CN115259113A - Method and device for continuously purifying lithium bis (fluorosulfonyl) imide - Google Patents
Method and device for continuously purifying lithium bis (fluorosulfonyl) imide Download PDFInfo
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Abstract
The invention discloses a method and a device for continuously purifying lithium bis (fluorosulfonyl) imide, wherein the method for continuously purifying the lithium bis (fluorosulfonyl) imide comprises the following steps: A1. contacting the lithium bis (fluorosulfonyl) imide solution with a leaching agent in at least one group of hollow fiber membrane modules to form a crystallization solution; A2. aging the crystallization solution in a crystallizer; A3. after curing, obtaining the lithium bis (fluorosulfonyl) imide product through decompression and suction filtration. The method has the advantages of uniform crystal size, simple operation, high product purity and the like.
Description
Technical Field
The invention relates to purification of fluorine-containing lithium salt, in particular to a method and a device for continuously purifying lithium bis (fluorosulfonyl) imide by a membrane solventing-out crystallization method.
Background
Lithium bis (fluorosulfonyl) imide (abbreviated as "LiFSI") is a novel lithium salt, has the advantages of high conductivity, high thermal stability, hydrolysis resistance, inhibition of swelling gas of battery bulges and the like, is applied to lithium ion battery electrolyte, is helpful to reduce the impedance of an electrode surface film, forms a stable passivation film with good ion conductivity, and thus improves the safety performance of high-rate charging and discharging of the battery. Therefore, the lithium bis (fluorosulfonyl) imide has a wide application prospect in the field of electrolytes, but needs to be applied to the electrolytes, and puts higher requirements on the purity of the lithium bis (fluorosulfonyl) imide.
Patent CN110540176A discloses a method for obtaining high-purity lithium bis (fluorosulfonyl) imide by reacting a crude lithium bis (fluorosulfonyl) imide with alkyl acyl chloride to obtain a mixed solution, and then performing evaporation treatment and organic solvent dissolution.
Patent CN106976849A discloses a method for removing water in crude lithium bis (fluorosulfonyl) imide by using organic acid anhydride, and recrystallizing through solvent polarity to obtain high-purity lithium bis (fluorosulfonyl) imide.
The purification of lithium bis (fluorosulfonyl) imide disclosed in the prior art is based on the reduction of the content of crude water and impurity ions, and the like, and the influence of the size, particle size and the like of crystals on the product quality and the application of the product quality to electrolyte is not studied, and the content of water, impurity ions and the like in the product in the prior art also has a large promotion space.
Disclosure of Invention
In order to solve the technical problems, the invention provides a continuous purification method of lithium bis (fluorosulfonyl) imide, which has the advantages of uniform crystal size, high product purity and good product quality.
The invention carries out the dispersion of the elution agent through at least one group of hollow fiber membrane components and the fractional addition of the elution agent to construct three areas of crystallization nucleation, growth and curing. In the at least one group of hollow fiber membrane components, the outer side (shell layer) of the membrane is a lithium bis (fluorosulfonyl) imide solution, the inner side (tube pass) of the membrane is a elutriation agent, and the transmembrane flux of the elutriation agent is adjusted through the pressure difference between the two sides of the membrane and the membrane material, so that the supersaturation degree of the outer side of the membrane is in different functional regions to control the particle size distribution and morphology of crystals, thereby obtaining a high-purity and high-quality lithium bis (fluorosulfonyl) imide product.
The purpose of the invention is realized by the following technical scheme:
a continuous purification process for lithium bis (fluorosulfonyl) imide, said continuous purification process comprising:
A1. contacting a lithium bis (fluorosulfonyl) imide solution with a solventing-out agent in at least one group of hollow fiber membrane modules to form a crystallization solution;
A2. aging the crystallization solution in a crystallizer;
A3. after curing, obtaining the lithium bis (fluorosulfonyl) imide product through decompression and suction filtration.
