KR20220125981A - Electrolyte for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to an electrolyte for a lithium secondary battery including a UV curable polymer matrix, a sulfide-based solid electrolyte and lithium salt, and a lithium secondary battery including the same. The electrolyte for a lithium secondary battery and the lithium secondary battery including the same according to the present invention can exhibit high ion conductivity characteristics like a conventional liquid electrolyte, and can solve the short problem that can occur between electrodes during a manufacturing process, thereby improving mechanical strength such as durability.

Description

Electrolyte for lithium secondary battery and lithium secondary battery including same

The present invention relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same.

As miniaturization and weight reduction of electronic equipment are realized and the use of portable electronic equipment is generalized, studies on secondary batteries having high energy density as their power sources are being actively conducted.

Examples of the secondary battery include a nickel-cadmium battery, a nickel-metal hydride battery, a nickel-metal hydride battery, a nickel-hydrogen battery, and a lithium secondary battery. In addition, research on lithium secondary batteries having high energy density per unit weight and capable of rapid charging is on the rise.

In general, a lithium secondary battery is manufactured by using a material capable of inserting and deintercalating lithium ions as a positive electrode and a negative electrode, charging a non-aqueous electrolyte between the positive electrode and a negative electrode, and oxidizing when lithium ions are inserted and desorbed from the positive electrode and negative electrode It generates electrical energy by reaction and reduction reaction.

On the other hand, since the liquid electrolyte is used, there is a risk of safety issues due to overheating and the like becoming a topic of discussion. In order to overcome the problems of lithium secondary batteries using liquid electrolytes, research and development of all-solid-state lithium secondary batteries using solid electrolytes are being actively conducted in recent years.

However, in the case of an all-solid lithium secondary battery using a solid electrolyte, the ionic conductivity of the solid electrolyte itself is generally low, and the positive electrode, (solid) electrolyte, and negative electrode constituting the battery are all in a solid phase, so that close contact and binding between the components are difficult. It is difficult, and each interface and the cell resistance of the battery are very large, so it is difficult to achieve high performance and high output of the battery.

Republic of Korea Patent Registration No. 10-1995829 and the like provide an invention for increasing ionic conductivity by adding a lithium-based solid electrolyte, but in the case of a lithium-based solid electrolyte, it is difficult to control the process conditions due to the volatilization of lithium in the sintering process, and the crystal There is a large difference in ionic conductivity depending on the structure, and the manufacturing process is complicated and difficult due to the difficulty of sintering.

Republic of Korea Patent Registration No. 10-1995829 (2019.07.03. Announcement)

An object of the present invention is to provide an electrolyte for a lithium secondary battery capable of increasing productivity by facilitating a battery manufacturing process by not using a separator, and a lithium secondary battery including the same.

Another object of the present invention is to provide an electrolyte for a lithium secondary battery having excellent ionic conductivity and durability, and a lithium secondary battery including the same.

The present invention provides an electrolyte for a lithium secondary battery comprising a UV-curable polymer matrix, a sulfide-based solid electrolyte, and a lithium salt.

In addition, the present invention provides a lithium secondary battery comprising the electrolyte for a lithium secondary battery.

The electrolyte for a lithium secondary battery according to the present invention and a lithium secondary battery including the same have an advantage in that the manufacturing process of the battery is easy and productivity can be increased by not using a separator.

In addition, the electrolyte for a lithium secondary battery according to the present invention and a lithium secondary battery including the same can exhibit high ionic conductivity like a conventional liquid electrolyte, and solve a short problem that may occur between electrodes during the manufacturing process. Therefore, mechanical strength such as durability can be improved.

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

In the present invention, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

<Electrolyte for lithium secondary battery>

The present invention provides an electrolyte for a lithium secondary battery comprising a UV-curable polymer matrix, a sulfide-based solid electrolyte, and a lithium salt.

(A) UV-curable polymer matrix

UV curable polymer matrix according to the present invention means a complex or mixture including a polymer structure that can be cured by light, preferably by UV, specifically (a1) radical generation by photopolymerizable compound and UV (a2) a photoinitiator is included.

