Preparation method of ionic liquid

Abstract

A method of preparing an ionic liquid includes the following steps. The halogen-containing compound is reacted with the first compound to form a second compound. The halogen-containing compound includes a halocarbon, a sulfonyl halide, or a combination thereof. The first compound comprises an amine compound with a tertiary amino group, a phosphine compound or a combination of the amine compound and the phosphine compound. The second compound includes a first quaternary ammonium salt, a first quaternary phosphonium salt, or a combination thereof. The second compound is reacted with a lithium salt in a microwave device to form a third compound. The third compound includes a second quaternary ammonium salt, a second quaternary phosphonium salt, or a combination thereof. The anions of the second compound and the third compound are different. The microwave power of the microwave device ranges from 700 watts to 1400 watts. The preparation of the ionic liquid in the microwave device can reduce the time for preparing the ionic liquid. According to the preparation method disclosed by the invention, the ionic liquid with low water content, high ionic conductivity, low viscosity and wide electrochemical stability window can be prepared.

Description

Technical Field

[0001] This invention relates to a method for preparing ionic liquids. Background Technology

[0002] Electrolytes are indispensable in batteries. Traditionally, liquid electrolytes have been commonly used in batteries. However, liquid electrolytes such as ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate have low ignition and volatilization points, which can easily raise safety concerns when the battery experiences thermal runaway.

[0003] Due to the aforementioned problems with liquid electrolytes, other types of electrolytes or electrolyte additives have been gradually developed, such as solid electrolytes, special additives, gelled electrolytes, and flame retardants. Solid electrolytes have complex interface and ion conductivity issues, thus limiting their widespread use. Special additives such as fluoroethylene carbonate, difluoroethylene carbonate, and 2,2,2-trifluoroethylmethyl carbonate, while possessing high ignition and boiling points, are expensive and difficult to produce, thus also limiting their application. Gelated electrolytes, due to the introduction of gelling substances, do not easily generate a large number of reactive interfaces, and the ignition and boiling problems still exist. Flame retardants, when introduced into the battery, cause problems such as increased internal resistance and poor reaction uniformity, thus hindering their widespread use. Therefore, there is an urgent need to develop other electrolytes that can improve flame resistance, battery stability, and ion conductivity. Summary of the Invention

[0004] This invention provides a method for preparing ionic liquids, comprising the following steps: reacting a halogen-containing compound with a first compound to form a second compound, wherein the halogen-containing compound includes a haloalkane, a sulfonyl halide, or a combination thereof, the first compound includes an amine compound having a tertiary amino group, a phosphine compound, or a combination thereof, and the second compound includes a first quaternary ammonium salt, a first quaternary phosphonium salt, or a combination thereof. Reacting the second compound with a lithium salt in a microwave device to form a third compound, wherein the third compound includes a second quaternary ammonium salt, a second quaternary phosphonium salt, or a combination thereof, the second and third compounds having different anions, and the microwave power of the microwave device being 700 watts to 1400 watts.

[0005] In some embodiments, amine compounds having tertiary amino groups include imidazole compounds, pyrrolidine compounds, pyridine compounds, pyrrole compounds, pyrazole compounds, imidazole compounds, pyrazoline compounds, or combinations thereof having structures as shown in formula (1-1). R1 and R5 are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl.

[0006] In some embodiments, the halohydrocarbon includes a structure as shown in formula (2-1), and the sulfonyl halide includes a structure as shown in formula (2-2).

[0007] R1'-X1 equation (2-1),

[0008] R2'-SO2X2 (2-2),

[0009] R1' and R2' are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, C4 to C6 heterocycloalkyl or C6 to C10 aryl, and X1 and X2 are independently fluorine, chlorine, bromine or iodine.

[0010] In some embodiments, the reaction pressure at which the second compound reacts with the lithium salt in a microwave device is greater than 1 atm and less than or equal to 2 atm.

[0011] In some embodiments, the method for preparing the ionic liquid further includes a heating operation after reacting the second compound with the lithium salt in a microwave device, wherein the heating operation is performed at a temperature of 60°C to 180°C.

[0012] In some implementations, the heating time is less than or equal to 6 hours.

[0013] This invention provides a method for preparing ionic liquids, comprising the following steps: reacting a halogen-containing compound with a first compound in a first microwave device to form a second compound, wherein the halogen-containing compound includes a haloalkane, a sulfonyl halide, or a combination thereof; the first compound includes an amine compound having a tertiary amino group, a phosphine compound, or a combination thereof; and the second compound includes a first quaternary ammonium salt, a first quaternary phosphonium salt, or a combination thereof, wherein the amine compound having a tertiary amino group includes structures as shown in formula (1-1), imidazole compounds, pyrrolidine compounds, pyridine compounds, pyrrole compounds, pyrazole compounds, imidazole compounds having structures as shown in formula (1-2), imidazoleline compounds, pyrazoline compounds, or combinations thereof. R1 to R5 are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl. The second compound is reacted with a lithium salt in a second microwave device to form a third compound, wherein the third compound includes a second quaternary ammonium salt, a second quaternary phosphonium salt, or a combination thereof, and the second and third compounds have different anions.

[0014] In some embodiments, the microwave power for reacting the halogenated compound with the first compound in the first microwave device and the microwave power for reacting the second compound with the lithium salt in the second microwave device are each between 700 watts and 1400 watts.

[0015] In some embodiments, the reaction pressure for reacting the halogenated compound with the first compound in the first microwave device and the reaction pressure for reacting the second compound with the lithium salt in the second microwave device are each greater than 1 atmosphere and less than or equal to 2 atmospheres.

[0016] In some embodiments, the reaction temperature for reacting the halogenated compound with the first compound in the first microwave device and the reaction temperature for reacting the second compound with the lithium salt in the second microwave device are each from 60°C to 250°C.

