KR102505092B1 - A composition for a gel polymer electrolyte, a gel polymer electrolyte and a manufacturing method thereof, and a secondary battery comprising the same - Google Patents

Abstract

A composition for a gel polymer electrolyte is provided. The composition for the gel polymer electrolyte may include a porous support containing a polymer, a liquid electrolyte containing either sodium or lithium, and an ionic liquid crosslinking agent having two or more double bond functional groups. .

Description

A composition for a gel polymer electrolyte, a gel polymer electrolyte and a method for preparing the same, and a secondary battery including the same. {A composition for a gel polymer electrolyte, a gel polymer electrolyte and a manufacturing method thereof, and a secondary battery comprising the same}

The present invention relates to a composition for a gel polymer electrolyte, a gel polymer electrolyte and a manufacturing method thereof, and a secondary battery including the same, and more specifically, a composition for a gel polymer electrolyte using an ionic crosslinking agent, a gel polymer electrolyte and a manufacturing method thereof, And it is related to a secondary battery including the same.

Lithium secondary battery is a type of secondary battery that can charge energy using an external power source, and has many advantages such as high energy density and long lifespan, so it is applied to various fields such as smartphones, tablet computers, and electric vehicles. However, due to the limited amount of lithium mineral resources, the resulting high production cost, and safety issues of lithium secondary batteries, there is a need for a new battery system that can replace them. Sodium secondary batteries are being actively studied as new battery systems for medium and large-sized energy storage devices because raw materials are plentiful and cheap, so production costs can be lowered, and there is little concern about environmental pollution. In general, since the sodium secondary battery uses a liquid electrolyte using a flammable organic solvent, it has the same safety problem as the lithium secondary battery. When an internal short circuit occurs due to sodium dendrite growth in the negative electrode during overcharging or an external shock, the internal temperature of the battery rises. In addition, ignition and fire occurring outside the battery also increase the internal temperature of the battery.

In this situation, when the temperature of the sodium secondary battery rises, the problem of fire due to the generation of combustible gas due to volatilization and decomposition of the electrolyte, the exothermic reaction due to the reaction between the electrolyte and the electrode, and the generation of oxygen due to the decomposition of the anode is solved. Have. Therefore, it is difficult to ensure safety from the point of view of applying sodium secondary batteries to medium and large-sized energy storage devices.

Accordingly, research on ionic liquid electrolytes and gel polymer electrolytes that can replace organic liquid electrolytes is being actively conducted. An ionic liquid refers to a salt in a liquid state composed only of ions and having a melting point below room temperature. Ionic liquid electrolytes have excellent flame retardant properties, but suffer from liquid leakage due to liquid phase properties, and poor battery properties due to high viscosity properties. The gel polymer electrolyte is prepared in a semi-solid form by a polymerization reaction of a crosslinking agent included in a precursor solution, and can partially solve the safety problem of a battery.

For example, Korean Patent Publication No. 10-2020-0060924 (Application No.: 10-2018-0146117, Applicant: Yonsei University Industry-University Cooperation Foundation) includes a sodium ion conductive solid electrolyte and a coating layer formed on one side of the solid electrolyte, , The coating layer discloses a solid electrolyte structure including at least one selected from the group consisting of bismuth (Bi), tin (Sn), and lead (Pb).

Republic of Korea Patent Publication No. 10-2020-0060924

One technical problem to be solved by the present invention is to provide a composition for a gel polymer electrolyte with improved flame retardancy, a gel polymer electrolyte and a manufacturing method thereof, and a secondary battery including the same.

Another technical problem to be solved by the present invention is to provide a composition for a gel polymer electrolyte with improved thermal stability and chemical stability, a gel polymer electrolyte and a manufacturing method thereof, and a secondary battery including the same.

Another technical problem to be solved by the present invention is to provide a composition for a gel polymer electrolyte having excellent electrical properties, a gel polymer electrolyte and a manufacturing method thereof, and a secondary battery including the same.

Another technical problem to be solved by the present invention is to provide a composition for a gel polymer electrolyte with improved reliability, a gel polymer electrolyte and a manufacturing method thereof, and a secondary battery including the same.

The technical problem to be solved by the present invention is not limited to the above.

In order to solve the above technical problems, the present invention provides a composition for a gel polymer electrolyte.

According to one embodiment, the composition for the gel polymer electrolyte is a porous support containing a polymer, a liquid electrolyte containing any one of sodium or lithium, and an ionic liquid having two or more double bond functional groups. Including a crosslinking agent, the double bond functional group may include mediating a crosslinking reaction of the ionic liquid crosslinking agent.

According to one embodiment, the ionic liquid crosslinking agent may include one represented by the following <Chemical Formula 1>.

<Formula 1>

R: An alkyl group having 1 to 8 carbon atoms.