In the step A1, the lithium bis (fluorosulfonyl) imide solution is contacted with a solvent in at least one group of hollow fiber membrane modules to realize nucleation and growth, and a crystal product is carried to enter a crystallizer for curing. The curing time is 2 to 6 hours, the crystallizer is started to stir during the curing process, and the stirring speed is 200 to 500rpm, preferably 300 to 400rpm.
The stirring speed is low, and the uniform distribution of supersaturation can not be quickly realized by adding the elution agent, so that the growth rates of the crystals in all directions are different, and the length-diameter ratio is increased; the stirring speed is too high, so that the collision degree between crystals is increased, the crystal form of the crystals is deteriorated, the number of broken crystals is increased, and the particle size distribution is enlarged.
And the elutriation agent returns to the elutriation agent storage container after passing through the at least one group of hollow fiber membrane modules to form a circulation loop.
The lithium bis (fluorosulfonyl) imide solution passes through the shell side of the at least one group of hollow fiber membrane modules, and the elution agent passes through the tube side of the at least one group of hollow fiber membrane modules.
When at least two groups of hollow fiber membrane modules are arranged, the lithium bis (fluorosulfonyl) imide solution sequentially passes through the at least two groups of hollow fiber membrane modules, and the elution agent is simultaneously communicated with the at least two groups of hollow fiber membrane modules.
The flow rate of the solventing-out agent flow is 120-300 mL/min.
Furthermore, the flow rate of the elution agent connected with the previous-stage hollow fiber membrane component is larger than that of the elution agent connected with the next-stage hollow fiber membrane component.
In a preferred embodiment, three groups of hollow fiber membrane modules are provided, the lithium bis (fluorosulfonyl) imide solution sequentially passes through the shell side of the first stage hollow fiber membrane module, the shell side of the second stage hollow fiber membrane module and the shell side of the third stage hollow fiber membrane module, and the elutriation agent is simultaneously introduced into the tube side of the first stage hollow fiber membrane module, the tube side of the second stage hollow fiber membrane module and the tube side of the third stage hollow fiber membrane module, wherein the flow rate of the elutriation agent in the first stage hollow fiber membrane module is greater than that of the second stage hollow fiber membrane module, and the flow rate of the second stage hollow fiber membrane module is greater than that of the third stage hollow fiber membrane module.
Preferably, the flow rate of the elution agent in the first-stage hollow fiber membrane module is 240 to 300mL/min, the flow rate in the second-stage hollow fiber membrane module is 180 to 240mL/min, and the flow rate in the third-stage hollow fiber membrane module is 120 to 180mL/min.
The hollow fiber membrane is selected from an organic membrane, an inorganic membrane or a composite membrane. Preferably, the organic film is selected from polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene, and a solvent-resistant material prepared by modifying polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene; the inorganic membrane is selected from a metal oxide membrane and/or a zeolite membrane; the composite membrane is selected from polyvinyl alcohol/micro sodium cellulose.
The lithium bis (fluorosulfonyl) imide solution is obtained by dissolving crude lithium bis (fluorosulfonyl) imide in an organic solvent or is a reaction solution for preparing lithium bis (fluorosulfonyl) imide.
The content of the lithium bis (fluorosulfonyl) imide in the lithium bis (fluorosulfonyl) imide solution is 20-90%, preferably 40-70%. Once the concentration of the lithium bis (fluorosulfonyl) imide is low, sufficient supersaturation cannot be provided for nucleation and crystal growth, and the yield of the obtained crystal product is low; the concentration is too large, the solution preparation time is increased, and the supersaturation degree control difficulty is increased due to the addition of the elution agent, so that the control of the crystal growth rate in the crystallization process is not facilitated.
Preferably, the organic solvent is at least one selected from the group consisting of ester compounds, carbonate compounds, ether compounds, nitrile compounds and ketone compounds.
More preferably, the ester compound is at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl formate, ethyl formate, propyl formate, and butyl formate;
the carbonate compound is selected from at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate;
the ether compound is at least one of diethyl ether, isopropyl ether and methyl tert-butyl ether;
the nitrile compound is acetonitrile;
the ketone compound is acetone.
