WO2018058837A1

WO2018058837A1 - Organic electrolyte solution for super capacitor, and super capacitor

Info

Publication number: WO2018058837A1
Application number: PCT/CN2016/113054
Authority: WO
Inventors: 石桥; 向晓霞
Original assignee: 深圳新宙邦科技股份有限公司
Priority date: 2016-09-29
Filing date: 2016-12-29
Publication date: 2018-04-05
Also published as: CN107887176A; CN107887176B

Abstract

An organic electrolyte solution for a super capacitor, and a super capacitor. The organic electrolyte solution comprises an organic electrolyte, a proton inert solvent, and an additive. A cation of the organic electrolyte is an N,N-dimethylpyrrolidine cation, and an anion is at least one of a tetrafluoroborate ion, a hexafluorophosphate ion, a bis(trifluoromethylsulfonate) ion, and a bis(fluorosulfonate) ion. The additive is selected from at least one of compounds represented by formula (1) below, wherein one to three of R₁-R₆ are fluorine-containing alkyl groups or fluorine, and the rest are alkyl groups having 1 to 5 carbon atoms or hydrogen. The organic electrolyte solution has good wettability, high conductivity, and high decomposition voltage.

Description

Organic electrolyte and super capacitor for super capacitor

Technical field

The present invention relates to the field of electrochemistry, and in particular to an organic electrolyte for a supercapacitor and a supercapacitor using the organic electrolyte.

Background technique

Supercapacitors, also known as gold capacitors, electrochemical capacitors, use ion adsorption (electric double layer capacitors) or surface rapid redox reactions (tantalum capacitors) to store energy. A supercapacitor is a new type of energy storage device between a battery and a conventional electrostatic capacitor. Supercapacitors store hundreds or thousands of times the charge of traditional solid electrolytic capacitors. They can be fully charged and discharged in seconds, have higher power input and output than batteries, and can be reached in less time. At the same time, supercapacitors have the advantages of short charge and discharge time, long storage life, high stability, wide operating temperature range (-40 ° C ~ 70 ° C), etc., so they are widely used in the field of consumer electronics, new energy power generation systems, distribution Energy storage systems, smart distributed power grid systems, new energy vehicles and other transportation fields, energy-saving elevator cranes and other load fields, electromagnetic bombs and other military equipment fields and motion control areas, involving new energy generation, smart grid, new energy vehicles Various industries such as energy-saving buildings and industrial energy-saving and emission reduction are standard full-scale low-carbon economic core products.

As one of the most promising energy storage devices in the field of new energy, supercapacitors have become one of the hotspots in the interdisciplinary fields of materials, power, physics and chemistry in the United States, Japan, South Korea and Russia. The main research objective is to prepare electrode materials with excellent performance and low cost; and electrolyte system materials with high conductivity, good chemical and thermal stability, high working voltage (electrochemical stability window width), and high energy density on this basis. High-capacitance and long-life supercapacitor energy storage devices for various electric hybrid vehicle hybrid systems and backup power supplies for electronic equipment.

Since propylene carbonate and acetonitrile have good electrochemical and chemical stability and good solubility to organic quaternary ammonium salts, they are widely used in electrolyte systems of supercapacitors. Commercially available supercapacitor electrolytes are mainly acetonitrile (AN) or propylene carbonate (PC) of tetraethylammonium tetrafluoroborate (Et ₄ NBF ₄ ) or methyltriethylammonium tetrafluoroborate (Et ₃ MeNBF ₄ ). )The solution. The upper limit of the AN system supercapacitor is only 2.7V, and the operating temperature range is -40°C to 65°C; the upper limit of the PC system supercapacitor is only 2.5V, and the operating temperature range is -40°C to 70°C. With the development of the over-capacity market, in order to improve safety and increase market competitiveness, the current conventional electrolyte can no longer meet the customer's requirements for high temperature and high pressure resistance of supercapacitors. Conventional electrolytes operating at high voltages and high temperatures can cause electrochemical decomposition of the electrolyte, resulting in a significant increase in pressure within the capacitor, a significant decrease in electrochemical performance, and ultimately failure of the capacitor. Therefore, sulfolane is gradually applied to the electrolyte system of supercapacitors, but the freezing point of sulfolane is high, it is difficult to use at room temperature, and the electrolyte of sulfolane alone is solidified at -20 ° C, and the supercapacitor prepared by the same is not -20 ° C. With charge and discharge performance.

