CN108573816B - Organic electrolyte for super capacitor and super capacitor - Google Patents

Abstract

The invention provides an organic electrolyte for a super capacitor and the super capacitor, aiming at solving the problem that the existing organic electrolyte for the super capacitor is insufficient in high-temperature and high-voltage performance. The organic electrolyte comprises a polar aprotic solvent and an organic electrolyte shown as a following structural formula 1, wherein the weight percentage content of ammonium ions and/or pyrrolidine methyl carbamate shown as a following structural formula 2 in the organic electrolyte is less than or equal to 1 percent based on 100 percent of the total weight of the organic electrolyte,

in the formula 1, R₁Is C1-C3 alkyl, A^‑Is an anion. The organic electrolyte for the super capacitor can improve the stability of the electrolyte, reduce the self-discharge of the capacitor, and has wider working temperature and high charge cut-off voltage.

Description

Organic Electrolytes and Supercapacitors for Supercapacitors

technical field

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

Background technique

Supercapacitors, also known as gold capacitors, electrochemical capacitors, store energy through ion adsorption (electric double-layer capacitors) or surface fast redox reactions (pseudocapacitors). Supercapacitors are a new type of energy storage device between batteries and traditional electrostatic capacitors. Supercapacitors can store hundreds or even thousands of times the charge of traditional solid-state electrolytic capacitors, can be fully charged and discharged in seconds, have higher power input or output than batteries, and can be achieved in less time. At the same time, supercapacitors have the advantages of short charging and discharging time, long storage life, high stability, and wide operating temperature range (-40 °C ~ 70 °C), so they are widely used in the field of consumer electronics, new energy power generation systems, distribution energy storage systems, intelligent distributed grid systems, transportation such as new energy vehicles, loads such as energy-saving elevator cranes, military equipment such as electromagnetic bombs, and motion control, involving new energy power generation, smart grids, new energy vehicles, energy-saving buildings, Industrial energy conservation and emission reduction and other industries belong to the standard full range of low-carbon economy core products.

As one of the most promising energy storage devices in the field of new energy, supercapacitors have become one of the research hotspots in the United States, Japan, South Korea, and Russia in the fields of materials, electricity, physics, and chemistry. The main research direction is to prepare electrode materials with excellent performance and low cost, and electrolyte system materials with high electrical conductivity, good chemical and thermal stability, and high working voltage (wide electrochemical stability window), and on this basis, prepare high-energy Supercapacitor energy storage devices with high density, high power density and long service life, which can be used in various electric hybrid vehicle hybrid power systems and backup power supply of electronic equipment.

Because propylene carbonate (PC) and acetonitrile (AN) have good electrochemical and chemical stability and good solubility for organic quaternary ammonium salts, they are widely used in the electrolyte system of supercapacitors. The current commercialized supercapacitor electrolytes mainly use solutions of tetraethylammonium tetrafluoroborate (Et ₄ NBF ₄ ) or methyltriethylammonium tetrafluoroborate (Et ₃ MeNBF ₄ ) in AN or PC. The upper limit of the voltage of the AN system supercapacitor is only 2.7V; the upper limit of the voltage of the PC system supercapacitor is only 2.5V. With the development of the supercapacitor market, for the sake of safety and to increase market competitiveness, the current conventional electrolyte system can no longer meet customers' requirements for high temperature and high pressure resistance of supercapacitors. Working under high voltage and high temperature of conventional electrolyte will cause electrochemical decomposition of the electrolyte, resulting in a significant increase in the pressure inside the capacitor, a significant decrease in the electrochemical performance, and ultimately lead to the failure of the capacitor.

To sum up, in order to meet the growing demand for use, it is urgent to develop an organic electrolyte with high electrical conductivity, good chemical and thermal stability, wide operating temperature range, high operating voltage (wide electrochemical stability window), and Supercapacitors using this electrolyte should achieve a good balance of high voltage resistance, wide operating temperature range and long life.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an organic electrolyte for supercapacitors, which aims to solve the problems of narrow working temperature range and low charge cut-off voltage of the existing organic electrolytes for supercapacitors.

Another object of the present invention is to provide a supercapacitor containing the above-mentioned organic electrolyte.