When only a sulfide-based solid electrolyte is included as an electrolyte for a lithium secondary battery, since there is no binder capable of fixing the inorganic sulfide-based solid electrolyte, it is difficult to achieve uniform performance due to precipitation and layer separation of the sulfide-based solid electrolyte. can occur

In addition, conventional polymers such as PVDF, CMC, and SBR have been used as binders, but the polymers may rather hinder the movement of lithium ions, and may cause a problem of lowering the lithium ion concentration of the prepared coating film.

The UV-curable polymer matrix according to the present invention can be easily applied through viscosity control without a separate solvent removal process before curing, and the molecular weight is increased through polymerization after curing so that the polymer matrix binds the sulfide-based solid electrolyte It can perform the role of a binder. In addition, the UV-curable polymer matrix may contain lithium ions, so that the concentration of lithium ions in the coating film is increased compared to a conventional general polymer binder, so that the mobility of lithium ions can be increased, and it can serve as a polymer electrolyte. .

(a1) photopolymerizable compound

The photopolymerizable compound included in the UV curable polymer matrix of the present invention is a compound that can be polymerized by the action of the photopolymerization initiator below (a2), and a monofunctional monomer, a bifunctional monomer, or a trifunctional monomer or more may be used, preferably may include monofunctional or polyfunctional (meth)acrylate having an unsaturated group of 1 to 20 functional groups.

The monofunctional or polyfunctional (meth)acrylate having an unsaturated group of 1 to 20 functional groups has 1 to 20, preferably 2 to 6, more preferably 2 to 4, polymerizable functional groups that are polymerizable unsaturated groups. may include.

If it does not include an unsaturated group, it may be difficult to form a film and the cured film may be damaged, and if the number of functional groups is out of the above range, the cured film may become too hard to cause a problem in that the ionic conductivity is lowered.

In addition, the photopolymerizable compound included in the UV curable polymer matrix of the present invention is specifically preferably a photopolymerizable compound containing an alkylene oxide, more preferably a photopolymerizable compound containing ethylene oxide and/or propylene oxide can be heard When the photopolymerizable compound includes an alkylene oxide, lithium ions can be stabilized by the electrostatic attraction with oxygen of the alkylene oxide, thereby facilitating the movement of lithium ions in the polymer matrix to improve the ionic conductivity of lithium ions can play a role in making

Examples of the photopolymerizable compound containing the alkylene oxide include an alkylene oxide-modified pentaerythritol (meth)acrylate compound, an alkylene oxide-modified dipentaerythritol (meth)acrylate compound, and an alkylene oxide-modified tree. and methylolpropane (meth)acrylate compounds, and alkylene oxide-modified glycerin (meth)acrylate compounds. More specifically, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylol Propane tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, propoxylate Tied pentaerythritol tetra(meth)acrylate, ethoxylated dipentaerythritol penta(meth)acrylate, propoxylated dipentaerythritol penta(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylic a rate, propoxylated dipentaerythritol hexa(meth)acrylate, or ethoxylated glycerin tri(meth)acrylate, etc. are mentioned.

The photopolymerizable compound included in the UV curable polymer matrix of the present invention may further include a conventional photopolymerizable compound that does not include an alkylene oxide. Specifically, a photopolymerizable compound using monofunctional monomers, difunctional monomers, and other polyfunctional monomers that do not contain ethylene oxide and propylene oxide may be mentioned.

Specific examples of the monofunctional monomer include nonylphenyl carbitol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-ethylhexyl carbitol acrylate, 2-hydroxyethyl acrylate, or N-vinyl acrylate. Rollidone, and the like, but is not limited thereto.

Specific examples of the bifunctional monomer include 1,6-hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and triethylene glycol di (meth) acrylate. , bis (acryloyloxyethyl) ether of bisphenol A, or 3-methylpentanediol di (meth) acrylate, but is not limited thereto.

Specific examples of the polyfunctional monomer include trimethylol propane tri (meth) acrylate, ethoxylated trimethylol propane tri (meth) acrylate, propoxylated trimethylol propane tri (meth) acrylate, pentaerythritol tri (meth)acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, ethoxylated dipentaerythritol hexa (meth) acrylate, propoxylated dipentaerythritol hexa (meth) acrylate or dipentaerythritol hexa(meth)acrylate, but is not limited thereto.

