KR20150022659A - Electrolyte and lithium secondary battery with the same - Google Patents

Abstract

The present invention relates to an electrolyte and a lithium secondary battery including the same. The electrolyte includes an aromatic hydrocarbon compound including an isocyanate group or an isothiocyanate group as an electrolyte additive, thereby improving battery properties of lithium secondary battery, especially life at room temperature and high temperature performance, and reducing initial resistance.

Description

ELECTROLYTE AND LITHIUM SECONDARY BATTERY WITH THE SAME BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

TECHNICAL FIELD The present invention relates to an electrolyte capable of improving the battery characteristics, particularly, the normal temperature lifetime and the high temperature performance of the lithium secondary battery and reducing the initial resistance, and a lithium secondary battery comprising the electrolyte.

Lithium secondary batteries can be used not only as portable power sources such as mobile phones, notebook computers, digital cameras and camcorders but also as power tools, electric bicycles, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles HEV, PHEV), and the like. As the application field is expanded and demand is increased, the external shape and size of the battery are variously changed, and performance and stability are demanded more than the characteristics required in the conventional small batteries. In order to meet such a demand, the performance of the battery should be stabilized in a condition where battery components are flowing in a large current.

The lithium secondary battery is manufactured by using a material capable of inserting and desorbing lithium ions as a cathode and an anode, providing a porous separator between the two electrodes, and injecting a liquid electrolyte. The insertion and extraction of lithium ions in the cathode and the anode, Electricity is generated or consumed by the redox reaction due to desorption.

Various non-aqueous solvents and additives have been studied as electrolyte-containing components in order to improve battery characteristics such as output characteristics, cycle characteristics, and storage characteristics of lithium ion batteries. In addition, even when a specific compound is added to an electrolyte as an additive for improving battery performance, performance of some items of most battery performance can be expected to be improved, but the performance of other items is rather reduced.

An object of the present invention is to provide an electrolyte capable of improving the battery characteristics, particularly the normal temperature service life and high temperature performance, and reducing the initial resistance of a lithium secondary battery.

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

In order to achieve the above object, an electrolyte according to an embodiment of the present invention includes an isocyanate-based compound; And an aromatic hydrocarbon compound containing an isothiocyanate group as an electrolyte additive.

Wherein the aromatic hydrocarbon is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, fluorene, pyrene, phenalene, indene, biphenylene, diphenylmethylene, tetrahydronaphthalene, dihydroanthracene, tetraphenylmethylene, triphenylmethylene, pyrrole, And furans.

Wherein the aromatic hydrocarbon compound is at least one selected from the group consisting of a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, a nitro group, an amino group, a thio group, a methylthio group, an alkoxy group, a haloalkoxy group, a perfluoroalkoxy group, , An ether group, an ester group, a carbonyl group, an acetal group, a ketone group, an alkyl group, a perfluoroalkyl group, a cycloalkyl group, a heterocycloalkyl group, an allyl group, a benzyl group, an aryl group, a heteroaryl group, May be further substituted.

The aromatic hydrocarbon compound may further include any one substituent selected from the group consisting of perfluoromethoxy, perfluoroethoxy, perfluoropropoxy, perfluorobutoxy, and combinations thereof.

The aromatic hydrocarbon compound may be represented by any one selected from the group consisting of the following formulas (1) to (6).

[Chemical Formula 1]

(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

The isocyanate compound may include a compound represented by the following general formula (7).

(7)

(Q) _m --R - (T) _n - (N.dbd.C.dbd.O) _z

R is any one of an aliphatic hydrocarbon and a monovalent to hexavalent residue of an aromatic hydrocarbon, T is an alkylene group, -SO ₂ -, -O- or -CO-, Q is an alkyl group, a cycloalkyl group, a hetero (Meth) acryloyl group, a (meth) acryloyl group, a (meth) acryloyl group, an alkylsulfonyl group, an alkylsulfonyl group, an arylsulfonyl group, an arylsulfonyl group, (Meth) acryloyloxy group, a hydroxyl group, a carboxyl group, a cyano group, an amino group, a thio group, a methylthio group, an aldehyde group, an epoxy group, an acyl group, an acetal group, an allyl group, Z is an integer of 1 to 6, m is an integer of 0 to 5, and n is an integer of 0 to 6.

The electrolyte may further include an organic solvent and a lithium salt.

A lithium secondary battery according to another embodiment of the present invention includes a cathode including a cathode active material, a cathode disposed opposite to the cathode, including a cathode active material, and an electrolyte interposed between the cathode and the anode.

The electrolyte according to the present invention can improve the battery characteristics, particularly the normal temperature service life and the high temperature performance, and reduce the initial resistance of the lithium secondary battery.

1 is an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention.
2 is a graph showing the capacities measured at room temperature of the batteries manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1.
3 is a graph showing the capacity retention rate measured at room temperature of the batteries manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1.
4 is a graph showing the capacities measured at 45 ° C of the batteries manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1.
5 is a graph showing the capacity retention rate measured at 45 ° C of the batteries manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1.
6 is a graph showing the capacities measured at room temperature of the batteries manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2.
7 is a graph showing the efficiency measured at room temperature of the battery manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2.
8 is a graph showing the capacities measured at 45 캜 of the batteries manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2.
9 is a graph showing the efficiencies measured at 45 캜 of the batteries manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2.
10 is a graph showing changes in thickness of the battery manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2 with time at a high temperature.
11 is a graph showing changes in internal resistance with time at a high temperature of the battery manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2.
12 is a graph showing the lifetime performance of the batteries manufactured in Examples 4-1 and 4-2, as measured at 45 캜.

The present invention is capable of various modifications and various embodiments and is intended to illustrate and describe the specific embodiments in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as comprise, having, or the like are intended to designate the presence of stated features, integers, steps, operations, elements, parts or combinations thereof, and may include one or more other features, , But do not preclude the presence or addition of one or more other features, elements, components, components, or combinations thereof.

As used herein, the combination thereof means that two or more substituents are bonded to each other through a single bond or a linking group, or two or more substituents are condensed and connected unless otherwise specified.

Unless otherwise specified herein, the halogen atom means any one selected from the group consisting of fluorine, chlorine, bromine and iodine.