The wettability of the electrolyte is a key factor affecting the quality of the core impregnation during the preparation process of the supercapacitor. The solvent systems currently used in commercialization are AN systems, PC systems, sulfolane systems, and mixtures thereof. Since the viscosity of AN is small, the AN system electrolyte generally does not have the problem of impregnation; the viscosity of the PC system electrolyte is larger than that of the AN system, so the impregnation time of the PC system electrolyte is generally longer than that of the AN system. The viscosity of the sulfolane system electrolyte is obviously increased, which can reach 3-5 times of the electrolyte of the PC system, so the problem of impregnation is particularly obvious. Under normal circumstances, the vacuuming process can significantly shorten the impregnation time of the cell, but the long-time vacuum process has the concern that the electrolyte composition changes greatly and the electrolyte moisture index exceeds the standard. Therefore, the supercapacitor manufacturer hopes to improve. Difficulty in impregnation caused by the properties of the electrolyte itself.

In order to pursue a high voltage of 3.0V and above, we found that the N,N-dimethylpyrrolidine cation electrolyte salt has excellent high voltage performance (see Patent 104979102A), but contains N,N-dimethylpyrrolidine cation electrolyte salt. The electrolyte still has a problem of poor wettability.

Summary of the invention

The invention provides an organic electrolyte for a supercapacitor, which comprises an additive capable of improving the wettability of the electrolyte, has the advantages of high electrical conductivity and high decomposition voltage, and provides a use of the organic electricity. Decomposed supercapacitor.

According to a first aspect of the present invention, there is provided an organic electrolyte for a supercapacitor comprising an organic electrolyte, an aprotic solvent and an additive, wherein the cation of the organic electrolyte is an N,N-dimethylpyrrolidine cation;

The anion of the above organic electrolyte is tetrafluoroborate ion (BF ₄ ^- ), hexafluorophosphate ion (PF ₆ ^- ), bis(trifluoromethylsulfonyl) ion (CF ₃ SO ₂ ) ₂ ^- , double ( At least one of fluorosulfonyl) ions;

The above additive is at least one selected from the group consisting of the compounds represented by the following formula (1):

Among them, 1 to 3 of R ₁ to R ₆ are fluorine-containing alkyl groups or fluorine; the others are alkyl groups having 1 to 5 carbon atoms or hydrogen.

As a further improvement, the above additives account for 0.1% by weight to 3% by weight based on the total mass of the above organic electrolytic solution.

As a further improvement, the concentration of the organic electrolyte in the organic electrolyte solution is 0.5 to 3.0 mol/L.

As a further improvement, the concentration of the organic electrolyte in the above organic electrolytic solution is 0.8 to 2 mol/L.

As a further improvement, the above additive is at least one of fluorobenzene and 1,2,3-trifluorobenzene.

As a further improvement, the above aprotic solvent is acetonitrile, propylene carbonate, sulfolane, dimethyl sulfone, dimethyl sulfoxide, γ-butyrolactone, propionitrile, methoxypropionitrile, γ-valerolactone. And one or a mixture of two or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

As a further improvement, the above aprotic solvent is acetonitrile, propylene carbonate, γ-butyrolactone, a mixture of sulfolane and dimethyl sulfone, a mixture of sulfolane and acetonitrile, or a mixture of sulfolane and ethyl methyl carbonate.

According to a second aspect of the present invention, there is provided a supercapacitor comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an organic electrolytic solution, the organic electrolytic solution being the organic electrolytic solution according to the first aspect.

As a further improvement, the operating voltage of the above supercapacitor is 2.7V or more.

As a further improvement, the above positive electrode and negative electrode are carbon material electrodes, and the above separator is cellulose separator paper.

