Imidazole zwitterionic compound, preparation method thereof and application of imidazole zwitterionic compound in battery

Abstract

The invention provides an imidazole zwitterionic compound, a preparation method of the imidazole zwitterionic compound and application of the imidazole zwitterionic compound in a battery. The structural formula of the imidazole zwitterionic compound is shown as a formula I, R1 is halogen, aryl or halogen-substituted aryl, and R2, R3, R4 and R5 are respectively and independently selected from H, halogen, CN, NO2, NH2, OH, COOH, SO2F, C1-C4 alkyl and halogen-substituted C1-C4 alkyl. The preparation method of the imidazole zwitterionic compound comprises the following steps: mixing a compound as shown in a formula II and a first solvent to form a first solution; dropwise adding and mixing the first solution and a second solution, and reacting to obtain a primary product, wherein the second solution is a mixed solution of a sulfonic acid isocyanate compound as shown in a formula III and a first solvent; and purifying and drying the primary product. As a novel substance, the imidazole zwitterionic compound has the advantages of both the ionic liquid and the sulfimide group, has a good application prospect, and can be applied to a secondary battery. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of material synthesis, and in particular to a compound used in a battery, and more particularly to an imidazole zwitterionic compound and a preparation method thereof, and an imidazole zwitterionic compound used in a battery and a preparation method thereof, and an application in a battery. Background Art

[0002] Zwitterionic compounds are molecules that carry both positive and negative charges but are electrically neutral. The most representative class of substances is amino acids ( + H3NCH2COO - ), where the positive charge center is NH3 + , the negative charge center is COO - , and is electrically neutral as a whole. The zwitterionic compounds that are currently being studied more are to replace the negative charge center with a sulfonate group or a phosphate group, or to attach different functional groups to the sulfonate group or the phosphate group, or to polymerize to form zwitterionic polymers to achieve different functions, such as sulfobetaine, phosphorylcholine, etc. However, the types of zwitterionic compounds that can be used are limited, and the structures and properties are relatively simple, especially zwitterionic compounds based on isocyanate, imidazole and their derivatives are rarely reported.

[0003] Therefore, developing new zwitterionic compounds and expanding their scope of application has become a common goal of academia and industry. Summary of the invention

[0004] Based on the above problems, the object of the present invention is to provide an imidazole zwitterionic compound and a preparation method thereof, and application in batteries. The preparation method is simple to operate, and the yield and purity of the target product are high. As a new substance, the imidazole zwitterionic compound includes a sulfonyl imide group and an imidazole ring, and has the advantages of both ionic liquids and sulfonyl imide groups, has good application prospects, and can be applied to secondary batteries.

[0005] To achieve the above-mentioned purpose, the first aspect of the present invention provides an imidazole zwitterionic compound, the structural formula of which is shown in Formula 1, R1 is a halogen, an aromatic group or a halogen-substituted aromatic group, and R2, R3, R4 and R5 are each independently selected from H, halogen, CN, NO2, NH2, OH, COOH, SO2F, a C1~C4 hydrocarbon group, and a halogen-substituted C1~C4 hydrocarbon group.

[0006] As a new substance, the imidazole zwitterionic compound of the present invention contains an imide group and an imidazole ring, has the advantages of both ionic liquid and sulfonyl imide group, has good application prospects, and can be applied to secondary batteries.

[0007] As a technical solution of the present invention, R1 is fluorine, chlorine, alkylbenzene or halogen-substituted alkylbenzene, and R2, R3, R4 and R5 are each independently selected from H, fluorine, chlorine, CN, NO2, NH2, OH, COOH, C1~C4 alkyl, halogen-substituted C1~C4 alkyl.

[0008] As a technical solution of the present invention, it includes at least one of compounds 1 to 7.

