KR20230012430A - Electrolyte composition, gel polymer electrolyte and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an electrolyte composition, a gel polymer electrolyte including a polymer network formed by a polymerization reaction of the electrolyte composition, and a lithium secondary battery including the same, wherein the electrolyte composition includes: lithium salt; a non-aqueous organic solvent; a compound represented by a specific formula; and a perfluoropolyether oligomer.

Description

Electrolyte composition, gel polymer electrolyte and lithium secondary battery including the same

The present invention relates to an electrolyte composition, a gel polymer electrolyte, and a lithium secondary battery including the same.

Recently, personal IT devices and computer networks have been developed due to the development of the information society, and as the dependence on electrical energy in the society as a whole has increased accordingly, the demand for highly stable lithium ion secondary batteries is gradually increasing. In particular, according to the trend of miniaturization and weight reduction of these electronic and communication devices, thinning and miniaturization of lithium secondary batteries, which are core components in this field, are required.

A lithium secondary battery can be divided into a lithium ion battery using a liquid electrolyte and a lithium polymer battery using a polymer electrolyte according to an applied electrolyte.

Lithium ion batteries have the advantage of realizing high capacity, but there is a risk of leakage and explosion due to the use of a liquid electrolyte containing lithium salt, and there is a disadvantage that battery design becomes complicated to improve this.

Lithium polymer batteries have advantages such as high flexibility and improved leakage because they use a solid polymer electrolyte or a gel polymer electrolyte containing electrolyte as an electrolyte, but the mobility of lithium ions is lowered by the polymer matrix formed in the polymer electrolyte, Compared to lithium ion batteries, ionic conductivity is relatively low. However, the use range of the lithium polymer battery is gradually expanding in that it can suppress side reactions between the electrode surface and the electrolyte and has high stability.

Among them, a lithium polymer battery to which the gel polymer electrolyte is applied is (i) coated on one side or both sides of an electrode and a separator with an electrolyte composition in which an organic solvent in which electrolyte salt is dissolved, a polymerization initiator, and a polymerizable monomer or oligomer are mixed, After curing (gelation) using heat or UV to form a gel polymer electrolyte membrane, an electrode assembly having the gel polymer electrolyte membrane formed thereon is wound or stacked to manufacture an electrode assembly, and the electrode or separator is inserted into a battery case. , It can be prepared by re-injecting the liquid electrolyte and impregnating the gel polymer electrolyte membrane, or (ii) injecting the electrolyte composition into the battery case in which the electrode assembly is accommodated, and then applying an appropriate temperature to gel (crosslinking) the electrolyte composition. ) It can be prepared through the steps of.

In this regard, when a lithium polymer battery is manufactured by injecting the electrolyte composition into a battery case in which an electrode assembly is accommodated, the surface of the electrolyte composition is pre-gelated at room temperature. There is a problem in that the tension increases and the wetting of the electrode decreases. These problems lead to deterioration of overall performance of the secondary battery in the future.

Therefore, it is necessary to develop a technology for an electrolyte composition having improved wettability when manufacturing a secondary battery including a gel polymer electrolyte.

Japanese Unexamined Patent Publication No. 2014-0043662

An object of the present invention is to provide an electrolyte composition having improved wettability for an electrode.

In addition, the present invention is intended to provide a gel polymer electrolyte with improved flame retardancy, rigidity and lithium ion conductivity of the polymer matrix, by including a polymer network formed by polymerization of the electrolyte composition.

In addition, the present invention is intended to provide a lithium secondary battery with improved cycle characteristics by including the gel polymer electrolyte.

In order to achieve the above object, the present invention

lithium salt;

non-aqueous organic solvent;

A compound represented by Formula 1 below; and

It provides an electrolyte composition comprising; perfluoropolyether oligomer.

[Formula 1]

In Formula 1,

R ₁ is hydrogen or an alkyl group having 1 to 3 carbon atoms;

n is an integer from 3 to 8;

In addition, the present invention is intended to provide a gel polymer electrolyte comprising a polymer network formed by polymerization of the electrolyte composition of the present invention.

In addition, in the present invention, the anode; cathode; a separator interposed between the negative electrode and the positive electrode; And to provide a lithium secondary battery comprising the gel polymer electrolyte of the present invention.

The electrolyte composition of the present invention includes a perfluoropolyether oligomer and a low molecular weight fluorine-based monomer, thereby improving the wettability of the electrolyte composition, thereby improving not only flame retardancy, but also the stiffness of the polymer matrix and the mobility of lithium ions. can be manufactured. Furthermore, a lithium secondary battery with improved cycle characteristics can be manufactured.

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the contents of the above-described invention, so the present invention is limited to those described in the drawings. It should not be construed as limiting.
1 is a graph showing evaluation results of low-temperature cycle characteristics of a secondary battery according to Experimental Example 1;
2 is a graph showing evaluation results of high-temperature cycle characteristics of a secondary battery according to Experimental Example 2;

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

The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

In addition, terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

Prior to describing the present invention, in this specification, terms such as "comprise", "include", "have" and the like are intended to indicate that embodied features, numbers, steps, components, or combinations thereof exist. However, it should be understood that it does not preclude the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

Meanwhile, in the description of "carbon number a to b" in the present specification, "a" and "b" mean the number of carbon atoms included in a specific functional group. That is, the functional group may include “a” to “b” carbon atoms. For example, "an alkylene group having 1 to 5 carbon atoms" refers to an alkylene group containing 1 to 5 carbon atoms, that is, -CH ₂ -, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, - CH ₂ (CH ₃ )CH-, -CH(CH ₃ )CH ₂ -, -CH(CH ₃ )CH ₂ CH ₂ -, and the like.

The term "alkylene group" means a branched or unbranched divalent unsaturated hydrocarbon group. In one embodiment, the alkylene group may be substituted or unsubstituted. The alkylene group may include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a tert-butylene group, a pentylene group, a 3-pentylene group, and the like.

In addition, in this specification, unless otherwise defined, "substitution" means that at least one hydrogen bonded to carbon is substituted with an element other than hydrogen, for example, with an alkyl group having 1 to 6 carbon atoms or fluorine. means substituted.

electrolyte composition

According to one embodiment, the present invention

lithium salt;

non-aqueous organic solvent;

A compound represented by Formula 1 below; and

It provides an electrolyte composition comprising; perfluoropolyether oligomer.

