IONIC LIQUIDS AND PREPARATION METHOD THEREOF

Abstract

The present disclosure provides an ionic liquid and a preparation method thereof, in particular, the present disclosure provides an ionic liquid whose halogen anions content and moisture content are low, and a method for preparing the same. The total content of halogen anions in the ionic liquid is less than 10 ppm, and moisture content in the ionic liquid is less than 50 ppm. The ionic liquid prepared by the method of the present disclosure is suitable for electrochemical systems which have high requirements for moisture content, such as lithium ion secondary batteries and electrochemical supercapacitors.

Claims

1. An ionic liquid, wherein a total content of halogen anions in the ionic liquid is less than 10 ppm, and moisture content in the ionic liquid is less than 50 ppm; the halogen anions are Cl.sup.−, Br.sup.− and I.sup.−.

2. The ionic liquid of claim 1, wherein the total content of halogen anions in the ionic liquid is less than 5 ppm.

3. The ionic liquid of claim 1, wherein a cation of the ionic liquid is selected from at least one of the following structures: ##STR00005## wherein each of said R, R′, R′.sub.1, and R′.sub.2 is selected from alkyl, alkenyl, alkynyl, phenyl or aryl; or each of said R, R′, R′.sub.1, and R′.sub.2 is an organic group comprising at least one element selected from boron, silicon, nitrogen, phosphorus, oxygen, sulfur, fluorine, chlorine, bromine and iodine; said organic group is alkyl, alkenyl, alkynyl, phenyl or aryl; wherein each of said R, R′, R′.sub.1 and R′.sub.2 is an independent substituent group; or at least two of said R, R′, R′.sub.1 and R′.sub.2 adjacent to each other joint into a ring; wherein each of said R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 is selected from hydrogen, alkyl, alkenyl, alkynyl, phenyl or aryl; or each of said R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 is a group comprising at least one element selected from the following: boron, silicon, nitrogen, phosphorus, oxygen, sulfur, fluorine, chlorine, bromine and iodine; wherein each of said R, R′, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R′.sub.1 and R′.sub.2 is an independent substituent group; or at least two of said R, R′, R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6, R′.sub.1 and R′.sub.2 adjacent to each other joint into a ring.

4. The ionic liquid of claim 1, wherein an anion of the ionic liquid is selected from at least one of the following: PF.sub.6.sup.−, BF.sub.4.sup.−, SO.sub.4.sup.2−, NO.sub.3.sup.−, F.sup.−, PO.sub.4.sup.3−, ClO.sub.4.sup.−, SiF.sub.6.sup.2−, CH.sub.3CO.sub.2.sup.−, CF.sub.3CO.sub.2.sup.−, C.sub.3F.sub.7CO.sub.2.sup.−, (CN).sub.2N.sup.−, ##STR00006##

