KR102355697B1 - Electrolyte and lithium secondary battery comprising the same - Google Patents

Abstract

[화학식 2]

상기 화학식 1 및 2에 있어서, 상기 R¹ 내지 R⁵ 및 상기 n은 명세서 중에서 정의한 바와 동일하다.
상기 전해질을 사용한 리튬 이차 전지는 고온에서의 충/방전 효율 및 저저항특성이 우수하며, 특히 고온 장기 수명 효율 및 내부 저항 상승율 저감 효과가 개선된다.The present invention relates to an electrolyte and a lithium secondary battery including the same, wherein the electrolyte includes a compound represented by the following formula (1) and a compound represented by the following formula (2).
[Formula 1]

[Formula 2]

In Formulas 1 and 2, R ¹ to R ⁵ and n are the same as defined in the specification.
The lithium secondary battery using the electrolyte has excellent charge/discharge efficiency and low resistance characteristics at high temperatures, and, in particular, has improved high-temperature long-term lifespan efficiency and internal resistance increase rate reduction effect.

Description

Electrolyte and lithium secondary battery including same

The present invention relates to an electrolyte and a lithium secondary battery including the same, and more particularly, when applied to a lithium secondary battery, it has excellent charge/discharge efficiency and low resistance characteristics at high temperature, and in particular, reduced long-term lifespan efficiency and internal resistance increase rate at high temperature It relates to an electrolyte capable of improving the effect and a lithium secondary battery including the same.

Lithium secondary batteries are used not only as portable power sources for mobile phones, notebook computers, digital cameras, and camcorders, but also as power tools, electric bicycles, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles, etc. Its application is rapidly expanding to medium and large power sources such as HEV and PHEV).

The external shape and size of the battery are also changing in various ways according to the expansion of the application field and the increase in demand, and better performance and stability than the characteristics required for the existing small battery are required. In order to meet these demands, battery components must be stably implemented under the condition that a large current flows.

A lithium secondary battery is manufactured by using a material capable of inserting and deintercalating lithium ions as a negative electrode and a positive electrode, installing a porous separator between the two electrodes, and then injecting a liquid electrolyte, and inserting and removing lithium ions in the negative electrode and positive electrode Electricity is generated or consumed by redox reactions following desorption.

In order to improve battery characteristics such as output characteristics, cycle characteristics, and storage characteristics of lithium secondary batteries, various studies have been made on non-aqueous solvents and additives as electrolyte-equipped components. In addition, even when a specific compound is added to the electrolyte as an additive to improve battery performance, performance improvement of some items of most battery performance can be expected, but the performance of other items is rather reduced.

Meanwhile, worldwide interest in the environment has been concentrated, and interest in eco-friendly vehicles is increasing, and domestic and foreign battery makers are making efforts to develop lithium secondary batteries for automobiles. In a lithium secondary battery for automobiles, one of the important characteristics is the charge/discharge efficiency at high temperature and the low resistance characteristic (DC-IR reduction). The present invention relates to a high-temperature charge/discharge efficiency improvement and low-resistance additive that can be applied to a lithium secondary battery for a vehicle.

US Publication No. 2013-0244122 (published on September 19, 2013)

An object of the present invention is that the lithium secondary battery using the electrolyte according to the present invention has excellent charge/discharge efficiency and low resistance characteristics at high temperature, and in particular, the effect of reducing the high temperature long-term lifespan efficiency and internal resistance increase rate is improved.

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

In order to achieve the above object, the electrolyte according to an embodiment of the present invention includes a compound represented by the following formula (1) and a compound represented by the following formula (2).

[Formula 1]

[Formula 2]

(In Formulas 1 and 2, R ¹ to R ⁵ are each independently any one selected from the group consisting of a hydrogen atom, a methyl group, and an ethyl group, and n is 0 or 1)

The compound represented by Formula 1 may be any one selected from the group consisting of compounds represented by Formulas 1-1 to 1-4 and mixtures thereof.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

The compound represented by Formula 2 may be any one selected from the group consisting of compounds represented by Formulas 2-1 to 2-5 and mixtures thereof.