[0017] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are intended to provide further illustration of the claimed invention. Attached Figure Description

[0018] The present invention can be more fully understood by reading the following detailed description of the embodiments and referring to the accompanying drawings.

[0019] Figure 1 and Figure 2 These are flowcharts of methods for preparing ionic liquids according to various embodiments of the present invention.

[0020] Figure 3 The Fourier transform infrared spectra of ionic liquids according to various embodiments of the present invention are shown.

[0021] Figure 4 Raman spectra of ionic liquids according to various embodiments of the present invention are shown.

[0022] Figure 5 and Figure 6 Linear sweep voltammetry curves of ionic liquids according to various embodiments of the present invention are shown respectively. Detailed Implementation

[0023] To make the description of the present invention more detailed and complete, illustrative descriptions of embodiments and specific implementations of the present invention are provided below; however, these are not the only forms of implementation or application of the present invention. The embodiments disclosed below can be combined or substituted with each other where advantageous, and other embodiments can be added to some embodiments without further description or explanation.

[0024] In this document, the range expressed as "from one value to another" is a concise way of representing a range to avoid listing all the values ​​in that range in the specification. Therefore, the description of a particular range of values ​​encompasses any value within that range as well as the smaller range of values ​​defined by that value, just as if the arbitrary value and the smaller range of values ​​were explicitly stated in the specification.

[0025] Although the methods disclosed herein are illustrated using a series of operations or steps, the order in which these operations or steps are shown should not be construed as a limitation of the invention. For example, some operations or steps may be performed in a different order and / or simultaneously with other steps. Furthermore, not all illustrated operations, steps, and / or features are required to achieve embodiments of the invention. Additionally, each operation or step described herein may comprise several sub-steps or actions.

[0026] This invention provides a method for preparing ionic liquids, which involves preparing the ionic liquid in a microwave device, thereby reducing the preparation time. Furthermore, the preparation method of this invention can produce ionic liquids with low water content, high ionic conductivity, low viscosity, and a wide electrochemical stability window. This makes the ionic liquid prepared by this invention more suitable as an electrolyte in batteries than liquid electrolytes, solid electrolytes, special additives, gelled electrolytes, or flame retardants.

[0027] Figure 1 This is a flowchart of a method 100 for preparing ionic liquids according to various embodiments of the present invention. (Refer to...) Figure 1 A method 100 for preparing an ionic liquid includes steps 110 and 120. In step 110, a halogen-containing compound is reacted with a first compound to form a second compound, wherein the halogen-containing compound includes a haloalkane, a sulfonyl halide, or a combination thereof, the first compound includes an amine compound having a tertiary amino group, a phosphine compound, or a combination thereof, and the second compound includes a first quaternary ammonium salt, a first quaternary phosphonium salt, or a combination thereof. In step 120, the second compound is reacted with a lithium salt in a microwave device to form a third compound, wherein the third compound includes a second quaternary ammonium salt, a second quaternary phosphonium salt, or a combination thereof, and the second and third compounds have different anions. The third compound is the ionic liquid. The microwave power of the microwave device is from 700 watts to 1400 watts, for example 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, or 1400 watts. When the microwave power is between 700 watts and 1400 watts, the reaction time for the formation of the third compound can be shortened.

[0028] In some embodiments, amine compounds having tertiary amino groups include compounds having the structure shown in formula (1-1), imidazole compounds, pyrrolidine compounds, pyridine compounds, pyrrole compounds, pyrazole compounds, compounds having the structure shown in formula (1-2), imidazoleline compounds, pyrazoleline compounds, or combinations thereof. Formulas (1-1) and (1-2) are shown below: R1 and R5 are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl. The number of carbon atoms in the C1 to C22 straight-chain alkyl and C1 to C22 branched alkyl can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or 22, and the number of carbon atoms in the C4 to C6 cycloalkyl and C4 to C6 heterocyclic alkyl can be 4, 5, or 6.

[0029] In some embodiments, the imidazole compounds, pyrrolidine compounds, pyridine compounds, pyrrole compounds, pyrazole compounds, imidazoleline compounds, and pyrazoleline compounds have structures as shown in formulas (1-3), (1-4), (1-5), (1-6), (1-7), (1-8), and (1-9), respectively. The structures are shown below:

[0030] R 10 With R 24 It can be independently a C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl. The number of carbon atoms in the C1 to C22 straight-chain alkyl and C1 to C22 branched alkyl can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or 22, and the number of carbon atoms in the C4 to C6 cycloalkyl and C4 to C6 heterocyclic alkyl can be 4, 5, or 6. R6 to R9, R 11 To R 23 With R 25 To R 35 It can be hydrogen, C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl. The number of carbon atoms in the C1 to C22 straight-chain alkyl and C1 to C22 branched alkyl can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or 22, and the number of carbon atoms in the C4 to C6 cycloalkyl and C4 to C6 heterocyclic alkyl can be 4, 5, or 6.

[0031] In some embodiments, the phosphine compounds have structures as shown in formulas (1-10): Where R 36 To R 38 It can be independently a C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl. The number of carbon atoms in the C1 to C22 straight-chain alkyl and C1 to C22 branched alkyl can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or 22, and the number of carbon atoms in the C4 to C6 cycloalkyl and C4 to C6 heterocyclic alkyl can be 4, 5, or 6.

[0032] In some embodiments, the halohydrocarbon includes a structure as shown in formula (2-1), and the sulfonyl halide includes a structure as shown in formula (2-2):

[0033] R1'-X1 equation (2-1),

[0034] R2'-SO2X2 (2-2),

[0035] R1' and R2' are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, C4 to C6 heterocycloalkyl, or C6 to C10 aryl, and X1 and X2 are independently fluorine, chlorine, bromine, or iodine. The number of carbon atoms in the C1 to C22 straight-chain alkyl and C1 to C22 branched alkyl can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or 22; the number of carbon atoms in the C4 to C6 cycloalkyl and C4 to C6 heterocycloalkyl can be 4, 5, or 6; and the number of carbon atoms in the C6 to C10 aryl can be 6, 7, 8, 9, or 10.