[Formula 1]

In Formula 1,

R ₁ is hydrogen or an alkyl group having 1 to 3 carbon atoms;

n is an integer from 3 to 8;

(One) lithium salt

First, the lithium salt is described as follows.

As the lithium salt, those commonly used in electrolytes for lithium secondary batteries may be used without limitation, for example, including Li ⁺ as a cation and F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- as an anion, N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , B ₁₀ Cl ₁₀ ^- , AlCl ₄ ^- , AlO ₄ ^- , PF ₆ ^- , CF ₃ SO ₃ ^- , CH ₃ CO ₂ ^- , CF ₃ CO ₂ ^- , AsF ₆ ^- , SbF ₆ ^- , CH ₃ SO ₃ ^- , (CF ₃ CF ₂ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , BF ₂ C ₂ O ₄ ^- , BC ₄ O ₈ ^- , PF ₄ C ₂ O ₄ ^- , PF ₂ C ₄ O ₈ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) at least one selected from the group consisting of ₂ CH ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- and SCN ^- .

Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF ₄ , LiClO ₄ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiAlO ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCH ₃ CO ₂ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiCH ₃ SO ₃ , LiFSI (Lithium bis(fluorosulfonyl) imide, LiN(SO ₂ F) ₂ ), LiBETI (lithium bis(pentafluoroethanesulfonyl) imide, LiN(SO ₂ CF ₂ CF ₃ ) ₂ and LiTFSI (lithium bis (trifluoromethanesulfonyl) imide, LiN (SO ₂ CF ₃ ) ₂ ) may be a single material or a mixture of two or more selected from the group consisting of, and in addition to the above-mentioned lithium salt, lithium salts commonly used in electrolyte solutions of lithium secondary batteries are not limited. Specifically, the lithium salt may include LiPF ₆ .

The lithium salt may be appropriately changed within a generally usable range, but in order to obtain an optimum effect of forming a film for preventing corrosion on the electrode surface, it is included in the electrolyte at a concentration of 0.8 M to 3.0 M, specifically 1.0 M to 3.0 M. can When the concentration of the lithium salt satisfies the above range, it is possible to control the viscosity of the non-aqueous electrolyte so as to realize optimal impregnability, improve the effect of improving the film, and improve the mobility of lithium ions, thereby increasing the capacity of the lithium secondary battery. The effect of improving characteristics and cycle characteristics can be obtained.

(2) non-aqueous organic solvent

In addition, the description of the non-aqueous organic solvent is as follows.

As the non-aqueous organic solvent, various organic solvents commonly used in lithium electrolytes may be used without limitation. Decomposition due to oxidation reactions in the charging and discharging process of a secondary battery can be minimized, and desired properties can be exhibited together with additives. There is no limit to the type of what can be done.

Specifically, the non-aqueous organic solvent may include at least one of a high-viscosity organic solvent that easily dissociates lithium salts in an electrolyte due to its high dielectric constant, and a linear carbonate-based organic solvent having a low viscosity and low dielectric constant.

Examples of the cyclic carbonate-based organic solvent include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, and 2,3-pentylene It may include at least one organic solvent selected from the group consisting of carbonate and vinylene carbonate, and among these, ethylene carbonate may be included.

The linear carbonate organic solvent is selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate It may include at least one organic solvent that is, and may specifically include ethylmethyl carbonate (EMC).

In the present invention, the cyclic carbonate-based organic solvent may be mixed with the linear carbonate-based organic solvent, and the mixing ratio of the cyclic carbonate-based organic solvent and the linear carbonate-based organic solvent is 10:90 to 80:20 by volume, specifically 50: 50 to 70:30 volume ratio.

When the volume ratio of the linear carbonate-based organic solvent to the cyclic carbonate-based organic solvent satisfies the above range, an electrolyte composition having higher electrical conductivity may be prepared.

In addition, the electrolyte composition of the present invention further includes a linear ester-based organic solvent and/or a cyclic ester-based organic solvent having relatively high stability at high temperature and high voltage driving compared to cyclic carbonate-based organic solvents, thereby generating gas during high voltage driving. While improving the disadvantages of cyclic carbonate-based organic solvents that cause a high ionic conductivity can be implemented.

Specific examples of the linear ester organic solvent include at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate. It may include at least one of ethyl propionate and propyl propionate.

In addition, the cyclic ester-based organic solvent may include at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

On the other hand, all other constituents of the electrolyte composition of the present invention except for the non-aqueous organic solvent, such as lithium salt, the compound of formula 1, and the oligomer, may be organic solvents unless otherwise specified.

(3) a compound represented by Formula 1

The electrolyte composition of the present invention may include a compound represented by Formula 1 as a low molecular weight fluorine-based monomer.

[Formula 1]

In Formula 1,

R ₁ is hydrogen or an alkyl group having 1 to 3 carbon atoms;

n is an integer from 3 to 8;

The compound represented by Formula 1 contains a double bond (C=C) functional group included in its molecular structure, so that it can more easily form a solid SEI film containing elemental fluorine on the surface of an anode during an electrochemical decomposition reaction. . In addition, the compound represented by Chemical Formula 1 contains three or more fluorine elements having excellent flame retardancy and non-combustibility, and thus can form a passivation film capable of securing excellent oxidation resistance on the surface of the anode. In addition, the compound represented by Formula 1 of the present invention contains two oxygen elements in its molecular structure, so it has higher oxidation stability than compounds containing three or more oxygen elements in its molecular structure, and is a robust SEI with low resistance on the electrode surface. can form

In particular, the compound represented by Formula 1 of the present invention has a structural feature in which an acrylate functional group and a terminal fluorine-substituted alkyl group are connected (bonded) through an ethylene group (-CH ₂ -CH ₂ -), Compared to compounds such as 2,2,3,3,4,4,4-heptafluoro butyl acrylate in which terminal fluorine-substituted alkyl groups are linked through a methylene group (-CH ₂ -), the molecular chain of the linking group portion is increased. As a result, high flexibility can be secured. Therefore, when preparing a gel polymer electrolyte, the compound represented by Chemical Formula 1 is uniformly distributed in a polymer matrix structure made of a perfluoropolyether oligomer described later to form a flexible polymer matrix structure, and mechanical stability and lithium A gel polymer electrolyte with improved ion mobility can be prepared.