5. A preparation method of the ionic liquid as described in claim 1, comprising the following steps: Step 1: preparing an ammonium salt or a phosphonium salt, reaction equations as below:
Q.sub.4Q.sub.5Q.sub.6N+[Q.sub.1Q.sub.2Q.sub.3NH].sup.+A.sup.−.fwdarw.[Q.sub.4Q.sub.5Q.sub.6NH].sup.+A.sup.−+Q.sub.1Q.sub.2Q.sub.3N  (a); or
Q.sub.4Q.sub.5Q.sub.6P+[Q.sub.1Q.sub.2Q.sub.3PH].sup.+A.sup.−.fwdarw.[Q.sub.4Q.sub.5Q.sub.6PH].sup.+A.sup.−+Q.sub.1Q.sub.2Q.sub.3P  (b); or
Q.sub.4Q.sub.5Q.sub.6N+[Q.sub.1Q.sub.2Q.sub.3PH].sup.+A.sup.−.fwdarw.[Q.sub.4Q.sub.5Q.sub.6NH].sup.+A.sup.−+Q.sub.1Q.sub.2Q.sub.3P  (c); or
Q.sub.4Q.sub.5Q.sub.6P+[Q.sub.1Q.sub.2Q.sub.3NH].sup.+A.sup.−.fwdarw.[Q.sub.4Q.sub.5Q.sub.6PH].sup.+A.sup.−+Q.sub.1Q.sub.2Q.sub.3N  (d); Step 2: the ammonium salt or the phosphonium salt prepared in step 1 reacts with a carbonate ester to produce a quaternary ammonium salt or a quaternary phosphonium salt, reaction equations as below:
[Q.sub.4Q.sub.5Q.sub.6NH].sup.+A.sup.−+RCO.sub.3R′.fwdarw.[Q.sub.4Q.sub.5Q.sub.6NR].sup.+A.sup.−+R′OH+CO.sub.2; or
[Q.sub.4Q.sub.5Q.sub.6PH].sup.+A.sup.−+RCO.sub.3R′.fwdarw.[Q.sub.4Q.sub.5Q.sub.6PR].sup.+A.sup.−+R′OH+CO.sub.2; wherein each of Q.sub.4, Q.sub.5, Q.sub.6, Q.sub.1, Q.sub.2 and Q.sub.3 is selected from hydrogen, alkyl, alkenyl, alkynyl, phenyl or aryl; or each of Q.sub.4, Q.sub.5, Q.sub.6, Q.sub.1, Q.sub.2 and Q.sub.3 is an organic group comprising at least one element selected from boron, silicon, nitrogen, phosphorus, oxygen, sulfur, fluorine, chlorine, bromine and iodine; said organic group is alkyl, alkenyl, alkynyl, phenyl or aryl; wherein each of said Q.sub.4, Q.sub.5, Q.sub.6, Q.sub.1, Q.sub.2 and Q.sub.3 is an independent substituent group; or at least two of said Q.sub.4, Q.sub.5, Q.sub.6, Q.sub.1, Q.sub.2 and Q.sub.3 adjacent to each other joint into a ring; wherein each of said R and R′ is selected from alkyl, alkenyl, alkynyl, phenyl or aryl; or each of said R and R′ is a group comprising at least one element selected from boron, silicon, nitrogen, phosphorus, oxygen, sulfur, fluorine, chlorine, bromine and iodine; wherein each of said R and R′ is an independent substituent group or R and R′ adjacent to each other joint into a ring; in reaction equation (a) of step 1, alkalinity of the Q.sub.4Q.sub.5Q.sub.6N is stronger than that of Q.sub.1Q.sub.2Q.sub.3N; or Q.sub.1Q.sub.2Q.sub.3N is a volatile gas and Q.sub.4Q.sub.5Q.sub.6N is a liquid or a solid whose boiling point is higher than that of Q.sub.1Q.sub.2Q.sub.3N; in reaction equation (b) of step 1, alkalinity of the Q.sub.4Q.sub.5Q.sub.6P is stronger than that of Q.sub.1Q.sub.2Q.sub.3P; or Q.sub.1Q.sub.2Q.sub.3P is a volatile gas and Q.sub.4Q.sub.5Q.sub.6P is a liquid or a solid whose boiling point is higher than that of Q.sub.1Q.sub.2Q.sub.3P; in reaction equation (c) of step 1, alkalinity of the Q.sub.4Q.sub.5Q.sub.6N is stronger than that of Q.sub.1Q.sub.2Q.sub.3P; or Q.sub.1Q.sub.2Q.sub.3P is a volatile gas and Q.sub.4Q.sub.5Q.sub.6N is a liquid or a solid whose boiling point is higher than that of Q.sub.1Q.sub.2Q.sub.3P; in reaction equation (d) of step 1, alkalinity of the Q.sub.4Q.sub.5Q.sub.6P is stronger than that of Q.sub.1Q.sub.2Q.sub.3N; or Q.sub.1Q.sub.2Q.sub.3N is a volatile gas and Q.sub.4Q.sub.5Q.sub.6P is a liquid or a solid whose boiling point is higher than that of Q.sub.1Q.sub.2Q.sub.3N.

6. The preparation method of the ionic liquid of claim 5, wherein said Q.sub.4Q.sub.5Q.sub.6N is at least one selected from N-propylpyrrolidine, N-butylpyrrolidine, N-ethylpiperidine, N-propylpiperidine, N-butylpiperidine, triethylamine and dimethyloctylamine.

7. The preparation method of the ionic liquid of claim 5, wherein said Q.sub.4Q.sub.5Q.sub.6N is at least one selected from dipropylamine, dioctyl amine, didecylamine and didodecylamine.

8. The preparation method of the ionic liquid of claim 5, wherein said Q.sub.4Q.sub.5Q.sub.6N is at least one selected from n-hexylamine, ethanolamine, tetradecylamine and hexadecylamine.

9. The preparation method of the ionic liquid of claim 5, wherein said Q.sub.4Q.sub.5Q.sub.6N is at least one selected from ethylimidazole, butylimidazole, pyridine and quinoline.

