Spiro quaternary ammonium salt electrolyte, preparation method thereof and electrolyte solution

Abstract

The invention provides a spiro quaternary ammonium salt electrolyte and a preparation method and electrolyte thereof, the spiro quaternary ammonium salt electrolyte is named 4-azacyclo-(3, 4)-octane tetrafluoroborate, and the preparation method comprises the following steps: dropwise adding 1-bromo-3-chloropropane into a solution containing diethyl ether and pyrrolidine, and reacting in a normal-temperature water bath to generate a white precipitate; filtering the white precipitate to obtain colorless transparent liquid; adding diluted hydrochloric acid into the colorless transparent liquid for extraction, then adding a NaOH dilute solution to enable the colorless transparent liquid to be alkaline, washing with diethyl ether, drying with anhydrous sodium sulfate to remove water, and then carrying out rotary evaporation to obtain colorless oily liquid; dropwise adding the colorless oily liquid into boiling water, and condensing and refluxing to finally obtain homogeneous-phase faint yellow liquid; washing with dichloromethane, and carrying out rotary evaporation to remove solvent water, so as to obtain an intermediate; and dropwise adding the intermediate into an aqueous solution containing ethanol and 50% HBF4, and reacting in a normal-temperature water bath to generate the spiro quaternary ammonium salt. The spiro quaternary ammonium salt electrolyte provided by the invention has higher specific capacitance, can stably work at a high voltage of 3.2 V, and has high energy density.

Description

Technical Field

[0001] The present invention belongs to the field of supercapacitors, and particularly relates to a spiro quaternary ammonium salt electrolyte, a preparation method thereof, and an electrolyte solution. Background Art

[0002] A supercapacitor refers to a new type of energy storage device between traditional capacitors and rechargeable batteries. It not only has the characteristics of rapid charge and discharge of capacitors, but also has a higher energy density than traditional capacitors. As a supplement to lithium batteries, energy supercapacitors have the advantages of high power density, long life, and good safety.

[0003] Compared with high-energy density energy storage devices such as lithium-ion batteries, the energy density of supercapacitors is relatively low, which cannot meet the requirements of long-term use of equipment, greatly limiting the application and development of supercapacitors. Currently, the mainstream commercial supercapacitors are symmetric capacitors with porous carbon materials with a high specific surface area as electrodes, including two identical electrode plates, current collectors, diaphragms, and electrolyte solutions, etc., and charge storage is achieved by the electric double layer formed at the interface between the electrode surface and the electrolyte solution. The energy density of a supercapacitor is proportional to the capacitance, and the capacitance value can be achieved by increasing the amount of charge stored per unit area.

[0004] Research has found that the type and volume of electrolyte salts have an impact on improving the utilization rate of porous carbon materials and the amount of charge stored per unit area, thereby affecting the specific capacitance and energy density of supercapacitors. Therefore, it is very necessary to develop a supercapacitor electrolyte that can provide a higher specific capacitance and a wide electrochemical stability window for the development of supercapacitors. Summary of the Invention

[0005] Aiming at the problems of low energy density and narrow chemical stability window of supercapacitors in the prior art, the present invention provides a spiro quaternary ammonium salt electrolyte, a preparation method thereof, and an electrolyte solution. The quaternary ammonium salt is simple to prepare, has a smaller ion size, and can effectively improve the specific capacitance of supercapacitors.

[0006] The technical solution of the present invention is as follows. A spiro quaternary ammonium salt electrolyte, named 4-aza-cyclo-(3,4)-octane tetrafluoroborate, has a cation that is a heterocyclic compound containing four- and five-membered rings, with 1 nitrogen atom as the only ring heteroatom, and the specific structural formula is as follows: 。

