KR20170052906A - 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 comprises a compound represented by Formula 1 as an electrolyte additive, so as to provide the electrolyte capable of improving battery characteristics of the lithium secondary battery, in particular, a high voltage and a high temperature performance, and lasting a life cycle of the battery. In Formula 1, R represents any one selected from the group consisting of an alkyl group, an aryl group, an alkenyl group, a cyano group, an amino group, a nitro group, an alkoxy group, a cycloalkyl group, a halogenated alkyl group, and combinations thereof, X represents P or P=O, and n represents an integer of 1 or 6.

Description

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

The present invention relates to a lithium secondary battery, particularly an electrolyte capable of forming a stable film at a high voltage, and a lithium secondary battery comprising the same.

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.

Also, according to the increase in the capacity and high energy of the battery, a demand for a high voltage battery having a full charge voltage of 4 V or more is increasing. However, conventional non-aqueous organic solvent electrolytes show a low oxidation voltage of 4.5 V or less, which makes it difficult to form a high-voltage lithium secondary battery together with a high-voltage cathode material.

The conventional phosphoric acid type additives have problems related to the electrolyte leakage which can not form a stable film at high voltage and in order to complement low thermal stability and low oxidation voltage, flame retardant vapor pressure, high thermal stability, high electrochemical stability, , An ionic liquid having a low toxicity was used as an electrolyte instead of a non-aqueous organic solvent. However, the ionic liquid causes a deterioration in the electrical characteristics of the lithium secondary battery, particularly in the output performance, and the ionic liquid is unstable and relatively high The ionic liquid is repeatedly decomposed on the surface of the negative electrode by the member of the electrode coating or inserted into the electrode due to the reduction potential during charging and discharging, which causes the electrode dropout and shortens the battery life.

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.

Therefore, development of an electrolyte capable of stably forming a film in a high-voltage lithium secondary battery is required.

Korea Patent Publication No. 2015-0022660

An object of the present invention is to provide an electrolyte capable of forming a film stably at a high battery voltage, especially at a high voltage of a lithium secondary battery.

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

To achieve the above object, an electrolyte according to an embodiment of the present invention includes a compound represented by the following formula (1) as an electrolyte additive.

[Chemical Formula 1]

Wherein R is any one selected from the group consisting of an alkyl group, an aryl group, an alkenyl group, a cyano group, an amino group, a nitro group, an alkoxy group, a cycloalkyl group, a halogenated alkyl group, P = O, and n is an integer of 0 to 6.

The R may be a cyano group.

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

The electrolyte additive may be included in an amount of 0.1 to 20% by weight based on the total weight of the electrolyte.

According to another aspect of the present invention, there is provided a lithium secondary battery including: a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material disposed opposite to the positive electrode; and an electrolyte interposed between the positive electrode and the negative electrode, Includes a compound represented by the following formula (1) as an electrolyte additive.

[Chemical Formula 1]

Wherein R is any one selected from the group consisting of an alkyl group, an aryl group, an alkenyl group, a cyano group, an amino group, a nitro group, an alkoxy group, a cycloalkyl group, a halogenated alkyl group, P = O, and n is an integer of 0 to 6.

The electrolyte according to the present invention can stably form a coating film even at high voltage, especially in a battery characteristic of a lithium secondary battery, and can improve the stability even in the life and high voltage state of the 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 a capacity evaluation result of a lithium secondary battery according to Experimental Example 1 of the present invention.

The present invention is capable of various modifications and various embodiments and is intended to illustrate and describe the specific embodiments in detail. It should be understood, however, that the invention is not intended to be limited to the particular 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.

The halogenated alkyl group means a part of the hydrogen atoms or the alkyl group in which the whole hydrogen atoms are substituted with halogen atoms and the halogenated alkoxy group means an alkoxy group in which part of the hydrogen atoms or the whole hydrogen atoms are substituted with halogen atoms. For example, the halogenated alkyl group includes a perfluoroalkyl group, and the halogenated alkoxy group is a perfluoroalkoxy group.

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 straight or branched alkyl group having 1 to 10 carbon atoms, an alkenyl group having 1 to 10 carbon atoms, an allyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, The halogenated alkyl group is a halogenated alkyl group having 1 to 10 carbon atoms, the halogenated alkoxy group is a halogenated alkoxy 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, Group means an aryl group having 6 to 30 carbon atoms, and the heteroaryl group means a heteroaryl group having 2 to 30 carbon atoms.