Unless otherwise stated, alkyl groups include primary alkyl groups, secondary alkyl groups, and tertiary alkyl groups.

Unless otherwise specified herein, a perfluoroalkyl group means an alkyl group in which some hydrogen atoms or all of the hydrogen atoms are replaced by fluorine, and the perfluoroalkoxy group means an alkoxy group in which some hydrogen atoms or all of the hydrogen atoms are substituted with fluorine do.

In the present specification, unless otherwise specified, all the compounds or substituents may be substituted or unsubstituted. The term "substituted" as used herein means that hydrogen is substituted with at least one substituent selected from the group consisting of a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, a nitro group, an amino group, a thio group, a methylthio group, an alkoxy group, a nitryl group, an aldehyde group, Substituted with any one selected from the group consisting of acetal, ketone, alkyl, perfluoroalkyl, cycloalkyl, heterocycloalkyl, allyl, benzyl, aryl, heteroaryl, .

Unless otherwise specified in the present specification, the alkyl group is a linear or branched alkyl group of 1 to 10 carbon atoms, an allyl group of 2 to 10 carbon atoms, an alkoxy group of 1 to 10 carbon atoms, a perfluoroalkyl group of 1 to 10 carbon atoms The perfluoroalkoxy group is a perfluoroalkoxy group having 1 to 10 carbon atoms, the cycloalkyl group is a cycloalkyl group having 3 to 32 carbon atoms, the heterocycloalkyl group is a heterocycloalkyl group having 2 to 32 carbon atoms, the aryl group has a carbon number of 6 An aryl group or a heteroaryl group having 2 to 30 carbon atoms means a heteroaryl group having 2 to 30 carbon atoms.

Unless otherwise specified herein, an aromatic hydrocarbon refers to a monocyclic or polycyclic compound having 6 to 30 carbon atoms and derivatives thereof containing at least one benzene ring, for example, a benzene ring, an aromatic ring having an alkyl side chain attached to a benzene ring Biphenyl in which two or more benzene rings are bonded by a single bond, such as toluene or xylene, a benzene ring in which two or more benzene rings such as fluorene, xanthene, and anthraquinone condensed with a cycloalkyl group or a heterocycloalkyl group are condensed Naphthalene, anthracene, and the like.

The aromatic hydrocarbon may also include heteroarylene containing a heteroatom in the aromatic ring, such as pyridine or pyrrole containing a nitrogen atom as a hetero atom, furan containing an oxygen atom as a halogen atom, or the like.

An electrolyte according to an embodiment of the present invention includes an isocyanate-based compound; And an aromatic hydrocarbon compound containing an isothiocyanate group.

Wherein the aromatic hydrocarbon is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, fluorene, pyrene, phenalene, indene, biphenylene, diphenylmethylene, tetrahydronaphthalene, dihydroanthracene, tetraphenylmethylene, triphenylmethylene, pyrrole, And furan, and may be preferably benzene.

Wherein the aromatic hydrocarbon compound is at least one selected from the group consisting of a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, a nitro group, an amino group, a thio group, a methylthio group, an alkoxy group, a haloalkoxy group, a perfluoroalkoxy group, , An ether group, an ester group, a carbonyl group, an acetal group, a ketone group, an alkyl group, a perfluoroalkyl group, a cycloalkyl group, a heterocycloalkyl group, an allyl group, a benzyl group, an aryl group, a heteroaryl group, , And may further preferably include a perfluoroalkoxy group.

The perfluoroalkoxy group may be perfluoromethoxy, perfluoroethoxy, perfluoropropoxy or perfluorobutoxy, and may preferably be perfluoromethoxy.

Specifically, the aromatic hydrocarbon compound may be represented by any one selected from the group consisting of the following formulas (1) to (6).

[Chemical Formula 1]

(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

The isocyanate compound may include a compound represented by the following general formula (7).

(7)

(Q) _m --R - (T) _n - (N.dbd.C.dbd.O) _z

R is any one of an aliphatic hydrocarbon and a monovalent to hexavalent residue of an aromatic hydrocarbon, T is an alkylene group, -SO ₂ -, -O- or -CO-, Q is an alkyl group, a cycloalkyl group, a hetero (Meth) acryloyl group, a (meth) acryloyl group, a (meth) acryloyl group, an alkylsulfonyl group, an alkylsulfonyl group, an arylsulfonyl group, an arylsulfonyl group, (Meth) acryloyloxy group, a hydroxyl group, a carboxyl group, a cyano group, an amino group, a thio group, a methylthio group, an aldehyde group, an epoxy group, an acyl group, an acetal group, an allyl group, Z is an integer of 1 to 6, m is an integer of 0 to 5, and n is an integer of 0 to 6.

The aliphatic hydrocarbon may be an alkane having 1 to 30 carbon atoms, a linear or branched alkane having 2 to 30 carbon atoms, a linear or branched alkane having 2 to 30 carbon atoms, a cycloalkane having 3 to 30 carbon atoms, a cycloalkane having 3 to 30 carbon atoms, Straight or branched C 1 -C 30 haloalkane, straight or branched C 1 -C 30 perfluoroalkane, straight or branched C 2 -C 30 haloalkene, A linear or branched perfluoroalkane having 2 to 30 carbon atoms, a linear or branched haloalkyne having 2 to 30 carbon atoms, a linear or branched perfluoroalkyne having 2 to 30 carbon atoms, a cycloalkylalkane having 4 to 50 carbon atoms, Lt; / RTI > to 50 dicycloalkylalkanes.

The aromatic hydrocarbon may be an aromatic hydrocarbon having 6 to 30 carbon atoms, an arylalkane having 7 to 50 carbon atoms, a diarylalkane having 13 to 60 carbon atoms, a haloarylene having 6 to 30 carbon atoms, a haloarylalkane having 7 to 40 carbon atoms, Heteroaryl, and heteroarylalkane having 4 to 30 carbon atoms.

Specifically, when R is a monovalent residue of an aliphatic hydrocarbon or an aromatic hydrocarbon, z is 1, m is 0, and n is 0 or 1.

