阅读说明：本技术 一种高纯度双氟磺酰亚胺盐的制备方法 (Preparation method of high-purity bis (fluorosulfonyl) imide salt ) 是由 杨斌 沈峰枫 于 2019-11-20 设计创作，主要内容包括：本发明涉及盐电池电解液添加剂制备技术领域,具体涉及一种高纯度双氟磺酰亚胺盐的制备方法。其制备原料至少包括双氟磺酰亚胺、M<Sup>+</Sup><Sub>n</Sub>X<Sup>n-</Sup>,其中,所述M选自Li、Na、K、Rb、Cs中任一种,所述X为包括B、O、N、P、Si至少一种元素的阴离子,n≥2。本发明提供的制备双氟磺酰亚胺盐的方法目标产物的转化率较高,反应产物单一,几乎没有副反应,产品纯度高；实施过程中几乎无三废,副产品和溶剂可以回收套用。(The invention relates to the technical field of preparation of salt battery electrolyte additives, in particular to a preparation method of high-purity bis (fluorosulfonyl) imide salt. The preparation raw materials at least comprise bis (fluorosulfonyl) imide and M + n X n‑ Wherein M is selected from any one of Li, Na, K, Rb and Cs, X is an anion comprising B, O, N, P, Si at least one element, and n is more than or equal to 2. The method for preparing the bis (fluorosulfonyl) imide salt has the advantages of high conversion rate of the target product, single reaction product, almost no side reaction and high product purity; the implementation process almost has no three wastes, and byproducts and solvents can be recycled and reused.)

1. The preparation method of the high-purity bis (fluorosulfonyl) imide salt is characterized in that the preparation raw materials at least comprise bis (fluorosulfonyl) imide and M⁺ _nX^n-，

Wherein M is selected from any one of Li, Na, K, Rb and Cs, X is an anion containing B, O, N, P, Si at least one element, and n is more than or equal to 2.

2. The method for preparing bis (fluorosulfonyl) imide salt according to claim 1 wherein said M is⁺ _nX^n-Is a multi-inorganic salt, and comprises at least one of sulfate, sulfite, thiosulfate, phosphate, monohydrogen phosphate, phosphite, pyrophosphate, silicate, hexafluorosilicate, borate, molybdate and chromate.

3. The method for preparing bis (fluorosulfonyl) imide salt according to claim 1 wherein said M is⁺ _nX^n-The polycarboxylic acid salt is at least one of oxalate, malonate, succinate, glutarate, adipate, sebacate, maleate, fumarate, tartrate, glutamate dihydrochloride, cyclohexanetrioate, phthalate, isophthalate, terephthalate, isophthalate, citrate, ethylenediaminetetraacetic acid tetrasalt, ethylenediaminetetraacetic acid trisalt and ethylenediaminetetraacetic acid disalt.

4. The method for preparing bis (fluorosulfonyl) imide salt according to claim 1 wherein said M is⁺ _nX^n-The compound is a polybasic organic phenate, and comprises at least one of catechol disalt, resorcinol disalt, hydroquinone disalt, biphenol disalt, bisphenol A disalt, salicylic acid disalt, p-hydroxybenzene sulfonic acid disalt, o-hydroxybenzene sulfonic acid disalt and 5-sulfo-1, 3-benzene dicarboxylic acid disalt.

5. The method for preparing bis (fluorosulfonyl) imide salt according to claim 1 wherein said M is⁺ _nX^n-Selected from the group consisting of lithium sulfate, sodium phosphate, dipotassium malonate, rubidium sulfate, dicesium isophthalate, dilithium chromate dihydrate, lithium metasilicate, 3-hydroxy-2-oxopropyl phosphate dilithium, lithium tetraborate, lithium silicate, dilithium glycerophosphate, lithium orthosilicate, lithium sulfite, lithium molybdate, dilithium diphosphate, lithium chromate, pentalithium triphosphate, dilithio phthalateAt least one of thiosulfate, dilithium hexafluorosilicate, dilithium adipate, dilithium sebacate, dilithium methylenebis (phosphonate), dilithium 2-butenedioate, lithium oxalate, dilithium diphosphate, lithium maleate, dilithium azelate, lithium dichromate, lithium tartrate, lithium citrate, disodium malonate, disodium 2-hydroxyglutarate, disodium phenolphthalein monophosphate, disodium octaborate, dipotassium silicate, dipotassium sulfate, dipotassium peroxymonosulfate, rubidium chromate, dilithium bisphenol A, and dilithium bisphenol AF.

6. The method for producing the bis (fluorosulfonyl) imide salt according to any one of claims 1 to 5, wherein M is⁺ _nX^n-Less than 500ppm, preferably less than 100 ppm.

7. The method for producing a bis (fluorosulfonyl) imide salt according to any one of claims 1 to 5, comprising the steps of: reacting bis-fluorosulfonylimide, M⁺ _nX^n-Mixing in non-aqueous solvent, reacting, and post-treating.

8. The method for preparing bis (fluorosulfonyl) imide salt according to claim 7 wherein said bis (fluorosulfonyl) imide is reacted with M⁺ _nX^n-In a molar ratio of 1: (0.5 to 4).

9. The method for preparing bis (fluorosulfonyl) imide salt according to claim 7, wherein the reaction temperature is-20 to 120 ℃ and the reaction time is 0.1 to 48 hours.