The present invention is achieved by an organic electrolyte for supercapacitors, comprising a polar aprotic solvent and an organic electrolyte represented by the following structural formula 1, wherein, based on the total weight of the organic electrolyte as 100%, In the organic electrolyte, the weight percentage of ammonium ions and/or methyl pyrrolidine carbamate shown in the following structural formula 2 is ≤ 1%,

In the formula 1, R ₁ is a C1-C3 alkyl group, and A ^- is an anion.

Further preferably, based on the total weight of the organic electrolyte as 100%, the sum of the weight percentages of the ammonium ions and/or the methyl pyrrolidine carbamate is ≤1%.

Preferably, in the formula 1, A ^- is tetrafluoroborate ion, hexafluorophosphate ion, bis(trifluoromethylsulfonyl) ion, bis(fluorosulfonyl) ion, perfluoroalkylsulfonic acid at least one of acid radicals.

Preferably, the polar aprotic solvent is acetonitrile, propylene carbonate, sulfolane, dimethyl sulfone or dimethyl sulfoxide, γ-butyrolactone, propionitrile, methoxypropionitrile, γ-valerolactone , at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

Preferably, in the organic electrolyte, the concentration of the organic electrolyte is 0.5-3.0 mol/L.

Further preferably, in the organic electrolyte, the concentration of the organic electrolyte is 0.8-2.0 mol/L.

And, a supercapacitor, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, wherein the organic electrolyte is the above-mentioned organic electrolyte.

Further, the polar aprotic solvent is acetonitrile, the charging cut-off voltage of the supercapacitor is 2.85-3.2V, and the working temperature of the supercapacitor is -50-65°C.

Further, the polar aprotic solvent is propylene carbonate, the charge cut-off voltage of the supercapacitor is 2.7-3.0V, and the working temperature of the supercapacitor is -40-70°C.

Preferably, the positive electrode and the negative electrode are both carbon material electrodes, and the separator is a fiber cloth separator.

The organic electrolyte for supercapacitors provided by the present invention can improve the electrical conductivity and stability (including chemical stability) of the organic electrolyte by controlling the content of ammonium ions and methyl pyrrolidine carbamate derived from the organic electrolyte. properties and thermal stability), reducing the self-discharge of the capacitor, so that the supercapacitor using the organic electrolyte can be used under high voltage, wide operating temperature range, and has high power density, energy density, and good cycle life. and high and low temperature performance.

The supercapacitor provided by the present invention contains the above-mentioned organic electrolyte. Therefore, it has the characteristics of high electrical conductivity, good chemical stability and thermal stability. More importantly, the use of the organic electrolyte enables the supercapacitor to It is used under high voltage, wide operating temperature range, and has high power density, energy density, good cycle life and high and low temperature performance.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

An embodiment of the present invention provides an organic electrolyte for a supercapacitor, comprising a polar aprotic solvent and an organic electrolyte represented by the following structural formula 1, wherein, based on the total weight of the organic electrolyte as 100%, the The weight percentage of ammonium ion and/or methyl pyrrolidine carbamate shown in the following structural formula 2 in the organic electrolyte is less than or equal to 1%,

In the formula 1, R ₁ is a C1-C3 alkyl group, and A ^- is an anion.

Specifically, in the organic electrolyte, preferably, the anion A ^- is tetrafluoroborate ion, hexafluorophosphate ion, bis(trifluoromethylsulfonyl) ion, bis(fluorosulfonyl) ion , at least one of perfluoroalkyl sulfonate. Further preferably, the anion A ^- is tetrafluoroborate ion, hexafluorophosphate ion.

As recorded in the CN104979102 Chinese invention patent filed by the applicant of the present application, the organic electrolyte using the organic electrolyte shown in formula 1 can expand the operating temperature range and prolong the service life of the supercapacitor to a certain extent, but the inventors The performance gains achieved by this scheme were found to be limited.

The inventors of the present invention conducted extensive experiments for analysis. In the above-mentioned organic electrolyte, the organic electrolyte is usually synthesized by two steps, specifically,

S01. The pyrrolidine shown in the following structural formula 3 or the N-substituted alkyl pyrrolidine and dimethyl carbonate (DMC) synthesize the intermediate shown in the following structural formula 4 through methylation reaction, and the reaction formula is as follows:

S02. the intermediate is reacted with ammonium salt NH ₄ A to obtain a crude product containing the organic electrolyte shown in the following structural formula 1, and the reaction formula is as follows:

Specifically, in the above step S01, in the formula 3, R ₁ is a C1-C3 alkyl group (an alkyl group with 1-3 carbon atoms), and the R ₂ is H or a C1-C3 alkyl group ( Alkyl having 1-3 carbon atoms).