[0007] The present invention provides a preparation method for the above spiro quaternary ammonium salt electrolyte, including the following steps: S1. Drop 1-bromo-3-chloropropane into a solution containing ether and pyrrolidine, and react in a constant temperature water bath at room temperature to form a white precipitate; S2. Filter and separate the system after the reaction in step S1, filter the white precipitate to obtain a colorless transparent liquid; add dilute hydrochloric acid for extraction to the colorless transparent liquid, then add dilute NaOH solution to make it alkaline, wash with ether, dry the obtained ether extract with anhydrous sodium sulfate to remove water, and then perform rotary evaporation to obtain a colorless oily liquid; S3. Drop the colorless oily liquid obtained in step S2 into boiling water, perform condensation reflux, and finally obtain a homogeneous pale yellow liquid; wash the obtained homogeneous pale yellow solution with dichloromethane, and then perform rotary evaporation to remove the solvent water to obtain the intermediate 4-aza-cyclo-(3,4)-octane chloride salt; S4. Drop the intermediate obtained in step S3 into an aqueous solution containing ethanol and 50% HBF 4 to react at room temperature in a water bath to generate a crude product of 4-aza-cyclo-(3,4)-octane tetrafluoroborate.

[0008] Furthermore, the purification process of the crude product of 4-aza-cyclo-(3,4)-octane tetrafluoroborate in step S4 includes: S5. Add anhydrous ethanol to the mixed reaction system in step S4, perform rotary evaporation and azeotropic distillation to remove the HCl aqueous solution, and then filter while it is hot; recrystallize and purify the crude product of 4-aza-cyclo-(3,4)-octane tetrafluoroborate dissolved in ethanol, collect the crystals, and dry them under vacuum to obtain the refined 4-aza-cyclo-(3,4)-octane tetrafluoroborate.

[0009] Preferably, in step S1, the molar ratio of pyrrolidine to 1-bromo-3-chloropropane is 2:1, and the reaction time is 12 h.

[0010] Preferably, in step S3, 1 drop of the colorless oily liquid is added to 400 ml of boiling water, and the condensation reflux reaction is carried out for 30 min.

[0011] Preferably, in step S5, the addition amount of ethanol is 200 ml each time, and the azeotropic distillation to remove HCl is repeated 3 - 5 times.

[0012] The present invention also provides a spiro quaternary ammonium salt electrolyte solution, which is prepared by dropping a quantitative propylene carbonate solvent into the above spiro quaternary ammonium salt electrolyte, and the concentration of the spiro quaternary ammonium salt electrolyte solution is 1 mol / kg.

[0013] The advantages of the present invention are as follows: a novel electrolyte AP-BF 4 is provided. Due to its smaller ion size, it can improve the solvent accessibility and the pore utilization rate of the electrode material, enabling the supercapacitor to have a higher specific capacitance. At the same time, it can work stably at a high voltage of 3.2 V, maintain 91% of the capacity after 15,000 cycles, and has excellent cycle performance, and achieves a high energy density of 42.67 Wh / kg; the energy density of the supercapacitor is effectively improved, meeting the application requirements of the supercapacitor for high working voltage. Description of the Drawings

[0014] Figure 1 is AP-BF 4 1H NMR spectrum of electrolyte salt 1 1H NMR diagram; Figure 2 is AP-BF 4 Cyclic voltammogram curves of AP-BF / PC capacitor samples at different voltages; Figure 3 is AP-BF at a conventional voltage of 2.7 V 4 Galvanostatic charge-discharge curves of AP-BF / PC capacitor samples; Figure 4 is AP-BF at a high voltage of 3.0 V 4 Galvanostatic charge-discharge curves of AP-BF / PC capacitor samples; Figure 5 is AP-BF at a high voltage of 3.2 V 4 Galvanostatic charge-discharge curves of AP-BF / PC capacitor samples; Figure 6 is AP-BF 4 Rate curves of AP-BF / PC capacitor samples at a voltage of 3.2 V; Figure 7 is AP-BF 4 Long cycle curves of AP-BF / PC capacitor samples at a current density of 2 A / g for 15,000 cycles. Detailed Embodiments

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0016] A spiroquaternary ammonium salt for supercapacitors provided by the present invention, named 4-azacyclo-(3,4)-octane tetrafluoroborate (hereinafter referred to as AP-BF 4 ), has the following structural formula: .

[0017] This spiroquaternary ammonium salt structurally includes a symmetric ring structure up and down. Its cation is a heterocyclic compound containing four- and five-membered rings, with 1 nitrogen atom as the only ring heteroatom; the four-ring and five-ring are connected together through the N + functional group, and it is the smallest spiroquaternary ammonium salt electrolyte applied in supercapacitors; 4-azacyclo-(3,4)-octane tetrafluoroborate is dissolved in propylene carbonate (PC) solvent to obtain a supercapacitor electrolyte.