[0009]

[0010]

[0011] The second aspect of the present invention provides a method for preparing an imidazole zwitterionic compound, comprising the steps of:

[0012] (1) mixing the compound represented by formula 2 and a first solvent to form a first solution;

[0013] (2) adding the first solution and the second solution dropwise and mixing them to react to obtain a primary product, wherein the second solution is a mixed solution of the sulfonic acid isocyanate compound shown in Formula 3 and the first solvent;

[0014] (3) purifying and drying the primary product,

[0015]

[0016] Wherein, R2, R3, R4 and R5 are each independently selected from H, halogen, CN, NO2, NH2, OH, COOH, SO2F, C1~C4 hydrocarbon group, halogen-substituted C1~C4 hydrocarbon group, and R1 is halogen, aromatic group or halogen-substituted aromatic group.

[0017] The preparation method of the present invention is simple, and can be prepared by reacting the imidazole compound shown in formula 2 and the sulfonic acid isocyanate compound shown in formula 3. The target product with high yield and purity can be obtained after purification and drying, and is easy to industrialize.

[0018] As a technical solution of the present invention, the first solvent includes at least one of a nitrile solvent, a halogenated hydrocarbon solvent, an ether solvent, an ester solvent, a ketone solvent and an aromatic hydrocarbon solvent.

[0019] As a technical solution of the present invention, the temperature during the mixing in step (1) is -40 to 50°C and the time is 15 to 60 hours.

[0020] As a technical solution of the present invention, the reaction temperature of step (2) is -20 to 10°C, and the reaction time is 1 to 24 hours.

[0021] As a technical solution of the present invention, the molar ratio of the compound represented by Formula 3 to the compound represented by Formula 2 is 1:1.0-1.2.

[0022] As a technical solution of the present invention, the purification is filtering or washing, and the drying condition is vacuum drying at 35 to 120° C. for 1 to 24 hours.

[0023] The third aspect of the present invention provides the use of imidazole zwitterionic compounds in secondary batteries. Imidazole zwitterionic compounds form a good protective film at the interface of positive and negative electrode materials, which can improve the electrochemical performance of the battery and have good application prospects. DETAILED DESCRIPTION

[0024] The imidazole zwitterionic compound of the present invention can be used as an intermediate in material synthesis or in batteries. In particular, the imidazole zwitterionic compound is used in secondary batteries such as lithium ion batteries or sodium ion batteries, and as a new conductive lithium salt, it can improve the electrochemical properties of secondary batteries, such as the cycle performance at high rates.

[0025] The structural formula of the imidazole zwitterionic compound of the present invention is shown in Formula 1.

[0026]

[0027] R1 is halogen, aromatic group or halogen substituted aromatic group, more preferably, R1 is fluorine, chlorine, bromine, phenyl, tolyl, ethylphenyl, fluorophenyl, fluorotoluene, fluoroethylbenzene. More preferably, R1 is fluorine, chlorine, phenyl, tolyl. R2, R3, R4 and R5 are each independently selected from H, halogen, CN, NO2, NH2, OH, COOH, SO2F, C1-C4 hydrocarbon group, halogen substituted C1-C4 hydrocarbon group. Further, R2, R3, R4 and R5 are each independently selected from H, fluorine, chlorine, bromine, CN, NO2, NH2, OH, COOH, SO2F, methyl, ethyl, propyl, isopropyl, butyl, fluoromethyl, fluoroethyl, fluoropropyl, fluoroisopropyl, fluorobutyl, difluoromethyl, difluoroethyl, difluoropropyl, difluoroisopropyl, difluorobutyl, vinyl, propenyl, isopropenyl, butenyl, fluoromethyl, fluorovinyl, fluoropropenyl, fluoroisopropenyl, fluorobutenyl, difluoromethyl, difluorovinyl, difluoropropenyl, difluoroisopropenyl and difluorobutenyl. ethynyl, propynyl, isopropynyl, butynyl, fluoroalkynyl, fluoroethynyl, fluoropropynyl, fluoroisopropynyl, fluorobutynyl, difluoromethylynyl, difluoroethynyl, difluoropropynyl, difluoroisopropynyl, difluorobutynyl. Methyl chloride, ethyl chloride, propyl chloride, isopropyl chloride, butyl chloride, dichloromethane, dichloroethyl, dichloropropyl, dichloroisopropyl, difluorobutyl, chloroform, vinyl chloride, propenyl chloride, isopropenyl chloride, butenyl chloride, dichloroform, dichlorovinyl, dichloropropenyl, dichloroisopropenyl, dichlorobutenyl. Fluoroalkynyl, fluoroethynyl, fluoropropynyl, fluoroisopropynyl, fluorobutynyl, difluoromethylynyl, difluoroethynyl, difluoropropynyl, difluoroisopropynyl, difluorobutynyl. Further, R2, R3, R4 and R5 are each independently selected from H, fluorine, bromine, CN, methylene, ethyl, propane, isopropyl, butane, fluoromethyl, fluoroethyl, fluoropropyl, fluoroisopropyl, fluorobutyl, difluoromethyl, difluoroethyl, difluoropropyl, difluoroisopropyl, difluorobutyl, etc.