Since there are two active sites in the DMC molecule, namely the alkyl carbon atom and the carbonyl carbon atom, when the pyrrolidine or N-substituted alkyl pyrrolidine reacts with the dimethyl carbonate, in the presence of a weak basic substance When the nucleophile is activated, the formed nucleophilic anion can attack one of the two active sites in DMC, possibly resulting in two different reaction pathways, and there is competition between the two pathways. Therefore, in the first-step synthesis process of the organic electrolyte, the by-product methyl pyrrolidine carbamate is inevitably generated, and the reaction formula is as follows:

The inventors of the present invention have found through in-depth research that when the organic electrolyte shown in structural formula 1 is synthesized by the above process, ammonium ions and methyl pyrrolidine carbamate as shown in structural formula 2 are inevitably present in the organic electrolyte obtained. Pyrrolidine, N-substituted alkyl pyrrolidine and other substances, and through a large number of experimental comparisons, it is found that the above-mentioned ammonium ions and the methyl pyrrolidine carbamate shown in structural formula 2 have a charge cut-off voltage and working temperature range of the organic electrolyte. obvious impact. When the content of the methyl pyrrolidine carbamate and the ammonium ion is relatively high, the charge cut-off voltage of the organic electrolyte is low, and the working temperature range is narrow. In view of this, the inventor of the present invention improves the charge cut-off voltage of the organic electrolyte and the supercapacitor applying the electrolyte, and expands its operating temperature range by controlling the content of methyl pyrrolidine carbamate and ammonium ions in the organic electrolyte. , prolong its service life.

Specifically, the method for controlling the content of the ammonium ion in the organic electrolyte and the methyl pyrrolidine carbamate shown in structural formula 2 is: using an organic solvent to recrystallize the organic electrolyte, so that the methyl pyrrolidine carbamate in the organic electrolyte is recrystallized. and/or the weight percentage of ammonium ions≤1%. Wherein, the organic solvent includes but is not limited to methanol, ethanol, acetonitrile and/or water. Preferably, the weight percentage content of methyl pyrrolidine carbamate and/or ammonium ions in the organic electrolyte is made to be ≤1% by the above method, more preferably based on the total weight of the organic electrolyte as 100%, so The weight percentage content of the ammonium ion and/or the methyl pyrrolidine carbamate is less than or equal to 1%.

Preferably, the polar aprotic solvent is acetonitrile, propylene carbonate, sulfolane, dimethyl sulfone or dimethyl sulfoxide, γ-butyrolactone, propionitrile, methoxypropionitrile, γ-valerolactone , at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, more preferably one of acetonitrile and propylene carbonate. When the polar aprotic solvent is acetonitrile, the supercapacitor (AN system) prepared by using the organic electrolyte has a charging cut-off voltage of 2.85-3.2V, an operating temperature range of -50-65°C, and It can maintain stable operation for a long time; when the polar aprotic solvent is propylene carbonate, the supercapacitor (PC system) prepared by using this organic electrolyte has a charging cut-off voltage of up to 2.7-3.0V and a working temperature range. It can reach -40～70℃, and can maintain stable work for a long time.

Preferably, in the organic electrolyte, the concentration of the organic electrolyte is 0.5-3.0 mol/L. If the concentration of the organic electrolyte is too high, its low-temperature performance will be reduced, or even solidified under low-temperature conditions to lose its performance. Further preferably, in the organic electrolyte, the concentration of the organic electrolyte is 0.8-2.0 mol/L.

The organic electrolyte for supercapacitors provided by the embodiments of the present invention can improve the conductivity and stability of the organic electrolyte by controlling the content of ammonium ions and methyl pyrrolidine carbamate derived from the organic electrolyte (including chemical stability and thermal stability), reducing the self-discharge of the capacitor, so that the supercapacitor using the organic electrolyte has a high charge cut-off voltage, a wide operating temperature range, and high power density, energy density, good Cycle life and high and low temperature performance.