Meanwhile, in Formula 1, R ₁ is hydrogen, n may be an integer of 4 to 8, and specifically n may be an integer of 5 to 8.

In Formula 1, when the integer value of n satisfies the above range, the thermal properties of the compound itself can be improved, and the stability of the film formed therefrom can be expected. Specifically, in Formula 1, when n is 3 or more, as fluorine atoms are included at a certain level or higher, flame retardancy and high-temperature durability of the electrolyte composition are improved, and gas generation and swelling during high-temperature storage can be suppressed. In addition, in Formula 1, when n is 8 or less, it is possible to prevent an increase in the viscosity and non-polarity of the electrolyte composition due to an excess of elemental fluorine, and it is possible to improve the solubility of the compound in the electrolyte composition. performance degradation can be avoided.

Specifically, the compound represented by Chemical Formula 1 may include at least one of oligomers represented by Chemical Formulas 1-1 and 1-2.

[Formula 1-1]

[Formula 1-2]

(4) perfluoropolyether oligomer

The electrolyte composition of the present invention may include a perfluoropolyether oligomer.

The perfluoropolyether oligomer may include an oligomer represented by Chemical Formula 2 below.

[Formula 2]

In Formula 2,

R is an alkylene group having 1 to 4 carbon atoms unsubstituted or substituted with fluorine,

R ₂ and R ₂ 'are each independently an alkylene group having 1 to 5 carbon atoms or -(CF ₂ ) _o -O- (o is an integer of 1 to 3);

R ₃ and R ₃ 'are each independently an alkylene group having 1 to 5 carbon atoms or -(R ₅ ) _o2 -O- (R ₅ is an unsubstituted or substituted alkylene group having 1 to 5 carbon atoms, and o2 is 1 to 3 is an integer of),

R ₄ is an aliphatic hydrocarbon group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group;

Ra, Rb, Rc and Rd are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms,

n, m and m' are each independently an integer from 1 to 10,

k is an integer from 10 to 1,000;

p and p' are each independently an integer of 0 or 1,

c and c1 are each independently an integer from 1 to 3;

d and d1 are each independently an integer of 1 or 2;

The perfluoropolyether oligomer represented by Chemical Formula 2 includes an acrylate group, which is a hydrophilic group capable of forming a cross-link by itself, at both ends of the structure, and a perfluoropolyether group, which is a hydrophobic part, in the main chain. By including a urethane group and/or a urea group therein, it is possible to secure a balanced affinity between the hydrophilic portion of the positive electrode or separator and the hydrophobic portion of the negative electrode or separator fabric, thereby reducing the viscosity and surface tension of the electrolyte composition. This secures the wettability of the electrolyte composition even when the lithium salt is contained in a high concentration of 1.5 M or more in the electrolyte composition, thereby lowering the interfacial resistance. Therefore, the impregnability of the electrolyte composition into the electrode and the separator can be improved.

Moreover, the perfluoropolyether oligomer is an electrochemically stable compound with high reduction stability, and has the ability to dissociate lithium salts, thereby minimizing the reduction reaction on the surface of the anode and improving lithium ion mobility. there is.

Therefore, in the case of a gel polymer electrolyte prepared using an electrolyte composition containing such a perfluoropolyether oligomer, conventional polymers having an alkylene oxide skeleton such as ethylene oxide, propylene oxide, and butylene oxide; Or, compared to gel polymer electrolytes prepared using dialkyl siloxanes, fluorosiloxanes, block copolymers and graft polymers having these units, side reactions with electrodes are reduced, and interface resistance between electrodes and electrolytes is reduced. reduced, it is possible to manufacture a lithium secondary battery with improved overall performance such as cycle life characteristics.

Meanwhile, in Formula 2, the aliphatic hydrocarbon group is an alkylene group having 1 to 20 carbon atoms; an alkylene group having 1 to 20 carbon atoms containing an isocyanate group (NCO); an alkoxylene group having 1 to 20 carbon atoms; An alkenylene group having 2 to 20 carbon atoms; or an alkynylene group having 2 to 20 carbon atoms.

In addition, in Formula 2, the alicyclic hydrocarbon group is a cycloalkylene group having 4 to 20 carbon atoms; A cycloalkenylene group having 4 to 20 carbon atoms; and a heterocycloalkylene group having 2 to 20 carbon atoms.

In addition, in Formula 2, the aromatic hydrocarbon group is an arylene group having 6 to 20 carbon atoms; Or it may be a heteroarylene group having 2 to 20 carbon atoms.

Specifically, in Formula 2, R is an alkylene group having 2 to 4 carbon atoms unsubstituted or substituted with fluorine, and R ₂ and R ₂ 'are each independently an alkylene group having 1 to 3 carbon atoms or -(CF ₂ ) _o -O- (o is an integer of 1 to 3), R ₃ and R ₃ 'are each independently an alkylene group having 2 to 5 carbon atoms or -(R ₅ ) _o2 -O- (R ₅ is unsubstituted or substituted An alkylene group having 2 to 5 carbon atoms, o2 is an integer of 1 to 3), R ₄ is an alicyclic hydrocarbon group, and Ra, Rb, Rc and Rd may each independently be hydrogen or an alkyl group having 1 or 2 carbon atoms. .

The oligomer represented by Chemical Formula 2 may include an oligomer represented by Chemical Formula 2-1 or Chemical Formula 2-2 below.

[Formula 2-1]

In Formula 2-1,

n1 is an integer from 1 to 10;

k1 is an integer from 10 to 1,000.

[Formula 2-2]

In Formula 2-2,

n2, m1 and m1' are each independently an integer from 1 to 10,

k2 is an integer from 10 to 1,000.

Specifically, the oligomer represented by Chemical Formula 2 may include an oligomer represented by Chemical Formula 2-2.

