Super capacitor electrolyte and super capacitor
By using the composite salt of tetrafluoroborate quaternary ammonium salt of difluorooxalic acid quaternary ammonium salt and acryl-1,3-sulfonate or 1,4-butansulfonate lactone as additives in the supercapacitor electrolyte solution, the concentration ratio and total concentration of the electrolyte salt are adjusted, and the efficiency reduction and safety risks of supercapacitors in high temperature environments are solved, and its high temperature performance and safety are significantly improved.
Patent Information
- Application Number
- CN202311719119.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-14
- Publication Date
- 2025-06-17
AI Technical Summary
When supercapacitors are used in high temperature environments, their internal resistance increases, their capacity is attenuated, their efficiency decreases, and there is a risk of combustion or explosion, which affects their safety and service life.
An electrolyte salt including tetrafluoroborate quaternary ammonium salt and difluoroxalic acid quaternary ammonium salt, as well as a supercapacitor electrolyte with acryl-1,3-sulfonate or 1,4-butansulfonate lactone as additives is used to adjust the molar concentration ratio and total concentration of the electrolyte salt to improve the high temperature performance of the electrolyte solution.
It significantly improves the high-temperature performance of the supercapacitor, reduces the DC internal resistance growth rate, enhances the thermal stability and safety of the electrolyte, and extends the service life of the supercapacitor.
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Abstract
Description
Technical Field
[0001] The present invention relates to an electrolyte for a supercapacitor and a supercapacitor. Background Art
[0002] Supercapacitors have the advantages of environmental friendliness, high stability, safety, and the ability to achieve rapid charge and discharge. Therefore, supercapacitors are widely used in various industries, such as starting power in internal combustion engines, aerospace, and auxiliary power sources for solar cells. In actual applications, supercapacitors often encounter situations of use in high-temperature environments or long-term high-power charge and discharge, so higher requirements are put forward for the high-temperature performance of supercapacitors.
[0003] When working in a high-temperature environment, the internal resistance of the supercapacitor will increase and the capacitance will decay, resulting in a decrease in the efficiency of the supercapacitor. Moreover, the power (energy) loss generated by the DC internal resistance will be converted into heat, causing a large amount of heat to be generated inside the supercapacitor. When the temperature is too high and the heat cannot be dissipated, there will be risks such as combustion or explosion of the supercapacitor, endangering the use of the supercapacitor.
[0004] Therefore, developing more electrolytes that can improve the high-temperature performance of supercapacitors and reduce the growth rate of internal resistance is still the focus of current supercapacitor research. Summary of the Invention
[0005] The purpose of the present invention is to provide an electrolyte that can improve the high-temperature performance of a supercapacitor and reduce the growth rate of DC internal resistance.
[0006] To achieve the above object, the technical solution adopted by the present invention is:
[0007] An electrolyte for a supercapacitor, which comprises an organic solvent, an electrolyte salt, and an additive. The electrolyte salt comprises a quaternary ammonium tetrafluoroborate and a quaternary ammonium difluorooxalate borate, and the additive is allyl-1,3-sultone and / or 1,4-butane sultone.
[0008] Preferably, the molar concentration ratio of the quaternary ammonium tetrafluoroborate to the quaternary ammonium difluorooxalate borate in the electrolyte for the supercapacitor is (1-6):1, and the total concentration of the quaternary ammonium tetrafluoroborate and the quaternary ammonium difluorooxalate borate in the electrolyte is 0.8-1.7 mol / L, which can more significantly improve the high-temperature performance of the supercapacitor.
[0009] More preferably, the molar concentration ratio of the quaternary ammonium tetrafluoroborate to the quaternary ammonium difluorooxalate borate in the electrolyte for the supercapacitor is (1.5-4):1, and the total concentration of the quaternary ammonium tetrafluoroborate and the quaternary ammonium difluorooxalate borate in the electrolyte is 1.0-1.5 mol / L.