And, an embodiment of the present invention also provides a supercapacitor, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, wherein the organic electrolyte is the above-mentioned organic electrolyte liquid.

In the embodiment of the present invention, the organic electrolyte is the above-mentioned organic electrolyte. Specifically, the organic electrolyte includes a polar aprotic solvent and an organic electrolyte represented by the following structural formula 1, wherein, based on the total weight of the organic electrolyte as 100%, the ammonium ions and/or all The weight percentage of the methyl pyrrolidine carbamate is less than or equal to 1%,

In the formula 1, R ₁ is a C1-C3 alkyl group, and A ^- is an anion.

Specifically, in the organic electrolyte, preferably, the anion A ^- is tetrafluoroborate ion, hexafluorophosphate ion, bis(trifluoromethylsulfonyl) ion, bis(fluorosulfonyl) ion , at least one of perfluoroalkyl sulfonate. Further preferably, the anion A ^- is tetrafluoroborate ion, hexafluorophosphate ion.

Further preferably, based on the total weight of the organic electrolyte as 100%, the sum of the weight percentages of the ammonium ions and/or the methyl pyrrolidine carbamate is ≤1%.

Preferably, the polar aprotic solvent is acetonitrile, propylene carbonate, sulfolane, dimethyl sulfone or dimethyl sulfoxide, γ-butyrolactone, propionitrile, methoxypropionitrile, γ-valerolactone , at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, more preferably one of acetonitrile and propylene carbonate. When the polar aprotic solvent is acetonitrile, the supercapacitor (AN system) prepared by using the organic electrolyte has a charging cut-off voltage of 2.85-3.2V, an operating temperature range of -50-65°C, and It can maintain stable operation for a long time; when the polar aprotic solvent is propylene carbonate, the supercapacitor (PC system) prepared by using this organic electrolyte has a charging cut-off voltage of up to 2.7-3.0V and a working temperature range. It can reach -40～70℃, and can maintain stable work for a long time.

Preferably, in the organic electrolyte, the concentration of the organic electrolyte is 0.5-3.0 mol/L. Further preferably, in the organic electrolyte, the concentration of the organic electrolyte is 0.8-2.0 mol/L.

In the embodiment of the present invention, the positive electrode, the negative electrode, and the separator disposed between the positive electrode and the negative electrode can adopt the conventional positive electrode, negative electrode, and separator of a supercapacitor. Preferably, the positive electrode and the negative electrode are both carbon material electrodes, and the separator is a fiber cloth separator.

The supercapacitor provided by the embodiment of the present invention contains the above-mentioned organic electrolyte, therefore, has the characteristics of high electrical conductivity, good chemical stability and thermal stability, and more importantly, the use of the organic electrolyte makes the supercapacitor Capacitors can be used in high voltage, wide operating temperature range, and have high power density, energy density, good cycle life and high and low temperature performance.

In the following, description will be given with reference to specific embodiments.

Example 1

A supercapacitor, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising an aprotic organic solvent, an organic electrolyte (solute), and an organic electrolyte derived from the Ammonium ions and methyl pyrrolidine carbamate in organic electrolytes. The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 1 of Table 1.

Wherein, the preparation method of the organic electrolyte is as follows:

S11. Place 35.6g of pyrrolidine (0.5mol), 100g of methanol, and 90g of dimethyl carbonate (1.0mol) in a 1L autoclave, and heat and react at 100° C. for 8h to obtain 200g of an intermediate reaction solution, wherein the following structural formula 5 The indicated intermediate compound content was 24.35% (wt), and the by-product methyl pyrrolidine carbamate content was 16.07% (wt).

S12. 200 g of the intermediate reaction solution and 35 g of ammonium fluoroborate (0.33 mol) were heated to reflux for reaction for 3 h, and the methanol and dimethyl carbonate were removed by rotary evaporation under reduced pressure at 60° C. to obtain N,N-dimethylpyrrolidine ammonium tetrafluoroborate Crude product solid 90.9g, wherein, the content of N,N-dimethylpyrrolidine ammonium tetrafluoroborate is 57.26% (wt), the content of methyl pyrrolidine carbamate is 35.08% (wt), and the content of ammonium ion is 1.19% % (wt).

