KR102335794B1 - Gel polymer electrolyte and electrochemical device comprising the same - Google Patents

Abstract

(화학식 1에서, R¹ 내지 R⁴는 각각 수소, 치환 또는 비치환된 탄소수 1 내지 5의 알킬기를 나타내고, n은 2 내지 10의 정수를 나타낸다.)The gel polymer electrolyte according to an embodiment of the present invention includes diacrylate or dimethacrylate represented by the following Chemical Formula 1, or a polymer or copolymer thereof.
[Formula 1]

(In Formula 1, R ¹ to R ⁴ each represent hydrogen, a substituted or unsubstituted C 1 to C 5 alkyl group, and n represents an integer from 2 to 10.)

Description

Gel polymer electrolyte and electrochemical device comprising same

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

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

Although liquid electrolytes are widely used in electrochemical devices, there is a problem that not only there is a possibility of leakage, but also the operation thereof becomes unstable under conditions such as high temperature and high voltage due to the volatility and instability of the solvent.

In order to solve this problem, a technique for applying a gel polymer electrolyte instead of a liquid electrolyte is being studied.

However, the generally known gel polymer electrolyte has a limitation in that the electrochemical properties are inferior to that of the conventional liquid electrolyte. Accordingly, a generally known gel polymer electrolyte is more unsuitable for a supercapacitor that requires higher output characteristics than a lithium ion battery.

An embodiment of the present invention provides a gel polymer electrolyte capable of stabilizing lifespan characteristics at a high driving voltage and securing durability at a high temperature at the same time and an electrochemical device including the same.

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

[Formula 1]

(In Formula 1, R ¹ to R ⁴ each represent hydrogen, a substituted or unsubstituted C 1 to C 5 alkyl group, and n represents an integer from 2 to 10.)

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

n may be an integer from 2 to 8.

1 to 7 wt% of a polymer or copolymer of diacrylate or dimethacrylate represented by Formula 1 may be included.

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 above-described gel polymer electrolyte.

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 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; It is interposed between the positive electrode and the negative electrode, and includes a separator including a gel polymer electrolyte, and the polymer electrolyte may be impregnated into the electrode active material of at least one of the positive electrode and the negative electrode.

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

In an embodiment of the present invention, the gel polymer electrolyte can be applied to a super capacitor that requires high output, and can be applied to a lithium ion battery to improve its performance.

1 is a graph of measuring the initial capacitance with respect to the charge/discharge rate in Experimental Example 1. Referring to FIG.
FIG. 2 is a graph of measuring the late-stage capacitance with respect to the charge/discharge rate in Experimental Example 1. Referring to FIG.
3 is a graph of measuring the capacitance decrease in Experimental Example 1. Referring to FIG.
4 is a graph of measuring the capacitance by weight % with respect to the charge/discharge rate in Experimental Example 1. Referring to FIG.
5 is a graph of measuring bulk resistance in Experimental Example 2.
6 is a graph of measuring the interface resistance in Experimental Example 2.
7 is a graph of ESR measurement in Experimental Example 2.
8 is a photograph of a state in which the anode active material is desorbed in Experimental Example 3. Referring to FIG.

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 stated. As used throughout this specification, the terms "about," "substantially," and the like are used in a sense at or close to the numerical value when the manufacturing and material tolerances inherent in the stated meaning are presented, and are intended to enhance the understanding of this application. To help, precise or absolute figures are used to prevent unfair use by unconscionable infringers of the stated disclosure. The term “step of” or “step of” to the extent used throughout this specification does not mean “step for”.

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

In the present specification, unless otherwise defined as "substitution", at least one hydrogen in the compound is a C1 to C30 alkyl group; C1 to C10 alkoxy group; silane group; an alkylsilane group; alkoxysilane group; It means that it is substituted with an ethyleneoxyl group.

As used herein, "hetero" refers to 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 is methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl and t-butyl. It indicates that it is selected from the group consisting of.

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

Unless otherwise defined herein, "copolymerization" may mean block copolymerization, random copolymerization, graft copolymerization or alternating copolymerization, and "copolymer" means block copolymer, random copolymer, graft copolymer or alternating copolymer. It can mean amalgamation.