[0010] Still more preferably, the molar concentration ratio of the quaternary ammonium tetrafluoroborate and the quaternary ammonium difluorooxaloborate in the supercapacitor electrolyte is (2-3):1, and the total concentration of the quaternary ammonium tetrafluoroborate and the quaternary ammonium difluorooxaloborate in the electrolyte is 1.1-1.3 mol / L.
[0011] Through actual data measurement, it is found that at the selected ratio, when the electrolyte concentration is lower than 0.8 mol / L, the conductivity of the electrolyte will decrease, thereby reducing the high-temperature performance of the electrolyte; when the electrolyte concentration is higher than 1.7 mol / L, the viscosity of the electrolyte will increase and the conductivity will decrease, thereby reducing the high-temperature performance of the electrolyte.
[0012] More preferably, the concentration of the quaternary ammonium tetrafluoroborate in the electrolyte is 0.6-1.4 mol / L.
[0013] More preferably, the concentration of the quaternary ammonium difluorooxaloborate in the electrolyte is 0.2-0.6 mol / L.
[0014] Preferably, the quaternary ammonium tetrafluoroborate is N,N-dimethylpyrrolidinium tetrafluoroborate.
[0015] Preferably, the quaternary ammonium difluorooxaloborate is N,N-dimethylpyrrolidinium difluorooxaloborate and / or 1-ethyl-1-methylpyrrolidinium difluorooxaloborate.
[0016] Preferably, the electrolyte salt is composed of quaternary ammonium tetrafluoroborate and quaternary ammonium difluorooxaloborate.
[0017] Preferably, the organic solvent is one or a combination of more of acetonitrile, propylene carbonate, γ-butyrolactone, sulfolane, 3-methoxypropionitrile, and dimethyl sulfoxide.
[0018] More preferably, the organic solvent is a combination of propylene carbonate, sulfolane, and dimethyl sulfoxide.
[0019] Still more preferably, the mass ratio of propylene carbonate, sulfolane, and dimethyl sulfoxide is (6-10):(0.8-1.5):1.
[0020] More preferably, the organic solvent is a combination of acetonitrile, γ-butyrolactone, and 3-methoxypropionitrile.
[0021] Still more preferably, the mass ratio of acetonitrile, γ-butyrolactone, and 3-methoxypropionitrile is (4-8):(1-3):1.
[0022] Preferably, the additive is 1%-10% of the total mass of the supercapacitor electrolyte, more preferably 1%-6%, and still more preferably 2%-5%.
[0023] The present invention also provides a supercapacitor, and the supercapacitor includes the above-mentioned supercapacitor electrolyte solution.
[0024] Preferably, the supercapacitor is an electric double layer supercapacitor, and the electrodes of the supercapacitor are activated carbon porous electrodes.
[0025] The electric double layer supercapacitor is a symmetric supercapacitor, and both electrodes are activated carbon porous electrodes.
[0026] The composite electrolyte salt used in the present invention has a more stable chemical structure compared with ordinary quaternary ammonium salts. In terms of performance, it combines the advantages of bis(oxalato)borate (BOB) and tetrafluoroborate (BF4) at the same time, which can make the electrode liquid system have higher thermal stability and lower impedance. The additives used in the present invention can effectively increase the initial boiling point of the electrolyte solution, and avoid situations such as gas generation, expansion, and rupture when the supercapacitor works in a high-temperature environment. Through their combined use and the adjustment of the dosage ratio, the high-temperature resistance and safety of the supercapacitor are significantly improved.
[0027] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:
[0028] The present invention combines the electrolyte salt formed by the compounding of quaternary ammonium tetrafluoroborate and quaternary ammonium difluorooxalate borate with allyl-1,3-sulfonic acid lactone or 1,4-butane sulfonic acid lactone as an additive, which improves the initial capacity of the supercapacitor and significantly improves the high-temperature performance of the supercapacitor. The electrolyte solution of the present invention can broaden the application of the supercapacitor in a high-temperature environment. Specific Embodiments
[0029] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in this industry.
