KR20110060253A - Electrolyte solution and super capacitor including the same - Google Patents

Abstract

PURPOSE: An electrolyte solution and a capacitor with a super-large capacitance including the same are provided to enhance an output characteristic and an operating voltage characteristic by using a solvent mixed with at least one kind of solvent having a high dielectric ratio and a high boiling point. CONSTITUTION: A mixed solvent is selected among propionitrile, gamma-butyrolactone, sulfuran and alkyl sulfuran. The electrolyte solution is made by mixing the mixed solvent with the electrolyte salt. The electrolyte salt includes cation selected from the group consisting of tetra-alkyl ammonium, pyrrole lithium, or Fife lithium spy. The electrolyte salt includes anion selected from the group consisting of tetra-fluoroborate, bis imide and tri-fluoromethyl sulfonate.

Description

Electrolytic solution and supercapacitor including the same

The present invention relates to an electrolyte solution and an ultracapacitor including the same, and more particularly, an electrolyte solution having a low gas generation even at a high temperature used in an ultracapacitor such as an electric double layer capacitor, and having an excellent high temperature reliability. It relates to a high capacity capacitor.

The ultracapacitor is an energy storage device with intermediate characteristics between an electrolytic capacitor and a secondary battery. It is capable of rapid charging and discharging, and has characteristics such as high efficiency, a wide operating temperature range, and a semi-permanent lifespan. Electric Double-Layer Capacitor) can be exemplified.

Ultracapacitors, such as electric double layer capacitors, have very important output characteristics, high temperature reliability (lifetime characteristics), and maximum operating voltage characteristics. In general, in the case of the secondary battery, since the output characteristics are lower and the high temperature reliability (life characteristic, etc.) is limited, compared to ultracapacitors such as electric double layer capacitors, the characteristics are very important as the differentiated characteristics of the capacitor. In addition, in capacitors, E = 1/2 × C × V ² (E = Energy, C = Capacitance, V = Voltage), which is important because the maximum operating voltage directly affects the maximum chargeable energy of the capacitor. This is big.

As an electrolyte solution used for a supercapacitor such as a conventional electric double layer capacitor, the solvent is mainly used acetonitrile (AN) or propylene carbonate (PC), and the electrolyte salt is tetraethylammonium tetrafluoro Ammonium salts such as borate (TEABF ₄ ) and lithium metal salts (eg LiBF ₄ , LiPF ₆ ) are often used.

However, when acetonitrile (AN) is used as the solvent of the electrolyte solution, the boiling point (81 to 82 ° C) of the solvent itself is low, so that a large amount of gas is generated at a relatively high temperature, and when propylene carbonate (PC) is used, The high boiling point (240 ℃) is advantageous in terms of high temperature reliability, but it is not necessarily advantageous for high voltage operation because it has a lot of side reactions compared to acetonitrile (AN), and it has a relatively low output characteristic due to its high viscosity and low conductivity. There are disadvantages.

Accordingly, an object of the present invention is to provide an electrolyte solution having a low amount of gas generation at a high temperature and excellent in high temperature reliability, and an ultracapacitor including the same.

In order to achieve the above object, the present invention, at least one solvent selected from the group consisting of propionitrile and gamma butyrolactone, alkyl gamma butyrolactone, propylene carbonate, glutaronitrile, sulfolane and alkyl sulfolane Mixed solvents mixed above; And an electrolyte salt.

Here, the electrolyte salt is a cation selected from the group consisting of a spiro structural compound of tetraalkyl ammonium, pyrrolidium, piperidium, pyrrolidium or piperidium and tetrafluoroborate, hexafluorophosphate, perchlorate, hexafluoroarsen It is preferable that an anion selected from the group consisting of nate, bis (trifluoromethylsulfonyl) imide and trifluoromethylsulfonate is bonded, and the weight ratio of the solvent mixed with the propionitrile and the propionitrile ( Propionitrile: solvent mixed with propionitrile) is preferably 1: 9 to 7: 3.

In addition, the present invention provides an ultracapacitor including the electrolyte solution.