That is, the oligomer represented by Chemical Formula 2 can help dissociate lithium salts in the main chain structure, transfer lithium ions more easily, and polypropylene that can impart flexible performance to the polymer main chain. As the oxide unit is included as a repeating unit, the number of lithium ions that can move in the electrolyte increases, the mobility of the lithium ion itself increases, and the mobility of the polymer increases, further improving the low-temperature cycle and output characteristics of the secondary battery. can make it

Meanwhile, the perfluoropolyether oligomer may be included in an amount of 0.1 wt % to 10 wt %, specifically 0.1 wt % to 15 wt %, in the electrolyte composition.

When the content of the perfluoropolyether oligomer satisfies the above range, surface tension of the electrolyte composition may be lowered to improve impregnability into an electrode, and stable mechanical properties due to gelation may be secured. In addition, it is possible to prevent disadvantages such as increase in resistance due to the addition of an excessive amount of oligomers and consequent decrease in capacity and restriction of movement of lithium ions, for example, decrease in ionic conductivity.

On the other hand, the weight average molecular weight (MW) of the perfluoropolyether oligomer is 1,000 g / mol to 100,000 g / mol, specifically 1,000 g / mol to 50,000 g / mol, more specifically 1,000 g / mol to 10,000 g / mol mol, and more specifically, 1,000 g/mol to 5,000 g/mol, and the range can be controlled by the number of repeating units. When the weight average molecular weight of the oligomer is within the above range, the mechanical strength of the non-aqueous electrolyte containing the oligomer can be effectively controlled.

For example, when the weight average molecular weight of the perfluoropolyether oligomer is 1,000 g/mol or more, mechanical strength can be improved. In addition, when the weight average molecular weight of the perfluoropolyether oligomer is 100,000 g / mol or less, the physical properties of the oligomer itself are prevented from being rigid, and the affinity for the electrolyte solvent is increased so that it can be easily dissolved. Formation of a uniform gel polymer electrolyte cannot be expected.

The weight average molecular weight can be measured using gel permeation chromatography (GPC). For example, after preparing a sample of a certain concentration, the GPC measurement system alliance 4 device is stabilized. When the instrument is stabilized, a chromatogram is obtained by injecting a standard sample and a sample sample into the instrument, and then the molecular weight can be calculated according to the analysis method (system: Alliance 4, column: Ultrahydrogel linearX2, eluent: 0.1M NaNO ₃ (pH 7.0) phosphate buffer, flow rate: 0.1 mL/min, temp: 40℃, injection: 100μL)

Meanwhile, in the electrolyte composition of the present invention, the compound represented by Formula 1 is present in an amount of 0.1 to 50 parts by weight, specifically 0.5 to 40 parts by weight, more specifically 1 to 30 parts by weight, based on 100 parts by weight of the perfluoropolyether oligomer. It may be included in parts by weight.

When the weight ratio of the compound represented by Formula 1 to the weight of the perfluoropolyether oligomer satisfies the above range, units derived from the compound represented by Formula 1 are uniformly distributed in the polymer matrix structure made of the perfluoropolyether oligomer. Distributed, it is possible to form a polymer matrix having a flexible structure, and furthermore, a gel polymer electrolyte with improved mechanical stability and lithium ion mobility can be prepared. That is, when the content of the compound represented by Formula 1 is 0.1 part by weight or more, a uniform gel polymer matrix can be formed due to an appropriate polymerization reaction, and when the content of the compound represented by Formula 1 is less than 50 parts by weight, , By controlling the polymerization reaction rate, it is possible to prevent the formation of a low molecular weight polymer matrix, so that the mechanical strength of the gel polymer electrolyte can be secured.

(5) polymerization initiator

The electrolyte composition of the present invention may further include a polymerization initiator for polymerization.

The polymerization initiator is a component included to carry out a radical reaction required in the preparation of a gel polymer electrolyte, decomposes by heat to form radicals, and reacts by free radical polymerization to form compounds represented by Formula 1 and oligomers represented by Formula 2. May cause polymerization reactions.

As such a polymerization initiator, conventional thermal or photo polymerization initiators known in the art may be used, and non-limiting examples include benzoyl peroxide, acetyl peroxide, dilauryl peroxide, Di-tert-butyl peroxide, t-butyl peroxy-2-ethyl-hexanoate, cumyl hydroperoxide , organic peroxides or hydroperoxides such as hydrogen peroxide, 2,2'-azobis (2-cyanobutane), 2,2'-azobis (methylbutyronitrile), 2, 2'-Azobis(isobutyronitrile) (AIBN; 2,2'-Azobis(iso-butyronitrile)), 2,2'-Azobisdimethyl-Valeronitrile (AMVN; 2,2'-Azobisdimethyl-Valeronitrile ) and the like.

The polymerization initiator is decomposed by heat in the battery, for example, at 30 ° C to 100 ° C, or decomposed at room temperature (25 ° C to 30 ° C) to form radicals, and polymerizable oligomers are converted into acrylates by free radical polymerization. A gel polymer electrolyte may be formed by reacting with the based compound.

The polymerization initiator may be included in an amount of 0.01 to 10 parts by weight, specifically 0.1 to 5 parts by weight, based on 100 parts by weight of the oligomer represented by Formula 2.

When the content of the polymerization initiator satisfies the above range, the gel polymer conversion rate may be increased to ensure gel polymer electrolyte properties, and the pre-gel reaction may be prevented, thereby improving wettability of the electrolyte solution to the electrode.

gel polymer electrolyte

In addition, the present invention can provide a gel polymer electrolyte comprising a polymer network formed by polymerization of the electrolyte composition of the present invention.

The polymerization reaction may use a conventional polymerization method.

Specifically, the gel polymer electrolyte of the present invention may be prepared by injecting the electrolyte composition of the present invention into a battery case in which an electrode assembly is accommodated, and then performing a polymerization reaction while applying heat, e-beam, or gamma rays.

Specifically, the polymerization reaction may be performed by thermal polymerization, and may be performed by reacting for 1 hour to 8 hours while applying heat of approximately 50° C. to 100° C.

lithium secondary battery

In addition, the present invention

It is possible to provide a lithium secondary battery including a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and the above-described gel polymer electrolyte of the present invention.

At this time, since the gel polymer electrolyte has been described above, a description thereof will be omitted, and other components will be described below.

(1) anode

The cathode according to the present invention may include a cathode active material layer including a cathode active material, and if necessary, the cathode active material layer may further include a conductive material and/or a binder.

