KR102555960B1 - Electrolytic solution additive for electrochemical device and electrolytic solution containing the same - Google Patents

Abstract

The present invention relates to an electrolyte solution additive for an electrochemical device capable of extending the operating temperature of the electrochemical device and an electrolyte solution including the same. The electrolyte solution for an electrochemical device according to the present invention includes an electrolyte, a solvent in which SL (Sulfolane) and AN (acetonitrile) are mixed, and an octamethylcyclotetrasiloxane additive.

Description

Electrolytic solution additive for electrochemical device and electrolytic solution containing the same}

The present invention relates to an electrolyte solution for an electrochemical device, and more particularly, to an electrolyte solution additive for an electrochemical device capable of extending the operating temperature of an electrochemical device and an electrolyte solution containing the same.

In the information age, high value-added industries that collect and utilize various useful information in real time through various information and communication devices are leading, and stable energy supply is recognized as an important factor to secure the reliability of these systems.

As part of securing stable energy, an electrochemical device that converts electrical energy into chemical energy, stores it, and then converts it into electrical energy when necessary is used.

These electrochemical devices include secondary batteries such as Ni-MH batteries, Ni-Cd batteries, lead-acid batteries and lithium secondary batteries, supercapacitors with high power density and almost unlimited charge and discharge life, aluminum electrolytic capacitors, and ceramic capacitors. etc.

In particular, supercapacitors include electric double layer capacitors (EDLC), pseudo capacitors, and hybrid capacitors such as lithium ion capacitors (LIC). There are molds, cans, etc. The can shape includes a cylindrical shape (wound shape), a prismatic shape, and the like. At this time, the cylindrical shape is manufactured by winding the cell into a jelly roll shape and then inserting it into a cylindrical case.

Here, the electric double layer capacitor is a capacitor using the electrostatic charge phenomenon generated in the electric double layer formed at the interface of different phases. Compared to batteries whose energy storage mechanism depends on oxidation and reduction processes, the electric double layer capacitor has faster charging and discharging speed, higher charge and discharge efficiency, and cycle characteristics. It is widely used for backup power, and the possibility as an auxiliary power source for electric vehicles in the future is infinite.

A pseudocapacitor is a capacitor that converts a chemical reaction into electrical energy and stores it using an oxidation-reduction reaction between an electrode and an electrochemical oxide reactant. Compared to electric double layer capacitors that store charges only in the double layer formed on the surface of the electrochemical double layer electrode, the pseudocapacitor can store charges up to the surface of the electrode material, so the storage capacity is about 5 times greater than that of electric double layer capacitors. RuOx, IrOx, MnOx, etc. are used as metal oxide electrode materials.

The lithium ion capacitor is a secondary battery system of a new concept that combines the high power and long life characteristics of conventional electric double layer capacitors with the high energy density of lithium ion batteries. Electric double-layer capacitors using the physical adsorption reaction of electric charges in the electric double-layer are limited in various application fields due to their low energy density despite their excellent output characteristics and lifespan characteristics. As a means to solve the problem of the electric double layer capacitor, a lithium ion capacitor using a carbon-based material capable of intercalating and deintercalating lithium ions as an anode active material has been proposed. Thus, the potential of the cathode can be drastically lowered, the cell voltage can be realized at a high voltage of 3.8 V or more, which is greatly improved compared to 2.5 V of the conventional electric double layer capacitor, and high energy density can be expressed.

However, since electrochemical decomposition and ion instability occur when an electrochemical device including a supercapacitor operates at a high temperature, the electrochemical device has a limitation in operating temperature.

Registered Patent Publication No. 2012-1118862 (2012.03.06. Notice)

In order to solve these problems, various studies are being conducted, such as using salts or solvents having high ionic conductivity or applying additives to electrolytes to improve properties.

Accordingly, an object of the present invention is to provide an electrolyte solution additive for an electrochemical device capable of extending the operating temperature of a supercapacitor and an electrolyte solution including the same.

In order to achieve the above object, the present invention is an additive added to an electrolyte solution for an electrochemical device, which is octamethylcyclotetrasiloxane added to an electrolyte solution containing an electrolyte, SL (Sulfolane) and AN (acetonitrile) Electrochemical An electrolyte solution additive for devices is provided.

The octamethylcyclotetrasiloxane may be added at less than 5 wt%.

0.5 to 1 wt% of the octamethylcyclotetrasiloxane may be added.

The present invention also provides an electrolyte; A solvent in which SL (Sulfolane) and AN (acetonitrile) are mixed; And octamethylcyclotetrasiloxane (octamethylcyclotetrasiloxane) of the additive; provides an electrolyte solution for an electrochemical device containing.

