KR20220009899A - Composition for solid polymer electrolyte, solid polymer electrolyte formed therefrom and lithium secondary battery comprising the same electrolyte - Google Patents

Abstract

The present invention relates to a composition for a solid polymer electrolyte, a solid polymer electrolyte formed therefrom, and a lithium secondary battery including the same, and specifically, to a composition for a solid polymer electrolyte having improved lithium ion mobility, improved ionic conductivity and excellent electrochemical stability, a solid polymer electrolyte formed therefrom, and a lithium secondary battery having improved output characteristics at low temperature and excellent electrochemical stability and safety, including the same.

Description

A composition for a solid polymer electrolyte, a solid polymer electrolyte formed therefrom, and a lithium secondary battery comprising the same

The present invention relates to a composition for a solid polymer electrolyte, a solid polymer electrolyte formed therefrom, and a lithium secondary battery comprising the same, and more particularly, to a solid with improved mobility of lithium ions, improved ionic conductivity, and excellent electrochemical stability. A composition for a polymer electrolyte, a solid polymer electrolyte formed therefrom, and a lithium secondary battery having improved output characteristics at low temperatures and excellent electrochemical stability and safety including the same are provided.

In order to increase the energy density of lithium ion batteries, various methods are being devised, and one of them is to use lithium metal for the negative electrode. However, a lithium ion battery using a lithium metal negative electrode has a problem in that the performance of the battery is significantly reduced due to a lithium dendrite phenomenon that occurs during charging/discharging. In addition, the conventional lithium ion battery has a problem of low stability of the battery by using a flammable liquid electrolyte. To improve this, research on the development of a solid-state battery using a solid electrolyte with high ionic conductivity and high electrochemical stability is being actively conducted.

In general, in an all-solid battery, a linear or crosslinked polymer of a homopolymer or copolymer based on ethylene oxide as an ion conductive polymer for forming a solid electrolyte is mainly used, but these polymers are crystallized There is a problem in that the output characteristics and electrochemical characteristics of the all-solid-state battery are deteriorated due to the low ionic conductivity at low temperature.

Accordingly, there is a demand for the development of a solid electrolyte having excellent ionic conductivity while improving output characteristics at low temperatures.

KR 10-2019-0096817 (2019.08.20.)

The present invention has been devised to solve the above problems, and the first object of the present invention is to improve lithium ion mobility, ion conductivity, and electrochemical stability of a composition for a solid polymer electrolyte and To provide a solid polymer electrolyte formed therefrom.

The second object of the present invention is to provide a lithium secondary battery having excellent electrochemical stability and safety while having excellent output characteristics at low temperatures by introducing the above-described solid polymer electrolyte.

In order to solve the above problems, the present invention provides a lithium salt; a first monomer which is an acrylate-based compound having a structure of Formula 1 below; and a second monomer that is a polyfunctional compound that is crosslinkable with the first monomer and includes at least two vinyl groups or acryloyl groups.

[Formula 1]

In a preferred embodiment of the present invention, the first monomer may be a compound represented by the following Chemical Formula 1-1.

[Formula 1-1]

In Formula 1-1,

R ¹ is hydrogen, C ₁ ~ C ₆ Alkyl group, C ₁ ~ C ₆ Haloalkyl group or C ₁ ~ C ₆ Heteroalkyl group,

R ^1` is absent, (CH ₂ CH ₂ O) _x , C ₁ ~ C ₁₀ Alkylene group, C ₁ ~ C ₅ Haloalkylene group, C ₁ ~ C ₁₀ Heteroalkylene group, C ₆ ~ C ₁₀ of an aromatic ring, a C ₅ ~ C ₁₀ aliphatic ring, or an amide group,

Said x is an integer of 1-10.

In a preferred embodiment of the present invention, the first monomer may be a compound represented by the following Chemical Formula 1-2.

[Formula 1-2]

In a preferred embodiment of the present invention, the second monomer may include at least one of compounds represented by the following Chemical Formulas 2-1 to 2-3.

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

In Formulas 2-1 to 2-3,

R ² are each independently hydrogen, a C ₁ ~ C ₆ alkyl group, a C ₁ ~ C ₆ haloalkyl group, or a C ₁ ~ C ₆ heteroalkyl group,

R ^2` are each independently a C ₁ ~ C ₆ alkylene group or a C ₁ ~ C ₆ haloalkylene group,

R ^2`` is each independently -(OCH ₂ CH ₂ ) _a1 -, -(OCH ₂ CH(CH ₃ )) _a2 - or -(OCH ₂ CH ₂ ) _a1 (OCH ₂ CH(CH ₃ )) _a2 - where a1 and a2 are integers from 1 to 10.

In a preferred embodiment of the present invention, the second monomer may be a compound represented by the following Chemical Formula 2-4.

[Formula 2-4]

In Formula 2-4, b is each independently an integer of 1 to 5.

In a preferred embodiment of the present invention, the second monomer may be a compound represented by the following Chemical Formula 2-5.

[Formula 2-5]

In Formula 2-5,

Wherein c is an integer of 1 to 5,

R ³ is each independently hydrogen, a C ₁ ~ C ₆ alkyl group, a C ₁ ~ C ₆ haloalkyl group, or a C ₁ ~ C ₆ heteroalkyl group.

In a preferred embodiment of the present invention, the lithium salt ^{contains Li +} as a ^{cation, F -} , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , ClO ₄ ^- , BF ₄ ^- , AlO ₄ ^- , AlCl ₄ ^- , PF ₆ ^- , SbF ₆ ^- , AsF ₆ ^- , BF ₂ C ₂ O ₄ ^- , BC 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 ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- It may include one or more selected from the group consisting of.

In a preferred embodiment of the present invention, the solid electrolyte composition may include the first monomer and the second monomer among the monomers in a weight ratio of 20:80 to 80:20.

In a preferred embodiment of the present invention, in the solid polymer electrolyte composition, the sum of the contents of the first monomer and the second monomer may be 5 to 50% by weight based on the total composition.

In a preferred embodiment of the present invention, the content of lithium salt in the solid polymer electrolyte composition may be 10 to 40% by weight based on the total composition.

In a preferred embodiment of the present invention, the solid polymer electrolyte composition may further include a plasticizer and a photoinitiator.

In a preferred embodiment of the present invention, the plasticizer is succinonitrile, glutaronitrile, polyethylene glycol dimethylether, tetraethylene glycol, ethylene carbonate ), propylene carbonate, tetraethylene glycol dimethylether (tetraglyme), dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctylphthalate (dioctyl phthalate), cyclic phosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide], 1 -Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide], N-methyl-N-propylpiperidinium bis(trifluoromethane Sulfonyl) imide [N-methyl-N-propylpiperidinium bis (trifluoromethanesulfonyl) imide], 1-ethyl-3-methylimidazolium trifluoromethane sulfonate (1-ethyl-3-methylimidazolium trifluoromethanesulfonate), N-butyl It may be at least one selected from -N-ethylpyrrolidinium bis(trifluoromethanesulfonyl)imide [N-butyl-Nethylpyrrolidinium bis(trifluoromethanesulfonyl)imide].