The organic electrolyte of the invention selects appropriate additives and electrolytes, and the viscosity of the electrolyte is low, especially the viscosity is low at low temperature, the surface tension is small, the contact angle to graphite is small, the wettability is good, the liquid core absorbs quickly, and the liquid is absorbed. It has a large amount and can be used at a high voltage of 3.0V, and has high power density, energy density, good cycle life, and high and low temperature performance.

detailed description

The invention will now be further described in detail by way of specific embodiments.

The organic electrolyte of the present invention comprises an organic electrolyte, an aprotic solvent and an additive, wherein the cation of the organic electrolyte is an N,N-dimethylpyrrolidine cation, the structure of which is as follows:

The anion of the organic electrolyte is tetrafluoroborate ion (BF ₄ ^- ), hexafluorophosphate ion (PF ₆ ^- ), bis(trifluoromethylsulfonyl) ion (CF ₃ SO ₂ ) ₂ ^- , bis (fluorine) At least one of a sulfonyl) ion. It is to be noted that the cation represented by the formula (1) may be combined with any of the above anions to form the organic electrolyte of the present invention, and the organic electrolyte system may contain a plurality of organic electrolytes in an anion mixed form.

The concentration of the organic electrolyte in the organic electrolyte is preferably in the range of 0.5 to 3.0 mol/L, and preferably, the concentration of the organic electrolyte is 0.8 to 2 mol/L.

The additive is selected from at least one of the compounds represented by the following formula (1):

Wherein, 1 to 3 of R ₁ to R ₆ are fluorine-containing alkyl groups or fluorine; the rest are alkyl groups having 1 to 5 carbon atoms or hydrogen, and the longer the carbon chain, the greater the steric hindrance. Not conducive to the migration of ions. It is to be noted that the compound represented by the formula (1) includes a plurality of specific compounds which can be used alone in the organic electrolytic solution of the present invention or in combination in the organic electrolytic solution of the present invention. In some embodiments of the invention, the additive is specifically fluorobenzene or 1,2,3-trifluorobenzene. The amount of the additive generally accounts for 0.1% by weight to 3% by weight of the total mass of the organic electrolyte to obtain a good effect, the content is too low, and the wettability is lowered; the content is too high, which affects the high and low temperature performance of the capacitor.

In the present invention, the aprotic solvent may be selected from the group consisting of acetonitrile, propylene carbonate, sulfolane, dimethyl sulfone, dimethyl sulfoxide, γ-butyrolactone, propionitrile, methoxypropionitrile, γ-valerolactone, One or a mixture of two or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. In some embodiments of the invention, the aprotic solvent is acetonitrile, propylene carbonate, gamma-butyrolactone, a mixture of sulfolane and dimethyl sulfone, a mixture of sulfolane and acetonitrile, or a mixture of sulfolane and ethyl methyl carbonate.

The supercapacitor prepared by using the organic electrolyte of the invention comprises a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an organic electrolyte, and the operating voltage of the supercapacitor of the invention is attributed to the performance advantage of the organic electrolyte of the invention It can reach above 2.7V, and has high power density, energy density and good cycle life, and can improve the high and low temperature performance of supercapacitors.

The invention is described in detail below by means of specific examples. It is to be understood that the examples are merely illustrative and are not intended to limit the scope of the invention.

In the following embodiments, the supercapacitor model is fabricated as follows:

The supercapacitor model is assembled in a glove box: the battery core includes two collector electrodes made of aluminum foil, two working electrodes made of activated carbon, and a fiber cloth separator interposed therebetween, and it should be noted that the present invention is not limited to this structure. . The cells were immersed in the following comparative examples and the electrolytes in the examples, and sealed with aluminum shells and colloidal particles.

The supercapacitor test process is as follows:

(1) Pre-circulation (10 times): 25 ° C, charge cut-off voltage U, constant current 10 mA / F for charging; then press the limit voltage U / 2, constant current 10 mA / F for discharge.

(2) In the 65 °C ~ 85 °C high temperature box, the constant current 10mA / F is charged to the upper limit voltage U, constant voltage (U) for a certain time; take out the supercapacitor and cool to 25 ° C, then charge and discharge test, the test conditions are the same as Cycle and calculate the capacity retention and ESR growth rate of the supercapacitor.