[0030] In the following examples and comparative examples, N,N-dimethylpyrrolidinium tetrafluoroborate was purchased from Hangzhou Feiman Fine Chemical Co., Ltd., with the brand name DMP-BF4 and the batch number 23071701.
[0031] N,N-dimethylpyrrolidinium difluorooxalate borate was prepared by the method of Example 1 of Patent CN115724805A.
[0032] 1-Ethyl-1-methylpyrrolidinium difluorooxalate borate is synthesized in the laboratory. The specific synthesis method is as follows: Weigh 93.5 g of 1-methylpyrrolidine and dilute it in 84 g of acetonitrile. Weigh 118.8 g of bromoethane and dilute it in 84 g of acetonitrile. Pour the acetonitrile solution of 1-methylpyrrolidine into the reaction kettle, start stirring, and then slowly add the acetonitrile solution of bromoethane. The reaction is carried out at 25 °C for 2 hours. After the reaction temperature drops to room temperature, add 121 g of sodium tetrafluoroborate and stir continuously for 4 hours. Filter the mixture in the reaction kettle, collect the filtrate, and evaporate the filtrate to dryness to obtain the intermediate product.
[0033] Add the above intermediate product, 90 g of anhydrous oxalic acid and an appropriate amount of acetonitrile into the reaction kettle. After heating to 60 °C, it is completely dissolved. Slowly add 129 g of dichlorodimethylsilane into the reaction kettle, control the temperature at 60 °C, and the reaction time is 7 h. After the reaction is complete, vacuum concentrate to obtain the crude product. After washing with toluene, it is purified by methanol crystallization. Then, it is filtered under reduced pressure to obtain the wet product. Finally, it is dried under vacuum to obtain the qualified product, and its structural formula is:
[0034]
[0035] In the following examples and comparative examples, reagents without special instructions are obtained commercially.
[0036] The technical solutions of the present invention are further described below through examples and comparative examples.
[0037] Example 1
[0038] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0039] Step 1: Dehydrate the organic solvent (formed by mixing acetonitrile and γ-butyrolactone in a mass ratio of 55:45) with 3A molecular sieve until the water content is less than 10 ppm, and vacuum dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate borate) until the water content is less than 50 ppm.
[0040] Step 2: In a glove box with a water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.6 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.3 mol / L of N,N-dimethylpyrrolidinium difluorooxalate borate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0041] Step 3: Add 6 wt% of 1,4-butanesultone to the basic electrolyte and stir evenly to obtain the final supercapacitor electrolyte.
[0042] Example 2
[0043] This embodiment provides a supercapacitor electrolyte, and its preparation method is as follows:
[0044] Step 1: Use 3A molecular sieve to dehydrate the organic solvent (formed by mixing acetonitrile and propylene carbonate in a mass ratio of 30:70) until the water content is less than 10 ppm, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate borate) until the water content is less than 50 ppm.
[0045] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.6 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.4 mol / L of N,N-dimethylpyrrolidinium difluorooxalate borate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0046] Step 3: Add 6 wt% of allyl-1,3-sultone to the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0047] Example 3
[0048] This embodiment provides a supercapacitor electrolyte, and its preparation method is as follows:
[0049] Step 1: Use 3A molecular sieve to dehydrate the organic solvent (formed by mixing propylene carbonate, sulfolane, and dimethyl sulfoxide in a mass ratio of 50:40:10) until the water content is less than 10 ppm, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and 1-ethyl-1-methylpyrrolidinium difluorooxalate borate) until the water content is less than 50 ppm.