The monovalent residue of the aliphatic hydrocarbon may be a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, a linear or branched alkynyl group having 2 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms , A cycloalkenyl group having 3 to 30 carbon atoms, a cycloalkynyl group having 3 to 30 carbon atoms, a linear or branched haloalkyl group having 1 to 30 carbon atoms, a linear or branched perfluoroalkyl group having 1 to 30 carbon atoms, A linear or branched perfluoroalkenyl group having 2 to 30 carbon atoms, a linear or branched haloalkynyl group having 2 to 30 carbon atoms, and a linear or branched 2 to 30 carbon atom-containing purple Lt; RTI ID = 0.0 > R < / RTI >

The monovalent residue of the aromatic hydrocarbon is selected from the group consisting of an aryl group having 6 to 30 carbon atoms, an aralkyl group having 7 to 40 carbon atoms, a haloaryl group having 6 to 30 carbon atoms, a haloaralkyl group having 7 to 40 carbon atoms, A heteroaryl group having 1 to 30 carbon atoms, and a heteroaralkyl group having 4 to 30 carbon atoms.

When R is a divalent residue of an aliphatic hydrocarbon or an aromatic hydrocarbon, z is 1 or 2, m is 0 or 1, and n is an integer of 0 to 2.

The divalent residue of the aliphatic hydrocarbon may be a linear or branched alkylene group having 1 to 30 carbon atoms, a cycloalkylene group having 3 to 30 carbon atoms, a linear or branched alkenylene group having 2 to 30 carbon atoms, a linear or branched alkylene group having 2 to 30 carbon atoms Straight or branched C 1 -C 30 haloalkylene, straight or branched C 1 -C 30 haloalkylene, straight or branched C 1 -C 30 perfluoroalkylene, straight or branched C 2 -C 30 haloalkenylene, straight or branched A perfluoroalkenylene group having 2 to 30 carbon atoms, a divalent residue of a cycloalkylalkane having 4 to 50 carbon atoms, and a divalent residue of a dicycloalkylalkane having 10 to 50 carbon atoms.

The divalent moiety of the aromatic hydrocarbon may be any of an arylene group having 6 to 30 carbon atoms, an aralkylene group having 7 to 40 carbon atoms, a heteroarylene group having 3 to 30 carbon atoms, and a heteroaralkylene group having 4 to 40 carbon atoms .

When R is a trivalent residue of an aliphatic hydrocarbon or an aromatic hydrocarbon, z is an integer of 1 to 3, m is an integer of 0 to 2, and n is an integer of 0 to 3. Z is an integer of 1 to 4, m is an integer of 0 to 3, and n is an integer of 0 to 4, when R is a quadrivalent residue of an aliphatic hydrocarbon or an aromatic hydrocarbon. Z is an integer of 1 to 5, m is an integer of 0 to 4, and n is an integer of 0 to 5. When R is a monovalent residue of an aliphatic hydrocarbon or an aromatic hydrocarbon, Z is an integer of 1 to 6, m is an integer of 0 to 5, and n is an integer of 0 to 6 when R is a hexa-valent residue of an aliphatic hydrocarbon or an aromatic hydrocarbon.

The 3- to 6-membered residue of the aliphatic hydrocarbon includes straight or branched alkane having 1 to 30 carbon atoms, straight or branched alkane having 2 to 30 carbon atoms, straight or branched alkane having 2 to 30 carbon atoms, An alkane, a cycloalkene having 3 to 30 carbon atoms, a cycloalkene having 3 to 30 carbon atoms, a linear or branched haloalkane having 1 to 30 carbon atoms, a linear or branched perfluoroalkane having 1 to 30 carbon atoms, A linear or branched perfluoroalkene having 2 to 30 carbon atoms, a linear or branched perfluoroalkene having 2 to 30 carbon atoms, a linear or branched perfluoroalkene having 2 to 30 carbon atoms, a linear or branched perfluoroalkene having 2 to 30 carbon atoms, Alkyl alkanes, and 3- to 6-membered residues of dicycloalkylalkane having 10 to 50 carbon atoms.

The 3- to 6-valent residues of the aromatic hydrocarbon include arenes having 6 to 30 carbon atoms, arylalkane having 7 to 50 carbon atoms, and diarylalkane having 3 to 6 carbon atoms having 13 to 60 carbon atoms.

T represents a linear or branched alkylene group having 1 to 10 carbon atoms, -SO ₂ -, -O- or -CO-.

Q represents a linear or branched alkyl group having 1 to 30 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, a heterocycloalkyl group having 2 to 30 carbon atoms, a straight or branched haloalkyl group having 1 to 30 carbon atoms, A linear or branched alkoxy group having 1 to 30 carbon atoms, a linear or branched haloalkoxy group having 1 to 30 carbon atoms, a linear or branched perfluoroalkoxy group having 1 to 30 carbon atoms, a perfluoroalkoxy group having 6 to 30 carbon atoms, (Meth) acryloyl group, a (meth) acryloyl group, a (meth) acryloyl group, a (meth) acryloyl group, an aryl group having 3 to 30 carbon atoms, a heteroaryl group having 3 to 30 carbon atoms, an aralkyl group having 7 to 40 carbon atoms, A hydroxyl group, a carboxyl group, a cyano group, an amino group, a thio group, a methylthio group, an aldehyde group, an epoxy group, an acyl group, an acetal group, an allyl group and combinations thereof It may be one.

In the above, when m is an integer of 2 to 5, Q of 2 or more may be all the same substituent, or some of them may be the same substituent or all of different substituents.

