KR20160078071A - 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 an electrolyte containing a compound represented by chemical formula 1 as an electrolyte additive. Therefore, the electrolyte can improve cell characteristics of the lithium secondary battery and particularly room temperature life and high temperature performance, and reduce an initial resistance. In chemical formula 1, R^1 to R^3 are a substituent of any one selected from the group consisting of an alkyl group, halogenated alkyl group, alkoxy group, nitrile group, nitro group, isocyanate group, and isothiocyanate group.

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.

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

[Chemical Formula 1]

(Wherein R &^lt; ¹ > to R &^lt; ³ &^gt; Is any one substituent selected from the group consisting of an alkyl group, a halogenated alkyl group, an alkoxy group, a nitrile group, a nitro group, an isocyanate group and an isothiocyanate group)

The electrolyte contains 0.1 to 10% by weight of the compound represented by Formula 1 based on the total weight of the electrolyte.

The compound represented by the formula (1) is represented by the following formula (2).

(2)

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

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).

[Chemical Formula 1]

(Wherein R &^lt; ¹ > to R &^lt; ³ &^gt; Is any one substituent selected from the group consisting of an alkyl group, a halogenated alkyl group, an alkoxy group, a nitrile group, a nitro group, an isocyanate group and an isothiocyanate group)

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.

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, the halogenated alkyl group means a part of hydrogen atoms or an alkyl group in which all hydrogen atoms are substituted with halogen atoms, and the halogenated alkyl group may be, for example, a perfluoroalkyl group, Quot; means an alkyl group in which a hydrogen atom or a whole hydrogen atom is substituted with fluorine.

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 means a linear or branched alkyl group having 1 to 10 carbon atoms, and a halogenated alkyl group means a halogenated alkyl group having 1 to 10 carbon atoms.

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 &^lt; ¹ > to R &^lt; ³ &^gt; Is any one substituent selected from the group consisting of an alkyl group, a halogenated alkyl group, an alkoxy group, a nitrile group, a nitro group, an isocyanate group and an isothiocyanate group.

The electrolyte additive may be contained in an amount of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, and more preferably 0.1 to 3% by weight based on the total weight of the electrolyte. If the content of the electrolyte additive is less than 0.1% by weight based on the total weight of the electrolyte, the effect of the addition may be insignificant. If the content of the electrolyte additive exceeds 10% by weight, ion conductivity may be lowered and battery performance may be deteriorated.

The electrolyte additive may specifically be a compound represented by the following general formula (2).

(2)

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 , 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 ), glutaronitrile 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 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 (3) can be used.

(3)

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

M and M 'are 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 : 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  One)

LiPF ₆ was added to a mixed solution (EC / EMC / DMC = 2/4/4) of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate Respectively. An aluminum pouch type lithium secondary battery was fabricated using the electrolyte prepared above and the positive and negative electrodes prepared above.

( Example  One)

LiPF ₆ was added to a mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (weight ratio: EC / EMC / DMC = 2/4/4) And 0.3 wt% of a compound represented by the following formula (2) 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.

(2)

[ Experimental Example : Evaluation of Life Characteristic of Lithium Secondary Battery]

The batteries manufactured in Comparative Examples 1 and 1 were charged at a CC / CV current of 1000 mA until a voltage of 4.2 V was reached, and discharging was repeated 500 times at a room temperature until a voltage of 2.7 V was reached with a current of 1000 mA, And the results are shown in Table 1 below.

additive 500cycle
Discharge capacity (mAh) efficiency(%) Comparative Example 1 none 724 mAh 82% @ 500 times Example 1 (2) 785 mAh 89% @ 500 times

Referring to Table 1, it can be seen that the capacity and efficiency of the lithium secondary battery manufactured in Example 1 is superior to that of the lithium secondary battery manufactured in Comparative Example 1.

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

Claims (5)

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

(Wherein R &^lt; ¹ &gt; to R &^lt; ³ &^gt; Is any one substituent selected from the group consisting of an alkyl group, a halogenated alkyl group, an alkoxy group, a nitrile group, a nitro group, an isocyanate group and an isothiocyanate group) The method according to claim 1,
Wherein the electrolyte comprises 0.1 to 10% by weight of the compound represented by Formula 1 based on the total weight of the electrolyte. The method according to claim 1,
Wherein the compound represented by the formula (1) is represented by the following formula (2).
(2)

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]

(Wherein R &^lt; ¹ &gt; to R &^lt; ³ &^gt; Is any one substituent selected from the group consisting of an alkyl group, a halogenated alkyl group, an alkoxy group, a nitrile group, a nitro group, an isocyanate group and an isothiocyanate group)

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