WO2016184176A1 - Preparation method for bis-(fluoro-sulfonyl) imide lithium salt - Google Patents

Abstract

Provided is a preparation method for lithium bis-(fluoro-sulfonyl) imide, comprising the following steps: (1) carrying out fluorination: synthesizing an intermediate bis-(fluoro-sulfonyl) imide by using bis-(chloro-sulfonyl) imide and hydrogen fluoride in presence of a catalyst; and (2) enabling the obtained bis-(fluoro-sulfonyl) imide and alkaline lithium to react, and carrying out solid-liquid separation after the reaction to obtain the lithium bis-(fluoro-sulfonyl) imide. The preparation method is low in cost, fewer in by-products and simple in aftertreatment, and is capable of guaranteeing the quality and purity of products, thereby being suitable for industrial production.

Description

Preparation method of lithium bisfluorosulfonimide salt Technical field

The present invention relates to the field of lithium batteries and lithium capacitors, and more particularly to a method for preparing a lithium bisfluorosulfonimide salt and use thereof.

Background technique

In the periodic table, fluorine is the most electronegative element. Often a introduction fluorine, significant change in their physical and chemical properties compound, therefore, many fluorine-containing lithium compounds, such as bis trifluoromethanesulfonyl imide (of LiTFSI) and lithium hexafluorophosphate (LiPF _6), is widely used Improve the electrical performance of batteries and capacitors. U.S. Patent No. 5,916,475 discloses a fluorine-containing lithium salt having a higher thermal stability and chemical stability than LiTFSI and LiPF ₆ , a higher conductivity and a lower corrosion rate - lithium bisfluorosulfonimide ( LiFSI), which is considered to be a possible alternative to LiPF ₆ in a lithium fluoride battery, will have excellent application prospects in lithium batteries and supercapacitors.

Most LiFSI synthesis methods first synthesize dichlorosulfonimide (HClSI), and then react with MFn (M is a group 11-15, element 4-6) to prepare the corresponding metal or organic base. bis fluorosulfonylimide salt intermediate, and then with LiOH or Li ₂ CO ₃ to cation-exchange reaction of LiFSI (US2013331609, US2012041233, EP2415757, US2011034716), these methods are disadvantageous in that, after the exchange reaction is difficult to achieve a balance The complete, unreacted intermediate MSFI (M refers to metal cations, organic base cations) is difficult to completely separate completely from LiSFI, resulting in a high quality product.

When LiFSI is directly reacted with LiF by HClSI (US2004097757), a large amount of corrosive gas HF is generated, and excess LiF and LiFSI are not easily separated.

Although it has also been reported that LiFSI is prepared by exchanging purified potassium bisfluorosulfonimide (KFSI) with LiClO ₄ metal, the potassium ions in the product tend to be high, which affects its practical application, and LiClO ₄ and KClO _{4 are formed} . There is a certain risk of explosion (Electrochimical Acta, 2012, 66, PP. 320-324, Polyhedron, 2006, 25, PP. 1292-1298, CN101747242, CN101747243, CN101654229). In addition, since LiClO ₄ generally requires a slight excess of participation in the reaction, its own hygroscopicity makes the final product contain a small amount of LiClO _{4 which} cannot be removed, so that the purity of the final product LiFSI cannot be guaranteed.

US8377406 discloses a method for preparing LiFSI by directly reacting difluorosulfonimide (HFSI) with lithium carbonate in an aqueous solution, but this method also has obvious disadvantages, and HFSI is strongly exothermic when dissolved in water, thereby causing decomposition of HFSI. The patent uses an ultra-low temperature (-78 ° C) method to prepare HFSI aqueous solution to solve the technical problem of HFSI violent heat release when dissolved in water, but this method increases a lot of energy consumption, and more importantly, LiFSI has very good water dissolution. Sex, extraction efficiency is very low, not suitable Industrial production.

JP2013091524 systematically studied the stability of LiFSI and found that LiFSI has a faster decomposition rate in the environment where the temperature exceeds 40 °C, and the larger the moisture, the faster the decomposition. Therefore, there is an urgent need in the art for a reagent to be cheap. The method has the advantages that the reaction is rapid and complete, the yield is high, the by-product is small, the lithium salt is easily removed, the synthesized lithium salt is not easily decomposed, and the post-treatment method is simple to prepare the lithium salt of bisfluorosulfonimide, thereby significantly reducing the cost of the product, and Make it more suitable for industrial production.