[0036] In some embodiments, the molar ratio of the halogenated compound to the first compound is 1:1 to 2:1, for example, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, or 2:1. When the molar ratio of the halogenated compound to the first compound is 1:1 to 2:1, the first compound can be completely reacted to form the second compound. In some embodiments, the reaction temperature for reacting the halogenated compound with the first compound is 25°C to 100°C, for example, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100°C. In some embodiments, the reaction time for reacting the halogenated compound with the first compound is 30 minutes to 60 minutes, for example, 30, 40, 50, or 60 minutes.

[0037] Please refer to this again. Figure 1 In some embodiments, before performing step 110, the first compound is placed in a sealed reaction vessel and stirred, followed by the addition of the halogen-containing compound to the sealed reaction vessel. In some embodiments, the temperature at which the first compound is stirred in the sealed reaction vessel is from 10°C to 100°C, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100°C. In some embodiments, the sealed reaction vessel is a reaction vessel. In some embodiments, the sealed reaction vessel is filled with an inert gas, such as nitrogen, argon, helium, or neon. Filling the sealed reaction vessel with an inert gas can prevent the formation of side reactions.

[0038] Please refer to this again. Figure 1More specifically, in step 110, the halogenated compound undergoes an alkylation reaction with the first compound to form the second compound. The hydrocarbon group of the halogenated compound (such as R1' in formula (2-1) and R2' in formula (2-2)) bonds to the tertiary amine or tertiary phosphine of the first compound to form the second compound.

[0039] In some embodiments, the second compound having the structure of 1-ethyl-3-methylimidazolium bromide (EMIM Br) is formed by reacting bromomethane with an imidazolium compound (having the structure shown in formulas (1-3), where R8 is ethyl and R6, R7, and R9 are hydrogen). In some embodiments, the second compound having the structure of N-methyl-N-butylpyrrolidinium bromide (Py14 Br) is formed by reacting bromobutane with a pyrrolidinium compound (having the structure shown in formulas (1-4), where R8 is ethyl and R9 is hydrogen). 10 For methyl, R 11 To R 14 The reaction is to form a hydrogen atom. In some embodiments, the second compound having the structure shown in formulas (2-3) is formed by reacting bromobutane with a pyridine compound (having the structure shown in formulas (1-5), R... 17 For methyl, R 15 R 16 R 18 R 19 The reaction is carried out by hydrogen. In some embodiments, the second compound having the structure shown in formula (2-4) is formed by reacting iodoethane with a compound having the structure shown in formula (1-2) (R3, R4, R5 are butyl). Formulas (2-3) and (2-4) are shown below:

[0040]

[0041] In some embodiments, the lithium salt includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorosulfimide (LiFSI), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium triflouromethanesulfonate (LiOTf), lithium acetate (CH3COOLi), compounds having the formula shown in formula (3-1), compounds having the formula shown in formula (3-2), compounds having the formula shown in formula (3-3), or combinations thereof. Formulas (3-1), (3-2), and (3-3) are shown below: Among them, R1”, R2” and R3” are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl or C4 to C6 heterocyclic alkyl. The number of carbon atoms in the C1 to C22 straight-chain alkyl and C1 to C22 branched alkyl can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20 or 22, and the number of carbon atoms in the C4 to C6 cycloalkyl and C4 to C6 heterocyclic alkyl can be 4, 5 or 6.

[0042] In some embodiments, the anion of the second compound includes a halide ion or a structure as shown in formula (4-1), wherein the halide ion includes a fluoride ion, a chloride ion, a bromide ion, or an iodide ion, and the anion of the third compound includes a bis(trifluoromethanesulfonyl)imide anion (TFSI). - ), bis(fluorosulfonyl)imide anion (FSI) - ), tetrafluoroborate anion (BF4) - ), hexafluorophosphate anion (PF6) - ), trifluoromethanesulfonic acid anion (OTf) - Acetate ions (CH3COO) - The structures shown in equation (4-2), equation (4-3), equation (4-4), or combinations thereof. Equations (4-1), (4-2), (4-3), and (4-4) are shown below: SO2X3 - Equation (4-1) Where X3 is fluorine, chlorine, bromine, or iodine, and R1”, R2”, and R3” are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl. The number of carbon atoms in the C1 to C22 straight-chain alkyl and C1 to C22 branched alkyl can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or 22, and the number of carbon atoms in the C4 to C6 cycloalkyl and C4 to C6 heterocyclic alkyl can be 4, 5, or 6.

[0043] In some embodiments, the molar ratio of the second compound to the lithium salt is 1:1 to 1:2, for example 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, or 1:2. When the molar ratio of the second compound to the lithium salt is 1:1 to 1:2, the second compound can be completely reacted to form the third compound.

[0044] In some embodiments, the reaction pressure at which the second compound reacts with the lithium salt in a microwave device is greater than 1 atm and less than or equal to 2 atm, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 atm. When the reaction pressure at which the second compound reacts with the lithium salt in a microwave device is greater than 1 atm and less than or equal to 2 atm, the reaction time for forming the third compound can be shortened. In some embodiments, the microwave device is a microwave-enabled reactor. In some embodiments, the reaction temperature at which the second compound reacts with the lithium salt in a microwave device is between 60°C and 250°C, for example, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, or 250°C. The reactivity is optimal when the reaction temperature for reacting the second compound with the lithium salt in a microwave device is between 60°C and 250°C. In some embodiments, the reaction time for reacting the second compound with the lithium salt in the microwave device is between 5 and 30 minutes, for example, 5, 10, 15, 20, 25, or 30 minutes. When the reaction time for reacting the second compound with the lithium salt in the microwave device is between 5 and 30 minutes, the pressure in the microwave device will not be excessive, and the reactivity is optimal.

