Process for the preparation of tris(perfluoroalkylsulfonyl)methane and salts thereof

Abstract

This invention discloses a method for preparing tris(perfluoroalkylsulfonyl)methane. The preparation method includes the following steps: the intermediate shown in formula [5] reacts with an oxidant under the action of a catalyst to generate tris(alkylsulfonyl)methane shown in formula [6]. The tris(alkylsulfonyl)methane shown in formula [6] is then electrolytically fluorinated to obtain tris(perfluoroalkylsulfonyl)methane represented by formula [1]. The reaction formula and definition are detailed in the specification. The obtained tris(perfluoroalkylsulfonyl)methane reacts with an alkali metal salt or a base in an organic system to obtain tris(alkylsulfonyl)formate shown in formula [2]. The reaction formula and definition are detailed in the specification. The preparation method provided by this invention has the advantages of inexpensive and readily available raw materials, high yield, mild reaction conditions, and suitability for industrial application.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, and in particular to a method for preparing tris(perfluoroalkylsulfonyl)methane and its salts. Background Technology

[0002] Tris(perfluoroalkylsulfonyl)methyl salts are substances used as Lewis acid catalysts or ion-conducting materials in fields such as organic synthesis and battery electrolytes. Compared to the traditional electrolyte lithium hexafluorophosphate, tris(trifluoromethylsulfonyl)methane lithium salts have higher hydrolysis resistance, thermal stability, and conductivity as lithium battery electrolytes. Therefore, when used as lithium battery additives in electrolytes, they can significantly improve the high and low temperature charge-discharge performance and rate capability of lithium-ion batteries.

[0003] Currently reported methods for preparing tris(trifluoromethylsulfonyl)methane include:

[0004] The non-patent literature *Handbook of Fluorous Chemistry* (2004), pp. 449-452, reports the preparation of tris(trifluoromethanesulfonyl)methane from di(trifluoromethanesulfonyl)methane by reacting it with trifluoromethanesulfonic anhydride after hydrogen removal from tert-butyllithium at temperatures below -78°C. The reported yield is 50%. However, this method requires extremely harsh low-temperature reaction conditions, and the raw material, tert-butyllithium, is highly flammable and explosive, posing poor safety risks. Furthermore, the raw material is expensive and difficult to obtain, making this route impractical for large-scale industrialization.

[0005] Central Glass Corporation's patent WO2008075672 discloses the synthesis of tris(trifluoromethanesulfonyl)methane using trifluoromethanesulfonyl fluoride and Grignard reagent methyl magnesium chloride as raw materials. The reported yields in the literature are low (the highest being 62%), and the raw materials are not easy to obtain. The safety and efficiency of Grignard reagent are difficult to meet the requirements for industrialization.

[0006] Japanese Patent JP2000226392A reports the synthesis of tris(trifluoromethanesulfonyl)methane using trifluoromethanesulfonyl chloride and methyllithium as raw materials at ultra-low temperatures with a yield of 31%. This method also suffers from drawbacks such as harsh reaction conditions, high safety risks, and low yield.

[0007] Chinese patent CN115557862A describes the synthesis of trifluoromethanesulfonylmethane intermediates using sodium trifluoromethylsulfinate and iodomethane. After dehydrogenation with sodium hydride, the intermediates react with sodium trifluoromethylsulfinate to obtain tris(trifluoromethylsulfonyl)methane. The raw materials for this route are readily available, but the author did not obtain the corresponding application results during the verification process of this route.

[0008] In summary, currently available methods for preparing tris(trifluoromethanesulfonyl)methane and its salts generally suffer from low product yields, difficulty in obtaining raw materials, high costs, harsh reaction conditions, and high safety risks, making them unsuitable for industrial-scale production. Therefore, a new process for preparing tris(trifluoromethanesulfonyl)methane needs to be developed. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing tris(trifluoromethylsulfonyl)methane and its salts, which has the advantages of low risk, high yield, mild reaction conditions and low cost, and is suitable for industrial production.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A method for preparing tris(perfluoroalkylsulfonyl)methane, the method comprising the following steps:

[0012] A1. Oxidation step: The intermediate shown in formula [5] reacts with an oxidant under the action of a catalyst to generate tri(alkylsulfonyl)methane shown in formula [6];

[0013] A2. Fluorination step: The tri(alkylsulfonyl)methane shown in formula [6] is electrolytically fluorinated to obtain the tri(perfluoroalkylsulfonyl)methane shown in formula [1];

[0014] The reaction formula is as follows:

[0015]

[0016] Where Rf represents C 1-4 Straight-chain or branched perfluoroalkyl groups, where X is a halogen and R is selected from C 1-4 Straight-chain or branched alkyl groups.