The solvent-out agent is selected from at least one of benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, cyclohexane, n-hexane and petroleum ether.
The invention also provides a lithium bis (fluorosulfonyl) imide product, which is obtained by any one of the continuous purification methods of the lithium bis (fluorosulfonyl) imide, wherein the length-diameter ratio of the lithium bis (fluorosulfonyl) imide product is 0.5-10, and the mesh number of products with the length ratio of not less than 80% is 50-250.
Preferably, the length-diameter ratio of the lithium bis (fluorosulfonyl) imide product is 0.5-5, and the mesh number of more than or equal to 80% of the products is 80-200 meshes.
The invention also provides a continuous purification device of the lithium bis (fluorosulfonyl) imide, which comprises:
the lithium bis (fluorosulfonyl) imide solution sequentially passes through the at least one group of hollow fiber membrane modules, and the elution agent is simultaneously connected with the at least one group of hollow fiber membrane modules;
the crystallizer is connected with the outlet of the at least one group of hollow fiber membrane modules;
and the filtering unit is connected with the outlet of the crystallizer, and a lithium bis (fluorosulfonyl) imide product is obtained through reduced pressure suction filtration.
The lithium bis (fluorosulfonyl) imide solution passes through the shell side of the at least one group of hollow fiber membrane modules, and the elution agent passes through the tube side of the at least one group of hollow fiber membrane modules.
Furthermore, the eluent returns to the eluent storage container after passing through the at least one group of hollow fiber membrane modules to form a circulation loop.
Further, the leaching agent enters the at least one group of hollow fiber membrane modules after being metered by a flowmeter.
The lithium bis (fluorosulfonyl) imide solution can be stored in a raw material tank and conveyed to the at least one group of hollow fiber membrane modules through a peristaltic pump. Further, the raw material tank is provided with a stirring device.
The elution agent is stored in an elution agent storage container and is conveyed to the at least one group of hollow fiber membrane modules through a magnetic circulating pump.
The crystallizer is provided with a stirring device, and the stirring speed is 200-500 rpm, preferably 300-400 rpm.
The filter unit of the invention adopts a decompression suction filtration device which comprises a vacuum pump.
Compared with the prior art, the invention has the following beneficial effects:
1. the method adopts the hollow fiber membrane component to realize the continuous purification of the lithium bis (fluorosulfonyl) imide, effectively controls the nucleation rate, has controllable crystal size and avoids explosive nucleation; the multi-group membrane component can realize the grading control of crystallization nucleation, crystallization growth and crystal curing, effectively control the growth of crystals, and obtain the crystals with uniform size and narrow particle size distribution.
2. The invention realizes the adjustment of the liquid permeation flux of the tube pass of the membrane component through the flow meter, controls the generation of crystal nucleus and the growth of crystal, and does not need to add other equipment for improving the mixing state of the elutriation agent and the solution.
3. The invention has simple operation and wide application range, can obtain products with high quality and high purity by controlling the flow rate, the temperature difference, the pressure difference, the supersaturation degree and the like of the feed liquid, and is suitable for being used as the electrolyte of the lithium ion battery.
Drawings
FIG. 1 is a microscopic appearance of a crude lithium bis (fluorosulfonyl) imide prepared according to the preparation example of the present invention;
FIG. 2 is a schematic structural diagram of a continuous purification apparatus for lithium bis (fluorosulfonyl) imide in example 1 of the present invention;
FIG. 3 is a microscopic image of a lithium bis (fluorosulfonylimide) product obtained in example 2 of the present invention;
FIG. 4 is a microscopic image of a lithium bis (fluorosulfonylimide) product obtained in example 3 of the present invention.
Detailed Description
The present invention is further illustrated by the following examples, which are not intended to limit the invention to these embodiments. It will be appreciated by those skilled in the art that the present invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.