10. The method of preparing bis-fluorosulfonylimide salt according to claim 7, wherein the post-treatment process comprises: filtering, concentrating under reduced pressure, and recrystallizing with poor solvent.

11. The method for producing a bis (fluorosulfonyl) imide salt according to any one of claims 8 to 10, wherein the nonaqueous solvent includes acetonitrile, propionitrile, butyronitrile, isobutyronitrile, malononitrile, cyclohexanenitrile, acrylonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 1, 4-dioxane, acetone, butanone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, nitromethane, N-dimethylformamide, N-dimethylacetamide, methyl formate, methyl acetate, ethyl acetate, butyl acetate, isopropyl acetate, γ -butyrolactone, ethyl trifluoroacetate, methyl trifluoroacetate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl ether, propyl ether, ethyl propyl ether, isopropyl ether, tert-butyl methyl ether, ethylene glycol dimethyl ether, ethyl acetate, propyl ether, ethyl acetate, methyl acetate, ethyl acetate, methyl acetate, dimethyl carbonate, ethyl carbonate, ethylene, Ethylene glycol methyl ethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, N-methyl-2-pyrrolidone, pentane, hexane, heptane, octane, isooctane, decane, dodecane, benzene, toluene, xylene, ethylbenzene, propylbenzene, trimethylbenzene, tetrahydronaphthalene, dichloromethane, dichloroethane, chloroform, trichloroethane, tetrachloroethane, tetrachloroethylene, trifluorotrichloroethane, chlorobutane, chlorocyclohexane, chlorobenzene, trichlorobenzene, fluorobenzene, and benzotrifluoride.

12. The method for producing a bis-fluorosulfonylimide salt according to any one of claims 8 to 10, wherein the water content of the nonaqueous solvent is less than 500ppm, preferably less than 100 ppm.

13. The process for the preparation of bis-fluorosulfonylimide salt according to claim 1, wherein said bis-fluorosulfonylimide has a purity of more than 99.5%, preferably more than 99.9%.

14. The method for preparing bis-fluorosulfonyl imide salt of claim 13 wherein said bis-fluorosulfonyl imide salt is purified by crystallization; the crystallization is carried out in an organic solvent, and the organic solvent comprises at least one of alkane, olefin, aromatic hydrocarbon and chlorohydrocarbon.

15. The method for preparing bis-fluorosulfonylimide salt according to claim 14, wherein the crystallization temperature of bis-fluorosulfonylimide is-50 ℃ to 100 ℃, preferably-20 ℃ to 17 ℃.

Technical Field

The application relates to the technical field of electrolyte additives, in particular to a simple, convenient, economical and easy-to-industrialize preparation method of high-purity bis (fluorosulfonyl) imide salt.

Background

In the electrolyte, lithium hexafluorophosphate is electrolyte lithium salt commonly used by the current lithium battery, and has the advantages of stable negative electrode, high conductivity, large discharge capacity, small internal resistance and high charge-discharge speed. The electrolyte has the advantages of outstanding ionic conductivity, excellent oxidation stability, low environmental pollution and the like, is the currently preferred lithium ion battery electrolyte, and is used as a main salt in a commercial lithium ion battery, the addition amount of the electrolyte is about 15 percent of the total amount of the electrolyte, and the concentration of the electrolyte is about 1 mol/L. Through technical development for many years, the lithium hexafluorophosphate produced at present is a high-purity product, and the purity reaches more than 99.99%. The national standard defines that the impurity chloride is less than 1ppm, the sulfate is less than 5ppm, the sodium ion in the cation is less than 2ppm, and other cations are less than 1 ppm. High purity lithium hexafluorophosphate is a key factor in ensuring safe operation of the battery.

However, lithium hexafluorophosphate has more defects in the use process, such as deformation of the battery caused by hydrogen fluoride generated in the presence of water, and reduction of the service life of the battery; does not resist high temperature, and generates decomposition reaction at 80-100 ℃ to generate phosphorus pentafluoride, lithium fluoride and the like.

US5916475 discloses a LiPF₆Lithium salt containing fluorine, lithium bis-fluorosulfonylimide (LiFSI), having better thermal and chemical stability, higher electrical conductivity and lower corrosion rate, and is believed to be a possible replacement for LiPF₆The bifluoride lithium salt has excellent application prospect in lithium batteries and super capacitors. Recent research (ACS Applied Materials)&Interfaces, Volume11, Issue29, Pages25833-25843, 2019) show that the solution prepared by using LiFSI as the main salt to prepare sulfolane is used as the electrolyte, not only has low flammability and high compatibility with lithium metal anode, but also has 1.0mA/cm²The current density of (2) was again maintained at 98% coulombic efficiency with 400 cycles. Chem electrochem, Volume5, Issue24, Pages4008-4014, 2018 report that LiFSI exhibits good stability and electrochemical performance in solid electrolyte polycarbonates even in high voltage (greater than 4V) solid state batteries. LiFSI is far beyond LiPF in the aspect of rapid charging and discharging₆(Electrochemistry Communications, Volume103, Pages109-113, 2019). Joule essue 8, Pages1548-1558, 2018 and ACS Energy Letters, Volume4, Issue2, Pages483-488, 2019 report that a non-combustible electrolyte prepared from LiFSI and triethyl phosphate (TEP) in an amount of 1.2mol/L not only has high safety, but also has high coulombic efficiency (CCE, 97% upto600 cycles). LiFSI has excellent comprehensive performance and shows surprising effects in lithium air batteries (Chinese Chemical Letters, Volume30, Issue6, Pages1289-1292, 2019), lithium sulfur batteries (Angewandte Chemie, International Edition, Volume58, Issue3, Pages791-795, 2019), and high-concentration (12M DME) solid-state batteries (Nano Energy, Volume50, Pages431-440, 2018). LiFSI provides multiple possibilities for the development of the lithium battery industry, and has a wide development space.However, when LiFSI is used as the main electrolyte of the electrolyte, the purity requirement is greatly increased, and impurities contained in the LiFSI, such as chloride ions, sulfate radicals, moisture, acidic substances, cations, etc., may adversely affect the positive electrode, negative electrode, separator, electrolyte solvent, additives, etc., of the battery, thereby affecting the safety and cycle life, and becoming a major bottleneck in the wide application of LiFSI in the battery.