10. The preparation method of the ionic liquid of claim 5, wherein said Q.sub.4Q.sub.5Q.sub.6P is at least one selected from methylphosphine, dimethylphosphine, trimethylphosphine, ethylphosphine, diethylphosphine, triethylphosphine, tripropylphosphine, di-butylphosphine, tri-tert-butylphosphine, tributylphosphine, tri-n-amyl phosphine, cyclohexyl phosphine, dicyclohexyl phosphine, tricyclohexyl phosphine, trihexylphosphine, trioctylphosphine, phenylphosphine, diphenylphosphine, triphenylphosphine, dimethylphenylphosphine, diethylphenylphosphine, diphenylbutylphosphine, tribenzylphosphine, trihydroxymethylphosphine, 2-chloroethanediethylphosphine and tris(pentafluoroethyl)phosphine.

11. The preparation method of the ionic liquid of claim 5, wherein in reaction equation (a) of step 1, Q.sub.1Q.sub.2Q.sub.3N is selected from one of the following: an amine whose alkalinity is lower than that of Q.sub.4Q.sub.5Q.sub.6N, a volatile amine, an ammonia whose alkalinity is lower than that of Q.sub.4Q.sub.5Q.sub.6N, and a volatile ammonia; the anion A.sup.− is selected from at least one of the following: PF.sub.6.sup.−, BF.sub.4.sup.−, SO.sub.4.sup.2−, NO.sub.3.sup.−, F.sup.−, PO.sub.4.sup.3−, ClO.sub.4.sup.−, SiF.sub.6.sup.2−, (C.sub.mF.sub.2m+1SO.sub.2)(C.sub.nF.sub.2n+1SO.sub.2)N.sup.−, (C.sub.xF.sub.2x+1SO.sub.2).sub.2N.sup.−, CF.sub.3SO.sub.3.sup.−, CH.sub.3CO.sub.2.sup.−, CF.sub.3CO.sub.2.sup.−, C.sub.3F.sub.7CO.sub.2.sup.− and (CN).sub.2N.sup.−, wherein m is an integer from 0 to 5, n is an integer from 0 to 5, x is an integer from 1 to 10.

12. The preparation method of the ionic liquid of claim 5, wherein in reaction equation (b) of step 1, Q.sub.1Q.sub.2Q.sub.3P is selected from one of the following: a phosphine whose alkalinity is lower than that of Q.sub.4Q.sub.5Q.sub.6P, a volatile phosphine or hydrogen phosphide; the anion A- is selected from at least one of the following: PF.sub.6.sup.−, BF.sub.4.sup.−, SO.sub.4.sup.2−, NO.sub.3.sup.−, F.sup.−, PO.sub.4.sup.3−, ClO.sub.4.sup.−, SiF.sub.6.sup.2−, (C.sub.mF.sub.2m+1SO.sub.2)(C.sub.nF.sub.2n+1SO.sub.2)N.sup.−, (C.sub.xF.sub.2x+1SO.sub.2).sub.2N.sup.−, CF.sub.3SO.sub.3.sup.−, CH.sub.3CO.sub.2.sup.−, CF.sub.3CO.sub.2.sup.−, C.sub.3F.sub.7CO.sub.2.sup.− and (CN).sub.2N.sup.−; wherein m is an integer from 0 to 5, n is an integer from 0 to 5, x is an integer from 1 to 10.

13. The preparation method of the ionic liquid of claim 5, wherein in reaction equation (c) of step 1, Q.sub.1Q.sub.2Q.sub.3P is selected from one of the following: a phosphine whose alkalinity is lower than that of Q.sub.4Q.sub.5Q.sub.6N, a volatile phosphine or hydrogen phosphide, the anion A.sup.− is selected from at least one of the following: PF.sub.6.sup.−, BF.sub.4.sup.−, SO.sub.4.sup.2−, NO.sub.3.sup.−, F.sup.−, PO.sub.4.sup.3−, ClO.sub.4.sup.−, SiF.sub.6.sup.2−, (C.sub.mF.sub.2m+1SO.sub.2)(C.sub.nF.sub.2n+1SO.sub.2)N.sup.−, (C.sub.xF.sub.2x+1SO.sub.2).sub.2N.sup.−, CF.sub.3SO.sub.3.sup.−, CH.sub.3CO.sub.2.sup.−, CF.sub.3CO.sub.2.sup.−, C.sub.3F.sub.7CO.sub.2.sup.− and (CN).sub.2N.sup.−, wherein m is an integer from 0 to 5, n is an integer from 0 to 5, x is an integer from 1 to 10.