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 the claims to be described later.

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

[Formula 1]

(In Formula 1, R ¹ to R ⁴ each represent hydrogen, a substituted or unsubstituted C 1 to C 5 alkyl group, and n represents an integer from 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 ionic conductivity of the polymer electrolyte can be improved.

In Formula 1, R ¹ to R ⁴ each represent hydrogen, a substituted or unsubstituted C 1 to C 5 alkyl group. Specifically, R ¹ and R ² may each be hydrogen or a methyl group, and R ³ and R ⁴ may be hydrogen.

In Formula 1, n represents an integer of 2 to 10. When n is too short, that is, when it is 1, the fluidity of the polymer is lowered relative to the same weight content, so that the ionic conductivity may be lowered. When n is too long, since the additive may not be impregnated between the active materials and further between the pores of the active material, it may be difficult to induce appropriate electrochemical performance of the monomer and the polymer. More specifically, n may be an integer of 2 to 8. When n includes different diacrylates or dimethacrylates, or polymers or copolymers thereof, their number average is determined as n.

The gel polymer electrolyte according to an embodiment of the present invention may contain 1 to 7% by weight of diacrylate or dimethacrylate represented by Chemical Formula 1. When too little diacrylate or dimethacrylate additive is included, the above-mentioned additive effect cannot be properly obtained. When the additive is included in the electrolyte too much, it may interfere with the flow of electrons through the electrolyte, thereby deteriorating the properties of the electrochemical device. More specifically, the gel polymer electrolyte may contain 3 to 5 wt% of an additive. In one embodiment of the present invention, diacrylate or dimethacrylate, or two or more polymers or copolymers thereof may be included, and in this case, the sum of the respective contents may correspond to 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, and cyclic carbonates, linear carbonates, lactones, ethers, esters, sulfoxides, acetonitrile, lactams , ketones and halogen derivatives thereof may be used alone or in combination of two or more. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC), and the like, 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 include gamma butyrolactone (GBL), examples of ethers include dibutyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1, 2-diethoxyethane and the like. Examples of the ester 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 includes dimethyl sulfoxide, and the lactam includes N-methyl-2-pyrrolidone (NMP), and the ketone includes polymethylvinyl ketone. In addition, these halogen derivatives can also be used, and it is not limited only to the electrolyte organic solvent exemplified above. In addition, these organic solvents can be used individually or in mixture of 2 or more types.

The gel polymer electrolyte may further include an electrolyte salt. The electrolyte salt is dissociated in the organic solvent and acts 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 and 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 electrolyte 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 the effective movement of cations.

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

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

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

A capacitor comprises an electrode comprising an anode and a cathode and a gel polymer electrolyte.

As the positive electrode and 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 airgel, conductive polymer, metal oxide, natural fiber, amorphous carbon, fullene (fullerene), nanotubes, graphene, and the like may be used, but is not limited thereto.

The two electrodes of the supercapacitor may be physically separated by a separator impregnated with the aforementioned gel polymer electrolyte additive and electrolyte, and ionically connected.

In an embodiment of the present invention, a polymer film or 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 to smoothly operate at a high voltage.

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

Such a polymer film or polymer electrolyte may be formed and impregnated on only one of the positive electrode or the negative electrode, or a polymer film or polymer may be formed and impregnated on both the positive electrode and the negative electrode. 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 polymerization or copolymerization of the electrolyte additive represented by Formula 1 above. As the double bond in the electrolyte additive is broken, a continuous addition reaction occurs, and the carbon chain lengthens to form a polymer.

Since the gel polymer electrolyte has been described above, the overlapping description will be omitted.

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

Method 1: assembling an electrode and a separator to produce an assembly; impregnating the assembly in an electrolyte including an electrolyte additive and not including an electrolyte salt; sealing and curing; After disassembling the assembly, injecting an electrolyte; It may include sealing.

Method 2: assembling an electrode and a separator to produce an assembly; injecting an electrolyte comprising an electrolyte additive and an electrolyte salt; It may include sealing and curing.