[0017] The Rf is preferably trifluoromethyl or pentafluoroethyl, R is preferably methyl or ethyl, and X is preferably bromine.

[0018] In step A1, the oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite, calcium hypochlorite, sodium periodate, potassium permanganate, potassium persulfate, sodium percarbonate, peracetic acid, m-chloroperoxybenzoic acid, ozone, or oxygen.

[0019] In step A1, the catalyst is selected from oxides or salts of transition metals or alkaline earth metals. Without a catalyst, the oxidation step results in incomplete oxidation of the intermediate, stopping at the sulfoxide intermediate. Therefore, the oxidation step requires both a catalyst and an oxidant.

[0020] Preferably, the oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite, or sodium periodate, and the catalyst is selected from at least one of titanium silicate molecular sieve, ruthenium trichloride, or sodium tungstate. Optimizing the selection of oxidant and catalyst types is more beneficial for improving the yield of tris(alkylsulfonyl)methane.

[0021] In step A1, the amount of catalyst fed is 0.1% to 10% of the mass of the intermediate shown in formula [5].

[0022] In step A2, the electrolytic fluorination method is as follows: tri(alkylsulfonyl)methane and anhydrous hydrogen fluoride are added to an electrolytic cell and fully dissolved before electrolysis. The mass ratio of tri(alkylsulfonyl)methane to anhydrous hydrogen fluoride is 1:2 to 5. The electrolysis temperature is controlled at 0℃ to 20℃. The electrolysis voltage is 4.5V to 10V DC, and the current is controlled at 10A to 100A. After the tri(alkylsulfonyl)methane and anhydrous hydrogen fluoride are fully dissolved in the electrolytic cell, nitrogen gas is fully purged before electrolytic fluorination can be carried out. During electrolytic fluorination, the input voltage needs to be continuously adjusted to control the electrolysis temperature. Given the low boiling point of anhydrous hydrogen fluoride, the temperature should be controlled below the boiling point of hydrogen fluoride to prevent excessive vaporization loss of hydrogen fluoride. The voltage and current directly affect the speed of electrolytic fluorination.

[0023] Preferably, the mass ratio of tris(alkylsulfonyl)methane to anhydrous hydrogen fluoride is 1:2-3, the electrolysis temperature is controlled at 5℃-15℃, the electrolysis voltage is 5V-7V DC, and the current is controlled at 40A-50A. Optimizing the above electrolytic fluorination conditions is more conducive to improving the yield of tris(perfluoroalkylsulfonyl)methane.

[0024] Furthermore, after the electrolytic fluorination is completed, the electrolyte is released from the bottom of the electrolytic cell, concentrated by distillation, and then purified by high-vacuum distillation of the crude product.

[0025] The intermediate shown in formula [5] is obtained by a thioetherification step: the sodium alkyl thiolate of formula [3] and the trihalomethane of formula [4] are reacted in a solvent to obtain the intermediate shown in formula [5]; the reaction formula is as follows:

[0026]

[0027] Specifically, sodium alkyl thiolate solid is dissolved in an organic solvent, and trihalomethane is added dropwise while the raw material is partially or completely dissolved. Because the reaction is violently exothermic, the reaction temperature needs to be controlled. The molar ratio of the trihalomethane to the sodium alkyl thiolate salt is 1:3 to 4, the reaction temperature is 0℃ to 100℃, and the reaction time is 1-10 hours.

[0028] Furthermore, the molar ratio of trihalomethane and sodium alkyl thiolate is 1:3 to 3.3, the reaction temperature is 20℃ to 50℃, and the reaction time is 1-4h; these process conditions are more conducive to improving the yield of the intermediate shown in formula [5].

[0029] In the thioetherification step, the solvent for the methyl thioetherification reaction can be an organic solvent selected from at least one of acetonitrile, toluene, methanol, ethanol, N,N-dimethylformamide, N,N-dimethylacetamide, ethyl acetate, diethyl carbonate, dimethyl carbonate, n-hexane, cyclohexane, diethyl ether, tetrahydrofuran, or petroleum ether, preferably acetonitrile or N,N-dimethylformamide. In the thioetherification step, the solvent for the methyl thioetherification reaction can be water. Alternatively, the raw material can be directly purchased as an aqueous solution of alkyl thiols, without the need for additional solvent.

[0030] The post-processing of the reaction product of the thioetherification step provided by the present invention is simple. After filtering out the solid salt, the product solution can be directly carried out in the next reaction step.