The photopolymerizable compound included in the UV curable polymer matrix of the present invention may be included in an amount of 10 to 90 wt%, preferably 10 to 20 wt%, based on the total weight of the UV curable polymer matrix. When included in the above range, the occurrence of damage to the polymer due to polymer polymerization and crosslinking reaction of the polymer during UV curing is small, and lithium ions are included and thus lithium ions can be moved, which is preferable. However, when included in an amount exceeding 90% by weight, the polymerization reaction occurs, but lithium ion conductivity decreases as the concentration of lithium ions in the polymer decreases, thereby reducing the performance of the battery. In addition, when included in less than 10% by weight, the molecular weight does not become sufficiently large despite polymerization, it may be difficult to maintain the coating film itself and may be easily broken.

(a2) photoinitiator

The photopolymerization initiator included in the UV curable polymer matrix of the present invention is a compound that generates radicals capable of initiating polymerization of the photopolymerizable compound by UV exposure.

As the photopolymerization initiator, for example, an acetophenone-based compound, a benzophenone-based compound, a biimidazole-based compound, a triazine-based compound, an oxime ester-based compound, and a thioxanthone-based compound may be used.

Specific examples of the acetophenone-based compound include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 2-hydroxy-1-[4-(2-hydroxyl) oxyethoxy)phenyl]-2-methylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one; 2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propane-1 -one, 2-(4-methylbenzyl)-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, etc. are mentioned.

Specific examples of the benzophenone-based compound include benzophenone, methyl O-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenylsulfide, 3,3',4,4'-tetra (tert) -Butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, etc. are mentioned.

Specific examples of the biimidazole compound include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2,3-dichloro Phenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(alkoxyphenyl)biimidazole , 2,2'-bis (2-chlorophenyl) -4,4', 5,5'-tetra (trialkoxyphenyl) biimidazole, 2,2-bis (2,6-dichlorophenyl) -4, 4'5,5'-tetraphenyl-1,2'-biimidazole or the imidazole compound in which the phenyl group at the 4,4',5,5'-position is substituted by the carboalkoxy group, etc. are mentioned. Among them, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2,3-dichlorophenyl)-4,4' ,5,5'-tetraphenylbiimidazole and 2,2-bis(2,6-dichlorophenyl)-4,4'5,5'-tetraphenyl-1,2'-biimidazole are preferably used do.

Specific examples of the triazine-based compound include 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6 -(4-Methoxynaphthyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-piperonyl-1,3,5-triazine, 2,4-bis (trichloromethyl)-6-(4-methoxystyryl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(5-methylfuran-2- yl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(furan-2-yl)ethenyl]-1,3,5-triazine , 2,4-bis(trichloromethyl)-6-[2-(4-diethylamino-2-methylphenyl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl )-6-[2-(3,4-dimethoxyphenyl)ethenyl]-1,3,5-triazine etc. are mentioned.

Specific examples of the oxime ester compound include o-ethoxycarbonyl-α-oxyimino-1-phenylpropan-1-one, 1,2-octadione,-1-(4-phenylthio)phenyl, -2 -(o-benzoyloxime), ethanone,-1-(9-ethyl)-6-(2-methylbenzoyl-3-yl)-,1-(o-acetyloxime), etc. are mentioned, Commercially available products CGI-124, CGI-224, BASF, Irgacure OXE-01, Irgacure OXE-02, Irgacure OXE-03, Adeka Corporation N-1919, NCI-831, etc. are mentioned as examples.

Specific examples of the thioxanthone-based compound include 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and the like. have.

The photopolymerization initiator may be used alone or in combination of two or more.

The photopolymerization initiator may be included in an amount of 0.1 to 10% by weight, preferably 1 to 5% by weight, based on the total weight of the UV curable polymer matrix. When the content of the photopolymerization initiator is included in less than 0.1% by weight, photocuring does not proceed sufficiently, so it may be difficult to implement mechanical properties or adhesion of the polymer matrix layer, and when it exceeds 10% by weight, poor adhesion due to curing shrinkage , cracks, curls, etc. may occur.

Furthermore, the present invention may further include a photopolymerization initiation aid. By further including a photopolymerization initiation aid, sensitivity and productivity may be improved.

As the photopolymerization initiation adjuvant, for example, at least one compound selected from the group consisting of carboxylic acid and sulfonic acid compounds may be preferably used.