[0045] Please refer to this again. Figure 1In some embodiments, before performing step 120, the second compound is dissolved in the first solvent, and then the second compound dissolved in the first solvent is placed in a reaction vessel. Next, the lithium salt is dissolved in the second solvent, and the lithium salt dissolved in the solvent is added to the reaction vessel and mixed with the second compound. In some embodiments, the first and second solvents are environmentally friendly polar solvents, such as water, methanol, ethanol, acetone, or combinations thereof. When the first and second solvents are each water, methanol, ethanol, acetone, or combinations thereof, the third compound formed after the reaction of the second compound with the lithium salt is easily separated from the byproducts. In some embodiments, the reaction vessel is a microwave device. In some embodiments, the mixing temperature for mixing the lithium salt dissolved in the solvent with the second compound is from 25°C to 100°C, for example, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100°C. The mixing time for mixing the solvent-soluble lithium salt with the second compound is 15 to 30 minutes, for example, 15, 20, 25, or 30 minutes. When the mixing time falls within this range, the solvent-soluble lithium salt and the second compound can be mixed quickly and uniformly.

[0046] Please refer to this again. Figure 1 In some embodiments, the method 100 for preparing the ionic liquid further includes a heating operation after reacting the second compound with the lithium salt in a microwave device, wherein the heating operation is performed at a temperature of 60°C to 180°C, for example, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, or 180°C. In some embodiments, the heating operation is performed for a duration of 6 hours or less, for example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 hours. When the heating operation is performed at a temperature of 60°C to 180°C, the reactivity of the second compound with the lithium salt is good and the generation of byproducts is less likely.

[0047] Please refer to this again. Figure 1 In some embodiments, after performing step 120, the third compound is separated from the byproduct and purified by a third solvent. In some embodiments, after performing step 120, the third compound is insoluble in the aforementioned first and second solvents to form a non-aqueous phase layer, and the byproduct is soluble in the first and second solvents to form an aqueous phase layer. In some embodiments, separating the third compound from the byproduct involves removing the aqueous phase layer containing the byproduct. In some embodiments, the third solvent includes water, methanol, ethanol, acetone, or combinations thereof.

[0048] Please continue to refer to Figure 1In some embodiments, after performing step 120, the third compound is mixed with a fourth solvent and then concentrated under reduced pressure to form a high-purity third compound. In some embodiments, the fourth solvent includes highly volatile and environmentally friendly solvents, such as methanol, ethanol, acetone, or combinations thereof. In some embodiments, the weight ratio of the third compound to the fourth solvent is from 3:1 to 19:1, for example, 3:1, 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, 17:1, or 19:1. In some embodiments, the temperature for reduced pressure concentration is from 30°C to 100°C, for example, 30, 40, 50, 60, 70, 80, 90, or 100°C. In some embodiments, the time for reduced pressure concentration is from 10 minutes to 60 minutes, for example, 10, 20, 30, 40, 50, or 60 minutes. Mixing the third compound with the fourth solvent helps to reduce the time for reduced pressure concentration. When the third compound is mixed with the fourth solvent and then concentrated under reduced pressure, the high-purity third compound has a low water content.

[0049] Please refer to this again. Figure 1 More specifically, in step 120, the second compound undergoes anion substitution reaction with a lithium salt to form a third compound, wherein the anion of the second compound is replaced by the anion of the lithium salt to form the third compound.

[0050] In some embodiments, a third compound having a 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIMTFSI) structure is formed by reacting a second compound having an EMIM Br structure with LiTFSI (lithium salt). In some embodiments, a third compound having a 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide (EMIM FSI) structure is formed by reacting a second compound having an EMIM Br structure with LiTFSI (lithium salt). In some embodiments, a third compound having an N-methyl-N-butylpyrrolidine bis(trifluoromethanesulfonyl)imide (Py14 TFSI) structure is formed by reacting a second compound having a Py14 Br structure with LiTFSI.

[0051] Figure 2 This is a flowchart of a method 200 for preparing ionic liquids according to various embodiments of the present invention. (Refer to...) Figure 2A method 200 for preparing an ionic liquid includes steps 210 and 220. In step 210, a halogen-containing compound is reacted with a first compound in a first microwave device to form a second compound, wherein the halogen-containing compound includes a haloalkane, a sulfonyl halide, or a combination thereof, the first compound includes an amine compound having a tertiary amino group, a phosphine compound, or a combination thereof, and the second compound includes a first quaternary ammonium salt, a first quaternary phosphonium salt, or a combination thereof. The amine compound having a tertiary amino group includes compounds of formula (1-1), imidazole compounds, pyrrolidine compounds, pyridine compounds, pyrrole compounds, pyrazole compounds, compounds having a structure shown in formula (1-2), imidazoleline compounds, pyrazoleline compounds, or combinations thereof. Formulas (1-1) and (1-2) are shown below: R1 to R5 are independently C1 to C22 straight-chain alkyl groups, C1 to C22 branched alkyl groups, C4 to C6 cycloalkyl groups, or C4 to C6 heterocyclic alkyl groups. The number of carbon atoms in the C1 to C22 straight-chain alkyl groups and C1 to C22 branched alkyl groups can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or 22, and the number of carbon atoms in the C4 to C6 cycloalkyl groups and C4 to C6 heterocyclic alkyl groups can be 4, 5, or 6. In step 220, the second compound is reacted with a lithium salt in a second microwave device to form a third compound, wherein the third compound includes a second quaternary ammonium salt, a second quaternary phosphonium salt, or a combination thereof, and the second and third compounds have different anions. The third compound is an ionic liquid. When the halogen-containing compound is reacted with the first compound in the first microwave device, the reaction time for forming the second compound can be shortened. When the second compound is reacted with a lithium salt in a microwave device, the reaction time for forming the third compound can be shortened. In some embodiments, the first microwave device and the second microwave device are the same device. In other embodiments, the first microwave device and the second microwave device are different devices.