Preparation examples
The crude product of lithium bis (fluorosulfonyl) imide adopted in the embodiment of the invention is prepared by the following steps:
1) The preparation method of the bis (chlorosulfonyl) imide comprises the following steps:
adding 220g of chlorosulfonyl isocyanate into a 500mL three-neck flask which is provided with a condenser tube, a thermometer and a magnetic stirrer, heating to the temperature of about 107 ℃, then dropwise adding 182g of chlorosulfonic acid for about 3h, after dropwise adding, continuously maintaining reflux reaction for about 13h, and cooling after the reaction is finished to obtain 330g of bischlorosulfonimide, wherein the reaction yield is about 98.8%.
2) Preparing bis (fluorosulfonyl) imide:
adding the bis (chlorosulfonyl) imide into a tubular reactor, wherein the inner diameter of the reactor is 20mm, the length of the reactor is 120cm, the material of the tube is 316L, and the inner lining is made of tetrafluoro material. Heating the tubular reactor to 100 ℃, introducing hydrogen fluoride gas from the bottom of the reactor, controlling the feeding speed of the hydrogen fluoride by using a mass flow meter, wherein the feeding speed of the hydrogen fluoride is 1450mL/min, the introduction amount of the hydrogen fluoride is 85g, reacting for 5h after the introduction, and discharging through the lower part of the tubular reactor after the reaction is finished. The obtained crude product of the bis (fluorosulfonyl) imide is rectified under reduced pressure to obtain 254g of the bis (fluorosulfonyl) imide product, the reaction yield is about 90%, and a sample is detected by ion chromatography, wherein the content of chloride ions is 20ppm, the content of fluoride ions is lower than 100ppm, and the content of sulfate ions is lower than 150ppm.
3) The preparation method of the crude product of the bis (fluorosulfonyl) imide comprises the following steps:
300g of butyl acetate and 52g of high-purity anhydrous lithium carbonate are added into a 500mL three-neck flask with a condenser pipe, a thermometer and a magnetic stirring device, the reaction temperature is controlled to be about 10 ℃, then the bis-fluorosulfonyl imide solution is dropwise added for about 1.5 hours, after the dropwise addition, the reaction is continued for about 1.5 hours, after the reaction is finished, the filtration is carried out, the filtrate is subjected to azeotropic dehydration by adding the butyl acetate, the reduced pressure concentration is carried out, then 600g of toluene is added, crystals are separated out, 256g of crude bis-fluorosulfonyl imide lithium is obtained after drying, and the crude product is in the form of powder.
FIG. 1 shows the appearance of the crude powder under a microscope, and it can be seen from FIG. 1 that the crude powder is a long rod-like crystal having an aspect ratio of up to 20, a non-uniform crystal size, and the presence of crushed crystals.
As can be seen by ion chromatographic analysis, the content of fluorine ions is 115.7ppm, the content of chlorine ions is 12.3ppm, and the content of sulfate ions is 254ppm; ICP analysis shows that the content of sodium ions is 16.2ppm, the content of potassium ions is 8.4ppm, the content of iron ions is 1.45ppm, and the content of other metal ions is less than 1ppm.
Example 1
This embodiment provides a continuous purification apparatus of lithium bis (fluorosulfonyl) imide, as shown in fig. 2, the continuous purification apparatus includes:
a solventing-out agent storage container 1 which stores a solventing-out agent and conveys the solventing-out agent to the tube side of at least one group of hollow fiber membrane modules through a magnetic circulating pump 2;
the flow meters comprise a first flow meter 3, a second flow meter 4 and a third flow meter 5 and are used for adjusting the flow of the elution agent entering the hollow fiber membrane module;
at least one group of hollow fiber membrane modules comprises a first-stage hollow fiber membrane module 6, a second-stage hollow fiber membrane module 7 and a third-stage hollow fiber membrane module 8, wherein the tube side outlet of each membrane module is communicated with the eluent storage container through a first valve 9; a second valve 13 is arranged between the first-stage hollow fiber membrane component and the second-stage hollow fiber membrane component, and a third valve 14 is arranged between the second-stage hollow fiber membrane component and the third-stage hollow fiber membrane component;
the feeding unit comprises a raw material tank 10, a raw material tank stirrer 11 and a peristaltic pump 12 for conveying a crude lithium bis (fluorosulfonyl) imide solution; the crude product lithium bis (fluorosulfonyl) imide solution flows through the first-stage hollow fiber membrane module, the second-stage hollow fiber membrane module and the third-stage hollow fiber membrane module, flows out of a shell pass outlet of the third-stage hollow fiber membrane module, and enters the crystallization unit through a fourth valve 15;
and the crystallization unit comprises a crystallizer 16, a crystallizer stirrer 17, a filtering device 18 and a vacuum pump 19.