The isocyanate compound may be at least one selected from the group consisting of methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, tert-butyl isocyanate, pentyl isocyanate, hexyl isocyanate, heptyl isocyanate, octyl isocyanate, nonyl isocyanate, decyl isocyanate, cyclopropyl isocyanate, Examples of the isocyanate compound include isocyanates such as isocyanate, cyclohexyl isocyanate, cyclohexylmethyl isocyanate, adamantyl isocyanate, vinyl isocyanate, allyl isocyanate, ethynyl isocyanate, propynyl isocyanate, trifluoromethyl isocyanate, pentafluoroethyl isocyanate, Laurylsulfonyl isocyanate, pentafluoroethylsulfonyl isocyanate, 1-isocyanate Methoxypropane, 1-isocyanato-3-ethoxypropane, 2-isocyanato-2-methylpropane, 1-iso 1-isocyanato-4-methoxypentane, 1-isocyanato-4-ethoxypentane, 1-isocyanato- Isocyanato-6-ethoxyhexane, acetylethylisocyanate, phenylisocyanate, benzylisocyanate, phenethyl isocyanate, 2-fluorophenylisocyanate, 3- Chlorophenyl isocyanate, 4-chlorophenyl isocyanate, 2-bromophenyl isocyanate, 3-bromophenyl isocyanate, 4-bromophenyl isocyanate, 4-fluorophenyl isocyanate, , 2-iodophenyl isocyanate, 3-iodophenyl Difluorophenyl isocyanate, 2,4-difluorophenyl isocyanate, 2,5-difluorophenyl isocyanate, 2-fluorophenyl isocyanate, 2,4-difluorophenyl isocyanate, , 6-difluorophenyl isocyanate, 3,5-difluorophenyl isocyanate, 2,3,4-trifluorophenyl isocyanate, 2,3,5-trifluorophenyl isocyanate, 2,3,6-tri Fluorophenyl isocyanate, 2,4,5-trifluorophenyl isocyanate, 2,4,6-trifluorophenyl isocyanate, 2,3,4,5,6-pentafluorophenyl isocyanate, 2-methylphenyl isocyanate, Methylphenyl isocyanate, 3-methylphenyl isocyanate, 4-methylphenyl isocyanate, 2-ethylphenyl isocyanate, 3-ethylphenyl isocyanate, 4- ethylphenyl isocyanate, 2- (trifluoromethyl) phenyl isocyanate, 3- (trifluoromethyl) phenyl (2,2,2-trifluoroethyl) phenyl isocyanate, 4- (trifluoromethyl) phenyl isocyanate, 2- (2,2,2-trifluoroethyl) phenyl isocyanate, 3- (Trifluoromethoxy) phenyl isocyanate, 2- (trifluoromethoxy) phenyl isocyanate, 3- (trifluoromethoxy) phenyl isocyanate, 4- (trifluoromethoxy) phenyl isocyanate, 2- (2,2,2-trifluoroethoxy) phenyl isocyanate, 3- (2,2,2-trifluoroethoxy) phenyl isocyanate, 4- (2,2,2-trifluoroethoxy) phenyl Isocyanate, 4-nitrophenyl isocyanate, phenylsulfonyl isocyanate, 4-fluorophenylsulfonyl isocyanate, 2-acetylphenyl isocyanate, 2-acetylphenyl isocyanate, 2-nitrophenyl isocyanate, Isocyanate, 2- Fluorobenzyl isocyanate, 4-chlorobenzyl isocyanate, 4-bromobenzyl isocyanate, 4-iodobenzyl isocyanate, 2,3-difluorobenzyl isocyanate, 2,4 Difluorobenzyl isocyanate, 2,5-difluorobenzyl isocyanate, 2,6-difluorobenzyl isocyanate, 2,3,4-trifluorobenzyl isocyanate, 2,3,5-trifluorobenzyl isocyanate , 2,3,6-trifluorobenzyl isocyanate, 2,4,5-trifluorobenzyl isocyanate, 2,4,6-trifluorobenzyl isocyanate, 2,3,4,5,6-pentafluoro Benzyl isocyanate, 4-trifluoromethyl benzyl isocyanate, 4- (3,3,3-trifluoroethyl) benzyl isocyanate, benzoyl isocyanate, 2-naphthyl isocyanate, 3-naphthyl isocyanate, 2- Thienyl isocyanate, 2- (isocyanatomethyl) furan, isocyanate, isocyanate, isocyanate, isocyanate, isocyanate, isocyanate, (2-phenylpropyl) isocyanate (3-phenylpropyl), isocyanate 3- (triethoxysilyl) propyl, isocyanate, Acrylates such as 2-isocyanatoethyl acrylate, 2-isocyanato methacrylate, monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, Heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, 1,3-diisocyanatopropene, 1,4-diisocyanate Diisocyanato-2-fluoropropane, 1,4-diisocyanato-2-fluorobutane, 1,4-diisocyanato-2,3- Diisocyanato-2-pentene, 1,5-diisocyanato-2-methylpentane, 1,6-diisocyanato-2-hexene, 1,6-di Isocyanato-3-hexene, 1,6-diisocyanato-3-fluorohexane, 1,6-diisocyanato-3,4-difluorohexane, 1-isocyanato- (Isocyanatomethyl) cyclohexane, 1,2-bis (isocyanatomethyl) cyclohexane, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4- Hexane, 1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, dicyclohexylmethane-4,4'-diisocyanate, dicyclo Hexyl methane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, isophone orone diisocyanate phenyl, phenyl 1,3-diisocyanate, phenyl 1,4-diisocyanate, toluene diisocyanate, xylene diisocyanate, 4-methyldiphenylmethane- , 5,2 ', 4', 6'-pentaisocyanate, and mixtures thereof.

When the electrolyte contains an isothiocyanate group-containing aromatic hydrocarbon compound together with an isocyanate compound as an electrolyte additive, the lifetime at high temperature of the battery can be improved.

Particularly, as the isocyanate compound, there can be mentioned isocyanate compounds such as 2- (trifluoromethoxy) phenyl isocyanate, 3- (trifluoromethoxy) phenyl isocyanate, 4- (trifluoromethoxy) phenyl isocyanate, 2- (Trifluoromethyl) phenyl isocyanate, 4- (trifluoromethyl) phenyl isocyanate, and a mixture thereof is used, the high temperature service life of the battery is further improved .

The aromatic hydrocarbon compound and isocyanate compound containing the isothiocyanate group may be contained in an amount of 0.1 to 10 wt%, preferably 0.1 to 5 wt%, more preferably 0.1 to 3 wt%, based on the total weight of the electrolytic solution, % ≪ / RTI > by weight. When the electrolyte additive is used in such a range, the high temperature service life of the battery can be improved.

The electrolyte may further include an organic solvent and a lithium salt in addition to the electrolyte additive.

The organic solvent may be any organic solvent that can act as a medium through which ions involved in an electrochemical reaction of a battery can move. Specifically, examples of the organic solvent include an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, a carbonate solvent, etc. These solvents may be used singly or in combination of two or more.