The electrolyte solution according to the present invention is a solvent having high dielectric constant and high boiling point such as propionitrile and (alkyl) gamma butyrolactone, propylene carbonate, glutaronitrile, and (alkyl) sulfolane, which have excellent high temperature reliability and voltage characteristics. It is characterized by using a mixed solvent in which one or more solvents are mixed. The ultracapacitor using the electrolyte solution has excellent high temperature reliability, output characteristics and maximum operating voltage characteristics, and a small amount of gas generated in the capacitor even at a high temperature.

Hereinafter, the present invention will be described in detail.

Electrolyte solution according to the present invention is propionitrile (propionitrile) and gamma butyrolactone (γ-butyrolactone), alkyl gamma butyrolactone, propylene carbonate (propylene carbonate), glutaronitrile (glutaronitrile), sulfolane (sulforane) and Mixed solvents and electrolyte salts in which at least one solvent selected from the group consisting of alkyl sulfolanes are mixed.

The mixed solvent used in the present invention has properties similar to acetonitrile, but has a higher boiling point, excellent high temperature reliability, and good propionitrile with good voltage characteristics. From the group consisting of gamma-butyrolactone, alkyl gamma-butyrolactone, propylene carbonate, glutaronitrile, sulfolane and alkyl sulfolane One or more solvents selected are mixed with the propionitrile. Here, the alkyl gamma butyrolactone is gamma butyrolactone substituted with an alkyl group having 1 to 4 carbon atoms, and the alkyl sulfolane is a sulfolane substituted with an alkyl group having 1 to 4 carbon atoms.

The weight ratio of the propionitrile and the solvent mixed with the propionitrile (a solvent mixed with propionitrile: propionitrile) is 1: 9 to 7: 3, preferably 2: 8 to 5: 5. When the weight ratio of the propionitrile and the solvent mixed with the propionitrile is out of the above range and the content of propionitrile having a relatively low electrolyte salt solubility is increased, it may be difficult to prepare a high concentration electrolyte solution, If the content of propionitrile is too small, there is a fear that the viscosity of the electrolyte solution increases and the conductivity, output characteristics, high temperature reliability, and the like decrease.

As the electrolyte salt used in the present invention, conventional electrolyte salts used in ultracapacitors such as electric double layer capacitors can be used, and preferably tetraalkyl ammonium (for example, tetraethyl ammonium, tetrapropyl ammonium, tetrabutyl). Spiro structural compounds (e.g., spiro-1,1'-bipyrrolidinium, spiro- peperidine-1,1'-pyrrolidinium), pyrrolidinium, peperidinium, pyrrolidium or piperidium etc.) borate (BF ₄ with positive and tetrafluoroethane are selected from the group consisting of ^-), phosphate (PF ₆ hexafluoro ^-), perchlorate (ClO ₄ ^-), carbonate Arsene hexafluorophosphate (AsF ₆ ^-), bis ( methylsulfonyl trifluoromethanesulfonyl) imide _{((CF 3 SO 2) 2} N - can be used for the electrolyte salt anion is coupled is selected from the group consisting of a) ^-), and trifluoromethyl sulfonate (SO ₃ CF ₃ .

The concentration of the electrolyte salt is preferably 0.5 to 2.0 M (molar concentration), more preferably 0.8 to 1.5 M. When the concentration of the electrolyte salt is less than 0.5M, the conductivity of the electrolyte solution may be lowered to increase the resistance of the capacitor. If the concentration exceeds 2.0M, the electrolyte salt may not be completely dissolved or may be partially precipitated at a low temperature. There is a fear that the conductivity of rather decreases.

The ultracapacitor according to the present invention includes the electrolyte solution. The ultracapacitor includes an electrode part consisting of a positive electrode and a negative electrode, a separator for electrically separating the positive electrode and the negative electrode, and the positive electrode and the negative electrode such that an electric double layer is formed on the surfaces of the positive electrode and the negative electrode when a predetermined voltage is applied. A typical electric double layer capacitor including an electrolyte solution filled in a space between them can be exemplified.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The following examples are intended to illustrate the present invention, but the scope of the present invention is not limited by the following examples.