Example 2
In this embodiment, the continuous purification apparatus of embodiment 1 is used to continuously purify lithium bis (fluorosulfonyl) imide, and the specific steps are as follows:
preparing a multi-stage membrane module from a PTFE hollow fiber membrane, preparing a butyl acetate solution of a crude product of lithium bis (fluorosulfonyl) imide in the preparation example at 25 ℃, adding the butyl acetate solution to a raw material tank 10, simultaneously opening a raw material tank stirrer 11, a second valve 13, a third valve 14, a fourth valve 15 and a crystallization tank stirrer 17, closing a discharge bottom valve of a crystallizer 16, adjusting the rotation speed of the raw material tank stirrer 11 to 400rpm, and adjusting the rotation speed of the crystallization tank stirrer 17 to 200rpm. And adding the solventing-out agent dichloromethane into the solventing-out agent tank 1, and opening the first-stage flow meter 3, the second-stage flow meter 4, the third-stage flow meter 5 and the first valve 9 to complete the circulation flow path of the solventing-out agent. And (3) opening the magnetic circulating pump 2, adjusting the tube pass flow of the 3-stage membrane component to 240mL/min, 160mL/min and 80mL/min, and respectively adjusting the corresponding permeation flux to 3mL/min, 2mL/min and 1mL/min. And opening the peristaltic pump 12, and adjusting the flow of the butyl acetate solution of the crude lithium bis (fluorosulfonyl) imide to be 6mL/min. And conveying the crystallization solution carrying the crystal product into a crystallizer 17 for 4 hours, opening a discharge bottom valve, allowing the crystallization solution to flow into a filtering device 18, and performing reduced pressure suction filtration and drying by using a vacuum pump 19 to obtain the lithium bis (fluorosulfonyl) imide product, wherein the one-way yield is 50%.
FIG. 3 shows a microscopic appearance of the prepared lithium bis (fluorosulfonyl) imide product, and it can be seen from FIG. 3 that the aspect ratio of the crystal is 3-4, the mesh number of the product is 80-200 mesh, and the particle size distribution is more concentrated.
Through ion chromatographic analysis, the content of fluorine ions is 11ppm, the content of chlorine ions is 4.3ppm, and the content of sulfate ions is 14ppm; by ICP analysis, the content of sodium ions was 4.4ppm, the content of potassium ions was 2.6ppm, the content of iron ions was 0.45ppm, and other metal ions were not detected.
Compared with the prior art, the three-level film auxiliary control crystallization can accurately control the addition of the solventing-out agent, complete the nucleation, growth and curing of the lithium bis (fluorosulfonyl) imide, and efficiently regulate and control the crystal nucleation and growth competitive relationship.