X ⁺ : among imidazolium, ammonium, pyridinium, pyrazolium, piperidinium, triazolium, thiazolium, oxazolium, pyridazinium, pyrimidinium, pyrazinium, phosphonium, pyrrolidinium and sulfonium any one cation.

Y ^- : BF ₄ , PF ₆ , ClO ₄ , CF ₃ SO ₃ , N(CF ₃ SO ₂ ) ₂ , N(C ₂ F ₅ SO ₂ ) ₂ , C(CF ₂ SO ₂ ) ₃ , AsF ₆ , SbF ₆ , AlCl ₄ , NbF ₆ , CF ₃ CO ₂ An anion of any one.

According to one embodiment, the ionic liquid crosslinking agent may be included in an amount of 30 wt% or more based on 100 wt% of the composition for a gel polymer electrolyte.

According to one embodiment, the polymer is polyamideimide, polyetherimide, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, and polyacrylonitrile. may include any one of them.

According to one embodiment, the porous support may include a plurality of fibers including the polymer.

In order to solve the above technical problems, the present invention provides a gel polymer electrolyte.

According to one embodiment, the gel polymer electrolyte may include a composition for a gel polymer electrolyte according to the above-described embodiment chemically cross-linked.

In order to solve the above technical problems, the present invention provides a secondary battery.

According to one embodiment, the secondary battery may include a positive electrode and a negative electrode disposed to face each other, and a gel polymer electrolyte according to the above-described embodiment disposed between the positive electrode and the negative electrode.

In order to solve the above technical problems, the present invention provides a method for preparing a gel polymer electrolyte.

According to one embodiment, the preparation method of the gel polymer electrolyte includes preparing a porous support containing a polymer, an ionic liquid crosslinking agent containing two or more double bond functional groups, and sodium or lithium. Preparing a liquid electrolyte comprising, preparing a composition for a gel polymer electrolyte by providing a mixed solution of the liquid electrolyte and the ionic liquid crosslinking agent to the porous support, and heat-treating the composition for a gel polymer electrolyte , chemically cross-linking the composition for a gel polymer electrolyte.

According to one embodiment, in the step of chemically cross-linking the composition for a gel polymer electrolyte, the composition for a gel polymer electrolyte may include heat treatment at a temperature of 70° C. or higher for 1 hour or more.

According to an embodiment, preparing the ionic liquid crosslinking agent and the liquid electrolyte may include preparing the ionic liquid crosslinking agent including two or more double bond functional groups, a base source including sodium or lithium, and It may include preparing the liquid electrolyte by mixing a solvent, and mixing the ionic liquid crosslinking agent and the liquid electrolyte.

According to one embodiment, when the base source includes sodium, the solvent may include ethylene carbonate (EC).

According to one embodiment, when the base source includes lithium, the solvent may include dimethyl carbonate (DMC).

According to one embodiment, when the base source contains lithium, the temperature at which the composition for a gel polymer electrolyte is heat-treated is lower than the temperature at which the composition for a gel polymer electrolyte is heat-treated when the base source contains sodium. can do.

A method for preparing a gel polymer electrolyte according to an embodiment of the present invention includes preparing a porous support containing a polymer, an ionic liquid crosslinking agent containing two or more double bond functional groups mediating crosslinking, and sodium or preparing a liquid electrolyte containing lithium, preparing a composition for a gel polymer electrolyte by providing a mixed solution of the liquid electrolyte and the ionic liquid crosslinking agent to the porous support, and the gel polymer A step of chemically cross-linking the composition for a gel polymer electrolyte by heat-treating the composition for an electrolyte may be included.

Accordingly, the secondary battery to which the gel polymer electrolyte is applied not only has high ion conductivity and charge and discharge characteristics, but also has improved flame retardancy compared to a conventional secondary battery to which a liquid electrolyte is applied, and can have high thermal stability.

1 is a flowchart illustrating a method for preparing a gel polymer electrolyte according to an embodiment of the present invention.
2 is a view showing a manufacturing process of a gel polymer electrolyte according to an embodiment of the present invention.
3 is a chemical formula showing a synthesis process of a crosslinking agent included in a composition for a gel polymer electrolyte according to an embodiment of the present invention.
4 is a chemical formula of a crosslinking agent included in a composition for a gel polymer electrolyte according to an embodiment of the present invention.
5 is a chemical formula showing a crosslinking reaction of a crosslinking agent included in a composition for a gel polymer electrolyte according to an embodiment of the present invention.
6 is a photograph of a polymer separator according to an experimental example of the present invention.
7 is a photograph of a gel polymer electrolyte according to Example 1 of the present invention.
8 is a photograph of the thermal stability of a polymer electrolyte according to an embodiment of the present invention.
9 is a photograph showing flame retardancy of polymer electrolytes according to Examples and Comparative Examples of the present invention.
10 is a graph showing the experimental results of FIG. 9 .
11 is a photograph showing wettability of a polymer separator according to Comparative Example 1 of the present invention.
12 is a photograph showing wettability of a polymer separator according to an experimental example of the present invention.
13 is a photograph comparing contact angles of polymer separators according to Comparative Example 1 and Experimental Example of the present invention.
14 is a diagram showing a ¹ HNMR spectrum of an ionic liquid crosslinking agent according to an experimental example of the present invention.
15 is a graph showing the ionic conductivity of the gel polymer electrolyte according to Example 1 of the present invention.
16 is a graph comparing charge and discharge characteristics of secondary batteries according to Example 3 and Comparative Example 3 of the present invention.
17 is a graph showing reliability of a secondary battery according to Example 3 of the present invention.
18 and 19 are views showing ¹ HNMR spectrum of the gel polymer electrolyte according to Experimental Example 3 of the present invention.
20 is a graph comparing the electrochemical stability of the gel polymer electrolyte according to Example 1 of the present invention and the polymer electrolyte according to Comparative Example 2.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical idea of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete, and the spirit of the present invention will be sufficiently conveyed to those skilled in the art.