Specific examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, But are not limited to, ethyl propionate,? -Butyrolactone, decanolide,? -Valerolactone, mevalonolactone,? -Caprolactone (? -caprolactone, 隆 -valerolactone, 竜 -caprolactone, and the like.

Specific examples of the ether solvent include dibutyl ether, tetraglyme, 2-methyltetrahydrofuran, tetrahydrofuran, and the like.

Specific examples of the ketone-based solvents include cyclohexanone and the like. Specific examples of the aromatic hydrocarbon organic solvent include benzene, fluorobenzene, chlorobenzene, iodobenzene, toluene, fluorotoluene, xylene, (xylene), and the like. Examples of the alkoxyalkane solvent include dimethoxy ethane and diethoxy ethane.

Specific examples of the carbonate solvent include dimethylcarbonate (DMC), diethylcarbonate (DEC), dipropylcarbonate (DPC), methylpropylcarbonate (MPC), ethylpropylcarbonate (EPC) , Methyl ethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylenes carbonate (BC) And fluoroethylene carbonate (FEC).

Among them, a carbonate-based solvent is preferably used as the organic solvent. Among the carbonate-based solvents, a carbonate-based organic solvent having a high ionic conductivity having a high ion conductivity capable of enhancing the charge / discharge performance of the battery, It may be preferable to use a mixture of a carbonate-based organic solvent having a low viscosity which can appropriately control the viscosity of the organic solvent having a high electrical conductivity. Specifically, an organic solvent having a high dielectric constant selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof, and an organic solvent having a low viscosity selected from the group consisting of ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, Can be mixed and used. More preferably, the organic solvent having a high dielectric constant and the organic solvent having a low viscosity are mixed at a volume ratio of 2: 8 to 8: 2, and more specifically, ethylene carbonate or propylene carbonate; Ethyl methyl carbonate; And dimethyl carbonate or diethyl carbonate in a volume ratio of 5: 1: 1 to 2: 5: 3, preferably 3: 5: 2.

The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (C ₂ F ₅ SO ₃ ) _{2 , LiN (C 2 F 5 SO} 2) 2, LiN (CF 3 SO 2) 2. _{LiN (C a F 2a + 1} SO 2) (C b F 2b + 1 SO 2) ( However, a and b is a natural number, preferably 1≤a≤20, 1≤b≤20 and Im), LiCl, LiI, LiB (C ₂ O ₄ ) _2, and mixtures thereof. It is preferable to use lithium hexafluorophosphate (LiPF ₆ ).

When the lithium salt is dissolved in the electrolyte, the lithium salt functions as a source of lithium ions in the lithium secondary battery and can promote the movement of lithium ions between the anode and the cathode. Accordingly, the lithium salt is preferably contained in the electrolyte at a concentration of about 0.6 mol% to 2 mol%. If the concentration of the lithium salt is less than 0.6 mol%, the conductivity of the electrolyte may be lowered and the performance of the electrolyte may be deteriorated. If the concentration exceeds 2 mol%, the viscosity of the electrolyte may increase and the mobility of the lithium ion may be lowered. Considering the conductivity of the electrolyte and the mobility of lithium ions, it is more preferable that the lithium salt is controlled to be approximately 0.7 mol% to 1.6 mol% in the electrolyte.

In addition to the above electrolyte components, the electrolyte may further include an additive (hereinafter, referred to as another additive) which can be generally used for an electrolyte for the purpose of improving lifetime characteristics of the battery, suppressing reduction of battery capacity, have.

Examples of the other additives include vinylene carbonate (vinylenecarbonate, VC), metal fluoride (metal fluoride, for example, LiF, RbF, TiF, AgF , AgF2, BaF 2, CaF 2, CdF 2, FeF 2, HgF ₂ , Hg ₂ F ₂ , MnF ₂ , NiF ₂ , PbF ₂ , SnF ₂ , SrF ₂ , XeF ₂ , ZnF ₂ , AlF ₃ , BF ₃ , BiF ₃ , CeF ₃ , CrF ₃ , DyF ₃ , EuF ₃ , GaF _{3, GdF 3, FeF 3,} HoF 3, InF 3, LaF 3, LuF 3, MnF 3, NdF 3, PrF 3, SbF 3, ScF 3, SmF 3, TbF 3, TiF 3, TmF 3, YF 3, _{YbF 3, TIF 3, CeF 4} , GeF 4, HfF 4, SiF 4, SnF 4, TiF 4, VF 4, ZrF4 4, NbF 5, SbF 5, TaF 5, BiF 5, MoF 6, ReF 6, SF 6 , WF ₆ , CoF ₂ , CoF ₃ , CrF ₂ , CsF, ErF ₃ , PF ₃ , PbF ₃ , PbF ₄ , ThF ₄ , TaF ₅ and SeF ₆ ), glutaronitrile Succinonitrile (SN), adiponitrile (AN), 4-tolunitrile, 1,3,6-hexanetricarbonitrile (1,3,6-hexanetricarbonitrile) Propylene sulfide (PS), 3,3'-T (3,3'-thiodipropionitrile, TPN), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylenecarbonate, fluorodimethyl carbonate fluoromethylcarbonate, fluorodimethylcarbonate, fluoroethylmethylcarbonate, lithium bis (trifluoromethylsulfonyl) imide, LiTFSI, lithium tetrafluoroborate (LiBF ₄ ), lithium bis Lithium bis (oxalato) borate, LiBOB, Lithium difluoro (oxalate) borate, LiDFOB, lithium (malonato oxalate) borate (Lithium (malonato oxalato) ) borate, LiMOB), lithium difluorophosphate (LiPO ₂ F ₂ ), LiPF ₂ C ₄ O ₈ , LiSO ₃ CF ₃ , LiPF ₄ (C ₂ O ₄ ), LiP (C ₂ O ₄ ) ₃ , LiC (SO ₃ CF ₃ ) ₃ , LiBF ₃ (CF ₃ CF ₂ ), LiPF ₃ (CF ₃ CF ₂ ) ₃ , Li ₂ B ₁₂ F ₁₂ , 1,3- , 3-propene sultone, biphenayl, cyclohexyl benzene, 4-fluorotoluene, succinic anhydride, Ethylene sulfate anhydride, and tris (methylsilyl) borate. These may be used singly or in combination of two or more kinds.