The solvent may include 10 to 50 wt% of the SL and 50 to 90 wt% of the AN.

And the electrolyte is SBPBF ₄ (spirobipyrrolidinium tetrafluoroborate), TEABF ₄ (tetraethylammonium tetrafluorborate), TEMABF ₄ (triethylmethylammonium tetrafluorborate), EMIBF ₄ (1-ethyl-3-methyl imidazolium tetrafluoroborate), EMITFSI (1-ethyl-3-methyl imidazolium bis (trifluoromethane sulfonyl)imide), LiClO ₄ , LiPF ₆ , LiAsF ₆ , or LiBF ₄ .

According to the present invention, the operating temperature of the electrochemical device can be extended by adding octamethylcyclotetrasiloxane to the electrolyte solution for the electrochemical device. That is, through a high-temperature, high-humidity load test at 85 ° C and 85% RH for the electrolyte solution to which octamethylcyclotetrasiloxane was added, compared to the electrolyte solution to which octamethylcyclotetrasiloxane was not added, AC-ESR (equivalence series resistance; equivalent It can be seen that the series resistance) decreased and the capacitance increased. The improvement in the resistance increase rate and the capacity decrease rate in the high temperature and high humidity load test means that the operating temperature of the electrochemical device using the electrolyte with octamethylcyclotetrasiloxane added as an additive has been extended.

It should be noted that in the following description, only parts necessary for understanding the embodiments of the present invention are described, and descriptions of other parts will be omitted without departing from the gist of the present invention.

The terms or words used in this specification and claims described below should not be construed as being limited to ordinary or dictionary meanings, and the inventors have appropriately used the concept of terms to describe their inventions in the best way. It should be interpreted as a meaning and concept consistent with the technical spirit of the present invention based on the principle that it can be defined in the following way. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical spirit of the present invention, so various equivalents that can replace them at the time of the present application. It should be understood that there may be variations and variations.

Hereinafter, the present invention will be described in more detail as follows.

The present invention relates to an additive added to an electrolyte solution for an electrochemical device and an electrolyte solution containing the same.

Here, the electrochemical device includes a supercapacitor.

The electrolyte solution according to the present invention includes an electrolyte, a solvent and an additive. As an additive, octamethylcyclotetrasiloxane represented by Formula 1 below is used.

[Formula 1]

The electrolyte may be an electrolyte applied to a supercapacitor. For example, electrolytes include SBPBF ₄ (spirobipyrrolidinium tetrafluoroborate), TEABF ₄ (tetraethylammonium tetrafluorborate), TEMABF ₄ (triethylmethylammonium tetrafluorborate), EMIBF ₄ (1-ethyl-3-methyl imidazolium tetrafluoroborate), EMITFSI (1-ethyl-3-methyl imidazolium bis( trifluoromethane sulfonyl)imide), LiClO ₄ , LiPF ₆ , LiAsF ₆ , or LiBF ₄ . The concentration of the electrolyte may be 0.5M to 10M, preferably 0.5M to 3M. For example, as an electrolyte, 1M SBPBF ₄ represented by Formula 2 may be used.

[Formula 2]

As a solvent, a mixed solvent of SL (Sulfolane) represented by Chemical Formula 3 and AN (acetonitrile) represented by Chemical Formula 4 was used.

[Formula 3]

[Formula 4]

Here, since SL has a higher viscosity than AN, when AN and SL are mixed together, the initial AC-ESR (equivalence series resistance) is greater than when AN alone is used, but the boiling point (285℃) of SL is higher than that of AN. This is because it is higher than the boiling point (82℃), so the resistance increase rate can be reduced in a high temperature and high humidity environment when SL and AN are mixed and used.

In this way, the composition ratio of the solvent for reducing the resistance increase rate may be 10 to 50 wt% of SL and 50 to 90 wt% of AN.

On the other hand, when using one of AN and SL as a solvent, even if octamethylcyclotetrasiloxane is added as an additive to the electrolyte, the improvement in the resistance increase rate and the capacity decrease rate due to the addition of the additive may be insignificant or degenerate. That is, as will be described later, an electrolyte solution using AN alone as a solvent and octamethylcyclotetrasiloxane as an additive may have a higher rate of resistance increase and a lower rate of capacity decrease than an electrolyte solution using a mixed solvent of AN and SL and no additive added. .

