2) can be performed at any suitable pressure, such as 1 atmosphere.

[0083] In this disclosure, any suitable method can be used for filtration, such as using one or more filter media, centrifugation, gravity separation, hydrocyclone, etc.

[0084] Preferably, the dried, purified fluorosulfonamide salt product can be stored at a reduced temperature, such as about 25°C or lower, in an inert gas, such as argon, in a dry, inert container, such as a dry polytetrafluoroethylene (PTFE) container or a nickel alloy that is inert to free fluoride, to inhibit the degradation of the fluorosulfonamide salt during storage.

[0085] In the following, specific embodiments are used to characterize the preparation of sulfonylimide lithium-ion conductive materials using the method of the present invention. However, it should be specifically noted that the scope of protection of this application is defined by the claims, and not limited to the specific embodiments.

[0086] Examples 1-12: Using FSA as a good solvent to prepare LiFSI lithium-ion conductive materials.

[0087] Examples 1-6: Adding unsuitable solvents.

[0088] Example 1: LIFSI (2000g) was dissolved in FSA (4666g) by stirring. Dichloromethane (6000g) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1700g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 90%, and quantitative analysis using gas chromatography headspace analysis showed an FSA residue of 0.15%.

[0089] Example 2: LIFSI (2000g) was dissolved in FSA (3000g) by stirring. Dichloromethane (6000g) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1840g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 92%, and quantitative analysis using gas chromatography headspace analysis showed an FSA residue of 0.12%.

[0090] Example 3: LIFSI (2000g) was dissolved in FSA (2000g) by stirring. Dichloromethane (6000g) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1900g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 95%, and quantitative analysis using gas chromatography headspace analysis showed an FSA residue of 0.1%.

[0091] Example 4: LIFSI (2000g) was dissolved in FSA (1333g) by stirring. Dichloromethane (6000g) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1920g of pure LIFSI. Quantitative analysis using IC microscopy showed a LIFSI yield of 96%, and quantitative analysis using gas chromatography headspace microscopy showed an FSA residue of 0.08%.

[0092] Example 5: LIFSI (2000g) was dissolved in FSA (857g) by stirring. Dichloromethane (6000g) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1960g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 98%, and quantitative analysis using gas chromatography headspace analysis showed an FSA residue of 0.03%.

[0093] Example 6: LIFSI (2000g) was dissolved in FSA (500g) by stirring. Dichloromethane (6000g) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1970g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 98.5%, and quantitative analysis using gas chromatography headspace analysis showed an FSA residue of 0.01%.

[0094] Table 1 below shows the results of adding unsuitable solvents to LIFSI at different concentrations in Examples 1-6. As can be seen from Table 1, using FSA as a good solvent, combined with the use of unsuitable solvents, yields excellent purification results and high yields, with minimal FSA residue.

[0095] Table 1

[0096]

[0097] (1) FSA residue measurement method:

[0098] Headspace conditions: headspace vial heating temperature: 110℃; quantitative loop temperature: 120℃; transfer line temperature: 130℃; sample preheating equilibrium time: 30 min; headspace pressurization time: 0.2 min; injection time: 1 min.

[0099] Chromatographic conditions: DB-624 column (30m × 0.32mm × 1.8μm); carrier gas: high-purity nitrogen, flow rate 2.0ml / min (constant); injection port temperature: 220℃; detector temperature: 250℃; injection volume: 1ml; split injection, split ratio 10:1. Temperature program: initial temperature 40℃, hold for 5 min, increase to 125℃ at a rate of 25℃ / min, hold for 3 min, then increase to 200℃ at a rate of 40℃ / min, hold for 4 min.

[0100] Plotting the standard curve:

[0101] Preparation of standard stock solution: Accurately weigh 0.1 g of analytical grade FSA into a 100 mL volumetric flask that has been filled with 20 mL of N,N-dimethylformamide, dilute to the mark with N,N-dimethylformamide, and shake well. The concentration is 1 mg / mL.

[0102] Take five 50 mL volumetric flasks and transfer 0.5 mL, 1.5 mL, 2.5 mL, 3.5 mL, and 5.0 mL of the standard stock solution to each flask. Dilute to the mark with (1+)N,N-dimethylformamide to obtain concentrations of 10 μg / mL, 30 μg / mL, 50 μg / mL, 70 μg / mL, and 100 μg / mL, respectively. Label them as S1, S2, S3, S4, and S5.

[0103] Accurately transfer 2 mL of the above solution into a 20 mL headspace vial and seal the vial. Perform instrumental analysis, plotting a standard curve with solvent content on the x-axis and peak area on the y-axis. Linearity should be above 0.999; otherwise, prepare a fresh standard solution.

[0104] Sample testing:

[0105] Accurately weigh the sample into a 25 mL volumetric flask, dilute to the mark with (1+)N,N-dimethylformamide, and mix well. Accurately transfer 2 mL of the solution into a 20 mL headspace vial and seal the vial. Perform the test. Calculate the sample concentration from the standard curve based on the peak area of ​​the tested sample. Calculate the FSA content in the sample using the weighed sample and the dilution volume.