Example 3
In this embodiment, the continuous purification apparatus of embodiment 1 is used to continuously purify lithium bis (fluorosulfonyl) imide, and the specific steps are as follows:
preparing a multistage membrane module from a PVDF hollow fiber membrane, preparing a ethyl methyl carbonate solution of the crude lithium bis (fluorosulfonyl) imide at 25 ℃, adding the solution with the concentration of 51.6% into a raw material tank 10, simultaneously opening a raw material tank stirrer 11, a second valve 13, a third valve 14, a fourth valve 15 and a crystallization tank stirrer 17, closing a discharge bottom valve of a crystallizer 16, adjusting the rotating speed of the raw material tank stirrer 11 to 400rpm, and adjusting the rotating speed of the crystallization tank stirrer 17 to 200rpm. And adding the solventing-out agent toluene into a solventing-out agent tank 1, and opening a first-stage flow meter 3, a second-stage flow meter 4, a third-stage flow meter 5 and a first valve 9 to complete a circulation flow path of the solventing-out agent. And (3) opening the magnetic circulating pump 2, adjusting the tube pass flow of the 3-stage membrane component to 240mL/min, 120mL/min and 60mL/min, and respectively adjusting the corresponding permeation flux to 4mL/min, 2mL/min and 1mL/min. And opening the peristaltic pump 12, and adjusting the flow of the butyl acetate solution of the crude lithium bis (fluorosulfonyl) imide to be 10mL/min. And conveying the crystallization solution carrying the crystal product into a crystallizer 17 for 6 hours, opening a discharge bottom valve, allowing the crystallization solution to flow into a filtering device 18, and performing reduced pressure suction filtration by using a vacuum pump 19 to obtain a lithium bis (fluorosulfonyl) imide product, wherein the one-way yield is 61.4%.
FIG. 4 shows a microscopic appearance of the lithium bis (fluorosulfonyl) imide product, and as can be seen from FIG. 4, the crystals are hexagonal prisms, the aspect ratio of the crystals is 0.5-1, the mesh number of the product is 150-200, and the particle size distribution is more concentrated.
Through ion chromatographic analysis, the content of fluorine ions is 16ppm, the content of chlorine ions is 2.8ppm, and the content of sulfate ions is 18.5ppm; by ICP analysis, the content of sodium ions was 2.68ppm, the content of potassium ions was 1.16ppm, the content of iron ions was 0.17ppm, and other metal ions were not detected.
Claims (19)
1. A method for continuously purifying lithium bis (fluorosulfonyl) imide is characterized by comprising the following steps: the continuous purification method comprises the following steps:
A1. contacting the lithium bis (fluorosulfonyl) imide solution with a leaching agent in at least one group of hollow fiber membrane modules to form a crystallization solution;
A2. aging the crystallization solution in a crystallizer;
A3. after curing, the product of the lithium bis (fluorosulfonyl) imide is obtained by decompression and suction filtration.
2. The method for continuously purifying lithium bis (fluorosulfonyl) imide according to claim 1, wherein: and the elutriation agent returns to the elutriation agent storage container after passing through the at least one group of hollow fiber membrane modules to form a circulation loop.
3. The continuous purification method of lithium bis (fluorosulfonylimide) according to claim 1 or 2, characterized in that: the lithium bis (fluorosulfonyl) imide solution passes through the shell side of the at least one group of hollow fiber membrane modules, and the elution agent passes through the tube side of the at least one group of hollow fiber membrane modules.
4. The method for continuously purifying lithium bis (fluorosulfonyl) imide according to claim 1, wherein: when at least two groups of hollow fiber membrane modules are arranged, the lithium bis (fluorosulfonyl) imide solution sequentially passes through the at least two groups of hollow fiber membrane modules, and the elution agent is simultaneously communicated with the at least two groups of hollow fiber membrane modules.
5. The continuous purification method of lithium bis (fluorosulfonylimide) according to claim 4, characterized in that: the flow rate of the elution agent connected with the previous-stage hollow fiber membrane component is larger than that of the elution agent connected with the next-stage hollow fiber membrane component.
6. The method for continuously purifying lithium bis (fluorosulfonyl) imide according to claim 4, wherein: the flow rate of the elution agent is 120-300 mL/min.
7. The method for continuously purifying lithium bis (fluorosulfonyl) imide according to any one of claims 1 to 6, wherein: the hollow fiber membrane is selected from an organic membrane, an inorganic membrane or a composite membrane.