The carboxylic acid compound is preferably aromatic heteroacetic acid, specifically phenylthioacetic acid, methylphenylthioacetic acid, ethylphenylthioacetic acid, methylethylphenylthioacetic acid, dimethylphenylthioacetic acid, methoxyphenylthioacetic acid, dimethoxyphenylthio Acetic acid, chlorophenylthioacetic acid, dichlorophenylthioacetic acid, N-phenylglycine, phenoxyacetic acid, naphthylthioacetic acid, N-naphthylglycine, naphthoxyacetic acid, etc. are mentioned.

The sulfonic acid compound is a generic term for compounds having a sulfonic acid group (-SO3H), cyclic or chain hydrocarbon-based sulfonic acid compounds such as methanesulfonic acid, aromatic sulfonic acids such as benzenesulfonic acid and toluenesulfonic acid, inorganic sulfonic acid compounds such as aminosulfonic acid, It may include at least one selected from the group consisting of halosulfonic acid and sulfamic acid.

When the photopolymerization initiation aid is further included, it is usually 10 moles or less per 1 mole of the photopolymerization initiator, preferably in the range of 0.01 to 5 moles. When a photopolymerization initiation aid is used within the above range, the polymerization efficiency is increased, the sensitivity of the UV-curable polymer matrix is further increased, and an effect of improving productivity can be expected.

(B) sulfide-based solid electrolyte

The electrolyte for a lithium secondary battery of the present invention includes a sulfide-based solid electrolyte.

The sulfide-based solid electrolyte is an electrolyte having excellent movement of lithium ions due to the crystal structure in the particles. When used in a mixture with a UV-curable polymer matrix and lithium salt, it reinforces the physical properties of the UV-curable polymer matrix as an inorganic filler, and a sulfide-based solid electrolyte It is possible to enable the movement of lithium ions through the electrolyte.

The sulfide-based solid electrolyte according to the present invention may have a crystal structure, for example, an argyrodite-type crystal structure, and the azirodite-type crystal structure is recognized as an azirodite-type crystal structure by those skilled in the art. It is not particularly limited as long as it is, but silver represented by the chemical formula Ag ₈ GeS ₆ may mean having a crystal structure of a germanium sulfide mineral.

In addition, the sulfide-based solid electrolyte according to the present invention may be represented by the following Chemical Formula 1

[Formula 1]

Li ₆ PS _5-a X _a

In Formula 1, X is at least one selected from Cl, Br, I and F, and a may be 0≤a≤5.

Solid electrolytes for lithium secondary batteries are largely divided into oxides and sulfides. At this time, compared to oxide-based solid electrolytes that require a high sintering temperature, sulfide-based solid electrolytes have disadvantages in that side reactions occur due to moisture, but have excellent ionic conductivity, and mechanical rigidity and physical properties of sulfides are more flexible than oxides. do. Such a sulfide can generally be produced by mechanical mixing of lithium sulfide and phosphorus pentasulfide, and when lithium halide is added to such a mixture, it has a crystal structure of azirodite, and the reaction sensitivity to moisture is relatively reduced. Therefore, when the sulfide-based solid electrolyte having Formula 1 is used, it can have resistance to pressure during application of the slurry due to its excellent ionic conductivity and flexibility, and has less side reactions caused by moisture in a dry room atmosphere with a low dew point, so that it is uniform. performance can be demonstrated.

The sulfide-based solid electrolyte included in the present invention is preferably mixed with a mixture of a UV curable polymer matrix and lithium salt to be described later in a weight ratio of 1:0.5 to 1:2. When mixed in the above weight ratio, there is an advantage that an electronic insulating film of an appropriate thickness can be generated between the release-treated films. As the mechanical properties are deteriorated, problems such as being torn by lithium dendrimers generated when the battery is driven and touching the electrodes may occur.

(C) lithium salt

The lithium salt serves as a source of lithium ions in the lithium secondary battery and facilitates the movement of lithium ions between the positive electrode and the negative electrode, thereby enabling the basic operation of the lithium battery.

Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN(SO ₂ F) ₂ , LiN(SO ₂ CF ₃ ) ₂ , Li(CF) ₃ SO ₂ ) ₂ N, LiN(SO ₃ C ₂ F ₅ ) ₂ , LiB(C ₂ O ₄ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , Li(CF ₃ SO ₃ ), LiC(SO ₂ ) CF ₃ ) ₃ , LiN(SO ₃ CF ₃ ) ₂ , LiC ₄ F ₉ SO ₃ , LiAlO ₄ , LiAlO ₂ , LiB(C ₂ O ₄ ) ₂ , LiAlCl ₄ , Li(CH ₃ CO ₂ ), Li(FSO) ₂ ) ₂ N, Li(CF ₃ SO ₂ ) ₃ C, LiCl, LiBr, or LiI, and the like, but are not limited thereto. These can be used individually or in mixture of 2 or more types.