[0028] Furthermore, the imidazole zwitterionic compound includes at least one of compounds 1 to 7. Of course, the imidazole zwitterionic compound may also be other compounds, at least one of which conforms to the structure shown in formula 1.

[0029]

[0030] The method for preparing the imidazole zwitterionic compound of the present invention may include the following steps.

[0031] (1) Mixing the compound represented by Formula 3 and a first solvent to form a first solution.

[0032] (2) The first solution and the second solution are added dropwise and mixed and reacted under certain heating conditions to obtain a primary product, wherein the second solution is a salt solution, and the salt solution is a mixed solution of tetrafluoroborate and the first solvent or a mixed solution of hexafluorophosphate and the first solvent.

[0033] (3) Purify and dry the primary product.

[0034] Wherein, R2, R3, R4 and R5 are each independently selected from H, halogen, CN, NO2, NH2, OH, COOH, SO2F, C1~C4 hydrocarbon group, halogen-substituted C1~C4 hydrocarbon group, and R1 is halogen, aromatic group or halogen-substituted aromatic group.

[0035]

[0036] The imidazole compound shown in Formula 2 can be obtained from commercial sources or obtained by substituent replacement reaction of commercially available substances. The imidazole compound can be N-methylimidazole, 1,4-dimethyl-1H-imidazole, 1-methyl-4-fluoro-1H-imidazole, 1-methyl-1H-imidazole-4-carbonitrile.

[0037] The sulfonic acid isocyanate compound shown in formula 3 can be chlorosulfonic acid isocyanate purchased directly, or it can be fluorosulfonic acid isocyanate obtained by replacing the chlorine in chlorosulfonic acid isocyanate. Specifically, anhydrous potassium fluoride can be heated to a certain temperature, and chlorosulfonic acid isocyanate can be added dropwise under condensation reflux stirring. After the addition is completed, the reaction is carried out at 100-160°C for 3-10 hours. After the reaction is completed, atmospheric distillation and fraction collection are carried out in turn to obtain fluorosulfonic acid isocyanate. The temperature of atmospheric distillation is 100°C, and the temperature range of collecting fractions is 65-100°C. Tolylsulfonic acid isocyanate can be prepared by reacting p-toluenesulfonamide with triphosgene.

[0038] The first solvent includes at least one of a nitrile solvent, a halogenated hydrocarbon solvent, an ether solvent, an ester solvent, a ketone solvent, and an aromatic hydrocarbon solvent. Specifically, the nitrile solvent is acetonitrile or butyronitrile, the halogenated hydrocarbon solvent is dichloromethane, chloroform, 1,2-dichloroethane or tetrachloroethane, the ether solvent is methyl tert-butyl ether, ethylene glycol dimethyl ether, tetrahydrofuran or dioxane, the ester solvent is dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate or propyl acetate, the ketone solvent is acetone, cyclohexanone or 4-methyl-2-pentanone, and the aromatic hydrocarbon solvent is benzene, toluene or xylene. Preferably, the first solvent is at least one of acetonitrile and dimethyl carbonate.

[0039] The temperature during mixing is 40 to 50° C., and further, the temperature during mixing is -10 to 10° C. As an example, the temperature may be, but is not limited to, -40° C., -35° C., -30° C., -25° C., -20° C., -15° C., -10° C., -5° C., 0° C., 5° C., 10° C., 15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C. The time is 15 to 60 hours, and as an example, the time may be, but is not limited to, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours, 40 hours, 45 hours, 50 hours, 55 hours, 60 hours.