The cathode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium composite metal oxide containing lithium and at least one metal such as cobalt, manganese, nickel, or aluminum. there is.

Specifically, the cathode active material is selected from among lithium-cobalt-based oxides (eg, LiCoO ₂ ) and lithium-nickel-manganese-cobalt-based oxides represented by Formula 3 in that they can improve capacity characteristics and stability of batteries. may contain at least one.

[Formula 3]

Li(Ni _x Co _y Mn _z ) O ₂

(In Formula 3, 0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1)

Specifically, the lithium-nickel-manganese-cobalt-based oxide may preferably contain 50 atm% or more of nickel, and representative examples thereof include Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.2 Co _0.3 )O ₂ , Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ and Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ may include at least one of them.

In addition, the cathode active material may include a lithium-manganese oxide (eg, LiMnO ₂ , LiMn ₂ O ₄ ) in addition to the lithium-cobalt-based oxide or the lithium-nickel-manganese-cobalt-based oxide. etc.), lithium-nickel-based oxide (eg, LiNiO ₂ , etc.), lithium-nickel-manganese-based oxide (eg, LiNi _{1 -Y} Mn _Y O ₂ (where 0<Y<1), LiMn _{2 - z} Ni _z O ₄ (where 0 < Z < 2), lithium-nickel-cobalt-based oxide (eg, LiNi _{1 - Y1} Co _Y1 O ₂ (where 0 < Y1 < 1), lithium -manganese-cobalt-based oxides (for example, LiCo _{1 - Y2} Mn _Y2 O ₂ (where 0<Y2 < 1), LiMn _{2 - z1} Co _z1 O ₄ (where 0 <Z1 <2), or Lithium-nickel-cobalt-transition metal (M) oxides (eg, Li(Ni _p2 Co _q2 Mn _r3 M _S2 )O ₂ where M is Al, Fe, V, Cr, Ti, Ta, Mg and It is selected from the group consisting of Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, respectively, 0 <p2 <1, 0 <q2 <1, 0 <r3 <1, 0 <s2 <1, p2 +q2+r3+s2=1)) and the like, any one or two or more of these compounds may be included, and such a cathode active material is LiMnO ₂ , LiNiO ₂ , or lithium nickel cobalt aluminum oxide (eg For example, Li(Ni _0.8 Co _0.15 Al _0.05 )O ₂ , etc.) may be included.

The positive electrode active material may be included in an amount of 90% to 99% by weight, specifically 93% to 98% by weight, based on the total weight of solids in the positive electrode active material layer.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, carbon such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black powder; graphite powders such as natural graphite, artificial graphite, and graphite having highly developed crystal structures; conductive fibers such as carbon fibers and metal fibers; Conductive powders, such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of solids in the positive electrode active material layer.

The binder is a component that serves to improve adhesion between the positive electrode active material particles and adhesion between the positive electrode active material and the current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of solids in the positive electrode active material layer. Examples of such a binder include a fluororesin-based binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber-based binders including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulosic binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; A polyalcohol-based binder containing polyvinyl alcohol; polyolefin binders including polyethylene and polypropylene; polyimide-based binders; polyester-based binder; A silane type binder etc. are mentioned.

The positive electrode of the present invention as described above may be manufactured according to a positive electrode manufacturing method known in the art. For example, the positive electrode is prepared by dissolving or dispersing a positive electrode active material, a binder and / or a conductive material in a solvent to prepare a positive electrode slurry, applying it on a positive electrode current collector, and then drying and rolling to form a positive electrode active material layer. Alternatively, it may be manufactured through a method of casting the positive electrode active material layer on a separate support and then laminating a film obtained by peeling the support on a positive electrode current collector.

The cathode current collector is not particularly limited as long as it does not cause chemical change in the battery and has conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, or carbon on the surface of aluminum or stainless steel. , nickel, titanium, silver or the like may be used. In addition, fine irregularities may be formed on the surface of the positive electrode current collector to enhance bonding strength of the positive electrode active material. The cathode current collector may include various forms such as a film, sheet, foil, net, porous material, foam, and non-woven fabric.

The solvent may include an organic solvent such as NMP (N-methyl-2-pyrrolidone), and may be used in an amount that provides a desired viscosity when the cathode active material and optionally a binder and/or a conductive material are included. For example, the active material slurry containing the cathode active material and optionally the binder and/or the conductive material may have a solid concentration of 10 wt% to 70 wt%, preferably 20 wt% to 60 wt%.

(2) Cathode

Next, the cathode is described.

The negative electrode according to the present invention includes a negative electrode active material layer including a negative electrode active material, and the negative electrode active material layer may further include a conductive material and/or a binder, if necessary.

The anode active material includes lithium metal, a carbon material capable of reversibly intercalating/deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and undoping lithium, and transition metal oxides. It may include at least one selected from the group consisting of transition metal oxides.

As the carbon material capable of reversibly intercalating/deintercalating the lithium ion, any carbon-based negative electrode active material commonly used in lithium ion secondary batteries may be used without particular limitation, and typical examples thereof include crystalline carbon, Amorphous carbon or a combination thereof may be used. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon). or hard carbon, mesophase pitch carbide, calcined coke, and the like.

Examples of the above metals or alloys of these metals and lithium include Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al And a metal selected from the group consisting of Sn or an alloy of these metals and lithium may be used.

Examples of the metal composite oxide include PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , Bi ₂ O ₅ , Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), and Sn _x Me _{1 - x} Me' _y O _z (Me: Mn, Fe , Pb, Ge; Me': Al, B, P, Si, Groups 1, 2, and 3 elements of the periodic table, halogen; 0<x≤1;1≤y≤3; 1≤z≤8) Anything selected from the group may be used.

Materials capable of doping and undoping the lithium include Si, SiO _x (0<x<2), Si—Y alloy (wherein Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, It is an element selected from the group consisting of rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn—Y (Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, and a rare earth element). It is an element selected from the group consisting of elements and combinations thereof, but not Sn), and the like, and at least one of these and SiO ₂ may be mixed and used. The element Y is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db (dubnium), Cr, Mo, W, Sg, Tc, Re, Bh , Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S , Se, Te, Po, and combinations thereof.