Example 1 Preparation of Electrolyte Solution

Propionitrile and propylene carbonate were purified to a high purity solvent of 99.95% (GC) or more using a 50-stage distillation apparatus, respectively, to prepare a mixed solvent of weight ratio 1: 2 (propionitrile: propylene carbonate). Next, tetraethylammonium tetrafluoroborate (trade name: SkyLyte-TEABF ₄ , manufacturer: SK Chemical Co., Ltd., 99.9%) was dissolved in the mixed solvent to prepare a 1M electrolyte solution. The conductivity of the prepared electrolyte solution was measured with a conductivity meter (Thermo, Orion 136S) at 25 ° C., and the results are shown in Table 1 below.

Example 2 Preparation of Electrolyte Solution

Propionitrile and gammabutyrolactone were purified using a 50-stage distillation apparatus to obtain a high purity solvent of 99.95% (GC) or more, respectively, and a mixed solvent of 1: 2 (propionitrile: gammabutyrolactone) by weight ratio. Was prepared. Next, tetraethylammonium tetrafluoroborate (trade name: SkyLyte-TEABF ₄ , manufacturer: SK Chemical Co., Ltd., 99.9%) was dissolved in the mixed solvent to prepare a 1M electrolyte solution. The conductivity of the prepared electrolyte solution was measured with a conductivity meter (Thermo, Orion 136S) at 25 ° C., and the results are shown in Table 1 below.

Example 3 Preparation of Electrolyte Solution

Propionitrile and α-methyl-gammabutyrolactone were purified to have a high purity solvent of 99.95% (GC) or more using a 50-stage distillation unit each, and a weight ratio of 1: 2 (propionitrile: α-methyl- A mixed solvent of gamma butyrolactone) was prepared. Next, tetraethylammonium tetrafluoroborate (trade name: SkyLyte-TEABF ₄ , manufacturer: SK Chemical Co., Ltd., 99.9%) was dissolved in the mixed solvent to prepare a 1M electrolyte solution. The conductivity of the prepared electrolyte solution was measured with a conductivity meter (Thermo, Orion 136S) at 25 ° C., and the results are shown in Table 1 below.

Comparative Example 1 Preparation of an Electrolyte Solution

Acetonitrile (AN) was purified to a high purity solvent of 99.95% (GC) or higher using a theoretical 50-stage distillation apparatus, and tetraethylammonium tetrafluoroborate (product name: SkyLyte-TEABF) was purified on purified acetonitrile (AN). ₄ , Manufacturer: SK Chemical Co., Ltd., 99.9%) was dissolved to prepare a 1M electrolyte solution. The conductivity of the prepared electrolyte solution was measured with a conductivity meter (Thermo, Orion 136S) at 25 ° C., and the results are shown in Table 1 below.

Comparative Example 2 Preparation of Electrolyte Solution

The propylene carbonate (PC) was purified to a high purity solvent of 99.95% (GC) or more using a 50-stage distillation unit, and tetraethylammonium tetrafluoroborate (product name: SkyLyte-TEABF) was purified on the purified propylene carbonate (PC). ₄ , Manufacturer: SK Chemical Co., Ltd., 99.9%) was dissolved to prepare a 1M electrolyte solution. The conductivity of the prepared electrolyte solution was measured with a conductivity meter (Thermo, Orion 136S) at 25 ° C., and the results are shown in Table 1 below.

Comparative Example 3 Preparation of Electrolyte Solution

Gamma-butyrolactone (GBL) was purified to a high purity solvent of 99.95% (GC) or more using a 50-stage distillation unit, and tetraethylammonium tetrafluoroborate (GBL) was purified to the purified gamma-butyrolactone (GBL). : SkyLyte-TEABF ₄ , manufacturer: SK Chemical Co., Ltd., 99.9%) was dissolved to prepare a 1M electrolyte solution. The conductivity of the prepared electrolyte solution was measured with a conductivity meter (Thermo, Orion 136S) at 25 ° C., and the results are shown in Table 1 below.