[0031] The present invention also provides a method for preparing tris(perfluoroalkylsulfonyl)formate, the method comprising: obtaining tris(perfluoroalkylsulfonyl)methane as shown in formula [1] according to the above preparation method; reacting tris(perfluoroalkylsulfonyl)methane as shown in formula [1] with an alkali metal salt or a base in an organic system to obtain tris(alkylsulfonyl)formate as shown in formula [2]; the reaction formula is as follows:

[0032]

[0033] Wherein, M represents an alkali metal element. The alkali metal M is preferably at least one selected from lithium, sodium, potassium, rubidium, and cesium. Lithium is more preferably preferred.

[0034] The alkali metal salts used in this invention are mainly halides and carbonates. Examples of M-bases are as follows: lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide.

[0035] Preferably, the alkali metal salt is selected from lithium chloride, lithium carbonate, cesium chloride, or cesium carbonate, and the alkali is selected from lithium hydroxide and cesium hydroxide; these process conditions are beneficial for improving the yield of tri(alkylsulfonyl)carbamate.

[0036] The molar ratio of tri(perfluoroalkylsulfonyl)methane to alkali metal is 1:1 to 1.5, and the reaction temperature is 0℃ to 80℃.

[0037] Furthermore, the molar ratio of tris(perfluoroalkylsulfonyl)methane to M metal in the reaction is 1:1 to 1.1, and the reaction temperature is 20℃ to 50℃; these process conditions are beneficial to improving the yield of tris(alkylsulfonyl)formate.

[0038] Salt formation in a solvent can easily yield high-purity products and avoid the introduction of water, eliminating the need for dehydration. The product can then be purified by recrystallization to obtain a high-purity product.

[0039] The choice of salt-forming solvent and recrystallization solvent mentioned in this invention is not overly restricted; both organic solvents and water are acceptable. Examples of organic solvents include: ethers such as diethyl ether, tetrahydrofuran, dioxane, butyl methyl ether, diisopropyl ether, and ethylene glycol dimethyl ether; alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol; alkanes such as n-pentane, n-hexane, n-heptane, and n-octane; alkyl ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; halogenated hydrocarbons such as dichloromethane and chloroform; nitriles such as acetonitrile and propionitrile; and aromatics such as benzene, toluene, and xylene. Each of these organic solvents can be used alone or in combination; furthermore, the solvent is selected from acetonitrile, tetrahydrofuran, and ethylene glycol dimethyl ether.

[0040] The present invention also provides an application of tri(perfluoroalkylsulfonyl)methane, using the above-mentioned tri(perfluoroalkylsulfonyl)methane as a photoacid.

[0041] The present invention also provides an application of tri(perfluoroalkylsulfonyl)carboxylate, specifically the application of the above-mentioned tri(perfluoroalkylsulfonyl)carboxylate as a lithium battery additive.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1. The method for preparing tris(perfluoroalkylsulfonyl)methane provided by this invention, compared with the traditional route, does not require the use of the highly flammable and explosive hazardous raw material tert-butyllithium, and the route is highly safe;

[0044] 2. The method for preparing tri(perfluoroalkylsulfonyl)methane provided by the present invention uses trihalomethane, sodium alkyl thiolate and other raw materials to prepare the intermediate shown in formula [5]. The raw materials are cheaper and easier to obtain than those of the existing technical route, and the route has low cost and high yield.

[0045] 3. The preparation method of tri(perfluoroalkylsulfonyl)formate provided by the present invention adopts a mild reaction condition, simple process, convenient post-processing, and is suitable for industrial production.

[0046] 4. The preparation method of tri(perfluoroalkylsulfonyl)formate provided by the present invention can be carried out in a one-pot process without purification in multiple steps, which not only reduces the amount of solvent used, making it economical and environmentally friendly, but also helps to improve the product yield.

[0047] 5. The tri(perfluoroalkylsulfonyl)formate prepared by this invention can effectively extend the cycle life of the battery and reduce the initial ACR impedance when used as a lithium battery additive. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0049] In a first aspect of this embodiment, an example of preparing tris(trifluoromethylsulfonyl)methane is provided.

[0050] Example 1

[0051] This embodiment provides a method for preparing tris(trifluoromethylsulfonyl)methane, the specific steps of which are as follows:

[0052]

[0053] S1. Thioetherification step: 110.3 g (1.58 mol) sodium methanethiol was added to a 2 L three-necked flask, along with 550 g of acetonitrile. Stirring was started, and the mixture was cooled to 20 °C. 126.5 g (0.5 mol) tribromomethane was added dropwise to the flask, with the temperature controlled between 20 °C and 30 °C during the addition. The reaction was vigorous. After the addition was complete, the mixture was kept at 30 °C for 4 hours, producing a large amount of solid salt. The mixture was filtered, and the solid was washed with a small amount of acetonitrile. The filtrates were combined. This filtrate can be directly used for oxidation. After concentration, 74.3 g of tri(methylthio)methane was obtained with a purity of 99.3% and a crude yield of 96.4%.