The concentration of the lithium salt may be 0.1 to 2.0 M, preferably 0.5 to 1.5 M. When the concentration is less than the above concentration, the conductivity of the electrolyte may be lowered and the electrolyte performance may be deteriorated. However, the concentration of the lithium salt is not limited within the above range, and may be appropriately added or decreased as necessary.

The lithium salt may be dissolved in an organic solvent and used.

organic solvent

The organic solvent may serve as a medium through which ions involved in the electrochemical reaction of the lithium secondary battery can move.

As the organic solvent, for example, a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a nitrile-based solvent, a ketone-based solvent, or an alcohol-based solvent may be used, and these may be used alone or in combination of two or more. However, in terms of solubility of the lithium salt, it is preferable to include a nitrile-based solvent, and more preferably, succinonitrile may be used.

In the case of a nitrile-based solvent, particularly succinonitrile, since it is in the form of a solid at room temperature, it may contain lithium ions as a solid electrolyte, and may serve to attract cations by being polarized with two cyano groups at the terminal, and in the electrolyte solution It can be used as an additive to remove impurities such as copper ions. In addition, since the length of the central saturated chain is shorter than that of adiponitrile, etc., which perform the same function, it is preferable not to interfere with lithium ion mobility.

As the carbonate-based solvent, for example, a chain-type carbonate-based solvent, a cyclic carbonate-based solvent, or a combination thereof may be used.

As the chain carbonate-based solvent, for example, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (methylpropyl carbonate, MPC) ), ethylpropyl carbonate (EPC), ethylmethyl carbonate (ethylmethyl carbonate, EMC) or a combination thereof, and the cyclic carbonate-based solvent is, for example, ethylene carbonate (EC), propylene carbonate (propylene carbonate, PC), butylene carbonate (BC), vinylethylene carbonate (VEC), etc. can be used.

Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, butyl propionate, γ-butyrolactone, decanolide ( decanolide), valerolactone, mevalonolactone, caprolactone, methyl formate, ethyl formate, propyl formate, etc. may be used.

Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, and 2-methyltetrahydrofuran. , tetrahydrofuran, etc. can be used.

Examples of the nitrile-based solvent include acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, succinonitrile or dicyanobutene can be used. have.

As the ketone solvent, for example, cyclohexanone or the like can be used.

As the alcohol-based solvent, for example, ethyl alcohol, isopropyl alcohol, or the like can be used.

When the nitrile-based solvent is included, it is preferably dissolved by mixing with a lithium salt after dissolving at a temperature of 50 to 70 °C. When the above temperature range is satisfied, when applied in a liquid phase, the viscosity is adjusted before UV curing, so that the coating process and thickness control are easy.

The content of the organic solvent is not particularly limited as long as it can dissolve the lithium salt, but may be included so that the concentration of the lithium salt is 0.1 to 2.0 M, preferably 0.5 to 1.5 M. In this case, the lithium salt and compound described above are preferable because the desired effect is excellent.

The electrolyte for a lithium secondary battery according to the present invention can exhibit high ionic conductivity like a conventional liquid electrolyte, and can solve a short-circuit problem that may occur between electrodes during the manufacturing process, thereby improving mechanical strength such as durability. can be improved

Specifically, the ionic conductivity of the electrolyte for a lithium secondary battery according to the present invention may be 10 Ω*cm or less, preferably 4 Ω*cm or less, based on 25°C.

<Lithium secondary battery>

The present invention may provide a lithium secondary battery including the above-described electrolyte for a lithium secondary battery.

The lithium secondary battery according to the present invention may constitute a solid lithium secondary battery by forming the above-described electrolyte layer for a lithium secondary battery between the positive electrode and the negative electrode.

The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector.

The positive and negative current collectors are not particularly limited and may be used as long as they have conductivity without causing a chemical change in the lithium secondary battery.

As the positive and negative active materials, as long as they can reversibly insert and release lithium ions, they may be used without particular limitation.