S13. Heat and stir 90 g of N,N-dimethylpyrrolidine ammonium tetrafluoroborate crude solid and 60 g of methanol at 60°C for 2 h, filter while hot to remove insoluble matter; add 100 g of isopropanol to the filtrate, stir at room temperature for 1 h, and filter The crystals were collected; the crystals were recrystallized twice according to the above-mentioned charging ratio and operation steps to obtain 40.5g of high-purity N,N-dimethylpyrrolidine ammonium tetrafluoroborate, wherein the ammonium ion content was 3.26ppm, and no pyrrole was detected. Methyl alkyl carbamate.

Example 2

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific types and contents of each component are shown in Example 2 of Table 1.

Example 3

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 3 in Table 1.

Example 4

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 4 in Table 1.

Example 5

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 5 in Table 1.

Example 6

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 6 in Table 1.

Example 7

A supercapacitor includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte including a polar aprotic organic solvent and an organic electrolyte (solute). The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 7 in Table 1.

Example 8

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 8 in Table 1.

Example 9

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 9 in Table 1.

Example 10

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 10 in Table 1.

Example 11

A supercapacitor includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte including a polar aprotic organic solvent and an organic electrolyte (solute). The concentration of the organic electrolyte, the specific type and content of each component are shown in Example 11 in Table 1.

Comparative Example 1

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Comparative Example 1 in Table 1.

Comparative Example 2

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Comparative Example 2 in Table 1.

Comparative Example 3

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Comparative Example 3 in Table 1.

Comparative Example 4

A supercapacitor includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte including a polar aprotic organic solvent and an organic electrolyte (solute). The concentration of the organic electrolyte, the specific type and content of each component are shown in Comparative Example 4 in Table 1.

Comparative Example 5

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component, are shown in Comparative Example 5 in Table 1.

Comparative Example 6

A supercapacitor comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte comprising a polar aprotic organic solvent, an organic electrolyte (solute), a Ammonium ions and methyl pyrrolidine carbamate in the organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Comparative Example 6 in Table 1.

Comparative Example 7

A supercapacitor includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte including a polar aprotic organic solvent and an organic electrolyte (solute). The concentration of the organic electrolyte, the specific type and content of each component are shown in Comparative Example 7 in Table 1.

Comparative Example 8

A supercapacitor, comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an organic electrolyte, the organic electrolyte is N,N containing ammonium ion, methyl pyrrolidine carbamate - Dimethylpyrrolidine ammonium salt is used as a solute, and an aprotic organic solvent is used to prepare an organic electrolyte. The concentration of the organic electrolyte, the specific type and content of each component are shown in Comparative Example 8 in Table 1.

Table 1

The supercapacitors of Examples 1-11 and Comparative Examples 1-8 of the present invention are all assembled in a glove box to form a supercapacitor model. Wherein, the cell includes two collector electrodes made of aluminum foil, two working electrodes made of activated carbon, and a fiber cloth separator inserted therebetween, but it is not limited to this structure. Immerse the cell in the electrolyte in the following comparative examples and examples, and use an aluminum shell and colloidal particles to form a seal.

The supercapacitors of Examples 1-11 and Comparative Examples 1-8 were tested for electrochemical performance. The test indicators and test methods were as follows. The capacity retention rate was ≤80%, and (or) the ESR growth rate was ≥100%, as the supercapacitor. criteria for life expectancy.

(1) Pre-cycle (10 times): 25°C, charge cut-off voltage U, constant current 10mA/F; then discharge at lower limit voltage U/2, constant current 10mA/F.

(2) In the high temperature box of 65℃～70℃, charge the constant current 10mA/F to the upper limit voltage U, and keep the constant voltage (U) for a certain period of time; take out the supercapacitor and cool it to 25℃, and then carry out the charge and discharge test, the test conditions are the same as the pre- Cycle, and calculate the capacity retention rate and ESR growth rate of the supercapacitor.

(3) When the capacity retention rate is less than or equal to 80%, and (or) the ESR growth rate is greater than or equal to 100%, it is used as the judgment standard for overcapacity life.

(4) In the high and low temperature box, under the working temperature range of -40°C to 20°C, after a constant temperature of 10°C for a certain period of time, the charge and discharge test is carried out. The test conditions are the same as the pre-cycle, and the capacity and ESR of the supercapacitor are calculated.