[0106] (2) LIFSI yield calculation method: (mass of dried LIFSI obtained / mass of crude LIFSI input) * 100%.

[0107] LIFSI content determination method: Ion chromatography was used with a Metrosep A Supp5 250 / 4.0 column. The mobile phase consisted of a mixture of 3.2 mmol / L sodium carbonate and 3.2 mmol / L sodium bicarbonate, 60% pure water, and 40% acetonitrile. Standard solutions with fluorochlorosulfate concentrations of 150 mg / L, 300 mg / L, 450 mg / L, 600 mg / L, and 750 mg / L were prepared, and a concentration curve was established. For sample preparation, 1-2 g was weighed, accurate to 0.1 mg, dissolved in acetonitrile, and diluted to the corresponding volume. The sample content was quantitatively determined using the external standard method. Calculation formula: Content = Product of sample test result and dilution volume divided by the weighed amount.

[0108] Examples 7-12: High and low temperature methods are used.

[0109] Example 7: 2000g of LIFSI was added to 4666g of FSA and heated to 75°C to dissolve. The mixture was then cooled to crystallize, filtered at 30°C, and dried. No LIFSI precipitated.

[0110] Example 8: 2000g of LIFSI was added to 3000g of FSA and heated to 75°C to dissolve. The solution was then cooled to crystallize, filtered at 30°C, and dried to obtain 100g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 5%, and quantitative analysis using headspace gas chromatography showed an FSA residue of 1000ppm.

[0111] Example 9: 2000g of LIFSI was added to 2000g of FSA and heated to 75°C to dissolve. The solution was then cooled to crystallize, filtered at 30°C, and dried to obtain 700g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 35%, and quantitative analysis using headspace gas chromatography showed an FSA residue of 700ppm.

[0112] Example 10: 2000g of LIFSI was dissolved by adding 1333g of FSA to 75°C, then cooled to crystallize, filtered at 30°C, and dried to obtain 1200g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 60%, and quantitative analysis using headspace gas chromatography showed an FSA residue of 250ppm.

[0113] Example 11: 2000g of LIFSI was dissolved in 857g of FSA by heating to 75°C, followed by cooling to crystallize, filtration at 30°C, and drying to obtain 1440g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 72%, and quantitative analysis using headspace gas chromatography showed an FSA residue of 200ppm.

[0114] Example 12: 2000g of LIFSI was dissolved in 500g of FSA by heating to 75°C, followed by cooling to crystallize, filtration at 30°C, and drying to obtain 1700g of pure LIFSI. Quantitative analysis using IC showed a LIFSI yield of 85%, and quantitative analysis using headspace gas chromatography showed an FSA residue of 180ppm.

[0115] Table 2 below shows the results of using different concentrations of LIFSI in Examples 7-12 with high and low temperature methods. As can be seen from Table 2, using FSA as a good solvent, combined with high and low temperature recrystallization, yields better purification results and less FSA residue.

[0116] Table 2

[0117]

[0118] Comparative Examples 1-6: LiFSI lithium-ion conductive materials were prepared using diethyl carbonate (DEC).

[0119] Comparative Example 1: LIFSI (2000g) was added to DEC (4666g) and stirred until dissolved. Dichloromethane (11.428kg) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes. No LIFSI precipitated.

[0120] Comparative Example 2: LIFSI (2000g) was added to DEC (3000g) and stirred until dissolved. Dichloromethane (11.428kg) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes. No LIFSI precipitated.

[0121] Comparative Example 3: LIFSI (2000g) was added to DEC (2000g) and stirred until dissolved. Dichloromethane (11.428kg) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 400g of pure LIFSI.

[0122] Quantitative analysis using IC showed a LIFSI yield of 20%, and quantitative analysis using gas-phase headspace analysis showed a DEC residue of 0.15%.

[0123] Comparative Example 4: LIFSI (2000g) was added to DEC (1333g) and stirred until dissolved. Dichloromethane (11.428kg) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1000g of pure LIFSI.

[0124] Quantitative analysis using IC showed a LIFSI yield of 50%, and quantitative analysis using gas chromatography headspace analysis showed a DEC residue of 0.15%.

[0125] Comparative Example 5: LIFSI (2000g) was added to DEC (857g) and stirred until dissolved. Dichloromethane (11.428kg) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1200g of pure LIFSI.

[0126] Quantitative analysis using IC showed a LIFSI yield of 60%, and quantitative analysis using gas chromatography headspace analysis showed a DEC residue of 0.15%.

[0127] Comparative Example 6: LIFSI (2000g) was added to DEC (500g) and stirred until dissolved. Dichloromethane (11.428kg) was added dropwise over 1.5 hours. After the addition was complete, the mixture was stirred for 30 minutes, filtered, and dried at 60°C for 1 hour to obtain 1640g of pure LIFSI.

[0128] Quantitative analysis using IC showed a LIFSI yield of 82%, and quantitative analysis using gas chromatography headspace analysis showed a DEC residue of 0.15%.