The present invention also includes a random copolymer formed by curing the solid polymer electrolyte composition to solve the above problems, and having a three-dimensional network structure in which the first monomer and the second monomer are copolymerized and crosslinked in a random order A solid polymer electrolyte is provided.

In addition, the present invention provides a positive electrode in order to solve the above problems; cathode; and a lithium secondary battery including the solid polymer electrolyte.

The solid polymer electrolyte according to the present invention suppresses crystallization to improve lithium ion mobility, improves ion conductivity, and has excellent electrochemical stability, thereby contributing to the improvement of stability and output of a lithium secondary battery.

The lithium secondary battery according to the present invention has excellent electrochemical stability and safety while having excellent output characteristics at low temperatures, and thus has characteristics suitable for use in electric vehicles and the like.

1 is a graph showing a Nyquist plot by measuring the impedance of a coin cell for measuring ionic conductivity prepared according to Example 1. FIG.
2 is a graph showing the results of electrochemical measurement up to 6V at a scan rate of 5mV according to the linear scanning voltammetry (LSV) of the coin cell for measuring ionic conductivity prepared according to Example 1. FIG.

Before a more detailed description of the present invention, the meaning of the terms used herein is defined.

As used herein, "polyfunctional" refers to a characteristic of two or more functional groups participating in a reaction, and "polyfunctional monomer" refers to two or more functional groups that can participate in a polymerization reaction, a branched polymer or a cross-linked polymer. It means a monomer capable of forming.

In the present specification, unless otherwise specified, the term "substituted or unsubstituted" of a substituent includes both substituted and unsubstituted cases, and in the case of substituted, the substituent is alkyl, acyl ( acyl), cycloalkyl (including dicycloalkyl and tricycloalkyl), haloalkyl, aryl, heteroaryl, heteroalicyclic, hydroxy , alkoxy, azide, amine, ketone, ether, amide, ester, triazole, isocyanate, arylalkyl Oxy (arylalkyloxy), aryloxy (aryloxy), mercapto (mercapto), alkylthio (alkylthio), arylthio (arylthio), cyano (cyano), halogen (halogen), carbonyl (carbonyl), thiocarbonyl ( thiocarbonyl), O-carbamyl (Ocarbamyl), N-carbamyl (N-carbamyl), O-thiocarbamyl (O-thiocarbamyl), N-thiocarbamyl (N-thiocarbamyl), C- amido (C- amido), N-amido (N-amido), S-sulfonamido (Ssulfonamido), N-sulfonamido (N-sulfonamido), C-carboxy (C-carboxy), O-carboxy (O-carboxy) , isocyanate, thiocyanate, isothiocyanate, nitro, silyl, trihalomethane sulfonyl, pyrrolidinone, pyrrolidine, piperidine, piperazine, morpholine, aldehyde, phosphorus, sulfur, phosphate phosphate, phosphite, sulfate, disulfide, oxy; and hydrocarbylmono- and di- (hydrocarbyldi-) substituted with one or more substituents individually and independently selected from amino groups, including substituted amino groups, and derivatives thereof; It is meant to comprehensively include cases substituted by various substituents commonly used in the art without being limited thereto.

의 구조를 가지는 것을 의미한다. 상기 R은 수소 또는 C1~C6의 알킬기를 나타낸다.In the present specification, "acryloyl group" includes a substituted or unsubstituted acryloyl group, preferably

It means to have a structure of R represents hydrogen or a C1-C6 alkyl group.

As used herein, "alkyl group" means an aliphatic hydrocarbon group having one bond arm. The alkyl group includes a substituted or unsubstituted alkyl group, and preferably represents at least one selected from the group consisting of methyl, ethyl, propyl, n-butyl, n-pentyl and n-hexyl groups.

As used herein, "alkylene group" refers to a substituted or unsubstituted alkylene group. The alkyl group preferably represents at least one selected from methylene, ethylene, propylene, butylene, pentylene and hexylene groups.

As used herein, the term “heteroalkyl group” means that at least one carbon of the alkyl group is substituted with a heteroatom.

As used herein, the term "heteroalkylene group" means that at least one carbon of the alkylene group is substituted with a heteroatom.

As used herein, "heteroatom" refers to atoms other than carbon and hydrogen.

As used herein, "aromatic ring" refers to a ring having a shared pi (π) electron system, and includes carbocyclic aryl and heterocyclic aryl. The term also includes monocyclic or fused ring polycyclic groups. Examples of carbocyclic aryl include a phenyl group, and examples of heterocyclic aryl include pyridine, furan, indole, and purine.

As used herein, the term "aliphatic ring" excludes aromatic compounds from among cyclic carbocyclic compounds, and includes substituted or unsubstituted cyclic compounds. In addition, the aliphatic ring includes a saturated aliphatic ring and an unsaturated aliphatic ring.

In the present specification, "haloalkyl group" specifically means that one or more hydrogens are substituted with halogen (F, Cl, Br, I) atoms in the alkyl group.

In addition, in this specification, the "haloalkylene group" specifically means that one or more hydrogens are substituted with a halogen atom in the alkylene group.

In addition, in the present specification, "amide group" refers to a -C(O)NH- bond, and the hydrogen bonded to nitrogen in the amide bond may be substituted or unsubstituted.

In addition, in the present specification, "there is no substituent" means a form in which both atoms are directly bonded without a corresponding substituent. For example, in a molecule of the form CH3-A-CH3, if there is no substituent A, the molecular formula is CH3-CH3.

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

(1) Solid polymer electrolyte composition

The present inventors have spurred research to solve the problem that the output of the secondary battery deteriorates, such as crystallization occurs and the ionic conductivity at a low temperature is significantly reduced in the conventional solid electrolyte for an all-solid-state battery, and reached the present invention.

The present invention provides a first monomer which is an acrylate-based compound having a structure of the following Chemical Formula 1 in order to solve the above problems; and

It provides a solid polymer electrolyte composition comprising a; It is possible to realize a solid polymer electrolyte with improved lithium ion mobility and ion conductivity by suppressing the

[Formula 1]

Since the cyclic carbonate structure as shown in Formula 1 has high nucleophilicity and electrophilicity, it can easily dissociate and solvate the lithium salt. In addition, lithium ions coordinated by a plurality of cyclic carbonates in the solid electrolyte and solvated can freely diffuse lithium ions by a change in local dipole density.

In addition, the polymer matrix generated from the monomer including the structure may inhibit crystallization than conventional polyethylene oxide polymers by having a bulk cyclic carbonate as a pendant group.

Therefore, the solid polymer electrolyte formed from the composition as described above can have excellent lithium ion mobility and ion conductivity because crystallization at low temperature is significantly suppressed compared to the conventional polyethylene oxide-based polymer electrolyte, thereby improving the low-temperature output characteristics of lithium secondary batteries. There are advantages that can be significantly improved.

In addition, there is an advantage in that the manufacturing process can be simplified by adding the monomers in an unpolymerized state instead of adding the polymer or polymer previously polymerized.

Preferably, the composition may further include a plasticizer, a curing agent, an organic solvent and other additives.

1) first monomer

The first monomer may be an acrylate-based compound having a structure represented by Formula 1 below.

[Formula 1]

In addition, the first monomer may be a compound including a derivative having a structure represented by Formula 1 above.