The other additives may be contained in an amount of 0.1 to 20% by weight, preferably 0.2 to 5% by weight, based on the total weight of the electrolyte.

According to another embodiment of the present invention, there is provided a lithium secondary battery including the electrolyte. The lithium secondary battery according to an embodiment of the present invention can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and the electrolyte used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, Etc., and can be divided into a bulk type and a thin film type depending on the size. The electrolyte according to the embodiment of the present invention may be particularly excellent for application to a lithium ion battery, an aluminum laminated battery and a lithium polymer battery.

Specifically, the lithium secondary battery includes a cathode including a cathode active material disposed opposite to each other, a cathode including a cathode active material, and the electrolyte interposed between the anode and the cathode.

1 is an exploded perspective view of a lithium secondary battery 1 according to an embodiment of the present invention. 1, a lithium secondary battery 1 according to another embodiment of the present invention includes a separator 7 between a cathode 3, an anode 5, the cathode 3, and an anode 5, (5) and the separator (7) are impregnated into the electrolyte (15) by injecting a non-aqueous electrolyte into the electrode assembly (9) have.

Conductive lead members 10 and 13 for collecting a current generated during a battery operation can be attached to the cathode 3 and the anode 5 respectively and the lead members 10 and 13 are respectively connected to the anode 5, And the current generated in the cathode (3) can be led to the positive electrode and the negative electrode terminal.

The anode 5 is prepared by mixing a cathode active material, a conductive agent and a binder to prepare a composition for forming a cathode active material layer, applying the composition for forming a cathode active material layer to a cathode current collector such as aluminum foil, can do.

As the cathode active material, a compound capable of reversibly intercalating and deintercalating lithium (a lithiated intercalation compound) can be used. Specifically, an olivine-type lithium metal compound represented by the following formula (8) can be used.

[Chemical Formula 8]

Li _x M _y M ' _z XO _4-w Y _w

M and M 'are each independently Fe, Ni, Co, Mn, Cr, Zr, Nb, Cu, V, Mo, Ti, Zn, Al, Ga, Mg, B, And X is an element selected from the group consisting of P, As, Bi, Sb, Mo, and combinations thereof, and Y is selected from the group consisting of F, S, and combinations thereof 0 <x? 1, 0 <y? 1, 0 <z? 1, 0 <x + y + z? 2, and 0? W?

Among these compounds, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Mn _(1-x) O ₂ (where 0 <x <1) and LiM _lx M _2y O ₂ (However, 0≤x≤1, 0≤y≤1, 0≤x + y≤1 , M 1 and M ₂ is one selected from the group consisting of Al, Sr, Mg and La are each independently One), and a mixture thereof.

The negative electrode 3 is prepared by mixing a negative electrode active material, a binder and an optional conductive agent in the same manner as the positive electrode 5 to prepare a composition for forming a negative electrode active material layer and then applying the composition to a negative electrode current collector such as a copper foil .

As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples of the negative electrode active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber and amorphous carbon. Further, in addition to the carbonaceous material, a compound including a metallic compound capable of alloying with lithium or a metallic compound and a carbonaceous material may be used as the negative electrode active material.

At least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys and Al alloys may be used as the metal capable of being alloyed with lithium. Further, a metal lithium thin film may be used as the negative electrode active material.

As the negative electrode active material, any one selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite, lithium metal, lithium-containing alloy, and mixtures thereof may be used in view of high stability.

On the other hand, since the electrolyte is the same as described above with respect to the electrolyte, the description thereof will be omitted. Since the lithium secondary battery can be manufactured by a conventional method, a detailed description thereof will be omitted herein. Although the pouch type lithium secondary battery is described as an example in the present embodiment, the present invention is not limited to the pouch type lithium secondary battery, and any shape can be used as long as it can operate as a battery.

As described above, the lithium secondary battery including the electrolyte according to the embodiment of the present invention can exhibit low DC-IR characteristics, high-temperature storage characteristics, and improved output characteristics, It can be useful for portable devices such as computers, digital cameras, camcorders, electric vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (HEV, PHEV) have.

Hereinafter, embodiments of the present invention will be described in detail 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.

[ Manufacturing example  1: electrolyte and The lithium secondary battery  Produce]

In the following, LiCoO ₂ as a positive electrode active material, carbon black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, n-methyl-2-pyrrolidone -2-pyrrolidone, NMP) was coated on an aluminum (Al) substrate. As the negative electrode, a slurry prepared by mixing MCFC (mesocarbon microbead) and carbon black, PVDF as a binder, and NMP as a solvent was coated on a copper (Cu) substrate, .

( Comparative Example  1-1)

0.5% by weight of vinylene carbonate (VC) was added to a mixed solution of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio by EC / EMC / DMC = 3/5/2) And LiPF _{6 of} 1.15 M to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Comparative Example  1-2)

0.5 part by weight of vinylene carbonate (VC) was added to a mixed solution of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) % And LiPF _{6 of} 1.15 M, and then 1% by weight of LiPO ₂ F ₂ was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. To produce an aluminum pouch-type lithium secondary battery.

( Example  1-1)

0.5 part by weight of vinylene carbonate (VC) was added to a mixed solution of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) % And LiPF _{6 of} 1.15 M, and then 1% by weight of the compound represented by the formula (1) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. The electrolytic solution thus prepared and the anode And an anode were used to produce an aluminum pouch-type lithium secondary battery.

[ Experimental Example  1-1: Evaluation of Capacity Property of Lithium Secondary Battery]

The batteries manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1 were charged at a constant current (CV) / CV (constant voltage) of 4.2 V (cut-off 1C) at a current of 740 mA , And discharged again to 2.7 V with a current of 740 mA. This procedure was repeated 500 times at room temperature and 45 ° C to measure capacity and mAh and capacity retention (%), respectively, and the results are shown in FIGS. 2 to 5, respectively.

FIG. 2 is a graph showing the capacities measured at room temperature of the batteries manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1, FIG. 3 is a graph showing the capacities measured in Comparative Examples 1-1 to 1-2 and Example 1- FIG. 4 is a graph showing the capacity measured at 45 ° C. of the battery manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1. FIG. 4 is a graph showing the capacity retention measured at room temperature , And FIG. 5 is a graph showing the capacity retention ratio measured at 45 ° C. of the batteries manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1.