There are many preparation methods of LiFSI, which can be summarized as indirect and direct methods. The indirect method is prepared by preparing a metal or organic base bis-fluorosulfonyl imide salt and then performing an exchange reaction with a lithium salt, and the indirect method is disclosed in patents US2013331609, US2012041233, EP2415757, US2011034716 and CN 104085864A. This method, in addition to the use of metals or bases, leads to the quality impact of the metal and base residues in the finished product, and the exchange reaction must be carried out in water and washed by repeated extractions, which results in the decomposition of LiFSI. The other method is a direct method for preparing LiFSI by reacting difluoride sulfimide with lithium salt. US8377406 discloses a process for the preparation of LiFSI by reacting bis-fluorosulfonylimide (HFSI) directly with lithium carbonate in an aqueous solution; both CN104925765A and CN108002355 report methods for preparing LiFSI from HFSI and lithium hydroxide, lithium carbonate, and lithium bicarbonate in organic solvent, the purity of the obtained product is only 99.86-99.88%, the impurity fluorine ion is 21-27ppm, the impurity chlorine ion is 4.7-7.8ppm, and the sulfate radical is 15-20 ppm. (ii) a CN106365132A reports a method for preparing LiFSI from HFSI and lithium fluoride under pressurized conditions; CN106241757A reports a process for preparing LiFSI by reacting HFSI with lithium chloride, the resulting product having from 5 to 8ppm chloride and from 15 to 23ppm sulfate. Such a direct method using an inorganic lithium salt generates water or a small-molecule strong acid (such as hydrogen chloride, hydrogen fluoride, etc.) during the reaction, which causes decomposition of raw materials and products or generation of chloride or fluoride ion residues, and must increase the content of the product through a complicated purification process. Arkema, France reported LiFSI crystallization purification (FR 3059994, Jun 15,2018) using high vacuum thin film distillation limit method, but the purity of the purified product was only 99.80% above, the impurity content was still high, the typical example is 40ppm of water, 22ppm of chloride ion, 7ppm of sulfate radical. This is caused by the way it takes LiFSI in water. The method of adding organic base and crystallization in CN201810242600 can only control the chloride ion to about 20 ppm. CN106976849 removes water from the product by adding acid anhydride and crystallizing in the post-treatment process, and the final water content can only reach 37-89ppm, and the purity is 99.91-99.96%.

At present, due to the limitation of LiFSI production technology, only low-specification LiFSI can be obtained and used as an additive in electrolyte, and certain defects of lithium hexafluorophosphate as a main salt are overcome. LiFSI must be a high purity product to exhibit its excellent electrochemical properties as a main salt of a lithium battery electrolyte. Therefore, the preparation of LiFSI with the content of more than 99.99 percent, the water content of less than 20ppm and the sum of all anions and cations of less than 10ppm is a technical problem to be overcome.

The invention provides a preparation method of high-specification LiFSI, which comprises the following steps of 1, taking high-purity HFSI as a raw material; 2. a non-aqueous reaction system is adopted, and water or strong acid and other by-products with destructive properties are not generated in the reaction; 3. the by-product has no destructive effect on the product; 4. the residue of the by-product is accurately controlled by crystallization of the poor solvent; multiple means are combined to achieve the final effect.

Disclosure of Invention

In order to solve the problems, the invention provides a preparation method of high-purity bis (fluorosulfonyl) imide salt, and the preparation raw materials at least comprise bis (fluorosulfonyl) imide and M⁺ _nX^n-，

Wherein M is selected from any one of Li, Na, K, Rb and Cs, X is an anion containing B, O, N, P, Si at least one element, and n is more than or equal to 2.

As a preferred technical solution, M is⁺ _nX^n-Is a multi-inorganic salt, and comprises at least one of sulfate, sulfite, thiosulfate, phosphate, monohydrogen phosphate, phosphite, pyrophosphate, silicate, hexafluorosilicate, borate, molybdate and chromate.

As a preferred technical solution, M is⁺ _nX^n-Is a polycarboxylic acid salt, a packageComprises at least one of oxalate, malonate, succinate, glutarate, adipate, sebacate, maleate, fumarate, tartrate, glutamate dihydrochloride, cyclohexanetrioate, phthalate, isophthalate, terephthalate, isophthalate, citrate, ethylenediaminetetraacetic acid tetrasalt, ethylenediaminetetraacetic acid trisalt and ethylenediaminetetraacetic acid disalt.