[0040] The reaction temperature of step (2) is -20 to 10°C. As an example, the reaction temperature may be, but is not limited to, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C. The reaction time is 1 to 24 hours. Preferably, the reaction time is 6 to 12 hours. As an example, the time may be, but is not limited to, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours. The molar ratio of the compound shown in Formula 3 to the compound shown in Formula 2 is 1:1.0 to 1.2. As an example, the molar ratio may be, but is not limited to, 1:1.0, 1:1.1, 1:1.2. Preferably, the molar ratio of the compound shown in Formula 3 to the salt solution is 1:1.

[0041] In step (3), purification is filtering or washing, and polar solvents / weakly polar solvents are used for washing. Polar solvents include acetonitrile, acetone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl acetate, propyl acetate, butyl acetate, ether, methyl tert-butyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and dioxane. Weakly polar solvents include dichloromethane, chloroform, n-hexane, cyclohexane, toluene, xylene, chlorobenzene, and fluorobenzene. The drying condition is vacuum drying at 35 to 120° C. for 1 to 24 hours, and the vacuum drying temperature can be, but is not limited to, 35° C., 45° C., 55° C., 65° C., 75° C., 85° C., 95° C., 105° C., 115° C., and 120° C. The drying time can be, but is not limited to, 1 h, 3 h, 5 h, 7 h, 9 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, or 24 h.

[0042] In order to better illustrate the purpose, technical scheme and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0043] Part I: Preparation of sulfonic acid isocyanate compounds shown in formula III

[0044] Example 1

[0045] This embodiment is for preparing fluorosulfonic acid isocyanate, and its preparation method includes the following steps.

[0046] 68.0g of anhydrous potassium fluoride was put into a multi-mouth flask equipped with a speed-regulating stirrer, a condensing reflux tube, and a constant-pressure dropping funnel. The stirrer was turned on for stirring. The multi-mouth flask was then placed in a water bath, the temperature of the water bath was controlled to be 100°C, the temperature of the cold water in the condensing reflux tube was -20°C, 141.5g of chlorosulfonic acid isocyanate was slowly added dropwise to the multi-mouth flask using a constant-pressure dropping funnel. After the addition was completed, the temperature of the water bath was controlled to be 130°C, and the reflux reaction was performed for 6h. After the reaction was completed, atmospheric distillation was performed at 100°C, and the fractions in the temperature range of 65-100°C were collected to obtain 106.0g of fluorosulfonic acid isocyanate, with a yield of 85.0% and a purity of 99.0%. Hydrogen spectrum: 19 F-NMR (CD3CN): 60.0 1F, indicating that fluorosulfonic acid isocyanate was synthesized.

[0047] The reaction equation for the preparation of fluorosulfonic acid isocyanate is shown below.

[0048]

[0049] Example 2

[0050] This embodiment is for preparing toluenesulfonic acid isocyanate, and its preparation method includes the following steps.

[0051] 86.04g of p-toluenesulfonamide and 86g of chlorobenzene are stirred and dissolved to obtain a toluenesulfonamide chlorobenzene solution, which is added to a constant pressure drop funnel. 148g of triphosgene is added to 100g of chlorobenzene, and after stirring and mixing, the p-toluenesulfonamide chlorobenzene solution is added to a reaction flask, and the temperature is raised to more than 90°C while stirring, and the temperature is controlled at 105°C for 4h. After the reaction is complete, the condenser tube and the receiving bottle are connected, and the solvent chlorobenzene is started to be recovered, and the vacuum degree is controlled to be -0.08Mpa, and the recovery temperature is 105°C. After the solvent chlorobenzene is recovered, the material is transferred to a distillation flask, and a vacuum pump is connected to evacuate to less than -0.095Mpa, and heated distillation is performed to obtain 97.73g of p-toluenesulfonyl isocyanate, and the detection content is 99.19%, and the experimental yield is 98.33%. Hydrogen spectrum: 1H NMR (400MHz, CD3CN): 2.43 (s, 3H), 7.43-7.44 (d, 2H), 7.46-7.47 (d, 2H), indicating that toluenesulfonic acid isocyanate was synthesized.

