KR101502926B1 - Polymer electrolyte for lithium secondary battery, and lithium secondary battery comprising same - Google Patents

Abstract

The present invention relates to a polymer electrolyte for a lithium secondary battery, and a lithium secondary battery comprising the same, wherein the electrolyte comprises an ionic liquid, a polymer forming compound, a lithium salt, and a non-aqueous organic electrolyte solution.

The polymer electrolyte for a lithium secondary battery has an improved ionic liquid and thus has a high safety at a high temperature. The composition of the ionic liquid and the polymer forming compound is optimized to provide a polymer electrolyte for a lithium secondary battery excellent in liquid retention and safety.

Lithium secondary batteries, electrolytes, ionic liquids, polymer forming compounds, lithium salts, non-aqueous organic electrolytes

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte for a lithium secondary battery, and a lithium secondary battery including the polymer electrolyte. 2. Description of the Related Art Polymer electrolytes for lithium secondary batteries,

1 is an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention;

Description of the Related Art

100: lithium secondary battery 113: cathode

112: anode 114: separator

110: electrode group 120: case

140: cap assembly

[Industrial Applications]

The present invention relates to a polymer electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same, and more particularly, to a polymer electrolyte for a lithium secondary battery securing excellent safety and ionic conductivity at the same time, and a lithium secondary battery comprising the polymer electrolyte .

BACKGROUND ART [0002]

Recently, with the development of advanced electronic industry, it has become possible to reduce the size and weight of electronic equipment, and the use of portable electronic devices is increasing. The need for a battery having a high energy density as a power source for such portable electronic devices has been increased, and research on lithium secondary batteries has been actively conducted. Lithium-transition metal oxides are used as the cathode active material of the lithium secondary battery, and carbon (crystalline or amorphous) or carbon composite material is used as the anode active material.

A lithium secondary battery using a liquid electrolyte uses an organic electrolyte having a low boiling point as an organic electrolyte constituting an electrolyte. In this case, a low-boiling organic electrolyte is used as a positive electrode, Ring phenomenon occurs. There is a problem that the reliability and safety of the battery at a high temperature is deteriorated.

In order to solve these problems, a method using a polymer solid electrolyte has been proposed. However, a gel polymer electrolyte having a moderate characteristic at present due to its low ion conductivity has been used. As a result, a battery having improved not only safety but also a reduced thickness and degree of freedom of shape has been born. However, ion conductivity is lower than that of a liquid electrolyte, and a liquid is used, so that a complete trust is not obtained.

In order to solve the above problems, it is an object of the present invention to improve the safety of an electrolyte itself by introducing a considerable amount of an ionic liquid into a liquid electrolyte, optimize the composition of an ionic liquid and a polymer forming compound, And to provide a polymer electrolyte for a secondary battery.

Another object of the present invention is to provide a lithium secondary battery comprising the polymer electrolyte.

According to an aspect of the present invention, there is provided an ionic liquid including: an ionic liquid; Polymer forming compounds; Lithium salts; And a non-aqueous organic electrolytic solution. The present invention also provides a polymer electrolyte for a lithium secondary battery.

It is preferable that the ionic liquid is formed by a combination of a cation and an anion, and the cation is a cation of a heterocyclic compound.

The hetero atom of the heterocyclic compound is preferably at least one selected from the group consisting of N, O, S, and combinations thereof.

The number of heteroatoms in the heterocyclic compound is preferably 1 to 4.

The cation of the heterocyclic compound may be at least one selected from the group consisting of pyridinium, pyridazinium, pyrimidinium, pyrazinium, pyrazolium, thiazolium, oxazolium, It is preferably a cation of a compound selected from the group consisting of triazolium, pyrolidium, piperidium, phosphonium, borate, and combinations thereof.

The ionic liquid is formed by a combination of a cation and an anion, and the anion is selected from the group consisting of bis (perfluoroethylsulfonyl) imide, bis (trifluoromethylsulfonyl) imide, tris (Trifluoromethylsulfonyl) imide, trifluoromethylsulfonylimide, trifluoromethylsulfonate, tris (pentafluoroethyl) trifluorophosphate, bis (trifluoromethylsulfonyl) imide, Tetrafluoroborate, tetrafluoroborate, hexafluorophosphate, and a combination thereof.

The ionic liquid is formed by a combination of a cation and an anion, and the anion is preferably an anion selected from the group consisting of AsF ₆ ^- , ClO ₄ ^- , PF ₆ ^- , BF ₄ ^- , and combinations thereof.

The ionic liquid is preferably 5 to 50% by weight, more preferably 5 to 30% by weight based on the total weight of the polymer electrolyte.