In this specification, when an element is referred to as being on another element, it means that it may be directly formed on the other element or a third element may be interposed therebetween. Also, in the drawings, the thicknesses of films and regions are exaggerated for effective explanation of technical content.

In addition, although terms such as first, second, and third are used to describe various elements in various embodiments of the present specification, these elements should not be limited by these terms. These terms are only used to distinguish one component from another. Therefore, what is referred to as a first element in one embodiment may be referred to as a second element in another embodiment. Each embodiment described and illustrated herein also includes its complementary embodiments. In addition, in this specification, 'and/or' is used to mean including at least one of the elements listed before and after.

In the specification, expressions in the singular number include plural expressions unless the context clearly dictates otherwise. In addition, the terms "comprise" or "having" are intended to designate that the features, numbers, steps, components, or combinations thereof described in the specification exist, but one or more other features, numbers, steps, or components. It should not be construed as excluding the possibility of the presence or addition of elements or combinations thereof. In addition, in this specification, "connection" is used to mean both indirectly and directly connecting a plurality of components.

In addition, in the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

1 is a flow chart illustrating a method for manufacturing a gel polymer electrolyte according to an embodiment of the present invention, FIG. 2 is a view showing a manufacturing process of a gel polymer electrolyte according to an embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. A chemical formula showing a synthesis process of a crosslinking agent included in the composition for a gel polymer electrolyte according to an example, and FIG. 4 is a chemical formula of a crosslinking agent included in a composition for a gel polymer electrolyte according to an embodiment of the present invention. FIG. 5 is an embodiment of the present invention. A chemical formula showing a crosslinking reaction of a crosslinking agent included in the composition for a gel polymer electrolyte according to the example.

1 to 5, a porous support 100 may be prepared (S100). According to one embodiment, preparing the porous support 100 may include preparing a polymer solution in which a polymer is mixed with a solvent, and electrospinning the polymer solution onto a target roller. For example, the polymer is any one of polyamideimide, polyetherimide, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, and polyacrylonitrile. may contain one.

More specifically, the polymer solution may be prepared by adding 17 wt% of polyamideimide (PAI) to a dimethylacetamide (N,N-Dimethylacetamide, DMAc) solvent and stirring at a temperature of 60°C. Thereafter, the porous support 100 may be prepared by electrospinning the polymer solution on a target roller at 180 rpm under conditions of an applied voltage of 10 kV and a solution supply rate of 0.4 ml/h. Accordingly, the porous support 100 may have a nonwoven fabric form composed of a plurality of fibers containing the polymer. In addition, as the porous support 100 is composed of a plurality of polymer fibers, it may have a porous structure.

An ionic liquid crosslinking agent and a liquid electrolyte may be prepared (S200).

According to one embodiment, the step of preparing the ionic liquid crosslinking agent is mixing a source containing bromine (Br) and a source containing amine (Amine) with a solvent to prepare a first preliminary solution, the first Preparing a second preliminary solution by injecting a mixed solution of a source containing chloride and a solvent into a preliminary solution, mixing the second preliminary solution and a source containing imidazole with the solvent preparing a third preliminary solution, and anion exchange by stirring the third preliminary solution with a source containing lithium.

More specifically, as shown in FIG. 3, 13.03 g of 6-bromo-hexanol and 8.7 g of triethylamine were mixed with 100 mL of tetrahydrofuran (THF) solvent. Thus, the first preliminary solution may be prepared. After maintaining the first preliminary solution at 0 ° C and forming an argon atmosphere, a mixture of 7.8 g of acryloyl chloride and 100 mL of tetrahydrofuran (THF) was slowly added to the first preliminary solution. The second preliminary solution may be prepared by injecting and stirring at room temperature for 24 hours. Thereafter, 10.82 g of the second preliminary solution and 7.56 g of allylimidazole (1-allylimidazole) may be mixed in 400 mL of an ethanol solvent and stirred at 70 ° C. for 48 hours to prepare the third preliminary solution. Finally, by mixing 10 g of the third preliminary solution and 10 g of lithium trifluoromethanesulfonyl imide in 30 mL of distilled water and stirring at 70 ° C. for 24 hours to anion exchange, the Ionic liquid crosslinkers can be prepared. Accordingly, the ionic liquid crosslinking agent may have a chemical structure shown in FIG. 4 .