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

[Formula 2-4]

[Formula 2-5]

The electrolyte may include 0.1 to 10% by weight of the compound represented by Formulas 1 and 2 based on the entire electrolyte.

The electrolyte is any one compound selected from the group consisting of fluoroethylene carbonate (FEC), lithium difluorophosphate (LiPO ₂ F ₂ ), a compound represented by the following Chemical Formula 3, and mixtures thereof may further include.

[Formula 3]

(In Formula 3, R ²¹ is selected from the group consisting of a functional group having a structure of Formulas 3-1 to 3-3, and R ²² is a halogen group, an alkyl group having 1 to 10 carbon atoms, and 1 to 10 carbon atoms. selected from the group consisting of a halogenated alkyl group, an aryl group having 6 to 30 carbon atoms, and a halogenated aryl group having 6 to 30 carbon atoms, wherein X ¹ and X ² are each independently oxygen (O) or sulfur (S), wherein M ₁ is selected from the group consisting of a transition metal element, a group 3B element, a group 4B element, and a group 5B element, and M ₂ is 1A is selected from the group consisting of a group element, a group 2A element, and aluminum (Al), and a is an integer from 1 to 4, b is an integer from 0 to 8, and c, d, e and f are each from 1 to is an integer of 3)

[Formula 3-1]

[Formula 3-2]

[Formula 3-3]

(In Formulas 3-1 to 3-3, R ³¹ is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 30 carbon atoms, and an arylene halogenated arylene group having 6 to 30 carbon atoms. selected from the group consisting of, wherein R ³² and R ³³ are each independently an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms, and a halogenated aryl group having 6 to 30 carbon atoms. selected from)

In the compound represented by Formula 3, R ²² is a halogen group, and X ¹ and X ² is oxygen (O), respectively, M ₁ is phosphorus (P), M ₂ is a group 1A element or a group 2A element, a is an integer of 1 to 3, and b is 2 or 4 is an integer, and c, d, e, and f may each be an integer of 1 to 3.

The compound represented by Formula 3 may be lithium difluorobis(oxalato)phosphate.

The compound represented by Formula 1 and the compound represented by Formula 2 and fluoroethylene carbonate (FEC), lithium difluorophosphate (LiPO ₂ F ₂ ), the compound represented by Formula 3 and these Any one or more compounds selected from the group consisting of a mixture of may be included in the electrolyte in a weight ratio of 1:10 to 10:1.

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

The organic solvent may be selected from the group consisting of an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, a carbonate solvent, and mixtures thereof.

The organic solvent may include a high dielectric constant organic solvent and a low viscosity organic solvent in a volume ratio of 2:8 to 8:2.

The high dielectric constant organic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof, and the low viscosity organic solvent is ethylmethylcarbonate, dimethylcarbonate, It may be selected from the group consisting of diethyl carbonate and mixtures thereof.

The organic solvent is one of ethylene carbonate and propylene carbonate; ethyl methyl carbonate; And one of dimethyl carbonate and diethyl carbonate may be included in a volume ratio of 5:1:1 to 2:5:3.

The lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 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 . It may be selected from the group consisting of LiN(C _a F _2a+1 SO ₂ )(C _b F _2b+1 SO ₂ ) (provided that a and b are natural numbers), LiCl, LiI, and mixtures thereof.

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

Other specific details of embodiments of the present invention are included in the detailed description below.

The lithium secondary battery using the electrolyte according to the present invention has excellent charge/discharge efficiency and low resistance characteristics at high temperatures, and in particular, the high temperature long-term lifespan efficiency and the effect of reducing the internal resistance (DC-IR) increase rate are improved.

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

Since the present invention can apply various transformations and can have various embodiments, specific embodiments are illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as 'comprising' or 'having' are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, and one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

All compounds or functional groups in the present specification may be substituted or unsubstituted unless otherwise specified. Here, 'substituted' means that at least one hydrogen included in the compound or functional group is a halogen atom, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group, a cycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a hydroxy group. , means substituted with a substituent selected from the group consisting of an alkoxy group having 1 to 10 carbon atoms, a carboxylic acid group, an aldehyde group, an epoxy group, a cyano group, a nitro group, an amino group, a sulfonic acid group, and derivatives thereof.

