CN114864299B

CN114864299B - Electrolyte and application thereof

Info

Publication number: CN114864299B
Application number: CN202210497087.2A
Authority: CN
Inventors: 张校刚; 唐雪晴; 李子翰; 肖德伟; 窦辉
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2022-05-09
Filing date: 2022-05-09
Publication date: 2023-03-21
Anticipated expiration: 2042-05-09
Also published as: CN114864299A

Abstract

The invention provides an electrolyte and application thereof, and belongs to the technical field of super capacitors. In the invention, the deep eutectic solvent has good low-temperature performance, and can be used as a solvent of the ionic liquid to prepare the electrolyte, so that the viscosity of the electrolyte and the internal resistance of the electrolyte at low temperature can be reduced, the phenomenon that the conductivity is reduced along with the reduction of temperature is reduced, the low-temperature performance of the electrolyte is improved, and the applicable temperature zone of the ionic liquid as the electrolyte is widened. In addition, the low-temperature capacity of the electrolyte is improved by further adjusting the proportion of the hydrogen bond donor to the hydrogen bond acceptor and the proportion of the deep eutectic solvent to the ionic liquid. The results of the examples show that the super capacitor assembled by the electrolyte provided by the invention can be normally charged and discharged within the temperature range of minus 40 ℃ to 40 ℃, and the capacitance can reach 12.33F/g at minus 40 ℃.

Description

Electrolyte and application thereof

Technical Field

The invention belongs to the technical field of super capacitors, and particularly relates to an electrolyte and application thereof.

Background

With the rapid application of advanced energy storage systems, the application range of energy storage systems is increasingly wide, such as in the fields of aerospace, electronic automobiles, military industry and the like, which require that energy storage systems not only need to be used safely and stably at room temperature, but also need to be used normally under extreme conditions (high temperature/low temperature), thus bringing new challenges to the energy storage field.

The super capacitor stores energy through electrostatic/non-faradaic reaction on the surface or near the surface of the electrode, has the advantages of high power density, long cycle life, wide working temperature and the like, and draws great attention of people. Although supercapacitors can operate at low temperatures, the large loss of capacity at low temperatures has severely hindered their use in aerospace, electronic automotive and military industries.

For supercapacitors, the electrolyte is the supporting system, which plays a decisive role. Both the energy density and the power density are proportional to the square of the operating voltage of the capacitor, which depends on the decomposition voltage of the electrolyte. Under extreme temperature conditions, the electrolyte in the energy storage device is easily decomposed or solidified, so that the equipment operation failure is caused. The ionic liquid is a salt formed by combining asymmetric organic cations with large radius and anions, wherein the melting point of the salt is lower than 100 ℃, the ionic liquid has low vapor pressure, high thermal stability and chemical stability, low flammability and wide voltage window, and compared with an organic electrolyte, the ionic liquid has higher conductivity and is widely concerned. Although ionic liquids enable supercapacitors to have good performance at room temperature, the viscosity of the ionic liquids is remarkably increased at low temperature, so that the internal resistance of the supercapacitors is greatly increased, the power output is reduced, and the capacitance is reduced, so that the viscosity of the supercapacitors is reduced and the ionic conductivity is improved by mixing the ionic liquids and organic solvents (such as acetonitrile and propylene carbonate), but the capacitance of the supercapacitors is still low after the organic solvents are added, and the application of the ionic liquids at lower temperature is greatly limited.

Disclosure of Invention

The invention aims to provide an electrolyte and application thereof, wherein the electrolyte provided by the invention not only can relieve the phenomenon that the capacitance is reduced along with the reduction of temperature, but also can be normally charged and discharged at the temperature of minus 40 ℃, and the capacitance can reach 12.33F/g at the temperature of minus 40 ℃.

The invention provides electrolyte, which comprises a deep eutectic solvent and ionic liquid which are mutually soluble;

the deep eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor comprises an alcohol;

the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:1 to 2;

the molar ratio of the ionic liquid to the deep eutectic solvent is 1:2 to 3.