Summary of the invention

In view of the above-discussed shortcomings of the prior art, it is an object of the present invention to provide a method for preparing a lithium fluorosulfonimide (LiFSI) for solving the problems in the prior art.

To achieve the above and other related objects, the present invention provides a method for preparing a lithium bisfluorosulfonimide (LiFSI), comprising the steps of:

(1) fluorination reaction: synthesis of intermediate difluorosulfonimide (HFSI) by dichlorosulfonimide (HClSI) and hydrogen fluoride (HF) under the action of a catalyst;

(2) The bisfluorosulfonimide (HFSI) obtained in the step 1 is reacted with basic lithium, and after the completion of the reaction, the solid-liquid separation is carried out to obtain a LiFSI product.

The reaction equation of the step 1 is as follows:

Preferably, in the step 1, the fluorination reaction is carried out by placing HClSI and a catalyst in a reaction device, and introducing HF gas to carry out the reaction.

Preferably, in the step 1, the catalyst is preferably a Lewis acid, more preferably a combination of one or more of SbCl ₅ , TiCl ₄ , SnCl ₄ , MoCl ₅ .

Preferably, in the step 1, the molar ratio of HClSI to the catalyst is preferably 1:0.05 ‰ to 1:1 ‰, more preferably 1:0.1 ‰ to 1:0.5 ‰.

Preferably, in the step 1, the molar ratio of HClSI to HF is preferably 1:1.4 to 1:4, more preferably 1:1.7 to 1:2.

Preferably, in the step 1, the reaction temperature of the reaction system is a reaction at 90 to 110 ° C, more preferably 100 to 105 ° C.

Preferably, in the step 1, the intermediate HFSI is synthesized by HClSI and HF under the action of a catalyst, and after the reaction is completed, the HF and HCl gases in the reaction system are removed to obtain an intermediate difluorosulfonimide.

More preferably, the method of removing HF and HCl gas in the reaction system is to distill the reaction system, or The reaction system was subjected to blowing and distillation.

Further preferably, the temperature at the time of blowing is room temperature, the blowing time is 10-20 hours, and the distillation is vacuum distillation.

Preferably, in the step (2), the basic lithium is a combination of one or more of LiOH, LiHCO ₃ or Li ₂ CO ₃ .

Preferably, the molar ratio of HFSI to lithium in basic lithium is preferably from 1:0.8 to 1:1, more preferably from 1:0.9 to 1:0.98.

When the basic lithium is LiOH, the reaction equation is as follows:

When the basic lithium is Li ₂ CO ₃ , the reaction equation is as follows:

When the basic lithium is Li ₂ HCO ₃ , the reaction equation is as follows:

Preferably, in the step (2), the product obtained in the step 1 is added to an alkaline lithium solvent system, and the reaction system is preferably cooled during the addition and/or reaction, preferably by dropwise addition.

More preferably, the reaction temperature of the reaction system is from 0 to 20 ° C, more preferably from 0 to 5 ° C.

More preferably, the solvent in the basic lithium solvent system is a low polar solvent, more preferably hexane, cyclohexane, dichloromethane, dichloroethane, toluene, xylene, chlorobenzene, dichlorobenzene. a combination of one or more of them.

Preferably, in the step (2), the bisfluorosulfonimide (HFSI) obtained in the step 1 is reacted with basic lithium, and after the reaction is completed, SOCl ₂ is added dropwise to the reaction system to complete the moisture in the system, and solid. The liquid is separated to obtain a LiFSI product.

More preferably, the addition of SOCl ₂ is carried out at room temperature.

Preferably, in the step (2), the bisfluorosulfonimide (HFSI) obtained in the step 1 is reacted with basic lithium, and the LiFSI product obtained by solid-liquid separation after the completion of the reaction is further subjected to beating treatment.

More preferably, the specific method of the beating treatment is: adding LiFSI obtained by solid-liquid separation into a beating solvent and a metal ion removing agent for beating treatment, thereby obtaining a purified LiFSI product.

Further preferably, the beating solvent is a low polar solvent, more preferably one or more of hexane, cyclohexane, dichloromethane, dichloroethane, toluene, xylene, chlorobenzene or dichlorobenzene. Combination of species.