[0052] In some embodiments, imidazole compounds, pyrrolidine compounds, pyridine compounds, pyrrole compounds, pyrazole compounds, imidazoline compounds, and pyrazoline compounds may refer to the structures shown above as formulas (1-3), (1-4), (1-5), (1-6), (1-7), (1-8), and (1-9), respectively. In some embodiments, phosphine compounds may refer to the structure shown above as formula (1-10). In some embodiments, haloalkanes and sulfonyl halides may refer to the structures shown above as formulas (2-1) and (2-2), respectively. In some embodiments, the lithium salt used in step 220 may refer to the lithium salt used in step 120.

[0053] In some embodiments, the microwave power for reacting the halogen-containing compound with the first compound in the first microwave device and the microwave power for reacting the second compound with the lithium salt in the second microwave device are each between 700 watts and 1400 watts, for example, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, or 1400 watts. When the microwave power for reacting the halogen-containing compound with the first compound in the first microwave device is 700 watts to 1400 watts, the reaction time for forming the second compound can be shortened. When the microwave power for reacting the second compound with the lithium salt in the second microwave device is 700 watts to 1400 watts, the reaction time for forming the third compound can be shortened.

[0054] In some embodiments, the reaction pressure for reacting the halogen-containing compound with the first compound in the first microwave device and the reaction pressure for reacting the second compound with the lithium salt in the second microwave device are each greater than 1 atm and less than or equal to 2 atm, for example, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 atm. When the reaction pressure for reacting the halogen-containing compound with the first compound in the first microwave device is greater than 1 atm and less than or equal to 2 atm, the reaction time for forming the second compound can be shortened. When the reaction pressure for reacting the second compound with the lithium salt in the second microwave device is greater than 1 atm and less than or equal to 2 atm, the reaction time for forming the third compound can be shortened. In some embodiments, the first and second microwave devices are microwave-enabled reaction vessels.

[0055] In some embodiments, the reaction temperature for reacting the halogen-containing compound with the first compound in the first microwave device and the reaction temperature for reacting the second compound with the lithium salt in the second microwave device are each from 60°C to 250°C, for example, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, or 250°C. Reactivity is better when the reaction temperature for reacting the halogen-containing compound with the first compound in the first microwave device and the reaction temperature for reacting the second compound with the lithium salt in the second microwave device are each from 60°C to 250°C. In some embodiments, the reaction time for reacting the halogen-containing compound with the first compound in the first microwave device and the reaction time for reacting the second compound with the lithium salt in the second microwave device are independently from 5 minutes to 30 minutes, for example, 5, 10, 15, 20, 25, or 30 minutes. When the reaction time of the halogen-containing compound with the first compound in the first microwave device is 5 to 30 minutes, the pressure in the first microwave device will not be excessive and the reactivity will be good. When the reaction time of the second compound with the lithium salt in the second microwave device is 5 to 30 minutes, the pressure in the second microwave device will not be excessive and the reactivity will be good.

[0056] In some embodiments, the anion of the second compound includes a halide ion or a structure as shown in formula (4-1), wherein the halide ion includes fluoride, chloride, bromide, or iodide ions, and the anion of the third compound includes a bis(trifluoromethanesulfonyl)imide anion (TFSI). - ), bis(fluorosulfonyl)imide anion (FSI) - ), tetrafluoroborate anion (BF4) - ), hexafluorophosphate anion (PF6) - ), trifluoromethanesulfonic acid anion (OTf) - Acetate ions (CH3COO) - The structures shown in equation (4-2), equation (4-3), equation (4-4), or combinations thereof. Equations (4-1), (4-2), (4-3), and (4-4) are shown below: SO2X3 - Equation (4-1) Where X3 is fluorine, chlorine, bromine, or iodine, and R1”, R2”, and R3” are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl. The number of carbon atoms in the C1 to C22 straight-chain alkyl and C1 to C22 branched alkyl can be 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, or 22, and the number of carbon atoms in the C4 to C6 cycloalkyl and C4 to C6 heterocyclic alkyl can be 4, 5, or 6.

[0057] In some embodiments, the molar ratio of the halogen-containing compound to the first compound is 1:1 to 2:1, for example, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, or 2:1, and the molar ratio of the second compound to the lithium salt is 1:1 to 1:2, for example, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, or 1:2. When the molar ratio of the halogen-containing compound to the first compound is 1:1 to 2:1, the first compound can react completely to form the second compound. When the molar ratio of the second compound to the lithium salt is 1:1 to 1:2, the second compound can react completely to form the third compound.

[0058] Please refer to this again. Figure 2 In some embodiments, prior to performing step 210, the halogen-containing compound and the first compound are placed in a sealed reaction vessel and stirred. In some embodiments, the temperature at which the first compound is stirred in the sealed reaction vessel is from 10°C to 100°C, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100°C. In some embodiments, the sealed reaction vessel is a reaction vessel.

[0059] Please refer to this again. Figure 2 In some embodiments, after performing step 220, a heating operation is performed, wherein the heating temperature is between 60°C and 180°C, for example, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, or 180°C. In some embodiments, the heating temperature is less than or equal to 6 hours, for example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 hours. When the heating temperature is between 60°C and 180°C, the second compound exhibits good reactivity with the lithium salt and is less likely to produce byproducts. In some embodiments, the advantages of other embodiments before and after performing step 220 can be referred to, respectively, the advantages of embodiments before and after performing step 120.