The polymer forming compound is preferably a monomer containing a methacrylate group.

The methacrylate group-containing monomer may be selected from the group consisting of polyethylene glycol dimethacrylate, poly (ester) (meth) acrylates substituted with (meth) acrylic acid esters, (meth) acrylic acid esters, poly Ester) (meth) acrylate, and combinations thereof.

The group having no radical-labile group is selected from the group consisting of an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 5 to 20 carbon atoms, an ether group having 1 to 20 carbon atoms, an ester group having 1 to 20 carbon atoms, It is preferably a substituent selected.

(= O) (CH ₂ ) ₃ CH ₃ , -OC (= O) Ar wherein Ar is an unsubstituted or substituted aromatic hydrocarbon group, -OC (= O) _{(CH 2) n O (CH} 2) n CH 3 (n is an integer of 1 to 20), -O (C = O ) (CH 2) n OC (= O) (CH 2) n CH 3 (n is (C = O) CH = CH ₂ , and combinations thereof.

The (meth) acrylic acid ester is _{-OC (= O) (CH 2} ) n OC (= O) CH = CH 2, -OC (= O) (CH 2) n OC (= O) C (CH 3) = CH ₂ (n is an integer of 1 to 20), and a combination thereof.

The methacrylate-containing monomer is preferably a compound having at least one carbon-carbon double bond at the end of the monomer.

The methacrylate-containing monomer may be selected from the group consisting of polyfunctional acrylates, poly (ethylene glycol) dimethacrylate, poly (ethylene glycol) diacrylate, poly (ethylene glycol) divinyl ether, ethylene glycol dimethacrylate, ethylene It is preferably selected from the group consisting of glycol diacrylate, ethylene glycol divinyl ether, hexanediol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol monoacrylate, caprolactone acrylate, and combinations thereof.

The methacrylate-containing monomer is preferably selected from the group consisting of the following general formulas (1), (2), and combinations thereof.

[Chemical Formula 1]

(2)

(Wherein R ₁ is H or an alkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 100,000, and R ₂ is H or an alkyl group having 1 to 6 carbon atoms)

The molar ratio of the methacrylic acid ester to the group having no radical reactivity is preferably from 1: 0.01 to 1: 100.

The polymer forming compound is preferably 1 to 30% by weight, more preferably 5 to 10% by weight based on the total weight of the polymer electrolyte.

Wherein the lithium salt is selected from the group consisting of LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , A group consisting of LiCl (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) wherein x and y are natural numbers of 1 to 30, LiCl, LiI, LiBOB, Is preferably selected.

The lithium salt is preferably 0.7 to 2.0 M, more preferably 1 to 1.3 M, based on the total concentration of the polymer electrolyte.

The non-aqueous organic electrolytic solution is preferably selected from the group consisting of carbonate, ester, ether, ketone, and combinations thereof.

The carbonate may be selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) Propylene carbonate (PC), butylene carbonate (BC), and combinations thereof.

According to another embodiment of the present invention, the polymer electrolyte; A positive electrode comprising a positive electrode active material capable of intercalating and deintercalating lithium; And a negative electrode comprising a negative active material capable of intercalating and deintercalating lithium.

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

According to an embodiment of the present invention, there is provided a polymer electrolyte for a lithium secondary battery comprising an ionic liquid, a polymer forming compound, a lithium salt, and a non-aqueous organic electrolytic solution.

The ionic liquid is ionic salts or molten salts which are composed of cations and anions. Ionic compounds such as salt, which are composed of cationic and nonmetal anions, are generally referred to as ionic liquids, which dissolve at a high temperature of 800 ° C or higher, and exist as liquids at a temperature of 100 ° C or lower. Particularly, an ionic liquid present as a liquid at room temperature is referred to as a room temperature ionic liquid (RTIL).

Ionic liquids are nonvolatile, non-toxic, non-flammable, and have excellent thermal stability and ionic conductivity. In addition, it has a unique polarity, which dissolves inorganic and organic metal compounds and exists as a liquid in a wide temperature range, and is applied to a wide range of chemical fields such as catalysts, separation, and electrochemistry.

Since the polymer electrolyte for a lithium secondary battery according to an embodiment of the present invention contains such an ionic liquid, the stability at a high temperature is greatly improved. Further, since the ionic liquid has excellent thermal stability and excellent ionic conductivity, when the ionic liquid is added to the electrolyte, the thermal stability can be improved without decreasing the ionic conductivity. Since the ionic liquid has high polarity and dissolves inorganic and organic metal compounds well and exists as a liquid even in a wide temperature range, it can be added to the composition for forming a polymer electrolyte through simple mixing and heating.