The solid polymer electrolyte according to the present invention contains a polymer polymerized including the monomer having the structure, so that crystallization at low temperature is suppressed, and thus lithium ion mobility, ion conductivity and electrochemical stability at low temperature are excellent.

In a preferred embodiment of the present invention, the first monomer may be a compound represented by the following Chemical Formula 1-1.

[Formula 1-1]

In Formula 1-1,

R ¹ is hydrogen, C ₁ ~ C ₆ Alkyl group, C ₁ ~ C ₆ Haloalkyl group or C ₁ ~ C ₆ Heteroalkyl group,

R ^1` is absent, (CH ₂ CH ₂ O) _x , C ₁ ~ C ₁₀ Alkylene group, C ₁ ~ C ₅ Haloalkylene group, C ₁ ~ C ₁₀ Heteroalkylene group, C ₆ ~ C ₁₀ of an aromatic ring, a C ₅ ~ C ₁₀ of an aliphatic ring, or an amide group,

Said x is an integer of 1-10.

The first monomer may preferably be a compound represented by the following Chemical Formula 1-2.

[Formula 1-2]

The first monomer may preferably be included in an amount of 1 to 40% by weight relative to the total composition. More preferably, it may be included in an amount of 3 to 20% by weight.

If the content of the first monomer is less than 1% by weight, the crosslinking density by the second monomer is high, so that the fluidity of the polymer chain is lowered, and the content of the cyclic carbonate that can implement high solvation of lithium salt is significantly reduced, so the ionic conductivity There may be a problem that decreases, and when it exceeds 40% by weight, the mechanical properties of the solid polymer electrolyte membrane formed by polymerization and crosslinking are deteriorated, so that the yield in the battery manufacturing process is reduced, and dendrites generated during charging/discharging are reduced. ), there may be a problem of poor stability for the phenomenon.

2) second monomer

In a preferred embodiment of the present invention, the second monomer, which is a polyfunctional compound that is crosslinkable with the first monomer and includes at least two vinyl groups or acryloyl groups, is represented by the following Chemical Formulas 2-1 to 2 It may include at least one of the compounds represented by -3.

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

In Formulas 2-1 to 2-3,

R ² are each independently hydrogen, a C ₁ ~ C ₆ alkyl group, a C ₁ ~ C ₆ haloalkyl group, or a C ₁ ~ C ₆ heteroalkyl group,

R ^2` are each independently a C ₁ ~ C ₆ alkylene group or a C ₁ ~ C ₆ haloalkylene group,

R ^2`` is each independently -(OCH ₂ CH ₂ ) _a1 -, -(OCH ₂ CH(CH ₃ )) _a2 - or -(OCH ₂ CH ₂ ) _a1 (OCH ₂ CH(CH ₃ )) _a2 - where a1 and a2 are integers from 1 to 10. a1 and a2 may be the same as or different from each other.

The R ^{2``</sup> may be in a direction in which an oxygen atom bonded to the outside <sup>of R 2``} among oxygen (O) in the substituent is ^{bonded to R 2`.}

Preferably, the second monomer may be a compound represented by the following Chemical Formula 2-4.

[Formula 2-4]

In Formula 2-4, b is each independently an integer of 1 to 5.

The second monomer may be more preferably a compound represented by the following Chemical Formula 2-4-1.

[Formula 2-4-1]

In a preferred embodiment of the present invention, the second monomer may be a compound represented by the following Chemical Formula 2-5.

[Formula 2-5]

In Formula 2-5,

Wherein c is an integer of 1 to 5,

R ³ is each independently hydrogen, a C ₁ ~ C ₆ alkyl group, a C ₁ ~ C ₆ haloalkyl group, or a C ₁ ~ C ₆ heteroalkyl group.

The second monomer can be polymerized in two or more directions by including two or more vinyl groups or acryloyl groups, and thus can form a branched, cross-linked, or network-type polymer rather than a linear polymer. The solid polymer electrolyte containing it has the advantage of having excellent mechanical properties.

The second monomer may preferably be a polyfunctional acrylate-based monomer including two or more acryloyl groups.

As described above, the acryloyl group may be each independently substituted or unsubstituted, for example, a methacryloyl group.

The second monomer may preferably be included in an amount of 1 to 40% by weight relative to the total composition. More preferably, it may be included in an amount of 3 to 20% by weight.

If the content of the second monomer is less than 1% by weight, there may be a problem in that the membrane of the solid polymer electrolyte is deteriorated, and if it exceeds 40% by weight, the polymer chain of the solid polymer electrolyte has reduced fluidity at low temperature. There may be a problem of a drop in ionic conductivity.

The solid electrolyte composition according to the present invention may include the first monomer and the second monomer among the monomers in a weight ratio of 20:80 to 80:20.

If the molar ratio between the monomers is greater than the weight ratio of the first monomer of 80:20, the mechanical properties of the membrane of the solid polymer electrolyte decrease, resulting in a decrease in the yield in the lithium ion battery manufacturing process, and dendrites that may occur during charging and discharging of the battery If the weight ratio of the second monomer is greater than 20:80, the content of the polyfunctional second monomer increases, resulting in an increase in the curing density after the solid polymer electrolyte composition is cured, resulting in a low polymer chain. There may be a problem in that the fluidity is lowered and the ionic conductivity is lowered.

In addition, by combining all of the first and second monomers, the monomers may be included in an amount of 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 12 to 30% by weight, based on the total weight of the solid polymer electrolyte composition. .

If the total content of the monomer is less than 5% by weight relative to the total composition, the content of the polymer constituting the polymer matrix is relatively decreased even after curing, so there may be a problem that the solid polymer electrolyte membrane is not properly formed, and 50% by weight When it exceeds, there may be a problem in that the ionic conductivity of the electrolyte decreases due to the relatively low content of lithium salts and plasticizers.

In addition, by combining all of the first and second monomers, the monomers may be included in an amount of 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 12 to 30% by weight, based on the total weight of the solid polymer electrolyte composition. .

If the total content of the monomer is less than 5% by weight relative to the total composition, the content of the polymer constituting the polymer matrix is relatively decreased even after curing, so there may be a problem that the solid polymer electrolyte membrane is not properly formed, and 50% by weight When it exceeds, there may be a problem in that the ionic conductivity of the electrolyte decreases due to the relatively low content of lithium salts and plasticizers.

3) lithium salt

The lithium salt is used as an electrolyte salt in a lithium secondary battery, and is used as a medium for transferring ions. Typically, lithium salts contain lithium cations (Li ⁺ ), F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , ClO ₄ ^- , BF ₄ ^- , AlO ₄ ^- , AlCl ₄ ^- , PF ₆ ^- , SbF ₆ ^- , AsF ₆ ^- , BF ₂ C ₂ O ₄ ^- , BC 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 ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- at least one anion selected from the group consisting of may include.

The lithium salt may be appropriately changed within a range that can be used in general, but may be included in an amount of 10 to 40 wt % in the solid polymer electrolyte composition in order to obtain an optimal effect of forming a film for preventing corrosion on the electrode surface.