[0060] Please refer to this again. Figure 2More specifically, in step 210, the halogen-containing compound is alkylated with the first compound to form the second compound. The hydrocarbon group of the halogen-containing compound (such as R1' in formula (2-1) and R2' in formula (2-2)) is bonded to a tertiary amine or tertiary phosphine of the first compound to form the second compound. In step 220, the second compound is anion-displaced with a lithium salt to form the third compound. The anion of the second compound is replaced by the anion of the lithium salt to form the third compound. In some embodiments, the structures of the second and third compounds formed in steps 210 and 220 may refer to the structures of the second and third compounds formed in steps 110 and 120, respectively.

[0061] The features of the present invention will be described in more detail below with reference to Examples 1 to 4. Although the following embodiments are described, the materials used, their quantities and ratios, processing details, and processing procedures may be appropriately changed without departing from the scope of the present invention. Therefore, the present invention should not be interpreted as limiting by the embodiments described below.

[0062] Experimental Example 1: Preparation of Ionic Liquids

[0063] In Example 1-1, methyl bromide in a molar ratio of 1.05:1 was reacted with an imidazole compound (having the structure shown in formulas (1-3), where R6, R7, and R9 are all hydrogen atoms, and R8 is an ethyl group) at 60°C for 30 minutes to form EMIM Br. EMIM Br in a molar ratio of 1:1.1 was dissolved separately in water with a lithium salt (LiTFSI and LiFSI mixed in a weight ratio of 8.5:1.5) and stirred at 60°C for 15 minutes to form a mixture. The mixture was then reacted at 1000 W for 30 minutes, followed by heating at 150°C for 6 hours to form EMIM TFSI / FSI.

[0064] In Examples 1-2, the EMIM TFSI / FSI of Example 1-1 was mixed with methanol at a weight ratio of 95:5 and then concentrated under reduced pressure at 30°C for 30 minutes to form high-purity EMIM TFSI / FSI.

[0065] In Examples 1-3, methyl bromoethane in a molar ratio of 1.05:1 was reacted with an imidazole compound (having the structure shown in formulas (1-3), where R6, R7, and R9 are all hydrogen atoms, and R8 is an ethyl group) at 60°C for 30 minutes to form EMIM Br. EMIM Br and LiTFSI in a molar ratio of 1:1.1 were separately dissolved in water and mixed at 60°C for 15 minutes to form a mixture. The mixture was then reacted at 1000 W for 30 minutes, followed by heating at 150°C for 6 hours to form EMIM TFSI. EMIM TFSI in a weight ratio of 95:5 was mixed with methanol and concentrated under reduced pressure at 30°C for 30 minutes to form high-purity EMIM TFSI.

[0066] In Examples 1-4, bromobutane was mixed with pyrrolidine compounds (having structures as shown in formulas (1-4)) in a molar ratio of 1.05:1. 10 For methyl, R 11 To R 14 Both are hydrogen-based compounds. Py14Br is formed by reacting Py14Br and LiTFSI (molar ratio 1:1.1) separately in water and mixed at 60°C for 15 minutes. The mixture is then reacted at 1000 W for 30 minutes, followed by heating at 150°C for 6 hours to form Py14 TFSI. Py14 TFSI (weight ratio 95:5) is then mixed with methanol and concentrated under reduced pressure at 30°C for 30 minutes to form high-purity Py14 TFSI.

[0067] Experimental Example 2: Measurement of Fourier-transform infrared (FTIR) and Raman spectra of ionic liquids

[0068] In Comparative Example 2-1, commercially available ionic liquid EMIM TFSI (trade name: 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, manufacturer: IOLITEC) was mixed with commercially available ionic liquid EMIM FSI (trade name: 1-Ethyl-3-methylimidazolium / bis(fluoromethanesulfonyl)imide, manufacturer: IOLITEC) to form ionic liquid EMIM TFSI / FSI, wherein the weight ratio of commercially available ionic liquid EMIM TFSI to commercially available ionic liquid EMIM FSI was 8.5:1.5.

[0069] The EMIM TFSI / FSI of Example 1-1, the high-purity EMIM TFSI / FSI of Example 1-2, and the ionic liquid EMIM TFSI / FSI of Comparative Example 2-1 were sequentially subjected to FTIR and Raman spectroscopy measurements.

[0070] FTIR measurement method and parameter settings: 50 μL of EMIM TFSI / FSI from Example 1-1, high-purity EMIM TFSI / FSI from Example 1-2, and ionic liquid EMIM TFSI / FSI from Comparative Example 2-1 were sequentially dropped onto the attenuated total reflection (ATR) FTIR window of a diamond substrate. The integration count was 16, the resolution class was 4, and the measurement was performed in ATR mode.

[0071] Raman measurement method and parameter settings: 50 μL of EMIM TFSI / FSI from Example 1-1, high-purity EMIM TFSI / FSI from Example 1-2, and ionic liquid EMIM TFSI / FSI from Comparative Example 2-1 were sequentially dropped onto a glass substrate. The wavelength of the light was 532 nm, the intensity was 9 mW, the aperture was 50 μm, the objective lens magnification was 50, the scanning integration time was 2 seconds, and the scan was repeated 150 times.