The ionic liquid is preferably a van der Waals volume comprises a large organic cation 100Å ³ or more. The larger the van der Waals volume of the organic cation is, the lattice energy of the molecule decreases and the ion conductivity is excellent.

The ionic liquid may be present in a liquid state at a wide temperature range, and particularly in a liquid state at an operating temperature of the battery, so that the ionic liquid itself can be used as an electrolyte. The ionic liquid used in the present invention is preferably present in a liquid state at a temperature of 100 ° C or lower, more preferably in a liquid state at a temperature of 50 ° C or lower, and more preferably in a liquid state at a temperature of 25 ° C or lower Most preferred. Depending on the application method, it is of course possible to use a substance existing in a liquid state at a different temperature.

The organic cation of the ionic liquid is preferably a cation of a heterocyclic compound. The heteroatom of the heterocyclic compound is preferably at least one selected from the group consisting of N, O, S, and combinations thereof. The number of heteroatoms is preferably 1 to 4, more preferably 1 to 2. Examples of the cation of such a heterocyclic compound include pyridinium, pyridazinium, pyrimidinium, pyrazinium, pyrazolium, thiazolium, oxazolium ( a cation of a compound selected from the group consisting of oxazolium, triazolium, pyrolidium, piperidium, phosphonium, borate, and combinations thereof can be preferably used. have.

The anion bonded to the cation is selected from the group consisting of bis (perfluoroethylsulfonyl) imide, bis (trifluoromethylsulfonyl) imide, tris (trifluoromethylsulfonylmethide), trifluoromethanesulfonimide , Trifluoromethylsulfonimide, trifluoromethylsulfonate, tris (pentafluoroethyl) trifluorophosphate, bis (trifluoromethylsulfonyl) imide, tetrafluoroborate, hexafluorophosphate, And an anion of a compound selected from the group consisting of combinations thereof.

In addition, anions selected from the group consisting of AsF ₆ ^- , ClO ₄ ^- , PF ₆ ^- , BF ₄ ^- , and combinations thereof can be preferably used as the anions to be bonded to the cations.

The combination of the cation and the anion has properties as an ionic liquid, and the obtained polymer electrolyte has a high ionic liquid content of 0.8 to 1.8 x 10 < ^-3 > S / cm Show ionic conductivity.

The ionic liquid may be used in an amount of 5 to 50% by weight, preferably 5 to 30% by weight, based on the total weight of the polymer electrolyte. That is, the content of the ionic liquid is preferably 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 wt% based on the total weight of the polymer electrolyte.

When the content of the ionic liquid is less than 5% by weight, the effect of improving the swelling and the ionic conductivity is not exhibited. When the ionic liquid exceeds 50% by weight, the breakdown of the negative electrode and the decrease of the ionic conductivity occur .

The polymer forming compound may be any compound which can be added to an electrolyte and form a polymer electrolyte through a polymerization reaction, but it is preferable to use a monomer containing a methacrylate group.

Examples of the monomer having a methacrylate group include polyfunctional acrylates, poly (ethylene glycol) dimethacrylates, poly (ethylene glycol) diacrylates, poly (Ethylene glycol) divinyl ether, ethylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol divinyl ether hexanediol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol monoacrylate, caprolactone acrylate , And a combination thereof. Of these, polyfunctional acrylates and poly (ethylene glycol) dimethacrylates are preferred, and polyfunctional acrylates are most preferred.

The polyfunctional acrylate is a polyol having at least three hydroxyl groups (-OH), in which some or all of the hydroxyl groups of the (poly) polyol are substituted with (meth) acrylic acid esters, The reactive hydroxyl groups refer to poly (ester) (meth) acrylates substituted with groups that are not reactive with radicals. Examples of such multifunctional acrylates include monomers represented by the following general formula (1) or (2).

[Chemical Formula 1]

(2)

(Wherein R ₁ is H or an alkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 100,000, and R ₂ is H or an alkyl group having 1 to 6 carbon atoms)

The monomer having a methacrylate group is obtained by converting at least one hydroxyl group into a (meth) acrylic acid ester in a (poly) polyester polyol having three or more hydroxyl groups, and reacting the remaining unreacted hydroxyl groups not partially substituted with (meth) By forming a polymer of poly (ester) (meth) acrylate substituted with a non-acrylate group having no radical reactivity, an acrylate group that does not participate in the polymerization reaction remains as an unreacted acrylic group to deteriorate the low temperature or high lifetime characteristics of the lithium secondary battery Can be eliminated.

