An ionic liquid electrolyte with a wide window and its preparation method and application

Abstract

The present invention relates to an ionic liquid electrolyte with a wide window, its preparation method and application, and belongs to the field of battery materials and energy storage technology. The present invention prepares 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid by a two-step method, uses the ionic liquid as an electrolyte, and mixes it with an organic co-solvent PC / ACN and water to prepare an electrolyte. The invention solves the problems of limited electrochemical window of aqueous electrolytes and flammable and explosive organic electrolytes, while improving the electrochemical window and specific capacitance of aqueous ionic liquid electrolytes. The wide-window ionic liquid electrolyte no longer relies on the harsh environment of water removal, providing new ideas for the development of new aqueous ionic liquid electrolytes. The preparation method is simple, easy to operate, and has a high yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials and energy storage, and particularly relates to a 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with a wide window, a preparation method thereof, and an application in supercapacitors. Background Art

[0002] As people's demand for sustainable energy continues to increase, the demand for efficient and reliable energy storage systems is also increasing. Supercapacitors, including pseudocapacitors and electrochemical double-layer capacitors, can provide greater power density than ordinary commercial batteries because their charge storage is based on surface reactions. However, aqueous electrolytes limit the range of operating voltage due to the low electrochemical decomposition voltage of water. Although organic electrolytes have good ionic conductivity, they are extremely unstable and have safety hazards such as flammability, toxicity, and volatility. Therefore, in order to make the energy density of supercapacitors greater than that of organic electrolytes, it is also necessary to ensure the stability of the electrolyte. It is necessary to find an electrolyte with a wide stable potential window.

[0003] Ionic liquids, defined as room-temperature molten salts, are primarily composed of organic cations and inorganic anions that can undergo almost unlimited structural changes with a melting point below 100°C. They offer a range of unique physical and chemical properties that make them very important in several energy applications, especially clean and sustainable energy storage and conversion materials and devices. In this regard, the wide electrochemical window, high electrochemical stability, and high thermal stability of ionic liquids make them very suitable as electrolytes for these energy storage systems. Therefore, developing a wide-window ionic liquid energy storage battery electrolyte is an innovative approach that meets current energy storage requirements. Summary of the Invention

[0004] The present invention aims to provide a preparation method and application of a wide-window ionic liquid energy storage battery electrolyte. A 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid is prepared by a two-step process, solving the safety issues of limited electrochemical window of aqueous electrolytes and flammability and explosiveness of organic electrolytes. At the same time, the electrochemical window and specific capacitance of the aqueous ionic liquid electrolyte are improved, making the wide-window ionic liquid electrolyte no longer dependent on the harsh environment of water removal. This provides new ideas for the development of new aqueous ionic liquid electrolytes, has great scientific significance and application value, and the preparation method is simple, easy to operate, and has a high yield.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with a wide window, wherein the 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid has the structural formula shown in (I):

[0007]

[0008] The preparation method of the above-mentioned 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with a wide window comprises the following steps:

[0009] 1) N-methylpyrrolidine is placed in a reactor, heated to 30° C. to 130° C., magnetically stirred, and 2-chloro-N,N-dimethylacetamide is added dropwise to the reactor using a constant pressure dropping funnel. The reaction is condensed and refluxed at 30° C. to 130° C. for 4 to 40 hours. After the reaction is completed, the intermediate crude product is placed in a refrigerator for 4 to 30 hours. After being taken out, the intermediate crude product is charged into another reactor, heated to 20° C. to 100° C., and a mixed solvent of acetonitrile and ethyl acetate is added to evaporate and recrystallize the intermediate crude product. After repeating the recrystallization operation 3-5 times, the intermediate crude product is vacuum dried at 50-150° C. to obtain the purified intermediate 1-methyl-1-N,N-dimethylacetamide pyrrole for standby use.

[0010] 2) dissolving 1-methyl-1-N,N-dimethylacetamide pyrrole in deionized water, adding bis(fluorosulfonyl)imide lithium salt, stirring, filtering, rotary evaporation to remove the solvent, and vacuum drying at 50-150° C. to obtain 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid;

[0011] 3) Preparation of electrolyte: The electrolyte was prepared using 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid as electrolyte, organic solvent PC / ACN as co-solvent, and water as solvent.

[0012] Furthermore, in the above preparation method, in step 1), 10 to 100 parts by mass of N-methylpyrrolidine and 150 to 600 parts by mass of 2-chloro-N,N-dimethylacetamide are added.

[0013] Furthermore, in the above preparation method, in step 1), 10 to 150 parts of acetonitrile and 20 to 150 parts of ethyl acetate are added by mass.

[0014] Furthermore, in the above preparation method, in step 2), 200 to 800 parts by mass of bis(fluorosulfonyl)imide lithium salt are added.