As shown in FIG. 4, the ionic liquid crosslinking agent may have two or more double bond functional groups. The double bond functional group may mediate a crosslinking reaction of the ionic liquid crosslinking agent in the step of chemically crosslinking a composition for a gel polymer electrolyte, which will be described later. That is, the ionic liquid crosslinking agent may have two or more double bond functional groups that mediate a crosslinking reaction.

Accordingly, the gel polymer electrolyte prepared through the crosslinking reaction of the ionic liquid crosslinking agent may form a polymer network having a relatively high crosslinking density. A polymer network having a high crosslinking density can suppress volatilization of a liquid electrolyte included in a composition for a gel polymer electrolyte described later, and reduce generation of combustible gas. Due to this, the flame retardancy of the gel polymer electrolyte to be described later can be improved.

In contrast, in the case of a polymer electrolyte prepared through a crosslinking agent having less than two double bond functional groups mediating the crosslinking reaction, the crosslinking density may be relatively low. Accordingly, compared to a gel polymer electrolyte prepared through the ionic liquid crosslinking agent having two or more double bond functional groups mediating the crosslinking reaction, a problem of low flame retardancy may occur.

According to one embodiment, the liquid electrolyte may be prepared by mixing a base source containing sodium or lithium with a solvent. More specifically, according to one embodiment, the source solution is sodium trifluoride at a concentration of 1.0M in a solvent in which ethylene carbonate (EC) and propylene carbonate (PC) have a ratio of 50:50 vol%. It may be prepared by mixing sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) with methanesulfonylimide. Unlike this, according to another embodiment, the source solution is ethylene carbonate (ethylene carbonate, EC) and dimethyl carbonate (dimethyl carbonate, DMC) in a solvent having a ratio of 30:70 vol%, 1.0 M concentration of lithium trifluoro Methanesulfonylimide (lithium bis (trifluoromethanesulfonyl) imide, LiTFSI) may be mixed and prepared.

A mixed solution 200 of the liquid electrolyte and the ionic liquid crosslinking agent may be provided to the porous support 100 . Accordingly, a composition 300 for a gel polymer electrolyte may be prepared (S300). More specifically, the composition 300 for the gel polymer electrolyte may be prepared by immersing the porous support 100 in the solution 200 in which the liquid electrolyte and the ionic liquid crosslinking agent are mixed.

According to one embodiment, in the composition for a gel polymer electrolyte, the ionic liquid crosslinking agent may be included in an amount of 30 wt% or more. In this case, the gel polymer electrolyte described later may have a semi-solid gel form. On the other hand, when the ionic liquid crosslinking agent is included in an amount of less than 30 wt%, the flowability of the gel polymer electrolyte described below may increase, causing a problem of not having a semi-solid gel form.

According to one embodiment, the composition for the gel polymer electrolyte may further include a thermal initiator. For example, the thermal initiator may include any one of azobisisobutyronitrile (AIBN), acetyl peroxide, and benzoyl peroxide.

The composition for a gel polymer electrolyte may be subjected to heat treatment and chemically cross-linked as shown in FIG. 5 . Accordingly, a gel polymer electrolyte may be prepared (S400). According to one embodiment, the composition for a gel polymer electrolyte may be heat-treated at a temperature of 70° C. or higher for 1 hour or more. Accordingly, the composition for a gel polymer electrolyte may have a high conversion rate of 96% or more.

According to one embodiment, when the base source contains lithium, the temperature at which the composition for a gel polymer electrolyte is heat treated may be different from the temperature at which the composition for a gel polymer electrolyte is heat treated when the base source contains sodium. . For example, when the base source contains lithium, the temperature at which the composition for a gel polymer electrolyte is heat treated may be lower than the temperature at which the composition for a gel polymer electrolyte is heat treated when the base source contains sodium.

More specifically, as described above, dimethyl carbonate (DMC) is used as a solvent for preparing the liquid electrolyte when the base source contains lithium, and when the base source contains sodium To prepare the liquid electrolyte Ethylene carbonate (EC) can be used as a solvent for Since dimethyl carbonate (DMC) has a relatively low boiling point compared to ethylene carbonate (EC), when heat-treated at the same temperature as ethylene carbonate (EC), dimethyl carbonate (DMC) may volatilize. Accordingly, when the base source contains lithium, the temperature at which the composition for a gel polymer electrolyte is heat treated may be lower than the temperature at which the composition for a gel polymer electrolyte is heat treated when the base source contains sodium.