The external shape of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape, a square shape, a pouch type, a thin film type, or a coin type using a can.

Hereinafter, examples will be given to describe the present specification in detail. However, the embodiments according to the present specification may be modified in various other forms, and the scope of the present specification is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present specification to those of ordinary skill in the art. In addition, "%" and "part" indicating the content hereinafter are based on weight unless otherwise specified.

Preparation Example 1: Preparation of electrolyte for lithium secondary battery

Comparative Example 1

LiC ₂ F ₆ NO ₄ S ₂ (LiTFSI) as a lithium salt was dissolved in succinonitrile (SN) (above TCI) at 60° C. at a concentration of 1 M to prepare an electrolyte for a lithium secondary battery.

Comparative Example 2

An electrolyte for a lithium secondary battery was prepared by mixing the solution prepared in Comparative Example 1 and a UV curable polymer matrix in a weight ratio of 85:15.

As the UV curable polymer matrix, ethoxylated trimethylolpropane triacrylate (M3130, Miwon Specialty Chemicals) having an average molecular weight of 428 g/mol as a photopolymerization compound and 1 wt% of Irgacure-184 as a photopolymerization initiator (Ciba) was mixed and used.

Comparative Example 3

In the lithium salt and UV curable polymer matrix mixture prepared in Comparative Example 2, aluminum oxide (Al ₂ O ₃ , average particle diameter: 300 nm, Ditto technology) was mixed in a weight ratio of 1:1 to obtain an electrolyte for a lithium secondary battery. prepared.

Comparative Example 4

An electrolyte for a lithium secondary battery was prepared by applying only a sulfide-based solid electrolyte (JK) having an azirodite crystal structure.

Comparative Example 5

Instead of the lithium salt prepared in Comparative Example 2 and the UV-curable polymer matrix mixture, a sulfide-based solid electrolyte was mixed with polyethylene glycol (Merck, molecular weight 600 g/mol) at a weight ratio of 1:2 to prepare an electrolyte for a lithium secondary battery. .

Example 1

An electrolyte for a lithium secondary battery was prepared by mixing the lithium salt and UV-curable polymer matrix mixture prepared in Comparative Example 2 with a sulfide-based solid electrolyte having an azirodite crystal structure (JK Corporation) in a weight ratio of 1:0.5.

Example 2

An electrolyte for a lithium secondary battery was prepared by mixing the lithium salt and UV-curable polymer matrix mixture prepared in Comparative Example 2 with a sulfide-based solid electrolyte (JK Corporation) having an azirodite crystal structure in a weight ratio of 1:1.

Example 3

An electrolyte for a lithium secondary battery was prepared by mixing the lithium salt and UV-curable polymer matrix mixture prepared in Comparative Example 2 with a sulfide-based solid electrolyte (JK Corporation) having an azirodite crystal structure in a weight ratio of 1:2.

Example 4

In Comparative Example 2, except that trimethylolpropane triacrylate (M300, Miwon Specialty Chemicals) having an average molecular weight of 256 g/mol was used as the photopolymerizable compound of the UV-curable polymer matrix was prepared in the same manner.

Experimental Example 1: Evaluation of peeling properties

The peeling characteristics of the electrolyte for a lithium secondary battery according to the Examples and Comparative Examples were evaluated. Specifically, on the release-treated surface of the first release-treated film, the electrolyte mixture for lithium secondary batteries according to the Examples and Comparative Examples was applied, and the second release-treated film was covered with the release-treated surface facing 305 nm After irradiating for 5 minutes with an LED UV lamp of 3 mW/cm ² , it was turned over and cured by irradiating UV light on both sides for a total of 10 minutes.

After UV curing, the second release-treated film was removed, and it was checked whether the lithium secondary battery electrolyte was peeled off from the first release-treated film without damage such as tearing.

The solid electrolyte prepared between the two release films should be easily peeled off from the release film and released to the electrode when applied between the electrodes, and if the solid electrolyte is damaged, a short circuit with the electrode may occur during operation.

Experimental Example 2: Electrode short evaluation

The electrode short circuit of the electrolyte for a lithium secondary battery according to Examples and Comparative Examples was evaluated.

Specifically, by measuring the resistance on the surface of the prepared solid electrolyte using a multi-tester, it was confirmed whether it had insulating properties. In addition, by stacking a solid electrolyte between two SUS, using a multi-tester between the upper and lower SUS to check whether electricity is energized, the results are shown in Table 1 below.