[0015] Furthermore, in the above preparation method, in step 3), 10 to 100 parts by mass of 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid, 50 to 500 parts of organic solvent PC / ACN, and 40 to 400 parts of water are added.

[0016] The above-mentioned 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with a wide window is used in supercapacitors.

[0017] Furthermore, in the above application, the supercapacitor includes a positive electrode, a negative electrode, a 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with a wide window, and a separator.

[0018] Preferably, in the above application, the positive electrode sheet and the negative electrode sheet are composed of activated carbon, a conductive material, a binder, and a current collector.

[0019] Preferably, in the above application, the current collector is one or more of titanium foil, stainless steel, and carbon cloth; and the separator is one or more of polyethylene, polyvinylidene fluoride, polypropylene, and glass fiber.

[0020] The beneficial effects of the present invention are:

[0021] 1. The ionic liquid mixed electrolyte provided by the present invention contains an amide pyrrole ionic liquid with cationic stability, which greatly improves the electrochemical window of the electrolyte.

[0022] 2. Using ionic liquids with a wide electrochemical window, high electrochemical stability and high thermal stability as electrolyte materials improves the electrochemical window and stability of aqueous organic electrolytes.

[0023] 3. A 1-methyl-1-N,N-dimethylacetamide pyrrolidine proposed by the present invention The bis(fluorosulfonyl)imide ionic liquid mixed electrolyte solves the problem of low electrochemical window of aqueous electrolytes and the safety hazards of organic electrolytes such as flammability, toxicity, and volatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the cyclic voltammetry curve of the battery prepared in Example 1.

[0025] Figure 2 This is the cyclic voltammetry curve of the battery prepared in Example 2.

[0026] Figure 3 This is the cyclic voltammetry curve of the battery prepared in Example 3.

[0027] Figure 4 This is the cyclic voltammetry curve of the battery prepared in Example 4. DETAILED DESCRIPTION

[0028] To make the purpose and technology of the embodiments of the present invention clearer, the technical solutions in the preferred embodiments of the present invention will be described in detail below. It should be understood that the embodiments cannot be construed as limiting the scope of protection of the present invention, and all technical categories implemented according to the present invention are within the scope of protection of the present invention. The reagents, instruments, or materials used are all conventional products that can be purchased on the market without indicating the manufacturer. The synthesis method and electrochemical performance of the present invention will be further elaborated below in conjunction with the examples.

[0029] Example 1

[0030] 1) 100 parts of N-methylpyrrolidine were placed in a reactor, heated to 55° C., magnetically stirred, and 150 parts of 2-chloro-N,N-dimethylacetamide were added dropwise to the reactor using a constant pressure dropping funnel. The mixture was condensed and refluxed at 65° C. for 16 hours. After the reaction, the crude intermediate product was placed in a refrigerator for 6 hours. After being taken out, the crude intermediate product was charged into another reactor, heated to 60° C., 20 parts of acetonitrile and 30 parts of ethyl acetate were added, and the crude intermediate product was evaporated and recrystallized. The recrystallization operation was repeated 3 times, and the product was vacuum dried at 75° C. to obtain the purified intermediate 1-methyl-1-N,N-dimethylacetamide pyrrole.

[0031] 2) 100 parts of 1-methyl-1-N,N-dimethylacetamide pyrrole were dissolved in 300 parts of deionized water, 200 parts of bis(fluorosulfonyl)imide lithium salt were added, stirred, filtered, and the solvent was removed by rotary evaporation. The mixture was vacuum dried at 75° C. to obtain the target ionic liquid 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide.

[0032] The structural formula of 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid is shown in (I):

[0033]

[0034] 3) Preparation of electrolyte: 100 parts of 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid, 50 parts of organic co-solvent PC / ACN and 100 parts of deionized water were mixed uniformly.

[0035] 4) Preparation of electrode sheets: Activated carbon (YP50F), conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1. Subsequently, the dispersant N-methylpyrrolidone (NMP) was added dropwise to the above mixture and the mixture was thoroughly ground. The ground slurry was applied to titanium foil and coated with the desired thickness using a four-sided wet film applicator. Finally, the titanium foil was placed in a vacuum drying oven at 60°C to form an electrode sheet of the desired shape.

[0036] 5) Battery assembly and testing: The electrode sheet, polyethylene separator, and the prepared 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte were assembled into a symmetrical button cell and the cell was compressed using a hydraulic press. Cyclic voltammetry was performed on the above cell with a test voltage range of 0-2.4V, a scan rate of 5mV / s, 10 cycles, and a test temperature of 24°C. Figure 1 The cyclic voltammetry curve is shown.