[0054] S2. Oxidation step: 74.3g (0.482mol) of tris(methylthio)methane and 350g of acetonitrile were added to a 1L three-necked flask, along with 18g of ruthenium trichloride aqueous solution (0.8%). The mixture was stirred and cooled to 20°C. 206.3g (0.964mol) of sodium periodate was slowly added, while maintaining the temperature between 20°C and 30°C. After the addition was complete, the mixture was kept at this temperature and stirred for 4 hours. The solid waste was filtered out, and the filtrate was concentrated to obtain 114.4g of viscous liquid tris(methylsulfonyl)methane with a purity of 98.9% and a crude yield of 95%.

[0055] S3. Fluorination step: 114.4g (0.458mol) of crude tris(methylsulfonyl)methane and 286g of anhydrous hydrogen fluoride were pumped into the electrolytic cell of an FC-15 electrolytic fluorination apparatus. After nitrogen purging, a DC voltage of 5V to 7V was supplied to the electrode plate group in the cell through a controllable rectifier; the current was controlled at 40A to 50A. The temperature in the cell was maintained at 5℃ to 15℃ by controlling the voltage. After complete fluorination, the electrolyte was released. After the hydrofluoric acid was recovered by distillation, the crude product was purified by distillation to obtain 170g of pure tris(trifluoromethylsulfonyl)methane with a purity of 99.5% and a yield of 90.2%.

[0056] Example 2

[0057] The preparation method of tris(trifluoromethanesulfonyl)methane provided in this embodiment is the same as that in Example 1, except that:

[0058] In the thioetherification step: 113.4 g (1.62 mol) of sodium methanethiol was added, and other conditions remained unchanged. After concentration, 74.8 g of crude tri(methylthio)methane was obtained with a purity of 99.5% and a crude yield of 97.2%.

[0059] In the oxidation step, 74.8 g (0.482 mol) of tris(methylthio)methane and 350 g of dichloromethane were added to a 1 L three-necked flask, along with 3 g of TS-1 titanium-silicon molecular sieve catalyst. The mixture was stirred and cooled to 20 °C, and 113 g of 30% hydrogen peroxide was slowly added dropwise while maintaining the temperature between 20 °C and 30 °C. After the addition was complete, the mixture was kept at this temperature and stirred for 2 hours, then heated to 50 °C and reacted for 10 hours. The catalyst was filtered, and the filtrate was concentrated to obtain 116 g of viscous liquid tris(methylsulfonyl)methane with a purity of 99% and a crude yield of 96.2%.

[0060] In the fluorination step: 116g (0.464mol) of crude tris(methylsulfonyl)methane and 300g of anhydrous hydrogen fluoride were pumped into the electrolytic cell of an FC-15 electrolytic fluorination device. After electrolytic fluorination, the crude product was distilled to obtain 175.8g of pure tris(trifluoromethylsulfonyl)methane with a purity of 99.4% and a yield of 92%.

[0061] Example 3

[0062] The preparation method of tris(trifluoromethanesulfonyl)methane provided in this embodiment is the same as that in Example 2, except that:

[0063] In the oxidation step, 74.8 g (0.482 mol) of tris(methylthio)methane and 350 g of dichloromethane were added to a 1 L three-necked flask, along with 4 g of sodium tungstate catalyst. The mixture was stirred and cooled to 20 °C, and 113 g of 30% hydrogen peroxide was slowly added dropwise while maintaining the temperature between 20 °C and 30 °C. After the addition was complete, the mixture was kept at this temperature and stirred for 2 hours. Then, the temperature was raised to 50 °C and the reaction was carried out for 10 hours. The catalyst was filtered, and the filtrate was concentrated to obtain 115.2 g of viscous liquid tris(methylsulfonyl)methane with a purity of 99% and a crude yield of 95.5%.

[0064] In the fluorination step: 115.2 g (0.461 mol) of crude tris(methylsulfonyl)methane and 300 g of anhydrous hydrogen fluoride were pumped into the electrolytic cell of an FC-15 electrolytic fluorination apparatus. After electrolytic fluorination, the crude product was distilled to obtain 175.5 g of pure tris(trifluoromethylsulfonyl)methane with a purity of 99.4% and a yield of 92.4%.