As a preferred technical solution, M is⁺ _nX^n-The compound is a polybasic organic phenate, and comprises at least one of catechol disalt, resorcinol disalt, hydroquinone disalt, biphenol disalt, bisphenol A disalt, salicylic acid disalt, p-hydroxybenzene sulfonic acid disalt, o-hydroxybenzene sulfonic acid disalt and 5-sulfo-1, 3-benzene dicarboxylic acid disalt.

As a preferred technical solution, M is⁺ _nX^n-Selected from the group consisting of lithium sulfate, sodium phosphate, dipotassium malonate, rubidium sulfate, dicesium isophthalate, dilithium chromate dihydrate, lithium metasilicate, 3-hydroxy-2-oxopropyl phosphate dilithium, lithium tetraborate, lithium silicate, dilithium glycerophosphate, lithium orthosilicate, lithium sulfite, lithium molybdate, dilithium diphosphate, lithium chromate, pentalithiotriphosphate, dilithio phthalate, dilithio thiosulfate, dilithio hexafluorosilicate, dilithio adipate, dilithio sebacate, diethylmethylenebis (phosphonate) dilithium, dilithio 2-butenedioate, lithium oxalate, dilithio diphosphate, lithium maleate, dilithio azelaic acid, lithium dichromate, lithium tartrate, lithium citrate, disodium malonate, disodium 2-hydroxyglutarate, disodium phenolphthalein monophosphate, disodium octaborate, dipotassium silicate, dipotassium sulfate, lithium chromate, lithium penta phosphate, dilithio sulfate, dilithio hexa, At least one of dipotassium peroxymonosulfate, rubidium chromate, dilithium bisphenol A, and dilithium bisphenol AF.

As a preferred technical solution, M is⁺ _nX^n-Less than 500ppm, preferably less than 100 ppm.

As a preferable technical scheme, the method comprises the following steps: reacting bis-fluorosulfonylimide, M⁺ _nX^n-Mixing the raw materials in a non-aqueous solvent, reacting,and (5) performing post-treatment to obtain the product.

As a preferred technical scheme, the bis (fluorosulfonyl) imide and M⁺ _nX^n-In a molar ratio of 1: (0.5 to 4).

As a preferable technical scheme, the reaction temperature is-20-120 ℃, and the reaction time is 0.1-48 h.

As a preferred technical solution, the post-treatment process includes: filtering, concentrating under reduced pressure, and recrystallizing with poor solvent.

As a preferable embodiment, the non-aqueous solvent includes acetonitrile, propionitrile, butyronitrile, isobutyronitrile, malononitrile, cyclohexanenitrile, acrylonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 1, 4-dioxane, acetone, butanone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, nitromethane, N-dimethylformamide, N-dimethylacetamide, methyl formate, methyl acetate, ethyl acetate, butyl acetate, isopropyl acetate, γ -butyrolactone, ethyl trifluoroacetate, methyl trifluoroacetate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl ether, propyl ether, ethyl ether, isopropyl ether, tert-butyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol methyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, propylene carbonate, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, ethylene glycol, Triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, N-methyl-2-pyrrolidone, pentane, hexane, heptane, octane, isooctane, decane, dodecane, benzene, toluene, xylene, ethylbenzene, propylbenzene, trimethylbenzene, tetrahydronaphthalene, dichloromethane, dichloroethane, chloroform, trichloroethane, tetrachloroethane, tetrachloroethylene, trifluorotrichloroethane, chlorobutane, chlorocyclohexane, chlorobenzene, trichlorobenzene, fluorobenzene, and trifluorotoluene.

In a preferred embodiment, the water content of the non-aqueous solvent is less than 1000ppm, preferably less than 100 ppm.

As a preferred technical scheme, the purity of the bis-fluorosulfonyl imide is more than 99.5%, and the preferred purity is more than 99.9%.

As a preferred technical scheme, the purity of the bis-fluorosulfonyl imide is improved by crystallization; the crystallization is carried out in an organic solvent, and the organic solvent comprises at least one of alkane, olefin, aromatic hydrocarbon and chlorohydrocarbon.

As a preferred technical scheme, the crystallization temperature of the bis-fluorosulfonyl imide is-50 ℃ to 100 ℃, and is preferably-20 ℃ to 17 ℃.

Has the advantages that: the invention provides a method for preparing high-purity bis (fluorosulfonyl) imide salt in a non-aqueous system, which has the advantages of mild reaction process, no side reaction, simple and convenient post-treatment, high yield and high purity.

Detailed Description

For purposes of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

When a range of values is disclosed herein, the range is considered to be continuous and includes both the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range-describing features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range from "1 to 10" should be considered to include any and all subranges between the minimum value of 1 and the maximum value of 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, and the like.

The first aspect of the invention provides a method for preparing a bis (fluorosulfonyl) imide salt, wherein the preparation raw materials at least comprise bis (fluorosulfonyl) imide and M⁺ _nX^n-，

Wherein M is selected from any one of Li, Na, K, Rb and Cs, X is an anion containing B, O, N, P, Si at least one element, and n is more than or equal to 2.

The general formula of the bis-fluorosulfonyl imide salt is MFSI, and the structure of the bis-fluorosulfonyl imide salt is shown as formula I:

in one embodiment, when M is Li, the MFSI is lithium bis (fluorosulfonylimide).