Further preferably, the metal ion removing agent is selected from the group consisting of 12-crown-4, 15-crown-5, 18-crown-6, bicyclohexane and -18-crown-6. .

The preparation method of the lithium bisfluorosulfonimide salt (LIFSI) according to the present invention has the following advantages:

1. With HF as fluorinating reagent, the cost is low, the raw materials are easily available, the fluorination is thorough under the action of the catalyst, and the by-products are less, and the by-product HCl can be absorbed only by alkali; most of the system after the reaction is completed. HF and HCl can be carried away by nitrogen blowing, and a small amount can be removed by distillation to ensure the purity and quality of the intermediate HFSI.

2. The reaction of bisfluorosulfonimide (HFSI) with LiOH or LiHCO ₃ and Li ₂ CO ₃ is fast and the reaction is thorough. The by-product produced is water (the solubility of water to LiFSI is very good, and there is water in the product. It is difficult to precipitate), which can be gently removed by SOCl ₂ at low temperature. After the water is removed, the product can be gradually precipitated to make the separation simple, and at the same time, by-product SO _{2 is formed} , and HCl (and CO ₂ ) are absorbed by the alkaline water. There are no other complicated by-products.

3. At the same time, since the equivalent number of bisfluorosulfonimide (HFSI) is greater than the equivalent number of lithium, all the basic lithium is completely reacted, and the excess HFSI is liquid, and the remaining SOCl ₂ (liquid) in the same system SO ₂ (gas), HCl (gas), or CO ₂ (gas) can be removed by filtration and beating to ensure the purity of the product.

4. Since the product is extremely sensitive to temperature, the product is easily decomposed under high temperature, so the invention successfully avoids the heating operation in the key salt forming step, thereby ensuring the quality and purity of the product.

5 The invention adopts non-aqueous system, has less waste, high yield, and all solvents can be conveniently recycled and used economically; the post-treatment uses crown ether to remove metal ions such as potassium and sodium which may be introduced in the system, and can improve LiFSI Quality and performance.

It can be seen that the present invention provides an economical and economical preparation method capable of obtaining high quality and high purity products, and is suitable for industrial production.

detailed description

The inventors of the present invention use hydrogen fluoride (HF) and bischlorosulfonimide (HClSI) as raw materials to fluorinate under the action of a catalyst to obtain an intermediate difluorosulfonimide (HFSI), which is further equivalent to a certain amount of basicity. Lithium reaction preparation to obtain high quality and high purity LiFSI (bisfluorosulfonimide lithium salt, CAS: 171611-11-3) products, thus providing a simple and efficient method to prepare high quality LiFSI, on this basis The invention has been made.

The invention provides a preparation method of lithium bisfluorosulfonimide (LiFSI), comprising the following steps:

(1) Fluorination reaction: The intermediate difluorosulfonimide (HFSI) is synthesized from dichlorosulfonimide (HClSI) and hydrogen fluoride (HF) under the action of a catalyst. The reaction equation is as follows:

In the step 1, the fluorination reaction is carried out by placing HClSI and a catalyst in a reaction device, and introducing HF gas to carry out the reaction.

In the step 1, the catalyst is preferably a Lewis acid, more preferably a combination of one or more of SbCl ₅ , TiCl ₄ , SnCl ₄ and MoCl ₅ , and the molar ratio of HClSI to the catalyst is preferably 1:0.05‰1. : 1‰, more preferably 1:0.1‰ to 1:0.5‰.

In the step 1, the molar ratio of HClSI to HF is preferably from 1:1.4 to 1:4, more preferably from 1:1.7 to 1:2.

In the step 1, the reaction temperature of the reaction system is preferably a reaction at 90 to 110 ° C, more preferably 100 to 105 ° C. The person skilled in the art can control the reaction time according to the progress of the reaction in the reaction system, and the preferred reaction time is 15 to 25 hours.