[0065] Example 4

[0066] This embodiment provides a method for preparing tris(pentafluoroethylsulfonyl)methane, the specific steps of which are as follows:

[0067]

[0068] S1. Thioetherification step: 132.7 g (1.58 mol) sodium ethanethiol was added to a 2 L three-necked flask, followed by 660 g of acetonitrile. Stirring was started, and the mixture was cooled to 20 °C. 126.5 g (0.5 mol) tribromomethane was added dropwise to the flask, with the temperature controlled between 20 °C and 30 °C during the addition. The reaction was vigorous. After the addition was complete, the mixture was kept at 30 °C for 4 h, producing a large amount of solid salt. The mixture was filtered, and the solid was washed with a small amount of acetonitrile. The filtrates were combined. This filtrate can be directly used for oxidation. After concentration, 93.4 g of crude tri(ethylthio)methane was obtained with a purity of 99.1% and a crude yield of 95.3%.

[0069] S2. Oxidation step: Add 93.4g (0.477mol) of tris(ethylthio)methane and 500g of acetonitrile to a 2L three-necked flask, add 23.5g of ruthenium trichloride aqueous solution (0.8%), stir and cool to 20℃, slowly add 206.3g (0.964mol) of sodium periodate, control the temperature at 20℃~30℃, keep warm and stir for 4 hours after the addition, filter the solid waste, concentrate the filtrate to obtain 133.4g of viscous liquid tris(ethylsulfonyl)methane with a purity of 98.4% and a crude yield of 95.8%.

[0070] S3. Fluorination Step: 133.4 g (0.457 mol) of crude tris(ethylsulfonyl)methane and 400 g of anhydrous hydrogen fluoride are pumped into the electrolytic cell of an FC-15 electrolytic fluorination unit. After purging with nitrogen, a DC voltage of 5V to 7V is supplied to the electrode plate assembly in the cell through a controllable rectifier; the current is controlled at... By controlling the voltage to maintain the temperature inside the tank at 5℃~15℃, after complete fluorination, the electrolyte is released, and after the hydrofluoric acid is recovered by distillation, the crude product is purified by distillation to obtain 233.7g of pure tri(pentafluoroethylsulfonyl)methane with a purity of 99.5% and a yield of 91%.

[0071] Example 5

[0072] The preparation method of tris(pentafluoroethylsulfonyl)methane provided in this embodiment is the same as that in Example 5, except that:

[0073] S2. Oxidation step: Add 93.4g (0.477mol) of tri(ethylthio)methane and 500g of acetonitrile to a 2L three-necked flask, add 4g of TS-1 titanium-silicon molecular sieve catalyst, stir and cool to 20℃, slowly add 113g of 30% hydrogen peroxide dropwise, control the temperature at 20℃~30℃, keep warm and stir for 4 hours after addition, filter to recover the catalyst, concentrate the filtrate to obtain 132g of viscous liquid tri(ethylsulfonyl)methane with a purity of 98.4% and a crude yield of 94.8%.

[0074] S3. Fluorination step: 132g (0.452mol) of crude tris(ethylsulfonyl)methane and 400g of anhydrous hydrogen fluoride were pumped into the electrolytic cell of an FC-15 electrolytic fluorination apparatus. After complete fluorination, the electrolyte was released, and after the hydrofluoric acid was recovered by distillation, the crude product was purified by distillation to obtain 232.7g of pure tris(pentafluoroethylsulfonyl)methane with a purity of 99.5% and a yield of 91.6%.

[0075] A second aspect of this embodiment provides an example of preparing tri(perfluoroalkylsulfonyl)carbamate.

[0076] Example 6

[0077] The preparation method of tris(perfluoroalkylsulfonyl)carbamate provided in this embodiment specifically includes: adding 170g (0.413mol) of tris(trifluoromethylsulfonyl)methane obtained in Example 1 to a 2L three-necked flask, adding 850g of acetonitrile, cooling to 20℃, and slowly adding 10.2g (0.425mol) of lithium hydroxide solid in batches. After the addition is complete, the reaction is carried out for 3 hours, and a large amount of solid precipitates. The solid is filtered, washed with acetonitrile, and the filtrate is concentrated to precipitate some solid. The solids are filtered and combined. The combined solids are added to dimethyl carbonate and recrystallized to obtain 165.6g of pure tris(trifluoromethylsulfonyl)methyl lithium salt with a purity greater than 99.5% and a yield of 96.1%.