[0052] The preparation reaction equation of toluenesulfonic acid isocyanate is shown below.

[0053]

[0054] Part II: Preparation of Imidazole Zwitterionic Compounds

[0055] Example 3

[0056] This embodiment is for preparing compound 1, and its preparation method includes the following steps.

[0057] (1) 16.6 g of N-methylimidazole and 80.0 g of dichloromethane were stirred at 0° C. for 10 min to form a first solution.

[0058] (2) The second solution was added dropwise to the first solution and reacted at 0°C for 20 hours to obtain a primary product. The second solution was formed by mixing 28.6 g of chlorosulfonic acid isocyanate and 80.0 g of dichloromethane.

[0059] (3) The primary product was filtered, washed with dichloromethane, and dried in vacuo at 60°C to obtain 41.5 g of compound 1 with a yield of 92.0% and a purity of 99.0%. Hydrogen spectrum: 1H NMR (400 MHz, CD3CN): 3.60 (s, 3H), 6.60 (s, 1H), 7.10 (t, 1H), 7.60 (t, 1H), indicating that compound 1 was synthesized.

[0060]

[0061] The preparation reaction formula of compound 1 of this example is shown below.

[0062] Example 4

[0063] This embodiment is for preparing compound 2, and its preparation method includes the following steps.

[0064] (1) 16.6 g of N-methylimidazole and 80.0 g of dichloromethane were stirred at 0° C. for 10 min to form a first solution.

[0065] (2) The second solution was added dropwise to the first solution and reacted at 0° C. for 20 h to obtain a primary product. The second solution was formed by uniformly mixing 25.3 g of fluorosulfonic acid isocyanate prepared in Example 1 and 80.0 g of dichloromethane.

[0066] (3) The primary product was filtered, washed with dichloromethane, and dried in vacuo at 60°C to obtain 39.0 g of compound 2 with a yield of 93.0% and a purity of 99.0%. Hydrogen spectrum: 1H NMR (400 MHz, CD3CN): 3.53 (s, 3H), 6.60 (s, 1H), 7.15 (t, 1H), 7.45 (t, 1H), 19 F-NMR (CD3CN): 61.01F, indicating that compound 2 was synthesized.

[0067]

[0068] The preparation reaction formula of compound 2 of this example is shown below.

[0069] Example 5

[0070] This embodiment is for preparing compound three, and its preparation method includes the following steps.

[0071] (1) 19.4 g of 1,4-dimethyl-1H-imidazole and 80.0 g of dichloromethane were mixed to form a first solution.

[0072] (2) The second solution was added dropwise to the first solution and reacted at 0°C for 20 hours to obtain a primary product. The second solution was formed by mixing 28.6 g of chlorosulfonic acid isocyanate and 80.0 g of dichloromethane.

[0073] (3) The primary product was filtered, washed with dichloromethane, and dried in vacuo at 70°C to obtain 44.9 g of compound III with a yield of 93.5% and a purity of 99.0%. Hydrogen spectrum: 1H NMR (400 MHz, CD3CN): 1.60 (s, 3H), 3.60 (s, 3H), 6.54 (s, 1H), 6.90 (s, 1H), indicating that compound III was synthesized.

[0074]

[0075] The preparation reaction formula of compound 3 of this embodiment is shown below.

[0076] Example 6

[0077] This embodiment is for preparing compound 4, and its preparation method includes the following steps.

[0078] (1) 19.4 g of 1,4-dimethyl-1H-imidazole and 80.0 g of dichloromethane were stirred at 0° C. for 10 min to form a first solution.

[0079] (2) The second solution was added dropwise to the first solution and reacted at 0° C. for 16 h to obtain a primary product. The second solution was formed by mixing 25.3 g of fluorosulfonic acid isocyanate prepared in Example 1 and 80.0 g of dichloromethane.