In addition, in the present specification, unless otherwise specified as 'a combination of these', two or more functional groups are a single bond, a double bond, a triple bond, an alkylene group having 1 to 10 carbon atoms (eg, methylene (-CH ₂ -), Ethylene (-CH ₂ CH ₂ -), etc.), a fluoroalkylene group having 1 to 10 carbon atoms (eg, fluoromethylene (-CF ₂ -), perfluoroethylene (-CF ₂ CF ₂ -), etc.) ), a hetero atom such as N, O, P, S, or Si or a functional group containing the same (specifically, an intramolecular carbonyl group (-C=O-), an ether group (-O-), an ester group (-COO) -), -S-, -NH- or -N=N- (heteroalkylene group including -N=N-, etc.) is bonded by a linking group, or two or more functional groups are condensed or connected.

The electrolyte according to an embodiment of the present invention includes a compound represented by the following formula (1) and a compound represented by the following formula (2).

The compound represented by Formula 1 has excellent charge/discharge efficiency and low resistance characteristics at high temperature, so it is a promising material for use as an electrolyte additive for lithium secondary batteries for automobiles, but there is a problem in that lifespan efficiency is lowered in high temperature long-term life evaluation. . However, when the compound represented by the formula (2) is used together with the compound represented by the formula (1), the high temperature performance and the effect of reducing the internal resistance increase rate are excellent.

[Formula 1]

In Formula 1, R ¹ and R ² are each independently any one selected from the group consisting of a hydrogen atom, a methyl group, and an ethyl group.

[Formula 2]

In Formula 2, R ³ to R ⁵ are each independently any one selected from the group consisting of a hydrogen atom, a methyl group, and an ethyl group, and n is 0 or 1.

Specifically, when the compound represented by Formula 1 is exemplified, it is the same as the compound represented by the following Formulas 1-1 to 1-4.

[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

Specifically, when the compound represented by Formula 2 is exemplified, it is the same as the compound represented by the following Formulas 2-1 to 2-5.

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

[Formula 2-4]

[Formula 2-5]

The electrolyte may include the compound represented by Chemical Formula 1 and the compound represented by Chemical Formula 2 in an amount of 0.1 to 10% by weight based on the entire electrolyte. When the content of the compound is less than 0.1% by weight, the effect according to the use of the compound is insignificant, and when it exceeds 10% by weight, there is a fear that the initial capacity is reduced. Preferably, a greater improvement effect can be obtained when the compounds represented by Chemical Formulas 1 and 2 are each independently included in an amount of 0.5 to 3% by weight based on the total weight of the electrolyte.

On the other hand, the electrolyte is fluoroethylene carbonate (fluoroethylene carbonate, FEC), lithium difluorophosphate (lithium difluorophosphate, LiPO ₂ F ₂ ), any one selected from the group consisting of compounds represented by the following formula (3) and mixtures thereof It may further include a compound of

Generally, in the case of high-voltage electrolyte additives, they adsorb to defect points or activation points on the surface of the anode of the electrochemical device to suppress the oxidative decomposition reaction of the non-aqueous electrolyte, or form a complex with the metal ions eluted from the anode so that the metal ions are electrodeposited on the cathode. refrain from doing However, the FEC, LiPO ₂ F ₂ and the compound represented by Chemical Formula 3 form a solid electrolyte interface (SEI) on the surface of the negative electrode and the positive electrode to stabilize the battery, and thus the battery characteristics of the lithium secondary battery, particularly high voltage and high temperature It can improve performance, suppress gas generation, and improve overcharge prevention properties. In particular, the _{compounds represented by FEC, LiPO 2} F ₂ and Chemical Formula 3 are selected because they can maximize the above effects in the electrolyte including the compounds represented by Chemical Formulas 1 and 2.