14. The preparation method of the ionic liquid of claim 5, wherein in reaction equation (d) of step 1, Q.sub.1Q.sub.2Q.sub.3N is selected from one of the following: an amine whose alkalinity is lower than that of Q.sub.4Q.sub.5Q.sub.6P, a volatile amine, an ammonia whose alkalinity is lower than that of Q.sub.4Q.sub.5Q.sub.6P and a volatile ammonia; the anion A.sup.− is selected from at least one of the following: PF.sub.6.sup.−, BF.sub.4.sup.−, SO.sub.4.sup.2−, NO.sub.3.sup.−, F.sup.−, PO.sub.4.sup.3−, ClO.sub.4.sup.−, SiF.sub.6.sup.2−, (C.sub.mF.sub.2m+1SO.sub.2)(C.sub.nF.sub.2n+1SO.sub.2)N.sup.−, (C.sub.xF.sub.2x+1SO.sub.2).sub.2N.sup.−, CF.sub.3SO.sub.3.sup.−, CH.sub.3CO.sub.2.sup.−, CF.sub.3CO.sub.2.sup.−, C.sub.3F.sub.7CO.sub.2.sup.− and (CN).sub.2N.sup.−, wherein m is an integer from 0 to 5, n is an integer from 0 to 5, x is an integer from 1 to 10.

15. The preparation method of the ionic liquid of claim 11, wherein said Q.sub.1Q.sub.2Q.sub.3N is selected from methylamine, dimethylamine, trimethylamine or ammonia.

16. The preparation method of the ionic liquid of claim 14, wherein said Q.sub.1Q.sub.2Q.sub.3N is selected from methylamine, dimethylamine, trimethylamine or ammonia.

17. The preparation method of the ionic liquid of claim 5, wherein a solvent is added into the reaction of step 1 and/or step 2; the solvent is selected from at least one of the following: alcohols, ethers, ketones, carbonates, nitriles, alkanes, halohydrocarbons and aromatic hydrocarbons.

18. The preparation method of the ionic liquid of claim 17, wherein the solvent is selected from at least one of the following: methanol, isopropanol, butanone and dimethyl carbonate.

19. The preparation method of the ionic liquid of claim 5, wherein the reaction temperature of step 1 is −20˜100° C.

20. The preparation method of the ionic liquid of claim 5, wherein the absolute pressure of the reaction in step 1 is 0.05˜2 Mpa.

21. The preparation method of the ionic liquid of claim 5, wherein the reaction time of step 1 is 0.1˜72 hours.

22. The preparation method of the ionic liquid of claim 5, wherein said RCO.sub.3R′ is selected from at least one of the following: dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl phenyl carbonate, diphenyl carbonate and dibenzyl carbonate.

23. The preparation method of the ionic liquid of claim 5, wherein the reaction temperature of step 2 is 60˜280° C.

24. The preparation method of the ionic liquid of claim 5, wherein the absolute pressure of the reaction in step 2 is 0.1˜3.0 Mpa.

25. The preparation method of the ionic liquid of claim 5, wherein the reaction time of step 2 is 0.1˜12 hours.

26. An electrolyte used in a lithium ion secondary battery, comprising the ionic liquid as described in claim 1.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0067] The present disclosure will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.

Embodiment 1

[0068] Previously, N-n-propyl pyrrole and anhydrous ammonium fluoride underwent a moisture removal treatment separately. After the moisture removal treatment, the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the N-n-propyl pyrrole is less than 5 ppm and moisture content thereof is less than 50 ppm; the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the anhydrous ammonium fluoride is less than 5 ppm and the moisture content thereof is less than 50 ppm. Next, under high purity nitrogen atmosphere, the treated N-n-propyl pyrrole (500 g, 4.42 mol) and anhydrous ammonium fluoride (4.41 mol) were added into a first reactor together, and 1000 mL mixed solvents of methanol and dimethyl carbonate were added into the first reactor. The content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the mixed solvents is less than 5 ppm and the moisture content thereof is less than 50 ppm. After addition, the mixture were reacted under 40° C. for 72 hours. After reaction, the liquid phase was transferred to a second reactor. Then, the temperature of the liquid phase was raised to 80° C. to distil out most solvents and unreacted reactants, and then the temperature was decreased to 60° C. to remove the low boiling point materials by vacuum distillation. Next, 1200 mL dimethyl carbonate was added into the second reactor under high purity nitrogen atmosphere, and reacted under 160° C. and 2.0 MPa for 8 hours, wherein the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the dimethyl carbonate is less than 5 ppm and the moisture content is less than 50 ppm. Some of the gas inside the reactor was released by the air evacuation valve to avoid excess pressure. After reaction, low boiling point materials were removed by vacuum distillation, and the reaction yielded N-methyl-N-propylpyrrolidine hydrofluoride (4.12 mol). According to the tests, the total content of Cl.sup.−, Br.sup.− and I.sup.− in the product is less than 5 ppm and moisture content is less than 50 ppm.