In one embodiment, when M is Na, MFSI is sodium bis (fluorosulfonylimide).

In one embodiment, when M is K, MFSI is potassium bis fluorosulfonylimide.

In one embodiment, when M is Rb, the MFSI is rubidium bis (fluorosulfonyl) imide.

In one embodiment, when M is Cs, the MFSI is cesium bis (fluorosulfonyl) imide.

As a preferred embodiment, said M⁺ _nX^n-Less than 500ppm, preferably less than 100 ppm.

Bis (fluorosulfonyl) imides

The structural formula of the bis-fluorosulfonyl imide is shown as a formula II:

as a preferred embodiment, the method of bis-chlorosulfonyl imide comprises the steps of: 825g of sulfamic acid and 1200g of chlorosulfonic acid were added to a 2000ml four-necked flask and the temperature was raised to 108 ℃. Beginning to drop 2730g of thionyl chloride, dropping for 12 hours, continuing to keep the temperature for 8 hours, and absorbing tail gas by water and liquid alkali. After the reaction is finished, water pump decompression is firstly carried out to remove excessive thionyl chloride, then oil pump decompression rectification is carried out, and 110 ℃/8.6mbar fractions are collected, thus obtaining the thionyl chloride.

As another preferred embodiment, the method of bis-chlorosulfonyl imide comprises the steps of: 1600g of bischlorosulfonimide were placed in a 1000mL PTFE reactor and the stirring was turned on. Adding 16g of methanol, heating to 100 ℃, starting to introduce 500g of anhydrous hydrogen fluoride gas at a constant speed, maintaining the reaction temperature at 100 +/-5 ℃, reacting for 16 hours, and stopping the reaction when the acid value is reduced to below 340 mgKOH/g. Introducing nitrogen to purge for 4 hours to remove hydrogen fluoride, rectifying the crude product, and collecting the fraction at 60-62 ℃/25mbar to obtain the product.

The applicant finds that the purity of the bis-fluorosulfonyl imide has a great influence on the yield and purity of the subsequently prepared high-purity bis-fluorosulfonyl imide salt.

As a preferred embodiment, the bis-fluorosulfonyl imide is purified by crystallization; the crystallization may be carried out in an organic solvent or in the absence of a solvent.

The crystallization can be crystallization under stirring state or static crystallization; the crystallization may be carried out by a batch crystallization or a continuous crystallization.

As a preferred embodiment, the crystallization is carried out in an organic solvent comprising at least one of an alkane, an alkene, an aromatic hydrocarbon, a chlorinated hydrocarbon.

As examples of alkanes, including but not limited to pentane, hexane, heptane, octane;

as examples of olefins, including but not limited to butadiene, cyclopentadiene, cyclohexene;

as examples of aromatic hydrocarbons, including but not limited to benzene, xylene, toluene;

examples of chlorinated hydrocarbons include, but are not limited to, chlorobenzene, fluorobenzene, dichlorobenzene, trifluorotoluene, dichloromethane, dichloroethane, dichloropropane, trichloroethane, tetrachloroethane, tetrachloroethylene.

As a preferred embodiment, the method for preparing the high-purity bis (fluorosulfonyl) imide product comprises the following steps:

450 and 550g of bis (fluorosulfonyl) imide rectification product are added into the reactor, and the stirring is started. Adding 150 and 250g of dichloromethane, heating to 40 +/-5 ℃, and stirring for dissolving; slowly cooling at a speed of 1-3 deg.C/hr, maintaining the crystallization temperature at-10 + -0.5 deg.C for 5-7 hr, filtering in a low-temperature glove box, and removing solvent under reduced pressure after the filter cake melts to obtain the final product.

As another preferred embodiment, the method for preparing the high-purity bis (fluorosulfonyl) imide product comprises the steps of:

450 and 550g of liquid bis (fluorosulfonyl) imide rectification product are added into a jacket reaction kettle, and stirring is started. Slowly cooling at a speed of 1-3 deg.C/hr, maintaining the crystallization temperature at 0 + -0.2 deg.C, maintaining the temperature for 5-7 hr, discharging the mother liquor, and melting the residual solid at 18-25 deg.C to obtain high-purity bis (fluorosulfonyl) imide product.

As a preferred embodiment, the purity of the bis-fluorosulfonylimide is more than 99.5%, preferably more than 99.9%.

⁺ _n ^n-MX

M is selected from any one of Li, Na, K, Rb and Cs, X is an anion comprising B, O, N, P, Si at least one element, and n is more than or equal to 2.

As an embodiment, the M⁺ _nX^n-One selected from polybasic inorganic salt, polybasic carboxylic salt and polybasic organic phenolate.

As a preferred embodiment, said M⁺ _nX^n-Is a multi-inorganic salt, and comprises at least one of sulfate, sulfite, thiosulfate, phosphate, monohydrogen phosphate, phosphite, pyrophosphate, silicate, hexafluorosilicate, borate, molybdate and chromate.

As a preferred embodimentSaid M is⁺ _nX^n-The polycarboxylic acid salt is at least one of oxalate, malonate, succinate, glutarate, adipate, sebacate, maleate, fumarate, tartrate, glutamate dihydrochloride, cyclohexanetrioate, phthalate, isophthalate, terephthalate, isophthalate, citrate, ethylenediaminetetraacetic acid tetrasalt, ethylenediaminetetraacetic acid trisalt and ethylenediaminetetraacetic acid disalt.