(3) When the capacity retention rate is ≤ 60%, and/or the ESR growth rate is ≥ 100%, it is used as a criterion for judging the life of the capacitor.

(4) In the high and low temperature chamber, in the working temperature range of -50 ° C ~ 20 ° C, after a certain time interval of 10 ° C constant temperature, charge and discharge test, the test conditions are the same as pre-cycle, and calculate the capacity and ESR of the supercapacitor.

The supercapacitor cell aspiration test procedure is as follows:

The liquid absorption test system is used for testing (using the principle that the core is related to gravity, buoyancy and tension during the liquid absorption process), and the battery type is Φ15*30. The electrolyte is instantaneously immersed in the cell, and the liquid absorption system automatically outputs the cell aspiration amount. The amount of liquid absorption is the amount of liquid absorbed by the electrode active material and the separator, and does not include the amount of adsorption in the winding space.

The contact angle test process is as follows:

A graphite sheet was used as a carrier for the electrolyte contact angle test, which was tested using a contact angle tester.

Example 1

Using N,N-dimethylpyrrolidine tetrafluoroborate as the solute, acetonitrile (AN) as the solvent, preparing 1.0mol/L electrolyte, and then adding 1% fluorobenzene according to the total mass of the electrolyte, the electrolyte composition Listed in Table 1, cell saturation aspiration time and aspirate mass are listed in Table 1, and the contact angle of the electrolyte and its conductivity at 25 ° C were measured. The results are shown in Table 1, respectively. The supercapacitor was fabricated using the electrolyte and tested for electrochemical performance. The life, capacity and ESR test results are listed in Table 1, respectively.

Example 2-8

The solute, solvent, additive, and concentration of the electrolyte were the same as those of Example 1. The solute, solvent, additive and concentration composition of the electrolyte of each example are listed in Tables 1-4. The cell saturation aspiration time and the mass of the liquid are listed in Tables 1-4, and the contact angle of the electrolyte and its The conductivity at 25 ° C is shown in Tables 1-4. Supercapacitors were fabricated using these electrolytes and tested for electrochemical performance. The life, capacity, and ESR test results are listed in Tables 1-4, respectively.

Comparative example 1

Using tetraethylammonium tetrafluoroborate as the solute and AN as the solvent, 1.0 mol/L electrolyte was prepared. The electrolyte composition is listed in Table 1. The cell saturation aspiration time and the liquid absorption mass are listed in Table 1, and determined. The contact angle of the electrolyte and its electrical conductivity at 25 ° C are shown in Table 1, respectively. The supercapacitor was fabricated using the electrolyte and tested for electrochemical performance. The life, capacity and ESR test results are listed in Table 1, respectively.

Comparative example 2-8

The solute, solvent, additive, and concentration of the electrolyte were the same as those of Comparative Example 1. The solute, solvent, additive and concentration composition of the electrolytes of each comparative example are listed in Table 1-4. The cell saturation aspiration time and the liquid absorption mass are listed in Table 1-4, and the contact angle of the electrolyte and its The conductivity at 25 ° C is shown in Tables 1-4. Supercapacitors were fabricated using these electrolytes and tested for electrochemical performance. The life, capacity, and ESR test results are listed in Tables 1-4, respectively.

Table 1 solute, solvent and concentration composition of the electrolyte of the respective examples and comparative examples of the AN system, conductivity data of the electrolyte at 25 ° C, capacitor capacity, ESR and life data

Table 1 (continued) AN system examples, comparative examples of the electrolyte solute, solvent and concentration composition, electrolyte 25 ° C conductivity data and capacitor capacity, ESR and life data

AN system electrolyte: Compared with the comparative example, the example has small contact angle, short liquid absorption time, large liquid absorption, good low temperature performance, and good high temperature and high voltage cycle life.

Table 2 propylene carbonate system examples, comparative examples of the electrolyte solute, solvent and concentration composition, electrolyte 25 ° C conductivity data and capacitor capacity, ESR and life data

Table 2 (continued) propylene carbonate system examples, comparative examples of the electrolyte solute, solvent and concentration composition, electrolyte 25 ° C conductivity data and capacitor capacity, ESR and life data

The propylene carbonate system electrolyte: Compared with the comparative example, the example has a small contact angle, a short liquid absorption time, a large liquid absorption, a good low temperature performance, and a good high temperature and high voltage cycle life.