Embodiment 2

[0069] Previously, N-n-propyl pyrrole and ammonium sulphate underwent a moisture removal treatment separately. After the treatment, the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the N-n-propyl pyrrole is less than 5 ppm and moisture content thereof is less than 50 ppm; and the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the ammonium sulphate is less than 5 ppm and the moisture content thereof is less than 50 ppm. Next, under high purity nitrogen atmosphere, the treated N-n-propyl pyrrole (500 g, 4.42 mol) and ammonium sulphate (2.00 mol) were added into a first reactor together, and 1500 mL anhydrous methanol was added into the first reactor. The content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the anhydrous methanol is less than 5 ppm and the moisture content thereof is less than 50 ppm. After addition, the temperature was raised to 68° C. and then the mixture reacted under condensing reflux for 24 hours. After reaction, the liquid phase was transferred to a second reactor. Then, the solvents and unreacted reactants were removed by distillation or vacuum distillation. Next, under high purity nitrogen atmosphere, 1000 mL dimethyl carbonate was added into the second reactor and reacted under 150° C. and 1.4 MPa for 6 hours, wherein the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the dimethyl carbonate is less than 5 ppm and the moisture content thereof is less than 50 ppm. Some of the gas inside the reactor was released by the air evaluation valve to avoid excess pressure. After reaction, low boiling point materials were removed by vacuum distillation. Further, the crude product was dried under nitrogen atmosphere to yield N-methyl-N-propylpyrrolidine sulphate (1.85 mol). According to the tests, the total content of Cl.sup.−, Br.sup.− and I.sup.− in the final product is less than 4 ppm and the moisture content is less than 20 ppm.

Embodiment 3

[0070] Previously, tributylamine and trimethylammonium tetrafluoroborate underwent a moisture removal treatment separately. After the treatment, the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the tributylamine is less than 5 ppm and moisture content thereof is less than 50 ppm; the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the trimethylammonium tetrafluoroborate is less than 5 ppm and the moisture content thereof is less than 50 ppm. Next, under high purity nitrogen atmosphere, the treated tributylamine (500 g, 2.70 mol) and trimethylammonium tetrafluoroborate (2.69 mol) were added into a first reactor together, 800 mL anhydrous ethanol was added into the first reactor. The content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the anhydrous ethanol is less than 5 ppm and the moisture content thereof is less than 50 ppm. After addition, the mixture were reacted under 80° C. for 12 hours. After reaction, the liquid phase was transferred to a second reactor, solvents and unreacted reactants were removed by distillation or vacuum distillation. Next, under high purity nitrogen atmosphere, 1000 mL dimethyl carbonate was added into the second reactor and reacted under 160° C. and 1.5 MPa for 6 hours, wherein the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the dimethyl carbonate is less than 5 ppm and the moisture content is less than 50 ppm. Some of the gas inside the reactor was released by the air evacuation valve to avoid excess pressure. After the reaction, low boiling point materials were removed by vacuum distillation. Further, the crude product is dried under nitrogen atmosphere to yield methyltributylammonium tetrafluoroborate (2.55 mol). According to the tests, the total content of Cl.sup.−, Br.sup.− and I.sup.− in the final product is less than 3 ppm and moisture content is less than 30 ppm.