Unless otherwise specified in the specification, an aryl group means a chemical group obtained by removing one hydrogen atom from a monocyclic or polycyclic compound having 2 to 30 carbon atoms including at least one benzene ring and derivatives thereof, Examples of the monocyclic or polycyclic compound containing a benzene ring include a benzene ring, biphenyl in which two or more benzene rings are bound by a single bond, such as toluene or xylene having an alkyl side chain attached to a benzene ring, etc., a benzene ring is a cycloalkyl group or a heterocyclo Naphthalene or anthracene condensed with two or more benzene rings such as fluorene, xanthene or anthraquinone condensed with an alkyl group, and the like.

Unless otherwise specified in the present specification, an alkenyl group is a chemical group obtained by removing a hydrogen atom from an alkene or a derivative thereof, and includes, for example, an allyl group or a vinyl group.

An electrolyte according to an embodiment of the present invention includes a compound represented by the following formula (1) as an electrolyte additive.

[Chemical Formula 1]

Wherein R is any one selected from the group consisting of an alkyl group, an aryl group, an alkenyl group, a cyano group, an amino group, a nitro group, an alkoxy group, a cycloalkyl group, a halogenated alkyl group and a combination thereof, preferably a cyano group Lt; / RTI >

In Formula 1, X is P or P = O.

Also, n is an integer of 0 to 6, preferably 0 to 4.

In the present invention, the specific examples of the formula (1) are as shown in the following formula (2) or (3).

(2)

(3)

In Formula 2 or 3, n is an integer of 0 to 6, preferably 0 to 4.

When R is a cyano group, the binding energy of the cyano group and the electrode is large, so that a stable film can be formed even at a high voltage, so that the stability and performance of the secondary battery can be improved.

INDUSTRIAL APPLICABILITY The electrolyte additive of the present invention is capable of stably forming a coating film even in a high-voltage state, thereby improving the high-voltage and high-temperature performance and maintaining the life of the secondary battery.

The electrolyte additive may be included in an amount of 0.1 to 20% by weight, preferably 0.2 to 10% by weight, and more preferably 0.5 to 5% by weight based on the total weight of the electrolyte.

If the amount of the electrolyte additive is less than 0.1 wt% based on the total weight of the electrolyte, SEI film may not be formed, and if it exceeds 20 wt%, the thick film is not preferable in view of resistance.

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).

Of these, it is preferable to use a carbonate-based solvent as the organic solvent. Among the carbonate-based solvents, a carbonate-based organic solvent having a high ionic conductivity, which can increase 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. More specifically, ethylene carbonate or propylene carbonate: ethyl methyl carbonate: Carbonate or diethyl carbonate can be used 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 in 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 lithium ion mobility 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 , AgF 2, BaF 2, CaF 2, CdF 2, FeF 2, HF 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 ), glutanonitrile Succinonitrile (SN), adiponitrile (AN), 4-tolunitrile, 1,3,6-hexanetricarbonitrile (1,3,6-hexanetricarbonitrile) , Propylene sulfide (PS), 3,3'- (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 tetrafluoroborate Lithium bis (oxalato) borate, LiBOB, Lithium difluoro (oxalate) borate, LiDFOB), lithium (malonate oxalate) borate malonato oxalato) borate, LiMOB), phosphates of lithium difluoro _{(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 2 CF} 3) 3, LiBF 3 (CF 3 CF 2), LiPF 3 (CF 3 CF 2) 3, Li 2 B 12 F 12, 1,3- propane sultone (1,3-propane sultone, 1,3-propene sultone, biphenayl, cyclohexyl benzene, 4-fluorotoluene, succinonohydride ( succinic anhydride, ethylene sulfate anhydride and tris (trimethylsilyl) borate). One of them may be used singly or two or more of them may be used in combination. have.

The other additives may be included 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 can be applied to a lithium ion battery, an aluminum laminated battery, and a lithium polymer battery, and more particularly to a high voltage 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 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 (4) can be used.

