KR102308599B1 - Electrolyte for Lithium Secondary Battery and Lithium Secondary Battery Containing the Same - Google Patents

Abstract

The present invention provides a lithium secondary battery electrolyte and a lithium secondary battery comprising the same, and the secondary battery electrolyte of the present invention has very excellent high-temperature stability, low-temperature discharge capacity and lifespan characteristics.

Description

Lithium secondary battery electrolyte and lithium secondary battery containing same

The present invention relates to a lithium secondary battery electrolyte and a lithium secondary battery containing the same, and more particularly, to a lithium secondary battery electrolyte containing a boron derivative and a lithium secondary battery including the same.

In recent years, portable electronic devices have been widely disseminated, and with the rapid miniaturization, weight reduction and thinning of these portable electronic devices, the battery, which is the power source, is also small, lightweight, capable of charging and discharging for a long time, and is a secondary battery with excellent high rate characteristics. Development is strongly demanded.

Among the currently applied secondary batteries, lithium secondary batteries developed in the early 1990s have a higher operating voltage and significantly higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and lead sulfate batteries using aqueous electrolyte solutions. is gaining popularity as However, such a lithium secondary battery has safety problems such as ignition and explosion due to the use of a non-aqueous electrolyte, and these problems become more serious as the capacity density of the battery increases.

In the case of a non-aqueous electrolyte secondary battery, a decrease in safety of the battery that occurs during continuous charging is a major problem. One of the causes that can affect this is heat generation due to the structural collapse of the anode. Its working principle is as follows. That is, the positive electrode active material of the non-aqueous electrolyte battery is made of a lithium-containing metal oxide capable of occluding and releasing lithium and/or lithium ions. Such a positive electrode active material is transformed into a thermally unstable structure as a large amount of lithium is released during overcharging. do. In such an overcharged state, when the battery temperature reaches a critical temperature due to an external physical shock, for example, exposure to high temperature, oxygen is released from the cathode active material having an unstable structure, and the released oxygen causes an exothermic decomposition reaction with an electrolyte solvent and the like. In particular, since the combustion of the electrolyte solution is further accelerated by oxygen released from the positive electrode, ignition and rupture of the battery due to thermal runaway are caused by such a chain exothermic reaction.

A method of adding an aromatic compound as a redox shuttle additive in an electrolyte solution is used to control ignition or explosion due to an increase in temperature inside the battery as described above. For example, Japanese Patent JP2002-260725 discloses a non-aqueous lithium ion battery capable of preventing overcharge current and thermal runaway by using an aromatic compound such as biphenyl. In addition, in U.S. Patent No. 5,879,834, a small amount of aromatic compounds such as biphenyl and 3-chlorothiophene are added to improve battery safety by electrochemically polymerizing under abnormal overvoltage conditions to increase internal resistance. A method for this is described.

However, in the case of using additives such as biphenyl, when a relatively high local voltage is generated at a general operating voltage, it is gradually decomposed during the charging and discharging process, or when the battery is discharged at a high temperature for a long period of time, the amount of biphenyl is gradually reduced. After 300 cycles of charging and discharging, there are problems in that safety cannot be guaranteed, and problems in storage characteristics.

Therefore, there is a need for research to improve safety at high and low temperatures while still having a high capacity retention rate.

Japanese Patent JP2002-260725 U.S. Patent No. 5,879,834

An object of the present invention is to provide a lithium secondary battery electrolyte solution having excellent high temperature and low temperature characteristics while maintaining good basic performance such as high rate charge/discharge characteristics and lifespan characteristics, and a lithium secondary battery including the same.

The present invention provides a lithium secondary battery electrolyte, the lithium secondary battery electrolyte of the present invention,

lithium salt;

non-aqueous organic solvents; and

and a boron derivative represented by the following formula (1).

[Formula 1]

(In Formula 1,

A or D is independently of each other (C6-C12)arylene or (C3-C10)alkylene;

Alkylene and arylene of A or D are cyano, hydroxy, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl or ( It may be further substituted with C6-C12)aryl, except that when A or D is alkylene, all carbons of the alkylene are substituted with alkyl at the same time.)

Preferably, Chemical Formula 1 according to an embodiment of the present invention may be represented by Chemical Formula 2 below.

[Formula 2]

(In Formula 2,

R ¹ to R ² are each independently hydrogen, cyano, hydroxy, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl or (C6-C12)aryl; o or p is an integer of 1 to 4 independently of each other, and when o and p are 2 or more, R ¹ and R ² may be different or the same as each other.)

In Formula 2 according to an embodiment of the present invention, R ¹ or R ⁴ may be each independently hydrogen or (C1-C10)alkyl.

In addition, in the lithium secondary battery electrolyte according to an embodiment of the present invention, Chemical Formula 1 may be represented by Chemical Formula 3 below.

[Formula 3]

(In Formula 3,

R ¹ to R ⁴ are each independently hydrogen, cyano, hydroxy, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl or (C6-C12)aryl;

Z is -(CR ⁵ R ⁶ )m-;

T is -(CR ⁷ R ⁸ )n-, and R ⁵ to R ⁸ are each independently hydrogen, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1 -C10)alkoxycarbonyl or (C6-C12)aryl, ^{except when R 1} to R ⁸ are all alkyl at the same time;

n and m are each independently an integer from 1 to 4.)