8. The continuous purification method of lithium bis (fluorosulfonyl) imide according to claim 7, characterized in that: the organic film is selected from polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene, and a solvent-resistant material prepared by modifying polytetrafluoroethylene, polyvinylidene fluoride, polyethylene or polypropylene; the inorganic membrane is selected from a metal oxide membrane and/or a zeolite membrane; the composite membrane is selected from polyvinyl alcohol/micro sodium cellulose.
9. The method for continuously purifying lithium bis (fluorosulfonyl) imide according to claim 1, wherein: the bis-fluorosulfonyl imide lithium solution is obtained by dissolving crude bis-fluorosulfonyl imide lithium in an organic solvent, or is a reaction solution for preparing bis-fluorosulfonyl imide lithium.
10. The continuous purification method of lithium bis (fluorosulfonyl) imide according to claim 9, characterized in that: the organic solvent is at least one selected from ester compounds, carbonate compounds, ether compounds, nitrile compounds and ketone compounds.
11. The continuous purification method of lithium bis (fluorosulfonyl) imide according to claim 10, characterized in that:
the ester compound is at least one selected from methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl formate, ethyl formate, propyl formate and butyl formate;
the carbonate compound is selected from at least one of dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate;
the ether compound is selected from at least one of diethyl ether, isopropyl ether and methyl tert-butyl ether;
the nitrile compound is acetonitrile;
the ketone compound is acetone.
12. The continuous purification method of lithium bis (fluorosulfonylimide) according to claim 1, characterized in that: the elution agent is selected from at least one of benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, dichloromethane, dichloroethane, chloroform, carbon tetrachloride, cyclohexane, n-hexane and petroleum ether.
13. The method for continuously purifying lithium bis (fluorosulfonyl) imide according to claim 1, wherein: the content of the lithium bis (fluorosulfonyl) imide in the lithium bis (fluorosulfonyl) imide solution is 20-90%.
14. A lithium bis (fluorosulfonyl) imide product, characterized in that: the method for continuously purifying the lithium bis (fluorosulfonyl) imide disclosed in any one of claims 1 to 13, wherein the aspect ratio of the lithium bis (fluorosulfonyl) imide product is 0.5-10, and the mesh number of more than or equal to 80% of the lithium bis (fluorosulfonyl) imide product is 50-250 meshes.
15. The lithium bis (fluorosulfonyl) imide product of claim 14 wherein: the length-diameter ratio of the lithium bis (fluorosulfonyl) imide product is 0.5-5, and the mesh number of more than or equal to 80% of the product is 80-200 meshes.
16. A device for continuously purifying lithium bis (fluorosulfonyl) imide is characterized in that: the continuous purification apparatus includes:
the lithium bis (fluorosulfonyl) imide solution sequentially passes through the at least one group of hollow fiber membrane modules, and the elution agent is simultaneously connected with the at least one group of hollow fiber membrane modules;
the crystallizer is connected with the outlet of the at least one group of hollow fiber membrane modules;
and the filtering unit is connected with an outlet of the crystallizer, and a lithium bis (fluorosulfonyl) imide product is obtained through reduced pressure suction filtration.
17. The apparatus for continuously purifying lithium bis (fluorosulfonyl) imide according to claim 16, wherein: and the elutriation agent returns to the elutriation agent storage container after passing through the at least one group of hollow fiber membrane modules to form a circulation loop.
18. The apparatus for continuously purifying lithium bis (fluorosulfonyl) imide according to claim 16, wherein: and the elutriation agent enters the at least one group of hollow fiber membrane modules after being metered by the flowmeter.
19. The apparatus for continuously purifying lithium bis (fluorosulfonyl) imide according to claim 16, wherein: the lithium bis (fluorosulfonyl) imide solution passes through the shell side of the at least one group of hollow fiber membrane modules, and the elution agent passes through the tube side of the at least one group of hollow fiber membrane modules.
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