[0050] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.7 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.3 mol / L of 1-ethyl-1-methylpyrrolidinium difluorooxalate borate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0051] Step 3: Add 5 wt% of allyl-1,3-sultone to the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0052] Example 4
[0053] This embodiment provides a supercapacitor electrolyte, and its preparation method is as follows:
[0054] Step 1: Dehydrate the organic solvent (formed by mixing propylene carbonate, sulfolane, and 3-methoxypropionitrile in a mass ratio of 60:20:20) with 3A molecular sieve until the water content is less than 10 ppm, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate borate) until the water content is less than 50 ppm.
[0055] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.8 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.5 mol / L of N,N-dimethylpyrrolidinium difluorooxalate borate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0056] Step 3: Add 5 wt% of allyl-1,3-sultone to the basic electrolyte and stir evenly to obtain the final supercapacitor electrolyte.
[0057] Example 5
[0058] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0059] Step 1: Dehydrate the organic solvent (formed by mixing propylene carbonate, sulfolane, and dimethyl sulfoxide in a mass ratio of 80:10:10) with 3A molecular sieve until the water content is less than 10 ppm, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate borate) until the water content is less than 50 ppm.
[0060] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.8 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.4 mol / L of N,N-dimethylpyrrolidinium difluorooxalate borate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0061] Step 3: Add 5 wt% of allyl-1,3-sultone to the basic electrolyte and stir evenly to obtain the final supercapacitor electrolyte.
[0062] Example 6
[0063] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0064] Step 1: Dehydrate the organic solvent (formed by mixing acetonitrile, γ-butyrolactone, and 3-methoxypropionitrile in a mass ratio of 50:30:20) with 3A molecular sieve until the water content is less than 10 ppm, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and 1-ethyl-1-methylpyrrolidinium difluorooxalate) until the water content is less than 50 ppm.
[0065] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 1 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.5 mol / L of 1-ethyl-1-methylpyrrolidinium difluorooxalate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0066] Step 3: Add 4 wt% of 1,4-butanesultone to the basic electrolyte and stir evenly to obtain the final supercapacitor electrolyte.
[0067] Example 7
[0068] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0069] Step 1: Dehydrate the organic solvent (formed by mixing acetonitrile, sulfolane, and 3-methoxypropionitrile in a mass ratio of 50:30:20) with 3A molecular sieve until the water content is less than 10 ppm, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and 1-ethyl-1-methylpyrrolidinium difluorooxalate) until the water content is less than 50 ppm.
[0070] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.9 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.3 mol / L of 1-ethyl-1-methylpyrrolidinium difluorooxalate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0071] Step 3: Add 4 wt% of allyl-1,3-sultone to the basic electrolyte and stir evenly to obtain the final supercapacitor electrolyte.
[0072] Example 8
[0073] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0074] Step 1: Dehydrate the organic solvent (formed by mixing acetonitrile, sulfolane, and dimethyl sulfoxide in a mass ratio of 50:30:20) with 3A molecular sieve until the water content is less than 10 ppm, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate borate) until the water content is less than 50 ppm.
[0075] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.9 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.3 mol / L of N,N-dimethylpyrrolidinium difluorooxalate borate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0076] Step 3: Add 4 wt% of allyl-1,3-sultone to the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0077] Example 9
[0078] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0079] Step 1: Dehydrate the organic solvent (formed by mixing propylene carbonate, sulfolane, and 3-methoxypropionitrile in a mass ratio of 40:30:30) with 3A molecular sieve until the water content is less than 10 ppm, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate borate) until the water content is less than 50 ppm.
[0080] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 1.2 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.4 mol / L of N,N-dimethylpyrrolidinium difluorooxalate borate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0081] Step 3: Add 5 wt% of 1,4-butanesultone to the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0082] Example 10
[0083] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0084] Step 1: Dehydrate the organic solvent (formed by mixing acetonitrile, γ-butyrolactone, and 3-methoxypropionitrile in a mass ratio of 60:30:10) to a water content of less than 10 ppm using 3A molecular sieve, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and 1-ethyl-1-methylpyrrolidinium difluorooxalate) to a water content of less than 50 ppm.