Formula 3 according to an embodiment of the present invention may be represented by Formula 4 or Formula 5 below.

[Formula 4]

[Formula 5]

(In Formulas 4 and 5,

R ¹¹ to R ²² are each independently hydrogen, halo(C1-C10)alkyl, (C1-C10)alkyl or (C1-C10)alkoxycarbonyl;

In Formula 4, when R ¹¹ to R ²² are all alkyl at the same time, and in Formula 5 Except when R ¹¹ to R ²² are alkyl at the same time.)

In the lithium secondary battery electrolyte according to an embodiment of the present invention, Chemical Formula 1 may be selected from the following structures, but is not limited thereto.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the boron derivative represented by Formula 1 may be included in an amount of 0.1 to 5% by weight based on the total weight of the electrolyte.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the electrolyte is one or two selected from the group consisting of an oxalatoborate-based compound, a fluorine-substituted carbonate-based compound, a vinylidene carbonate-based compound, and a sulfinyl group-containing compound It may further include the above additives.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the electrolyte is lithium difluoro oxalatoborate (LiFOB), lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, propylene sulfite, diallyl sulfonate , ethane sultone, propane sulton (PS), butane sultone (butane sulton), ethene sultone, butene sultone and may further include an additive selected from the group consisting of propene sultone (PRS).

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the additive may be included in an amount of 0.1% to 5.0% by weight based on the total weight of the electrolyte.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the non-aqueous organic solvent may be selected from a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a mixed solvent thereof, and the cyclic carbonate is ethylene carbonate, propylene carbonate , butylene carbonate, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, and may be selected from the group consisting of mixtures thereof, the linear carbonate is dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl It may be selected from the group consisting of carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, and mixtures thereof.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the non-aqueous organic solvent may have a mixing volume ratio of the linear carbonate solvent: the cyclic carbonate solvent of 1 to 9: 1.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the lithium salt is LiPF ₆ , LiBF ₄ , LiClO ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO _{2 )} ) ₂ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiN(SO ₂ F) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC ₆ H ₅ SO ₃ , LiSCN, LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x and y are natural numbers), LiCl, LiI and LiB(C ₂ O ₄ ) ₂ One selected from the group consisting of or two or more.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the lithium salt may be present in a concentration of 0.1 to 2.0 M.

In addition, the present invention provides a lithium secondary battery comprising the lithium secondary battery electrolyte according to the present invention.

The lithium secondary battery electrolyte according to the present invention has excellent high-temperature storage characteristics by remarkably improved battery swelling at high temperatures by including boron derivatives.

In addition, the lithium secondary battery electrolyte according to the present invention is chemically stable, and more specifically, by including a boron derivative that is more stable than bis(pinacolato)diboron in which all substituents are alkyl, not only the capacity recovery rate at high temperature but also the discharge capacity at low temperature can also be significantly increased.

In addition, the lithium secondary battery electrolyte according to the present invention is selected from the group consisting of a boron derivative represented by Formula 1 of the present invention, an oxalatoborate-based compound, a fluorine-substituted carbonate-based compound, a vinylidene carbonate-based compound, and a sulfinyl group-containing compound By further including one or two or more additives, it has better lifespan characteristics, high temperature stability and low temperature characteristics.

In addition, the lithium secondary battery of the present invention has excellent high-temperature storage stability and low-temperature characteristics while maintaining good basic performance such as high-efficiency charge/discharge characteristics and lifespan characteristics by employing the lithium secondary battery electrolyte of the present invention containing boron derivatives.

Hereinafter, the present invention will be described in more detail. If there is no other definition in the technical and scientific terms used at this time, it has the meaning commonly understood by those of ordinary skill in the technical field to which this invention belongs, and may unnecessarily obscure the subject matter of the present invention in the following description. Descriptions of possible known functions and configurations will be omitted.

The present invention relates to a lithium secondary battery electrolyte solution for providing a battery having high high-temperature storage characteristics and high lifespan characteristics and excellent discharge capacity at low temperatures.

The present invention is a lithium salt; non-aqueous organic solvents; And a boron derivative represented by the following formula (1); provides a lithium secondary battery electrolyte comprising:

[Formula 1]

(In Formula 1,

A or D is independently of each other (C6-C12)arylene or (C3-C10)alkylene;

Alkylene and arylene of A or D are cyano, hydroxy, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl or ( It may be further substituted with C6-C12)aryl, except that when A or D is alkylene, all carbons of the alkylene are substituted with alkyl at the same time.)

The secondary battery electrolyte of the present invention contains a boron derivative, specifically, the boron derivative represented by Formula 1, so that the capacity recovery rate at high temperature is high, and the thickness change rate is low, so it is more stable at high temperature.

More specifically, the boron derivative of the present invention is chemically stable, and in order to have performance as an additive, in Formula 1 above, D is used to form a fused ring with arylene, or as an alkylene having 2 or more carbon atoms, a hetero containing two oxygens and boron. By forming a ring, it is possible to improve high-temperature and low-temperature characteristics while being chemically stable.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, Chemical Formula 1 may be preferably represented by the following Chemical Formula 2 in terms of chemical stability and electrical properties.

[Formula 2]

(In Formula 2,

R ¹ to R ² are each independently hydrogen, cyano, hydroxy, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl or (C6-C12)aryl; o or p is an integer of 1 to 4 independently of each other, and when o and p are 2 or more, R ¹ and R ² may be different or the same as each other.)