Examples of the transition metal oxide include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

The negative active material may be included in an amount of 80% to 99% by weight based on the total weight of solids in the negative active material layer.

The conductive material is a component for further improving the conductivity of the negative active material, and may be added in an amount of 1 to 20% by weight based on the total weight of solids in the negative active material layer. The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; Conductive powders, such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the negative electrode active material layer. Examples of such binders include fluororesin-based binders including polyvinylidene fluoride or polytetrafluoroethylene; rubber-based binders including styrene-butadiene rubber, acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulosic binders including carboxymethylcellulose, starch, hydroxypropylcellulose, and regenerated cellulose; A polyalcohol-based binder containing polyvinyl alcohol; polyolefin binders including polyethylene and polypropylene; polyimide-based binders; polyester-based binder; A silane type binder etc. are mentioned.

The negative electrode may be manufactured according to a negative electrode manufacturing method known in the art. For example, the negative electrode is prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent to prepare a negative electrode active material slurry, applying it on a negative electrode current collector, rolling and drying to form a negative electrode active material layer, Alternatively, it may be prepared by casting the negative electrode active material layer on a separate support and then laminating a film obtained by peeling the support on the negative electrode current collector.

The negative current collector generally has a thickness of 3 to 500 μm. The negative electrode current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel A surface treated with carbon, nickel, titanium, silver, or the like, an aluminum-cadmium alloy, or the like may be used. In addition, like the positive electrode current collector, fine irregularities may be formed on the surface of the negative electrode current collector to enhance the bonding strength of the negative electrode active material, and may include various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics. there is.

The solvent may include water or an organic solvent such as NMP or alcohol, and may be used in an amount that provides a desired viscosity when the negative electrode active material and optionally a binder or conductive material are included. For example, the solid content of the active material slurry including the negative electrode active material and, optionally, the binder and the conductive material may be included to be 50 wt% to 75 wt%, preferably 50 wt% to 65 wt%.

(3) separator

The lithium secondary battery according to the present invention includes a separator between the positive electrode and the negative electrode.

The separator separates the negative electrode and the positive electrode and provides a passage for the movement of lithium ions, and can be used without particular limitation as long as it is used as a separator in a lithium secondary battery. It is desirable that this excellent

Specifically, a porous polymer film as a separator, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer. Alternatively, a laminated structure of two or more layers thereof may be used. In addition, conventional porous non-woven fabrics, for example, non-woven fabrics made of high-melting glass fibers, polyethylene terephthalate fibers, and the like may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be selectively used in a single layer or multilayer structure.

The lithium secondary battery according to the present invention as described above can be usefully used in portable devices such as mobile phones, notebook computers, digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack may include a power tool; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Alternatively, it may be used as a power source for one or more medium or large-sized devices among power storage systems.

The appearance of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but also can be preferably used as a unit cell in a medium-large battery module including a plurality of battery cells.

Hereinafter, the present invention will be described in detail through examples.

At this time, the embodiments according to the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Example One.

(Preparation of Electrolyte Composition)

LiPF ₆ was added to 97.68 g of a non-aqueous organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), ethyl propionate (EP) and propyl propionate (PP) in a volume ratio of 20:10:20:50. After dissolving to 1.0 M, 2.0 g of the oligomer represented by Formula 2-2 (n2=5, m1=1, m1'=1, k2=4, weight average molecular weight: 3,000 g/mol), Formula 1-1 An electrolyte composition was prepared by adding 0.3 g of the indicated compound and 0.02 g of a polymerization initiator (see Table 1 below).

(Anode manufacturing)

Cathode active material (LiCoO ₂ ), conductive material (carbon black), and binder (polyvinylidene fluoride) were added to N-methyl-2-pyrrolidone (NMP) as a solvent in a weight ratio of 97.5:1:1.5. A slurry (solids concentration 60% by weight) was prepared. The positive electrode active material slurry was applied to a positive electrode current collector (Al thin film) having a thickness of 15 μm, dried, and then subjected to a roll press to prepare a positive electrode.

(cathode manufacturing)

An anode active material slurry (solid content concentration: 50% by weight) was prepared by adding a cathode active material (graphite), a conductive material (carbon black), and a binder (polyvinylidene fluoride) to distilled water in a weight ratio of 96:0.5:3.5. The negative electrode active material slurry was applied to a negative electrode current collector (Cu thin film) having a thickness of 8 μm, dried, and then rolled pressed to prepare a negative electrode.

(Secondary battery manufacturing)

An electrode assembly was prepared by laminating the positive and negative electrodes prepared by the above method together with a polyethylene porous film as a separator, then putting it into a battery case, injecting 6 mL of the electrolyte composition, sealing, and aging for 2 days did Thereafter, a pouch-type lithium secondary battery (4.45V, 4100 mAh) including a gel polymer electrolyte was prepared by performing a thermal polymerization reaction by curing at 70° C. for 5 hours.

Example 2.

Example 1 except that an electrolyte composition was prepared by adding 1.0 g of an oligomer represented by Formula 2-2, 0.15 g of a compound represented by Formula 1-1, and 0.01 g of a polymerization initiator to 98.84 g of a non-aqueous organic solvent. A pouch-type lithium secondary battery was prepared in the same manner as in (see Table 1 below).

Example 3.

A pouch-type lithium secondary battery was prepared in the same manner as in Example 1, except that the electrolyte composition was prepared by adding the compound represented by Formula 1-2 instead of the compound represented by Formula 1-1 (Table below). 1).

Example 4.

A pouch-type lithium secondary battery was prepared in the same manner as in Example 2, except that the electrolyte composition was prepared by adding the compound represented by Formula 1-2 instead of the compound represented by Formula 1-1 (Table below). 1).

Example 5.

2.0 g of the oligomer represented by Formula 2-2, 0.002 g of a compound represented by Formula 1-1, and 0.02 g of a polymerization initiator were added to 97.978 g of a non-aqueous organic solvent to prepare an electrolyte composition as in Example 1. A pouch-type lithium secondary battery was prepared in the same manner as in (see Table 1 below).

Example 6.

Example 1 except that an electrolyte composition was prepared by adding 2.0 g of oligomer represented by Formula 2-2, 1.0 g of compound represented by Formula 1-1, and 0.02 g of polymerization initiator to 96.98 g of non-aqueous organic solvent. A pouch-type lithium secondary battery was prepared in the same manner as in (see Table 1 below).