In the step 1, the intermediate HFSI is synthesized by the action of HClSI and HF under the action of a catalyst, and after the reaction is completed, the HF and HCl gases in the reaction system are removed to obtain an intermediate difluorosulfonimide. The method of removing HF and HCl gas in the reaction system is preferably a method of distilling the reaction system or blowing and distilling the reaction system, and in a preferred embodiment of the present invention, the method of removing HF and HCl gas in the reaction system In order to carry out the blowing of the reaction system, distillation is carried out. The temperature at the time of blowing is preferably room temperature, and the optional gas to be blown includes, but not limited to, a combination of one or more of nitrogen, various inert gases, and the like, and those skilled in the art can adjust according to the size of the reaction system, the acidity of the exhaust gas, and the like. The amount of blowing gas and the blowing time are introduced, and the preferred blowing time is 10-20 hours. The specific conditions of the distillation are not particularly limited as long as the object of the present invention is not limited, and distillation under reduced pressure is preferred.

(2) Salt formation reaction: The bisfluorosulfonimide (HFSI) obtained in the step 1 is reacted with basic lithium, and after the completion of the reaction, the solid-liquid separation is carried out to obtain a LiFSI product.

In the step (2), the basic lithium is preferably a combination of one or more of LiOH, LiHCO ₃ or Li ₂ CO ₃ , and the molar ratio of HFSI to lithium in the basic lithium is preferably 1:0.8 1:1, more preferably 1:0.9 to 1:0.98. The LiOH may be LiOH.H ₂ O.

When the basic lithium is LiOH, the reaction equation is as follows:

When the basic lithium is Li ₂ CO ₃ , the reaction equation is as follows:

When the basic lithium is Li ₂ HCO ₃ , the reaction equation is as follows:

In the step (2), it is preferred to add the product obtained in the step 1 to an alkaline lithium solvent system, and preferably to cool the reaction system during the addition and/or reaction, preferably by dropwise addition. More preferably, the reaction system is reversed The reaction is carried out at a temperature of from 0 to 20 ° C, more preferably from 0 to 5 ° C. The person skilled in the art can control the reaction time according to the progress of the reaction in the reaction system, and the preferred reaction time is 1 to 5 hours. The solvent in the basic lithium solvent system is preferably a low polarity solvent, specifically including but not limited to hexane, cyclohexane, dichloromethane, dichloroethane, toluene, xylene, chlorobenzene, dichlorobenzene. One or more combinations. Those skilled in the art can adjust the amount of the solvent in the alkaline lithium solvent system according to the actual situation, and the amount is preferably 3-4 times the weight of the product LiFSI.

In the step (2), it is preferred to react the bisfluorosulfonimide (HFSI) obtained in the step 1 with basic lithium, and after the reaction is completed, the SOCl ₂ is added dropwise to the reaction system to complete the reaction of the water in the system, and the solid solution Separation, the LiFSI product is obtained. The dropwise addition of SOCl ₂ is preferably carried out at room temperature, and those skilled in the art can adjust the amount of SOCl ₂ according to the actual conditions of the reaction system. Preferably, the molar ratio of HFSI to SOCl ₂ is 1:0.5 to 1:4, more preferably for LiOH. H ₂ O is 1:2.4 to 1:3.2, 1:1.2 to 1:1.6 for LiHCO _{3 and} 1:0.6 to 1:0.8 for Li ₂ CO ₃ .

In the step (2), the bisfluorosulfonimide (HFSI) obtained in the step 1 is reacted with basic lithium, and the LiFSI product obtained by the solid-liquid separation after the completion of the reaction is further subjected to a beating treatment, and the specific method of the beating treatment is as follows: The LiFSI obtained by solid-liquid separation is added to a beating solvent and a metal ion removing agent for beating treatment to obtain a purified LiFSI product. The beating solvent is preferably a low polar solvent, specifically including but not limited to one or more of hexane, cyclohexane, dichloromethane, dichloroethane, toluene, xylene, chlorobenzene, dichlorobenzene. The combination. A person skilled in the art can adjust the amount of the beating solvent according to the actual situation, and the amount is preferably 3-6 times the weight of LiFSI. The metal ion removing agent may be selected from various metal ion removing agents in the art, and preferred metal ion removing agents include, but are not limited to, 12-crown-4, 15-crown-5, 18-crown-6, and dicyclohexane. A combination of one or more of -18-crown-6. Those skilled in the art can adjust the amount of the metal ion removing agent according to the actual situation. The preferred metal ion removing agent is used in an amount of 0.02% to 0.2% by weight of LiFSI.

The invention also provides the use of the preparation method of the lithium salt of bisfluorosulfonylimide in the field of preparation of lithium bisfluorosulfonimide.