[0037] Example 2

[0038] 1) 100 parts of N-methylpyrrolidine were placed in a reactor, heated to 65° C., magnetically stirred, and 300 parts of 2-chloro-N,N-dimethylacetamide were added dropwise to the reactor using a constant pressure dropping funnel. The mixture was condensed and refluxed at 75° C. for 18 hours. After the reaction was completed, the crude intermediate product was placed in a refrigerator for 6 hours. After being taken out, the crude intermediate product was charged into another reactor, heated to 60° C., 30 parts of acetonitrile and 40 parts of ethyl acetate were added, and the crude intermediate product was evaporated and recrystallized. The recrystallization operation was repeated 3 times, and the product was vacuum dried at 85° C. to obtain the purified intermediate 1-methyl-1-N,N-dimethylacetamide pyrrole.

[0039] 2) 100 parts of 1-methyl-1-N,N-dimethylacetamide pyrrole were dissolved in 350 parts of deionized water, 400 parts of bis(fluorosulfonyl)imide lithium salt were added, stirred, filtered, and the solvent was removed by rotary evaporation. The mixture was vacuum dried at 85° C. to obtain the target ionic liquid 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide.

[0040] 3) Preparation of electrolyte: 100 parts of 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid, 200 parts of organic co-solvent PC / ACN and 150 parts of deionized water were mixed uniformly.

[0041] 4) Preparation of electrode sheets: Activated carbon (YP50F), conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1. Subsequently, the dispersant N-methylpyrrolidone (NMP) was added dropwise to the above mixture and the mixture was thoroughly ground. The ground slurry was applied to titanium foil and coated with the desired thickness using a four-sided wet film applicator. Finally, the titanium foil was placed in a vacuum drying oven at 60°C to form an electrode sheet of the desired shape.

[0042] 5) Battery assembly and testing: The electrode sheet, the separator polyvinylidene fluoride and the prepared 1-methyl-1-N,N-dimethylacetamide pyrrolidine The bis(fluorosulfonyl)imide ionic liquid electrolyte was assembled in a symmetrical button cell and the cell was compressed using a hydraulic press. Cyclic voltammetry was performed on the cell with a test voltage range of 0-2.4V, a scan rate of 5mV / s, 10 cycles, and a test temperature of 24°C. Figure 2 The cyclic voltammetry curve is shown.

[0043] Example 3

[0044] 1) 100 parts of N-methylpyrrolidine were placed in a reactor, heated to 75° C., magnetically stirred, and 500 parts of 2-chloro-N,N-dimethylacetamide were added dropwise to the reactor using a constant pressure dropping funnel. The mixture was condensed and refluxed at 85° C. for 15 hours. After the reaction, the crude intermediate product was placed in a refrigerator for 6 hours. After being taken out, the crude intermediate product was charged into another reactor, heated to 60° C., 20 parts of acetonitrile and 50 parts of ethyl acetate were added, and the crude intermediate product was evaporated and recrystallized. The recrystallization operation was repeated 3 times, and the product was vacuum dried at 80° C. to obtain the purified intermediate 1-methyl-1-N,N-dimethylacetamide pyrrole.

[0045] 2) Dissolve 100 parts of 1-methyl-1-N,N-dimethylacetamide pyrrole in 200 parts of deionized water, add 600 parts of bis(fluorosulfonyl)imide lithium salt, stir, filter, and rotary evaporate to remove the solvent. Dry in vacuo at 80° C. to obtain the target ionic liquid 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide.

[0046] 3) Preparation of electrolyte: 100 parts of 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid, 350 parts of organic co-solvent PC / ACN and 200 parts of deionized water were mixed uniformly.

[0047] 4) Preparation of electrode sheets: Activated carbon (YP50F), conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1. Subsequently, the dispersant N-methylpyrrolidone (NMP) was added dropwise to the above mixture and the mixture was thoroughly ground. The ground slurry was applied to titanium foil and coated with the desired thickness using a four-sided wet film applicator. Finally, the titanium foil was placed in a vacuum drying oven at 60°C to form an electrode sheet of the desired shape.

[0048] 5) Battery assembly and testing: The electrode sheet, diaphragm glass fiber and the prepared 1-methyl-1-N,N-dimethylacetamide pyrrolidine The bis(fluorosulfonyl)imide ionic liquid electrolyte was assembled in a symmetrical button cell and the cell was compressed using a hydraulic press. Cyclic voltammetry was performed on the cell with a test voltage range of 0-2.4V, a scan rate of 5mV / s, 10 cycles, and a test temperature of 24°C. Figure 3 The cyclic voltammetry curve is shown.