[Formula 3]

In Formula 3, R ²¹ is selected from the group consisting of functional groups having structures of Formulas 3-1 to 3-3 below.

[Formula 3-1]

[Formula 3-2]

[Formula 3-3]

In Formulas 3-1 to 3-3, R ³¹ is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 30 carbon atoms, and a halogenated arylene group having 6 to 30 carbon atoms. selected from the group, wherein R ³² and R ³³ are each independently an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms, and a halogenated aryl group having 6 to 30 carbon atoms. is chosen

In addition, in Formula 3, R ²² is selected from the group consisting of a halogen group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms, and a halogenated aryl group having 6 to 30 carbon atoms. and x ¹ and X ² are each independently oxygen (O) or sulfur (S), and M ¹ is a transition metal element, or selected from the group consisting of a group 3B element, a group 4B element, and a group 5B element in the short-period periodic table. and M ² is selected from the group consisting of a group 1A element, a group 2A element, and aluminum (Al) in the short-period periodic table, and a is an integer from 1 to 4, and b is from 0 to 8 Integer, c, d, e and f are each an integer of 1 to 3.

Preferably, in Formula 3, R ²¹ is selected from the group consisting of a functional group having the structures of Formulas 3 to 5, and R ²² is a halogen group, preferably a fluoro group. In addition, the X ¹ and X ² may both be oxygen (O). M ₁ may be phosphorus (P), and M ₂ may be a group 1A or 2A element in the short-period periodic table, and more preferably lithium. And, a is an integer of 1 to 3, b is an integer of 2 or 4, and c, d, e, and f may be an integer of 1 to 3, respectively.

Specifically, the compound represented by Formula 3 may be lithium tetrafluoro(oxalato)phosphate or lithium difluorobis(oxalato)phosphate, etc. Among them, lithium difluorobis(oxalato)phosphate represented by the following formula (3a) may be more preferable in terms of improvement effect:

[Formula 3a]

The FEC, LiPO ₂ F ₂ and the compound represented by Formula 3 may be included in an amount of 0.1 to 10 wt%, preferably 0.5 to 3 wt%, based on the total weight of the electrolyte. When the content of the compound is less than 0.1% by weight, the effect of the use of the compound is insignificant, and when it exceeds 10% by weight, there is a risk that the lifespan maintenance rate may decrease, and if the content is too large, there is a risk of side reactions have.

In addition, the compound represented by Formula 1 and the compound represented by Formula 2 and fluoroethylene carbonate (FEC), lithium difluorophosphate (LiPO ₂ F ₂ ), represented by the following Formula 3 Any one or more compounds selected from the group consisting of compounds and mixtures thereof may be included in the electrolyte in a weight ratio of 1:10 to 10:1, preferably in a weight ratio of 5:1 to 5:1. _{When the amount of FEC, LiPO 2} F ₂ and the compound represented by Formula 3 is too low in the content of the compound represented by Formula 1 and the compound represented by Formula 2 _{, the FEC, LiPO 2} F ₂ and Formula 3 represented by the swelling property improving effect of the use of a compound negligible, and that the FEC, LiPO ₂ F ₂ and the content of the compound represented by General formula (3) relative to the content of the compound represented by formula and formula 2 represented by the formula (1) If it is too high, there may be a problem of deterioration of the overall lifespan maintenance rate.

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

The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, a carbonate solvent, etc. may be used, and among these solvents, one type alone or two or more types may be mixed.

Specific examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, and ethyl propionate. Cypionate (ethyl propionate), γ-butyrolactone (γ-butyrolactone), decanolide (decanolide), γ-valerolactone (γ-valerolactone), mevalonolactone (mevalonolactone), γ-caprolactone (γ -caprolactone), δ-valerolactone, or ε-caprolactone (ε-caprolactone).

Specific examples of the ether-based solvent include dibutyl ether, tetraglyme, 2-methyltetrahydrofuran, or tetrahydrofuran.

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

Specific examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC) , methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylenes carbonate (BC), or fluoro and ethylene carbonate (FEC).