Embodiment 4

[0071] Previously, N-n-butyl piperidine and bis(trifluoromethylsulfonyl)imide ammonium salt underwent a moisture removal treatment separately. After the moisture removal treatment, the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the N-n-butylpiperidine is less than 5 ppm and moisture content thereof is less than 50 ppm; and the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the bis(trifluoromethylsulfonyl)imide ammonium salt is less than 5 ppm and moisture content thereof is less than 50 ppm. Next, under high purity nitrogen atmosphere, the treated N-n-butylpiperidine (650 g, 4.61 mol) and bis(trifluoromethylsulfonyl)imide ammonia salt (4.60 mol) were added into a first reactor together, and 1500 mL anhydrous methanol was added into the first reactor. The content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and moisture content is less than 50 ppm. After addition, the temperature was raised to 60° C., and the mixture was reacted under 60° C. for 48 hours. After the reaction, the liquid phase was transferred to a second reactor, and then the solvents and unreacted reactants were removed by distillation or vacuum distillation. Next, 1000 mL dimethyl carbonate was added into the second reactor under high purity nitrogen atmosphere, and reacted under 160° C. and 1.6 MPa for 6 hours, wherein the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the dimethyl carbonate is less than 5 ppm and the moisture content thereof is less than 50 ppm. Some of the gas inside the reactor was released by the air evaluation valve to avoid excess pressure. After reaction, low boiling point materials were removed by vacuum distillation. Further, the crude product was dried under nitrogen atmosphere to yield N-methyl-N-butylpiperidine bis(trifluoromethylsulfonyl)imide (4.22 mol). According to the tests, the total content of Cl.sup.−, Br.sup.− and I.sup.− in the product is less than 3 ppm and the moisture content thereof is less than 40 ppm.

Embodiment 5

[0072] Previously, triethylphosphine and bis(trifluoromethylsulfonyl)imide phosphonium salt underwent a moisture removal treatment separately. After the treatment, the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the triethylphosphine is less than 5 ppm and moisture content thereof is less than 50 ppm; and the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the bis(trifluoromethylsulfonyl)imide phosphonium salt is less than 5 ppm and moisture content thereof is less than 50 ppm. Next, under high purity nitrogen atmosphere, the treated triethylphosphine (300 g, 2.54 mol), treated bis(trifluoromethylsulfonyl)imide phosphonium salt (2.53 mol), and 1000 mL anhydrous methanol were added into a first reactor together. The content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the anhydrous methanol is less than 5 ppm and moisture content thereof is less than 50 ppm. Then the temperature was raised to 60° C. and the reaction continued for 3 hours at 60° C. After the reaction, liquid phase was transferred to a second reactor, and the solvents and unreacted reactants were removed by distillation or vacuum distillation. Next, 900 mL diethylcarbonate was added into the second reactor under high purity nitrogen atmosphere, and reacted under 180° C. and 1.8 MPa for 12 hours, wherein the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and moisture content thereof is less than 50 ppm. Some of the gas inside the reactor was released by the air evacuation valve to avoid excess pressure. After reaction, low boiling point materials were removed by vacuum distillation to yield a crude product. Further, the crude product was dried under nitrogen atmosphere to yield tetraethyl quaternary phosphonium bis(trifluoromethylsulfonyl)imide (1.20 mol). According to the tests, the total content of Cl.sup.−, Br.sup.− and I.sup.− in the product is less than 5 ppm and the moisture content thereof is less than 50 ppm.

Embodiment 6

[0073] Previously, N-n-propyl pyrrole and bis(fluorosulfonyl)imide phosphonium salt underwent a moisture removal treatment separately. After the treatment, the content of the halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the N-n-propyl pyrrole is less than 5 ppm and moisture content thereof is less than 50 ppm; and the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the bis(fluorosulfonyl)imide phosphonium salt is less than 5 ppm and the moisture content thereof is less than 50 ppm. Next, under high purity nitrogen atmosphere, the treated N-n-propyl pyrrole (500 g, 4.42 mol) and the treated bis(fluorosulfonyl)imide phosphonium salt (4.41 mol), together with 1200 mL treated dimethyl carbonate were added into a first reactor. The content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in the dimethyl carbonate is less than 5 ppm and the moisture content thereof is less than 50 ppm. Mixing them uniformly and raising temperature to 80° C., the reaction took place at 80° C. for 24 hours. After the reaction, liquid phase was transferred to a second reactor, solvents and unreacted reactants were removed by distillation or vacuum distillation. Next, 900 mL dimethyl carbonate was further added into the second reactor, and then reacted at 160° C. and 1.8 MPa for 5 hours, wherein the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and moisture content thereof is less than 50 ppm. Some of the gas inside the reactor was released by the air evacuation valve to avoid excess pressure. After reaction, low boiling point materials were removed by vacuum distillation to yield a crude product. The crude product was further dried under nitrogen atmosphere to yield N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (4.00 mol). According to the tests, the total content of Cl.sup.−, Br.sup.− and I.sup.− in the product is less than 4 ppm and moisture content is less than 50 ppm.