[0085] Step 2: In a glove box with water and oxygen contents below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.9 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.3 mol / L of 1-ethyl-1-methylpyrrolidinium difluorooxalate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0086] Step 3: Add 5 wt% of allyl-1,3-sultone to the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0087] Example 11
[0088] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0089] Step 1: Dehydrate the organic solvent (formed by mixing propylene carbonate and sulfolane in a mass ratio of 80:20) to a water content of less than 10 ppm using 3A molecular sieve, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate) to a water content of less than 50 ppm.
[0090] Step 2: In a glove box with water and oxygen contents below 2 ppm (dew point -70 °C), add the organic solvent to a volumetric flask, and add 0.8 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.3 mol / L of N,N-dimethylpyrrolidinium difluorooxalate to the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0091] Step 3: Add 3 wt% of allyl-1,3-sultone to the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0092] Example 12
[0093] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0094] Step 1: Dehydrate the organic solvent (propylene carbonate) to a water content of less than 10 ppm using 3A molecular sieve, and vacuum-dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and 1-ethyl-1-methylpyrrolidinium difluorooxalate) to a water content of less than 50 ppm.
[0095] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add an organic solvent into a volumetric flask, and add 1.0 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.3 mol / L of 1-ethyl-1-methylpyrrolidinium difluorooxalate borate into the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0096] Step 3: Add 3 wt% of allyl-1,3-sultone into the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0097] Example 13
[0098] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0099] Step 1: Dehydrate the organic solvent (acetonitrile) with 3A molecular sieve to make the water content less than 10 ppm, and vacuum dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate borate) to make the water content less than 50 ppm.
[0100] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add an organic solvent into a volumetric flask, and add 1.1 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.2 mol / L of N,N-dimethylpyrrolidinium difluorooxalate borate into the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0101] Step 3: Add 5 wt% of allyl-1,3-sultone into the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0102] Example 14
[0103] This example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0104] Step 1: Dehydrate the organic solvent (acetonitrile, γ-butyrolactone, sulfolane in a mass ratio of 60:20:20) with 3A molecular sieve to make the water content less than 10 ppm, and vacuum dry the electrolyte salts (N,N-dimethylpyrrolidinium tetrafluoroborate and N,N-dimethylpyrrolidinium difluorooxalate borate) to make the water content less than 50 ppm.
[0105] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add an organic solvent into a volumetric flask, and add 1.3 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.5 mol / L of N,N-dimethylpyrrolidinium difluorooxalate borate into the organic solvent, and stir to form a homogeneous liquid as the basic electrolyte.
[0106] Step 3: Add 5 wt% of allyl-1,3-sultone into the basic electrolyte, and stir evenly to obtain the final supercapacitor electrolyte.
[0107] Comparative Example 1
[0108] This comparative example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0109] Step 1: Dehydrate the organic solvent (propylene carbonate, sulfolane in a mass ratio of 80:20) to a water content of less than 10 ppm with 3A molecular sieve, and vacuum dry the electrolyte salt (N,N-dimethylpyrrolidinium tetrafluoroborate) to a water content of less than 50 ppm.
[0110] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add an organic solvent into a volumetric flask, and add 1.2 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate into the organic solvent, and stir evenly to obtain the final supercapacitor electrolyte.
[0111] Comparative Example 2
[0112] This comparative example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0113] Step 1: Dehydrate the organic solvent (acetonitrile, γ-butyrolactone, sulfolane in a mass ratio of 60:20:20) to a water content of less than 10 ppm with 3A molecular sieve, and vacuum dry the electrolyte salt (N,N-dimethylpyrrolidinium tetrafluoroborate) to a water content of less than 50 ppm.
[0114] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add an organic solvent into a volumetric flask, and add 1.2 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate into the organic solvent, and stir evenly to obtain the final supercapacitor electrolyte.