Formula 2 according to an embodiment of the present invention is a heteroalicyclic cyclic compound containing oxygen and boron fused with a benzene ring, which is decomposed at the negative electrode to efficiently form an SEI film, so that it has excellent high-temperature stability and low-temperature characteristics.

In Formula 2 according to an embodiment of the present invention, R ¹ or R ⁴ may be each independently hydrogen or (C1-C10)alkyl.

In addition, Chemical Formula 1 according to an embodiment of the present invention may be represented by Chemical Formula 3 below.

[Formula 3]

(In Formula 3,

R ¹ to R ⁴ are each independently hydrogen, cyano, hydroxy, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl or (C6-C12)aryl;

Z is -(CR ⁵ R ⁶ )m-;

T is -(CR ⁷ R ⁸ )n-, and R ⁵ to R ⁸ are each independently hydrogen, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1 -C10)alkoxycarbonyl or (C6-C12)aryl, ^{except when R 1} to R ⁸ are simultaneously alkyl;

n and m are each independently an integer from 1 to 4.)

Formula 3 according to an embodiment of the present invention is also decomposed at the negative electrode into a heteroalicyclic compound containing oxygen and boron to efficiently form an SEI film, so that it has excellent high-temperature stability and low-temperature characteristics.

Formula 3 according to an embodiment of the present invention may be preferably represented by the following Formula 4 or Formula 5 in terms of chemical stability and electrical properties.

[Formula 4]

[Formula 5]

(In Formulas 4 and 5,

R ¹¹ to R ²² are each independently hydrogen, halo(C1-C10)alkyl, (C1-C10)alkyl or (C1-C10)alkoxycarbonyl;

In Formula 4, when R ¹¹ to R ²² are all alkyl at the same time, and in Formula 5 Except when R ¹¹ to R ²² are all alkyl at the same time.)

In Formula 4 according to an embodiment of the present invention, R ¹¹ to R ¹⁸ may be more preferably hydrogen, halo (C1-C10) alkyl or (C1-C10) alkoxycarbonyl, and in Formula 5, R ¹¹ to R ²² may be more preferably hydrogen or (C1-C10)alkyl, except for alkyl at the same time.

The exact cause of the light compound in the case where all of the substituents of the carbons of Chemical Formulas 4 and 5 are alkyl is unknown, but battery characteristics such as high temperature stability of lithium secondary batteries employing an electrolyte containing them are not improved.

More specifically, the boron derivative of the present invention may be selected from the following structures, but is not limited thereto:

본 발명에 기재된 「알킬」, 「알콕시」 및 그 외 「알킬」부분을 포함하는 치환체는 직쇄 또는 분쇄 형태를 모두 포함하며, 1 내지 10개의 탄소원자 바람직하게는 1 내지 6, 보다 바람직하게는 1 내지 4의 탄소원자를 갖는다.

The substituents containing "alkyl", "alkoxy" and other "alkyl" moieties described in the present invention include both straight-chain or pulverized forms, and have 1 to 10 carbon atoms, preferably 1 to 6, more preferably 1 to 4 carbon atoms.

In addition, the "aryl" described in the present invention is an organic radical derived from an aromatic hydrocarbon by removal of one hydrogen, and is preferably a single or fused group containing 4 to 7, preferably 5 or 6 ring atoms in each ring. It includes a ring system, and includes a form in which a plurality of aryls are connected by a single bond. Specific examples include, but are not limited to, phenyl, naphthyl, biphenyl, anthryl, indenyl, fluorenyl, and the like.

As used herein, halogen-substituted alkyl or haloalkyl means that one or more hydrogens present in the alkyl are substituted with halogen.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the boron derivative of Formula 1 may be included in an amount of 0.1 to 5% by weight based on the total weight of the secondary battery electrolyte, and more preferably 1 to 3 in terms of high temperature stability. included in weight percent. When the content of the boron derivative of Formula 1 is less than 0.1% by weight, there is no additive effect such as low high-temperature stability or insignificant improvement in capacity retention, and the effect of improving the discharge capacity or output of the lithium secondary battery is insignificant, 5 When included in an excess of weight %, such as rapid deterioration of life occurs, rather, the characteristics of the lithium secondary battery is deteriorated.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the electrolyte is a lifespan improving additive for improving battery life, and an oxalatoborate-based compound, a fluorine-substituted carbonate-based compound, a vinylidene carbonate-based compound, and a sulfinyl group One or two or more additives selected from the group consisting of containing compounds may be further included.

The oxalatoborate-based compound may be a compound represented by the following Chemical Formula 11 or lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB).

[Formula 11]

(In Formula 11, R ₁₁ and R ₁₂ are each independently a halogen atom, or a C1 to C10 alkyl group in which at least one is substituted with halogen.)

Specific examples of the oxalatoborate-based additive include LiB(C ₂ O ₄ )F ₂ (lithium difluoro oxalatoborate, LiFOB) or LiB(C ₂ O ₄ ) ₂ (lithium bisoxalatoborate, LiBOB). can be heard

The fluorine-substituted carbonate-based compound may be fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), fluorodimethyl carbonate (FDMC), fluoroethylmethyl carbonate (FEMC), or a combination thereof.

The vinylidene carbonate-based compound may be vinylene carbonate (VC), vinyl ethylene carbonate (VEC), or a mixture thereof.