Ion transfer properties of the solid polymer electrolyte composition of the present invention by incorporating a lithium salt in an amount within the above range, a polymer electrolyte composition, the lithium cationic high lithium cation (Li ⁺⁾ due to the increase of existing in the (i. E., Cation transport rate ( transference number)), and by achieving the effect of reducing the diffusion resistance of lithium ions, the effect of improving cycle capacity characteristics can be realized. At this time, when the content of the lithium salt is less than 10% by weight, it is difficult to secure sufficient ionic conductivity of the lithium ions due to the relatively low content of lithium ions. In addition, if the concentration of the lithium salt exceeds 40% by weight, the lithium salt is not solvated in the polymer matrix and a large amount of lithium salt forming an ion-pair exists in the polymer matrix, so there is no significant increase in effectiveness and economically Since it is disadvantageous, it is preferable to appropriately adjust it for the purpose within the above content range.

4) plasticizer

The solid polymer electrolyte composition according to the present invention may further include a plasticizer.

The plasticizer lowers the crystallinity between the polymer chains forming the solid polymer electrolyte, thereby facilitating the transfer of lithium ions at low temperature, improving the processability of the solid polymer electrolyte, and making it easy to control the mechanical strength.

The plasticizer is preferably succinonitrile, glutaronitrile, polyethylene glycol dimethylether, tetraethylene glycol, ethylene carbonate, propylene carbonate ), tetraethylene glycol dimethylether (tetraglyme), dimethyl phthalate (dimethyl phthalate), diethyl phthalate (diethyl phthalate), dibutyl phthalate (dibutyl phthalate), dioctyl phthalate (dioctyl phthalate), cyclic Phosphate (cyclic phosphate), 1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide [1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide], 1-butyl-3-methyl Midazolium bis(trifluoromethanesulfonyl)imide [1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide], N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide [N -methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide], 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1-ethyl-3-methylimidazolium trifluoromethanesulfonate), N-butyl-N-ethylpyrrolidinium It may include one or more selected from bis(trifluoromethanesulfonyl)imide [N-butyl-Methylpyrrolidinium bis(trifluoromethanesulfonyl)imide], but is not necessarily limited thereto.

The content of the plasticizer may be 10 to 80 wt% in the total solid polymer electrolyte composition. If the content of the plasticizer is less than 10% by weight, there may be a problem in that the crystallinity at low temperature of the solid polymer electrolyte is increased and the ionic conductivity is lowered, and when it exceeds 80% by weight, the mechanical properties of the solid polymer electrolyte are lowered. There may be a problem.

The content of the plasticizer may be preferably 30 to 80% by weight, more preferably 40 to 70% by weight.

5) Initiator

In addition, the solid polymer electrolyte composition according to the present invention can form a solid polymer electrolyte by a crosslinking reaction of monomers. As polymerization reaction and crosslinking reaction occur, the solid polymer electrolyte composition is cured to form a solid polymer electrolyte. The solid polymer electrolyte composition may further include an initiator for triggering such a crosslinking reaction. The initiator may preferably be a photoinitiator, and the crosslinking reaction may occur by irradiation of ultraviolet rays.

Examples of the photoinitiator include 1-phenyl-2-hydroxy-2-methyl propane-1-one (HMPP), phenylbis (2,4 ,6-trimethylbenzoyl)phosphine oxide, chloroacetophenone, diethoxy acetophenone, hydroxy acetophenone, 1-hydroxychlorohexyl phenyl ketone , α-aminoacetophenone (α-Aminoacetophenone), benzoin ether (Benzoin Ether), benzyl dimethyl ketal (Benzyl Dimethyl Ketal), benzophenone (Benzophenone), and oxanthone (Thioxanthone), etc., necessarily limited to these It is not, and these can be used individually by 1 type or in mixture of 2 or more types.

In addition, the initiator may be included in an amount of 0.001 to 10 parts by weight, specifically 0.03 to 3 parts by weight, based on 100 parts by weight of the total monomer.

When the initiator is included in an amount within the range of 0.001 to 10 parts by weight, it is possible to increase the curing conversion rate to form a stable solid polymer electrolyte membrane, and to prevent a pre-gel reaction, resulting in the aging of the solid electrolyte composition change can be minimized.

The solid polymer electrolyte composition according to the present invention may form a solid polymer electrolyte by cross-linking between the monomers. Preferably, the solid polymer electrolyte composition containing the monomers, a plasticizer, a lithium salt and an initiator is irradiated with UV light to undergo photopolymerization and crosslinking reaction.

After the step of forming the polymer crosslinked structure by UV irradiation as described above in order to prepare a solid electrolyte, the step of drying the obtained material may be further included.

The drying step may be performed for several hours under hot air or vacuum drying conditions.

6) organic solvents

In a preferred embodiment of the present invention, the solid polymer electrolyte composition may further include an organic solvent in order to adjust the viscosity or to improve solubility between the monomers used. Organic solvents that can be used include tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylformamide (DMF), acetonitrile, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide ( DMSO), dimethylacetamide (DMAc), dichloromethane, acetone, isopropyl alcohol, methyl ethyl ketone (MEK), etc., but are not necessarily limited thereto, and at least one of them can be selected to use.

(2) solid polymer electrolyte

The present invention also provides a solid polymer electrolyte comprising a random copolymer in which the solid polymer electrolyte composition is cured by a crosslinking reaction, and wherein the monomers are copolymerized in a random order.

The curing method is not particularly limited, and as described above, the composition may be cured by polymerizing and crosslinking the monomers in the composition through a method commonly known in the art.

Specifically, the solid polymer electrolyte can be prepared by coating the solid polymer electrolyte composition on the surface of a film or electrode, and curing the solid polymer electrolyte composition by polymerization and crosslinking by UV irradiation.

The coating method may use a known coating method such as slot die, gravure coating, spin coating, spray coating, roll coating, casting, screen printing or inkjet printing.

The solid polymer electrolyte according to the present invention prepared by this method may have a form in which lithium salt and plasticizer are evenly dispersed in a polymer matrix having a three-dimensional network structure formed by cross-linking reaction of monomers included in the composition. . Therefore, the solid polymer electrolyte of the present invention can exhibit high ionic conductivity at low temperatures.

The polymer matrix may be one in which the first monomer and the second monomer are polymerized and crosslinked in a random order to form a three-dimensional network structure. This structure can lower crystallinity by inhibiting the interaction between polymer chains in the solid polymer electrolyte and improve ionic conductivity at low temperatures, compared to a conventional polymer matrix having a block copolymer form.

(3) lithium secondary battery

In addition, the present invention is a positive electrode; cathode; And it provides a lithium secondary battery comprising the solid polymer electrolyte according to the present invention.

The lithium secondary battery may be manufactured according to a conventional method known in the art. For example, it may be prepared by coating the solid polymer electrolyte composition on a positive electrode, curing the composition, and stacking the negative electrode.

1) Anode

The positive electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , nickel, titanium, silver, etc. may be used.

