KR20200083367A - Gel polymer electrolyte and electrochemical device comprising the same - Google Patents

Abstract

A gel polymer electrolyte according to an embodiment of the present invention includes a diacrylate or dimethacrylate represented by chemical formula 1, or a polymer or a copolymer thereof. In chemical formula 1, R 1 to R 4 each represents hydrogen, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and n is an integer of 2 to 10. Therefore, the present invention can secure durability at high temperatures while stabilizing life characteristics at a high driving voltage.

Description

Gel polymer electrolyte and electrochemical device comprising the same {GEL POLYMER ELECTROLYTE AND ELECTROCHEMICAL DEVICE COMPRISING THE SAME}

One embodiment of the present invention relates to a gel polymer electrolyte and an electrochemical device comprising the same.

Recently, as interest in energy storage and conversion technology has increased, interest in various types of electrochemical devices has been focused.

Liquid electrolytes are widely used in electrochemical devices, but there is a problem that the driving becomes unstable under conditions such as high temperature and high voltage due to the volatile and instability of the solvent, as well as the possibility of leakage.

To solve this problem, a technique of applying a gel polymer electrolyte in place of a liquid electrolyte has been studied.

However, the gel polymer electrolyte, which is generally known, has a limitation in that electrochemical properties are inferior to conventional liquid electrolytes. Thus, a generally known gel polymer electrolyte is more unsuitable for supercapacitors that require higher output characteristics than lithium ion batteries.

An embodiment of the present invention provides a gel polymer electrolyte and an electrochemical device including the same, which can secure the durability at high temperature while stabilizing life characteristics at a high driving voltage.

The gel polymer electrolyte according to an embodiment of the present invention includes a diacrylate or dimethacrylate represented by Formula 1 below, or a polymer or copolymer thereof.

[Formula 1]

(In the formula (1), R ¹ to R ⁴ each represents hydrogen, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and n represents an integer of 2 to 10.)

R ¹ and R ² are each a hydrogen or methyl group, and R ³ and R ⁴ may be hydrogen.

n may be an integer from 2 to 8.

It may contain 1 to 7% by weight of a polymer or copolymer of diacrylate or dimethacrylate represented by the formula (1).

The gel polymer electrolyte may further include an organic solvent and an electrolyte salt.

The electrochemical device according to an embodiment of the present invention includes the gel polymer electrolyte described above.

An electrochemical device according to an embodiment of the present invention includes an anode and a cathode; A polymer film interposed between the positive electrode and the negative electrode, including a separator including the gel polymer electrolyte, and a polymer film formed on the surface of at least one of the positive electrode and the negative electrode may be formed.

An electrochemical device according to an embodiment of the present invention includes an anode and a cathode; A polymer electrolyte may be impregnated between the positive electrode and the negative electrode, including a separator comprising a gel polymer electrolyte, and an electrode active material of at least one of the positive electrode and the negative electrode.

By using a gel polymer electrolyte in one embodiment of the present invention, it is possible to secure durability at high temperature while stabilizing life characteristics at a high driving voltage.

In one embodiment of the present invention, the gel polymer electrolyte may be applied to a super capacitor requiring high power, and applied to a lithium ion battery to improve its performance.

1 is a graph measuring the initial capacitance for charge/discharge rate in Experimental Example 1.
FIG. 2 is a graph measuring late capacitance for charge/discharge rate in Experimental Example 1.
3 is a graph measuring capacitance reduction in Experimental Example 1.
FIG. 4 is a graph measuring capacitance by weight% with respect to charge/discharge rate in Experimental Example 1.
5 is a graph measuring bulk resistance in Experimental Example 2.
6 is a graph measuring the interface resistance in Experimental Example 2.
7 is a graph measuring ESR in Experimental Example 2.
8 is a photograph of the desorption state of the negative electrode active material in Experimental Example 3.

In the present specification, when a part “includes” a certain component, this means that other components may be further included rather than excluding other components, unless otherwise specified. The terms "about", "substantially", and the like, as used throughout this specification, are used in or at a value close to that value when manufacturing and material tolerances specific to the stated meaning are given, and are understood herein. To help, accurate or absolute figures are used to prevent unconscionable abusers from unduly using the disclosed disclosure. The term “~(steps)” or “steps of” to the extent used throughout this specification does not mean “steps for”.

In the present specification, the term "combination of these" included in the expression of the marki form means one or more mixtures or combinations selected from the group consisting of the elements described in the expression of the marki form, the components It means to include one or more selected from the group consisting of.

"Substitution" in the present specification, unless otherwise defined, at least one hydrogen of the compound is a C1 to C30 alkyl group; C1 to C10 alkoxy groups; Silane group; Alkyl silane groups; Alkoxysilane group; Means substituted with ethyleneoxyl group.