Example 7.

2.0 g of oligomer represented by Formula 2-2, 0.001 g of compound represented by Formula 1-1, and 0.02 g of polymerization initiator were added to 97.979 g of non-aqueous organic solvent to prepare an electrolyte composition as in Example 1. A pouch-type lithium secondary battery was prepared in the same manner as in (see Table 1 below).

Example 8.

Example 1 except that an electrolyte composition was prepared by adding 2.0 g of oligomer represented by Formula 2-2, 1.2 g of compound represented by Formula 1-1, and 0.02 g of polymerization initiator to 96.78 g of non-aqueous organic solvent. A pouch-type lithium secondary battery was prepared in the same manner as in (see Table 1 below).

Example 9.

Example 1 except that the oligomer represented by Formula 2-1 (n1 = 5, k2 = 7, weight average molecular weight: 4,000 g / mol) was used instead of the oligomer represented by Formula 2-2. A lithium secondary battery was manufactured in the same manner (see Table 1 below).

Example 10.

A lithium secondary battery was prepared in the same manner as in Example 2, except that the oligomer represented by Chemical Formula 2-1 was used instead of the oligomer represented by Chemical Formula 2-2 (see Table 1 below).

comparative example One.

A lithium secondary battery was prepared in the same manner as in Example 1, except that LiPF ₆ was dissolved in 100 g of a non-aqueous organic solvent to a concentration of 1.0 M, and an electrolyte composition was prepared without adding an additive (see Table 1 below). ).

comparative example 2.

Pouch-type lithium secondary battery in the same manner as in Example 1, except that the electrolyte composition was prepared by adding only 0.02 g of polymerization initiator and 2.0 g of oligos represented by Chemical Formula 2-2 to 97.98 g of non-aqueous organic solvent. was prepared (see Table 1 below).

comparative example 3.

A pouch-type lithium secondary battery was prepared in the same manner as in Example 1, except that the electrolyte composition was prepared by adding only 0.3 g of the compound represented by Formula 1-1 to 97.98 g of the non-aqueous organic solvent (Table below). 1).

comparative example 4.

Example 1 except that an electrolyte composition was prepared by adding 0.3 g of a compound represented by Formula 3, 2.0 g of an oligomer represented by Formula 2-2, and 0.02 g of a polymerization initiator to 97.68 g of a non-aqueous organic solvent. A pouch-type lithium secondary battery was prepared in the same manner as in (see Table 1 below).

[Formula 3]

comparative example 5.

Example 1 except that an electrolyte composition was prepared by adding 0.3 g of a compound represented by Formula 4, 2.0 g of an oligomer represented by Formula 2-2, and 0.02 g of a polymerization initiator to 97.68 g of a non-aqueous organic solvent. A pouch-type lithium secondary battery was prepared in the same manner as in (see Table 1 below).

[Formula 4]

non-aqueous
organic solvent
Content (g) monomer oligomer Oligomer and monomer weight ratio at polymerization start
content
(g) chemical formula content
(g) chemical formula weight average
Molecular Weight (Mw) content
(g) Example 1 97.68 1-1 0.3 2-2 3,000 2 100:15 0.02 Example 2 98.84 1-1 0.15 2-2 3,000 One 100:15 0.01 Example 3 97.68 1-2 0.3 2-2 3,000 2 100:15 0.02 Example 4 98.84 1-2 0.15 2-2 3,000 One 100:15 0.01 Example 5 97.978 1-1 0.002 2-2 3,000 2 100:0.1 0.02 Example 6 96.98 1-1 One 2-2 3,000 2 100:50 0.02 Example 7 97.979 1-1 0.001 2-2 3,000 2 100:0.05 0.02 Example 8 96.98 1-1 1.2 2-2 3,000 2 100:60 0.02 Example 9 97.68 1-1 0.3 2-1 4,000 2 100:15 0.02 Example 10 98.84 1-1 0.15 2-1 4,000 One 100:15 0.01 Comparative Example 1 100 - - - - - - Comparative Example 2 97.98 - - 2-2 3,000 2 - 0.02 Comparative Example 3 99.70 1-1 0.3 - - - - Comparative Example 4 97.68 3 0.3 2-2 3,000 2 1:15 0.02 Comparative Example 5 97.68 4 0.3 2-2 3,000 2 1:15 0.02

[ Experimental Example ]

Experimental example 1. Evaluation of low temperature (15℃) cycle characteristics

The secondary batteries prepared in Examples 1 to 10 and the secondary batteries prepared in Comparative Examples 1 to 5 were each activated at 0.1C CC. Subsequently, using a PESC05-0.5 charger/discharger (manufacturer: PNE Solution, 5V, 500 mA) at 25 ° C, charge with 0.33C CC up to 4.45V under constant current-constant voltage (CC-CV) charging conditions, and then 0.05 C current cut and discharged at 0.33 C up to 2.5V under CC conditions. Two cycles were performed with the charging and discharging as one cycle.

Then, it was charged at 0.33 C / 4.45 V constant current-constant voltage at 15 ° C (cut-off 0.05 C), and 100 cycles were performed with a 0.2 C 2.5 V CC cycle as one cycle. At this time, 0.1C discharge was performed at 1 cycle and 50 cycles to check the capacity, and the results are shown in FIG. 1 .

Referring to FIG. 1 , it can be seen that the low-temperature cycle capacity of the secondary batteries of Comparative Examples 1 to 5 is lower than that of the secondary batteries of Examples 1 to 10 of the present invention.

On the other hand, in the case of the secondary battery of Example 7 in which the compound represented by Formula 1 is slightly less than the perfluoropolyether oligomer in the electrolyte composition, the lithium ion conductivity decreases as the content of the compound represented by Formula 1 in the polymer network structure decreases. is lowered, and it can be seen that the low-temperature cycle capacity is slightly lowered compared to the secondary batteries of Examples 1 to 6.

In addition, in the case of the secondary battery of Example 8, in which the compound represented by Formula 1 is contained in the electrolyte composition in a slightly larger amount than the perfluoropolyether oligomer, the matrix molecular weight is reduced due to the fast polymerization reaction rate, and the surface of the electrode As a thick film was formed, the resistance increased, and it can be seen that the low-temperature cycle capacity was relatively reduced compared to the secondary batteries of Examples 1 to 6.