The positive active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium composite metal oxide including lithium and one or more metals such as cobalt, manganese, nickel or aluminum. have. More specifically, the lithium composite metal oxide is a lithium-manganese-based oxide (eg, LiMnO ₂ , LiMn ₂ O _{4 ,} etc.), a lithium-cobalt-based oxide (eg, LiCoO ₂ etc.), lithium-nickel-based oxide (eg, LiNiO _{2 ,} etc.), lithium-nickel-manganese oxide (eg, LiNi _1-Y Mn _Y O ₂ (here, 0<Y<1), LiMn _2-z Ni _z O ₄ ( Here, 0<Z<2, etc.), lithium-nickel-cobalt-based oxides (eg, LiNi _1-Y1 Co _Y1 O ₂ (here, 0<Y1<1), etc.), lithium-manganese-cobalt based oxides (eg, LiCo _1-Y2 Mn _Y2 O ₂ (here, 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (here, 0<Z1<2), etc.), lithium-nickel -Manganese-cobalt oxide (for example, Li(Ni _p Co _q Mn _r1 )O ₂ (here, 0<p<1, 0<q<1, 0<r1<1, p+q+r1= 1) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium- Nickel-cobalt-transition metal (M) oxide (eg, Li(Ni _p2 Co _q2 Mn _r3 MS ₂ )O ₂ , where M is Al, Fe, V, Cr, Ti, Ta, Mg and Mo selected from the group consisting of, p2, q2, r3 and s2 are each independent atomic fractions of elements, 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, p2 + q2 +r3+s2=1)) and the like, and any one or two or more compounds may be included.

_{Among them, the lithium composite metal oxide is LiCoO 2} , LiMnO ₂ , LiNiO ₂ , lithium nickel manganese cobalt oxide (for example, Li (Ni _1/3 Mn _1/3 Co _{1 ) in} terms of improving the capacity characteristics and stability of the battery. _/3 )O ₂ , Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 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 ,} etc.), or lithium nickel cobalt aluminum oxide (eg, Li(Ni _0.8 Co _0.15 Al _0.05 )O _{2 ,} etc.).

The positive active material may be included in an amount of 80% to 99% by weight based on the total weight of the solid content in the positive electrode slurry.

The binder is a component that assists in bonding between the active material and the conductive material and bonding to 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 positive electrode slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro roethylene, polyethylene, polypropylene, ethylene-propylene-diene ter monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, various copolymers, and the like.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the positive electrode slurry.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or carbon powder such as thermal black; Graphite powder, such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, 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 solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount having a desirable viscosity when the positive active material and optionally a binder and a conductive material are included. For example, it may be included so that the solid content concentration in the slurry including the positive electrode active material, and optionally the binder and the conductive material is 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

2) cathode

In addition, the negative electrode may be manufactured by forming a negative electrode mixture layer on the negative electrode current collector. The negative electrode mixture layer may be formed by coating a negative electrode slurry including a negative electrode active material, a binder, a conductive material and a solvent on a negative electrode current collector, drying and rolling.

The negative electrode current collector generally has a thickness of 3 to 500 μm. Such a negative current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel. A surface treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. may be used on the surface. In addition, like the positive electrode current collector, the bonding strength of the negative electrode active material may be strengthened by forming fine irregularities on the surface, and may be used in various forms such as a film, sheet, foil, net, porous body, foam, non-woven body, and the like.

In addition, the negative active material is 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, and lithium doping and de-doping. It may include at least one selected from the group consisting of materials, and transition metal oxides.

As a carbon material capable of reversibly intercalating/deintercalating lithium ions, any carbon-based negative active material generally used in lithium ion secondary batteries may be used without particular limitation, and representative examples thereof include crystalline carbon, Amorphous carbon or these may be used together. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake, 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, and calcined coke.

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, elements of Groups 1, 2, and 3 of the periodic table, halogen; 0<x≤1;1≤y≤3; 1≤z≤8) One selected from the group may be used.

Examples of the material capable of doping and dedoping lithium include Si, SiO _x (0<x≤2), Si-Y alloy (wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, An element selected from the group consisting of rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn-Y (wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth) It is an element selected from the group consisting of elements and combinations thereof, and is not Sn), and at least one of these and SiO ₂ may be mixed and used. The element Y includes Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, 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, It may be selected from the group consisting of 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 the solids in the negative electrode slurry.

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 slurry. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoro and roethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 1 to 20 wt % based on the total weight of the solid content in the negative electrode slurry. The conductive material may be the same as or different from the conductive material used in manufacturing the anode, for example, carbon black, acetylene black (or Denka black), Ketjen black, channel black, furnace black, lamp black, or thermal black. carbon powder, such as; Graphite powder, such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, 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 solvent may include water or an organic solvent such as NMP, alcohol, and the like, and may be used in an amount to have a desirable viscosity when the negative electrode active material and, optionally, a binder and a conductive material are included. For example, it may be included so that the solid content concentration in the slurry including the negative active material, and optionally the binder and the conductive material is 50 wt% to 95 wt%, preferably 70 wt% to 90 wt%.

The lithium secondary battery including the positive electrode and the solid polymer electrolyte according to the present invention as described above suppresses crystallization of the electrolyte at low temperature while maintaining the electrochemical stability of the solid polymer electrolyte, so that the output of the battery is not significantly reduced even at low temperatures. There is an advantage of maintaining excellent lithium ion mobility and excellent ion conductivity.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, it does not mean that the scope of the present invention is limited to the scope of the embodiment, the embodiment is only for helping understanding as a specific application example of the present invention, those of ordinary skill in the art will It will be understood that the same technical idea may be implemented by changing, deleting, or adding a configuration in the .

<Synthesis example>

Synthesis Example 1: Synthesis of (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate (ODMA)

10 g of 4-(hydroxymethyl)-1,3-dioxolan-2-one was dissolved in 100 mL of dichloromethane. Then, 1.1 equivalents of triethylamine and methacryloyl chloride were added dropwise at 0° C. and stirred at room temperature for 24 hours to obtain (2-oxo-1,3-dioxolan-4-yl)methyl methacrylate (ODMA). Chemical formula is as follows.

[Formula of ODMA]

Synthesis Example 2: Synthesis of 4-(2-oxo-1,3-dioxolan-4-yl)butyl 2-methylprop-2-enoate

In a 250 mL round-bottom flask, 10 g of 4-(oxiran-2-yl)butan-1-ol and 100 mL of DMF were added and dissolved, and then 0.05 g of tetraethylammonium hydroxide was added and dissolved. Thereafter, while maintaining the temperature at 70° C., stirring was performed for 5 hours while adding _{CO 2 gas.} After completion of the reaction, 1.1 equivalents of triethylamine and methacryloyl chloride were added dropwise at 0° C., stirred at room temperature for 24 hours, and 4-(2-oxo-1,3-dioxolan-4-yl)butyl-2-methylprop- 2-enoate (ODBMPE) was obtained. Its chemical formula is as follows.

[Formula of ODBC]

Synthesis Example 3: Synthesis of [(2-oxo-1,3-dioxolan-4-yl)formamido]methyl 2-methylprop-2-enoate

After dissolving 10 g of 2-isocyanatoethyl methacrylate in 100 mL of THF in a 250 mL round-bottom flask, 1 mol% of dibutyl tin dilaurate was added, the temperature was increased to 70 ° C, and stirring was continued, 2-oxo-1,3-dioxolane-4 -carboxylic acid is added while slowly dropping 6.74 g, and after completion of the addition, the reaction is terminated by continuously stirring for 4 hours. Through this, [(2-oxo-1,3-dioxolan-4-yl)formamido]methyl 2-methylprop-2-enoate (ODAME) was obtained.