The sulfinyl group (S=O)-containing compound may be sulfone, sulfite, sulfonate and sultone (cyclic sulfonate), and these may be used alone or in combination. Specifically, the sulfone may be represented by the following Chemical Formula 12, and may be divinyl sulfone. The sulfite may be represented by the following Chemical Formula 13, and may be ethylene sulfite or propylene sulfite. The sulfonate may be represented by the following Chemical Formula 14, and may be diallyl sulfonate. In addition, non-limiting examples of sultone include ethane sultone, propane sulton, butane sulton, ethene sultone, butene sultone, propene sultone, and the like.

[Formula 12]

[Formula 13]

[Formula 14]

(In Formulas 12, 13, and 14, R ₁₃ and R ₁₄ are each independently hydrogen, a halogen atom, a C1-C10 alkyl group, a C2-C10 alkenyl group, a halogen-substituted C1-C10 alkyl group, or a halogen; It is a substituted C2-C10 alkenyl group.)

In the lithium secondary battery electrolyte according to an embodiment of the present invention, more preferably, the electrolyte is lithium difluoro oxalatoborate (LiFOB), lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), fluorine Roethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, propylene sulfite, diallyl sulfonate ( It may further include an additive selected from the group consisting of diallyl sulfonate), ethane sultone, propane sulton (PS), butane sulton, ethene sultone, butene sultone and propene sultone (PRS), more preferably Lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), vinylene carbonate (VC), vinylethylene carbonate (VEC), ethylene sulfite, ethane sultone, propane sulton , PS) may further include one or two or more additives selected from.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the content of the additive is not particularly limited, but is more preferably 0.1 to 5% by weight based on the total weight of the electrolyte in order to improve battery life in the secondary battery electrolyte. For example, it may be included in an amount of 0.1 to 3% by weight.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the non-aqueous organic solvent may include carbonate, ester, ether, or ketone alone or a mixed solvent thereof, but a cyclic carbonate-based solvent, a linear carbonate-based solvent, and It is preferably selected from these mixed solvents, and it is most preferable to use a mixture of a cyclic carbonate-based solvent and a linear carbonate-based solvent. The cyclic carbonate solvent has a large polarity and can sufficiently dissociate lithium ions, but has a disadvantage in that the ionic conductivity is small due to a large viscosity. Accordingly, the characteristics of the lithium secondary battery can be optimized by mixing the cyclic carbonate solvent with a linear carbonate solvent having a low polarity but low viscosity.

The cyclic carbonate-based solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, and mixtures thereof, and the linear carbonate-based solvent is dimethyl carbonate, It may be selected from the group consisting of diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, and mixtures thereof.

In the lithium secondary battery electrolyte according to an embodiment of the present invention, the non-aqueous organic solvent is a mixed solvent of a cyclic carbonate-based solvent and a linear carbonate-based solvent, and a mixing volume ratio of the linear carbonate solvent: the cyclic carbonate solvent is 1 to 9: 1 may be used, preferably mixed in a volume ratio of 1.5 to 4:1.

In the high voltage lithium secondary battery electrolyte according to an embodiment of the present invention, the lithium salt is not limited, but LiPF ₆ , LiBF ₄ , LiClO ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiN(SO ₂ F) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC ₆ H ₅ SO ₃ , LiSCN, LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x and y are natural numbers), LiCl, LiI and LiB(C ₂ O ₄ ) ₂ as It may be one or two or more selected from the group consisting of.

The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0 M, more preferably used within the range of 0.7 to 1.6 M. If the concentration of the lithium salt is less than 0.1 M, the conductivity of the electrolyte is lowered and the performance of the electrolyte is deteriorated. The lithium salt serves as a source of lithium ions in the battery to enable the basic operation of the lithium secondary battery.

The lithium secondary battery electrolyte of the present invention is generally stable in a temperature range of -20°C to 60°C, and maintains electrochemically stable characteristics even at a voltage of 4.4V, so it can be applied to all lithium secondary batteries such as lithium ion batteries and lithium polymer batteries can

In addition, the present invention provides a lithium secondary battery comprising the lithium secondary battery electrolyte.

Non-limiting examples of the secondary battery include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The lithium secondary battery prepared from the lithium secondary battery electrolyte according to the present invention exhibits a high temperature storage efficiency of 75% or more, and at the same time, the thickness increase rate of the battery when left at a high temperature for a long period of time is very low, preferably 1 to 15%, rather than 1 to 20%. characterized in that

The lithium secondary battery of the present invention includes a positive electrode and a negative electrode.

The positive electrode includes a positive electrode active material capable of intercalating and deintercalating lithium ions, and the positive active material is preferably a composite metal oxide with lithium and at least one selected from cobalt, manganese, and nickel. The solid solution ratio between metals can be made variously, and in addition to these metals, Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, Zr, Mn, Cr, Fe, An element selected from the group consisting of Sr, V and rare earth elements may be further included. As a specific example of the positive active material, a compound represented by any one of the following formulas may be used:

Li _a A _1-b B _b D ₂ (wherein 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5); Li _a E _1-b B _b O _2-c D _c (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE _2-b B _b O _4-c D _c (wherein 0 ≤ b ≤ 0.5 and 0 ≤ c ≤ 0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (wherein 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li _a NiG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a CoG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a MnG _b O ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2); and LiFePO ₄ .