Among them, it is preferable to use a carbonate-based solvent as the organic solvent, and more preferably among the carbonate-based solvents, a carbonate-based organic solvent having high ionic conductivity capable of increasing the charge/discharge performance of a battery, and the intrinsic It may be preferable to use a mixture of a carbonate-based organic solvent having a low viscosity that can appropriately adjust the viscosity of the organic solvent of the totality. Specifically, an organic solvent of high dielectric constant selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof, and an organic solvent of low viscosity selected from the group consisting of ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, and mixtures thereof. It can be used by mixing. More preferably, the high dielectric constant organic solvent and the low viscosity organic solvent are mixed in 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 may be mixed in a volume ratio of 5:1:1 to 2:5:3, and preferably mixed in a volume ratio of 3:5:2.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, as the lithium salt, LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 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 ) (provided that a and b are natural numbers, preferably 1≤a≤20, and 1≤b≤20), LiCl, LiI, and one selected from the group consisting of mixtures thereof may be used, and lithium hexafluorophosphate (LiPF ₆ ) is preferably used.

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 may promote movement of lithium ions between the positive electrode and the negative electrode. 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 thus electrolyte performance may be deteriorated. Considering the conductivity of the electrolyte and the mobility of lithium ions, it may be more preferable that the lithium salt be adjusted to approximately 0.7 mol% to 1.6 mol% in the electrolyte.

In addition to the electrolyte components, the electrolyte further includes additives (hereinafter referred to as 'other additives') that can be generally used in the electrolyte for the purpose of improving battery life characteristics, suppressing reduction in battery capacity, and improving battery discharge capacity. can do.

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, 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 , SeF 6 ,} etc.), glutaronitrile (GN), Succinonitrile (SN), adiponitrile (AN), 4-tolunitrile (4-tolunitrile), 1,3,6-hexane tricarbonitrile (1,3,6-hexanetricarbonitrile) , propylene sulfide (PS), 3,3'-thiodipropionitrile (TPN), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC) ), difluoroethylene carbonate (difluoroethylenecarbo nate), fluorodimethylcarbonate, fluoroethylmethylcarbonate, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium tetrafluoroborate (Lithium) tetrafluoroborate, LiBF ₄ ), Lithium bis(oxalato)borate (LiBOB), Lithium difluoro (oxalato) borate (LiDFOB), Lithium (malonato oxalato)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 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-propanesultone(1,3-propane sultone), 1,3-propene sultone, biphenayl, cyclohexyl benzene, 4-fluorotoluene, succinoanhydride ( succinic anhydride), ethylene sulfate anhydride, tris(trimethylsilyl)borate, and the like, and may include one type alone or a mixture of two or more thereof. have.

The other additives may be included in an amount of 0.1 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. A lithium secondary battery according to an embodiment of the present invention may be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of separator and electrolyte used, and may be cylindrical, prismatic, coin-type, or pouch-type according to the shape. and the like, and may be divided into a bulk type and a thin film type according to 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 laminate battery, and a lithium polymer battery.

In detail, the lithium secondary battery includes a positive electrode including a positive electrode active material disposed opposite to each other, a negative electrode including a negative electrode active material, and the electrolyte interposed between the positive electrode and the negative electrode.

1 is an exploded perspective view of a lithium secondary battery 1 according to an embodiment of the present invention. Referring to FIG. 1 , a lithium secondary battery 1 according to another embodiment of the present invention includes a negative electrode 3 , a positive electrode 5 , and a separator 7 between the negative electrode 3 and the positive electrode 5 . to prepare an electrode assembly 9 by placing it, placing it in a case 15, and injecting a non-aqueous electrolyte so that the negative electrode 3, the positive electrode 5 and the separator 7 are impregnated with the electrolyte. have.

Conductive lead members 10 and 13 for collecting current generated during battery operation may be attached to the negative electrode 3 and the positive electrode 5, respectively, and the lead members 10 and 13 are respectively the positive electrode 5 And it is possible to induce the current generated in the negative electrode 3 to the positive and negative terminals.