Referring to FIGS. 2 to 5, it can be seen that Comparative Example 1-2 using LiPO ₂ F ₂ having the best performance among commercially available additives has better capacity and capacity retention at room temperature and 45 ° C. than Comparative Example 1-1 , And the case of Example 1-1 using the additive of the present invention is superior in the capacity and capacity retention rate at room temperature and 45 캜 than that of Comparative Example 1-2.

[ Experimental Example  1-2: Evaluation of storage characteristics of lithium secondary battery]

The batteries manufactured in Comparative Examples 1-1 to 1-2 and Example 1-1 were measured for DC-IR at 60 ° C. The results are shown in Table 1 below. The cells prepared in Comparative Examples 1-1 to 1-2 and 1-1 were allowed to stand at 60 DEG C for 30 days, and the capacity retention was measured. The results are shown in Table 2 below.

Resistance (mΩ) Comparative Example 1-1 71.6 Comparative Example 1-2 70.69 Example 1-1 70.4

Capacity retention (%) Early After 10 days After 30 days Comparative Example 1-1 100 92 86 Comparative Example 1-2 100 92 88 Example 1-1 100 93 89

Referring to Tables 1 and 2, it can be seen that Comparative Example 1-2 using LiPO ₂ F ₂ having the best performance among commercial additives has better preservation characteristics than Comparative Example 1-1. It was found that the storage characteristics of Example 1-1 were better than those of Comparative Example 1-2.

[ Manufacturing example  2: electrolyte and The lithium secondary battery  Produce]

In the following, LiCoO ₂ as a positive electrode active material, carbon black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, n-methyl-2-pyrrolidone -2-pyrrolidone, NMP) was coated on an aluminum (Al) substrate. As the negative electrode, a slurry prepared by mixing MCFC (mesocarbon microbead) and carbon black, PVDF as a binder, and NMP as a solvent was coated on a copper (Cu) substrate, .

( Comparative Example  2-1)

1.0% by weight of vinylene carbonate (VC) was added to a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (mixing ratio by weight of EC / EMC / DMC = 3/5/2) And LiPF _{6 of} 1.15 M to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  2-1)

1.0% by weight of vinylene carbonate (VC) was added to a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (mixing ratio by weight of EC / EMC / DMC = 3/5/2) And LiPF _{6 of} 1.15 M, and 0.5 wt% of the compound represented by the formula (1) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  2-2)

1.0% by weight of vinylene carbonate (VC) was added to a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (mixing ratio by weight of EC / EMC / DMC = 3/5/2) And LiPF _{6 of} 1.15 M, and then 0.5% by weight of 4- (trifluoromethoxy) phenyl isocyanate was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

[ Experimental Example  2-1: Capacity Characteristic Evaluation of Lithium Secondary Battery]

The batteries prepared in Comparative Example 2-1 and Examples 2-1 to 2-2 were charged at 910 mAh under CC / CV (1.5C-0.05C) conditions and CC (1.5C, 2.7V-4.2V) Lt; / RTI &gt;

This process was repeated twice at room temperature and 45 ° C for 300 times to measure capacity (mAh) and efficiency (%). The results are shown in FIGS. 6 to 9, respectively.

FIG. 6 is a graph showing the capacity measured at room temperature of the battery manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2, FIG. 7 is a graph showing the capacity measured in Comparative Example 2-1 and Examples 2-1 to 2- FIG. 8 is a graph showing the capacity measured at 45 ° C of the battery manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2, and FIG. 9 is a graph showing the efficiencies measured at 45 캜 of the batteries manufactured in Comparative Example 2-1 and Examples 2-1 to 2-2.

6 to 9, it can be seen that Example 2-1 in which an additive containing an isothiocyanate group was used had better capacity and efficiency as measured at room temperature and 45 ° C compared to Example 2-2 in which an additive containing an isocyanate group was used It can be seen that it is excellent.

[ Experimental Example  2-2: Evaluation of high-temperature characteristics of lithium secondary battery]

The initial thickness and internal resistance (IR) of the batteries prepared in Comparative Examples 2-1 and 2-1 to 2-2 were measured and stored at 70 캜 for 2 hours at intervals of 15 minutes, Thickness and IR were measured at intervals of 30 minutes until 3 hours after the time, and the results are shown in Figs. 10 and 11.

10 is a graph showing changes in thickness of the battery manufactured at Comparative Example 2-1 and Examples 2-1 to 2-2 with time at a high temperature, To 2-2 are graphs showing changes in internal resistance with time at a high temperature of a battery fabricated at a high temperature.

10 and 11, in Example 2-1 in which an additive containing an isothiocyanate group was used, the change in thickness at high temperature and the increase in internal resistance were smaller than that in Example 2-2 in which an additive containing an isocyanate group was used Less.

[ Manufacturing example  3: electrolyte and The lithium secondary battery  Produce]

In the following, LiCoO ₂ as a positive electrode active material, carbon black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, n-methyl-2-pyrrolidone -2-pyrrolidone, NMP) was coated on an aluminum (Al) substrate. As the negative electrode, a slurry prepared by mixing MCFC (mesocarbon microbead) and carbon black, PVDF as a binder, and NMP as a solvent was coated on a copper (Cu) substrate, .

( Comparative Example  3-1)

LiPF ₆ was added to 1.15 M in a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) Thereby preparing an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  3-1)

LiPF ₆ was added to 1.15 M in a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) Then, 0.3% by weight of the compound represented by the formula (1) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  3-2)

LiPF ₆ was added to 1.15 M in a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) Thereafter, 0.3% by weight of the compound represented by the general formula (2) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  3-3)

LiPF ₆ was added to 1.15 M in a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) Thereafter, 0.3% by weight of the compound represented by the formula (3) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  3-4)

LiPF ₆ was added to 1.15 M in a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) Thereafter, 0.3% by weight of the compound represented by the formula (4) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  3-5)

LiPF ₆ was added to 1.15 M in a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) Thereafter, 0.3% by weight of the compound represented by the formula (5) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  3-6)

LiPF ₆ was added to 1.15 M in a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (mixing ratio of EC / EMC / DMC = 3/5/2) Thereafter, 0.3% by weight of the compound represented by the formula (6) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. An Al-pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