As a preferred embodiment, said M⁺ _nX^n-The compound is a polybasic organic phenate, and comprises at least one of catechol disalt, resorcinol disalt, hydroquinone disalt, biphenol disalt, bisphenol A disalt, salicylic acid disalt, p-hydroxybenzene sulfonic acid disalt, o-hydroxybenzene sulfonic acid disalt and 5-sulfo-1, 3-benzene dicarboxylic acid disalt.

As a preferred embodiment, said M⁺ _nX^n-Selected from the group consisting of lithium sulfate, sodium phosphate, dipotassium malonate, rubidium sulfate, dicesium isophthalate, dilithium chromate dihydrate, lithium metasilicate, 3-hydroxy-2-oxopropyl phosphate dilithium, lithium tetraborate, lithium silicate, dilithium glycerophosphate, lithium orthosilicate, lithium sulfite, lithium molybdate, dilithium diphosphate, lithium chromate, pentalithiotriphosphate, dilithio phthalate, dilithio thiosulfate, dilithio hexafluorosilicate, dilithio adipate, dilithio sebacate, diethylmethylenebis (phosphonate) dilithium, dilithio 2-butenedioate, lithium oxalate, dilithio diphosphate, lithium maleate, dilithio azelaic acid, lithium dichromate, lithium tartrate, lithium citrate, disodium malonate, disodium 2-hydroxyglutarate, disodium phenolphthalein monophosphate, disodium octaborate, dipotassium silicate, dipotassium sulfate, lithium chromate, lithium penta phosphate, dilithio sulfate, dilithio hexa, At least one of dipotassium peroxymonosulfate, rubidium chromate, dilithium bisphenol A, and dilithium bisphenol AF.

The CAS number of the lithium dichromate is 14307-35-8. The CAS number of the lithium metasilicate is 10102-24-6. The CAS number of the 3-hydroxy-2-oxopropyl phosphate dilithium is 102783-56-2. The lithium silicate has a CAS number of 12627-14-4. The CAS number of the glycerophosphate dilithium is 1300-23-8. The CAS number for the lithium orthosilicate is 13453-84-4. The CAS number of the tetralithium diphosphate is 13843-41-9. The CAS number of the pentalithium triphosphate is 15804-33-8. The CAS number of the dilithium phthalate is 15968-00-0. The CAS number of the dilithio sulfuric ester is 16992-28-2. The CAS number of the dilithium silicate is 17347-95-4. The CAS number for dilithium adipate is 18621-94-8. The CAS number of the lithium sebacate is 19370-86-6. The CAS number of the diethyl methylenebis (phosphonate) salt is 194931-67-4. The CAS number of the lithium salt of butenedioic acid is 24820-18-6. The CAS number of the dilithium diphosphate is 33943-47-4. The CAS number of the lithium maleate is 34895-26-6. The CAS number of dilithium azelate is 38900-29-7. The CAS number of the lithium dichromate is 52478-50-9. The CAS number of the lithium tartrate is 868-17-7. The CAS number of the bisphenol A dilithium is 67306-98-3. The CAS number of the bisphenol AF dilithium is 128968-16-1.

In one embodiment, the method for preparing the bis-fluorosulfonyl imide salt comprises the following steps:

reacting bis-fluorosulfonylimide, M⁺ _nX^n-Mixing in non-aqueous solvent, reacting, and post-treating.

In one embodiment, the preparation of the bis-fluorosulfonyl imide salt is performed under a dry inert gas atmosphere.

In one embodiment, the dry inert gas comprises one or more combinations of nitrogen, argon, or helium.

Preferably, the dry inert gas is nitrogen.

In one embodiment, the reaction temperature is-20 to 120 ℃, and the stability of materials, the safety and the controllability of the reaction, the purity of the bis-fluorosulfonyl imide salt and other factors are considered, and the reaction temperature is preferably 0 to 40 ℃.

In one embodiment, the reaction time is 0.1 to 48 hours, and the stability of the materials, the safety and the controllability of the reaction, the purity of the bis-fluorosulfonyl imide salt, and the like are taken into consideration, preferably 1 to 20 hours, and more preferably 1 to 15 hours.

In a preferred embodiment, the non-aqueous solvent includes acetonitrile, propionitrile, butyronitrile, isobutyronitrile, malononitrile, cyclohexanenitrile, acrylonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 1, 4-dioxane, acetone, butanone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, nitromethane, N-dimethylformamide, N-dimethylacetamide, methyl formate, methyl acetate, ethyl acetate, butyl acetate, isopropyl acetate, γ -butyrolactone, ethyl trifluoroacetate, methyl trifluoroacetate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl ether, propyl ether, ethyl propyl ether, isopropyl ether, tert-butyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol methyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, propylene carbonate, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, ethylene glycol dimethyl ether, propylene carbonate, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, Triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, N-methyl-2-pyrrolidone, pentane, hexane, heptane, octane, isooctane, decane, dodecane, benzene, toluene, xylene, ethylbenzene, propylbenzene, trimethylbenzene, tetrahydronaphthalene, dichloromethane, dichloroethane, chloroform, trichloroethane, tetrachloroethane, tetrachloroethylene, trifluorotrichloroethane, chlorobutane, chlorocyclohexane, chlorobenzene, trichlorobenzene, fluorobenzene, and trifluorotoluene.