Preferably, the ionic liquid comprises 1-ethyl-3-methyltetrafluoroboric acid imidazole.

Preferably, the hydrogen bond acceptor comprises a sulfone compound.

Preferably, the sulfone compound includes dimethyl sulfoxide.

Preferably, the alcohol comprises a glycol.

Preferably, the glycol is ethylene glycol.

Preferably, the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:1 or 1:2.

preferably, the molar ratio of the ionic liquid to the deep eutectic solvent is 1:2 or 1:3.

preferably, the electrolyte has a freezing point lower than-90 ℃ and a boiling point higher than 50 ℃.

The invention also provides application of the electrolyte in the scheme in a super capacitor.

The invention provides an electrolyte, which comprises a deep eutectic solvent and an ionic liquid which are mutually soluble; the deep eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor comprises an alcohol; the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:1 to 2; the molar ratio of the ionic liquid to the deep eutectic solvent is 1:2 to 3. The deep eutectic solvent has good low-temperature performance, can be used as the solvent of the ionic liquid to prepare the electrolyte, and can reduce the viscosity of the electrolyte and the internal resistance of the electrolyte under the low-temperature condition, thereby relieving the phenomenon that the electric capacity of the ionic liquid is reduced along with the reduction of the temperature. In addition, the low-temperature capacity of the electrolyte is improved by adjusting the proportion of the hydrogen bond donor to the hydrogen bond acceptor and the proportion of the deep eutectic solvent to the ionic liquid. The results of the examples show that the freezing point of the electrolyte provided by the invention is lower than-90 ℃, the super capacitor assembled by the electrolyte provided by the invention can be normally charged and discharged at-40 ℃, and the capacitance can reach 12.33F/g at-40 ℃.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a differential scanning calorimetry test curve for the electrolyte of example 1;

FIG. 2 is a differential scanning calorimetry test curve for the electrolyte of comparative example 3;

FIG. 3 is a differential scanning calorimetry test curve for the electrolyte of comparative example 4;

FIG. 4 is a CV curve of the super capacitor in application example 1 at different temperatures;

FIG. 5 is a charging and discharging curve of the super capacitor in application example 1 at different temperatures;

FIG. 6 is a CV curve of the super capacitor in application example 2 at different temperatures;

FIG. 7 is a charging and discharging curve of the super capacitor in application example 2 at different temperatures;

FIG. 8 is a CV curve of a supercapacitor of comparative application example 1 at different temperatures;

FIG. 9 is a graph showing the charging and discharging curves of the supercapacitor in comparative application example 1 at different temperatures;

FIG. 10 is a CV curve of a supercapacitor of comparative application example 2 at different temperatures;

FIG. 11 is a graph showing the charging and discharging curves of the supercapacitor in comparative application example 2 at different temperatures;

FIG. 12 is a CV curve of a supercapacitor of comparative application example 3 at different temperatures;

fig. 13 is a charge and discharge curve of the supercapacitor of comparative application example 3 at different temperatures;

FIG. 14 is a CV curve of a supercapacitor of comparative application example 4 at different temperatures;

fig. 15 is a charge and discharge curve of the supercapacitor of comparative application example 4 at different temperatures.

Detailed Description

the molar ratio of the ionic liquid to the deep eutectic solvent is 1:2 to 3.

In the present invention, the freezing point of the electrolyte is preferably lower than-90 ℃ and the boiling point is preferably higher than 50 ℃. The molar ratio of the ionic liquid to the deep eutectic solvent is 1:2 to 3, more preferably 1:2 or 1:3. in the present invention, the ionic liquid preferably includes 1-ethyl-3-methyltetrafluoroboric acid imidazole; the deep eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor, wherein the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1:1 to 2, more preferably 1:1 or 1:2. in the present invention, the hydrogen bond donor includes alcohol, and the hydrogen bond acceptor preferably includes sulfone compound. In the present invention, the alcohol preferably comprises a glycol, which is preferably ethylene glycol; the sulfone compound preferably comprises dimethyl sulfoxide. Dimethyl sulfoxide has high polarity, high boiling point and good thermal stability.