The positive electrode 5 is manufactured by mixing a positive electrode active material, a conductive agent and a binder to prepare a composition for forming a positive electrode active material layer, applying the composition for forming a positive electrode active material layer on a positive electrode current collector such as aluminum foil, and then rolling can do.

As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) may be used. Specifically, an olivine-type lithium metal compound represented by the following Chemical Formula 6 may be used.

[Formula 6]

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

(In Formula 6, M and M' are each independently Fe, Ni, Co, Mn, Cr, Zr, Nb, Cu, V, Mo, Ti, Zn, Al, Ga, Mg, B, and combinations thereof is an element selected from the group consisting of, 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. element, 0<x≤1, 0<y≤1, 0<z≤1, 0<x+y+z≤2, 0≤w≤0.5)

Among the above compounds, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Mn _(1-x) O ₂ (provided that 0<x<1), LiM _lx M _2y O ₂ (provided that 0≤x≤1, 0≤y≤1, 0≤x+y≤1, M ₁ and M ₂ are each independently selected from the group consisting of Al, Sr, Mg and La one) and mixtures thereof may be preferably used.

The negative electrode 3 is prepared by mixing a negative electrode active material, a binder and optionally a 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 coating it on a negative electrode current collector such as copper foil. can

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

As the metal capable of alloying with lithium, at least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, and Al alloy may be used. In addition, a metal lithium thin film may be used as the negative electrode active material.

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

On the other hand, since the electrolyte is the same as described in the section related to the electrolyte, the description thereof is omitted. Since the lithium secondary battery may be manufactured by a conventional method, a detailed description thereof will be omitted herein. In this embodiment, a pouch-type lithium secondary battery has been described as an example, but the technology of the present invention is not limited to a pouch-type lithium secondary battery, and any shape may be possible as long as it can operate as a battery.

As described above, the lithium secondary battery including the electrolyte according to an embodiment of the present invention can exhibit low DC-IR characteristics, high temperature storage characteristics, and improved output characteristics, so that a fast charging speed is required for mobile phones and notebook computers. It can be useful for portable devices such as computers, digital cameras, and camcorders, electric vehicles such as hybrid electric vehicles (HEVs) and plug-in hybrid electric vehicles (PHEVs), and medium to large-sized energy storage systems. have.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

[ Example and comparative example : Preparation of electrolyte]

_{0.9M LiPF 6} as a lithium salt, a mixed solvent in which ethylene carbonate (EC), ethylmethylcarbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 30:50:20 as an organic solvent, and Table 1 below As shown in , an electrolyte was prepared using the compound represented by Formula 1 and the compound represented by Formula 2 above.

Chemical Formula 1 Type Formula 1 content 2 types of chemical formula Formula 2 content FEC LiPO ₂ F ₂ Lithium difluorobis(oxalato)phosphate Comparative Example 1 Formula 1-1 0.8 - - - - - Comparative Example 2 - - Formula 2-1 0.8 - - - Example 1 Formula 1-1 0.3 Formula 2-1 0.5 - - - Example 2 Formula 1-1 0.3 Formula 2-1 0.5 One 0.5 - Example 3 Formula 1-1 0.3 Formula 2-1 0.5 - - One Example 4 Formula 1-1 0.3 Formula 2-1 0.5 One - - Example 5 Formula 1-1 0.3 Formula 2-1 0.5 - - 1.3 Example 6 Formula 1-1 0.3 Formula 2-1 0.5 0.5 One Example 7 Formula 1-2 0.3 Formula 2-1 0.5 - - - Example 8 Formula 1-3 0.3 Formula 2-1 0.5 - - - Example 9 Formula 1-4 0.3 Formula 2-1 0.5 - - - Example 10 Formula 1-1 0.3 Formula 2-2 0.5 - - - Example 11 Formula 1-1 0.3 Formula 2-3 0.5 - - - Example 12 Formula 1-1 0.3 Formula 2-4 0.5 - - - Example 13 Formula 1-1 0.3 Formula 2-5 0.5 - - -

(Unit: % by weight)