[0072] Figure 3 The Fourier transform infrared (FTIR) spectra of ionic liquids according to various embodiments of the present invention are shown. Curve 310 is the FTIR plot of Example 1-1, curve 320 is the FTIR plot of Example 1-2, and curve 330 is the FTIR plot of Comparative Example 2-1. Figure 3 As shown, the FTIR spectra of curves 310 to 330 are essentially the same. Therefore, it can be concluded that the ionic liquid EMIM TFSI / FSI (curve 310), the high-purity ionic liquid EMIM TFSI / FSI (curve 320), and the ionic liquid EMIM TFSI / FSI (curve 330) prepared in this invention have the same structure. Figure 4 Raman spectra of ionic liquids according to various embodiments of the present invention are shown. Curve 340 is the Raman spectrum of Example 1-1, curve 350 is the Raman spectrum of Example 1-2, and curve 360 ​​is the Raman spectrum of Comparative Example 2-1. Figure 4 As shown, the Raman spectra of curves 340 to 360 are essentially identical. This indicates that the prepared ionic liquid EMIM TFSI / FSI (curve 340), the high-purity ionic liquid EMIM TFSI / FSI (curve 350), and the ionic liquid EMIM TFSI / FSI (curve 360) have the same structure. Therefore, the FTIR and Raman spectra demonstrate that the method of preparing ionic liquids according to this invention can successfully produce liquids with the same structure as mixed commercially available ionic liquids.

[0073] Experiment Example 3: Measuring the conductivity, water content, and viscosity of ionic liquids

[0074] The commercially available ionic liquid used in Experiment Example 3 was EMIM TFSI (trade name: 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, manufacturer: IOLITEC).

[0075] Example 3-1 and Comparative Example 3-1 respectively involved dropping 50 microliters of high-purity EMIM TFSI from Examples 1-3 and commercially available ionic liquid EMIM TFSI into a separator membrane, and then assembling them with two stainless steel caps to form a button cell.

[0076] The conductivity of the high-purity EMIM TFSI from Examples 1-3, the commercially available ionic liquid EMIM TFSI, the button cell from Example 3-1, and the button cell from Comparative Example 3-1 were measured sequentially. The conductivity was measured as follows: the probe of a conductivity meter was immersed in the high-purity EMIM TFSI from Examples 1-3 and the commercially available ionic liquid EMIM TFSI from Examples 1-3, respectively, and the ionic liquid was then measured. The button cell from Example 3-1 and the button cell from Comparative Example 3-1 were measured using a potentiostatic galvanometer.

[0077] Table 1. Measurement of Conductivity

[0078] Electrical conductivity (S / cm) Examples 1-3 <![CDATA[8.3x10 -3 ]]> Example 3-1 <![CDATA[1.2x10 -3 ]]> Commercially available ionic liquid EMIM TFSI <![CDATA[8x10 -3 ]]> Comparative Example 3-1 <![CDATA[1x10 -3 ]]>

[0079] Referring to Table 1, the conductivity of the EMIM TFSI from Examples 1-3 and the button cell from Example 3-1 is greater than that of the commercially available ionic liquid EMIM TFSI and the button cell from Comparative Example 3-1, respectively. Therefore, it can be seen that the high-purity EMIM TFSI prepared by this invention (Examples 1-3) and the button cell prepared from EMIM TFSI (Example 3-1) have higher ionic conductivity than the commercially available ionic liquid EMIM TFSI and the button cell prepared from the commercially available ionic liquid EMIM TFSI (Comparative Example 3-1). Thus, as shown in Table 1, the method for preparing ionic liquids according to this invention can produce ionic liquids with higher ionic conductivity than commercially available ionic liquids.

[0080] The water content of the high-purity EMIM TFSI from Examples 1-3 and the commercially available ionic liquid EMIM TFSI was measured sequentially. The water content was measured as follows: 1 ml of the high-purity EMIM TFSI from Examples 1-3 and the commercially available ionic liquid EMIM TFSI were injected separately into the titration tank of a coulometric moisture analyzer for measurement.

[0081] Table 2. Measurement of Moisture Content

[0082] Moisture content (ppm) Examples 1-3 93 Commercially available ionic liquid EMIM TFSI 167

[0083] Referring to Table 2, the water content of EMIM TFSI in Examples 1-3 is greater than that of commercially available ionic liquid EMIM TFSI. Therefore, it can be seen that the high-purity ionic liquid EMIM TFSI (Examples 1-3) prepared by this invention has a lower water content than commercially available ionic liquid EMIM TFSI. Thus, Table 2 demonstrates that the method for preparing ionic liquids according to this invention can produce liquids with a lower water content than commercially available ionic liquids.

[0084] The viscosities of the high-purity ionic liquids from Examples 1-3 and commercially available ionic liquids were measured sequentially. The viscosity was measured as follows: 1 ml of the high-purity EMIM TFSI from Examples 1-3 and the commercially available ionic liquid EMIM TFSI were respectively loaded into the injection syringe of the viscometer and then measured.

[0085] Table 3. Viscosity Measurement

[0086] Viscosity (cP, 25℃) Examples 1-3 93 Commercially available ionic liquid EMIM TFSI 167

[0087] Referring to Table 3, the viscosity of the high-purity ionic liquid EMIM TFSI in Examples 1-3 is greater than that of commercially available ionic liquid EMIM TFSI. Therefore, it can be seen that the high-purity EMIM TFSI prepared by this invention (Examples 1-3) has a lower viscosity than commercially available ionic liquid EMIM TFSI. Thus, as shown in Table 3, the method for preparing ionic liquids according to this invention can produce liquids with lower viscosity than commercially available ionic liquids.

[0088] Experiment Example 4: Linear sweep voltammetry (LSV) for measuring ionic liquids.

[0089] The high-purity EMIM TFSI from Examples 1-3 and the high-purity Py14 TFSI from Examples 1-4 were sequentially subjected to LSV plot measurements.

[0090] LSV measurement method and parameter settings: 50 μL of high-purity EMIM TFSI from Examples 1-3 and high-purity Py14 TFSI from Examples 1-4 were dropped into a separator membrane, and then assembled with two stainless steel caps to form a button cell. The button cell was then measured. The scan rate was 5 mV / s.