The electrolyte is prepared by taking the deep eutectic solvent as the solvent of the ionic liquid, so that the viscosity of the electrolyte and the internal resistance of the electrolyte under the low-temperature condition can be reduced, the phenomenon that the electric capacity of the ionic liquid is reduced along with the reduction of the temperature is relieved, in addition, the melting point of the deep eutectic solvent is low, the solidification temperature of the electrolyte can be reduced, and the low-temperature performance of the electrolyte is improved. In addition, the electrolyte is prepared by selecting the ionic liquid with good thermal stability and the high-boiling-point deep eutectic solvent, so that the boiling point of the prepared electrolyte is also high, and the temperature area range of the electrolyte is enlarged. In addition, the low-temperature capacity of the electrolyte is improved by adjusting the proportion of the hydrogen bond donor to the hydrogen bond acceptor and the proportion of the deep eutectic solvent to the ionic liquid.

The invention also provides a preparation method of the electrolyte, which preferably comprises the following steps:

carrying out first mixing on a hydrogen bond donor and a hydrogen bond acceptor to obtain a deep eutectic solvent;

and carrying out second mixing on the deep eutectic solvent and the ionic liquid to obtain the electrolyte.

In the present invention, the first mixing and the second mixing are preferably performed by magnetic stirring, and the rotation speed of the magnetic stirring is independently preferably 200 to 400rpm, and more preferably 300rpm. In the present invention, the time for the first mixing and the second mixing is not particularly limited, and the solution obtained by the first mixing and the second mixing may be mixed until the mixture is homogeneous and colorless.

In the present invention, the first mixing and the second mixing are preferably performed in an environment free of water and oxygen, so that the electrolyte is prevented from being contaminated with water and oxygen.

In order to further illustrate the present invention, the following detailed description of an electrolyte and its application provided by the present invention is made with reference to the accompanying drawings and examples, which should not be construed as limiting the scope of the present invention. In the application example, the capacity is calculated by using the amount of the activated carbon, and the calculation formula is shown as formula 1:

c = (I Δ t)/(m Δ V) formula 1

In formula 1, I is a current (A);

Δ t is the discharge time(s);

m is the activated carbon mass (g);

Δ V is a voltage interval (V).

Example 1

Adding ethylene glycol into dimethyl sulfoxide, and magnetically stirring at 300rpm while adding the ethylene glycol to form homogeneous colorless solution, namely the deep eutectic solvent. Wherein the molar ratio of the ethylene glycol to the dimethyl sulfoxide is 1:1.

and (2) uniformly adding 1-ethyl-3-methyltetrafluoroboric acid imidazole into the prepared deep eutectic solvent, and magnetically stirring at the rotating speed of 300rpm while adding until a homogeneous colorless solution is formed, thus obtaining the electrolyte. Wherein the molar ratio of the 1-ethyl-3-methyltetrafluoroboric acid imidazole to the deep eutectic solvent is 1:2.

the above preparation steps were all completed in a glove box filled with argon.

The electrolyte prepared in example 1 was subjected to a differential scanning calorimetry test, and the results are shown in fig. 1. As can be seen from FIG. 1, the electrolyte in example 1 showed no exothermic peak (upward peak) at-90 ℃ and the freezing point was seen to be lower than-90 ℃; no endothermic peak (downward peak) appeared at 50 ℃ and a boiling point higher than 50 ℃ was seen.

Example 2

(1) Adding ethylene glycol into dimethyl sulfoxide, and magnetically stirring at 300rpm while adding the ethylene glycol until a homogeneous colorless solution is formed, thus obtaining the deep eutectic solvent. Wherein the molar ratio of the ethylene glycol to the dimethyl sulfoxide is 1:2.