In addition, by using octamethylcyclotetrasiloxane as an additive, it is possible to improve the resistance increase rate and the capacity decrease rate of the electrochemical device in a high-temperature, high-humidity environment. Octamethylcyclotetrasiloxane may be added in an amount of less than 5 wt% as an additive to the electrolyte solution. When octamethylcyclotetrasiloxane is added in an amount of 5 wt% or more, the resistance increase rate and the capacity decrease rate may deteriorate.

Preferably, 0.5 to 1 wt% of octamethylcyclotetrasiloxane may be added to the electrolyte as an additive. That is, when the additive is added in an amount of 1 wt% or less, the effect of improving the resistance increase rate and the capacity decrease rate can be expected. In addition, when the additive is added in an amount of less than 0.5 wt%, the improvement in the resistance increase rate and the capacity decrease rate due to the addition of the additive may be insignificant.

[Examples and Comparative Examples]

In order to confirm the electrochemical characteristics of the electrolyte solution according to the present invention, electrolyte solutions according to Examples and Comparative Examples were prepared as shown in Table 1 below. An electrochemical device including the electrolyte solution according to the prepared Examples and Comparative Examples was manufactured, and a high-temperature, high-humidity load test was performed while applying 2.7V at 85 ° C. and 85% RH. The high temperature and high humidity load test results are shown in Table 1. Electrochemical devices according to Comparative Examples and Examples were manufactured with a diameter of 10 mm and a height of 30 mm by EDLC.

Referring to Table 1, the electrolyte solution to which no additives were added according to Comparative Example 1 includes an electrolyte 1M SBPBF ₄ and solvents AN and SL.

In the electrolyte solution according to Example 1, 0.5 wt% of the additive was added to the electrolyte solution according to Comparative Example 1. In the electrolyte solution according to Example 2, 1 wt% of the additive was added to the electrolyte solution according to Comparative Example 1.

Based on the electrolyte according to Comparative Example 1, a high-temperature and high-humidity load test was performed on the electrochemical device including the electrolyte according to Example 1, Example 2, Comparative Example 2, and Comparative Example 3 to measure AC-ESR and capacitance ) was evaluated.

As a result of the high temperature and high humidity load test, it can be confirmed that the electrolyte according to Example 2 decreased by about 6.8% in AC-ESR and increased in capacitance by about 2.9% compared to the electrolyte according to Comparative Example 1 at 1000 hours (hr). .

As a result of the high temperature and high humidity load test, it can be seen that the AC-ESR and capacitance characteristics of Example 2 in which 1 wt% of the additive is added are improved compared to Example 1 in which 0.5 wt% of the additive is added.

However, in the case of Comparative Example 2 in which 5 wt% of the additive was added, it can be seen that the AC-ESR increased by about 14.1% and the capacitance decreased by about 13.4% compared to Comparative Example 1.

Therefore, it can be seen that the amount of the additive added to the electrolyte solution is preferably less than 5 wt%.

And in the case of Comparative Example 3 in which AN was used alone as the solvent of the electrolyte and 1 wt% of the additive was added, it can be seen that the AC-ESR increased by about 965.2% and the capacitance decreased by about 95.2% compared to Comparative Example 1. .

Therefore, it can be confirmed that it is preferable to use a mixed solvent of AN and SL as the solvent of the electrolyte solution.

As such, it can be confirmed that the electrolyte solutions according to Examples 1 and 2 improved the resistance increase rate and the capacity decrease rate in the high-temperature, high-humidity load test. This means that by adding octamethylcyclotetrasiloxane as an additive to the electrolyte solution, the operating temperature of the electrochemical device using the electrolyte solution according to Examples 1 and 2 was extended.

On the other hand, the embodiments disclosed in this specification and drawings are only presented as specific examples to aid understanding, and are not intended to limit the scope of the present invention. In addition to the embodiments disclosed herein, it is obvious to those skilled in the art that other modifications based on the technical idea of the present invention can be implemented.

Claims (8)

As an electrolyte for a supercapacitor,
electrolyte of SBPBF ₄ (spirobipyrrolidinium tetrafluoroborate);
A solvent in which SL (Sulfolane) and AN (acetonitrile) are mixed; and
An additive of octamethylcyclotetrasiloxane added to extend the operating temperature of the supercapacitor by improving the resistance increase rate and capacity decrease rate of the supercapacitor;
0.5 to 1 wt% of the octamethylcyclotetrasiloxane is added,
The solvent is an electrolyte solution for a supercapacitor, characterized in that composed of 10 to 50 wt% of the SL and 50 to 90 wt% of the AN. delete delete delete delete delete delete delete