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; I is Cr, V, Fe, Sc, Y or a combination thereof; J may be V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

The negative electrode includes an anode active material capable of intercalating and deintercalating lithium ions, and as such a negative active material, a carbon material such as crystalline carbon, amorphous carbon, carbon composite material, carbon fiber, lithium metal, an alloy of lithium and other elements, etc. may be used. can For example, the amorphous carbon includes hard carbon, coke, mesocarbon microbead (MCMB) calcined at 1500° C. or lower, mesophase pitch-based carbon fiber (MPCF), and the like. As crystalline carbon, there are graphite-based materials, and specific examples thereof include natural graphite, graphitized coke, graphitized MCMB, and graphitized MPCF. The carbon material is preferably a material having an interplanar distance of 3.35 to 3.38 Å, and a crystallite size (Lc) of at least 20 nm by X-ray diffraction. As another element alloying with lithium, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium may be used.

The positive electrode or negative electrode may be prepared by dispersing an electrode active material, a binder and a conductive material, and, if necessary, a thickener in a solvent to prepare an electrode slurry composition, and applying the slurry composition to an electrode current collector. As the positive electrode current collector, aluminum or an aluminum alloy may be commonly used, and as the negative electrode current collector, copper or a copper alloy may be commonly used. The positive electrode current collector and the negative electrode current collector may be in the form of a foil or a mesh.

The binder is a material that acts as a paste of the active material, mutual adhesion of the active material, adhesion to the current collector, and a buffer effect against expansion and contraction of the active material, for example, polyvinylidene fluoride (PVdF), polyhexafluoro Propylene-polyvinylidene fluoride copolymer (PVdF/HFP)), poly(vinyl acetate), polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, alkylated polyethylene oxide, polyvinyl ether, poly(methyl meta acrylate), poly(ethyl acrylate), polytetrafluoroethylene, polyvinyl chloride, polyacrylonitrile, polyvinylpyridine, styrene-butadiene rubber, and acrylonitrile-butadiene rubber. The content of the binder is 0.1 to 30% by weight, preferably 1 to 10% by weight based on the electrode active material. When the content of the binder is too small, the adhesive force between the electrode active material and the current collector is insufficient, and when the content of the binder is too large, the adhesive strength is improved, but the content of the electrode active material is reduced by that much, which is disadvantageous in increasing the battery capacity.

The conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause a chemical change can be used in the constituted battery. At least one selected from the group consisting of conductive agents may be used. Examples of the graphite-based conductive agent include artificial graphite, natural graphite, and the like, and examples of the carbon black-based conductive agent include acetylene black, ketjen black, denka black, thermal black, and channel black. (channel black) and the like, and examples of the metal-based or metal compound-based conductive agent include perovskite such as _{tin, tin oxide, tin phosphate (SnPO 4} ), titanium oxide, potassium titanate, LaSrCoO ₃ , and LaSrMnO _{3 .} there is material However, it is not limited to the conductive agents listed above.

The content of the conductive agent is preferably 0.1 to 10% by weight based on the electrode active material. When the content of the conductive agent is less than 0.1% by weight, the electrochemical properties are deteriorated, and when it exceeds 10% by weight, the energy density per weight is reduced.

The thickener is not particularly limited as long as it can play a role in controlling the viscosity of the active material slurry, but for example, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. may be used.

A non-aqueous solvent or an aqueous solvent is used as a solvent in which the electrode active material, binder, conductive material, and the like are dispersed. Examples of the non-aqueous solvent include N-methyl-2-pyrroldidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran.

The lithium secondary battery of the present invention may include a separator that prevents a short circuit between the positive electrode and the negative electrode and provides a passage for lithium ions, such as polypropylene, polyethylene, polyethylene/polypropylene, polyethylene/polypropylene/ Polyolefin-based polymer membranes such as polyethylene, polypropylene/polyethylene/polypropylene, or multilayers thereof, microporous films, woven fabrics and nonwoven fabrics may be used. In addition, a film coated with a resin having excellent stability on the porous polyolefin film may be used.

The lithium secondary battery of the present invention may be formed in other shapes such as a cylindrical shape, a pouch shape, etc. in addition to the prismatic shape.

Hereinafter, Examples and Comparative Examples of the present invention will be described. However, the following examples are only preferred examples of the present invention, and the present invention is not limited thereto. It is considered that all lithium salts are dissociated so that the lithium ion concentration becomes 1 mole (1M), and a lithium salt _{such as LiPF 6} can be dissolved in a basic solvent to form a base electrolyte solution so that the concentration becomes 1 mole (1M). .

[Example 1] Synthesis of bis(catecolato)diboron (2,2'-Bis(1,3,2-benzodioxaborole, hereinafter referred to as 'PEA04')

At room temperature, tetrakis(dimethylamino)diboron (2.0 g) was added to a mixture of 1,2-dihydroxybenzene (2.4 g) and diethyl ether (20 mL). After stirring for 18 hours, dimethylamine and diethyl ether were removed by distillation under reduced pressure. After dissolving the product in diethyl ether, the temperature was lowered to 0 °C, and 1N hydrochloric acid aqueous solution was added thereto. After stirring for 12 hours, the product was extracted with toluene and toluene was removed by vacuum distillation. After washing the product with acetonitrile, bis(catecolato)diboron (2.2 g) was obtained through vacuum drying.