(2) And (2) uniformly adding 1-ethyl-3-methyltetrafluoroboric acid imidazole into the prepared deep eutectic solvent, and magnetically stirring at the rotating speed of 300rpm while adding the materials until a homogeneous colorless solution is formed, thus obtaining the electrolyte. Wherein the molar ratio of the 1-ethyl-3-methyltetrafluoroboric acid imidazole to the deep eutectic solvent is 1:3.

Comparative example 1

(1) Adding ethylene glycol into dimethyl sulfoxide, and magnetically stirring at 300rpm while adding the ethylene glycol until a homogeneous colorless solution is formed, thus obtaining the deep eutectic solvent. Wherein the molar ratio of the ethylene glycol to the dimethyl sulfoxide is 1:1.

(2) And (2) uniformly adding 1-ethyl-3-methyltetrafluoroboric acid imidazole into the prepared deep eutectic solvent, and magnetically stirring at the rotating speed of 300rpm while adding the materials until a homogeneous colorless solution is formed, thus obtaining the electrolyte. Wherein the molar ratio of the 1-ethyl-3-methyltetrafluoroboric acid imidazole to the deep eutectic solvent is 1:1.

Comparative example 2

(1) Adding ethylene glycol into dimethyl sulfoxide, and magnetically stirring at 300rpm while adding the ethylene glycol until a homogeneous colorless solution is formed, thus obtaining the deep eutectic solvent. Wherein the molar ratio of the ethylene glycol to the dimethyl sulfoxide is 2:1.

(2) And (2) uniformly adding 1-ethyl-3-methyltetrafluoroborate imidazole into the prepared deep eutectic solvent, and magnetically stirring at the rotating speed of 300rpm while adding the materials until a homogeneous colorless solution is formed, thus obtaining the electrolyte. Wherein the molar ratio of the 1-ethyl-3-methyltetrafluoroboric acid imidazole to the deep eutectic solvent is 1:3.

Comparative example 3

(1) Adding 2, 2-Trifluoroacetamide (TFA) into dimethyl sulfoxide, and magnetically stirring at the rotation speed of 300rpm while adding the materials until a homogeneous colorless solution is formed, namely the deep eutectic solvent. Wherein the molar ratio of the 2, 2-trifluoroacetamide to the dimethyl sulfoxide is 1:1.

(2) And (2) uniformly adding 1-ethyl-3-methyltetrafluoroboric acid imidazole into the prepared deep eutectic solvent, and magnetically stirring at the rotating speed of 300rpm while adding the materials until a homogeneous colorless solution is formed, thus obtaining the electrolyte. Wherein the molar ratio of the 1-ethyl-3-methyltetrafluoroboric acid imidazole to the deep eutectic solvent is 1:2.

The electrolyte prepared in comparative example 3 was subjected to a differential scanning calorimetry test, and the results are shown in fig. 2. As can be seen from FIG. 2, the electrolyte in comparative example 3 did not show an exothermic peak (upward peak) at-90 ℃ and was seen to have a freezing point below-90 ℃; no endothermic peak (downward peak) appeared at 50 ℃ and a boiling point higher than 50 ℃ was seen.

Comparative example 4

1-ethyl-3-methyltetrafluoroborate imidazole is uniformly added into dimethyl sulfoxide, and magnetic stirring is carried out at the rotating speed of 300rpm while adding materials until a homogeneous colorless solution is formed, thus obtaining the electrolyte. Wherein the molar ratio of the 1-ethyl-3-methyltetrafluoroboric acid imidazole to the dimethyl sulfoxide is 1:1.

The electrolyte of comparative example 4 was subjected to a differential scanning calorimetry test and the results are shown in fig. 3. As can be seen from FIG. 3, the electrolyte of example 4 showed no exothermic peak (upward peak) at-90 ℃ and the freezing point was seen to be lower than-90 ℃; no endothermic peak (downward peak) appeared at 50 ℃ and a boiling point higher than 50 ℃ was seen.

Application example 1

A supercapacitor was assembled in a glove box filled with argon gas using the electrolyte of example 1 (the amount of electrolyte used was 300 uL) and 0.001g of activated carbon as a working electrode.