The test results of the AN system are shown in Table 2 (Examples 1-7, Comparative Examples 1-4), and the test results of the propylene carbonate system are shown in Table 3 (Examples 8-11, Comparative Examples 5-8).

Table 2

table 3

See Table 1, Table 2, in AN system electrolyte (embodiment 1-7, comparative example 1-4):

Comparing Examples 1-7 and 1-3, in Examples 1-7, the weight percentage of the ammonium ions and/or methyl pyrrolidine carbamate in the organic electrolyte is ≤0.5%. In Comparative Examples 1-3, the weight percentage of the ammonium ions and/or methyl pyrrolidine carbamate in the organic electrolyte is greater than or equal to 2%. The supercapacitors obtained in Examples 1-7 have the capacitor capacity and capacitor ESR under the conditions of 20°C and voltages of 2.85V and 3.0V, -50°C and voltages of 2.85V and 3.0V, respectively, and at 65°C and voltage. The life of the capacitor under the conditions of 2.85V, 3.0V and 3.2V is better than that of Comparative Examples 1-3, and its overall performance is better, especially the high and low temperature performance under high voltage conditions (3.0V) and high temperature (65℃, 2.85V) , 3.0V, 3.2V), the service life advantage is obvious, and the supercapacitor has a higher charge cut-off voltage and a wider operating temperature range.

Comparing Example 7 and Comparative Example 4, in Example 7, N,N-dimethylpyrrolidine tetrafluoroborate was used as the organic electrolyte, while tetraethylammonium tetrafluoroborate was used in Comparative Example 4, neither of which was used. Contains ammonium ions, methyl pyrrolidine carbamate. The results show that the conductivity, 20 ℃ capacitor capacity, 20 ℃ capacitor ESR of Comparative Example 4 using tetraethylammonium tetrafluoroborate as the electrolyte are comparable to those of Example 4 using N,N-dimethylpyrrolidine tetrafluoroborate 7 is equivalent, but its -50 ℃ capacitor capacity is poor, which cannot meet the use requirements of supercapacitors in low-temperature and high-voltage environments, and its service life at 65 ℃ is significantly weaker than that of Example 7. It can be seen that in the embodiment of the present invention, N,N-dimethylpyrrolidine tetrafluoroborate is used as the organic electrolyte, which is beneficial to improve the low temperature and high pressure performance and the high temperature service life.

Comparative Examples 1-7, especially Example 3 and Example 7, when the organic electrolyte concentration increases, it is beneficial to improve the electrical conductivity, but the low temperature state solidifies and cannot be used, that is, the low temperature performance is not good. Therefore, the present invention The concentration of the organic electrolyte described in the embodiment should not be too high, preferably controlled within 2 mol/L. Comparing Examples 1, 2, 5, and 7, on the whole, the smaller the proportion of ammonium ions and/or methyl pyrrolidine carbamate in the organic electrolyte, the better the overall performance. Especially when the content of ammonium ion and methyl pyrrolidinecarboxylate in the organic electrolyte is less than or equal to 0.1 wt%, the supercapacitor using the electrolyte shows good low temperature performance and has a good high temperature and high voltage cycle life. When the content of ammonium ion and methyl pyrrolidinecarboxylate exceeds this range, the high and low temperature performance decreases.

See Table 1, Table 3, in propylene carbonate system electrolyte (embodiment 8-11, comparative example 5-8):

Comparative Example 8-11 and Comparative Example 5-7, in Example 8-11, the weight percentages of the ammonium ion and methyl pyrrolidine carbamate in the organic electrolyte are respectively ≤ 1%, ammonium The weight percentage of the sum of radical ions and methyl pyrrolidine carbamate in the organic electrolyte is less than or equal to 1%. In Comparative Examples 5-7, the weight percentage of the ammonium ion or methyl pyrrolidine carbamate in the organic electrolyte is 5%, accounting for 2% by weight of the organic electrolyte. The supercapacitors obtained in Examples 8-11 have the capacitor capacity and capacitor ESR under the conditions of 20°C and voltages of 2.85V and 3.0V, -40°C and voltages of 2.7V and 3.0V, respectively, and 70°C and voltages of 2.7V and 3.0V. The life of the capacitor under the conditions of 2.7V and 3.0V is better than that of Comparative Examples 5-8, and its overall performance is better, especially the high and low temperature performance under high voltage conditions (3.0V) and high temperature (70℃, 2.7V, 3.0V) ) under the condition of obvious advantages, the supercapacitor has a higher charge cut-off voltage and a wider operating temperature range.