The polyester polyol having three or more hydroxyl groups may be any of those synthesized by a method known in the art, for example, condensation polymerization of hydroxycarboxylic acid, ring-opening polymerization of lactone, or condensation polymerization of glycol and dicarboxylic acid, Commercially available products may also be used. Specific examples of the polyester polyol having three or more hydroxyl groups include trialkylols such as trimethylol, triethylol and tripropylol, various glycerols, pentaerythritol, dipentaerythritol, And the like.

(Meth) acrylic acid esters of the present invention by replacing some or all of the hydroxyl groups of such polyester polyol with (meth) acrylic acid ester and then replacing some unreacted hydroxyl groups remaining unreacted with groups having no radical reactivity. Acrylate or a polymer thereof.

The method of replacing part or all of the hydroxyl groups with (meth) acrylic acid esters can be carried out under the general esterification reaction conditions. For example, a method of condensing a polyester polyol and a (meth) acrylic acid halide in the presence of a base catalyst, and a method of condensing a polyester polyol and (meth) acrylic acid in the presence of an acid catalyst.

First, a method of condensing a polyester polyol and a (meth) acrylic acid halide in the presence of a base catalyst will be described.

Acrylic acid chloride or (meth) acrylic acid chloride is suitable as the (meth) acrylic acid halide, and the amount of the (meth) acrylic acid halide used is suitably 0.5 to 5 equivalents based on 1 mol of the hydroxyl group of the polyester polyol.

Examples of the base catalyst include organic bases such as triethylamine, pyridine, dimethylaminopyridine, and diazabicyclo-undecene; or inorganic bases such as lithium carbonate, sodium carbonate, potassium carbonate, lithium hydroxide, sodium hydroxide, and potassium hydroxide. The amount of the base catalyst to be used is suitably 1.0 to 5 equivalents based on the (meth) acrylic acid halide.

The reaction may be carried out in the presence of a solvent or without a solvent. Examples of the usable solvent include halogenated hydrocarbons such as dichloroethane, chloroform and dichloroethane, aromatic hydrocarbons such as benzene, toluene and xylene, saturated hydrocarbons such as hexane, heptane, decane and cyclohexane, diethyl ether, diisopropylether, tetra Ethers such as tetrahydrofuran and the like can be used.

The above reaction can be carried out generally at -20 to 100 ° C, preferably at -5 to 50 ° C.

In the method of condensing a polyester polyol with (meth) acrylic acid, the amount of (meth) acrylic acid to be used is suitably 0.1 to 10 moles per 1 mole of the hydroxyl group of the polyester polyol. Examples of the acid catalyst include sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, hydrochloric acid, phosphoric acid, tungstate, and phosphomolybdic acid. The amount of the acid catalyst to be used is preferably 0.01 to 10% by weight based on the polyester polyol.

The reaction may be carried out in an inert solvent, for example, aromatic hydrocarbons such as benzene, toluene, and xylene, or saturated hydrocarbons such as hexane, heptane, decane, cyclohexane, and the like. The solvent is used in an amount of 0.1 to 10 parts by weight based on the polyester polyol. The reaction temperature is 50 to 200 占 폚, preferably 70 to 150 占 폚.

In the above-mentioned method, part or all of the hydroxyl groups contained in the polyester polyol are substituted with (meth) acrylic acid esters. Substituted (meth) acrylic acid ester is _{-OC (= O) (CH 2} ) n OC (= O) CH = CH 2, -OC (CH 2) n C (CH 3) = CH 2 (n is a number ranging from 1 to 20 , And a combination thereof. [0033] The term " a "

Subsequently, the unreacted unreacted hydroxyl groups are replaced with groups having no radical reactivity.

The group having no radical reactivity is at least one member selected from the group consisting of an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, an ether group having 1 to 20 carbon atoms, _{(= O) (CH 2)} 2 CH 3, -O (C = O) Ar ( wherein, Ar is a group of the beach or substituted aromatic hydrocarbons), -OC (= O) ( CH 2) n O (CH ₂ ) _n (CH ₃ ) (n is an integer of 1 to 20), -O (C═O) (CH ₂ ) _n OC (═O) (CH ₂ ) _n CH ₃ , -O (C = O) CH = CH ₂ , and combinations thereof.

As an example of the method, the residual hydroxyl group is esterified using a compound containing a group having no radical reactivity equivalent to an equivalent or more equivalent to the hydroxyl group remaining in the obtained product. The compound containing the group having no radical reactivity is a compound having a carbonylic acid or a halogen compound having an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an aromatic hydrocarbon group having 5 to 20 carbon atoms, an ether group having 1 to 20 carbon atoms, an ester having 1 to 20 carbon atoms Carbonyl group or a halogen compound of the skeleton may be used. Representative examples of the compound including the group having no radical reactivity include butylcarboxylic acid.