In one embodiment, the non-aqueous solvent has a moisture content of less than 500ppm, preferably less than 100 ppm. In one embodiment, the amount of the non-aqueous solvent is 0.2 to 10 times of the theoretical weight of the bis-fluorosulfonyl imide salt, and preferably 1 to 3 times of the theoretical weight of the bis-fluorosulfonyl imide salt, considering the yield and purity of the product.

In one embodiment, the bis-fluorosulfonylimide is reacted with M⁺ _nX^n-In a molar ratio of 1: (0.5 to 4).

In a preferred embodiment, the bis-fluorosulfonylimide is reacted with M⁺ _nX^n-In a molar ratio of 1:

(0.5～2)。

the bis (fluorosulfonyl) imide or M⁺ _nX^n-The mixing method with the nonaqueous solvent is not limited and is within the scope of the present invention, and generally, is suitable for industrial production.

In one embodiment, the post-processing procedure comprises: filtering, concentrating under reduced pressure, and recrystallizing with poor solvent.

In a preferred embodiment, the post-treatment process comprises: filtering, concentrating under reduced pressure, recrystallizing with poor solvent, filtering, and oven drying.

The aim of filtering in the post-treatment process of the bis (fluorosulfonyl) imide salt solution is to remove byproducts in the bis (fluorosulfonyl) imide salt solution.

The purpose of the re-filtration is to remove the filtrate to give the bis-fluorosulfonylimide salt.

The non-aqueous solvent is removed by vacuum concentration, i.e., vacuum distillation.

In one embodiment, the vacuum degree of the reduced pressure concentration is 100Pa to 10kPa, and the temperature range is 0 to60 ℃.

In one embodiment, the poor solvent comprises a combination of one or more of benzene, toluene, o-xylene, m-xylene, p-xylene, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzene, hexane, heptane, octane, dichloromethane, trichloromethane, carbon tetrachloride, 1, 2-dichloroethane, 1,1, 2-trichloroethane, tetrachloroethane, tetrachloroethylene, 1,2, 3-trichloropropane, n-propyl ether, n-butyl ether, isopropyl ether, ethylene glycol dibutyl ether.

If the nonaqueous solvent added during the reaction is a combination of two or more solvents and the poor solvent is already contained, the poor solvent may not be added during the crystallization.

In one embodiment, the amount of the poor solvent is 1 to 50 times of the theoretical weight of the bis-fluorosulfonyl imide salt, and the yield and purity of the bis-fluorosulfonyl imide salt are considered, preferably 2 to 10 times of the theoretical weight of the bis-fluorosulfonyl imide salt.

In one embodiment, the drying degree of vacuum is 100 Pa-10 kPa, and the temperature range is 0-60 ℃. The specific embodiments are not intended to be limiting, but are within the scope of the invention, which is generally convenient for commercial operations.

The principle of the invention is as follows:

HFSI+M⁺ _nX^n-→MFSI+M⁺ _(n-1)HX^(n-1)-；

the applicant has found that a specific ratio of bis-fluorosulfonylimide (HFSI) to M⁺ _nX^n-(n is not less than 2), the reaction in a non-aqueous solvent is followed by a series of post-treatments such as filtration, concentration under reduced pressure, and crystallization with poor solvent, thereby obtaining a high-quality and high-yield bis (fluorosulfonyl) imide salt, since HFSI is a strong acid and M is a strong acid⁺ _nX^n-The catalyst is a weak base, and the acid and the base are contacted to generate acid-base neutralization reaction, so that the conversion is very easy to complete, and no side reaction is found. And in a suitable reaction solvent, the starting material HFSI and the product formed are dissolved in the reaction solvent, starting material M⁺ _nX^n-And the by-product M formed⁺ _(n-1)HX^(n-1)-Insoluble in the reaction solvent, and filtering after the reaction to obtain the product solution and the byproduct solid. And concentrating the product solution and adding a poor solvent to separate out, thereby obtaining the high-quality and high-yield bis-fluorosulfonyl imide salt. By-product M⁺ _(n-1)HX^(n-1)-With basic salts MOH or M₂CO₃Neutralizing in water phase, filtering, drying, and converting into main material M⁺ _nX^n-Thereby achieving the effects of recycling and not generating three wastes. The Applicant has also found that said M⁺ _nX^n-In the case of (n ═ 1), the purity, yield and the like of the resulting bis (fluorosulfonyl) imide salt are reduced to some extent, and this is mainly caused by the formation of water or an acid dissolved in the reaction system. If MX is lithium hydroxide, sodium hydroxide or potassium hydroxide, 1 equivalent of water is generated, and the side reaction of MFSI hydrolysis of the product occurs to generate hetero ions. For example, MX is LiCl, LiF, NaBr, KI, LiBF₄、LiClO₄When the reaction is carried out, another molecule is a strongly acidic substance, wherein the reaction conversion is incomplete, and the strong acids are HCl, HF, HBr, HI and HBF₄、HClO₄The water-soluble organic compound has certain solubility in a non-aqueous solvent, and is difficult to remove, so that the impurity ions are remained; even strong acid reacts with certain polar solvents, such as acetonitrile, ether solvents, amide solvents, ester solvents and the like to generate alcohol acid impuritiesFurther reducing the quality of the product.