[Formula of ODAME]

Synthesis Example 4: Synthesis of 2-[(2-oxo-1,3-dioxolan-4-yl)methoxy]ethyl 2-methylprop-2-enoate

After dissolving 10 g of 2-hydroxyethyl methacrylate in 100 mL of THF in a 250 mL round bottom flask, 5 g of 15% NaOH was added and stirred. Thereafter, stirring was continued by increasing the temperature to 70° C., and 1.0 equivalent of 4-chloromethyl-1,3-dioxolan-2-one was dissolved in 30 mL of THF and the reaction was carried out dropwise. After stirring for 1 hour, the temperature is lowered to room temperature and the reaction is terminated while neutralizing with HCl. Through this, 2-[(2-oxo-1,3-dioxolan-4-yl)methoxy]ethyl-2-methylprop-2-enoate (ODMEME) was obtained. Its chemical formula is as follows.

[Chemical formula of ODMEME]

Synthesis Example 5: Synthesis of 2-[4-(2-oxo-1,3-dioxolan-4-yl)butyoxyl]ethyl 2-methylprop-2-enoate

After dissolving 10 g of 2-(4-chlorobutyl)oxirane in 100 mL of THF in a 250 mL round flask, 0.05 g of tetraethylammonium hydroxide was added, and while maintaining the temperature at 70° C., CO ₂ gas was introduced while stirring was performed for 5 hours. Through this, 4-(4-chlorobutyl)-1,3-dioxolan-2-one was prepared. After that, prepare another 250mL round-bottom flask, dissolve 2-hydroxyethyl methacrylate in the same amount as 2-(4-chlrorobutyl)oxirane, add 5g of 15% NaOH, and stir. Thereafter, stirring was continued by increasing the temperature to 70° C., and the reaction was carried out while dropping the previously prepared 4-(4-chlorobutyl)-1,3-dioxolan-2-one in the same equivalent amount. After stirring for 1 hour, the temperature is lowered to room temperature and the reaction is terminated while neutralizing with HCl. Through this, 2-[4-(2-oxo-1,3-dioxolan-4-yl)butyoxyl]ethyl-2-methylprop-2-enoate (ODBEPE) was obtained.

[Formula of ODBC]

Synthesis Example 6: Synthesis of (2-oxo-1,3-dioxolan-4-yl)methyl 2-methylidenebutanoate

Dissolve 10 g of 4-(hydroxymethyl)-1,3-dioxolan-2-one in 100 mL of dichloromethane. After that, 1.1 equivalents of triethylamine and 2-methylidenebutanoyl chloride were added dropwise at 0° C. and stirred at room temperature for 24 hours to obtain (2-oxo-1,3-dioxolan-4-yl)methyl-2-methylidenebutanoate (ODMI). did

[Formula of ODMI]

Synthesis Example 7: Synthesis of (2-oxo-1,3-dioxolan-4-yl)methyl 2-(trifluoromethyl)prop-2-enoate

Dissolve 10 g of 4-(hydroxymethyl)-1,3-dioxolan-2-one in 100 mL of dichloromethane. After that, 1.1 equivalents of triethylamine and 2-(trifluoromethyl)acryloyl chloride were added dropwise at 0°C and stirred at room temperature for 24 hours (2-oxo-1,3-dioxolan-4-yl)methyl-2-(trifluoromethyl)prop- 2-enoate (ODTFE) was obtained.

[Formula of ODTFE]

Synthesis Example 8: Synthesis of (2-oxo-1,3-dioxolan-4-yl)methyl 6-bromo-2-methylidenehexanoate

Dissolve 8 g of 4-(hydroxymethyl)-1,3-dioxolan-2-one in 100 mL of dichloromethane. After that, 1.1 equivalents of triethylamine and 4-bromobut-2-enyl chloride were added dropwise at 0° C. and stirred at room temperature for 24 hours (2-oxo-1,3-dioxolan-4-yl)methyl-6-bromo-2 -methylidenehexanoate (ODBMI) was obtained.

[Formula of ODBMI]

Synthesis Example 9: Synthesis of 2-oxo-1,3-dioxolan-4-yl 2-methoxyprop-2-enoate

8 g of 4-(hydroxymethyl)-1,3-dioxolan-2-one was dissolved in 100 mL of dichloromethane. After that, 1.1 equivalents of triethylamine and 2-(methoxymethyl)prop-2-enoyl chloride were added dropwise at 0°C, stirred at room temperature for 24 hours, and 2-oxo-1,3-dioxolan-4-yl 2-methoxyprop-2-enoate (ODMPE) was obtained.

[Chemical formula of ODMPE]

<Example>

Example 1: Preparation of Solid Electrolyte and Coin Cell

Using the compound prepared in Synthesis Example 1 as a first monomer, trimethylolpropane ethoxylate triacrylate as a second monomer, LiTFSI as a lithium salt, and succinonitrile as a plasticizer were added, but mixed in a weight ratio of 4: 11: 23: 62. A solid electrolyte composition was prepared by adding 0.05 parts by weight of irgacure 819 as a photoinitiator based on 100 parts by weight of the sum of the first and second monomers.

The prepared solid electrolyte composition was applied on a glass substrate and irradiated with UV of 365 nm wavelength for 5 minutes to prepare a 200 μm solid electrolyte membrane. This was peeled from the glass plate, and this was laminated between lithium metal to prepare a 2032 coin cell for ion conductivity test. In addition, the solid electrolyte membrane was laminated between lithium metal and stainless steel to prepare a coin cell for ESW (Electrochemical Stability Window) measurement.

Here, the chemical formula of the second monomer, trimethylolpropane ethoxylate triacrylate, is as follows.

[Formula of trimethylolpropane ethoxylate triacrylate]

Examples 2 to 5: Preparation of solid electrolyte and coin cell

A coin cell was prepared in the same manner as in Example 1, but the mixing weight ratio of the first monomer, the second monomer, lithium salt (LiTFSI), and the plasticizer (succinonitrile) was varied as shown in Table 1 A solid electrolyte composition prepared by The point in which a coin cell was manufactured was different. This was also manufactured by dividing it into a coin cell for ion conductivity measurement and a coin cell for ESW measurement.

Examples 6 to 10: Preparation of Solid Electrolyte and Coin Cell

The compound prepared in Synthesis Example 2 was used as a first monomer, poly(ethylene glycol) diacrylate (weight average molecular weight: 700 g/mol), LiPF ₆ as a lithium salt, and glutaronitrile as a plasticizer were added in the weight ratio as shown in Table 1, A solid electrolyte composition was prepared. A solid electrolyte membrane and a coin cell were manufactured using the prepared solid compositions in the same manner as in Example 1. Each coin cell was manufactured by dividing it into a coin cell for ion conductivity measurement and a coin cell for ESW measurement.