[0129] Table 3 below shows the results of using DEC with different concentrations of LIFSI in Comparative Examples 1-6, combined with high and low temperature methods. As can be seen from Table 3, compared to Examples 7-12, the purification effect and yield using diethyl carbonate were poor, and more DEC residue was present.

[0130] Table 3

[0131]

[0132] (3) The method for measuring DEC residues is the same as that for measuring FSA residues in (1).

Claims

1. A lithium-ion conductive material, characterized in that, It contains lithium sulfonylimide represented by the following general formula (I): In the formula, X and Y can be the same or different, and each is independently represented by C. m F 2m+1 where m≥0; The lithium-ion conductive material is prepared by purification of good solvent molecules represented by the following general formulas (II) and / or (III): In the formula, R 1 For F, Cl, CF3, C n H 2n+1 C n H 2n+1-x F x One or any combination thereof; R 2 and R 3 Whether they are the same or different, and each is independently CF3, C n H 2n+1 Or C n H 2n+1-x F x ;R 4 C k H 2k-q F q Or (CH2) k-1 The ring-based structure of O, where n ≥ 1, k ≥ 3, 0 ≤ q ≤ 2k, 1 <x≤2n+1; The lithium-ion conductive material contains greater than 0 and less than 95% by weight of the above-mentioned good solvent molecules.

2. The lithium-ion conductive material as described in claim 1, characterized in that, The proportion of the good solvent molecules is 10ppm-5000ppm, 5000ppm-50%, or 50%-95%.

3. The lithium-ion conductive material as described in claim 1, characterized in that, It further comprises 1-20% by weight of one or more of carbonates, carboxylic esters and ethers, based on the weight of the lithium-ion conductive material; and impurity ions, including sodium ions and potassium ions.

4. The lithium-ion conductive material as described in claim 1, characterized in that, R 1 It is F.

5. The lithium-ion conductive material as described in claim 1, characterized in that, R 4 This includes TFSPY, TFSPD, and TFSMP, represented by the following general formulas:

6. The lithium-ion conductive material according to any one of claims 1-5, characterized in that, The lithium-ion conductive material can be solid or liquid.

7. A method for purifying the lithium-ion conductive material according to claim 1, characterized in that, The method includes the following steps: (1) Obtain crude lithium-ion conductive material containing sulfonylimide salt represented by general formula (I); (2) The crude lithium-ion conductive material obtained in step (1) is mixed evenly with a good solvent represented by general formula (II) and / or (III) to form a treatment solution; (3) Recrystallize the treated solution obtained in step (2) to obtain recrystallized mother liquor and / or crystals; and (4) Remove impurities from the mother liquor and / or crystals obtained in step (3) to obtain the lithium-ion conductive material.

8. The method as described in claim 7, characterized in that, In step (3), the recrystallization is carried out in the following manner: Adding a poor solvent, such as a sulfonamide salt, to the treatment solution for recrystallization; preferably, the poor solvent includes, but is not limited to, one or any combination of the following solvents: C 1-20 Aromatic hydrocarbons, halogenated C 1-20 Aromatics, C 1-20 Alkanes, chloroform, toluene, dichloromethane, and dichloroethane.

9. The method as described in claim 7, characterized in that, In step (3), the recrystallization is carried out using a high and low temperature method, wherein the high and low temperature range is -40℃ to 150℃, preferably room temperature to 80℃.

10. The method as described in claim 7, characterized in that, In step (4), the impurity removal process includes at least one of the following: filtration, washing, drying, distillation, extraction, separation and / or cyclic repeating of the above operations.

11. The method as described in claim 8, characterized in that, The good solvent is further added to the crystal obtained in step (3), and the bad solvent is evaporated.

12. The method as described in claim 7, characterized in that, The method also includes filtering and centrifuging to remove impurities that are not soluble in good solvents.

13. The method as described in claim 10, characterized in that, The impurity removal process includes filtration and / or drying, wherein impurities soluble in a good solvent are retained in the mother liquor of the treatment solution to obtain a further treatment solution; and insoluble substances are removed from the further treatment solution to separate the sulfonamide salt and obtain the lithium-ion conductive material.

14. The method as described in claim 7, characterized in that, Before proceeding to step (3), the treatment liquid obtained in step (2) is dehydrated, wherein the dehydration is carried out by molecular sieve dehydration, solvent concentration dehydration or sacrificial heating dehydration.

15. The method as described in claim 7, characterized in that, If the treatment liquid obtained in step (2) is not dehydrated before step (3), the crystal is separated from the mother liquor and the mother liquor is heated to a temperature greater than 80°C to 100°C to cause the lithium sulfonamide in the mother liquor to react and decompose with water to form an insoluble substance. Then, the insoluble substance is removed by filtration.

16. The method as described in claim 7, characterized in that, In step (2), one or more of carbonates, carboxylic acid esters and ethers, weighing 1-20% by weight of the lithium-ion conductive material, are mixed uniformly with a good solvent.

17. The method as described in claim 13 or 15, characterized in that, The insoluble substances include: lithium chloride, lithium fluoride, lithium sulfate, lithium fluorosulfate, hydrogen fluoride, and fluorosulfonic acid.

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