[0018] AP-BF 4 The model numbers of the equipment used in the preparation process and the information of the manufacturers are as follows: Electronic balance, model MS204S, METTLER TOLEDO, Switzerland; Constant temperature magnetic stirrer, model 85-2, Yuhua Co., Ltd., Gongyi, Henan; Numerical control ultrasonic cleaner, model KQ-300DB, Kunshan Ultrasonic Instrument Co., Ltd.; Electric thermostatic blast drying oven, model DHG-9070A, Shanghai Yiheng Scientific Instrument Co., Ltd.; Vacuum drying oven, model DFZ-6049, Shanghai Yiheng Scientific Instrument Co., Ltd.; Film punching machine, model SZ-50-18, Shenzhen Yongxingye Precision Machinery Mould Co., Ltd.; Glove box, model XY120-75-1, Shenzhen Yongxingye Precision Mould Co., Ltd.; Button cell sealer, model SY160, Shenzhen Yongxingye Precision Mould Co., Ltd.; Autolab electrochemical workstation, model PGSTAT 128N, Metrohm, Switzerland; Electrochemical analyzer, model CHI604E, Shanghai Chenhua Instrument Co., Ltd.; Nuclear magnetic resonance spectrometer, model Bruker Avance-500MHz, Bruker;

[0019] AP-BF 4 The reagent information used in the preparation process is as follows: Anhydrous ether (C 4 H 10 O), analytical pure, Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.; Anhydrous ethanol (C 2 H 6 O), analytical pure, Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.; 1-Bromo-3-chloropropane, analytical pure, Shanghai Macklin Biochemical Co., Ltd.; Pyrrolidine, analytical pure, Shanghai Macklin Biochemical Co., Ltd.; Dichloromethane, analytical pure, Tianjin Fengchuan Chemical Reagent Technology Co., Ltd.; 50% Aqueous solution of fluoboric acid, analytical pure, Shanghai Macklin Biochemical Co., Ltd.; High purity argon gas (Ar 2 ), purity 99.99%, Tianjin Huanyu Gas Co., Ltd.; TF40 diaphragm, battery grade, Nippon Kodo Co., Ltd. (NKK); Battery case, model CR2430, Shenzhen Yongxingye Precision Abrasives Co., Ltd.

[0020] The above-mentioned AP-BF 4 The preparation method includes: S1. Drop 1-bromo-3-chloropropane into the solution containing ether and pyrrolidine, and react at room temperature in a water bath to form a white precipitate; S2. Filter and separate the system after the reaction in step S1, filter the white precipitate to obtain a colorless transparent liquid; add 10% hydrochloric acid for extraction in the colorless transparent liquid, then add 20% NaOH solution to make it alkaline, wash with ether, and dry the obtained ether extract with anhydrous sodium sulfate to remove water, and then rotary evaporate to obtain a colorless oily liquid; S3. Drop the colorless oily liquid obtained in step S2 into boiling water, carry out condensation reflux, and finally obtain a homogeneous light yellow liquid; wash the obtained homogeneous light yellow solution with dichloromethane, and then rotary evaporate to remove the solvent water to obtain the intermediate 4-azacyclo-(3,4)-octane chloride salt (abbreviation: AP-Cl), for use; S4. Drop the AP-Cl obtained in step S3 into the aqueous solution containing ethanol and 50% HBF 4 , and react at room temperature in a water bath to form the crude product of AP-BF 4 ; S5. Add anhydrous ethanol to the mixed reaction system in step S4, rotary evaporate and azeotrope to remove the HCl aqueous solution, and then filter while it is hot; recrystallize and purify the crude product of AP-BF 4 dissolved in ethanol 3-5 times, collect the crystals, and vacuum dry to obtain the refined AP-BF 4 electrolyte salt.

[0021] Among them, the molar ratio of pyrrolidine to 1-bromo-3-chloropropane in step S1 is 2:1, and the reaction time is 12 h.

[0022] In step S3, drop 1 drop of the colorless oily liquid into 400 ml of boiling water, and carry out condensation reflux reaction for 30 min.