The preparation method of LiFSI provided by the invention adopts HF catalytic fluorination method to obtain HClSI, and the latter is completely reacted with alkaline lithium, and after simple and economical post-treatment, high-quality and high-purity LiFSI products can be purified. The method has simple reaction steps and reasonable cost, and is suitable for large-scale industrialization.

The embodiments of the present invention are described below by way of specific examples, and those skilled in the art can readily understand other advantages and effects of the present invention from the disclosure of the present disclosure. The present invention may be embodied or applied in various other specific embodiments, and various modifications and changes can be made without departing from the spirit and scope of the invention.

It should be noted that the process equipment or apparatus not specifically noted in the following examples employ conventional equipment or apparatus in the art.

In addition, it should be understood that one or more of the method steps recited in the present invention are not exclusive of other method steps that may be present before or after the combination step, or that other method steps can be inserted between the steps specifically mentioned, unless otherwise Have instructions; It should also be understood that the combined connection relationship between one or more devices/devices referred to in the present invention does not exclude that there may be other devices/devices or two of those explicitly mentioned before or after the combined device/device. Other devices/devices can also be inserted between the devices/devices unless otherwise stated. Moreover, unless otherwise indicated, the numbering of each method step is merely a convenient means of identifying the various method steps, and is not intended to limit the order of the various method steps or to limit the scope of the invention, the relative In the case where the technical content is not substantially changed, it is considered to be a scope in which the present invention can be implemented.

Experiment: HClSI was prepared by mixing commercially available sulfamic acid, thionyl chloride, chlorosulfonic acid by the literature procedure (CN103935970, US2011034716, US4350685), and other reagents were commercially available.

Example 1

In a 1000 mL reaction flask, 1235 g of HClSI and 0.5 g of SbCl _{5 were} added, and the temperature was raised to 100-105 ° C, and about 230 g of HF gas was slowly introduced under stirring. After reacting for 20 hours, the temperature was lowered to room temperature, and nitrogen gas was blown for 15 hours to obtain a crude product of about 900 g. Short steaming gave 865.6 g of product with a yield of 82.8%.

Example 2

In a 1000 mL reaction flask, 1230 g of HClSI and 0.47 g of MoCl _{5 were} added, and the temperature was raised to 100-105 ° C, and about 216 g of HF gas was slowly introduced under stirring. After reacting for 22 hours, the temperature was lowered to room temperature, and nitrogen gas was blown for 15 hours to obtain a crude product of about 896 g. Short steaming gave 864.8 g of product with a yield of 83.1%.

Example 3

In a 1000 mL reaction flask, 543 g of dichloroethane and 42.0 g of LiOH·H ₂ O were added, and the temperature was lowered to 0-5 ° C, and 192.5 g of bisfluorosulfonimide (HFSI, Example 1) was added dropwise with stirring, and stirred for 2 hours. Then, the temperature was raised to 20-25 ° C, 357 g of SOCl _{2 was} added dropwise, and stirred for 16 h. After filtration, the filter cake was beaten with 600 g of dichloroethane and 0.17 g of 18-crown-6, filtered and dried to obtain 169.2 g of a product, yield 90.4%.

The test results were: AAS (ppm): Na: 5.6, K: 2.3, Fe < 1, Ca < 1. IC (ppm): Cl ^- : 4.7, F ^- : 27, SO ₄ ^2- : 17

Example 4

To a 1000 mL reaction flask, 550 g of toluene and 36 g of Li ₂ CO ₃ were added, and the temperature was lowered to 0-5 ° C. 181 g of bisfluorosulfonimide (HFSI, Example 2) was added dropwise with stirring, and the mixture was stirred for 2 hours, and then the temperature was raised to 20-25. °C, 95g of SOCl2 was added dropwise and stirred for 16 h. After filtration, the filter cake was beaten with 600 g of toluene and 0.15 g of 15-crown-5, filtered and dried to obtain 170.6 g of a product, yield 91.2%.