At different temperatures, using CHI760EThe electrochemical performance of the super capacitor is tested by a chemical workstation, and the sweep speed is 5mVs ^-1 : FIG. 4 is a CV curve of the super capacitor in application example 1 at different temperatures; FIG. 5 is a charging and discharging curve of the super capacitor in application example 1 at different temperatures; table 1 shows the capacity of the supercapacitor in application example 1 at different temperatures.

As can be seen from fig. 4, the window of the super capacitor in this application example is 2.2V; as can be seen from FIG. 5, the current density was 0.5A/g, and the voltage cut-off range was 0 to 2.2V.

Table 1 capacity of supercapacitor in application example 1 at different temperatures

Temperature of	-40℃	-30℃	-20℃	-10℃	0℃	25℃	30℃	40℃
									capacity/F/g	12.33	20.36	24.52	26.39	27.54	29.00	29.27	29.73

Application example 2

A supercapacitor was assembled in a glove box filled with argon gas using the electrolyte of example 2 (the amount of electrolyte was 300 uL) and 0.001g of activated carbon as a working electrode.

The electrochemical performance of the supercapacitor was tested at different temperatures using a CHI760E electrochemical workstation, with a sweep rate of 5mVs ^-1 : FIG. 6 is a CV curve of the super capacitor in application example 2 at different temperatures; FIG. 7 is a charge-discharge curve of the super capacitor in application example 2 at different temperatures; table 2 shows the capacity of the supercapacitor in application example 2 at different temperatures.

As can be seen from fig. 6, the window of the super capacitor in this application is 2.2V; as can be seen from FIG. 7, the current density of the super capacitor in this application is 0.5A/g, wherein the voltage cut-off range is 0-2.2V.

Table 2 capacity of supercapacitor of application example 2 at different temperatures

Comparative application example 1

The electrolyte of comparative example 1 (the amount of electrolyte used was 300 uL) was used, and 0.001g of activated carbon was used as a working electrode, and a supercapacitor was assembled in a glove box filled with argon gas.

Electrochemical performance of the supercapacitor at different temperatures using CHI760E electrochemical workstationLine test, sweep speed 5mVs ^-1 : FIG. 8 is a CV curve of a supercapacitor of comparative application example 1 at different temperatures; FIG. 9 is a charge-discharge curve of the super capacitor in application example 2 at different temperatures; table 3 shows the capacity of the supercapacitor of comparative application example 1 at different temperatures.

As can be seen from fig. 8, the window of the supercapacitor in the comparative application example is 2.2V; as can be seen from FIG. 9, the current density was 0.5A/g, and the voltage cut-off range was 0 to 2.2V.

Table 3 compares the capacity of the supercapacitor of application example 1 at different temperatures

Temperature of	-40℃	-30℃	-20℃	-10℃	0℃	25℃	30℃	40℃
									capacity/F/g	4.59	15.79	20.39	22.93	24.78	25.77	25.83	26.55

Comparative application example 2

A supercapacitor was assembled in a glove box filled with argon using the electrolyte of comparative example 2 (the amount of electrolyte was 300 uL) and 0.001g of activated carbon as a working electrode.

The electrochemical performance of the supercapacitor was tested at different temperatures using a CHI760E electrochemical workstation, with a sweep rate of 5mVs ^-1 : FIG. 10 is a CV curve of a supercapacitor of comparative application example 2 at different temperatures; FIG. 11 is a graph showing the charging and discharging curves of the supercapacitor in comparative application example 2 at different temperatures; table 4 shows the capacity of the supercapacitor of application example 3 at different temperatures.

As can be seen from fig. 10, the window of the supercapacitor in this comparative application example is 2.2V; as can be seen from FIG. 11, the current density of the super capacitor in this application is 0.5A/g, wherein the voltage cut-off range is 0-2.2V.