Alternatively, a modified polyester polyol in which the molecular structure of the polyol is changed by ring-opening polymerization of the polyester polyol together with the lactone-based compound may be used in the esterification step. When the modified polyester polyol is used, the length of the hydroxyl group acting as a reactor in the molecular skeleton can be controlled, and it is effective to change physical properties of the electrolyte, which is the final product. As the lactone compound,? -Caprolactone,? -Caprolactone, or the like can be used. The lactone-based compound can be used in an arbitrary ratio with respect to the total number of hydroxyl groups of the polyester polyol. Therefore, the amount of the lactone compound to be used in the present invention is not particularly limited. However, considering the solubility of the modified polyester polyol in which the lactone compound is substituted and the molecular size of the lactone compound, %, Particularly preferably 0.01 to 10 moles per mole of the hydroxyl group of the polyol.

As catalysts for promoting the ring-opening polymerization reaction, organic titanium compounds, organotin compounds, and organic carboxylic acid metal salts of various metals can be used. Examples of the organic titanic compound include tetrapropyl titanate and the like.

The addition amount of the catalyst is preferably 0.001 to 1 part by weight based on 100 parts by weight of the lactone compound.

When the modified polyester polyol is used, an esterification reaction is carried out by adding a compound containing acrylic acid and its derivative and a group having no radical reactivity to the modified polyester polyol together. The molar ratio of the acrylic acid and its derivative to the compound containing the group having no radical reactivity is adjusted so that part or all of the hydroxyl groups contained in the modified polyester polyol are substituted with the (meth) acrylic acid ester, and the remaining part of the unreacted The hydroxyl groups can be controlled in proportion to substitution with groups that are not reactive with the radicals.

In the above-mentioned method, some or all of the hydroxyl groups of the polyester polyol are converted into (meth) acrylic acid esters, and unreacted hydroxyl groups not partially substituted with the (meth) acrylic acid ester of the remaining unreacted hydroxyl groups are replaced with Poly (ester) (meth) acrylate or a polymer thereof is prepared.

Preferable examples of the poly (ester) (meth) acrylate may be represented by the following formula (3).

(3)

The molar ratio of the (meth) acrylic acid ester to the group having no radical reactivity is preferably from 1: 0.01 to 1: 100. When the molar ratio of the (meth) acrylic acid ester to the group having no radical reactivity is less than 1: 0.01, the degree of crosslinking of the polymer is increased to decrease the ion conductivity. When the ratio is more than 1: 100, And thus it is not preferable.

The polymer-forming compound of the present invention is preferably contained in an amount of 1 to 30% by weight, more preferably 1 to 10% by weight, and further preferably 5 to 10% by weight based on the total weight of the polymer electrolyte . That is, the content of the polymer forming compound is preferably 1, 5, 10, 15, 20, 25, and 30% by weight based on the total weight of the polymer electrolyte.

When the content of the polymer forming compound is less than 1% by weight, sufficient strength as a polymer can not be exhibited, and safety and cycle life characteristics are deteriorated. When the content is more than 30% by weight, the ion conductivity of the electrolyte deteriorates .

As the lithium salt, any lithium salt added to a conventional battery electrolyte may be used. Examples thereof include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , And LiB (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) wherein x and y are natural numbers of 1 to 30, LiCl, LiI, LiBOB, Can be preferably used. Wherein the electrolyte is selected from the group consisting of LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , CF ₃ SO ₃ Li, Can be more preferably used.

The concentration of the lithium salt is preferably in the range of 0.7 to 2.0 M, more preferably in the range of 1 to 1.3 M, based on the entire polymer electrolyte. That is, it is preferable that the concentration of the lithium salt is 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 2.0 M for the entire polymer electrolyte.

When the concentration of the lithium salt is less than 0.7M, the conductivity of the polymer electrolyte is lowered and the performance of the polymer electrolyte deteriorates. When the concentration exceeds 2.0M, the viscosity of the polymer electrolyte increases and the mobility of the lithium ion decreases.

As the non-aqueous organic electrolytic solution, a solvent selected from the group consisting of carbonate, ester, ether, ketone, and combinations thereof may be used.

Examples of the carbonate include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC) , Propylene carbonate (PC), butylene carbonate (BC), and combinations thereof, and the ester may be selected from the group consisting of n-methyl acetate, n-ethyl acetate, n-propyl acetate, And combinations thereof.