Comparing Example 11 and Comparative Example 8, in Example 11, N,N-dimethylpyrrolidine tetrafluoroborate was used as the organic electrolyte, while methyltriethylammonium tetrafluoroborate was used in Comparative Example 8, and both were used. All contain no ammonium ions and methyl pyrrolidine carbamate. The results show that the comparative example 8 using methyltriethylammonium tetrafluoroborate as the electrolyte has slightly better electrical conductivity than the example 11 using N,N-dimethylpyrrolidine tetrafluoroborate, and other properties The preparations were all worse than those of Example 11, and could not meet the use requirements of supercapacitors in high and low temperature and high voltage environments. It can be seen that in the embodiment of the present invention, N,N-dimethylpyrrolidine tetrafluoroborate is used as the organic electrolyte, which is beneficial to improve the low temperature and high pressure performance and the high temperature service life.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (9)

1. an organic electrolyte for supercapacitor, is characterized in that, comprises polar aprotic solvent, the organic electrolyte shown in following structural formula 1 and the by-product ammonium ion that the organic electrolyte shown in structural formula 1 introduces and /or the methyl pyrrolidine carbamate represented by the following structural formula 2, wherein, When the by-product introduced by the organic electrolyte represented by the structural formula 1 is ammonium ions, based on the total weight of the organic electrolyte as 100%, the weight percentage of ammonium ions is less than or equal to 1%, and not 0 ; When the by-product introduced into the organic electrolyte represented by the structural formula 1 is methyl pyrrolidine carbamate represented by the following structural formula 2, the total weight of the organic electrolyte is 100%, and the pyrrole represented by the following structural formula 2 The weight percentage of methyl alkyl carbamate is less than or equal to 1%, and not 0; When the by-products introduced by the organic electrolyte represented by the structural formula 1 are ammonium ions and methyl pyrrolidine carbamate represented by the following structural formula 2, based on the total weight of the organic electrolyte as 100%, the ammonium ions and the weight percentage of methyl pyrrolidine carbamate shown in the following structural formula 2≤1%, and not 0;

In the formula 1, R ₁ is a C1-C3 alkyl group, and A ^- is an anion. 2. the organic electrolyte for supercapacitor as claimed in claim 1, is characterized in that, in described formula 1, anion A ^- is tetrafluoroborate ion, hexafluorophosphate ion, bis(trifluoromethyl) at least one of sulfonyl) ion, bis(fluorosulfonyl) ion and perfluoroalkyl sulfonate. 3. The organic electrolyte for supercapacitor according to any one of claims 1-2, wherein the polar aprotic solvent is acetonitrile, propylene carbonate, sulfolane, dimethyl sulfone or dimethyl sulfone At least one of sulfoxide, γ-butyrolactone, propionitrile, methoxypropionitrile, γ-valerolactone, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. 4. The organic electrolyte for supercapacitors according to any one of claims 1-2, wherein in the organic electrolyte, the concentration of the organic electrolyte is 0.5-3.0 mol/L. 5 . The organic electrolyte for supercapacitors according to claim 4 , wherein, in the organic electrolyte, the concentration of the organic electrolyte is 0.8-2.0 mol/L. 6 . 6. a kind of supercapacitor, comprising positive pole, negative pole, the separator that is arranged between described positive pole and described negative pole and organic electrolyte, it is characterized in that, described organic electrolyte is the arbitrary described in claim 1-5 organic electrolyte. 7. The supercapacitor according to claim 6, wherein the polar aprotic solvent is acetonitrile, the charge cut-off voltage of the supercapacitor is 2.85-3.2V, and the working temperature of the supercapacitor is -50 ~65°C. 8. The supercapacitor according to claim 6, wherein the polar aprotic solvent is propylene carbonate, the charge cut-off voltage of the supercapacitor is 2.7-3.0V, and the working temperature of the supercapacitor is -40～70℃. 9. The supercapacitor according to claim 7 or 8, wherein the positive electrode and the negative electrode are both carbon material electrodes, and the separator is a fiber cloth separator.