¹ H NMR (CD ₂ Cl ₂ , 500 MHz) δ 7.38 (m, 4H), 7.20 (m, 4H)

[Example 2] Synthesis of bis(ethyleneglycolato)diboron (hereinafter referred to as 'PEA76')

Dissolve 2.48 g of ethylene glycol (40 mmol) and 3.96 g of tetrakis (dimethylamino) diboron (20 mmol) in 20 ml of hexane in a 100 ml round-bottom flask. , The temperature was raised to ^{50 o} _{C under N 2 environment.} After the reaction was carried out at 50 ^o C for 24 hours, the temperature was lowered to room temperature. The solvent was removed by distillation under reduced pressure, and recrystallized from dichloromethane and hexane to obtain 1.9 g of the title compound.

¹ H-NMR (400 MHz, CDCl ₃ ) δ: 4.07 (s, J=5.6 Hz, 8H)

[Example 3] [2,2']bi[[1,3,2]dioxaborinanyl]([2,2']bi[[1,3,2]dioxaborinanyl]), hereinafter 'PEA75' ) synthesis

In a 100 ml round-bottom flask, 3.08 g of 1,3-propanediol (40 mmol) and 3.96 g of tetrakis (dimethylamino) in 20 ml of hexane diboron, 20 mmol) was dissolved, and the temperature was raised to ^{50 o} _{C under N 2 environment.} After the reaction was carried out at 50 ^o C for 24 hours, the temperature was lowered to room temperature. The solvent was removed by distillation under reduced pressure and recrystallized from dichloromethane and hexane to obtain 2.5 g of the title compound.

¹ H-NMR (400 MHz, CDCl ₃ ) δ: 3.95 (t, J=5.6 Hz, 8H), 1.94 (quin, J=5.2 Hz, 4H)

[Example 4] 5,5,5',5'-tetramethyl-2,2'-bi (1,3,2.dioxaborinane) (5,5,5',5'-tetramethyl-2 ,2'-bi(1,3,2-dioxaborinane), hereinafter referred to as 'PEA66')

In a 100 ml round bottom flask, in 30 ml of toluene, 4.17 g of 2,2-dimethyl-1,3-propanediol (40 mmol) and 3.96 g of tetra After dissolving kiss (dimethylamino) diboron (tetrakis (dimethylamino) diboron, 20 mmol), the temperature was raised to ^{50 o} _{C under N 2 environment.} After performing the reaction overnight at 50 ^o C, the temperature was lowered to room temperature. After filtering the crystals formed at room temperature, the filtrate was vacuum dried to obtain 2.8 g of the title compound.

¹ H-NMR (400 MHz, CDCl ₃ ) δ: 3.57 (s, 8H), 0.92 (s, 12H)

[Example 5] 4,4,4',4',5,5,5',5'-octakis(trifluoromethyl)-2,2'-bi(1,3,2-dioxabo Rolan) (4,4,4',4',5,5,5',5'-octakis(trifluoromethyl)-2,2'-bi(1,3,2-dioxaborolane), hereinafter referred to as 'PEA69' )

13.4 g of hexafluoro-2,3-bis(trifluoromethyl)-2,3-butanediol (Hexafluoro-2,3-bis(trifluoromethyl)- 2,3-butanediol, 40 mmol) and 3.96 g of tetrakis(dimethylamino)diboron (20 mmol) were dissolved, and then the temperature was raised to ^{50 o} _{C in an N 2 environment.} After the reaction was carried out at 50 ^o C for 24 hours, the temperature was lowered to room temperature. After filtering the crystals formed at room temperature, the filtrate was vacuum dried to obtain 12 g of the title compound.

[Example 6] (4R,4'R,5R,5'R)-tetraisopropyl [2,2'-ratio (1,3,2-dioxaborolane)]-4,4',5, 5'-tetracarboxylate ((4R,4'R,5R,5'R)-tetraisopropyl [2,2'-bi(1,3,2-dioxaborolane)]-4,4',5,5' -tetracarboxylate, hereinafter referred to as 'PEA74')

In a 100 ml round-bottom flask, in 30 ml of toluene, 9.37 g of diisopropyl-L-tartrate (40 mmol) and 3.96 g of tetrakis (dimethylamino) diboron (tetrakis ( After dissolving dimethylamino)diboron, 20 mmol), the temperature was raised to ^{50 o} _{C under N 2 environment.} After performing the reaction overnight at 50 ^o C, the temperature was lowered to room temperature. Toluene was removed by distillation under reduced pressure, and then vacuum dried to obtain 9.5 g of the title compound.

¹ H-NMR (400 MHz, CDCl ₃ ) δ: 4.93 (sep, J=6.8 Hz, 4H), 4.77 (s, 4H), 1.32 (d, J=6.8 Hz, 24H)

[Comparative Example 1] Synthesis of bis (pinacolato) diboron (bis (pinacolato) diboron, hereinafter referred to as 'PEA03')

At room temperature, tetrakis(dimethylamino)diboron (2.0 g) was added to a mixture of anhydrous phytachol (2.4 g) and diethyl ether (20 mL). After stirring for 18 hours, dimethylamine and diethyl ether were removed by distillation under reduced pressure. Bis (pinacolato) diboron (2.2 g) as a colorless solid was obtained through sublimation purification in vacuo.