Examples 11 to 15: Preparation of Solid Electrolyte and Coin Cell

The compound prepared in Synthesis Example 3 was used as a first monomer, 3-(acryloyloxy)-2-hydroxypropyl methacrylate as a second monomer, LiTFSI and LIBOB were mixed as lithium salts, and succinonitrile was used as a plasticizer in Table 1, respectively. As shown, it was added by adjusting the weight ratio. As a photoinitiator, Irgacure 819 was introduced in the same amount as in Example 1 to prepare a solid electrolyte composition. A solid electrolyte membrane and a coin cell were manufactured using the prepared solid compositions in the same manner as in Example 1. As in Example 1, the coin cell was prepared by dividing it into a coin cell for measuring ionic conductivity and a coin cell for measuring ESW.

Examples 16-21: Preparation of Solid Electrolyte and Coin Cell

Example 16 is the compound synthesized in Synthesis Example 4, Example 17 is the compound synthesized in Synthesis Example 5, Example 18 is the compound synthesized in Synthesis Example 6, Example 19 is the compound synthesized in Synthesis Example 7, Example 20, the compound synthesized in Synthesis Example 8, and Example 21, the compound synthesized in Synthesis Example 9 was used as a first monomer, respectively. For these, trimethylolpropane ethoxylate triacrylate was used as the second monomer, LiTFSI was used as the lithium salt, and succinonitrile was used as the plasticizer, and the weight ratio of the first monomer, the second monomer, the lithium salt and the plasticizer was 4: 11: 23: 62. After mixing, irgacure 819 as a photoinitiator was added in an amount of 0.05 parts by weight based on the sum of the weights of the first and second monomers equal to 100, and polymerized to prepare a solid electrolyte composition. A solid electrolyte membrane was prepared from the prepared composition in the same manner as in Example 1, and a coin cell was manufactured using this. Coin cells were separately manufactured into coin cells for ion conductivity and ESW measurement, respectively.

Mixing ratio (wt%) ionic conductivity
(mS/cm) electrochemical
stability
(v) first monomer second monomer lithium salt plasticizer Example 1 ODMA/4 11 23 62 1.9 5.2 Example 2 ODMA / 11 4 23 62 2.3 5.0 Example 3 ODMA/5 15 30 50 1.5 4.9 Example 4 ODMA / 15 5 30 50 1.7 5.1 Example 5 ODMA / 19 6 20 55 1.2 4.8 Example 6 ODBMPE / 4 11 23 62 1.7 5.0 Example 7 ODBMPE / 11 4 23 62 1.8 5.1 Example 8 ODBMPE / 25 5 20 50 1.1 5.1 Example 9 ODBMPE / 15 5 20 60 1.3 5.0 Example 10 ODBMPE / 10 10 30 50 1.5 4.9 Example 11 ODAME / 5 5 30 60 1.1 4.9 Example 12 ODAME / 4 11 25 60 1.0 4.8 Example 13 ODAME / 11 4 25 60 1.7 5.0 Example 14 ODAME / 15 5 30 50 1.6 5.1 Example 15 ODAME / 20 10 30 40 1.4 5.0 Example 16 ODMEME / 4 11 23 62 1.5 5.1 Example 17 ODBEPE / 4 11 23 62 1.4 5.0 Example 18 ODMI / 4 11 23 62 1.3 5.2 Example 19 ODTFE / 4 11 23 62 1.1 5.1 Example 20 ODMBI / 4 11 23 62 1.0 4.9 Example 21 ODMPE/4 11 23 62 1.3 4.8

Comparative Example 1: Preparation of solid electrolyte and coin cell

Poly(ethylene glycol) diacrylate (PEDGA, weight average molecular weight: 700), a monomer having a bifunctional group, is used, LiTFSI is used as a lithium salt, and succinonitrile is used as a plasticizer, but a monomer: lithium salt (LiTFSI): a plasticizer (Succinonitrile) A solid electrolyte composition was prepared by mixing the mixture at a weight ratio of 30:20:50, adding 0.05 parts by weight of photoinitiator irgacure 819 to 100 parts by weight of the monomer, and polymerizing the monomer. A solid electrolyte membrane and a coin cell were manufactured using this solid electrolyte composition in the same manner as in Example 1. In manufacturing the coin cell, a coin cell for measuring ionic conductivity and a coin cell for measuring ESW were separately manufactured.

Comparative Example 2: Preparation of Solid Electrolyte and Coin Cell

Using the compound prepared in Synthesis Example 1 as a monomer, LiTFSI as a lithium salt and succinonitrile as a plasticizer were mixed, but a monomer: lithium salt (LiTFSI): a plasticizer (succinonitrile) was mixed in a weight ratio of 25: 13: 62, and a photoinitiator was added to prepare a solid electrolyte composition, a solid electrolyte membrane, and a coin cell in the same manner as in Example 1. In manufacturing the coin cell, coin cells for ion conductivity measurement and ESW measurement were separately prepared as in Example 1.

Comparative Example 3: Preparation of solid electrolyte and coin cell

Polyethylene oxide (weight average molecular weight: 10,000 g/mol) as an ion conductive polymer, LiTFSI as a lithium salt, and succinonitrile as a plasticizer are used, and the weight ratio is polyethylene oxide: lithium salt (LiTFSI): plasticizer (succinonitrile) 20: 30: 50 was mixed and dissolved in a THF solvent to prepare a solid electrolyte composition, which was then cast on a glass substrate. The cast solid electrolyte composition was evaporated under a temperature of 50° C. to prepare a solid electrolyte membrane.

A coin cell was prepared in the same manner as in Example 1, but the prepared solid electrolyte membrane was divided into coin cells for ion conductivity measurement and ESW measurement as in Example 1.

Comparative Example 4: Preparation of Solid Electrolyte and Coin Cell

Poly(ethylene glycol) diacrylate (PEGDA, weight average molecular weight: 700) as the polyethylene oxide of Comparative Example 3 as an ion conductive polymer and a bifunctional monomer, LiTFSI as a lithium salt, and succinonitrile as a plasticizer were used, and polyethylene oxide: bifunctional Monomer: lithium salt (LiTFSI): plasticizer (succinonitrile) was mixed in a weight ratio of 15: 5: 30: 50, dissolved in THF solvent, and photoinitiator irgacure 819 was additionally added in an amount of 0.05 parts by weight based on 100 parts by weight of the monomer to form a solid electrolyte composition prepared.

The solid electrolyte composition was prepared as a solid electrolyte membrane in the same manner as in Example 1, and a coin cell was prepared in the same manner as in Example 1 using this, but the coin cell for ion conductivity measurement and ESW measurement were separately prepared. .

Each of the materials used in Comparative Examples 1 to 4 and their content ratios are shown in Table 2 below.

Mixing ratio (wt%) ionic conductivity
(mS/cm) ESW
(v) Ion conductive material lithium salt plasticizer Kinds content Comparative Example 1 PEGDA 30 20 50 0.3 4.2 Comparative Example 2 ODMA 25 13 62 0.4 3.8 Comparative Example 3 polyethylene oxide 20 30 50 0.05 4.2 Comparative Example 4 polyethylene oxide 15 30 50 0.07 4.3 PEGDA 5

<Test Example>

Test Example 1: Ionic Conductivity Measurement

The ionic conductivity of the polymer solid electrolyte can be obtained by using Equation 1 below after measuring the impedance. For the measurement, coin cell samples prepared for ionic conductivity measurement in Examples 1 to 15 and Comparative Examples 1 to 4 were prepared.