[ Experimental Example  3: Life characteristic evaluation of lithium secondary battery]

The batteries prepared in Comparative Example 3-1 and Examples 3-1 to 3-6 were charged at a CC / CV current of 1000 mA until the voltage reached 4.2 V, and discharged at a current of 1000 mA until the voltage reached 2.7 V The capacity characteristics and the efficiency were measured by repeating 300 times at room temperature. The results are shown in Table 3 below.

additive 300 cycle discharging capacity (mAh) efficiency(%) Comparative Example 3-1 none 840.2 80.2 Example 3-1 Formula 1 855.4 82 Example 3-2 (2) 850.3 81.6 Example 3-3 (3) 851.7 81.8 Example 3-4 Formula 4 850.9 81.8 Example 3-5 Formula 5 847.7 81.4 Examples 3-6 6 849.3 81.6

Referring to Table 3, it can be seen that Examples 3-1 to 3-6 using the additive according to the present invention are superior in 300 cycle discharge capacity and efficiency to Comparative Example 3-1.

[Preparation Example 4: Preparation of electrolytic solution and lithium secondary battery]

In the following, LiCoO ₂ as a positive electrode active material, carbon black as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, n-methyl-2-pyrrolidone -2-pyrrolidone, NMP) was coated on an aluminum (Al) substrate. As the negative electrode, a slurry prepared by mixing MCFC (mesocarbon microbead) and carbon black, PVDF as a binder, and NMP as a solvent was coated on a copper (Cu) substrate, .

(Example 4-1)

Vinylene carbonate (VC) 1.0 was added to a mixed solution of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) (mixing ratio by weight: EC / EMC / DEC = 3/5/2) By weight and LiPF _{6 of} 1.15 M, and then 0.5% by weight of the compound represented by the general formula (1) was added as an electrolyte additive to the total weight of the obtained mixed solution to prepare an electrolytic solution. A lithium secondary battery of an aluminum pouch type (Al-pouch type) was manufactured by using the anode and the cathode.

(Example 4-2)

Vinylene carbonate (VC) 1.0 was added to a mixed solution of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) (mixing ratio by weight: EC / EMC / DEC = 3/5/2) added% by weight and LiPF ₆ was added to a 1.15M, of the formula (1) as the electrolyte additive of the obtained mixed solution was 0.5% by weight of the total weight of the compound and 4- (trifluoromethoxy) phenyl isocyanate, 0.5 weight% A lithium secondary battery of the aluminum pouch type (Al-pouch type) was produced by using the prepared electrolyte and the positive and negative electrodes prepared above.

[Experimental Example 4: Evaluation of Capacity Characteristics of Lithium Secondary Battery]

The batteries manufactured in Examples 4-1 and 4-2 were charged at 910 mAh under CC / CV (1.5C-0.05C) conditions and discharged under CC (1.5C, 2.7V-4.2V) conditions.

This process was repeated 500 times at 45 ° C to measure the capacity (mAh). The results are shown in FIG. 12, respectively.

12 is a graph showing the lifetime performance of the batteries manufactured in Examples 4-1 and 4-2, as measured at 45 캜.

12, Example 4-2 using an additive containing an isocyanate compound and an aromatic hydrocarbon compound showed better lifetime performance at 45 ° C than Example 4-1 using an additive containing an aromatic hydrocarbon compound Able to know.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

1: Lithium secondary battery
3: cathode 5: anode
7: separator 9: electrode assembly
10, 13: lead member 15: case

Claims (8)

Isocyanate compounds and
An electrolyte comprising an aromatic hydrocarbon compound comprising an isothiocyanate group.
The method according to claim 1,
Wherein the aromatic hydrocarbon is selected from the group consisting of benzene, naphthalene, anthracene, phenanthrene, fluorene, pyrene, phenalene, indene, biphenylene, diphenylmethylene, tetrahydronaphthalene, dihydroanthracene, tetraphenylmethylene, triphenylmethylene, pyrrole, &Lt; / RTI &gt; and furan.
The method according to claim 1,
Wherein the aromatic hydrocarbon compound is at least one selected from the group consisting of a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, a nitro group, an amino group, a thio group, a methylthio group, an alkoxy group, a haloalkoxy group, a perfluoroalkoxy group, , An ether group, an ester group, a carbonyl group, an acetal group, a ketone group, an alkyl group, a perfluoroalkyl group, a cycloalkyl group, a heterocycloalkyl group, an allyl group, a benzyl group, an aryl group, a heteroaryl group, &Lt; / RTI &gt; wherein the electrolyte further comprises one of the substituents.
The method of claim 3,
Wherein the aromatic hydrocarbon compound further comprises any one substituent selected from the group consisting of perfluoromethoxy, perfluoroethoxy, perfluoropropoxy, perfluorobutoxy, and combinations thereof.
The method according to claim 1,
Wherein the aromatic hydrocarbon compound is represented by any one selected from the group consisting of the following formulas (1) to (6).
[Chemical Formula 1]

(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

The method according to claim 1,
Wherein the isocyanate compound comprises a compound represented by the following formula (7): &lt; EMI ID =
(7)
(Q) _m --R - (T) _n - (N.dbd.C.dbd.O) _z
R is any one of an aliphatic hydrocarbon and a monovalent to hexavalent residue of an aromatic hydrocarbon, T is an alkylene group, -SO ₂ -, -O- or -CO-, Q is an alkyl group, a cycloalkyl group, a hetero (Meth) acryloyl group, a (meth) acryloyl group, a (meth) acryloyl group, an alkylsulfonyl group, an alkylsulfonyl group, an arylsulfonyl group, an arylsulfonyl group, (Meth) acryloyloxy group, a hydroxyl group, a carboxyl group, a cyano group, an amino group, a thio group, a methylthio group, an aldehyde group, an epoxy group, an acyl group, an acetal group, an allyl group, Z is an integer of 1 to 6, m is an integer of 0 to 5, and n is an integer of 0 to 6.
The method according to claim 1,
Wherein the electrolyte further comprises an organic solvent and a lithium salt.
An anode including a cathode active material,
A negative electrode disposed opposite to the positive electrode and including a negative electrode active material, and
The lithium secondary battery according to claim 1, wherein the electrolyte is interposed between the positive electrode and the negative electrode.

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