[0080] (3) The primary product was filtered, washed with dichloromethane, and dried in vacuo at 60°C to obtain 43.4 g of compound 4 with a yield of 97.0% and a purity of 99.0%. Hydrogen spectrum: 1H NMR (400 MHz, CD3CN): 1.34 (s, 3H), 3.70 (s, 3H), 6.56 (s, 1H), 7.0 (s, 1H), 19 F-NMR (CD3CN): 61.51F, indicating that compound 4 was synthesized.

[0081] The preparation reaction equation of compound 4 of this embodiment is shown below.

[0082] Example 7

[0083] This embodiment is for preparing compound 5, and its preparation method includes the following steps.

[0084] (1) 20.0 g of 1-methyl-4-fluoro-1H-imidazole and 80 g of dichloromethane were stirred at 0° C. for 10 min to form a first solution.

[0085] (2) The second solution was added dropwise to the first solution and reacted at 0° C. for 16 h to obtain a primary product. The second solution was formed by uniformly mixing 25.3 g of fluorosulfonic acid isocyanate obtained in Example 1 and 80 g of dichloromethane.

[0086] (3) The primary product was filtered, washed with dichloromethane, and dried in vacuo at 70°C to obtain 43.5 g of compound 5 with a yield of 95.5% and a purity of 99.0%. Hydrogen spectrum: 1H NMR (400 MHz, CD3CN): 3.70 (s, 3H), 6.58 (s, 1H), 7.2 (s, 1H), 19 F-NMR (CD3CN): 41.51F, 61.51F, indicating that compound 5 was synthesized.

[0087]

[0088] The preparation reaction formula of compound 5 of this example is shown below.

[0089] Example 8

[0090] This embodiment is for preparing compound 6, and its preparation method includes the following steps.

[0091] (1) 21.6 g of 1-methyl-1H-imidazole-4-carbonitrile and 80 g of toluene were stirred at -2°C for 15 min to form a first solution.

[0092] (2) The second solution was added dropwise to the first solution and reacted at -2°C for 20 hours to obtain a primary product. The second solution was formed by uniformly mixing 25.3 g of fluorine acid isocyanate obtained in Example 1 and 80 g of toluene.

[0093]

[0094]

[0095] (3) The primary product was filtered, washed with toluene, and dried in vacuo at 100°C to obtain 43.4 g of compound VI with a yield of 92.3% and a purity of 99.0%. Hydrogen spectrum: 1H NMR (400 MHz, CD3CN): 3.40 (s, 3H), 6.43 (s, 1H), 7.4 (s, 1H), 19F-NMR (CD3CN): 61.51F, indicating that compound VI was synthesized.

[0096] The preparation reaction formula of compound 6 of this example is shown below.

[0097] Example 9

[0098] This embodiment is for preparing compound VII, and its preparation method includes the following steps.

[0099] (1) 16.6 g of N-methylimidazole and 80 g of toluene were stirred at 0° C. for 10 min to form a first solution.

[0100] (2) The second solution was added dropwise to the first solution and reacted at 0°C for 20 hours to obtain the primary product.

[0101] 39.9 g of p-toluenesulfonic acid isocyanate prepared in Example 2 and 80 g of toluene were mixed uniformly to form a flask.

[0102] (3) The primary product was filtered, washed with toluene, and dried in vacuo at 100°C to obtain 54.3 g of compound VII with a yield of 96.0% and a purity of 99%. Hydrogen spectrum: 1H NMR (400 MHz, CD3CN): 2.40 (s, 3H), 3.40 (s, 3H), 7.1 (t, 7H), indicating that compound VII was synthesized.

[0103] The preparation reaction formula of compound VII of this example is shown below.

[0104] Part III: Application of Imidazole Zwitterionic Compounds in Secondary Batteries

[0105] 1.5 g of compounds 1 to 7 obtained in Examples 3 to 9 and 86.0 g of a non-aqueous organic solvent (ethylene carbonate EC, diethyl carbonate DEC, ethyl methyl carbonate EMC in a mass ratio of 3:2:1) were mixed evenly, and then 12.5 g of lithium hexafluorophosphate LiPF6 was added and mixed evenly to prepare non-aqueous electrolytes 1# to 7#.