[Chemical Formula 4]

Li _x M _y M ' _z XO _{4 - w} Y _w

In Formula 4, M and M 'are each independently Fe, Ni, Co, Mn, Cr, Zr, Nb, Cu, V, Mo, Ti, Zn, Al, Ga, Mg, B, X is an element selected from the group consisting of P, As, Bi, Sb, Mo, and combinations thereof, and Y is an element selected from the group consisting of F, S, 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 a stable film formation even at a high voltage, and can be applied to a portable device such as a cellular phone, a notebook computer, a digital camera, Such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (HEV, PHEV), and a medium to large-sized energy storage system.

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 : Electrolyte and The lithium secondary battery  Produce]

( Example  One)

Was added to a mixed solution (weight ratio: EC / EMC / DMC = 2/4/4) of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) to make LiPF ₆ 1.15M, An electrolyte was prepared by adding 1 wt% of the compound represented by Formula 2 as an electrolyte additive to the total weight of the mixed solution. An aluminum pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  2)

Was added to a mixed solution (weight ratio: EC / EMC / DMC = 2/4/4) of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) to make LiPF ₆ 1.15M, 1% by weight of the compound represented by the formula (3) as an electrolyte additive was added to the total weight of the mixed solution to prepare an electrolyte. An aluminum pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Comparative Example  One)

Was added to a mixed solution (weight ratio: EC / EMC / DMC = 2/4/4) of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) to make LiPF ₆ 1.15M, An electrolyte was prepared by adding 1 wt% of a compound represented by the following formula (5) as an electrolyte additive to the total weight of the mixed solution. An aluminum pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

[Chemical Formula 5]

(In the above formula (5), R ³¹ is a cyano group, and X ³¹ and X ³² are a fluoro group.)

 [ Experimental Example  One: The lithium secondary battery  Capacity and battery life evaluation]

The batteries manufactured in Examples 1 and 2 and Comparative Example 1 were repeatedly cycled at a high temperature (660 ° C.) for 1 C and 1 C discharge at 750 mA / 4.45 V (CC / CV) The capacity and efficiency were measured and the results of the capacity evaluation of the lithium secondary battery were shown in a graph and a table as shown in FIG. 2 and Table 1 below.

As shown in FIG. 2 and Table 1, in the case of Examples 1 and 2 of the present invention, the battery capacity was about 640 to 670 mAh, which was about 750 mAh at the initial charging and discharging times of 200 cycles, and about 85.2 to 87.2% While in the case of Comparative Example 1, after 200 cycles, the battery capacity of about 750 mAh was reduced to about 70.2% of the initial capacity by about 530 mAh.

[ Experimental Example  2: The lithium secondary battery  Evaluation of high temperature storage capacity]

The batteries prepared in Examples 1 and 2 and Comparative Example 1 were charged to 4.45 V under the condition of 455 mA (CC / CV), and left at 60 DEG C for 30 days. After 30 days, the battery was again charged to 4.45 V under the condition of 455 mA (CC / CV) and the recovery capacity was measured. The results are shown in Table 1 below.

As a result, in Examples 1 and 2, it was charged up to 4.03 V and showed a recovery capacity superior to 3.91 V of Comparative Example 1.

Example 1 Example 2 Comparative Example 1 Battery life evaluation (4.45 V) Efficiency (660 ℃ / 1C charge / 1C discharge) 87.2% 85.2% 70.2% 4.45 V After charging, 60 ℃ storage evaluation (30 days after leaving voltage) 4.03 V 4.03 V 3.91 V

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

Claims (5)

An electrolyte comprising a compound represented by the following formula (1) as an electrolyte additive.
[Chemical Formula 1]

(In the formula 1,
R is any one selected from the group consisting of an alkyl group, an aryl group, an alkenyl group, a cyano group, an amino group, a nitro group, an alkoxy group, a cycloalkyl group, a halogenated alkyl group and a combination thereof, X is P or P = and n is an integer of 0 to 6) The method according to claim 1,
Wherein R is a cyano group. The method according to claim 1,
Wherein the electrolyte additive is contained in an amount of 0.1 to 20% by weight based on the total weight of the electrolyte. 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
And an electrolyte interposed between the anode and the cathode,
Wherein the electrolyte comprises a compound represented by the following formula (1).
[Chemical Formula 1]

(In the formula 1,
R is any one selected from the group consisting of an alkyl group, an aryl group, an alkenyl group, a cyano group, an amino group, a nitro group, an alkoxy group, a cycloalkyl group, a halogenated alkyl group and a combination thereof, X is P or P = and n is an integer of 0 to 6)

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