[0115] Comparative Example 3
[0116] This comparative example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0117] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add an organic solvent into a volumetric flask, and add 1.2 mol / L of 5,5-spirobipyrrolidinium tetrafluoroborate (SBP-BF4) into the organic solvent, and stir evenly to obtain the final supercapacitor electrolyte.
[0118] Comparative Example 4
[0119] This comparative example provides a supercapacitor electrolyte, and its preparation method is as follows:
[0120] Step 1: Dehydrate an organic solvent (propylene carbonate, sulfolane, dimethyl sulfoxide in a mass ratio of 50:40:10) to less than 10 ppm of water with 3A molecular sieve, and vacuum dry the electrolyte salt (N,N-dimethylpyrrolidinium tetrafluoroborate) to less than 50 ppm of water.
[0121] Step 2: In a glove box with water and oxygen content below 2 ppm (dew point -70 °C), add an organic solvent into a volumetric flask, and add 0.5 mol / L of N,N-dimethylpyrrolidinium tetrafluoroborate and 0.2 mol / L of 1-ethyl-1-methylpyrrolidinium difluorooxalate borate into the organic solvent, and stir evenly to obtain the final supercapacitor electrolyte.
[0122] In an environment with water and oxygen content below 2 ppm (dew point -70 °C), inject the supercapacitor electrolytes of the above Examples 1-14 and Comparative Examples 1-4 into the 25F supercapacitor housing respectively to make the final supercapacitors. The supercapacitors used are cylindrical supercapacitors (cylindrical, diameter 1.5 cm, height 3.0 cm). The supercapacitor electrode material is composed of activated carbon, acetylene black, and binder in a mass ratio of 8:1:1, with a thickness of 300 μm. The activated carbon material is coated on the aluminum foil by a film rolling process to make the supercapacitor electrode, and the designed capacity is 25F. The activated carbon is purchased from Kureha Corporation, Japan, model: YP-50F; the acetylene black is purchased from Shenzhen Kejing Zhida Technology Co., Ltd., model: EQ-Lib-AB; the binder is PTFE (polytetrafluoroethylene), purchased from Shenzhen Kejing Zhida Technology Co., Ltd., model: EQ-Lib-PTFE. Test the high-temperature aging performance and DC internal resistance of each supercapacitor on a battery test cabinet. 10 groups of supercapacitors are prepared for testing in each example and comparative example.
[0123] The high-temperature aging and internal resistance test method is as follows: Taking the supercapacitor prepared with the supercapacitor electrolyte of Example 1 as an example, 10 groups of supercapacitors are respectively placed in a high-temperature chamber, and parameters are set on the battery test cabinet. The voltage range is 0.1 - 2.85V, and the discharge current is 1875mA. After charging and discharging cycles for 25 weeks at room temperature of 25°C, the discharge capacity of each group of supercapacitors is tested, and the average value is recorded as the initial discharge capacity at 25°C; the DC internal resistance of each group of supercapacitors is tested, and the average value is recorded as the initial DC internal resistance at 25°C. Then the high-temperature chamber is heated to 85°C, and constant voltage charging is carried out at 2.85V at 85°C. After 1800 hours, the temperature of the high-temperature chamber is lowered to room temperature of 25°C and maintained for 24 hours. Then parameters are set on the battery test cabinet, the voltage range is 0.1 - 2.85V, and the discharge current is 1875mA. After the supercapacitors are charged and discharged in cycles for 25 weeks, the discharge capacity of each group of supercapacitors is tested, and the average value is recorded as the discharge capacity after constant voltage at 85°C for 1800 hours; the DC internal resistance of each group of supercapacitors is tested, and the average value is recorded as the DC internal resistance after constant voltage at 85°C for 1800 hours. The high-temperature aging data are shown in Table 1, and the DC internal resistance data are shown in Table 2.