The gel polymer electrolyte may be used as an electrolyte for a secondary battery. For example, the gel polymer electrolyte may be disposed between a sodium metal negative electrode and a Na ₃ V ₂ (PO ₄ ) ₃ positive electrode. The secondary battery to which the gel polymer electrolyte is applied not only has high ionic conductivity and charge/discharge characteristics, but also has improved flame retardancy compared to a conventional secondary battery to which a liquid electrolyte is applied, and thus can have high thermal stability.

In the above, a composition for a gel polymer electrolyte according to an embodiment of the present invention, a gel polymer electrolyte, a method for preparing the same, and a secondary battery including the same have been described. Hereinafter, specific experimental examples and characteristic evaluation results of a composition for a gel polymer electrolyte, a gel polymer electrolyte, and a manufacturing method thereof according to an embodiment of the present invention, and a secondary battery including the same will be described.

Polymer Separation Membrane Manufacturing According to Experimental Examples

A polymer solution was prepared by adding 17 wt% of polyamideimide (PAI) to a dimethylacetamide (N,N-Dimethylacetamide, DMAc) solvent and stirring at a temperature of 60°C. Thereafter, the polymer solution was electrospun on a target roller at 180 rpm under conditions of an applied voltage of 10 kV and a solution supply rate of 0.4 ml/h to prepare a polymer separator according to the experimental example.

Preparation of ionic liquid crosslinking agent according to experimental example

A first pre-solution was prepared by mixing 13.03 g of 6-bromo-hexanol and 8.7 g of triethylamine with 100 mL of tetrahydrofuran (THF) solvent. After maintaining the first preliminary solution at 0 ° C and forming an argon atmosphere, a mixture of 7.8 g of acryloyl chloride and 100 mL of tetrahydrofuran (THF) was slowly added to the first preliminary solution. After pouring, a second preliminary solution was prepared by stirring at room temperature for 24 hours. Thereafter, 10.82 g of the second preliminary solution and 7.56 g of allylimidazole (1-allylimidazole) were mixed in 400 mL of an ethanol solvent and stirred at 70 ° C. for 48 hours to prepare a third preliminary solution. Finally, by mixing 10 g of the third preliminary solution and 10 g of lithium trifluoromethanesulfonyl imide (lithium bis (trifluoromethanesulfonyl) imide) in 30 mL of distilled water and stirring at 70 ° C. for 24 hours to anion exchange, experiment An ionic liquid crosslinker according to the example was prepared.

Preparation of liquid electrolyte according to experimental example

Sodium bis(trifluoromethanesulfonyl)imide at a concentration of 1.0M in a solvent in which ethylene carbonate (EC) and propylene carbonate (PC) have a ratio of 50:50 vol%, NaTFSI) was mixed to prepare a liquid electrolyte according to the experimental example.

Preparation of gel polymer electrolyte according to Example 1

A gel polymer electrolyte according to Example 1 was prepared by immersing the polymer separator according to the Experimental Example in a mixed solution of the liquid electrolyte and the ionic liquid crosslinking agent according to the above-described Experimental Example and then heat-treating.

Preparation of gel polymer electrolyte according to Example 2

A gel polymer electrolyte according to Example 2 was prepared by immersing the polymer separator according to the Experimental Example in a mixed solution of the liquid electrolyte, the ionic liquid crosslinking agent, and azobisisobutyronitrile (AIBN) according to the above-described Experimental Example and then heat-treating.

Manufacturing a secondary battery according to Example 3

A secondary battery according to Example 3 was prepared in which the gel polymer electrolyte according to Example 1 was provided between the Na ₃ V ₂ (PO ₄ ) ₃ positive electrode disposed to face the sodium metal negative electrode.

Preparation of a polymer separator according to Comparative Example 1

A polymer separator according to Comparative Example 1 prepared by stretching a polyethylene (PE) film was prepared.

Preparation of polymer electrolyte according to Comparative Example 2

The polymer electrolyte according to Comparative Example 2 was prepared by soaking the polymer separator according to Comparative Example 1 with the liquid electrolyte according to the embodiment.

Secondary battery according to Comparative Example 3

A secondary battery according to Comparative Example 3 was manufactured, in which the polymer electrolyte according to Comparative Example 2 was provided between the Na ₃ V ₂ (PO ₄ ) ₃ positive electrode disposed to face the sodium metal negative electrode.