¹ H NMR (CDCl ₃ , 500 MHz) δ1.26 (s, 24H)

[Examples 7-19 and Comparative Examples 2-5]

Electrolyte solution is ethylene carbonate (EC): ethyl methyl carbonate (EMC) a 3:07 volume ratio of the solution obtained by dissolving to a 1.0 M solution of LiPF ₆ in a mixed solvent base electrolytic solution (1M in of LiPF _6, EC / EMC = 3 : 7) and was prepared by additionally adding the components listed in Table 1 below.

A battery to which the non-aqueous electrolyte is applied was prepared as follows.

_{LiNiCoMnO 2} and LiMn ₂ O ₄ as a cathode active material were mixed in a weight ratio of 1:1, polyvinylidene fluoride (PVdF) as a binder and carbon as a conductive agent were mixed in a weight ratio of 92:4:4, and then N- A positive electrode slurry was prepared by dispersing in methyl-2-pyrrolidone. The slurry was coated on an aluminum foil having a thickness of 20 μm, dried and rolled to prepare a positive electrode. An anode active material slurry was prepared by mixing artificial graphite as an anode active material, styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickener in a weight ratio of 96:2:2 and then dispersing in water. This slurry was coated on a copper foil having a thickness of 15 μm, dried and rolled to prepare a negative electrode.

A cell was constructed using a pouch having a size of 8 mm thick x 270 mm x 185 mm thick by stacking a film separator of a polyethylene (PE) material having a thickness of 25 μm between the prepared electrodes. , a 25Ah class lithium secondary battery for EV was prepared by injecting the non-aqueous electrolyte.

The performance of the 25Ah class battery for EV manufactured in this way was evaluated as follows. Evaluation items are as follows.

*Evaluation items*

1. -20℃ 1C discharge capacity: After charging at room temperature at 25A, 4.2V CC-CV for 3 hours, and leaving it at -20℃ for 4 hours, after discharging at a current of 25A and CC to 2.7V, the usable capacity compared to the initial capacity (%) was measured.

2. Capacity recovery rate for 30 days at 60℃: After 3 hours of charging at room temperature at 4.2V, 25A CC-CV, and left at 60℃ for 30 days, after discharging at a current of 25A and CC to 2.7V, the recovery rate compared to the initial capacity (%) was measured.

3. Thickness increase rate after 30 days at 60℃: After 3 hours of charging with 4.4V, 12.5A CC-CV at room temperature, the thickness of the battery is called A, and 30 at 60℃ and atmospheric pressure exposed to the atmosphere using a sealed thermostat. When the thickness of the battery left alone is B, the increase rate of the thickness was calculated as in Equation 1 below.

[Equation 1]

(B-A)/A × 100(%)

4. Room temperature life: After charging for 3 hours at 4.2V, 50A CC-CV at room temperature, discharge up to 2.7V at 2.7V and 25A current 500 times. In this case, the first discharge capacity was C, and the capacity retention rate during the life was calculated by dividing the 300th discharge capacity by the first discharge capacity.

Electrolyte composition 60℃ after 30 days Capacity retention over life -20℃ discharge
Volume capacity recovery rate thickness increase rate Example 7 Basic electrolyte + PEA04 1wt% 81% 12% 81% 83% Example 8 Basic electrolyte + PEA04 0.5wt% 91% 14% 85% 76% Example 9 Basic electrolyte + PEA04 3wt% 76% 9% 74% 72% Example 10 Basic electrolyte + PEA04 1wt% + VC 1wt% 87% 9% 87% 77% Example 11 Basic electrolyte+PEA04 1wt%+VC 0.5wt%+PS 0.5wt% 88% 2% 88% 72% Example 12 Basic electrolyte+PEA04 1wt%+VC 0.5wt%+LiBOB 0.5wt% 89% 4% 91% 78% Example 13 Basic electrolyte + PEA66 1wt% 75% 9% 83% 88% Example 14 Basic electrolyte + PEA69 1wt% 81% 7% 84% 84% Example 15 Basic electrolyte + PEA74 1wt% 85% 4% 88% 86% Example 16 Basic electrolyte + PEA75 1wt% 78% 8% 81% 85% Example 17 Basic electrolyte + PEA76 1wt% 75% 10% 78% 78% Example 18 Basic electrolyte+PEA74 1wt%+VC 0.5wt%+PS 0.5wt% 91% One% 91% 82% Example 19 Basic electrolyte+PEA74 1wt%+VC 0.5wt%+LiBOB 0.5wt% 89% 2% 92% 84% Comparative Example 2 basic electrolyte 37% 30% 20% 55% Remark example 3 Basic electrolyte+VC 1wt%+PS 1wt% 60% 12% 61% 48% Comparative Example 4 Basic electrolyte + PEA03 1wt% 12% 50% 54% 89% Comparative Example 5 Basic electrolyte+PEA03 1wt%+VC 0.5wt%+PS 0.5wt% 28% 35% 61% 60% Basic electrolyte: 1M LiPF ₆ , EC/EMC=3:7

LiBOB: Lithium-bis(Oxalato)Borate
VC : Vinylene carbonate
PS: 1,3-propane sultone

As shown in Table 1, it can be seen that the lithium secondary battery containing the lithium secondary battery electrolyte according to the present invention showed a high capacity recovery rate even after 30 days at 60°C, and the thickness increase rate was also very low.