[0091] Figure 5 and Figure 6 Linear sweep voltammetry (LSV) curves of ionic liquids according to various embodiments of the present invention are shown. Figure 5 In the diagram, curve 370 represents the LSV curves of Examples 1-3. Figure 6In the figure, curve 380 represents the LSV curves for Examples 1-4. The LSV curves were measured using stainless steel as the working electrode and lithium metal as both the counter and reference electrodes. See also... Figure 5 and Figure 6 Curves 370 and 380 show almost no current at voltages below 5 volts (V), with current only appearing between 5V and 5.5V. Therefore, the high-purity ionic liquid prepared in this invention (curves 370 and 380) has an electrochemical stability window greater than 5V.

[0092] In summary, this invention provides a method for preparing ionic liquids. Specifically, the method includes preparing the ionic liquid in a microwave device to effectively shorten the reaction time. In some embodiments, using a microwave power of 700 watts to 1400 watts in the microwave device and / or a reaction pressure greater than 1 atm and less than or equal to 2 atm in the microwave device can shorten the preparation time of the ionic liquid. In some embodiments, the water content of the ionic liquid is reduced after vacuum concentration. Furthermore, the ionic liquid prepared by the method of this invention can possess characteristics such as low water content, high ionic conductivity, low viscosity, and an electrochemical stability window greater than 5V. Therefore, the ionic liquid prepared by the method of this invention is suitable for use in the battery field.

[0093] Although the invention has been described in considerable detail with reference to certain embodiments, other embodiments may also be possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.

[0094] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. In view of the foregoing, the present invention is intended to cover modifications and variations of the invention falling within the appended claims.

[0095] [Symbol Explanation]

[0096] 100, 200: Method

[0097] 110, 120, 210, 220: Steps

[0098] 310, 320, 330, 340, 350, 360, 370, 380: Curves.

Claims

1. A method for preparing ionic liquids, characterized in that, include: A halogenated compound is reacted with a first compound to form a second compound, wherein the halogenated compound includes a halocarbon, a sulfonyl halide, or a combination thereof, the first compound includes an amine compound having a tertiary amino group, a phosphine compound, or a combination thereof, and the second compound includes a first quaternary ammonium salt, a first quaternary phosphonium salt, or a combination thereof; as well as The second compound is reacted with a lithium salt in a microwave device to form a third compound, wherein the third compound comprises a second quaternary ammonium salt, a second quaternary phosphonium salt, or a combination thereof, the second compound and the third compound have different anions, and the microwave device has a microwave power of 700 watts to 1400 watts.

2. The method for preparing ionic liquids according to claim 1, wherein the amine compound having a tertiary amino group includes imidazole compounds, pyrrolidine compounds, pyridine compounds, pyrrole compounds, pyrazole compounds, imidazole compounds, pyrazoline compounds, pyrazoline compounds, or combinations thereof having a structure as shown in formula (1-1). R1 to R5 are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl or C4 to C6 heterocyclic alkyl.

3. The method for preparing an ionic liquid according to claim 1, wherein the halohydrocarbon has a structure as shown in formula (2-1), and the sulfonyl halide has a structure as shown in formula (2-2). R1'-X1 equation (2-1), R2'-SO2X2 (2-2), R1' and R2' are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, C4 to C6 heterocycloalkyl or C6 to C10 aryl, and X1 and X2 are independently fluorine, chlorine, bromine or iodine.

4. The method for preparing an ionic liquid according to any one of claims 1 to 3, wherein the reaction pressure at which the second compound reacts with the lithium salt in the microwave device is greater than 1 atm and less than or equal to 2 atm.

5. The method for preparing ionic liquids according to any one of claims 1 to 3, wherein, It also includes a heating operation after reacting the second compound with the lithium salt in the microwave device, wherein the heating operation is performed at a temperature of 60°C to 180°C.

6. The method for preparing ionic liquid according to claim 5, wherein the heating time of the heating operation is less than or equal to 6 hours.

7. A method for preparing ionic liquids, characterized in that, include: A halogenated compound is reacted with a first compound in a first microwave apparatus to form a second compound, wherein the halogenated compound includes a halocarbon, a sulfonyl halide, or a combination thereof; the first compound includes an amine compound having a tertiary amino group, a phosphine compound, or a combination thereof; and the second compound includes a first quaternary ammonium salt, a first quaternary phosphonium salt, or a combination thereof. The amine compound having a tertiary amino group includes imidazole compounds, pyrrolidine compounds, pyridine compounds, pyrrole compounds, pyrazole compounds, imidazole compounds, pyrazoline compounds, pyrazoline compounds, or combinations thereof having a structure as shown in formula (1-1). Wherein R1 to R5 are independently C1 to C22 straight-chain alkyl, C1 to C22 branched alkyl, C4 to C6 cycloalkyl, or C4 to C6 heterocyclic alkyl; and The second compound is reacted with a lithium salt in a second microwave device to form a third compound, wherein the third compound comprises a second quaternary ammonium salt, a second quaternary phosphonium salt, or a combination thereof, and the second compound and the third compound have different anions.

8. The method for preparing an ionic liquid according to claim 7, wherein the microwave power for reacting the halogen-containing compound with the first compound in the first microwave device and the microwave power for reacting the second compound with the lithium salt in the second microwave device are each from 700 watts to 1400 watts.

9. The method for preparing an ionic liquid according to claim 7 or 8, wherein the reaction pressure at which the halogen-containing compound reacts with the first compound in the first microwave device and the reaction pressure at which the second compound reacts with the lithium salt in the second microwave device are each greater than 1 atmosphere and less than or equal to 2 atmospheres.

10. The method for preparing an ionic liquid according to claim 7 or 8, wherein the reaction temperature at which the halogen-containing compound reacts with the first compound in the first microwave device and the reaction temperature at which the second compound reacts with the lithium salt in the second microwave device are each from 60°C to 250°C.

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