<Evaluation criteria>

Good: No electricity

Bad: When energized

Experimental Example 3: Ion conductivity evaluation

The ionic conductivity of the electrolyte for a lithium secondary battery according to the above Examples and Comparative Examples was evaluated.

Specifically, the electrolyte for a lithium secondary battery according to the prepared Examples and Comparative Examples was applied between stainless steels (SUS), irradiated with UV, and cured to prepare SUS/electrolyte/SUS form. In order to evaluate the ionic conductivity, an AC voltage was applied to the SUS. At this time, the application conditions were set to an amplitude of 5 to 10 mV and a measurement frequency range of 0.1 to 1 MHz. Ion conductivity was calculated using Equation 1 below using the measured impedance, area, and thickness, and the results are shown in Table 1 below.

[Equation 1]

σ: ionic conductivity, R _b : impedance resistance, l: thickness of cured electrolyte (cm), A: area of SUS (cm ² )

hardenable Peeling property evaluation electrode short ionic conductivity
(Ω*cm) Comparative Example 1 impossible not rated Good not measurable Comparative Example 2 possible Ripped error not measurable Comparative Example 3 possible Ripped Good 4.503 Comparative Example 4 impossible not rated error not measurable Comparative Example 5 impossible not rated Good 3.861 Example 1 possible Good Good 3.206 Example 2 possible Good Good 3.141 Example 3 possible Good Good 3.089 Example 4 possible Good Good 4.174

In the case of Examples including all of the UV-curable polymer matrix, the sulfide-based solid electrolyte, and the lithium salt according to the present invention, it can be confirmed that mechanical strength such as durability is excellent as a result of evaluation of peeling properties. In particular, when the UV-curable polymer matrix is photopolymerizable including alkylene oxide, it can exhibit high ionic conductivity like a conventional liquid electrolyte, and can solve a short problem that may occur between electrodes during the manufacturing process. can confirm.

Claims (10)

An electrolyte for a lithium secondary battery comprising a UV curable polymer matrix, a sulfide-based solid electrolyte, and a lithium salt.
According to claim 1,
The UV-curable polymer matrix comprises a photopolymerizable compound and a photopolymerization initiator, an electrolyte for a lithium secondary battery.
3. The method of claim 2,
The photopolymerizable compound is an electrolyte for a lithium secondary battery, characterized in that it comprises a photopolymerizable compound containing an alkylene oxide.
4. The method of claim 3,
The photopolymerizable compound comprising the alkylene oxide. Ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth) ) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, propoxylated pentaerythritol tetra (meth) acrylate, ethoxylated dipentaerythritol penta (meth) acrylate, propoxylated dipenta group consisting of erythritol penta (meth) acrylate, ethoxylated dipentaerythritol hexa (meth) acrylate, propoxylated dipentaerythritol hexa (meth) acrylate and ethoxylated glycerin tri (meth) acrylate An electrolyte for a lithium secondary battery, characterized in that at least one selected from
3. The method of claim 2,
The photopolymerizable compound is an electrolyte for a lithium secondary battery, characterized in that it is contained in an amount of 10 to 90% by weight based on the total weight of the UV-curable polymer matrix.
3. The method of claim 2,
The photopolymerization initiator is an electrolyte for a lithium secondary battery, characterized in that it is included in an amount of 0.1 to 10% by weight based on the total weight of the electrolyte for a lithium secondary battery.
According to claim 1,
The sulfide-based solid electrolyte is an electrolyte for a lithium secondary battery, characterized in that it has an Argyrodite-type crystal structure represented by the following Chemical Formula 1:
[Formula 1]
Li ₆ PS _5-a X _a
In Formula 1,
X is at least one selected from the group consisting of Cl, Br, I and F, and a is 0≤a≤5.
According to claim 1,
The UV-curable polymer matrix and the sulfide-based solid electrolyte are mixed in a weight ratio of 1:0.5 to 1:2, an electrolyte for a lithium secondary battery.
According to claim 1,
The electrolyte for a lithium secondary battery, characterized in that the ionic conductivity of the electrolyte is 4 Ω * cm or less based on 25 °C.
anode; cathode; and a lithium secondary battery comprising the electrolyte for a lithium secondary battery of any one of claims 1 to 9.