As used herein, "hetero" means an atom selected from the group consisting of N, O, S, and P, unless otherwise defined.

The alkyl group may be a C1 to C20 alkyl group, specifically, a C1 to C6 lower alkyl group, a C7 to C10 intermediate alkyl group, or a C11 to C20 higher alkyl group.

For example, a C1 to C4 alkyl group means that there are 1 to 4 carbon atoms in the alkyl chain, which are methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl and t-butyl. It is selected from the group consisting of.

Typical alkyl groups include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, t-butyl group, pentyl group, hexyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, and cyclohexyl group. .

Unless otherwise defined herein, “copolymerization” may mean block copolymerization, random copolymerization, graft copolymerization, or alternating copolymerization, and “copolymer” is a block copolymer, random copolymer, graft copolymer, or alternating copolymerization. It can mean coalescence.

Based on the above definition, embodiments of the present invention will be described in detail. However, these are presented as examples, and the present invention is not limited thereto, and the present invention is only defined by the scope of claims to be described later.

The gel polymer electrolyte according to an embodiment of the present invention includes a diacrylate or dimethacrylate represented by Formula 1 below, or a polymer or copolymer thereof (hereinafter, also referred to as “electrolyte additive”).

[Formula 1]

(In the formula (1), R ¹ to R ⁴ each represents hydrogen, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and n represents an integer of 2 to 10.)

In one embodiment of the present invention, a monomer having two acrylate or methacrylate groups per molecule is used. As such, by using a monomer having two acrylate or methacrylate groups per molecule, sufficient gelation can be induced to improve physical performance as a gel polymer electrolyte.

In one embodiment of the present invention, a substituted or unsubstituted poly(ethylene oxy group) is used as a linking group between acrylate or methacrylate groups. The substituted or unsubstituted poly(ethylene oxy group) is advantageous in that it can improve the ionic conductivity of the polymer electrolyte.

In the formula (1), R ¹ to R ⁴ each represents hydrogen, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms. Specifically, R ¹ and R ² are each a hydrogen or methyl group, and R ³ and R ⁴ may be hydrogen.

In the formula (1), n represents an integer of 2 to 10. When n is too short, that is, when 1, the fluidity of the polymer is reduced compared to the same weight content, which may lower the ionic conductivity. If n is too long, it may be difficult to induce proper electrochemical performance of monomers and polymers because additives between active materials and even between active material pores may not be impregnated. More specifically, n may be an integer from 2 to 8. When n contains different diacrylates or dimethacrylates, or polymers or copolymers thereof, the number average of these is judged as n.

The gel polymer electrolyte according to an embodiment of the present invention may include 1 to 7% by weight of diacrylate or dimethacrylate represented by Chemical Formula 1. If too little diacrylate or dimethacrylate additive is included, the above-described addition effect cannot be adequately obtained. If the additive is contained too much in the electrolyte, it may interfere with the exchange of electrons through the electrolyte and deteriorate the properties of the electrochemical device. More specifically, the gel polymer electrolyte may contain 3 to 5% by weight of additives. In one embodiment of the present invention, diacrylate or dimethacrylate, or two or more of these polymers or copolymers may be included, and in this case, the sum of the respective contents may fall within the above-described range.

The gel polymer electrolyte may further include an organic solvent. The organic solvent is used to dissolve or dissociate the electrolyte salt, and is not particularly limited as long as it is used as an organic solvent of a conventional electrolyte. Cyclic carbonate, linear carbonate, lactone, ether, ester, sulfoxide, acetonitrile, lactam , Ketone and their halogen derivatives, respectively, or may be used by mixing two or more kinds. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), and examples of linear carbonates include diethyl carbonate (DEC), dimethyl carbonate (DMC) ), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC). Examples of lactones are gamma-butyrolactone (GBL), and examples of ethers are dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1, 2-diethoxy ethane. Examples of such esters include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl pivalate, and the like. In addition, the sulfoxide is dimethyl sulfoxide and the like, the lactam is N-methyl-2-pyrrolidone (NMP), and the like, and the ketone is polymethylvinyl ketone. In addition, these halogen derivatives can also be used, and are not limited to the above-exemplified electrolyte organic solvents. In addition, these organic solvents may be used alone or in combination of two or more.

The gel polymer electrolyte may further include an electrolyte salt. The electrolyte salt dissociates in an organic solvent to act as a component of ion conduction in the electrochemical device, and may serve to promote the movement of cations between the anode and the cathode. For example, SBPBF ₄ (spirobipyrrolidinium tetrafluoroborate), TEABF ₄ , EMIBF ₄ , TEMABF ₄ , LIPF ₆ , LiBF ₄ , LiTFSI, LiBETI, LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ )(where x, y are natural numbers) , LiCl, LiI, or a combination thereof. The content of the electrolyte salt in the gel polymer electrolyte is the number of moles (mol) relative to the electrolytic solvent (L) in the electrolyte, and may be 0.5 to 3.0 M. In this case, the gel polymer electrolyte may have an appropriate viscosity in the form of a gel, and the electrolyte salt may be dissolved in an organic solvent to contribute to effective movement of cations.