Table 3 γ-butyrolactone system examples, comparative examples of the electrolyte solute, solvent and concentration composition, electrolyte 25 ° C conductivity data and capacitor capacity, ESR and life data

Table 3 (continued) γ-butyrolactone system Examples, comparative examples of the solute, solvent and concentration composition of the electrolyte, electrolyte 25 ° C conductivity data and capacitor capacity, ESR and life data

Γ-butyrolactone system electrolyte: Compared with the comparative example, the examples have small contact angle, short liquid absorption time, large liquid absorption, good low temperature performance, and good high temperature and high voltage cycle life.

Table 4 sulfolane and ethyl methyl carbonate mixed solvent system Examples, comparative examples of the electrolyte solution solute, solvent and concentration composition, electrolyte 25 ° C conductivity data and capacitor capacity, ESR and life data

Table 4 (continued) sulfolane and ethyl methyl carbonate mixed solvent system Examples, comparative examples of the electrolyte solute, solvent and concentration composition, electrolyte 25 ° C conductivity data and capacitor capacity, ESR and life data

Sulfolane and ethyl methyl carbonate mixed solvent system electrolyte: Compared with the comparative example, the example has small contact angle, short liquid absorption time, large liquid absorption, good low temperature performance, and good high temperature and high voltage cycle life.

The above is a further detailed description of the present invention in connection with the specific embodiments, and the specific embodiments of the present invention are not limited to the description. It will be apparent to those skilled in the art that the present invention may be made without departing from the spirit and scope of the invention.

Claims

An organic electrolyte for a supercapacitor, comprising an organic electrolyte, an aprotic solvent and an additive, wherein the cation of the organic electrolyte is an N,N-dimethylpyrrolidine cation,

The anion of the organic electrolyte is at least one of a tetrafluoroborate ion, a hexafluorophosphate ion, a bis(trifluoromethylsulfonyl) ion, and a bis(fluorosulfonyl) ion;

The additive is selected from at least one of the compounds represented by the following formula (1):

Among them, 1 to 3 of R 1 to R 6 are fluorine-containing alkyl groups or fluorine; the others are alkyl groups having 1 to 5 carbon atoms or hydrogen.
The organic electrolytic solution according to claim 1, wherein the additive accounts for 0.1% by weight to 3% by weight based on the total mass of the organic electrolytic solution.
The organic electrolyte according to claim 1, wherein the concentration of the organic electrolyte in the organic electrolyte is 0.5 to 3.0 mol/L.
The organic electrolytic solution according to claim 3, wherein a concentration of the organic electrolyte in the organic electrolytic solution is 0.8 to 2 mol/L.
The organic electrolytic solution according to any one of claims 1 to 4, wherein the additive is at least one of fluorobenzene and 1,2,3-trifluorobenzene.
The organic electrolyte according to any one of claims 1 to 4, wherein the aprotic solvent is acetonitrile, propylene carbonate, sulfolane, dimethyl sulfone, dimethyl sulfoxide, γ-butyrolactone. , propionitrile, methoxypropionitrile, γ-valerolactone, ethylene carbonate, carbonic acid One or a mixture of two or more of dimethyl ester, diethyl carbonate, and ethyl methyl carbonate.
The organic electrolyte according to claim 6, wherein the aprotic solvent is acetonitrile, propylene carbonate, γ-butyrolactone, a mixture of sulfolane and dimethyl sulfone, a mixture of sulfolane and acetonitrile, or sulfolane. And a mixture of ethyl methyl carbonate.
A supercapacitor comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an organic electrolyte, wherein the organic electrolyte is the organic electrolyte according to any one of claims 1 to 7. .
The supercapacitor according to claim 8, wherein the operating voltage of the supercapacitor is 2.7V or more.
The supercapacitor according to claim 8 or 9, wherein the positive electrode and the negative electrode are carbon material electrodes, and the separator is cellulose separator paper.