[0078] Example 7

[0079] 175.8 g (0.427 mol) of tris(trifluoromethanesulfonyl)methane prepared in Example 2 was added to a 2 L three-necked flask, followed by 850 g of acetonitrile. The mixture was cooled to 20 °C, and 32.5 g (0.44 mol) of lithium carbonate solid was slowly added in batches. After the reaction was completed, a large amount of solid precipitated. The solid was filtered, washed with acetonitrile, and the filtrate was concentrated. Some solid precipitated, and the filtrate was filtered and combined. The combined solid was added to dimethyl carbonate and recrystallized to obtain 170.8 g of pure tris(trifluoromethanesulfonyl)methyl lithium salt with a purity greater than 99.5% and a yield of 95.7%.

[0080] Example 8

[0081] 175.8 g (0.426 mol) of tris(trifluoromethanesulfonyl)methane prepared in Example 3 was added to a 2 L three-necked flask, followed by 850 g of acetonitrile. The mixture was cooled to 20 °C, and 18.6 g (0.44 mol) of lithium chloride solid was slowly added in batches. After the reaction was completed, a large amount of solid precipitated. The solid was filtered, washed with acetonitrile, and the filtrate was concentrated. Some solid precipitated, and the filtrate was filtered and combined. The combined solid was added to dimethyl carbonate and recrystallized to obtain 169 g of pure tris(trifluoromethanesulfonyl)methyl lithium salt with a purity greater than 99.5% and a yield of 94.9%.

[0082] Example 9

[0083] The preparation method of tri(perfluoroalkylsulfonyl)formate provided in this embodiment is the same as that in Example 6, except that 1000g of acetonitrile is added and 71.5g (0.425mol) of solid cesium chloride is added slowly in batches.

[0084] In this example, 218.1 g of pure tris(trifluoromethanesulfonyl)methyl cesium salt was obtained with a purity greater than 99.5% and a yield of 97%.

[0085] Example 10

[0086] 233.7 g (0.416 mol) of tris(pentafluoroethylsulfonyl)methane prepared in Example 5 was added to a 2 L three-necked flask, followed by 1000 g of acetonitrile. The mixture was cooled to 20 °C, and 10.3 g (0.428 mol) of lithium hydroxide solid was slowly added in batches. After the reaction was completed, a large amount of solid precipitated. The solid was filtered, washed with acetonitrile, and the filtrate was concentrated. Some solid precipitated, and the filtrate was filtered and combined. The combined solid was added to dimethyl carbonate and recrystallized to obtain 227.8 g of pure tris(pentafluoroethylsulfonyl)methyl lithium salt with a purity greater than 99.5% and a yield of 96.4%.

[0087] Example 11

[0088] S4. Salt formation step: 116.4 g (0.207 mol) of tris(pentafluoroethylsulfonyl)methane prepared in Example 6 was added to a 1 L three-necked flask, 600 g of acetonitrile was added, the temperature was lowered to 20 °C, and 9.1 g (0.213 mol) of lithium chloride solid was slowly added in batches. After the addition was completed, the reaction was carried out for 3 hours, and a large amount of solid precipitated. The solid was filtered, washed with acetonitrile, and the filtrate was concentrated. Some solid precipitated, filtered and combined. The combined solid was added to dimethyl carbonate and recrystallized to obtain 112.6 g of pure tris(pentafluoroethylsulfonyl)methyl lithium salt with a purity greater than 99.5% and a yield of 95.8%.

[0089] Example 12

[0090] 116.9 g (0.208 mol) of tris(pentafluoroethylsulfonyl)methane prepared in Example 5 was added to a 2 L three-necked flask, followed by 600 g of acetonitrile. The mixture was cooled to 20 °C, and 36 g (0.214 mol) of cesium chloride solid was slowly added in batches. After the addition was complete, the reaction was carried out for 3 hours, during which a large amount of solid precipitated. The solid was filtered, washed with acetonitrile, and the filtrate was concentrated. Some solid precipitated, and the filtrate was filtered and combined. The combined solid was added to dimethyl carbonate and recrystallized to obtain 139.5 g of pure tris(pentafluoroethylsulfonyl)methyl cesium salt with a purity greater than 99.5% and a yield of 96.6%.

[0091] The third aspect of this embodiment provides an example of the application of tris(perfluoroalkylsulfonyl)carbamate in lithium battery additives. Preparation of the basic electrolyte: In an argon-filled glove box (moisture < 5 ppm, oxygen < 10 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are uniformly mixed at a mass ratio of EC:EMC:DEC = 4:4:2. Then, lithium hexafluorophosphate (LiPF6) is slowly added to the mixed solution until the molar concentration reaches 1.0 mol / L to obtain the basic electrolyte.

[0092] Application Example 1

[0093] The electrolyte of this application example was obtained by adding 0.1 wt% of lithium tris(trifluoromethanesulfonyl)methyl ester prepared in Example 6 to the base electrolyte.