The electrochemical device according to an embodiment of the present invention includes the gel polymer electrolyte described above.

In one embodiment of the present invention, the electrochemical device may be a supercapacitor (SC) or a lithium ion battery. Supercapacitors include an electrostatic double-layer capacitor, an electrochemical pseudocapacitor, and a hybrid capacitor.

Hereinafter, each configuration of the electrochemical device will be described in detail. Hereinafter, a supercapacitor will be described as an example, but a person skilled in the art can easily convert the technical idea of adding an electrolyte additive into a lithium ion battery.

The capacitor includes an electrode including a positive electrode and a negative electrode, and a gel polymer electrolyte.

As a positive electrode and a negative electrode active material that can be applied as an electrode active material, any carbon material having a double layer capacity is possible, for example, activated carbon, activated carbon fiber, carbon aerogel, conductive polymer, metal oxide, natural fiber, amorphous carbon, flaren (fullerene), nanotubes and graphene (graphene), etc. may be used, but is not limited thereto.

The two electrodes of the supercapacitor may be physically separated by the above-described gel polymer electrolyte additive and the separator impregnated with the electrolyte, and at the same time, an ionic connection may be made.

In an embodiment of the present invention, a polymer film or a polymer is formed and impregnated on the surface of at least one of the positive electrode and the negative electrode to prevent peeling of the active material from the electrode and smoothly operate at high voltage.

That is, a polymer film may be formed on the surface of at least one of the positive electrode and the negative electrode, or a polymer electrolyte may be impregnated in the electrode active material of at least one of the positive electrode and the negative electrode.

The polymer membrane or the polymer electrolyte may be formed and impregnated only in one of the anode or cathode, or the polymer membrane or polymer may be formed and impregnated in both the anode and the cathode. The surface of the electrode means the surface in the direction of the electrolyte.

The polymer membrane or the polymer electrolyte may include a polymer obtained by polymerizing or copolymerizing an electrolyte additive represented by Chemical Formula 1. As the double bond in the electrolyte additive is broken, a continuous addition reaction occurs, and the carbon chain is lengthened to form a polymer.

Since the gel polymer electrolyte has been described above, overlapping descriptions are omitted.

The method of manufacturing an electrochemical device according to an embodiment of the present invention may be the following four methods.

Method 1: assembling the electrode and separator to produce an assembly; Impregnating the assembly with an electrolyte containing an electrolyte additive and no electrolyte salt; Sealing and curing; Injecting the electrolyte after disassembling the assembly; And sealing.

Method 2: assembling the electrode and separator to produce an assembly; Injecting an electrolyte containing an electrolyte additive and an electrolyte salt; Sealing and curing.

Method 3: coating or impregnating an electrolyte containing an electrolyte additive and an electrolyte salt on the electrode; Manufacturing an assembly by assembling the electrode and the separator; Sealing and curing.

Hereinafter, preferred embodiments of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited to the following examples.

Comparative Example 1

Acetonitrile solvent in which SBPBF ₄ (spirobipyrrolidinium tetrafluoroborate) at a concentration of 1.0 M was dissolved was used as a basic electrolyte.

Comparative Example 2

5% by weight of ethylene glycol dimethacrylate was added to the electrolyte of Comparative Example 1 to prepare an electrolyte.

Comparative Example 3

An electrolyte was prepared by adding 5% by weight of polyethylene glycol dimethacrylate (n = 13) to the electrolyte of Comparative Example 1.

Example 1

An electrolyte was prepared by adding 5 wt% of diethylene glycol dimethacrylate to the electrolyte of Comparative Example 1.

Example 2

An electrolyte was prepared by adding 5% by weight of polyethylene glycol dimethacrylate (n = 4 to 5) to the electrolyte of Comparative Example 1.

Example 3

An electrolyte was prepared by adding 5% by weight of polyethylene glycol dimethacrylate (n = 8 to 9) to the electrolyte of Comparative Example 1.

Battery Manufacturing

Between two activated carbon electrodes, a cellulose separator was interposed and assembled into a pouch cell.

의 열을 가하여 겔화하였다.Inject the electrolyte prepared in Comparative Examples 1 and 2 and Example 1 into the cell, 60 for 12 hours

Gelation was performed by adding heat.