[ production example : Preparation of lithium secondary battery]

A composition for forming a cathode active material layer comprising 85 wt% of lithium cobalt oxide (LiCoO ₂ ) as a cathode active material, 7.5 wt% of polyvinylidene fluoride as a binder, and 7.5 wt% of super-P carbon as a conductive material, as a current collector, aluminum foil After coating on the top, drying was performed to prepare a positive electrode. In addition, after coating a composition for forming an anode active material layer comprising 88 wt% of artificial graphite as an anode active material, 4 wt% of super-P carbon as a conductive material and 8 wt% of polyvinylidene fluoride as a binder on a copper foil as a current collector, It dried to prepare a negative electrode. A separator was placed on the positive electrode prepared above, and then a carbon negative electrode was placed there again, the electrolytes prepared in Examples and Comparative Examples were respectively injected, and the lithium secondary battery was prepared by vacuum packaging in an aluminum pouch.

In order to evaluate the lifespan characteristics according to the charging and discharging of the lithium secondary battery containing the electrolyte according to the present invention, after each injection of the electrolyte prepared in the above Preparation Example into a 1Ah class pouch cell, CC (Constant current) / It was charged at 4.2V (0.5C rate) under CV (constant voltage) conditions, and was discharged to 2.7V under CC (0.5C rate) conditions after resting for 10 minutes. At this time, the standard capacity (Normal capacity) was 1000mAh. The charging and discharging were repeated as one cycle and 300 cycles were repeated to measure the capacity change according to the charging and discharging. The results are shown in Tables 2 and 3 below.

Battery life efficiency (45℃ Cycle Efficiency(%)) Initial Cycle 300 cycles Comparative Example 1 100 77.9 Comparative Example 2 100 72.6 Example 1 100 83.4 Example 2 100 84.0 Example 7 100 82.1

DC-IR (mΩ) after standing at 60℃ 0 weeks 4 weeks Comparative Example 1 35.2 61.4 Comparative Example 2 33.7 62.9 Example 1 32.9 56.4 Example 2 31.3 54.3 Example 7 31.7 58.8

As a result of the battery life efficiency test and low resistance test result, Examples 1 to 3, which are batteries including an electrolyte including the compound represented by Formula 1 and the compound represented by Formula 2 at the same time, showed significantly increased charge/discharge efficiency at high temperature. And compared to the batteries of Comparative Example 1 and Comparative Example 2 containing only the compound represented by Formula 1 and containing only the compound represented by Formula 1 while exhibiting charge DC-IR, the high temperature long-term lifespan efficiency and the internal resistance increase rate reduction effect were improved. It was found that the same level of results were obtained for Examples 3 to 6 and 8 to 13.

In particular, in the case of Example 2 further comprising fluoroethylene carbonate (FEC) and lithium difluorophosphate (LiPO ₂ F ₂ ), the battery life efficiency and DC-IR values were obtained in Examples 1 and 3 was even better.

In the above, an embodiment of the present invention has been described, but those of ordinary skill in the art can add, change, delete or add components within the scope that does not depart from the spirit of the present invention described in the claims. It will be possible to variously modify and change the present invention by, etc., which will also be included within the scope of the present invention.

1: lithium secondary battery
3: negative electrode 5: positive electrode
7: separator 9: electrode assembly
10, 13: lead member 15: case

Claims (15)

any one compound selected from the group consisting of compounds represented by the following Chemical Formulas 1-1 to 1-4 and mixtures thereof; and
An electrolyte comprising a; any one compound selected from the group consisting of compounds represented by the following Chemical Formulas 2-1 to 2-5 and mixtures thereof.
[Formula 1-1]

[Formula 1-2]

[Formula 1-3]

[Formula 1-4]

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

[Formula 2-4]

[Formula 2-5]

delete delete According to claim 1,
The electrolyte is an electrolyte comprising 0.1 to 10% by weight of the compound represented by Formulas 1-1 to 1-4 and the compound represented by Formulas 2-1 to 2-5 with respect to the entire electrolyte. According to claim 1,
The electrolyte is any one compound selected from the group consisting of fluoroethylene carbonate (FEC), lithium difluorophosphate (LiPO ₂ F ₂ ), a compound represented by the following Chemical Formula 3, and mixtures thereof Electrolyte that further comprises.
[Formula 3]