The configurations of Examples 1 to 3 and Comparative Examples 1 to 3 described above are summarized in <Table 1> below.

division composition final form Example 1 PAI Separator + Liquid Electrolyte + Ionic Liquid Crosslinking Agent gel polyelectrolyte Example 2 PAI Separator + Liquid Electrolyte + Ionic Liquid Crosslinker + AIBN gel polyelectrolyte Example 3 Sodium metal cathode/PAI separator + liquid electrolyte + ionic liquid cross-linking agent/ Na ₃ V ₂ (PO ₄ ) ₃ anode secondary battery Comparative Example 1 PE separator polymer separator Comparative Example 2 PE separator + liquid electrolyte polyelectrolyte Comparative Example 3 Sodium metal cathode/ PE separator + liquid electrolyte/ Na ₃ V ₂ (PO ₄ ) ₃ anode secondary battery

6 is a photograph of a polymer separator according to an experimental example of the present invention.

Referring to FIG. 6, the polymer separator according to the experimental example was photographed using a scanning electron microscope (SEM). As can be seen in FIG. 6, it was confirmed that the polymer separator was composed of a plurality of polymer fibers and had a porous structure.

7 is a photograph of a gel polymer electrolyte according to Example 1 of the present invention.

Referring to FIG. 7, a gel polymer electrolyte was prepared according to Example 1, but the content of the ionic liquid crosslinking agent was controlled to 10 wt%, 20 wt%, 25 wt%, 30 wt%, and 40 wt%, The state of the gel polymer electrolyte prepared according to each content was photographed.

As can be seen in FIG. 7, the gel polymer electrolytes containing 10 wt%, 20 wt%, and 25 wt% of the ionic liquid crosslinking agent do not have a semi-solid gel state due to high fluidity, but the content of the ionic liquid crosslinking agent It was confirmed that the 30 wt% and 40 wt% gel polymer electrolytes had a semi-solid gel state. Accordingly, when preparing the gel polymer electrolyte according to the above embodiment, the gel polymer electrolyte is prepared in a semi-solid gel state by controlling the content of the ionic liquid crosslinking agent included in the composition for the gel polymer electrolyte to 30 wt% or more. it can be known that

8 is a photograph of the thermal stability of a polymer electrolyte according to an embodiment of the present invention.

Referring to FIG. 8 , the gel polymer electrolyte according to Example 1 and the polymer separator according to Comparative Example 1 were stored at a temperature of 150° C. for 1 hour, and shape changes were photographed. As can be seen in FIG. 8, it was confirmed that the shape change occurred in the polymer separator according to Comparative Example 1, but the shape change did not occur in the case of the gel polymer electrolyte according to Example 1. Accordingly, it was found that the gel polymer electrolyte according to Example 1 had excellent thermal stability.

FIG. 9 is a photograph showing the flame retardancy of polymer electrolytes according to Examples and Comparative Examples of the present invention, and FIG. 10 is a graph showing the test results of FIG. 9 .

9 (a) to (c), after burning the polymer electrolyte according to Comparative Example 2, the gel polymer electrolyte according to Example 1, and the gel polymer electrolyte according to Example 2, the degree of ignition was photographed. 10, the self-extinguishing time (s) after burning the polymer electrolyte according to Comparative Example 2, the gel polymer electrolyte according to Example 1, and the gel polymer electrolyte according to Example 2 / g) was measured and expressed.

As can be seen in (a) to (c) of FIG. 9, the polymer electrolyte according to Comparative Example 2 was ignited to the extent that it was clearly visible to the naked eye, but the polymer electrolyte according to Example 1 was the polymer according to Comparative Example 2. The degree of ignition was lower than that of the electrolyte, and it was confirmed that the polymer electrolyte according to Example 2 was not ignited. In addition, as can be seen in FIG. 10 , it was confirmed that the self-ignition time of the polymer electrolytes according to Examples 1 and 2 was significantly shorter than that of the polymer electrolytes according to Comparative Example 1. Accordingly, it was found that the gel polymer electrolytes according to Examples 1 and 2 had excellent flame retardancy.

11 is a photograph of the wettability test of the polymer separator according to Comparative Example 1 of the present invention, and FIG. 12 is a photograph of the wettability test of the polymer separator according to Experimental Example of the present invention.

11 and 12, after preparing the polymer separator according to Comparative Example 1 and the polymer separator according to Experimental Example, wettability was tested by dropping a liquid on each polymer separator. (a) of each figure shows a photograph taken immediately after dropping the liquid, and (b) shows a state after 5 minutes from the state of (a).

As can be seen in FIG. 11, the polymer separator according to Comparative Example 1 did not absorb liquid, but as can be seen in FIG. 12, it was confirmed that liquid absorption occurred in the polymer separator according to Experimental Example. Accordingly, it was found that the polymer separator according to Experimental Example made of polyamideimide (PAI) had better wettability than the polymer separator according to Comparative Example 1 made of polyethylene (PE).

13 is a photograph comparing contact angles of polymer separators according to Comparative Example 1 and Experimental Example of the present invention.