In the non-aqueous organic electrolytic solution, it is preferable to use a mixture of a cyclic carbonate and a chain carbonate in the case of the carbonate system. In this case, the cyclic carbonate and the chain carbonate are preferably mixed in a volume ratio of 1: 1 to 1: 9. The electrolyte should preferably be mixed in the above volume ratio.

The polymer electrolyte may be a gel-like physical gel polymer electrolyte which is applied outside the cell before the polymerizing process, and the polymer electrolyte may be left in a state of about 75 ° C after assembling the cell to form a gel state Of a chemical gel polymer electrolyte.

The polymer electrolyte may further include a polymerization initiator. Examples of the polymerization initiator include an azobenzene-based initiator or a peroxide-based polymerization initiator. Preferred examples thereof include isobutyl peroxide, lauroyl peroxide, benzoyl peroxide, m-toluene Butylperoxy-2-ethylhexanoate, t-butylperoxyvivarate, t-butyloxy neodecanate, diisopropyl peroxy dicarbonate, diethoxy (4-t-butylcyclohexyl) peroxy dicarbonate, dimethoxyisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, 3,3,5-trimethylhexanoyl peroxide , And a combination of these.

The polymerization initiator is preferably 0.02 to 2% by weight based on the total weight of the polymer electrolyte. When the content of the polymerization initiator is less than 0.02% by weight, the polymerization reaction rate of the polymer electrolyte slows down. When the content of the polymerization initiator is more than 2% by weight, the effect of the addition is not increased.

According to another embodiment of the present invention, there is provided a lithium secondary battery comprising the polymer electrolyte, a positive electrode including a positive electrode active material capable of intercalating and deintercalating lithium, and a negative electrode active material capable of intercalating and deintercalating lithium And a negative electrode including the negative electrode.

The lithium secondary battery according to an embodiment of the present invention may be manufactured through the following process. The polymer forming compound is added to a non-aqueous organic electrolytic solution containing an ionic liquid and a lithium salt to prepare a composition for forming a polymer electrolyte. The positive electrode and the negative electrode are prepared according to a conventional method used in the production of a lithium secondary battery. Then, a separator is inserted between the positive electrode and the negative electrode, and the separator is wound or stacked to form an electrode assembly and put into a case.

The composition for forming a polymer electrolyte is injected into a case to impregnate the electrode assembly. The impregnated electrode assembly is subjected to a polymerization reaction by heat treatment or UV irradiation, and the case is sealed to produce a lithium secondary battery. The heat treatment temperature in the polymerization reaction varies depending on the half-life period of the initiator of the radical reaction used, but is preferably 40 to 110 占 폚, more preferably 60 to 85 占 폚. If the temperature of the thermal polymerization is too low, a large amount of unreacted monomer remains or the reaction time becomes long, resulting in a cost of the manufacturing process. When the reaction temperature is too high, the amount of decomposition of the lithium salt is greatly increased.

The lithium secondary battery may be manufactured by the following process. First, the polymer-forming compound is added to a non-aqueous organic electrolytic solution containing an ionic liquid and a lithium salt to prepare a composition for forming a polymer electrolyte, which is coated on a substrate and then subjected to heat treatment or UV irradiation treatment Polymerization of the polymer is carried out.

Thereafter, the polymer electrolyte membrane is peeled from the substrate to obtain a polymer electrolyte in the form of a film. The thickness of the polymer electrolyte is preferably in the range of 5 to 90 占 퐉, and the ion conductivity of the polymer electrolyte is excellent in this range. The polymer electrolyte membrane is inserted between the positive electrode and the negative electrode manufactured according to a conventional method used in the production of a lithium secondary battery to form an electrode assembly and then the battery assembly is housed in a battery case and sealed to complete a polymer electrolyte lithium secondary battery . In the production of the polymer electrolyte lithium secondary battery, an electrode assembly may be manufactured by interposing a separator between the positive electrode and the negative electrode.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

1 is an exploded perspective view illustrating a lithium secondary battery according to an embodiment of the present invention. FIG. 1 shows a configuration of a cylindrical battery according to the present invention. However, it is needless to say that the battery of the present invention is not limited to FIG. 1 but may be square or pouch type.

1, the secondary battery 100 according to the present embodiment includes an electrode group 110 in which an anode 112 and a cathode 113 are sandwiched by a separator 114, and a polymer electrolyte And a case 120 having an opening at one end thereof to receive the electrode assembly 110. A cap assembly 140 for sealing the case 120 is installed in the opening of the case 120.

The cathode 113 includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes a negative electrode active material.

The negative electrode active material may be selected from the group consisting of a material capable of forming an alloy with lithium, a transition metal oxide, a material capable of doping and dedoping lithium, a material capable of reversibly reacting with lithium to form a compound, Materials can be used.