The applicants have found that the choice of non-aqueous solvent, the amount of poor solvent used, has a large impact on product yield and purity. The non-aqueous solvent with larger polarity is selected, the raw material has better solubility in the non-aqueous solvent, the reaction is favorably carried out in the forward direction, but the by-product M is increased due to overlarge polarity⁺ _(n-1)HX^(n-1)-Solubility in solvents. By adding another solvent with lower polarity for combination, the best effects of complete reaction conversion and small dissolved amount of byproducts can be achieved. In the process of decompression desolventizing, a small amount of residual impurities are dissolved by accurately controlling the residual amount of the non-aqueous solvent with larger polarity; in the crystallization process, the adding amount of the poor solvent is accurately controlled to obtain higher yield; the two are combined with each other, and the best effect of high yield and high purity can be obtained.

The applicant has found that M⁺ _nX^n-A slight excess can improve the yield and purity of the product. Presumably the possible reason is a slight excess of M⁺ _nX^n-Can promote the reaction to be completely converted and simultaneously residual M⁺ _nX^n-Can be easily removed by filtration without affecting product quality. When bis-fluorosulfonylimide is reacted with M⁺ _nX^n-In a molar ratio of 1: (0.5-4), the yield and purity of the bis (fluorosulfonyl) imide salt are good, and improper control can result in failure to obtain a high-quality target product, so that the discovery of the application is difficult.

In addition, the solvents and reagents used were purchased from Shanghai Allantin Biotechnology Ltd, unless otherwise stated.

The present invention will be specifically described below by way of examples.

Preparation example 1

A process for preparing a bischlorosulfonimide comprising the steps of: 825g of sulfamic acid and 1200g of chlorosulfonic acid were added to a 2000ml four-necked flask and the temperature was raised to 108 ℃. Beginning to drop 2730g of thionyl chloride, dropping for 12 hours, continuing to keep the temperature for 8 hours, and absorbing tail gas by water and liquid alkali. After the reaction is finished, water pump decompression is carried out to remove excessive thionyl chloride, then oil pump decompression rectification is carried out, 110 ℃/8.6mbar fractions are collected, 1386g of middle fractions are obtained, the content is 98.5%, and the yield is 77%.

Preparation example 2

A method of preparing bis-fluorosulfonylimide, comprising the steps of: 1600g of bischlorosulfonimide were placed in a 1000mL PTFE reactor and the stirring was turned on. Adding 16g of methanol, heating to 100 ℃, starting to introduce 500g of anhydrous hydrogen fluoride gas at a constant speed, maintaining the reaction temperature at 100 +/-5 ℃, reacting for 16 hours, and stopping the reaction when the acid value is reduced to below 340 mgKOH/g. Introducing nitrogen to purge for 4 hours to remove hydrogen fluoride, rectifying the crude product, collecting 60-62 ℃/25mbar fraction to obtain 1150g of fraction in the rectified product, namely the difluoride sulfimide rectified product, wherein the yield is 85.0%. 99.0% of purity, 0.45% of sulfate radical, 0.20% of fluoride ion, 0.004% of chloride ion and 0.35% of sulfamic acid.

Purification example 1

The preparation method of the high-purity bis (fluorosulfonyl) imide product comprises the following steps:

500g of bis (fluorosulfonyl) imide distillate was added to a 1000mL PTFE reactor and the stirring was turned on. Adding 200g of dichloromethane, heating to 40 ℃, and stirring for dissolving; and (3) slowly cooling the solution by using a ice salt bath at a cooling speed of 2 ℃ per hour, finally maintaining the crystallization temperature at minus 10 +/-0.2 ℃, preserving the temperature for 6 hours, filtering the solution in a low-temperature glove box, and removing the solvent under reduced pressure after a filter cake is melted to obtain 380g of the bis (fluorosulfonyl) imide with the yield of 76%. 99.97% purity, 76ppm sulfate radical, 55ppm fluorinion, 8ppm chloridion and 88ppm sulfamic acid.

¹H-NMR(CDCl3)：7.81，s，1H。¹⁹F-NMR (CDCl 3): 58.9. melting point: 17 deg.C

Purification example 2

The preparation method of the high-purity bis (fluorosulfonyl) imide product comprises the following steps:

500g of liquid bis (fluorosulfonyl) imide distillate was added to a 1000mL jacketed kettle and the stirring was turned off. The temperature of the ice salt bath begins to be slowly reduced, the temperature reduction speed is about 2 degrees/hour, the crystallization temperature is finally maintained at 0 +/-0.2 ℃, the temperature is kept for 6 hours, mother liquor is discharged, residual solid is slightly heated to 20 ℃ and is melted to obtain 460g of the high-purity product of the bis (fluorosulfonyl) imide, and the yield is 92%. Purity 99.95%, sulfate radical 123ppm, fluoride ion 77ppm, chloride ion 10ppm, sulfamic acid 220 ppm.

The detection method of the bis (fluorosulfonyl) imide comprises the following steps: the purity of the bis (fluorosulfonyl) imide is measured by selecting ion chromatography; yield (%) — actual product mass/theoretical product mass × 100%; the chloride ion detection method comprises the following steps: detecting by an ion chromatograph; the water content detection method comprises the following steps: the water content was measured by using Karl Fischer moisture meter of Mettler-Tollido corporation; the acid value detection method comprises the following steps: the test is carried out according to the national standard GB/T4954-2002 petroleum product and lubricant neutralization value determination method.