Referring to FIG. 13 (a), the contact angle of the polymer separator according to Comparative Example 1 was measured and shown, and referring to FIG. 13 (b), the contact angle of the polymer separator according to Experimental Example was measured and shown. . As can be seen in (a) and (b) of FIG. 13, the polymer separator according to Comparative Example 1 exhibited a contact angle of 57.5 °, whereas the polymer separator according to Experimental Example exhibited a contact angle of 17.2 °. That is, it was found that the polymer separator according to Experimental Example made of polyamideimide (PAI) had a lower contact angle than the polymer separator according to Comparative Example 1 made of polyethylene (PE).

14 is a diagram showing a ¹ HNMR spectrum of an ionic liquid crosslinking agent according to an experimental example of the present invention.

Referring to FIG. 14, ¹ HNMR (nuclear magnetic resonance) spectrum of the ionic liquid crosslinking agent according to the experimental example is shown, and through this, the ionic liquid crosslinking agent according to the experimental example has the chemical structure shown in FIG. I was able to confirm.

15 is a graph showing the ionic conductivity of the gel polymer electrolyte according to Example 1 of the present invention.

Referring to FIG. 15, a gel polymer electrolyte was prepared according to Example 1, but the content of the ionic liquid crosslinking agent was controlled to 10 wt%, 20 wt%, 25 wt%, 30 wt%, and 40 wt%, The ion conductivity of the gel polymer electrolyte prepared according to each content was measured and shown. As can be seen in FIG. 15, the ionic conductivity decreases as the content of the ionic liquid crosslinking agent increases, but the gel polymer electrolyte with 30 wt% of the ionic liquid crosslinking agent shows a high ionic conductivity of about 2.1 mS/cm. I was able to confirm.

16 is a graph comparing charge and discharge characteristics of secondary batteries according to Example 3 and Comparative Example 3 of the present invention.

Referring to FIG. 16, the secondary battery according to Example 3 and the secondary battery according to Comparative Example 3 were each subjected to a charge/discharge experiment at a current density of 0.2 C in a voltage range of 2.5 to 4.0 V.

As can be seen in FIG. 16, the secondary battery according to Example 3 has a similar level of discharge compared to the secondary battery according to Comparative Example 3 to which a liquid electrolyte is applied, even though a non-flowable semi-solid gel polymer electrolyte is applied. It was confirmed that it exhibited a high capacity and a high capacity retention rate.

17 is a graph showing reliability of a secondary battery according to Example 3 of the present invention.

Referring to FIG. 17, a charge/discharge experiment was performed on the secondary battery according to Example 3, a charge/discharge cycle was performed multiple times, and a voltage curve according to the cycle was shown. As can be seen in FIG. 17, it can be seen that the voltage curve of the secondary battery according to Example 3 appears substantially constant even though the number of charge/discharge cycles increases. Accordingly, it was found that the secondary battery according to Example 3 had excellent reliability.

18 and 19 are views showing ¹ HNMR spectrum of the gel polymer electrolyte according to Experimental Example 3 of the present invention.

Referring to FIG. 18, ^{the 1} HNMR spectrum was shown for the state before crosslinking of the gel polymer electrolyte according to Experimental Example 3, and referring to FIG. 19, the gel polymer electrolyte according to Experimental Example 3 at a temperature of 70 ° C. ¹ HNMR spectrum is shown for the cross-linked state for 1 hour. In addition, after variously controlling the crosslinking temperature and time of the gel polymer electrolyte according to Experimental Example 3, the conversion rate was measured for each. After controlling the crosslinking time to 1 hour, the conversion rate measured while changing the crosslinking temperature is summarized in <Table 2> below, and the conversion rate measured while changing the crosslinking time after controlling the crosslinking temperature to 70 ° C is shown in <Table 2> below. It is organized through Table 3>.

crosslinking temperature conversion rate before bridge 0 % 50℃ 33.0% 60℃ 60.5% 70℃ 96.5%

bridge time conversion rate before bridge 0 % 30 minutes 40.3% 1 hours 96.5% 2 hours 97.1%

As can be seen in <Table 2> and <Table 3>, when preparing the gel polymer electrolyte according to Example 3, by controlling the crosslinking temperature to 70 ° C. or more and the crosslinking time to 1 hour or more, 96% or more It was confirmed that a high conversion rate could be obtained.

20 is a graph comparing the electrochemical stability of the gel polymer electrolyte according to Example 1 of the present invention and the polymer electrolyte according to Comparative Example 2.

Referring to FIG. 20, for the gel polymer electrolyte according to Example 1 and the polymer electrolyte according to Comparative Example 2, the current density (mA/cm ² ) according to the applied potential (V vs Na/Na+) was measured and shown. .