The test results were: AAS (ppm): Na: 3.7, K: 3.5, Fe < 1, Ca < 1. IC (ppm): Cl ^- : 7.8, F ^- : 14, SO4 ^2- : 20

Example 5

In a 1000 mL reaction flask, 500 g of cyclohexane and 68 g of LiHCO ₃ were added, and the temperature was lowered to 0-5 ° C. 188.5 g of bisfluorosulfonimide (HFSI, Example 1) was added dropwise with stirring, and the mixture was stirred for 2 h, and then the temperature was raised to 20- At 25 ° C, 161 g of SOCl _{2 was} added dropwise and stirred for 16 h. After filtration, the cake was beaten with 550 g of cyclohexane and 0.17 g of 18-crown-6, filtered and dried to give a product of 170.2 g, yield 91.0%.

The test results were: AAS (ppm): Na: 4.4, K: 3.0, Fe < 1, Ca < 1. IC (ppm): Cl ^- : 6.1, F ^- : 21, SO ₄ ^2- : 15

In summary, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

The above-described embodiments are merely illustrative of the principles of the invention and its effects, and are not intended to limit the invention. Modifications or variations of the above-described embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and scope of the invention will be covered by the appended claims.

Claims (9)

1. A preparation method of a lithium salt of bisfluorosulfonimide, comprising the following steps:

   (1) fluorination reaction: synthesis of intermediate bisfluorosulfonimide by dichlorosulfonimide and hydrogen fluoride under the action of a catalyst;

   (2) The bisfluorosulfonimide obtained in the step 1 is reacted with basic lithium, and after the completion of the reaction, the solid-liquid separation is carried out to obtain a LiFSI product.
2. The method for preparing a lithium salt of a bisfluorosulfonimide according to claim 1, wherein in the step 1, the fluorination reaction is carried out by placing HClSI and a catalyst in a reaction device. The reaction was carried out by introducing HF gas.
3. The method for preparing a lithium salt of a bisfluorosulfonimide according to claim 1, wherein in the step 1, the catalyst is Lewis acid;

   And/or, in the step 1, the molar ratio of HClSI to the catalyst is 1:0.05 ‰ to 1:1 ‰;

   And/or, in the step 1, the molar ratio of HClSI to HF is 1:1.4 to 1:4;

   And/or, in the step 1, the reaction temperature of the reaction system is reacted at 90 to 110 °C.
4. The method for preparing a lithium salt of a bisfluorosulfonimide according to claim 1, wherein in the step 1, the intermediate HFSI is synthesized by the action of HClSI and HF under the action of a catalyst, and the reaction system is removed after the reaction is completed. HF and HCl gases.
5. The method for preparing a lithium salt of a bisfluorosulfonimide according to claim 4, wherein the method for removing HF and HCl gas in the reaction system is to distill the reaction system or to carry out the reaction system. Advocate and distill.
6. The method for preparing a lithium salt of a bisfluorosulfonimide according to claim 5, wherein the temperature at the time of blowing is room temperature;

   And/or, the distillation is a vacuum distillation.
7. The method for preparing a lithium salt of a bisfluorosulfonimide according to claim 1, wherein in the step 2, the basic lithium is one of LiOH, LiHCO ₃ or Li ₂ CO ₃ . Or a combination of multiples;

   And/or, in the step 2, the molar ratio of HFSI to lithium in alkaline lithium is 1:0.8 to 1:1;

   And/or, in the step 2, the product obtained in the step 1 is added to an alkaline lithium solvent system, and the solvent in the basic lithium solvent system is a low polar solvent;

   And/or, in the step 2, the reaction temperature of the reaction system is reacted at 0 to 20 ° C;

   And/or, in the step 2, the bisfluorosulfonimide obtained in the step 1 is reacted with basic lithium. After the reaction is completed, SOCl ₂ is added dropwise to the reaction system to complete the reaction of the water in the system, followed by solid-liquid separation.
8. The method for preparing a lithium salt of a bisfluorosulfonimide according to claim 1, wherein in the step 2, The bisfluorosulfonimide obtained in the first step is reacted with the basic lithium, and the LiFSI product obtained by the solid-liquid separation after the completion of the reaction is further subjected to a beating treatment. The specific method of the beating treatment is: adding the LiFSI obtained by the solid-liquid separation to the beating solvent and the metal ion. The remover is subjected to a beating treatment to obtain a purified LiFSI product.
9. The method for preparing a lithium salt of a bisfluorosulfonimide according to claim 8, wherein the beating solvent is a low polar solvent;

   And/or, the metal ion removing agent is selected from the group consisting of 12-crown-4, 15-crown-5, 18-crown-6, bicyclohexane and -18-crown-6. .