Table 4 comparison of the capacity of the supercapacitor of application example 2 at different temperatures

Temperature of	-40℃	-30℃	-20℃	-10℃	0℃	25℃	30℃	40℃
									capacity/F/g	6.79	13.92	17.57	19.65	21.12	22.35	21.90	22.76

Comparative application example 3

The electrolyte of comparative example 3 (the amount of electrolyte used was 300 uL) was used, and 0.001g of activated carbon was used as a working electrode, and a supercapacitor was assembled in a glove box filled with argon gas.

The electrochemical performance of the supercapacitor was tested at different temperatures using a CHI760E electrochemical workstation, with a sweep rate of 5mVs ^-1 : FIG. 12 is a CV curve of the supercapacitor of application example 5 at different temperatures; fig. 13 is a charge and discharge curve of the supercapacitor of comparative application example 3 at different temperatures; table 5 shows the capacity of the supercapacitor of comparative application example 3 at different temperatures.

As can be seen from fig. 12, the window of the super capacitor in this application is 2.2V; as can be seen from FIG. 13, the current density of the super capacitor in this application is 0.5A/g, wherein the voltage cut-off range is 0-2.2V.

Table 5 compares the capacity of the supercapacitor of application example 3 at different temperatures

Temperature of	-40℃	-30℃	-20℃	-10℃	0℃	25℃	30℃	40℃
									capacity/F/g	1.05	4.91	12.57	19.91	21.11	24.18	24.26	24.55

Comparative application example 4

A supercapacitor was assembled in a glove box filled with argon using the electrolyte of comparative example 4 (the amount of electrolyte was 300 uL) and 0.001g of activated carbon as a working electrode.

The electrochemical performance of the supercapacitor was tested at different temperatures using a CHI760E electrochemical workstation, with a sweep rate of 5mVs ^-1 : FIG. 14 is a CV curve of a supercapacitor of comparative application example 4 at different temperatures; FIG. 15 is a graph showing the charging and discharging curves of the supercapacitor of comparative application example 4 at different temperatures; table 6 shows the capacity of the supercapacitor of comparative application example 4 at different temperatures.

As can be seen from fig. 14, the window of the supercapacitor in the comparative application example is 2.2V; as can be seen from FIG. 15, the current density of the supercapacitor in this application is 0.5A/g.

Table 6 compares the capacity of the supercapacitor of application example 4 at different temperatures

Temperature of	-40℃	-30℃	-20℃	-10℃	0℃	25℃	30℃	40℃
									capacity/F/g	6.62	14.62	19.99	22.58	23.85	25.58	25.81	26.01

From the results of the above examples and comparative examples, it can be seen that the electrolyte provided by the present invention has an extremely low freezing point and an extremely high boiling point, and the supercapacitor assembled with the electrolyte of the present invention has the characteristics of normal charge and discharge in the temperature range of-40 ℃ to 40 ℃, and has good stability and electrochemical properties.

Although the above embodiments have been described in detail, they are only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive step according to the embodiments, and all of the embodiments belong to the protection scope of the present invention.

Claims

1. The electrolyte is characterized by consisting of a deep eutectic solvent and an ionic liquid which are mutually soluble;

the deep eutectic solvent is a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor is an alcohol;

the molar ratio of the ionic liquid to the deep eutectic solvent is 1:2 to 3;

the ionic liquid is 1-ethyl-3-methyltetrafluoroborate imidazole;

the hydrogen bond acceptor is a sulfone compound.

2. The electrolyte of claim 1, wherein the sulfone compound comprises dimethyl sulfoxide.

3. The electrolyte of claim 1, wherein the alcohol comprises a glycol.

4. The electrolyte of claim 3, wherein the glycol comprises ethylene glycol.

5. The electrolyte of claim 1, wherein the molar ratio of hydrogen bond donor to hydrogen bond acceptor is 1:1 or 1:2.

6. the electrolyte of claim 1, wherein the ionic liquid and deep eutectic solvent are present in a molar ratio of 1:2 or 1:3.

7. the electrolyte of claim 1, wherein the electrolyte has a freezing point below-90 ℃ and a boiling point above 50 ℃.

8. Use of the electrolyte of any one of claims 1 to 7 in a supercapacitor.