After each coin cell sample was brought into contact with the substrate, an AC voltage was applied to the coin cell through both electrodes. At this time, the measurement frequency was set to a frequency range of 1.0 MHz to 0.1 Hz as the applied conditions, and the impedance was measured using a VMP3 manufactured by BioLogic. The resistance of the bulk electrolyte was obtained from the intersection point where the semicircle or straight line of the measured impedance trace meets the real side, and the ionic conductivity of the polymer solid electrolyte membrane was calculated from the area and thickness of the sample according to Equation 1 below.

[Equation 1]

σ: ionic conductivity (S/cm)

R: The intersection of the impedance trajectory and the real axis

A: the width of the solid electrolyte membrane

t: the thickness of the solid electrolyte membrane

Test Example 2: ESW (Electrochemical Stability Window) Measurement

Using the stainless steel electrode of the coin cell for ESW measurement prepared according to Examples and Comparative Examples as the measurement electrode, and lithium metal as the counter electrode, the linear scanning voltammetry (LSV) at a scan rate of 5 mV up to 6 V ) to measure ESW. The results are shown in Tables 1 and 2, respectively.

Referring to Tables 1 and 2, Comparative Example 1 including only a bifunctional acrylate-based monomer without a first monomer having a structure according to Formula 1, including only the first monomer and not including a bifunctional or higher monomer crosslinkable therewith Comparative Example 2, Comparative Example 3 containing only the polyethylene oxide polymer, and Comparative Example 4 including only the polyethylene oxide polymer and the diacrylate monomer crosslinkable therewith all had significantly low ionic conductivity of less than 1.0 mS/cm.

In contrast, the coin cells including the solid electrolyte of the embodiment including the first monomer having the structure according to Formula 1 and the solid electrolyte of the embodiment including the cross-linkable bifunctional or higher monomer all had an ionic conductivity of 1.0 mS/cm or more. It showed a higher numerical value than the comparative example.

Also in Test Example 2 regarding ESW, the ESW of a coin cell comprising a solid electrolyte formed by polymerization and crosslinking by including the monomer according to Example together with a cross-linkable bifunctional or higher monomer is a solid according to Comparative Example lacking at least one of them It was confirmed that it was superior to the coin cell containing the electrolyte.

Claims (14)

lithium salt;
a first monomer which is an acrylate-based compound having a structure of Formula 1 below; and a second monomer that is crosslinkable with the first monomer and is a polyfunctional compound including at least two vinyl groups or acryloyl groups;
[Formula 1]

According to claim 1,
The first monomer is a solid polymer electrolyte composition, characterized in that the compound represented by the following formula 1-1:
[Formula 1-1]

In Formula 1-1,
R ¹ is hydrogen, C ₁ ~ C ₆ Alkyl group, C ₁ ~ C ₆ Haloalkyl group or C ₁ ~ C ₆ heteroalkyl group, R ^{1 `} is absent, (CH ₂ CH ₂ O) _x , C ₁ ~ C ₁₀ Alkylene group, C ₁ ~ C ₅ Haloalkylene group, C ₁ ~ C ₁₀ Heteroalkylene group, C ₆ ~ C ₁₀ Aromatic ring, C ₅ ~ C ₁₀ Aliphatic ring, or one of the amide group is,
Said x is an integer of 1-10.
According to claim 1,
The first monomer is a solid polymer electrolyte composition, characterized in that the compound represented by the following formula 1-2:
[Formula 1-2]

According to claim 1,
The second monomer is a solid polymer electrolyte composition comprising at least one of the compounds represented by the following Chemical Formulas 2-1 to 2-3:
[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

In Formulas 2-1 to 2-3,
R ² are each independently hydrogen, a C ₁ ~ C ₆ alkyl group, a C ₁ ~ C ₆ haloalkyl group, or a C ₁ ~ C ₆ heteroalkyl group,
R ^2` are each independently a C ₁ ~ C ₆ alkylene group or a C ₁ ~ C ₆ haloalkylene group,
R ^2`` is each independently -(OCH ₂ CH ₂ ) _a1 -, -(OCH ₂ CH(CH ₃ )) _a2 - or -(OCH ₂ CH ₂ ) _a1 (OCH ₂ CH(CH ₃ )) _a2 - where a1 and a2 are integers from 1 to 10.
According to claim 1,
The second monomer is a solid polymer electrolyte composition, characterized in that the compound represented by the following formula 2-4:
[Formula 2-4]

In Formula 2-4, b is each independently an integer of 1 to 5.
According to claim 1,
The second monomer is a solid polymer electrolyte composition, characterized in that the compound represented by the following Chemical Formula 2-5:
[Formula 2-5]

In Formula 2-5,
Wherein c is an integer of 1 to 5,
R ³ is each independently hydrogen, a C ₁ ~ C ₆ alkyl group, a C ₁ ~ C ₆ haloalkyl group, or a C ₁ ~ C ₆ heteroalkyl group.
According to claim 1,
The lithium salt ^{contains Li +} as a ^{cation and F -} , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , ClO ₄ ^- , BF ₄ ^- , AlO ₄ ^- , AlCl as an anion. ₄ ^- , PF ₆ ^- , SbF ₆ ^- , AsF ₆ ^- , BF ₂ C ₂ O ₄ ^- , BC 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 ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- comprising at least one selected from the group consisting of A solid polymer electrolyte composition, characterized.
According to claim 1,
The solid polymer electrolyte composition comprises the first monomer and the second monomer among the monomers in a weight ratio of 20:80 to 80:20.
According to claim 1,
The solid polymer electrolyte composition of the solid polymer electrolyte composition, characterized in that the sum of the content of the first monomer and the second monomer is 5 to 50% by weight based on the total composition.
According to claim 1,
The solid polymer electrolyte composition, characterized in that the content of the lithium salt in the solid polymer electrolyte composition is 10 to 40% by weight relative to the total composition.
According to claim 1,
The solid polymer electrolyte composition further comprises a plasticizer and an initiator.
12. The method of claim 11,
The plasticizer is succinonitrile, glutaronitrile, polyethylene glycol dimethylether, tetraethylene glycol, ethylene carbonate, propylene carbonate, tetra Ethylene glycol dimethyl ether (tetraglyme), dimethyl phthalate (dimethyl phthalate), diethyl phthalate (diethyl phthalate), dibutyl phthalate (dibutyl phthalate), dioctyl phthalate (dioctyl phthalate), cyclic phosphate (cyclic) phosphate), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide], 1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl)imide [1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide], N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide [N-methyl- N-propylpiperidinium bis(trifluoromethanesulfonyl)imide], 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1-ethyl-3-methylimidazolium trifluoromethanesulfonate), N-butyl-N-ethylpyrrolidinium bis(tri A solid polymer electrolyte composition comprising at least one selected from fluoromethanesulfonyl)imide [N-butyl-Nethylpyrrolidinium bis(trifluoromethanesulfonyl)imide].
The solid polymer electrolyte composition according to any one of claims 1 to 12 is formed by curing, and the first monomer and the second monomer are copolymerized and crosslinked in a random order to obtain a random copolymer having a three-dimensional network structure. A solid polymer electrolyte comprising.
anode; cathode; And a lithium secondary battery comprising the solid polymer electrolyte according to claim 13.

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