Embodiment 7

[0074] Under high purity nitrogen atmosphere, N,N-dimethyl octylamine (400 g, 2.55 mol) and bis(trifluoromethylsulfonyl)imide (2.55 mol) were added into a first reactor, together with 1000 mL anhydrous methanol. In N,N-dimethyl octylamine, the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and moisture content is less than 50 ppm; In bis(trifluoromethylsulfonyl)imide, the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and moisture content is less than 50 ppm; In anhydrous methanol, the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and moisture content is less than 50 ppm. Next, mixed them to be uniform, and the temperature was raised to 60° C., the reaction continued at 60° C. for 36 hours. After the reaction, liquid phase was transferred to a second reactor, solvents and unreacted reactants were removed by distillation or vacuum distillation. Then, 1200 mL dimethyl carbonate was further added into the second reactor under high purity nitrogen atmosphere, and then reacted at 160° C. and 1.7 MPa for 8 hours, wherein the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and moisture content is less than 50 ppm. Some of the gas inside the reactor was released by the air evacuation valve to avoid excess pressure. After reaction, low boiling point materials were removed by vacuum distillation to yield a crude product. The crude product was further dried under nitrogen atmosphere to yield N,N,N-trimethyl octyl ammonium bis(trifluoromethylsulfonyl)imide (2.24 mol). According to the tests, the total content of Cl.sup.−, Br.sup.−, I.sup.− in the final product is less than 5 ppm and the moisture content is less than 50 ppm.

Embodiment 8

[0075] N-n-butyl piperidine (480 g, 3.40 mol) and phosphonium fluoride (3.38 mol) were added into a first reactor and mixed to be uniform under high purity nitrogen atmosphere, wherein the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in N-n-butyl piperidine is less than 5 ppm and moisture content therein is less than 50 ppm; the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in phosphonium fluoride is less than 5 ppm and moisture content therein is less than 50 ppm. Raising the temperature to 95° C. and reacting for 0.1 hours, and then decreasing the temperature to 80° C. and removing gas by decompression. Next, 900 mL dimethyl carbonate was further added into the reactor under high purity nitrogen atmosphere, wherein the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and the moisture content is less than 50 ppm. Reacting at 160° C. and 1.8 MPa for 5 hours. Some of the gas inside the reactor was released by the air evacuation valve to avoid excess pressure. After reaction, low boiling point materials were removed by vacuum distillation to yield a crude product. The crude product was further dried under nitrogen atmosphere to yield N-methyl-N-butyl piperidinium hydrofluoride (2.68 mol). According to the tests, the total content of Cl.sup.−, Br.sup.−, I.sup.− in the product is less than 5 ppm and moisture content is less than 40 ppm.

Embodiment 9

[0076] N-ethyl pyrrolidine (450 g, 4.55 mol) and phosphonium fluoride (4.52 mol) were added into a first reactor under high purity nitrogen atmosphere, and mixed to be uniform at −20° C. and reacted for 5 hours, wherein the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in N-ethyl pyrrolidine is less than 5 ppm and moisture content therein is less than 50 ppm; and the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) in phosphonium fluoride is less than 5 ppm and moisture content therein is less than 50 ppm. Removing gas by decompression, 1000 mL dimethyl carbonate was further added into the reactor under high purity nitrogen atmosphere, wherein the content of halogen anions (Cl.sup.−, Br.sup.−, I.sup.−) is less than 5 ppm and moisture content is less than 50 ppm. After addition, reacting at 90° C. and 2.4 MPa for 36 hours. Some of the gas inside the reactor was released by the air evacuation valve to avoid excess pressure. After reaction, low boiling point materials were removed by vacuum distillation to yield a crude product. The crude product was further dried under nitrogen atmosphere to yield N-methyl-N-ethyl pyrrolidinium hydrofluoride (3.42 mol). According to the tests, the total content of Cl.sup.−, Br.sup.−, I.sup.− in the product is less than 3 ppm and the moisture content is less than 40 ppm.

[0077] It will be understood that the above particular embodiments are shown and described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiments thereof without departing from the scope of the disclosure. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.