[0023] In step S5, the amount of ethanol added is 200 ml each time, and the azeotropic removal of HCl is repeated 3 times or more, preferably 3-5 times.

[0024] Perform nuclear magnetic resonance hydrogen spectrum test on the obtained refined AP-BF 4 electrolyte salt, and the test results are as Figure 1 shown.

[0025] Figure 1 It can be seen that using heavy water (D 2 O) as the solvent, AP-BF4 The electrolyte salt has the following characteristic peaks: 1 1H NMR (D 2 2O) δ: 4.20 ppm (t, 4H), δ: 3.49 ppm (t, 4H), δ: 2.50 ppm (m, 2H), δ: 1.97 (s, 4H); AP-BF 4 There are four hydrogens in different environments in the structure, and the ratio of their numbers is 2:2:2:1, which is consistent with the integral area ratio of the four characteristic peaks in the hydrogen spectrum, proving that the synthesis of the target product is correct. Moreover, there are no other impurity peaks in the spectrum, indicating that the synthesized AP-BF 4 electrolyte salt has a high purity.

[0026] AP-BF 4 Preparation of electrolyte solution and testing of electrochemical performance: Preparation of electrolyte solution: Take the prepared refined AP-BF 4 and place it in a vacuum oven at 80 °C for more than 24 h, then transfer it to a glove box filled with argon (H 2 2O ≤ 0.1 ppm, O 2 2 ≤ 0.1 ppm). Take a certain mass of AP-BF4 and add it to a sample bottle, then drop a quantitative amount of PC solvent, tighten the bottle cap, and shake the sample bottle until the electrolyte salt is completely dissolved to prepare an AP-BF 4 / PC electrolyte solution. Add 4 Å molecular sieve and let it stand for more than one week. During this period, use a Karl Fischer moisture tester to measure the water content in the electrolyte solution. The electrolyte solution can be used only when the water content is lower than 10 ppm.

[0027] Preparation of electrode sheets: Mix three components of activated carbon (YP-50F), conductive carbon black (Super P), and binder (PTFE) in a small beaker according to the mass ratio of 82:10:8. Drop anhydrous ethanol in small amounts and stir with a spatula until the slurry becomes like putty. Roll it into an electrode sheet with a thickness of 90 μm on a rolling machine. Finally, compound the electrode sheet with a coated aluminum foil current collector and roll it 2 - 3 times. After drying for 4 h, punch the electrode sheet into small round electrodes with a diameter of φ13 mm on a punching machine, and weigh them after placing them in a vacuum drying oven at 100 °C for 12 h for later use; Assembly of capacitor samples: The assembly process is carried out in a glove box filled with argon. Assemble in the order of negative electrode shell, electrode sheet, separator, electrode sheet, gasket, spring sheet, and positive electrode shell. Before assembly, 1 - 2 drops of electrolyte solution need to be dropped on the electrode sheet and the separator in advance for infiltration. Note that the electrode sheets should be symmetrically placed on both sides of the separator. Before installing the positive electrode shell, a few drops of electrolyte solution need to be dropped in the center of the spring sheet to ensure full infiltration of the internal electrolyte solution. After assembly, seal it on a sealing machine to obtain AP-BF 4 / PC button capacitors were subjected to electrochemical tests after being placed for 24 h.

[0028] Electrochemical performance test: Figure 2 For AP-BF 4 / PC capacitor samples, the cyclic voltammetry curves at different voltages show that AP-BF 4 can still maintain a good rectangular shape at a maximum voltage of 3.2 V.

[0029] Figure 3 , Figure 4 , Figure 5 are the galvanostatic charge-discharge curves of AP-BF 4 / PC capacitor samples at conventional voltage of 2.7 V, high voltages of 3.0 V and 3.2 V respectively; it can be seen that AP-BF 4 the galvanostatic charge-discharge curves of capacitor samples show a typical symmetric triangular shape, the curves have good linearity, hardly deform and have extremely small voltage drops.

[0030] Figure 6 For AP-BF 4 / PC capacitor samples, the rate curves at 3.2 V voltage; from Figure 6 it can be known that as the current density increases, a specific capacitance of 92 F / g can be provided at a current density of 10 A / g, and the capacity retention rate is 75.21%.