On the other hand, it can be seen that the secondary battery electrolyte solution that does not contain the boron derivative of the present invention has a low high-temperature capacity recovery rate, and the thickness increase rate is also very high at a whopping 30%, resulting in poor stability.

In addition, the secondary battery employing the electrolyte containing the compound of Comparative Example 1 having a structure different from that of the boron derivative of the present invention had a rather high low-temperature discharge capacity, but low high-temperature storage stability.

When the commercialized compound of Comparative Example 1 ((Allychem Co. LTD, purity 99%) was used, the electrolyte solution turned brown when added. Therefore, the compound of Comparative Example 1 was chemically somewhat unstable and thus compared during high temperature stability experiments. It is judged that the compound of Example 1 is decomposed and cannot improve high-temperature stability.

Therefore, it can be seen that the boron derivative represented by Formula 1 of the present invention is stable unlike the compound of Comparative Example 1, and thus high-temperature stability and low-temperature discharge capacity can also be improved.

In addition, the secondary battery electrolyte of the present invention includes a boron derivative represented by Formula 1 of the present invention, lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), vinylene carbonate (VC), and vinylethylene carbonate (VEC). ), ethylene sulfite (ethylene sulfite), ethane sultone, propane sulton (propane sulton, PS) by further including one or more additives selected from the high-temperature storage stability, low-temperature discharge capacity and lifespan characteristics to further improve the secondary battery of the present invention A lithium secondary battery containing an electrolyte has very high efficiency, stability, and lifespan characteristics.

As described above, the embodiments of the present invention have been described in detail, but those of ordinary skill in the art to which the present invention pertains can view the present invention without departing from the spirit and scope of the present invention as defined in the appended claims. The invention may be practiced with various modifications. Accordingly, modifications of future embodiments of the present invention will not depart from the technology of the present invention.

Claims (16)

lithium salt;
non-aqueous organic solvents; and
A secondary battery electrolyte comprising a boron derivative represented by the following Chemical Formula 2, Chemical Formula 4 or Chemical Formula 5:
[Formula 2]

(In Formula 2,
R ¹ and R ² are independently of each other hydrogen, cyano, hydroxy, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl or (C6-C12)aryl; o and p are each independently an integer of 1 to 4, and when o and p are 2 or more, two or more R ¹ may be different or the same as each other, and two or more R ² may be different or the same as each other.)
[Formula 4]

[Formula 5]

(In Formulas 4 and 5,
R ¹¹ to R ²² are each independently hydrogen, halo(C1-C10)alkyl, (C1-C10)alkyl or (C1-C10)alkoxycarbonyl;
^{When R 11} to R ¹⁸ in Formula 4 are all (C1-C10)alkyl, and in Formula 5 Except when R ¹¹ to R ²² are all (C1-C10)alkyl.) delete The method of claim 1,
In Formula 2, R ¹ and R ² are each independently hydrogen, halogen, or halo (C1-C10)alkyl. delete delete The method of claim 1,
The boron derivative is a secondary battery electrolyte that is selected from the following compounds:

The method of claim 1,
The boron derivative is a secondary battery electrolyte that is included in 0.1 to 5% by weight based on the total weight of the electrolyte. The method of claim 1,
The electrolyte solution is a secondary battery electrolyte solution further comprising one or two or more additives selected from the group consisting of an oxalatoborate-based compound, a fluorine-substituted carbonate-based compound, a vinylidene carbonate-based compound, and a sulfinyl group-containing compound. 9. The method of claim 8,
The electrolyte solution is lithium difluoro oxalatoborate (LiFOB), lithium bisoxalatoborate (LiB(C ₂ O ₄ ) ₂ , LiBOB), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, propylene sulfite, diallyl sulfonate, ethane sultone, propane sulton (PS), butane A secondary battery electrolyte further comprising an additive selected from the group consisting of sultone (butane sulton), ethene sultone, butene sultone, and propene sultone (PS). 9. The method of claim 8,
The additive is a secondary battery electrolyte containing 0.1 to 5.0% by weight based on the total weight of the electrolyte. The method of claim 1,
The non-aqueous organic solvent is a secondary battery electrolyte solution selected from a cyclic carbonate-based solvent, a linear carbonate-based solvent, and a mixed solvent thereof. 12. The method of claim 11,
The cyclic carbonate is selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, and mixtures thereof, and the linear carbonate is dimethyl carbonate, diethyl carbonate, dipropyl A secondary battery electrolyte selected from the group consisting of carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, and mixtures thereof. 12. The method of claim 11,
The non-aqueous organic solvent is a secondary battery electrolyte having a mixing volume ratio of a linear carbonate solvent: a cyclic carbonate solvent of 1 to 9: 1. The method of claim 1,
The lithium salt is LiPF ₆ , LiBF ₄ , LiClO ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiN(SO ₂ F) ₂ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC ₆ H ₅ SO ₃ , LiSCN, LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ) (where x and y are natural numbers), LiCl, LiI, and LiB(C ₂ O ₄ ) ₂ One or two or more secondary battery electrolytes selected from the group consisting of. The method of claim 1,
The lithium salt is present in a concentration of 0.1 to 2.0 M secondary battery electrolyte. A lithium secondary battery comprising the secondary battery electrolyte according to any one of claims 1, 3, and 6 to 15.