(In Formula 3,
wherein R ²¹ is selected from the group consisting of a functional group having a structure represented by the following Chemical Formulas 3-1 to 3-3,
wherein R ²² is selected from the group consisting of a halogen group, an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms, and a halogenated aryl group having 6 to 30 carbon atoms,
said X ¹ And X ² are each independently oxygen (O) or sulfur (S),
Wherein M ₁ is selected from the group consisting of a transition metal element, a 3B group element, a 4B group element, and a 5B group element,
The M ₂ is selected from the group consisting of a group 1A element, a group 2A element, and aluminum (Al), and
wherein a is an integer from 1 to 4, b is an integer from 0 to 8, and c, d, e and f are each an integer from 1 to 3,
[Formula 3-1]

[Formula 3-2]

[Formula 3-3]

In Formulas 3-1 to 3-3, R ³¹ is an alkylene group having 1 to 10 carbon atoms, a halogenated alkylene group having 1 to 10 carbon atoms, an arylene group having 6 to 30 carbon atoms, and a halogenated arylene group having 6 to 30 carbon atoms. selected from the group, wherein R ³² and R ³³ are each independently an alkyl group having 1 to 10 carbon atoms, a halogenated alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms, and a halogenated aryl group having 6 to 30 carbon atoms. is chosen) 6. The method of claim 5,
In the compound represented by Formula 3, R ²² is a halogen group, and X ¹ and X ² is oxygen (O), respectively, M ₁ is phosphorus (P), M ₂ is a group 1A element or a group 2A element, a is an integer of 1 to 3, and b is 2 or 4 of an integer, and c, d, e and f are each an integer of 1 to 3. The electrolyte. 6. The method of claim 5,
The compound represented by the formula (3) is lithium difluorobis (oxalato) phosphate (lithium difluorobis (oxalato) phosphate) electrolyte. 6. The method of claim 5,
The compound represented by Formulas 1-1 to 1-4 of claim 1, the compound represented by Formulas 2-1 to 2-5, and the fluoroethylene carbonate (FEC) of claim 5, lithium difluorophosphate (lithium difluorophosphate, LiPO ₂ F ₂ ), any one or more compounds selected from the group consisting of compounds represented by the following formula (3) and mixtures thereof are included in the electrolyte in a weight ratio of 1:10 to 10:1 electrolyte. According to claim 1,
The electrolyte further comprises an organic solvent and a lithium salt. 10. The method of claim 9,
The organic solvent is an electrolyte selected from the group consisting of an ester solvent, an ether solvent, a ketone solvent, an aromatic hydrocarbon solvent, an alkoxyalkane solvent, a carbonate solvent, and mixtures thereof. 10. The method of claim 9,
The organic solvent is an electrolyte comprising a high dielectric constant organic solvent and a low viscosity organic solvent in a volume ratio of 2:8 to 8:2. 12. The method of claim 11,
The high dielectric constant organic solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof,
The low-viscosity organic solvent is an electrolyte selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and mixtures thereof. 12. The method of claim 11,
The organic solvent is one of ethylene carbonate and propylene carbonate; ethyl methyl carbonate; And an electrolyte comprising one of dimethyl carbonate and diethyl carbonate in a volume ratio of 5:1:1 to 2:5:3. 10. The method of claim 9,
The lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 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 . An electrolyte selected from the group consisting of LiN(C _a F _2a+1 SO ₂ )(C _b F _2b+1 SO ₂ ), provided that a and b are natural numbers, LiCl, LiI, and mixtures thereof. A positive electrode comprising a positive electrode active material;
a negative electrode disposed opposite to the positive electrode and including an anode active material; and
Interposed between the positive electrode and the negative electrode, a lithium secondary battery comprising the electrolyte according to claim 1 .

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