[0106] 87.5 g of non-aqueous organic solvent (ethylene carbonate EC, diethyl carbonate DEC, ethyl methyl carbonate EMC in a mass ratio of 3:2:1) and 12.5 g of lithium hexafluorophosphate LiPF6 were mixed evenly to prepare non-aqueous electrolyte 8#.

[0107] Lithium cobalt oxide was used as the positive electrode material and lithium metal was used as the counter electrode. Non-aqueous electrolytes 1# to 8# were injected respectively to assemble button batteries 1# to 8#. At room temperature (25°C), the button batteries were charged and discharged at 4.0C / 4.0C (the battery discharge capacity was recorded as C0), the upper limit voltage was 4.1V, and then 4.0C / 4.0C was charged and discharged for 200 weeks, and the capacity retention rate was calculated.

[0108] Capacity retention rate = (battery capacity C1 after 200 cycles / battery initial capacity C0) * 100%

[0109] Table 1 Electrochemical performance test results of each example

[0110]

[0111] From the results in Table 1, it can be seen that the cycle performance of button cells 1 to 7# is better than that of button cell 8#. This is because the electrolyte of button cells 1 to 7# contains imidazole zwitterionic compounds, which have the advantages of both ionic liquids and sulfonyl imide groups, can improve the conductivity of the material, and thus improve the cycle performance of the battery at high rates.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. An imidazole zwitterionic compound, characterized in that: The structural formula is as shown in Formula 1, R1 is a halogen, an aromatic group or a halogen-substituted aromatic group, R2, R3, R4 and R5 are each independently selected from H, a halogen, CN, NO2, NH2, OH, COOH, SO2F, a C1-C4 hydrocarbon group, a halogen-substituted C1-C4 hydrocarbon group, 2. The imidazole zwitterionic compound according to claim 1, characterized in that R1 is fluorine, chlorine, alkylbenzene or halogen-substituted alkylbenzene, and R2, R3, R4 and R5 are each independently selected from H, fluorine, chlorine, CN, NO2, NH2, OH, COOH, C1-C4 alkyl, and halogen-substituted C1-C4 alkyl.

3. The imidazole zwitterionic compound according to claim 1, characterized in that: including at least one of Compounds 1 to 7, 4. The method for preparing an imidazole zwitterionic compound according to any one of claims 1 to 3, characterized in that: Includes steps: (1) mixing the compound represented by formula 2 and a first solvent to form a first solution; (2) adding the first solution and the second solution dropwise and mixing them to react to obtain a primary product, wherein the second solution is a mixed solution of the sulfonic acid isocyanate compound shown in Formula 3 and the first solvent; (3) purifying and drying the primary product, Wherein, R2, R3, R4 and R5 are each independently selected from H, halogen, CN, NO2, NH2, OH, COOH, SO2F, C1~C4 hydrocarbon group, halogen-substituted C1~C4 hydrocarbon group, and R1 is halogen, aromatic group or halogen-substituted aromatic group.

5. The method for preparing the imidazole zwitterionic compound according to claim 4, characterized in that: The first solvent includes at least one of a nitrile solvent, a halogenated hydrocarbon solvent, an ether solvent, an ester solvent, a ketone solvent and an aromatic hydrocarbon solvent.

6. The method for preparing the imidazole zwitterionic compound according to claim 4, characterized in that: The temperature during the mixing in step (1) is -40 to 50° C. and the mixing time is 15 to 60 hours.

7. The method for preparing the imidazole zwitterionic compound according to claim 4, characterized in that: The reaction temperature of step (2) is -20 to 10°C, and the reaction time is 1 to 24 hours.

8. The method for preparing the imidazole zwitterionic compound according to claim 4, characterized in that: The molar ratio of the compound represented by Formula 3 to the compound represented by Formula 2 is 1:1.0-1.

2.

9. The method for preparing the imidazole zwitterionic compound according to claim 4, characterized in that: The purification is filtering or washing, and the drying condition is vacuum drying at 35-120° C. for 1-24 hours.

10. Use of the imidazolium zwitterionic compound prepared by the method for preparing the imidazolium zwitterionic compound according to any one of claims 1 to 3 or any one of claims 4 to 9 in a secondary battery.

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