[0049] Example 4

[0050] 1) 100 parts of N-methylpyrrolidine were placed in a reactor, heated to 70° C., magnetically stirred, and 600 parts of 2-chloro-N,N-dimethylacetamide were added dropwise to the reactor using a constant pressure dropping funnel. The mixture was condensed and refluxed at 80° C. for 17 hours. After the reaction, the crude intermediate product was placed in a refrigerator for 6 hours. After being taken out, the crude intermediate product was charged into another reactor, heated to 60° C., 50 parts of acetonitrile and 60 parts of ethyl acetate were added, and the crude intermediate product was evaporated and recrystallized. The recrystallization operation was repeated 3 times, and the product was vacuum dried at 70° C. to obtain the purified intermediate 1-methyl-1-N,N-dimethylacetamide pyrrole.

[0051] 2) 100 parts of 1-methyl-1-N,N-dimethylacetamide pyrrole were dissolved in 250 parts of deionized water, 800 parts of bis(fluorosulfonyl)imide lithium salt were added, stirred, filtered, and the solvent was removed by rotary evaporation. The mixture was vacuum dried at 70°C to obtain the target ionic liquid 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide.

[0052] 3) Preparation of electrolyte: 100 parts of 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid, 500 parts of organic co-solvent PC / ACN and 400 parts of deionized water were mixed uniformly.

[0053] 4) Preparation of electrode sheets: Activated carbon (YP50F), conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1. Subsequently, the dispersant N-methylpyrrolidone (NMP) was added dropwise to the above mixture and the mixture was thoroughly ground. The ground slurry was applied to titanium foil and coated with the desired thickness using a four-sided wet film applicator. Finally, the titanium foil was placed in a vacuum drying oven at 60°C to form an electrode sheet of the desired shape.

[0054] 5) Battery assembly and testing: The electrode sheet, polypropylene separator, and the prepared 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte were assembled into a symmetrical button cell and the cell was compressed using a hydraulic press. Cyclic voltammetry was performed on the above cell with a test voltage range of 0-2.4V, a scan rate of 5mV / s, 10 cycles, and a test temperature of 24°C. Figure 4 The cyclic voltammetry curve is shown.

Claims

1. A 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with a wide window, characterized in that: The 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid has the structural formula shown in (I):

2. The method for preparing a 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte having a wide window according to claim 1, characterized in that: The steps include: 1) N-methylpyrrolidine is placed in a reactor, heated to 30° C. to 130° C., magnetically stirred, and 2-chloro-N,N-dimethylacetamide is added dropwise to the reactor using a constant pressure dropping funnel. The reaction is condensed and refluxed at 30° C. to 130° C. for 4 to 40 hours. After the reaction is completed, the intermediate crude product is placed in a refrigerator for 4 to 30 hours. After being taken out, the intermediate crude product is charged into another reactor, heated to 20° C. to 100° C., and a mixed solvent of acetonitrile and ethyl acetate is added to evaporate and recrystallize the intermediate crude product. After repeating the recrystallization operation 3-5 times, the intermediate crude product is vacuum dried at 50-150° C. to obtain the purified intermediate 1-methyl-1-N,N-dimethylacetamide pyrrole for standby use. 2) dissolving 1-methyl-1-N,N-dimethylacetamide pyrrole in deionized water, adding bis(fluorosulfonyl)imide lithium salt, stirring, filtering, rotary evaporation to remove the solvent, and vacuum drying at 50-150° C. to obtain 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid; 3) Preparation of electrolyte: The electrolyte was prepared using 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid as electrolyte, organic solvent PC / ACN as co-solvent, and water as solvent.

3. The preparation method according to claim 2, characterized in that In step 1), 10 to 100 parts by mass of N-methylpyrrolidine and 150 to 600 parts by mass of 2-chloro-N,N-dimethylacetamide are added.

4. The preparation method according to claim 2, characterized in that In step 1), 10 to 150 parts of acetonitrile and 20 to 150 parts of ethyl acetate are added by mass.

5. The preparation method according to claim 2, characterized in that In step 2), 200 to 800 parts by mass of lithium bis(fluorosulfonyl)imide salt are added.

6. The preparation method according to claim 2, characterized in that In step 3), 10 to 100 parts by mass of 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid, 50 to 500 parts by mass of organic solvent PC / ACN, and 40 to 400 parts by mass of water are added.

7. Use of the 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with a wide window as claimed in claim 1 in a supercapacitor.

8. The use according to claim 7, characterized in that The supercapacitor comprises a positive electrode sheet, a negative electrode sheet, a 1-methyl-1-N,N-dimethylacetamide pyrrolidinium bis(fluorosulfonyl)imide ionic liquid electrolyte with a wide window, and a separator.

9. The use according to claim 8, characterized in that The positive electrode sheet and the negative electrode sheet are composed of activated carbon, conductive material, binder and current collector.

10. The use according to claim 9, characterized in that The current collector is one or more of titanium foil, stainless steel, and carbon cloth; the separator is one or more of polyethylene, polyvinylidene fluoride, polypropylene, and glass fiber.

Images