Experimental Example 1: Measurement of charge and discharge performance by electrolyte

The prepared cells were tested at a rate of 0.1, 0.2, 0.4, 0.8, 1.6, 3.2 A g ^-1 for each rate at 20°C CC (constant current; galvanostatic) charge, CC discharge, 0 to 3.0 V charging and discharging 5 times for each rate Was conducted. The 5th cycle capacity at each rate at the initial 20 ^o C was measured and shown in FIG. 1, and the prepared cell was left at 65 ^o C with a 3.0 V CV (constant voltage; potentiostat) charge for 48 hours, and then the cell was 20. ^In FIG. 2, the fifth cycle capacity for each rate was measured in C.

As shown in FIG. 1, it can be seen that in Examples 1 to 3 and Comparative Examples 2 and 3, the initial capacitance was slightly decreased compared to Comparative Example 1. In the case of Comparative Example 3 in which the number of n is relatively large, it can be seen that the amount of capacitance reduction is larger than Comparative Example 2 in which the number of n is small and Examples 1 to 3. In addition, it can be seen that the capacitance reduction phenomenon is relatively small compared to the liquid electrolyte of the existing gel polymer electrolyte.

As shown in Fig. 2, after leaving 3.0 V for 48 hours at a high temperature, it can be seen that the capacitances of Examples 1 to 3 were improved by about 900% compared to Comparative Example 1 at high rates. In addition, it can be seen that the capacitance improved by about 30% compared to Comparative Example 2.

The amount of decrease in the capacitance at 20 ^o C in the late stages is shown in FIG. 3 after the 3.0 V for 48 hours at 65 ^o C compared to the capacitance at the initial 20 ^o C of the cells.

As shown in Figure 3, the amount of reduced capacitance at 3.2 A g ^-1 is about 95% in Comparative Example 1, while Examples 1 to 3 are about 50%, half of which, it can be seen that the reduction in capacitance is suppressed. , Comparative Example 2 can be confirmed that the inhibitory effect is about 12%.

As shown in FIG. 4, in Example 1, which is a 5% by weight cell, there was almost no decrease in capacitance by charge/discharge rate compared to Comparative Example 1, but in case of Comparative Examples 4 to 5 by 10-15% by weight, capacitance by charge/discharge rate It can be seen that the decrease is much larger than Comparative Example 1.

Experimental Example 2: EIS resistance evaluation

After the prepared cell was subjected to a constant voltage test of the initial resistance of 65°C and EIS at 0V and 3.0V for 48 hours, the values of each resistance component of EIS at 65°C and 0V were compared, and FIGS. 5 to 7 were compared. It is shown in.

In the case of bulk resistance and ESR, a large difference was not seen in Comparative Examples 1 to 3 and Examples 1 to 3, but a very large difference in interface resistance was confirmed.

Through this, it was confirmed that the increase in resistance in Comparative Example 1 was due to a large increase in interface resistance.

Experimental Example 3: Active material desorption inhibition evaluation

The prepared cell was photographed in a negative electrode state after a constant voltage test for 65°C, 3.0V, and 48 hours, and shown in FIG. 8. As shown in Figure 8, in the case of Comparative Example 1, it was confirmed that almost all active materials were desorbed. This is confirmed to be one of the causes of performance degradation of Comparative Example 1. It was confirmed that Examples 1 to 3 had less tally than Comparative Example 1.

The present invention is not limited to the above embodiments, but may be manufactured in various different forms, and a person having ordinary skill in the art to which the present invention pertains may have other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that can be carried out. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (8)

A gel polymer electrolyte comprising a diacrylate or dimethacrylate represented by Formula 1 below, or a polymer or copolymer thereof.
[Formula 1]

(In the formula (1), R ¹ to R ⁴ each represents hydrogen, a substituted or unsubstituted alkyl group having 1 to 5 carbon atoms, and n represents an integer of 2 to 10.) According to claim 1,
The R ¹ and R ² are each a hydrogen or methyl group, and the R ³ and R ⁴ are hydrogen gel polymer electrolyte. According to claim 1,
The n is an integer of 2 to 8 gel polymer electrolyte. According to claim 1,
A gel polymer electrolyte comprising 1 to 7% by weight of diacrylate or dimethacrylate represented by Formula 1 or a polymer or copolymer thereof. According to claim 1,
The gel polymer electrolyte is a gel polymer electrolyte further comprising an organic solvent and an electrolyte salt. An electrochemical device comprising the gel polymer electrolyte according to any one of claims 1 to 5. The method of claim 6,
Anode and cathode;
Interposed between the positive electrode and the negative electrode, comprising a separator comprising the gel polymer electrolyte,
An electrochemical device in which a polymer film is formed on the surface of at least one of the positive electrode and the negative electrode. The method of claim 6,
Anode and cathode; And
Interposed between the positive electrode and the negative electrode, comprising a separator comprising the gel polymer electrolyte,
An electrochemical device in which a polymer electrolyte is impregnated into an electrode active material of at least one of the positive electrode and the negative electrode.

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