As can be seen in FIG. 20, in the case of the polymer electrolyte according to Comparative Example 2, as the applied potential increases, the current density increases rapidly, but in the case of the gel polymer electrolyte according to Example 1, the applied potential is 5.0 to 5.5. It was confirmed that the current density increased in the section and then decreased again after 5.5 applied potential. Accordingly, the gel polymer electrolyte according to Example 1 made of a polyamideimide (PAI) polymer separator has higher electrochemical stability than the polymer electrolyte according to Comparative Example 2 made of a polyethylene (PE) polymer separator. could find out

In the above, the present invention has been described in detail using preferred embodiments, but the scope of the present invention is not limited to specific embodiments, and should be interpreted according to the appended claims. In addition, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

100: porous support
200: mixed solution of liquid electrolyte and ionic liquid crosslinking agent
300: composition for gel polymer electrolyte

Claims (13)

A porous support containing a polymer, a liquid electrolyte containing either sodium or lithium, and an ionic liquid crosslinking agent having two or more double bond functional groups,
The double bond functional group includes mediating a crosslinking reaction of the ionic liquid crosslinking agent,
The ionic liquid crosslinking agent is a composition for a gel polymer electrolyte comprising one represented by the following <Chemical Formula 1>.
<Formula 1>

R: An alkyl group having 1 to 8 carbon atoms.
X ⁺ : among imidazolium, ammonium, pyridinium, pyrazolium, piperidinium, triazolium, thiazolium, oxazolium, pyridazinium, pyrimidinium, pyrazinium, phosphonium, pyrrolidinium and sulfonium any one cation.
Y ^- : BF ₄ , PF ₆ , ClO ₄ , CF ₃ SO ₃ , N(CF ₃ SO ₂ ) ₂ , N(C ₂ F ₅ SO ₂ ) ₂ , C(CF ₂ SO ₂ ) ₃ , AsF ₆ , SbF ₆ , AlCl ₄ , NbF ₆ , CF ₃ CO ₂ An anion of any one.
delete According to claim 1,
The ionic liquid crosslinking agent is a composition for a gel polymer electrolyte containing 30 wt% or more based on 100 wt% of the composition for a gel polymer electrolyte.
According to claim 1,
The polymer includes any one of polyamideimide, polyetherimide, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, and polyacrylonitrile. A composition for a gel polymer electrolyte.
According to claim 1,
The porous support is a composition for a gel polymer electrolyte comprising a plurality of fibers containing the polymer.
A gel polymer electrolyte comprising a chemically cross-linked composition for a gel polymer electrolyte according to claim 1.
an anode and a cathode disposed opposite to each other; and
A secondary battery comprising the gel polymer electrolyte according to claim 6 disposed between the positive electrode and the negative electrode.
Preparing a porous support containing a polymer;
Preparing a liquid electrolyte containing an ionic liquid crosslinking agent containing two or more double bond functional groups and sodium or lithium;
preparing a composition for a gel polymer electrolyte by providing a mixed solution of the liquid electrolyte and the ionic liquid crosslinking agent to the porous support; and
Heat-treating the composition for a gel polymer electrolyte to chemically cross-link the composition for a gel polymer electrolyte,
The ionic liquid crosslinking agent is a method for producing a gel polymer electrolyte comprising one represented by the following <Formula 1>.
<Formula 1>

R: An alkyl group having 1 to 8 carbon atoms.
X ⁺ : among imidazolium, ammonium, pyridinium, pyrazolium, piperidinium, triazolium, thiazolium, oxazolium, pyridazinium, pyrimidinium, pyrazinium, phosphonium, pyrrolidinium and sulfonium any one cation.
Y ^- : BF ₄ , PF ₆ , ClO ₄ , CF ₃ SO ₃ , N(CF ₃ SO ₂ ) ₂ , N(C ₂ F ₅ SO ₂ ) ₂ , C(CF ₂ SO ₂ ) ₃ , AsF ₆ , SbF ₆ , AlCl ₄ , NbF ₆ , CF ₃ CO ₂ An anion of any one.
According to claim 8,
In the step of chemically cross-linking the composition for a gel polymer electrolyte,
The composition for the gel polymer electrolyte, a method for producing a gel polymer electrolyte comprising a heat treatment for at least 1 hour at a temperature of 70 ℃ or more.
According to claim 8,
Preparing the ionic liquid crosslinking agent and the liquid electrolyte,
Preparing the ionic liquid crosslinking agent containing two or more double bond functional groups; and
Method for producing a gel polymer electrolyte comprising the step of preparing the liquid electrolyte by mixing a base source containing sodium or lithium and a solvent.
According to claim 10,
When the base source contains sodium, the solvent is a method for producing a gel polymer electrolyte comprising ethylene carbonate (ethylene carbonate, EC).
According to claim 10,
When the base source contains lithium, the solvent is a method for producing a gel polymer electrolyte comprising dimethyl carbonate (DMC).
According to claim 10,
When the base source contains lithium, the temperature at which the composition for the gel polymer electrolyte is heat-treated is lower than the temperature at which the composition for the gel polymer electrolyte is heat-treated when the base source contains sodium Preparation of a gel polymer electrolyte comprising method.

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