As the material which can be alloyed with lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Pb, Sb, Bi, and combinations thereof. The transition metal oxide, a material capable of doping and dedoping lithium, or a material capable of reversibly reacting with lithium to form a compound includes vanadium oxide, lithium vanadium oxide, Si, SiO _x (0 < 2), Sn, SnO ₂ , composite tin alloys, and combinations thereof.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to adhere the negative electrode active material particles to each other and adhere the negative electrode active material to the current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride , Polymers containing carboxylated polyvinyl chloride, polyvinyl difluoride, ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene- Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, or metal fibers may be used, and conductive materials such as polyphenylene derivatives may be mixed and used.

The anode current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foil, polymer substrate coated with a conductive metal, and combinations thereof .

The anode 112 includes a current collector and a cathode active material layer formed on the current collector.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Specifically, a compound represented by any one of the following formulas (4) to (27) may be used.

[Chemical Formula 4]

Li _{aa 1 - b} B _b D ₂

(In the above formula, 0.95? A? 1.1, and 0? B? 0.5)

[Chemical Formula 5]

Li _a E _{1 - b} B _b O _{2 - c} F _c

(In the above formula, 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05)

[Chemical Formula 6]

LiE _{2 - b} B _b O _{4 - c} F _c

(In the above formula, 0? B? 0.5, 0? C? 0.05)

(7)

Li _a Ni _{1 -b- c} Co _b B _c D _?

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <?? 2)

[Chemical Formula 8]

Li _a Ni _{1 -b- c} Co _b B _c O _{2 - ?} F _?

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <? <2)

[Chemical Formula 9]

Li _a Ni _{1 -b- c} Co _b B _c O _{2 - ?} F ₂

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <? <2)

[Chemical formula 10]

Li _a Ni _{1 -b- c} Mn _b B _c D _?

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <?? 2)

(11)

Li _a Ni _{1 - b - c} Mn _b B _c O _{2 - ?} F _?

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <? <2)

[Chemical Formula 12]

Li _a Ni _{1 - b - c} Mn _b B _c O _{2 - ?} F ₂

(Where 0.95? A? 1.1, 0? B? 0.5, 0? C? 0.05, 0 <? <2)

[Chemical Formula 13]

Li _a Ni _b e _c G _d O ₂

(Where 0.90? A? 1.1, 0? B? 0.9, 0? C? 0.5, and 0.001? D? 0.1).

[Chemical Formula 14]

Li _a Ni _b Co _c Mn _d G _e O ₂

(In the above formula, 0.90? A? 1.1, 0? B? 0.9, 0? C? 0.5, 0? D? 0.5, and 0.001? E? 0.1.

[Chemical Formula 15]

Li _a NiG _b O ₂

(In the above formula, 0.90? A? 1.1 and 0.001? B? 0.1).

[Chemical Formula 16]

Li _a CoG _b O ₂

(In the above formula, 0.90? A? 1.1 and 0.001? B? 0.1).

[Chemical Formula 17]

Li _a MnG _b O ₂

(In the above formula, 0.90? A? 1.1 and 0.001? B? 0.1).

[Chemical Formula 18]

Li _a Mn ₂ G _b O ₄

(In the above formula, 0.90? A? 1.1 and 0.001? B? 0.1).

[Chemical Formula 19]

QO ₂

[Chemical Formula 20]

QS ₂

[Chemical Formula 21]

LiQS ₂

[Chemical Formula 22]

V ₂ O ₅

(23)

LiV ₂ O ₅

&Lt; EMI ID =

LiIO ₂

(25)

LiNiVO ₄

(26)

Li _(3-f) J ₂ (PO ₄ ) ₃

(Where 0? F? 3 in the above formula).

(27)

Li _(3-f) Fe ₂ (PO ₄ ) ₃

(0? F? 2 in the above formula).

Wherein A is selected from the group consisting of Ni, Co, Mn, and combinations thereof, B is at least one element selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, And D is selected from the group consisting of O, F, S, P, and combinations thereof, E is selected from the group consisting of Co, Mn, and combinations thereof, and F Wherein G is selected from the group consisting of F, S, P and combinations thereof and G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, Lanthanon elements and combinations thereof And Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof, I is selected from the group consisting of Cr, V, Fe, Sc, Y, Mn, Co, Ni, Cu, and combinations thereof.

Also, the addition may be an inorganic sulfur (elemental sulfur) and a sulfur-based compound, in the sulfur-based compound is a Li ₂ S _n (n≥1) dissolved in a Li ₂ S _n (n≥1), caviar solrayiteu (catholyte) , An organic sulfur compound or a carbon-sulfur polymer ((C ₂ S _f ) _n : f = 2.5 to 50, n≥2).