Experimental Example 2. High temperature (45 ℃) cycle characteristics evaluation

The secondary batteries prepared in Examples 1 to 10 and the secondary batteries prepared in Comparative Examples 1 to 5 were each activated at 0.1C CC. Subsequently, using a PESC05-0.5 charger/discharger (manufacturer: PNE Solution, 5V, 500 mA) at 25 ° C, charge with 0.33C CC up to 4.45V under constant current-constant voltage (CC-CV) charging conditions, and then 0.05 C current cut and discharged at 0.33 C up to 2.5V under CC conditions. Two cycles were performed with the charging and discharging as one cycle.

Then, it was charged at 0.33 C/4.45 V constant current-constant voltage at 45°C (cut-off 0.05 C), and 100 cycles were performed with a 0.5C 2.5V CC cycle as one cycle. At this time, 0.1C discharge was performed at 1 cycle and 50 cycles to check the capacity, and the results are shown in FIG. 2 .

Referring to FIG. 2 , it can be seen that the secondary batteries of Examples 1 to 10 of the present invention have improved high-temperature cycle capacity of the secondary batteries of Comparative Examples 1 to 5.

On the other hand, in the case of the secondary battery of Example 7 in which the compound represented by Formula 1 is slightly less than the perfluoropolyether oligomer in the electrolyte composition, the lithium ion conductivity decreases as the content of the compound represented by Formula 1 in the polymer network structure decreases. is lowered, it can be seen that the high-temperature cycle capacity is slightly lowered compared to the secondary batteries of Examples 1 to 6.

In addition, in the case of the secondary battery of Example 8, in which the compound represented by Formula 1 was contained in the electrolyte composition in a relatively large amount compared to the perfluoropolyether oligomer, the rapid polymerization reaction rate caused a decrease in matrix molecular weight, resulting in a gel polymer electrolyte. It can be seen that the mechanical strength is lowered, and the high-temperature cycle capacity is relatively lowered compared to the secondary batteries of Examples 1 to 6.

Claims (14)

lithium salt;
non-aqueous organic solvent;
A compound represented by Formula 1 below; and
Electrolyte composition comprising; perfluoropolyether oligomer:
[Formula 1]

In Formula 1,
R ₁ is hydrogen or an alkyl group having 1 to 3 carbon atoms;
n is an integer from 3 to 8;
The method of claim 1,
In Formula 1, R ₁ is hydrogen, and n is an integer of 4 to 8 electrolyte composition.
The method of claim 1,
In Formula 1, R ₁ is hydrogen, and n is an integer of 5 to 8 electrolyte composition.
The method of claim 1,
The electrolyte composition wherein the compound represented by Chemical Formula 1 is at least one of oligomers represented by Chemical Formulas 1-1 and 1-2.
[Formula 1-1]

[Formula 1-2]

The method of claim 1,
Electrolyte composition wherein the perfluoropolyether oligomer includes an oligomer represented by Formula 2 below:
[Formula 2]

In Formula 2,
R is an alkylene group having 1 to 4 carbon atoms unsubstituted or substituted with fluorine,
R ₂ and R ₂ 'are each independently an alkylene group having 1 to 5 carbon atoms or -(CF ₂ ) _o -O- (o is an integer of 1 to 3);
R ₃ and R ₃ 'are each independently an alkylene group having 1 to 5 carbon atoms or -(R ₅ ) _o2 -O- (R ₅ is an unsubstituted or substituted alkylene group having 1 to 5 carbon atoms, and o2 is 1 to 3 is an integer of),
R ₄ is an aliphatic hydrocarbon group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group;
Ra, Rb, Rc and Rd are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms,
n, m and m' are each independently an integer from 1 to 10,
k is an integer from 10 to 1,000;
p and p' are each independently an integer of 0 or 1,
c and c1 are each independently an integer from 1 to 3;
d and d1 are each independently an integer of 1 or 2;
The method of claim 5,
In Formula 2, R is an alkylene group having 2 to 4 carbon atoms unsubstituted or substituted with fluorine, and R ₂ and R ₂ 'are each independently an alkylene group having 1 to 3 carbon atoms or -(CF ₂ ) _o -O- (o is an integer of 1 to 3), and R ₃ and R ₃ 'are each independently an alkylene group having 2 to 5 carbon atoms or -(R ₅ ) _o2 -O- (R ₅ is unsubstituted or substituted 2 to 5 carbon atoms) 5 alkylene group, o2 is an integer of 1 to 3), R ₄ is an alicyclic hydrocarbon group, and Ra, Rb, Rc and Rd are each independently hydrogen or an alkyl group having 1 or 2 carbon atoms.
The method of claim 5,
An electrolyte composition wherein the oligomer represented by Formula 2 includes at least one of the following oligomers represented by Formula 2-1 and Formula 2-2:
[Formula 2-1]

In Formula 2-1,
n1 is an integer from 1 to 10;
k1 is an integer from 10 to 1,000.
[Formula 2-2]

In Formula 2-2,
n2, m1 and m1' are each independently an integer from 1 to 10,
k2 is an integer from 10 to 1,000.
The method of claim 5,
The oligomer represented by Chemical Formula 2 is an electrolyte composition represented by Chemical Formula 2-2.
The method of claim 1,
The electrolyte composition of claim 1, wherein the perfluoropolyether oligomer is included in an amount of 0.1% to 10% by weight based on the total weight of the electrolyte composition.
The method of claim 1,
The compound represented by Formula 1 is included in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the perfluoropolyether oligomer.
The method of claim 1,
The electrolyte composition wherein the compound represented by Formula 1 is included in an amount of 0.5 to 40 parts by weight based on 100 parts by weight of the perfluoropolyether oligomer.
The method of claim 1,
The electrolyte composition further comprises a polymerization initiator.
A gel polymer electrolyte comprising a polymer network formed by polymerization of the electrolyte composition of claim 1.
anode; cathode; a separator interposed between the positive electrode and the negative electrode; and
A lithium secondary battery comprising the; gel polymer electrolyte of claim 13.

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