[0094] Application Example 2

[0095] The electrolyte of this application example was obtained by adding 0.5 wt% of lithium tris(trifluoromethanesulfonyl)methyl ester prepared in Example 6 to the base electrolyte.

[0096] Application Example 3

[0097] The electrolyte of this application example was obtained by adding 1.0 wt% of lithium tris(trifluoromethanesulfonyl)methyl ester prepared in Example 6 to the base electrolyte.

[0098] Application Example 4

[0099] The electrolyte of this application example was obtained by adding 2.0 wt% of lithium tris(trifluoromethanesulfonyl)methyl ester prepared in Example 6 to the base electrolyte.

[0100] Application Example 5

[0101] The electrolyte of this application example was obtained by adding 5.0 wt% of lithium tris(trifluoromethanesulfonyl)methyl ester prepared in Example 6 to the base electrolyte.

[0102] Application Comparative Example 1

[0103] The base electrolyte is left untreated to obtain the comparative electrolyte for this application.

[0104] Electrochemical performance testing

[0105] The electrolytes used in the above application examples and comparative examples were used to fabricate 1260mAh capacity soft-pack lithium-ion batteries. Each lithium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive electrode active material is a ternary positive electrode (LiNi0.6Co0.2Mn0.2O2), and the negative electrode active material is high-capacity graphite. The preparation process is as follows: the positive electrode, separator, and negative electrode are wound together into a core, sealed with an aluminum-plastic film, and then baked to ensure the electrode moisture content meets requirements. After baking, the cell is injected with electrolyte, and after standing, formation, capacity testing, and aging processes, the finished lithium-ion battery soft-pack cell is obtained.

[0106] The lithium-ion batteries prepared above were subjected to performance tests (test voltage 2.8–4.4V), mainly including:

[0107] (1) Initial ACR impedance

[0108] At room temperature, the battery capacity was adjusted to 50% SOC (state of charge) using the standard charging current. The internal resistance (mΩ) of the lithium battery at a fixed tab position after capacity grading was measured at a frequency of 1KHz using a Japanese Hioki internal resistance meter. This resistance was recorded as the initial ACR impedance (AC internal resistance).

[0109] (2) 60℃ high temperature storage test: Charge the battery to 100% SOC and store it in an oven at 60±2℃ for 14 days. Test the volume before and after storage to obtain the volume expansion rate of the single cell before and after storage at 60℃; test the DCR value after storage at room temperature and calculate the percentage value of the initial DCR, which is recorded as the discharge DCR change rate.

[0110] (3) 80℃ high temperature storage test: Charge the battery to 100% SOC and store it in an 80±2℃ oven for 14 days. Test the volume before and after storage to obtain the volume expansion rate of the single cell before and after storage at 80℃; test the DCR value after storage at room temperature and calculate the percentage value of the initial DCR, which is recorded as the discharge DCR change rate.

[0111] (4) 45℃ high temperature cycle test: The battery is cycled in an oven at 45±1℃ with a charge / discharge current of 1C / 1C. The discharge capacity is calculated every week. The cycle is stopped after 500 cycles, and the capacity retention rate after the cycle is calculated.

[0112] The results of the various electrochemical performance tests are shown in Table 1 below:

[0113] Table 1 Electrochemical performance test results

[0114]

[0115] By comparing Application Examples 1-5 with Application Comparative Example 1, it can be seen that the electrolyte using the lithium tris(trifluoromethanesulfonyl)methyl ester compound prepared in this invention as an additive can, compared with the basic electrolyte, both suppress gas generation during high-temperature storage at 60°C and 80°C and improve the cycle performance of the battery at 45°C. This is mainly because the decomposition temperature of lithium tris(trifluoromethanesulfonyl)methane is above 300°C, which significantly improves thermal stability and safety compared to the decomposition temperature of lithium hexafluorophosphate at 60°C. Furthermore, it exhibits superior hydrolysis resistance and produces no hydrogen fluoride, thus greatly mitigating the corrosion of the cathode material and extending the battery's cycle life.

[0116] By comparing Application Examples 1-5 with Application Comparative Example 1, it can be seen that the electrolyte using the lithium tri(trifluoromethanesulfonyl)methyl ester compound prepared in this invention as an additive can effectively reduce the initial ACR impedance compared to the basic electrolyte. This is because tri(trifluoromethanesulfonyl)methane has higher acidity, so lithium ions are more easily desorbed, thus resulting in higher conductivity.