Further, a cathode active material having a coating layer on the surface of the compound may be used, or a compound having a coating layer may be mixed with the cathode active material.

Wherein the coating layer comprises a coating element compound selected from the group consisting of an oxide of a coating element, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, a hydroxycarbonate of a coating element, . The compound constituting these coating layers may be amorphous or crystalline. The coating element may be selected from the group consisting of Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As and Zr or a combination thereof.

The coating layer may be formed by using any of these elements in a coating method that does not adversely affect the physical properties of the cathode active material (for example, spray coating, dipping, etc.) It will be understood by those skilled in the art that a detailed description will be omitted.

The positive electrode active material layer may further include a binder and a conductive material, and the binder and the conductive material may be the same as the binder and the conductive material described in the negative electrode active material layer.

As the current collector, Al may be used, but the present invention is not limited thereto.

As the polymer electrolyte, a polymer electrolyte including an ionic liquid, a polymer forming compound, a lithium salt, and a non-aqueous organic electrolytic solution according to an embodiment of the present invention is used.

Also, depending on the type of the lithium secondary battery, the separator 114 may exist between the positive electrode 112 and the negative electrode 113. The separator 114 may be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more thereof. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, a polypropylene / polyethylene / Polypropylene three-layer separator, or the like can be used.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Since the polymer electrolyte for a lithium secondary battery of the present invention contains an ionic liquid, the stability at high temperature is greatly improved.

INDUSTRIAL APPLICABILITY The polymer electrolyte for a lithium secondary battery of the present invention has excellent physical safety and lyophilicity, enables thinning of the battery, and improves the degree of freedom in shape.

Claims (26)

Ionic liquids; Polymer forming compounds; Lithium salts; And Non-aqueous organic electrolyte solution / RTI &gt; The polymer forming compound is a monomer containing a methacrylate group, Wherein the monomer having a methacrylate group is selected from the group consisting of the following general formulas (1), (2), and combinations thereof: (1) a polyelectrolyte for a lithium secondary battery in a gel state, [Chemical Formula 1]

(2)

In the general formulas (1) and (2), R ₁ is H or an alkyl group having 1 to 6 carbon atoms, n is an integer of 1 to 100,000, and R ₂ is H or an alkyl group having 1 to 6 carbon atoms. The method according to claim 1, The ionic liquid is formed by a combination of a cation and an anion, Wherein the cation is a cation of a heterocyclic compound. 3. The method of claim 2, Wherein the heteroatom of the heterocyclic compound is at least one selected from the group consisting of N, O, S, and combinations thereof. 3. The method of claim 2, Wherein the number of heteroatoms in the heterocyclic compound is 1 to 4. 3. The method of claim 2, The cation of the heterocyclic compound may be at least one selected from the group consisting of pyridinium, pyridazinium, pyrimidinium, pyrazinium, pyrazolium, thiazolium, oxazolium, Wherein the cation is a cation of a compound selected from the group consisting of triazolium, pyrolidium, piperidium, phosphonium, borate, and combinations thereof. Polymer electrolyte. The method according to claim 1, The ionic liquid is formed by a combination of a cation and an anion, The anion may be selected from the group consisting of bis (perfluoroethylsulfonyl) imide, bis (trifluoromethylsulfonyl) imide, tris (trifluoromethylsulfonylmethide), trifluoromethanesulfonimide, (Trifluoromethylsulfonyl) imide, tetrafluoroborate, hexafluorophosphate, and combinations thereof, as well as combinations thereof, such as methylsulfonimide, trifluoromethylsulfonate, tris (pentafluoroethyl) trifluorophosphate, bis Wherein the polymer electrolyte is an anion of a compound selected from the group consisting of lithium, lithium, and lithium. The method according to claim 1, The ionic liquid is formed by a combination of a cation and an anion, Wherein the anion is an anion selected from the group consisting of AsF ₆ ^- , ClO ₄ ^- , PF ₆ ^- , BF ₄ ^- , and combinations thereof. The method according to claim 1, Wherein the ionic liquid is 5 to 50 wt% based on the total weight of the polymer electrolyte. delete delete delete delete delete delete delete delete delete delete The method according to claim 1, Wherein the polymer forming compound is 1 to 30% by weight based on the total weight of the polymer electrolyte. delete delete delete delete delete delete A polymer electrolyte according to any one of claims 1 to 8 and 19; A positive electrode comprising a positive electrode active material capable of intercalating and deintercalating lithium; And A negative electrode including a negative electrode active material capable of intercalating and deintercalating lithium &Lt; / RTI &gt;

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