[0124] Table 1
[0125]
[0126] Table 2
[0127]
[0128]
[0129] As can be seen from Table 1 and Table 2, the electrolyte salt formed by compounding quaternary ammonium tetrafluoroborate and quaternary ammonium difluorooxalate, and the electrolyte using allyl-1,3-sulfonic acid lactone or 1,4-butane sulfonic acid lactone as an additive can improve the initial capacity of the supercapacitor and significantly improve the high-temperature performance of the supercapacitor.
[0130] Tables 1 and 2 show that when using a composite salt of quaternary ammonium tetrafluoroborate and quaternary ammonium difluorooxaloborate as the electrolyte and using allyl-1,3-sultone or 1,4-butanesultone as the additive, for a combination of one or more of organic solvents such as acetonitrile, propylene carbonate, γ-butyrolactone, sulfolane, 3-methoxypropionitrile and dimethyl sulfoxide, the high-temperature performance of the supercapacitor can be significantly improved. When the concentration ratio of quaternary ammonium tetrafluoroborate and quaternary ammonium difluorooxaloborate is controlled at (1-6):1 and the total concentration of the electrolyte salt in the electrolyte is controlled at 0.8-1.7 mol / L, the improvement of the high-temperature performance of the supercapacitor is more obvious. The high-temperature capacity retention rate and the growth rate of the high-temperature internal resistance of some more preferred electrolytes are significantly better than those of the current mainstream electrolytes in the market. For example, the initial discharge capacities of Example 5 and Example 10 are higher than the designed capacity by 3-4 F. After accelerating aging for 1800 hours at 85 °C, the capacity retention rates are as high as 85.92% and 85.83% respectively, while the growth rates of the internal resistance are only 227% and 263% respectively (relative to the initial value at 25 °C).
[0131] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims
1. A supercapacitor electrolyte, which comprises an organic solvent, an electrolyte salt and an additive, and is characterized in that, The electrolyte salt includes quaternary ammonium tetrafluoroborate and quaternary ammonium difluorooxaloborate, and the additive is allyl-1,3-sultone and / or 1,4-butanesultone.
2. The supercapacitor electrolyte according to claim 1, characterized in that, The molar concentration ratio of the quaternary ammonium tetrafluoroborate and the quaternary ammonium difluorooxaloborate in the supercapacitor electrolyte is (1-6):1, and the total concentration of the quaternary ammonium tetrafluoroborate and the quaternary ammonium difluorooxaloborate in the electrolyte is 0.8-1.7 mol / L.
3. The supercapacitor electrolyte according to claim 2, characterized in that, The concentration of the quaternary ammonium tetrafluoroborate in the electrolyte is 0.6-1.4 mol / L.
4. The supercapacitor electrolyte according to claim 2, characterized in that, The concentration of the quaternary ammonium difluorooxaloborate in the electrolyte is 0.2-0.6 mol / L.
5. The supercapacitor electrolyte according to claim 1, characterized in that, The quaternary ammonium tetrafluoroborate is N,N-dimethylpyrrolidinium tetrafluoroborate.
6. The supercapacitor electrolyte according to claim 1, characterized in that, The quaternary ammonium difluorooxaloborate is N,N-dimethylpyrrolidinium difluorooxaloborate and / or 1-ethyl-1-methylpyrrolidinium difluorooxaloborate.
7. The supercapacitor electrolyte according to claim 1, characterized in that, The electrolyte salt consists of quaternary ammonium tetrafluoroborate and quaternary ammonium difluorooxaloborate.
8. The supercapacitor electrolyte according to claim 1, characterized in that, The organic solvent is one or a combination of more of acetonitrile, propylene carbonate, γ-butyrolactone, sulfolane, 3-methoxypropionitrile, dimethyl sulfoxide; and / or, the additive is 1%-10% of the total mass of the supercapacitor electrolyte.
9. A supercapacitor, characterized in that, The supercapacitor includes the supercapacitor electrolyte described in any one of claims 1 to 8.
10. The supercapacitor according to claim 9, characterized in that, The supercapacitor is an electric double layer supercapacitor, and the electrodes of the supercapacitor are activated carbon porous electrodes.