[0117] Comparing Examples 1-5 reveals that as the amount of lithium tris(trifluoromethanesulfonyl)methyl oxide compound added to the electrolyte increases to a certain level, the electrolyte impedance exhibits a curve that first decreases and then increases. Although the battery still exhibits good suppression of high-temperature gas generation, its high-temperature cycling performance begins to decline due to the increased battery impedance. In summary, an addition amount of lithium tris(trifluoromethanesulfonyl)methyl oxide compound to the electrolyte of 0.5–2 wt% is preferred.

Claims

1. A process for the preparation of tris(perfluoroalkylsulfonyl)methane, characterized in that, The preparation method includes the following steps: A1. Oxidation step: The intermediate shown in formula [5] reacts with an oxidant under the action of a catalyst to generate tri(alkylsulfonyl)methane shown in formula [6]; A2. Fluorination step: The tri(alkylsulfonyl)methane shown in formula [6] is electrolytically fluorinated to obtain the tri(perfluoroalkylsulfonyl)methane shown in formula [1]; The reaction formula is as follows: Where Rf represents C 1-4 Straight-chain or branched perfluoroalkyl groups, where X is a halogen and R is selected from C 1-4 Straight-chain or branched alkyl groups.

2. The method for preparing tris(perfluoroalkylsulfonyl)methane according to claim 1, characterized in that, Rf is selected from trifluoromethyl or pentafluoroethyl, R is selected from methyl or ethyl, and X is bromine.

3. The method for preparing tris(perfluoroalkylsulfonyl)methane according to claim 1, characterized in that, In step A1, the oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite, calcium hypochlorite, sodium periodate, potassium permanganate, potassium persulfate, sodium percarbonate, peracetic acid, m-chloroperoxybenzoic acid, ozone, or oxygen.

4. The method for preparing tris(perfluoroalkylsulfonyl)methane according to claim 1, characterized in that, In step A1, the catalyst is selected from oxides or salts of transition metal elements and oxides or salts of alkaline earth metals.

5. The method for preparing tris(perfluoroalkylsulfonyl)methane according to claim 1, characterized in that, In step A1, the oxidant is selected from at least one of hydrogen peroxide, sodium hypochlorite, or sodium periodate, and the catalyst is selected from at least one of titanium silicate molecular sieve, ruthenium trichloride, or sodium tungstate.

6. The method for preparing tris(perfluoroalkylsulfonyl)methane according to claim 1, characterized in that, In step A2, the electrolytic fluorination method is as follows: tri(alkylsulfonyl)methane and anhydrous hydrogen fluoride are added to an electrolytic cell and fully dissolved before electrolysis. The mass ratio of tri(alkylsulfonyl)methane to anhydrous hydrogen fluoride is 1:2 to 5. The electrolysis temperature is controlled at 0°C to 20°C. The electrolysis voltage is a direct current of 4.5V to 10V, and the current is controlled at 10A to 100A.

7. The method for preparing tris(perfluoroalkylsulfonyl)methane according to claim 1, characterized in that, The intermediate shown in formula [5] is obtained by a thioetherification step: the sodium alkyl thiolate of formula [3] and the trihalomethane of formula [4] are reacted in a solvent to obtain the intermediate shown in formula [5]; the reaction formula is as follows:

8. The method for preparing tris(perfluoroalkylsulfonyl)methane according to claim 1, characterized in that, The molar ratio of the trihalomethane and the sodium alkyl thiolate is 1:3 to 4, the reaction temperature is 0℃ to 100℃, and the reaction time is 1-10h.

9. A method for preparing a tri(perfluoroalkylsulfonyl)carbamate, characterized in that, The preparation method includes: (1) Tris(perfluoroalkylsulfonyl)methane as shown in Formula [1] is obtained by any of the preparation methods according to claims 1-8; (2) The tri(perfluoroalkylsulfonyl)methane shown in formula [1] is reacted with an alkali metal salt or a base in an organic system to obtain the tri(alkylsulfonyl)formate shown in formula [2]; the reaction formula is as follows: Where M represents an alkali metal element.

10. The method for preparing tris(perfluoroalkylsulfonyl)formate according to claim 9, characterized in that, The alkali metal salt is selected from lithium chloride, lithium carbonate, cesium chloride, or cesium carbonate, and the alkali is selected from lithium hydroxide and cesium hydroxide.

11. An application of tris(perfluoroalkylsulfonyl)methane, characterized in that: The use of tri(perfluoroalkylsulfonyl)methane as a photoacid as described in any one of claims 1-8 of formula [1].

12. The application of a tri(perfluoroalkylsulfonyl)carbamate, characterized in that: The application of tri(perfluoroalkylsulfonyl)formate of formula [2] as a lithium battery additive according to any one of claims 9-10, wherein the alkali metal element is lithium.

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