[Examples 4 to 6 and Comparative Examples 4 to 6] Preparation of Electric Double Layer Capacitor

First, the slurry liquid prepared by mixing activated carbon (BP-20): binder (PVDF): conductive material (SPB) = 90: 7: 3 is coated on aluminum foil (Al Foil) and roll pressed to give a positive electrode and An activated carbon electrode used as a negative electrode was prepared. Next, the prepared electrode was cut into a size of 5 cm 크기 5 cm, and the anode, the separator (Celgard, PP), and the cathode were put on the pouch, and then inserted into a pouch. The solution was injected into a pouch to prepare a pouch type capacitor. The basic characteristics (capacitance) of capacitors manufactured by using an electrochemical analyzer (CH Instrument, product name: 608B) were evaluated, and a high temperature acceleration test was conducted at 75 ° C. for 1000 hours. The change of the characteristics (% reduction in capacitance) was compared, and the change in pouch thickness according to the gas generated inside the pouch type capacitor was compared. The results are shown in Table 1 below.

Capacitor Electrolyte solution Electrolyte solution
Conductivity (25 ℃) High temperature acceleration test Capacitance reduction rate Pouch Thickness Change Example 4 Example 1 22.9 mS / cm -10% +3 mm Example 5 Example 2 24.5 mS / cm -12% +3 mm Example 6 Example 3 24.3 mS / cm -7% +2 mm Comparative Example 4 Comparative Example 1 55.1 mS / cm -14% +8 mm Comparative Example 5 Comparative Example 2 13.7 mS / cm -17% +3 mm Comparative Example 6 Comparative Example 3 17.5 mS / cm -20% +4 mm

From Table 1, the capacitor (Comparative Example 4) to which the electrolyte solution (Comparative Example 1) using acetonitrile (AN) as a solvent is high in conductivity, but the pouch is inflated due to the large amount of gas generated at high temperature (75 ° C). It can be seen that it is not suitable to use at high temperature, and the capacitor (Comparative Example 5) and the gamma butyrolactone (GBL) to which the electrolyte solution (Comparative Example 2) using propylene carbonate (PC) as the solvent are used as the solvent. It can be seen that the capacitor (Comparative Example 6) to which the solution (Comparative Example 3) is applied has a relatively higher rate of decrease in capacitance after the high temperature acceleration test.

However, it can be seen that the capacitors (Examples 4 to 6) to which the electrolyte solutions (Examples 1 to 3) according to the present invention are applied have a very low capacitance reduction rate and a small amount of gas generated according to the high temperature acceleration test. It can be seen that the conductivity of can be greatly improved.

From the above results, the electrolyte solution of the present invention is useful for ultracapacitors such as electric double layer capacitors, and the supercapacitors using the electrolyte solution have excellent high temperature reliability, output characteristics and maximum operating voltage characteristics, It can be seen that the generation amount is small.

Claims (5)

Mixed solvents of at least one of propionitrile and a solvent selected from the group consisting of gamma butyrolactone, alkyl gamma butyrolactone, propylene carbonate, glutaronitrile, sulfolane and alkyl sulfolane; And an electrolyte salt. The method of claim 1, wherein the electrolyte salt is tetrafluoroborate, hexafluorophosphate, perchlorate, a cation selected from the group consisting of spiro structural compounds of tetraalkyl ammonium, pyrrolidium, piperidium, pyrrolidium or piperidium, An electrolyte solution in which an anion selected from the group consisting of hexafluoroarsenate, bis (trifluoromethylsulfonyl) imide, and trifluoromethylsulfonate is bonded. The electrolyte solution of claim 1, wherein the alkyl gamma butyrolactone is gamma butyrolactone substituted with an alkyl group having 1 to 4 carbon atoms, and the alkyl sulfolane is a sulfolane substituted with an alkyl group having 1 to 4 carbon atoms. The electrolyte solution of claim 1, wherein the weight ratio of the propionitrile and the solvent mixed with the propionitrile (propionitrile: propionitrile) is 1: 9 to 7: 3. Propionitrile and a mixed solvent comprising at least one solvent selected from the group consisting of gamma butyrolactone, alkyl gamma butyrolactone, propylene carbonate, glutaronitrile, sulfolane and alkyl sulfolane, and an electrolyte salt Ultracapacitor comprising a prepared electrolyte solution.