[0031] Figure 7 For AP-BF 4 / PC capacitor samples, the long cycle curves at a current density of 2 A / g for 15,000 cycles; from Figure 7 it can be seen that after repeating the cycle 15,000 times, AP-BF 4 / PC capacitor samples can still maintain 90.12% of the initial capacitance value, indicating that AP-BF 4 / PC electrolyte has excellent cycle performance.

[0032] It can be seen that the novel electrolyte AP-BF provided by the present invention 4 due to its smaller ion size, can improve the solvent accessibility and the pore utilization rate of electrode materials, enable the supercapacitor to have a higher specific capacitance, and at the same time can stably operate at a high voltage of 3.2 V, effectively improving the energy density of the supercapacitor.

[0033] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art of this patent, without departing from the scope of the technical solution of the present invention, can make some changes or modifications using the technical content prompted above as equivalent embodiments of equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the present invention's solution.

Claims

1. A spirocyclic quaternary ammonium salt electrolyte, characterized in that: The name is 4-azacyclo-(3,4)-octane tetrafluoroborate, and its cation is a heterocyclic compound containing four or five-membered rings, with a nitrogen atom as the only ring heteroatom, and the structural formula is as follows: 。 2. A method for preparing a spirocyclic quaternary ammonium salt electrolyte, characterized in that: The method for preparing the spirocyclic quaternary ammonium salt electrolyte according to claim 1 comprises the following steps: S1. Add 1-bromo-3-chloropropane dropwise to a solution containing ether and pyrrolidine, and react in a water bath at room temperature to generate a white precipitate; S2, filtering and separating the system after the reaction in step S1, filtering the white precipitate to obtain a colorless transparent liquid; adding dilute hydrochloric acid to the colorless transparent liquid for extraction, then adding a dilute NaOH solution to make it alkaline, washing with ether, and drying the obtained ether extract with anhydrous sodium sulfate to remove water, and then rotary evaporating to obtain a colorless oily liquid; S3, adding the colorless oily liquid obtained in step S2 dropwise into boiling water, condensing and refluxing, and finally obtaining a homogeneous light yellow liquid; washing the homogeneous light yellow solution with dichloromethane, and then removing the solvent water by rotary evaporation to obtain the intermediate chlorinated 4-azaheterocyclic-(3,4)-octane salt; S4. Add the intermediate obtained in step S3 dropwise to an aqueous solution containing ethanol and 50% HBF4, and react in a water bath at room temperature to generate a crude product of 4-azacyclo-(3,4)-octane tetrafluoroborate.

3. The method for preparing the spirocyclic quaternary ammonium salt electrolyte according to claim 2, characterized in that: The purification process of the crude product of 4-azacyclo-(3,4)-octane tetrafluoroborate in step S4 comprises: S5. Add anhydrous ethanol to the mixed reaction system in step S4, remove the HCL aqueous solution by rotary evaporation, and then filter while hot; recrystallize and purify the crude product of 4-azacyclic-(3,4)-octane tetrafluoroborate dissolved in ethanol, collect the crystals, and vacuum dry to obtain refined 4-azacyclic-(3,4)-octane tetrafluoroborate.

4. The method for preparing a spirocyclic quaternary ammonium salt electrolyte according to claim 2, wherein: In step S1, the molar ratio of pyrrolidine to 1-bromo-3-chloropropane is 2:1, and the reaction time is 12 h.

5. The method for preparing the spirocyclic quaternary ammonium salt electrolyte according to claim 2, characterized in that: In step S3, 1 drop of colorless oily liquid is added into 400 ml of boiling water, and the mixture is condensed and refluxed for 30 minutes.

6. The method for preparing the spirocyclic quaternary ammonium salt electrolyte according to claim 3, characterized in that In step S5, the amount of ethanol added is 200 ml each time, and the azeotropic removal of HCL is repeated 3-5 times.

7. A spirocyclic quaternary ammonium salt electrolyte, characterized in that: The method is prepared by adding a certain amount of propylene carbonate solvent to the spirocyclic quaternary ammonium salt electrolyte in claim 1, and the concentration of the spirocyclic quaternary ammonium salt electrolyte is 1 mol / kg.

Images