Method 3: Applying or impregnating an electrolyte comprising an electrolyte additive and an electrolyte salt on the electrode; manufacturing an assembly by assembling an electrode and a separator; It may include 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 thereto.

Comparative Example 1

_{An acetonitrile solvent in which SBPBF 4} (spirobipyrrolidinium tetrafluoroborate) at a concentration of 1.0M was dissolved was used as a basic electrolyte.

Comparative Example 2

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

Comparative Example 3

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

Example 1

5 wt% of diethylene glycol dimethacrylate was added to the electrolyte of Comparative Example 1 to prepare an electrolyte.

Example 2

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

Example 3

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

manufacture of batteries

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

의 열을 가하여 겔화하였다.The electrolytes prepared in Comparative Examples 1 to 2 and Example 1 were injected into the cell, and 60 for 12 hours

It was gelled by applying heat.

Experimental Example 1: Measurement of charge/discharge performance for each electrolyte

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

As shown in FIG. 1 , in Examples 1 to 3, Comparative Examples 2 and 3, it can be confirmed that the initial capacitance is 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 capacitance reduction amount is larger than Comparative Examples 2 and Examples 1 to 3 in which the number of n is small. 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 standing at 3.0 V at a high temperature for 48 hours, it can be confirmed that the capacitance of Examples 1 to 3 is improved by about 900% compared to Comparative Example 1 at a high rate. In addition, it can be confirmed that the capacitance is improved by about 30% compared to Comparative Example 2.

capacitance than in the initial 20 ^o C 65 ^o C 48 of the cell sigan 3.0 V and then allowed to stand exhibited a decrease in capacitance reviews 20 ^o C in Fig.

As shown in Figure 3, ^{the capacitance reduction amount at 3.2 A g -1} Comparative Example 1 is about 95%, whereas Examples 1 to 3 are about 50%, which is half thereof, confirming that the capacitance reduction is suppressed, , it can be confirmed that there is an inhibitory effect of about 12% compared to Comparative Example 2.

As shown in FIG. 4, in Example 1, which is a cell of 5 wt%, there was hardly any decrease in capacitance by charge/discharge rate compared to Comparative Example 1, but in Comparative Examples 4 to 5 of 10 to 15 wt%, the capacitance by charge/discharge rate It can be seen that the decrease is significantly larger than that of Comparative Example 1.

Experimental Example 2: EIS resistance evaluation

5 to 7 by comparing the values of each resistance component of EIS at 65°C and 0V in the initial stage of the prepared cell and each resistance component of EIS at 65°C and 0V in the late 65°C after performing a constant voltage test at 3.0V for 48 hours. shown in

In the case of bulk resistance and ESR, there was no significant difference between Comparative Examples 1 to 3 and Examples 1 to 3, but a very large difference was confirmed in the interface resistance.

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

Experimental Example 3: Evaluation of Active Material Desorption Inhibition

The prepared cell was shown in FIG. 8 by taking pictures of the cathode state after a constant voltage test at 65° C., 3.0 V, and 48 hours. As shown in FIG. 8 , in 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 showed less desorption compared to Comparative Example 1.

The present invention is not limited to the above embodiments, but can be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as 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 1 to 7 wt% of dimethacrylate represented by the following formula (1), or a polymer thereof.
[Formula 1]

(In Formula 1, R ¹ and R ² are methyl groups, R ³ and R ⁴ are hydrogen, and n is an integer of 2 to 10.) delete According to claim 1,
Wherein n is an integer of 2 to 8 gel polymer electrolyte. delete According to claim 1,
The gel polymer electrolyte further comprises an organic solvent and an electrolyte salt. An electrochemical device comprising the gel polymer electrolyte according to any one of claims 1 to 5. 7. The method of claim 6,
positive and negative poles;
A separator interposed between the positive electrode and the negative electrode and including the gel polymer electrolyte,
An electrochemical device in which a polymer film is formed on the surface of at least one of the anode and the cathode. 7. The method of claim 6,
positive and negative poles; and
A separator interposed between the positive electrode and the negative electrode and including 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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